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.
401 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
403 Forces specified clocksource (if available) to be used
404 when calculating gettimeofday(). If specified
405 clocksource is not available, it defaults to PIT.
406 Format: { pit | tsc | cyclone | pmtmr }
408 clocksource= [GENERIC_TIME] Override the default clocksource
410 Override the default clocksource and use the clocksource
411 with the name specified.
412 Some clocksource names to choose from, depending on
414 [all] jiffies (this is the base, fallback clocksource)
416 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
417 pxa_timer,timer3,32k_counter,timer0_1
419 [X86-32] pit,hpet,tsc,vmi-timer;
420 scx200_hrt on Geode; cyclone on IBM x440
428 clearcpuid=BITNUM [X86]
429 Disable CPUID feature X for the kernel. See
430 include/asm-x86/cpufeature.h for the valid bit numbers.
431 Note the Linux specific bits are not necessarily
432 stable over kernel options, but the vendor specific
434 Also note that user programs calling CPUID directly
435 or using the feature without checking anything
436 will still see it. This just prevents it from
437 being used by the kernel or shown in /proc/cpuinfo.
438 Also note the kernel might malfunction if you disable
441 code_bytes [IA32/X86_64] How many bytes of object code to print
448 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
449 over the 8254 in addition to over the IO-APIC. The
450 kernel tries to set a sensible default.
452 hpet= [X86-32,HPET] option to control HPET usage
453 Format: { enable (default) | disable | force }
454 disable: disable HPET and use PIT instead
455 force: allow force enabled of undocumented chips (ICH4,
458 com20020= [HW,NET] ARCnet - COM20020 chipset
460 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
462 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
466 ARCnet - COM90xx chipset (memory-mapped buffers)
467 Format: <io>[,<irq>[,<memstart>]]
469 condev= [HW,S390] console device
472 console= [KNL] Output console device and options.
474 tty<n> Use the virtual console device <n>.
478 Use the specified serial port. The options are of
479 the form "bbbbpnf", where "bbbb" is the baud rate,
480 "p" is parity ("n", "o", or "e"), "n" is number of
481 bits, and "f" is flow control ("r" for RTS or
482 omit it). Default is "9600n8".
484 See Documentation/serial-console.txt for more
486 Documentation/networking/netconsole.txt for an
489 uart[8250],io,<addr>[,options]
490 uart[8250],mmio,<addr>[,options]
491 Start an early, polled-mode console on the 8250/16550
492 UART at the specified I/O port or MMIO address,
493 switching to the matching ttyS device later. The
494 options are the same as for ttyS, above.
496 If the device connected to the port is not a TTY but a braille
497 device, prepend "brl," before the device type, for instance
499 For now, only VisioBraille is supported.
501 earlycon= [KNL] Output early console device and options.
502 uart[8250],io,<addr>[,options]
503 uart[8250],mmio,<addr>[,options]
504 Start an early, polled-mode console on the 8250/16550
505 UART at the specified I/O port or MMIO address.
506 The options are the same as for ttyS, above.
509 [HW] Never suspend the console
510 Disable suspending of consoles during suspend and
511 hibernate operations. Once disabled, debugging
512 messages can reach various consoles while the rest
513 of the system is being put to sleep (ie, while
514 debugging driver suspend/resume hooks). This may
515 not work reliably with all consoles, but is known
516 to work with serial and VGA consoles.
518 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
520 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
522 crashkernel=nn[KMG]@ss[KMG]
523 [KNL] Reserve a chunk of physical memory to
524 hold a kernel to switch to with kexec on panic.
526 crashkernel=range1:size1[,range2:size2,...][@offset]
527 [KNL] Same as above, but depends on the memory
528 in the running system. The syntax of range is
529 start-[end] where start and end are both
530 a memory unit (amount[KMG]). See also
531 Documentation/kdump/kdump.txt for a example.
534 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
539 cs89x0_media= [HW,NET]
540 Format: { rj45 | aui | bnc }
543 See header of drivers/s390/block/dasd_devmap.c.
545 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
546 (one device per port)
547 Format: <port#>,<type>
548 See also Documentation/input/joystick-parport.txt
550 debug [KNL] Enable kernel debugging (events log level).
553 [KNL] verbose self-tests
555 Print debugging info while doing the locking API
557 We default to 0 (no extra messages), setting it to
558 1 will print _a lot_ more information - normally
559 only useful to kernel developers.
561 debug_objects [KNL] Enable object debugging
563 decnet.addr= [HW,NET]
564 Format: <area>[,<node>]
565 See also Documentation/networking/decnet.txt.
568 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
569 Change the default blue palette of the console.
570 This is a 16-member array composed of values
574 Format: <green0>,<green1>,<green2>,...,<green15>
575 Change the default green palette of the console.
576 This is a 16-member array composed of values
580 Format: <red0>,<red1>,<red2>,...,<red15>
581 Change the default red palette of the console.
582 This is a 16-member array composed of values
588 Set system-wide default UTF-8 mode for all tty's.
589 Default is 1, i.e. UTF-8 mode is enabled for all
590 newly opened terminals.
593 Set number of hash buckets for dentry cache.
596 IO parameters + enable/disable command.
598 digiepca= [HW,SERIAL]
599 See drivers/char/README.epca and
600 Documentation/digiepca.txt.
602 disable_mtrr_cleanup [X86]
603 enable_mtrr_cleanup [X86]
604 The kernel tries to adjust MTRR layout from continuous
605 to discrete, to make X server driver able to add WB
606 entry later. This parameter enables/disables that.
608 mtrr_chunk_size=nn[KMG] [X86]
609 used for mtrr cleanup. It is largest continous chunk
610 that could hold holes aka. UC entries.
612 mtrr_gran_size=nn[KMG] [X86]
613 used for mtrr cleanup. It is granity of mtrr block.
614 Big value could prevent small alignment use up MTRRs.
616 disable_mtrr_trim [X86, Intel and AMD only]
617 By default the kernel will trim any uncacheable
618 memory out of your available memory pool based on
619 MTRR settings. This parameter disables that behavior,
620 possibly causing your machine to run very slowly.
