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/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 }
151 See Documentation/power/video.txt
153 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
154 Format: { level | edge | high | low }
156 acpi_irq_balance [HW,ACPI]
157 ACPI will balance active IRQs
160 acpi_irq_nobalance [HW,ACPI]
161 ACPI will not move active IRQs (default)
164 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
166 Format: <irq>,<irq>...
168 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
169 Format: <irq>,<irq>...
171 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
173 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
174 Format: To spoof as Windows 98: ="Microsoft Windows"
176 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
177 acpi_osi="string1" # add string1 -- only one string
178 acpi_osi="!string2" # remove built-in string2
179 acpi_osi= # disable all strings
181 acpi_serialize [HW,ACPI] force serialization of AML methods
183 acpi_skip_timer_override [HW,ACPI]
184 Recognize and ignore IRQ0/pin2 Interrupt Override.
185 For broken nForce2 BIOS resulting in XT-PIC timer.
186 acpi_use_timer_override [HW,ACPI}
187 Use timer override. For some broken Nvidia NF5 boards
188 that require a timer override, but don't have
191 acpi.debug_layer= [HW,ACPI]
193 Each bit of the <int> indicates an ACPI debug layer,
194 1: enable, 0: disable. It is useful for boot time
195 debugging. After system has booted up, it can be set
196 via /sys/module/acpi/parameters/debug_layer.
197 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
198 Available bits (add the numbers together) to enable debug output
199 for specific parts of the ACPI subsystem:
200 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
201 0x10 namespace 0x20 parser 0x40 dispatcher
202 0x80 executer 0x100 resources 0x200 acpica debugger
203 0x400 os services 0x800 acpica disassembler.
204 The number can be in decimal or prefixed with 0x in hex.
205 Warning: Many of these options can produce a lot of
206 output and make your system unusable. Be very careful.
208 acpi.debug_level= [HW,ACPI]
210 Each bit of the <int> indicates an ACPI debug level,
211 1: enable, 0: disable. It is useful for boot time
212 debugging. After system has booted up, it can be set
213 via /sys/module/acpi/parameters/debug_level.
214 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
215 Available bits (add the numbers together) to enable different
216 debug output levels of the ACPI subsystem:
217 0x01 error 0x02 warn 0x04 init 0x08 debug object
218 0x10 info 0x20 init names 0x40 parse 0x80 load
219 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
220 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
221 0x10000 resources 0x20000 user requests 0x40000 package.
222 The number can be in decimal or prefixed with 0x in hex.
223 Warning: Many of these options can produce a lot of
224 output and make your system unusable. Be very careful.
226 acpi_pm_good [X86-32,X86-64]
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
232 { off | try_unsupported }
233 off: disable AGP support
234 try_unsupported: try to drive unsupported chipsets
235 (may crash computer or cause data corruption)
237 enable_timer_pin_1 [i386,x86-64]
238 Enable PIN 1 of APIC timer
239 Can be useful to work around chipset bugs
240 (in particular on some ATI chipsets).
241 The kernel tries to set a reasonable default.
243 disable_timer_pin_1 [i386,x86-64]
244 Disable PIN 1 of APIC timer
245 Can be useful to work around chipset bugs.
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
251 See header of drivers/scsi/advansys.c.
253 advwdt= [HW,WDT] Advantech WDT
254 Format: <iostart>,<iostop>
256 aedsp16= [HW,OSS] Audio Excel DSP 16
257 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
258 See also header of sound/oss/aedsp16.c.
261 See Documentation/scsi/aha152x.txt.
264 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267 See Documentation/scsi/aic7xxx.txt.
270 See Documentation/scsi/aic79xx.txt.
272 amijoy.map= [HW,JOY] Amiga joystick support
273 Map of devices attached to JOY0DAT and JOY1DAT
275 See also Documentation/kernel/input/joystick.txt
277 analog.map= [HW,JOY] Analog joystick and gamepad support
278 Specifies type or capabilities of an analog joystick
279 connected to one of 16 gameports
280 Format: <type1>,<type2>,..<type16>
283 Power management functions (SPARCstation-4/5 + deriv.)
285 Disable APC CPU standby support. SPARCstation-Fox does
286 not play well with APC CPU idle - disable it if you have
287 APC and your system crashes randomly.
289 apic= [APIC,i386] Advanced Programmable Interrupt Controller
290 Change the output verbosity whilst booting
291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
298 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
299 Format: <io>,<irq>,<nodeID>
303 atarimouse= [HW,MOUSE] Atari Mouse
305 atascsi= [HW,SCSI] Atari SCSI
307 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
308 EzKey and similar keyboards
310 atkbd.reset= [HW] Reset keyboard during initialization
312 atkbd.set= [HW] Select keyboard code set
313 Format: <int> (2 = AT (default), 3 = PS/2)
315 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 atkbd.softraw= [HW] Choose between synthetic and real raw mode
319 Format: <bool> (0 = real, 1 = synthetic (default))
321 atkbd.softrepeat= [HW]
322 Use software keyboard repeat
326 baycom_epp= [HW,AX25]
329 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
331 See header of drivers/net/hamradio/baycom_par.c.
333 baycom_ser_fdx= [HW,AX25]
334 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
335 Format: <io>,<irq>,<mode>[,<baud>]
336 See header of drivers/net/hamradio/baycom_ser_fdx.c.
338 baycom_ser_hdx= [HW,AX25]
339 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
340 Format: <io>,<irq>,<mode>
341 See header of drivers/net/hamradio/baycom_ser_hdx.c.
343 boot_delay= Milliseconds to delay each printk during boot.
344 Values larger than 10 seconds (10000) are changed to
348 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
349 bttv.radio= Most important insmod options are available as
351 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
352 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355 See drivers/scsi/BusLogic.c, comment before function
356 BusLogic_ParseDriverOptions().
358 c101= [NET] Moxa C101 synchronous serial card
360 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
361 Sometimes CPU hardware bugs make them report the cache
362 size incorrectly. The kernel will attempt work arounds
363 to fix known problems, but for some CPUs it is not
364 possible to determine what the correct size should be.
365 This option provides an override for these situations.
368 [SECURITY] Disable capabilities. This would normally
369 be used only if an alternative security model is to be
370 configured. Potentially dangerous and should only be
371 used if you are entirely sure of the consequences.
373 ccw_timeout_log [S390]
374 See Documentation/s390/CommonIO for details.
376 checkreqprot [SELINUX] Set initial checkreqprot flag value.
