| blob | ac613a661f46b6c404012e8e9ffe333880e005ec |
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 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 KMEMTRACE kmemtrace is enabled.
53 LIBATA Libata driver is enabled
54 LP Printer support is enabled.
55 LOOP Loopback device support is enabled.
56 M68k M68k architecture is enabled.
57 These options have more detailed description inside of
58 Documentation/m68k/kernel-options.txt.
59 MCA MCA bus support is enabled.
60 MDA MDA console support is enabled.
61 MOUSE Appropriate mouse support is enabled.
62 MSI Message Signaled Interrupts (PCI).
63 MTD MTD (Memory Technology Device) support is enabled.
64 NET Appropriate network support is enabled.
65 NUMA NUMA support is enabled.
66 GENERIC_TIME The generic timeofday code is enabled.
67 NFS Appropriate NFS support is enabled.
68 OSS OSS sound support is enabled.
69 PV_OPS A paravirtualized kernel is enabled.
70 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
71 PARISC The PA-RISC architecture is enabled.
72 PCI PCI bus support is enabled.
73 PCIE PCI Express support is enabled.
74 PCMCIA The PCMCIA subsystem is enabled.
75 PNP Plug & Play support is enabled.
76 PPC PowerPC architecture is enabled.
77 PPT Parallel port support is enabled.
78 PS2 Appropriate PS/2 support is enabled.
79 RAM RAM disk support is enabled.
80 ROOTPLUG The example Root Plug LSM is enabled.
81 S390 S390 architecture is enabled.
82 SCSI Appropriate SCSI support is enabled.
83 A lot of drivers has their options described inside of
84 Documentation/scsi/.
85 SECURITY Different security models are enabled.
86 SELINUX SELinux support is enabled.
87 SERIAL Serial support is enabled.
88 SH SuperH architecture is enabled.
89 SMP The kernel is an SMP kernel.
90 SPARC Sparc architecture is enabled.
91 SWSUSP Software suspend (hibernation) is enabled.
92 SUSPEND System suspend states are enabled.
93 FTRACE Function tracing enabled.
94 TS Appropriate touchscreen support is enabled.
95 UMS USB Mass Storage support is enabled.
96 USB USB support is enabled.
97 USBHID USB Human Interface Device support is enabled.
98 V4L Video For Linux support is enabled.
99 VGA The VGA console has been enabled.
100 VT Virtual terminal support is enabled.
101 WDT Watchdog support is enabled.
102 XT IBM PC/XT MFM hard disk support is enabled.
103 X86-32 X86-32, aka i386 architecture is enabled.
104 X86-64 X86-64 architecture is enabled.
105 More X86-64 boot options can be found in
106 Documentation/x86/x86_64/boot-options.txt .
107 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
109 In addition, the following text indicates that the option:
111 BUGS= Relates to possible processor bugs on the said processor.
112 KNL Is a kernel start-up parameter.
113 BOOT Is a boot loader parameter.
115 Parameters denoted with BOOT are actually interpreted by the boot
116 loader, and have no meaning to the kernel directly.
117 Do not modify the syntax of boot loader parameters without extreme
118 need or coordination with <Documentation/x86/i386/boot.txt>.
120 There are also arch-specific kernel-parameters not documented here.
121 See for example <Documentation/x86/x86_64/boot-options.txt>.
123 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
124 a trailing = on the name of any parameter states that that parameter will
125 be entered as an environment variable, whereas its absence indicates that
126 it will appear as a kernel argument readable via /proc/cmdline by programs
127 running once the system is up.
129 The number of kernel parameters is not limited, but the length of the
130 complete command line (parameters including spaces etc.) is limited to
131 a fixed number of characters. This limit depends on the architecture
132 and is between 256 and 4096 characters. It is defined in the file
133 ./include/asm/setup.h as COMMAND_LINE_SIZE.
136 acpi= [HW,ACPI,X86-64,i386]
137 Advanced Configuration and Power Interface
138 Format: { force | off | ht | strict | noirq }
139 force -- enable ACPI if default was off
140 off -- disable ACPI if default was on
141 noirq -- do not use ACPI for IRQ routing
142 ht -- run only enough ACPI to enable Hyper Threading
143 strict -- Be less tolerant of platforms that are not
144 strictly ACPI specification compliant.
145 rsdt -- prefer RSDT over (default) XSDT
147 See also Documentation/power/pm.txt, pci=noacpi
149 acpi_apic_instance= [ACPI, IOAPIC]
150 Format: <int>
151 2: use 2nd APIC table, if available
152 1,0: use 1st APIC table
153 default: 0
155 acpi_sleep= [HW,ACPI] Sleep options
156 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
157 old_ordering, s4_nonvs }
158 See Documentation/power/video.txt for information on
159 s3_bios and s3_mode.
160 s3_beep is for debugging; it makes the PC's speaker beep
161 as soon as the kernel's real-mode entry point is called.
162 s4_nohwsig prevents ACPI hardware signature from being
163 used during resume from hibernation.
164 old_ordering causes the ACPI 1.0 ordering of the _PTS
165 control method, with respect to putting devices into
166 low power states, to be enforced (the ACPI 2.0 ordering
167 of _PTS is used by default).
168 s4_nonvs prevents the kernel from saving/restoring the
169 ACPI NVS memory during hibernation.
171 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
172 Format: { level | edge | high | low }
174 acpi_irq_balance [HW,ACPI]
175 ACPI will balance active IRQs
176 default in APIC mode
178 acpi_irq_nobalance [HW,ACPI]
179 ACPI will not move active IRQs (default)
180 default in PIC mode
182 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
183 use by PCI
184 Format: <irq>,<irq>...
186 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
187 Format: <irq>,<irq>...
189 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
191 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
192 Format: To spoof as Windows 98: ="Microsoft Windows"
194 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
195 acpi_osi="string1" # add string1 -- only one string
196 acpi_osi="!string2" # remove built-in string2
197 acpi_osi= # disable all strings
199 acpi_serialize [HW,ACPI] force serialization of AML methods
201 acpi_skip_timer_override [HW,ACPI]
202 Recognize and ignore IRQ0/pin2 Interrupt Override.
203 For broken nForce2 BIOS resulting in XT-PIC timer.
204 acpi_use_timer_override [HW,ACPI]
205 Use timer override. For some broken Nvidia NF5 boards
206 that require a timer override, but don't have
207 HPET
209 acpi_backlight= [HW,ACPI]
210 acpi_backlight=vendor
211 acpi_backlight=video
212 If set to vendor, prefer vendor specific driver
213 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
214 of the ACPI video.ko driver.
216 acpi_display_output= [HW,ACPI]
217 acpi_display_output=vendor
218 acpi_display_output=video
219 See above.
221 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
222 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
223 Format: <int>
224 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
225 debug output. Bits in debug_layer correspond to a
226 _COMPONENT in an ACPI source file, e.g.,
227 #define _COMPONENT ACPI_PCI_COMPONENT
228 Bits in debug_level correspond to a level in
229 ACPI_DEBUG_PRINT statements, e.g.,
230 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
231 The debug_level mask defaults to "info". See
232 Documentation/acpi/debug.txt for more information about
233 debug layers and levels.
235 Enable processor driver info messages:
236 acpi.debug_layer=0x20000000
237 Enable PCI/PCI interrupt routing info messages:
238 acpi.debug_layer=0x400000
239 Enable AML "Debug" output, i.e., stores to the Debug
240 object while interpreting AML:
241 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
242 Enable all messages related to ACPI hardware:
243 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
245 Some values produce so much output that the system is
246 unusable. The "log_buf_len" parameter may be useful
247 if you need to capture more output.
249 acpi.power_nocheck= [HW,ACPI]
250 Format: 1/0 enable/disable the check of power state.
251 On some bogus BIOS the _PSC object/_STA object of
252 power resource can't return the correct device power
253 state. In such case it is unneccessary to check its
254 power state again in power transition.
255 1 : disable the power state check
257 acpi_pm_good [X86-32,X86-64]
258 Override the pmtimer bug detection: force the kernel
259 to assume that this machine's pmtimer latches its value
260 and always returns good values.
262 agp= [AGP]
263 { off | try_unsupported }
264 off: disable AGP support
265 try_unsupported: try to drive unsupported chipsets
266 (may crash computer or cause data corruption)
268 enable_timer_pin_1 [i386,x86-64]
269 Enable PIN 1 of APIC timer
270 Can be useful to work around chipset bugs
271 (in particular on some ATI chipsets).
272 The kernel tries to set a reasonable default.
274 disable_timer_pin_1 [i386,x86-64]
275 Disable PIN 1 of APIC timer
276 Can be useful to work around chipset bugs.
278 ad1848= [HW,OSS]
279 Format: <io>,<irq>,<dma>,<dma2>,<type>
281 advansys= [HW,SCSI]
282 See header of drivers/scsi/advansys.c.
284 advwdt= [HW,WDT] Advantech WDT
285 Format: <iostart>,<iostop>
287 aedsp16= [HW,OSS] Audio Excel DSP 16
288 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
289 See also header of sound/oss/aedsp16.c.
291 aha152x= [HW,SCSI]
292 See Documentation/scsi/aha152x.txt.
294 aha1542= [HW,SCSI]
295 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
297 aic7xxx= [HW,SCSI]
298 See Documentation/scsi/aic7xxx.txt.
300 aic79xx= [HW,SCSI]
301 See Documentation/scsi/aic79xx.txt.
303 amd_iommu= [HW,X86-84]
304 Pass parameters to the AMD IOMMU driver in the system.
305 Possible values are:
306 isolate - enable device isolation (each device, as far
307 as possible, will get its own protection
308 domain) [default]
309 share - put every device behind one IOMMU into the
310 same protection domain
311 fullflush - enable flushing of IO/TLB entries when
312 they are unmapped. Otherwise they are
313 flushed before they will be reused, which
314 is a lot of faster
316 amd_iommu_size= [HW,X86-64]
317 Define the size of the aperture for the AMD IOMMU
318 driver. Possible values are:
319 '32M', '64M' (default), '128M', '256M', '512M', '1G'
321 amijoy.map= [HW,JOY] Amiga joystick support
322 Map of devices attached to JOY0DAT and JOY1DAT
323 Format: <a>,<b>
324 See also Documentation/kernel/input/joystick.txt
326 analog.map= [HW,JOY] Analog joystick and gamepad support
327 Specifies type or capabilities of an analog joystick
328 connected to one of 16 gameports
329 Format: <type1>,<type2>,..<type16>
331 apc= [HW,SPARC]
332 Power management functions (SPARCstation-4/5 + deriv.)
333 Format: noidle
334 Disable APC CPU standby support. SPARCstation-Fox does
335 not play well with APC CPU idle - disable it if you have
336 APC and your system crashes randomly.
338 apic= [APIC,i386] Advanced Programmable Interrupt Controller
339 Change the output verbosity whilst booting
340 Format: { quiet (default) | verbose | debug }
341 Change the amount of debugging information output
342 when initialising the APIC and IO-APIC components.