622 dmasound= [HW,OSS] Sound subsystem buffers
628 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
630 earlyprintk=serial[,ttySn[,baudrate]]
632 Append ",keep" to not disable it when the real console
635 Only vga or serial at a time, not both.
637 Currently only ttyS0 and ttyS1 are supported.
639 Interaction with the standard serial driver is not
642 The VGA output is eventually overwritten by the real
648 Format: {"off" | "on" | "skip[mbr]"}
650 eisa_irq_edge= [PARISC,HW]
651 See header of drivers/parisc/eisa.c.
654 See comment before function elanfreq_setup() in
655 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
658 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
659 See Documentation/block/as-iosched.txt and
660 Documentation/block/deadline-iosched.txt for details.
662 elfcorehdr= [X86-32, X86_64]
663 Specifies physical address of start of kernel core
664 image elf header. Generally kexec loader will
665 pass this option to capture kernel.
666 See Documentation/kdump/kdump.txt for details.
668 enforcing [SELINUX] Set initial enforcing status.
670 See security/selinux/Kconfig help text.
671 0 -- permissive (log only, no denials).
672 1 -- enforcing (deny and log).
674 Value can be changed at runtime via /selinux/enforce.
677 Format: <spdif>,[<nomix>,[<amplifier>]]
678 See also header of sound/oss/es1371.c.
680 ether= [HW,NET] Ethernet cards parameters
681 This option is obsoleted by the "netdev=" option, which
682 has equivalent usage. See its documentation for details.
684 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
689 fail_make_request=[KNL]
690 General fault injection mechanism.
691 Format: <interval>,<probability>,<space>,<times>
692 See also /Documentation/fault-injection/.
695 See header of drivers/scsi/fd_mcs.c.
698 See header of drivers/scsi/fdomain.c.
701 See Documentation/floppy.txt.
703 force_pal_cache_flush
704 [IA-64] Avoid check_sal_cache_flush which may hang on
705 buggy SAL_CACHE_FLUSH implementations. Using this
706 parameter will force ia64_sal_cache_flush to call
707 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
710 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
711 support via parallel port (up to 5 devices per port)
712 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
713 See also Documentation/input/joystick-parport.txt
717 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
722 See header of drivers/scsi/gdth.c.
724 gpt [EFI] Forces disk with valid GPT signature but
725 invalid Protective MBR to be treated as GPT.
729 hashdist= [KNL,NUMA] Large hashes allocated during boot
730 are distributed across NUMA nodes. Defaults on
731 for IA-64, off otherwise.
732 Format: 0 | 1 (for off | on)
734 hcl= [IA-64] SGI's Hardware Graph compatibility layer
736 hd= [EIDE] (E)IDE hard drive subsystem geometry
737 Format: <cyl>,<head>,<sect>
739 hd?= [HW] (E)IDE subsystem
740 hd?lun= See Documentation/ide/ide.txt.
742 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
743 size of <nn>. This works even on boxes that have no
744 highmem otherwise. This also works to reduce highmem
745 size on bigger boxes.
747 highres= [KNL] Enable/disable high resolution timer mode.
748 Valid parameters: "on", "off"
752 See Documentation/isdn/README.HiSax.
754 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
755 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
757 i8042.direct [HW] Put keyboard port into non-translated mode
758 i8042.dumbkbd [HW] Pretend that controller can only read data from
759 keyboard and cannot control its state
760 (Don't attempt to blink the leds)
761 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
762 i8042.nokbd [HW] Don't check/create keyboard port
763 i8042.noloop [HW] Disable the AUX Loopback command while probing
765 i8042.nomux [HW] Don't check presence of an active multiplexing
767 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
770 [HW] Frequency with which keyboard LEDs should blink
771 when kernel panics (default is 0.5 sec)
772 i8042.reset [HW] Reset the controller during init and cleanup
773 i8042.unlock [HW] Unlock (ignore) the keylock
777 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
778 indicates that the driver is running on unsupported
780 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
781 does not match list of supported models.
783 [HW] Report power status in /proc/i8k
784 (disabled by default)
785 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
788 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
789 See Documentation/mca.txt.
792 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
794 ide= [HW] (E)IDE subsystem
795 Format: ide=nodma or ide=doubler
796 See Documentation/ide/ide.txt.
798 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
799 See Documentation/ide/ide.txt.
802 Format: idle=poll or idle=mwait
803 Poll forces a polling idle loop that can slightly improves the performance
804 of waking up a idle CPU, but will use a lot of power and make the system
805 run hot. Not recommended.
806 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
807 to not use it because it doesn't save as much power as a normal idle
808 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
811 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
812 Claim all unknown PCI IDE storage controllers.
814 ignore_loglevel [KNL]
815 Ignore loglevel setting - this will print /all/
816 kernel messages to the console. Useful for debugging.
819 Set number of hash buckets for inode cache.
822 See header of drivers/scsi/in2000.c.
826 Run specified binary instead of /sbin/init as init
829 initcall_debug [KNL] Trace initcalls as they are executed. Useful
830 for working out where the kernel is dying during
833 initrd= [BOOT] Specify the location of the initial ramdisk
835 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
853 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
855 Disable intel iommu driver.
856 igfx_off [Default Off]
857 By default, gfx is mapped as normal device. If a gfx
858 device has a dedicated DMAR unit, the DMAR unit is
859 bypassed by not enabling DMAR with this option. In
860 this case, gfx device will use physical address for
863 With this option iommu will not optimize to look
864 for io virtual address below 32 bit forcing dual
865 address cycle on pci bus for cards supporting greater
866 than 32 bit addressing. The default is to look
867 for translation below 32 bit and if not available
868 then look in the higher range.
870 With this option on every unmap_single operation will
871 result in a hardware IOTLB flush operation as opposed
872 to batching them for performance.
874 io_delay= [X86-32,X86-64] I/O delay method
876 Standard port 0x80 based delay
878 Alternate port 0xed based delay (needed on some systems)
880 Simple two microseconds delay
884 io7= [HW] IO7 for Marvel based alpha systems
885 See comment before marvel_specify_io7 in
886 arch/alpha/kernel/core_marvel.c.
