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 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend is enabled.
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
99 X86-32 X86-32, aka i386 architecture is enabled.
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
104 In addition, the following text indicates that the option:
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/power/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
156 Format: { level | edge | high | low }
158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
168 Format: <irq>,<irq>...
170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
171 Format: <irq>,<irq>...
173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
183 acpi_serialize [HW,ACPI] force serialization of AML methods
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
193 acpi.debug_layer= [HW,ACPI]
195 Each bit of the <int> indicates an ACPI debug layer,
196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
210 acpi.debug_level= [HW,ACPI]
212 Each bit of the <int> indicates an ACPI debug level,
213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
228 acpi_pm_good [X86-32,X86-64]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
243 The kernel tries to set a reasonable default.
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
253 See header of drivers/scsi/advansys.c.
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
263 See Documentation/scsi/aha152x.txt.
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
269 See Documentation/scsi/aic7xxx.txt.
272 See Documentation/scsi/aic79xx.txt.
274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
277 See also Documentation/kernel/input/joystick.txt
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
285 Power management functions (SPARCstation-4/5 + deriv.)
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
305 atarimouse= [HW,MOUSE] Atari Mouse
307 atascsi= [HW,SCSI] Atari SCSI
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
312 atkbd.reset= [HW] Reset keyboard during initialization
314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
328 baycom_epp= [HW,AX25]
331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
333 See header of drivers/net/hamradio/baycom_par.c.
335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
369 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
395 Value can be changed at runtime via
396 /selinux/checkreqprot.
399 See Documentation/s390/CommonIO for details.
402 See Documentation/s390/CommonIO for details.
404 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
406 Forces specified clocksource (if available) to be used
407 when calculating gettimeofday(). If specified
408 clocksource is not available, it defaults to PIT.
409 Format: { pit | tsc | cyclone | pmtmr }
411 clocksource= [GENERIC_TIME] Override the default clocksource
413 Override the default clocksource and use the clocksource
414 with the name specified.
415 Some clocksource names to choose from, depending on
417 [all] jiffies (this is the base, fallback clocksource)
419 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
420 pxa_timer,timer3,32k_counter,timer0_1
422 [X86-32] pit,hpet,tsc,vmi-timer;
423 scx200_hrt on Geode; cyclone on IBM x440
431 clearcpuid=BITNUM [X86]
432 Disable CPUID feature X for the kernel. See
433 include/asm-x86/cpufeature.h for the valid bit numbers.
434 Note the Linux specific bits are not necessarily
435 stable over kernel options, but the vendor specific
437 Also note that user programs calling CPUID directly
438 or using the feature without checking anything
439 will still see it. This just prevents it from
440 being used by the kernel or shown in /proc/cpuinfo.
441 Also note the kernel might malfunction if you disable
444 code_bytes [IA32/X86_64] How many bytes of object code to print
451 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
452 over the 8254 in addition to over the IO-APIC. The
453 kernel tries to set a sensible default.
455 hpet= [X86-32,HPET] option to control HPET usage
456 Format: { enable (default) | disable | force }
457 disable: disable HPET and use PIT instead
458 force: allow force enabled of undocumented chips (ICH4,
461 com20020= [HW,NET] ARCnet - COM20020 chipset
463 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
465 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
469 ARCnet - COM90xx chipset (memory-mapped buffers)
470 Format: <io>[,<irq>[,<memstart>]]
472 condev= [HW,S390] console device
475 console= [KNL] Output console device and options.
477 tty<n> Use the virtual console device <n>.
481 Use the specified serial port. The options are of
482 the form "bbbbpnf", where "bbbb" is the baud rate,
483 "p" is parity ("n", "o", or "e"), "n" is number of
484 bits, and "f" is flow control ("r" for RTS or
485 omit it). Default is "9600n8".
487 See Documentation/serial-console.txt for more
489 Documentation/networking/netconsole.txt for an
492 uart[8250],io,<addr>[,options]
493 uart[8250],mmio,<addr>[,options]
494 Start an early, polled-mode console on the 8250/16550
495 UART at the specified I/O port or MMIO address,
496 switching to the matching ttyS device later. The
497 options are the same as for ttyS, above.
499 earlycon= [KNL] Output early console device and options.
500 uart[8250],io,<addr>[,options]
501 uart[8250],mmio,<addr>[,options]
502 Start an early, polled-mode console on the 8250/16550
503 UART at the specified I/O port or MMIO address.
504 The options are the same as for ttyS, above.
507 [HW] Never suspend the console
508 Disable suspending of consoles during suspend and
509 hibernate operations. Once disabled, debugging
510 messages can reach various consoles while the rest
511 of the system is being put to sleep (ie, while
512 debugging driver suspend/resume hooks). This may
513 not work reliably with all consoles, but is known
514 to work with serial and VGA consoles.
516 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
518 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
520 crashkernel=nn[KMG]@ss[KMG]
521 [KNL] Reserve a chunk of physical memory to
522 hold a kernel to switch to with kexec on panic.
524 crashkernel=range1:size1[,range2:size2,...][@offset]
525 [KNL] Same as above, but depends on the memory
526 in the running system. The syntax of range is
527 start-[end] where start and end are both
528 a memory unit (amount[KMG]). See also
529 Documentation/kdump/kdump.txt for a example.
532 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
537 cs89x0_media= [HW,NET]
538 Format: { rj45 | aui | bnc }
541 See header of drivers/s390/block/dasd_devmap.c.
543 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
544 (one device per port)
545 Format: <port#>,<type>
546 See also Documentation/input/joystick-parport.txt
548 debug [KNL] Enable kernel debugging (events log level).
551 [KNL] verbose self-tests
553 Print debugging info while doing the locking API
555 We default to 0 (no extra messages), setting it to
556 1 will print _a lot_ more information - normally
557 only useful to kernel developers.
559 decnet.addr= [HW,NET]
560 Format: <area>[,<node>]
561 See also Documentation/networking/decnet.txt.
564 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
565 Change the default blue palette of the console.
566 This is a 16-member array composed of values
570 Format: <green0>,<green1>,<green2>,...,<green15>
571 Change the default green palette of the console.
572 This is a 16-member array composed of values
576 Format: <red0>,<red1>,<red2>,...,<red15>
577 Change the default red palette of the console.
578 This is a 16-member array composed of values
584 Set system-wide default UTF-8 mode for all tty's.
585 Default is 1, i.e. UTF-8 mode is enabled for all
586 newly opened terminals.
