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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Finally, the [KMG] suffix is commonly described after a number of kernel
148 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150 bytes respectively. Such letter suffixes can also be entirely omitted.
153 acpi= [HW,ACPI,X86]
154 Advanced Configuration and Power Interface
155 Format: { force | off | strict | noirq | rsdt }
156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
159 strict -- Be less tolerant of platforms that are not
160 strictly ACPI specification compliant.
161 rsdt -- prefer RSDT over (default) XSDT
162 copy_dsdt -- copy DSDT to memory
164 See also Documentation/power/pm.txt, pci=noacpi
166 acpi_apic_instance= [ACPI, IOAPIC]
167 Format: <int>
168 2: use 2nd APIC table, if available
169 1,0: use 1st APIC table
170 default: 0
172 acpi_backlight= [HW,ACPI]
173 acpi_backlight=vendor
174 acpi_backlight=video
175 If set to vendor, prefer vendor specific driver
176 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
177 of the ACPI video.ko driver.
179 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
180 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
181 Format: <int>
182 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
183 debug output. Bits in debug_layer correspond to a
184 _COMPONENT in an ACPI source file, e.g.,
185 #define _COMPONENT ACPI_PCI_COMPONENT
186 Bits in debug_level correspond to a level in
187 ACPI_DEBUG_PRINT statements, e.g.,
188 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
189 The debug_level mask defaults to "info". See
190 Documentation/acpi/debug.txt for more information about
191 debug layers and levels.
193 Enable processor driver info messages:
194 acpi.debug_layer=0x20000000
195 Enable PCI/PCI interrupt routing info messages:
196 acpi.debug_layer=0x400000
197 Enable AML "Debug" output, i.e., stores to the Debug
198 object while interpreting AML:
199 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
200 Enable all messages related to ACPI hardware:
201 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
203 Some values produce so much output that the system is
204 unusable. The "log_buf_len" parameter may be useful
205 if you need to capture more output.
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 bulk_remove=off [PPC] This parameter disables the use of the pSeries
407 firmware feature for flushing multiple hpte entries
408 at a time.
410 c101= [NET] Moxa C101 synchronous serial card
412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
419 capability.disable=
420 [SECURITY] Disable capabilities. This would normally
421 be used only if an alternative security model is to be
422 configured. Potentially dangerous and should only be
423 used if you are entirely sure of the consequences.
425 ccw_timeout_log [S390]
426 See Documentation/s390/CommonIO for details.
428 cgroup_disable= [KNL] Disable a particular controller
429 Format: {name of the controller(s) to disable}
430 {Currently supported controllers - "memory"}
432 checkreqprot [SELINUX] Set initial checkreqprot flag value.
433 Format: { "0" | "1" }
434 See security/selinux/Kconfig help text.
435 0 -- check protection applied by kernel (includes
436 any implied execute protection).
437 1 -- check protection requested by application.
438 Default value is set via a kernel config option.
439 Value can be changed at runtime via
440 /selinux/checkreqprot.
442 cio_ignore= [S390]
443 See Documentation/s390/CommonIO for details.
445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
446 [Deprecated]
447 Forces specified clocksource (if available) to be used
448 when calculating gettimeofday(). If specified
449 clocksource is not available, it defaults to PIT.
450 Format: { pit | tsc | cyclone | pmtmr }
452 clocksource= Override the default clocksource
453 Format: <string>
454 Override the default clocksource and use the clocksource
455 with the name specified.
456 Some clocksource names to choose from, depending on
457 the platform:
458 [all] jiffies (this is the base, fallback clocksource)
459 [ACPI] acpi_pm
460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461 pxa_timer,timer3,32k_counter,timer0_1
462 [AVR32] avr32
463 [X86-32] pit,hpet,tsc;
464 scx200_hrt on Geode; cyclone on IBM x440
465 [MIPS] MIPS
466 [PARISC] cr16
467 [S390] tod
468 [SH] SuperH
469 [SPARC64] tick
470 [X86-64] hpet,tsc
472 clearcpuid=BITNUM [X86]
473 Disable CPUID feature X for the kernel. See
474 arch/x86/include/asm/cpufeature.h for the valid bit
475 numbers. Note the Linux specific bits are not necessarily
476 stable over kernel options, but the vendor specific
477 ones should be.
478 Also note that user programs calling CPUID directly
479 or using the feature without checking anything
480 will still see it. This just prevents it from
481 being used by the kernel or shown in /proc/cpuinfo.
482 Also note the kernel might malfunction if you disable
483 some critical bits.
485 cmo_free_hint= [PPC] Format: { yes | no }
486 Specify whether pages are marked as being inactive
487 when they are freed. This is used in CMO environments
488 to determine OS memory pressure for page stealing by
489 a hypervisor.
490 Default: yes
492 code_bytes [X86] How many bytes of object code to print
493 in an oops report.
494 Range: 0 - 8192
495 Default: 64
497 com20020= [HW,NET] ARCnet - COM20020 chipset
498 Format:
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
502 Format: <io>[,<irq>]
504 com90xx= [HW,NET]
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
509 conmode=
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
515 ttyS<n>[,options]
516 ttyUSB0[,options]
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
524 information. See
525 Documentation/networking/netconsole.txt for an
526 alternative.
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
537 console=brl,ttyS0
538 For now, only VisioBraille is supported.
540 consoleblank= [KNL] The console blank (screen saver) timeout in
541 seconds. Defaults to 10*60 = 10mins. A value of 0
542 disables the blank timer.
544 coredump_filter=
545 [KNL] Change the default value for
546 /proc/<pid>/coredump_filter.
547 See also Documentation/filesystems/proc.txt.
549 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
550 Format:
551 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
553 crashkernel=size[KMG][@offset[KMG]]
554 [KNL] Using kexec, Linux can switch to a 'crash kernel'
555 upon panic. This parameter reserves the physical
556 memory region [offset, offset + size] for that kernel
557 image. If '@offset' is omitted, then a suitable offset
558 is selected automatically. Check
559 Documentation/kdump/kdump.txt for further details.
561 crashkernel=range1:size1[,range2:size2,...][@offset]
562 [KNL] Same as above, but depends on the memory
563 in the running system. The syntax of range is
564 start-[end] where start and end are both
565 a memory unit (amount[KMG]). See also
566 Documentation/kdump/kdump.txt for an example.
568 cs89x0_dma= [HW,NET]
569 Format: <dma>
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
574 dasd= [HW,NET]
575 See header of drivers/s390/block/dasd_devmap.c.
577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578 (one device per port)
579 Format: <port#>,<type>
580 See also Documentation/input/joystick-parport.txt
582 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
583 time. See Documentation/dynamic-debug-howto.txt for
584 details.
586 debug [KNL] Enable kernel debugging (events log level).
588 debug_locks_verbose=
589 [KNL] verbose self-tests
590 Format=<0|1>
591 Print debugging info while doing the locking API
592 self-tests.
593 We default to 0 (no extra messages), setting it to
594 1 will print _a lot_ more information - normally
595 only useful to kernel developers.
597 debug_objects [KNL] Enable object debugging
599 no_debug_objects
600 [KNL] Disable object debugging
602 debugpat [X86] Enable PAT debugging
604 decnet.addr= [HW,NET]
605 Format: <area>[,<node>]
606 See also Documentation/networking/decnet.txt.
608 default_hugepagesz=
609 [same as hugepagesz=] The size of the default
610 HugeTLB page size. This is the size represented by
611 the legacy /proc/ hugepages APIs, used for SHM, and
612 default size when mounting hugetlbfs filesystems.
613 Defaults to the default architecture's huge page size
614 if not specified.
616 dhash_entries= [KNL]
617 Set number of hash buckets for dentry cache.
619 digi= [HW,SERIAL]
620 IO parameters + enable/disable command.
622 digiepca= [HW,SERIAL]
623 See drivers/char/README.epca and
624 Documentation/serial/digiepca.txt.
626 disable= [IPV6]
627 See Documentation/networking/ipv6.txt.
629 disable_ipv6= [IPV6]
630 See Documentation/networking/ipv6.txt.
632 disable_mtrr_cleanup [X86]
633 The kernel tries to adjust MTRR layout from continuous
634 to discrete, to make X server driver able to add WB
635 entry later. This parameter disables that.
637 disable_mtrr_trim [X86, Intel and AMD only]
638 By default the kernel will trim any uncacheable
639 memory out of your available memory pool based on
640 MTRR settings. This parameter disables that behavior,
641 possibly causing your machine to run very slowly.
643 disable_timer_pin_1 [X86]
644 Disable PIN 1 of APIC timer
645 Can be useful to work around chipset bugs.
647 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
648 this option disables the debugging code at boot.
650 dma_debug_entries=<number>
651 This option allows to tune the number of preallocated
652 entries for DMA-API debugging code. One entry is
653 required per DMA-API allocation. Use this if the
654 DMA-API debugging code disables itself because the
655 architectural default is too low.