889 See Documentation/filesystems/nfsroot.txt.
891 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
892 See comment before ip2_setup() in
893 drivers/char/ip2/ip2base.c.
895 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
896 See header of drivers/scsi/ips.c.
898 ports= [IP_VS_FTP] IPVS ftp helper module
900 Up to 8 (IP_VS_APP_MAX_PORTS) ports
902 Format: <port>,<port>....
905 When an interrupt is not handled search all handlers
906 for it. Intended to get systems with badly broken
910 When an interrupt is not handled search all handlers
911 for it. Also check all handlers each timer
912 interrupt. Intended to get systems with badly broken
916 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
918 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
920 <cpu number>,...,<cpu number>
922 <cpu number>-<cpu number> (must be a positive range in ascending order)
924 <cpu number>,...,<cpu number>-<cpu number>
925 This option can be used to specify one or more CPUs
926 to isolate from the general SMP balancing and scheduling
927 algorithms. The only way to move a process onto or off
928 an "isolated" CPU is via the CPU affinity syscalls.
929 <cpu number> begins at 0 and the maximum value is
930 "number of CPUs in system - 1".
932 This option is the preferred way to isolate CPUs. The
933 alternative -- manually setting the CPU mask of all
934 tasks in the system -- can cause problems and
935 suboptimal load balancer performance.
939 js= [HW,JOY] Analog joystick
940 See Documentation/input/joystick.txt.
942 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
943 specifies the amount of memory usable by the kernel
944 for non-movable allocations. The requested amount is
945 spread evenly throughout all nodes in the system. The
946 remaining memory in each node is used for Movable
947 pages. In the event, a node is too small to have both
948 kernelcore and Movable pages, kernelcore pages will
949 take priority and other nodes will have a larger number
950 of kernelcore pages. The Movable zone is used for the
951 allocation of pages that may be reclaimed or moved
952 by the page migration subsystem. This means that
953 HugeTLB pages may not be allocated from this zone.
954 Note that allocations like PTEs-from-HighMem still
955 use the HighMem zone if it exists, and the Normal
958 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
959 is similar to kernelcore except it specifies the
960 amount of memory used for migratable allocations.
961 If both kernelcore and movablecore is specified,
962 then kernelcore will be at *least* the specified
963 value but may be more. If movablecore on its own
964 is specified, the administrator must be careful
965 that the amount of memory usable for all allocations
970 kstack=N [X86-32,X86-64] Print N words from the kernel stack
973 kgdboc= [HW] kgdb over consoles.
974 Requires a tty driver that supports console polling.
975 (only serial suported for now)
976 Format: <serial_device>[,baud]
982 lapic [X86-32,APIC] Enable the local APIC even if BIOS
985 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
988 libata.dma= [LIBATA] DMA control
989 libata.dma=0 Disable all PATA and SATA DMA
990 libata.dma=1 PATA and SATA Disk DMA only
991 libata.dma=2 ATAPI (CDROM) DMA only
992 libata.dma=4 Compact Flash DMA only
993 Combinations also work, so libata.dma=3 enables DMA
994 for disks and CDROMs, but not CFs.
996 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1000 libata.force= [LIBATA] Force configurations. The format is comma
1001 separated list of "[ID:]VAL" where ID is
1002 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1003 matching port, link or device. Basically, it matches
1004 the ATA ID string printed on console by libata. If
1005 the whole ID part is omitted, the last PORT and DEVICE
1006 values are used. If ID hasn't been specified yet, the
1007 configuration applies to all ports, links and devices.
1009 If only DEVICE is omitted, the parameter applies to
1010 the port and all links and devices behind it. DEVICE
1011 number of 0 either selects the first device or the
1012 first fan-out link behind PMP device. It does not
1013 select the host link. DEVICE number of 15 selects the
1014 host link and device attached to it.
1016 The VAL specifies the configuration to force. As long
1017 as there's no ambiguity shortcut notation is allowed.
1018 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1019 The following configurations can be forced.
1021 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1022 Any ID with matching PORT is used.
1024 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1026 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1027 udma[/][16,25,33,44,66,100,133] notation is also
1030 * [no]ncq: Turn on or off NCQ.
1032 If there are multiple matching configurations changing
1033 the same attribute, the last one is used.
1035 load_ramdisk= [RAM] List of ramdisks to load from floppy
1036 See Documentation/ramdisk.txt.
1038 lockd.nlm_grace_period=P [NFS] Assign grace period.
1041 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1044 lockd.nlm_timeout=T [NFS] Assign timeout value.
1047 lockd.nlm_udpport=M [NFS] Assign UDP port.
1050 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1053 loglevel= All Kernel Messages with a loglevel smaller than the
1054 console loglevel will be printed to the console. It can
1055 also be changed with klogd or other programs. The
1056 loglevels are defined as follows:
1058 0 (KERN_EMERG) system is unusable
1059 1 (KERN_ALERT) action must be taken immediately
1060 2 (KERN_CRIT) critical conditions
1061 3 (KERN_ERR) error conditions
1062 4 (KERN_WARNING) warning conditions
1063 5 (KERN_NOTICE) normal but significant condition
1064 6 (KERN_INFO) informational
1065 7 (KERN_DEBUG) debug-level messages
1067 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1068 Format: { n | nk | nM }
1069 n must be a power of two. The default size
1070 is set in the kernel config file.
1072 logo.nologo [FB] Disables display of the built-in Linux logo.
1073 This may be used to provide more screen space for
1074 kernel log messages and is useful when debugging
1075 kernel boot problems.
1077 lp=0 [LP] Specify parallel ports to use, e.g,
1078 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1079 lp=reset first parallel port). 'lp=0' disables the
1080 lp=auto printer driver. 'lp=reset' (which can be
1081 specified in addition to the ports) causes
1082 attached printers to be reset. Using
1083 lp=port1,port2,... specifies the parallel ports
1084 to associate lp devices with, starting with
1085 lp0. A port specification may be 'none' to skip
1086 that lp device, or a parport name such as
1087 'parport0'. Specifying 'lp=auto' instead of a
1088 port specification list means that device IDs
1089 from each port should be examined, to see if
1090 an IEEE 1284-compliant printer is attached; if
1091 so, the driver will manage that printer.