344 apm= [APM] Advanced Power Management
345 See header of arch/x86/kernel/apm_32.c.
347 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
348 Format: <io>,<irq>,<nodeID>
350 ataflop= [HW,M68k]
352 atarimouse= [HW,MOUSE] Atari Mouse
354 atascsi= [HW,SCSI] Atari SCSI
356 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
357 EzKey and similar keyboards
359 atkbd.reset= [HW] Reset keyboard during initialization
361 atkbd.set= [HW] Select keyboard code set
362 Format: <int> (2 = AT (default), 3 = PS/2)
364 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
365 keyboards
367 atkbd.softraw= [HW] Choose between synthetic and real raw mode
368 Format: <bool> (0 = real, 1 = synthetic (default))
370 atkbd.softrepeat= [HW]
371 Use software keyboard repeat
373 autotest [IA64]
375 baycom_epp= [HW,AX25]
376 Format: <io>,<mode>
378 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
379 Format: <io>,<mode>
380 See header of drivers/net/hamradio/baycom_par.c.
382 baycom_ser_fdx= [HW,AX25]
383 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
384 Format: <io>,<irq>,<mode>[,<baud>]
385 See header of drivers/net/hamradio/baycom_ser_fdx.c.
387 baycom_ser_hdx= [HW,AX25]
388 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
389 Format: <io>,<irq>,<mode>
390 See header of drivers/net/hamradio/baycom_ser_hdx.c.
392 boot_delay= Milliseconds to delay each printk during boot.
393 Values larger than 10 seconds (10000) are changed to
394 no delay (0).
395 Format: integer
397 bootmem_debug [KNL] Enable bootmem allocator debug messages.
399 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
400 bttv.radio= Most important insmod options are available as
401 kernel args too.
402 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
403 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405 BusLogic= [HW,SCSI]
406 See drivers/scsi/BusLogic.c, comment before function
407 BusLogic_ParseDriverOptions().
409 c101= [NET] Moxa C101 synchronous serial card
411 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
412 Sometimes CPU hardware bugs make them report the cache
413 size incorrectly. The kernel will attempt work arounds
414 to fix known problems, but for some CPUs it is not
415 possible to determine what the correct size should be.
416 This option provides an override for these situations.
418 security= [SECURITY] Choose a security module to enable at boot.
419 If this boot parameter is not specified, only the first
420 security module asking for security registration will be
421 loaded. An invalid security module name will be treated
422 as if no module has been chosen.
424 capability.disable=
425 [SECURITY] Disable capabilities. This would normally
426 be used only if an alternative security model is to be
427 configured. Potentially dangerous and should only be
428 used if you are entirely sure of the consequences.
430 ccw_timeout_log [S390]
431 See Documentation/s390/CommonIO for details.
433 cgroup_disable= [KNL] Disable a particular controller
434 Format: {name of the controller(s) to disable}
435 {Currently supported controllers - "memory"}
437 checkreqprot [SELINUX] Set initial checkreqprot flag value.
438 Format: { "0" | "1" }
439 See security/selinux/Kconfig help text.
440 0 -- check protection applied by kernel (includes
441 any implied execute protection).
442 1 -- check protection requested by application.
443 Default value is set via a kernel config option.
444 Value can be changed at runtime via
445 /selinux/checkreqprot.
447 cio_ignore= [S390]
448 See Documentation/s390/CommonIO for details.
450 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
451 [Deprecated]
452 Forces specified clocksource (if available) to be used
453 when calculating gettimeofday(). If specified
454 clocksource is not available, it defaults to PIT.
455 Format: { pit | tsc | cyclone | pmtmr }
457 clocksource= [GENERIC_TIME] Override the default clocksource
458 Format: <string>
459 Override the default clocksource and use the clocksource
460 with the name specified.
461 Some clocksource names to choose from, depending on
462 the platform:
463 [all] jiffies (this is the base, fallback clocksource)
464 [ACPI] acpi_pm
465 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
466 pxa_timer,timer3,32k_counter,timer0_1
467 [AVR32] avr32
468 [X86-32] pit,hpet,tsc,vmi-timer;
469 scx200_hrt on Geode; cyclone on IBM x440
470 [MIPS] MIPS
471 [PARISC] cr16
472 [S390] tod
473 [SH] SuperH
474 [SPARC64] tick
475 [X86-64] hpet,tsc
477 clearcpuid=BITNUM [X86]
478 Disable CPUID feature X for the kernel. See
479 arch/x86/include/asm/cpufeature.h for the valid bit
480 numbers. Note the Linux specific bits are not necessarily
481 stable over kernel options, but the vendor specific
482 ones should be.
483 Also note that user programs calling CPUID directly
484 or using the feature without checking anything
485 will still see it. This just prevents it from
486 being used by the kernel or shown in /proc/cpuinfo.
487 Also note the kernel might malfunction if you disable
488 some critical bits.
490 code_bytes [IA32/X86_64] How many bytes of object code to print
491 in an oops report.
492 Range: 0 - 8192
493 Default: 64
495 hpet= [X86-32,HPET] option to control HPET usage
496 Format: { enable (default) | disable | force }
497 disable: disable HPET and use PIT instead
498 force: allow force enabled of undocumented chips (ICH4,
499 VIA, nVidia)
501 com20020= [HW,NET] ARCnet - COM20020 chipset
502 Format:
503 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
505 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
506 Format: <io>[,<irq>]
508 com90xx= [HW,NET]
509 ARCnet - COM90xx chipset (memory-mapped buffers)
510 Format: <io>[,<irq>[,<memstart>]]
512 condev= [HW,S390] console device
513 conmode=
515 console= [KNL] Output console device and options.
517 tty<n> Use the virtual console device <n>.
519 ttyS<n>[,options]
520 ttyUSB0[,options]
521 Use the specified serial port. The options are of
522 the form "bbbbpnf", where "bbbb" is the baud rate,
523 "p" is parity ("n", "o", or "e"), "n" is number of
524 bits, and "f" is flow control ("r" for RTS or
525 omit it). Default is "9600n8".
527 See Documentation/serial-console.txt for more
528 information. See
529 Documentation/networking/netconsole.txt for an
530 alternative.
532 uart[8250],io,<addr>[,options]
533 uart[8250],mmio,<addr>[,options]
534 Start an early, polled-mode console on the 8250/16550
535 UART at the specified I/O port or MMIO address,
536 switching to the matching ttyS device later. The
537 options are the same as for ttyS, above.
539 If the device connected to the port is not a TTY but a braille
540 device, prepend "brl," before the device type, for instance
541 console=brl,ttyS0
542 For now, only VisioBraille is supported.
544 earlycon= [KNL] Output early console device and options.
545 uart[8250],io,<addr>[,options]
546 uart[8250],mmio,<addr>[,options]
547 Start an early, polled-mode console on the 8250/16550
548 UART at the specified I/O port or MMIO address.
549 The options are the same as for ttyS, above.
551 no_console_suspend
552 [HW] Never suspend the console
553 Disable suspending of consoles during suspend and
554 hibernate operations. Once disabled, debugging
555 messages can reach various consoles while the rest
556 of the system is being put to sleep (ie, while
557 debugging driver suspend/resume hooks). This may
558 not work reliably with all consoles, but is known
559 to work with serial and VGA consoles.
561 coredump_filter=
562 [KNL] Change the default value for
563 /proc/<pid>/coredump_filter.
564 See also Documentation/filesystems/proc.txt.
566 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
567 Format:
568 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
570 crashkernel=nn[KMG]@ss[KMG]
571 [KNL] Reserve a chunk of physical memory to
572 hold a kernel to switch to with kexec on panic.
574 crashkernel=range1:size1[,range2:size2,...][@offset]
575 [KNL] Same as above, but depends on the memory
576 in the running system. The syntax of range is
577 start-[end] where start and end are both
578 a memory unit (amount[KMG]). See also
579 Documentation/kdump/kdump.txt for a example.
581 cs4232= [HW,OSS]
582 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
584 cs89x0_dma= [HW,NET]
585 Format: <dma>
587 cs89x0_media= [HW,NET]
588 Format: { rj45 | aui | bnc }
590 dasd= [HW,NET]
591 See header of drivers/s390/block/dasd_devmap.c.
593 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
594 (one device per port)
595 Format: <port#>,<type>
596 See also Documentation/input/joystick-parport.txt
598 debug [KNL] Enable kernel debugging (events log level).
600 debug_locks_verbose=
601 [KNL] verbose self-tests
602 Format=<0|1>
603 Print debugging info while doing the locking API
604 self-tests.
605 We default to 0 (no extra messages), setting it to
606 1 will print _a lot_ more information - normally
607 only useful to kernel developers.
609 debug_objects [KNL] Enable object debugging
611 debugpat [X86] Enable PAT debugging
613 decnet.addr= [HW,NET]
614 Format: <area>[,<node>]
615 See also Documentation/networking/decnet.txt.
617 vt.default_blu= [VT]
618 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
619 Change the default blue palette of the console.
620 This is a 16-member array composed of values
621 ranging from 0-255.
623 vt.default_grn= [VT]
624 Format: <green0>,<green1>,<green2>,...,<green15>
625 Change the default green palette of the console.
626 This is a 16-member array composed of values
627 ranging from 0-255.
629 vt.default_red= [VT]
630 Format: <red0>,<red1>,<red2>,...,<red15>
631 Change the default red palette of the console.
632 This is a 16-member array composed of values
633 ranging from 0-255.
