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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 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
148 acpi= [HW,ACPI,X86]
149 Advanced Configuration and Power Interface
150 Format: { force | off | strict | noirq | rsdt }
151 force -- enable ACPI if default was off
152 off -- disable ACPI if default was on
153 noirq -- do not use ACPI for IRQ routing
154 strict -- Be less tolerant of platforms that are not
155 strictly ACPI specification compliant.
156 rsdt -- prefer RSDT over (default) XSDT
157 copy_dsdt -- copy DSDT to memory
159 See also Documentation/power/pm.txt, pci=noacpi
161 acpi_apic_instance= [ACPI, IOAPIC]
162 Format: <int>
163 2: use 2nd APIC table, if available
164 1,0: use 1st APIC table
165 default: 0
167 acpi_backlight= [HW,ACPI]
168 acpi_backlight=vendor
169 acpi_backlight=video
170 If set to vendor, prefer vendor specific driver
171 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
172 of the ACPI video.ko driver.
174 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
175 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
176 Format: <int>
177 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
178 debug output. Bits in debug_layer correspond to a
179 _COMPONENT in an ACPI source file, e.g.,
180 #define _COMPONENT ACPI_PCI_COMPONENT
181 Bits in debug_level correspond to a level in
182 ACPI_DEBUG_PRINT statements, e.g.,
183 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
184 The debug_level mask defaults to "info". See
185 Documentation/acpi/debug.txt for more information about
186 debug layers and levels.
188 Enable processor driver info messages:
189 acpi.debug_layer=0x20000000
190 Enable PCI/PCI interrupt routing info messages:
191 acpi.debug_layer=0x400000
192 Enable AML "Debug" output, i.e., stores to the Debug
193 object while interpreting AML:
194 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
195 Enable all messages related to ACPI hardware:
196 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
198 Some values produce so much output that the system is
199 unusable. The "log_buf_len" parameter may be useful
200 if you need to capture more output.
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
204 default in APIC mode
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
208 default in PIC mode
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 use by PCI
215 Format: <irq>,<irq>...
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
227 acpi_pm_good [X86]
228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
232 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
233 Format: { level | edge | high | low }
235 acpi_serialize [HW,ACPI] force serialization of AML methods
237 acpi_skip_timer_override [HW,ACPI]
238 Recognize and ignore IRQ0/pin2 Interrupt Override.
239 For broken nForce2 BIOS resulting in XT-PIC timer.
241 acpi_sleep= [HW,ACPI] Sleep options
242 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
243 old_ordering, s4_nonvs, sci_force_enable }
244 See Documentation/power/video.txt for information on
245 s3_bios and s3_mode.
246 s3_beep is for debugging; it makes the PC's speaker beep
247 as soon as the kernel's real-mode entry point is called.
248 s4_nohwsig prevents ACPI hardware signature from being
249 used during resume from hibernation.
250 old_ordering causes the ACPI 1.0 ordering of the _PTS
251 control method, with respect to putting devices into
252 low power states, to be enforced (the ACPI 2.0 ordering
253 of _PTS is used by default).
254 nonvs prevents the kernel from saving/restoring the
255 ACPI NVS memory during suspend/hibernation and resume.
256 sci_force_enable causes the kernel to set SCI_EN directly
257 on resume from S1/S3 (which is against the ACPI spec,
258 but some broken systems don't work without it).
260 acpi_use_timer_override [HW,ACPI]
261 Use timer override. For some broken Nvidia NF5 boards
262 that require a timer override, but don't have HPET
264 acpi_enforce_resources= [ACPI]
265 { strict | lax | no }
266 Check for resource conflicts between native drivers
267 and ACPI OperationRegions (SystemIO and SystemMemory
268 only). IO ports and memory declared in ACPI might be
269 used by the ACPI subsystem in arbitrary AML code and
270 can interfere with legacy drivers.
271 strict (default): access to resources claimed by ACPI
272 is denied; legacy drivers trying to access reserved
273 resources will fail to bind to device using them.
274 lax: access to resources claimed by ACPI is allowed;
275 legacy drivers trying to access reserved resources
276 will bind successfully but a warning message is logged.
277 no: ACPI OperationRegions are not marked as reserved,
278 no further checks are performed.
280 add_efi_memmap [EFI; X86] Include EFI memory map in
281 kernel's map of available physical RAM.
283 agp= [AGP]
284 { off | try_unsupported }
285 off: disable AGP support
286 try_unsupported: try to drive unsupported chipsets
287 (may crash computer or cause data corruption)
289 ALSA [HW,ALSA]
290 See Documentation/sound/alsa/alsa-parameters.txt
292 alignment= [KNL,ARM]
293 Allow the default userspace alignment fault handler
294 behaviour to be specified. Bit 0 enables warnings,
295 bit 1 enables fixups, and bit 2 sends a segfault.
297 amd_iommu= [HW,X86-84]
298 Pass parameters to the AMD IOMMU driver in the system.
299 Possible values are:
300 fullflush - enable flushing of IO/TLB entries when
301 they are unmapped. Otherwise they are
302 flushed before they will be reused, which
303 is a lot of faster
304 off - do not initialize any AMD IOMMU found in
305 the system
307 amijoy.map= [HW,JOY] Amiga joystick support
308 Map of devices attached to JOY0DAT and JOY1DAT
309 Format: <a>,<b>
310 See also Documentation/kernel/input/joystick.txt
312 analog.map= [HW,JOY] Analog joystick and gamepad support
313 Specifies type or capabilities of an analog joystick
314 connected to one of 16 gameports
315 Format: <type1>,<type2>,..<type16>
317 apc= [HW,SPARC]
318 Power management functions (SPARCstation-4/5 + deriv.)
319 Format: noidle
320 Disable APC CPU standby support. SPARCstation-Fox does
321 not play well with APC CPU idle - disable it if you have
322 APC and your system crashes randomly.
324 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
325 Change the output verbosity whilst booting
326 Format: { quiet (default) | verbose | debug }
327 Change the amount of debugging information output
328 when initialising the APIC and IO-APIC components.
330 autoconf= [IPV6]
331 See Documentation/networking/ipv6.txt.
333 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
334 Limit apic dumping. The parameter defines the maximal
335 number of local apics being dumped. Also it is possible
336 to set it to "all" by meaning -- no limit here.
337 Format: { 1 (default) | 2 | ... | all }.
338 The parameter valid if only apic=debug or
339 apic=verbose is specified.
340 Example: apic=debug show_lapic=all
342 apm= [APM] Advanced Power Management
343 See header of arch/x86/kernel/apm_32.c.
345 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
346 Format: <io>,<irq>,<nodeID>
348 ataflop= [HW,M68k]
350 atarimouse= [HW,MOUSE] Atari Mouse
352 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
353 EzKey and similar keyboards
355 atkbd.reset= [HW] Reset keyboard during initialization
357 atkbd.set= [HW] Select keyboard code set
358 Format: <int> (2 = AT (default), 3 = PS/2)
360 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
361 keyboards
363 atkbd.softraw= [HW] Choose between synthetic and real raw mode
364 Format: <bool> (0 = real, 1 = synthetic (default))
366 atkbd.softrepeat= [HW]
367 Use software keyboard repeat
369 autotest [IA64]
371 baycom_epp= [HW,AX25]
372 Format: <io>,<mode>
374 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
375 Format: <io>,<mode>
376 See header of drivers/net/hamradio/baycom_par.c.
378 baycom_ser_fdx= [HW,AX25]
379 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
380 Format: <io>,<irq>,<mode>[,<baud>]
381 See header of drivers/net/hamradio/baycom_ser_fdx.c.
383 baycom_ser_hdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
385 Format: <io>,<irq>,<mode>
386 See header of drivers/net/hamradio/baycom_ser_hdx.c.
388 boot_delay= Milliseconds to delay each printk during boot.
389 Values larger than 10 seconds (10000) are changed to
390 no delay (0).
391 Format: integer
393 bootmem_debug [KNL] Enable bootmem allocator debug messages.
395 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
396 bttv.radio= Most important insmod options are available as
397 kernel args too.
398 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
399 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
401 bulk_remove=off [PPC] This parameter disables the use of the pSeries
402 firmware feature for flushing multiple hpte entries
403 at a time.
405 c101= [NET] Moxa C101 synchronous serial card
407 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
408 Sometimes CPU hardware bugs make them report the cache
409 size incorrectly. The kernel will attempt work arounds
410 to fix known problems, but for some CPUs it is not
411 possible to determine what the correct size should be.
412 This option provides an override for these situations.
414 capability.disable=
415 [SECURITY] Disable capabilities. This would normally
416 be used only if an alternative security model is to be
417 configured. Potentially dangerous and should only be
418 used if you are entirely sure of the consequences.
420 ccw_timeout_log [S390]
421 See Documentation/s390/CommonIO for details.
423 cgroup_disable= [KNL] Disable a particular controller
424 Format: {name of the controller(s) to disable}
425 {Currently supported controllers - "memory"}
427 checkreqprot [SELINUX] Set initial checkreqprot flag value.
428 Format: { "0" | "1" }
429 See security/selinux/Kconfig help text.
430 0 -- check protection applied by kernel (includes
431 any implied execute protection).
432 1 -- check protection requested by application.
433 Default value is set via a kernel config option.
434 Value can be changed at runtime via
435 /selinux/checkreqprot.
437 cio_ignore= [S390]
438 See Documentation/s390/CommonIO for details.
440 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
441 [Deprecated]
442 Forces specified clocksource (if available) to be used
443 when calculating gettimeofday(). If specified
444 clocksource is not available, it defaults to PIT.
445 Format: { pit | tsc | cyclone | pmtmr }
447 clocksource= Override the default clocksource
448 Format: <string>
449 Override the default clocksource and use the clocksource
450 with the name specified.
451 Some clocksource names to choose from, depending on
452 the platform:
453 [all] jiffies (this is the base, fallback clocksource)
454 [ACPI] acpi_pm
455 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
456 pxa_timer,timer3,32k_counter,timer0_1
457 [AVR32] avr32
458 [X86-32] pit,hpet,tsc;
459 scx200_hrt on Geode; cyclone on IBM x440
460 [MIPS] MIPS
461 [PARISC] cr16
462 [S390] tod
463 [SH] SuperH
464 [SPARC64] tick
465 [X86-64] hpet,tsc
467 clearcpuid=BITNUM [X86]
468 Disable CPUID feature X for the kernel. See
469 arch/x86/include/asm/cpufeature.h for the valid bit
470 numbers. Note the Linux specific bits are not necessarily
471 stable over kernel options, but the vendor specific
472 ones should be.
473 Also note that user programs calling CPUID directly
474 or using the feature without checking anything
475 will still see it. This just prevents it from
476 being used by the kernel or shown in /proc/cpuinfo.