589 Set number of hash buckets for dentry cache.
592 IO parameters + enable/disable command.
594 digiepca= [HW,SERIAL]
595 See drivers/char/README.epca and
596 Documentation/digiepca.txt.
598 disable_mtrr_trim [X86, Intel and AMD only]
599 By default the kernel will trim any uncacheable
600 memory out of your available memory pool based on
601 MTRR settings. This parameter disables that behavior,
602 possibly causing your machine to run very slowly.
604 dmasound= [HW,OSS] Sound subsystem buffers
610 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
612 earlyprintk=serial[,ttySn[,baudrate]]
614 Append ",keep" to not disable it when the real console
617 Only vga or serial at a time, not both.
619 Currently only ttyS0 and ttyS1 are supported.
621 Interaction with the standard serial driver is not
624 The VGA output is eventually overwritten by the real
630 Format: {"of[f]" | "sk[ipmbr]"}
631 See comment in arch/i386/boot/edd.S
633 eisa_irq_edge= [PARISC,HW]
634 See header of drivers/parisc/eisa.c.
637 See comment before function elanfreq_setup() in
638 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
641 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
642 See Documentation/block/as-iosched.txt and
643 Documentation/block/deadline-iosched.txt for details.
645 elfcorehdr= [X86-32, X86_64]
646 Specifies physical address of start of kernel core
647 image elf header. Generally kexec loader will
648 pass this option to capture kernel.
649 See Documentation/kdump/kdump.txt for details.
651 enforcing [SELINUX] Set initial enforcing status.
653 See security/selinux/Kconfig help text.
654 0 -- permissive (log only, no denials).
655 1 -- enforcing (deny and log).
657 Value can be changed at runtime via /selinux/enforce.
660 Format: <spdif>,[<nomix>,[<amplifier>]]
661 See also header of sound/oss/es1371.c.
663 ether= [HW,NET] Ethernet cards parameters
664 This option is obsoleted by the "netdev=" option, which
665 has equivalent usage. See its documentation for details.
667 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
672 fail_make_request=[KNL]
673 General fault injection mechanism.
674 Format: <interval>,<probability>,<space>,<times>
675 See also /Documentation/fault-injection/.
678 See header of drivers/scsi/fd_mcs.c.
681 See header of drivers/scsi/fdomain.c.
684 See Documentation/floppy.txt.
687 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
688 support via parallel port (up to 5 devices per port)
689 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
690 See also Documentation/input/joystick-parport.txt
694 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
699 See header of drivers/scsi/gdth.c.
701 gpt [EFI] Forces disk with valid GPT signature but
702 invalid Protective MBR to be treated as GPT.
706 hashdist= [KNL,NUMA] Large hashes allocated during boot
707 are distributed across NUMA nodes. Defaults on
708 for IA-64, off otherwise.
709 Format: 0 | 1 (for off | on)
711 hcl= [IA-64] SGI's Hardware Graph compatibility layer
713 hd= [EIDE] (E)IDE hard drive subsystem geometry
714 Format: <cyl>,<head>,<sect>
716 hd?= [HW] (E)IDE subsystem
717 hd?lun= See Documentation/ide/ide.txt.
719 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
720 size of <nn>. This works even on boxes that have no
721 highmem otherwise. This also works to reduce highmem
722 size on bigger boxes.
724 highres= [KNL] Enable/disable high resolution timer mode.
725 Valid parameters: "on", "off"
729 See Documentation/isdn/README.HiSax.
731 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
732 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
734 i8042.direct [HW] Put keyboard port into non-translated mode
735 i8042.dumbkbd [HW] Pretend that controller can only read data from
736 keyboard and cannot control its state
737 (Don't attempt to blink the leds)
738 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
739 i8042.nokbd [HW] Don't check/create keyboard port
740 i8042.noloop [HW] Disable the AUX Loopback command while probing
742 i8042.nomux [HW] Don't check presence of an active multiplexing
744 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
747 [HW] Frequency with which keyboard LEDs should blink
748 when kernel panics (default is 0.5 sec)
749 i8042.reset [HW] Reset the controller during init and cleanup
750 i8042.unlock [HW] Unlock (ignore) the keylock
754 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
755 indicates that the driver is running on unsupported
757 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
758 does not match list of supported models.
760 [HW] Report power status in /proc/i8k
761 (disabled by default)
762 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
765 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
766 See Documentation/mca.txt.
769 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
771 ide= [HW] (E)IDE subsystem
772 Format: ide=nodma or ide=doubler
773 See Documentation/ide/ide.txt.
775 ide?= [HW] (E)IDE subsystem
776 Format: ide?=ata66 or chipset specific parameters.
777 See Documentation/ide/ide.txt.
779 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
780 See Documentation/ide/ide.txt.
783 Format: idle=poll or idle=mwait
784 Poll forces a polling idle loop that can slightly improves the performance
785 of waking up a idle CPU, but will use a lot of power and make the system
786 run hot. Not recommended.
787 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
788 to not use it because it doesn't save as much power as a normal idle
789 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
792 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
793 Claim all unknown PCI IDE storage controllers.
795 ignore_loglevel [KNL]
796 Ignore loglevel setting - this will print /all/
797 kernel messages to the console. Useful for debugging.
800 Set number of hash buckets for inode cache.
803 See header of drivers/scsi/in2000.c.
807 Run specified binary instead of /sbin/init as init
810 initcall_debug [KNL] Trace initcalls as they are executed. Useful
811 for working out where the kernel is dying during
814 initrd= [BOOT] Specify the location of the initial ramdisk
816 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
834 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
836 Disable intel iommu driver.
837 igfx_off [Default Off]
838 By default, gfx is mapped as normal device. If a gfx
839 device has a dedicated DMAR unit, the DMAR unit is
840 bypassed by not enabling DMAR with this option. In
841 this case, gfx device will use physical address for
844 With this option iommu will not optimize to look
845 for io virtual address below 32 bit forcing dual
846 address cycle on pci bus for cards supporting greater
847 than 32 bit addressing. The default is to look
848 for translation below 32 bit and if not available
849 then look in the higher range.