635 vt.default_utf8=
636 [VT]
637 Format=<0|1>
638 Set system-wide default UTF-8 mode for all tty's.
639 Default is 1, i.e. UTF-8 mode is enabled for all
640 newly opened terminals.
642 dhash_entries= [KNL]
643 Set number of hash buckets for dentry cache.
645 digi= [HW,SERIAL]
646 IO parameters + enable/disable command.
648 digiepca= [HW,SERIAL]
649 See drivers/char/README.epca and
650 Documentation/serial/digiepca.txt.
652 disable_mtrr_cleanup [X86]
653 enable_mtrr_cleanup [X86]
654 The kernel tries to adjust MTRR layout from continuous
655 to discrete, to make X server driver able to add WB
656 entry later. This parameter enables/disables that.
658 mtrr_chunk_size=nn[KMG] [X86]
659 used for mtrr cleanup. It is largest continous chunk
660 that could hold holes aka. UC entries.
662 mtrr_gran_size=nn[KMG] [X86]
663 Used for mtrr cleanup. It is granularity of mtrr block.
664 Default is 1.
665 Large value could prevent small alignment from
666 using up MTRRs.
668 mtrr_spare_reg_nr=n [X86]
669 Format: <integer>
670 Range: 0,7 : spare reg number
671 Default : 1
672 Used for mtrr cleanup. It is spare mtrr entries number.
673 Set to 2 or more if your graphical card needs more.
675 disable_mtrr_trim [X86, Intel and AMD only]
676 By default the kernel will trim any uncacheable
677 memory out of your available memory pool based on
678 MTRR settings. This parameter disables that behavior,
679 possibly causing your machine to run very slowly.
681 dmasound= [HW,OSS] Sound subsystem buffers
683 dscc4.setup= [NET]
685 dtc3181e= [HW,SCSI]
687 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
688 earlyprintk=vga
689 earlyprintk=serial[,ttySn[,baudrate]]
690 earlyprintk=dbgp
692 Append ",keep" to not disable it when the real console
693 takes over.
695 Only vga or serial or usb debug port at a time.
697 Currently only ttyS0 and ttyS1 are supported.
699 Interaction with the standard serial driver is not
700 very good.
702 The VGA output is eventually overwritten by the real
703 console.
705 eata= [HW,SCSI]
707 edd= [EDD]
708 Format: {"off" | "on" | "skip[mbr]"}
710 eisa_irq_edge= [PARISC,HW]
711 See header of drivers/parisc/eisa.c.
713 elanfreq= [X86-32]
714 See comment before function elanfreq_setup() in
715 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
717 elevator= [IOSCHED]
718 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
719 See Documentation/block/as-iosched.txt and
720 Documentation/block/deadline-iosched.txt for details.
722 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
723 Specifies physical address of start of kernel core
724 image elf header. Generally kexec loader will
725 pass this option to capture kernel.
726 See Documentation/kdump/kdump.txt for details.
728 enforcing [SELINUX] Set initial enforcing status.
729 Format: {"0" | "1"}
730 See security/selinux/Kconfig help text.
731 0 -- permissive (log only, no denials).
732 1 -- enforcing (deny and log).
733 Default value is 0.
734 Value can be changed at runtime via /selinux/enforce.
736 es1371= [HW,OSS]
737 Format: <spdif>,[<nomix>,[<amplifier>]]
738 See also header of sound/oss/es1371.c.
740 ether= [HW,NET] Ethernet cards parameters
741 This option is obsoleted by the "netdev=" option, which
742 has equivalent usage. See its documentation for details.
744 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
745 Format: <io>[,<irq>]
747 failslab=
748 fail_page_alloc=
749 fail_make_request=[KNL]
750 General fault injection mechanism.
751 Format: <interval>,<probability>,<space>,<times>
752 See also /Documentation/fault-injection/.
754 fd_mcs= [HW,SCSI]
755 See header of drivers/scsi/fd_mcs.c.
757 fdomain= [HW,SCSI]
758 See header of drivers/scsi/fdomain.c.
760 floppy= [HW]
761 See Documentation/blockdev/floppy.txt.
763 force_pal_cache_flush
764 [IA-64] Avoid check_sal_cache_flush which may hang on
765 buggy SAL_CACHE_FLUSH implementations. Using this
766 parameter will force ia64_sal_cache_flush to call
767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
769 ftrace=[tracer]
770 [ftrace] will set and start the specified tracer
771 as early as possible in order to facilitate early
772 boot debugging.
774 ftrace_dump_on_oops
775 [ftrace] will dump the trace buffers on oops.
777 gamecon.map[2|3]=
778 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
779 support via parallel port (up to 5 devices per port)
780 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
781 See also Documentation/input/joystick-parport.txt
783 gamma= [HW,DRM]
785 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
786 Format: off | on
787 default: on
789 gdth= [HW,SCSI]
790 See header of drivers/scsi/gdth.c.
792 gpt [EFI] Forces disk with valid GPT signature but
793 invalid Protective MBR to be treated as GPT.
795 gvp11= [HW,SCSI]
797 hashdist= [KNL,NUMA] Large hashes allocated during boot
798 are distributed across NUMA nodes. Defaults on
799 for IA-64, off otherwise.
800 Format: 0 | 1 (for off | on)
802 hcl= [IA-64] SGI's Hardware Graph compatibility layer
804 hd= [EIDE] (E)IDE hard drive subsystem geometry
805 Format: <cyl>,<head>,<sect>
807 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
808 size of <nn>. This works even on boxes that have no
809 highmem otherwise. This also works to reduce highmem
810 size on bigger boxes.
812 highres= [KNL] Enable/disable high resolution timer mode.
813 Valid parameters: "on", "off"
814 Default: "on"
816 hisax= [HW,ISDN]
817 See Documentation/isdn/README.HiSax.
819 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
820 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
821 On x86-64 and powerpc, this option can be specified
822 multiple times interleaved with hugepages= to reserve
823 huge pages of different sizes. Valid pages sizes on
824 x86-64 are 2M (when the CPU supports "pse") and 1G
825 (when the CPU supports the "pdpe1gb" cpuinfo flag)
826 Note that 1GB pages can only be allocated at boot time
827 using hugepages= and not freed afterwards.
828 default_hugepagesz=
829 [same as hugepagesz=] The size of the default
830 HugeTLB page size. This is the size represented by
831 the legacy /proc/ hugepages APIs, used for SHM, and
832 default size when mounting hugetlbfs filesystems.
833 Defaults to the default architecture's huge page size
834 if not specified.
836 hlt [BUGS=ARM,SH]
838 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
839 terminal devices. Valid values: 0..8
841 i8042.debug [HW] Toggle i8042 debug mode
842 i8042.direct [HW] Put keyboard port into non-translated mode
843 i8042.dumbkbd [HW] Pretend that controller can only read data from
844 keyboard and cannot control its state
845 (Don't attempt to blink the leds)
846 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
847 i8042.nokbd [HW] Don't check/create keyboard port
848 i8042.noloop [HW] Disable the AUX Loopback command while probing
849 for the AUX port
850 i8042.nomux [HW] Don't check presence of an active multiplexing
851 controller
852 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
853 controllers
854 i8042.panicblink=
855 [HW] Frequency with which keyboard LEDs should blink
856 when kernel panics (default is 0.5 sec)
857 i8042.reset [HW] Reset the controller during init and cleanup
858 i8042.unlock [HW] Unlock (ignore) the keylock
860 i810= [HW,DRM]
862 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
863 indicates that the driver is running on unsupported
864 hardware.
865 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
866 does not match list of supported models.
867 i8k.power_status
868 [HW] Report power status in /proc/i8k
869 (disabled by default)
870 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
871 capability is set.
873 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
874 See Documentation/mca.txt.
876 icn= [HW,ISDN]
877 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
879 ide= [HW] (E)IDE subsystem
880 Format: ide=nodma or ide=doubler
881 See Documentation/ide/ide.txt.
883 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
884 See Documentation/ide/ide.txt.
886 idle= [X86]
887 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
888 Poll forces a polling idle loop that can slightly
889 improve the performance of waking up a idle CPU, but
890 will use a lot of power and make the system run hot.
891 Not recommended.
892 idle=mwait: On systems which support MONITOR/MWAIT but
893 the kernel chose to not use it because it doesn't save
894 as much power as a normal idle loop, use the
895 MONITOR/MWAIT idle loop anyways. Performance should be
896 the same as idle=poll.
897 idle=halt: Halt is forced to be used for CPU idle.
898 In such case C2/C3 won't be used again.
899 idle=nomwait: Disable mwait for CPU C-states
901 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
902 Claim all unknown PCI IDE storage controllers.
904 ignore_loglevel [KNL]
905 Ignore loglevel setting - this will print /all/
906 kernel messages to the console. Useful for debugging.
908 ihash_entries= [KNL]
909 Set number of hash buckets for inode cache.
911 in2000= [HW,SCSI]
912 See header of drivers/scsi/in2000.c.
914 init= [KNL]
915 Format: <full_path>
916 Run specified binary instead of /sbin/init as init
917 process.
919 initcall_debug [KNL] Trace initcalls as they are executed. Useful
920 for working out where the kernel is dying during
921 startup.
923 initrd= [BOOT] Specify the location of the initial ramdisk
925 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
926 Format: <irq>
928 inttest= [IA64]
930 iomem= Disable strict checking of access to MMIO memory
931 strict regions from userspace.
932 relaxed
934 iommu= [x86]
935 off
936 force
937 noforce
938 biomerge
939 panic
940 nopanic
941 merge
942 nomerge
943 forcesac
944 soft
947 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
948 off
949 Disable intel iommu driver.
950 igfx_off [Default Off]
951 By default, gfx is mapped as normal device. If a gfx
952 device has a dedicated DMAR unit, the DMAR unit is
953 bypassed by not enabling DMAR with this option. In
954 this case, gfx device will use physical address for
955 DMA.
956 forcedac [x86_64]
957 With this option iommu will not optimize to look
958 for io virtual address below 32 bit forcing dual
959 address cycle on pci bus for cards supporting greater
960 than 32 bit addressing. The default is to look
961 for translation below 32 bit and if not available
962 then look in the higher range.