377 Format: { "0" | "1" }
378 See security/selinux/Kconfig help text.
379 0 -- check protection applied by kernel (includes
380 any implied execute protection).
381 1 -- check protection requested by application.
382 Default value is set via a kernel config option.
383 Value can be changed at runtime via
384 /selinux/checkreqprot.
387 See Documentation/s390/CommonIO for details.
390 See Documentation/s390/CommonIO for details.
392 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
394 Forces specified clocksource (if available) to be used
395 when calculating gettimeofday(). If specified
396 clocksource is not available, it defaults to PIT.
397 Format: { pit | tsc | cyclone | pmtmr }
399 clocksource= [GENERIC_TIME] Override the default clocksource
401 Override the default clocksource and use the clocksource
402 with the name specified.
403 Some clocksource names to choose from, depending on
405 [all] jiffies (this is the base, fallback clocksource)
407 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
408 pxa_timer,timer3,32k_counter,timer0_1
410 [X86-32] pit,hpet,tsc,vmi-timer;
411 scx200_hrt on Geode; cyclone on IBM x440
419 clearcpuid=BITNUM [X86]
420 Disable CPUID feature X for the kernel. See
421 include/asm-x86/cpufeature.h for the valid bit numbers.
422 Note the Linux specific bits are not necessarily
423 stable over kernel options, but the vendor specific
425 Also note that user programs calling CPUID directly
426 or using the feature without checking anything
427 will still see it. This just prevents it from
428 being used by the kernel or shown in /proc/cpuinfo.
429 Also note the kernel might malfunction if you disable
432 code_bytes [IA32/X86_64] How many bytes of object code to print
439 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
440 over the 8254 in addition to over the IO-APIC. The
441 kernel tries to set a sensible default.
443 hpet= [X86-32,HPET] option to control HPET usage
444 Format: { enable (default) | disable | force }
445 disable: disable HPET and use PIT instead
446 force: allow force enabled of undocumented chips (ICH4,
449 com20020= [HW,NET] ARCnet - COM20020 chipset
451 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
453 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
457 ARCnet - COM90xx chipset (memory-mapped buffers)
458 Format: <io>[,<irq>[,<memstart>]]
460 condev= [HW,S390] console device
463 console= [KNL] Output console device and options.
465 tty<n> Use the virtual console device <n>.
469 Use the specified serial port. The options are of
470 the form "bbbbpnf", where "bbbb" is the baud rate,
471 "p" is parity ("n", "o", or "e"), "n" is number of
472 bits, and "f" is flow control ("r" for RTS or
473 omit it). Default is "9600n8".
475 See Documentation/serial-console.txt for more
477 Documentation/networking/netconsole.txt for an
480 uart[8250],io,<addr>[,options]
481 uart[8250],mmio,<addr>[,options]
482 Start an early, polled-mode console on the 8250/16550
483 UART at the specified I/O port or MMIO address,
484 switching to the matching ttyS device later. The
485 options are the same as for ttyS, above.
487 earlycon= [KNL] Output early console device and options.
488 uart[8250],io,<addr>[,options]
489 uart[8250],mmio,<addr>[,options]
490 Start an early, polled-mode console on the 8250/16550
491 UART at the specified I/O port or MMIO address.
492 The options are the same as for ttyS, above.
495 [HW] Never suspend the console
496 Disable suspending of consoles during suspend and
497 hibernate operations. Once disabled, debugging
498 messages can reach various consoles while the rest
499 of the system is being put to sleep (ie, while
500 debugging driver suspend/resume hooks). This may
501 not work reliably with all consoles, but is known
502 to work with serial and VGA consoles.
504 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
506 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
508 crashkernel=nn[KMG]@ss[KMG]
509 [KNL] Reserve a chunk of physical memory to
510 hold a kernel to switch to with kexec on panic.
512 crashkernel=range1:size1[,range2:size2,...][@offset]
513 [KNL] Same as above, but depends on the memory
514 in the running system. The syntax of range is
515 start-[end] where start and end are both
516 a memory unit (amount[KMG]). See also
517 Documentation/kdump/kdump.txt for a example.
520 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
525 cs89x0_media= [HW,NET]
526 Format: { rj45 | aui | bnc }
529 See header of drivers/s390/block/dasd_devmap.c.
531 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
532 (one device per port)
533 Format: <port#>,<type>
534 See also Documentation/input/joystick-parport.txt
536 debug [KNL] Enable kernel debugging (events log level).
539 [KNL] verbose self-tests
541 Print debugging info while doing the locking API
543 We default to 0 (no extra messages), setting it to
544 1 will print _a lot_ more information - normally
545 only useful to kernel developers.
548 Format: <area>[,<node>]
549 See also Documentation/networking/decnet.txt.
552 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
553 Change the default blue palette of the console.
554 This is a 16-member array composed of values
558 Format: <green0>,<green1>,<green2>,...,<green15>
559 Change the default green palette of the console.
560 This is a 16-member array composed of values
564 Format: <red0>,<red1>,<red2>,...,<red15>
565 Change the default red palette of the console.
566 This is a 16-member array composed of values
572 Set system-wide default UTF-8 mode for all tty's.
573 Default is 1, i.e. UTF-8 mode is enabled for all
574 newly opened terminals.
577 Set number of hash buckets for dentry cache.
580 IO parameters + enable/disable command.
582 digiepca= [HW,SERIAL]
583 See drivers/char/README.epca and
584 Documentation/digiepca.txt.
586 disable_mtrr_trim [X86-64, Intel only]
587 By default the kernel will trim any uncacheable
588 memory out of your available memory pool based on
589 MTRR settings. This parameter disables that behavior,
590 possibly causing your machine to run very slowly.
592 dmasound= [HW,OSS] Sound subsystem buffers
598 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
600 earlyprintk=serial[,ttySn[,baudrate]]
602 Append ",keep" to not disable it when the real console
605 Only vga or serial at a time, not both.
607 Currently only ttyS0 and ttyS1 are supported.
609 Interaction with the standard serial driver is not
612 The VGA output is eventually overwritten by the real
618 Format: {"of[f]" | "sk[ipmbr]"}
619 See comment in arch/i386/boot/edd.S
621 eisa_irq_edge= [PARISC,HW]
622 See header of drivers/parisc/eisa.c.
625 See comment before function elanfreq_setup() in
626 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
629 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
630 See Documentation/block/as-iosched.txt and
631 Documentation/block/deadline-iosched.txt for details.
633 elfcorehdr= [X86-32, X86_64]
634 Specifies physical address of start of kernel core
635 image elf header. Generally kexec loader will
636 pass this option to capture kernel.
