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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 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
47 EFI EFI Partitioning (GPT) is enabled
48 EIDE EIDE/ATAPI support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
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_display_output= [HW,ACPI]
203 acpi_display_output=vendor
204 acpi_display_output=video
205 See above.
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
209 default in APIC mode
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
213 default in PIC mode
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 use by PCI
220 Format: <irq>,<irq>...
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
232 acpi_pm_good [X86]
233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
240 acpi_serialize [HW,ACPI] force serialization of AML methods
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248 old_ordering, s4_nonvs, sci_force_enable }
249 See Documentation/power/video.txt for information on
250 s3_bios and s3_mode.
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
288 agp= [AGP]
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
294 ALSA [HW,ALSA]
295 See Documentation/sound/alsa/alsa-parameters.txt
297 alignment= [KNL,ARM]
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
309 off - do not initialize any AMD IOMMU found in
310 the system
312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
314 Format: <a>,<b>
315 See also Documentation/kernel/input/joystick.txt
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
322 apc= [HW,SPARC]
323 Power management functions (SPARCstation-4/5 + deriv.)
324 Format: noidle
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
330 Change the output verbosity whilst booting
331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
335 autoconf= [IPV6]
336 See Documentation/networking/ipv6.txt.
338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
347 apm= [APM] Advanced Power Management
348 See header of arch/x86/kernel/apm_32.c.
350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
353 ataflop= [HW,M68k]
355 atarimouse= [HW,MOUSE] Atari Mouse
357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
360 atkbd.reset= [HW] Reset keyboard during initialization
362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
366 keyboards
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
374 autotest [IA64]
376 baycom_epp= [HW,AX25]
377 Format: <io>,<mode>
379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380 Format: <io>,<mode>
381 See header of drivers/net/hamradio/baycom_par.c.
383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
395 no delay (0).
396 Format: integer
398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401 bttv.radio= Most important insmod options are available as
402 kernel args too.
403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
406 c101= [NET] Moxa C101 synchronous serial card
408 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
409 Sometimes CPU hardware bugs make them report the cache
410 size incorrectly. The kernel will attempt work arounds
411 to fix known problems, but for some CPUs it is not
412 possible to determine what the correct size should be.
413 This option provides an override for these situations.
415 capability.disable=
416 [SECURITY] Disable capabilities. This would normally
417 be used only if an alternative security model is to be
418 configured. Potentially dangerous and should only be
419 used if you are entirely sure of the consequences.
421 ccw_timeout_log [S390]
422 See Documentation/s390/CommonIO for details.
424 cgroup_disable= [KNL] Disable a particular controller
425 Format: {name of the controller(s) to disable}
426 {Currently supported controllers - "memory"}
428 checkreqprot [SELINUX] Set initial checkreqprot flag value.
429 Format: { "0" | "1" }
430 See security/selinux/Kconfig help text.
431 0 -- check protection applied by kernel (includes
432 any implied execute protection).
433 1 -- check protection requested by application.
434 Default value is set via a kernel config option.
435 Value can be changed at runtime via
436 /selinux/checkreqprot.
438 cio_ignore= [S390]
439 See Documentation/s390/CommonIO for details.
441 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
442 [Deprecated]
443 Forces specified clocksource (if available) to be used
444 when calculating gettimeofday(). If specified
445 clocksource is not available, it defaults to PIT.
446 Format: { pit | tsc | cyclone | pmtmr }
448 clocksource= Override the default clocksource
449 Format: <string>
450 Override the default clocksource and use the clocksource
451 with the name specified.
452 Some clocksource names to choose from, depending on
453 the platform:
454 [all] jiffies (this is the base, fallback clocksource)
455 [ACPI] acpi_pm
456 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
457 pxa_timer,timer3,32k_counter,timer0_1
458 [AVR32] avr32
459 [X86-32] pit,hpet,tsc;
460 scx200_hrt on Geode; cyclone on IBM x440
461 [MIPS] MIPS
462 [PARISC] cr16
463 [S390] tod
464 [SH] SuperH
465 [SPARC64] tick
466 [X86-64] hpet,tsc
468 clearcpuid=BITNUM [X86]
469 Disable CPUID feature X for the kernel. See
470 arch/x86/include/asm/cpufeature.h for the valid bit
471 numbers. Note the Linux specific bits are not necessarily
472 stable over kernel options, but the vendor specific
473 ones should be.
474 Also note that user programs calling CPUID directly
475 or using the feature without checking anything
476 will still see it. This just prevents it from
477 being used by the kernel or shown in /proc/cpuinfo.
478 Also note the kernel might malfunction if you disable
479 some critical bits.
481 cmo_free_hint= [PPC] Format: { yes | no }
482 Specify whether pages are marked as being inactive
483 when they are freed. This is used in CMO environments
484 to determine OS memory pressure for page stealing by
485 a hypervisor.
486 Default: yes
488 code_bytes [X86] How many bytes of object code to print
489 in an oops report.
490 Range: 0 - 8192
491 Default: 64
493 com20020= [HW,NET] ARCnet - COM20020 chipset
494 Format:
495 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
497 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
498 Format: <io>[,<irq>]
500 com90xx= [HW,NET]
501 ARCnet - COM90xx chipset (memory-mapped buffers)
502 Format: <io>[,<irq>[,<memstart>]]
504 condev= [HW,S390] console device
505 conmode=
507 console= [KNL] Output console device and options.
509 tty<n> Use the virtual console device <n>.
511 ttyS<n>[,options]
512 ttyUSB0[,options]
513 Use the specified serial port. The options are of
514 the form "bbbbpnf", where "bbbb" is the baud rate,
515 "p" is parity ("n", "o", or "e"), "n" is number of
516 bits, and "f" is flow control ("r" for RTS or
517 omit it). Default is "9600n8".
519 See Documentation/serial-console.txt for more
520 information. See
521 Documentation/networking/netconsole.txt for an
522 alternative.
524 uart[8250],io,<addr>[,options]
525 uart[8250],mmio,<addr>[,options]
526 Start an early, polled-mode console on the 8250/16550
527 UART at the specified I/O port or MMIO address,
528 switching to the matching ttyS device later. The
529 options are the same as for ttyS, above.
531 If the device connected to the port is not a TTY but a braille
532 device, prepend "brl," before the device type, for instance
533 console=brl,ttyS0
534 For now, only VisioBraille is supported.
536 consoleblank= [KNL] The console blank (screen saver) timeout in
537 seconds. Defaults to 10*60 = 10mins. A value of 0
538 disables the blank timer.
540 coredump_filter=
541 [KNL] Change the default value for
542 /proc/<pid>/coredump_filter.
543 See also Documentation/filesystems/proc.txt.
545 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
546 Format:
547 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
549 crashkernel=nn[KMG]@ss[KMG]
550 [KNL] Reserve a chunk of physical memory to
551 hold a kernel to switch to with kexec on panic.
553 crashkernel=range1:size1[,range2:size2,...][@offset]
554 [KNL] Same as above, but depends on the memory
555 in the running system. The syntax of range is
556 start-[end] where start and end are both
557 a memory unit (amount[KMG]). See also
558 Documentation/kdump/kdump.txt for a example.
560 cs89x0_dma= [HW,NET]
561 Format: <dma>
563 cs89x0_media= [HW,NET]
564 Format: { rj45 | aui | bnc }
566 dasd= [HW,NET]
567 See header of drivers/s390/block/dasd_devmap.c.
569 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
570 (one device per port)
571 Format: <port#>,<type>
572 See also Documentation/input/joystick-parport.txt
574 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
575 time. See Documentation/dynamic-debug-howto.txt for
576 details.
578 debug [KNL] Enable kernel debugging (events log level).
580 debug_locks_verbose=
581 [KNL] verbose self-tests
582 Format=<0|1>
583 Print debugging info while doing the locking API
584 self-tests.
585 We default to 0 (no extra messages), setting it to
586 1 will print _a lot_ more information - normally
587 only useful to kernel developers.
589 debug_objects [KNL] Enable object debugging
591 no_debug_objects
592 [KNL] Disable object debugging
594 debugpat [X86] Enable PAT debugging
596 decnet.addr= [HW,NET]
597 Format: <area>[,<node>]
598 See also Documentation/networking/decnet.txt.
600 default_hugepagesz=
601 [same as hugepagesz=] The size of the default
602 HugeTLB page size. This is the size represented by
603 the legacy /proc/ hugepages APIs, used for SHM, and
604 default size when mounting hugetlbfs filesystems.
605 Defaults to the default architecture's huge page size
606 if not specified.
608 dhash_entries= [KNL]
609 Set number of hash buckets for dentry cache.
611 digi= [HW,SERIAL]
612 IO parameters + enable/disable command.
614 digiepca= [HW,SERIAL]
615 See drivers/char/README.epca and
616 Documentation/serial/digiepca.txt.
618 disable= [IPV6]
619 See Documentation/networking/ipv6.txt.
621 disable_ipv6= [IPV6]
622 See Documentation/networking/ipv6.txt.
624 disable_mtrr_cleanup [X86]
625 The kernel tries to adjust MTRR layout from continuous
626 to discrete, to make X server driver able to add WB
627 entry later. This parameter disables that.
629 disable_mtrr_trim [X86, Intel and AMD only]
630 By default the kernel will trim any uncacheable
631 memory out of your available memory pool based on
632 MTRR settings. This parameter disables that behavior,
633 possibly causing your machine to run very slowly.
635 disable_timer_pin_1 [X86]
636 Disable PIN 1 of APIC timer
637 Can be useful to work around chipset bugs.
639 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
640 this option disables the debugging code at boot.
642 dma_debug_entries=<number>
643 This option allows to tune the number of preallocated
644 entries for DMA-API debugging code. One entry is
645 required per DMA-API allocation. Use this if the
646 DMA-API debugging code disables itself because the
647 architectural default is too low.
649 dma_debug_driver=<driver_name>
650 With this option the DMA-API debugging driver
651 filter feature can be enabled at boot time. Just
652 pass the driver to filter for as the parameter.