963 strict [Default Off]
964 With this option on every unmap_single operation will
965 result in a hardware IOTLB flush operation as opposed
966 to batching them for performance.
968 io_delay= [X86-32,X86-64] I/O delay method
969 0x80
970 Standard port 0x80 based delay
971 0xed
972 Alternate port 0xed based delay (needed on some systems)
973 udelay
974 Simple two microseconds delay
975 none
976 No delay
978 io7= [HW] IO7 for Marvel based alpha systems
979 See comment before marvel_specify_io7 in
980 arch/alpha/kernel/core_marvel.c.
982 ip= [IP_PNP]
983 See Documentation/filesystems/nfsroot.txt.
985 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
986 See comment before ip2_setup() in
987 drivers/char/ip2/ip2base.c.
989 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
990 See header of drivers/scsi/ips.c.
992 ports= [IP_VS_FTP] IPVS ftp helper module
993 Default is 21.
994 Up to 8 (IP_VS_APP_MAX_PORTS) ports
995 may be specified.
996 Format: <port>,<port>....
998 irqfixup [HW]
999 When an interrupt is not handled search all handlers
1000 for it. Intended to get systems with badly broken
1001 firmware running.
1003 irqpoll [HW]
1004 When an interrupt is not handled search all handlers
1005 for it. Also check all handlers each timer
1006 interrupt. Intended to get systems with badly broken
1007 firmware running.
1009 isapnp= [ISAPNP]
1010 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1012 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1013 Format:
1014 <cpu number>,...,<cpu number>
1015 or
1016 <cpu number>-<cpu number>
1017 (must be a positive range in ascending order)
1018 or a mixture
1019 <cpu number>,...,<cpu number>-<cpu number>
1021 This option can be used to specify one or more CPUs
1022 to isolate from the general SMP balancing and scheduling
1023 algorithms. You can move a process onto or off an
1024 "isolated" CPU via the CPU affinity syscalls or cpuset.
1025 <cpu number> begins at 0 and the maximum value is
1026 "number of CPUs in system - 1".
1028 This option is the preferred way to isolate CPUs. The
1029 alternative -- manually setting the CPU mask of all
1030 tasks in the system -- can cause problems and
1031 suboptimal load balancer performance.
1033 iucv= [HW,NET]
1035 js= [HW,JOY] Analog joystick
1036 See Documentation/input/joystick.txt.
1038 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1039 specifies the amount of memory usable by the kernel
1040 for non-movable allocations. The requested amount is
1041 spread evenly throughout all nodes in the system. The
1042 remaining memory in each node is used for Movable
1043 pages. In the event, a node is too small to have both
1044 kernelcore and Movable pages, kernelcore pages will
1045 take priority and other nodes will have a larger number
1046 of kernelcore pages. The Movable zone is used for the
1047 allocation of pages that may be reclaimed or moved
1048 by the page migration subsystem. This means that
1049 HugeTLB pages may not be allocated from this zone.
1050 Note that allocations like PTEs-from-HighMem still
1051 use the HighMem zone if it exists, and the Normal
1052 zone if it does not.
1054 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1055 Controls whether kmemtrace is enabled
1056 at boot-time.
1058 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1059 subbufs kmemtrace's relay channel has. Set this
1060 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1061 you experience buffer overruns.
1063 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1064 is similar to kernelcore except it specifies the
1065 amount of memory used for migratable allocations.
1066 If both kernelcore and movablecore is specified,
1067 then kernelcore will be at *least* the specified
1068 value but may be more. If movablecore on its own
1069 is specified, the administrator must be careful
1070 that the amount of memory usable for all allocations
1071 is not too small.
1073 keepinitrd [HW,ARM]
1075 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1076 in oops dumps.
1078 kgdboc= [HW] kgdb over consoles.
1079 Requires a tty driver that supports console polling.
1080 (only serial suported for now)
1081 Format: <serial_device>[,baud]
1083 kmac= [MIPS] korina ethernet MAC address.
1084 Configure the RouterBoard 532 series on-chip
1085 Ethernet adapter MAC address.
1087 l2cr= [PPC]
1089 l3cr= [PPC]
1091 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1092 disabled it.
1094 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer
1095 in C2 power state.
1097 libata.dma= [LIBATA] DMA control
1098 libata.dma=0 Disable all PATA and SATA DMA
1099 libata.dma=1 PATA and SATA Disk DMA only
1100 libata.dma=2 ATAPI (CDROM) DMA only
1101 libata.dma=4 Compact Flash DMA only
1102 Combinations also work, so libata.dma=3 enables DMA
1103 for disks and CDROMs, but not CFs.
1105 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1106 when set.
1107 Format: <int>
1109 libata.force= [LIBATA] Force configurations. The format is comma
1110 separated list of "[ID:]VAL" where ID is
1111 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1112 matching port, link or device. Basically, it matches
1113 the ATA ID string printed on console by libata. If
1114 the whole ID part is omitted, the last PORT and DEVICE
1115 values are used. If ID hasn't been specified yet, the
1116 configuration applies to all ports, links and devices.
1118 If only DEVICE is omitted, the parameter applies to
1119 the port and all links and devices behind it. DEVICE
1120 number of 0 either selects the first device or the
1121 first fan-out link behind PMP device. It does not
1122 select the host link. DEVICE number of 15 selects the
1123 host link and device attached to it.
1125 The VAL specifies the configuration to force. As long
1126 as there's no ambiguity shortcut notation is allowed.
1127 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1128 The following configurations can be forced.
1130 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1131 Any ID with matching PORT is used.
1133 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1135 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1136 udma[/][16,25,33,44,66,100,133] notation is also
1137 allowed.
1139 * [no]ncq: Turn on or off NCQ.
1141 * nohrst, nosrst, norst: suppress hard, soft
1142 and both resets.
1144 If there are multiple matching configurations changing
1145 the same attribute, the last one is used.
1147 lmb=debug [KNL] Enable lmb debug messages.
1149 load_ramdisk= [RAM] List of ramdisks to load from floppy
1150 See Documentation/blockdev/ramdisk.txt.
1152 lockd.nlm_grace_period=P [NFS] Assign grace period.
1153 Format: <integer>
1155 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1156 Format: <integer>
1158 lockd.nlm_timeout=T [NFS] Assign timeout value.
1159 Format: <integer>
1161 lockd.nlm_udpport=M [NFS] Assign UDP port.
1162 Format: <integer>
1164 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1165 Format: <irq>
1167 loglevel= All Kernel Messages with a loglevel smaller than the
1168 console loglevel will be printed to the console. It can
1169 also be changed with klogd or other programs. The
1170 loglevels are defined as follows:
1172 0 (KERN_EMERG) system is unusable
1173 1 (KERN_ALERT) action must be taken immediately
1174 2 (KERN_CRIT) critical conditions
1175 3 (KERN_ERR) error conditions
1176 4 (KERN_WARNING) warning conditions
1177 5 (KERN_NOTICE) normal but significant condition
1178 6 (KERN_INFO) informational
1179 7 (KERN_DEBUG) debug-level messages
1181 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1182 Format: { n | nk | nM }
1183 n must be a power of two. The default size
1184 is set in the kernel config file.
1186 logo.nologo [FB] Disables display of the built-in Linux logo.
1187 This may be used to provide more screen space for
1188 kernel log messages and is useful when debugging
1189 kernel boot problems.
1191 lp=0 [LP] Specify parallel ports to use, e.g,
1192 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1193 lp=reset first parallel port). 'lp=0' disables the
1194 lp=auto printer driver. 'lp=reset' (which can be
1195 specified in addition to the ports) causes
1196 attached printers to be reset. Using
1197 lp=port1,port2,... specifies the parallel ports
1198 to associate lp devices with, starting with
1199 lp0. A port specification may be 'none' to skip
1200 that lp device, or a parport name such as
1201 'parport0'. Specifying 'lp=auto' instead of a
1202 port specification list means that device IDs
1203 from each port should be examined, to see if
1204 an IEEE 1284-compliant printer is attached; if
1205 so, the driver will manage that printer.
1206 See also header of drivers/char/lp.c.
1208 lpj=n [KNL]
1209 Sets loops_per_jiffy to given constant, thus avoiding
1210 time-consuming boot-time autodetection (up to 250 ms per
1211 CPU). 0 enables autodetection (default). To determine
1212 the correct value for your kernel, boot with normal
1213 autodetection and see what value is printed. Note that
1214 on SMP systems the preset will be applied to all CPUs,
1215 which is likely to cause problems if your CPUs need
1216 significantly divergent settings. An incorrect value
1217 will cause delays in the kernel to be wrong, leading to
1218 unpredictable I/O errors and other breakage. Although
1219 unlikely, in the extreme case this might damage your
1220 hardware.
1222 ltpc= [NET]
1223 Format: <io>,<irq>,<dma>
1225 mac5380= [HW,SCSI] Format:
1226 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1228 machvec= [IA64] Force the use of a particular machine-vector
1229 (machvec) in a generic kernel.
1230 Example: machvec=hpzx1_swiotlb
1232 max_loop= [LOOP] Maximum number of loopback devices that can
1233 be mounted
1234 Format: <1-256>
1236 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1237 should make use of. maxcpus=n : n >= 0 limits the
1238 kernel to using 'n' processors. n=0 is a special case,
1239 it is equivalent to "nosmp", which also disables
1240 the IO APIC.
1242 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1243 or equal to this physical address is ignored.
1245 max_luns= [SCSI] Maximum number of LUNs to probe.
1246 Should be between 1 and 2^32-1.
1248 max_report_luns=
1249 [SCSI] Maximum number of LUNs received.
1250 Should be between 1 and 16384.
1252 mcatest= [IA-64]
1254 mce [X86-32] Machine Check Exception
1256 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1258 md= [HW] RAID subsystems devices and level
1259 See Documentation/md.txt.
1261 mdacon= [MDA]
1262 Format: <first>,<last>
1263 Specifies range of consoles to be captured by the MDA.
1265 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1266 Amount of memory to be used when the kernel is not able
1267 to see the whole system memory or for test.
