1 HXCOMM Use
DEFHEADING() to define headings
in both help text and rST
.
2 HXCOMM Text between SRST and ERST is copied to the rST version and
3 HXCOMM discarded from C version
.
4 HXCOMM
DEF(option
, HAS_ARG
/0, opt_enum
, opt_help
, arch_mask
) is used to
5 HXCOMM construct option structures
, enums and help message
for specified
7 HXCOMM HXCOMM can be used
for comments
, discarded from both rST and C
.
9 DEFHEADING(Standard options
:)
11 DEF("help", 0, QEMU_OPTION_h
,
12 "-h or -help display this help and exit\n", QEMU_ARCH_ALL
)
18 DEF("version", 0, QEMU_OPTION_version
,
19 "-version display version information and exit\n", QEMU_ARCH_ALL
)
22 Display version information and exit
25 DEF("machine", HAS_ARG
, QEMU_OPTION_machine
, \
26 "-machine [type=]name[,prop[=value][,...]]\n"
27 " selects emulated machine ('-machine help' for list)\n"
28 " property accel=accel1[:accel2[:...]] selects accelerator\n"
29 " supported accelerators are kvm, xen, hax, hvf, nvmm, whpx or tcg (default: tcg)\n"
30 " vmport=on|off|auto controls emulation of vmport (default: auto)\n"
31 " dump-guest-core=on|off include guest memory in a core dump (default=on)\n"
32 " mem-merge=on|off controls memory merge support (default: on)\n"
33 " aes-key-wrap=on|off controls support for AES key wrapping (default=on)\n"
34 " dea-key-wrap=on|off controls support for DEA key wrapping (default=on)\n"
35 " suppress-vmdesc=on|off disables self-describing migration (default=off)\n"
36 " nvdimm=on|off controls NVDIMM support (default=off)\n"
37 " memory-encryption=@var{} memory encryption object to use (default=none)\n"
38 " hmat=on|off controls ACPI HMAT support (default=off)\n"
39 " memory-backend='backend-id' specifies explicitly provided backend for main RAM (default=none)\n",
42 ``
-machine
[type
=]name
[,prop
=value
[,...]]``
43 Select the emulated machine by name
. Use ``
-machine help`` to list
46 For architectures which aim to support live migration compatibility
47 across releases
, each release will introduce a
new versioned machine
48 type
. For example
, the
2.8.0 release introduced machine types
49 "pc-i440fx-2.8" and
"pc-q35-2.8" for the x86\_64
/i686 architectures
.
51 To allow live migration of guests from QEMU version
2.8.0, to QEMU
52 version
2.9.0, the
2.9.0 version must support the
"pc-i440fx-2.8"
53 and
"pc-q35-2.8" machines too
. To allow users live migrating VMs to
54 skip multiple intermediate releases when upgrading
, new releases of
55 QEMU will support machine types from many previous versions
.
57 Supported machine properties are
:
59 ``accel
=accels1
[:accels2
[:...]]``
60 This is used to enable an accelerator
. Depending on the target
61 architecture
, kvm
, xen
, hax
, hvf
, nvmm
, whpx or tcg can be available
.
62 By
default, tcg is used
. If there is more than one accelerator
63 specified
, the next one is used
if the previous one fails to
66 ``vmport
=on|off|auto``
67 Enables emulation of VMWare IO port
, for vmmouse etc
. auto says
68 to select the value based on accel
. For accel
=xen the
default is
69 off otherwise the
default is on
.
71 ``dump
-guest
-core
=on|off``
72 Include guest memory
in a core dump
. The
default is on
.
75 Enables or disables memory merge support
. This feature
, when
76 supported by the host
, de
-duplicates identical memory pages
77 among VMs
instances (enabled by
default).
79 ``aes
-key
-wrap
=on|off``
80 Enables or disables AES key wrapping support on s390
-ccw hosts
.
81 This feature controls whether AES wrapping keys will be created
82 to allow execution of AES cryptographic functions
. The
default
85 ``dea
-key
-wrap
=on|off``
86 Enables or disables DEA key wrapping support on s390
-ccw hosts
.
87 This feature controls whether DEA wrapping keys will be created
88 to allow execution of DEA cryptographic functions
. The
default
92 Enables or disables NVDIMM support
. The
default is off
.
94 ``memory
-encryption
=``
95 Memory encryption object to use
. The
default is none
.
98 Enables or disables ACPI Heterogeneous Memory Attribute Table
99 (HMAT
) support
. The
default is off
.
101 ``memory
-backend
='id'``
102 An alternative to legacy ``
-mem
-path`` and ``mem
-prealloc`` options
.
103 Allows to use a memory backend as main RAM
.
108 -object memory
-backend
-file
,id
=pc
.ram
,size
=512M
,mem
-path
=/hugetlbfs
,prealloc
=on
,share
=on
109 -machine memory
-backend
=pc
.ram
112 Migration compatibility note
:
114 * as backend id one shall use value of
'default-ram-id', advertised by
115 machine
type (available via ``query
-machines`` QMP command
), if migration
116 to
/from old
QEMU (<5.0) is expected
.
117 * for machine types
4.0 and older
, user shall
118 use ``x
-use
-canonical
-path
-for-ramblock
-id
=off`` backend option
119 if migration to
/from old
QEMU (<5.0) is expected
.
124 -object memory
-backend
-ram
,id
=pc
.ram
,size
=512M
,x
-use
-canonical
-path
-for-ramblock
-id
=off
125 -machine memory
-backend
=pc
.ram
129 DEF("M", HAS_ARG
, QEMU_OPTION_M
,
130 " sgx-epc.0.memdev=memid,sgx-epc.0.node=numaid\n",
134 ``sgx
-epc
.0.memdev
=@
var{memid
},sgx
-epc
.0.node
=@
var{numaid
}``
135 Define an SGX EPC section
.
138 DEF("cpu", HAS_ARG
, QEMU_OPTION_cpu
,
139 "-cpu cpu select CPU ('-cpu help' for list)\n", QEMU_ARCH_ALL
)
142 Select CPU
model (``
-cpu help``
for list and additional feature
146 DEF("accel", HAS_ARG
, QEMU_OPTION_accel
,
147 "-accel [accel=]accelerator[,prop[=value][,...]]\n"
148 " select accelerator (kvm, xen, hax, hvf, nvmm, whpx or tcg; use 'help' for a list)\n"
149 " igd-passthru=on|off (enable Xen integrated Intel graphics passthrough, default=off)\n"
150 " kernel-irqchip=on|off|split controls accelerated irqchip support (default=on)\n"
151 " kvm-shadow-mem=size of KVM shadow MMU in bytes\n"
152 " split-wx=on|off (enable TCG split w^x mapping)\n"
153 " tb-size=n (TCG translation block cache size)\n"
154 " dirty-ring-size=n (KVM dirty ring GFN count, default 0)\n"
155 " thread=single|multi (enable multi-threaded TCG)\n", QEMU_ARCH_ALL
)
157 ``
-accel name
[,prop
=value
[,...]]``
158 This is used to enable an accelerator
. Depending on the target
159 architecture
, kvm
, xen
, hax
, hvf
, nvmm
, whpx or tcg can be available
. By
160 default, tcg is used
. If there is more than one accelerator
161 specified
, the next one is used
if the previous one fails to
164 ``igd
-passthru
=on|off``
165 When Xen is
in use
, this option controls whether Intel
166 integrated graphics devices can be passed through to the guest
169 ``kernel
-irqchip
=on|off|split``
170 Controls KVM
in-kernel irqchip support
. The
default is full
171 acceleration of the interrupt controllers
. On x86
, split irqchip
172 reduces the kernel attack surface
, at a performance cost
for
173 non
-MSI interrupts
. Disabling the
in-kernel irqchip completely
174 is not recommended except
for debugging purposes
.
176 ``kvm
-shadow
-mem
=size``
177 Defines the size of the KVM shadow MMU
.
180 Controls the use of split w^x mapping
for the TCG code generation
181 buffer
. Some operating systems require
this to be enabled
, and
in
182 such a
case this will
default on
. On other operating systems
, this
183 will
default off
, but one may enable
this for testing or debugging
.
186 Controls the
size (in MiB
) of the TCG translation block cache
.
188 ``thread
=single|multi``
189 Controls number of TCG threads
. When the TCG is multi
-threaded
190 there will be one thread per vCPU therefore taking advantage of
191 additional host cores
. The
default is to enable multi
-threading
192 where both the back
-end and front
-ends support it and no
193 incompatible TCG features have been
enabled (e
.g
.
196 ``dirty
-ring
-size
=n``
197 When the KVM accelerator is used
, it controls the size of the per
-vCPU
198 dirty page ring
buffer (number of entries
for each vCPU
). It should
199 be a value that is power of two
, and it should be
1024 or
bigger (but
200 still less than the maximum value that the kernel supports
). 4096
201 could be a good initial value
if you have no idea which is the best
.
202 Set
this value to
0 to disable the feature
. By
default, this feature
203 is
disabled (dirty
-ring
-size
=0). When enabled
, KVM will instead
204 record dirty pages
in a bitmap
.
208 DEF("smp", HAS_ARG
, QEMU_OPTION_smp
,
209 "-smp [[cpus=]n][,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,clusters=clusters][,cores=cores][,threads=threads]\n"
210 " set the number of initial CPUs to 'n' [default=1]\n"
211 " maxcpus= maximum number of total CPUs, including\n"
212 " offline CPUs for hotplug, etc\n"
213 " sockets= number of sockets on the machine board\n"
214 " dies= number of dies in one socket\n"
215 " clusters= number of clusters in one die\n"
216 " cores= number of cores in one cluster\n"
217 " threads= number of threads in one core\n"
218 "Note: Different machines may have different subsets of the CPU topology\n"
219 " parameters supported, so the actual meaning of the supported parameters\n"
220 " will vary accordingly. For example, for a machine type that supports a\n"
221 " three-level CPU hierarchy of sockets/cores/threads, the parameters will\n"
222 " sequentially mean as below:\n"
223 " sockets means the number of sockets on the machine board\n"
224 " cores means the number of cores in one socket\n"
225 " threads means the number of threads in one core\n"
226 " For a particular machine type board, an expected CPU topology hierarchy\n"
227 " can be defined through the supported sub-option. Unsupported parameters\n"
228 " can also be provided in addition to the sub-option, but their values\n"
229 " must be set as 1 in the purpose of correct parsing.\n",
232 ``
-smp
[[cpus
=]n
][,maxcpus
=maxcpus
][,sockets
=sockets
][,dies
=dies
][,clusters
=clusters
][,cores
=cores
][,threads
=threads
]``
233 Simulate a SMP system with
'\ ``n``\ ' CPUs initially present on
234 the machine type board
. On boards supporting CPU hotplug
, the optional
235 '\ ``maxcpus``\ ' parameter can be set to enable further CPUs to be
236 added at runtime
. When both parameters are omitted
, the maximum number
237 of CPUs will be calculated from the provided topology members and the
238 initial CPU count will match the maximum number
. When only one of them
239 is given then the omitted one will be set to its counterpart
's value.
240 Both parameters may be specified, but the maximum number of CPUs must
241 be equal to or greater than the initial CPU count. Product of the
242 CPU topology hierarchy must be equal to the maximum number of CPUs.
243 Both parameters are subject to an upper limit that is determined by
244 the specific machine type chosen.
246 To control reporting of CPU topology information, values of the topology
247 parameters can be specified. Machines may only support a subset of the
248 parameters and different machines may have different subsets supported
249 which vary depending on capacity of the corresponding CPU targets. So
250 for a particular machine type board, an expected topology hierarchy can
251 be defined through the supported sub-option. Unsupported parameters can
252 also be provided in addition to the sub-option, but their values must be
253 set as 1 in the purpose of correct parsing.
255 Either the initial CPU count, or at least one of the topology parameters
256 must be specified. The specified parameters must be greater than zero,
257 explicit configuration like "cpus=0" is not allowed. Values for any
258 omitted parameters will be computed from those which are given.
260 For example, the following sub-option defines a CPU topology hierarchy
261 (2 sockets totally on the machine, 2 cores per socket, 2 threads per
262 core) for a machine that only supports sockets/cores/threads.
263 Some members of the option can be omitted but their values will be
264 automatically computed:
268 -smp 8,sockets=2,cores=2,threads=2,maxcpus=8
270 The following sub-option defines a CPU topology hierarchy (2 sockets
271 totally on the machine, 2 dies per socket, 2 cores per die, 2 threads
272 per core) for PC machines which support sockets/dies/cores/threads.
273 Some members of the option can be omitted but their values will be
274 automatically computed:
278 -smp 16,sockets=2,dies=2,cores=2,threads=2,maxcpus=16
280 The following sub-option defines a CPU topology hierarchy (2 sockets
281 totally on the machine, 2 clusters per socket, 2 cores per cluster,
282 2 threads per core) for ARM virt machines which support sockets/clusters
283 /cores/threads. Some members of the option can be omitted but their values
284 will be automatically computed:
288 -smp 16,sockets=2,clusters=2,cores=2,threads=2,maxcpus=16
290 Historically preference was given to the coarsest topology parameters
291 when computing missing values (ie sockets preferred over cores, which
292 were preferred over threads), however, this behaviour is considered
293 liable to change. Prior to 6.2 the preference was sockets over cores
294 over threads. Since 6.2 the preference is cores over sockets over threads.
296 For example, the following option defines a machine board with 2 sockets
297 of 1 core before 6.2 and 1 socket of 2 cores after 6.2:
304 DEF("numa", HAS_ARG, QEMU_OPTION_numa,
305 "-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=node]\n"
306 "-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=node]\n"
307 "-numa dist,src=source,dst=destination,val=distance\n"
308 "-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]\n"
309 "-numa hmat-lb,initiator=node,target=node,hierarchy=memory|first-level|second-level|third-level,data-type=access-latency|read-latency|write-latency[,latency=lat][,bandwidth=bw]\n"
310 "-numa hmat-cache,node-id=node,size=size,level=level[,associativity=none|direct|complex][,policy=none|write-back|write-through][,line=size]\n",
313 ``-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]``
315 ``-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]``
317 ``-numa dist,src=source,dst=destination,val=distance``
319 ``-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]``
321 ``-numa hmat-lb,initiator=node,target=node,hierarchy=hierarchy,data-type=tpye[,latency=lat][,bandwidth=bw]``
323 ``-numa hmat-cache,node-id=node,size=size,level=level[,associativity=str][,policy=str][,line=size]``
324 Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA
325 distance from a source node to a destination node. Set the ACPI
326 Heterogeneous Memory Attributes for the given nodes.
328 Legacy VCPU assignment uses '\ ``cpus``\
' option where firstcpu and
329 lastcpu are CPU indexes. Each '\ ``cpus``\
' option represent a
330 contiguous range of CPU indexes (or a single VCPU if lastcpu is
331 omitted). A non-contiguous set of VCPUs can be represented by
332 providing multiple '\ ``cpus``\
' options. If '\ ``cpus``\
' is
333 omitted on all nodes, VCPUs are automatically split between them.
335 For example, the following option assigns VCPUs 0, 1, 2 and 5 to a
340 -numa node,cpus=0-2,cpus=5
342 '\ ``cpu``\
' option is a new alternative to '\ ``cpus``\
' option
343 which uses '\ ``socket
-id|core
-id|thread
-id``\
' properties to
344 assign CPU objects to a node using topology layout properties of
345 CPU. The set of properties is machine specific, and depends on used
346 machine type/'\ ``smp``\
' options. It could be queried with
347 '\ ``hotpluggable
-cpus``\
' monitor command. '\ ``node
-id``\
'
348 property specifies node to which CPU object will be assigned, it's
349 required
for node to be declared with
'\ ``node``\ ' option before
350 it
's used with '\ ``cpu``\
' option.
357 -smp 1,sockets=2,maxcpus=2 \
358 -numa node,nodeid=0 -numa node,nodeid=1 \
359 -numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
361 Legacy '\ ``mem``\
' assigns a given RAM amount to a node (not supported
362 for 5.1 and newer machine types). '\ ``memdev``\
' assigns RAM from
363 a given memory backend device to a node. If '\ ``mem``\
' and
364 '\ ``memdev``\
' are omitted in all nodes, RAM is split equally between them.
367 '\ ``mem``\
' and '\ ``memdev``\
' are mutually exclusive.
368 Furthermore, if one node uses '\ ``memdev``\
', all of them have to
371 '\ ``initiator``\
' is an additional option that points to an
372 initiator NUMA node that has best performance (the lowest latency or
373 largest bandwidth) to this NUMA node. Note that this option can be
374 set only when the machine property 'hmat
' is set to 'on
'.
376 Following example creates a machine with 2 NUMA nodes, node 0 has
377 CPU. node 1 has only memory, and its initiator is node 0. Note that
378 because node 0 has CPU, by default the initiator of node 0 is itself
384 -m 2G,slots=2,maxmem=4G \
385 -object memory-backend-ram,size=1G,id=m0 \
386 -object memory-backend-ram,size=1G,id=m1 \
387 -numa node,nodeid=0,memdev=m0 \
388 -numa node,nodeid=1,memdev=m1,initiator=0 \
389 -smp 2,sockets=2,maxcpus=2 \
390 -numa cpu,node-id=0,socket-id=0 \
391 -numa cpu,node-id=0,socket-id=1
393 source and destination are NUMA node IDs. distance is the NUMA
394 distance from source to destination. The distance from a node to
395 itself is always 10. If any pair of nodes is given a distance, then
396 all pairs must be given distances. Although, when distances are only
397 given in one direction for each pair of nodes, then the distances in
398 the opposite directions are assumed to be the same. If, however, an
399 asymmetrical pair of distances is given for even one node pair, then
400 all node pairs must be provided distance values for both directions,
401 even when they are symmetrical. When a node is unreachable from
402 another node, set the pair's distance to
255.
404 Note that the
-``numa`` option doesn
't allocate any of the specified
405 resources, it just assigns existing resources to NUMA nodes. This
406 means that one still has to use the ``-m``, ``-smp`` options to
407 allocate RAM and VCPUs respectively.
409 Use '\ ``hmat
-lb``\
' to set System Locality Latency and Bandwidth
410 Information between initiator and target NUMA nodes in ACPI
411 Heterogeneous Attribute Memory Table (HMAT). Initiator NUMA node can
412 create memory requests, usually it has one or more processors.
413 Target NUMA node contains addressable memory.
415 In '\ ``hmat
-lb``\
' option, node are NUMA node IDs. hierarchy is
416 the memory hierarchy of the target NUMA node: if hierarchy is
417 'memory
', the structure represents the memory performance; if
418 hierarchy is 'first
-level\|second
-level\|third
-level
', this
419 structure represents aggregated performance of memory side caches
420 for each domain. type of 'data
-type
' is type of data represented by
421 this structure instance: if 'hierarchy
' is 'memory
', 'data
-type
' is
422 'access\|read\|write
' latency or 'access\|read\|write
' bandwidth of
423 the target memory; if 'hierarchy
' is
424 'first
-level\|second
-level\|third
-level
', 'data
-type
' is
425 'access\|read\|write
' hit latency or 'access\|read\|write
' hit
426 bandwidth of the target memory side cache.
428 lat is latency value in nanoseconds. bw is bandwidth value, the
429 possible value and units are NUM[M\|G\|T], mean that the bandwidth
430 value are NUM byte per second (or MB/s, GB/s or TB/s depending on
431 used suffix). Note that if latency or bandwidth value is 0, means
432 the corresponding latency or bandwidth information is not provided.
434 In '\ ``hmat
-cache``\
' option, node-id is the NUMA-id of the memory
435 belongs. size is the size of memory side cache in bytes. level is
436 the cache level described in this structure, note that the cache
437 level 0 should not be used with '\ ``hmat
-cache``\
' option.
438 associativity is the cache associativity, the possible value is
439 'none
/direct(direct
-mapped
)/complex(complex cache indexing
)'. policy
440 is the write policy. line is the cache Line size in bytes.
442 For example, the following options describe 2 NUMA nodes. Node 0 has
443 2 cpus and a ram, node 1 has only a ram. The processors in node 0
444 access memory in node 0 with access-latency 5 nanoseconds,
445 access-bandwidth is 200 MB/s; The processors in NUMA node 0 access
446 memory in NUMA node 1 with access-latency 10 nanoseconds,
447 access-bandwidth is 100 MB/s. And for memory side cache information,
448 NUMA node 0 and 1 both have 1 level memory cache, size is 10KB,
449 policy is write-back, the cache Line size is 8 bytes:
455 -object memory-backend-ram,size=1G,id=m0 \
456 -object memory-backend-ram,size=1G,id=m1 \
457 -smp 2,sockets=2,maxcpus=2 \
458 -numa node,nodeid=0,memdev=m0 \
459 -numa node,nodeid=1,memdev=m1,initiator=0 \
460 -numa cpu,node-id=0,socket-id=0 \
461 -numa cpu,node-id=0,socket-id=1 \
462 -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5 \
463 -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=200M \
464 -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=10 \
465 -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=100M \
466 -numa hmat-cache,node-id=0,size=10K,level=1,associativity=direct,policy=write-back,line=8 \
467 -numa hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8
470 DEF("cxl-fixed-memory-window", HAS_ARG, QEMU_OPTION_cxl_fixed_memory_window,
471 "-cxl-fixed-memory-window targets.0=firsttarget,targets.1=secondtarget,size=size[,interleave-granularity=granularity]\n",
474 ``-cxl-fixed-memory-window targets.0=firsttarget,targets.1=secondtarget,size=size[,interleave-granularity=granularity]``
475 Define a CXL Fixed Memory Window (CFMW).
477 Described in the CXL 2.0 ECN: CEDT CFMWS & QTG _DSM.
479 They are regions of Host Physical Addresses (HPA) on a system which
480 may be interleaved across one or more CXL host bridges. The system
481 software will assign particular devices into these windows and
482 configure the downstream Host-managed Device Memory (HDM) decoders
483 in root ports, switch ports and devices appropriately to meet the
484 interleave requirements before enabling the memory devices.
486 ``targets.X=firsttarget`` provides the mapping to CXL host bridges
487 which may be identified by the id provied in the -device entry.
488 Multiple entries are needed to specify all the targets when
489 the fixed memory window represents interleaved memory. X is the
492 ``size=size`` sets the size of the CFMW. This must be a multiple of
493 256MiB. The region will be aligned to 256MiB but the location is
494 platform and configuration dependent.
496 ``interleave-granularity=granularity`` sets the granularity of
497 interleave. Default 256KiB. Only 256KiB, 512KiB, 1024KiB, 2048KiB
498 4096KiB, 8192KiB and 16384KiB granularities supported.
504 -cxl-fixed-memory-window targets.0=cxl.0,targets.1=cxl.1,size=128G,interleave-granularity=512k
508 DEF("add-fd", HAS_ARG, QEMU_OPTION_add_fd,
509 "-add-fd fd=fd,set=set[,opaque=opaque]\n"
510 " Add 'fd
' to fd 'set
'\n", QEMU_ARCH_ALL)
512 ``-add-fd fd=fd,set=set[,opaque=opaque]``
513 Add a file descriptor to an fd set. Valid options are:
516 This option defines the file descriptor of which a duplicate is
517 added to fd set. The file descriptor cannot be stdin, stdout, or
521 This option defines the ID of the fd set to add the file
525 This option defines a free-form string that can be used to
528 You can open an image using pre-opened file descriptors from an fd
534 -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \\
535 -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \\
536 -drive file=/dev/fdset/2,index=0,media=disk
539 DEF("set", HAS_ARG, QEMU_OPTION_set,
540 "-set group.id.arg=value\n"
541 " set <arg> parameter for item <id> of type <group>\n"
542 " i.e. -set drive.$id.file=/path/to/image\n", QEMU_ARCH_ALL)
544 ``-set group.id.arg=value``
545 Set parameter arg for item id of type group
548 DEF("global", HAS_ARG, QEMU_OPTION_global,
549 "-global driver.property=value\n"
550 "-global driver=driver,property=property,value=value\n"
551 " set a global default for a driver property\n",
554 ``-global driver.prop=value``
556 ``-global driver=driver,property=property,value=value``
557 Set default value of driver's property prop to value
, e
.g
.:
561 |qemu_system_x86|
-global ide
-hd
.physical_block_size
=4096 disk
-image
.img
563 In particular
, you can use
this to set driver properties
for devices
564 which are created automatically by the machine model
. To create a
565 device which is not created automatically and set properties on it
,
568 -global driver
.prop
=value is shorthand
for -global
569 driver
=driver
,property
=prop
,value
=value
. The longhand syntax works
570 even when driver contains a dot
.
573 DEF("boot", HAS_ARG
, QEMU_OPTION_boot
,
574 "-boot [order=drives][,once=drives][,menu=on|off]\n"
575 " [,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_time][,strict=on|off]\n"
576 " 'drives': floppy (a), hard disk (c), CD-ROM (d), network (n)\n"
577 " 'sp_name': the file's name that would be passed to bios as logo picture, if menu=on\n"
578 " 'sp_time': the period that splash picture last if menu=on, unit is ms\n"
579 " 'rb_timeout': the timeout before guest reboot when boot failed, unit is ms\n",
582 ``
-boot
[order
=drives
][,once
=drives
][,menu
=on|off
][,splash
=sp_name
][,splash
-time
=sp_time
][,reboot
-timeout
=rb_timeout
][,strict
=on|off
]``
583 Specify boot order drives as a string of drive letters
. Valid drive
584 letters depend on the target architecture
. The x86 PC uses
: a
, b
585 (floppy
1 and
2), c (first hard disk
), d (first CD
-ROM
), n
-p
586 (Etherboot from network adapter
1-4), hard disk boot is the
default.
587 To apply a particular boot order only on the first startup
, specify
588 it via ``once``
. Note that the ``order`` or ``once`` parameter
589 should not be used together with the ``bootindex`` property of
590 devices
, since the firmware implementations normally
do not support
591 both at the same time
.
593 Interactive boot menus
/prompts can be enabled via ``menu
=on`` as far
594 as firmware
/BIOS supports them
. The
default is non
-interactive boot
.
596 A splash picture could be passed to bios
, enabling user to show it
597 as logo
, when option splash
=sp\_name is given and menu
=on
, If
598 firmware
/BIOS supports them
. Currently Seabios
for X86 system
599 support it
. limitation
: The splash file could be a jpeg file or a
600 BMP file
in 24 BPP
format(true color
). The resolution should be
601 supported by the SVGA mode
, so the recommended is
320x240
, 640x480
,
604 A timeout could be passed to bios
, guest will pause
for rb\_timeout
605 ms when boot failed
, then reboot
. If rb\_timeout is
'-1', guest will
606 not reboot
, qemu passes
'-1' to bios by
default. Currently Seabios
607 for X86 system support it
.
609 Do strict boot via ``strict
=on`` as far as firmware
/BIOS supports
610 it
. This only effects when boot priority is changed by bootindex
611 options
. The
default is non
-strict boot
.
