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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
156 acpi= [HW,ACPI,X86]
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
175 Format: <int>
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
178 default: 0
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
182 acpi_backlight=video
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
189 Format: <int>
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
217 default in APIC mode
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
221 default in PIC mode
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
227 use by PCI
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
240 acpi_pm_good [X86]
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
258 s3_bios and s3_mode.
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
296 agp= [AGP]
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
302 ALSA [HW,ALSA]
303 See Documentation/sound/alsa/alsa-parameters.txt
305 alignment= [KNL,ARM]
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
325 Possible values are:
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
329 is a lot of faster
330 off - do not initialize any AMD IOMMU found in
331 the system
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
346 Format: <a>,<b>
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
354 apc= [HW,SPARC]
355 Power management functions (SPARCstation-4/5 + deriv.)
356 Format: noidle
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
367 autoconf= [IPV6]
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
385 ataflop= [HW,M68k]
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
398 keyboards
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
407 Format: <io>,<mode>
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
410 Format: <io>,<mode>
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
425 no delay (0).
426 Format: integer
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
432 kernel args too.
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
434 bttv.tuner=
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
438 at a time.
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
466 cio_ignore= [S390]
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
470 [Deprecated]
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
477 Format: <string>
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
481 the platform:
482 [all] jiffies (this is the base, fallback clocksource)
483 [ACPI] acpi_pm
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
486 [AVR32] avr32
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
489 [MIPS] MIPS
490 [PARISC] cr16
491 [S390] tod
492 [SH] SuperH
493 [SPARC64] tick
494 [X86-64] hpet,tsc
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
501 ones should be.
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
507 some critical bits.
509 cma=nn[MG] [ARM,KNL]
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
518 a hypervisor.
519 Default: yes
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
526 in an oops report.
527 Range: 0 - 8192
528 Default: 64
530 com20020= [HW,NET] ARCnet - COM20020 chipset
531 Format:
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
535 Format: <io>[,<irq>]
537 com90xx= [HW,NET]
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
542 conmode=
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
548 ttyS<n>[,options]
549 ttyUSB0[,options]
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
557 information. See
558 Documentation/networking/netconsole.txt for an
559 alternative.
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
568 If the device connected to the port is not a TTY but a braille
569 device, prepend "brl," before the device type, for instance
570 console=brl,ttyS0
571 For now, only VisioBraille is supported.
573 consoleblank= [KNL] The console blank (screen saver) timeout in
574 seconds. Defaults to 10*60 = 10mins. A value of 0
575 disables the blank timer.
577 coredump_filter=
578 [KNL] Change the default value for
579 /proc/<pid>/coredump_filter.
580 See also Documentation/filesystems/proc.txt.
582 cpuidle.off=1 [CPU_IDLE]
583 disable the cpuidle sub-system
585 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
586 Format:
587 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
589 crashkernel=size[KMG][@offset[KMG]]
590 [KNL] Using kexec, Linux can switch to a 'crash kernel'
591 upon panic. This parameter reserves the physical
592 memory region [offset, offset + size] for that kernel
593 image. If '@offset' is omitted, then a suitable offset
594 is selected automatically. Check
595 Documentation/kdump/kdump.txt for further details.
597 crashkernel=range1:size1[,range2:size2,...][@offset]
598 [KNL] Same as above, but depends on the memory
599 in the running system. The syntax of range is
600 start-[end] where start and end are both
601 a memory unit (amount[KMG]). See also
602 Documentation/kdump/kdump.txt for an example.
604 cs89x0_dma= [HW,NET]
605 Format: <dma>
607 cs89x0_media= [HW,NET]
608 Format: { rj45 | aui | bnc }
610 dasd= [HW,NET]
611 See header of drivers/s390/block/dasd_devmap.c.
613 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
614 (one device per port)
615 Format: <port#>,<type>
616 See also Documentation/input/joystick-parport.txt
618 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
619 time. See Documentation/dynamic-debug-howto.txt for
620 details. Deprecated, see dyndbg.
622 debug [KNL] Enable kernel debugging (events log level).
624 debug_locks_verbose=
625 [KNL] verbose self-tests
626 Format=<0|1>
627 Print debugging info while doing the locking API
628 self-tests.
629 We default to 0 (no extra messages), setting it to
630 1 will print _a lot_ more information - normally
631 only useful to kernel developers.
633 debug_objects [KNL] Enable object debugging
635 no_debug_objects
636 [KNL] Disable object debugging
638 debug_guardpage_minorder=
639 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
640 parameter allows control of the order of pages that will
641 be intentionally kept free (and hence protected) by the
642 buddy allocator. Bigger value increase the probability
643 of catching random memory corruption, but reduce the
644 amount of memory for normal system use. The maximum
645 possible value is MAX_ORDER/2. Setting this parameter
646 to 1 or 2 should be enough to identify most random
647 memory corruption problems caused by bugs in kernel or
648 driver code when a CPU writes to (or reads from) a
649 random memory location. Note that there exists a class
650 of memory corruptions problems caused by buggy H/W or
651 F/W or by drivers badly programing DMA (basically when
652 memory is written at bus level and the CPU MMU is
653 bypassed) which are not detectable by
654 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
655 tracking down these problems.
657 debugpat [X86] Enable PAT debugging
659 decnet.addr= [HW,NET]
660 Format: <area>[,<node>]
661 See also Documentation/networking/decnet.txt.
663 default_hugepagesz=
664 [same as hugepagesz=] The size of the default
665 HugeTLB page size. This is the size represented by
666 the legacy /proc/ hugepages APIs, used for SHM, and
667 default size when mounting hugetlbfs filesystems.
668 Defaults to the default architecture's huge page size
669 if not specified.
671 dhash_entries= [KNL]
672 Set number of hash buckets for dentry cache.
674 digi= [HW,SERIAL]
675 IO parameters + enable/disable command.
677 digiepca= [HW,SERIAL]
678 See drivers/char/README.epca and
679 Documentation/serial/digiepca.txt.
681 disable= [IPV6]
682 See Documentation/networking/ipv6.txt.
684 disable_ddw [PPC/PSERIES]
685 Disable Dynamic DMA Window support. Use this if
686 to workaround buggy firmware.
688 disable_ipv6= [IPV6]
689 See Documentation/networking/ipv6.txt.
691 disable_mtrr_cleanup [X86]
692 The kernel tries to adjust MTRR layout from continuous
693 to discrete, to make X server driver able to add WB
694 entry later. This parameter disables that.
696 disable_mtrr_trim [X86, Intel and AMD only]
697 By default the kernel will trim any uncacheable
698 memory out of your available memory pool based on
699 MTRR settings. This parameter disables that behavior,
700 possibly causing your machine to run very slowly.
702 disable_timer_pin_1 [X86]
703 Disable PIN 1 of APIC timer
704 Can be useful to work around chipset bugs.
706 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
707 this option disables the debugging code at boot.
709 dma_debug_entries=<number>
710 This option allows to tune the number of preallocated
711 entries for DMA-API debugging code. One entry is
712 required per DMA-API allocation. Use this if the
713 DMA-API debugging code disables itself because the
714 architectural default is too low.
716 dma_debug_driver=<driver_name>
717 With this option the DMA-API debugging driver
718 filter feature can be enabled at boot time. Just
719 pass the driver to filter for as the parameter.
720 The filter can be disabled or changed to another
721 driver later using sysfs.
723 drm_kms_helper.edid_firmware=[<connector>:]<file>
724 Broken monitors, graphic adapters and KVMs may
725 send no or incorrect EDID data sets. This parameter
726 allows to specify an EDID data set in the
727 /lib/firmware directory that is used instead.
728 Generic built-in EDID data sets are used, if one of
729 edid/1024x768.bin, edid/1280x1024.bin,
730 edid/1680x1050.bin, or edid/1920x1080.bin is given
731 and no file with the same name exists. Details and
732 instructions how to build your own EDID data are
733 available in Documentation/EDID/HOWTO.txt. An EDID
734 data set will only be used for a particular connector,
735 if its name and a colon are prepended to the EDID
736 name.
738 dscc4.setup= [NET]
740 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
741 module.dyndbg[="val"]
742 Enable debug messages at boot time. See
743 Documentation/dynamic-debug-howto.txt for details.
745 earlycon= [KNL] Output early console device and options.
746 uart[8250],io,<addr>[,options]
747 uart[8250],mmio,<addr>[,options]
748 uart[8250],mmio32,<addr>[,options]
749 Start an early, polled-mode console on the 8250/16550
750 UART at the specified I/O port or MMIO address.
751 MMIO inter-register address stride is either 8-bit
752 (mmio) or 32-bit (mmio32).
753 The options are the same as for ttyS, above.
755 earlyprintk= [X86,SH,BLACKFIN]
756 earlyprintk=vga
757 earlyprintk=serial[,ttySn[,baudrate]]
758 earlyprintk=ttySn[,baudrate]
759 earlyprintk=dbgp[debugController#]
761 Append ",keep" to not disable it when the real console
762 takes over.
764 Only vga or serial or usb debug port at a time.
766 Currently only ttyS0 and ttyS1 are supported.
768 Interaction with the standard serial driver is not
769 very good.
771 The VGA output is eventually overwritten by the real
772 console.
774 ekgdboc= [X86,KGDB] Allow early kernel console debugging
775 ekgdboc=kbd
777 This is designed to be used in conjunction with
778 the boot argument: earlyprintk=vga
780 edd= [EDD]
781 Format: {"off" | "on" | "skip[mbr]"}
783 eisa_irq_edge= [PARISC,HW]
784 See header of drivers/parisc/eisa.c.
786 elanfreq= [X86-32]
787 See comment before function elanfreq_setup() in
788 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
790 elevator= [IOSCHED]
791 Format: {"cfq" | "deadline" | "noop"}
792 See Documentation/block/cfq-iosched.txt and
793 Documentation/block/deadline-iosched.txt for details.
795 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
796 Specifies physical address of start of kernel core
797 image elf header and optionally the size. Generally
798 kexec loader will pass this option to capture kernel.
799 See Documentation/kdump/kdump.txt for details.
801 enable_mtrr_cleanup [X86]
802 The kernel tries to adjust MTRR layout from continuous
803 to discrete, to make X server driver able to add WB
804 entry later. This parameter enables that.
806 enable_timer_pin_1 [X86]
807 Enable PIN 1 of APIC timer
808 Can be useful to work around chipset bugs
809 (in particular on some ATI chipsets).
810 The kernel tries to set a reasonable default.
812 enforcing [SELINUX] Set initial enforcing status.
813 Format: {"0" | "1"}
814 See security/selinux/Kconfig help text.
815 0 -- permissive (log only, no denials).
816 1 -- enforcing (deny and log).
817 Default value is 0.
818 Value can be changed at runtime via /selinux/enforce.
820 erst_disable [ACPI]
821 Disable Error Record Serialization Table (ERST)
822 support.
824 ether= [HW,NET] Ethernet cards parameters
825 This option is obsoleted by the "netdev=" option, which
826 has equivalent usage. See its documentation for details.
828 evm= [EVM]
829 Format: { "fix" }
830 Permit 'security.evm' to be updated regardless of
831 current integrity status.
833 failslab=
834 fail_page_alloc=
835 fail_make_request=[KNL]
836 General fault injection mechanism.
837 Format: <interval>,<probability>,<space>,<times>
838 See also Documentation/fault-injection/.
840 floppy= [HW]
841 See Documentation/blockdev/floppy.txt.
843 force_pal_cache_flush
844 [IA-64] Avoid check_sal_cache_flush which may hang on
845 buggy SAL_CACHE_FLUSH implementations. Using this
846 parameter will force ia64_sal_cache_flush to call
847 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
849 ftrace=[tracer]
850 [FTRACE] will set and start the specified tracer
851 as early as possible in order to facilitate early
852 boot debugging.