637 See Documentation/kdump/kdump.txt for details.
639 enforcing [SELINUX] Set initial enforcing status.
641 See security/selinux/Kconfig help text.
642 0 -- permissive (log only, no denials).
643 1 -- enforcing (deny and log).
645 Value can be changed at runtime via /selinux/enforce.
648 Format: <spdif>,[<nomix>,[<amplifier>]]
649 See also header of sound/oss/es1371.c.
651 ether= [HW,NET] Ethernet cards parameters
652 This option is obsoleted by the "netdev=" option, which
653 has equivalent usage. See its documentation for details.
655 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
660 fail_make_request=[KNL]
661 General fault injection mechanism.
662 Format: <interval>,<probability>,<space>,<times>
663 See also /Documentation/fault-injection/.
666 See header of drivers/scsi/fd_mcs.c.
669 See header of drivers/scsi/fdomain.c.
672 See Documentation/floppy.txt.
675 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
676 support via parallel port (up to 5 devices per port)
677 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
678 See also Documentation/input/joystick-parport.txt
682 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
687 See header of drivers/scsi/gdth.c.
689 gpt [EFI] Forces disk with valid GPT signature but
690 invalid Protective MBR to be treated as GPT.
694 hashdist= [KNL,NUMA] Large hashes allocated during boot
695 are distributed across NUMA nodes. Defaults on
696 for IA-64, off otherwise.
697 Format: 0 | 1 (for off | on)
699 hcl= [IA-64] SGI's Hardware Graph compatibility layer
701 hd= [EIDE] (E)IDE hard drive subsystem geometry
702 Format: <cyl>,<head>,<sect>
704 hd?= [HW] (E)IDE subsystem
705 hd?lun= See Documentation/ide.txt.
707 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
708 size of <nn>. This works even on boxes that have no
709 highmem otherwise. This also works to reduce highmem
710 size on bigger boxes.
712 highres= [KNL] Enable/disable high resolution timer mode.
713 Valid parameters: "on", "off"
717 See Documentation/isdn/README.HiSax.
719 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
721 i8042.direct [HW] Put keyboard port into non-translated mode
722 i8042.dumbkbd [HW] Pretend that controller can only read data from
723 keyboard and cannot control its state
724 (Don't attempt to blink the leds)
725 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
726 i8042.nokbd [HW] Don't check/create keyboard port
727 i8042.nomux [HW] Don't check presence of an active multiplexing
729 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
732 [HW] Frequency with which keyboard LEDs should blink
733 when kernel panics (default is 0.5 sec)
734 i8042.reset [HW] Reset the controller during init and cleanup
735 i8042.unlock [HW] Unlock (ignore) the keylock
739 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
740 indicates that the driver is running on unsupported
742 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
743 does not match list of supported models.
745 [HW] Report power status in /proc/i8k
746 (disabled by default)
747 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
750 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
751 See Documentation/mca.txt.
754 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
756 ide= [HW] (E)IDE subsystem
757 Format: ide=nodma or ide=doubler or ide=reverse
758 See Documentation/ide.txt.
760 ide?= [HW] (E)IDE subsystem
761 Format: ide?=noprobe or chipset specific parameters.
762 See Documentation/ide.txt.
764 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
765 See Documentation/ide.txt.
768 Format: idle=poll or idle=mwait
769 Poll forces a polling idle loop that can slightly improves the performance
770 of waking up a idle CPU, but will use a lot of power and make the system
771 run hot. Not recommended.
772 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
773 to not use it because it doesn't save as much power as a normal idle
774 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
777 ignore_loglevel [KNL]
778 Ignore loglevel setting - this will print /all/
779 kernel messages to the console. Useful for debugging.
782 Set number of hash buckets for inode cache.
785 See header of drivers/scsi/in2000.c.
789 Run specified binary instead of /sbin/init as init
792 initcall_debug [KNL] Trace initcalls as they are executed. Useful
793 for working out where the kernel is dying during
796 initrd= [BOOT] Specify the location of the initial ramdisk
798 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
803 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
805 Disable intel iommu driver.
806 igfx_off [Default Off]
807 By default, gfx is mapped as normal device. If a gfx
808 device has a dedicated DMAR unit, the DMAR unit is
809 bypassed by not enabling DMAR with this option. In
810 this case, gfx device will use physical address for
813 With this option iommu will not optimize to look
814 for io virtual address below 32 bit forcing dual
815 address cycle on pci bus for cards supporting greater
816 than 32 bit addressing. The default is to look
817 for translation below 32 bit and if not available
818 then look in the higher range.
820 io_delay= [X86-32,X86-64] I/O delay method
822 Standard port 0x80 based delay
824 Alternate port 0xed based delay (needed on some systems)
826 Simple two microseconds delay
830 io7= [HW] IO7 for Marvel based alpha systems
831 See comment before marvel_specify_io7 in
832 arch/alpha/kernel/core_marvel.c.
835 See Documentation/nfsroot.txt.
837 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
838 See comment before ip2_setup() in
839 drivers/char/ip2/ip2base.c.
841 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
842 See header of drivers/scsi/ips.c.
844 ports= [IP_VS_FTP] IPVS ftp helper module
846 Up to 8 (IP_VS_APP_MAX_PORTS) ports
848 Format: <port>,<port>....
851 When an interrupt is not handled search all handlers
852 for it. Intended to get systems with badly broken
856 When an interrupt is not handled search all handlers
857 for it. Also check all handlers each timer
858 interrupt. Intended to get systems with badly broken
862 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
864 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
866 <cpu number>,...,<cpu number>
868 <cpu number>-<cpu number> (must be a positive range in ascending order)
870 <cpu number>,...,<cpu number>-<cpu number>
871 This option can be used to specify one or more CPUs
872 to isolate from the general SMP balancing and scheduling
873 algorithms. The only way to move a process onto or off
874 an "isolated" CPU is via the CPU affinity syscalls.
875 <cpu number> begins at 0 and the maximum value is
876 "number of CPUs in system - 1".
878 This option is the preferred way to isolate CPUs. The
879 alternative -- manually setting the CPU mask of all
880 tasks in the system -- can cause problems and
881 suboptimal load balancer performance.