653 The filter can be disabled or changed to another
654 driver later using sysfs.
656 dscc4.setup= [NET]
658 dynamic_printk Enables pr_debug()/dev_dbg() calls if
659 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
660 These can also be switched on/off via
661 <debugfs>/dynamic_printk/modules
663 earlycon= [KNL] Output early console device and options.
664 uart[8250],io,<addr>[,options]
665 uart[8250],mmio,<addr>[,options]
666 uart[8250],mmio32,<addr>[,options]
667 Start an early, polled-mode console on the 8250/16550
668 UART at the specified I/O port or MMIO address.
669 MMIO inter-register address stride is either 8bit (mmio)
670 or 32bit (mmio32).
671 The options are the same as for ttyS, above.
673 earlyprintk= [X86,SH,BLACKFIN]
674 earlyprintk=vga
675 earlyprintk=serial[,ttySn[,baudrate]]
676 earlyprintk=ttySn[,baudrate]
677 earlyprintk=dbgp[debugController#]
679 Append ",keep" to not disable it when the real console
680 takes over.
682 Only vga or serial or usb debug port at a time.
684 Currently only ttyS0 and ttyS1 are supported.
686 Interaction with the standard serial driver is not
687 very good.
689 The VGA output is eventually overwritten by the real
690 console.
692 ekgdboc= [X86,KGDB] Allow early kernel console debugging
693 ekgdboc=kbd
695 This is desgined to be used in conjunction with
696 the boot argument: earlyprintk=vga
698 edd= [EDD]
699 Format: {"off" | "on" | "skip[mbr]"}
701 eisa_irq_edge= [PARISC,HW]
702 See header of drivers/parisc/eisa.c.
704 elanfreq= [X86-32]
705 See comment before function elanfreq_setup() in
706 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
708 elevator= [IOSCHED]
709 Format: {"cfq" | "deadline" | "noop"}
710 See Documentation/block/as-iosched.txt and
711 Documentation/block/deadline-iosched.txt for details.
713 elfcorehdr= [IA64,PPC,SH,X86]
714 Specifies physical address of start of kernel core
715 image elf header. Generally kexec loader will
716 pass this option to capture kernel.
717 See Documentation/kdump/kdump.txt for details.
719 enable_mtrr_cleanup [X86]
720 The kernel tries to adjust MTRR layout from continuous
721 to discrete, to make X server driver able to add WB
722 entry later. This parameter enables that.
724 enable_timer_pin_1 [X86]
725 Enable PIN 1 of APIC timer
726 Can be useful to work around chipset bugs
727 (in particular on some ATI chipsets).
728 The kernel tries to set a reasonable default.
730 enforcing [SELINUX] Set initial enforcing status.
731 Format: {"0" | "1"}
732 See security/selinux/Kconfig help text.
733 0 -- permissive (log only, no denials).
734 1 -- enforcing (deny and log).
735 Default value is 0.
736 Value can be changed at runtime via /selinux/enforce.
738 erst_disable [ACPI]
739 Disable Error Record Serialization Table (ERST)
740 support.
742 ether= [HW,NET] Ethernet cards parameters
743 This option is obsoleted by the "netdev=" option, which
744 has equivalent usage. See its documentation for details.
746 failslab=
747 fail_page_alloc=
748 fail_make_request=[KNL]
749 General fault injection mechanism.
750 Format: <interval>,<probability>,<space>,<times>
751 See also /Documentation/fault-injection/.
753 floppy= [HW]
754 See Documentation/blockdev/floppy.txt.
756 force_pal_cache_flush
757 [IA-64] Avoid check_sal_cache_flush which may hang on
758 buggy SAL_CACHE_FLUSH implementations. Using this
759 parameter will force ia64_sal_cache_flush to call
760 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
762 ftrace=[tracer]
763 [FTRACE] will set and start the specified tracer
764 as early as possible in order to facilitate early
765 boot debugging.
767 ftrace_dump_on_oops[=orig_cpu]
768 [FTRACE] will dump the trace buffers on oops.
769 If no parameter is passed, ftrace will dump
770 buffers of all CPUs, but if you pass orig_cpu, it will
771 dump only the buffer of the CPU that triggered the
772 oops.
774 ftrace_filter=[function-list]
775 [FTRACE] Limit the functions traced by the function
776 tracer at boot up. function-list is a comma separated
777 list of functions. This list can be changed at run
778 time by the set_ftrace_filter file in the debugfs
779 tracing directory.
781 ftrace_notrace=[function-list]
782 [FTRACE] Do not trace the functions specified in
783 function-list. This list can be changed at run time
784 by the set_ftrace_notrace file in the debugfs
785 tracing directory.
787 ftrace_graph_filter=[function-list]
788 [FTRACE] Limit the top level callers functions traced
789 by the function graph tracer at boot up.
790 function-list is a comma separated list of functions
791 that can be changed at run time by the
792 set_graph_function file in the debugfs tracing directory.
794 gamecon.map[2|3]=
795 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
796 support via parallel port (up to 5 devices per port)
797 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
798 See also Documentation/input/joystick-parport.txt
800 gamma= [HW,DRM]
802 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
803 Format: off | on
804 default: on
806 gcov_persist= [GCOV] When non-zero (default), profiling data for
807 kernel modules is saved and remains accessible via
808 debugfs, even when the module is unloaded/reloaded.
809 When zero, profiling data is discarded and associated
810 debugfs files are removed at module unload time.
812 gpt [EFI] Forces disk with valid GPT signature but
813 invalid Protective MBR to be treated as GPT.
815 hashdist= [KNL,NUMA] Large hashes allocated during boot
816 are distributed across NUMA nodes. Defaults on
817 for 64bit NUMA, off otherwise.
818 Format: 0 | 1 (for off | on)
820 hcl= [IA-64] SGI's Hardware Graph compatibility layer
822 hd= [EIDE] (E)IDE hard drive subsystem geometry
823 Format: <cyl>,<head>,<sect>
825 hest_disable [ACPI]
826 Disable Hardware Error Source Table (HEST) support;
827 corresponding firmware-first mode error processing
828 logic will be disabled.
830 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
831 size of <nn>. This works even on boxes that have no
832 highmem otherwise. This also works to reduce highmem
833 size on bigger boxes.
835 highres= [KNL] Enable/disable high resolution timer mode.
836 Valid parameters: "on", "off"
837 Default: "on"
839 hisax= [HW,ISDN]
840 See Documentation/isdn/README.HiSax.
842 hlt [BUGS=ARM,SH]
844 hpet= [X86-32,HPET] option to control HPET usage
845 Format: { enable (default) | disable | force |
846 verbose }
847 disable: disable HPET and use PIT instead
848 force: allow force enabled of undocumented chips (ICH4,
849 VIA, nVidia)
850 verbose: show contents of HPET registers during setup
852 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
853 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
854 On x86-64 and powerpc, this option can be specified
855 multiple times interleaved with hugepages= to reserve
856 huge pages of different sizes. Valid pages sizes on
857 x86-64 are 2M (when the CPU supports "pse") and 1G
858 (when the CPU supports the "pdpe1gb" cpuinfo flag)
859 Note that 1GB pages can only be allocated at boot time
860 using hugepages= and not freed afterwards.
862 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
863 terminal devices. Valid values: 0..8
864 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
865 If specified, z/VM IUCV HVC accepts connections
866 from listed z/VM user IDs only.
868 i2c_bus= [HW] Override the default board specific I2C bus speed
869 or register an additional I2C bus that is not
870 registered from board initialization code.
871 Format:
872 <bus_id>,<clkrate>
874 i8042.debug [HW] Toggle i8042 debug mode
875 i8042.direct [HW] Put keyboard port into non-translated mode
876 i8042.dumbkbd [HW] Pretend that controller can only read data from
877 keyboard and cannot control its state
878 (Don't attempt to blink the leds)
879 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
880 i8042.nokbd [HW] Don't check/create keyboard port
881 i8042.noloop [HW] Disable the AUX Loopback command while probing
882 for the AUX port
883 i8042.nomux [HW] Don't check presence of an active multiplexing
884 controller
885 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
886 controllers
887 i8042.reset [HW] Reset the controller during init and cleanup
888 i8042.unlock [HW] Unlock (ignore) the keylock
890 i810= [HW,DRM]
892 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
893 indicates that the driver is running on unsupported
894 hardware.
895 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
896 does not match list of supported models.
897 i8k.power_status
898 [HW] Report power status in /proc/i8k
899 (disabled by default)
900 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
901 capability is set.
903 icn= [HW,ISDN]
904 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
906 ide-core.nodma= [HW] (E)IDE subsystem
907 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
908 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
909 .cdrom .chs .ignore_cable are additional options
910 See Documentation/ide/ide.txt.
912 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
913 Claim all unknown PCI IDE storage controllers.
915 idle= [X86]
916 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
917 Poll forces a polling idle loop that can slightly
918 improve the performance of waking up a idle CPU, but
919 will use a lot of power and make the system run hot.
920 Not recommended.
921 idle=mwait: On systems which support MONITOR/MWAIT but
922 the kernel chose to not use it because it doesn't save
923 as much power as a normal idle loop, use the
924 MONITOR/MWAIT idle loop anyways. Performance should be
925 the same as idle=poll.
926 idle=halt: Halt is forced to be used for CPU idle.
927 In such case C2/C3 won't be used again.
928 idle=nomwait: Disable mwait for CPU C-states
930 ignore_loglevel [KNL]
931 Ignore loglevel setting - this will print /all/
932 kernel messages to the console. Useful for debugging.
934 ihash_entries= [KNL]
935 Set number of hash buckets for inode cache.
937 ima_audit= [IMA]
938 Format: { "0" | "1" }
939 0 -- integrity auditing messages. (Default)
940 1 -- enable informational integrity auditing messages.
942 ima_hash= [IMA]
943 Format: { "sha1" | "md5" }
944 default: "sha1"
946 ima_tcb [IMA]
947 Load a policy which meets the needs of the Trusted
948 Computing Base. This means IMA will measure all
949 programs exec'd, files mmap'd for exec, and all files
950 opened for read by uid=0.