615 #
try to boot from network first
, then from hard disk
616 |qemu_system_x86|
-boot order
=nc
617 # boot from CD
-ROM first
, switch back to
default order after reboot
618 |qemu_system_x86|
-boot once
=d
619 # boot with a splash picture
for 5 seconds
.
620 |qemu_system_x86|
-boot menu
=on
,splash
=/root
/boot
.bmp
,splash
-time
=5000
622 Note
: The legacy format
'-boot drives' is still supported but its
623 use is discouraged as it may be removed from future versions
.
626 DEF("m", HAS_ARG
, QEMU_OPTION_m
,
627 "-m [size=]megs[,slots=n,maxmem=size]\n"
628 " configure guest RAM\n"
629 " size: initial amount of guest memory\n"
630 " slots: number of hotplug slots (default: none)\n"
631 " maxmem: maximum amount of guest memory (default: none)\n"
632 "NOTE: Some architectures might enforce a specific granularity\n",
635 ``
-m
[size
=]megs
[,slots
=n
,maxmem
=size
]``
636 Sets guest startup RAM size to megs megabytes
. Default is
128 MiB
.
637 Optionally
, a suffix of
"M" or
"G" can be used to signify a value
in
638 megabytes or gigabytes respectively
. Optional pair slots
, maxmem
639 could be used to set amount of hotpluggable memory slots and maximum
640 amount of memory
. Note that maxmem must be aligned to the page size
.
642 For example
, the following command
-line sets the guest startup RAM
643 size to
1GB
, creates
3 slots to hotplug additional memory and sets
644 the maximum memory the guest can reach to
4GB
:
648 |qemu_system|
-m
1G
,slots
=3,maxmem
=4G
650 If slots and maxmem are not specified
, memory hotplug won
't be
651 enabled and the guest startup RAM will never increase.
654 DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
655 "-mem-path FILE provide backing storage for guest RAM\n", QEMU_ARCH_ALL)
658 Allocate guest RAM from a temporarily created file in path.
661 DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
662 "-mem-prealloc preallocate guest memory (use with -mem-path)\n",
666 Preallocate memory when using -mem-path.
669 DEF("k", HAS_ARG, QEMU_OPTION_k,
670 "-k language use keyboard layout (for example 'fr
' for French)\n",
674 Use keyboard layout language (for example ``fr`` for French). This
675 option is only needed where it is not easy to get raw PC keycodes
676 (e.g. on Macs, with some X11 servers or with a VNC or curses
677 display). You don't normally need to use it on PC
/Linux or
680 The available layouts are
:
684 ar de
-ch es fo fr
-ca hu ja mk no pt
-br sv
685 da en
-gb et fr fr
-ch is lt nl pl ru th
686 de en
-us fi fr
-be hr it lv nl
-be pt sl tr
688 The
default is ``en
-us``
.
692 HXCOMM Deprecated by
-audiodev
693 DEF("audio-help", 0, QEMU_OPTION_audio_help
,
694 "-audio-help show -audiodev equivalent of the currently specified audio settings\n",
698 Will show the
-audiodev equivalent of the currently specified
699 (deprecated
) environment variables
.
702 DEF("audiodev", HAS_ARG
, QEMU_OPTION_audiodev
,
703 "-audiodev [driver=]driver,id=id[,prop[=value][,...]]\n"
704 " specifies the audio backend to use\n"
705 " id= identifier of the backend\n"
706 " timer-period= timer period in microseconds\n"
707 " in|out.mixing-engine= use mixing engine to mix streams inside QEMU\n"
708 " in|out.fixed-settings= use fixed settings for host audio\n"
709 " in|out.frequency= frequency to use with fixed settings\n"
710 " in|out.channels= number of channels to use with fixed settings\n"
711 " in|out.format= sample format to use with fixed settings\n"
712 " valid values: s8, s16, s32, u8, u16, u32, f32\n"
713 " in|out.voices= number of voices to use\n"
714 " in|out.buffer-length= length of buffer in microseconds\n"
715 "-audiodev none,id=id,[,prop[=value][,...]]\n"
716 " dummy driver that discards all output\n"
717 #ifdef CONFIG_AUDIO_ALSA
718 "-audiodev alsa,id=id[,prop[=value][,...]]\n"
719 " in|out.dev= name of the audio device to use\n"
720 " in|out.period-length= length of period in microseconds\n"
721 " in|out.try-poll= attempt to use poll mode\n"
722 " threshold= threshold (in microseconds) when playback starts\n"
724 #ifdef CONFIG_AUDIO_COREAUDIO
725 "-audiodev coreaudio,id=id[,prop[=value][,...]]\n"
726 " in|out.buffer-count= number of buffers\n"
728 #ifdef CONFIG_AUDIO_DSOUND
729 "-audiodev dsound,id=id[,prop[=value][,...]]\n"
730 " latency= add extra latency to playback in microseconds\n"
732 #ifdef CONFIG_AUDIO_OSS
733 "-audiodev oss,id=id[,prop[=value][,...]]\n"
734 " in|out.dev= path of the audio device to use\n"
735 " in|out.buffer-count= number of buffers\n"
736 " in|out.try-poll= attempt to use poll mode\n"
737 " try-mmap= try using memory mapped access\n"
738 " exclusive= open device in exclusive mode\n"
739 " dsp-policy= set timing policy (0..10), -1 to use fragment mode\n"
741 #ifdef CONFIG_AUDIO_PA
742 "-audiodev pa,id=id[,prop[=value][,...]]\n"
743 " server= PulseAudio server address\n"
744 " in|out.name= source/sink device name\n"
745 " in|out.latency= desired latency in microseconds\n"
747 #ifdef CONFIG_AUDIO_SDL
748 "-audiodev sdl,id=id[,prop[=value][,...]]\n"
749 " in|out.buffer-count= number of buffers\n"
752 "-audiodev spice,id=id[,prop[=value][,...]]\n"
754 #ifdef CONFIG_DBUS_DISPLAY
755 "-audiodev dbus,id=id[,prop[=value][,...]]\n"
757 "-audiodev wav,id=id[,prop[=value][,...]]\n"
758 " path= path of wav file to record\n",
761 ``
-audiodev
[driver
=]driver
,id
=id
[,prop
[=value
][,...]]``
762 Adds a
new audio backend driver identified by id
. There are global
763 and driver specific properties
. Some values can be set differently
764 for input and output
, they
're marked with ``in|out.``. You can set
765 the input's property with ``
in.prop`` and the output
's property with
766 ``out.prop``. For example:
770 -audiodev alsa,id=example,in.frequency=44110,out.frequency=8000
771 -audiodev alsa,id=example,out.channels=1 # leaves in.channels unspecified
773 NOTE: parameter validation is known to be incomplete, in many cases
774 specifying an invalid option causes QEMU to print an error message
775 and continue emulation without sound.
777 Valid global options are:
780 Identifies the audio backend.
782 ``timer-period=period``
783 Sets the timer period used by the audio subsystem in
784 microseconds. Default is 10000 (10 ms).
786 ``in|out.mixing-engine=on|off``
787 Use QEMU's mixing engine to mix all streams inside QEMU and
788 convert audio formats when not supported by the backend
. When
789 off
, fixed
-settings must be off too
. Note that disabling
this
790 option means that the selected backend must support multiple
791 streams and the audio formats used by the virtual cards
,
792 otherwise you
'll get no sound. It's not recommended to disable
793 this option unless you want to use
5.1 or
7.1 audio
, as mixing
794 engine only supports mono and stereo audio
. Default is on
.
796 ``
in|out
.fixed
-settings
=on|off``
797 Use fixed settings
for host audio
. When off
, it will change
798 based on how the guest opens the sound card
. In
this case you
799 must not specify frequency
, channels or format
. Default is on
.
801 ``
in|out
.frequency
=frequency``
802 Specify the frequency to use when
using fixed
-settings
. Default
805 ``
in|out
.channels
=channels``
806 Specify the number of channels to use when
using fixed
-settings
.
807 Default is
2 (stereo
).
809 ``
in|out
.format
=format``
810 Specify the sample format to use when
using fixed
-settings
.
811 Valid values are
: ``s8``
, ``s16``
, ``s32``
, ``u8``
, ``u16``
,
812 ``u32``
, ``f32``
. Default is ``s16``
.
814 ``
in|out
.voices
=voices``
815 Specify the number of voices to use
. Default is
1.
817 ``
in|out
.buffer
-length
=usecs``
818 Sets the size of the buffer
in microseconds
.
820 ``
-audiodev none
,id
=id
[,prop
[=value
][,...]]``
821 Creates a dummy backend that discards all outputs
. This backend has
822 no backend specific properties
.
824 ``
-audiodev alsa
,id
=id
[,prop
[=value
][,...]]``
825 Creates backend
using the ALSA
. This backend is only available on
828 ALSA specific options are
:
830 ``
in|out
.dev
=device``
831 Specify the ALSA device to use
for input and
/or output
. Default
834 ``
in|out
.period
-length
=usecs``
835 Sets the period length
in microseconds
.
837 ``
in|out
.try-poll
=on|off``
838 Attempt to use poll mode with the device
. Default is on
.
840 ``threshold
=threshold``
841 Threshold (in microseconds
) when playback starts
. Default is
0.
843 ``
-audiodev coreaudio
,id
=id
[,prop
[=value
][,...]]``
844 Creates a backend
using Apple
's Core Audio. This backend is only
845 available on Mac OS and only supports playback.
847 Core Audio specific options are:
849 ``in|out.buffer-count=count``
850 Sets the count of the buffers.
852 ``-audiodev dsound,id=id[,prop[=value][,...]]``
853 Creates a backend using Microsoft's DirectSound
. This backend is
854 only available on Windows and only supports playback
.
856 DirectSound specific options are
:
859 Add extra usecs microseconds latency to playback
. Default is
862 ``
-audiodev oss
,id
=id
[,prop
[=value
][,...]]``
863 Creates a backend
using OSS
. This backend is available on most
866 OSS specific options are
:
868 ``
in|out
.dev
=device``
869 Specify the file name of the OSS device to use
. Default is
872 ``
in|out
.buffer
-count
=count``
873 Sets the count of the buffers
.
875 ``
in|out
.try-poll
=on|of``
876 Attempt to use poll mode with the device
. Default is on
.
879 Try
using memory mapped device access
. Default is off
.
882 Open the device
in exclusive
mode (vmix won
't work in this
883 case). Default is off.
885 ``dsp-policy=policy``
886 Sets the timing policy (between 0 and 10, where smaller number
887 means smaller latency but higher CPU usage). Use -1 to use
888 buffer sizes specified by ``buffer`` and ``buffer-count``. This
889 option is ignored if you do not have OSS 4. Default is 5.
891 ``-audiodev pa,id=id[,prop[=value][,...]]``
892 Creates a backend using PulseAudio. This backend is available on
895 PulseAudio specific options are:
898 Sets the PulseAudio server to connect to.
901 Use the specified source/sink for recording/playback.
903 ``in|out.latency=usecs``
904 Desired latency in microseconds. The PulseAudio server will try
905 to honor this value but actual latencies may be lower or higher.
907 ``-audiodev sdl,id=id[,prop[=value][,...]]``
908 Creates a backend using SDL. This backend is available on most
909 systems, but you should use your platform's native backend
if
912 SDL specific options are
:
914 ``
in|out
.buffer
-count
=count``
915 Sets the count of the buffers
.
917 ``
-audiodev spice
,id
=id
[,prop
[=value
][,...]]``
918 Creates a backend that sends audio through SPICE
. This backend
919 requires ``
-spice`` and automatically selected
in that
case, so
920 usually you can ignore
this option
. This backend has no backend
923 ``
-audiodev wav
,id
=id
[,prop
[=value
][,...]]``
924 Creates a backend that writes audio to a WAV file
.
926 Backend specific options are
:
929 Write recorded audio into the specified file
. Default is
933 DEF("soundhw", HAS_ARG
, QEMU_OPTION_soundhw
,
934 "-soundhw c1,... enable audio support\n"
935 " and only specified sound cards (comma separated list)\n"
936 " use '-soundhw help' to get the list of supported cards\n"
937 " use '-soundhw all' to enable all of them\n", QEMU_ARCH_ALL
)
939 ``
-soundhw card1
[,card2
,...] or
-soundhw all``
940 Enable audio and selected sound hardware
. Use
'help' to print all
941 available sound hardware
. For example
:
945 |qemu_system_x86|
-soundhw sb16
,adlib disk
.img
946 |qemu_system_x86|
-soundhw es1370 disk
.img
947 |qemu_system_x86|
-soundhw ac97 disk
.img
948 |qemu_system_x86|
-soundhw hda disk
.img
949 |qemu_system_x86|
-soundhw all disk
.img
950 |qemu_system_x86|
-soundhw help
952 Note that Linux
's i810\_audio OSS kernel (for AC97) module might
953 require manually specifying clocking.
957 modprobe i810_audio clocking=48000
960 DEF("device", HAS_ARG, QEMU_OPTION_device,
961 "-device driver[,prop[=value][,...]]\n"
962 " add device (based on driver)\n"
963 " prop=value,... sets driver properties\n"
964 " use '-device help
' to print all possible drivers\n"
965 " use '-device driver
,help
' to print all possible properties\n",
968 ``-device driver[,prop[=value][,...]]``
969 Add device driver. prop=value sets driver properties. Valid
970 properties depend on the driver. To get help on possible drivers and
971 properties, use ``-device help`` and ``-device driver,help``.
975 ``-device ipmi-bmc-sim,id=id[,prop[=value][,...]]``
976 Add an IPMI BMC. This is a simulation of a hardware management
977 interface processor that normally sits on a system. It provides a
978 watchdog and the ability to reset and power control the system. You
979 need to connect this to an IPMI interface to make it useful
981 The IPMI slave address to use for the BMC. The default is 0x20. This
982 address is the BMC's address on the I2C network of management
983 controllers
. If you don
't know what this means, it is safe to ignore
987 The BMC id for interfaces to use this device.
990 Define slave address to use for the BMC. The default is 0x20.
993 file containing raw Sensor Data Records (SDR) data. The default
997 size of a Field Replaceable Unit (FRU) area. The default is
1000 ``frudatafile=file``
1001 file containing raw Field Replaceable Unit (FRU) inventory data.
1002 The default is none.
1005 value for the GUID for the BMC, in standard UUID format. If this
1006 is set, get "Get GUID" command to the BMC will return it.
1007 Otherwise "Get GUID" will return an error.
1009 ``-device ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val]``
1010 Add a connection to an external IPMI BMC simulator. Instead of
1011 locally emulating the BMC like the above item, instead connect to an
1012 external entity that provides the IPMI services.
1014 A connection is made to an external BMC simulator. If you do this,
1015 it is strongly recommended that you use the "reconnect=" chardev
1016 option to reconnect to the simulator if the connection is lost. Note
1017 that if this is not used carefully, it can be a security issue, as
1018 the interface has the ability to send resets, NMIs, and power off
1019 the VM. It's best
if QEMU makes a connection to an external
1020 simulator running on a secure port on localhost
, so neither the
1021 simulator nor QEMU is exposed to any outside network
.
1023 See the
"lanserv/README.vm" file
in the OpenIPMI library
for more
1024 details on the external
interface.
1026 ``
-device isa
-ipmi
-kcs
,bmc
=id
[,ioport
=val
][,irq
=val
]``
1027 Add a KCS IPMI interafce on the ISA bus
. This also adds a
1028 corresponding ACPI and SMBIOS entries
, if appropriate
.
1031 The BMC to connect to
, one of ipmi
-bmc
-sim or ipmi
-bmc
-extern
1035 Define the I
/O address of the
interface. The
default is
0xca0
1039 Define the interrupt to use
. The
default is
5. To disable
1040 interrupts
, set
this to
0.
1042 ``
-device isa
-ipmi
-bt
,bmc
=id
[,ioport
=val
][,irq
=val
]``
1043 Like the KCS
interface, but defines a BT
interface. The
default port
1044 is
0xe4 and the
default interrupt is
5.
1046 ``
-device pci
-ipmi
-kcs
,bmc
=id``
1047 Add a KCS IPMI interafce on the PCI bus
.
1050 The BMC to connect to
, one of ipmi
-bmc
-sim or ipmi
-bmc
-extern above
.
1052 ``
-device pci
-ipmi
-bt
,bmc
=id``
1053 Like the KCS
interface, but defines a BT
interface on the PCI bus
.
1055 ``
-device intel
-iommu
[,option
=...]``
1056 This is only supported by ``
-machine q35``
, which will enable Intel VT
-d
1057 emulation within the guest
. It supports below options
:
1059 ``intremap
=on|off``
(default: auto
)
1060 This enables interrupt remapping feature
. It
's required to enable
1061 complete x2apic. Currently it only supports kvm kernel-irqchip modes
1062 ``off`` or ``split``, while full kernel-irqchip is not yet supported.
1063 The default value is "auto", which will be decided by the mode of
1066 ``caching-mode=on|off`` (default: off)
1067 This enables caching mode for the VT-d emulated device. When
1068 caching-mode is enabled, each guest DMA buffer mapping will generate an
1069 IOTLB invalidation from the guest IOMMU driver to the vIOMMU device in
1070 a synchronous way. It is required for ``-device vfio-pci`` to work
1071 with the VT-d device, because host assigned devices requires to setup
1072 the DMA mapping on the host before guest DMA starts.
1074 ``device-iotlb=on|off`` (default: off)
1075 This enables device-iotlb capability for the emulated VT-d device. So
1076 far virtio/vhost should be the only real user for this parameter,
1077 paired with ats=on configured for the device.
1079 ``aw-bits=39|48`` (default: 39)
1080 This decides the address width of IOVA address space. The address
1081 space has 39 bits width for 3-level IOMMU page tables, and 48 bits for
1082 4-level IOMMU page tables.
1084 Please also refer to the wiki page for general scenarios of VT-d
1085 emulation in QEMU: https://wiki.qemu.org/Features/VT-d.
1089 DEF("name", HAS_ARG, QEMU_OPTION_name,
1090 "-name string1[,process=string2][,debug-threads=on|off]\n"
1091 " set the name of the guest\n"
1092 " string1 sets the window title and string2 the process name\n"
1093 " When debug-threads is enabled, individual threads are given a separate name\n"
1094 " NOTE: The thread names are for debugging and not a stable API.\n",
1098 Sets the name of the guest. This name will be displayed in the SDL
1099 window caption. The name will also be used for the VNC server. Also
1100 optionally set the top visible process name in Linux. Naming of
1101 individual threads can also be enabled on Linux to aid debugging.
1104 DEF("uuid", HAS_ARG, QEMU_OPTION_uuid,
1105 "-uuid %08x-%04x-%04x-%04x-%012x\n"
1106 " specify machine UUID\n", QEMU_ARCH_ALL)
1114 DEFHEADING(Block device options:)
1116 DEF("fda", HAS_ARG, QEMU_OPTION_fda,
1117 "-fda/-fdb file use 'file
' as floppy disk 0/1 image\n", QEMU_ARCH_ALL)
1118 DEF("fdb", HAS_ARG, QEMU_OPTION_fdb, "", QEMU_ARCH_ALL)
1123 Use file as floppy disk 0/1 image (see the :ref:`disk images` chapter in
1124 the System Emulation Users Guide).
1127 DEF("hda", HAS_ARG, QEMU_OPTION_hda,
1128 "-hda/-hdb file use 'file
' as IDE hard disk 0/1 image\n", QEMU_ARCH_ALL)
1129 DEF("hdb", HAS_ARG, QEMU_OPTION_hdb, "", QEMU_ARCH_ALL)
1130 DEF("hdc", HAS_ARG, QEMU_OPTION_hdc,
1131 "-hdc/-hdd file use 'file
' as IDE hard disk 2/3 image\n", QEMU_ARCH_ALL)
1132 DEF("hdd", HAS_ARG, QEMU_OPTION_hdd, "", QEMU_ARCH_ALL)
1141 Use file as hard disk 0, 1, 2 or 3 image (see the :ref:`disk images`
1142 chapter in the System Emulation Users Guide).
1145 DEF("cdrom", HAS_ARG, QEMU_OPTION_cdrom,
1146 "-cdrom file use 'file
' as IDE cdrom image (cdrom is ide1 master)\n",
1150 Use file as CD-ROM image (you cannot use ``-hdc`` and ``-cdrom`` at
1151 the same time). You can use the host CD-ROM by using ``/dev/cdrom``
1155 DEF("blockdev", HAS_ARG, QEMU_OPTION_blockdev,
1156 "-blockdev [driver=]driver[,node-name=N][,discard=ignore|unmap]\n"
1157 " [,cache.direct=on|off][,cache.no-flush=on|off]\n"
1158 " [,read-only=on|off][,auto-read-only=on|off]\n"
1159 " [,force-share=on|off][,detect-zeroes=on|off|unmap]\n"
1160 " [,driver specific parameters...]\n"
1161 " configure a block backend\n", QEMU_ARCH_ALL)
1163 ``-blockdev option[,option[,option[,...]]]``
1164 Define a new block driver node. Some of the options apply to all
1165 block drivers, other options are only accepted for a specific block
1166 driver. See below for a list of generic options and options for the
1167 most common block drivers.
1169 Options that expect a reference to another node (e.g. ``file``) can
1170 be given in two ways. Either you specify the node name of an already
1171 existing node (file=node-name), or you define a new node inline,
1172 adding options for the referenced node after a dot
1173 (file.filename=path,file.aio=native).
1175 A block driver node created with ``-blockdev`` can be used for a
1176 guest device by specifying its node name for the ``drive`` property
1177 in a ``-device`` argument that defines a block device.
1179 ``Valid options for any block driver node:``
1181 Specifies the block driver to use for the given node.
1184 This defines the name of the block driver node by which it
1185 will be referenced later. The name must be unique, i.e. it
1186 must not match the name of a different block driver node, or
1187 (if you use ``-drive`` as well) the ID of a drive.
1189 If no node name is specified, it is automatically generated.
1190 The generated node name is not intended to be predictable
1191 and changes between QEMU invocations. For the top level, an
1192 explicit node name must be specified.
1195 Open the node read-only. Guest write attempts will fail.
1197 Note that some block drivers support only read-only access,
1198 either generally or in certain configurations. In this case,
1199 the default value ``read-only=off`` does not work and the
1200 option must be specified explicitly.
1203 If ``auto-read-only=on`` is set, QEMU may fall back to
1204 read-only usage even when ``read-only=off`` is requested, or
1205 even switch between modes as needed, e.g. depending on
1206 whether the image file is writable or whether a writing user
1207 is attached to the node.
1210 Override the image locking system of QEMU by forcing the
1211 node to utilize weaker shared access for permissions where
1212 it would normally request exclusive access. When there is
1213 the potential for multiple instances to have the same file
1214 open (whether this invocation of QEMU is the first or the
1215 second instance), both instances must permit shared access
1216 for the second instance to succeed at opening the file.
1218 Enabling ``force-share=on`` requires ``read-only=on``.
1221 The host page cache can be avoided with ``cache.direct=on``.
1222 This will attempt to do disk IO directly to the guest's
1223 memory
. QEMU may still perform an internal copy of the data
.
1226 In
case you don
't care about data integrity over host
1227 failures, you can use ``cache.no-flush=on``. This option
1228 tells QEMU that it never needs to write any data to the disk
1229 but can instead keep things in cache. If anything goes
1230 wrong, like your host losing power, the disk storage getting
1231 disconnected accidentally, etc. your image will most
1232 probably be rendered unusable.
1235 discard is one of "ignore" (or "off") or "unmap" (or "on")
1236 and controls whether ``discard`` (also known as ``trim`` or
1237 ``unmap``) requests are ignored or passed to the filesystem.
1238 Some machine types may not support discard requests.
1240 ``detect-zeroes=detect-zeroes``
1241 detect-zeroes is "off", "on" or "unmap" and enables the
1242 automatic conversion of plain zero writes by the OS to
1243 driver specific optimized zero write commands. You may even
1244 choose "unmap" if discard is set to "unmap" to allow a zero
1245 write to be converted to an ``unmap`` operation.
1247 ``Driver-specific options for file``
1248 This is the protocol-level block driver for accessing regular
1252 The path to the image file in the local filesystem
1255 Specifies the AIO backend (threads/native/io_uring,
1259 Specifies whether the image file is protected with Linux OFD
1260 / POSIX locks. The default is to use the Linux Open File
1261 Descriptor API if available, otherwise no lock is applied.
1262 (auto/on/off, default: auto)
1268 -blockdev driver=file,node-name=disk,filename=disk.img
1270 ``Driver-specific options for raw``
1271 This is the image format block driver for raw images. It is
1272 usually stacked on top of a protocol level block driver such as
1276 Reference to or definition of the data source block driver
1277 node (e.g. a ``file`` driver node)
1283 -blockdev driver=file,node-name=disk_file,filename=disk.img
1284 -blockdev driver=raw,node-name=disk,file=disk_file
1290 -blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img
1292 ``Driver-specific options for qcow2``
1293 This is the image format block driver for qcow2 images. It is
1294 usually stacked on top of a protocol level block driver such as
1298 Reference to or definition of the data source block driver
1299 node (e.g. a ``file`` driver node)
1302 Reference to or definition of the backing file block device
1303 (default is taken from the image file). It is allowed to
1304 pass ``null`` here in order to disable the default backing
1308 Whether to enable the lazy refcounts feature (on/off;
1309 default is taken from the image file)
1312 The maximum total size of the L2 table and refcount block
1313 caches in bytes (default: the sum of l2-cache-size and
1314 refcount-cache-size)
1317 The maximum size of the L2 table cache in bytes (default: if
1318 cache-size is not specified - 32M on Linux platforms, and 8M
1319 on non-Linux platforms; otherwise, as large as possible
1320 within the cache-size, while permitting the requested or the
1321 minimal refcount cache size)
1323 ``refcount-cache-size``
1324 The maximum size of the refcount block cache in bytes
1325 (default: 4 times the cluster size; or if cache-size is
1326 specified, the part of it which is not used for the L2
1329 ``cache-clean-interval``
1330 Clean unused entries in the L2 and refcount caches. The
1331 interval is in seconds. The default value is 600 on
1332 supporting platforms, and 0 on other platforms. Setting it
1333 to 0 disables this feature.