477 Also note the kernel might malfunction if you disable
478 some critical bits.
480 cmo_free_hint= [PPC] Format: { yes | no }
481 Specify whether pages are marked as being inactive
482 when they are freed. This is used in CMO environments
483 to determine OS memory pressure for page stealing by
484 a hypervisor.
485 Default: yes
487 code_bytes [X86] How many bytes of object code to print
488 in an oops report.
489 Range: 0 - 8192
490 Default: 64
492 com20020= [HW,NET] ARCnet - COM20020 chipset
493 Format:
494 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
496 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
497 Format: <io>[,<irq>]
499 com90xx= [HW,NET]
500 ARCnet - COM90xx chipset (memory-mapped buffers)
501 Format: <io>[,<irq>[,<memstart>]]
503 condev= [HW,S390] console device
504 conmode=
506 console= [KNL] Output console device and options.
508 tty<n> Use the virtual console device <n>.
510 ttyS<n>[,options]
511 ttyUSB0[,options]
512 Use the specified serial port. The options are of
513 the form "bbbbpnf", where "bbbb" is the baud rate,
514 "p" is parity ("n", "o", or "e"), "n" is number of
515 bits, and "f" is flow control ("r" for RTS or
516 omit it). Default is "9600n8".
518 See Documentation/serial-console.txt for more
519 information. See
520 Documentation/networking/netconsole.txt for an
521 alternative.
523 uart[8250],io,<addr>[,options]
524 uart[8250],mmio,<addr>[,options]
525 Start an early, polled-mode console on the 8250/16550
526 UART at the specified I/O port or MMIO address,
527 switching to the matching ttyS device later. The
528 options are the same as for ttyS, above.
530 If the device connected to the port is not a TTY but a braille
531 device, prepend "brl," before the device type, for instance
532 console=brl,ttyS0
533 For now, only VisioBraille is supported.
535 consoleblank= [KNL] The console blank (screen saver) timeout in
536 seconds. Defaults to 10*60 = 10mins. A value of 0
537 disables the blank timer.
539 coredump_filter=
540 [KNL] Change the default value for
541 /proc/<pid>/coredump_filter.
542 See also Documentation/filesystems/proc.txt.
544 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
545 Format:
546 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
548 crashkernel=nn[KMG]@ss[KMG]
549 [KNL] Reserve a chunk of physical memory to
550 hold a kernel to switch to with kexec on panic.
552 crashkernel=range1:size1[,range2:size2,...][@offset]
553 [KNL] Same as above, but depends on the memory
554 in the running system. The syntax of range is
555 start-[end] where start and end are both
556 a memory unit (amount[KMG]). See also
557 Documentation/kdump/kdump.txt for a example.
559 cs89x0_dma= [HW,NET]
560 Format: <dma>
562 cs89x0_media= [HW,NET]
563 Format: { rj45 | aui | bnc }
565 dasd= [HW,NET]
566 See header of drivers/s390/block/dasd_devmap.c.
568 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
569 (one device per port)
570 Format: <port#>,<type>
571 See also Documentation/input/joystick-parport.txt
573 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
574 time. See Documentation/dynamic-debug-howto.txt for
575 details.
577 debug [KNL] Enable kernel debugging (events log level).
579 debug_locks_verbose=
580 [KNL] verbose self-tests
581 Format=<0|1>
582 Print debugging info while doing the locking API
583 self-tests.
584 We default to 0 (no extra messages), setting it to
585 1 will print _a lot_ more information - normally
586 only useful to kernel developers.
588 debug_objects [KNL] Enable object debugging
590 no_debug_objects
591 [KNL] Disable object debugging
593 debugpat [X86] Enable PAT debugging
595 decnet.addr= [HW,NET]
596 Format: <area>[,<node>]
597 See also Documentation/networking/decnet.txt.
599 default_hugepagesz=
600 [same as hugepagesz=] The size of the default
601 HugeTLB page size. This is the size represented by
602 the legacy /proc/ hugepages APIs, used for SHM, and
603 default size when mounting hugetlbfs filesystems.
604 Defaults to the default architecture's huge page size
605 if not specified.
607 dhash_entries= [KNL]
608 Set number of hash buckets for dentry cache.
610 digi= [HW,SERIAL]
611 IO parameters + enable/disable command.
613 digiepca= [HW,SERIAL]
614 See drivers/char/README.epca and
615 Documentation/serial/digiepca.txt.
617 disable= [IPV6]
618 See Documentation/networking/ipv6.txt.
620 disable_ipv6= [IPV6]
621 See Documentation/networking/ipv6.txt.
623 disable_mtrr_cleanup [X86]
624 The kernel tries to adjust MTRR layout from continuous
625 to discrete, to make X server driver able to add WB
626 entry later. This parameter disables that.
628 disable_mtrr_trim [X86, Intel and AMD only]
629 By default the kernel will trim any uncacheable
630 memory out of your available memory pool based on
631 MTRR settings. This parameter disables that behavior,
632 possibly causing your machine to run very slowly.
634 disable_timer_pin_1 [X86]
635 Disable PIN 1 of APIC timer
636 Can be useful to work around chipset bugs.
638 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
639 this option disables the debugging code at boot.
641 dma_debug_entries=<number>
642 This option allows to tune the number of preallocated
643 entries for DMA-API debugging code. One entry is
644 required per DMA-API allocation. Use this if the
645 DMA-API debugging code disables itself because the
646 architectural default is too low.
648 dma_debug_driver=<driver_name>
649 With this option the DMA-API debugging driver
650 filter feature can be enabled at boot time. Just
651 pass the driver to filter for as the parameter.
652 The filter can be disabled or changed to another
653 driver later using sysfs.
655 dscc4.setup= [NET]
657 earlycon= [KNL] Output early console device and options.
658 uart[8250],io,<addr>[,options]
659 uart[8250],mmio,<addr>[,options]
660 uart[8250],mmio32,<addr>[,options]
661 Start an early, polled-mode console on the 8250/16550
662 UART at the specified I/O port or MMIO address.
663 MMIO inter-register address stride is either 8bit (mmio)
664 or 32bit (mmio32).
665 The options are the same as for ttyS, above.
667 earlyprintk= [X86,SH,BLACKFIN]
668 earlyprintk=vga
669 earlyprintk=serial[,ttySn[,baudrate]]
670 earlyprintk=ttySn[,baudrate]
671 earlyprintk=dbgp[debugController#]
673 Append ",keep" to not disable it when the real console
674 takes over.
676 Only vga or serial or usb debug port at a time.
678 Currently only ttyS0 and ttyS1 are supported.
680 Interaction with the standard serial driver is not
681 very good.
683 The VGA output is eventually overwritten by the real
684 console.
686 ekgdboc= [X86,KGDB] Allow early kernel console debugging
687 ekgdboc=kbd
689 This is desgined to be used in conjunction with
690 the boot argument: earlyprintk=vga
692 edd= [EDD]
693 Format: {"off" | "on" | "skip[mbr]"}
695 eisa_irq_edge= [PARISC,HW]
696 See header of drivers/parisc/eisa.c.
698 elanfreq= [X86-32]
699 See comment before function elanfreq_setup() in
700 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
702 elevator= [IOSCHED]
703 Format: {"cfq" | "deadline" | "noop"}
704 See Documentation/block/as-iosched.txt and
705 Documentation/block/deadline-iosched.txt for details.
707 elfcorehdr= [IA64,PPC,SH,X86]
708 Specifies physical address of start of kernel core
709 image elf header. Generally kexec loader will
710 pass this option to capture kernel.
711 See Documentation/kdump/kdump.txt for details.
713 enable_mtrr_cleanup [X86]
714 The kernel tries to adjust MTRR layout from continuous
715 to discrete, to make X server driver able to add WB
716 entry later. This parameter enables that.
718 enable_timer_pin_1 [X86]
719 Enable PIN 1 of APIC timer
720 Can be useful to work around chipset bugs
721 (in particular on some ATI chipsets).
722 The kernel tries to set a reasonable default.
724 enforcing [SELINUX] Set initial enforcing status.
725 Format: {"0" | "1"}
726 See security/selinux/Kconfig help text.
727 0 -- permissive (log only, no denials).
728 1 -- enforcing (deny and log).
729 Default value is 0.
730 Value can be changed at runtime via /selinux/enforce.
732 erst_disable [ACPI]
733 Disable Error Record Serialization Table (ERST)
734 support.
736 ether= [HW,NET] Ethernet cards parameters
737 This option is obsoleted by the "netdev=" option, which
738 has equivalent usage. See its documentation for details.
740 failslab=
741 fail_page_alloc=
742 fail_make_request=[KNL]
743 General fault injection mechanism.
744 Format: <interval>,<probability>,<space>,<times>
745 See also /Documentation/fault-injection/.
747 floppy= [HW]
748 See Documentation/blockdev/floppy.txt.
750 force_pal_cache_flush
751 [IA-64] Avoid check_sal_cache_flush which may hang on
752 buggy SAL_CACHE_FLUSH implementations. Using this
753 parameter will force ia64_sal_cache_flush to call
754 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
756 ftrace=[tracer]
757 [FTRACE] will set and start the specified tracer
758 as early as possible in order to facilitate early
759 boot debugging.
761 ftrace_dump_on_oops[=orig_cpu]
762 [FTRACE] will dump the trace buffers on oops.
763 If no parameter is passed, ftrace will dump
764 buffers of all CPUs, but if you pass orig_cpu, it will
765 dump only the buffer of the CPU that triggered the
766 oops.
768 ftrace_filter=[function-list]
769 [FTRACE] Limit the functions traced by the function
770 tracer at boot up. function-list is a comma separated
771 list of functions. This list can be changed at run
772 time by the set_ftrace_filter file in the debugfs
773 tracing directory.
775 ftrace_notrace=[function-list]
776 [FTRACE] Do not trace the functions specified in
777 function-list. This list can be changed at run time
778 by the set_ftrace_notrace file in the debugfs
779 tracing directory.
781 ftrace_graph_filter=[function-list]
782 [FTRACE] Limit the top level callers functions traced
783 by the function graph tracer at boot up.
784 function-list is a comma separated list of functions
785 that can be changed at run time by the
786 set_graph_function file in the debugfs tracing directory.
788 gamecon.map[2|3]=
789 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
790 support via parallel port (up to 5 devices per port)
791 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
792 See also Documentation/input/joystick-parport.txt
794 gamma= [HW,DRM]
796 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
797 Format: off | on
798 default: on
800 gcov_persist= [GCOV] When non-zero (default), profiling data for
801 kernel modules is saved and remains accessible via
802 debugfs, even when the module is unloaded/reloaded.