1268 [X86-32] Use together with memmap= to avoid physical
1269 address space collisions. Without memmap= PCI devices
1270 could be placed at addresses belonging to unused RAM.
1272 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1273 memory.
1275 memchunk=nn[KMG]
1276 [KNL,SH] Allow user to override the default size for
1277 per-device physically contiguous DMA buffers.
1279 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1280 E820 memory map, as specified by the user.
1281 Such memmap=exactmap lines can be constructed based on
1282 BIOS output or other requirements. See the memmap=nn@ss
1283 option description.
1285 memmap=nn[KMG]@ss[KMG]
1286 [KNL] Force usage of a specific region of memory
1287 Region of memory to be used, from ss to ss+nn.
1289 memmap=nn[KMG]#ss[KMG]
1290 [KNL,ACPI] Mark specific memory as ACPI data.
1291 Region of memory to be used, from ss to ss+nn.
1293 memmap=nn[KMG]$ss[KMG]
1294 [KNL,ACPI] Mark specific memory as reserved.
1295 Region of memory to be used, from ss to ss+nn.
1296 Example: Exclude memory from 0x18690000-0x1869ffff
1297 memmap=64K$0x18690000
1298 or
1299 memmap=0x10000$0x18690000
1301 memory_corruption_check=0/1 [X86]
1302 Some BIOSes seem to corrupt the first 64k of
1303 memory when doing things like suspend/resume.
1304 Setting this option will scan the memory
1305 looking for corruption. Enabling this will
1306 both detect corruption and prevent the kernel
1307 from using the memory being corrupted.
1308 However, its intended as a diagnostic tool; if
1309 repeatable BIOS-originated corruption always
1310 affects the same memory, you can use memmap=
1311 to prevent the kernel from using that memory.
1313 memory_corruption_check_size=size [X86]
1314 By default it checks for corruption in the low
1315 64k, making this memory unavailable for normal
1316 use. Use this parameter to scan for
1317 corruption in more or less memory.
1319 memory_corruption_check_period=seconds [X86]
1320 By default it checks for corruption every 60
1321 seconds. Use this parameter to check at some
1322 other rate. 0 disables periodic checking.
1324 memtest= [KNL,X86] Enable memtest
1325 Format: <integer>
1326 range: 0,4 : pattern number
1327 default : 0 <disable>
1329 meye.*= [HW] Set MotionEye Camera parameters
1330 See Documentation/video4linux/meye.txt.
1332 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1333 Multi-Function General Purpose Timers on AMD Geode
1334 platforms.
1336 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1337 the BIOS has incorrectly applied a workaround. TinyBIOS
1338 version 0.98 is known to be affected, 0.99 fixes the
1339 problem by letting the user disable the workaround.
1341 mga= [HW,DRM]
1343 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1344 physical address is ignored.
1346 mminit_loglevel=
1347 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1348 parameter allows control of the logging verbosity for
1349 the additional memory initialisation checks. A value
1350 of 0 disables mminit logging and a level of 4 will
1351 log everything. Information is printed at KERN_DEBUG
1352 so loglevel=8 may also need to be specified.
1354 mousedev.tap_time=
1355 [MOUSE] Maximum time between finger touching and
1356 leaving touchpad surface for touch to be considered
1357 a tap and be reported as a left button click (for
1358 touchpads working in absolute mode only).
1359 Format: <msecs>
1360 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1361 reporting absolute coordinates, such as tablets
1362 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1363 reporting absolute coordinates, such as tablets
1365 mpu401= [HW,OSS]
1366 Format: <io>,<irq>
1368 MTD_Partition= [MTD]
1369 Format: <name>,<region-number>,<size>,<offset>
1371 MTD_Region= [MTD] Format:
1372 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1374 mtdparts= [MTD]
1375 See drivers/mtd/cmdlinepart.c.
1377 mtdset= [ARM]
1378 ARM/S3C2412 JIVE boot control
1380 See arch/arm/mach-s3c2412/mach-jive.c
1382 mtouchusb.raw_coordinates=
1383 [HW] Make the MicroTouch USB driver use raw coordinates
1384 ('y', default) or cooked coordinates ('n')
1386 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1388 NCR_D700= [HW,SCSI]
1389 See header of drivers/scsi/NCR_D700.c.
1391 ncr5380= [HW,SCSI]
1393 ncr53c400= [HW,SCSI]
1395 ncr53c400a= [HW,SCSI]
1397 ncr53c406a= [HW,SCSI]
1399 ncr53c8xx= [HW,SCSI]
1401 netdev= [NET] Network devices parameters
1402 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1403 Note that mem_start is often overloaded to mean
1404 something different and driver-specific.
1405 This usage is only documented in each driver source
1406 file if at all.
1408 nf_conntrack.acct=
1409 [NETFILTER] Enable connection tracking flow accounting
1410 0 to disable accounting
1411 1 to enable accounting
1412 Default value depends on CONFIG_NF_CT_ACCT that is
1413 going to be removed in 2.6.29.
1415 nfsaddrs= [NFS]
1416 See Documentation/filesystems/nfsroot.txt.
1418 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1419 See Documentation/filesystems/nfsroot.txt.
1421 nfs.callback_tcpport=
1422 [NFS] set the TCP port on which the NFSv4 callback
1423 channel should listen.
1425 nfs.idmap_cache_timeout=
1426 [NFS] set the maximum lifetime for idmapper cache
1427 entries.
1429 nfs.enable_ino64=
1430 [NFS] enable 64-bit inode numbers.
1431 If zero, the NFS client will fake up a 32-bit inode
1432 number for the readdir() and stat() syscalls instead
1433 of returning the full 64-bit number.
1434 The default is to return 64-bit inode numbers.
1436 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1437 when a NMI is triggered.
1438 Format: [state][,regs][,debounce][,die]
1440 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1441 Format: [panic,][num]
1442 Valid num: 0,1,2
1443 0 - turn nmi_watchdog off
1444 1 - use the IO-APIC timer for the NMI watchdog
1445 2 - use the local APIC for the NMI watchdog using
1446 a performance counter. Note: This will use one performance
1447 counter and the local APIC's performance vector.
1448 When panic is specified panic when an NMI watchdog timeout occurs.
1449 This is useful when you use a panic=... timeout and need the box
1450 quickly up again.
1451 Instead of 1 and 2 it is possible to use the following
1452 symbolic names: lapic and ioapic
1453 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1455 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1456 emulation library even if a 387 maths coprocessor
1457 is present.
1459 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1460 caches in the slab allocator. Saves per-node memory,
1461 but will impact performance.
1463 noalign [KNL,ARM]
1465 noapic [SMP,APIC] Tells the kernel to not make use of any
1466 IOAPICs that may be present in the system.
1468 nobats [PPC] Do not use BATs for mapping kernel lowmem
1469 on "Classic" PPC cores.
1471 nocache [ARM]
1473 nodelayacct [KNL] Disable per-task delay accounting
1475 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1477 nodsp [SH] Disable hardware DSP at boot time.
1479 noefi [X86-32,X86-64] Disable EFI runtime services support.
1481 noexec [IA-64]
1483 noexec [X86-32,X86-64]
1484 On X86-32 available only on PAE configured kernels.
1485 noexec=on: enable non-executable mappings (default)
1486 noexec=off: disable non-executable mappings
1488 noexec32 [X86-64]
1489 This affects only 32-bit executables.
1490 noexec32=on: enable non-executable mappings (default)
1491 read doesn't imply executable mappings
1492 noexec32=off: disable non-executable mappings
1493 read implies executable mappings
1495 nofpu [SH] Disable hardware FPU at boot time.
1497 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1498 register save and restore. The kernel will only save
1499 legacy floating-point registers on task switch.
1501 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1503 nohlt [BUGS=ARM,SH]
1505 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1506 instruction doesn't work correctly and not to
1507 use it.
1509 no_file_caps Tells the kernel not to honor file capabilities. The
1510 only way then for a file to be executed with privilege
1511 is to be setuid root or executed by root.
1513 nohalt [IA-64] Tells the kernel not to use the power saving
1514 function PAL_HALT_LIGHT when idle. This increases
1515 power-consumption. On the positive side, it reduces
1516 interrupt wake-up latency, which may improve performance
1517 in certain environments such as networked servers or
1518 real-time systems.
1520 nohz= [KNL] Boottime enable/disable dynamic ticks
1521 Valid arguments: on, off
1522 Default: on
1524 noirqdebug [X86-32] Disables the code which attempts to detect and
1525 disable unhandled interrupt sources.
1527 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1528 broken timer IRQ sources.
1530 noisapnp [ISAPNP] Disables ISA PnP code.
1532 noinitrd [RAM] Tells the kernel not to load any configured
1533 initial RAM disk.
1535 nointroute [IA-64]
1537 nojitter [IA64] Disables jitter checking for ITC timers.
1539 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1541 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1543 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1545 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1546 default x2apic cluster mode on platforms
1547 supporting x2apic.
1549 noltlbs [PPC] Do not use large page/tlb entries for kernel
1550 lowmem mapping on PPC40x.
1552 nomca [IA-64] Disable machine check abort handling
1554 nomce [X86-32] Machine Check Exception
1556 nomfgpt [X86-32] Disable Multi-Function General Purpose
1557 Timer usage (for AMD Geode machines).
1559 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1561 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1562 with UP alternatives
1564 noresidual [PPC] Don't use residual data on PReP machines.
1566 noresume [SWSUSP] Disables resume and restores original swap
1567 space.
1569 no-scroll [VGA] Disables scrollback.
1570 This is required for the Braillex ib80-piezo Braille
1571 reader made by F.H. Papenmeier (Germany).
1573 nosbagart [IA-64]
1575 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1577 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1578 and disable the IO APIC. legacy for "maxcpus=0".
1580 nosoftlockup [KNL] Disable the soft-lockup detector.
1582 noswapaccount [KNL] Disable accounting of swap in memory resource
1583 controller. (See Documentation/controllers/memory.txt)
1585 nosync [HW,M68K] Disables sync negotiation for all devices.