1335 ``pass-discard-request``
1336 Whether discard requests to the qcow2 device should be
1337 forwarded to the data source (on/off; default: on if
1338 discard=unmap is specified, off otherwise)
1340 ``pass-discard-snapshot``
1341 Whether discard requests for the data source should be
1342 issued when a snapshot operation (e.g. deleting a snapshot)
1343 frees clusters in the qcow2 file (on/off; default: on)
1345 ``pass-discard-other``
1346 Whether discard requests for the data source should be
1347 issued on other occasions where a cluster gets freed
1348 (on/off; default: off)
1351 Which overlap checks to perform for writes to the image
1352 (none/constant/cached/all; default: cached). For details or
1353 finer granularity control refer to the QAPI documentation of
1360 -blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
1361 -blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216
1367 -blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2
1369 ``Driver-specific options for other drivers``
1370 Please refer to the QAPI documentation of the ``blockdev-add``
1374 DEF("drive", HAS_ARG, QEMU_OPTION_drive,
1375 "-drive [file=file][,if=type][,bus=n][,unit=m][,media=d][,index=i]\n"
1376 " [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n"
1377 " [,snapshot=on|off][,rerror=ignore|stop|report]\n"
1378 " [,werror=ignore|stop|report|enospc][,id=name]\n"
1379 " [,aio=threads|native|io_uring]\n"
1380 " [,readonly=on|off][,copy-on-read=on|off]\n"
1381 " [,discard=ignore|unmap][,detect-zeroes=on|off|unmap]\n"
1382 " [[,bps=b]|[[,bps_rd=r][,bps_wr=w]]]\n"
1383 " [[,iops=i]|[[,iops_rd=r][,iops_wr=w]]]\n"
1384 " [[,bps_max=bm]|[[,bps_rd_max=rm][,bps_wr_max=wm]]]\n"
1385 " [[,iops_max=im]|[[,iops_rd_max=irm][,iops_wr_max=iwm]]]\n"
1386 " [[,iops_size=is]]\n"
1388 " use 'file
' as a drive image\n", QEMU_ARCH_ALL)
1390 ``-drive option[,option[,option[,...]]]``
1391 Define a new drive. This includes creating a block driver node (the
1392 backend) as well as a guest device, and is mostly a shortcut for
1393 defining the corresponding ``-blockdev`` and ``-device`` options.
1395 ``-drive`` accepts all options that are accepted by ``-blockdev``.
1396 In addition, it knows the following options:
1399 This option defines which disk image (see the :ref:`disk images`
1400 chapter in the System Emulation Users Guide) to use with this drive.
1401 If the filename contains comma, you must double it (for instance,
1402 "file=my,,file" to use file "my,file").
1404 Special files such as iSCSI devices can be specified using
1405 protocol specific URLs. See the section for "Device URL Syntax"
1406 for more information.
1409 This option defines on which type on interface the drive is
1410 connected. Available types are: ide, scsi, sd, mtd, floppy,
1411 pflash, virtio, none.
1413 ``bus=bus,unit=unit``
1414 These options define where is connected the drive by defining
1415 the bus number and the unit id.
1418 This option defines where the drive is connected by using an
1419 index in the list of available connectors of a given interface
1423 This option defines the type of the media: disk or cdrom.
1425 ``snapshot=snapshot``
1426 snapshot is "on" or "off" and controls snapshot mode for the
1427 given drive (see ``-snapshot``).
1430 cache is "none", "writeback", "unsafe", "directsync" or
1431 "writethrough" and controls how the host cache is used to access
1432 block data. This is a shortcut that sets the ``cache.direct``
1433 and ``cache.no-flush`` options (as in ``-blockdev``), and
1434 additionally ``cache.writeback``, which provides a default for
1435 the ``write-cache`` option of block guest devices (as in
1436 ``-device``). The modes correspond to the following settings:
1438 ============= =============== ============ ==============
1439 \ cache.writeback cache.direct cache.no-flush
1440 ============= =============== ============ ==============
1441 writeback on off off
1443 writethrough off off off
1444 directsync off on off
1446 ============= =============== ============ ==============
1448 The default mode is ``cache=writeback``.
1451 aio is "threads", "native", or "io_uring" and selects between pthread
1452 based disk I/O, native Linux AIO, or Linux io_uring API.
1455 Specify which disk format will be used rather than detecting the
1456 format. Can be used to specify format=raw to avoid interpreting
1457 an untrusted format header.
1459 ``werror=action,rerror=action``
1460 Specify which action to take on write and read errors. Valid
1461 actions are: "ignore" (ignore the error and try to continue),
1462 "stop" (pause QEMU), "report" (report the error to the guest),
1463 "enospc" (pause QEMU only if the host disk is full; report the
1464 error to the guest otherwise). The default setting is
1465 ``werror=enospc`` and ``rerror=report``.
1467 ``copy-on-read=copy-on-read``
1468 copy-on-read is "on" or "off" and enables whether to copy read
1469 backing file sectors into the image file.
1471 ``bps=b,bps_rd=r,bps_wr=w``
1472 Specify bandwidth throttling limits in bytes per second, either
1473 for all request types or for reads or writes only. Small values
1474 can lead to timeouts or hangs inside the guest. A safe minimum
1475 for disks is 2 MB/s.
1477 ``bps_max=bm,bps_rd_max=rm,bps_wr_max=wm``
1478 Specify bursts in bytes per second, either for all request types
1479 or for reads or writes only. Bursts allow the guest I/O to spike
1480 above the limit temporarily.
1482 ``iops=i,iops_rd=r,iops_wr=w``
1483 Specify request rate limits in requests per second, either for
1484 all request types or for reads or writes only.
1486 ``iops_max=bm,iops_rd_max=rm,iops_wr_max=wm``
1487 Specify bursts in requests per second, either for all request
1488 types or for reads or writes only. Bursts allow the guest I/O to
1489 spike above the limit temporarily.
1492 Let every is bytes of a request count as a new request for iops
1493 throttling purposes. Use this option to prevent guests from
1494 circumventing iops limits by sending fewer but larger requests.
1497 Join a throttling quota group with given name g. All drives that
1498 are members of the same group are accounted for together. Use
1499 this option to prevent guests from circumventing throttling
1500 limits by using many small disks instead of a single larger
1503 By default, the ``cache.writeback=on`` mode is used. It will report
1504 data writes as completed as soon as the data is present in the host
1505 page cache. This is safe as long as your guest OS makes sure to
1506 correctly flush disk caches where needed. If your guest OS does not
1507 handle volatile disk write caches correctly and your host crashes or
1508 loses power, then the guest may experience data corruption.
1510 For such guests, you should consider using ``cache.writeback=off``.
1511 This means that the host page cache will be used to read and write
1512 data, but write notification will be sent to the guest only after
1513 QEMU has made sure to flush each write to the disk. Be aware that
1514 this has a major impact on performance.
1516 When using the ``-snapshot`` option, unsafe caching is always used.
1518 Copy-on-read avoids accessing the same backing file sectors
1519 repeatedly and is useful when the backing file is over a slow
1520 network. By default copy-on-read is off.
1522 Instead of ``-cdrom`` you can use:
1526 |qemu_system| -drive file=file,index=2,media=cdrom
1528 Instead of ``-hda``, ``-hdb``, ``-hdc``, ``-hdd``, you can use:
1532 |qemu_system| -drive file=file,index=0,media=disk
1533 |qemu_system| -drive file=file,index=1,media=disk
1534 |qemu_system| -drive file=file,index=2,media=disk
1535 |qemu_system| -drive file=file,index=3,media=disk
1537 You can open an image using pre-opened file descriptors from an fd
1543 -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \\
1544 -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \\
1545 -drive file=/dev/fdset/2,index=0,media=disk
1547 You can connect a CDROM to the slave of ide0:
1551 |qemu_system_x86| -drive file=file,if=ide,index=1,media=cdrom
1553 If you don't specify the
"file=" argument
, you define an empty
1558 |qemu_system_x86|
-drive
if=ide
,index
=1,media
=cdrom
1560 Instead of ``
-fda``
, ``
-fdb``
, you can use
:
1564 |qemu_system_x86|
-drive file
=file
,index
=0,if=floppy
1565 |qemu_system_x86|
-drive file
=file
,index
=1,if=floppy
1567 By
default, interface is
"ide" and index is automatically
1572 |qemu_system_x86|
-drive file
=a
-drive file
=b
"
1574 is interpreted like:
1578 |qemu_system_x86| -hda a -hdb b
1581 DEF("mtdblock
", HAS_ARG, QEMU_OPTION_mtdblock,
1582 "-mtdblock file use
'file' as on
-board Flash memory image
\n",
1586 Use file as on-board Flash memory image.
1589 DEF("sd
", HAS_ARG, QEMU_OPTION_sd,
1590 "-sd file use
'file' as SecureDigital card image
\n", QEMU_ARCH_ALL)
1593 Use file as SecureDigital card image.
1596 DEF("pflash
", HAS_ARG, QEMU_OPTION_pflash,
1597 "-pflash file use
'file' as a parallel flash image
\n", QEMU_ARCH_ALL)
1600 Use file as a parallel flash image.
1603 DEF("snapshot
", 0, QEMU_OPTION_snapshot,
1604 "-snapshot write to temporary files instead of disk image files
\n",
1608 Write to temporary files instead of disk image files. In this case,
1609 the raw disk image you use is not written back. You can however
1610 force the write back by pressing C-a s (see the :ref:`disk images`
1611 chapter in the System Emulation Users Guide).
1614 DEF("fsdev
", HAS_ARG, QEMU_OPTION_fsdev,
1615 "-fsdev local
,id
=id
,path
=path
,security_model
=mapped
-xattr|mapped
-file|passthrough|none
\n"
1616 " [,writeout
=immediate
][,readonly
=on
][,fmode
=fmode
][,dmode
=dmode
]\n"
1617 " [[,throttling
.bps
-total
=b
]|
[[,throttling
.bps
-read
=r
][,throttling
.bps
-write
=w
]]]\n"
1618 " [[,throttling
.iops
-total
=i
]|
[[,throttling
.iops
-read
=r
][,throttling
.iops
-write
=w
]]]\n"
1619 " [[,throttling
.bps
-total
-max
=bm
]|
[[,throttling
.bps
-read
-max
=rm
][,throttling
.bps
-write
-max
=wm
]]]\n"
1620 " [[,throttling
.iops
-total
-max
=im
]|
[[,throttling
.iops
-read
-max
=irm
][,throttling
.iops
-write
-max
=iwm
]]]\n"
1621 " [[,throttling
.iops
-size
=is
]]\n"
1622 "-fsdev proxy
,id
=id
,socket
=socket
[,writeout
=immediate
][,readonly
=on
]\n"
1623 "-fsdev proxy
,id
=id
,sock_fd
=sock_fd
[,writeout
=immediate
][,readonly
=on
]\n"
1624 "-fsdev synth
,id
=id
\n",
1628 ``-fsdev local,id=id,path=path,security_model=security_model [,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode] [,throttling.option=value[,throttling.option=value[,...]]]``
1630 ``-fsdev proxy,id=id,socket=socket[,writeout=writeout][,readonly=on]``
1632 ``-fsdev proxy,id=id,sock_fd=sock_fd[,writeout=writeout][,readonly=on]``
1634 ``-fsdev synth,id=id[,readonly=on]``
1635 Define a new file system device. Valid options are:
1638 Accesses to the filesystem are done by QEMU.
1641 Accesses to the filesystem are done by virtfs-proxy-helper(1).
1644 Synthetic filesystem, only used by QTests.
1647 Specifies identifier for this device.
1650 Specifies the export path for the file system device. Files
1651 under this path will be available to the 9p client on the guest.
1653 ``security_model=security_model``
1654 Specifies the security model to be used for this export path.
1655 Supported security models are "passthrough
", "mapped
-xattr
",
1656 "mapped
-file
" and "none
". In "passthrough
" security model, files
1657 are stored using the same credentials as they are created on the
1658 guest. This requires QEMU to run as root. In "mapped
-xattr
"
1659 security model, some of the file attributes like uid, gid, mode
1660 bits and link target are stored as file attributes. For
1661 "mapped
-file
" these attributes are stored in the hidden
1662 .virtfs\_metadata directory. Directories exported by this
1663 security model cannot interact with other unix tools. "none
"
1664 security model is same as passthrough except the sever won't
1665 report failures if it fails to set file attributes like
1666 ownership. Security model is mandatory only for local fsdriver.
1667 Other fsdrivers (like proxy) don't take security model as a
1670 ``writeout=writeout``
1671 This is an optional argument. The only supported value is
1672 "immediate
". This means that host page cache will be used to
1673 read and write data but write notification will be sent to the
1674 guest only when the data has been reported as written by the
1678 Enables exporting 9p share as a readonly mount for guests. By
1679 default read-write access is given.
1682 Enables proxy filesystem driver to use passed socket file for
1683 communicating with virtfs-proxy-helper(1).
1686 Enables proxy filesystem driver to use passed socket descriptor
1687 for communicating with virtfs-proxy-helper(1). Usually a helper
1688 like libvirt will create socketpair and pass one of the fds as
1692 Specifies the default mode for newly created files on the host.
1693 Works only with security models "mapped
-xattr
" and
1697 Specifies the default mode for newly created directories on the
1698 host. Works only with security models "mapped
-xattr
" and
1701 ``throttling.bps-total=b,throttling.bps-read=r,throttling.bps-write=w``
1702 Specify bandwidth throttling limits in bytes per second, either
1703 for all request types or for reads or writes only.
1705 ``throttling.bps-total-max=bm,bps-read-max=rm,bps-write-max=wm``
1706 Specify bursts in bytes per second, either for all request types
1707 or for reads or writes only. Bursts allow the guest I/O to spike
1708 above the limit temporarily.
1710 ``throttling.iops-total=i,throttling.iops-read=r, throttling.iops-write=w``
1711 Specify request rate limits in requests per second, either for
1712 all request types or for reads or writes only.
1714 ``throttling.iops-total-max=im,throttling.iops-read-max=irm, throttling.iops-write-max=iwm``
1715 Specify bursts in requests per second, either for all request
1716 types or for reads or writes only. Bursts allow the guest I/O to
1717 spike above the limit temporarily.
1719 ``throttling.iops-size=is``
1720 Let every is bytes of a request count as a new request for iops
1721 throttling purposes.
1723 -fsdev option is used along with -device driver "virtio
-9p
-...".
1725 ``-device virtio-9p-type,fsdev=id,mount_tag=mount_tag``
1726 Options for virtio-9p-... driver are:
1729 Specifies the variant to be used. Supported values are "pci
",
1730 "ccw
" or "device
", depending on the machine type.
1733 Specifies the id value specified along with -fsdev option.
1735 ``mount_tag=mount_tag``
1736 Specifies the tag name to be used by the guest to mount this
1740 DEF("virtfs
", HAS_ARG, QEMU_OPTION_virtfs,
1741 "-virtfs local
,path
=path
,mount_tag
=tag
,security_model
=mapped
-xattr|mapped
-file|passthrough|none
\n"
1742 " [,id
=id
][,writeout
=immediate
][,readonly
=on
][,fmode
=fmode
][,dmode
=dmode
][,multidevs
=remap|forbid|warn
]\n"
1743 "-virtfs proxy
,mount_tag
=tag
,socket
=socket
[,id
=id
][,writeout
=immediate
][,readonly
=on
]\n"
1744 "-virtfs proxy
,mount_tag
=tag
,sock_fd
=sock_fd
[,id
=id
][,writeout
=immediate
][,readonly
=on
]\n"
1745 "-virtfs synth
,mount_tag
=tag
[,id
=id
][,readonly
=on
]\n",
1749 ``-virtfs local,path=path,mount_tag=mount_tag ,security_model=security_model[,writeout=writeout][,readonly=on] [,fmode=fmode][,dmode=dmode][,multidevs=multidevs]``
1751 ``-virtfs proxy,socket=socket,mount_tag=mount_tag [,writeout=writeout][,readonly=on]``
1753 ``-virtfs proxy,sock_fd=sock_fd,mount_tag=mount_tag [,writeout=writeout][,readonly=on]``
1755 ``-virtfs synth,mount_tag=mount_tag``
1756 Define a new virtual filesystem device and expose it to the guest using
1757 a virtio-9p-device (a.k.a. 9pfs), which essentially means that a certain
1758 directory on host is made directly accessible by guest as a pass-through
1759 file system by using the 9P network protocol for communication between
1760 host and guests, if desired even accessible, shared by several guests
1763 Note that ``-virtfs`` is actually just a convenience shortcut for its
1764 generalized form ``-fsdev -device virtio-9p-pci``.
1766 The general form of pass-through file system options are:
1769 Accesses to the filesystem are done by QEMU.
1772 Accesses to the filesystem are done by virtfs-proxy-helper(1).
1775 Synthetic filesystem, only used by QTests.
1778 Specifies identifier for the filesystem device
1781 Specifies the export path for the file system device. Files
1782 under this path will be available to the 9p client on the guest.
1784 ``security_model=security_model``
1785 Specifies the security model to be used for this export path.
1786 Supported security models are "passthrough
", "mapped
-xattr
",
1787 "mapped
-file
" and "none
". In "passthrough
" security model, files
1788 are stored using the same credentials as they are created on the
1789 guest. This requires QEMU to run as root. In "mapped
-xattr
"
1790 security model, some of the file attributes like uid, gid, mode
1791 bits and link target are stored as file attributes. For
1792 "mapped
-file
" these attributes are stored in the hidden
1793 .virtfs\_metadata directory. Directories exported by this
1794 security model cannot interact with other unix tools. "none
"
1795 security model is same as passthrough except the sever won't
1796 report failures if it fails to set file attributes like
1797 ownership. Security model is mandatory only for local fsdriver.
1798 Other fsdrivers (like proxy) don't take security model as a
1801 ``writeout=writeout``
1802 This is an optional argument. The only supported value is
1803 "immediate
". This means that host page cache will be used to
1804 read and write data but write notification will be sent to the
1805 guest only when the data has been reported as written by the
1809 Enables exporting 9p share as a readonly mount for guests. By
1810 default read-write access is given.
1813 Enables proxy filesystem driver to use passed socket file for
1814 communicating with virtfs-proxy-helper(1). Usually a helper like
1815 libvirt will create socketpair and pass one of the fds as
1819 Enables proxy filesystem driver to use passed 'sock\_fd' as the
1820 socket descriptor for interfacing with virtfs-proxy-helper(1).
1823 Specifies the default mode for newly created files on the host.
1824 Works only with security models "mapped
-xattr
" and
1828 Specifies the default mode for newly created directories on the
1829 host. Works only with security models "mapped
-xattr
" and
1832 ``mount_tag=mount_tag``
1833 Specifies the tag name to be used by the guest to mount this
1836 ``multidevs=multidevs``
1837 Specifies how to deal with multiple devices being shared with a
1838 9p export. Supported behaviours are either "remap
", "forbid
" or
1839 "warn
". The latter is the default behaviour on which virtfs 9p
1840 expects only one device to be shared with the same export, and
1841 if more than one device is shared and accessed via the same 9p
1842 export then only a warning message is logged (once) by qemu on
1843 host side. In order to avoid file ID collisions on guest you
1844 should either create a separate virtfs export for each device to
1845 be shared with guests (recommended way) or you might use "remap
"
1846 instead which allows you to share multiple devices with only one
1847 export instead, which is achieved by remapping the original
1848 inode numbers from host to guest in a way that would prevent
1849 such collisions. Remapping inodes in such use cases is required
1850 because the original device IDs from host are never passed and
1851 exposed on guest. Instead all files of an export shared with
1852 virtfs always share the same device id on guest. So two files
1853 with identical inode numbers but from actually different devices
1854 on host would otherwise cause a file ID collision and hence
1855 potential misbehaviours on guest. "forbid
" on the other hand
1856 assumes like "warn
" that only one device is shared by the same
1857 export, however it will not only log a warning message but also
1858 deny access to additional devices on guest. Note though that
1859 "forbid
" does currently not block all possible file access
1860 operations (e.g. readdir() would still return entries from other
1864 DEF("iscsi
", HAS_ARG, QEMU_OPTION_iscsi,
1865 "-iscsi
[user
=user
][,password
=password
]\n"
1866 " [,header
-digest
=CRC32C|CR32C
-NONE|NONE
-CRC32C|NONE
\n"
1867 " [,initiator
-name
=initiator
-iqn
][,id
=target
-iqn
]\n"
1868 " [,timeout
=timeout
]\n"
1869 " iSCSI session parameters
\n", QEMU_ARCH_ALL)
1873 Configure iSCSI session parameters.
1878 DEFHEADING(USB convenience options:)
1880 DEF("usb
", 0, QEMU_OPTION_usb,
1881 "-usb enable on
-board USB host
controller (if not enabled by
default)\n",
1885 Enable USB emulation on machine types with an on-board USB host
1886 controller (if not enabled by default). Note that on-board USB host
1887 controllers may not support USB 3.0. In this case
1888 ``-device qemu-xhci`` can be used instead on machines with PCI.
1891 DEF("usbdevice
", HAS_ARG, QEMU_OPTION_usbdevice,
1892 "-usbdevice name add the host or guest USB device
'name'\n",
1895 ``-usbdevice devname``
1896 Add the USB device devname, and enable an on-board USB controller
1897 if possible and necessary (just like it can be done via
1898 ``-machine usb=on``). Note that this option is mainly intended for
1899 the user's convenience only. More fine-grained control can be
1900 achieved by selecting a USB host controller (if necessary) and the
1901 desired USB device via the ``-device`` option instead. For example,
1902 instead of using ``-usbdevice mouse`` it is possible to use
1903 ``-device qemu-xhci -device usb-mouse`` to connect the USB mouse
1904 to a USB 3.0 controller instead (at least on machines that support
1905 PCI and do not have an USB controller enabled by default yet).
1906 For more details, see the chapter about
1907 :ref:`Connecting USB devices` in the System Emulation Users Guide.
1908 Possible devices for devname are:
1911 Braille device. This will use BrlAPI to display the braille
1912 output on a real or fake device (i.e. it also creates a
1913 corresponding ``braille`` chardev automatically beside the
1914 ``usb-braille`` USB device).
1917 Standard USB keyboard. Will override the PS/2 keyboard (if present).
1920 Virtual Mouse. This will override the PS/2 mouse emulation when
1924 Pointer device that uses absolute coordinates (like a
1925 touchscreen). This means QEMU is able to report the mouse
1926 position without having to grab the mouse. Also overrides the
1927 PS/2 mouse emulation when activated.
1930 Wacom PenPartner USB tablet.
1937 DEFHEADING(Display options:)
1939 DEF("display
", HAS_ARG, QEMU_OPTION_display,
1940 #if defined(CONFIG_SPICE)
1941 "-display spice
-app
[,gl
=on|off
]\n"
1943 #if defined(CONFIG_SDL)
1944 "-display sdl
[,alt_grab
=on|off
][,ctrl_grab
=on|off
][,gl
=on|core|es|off
]\n"
1945 " [,grab
-mod
=<mod
>][,show
-cursor
=on|off
][,window
-close
=on|off
]\n"
1947 #if defined(CONFIG_GTK)
1948 "-display gtk
[,full
-screen
=on|off
][,gl
=on|off
][,grab
-on
-hover
=on|off
]\n"
1949 " [,show
-cursor
=on|off
][,window
-close
=on|off
]\n"
1951 #if defined(CONFIG_VNC)
1952 "-display vnc
=<display
>[,<optargs
>]\n"
1954 #if defined(CONFIG_CURSES)
1955 "-display curses
[,charset
=<encoding
>]\n"
1957 #if defined(CONFIG_COCOA)
1958 "-display cocoa
[,full
-grab
=on|off
][,swap
-opt
-cmd
=on|off
]\n"
1960 #if defined(CONFIG_OPENGL)
1961 "-display egl
-headless
[,rendernode
=<file
>]\n"
1963 #if defined(CONFIG_DBUS_DISPLAY)
1964 "-display dbus
[,addr
=<dbusaddr
>]\n"
1965 " [,gl
=on|core|es|off
][,rendernode
=<file
>]\n"
1967 #if defined(CONFIG_COCOA)
1968 "-display cocoa
[,show
-cursor
=on|off
][,left
-command
-key
=on|off
]\n"
1971 " select display backend type
\n"
1972 " The
default display is equivalent to
\n "
1973 #if defined(CONFIG_GTK)
1974 "\"-display gtk
\"\n"
1975 #elif defined(CONFIG_SDL)
1976 "\"-display sdl
\"\n"
1977 #elif defined(CONFIG_COCOA)
1978 "\"-display cocoa
\"\n"
1979 #elif defined(CONFIG_VNC)
1980 "\"-vnc localhost
:0,to
=99,id
=default\"\n"
1982 "\"-display none
\"\n"
1987 Select type of display to use. This option is a replacement for the
1988 old style -sdl/-curses/... options. Use ``-display help`` to list
1989 the available display types. Valid values for type are
1991 ``spice-app[,gl=on|off]``
1992 Start QEMU as a Spice server and launch the default Spice client
1993 application. The Spice server will redirect the serial consoles
1994 and QEMU monitors. (Since 4.0)
1997 Export the display over D-Bus interfaces. (Since 7.0)
1999 The connection is registered with the "org
.qemu
" name (and queued when
2002 ``addr=<dbusaddr>`` : D-Bus bus address to connect to.
2004 ``p2p=yes|no`` : Use peer-to-peer connection, accepted via QMP ``add_client``.
2006 ``gl=on|off|core|es`` : Use OpenGL for rendering (the D-Bus interface
2007 will share framebuffers with DMABUF file descriptors).
2010 Display video output via SDL (usually in a separate graphics
2011 window; see the SDL documentation for other possibilities).
2012 Valid parameters are:
2014 ``grab-mod=<mods>`` : Used to select the modifier keys for toggling
2015 the mouse grabbing in conjunction with the "g
" key. ``<mods>`` can be
2016 either ``lshift-lctrl-lalt`` or ``rctrl``.
2018 ``alt_grab=on|off`` : Use Control+Alt+Shift-g to toggle mouse grabbing.
2019 This parameter is deprecated - use ``grab-mod`` instead.
2021 ``ctrl_grab=on|off`` : Use Right-Control-g to toggle mouse grabbing.
2022 This parameter is deprecated - use ``grab-mod`` instead.
2024 ``gl=on|off|core|es`` : Use OpenGL for displaying
2026 ``show-cursor=on|off`` : Force showing the mouse cursor
2028 ``window-close=on|off`` : Allow to quit qemu with window close button
2031 Display video output in a GTK window. This interface provides
2032 drop-down menus and other UI elements to configure and control
2033 the VM during runtime. Valid parameters are:
2035 ``full-screen=on|off`` : Start in fullscreen mode
2037 ``gl=on|off`` : Use OpenGL for displaying
2039 ``grab-on-hover=on|off`` : Grab keyboard input on mouse hover
2041 ``show-cursor=on|off`` : Force showing the mouse cursor
2043 ``window-close=on|off`` : Allow to quit qemu with window close button
2045 ``curses[,charset=<encoding>]``
2046 Display video output via curses. For graphics device models
2047 which support a text mode, QEMU can display this output using a
2048 curses/ncurses interface. Nothing is displayed when the graphics
2049 device is in graphical mode or if the graphics device does not
2050 support a text mode. Generally only the VGA device models
2051 support text mode. The font charset used by the guest can be
2052 specified with the ``charset`` option, for example
2053 ``charset=CP850`` for IBM CP850 encoding. The default is
2057 Display video output in a Cocoa window. Mac only. This interface
2058 provides drop-down menus and other UI elements to configure and
2059 control the VM during runtime. Valid parameters are:
2061 ``show-cursor=on|off`` : Force showing the mouse cursor
2063 ``left-command-key=on|off`` : Disable forwarding left command key to host
2065 ``egl-headless[,rendernode=<file>]``
2066 Offload all OpenGL operations to a local DRI device. For any
2067 graphical display, this display needs to be paired with either
2068 VNC or SPICE displays.
2071 Start a VNC server on display <display>
2074 Do not display video output. The guest will still see an
2075 emulated graphics card, but its output will not be displayed to
2076 the QEMU user. This option differs from the -nographic option in
2077 that it only affects what is done with video output; -nographic
2078 also changes the destination of the serial and parallel port
2082 DEF("nographic
", 0, QEMU_OPTION_nographic,
2083 "-nographic disable graphical output and redirect serial I
/Os to console
\n",
2087 Normally, if QEMU is compiled with graphical window support, it
2088 displays output such as guest graphics, guest console, and the QEMU
2089 monitor in a window. With this option, you can totally disable
2090 graphical output so that QEMU is a simple command line application.