851 With this option on every unmap_single operation will
852 result in a hardware IOTLB flush operation as opposed
853 to batching them for performance.
855 io_delay= [X86-32,X86-64] I/O delay method
857 Standard port 0x80 based delay
859 Alternate port 0xed based delay (needed on some systems)
861 Simple two microseconds delay
865 io7= [HW] IO7 for Marvel based alpha systems
866 See comment before marvel_specify_io7 in
867 arch/alpha/kernel/core_marvel.c.
870 See Documentation/filesystems/nfsroot.txt.
872 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
873 See comment before ip2_setup() in
874 drivers/char/ip2/ip2base.c.
876 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
877 See header of drivers/scsi/ips.c.
879 ports= [IP_VS_FTP] IPVS ftp helper module
881 Up to 8 (IP_VS_APP_MAX_PORTS) ports
883 Format: <port>,<port>....
886 When an interrupt is not handled search all handlers
887 for it. Intended to get systems with badly broken
891 When an interrupt is not handled search all handlers
892 for it. Also check all handlers each timer
893 interrupt. Intended to get systems with badly broken
897 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
899 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
901 <cpu number>,...,<cpu number>
903 <cpu number>-<cpu number> (must be a positive range in ascending order)
905 <cpu number>,...,<cpu number>-<cpu number>
906 This option can be used to specify one or more CPUs
907 to isolate from the general SMP balancing and scheduling
908 algorithms. The only way to move a process onto or off
909 an "isolated" CPU is via the CPU affinity syscalls.
910 <cpu number> begins at 0 and the maximum value is
911 "number of CPUs in system - 1".
913 This option is the preferred way to isolate CPUs. The
914 alternative -- manually setting the CPU mask of all
915 tasks in the system -- can cause problems and
916 suboptimal load balancer performance.
920 js= [HW,JOY] Analog joystick
921 See Documentation/input/joystick.txt.
923 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
924 specifies the amount of memory usable by the kernel
925 for non-movable allocations. The requested amount is
926 spread evenly throughout all nodes in the system. The
927 remaining memory in each node is used for Movable
928 pages. In the event, a node is too small to have both
929 kernelcore and Movable pages, kernelcore pages will
930 take priority and other nodes will have a larger number
931 of kernelcore pages. The Movable zone is used for the
932 allocation of pages that may be reclaimed or moved
933 by the page migration subsystem. This means that
934 HugeTLB pages may not be allocated from this zone.
935 Note that allocations like PTEs-from-HighMem still
936 use the HighMem zone if it exists, and the Normal
939 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
940 is similar to kernelcore except it specifies the
941 amount of memory used for migratable allocations.
942 If both kernelcore and movablecore is specified,
943 then kernelcore will be at *least* the specified
944 value but may be more. If movablecore on its own
945 is specified, the administrator must be careful
946 that the amount of memory usable for all allocations
951 kstack=N [X86-32,X86-64] Print N words from the kernel stack
954 kgdboc= [HW] kgdb over consoles.
955 Requires a tty driver that supports console polling.
956 (only serial suported for now)
957 Format: <serial_device>[,baud]
961 lapic [X86-32,APIC] Enable the local APIC even if BIOS
964 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
967 libata.dma= [LIBATA] DMA control
968 libata.dma=0 Disable all PATA and SATA DMA
969 libata.dma=1 PATA and SATA Disk DMA only
970 libata.dma=2 ATAPI (CDROM) DMA only
971 libata.dma=4 Compact Flash DMA only
972 Combinations also work, so libata.dma=3 enables DMA
973 for disks and CDROMs, but not CFs.
975 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
979 libata.force= [LIBATA] Force configurations. The format is comma
980 separated list of "[ID:]VAL" where ID is
981 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
982 matching port, link or device. Basically, it matches
983 the ATA ID string printed on console by libata. If
984 the whole ID part is omitted, the last PORT and DEVICE
985 values are used. If ID hasn't been specified yet, the
986 configuration applies to all ports, links and devices.
988 If only DEVICE is omitted, the parameter applies to
989 the port and all links and devices behind it. DEVICE
990 number of 0 either selects the first device or the
991 first fan-out link behind PMP device. It does not
992 select the host link. DEVICE number of 15 selects the
993 host link and device attached to it.
995 The VAL specifies the configuration to force. As long
996 as there's no ambiguity shortcut notation is allowed.
997 For example, both 1.5 and 1.5G would work for 1.5Gbps.
998 The following configurations can be forced.
1000 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1001 Any ID with matching PORT is used.
1003 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1005 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1006 udma[/][16,25,33,44,66,100,133] notation is also
1009 * [no]ncq: Turn on or off NCQ.
1011 If there are multiple matching configurations changing
1012 the same attribute, the last one is used.
1014 load_ramdisk= [RAM] List of ramdisks to load from floppy
1015 See Documentation/ramdisk.txt.
1017 lockd.nlm_grace_period=P [NFS] Assign grace period.
1020 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1023 lockd.nlm_timeout=T [NFS] Assign timeout value.
1026 lockd.nlm_udpport=M [NFS] Assign UDP port.
1029 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1032 loglevel= All Kernel Messages with a loglevel smaller than the
1033 console loglevel will be printed to the console. It can
1034 also be changed with klogd or other programs. The
1035 loglevels are defined as follows:
1037 0 (KERN_EMERG) system is unusable
1038 1 (KERN_ALERT) action must be taken immediately
1039 2 (KERN_CRIT) critical conditions
1040 3 (KERN_ERR) error conditions
1041 4 (KERN_WARNING) warning conditions
1042 5 (KERN_NOTICE) normal but significant condition
1043 6 (KERN_INFO) informational
1044 7 (KERN_DEBUG) debug-level messages
1046 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1047 Format: { n | nk | nM }
1048 n must be a power of two. The default size
1049 is set in the kernel config file.
1051 logo.nologo [FB] Disables display of the built-in Linux logo.