1092 See also header of drivers/char/lp.c.
1095 Sets loops_per_jiffy to given constant, thus avoiding
1096 time-consuming boot-time autodetection (up to 250 ms per
1097 CPU). 0 enables autodetection (default). To determine
1098 the correct value for your kernel, boot with normal
1099 autodetection and see what value is printed. Note that
1100 on SMP systems the preset will be applied to all CPUs,
1101 which is likely to cause problems if your CPUs need
1102 significantly divergent settings. An incorrect value
1103 will cause delays in the kernel to be wrong, leading to
1104 unpredictable I/O errors and other breakage. Although
1105 unlikely, in the extreme case this might damage your
1109 Format: <io>,<irq>,<dma>
1111 mac5380= [HW,SCSI] Format:
1112 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1114 machvec= [IA64] Force the use of a particular machine-vector
1115 (machvec) in a generic kernel.
1116 Example: machvec=hpzx1_swiotlb
1118 max_loop= [LOOP] Maximum number of loopback devices that can
1122 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1123 should make use of. maxcpus=n : n >= 0 limits the
1124 kernel to using 'n' processors. n=0 is a special case,
1125 it is equivalent to "nosmp", which also disables
1128 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1129 equal to this physical address is ignored.
1131 max_luns= [SCSI] Maximum number of LUNs to probe.
1132 Should be between 1 and 2^32-1.
1135 [SCSI] Maximum number of LUNs received.
1136 Should be between 1 and 16384.
1140 mce [X86-32] Machine Check Exception
1142 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1144 md= [HW] RAID subsystems devices and level
1145 See Documentation/md.txt.
1148 Format: <first>,<last>
1149 Specifies range of consoles to be captured by the MDA.
1151 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1152 Amount of memory to be used when the kernel is not able
1153 to see the whole system memory or for test.
1154 [X86-32] Use together with memmap= to avoid physical
1155 address space collisions. Without memmap= PCI devices
1156 could be placed at addresses belonging to unused RAM.
1158 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1161 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1162 E820 memory map, as specified by the user.
1163 Such memmap=exactmap lines can be constructed based on
1164 BIOS output or other requirements. See the memmap=nn@ss
1167 memmap=nn[KMG]@ss[KMG]
1168 [KNL] Force usage of a specific region of memory
1169 Region of memory to be used, from ss to ss+nn.
1171 memmap=nn[KMG]#ss[KMG]
1172 [KNL,ACPI] Mark specific memory as ACPI data.
1173 Region of memory to be used, from ss to ss+nn.
1175 memmap=nn[KMG]$ss[KMG]
1176 [KNL,ACPI] Mark specific memory as reserved.
1177 Region of memory to be used, from ss to ss+nn.
1178 Example: Exclude memory from 0x18690000-0x1869ffff
1179 memmap=64K$0x18690000
1181 memmap=0x10000$0x18690000
1183 memtest= [KNL,X86_64] Enable memtest
1185 range: 0,4 : pattern number
1186 default : 0 <disable>
1188 meye.*= [HW] Set MotionEye Camera parameters
1189 See Documentation/video4linux/meye.txt.
1191 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1192 Multi-Function General Purpose Timers on AMD Geode
1195 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1196 the BIOS has incorrectly applied a workaround. TinyBIOS
1197 version 0.98 is known to be affected, 0.99 fixes the
1198 problem by letting the user disable the workaround.
1203 [MOUSE] Maximum time between finger touching and
1204 leaving touchpad surface for touch to be considered
1205 a tap and be reported as a left button click (for
1206 touchpads working in absolute mode only).
1208 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1209 reporting absolute coordinates, such as tablets
1210 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1211 reporting absolute coordinates, such as tablets
1216 MTD_Partition= [MTD]
1217 Format: <name>,<region-number>,<size>,<offset>
1219 MTD_Region= [MTD] Format:
1220 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1223 See drivers/mtd/cmdlinepart.c.
1225 mtouchusb.raw_coordinates=
1226 [HW] Make the MicroTouch USB driver use raw coordinates
1227 ('y', default) or cooked coordinates ('n')
1229 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1232 See header of drivers/scsi/NCR_D700.c.
1236 ncr53c400= [HW,SCSI]
1238 ncr53c400a= [HW,SCSI]
1240 ncr53c406a= [HW,SCSI]
1242 ncr53c8xx= [HW,SCSI]
1244 netdev= [NET] Network devices parameters
1245 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1246 Note that mem_start is often overloaded to mean
1247 something different and driver-specific.
1248 This usage is only documented in each driver source
1252 See Documentation/filesystems/nfsroot.txt.
1254 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1255 See Documentation/filesystems/nfsroot.txt.
1257 nfs.callback_tcpport=
1258 [NFS] set the TCP port on which the NFSv4 callback
1259 channel should listen.
1261 nfs.idmap_cache_timeout=
1262 [NFS] set the maximum lifetime for idmapper cache
1266 [NFS] enable 64-bit inode numbers.
1267 If zero, the NFS client will fake up a 32-bit inode
1268 number for the readdir() and stat() syscalls instead
1269 of returning the full 64-bit number.
1270 The default is to return 64-bit inode numbers.
1272 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1273 when a NMI is triggered.
1274 Format: [state][,regs][,debounce][,die]
1276 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1278 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1279 emulation library even if a 387 maths coprocessor
1282 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1283 caches in the slab allocator. Saves per-node memory,
1284 but will impact performance.
1288 noapic [SMP,APIC] Tells the kernel to not make use of any
1289 IOAPICs that may be present in the system.
1291 nobats [PPC] Do not use BATs for mapping kernel lowmem
1292 on "Classic" PPC cores.
1296 nodelayacct [KNL] Disable per-task delay accounting
1298 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1300 noefi [X86-32,X86-64] Disable EFI runtime services support.