2091 The emulated serial port is redirected on the console and muxed with
2092 the monitor (unless redirected elsewhere explicitly). Therefore, you
2093 can still use QEMU to debug a Linux kernel with a serial console.
2094 Use C-a h for help on switching between the console and monitor.
2097 DEF("curses
", 0, QEMU_OPTION_curses,
2098 "-curses shorthand
for -display curses
\n",
2102 Normally, if QEMU is compiled with graphical window support, it
2103 displays output such as guest graphics, guest console, and the QEMU
2104 monitor in a window. With this option, QEMU can display the VGA
2105 output when in text mode using a curses/ncurses interface. Nothing
2106 is displayed in graphical mode.
2109 DEF("alt
-grab
", 0, QEMU_OPTION_alt_grab,
2110 "-alt
-grab use Ctrl
-Alt
-Shift to grab
mouse (instead of Ctrl
-Alt
)\n",
2114 Use Ctrl-Alt-Shift to grab mouse (instead of Ctrl-Alt). Note that
2115 this also affects the special keys (for fullscreen, monitor-mode
2116 switching, etc). This option is deprecated - please use
2117 ``-display sdl,grab-mod=lshift-lctrl-lalt`` instead.
2120 DEF("ctrl
-grab
", 0, QEMU_OPTION_ctrl_grab,
2121 "-ctrl
-grab use Right
-Ctrl to grab
mouse (instead of Ctrl
-Alt
)\n",
2125 Use Right-Ctrl to grab mouse (instead of Ctrl-Alt). Note that this
2126 also affects the special keys (for fullscreen, monitor-mode
2127 switching, etc). This option is deprecated - please use
2128 ``-display sdl,grab-mod=rctrl`` instead.
2131 DEF("sdl
", 0, QEMU_OPTION_sdl,
2132 "-sdl shorthand
for -display sdl
\n", QEMU_ARCH_ALL)
2139 DEF("spice
", HAS_ARG, QEMU_OPTION_spice,
2140 "-spice
[port
=port
][,tls
-port
=secured
-port
][,x509
-dir
=<dir
>]\n"
2141 " [,x509
-key
-file
=<file
>][,x509
-key
-password
=<file
>]\n"
2142 " [,x509
-cert
-file
=<file
>][,x509
-cacert
-file
=<file
>]\n"
2143 " [,x509
-dh
-key
-file
=<file
>][,addr
=addr
]\n"
2144 " [,ipv4
=on|off
][,ipv6
=on|off
][,unix
=on|off
]\n"
2145 " [,tls
-ciphers
=<list
>]\n"
2146 " [,tls
-channel
=[main|display|cursor|inputs|record|playback
]]\n"
2147 " [,plaintext
-channel
=[main|display|cursor|inputs|record|playback
]]\n"
2148 " [,sasl
=on|off
][,disable
-ticketing
=on|off
]\n"
2149 " [,password
=<string
>][,password
-secret
=<secret
-id
>]\n"
2150 " [,image
-compression
=[auto_glz|auto_lz|quic|glz|lz|off
]]\n"
2151 " [,jpeg
-wan
-compression
=[auto|
never|always
]]\n"
2152 " [,zlib
-glz
-wan
-compression
=[auto|
never|always
]]\n"
2153 " [,streaming
-video
=[off|all|filter
]][,disable
-copy
-paste
=on|off
]\n"
2154 " [,disable
-agent
-file
-xfer
=on|off
][,agent
-mouse
=[on|off
]]\n"
2155 " [,playback
-compression
=[on|off
]][,seamless
-migration
=[on|off
]]\n"
2156 " [,gl
=[on|off
]][,rendernode
=<file
>]\n"
2158 " at least one of
{port
, tls
-port
} is mandatory
\n",
2162 ``-spice option[,option[,...]]``
2163 Enable the spice remote desktop protocol. Valid options are
2166 Set the TCP port spice is listening on for plaintext channels.
2169 Set the IP address spice is listening on. Default is any
2172 ``ipv4=on|off``; \ ``ipv6=on|off``; \ ``unix=on|off``
2173 Force using the specified IP version.
2175 ``password=<string>``
2176 Set the password you need to authenticate.
2178 This option is deprecated and insecure because it leaves the
2179 password visible in the process listing. Use ``password-secret``
2182 ``password-secret=<secret-id>``
2183 Set the ID of the ``secret`` object containing the password
2184 you need to authenticate.
2187 Require that the client use SASL to authenticate with the spice.
2188 The exact choice of authentication method used is controlled
2189 from the system / user's SASL configuration file for the 'qemu'
2190 service. This is typically found in /etc/sasl2/qemu.conf. If
2191 running QEMU as an unprivileged user, an environment variable
2192 SASL\_CONF\_PATH can be used to make it search alternate
2193 locations for the service config. While some SASL auth methods
2194 can also provide data encryption (eg GSSAPI), it is recommended
2195 that SASL always be combined with the 'tls' and 'x509' settings
2196 to enable use of SSL and server certificates. This ensures a
2197 data encryption preventing compromise of authentication
2200 ``disable-ticketing=on|off``
2201 Allow client connects without authentication.
2203 ``disable-copy-paste=on|off``
2204 Disable copy paste between the client and the guest.
2206 ``disable-agent-file-xfer=on|off``
2207 Disable spice-vdagent based file-xfer between the client and the
2211 Set the TCP port spice is listening on for encrypted channels.
2214 Set the x509 file directory. Expects same filenames as -vnc
2217 ``x509-key-file=<file>``; \ ``x509-key-password=<file>``; \ ``x509-cert-file=<file>``; \ ``x509-cacert-file=<file>``; \ ``x509-dh-key-file=<file>``
2218 The x509 file names can also be configured individually.
2220 ``tls-ciphers=<list>``
2221 Specify which ciphers to use.
2223 ``tls-channel=[main|display|cursor|inputs|record|playback]``; \ ``plaintext-channel=[main|display|cursor|inputs|record|playback]``
2224 Force specific channel to be used with or without TLS
2225 encryption. The options can be specified multiple times to
2226 configure multiple channels. The special name "default" can be
2227 used to set the default mode. For channels which are not
2228 explicitly forced into one mode the spice client is allowed to
2229 pick tls/plaintext as he pleases.
2231 ``image-compression=[auto_glz|auto_lz|quic|glz|lz|off]``
2232 Configure image compression (lossless). Default is auto\_glz.
2234 ``jpeg-wan-compression=[auto|never|always]``; \ ``zlib-glz-wan-compression=[auto|never|always]``
2235 Configure wan image compression (lossy for slow links). Default
2238 ``streaming-video=[off|all|filter]``
2239 Configure video stream detection. Default is off.
2241 ``agent-mouse=[on|off]``
2242 Enable/disable passing mouse events via vdagent. Default is on.
2244 ``playback-compression=[on|off]``
2245 Enable/disable audio stream compression (using celt 0.5.1).
2248 ``seamless-migration=[on|off]``
2249 Enable/disable spice seamless migration. Default is off.
2252 Enable/disable OpenGL context. Default is off.
2254 ``rendernode=<file>``
2255 DRM render node for OpenGL rendering. If not specified, it will
2256 pick the first available. (Since 2.9)
2259 DEF("portrait
", 0, QEMU_OPTION_portrait,
2260 "-portrait rotate graphical output
90 deg
left (only PXA LCD
)\n",
2264 Rotate graphical output 90 deg left (only PXA LCD).
2267 DEF("rotate
", HAS_ARG, QEMU_OPTION_rotate,
2268 "-rotate
<deg
> rotate graphical output some deg
left (only PXA LCD
)\n",
2272 Rotate graphical output some deg left (only PXA LCD).
2275 DEF("vga
", HAS_ARG, QEMU_OPTION_vga,
2276 "-vga
[std|cirrus|vmware|qxl|xenfb|tcx|cg3|virtio|none
]\n"
2277 " select video card type
\n", QEMU_ARCH_ALL)
2280 Select type of VGA card to emulate. Valid values for type are
2283 Cirrus Logic GD5446 Video card. All Windows versions starting
2284 from Windows 95 should recognize and use this graphic card. For
2285 optimal performances, use 16 bit color depth in the guest and
2286 the host OS. (This card was the default before QEMU 2.2)
2289 Standard VGA card with Bochs VBE extensions. If your guest OS
2290 supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if
2291 you want to use high resolution modes (>= 1280x1024x16) then you
2292 should use this option. (This card is the default since QEMU
2296 VMWare SVGA-II compatible adapter. Use it if you have
2297 sufficiently recent XFree86/XOrg server or Windows guest with a
2298 driver for this card.
2301 QXL paravirtual graphic card. It is VGA compatible (including
2302 VESA 2.0 VBE support). Works best with qxl guest drivers
2303 installed though. Recommended choice when using the spice
2307 (sun4m only) Sun TCX framebuffer. This is the default
2308 framebuffer for sun4m machines and offers both 8-bit and 24-bit
2309 colour depths at a fixed resolution of 1024x768.
2312 (sun4m only) Sun cgthree framebuffer. This is a simple 8-bit
2313 framebuffer for sun4m machines available in both 1024x768
2314 (OpenBIOS) and 1152x900 (OBP) resolutions aimed at people
2315 wishing to run older Solaris versions.
2324 DEF("full
-screen
", 0, QEMU_OPTION_full_screen,
2325 "-full
-screen start
in full screen
\n", QEMU_ARCH_ALL)
2328 Start in full screen.
2331 DEF("g
", HAS_ARG, QEMU_OPTION_g ,
2332 "-g WxH
[xDEPTH
] Set the initial graphical resolution and depth
\n",
2333 QEMU_ARCH_PPC | QEMU_ARCH_SPARC | QEMU_ARCH_M68K)
2335 ``-g`` *width*\ ``x``\ *height*\ ``[x``\ *depth*\ ``]``
2336 Set the initial graphical resolution and depth (PPC, SPARC only).
2338 For PPC the default is 800x600x32.
2340 For SPARC with the TCX graphics device, the default is 1024x768x8
2341 with the option of 1024x768x24. For cgthree, the default is
2342 1024x768x8 with the option of 1152x900x8 for people who wish to use
2346 DEF("vnc
", HAS_ARG, QEMU_OPTION_vnc ,
2347 "-vnc
<display
> shorthand
for -display vnc
=<display
>\n", QEMU_ARCH_ALL)
2349 ``-vnc display[,option[,option[,...]]]``
2350 Normally, if QEMU is compiled with graphical window support, it
2351 displays output such as guest graphics, guest console, and the QEMU
2352 monitor in a window. With this option, you can have QEMU listen on
2353 VNC display display and redirect the VGA display over the VNC
2354 session. It is very useful to enable the usb tablet device when
2355 using this option (option ``-device usb-tablet``). When using the
2356 VNC display, you must use the ``-k`` parameter to set the keyboard
2357 layout if you are not using en-us. Valid syntax for the display is
2360 With this option, QEMU will try next available VNC displays,
2361 until the number L, if the origianlly defined "-vnc display
" is
2362 not available, e.g. port 5900+display is already used by another
2363 application. By default, to=0.
2366 TCP connections will only be allowed from host on display d. By
2367 convention the TCP port is 5900+d. Optionally, host can be
2368 omitted in which case the server will accept connections from
2372 Connections will be allowed over UNIX domain sockets where path
2373 is the location of a unix socket to listen for connections on.
2376 VNC is initialized but not started. The monitor ``change``
2377 command can be used to later start the VNC server.
2379 Following the display value there may be one or more option flags
2380 separated by commas. Valid options are
2383 Connect to a listening VNC client via a "reverse
" connection.
2384 The client is specified by the display. For reverse network
2385 connections (host:d,``reverse``), the d argument is a TCP port
2386 number, not a display number.
2388 ``websocket=on|off``
2389 Opens an additional TCP listening port dedicated to VNC
2390 Websocket connections. If a bare websocket option is given, the
2391 Websocket port is 5700+display. An alternative port can be
2392 specified with the syntax ``websocket``\ =port.
2394 If host is specified connections will only be allowed from this
2395 host. It is possible to control the websocket listen address
2396 independently, using the syntax ``websocket``\ =host:port.
2398 If no TLS credentials are provided, the websocket connection
2399 runs in unencrypted mode. If TLS credentials are provided, the
2400 websocket connection requires encrypted client connections.
2403 Require that password based authentication is used for client
2406 The password must be set separately using the ``set_password``
2407 command in the :ref:`QEMU monitor`. The
2408 syntax to change your password is:
2409 ``set_password <protocol> <password>`` where <protocol> could be
2410 either "vnc
" or "spice
".
2412 If you would like to change <protocol> password expiration, you
2413 should use ``expire_password <protocol> <expiration-time>``
2414 where expiration time could be one of the following options:
2415 now, never, +seconds or UNIX time of expiration, e.g. +60 to
2416 make password expire in 60 seconds, or 1335196800 to make
2417 password expire on "Mon Apr
23 12:00:00 EDT
2012" (UNIX time for
2418 this date and time).
2420 You can also use keywords "now
" or "never" for the expiration
2421 time to allow <protocol> password to expire immediately or never
2424 ``password-secret=<secret-id>``
2425 Require that password based authentication is used for client
2426 connections, using the password provided by the ``secret``
2427 object identified by ``secret-id``.
2430 Provides the ID of a set of TLS credentials to use to secure the
2431 VNC server. They will apply to both the normal VNC server socket
2432 and the websocket socket (if enabled). Setting TLS credentials
2433 will cause the VNC server socket to enable the VeNCrypt auth
2434 mechanism. The credentials should have been previously created
2435 using the ``-object tls-creds`` argument.
2438 Provides the ID of the QAuthZ authorization object against which
2439 the client's x509 distinguished name will validated. This object
2440 is only resolved at time of use, so can be deleted and recreated
2441 on the fly while the VNC server is active. If missing, it will
2442 default to denying access.
2445 Require that the client use SASL to authenticate with the VNC
2446 server. The exact choice of authentication method used is
2447 controlled from the system / user's SASL configuration file for
2448 the 'qemu' service. This is typically found in
2449 /etc/sasl2/qemu.conf. If running QEMU as an unprivileged user,
2450 an environment variable SASL\_CONF\_PATH can be used to make it
2451 search alternate locations for the service config. While some
2452 SASL auth methods can also provide data encryption (eg GSSAPI),
2453 it is recommended that SASL always be combined with the 'tls'
2454 and 'x509' settings to enable use of SSL and server
2455 certificates. This ensures a data encryption preventing
2456 compromise of authentication credentials. See the
2457 :ref:`VNC security` section in the System Emulation Users Guide
2458 for details on using SASL authentication.
2461 Provides the ID of the QAuthZ authorization object against which
2462 the client's SASL username will validated. This object is only
2463 resolved at time of use, so can be deleted and recreated on the
2464 fly while the VNC server is active. If missing, it will default
2468 Legacy method for enabling authorization of clients against the
2469 x509 distinguished name and SASL username. It results in the
2470 creation of two ``authz-list`` objects with IDs of
2471 ``vnc.username`` and ``vnc.x509dname``. The rules for these
2472 objects must be configured with the HMP ACL commands.
2474 This option is deprecated and should no longer be used. The new
2475 ``sasl-authz`` and ``tls-authz`` options are a replacement.
2478 Enable lossy compression methods (gradient, JPEG, ...). If this
2479 option is set, VNC client may receive lossy framebuffer updates
2480 depending on its encoding settings. Enabling this option can
2481 save a lot of bandwidth at the expense of quality.
2483 ``non-adaptive=on|off``
2484 Disable adaptive encodings. Adaptive encodings are enabled by
2485 default. An adaptive encoding will try to detect frequently
2486 updated screen regions, and send updates in these regions using
2487 a lossy encoding (like JPEG). This can be really helpful to save
2488 bandwidth when playing videos. Disabling adaptive encodings
2489 restores the original static behavior of encodings like Tight.
2491 ``share=[allow-exclusive|force-shared|ignore]``
2492 Set display sharing policy. 'allow-exclusive' allows clients to
2493 ask for exclusive access. As suggested by the rfb spec this is
2494 implemented by dropping other connections. Connecting multiple
2495 clients in parallel requires all clients asking for a shared
2496 session (vncviewer: -shared switch). This is the default.
2497 'force-shared' disables exclusive client access. Useful for
2498 shared desktop sessions, where you don't want someone forgetting
2499 specify -shared disconnect everybody else. 'ignore' completely
2500 ignores the shared flag and allows everybody connect
2501 unconditionally. Doesn't conform to the rfb spec but is
2502 traditional QEMU behavior.
2505 Set keyboard delay, for key down and key up events, in
2506 milliseconds. Default is 10. Keyboards are low-bandwidth
2507 devices, so this slowdown can help the device and guest to keep
2508 up and not lose events in case events are arriving in bulk.
2509 Possible causes for the latter are flaky network connections, or
2510 scripts for automated testing.
2512 ``audiodev=audiodev``
2513 Use the specified audiodev when the VNC client requests audio
2514 transmission. When not using an -audiodev argument, this option
2515 must be omitted, otherwise is must be present and specify a
2518 ``power-control=on|off``
2519 Permit the remote client to issue shutdown, reboot or reset power
2523 ARCHHEADING(, QEMU_ARCH_I386)
2525 ARCHHEADING(i386 target only:, QEMU_ARCH_I386)
2527 DEF("win2k
-hack
", 0, QEMU_OPTION_win2k_hack,
2528 "-win2k
-hack use it when installing Windows
2000 to avoid a disk full bug
\n",
2532 Use it when installing Windows 2000 to avoid a disk full bug. After
2533 Windows 2000 is installed, you no longer need this option (this
2534 option slows down the IDE transfers).
2537 DEF("no
-fd
-bootchk
", 0, QEMU_OPTION_no_fd_bootchk,
2538 "-no
-fd
-bootchk disable boot signature checking
for floppy disks
\n",
2542 Disable boot signature checking for floppy disks in BIOS. May be
2543 needed to boot from old floppy disks.
2546 DEF("no
-acpi
", 0, QEMU_OPTION_no_acpi,
2547 "-no
-acpi disable ACPI
\n", QEMU_ARCH_I386 | QEMU_ARCH_ARM)
2550 Disable ACPI (Advanced Configuration and Power Interface) support.
2551 Use it if your guest OS complains about ACPI problems (PC target
2555 DEF("no
-hpet
", 0, QEMU_OPTION_no_hpet,
2556 "-no
-hpet disable HPET
\n", QEMU_ARCH_I386)
2559 Disable HPET support.
2562 DEF("acpitable
", HAS_ARG, QEMU_OPTION_acpitable,
2563 "-acpitable
[sig
=str
][,rev
=n
][,oem_id
=str
][,oem_table_id
=str
][,oem_rev
=n
][,asl_compiler_id
=str
][,asl_compiler_rev
=n
][,{data|file
}=file1
[:file2
]...]\n"
2564 " ACPI table description
\n", QEMU_ARCH_I386)
2566 ``-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n] [,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...]``
2567 Add ACPI table with specified header fields and context from
2568 specified files. For file=, take whole ACPI table from the specified
2569 files, including all ACPI headers (possible overridden by other
2570 options). For data=, only data portion of the table is used, all
2571 header information is specified in the command line. If a SLIC table
2572 is supplied to QEMU, then the SLIC's oem\_id and oem\_table\_id
2573 fields will override the same in the RSDT and the FADT (a.k.a.
2574 FACP), in order to ensure the field matches required by the
2575 Microsoft SLIC spec and the ACPI spec.
2578 DEF("smbios
", HAS_ARG, QEMU_OPTION_smbios,
2579 "-smbios file
=binary
\n"
2580 " load SMBIOS entry from binary file
\n"
2581 "-smbios type
=0[,vendor
=str
][,version
=str
][,date
=str
][,release
=%d
.%d
]\n"
2583 " specify SMBIOS type
0 fields
\n"
2584 "-smbios type
=1[,manufacturer
=str
][,product
=str
][,version
=str
][,serial
=str
]\n"
2585 " [,uuid
=uuid
][,sku
=str
][,family
=str
]\n"
2586 " specify SMBIOS type
1 fields
\n"
2587 "-smbios type
=2[,manufacturer
=str
][,product
=str
][,version
=str
][,serial
=str
]\n"
2588 " [,asset
=str
][,location
=str
]\n"
2589 " specify SMBIOS type
2 fields
\n"
2590 "-smbios type
=3[,manufacturer
=str
][,version
=str
][,serial
=str
][,asset
=str
]\n"
2592 " specify SMBIOS type
3 fields
\n"
2593 "-smbios type
=4[,sock_pfx
=str
][,manufacturer
=str
][,version
=str
][,serial
=str
]\n"
2594 " [,asset
=str
][,part
=str
][,max
-speed
=%d
][,current
-speed
=%d
]\n"
2595 " [,processor
-id
=%d
]\n"
2596 " specify SMBIOS type
4 fields
\n"
2597 "-smbios type
=11[,value
=str
][,path
=filename
]\n"
2598 " specify SMBIOS type
11 fields
\n"
2599 "-smbios type
=17[,loc_pfx
=str
][,bank
=str
][,manufacturer
=str
][,serial
=str
]\n"
2600 " [,asset
=str
][,part
=str
][,speed
=%d
]\n"
2601 " specify SMBIOS type
17 fields
\n"
2602 "-smbios type
=41[,designation
=str
][,kind
=str
][,instance
=%d
][,pcidev
=str
]\n"
2603 " specify SMBIOS type
41 fields
\n",
2604 QEMU_ARCH_I386 | QEMU_ARCH_ARM)
2606 ``-smbios file=binary``
2607 Load SMBIOS entry from binary file.
2609 ``-smbios type=0[,vendor=str][,version=str][,date=str][,release=%d.%d][,uefi=on|off]``
2610 Specify SMBIOS type 0 fields
2612 ``-smbios type=1[,manufacturer=str][,product=str][,version=str][,serial=str][,uuid=uuid][,sku=str][,family=str]``
2613 Specify SMBIOS type 1 fields
2615 ``-smbios type=2[,manufacturer=str][,product=str][,version=str][,serial=str][,asset=str][,location=str]``
2616 Specify SMBIOS type 2 fields
2618 ``-smbios type=3[,manufacturer=str][,version=str][,serial=str][,asset=str][,sku=str]``
2619 Specify SMBIOS type 3 fields
2621 ``-smbios type=4[,sock_pfx=str][,manufacturer=str][,version=str][,serial=str][,asset=str][,part=str][,processor-id=%d]``
2622 Specify SMBIOS type 4 fields
2624 ``-smbios type=11[,value=str][,path=filename]``
2625 Specify SMBIOS type 11 fields
2627 This argument can be repeated multiple times, and values are added in the order they are parsed.
2628 Applications intending to use OEM strings data are encouraged to use their application name as
2629 a prefix for the value string. This facilitates passing information for multiple applications
2632 The ``value=str`` syntax provides the string data inline, while the ``path=filename`` syntax
2633 loads data from a file on disk. Note that the file is not permitted to contain any NUL bytes.
2635 Both the ``value`` and ``path`` options can be repeated multiple times and will be added to
2636 the SMBIOS table in the order in which they appear.
2638 Note that on the x86 architecture, the total size of all SMBIOS tables is limited to 65535
2639 bytes. Thus the OEM strings data is not suitable for passing large amounts of data into the
2640 guest. Instead it should be used as a indicator to inform the guest where to locate the real
2641 data set, for example, by specifying the serial ID of a block device.
2643 An example passing three strings is
2647 -smbios type=11,value=cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/,\\
2648 value=anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os,\\
2649 path=/some/file/with/oemstringsdata.txt
2651 In the guest OS this is visible with the ``dmidecode`` command
2656 Handle 0x0E00, DMI type 11, 5 bytes
2658 String 1: cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/
2659 String 2: anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os
2660 String 3: myapp:some extra data
2663 ``-smbios type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str][,asset=str][,part=str][,speed=%d]``
2664 Specify SMBIOS type 17 fields
2666 ``-smbios type=41[,designation=str][,kind=str][,instance=%d][,pcidev=str]``
2667 Specify SMBIOS type 41 fields
2669 This argument can be repeated multiple times. Its main use is to allow network interfaces be created
2670 as ``enoX`` on Linux, with X being the instance number, instead of the name depending on the interface
2671 position on the PCI bus.