657 dma_debug_driver=<driver_name>
658 With this option the DMA-API debugging driver
659 filter feature can be enabled at boot time. Just
660 pass the driver to filter for as the parameter.
661 The filter can be disabled or changed to another
662 driver later using sysfs.
664 dscc4.setup= [NET]
666 earlycon= [KNL] Output early console device and options.
667 uart[8250],io,<addr>[,options]
668 uart[8250],mmio,<addr>[,options]
669 uart[8250],mmio32,<addr>[,options]
670 Start an early, polled-mode console on the 8250/16550
671 UART at the specified I/O port or MMIO address.
672 MMIO inter-register address stride is either 8bit (mmio)
673 or 32bit (mmio32).
674 The options are the same as for ttyS, above.
676 earlyprintk= [X86,SH,BLACKFIN]
677 earlyprintk=vga
678 earlyprintk=serial[,ttySn[,baudrate]]
679 earlyprintk=ttySn[,baudrate]
680 earlyprintk=dbgp[debugController#]
682 Append ",keep" to not disable it when the real console
683 takes over.
685 Only vga or serial or usb debug port at a time.
687 Currently only ttyS0 and ttyS1 are supported.
689 Interaction with the standard serial driver is not
690 very good.
692 The VGA output is eventually overwritten by the real
693 console.
695 ekgdboc= [X86,KGDB] Allow early kernel console debugging
696 ekgdboc=kbd
698 This is desgined to be used in conjunction with
699 the boot argument: earlyprintk=vga
701 edd= [EDD]
702 Format: {"off" | "on" | "skip[mbr]"}
704 eisa_irq_edge= [PARISC,HW]
705 See header of drivers/parisc/eisa.c.
707 elanfreq= [X86-32]
708 See comment before function elanfreq_setup() in
709 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
711 elevator= [IOSCHED]
712 Format: {"cfq" | "deadline" | "noop"}
713 See Documentation/block/as-iosched.txt and
714 Documentation/block/deadline-iosched.txt for details.
716 elfcorehdr= [IA64,PPC,SH,X86]
717 Specifies physical address of start of kernel core
718 image elf header. Generally kexec loader will
719 pass this option to capture kernel.
720 See Documentation/kdump/kdump.txt for details.
722 enable_mtrr_cleanup [X86]
723 The kernel tries to adjust MTRR layout from continuous
724 to discrete, to make X server driver able to add WB
725 entry later. This parameter enables that.
727 enable_timer_pin_1 [X86]
728 Enable PIN 1 of APIC timer
729 Can be useful to work around chipset bugs
730 (in particular on some ATI chipsets).
731 The kernel tries to set a reasonable default.
733 enforcing [SELINUX] Set initial enforcing status.
734 Format: {"0" | "1"}
735 See security/selinux/Kconfig help text.
736 0 -- permissive (log only, no denials).
737 1 -- enforcing (deny and log).
738 Default value is 0.
739 Value can be changed at runtime via /selinux/enforce.
741 erst_disable [ACPI]
742 Disable Error Record Serialization Table (ERST)
743 support.
745 ether= [HW,NET] Ethernet cards parameters
746 This option is obsoleted by the "netdev=" option, which
747 has equivalent usage. See its documentation for details.
749 failslab=
750 fail_page_alloc=
751 fail_make_request=[KNL]
752 General fault injection mechanism.
753 Format: <interval>,<probability>,<space>,<times>
754 See also /Documentation/fault-injection/.
756 floppy= [HW]
757 See Documentation/blockdev/floppy.txt.
759 force_pal_cache_flush
760 [IA-64] Avoid check_sal_cache_flush which may hang on
761 buggy SAL_CACHE_FLUSH implementations. Using this
762 parameter will force ia64_sal_cache_flush to call
763 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
765 ftrace=[tracer]
766 [FTRACE] will set and start the specified tracer
767 as early as possible in order to facilitate early
768 boot debugging.
770 ftrace_dump_on_oops[=orig_cpu]
771 [FTRACE] will dump the trace buffers on oops.
772 If no parameter is passed, ftrace will dump
773 buffers of all CPUs, but if you pass orig_cpu, it will
774 dump only the buffer of the CPU that triggered the
775 oops.
777 ftrace_filter=[function-list]
778 [FTRACE] Limit the functions traced by the function
779 tracer at boot up. function-list is a comma separated
780 list of functions. This list can be changed at run
781 time by the set_ftrace_filter file in the debugfs
782 tracing directory.
784 ftrace_notrace=[function-list]
785 [FTRACE] Do not trace the functions specified in
786 function-list. This list can be changed at run time
787 by the set_ftrace_notrace file in the debugfs
788 tracing directory.
790 ftrace_graph_filter=[function-list]
791 [FTRACE] Limit the top level callers functions traced
792 by the function graph tracer at boot up.
793 function-list is a comma separated list of functions
794 that can be changed at run time by the
795 set_graph_function file in the debugfs tracing directory.
797 gamecon.map[2|3]=
798 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
799 support via parallel port (up to 5 devices per port)
800 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
801 See also Documentation/input/joystick-parport.txt
803 gamma= [HW,DRM]
805 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
806 Format: off | on
807 default: on
809 gcov_persist= [GCOV] When non-zero (default), profiling data for
810 kernel modules is saved and remains accessible via
811 debugfs, even when the module is unloaded/reloaded.
812 When zero, profiling data is discarded and associated
813 debugfs files are removed at module unload time.
815 gpt [EFI] Forces disk with valid GPT signature but
816 invalid Protective MBR to be treated as GPT.
818 hashdist= [KNL,NUMA] Large hashes allocated during boot
819 are distributed across NUMA nodes. Defaults on
820 for 64bit NUMA, off otherwise.
821 Format: 0 | 1 (for off | on)
823 hcl= [IA-64] SGI's Hardware Graph compatibility layer
825 hd= [EIDE] (E)IDE hard drive subsystem geometry
826 Format: <cyl>,<head>,<sect>
828 hest_disable [ACPI]
829 Disable Hardware Error Source Table (HEST) support;
830 corresponding firmware-first mode error processing
831 logic will be disabled.
833 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
834 size of <nn>. This works even on boxes that have no
835 highmem otherwise. This also works to reduce highmem
836 size on bigger boxes.
838 highres= [KNL] Enable/disable high resolution timer mode.
839 Valid parameters: "on", "off"
840 Default: "on"
842 hisax= [HW,ISDN]
843 See Documentation/isdn/README.HiSax.
845 hlt [BUGS=ARM,SH]
847 hpet= [X86-32,HPET] option to control HPET usage
848 Format: { enable (default) | disable | force |
849 verbose }
850 disable: disable HPET and use PIT instead
851 force: allow force enabled of undocumented chips (ICH4,
852 VIA, nVidia)
853 verbose: show contents of HPET registers during setup
855 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
856 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
857 On x86-64 and powerpc, this option can be specified
858 multiple times interleaved with hugepages= to reserve
859 huge pages of different sizes. Valid pages sizes on
860 x86-64 are 2M (when the CPU supports "pse") and 1G
861 (when the CPU supports the "pdpe1gb" cpuinfo flag)
862 Note that 1GB pages can only be allocated at boot time
863 using hugepages= and not freed afterwards.
865 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
866 terminal devices. Valid values: 0..8
867 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
868 If specified, z/VM IUCV HVC accepts connections
869 from listed z/VM user IDs only.
871 i2c_bus= [HW] Override the default board specific I2C bus speed
872 or register an additional I2C bus that is not
873 registered from board initialization code.
874 Format:
875 <bus_id>,<clkrate>
877 i8042.debug [HW] Toggle i8042 debug mode
878 i8042.direct [HW] Put keyboard port into non-translated mode
879 i8042.dumbkbd [HW] Pretend that controller can only read data from
880 keyboard and cannot control its state
881 (Don't attempt to blink the leds)
882 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
883 i8042.nokbd [HW] Don't check/create keyboard port
884 i8042.noloop [HW] Disable the AUX Loopback command while probing
885 for the AUX port
886 i8042.nomux [HW] Don't check presence of an active multiplexing
887 controller
888 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
889 controllers
890 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
891 i8042.reset [HW] Reset the controller during init and cleanup
892 i8042.unlock [HW] Unlock (ignore) the keylock
894 i810= [HW,DRM]
896 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
897 indicates that the driver is running on unsupported
898 hardware.
899 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
900 does not match list of supported models.
901 i8k.power_status
902 [HW] Report power status in /proc/i8k
903 (disabled by default)
904 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
905 capability is set.
907 icn= [HW,ISDN]
908 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
910 ide-core.nodma= [HW] (E)IDE subsystem
911 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
912 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
913 .cdrom .chs .ignore_cable are additional options
914 See Documentation/ide/ide.txt.
916 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
917 Claim all unknown PCI IDE storage controllers.
919 idle= [X86]
920 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
921 Poll forces a polling idle loop that can slightly
922 improve the performance of waking up a idle CPU, but
923 will use a lot of power and make the system run hot.