885 js= [HW,JOY] Analog joystick
886 See Documentation/input/joystick.txt.
888 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
889 specifies the amount of memory usable by the kernel
890 for non-movable allocations. The requested amount is
891 spread evenly throughout all nodes in the system. The
892 remaining memory in each node is used for Movable
893 pages. In the event, a node is too small to have both
894 kernelcore and Movable pages, kernelcore pages will
895 take priority and other nodes will have a larger number
896 of kernelcore pages. The Movable zone is used for the
897 allocation of pages that may be reclaimed or moved
898 by the page migration subsystem. This means that
899 HugeTLB pages may not be allocated from this zone.
900 Note that allocations like PTEs-from-HighMem still
901 use the HighMem zone if it exists, and the Normal
904 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
905 is similar to kernelcore except it specifies the
906 amount of memory used for migratable allocations.
907 If both kernelcore and movablecore is specified,
908 then kernelcore will be at *least* the specified
909 value but may be more. If movablecore on its own
910 is specified, the administrator must be careful
911 that the amount of memory usable for all allocations
916 kstack=N [X86-32,X86-64] Print N words from the kernel stack
921 lapic [X86-32,APIC] Enable the local APIC even if BIOS
924 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
927 libata.dma= [LIBATA] DMA control
928 libata.dma=0 Disable all PATA and SATA DMA
929 libata.dma=1 PATA and SATA Disk DMA only
930 libata.dma=2 ATAPI (CDROM) DMA only
931 libata.dma=4 Compact Flash DMA only
932 Combinations also work, so libata.dma=3 enables DMA
933 for disks and CDROMs, but not CFs.
935 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
939 load_ramdisk= [RAM] List of ramdisks to load from floppy
940 See Documentation/ramdisk.txt.
942 lockd.nlm_grace_period=P [NFS] Assign grace period.
945 lockd.nlm_tcpport=N [NFS] Assign TCP port.
948 lockd.nlm_timeout=T [NFS] Assign timeout value.
951 lockd.nlm_udpport=M [NFS] Assign UDP port.
954 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
957 loglevel= All Kernel Messages with a loglevel smaller than the
958 console loglevel will be printed to the console. It can
959 also be changed with klogd or other programs. The
960 loglevels are defined as follows:
962 0 (KERN_EMERG) system is unusable
963 1 (KERN_ALERT) action must be taken immediately
964 2 (KERN_CRIT) critical conditions
965 3 (KERN_ERR) error conditions
966 4 (KERN_WARNING) warning conditions
967 5 (KERN_NOTICE) normal but significant condition
968 6 (KERN_INFO) informational
969 7 (KERN_DEBUG) debug-level messages
971 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
972 Format: { n | nk | nM }
973 n must be a power of two. The default size
974 is set in the kernel config file.
976 logo.nologo [FB] Disables display of the built-in Linux logo.
977 This may be used to provide more screen space for
978 kernel log messages and is useful when debugging
979 kernel boot problems.
981 lp=0 [LP] Specify parallel ports to use, e.g,
982 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
983 lp=reset first parallel port). 'lp=0' disables the
984 lp=auto printer driver. 'lp=reset' (which can be
985 specified in addition to the ports) causes
986 attached printers to be reset. Using
987 lp=port1,port2,... specifies the parallel ports
988 to associate lp devices with, starting with
989 lp0. A port specification may be 'none' to skip
990 that lp device, or a parport name such as
991 'parport0'. Specifying 'lp=auto' instead of a
992 port specification list means that device IDs
993 from each port should be examined, to see if
994 an IEEE 1284-compliant printer is attached; if
995 so, the driver will manage that printer.
996 See also header of drivers/char/lp.c.
999 Sets loops_per_jiffy to given constant, thus avoiding
1000 time-consuming boot-time autodetection (up to 250 ms per
1001 CPU). 0 enables autodetection (default). To determine
1002 the correct value for your kernel, boot with normal
1003 autodetection and see what value is printed. Note that
1004 on SMP systems the preset will be applied to all CPUs,
1005 which is likely to cause problems if your CPUs need
1006 significantly divergent settings. An incorrect value
1007 will cause delays in the kernel to be wrong, leading to
1008 unpredictable I/O errors and other breakage. Although
1009 unlikely, in the extreme case this might damage your
1013 Format: <io>,<irq>,<dma>
1015 mac5380= [HW,SCSI] Format:
1016 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1018 mac53c9x= [HW,SCSI] Format:
1019 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1021 machvec= [IA64] Force the use of a particular machine-vector
1022 (machvec) in a generic kernel.
1023 Example: machvec=hpzx1_swiotlb
1025 max_loop= [LOOP] Maximum number of loopback devices that can
1029 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1030 should make use of. maxcpus=n : n >= 0 limits the
1031 kernel to using 'n' processors. n=0 is a special case,
1032 it is equivalent to "nosmp", which also disables
1035 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1036 equal to this physical address is ignored.
1038 max_luns= [SCSI] Maximum number of LUNs to probe.
1039 Should be between 1 and 2^32-1.
1042 [SCSI] Maximum number of LUNs received.
1043 Should be between 1 and 16384.
1045 mca-pentium [BUGS=X86-32]
1049 mce [X86-32] Machine Check Exception
1051 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1053 md= [HW] RAID subsystems devices and level
1054 See Documentation/md.txt.
1057 Format: <first>,<last>
1058 Specifies range of consoles to be captured by the MDA.
1060 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1061 Amount of memory to be used when the kernel is not able
1062 to see the whole system memory or for test.
1063 [X86-32] Use together with memmap= to avoid physical
1064 address space collisions. Without memmap= PCI devices
1065 could be placed at addresses belonging to unused RAM.
1067 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1070 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1071 E820 memory map, as specified by the user.
1072 Such memmap=exactmap lines can be constructed based on
1073 BIOS output or other requirements. See the memmap=nn@ss
1076 memmap=nn[KMG]@ss[KMG]
1077 [KNL] Force usage of a specific region of memory
1078 Region of memory to be used, from ss to ss+nn.
1080 memmap=nn[KMG]#ss[KMG]
1081 [KNL,ACPI] Mark specific memory as ACPI data.
1082 Region of memory to be used, from ss to ss+nn.
1084 memmap=nn[KMG]$ss[KMG]
1085 [KNL,ACPI] Mark specific memory as reserved.
1086 Region of memory to be used, from ss to ss+nn.
1088 meye.*= [HW] Set MotionEye Camera parameters
1089 See Documentation/video4linux/meye.txt.
1091 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1092 Multi-Function General Purpose Timers on AMD Geode
1098 [MOUSE] Maximum time between finger touching and
1099 leaving touchpad surface for touch to be considered
1100 a tap and be reported as a left button click (for
1101 touchpads working in absolute mode only).