1587 notsc [BUGS=X86-32] Disable Time Stamp Counter
1589 nousb [USB] Disable the USB subsystem
1591 nowb [ARM]
1593 nptcg= [IA64] Override max number of concurrent global TLB
1594 purges which is reported from either PAL_VM_SUMMARY or
1595 SAL PALO.
1597 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1598 one of ['zone', 'node', 'default'] can be specified
1599 This can be set from sysctl after boot.
1600 See Documentation/sysctl/vm.txt for details.
1602 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1604 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1605 See Documentation/debugging-via-ohci1394.txt for more
1606 info.
1608 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1609 Rather than timing out after 20 ms if an EC
1610 command is not properly ACKed, override the length
1611 of the timeout. We have interrupts disabled while
1612 waiting for the ACK, so if this is set too high
1613 interrupts *may* be lost!
1615 opl3= [HW,OSS]
1616 Format: <io>
1618 oprofile.timer= [HW]
1619 Use timer interrupt instead of performance counters
1621 osst= [HW,SCSI] SCSI Tape Driver
1622 Format: <buffer_size>,<write_threshold>
1623 See also Documentation/scsi/st.txt.
1625 panic= [KNL] Kernel behaviour on panic
1626 Format: <timeout>
1628 parkbd.port= [HW] Parallel port number the keyboard adapter is
1629 connected to, default is 0.
1630 Format: <parport#>
1631 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1632 0 for XT, 1 for AT (default is AT).
1633 Format: <mode>
1635 parport= [HW,PPT] Specify parallel ports. 0 disables.
1636 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1637 Use 'auto' to force the driver to use any
1638 IRQ/DMA settings detected (the default is to
1639 ignore detected IRQ/DMA settings because of
1640 possible conflicts). You can specify the base
1641 address, IRQ, and DMA settings; IRQ and DMA
1642 should be numbers, or 'auto' (for using detected
1643 settings on that particular port), or 'nofifo'
1644 (to avoid using a FIFO even if it is detected).
1645 Parallel ports are assigned in the order they
1646 are specified on the command line, starting
1647 with parport0.
1649 parport_init_mode= [HW,PPT]
1650 Configure VIA parallel port to operate in
1651 a specific mode. This is necessary on Pegasos
1652 computer where firmware has no options for setting
1653 up parallel port mode and sets it to spp.
1654 Currently this function knows 686a and 8231 chips.
1655 Format: [spp|ps2|epp|ecp|ecpepp]
1657 pas2= [HW,OSS] Format:
1658 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1660 pas16= [HW,SCSI]
1661 See header of drivers/scsi/pas16.c.
1663 pause_on_oops=
1664 Halt all CPUs after the first oops has been printed for
1665 the specified number of seconds. This is to be used if
1666 your oopses keep scrolling off the screen.
1668 pcbit= [HW,ISDN]
1670 pcd. [PARIDE]
1671 See header of drivers/block/paride/pcd.c.
1672 See also Documentation/blockdev/paride.txt.
1674 pci=option[,option...] [PCI] various PCI subsystem options:
1675 off [X86] don't probe for the PCI bus
1676 bios [X86-32] force use of PCI BIOS, don't access
1677 the hardware directly. Use this if your machine
1678 has a non-standard PCI host bridge.
1679 nobios [X86-32] disallow use of PCI BIOS, only direct
1680 hardware access methods are allowed. Use this
1681 if you experience crashes upon bootup and you
1682 suspect they are caused by the BIOS.
1683 conf1 [X86] Force use of PCI Configuration
1684 Mechanism 1.
1685 conf2 [X86] Force use of PCI Configuration
1686 Mechanism 2.
1687 noaer [PCIE] If the PCIEAER kernel config parameter is
1688 enabled, this kernel boot option can be used to
1689 disable the use of PCIE advanced error reporting.
1690 nodomains [PCI] Disable support for multiple PCI
1691 root domains (aka PCI segments, in ACPI-speak).
1692 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1693 Configuration
1694 nomsi [MSI] If the PCI_MSI kernel config parameter is
1695 enabled, this kernel boot option can be used to
1696 disable the use of MSI interrupts system-wide.
1697 noioapicquirk [APIC] Disable all boot interrupt quirks.
1698 Safety option to keep boot IRQs enabled. This
1699 should never be necessary.
1700 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1701 primary IO-APIC for bridges that cannot disable
1702 boot IRQs. This fixes a source of spurious IRQs
1703 when the system masks IRQs.
1704 noioapicreroute [APIC] Disable workaround that uses the
1705 boot IRQ equivalent of an IRQ that connects to
1706 a chipset where boot IRQs cannot be disabled.
1707 The opposite of ioapicreroute.
1708 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1709 routing table. These calls are known to be buggy
1710 on several machines and they hang the machine
1711 when used, but on other computers it's the only
1712 way to get the interrupt routing table. Try
1713 this option if the kernel is unable to allocate
1714 IRQs or discover secondary PCI buses on your
1715 motherboard.
1716 rom [X86] Assign address space to expansion ROMs.
1717 Use with caution as certain devices share
1718 address decoders between ROMs and other
1719 resources.
1720 norom [X86] Do not assign address space to
1721 expansion ROMs that do not already have
1722 BIOS assigned address ranges.
1723 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1724 assigned automatically to PCI devices. You can
1725 make the kernel exclude IRQs of your ISA cards
1726 this way.
1727 pirqaddr=0xAAAAA [X86] Specify the physical address
1728 of the PIRQ table (normally generated
1729 by the BIOS) if it is outside the
1730 F0000h-100000h range.
1731 lastbus=N [X86] Scan all buses thru bus #N. Can be
1732 useful if the kernel is unable to find your
1733 secondary buses and you want to tell it
1734 explicitly which ones they are.
1735 assign-busses [X86] Always assign all PCI bus
1736 numbers ourselves, overriding
1737 whatever the firmware may have done.
1738 usepirqmask [X86] Honor the possible IRQ mask stored
1739 in the BIOS $PIR table. This is needed on
1740 some systems with broken BIOSes, notably
1741 some HP Pavilion N5400 and Omnibook XE3
1742 notebooks. This will have no effect if ACPI
1743 IRQ routing is enabled.
1744 noacpi [X86] Do not use ACPI for IRQ routing
1745 or for PCI scanning.
1746 use_crs [X86] Use _CRS for PCI resource
1747 allocation.
1748 routeirq Do IRQ routing for all PCI devices.
1749 This is normally done in pci_enable_device(),
1750 so this option is a temporary workaround
1751 for broken drivers that don't call it.
1752 skip_isa_align [X86] do not align io start addr, so can
1753 handle more pci cards
1754 firmware [ARM] Do not re-enumerate the bus but instead
1755 just use the configuration from the
1756 bootloader. This is currently used on
1757 IXP2000 systems where the bus has to be
1758 configured a certain way for adjunct CPUs.
1759 noearly [X86] Don't do any early type 1 scanning.
1760 This might help on some broken boards which
1761 machine check when some devices' config space
1762 is read. But various workarounds are disabled
1763 and some IOMMU drivers will not work.
1764 bfsort Sort PCI devices into breadth-first order.
1765 This sorting is done to get a device
1766 order compatible with older (<= 2.4) kernels.
1767 nobfsort Don't sort PCI devices into breadth-first order.
1768 cbiosize=nn[KMG] The fixed amount of bus space which is
1769 reserved for the CardBus bridge's IO window.
1770 The default value is 256 bytes.
1771 cbmemsize=nn[KMG] The fixed amount of bus space which is
1772 reserved for the CardBus bridge's memory
1773 window. The default value is 64 megabytes.
1775 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1776 Management.
1777 off Disable ASPM.
1778 force Enable ASPM even on devices that claim not to support it.
1779 WARNING: Forcing ASPM on may cause system lockups.
1781 pcmv= [HW,PCMCIA] BadgePAD 4
1783 pd. [PARIDE]
1784 See Documentation/blockdev/paride.txt.
1786 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1787 boot time.
1788 Format: { 0 | 1 }
1789 See arch/parisc/kernel/pdc_chassis.c
1791 pf. [PARIDE]
1792 See Documentation/blockdev/paride.txt.
1794 pg. [PARIDE]
1795 See Documentation/blockdev/paride.txt.
1797 pirq= [SMP,APIC] Manual mp-table setup
1798 See Documentation/x86/i386/IO-APIC.txt.
1800 plip= [PPT,NET] Parallel port network link
1801 Format: { parport<nr> | timid | 0 }
1802 See also Documentation/parport.txt.
1804 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1805 Override pmtimer IOPort with a hex value.
1806 e.g. pmtmr=0x508
1808 pnp.debug [PNP]
1809 Enable PNP debug messages. This depends on the
1810 CONFIG_PNP_DEBUG_MESSAGES option.
1812 pnpacpi= [ACPI]
1813 { off }
1815 pnpbios= [ISAPNP]
1816 { on | off | curr | res | no-curr | no-res }
1818 pnp_reserve_irq=
1819 [ISAPNP] Exclude IRQs for the autoconfiguration
1821 pnp_reserve_dma=
1822 [ISAPNP] Exclude DMAs for the autoconfiguration
1824 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1825 Ranges are in pairs (I/O port base and size).
1827 pnp_reserve_mem=
1828 [ISAPNP] Exclude memory regions for the
1829 autoconfiguration.
1830 Ranges are in pairs (memory base and size).
1832 dynamic_printk Enables pr_debug()/dev_dbg() calls if
1833 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1834 These can also be switched on/off via
1835 <debugfs>/dynamic_printk/modules
1837 print-fatal-signals=
1838 [KNL] debug: print fatal signals
1839 print-fatal-signals=1: print segfault info to
1840 the kernel console.
1841 default: off.
1843 printk.time= Show timing data prefixed to each printk message line
1844 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1846 profile= [KNL] Enable kernel profiling via /proc/profile
1847 Format: [schedule,]<number>
1848 Param: "schedule" - profile schedule points.
1849 Param: <number> - step/bucket size as a power of 2 for
1850 statistical time based profiling.
1851 Param: "sleep" - profile D-state sleeping (millisecs).
1852 Requires CONFIG_SCHEDSTATS
1853 Param: "kvm" - profile VM exits.
1855 processor.max_cstate= [HW,ACPI]
1856 Limit processor to maximum C-state
1857 max_cstate=9 overrides any DMI blacklist limit.