1304 noexec [X86-32,X86-64]
1305 On X86-32 available only on PAE configured kernels.
1306 noexec=on: enable non-executable mappings (default)
1307 noexec=off: disable non-executable mappings
1310 This affects only 32-bit executables.
1311 noexec32=on: enable non-executable mappings (default)
1312 read doesn't imply executable mappings
1313 noexec32=off: disable non-executable mappings
1314 read implies executable mappings
1316 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1317 register save and restore. The kernel will only save
1318 legacy floating-point registers on task switch.
1320 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1324 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1325 instruction doesn't work correctly and not to
1328 nohalt [IA-64] Tells the kernel not to use the power saving
1329 function PAL_HALT_LIGHT when idle. This increases
1330 power-consumption. On the positive side, it reduces
1331 interrupt wake-up latency, which may improve performance
1332 in certain environments such as networked servers or
1335 nohz= [KNL] Boottime enable/disable dynamic ticks
1336 Valid arguments: on, off
1339 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1341 noirqdebug [X86-32] Disables the code which attempts to detect and
1342 disable unhandled interrupt sources.
1344 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1345 broken timer IRQ sources.
1347 noisapnp [ISAPNP] Disables ISA PnP code.
1349 noinitrd [RAM] Tells the kernel not to load any configured
1354 nojitter [IA64] Disables jitter checking for ITC timers.
1356 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1358 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1360 noltlbs [PPC] Do not use large page/tlb entries for kernel
1361 lowmem mapping on PPC40x.
1363 nomca [IA-64] Disable machine check abort handling
1365 nomce [X86-32] Machine Check Exception
1367 nomfgpt [X86-32] Disable Multi-Function General Purpose
1368 Timer usage (for AMD Geode machines).
1370 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1372 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1373 with UP alternatives
1375 noresidual [PPC] Don't use residual data on PReP machines.
1377 noresume [SWSUSP] Disables resume and restores original swap
1380 no-scroll [VGA] Disables scrollback.
1381 This is required for the Braillex ib80-piezo Braille
1382 reader made by F.H. Papenmeier (Germany).
1386 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1388 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1389 and disable the IO APIC. legacy for "maxcpus=0".
1391 nosoftlockup [KNL] Disable the soft-lockup detector.
1393 nosync [HW,M68K] Disables sync negotiation for all devices.
1395 notsc [BUGS=X86-32] Disable Time Stamp Counter
1397 nousb [USB] Disable the USB subsystem
1401 nptcg= [IA64] Override max number of concurrent global TLB
1402 purges which is reported from either PAL_VM_SUMMARY or
1405 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1406 one of ['zone', 'node', 'default'] can be specified
1407 This can be set from sysctl after boot.
1408 See Documentation/sysctl/vm.txt for details.
1410 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1412 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1413 Rather than timing out after 20 ms if an EC
1414 command is not properly ACKed, override the length
1415 of the timeout. We have interrupts disabled while
1416 waiting for the ACK, so if this is set too high
1417 interrupts *may* be lost!
1422 oprofile.timer= [HW]
1423 Use timer interrupt instead of performance counters
1425 osst= [HW,SCSI] SCSI Tape Driver
1426 Format: <buffer_size>,<write_threshold>
1427 See also Documentation/scsi/st.txt.
1429 panic= [KNL] Kernel behaviour on panic
1432 parkbd.port= [HW] Parallel port number the keyboard adapter is
1433 connected to, default is 0.
1435 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1436 0 for XT, 1 for AT (default is AT).
1439 parport= [HW,PPT] Specify parallel ports. 0 disables.
1440 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1441 Use 'auto' to force the driver to use any
1442 IRQ/DMA settings detected (the default is to
1443 ignore detected IRQ/DMA settings because of
1444 possible conflicts). You can specify the base
1445 address, IRQ, and DMA settings; IRQ and DMA
1446 should be numbers, or 'auto' (for using detected
1447 settings on that particular port), or 'nofifo'
1448 (to avoid using a FIFO even if it is detected).
1449 Parallel ports are assigned in the order they
1450 are specified on the command line, starting
1453 parport_init_mode= [HW,PPT]
1454 Configure VIA parallel port to operate in
1455 a specific mode. This is necessary on Pegasos
1456 computer where firmware has no options for setting
1457 up parallel port mode and sets it to spp.
1458 Currently this function knows 686a and 8231 chips.
1459 Format: [spp|ps2|epp|ecp|ecpepp]
1461 pas2= [HW,OSS] Format:
1462 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1465 See header of drivers/scsi/pas16.c.
1468 Halt all CPUs after the first oops has been printed for
1469 the specified number of seconds. This is to be used if
1470 your oopses keep scrolling off the screen.
1475 See header of drivers/block/paride/pcd.c.
1476 See also Documentation/paride.txt.
1478 pci=option[,option...] [PCI] various PCI subsystem options:
1479 off [X86-32] don't probe for the PCI bus
1480 bios [X86-32] force use of PCI BIOS, don't access
1481 the hardware directly. Use this if your machine
1482 has a non-standard PCI host bridge.
1483 nobios [X86-32] disallow use of PCI BIOS, only direct
1484 hardware access methods are allowed. Use this
1485 if you experience crashes upon bootup and you
1486 suspect they are caused by the BIOS.
1487 conf1 [X86-32] Force use of PCI Configuration
1489 conf2 [X86-32] Force use of PCI Configuration
1491 noaer [PCIE] If the PCIEAER kernel config parameter is
1492 enabled, this kernel boot option can be used to
1493 disable the use of PCIE advanced error reporting.
1494 nodomains [PCI] Disable support for multiple PCI
1495 root domains (aka PCI segments, in ACPI-speak).
1496 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1498 nomsi [MSI] If the PCI_MSI kernel config parameter is
1499 enabled, this kernel boot option can be used to
1500 disable the use of MSI interrupts system-wide.
1501 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1502 routing table. These calls are known to be buggy
1503 on several machines and they hang the machine
1504 when used, but on other computers it's the only
1505 way to get the interrupt routing table. Try
1506 this option if the kernel is unable to allocate
1507 IRQs or discover secondary PCI buses on your
1509 rom [X86-32] Assign address space to expansion ROMs.