803 When zero, profiling data is discarded and associated
804 debugfs files are removed at module unload time.
806 gpt [EFI] Forces disk with valid GPT signature but
807 invalid Protective MBR to be treated as GPT.
809 hashdist= [KNL,NUMA] Large hashes allocated during boot
810 are distributed across NUMA nodes. Defaults on
811 for 64bit NUMA, off otherwise.
812 Format: 0 | 1 (for off | on)
814 hcl= [IA-64] SGI's Hardware Graph compatibility layer
816 hd= [EIDE] (E)IDE hard drive subsystem geometry
817 Format: <cyl>,<head>,<sect>
819 hest_disable [ACPI]
820 Disable Hardware Error Source Table (HEST) support;
821 corresponding firmware-first mode error processing
822 logic will be disabled.
824 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
825 size of <nn>. This works even on boxes that have no
826 highmem otherwise. This also works to reduce highmem
827 size on bigger boxes.
829 highres= [KNL] Enable/disable high resolution timer mode.
830 Valid parameters: "on", "off"
831 Default: "on"
833 hisax= [HW,ISDN]
834 See Documentation/isdn/README.HiSax.
836 hlt [BUGS=ARM,SH]
838 hpet= [X86-32,HPET] option to control HPET usage
839 Format: { enable (default) | disable | force |
840 verbose }
841 disable: disable HPET and use PIT instead
842 force: allow force enabled of undocumented chips (ICH4,
843 VIA, nVidia)
844 verbose: show contents of HPET registers during setup
846 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
847 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
848 On x86-64 and powerpc, this option can be specified
849 multiple times interleaved with hugepages= to reserve
850 huge pages of different sizes. Valid pages sizes on
851 x86-64 are 2M (when the CPU supports "pse") and 1G
852 (when the CPU supports the "pdpe1gb" cpuinfo flag)
853 Note that 1GB pages can only be allocated at boot time
854 using hugepages= and not freed afterwards.
856 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
857 terminal devices. Valid values: 0..8
858 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
859 If specified, z/VM IUCV HVC accepts connections
860 from listed z/VM user IDs only.
862 i2c_bus= [HW] Override the default board specific I2C bus speed
863 or register an additional I2C bus that is not
864 registered from board initialization code.
865 Format:
866 <bus_id>,<clkrate>
868 i8042.debug [HW] Toggle i8042 debug mode
869 i8042.direct [HW] Put keyboard port into non-translated mode
870 i8042.dumbkbd [HW] Pretend that controller can only read data from
871 keyboard and cannot control its state
872 (Don't attempt to blink the leds)
873 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
874 i8042.nokbd [HW] Don't check/create keyboard port
875 i8042.noloop [HW] Disable the AUX Loopback command while probing
876 for the AUX port
877 i8042.nomux [HW] Don't check presence of an active multiplexing
878 controller
879 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
880 controllers
881 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
882 i8042.reset [HW] Reset the controller during init and cleanup
883 i8042.unlock [HW] Unlock (ignore) the keylock
885 i810= [HW,DRM]
887 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
888 indicates that the driver is running on unsupported
889 hardware.
890 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
891 does not match list of supported models.
892 i8k.power_status
893 [HW] Report power status in /proc/i8k
894 (disabled by default)
895 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
896 capability is set.
898 icn= [HW,ISDN]
899 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
901 ide-core.nodma= [HW] (E)IDE subsystem
902 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
903 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
904 .cdrom .chs .ignore_cable are additional options
905 See Documentation/ide/ide.txt.
907 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
908 Claim all unknown PCI IDE storage controllers.
910 idle= [X86]
911 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
912 Poll forces a polling idle loop that can slightly
913 improve the performance of waking up a idle CPU, but
914 will use a lot of power and make the system run hot.
915 Not recommended.
916 idle=mwait: On systems which support MONITOR/MWAIT but
917 the kernel chose to not use it because it doesn't save
918 as much power as a normal idle loop, use the
919 MONITOR/MWAIT idle loop anyways. Performance should be
920 the same as idle=poll.
921 idle=halt: Halt is forced to be used for CPU idle.
922 In such case C2/C3 won't be used again.
923 idle=nomwait: Disable mwait for CPU C-states
925 ignore_loglevel [KNL]
926 Ignore loglevel setting - this will print /all/
927 kernel messages to the console. Useful for debugging.
929 ihash_entries= [KNL]
930 Set number of hash buckets for inode cache.
932 ima_audit= [IMA]
933 Format: { "0" | "1" }
934 0 -- integrity auditing messages. (Default)
935 1 -- enable informational integrity auditing messages.
937 ima_hash= [IMA]
938 Format: { "sha1" | "md5" }
939 default: "sha1"
941 ima_tcb [IMA]
942 Load a policy which meets the needs of the Trusted
943 Computing Base. This means IMA will measure all
944 programs exec'd, files mmap'd for exec, and all files
945 opened for read by uid=0.
947 init= [KNL]
948 Format: <full_path>
949 Run specified binary instead of /sbin/init as init
950 process.
952 initcall_debug [KNL] Trace initcalls as they are executed. Useful
953 for working out where the kernel is dying during
954 startup.
956 initrd= [BOOT] Specify the location of the initial ramdisk
958 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
959 Format: <irq>
961 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
962 on
963 Enable intel iommu driver.
964 off
965 Disable intel iommu driver.
966 igfx_off [Default Off]
967 By default, gfx is mapped as normal device. If a gfx
968 device has a dedicated DMAR unit, the DMAR unit is
969 bypassed by not enabling DMAR with this option. In
970 this case, gfx device will use physical address for
971 DMA.
972 forcedac [x86_64]
973 With this option iommu will not optimize to look
974 for io virtual address below 32 bit forcing dual
975 address cycle on pci bus for cards supporting greater
976 than 32 bit addressing. The default is to look
977 for translation below 32 bit and if not available
978 then look in the higher range.
979 strict [Default Off]
980 With this option on every unmap_single operation will
981 result in a hardware IOTLB flush operation as opposed
982 to batching them for performance.
984 intremap= [X86-64, Intel-IOMMU]
985 Format: { on (default) | off | nosid }
986 on enable Interrupt Remapping (default)
987 off disable Interrupt Remapping
988 nosid disable Source ID checking
990 inttest= [IA64]
992 iomem= Disable strict checking of access to MMIO memory
993 strict regions from userspace.
994 relaxed
996 iommu= [x86]
997 off
998 force
999 noforce
1000 biomerge
1001 panic
1002 nopanic
1003 merge
1004 nomerge
1005 forcesac
1006 soft
1007 pt [x86, IA64]
1009 io7= [HW] IO7 for Marvel based alpha systems
1010 See comment before marvel_specify_io7 in
1011 arch/alpha/kernel/core_marvel.c.
1013 io_delay= [X86] I/O delay method
1014 0x80
1015 Standard port 0x80 based delay
1016 0xed
1017 Alternate port 0xed based delay (needed on some systems)
1018 udelay
1019 Simple two microseconds delay
1020 none
1021 No delay
1023 ip= [IP_PNP]
1024 See Documentation/filesystems/nfs/nfsroot.txt.
1026 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1027 See comment before ip2_setup() in
1028 drivers/char/ip2/ip2base.c.
1030 irqfixup [HW]
1031 When an interrupt is not handled search all handlers
1032 for it. Intended to get systems with badly broken
1033 firmware running.
1035 irqpoll [HW]
1036 When an interrupt is not handled search all handlers
1037 for it. Also check all handlers each timer
1038 interrupt. Intended to get systems with badly broken
1039 firmware running.
1041 isapnp= [ISAPNP]
1042 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1044 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1045 Format:
1046 <cpu number>,...,<cpu number>
1047 or
1048 <cpu number>-<cpu number>
1049 (must be a positive range in ascending order)
1050 or a mixture
1051 <cpu number>,...,<cpu number>-<cpu number>
1053 This option can be used to specify one or more CPUs
1054 to isolate from the general SMP balancing and scheduling
1055 algorithms. You can move a process onto or off an
1056 "isolated" CPU via the CPU affinity syscalls or cpuset.
1057 <cpu number> begins at 0 and the maximum value is
1058 "number of CPUs in system - 1".
1060 This option is the preferred way to isolate CPUs. The
1061 alternative -- manually setting the CPU mask of all
1062 tasks in the system -- can cause problems and
1063 suboptimal load balancer performance.
1065 iucv= [HW,NET]
1067 js= [HW,JOY] Analog joystick
1068 See Documentation/input/joystick.txt.
1070 keepinitrd [HW,ARM]
1072 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1073 specifies the amount of memory usable by the kernel
1074 for non-movable allocations. The requested amount is
1075 spread evenly throughout all nodes in the system. The
1076 remaining memory in each node is used for Movable
1077 pages. In the event, a node is too small to have both
1078 kernelcore and Movable pages, kernelcore pages will
1079 take priority and other nodes will have a larger number
1080 of kernelcore pages. The Movable zone is used for the
1081 allocation of pages that may be reclaimed or moved
1082 by the page migration subsystem. This means that
1083 HugeTLB pages may not be allocated from this zone.
1084 Note that allocations like PTEs-from-HighMem still
1085 use the HighMem zone if it exists, and the Normal
1086 zone if it does not.
1088 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1089 Format: <Controller#>[,poll interval]
1090 The controller # is the number of the ehci usb debug
1091 port as it is probed via PCI. The poll interval is
1092 optional and is the number seconds in between
1093 each poll cycle to the debug port in case you need
1094 the functionality for interrupting the kernel with
1095 gdb or control-c on the dbgp connection. When
1096 not using this parameter you use sysrq-g to break into
1097 the kernel debugger.
1099 kgdboc= [KGDB,HW] kgdb over consoles.
1100 Requires a tty driver that supports console polling,
1101 or a supported polling keyboard driver (non-usb).
1102 Serial only format: <serial_device>[,baud]
1103 keyboard only format: kbd
1104 keyboard and serial format: kbd,<serial_device>[,baud]
1105 Optional Kernel mode setting:
1106 kms, kbd format: kms,kbd
1107 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1109 kgdbwait [KGDB] Stop kernel execution and enter the
1110 kernel debugger at the earliest opportunity.
1112 kmac= [MIPS] korina ethernet MAC address.
1113 Configure the RouterBoard 532 series on-chip
1114 Ethernet adapter MAC address.
1116 kmemleak= [KNL] Boot-time kmemleak enable/disable
1117 Valid arguments: on, off
1118 Default: on
1120 kstack=N [X86] Print N words from the kernel stack
1121 in oops dumps.
1123 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1124 Default is 0 (don't ignore, but inject #GP)
1126 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1127 Default is 1 (enabled)
1129 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1130 KVM MMU at runtime.
