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 amd_iommu= [HW,X86-84]
275 Pass parameters to the AMD IOMMU driver in the system.
277 off - disable the driver for AMD IOMMU
278 isolate - enable device isolation (each device, as far
279 as possible, will get its own protection
281 amd_iommu_size= [HW,X86-64]
282 Define the size of the aperture for the AMD IOMMU
283 driver. Possible values are:
284 '32M', '64M' (default), '128M', '256M', '512M', '1G'
286 amijoy.map= [HW,JOY] Amiga joystick support
287 Map of devices attached to JOY0DAT and JOY1DAT
289 See also Documentation/kernel/input/joystick.txt
291 analog.map= [HW,JOY] Analog joystick and gamepad support
292 Specifies type or capabilities of an analog joystick
293 connected to one of 16 gameports
294 Format: <type1>,<type2>,..<type16>
297 Power management functions (SPARCstation-4/5 + deriv.)
299 Disable APC CPU standby support. SPARCstation-Fox does
300 not play well with APC CPU idle - disable it if you have
301 APC and your system crashes randomly.
303 apic= [APIC,i386] Advanced Programmable Interrupt Controller
304 Change the output verbosity whilst booting
305 Format: { quiet (default) | verbose | debug }
306 Change the amount of debugging information output
307 when initialising the APIC and IO-APIC components.
309 apm= [APM] Advanced Power Management
310 See header of arch/i386/kernel/apm.c.
312 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
313 Format: <io>,<irq>,<nodeID>
317 atarimouse= [HW,MOUSE] Atari Mouse
319 atascsi= [HW,SCSI] Atari SCSI
321 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
322 EzKey and similar keyboards
324 atkbd.reset= [HW] Reset keyboard during initialization
326 atkbd.set= [HW] Select keyboard code set
327 Format: <int> (2 = AT (default), 3 = PS/2)
329 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
332 atkbd.softraw= [HW] Choose between synthetic and real raw mode
333 Format: <bool> (0 = real, 1 = synthetic (default))
335 atkbd.softrepeat= [HW]
336 Use software keyboard repeat
340 baycom_epp= [HW,AX25]
343 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
345 See header of drivers/net/hamradio/baycom_par.c.
347 baycom_ser_fdx= [HW,AX25]
348 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
349 Format: <io>,<irq>,<mode>[,<baud>]
350 See header of drivers/net/hamradio/baycom_ser_fdx.c.
352 baycom_ser_hdx= [HW,AX25]
353 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
354 Format: <io>,<irq>,<mode>
355 See header of drivers/net/hamradio/baycom_ser_hdx.c.
357 boot_delay= Milliseconds to delay each printk during boot.
358 Values larger than 10 seconds (10000) are changed to
362 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
363 bttv.radio= Most important insmod options are available as
365 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
366 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
369 See drivers/scsi/BusLogic.c, comment before function
370 BusLogic_ParseDriverOptions().
372 c101= [NET] Moxa C101 synchronous serial card
374 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
375 Sometimes CPU hardware bugs make them report the cache
376 size incorrectly. The kernel will attempt work arounds
377 to fix known problems, but for some CPUs it is not
378 possible to determine what the correct size should be.
379 This option provides an override for these situations.
381 security= [SECURITY] Choose a security module to enable at boot.
382 If this boot parameter is not specified, only the first
383 security module asking for security registration will be
384 loaded. An invalid security module name will be treated
385 as if no module has been chosen.
388 [SECURITY] Disable capabilities. This would normally
389 be used only if an alternative security model is to be
390 configured. Potentially dangerous and should only be
391 used if you are entirely sure of the consequences.
393 ccw_timeout_log [S390]
394 See Documentation/s390/CommonIO for details.
396 cgroup_disable= [KNL] Disable a particular controller
397 Format: {name of the controller(s) to disable}
398 {Currently supported controllers - "memory"}
400 checkreqprot [SELINUX] Set initial checkreqprot flag value.
401 Format: { "0" | "1" }
402 See security/selinux/Kconfig help text.
403 0 -- check protection applied by kernel (includes
404 any implied execute protection).
405 1 -- check protection requested by application.
406 Default value is set via a kernel config option.
407 Value can be changed at runtime via
408 /selinux/checkreqprot.
411 See Documentation/s390/CommonIO for details.
413 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
415 Forces specified clocksource (if available) to be used
416 when calculating gettimeofday(). If specified
417 clocksource is not available, it defaults to PIT.
418 Format: { pit | tsc | cyclone | pmtmr }
420 clocksource= [GENERIC_TIME] Override the default clocksource
422 Override the default clocksource and use the clocksource
423 with the name specified.
424 Some clocksource names to choose from, depending on
426 [all] jiffies (this is the base, fallback clocksource)
428 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
429 pxa_timer,timer3,32k_counter,timer0_1
431 [X86-32] pit,hpet,tsc,vmi-timer;
432 scx200_hrt on Geode; cyclone on IBM x440
440 clearcpuid=BITNUM [X86]
441 Disable CPUID feature X for the kernel. See
442 include/asm-x86/cpufeature.h for the valid bit numbers.
443 Note the Linux specific bits are not necessarily
444 stable over kernel options, but the vendor specific
446 Also note that user programs calling CPUID directly
447 or using the feature without checking anything
448 will still see it. This just prevents it from
449 being used by the kernel or shown in /proc/cpuinfo.
450 Also note the kernel might malfunction if you disable
453 code_bytes [IA32/X86_64] How many bytes of object code to print
460 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
461 over the 8254 in addition to over the IO-APIC. The
462 kernel tries to set a sensible default.
464 hpet= [X86-32,HPET] option to control HPET usage
465 Format: { enable (default) | disable | force }
466 disable: disable HPET and use PIT instead
467 force: allow force enabled of undocumented chips (ICH4,
470 com20020= [HW,NET] ARCnet - COM20020 chipset
472 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
474 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
478 ARCnet - COM90xx chipset (memory-mapped buffers)
479 Format: <io>[,<irq>[,<memstart>]]
481 condev= [HW,S390] console device
484 console= [KNL] Output console device and options.
486 tty<n> Use the virtual console device <n>.
490 Use the specified serial port. The options are of
491 the form "bbbbpnf", where "bbbb" is the baud rate,
492 "p" is parity ("n", "o", or "e"), "n" is number of
493 bits, and "f" is flow control ("r" for RTS or
494 omit it). Default is "9600n8".