1052 This may be used to provide more screen space for
1053 kernel log messages and is useful when debugging
1054 kernel boot problems.
1056 lp=0 [LP] Specify parallel ports to use, e.g,
1057 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1058 lp=reset first parallel port). 'lp=0' disables the
1059 lp=auto printer driver. 'lp=reset' (which can be
1060 specified in addition to the ports) causes
1061 attached printers to be reset. Using
1062 lp=port1,port2,... specifies the parallel ports
1063 to associate lp devices with, starting with
1064 lp0. A port specification may be 'none' to skip
1065 that lp device, or a parport name such as
1066 'parport0'. Specifying 'lp=auto' instead of a
1067 port specification list means that device IDs
1068 from each port should be examined, to see if
1069 an IEEE 1284-compliant printer is attached; if
1070 so, the driver will manage that printer.
1071 See also header of drivers/char/lp.c.
1074 Sets loops_per_jiffy to given constant, thus avoiding
1075 time-consuming boot-time autodetection (up to 250 ms per
1076 CPU). 0 enables autodetection (default). To determine
1077 the correct value for your kernel, boot with normal
1078 autodetection and see what value is printed. Note that
1079 on SMP systems the preset will be applied to all CPUs,
1080 which is likely to cause problems if your CPUs need
1081 significantly divergent settings. An incorrect value
1082 will cause delays in the kernel to be wrong, leading to
1083 unpredictable I/O errors and other breakage. Although
1084 unlikely, in the extreme case this might damage your
1088 Format: <io>,<irq>,<dma>
1090 mac5380= [HW,SCSI] Format:
1091 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1093 mac53c9x= [HW,SCSI] Format:
1094 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1096 machvec= [IA64] Force the use of a particular machine-vector
1097 (machvec) in a generic kernel.
1098 Example: machvec=hpzx1_swiotlb
1100 max_loop= [LOOP] Maximum number of loopback devices that can
1104 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1105 should make use of. maxcpus=n : n >= 0 limits the
1106 kernel to using 'n' processors. n=0 is a special case,
1107 it is equivalent to "nosmp", which also disables
1110 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1111 equal to this physical address is ignored.
1113 max_luns= [SCSI] Maximum number of LUNs to probe.
1114 Should be between 1 and 2^32-1.
1117 [SCSI] Maximum number of LUNs received.
1118 Should be between 1 and 16384.
1122 mce [X86-32] Machine Check Exception
1124 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1126 md= [HW] RAID subsystems devices and level
1127 See Documentation/md.txt.
1130 Format: <first>,<last>
1131 Specifies range of consoles to be captured by the MDA.
1133 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1134 Amount of memory to be used when the kernel is not able
1135 to see the whole system memory or for test.
1136 [X86-32] Use together with memmap= to avoid physical
1137 address space collisions. Without memmap= PCI devices
1138 could be placed at addresses belonging to unused RAM.
1140 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1143 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1144 E820 memory map, as specified by the user.
1145 Such memmap=exactmap lines can be constructed based on
1146 BIOS output or other requirements. See the memmap=nn@ss
1149 memmap=nn[KMG]@ss[KMG]
1150 [KNL] Force usage of a specific region of memory
1151 Region of memory to be used, from ss to ss+nn.
1153 memmap=nn[KMG]#ss[KMG]
1154 [KNL,ACPI] Mark specific memory as ACPI data.
1155 Region of memory to be used, from ss to ss+nn.
1157 memmap=nn[KMG]$ss[KMG]
1158 [KNL,ACPI] Mark specific memory as reserved.
1159 Region of memory to be used, from ss to ss+nn.
1160 Example: Exclude memory from 0x18690000-0x1869ffff
1161 memmap=64K$0x18690000
1163 memmap=0x10000$0x18690000
1165 memtest= [KNL,X86_64] Enable memtest
1167 range: 0,4 : pattern number
1168 default : 0 <disable>
1170 meye.*= [HW] Set MotionEye Camera parameters
1171 See Documentation/video4linux/meye.txt.
1173 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1174 Multi-Function General Purpose Timers on AMD Geode
1177 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1178 the BIOS has incorrectly applied a workaround. TinyBIOS
1179 version 0.98 is known to be affected, 0.99 fixes the
1180 problem by letting the user disable the workaround.
1185 [MOUSE] Maximum time between finger touching and
1186 leaving touchpad surface for touch to be considered
1187 a tap and be reported as a left button click (for
1188 touchpads working in absolute mode only).
1190 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1191 reporting absolute coordinates, such as tablets
1192 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1193 reporting absolute coordinates, such as tablets
1198 MTD_Partition= [MTD]
1199 Format: <name>,<region-number>,<size>,<offset>
1201 MTD_Region= [MTD] Format:
1202 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1205 See drivers/mtd/cmdlinepart.c.
1207 mtouchusb.raw_coordinates=
1208 [HW] Make the MicroTouch USB driver use raw coordinates
1209 ('y', default) or cooked coordinates ('n')
1211 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1214 See header of drivers/scsi/NCR_D700.c.
1218 ncr53c400= [HW,SCSI]
1220 ncr53c400a= [HW,SCSI]
1222 ncr53c406a= [HW,SCSI]
1224 ncr53c8xx= [HW,SCSI]
1226 netdev= [NET] Network devices parameters
1227 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1228 Note that mem_start is often overloaded to mean
1229 something different and driver-specific.
1230 This usage is only documented in each driver source
1234 See Documentation/filesystems/nfsroot.txt.
1236 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1237 See Documentation/filesystems/nfsroot.txt.
1239 nfs.callback_tcpport=
1240 [NFS] set the TCP port on which the NFSv4 callback
1241 channel should listen.
1243 nfs.idmap_cache_timeout=
1244 [NFS] set the maximum lifetime for idmapper cache
1248 [NFS] enable 64-bit inode numbers.
1249 If zero, the NFS client will fake up a 32-bit inode
1250 number for the readdir() and stat() syscalls instead
1251 of returning the full 64-bit number.
1252 The default is to return 64-bit inode numbers.
1254 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1255 when a NMI is triggered.