1510 Use with caution as certain devices share
1511 address decoders between ROMs and other
1513 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1514 assigned automatically to PCI devices. You can
1515 make the kernel exclude IRQs of your ISA cards
1517 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1518 of the PIRQ table (normally generated
1519 by the BIOS) if it is outside the
1520 F0000h-100000h range.
1521 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1522 useful if the kernel is unable to find your
1523 secondary buses and you want to tell it
1524 explicitly which ones they are.
1525 assign-busses [X86-32] Always assign all PCI bus
1526 numbers ourselves, overriding
1527 whatever the firmware may have done.
1528 usepirqmask [X86-32] Honor the possible IRQ mask stored
1529 in the BIOS $PIR table. This is needed on
1530 some systems with broken BIOSes, notably
1531 some HP Pavilion N5400 and Omnibook XE3
1532 notebooks. This will have no effect if ACPI
1533 IRQ routing is enabled.
1534 noacpi [X86-32] Do not use ACPI for IRQ routing
1535 or for PCI scanning.
1536 use_crs [X86-32] Use _CRS for PCI resource
1538 routeirq Do IRQ routing for all PCI devices.
1539 This is normally done in pci_enable_device(),
1540 so this option is a temporary workaround
1541 for broken drivers that don't call it.
1542 skip_isa_align [X86] do not align io start addr, so can
1543 handle more pci cards
1544 firmware [ARM] Do not re-enumerate the bus but instead
1545 just use the configuration from the
1546 bootloader. This is currently used on
1547 IXP2000 systems where the bus has to be
1548 configured a certain way for adjunct CPUs.
1549 noearly [X86] Don't do any early type 1 scanning.
1550 This might help on some broken boards which
1551 machine check when some devices' config space
1552 is read. But various workarounds are disabled
1553 and some IOMMU drivers will not work.
1554 bfsort Sort PCI devices into breadth-first order.
1555 This sorting is done to get a device
1556 order compatible with older (<= 2.4) kernels.
1557 nobfsort Don't sort PCI devices into breadth-first order.
1558 cbiosize=nn[KMG] The fixed amount of bus space which is
1559 reserved for the CardBus bridge's IO window.
1560 The default value is 256 bytes.
1561 cbmemsize=nn[KMG] The fixed amount of bus space which is
1562 reserved for the CardBus bridge's memory
1563 window. The default value is 64 megabytes.
1565 pcmv= [HW,PCMCIA] BadgePAD 4
1568 See Documentation/paride.txt.
1570 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1573 See arch/parisc/kernel/pdc_chassis.c
1576 See Documentation/paride.txt.
1579 See Documentation/paride.txt.
1581 pirq= [SMP,APIC] Manual mp-table setup
1582 See Documentation/i386/IO-APIC.txt.
1584 plip= [PPT,NET] Parallel port network link
1585 Format: { parport<nr> | timid | 0 }
1586 See also Documentation/parport.txt.
1592 { on | off | curr | res | no-curr | no-res }
1595 [ISAPNP] Exclude IRQs for the autoconfiguration
1598 [ISAPNP] Exclude DMAs for the autoconfiguration
1600 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1601 Ranges are in pairs (I/O port base and size).
1604 [ISAPNP] Exclude memory regions for the
1606 Ranges are in pairs (memory base and size).
1608 print-fatal-signals=
1609 [KNL] debug: print fatal signals
1610 print-fatal-signals=1: print segfault info to
1614 printk.time= Show timing data prefixed to each printk message line
1615 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1617 profile= [KNL] Enable kernel profiling via /proc/profile
1618 Format: [schedule,]<number>
1619 Param: "schedule" - profile schedule points.
1620 Param: <number> - step/bucket size as a power of 2 for
1621 statistical time based profiling.
1622 Param: "sleep" - profile D-state sleeping (millisecs).
1623 Requires CONFIG_SCHEDSTATS
1624 Param: "kvm" - profile VM exits.
1626 processor.max_cstate= [HW,ACPI]
1627 Limit processor to maximum C-state
1628 max_cstate=9 overrides any DMI blacklist limit.
1630 processor.nocst [HW,ACPI]
1631 Ignore the _CST method to determine C-states,
1632 instead using the legacy FADT method
1634 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1636 See Documentation/ramdisk.txt.
1638 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1639 probe for; one of (bare|imps|exps|lifebook|any).
1640 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1642 psmouse.resetafter= [HW,MOUSE]
1643 Try to reset the device after so many bad packets
1646 [HW,MOUSE] Set desired mouse resolution, in dpi.
1647 psmouse.smartscroll=
1648 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1649 0 = disabled, 1 = enabled (default).
1651 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1653 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1656 See Documentation/paride.txt.
1659 [KNL] Number of legacy pty's. Overwrites compiled-in
1662 quiet [KNL] Disable most log messages
1667 See Documentation/md.txt.
1669 ramdisk_blocksize= [RAM]
1670 See Documentation/ramdisk.txt.
1672 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1673 See Documentation/ramdisk.txt.
1675 rcupdate.blimit= [KNL,BOOT]
1676 Set maximum number of finished RCU callbacks to process
1679 rcupdate.qhimark= [KNL,BOOT]
1680 Set threshold of queued
1681 RCU callbacks over which batch limiting is disabled.
1683 rcupdate.qlowmark= [KNL,BOOT]
1684 Set threshold of queued RCU callbacks below which
1685 batch limiting is re-enabled.
1689 Run specified binary instead of /init from the ramdisk,
1690 used for early userspace startup. See initrd.
1692 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1693 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1694 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1696 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1698 reservetop= [X86-32]
1700 Reserves a hole at the top of the kernel virtual
1703 reset_devices [KNL] Force drivers to reset the underlying device
1704 during initialization.
1707 Specify the partition device for software suspend
1709 resume_offset= [SWSUSP]
1710 Specify the offset from the beginning of the partition
1711 given by "resume=" at which the swap header is located,
1712 in <PAGE_SIZE> units (needed only for swap files).