496 See Documentation/serial-console.txt for more
498 Documentation/networking/netconsole.txt for an
501 uart[8250],io,<addr>[,options]
502 uart[8250],mmio,<addr>[,options]
503 Start an early, polled-mode console on the 8250/16550
504 UART at the specified I/O port or MMIO address,
505 switching to the matching ttyS device later. The
506 options are the same as for ttyS, above.
508 If the device connected to the port is not a TTY but a braille
509 device, prepend "brl," before the device type, for instance
511 For now, only VisioBraille is supported.
513 earlycon= [KNL] Output early console device and options.
514 uart[8250],io,<addr>[,options]
515 uart[8250],mmio,<addr>[,options]
516 Start an early, polled-mode console on the 8250/16550
517 UART at the specified I/O port or MMIO address.
518 The options are the same as for ttyS, above.
521 [HW] Never suspend the console
522 Disable suspending of consoles during suspend and
523 hibernate operations. Once disabled, debugging
524 messages can reach various consoles while the rest
525 of the system is being put to sleep (ie, while
526 debugging driver suspend/resume hooks). This may
527 not work reliably with all consoles, but is known
528 to work with serial and VGA consoles.
530 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
532 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
534 crashkernel=nn[KMG]@ss[KMG]
535 [KNL] Reserve a chunk of physical memory to
536 hold a kernel to switch to with kexec on panic.
538 crashkernel=range1:size1[,range2:size2,...][@offset]
539 [KNL] Same as above, but depends on the memory
540 in the running system. The syntax of range is
541 start-[end] where start and end are both
542 a memory unit (amount[KMG]). See also
543 Documentation/kdump/kdump.txt for a example.
546 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
551 cs89x0_media= [HW,NET]
552 Format: { rj45 | aui | bnc }
555 See header of drivers/s390/block/dasd_devmap.c.
557 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
558 (one device per port)
559 Format: <port#>,<type>
560 See also Documentation/input/joystick-parport.txt
562 debug [KNL] Enable kernel debugging (events log level).
565 [KNL] verbose self-tests
567 Print debugging info while doing the locking API
569 We default to 0 (no extra messages), setting it to
570 1 will print _a lot_ more information - normally
571 only useful to kernel developers.
573 debug_objects [KNL] Enable object debugging
575 decnet.addr= [HW,NET]
576 Format: <area>[,<node>]
577 See also Documentation/networking/decnet.txt.
580 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
581 Change the default blue palette of the console.
582 This is a 16-member array composed of values
586 Format: <green0>,<green1>,<green2>,...,<green15>
587 Change the default green palette of the console.
588 This is a 16-member array composed of values
592 Format: <red0>,<red1>,<red2>,...,<red15>
593 Change the default red palette of the console.
594 This is a 16-member array composed of values
600 Set system-wide default UTF-8 mode for all tty's.
601 Default is 1, i.e. UTF-8 mode is enabled for all
602 newly opened terminals.
605 Set number of hash buckets for dentry cache.
608 IO parameters + enable/disable command.
610 digiepca= [HW,SERIAL]
611 See drivers/char/README.epca and
612 Documentation/digiepca.txt.
614 disable_mtrr_trim [X86, Intel and AMD only]
615 By default the kernel will trim any uncacheable
616 memory out of your available memory pool based on
617 MTRR settings. This parameter disables that behavior,
618 possibly causing your machine to run very slowly.
620 dmasound= [HW,OSS] Sound subsystem buffers
626 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
628 earlyprintk=serial[,ttySn[,baudrate]]
630 Append ",keep" to not disable it when the real console
633 Only vga or serial at a time, not both.
635 Currently only ttyS0 and ttyS1 are supported.
637 Interaction with the standard serial driver is not
640 The VGA output is eventually overwritten by the real
646 Format: {"off" | "on" | "skip[mbr]"}
648 eisa_irq_edge= [PARISC,HW]
649 See header of drivers/parisc/eisa.c.
652 See comment before function elanfreq_setup() in
653 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
656 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
657 See Documentation/block/as-iosched.txt and
658 Documentation/block/deadline-iosched.txt for details.
660 elfcorehdr= [X86-32, X86_64]
661 Specifies physical address of start of kernel core
662 image elf header. Generally kexec loader will
663 pass this option to capture kernel.
664 See Documentation/kdump/kdump.txt for details.
666 enforcing [SELINUX] Set initial enforcing status.
668 See security/selinux/Kconfig help text.
669 0 -- permissive (log only, no denials).
670 1 -- enforcing (deny and log).
672 Value can be changed at runtime via /selinux/enforce.
675 Format: <spdif>,[<nomix>,[<amplifier>]]
676 See also header of sound/oss/es1371.c.
678 ether= [HW,NET] Ethernet cards parameters
679 This option is obsoleted by the "netdev=" option, which
680 has equivalent usage. See its documentation for details.
682 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
687 fail_make_request=[KNL]
688 General fault injection mechanism.
689 Format: <interval>,<probability>,<space>,<times>
690 See also /Documentation/fault-injection/.
693 See header of drivers/scsi/fd_mcs.c.
696 See header of drivers/scsi/fdomain.c.
699 See Documentation/floppy.txt.
701 force_pal_cache_flush
702 [IA-64] Avoid check_sal_cache_flush which may hang on
703 buggy SAL_CACHE_FLUSH implementations. Using this
704 parameter will force ia64_sal_cache_flush to call
705 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
708 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
709 support via parallel port (up to 5 devices per port)
710 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
711 See also Documentation/input/joystick-parport.txt
715 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
720 See header of drivers/scsi/gdth.c.
722 gpt [EFI] Forces disk with valid GPT signature but
723 invalid Protective MBR to be treated as GPT.
727 hashdist= [KNL,NUMA] Large hashes allocated during boot
728 are distributed across NUMA nodes. Defaults on
729 for IA-64, off otherwise.
730 Format: 0 | 1 (for off | on)
732 hcl= [IA-64] SGI's Hardware Graph compatibility layer
734 hd= [EIDE] (E)IDE hard drive subsystem geometry
735 Format: <cyl>,<head>,<sect>
737 hd?= [HW] (E)IDE subsystem
738 hd?lun= See Documentation/ide/ide.txt.
740 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
741 size of <nn>. This works even on boxes that have no
742 highmem otherwise. This also works to reduce highmem
743 size on bigger boxes.
745 highres= [KNL] Enable/disable high resolution timer mode.