1256 Format: [state][,regs][,debounce][,die]
1258 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1260 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1261 emulation library even if a 387 maths coprocessor
1264 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1265 caches in the slab allocator. Saves per-node memory,
1266 but will impact performance.
1270 noapic [SMP,APIC] Tells the kernel to not make use of any
1271 IOAPICs that may be present in the system.
1273 nobats [PPC] Do not use BATs for mapping kernel lowmem
1274 on "Classic" PPC cores.
1278 nodelayacct [KNL] Disable per-task delay accounting
1280 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1282 noefi [X86-32,X86-64] Disable EFI runtime services support.
1286 noexec [X86-32,X86-64]
1287 noexec=on: enable non-executable mappings (default)
1288 noexec=off: disable nn-executable mappings
1290 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1291 register save and restore. The kernel will only save
1292 legacy floating-point registers on task switch.
1294 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1298 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1299 instruction doesn't work correctly and not to
1302 nohalt [IA-64] Tells the kernel not to use the power saving
1303 function PAL_HALT_LIGHT when idle. This increases
1304 power-consumption. On the positive side, it reduces
1305 interrupt wake-up latency, which may improve performance
1306 in certain environments such as networked servers or
1309 nohz= [KNL] Boottime enable/disable dynamic ticks
1310 Valid arguments: on, off
1313 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1315 noirqdebug [X86-32] Disables the code which attempts to detect and
1316 disable unhandled interrupt sources.
1318 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1319 broken timer IRQ sources.
1321 noisapnp [ISAPNP] Disables ISA PnP code.
1323 noinitrd [RAM] Tells the kernel not to load any configured
1328 nojitter [IA64] Disables jitter checking for ITC timers.
1330 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1332 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1334 noltlbs [PPC] Do not use large page/tlb entries for kernel
1335 lowmem mapping on PPC40x.
1337 nomca [IA-64] Disable machine check abort handling
1339 nomce [X86-32] Machine Check Exception
1341 nomfgpt [X86-32] Disable Multi-Function General Purpose
1342 Timer usage (for AMD Geode machines).
1344 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1346 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1347 with UP alternatives
1349 noresidual [PPC] Don't use residual data on PReP machines.
1351 noresume [SWSUSP] Disables resume and restores original swap
1354 no-scroll [VGA] Disables scrollback.
1355 This is required for the Braillex ib80-piezo Braille
1356 reader made by F.H. Papenmeier (Germany).
1360 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1362 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1363 and disable the IO APIC. legacy for "maxcpus=0".
1365 nosoftlockup [KNL] Disable the soft-lockup detector.
1367 nosync [HW,M68K] Disables sync negotiation for all devices.
1369 notsc [BUGS=X86-32] Disable Time Stamp Counter
1371 nousb [USB] Disable the USB subsystem
1375 nptcg= [IA64] Override max number of concurrent global TLB
1376 purges which is reported from either PAL_VM_SUMMARY or
1379 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1380 one of ['zone', 'node', 'default'] can be specified
1381 This can be set from sysctl after boot.
1382 See Documentation/sysctl/vm.txt for details.
1384 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1389 oprofile.timer= [HW]
1390 Use timer interrupt instead of performance counters
1392 osst= [HW,SCSI] SCSI Tape Driver
1393 Format: <buffer_size>,<write_threshold>
1394 See also Documentation/scsi/st.txt.
1396 panic= [KNL] Kernel behaviour on panic
1399 parkbd.port= [HW] Parallel port number the keyboard adapter is
1400 connected to, default is 0.
1402 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1403 0 for XT, 1 for AT (default is AT).
1406 parport= [HW,PPT] Specify parallel ports. 0 disables.
1407 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1408 Use 'auto' to force the driver to use any
1409 IRQ/DMA settings detected (the default is to
1410 ignore detected IRQ/DMA settings because of
1411 possible conflicts). You can specify the base
1412 address, IRQ, and DMA settings; IRQ and DMA
1413 should be numbers, or 'auto' (for using detected
1414 settings on that particular port), or 'nofifo'
1415 (to avoid using a FIFO even if it is detected).
1416 Parallel ports are assigned in the order they
1417 are specified on the command line, starting
1420 parport_init_mode= [HW,PPT]
1421 Configure VIA parallel port to operate in
1422 a specific mode. This is necessary on Pegasos
1423 computer where firmware has no options for setting
1424 up parallel port mode and sets it to spp.
1425 Currently this function knows 686a and 8231 chips.
1426 Format: [spp|ps2|epp|ecp|ecpepp]
1428 pas2= [HW,OSS] Format:
1429 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1432 See header of drivers/scsi/pas16.c.
1435 Halt all CPUs after the first oops has been printed for
1436 the specified number of seconds. This is to be used if
1437 your oopses keep scrolling off the screen.
1442 See header of drivers/block/paride/pcd.c.
1443 See also Documentation/paride.txt.
1445 pci=option[,option...] [PCI] various PCI subsystem options:
1446 off [X86-32] don't probe for the PCI bus
1447 bios [X86-32] force use of PCI BIOS, don't access
1448 the hardware directly. Use this if your machine
1449 has a non-standard PCI host bridge.
1450 nobios [X86-32] disallow use of PCI BIOS, only direct
1451 hardware access methods are allowed. Use this
1452 if you experience crashes upon bootup and you
1453 suspect they are caused by the BIOS.
1454 conf1 [X86-32] Force use of PCI Configuration
1456 conf2 [X86-32] Force use of PCI Configuration
1458 noaer [PCIE] If the PCIEAER kernel config parameter is
1459 enabled, this kernel boot option can be used to
1460 disable the use of PCIE advanced error reporting.
1461 nodomains [PCI] Disable support for multiple PCI
1462 root domains (aka PCI segments, in ACPI-speak).
1463 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1465 nomsi [MSI] If the PCI_MSI kernel config parameter is
1466 enabled, this kernel boot option can be used to
1467 disable the use of MSI interrupts system-wide.
1468 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1469 routing table. These calls are known to be buggy
1470 on several machines and they hang the machine
1471 when used, but on other computers it's the only
1472 way to get the interrupt routing table. Try
1473 this option if the kernel is unable to allocate
1474 IRQs or discover secondary PCI buses on your
1476 rom [X86-32] Assign address space to expansion ROMs.