2673 Here is an example of use:
2677 -netdev user,id=internet \\
2678 -device virtio-net-pci,mac=50:54:00:00:00:42,netdev=internet,id=internet-dev \\
2679 -smbios type=41,designation='Onboard LAN',instance=1,kind=ethernet,pcidev=internet-dev
2681 In the guest OS, the device should then appear as ``eno1``:
2686 lo UNKNOWN 00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
2687 eno1 UP 50:54:00:00:00:42 <BROADCAST,MULTICAST,UP,LOWER_UP>
2689 Currently, the PCI device has to be attached to the root bus.
2695 DEFHEADING(Network options:)
2697 DEF("netdev
", HAS_ARG, QEMU_OPTION_netdev,
2699 "-netdev user
,id
=str
[,ipv4
=on|off
][,net
=addr
[/mask
]][,host
=addr
]\n"
2700 " [,ipv6
=on|off
][,ipv6
-net
=addr
[/int
]][,ipv6
-host
=addr
]\n"
2701 " [,restrict
=on|off
][,hostname
=host
][,dhcpstart
=addr
]\n"
2702 " [,dns
=addr
][,ipv6
-dns
=addr
][,dnssearch
=domain
][,domainname
=domain
]\n"
2703 " [,tftp
=dir
][,tftp
-server
-name
=name
][,bootfile
=f
][,hostfwd
=rule
][,guestfwd
=rule
]"
2705 "[,smb
=dir
[,smbserver
=addr
]]\n"
2707 " configure a user mode network backend with ID
'str',\n"
2708 " its DHCP server and optional services
\n"
2711 "-netdev tap
,id
=str
,ifname
=name
\n"
2712 " configure a host TAP network backend with ID
'str'\n"
2714 "-netdev tap
,id
=str
[,fd
=h
][,fds
=x
:y
:...:z
][,ifname
=name
][,script
=file
][,downscript
=dfile
]\n"
2715 " [,br
=bridge
][,helper
=helper
][,sndbuf
=nbytes
][,vnet_hdr
=on|off
][,vhost
=on|off
]\n"
2716 " [,vhostfd
=h
][,vhostfds
=x
:y
:...:z
][,vhostforce
=on|off
][,queues
=n
]\n"
2718 " configure a host TAP network backend with ID
'str'\n"
2719 " connected to a
bridge (default=" DEFAULT_BRIDGE_INTERFACE ")\n"
2720 " use network scripts
'file' (default=" DEFAULT_NETWORK_SCRIPT ")\n"
2721 " to configure it and
'dfile' (default=" DEFAULT_NETWORK_DOWN_SCRIPT ")\n"
2722 " to deconfigure it
\n"
2723 " use
'[down]script=no' to disable script execution
\n"
2724 " use network helper
'helper' (default=" DEFAULT_BRIDGE_HELPER ") to
\n"
2726 " use
'fd=h' to connect to an already opened TAP
interface\n"
2727 " use
'fds=x:y:...:z' to connect to already opened multiqueue capable TAP interfaces
\n"
2728 " use
'sndbuf=nbytes' to limit the size of the send
buffer (the
\n"
2729 " default is disabled
'sndbuf=0' to enable flow control set
'sndbuf=1048576')\n"
2730 " use vnet_hdr
=off to avoid enabling the IFF_VNET_HDR tap flag
\n"
2731 " use vnet_hdr
=on to make the lack of IFF_VNET_HDR support an error condition
\n"
2732 " use vhost
=on to enable experimental
in kernel accelerator
\n"
2733 " (only has effect
for virtio guests which use MSIX
)\n"
2734 " use vhostforce
=on to force vhost on
for non
-MSIX virtio guests
\n"
2735 " use
'vhostfd=h' to connect to an already opened vhost net device
\n"
2736 " use
'vhostfds=x:y:...:z to connect to multiple already opened vhost net devices\n"
2737 " use 'queues
=n
' to specify the number of queues to be created for multiqueue TAP\n"
2738 " use 'poll
-us
=n
' to specify the maximum number of microseconds that could be\n"
2739 " spent on busy polling for vhost net\n"
2740 "-netdev bridge,id=str[,br=bridge][,helper=helper]\n"
2741 " configure a host TAP network backend with ID 'str
' that is\n"
2742 " connected to a bridge (default=" DEFAULT_BRIDGE_INTERFACE ")\n"
2743 " using the program 'helper (default=" DEFAULT_BRIDGE_HELPER ")\n"
2746 "-netdev l2tpv3
,id
=str
,src
=srcaddr
,dst
=dstaddr
[,srcport
=srcport
][,dstport
=dstport
]\n"
2747 " [,rxsession
=rxsession
],txsession
=txsession
[,ipv6
=on|off
][,udp
=on|off
]\n"
2748 " [,cookie64
=on|off
][,counter
][,pincounter
][,txcookie
=txcookie
]\n"
2749 " [,rxcookie
=rxcookie
][,offset
=offset
]\n"
2750 " configure a network backend with ID
'str' connected to
\n"
2751 " an Ethernet over L2TPv3 pseudowire
.\n"
2752 " Linux kernel
3.3+ as well as most routers can talk
\n"
2753 " L2TPv3
. This transport allows connecting a VM to a VM
,\n"
2754 " VM to a router and even VM to Host
. It is a nearly
-universal
\n"
2755 " standard (RFC3931
). Note
- this implementation uses
static\n"
2756 " pre
-configured
tunnels (same as the Linux kernel
).\n"
2757 " use
'src=' to specify source address
\n"
2758 " use
'dst=' to specify destination address
\n"
2759 " use
'udp=on' to specify udp encapsulation
\n"
2760 " use
'srcport=' to specify source udp port
\n"
2761 " use
'dstport=' to specify destination udp port
\n"
2762 " use
'ipv6=on' to force v6
\n"
2763 " L2TPv3 uses cookies to prevent misconfiguration as
\n"
2764 " well as a weak security measure
\n"
2765 " use
'rxcookie=0x012345678' to specify a rxcookie
\n"
2766 " use
'txcookie=0x012345678' to specify a txcookie
\n"
2767 " use
'cookie64=on' to set cookie size to
64 bit
, otherwise
32\n"
2768 " use
'counter=off' to force a
'cut-down' L2TPv3 with no counter
\n"
2769 " use
'pincounter=on' to work around broken counter handling
in peer
\n"
2770 " use
'offset=X' to add an extra offset between header and data
\n"
2772 "-netdev socket
,id
=str
[,fd
=h
][,listen
=[host
]:port
][,connect
=host
:port
]\n"
2773 " configure a network backend to connect to another network
\n"
2774 " using a socket connection
\n"
2775 "-netdev socket
,id
=str
[,fd
=h
][,mcast
=maddr
:port
[,localaddr
=addr
]]\n"
2776 " configure a network backend to connect to a multicast maddr and port
\n"
2777 " use
'localaddr=addr' to specify the host address to send packets from
\n"
2778 "-netdev socket
,id
=str
[,fd
=h
][,udp
=host
:port
][,localaddr
=host
:port
]\n"
2779 " configure a network backend to connect to another network
\n"
2780 " using an UDP tunnel
\n"
2782 "-netdev vde
,id
=str
[,sock
=socketpath
][,port
=n
][,group
=groupname
][,mode
=octalmode
]\n"
2783 " configure a network backend to connect to port
'n' of a vde
switch\n"
2784 " running on host and listening
for incoming connections on
'socketpath'.\n"
2785 " Use group
'groupname' and mode
'octalmode' to change
default\n"
2786 " ownership and permissions
for communication port
.\n"
2788 #ifdef CONFIG_NETMAP
2789 "-netdev netmap
,id
=str
,ifname
=name
[,devname
=nmname
]\n"
2790 " attach to the existing netmap
-enabled network
interface 'name', or to a
\n"
2791 " VALE
port (created on the fly
) called
'name' ('nmname' is name of the
\n"
2792 " netmap device
, defaults to
'/dev/netmap')\n"
2795 "-netdev vhost
-user
,id
=str
,chardev
=dev
[,vhostforce
=on|off
]\n"
2796 " configure a vhost
-user network
, backed by a chardev
'dev'\n"
2799 "-netdev vhost
-vdpa
,id
=str
,vhostdev
=/path
/to
/dev
\n"
2800 " configure a vhost
-vdpa network
,Establish a vhost
-vdpa netdev
\n"
2802 "-netdev hubport
,id
=str
,hubid
=n
[,netdev
=nd
]\n"
2803 " configure a hub port on the hub with ID
'n'\n", QEMU_ARCH_ALL)
2804 DEF("nic
", HAS_ARG, QEMU_OPTION_nic,
2815 #ifdef CONFIG_NETMAP
2821 "socket
][,option
][,...][mac
=macaddr
]\n"
2822 " initialize an on
-board
/ default host
NIC (using MAC address
\n"
2823 " macaddr
) and connect it to the given host network backend
\n"
2824 "-nic none use it alone to have zero network
devices (the
default is to
\n"
2825 " provided a
'user' network connection
)\n",
2827 DEF("net
", HAS_ARG, QEMU_OPTION_net,
2828 "-net nic
[,macaddr
=mac
][,model
=type
][,name
=str
][,addr
=str
][,vectors
=v
]\n"
2829 " configure or create an on
-board (or machine
default) NIC and
\n"
2830 " connect it to hub
0 (please use
-nic unless you need a hub
)\n"
2840 #ifdef CONFIG_NETMAP
2843 "socket
][,option
][,option
][,...]\n"
2844 " old way to initialize a host network
interface\n"
2845 " (use the
-netdev option
if possible instead
)\n", QEMU_ARCH_ALL)
2847 ``-nic [tap|bridge|user|l2tpv3|vde|netmap|vhost-user|socket][,...][,mac=macaddr][,model=mn]``
2848 This option is a shortcut for configuring both the on-board
2849 (default) guest NIC hardware and the host network backend in one go.
2850 The host backend options are the same as with the corresponding
2851 ``-netdev`` options below. The guest NIC model can be set with
2852 ``model=modelname``. Use ``model=help`` to list the available device
2853 types. The hardware MAC address can be set with ``mac=macaddr``.
2855 The following two example do exactly the same, to show how ``-nic``
2856 can be used to shorten the command line length:
2860 |qemu_system| -netdev user,id=n1,ipv6=off -device e1000,netdev=n1,mac=52:54:98:76:54:32
2861 |qemu_system| -nic user,ipv6=off,model=e1000,mac=52:54:98:76:54:32
2864 Indicate that no network devices should be configured. It is used to
2865 override the default configuration (default NIC with "user
" host
2866 network backend) which is activated if no other networking options
2869 ``-netdev user,id=id[,option][,option][,...]``
2870 Configure user mode host network backend which requires no
2871 administrator privilege to run. Valid options are:
2874 Assign symbolic name for use in monitor commands.
2876 ``ipv4=on|off and ipv6=on|off``
2877 Specify that either IPv4 or IPv6 must be enabled. If neither is
2878 specified both protocols are enabled.
2881 Set IP network address the guest will see. Optionally specify
2882 the netmask, either in the form a.b.c.d or as number of valid
2883 top-most bits. Default is 10.0.2.0/24.
2886 Specify the guest-visible address of the host. Default is the
2887 2nd IP in the guest network, i.e. x.x.x.2.
2889 ``ipv6-net=addr[/int]``
2890 Set IPv6 network address the guest will see (default is
2891 fec0::/64). The network prefix is given in the usual hexadecimal
2892 IPv6 address notation. The prefix size is optional, and is given
2893 as the number of valid top-most bits (default is 64).
2896 Specify the guest-visible IPv6 address of the host. Default is
2897 the 2nd IPv6 in the guest network, i.e. xxxx::2.
2900 If this option is enabled, the guest will be isolated, i.e. it
2901 will not be able to contact the host and no guest IP packets
2902 will be routed over the host to the outside. This option does
2903 not affect any explicitly set forwarding rules.
2906 Specifies the client hostname reported by the built-in DHCP
2910 Specify the first of the 16 IPs the built-in DHCP server can
2911 assign. Default is the 15th to 31st IP in the guest network,
2912 i.e. x.x.x.15 to x.x.x.31.
2915 Specify the guest-visible address of the virtual nameserver. The
2916 address must be different from the host address. Default is the
2917 3rd IP in the guest network, i.e. x.x.x.3.
2920 Specify the guest-visible address of the IPv6 virtual
2921 nameserver. The address must be different from the host address.
2922 Default is the 3rd IP in the guest network, i.e. xxxx::3.
2924 ``dnssearch=domain``
2925 Provides an entry for the domain-search list sent by the
2926 built-in DHCP server. More than one domain suffix can be
2927 transmitted by specifying this option multiple times. If
2928 supported, this will cause the guest to automatically try to
2929 append the given domain suffix(es) in case a domain name can not
2936 |qemu_system| -nic user,dnssearch=mgmt.example.org,dnssearch=example.org
2938 ``domainname=domain``
2939 Specifies the client domain name reported by the built-in DHCP
2943 When using the user mode network stack, activate a built-in TFTP
2944 server. The files in dir will be exposed as the root of a TFTP
2945 server. The TFTP client on the guest must be configured in
2946 binary mode (use the command ``bin`` of the Unix TFTP client).
2948 ``tftp-server-name=name``
2949 In BOOTP reply, broadcast name as the "TFTP server name
"
2950 (RFC2132 option 66). This can be used to advise the guest to
2951 load boot files or configurations from a different server than
2955 When using the user mode network stack, broadcast file as the
2956 BOOTP filename. In conjunction with ``tftp``, this can be used
2957 to network boot a guest from a local directory.
2959 Example (using pxelinux):
2963 |qemu_system| -hda linux.img -boot n -device e1000,netdev=n1 \\
2964 -netdev user,id=n1,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
2966 ``smb=dir[,smbserver=addr]``
2967 When using the user mode network stack, activate a built-in SMB
2968 server so that Windows OSes can access to the host files in
2969 ``dir`` transparently. The IP address of the SMB server can be
2970 set to addr. By default the 4th IP in the guest network is used,
2973 In the guest Windows OS, the line:
2979 must be added in the file ``C:\WINDOWS\LMHOSTS`` (for windows
2980 9x/Me) or ``C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS`` (Windows
2983 Then ``dir`` can be accessed in ``\\smbserver\qemu``.
2985 Note that a SAMBA server must be installed on the host OS.
2987 ``hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport``
2988 Redirect incoming TCP or UDP connections to the host port
2989 hostport to the guest IP address guestaddr on guest port
2990 guestport. If guestaddr is not specified, its value is x.x.x.15
2991 (default first address given by the built-in DHCP server). By
2992 specifying hostaddr, the rule can be bound to a specific host
2993 interface. If no connection type is set, TCP is used. This
2994 option can be given multiple times.
2996 For example, to redirect host X11 connection from screen 1 to
2997 guest screen 0, use the following:
3002 |qemu_system| -nic user,hostfwd=tcp:127.0.0.1:6001-:6000
3003 # this host xterm should open in the guest X11 server
3006 To redirect telnet connections from host port 5555 to telnet
3007 port on the guest, use the following:
3012 |qemu_system| -nic user,hostfwd=tcp::5555-:23
3013 telnet localhost 5555
3015 Then when you use on the host ``telnet localhost 5555``, you
3016 connect to the guest telnet server.
3018 ``guestfwd=[tcp]:server:port-dev``; \ ``guestfwd=[tcp]:server:port-cmd:command``
3019 Forward guest TCP connections to the IP address server on port
3020 port to the character device dev or to a program executed by
3021 cmd:command which gets spawned for each connection. This option
3022 can be given multiple times.
3024 You can either use a chardev directly and have that one used
3025 throughout QEMU's lifetime, like in the following example:
3029 # open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
3030 # the guest accesses it
3031 |qemu_system| -nic user,guestfwd=tcp:10.0.2.100:1234-tcp:10.10.1.1:4321
3033 Or you can execute a command on every TCP connection established
3034 by the guest, so that QEMU behaves similar to an inetd process
3035 for that virtual server:
3039 # call "netcat
10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
3040 # and connect the TCP stream to its stdin/stdout
3041 |qemu_system| -nic 'user,id=n1,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'
3043 ``-netdev tap,id=id[,fd=h][,ifname=name][,script=file][,downscript=dfile][,br=bridge][,helper=helper]``
3044 Configure a host TAP network backend with ID id.
3046 Use the network script file to configure it and the network script
3047 dfile to deconfigure it. If name is not provided, the OS
3048 automatically provides one. The default network configure script is
3049 ``/etc/qemu-ifup`` and the default network deconfigure script is
3050 ``/etc/qemu-ifdown``. Use ``script=no`` or ``downscript=no`` to
3051 disable script execution.
3053 If running QEMU as an unprivileged user, use the network helper
3054 to configure the TAP interface and attach it to the bridge.
3055 The default network helper executable is
3056 ``/path/to/qemu-bridge-helper`` and the default bridge device is
3059 ``fd``\ =h can be used to specify the handle of an already opened
3066 #launch a QEMU instance with the default network script
3067 |qemu_system| linux.img -nic tap
3071 #launch a QEMU instance with two NICs, each one connected
3073 |qemu_system| linux.img \\
3074 -netdev tap,id=nd0,ifname=tap0 -device e1000,netdev=nd0 \\
3075 -netdev tap,id=nd1,ifname=tap1 -device rtl8139,netdev=nd1
3079 #launch a QEMU instance with the default network helper to
3080 #connect a TAP device to bridge br0
3081 |qemu_system| linux.img -device virtio-net-pci,netdev=n1 \\
3082 -netdev tap,id=n1,"helper
=/path
/to
/qemu
-bridge
-helper
"
3084 ``-netdev bridge,id=id[,br=bridge][,helper=helper]``
3085 Connect a host TAP network interface to a host bridge device.
3087 Use the network helper helper to configure the TAP interface and
3088 attach it to the bridge. The default network helper executable is
3089 ``/path/to/qemu-bridge-helper`` and the default bridge device is
3096 #launch a QEMU instance with the default network helper to
3097 #connect a TAP device to bridge br0
3098 |qemu_system| linux.img -netdev bridge,id=n1 -device virtio-net,netdev=n1
3102 #launch a QEMU instance with the default network helper to
3103 #connect a TAP device to bridge qemubr0
3104 |qemu_system| linux.img -netdev bridge,br=qemubr0,id=n1 -device virtio-net,netdev=n1
3106 ``-netdev socket,id=id[,fd=h][,listen=[host]:port][,connect=host:port]``
3107 This host network backend can be used to connect the guest's network
3108 to another QEMU virtual machine using a TCP socket connection. If
3109 ``listen`` is specified, QEMU waits for incoming connections on port
3110 (host is optional). ``connect`` is used to connect to another QEMU
3111 instance using the ``listen`` option. ``fd``\ =h specifies an
3112 already opened TCP socket.
3118 # launch a first QEMU instance
3119 |qemu_system| linux.img \\
3120 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \\
3121 -netdev socket,id=n1,listen=:1234
3122 # connect the network of this instance to the network of the first instance
3123 |qemu_system| linux.img \\
3124 -device e1000,netdev=n2,mac=52:54:00:12:34:57 \\
3125 -netdev socket,id=n2,connect=127.0.0.1:1234
3127 ``-netdev socket,id=id[,fd=h][,mcast=maddr:port[,localaddr=addr]]``
3128 Configure a socket host network backend to share the guest's network
3129 traffic with another QEMU virtual machines using a UDP multicast
3130 socket, effectively making a bus for every QEMU with same multicast
3131 address maddr and port. NOTES:
3133 1. Several QEMU can be running on different hosts and share same bus
3134 (assuming correct multicast setup for these hosts).
3136 2. mcast support is compatible with User Mode Linux (argument
3137 ``ethN=mcast``), see http://user-mode-linux.sf.net.
3139 3. Use ``fd=h`` to specify an already opened UDP multicast socket.
3145 # launch one QEMU instance
3146 |qemu_system| linux.img \\
3147 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \\
3148 -netdev socket,id=n1,mcast=230.0.0.1:1234
3149 # launch another QEMU instance on same "bus
"
3150 |qemu_system| linux.img \\
3151 -device e1000,netdev=n2,mac=52:54:00:12:34:57 \\
3152 -netdev socket,id=n2,mcast=230.0.0.1:1234
3153 # launch yet another QEMU instance on same "bus
"
3154 |qemu_system| linux.img \\
3155 -device e1000,netdev=n3,mac=52:54:00:12:34:58 \\
3156 -netdev socket,id=n3,mcast=230.0.0.1:1234
3158 Example (User Mode Linux compat.):
3162 # launch QEMU instance (note mcast address selected is UML's default)
3163 |qemu_system| linux.img \\
3164 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \\
3165 -netdev socket,id=n1,mcast=239.192.168.1:1102
3167 /path/to/linux ubd0=/path/to/root_fs eth0=mcast
3169 Example (send packets from host's 1.2.3.4):
3173 |qemu_system| linux.img \\
3174 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \\
3175 -netdev socket,id=n1,mcast=239.192.168.1:1102,localaddr=1.2.3.4
3177 ``-netdev l2tpv3,id=id,src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6=on|off][,udp=on|off][,cookie64][,counter][,pincounter][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset]``
3178 Configure a L2TPv3 pseudowire host network backend. L2TPv3 (RFC3931)
3179 is a popular protocol to transport Ethernet (and other Layer 2) data
3180 frames between two systems. It is present in routers, firewalls and
3181 the Linux kernel (from version 3.3 onwards).
3183 This transport allows a VM to communicate to another VM, router or
3187 source address (mandatory)
3190 destination address (mandatory)
3193 select udp encapsulation (default is ip).
3199 destination udp port.
3202 force v6, otherwise defaults to v4.
3204 ``rxcookie=rxcookie``; \ ``txcookie=txcookie``
3205 Cookies are a weak form of security in the l2tpv3 specification.
3206 Their function is mostly to prevent misconfiguration. By default
3210 Set cookie size to 64 bit instead of the default 32
3213 Force a 'cut-down' L2TPv3 with no counter as in
3214 draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00
3217 Work around broken counter handling in peer. This may also help
3218 on networks which have packet reorder.
3221 Add an extra offset between header and data
3223 For example, to attach a VM running on host 4.3.2.1 via L2TPv3 to
3224 the bridge br-lan on the remote Linux host 1.2.3.4:
3228 # Setup tunnel on linux host using raw ip as encapsulation
3230 ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \\
3231 encap udp udp_sport 16384 udp_dport 16384
3232 ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \\
3233 0xFFFFFFFF peer_session_id 0xFFFFFFFF
3234 ifconfig vmtunnel0 mtu 1500
3235 ifconfig vmtunnel0 up
3236 brctl addif br-lan vmtunnel0
3240 # launch QEMU instance - if your network has reorder or is very lossy add ,pincounter
3242 |qemu_system| linux.img -device e1000,netdev=n1 \\
3243 -netdev l2tpv3,id=n1,src=4.2.3.1,dst=1.2.3.4,udp,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter
3245 ``-netdev vde,id=id[,sock=socketpath][,port=n][,group=groupname][,mode=octalmode]``
3246 Configure VDE backend to connect to PORT n of a vde switch running
3247 on host and listening for incoming connections on socketpath. Use
3248 GROUP groupname and MODE octalmode to change default ownership and
3249 permissions for communication port. This option is only available if
3250 QEMU has been compiled with vde support enabled.
3257 vde_switch -F -sock /tmp/myswitch
3258 # launch QEMU instance
3259 |qemu_system| linux.img -nic vde,sock=/tmp/myswitch
3261 ``-netdev vhost-user,chardev=id[,vhostforce=on|off][,queues=n]``
3262 Establish a vhost-user netdev, backed by a chardev id. The chardev
3263 should be a unix domain socket backed one. The vhost-user uses a
3264 specifically defined protocol to pass vhost ioctl replacement
3265 messages to an application on the other end of the socket. On
3266 non-MSIX guests, the feature can be forced with vhostforce. Use
3267 'queues=n' to specify the number of queues to be created for
3268 multiqueue vhost-user.
3274 qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \
3275 -numa node,memdev=mem \
3276 -chardev socket,id=chr0,path=/path/to/socket \
3277 -netdev type=vhost-user,id=net0,chardev=chr0 \
3278 -device virtio-net-pci,netdev=net0
3280 ``-netdev vhost-vdpa,vhostdev=/path/to/dev``
3281 Establish a vhost-vdpa netdev.
3283 vDPA device is a device that uses a datapath which complies with
3284 the virtio specifications with a vendor specific control path.
3285 vDPA devices can be both physically located on the hardware or
3286 emulated by software.
3288 ``-netdev hubport,id=id,hubid=hubid[,netdev=nd]``
3289 Create a hub port on the emulated hub with ID hubid.
3291 The hubport netdev lets you connect a NIC to a QEMU emulated hub
3292 instead of a single netdev. Alternatively, you can also connect the
3293 hubport to another netdev with ID nd by using the ``netdev=nd``
3296 ``-net nic[,netdev=nd][,macaddr=mac][,model=type] [,name=name][,addr=addr][,vectors=v]``
3297 Legacy option to configure or create an on-board (or machine
3298 default) Network Interface Card(NIC) and connect it either to the
3299 emulated hub with ID 0 (i.e. the default hub), or to the netdev nd.
3300 If model is omitted, then the default NIC model associated with the
3301 machine type is used. Note that the default NIC model may change in
3302 future QEMU releases, so it is highly recommended to always specify
3303 a model. Optionally, the MAC address can be changed to mac, the
3304 device address set to addr (PCI cards only), and a name can be
3305 assigned for use in monitor commands. Optionally, for PCI cards, you
3306 can specify the number v of MSI-X vectors that the card should have;
3307 this option currently only affects virtio cards; set v = 0 to
3308 disable MSI-X. If no ``-net`` option is specified, a single NIC is
3309 created. QEMU can emulate several different models of network card.
3310 Use ``-net nic,model=help`` for a list of available devices for your
3313 ``-net user|tap|bridge|socket|l2tpv3|vde[,...][,name=name]``
3314 Configure a host network backend (with the options corresponding to
3315 the same ``-netdev`` option) and connect it to the emulated hub 0
3316 (the default hub). Use name to specify the name of the hub port.
3321 DEFHEADING(Character device options:)
3323 DEF("chardev
", HAS_ARG, QEMU_OPTION_chardev,
3325 "-chardev
null,id
=id
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3326 "-chardev socket
,id
=id
[,host
=host
],port
=port
[,to
=to
][,ipv4
=on|off
][,ipv6
=on|off
][,nodelay
=on|off
]\n"
3327 " [,server
=on|off
][,wait
=on|off
][,telnet
=on|off
][,websocket
=on|off
][,reconnect
=seconds
][,mux
=on|off
]\n"
3328 " [,logfile
=PATH
][,logappend
=on|off
][,tls
-creds
=ID
][,tls
-authz
=ID
] (tcp
)\n"
3329 "-chardev socket
,id
=id
,path
=path
[,server
=on|off
][,wait
=on|off
][,telnet
=on|off
][,websocket
=on|off
][,reconnect
=seconds
]\n"
3330 " [,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
][,abstract
=on|off
][,tight
=on|off
] (unix
)\n"
3331 "-chardev udp
,id
=id
[,host
=host
],port
=port
[,localaddr
=localaddr
]\n"
3332 " [,localport
=localport
][,ipv4
=on|off
][,ipv6
=on|off
][,mux
=on|off
]\n"
3333 " [,logfile
=PATH
][,logappend
=on|off
]\n"
3334 "-chardev msmouse
,id
=id
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3335 "-chardev vc
,id
=id
[[,width
=width
][,height
=height
]][[,cols
=cols
][,rows
=rows
]]\n"
3336 " [,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3337 "-chardev ringbuf
,id
=id
[,size
=size
][,logfile
=PATH
][,logappend
=on|off
]\n"
3338 "-chardev file
,id
=id
,path
=path
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3339 "-chardev pipe
,id
=id
,path
=path
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3341 "-chardev console
,id
=id
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3342 "-chardev serial
,id
=id
,path
=path
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3344 "-chardev pty
,id
=id
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3345 "-chardev stdio
,id
=id
[,mux
=on|off
][,signal
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3347 #ifdef CONFIG_BRLAPI
3348 "-chardev braille
,id
=id
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3350 #if defined(__linux__) || defined(__sun__) || defined(__FreeBSD__) \
3351 || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
3352 "-chardev serial
,id
=id
,path
=path
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3353 "-chardev tty
,id
=id
,path
=path
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3355 #if defined(__linux__) || defined(__FreeBSD__) || defined(__DragonFly__)
3356 "-chardev parallel
,id
=id
,path
=path
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3357 "-chardev parport
,id
=id
,path
=path
[,mux
=on|off
][,logfile
=PATH
][,logappend
=on|off
]\n"
3359 #if defined(CONFIG_SPICE)
3360 "-chardev spicevmc
,id
=id
,name
=name
[,debug
=debug
][,logfile
=PATH
][,logappend
=on|off
]\n"
3361 "-chardev spiceport
,id
=id
,name
=name
[,debug
=debug
][,logfile
=PATH
][,logappend
=on|off
]\n"
3367 The general form of a character device option is:
3369 ``-chardev backend,id=id[,mux=on|off][,options]``
3370 Backend is one of: ``null``, ``socket``, ``udp``, ``msmouse``,
3371 ``vc``, ``ringbuf``, ``file``, ``pipe``, ``console``, ``serial``,
3372 ``pty``, ``stdio``, ``braille``, ``tty``, ``parallel``, ``parport``,
3373 ``spicevmc``, ``spiceport``. The specific backend will determine the
3376 Use ``-chardev help`` to print all available chardev backend types.
3378 All devices must have an id, which can be any string up to 127
3379 characters long. It is used to uniquely identify this device in
3380 other command line directives.