1131 Default is 0 (off)
1133 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1134 Default is 1 (enabled)
1136 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1137 for all guests.
1138 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1140 kvm-intel.bypass_guest_pf=
1141 [KVM,Intel] Disables bypassing of guest page faults
1142 on Intel chips. Default is 1 (enabled)
1144 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1145 (virtualized MMU) support on capable Intel chips.
1146 Default is 1 (enabled)
1148 kvm-intel.emulate_invalid_guest_state=
1149 [KVM,Intel] Enable emulation of invalid guest states
1150 Default is 0 (disabled)
1152 kvm-intel.flexpriority=
1153 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1154 Default is 1 (enabled)
1156 kvm-intel.unrestricted_guest=
1157 [KVM,Intel] Disable unrestricted guest feature
1158 (virtualized real and unpaged mode) on capable
1159 Intel chips. Default is 1 (enabled)
1161 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1162 feature (tagged TLBs) on capable Intel chips.
1163 Default is 1 (enabled)
1165 l2cr= [PPC]
1167 l3cr= [PPC]
1169 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1170 disabled it.
1172 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1173 in C2 power state.
1175 libata.dma= [LIBATA] DMA control
1176 libata.dma=0 Disable all PATA and SATA DMA
1177 libata.dma=1 PATA and SATA Disk DMA only
1178 libata.dma=2 ATAPI (CDROM) DMA only
1179 libata.dma=4 Compact Flash DMA only
1180 Combinations also work, so libata.dma=3 enables DMA
1181 for disks and CDROMs, but not CFs.
1183 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1184 libata.ignore_hpa=0 keep BIOS limits (default)
1185 libata.ignore_hpa=1 ignore limits, using full disk
1187 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1188 when set.
1189 Format: <int>
1191 libata.force= [LIBATA] Force configurations. The format is comma
1192 separated list of "[ID:]VAL" where ID is
1193 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1194 matching port, link or device. Basically, it matches
1195 the ATA ID string printed on console by libata. If
1196 the whole ID part is omitted, the last PORT and DEVICE
1197 values are used. If ID hasn't been specified yet, the
1198 configuration applies to all ports, links and devices.
1200 If only DEVICE is omitted, the parameter applies to
1201 the port and all links and devices behind it. DEVICE
1202 number of 0 either selects the first device or the
1203 first fan-out link behind PMP device. It does not
1204 select the host link. DEVICE number of 15 selects the
1205 host link and device attached to it.
1207 The VAL specifies the configuration to force. As long
1208 as there's no ambiguity shortcut notation is allowed.
1209 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1210 The following configurations can be forced.
1212 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1213 Any ID with matching PORT is used.
1215 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1217 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1218 udma[/][16,25,33,44,66,100,133] notation is also
1219 allowed.
1221 * [no]ncq: Turn on or off NCQ.
1223 * nohrst, nosrst, norst: suppress hard, soft
1224 and both resets.
1226 * dump_id: dump IDENTIFY data.
1228 If there are multiple matching configurations changing
1229 the same attribute, the last one is used.
1231 memblock=debug [KNL] Enable memblock debug messages.
1233 load_ramdisk= [RAM] List of ramdisks to load from floppy
1234 See Documentation/blockdev/ramdisk.txt.
1236 lockd.nlm_grace_period=P [NFS] Assign grace period.
1237 Format: <integer>
1239 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1240 Format: <integer>
1242 lockd.nlm_timeout=T [NFS] Assign timeout value.
1243 Format: <integer>
1245 lockd.nlm_udpport=M [NFS] Assign UDP port.
1246 Format: <integer>
1248 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1249 Format: <irq>
1251 loglevel= All Kernel Messages with a loglevel smaller than the
1252 console loglevel will be printed to the console. It can
1253 also be changed with klogd or other programs. The
1254 loglevels are defined as follows:
1256 0 (KERN_EMERG) system is unusable
1257 1 (KERN_ALERT) action must be taken immediately
1258 2 (KERN_CRIT) critical conditions
1259 3 (KERN_ERR) error conditions
1260 4 (KERN_WARNING) warning conditions
1261 5 (KERN_NOTICE) normal but significant condition
1262 6 (KERN_INFO) informational
1263 7 (KERN_DEBUG) debug-level messages
1265 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1266 Format: { n | nk | nM }
1267 n must be a power of two. The default size
1268 is set in the kernel config file.
1270 logo.nologo [FB] Disables display of the built-in Linux logo.
1271 This may be used to provide more screen space for
1272 kernel log messages and is useful when debugging
1273 kernel boot problems.
1275 lp=0 [LP] Specify parallel ports to use, e.g,
1276 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1277 lp=reset first parallel port). 'lp=0' disables the
1278 lp=auto printer driver. 'lp=reset' (which can be
1279 specified in addition to the ports) causes
1280 attached printers to be reset. Using
1281 lp=port1,port2,... specifies the parallel ports
1282 to associate lp devices with, starting with
1283 lp0. A port specification may be 'none' to skip
1284 that lp device, or a parport name such as
1285 'parport0'. Specifying 'lp=auto' instead of a
1286 port specification list means that device IDs
1287 from each port should be examined, to see if
1288 an IEEE 1284-compliant printer is attached; if
1289 so, the driver will manage that printer.
1290 See also header of drivers/char/lp.c.
1292 lpj=n [KNL]
1293 Sets loops_per_jiffy to given constant, thus avoiding
1294 time-consuming boot-time autodetection (up to 250 ms per
1295 CPU). 0 enables autodetection (default). To determine
1296 the correct value for your kernel, boot with normal
1297 autodetection and see what value is printed. Note that
1298 on SMP systems the preset will be applied to all CPUs,
1299 which is likely to cause problems if your CPUs need
1300 significantly divergent settings. An incorrect value
1301 will cause delays in the kernel to be wrong, leading to
1302 unpredictable I/O errors and other breakage. Although
1303 unlikely, in the extreme case this might damage your
1304 hardware.
1306 ltpc= [NET]
1307 Format: <io>,<irq>,<dma>
1309 machvec= [IA64] Force the use of a particular machine-vector
1310 (machvec) in a generic kernel.
1311 Example: machvec=hpzx1_swiotlb
1313 machtype= [Loongson] Share the same kernel image file between different
1314 yeeloong laptop.
1315 Example: machtype=lemote-yeeloong-2f-7inch
1317 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1318 than or equal to this physical address is ignored.
1320 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1321 should make use of. maxcpus=n : n >= 0 limits the
1322 kernel to using 'n' processors. n=0 is a special case,
1323 it is equivalent to "nosmp", which also disables
1324 the IO APIC.
1326 max_loop= [LOOP] Maximum number of loopback devices that can
1327 be mounted
1328 Format: <1-256>
1330 mcatest= [IA-64]
1332 mce [X86-32] Machine Check Exception
1334 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1336 md= [HW] RAID subsystems devices and level
1337 See Documentation/md.txt.
1339 mdacon= [MDA]
1340 Format: <first>,<last>
1341 Specifies range of consoles to be captured by the MDA.
1343 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1344 Amount of memory to be used when the kernel is not able
1345 to see the whole system memory or for test.
1346 [X86-32] Use together with memmap= to avoid physical
1347 address space collisions. Without memmap= PCI devices
1348 could be placed at addresses belonging to unused RAM.
1350 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1351 memory.
1353 memchunk=nn[KMG]
1354 [KNL,SH] Allow user to override the default size for
1355 per-device physically contiguous DMA buffers.
1357 memmap=exactmap [KNL,X86] Enable setting of an exact
1358 E820 memory map, as specified by the user.
1359 Such memmap=exactmap lines can be constructed based on
1360 BIOS output or other requirements. See the memmap=nn@ss
1361 option description.
1363 memmap=nn[KMG]@ss[KMG]
1364 [KNL] Force usage of a specific region of memory
1365 Region of memory to be used, from ss to ss+nn.
1367 memmap=nn[KMG]#ss[KMG]
1368 [KNL,ACPI] Mark specific memory as ACPI data.
1369 Region of memory to be used, from ss to ss+nn.
1371 memmap=nn[KMG]$ss[KMG]
1372 [KNL,ACPI] Mark specific memory as reserved.
1373 Region of memory to be used, from ss to ss+nn.
1374 Example: Exclude memory from 0x18690000-0x1869ffff
1375 memmap=64K$0x18690000
1376 or
1377 memmap=0x10000$0x18690000
1379 memory_corruption_check=0/1 [X86]
1380 Some BIOSes seem to corrupt the first 64k of
1381 memory when doing things like suspend/resume.
1382 Setting this option will scan the memory
1383 looking for corruption. Enabling this will
1384 both detect corruption and prevent the kernel
1385 from using the memory being corrupted.
1386 However, its intended as a diagnostic tool; if
1387 repeatable BIOS-originated corruption always
1388 affects the same memory, you can use memmap=
1389 to prevent the kernel from using that memory.
1391 memory_corruption_check_size=size [X86]
1392 By default it checks for corruption in the low
1393 64k, making this memory unavailable for normal
1394 use. Use this parameter to scan for
1395 corruption in more or less memory.
1397 memory_corruption_check_period=seconds [X86]
1398 By default it checks for corruption every 60
1399 seconds. Use this parameter to check at some
1400 other rate. 0 disables periodic checking.
1402 memtest= [KNL,X86] Enable memtest
1403 Format: <integer>
1404 default : 0 <disable>
1405 Specifies the number of memtest passes to be
1406 performed. Each pass selects another test
1407 pattern from a given set of patterns. Memtest
1408 fills the memory with this pattern, validates
1409 memory contents and reserves bad memory
1410 regions that are detected.
1412 meye.*= [HW] Set MotionEye Camera parameters
1413 See Documentation/video4linux/meye.txt.
1415 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1416 Multi-Function General Purpose Timers on AMD Geode
1417 platforms.
1419 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1420 the BIOS has incorrectly applied a workaround. TinyBIOS
1421 version 0.98 is known to be affected, 0.99 fixes the
1422 problem by letting the user disable the workaround.
1424 mga= [HW,DRM]
1426 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1427 physical address is ignored.
1429 mini2440= [ARM,HW,KNL]
1430 Format:[0..2][b][c][t]
1431 Default: "0tb"
1432 MINI2440 configuration specification:
1433 0 - The attached screen is the 3.5" TFT
1434 1 - The attached screen is the 7" TFT
1435 2 - The VGA Shield is attached (1024x768)
1436 Leaving out the screen size parameter will not load
1437 the TFT driver, and the framebuffer will be left
1438 unconfigured.
1439 b - Enable backlight. The TFT backlight pin will be
1440 linked to the kernel VESA blanking code and a GPIO
1441 LED. This parameter is not necessary when using the
1442 VGA shield.
1443 c - Enable the s3c camera interface.