1477 Use with caution as certain devices share
1478 address decoders between ROMs and other
1480 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1481 assigned automatically to PCI devices. You can
1482 make the kernel exclude IRQs of your ISA cards
1484 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1485 of the PIRQ table (normally generated
1486 by the BIOS) if it is outside the
1487 F0000h-100000h range.
1488 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1489 useful if the kernel is unable to find your
1490 secondary buses and you want to tell it
1491 explicitly which ones they are.
1492 assign-busses [X86-32] Always assign all PCI bus
1493 numbers ourselves, overriding
1494 whatever the firmware may have done.
1495 usepirqmask [X86-32] Honor the possible IRQ mask stored
1496 in the BIOS $PIR table. This is needed on
1497 some systems with broken BIOSes, notably
1498 some HP Pavilion N5400 and Omnibook XE3
1499 notebooks. This will have no effect if ACPI
1500 IRQ routing is enabled.
1501 noacpi [X86-32] Do not use ACPI for IRQ routing
1502 or for PCI scanning.
1503 use_crs [X86-32] Use _CRS for PCI resource
1505 routeirq Do IRQ routing for all PCI devices.
1506 This is normally done in pci_enable_device(),
1507 so this option is a temporary workaround
1508 for broken drivers that don't call it.
1509 firmware [ARM] Do not re-enumerate the bus but instead
1510 just use the configuration from the
1511 bootloader. This is currently used on
1512 IXP2000 systems where the bus has to be
1513 configured a certain way for adjunct CPUs.
1514 noearly [X86] Don't do any early type 1 scanning.
1515 This might help on some broken boards which
1516 machine check when some devices' config space
1517 is read. But various workarounds are disabled
1518 and some IOMMU drivers will not work.
1519 bfsort Sort PCI devices into breadth-first order.
1520 This sorting is done to get a device
1521 order compatible with older (<= 2.4) kernels.
1522 nobfsort Don't sort PCI devices into breadth-first order.
1523 cbiosize=nn[KMG] The fixed amount of bus space which is
1524 reserved for the CardBus bridge's IO window.
1525 The default value is 256 bytes.
1526 cbmemsize=nn[KMG] The fixed amount of bus space which is
1527 reserved for the CardBus bridge's memory
1528 window. The default value is 64 megabytes.
1530 pcmv= [HW,PCMCIA] BadgePAD 4
1533 See Documentation/paride.txt.
1535 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1538 See arch/parisc/kernel/pdc_chassis.c
1541 See Documentation/paride.txt.
1544 See Documentation/paride.txt.
1546 pirq= [SMP,APIC] Manual mp-table setup
1547 See Documentation/i386/IO-APIC.txt.
1549 plip= [PPT,NET] Parallel port network link
1550 Format: { parport<nr> | timid | 0 }
1551 See also Documentation/parport.txt.
1557 { on | off | curr | res | no-curr | no-res }
1560 [ISAPNP] Exclude IRQs for the autoconfiguration
1563 [ISAPNP] Exclude DMAs for the autoconfiguration
1565 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1566 Ranges are in pairs (I/O port base and size).
1569 [ISAPNP] Exclude memory regions for the
1571 Ranges are in pairs (memory base and size).
1573 print-fatal-signals=
1574 [KNL] debug: print fatal signals
1575 print-fatal-signals=1: print segfault info to
1579 printk.time= Show timing data prefixed to each printk message line
1580 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1582 profile= [KNL] Enable kernel profiling via /proc/profile
1583 Format: [schedule,]<number>
1584 Param: "schedule" - profile schedule points.
1585 Param: <number> - step/bucket size as a power of 2 for
1586 statistical time based profiling.
1587 Param: "sleep" - profile D-state sleeping (millisecs).
1588 Requires CONFIG_SCHEDSTATS
1589 Param: "kvm" - profile VM exits.
1591 processor.max_cstate= [HW,ACPI]
1592 Limit processor to maximum C-state
1593 max_cstate=9 overrides any DMI blacklist limit.
1595 processor.nocst [HW,ACPI]
1596 Ignore the _CST method to determine C-states,
1597 instead using the legacy FADT method
1599 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1601 See Documentation/ramdisk.txt.
1603 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1604 probe for; one of (bare|imps|exps|lifebook|any).
1605 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1607 psmouse.resetafter= [HW,MOUSE]
1608 Try to reset the device after so many bad packets
1611 [HW,MOUSE] Set desired mouse resolution, in dpi.
1612 psmouse.smartscroll=
1613 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1614 0 = disabled, 1 = enabled (default).
1616 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1618 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1621 See Documentation/paride.txt.
1624 [KNL] Number of legacy pty's. Overwrites compiled-in
1627 quiet [KNL] Disable most log messages
1632 See Documentation/md.txt.
1634 ramdisk_blocksize= [RAM]
1635 See Documentation/ramdisk.txt.
1637 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1638 See Documentation/ramdisk.txt.
1640 rcupdate.blimit= [KNL,BOOT]
1641 Set maximum number of finished RCU callbacks to process
1644 rcupdate.qhimark= [KNL,BOOT]
1645 Set threshold of queued
1646 RCU callbacks over which batch limiting is disabled.
1648 rcupdate.qlowmark= [KNL,BOOT]
1649 Set threshold of queued RCU callbacks below which
1650 batch limiting is re-enabled.
1654 Run specified binary instead of /init from the ramdisk,
1655 used for early userspace startup. See initrd.
1657 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1658 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1659 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1661 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1663 reservetop= [X86-32]
1665 Reserves a hole at the top of the kernel virtual
1668 reset_devices [KNL] Force drivers to reset the underlying device
1669 during initialization.
1672 Specify the partition device for software suspend
1674 resume_offset= [SWSUSP]
1675 Specify the offset from the beginning of the partition
1676 given by "resume=" at which the swap header is located,
1677 in <PAGE_SIZE> units (needed only for swap files).