854 ftrace_dump_on_oops[=orig_cpu]
855 [FTRACE] will dump the trace buffers on oops.
856 If no parameter is passed, ftrace will dump
857 buffers of all CPUs, but if you pass orig_cpu, it will
858 dump only the buffer of the CPU that triggered the
859 oops.
861 ftrace_filter=[function-list]
862 [FTRACE] Limit the functions traced by the function
863 tracer at boot up. function-list is a comma separated
864 list of functions. This list can be changed at run
865 time by the set_ftrace_filter file in the debugfs
866 tracing directory.
868 ftrace_notrace=[function-list]
869 [FTRACE] Do not trace the functions specified in
870 function-list. This list can be changed at run time
871 by the set_ftrace_notrace file in the debugfs
872 tracing directory.
874 ftrace_graph_filter=[function-list]
875 [FTRACE] Limit the top level callers functions traced
876 by the function graph tracer at boot up.
877 function-list is a comma separated list of functions
878 that can be changed at run time by the
879 set_graph_function file in the debugfs tracing directory.
881 gamecon.map[2|3]=
882 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
883 support via parallel port (up to 5 devices per port)
884 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
885 See also Documentation/input/joystick-parport.txt
887 gamma= [HW,DRM]
889 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
890 Format: off | on
891 default: on
893 gcov_persist= [GCOV] When non-zero (default), profiling data for
894 kernel modules is saved and remains accessible via
895 debugfs, even when the module is unloaded/reloaded.
896 When zero, profiling data is discarded and associated
897 debugfs files are removed at module unload time.
899 gpt [EFI] Forces disk with valid GPT signature but
900 invalid Protective MBR to be treated as GPT.
902 grcan.enable0= [HW] Configuration of physical interface 0. Determines
903 the "Enable 0" bit of the configuration register.
904 Format: 0 | 1
905 Default: 0
906 grcan.enable1= [HW] Configuration of physical interface 1. Determines
907 the "Enable 0" bit of the configuration register.
908 Format: 0 | 1
909 Default: 0
910 grcan.select= [HW] Select which physical interface to use.
911 Format: 0 | 1
912 Default: 0
913 grcan.txsize= [HW] Sets the size of the tx buffer.
914 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
915 Default: 1024
916 grcan.rxsize= [HW] Sets the size of the rx buffer.
917 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
918 Default: 1024
920 hashdist= [KNL,NUMA] Large hashes allocated during boot
921 are distributed across NUMA nodes. Defaults on
922 for 64-bit NUMA, off otherwise.
923 Format: 0 | 1 (for off | on)
925 hcl= [IA-64] SGI's Hardware Graph compatibility layer
927 hd= [EIDE] (E)IDE hard drive subsystem geometry
928 Format: <cyl>,<head>,<sect>
930 hest_disable [ACPI]
931 Disable Hardware Error Source Table (HEST) support;
932 corresponding firmware-first mode error processing
933 logic will be disabled.
935 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
936 size of <nn>. This works even on boxes that have no
937 highmem otherwise. This also works to reduce highmem
938 size on bigger boxes.
940 highres= [KNL] Enable/disable high resolution timer mode.
941 Valid parameters: "on", "off"
942 Default: "on"
944 hisax= [HW,ISDN]
945 See Documentation/isdn/README.HiSax.
947 hlt [BUGS=ARM,SH]
949 hpet= [X86-32,HPET] option to control HPET usage
950 Format: { enable (default) | disable | force |
951 verbose }
952 disable: disable HPET and use PIT instead
953 force: allow force enabled of undocumented chips (ICH4,
954 VIA, nVidia)
955 verbose: show contents of HPET registers during setup
957 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
958 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
959 On x86-64 and powerpc, this option can be specified
960 multiple times interleaved with hugepages= to reserve
961 huge pages of different sizes. Valid pages sizes on
962 x86-64 are 2M (when the CPU supports "pse") and 1G
963 (when the CPU supports the "pdpe1gb" cpuinfo flag)
964 Note that 1GB pages can only be allocated at boot time
965 using hugepages= and not freed afterwards.
967 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
968 terminal devices. Valid values: 0..8
969 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
970 If specified, z/VM IUCV HVC accepts connections
971 from listed z/VM user IDs only.
973 keep_bootcon [KNL]
974 Do not unregister boot console at start. This is only
975 useful for debugging when something happens in the window
976 between unregistering the boot console and initializing
977 the real console.
979 i2c_bus= [HW] Override the default board specific I2C bus speed
980 or register an additional I2C bus that is not
981 registered from board initialization code.
982 Format:
983 <bus_id>,<clkrate>
985 i8042.debug [HW] Toggle i8042 debug mode
986 i8042.direct [HW] Put keyboard port into non-translated mode
987 i8042.dumbkbd [HW] Pretend that controller can only read data from
988 keyboard and cannot control its state
989 (Don't attempt to blink the leds)
990 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
991 i8042.nokbd [HW] Don't check/create keyboard port
992 i8042.noloop [HW] Disable the AUX Loopback command while probing
993 for the AUX port
994 i8042.nomux [HW] Don't check presence of an active multiplexing
995 controller
996 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
997 controllers
998 i8042.notimeout [HW] Ignore timeout condition signalled by controller
999 i8042.reset [HW] Reset the controller during init and cleanup
1000 i8042.unlock [HW] Unlock (ignore) the keylock
1002 i810= [HW,DRM]
1004 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1005 indicates that the driver is running on unsupported
1006 hardware.
1007 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1008 does not match list of supported models.
1009 i8k.power_status
1010 [HW] Report power status in /proc/i8k
1011 (disabled by default)
1012 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1013 capability is set.
1015 i915.invert_brightness=
1016 [DRM] Invert the sense of the variable that is used to
1017 set the brightness of the panel backlight. Normally a
1018 brightness value of 0 indicates backlight switched off,
1019 and the maximum of the brightness value sets the backlight
1020 to maximum brightness. If this parameter is set to 0
1021 (default) and the machine requires it, or this parameter
1022 is set to 1, a brightness value of 0 sets the backlight
1023 to maximum brightness, and the maximum of the brightness
1024 value switches the backlight off.
1025 -1 -- never invert brightness
1026 0 -- machine default
1027 1 -- force brightness inversion
1029 icn= [HW,ISDN]
1030 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1032 ide-core.nodma= [HW] (E)IDE subsystem
1033 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1034 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1035 .cdrom .chs .ignore_cable are additional options
1036 See Documentation/ide/ide.txt.
1038 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1039 Claim all unknown PCI IDE storage controllers.
1041 idle= [X86]
1042 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1043 Poll forces a polling idle loop that can slightly
1044 improve the performance of waking up a idle CPU, but
1045 will use a lot of power and make the system run hot.
1046 Not recommended.
1047 idle=mwait: On systems which support MONITOR/MWAIT but
1048 the kernel chose to not use it because it doesn't save
1049 as much power as a normal idle loop, use the
1050 MONITOR/MWAIT idle loop anyways. Performance should be
1051 the same as idle=poll.
1052 idle=halt: Halt is forced to be used for CPU idle.
1053 In such case C2/C3 won't be used again.
1054 idle=nomwait: Disable mwait for CPU C-states
1056 ignore_loglevel [KNL]
1057 Ignore loglevel setting - this will print /all/
1058 kernel messages to the console. Useful for debugging.
1059 We also add it as printk module parameter, so users
1060 could change it dynamically, usually by
1061 /sys/module/printk/parameters/ignore_loglevel.
1063 ihash_entries= [KNL]
1064 Set number of hash buckets for inode cache.
1066 ima_appraise= [IMA] appraise integrity measurements
1067 Format: { "off" | "enforce" | "fix" }
1068 default: "enforce"
1070 ima_appraise_tcb [IMA]
1071 The builtin appraise policy appraises all files
1072 owned by uid=0.
1074 ima_audit= [IMA]
1075 Format: { "0" | "1" }
1076 0 -- integrity auditing messages. (Default)
1077 1 -- enable informational integrity auditing messages.
1079 ima_hash= [IMA]
1080 Format: { "sha1" | "md5" }
1081 default: "sha1"
1083 ima_tcb [IMA]
1084 Load a policy which meets the needs of the Trusted
1085 Computing Base. This means IMA will measure all
1086 programs exec'd, files mmap'd for exec, and all files
1087 opened for read by uid=0.
1089 init= [KNL]
1090 Format: <full_path>
1091 Run specified binary instead of /sbin/init as init
1092 process.
1094 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1095 for working out where the kernel is dying during
1096 startup.
1098 initrd= [BOOT] Specify the location of the initial ramdisk
1100 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1101 Format: <irq>
1103 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1104 on
1105 Enable intel iommu driver.
1106 off
1107 Disable intel iommu driver.
1108 igfx_off [Default Off]
1109 By default, gfx is mapped as normal device. If a gfx
1110 device has a dedicated DMAR unit, the DMAR unit is
1111 bypassed by not enabling DMAR with this option. In
1112 this case, gfx device will use physical address for
1113 DMA.
1114 forcedac [x86_64]
1115 With this option iommu will not optimize to look
1116 for io virtual address below 32-bit forcing dual
1117 address cycle on pci bus for cards supporting greater
1118 than 32-bit addressing. The default is to look
1119 for translation below 32-bit and if not available
1120 then look in the higher range.
1121 strict [Default Off]
1122 With this option on every unmap_single operation will
1123 result in a hardware IOTLB flush operation as opposed
1124 to batching them for performance.
1125 sp_off [Default Off]
1126 By default, super page will be supported if Intel IOMMU
1127 has the capability. With this option, super page will
1128 not be supported.
1130 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1131 0 disables intel_idle and fall back on acpi_idle.
1132 1 to 6 specify maximum depth of C-state.
1134 intremap= [X86-64, Intel-IOMMU]
1135 on enable Interrupt Remapping (default)
1136 off disable Interrupt Remapping
1137 nosid disable Source ID checking
1138 no_x2apic_optout
1139 BIOS x2APIC opt-out request will be ignored
1141 iomem= Disable strict checking of access to MMIO memory
1142 strict regions from userspace.
1143 relaxed
1145 iommu= [x86]
1146 off
1147 force
1148 noforce
1149 biomerge
1150 panic
1151 nopanic
1152 merge
1153 nomerge
1154 forcesac
1155 soft
1156 pt [x86, IA-64]
1159 io7= [HW] IO7 for Marvel based alpha systems
1160 See comment before marvel_specify_io7 in
1161 arch/alpha/kernel/core_marvel.c.
1163 io_delay= [X86] I/O delay method
1164 0x80
1165 Standard port 0x80 based delay
1166 0xed
1167 Alternate port 0xed based delay (needed on some systems)
1168 udelay
1169 Simple two microseconds delay
1170 none
1171 No delay
1173 ip= [IP_PNP]
1174 See Documentation/filesystems/nfs/nfsroot.txt.
1176 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1177 See comment before ip2_setup() in
1178 drivers/char/ip2/ip2base.c.
1180 irqfixup [HW]
1181 When an interrupt is not handled search all handlers
1182 for it. Intended to get systems with badly broken
1183 firmware running.
1185 irqpoll [HW]
1186 When an interrupt is not handled search all handlers
1187 for it. Also check all handlers each timer
1188 interrupt. Intended to get systems with badly broken
1189 firmware running.
1191 isapnp= [ISAPNP]
1192 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1194 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1195 Format:
1196 <cpu number>,...,<cpu number>
1197 or
1198 <cpu number>-<cpu number>
1199 (must be a positive range in ascending order)
1200 or a mixture
1201 <cpu number>,...,<cpu number>-<cpu number>
1203 This option can be used to specify one or more CPUs
1204 to isolate from the general SMP balancing and scheduling
1205 algorithms. You can move a process onto or off an
1206 "isolated" CPU via the CPU affinity syscalls or cpuset.