924 Not recommended.
925 idle=mwait: On systems which support MONITOR/MWAIT but
926 the kernel chose to not use it because it doesn't save
927 as much power as a normal idle loop, use the
928 MONITOR/MWAIT idle loop anyways. Performance should be
929 the same as idle=poll.
930 idle=halt: Halt is forced to be used for CPU idle.
931 In such case C2/C3 won't be used again.
932 idle=nomwait: Disable mwait for CPU C-states
934 ignore_loglevel [KNL]
935 Ignore loglevel setting - this will print /all/
936 kernel messages to the console. Useful for debugging.
938 ihash_entries= [KNL]
939 Set number of hash buckets for inode cache.
941 ima_audit= [IMA]
942 Format: { "0" | "1" }
943 0 -- integrity auditing messages. (Default)
944 1 -- enable informational integrity auditing messages.
946 ima_hash= [IMA]
947 Format: { "sha1" | "md5" }
948 default: "sha1"
950 ima_tcb [IMA]
951 Load a policy which meets the needs of the Trusted
952 Computing Base. This means IMA will measure all
953 programs exec'd, files mmap'd for exec, and all files
954 opened for read by uid=0.
956 init= [KNL]
957 Format: <full_path>
958 Run specified binary instead of /sbin/init as init
959 process.
961 initcall_debug [KNL] Trace initcalls as they are executed. Useful
962 for working out where the kernel is dying during
963 startup.
965 initrd= [BOOT] Specify the location of the initial ramdisk
967 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
968 Format: <irq>
970 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
971 on
972 Enable intel iommu driver.
973 off
974 Disable intel iommu driver.
975 igfx_off [Default Off]
976 By default, gfx is mapped as normal device. If a gfx
977 device has a dedicated DMAR unit, the DMAR unit is
978 bypassed by not enabling DMAR with this option. In
979 this case, gfx device will use physical address for
980 DMA.
981 forcedac [x86_64]
982 With this option iommu will not optimize to look
983 for io virtual address below 32 bit forcing dual
984 address cycle on pci bus for cards supporting greater
985 than 32 bit addressing. The default is to look
986 for translation below 32 bit and if not available
987 then look in the higher range.
988 strict [Default Off]
989 With this option on every unmap_single operation will
990 result in a hardware IOTLB flush operation as opposed
991 to batching them for performance.
993 intremap= [X86-64, Intel-IOMMU]
994 Format: { on (default) | off | nosid }
995 on enable Interrupt Remapping (default)
996 off disable Interrupt Remapping
997 nosid disable Source ID checking
999 inttest= [IA64]
1001 iomem= Disable strict checking of access to MMIO memory
1002 strict regions from userspace.
1003 relaxed
1005 iommu= [x86]
1006 off
1007 force
1008 noforce
1009 biomerge
1010 panic
1011 nopanic
1012 merge
1013 nomerge
1014 forcesac
1015 soft
1016 pt [x86, IA64]
1018 io7= [HW] IO7 for Marvel based alpha systems
1019 See comment before marvel_specify_io7 in
1020 arch/alpha/kernel/core_marvel.c.
1022 io_delay= [X86] I/O delay method
1023 0x80
1024 Standard port 0x80 based delay
1025 0xed
1026 Alternate port 0xed based delay (needed on some systems)
1027 udelay
1028 Simple two microseconds delay
1029 none
1030 No delay
1032 ip= [IP_PNP]
1033 See Documentation/filesystems/nfs/nfsroot.txt.
1035 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1036 See comment before ip2_setup() in
1037 drivers/char/ip2/ip2base.c.
1039 irqfixup [HW]
1040 When an interrupt is not handled search all handlers
1041 for it. Intended to get systems with badly broken
1042 firmware running.
1044 irqpoll [HW]
1045 When an interrupt is not handled search all handlers
1046 for it. Also check all handlers each timer
1047 interrupt. Intended to get systems with badly broken
1048 firmware running.
1050 isapnp= [ISAPNP]
1051 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1053 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1054 Format:
1055 <cpu number>,...,<cpu number>
1056 or
1057 <cpu number>-<cpu number>
1058 (must be a positive range in ascending order)
1059 or a mixture
1060 <cpu number>,...,<cpu number>-<cpu number>
1062 This option can be used to specify one or more CPUs
1063 to isolate from the general SMP balancing and scheduling
1064 algorithms. You can move a process onto or off an
1065 "isolated" CPU via the CPU affinity syscalls or cpuset.
1066 <cpu number> begins at 0 and the maximum value is
1067 "number of CPUs in system - 1".
1069 This option is the preferred way to isolate CPUs. The
1070 alternative -- manually setting the CPU mask of all
1071 tasks in the system -- can cause problems and
1072 suboptimal load balancer performance.
1074 iucv= [HW,NET]
1076 js= [HW,JOY] Analog joystick
1077 See Documentation/input/joystick.txt.
1079 keepinitrd [HW,ARM]
1081 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1082 specifies the amount of memory usable by the kernel
1083 for non-movable allocations. The requested amount is
1084 spread evenly throughout all nodes in the system. The
1085 remaining memory in each node is used for Movable
1086 pages. In the event, a node is too small to have both
1087 kernelcore and Movable pages, kernelcore pages will
1088 take priority and other nodes will have a larger number
1089 of kernelcore pages. The Movable zone is used for the
1090 allocation of pages that may be reclaimed or moved
1091 by the page migration subsystem. This means that
1092 HugeTLB pages may not be allocated from this zone.
1093 Note that allocations like PTEs-from-HighMem still
1094 use the HighMem zone if it exists, and the Normal
1095 zone if it does not.
1097 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1098 Format: <Controller#>[,poll interval]
1099 The controller # is the number of the ehci usb debug
1100 port as it is probed via PCI. The poll interval is
1101 optional and is the number seconds in between
1102 each poll cycle to the debug port in case you need
1103 the functionality for interrupting the kernel with
1104 gdb or control-c on the dbgp connection. When
1105 not using this parameter you use sysrq-g to break into
1106 the kernel debugger.
1108 kgdboc= [KGDB,HW] kgdb over consoles.
1109 Requires a tty driver that supports console polling,
1110 or a supported polling keyboard driver (non-usb).
1111 Serial only format: <serial_device>[,baud]
1112 keyboard only format: kbd
1113 keyboard and serial format: kbd,<serial_device>[,baud]
1114 Optional Kernel mode setting:
1115 kms, kbd format: kms,kbd
1116 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1118 kgdbwait [KGDB] Stop kernel execution and enter the
1119 kernel debugger at the earliest opportunity.
1121 kmac= [MIPS] korina ethernet MAC address.
1122 Configure the RouterBoard 532 series on-chip
1123 Ethernet adapter MAC address.
1125 kmemleak= [KNL] Boot-time kmemleak enable/disable
1126 Valid arguments: on, off
1127 Default: on
1129 kstack=N [X86] Print N words from the kernel stack
1130 in oops dumps.
1132 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1133 Default is 0 (don't ignore, but inject #GP)
1135 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1136 Default is 1 (enabled)
1138 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1139 KVM MMU at runtime.
1140 Default is 0 (off)
1142 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1143 Default is 1 (enabled)
1145 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1146 for all guests.
1147 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1149 kvm-intel.bypass_guest_pf=
1150 [KVM,Intel] Disables bypassing of guest page faults
1151 on Intel chips. Default is 1 (enabled)
1153 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1154 (virtualized MMU) support on capable Intel chips.
1155 Default is 1 (enabled)
1157 kvm-intel.emulate_invalid_guest_state=
1158 [KVM,Intel] Enable emulation of invalid guest states
1159 Default is 0 (disabled)
1161 kvm-intel.flexpriority=
1162 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1163 Default is 1 (enabled)
1165 kvm-intel.unrestricted_guest=
1166 [KVM,Intel] Disable unrestricted guest feature
1167 (virtualized real and unpaged mode) on capable
1168 Intel chips. Default is 1 (enabled)
1170 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1171 feature (tagged TLBs) on capable Intel chips.
1172 Default is 1 (enabled)
1174 l2cr= [PPC]
1176 l3cr= [PPC]
1178 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1179 disabled it.
1181 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1182 in C2 power state.
1184 libata.dma= [LIBATA] DMA control
1185 libata.dma=0 Disable all PATA and SATA DMA
1186 libata.dma=1 PATA and SATA Disk DMA only
1187 libata.dma=2 ATAPI (CDROM) DMA only
1188 libata.dma=4 Compact Flash DMA only
1189 Combinations also work, so libata.dma=3 enables DMA
1190 for disks and CDROMs, but not CFs.
1192 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1193 libata.ignore_hpa=0 keep BIOS limits (default)
1194 libata.ignore_hpa=1 ignore limits, using full disk
1196 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1197 when set.