952 init= [KNL]
953 Format: <full_path>
954 Run specified binary instead of /sbin/init as init
955 process.
957 initcall_debug [KNL] Trace initcalls as they are executed. Useful
958 for working out where the kernel is dying during
959 startup.
961 initrd= [BOOT] Specify the location of the initial ramdisk
963 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
964 Format: <irq>
966 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
967 on
968 Enable intel iommu driver.
969 off
970 Disable intel iommu driver.
971 igfx_off [Default Off]
972 By default, gfx is mapped as normal device. If a gfx
973 device has a dedicated DMAR unit, the DMAR unit is
974 bypassed by not enabling DMAR with this option. In
975 this case, gfx device will use physical address for
976 DMA.
977 forcedac [x86_64]
978 With this option iommu will not optimize to look
979 for io virtual address below 32 bit forcing dual
980 address cycle on pci bus for cards supporting greater
981 than 32 bit addressing. The default is to look
982 for translation below 32 bit and if not available
983 then look in the higher range.
984 strict [Default Off]
985 With this option on every unmap_single operation will
986 result in a hardware IOTLB flush operation as opposed
987 to batching them for performance.
989 intremap= [X86-64, Intel-IOMMU]
990 Format: { on (default) | off | nosid }
991 on enable Interrupt Remapping (default)
992 off disable Interrupt Remapping
993 nosid disable Source ID checking
995 inttest= [IA64]
997 iomem= Disable strict checking of access to MMIO memory
998 strict regions from userspace.
999 relaxed
1001 iommu= [x86]
1002 off
1003 force
1004 noforce
1005 biomerge
1006 panic
1007 nopanic
1008 merge
1009 nomerge
1010 forcesac
1011 soft
1012 pt [x86, IA64]
1014 io7= [HW] IO7 for Marvel based alpha systems
1015 See comment before marvel_specify_io7 in
1016 arch/alpha/kernel/core_marvel.c.
1018 io_delay= [X86] I/O delay method
1019 0x80
1020 Standard port 0x80 based delay
1021 0xed
1022 Alternate port 0xed based delay (needed on some systems)
1023 udelay
1024 Simple two microseconds delay
1025 none
1026 No delay
1028 ip= [IP_PNP]
1029 See Documentation/filesystems/nfs/nfsroot.txt.
1031 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1032 See comment before ip2_setup() in
1033 drivers/char/ip2/ip2base.c.
1035 irqfixup [HW]
1036 When an interrupt is not handled search all handlers
1037 for it. Intended to get systems with badly broken
1038 firmware running.
1040 irqpoll [HW]
1041 When an interrupt is not handled search all handlers
1042 for it. Also check all handlers each timer
1043 interrupt. Intended to get systems with badly broken
1044 firmware running.
1046 isapnp= [ISAPNP]
1047 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1049 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1050 Format:
1051 <cpu number>,...,<cpu number>
1052 or
1053 <cpu number>-<cpu number>
1054 (must be a positive range in ascending order)
1055 or a mixture
1056 <cpu number>,...,<cpu number>-<cpu number>
1058 This option can be used to specify one or more CPUs
1059 to isolate from the general SMP balancing and scheduling
1060 algorithms. You can move a process onto or off an
1061 "isolated" CPU via the CPU affinity syscalls or cpuset.
1062 <cpu number> begins at 0 and the maximum value is
1063 "number of CPUs in system - 1".
1065 This option is the preferred way to isolate CPUs. The
1066 alternative -- manually setting the CPU mask of all
1067 tasks in the system -- can cause problems and
1068 suboptimal load balancer performance.
1070 iucv= [HW,NET]
1072 js= [HW,JOY] Analog joystick
1073 See Documentation/input/joystick.txt.
1075 keepinitrd [HW,ARM]
1077 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1078 specifies the amount of memory usable by the kernel
1079 for non-movable allocations. The requested amount is
1080 spread evenly throughout all nodes in the system. The
1081 remaining memory in each node is used for Movable
1082 pages. In the event, a node is too small to have both
1083 kernelcore and Movable pages, kernelcore pages will
1084 take priority and other nodes will have a larger number
1085 of kernelcore pages. The Movable zone is used for the
1086 allocation of pages that may be reclaimed or moved
1087 by the page migration subsystem. This means that
1088 HugeTLB pages may not be allocated from this zone.
1089 Note that allocations like PTEs-from-HighMem still
1090 use the HighMem zone if it exists, and the Normal
1091 zone if it does not.
1093 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1094 Format: <Controller#>[,poll interval]
1095 The controller # is the number of the ehci usb debug
1096 port as it is probed via PCI. The poll interval is
1097 optional and is the number seconds in between
1098 each poll cycle to the debug port in case you need
1099 the functionality for interrupting the kernel with
1100 gdb or control-c on the dbgp connection. When
1101 not using this parameter you use sysrq-g to break into
1102 the kernel debugger.
1104 kgdboc= [KGDB,HW] kgdb over consoles.
1105 Requires a tty driver that supports console polling,
1106 or a supported polling keyboard driver (non-usb).
1107 Serial only format: <serial_device>[,baud]
1108 keyboard only format: kbd
1109 keyboard and serial format: kbd,<serial_device>[,baud]
1110 Optional Kernel mode setting:
1111 kms, kbd format: kms,kbd
1112 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1114 kgdbwait [KGDB] Stop kernel execution and enter the
1115 kernel debugger at the earliest opportunity.
1117 kmac= [MIPS] korina ethernet MAC address.
1118 Configure the RouterBoard 532 series on-chip
1119 Ethernet adapter MAC address.
1121 kmemleak= [KNL] Boot-time kmemleak enable/disable
1122 Valid arguments: on, off
1123 Default: on
1125 kstack=N [X86] Print N words from the kernel stack
1126 in oops dumps.
1128 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1129 Default is 0 (don't ignore, but inject #GP)
1131 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1132 Default is 1 (enabled)
1134 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1135 KVM MMU at runtime.
1136 Default is 0 (off)
1138 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1139 Default is 1 (enabled)
1141 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1142 for all guests.
1143 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1145 kvm-intel.bypass_guest_pf=
1146 [KVM,Intel] Disables bypassing of guest page faults
1147 on Intel chips. Default is 1 (enabled)
1149 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1150 (virtualized MMU) support on capable Intel chips.
1151 Default is 1 (enabled)
1153 kvm-intel.emulate_invalid_guest_state=
1154 [KVM,Intel] Enable emulation of invalid guest states
1155 Default is 0 (disabled)
1157 kvm-intel.flexpriority=
1158 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1159 Default is 1 (enabled)
1161 kvm-intel.unrestricted_guest=
1162 [KVM,Intel] Disable unrestricted guest feature
1163 (virtualized real and unpaged mode) on capable
1164 Intel chips. Default is 1 (enabled)
1166 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1167 feature (tagged TLBs) on capable Intel chips.
1168 Default is 1 (enabled)
1170 l2cr= [PPC]
1172 l3cr= [PPC]
1174 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1175 disabled it.
1177 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1178 in C2 power state.
1180 libata.dma= [LIBATA] DMA control
1181 libata.dma=0 Disable all PATA and SATA DMA
1182 libata.dma=1 PATA and SATA Disk DMA only
1183 libata.dma=2 ATAPI (CDROM) DMA only
1184 libata.dma=4 Compact Flash DMA only
1185 Combinations also work, so libata.dma=3 enables DMA
1186 for disks and CDROMs, but not CFs.
1188 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1189 libata.ignore_hpa=0 keep BIOS limits (default)
1190 libata.ignore_hpa=1 ignore limits, using full disk
1192 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1193 when set.
1194 Format: <int>
1196 libata.force= [LIBATA] Force configurations. The format is comma
1197 separated list of "[ID:]VAL" where ID is
1198 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1199 matching port, link or device. Basically, it matches
1200 the ATA ID string printed on console by libata. If
1201 the whole ID part is omitted, the last PORT and DEVICE
1202 values are used. If ID hasn't been specified yet, the
1203 configuration applies to all ports, links and devices.
1205 If only DEVICE is omitted, the parameter applies to
1206 the port and all links and devices behind it. DEVICE
1207 number of 0 either selects the first device or the
1208 first fan-out link behind PMP device. It does not
1209 select the host link. DEVICE number of 15 selects the
1210 host link and device attached to it.
1212 The VAL specifies the configuration to force. As long
1213 as there's no ambiguity shortcut notation is allowed.
1214 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1215 The following configurations can be forced.
1217 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1218 Any ID with matching PORT is used.
1220 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1222 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1223 udma[/][16,25,33,44,66,100,133] notation is also
1224 allowed.
1226 * [no]ncq: Turn on or off NCQ.
1228 * nohrst, nosrst, norst: suppress hard, soft
1229 and both resets.
1231 * dump_id: dump IDENTIFY data.
1233 If there are multiple matching configurations changing
1234 the same attribute, the last one is used.
1236 memblock=debug [KNL] Enable memblock debug messages.
1238 load_ramdisk= [RAM] List of ramdisks to load from floppy
1239 See Documentation/blockdev/ramdisk.txt.
1241 lockd.nlm_grace_period=P [NFS] Assign grace period.
1242 Format: <integer>
1244 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1245 Format: <integer>
1247 lockd.nlm_timeout=T [NFS] Assign timeout value.
1248 Format: <integer>
1250 lockd.nlm_udpport=M [NFS] Assign UDP port.
1251 Format: <integer>
1253 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1254 Format: <irq>
1256 loglevel= All Kernel Messages with a loglevel smaller than the
1257 console loglevel will be printed to the console. It can
1258 also be changed with klogd or other programs. The
1259 loglevels are defined as follows:
1261 0 (KERN_EMERG) system is unusable
1262 1 (KERN_ALERT) action must be taken immediately
1263 2 (KERN_CRIT) critical conditions
1264 3 (KERN_ERR) error conditions
1265 4 (KERN_WARNING) warning conditions
1266 5 (KERN_NOTICE) normal but significant condition
1267 6 (KERN_INFO) informational
1268 7 (KERN_DEBUG) debug-level messages
1270 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1271 Format: { n | nk | nM }
1272 n must be a power of two. The default size
1273 is set in the kernel config file.