1207 <cpu number> begins at 0 and the maximum value is
1208 "number of CPUs in system - 1".
1210 This option is the preferred way to isolate CPUs. The
1211 alternative -- manually setting the CPU mask of all
1212 tasks in the system -- can cause problems and
1213 suboptimal load balancer performance.
1215 iucv= [HW,NET]
1217 js= [HW,JOY] Analog joystick
1218 See Documentation/input/joystick.txt.
1220 keepinitrd [HW,ARM]
1222 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1223 specifies the amount of memory usable by the kernel
1224 for non-movable allocations. The requested amount is
1225 spread evenly throughout all nodes in the system. The
1226 remaining memory in each node is used for Movable
1227 pages. In the event, a node is too small to have both
1228 kernelcore and Movable pages, kernelcore pages will
1229 take priority and other nodes will have a larger number
1230 of kernelcore pages. The Movable zone is used for the
1231 allocation of pages that may be reclaimed or moved
1232 by the page migration subsystem. This means that
1233 HugeTLB pages may not be allocated from this zone.
1234 Note that allocations like PTEs-from-HighMem still
1235 use the HighMem zone if it exists, and the Normal
1236 zone if it does not.
1238 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1239 Format: <Controller#>[,poll interval]
1240 The controller # is the number of the ehci usb debug
1241 port as it is probed via PCI. The poll interval is
1242 optional and is the number seconds in between
1243 each poll cycle to the debug port in case you need
1244 the functionality for interrupting the kernel with
1245 gdb or control-c on the dbgp connection. When
1246 not using this parameter you use sysrq-g to break into
1247 the kernel debugger.
1249 kgdboc= [KGDB,HW] kgdb over consoles.
1250 Requires a tty driver that supports console polling,
1251 or a supported polling keyboard driver (non-usb).
1252 Serial only format: <serial_device>[,baud]
1253 keyboard only format: kbd
1254 keyboard and serial format: kbd,<serial_device>[,baud]
1255 Optional Kernel mode setting:
1256 kms, kbd format: kms,kbd
1257 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1259 kgdbwait [KGDB] Stop kernel execution and enter the
1260 kernel debugger at the earliest opportunity.
1262 kmac= [MIPS] korina ethernet MAC address.
1263 Configure the RouterBoard 532 series on-chip
1264 Ethernet adapter MAC address.
1266 kmemleak= [KNL] Boot-time kmemleak enable/disable
1267 Valid arguments: on, off
1268 Default: on
1270 kstack=N [X86] Print N words from the kernel stack
1271 in oops dumps.
1273 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1274 Default is 0 (don't ignore, but inject #GP)
1276 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1277 KVM MMU at runtime.
1278 Default is 0 (off)
1280 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1281 Default is 1 (enabled)
1283 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1284 for all guests.
1285 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1287 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1288 (virtualized MMU) support on capable Intel chips.
1289 Default is 1 (enabled)
1291 kvm-intel.emulate_invalid_guest_state=
1292 [KVM,Intel] Enable emulation of invalid guest states
1293 Default is 0 (disabled)
1295 kvm-intel.flexpriority=
1296 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1297 Default is 1 (enabled)
1299 kvm-intel.nested=
1300 [KVM,Intel] Enable VMX nesting (nVMX).
1301 Default is 0 (disabled)
1303 kvm-intel.unrestricted_guest=
1304 [KVM,Intel] Disable unrestricted guest feature
1305 (virtualized real and unpaged mode) on capable
1306 Intel chips. Default is 1 (enabled)
1308 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1309 feature (tagged TLBs) on capable Intel chips.
1310 Default is 1 (enabled)
1312 l2cr= [PPC]
1314 l3cr= [PPC]
1316 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1317 disabled it.
1319 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1320 value for LAPIC timer one-shot implementation. Default
1321 back to the programmable timer unit in the LAPIC.
1323 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1324 in C2 power state.
1326 libata.dma= [LIBATA] DMA control
1327 libata.dma=0 Disable all PATA and SATA DMA
1328 libata.dma=1 PATA and SATA Disk DMA only
1329 libata.dma=2 ATAPI (CDROM) DMA only
1330 libata.dma=4 Compact Flash DMA only
1331 Combinations also work, so libata.dma=3 enables DMA
1332 for disks and CDROMs, but not CFs.
1334 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1335 libata.ignore_hpa=0 keep BIOS limits (default)
1336 libata.ignore_hpa=1 ignore limits, using full disk
1338 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1339 when set.
1340 Format: <int>
1342 libata.force= [LIBATA] Force configurations. The format is comma
1343 separated list of "[ID:]VAL" where ID is
1344 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1345 matching port, link or device. Basically, it matches
1346 the ATA ID string printed on console by libata. If
1347 the whole ID part is omitted, the last PORT and DEVICE
1348 values are used. If ID hasn't been specified yet, the
1349 configuration applies to all ports, links and devices.
1351 If only DEVICE is omitted, the parameter applies to
1352 the port and all links and devices behind it. DEVICE
1353 number of 0 either selects the first device or the
1354 first fan-out link behind PMP device. It does not
1355 select the host link. DEVICE number of 15 selects the
1356 host link and device attached to it.
1358 The VAL specifies the configuration to force. As long
1359 as there's no ambiguity shortcut notation is allowed.
1360 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1361 The following configurations can be forced.
1363 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1364 Any ID with matching PORT is used.
1366 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1368 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1369 udma[/][16,25,33,44,66,100,133] notation is also
1370 allowed.
1372 * [no]ncq: Turn on or off NCQ.
1374 * nohrst, nosrst, norst: suppress hard, soft
1375 and both resets.
1377 * rstonce: only attempt one reset during
1378 hot-unplug link recovery
1380 * dump_id: dump IDENTIFY data.
1382 If there are multiple matching configurations changing
1383 the same attribute, the last one is used.
1385 memblock=debug [KNL] Enable memblock debug messages.
1387 load_ramdisk= [RAM] List of ramdisks to load from floppy
1388 See Documentation/blockdev/ramdisk.txt.
1390 lockd.nlm_grace_period=P [NFS] Assign grace period.
1391 Format: <integer>
1393 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1394 Format: <integer>
1396 lockd.nlm_timeout=T [NFS] Assign timeout value.
1397 Format: <integer>
1399 lockd.nlm_udpport=M [NFS] Assign UDP port.
1400 Format: <integer>
1402 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1403 Format: <irq>
1405 loglevel= All Kernel Messages with a loglevel smaller than the
1406 console loglevel will be printed to the console. It can
1407 also be changed with klogd or other programs. The
1408 loglevels are defined as follows:
1410 0 (KERN_EMERG) system is unusable
1411 1 (KERN_ALERT) action must be taken immediately
1412 2 (KERN_CRIT) critical conditions
1413 3 (KERN_ERR) error conditions
1414 4 (KERN_WARNING) warning conditions
1415 5 (KERN_NOTICE) normal but significant condition
1416 6 (KERN_INFO) informational
1417 7 (KERN_DEBUG) debug-level messages
1419 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1420 in bytes. n must be a power of two. The default
1421 size is set in the kernel config file.
1423 logo.nologo [FB] Disables display of the built-in Linux logo.
1424 This may be used to provide more screen space for
1425 kernel log messages and is useful when debugging
1426 kernel boot problems.
1428 lp=0 [LP] Specify parallel ports to use, e.g,
1429 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1430 lp=reset first parallel port). 'lp=0' disables the
1431 lp=auto printer driver. 'lp=reset' (which can be
1432 specified in addition to the ports) causes
1433 attached printers to be reset. Using
1434 lp=port1,port2,... specifies the parallel ports
1435 to associate lp devices with, starting with
1436 lp0. A port specification may be 'none' to skip
1437 that lp device, or a parport name such as
1438 'parport0'. Specifying 'lp=auto' instead of a
1439 port specification list means that device IDs
1440 from each port should be examined, to see if
1441 an IEEE 1284-compliant printer is attached; if
1442 so, the driver will manage that printer.
1443 See also header of drivers/char/lp.c.
1445 lpj=n [KNL]
1446 Sets loops_per_jiffy to given constant, thus avoiding
1447 time-consuming boot-time autodetection (up to 250 ms per
1448 CPU). 0 enables autodetection (default). To determine
1449 the correct value for your kernel, boot with normal
1450 autodetection and see what value is printed. Note that
1451 on SMP systems the preset will be applied to all CPUs,
1452 which is likely to cause problems if your CPUs need
1453 significantly divergent settings. An incorrect value
1454 will cause delays in the kernel to be wrong, leading to
1455 unpredictable I/O errors and other breakage. Although
1456 unlikely, in the extreme case this might damage your
1457 hardware.
1459 ltpc= [NET]
1460 Format: <io>,<irq>,<dma>
1462 machvec= [IA-64] Force the use of a particular machine-vector
1463 (machvec) in a generic kernel.
1464 Example: machvec=hpzx1_swiotlb
1466 machtype= [Loongson] Share the same kernel image file between different
1467 yeeloong laptop.
1468 Example: machtype=lemote-yeeloong-2f-7inch
1470 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1471 than or equal to this physical address is ignored.
1473 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1474 should make use of. maxcpus=n : n >= 0 limits the
1475 kernel to using 'n' processors. n=0 is a special case,
1476 it is equivalent to "nosmp", which also disables
1477 the IO APIC.
1479 max_loop= [LOOP] The number of loop block devices that get
1480 (loop.max_loop) unconditionally pre-created at init time. The default
1481 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1482 of statically allocating a predefined number, loop
1483 devices can be requested on-demand with the
1484 /dev/loop-control interface.
1486 mce [X86-32] Machine Check Exception
1488 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1490 md= [HW] RAID subsystems devices and level
1491 See Documentation/md.txt.
1493 mdacon= [MDA]
1494 Format: <first>,<last>
1495 Specifies range of consoles to be captured by the MDA.
1497 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1498 Amount of memory to be used when the kernel is not able
1499 to see the whole system memory or for test.
1500 [X86] Work as limiting max address. Use together
1501 with memmap= to avoid physical address space collisions.
1502 Without memmap= PCI devices could be placed at addresses
1503 belonging to unused RAM.
1505 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1506 memory.
1508 memchunk=nn[KMG]
1509 [KNL,SH] Allow user to override the default size for
1510 per-device physically contiguous DMA buffers.
1512 memmap=exactmap [KNL,X86] Enable setting of an exact
1513 E820 memory map, as specified by the user.
1514 Such memmap=exactmap lines can be constructed based on
1515 BIOS output or other requirements. See the memmap=nn@ss
1516 option description.
1518 memmap=nn[KMG]@ss[KMG]
1519 [KNL] Force usage of a specific region of memory
1520 Region of memory to be used, from ss to ss+nn.
1522 memmap=nn[KMG]#ss[KMG]
1523 [KNL,ACPI] Mark specific memory as ACPI data.
1524 Region of memory to be used, from ss to ss+nn.
1526 memmap=nn[KMG]$ss[KMG]
1527 [KNL,ACPI] Mark specific memory as reserved.
1528 Region of memory to be used, from ss to ss+nn.
1529 Example: Exclude memory from 0x18690000-0x1869ffff
1530 memmap=64K$0x18690000
1531 or
1532 memmap=0x10000$0x18690000
1534 memory_corruption_check=0/1 [X86]
1535 Some BIOSes seem to corrupt the first 64k of
1536 memory when doing things like suspend/resume.
1537 Setting this option will scan the memory
1538 looking for corruption. Enabling this will
1539 both detect corruption and prevent the kernel
1540 from using the memory being corrupted.
1541 However, its intended as a diagnostic tool; if
1542 repeatable BIOS-originated corruption always
1543 affects the same memory, you can use memmap=
1544 to prevent the kernel from using that memory.