746 Valid parameters: "on", "off"
750 See Documentation/isdn/README.HiSax.
752 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
753 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
755 i8042.direct [HW] Put keyboard port into non-translated mode
756 i8042.dumbkbd [HW] Pretend that controller can only read data from
757 keyboard and cannot control its state
758 (Don't attempt to blink the leds)
759 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
760 i8042.nokbd [HW] Don't check/create keyboard port
761 i8042.noloop [HW] Disable the AUX Loopback command while probing
763 i8042.nomux [HW] Don't check presence of an active multiplexing
765 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
768 [HW] Frequency with which keyboard LEDs should blink
769 when kernel panics (default is 0.5 sec)
770 i8042.reset [HW] Reset the controller during init and cleanup
771 i8042.unlock [HW] Unlock (ignore) the keylock
775 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
776 indicates that the driver is running on unsupported
778 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
779 does not match list of supported models.
781 [HW] Report power status in /proc/i8k
782 (disabled by default)
783 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
786 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
787 See Documentation/mca.txt.
790 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
792 ide= [HW] (E)IDE subsystem
793 Format: ide=nodma or ide=doubler
794 See Documentation/ide/ide.txt.
796 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
797 See Documentation/ide/ide.txt.
800 Format: idle=poll or idle=mwait
801 Poll forces a polling idle loop that can slightly improves the performance
802 of waking up a idle CPU, but will use a lot of power and make the system
803 run hot. Not recommended.
804 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
805 to not use it because it doesn't save as much power as a normal idle
806 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
809 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
810 Claim all unknown PCI IDE storage controllers.
812 ignore_loglevel [KNL]
813 Ignore loglevel setting - this will print /all/
814 kernel messages to the console. Useful for debugging.
817 Set number of hash buckets for inode cache.
820 See header of drivers/scsi/in2000.c.
824 Run specified binary instead of /sbin/init as init
827 initcall_debug [KNL] Trace initcalls as they are executed. Useful
828 for working out where the kernel is dying during
831 initrd= [BOOT] Specify the location of the initial ramdisk
833 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
851 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
853 Disable intel iommu driver.
854 igfx_off [Default Off]
855 By default, gfx is mapped as normal device. If a gfx
856 device has a dedicated DMAR unit, the DMAR unit is
857 bypassed by not enabling DMAR with this option. In
858 this case, gfx device will use physical address for
861 With this option iommu will not optimize to look
862 for io virtual address below 32 bit forcing dual
863 address cycle on pci bus for cards supporting greater
864 than 32 bit addressing. The default is to look
865 for translation below 32 bit and if not available
866 then look in the higher range.
868 With this option on every unmap_single operation will
869 result in a hardware IOTLB flush operation as opposed
870 to batching them for performance.
872 io_delay= [X86-32,X86-64] I/O delay method
874 Standard port 0x80 based delay
876 Alternate port 0xed based delay (needed on some systems)
878 Simple two microseconds delay
882 io7= [HW] IO7 for Marvel based alpha systems
883 See comment before marvel_specify_io7 in
884 arch/alpha/kernel/core_marvel.c.
887 See Documentation/filesystems/nfsroot.txt.
889 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
890 See comment before ip2_setup() in
891 drivers/char/ip2/ip2base.c.
893 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
894 See header of drivers/scsi/ips.c.
896 ports= [IP_VS_FTP] IPVS ftp helper module
898 Up to 8 (IP_VS_APP_MAX_PORTS) ports
900 Format: <port>,<port>....
903 When an interrupt is not handled search all handlers
904 for it. Intended to get systems with badly broken
908 When an interrupt is not handled search all handlers
909 for it. Also check all handlers each timer
910 interrupt. Intended to get systems with badly broken
914 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
916 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
918 <cpu number>,...,<cpu number>
920 <cpu number>-<cpu number> (must be a positive range in ascending order)
922 <cpu number>,...,<cpu number>-<cpu number>
923 This option can be used to specify one or more CPUs
924 to isolate from the general SMP balancing and scheduling
925 algorithms. The only way to move a process onto or off
926 an "isolated" CPU is via the CPU affinity syscalls.
927 <cpu number> begins at 0 and the maximum value is
928 "number of CPUs in system - 1".
930 This option is the preferred way to isolate CPUs. The
931 alternative -- manually setting the CPU mask of all
932 tasks in the system -- can cause problems and
933 suboptimal load balancer performance.
937 js= [HW,JOY] Analog joystick
938 See Documentation/input/joystick.txt.
940 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
941 specifies the amount of memory usable by the kernel
942 for non-movable allocations. The requested amount is
943 spread evenly throughout all nodes in the system. The
944 remaining memory in each node is used for Movable
945 pages. In the event, a node is too small to have both
946 kernelcore and Movable pages, kernelcore pages will
947 take priority and other nodes will have a larger number
948 of kernelcore pages. The Movable zone is used for the
949 allocation of pages that may be reclaimed or moved
950 by the page migration subsystem. This means that
951 HugeTLB pages may not be allocated from this zone.
952 Note that allocations like PTEs-from-HighMem still
953 use the HighMem zone if it exists, and the Normal
956 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
957 is similar to kernelcore except it specifies the
958 amount of memory used for migratable allocations.
959 If both kernelcore and movablecore is specified,
960 then kernelcore will be at *least* the specified
961 value but may be more. If movablecore on its own
962 is specified, the administrator must be careful
963 that the amount of memory usable for all allocations
968 kstack=N [X86-32,X86-64] Print N words from the kernel stack
971 kgdboc= [HW] kgdb over consoles.
972 Requires a tty driver that supports console polling.
973 (only serial suported for now)
974 Format: <serial_device>[,baud]
980 lapic [X86-32,APIC] Enable the local APIC even if BIOS
983 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
986 libata.dma= [LIBATA] DMA control
987 libata.dma=0 Disable all PATA and SATA DMA
988 libata.dma=1 PATA and SATA Disk DMA only
989 libata.dma=2 ATAPI (CDROM) DMA only
990 libata.dma=4 Compact Flash DMA only
991 Combinations also work, so libata.dma=3 enables DMA
992 for disks and CDROMs, but not CFs.
994 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
998 libata.force= [LIBATA] Force configurations. The format is comma
999 separated list of "[ID:]VAL" where ID is
1000 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1001 matching port, link or device. Basically, it matches
1002 the ATA ID string printed on console by libata. If
1003 the whole ID part is omitted, the last PORT and DEVICE
1004 values are used. If ID hasn't been specified yet, the
1005 configuration applies to all ports, links and devices.
1007 If only DEVICE is omitted, the parameter applies to
1008 the port and all links and devices behind it. DEVICE
1009 number of 0 either selects the first device or the
1010 first fan-out link behind PMP device. It does not
1011 select the host link. DEVICE number of 15 selects the
1012 host link and device attached to it.