1275 logo.nologo [FB] Disables display of the built-in Linux logo.
1276 This may be used to provide more screen space for
1277 kernel log messages and is useful when debugging
1278 kernel boot problems.
1280 lp=0 [LP] Specify parallel ports to use, e.g,
1281 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1282 lp=reset first parallel port). 'lp=0' disables the
1283 lp=auto printer driver. 'lp=reset' (which can be
1284 specified in addition to the ports) causes
1285 attached printers to be reset. Using
1286 lp=port1,port2,... specifies the parallel ports
1287 to associate lp devices with, starting with
1288 lp0. A port specification may be 'none' to skip
1289 that lp device, or a parport name such as
1290 'parport0'. Specifying 'lp=auto' instead of a
1291 port specification list means that device IDs
1292 from each port should be examined, to see if
1293 an IEEE 1284-compliant printer is attached; if
1294 so, the driver will manage that printer.
1295 See also header of drivers/char/lp.c.
1297 lpj=n [KNL]
1298 Sets loops_per_jiffy to given constant, thus avoiding
1299 time-consuming boot-time autodetection (up to 250 ms per
1300 CPU). 0 enables autodetection (default). To determine
1301 the correct value for your kernel, boot with normal
1302 autodetection and see what value is printed. Note that
1303 on SMP systems the preset will be applied to all CPUs,
1304 which is likely to cause problems if your CPUs need
1305 significantly divergent settings. An incorrect value
1306 will cause delays in the kernel to be wrong, leading to
1307 unpredictable I/O errors and other breakage. Although
1308 unlikely, in the extreme case this might damage your
1309 hardware.
1311 ltpc= [NET]
1312 Format: <io>,<irq>,<dma>
1314 machvec= [IA64] Force the use of a particular machine-vector
1315 (machvec) in a generic kernel.
1316 Example: machvec=hpzx1_swiotlb
1318 machtype= [Loongson] Share the same kernel image file between different
1319 yeeloong laptop.
1320 Example: machtype=lemote-yeeloong-2f-7inch
1322 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1323 than or equal to this physical address is ignored.
1325 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1326 should make use of. maxcpus=n : n >= 0 limits the
1327 kernel to using 'n' processors. n=0 is a special case,
1328 it is equivalent to "nosmp", which also disables
1329 the IO APIC.
1331 max_loop= [LOOP] Maximum number of loopback devices that can
1332 be mounted
1333 Format: <1-256>
1335 mcatest= [IA-64]
1337 mce [X86-32] Machine Check Exception
1339 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1341 md= [HW] RAID subsystems devices and level
1342 See Documentation/md.txt.
1344 mdacon= [MDA]
1345 Format: <first>,<last>
1346 Specifies range of consoles to be captured by the MDA.
1348 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1349 Amount of memory to be used when the kernel is not able
1350 to see the whole system memory or for test.
1351 [X86-32] Use together with memmap= to avoid physical
1352 address space collisions. Without memmap= PCI devices
1353 could be placed at addresses belonging to unused RAM.
1355 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1356 memory.
1358 memchunk=nn[KMG]
1359 [KNL,SH] Allow user to override the default size for
1360 per-device physically contiguous DMA buffers.
1362 memmap=exactmap [KNL,X86] Enable setting of an exact
1363 E820 memory map, as specified by the user.
1364 Such memmap=exactmap lines can be constructed based on
1365 BIOS output or other requirements. See the memmap=nn@ss
1366 option description.
1368 memmap=nn[KMG]@ss[KMG]
1369 [KNL] Force usage of a specific region of memory
1370 Region of memory to be used, from ss to ss+nn.
1372 memmap=nn[KMG]#ss[KMG]
1373 [KNL,ACPI] Mark specific memory as ACPI data.
1374 Region of memory to be used, from ss to ss+nn.
1376 memmap=nn[KMG]$ss[KMG]
1377 [KNL,ACPI] Mark specific memory as reserved.
1378 Region of memory to be used, from ss to ss+nn.
1379 Example: Exclude memory from 0x18690000-0x1869ffff
1380 memmap=64K$0x18690000
1381 or
1382 memmap=0x10000$0x18690000
1384 memory_corruption_check=0/1 [X86]
1385 Some BIOSes seem to corrupt the first 64k of
1386 memory when doing things like suspend/resume.
1387 Setting this option will scan the memory
1388 looking for corruption. Enabling this will
1389 both detect corruption and prevent the kernel
1390 from using the memory being corrupted.
1391 However, its intended as a diagnostic tool; if
1392 repeatable BIOS-originated corruption always
1393 affects the same memory, you can use memmap=
1394 to prevent the kernel from using that memory.
1396 memory_corruption_check_size=size [X86]
1397 By default it checks for corruption in the low
1398 64k, making this memory unavailable for normal
1399 use. Use this parameter to scan for
1400 corruption in more or less memory.
1402 memory_corruption_check_period=seconds [X86]
1403 By default it checks for corruption every 60
1404 seconds. Use this parameter to check at some
1405 other rate. 0 disables periodic checking.
1407 memtest= [KNL,X86] Enable memtest
1408 Format: <integer>
1409 default : 0 <disable>
1410 Specifies the number of memtest passes to be
1411 performed. Each pass selects another test
1412 pattern from a given set of patterns. Memtest
1413 fills the memory with this pattern, validates
1414 memory contents and reserves bad memory
1415 regions that are detected.
1417 meye.*= [HW] Set MotionEye Camera parameters
1418 See Documentation/video4linux/meye.txt.
1420 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1421 Multi-Function General Purpose Timers on AMD Geode
1422 platforms.
1424 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1425 the BIOS has incorrectly applied a workaround. TinyBIOS
1426 version 0.98 is known to be affected, 0.99 fixes the
1427 problem by letting the user disable the workaround.
1429 mga= [HW,DRM]
1431 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1432 physical address is ignored.
1434 mini2440= [ARM,HW,KNL]
1435 Format:[0..2][b][c][t]
1436 Default: "0tb"
1437 MINI2440 configuration specification:
1438 0 - The attached screen is the 3.5" TFT
1439 1 - The attached screen is the 7" TFT
1440 2 - The VGA Shield is attached (1024x768)
1441 Leaving out the screen size parameter will not load
1442 the TFT driver, and the framebuffer will be left
1443 unconfigured.
1444 b - Enable backlight. The TFT backlight pin will be
1445 linked to the kernel VESA blanking code and a GPIO
1446 LED. This parameter is not necessary when using the
1447 VGA shield.
1448 c - Enable the s3c camera interface.
1449 t - Reserved for enabling touchscreen support. The
1450 touchscreen support is not enabled in the mainstream
1451 kernel as of 2.6.30, a preliminary port can be found
1452 in the "bleeding edge" mini2440 support kernel at
1453 http://repo.or.cz/w/linux-2.6/mini2440.git
1455 mminit_loglevel=
1456 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1457 parameter allows control of the logging verbosity for
1458 the additional memory initialisation checks. A value
1459 of 0 disables mminit logging and a level of 4 will
1460 log everything. Information is printed at KERN_DEBUG
1461 so loglevel=8 may also need to be specified.
1463 mousedev.tap_time=
1464 [MOUSE] Maximum time between finger touching and
1465 leaving touchpad surface for touch to be considered
1466 a tap and be reported as a left button click (for
1467 touchpads working in absolute mode only).
1468 Format: <msecs>
1469 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1470 reporting absolute coordinates, such as tablets
1471 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1472 reporting absolute coordinates, such as tablets
1474 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1475 is similar to kernelcore except it specifies the
1476 amount of memory used for migratable allocations.
1477 If both kernelcore and movablecore is specified,
1478 then kernelcore will be at *least* the specified
1479 value but may be more. If movablecore on its own
1480 is specified, the administrator must be careful
1481 that the amount of memory usable for all allocations
1482 is not too small.
1484 MTD_Partition= [MTD]
1485 Format: <name>,<region-number>,<size>,<offset>
1487 MTD_Region= [MTD] Format:
1488 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1490 mtdparts= [MTD]
1491 See drivers/mtd/cmdlinepart.c.
1493 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1495 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1497 boundary - index of last SLC block on Flex-OneNAND.
1498 The remaining blocks are configured as MLC blocks.
1499 lock - Configure if Flex-OneNAND boundary should be locked.
1500 Once locked, the boundary cannot be changed.
1501 1 indicates lock status, 0 indicates unlock status.
1503 mtdset= [ARM]
1504 ARM/S3C2412 JIVE boot control
1506 See arch/arm/mach-s3c2412/mach-jive.c
1508 mtouchusb.raw_coordinates=
1509 [HW] Make the MicroTouch USB driver use raw coordinates
1510 ('y', default) or cooked coordinates ('n')
1512 mtrr_chunk_size=nn[KMG] [X86]
1513 used for mtrr cleanup. It is largest continuous chunk
1514 that could hold holes aka. UC entries.
1516 mtrr_gran_size=nn[KMG] [X86]
1517 Used for mtrr cleanup. It is granularity of mtrr block.
1518 Default is 1.
1519 Large value could prevent small alignment from
1520 using up MTRRs.
1522 mtrr_spare_reg_nr=n [X86]
1523 Format: <integer>
1524 Range: 0,7 : spare reg number
1525 Default : 1
1526 Used for mtrr cleanup. It is spare mtrr entries number.
1527 Set to 2 or more if your graphical card needs more.
1529 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1531 netdev= [NET] Network devices parameters
1532 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1533 Note that mem_start is often overloaded to mean
1534 something different and driver-specific.
1535 This usage is only documented in each driver source
1536 file if at all.