1444 t - Reserved for enabling touchscreen support. The
1445 touchscreen support is not enabled in the mainstream
1446 kernel as of 2.6.30, a preliminary port can be found
1447 in the "bleeding edge" mini2440 support kernel at
1448 http://repo.or.cz/w/linux-2.6/mini2440.git
1450 mminit_loglevel=
1451 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1452 parameter allows control of the logging verbosity for
1453 the additional memory initialisation checks. A value
1454 of 0 disables mminit logging and a level of 4 will
1455 log everything. Information is printed at KERN_DEBUG
1456 so loglevel=8 may also need to be specified.
1458 mousedev.tap_time=
1459 [MOUSE] Maximum time between finger touching and
1460 leaving touchpad surface for touch to be considered
1461 a tap and be reported as a left button click (for
1462 touchpads working in absolute mode only).
1463 Format: <msecs>
1464 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1465 reporting absolute coordinates, such as tablets
1466 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1467 reporting absolute coordinates, such as tablets
1469 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1470 is similar to kernelcore except it specifies the
1471 amount of memory used for migratable allocations.
1472 If both kernelcore and movablecore is specified,
1473 then kernelcore will be at *least* the specified
1474 value but may be more. If movablecore on its own
1475 is specified, the administrator must be careful
1476 that the amount of memory usable for all allocations
1477 is not too small.
1479 MTD_Partition= [MTD]
1480 Format: <name>,<region-number>,<size>,<offset>
1482 MTD_Region= [MTD] Format:
1483 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1485 mtdparts= [MTD]
1486 See drivers/mtd/cmdlinepart.c.
1488 multitce=off [PPC] This parameter disables the use of the pSeries
1489 firmware feature for updating multiple TCE entries
1490 at a time.
1492 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1494 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1496 boundary - index of last SLC block on Flex-OneNAND.
1497 The remaining blocks are configured as MLC blocks.
1498 lock - Configure if Flex-OneNAND boundary should be locked.
1499 Once locked, the boundary cannot be changed.
1500 1 indicates lock status, 0 indicates unlock status.
1502 mtdset= [ARM]
1503 ARM/S3C2412 JIVE boot control
1505 See arch/arm/mach-s3c2412/mach-jive.c
1507 mtouchusb.raw_coordinates=
1508 [HW] Make the MicroTouch USB driver use raw coordinates
1509 ('y', default) or cooked coordinates ('n')
1511 mtrr_chunk_size=nn[KMG] [X86]
1512 used for mtrr cleanup. It is largest continuous chunk
1513 that could hold holes aka. UC entries.
1515 mtrr_gran_size=nn[KMG] [X86]
1516 Used for mtrr cleanup. It is granularity of mtrr block.
1517 Default is 1.
1518 Large value could prevent small alignment from
1519 using up MTRRs.
1521 mtrr_spare_reg_nr=n [X86]
1522 Format: <integer>
1523 Range: 0,7 : spare reg number
1524 Default : 1
1525 Used for mtrr cleanup. It is spare mtrr entries number.
1526 Set to 2 or more if your graphical card needs more.
1528 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1530 netdev= [NET] Network devices parameters
1531 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1532 Note that mem_start is often overloaded to mean
1533 something different and driver-specific.
1534 This usage is only documented in each driver source
1535 file if at all.
1537 nf_conntrack.acct=
1538 [NETFILTER] Enable connection tracking flow accounting
1539 0 to disable accounting
1540 1 to enable accounting
1541 Default value is 0.
1543 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1544 See Documentation/filesystems/nfs/nfsroot.txt.
1546 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1547 See Documentation/filesystems/nfs/nfsroot.txt.
1549 nfsrootdebug [NFS] enable nfsroot debugging messages.
1550 See Documentation/filesystems/nfs/nfsroot.txt.
1552 nfs.callback_tcpport=
1553 [NFS] set the TCP port on which the NFSv4 callback
1554 channel should listen.
1556 nfs.cache_getent=
1557 [NFS] sets the pathname to the program which is used
1558 to update the NFS client cache entries.
1560 nfs.cache_getent_timeout=
1561 [NFS] sets the timeout after which an attempt to
1562 update a cache entry is deemed to have failed.
1564 nfs.idmap_cache_timeout=
1565 [NFS] set the maximum lifetime for idmapper cache
1566 entries.
1568 nfs.enable_ino64=
1569 [NFS] enable 64-bit inode numbers.
1570 If zero, the NFS client will fake up a 32-bit inode
1571 number for the readdir() and stat() syscalls instead
1572 of returning the full 64-bit number.
1573 The default is to return 64-bit inode numbers.
1575 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1576 when a NMI is triggered.
1577 Format: [state][,regs][,debounce][,die]
1579 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1580 Format: [panic,][num]
1581 Valid num: 0
1582 0 - turn nmi_watchdog off
1583 When panic is specified, panic when an NMI watchdog
1584 timeout occurs.
1585 This is useful when you use a panic=... timeout and
1586 need the box quickly up again.
1588 netpoll.carrier_timeout=
1589 [NET] Specifies amount of time (in seconds) that
1590 netpoll should wait for a carrier. By default netpoll
1591 waits 4 seconds.
1593 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1594 emulation library even if a 387 maths coprocessor
1595 is present.
1597 no_console_suspend
1598 [HW] Never suspend the console
1599 Disable suspending of consoles during suspend and
1600 hibernate operations. Once disabled, debugging
1601 messages can reach various consoles while the rest
1602 of the system is being put to sleep (ie, while
1603 debugging driver suspend/resume hooks). This may
1604 not work reliably with all consoles, but is known
1605 to work with serial and VGA consoles.
1607 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1608 caches in the slab allocator. Saves per-node memory,
1609 but will impact performance.
1611 noalign [KNL,ARM]
1613 noapic [SMP,APIC] Tells the kernel to not make use of any
1614 IOAPICs that may be present in the system.
1616 noautogroup Disable scheduler automatic task group creation.
1618 nobats [PPC] Do not use BATs for mapping kernel lowmem
1619 on "Classic" PPC cores.
1621 nocache [ARM]
1623 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1625 nodelayacct [KNL] Disable per-task delay accounting
1627 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1629 nodsp [SH] Disable hardware DSP at boot time.
1631 noefi [X86] Disable EFI runtime services support.
1633 noexec [IA-64]
1635 noexec [X86]
1636 On X86-32 available only on PAE configured kernels.
1637 noexec=on: enable non-executable mappings (default)
1638 noexec=off: disable non-executable mappings
1640 noexec32 [X86-64]
1641 This affects only 32-bit executables.
1642 noexec32=on: enable non-executable mappings (default)
1643 read doesn't imply executable mappings
1644 noexec32=off: disable non-executable mappings
1645 read implies executable mappings
1647 nofpu [SH] Disable hardware FPU at boot time.
1649 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1650 register save and restore. The kernel will only save
1651 legacy floating-point registers on task switch.
1653 noxsave [BUGS=X86] Disables x86 extended register state save
1654 and restore using xsave. The kernel will fallback to
1655 enabling legacy floating-point and sse state.
1657 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1658 wfi(ARM) instruction doesn't work correctly and not to
1659 use it. This is also useful when using JTAG debugger.
1661 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1662 instruction doesn't work correctly and not to
1663 use it.
1665 no_file_caps Tells the kernel not to honor file capabilities. The
1666 only way then for a file to be executed with privilege
1667 is to be setuid root or executed by root.
1669 nohalt [IA-64] Tells the kernel not to use the power saving
1670 function PAL_HALT_LIGHT when idle. This increases
1671 power-consumption. On the positive side, it reduces
1672 interrupt wake-up latency, which may improve performance
1673 in certain environments such as networked servers or
1674 real-time systems.
1676 nohz= [KNL] Boottime enable/disable dynamic ticks
1677 Valid arguments: on, off
1678 Default: on
1680 noiotrap [SH] Disables trapped I/O port accesses.
1682 noirqdebug [X86-32] Disables the code which attempts to detect and
1683 disable unhandled interrupt sources.
1685 no_timer_check [X86,APIC] Disables the code which tests for
1686 broken timer IRQ sources.
1688 noisapnp [ISAPNP] Disables ISA PnP code.
1690 noinitrd [RAM] Tells the kernel not to load any configured
1691 initial RAM disk.
1693 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1694 remapping.
1695 [Deprecated - use intremap=off]
1697 nointroute [IA-64]
1699 nojitter [IA64] Disables jitter checking for ITC timers.
1701 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1703 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1704 fault handling.
1706 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1708 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1710 noltlbs [PPC] Do not use large page/tlb entries for kernel
1711 lowmem mapping on PPC40x.
1713 nomca [IA-64] Disable machine check abort handling
1715 nomce [X86-32] Machine Check Exception
1717 nomfgpt [X86-32] Disable Multi-Function General Purpose
1718 Timer usage (for AMD Geode machines).
1720 nopat [X86] Disable PAT (page attribute table extension of
1721 pagetables) support.
1723 norandmaps Don't use address space randomization. Equivalent to
1724 echo 0 > /proc/sys/kernel/randomize_va_space
1726 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1728 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1729 with UP alternatives
1731 noresidual [PPC] Don't use residual data on PReP machines.
1733 noresume [SWSUSP] Disables resume and restores original swap
1734 space.
1736 no-scroll [VGA] Disables scrollback.
1737 This is required for the Braillex ib80-piezo Braille
1738 reader made by F.H. Papenmeier (Germany).
1740 nosbagart [IA-64]
1742 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1744 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1745 and disable the IO APIC. legacy for "maxcpus=0".
1747 nosoftlockup [KNL] Disable the soft-lockup detector.
1749 noswapaccount [KNL] Disable accounting of swap in memory resource
1750 controller. (See Documentation/cgroups/memory.txt)
1752 nosync [HW,M68K] Disables sync negotiation for all devices.
1754 notsc [BUGS=X86-32] Disable Time Stamp Counter
1756 nousb [USB] Disable the USB subsystem
1758 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1760 nowb [ARM]
1762 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1764 nptcg= [IA64] Override max number of concurrent global TLB
1765 purges which is reported from either PAL_VM_SUMMARY or
1766 SAL PALO.
1768 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1769 could support. nr_cpus=n : n >= 1 limits the kernel to
1770 supporting 'n' processors. Later in runtime you can not
1771 use hotplug cpu feature to put more cpu back to online.
1772 just like you compile the kernel NR_CPUS=n
1774 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1776 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1777 one of ['zone', 'node', 'default'] can be specified
1778 This can be set from sysctl after boot.
1779 See Documentation/sysctl/vm.txt for details.
1781 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1782 See Documentation/debugging-via-ohci1394.txt for more
1783 info.