1198 Format: <int>
1200 libata.force= [LIBATA] Force configurations. The format is comma
1201 separated list of "[ID:]VAL" where ID is
1202 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1203 matching port, link or device. Basically, it matches
1204 the ATA ID string printed on console by libata. If
1205 the whole ID part is omitted, the last PORT and DEVICE
1206 values are used. If ID hasn't been specified yet, the
1207 configuration applies to all ports, links and devices.
1209 If only DEVICE is omitted, the parameter applies to
1210 the port and all links and devices behind it. DEVICE
1211 number of 0 either selects the first device or the
1212 first fan-out link behind PMP device. It does not
1213 select the host link. DEVICE number of 15 selects the
1214 host link and device attached to it.
1216 The VAL specifies the configuration to force. As long
1217 as there's no ambiguity shortcut notation is allowed.
1218 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1219 The following configurations can be forced.
1221 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1222 Any ID with matching PORT is used.
1224 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1226 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1227 udma[/][16,25,33,44,66,100,133] notation is also
1228 allowed.
1230 * [no]ncq: Turn on or off NCQ.
1232 * nohrst, nosrst, norst: suppress hard, soft
1233 and both resets.
1235 * dump_id: dump IDENTIFY data.
1237 If there are multiple matching configurations changing
1238 the same attribute, the last one is used.
1240 memblock=debug [KNL] Enable memblock debug messages.
1242 load_ramdisk= [RAM] List of ramdisks to load from floppy
1243 See Documentation/blockdev/ramdisk.txt.
1245 lockd.nlm_grace_period=P [NFS] Assign grace period.
1246 Format: <integer>
1248 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1249 Format: <integer>
1251 lockd.nlm_timeout=T [NFS] Assign timeout value.
1252 Format: <integer>
1254 lockd.nlm_udpport=M [NFS] Assign UDP port.
1255 Format: <integer>
1257 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1258 Format: <irq>
1260 loglevel= All Kernel Messages with a loglevel smaller than the
1261 console loglevel will be printed to the console. It can
1262 also be changed with klogd or other programs. The
1263 loglevels are defined as follows:
1265 0 (KERN_EMERG) system is unusable
1266 1 (KERN_ALERT) action must be taken immediately
1267 2 (KERN_CRIT) critical conditions
1268 3 (KERN_ERR) error conditions
1269 4 (KERN_WARNING) warning conditions
1270 5 (KERN_NOTICE) normal but significant condition
1271 6 (KERN_INFO) informational
1272 7 (KERN_DEBUG) debug-level messages
1274 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1275 in bytes. n must be a power of two. The default
1276 size is set in the kernel config file.
1278 logo.nologo [FB] Disables display of the built-in Linux logo.
1279 This may be used to provide more screen space for
1280 kernel log messages and is useful when debugging
1281 kernel boot problems.
1283 lp=0 [LP] Specify parallel ports to use, e.g,
1284 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1285 lp=reset first parallel port). 'lp=0' disables the
1286 lp=auto printer driver. 'lp=reset' (which can be
1287 specified in addition to the ports) causes
1288 attached printers to be reset. Using
1289 lp=port1,port2,... specifies the parallel ports
1290 to associate lp devices with, starting with
1291 lp0. A port specification may be 'none' to skip
1292 that lp device, or a parport name such as
1293 'parport0'. Specifying 'lp=auto' instead of a
1294 port specification list means that device IDs
1295 from each port should be examined, to see if
1296 an IEEE 1284-compliant printer is attached; if
1297 so, the driver will manage that printer.
1298 See also header of drivers/char/lp.c.
1300 lpj=n [KNL]
1301 Sets loops_per_jiffy to given constant, thus avoiding
1302 time-consuming boot-time autodetection (up to 250 ms per
1303 CPU). 0 enables autodetection (default). To determine
1304 the correct value for your kernel, boot with normal
1305 autodetection and see what value is printed. Note that
1306 on SMP systems the preset will be applied to all CPUs,
1307 which is likely to cause problems if your CPUs need
1308 significantly divergent settings. An incorrect value
1309 will cause delays in the kernel to be wrong, leading to
1310 unpredictable I/O errors and other breakage. Although
1311 unlikely, in the extreme case this might damage your
1312 hardware.
1314 ltpc= [NET]
1315 Format: <io>,<irq>,<dma>
1317 machvec= [IA64] Force the use of a particular machine-vector
1318 (machvec) in a generic kernel.
1319 Example: machvec=hpzx1_swiotlb
1321 machtype= [Loongson] Share the same kernel image file between different
1322 yeeloong laptop.
1323 Example: machtype=lemote-yeeloong-2f-7inch
1325 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1326 than or equal to this physical address is ignored.
1328 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1329 should make use of. maxcpus=n : n >= 0 limits the
1330 kernel to using 'n' processors. n=0 is a special case,
1331 it is equivalent to "nosmp", which also disables
1332 the IO APIC.
1334 max_loop= [LOOP] Maximum number of loopback devices that can
1335 be mounted
1336 Format: <1-256>
1338 mcatest= [IA-64]
1340 mce [X86-32] Machine Check Exception
1342 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1344 md= [HW] RAID subsystems devices and level
1345 See Documentation/md.txt.
1347 mdacon= [MDA]
1348 Format: <first>,<last>
1349 Specifies range of consoles to be captured by the MDA.
1351 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1352 Amount of memory to be used when the kernel is not able
1353 to see the whole system memory or for test.
1354 [X86-32] Use together with memmap= to avoid physical
1355 address space collisions. Without memmap= PCI devices
1356 could be placed at addresses belonging to unused RAM.
1358 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1359 memory.
1361 memchunk=nn[KMG]
1362 [KNL,SH] Allow user to override the default size for
1363 per-device physically contiguous DMA buffers.
1365 memmap=exactmap [KNL,X86] Enable setting of an exact
1366 E820 memory map, as specified by the user.
1367 Such memmap=exactmap lines can be constructed based on
1368 BIOS output or other requirements. See the memmap=nn@ss
1369 option description.
1371 memmap=nn[KMG]@ss[KMG]
1372 [KNL] Force usage of a specific region of memory
1373 Region of memory to be used, from ss to ss+nn.
1375 memmap=nn[KMG]#ss[KMG]
1376 [KNL,ACPI] Mark specific memory as ACPI data.
1377 Region of memory to be used, from ss to ss+nn.
1379 memmap=nn[KMG]$ss[KMG]
1380 [KNL,ACPI] Mark specific memory as reserved.
1381 Region of memory to be used, from ss to ss+nn.
1382 Example: Exclude memory from 0x18690000-0x1869ffff
1383 memmap=64K$0x18690000
1384 or
1385 memmap=0x10000$0x18690000
1387 memory_corruption_check=0/1 [X86]
1388 Some BIOSes seem to corrupt the first 64k of
1389 memory when doing things like suspend/resume.
1390 Setting this option will scan the memory
1391 looking for corruption. Enabling this will
1392 both detect corruption and prevent the kernel
1393 from using the memory being corrupted.
1394 However, its intended as a diagnostic tool; if
1395 repeatable BIOS-originated corruption always
1396 affects the same memory, you can use memmap=
1397 to prevent the kernel from using that memory.
1399 memory_corruption_check_size=size [X86]
1400 By default it checks for corruption in the low
1401 64k, making this memory unavailable for normal
1402 use. Use this parameter to scan for
1403 corruption in more or less memory.
1405 memory_corruption_check_period=seconds [X86]
1406 By default it checks for corruption every 60
1407 seconds. Use this parameter to check at some
1408 other rate. 0 disables periodic checking.
1410 memtest= [KNL,X86] Enable memtest
1411 Format: <integer>
1412 default : 0 <disable>
1413 Specifies the number of memtest passes to be
1414 performed. Each pass selects another test
1415 pattern from a given set of patterns. Memtest
1416 fills the memory with this pattern, validates
1417 memory contents and reserves bad memory
1418 regions that are detected.
1420 meye.*= [HW] Set MotionEye Camera parameters
1421 See Documentation/video4linux/meye.txt.
1423 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1424 Multi-Function General Purpose Timers on AMD Geode
1425 platforms.
1427 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1428 the BIOS has incorrectly applied a workaround. TinyBIOS
1429 version 0.98 is known to be affected, 0.99 fixes the
1430 problem by letting the user disable the workaround.
1432 mga= [HW,DRM]
1434 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1435 physical address is ignored.
1437 mini2440= [ARM,HW,KNL]
1438 Format:[0..2][b][c][t]
1439 Default: "0tb"
1440 MINI2440 configuration specification:
1441 0 - The attached screen is the 3.5" TFT
1442 1 - The attached screen is the 7" TFT
1443 2 - The VGA Shield is attached (1024x768)
1444 Leaving out the screen size parameter will not load
1445 the TFT driver, and the framebuffer will be left
1446 unconfigured.