1546 memory_corruption_check_size=size [X86]
1547 By default it checks for corruption in the low
1548 64k, making this memory unavailable for normal
1549 use. Use this parameter to scan for
1550 corruption in more or less memory.
1552 memory_corruption_check_period=seconds [X86]
1553 By default it checks for corruption every 60
1554 seconds. Use this parameter to check at some
1555 other rate. 0 disables periodic checking.
1557 memtest= [KNL,X86] Enable memtest
1558 Format: <integer>
1559 default : 0 <disable>
1560 Specifies the number of memtest passes to be
1561 performed. Each pass selects another test
1562 pattern from a given set of patterns. Memtest
1563 fills the memory with this pattern, validates
1564 memory contents and reserves bad memory
1565 regions that are detected.
1567 meye.*= [HW] Set MotionEye Camera parameters
1568 See Documentation/video4linux/meye.txt.
1570 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1571 Multi-Function General Purpose Timers on AMD Geode
1572 platforms.
1574 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1575 the BIOS has incorrectly applied a workaround. TinyBIOS
1576 version 0.98 is known to be affected, 0.99 fixes the
1577 problem by letting the user disable the workaround.
1579 mga= [HW,DRM]
1581 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1582 physical address is ignored.
1584 mini2440= [ARM,HW,KNL]
1585 Format:[0..2][b][c][t]
1586 Default: "0tb"
1587 MINI2440 configuration specification:
1588 0 - The attached screen is the 3.5" TFT
1589 1 - The attached screen is the 7" TFT
1590 2 - The VGA Shield is attached (1024x768)
1591 Leaving out the screen size parameter will not load
1592 the TFT driver, and the framebuffer will be left
1593 unconfigured.
1594 b - Enable backlight. The TFT backlight pin will be
1595 linked to the kernel VESA blanking code and a GPIO
1596 LED. This parameter is not necessary when using the
1597 VGA shield.
1598 c - Enable the s3c camera interface.
1599 t - Reserved for enabling touchscreen support. The
1600 touchscreen support is not enabled in the mainstream
1601 kernel as of 2.6.30, a preliminary port can be found
1602 in the "bleeding edge" mini2440 support kernel at
1603 http://repo.or.cz/w/linux-2.6/mini2440.git
1605 mminit_loglevel=
1606 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1607 parameter allows control of the logging verbosity for
1608 the additional memory initialisation checks. A value
1609 of 0 disables mminit logging and a level of 4 will
1610 log everything. Information is printed at KERN_DEBUG
1611 so loglevel=8 may also need to be specified.
1613 module.sig_enforce
1614 [KNL] When CONFIG_MODULE_SIG is set, this means that
1615 modules without (valid) signatures will fail to load.
1616 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1617 is always true, so this option does nothing.
1619 mousedev.tap_time=
1620 [MOUSE] Maximum time between finger touching and
1621 leaving touchpad surface for touch to be considered
1622 a tap and be reported as a left button click (for
1623 touchpads working in absolute mode only).
1624 Format: <msecs>
1625 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1626 reporting absolute coordinates, such as tablets
1627 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1628 reporting absolute coordinates, such as tablets
1630 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1631 is similar to kernelcore except it specifies the
1632 amount of memory used for migratable allocations.
1633 If both kernelcore and movablecore is specified,
1634 then kernelcore will be at *least* the specified
1635 value but may be more. If movablecore on its own
1636 is specified, the administrator must be careful
1637 that the amount of memory usable for all allocations
1638 is not too small.
1640 MTD_Partition= [MTD]
1641 Format: <name>,<region-number>,<size>,<offset>
1643 MTD_Region= [MTD] Format:
1644 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1646 mtdparts= [MTD]
1647 See drivers/mtd/cmdlinepart.c.
1649 multitce=off [PPC] This parameter disables the use of the pSeries
1650 firmware feature for updating multiple TCE entries
1651 at a time.
1653 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1655 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1657 boundary - index of last SLC block on Flex-OneNAND.
1658 The remaining blocks are configured as MLC blocks.
1659 lock - Configure if Flex-OneNAND boundary should be locked.
1660 Once locked, the boundary cannot be changed.
1661 1 indicates lock status, 0 indicates unlock status.
1663 mtdset= [ARM]
1664 ARM/S3C2412 JIVE boot control
1666 See arch/arm/mach-s3c2412/mach-jive.c
1668 mtouchusb.raw_coordinates=
1669 [HW] Make the MicroTouch USB driver use raw coordinates
1670 ('y', default) or cooked coordinates ('n')
1672 mtrr_chunk_size=nn[KMG] [X86]
1673 used for mtrr cleanup. It is largest continuous chunk
1674 that could hold holes aka. UC entries.
1676 mtrr_gran_size=nn[KMG] [X86]
1677 Used for mtrr cleanup. It is granularity of mtrr block.
1678 Default is 1.
1679 Large value could prevent small alignment from
1680 using up MTRRs.
1682 mtrr_spare_reg_nr=n [X86]
1683 Format: <integer>
1684 Range: 0,7 : spare reg number
1685 Default : 1
1686 Used for mtrr cleanup. It is spare mtrr entries number.
1687 Set to 2 or more if your graphical card needs more.
1689 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1691 netdev= [NET] Network devices parameters
1692 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1693 Note that mem_start is often overloaded to mean
1694 something different and driver-specific.
1695 This usage is only documented in each driver source
1696 file if at all.
1698 nf_conntrack.acct=
1699 [NETFILTER] Enable connection tracking flow accounting
1700 0 to disable accounting
1701 1 to enable accounting
1702 Default value is 0.
1704 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1705 See Documentation/filesystems/nfs/nfsroot.txt.
1707 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1708 See Documentation/filesystems/nfs/nfsroot.txt.
1710 nfsrootdebug [NFS] enable nfsroot debugging messages.
1711 See Documentation/filesystems/nfs/nfsroot.txt.
1713 nfs.callback_tcpport=
1714 [NFS] set the TCP port on which the NFSv4 callback
1715 channel should listen.
1717 nfs.cache_getent=
1718 [NFS] sets the pathname to the program which is used
1719 to update the NFS client cache entries.
1721 nfs.cache_getent_timeout=
1722 [NFS] sets the timeout after which an attempt to
1723 update a cache entry is deemed to have failed.
1725 nfs.idmap_cache_timeout=
1726 [NFS] set the maximum lifetime for idmapper cache
1727 entries.
1729 nfs.enable_ino64=
1730 [NFS] enable 64-bit inode numbers.
1731 If zero, the NFS client will fake up a 32-bit inode
1732 number for the readdir() and stat() syscalls instead
1733 of returning the full 64-bit number.
1734 The default is to return 64-bit inode numbers.
1736 nfs.max_session_slots=
1737 [NFSv4.1] Sets the maximum number of session slots
1738 the client will attempt to negotiate with the server.
1739 This limits the number of simultaneous RPC requests
1740 that the client can send to the NFSv4.1 server.
1741 Note that there is little point in setting this
1742 value higher than the max_tcp_slot_table_limit.
1744 nfs.nfs4_disable_idmapping=
1745 [NFSv4] When set to the default of '1', this option
1746 ensures that both the RPC level authentication
1747 scheme and the NFS level operations agree to use
1748 numeric uids/gids if the mount is using the
1749 'sec=sys' security flavour. In effect it is
1750 disabling idmapping, which can make migration from
1751 legacy NFSv2/v3 systems to NFSv4 easier.
1752 Servers that do not support this mode of operation
1753 will be autodetected by the client, and it will fall
1754 back to using the idmapper.
1755 To turn off this behaviour, set the value to '0'.
1756 nfs.nfs4_unique_id=
1757 [NFS4] Specify an additional fixed unique ident-
1758 ification string that NFSv4 clients can insert into
1759 their nfs_client_id4 string. This is typically a
1760 UUID that is generated at system install time.
1762 nfs.send_implementation_id =
1763 [NFSv4.1] Send client implementation identification
1764 information in exchange_id requests.
1765 If zero, no implementation identification information
1766 will be sent.
1767 The default is to send the implementation identification
1768 information.
1770 nfsd.nfs4_disable_idmapping=
1771 [NFSv4] When set to the default of '1', the NFSv4
1772 server will return only numeric uids and gids to
1773 clients using auth_sys, and will accept numeric uids
1774 and gids from such clients. This is intended to ease
1775 migration from NFSv2/v3.
1777 objlayoutdriver.osd_login_prog=
1778 [NFS] [OBJLAYOUT] sets the pathname to the program which
1779 is used to automatically discover and login into new
1780 osd-targets. Please see:
1781 Documentation/filesystems/pnfs.txt for more explanations
1783 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1784 when a NMI is triggered.
1785 Format: [state][,regs][,debounce][,die]
1787 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1788 Format: [panic,][nopanic,][num]
1789 Valid num: 0
1790 0 - turn nmi_watchdog off
1791 When panic is specified, panic when an NMI watchdog
1792 timeout occurs (or 'nopanic' to override the opposite
1793 default).
1794 This is useful when you use a panic=... timeout and
1795 need the box quickly up again.
1797 netpoll.carrier_timeout=
1798 [NET] Specifies amount of time (in seconds) that
1799 netpoll should wait for a carrier. By default netpoll
1800 waits 4 seconds.
1802 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1803 emulation library even if a 387 maths coprocessor
1804 is present.
1806 no_console_suspend
1807 [HW] Never suspend the console
1808 Disable suspending of consoles during suspend and
1809 hibernate operations. Once disabled, debugging
1810 messages can reach various consoles while the rest
1811 of the system is being put to sleep (ie, while
1812 debugging driver suspend/resume hooks). This may
1813 not work reliably with all consoles, but is known
1814 to work with serial and VGA consoles.
1815 To facilitate more flexible debugging, we also add
1816 console_suspend, a printk module parameter to control
1817 it. Users could use console_suspend (usually
1818 /sys/module/printk/parameters/console_suspend) to
1819 turn on/off it dynamically.
1821 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1822 caches in the slab allocator. Saves per-node memory,
1823 but will impact performance.
1825 noalign [KNL,ARM]
1827 noapic [SMP,APIC] Tells the kernel to not make use of any
1828 IOAPICs that may be present in the system.
1830 noautogroup Disable scheduler automatic task group creation.
1832 nobats [PPC] Do not use BATs for mapping kernel lowmem
1833 on "Classic" PPC cores.
1835 nocache [ARM]
1837 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1839 nodelayacct [KNL] Disable per-task delay accounting
1841 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1843 nodsp [SH] Disable hardware DSP at boot time.
1845 noefi [X86] Disable EFI runtime services support.
1847 noexec [IA-64]
1849 noexec [X86]
1850 On X86-32 available only on PAE configured kernels.
1851 noexec=on: enable non-executable mappings (default)
1852 noexec=off: disable non-executable mappings
1854 nosmap [X86]
1855 Disable SMAP (Supervisor Mode Access Prevention)
1856 even if it is supported by processor.
1858 nosmep [X86]
1859 Disable SMEP (Supervisor Mode Execution Prevention)
1860 even if it is supported by processor.
1862 noexec32 [X86-64]
1863 This affects only 32-bit executables.
1864 noexec32=on: enable non-executable mappings (default)
1865 read doesn't imply executable mappings
1866 noexec32=off: disable non-executable mappings
1867 read implies executable mappings
1869 nofpu [SH] Disable hardware FPU at boot time.
1871 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1872 register save and restore. The kernel will only save
1873 legacy floating-point registers on task switch.
1875 noxsave [BUGS=X86] Disables x86 extended register state save
1876 and restore using xsave. The kernel will fallback to
1877 enabling legacy floating-point and sse state.