1103 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1104 reporting absolute coordinates, such as tablets
1105 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1106 reporting absolute coordinates, such as tablets
1111 MTD_Partition= [MTD]
1112 Format: <name>,<region-number>,<size>,<offset>
1114 MTD_Region= [MTD] Format:
1115 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1118 See drivers/mtd/cmdlinepart.c.
1120 mtouchusb.raw_coordinates=
1121 [HW] Make the MicroTouch USB driver use raw coordinates
1122 ('y', default) or cooked coordinates ('n')
1124 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1127 See header of drivers/scsi/NCR_D700.c.
1131 ncr53c400= [HW,SCSI]
1133 ncr53c400a= [HW,SCSI]
1135 ncr53c406a= [HW,SCSI]
1137 ncr53c8xx= [HW,SCSI]
1139 netdev= [NET] Network devices parameters
1140 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1141 Note that mem_start is often overloaded to mean
1142 something different and driver-specific.
1143 This usage is only documented in each driver source
1147 See Documentation/nfsroot.txt.
1149 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1150 See Documentation/nfsroot.txt.
1152 nfs.callback_tcpport=
1153 [NFS] set the TCP port on which the NFSv4 callback
1154 channel should listen.
1156 nfs.idmap_cache_timeout=
1157 [NFS] set the maximum lifetime for idmapper cache
1161 [NFS] enable 64-bit inode numbers.
1162 If zero, the NFS client will fake up a 32-bit inode
1163 number for the readdir() and stat() syscalls instead
1164 of returning the full 64-bit number.
1165 The default is to return 64-bit inode numbers.
1167 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1168 when a NMI is triggered.
1169 Format: [state][,regs][,debounce][,die]
1171 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1173 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1174 emulation library even if a 387 maths coprocessor
1177 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1178 caches in the slab allocator. Saves per-node memory,
1179 but will impact performance.
1183 noapic [SMP,APIC] Tells the kernel to not make use of any
1184 IOAPICs that may be present in the system.
1186 nobats [PPC] Do not use BATs for mapping kernel lowmem
1187 on "Classic" PPC cores.
1191 nodelayacct [KNL] Disable per-task delay accounting
1193 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1195 noefi [X86-32,X86-64] Disable EFI runtime services support.
1199 noexec [X86-32,X86-64]
1200 noexec=on: enable non-executable mappings (default)
1201 noexec=off: disable nn-executable mappings
1203 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1204 register save and restore. The kernel will only save
1205 legacy floating-point registers on task switch.
1207 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1211 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1212 instruction doesn't work correctly and not to
1215 nohalt [IA-64] Tells the kernel not to use the power saving
1216 function PAL_HALT_LIGHT when idle. This increases
1217 power-consumption. On the positive side, it reduces
1218 interrupt wake-up latency, which may improve performance
1219 in certain environments such as networked servers or
1222 nohz= [KNL] Boottime enable/disable dynamic ticks
1223 Valid arguments: on, off
1226 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1228 noirqdebug [X86-32] Disables the code which attempts to detect and
1229 disable unhandled interrupt sources.
1231 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1232 broken timer IRQ sources.
1234 noisapnp [ISAPNP] Disables ISA PnP code.
1236 noinitrd [RAM] Tells the kernel not to load any configured
1241 nojitter [IA64] Disables jitter checking for ITC timers.
1243 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1245 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1247 noltlbs [PPC] Do not use large page/tlb entries for kernel
1248 lowmem mapping on PPC40x.
1250 nomca [IA-64] Disable machine check abort handling
1252 nomce [X86-32] Machine Check Exception
1254 nomfgpt [X86-32] Disable Multi-Function General Purpose
1255 Timer usage (for AMD Geode machines).
1257 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1259 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1260 with UP alternatives
1262 noresidual [PPC] Don't use residual data on PReP machines.
1264 noresume [SWSUSP] Disables resume and restores original swap
1267 no-scroll [VGA] Disables scrollback.
1268 This is required for the Braillex ib80-piezo Braille
1269 reader made by F.H. Papenmeier (Germany).
1273 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1275 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1276 and disable the IO APIC. legacy for "maxcpus=0".
1278 nosoftlockup [KNL] Disable the soft-lockup detector.
1280 nosync [HW,M68K] Disables sync negotiation for all devices.
1282 notsc [BUGS=X86-32] Disable Time Stamp Counter
1284 nousb [USB] Disable the USB subsystem
1288 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1289 one of ['zone', 'node', 'default'] can be specified
1290 This can be set from sysctl after boot.
1291 See Documentation/sysctl/vm.txt for details.
1293 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1298 oprofile.timer= [HW]
1299 Use timer interrupt instead of performance counters
1301 osst= [HW,SCSI] SCSI Tape Driver
1302 Format: <buffer_size>,<write_threshold>
1303 See also Documentation/scsi/st.txt.
1305 panic= [KNL] Kernel behaviour on panic
1308 parkbd.port= [HW] Parallel port number the keyboard adapter is
1309 connected to, default is 0.
1311 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1312 0 for XT, 1 for AT (default is AT).
1315 parport= [HW,PPT] Specify parallel ports. 0 disables.
1316 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1317 Use 'auto' to force the driver to use any
1318 IRQ/DMA settings detected (the default is to
1319 ignore detected IRQ/DMA settings because of
1320 possible conflicts). You can specify the base
1321 address, IRQ, and DMA settings; IRQ and DMA
1322 should be numbers, or 'auto' (for using detected
1323 settings on that particular port), or 'nofifo'
1324 (to avoid using a FIFO even if it is detected).
1325 Parallel ports are assigned in the order they
1326 are specified on the command line, starting
1329 parport_init_mode= [HW,PPT]
1330 Configure VIA parallel port to operate in
1331 a specific mode. This is necessary on Pegasos
1332 computer where firmware has no options for setting
1333 up parallel port mode and sets it to spp.
1334 Currently this function knows 686a and 8231 chips.
1335 Format: [spp|ps2|epp|ecp|ecpepp]
1337 pas2= [HW,OSS] Format:
1338 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1341 See header of drivers/scsi/pas16.c.
1344 Halt all CPUs after the first oops has been printed for
1345 the specified number of seconds. This is to be used if
1346 your oopses keep scrolling off the screen.
1351 See header of drivers/block/paride/pcd.c.
1352 See also Documentation/paride.txt.
1354 pci=option[,option...] [PCI] various PCI subsystem options:
1355 off [X86-32] don't probe for the PCI bus
1356 bios [X86-32] force use of PCI BIOS, don't access
1357 the hardware directly. Use this if your machine
1358 has a non-standard PCI host bridge.