1447 b - Enable backlight. The TFT backlight pin will be
1448 linked to the kernel VESA blanking code and a GPIO
1449 LED. This parameter is not necessary when using the
1450 VGA shield.
1451 c - Enable the s3c camera interface.
1452 t - Reserved for enabling touchscreen support. The
1453 touchscreen support is not enabled in the mainstream
1454 kernel as of 2.6.30, a preliminary port can be found
1455 in the "bleeding edge" mini2440 support kernel at
1456 http://repo.or.cz/w/linux-2.6/mini2440.git
1458 mminit_loglevel=
1459 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1460 parameter allows control of the logging verbosity for
1461 the additional memory initialisation checks. A value
1462 of 0 disables mminit logging and a level of 4 will
1463 log everything. Information is printed at KERN_DEBUG
1464 so loglevel=8 may also need to be specified.
1466 mousedev.tap_time=
1467 [MOUSE] Maximum time between finger touching and
1468 leaving touchpad surface for touch to be considered
1469 a tap and be reported as a left button click (for
1470 touchpads working in absolute mode only).
1471 Format: <msecs>
1472 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1473 reporting absolute coordinates, such as tablets
1474 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1475 reporting absolute coordinates, such as tablets
1477 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1478 is similar to kernelcore except it specifies the
1479 amount of memory used for migratable allocations.
1480 If both kernelcore and movablecore is specified,
1481 then kernelcore will be at *least* the specified
1482 value but may be more. If movablecore on its own
1483 is specified, the administrator must be careful
1484 that the amount of memory usable for all allocations
1485 is not too small.
1487 MTD_Partition= [MTD]
1488 Format: <name>,<region-number>,<size>,<offset>
1490 MTD_Region= [MTD] Format:
1491 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1493 mtdparts= [MTD]
1494 See drivers/mtd/cmdlinepart.c.
1496 multitce=off [PPC] This parameter disables the use of the pSeries
1497 firmware feature for updating multiple TCE entries
1498 at a time.
1500 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1502 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1504 boundary - index of last SLC block on Flex-OneNAND.
1505 The remaining blocks are configured as MLC blocks.
1506 lock - Configure if Flex-OneNAND boundary should be locked.
1507 Once locked, the boundary cannot be changed.
1508 1 indicates lock status, 0 indicates unlock status.
1510 mtdset= [ARM]
1511 ARM/S3C2412 JIVE boot control
1513 See arch/arm/mach-s3c2412/mach-jive.c
1515 mtouchusb.raw_coordinates=
1516 [HW] Make the MicroTouch USB driver use raw coordinates
1517 ('y', default) or cooked coordinates ('n')
1519 mtrr_chunk_size=nn[KMG] [X86]
1520 used for mtrr cleanup. It is largest continuous chunk
1521 that could hold holes aka. UC entries.
1523 mtrr_gran_size=nn[KMG] [X86]
1524 Used for mtrr cleanup. It is granularity of mtrr block.
1525 Default is 1.
1526 Large value could prevent small alignment from
1527 using up MTRRs.
1529 mtrr_spare_reg_nr=n [X86]
1530 Format: <integer>
1531 Range: 0,7 : spare reg number
1532 Default : 1
1533 Used for mtrr cleanup. It is spare mtrr entries number.
1534 Set to 2 or more if your graphical card needs more.
1536 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1538 netdev= [NET] Network devices parameters
1539 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1540 Note that mem_start is often overloaded to mean
1541 something different and driver-specific.
1542 This usage is only documented in each driver source
1543 file if at all.
1545 nf_conntrack.acct=
1546 [NETFILTER] Enable connection tracking flow accounting
1547 0 to disable accounting
1548 1 to enable accounting
1549 Default value is 0.
1551 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1552 See Documentation/filesystems/nfs/nfsroot.txt.
1554 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1555 See Documentation/filesystems/nfs/nfsroot.txt.
1557 nfsrootdebug [NFS] enable nfsroot debugging messages.
1558 See Documentation/filesystems/nfs/nfsroot.txt.
1560 nfs.callback_tcpport=
1561 [NFS] set the TCP port on which the NFSv4 callback
1562 channel should listen.
1564 nfs.cache_getent=
1565 [NFS] sets the pathname to the program which is used
1566 to update the NFS client cache entries.
1568 nfs.cache_getent_timeout=
1569 [NFS] sets the timeout after which an attempt to
1570 update a cache entry is deemed to have failed.
1572 nfs.idmap_cache_timeout=
1573 [NFS] set the maximum lifetime for idmapper cache
1574 entries.
1576 nfs.enable_ino64=
1577 [NFS] enable 64-bit inode numbers.
1578 If zero, the NFS client will fake up a 32-bit inode
1579 number for the readdir() and stat() syscalls instead
1580 of returning the full 64-bit number.
1581 The default is to return 64-bit inode numbers.
1583 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1584 when a NMI is triggered.
1585 Format: [state][,regs][,debounce][,die]
1587 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1588 Format: [panic,][num]
1589 Valid num: 0
1590 0 - turn nmi_watchdog off
1591 When panic is specified, panic when an NMI watchdog
1592 timeout occurs.
1593 This is useful when you use a panic=... timeout and
1594 need the box quickly up again.
1596 netpoll.carrier_timeout=
1597 [NET] Specifies amount of time (in seconds) that
1598 netpoll should wait for a carrier. By default netpoll
1599 waits 4 seconds.
1601 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1602 emulation library even if a 387 maths coprocessor
1603 is present.
1605 no_console_suspend
1606 [HW] Never suspend the console
1607 Disable suspending of consoles during suspend and
1608 hibernate operations. Once disabled, debugging
1609 messages can reach various consoles while the rest
1610 of the system is being put to sleep (ie, while
1611 debugging driver suspend/resume hooks). This may
1612 not work reliably with all consoles, but is known
1613 to work with serial and VGA consoles.
1615 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1616 caches in the slab allocator. Saves per-node memory,
1617 but will impact performance.
1619 noalign [KNL,ARM]
1621 noapic [SMP,APIC] Tells the kernel to not make use of any
1622 IOAPICs that may be present in the system.
1624 noautogroup Disable scheduler automatic task group creation.
1626 nobats [PPC] Do not use BATs for mapping kernel lowmem
1627 on "Classic" PPC cores.
1629 nocache [ARM]
1631 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1633 nodelayacct [KNL] Disable per-task delay accounting
1635 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1637 nodsp [SH] Disable hardware DSP at boot time.
1639 noefi [X86] Disable EFI runtime services support.
1641 noexec [IA-64]
1643 noexec [X86]
1644 On X86-32 available only on PAE configured kernels.
1645 noexec=on: enable non-executable mappings (default)
1646 noexec=off: disable non-executable mappings
1648 noexec32 [X86-64]
1649 This affects only 32-bit executables.
1650 noexec32=on: enable non-executable mappings (default)
1651 read doesn't imply executable mappings
1652 noexec32=off: disable non-executable mappings
1653 read implies executable mappings
1655 nofpu [SH] Disable hardware FPU at boot time.
1657 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1658 register save and restore. The kernel will only save
1659 legacy floating-point registers on task switch.
1661 noxsave [BUGS=X86] Disables x86 extended register state save
1662 and restore using xsave. The kernel will fallback to
1663 enabling legacy floating-point and sse state.
1665 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1666 wfi(ARM) instruction doesn't work correctly and not to
1667 use it. This is also useful when using JTAG debugger.
1669 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1670 instruction doesn't work correctly and not to
1671 use it.
1673 no_file_caps Tells the kernel not to honor file capabilities. The
1674 only way then for a file to be executed with privilege
1675 is to be setuid root or executed by root.
1677 nohalt [IA-64] Tells the kernel not to use the power saving
1678 function PAL_HALT_LIGHT when idle. This increases
1679 power-consumption. On the positive side, it reduces
1680 interrupt wake-up latency, which may improve performance
1681 in certain environments such as networked servers or
1682 real-time systems.
1684 nohz= [KNL] Boottime enable/disable dynamic ticks
1685 Valid arguments: on, off
1686 Default: on
1688 noiotrap [SH] Disables trapped I/O port accesses.
1690 noirqdebug [X86-32] Disables the code which attempts to detect and
1691 disable unhandled interrupt sources.
1693 no_timer_check [X86,APIC] Disables the code which tests for
1694 broken timer IRQ sources.
1696 noisapnp [ISAPNP] Disables ISA PnP code.
1698 noinitrd [RAM] Tells the kernel not to load any configured
1699 initial RAM disk.
1701 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1702 remapping.
1703 [Deprecated - use intremap=off]
1705 nointroute [IA-64]
1707 nojitter [IA64] Disables jitter checking for ITC timers.
1709 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1711 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1712 fault handling.
1714 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1716 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1718 noltlbs [PPC] Do not use large page/tlb entries for kernel
1719 lowmem mapping on PPC40x.