1879 eagerfpu= [X86]
1880 on enable eager fpu restore
1881 off disable eager fpu restore
1882 auto selects the default scheme, which automatically
1883 enables eagerfpu restore for xsaveopt.
1885 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1886 wfi(ARM) instruction doesn't work correctly and not to
1887 use it. This is also useful when using JTAG debugger.
1889 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1890 instruction doesn't work correctly and not to
1891 use it.
1893 no_file_caps Tells the kernel not to honor file capabilities. The
1894 only way then for a file to be executed with privilege
1895 is to be setuid root or executed by root.
1897 nohalt [IA-64] Tells the kernel not to use the power saving
1898 function PAL_HALT_LIGHT when idle. This increases
1899 power-consumption. On the positive side, it reduces
1900 interrupt wake-up latency, which may improve performance
1901 in certain environments such as networked servers or
1902 real-time systems.
1904 nohz= [KNL] Boottime enable/disable dynamic ticks
1905 Valid arguments: on, off
1906 Default: on
1908 noiotrap [SH] Disables trapped I/O port accesses.
1910 noirqdebug [X86-32] Disables the code which attempts to detect and
1911 disable unhandled interrupt sources.
1913 no_timer_check [X86,APIC] Disables the code which tests for
1914 broken timer IRQ sources.
1916 noisapnp [ISAPNP] Disables ISA PnP code.
1918 noinitrd [RAM] Tells the kernel not to load any configured
1919 initial RAM disk.
1921 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1922 remapping.
1923 [Deprecated - use intremap=off]
1925 nointroute [IA-64]
1927 nojitter [IA-64] Disables jitter checking for ITC timers.
1929 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1931 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1932 fault handling.
1934 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1935 steal time is computed, but won't influence scheduler
1936 behaviour
1938 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1940 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1942 noltlbs [PPC] Do not use large page/tlb entries for kernel
1943 lowmem mapping on PPC40x.
1945 nomca [IA-64] Disable machine check abort handling
1947 nomce [X86-32] Machine Check Exception
1949 nomfgpt [X86-32] Disable Multi-Function General Purpose
1950 Timer usage (for AMD Geode machines).
1952 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1953 shutdown the other cpus. Instead use the REBOOT_VECTOR
1954 irq.
1956 nomodule Disable module load
1958 nopat [X86] Disable PAT (page attribute table extension of
1959 pagetables) support.
1961 norandmaps Don't use address space randomization. Equivalent to
1962 echo 0 > /proc/sys/kernel/randomize_va_space
1964 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1966 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1967 with UP alternatives
1969 noresidual [PPC] Don't use residual data on PReP machines.
1971 nordrand [X86] Disable the direct use of the RDRAND
1972 instruction even if it is supported by the
1973 processor. RDRAND is still available to user
1974 space applications.
1976 noresume [SWSUSP] Disables resume and restores original swap
1977 space.
1979 no-scroll [VGA] Disables scrollback.
1980 This is required for the Braillex ib80-piezo Braille
1981 reader made by F.H. Papenmeier (Germany).
1983 nosbagart [IA-64]
1985 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1987 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1988 and disable the IO APIC. legacy for "maxcpus=0".
1990 nosoftlockup [KNL] Disable the soft-lockup detector.
1992 nosync [HW,M68K] Disables sync negotiation for all devices.
1994 notsc [BUGS=X86-32] Disable Time Stamp Counter
1996 nousb [USB] Disable the USB subsystem
1998 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2000 nowb [ARM]
2002 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2004 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2005 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2006 Some features depend on CPU0. Known dependencies are:
2007 1. Resume from suspend/hibernate depends on CPU0.
2008 Suspend/hibernate will fail if CPU0 is offline and you
2009 need to online CPU0 before suspend/hibernate.
2010 2. PIC interrupts also depend on CPU0. CPU0 can't be
2011 removed if a PIC interrupt is detected.
2012 It's said poweroff/reboot may depend on CPU0 on some
2013 machines although I haven't seen such issues so far
2014 after CPU0 is offline on a few tested machines.
2015 If the dependencies are under your control, you can
2016 turn on cpu0_hotplug.
2018 nptcg= [IA-64] Override max number of concurrent global TLB
2019 purges which is reported from either PAL_VM_SUMMARY or
2020 SAL PALO.
2022 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2023 could support. nr_cpus=n : n >= 1 limits the kernel to
2024 supporting 'n' processors. Later in runtime you can not
2025 use hotplug cpu feature to put more cpu back to online.
2026 just like you compile the kernel NR_CPUS=n
2028 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2030 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2031 Allowed values are enable and disable
2033 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2034 one of ['zone', 'node', 'default'] can be specified
2035 This can be set from sysctl after boot.
2036 See Documentation/sysctl/vm.txt for details.
2038 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2039 See Documentation/debugging-via-ohci1394.txt for more
2040 info.
2042 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2043 Rather than timing out after 20 ms if an EC
2044 command is not properly ACKed, override the length
2045 of the timeout. We have interrupts disabled while
2046 waiting for the ACK, so if this is set too high
2047 interrupts *may* be lost!
2049 omap_mux= [OMAP] Override bootloader pin multiplexing.
2050 Format: <mux_mode0.mode_name=value>...
2051 For example, to override I2C bus2:
2052 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2054 oprofile.timer= [HW]
2055 Use timer interrupt instead of performance counters
2057 oprofile.cpu_type= Force an oprofile cpu type
2058 This might be useful if you have an older oprofile
2059 userland or if you want common events.
2060 Format: { arch_perfmon }
2061 arch_perfmon: [X86] Force use of architectural
2062 perfmon on Intel CPUs instead of the
2063 CPU specific event set.
2064 timer: [X86] Force use of architectural NMI
2065 timer mode (see also oprofile.timer
2066 for generic hr timer mode)
2067 [s390] Force legacy basic mode sampling
2068 (report cpu_type "timer")
2070 oops=panic Always panic on oopses. Default is to just kill the
2071 process, but there is a small probability of
2072 deadlocking the machine.
2073 This will also cause panics on machine check exceptions.
2074 Useful together with panic=30 to trigger a reboot.
2076 OSS [HW,OSS]
2077 See Documentation/sound/oss/oss-parameters.txt
2079 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2080 timeout > 0: seconds before rebooting
2081 timeout = 0: wait forever
2082 timeout < 0: reboot immediately
2083 Format: <timeout>
2085 parkbd.port= [HW] Parallel port number the keyboard adapter is
2086 connected to, default is 0.
2087 Format: <parport#>
2088 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2089 0 for XT, 1 for AT (default is AT).
2090 Format: <mode>
2092 parport= [HW,PPT] Specify parallel ports. 0 disables.
2093 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2094 Use 'auto' to force the driver to use any
2095 IRQ/DMA settings detected (the default is to
2096 ignore detected IRQ/DMA settings because of
2097 possible conflicts). You can specify the base
2098 address, IRQ, and DMA settings; IRQ and DMA
2099 should be numbers, or 'auto' (for using detected
2100 settings on that particular port), or 'nofifo'
2101 (to avoid using a FIFO even if it is detected).
2102 Parallel ports are assigned in the order they
2103 are specified on the command line, starting
2104 with parport0.
2106 parport_init_mode= [HW,PPT]
2107 Configure VIA parallel port to operate in
2108 a specific mode. This is necessary on Pegasos
2109 computer where firmware has no options for setting
2110 up parallel port mode and sets it to spp.
2111 Currently this function knows 686a and 8231 chips.
2112 Format: [spp|ps2|epp|ecp|ecpepp]
2114 pause_on_oops=
2115 Halt all CPUs after the first oops has been printed for
2116 the specified number of seconds. This is to be used if
2117 your oopses keep scrolling off the screen.
2119 pcbit= [HW,ISDN]
2121 pcd. [PARIDE]
2122 See header of drivers/block/paride/pcd.c.
2123 See also Documentation/blockdev/paride.txt.
2125 pci=option[,option...] [PCI] various PCI subsystem options:
2126 earlydump [X86] dump PCI config space before the kernel
2127 changes anything
2128 off [X86] don't probe for the PCI bus
2129 bios [X86-32] force use of PCI BIOS, don't access
2130 the hardware directly. Use this if your machine
2131 has a non-standard PCI host bridge.
2132 nobios [X86-32] disallow use of PCI BIOS, only direct
2133 hardware access methods are allowed. Use this
2134 if you experience crashes upon bootup and you
2135 suspect they are caused by the BIOS.
2136 conf1 [X86] Force use of PCI Configuration
2137 Mechanism 1.
2138 conf2 [X86] Force use of PCI Configuration
2139 Mechanism 2.
2140 noaer [PCIE] If the PCIEAER kernel config parameter is
2141 enabled, this kernel boot option can be used to
2142 disable the use of PCIE advanced error reporting.
2143 nodomains [PCI] Disable support for multiple PCI
2144 root domains (aka PCI segments, in ACPI-speak).
2145 nommconf [X86] Disable use of MMCONFIG for PCI
2146 Configuration
2147 check_enable_amd_mmconf [X86] check for and enable
2148 properly configured MMIO access to PCI
2149 config space on AMD family 10h CPU
2150 nomsi [MSI] If the PCI_MSI kernel config parameter is
2151 enabled, this kernel boot option can be used to
2152 disable the use of MSI interrupts system-wide.
2153 noioapicquirk [APIC] Disable all boot interrupt quirks.
2154 Safety option to keep boot IRQs enabled. This
2155 should never be necessary.
2156 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2157 primary IO-APIC for bridges that cannot disable
2158 boot IRQs. This fixes a source of spurious IRQs
2159 when the system masks IRQs.
2160 noioapicreroute [APIC] Disable workaround that uses the
2161 boot IRQ equivalent of an IRQ that connects to
2162 a chipset where boot IRQs cannot be disabled.
2163 The opposite of ioapicreroute.
2164 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2165 routing table. These calls are known to be buggy
2166 on several machines and they hang the machine
2167 when used, but on other computers it's the only
2168 way to get the interrupt routing table. Try
2169 this option if the kernel is unable to allocate
2170 IRQs or discover secondary PCI buses on your
2171 motherboard.
2172 rom [X86] Assign address space to expansion ROMs.
2173 Use with caution as certain devices share
2174 address decoders between ROMs and other
2175 resources.
2176 norom [X86] Do not assign address space to
2177 expansion ROMs that do not already have
2178 BIOS assigned address ranges.
2179 nobar [X86] Do not assign address space to the
2180 BARs that weren't assigned by the BIOS.
2181 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2182 assigned automatically to PCI devices. You can
2183 make the kernel exclude IRQs of your ISA cards
2184 this way.
2185 pirqaddr=0xAAAAA [X86] Specify the physical address
2186 of the PIRQ table (normally generated
2187 by the BIOS) if it is outside the
2188 F0000h-100000h range.
2189 lastbus=N [X86] Scan all buses thru bus #N. Can be
2190 useful if the kernel is unable to find your
2191 secondary buses and you want to tell it
2192 explicitly which ones they are.
2193 assign-busses [X86] Always assign all PCI bus
2194 numbers ourselves, overriding
2195 whatever the firmware may have done.
2196 usepirqmask [X86] Honor the possible IRQ mask stored
2197 in the BIOS $PIR table. This is needed on
2198 some systems with broken BIOSes, notably
2199 some HP Pavilion N5400 and Omnibook XE3
2200 notebooks. This will have no effect if ACPI
2201 IRQ routing is enabled.
2202 noacpi [X86] Do not use ACPI for IRQ routing
2203 or for PCI scanning.
2204 use_crs [X86] Use PCI host bridge window information
2205 from ACPI. On BIOSes from 2008 or later, this
2206 is enabled by default. If you need to use this,
2207 please report a bug.
2208 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2209 If you need to use this, please report a bug.
2210 routeirq Do IRQ routing for all PCI devices.