1014 The VAL specifies the configuration to force. As long
1015 as there's no ambiguity shortcut notation is allowed.
1016 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1017 The following configurations can be forced.
1019 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1020 Any ID with matching PORT is used.
1022 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1024 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1025 udma[/][16,25,33,44,66,100,133] notation is also
1028 * [no]ncq: Turn on or off NCQ.
1030 If there are multiple matching configurations changing
1031 the same attribute, the last one is used.
1033 load_ramdisk= [RAM] List of ramdisks to load from floppy
1034 See Documentation/ramdisk.txt.
1036 lockd.nlm_grace_period=P [NFS] Assign grace period.
1039 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1042 lockd.nlm_timeout=T [NFS] Assign timeout value.
1045 lockd.nlm_udpport=M [NFS] Assign UDP port.
1048 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1051 loglevel= All Kernel Messages with a loglevel smaller than the
1052 console loglevel will be printed to the console. It can
1053 also be changed with klogd or other programs. The
1054 loglevels are defined as follows:
1056 0 (KERN_EMERG) system is unusable
1057 1 (KERN_ALERT) action must be taken immediately
1058 2 (KERN_CRIT) critical conditions
1059 3 (KERN_ERR) error conditions
1060 4 (KERN_WARNING) warning conditions
1061 5 (KERN_NOTICE) normal but significant condition
1062 6 (KERN_INFO) informational
1063 7 (KERN_DEBUG) debug-level messages
1065 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1066 Format: { n | nk | nM }
1067 n must be a power of two. The default size
1068 is set in the kernel config file.
1070 logo.nologo [FB] Disables display of the built-in Linux logo.
1071 This may be used to provide more screen space for
1072 kernel log messages and is useful when debugging
1073 kernel boot problems.
1075 lp=0 [LP] Specify parallel ports to use, e.g,
1076 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1077 lp=reset first parallel port). 'lp=0' disables the
1078 lp=auto printer driver. 'lp=reset' (which can be
1079 specified in addition to the ports) causes
1080 attached printers to be reset. Using
1081 lp=port1,port2,... specifies the parallel ports
1082 to associate lp devices with, starting with
1083 lp0. A port specification may be 'none' to skip
1084 that lp device, or a parport name such as
1085 'parport0'. Specifying 'lp=auto' instead of a
1086 port specification list means that device IDs
1087 from each port should be examined, to see if
1088 an IEEE 1284-compliant printer is attached; if
1089 so, the driver will manage that printer.
1090 See also header of drivers/char/lp.c.
1093 Sets loops_per_jiffy to given constant, thus avoiding
1094 time-consuming boot-time autodetection (up to 250 ms per
1095 CPU). 0 enables autodetection (default). To determine
1096 the correct value for your kernel, boot with normal
1097 autodetection and see what value is printed. Note that
1098 on SMP systems the preset will be applied to all CPUs,
1099 which is likely to cause problems if your CPUs need
1100 significantly divergent settings. An incorrect value
1101 will cause delays in the kernel to be wrong, leading to
1102 unpredictable I/O errors and other breakage. Although
1103 unlikely, in the extreme case this might damage your
1107 Format: <io>,<irq>,<dma>
1109 mac5380= [HW,SCSI] Format:
1110 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1112 machvec= [IA64] Force the use of a particular machine-vector
1113 (machvec) in a generic kernel.
1114 Example: machvec=hpzx1_swiotlb
1116 max_loop= [LOOP] Maximum number of loopback devices that can
1120 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1121 should make use of. maxcpus=n : n >= 0 limits the
1122 kernel to using 'n' processors. n=0 is a special case,
1123 it is equivalent to "nosmp", which also disables
1126 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1127 equal to this physical address is ignored.
1129 max_luns= [SCSI] Maximum number of LUNs to probe.
1130 Should be between 1 and 2^32-1.
1133 [SCSI] Maximum number of LUNs received.
1134 Should be between 1 and 16384.
1138 mce [X86-32] Machine Check Exception
1140 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1142 md= [HW] RAID subsystems devices and level
1143 See Documentation/md.txt.
1146 Format: <first>,<last>
1147 Specifies range of consoles to be captured by the MDA.
1149 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1150 Amount of memory to be used when the kernel is not able
1151 to see the whole system memory or for test.
1152 [X86-32] Use together with memmap= to avoid physical
1153 address space collisions. Without memmap= PCI devices
1154 could be placed at addresses belonging to unused RAM.
1156 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1159 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1160 E820 memory map, as specified by the user.
1161 Such memmap=exactmap lines can be constructed based on
1162 BIOS output or other requirements. See the memmap=nn@ss
1165 memmap=nn[KMG]@ss[KMG]
1166 [KNL] Force usage of a specific region of memory
1167 Region of memory to be used, from ss to ss+nn.
1169 memmap=nn[KMG]#ss[KMG]
1170 [KNL,ACPI] Mark specific memory as ACPI data.
1171 Region of memory to be used, from ss to ss+nn.
1173 memmap=nn[KMG]$ss[KMG]
1174 [KNL,ACPI] Mark specific memory as reserved.
1175 Region of memory to be used, from ss to ss+nn.
1176 Example: Exclude memory from 0x18690000-0x1869ffff
1177 memmap=64K$0x18690000
1179 memmap=0x10000$0x18690000
1181 memtest= [KNL,X86_64] Enable memtest
1183 range: 0,4 : pattern number
1184 default : 0 <disable>
1186 meye.*= [HW] Set MotionEye Camera parameters
1187 See Documentation/video4linux/meye.txt.
1189 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1190 Multi-Function General Purpose Timers on AMD Geode
1193 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1194 the BIOS has incorrectly applied a workaround. TinyBIOS
1195 version 0.98 is known to be affected, 0.99 fixes the
1196 problem by letting the user disable the workaround.
1201 [MOUSE] Maximum time between finger touching and
1202 leaving touchpad surface for touch to be considered
1203 a tap and be reported as a left button click (for
1204 touchpads working in absolute mode only).
1206 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1207 reporting absolute coordinates, such as tablets
1208 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1209 reporting absolute coordinates, such as tablets
1214 MTD_Partition= [MTD]
1215 Format: <name>,<region-number>,<size>,<offset>
1217 MTD_Region= [MTD] Format:
1218 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1221 See drivers/mtd/cmdlinepart.c.
1223 mtouchusb.raw_coordinates=
1224 [HW] Make the MicroTouch USB driver use raw coordinates
1225 ('y', default) or cooked coordinates ('n')
1227 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1230 See header of drivers/scsi/NCR_D700.c.