1721 nomca [IA-64] Disable machine check abort handling
1723 nomce [X86-32] Machine Check Exception
1725 nomfgpt [X86-32] Disable Multi-Function General Purpose
1726 Timer usage (for AMD Geode machines).
1728 nopat [X86] Disable PAT (page attribute table extension of
1729 pagetables) support.
1731 norandmaps Don't use address space randomization. Equivalent to
1732 echo 0 > /proc/sys/kernel/randomize_va_space
1734 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1736 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1737 with UP alternatives
1739 noresidual [PPC] Don't use residual data on PReP machines.
1741 noresume [SWSUSP] Disables resume and restores original swap
1742 space.
1744 no-scroll [VGA] Disables scrollback.
1745 This is required for the Braillex ib80-piezo Braille
1746 reader made by F.H. Papenmeier (Germany).
1748 nosbagart [IA-64]
1750 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1752 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1753 and disable the IO APIC. legacy for "maxcpus=0".
1755 nosoftlockup [KNL] Disable the soft-lockup detector.
1757 noswapaccount [KNL] Disable accounting of swap in memory resource
1758 controller. (See Documentation/cgroups/memory.txt)
1760 nosync [HW,M68K] Disables sync negotiation for all devices.
1762 notsc [BUGS=X86-32] Disable Time Stamp Counter
1764 nousb [USB] Disable the USB subsystem
1766 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1768 nowb [ARM]
1770 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1772 nptcg= [IA64] Override max number of concurrent global TLB
1773 purges which is reported from either PAL_VM_SUMMARY or
1774 SAL PALO.
1776 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1777 could support. nr_cpus=n : n >= 1 limits the kernel to
1778 supporting 'n' processors. Later in runtime you can not
1779 use hotplug cpu feature to put more cpu back to online.
1780 just like you compile the kernel NR_CPUS=n
1782 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1784 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1785 one of ['zone', 'node', 'default'] can be specified
1786 This can be set from sysctl after boot.
1787 See Documentation/sysctl/vm.txt for details.
1789 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1790 See Documentation/debugging-via-ohci1394.txt for more
1791 info.
1793 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1794 Rather than timing out after 20 ms if an EC
1795 command is not properly ACKed, override the length
1796 of the timeout. We have interrupts disabled while
1797 waiting for the ACK, so if this is set too high
1798 interrupts *may* be lost!
1800 omap_mux= [OMAP] Override bootloader pin multiplexing.
1801 Format: <mux_mode0.mode_name=value>...
1802 For example, to override I2C bus2:
1803 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1805 oprofile.timer= [HW]
1806 Use timer interrupt instead of performance counters
1808 oprofile.cpu_type= Force an oprofile cpu type
1809 This might be useful if you have an older oprofile
1810 userland or if you want common events.
1811 Format: { arch_perfmon }
1812 arch_perfmon: [X86] Force use of architectural
1813 perfmon on Intel CPUs instead of the
1814 CPU specific event set.
1816 OSS [HW,OSS]
1817 See Documentation/sound/oss/oss-parameters.txt
1819 panic= [KNL] Kernel behaviour on panic
1820 Format: <timeout>
1822 parkbd.port= [HW] Parallel port number the keyboard adapter is
1823 connected to, default is 0.
1824 Format: <parport#>
1825 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1826 0 for XT, 1 for AT (default is AT).
1827 Format: <mode>
1829 parport= [HW,PPT] Specify parallel ports. 0 disables.
1830 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1831 Use 'auto' to force the driver to use any
1832 IRQ/DMA settings detected (the default is to
1833 ignore detected IRQ/DMA settings because of
1834 possible conflicts). You can specify the base
1835 address, IRQ, and DMA settings; IRQ and DMA
1836 should be numbers, or 'auto' (for using detected
1837 settings on that particular port), or 'nofifo'
1838 (to avoid using a FIFO even if it is detected).
1839 Parallel ports are assigned in the order they
1840 are specified on the command line, starting
1841 with parport0.
1843 parport_init_mode= [HW,PPT]
1844 Configure VIA parallel port to operate in
1845 a specific mode. This is necessary on Pegasos
1846 computer where firmware has no options for setting
1847 up parallel port mode and sets it to spp.
1848 Currently this function knows 686a and 8231 chips.
1849 Format: [spp|ps2|epp|ecp|ecpepp]
1851 pause_on_oops=
1852 Halt all CPUs after the first oops has been printed for
1853 the specified number of seconds. This is to be used if
1854 your oopses keep scrolling off the screen.
1856 pcbit= [HW,ISDN]
1858 pcd. [PARIDE]
1859 See header of drivers/block/paride/pcd.c.
1860 See also Documentation/blockdev/paride.txt.
1862 pci=option[,option...] [PCI] various PCI subsystem options:
1863 earlydump [X86] dump PCI config space before the kernel
1864 changes anything
1865 off [X86] don't probe for the PCI bus
1866 bios [X86-32] force use of PCI BIOS, don't access
1867 the hardware directly. Use this if your machine
1868 has a non-standard PCI host bridge.
1869 nobios [X86-32] disallow use of PCI BIOS, only direct
1870 hardware access methods are allowed. Use this
1871 if you experience crashes upon bootup and you
1872 suspect they are caused by the BIOS.
1873 conf1 [X86] Force use of PCI Configuration
1874 Mechanism 1.
1875 conf2 [X86] Force use of PCI Configuration
1876 Mechanism 2.
1877 noaer [PCIE] If the PCIEAER kernel config parameter is
1878 enabled, this kernel boot option can be used to
1879 disable the use of PCIE advanced error reporting.
1880 nodomains [PCI] Disable support for multiple PCI
1881 root domains (aka PCI segments, in ACPI-speak).
1882 nommconf [X86] Disable use of MMCONFIG for PCI
1883 Configuration
1884 check_enable_amd_mmconf [X86] check for and enable
1885 properly configured MMIO access to PCI
1886 config space on AMD family 10h CPU
1887 nomsi [MSI] If the PCI_MSI kernel config parameter is
1888 enabled, this kernel boot option can be used to
1889 disable the use of MSI interrupts system-wide.
1890 noioapicquirk [APIC] Disable all boot interrupt quirks.
1891 Safety option to keep boot IRQs enabled. This
1892 should never be necessary.
1893 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1894 primary IO-APIC for bridges that cannot disable
1895 boot IRQs. This fixes a source of spurious IRQs
1896 when the system masks IRQs.
1897 noioapicreroute [APIC] Disable workaround that uses the
1898 boot IRQ equivalent of an IRQ that connects to
1899 a chipset where boot IRQs cannot be disabled.
1900 The opposite of ioapicreroute.
1901 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1902 routing table. These calls are known to be buggy
1903 on several machines and they hang the machine
1904 when used, but on other computers it's the only
1905 way to get the interrupt routing table. Try
1906 this option if the kernel is unable to allocate
1907 IRQs or discover secondary PCI buses on your
1908 motherboard.
1909 rom [X86] Assign address space to expansion ROMs.
1910 Use with caution as certain devices share
1911 address decoders between ROMs and other
1912 resources.
1913 norom [X86] Do not assign address space to
1914 expansion ROMs that do not already have
1915 BIOS assigned address ranges.
1916 nobar [X86] Do not assign address space to the
1917 BARs that weren't assigned by the BIOS.
1918 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1919 assigned automatically to PCI devices. You can
1920 make the kernel exclude IRQs of your ISA cards
1921 this way.
1922 pirqaddr=0xAAAAA [X86] Specify the physical address
1923 of the PIRQ table (normally generated
1924 by the BIOS) if it is outside the
1925 F0000h-100000h range.
1926 lastbus=N [X86] Scan all buses thru bus #N. Can be
1927 useful if the kernel is unable to find your
1928 secondary buses and you want to tell it
1929 explicitly which ones they are.
1930 assign-busses [X86] Always assign all PCI bus
1931 numbers ourselves, overriding
1932 whatever the firmware may have done.
1933 usepirqmask [X86] Honor the possible IRQ mask stored
1934 in the BIOS $PIR table. This is needed on
1935 some systems with broken BIOSes, notably
1936 some HP Pavilion N5400 and Omnibook XE3
1937 notebooks. This will have no effect if ACPI
1938 IRQ routing is enabled.
1939 noacpi [X86] Do not use ACPI for IRQ routing
1940 or for PCI scanning.
1941 use_crs [X86] Use PCI host bridge window information
1942 from ACPI. On BIOSes from 2008 or later, this
1943 is enabled by default. If you need to use this,
1944 please report a bug.
1945 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1946 If you need to use this, please report a bug.
1947 routeirq Do IRQ routing for all PCI devices.
1948 This is normally done in pci_enable_device(),
1949 so this option is a temporary workaround
1950 for broken drivers that don't call it.