3382 A character device may be used in multiplexing mode by multiple
3383 front-ends. Specify ``mux=on`` to enable this mode. A multiplexer is
3384 a "1:N
" device, and here the "1" end is your specified chardev
3385 backend, and the "N
" end is the various parts of QEMU that can talk
3386 to a chardev. If you create a chardev with ``id=myid`` and
3387 ``mux=on``, QEMU will create a multiplexer with your specified ID,
3388 and you can then configure multiple front ends to use that chardev
3389 ID for their input/output. Up to four different front ends can be
3390 connected to a single multiplexed chardev. (Without multiplexing
3391 enabled, a chardev can only be used by a single front end.) For
3392 instance you could use this to allow a single stdio chardev to be
3393 used by two serial ports and the QEMU monitor:
3397 -chardev stdio,mux=on,id=char0 \
3398 -mon chardev=char0,mode=readline \
3399 -serial chardev:char0 \
3400 -serial chardev:char0
3402 You can have more than one multiplexer in a system configuration;
3403 for instance you could have a TCP port multiplexed between UART 0
3404 and UART 1, and stdio multiplexed between the QEMU monitor and a
3409 -chardev stdio,mux=on,id=char0 \
3410 -mon chardev=char0,mode=readline \
3411 -parallel chardev:char0 \
3412 -chardev tcp,...,mux=on,id=char1 \
3413 -serial chardev:char1 \
3414 -serial chardev:char1
3416 When you're using a multiplexed character device, some escape
3417 sequences are interpreted in the input. See the chapter about
3418 :ref:`keys in the character backend multiplexer` in the
3419 System Emulation Users Guide for more details.
3421 Note that some other command line options may implicitly create
3422 multiplexed character backends; for instance ``-serial mon:stdio``
3423 creates a multiplexed stdio backend connected to the serial port and
3424 the QEMU monitor, and ``-nographic`` also multiplexes the console
3425 and the monitor to stdio.
3427 There is currently no support for multiplexing in the other
3428 direction (where a single QEMU front end takes input and output from
3431 Every backend supports the ``logfile`` option, which supplies the
3432 path to a file to record all data transmitted via the backend. The
3433 ``logappend`` option controls whether the log file will be truncated
3434 or appended to when opened.
3436 The available backends are:
3438 ``-chardev null,id=id``
3439 A void device. This device will not emit any data, and will drop any
3440 data it receives. The null backend does not take any options.
3442 ``-chardev socket,id=id[,TCP options or unix options][,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect=seconds][,tls-creds=id][,tls-authz=id]``
3443 Create a two-way stream socket, which can be either a TCP or a unix
3444 socket. A unix socket will be created if ``path`` is specified.
3445 Behaviour is undefined if TCP options are specified for a unix
3448 ``server=on|off`` specifies that the socket shall be a listening socket.
3450 ``wait=on|off`` specifies that QEMU should not block waiting for a client
3451 to connect to a listening socket.
3453 ``telnet=on|off`` specifies that traffic on the socket should interpret
3454 telnet escape sequences.
3456 ``websocket=on|off`` specifies that the socket uses WebSocket protocol for
3459 ``reconnect`` sets the timeout for reconnecting on non-server
3460 sockets when the remote end goes away. qemu will delay this many
3461 seconds and then attempt to reconnect. Zero disables reconnecting,
3464 ``tls-creds`` requests enablement of the TLS protocol for
3465 encryption, and specifies the id of the TLS credentials to use for
3466 the handshake. The credentials must be previously created with the
3467 ``-object tls-creds`` argument.
3469 ``tls-auth`` provides the ID of the QAuthZ authorization object
3470 against which the client's x509 distinguished name will be
3471 validated. This object is only resolved at time of use, so can be
3472 deleted and recreated on the fly while the chardev server is active.
3473 If missing, it will default to denying access.
3475 TCP and unix socket options are given below:
3477 ``TCP options: port=port[,host=host][,to=to][,ipv4=on|off][,ipv6=on|off][,nodelay=on|off]``
3478 ``host`` for a listening socket specifies the local address to
3479 be bound. For a connecting socket species the remote host to
3480 connect to. ``host`` is optional for listening sockets. If not
3481 specified it defaults to ``0.0.0.0``.
3483 ``port`` for a listening socket specifies the local port to be
3484 bound. For a connecting socket specifies the port on the remote
3485 host to connect to. ``port`` can be given as either a port
3486 number or a service name. ``port`` is required.
3488 ``to`` is only relevant to listening sockets. If it is
3489 specified, and ``port`` cannot be bound, QEMU will attempt to
3490 bind to subsequent ports up to and including ``to`` until it
3491 succeeds. ``to`` must be specified as a port number.
3493 ``ipv4=on|off`` and ``ipv6=on|off`` specify that either IPv4
3494 or IPv6 must be used. If neither is specified the socket may
3495 use either protocol.
3497 ``nodelay=on|off`` disables the Nagle algorithm.
3499 ``unix options: path=path[,abstract=on|off][,tight=on|off]``
3500 ``path`` specifies the local path of the unix socket. ``path``
3502 ``abstract=on|off`` specifies the use of the abstract socket namespace,
3503 rather than the filesystem. Optional, defaults to false.
3504 ``tight=on|off`` sets the socket length of abstract sockets to their minimum,
3505 rather than the full sun_path length. Optional, defaults to true.
3507 ``-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr][,localport=localport][,ipv4=on|off][,ipv6=on|off]``
3508 Sends all traffic from the guest to a remote host over UDP.
3510 ``host`` specifies the remote host to connect to. If not specified
3511 it defaults to ``localhost``.
3513 ``port`` specifies the port on the remote host to connect to.
3514 ``port`` is required.
3516 ``localaddr`` specifies the local address to bind to. If not
3517 specified it defaults to ``0.0.0.0``.
3519 ``localport`` specifies the local port to bind to. If not specified
3520 any available local port will be used.
3522 ``ipv4=on|off`` and ``ipv6=on|off`` specify that either IPv4 or IPv6 must be used.
3523 If neither is specified the device may use either protocol.
3525 ``-chardev msmouse,id=id``
3526 Forward QEMU's emulated msmouse events to the guest. ``msmouse``
3527 does not take any options.
3529 ``-chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]``
3530 Connect to a QEMU text console. ``vc`` may optionally be given a
3533 ``width`` and ``height`` specify the width and height respectively
3534 of the console, in pixels.
3536 ``cols`` and ``rows`` specify that the console be sized to fit a
3537 text console with the given dimensions.
3539 ``-chardev ringbuf,id=id[,size=size]``
3540 Create a ring buffer with fixed size ``size``. size must be a power
3541 of two and defaults to ``64K``.
3543 ``-chardev file,id=id,path=path``
3544 Log all traffic received from the guest to a file.
3546 ``path`` specifies the path of the file to be opened. This file will
3547 be created if it does not already exist, and overwritten if it does.
3548 ``path`` is required.
3550 ``-chardev pipe,id=id,path=path``
3551 Create a two-way connection to the guest. The behaviour differs
3552 slightly between Windows hosts and other hosts:
3554 On Windows, a single duplex pipe will be created at
3557 On other hosts, 2 pipes will be created called ``path.in`` and
3558 ``path.out``. Data written to ``path.in`` will be received by the
3559 guest. Data written by the guest can be read from ``path.out``. QEMU
3560 will not create these fifos, and requires them to be present.
3562 ``path`` forms part of the pipe path as described above. ``path`` is
3565 ``-chardev console,id=id``
3566 Send traffic from the guest to QEMU's standard output. ``console``
3567 does not take any options.
3569 ``console`` is only available on Windows hosts.
3571 ``-chardev serial,id=id,path=path``
3572 Send traffic from the guest to a serial device on the host.
3574 On Unix hosts serial will actually accept any tty device, not only
3577 ``path`` specifies the name of the serial device to open.
3579 ``-chardev pty,id=id``
3580 Create a new pseudo-terminal on the host and connect to it. ``pty``
3581 does not take any options.
3583 ``pty`` is not available on Windows hosts.
3585 ``-chardev stdio,id=id[,signal=on|off]``
3586 Connect to standard input and standard output of the QEMU process.
3588 ``signal`` controls if signals are enabled on the terminal, that
3589 includes exiting QEMU with the key sequence Control-c. This option
3590 is enabled by default, use ``signal=off`` to disable it.
3592 ``-chardev braille,id=id``
3593 Connect to a local BrlAPI server. ``braille`` does not take any
3596 ``-chardev tty,id=id,path=path``
3597 ``tty`` is only available on Linux, Sun, FreeBSD, NetBSD, OpenBSD
3598 and DragonFlyBSD hosts. It is an alias for ``serial``.
3600 ``path`` specifies the path to the tty. ``path`` is required.
3602 ``-chardev parallel,id=id,path=path``
3604 ``-chardev parport,id=id,path=path``
3605 ``parallel`` is only available on Linux, FreeBSD and DragonFlyBSD
3608 Connect to a local parallel port.
3610 ``path`` specifies the path to the parallel port device. ``path`` is
3613 ``-chardev spicevmc,id=id,debug=debug,name=name``
3614 ``spicevmc`` is only available when spice support is built in.
3616 ``debug`` debug level for spicevmc
3618 ``name`` name of spice channel to connect to
3620 Connect to a spice virtual machine channel, such as vdiport.
3622 ``-chardev spiceport,id=id,debug=debug,name=name``
3623 ``spiceport`` is only available when spice support is built in.
3625 ``debug`` debug level for spicevmc
3627 ``name`` name of spice port to connect to
3629 Connect to a spice port, allowing a Spice client to handle the
3630 traffic identified by a name (preferably a fqdn).
3636 DEFHEADING(TPM device options:)
3638 DEF("tpmdev
", HAS_ARG, QEMU_OPTION_tpmdev, \
3639 "-tpmdev passthrough
,id
=id
[,path
=path
][,cancel
-path
=path
]\n"
3640 " use path to provide path to a character device
; default is
/dev
/tpm0
\n"
3641 " use cancel
-path to provide path to TPM
's cancel sysfs entry; if\n"
3642 " not provided it will be searched for in /sys/class/misc/tpm?/device\n"
3643 "-tpmdev emulator,id=id,chardev=dev\n"
3644 " configure the TPM device using chardev backend\n",
3647 The general form of a TPM device option is:
3649 ``-tpmdev backend,id=id[,options]``
3650 The specific backend type will determine the applicable options. The
3651 ``-tpmdev`` option creates the TPM backend and requires a
3652 ``-device`` option that specifies the TPM frontend interface model.
3654 Use ``-tpmdev help`` to print all available TPM backend types.
3656 The available backends are:
3658 ``-tpmdev passthrough,id=id,path=path,cancel-path=cancel-path``
3659 (Linux-host only) Enable access to the host's TPM
using the
3662 ``path`` specifies the path to the host
's TPM device, i.e., on a
3663 Linux host this would be ``/dev/tpm0``. ``path`` is optional and by
3664 default ``/dev/tpm0`` is used.
3666 ``cancel-path`` specifies the path to the host TPM device's sysfs
3667 entry allowing
for cancellation of an ongoing TPM command
.
3668 ``cancel
-path`` is optional and by
default QEMU will search
for the
3671 Some notes about
using the host
's TPM with the passthrough driver:
3673 The TPM device accessed by the passthrough driver must not be used
3674 by any other application on the host.
3676 Since the host's
firmware (BIOS
/UEFI
) has already initialized the
3677 TPM
, the VM
's firmware (BIOS/UEFI) will not be able to initialize
3678 the TPM again and may therefore not show a TPM-specific menu that
3679 would otherwise allow the user to configure the TPM, e.g., allow the
3680 user to enable/disable or activate/deactivate the TPM. Further, if
3681 TPM ownership is released from within a VM then the host's TPM will
3682 get disabled and deactivated
. To enable and activate the TPM again
3683 afterwards
, the host has to be rebooted and the user is required to
3684 enter the firmware
's menu to enable and activate the TPM. If the TPM
3685 is left disabled and/or deactivated most TPM commands will fail.
3687 To create a passthrough TPM use the following two options:
3691 -tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0
3693 Note that the ``-tpmdev`` id is ``tpm0`` and is referenced by
3694 ``tpmdev=tpm0`` in the device option.
3696 ``-tpmdev emulator,id=id,chardev=dev``
3697 (Linux-host only) Enable access to a TPM emulator using Unix domain
3698 socket based chardev backend.
3700 ``chardev`` specifies the unique ID of a character device backend
3701 that provides connection to the software TPM server.
3703 To create a TPM emulator backend device with chardev socket backend:
3707 -chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0
3714 DEFHEADING(Linux/Multiboot boot specific:)
3716 When using these options, you can use a given Linux or Multiboot kernel
3717 without installing it in the disk image. It can be useful for easier
3718 testing of various kernels.
3723 DEF("kernel", HAS_ARG, QEMU_OPTION_kernel, \
3724 "-kernel bzImage use 'bzImage
' as kernel image\n", QEMU_ARCH_ALL)
3727 Use bzImage as kernel image. The kernel can be either a Linux kernel
3728 or in multiboot format.
3731 DEF("append", HAS_ARG, QEMU_OPTION_append, \
3732 "-append cmdline use 'cmdline
' as kernel command line\n", QEMU_ARCH_ALL)
3735 Use cmdline as kernel command line
3738 DEF("initrd", HAS_ARG, QEMU_OPTION_initrd, \
3739 "-initrd file use 'file
' as initial ram disk\n", QEMU_ARCH_ALL)
3742 Use file as initial ram disk.
3744 ``-initrd "file1 arg=foo,file2"``
3745 This syntax is only available with multiboot.
3747 Use file1 and file2 as modules and pass arg=foo as parameter to the
3751 DEF("dtb", HAS_ARG, QEMU_OPTION_dtb, \
3752 "-dtb file use 'file
' as device tree image\n", QEMU_ARCH_ALL)
3755 Use file as a device tree binary (dtb) image and pass it to the
3761 DEFHEADING(Debug/Expert options:)
3763 DEF("compat", HAS_ARG, QEMU_OPTION_compat,
3764 "-compat [deprecated-input=accept|reject|crash][,deprecated-output=accept|hide]\n"
3765 " Policy for handling deprecated management interfaces\n"
3766 "-compat [unstable-input=accept|reject|crash][,unstable-output=accept|hide]\n"
3767 " Policy for handling unstable management interfaces\n",
3770 ``-compat [deprecated-input=@var{input-policy}][,deprecated-output=@var{output-policy}]``
3771 Set policy for handling deprecated management interfaces (experimental):
3773 ``deprecated-input=accept`` (default)
3774 Accept deprecated commands and arguments
3775 ``deprecated-input=reject``
3776 Reject deprecated commands and arguments
3777 ``deprecated-input=crash``
3778 Crash on deprecated commands and arguments
3779 ``deprecated-output=accept`` (default)
3780 Emit deprecated command results and events
3781 ``deprecated-output=hide``
3782 Suppress deprecated command results and events
3784 Limitation: covers only syntactic aspects of QMP.
3786 ``-compat [unstable-input=@var{input-policy}][,unstable-output=@var{output-policy}]``
3787 Set policy for handling unstable management interfaces (experimental):
3789 ``unstable-input=accept`` (default)
3790 Accept unstable commands and arguments
3791 ``unstable-input=reject``
3792 Reject unstable commands and arguments
3793 ``unstable-input=crash``
3794 Crash on unstable commands and arguments
3795 ``unstable-output=accept`` (default)
3796 Emit unstable command results and events
3797 ``unstable-output=hide``
3798 Suppress unstable command results and events
3800 Limitation: covers only syntactic aspects of QMP.
3803 DEF("fw_cfg", HAS_ARG, QEMU_OPTION_fwcfg,
3804 "-fw_cfg [name=]<name>,file=<file>\n"
3805 " add named fw_cfg entry with contents from file\n"
3806 "-fw_cfg [name=]<name>,string=<str>\n"
3807 " add named fw_cfg entry with contents from string\n",
3810 ``-fw_cfg [name=]name,file=file``
3811 Add named fw\_cfg entry with contents from file file.
3813 ``-fw_cfg [name=]name,string=str``
3814 Add named fw\_cfg entry with contents from string str.
3816 The terminating NUL character of the contents of str will not be
3817 included as part of the fw\_cfg item data. To insert contents with
3818 embedded NUL characters, you have to use the file parameter.
3820 The fw\_cfg entries are passed by QEMU through to the guest.
3826 -fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin
3828 creates an fw\_cfg entry named opt/com.mycompany/blob with contents
3829 from ./my\_blob.bin.
3832 DEF("serial", HAS_ARG, QEMU_OPTION_serial, \
3833 "-serial dev redirect the serial port to char device 'dev
'\n",
3837 Redirect the virtual serial port to host character device dev. The
3838 default device is ``vc`` in graphical mode and ``stdio`` in non
3841 This option can be used several times to simulate up to 4 serial
3844 Use ``-serial none`` to disable all serial ports.
3846 Available character devices are:
3849 Virtual console. Optionally, a width and height can be given in
3856 It is also possible to specify width or height in characters:
3863 [Linux only] Pseudo TTY (a new PTY is automatically allocated)
3866 No device is allocated.
3872 Use a named character device defined with the ``-chardev``
3876 [Linux only] Use host tty, e.g. ``/dev/ttyS0``. The host serial
3877 port parameters are set according to the emulated ones.
3880 [Linux only, parallel port only] Use host parallel port N.
3881 Currently SPP and EPP parallel port features can be used.
3884 Write output to filename. No character can be read.
3887 [Unix only] standard input/output
3893 [Windows only] Use host serial port n
3895 ``udp:[remote_host]:remote_port[@[src_ip]:src_port]``
3896 This implements UDP Net Console. When remote\_host or src\_ip
3897 are not specified they default to ``0.0.0.0``. When not using a
3898 specified src\_port a random port is automatically chosen.
3900 If you just want a simple readonly console you can use
3901 ``netcat`` or ``nc``, by starting QEMU with:
3902 ``-serial udp::4555`` and nc as: ``nc -u -l -p 4555``. Any time
3903 QEMU writes something to that port it will appear in the
3906 If you plan to send characters back via netconsole or you want
3907 to stop and start QEMU a lot of times, you should have QEMU use
3908 the same source port each time by using something like ``-serial
3909 udp::4555@:4556`` to QEMU. Another approach is to use a patched
3910 version of netcat which can listen to a TCP port and send and
3911 receive characters via udp. If you have a patched version of
3912 netcat which activates telnet remote echo and single char
3913 transfer, then you can use the following options to set up a
3914 netcat redirector to allow telnet on port 5555 to access the
3918 -serial udp::4555@:4556
3921 -u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T
3926 ``tcp:[host]:port[,server=on|off][,wait=on|off][,nodelay=on|off][,reconnect=seconds]``
3927 The TCP Net Console has two modes of operation. It can send the
3928 serial I/O to a location or wait for a connection from a
3929 location. By default the TCP Net Console is sent to host at the
3930 port. If you use the ``server=on`` option QEMU will wait for a client
3931 socket application to connect to the port before continuing,
3932 unless the ``wait=on|off`` option was specified. The ``nodelay=on|off``
3933 option disables the Nagle buffering algorithm. The ``reconnect=on``
3934 option only applies if ``server=no`` is set, if the connection goes
3935 down it will attempt to reconnect at the given interval. If host
3936 is omitted, 0.0.0.0 is assumed. Only one TCP connection at a
3937 time is accepted. You can use ``telnet=on`` to connect to the
3938 corresponding character device.
3940 ``Example to send tcp console to 192.168.0.2 port 4444``
3941 -serial tcp:192.168.0.2:4444
3943 ``Example to listen and wait on port 4444 for connection``
3944 -serial tcp::4444,server=on
3946 ``Example to not wait and listen on ip 192.168.0.100 port 4444``
3947 -serial tcp:192.168.0.100:4444,server=on,wait=off
3949 ``telnet:host:port[,server=on|off][,wait=on|off][,nodelay=on|off]``
3950 The telnet protocol is used instead of raw tcp sockets. The
3951 options work the same as if you had specified ``-serial tcp``.
3952 The difference is that the port acts like a telnet server or
3953 client using telnet option negotiation. This will also allow you
3954 to send the MAGIC\_SYSRQ sequence if you use a telnet that
3955 supports sending the break sequence. Typically in unix telnet
3956 you do it with Control-] and then type "send break" followed by
3957 pressing the enter key.
3959 ``websocket:host:port,server=on[,wait=on|off][,nodelay=on|off]``
3960 The WebSocket protocol is used instead of raw tcp socket. The
3961 port acts as a WebSocket server. Client mode is not supported.
3963 ``unix:path[,server=on|off][,wait=on|off][,reconnect=seconds]``
3964 A unix domain socket is used instead of a tcp socket. The option
3965 works the same as if you had specified ``-serial tcp`` except
3966 the unix domain socket path is used for connections.
3969 This is a special option to allow the monitor to be multiplexed
3970 onto another serial port. The monitor is accessed with key
3971 sequence of Control-a and then pressing c. dev\_string should be
3972 any one of the serial devices specified above. An example to
3973 multiplex the monitor onto a telnet server listening on port
3976 ``-serial mon:telnet::4444,server=on,wait=off``
3978 When the monitor is multiplexed to stdio in this way, Ctrl+C
3979 will not terminate QEMU any more but will be passed to the guest
3983 Braille device. This will use BrlAPI to display the braille
3984 output on a real or fake device.
3987 Three button serial mouse. Configure the guest to use Microsoft
3991 DEF("parallel", HAS_ARG, QEMU_OPTION_parallel, \
3992 "-parallel dev redirect the parallel port to char device 'dev
'\n",
3996 Redirect the virtual parallel port to host device dev (same devices
3997 as the serial port). On Linux hosts, ``/dev/parportN`` can be used
3998 to use hardware devices connected on the corresponding host parallel
4001 This option can be used several times to simulate up to 3 parallel
4004 Use ``-parallel none`` to disable all parallel ports.
4007 DEF("monitor", HAS_ARG, QEMU_OPTION_monitor, \
4008 "-monitor dev redirect the monitor to char device 'dev
'\n",
4012 Redirect the monitor to host device dev (same devices as the serial
4013 port). The default device is ``vc`` in graphical mode and ``stdio``
4014 in non graphical mode. Use ``-monitor none`` to disable the default
4017 DEF("qmp", HAS_ARG, QEMU_OPTION_qmp, \
4018 "-qmp dev like -monitor but opens in 'control
' mode\n",
4022 Like -monitor but opens in 'control
' mode.
4024 DEF("qmp-pretty", HAS_ARG, QEMU_OPTION_qmp_pretty, \
4025 "-qmp-pretty dev like -qmp but uses pretty JSON formatting\n",
4029 Like -qmp but uses pretty JSON formatting.
4032 DEF("mon", HAS_ARG, QEMU_OPTION_mon, \
4033 "-mon [chardev=]name[,mode=readline|control][,pretty[=on|off]]\n", QEMU_ARCH_ALL)
4035 ``-mon [chardev=]name[,mode=readline|control][,pretty[=on|off]]``
4036 Setup monitor on chardev name. ``mode=control`` configures
4037 a QMP monitor (a JSON RPC-style protocol) and it is not the
4038 same as HMP, the human monitor that has a "(qemu)" prompt.
4039 ``pretty`` is only valid when ``mode=control``,
4040 turning on JSON pretty printing to ease
4041 human reading and debugging.
4044 DEF("debugcon", HAS_ARG, QEMU_OPTION_debugcon, \
4045 "-debugcon dev redirect the debug console to char device 'dev
'\n",
4049 Redirect the debug console to host device dev (same devices as the
4050 serial port). The debug console is an I/O port which is typically
4051 port 0xe9; writing to that I/O port sends output to this device. The
4052 default device is ``vc`` in graphical mode and ``stdio`` in non
4056 DEF("pidfile", HAS_ARG, QEMU_OPTION_pidfile, \
4057 "-pidfile file write PID to 'file
'\n", QEMU_ARCH_ALL)
4060 Store the QEMU process PID in file. It is useful if you launch QEMU
4064 DEF("singlestep", 0, QEMU_OPTION_singlestep, \
4065 "-singlestep always run in singlestep mode\n", QEMU_ARCH_ALL)
4068 Run the emulation in single step mode.
4071 DEF("preconfig", 0, QEMU_OPTION_preconfig, \
4072 "--preconfig pause QEMU before machine is initialized (experimental)\n",
4076 Pause QEMU for interactive configuration before the machine is
4077 created, which allows querying and configuring properties that will
4078 affect machine initialization. Use QMP command 'x
-exit
-preconfig
' to
4079 exit the preconfig state and move to the next state (i.e. run guest
4080 if -S isn't used or pause the second time
if -S is used
). This
4081 option is experimental
.
4084 DEF("S", 0, QEMU_OPTION_S
, \
4085 "-S freeze CPU at startup (use 'c' to start execution)\n",
4089 Do not start CPU at
startup (you must type
'c' in the monitor
).
4092 DEF("overcommit", HAS_ARG
, QEMU_OPTION_overcommit
,
4093 "-overcommit [mem-lock=on|off][cpu-pm=on|off]\n"
4094 " run qemu with overcommit hints\n"
4095 " mem-lock=on|off controls memory lock support (default: off)\n"
4096 " cpu-pm=on|off controls cpu power management (default: off)\n",
4099 ``
-overcommit mem
-lock
=on|off``
4101 ``
-overcommit cpu
-pm
=on|off``
4102 Run qemu with hints about host resource overcommit
. The
default is
4103 to assume that host overcommits all resources
.