1538 nf_conntrack.acct=
1539 [NETFILTER] Enable connection tracking flow accounting
1540 0 to disable accounting
1541 1 to enable accounting
1542 Default value is 0.
1544 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1545 See Documentation/filesystems/nfs/nfsroot.txt.
1547 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1548 See Documentation/filesystems/nfs/nfsroot.txt.
1550 nfsrootdebug [NFS] enable nfsroot debugging messages.
1551 See Documentation/filesystems/nfs/nfsroot.txt.
1553 nfs.callback_tcpport=
1554 [NFS] set the TCP port on which the NFSv4 callback
1555 channel should listen.
1557 nfs.cache_getent=
1558 [NFS] sets the pathname to the program which is used
1559 to update the NFS client cache entries.
1561 nfs.cache_getent_timeout=
1562 [NFS] sets the timeout after which an attempt to
1563 update a cache entry is deemed to have failed.
1565 nfs.idmap_cache_timeout=
1566 [NFS] set the maximum lifetime for idmapper cache
1567 entries.
1569 nfs.enable_ino64=
1570 [NFS] enable 64-bit inode numbers.
1571 If zero, the NFS client will fake up a 32-bit inode
1572 number for the readdir() and stat() syscalls instead
1573 of returning the full 64-bit number.
1574 The default is to return 64-bit inode numbers.
1576 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1577 when a NMI is triggered.
1578 Format: [state][,regs][,debounce][,die]
1580 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1581 Format: [panic,][num]
1582 Valid num: 0,1,2
1583 0 - turn nmi_watchdog off
1584 1 - use the IO-APIC timer for the NMI watchdog
1585 2 - use the local APIC for the NMI watchdog using
1586 a performance counter. Note: This will use one
1587 performance counter and the local APIC's performance
1588 vector.
1589 When panic is specified, panic when an NMI watchdog
1590 timeout occurs.
1591 This is useful when you use a panic=... timeout and
1592 need the box quickly up again.
1593 Instead of 1 and 2 it is possible to use the following
1594 symbolic names: lapic and ioapic
1595 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1597 netpoll.carrier_timeout=
1598 [NET] Specifies amount of time (in seconds) that
1599 netpoll should wait for a carrier. By default netpoll
1600 waits 4 seconds.
1602 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1603 emulation library even if a 387 maths coprocessor
1604 is present.
1606 no_console_suspend
1607 [HW] Never suspend the console
1608 Disable suspending of consoles during suspend and
1609 hibernate operations. Once disabled, debugging
1610 messages can reach various consoles while the rest
1611 of the system is being put to sleep (ie, while
1612 debugging driver suspend/resume hooks). This may
1613 not work reliably with all consoles, but is known
1614 to work with serial and VGA consoles.
1616 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1617 caches in the slab allocator. Saves per-node memory,
1618 but will impact performance.
1620 noalign [KNL,ARM]
1622 noapic [SMP,APIC] Tells the kernel to not make use of any
1623 IOAPICs that may be present in the system.
1625 nobats [PPC] Do not use BATs for mapping kernel lowmem
1626 on "Classic" PPC cores.
1628 nocache [ARM]
1630 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1632 nodelayacct [KNL] Disable per-task delay accounting
1634 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1636 nodsp [SH] Disable hardware DSP at boot time.
1638 noefi [X86] Disable EFI runtime services support.
1640 noexec [IA-64]
1642 noexec [X86]
1643 On X86-32 available only on PAE configured kernels.
1644 noexec=on: enable non-executable mappings (default)
1645 noexec=off: disable non-executable mappings
1647 noexec32 [X86-64]
1648 This affects only 32-bit executables.
1649 noexec32=on: enable non-executable mappings (default)
1650 read doesn't imply executable mappings
1651 noexec32=off: disable non-executable mappings
1652 read implies executable mappings
1654 nofpu [SH] Disable hardware FPU at boot time.
1656 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1657 register save and restore. The kernel will only save
1658 legacy floating-point registers on task switch.
1660 noxsave [BUGS=X86] Disables x86 extended register state save
1661 and restore using xsave. The kernel will fallback to
1662 enabling legacy floating-point and sse state.
1664 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1665 wfi(ARM) instruction doesn't work correctly and not to
1666 use it. This is also useful when using JTAG debugger.
1668 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1669 instruction doesn't work correctly and not to
1670 use it.
1672 no_file_caps Tells the kernel not to honor file capabilities. The
1673 only way then for a file to be executed with privilege
1674 is to be setuid root or executed by root.
1676 nohalt [IA-64] Tells the kernel not to use the power saving
1677 function PAL_HALT_LIGHT when idle. This increases
1678 power-consumption. On the positive side, it reduces
1679 interrupt wake-up latency, which may improve performance
1680 in certain environments such as networked servers or
1681 real-time systems.
1683 nohz= [KNL] Boottime enable/disable dynamic ticks
1684 Valid arguments: on, off
1685 Default: on
1687 noiotrap [SH] Disables trapped I/O port accesses.
1689 noirqdebug [X86-32] Disables the code which attempts to detect and
1690 disable unhandled interrupt sources.
1692 no_timer_check [X86,APIC] Disables the code which tests for
1693 broken timer IRQ sources.
1695 noisapnp [ISAPNP] Disables ISA PnP code.
1697 noinitrd [RAM] Tells the kernel not to load any configured
1698 initial RAM disk.
1700 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1701 remapping.
1702 [Deprecated - use intremap=off]
1704 nointroute [IA-64]
1706 nojitter [IA64] Disables jitter checking for ITC timers.
1708 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1710 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1712 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1714 noltlbs [PPC] Do not use large page/tlb entries for kernel
1715 lowmem mapping on PPC40x.
1717 nomca [IA-64] Disable machine check abort handling
1719 nomce [X86-32] Machine Check Exception
1721 nomfgpt [X86-32] Disable Multi-Function General Purpose
1722 Timer usage (for AMD Geode machines).
1724 nopat [X86] Disable PAT (page attribute table extension of
1725 pagetables) support.
1727 norandmaps Don't use address space randomization. Equivalent to
1728 echo 0 > /proc/sys/kernel/randomize_va_space
1730 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1732 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1733 with UP alternatives
1735 noresidual [PPC] Don't use residual data on PReP machines.
1737 noresume [SWSUSP] Disables resume and restores original swap
1738 space.
1740 no-scroll [VGA] Disables scrollback.
1741 This is required for the Braillex ib80-piezo Braille
1742 reader made by F.H. Papenmeier (Germany).
1744 nosbagart [IA-64]
1746 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1748 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1749 and disable the IO APIC. legacy for "maxcpus=0".
1751 nosoftlockup [KNL] Disable the soft-lockup detector.
1753 noswapaccount [KNL] Disable accounting of swap in memory resource
1754 controller. (See Documentation/cgroups/memory.txt)
1756 nosync [HW,M68K] Disables sync negotiation for all devices.
1758 notsc [BUGS=X86-32] Disable Time Stamp Counter
1760 nousb [USB] Disable the USB subsystem
1762 nowatchdog [KNL] Disable the lockup detector.
1764 nowb [ARM]
1766 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1768 nptcg= [IA64] Override max number of concurrent global TLB
1769 purges which is reported from either PAL_VM_SUMMARY or
1770 SAL PALO.
1772 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1773 could support. nr_cpus=n : n >= 1 limits the kernel to
1774 supporting 'n' processors. Later in runtime you can not
1775 use hotplug cpu feature to put more cpu back to online.
1776 just like you compile the kernel NR_CPUS=n
1778 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1780 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1781 one of ['zone', 'node', 'default'] can be specified
1782 This can be set from sysctl after boot.
1783 See Documentation/sysctl/vm.txt for details.
1785 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1786 See Documentation/debugging-via-ohci1394.txt for more
1787 info.
1789 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1790 Rather than timing out after 20 ms if an EC
1791 command is not properly ACKed, override the length
1792 of the timeout. We have interrupts disabled while
1793 waiting for the ACK, so if this is set too high
1794 interrupts *may* be lost!
1796 omap_mux= [OMAP] Override bootloader pin multiplexing.
1797 Format: <mux_mode0.mode_name=value>...
1798 For example, to override I2C bus2:
1799 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1801 oprofile.timer= [HW]
1802 Use timer interrupt instead of performance counters
1804 oprofile.cpu_type= Force an oprofile cpu type
1805 This might be useful if you have an older oprofile
1806 userland or if you want common events.
1807 Format: { arch_perfmon }
1808 arch_perfmon: [X86] Force use of architectural
1809 perfmon on Intel CPUs instead of the
1810 CPU specific event set.
1812 OSS [HW,OSS]
1813 See Documentation/sound/oss/oss-parameters.txt
1815 panic= [KNL] Kernel behaviour on panic
1816 Format: <timeout>
1818 parkbd.port= [HW] Parallel port number the keyboard adapter is
1819 connected to, default is 0.
1820 Format: <parport#>
1821 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1822 0 for XT, 1 for AT (default is AT).
1823 Format: <mode>
1825 parport= [HW,PPT] Specify parallel ports. 0 disables.
1826 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1827 Use 'auto' to force the driver to use any
1828 IRQ/DMA settings detected (the default is to
1829 ignore detected IRQ/DMA settings because of
1830 possible conflicts). You can specify the base
1831 address, IRQ, and DMA settings; IRQ and DMA
1832 should be numbers, or 'auto' (for using detected
1833 settings on that particular port), or 'nofifo'
1834 (to avoid using a FIFO even if it is detected).
1835 Parallel ports are assigned in the order they
1836 are specified on the command line, starting
1837 with parport0.
1839 parport_init_mode= [HW,PPT]
1840 Configure VIA parallel port to operate in
1841 a specific mode. This is necessary on Pegasos
1842 computer where firmware has no options for setting
1843 up parallel port mode and sets it to spp.
1844 Currently this function knows 686a and 8231 chips.
1845 Format: [spp|ps2|epp|ecp|ecpepp]
1847 pause_on_oops=
1848 Halt all CPUs after the first oops has been printed for
1849 the specified number of seconds. This is to be used if
1850 your oopses keep scrolling off the screen.