1951 skip_isa_align [X86] do not align io start addr, so can
1952 handle more pci cards
1953 firmware [ARM] Do not re-enumerate the bus but instead
1954 just use the configuration from the
1955 bootloader. This is currently used on
1956 IXP2000 systems where the bus has to be
1957 configured a certain way for adjunct CPUs.
1958 noearly [X86] Don't do any early type 1 scanning.
1959 This might help on some broken boards which
1960 machine check when some devices' config space
1961 is read. But various workarounds are disabled
1962 and some IOMMU drivers will not work.
1963 bfsort Sort PCI devices into breadth-first order.
1964 This sorting is done to get a device
1965 order compatible with older (<= 2.4) kernels.
1966 nobfsort Don't sort PCI devices into breadth-first order.
1967 cbiosize=nn[KMG] The fixed amount of bus space which is
1968 reserved for the CardBus bridge's IO window.
1969 The default value is 256 bytes.
1970 cbmemsize=nn[KMG] The fixed amount of bus space which is
1971 reserved for the CardBus bridge's memory
1972 window. The default value is 64 megabytes.
1973 resource_alignment=
1974 Format:
1975 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1976 Specifies alignment and device to reassign
1977 aligned memory resources.
1978 If <order of align> is not specified,
1979 PAGE_SIZE is used as alignment.
1980 PCI-PCI bridge can be specified, if resource
1981 windows need to be expanded.
1982 ecrc= Enable/disable PCIe ECRC (transaction layer
1983 end-to-end CRC checking).
1984 bios: Use BIOS/firmware settings. This is the
1985 the default.
1986 off: Turn ECRC off
1987 on: Turn ECRC on.
1989 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1990 Management.
1991 off Disable ASPM.
1992 force Enable ASPM even on devices that claim not to support it.
1993 WARNING: Forcing ASPM on may cause system lockups.
1995 pcie_ports= [PCIE] PCIe ports handling:
1996 auto Ask the BIOS whether or not to use native PCIe services
1997 associated with PCIe ports (PME, hot-plug, AER). Use
1998 them only if that is allowed by the BIOS.
1999 native Use native PCIe services associated with PCIe ports
2000 unconditionally.
2001 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2002 ports driver.
2004 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2005 nomsi Do not use MSI for native PCIe PME signaling (this makes
2006 all PCIe root ports use INTx for all services).
2008 pcmv= [HW,PCMCIA] BadgePAD 4
2010 pd. [PARIDE]
2011 See Documentation/blockdev/paride.txt.
2013 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2014 boot time.
2015 Format: { 0 | 1 }
2016 See arch/parisc/kernel/pdc_chassis.c
2018 percpu_alloc= Select which percpu first chunk allocator to use.
2019 Currently supported values are "embed" and "page".
2020 Archs may support subset or none of the selections.
2021 See comments in mm/percpu.c for details on each
2022 allocator. This parameter is primarily for debugging
2023 and performance comparison.
2025 pf. [PARIDE]
2026 See Documentation/blockdev/paride.txt.
2028 pg. [PARIDE]
2029 See Documentation/blockdev/paride.txt.
2031 pirq= [SMP,APIC] Manual mp-table setup
2032 See Documentation/x86/i386/IO-APIC.txt.
2034 plip= [PPT,NET] Parallel port network link
2035 Format: { parport<nr> | timid | 0 }
2036 See also Documentation/parport.txt.
2038 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2039 Override pmtimer IOPort with a hex value.
2040 e.g. pmtmr=0x508
2042 pnp.debug [PNP]
2043 Enable PNP debug messages. This depends on the
2044 CONFIG_PNP_DEBUG_MESSAGES option.
2046 pnpacpi= [ACPI]
2047 { off }
2049 pnpbios= [ISAPNP]
2050 { on | off | curr | res | no-curr | no-res }
2052 pnp_reserve_irq=
2053 [ISAPNP] Exclude IRQs for the autoconfiguration
2055 pnp_reserve_dma=
2056 [ISAPNP] Exclude DMAs for the autoconfiguration
2058 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2059 Ranges are in pairs (I/O port base and size).
2061 pnp_reserve_mem=
2062 [ISAPNP] Exclude memory regions for the
2063 autoconfiguration.
2064 Ranges are in pairs (memory base and size).
2066 ports= [IP_VS_FTP] IPVS ftp helper module
2067 Default is 21.
2068 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2069 may be specified.
2070 Format: <port>,<port>....
2072 print-fatal-signals=
2073 [KNL] debug: print fatal signals
2075 If enabled, warn about various signal handling
2076 related application anomalies: too many signals,
2077 too many POSIX.1 timers, fatal signals causing a
2078 coredump - etc.
2080 If you hit the warning due to signal overflow,
2081 you might want to try "ulimit -i unlimited".
2083 default: off.
2085 printk.time= Show timing data prefixed to each printk message line
2086 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2088 processor.max_cstate= [HW,ACPI]
2089 Limit processor to maximum C-state
2090 max_cstate=9 overrides any DMI blacklist limit.
2092 processor.nocst [HW,ACPI]
2093 Ignore the _CST method to determine C-states,
2094 instead using the legacy FADT method
2096 profile= [KNL] Enable kernel profiling via /proc/profile
2097 Format: [schedule,]<number>
2098 Param: "schedule" - profile schedule points.
2099 Param: <number> - step/bucket size as a power of 2 for
2100 statistical time based profiling.
2101 Param: "sleep" - profile D-state sleeping (millisecs).
2102 Requires CONFIG_SCHEDSTATS
2103 Param: "kvm" - profile VM exits.
2105 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2106 before loading.
2107 See Documentation/blockdev/ramdisk.txt.
2109 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2110 probe for; one of (bare|imps|exps|lifebook|any).
2111 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2112 per second.
2113 psmouse.resetafter= [HW,MOUSE]
2114 Try to reset the device after so many bad packets
2115 (0 = never).
2116 psmouse.resolution=
2117 [HW,MOUSE] Set desired mouse resolution, in dpi.
2118 psmouse.smartscroll=
2119 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2120 0 = disabled, 1 = enabled (default).
2122 pt. [PARIDE]
2123 See Documentation/blockdev/paride.txt.
2125 pty.legacy_count=
2126 [KNL] Number of legacy pty's. Overwrites compiled-in
2127 default number.
2129 quiet [KNL] Disable most log messages
2131 r128= [HW,DRM]
2133 raid= [HW,RAID]
2134 See Documentation/md.txt.
2136 ramdisk_blocksize= [RAM]
2137 See Documentation/blockdev/ramdisk.txt.
2139 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2140 See Documentation/blockdev/ramdisk.txt.
2142 rcupdate.blimit= [KNL,BOOT]
2143 Set maximum number of finished RCU callbacks to process
2144 in one batch.
2146 rcupdate.qhimark= [KNL,BOOT]
2147 Set threshold of queued
2148 RCU callbacks over which batch limiting is disabled.
2150 rcupdate.qlowmark= [KNL,BOOT]
2151 Set threshold of queued RCU callbacks below which
2152 batch limiting is re-enabled.
2154 rdinit= [KNL]
2155 Format: <full_path>
2156 Run specified binary instead of /init from the ramdisk,
2157 used for early userspace startup. See initrd.
2159 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2160 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2161 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2163 relax_domain_level=
2164 [KNL, SMP] Set scheduler's default relax_domain_level.
2165 See Documentation/cgroups/cpusets.txt.
2167 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2169 reservetop= [X86-32]
2170 Format: nn[KMG]
2171 Reserves a hole at the top of the kernel virtual
2172 address space.
2174 reservelow= [X86]
2175 Format: nn[K]
2176 Set the amount of memory to reserve for BIOS at
2177 the bottom of the address space.
2179 reset_devices [KNL] Force drivers to reset the underlying device
2180 during initialization.
2182 resume= [SWSUSP]
2183 Specify the partition device for software suspend
2185 resume_offset= [SWSUSP]
2186 Specify the offset from the beginning of the partition
2187 given by "resume=" at which the swap header is located,
2188 in <PAGE_SIZE> units (needed only for swap files).
2189 See Documentation/power/swsusp-and-swap-files.txt
2191 hibernate= [HIBERNATION]
2192 noresume Don't check if there's a hibernation image
2193 present during boot.
2194 nocompress Don't compress/decompress hibernation images.
2196 retain_initrd [RAM] Keep initrd memory after extraction
2198 rhash_entries= [KNL,NET]
2199 Set number of hash buckets for route cache
2201 riscom8= [HW,SERIAL]
2202 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2204 ro [KNL] Mount root device read-only on boot
2206 root= [KNL] Root filesystem
2208 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2209 mount the root filesystem
2211 rootflags= [KNL] Set root filesystem mount option string
2213 rootfstype= [KNL] Set root filesystem type
2215 rootwait [KNL] Wait (indefinitely) for root device to show up.
2216 Useful for devices that are detected asynchronously
2217 (e.g. USB and MMC devices).