1859 processor.nocst [HW,ACPI]
1860 Ignore the _CST method to determine C-states,
1861 instead using the legacy FADT method
1863 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1864 before loading.
1865 See Documentation/blockdev/ramdisk.txt.
1867 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1868 probe for; one of (bare|imps|exps|lifebook|any).
1869 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1870 per second.
1871 psmouse.resetafter= [HW,MOUSE]
1872 Try to reset the device after so many bad packets
1873 (0 = never).
1874 psmouse.resolution=
1875 [HW,MOUSE] Set desired mouse resolution, in dpi.
1876 psmouse.smartscroll=
1877 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1878 0 = disabled, 1 = enabled (default).
1880 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1881 Format:
1882 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1884 pt. [PARIDE]
1885 See Documentation/blockdev/paride.txt.
1887 pty.legacy_count=
1888 [KNL] Number of legacy pty's. Overwrites compiled-in
1889 default number.
1891 quiet [KNL] Disable most log messages
1893 r128= [HW,DRM]
1895 raid= [HW,RAID]
1896 See Documentation/md.txt.
1898 ramdisk_blocksize= [RAM]
1899 See Documentation/blockdev/ramdisk.txt.
1901 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1902 See Documentation/blockdev/ramdisk.txt.
1904 rcupdate.blimit= [KNL,BOOT]
1905 Set maximum number of finished RCU callbacks to process
1906 in one batch.
1908 rcupdate.qhimark= [KNL,BOOT]
1909 Set threshold of queued
1910 RCU callbacks over which batch limiting is disabled.
1912 rcupdate.qlowmark= [KNL,BOOT]
1913 Set threshold of queued RCU callbacks below which
1914 batch limiting is re-enabled.
1916 rdinit= [KNL]
1917 Format: <full_path>
1918 Run specified binary instead of /init from the ramdisk,
1919 used for early userspace startup. See initrd.
1921 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1922 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1923 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1925 relax_domain_level=
1926 [KNL, SMP] Set scheduler's default relax_domain_level.
1927 See Documentation/cpusets.txt.
1929 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1931 reservetop= [X86-32]
1932 Format: nn[KMG]
1933 Reserves a hole at the top of the kernel virtual
1934 address space.
1936 reset_devices [KNL] Force drivers to reset the underlying device
1937 during initialization.
1939 resume= [SWSUSP]
1940 Specify the partition device for software suspend
1942 resume_offset= [SWSUSP]
1943 Specify the offset from the beginning of the partition
1944 given by "resume=" at which the swap header is located,
1945 in <PAGE_SIZE> units (needed only for swap files).
1946 See Documentation/power/swsusp-and-swap-files.txt
1948 retain_initrd [RAM] Keep initrd memory after extraction
1950 rhash_entries= [KNL,NET]
1951 Set number of hash buckets for route cache
1953 riscom8= [HW,SERIAL]
1954 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1956 ro [KNL] Mount root device read-only on boot
1958 root= [KNL] Root filesystem
1960 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1961 mount the root filesystem
1963 rootflags= [KNL] Set root filesystem mount option string
1965 rootfstype= [KNL] Set root filesystem type
1967 rootwait [KNL] Wait (indefinitely) for root device to show up.
1968 Useful for devices that are detected asynchronously
1969 (e.g. USB and MMC devices).
1971 root_plug.vendor_id=
1972 [ROOTPLUG] Override the default vendor ID
1974 root_plug.product_id=
1975 [ROOTPLUG] Override the default product ID
1977 root_plug.debug=
1978 [ROOTPLUG] Enable debugging output
1980 rw [KNL] Mount root device read-write on boot
1982 S [KNL] Run init in single mode
1984 sa1100ir [NET]
1985 See drivers/net/irda/sa1100_ir.c.
1987 sbni= [NET] Granch SBNI12 leased line adapter
1989 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1990 Format: <io>[,<timeout>[,<isapnp>]]
1992 scsi_debug_*= [SCSI]
1993 See drivers/scsi/scsi_debug.c.
1995 scsi_default_dev_flags=
1996 [SCSI] SCSI default device flags
1997 Format: <integer>
1999 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2000 Format: <vendor>:<model>:<flags>
2001 (flags are integer value)
2003 scsi_logging_level= [SCSI] a bit mask of logging levels
2004 See drivers/scsi/scsi_logging.h for bits. Also
2005 settable via sysctl at dev.scsi.logging_level
2006 (/proc/sys/dev/scsi/logging_level).
2007 There is also a nice 'scsi_logging_level' script in the
2008 S390-tools package, available for download at
2009 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2011 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2012 discovered. async scans them in kernel threads,
2013 allowing boot to proceed. none ignores them, expecting
2014 user space to do the scan.
2016 selinux [SELINUX] Disable or enable SELinux at boot time.
2017 Format: { "0" | "1" }
2018 See security/selinux/Kconfig help text.
2019 0 -- disable.
2020 1 -- enable.
2021 Default value is set via kernel config option.
2022 If enabled at boot time, /selinux/disable can be used
2023 later to disable prior to initial policy load.
2025 selinux_compat_net =
2026 [SELINUX] Set initial selinux_compat_net flag value.
2027 Format: { "0" | "1" }
2028 0 -- use new secmark-based packet controls
2029 1 -- use legacy packet controls
2030 Default value is 0 (preferred).
2031 Value can be changed at runtime via
2032 /selinux/compat_net.
2034 serialnumber [BUGS=X86-32]
2036 shapers= [NET]
2037 Maximal number of shapers.
2039 show_msr= [x86] show boot-time MSR settings
2040 Format: { <integer> }
2041 Show boot-time (BIOS-initialized) MSR settings.
2042 The parameter means the number of CPUs to show,
2043 for example 1 means boot CPU only.
2045 sim710= [SCSI,HW]
2046 See header of drivers/scsi/sim710.c.
2048 simeth= [IA-64]
2049 simscsi=
2051 slram= [HW,MTD]
2053 slub_debug[=options[,slabs]] [MM, SLUB]
2054 Enabling slub_debug allows one to determine the
2055 culprit if slab objects become corrupted. Enabling
2056 slub_debug can create guard zones around objects and
2057 may poison objects when not in use. Also tracks the
2058 last alloc / free. For more information see
2059 Documentation/vm/slub.txt.
2061 slub_max_order= [MM, SLUB]
2062 Determines the maximum allowed order for slabs.
2063 A high setting may cause OOMs due to memory
2064 fragmentation. For more information see
2065 Documentation/vm/slub.txt.
2067 slub_min_objects= [MM, SLUB]
2068 The minimum number of objects per slab. SLUB will
2069 increase the slab order up to slub_max_order to
2070 generate a sufficiently large slab able to contain
2071 the number of objects indicated. The higher the number
2072 of objects the smaller the overhead of tracking slabs
2073 and the less frequently locks need to be acquired.
2074 For more information see Documentation/vm/slub.txt.
2076 slub_min_order= [MM, SLUB]
2077 Determines the mininum page order for slabs. Must be
2078 lower than slub_max_order.
2079 For more information see Documentation/vm/slub.txt.
2081 slub_nomerge [MM, SLUB]
2082 Disable merging of slabs with similar size. May be
2083 necessary if there is some reason to distinguish
2084 allocs to different slabs. Debug options disable
2085 merging on their own.
2086 For more information see Documentation/vm/slub.txt.
2088 smart2= [HW]
2089 Format: <io1>[,<io2>[,...,<io8>]]
2091 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2092 attempt to substitute SMP alternatives once at boot.
2094 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2095 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2096 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2097 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2098 smsc-ircc2.ircc_irq= [HW] IRQ line
2099 smsc-ircc2.ircc_dma= [HW] DMA channel
2100 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2101 0: Toshiba Satellite 1800 (GP data pin select)
2102 1: Fast pin select (default)
2103 2: ATC IRMode
2105 snd-ad1816a= [HW,ALSA]
2107 snd-ad1848= [HW,ALSA]
2109 snd-ali5451= [HW,ALSA]
2111 snd-als100= [HW,ALSA]
2113 snd-als4000= [HW,ALSA]
2115 snd-azt2320= [HW,ALSA]
2117 snd-cmi8330= [HW,ALSA]
2119 snd-cmipci= [HW,ALSA]
2121 snd-cs4231= [HW,ALSA]
2123 snd-cs4232= [HW,ALSA]
2125 snd-cs4236= [HW,ALSA]
2127 snd-cs4281= [HW,ALSA]
2129 snd-cs46xx= [HW,ALSA]
2131 snd-dt019x= [HW,ALSA]
2133 snd-dummy= [HW,ALSA]
2135 snd-emu10k1= [HW,ALSA]
2137 snd-ens1370= [HW,ALSA]
2139 snd-ens1371= [HW,ALSA]
2141 snd-es968= [HW,ALSA]
2143 snd-es1688= [HW,ALSA]
2145 snd-es18xx= [HW,ALSA]
2147 snd-es1938= [HW,ALSA]
2149 snd-es1968= [HW,ALSA]
2151 snd-fm801= [HW,ALSA]
2153 snd-gusclassic= [HW,ALSA]
2155 snd-gusextreme= [HW,ALSA]
2157 snd-gusmax= [HW,ALSA]
2159 snd-hdsp= [HW,ALSA]
2161 snd-ice1712= [HW,ALSA]
2163 snd-intel8x0= [HW,ALSA]
2165 snd-interwave= [HW,ALSA]
2167 snd-interwave-stb=
2168 [HW,ALSA]
2170 snd-korg1212= [HW,ALSA]
2172 snd-maestro3= [HW,ALSA]
2174 snd-mpu401= [HW,ALSA]
2176 snd-mtpav= [HW,ALSA]
2178 snd-nm256= [HW,ALSA]
2180 snd-opl3sa2= [HW,ALSA]
2182 snd-opti92x-ad1848=
2183 [HW,ALSA]
2185 snd-opti92x-cs4231=
2186 [HW,ALSA]
2188 snd-opti93x= [HW,ALSA]
2190 snd-pmac= [HW,ALSA]
2192 snd-rme32= [HW,ALSA]
2194 snd-rme96= [HW,ALSA]
2196 snd-rme9652= [HW,ALSA]
2198 snd-sb8= [HW,ALSA]
2200 snd-sb16= [HW,ALSA]
2202 snd-sbawe= [HW,ALSA]
2204 snd-serial= [HW,ALSA]
2206 snd-sgalaxy= [HW,ALSA]
2208 snd-sonicvibes= [HW,ALSA]
2210 snd-sun-amd7930=
2211 [HW,ALSA]
2213 snd-sun-cs4231= [HW,ALSA]
2215 snd-trident= [HW,ALSA]
2217 snd-usb-audio= [HW,ALSA,USB]
2219 snd-via82xx= [HW,ALSA]
2221 snd-virmidi= [HW,ALSA]
2223 snd-wavefront= [HW,ALSA]
2225 snd-ymfpci= [HW,ALSA]
2227 softlockup_panic=
2228 [KNL] Should the soft-lockup detector generate panics.