1785 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1786 Rather than timing out after 20 ms if an EC
1787 command is not properly ACKed, override the length
1788 of the timeout. We have interrupts disabled while
1789 waiting for the ACK, so if this is set too high
1790 interrupts *may* be lost!
1792 omap_mux= [OMAP] Override bootloader pin multiplexing.
1793 Format: <mux_mode0.mode_name=value>...
1794 For example, to override I2C bus2:
1795 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1797 oprofile.timer= [HW]
1798 Use timer interrupt instead of performance counters
1800 oprofile.cpu_type= Force an oprofile cpu type
1801 This might be useful if you have an older oprofile
1802 userland or if you want common events.
1803 Format: { arch_perfmon }
1804 arch_perfmon: [X86] Force use of architectural
1805 perfmon on Intel CPUs instead of the
1806 CPU specific event set.
1808 OSS [HW,OSS]
1809 See Documentation/sound/oss/oss-parameters.txt
1811 panic= [KNL] Kernel behaviour on panic
1812 Format: <timeout>
1814 parkbd.port= [HW] Parallel port number the keyboard adapter is
1815 connected to, default is 0.
1816 Format: <parport#>
1817 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1818 0 for XT, 1 for AT (default is AT).
1819 Format: <mode>
1821 parport= [HW,PPT] Specify parallel ports. 0 disables.
1822 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1823 Use 'auto' to force the driver to use any
1824 IRQ/DMA settings detected (the default is to
1825 ignore detected IRQ/DMA settings because of
1826 possible conflicts). You can specify the base
1827 address, IRQ, and DMA settings; IRQ and DMA
1828 should be numbers, or 'auto' (for using detected
1829 settings on that particular port), or 'nofifo'
1830 (to avoid using a FIFO even if it is detected).
1831 Parallel ports are assigned in the order they
1832 are specified on the command line, starting
1833 with parport0.
1835 parport_init_mode= [HW,PPT]
1836 Configure VIA parallel port to operate in
1837 a specific mode. This is necessary on Pegasos
1838 computer where firmware has no options for setting
1839 up parallel port mode and sets it to spp.
1840 Currently this function knows 686a and 8231 chips.
1841 Format: [spp|ps2|epp|ecp|ecpepp]
1843 pause_on_oops=
1844 Halt all CPUs after the first oops has been printed for
1845 the specified number of seconds. This is to be used if
1846 your oopses keep scrolling off the screen.
1848 pcbit= [HW,ISDN]
1850 pcd. [PARIDE]
1851 See header of drivers/block/paride/pcd.c.
1852 See also Documentation/blockdev/paride.txt.
1854 pci=option[,option...] [PCI] various PCI subsystem options:
1855 earlydump [X86] dump PCI config space before the kernel
1856 changes anything
1857 off [X86] don't probe for the PCI bus
1858 bios [X86-32] force use of PCI BIOS, don't access
1859 the hardware directly. Use this if your machine
1860 has a non-standard PCI host bridge.
1861 nobios [X86-32] disallow use of PCI BIOS, only direct
1862 hardware access methods are allowed. Use this
1863 if you experience crashes upon bootup and you
1864 suspect they are caused by the BIOS.
1865 conf1 [X86] Force use of PCI Configuration
1866 Mechanism 1.
1867 conf2 [X86] Force use of PCI Configuration
1868 Mechanism 2.
1869 noaer [PCIE] If the PCIEAER kernel config parameter is
1870 enabled, this kernel boot option can be used to
1871 disable the use of PCIE advanced error reporting.
1872 nodomains [PCI] Disable support for multiple PCI
1873 root domains (aka PCI segments, in ACPI-speak).
1874 nommconf [X86] Disable use of MMCONFIG for PCI
1875 Configuration
1876 check_enable_amd_mmconf [X86] check for and enable
1877 properly configured MMIO access to PCI
1878 config space on AMD family 10h CPU
1879 nomsi [MSI] If the PCI_MSI kernel config parameter is
1880 enabled, this kernel boot option can be used to
1881 disable the use of MSI interrupts system-wide.
1882 noioapicquirk [APIC] Disable all boot interrupt quirks.
1883 Safety option to keep boot IRQs enabled. This
1884 should never be necessary.
1885 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1886 primary IO-APIC for bridges that cannot disable
1887 boot IRQs. This fixes a source of spurious IRQs
1888 when the system masks IRQs.
1889 noioapicreroute [APIC] Disable workaround that uses the
1890 boot IRQ equivalent of an IRQ that connects to
1891 a chipset where boot IRQs cannot be disabled.
1892 The opposite of ioapicreroute.
1893 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1894 routing table. These calls are known to be buggy
1895 on several machines and they hang the machine
1896 when used, but on other computers it's the only
1897 way to get the interrupt routing table. Try
1898 this option if the kernel is unable to allocate
1899 IRQs or discover secondary PCI buses on your
1900 motherboard.
1901 rom [X86] Assign address space to expansion ROMs.
1902 Use with caution as certain devices share
1903 address decoders between ROMs and other
1904 resources.
1905 norom [X86] Do not assign address space to
1906 expansion ROMs that do not already have
1907 BIOS assigned address ranges.
1908 nobar [X86] Do not assign address space to the
1909 BARs that weren't assigned by the BIOS.
1910 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1911 assigned automatically to PCI devices. You can
1912 make the kernel exclude IRQs of your ISA cards
1913 this way.
1914 pirqaddr=0xAAAAA [X86] Specify the physical address
1915 of the PIRQ table (normally generated
1916 by the BIOS) if it is outside the
1917 F0000h-100000h range.
1918 lastbus=N [X86] Scan all buses thru bus #N. Can be
1919 useful if the kernel is unable to find your
1920 secondary buses and you want to tell it
1921 explicitly which ones they are.
1922 assign-busses [X86] Always assign all PCI bus
1923 numbers ourselves, overriding
1924 whatever the firmware may have done.
1925 usepirqmask [X86] Honor the possible IRQ mask stored
1926 in the BIOS $PIR table. This is needed on
1927 some systems with broken BIOSes, notably
1928 some HP Pavilion N5400 and Omnibook XE3
1929 notebooks. This will have no effect if ACPI
1930 IRQ routing is enabled.
1931 noacpi [X86] Do not use ACPI for IRQ routing
1932 or for PCI scanning.
1933 use_crs [X86] Use PCI host bridge window information
1934 from ACPI. On BIOSes from 2008 or later, this
1935 is enabled by default. If you need to use this,
1936 please report a bug.
1937 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1938 If you need to use this, please report a bug.
1939 routeirq Do IRQ routing for all PCI devices.
1940 This is normally done in pci_enable_device(),
1941 so this option is a temporary workaround
1942 for broken drivers that don't call it.
1943 skip_isa_align [X86] do not align io start addr, so can
1944 handle more pci cards
1945 firmware [ARM] Do not re-enumerate the bus but instead
1946 just use the configuration from the
1947 bootloader. This is currently used on
1948 IXP2000 systems where the bus has to be
1949 configured a certain way for adjunct CPUs.
1950 noearly [X86] Don't do any early type 1 scanning.
1951 This might help on some broken boards which
1952 machine check when some devices' config space
1953 is read. But various workarounds are disabled
1954 and some IOMMU drivers will not work.
1955 bfsort Sort PCI devices into breadth-first order.
1956 This sorting is done to get a device
1957 order compatible with older (<= 2.4) kernels.
1958 nobfsort Don't sort PCI devices into breadth-first order.
1959 cbiosize=nn[KMG] The fixed amount of bus space which is
1960 reserved for the CardBus bridge's IO window.
1961 The default value is 256 bytes.
1962 cbmemsize=nn[KMG] The fixed amount of bus space which is
1963 reserved for the CardBus bridge's memory
1964 window. The default value is 64 megabytes.
1965 resource_alignment=
1966 Format:
1967 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1968 Specifies alignment and device to reassign
1969 aligned memory resources.
1970 If <order of align> is not specified,
1971 PAGE_SIZE is used as alignment.
1972 PCI-PCI bridge can be specified, if resource
1973 windows need to be expanded.
1974 ecrc= Enable/disable PCIe ECRC (transaction layer
1975 end-to-end CRC checking).
1976 bios: Use BIOS/firmware settings. This is the
1977 the default.
1978 off: Turn ECRC off
1979 on: Turn ECRC on.
1981 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1982 Management.
1983 off Disable ASPM.
1984 force Enable ASPM even on devices that claim not to support it.
1985 WARNING: Forcing ASPM on may cause system lockups.
1987 pcie_ports= [PCIE] PCIe ports handling:
1988 auto Ask the BIOS whether or not to use native PCIe services
1989 associated with PCIe ports (PME, hot-plug, AER). Use
1990 them only if that is allowed by the BIOS.
1991 native Use native PCIe services associated with PCIe ports
1992 unconditionally.
1993 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1994 ports driver.
1996 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
1997 nomsi Do not use MSI for native PCIe PME signaling (this makes
1998 all PCIe root ports use INTx for all services).
2000 pcmv= [HW,PCMCIA] BadgePAD 4
2002 pd. [PARIDE]
2003 See Documentation/blockdev/paride.txt.
2005 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2006 boot time.
2007 Format: { 0 | 1 }
2008 See arch/parisc/kernel/pdc_chassis.c
2010 percpu_alloc= Select which percpu first chunk allocator to use.
2011 Currently supported values are "embed" and "page".
2012 Archs may support subset or none of the selections.
2013 See comments in mm/percpu.c for details on each
2014 allocator. This parameter is primarily for debugging
2015 and performance comparison.
2017 pf. [PARIDE]
2018 See Documentation/blockdev/paride.txt.
2020 pg. [PARIDE]
2021 See Documentation/blockdev/paride.txt.
2023 pirq= [SMP,APIC] Manual mp-table setup
2024 See Documentation/x86/i386/IO-APIC.txt.
2026 plip= [PPT,NET] Parallel port network link
2027 Format: { parport<nr> | timid | 0 }
2028 See also Documentation/parport.txt.
2030 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2031 Override pmtimer IOPort with a hex value.
2032 e.g. pmtmr=0x508
2034 pnp.debug [PNP]
2035 Enable PNP debug messages. This depends on the
2036 CONFIG_PNP_DEBUG_MESSAGES option.
2038 pnpacpi= [ACPI]
2039 { off }
2041 pnpbios= [ISAPNP]
2042 { on | off | curr | res | no-curr | no-res }
2044 pnp_reserve_irq=
2045 [ISAPNP] Exclude IRQs for the autoconfiguration
2047 pnp_reserve_dma=
2048 [ISAPNP] Exclude DMAs for the autoconfiguration
2050 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2051 Ranges are in pairs (I/O port base and size).