1678 See Documentation/power/swsusp-and-swap-files.txt
1680 retain_initrd [RAM] Keep initrd memory after extraction
1682 rhash_entries= [KNL,NET]
1683 Set number of hash buckets for route cache
1685 riscom8= [HW,SERIAL]
1686 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1688 ro [KNL] Mount root device read-only on boot
1690 root= [KNL] Root filesystem
1692 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1693 mount the root filesystem
1695 rootflags= [KNL] Set root filesystem mount option string
1697 rootfstype= [KNL] Set root filesystem type
1699 rootwait [KNL] Wait (indefinitely) for root device to show up.
1700 Useful for devices that are detected asynchronously
1701 (e.g. USB and MMC devices).
1703 root_plug.vendor_id=
1704 [ROOTPLUG] Override the default vendor ID
1706 root_plug.product_id=
1707 [ROOTPLUG] Override the default product ID
1710 [ROOTPLUG] Enable debugging output
1712 rw [KNL] Mount root device read-write on boot
1714 S [KNL] Run init in single mode
1717 See drivers/net/irda/sa1100_ir.c.
1719 sbni= [NET] Granch SBNI12 leased line adapter
1721 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1722 Format: <io>[,<timeout>[,<isapnp>]]
1724 scsi_debug_*= [SCSI]
1725 See drivers/scsi/scsi_debug.c.
1727 scsi_default_dev_flags=
1728 [SCSI] SCSI default device flags
1731 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1732 Format: <vendor>:<model>:<flags>
1733 (flags are integer value)
1735 scsi_logging_level= [SCSI] a bit mask of logging levels
1736 See drivers/scsi/scsi_logging.h for bits. Also
1737 settable via sysctl at dev.scsi.logging_level
1738 (/proc/sys/dev/scsi/logging_level).
1739 There is also a nice 'scsi_logging_level' script in the
1740 S390-tools package, available for download at
1741 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1743 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1744 discovered. async scans them in kernel threads,
1745 allowing boot to proceed. none ignores them, expecting
1746 user space to do the scan.
1748 selinux [SELINUX] Disable or enable SELinux at boot time.
1749 Format: { "0" | "1" }
1750 See security/selinux/Kconfig help text.
1753 Default value is set via kernel config option.
1754 If enabled at boot time, /selinux/disable can be used
1755 later to disable prior to initial policy load.
1757 selinux_compat_net =
1758 [SELINUX] Set initial selinux_compat_net flag value.
1759 Format: { "0" | "1" }
1760 0 -- use new secmark-based packet controls
1761 1 -- use legacy packet controls
1762 Default value is 0 (preferred).
1763 Value can be changed at runtime via
1764 /selinux/compat_net.
1766 serialnumber [BUGS=X86-32]
1769 Maximal number of shapers.
1772 See header of drivers/scsi/sim710.c.
1779 slub_debug[=options[,slabs]] [MM, SLUB]
1780 Enabling slub_debug allows one to determine the
1781 culprit if slab objects become corrupted. Enabling
1782 slub_debug can create guard zones around objects and
1783 may poison objects when not in use. Also tracks the
1784 last alloc / free. For more information see
1785 Documentation/vm/slub.txt.
1787 slub_max_order= [MM, SLUB]
1788 Determines the maximum allowed order for slabs.
1789 A high setting may cause OOMs due to memory
1790 fragmentation. For more information see
1791 Documentation/vm/slub.txt.
1793 slub_min_objects= [MM, SLUB]
1794 The minimum number of objects per slab. SLUB will
1795 increase the slab order up to slub_max_order to
1796 generate a sufficiently large slab able to contain
1797 the number of objects indicated. The higher the number
1798 of objects the smaller the overhead of tracking slabs
1799 and the less frequently locks need to be acquired.
1800 For more information see Documentation/vm/slub.txt.
1802 slub_min_order= [MM, SLUB]
1803 Determines the mininum page order for slabs. Must be
1804 lower than slub_max_order.
1805 For more information see Documentation/vm/slub.txt.
1807 slub_nomerge [MM, SLUB]
1808 Disable merging of slabs with similar size. May be
1809 necessary if there is some reason to distinguish
1810 allocs to different slabs. Debug options disable
1811 merging on their own.
1812 For more information see Documentation/vm/slub.txt.
1815 Format: <io1>[,<io2>[,...,<io8>]]
1817 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1818 attempt to substitute SMP alternatives once at boot.
1820 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1821 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1822 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1823 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1824 smsc-ircc2.ircc_irq= [HW] IRQ line
1825 smsc-ircc2.ircc_dma= [HW] DMA channel
1826 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1827 0: Toshiba Satellite 1800 (GP data pin select)
1828 1: Fast pin select (default)
1831 snd-ad1816a= [HW,ALSA]
1833 snd-ad1848= [HW,ALSA]
1835 snd-ali5451= [HW,ALSA]
1837 snd-als100= [HW,ALSA]
1839 snd-als4000= [HW,ALSA]
1841 snd-azt2320= [HW,ALSA]
1843 snd-cmi8330= [HW,ALSA]
1845 snd-cmipci= [HW,ALSA]
1847 snd-cs4231= [HW,ALSA]
1849 snd-cs4232= [HW,ALSA]
1851 snd-cs4236= [HW,ALSA]
1853 snd-cs4281= [HW,ALSA]
1855 snd-cs46xx= [HW,ALSA]
1857 snd-dt019x= [HW,ALSA]
1859 snd-dummy= [HW,ALSA]
1861 snd-emu10k1= [HW,ALSA]
1863 snd-ens1370= [HW,ALSA]
1865 snd-ens1371= [HW,ALSA]
1867 snd-es968= [HW,ALSA]
1869 snd-es1688= [HW,ALSA]
1871 snd-es18xx= [HW,ALSA]
1873 snd-es1938= [HW,ALSA]
1875 snd-es1968= [HW,ALSA]
1877 snd-fm801= [HW,ALSA]
1879 snd-gusclassic= [HW,ALSA]
1881 snd-gusextreme= [HW,ALSA]
1883 snd-gusmax= [HW,ALSA]
1887 snd-ice1712= [HW,ALSA]
1889 snd-intel8x0= [HW,ALSA]
1891 snd-interwave= [HW,ALSA]
1896 snd-korg1212= [HW,ALSA]
1898 snd-maestro3= [HW,ALSA]
1900 snd-mpu401= [HW,ALSA]
1902 snd-mtpav= [HW,ALSA]
1904 snd-nm256= [HW,ALSA]
1906 snd-opl3sa2= [HW,ALSA]
1914 snd-opti93x= [HW,ALSA]
1918 snd-rme32= [HW,ALSA]
1920 snd-rme96= [HW,ALSA]
1922 snd-rme9652= [HW,ALSA]
1928 snd-sbawe= [HW,ALSA]
1930 snd-serial= [HW,ALSA]
1932 snd-sgalaxy= [HW,ALSA]
1934 snd-sonicvibes= [HW,ALSA]
1939 snd-sun-cs4231= [HW,ALSA]
1941 snd-trident= [HW,ALSA]
1943 snd-usb-audio= [HW,ALSA,USB]
1945 snd-via82xx= [HW,ALSA]
1947 snd-virmidi= [HW,ALSA]
1949 snd-wavefront= [HW,ALSA]
1951 snd-ymfpci= [HW,ALSA]
1953 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1954 See Documentation/sonypi.txt
1956 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1957 See Documentation/specialix.txt.