1234 ncr53c400= [HW,SCSI]
1236 ncr53c400a= [HW,SCSI]
1238 ncr53c406a= [HW,SCSI]
1240 ncr53c8xx= [HW,SCSI]
1242 netdev= [NET] Network devices parameters
1243 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1244 Note that mem_start is often overloaded to mean
1245 something different and driver-specific.
1246 This usage is only documented in each driver source
1250 See Documentation/filesystems/nfsroot.txt.
1252 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1253 See Documentation/filesystems/nfsroot.txt.
1255 nfs.callback_tcpport=
1256 [NFS] set the TCP port on which the NFSv4 callback
1257 channel should listen.
1259 nfs.idmap_cache_timeout=
1260 [NFS] set the maximum lifetime for idmapper cache
1264 [NFS] enable 64-bit inode numbers.
1265 If zero, the NFS client will fake up a 32-bit inode
1266 number for the readdir() and stat() syscalls instead
1267 of returning the full 64-bit number.
1268 The default is to return 64-bit inode numbers.
1270 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1271 when a NMI is triggered.
1272 Format: [state][,regs][,debounce][,die]
1274 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1276 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1277 emulation library even if a 387 maths coprocessor
1280 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1281 caches in the slab allocator. Saves per-node memory,
1282 but will impact performance.
1286 noapic [SMP,APIC] Tells the kernel to not make use of any
1287 IOAPICs that may be present in the system.
1289 nobats [PPC] Do not use BATs for mapping kernel lowmem
1290 on "Classic" PPC cores.
1294 nodelayacct [KNL] Disable per-task delay accounting
1296 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1298 noefi [X86-32,X86-64] Disable EFI runtime services support.
1302 noexec [X86-32,X86-64]
1303 On X86-32 available only on PAE configured kernels.
1304 noexec=on: enable non-executable mappings (default)
1305 noexec=off: disable non-executable mappings
1308 This affects only 32-bit executables.
1309 noexec32=on: enable non-executable mappings (default)
1310 read doesn't imply executable mappings
1311 noexec32=off: disable non-executable mappings
1312 read implies executable mappings
1314 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1315 register save and restore. The kernel will only save
1316 legacy floating-point registers on task switch.
1318 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1322 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1323 instruction doesn't work correctly and not to
1326 nohalt [IA-64] Tells the kernel not to use the power saving
1327 function PAL_HALT_LIGHT when idle. This increases
1328 power-consumption. On the positive side, it reduces
1329 interrupt wake-up latency, which may improve performance
1330 in certain environments such as networked servers or
1333 nohz= [KNL] Boottime enable/disable dynamic ticks
1334 Valid arguments: on, off
1337 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1339 noirqdebug [X86-32] Disables the code which attempts to detect and
1340 disable unhandled interrupt sources.
1342 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1343 broken timer IRQ sources.
1345 noisapnp [ISAPNP] Disables ISA PnP code.
1347 noinitrd [RAM] Tells the kernel not to load any configured
1352 nojitter [IA64] Disables jitter checking for ITC timers.
1354 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1356 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1358 noltlbs [PPC] Do not use large page/tlb entries for kernel
1359 lowmem mapping on PPC40x.
1361 nomca [IA-64] Disable machine check abort handling
1363 nomce [X86-32] Machine Check Exception
1365 nomfgpt [X86-32] Disable Multi-Function General Purpose
1366 Timer usage (for AMD Geode machines).
1368 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1370 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1371 with UP alternatives
1373 noresidual [PPC] Don't use residual data on PReP machines.
1375 noresume [SWSUSP] Disables resume and restores original swap
1378 no-scroll [VGA] Disables scrollback.
1379 This is required for the Braillex ib80-piezo Braille
1380 reader made by F.H. Papenmeier (Germany).
1384 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1386 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1387 and disable the IO APIC. legacy for "maxcpus=0".
1389 nosoftlockup [KNL] Disable the soft-lockup detector.
1391 nosync [HW,M68K] Disables sync negotiation for all devices.
1393 notsc [BUGS=X86-32] Disable Time Stamp Counter
1395 nousb [USB] Disable the USB subsystem
1399 nptcg= [IA64] Override max number of concurrent global TLB
1400 purges which is reported from either PAL_VM_SUMMARY or
1403 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1404 one of ['zone', 'node', 'default'] can be specified
1405 This can be set from sysctl after boot.
1406 See Documentation/sysctl/vm.txt for details.
1408 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1410 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1411 Rather than timing out after 20 ms if an EC
1412 command is not properly ACKed, override the length
1413 of the timeout. We have interrupts disabled while
1414 waiting for the ACK, so if this is set too high
1415 interrupts *may* be lost!
1420 oprofile.timer= [HW]
1421 Use timer interrupt instead of performance counters
1423 osst= [HW,SCSI] SCSI Tape Driver
1424 Format: <buffer_size>,<write_threshold>
1425 See also Documentation/scsi/st.txt.
1427 panic= [KNL] Kernel behaviour on panic
1430 parkbd.port= [HW] Parallel port number the keyboard adapter is
1431 connected to, default is 0.
1433 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1434 0 for XT, 1 for AT (default is AT).
1437 parport= [HW,PPT] Specify parallel ports. 0 disables.
1438 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1439 Use 'auto' to force the driver to use any
1440 IRQ/DMA settings detected (the default is to
1441 ignore detected IRQ/DMA settings because of
1442 possible conflicts). You can specify the base
1443 address, IRQ, and DMA settings; IRQ and DMA
1444 should be numbers, or 'auto' (for using detected
1445 settings on that particular port), or 'nofifo'
1446 (to avoid using a FIFO even if it is detected).
1447 Parallel ports are assigned in the order they
1448 are specified on the command line, starting
1451 parport_init_mode= [HW,PPT]
1452 Configure VIA parallel port to operate in
1453 a specific mode. This is necessary on Pegasos
1454 computer where firmware has no options for setting
1455 up parallel port mode and sets it to spp.
1456 Currently this function knows 686a and 8231 chips.
1457 Format: [spp|ps2|epp|ecp|ecpepp]
1459 pas2= [HW,OSS] Format:
1460 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1463 See header of drivers/scsi/pas16.c.
1466 Halt all CPUs after the first oops has been printed for
1467 the specified number of seconds. This is to be used if
1468 your oopses keep scrolling off the screen.
1473 See header of drivers/block/paride/pcd.c.
1474 See also Documentation/paride.txt.
1476 pci=option[,option...] [PCI] various PCI subsystem options:
1477 off [X86-32] don't probe for the PCI bus
1478 bios [X86-32] force use of PCI BIOS, don't access
1479 the hardware directly. Use this if your machine
1480 has a non-standard PCI host bridge.