2211 This is normally done in pci_enable_device(),
2212 so this option is a temporary workaround
2213 for broken drivers that don't call it.
2214 skip_isa_align [X86] do not align io start addr, so can
2215 handle more pci cards
2216 firmware [ARM] Do not re-enumerate the bus but instead
2217 just use the configuration from the
2218 bootloader. This is currently used on
2219 IXP2000 systems where the bus has to be
2220 configured a certain way for adjunct CPUs.
2221 noearly [X86] Don't do any early type 1 scanning.
2222 This might help on some broken boards which
2223 machine check when some devices' config space
2224 is read. But various workarounds are disabled
2225 and some IOMMU drivers will not work.
2226 bfsort Sort PCI devices into breadth-first order.
2227 This sorting is done to get a device
2228 order compatible with older (<= 2.4) kernels.
2229 nobfsort Don't sort PCI devices into breadth-first order.
2230 cbiosize=nn[KMG] The fixed amount of bus space which is
2231 reserved for the CardBus bridge's IO window.
2232 The default value is 256 bytes.
2233 cbmemsize=nn[KMG] The fixed amount of bus space which is
2234 reserved for the CardBus bridge's memory
2235 window. The default value is 64 megabytes.
2236 resource_alignment=
2237 Format:
2238 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2239 Specifies alignment and device to reassign
2240 aligned memory resources.
2241 If <order of align> is not specified,
2242 PAGE_SIZE is used as alignment.
2243 PCI-PCI bridge can be specified, if resource
2244 windows need to be expanded.
2245 ecrc= Enable/disable PCIe ECRC (transaction layer
2246 end-to-end CRC checking).
2247 bios: Use BIOS/firmware settings. This is the
2248 the default.
2249 off: Turn ECRC off
2250 on: Turn ECRC on.
2251 realloc= Enable/disable reallocating PCI bridge resources
2252 if allocations done by BIOS are too small to
2253 accommodate resources required by all child
2254 devices.
2255 off: Turn realloc off
2256 on: Turn realloc on
2257 realloc same as realloc=on
2258 noari do not use PCIe ARI.
2259 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2260 only look for one device below a PCIe downstream
2261 port.
2263 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2264 Management.
2265 off Disable ASPM.
2266 force Enable ASPM even on devices that claim not to support it.
2267 WARNING: Forcing ASPM on may cause system lockups.
2269 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2270 nomsi Do not use MSI for PCI Express Native Hotplug (this
2271 makes all PCIe ports use INTx for hotplug services).
2273 pcie_ports= [PCIE] PCIe ports handling:
2274 auto Ask the BIOS whether or not to use native PCIe services
2275 associated with PCIe ports (PME, hot-plug, AER). Use
2276 them only if that is allowed by the BIOS.
2277 native Use native PCIe services associated with PCIe ports
2278 unconditionally.
2279 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2280 ports driver.
2282 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2283 nomsi Do not use MSI for native PCIe PME signaling (this makes
2284 all PCIe root ports use INTx for all services).
2286 pcmv= [HW,PCMCIA] BadgePAD 4
2288 pd. [PARIDE]
2289 See Documentation/blockdev/paride.txt.
2291 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2292 boot time.
2293 Format: { 0 | 1 }
2294 See arch/parisc/kernel/pdc_chassis.c
2296 percpu_alloc= Select which percpu first chunk allocator to use.
2297 Currently supported values are "embed" and "page".
2298 Archs may support subset or none of the selections.
2299 See comments in mm/percpu.c for details on each
2300 allocator. This parameter is primarily for debugging
2301 and performance comparison.
2303 pf. [PARIDE]
2304 See Documentation/blockdev/paride.txt.
2306 pg. [PARIDE]
2307 See Documentation/blockdev/paride.txt.
2309 pirq= [SMP,APIC] Manual mp-table setup
2310 See Documentation/x86/i386/IO-APIC.txt.
2312 plip= [PPT,NET] Parallel port network link
2313 Format: { parport<nr> | timid | 0 }
2314 See also Documentation/parport.txt.
2316 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2317 Override pmtimer IOPort with a hex value.
2318 e.g. pmtmr=0x508
2320 pnp.debug=1 [PNP]
2321 Enable PNP debug messages (depends on the
2322 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2323 via /sys/module/pnp/parameters/debug. We always show
2324 current resource usage; turning this on also shows
2325 possible settings and some assignment information.
2327 pnpacpi= [ACPI]
2328 { off }
2330 pnpbios= [ISAPNP]
2331 { on | off | curr | res | no-curr | no-res }
2333 pnp_reserve_irq=
2334 [ISAPNP] Exclude IRQs for the autoconfiguration
2336 pnp_reserve_dma=
2337 [ISAPNP] Exclude DMAs for the autoconfiguration
2339 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2340 Ranges are in pairs (I/O port base and size).
2342 pnp_reserve_mem=
2343 [ISAPNP] Exclude memory regions for the
2344 autoconfiguration.
2345 Ranges are in pairs (memory base and size).
2347 ports= [IP_VS_FTP] IPVS ftp helper module
2348 Default is 21.
2349 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2350 may be specified.
2351 Format: <port>,<port>....
2353 print-fatal-signals=
2354 [KNL] debug: print fatal signals
2356 If enabled, warn about various signal handling
2357 related application anomalies: too many signals,
2358 too many POSIX.1 timers, fatal signals causing a
2359 coredump - etc.
2361 If you hit the warning due to signal overflow,
2362 you might want to try "ulimit -i unlimited".
2364 default: off.
2366 printk.always_kmsg_dump=
2367 Trigger kmsg_dump for cases other than kernel oops or
2368 panics
2369 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2370 default: disabled
2372 printk.time= Show timing data prefixed to each printk message line
2373 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2375 processor.max_cstate= [HW,ACPI]
2376 Limit processor to maximum C-state
2377 max_cstate=9 overrides any DMI blacklist limit.
2379 processor.nocst [HW,ACPI]
2380 Ignore the _CST method to determine C-states,
2381 instead using the legacy FADT method
2383 profile= [KNL] Enable kernel profiling via /proc/profile
2384 Format: [schedule,]<number>
2385 Param: "schedule" - profile schedule points.
2386 Param: <number> - step/bucket size as a power of 2 for
2387 statistical time based profiling.
2388 Param: "sleep" - profile D-state sleeping (millisecs).
2389 Requires CONFIG_SCHEDSTATS
2390 Param: "kvm" - profile VM exits.
2392 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2393 before loading.
2394 See Documentation/blockdev/ramdisk.txt.
2396 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2397 probe for; one of (bare|imps|exps|lifebook|any).
2398 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2399 per second.
2400 psmouse.resetafter= [HW,MOUSE]
2401 Try to reset the device after so many bad packets
2402 (0 = never).
2403 psmouse.resolution=
2404 [HW,MOUSE] Set desired mouse resolution, in dpi.
2405 psmouse.smartscroll=
2406 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2407 0 = disabled, 1 = enabled (default).
2409 pstore.backend= Specify the name of the pstore backend to use
2411 pt. [PARIDE]
2412 See Documentation/blockdev/paride.txt.
2414 pty.legacy_count=
2415 [KNL] Number of legacy pty's. Overwrites compiled-in
2416 default number.
2418 quiet [KNL] Disable most log messages
2420 r128= [HW,DRM]
2422 raid= [HW,RAID]
2423 See Documentation/md.txt.
2425 ramdisk_blocksize= [RAM]
2426 See Documentation/blockdev/ramdisk.txt.
2428 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2429 See Documentation/blockdev/ramdisk.txt.
2431 rcu_nocbs= [KNL,BOOT]
2432 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2433 the specified list of CPUs to be no-callback CPUs.
2434 Invocation of these CPUs' RCU callbacks will
2435 be offloaded to "rcuoN" kthreads created for
2436 that purpose. This reduces OS jitter on the
2437 offloaded CPUs, which can be useful for HPC and
2438 real-time workloads. It can also improve energy
2439 efficiency for asymmetric multiprocessors.
2441 rcu_nocb_poll [KNL,BOOT]
2442 Rather than requiring that offloaded CPUs
2443 (specified by rcu_nocbs= above) explicitly
2444 awaken the corresponding "rcuoN" kthreads,
2445 make these kthreads poll for callbacks.
2446 This improves the real-time response for the
2447 offloaded CPUs by relieving them of the need to
2448 wake up the corresponding kthread, but degrades
2449 energy efficiency by requiring that the kthreads
2450 periodically wake up to do the polling.
2452 rcutree.blimit= [KNL,BOOT]
2453 Set maximum number of finished RCU callbacks to process
2454 in one batch.
2456 rcutree.fanout_leaf= [KNL,BOOT]
2457 Increase the number of CPUs assigned to each
2458 leaf rcu_node structure. Useful for very large
2459 systems.
2461 rcutree.qhimark= [KNL,BOOT]
2462 Set threshold of queued
2463 RCU callbacks over which batch limiting is disabled.
2465 rcutree.qlowmark= [KNL,BOOT]
2466 Set threshold of queued RCU callbacks below which
2467 batch limiting is re-enabled.
2469 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2470 Suppress RCU CPU stall warning messages.
2472 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2473 Set timeout for RCU CPU stall warning messages.
2475 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2476 Set delay from grace-period initialization to
2477 first attempt to force quiescent states.
2478 Units are jiffies, minimum value is zero,
2479 and maximum value is HZ.
2481 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2482 Set delay between subsequent attempts to force
2483 quiescent states. Units are jiffies, minimum
2484 value is one, and maximum value is HZ.
2486 rcutorture.fqs_duration= [KNL,BOOT]
2487 Set duration of force_quiescent_state bursts.
2489 rcutorture.fqs_holdoff= [KNL,BOOT]
2490 Set holdoff time within force_quiescent_state bursts.
2492 rcutorture.fqs_stutter= [KNL,BOOT]
2493 Set wait time between force_quiescent_state bursts.
2495 rcutorture.irqreader= [KNL,BOOT]
2496 Test RCU readers from irq handlers.
2498 rcutorture.n_barrier_cbs= [KNL,BOOT]
2499 Set callbacks/threads for rcu_barrier() testing.
2501 rcutorture.nfakewriters= [KNL,BOOT]
2502 Set number of concurrent RCU writers. These just
2503 stress RCU, they don't participate in the actual
2504 test, hence the "fake".
2506 rcutorture.nreaders= [KNL,BOOT]
2507 Set number of RCU readers.
2509 rcutorture.onoff_holdoff= [KNL,BOOT]
2510 Set time (s) after boot for CPU-hotplug testing.
2512 rcutorture.onoff_interval= [KNL,BOOT]
2513 Set time (s) between CPU-hotplug operations, or
2514 zero to disable CPU-hotplug testing.
2516 rcutorture.shuffle_interval= [KNL,BOOT]
2517 Set task-shuffle interval (s). Shuffling tasks
2518 allows some CPUs to go into dyntick-idle mode
2519 during the rcutorture test.
2521 rcutorture.shutdown_secs= [KNL,BOOT]
2522 Set time (s) after boot system shutdown. This
2523 is useful for hands-off automated testing.
2525 rcutorture.stall_cpu= [KNL,BOOT]
2526 Duration of CPU stall (s) to test RCU CPU stall
2527 warnings, zero to disable.
2529 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2530 Time to wait (s) after boot before inducing stall.
2532 rcutorture.stat_interval= [KNL,BOOT]
2533 Time (s) between statistics printk()s.
2535 rcutorture.stutter= [KNL,BOOT]
2536 Time (s) to stutter testing, for example, specifying
2537 five seconds causes the test to run for five seconds,
2538 wait for five seconds, and so on. This tests RCU's
2539 ability to transition abruptly to and from idle.
2541 rcutorture.test_boost= [KNL,BOOT]
2542 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2543 "Maybe" means test if the RCU implementation
2544 under test support RCU priority boosting.