4105 Locking qemu and guest memory can be enabled via ``mem
-lock
=on``
4106 (disabled by
default). This works when host memory is not
4107 overcommitted and reduces the worst
-case latency
for guest
.
4109 Guest ability to manage power state of host
cpus (increasing latency
4110 for other processes on the same host cpu
, but decreasing latency
for
4111 guest
) can be enabled via ``cpu
-pm
=on``
(disabled by
default). This
4112 works best when host CPU is not overcommitted
. When used
, host
4113 estimates of CPU cycle and power utilization will be incorrect
, not
4114 taking into account guest idle time
.
4117 DEF("gdb", HAS_ARG
, QEMU_OPTION_gdb
, \
4118 "-gdb dev accept gdb connection on 'dev'. (QEMU defaults to starting\n"
4119 " the guest without waiting for gdb to connect; use -S too\n"
4120 " if you want it to not start execution.)\n",
4124 Accept a gdb connection on device
dev (see the
:ref
:`GDB usage` chapter
4125 in the System Emulation Users Guide
). Note that
this option does not pause QEMU
4126 execution
-- if you want QEMU to not start the guest until you
4127 connect with gdb and issue a ``
continue`` command
, you will need to
4128 also pass the ``
-S`` option to QEMU
.
4130 The most usual configuration is to listen on a local TCP socket
::
4134 but you can specify other backends
; UDP
, pseudo TTY
, or even stdio
4135 are all reasonable use cases
. For example
, a stdio connection
4136 allows you to start QEMU from within gdb and establish the
4137 connection via a pipe
:
4141 (gdb
) target remote | exec |qemu_system|
-gdb stdio
...
4144 DEF("s", 0, QEMU_OPTION_s
, \
4145 "-s shorthand for -gdb tcp::" DEFAULT_GDBSTUB_PORT
"\n",
4149 Shorthand
for -gdb tcp
::1234, i
.e
. open a gdbserver on TCP port
1234
4150 (see the
:ref
:`GDB usage` chapter
in the System Emulation Users Guide
).
4153 DEF("d", HAS_ARG
, QEMU_OPTION_d
, \
4154 "-d item1,... enable logging of specified items (use '-d help' for a list of log items)\n",
4158 Enable logging of specified items
. Use
'-d help' for a list of log
4162 DEF("D", HAS_ARG
, QEMU_OPTION_D
, \
4163 "-D logfile output log to logfile (default stderr)\n",
4167 Output log
in logfile instead of to stderr
4170 DEF("dfilter", HAS_ARG
, QEMU_OPTION_DFILTER
, \
4171 "-dfilter range,.. filter debug output to range of addresses (useful for -d cpu,exec,etc..)\n",
4174 ``
-dfilter range1
[,...]``
4175 Filter debug output to that relevant to a range of target addresses
.
4176 The filter spec can be either start
+size
, start
-size or start
..end
4177 where start end and size are the addresses and sizes required
. For
4182 -dfilter
0x8000..0x8fff
,0xffffffc000080000+0x200,0xffffffc000060000-0x1000
4184 Will dump output
for any code
in the
0x1000 sized block starting at
4185 0x8000 and the
0x200 sized block starting at
0xffffffc000080000 and
4186 another
0x1000 sized block starting at
0xffffffc00005f000.
4189 DEF("seed", HAS_ARG
, QEMU_OPTION_seed
, \
4190 "-seed number seed the pseudo-random number generator\n",
4194 Force the guest to use a deterministic pseudo
-random number
4195 generator
, seeded with number
. This does not affect crypto routines
4199 DEF("L", HAS_ARG
, QEMU_OPTION_L
, \
4200 "-L path set the directory for the BIOS, VGA BIOS and keymaps\n",
4204 Set the directory
for the BIOS
, VGA BIOS and keymaps
.
4206 To list all the data directories
, use ``
-L help``
.
4209 DEF("bios", HAS_ARG
, QEMU_OPTION_bios
, \
4210 "-bios file set the filename for the BIOS\n", QEMU_ARCH_ALL
)
4213 Set the filename
for the BIOS
.
4216 DEF("enable-kvm", 0, QEMU_OPTION_enable_kvm
, \
4217 "-enable-kvm enable KVM full virtualization support\n",
4218 QEMU_ARCH_ARM | QEMU_ARCH_I386 | QEMU_ARCH_MIPS | QEMU_ARCH_PPC |
4219 QEMU_ARCH_RISCV | QEMU_ARCH_S390X
)
4222 Enable KVM full virtualization support
. This option is only
4223 available
if KVM support is enabled when compiling
.
4226 DEF("xen-domid", HAS_ARG
, QEMU_OPTION_xen_domid
,
4227 "-xen-domid id specify xen guest domain id\n",
4228 QEMU_ARCH_ARM | QEMU_ARCH_I386
)
4229 DEF("xen-attach", 0, QEMU_OPTION_xen_attach
,
4230 "-xen-attach attach to existing xen domain\n"
4231 " libxl will use this when starting QEMU\n",
4232 QEMU_ARCH_ARM | QEMU_ARCH_I386
)
4233 DEF("xen-domid-restrict", 0, QEMU_OPTION_xen_domid_restrict
,
4234 "-xen-domid-restrict restrict set of available xen operations\n"
4235 " to specified domain id. (Does not affect\n"
4236 " xenpv machine type).\n",
4237 QEMU_ARCH_ARM | QEMU_ARCH_I386
)
4240 Specify xen guest domain
id (XEN only
).
4243 Attach to existing xen domain
. libxl will use
this when starting
4244 QEMU (XEN only
). Restrict set of available xen operations to
4245 specified domain
id (XEN only
).
4248 DEF("no-reboot", 0, QEMU_OPTION_no_reboot
, \
4249 "-no-reboot exit instead of rebooting\n", QEMU_ARCH_ALL
)
4252 Exit instead of rebooting
.
4255 DEF("no-shutdown", 0, QEMU_OPTION_no_shutdown
, \
4256 "-no-shutdown stop before shutdown\n", QEMU_ARCH_ALL
)
4259 Don
't exit QEMU on guest shutdown, but instead only stop the
4260 emulation. This allows for instance switching to monitor to commit
4261 changes to the disk image.
4264 DEF("action", HAS_ARG, QEMU_OPTION_action,
4265 "-action reboot=reset|shutdown\n"
4266 " action when guest reboots [default=reset]\n"
4267 "-action shutdown=poweroff|pause\n"
4268 " action when guest shuts down [default=poweroff]\n"
4269 "-action panic=pause|shutdown|none\n"
4270 " action when guest panics [default=shutdown]\n"
4271 "-action watchdog=reset|shutdown|poweroff|inject-nmi|pause|debug|none\n"
4272 " action when watchdog fires [default=reset]\n",
4275 ``-action event=action``
4276 The action parameter serves to modify QEMU's
default behavior when
4277 certain guest events occur
. It provides a generic method
for specifying the
4278 same behaviors that are modified by the ``
-no
-reboot`` and ``
-no
-shutdown``
4283 ``
-action panic
=none``
4284 ``
-action reboot
=shutdown
,shutdown
=pause``
4285 ``
-watchdog i6300esb
-action watchdog
=pause``
4289 DEF("loadvm", HAS_ARG
, QEMU_OPTION_loadvm
, \
4290 "-loadvm [tag|id]\n" \
4291 " start right away with a saved state (loadvm in monitor)\n",
4295 Start right away with a saved
state (``loadvm``
in monitor
)
4299 DEF("daemonize", 0, QEMU_OPTION_daemonize
, \
4300 "-daemonize daemonize QEMU after initializing\n", QEMU_ARCH_ALL
)
4304 Daemonize the QEMU process after initialization
. QEMU will not
4305 detach from standard IO until it is ready to receive connections on
4306 any of its devices
. This option is a useful way
for external
4307 programs to launch QEMU without having to cope with initialization
4311 DEF("option-rom", HAS_ARG
, QEMU_OPTION_option_rom
, \
4312 "-option-rom rom load a file, rom, into the option ROM space\n",
4315 ``
-option
-rom file``
4316 Load the contents of file as an option ROM
. This option is useful to
4317 load things like EtherBoot
.
4320 DEF("rtc", HAS_ARG
, QEMU_OPTION_rtc
, \
4321 "-rtc [base=utc|localtime|<datetime>][,clock=host|rt|vm][,driftfix=none|slew]\n" \
4322 " set the RTC base and clock, enable drift fix for clock ticks (x86 only)\n",
4326 ``
-rtc
[base
=utc|localtime|datetime
][,clock
=host|rt|vm
][,driftfix
=none|slew
]``
4327 Specify ``base`` as ``utc`` or ``localtime`` to let the RTC start at
4328 the current UTC or local time
, respectively
. ``localtime`` is
4329 required
for correct date
in MS
-DOS or Windows
. To start at a
4330 specific point
in time
, provide datetime
in the format
4331 ``
2006-06-17T16
:01:21`` or ``
2006-06-17``
. The
default base is UTC
.
4333 By
default the RTC is driven by the host system time
. This allows
4334 using of the RTC as accurate reference clock inside the guest
,
4335 specifically
if the host time is smoothly following an accurate
4336 external reference clock
, e
.g
. via NTP
. If you want to isolate the
4337 guest time from the host
, you can set ``clock`` to ``rt`` instead
,
4338 which provides a host monotonic clock
if host support it
. To even
4339 prevent the RTC from progressing during suspension
, you can set
4340 ``clock`` to ``vm``
(virtual clock
). '\ ``clock=vm``\ ' is
4341 recommended especially
in icount mode
in order to preserve
4342 determinism
; however
, note that
in icount mode the speed of the
4343 virtual clock is variable and can
in general differ from the host
4346 Enable ``driftfix``
(i386 targets only
) if you experience time drift
4347 problems
, specifically with Windows
' ACPI HAL. This option will try
4348 to figure out how many timer interrupts were not processed by the
4349 Windows guest and will re-inject them.
4352 DEF("icount", HAS_ARG, QEMU_OPTION_icount, \
4353 "-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=<filename>[,rrsnapshot=<snapshot>]]\n" \
4354 " enable virtual instruction counter with 2^N clock ticks per\n" \
4355 " instruction, enable aligning the host and virtual clocks\n" \
4356 " or disable real time cpu sleeping, and optionally enable\n" \
4357 " record-and-replay mode\n", QEMU_ARCH_ALL)
4359 ``-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=filename[,rrsnapshot=snapshot]]``
4360 Enable virtual instruction counter. The virtual cpu will execute one
4361 instruction every 2^N ns of virtual time. If ``auto`` is specified
4362 then the virtual cpu speed will be automatically adjusted to keep
4363 virtual time within a few seconds of real time.
4365 Note that while this option can give deterministic behavior, it does
4366 not provide cycle accurate emulation. Modern CPUs contain
4367 superscalar out of order cores with complex cache hierarchies. The
4368 number of instructions executed often has little or no correlation
4369 with actual performance.
4371 When the virtual cpu is sleeping, the virtual time will advance at
4372 default speed unless ``sleep=on`` is specified. With
4373 ``sleep=on``, the virtual time will jump to the next timer
4374 deadline instantly whenever the virtual cpu goes to sleep mode and
4375 will not advance if no timer is enabled. This behavior gives
4376 deterministic execution times from the guest point of view.
4377 The default if icount is enabled is ``sleep=off``.
4378 ``sleep=on`` cannot be used together with either ``shift=auto``
4381 ``align=on`` will activate the delay algorithm which will try to
4382 synchronise the host clock and the virtual clock. The goal is to
4383 have a guest running at the real frequency imposed by the shift
4384 option. Whenever the guest clock is behind the host clock and if
4385 ``align=on`` is specified then we print a message to the user to
4386 inform about the delay. Currently this option does not work when
4387 ``shift`` is ``auto``. Note: The sync algorithm will work for those
4388 shift values for which the guest clock runs ahead of the host clock.
4389 Typically this happens when the shift value is high (how high
4390 depends on the host machine). The default if icount is enabled
4393 When the ``rr`` option is specified deterministic record/replay is
4394 enabled. The ``rrfile=`` option must also be provided to
4395 specify the path to the replay log. In record mode data is written
4396 to this file, and in replay mode it is read back.
4397 If the ``rrsnapshot`` option is given then it specifies a VM snapshot
4398 name. In record mode, a new VM snapshot with the given name is created
4399 at the start of execution recording. In replay mode this option
4400 specifies the snapshot name used to load the initial VM state.
4403 DEF("watchdog", HAS_ARG, QEMU_OPTION_watchdog, \
4404 "-watchdog model\n" \
4405 " enable virtual hardware watchdog [default=none]\n",
4409 Create a virtual hardware watchdog device. Once enabled (by a guest
4410 action), the watchdog must be periodically polled by an agent inside
4411 the guest or else the guest will be restarted. Choose a model for
4412 which your guest has drivers.
4414 The model is the model of hardware watchdog to emulate. Use
4415 ``-watchdog help`` to list available hardware models. Only one
4416 watchdog can be enabled for a guest.
4418 The following models may be available:
4421 iBASE 700 is a very simple ISA watchdog with a single timer.
4424 Intel 6300ESB I/O controller hub is a much more featureful
4425 PCI-based dual-timer watchdog.
4428 A virtual watchdog for s390x backed by the diagnose 288
4429 hypercall (currently KVM only).
4432 DEF("watchdog-action", HAS_ARG, QEMU_OPTION_watchdog_action, \
4433 "-watchdog-action reset|shutdown|poweroff|inject-nmi|pause|debug|none\n" \
4434 " action when watchdog fires [default=reset]\n",
4437 ``-watchdog-action action``
4438 The action controls what QEMU will do when the watchdog timer
4439 expires. The default is ``reset`` (forcefully reset the guest).
4440 Other possible actions are: ``shutdown`` (attempt to gracefully
4441 shutdown the guest), ``poweroff`` (forcefully poweroff the guest),
4442 ``inject-nmi`` (inject a NMI into the guest), ``pause`` (pause the
4443 guest), ``debug`` (print a debug message and continue), or ``none``
4446 Note that the ``shutdown`` action requires that the guest responds
4447 to ACPI signals, which it may not be able to do in the sort of
4448 situations where the watchdog would have expired, and thus
4449 ``-watchdog-action shutdown`` is not recommended for production use.
4453 ``-watchdog i6300esb -watchdog-action pause``; \ ``-watchdog ib700``
4457 DEF("echr", HAS_ARG, QEMU_OPTION_echr, \
4458 "-echr chr set terminal escape character instead of ctrl-a\n",
4461 ``-echr numeric_ascii_value``
4462 Change the escape character used for switching to the monitor when
4463 using monitor and serial sharing. The default is ``0x01`` when using
4464 the ``-nographic`` option. ``0x01`` is equal to pressing
4465 ``Control-a``. You can select a different character from the ascii
4466 control keys where 1 through 26 map to Control-a through Control-z.
4467 For instance you could use the either of the following to change the
4468 escape character to Control-t.
4470 ``-echr 0x14``; \ ``-echr 20``
4474 DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \
4475 "-incoming tcp:[host]:port[,to=maxport][,ipv4=on|off][,ipv6=on|off]\n" \
4476 "-incoming rdma:host:port[,ipv4=on|off][,ipv6=on|off]\n" \
4477 "-incoming unix:socketpath\n" \
4478 " prepare for incoming migration, listen on\n" \
4479 " specified protocol and socket address\n" \
4480 "-incoming fd:fd\n" \
4481 "-incoming exec:cmdline\n" \
4482 " accept incoming migration on given file descriptor\n" \
4483 " or from given external command\n" \
4484 "-incoming defer\n" \
4485 " wait for the URI to be specified via migrate_incoming\n",
4488 ``-incoming tcp:[host]:port[,to=maxport][,ipv4=on|off][,ipv6=on|off]``
4490 ``-incoming rdma:host:port[,ipv4=on|off][,ipv6=on|off]``
4491 Prepare for incoming migration, listen on a given tcp port.
4493 ``-incoming unix:socketpath``
4494 Prepare for incoming migration, listen on a given unix socket.
4497 Accept incoming migration from a given filedescriptor.
4499 ``-incoming exec:cmdline``
4500 Accept incoming migration as an output from specified external
4504 Wait for the URI to be specified via migrate\_incoming. The monitor
4505 can be used to change settings (such as migration parameters) prior
4506 to issuing the migrate\_incoming to allow the migration to begin.
4509 DEF("only-migratable", 0, QEMU_OPTION_only_migratable, \
4510 "-only-migratable allow only migratable devices\n", QEMU_ARCH_ALL)
4512 ``-only-migratable``
4513 Only allow migratable devices. Devices will not be allowed to enter
4514 an unmigratable state.
4517 DEF("nodefaults", 0, QEMU_OPTION_nodefaults, \
4518 "-nodefaults don't create
default devices
\n", QEMU_ARCH_ALL)
4521 Don't create default devices. Normally, QEMU sets the default
4522 devices like serial port, parallel port, virtual console, monitor
4523 device, VGA adapter, floppy and CD-ROM drive and others. The
4524 ``-nodefaults`` option will disable all those default devices.
4528 DEF("chroot
", HAS_ARG, QEMU_OPTION_chroot, \
4529 "-chroot dir chroot to dir just before starting the VM
\n",
4534 Immediately before starting guest execution, chroot to the specified
4535 directory. Especially useful in combination with -runas.
4539 DEF("runas
", HAS_ARG, QEMU_OPTION_runas, \
4540 "-runas user change to user id user just before starting the VM
\n" \
4541 " user can be numeric uid
:gid instead
\n",
4546 Immediately before starting guest execution, drop root privileges,
4547 switching to the specified user.
4550 DEF("prom
-env
", HAS_ARG, QEMU_OPTION_prom_env,
4551 "-prom
-env variable
=value
\n"
4552 " set OpenBIOS nvram variables
\n",
4553 QEMU_ARCH_PPC | QEMU_ARCH_SPARC)
4555 ``-prom-env variable=value``
4556 Set OpenBIOS nvram variable to given value (PPC, SPARC only).
4560 qemu-system-sparc -prom-env 'auto-boot?=false' \
4561 -prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
4565 qemu-system-ppc -prom-env 'auto-boot?=false' \
4566 -prom-env 'boot-device=hd:2,\yaboot' \
4567 -prom-env 'boot-args=conf=hd:2,\yaboot.conf'
4569 DEF("semihosting
", 0, QEMU_OPTION_semihosting,
4570 "-semihosting semihosting mode
\n",
4571 QEMU_ARCH_ARM | QEMU_ARCH_M68K | QEMU_ARCH_XTENSA |
4572 QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2 | QEMU_ARCH_RISCV)
4575 Enable semihosting mode (ARM, M68K, Xtensa, MIPS, Nios II, RISC-V only).
4577 Note that this allows guest direct access to the host filesystem, so
4578 should only be used with a trusted guest OS.
4580 See the -semihosting-config option documentation for further
4581 information about the facilities this enables.
4583 DEF("semihosting
-config
", HAS_ARG, QEMU_OPTION_semihosting_config,
4584 "-semihosting
-config
[enable
=on|off
][,target
=native|gdb|auto
][,chardev
=id
][,arg
=str
[,...]]\n" \
4585 " semihosting configuration
\n",
4586 QEMU_ARCH_ARM | QEMU_ARCH_M68K | QEMU_ARCH_XTENSA |
4587 QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2 | QEMU_ARCH_RISCV)
4589 ``-semihosting-config [enable=on|off][,target=native|gdb|auto][,chardev=id][,arg=str[,...]]``
4590 Enable and configure semihosting (ARM, M68K, Xtensa, MIPS, Nios II, RISC-V
4593 Note that this allows guest direct access to the host filesystem, so
4594 should only be used with a trusted guest OS.
4596 On Arm this implements the standard semihosting API, version 2.0.
4598 On M68K this implements the "ColdFire GDB
" interface used by
4601 Xtensa semihosting provides basic file IO calls, such as
4602 open/read/write/seek/select. Tensilica baremetal libc for ISS and
4603 linux platform "sim
" use this interface.
4605 On RISC-V this implements the standard semihosting API, version 0.2.
4607 ``target=native|gdb|auto``
4608 Defines where the semihosting calls will be addressed, to QEMU
4609 (``native``) or to GDB (``gdb``). The default is ``auto``, which
4610 means ``gdb`` during debug sessions and ``native`` otherwise.
4613 Send the output to a chardev backend output for native or auto
4614 output when not in gdb
4616 ``arg=str1,arg=str2,...``
4617 Allows the user to pass input arguments, and can be used
4618 multiple times to build up a list. The old-style
4619 ``-kernel``/``-append`` method of passing a command line is
4620 still supported for backward compatibility. If both the
4621 ``--semihosting-config arg`` and the ``-kernel``/``-append`` are
4622 specified, the former is passed to semihosting as it always
4625 DEF("old
-param
", 0, QEMU_OPTION_old_param,
4626 "-old
-param old param mode
\n", QEMU_ARCH_ARM)
4629 Old param mode (ARM only).
4632 DEF("sandbox
", HAS_ARG, QEMU_OPTION_sandbox, \
4633 "-sandbox on
[,obsolete
=allow|deny
][,elevateprivileges
=allow|deny|children
]\n" \
4634 " [,spawn
=allow|deny
][,resourcecontrol
=allow|deny
]\n" \
4635 " Enable seccomp mode
2 system call
filter (default 'off').\n" \
4636 " use
'obsolete' to allow obsolete system calls that are provided
\n" \
4637 " by the kernel
, but typically no longer used by modern
\n" \
4638 " C library implementations
.\n" \
4639 " use
'elevateprivileges' to allow or deny the QEMU process ability
\n" \
4640 " to elevate privileges
using set
*uid|gid system calls
.\n" \
4641 " The value
'children' will deny set
*uid|gid system calls
for\n" \
4642 " main QEMU process but will allow forks and execves to run unprivileged
\n" \
4643 " use
'spawn' to avoid QEMU to spawn
new threads or processes by
\n" \
4644 " blocking
*fork and execve
\n" \
4645 " use
'resourcecontrol' to disable process affinity and schedular priority
\n",
4648 ``-sandbox arg[,obsolete=string][,elevateprivileges=string][,spawn=string][,resourcecontrol=string]``
4649 Enable Seccomp mode 2 system call filter. 'on' will enable syscall
4650 filtering and 'off' will disable it. The default is 'off'.
4653 Enable Obsolete system calls
4655 ``elevateprivileges=string``
4656 Disable set\*uid\|gid system calls
4659 Disable \*fork and execve
4661 ``resourcecontrol=string``
4662 Disable process affinity and schedular priority
4665 DEF("readconfig
", HAS_ARG, QEMU_OPTION_readconfig,
4666 "-readconfig
<file
>\n"
4667 " read config file
\n", QEMU_ARCH_ALL)
4669 ``-readconfig file``
4670 Read device configuration from file. This approach is useful when
4671 you want to spawn QEMU process with many command line options but
4672 you don't want to exceed the command line character limit.
4675 DEF("no
-user
-config
", 0, QEMU_OPTION_nouserconfig,
4677 " do not load
default user
-provided config files at startup
\n",
4681 The ``-no-user-config`` option makes QEMU not load any of the
4682 user-provided config files on sysconfdir.
4685 DEF("trace", HAS_ARG, QEMU_OPTION_trace,
4686 "-trace [[enable
=]<pattern
>][,events
=<file
>][,file
=<file
>]\n"
4687 " specify tracing options
\n",
4690 ``-trace [[enable=]pattern][,events=file][,file=file]``
4691 .. include:: ../qemu-option-trace.rst.inc
4694 DEF("plugin
", HAS_ARG, QEMU_OPTION_plugin,
4695 "-plugin
[file
=]<file
>[,<argname
>=<argvalue
>]\n"
4699 ``-plugin file=file[,argname=argvalue]``
4703 Load the given plugin from a shared library file.
4705 ``argname=argvalue``
4706 Argument passed to the plugin. (Can be given multiple times.)
4710 DEF("qtest
", HAS_ARG, QEMU_OPTION_qtest, "", QEMU_ARCH_ALL)
4711 DEF("qtest
-log
", HAS_ARG, QEMU_OPTION_qtest_log, "", QEMU_ARCH_ALL)
4713 DEF("msg
", HAS_ARG, QEMU_OPTION_msg,
4714 "-msg
[timestamp
[=on|off
]][,guest
-name
=[on|off
]]\n"
4715 " control error message format
\n"
4716 " timestamp
=on enables
timestamps (default: off
)\n"
4717 " guest
-name
=on enables guest name prefix but only
if\n"
4718 " -name guest option is
set (default: off
)\n",
4721 ``-msg [timestamp[=on|off]][,guest-name[=on|off]]``
4722 Control error message format.
4724 ``timestamp=on|off``
4725 Prefix messages with a timestamp. Default is off.
4727 ``guest-name=on|off``
4728 Prefix messages with guest name but only if -name guest option is set
4729 otherwise the option is ignored. Default is off.
4732 DEF("dump
-vmstate
", HAS_ARG, QEMU_OPTION_dump_vmstate,
4733 "-dump
-vmstate
<file
>\n"
4734 " Output vmstate information
in JSON format to file
.\n"
4735 " Use the scripts
/vmstate
-static-checker
.py file to
\n"
4736 " check
for possible regressions
in migration code
\n"
4737 " by comparing two such vmstate dumps
.\n",
4740 ``-dump-vmstate file``
4741 Dump json-encoded vmstate information for current machine type to
4745 DEF("enable
-sync
-profile
", 0, QEMU_OPTION_enable_sync_profile,
4746 "-enable
-sync
-profile
\n"
4747 " enable synchronization profiling
\n",
4750 ``-enable-sync-profile``
4751 Enable synchronization profiling.
4756 DEFHEADING(Generic object creation:)
4758 DEF("object
", HAS_ARG, QEMU_OPTION_object,
4759 "-object TYPENAME
[,PROP1
=VALUE1
,...]\n"
4760 " create a
new object of type TYPENAME setting properties
\n"
4761 " in the order they are specified
. Note that the
'id'\n"
4762 " property must be set
. These objects are placed
in the
\n"
4763 " '/objects' path
.\n",
4766 ``-object typename[,prop1=value1,...]``
4767 Create a new object of type typename setting properties in the order
4768 they are specified. Note that the 'id' property must be set. These
4769 objects are placed in the '/objects' path.
4771 ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,readonly=on|off``
4772 Creates a memory file backend object, which can be used to back
4773 the guest RAM with huge pages.
4775 The ``id`` parameter is a unique ID that will be used to
4776 reference this memory region in other parameters, e.g. ``-numa``,
4777 ``-device nvdimm``, etc.
4779 The ``size`` option provides the size of the memory region, and
4780 accepts common suffixes, e.g. ``500M``.
4782 The ``mem-path`` provides the path to either a shared memory or
4783 huge page filesystem mount.
4785 The ``share`` boolean option determines whether the memory
4786 region is marked as private to QEMU, or shared. The latter
4787 allows a co-operating external process to access the QEMU memory
4790 The ``share`` is also required for pvrdma devices due to
4791 limitations in the RDMA API provided by Linux.