1713 See Documentation/power/swsusp-and-swap-files.txt
1715 retain_initrd [RAM] Keep initrd memory after extraction
1717 rhash_entries= [KNL,NET]
1718 Set number of hash buckets for route cache
1720 riscom8= [HW,SERIAL]
1721 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1723 ro [KNL] Mount root device read-only on boot
1725 root= [KNL] Root filesystem
1727 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1728 mount the root filesystem
1730 rootflags= [KNL] Set root filesystem mount option string
1732 rootfstype= [KNL] Set root filesystem type
1734 rootwait [KNL] Wait (indefinitely) for root device to show up.
1735 Useful for devices that are detected asynchronously
1736 (e.g. USB and MMC devices).
1738 root_plug.vendor_id=
1739 [ROOTPLUG] Override the default vendor ID
1741 root_plug.product_id=
1742 [ROOTPLUG] Override the default product ID
1745 [ROOTPLUG] Enable debugging output
1747 rw [KNL] Mount root device read-write on boot
1749 S [KNL] Run init in single mode
1752 See drivers/net/irda/sa1100_ir.c.
1754 sbni= [NET] Granch SBNI12 leased line adapter
1756 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1757 Format: <io>[,<timeout>[,<isapnp>]]
1759 scsi_debug_*= [SCSI]
1760 See drivers/scsi/scsi_debug.c.
1762 scsi_default_dev_flags=
1763 [SCSI] SCSI default device flags
1766 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1767 Format: <vendor>:<model>:<flags>
1768 (flags are integer value)
1770 scsi_logging_level= [SCSI] a bit mask of logging levels
1771 See drivers/scsi/scsi_logging.h for bits. Also
1772 settable via sysctl at dev.scsi.logging_level
1773 (/proc/sys/dev/scsi/logging_level).
1774 There is also a nice 'scsi_logging_level' script in the
1775 S390-tools package, available for download at
1776 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1778 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1779 discovered. async scans them in kernel threads,
1780 allowing boot to proceed. none ignores them, expecting
1781 user space to do the scan.
1783 selinux [SELINUX] Disable or enable SELinux at boot time.
1784 Format: { "0" | "1" }
1785 See security/selinux/Kconfig help text.
1788 Default value is set via kernel config option.
1789 If enabled at boot time, /selinux/disable can be used
1790 later to disable prior to initial policy load.
1792 selinux_compat_net =
1793 [SELINUX] Set initial selinux_compat_net flag value.
1794 Format: { "0" | "1" }
1795 0 -- use new secmark-based packet controls
1796 1 -- use legacy packet controls
1797 Default value is 0 (preferred).
1798 Value can be changed at runtime via
1799 /selinux/compat_net.
1801 serialnumber [BUGS=X86-32]
1804 Maximal number of shapers.
1807 See header of drivers/scsi/sim710.c.
1814 slub_debug[=options[,slabs]] [MM, SLUB]
1815 Enabling slub_debug allows one to determine the
1816 culprit if slab objects become corrupted. Enabling
1817 slub_debug can create guard zones around objects and
1818 may poison objects when not in use. Also tracks the
1819 last alloc / free. For more information see
1820 Documentation/vm/slub.txt.
1822 slub_max_order= [MM, SLUB]
1823 Determines the maximum allowed order for slabs.
1824 A high setting may cause OOMs due to memory
1825 fragmentation. For more information see
1826 Documentation/vm/slub.txt.
1828 slub_min_objects= [MM, SLUB]
1829 The minimum number of objects per slab. SLUB will
1830 increase the slab order up to slub_max_order to
1831 generate a sufficiently large slab able to contain
1832 the number of objects indicated. The higher the number
1833 of objects the smaller the overhead of tracking slabs
1834 and the less frequently locks need to be acquired.
1835 For more information see Documentation/vm/slub.txt.
1837 slub_min_order= [MM, SLUB]
1838 Determines the mininum page order for slabs. Must be
1839 lower than slub_max_order.
1840 For more information see Documentation/vm/slub.txt.
1842 slub_nomerge [MM, SLUB]
1843 Disable merging of slabs with similar size. May be
1844 necessary if there is some reason to distinguish
1845 allocs to different slabs. Debug options disable
1846 merging on their own.
1847 For more information see Documentation/vm/slub.txt.
1850 Format: <io1>[,<io2>[,...,<io8>]]
1852 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1853 attempt to substitute SMP alternatives once at boot.
1855 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1856 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1857 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1858 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1859 smsc-ircc2.ircc_irq= [HW] IRQ line
1860 smsc-ircc2.ircc_dma= [HW] DMA channel
1861 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1862 0: Toshiba Satellite 1800 (GP data pin select)
1863 1: Fast pin select (default)
1866 snd-ad1816a= [HW,ALSA]
1868 snd-ad1848= [HW,ALSA]
1870 snd-ali5451= [HW,ALSA]
1872 snd-als100= [HW,ALSA]
1874 snd-als4000= [HW,ALSA]
1876 snd-azt2320= [HW,ALSA]
1878 snd-cmi8330= [HW,ALSA]
1880 snd-cmipci= [HW,ALSA]
1882 snd-cs4231= [HW,ALSA]
1884 snd-cs4232= [HW,ALSA]
1886 snd-cs4236= [HW,ALSA]
1888 snd-cs4281= [HW,ALSA]
1890 snd-cs46xx= [HW,ALSA]
1892 snd-dt019x= [HW,ALSA]
1894 snd-dummy= [HW,ALSA]
1896 snd-emu10k1= [HW,ALSA]
1898 snd-ens1370= [HW,ALSA]
1900 snd-ens1371= [HW,ALSA]
1902 snd-es968= [HW,ALSA]
1904 snd-es1688= [HW,ALSA]
1906 snd-es18xx= [HW,ALSA]
1908 snd-es1938= [HW,ALSA]
1910 snd-es1968= [HW,ALSA]
1912 snd-fm801= [HW,ALSA]
1914 snd-gusclassic= [HW,ALSA]
1916 snd-gusextreme= [HW,ALSA]
1918 snd-gusmax= [HW,ALSA]
1922 snd-ice1712= [HW,ALSA]
1924 snd-intel8x0= [HW,ALSA]
1926 snd-interwave= [HW,ALSA]
1931 snd-korg1212= [HW,ALSA]
1933 snd-maestro3= [HW,ALSA]
1935 snd-mpu401= [HW,ALSA]
1937 snd-mtpav= [HW,ALSA]
1939 snd-nm256= [HW,ALSA]
1941 snd-opl3sa2= [HW,ALSA]
1949 snd-opti93x= [HW,ALSA]
1953 snd-rme32= [HW,ALSA]
1955 snd-rme96= [HW,ALSA]
1957 snd-rme9652= [HW,ALSA]
1963 snd-sbawe= [HW,ALSA]
1965 snd-serial= [HW,ALSA]
1967 snd-sgalaxy= [HW,ALSA]
1969 snd-sonicvibes= [HW,ALSA]
1974 snd-sun-cs4231= [HW,ALSA]
1976 snd-trident= [HW,ALSA]
1978 snd-usb-audio= [HW,ALSA,USB]
1980 snd-via82xx= [HW,ALSA]
1982 snd-virmidi= [HW,ALSA]
1984 snd-wavefront= [HW,ALSA]
1986 snd-ymfpci= [HW,ALSA]
1988 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1989 See Documentation/sonypi.txt
1991 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1992 See Documentation/specialix.txt.