2230 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2231 See Documentation/sonypi.txt
2233 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2234 See Documentation/serial/specialix.txt.
2236 spia_io_base= [HW,MTD]
2237 spia_fio_base=
2238 spia_pedr=
2239 spia_peddr=
2241 sscape= [HW,OSS]
2242 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2244 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2245 See Documentation/scsi/st.txt.
2247 stacktrace [FTRACE]
2248 Enabled the stack tracer on boot up.
2250 sti= [PARISC,HW]
2251 Format: <num>
2252 Set the STI (builtin display/keyboard on the HP-PARISC
2253 machines) console (graphic card) which should be used
2254 as the initial boot-console.
2255 See also comment in drivers/video/console/sticore.c.
2257 sti_font= [HW]
2258 See comment in drivers/video/console/sticore.c.
2260 stifb= [HW]
2261 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2263 sunrpc.pool_mode=
2264 [NFS]
2265 Control how the NFS server code allocates CPUs to
2266 service thread pools. Depending on how many NICs
2267 you have and where their interrupts are bound, this
2268 option will affect which CPUs will do NFS serving.
2269 Note: this parameter cannot be changed while the
2270 NFS server is running.
2272 auto the server chooses an appropriate mode
2273 automatically using heuristics
2274 global a single global pool contains all CPUs
2275 percpu one pool for each CPU
2276 pernode one pool for each NUMA node (equivalent
2277 to global on non-NUMA machines)
2279 swiotlb= [IA-64] Number of I/O TLB slabs
2281 switches= [HW,M68k]
2283 sym53c416= [HW,SCSI]
2284 See header of drivers/scsi/sym53c416.c.
2286 sysrq_always_enabled
2287 [KNL]
2288 Ignore sysrq setting - this boot parameter will
2289 neutralize any effect of /proc/sys/kernel/sysrq.
2290 Useful for debugging.
2292 t128= [HW,SCSI]
2293 See header of drivers/scsi/t128.c.
2295 tdfx= [HW,DRM]
2297 test_suspend= [SUSPEND]
2298 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2299 standby suspend) as the system sleep state to briefly
2300 enter during system startup. The system is woken from
2301 this state using a wakeup-capable RTC alarm.
2303 thash_entries= [KNL,NET]
2304 Set number of hash buckets for TCP connection
2306 thermal.act= [HW,ACPI]
2307 -1: disable all active trip points in all thermal zones
2308 <degrees C>: override all lowest active trip points
2310 thermal.crt= [HW,ACPI]
2311 -1: disable all critical trip points in all thermal zones
2312 <degrees C>: override all critical trip points
2314 thermal.nocrt= [HW,ACPI]
2315 Set to disable actions on ACPI thermal zone
2316 critical and hot trip points.
2318 thermal.off= [HW,ACPI]
2319 1: disable ACPI thermal control
2321 thermal.psv= [HW,ACPI]
2322 -1: disable all passive trip points
2323 <degrees C>: override all passive trip points to this
2324 value
2326 thermal.tzp= [HW,ACPI]
2327 Specify global default ACPI thermal zone polling rate
2328 <deci-seconds>: poll all this frequency
2329 0: no polling (default)
2331 tmscsim= [HW,SCSI]
2332 See comment before function dc390_setup() in
2333 drivers/scsi/tmscsim.c.
2335 topology= [S390]
2336 Format: {off | on}
2337 Specify if the kernel should make use of the cpu
2338 topology informations if the hardware supports these.
2339 The scheduler will make use of these informations and
2340 e.g. base its process migration decisions on it.
2341 Default is off.
2343 tp720= [HW,PS2]
2345 trix= [HW,OSS] MediaTrix AudioTrix Pro
2346 Format:
2347 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2349 tsc= Disable clocksource-must-verify flag for TSC.
2350 Format: <string>
2351 [x86] reliable: mark tsc clocksource as reliable, this
2352 disables clocksource verification at runtime.
2353 Used to enable high-resolution timer mode on older
2354 hardware, and in virtualized environment.
2356 turbografx.map[2|3]= [HW,JOY]
2357 TurboGraFX parallel port interface
2358 Format:
2359 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2360 See also Documentation/input/joystick-parport.txt
2362 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2363 See header of drivers/scsi/u14-34f.c.
2365 uart401= [HW,OSS]
2366 Format: <io>,<irq>
2368 uart6850= [HW,OSS]
2369 Format: <io>,<irq>
2371 uhci-hcd.ignore_oc=
2372 [USB] Ignore overcurrent events (default N).
2373 Some badly-designed motherboards generate lots of
2374 bogus events, for ports that aren't wired to
2375 anything. Set this parameter to avoid log spamming.
2376 Note that genuine overcurrent events won't be
2377 reported either.
2379 unknown_nmi_panic
2380 [X86-32,X86-64]
2381 Set unknown_nmi_panic=1 early on boot.
2383 usbcore.autosuspend=
2384 [USB] The autosuspend time delay (in seconds) used
2385 for newly-detected USB devices (default 2). This
2386 is the time required before an idle device will be
2387 autosuspended. Devices for which the delay is set
2388 to a negative value won't be autosuspended at all.
2390 usbcore.usbfs_snoop=
2391 [USB] Set to log all usbfs traffic (default 0 = off).
2393 usbcore.blinkenlights=
2394 [USB] Set to cycle leds on hubs (default 0 = off).
2396 usbcore.old_scheme_first=
2397 [USB] Start with the old device initialization
2398 scheme (default 0 = off).
2400 usbcore.use_both_schemes=
2401 [USB] Try the other device initialization scheme
2402 if the first one fails (default 1 = enabled).
2404 usbcore.initial_descriptor_timeout=
2405 [USB] Specifies timeout for the initial 64-byte
2406 USB_REQ_GET_DESCRIPTOR request in milliseconds
2407 (default 5000 = 5.0 seconds).
2409 usbhid.mousepoll=
2410 [USBHID] The interval which mice are to be polled at.
2412 usb-storage.delay_use=
2413 [UMS] The delay in seconds before a new device is
2414 scanned for Logical Units (default 5).
2416 usb-storage.quirks=
2417 [UMS] A list of quirks entries to supplement or
2418 override the built-in unusual_devs list. List
2419 entries are separated by commas. Each entry has
2420 the form VID:PID:Flags where VID and PID are Vendor
2421 and Product ID values (4-digit hex numbers) and
2422 Flags is a set of characters, each corresponding
2423 to a common usb-storage quirk flag as follows:
2424 a = SANE_SENSE (collect more than 18 bytes
2425 of sense data);
2426 c = FIX_CAPACITY (decrease the reported
2427 device capacity by one sector);
2428 h = CAPACITY_HEURISTICS (decrease the
2429 reported device capacity by one
2430 sector if the number is odd);
2431 i = IGNORE_DEVICE (don't bind to this
2432 device);
2433 l = NOT_LOCKABLE (don't try to lock and
2434 unlock ejectable media);
2435 m = MAX_SECTORS_64 (don't transfer more
2436 than 64 sectors = 32 KB at a time);
2437 o = CAPACITY_OK (accept the capacity
2438 reported by the device);
2439 r = IGNORE_RESIDUE (the device reports
2440 bogus residue values);
2441 s = SINGLE_LUN (the device has only one
2442 Logical Unit);
2443 w = NO_WP_DETECT (don't test whether the
2444 medium is write-protected).
2445 Example: quirks=0419:aaf5:rl,0421:0433:rc
2447 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2448 kernel's map of available physical RAM.
2450 vdso= [X86-32,SH,x86-64]
2451 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2452 vdso=1: enable VDSO (default)
2453 vdso=0: disable VDSO mapping
2455 vdso32= [X86-32,X86-64]
2456 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2457 vdso32=1: enable 32-bit VDSO (default)
2458 vdso32=0: disable 32-bit VDSO mapping
2460 vector= [IA-64,SMP]
2461 vector=percpu: enable percpu vector domain
2463 video= [FB] Frame buffer configuration
2464 See Documentation/fb/modedb.txt.
2466 vga= [BOOT,X86-32] Select a particular video mode
2467 See Documentation/x86/i386/boot.txt and
2468 Documentation/svga.txt.
2469 Use vga=ask for menu.
2470 This is actually a boot loader parameter; the value is
2471 passed to the kernel using a special protocol.
2473 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2474 size of <nn>. This can be used to increase the
2475 minimum size (128MB on x86). It can also be used to
2476 decrease the size and leave more room for directly
2477 mapped kernel RAM.
2479 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2480 Format: <command>
2482 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2483 Format: <command>
2485 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2486 Format: <command>
2488 waveartist= [HW,OSS]
2489 Format: <io>,<irq>,<dma>,<dma2>
2491 wd33c93= [HW,SCSI]
2492 See header of drivers/scsi/wd33c93.c.
2494 wd7000= [HW,SCSI]
2495 See header of drivers/scsi/wd7000.c.
2497 wdt= [WDT] Watchdog
2498 See Documentation/watchdog/wdt.txt.
2500 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2501 xd_geo= See header of drivers/block/xd.c.
2503 xirc2ps_cs= [NET,PCMCIA]
2504 Format:
2505 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2507 norandmaps Don't use address space randomization. Equivalent to
2508 echo 0 > /proc/sys/kernel/randomize_va_space
2510 ______________________________________________________________________
2512 TODO:
2514 Add documentation for ALSA options.
2515 Add more DRM drivers.