2546 rcutorture.test_boost_duration= [KNL,BOOT]
2547 Duration (s) of each individual boost test.
2549 rcutorture.test_boost_interval= [KNL,BOOT]
2550 Interval (s) between each boost test.
2552 rcutorture.test_no_idle_hz= [KNL,BOOT]
2553 Test RCU's dyntick-idle handling. See also the
2554 rcutorture.shuffle_interval parameter.
2556 rcutorture.torture_type= [KNL,BOOT]
2557 Specify the RCU implementation to test.
2559 rcutorture.verbose= [KNL,BOOT]
2560 Enable additional printk() statements.
2562 rdinit= [KNL]
2563 Format: <full_path>
2564 Run specified binary instead of /init from the ramdisk,
2565 used for early userspace startup. See initrd.
2567 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2568 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2569 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2571 relax_domain_level=
2572 [KNL, SMP] Set scheduler's default relax_domain_level.
2573 See Documentation/cgroups/cpusets.txt.
2575 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2577 reservetop= [X86-32]
2578 Format: nn[KMG]
2579 Reserves a hole at the top of the kernel virtual
2580 address space.
2582 reservelow= [X86]
2583 Format: nn[K]
2584 Set the amount of memory to reserve for BIOS at
2585 the bottom of the address space.
2587 reset_devices [KNL] Force drivers to reset the underlying device
2588 during initialization.
2590 resume= [SWSUSP]
2591 Specify the partition device for software suspend
2592 Format:
2593 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2595 resume_offset= [SWSUSP]
2596 Specify the offset from the beginning of the partition
2597 given by "resume=" at which the swap header is located,
2598 in <PAGE_SIZE> units (needed only for swap files).
2599 See Documentation/power/swsusp-and-swap-files.txt
2601 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2602 read the resume files
2604 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2605 Useful for devices that are detected asynchronously
2606 (e.g. USB and MMC devices).
2608 hibernate= [HIBERNATION]
2609 noresume Don't check if there's a hibernation image
2610 present during boot.
2611 nocompress Don't compress/decompress hibernation images.
2613 retain_initrd [RAM] Keep initrd memory after extraction
2615 rhash_entries= [KNL,NET]
2616 Set number of hash buckets for route cache
2618 riscom8= [HW,SERIAL]
2619 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2621 ro [KNL] Mount root device read-only on boot
2623 root= [KNL] Root filesystem
2624 See name_to_dev_t comment in init/do_mounts.c.
2626 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2627 mount the root filesystem
2629 rootflags= [KNL] Set root filesystem mount option string
2631 rootfstype= [KNL] Set root filesystem type
2633 rootwait [KNL] Wait (indefinitely) for root device to show up.
2634 Useful for devices that are detected asynchronously
2635 (e.g. USB and MMC devices).
2637 rw [KNL] Mount root device read-write on boot
2639 S [KNL] Run init in single mode
2641 sa1100ir [NET]
2642 See drivers/net/irda/sa1100_ir.c.
2644 sbni= [NET] Granch SBNI12 leased line adapter
2646 sched_debug [KNL] Enables verbose scheduler debug messages.
2648 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2649 xtime_lock contention on larger systems, and/or RCU lock
2650 contention on all systems with CONFIG_MAXSMP set.
2651 Format: { "0" | "1" }
2652 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2653 1 -- enable.
2654 Note: increases power consumption, thus should only be
2655 enabled if running jitter sensitive (HPC/RT) workloads.
2657 security= [SECURITY] Choose a security module to enable at boot.
2658 If this boot parameter is not specified, only the first
2659 security module asking for security registration will be
2660 loaded. An invalid security module name will be treated
2661 as if no module has been chosen.
2663 selinux= [SELINUX] Disable or enable SELinux at boot time.
2664 Format: { "0" | "1" }
2665 See security/selinux/Kconfig help text.
2666 0 -- disable.
2667 1 -- enable.
2668 Default value is set via kernel config option.
2669 If enabled at boot time, /selinux/disable can be used
2670 later to disable prior to initial policy load.
2672 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2673 Format: { "0" | "1" }
2674 See security/apparmor/Kconfig help text
2675 0 -- disable.
2676 1 -- enable.
2677 Default value is set via kernel config option.
2679 serialnumber [BUGS=X86-32]
2681 shapers= [NET]
2682 Maximal number of shapers.
2684 show_msr= [x86] show boot-time MSR settings
2685 Format: { <integer> }
2686 Show boot-time (BIOS-initialized) MSR settings.
2687 The parameter means the number of CPUs to show,
2688 for example 1 means boot CPU only.
2690 simeth= [IA-64]
2691 simscsi=
2693 slram= [HW,MTD]
2695 slab_max_order= [MM, SLAB]
2696 Determines the maximum allowed order for slabs.
2697 A high setting may cause OOMs due to memory
2698 fragmentation. Defaults to 1 for systems with
2699 more than 32MB of RAM, 0 otherwise.
2701 slub_debug[=options[,slabs]] [MM, SLUB]
2702 Enabling slub_debug allows one to determine the
2703 culprit if slab objects become corrupted. Enabling
2704 slub_debug can create guard zones around objects and
2705 may poison objects when not in use. Also tracks the
2706 last alloc / free. For more information see
2707 Documentation/vm/slub.txt.
2709 slub_max_order= [MM, SLUB]
2710 Determines the maximum allowed order for slabs.
2711 A high setting may cause OOMs due to memory
2712 fragmentation. For more information see
2713 Documentation/vm/slub.txt.
2715 slub_min_objects= [MM, SLUB]
2716 The minimum number of objects per slab. SLUB will
2717 increase the slab order up to slub_max_order to
2718 generate a sufficiently large slab able to contain
2719 the number of objects indicated. The higher the number
2720 of objects the smaller the overhead of tracking slabs
2721 and the less frequently locks need to be acquired.
2722 For more information see Documentation/vm/slub.txt.
2724 slub_min_order= [MM, SLUB]
2725 Determines the minimum page order for slabs. Must be
2726 lower than slub_max_order.
2727 For more information see Documentation/vm/slub.txt.
2729 slub_nomerge [MM, SLUB]
2730 Disable merging of slabs with similar size. May be
2731 necessary if there is some reason to distinguish
2732 allocs to different slabs. Debug options disable
2733 merging on their own.
2734 For more information see Documentation/vm/slub.txt.
2736 smart2= [HW]
2737 Format: <io1>[,<io2>[,...,<io8>]]
2739 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2740 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2741 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2742 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2743 smsc-ircc2.ircc_irq= [HW] IRQ line
2744 smsc-ircc2.ircc_dma= [HW] DMA channel
2745 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2746 0: Toshiba Satellite 1800 (GP data pin select)
2747 1: Fast pin select (default)
2748 2: ATC IRMode
2750 softlockup_panic=
2751 [KNL] Should the soft-lockup detector generate panics.
2752 Format: <integer>
2754 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2755 See Documentation/laptops/sonypi.txt
2757 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2758 See Documentation/serial/specialix.txt.
2760 spia_io_base= [HW,MTD]
2761 spia_fio_base=
2762 spia_pedr=
2763 spia_peddr=
2765 stacktrace [FTRACE]
2766 Enabled the stack tracer on boot up.
2768 stacktrace_filter=[function-list]
2769 [FTRACE] Limit the functions that the stack tracer
2770 will trace at boot up. function-list is a comma separated
2771 list of functions. This list can be changed at run
2772 time by the stack_trace_filter file in the debugfs
2773 tracing directory. Note, this enables stack tracing
2774 and the stacktrace above is not needed.
2776 sti= [PARISC,HW]
2777 Format: <num>
2778 Set the STI (builtin display/keyboard on the HP-PARISC
2779 machines) console (graphic card) which should be used
2780 as the initial boot-console.
2781 See also comment in drivers/video/console/sticore.c.
2783 sti_font= [HW]
2784 See comment in drivers/video/console/sticore.c.
2786 stifb= [HW]
2787 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2789 sunrpc.min_resvport=
2790 sunrpc.max_resvport=
2791 [NFS,SUNRPC]
2792 SunRPC servers often require that client requests
2793 originate from a privileged port (i.e. a port in the
2794 range 0 < portnr < 1024).
2795 An administrator who wishes to reserve some of these
2796 ports for other uses may adjust the range that the
2797 kernel's sunrpc client considers to be privileged
2798 using these two parameters to set the minimum and
2799 maximum port values.
2801 sunrpc.pool_mode=
2802 [NFS]
2803 Control how the NFS server code allocates CPUs to
2804 service thread pools. Depending on how many NICs
2805 you have and where their interrupts are bound, this
2806 option will affect which CPUs will do NFS serving.
2807 Note: this parameter cannot be changed while the
2808 NFS server is running.
2810 auto the server chooses an appropriate mode
2811 automatically using heuristics
2812 global a single global pool contains all CPUs
2813 percpu one pool for each CPU
2814 pernode one pool for each NUMA node (equivalent
2815 to global on non-NUMA machines)
2817 sunrpc.tcp_slot_table_entries=
2818 sunrpc.udp_slot_table_entries=
2819 [NFS,SUNRPC]
2820 Sets the upper limit on the number of simultaneous
2821 RPC calls that can be sent from the client to a
2822 server. Increasing these values may allow you to
2823 improve throughput, but will also increase the
2824 amount of memory reserved for use by the client.
2826 swapaccount[=0|1]
2827 [KNL] Enable accounting of swap in memory resource
2828 controller if no parameter or 1 is given or disable
2829 it if 0 is given (See Documentation/cgroups/memory.txt)
2831 swiotlb= [IA-64] Number of I/O TLB slabs
2833 switches= [HW,M68k]
2835 sysfs.deprecated=0|1 [KNL]
2836 Enable/disable old style sysfs layout for old udev
2837 on older distributions. When this option is enabled
2838 very new udev will not work anymore. When this option
2839 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2840 in older udev will not work anymore.
2841 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2842 the kernel configuration.
2844 sysrq_always_enabled
2845 [KNL]
2846 Ignore sysrq setting - this boot parameter will
2847 neutralize any effect of /proc/sys/kernel/sysrq.
2848 Useful for debugging.
2850 tdfx= [HW,DRM]
2852 test_suspend= [SUSPEND]
2853 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2854 standby suspend) as the system sleep state to briefly
2855 enter during system startup. The system is woken from
2856 this state using a wakeup-capable RTC alarm.
2858 thash_entries= [KNL,NET]
2859 Set number of hash buckets for TCP connection
2861 thermal.act= [HW,ACPI]
2862 -1: disable all active trip points in all thermal zones
2863 <degrees C>: override all lowest active trip points
2865 thermal.crt= [HW,ACPI]
2866 -1: disable all critical trip points in all thermal zones
2867 <degrees C>: override all critical trip points
2869 thermal.nocrt= [HW,ACPI]
2870 Set to disable actions on ACPI thermal zone
2871 critical and hot trip points.
2873 thermal.off= [HW,ACPI]
2874 1: disable ACPI thermal control
2876 thermal.psv= [HW,ACPI]
2877 -1: disable all passive trip points
2878 <degrees C>: override all passive trip points to this
2879 value
2881 thermal.tzp= [HW,ACPI]
2882 Specify global default ACPI thermal zone polling rate
2883 <deci-seconds>: poll all this frequency
2884 0: no polling (default)
2886 threadirqs [KNL]
2887 Force threading of all interrupt handlers except those
2888 marked explicitly IRQF_NO_THREAD.
2890 topology= [S390]
2891 Format: {off | on}
2892 Specify if the kernel should make use of the cpu
2893 topology information if the hardware supports this.
2894 The scheduler will make use of this information and
2895 e.g. base its process migration decisions on it.