1852 pcbit= [HW,ISDN]
1854 pcd. [PARIDE]
1855 See header of drivers/block/paride/pcd.c.
1856 See also Documentation/blockdev/paride.txt.
1858 pci=option[,option...] [PCI] various PCI subsystem options:
1859 earlydump [X86] dump PCI config space before the kernel
1860 changes anything
1861 off [X86] don't probe for the PCI bus
1862 bios [X86-32] force use of PCI BIOS, don't access
1863 the hardware directly. Use this if your machine
1864 has a non-standard PCI host bridge.
1865 nobios [X86-32] disallow use of PCI BIOS, only direct
1866 hardware access methods are allowed. Use this
1867 if you experience crashes upon bootup and you
1868 suspect they are caused by the BIOS.
1869 conf1 [X86] Force use of PCI Configuration
1870 Mechanism 1.
1871 conf2 [X86] Force use of PCI Configuration
1872 Mechanism 2.
1873 noaer [PCIE] If the PCIEAER kernel config parameter is
1874 enabled, this kernel boot option can be used to
1875 disable the use of PCIE advanced error reporting.
1876 nodomains [PCI] Disable support for multiple PCI
1877 root domains (aka PCI segments, in ACPI-speak).
1878 nommconf [X86] Disable use of MMCONFIG for PCI
1879 Configuration
1880 check_enable_amd_mmconf [X86] check for and enable
1881 properly configured MMIO access to PCI
1882 config space on AMD family 10h CPU
1883 nomsi [MSI] If the PCI_MSI kernel config parameter is
1884 enabled, this kernel boot option can be used to
1885 disable the use of MSI interrupts system-wide.
1886 noioapicquirk [APIC] Disable all boot interrupt quirks.
1887 Safety option to keep boot IRQs enabled. This
1888 should never be necessary.
1889 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1890 primary IO-APIC for bridges that cannot disable
1891 boot IRQs. This fixes a source of spurious IRQs
1892 when the system masks IRQs.
1893 noioapicreroute [APIC] Disable workaround that uses the
1894 boot IRQ equivalent of an IRQ that connects to
1895 a chipset where boot IRQs cannot be disabled.
1896 The opposite of ioapicreroute.
1897 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1898 routing table. These calls are known to be buggy
1899 on several machines and they hang the machine
1900 when used, but on other computers it's the only
1901 way to get the interrupt routing table. Try
1902 this option if the kernel is unable to allocate
1903 IRQs or discover secondary PCI buses on your
1904 motherboard.
1905 rom [X86] Assign address space to expansion ROMs.
1906 Use with caution as certain devices share
1907 address decoders between ROMs and other
1908 resources.
1909 norom [X86] Do not assign address space to
1910 expansion ROMs that do not already have
1911 BIOS assigned address ranges.
1912 nobar [X86] Do not assign address space to the
1913 BARs that weren't assigned by the BIOS.
1914 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1915 assigned automatically to PCI devices. You can
1916 make the kernel exclude IRQs of your ISA cards
1917 this way.
1918 pirqaddr=0xAAAAA [X86] Specify the physical address
1919 of the PIRQ table (normally generated
1920 by the BIOS) if it is outside the
1921 F0000h-100000h range.
1922 lastbus=N [X86] Scan all buses thru bus #N. Can be
1923 useful if the kernel is unable to find your
1924 secondary buses and you want to tell it
1925 explicitly which ones they are.
1926 assign-busses [X86] Always assign all PCI bus
1927 numbers ourselves, overriding
1928 whatever the firmware may have done.
1929 usepirqmask [X86] Honor the possible IRQ mask stored
1930 in the BIOS $PIR table. This is needed on
1931 some systems with broken BIOSes, notably
1932 some HP Pavilion N5400 and Omnibook XE3
1933 notebooks. This will have no effect if ACPI
1934 IRQ routing is enabled.
1935 noacpi [X86] Do not use ACPI for IRQ routing
1936 or for PCI scanning.
1937 use_crs [X86] Use PCI host bridge window information
1938 from ACPI. On BIOSes from 2008 or later, this
1939 is enabled by default. If you need to use this,
1940 please report a bug.
1941 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1942 If you need to use this, please report a bug.
1943 routeirq Do IRQ routing for all PCI devices.
1944 This is normally done in pci_enable_device(),
1945 so this option is a temporary workaround
1946 for broken drivers that don't call it.
1947 skip_isa_align [X86] do not align io start addr, so can
1948 handle more pci cards
1949 firmware [ARM] Do not re-enumerate the bus but instead
1950 just use the configuration from the
1951 bootloader. This is currently used on
1952 IXP2000 systems where the bus has to be
1953 configured a certain way for adjunct CPUs.
1954 noearly [X86] Don't do any early type 1 scanning.
1955 This might help on some broken boards which
1956 machine check when some devices' config space
1957 is read. But various workarounds are disabled
1958 and some IOMMU drivers will not work.
1959 bfsort Sort PCI devices into breadth-first order.
1960 This sorting is done to get a device
1961 order compatible with older (<= 2.4) kernels.
1962 nobfsort Don't sort PCI devices into breadth-first order.
1963 cbiosize=nn[KMG] The fixed amount of bus space which is
1964 reserved for the CardBus bridge's IO window.
1965 The default value is 256 bytes.
1966 cbmemsize=nn[KMG] The fixed amount of bus space which is
1967 reserved for the CardBus bridge's memory
1968 window. The default value is 64 megabytes.
1969 resource_alignment=
1970 Format:
1971 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1972 Specifies alignment and device to reassign
1973 aligned memory resources.
1974 If <order of align> is not specified,
1975 PAGE_SIZE is used as alignment.
1976 PCI-PCI bridge can be specified, if resource
1977 windows need to be expanded.
1978 ecrc= Enable/disable PCIe ECRC (transaction layer
1979 end-to-end CRC checking).
1980 bios: Use BIOS/firmware settings. This is the
1981 the default.
1982 off: Turn ECRC off
1983 on: Turn ECRC on.
1985 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1986 Management.
1987 off Disable ASPM.
1988 force Enable ASPM even on devices that claim not to support it.
1989 WARNING: Forcing ASPM on may cause system lockups.
1991 pcie_ports= [PCIE] PCIe ports handling:
1992 auto Ask the BIOS whether or not to use native PCIe services
1993 associated with PCIe ports (PME, hot-plug, AER). Use
1994 them only if that is allowed by the BIOS.
1995 native Use native PCIe services associated with PCIe ports
1996 unconditionally.
1997 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1998 ports driver.
2000 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2001 nomsi Do not use MSI for native PCIe PME signaling (this makes
2002 all PCIe root ports use INTx for all services).
2004 pcmv= [HW,PCMCIA] BadgePAD 4
2006 pd. [PARIDE]
2007 See Documentation/blockdev/paride.txt.
2009 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2010 boot time.
2011 Format: { 0 | 1 }
2012 See arch/parisc/kernel/pdc_chassis.c
2014 percpu_alloc= Select which percpu first chunk allocator to use.
2015 Currently supported values are "embed" and "page".
2016 Archs may support subset or none of the selections.
2017 See comments in mm/percpu.c for details on each
2018 allocator. This parameter is primarily for debugging
2019 and performance comparison.
2021 pf. [PARIDE]
2022 See Documentation/blockdev/paride.txt.
2024 pg. [PARIDE]
2025 See Documentation/blockdev/paride.txt.
2027 pirq= [SMP,APIC] Manual mp-table setup
2028 See Documentation/x86/i386/IO-APIC.txt.
2030 plip= [PPT,NET] Parallel port network link
2031 Format: { parport<nr> | timid | 0 }
2032 See also Documentation/parport.txt.
2034 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2035 Override pmtimer IOPort with a hex value.
2036 e.g. pmtmr=0x508
2038 pnp.debug [PNP]
2039 Enable PNP debug messages. This depends on the
2040 CONFIG_PNP_DEBUG_MESSAGES option.
2042 pnpacpi= [ACPI]
2043 { off }
2045 pnpbios= [ISAPNP]
2046 { on | off | curr | res | no-curr | no-res }
2048 pnp_reserve_irq=
2049 [ISAPNP] Exclude IRQs for the autoconfiguration
2051 pnp_reserve_dma=
2052 [ISAPNP] Exclude DMAs for the autoconfiguration
2054 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2055 Ranges are in pairs (I/O port base and size).
2057 pnp_reserve_mem=
2058 [ISAPNP] Exclude memory regions for the
2059 autoconfiguration.
2060 Ranges are in pairs (memory base and size).
2062 ports= [IP_VS_FTP] IPVS ftp helper module
2063 Default is 21.
2064 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2065 may be specified.
2066 Format: <port>,<port>....
2068 print-fatal-signals=
2069 [KNL] debug: print fatal signals
2071 If enabled, warn about various signal handling
2072 related application anomalies: too many signals,
2073 too many POSIX.1 timers, fatal signals causing a
2074 coredump - etc.
2076 If you hit the warning due to signal overflow,
2077 you might want to try "ulimit -i unlimited".
2079 default: off.
2081 printk.time= Show timing data prefixed to each printk message line
2082 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2084 processor.max_cstate= [HW,ACPI]
2085 Limit processor to maximum C-state
2086 max_cstate=9 overrides any DMI blacklist limit.
2088 processor.nocst [HW,ACPI]
2089 Ignore the _CST method to determine C-states,
2090 instead using the legacy FADT method
2092 profile= [KNL] Enable kernel profiling via /proc/profile
2093 Format: [schedule,]<number>
2094 Param: "schedule" - profile schedule points.
2095 Param: <number> - step/bucket size as a power of 2 for
2096 statistical time based profiling.
2097 Param: "sleep" - profile D-state sleeping (millisecs).
2098 Requires CONFIG_SCHEDSTATS
2099 Param: "kvm" - profile VM exits.
2101 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2102 before loading.
2103 See Documentation/blockdev/ramdisk.txt.
2105 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2106 probe for; one of (bare|imps|exps|lifebook|any).