1481 nobios [X86-32] disallow use of PCI BIOS, only direct
1482 hardware access methods are allowed. Use this
1483 if you experience crashes upon bootup and you
1484 suspect they are caused by the BIOS.
1485 conf1 [X86-32] Force use of PCI Configuration
1487 conf2 [X86-32] Force use of PCI Configuration
1489 noaer [PCIE] If the PCIEAER kernel config parameter is
1490 enabled, this kernel boot option can be used to
1491 disable the use of PCIE advanced error reporting.
1492 nodomains [PCI] Disable support for multiple PCI
1493 root domains (aka PCI segments, in ACPI-speak).
1494 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1496 nomsi [MSI] If the PCI_MSI kernel config parameter is
1497 enabled, this kernel boot option can be used to
1498 disable the use of MSI interrupts system-wide.
1499 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1500 routing table. These calls are known to be buggy
1501 on several machines and they hang the machine
1502 when used, but on other computers it's the only
1503 way to get the interrupt routing table. Try
1504 this option if the kernel is unable to allocate
1505 IRQs or discover secondary PCI buses on your
1507 rom [X86-32] Assign address space to expansion ROMs.
1508 Use with caution as certain devices share
1509 address decoders between ROMs and other
1511 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1512 assigned automatically to PCI devices. You can
1513 make the kernel exclude IRQs of your ISA cards
1515 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1516 of the PIRQ table (normally generated
1517 by the BIOS) if it is outside the
1518 F0000h-100000h range.
1519 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1520 useful if the kernel is unable to find your
1521 secondary buses and you want to tell it
1522 explicitly which ones they are.
1523 assign-busses [X86-32] Always assign all PCI bus
1524 numbers ourselves, overriding
1525 whatever the firmware may have done.
1526 usepirqmask [X86-32] Honor the possible IRQ mask stored
1527 in the BIOS $PIR table. This is needed on
1528 some systems with broken BIOSes, notably
1529 some HP Pavilion N5400 and Omnibook XE3
1530 notebooks. This will have no effect if ACPI
1531 IRQ routing is enabled.
1532 noacpi [X86-32] Do not use ACPI for IRQ routing
1533 or for PCI scanning.
1534 use_crs [X86-32] Use _CRS for PCI resource
1536 routeirq Do IRQ routing for all PCI devices.
1537 This is normally done in pci_enable_device(),
1538 so this option is a temporary workaround
1539 for broken drivers that don't call it.
1540 skip_isa_align [X86] do not align io start addr, so can
1541 handle more pci cards
1542 firmware [ARM] Do not re-enumerate the bus but instead
1543 just use the configuration from the
1544 bootloader. This is currently used on
1545 IXP2000 systems where the bus has to be
1546 configured a certain way for adjunct CPUs.
1547 noearly [X86] Don't do any early type 1 scanning.
1548 This might help on some broken boards which
1549 machine check when some devices' config space
1550 is read. But various workarounds are disabled
1551 and some IOMMU drivers will not work.
1552 bfsort Sort PCI devices into breadth-first order.
1553 This sorting is done to get a device
1554 order compatible with older (<= 2.4) kernels.
1555 nobfsort Don't sort PCI devices into breadth-first order.
1556 cbiosize=nn[KMG] The fixed amount of bus space which is
1557 reserved for the CardBus bridge's IO window.
1558 The default value is 256 bytes.
1559 cbmemsize=nn[KMG] The fixed amount of bus space which is
1560 reserved for the CardBus bridge's memory
1561 window. The default value is 64 megabytes.
1563 pcmv= [HW,PCMCIA] BadgePAD 4
1566 See Documentation/paride.txt.
1568 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1571 See arch/parisc/kernel/pdc_chassis.c
1574 See Documentation/paride.txt.
1577 See Documentation/paride.txt.
1579 pirq= [SMP,APIC] Manual mp-table setup
1580 See Documentation/i386/IO-APIC.txt.
1582 plip= [PPT,NET] Parallel port network link
1583 Format: { parport<nr> | timid | 0 }
1584 See also Documentation/parport.txt.
1590 { on | off | curr | res | no-curr | no-res }
1593 [ISAPNP] Exclude IRQs for the autoconfiguration
1596 [ISAPNP] Exclude DMAs for the autoconfiguration
1598 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1599 Ranges are in pairs (I/O port base and size).
1602 [ISAPNP] Exclude memory regions for the
1604 Ranges are in pairs (memory base and size).
1606 print-fatal-signals=
1607 [KNL] debug: print fatal signals
1608 print-fatal-signals=1: print segfault info to
1612 printk.time= Show timing data prefixed to each printk message line
1613 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1615 profile= [KNL] Enable kernel profiling via /proc/profile
1616 Format: [schedule,]<number>
1617 Param: "schedule" - profile schedule points.
1618 Param: <number> - step/bucket size as a power of 2 for
1619 statistical time based profiling.
1620 Param: "sleep" - profile D-state sleeping (millisecs).
1621 Requires CONFIG_SCHEDSTATS
1622 Param: "kvm" - profile VM exits.
1624 processor.max_cstate= [HW,ACPI]
1625 Limit processor to maximum C-state
1626 max_cstate=9 overrides any DMI blacklist limit.
1628 processor.nocst [HW,ACPI]
1629 Ignore the _CST method to determine C-states,
1630 instead using the legacy FADT method
1632 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1634 See Documentation/ramdisk.txt.
1636 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1637 probe for; one of (bare|imps|exps|lifebook|any).
1638 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1640 psmouse.resetafter= [HW,MOUSE]
1641 Try to reset the device after so many bad packets
1644 [HW,MOUSE] Set desired mouse resolution, in dpi.
1645 psmouse.smartscroll=
1646 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1647 0 = disabled, 1 = enabled (default).
1649 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1651 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1654 See Documentation/paride.txt.
1657 [KNL] Number of legacy pty's. Overwrites compiled-in
1660 quiet [KNL] Disable most log messages
1665 See Documentation/md.txt.
1667 ramdisk_blocksize= [RAM]
1668 See Documentation/ramdisk.txt.
1670 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1671 See Documentation/ramdisk.txt.
1673 rcupdate.blimit= [KNL,BOOT]
1674 Set maximum number of finished RCU callbacks to process
1677 rcupdate.qhimark= [KNL,BOOT]
1678 Set threshold of queued
1679 RCU callbacks over which batch limiting is disabled.
1681 rcupdate.qlowmark= [KNL,BOOT]
1682 Set threshold of queued RCU callbacks below which
1683 batch limiting is re-enabled.