2896 Default is on.
2898 tp720= [HW,PS2]
2900 tpm_suspend_pcr=[HW,TPM]
2901 Format: integer pcr id
2902 Specify that at suspend time, the tpm driver
2903 should extend the specified pcr with zeros,
2904 as a workaround for some chips which fail to
2905 flush the last written pcr on TPM_SaveState.
2906 This will guarantee that all the other pcrs
2907 are saved.
2909 trace_buf_size=nn[KMG]
2910 [FTRACE] will set tracing buffer size.
2912 trace_event=[event-list]
2913 [FTRACE] Set and start specified trace events in order
2914 to facilitate early boot debugging.
2915 See also Documentation/trace/events.txt
2917 trace_options=[option-list]
2918 [FTRACE] Enable or disable tracer options at boot.
2919 The option-list is a comma delimited list of options
2920 that can be enabled or disabled just as if you were
2921 to echo the option name into
2923 /sys/kernel/debug/tracing/trace_options
2925 For example, to enable stacktrace option (to dump the
2926 stack trace of each event), add to the command line:
2928 trace_options=stacktrace
2930 See also Documentation/trace/ftrace.txt "trace options"
2931 section.
2933 transparent_hugepage=
2934 [KNL]
2935 Format: [always|madvise|never]
2936 Can be used to control the default behavior of the system
2937 with respect to transparent hugepages.
2938 See Documentation/vm/transhuge.txt for more details.
2940 tsc= Disable clocksource stability checks for TSC.
2941 Format: <string>
2942 [x86] reliable: mark tsc clocksource as reliable, this
2943 disables clocksource verification at runtime, as well
2944 as the stability checks done at bootup. Used to enable
2945 high-resolution timer mode on older hardware, and in
2946 virtualized environment.
2947 [x86] noirqtime: Do not use TSC to do irq accounting.
2948 Used to run time disable IRQ_TIME_ACCOUNTING on any
2949 platforms where RDTSC is slow and this accounting
2950 can add overhead.
2952 turbografx.map[2|3]= [HW,JOY]
2953 TurboGraFX parallel port interface
2954 Format:
2955 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2956 See also Documentation/input/joystick-parport.txt
2958 udbg-immortal [PPC] When debugging early kernel crashes that
2959 happen after console_init() and before a proper
2960 console driver takes over, this boot options might
2961 help "seeing" what's going on.
2963 uhash_entries= [KNL,NET]
2964 Set number of hash buckets for UDP/UDP-Lite connections
2966 uhci-hcd.ignore_oc=
2967 [USB] Ignore overcurrent events (default N).
2968 Some badly-designed motherboards generate lots of
2969 bogus events, for ports that aren't wired to
2970 anything. Set this parameter to avoid log spamming.
2971 Note that genuine overcurrent events won't be
2972 reported either.
2974 unknown_nmi_panic
2975 [X86] Cause panic on unknown NMI.
2977 usbcore.authorized_default=
2978 [USB] Default USB device authorization:
2979 (default -1 = authorized except for wireless USB,
2980 0 = not authorized, 1 = authorized)
2982 usbcore.autosuspend=
2983 [USB] The autosuspend time delay (in seconds) used
2984 for newly-detected USB devices (default 2). This
2985 is the time required before an idle device will be
2986 autosuspended. Devices for which the delay is set
2987 to a negative value won't be autosuspended at all.
2989 usbcore.usbfs_snoop=
2990 [USB] Set to log all usbfs traffic (default 0 = off).
2992 usbcore.blinkenlights=
2993 [USB] Set to cycle leds on hubs (default 0 = off).
2995 usbcore.old_scheme_first=
2996 [USB] Start with the old device initialization
2997 scheme (default 0 = off).
2999 usbcore.usbfs_memory_mb=
3000 [USB] Memory limit (in MB) for buffers allocated by
3001 usbfs (default = 16, 0 = max = 2047).
3003 usbcore.use_both_schemes=
3004 [USB] Try the other device initialization scheme
3005 if the first one fails (default 1 = enabled).
3007 usbcore.initial_descriptor_timeout=
3008 [USB] Specifies timeout for the initial 64-byte
3009 USB_REQ_GET_DESCRIPTOR request in milliseconds
3010 (default 5000 = 5.0 seconds).
3012 usbhid.mousepoll=
3013 [USBHID] The interval which mice are to be polled at.
3015 usb-storage.delay_use=
3016 [UMS] The delay in seconds before a new device is
3017 scanned for Logical Units (default 5).
3019 usb-storage.quirks=
3020 [UMS] A list of quirks entries to supplement or
3021 override the built-in unusual_devs list. List
3022 entries are separated by commas. Each entry has
3023 the form VID:PID:Flags where VID and PID are Vendor
3024 and Product ID values (4-digit hex numbers) and
3025 Flags is a set of characters, each corresponding
3026 to a common usb-storage quirk flag as follows:
3027 a = SANE_SENSE (collect more than 18 bytes
3028 of sense data);
3029 b = BAD_SENSE (don't collect more than 18
3030 bytes of sense data);
3031 c = FIX_CAPACITY (decrease the reported
3032 device capacity by one sector);
3033 d = NO_READ_DISC_INFO (don't use
3034 READ_DISC_INFO command);
3035 e = NO_READ_CAPACITY_16 (don't use
3036 READ_CAPACITY_16 command);
3037 h = CAPACITY_HEURISTICS (decrease the
3038 reported device capacity by one
3039 sector if the number is odd);
3040 i = IGNORE_DEVICE (don't bind to this
3041 device);
3042 l = NOT_LOCKABLE (don't try to lock and
3043 unlock ejectable media);
3044 m = MAX_SECTORS_64 (don't transfer more
3045 than 64 sectors = 32 KB at a time);
3046 n = INITIAL_READ10 (force a retry of the
3047 initial READ(10) command);
3048 o = CAPACITY_OK (accept the capacity
3049 reported by the device);
3050 p = WRITE_CACHE (the device cache is ON
3051 by default);
3052 r = IGNORE_RESIDUE (the device reports
3053 bogus residue values);
3054 s = SINGLE_LUN (the device has only one
3055 Logical Unit);
3056 w = NO_WP_DETECT (don't test whether the
3057 medium is write-protected).
3058 Example: quirks=0419:aaf5:rl,0421:0433:rc
3060 user_debug= [KNL,ARM]
3061 Format: <int>
3062 See arch/arm/Kconfig.debug help text.
3063 1 - undefined instruction events
3064 2 - system calls
3065 4 - invalid data aborts
3066 8 - SIGSEGV faults
3067 16 - SIGBUS faults
3068 Example: user_debug=31
3070 userpte=
3071 [X86] Flags controlling user PTE allocations.
3073 nohigh = do not allocate PTE pages in
3074 HIGHMEM regardless of setting
3075 of CONFIG_HIGHPTE.
3077 vdso= [X86,SH]
3078 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3079 vdso=1: enable VDSO (default)
3080 vdso=0: disable VDSO mapping
3082 vdso32= [X86]
3083 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3084 vdso32=1: enable 32-bit VDSO (default)
3085 vdso32=0: disable 32-bit VDSO mapping
3087 vector= [IA-64,SMP]
3088 vector=percpu: enable percpu vector domain
3090 video= [FB] Frame buffer configuration
3091 See Documentation/fb/modedb.txt.
3093 virtio_mmio.device=
3094 [VMMIO] Memory mapped virtio (platform) device.
3096 <size>@<baseaddr>:<irq>[:<id>]
3097 where:
3098 <size> := size (can use standard suffixes
3099 like K, M and G)
3100 <baseaddr> := physical base address
3101 <irq> := interrupt number (as passed to
3102 request_irq())
3103 <id> := (optional) platform device id
3104 example:
3105 virtio_mmio.device=1K@0x100b0000:48:7
3107 Can be used multiple times for multiple devices.
3109 vga= [BOOT,X86-32] Select a particular video mode
3110 See Documentation/x86/boot.txt and
3111 Documentation/svga.txt.
3112 Use vga=ask for menu.
3113 This is actually a boot loader parameter; the value is
3114 passed to the kernel using a special protocol.
3116 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3117 size of <nn>. This can be used to increase the
3118 minimum size (128MB on x86). It can also be used to
3119 decrease the size and leave more room for directly
3120 mapped kernel RAM.
3122 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3123 Format: <command>
3125 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3126 Format: <command>
3128 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3129 Format: <command>
3131 vsyscall= [X86-64]
3132 Controls the behavior of vsyscalls (i.e. calls to
3133 fixed addresses of 0xffffffffff600x00 from legacy
3134 code). Most statically-linked binaries and older
3135 versions of glibc use these calls. Because these
3136 functions are at fixed addresses, they make nice
3137 targets for exploits that can control RIP.
3139 emulate [default] Vsyscalls turn into traps and are
3140 emulated reasonably safely.
3142 native Vsyscalls are native syscall instructions.
3143 This is a little bit faster than trapping
3144 and makes a few dynamic recompilers work
3145 better than they would in emulation mode.
3146 It also makes exploits much easier to write.
3148 none Vsyscalls don't work at all. This makes
3149 them quite hard to use for exploits but
3150 might break your system.
3152 vt.cur_default= [VT] Default cursor shape.
3153 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3154 the parameters of the <Esc>[?A;B;Cc escape sequence;
3155 see VGA-softcursor.txt. Default: 2 = underline.
3157 vt.default_blu= [VT]
3158 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3159 Change the default blue palette of the console.
3160 This is a 16-member array composed of values
3161 ranging from 0-255.
3163 vt.default_grn= [VT]
3164 Format: <green0>,<green1>,<green2>,...,<green15>
3165 Change the default green palette of the console.
3166 This is a 16-member array composed of values
3167 ranging from 0-255.
3169 vt.default_red= [VT]
3170 Format: <red0>,<red1>,<red2>,...,<red15>
3171 Change the default red palette of the console.
3172 This is a 16-member array composed of values
3173 ranging from 0-255.
3175 vt.default_utf8=
3176 [VT]
3177 Format=<0|1>
3178 Set system-wide default UTF-8 mode for all tty's.
3179 Default is 1, i.e. UTF-8 mode is enabled for all
3180 newly opened terminals.
3182 vt.global_cursor_default=
3183 [VT]
3184 Format=<-1|0|1>
3185 Set system-wide default for whether a cursor
3186 is shown on new VTs. Default is -1,
3187 i.e. cursors will be created by default unless
3188 overridden by individual drivers. 0 will hide
3189 cursors, 1 will display them.
3191 watchdog timers [HW,WDT] For information on watchdog timers,
3192 see Documentation/watchdog/watchdog-parameters.txt
3193 or other driver-specific files in the
3194 Documentation/watchdog/ directory.
3196 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3197 default x2apic cluster mode on platforms
3198 supporting x2apic.
3200 x86_mrst_timer= [X86-32,APBT]
3201 Choose timer option for x86 Moorestown MID platform.
3202 Two valid options are apbt timer only and lapic timer
3203 plus one apbt timer for broadcast timer.
3204 x86_mrst_timer=apbt_only | lapic_and_apbt
3206 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3207 xd_geo= See header of drivers/block/xd.c.
3209 xen_emul_unplug= [HW,X86,XEN]
3210 Unplug Xen emulated devices
3211 Format: [unplug0,][unplug1]
3212 ide-disks -- unplug primary master IDE devices
3213 aux-ide-disks -- unplug non-primary-master IDE devices
3214 nics -- unplug network devices
3215 all -- unplug all emulated devices (NICs and IDE disks)
3216 unnecessary -- unplugging emulated devices is
3217 unnecessary even if the host did not respond to
3218 the unplug protocol
3219 never -- do not unplug even if version check succeeds
3221 xirc2ps_cs= [NET,PCMCIA]
3222 Format:
3223 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3225 ______________________________________________________________________
3227 TODO:
3229 Add more DRM drivers.