2107 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2108 per second.
2109 psmouse.resetafter= [HW,MOUSE]
2110 Try to reset the device after so many bad packets
2111 (0 = never).
2112 psmouse.resolution=
2113 [HW,MOUSE] Set desired mouse resolution, in dpi.
2114 psmouse.smartscroll=
2115 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2116 0 = disabled, 1 = enabled (default).
2118 pt. [PARIDE]
2119 See Documentation/blockdev/paride.txt.
2121 pty.legacy_count=
2122 [KNL] Number of legacy pty's. Overwrites compiled-in
2123 default number.
2125 quiet [KNL] Disable most log messages
2127 r128= [HW,DRM]
2129 raid= [HW,RAID]
2130 See Documentation/md.txt.
2132 ramdisk_blocksize= [RAM]
2133 See Documentation/blockdev/ramdisk.txt.
2135 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2136 See Documentation/blockdev/ramdisk.txt.
2138 rcupdate.blimit= [KNL,BOOT]
2139 Set maximum number of finished RCU callbacks to process
2140 in one batch.
2142 rcupdate.qhimark= [KNL,BOOT]
2143 Set threshold of queued
2144 RCU callbacks over which batch limiting is disabled.
2146 rcupdate.qlowmark= [KNL,BOOT]
2147 Set threshold of queued RCU callbacks below which
2148 batch limiting is re-enabled.
2150 rdinit= [KNL]
2151 Format: <full_path>
2152 Run specified binary instead of /init from the ramdisk,
2153 used for early userspace startup. See initrd.
2155 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2156 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2157 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2159 relax_domain_level=
2160 [KNL, SMP] Set scheduler's default relax_domain_level.
2161 See Documentation/cgroups/cpusets.txt.
2163 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2165 reservetop= [X86-32]
2166 Format: nn[KMG]
2167 Reserves a hole at the top of the kernel virtual
2168 address space.
2170 reservelow= [X86]
2171 Format: nn[K]
2172 Set the amount of memory to reserve for BIOS at
2173 the bottom of the address space.
2175 reset_devices [KNL] Force drivers to reset the underlying device
2176 during initialization.
2178 resource_alloc_from_bottom
2179 Allocate new resources from the beginning of available
2180 space, not the end. If you need to use this, please
2181 report a bug.
2183 resume= [SWSUSP]
2184 Specify the partition device for software suspend
2186 resume_offset= [SWSUSP]
2187 Specify the offset from the beginning of the partition
2188 given by "resume=" at which the swap header is located,
2189 in <PAGE_SIZE> units (needed only for swap files).
2190 See Documentation/power/swsusp-and-swap-files.txt
2192 hibernate= [HIBERNATION]
2193 noresume Don't check if there's a hibernation image
2194 present during boot.
2195 nocompress Don't compress/decompress hibernation images.
2197 retain_initrd [RAM] Keep initrd memory after extraction
2199 rhash_entries= [KNL,NET]
2200 Set number of hash buckets for route cache
2202 riscom8= [HW,SERIAL]
2203 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2205 ro [KNL] Mount root device read-only on boot
2207 root= [KNL] Root filesystem
2209 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2210 mount the root filesystem
2212 rootflags= [KNL] Set root filesystem mount option string
2214 rootfstype= [KNL] Set root filesystem type
2216 rootwait [KNL] Wait (indefinitely) for root device to show up.
2217 Useful for devices that are detected asynchronously
2218 (e.g. USB and MMC devices).
2220 rw [KNL] Mount root device read-write on boot
2222 S [KNL] Run init in single mode
2224 sa1100ir [NET]
2225 See drivers/net/irda/sa1100_ir.c.
2227 sbni= [NET] Granch SBNI12 leased line adapter
2229 sched_debug [KNL] Enables verbose scheduler debug messages.
2231 security= [SECURITY] Choose a security module to enable at boot.
2232 If this boot parameter is not specified, only the first
2233 security module asking for security registration will be
2234 loaded. An invalid security module name will be treated
2235 as if no module has been chosen.
2237 selinux= [SELINUX] Disable or enable SELinux at boot time.
2238 Format: { "0" | "1" }
2239 See security/selinux/Kconfig help text.
2240 0 -- disable.
2241 1 -- enable.
2242 Default value is set via kernel config option.
2243 If enabled at boot time, /selinux/disable can be used
2244 later to disable prior to initial policy load.
2246 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2247 Format: { "0" | "1" }
2248 See security/apparmor/Kconfig help text
2249 0 -- disable.
2250 1 -- enable.
2251 Default value is set via kernel config option.
2253 serialnumber [BUGS=X86-32]
2255 shapers= [NET]
2256 Maximal number of shapers.
2258 show_msr= [x86] show boot-time MSR settings
2259 Format: { <integer> }
2260 Show boot-time (BIOS-initialized) MSR settings.
2261 The parameter means the number of CPUs to show,
2262 for example 1 means boot CPU only.
2264 simeth= [IA-64]
2265 simscsi=
2267 slram= [HW,MTD]
2269 slub_debug[=options[,slabs]] [MM, SLUB]
2270 Enabling slub_debug allows one to determine the
2271 culprit if slab objects become corrupted. Enabling
2272 slub_debug can create guard zones around objects and
2273 may poison objects when not in use. Also tracks the
2274 last alloc / free. For more information see
2275 Documentation/vm/slub.txt.
2277 slub_max_order= [MM, SLUB]
2278 Determines the maximum allowed order for slabs.
2279 A high setting may cause OOMs due to memory
2280 fragmentation. For more information see
2281 Documentation/vm/slub.txt.
2283 slub_min_objects= [MM, SLUB]
2284 The minimum number of objects per slab. SLUB will
2285 increase the slab order up to slub_max_order to
2286 generate a sufficiently large slab able to contain
2287 the number of objects indicated. The higher the number
2288 of objects the smaller the overhead of tracking slabs
2289 and the less frequently locks need to be acquired.
2290 For more information see Documentation/vm/slub.txt.
2292 slub_min_order= [MM, SLUB]
2293 Determines the mininum page order for slabs. Must be
2294 lower than slub_max_order.
2295 For more information see Documentation/vm/slub.txt.
2297 slub_nomerge [MM, SLUB]
2298 Disable merging of slabs with similar size. May be
2299 necessary if there is some reason to distinguish
2300 allocs to different slabs. Debug options disable
2301 merging on their own.
2302 For more information see Documentation/vm/slub.txt.
2304 smart2= [HW]
2305 Format: <io1>[,<io2>[,...,<io8>]]
2307 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2308 attempt to substitute SMP alternatives once at boot.
2310 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2311 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2312 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2313 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2314 smsc-ircc2.ircc_irq= [HW] IRQ line
2315 smsc-ircc2.ircc_dma= [HW] DMA channel
2316 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2317 0: Toshiba Satellite 1800 (GP data pin select)
2318 1: Fast pin select (default)
2319 2: ATC IRMode
2321 softlockup_panic=
2322 [KNL] Should the soft-lockup detector generate panics.
2324 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2325 See Documentation/sonypi.txt
2327 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2328 See Documentation/serial/specialix.txt.
2330 spia_io_base= [HW,MTD]
2331 spia_fio_base=
2332 spia_pedr=
2333 spia_peddr=
2335 stacktrace [FTRACE]
2336 Enabled the stack tracer on boot up.
2338 sti= [PARISC,HW]
2339 Format: <num>
2340 Set the STI (builtin display/keyboard on the HP-PARISC
2341 machines) console (graphic card) which should be used
2342 as the initial boot-console.
2343 See also comment in drivers/video/console/sticore.c.
2345 sti_font= [HW]
2346 See comment in drivers/video/console/sticore.c.
2348 stifb= [HW]
2349 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2351 sunrpc.min_resvport=
2352 sunrpc.max_resvport=
2353 [NFS,SUNRPC]
2354 SunRPC servers often require that client requests
2355 originate from a privileged port (i.e. a port in the
2356 range 0 < portnr < 1024).
2357 An administrator who wishes to reserve some of these
2358 ports for other uses may adjust the range that the
2359 kernel's sunrpc client considers to be privileged
2360 using these two parameters to set the minimum and
2361 maximum port values.
2363 sunrpc.pool_mode=
2364 [NFS]
2365 Control how the NFS server code allocates CPUs to
2366 service thread pools. Depending on how many NICs
2367 you have and where their interrupts are bound, this
2368 option will affect which CPUs will do NFS serving.
2369 Note: this parameter cannot be changed while the
2370 NFS server is running.
2372 auto the server chooses an appropriate mode
2373 automatically using heuristics
2374 global a single global pool contains all CPUs
2375 percpu one pool for each CPU
2376 pernode one pool for each NUMA node (equivalent
2377 to global on non-NUMA machines)
2379 sunrpc.tcp_slot_table_entries=
2380 sunrpc.udp_slot_table_entries=
2381 [NFS,SUNRPC]
2382 Sets the upper limit on the number of simultaneous
2383 RPC calls that can be sent from the client to a
2384 server. Increasing these values may allow you to
2385 improve throughput, but will also increase the
2386 amount of memory reserved for use by the client.
2388 swapaccount[=0|1]
2389 [KNL] Enable accounting of swap in memory resource
2390 controller if no parameter or 1 is given or disable
2391 it if 0 is given (See Documentation/cgroups/memory.txt)
2393 swiotlb= [IA-64] Number of I/O TLB slabs
2395 switches= [HW,M68k]
2397 sysfs.deprecated=0|1 [KNL]
2398 Enable/disable old style sysfs layout for old udev
2399 on older distributions. When this option is enabled
2400 very new udev will not work anymore. When this option
2401 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2402 in older udev will not work anymore.
2403 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2404 the kernel configuration.
2406 sysrq_always_enabled
2407 [KNL]
2408 Ignore sysrq setting - this boot parameter will
2409 neutralize any effect of /proc/sys/kernel/sysrq.