1687 Run specified binary instead of /init from the ramdisk,
1688 used for early userspace startup. See initrd.
1690 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1691 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1692 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1694 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1696 reservetop= [X86-32]
1698 Reserves a hole at the top of the kernel virtual
1701 reset_devices [KNL] Force drivers to reset the underlying device
1702 during initialization.
1705 Specify the partition device for software suspend
1707 resume_offset= [SWSUSP]
1708 Specify the offset from the beginning of the partition
1709 given by "resume=" at which the swap header is located,
1710 in <PAGE_SIZE> units (needed only for swap files).
1711 See Documentation/power/swsusp-and-swap-files.txt
1713 retain_initrd [RAM] Keep initrd memory after extraction
1715 rhash_entries= [KNL,NET]
1716 Set number of hash buckets for route cache
1718 riscom8= [HW,SERIAL]
1719 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1721 ro [KNL] Mount root device read-only on boot
1723 root= [KNL] Root filesystem
1725 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1726 mount the root filesystem
1728 rootflags= [KNL] Set root filesystem mount option string
1730 rootfstype= [KNL] Set root filesystem type
1732 rootwait [KNL] Wait (indefinitely) for root device to show up.
1733 Useful for devices that are detected asynchronously
1734 (e.g. USB and MMC devices).
1736 root_plug.vendor_id=
1737 [ROOTPLUG] Override the default vendor ID
1739 root_plug.product_id=
1740 [ROOTPLUG] Override the default product ID
1743 [ROOTPLUG] Enable debugging output
1745 rw [KNL] Mount root device read-write on boot
1747 S [KNL] Run init in single mode
1750 See drivers/net/irda/sa1100_ir.c.
1752 sbni= [NET] Granch SBNI12 leased line adapter
1754 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1755 Format: <io>[,<timeout>[,<isapnp>]]
1757 scsi_debug_*= [SCSI]
1758 See drivers/scsi/scsi_debug.c.
1760 scsi_default_dev_flags=
1761 [SCSI] SCSI default device flags
1764 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1765 Format: <vendor>:<model>:<flags>
1766 (flags are integer value)
1768 scsi_logging_level= [SCSI] a bit mask of logging levels
1769 See drivers/scsi/scsi_logging.h for bits. Also
1770 settable via sysctl at dev.scsi.logging_level
1771 (/proc/sys/dev/scsi/logging_level).
1772 There is also a nice 'scsi_logging_level' script in the
1773 S390-tools package, available for download at
1774 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1776 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1777 discovered. async scans them in kernel threads,
1778 allowing boot to proceed. none ignores them, expecting
1779 user space to do the scan.
1781 selinux [SELINUX] Disable or enable SELinux at boot time.
1782 Format: { "0" | "1" }
1783 See security/selinux/Kconfig help text.
1786 Default value is set via kernel config option.
1787 If enabled at boot time, /selinux/disable can be used
1788 later to disable prior to initial policy load.
1790 selinux_compat_net =
1791 [SELINUX] Set initial selinux_compat_net flag value.
1792 Format: { "0" | "1" }
1793 0 -- use new secmark-based packet controls
1794 1 -- use legacy packet controls
1795 Default value is 0 (preferred).
1796 Value can be changed at runtime via
1797 /selinux/compat_net.
1799 serialnumber [BUGS=X86-32]
1802 Maximal number of shapers.
1805 See header of drivers/scsi/sim710.c.
1812 slub_debug[=options[,slabs]] [MM, SLUB]
1813 Enabling slub_debug allows one to determine the
1814 culprit if slab objects become corrupted. Enabling
1815 slub_debug can create guard zones around objects and
1816 may poison objects when not in use. Also tracks the
1817 last alloc / free. For more information see
1818 Documentation/vm/slub.txt.
1820 slub_max_order= [MM, SLUB]
1821 Determines the maximum allowed order for slabs.
1822 A high setting may cause OOMs due to memory
1823 fragmentation. For more information see
1824 Documentation/vm/slub.txt.
1826 slub_min_objects= [MM, SLUB]
1827 The minimum number of objects per slab. SLUB will
1828 increase the slab order up to slub_max_order to
1829 generate a sufficiently large slab able to contain
1830 the number of objects indicated. The higher the number
1831 of objects the smaller the overhead of tracking slabs
1832 and the less frequently locks need to be acquired.
1833 For more information see Documentation/vm/slub.txt.
1835 slub_min_order= [MM, SLUB]
1836 Determines the mininum page order for slabs. Must be
1837 lower than slub_max_order.
1838 For more information see Documentation/vm/slub.txt.
1840 slub_nomerge [MM, SLUB]
1841 Disable merging of slabs with similar size. May be
1842 necessary if there is some reason to distinguish
1843 allocs to different slabs. Debug options disable
1844 merging on their own.
1845 For more information see Documentation/vm/slub.txt.
1848 Format: <io1>[,<io2>[,...,<io8>]]
1850 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1851 attempt to substitute SMP alternatives once at boot.