1359 nobios [X86-32] disallow use of PCI BIOS, only direct
1360 hardware access methods are allowed. Use this
1361 if you experience crashes upon bootup and you
1362 suspect they are caused by the BIOS.
1363 conf1 [X86-32] Force use of PCI Configuration
1365 conf2 [X86-32] Force use of PCI Configuration
1367 noaer [PCIE] If the PCIEAER kernel config parameter is
1368 enabled, this kernel boot option can be used to
1369 disable the use of PCIE advanced error reporting.
1370 nodomains [PCI] Disable support for multiple PCI
1371 root domains (aka PCI segments, in ACPI-speak).
1372 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1374 nomsi [MSI] If the PCI_MSI kernel config parameter is
1375 enabled, this kernel boot option can be used to
1376 disable the use of MSI interrupts system-wide.
1377 nosort [X86-32] Don't sort PCI devices according to
1378 order given by the PCI BIOS. This sorting is
1379 done to get a device order compatible with
1381 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1382 routing table. These calls are known to be buggy
1383 on several machines and they hang the machine
1384 when used, but on other computers it's the only
1385 way to get the interrupt routing table. Try
1386 this option if the kernel is unable to allocate
1387 IRQs or discover secondary PCI buses on your
1389 rom [X86-32] Assign address space to expansion ROMs.
1390 Use with caution as certain devices share
1391 address decoders between ROMs and other
1393 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1394 assigned automatically to PCI devices. You can
1395 make the kernel exclude IRQs of your ISA cards
1397 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1398 of the PIRQ table (normally generated
1399 by the BIOS) if it is outside the
1400 F0000h-100000h range.
1401 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1402 useful if the kernel is unable to find your
1403 secondary buses and you want to tell it
1404 explicitly which ones they are.
1405 assign-busses [X86-32] Always assign all PCI bus
1406 numbers ourselves, overriding
1407 whatever the firmware may have done.
1408 usepirqmask [X86-32] Honor the possible IRQ mask stored
1409 in the BIOS $PIR table. This is needed on
1410 some systems with broken BIOSes, notably
1411 some HP Pavilion N5400 and Omnibook XE3
1412 notebooks. This will have no effect if ACPI
1413 IRQ routing is enabled.
1414 noacpi [X86-32] Do not use ACPI for IRQ routing
1415 or for PCI scanning.
1416 use_crs [X86-32] Use _CRS for PCI resource
1418 routeirq Do IRQ routing for all PCI devices.
1419 This is normally done in pci_enable_device(),
1420 so this option is a temporary workaround
1421 for broken drivers that don't call it.
1422 firmware [ARM] Do not re-enumerate the bus but instead
1423 just use the configuration from the
1424 bootloader. This is currently used on
1425 IXP2000 systems where the bus has to be
1426 configured a certain way for adjunct CPUs.
1427 noearly [X86] Don't do any early type 1 scanning.
1428 This might help on some broken boards which
1429 machine check when some devices' config space
1430 is read. But various workarounds are disabled
1431 and some IOMMU drivers will not work.
1432 bfsort Sort PCI devices into breadth-first order.
1433 This sorting is done to get a device
1434 order compatible with older (<= 2.4) kernels.
1435 nobfsort Don't sort PCI devices into breadth-first order.
1436 cbiosize=nn[KMG] The fixed amount of bus space which is
1437 reserved for the CardBus bridge's IO window.
1438 The default value is 256 bytes.
1439 cbmemsize=nn[KMG] The fixed amount of bus space which is
1440 reserved for the CardBus bridge's memory
1441 window. The default value is 64 megabytes.
1443 pcmv= [HW,PCMCIA] BadgePAD 4
1446 See Documentation/paride.txt.
1448 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1451 See arch/parisc/kernel/pdc_chassis.c
1454 See Documentation/paride.txt.
1457 See Documentation/paride.txt.
1459 pirq= [SMP,APIC] Manual mp-table setup
1460 See Documentation/i386/IO-APIC.txt.
1462 plip= [PPT,NET] Parallel port network link
1463 Format: { parport<nr> | timid | 0 }
1464 See also Documentation/parport.txt.
1470 { on | off | curr | res | no-curr | no-res }
1473 [ISAPNP] Exclude IRQs for the autoconfiguration
1476 [ISAPNP] Exclude DMAs for the autoconfiguration
1478 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1479 Ranges are in pairs (I/O port base and size).
1482 [ISAPNP] Exclude memory regions for the
1484 Ranges are in pairs (memory base and size).
1486 print-fatal-signals=
1487 [KNL] debug: print fatal signals
1488 print-fatal-signals=1: print segfault info to
1492 printk.time= Show timing data prefixed to each printk message line
1493 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1495 profile= [KNL] Enable kernel profiling via /proc/profile
1496 Format: [schedule,]<number>
1497 Param: "schedule" - profile schedule points.
1498 Param: <number> - step/bucket size as a power of 2 for
1499 statistical time based profiling.
1500 Param: "sleep" - profile D-state sleeping (millisecs).
1501 Requires CONFIG_SCHEDSTATS
1502 Param: "kvm" - profile VM exits.
1504 processor.max_cstate= [HW,ACPI]
1505 Limit processor to maximum C-state
1506 max_cstate=9 overrides any DMI blacklist limit.
1508 processor.nocst [HW,ACPI]
1509 Ignore the _CST method to determine C-states,
1510 instead using the legacy FADT method
1512 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1514 See Documentation/ramdisk.txt.
1516 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1517 probe for; one of (bare|imps|exps|lifebook|any).
1518 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1520 psmouse.resetafter= [HW,MOUSE]
1521 Try to reset the device after so many bad packets
1524 [HW,MOUSE] Set desired mouse resolution, in dpi.
1525 psmouse.smartscroll=
1526 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1527 0 = disabled, 1 = enabled (default).
1529 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1531 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1534 See Documentation/paride.txt.
1537 [KNL] Number of legacy pty's. Overwrites compiled-in
1540 quiet [KNL] Disable most log messages
1545 See Documentation/md.txt.
1547 ramdisk_blocksize= [RAM]
1548 See Documentation/ramdisk.txt.
1550 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1551 See Documentation/ramdisk.txt.
1553 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1554 RCU callbacks to process in one batch.
1556 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1557 RCU callbacks over which batch limiting is disabled.
1559 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1560 RCU callbacks below which batch limiting is re-enabled.
1564 Run specified binary instead of /init from the ramdisk,
1565 used for early userspace startup. See initrd.