2219 rw [KNL] Mount root device read-write on boot
2221 S [KNL] Run init in single mode
2223 sa1100ir [NET]
2224 See drivers/net/irda/sa1100_ir.c.
2226 sbni= [NET] Granch SBNI12 leased line adapter
2228 sched_debug [KNL] Enables verbose scheduler debug messages.
2230 security= [SECURITY] Choose a security module to enable at boot.
2231 If this boot parameter is not specified, only the first
2232 security module asking for security registration will be
2233 loaded. An invalid security module name will be treated
2234 as if no module has been chosen.
2236 selinux= [SELINUX] Disable or enable SELinux at boot time.
2237 Format: { "0" | "1" }
2238 See security/selinux/Kconfig help text.
2239 0 -- disable.
2240 1 -- enable.
2241 Default value is set via kernel config option.
2242 If enabled at boot time, /selinux/disable can be used
2243 later to disable prior to initial policy load.
2245 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2246 Format: { "0" | "1" }
2247 See security/apparmor/Kconfig help text
2248 0 -- disable.
2249 1 -- enable.
2250 Default value is set via kernel config option.
2252 serialnumber [BUGS=X86-32]
2254 shapers= [NET]
2255 Maximal number of shapers.
2257 show_msr= [x86] show boot-time MSR settings
2258 Format: { <integer> }
2259 Show boot-time (BIOS-initialized) MSR settings.
2260 The parameter means the number of CPUs to show,
2261 for example 1 means boot CPU only.
2263 simeth= [IA-64]
2264 simscsi=
2266 slram= [HW,MTD]
2268 slub_debug[=options[,slabs]] [MM, SLUB]
2269 Enabling slub_debug allows one to determine the
2270 culprit if slab objects become corrupted. Enabling
2271 slub_debug can create guard zones around objects and
2272 may poison objects when not in use. Also tracks the
2273 last alloc / free. For more information see
2274 Documentation/vm/slub.txt.
2276 slub_max_order= [MM, SLUB]
2277 Determines the maximum allowed order for slabs.
2278 A high setting may cause OOMs due to memory
2279 fragmentation. For more information see
2280 Documentation/vm/slub.txt.
2282 slub_min_objects= [MM, SLUB]
2283 The minimum number of objects per slab. SLUB will
2284 increase the slab order up to slub_max_order to
2285 generate a sufficiently large slab able to contain
2286 the number of objects indicated. The higher the number
2287 of objects the smaller the overhead of tracking slabs
2288 and the less frequently locks need to be acquired.
2289 For more information see Documentation/vm/slub.txt.
2291 slub_min_order= [MM, SLUB]
2292 Determines the mininum page order for slabs. Must be
2293 lower than slub_max_order.
2294 For more information see Documentation/vm/slub.txt.
2296 slub_nomerge [MM, SLUB]
2297 Disable merging of slabs with similar size. May be
2298 necessary if there is some reason to distinguish
2299 allocs to different slabs. Debug options disable
2300 merging on their own.
2301 For more information see Documentation/vm/slub.txt.
2303 smart2= [HW]
2304 Format: <io1>[,<io2>[,...,<io8>]]
2306 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2307 attempt to substitute SMP alternatives once at boot.
2309 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2310 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2311 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2312 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2313 smsc-ircc2.ircc_irq= [HW] IRQ line
2314 smsc-ircc2.ircc_dma= [HW] DMA channel
2315 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2316 0: Toshiba Satellite 1800 (GP data pin select)
2317 1: Fast pin select (default)
2318 2: ATC IRMode
2320 softlockup_panic=
2321 [KNL] Should the soft-lockup detector generate panics.
2323 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2324 See Documentation/sonypi.txt
2326 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2327 See Documentation/serial/specialix.txt.
2329 spia_io_base= [HW,MTD]
2330 spia_fio_base=
2331 spia_pedr=
2332 spia_peddr=
2334 stacktrace [FTRACE]
2335 Enabled the stack tracer on boot up.
2337 sti= [PARISC,HW]
2338 Format: <num>
2339 Set the STI (builtin display/keyboard on the HP-PARISC
2340 machines) console (graphic card) which should be used
2341 as the initial boot-console.
2342 See also comment in drivers/video/console/sticore.c.
2344 sti_font= [HW]
2345 See comment in drivers/video/console/sticore.c.
2347 stifb= [HW]
2348 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2350 sunrpc.min_resvport=
2351 sunrpc.max_resvport=
2352 [NFS,SUNRPC]
2353 SunRPC servers often require that client requests
2354 originate from a privileged port (i.e. a port in the
2355 range 0 < portnr < 1024).
2356 An administrator who wishes to reserve some of these
2357 ports for other uses may adjust the range that the
2358 kernel's sunrpc client considers to be privileged
2359 using these two parameters to set the minimum and
2360 maximum port values.
2362 sunrpc.pool_mode=
2363 [NFS]
2364 Control how the NFS server code allocates CPUs to
2365 service thread pools. Depending on how many NICs
2366 you have and where their interrupts are bound, this
2367 option will affect which CPUs will do NFS serving.
2368 Note: this parameter cannot be changed while the
2369 NFS server is running.
2371 auto the server chooses an appropriate mode
2372 automatically using heuristics
2373 global a single global pool contains all CPUs
2374 percpu one pool for each CPU
2375 pernode one pool for each NUMA node (equivalent
2376 to global on non-NUMA machines)
2378 sunrpc.tcp_slot_table_entries=
2379 sunrpc.udp_slot_table_entries=
2380 [NFS,SUNRPC]
2381 Sets the upper limit on the number of simultaneous
2382 RPC calls that can be sent from the client to a
2383 server. Increasing these values may allow you to
2384 improve throughput, but will also increase the
2385 amount of memory reserved for use by the client.
2387 swapaccount[=0|1]
2388 [KNL] Enable accounting of swap in memory resource
2389 controller if no parameter or 1 is given or disable
2390 it if 0 is given (See Documentation/cgroups/memory.txt)
2392 swiotlb= [IA-64] Number of I/O TLB slabs
2394 switches= [HW,M68k]
2396 sysfs.deprecated=0|1 [KNL]
2397 Enable/disable old style sysfs layout for old udev
2398 on older distributions. When this option is enabled
2399 very new udev will not work anymore. When this option
2400 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2401 in older udev will not work anymore.
2402 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2403 the kernel configuration.
2405 sysrq_always_enabled
2406 [KNL]
2407 Ignore sysrq setting - this boot parameter will
2408 neutralize any effect of /proc/sys/kernel/sysrq.
2409 Useful for debugging.
2411 tdfx= [HW,DRM]
2413 test_suspend= [SUSPEND]
2414 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2415 standby suspend) as the system sleep state to briefly
2416 enter during system startup. The system is woken from
2417 this state using a wakeup-capable RTC alarm.
2419 thash_entries= [KNL,NET]
2420 Set number of hash buckets for TCP connection
2422 thermal.act= [HW,ACPI]
2423 -1: disable all active trip points in all thermal zones
2424 <degrees C>: override all lowest active trip points
2426 thermal.crt= [HW,ACPI]
2427 -1: disable all critical trip points in all thermal zones
2428 <degrees C>: override all critical trip points
2430 thermal.nocrt= [HW,ACPI]
2431 Set to disable actions on ACPI thermal zone
2432 critical and hot trip points.
2434 thermal.off= [HW,ACPI]
2435 1: disable ACPI thermal control
2437 thermal.psv= [HW,ACPI]
2438 -1: disable all passive trip points
2439 <degrees C>: override all passive trip points to this
2440 value
2442 thermal.tzp= [HW,ACPI]
2443 Specify global default ACPI thermal zone polling rate
2444 <deci-seconds>: poll all this frequency
2445 0: no polling (default)
2447 topology= [S390]
2448 Format: {off | on}
2449 Specify if the kernel should make use of the cpu
2450 topology informations if the hardware supports these.
2451 The scheduler will make use of these informations and
2452 e.g. base its process migration decisions on it.
2453 Default is on.
2455 tp720= [HW,PS2]
2457 tpm_suspend_pcr=[HW,TPM]
2458 Format: integer pcr id
2459 Specify that at suspend time, the tpm driver
2460 should extend the specified pcr with zeros,
2461 as a workaround for some chips which fail to
2462 flush the last written pcr on TPM_SaveState.
2463 This will guarantee that all the other pcrs
2464 are saved.
2466 trace_buf_size=nn[KMG]
2467 [FTRACE] will set tracing buffer size.
2469 trace_event=[event-list]
2470 [FTRACE] Set and start specified trace events in order
2471 to facilitate early boot debugging.
2472 See also Documentation/trace/events.txt
2474 tsc= Disable clocksource stability checks for TSC.
2475 Format: <string>
2476 [x86] reliable: mark tsc clocksource as reliable, this
2477 disables clocksource verification at runtime, as well
2478 as the stability checks done at bootup. Used to enable
2479 high-resolution timer mode on older hardware, and in
2480 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.