1994 spia_io_base= [HW,MTD]
2000 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2002 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2003 See Documentation/scsi/st.txt.
2007 Set the STI (builtin display/keyboard on the HP-PARISC
2008 machines) console (graphic card) which should be used
2009 as the initial boot-console.
2010 See also comment in drivers/video/console/sticore.c.
2013 See comment in drivers/video/console/sticore.c.
2016 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2020 Control how the NFS server code allocates CPUs to
2021 service thread pools. Depending on how many NICs
2022 you have and where their interrupts are bound, this
2023 option will affect which CPUs will do NFS serving.
2024 Note: this parameter cannot be changed while the
2025 NFS server is running.
2027 auto the server chooses an appropriate mode
2028 automatically using heuristics
2029 global a single global pool contains all CPUs
2030 percpu one pool for each CPU
2031 pernode one pool for each NUMA node (equivalent
2032 to global on non-NUMA machines)
2034 swiotlb= [IA-64] Number of I/O TLB slabs
2038 sym53c416= [HW,SCSI]
2039 See header of drivers/scsi/sym53c416.c.
2041 sysrq_always_enabled
2043 Ignore sysrq setting - this boot parameter will
2044 neutralize any effect of /proc/sys/kernel/sysrq.
2045 Useful for debugging.
2048 See header of drivers/scsi/t128.c.
2052 thash_entries= [KNL,NET]
2053 Set number of hash buckets for TCP connection
2055 thermal.act= [HW,ACPI]
2056 -1: disable all active trip points in all thermal zones
2057 <degrees C>: override all lowest active trip points
2059 thermal.crt= [HW,ACPI]
2060 -1: disable all critical trip points in all thermal zones
2061 <degrees C>: lower all critical trip points
2063 thermal.nocrt= [HW,ACPI]
2064 Set to disable actions on ACPI thermal zone
2065 critical and hot trip points.
2067 thermal.off= [HW,ACPI]
2068 1: disable ACPI thermal control
2070 thermal.psv= [HW,ACPI]
2071 -1: disable all passive trip points
2072 <degrees C>: override all passive trip points to this value
2074 thermal.tzp= [HW,ACPI]
2075 Specify global default ACPI thermal zone polling rate
2076 <deci-seconds>: poll all this frequency
2077 0: no polling (default)
2079 tipar.timeout= [HW,PPT]
2080 Set communications timeout in tenths of a second
2083 tipar.delay= [HW,PPT]
2084 Set inter-bit delay in microseconds (default 10).
2087 See comment before function dc390_setup() in
2088 drivers/scsi/tmscsim.c.
2092 trix= [HW,OSS] MediaTrix AudioTrix Pro
2094 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2096 turbografx.map[2|3]= [HW,JOY]
2097 TurboGraFX parallel port interface
2099 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2100 See also Documentation/input/joystick-parport.txt
2102 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2103 See header of drivers/scsi/u14-34f.c.
2112 [USB] Ignore overcurrent events (default N).
2113 Some badly-designed motherboards generate lots of
2114 bogus events, for ports that aren't wired to
2115 anything. Set this parameter to avoid log spamming.
2116 Note that genuine overcurrent events won't be
2119 usbcore.autosuspend=
2120 [USB] The autosuspend time delay (in seconds) used
2121 for newly-detected USB devices (default 2). This
2122 is the time required before an idle device will be
2123 autosuspended. Devices for which the delay is set
2124 to a negative value won't be autosuspended at all.
2127 [USBHID] The interval which mice are to be polled at.
2129 vdso= [X86-32,SH,x86-64]
2130 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2131 vdso=1: enable VDSO (default)
2132 vdso=0: disable VDSO mapping
2134 vdso32= [X86-32,X86-64]
2135 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2136 vdso32=1: enable 32-bit VDSO (default)
2137 vdso32=0: disable 32-bit VDSO mapping
2140 vector=percpu: enable percpu vector domain
2142 video= [FB] Frame buffer configuration
2143 See Documentation/fb/modedb.txt.
2145 vga= [BOOT,X86-32] Select a particular video mode
2146 See Documentation/i386/boot.txt and
2147 Documentation/svga.txt.
2148 Use vga=ask for menu.
2149 This is actually a boot loader parameter; the value is
2150 passed to the kernel using a special protocol.
2152 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2153 size of <nn>. This can be used to increase the
2154 minimum size (128MB on x86). It can also be used to
2155 decrease the size and leave more room for directly
2158 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2161 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2164 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2167 waveartist= [HW,OSS]
2168 Format: <io>,<irq>,<dma>,<dma2>
2171 See header of drivers/scsi/wd33c93.c.
2174 See header of drivers/scsi/wd7000.c.
2177 See Documentation/watchdog/wdt.txt.
2179 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2180 xd_geo= See header of drivers/block/xd.c.
2182 xirc2ps_cs= [NET,PCMCIA]
2184 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2186 norandmaps Don't use address space randomization
2187 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2189 ______________________________________________________________________
2193 Add documentation for ALSA options.
2194 Add more DRM drivers.