2053 pnp_reserve_mem=
2054 [ISAPNP] Exclude memory regions for the
2055 autoconfiguration.
2056 Ranges are in pairs (memory base and size).
2058 ports= [IP_VS_FTP] IPVS ftp helper module
2059 Default is 21.
2060 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2061 may be specified.
2062 Format: <port>,<port>....
2064 print-fatal-signals=
2065 [KNL] debug: print fatal signals
2067 If enabled, warn about various signal handling
2068 related application anomalies: too many signals,
2069 too many POSIX.1 timers, fatal signals causing a
2070 coredump - etc.
2072 If you hit the warning due to signal overflow,
2073 you might want to try "ulimit -i unlimited".
2075 default: off.
2077 printk.time= Show timing data prefixed to each printk message line
2078 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2080 processor.max_cstate= [HW,ACPI]
2081 Limit processor to maximum C-state
2082 max_cstate=9 overrides any DMI blacklist limit.
2084 processor.nocst [HW,ACPI]
2085 Ignore the _CST method to determine C-states,
2086 instead using the legacy FADT method
2088 profile= [KNL] Enable kernel profiling via /proc/profile
2089 Format: [schedule,]<number>
2090 Param: "schedule" - profile schedule points.
2091 Param: <number> - step/bucket size as a power of 2 for
2092 statistical time based profiling.
2093 Param: "sleep" - profile D-state sleeping (millisecs).
2094 Requires CONFIG_SCHEDSTATS
2095 Param: "kvm" - profile VM exits.
2097 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2098 before loading.
2099 See Documentation/blockdev/ramdisk.txt.
2101 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2102 probe for; one of (bare|imps|exps|lifebook|any).
2103 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2104 per second.
2105 psmouse.resetafter= [HW,MOUSE]
2106 Try to reset the device after so many bad packets
2107 (0 = never).
2108 psmouse.resolution=
2109 [HW,MOUSE] Set desired mouse resolution, in dpi.
2110 psmouse.smartscroll=
2111 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2112 0 = disabled, 1 = enabled (default).
2114 pt. [PARIDE]
2115 See Documentation/blockdev/paride.txt.
2117 pty.legacy_count=
2118 [KNL] Number of legacy pty's. Overwrites compiled-in
2119 default number.
2121 quiet [KNL] Disable most log messages
2123 r128= [HW,DRM]
2125 raid= [HW,RAID]
2126 See Documentation/md.txt.
2128 ramdisk_blocksize= [RAM]
2129 See Documentation/blockdev/ramdisk.txt.
2131 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2132 See Documentation/blockdev/ramdisk.txt.
2134 rcupdate.blimit= [KNL,BOOT]
2135 Set maximum number of finished RCU callbacks to process
2136 in one batch.
2138 rcupdate.qhimark= [KNL,BOOT]
2139 Set threshold of queued
2140 RCU callbacks over which batch limiting is disabled.
2142 rcupdate.qlowmark= [KNL,BOOT]
2143 Set threshold of queued RCU callbacks below which
2144 batch limiting is re-enabled.
2146 rdinit= [KNL]
2147 Format: <full_path>
2148 Run specified binary instead of /init from the ramdisk,
2149 used for early userspace startup. See initrd.
2151 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2152 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2153 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2155 relax_domain_level=
2156 [KNL, SMP] Set scheduler's default relax_domain_level.
2157 See Documentation/cgroups/cpusets.txt.
2159 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2161 reservetop= [X86-32]
2162 Format: nn[KMG]
2163 Reserves a hole at the top of the kernel virtual
2164 address space.
2166 reservelow= [X86]
2167 Format: nn[K]
2168 Set the amount of memory to reserve for BIOS at
2169 the bottom of the address space.
2171 reset_devices [KNL] Force drivers to reset the underlying device
2172 during initialization.
2174 resume= [SWSUSP]
2175 Specify the partition device for software suspend
2177 resume_offset= [SWSUSP]
2178 Specify the offset from the beginning of the partition
2179 given by "resume=" at which the swap header is located,
2180 in <PAGE_SIZE> units (needed only for swap files).
2181 See Documentation/power/swsusp-and-swap-files.txt
2183 hibernate= [HIBERNATION]
2184 noresume Don't check if there's a hibernation image
2185 present during boot.
2186 nocompress Don't compress/decompress hibernation images.
2188 retain_initrd [RAM] Keep initrd memory after extraction
2190 rhash_entries= [KNL,NET]
2191 Set number of hash buckets for route cache
2193 riscom8= [HW,SERIAL]
2194 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2196 ro [KNL] Mount root device read-only on boot
2198 root= [KNL] Root filesystem
2200 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2201 mount the root filesystem
2203 rootflags= [KNL] Set root filesystem mount option string
2205 rootfstype= [KNL] Set root filesystem type
2207 rootwait [KNL] Wait (indefinitely) for root device to show up.
2208 Useful for devices that are detected asynchronously
2209 (e.g. USB and MMC devices).
2211 rw [KNL] Mount root device read-write on boot
2213 S [KNL] Run init in single mode
2215 sa1100ir [NET]
2216 See drivers/net/irda/sa1100_ir.c.
2218 sbni= [NET] Granch SBNI12 leased line adapter
2220 sched_debug [KNL] Enables verbose scheduler debug messages.
2222 security= [SECURITY] Choose a security module to enable at boot.
2223 If this boot parameter is not specified, only the first
2224 security module asking for security registration will be
2225 loaded. An invalid security module name will be treated
2226 as if no module has been chosen.
2228 selinux= [SELINUX] Disable or enable SELinux at boot time.
2229 Format: { "0" | "1" }
2230 See security/selinux/Kconfig help text.
2231 0 -- disable.
2232 1 -- enable.
2233 Default value is set via kernel config option.
2234 If enabled at boot time, /selinux/disable can be used
2235 later to disable prior to initial policy load.
2237 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2238 Format: { "0" | "1" }
2239 See security/apparmor/Kconfig help text
2240 0 -- disable.
2241 1 -- enable.
2242 Default value is set via kernel config option.
2244 serialnumber [BUGS=X86-32]
2246 shapers= [NET]
2247 Maximal number of shapers.
2249 show_msr= [x86] show boot-time MSR settings
2250 Format: { <integer> }
2251 Show boot-time (BIOS-initialized) MSR settings.
2252 The parameter means the number of CPUs to show,
2253 for example 1 means boot CPU only.
2255 simeth= [IA-64]
2256 simscsi=
2258 slram= [HW,MTD]
2260 slub_debug[=options[,slabs]] [MM, SLUB]
2261 Enabling slub_debug allows one to determine the
2262 culprit if slab objects become corrupted. Enabling
2263 slub_debug can create guard zones around objects and
2264 may poison objects when not in use. Also tracks the
2265 last alloc / free. For more information see
2266 Documentation/vm/slub.txt.
2268 slub_max_order= [MM, SLUB]
2269 Determines the maximum allowed order for slabs.
2270 A high setting may cause OOMs due to memory
2271 fragmentation. For more information see
2272 Documentation/vm/slub.txt.
2274 slub_min_objects= [MM, SLUB]
2275 The minimum number of objects per slab. SLUB will
2276 increase the slab order up to slub_max_order to
2277 generate a sufficiently large slab able to contain
2278 the number of objects indicated. The higher the number
2279 of objects the smaller the overhead of tracking slabs
2280 and the less frequently locks need to be acquired.
2281 For more information see Documentation/vm/slub.txt.
2283 slub_min_order= [MM, SLUB]
2284 Determines the mininum page order for slabs. Must be
2285 lower than slub_max_order.
2286 For more information see Documentation/vm/slub.txt.
2288 slub_nomerge [MM, SLUB]
2289 Disable merging of slabs with similar size. May be
2290 necessary if there is some reason to distinguish
2291 allocs to different slabs. Debug options disable
2292 merging on their own.
2293 For more information see Documentation/vm/slub.txt.
2295 smart2= [HW]
2296 Format: <io1>[,<io2>[,...,<io8>]]
2298 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2299 attempt to substitute SMP alternatives once at boot.
2301 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2302 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2303 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2304 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2305 smsc-ircc2.ircc_irq= [HW] IRQ line
2306 smsc-ircc2.ircc_dma= [HW] DMA channel
2307 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2308 0: Toshiba Satellite 1800 (GP data pin select)
2309 1: Fast pin select (default)
2310 2: ATC IRMode
2312 softlockup_panic=
2313 [KNL] Should the soft-lockup detector generate panics.
2315 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2316 See Documentation/sonypi.txt
2318 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2319 See Documentation/serial/specialix.txt.
2321 spia_io_base= [HW,MTD]
2322 spia_fio_base=
2323 spia_pedr=
2324 spia_peddr=
2326 stacktrace [FTRACE]
2327 Enabled the stack tracer on boot up.
2329 sti= [PARISC,HW]
2330 Format: <num>
2331 Set the STI (builtin display/keyboard on the HP-PARISC
2332 machines) console (graphic card) which should be used
2333 as the initial boot-console.
2334 See also comment in drivers/video/console/sticore.c.
2336 sti_font= [HW]
2337 See comment in drivers/video/console/sticore.c.
2339 stifb= [HW]
2340 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2342 sunrpc.min_resvport=
2343 sunrpc.max_resvport=
2344 [NFS,SUNRPC]
2345 SunRPC servers often require that client requests
2346 originate from a privileged port (i.e. a port in the
2347 range 0 < portnr < 1024).
2348 An administrator who wishes to reserve some of these
2349 ports for other uses may adjust the range that the
2350 kernel's sunrpc client considers to be privileged
2351 using these two parameters to set the minimum and
2352 maximum port values.
2354 sunrpc.pool_mode=
2355 [NFS]
2356 Control how the NFS server code allocates CPUs to
2357 service thread pools. Depending on how many NICs
2358 you have and where their interrupts are bound, this
2359 option will affect which CPUs will do NFS serving.
2360 Note: this parameter cannot be changed while the
2361 NFS server is running.
2363 auto the server chooses an appropriate mode
2364 automatically using heuristics
2365 global a single global pool contains all CPUs
2366 percpu one pool for each CPU
2367 pernode one pool for each NUMA node (equivalent
2368 to global on non-NUMA machines)
2370 sunrpc.tcp_slot_table_entries=
2371 sunrpc.udp_slot_table_entries=
2372 [NFS,SUNRPC]
2373 Sets the upper limit on the number of simultaneous
2374 RPC calls that can be sent from the client to a
2375 server. Increasing these values may allow you to
2376 improve throughput, but will also increase the
2377 amount of memory reserved for use by the client.