4793 Setting share=on might affect the ability to configure NUMA
4794 bindings for the memory backend under some circumstances, see
4795 Documentation/vm/numa\_memory\_policy.txt on the Linux kernel
4796 source tree for additional details.
4798 Setting the ``discard-data`` boolean option to on indicates that
4799 file contents can be destroyed when QEMU exits, to avoid
4800 unnecessarily flushing data to the backing file. Note that
4801 ``discard-data`` is only an optimization, and QEMU might not
4802 discard file contents if it aborts unexpectedly or is terminated
4805 The ``merge`` boolean option enables memory merge, also known as
4806 MADV\_MERGEABLE, so that Kernel Samepage Merging will consider
4807 the pages for memory deduplication.
4809 Setting the ``dump`` boolean option to off excludes the memory
4810 from core dumps. This feature is also known as MADV\_DONTDUMP.
4812 The ``prealloc`` boolean option enables memory preallocation.
4814 The ``host-nodes`` option binds the memory range to a list of
4817 The ``policy`` option sets the NUMA policy to one of the
4824 prefer the given host node list for allocation
4827 restrict memory allocation to the given host node list
4830 interleave memory allocations across the given host node
4833 The ``align`` option specifies the base address alignment when
4834 QEMU mmap(2) ``mem-path``, and accepts common suffixes, eg
4835 ``2M``. Some backend store specified by ``mem-path`` requires an
4836 alignment different than the default one used by QEMU, eg the
4837 device DAX /dev/dax0.0 requires 2M alignment rather than 4K. In
4838 such cases, users can specify the required alignment via this
4841 The ``pmem`` option specifies whether the backing file specified
4842 by ``mem-path`` is in host persistent memory that can be
4843 accessed using the SNIA NVM programming model (e.g. Intel
4844 NVDIMM). If ``pmem`` is set to 'on', QEMU will take necessary
4845 operations to guarantee the persistence of its own writes to
4846 ``mem-path`` (e.g. in vNVDIMM label emulation and live
4847 migration). Also, we will map the backend-file with MAP\_SYNC
4848 flag, which ensures the file metadata is in sync for
4849 ``mem-path`` in case of host crash or a power failure. MAP\_SYNC
4850 requires support from both the host kernel (since Linux kernel
4851 4.15) and the filesystem of ``mem-path`` mounted with DAX
4854 The ``readonly`` option specifies whether the backing file is opened
4855 read-only or read-write (default).
4857 ``-object memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave``
4858 Creates a memory backend object, which can be used to back the
4859 guest RAM. Memory backend objects offer more control than the
4860 ``-m`` option that is traditionally used to define guest RAM.
4861 Please refer to ``memory-backend-file`` for a description of the
4864 ``-object memory-backend-memfd,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave,seal=on|off,hugetlb=on|off,hugetlbsize=size``
4865 Creates an anonymous memory file backend object, which allows
4866 QEMU to share the memory with an external process (e.g. when
4867 using vhost-user). The memory is allocated with memfd and
4868 optional sealing. (Linux only)
4870 The ``seal`` option creates a sealed-file, that will block
4871 further resizing the memory ('on' by default).
4873 The ``hugetlb`` option specify the file to be created resides in
4874 the hugetlbfs filesystem (since Linux 4.14). Used in conjunction
4875 with the ``hugetlb`` option, the ``hugetlbsize`` option specify
4876 the hugetlb page size on systems that support multiple hugetlb
4877 page sizes (it must be a power of 2 value supported by the
4880 In some versions of Linux, the ``hugetlb`` option is
4881 incompatible with the ``seal`` option (requires at least Linux
4884 Please refer to ``memory-backend-file`` for a description of the
4887 The ``share`` boolean option is on by default with memfd.
4889 ``-object rng-builtin,id=id``
4890 Creates a random number generator backend which obtains entropy
4891 from QEMU builtin functions. The ``id`` parameter is a unique ID
4892 that will be used to reference this entropy backend from the
4893 ``virtio-rng`` device. By default, the ``virtio-rng`` device
4894 uses this RNG backend.
4896 ``-object rng-random,id=id,filename=/dev/random``
4897 Creates a random number generator backend which obtains entropy
4898 from a device on the host. The ``id`` parameter is a unique ID
4899 that will be used to reference this entropy backend from the
4900 ``virtio-rng`` device. The ``filename`` parameter specifies
4901 which file to obtain entropy from and if omitted defaults to
4904 ``-object rng-egd,id=id,chardev=chardevid``
4905 Creates a random number generator backend which obtains entropy
4906 from an external daemon running on the host. The ``id``
4907 parameter is a unique ID that will be used to reference this
4908 entropy backend from the ``virtio-rng`` device. The ``chardev``
4909 parameter is the unique ID of a character device backend that
4910 provides the connection to the RNG daemon.
4912 ``-object tls-creds-anon,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off``
4913 Creates a TLS anonymous credentials object, which can be used to
4914 provide TLS support on network backends. The ``id`` parameter is
4915 a unique ID which network backends will use to access the
4916 credentials. The ``endpoint`` is either ``server`` or ``client``
4917 depending on whether the QEMU network backend that uses the
4918 credentials will be acting as a client or as a server. If
4919 ``verify-peer`` is enabled (the default) then once the handshake
4920 is completed, the peer credentials will be verified, though this
4921 is a no-op for anonymous credentials.
4923 The dir parameter tells QEMU where to find the credential files.
4924 For server endpoints, this directory may contain a file
4925 dh-params.pem providing diffie-hellman parameters to use for the
4926 TLS server. If the file is missing, QEMU will generate a set of
4927 DH parameters at startup. This is a computationally expensive
4928 operation that consumes random pool entropy, so it is
4929 recommended that a persistent set of parameters be generated
4932 ``-object tls-creds-psk,id=id,endpoint=endpoint,dir=/path/to/keys/dir[,username=username]``
4933 Creates a TLS Pre-Shared Keys (PSK) credentials object, which
4934 can be used to provide TLS support on network backends. The
4935 ``id`` parameter is a unique ID which network backends will use
4936 to access the credentials. The ``endpoint`` is either ``server``
4937 or ``client`` depending on whether the QEMU network backend that
4938 uses the credentials will be acting as a client or as a server.
4939 For clients only, ``username`` is the username which will be
4940 sent to the server. If omitted it defaults to "qemu
".
4942 The dir parameter tells QEMU where to find the keys file. It is
4943 called "dir
/keys
.psk
" and contains "username
:key
" pairs. This
4944 file can most easily be created using the GnuTLS ``psktool``
4947 For server endpoints, dir may also contain a file dh-params.pem
4948 providing diffie-hellman parameters to use for the TLS server.
4949 If the file is missing, QEMU will generate a set of DH
4950 parameters at startup. This is a computationally expensive
4951 operation that consumes random pool entropy, so it is
4952 recommended that a persistent set of parameters be generated up
4955 ``-object tls-creds-x509,id=id,endpoint=endpoint,dir=/path/to/cred/dir,priority=priority,verify-peer=on|off,passwordid=id``
4956 Creates a TLS anonymous credentials object, which can be used to
4957 provide TLS support on network backends. The ``id`` parameter is
4958 a unique ID which network backends will use to access the
4959 credentials. The ``endpoint`` is either ``server`` or ``client``
4960 depending on whether the QEMU network backend that uses the
4961 credentials will be acting as a client or as a server. If
4962 ``verify-peer`` is enabled (the default) then once the handshake
4963 is completed, the peer credentials will be verified. With x509
4964 certificates, this implies that the clients must be provided
4965 with valid client certificates too.
4967 The dir parameter tells QEMU where to find the credential files.
4968 For server endpoints, this directory may contain a file
4969 dh-params.pem providing diffie-hellman parameters to use for the
4970 TLS server. If the file is missing, QEMU will generate a set of
4971 DH parameters at startup. This is a computationally expensive
4972 operation that consumes random pool entropy, so it is
4973 recommended that a persistent set of parameters be generated
4976 For x509 certificate credentials the directory will contain
4977 further files providing the x509 certificates. The certificates
4978 must be stored in PEM format, in filenames ca-cert.pem,
4979 ca-crl.pem (optional), server-cert.pem (only servers),
4980 server-key.pem (only servers), client-cert.pem (only clients),
4981 and client-key.pem (only clients).
4983 For the server-key.pem and client-key.pem files which contain
4984 sensitive private keys, it is possible to use an encrypted
4985 version by providing the passwordid parameter. This provides the
4986 ID of a previously created ``secret`` object containing the
4987 password for decryption.
4989 The priority parameter allows to override the global default
4990 priority used by gnutls. This can be useful if the system
4991 administrator needs to use a weaker set of crypto priorities for
4992 QEMU without potentially forcing the weakness onto all
4993 applications. Or conversely if one wants wants a stronger
4994 default for QEMU than for all other applications, they can do
4995 this through this parameter. Its format is a gnutls priority
4996 string as described at
4997 https://gnutls.org/manual/html_node/Priority-Strings.html.
4999 ``-object tls-cipher-suites,id=id,priority=priority``
5000 Creates a TLS cipher suites object, which can be used to control
5001 the TLS cipher/protocol algorithms that applications are permitted
5004 The ``id`` parameter is a unique ID which frontends will use to
5005 access the ordered list of permitted TLS cipher suites from the
5008 The ``priority`` parameter allows to override the global default
5009 priority used by gnutls. This can be useful if the system
5010 administrator needs to use a weaker set of crypto priorities for
5011 QEMU without potentially forcing the weakness onto all
5012 applications. Or conversely if one wants wants a stronger
5013 default for QEMU than for all other applications, they can do
5014 this through this parameter. Its format is a gnutls priority
5015 string as described at
5016 https://gnutls.org/manual/html_node/Priority-Strings.html.
5018 An example of use of this object is to control UEFI HTTPS Boot.
5019 The tls-cipher-suites object exposes the ordered list of permitted
5020 TLS cipher suites from the host side to the guest firmware, via
5021 fw_cfg. The list is represented as an array of IANA_TLS_CIPHER
5022 objects. The firmware uses the IANA_TLS_CIPHER array for configuring
5025 In the following example, the priority at which the host-side policy
5026 is retrieved is given by the ``priority`` property.
5027 Given that QEMU uses GNUTLS, ``priority=@SYSTEM`` may be used to
5028 refer to /etc/crypto-policies/back-ends/gnutls.config.
5033 -object tls-cipher-suites,id=mysuite0,priority=@SYSTEM \\
5034 -fw_cfg name=etc/edk2/https/ciphers,gen_id=mysuite0
5036 ``-object filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off][,position=head|tail|id=<id>][,insert=behind|before]``
5037 Interval t can't be 0, this filter batches the packet delivery:
5038 all packets arriving in a given interval on netdev netdevid are
5039 delayed until the end of the interval. Interval is in
5040 microseconds. ``status`` is optional that indicate whether the
5041 netfilter is on (enabled) or off (disabled), the default status
5042 for netfilter will be 'on'.
5044 queue all\|rx\|tx is an option that can be applied to any
5047 ``all``: the filter is attached both to the receive and the
5048 transmit queue of the netdev (default).
5050 ``rx``: the filter is attached to the receive queue of the
5051 netdev, where it will receive packets sent to the netdev.
5053 ``tx``: the filter is attached to the transmit queue of the
5054 netdev, where it will receive packets sent by the netdev.
5056 position head\|tail\|id=<id> is an option to specify where the
5057 filter should be inserted in the filter list. It can be applied
5060 ``head``: the filter is inserted at the head of the filter list,
5061 before any existing filters.
5063 ``tail``: the filter is inserted at the tail of the filter list,
5064 behind any existing filters (default).
5066 ``id=<id>``: the filter is inserted before or behind the filter
5067 specified by <id>, see the insert option below.
5069 insert behind\|before is an option to specify where to insert
5070 the new filter relative to the one specified with
5071 position=id=<id>. It can be applied to any netfilter.
5073 ``before``: insert before the specified filter.
5075 ``behind``: insert behind the specified filter (default).
5077 ``-object filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]``
5078 filter-mirror on netdev netdevid,mirror net packet to
5079 chardevchardevid, if it has the vnet\_hdr\_support flag,
5080 filter-mirror will mirror packet with vnet\_hdr\_len.
5082 ``-object filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]``
5083 filter-redirector on netdev netdevid,redirect filter's net
5084 packet to chardev chardevid,and redirect indev's packet to
5085 filter.if it has the vnet\_hdr\_support flag, filter-redirector
5086 will redirect packet with vnet\_hdr\_len. Create a
5087 filter-redirector we need to differ outdev id from indev id, id
5088 can not be the same. we can just use indev or outdev, but at
5089 least one of indev or outdev need to be specified.
5091 ``-object filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]``
5092 Filter-rewriter is a part of COLO project.It will rewrite tcp
5093 packet to secondary from primary to keep secondary tcp
5094 connection,and rewrite tcp packet to primary from secondary make
5095 tcp packet can be handled by client.if it has the
5096 vnet\_hdr\_support flag, we can parse packet with vnet header.
5098 usage: colo secondary: -object
5099 filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object
5100 filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 -object
5101 filter-rewriter,id=rew0,netdev=hn0,queue=all
5103 ``-object filter-dump,id=id,netdev=dev[,file=filename][,maxlen=len][,position=head|tail|id=<id>][,insert=behind|before]``
5104 Dump the network traffic on netdev dev to the file specified by
5105 filename. At most len bytes (64k by default) per packet are
5106 stored. The file format is libpcap, so it can be analyzed with
5107 tools such as tcpdump or Wireshark.
5109 ``-object colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid,iothread=id[,vnet_hdr_support][,notify_dev=id][,compare_timeout=@var{ms}][,expired_scan_cycle=@var{ms}][,max_queue_size=@var{size}]``
5110 Colo-compare gets packet from primary\_in chardevid and
5111 secondary\_in, then compare whether the payload of primary packet
5112 and secondary packet are the same. If same, it will output
5113 primary packet to out\_dev, else it will notify COLO-framework to do
5114 checkpoint and send primary packet to out\_dev. In order to
5115 improve efficiency, we need to put the task of comparison in
5116 another iothread. If it has the vnet\_hdr\_support flag,
5117 colo compare will send/recv packet with vnet\_hdr\_len.
5118 The compare\_timeout=@var{ms} determines the maximum time of the
5119 colo-compare hold the packet. The expired\_scan\_cycle=@var{ms}
5120 is to set the period of scanning expired primary node network packets.
5121 The max\_queue\_size=@var{size} is to set the max compare queue
5122 size depend on user environment.
5123 If user want to use Xen COLO, need to add the notify\_dev to
5124 notify Xen colo-frame to do checkpoint.
5126 COLO-compare must be used with the help of filter-mirror,
5127 filter-redirector and filter-rewriter.
5134 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
5135 -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
5136 -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
5137 -chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
5138 -chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
5139 -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
5140 -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
5141 -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
5142 -object iothread,id=iothread1
5143 -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
5144 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
5145 -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
5146 -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1
5149 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
5150 -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
5151 -chardev socket,id=red0,host=3.3.3.3,port=9003
5152 -chardev socket,id=red1,host=3.3.3.3,port=9004
5153 -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
5154 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
5160 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
5161 -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
5162 -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
5163 -chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
5164 -chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
5165 -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
5166 -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
5167 -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
5168 -chardev socket,id=notify_way,host=3.3.3.3,port=9009,server=on,wait=off
5169 -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
5170 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
5171 -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
5172 -object iothread,id=iothread1
5173 -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,notify_dev=nofity_way,iothread=iothread1
5176 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
5177 -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
5178 -chardev socket,id=red0,host=3.3.3.3,port=9003
5179 -chardev socket,id=red1,host=3.3.3.3,port=9004
5180 -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
5181 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
5183 If you want to know the detail of above command line, you can
5184 read the colo-compare git log.
5186 ``-object cryptodev-backend-builtin,id=id[,queues=queues]``
5187 Creates a cryptodev backend which executes crypto opreation from
5188 the QEMU cipher APIS. The id parameter is a unique ID that will
5189 be used to reference this cryptodev backend from the
5190 ``virtio-crypto`` device. The queues parameter is optional,
5191 which specify the queue number of cryptodev backend, the default
5198 -object cryptodev-backend-builtin,id=cryptodev0 \\
5199 -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \\
5202 ``-object cryptodev-vhost-user,id=id,chardev=chardevid[,queues=queues]``
5203 Creates a vhost-user cryptodev backend, backed by a chardev
5204 chardevid. The id parameter is a unique ID that will be used to
5205 reference this cryptodev backend from the ``virtio-crypto``
5206 device. The chardev should be a unix domain socket backed one.
5207 The vhost-user uses a specifically defined protocol to pass
5208 vhost ioctl replacement messages to an application on the other
5209 end of the socket. The queues parameter is optional, which
5210 specify the queue number of cryptodev backend for multiqueue
5211 vhost-user, the default of queues is 1.
5217 -chardev socket,id=chardev0,path=/path/to/socket \\
5218 -object cryptodev-vhost-user,id=cryptodev0,chardev=chardev0 \\
5219 -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \\
5222 ``-object secret,id=id,data=string,format=raw|base64[,keyid=secretid,iv=string]``
5224 ``-object secret,id=id,file=filename,format=raw|base64[,keyid=secretid,iv=string]``
5225 Defines a secret to store a password, encryption key, or some
5226 other sensitive data. The sensitive data can either be passed
5227 directly via the data parameter, or indirectly via the file
5228 parameter. Using the data parameter is insecure unless the
5229 sensitive data is encrypted.
5231 The sensitive data can be provided in raw format (the default),
5232 or base64. When encoded as JSON, the raw format only supports
5233 valid UTF-8 characters, so base64 is recommended for sending
5234 binary data. QEMU will convert from which ever format is
5235 provided to the format it needs internally. eg, an RBD password
5236 can be provided in raw format, even though it will be base64
5237 encoded when passed onto the RBD sever.
5239 For added protection, it is possible to encrypt the data
5240 associated with a secret using the AES-256-CBC cipher. Use of
5241 encryption is indicated by providing the keyid and iv
5242 parameters. The keyid parameter provides the ID of a previously
5243 defined secret that contains the AES-256 decryption key. This
5244 key should be 32-bytes long and be base64 encoded. The iv
5245 parameter provides the random initialization vector used for
5246 encryption of this particular secret and should be a base64
5247 encrypted string of the 16-byte IV.
5249 The simplest (insecure) usage is to provide the secret inline
5253 # |qemu_system| -object secret,id=sec0,data=letmein,format=raw
5255 The simplest secure usage is to provide the secret via a file
5257 # printf "letmein
" > mypasswd.txt # QEMU\_SYSTEM\_MACRO -object
5258 secret,id=sec0,file=mypasswd.txt,format=raw
5260 For greater security, AES-256-CBC should be used. To illustrate
5261 usage, consider the openssl command line tool which can encrypt
5262 the data. Note that when encrypting, the plaintext must be
5263 padded to the cipher block size (32 bytes) using the standard
5264 PKCS#5/6 compatible padding algorithm.
5266 First a master key needs to be created in base64 encoding:
5270 # openssl rand -base64 32 > key.b64
5271 # KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X
"')
5273 Each secret to be encrypted needs to have a random
5274 initialization vector generated. These do not need to be kept
5279 # openssl rand -base64 16 > iv.b64
5280 # IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X
"')
5282 The secret to be defined can now be encrypted, in this case
5283 we're telling openssl to base64 encode the result, but it could
5284 be left as raw bytes if desired.
5288 # SECRET=$(printf "letmein
" |
5289 openssl enc -aes-256-cbc -a -K $KEY -iv $IV)
5291 When launching QEMU, create a master secret pointing to
5292 ``key.b64`` and specify that to be used to decrypt the user
5293 password. Pass the contents of ``iv.b64`` to the second secret
5298 -object secret,id=secmaster0,format=base64,file=key.b64 \\
5299 -object secret,id=sec0,keyid=secmaster0,format=base64,\\
5300 data=$SECRET,iv=$(<iv.b64)
5302 ``-object sev-guest,id=id,cbitpos=cbitpos,reduced-phys-bits=val,[sev-device=string,policy=policy,handle=handle,dh-cert-file=file,session-file=file,kernel-hashes=on|off]``
5303 Create a Secure Encrypted Virtualization (SEV) guest object,
5304 which can be used to provide the guest memory encryption support
5307 When memory encryption is enabled, one of the physical address
5308 bit (aka the C-bit) is utilized to mark if a memory page is
5309 protected. The ``cbitpos`` is used to provide the C-bit
5310 position. The C-bit position is Host family dependent hence user
5311 must provide this value. On EPYC, the value should be 47.
5313 When memory encryption is enabled, we loose certain bits in
5314 physical address space. The ``reduced-phys-bits`` is used to
5315 provide the number of bits we loose in physical address space.
5316 Similar to C-bit, the value is Host family dependent. On EPYC,
5317 the value should be 5.
5319 The ``sev-device`` provides the device file to use for
5320 communicating with the SEV firmware running inside AMD Secure
5321 Processor. The default device is '/dev/sev'. If hardware
5322 supports memory encryption then /dev/sev devices are created by
5325 The ``policy`` provides the guest policy to be enforced by the
5326 SEV firmware and restrict what configuration and operational
5327 commands can be performed on this guest by the hypervisor. The
5328 policy should be provided by the guest owner and is bound to the
5329 guest and cannot be changed throughout the lifetime of the
5330 guest. The default is 0.
5332 If guest ``policy`` allows sharing the key with another SEV
5333 guest then ``handle`` can be use to provide handle of the guest
5334 from which to share the key.
5336 The ``dh-cert-file`` and ``session-file`` provides the guest
5337 owner's Public Diffie-Hillman key defined in SEV spec. The PDH
5338 and session parameters are used for establishing a cryptographic
5339 session with the guest owner to negotiate keys used for
5340 attestation. The file must be encoded in base64.
5342 The ``kernel-hashes`` adds the hashes of given kernel/initrd/
5343 cmdline to a designated guest firmware page for measured Linux
5344 boot with -kernel. The default is off. (Since 6.2)
5346 e.g to launch a SEV guest
5350 # |qemu_system_x86| \\
5352 -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=5 \\
5353 -machine ...,memory-encryption=sev0 \\
5356 ``-object authz-simple,id=id,identity=string``
5357 Create an authorization object that will control access to
5360 The ``identity`` parameter is identifies the user and its format
5361 depends on the network service that authorization object is
5362 associated with. For authorizing based on TLS x509 certificates,
5363 the identity must be the x509 distinguished name. Note that care
5364 must be taken to escape any commas in the distinguished name.
5366 An example authorization object to validate a x509 distinguished
5367 name would look like:
5373 -object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,O=Example Org,,L=London,,ST=London,,C=GB' \\
5376 Note the use of quotes due to the x509 distinguished name
5377 containing whitespace, and escaping of ','.
5379 ``-object authz-listfile,id=id,filename=path,refresh=on|off``
5380 Create an authorization object that will control access to
5383 The ``filename`` parameter is the fully qualified path to a file
5384 containing the access control list rules in JSON format.
5386 An example set of rules that match against SASL usernames might
5393 { "match
": "fred
", "policy
": "allow
", "format
": "exact
" },
5394 { "match
": "bob
", "policy
": "allow
", "format
": "exact
" },
5395 { "match
": "danb
", "policy
": "deny
", "format
": "glob
" },
5396 { "match
": "dan
*", "policy
": "allow
", "format
": "exact
" },
5401 When checking access the object will iterate over all the rules
5402 and the first rule to match will have its ``policy`` value
5403 returned as the result. If no rules match, then the default
5404 ``policy`` value is returned.
5406 The rules can either be an exact string match, or they can use
5407 the simple UNIX glob pattern matching to allow wildcards to be
5410 If ``refresh`` is set to true the file will be monitored and
5411 automatically reloaded whenever its content changes.
5413 As with the ``authz-simple`` object, the format of the identity
5414 strings being matched depends on the network service, but is
5415 usually a TLS x509 distinguished name, or a SASL username.
5417 An example authorization object to validate a SASL username
5424 -object authz-simple,id=auth0,filename=/etc/qemu/vnc-sasl.acl,refresh=on \\
5427 ``-object authz-pam,id=id,service=string``
5428 Create an authorization object that will control access to
5431 The ``service`` parameter provides the name of a PAM service to
5432 use for authorization. It requires that a file
5433 ``/etc/pam.d/service`` exist to provide the configuration for
5434 the ``account`` subsystem.
5436 An example authorization object to validate a TLS x509
5437 distinguished name would look like:
5443 -object authz-pam,id=auth0,service=qemu-vnc \\
5446 There would then be a corresponding config file for PAM at
5447 ``/etc/pam.d/qemu-vnc`` that contains:
5451 account requisite pam_listfile.so item=user sense=allow \
5452 file=/etc/qemu/vnc.allow
5454 Finally the ``/etc/qemu/vnc.allow`` file would contain the list
5455 of x509 distingished names that are permitted access
5459 CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB
5461 ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch``
5462 Creates a dedicated event loop thread that devices can be
5463 assigned to. This is known as an IOThread. By default device
5464 emulation happens in vCPU threads or the main event loop thread.
5465 This can become a scalability bottleneck. IOThreads allow device
5466 emulation and I/O to run on other host CPUs.
5468 The ``id`` parameter is a unique ID that will be used to
5469 reference this IOThread from ``-device ...,iothread=id``.
5470 Multiple devices can be assigned to an IOThread. Note that not
5471 all devices support an ``iothread`` parameter.
5473 The ``query-iothreads`` QMP command lists IOThreads and reports
5474 their thread IDs so that the user can configure host CPU
5477 IOThreads use an adaptive polling algorithm to reduce event loop
5478 latency. Instead of entering a blocking system call to monitor
5479 file descriptors and then pay the cost of being woken up when an
5480 event occurs, the polling algorithm spins waiting for events for
5481 a short time. The algorithm's default parameters are suitable
5482 for many cases but can be adjusted based on knowledge of the
5483 workload and/or host device latency.
5485 The ``poll-max-ns`` parameter is the maximum number of
5486 nanoseconds to busy wait for events. Polling can be disabled by
5487 setting this value to 0.
5489 The ``poll-grow`` parameter is the multiplier used to increase
5490 the polling time when the algorithm detects it is missing events
5491 due to not polling long enough.
5493 The ``poll-shrink`` parameter is the divisor used to decrease
5494 the polling time when the algorithm detects it is spending too
5495 long polling without encountering events.
5497 The ``aio-max-batch`` parameter is the maximum number of requests
5498 in a batch for the AIO engine, 0 means that the engine will use
5501 The IOThread parameters can be modified at run-time using the
5502 ``qom-set`` command (where ``iothread1`` is the IOThread's
5507 (qemu) qom-set /objects/iothread1 poll-max-ns 100000
5511 HXCOMM This is the last statement. Insert new options before this line!