1567 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1568 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1569 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1571 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1573 reservetop= [X86-32]
1575 Reserves a hole at the top of the kernel virtual
1578 reset_devices [KNL] Force drivers to reset the underlying device
1579 during initialization.
1582 Specify the partition device for software suspend
1584 resume_offset= [SWSUSP]
1585 Specify the offset from the beginning of the partition
1586 given by "resume=" at which the swap header is located,
1587 in <PAGE_SIZE> units (needed only for swap files).
1588 See Documentation/power/swsusp-and-swap-files.txt
1590 retain_initrd [RAM] Keep initrd memory after extraction
1592 rhash_entries= [KNL,NET]
1593 Set number of hash buckets for route cache
1595 riscom8= [HW,SERIAL]
1596 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1598 ro [KNL] Mount root device read-only on boot
1600 root= [KNL] Root filesystem
1602 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1603 mount the root filesystem
1605 rootflags= [KNL] Set root filesystem mount option string
1607 rootfstype= [KNL] Set root filesystem type
1609 rootwait [KNL] Wait (indefinitely) for root device to show up.
1610 Useful for devices that are detected asynchronously
1611 (e.g. USB and MMC devices).
1613 root_plug.vendor_id=
1614 [ROOTPLUG] Override the default vendor ID
1616 root_plug.product_id=
1617 [ROOTPLUG] Override the default product ID
1620 [ROOTPLUG] Enable debugging output
1622 rw [KNL] Mount root device read-write on boot
1624 S [KNL] Run init in single mode
1627 See drivers/net/irda/sa1100_ir.c.
1629 sbni= [NET] Granch SBNI12 leased line adapter
1631 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1632 Format: <io>[,<timeout>[,<isapnp>]]
1634 scsi_debug_*= [SCSI]
1635 See drivers/scsi/scsi_debug.c.
1637 scsi_default_dev_flags=
1638 [SCSI] SCSI default device flags
1641 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1642 Format: <vendor>:<model>:<flags>
1643 (flags are integer value)
1645 scsi_logging_level= [SCSI] a bit mask of logging levels
1646 See drivers/scsi/scsi_logging.h for bits. Also
1647 settable via sysctl at dev.scsi.logging_level
1648 (/proc/sys/dev/scsi/logging_level).
1649 There is also a nice 'scsi_logging_level' script in the
1650 S390-tools package, available for download at
1651 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1653 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1654 discovered. async scans them in kernel threads,
1655 allowing boot to proceed. none ignores them, expecting
1656 user space to do the scan.
1658 selinux [SELINUX] Disable or enable SELinux at boot time.
1659 Format: { "0" | "1" }
1660 See security/selinux/Kconfig help text.
1663 Default value is set via kernel config option.
1664 If enabled at boot time, /selinux/disable can be used
1665 later to disable prior to initial policy load.
1667 selinux_compat_net =
1668 [SELINUX] Set initial selinux_compat_net flag value.
1669 Format: { "0" | "1" }
1670 0 -- use new secmark-based packet controls
1671 1 -- use legacy packet controls
1672 Default value is 0 (preferred).
1673 Value can be changed at runtime via
1674 /selinux/compat_net.
1676 serialnumber [BUGS=X86-32]
1679 Maximal number of shapers.
1682 See header of drivers/scsi/sim710.c.
1689 slub_debug[=options[,slabs]] [MM, SLUB]
1690 Enabling slub_debug allows one to determine the
1691 culprit if slab objects become corrupted. Enabling
1692 slub_debug can create guard zones around objects and
1693 may poison objects when not in use. Also tracks the
1694 last alloc / free. For more information see
1695 Documentation/vm/slub.txt.
1697 slub_max_order= [MM, SLUB]
1698 Determines the maximum allowed order for slabs.
1699 A high setting may cause OOMs due to memory
1700 fragmentation. For more information see
1701 Documentation/vm/slub.txt.
1703 slub_min_objects= [MM, SLUB]
1704 The minimum number of objects per slab. SLUB will
1705 increase the slab order up to slub_max_order to
1706 generate a sufficiently large slab able to contain
1707 the number of objects indicated. The higher the number
1708 of objects the smaller the overhead of tracking slabs
1709 and the less frequently locks need to be acquired.
1710 For more information see Documentation/vm/slub.txt.
1712 slub_min_order= [MM, SLUB]
1713 Determines the mininum page order for slabs. Must be
1714 lower than slub_max_order.
1715 For more information see Documentation/vm/slub.txt.
1717 slub_nomerge [MM, SLUB]
1718 Disable merging of slabs with similar size. May be
1719 necessary if there is some reason to distinguish
1720 allocs to different slabs. Debug options disable
1721 merging on their own.
1722 For more information see Documentation/vm/slub.txt.
1725 Format: <io1>[,<io2>[,...,<io8>]]
1727 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1728 attempt to substitute SMP alternatives once at boot.
1730 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1731 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1732 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1733 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1734 smsc-ircc2.ircc_irq= [HW] IRQ line
1735 smsc-ircc2.ircc_dma= [HW] DMA channel
1736 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1737 0: Toshiba Satellite 1800 (GP data pin select)
1738 1: Fast pin select (default)
1741 snd-ad1816a= [HW,ALSA]
1743 snd-ad1848= [HW,ALSA]
1745 snd-ali5451= [HW,ALSA]
1747 snd-als100= [HW,ALSA]
1749 snd-als4000= [HW,ALSA]
1751 snd-azt2320= [HW,ALSA]
1753 snd-cmi8330= [HW,ALSA]
1755 snd-cmipci= [HW,ALSA]
1757 snd-cs4231= [HW,ALSA]
1759 snd-cs4232= [HW,ALSA]
1761 snd-cs4236= [HW,ALSA]
1763 snd-cs4281= [HW,ALSA]
1765 snd-cs46xx= [HW,ALSA]
1767 snd-dt019x= [HW,ALSA]
1769 snd-dummy= [HW,ALSA]
1771 snd-emu10k1= [HW,ALSA]
1773 snd-ens1370= [HW,ALSA]
1775 snd-ens1371= [HW,ALSA]
1777 snd-es968= [HW,ALSA]
1779 snd-es1688= [HW,ALSA]
1781 snd-es18xx= [HW,ALSA]
1783 snd-es1938= [HW,ALSA]
1785 snd-es1968= [HW,ALSA]
1787 snd-fm801= [HW,ALSA]
1789 snd-gusclassic= [HW,ALSA]
1791 snd-gusextreme= [HW,ALSA]
1793 snd-gusmax= [HW,ALSA]
1797 snd-ice1712= [HW,ALSA]
1799 snd-intel8x0= [HW,ALSA]
1801 snd-interwave= [HW,ALSA]
1806 snd-korg1212= [HW,ALSA]
1808 snd-maestro3= [HW,ALSA]
1810 snd-mpu401= [HW,ALSA]
1812 snd-mtpav= [HW,ALSA]
1814 snd-nm256= [HW,ALSA]
1816 snd-opl3sa2= [HW,ALSA]
1824 snd-opti93x= [HW,ALSA]
1828 snd-rme32= [HW,ALSA]
1830 snd-rme96= [HW,ALSA]
1832 snd-rme9652= [HW,ALSA]
1838 snd-sbawe= [HW,ALSA]
1840 snd-serial= [HW,ALSA]
1842 snd-sgalaxy= [HW,ALSA]
1844 snd-sonicvibes= [HW,ALSA]
1849 snd-sun-cs4231= [HW,ALSA]
1851 snd-trident= [HW,ALSA]
1853 snd-usb-audio= [HW,ALSA,USB]
1855 snd-via82xx= [HW,ALSA]
1857 snd-virmidi= [HW,ALSA]
1859 snd-wavefront= [HW,ALSA]
1861 snd-ymfpci= [HW,ALSA]
1863 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1864 See Documentation/sonypi.txt
1866 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1867 See Documentation/specialix.txt.