2379 swapaccount[=0|1]
2380 [KNL] Enable accounting of swap in memory resource
2381 controller if no parameter or 1 is given or disable
2382 it if 0 is given (See Documentation/cgroups/memory.txt)
2384 swiotlb= [IA-64] Number of I/O TLB slabs
2386 switches= [HW,M68k]
2388 sysfs.deprecated=0|1 [KNL]
2389 Enable/disable old style sysfs layout for old udev
2390 on older distributions. When this option is enabled
2391 very new udev will not work anymore. When this option
2392 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2393 in older udev will not work anymore.
2394 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2395 the kernel configuration.
2397 sysrq_always_enabled
2398 [KNL]
2399 Ignore sysrq setting - this boot parameter will
2400 neutralize any effect of /proc/sys/kernel/sysrq.
2401 Useful for debugging.
2403 tdfx= [HW,DRM]
2405 test_suspend= [SUSPEND]
2406 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2407 standby suspend) as the system sleep state to briefly
2408 enter during system startup. The system is woken from
2409 this state using a wakeup-capable RTC alarm.
2411 thash_entries= [KNL,NET]
2412 Set number of hash buckets for TCP connection
2414 thermal.act= [HW,ACPI]
2415 -1: disable all active trip points in all thermal zones
2416 <degrees C>: override all lowest active trip points
2418 thermal.crt= [HW,ACPI]
2419 -1: disable all critical trip points in all thermal zones
2420 <degrees C>: override all critical trip points
2422 thermal.nocrt= [HW,ACPI]
2423 Set to disable actions on ACPI thermal zone
2424 critical and hot trip points.
2426 thermal.off= [HW,ACPI]
2427 1: disable ACPI thermal control
2429 thermal.psv= [HW,ACPI]
2430 -1: disable all passive trip points
2431 <degrees C>: override all passive trip points to this
2432 value
2434 thermal.tzp= [HW,ACPI]
2435 Specify global default ACPI thermal zone polling rate
2436 <deci-seconds>: poll all this frequency
2437 0: no polling (default)
2439 topology= [S390]
2440 Format: {off | on}
2441 Specify if the kernel should make use of the cpu
2442 topology informations if the hardware supports these.
2443 The scheduler will make use of these informations and
2444 e.g. base its process migration decisions on it.
2445 Default is on.
2447 tp720= [HW,PS2]
2449 tpm_suspend_pcr=[HW,TPM]
2450 Format: integer pcr id
2451 Specify that at suspend time, the tpm driver
2452 should extend the specified pcr with zeros,
2453 as a workaround for some chips which fail to
2454 flush the last written pcr on TPM_SaveState.
2455 This will guarantee that all the other pcrs
2456 are saved.
2458 trace_buf_size=nn[KMG]
2459 [FTRACE] will set tracing buffer size.
2461 trace_event=[event-list]
2462 [FTRACE] Set and start specified trace events in order
2463 to facilitate early boot debugging.
2464 See also Documentation/trace/events.txt
2466 tsc= Disable clocksource stability checks for TSC.
2467 Format: <string>
2468 [x86] reliable: mark tsc clocksource as reliable, this
2469 disables clocksource verification at runtime, as well
2470 as the stability checks done at bootup. Used to enable
2471 high-resolution timer mode on older hardware, and in
2472 virtualized environment.
2473 [x86] noirqtime: Do not use TSC to do irq accounting.
2474 Used to run time disable IRQ_TIME_ACCOUNTING on any
2475 platforms where RDTSC is slow and this accounting
2476 can add overhead.
2478 turbografx.map[2|3]= [HW,JOY]
2479 TurboGraFX parallel port interface
2480 Format:
2481 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2482 See also Documentation/input/joystick-parport.txt
2484 uhash_entries= [KNL,NET]
2485 Set number of hash buckets for UDP/UDP-Lite connections
2487 uhci-hcd.ignore_oc=
2488 [USB] Ignore overcurrent events (default N).
2489 Some badly-designed motherboards generate lots of
2490 bogus events, for ports that aren't wired to
2491 anything. Set this parameter to avoid log spamming.
2492 Note that genuine overcurrent events won't be
2493 reported either.
2495 unknown_nmi_panic
2496 [X86]
2497 Set unknown_nmi_panic=1 early on boot.
2499 usbcore.autosuspend=
2500 [USB] The autosuspend time delay (in seconds) used
2501 for newly-detected USB devices (default 2). This
2502 is the time required before an idle device will be
2503 autosuspended. Devices for which the delay is set
2504 to a negative value won't be autosuspended at all.
2506 usbcore.usbfs_snoop=
2507 [USB] Set to log all usbfs traffic (default 0 = off).
2509 usbcore.blinkenlights=
2510 [USB] Set to cycle leds on hubs (default 0 = off).
2512 usbcore.old_scheme_first=
2513 [USB] Start with the old device initialization
2514 scheme (default 0 = off).
2516 usbcore.use_both_schemes=
2517 [USB] Try the other device initialization scheme
2518 if the first one fails (default 1 = enabled).
2520 usbcore.initial_descriptor_timeout=
2521 [USB] Specifies timeout for the initial 64-byte
2522 USB_REQ_GET_DESCRIPTOR request in milliseconds
2523 (default 5000 = 5.0 seconds).
2525 usbhid.mousepoll=
2526 [USBHID] The interval which mice are to be polled at.
2528 usb-storage.delay_use=
2529 [UMS] The delay in seconds before a new device is
2530 scanned for Logical Units (default 5).
2532 usb-storage.quirks=
2533 [UMS] A list of quirks entries to supplement or
2534 override the built-in unusual_devs list. List
2535 entries are separated by commas. Each entry has
2536 the form VID:PID:Flags where VID and PID are Vendor
2537 and Product ID values (4-digit hex numbers) and
2538 Flags is a set of characters, each corresponding
2539 to a common usb-storage quirk flag as follows:
2540 a = SANE_SENSE (collect more than 18 bytes
2541 of sense data);
2542 b = BAD_SENSE (don't collect more than 18
2543 bytes of sense data);
2544 c = FIX_CAPACITY (decrease the reported
2545 device capacity by one sector);
2546 h = CAPACITY_HEURISTICS (decrease the
2547 reported device capacity by one
2548 sector if the number is odd);
2549 i = IGNORE_DEVICE (don't bind to this
2550 device);
2551 l = NOT_LOCKABLE (don't try to lock and
2552 unlock ejectable media);
2553 m = MAX_SECTORS_64 (don't transfer more
2554 than 64 sectors = 32 KB at a time);
2555 o = CAPACITY_OK (accept the capacity
2556 reported by the device);
2557 r = IGNORE_RESIDUE (the device reports
2558 bogus residue values);
2559 s = SINGLE_LUN (the device has only one
2560 Logical Unit);
2561 w = NO_WP_DETECT (don't test whether the
2562 medium is write-protected).
2563 Example: quirks=0419:aaf5:rl,0421:0433:rc
2565 userpte=
2566 [X86] Flags controlling user PTE allocations.
2568 nohigh = do not allocate PTE pages in
2569 HIGHMEM regardless of setting
2570 of CONFIG_HIGHPTE.
2572 vdso= [X86,SH]
2573 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2574 vdso=1: enable VDSO (default)
2575 vdso=0: disable VDSO mapping
2577 vdso32= [X86]
2578 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2579 vdso32=1: enable 32-bit VDSO (default)
2580 vdso32=0: disable 32-bit VDSO mapping
2582 vector= [IA-64,SMP]
2583 vector=percpu: enable percpu vector domain
2585 video= [FB] Frame buffer configuration
2586 See Documentation/fb/modedb.txt.
2588 vga= [BOOT,X86-32] Select a particular video mode
2589 See Documentation/x86/boot.txt and
2590 Documentation/svga.txt.
2591 Use vga=ask for menu.
2592 This is actually a boot loader parameter; the value is
2593 passed to the kernel using a special protocol.
2595 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2596 size of <nn>. This can be used to increase the
2597 minimum size (128MB on x86). It can also be used to
2598 decrease the size and leave more room for directly
2599 mapped kernel RAM.
2601 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2602 Format: <command>
2604 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2605 Format: <command>
2607 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2608 Format: <command>
2610 vt.cur_default= [VT] Default cursor shape.
2611 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2612 the parameters of the <Esc>[?A;B;Cc escape sequence;
2613 see VGA-softcursor.txt. Default: 2 = underline.
2615 vt.default_blu= [VT]
2616 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2617 Change the default blue palette of the console.
2618 This is a 16-member array composed of values
2619 ranging from 0-255.
2621 vt.default_grn= [VT]
2622 Format: <green0>,<green1>,<green2>,...,<green15>
2623 Change the default green palette of the console.
2624 This is a 16-member array composed of values
2625 ranging from 0-255.
2627 vt.default_red= [VT]
2628 Format: <red0>,<red1>,<red2>,...,<red15>
2629 Change the default red palette of the console.
2630 This is a 16-member array composed of values
2631 ranging from 0-255.
2633 vt.default_utf8=
2634 [VT]
2635 Format=<0|1>
2636 Set system-wide default UTF-8 mode for all tty's.
2637 Default is 1, i.e. UTF-8 mode is enabled for all
2638 newly opened terminals.
2640 vt.global_cursor_default=
2641 [VT]
2642 Format=<-1|0|1>
2643 Set system-wide default for whether a cursor
2644 is shown on new VTs. Default is -1,
2645 i.e. cursors will be created by default unless
2646 overridden by individual drivers. 0 will hide
2647 cursors, 1 will display them.
2649 watchdog timers [HW,WDT] For information on watchdog timers,
2650 see Documentation/watchdog/watchdog-parameters.txt
2651 or other driver-specific files in the
2652 Documentation/watchdog/ directory.
2654 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2655 default x2apic cluster mode on platforms
2656 supporting x2apic.
2658 x86_mrst_timer= [X86-32,APBT]
2659 Choose timer option for x86 Moorestown MID platform.
2660 Two valid options are apbt timer only and lapic timer
2661 plus one apbt timer for broadcast timer.
2662 x86_mrst_timer=apbt_only | lapic_and_apbt
2664 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2665 xd_geo= See header of drivers/block/xd.c.
2667 xen_emul_unplug= [HW,X86,XEN]
2668 Unplug Xen emulated devices
2669 Format: [unplug0,][unplug1]
2670 ide-disks -- unplug primary master IDE devices
2671 aux-ide-disks -- unplug non-primary-master IDE devices
2672 nics -- unplug network devices
2673 all -- unplug all emulated devices (NICs and IDE disks)
2674 unnecessary -- unplugging emulated devices is
2675 unnecessary even if the host did not respond to
2676 the unplug protocol
2677 never -- do not unplug even if version check succeeds
2679 xirc2ps_cs= [NET,PCMCIA]
2680 Format:
2681 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2683 ______________________________________________________________________
2685 TODO:
2687 Add more DRM drivers.