2410 Useful for debugging.
2412 tdfx= [HW,DRM]
2414 test_suspend= [SUSPEND]
2415 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2416 standby suspend) as the system sleep state to briefly
2417 enter during system startup. The system is woken from
2418 this state using a wakeup-capable RTC alarm.
2420 thash_entries= [KNL,NET]
2421 Set number of hash buckets for TCP connection
2423 thermal.act= [HW,ACPI]
2424 -1: disable all active trip points in all thermal zones
2425 <degrees C>: override all lowest active trip points
2427 thermal.crt= [HW,ACPI]
2428 -1: disable all critical trip points in all thermal zones
2429 <degrees C>: override all critical trip points
2431 thermal.nocrt= [HW,ACPI]
2432 Set to disable actions on ACPI thermal zone
2433 critical and hot trip points.
2435 thermal.off= [HW,ACPI]
2436 1: disable ACPI thermal control
2438 thermal.psv= [HW,ACPI]
2439 -1: disable all passive trip points
2440 <degrees C>: override all passive trip points to this
2441 value
2443 thermal.tzp= [HW,ACPI]
2444 Specify global default ACPI thermal zone polling rate
2445 <deci-seconds>: poll all this frequency
2446 0: no polling (default)
2448 topology= [S390]
2449 Format: {off | on}
2450 Specify if the kernel should make use of the cpu
2451 topology informations if the hardware supports these.
2452 The scheduler will make use of these informations and
2453 e.g. base its process migration decisions on it.
2454 Default is on.
2456 tp720= [HW,PS2]
2458 tpm_suspend_pcr=[HW,TPM]
2459 Format: integer pcr id
2460 Specify that at suspend time, the tpm driver
2461 should extend the specified pcr with zeros,
2462 as a workaround for some chips which fail to
2463 flush the last written pcr on TPM_SaveState.
2464 This will guarantee that all the other pcrs
2465 are saved.
2467 trace_buf_size=nn[KMG]
2468 [FTRACE] will set tracing buffer size.
2470 trace_event=[event-list]
2471 [FTRACE] Set and start specified trace events in order
2472 to facilitate early boot debugging.
2473 See also Documentation/trace/events.txt
2475 tsc= Disable clocksource-must-verify flag for TSC.
2476 Format: <string>
2477 [x86] reliable: mark tsc clocksource as reliable, this
2478 disables clocksource verification at runtime.
2479 Used to enable high-resolution timer mode on older
2480 hardware, and in virtualized environment.
2481 [x86] noirqtime: Do not use TSC to do irq accounting.
2482 Used to run time disable IRQ_TIME_ACCOUNTING on any
2483 platforms where RDTSC is slow and this accounting
2484 can add overhead.
2486 turbografx.map[2|3]= [HW,JOY]
2487 TurboGraFX parallel port interface
2488 Format:
2489 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2490 See also Documentation/input/joystick-parport.txt
2492 uhash_entries= [KNL,NET]
2493 Set number of hash buckets for UDP/UDP-Lite connections
2495 uhci-hcd.ignore_oc=
2496 [USB] Ignore overcurrent events (default N).
2497 Some badly-designed motherboards generate lots of
2498 bogus events, for ports that aren't wired to
2499 anything. Set this parameter to avoid log spamming.
2500 Note that genuine overcurrent events won't be
2501 reported either.
2503 unknown_nmi_panic
2504 [X86]
2505 Set unknown_nmi_panic=1 early on boot.
2507 usbcore.autosuspend=
2508 [USB] The autosuspend time delay (in seconds) used
2509 for newly-detected USB devices (default 2). This
2510 is the time required before an idle device will be
2511 autosuspended. Devices for which the delay is set
2512 to a negative value won't be autosuspended at all.
2514 usbcore.usbfs_snoop=
2515 [USB] Set to log all usbfs traffic (default 0 = off).
2517 usbcore.blinkenlights=
2518 [USB] Set to cycle leds on hubs (default 0 = off).
2520 usbcore.old_scheme_first=
2521 [USB] Start with the old device initialization
2522 scheme (default 0 = off).
2524 usbcore.use_both_schemes=
2525 [USB] Try the other device initialization scheme
2526 if the first one fails (default 1 = enabled).
2528 usbcore.initial_descriptor_timeout=
2529 [USB] Specifies timeout for the initial 64-byte
2530 USB_REQ_GET_DESCRIPTOR request in milliseconds
2531 (default 5000 = 5.0 seconds).
2533 usbhid.mousepoll=
2534 [USBHID] The interval which mice are to be polled at.
2536 usb-storage.delay_use=
2537 [UMS] The delay in seconds before a new device is
2538 scanned for Logical Units (default 5).
2540 usb-storage.quirks=
2541 [UMS] A list of quirks entries to supplement or
2542 override the built-in unusual_devs list. List
2543 entries are separated by commas. Each entry has
2544 the form VID:PID:Flags where VID and PID are Vendor
2545 and Product ID values (4-digit hex numbers) and
2546 Flags is a set of characters, each corresponding
2547 to a common usb-storage quirk flag as follows:
2548 a = SANE_SENSE (collect more than 18 bytes
2549 of sense data);
2550 b = BAD_SENSE (don't collect more than 18
2551 bytes of sense data);
2552 c = FIX_CAPACITY (decrease the reported
2553 device capacity by one sector);
2554 h = CAPACITY_HEURISTICS (decrease the
2555 reported device capacity by one
2556 sector if the number is odd);
2557 i = IGNORE_DEVICE (don't bind to this
2558 device);
2559 l = NOT_LOCKABLE (don't try to lock and
2560 unlock ejectable media);
2561 m = MAX_SECTORS_64 (don't transfer more
2562 than 64 sectors = 32 KB at a time);
2563 o = CAPACITY_OK (accept the capacity
2564 reported by the device);
2565 r = IGNORE_RESIDUE (the device reports
2566 bogus residue values);
2567 s = SINGLE_LUN (the device has only one
2568 Logical Unit);
2569 w = NO_WP_DETECT (don't test whether the
2570 medium is write-protected).
2571 Example: quirks=0419:aaf5:rl,0421:0433:rc
2573 userpte=
2574 [X86] Flags controlling user PTE allocations.
2576 nohigh = do not allocate PTE pages in
2577 HIGHMEM regardless of setting
2578 of CONFIG_HIGHPTE.
2580 vdso= [X86,SH]
2581 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2582 vdso=1: enable VDSO (default)
2583 vdso=0: disable VDSO mapping
2585 vdso32= [X86]
2586 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2587 vdso32=1: enable 32-bit VDSO (default)
2588 vdso32=0: disable 32-bit VDSO mapping
2590 vector= [IA-64,SMP]
2591 vector=percpu: enable percpu vector domain
2593 video= [FB] Frame buffer configuration
2594 See Documentation/fb/modedb.txt.
2596 vga= [BOOT,X86-32] Select a particular video mode
2597 See Documentation/x86/boot.txt and
2598 Documentation/svga.txt.
2599 Use vga=ask for menu.
2600 This is actually a boot loader parameter; the value is
2601 passed to the kernel using a special protocol.
2603 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2604 size of <nn>. This can be used to increase the
2605 minimum size (128MB on x86). It can also be used to
2606 decrease the size and leave more room for directly
2607 mapped kernel RAM.
2609 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2610 Format: <command>
2612 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2613 Format: <command>
2615 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2616 Format: <command>
2618 vt.cur_default= [VT] Default cursor shape.
2619 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2620 the parameters of the <Esc>[?A;B;Cc escape sequence;
2621 see VGA-softcursor.txt. Default: 2 = underline.
2623 vt.default_blu= [VT]
2624 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2625 Change the default blue palette of the console.
2626 This is a 16-member array composed of values
2627 ranging from 0-255.
2629 vt.default_grn= [VT]
2630 Format: <green0>,<green1>,<green2>,...,<green15>
2631 Change the default green palette of the console.
2632 This is a 16-member array composed of values
2633 ranging from 0-255.
2635 vt.default_red= [VT]
2636 Format: <red0>,<red1>,<red2>,...,<red15>
2637 Change the default red palette of the console.
2638 This is a 16-member array composed of values
2639 ranging from 0-255.
2641 vt.default_utf8=
2642 [VT]
2643 Format=<0|1>
2644 Set system-wide default UTF-8 mode for all tty's.
2645 Default is 1, i.e. UTF-8 mode is enabled for all
2646 newly opened terminals.
2648 vt.global_cursor_default=
2649 [VT]
2650 Format=<-1|0|1>
2651 Set system-wide default for whether a cursor
2652 is shown on new VTs. Default is -1,
2653 i.e. cursors will be created by default unless
2654 overridden by individual drivers. 0 will hide
2655 cursors, 1 will display them.
2657 watchdog timers [HW,WDT] For information on watchdog timers,
2658 see Documentation/watchdog/watchdog-parameters.txt
2659 or other driver-specific files in the
2660 Documentation/watchdog/ directory.
2662 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2663 default x2apic cluster mode on platforms
2664 supporting x2apic.
2666 x86_mrst_timer= [X86-32,APBT]
2667 Choose timer option for x86 Moorestown MID platform.
2668 Two valid options are apbt timer only and lapic timer
2669 plus one apbt timer for broadcast timer.
2670 x86_mrst_timer=apbt_only | lapic_and_apbt
2672 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2673 xd_geo= See header of drivers/block/xd.c.
2675 xen_emul_unplug= [HW,X86,XEN]
2676 Unplug Xen emulated devices
2677 Format: [unplug0,][unplug1]
2678 ide-disks -- unplug primary master IDE devices
2679 aux-ide-disks -- unplug non-primary-master IDE devices
2680 nics -- unplug network devices
2681 all -- unplug all emulated devices (NICs and IDE disks)
2682 unnecessary -- unplugging emulated devices is
2683 unnecessary even if the host did not respond to
2684 the unplug protocol
2685 never -- do not unplug even if version check succeeds
2687 xirc2ps_cs= [NET,PCMCIA]
2688 Format:
2689 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2691 ______________________________________________________________________
2693 TODO:
2695 Add more DRM drivers.