1853 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1854 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1855 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1856 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1857 smsc-ircc2.ircc_irq= [HW] IRQ line
1858 smsc-ircc2.ircc_dma= [HW] DMA channel
1859 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1860 0: Toshiba Satellite 1800 (GP data pin select)
1861 1: Fast pin select (default)
1864 snd-ad1816a= [HW,ALSA]
1866 snd-ad1848= [HW,ALSA]
1868 snd-ali5451= [HW,ALSA]
1870 snd-als100= [HW,ALSA]
1872 snd-als4000= [HW,ALSA]
1874 snd-azt2320= [HW,ALSA]
1876 snd-cmi8330= [HW,ALSA]
1878 snd-cmipci= [HW,ALSA]
1880 snd-cs4231= [HW,ALSA]
1882 snd-cs4232= [HW,ALSA]
1884 snd-cs4236= [HW,ALSA]
1886 snd-cs4281= [HW,ALSA]
1888 snd-cs46xx= [HW,ALSA]
1890 snd-dt019x= [HW,ALSA]
1892 snd-dummy= [HW,ALSA]
1894 snd-emu10k1= [HW,ALSA]
1896 snd-ens1370= [HW,ALSA]
1898 snd-ens1371= [HW,ALSA]
1900 snd-es968= [HW,ALSA]
1902 snd-es1688= [HW,ALSA]
1904 snd-es18xx= [HW,ALSA]
1906 snd-es1938= [HW,ALSA]
1908 snd-es1968= [HW,ALSA]
1910 snd-fm801= [HW,ALSA]
1912 snd-gusclassic= [HW,ALSA]
1914 snd-gusextreme= [HW,ALSA]
1916 snd-gusmax= [HW,ALSA]
1920 snd-ice1712= [HW,ALSA]
1922 snd-intel8x0= [HW,ALSA]
1924 snd-interwave= [HW,ALSA]
1929 snd-korg1212= [HW,ALSA]
1931 snd-maestro3= [HW,ALSA]
1933 snd-mpu401= [HW,ALSA]
1935 snd-mtpav= [HW,ALSA]
1937 snd-nm256= [HW,ALSA]
1939 snd-opl3sa2= [HW,ALSA]
1947 snd-opti93x= [HW,ALSA]
1951 snd-rme32= [HW,ALSA]
1953 snd-rme96= [HW,ALSA]
1955 snd-rme9652= [HW,ALSA]
1961 snd-sbawe= [HW,ALSA]
1963 snd-serial= [HW,ALSA]
1965 snd-sgalaxy= [HW,ALSA]
1967 snd-sonicvibes= [HW,ALSA]
1972 snd-sun-cs4231= [HW,ALSA]
1974 snd-trident= [HW,ALSA]
1976 snd-usb-audio= [HW,ALSA,USB]
1978 snd-via82xx= [HW,ALSA]
1980 snd-virmidi= [HW,ALSA]
1982 snd-wavefront= [HW,ALSA]
1984 snd-ymfpci= [HW,ALSA]
1986 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1987 See Documentation/sonypi.txt
1989 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1990 See Documentation/specialix.txt.
1992 spia_io_base= [HW,MTD]
1998 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2000 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2001 See Documentation/scsi/st.txt.
2005 Set the STI (builtin display/keyboard on the HP-PARISC
2006 machines) console (graphic card) which should be used
2007 as the initial boot-console.
2008 See also comment in drivers/video/console/sticore.c.
2011 See comment in drivers/video/console/sticore.c.
2014 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2018 Control how the NFS server code allocates CPUs to
2019 service thread pools. Depending on how many NICs
2020 you have and where their interrupts are bound, this
2021 option will affect which CPUs will do NFS serving.
2022 Note: this parameter cannot be changed while the
2023 NFS server is running.
2025 auto the server chooses an appropriate mode
2026 automatically using heuristics
2027 global a single global pool contains all CPUs
2028 percpu one pool for each CPU
2029 pernode one pool for each NUMA node (equivalent
2030 to global on non-NUMA machines)
2032 swiotlb= [IA-64] Number of I/O TLB slabs
2036 sym53c416= [HW,SCSI]
2037 See header of drivers/scsi/sym53c416.c.
2039 sysrq_always_enabled
2041 Ignore sysrq setting - this boot parameter will
2042 neutralize any effect of /proc/sys/kernel/sysrq.
2043 Useful for debugging.
2046 See header of drivers/scsi/t128.c.
2050 thash_entries= [KNL,NET]
2051 Set number of hash buckets for TCP connection
2053 thermal.act= [HW,ACPI]
2054 -1: disable all active trip points in all thermal zones
2055 <degrees C>: override all lowest active trip points
2057 thermal.crt= [HW,ACPI]
2058 -1: disable all critical trip points in all thermal zones
2059 <degrees C>: lower all critical trip points
2061 thermal.nocrt= [HW,ACPI]
2062 Set to disable actions on ACPI thermal zone
2063 critical and hot trip points.
2065 thermal.off= [HW,ACPI]
2066 1: disable ACPI thermal control
2068 thermal.psv= [HW,ACPI]
2069 -1: disable all passive trip points
2070 <degrees C>: override all passive trip points to this value
2072 thermal.tzp= [HW,ACPI]
2073 Specify global default ACPI thermal zone polling rate
2074 <deci-seconds>: poll all this frequency
2075 0: no polling (default)
2077 tipar.timeout= [HW,PPT]
2078 Set communications timeout in tenths of a second
2081 tipar.delay= [HW,PPT]
2082 Set inter-bit delay in microseconds (default 10).
2085 See comment before function dc390_setup() in
2086 drivers/scsi/tmscsim.c.
2090 trix= [HW,OSS] MediaTrix AudioTrix Pro
2092 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2094 turbografx.map[2|3]= [HW,JOY]
2095 TurboGraFX parallel port interface
2097 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2098 See also Documentation/input/joystick-parport.txt
2100 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2101 See header of drivers/scsi/u14-34f.c.
2110 [USB] Ignore overcurrent events (default N).
2111 Some badly-designed motherboards generate lots of
2112 bogus events, for ports that aren't wired to
2113 anything. Set this parameter to avoid log spamming.
2114 Note that genuine overcurrent events won't be
2117 usbcore.autosuspend=
2118 [USB] The autosuspend time delay (in seconds) used
2119 for newly-detected USB devices (default 2). This
2120 is the time required before an idle device will be
2121 autosuspended. Devices for which the delay is set
2122 to a negative value won't be autosuspended at all.
2125 [USBHID] The interval which mice are to be polled at.
2127 vdso= [X86-32,SH,x86-64]
2128 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2129 vdso=1: enable VDSO (default)
2130 vdso=0: disable VDSO mapping
2132 vdso32= [X86-32,X86-64]
2133 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2134 vdso32=1: enable 32-bit VDSO (default)
2135 vdso32=0: disable 32-bit VDSO mapping
2138 vector=percpu: enable percpu vector domain
2140 video= [FB] Frame buffer configuration
2141 See Documentation/fb/modedb.txt.
2143 vga= [BOOT,X86-32] Select a particular video mode
2144 See Documentation/i386/boot.txt and
2145 Documentation/svga.txt.
2146 Use vga=ask for menu.
2147 This is actually a boot loader parameter; the value is
2148 passed to the kernel using a special protocol.
2150 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2151 size of <nn>. This can be used to increase the
2152 minimum size (128MB on x86). It can also be used to
2153 decrease the size and leave more room for directly
2156 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2159 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2162 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2165 waveartist= [HW,OSS]
2166 Format: <io>,<irq>,<dma>,<dma2>
2169 See header of drivers/scsi/wd33c93.c.
2172 See header of drivers/scsi/wd7000.c.
2175 See Documentation/watchdog/wdt.txt.
2177 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2178 xd_geo= See header of drivers/block/xd.c.
2180 xirc2ps_cs= [NET,PCMCIA]
2182 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2184 norandmaps Don't use address space randomization
2185 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2187 ______________________________________________________________________
2191 Add documentation for ALSA options.
2192 Add more DRM drivers.