1869 spia_io_base= [HW,MTD]
1875 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1877 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1878 See Documentation/scsi/st.txt.
1881 See header of drivers/scsi/seagate.c.
1885 Set the STI (builtin display/keyboard on the HP-PARISC
1886 machines) console (graphic card) which should be used
1887 as the initial boot-console.
1888 See also comment in drivers/video/console/sticore.c.
1891 See comment in drivers/video/console/sticore.c.
1894 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1898 Control how the NFS server code allocates CPUs to
1899 service thread pools. Depending on how many NICs
1900 you have and where their interrupts are bound, this
1901 option will affect which CPUs will do NFS serving.
1902 Note: this parameter cannot be changed while the
1903 NFS server is running.
1905 auto the server chooses an appropriate mode
1906 automatically using heuristics
1907 global a single global pool contains all CPUs
1908 percpu one pool for each CPU
1909 pernode one pool for each NUMA node (equivalent
1910 to global on non-NUMA machines)
1912 swiotlb= [IA-64] Number of I/O TLB slabs
1916 sym53c416= [HW,SCSI]
1917 See header of drivers/scsi/sym53c416.c.
1919 sysrq_always_enabled
1921 Ignore sysrq setting - this boot parameter will
1922 neutralize any effect of /proc/sys/kernel/sysrq.
1923 Useful for debugging.
1926 See header of drivers/scsi/t128.c.
1930 thash_entries= [KNL,NET]
1931 Set number of hash buckets for TCP connection
1933 thermal.act= [HW,ACPI]
1934 -1: disable all active trip points in all thermal zones
1935 <degrees C>: override all lowest active trip points
1937 thermal.crt= [HW,ACPI]
1938 -1: disable all critical trip points in all thermal zones
1939 <degrees C>: lower all critical trip points
1941 thermal.nocrt= [HW,ACPI]
1942 Set to disable actions on ACPI thermal zone
1943 critical and hot trip points.
1945 thermal.off= [HW,ACPI]
1946 1: disable ACPI thermal control
1948 thermal.psv= [HW,ACPI]
1949 -1: disable all passive trip points
1950 <degrees C>: override all passive trip points to this value
1952 thermal.tzp= [HW,ACPI]
1953 Specify global default ACPI thermal zone polling rate
1954 <deci-seconds>: poll all this frequency
1955 0: no polling (default)
1957 time Show timing data prefixed to each printk message line
1958 [deprecated, see 'printk.time']
1960 tipar.timeout= [HW,PPT]
1961 Set communications timeout in tenths of a second
1964 tipar.delay= [HW,PPT]
1965 Set inter-bit delay in microseconds (default 10).
1968 See header of drivers/scsi/seagate.c.
1971 See comment before function dc390_setup() in
1972 drivers/scsi/tmscsim.c.
1976 trix= [HW,OSS] MediaTrix AudioTrix Pro
1978 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1980 turbografx.map[2|3]= [HW,JOY]
1981 TurboGraFX parallel port interface
1983 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1984 See also Documentation/input/joystick-parport.txt
1986 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1987 See header of drivers/scsi/u14-34f.c.
1996 [USB] Ignore overcurrent events (default N).
1997 Some badly-designed motherboards generate lots of
1998 bogus events, for ports that aren't wired to
1999 anything. Set this parameter to avoid log spamming.
2000 Note that genuine overcurrent events won't be
2003 usbcore.autosuspend=
2004 [USB] The autosuspend time delay (in seconds) used
2005 for newly-detected USB devices (default 2). This
2006 is the time required before an idle device will be
2007 autosuspended. Devices for which the delay is set
2008 to a negative value won't be autosuspended at all.
2011 [USBHID] The interval which mice are to be polled at.
2013 vdso= [X86-32,SH,x86-64]
2014 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2015 vdso=1: enable VDSO (default)
2016 vdso=0: disable VDSO mapping
2018 vdso32= [X86-32,X86-64]
2019 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2020 vdso32=1: enable 32-bit VDSO (default)
2021 vdso32=0: disable 32-bit VDSO mapping
2024 vector=percpu: enable percpu vector domain
2026 video= [FB] Frame buffer configuration
2027 See Documentation/fb/modedb.txt.
2029 vga= [BOOT,X86-32] Select a particular video mode
2030 See Documentation/i386/boot.txt and
2031 Documentation/svga.txt.
2032 Use vga=ask for menu.
2033 This is actually a boot loader parameter; the value is
2034 passed to the kernel using a special protocol.
2036 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2037 size of <nn>. This can be used to increase the
2038 minimum size (128MB on x86). It can also be used to
2039 decrease the size and leave more room for directly
2042 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2045 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2048 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2051 waveartist= [HW,OSS]
2052 Format: <io>,<irq>,<dma>,<dma2>
2055 See header of drivers/scsi/wd33c93.c.
2058 See header of drivers/scsi/wd7000.c.
2061 See Documentation/watchdog/wdt.txt.
2063 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2064 xd_geo= See header of drivers/block/xd.c.
2066 xirc2ps_cs= [NET,PCMCIA]
2068 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2070 norandmaps Don't use address space randomization
2071 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2073 ______________________________________________________________________
2077 Add documentation for ALSA options.
2078 Add more DRM drivers.