1959 spia_io_base= [HW,MTD]
1965 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1967 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1968 See Documentation/scsi/st.txt.
1972 Set the STI (builtin display/keyboard on the HP-PARISC
1973 machines) console (graphic card) which should be used
1974 as the initial boot-console.
1975 See also comment in drivers/video/console/sticore.c.
1978 See comment in drivers/video/console/sticore.c.
1981 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1985 Control how the NFS server code allocates CPUs to
1986 service thread pools. Depending on how many NICs
1987 you have and where their interrupts are bound, this
1988 option will affect which CPUs will do NFS serving.
1989 Note: this parameter cannot be changed while the
1990 NFS server is running.
1992 auto the server chooses an appropriate mode
1993 automatically using heuristics
1994 global a single global pool contains all CPUs
1995 percpu one pool for each CPU
1996 pernode one pool for each NUMA node (equivalent
1997 to global on non-NUMA machines)
1999 swiotlb= [IA-64] Number of I/O TLB slabs
2003 sym53c416= [HW,SCSI]
2004 See header of drivers/scsi/sym53c416.c.
2006 sysrq_always_enabled
2008 Ignore sysrq setting - this boot parameter will
2009 neutralize any effect of /proc/sys/kernel/sysrq.
2010 Useful for debugging.
2013 See header of drivers/scsi/t128.c.
2017 thash_entries= [KNL,NET]
2018 Set number of hash buckets for TCP connection
2020 thermal.act= [HW,ACPI]
2021 -1: disable all active trip points in all thermal zones
2022 <degrees C>: override all lowest active trip points
2024 thermal.crt= [HW,ACPI]
2025 -1: disable all critical trip points in all thermal zones
2026 <degrees C>: lower all critical trip points
2028 thermal.nocrt= [HW,ACPI]
2029 Set to disable actions on ACPI thermal zone
2030 critical and hot trip points.
2032 thermal.off= [HW,ACPI]
2033 1: disable ACPI thermal control
2035 thermal.psv= [HW,ACPI]
2036 -1: disable all passive trip points
2037 <degrees C>: override all passive trip points to this value
2039 thermal.tzp= [HW,ACPI]
2040 Specify global default ACPI thermal zone polling rate
2041 <deci-seconds>: poll all this frequency
2042 0: no polling (default)
2044 tipar.timeout= [HW,PPT]
2045 Set communications timeout in tenths of a second
2048 tipar.delay= [HW,PPT]
2049 Set inter-bit delay in microseconds (default 10).
2052 See comment before function dc390_setup() in
2053 drivers/scsi/tmscsim.c.
2057 trix= [HW,OSS] MediaTrix AudioTrix Pro
2059 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2061 turbografx.map[2|3]= [HW,JOY]
2062 TurboGraFX parallel port interface
2064 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2065 See also Documentation/input/joystick-parport.txt
2067 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2068 See header of drivers/scsi/u14-34f.c.
2077 [USB] Ignore overcurrent events (default N).
2078 Some badly-designed motherboards generate lots of
2079 bogus events, for ports that aren't wired to
2080 anything. Set this parameter to avoid log spamming.
2081 Note that genuine overcurrent events won't be
2084 usbcore.autosuspend=
2085 [USB] The autosuspend time delay (in seconds) used
2086 for newly-detected USB devices (default 2). This
2087 is the time required before an idle device will be
2088 autosuspended. Devices for which the delay is set
2089 to a negative value won't be autosuspended at all.
2092 [USBHID] The interval which mice are to be polled at.
2094 vdso= [X86-32,SH,x86-64]
2095 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2096 vdso=1: enable VDSO (default)
2097 vdso=0: disable VDSO mapping
2099 vdso32= [X86-32,X86-64]
2100 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2101 vdso32=1: enable 32-bit VDSO (default)
2102 vdso32=0: disable 32-bit VDSO mapping
2105 vector=percpu: enable percpu vector domain
2107 video= [FB] Frame buffer configuration
2108 See Documentation/fb/modedb.txt.
2110 vga= [BOOT,X86-32] Select a particular video mode
2111 See Documentation/i386/boot.txt and
2112 Documentation/svga.txt.
2113 Use vga=ask for menu.
2114 This is actually a boot loader parameter; the value is
2115 passed to the kernel using a special protocol.
2117 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2118 size of <nn>. This can be used to increase the
2119 minimum size (128MB on x86). It can also be used to
2120 decrease the size and leave more room for directly
2123 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2126 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2129 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2132 waveartist= [HW,OSS]
2133 Format: <io>,<irq>,<dma>,<dma2>
2136 See header of drivers/scsi/wd33c93.c.
2139 See header of drivers/scsi/wd7000.c.
2142 See Documentation/watchdog/wdt.txt.
2144 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2145 xd_geo= See header of drivers/block/xd.c.
2147 xirc2ps_cs= [NET,PCMCIA]
2149 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2151 norandmaps Don't use address space randomization
2152 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2154 ______________________________________________________________________
2158 Add documentation for ALSA options.
2159 Add more DRM drivers.