4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend is enabled.
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
99 X86-32 X86-32, aka i386 architecture is enabled.
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
104 In addition, the following text indicates that the option:
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode, 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_new_pts_ordering [HW,ACPI]
174 Enforce the ACPI 2.0 ordering of the _PTS control
175 method wrt putting devices into low power states
176 default: pre ACPI 2.0 ordering of _PTS
178 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
180 acpi_no_initrd_override [KNL,ACPI]
181 Disable loading custom ACPI tables from the initramfs
183 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
184 Format: To spoof as Windows 98: ="Microsoft Windows"
186 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
187 acpi_osi="string1" # add string1 -- only one string
188 acpi_osi="!string2" # remove built-in string2
189 acpi_osi= # disable all strings
191 acpi_serialize [HW,ACPI] force serialization of AML methods
193 acpi_skip_timer_override [HW,ACPI]
194 Recognize and ignore IRQ0/pin2 Interrupt Override.
195 For broken nForce2 BIOS resulting in XT-PIC timer.
196 acpi_use_timer_override [HW,ACPI}
197 Use timer override. For some broken Nvidia NF5 boards
198 that require a timer override, but don't have
201 acpi.debug_layer= [HW,ACPI]
203 Each bit of the <int> indicates an ACPI debug layer,
204 1: enable, 0: disable. It is useful for boot time
205 debugging. After system has booted up, it can be set
206 via /sys/module/acpi/parameters/debug_layer.
207 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
208 Available bits (add the numbers together) to enable debug output
209 for specific parts of the ACPI subsystem:
210 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
211 0x10 namespace 0x20 parser 0x40 dispatcher
212 0x80 executer 0x100 resources 0x200 acpica debugger
213 0x400 os services 0x800 acpica disassembler.
214 The number can be in decimal or prefixed with 0x in hex.
215 Warning: Many of these options can produce a lot of
216 output and make your system unusable. Be very careful.
218 acpi.debug_level= [HW,ACPI]
220 Each bit of the <int> indicates an ACPI debug level,
221 1: enable, 0: disable. It is useful for boot time
222 debugging. After system has booted up, it can be set
223 via /sys/module/acpi/parameters/debug_level.
224 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
225 Available bits (add the numbers together) to enable different
226 debug output levels of the ACPI subsystem:
227 0x01 error 0x02 warn 0x04 init 0x08 debug object
228 0x10 info 0x20 init names 0x40 parse 0x80 load
229 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
230 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
231 0x10000 resources 0x20000 user requests 0x40000 package.
232 The number can be in decimal or prefixed with 0x in hex.
233 Warning: Many of these options can produce a lot of
234 output and make your system unusable. Be very careful.
236 acpi_pm_good [X86-32,X86-64]
237 Override the pmtimer bug detection: force the kernel
238 to assume that this machine's pmtimer latches its value
239 and always returns good values.
242 { off | try_unsupported }
243 off: disable AGP support
244 try_unsupported: try to drive unsupported chipsets
245 (may crash computer or cause data corruption)
247 enable_timer_pin_1 [i386,x86-64]
248 Enable PIN 1 of APIC timer
249 Can be useful to work around chipset bugs
250 (in particular on some ATI chipsets).
251 The kernel tries to set a reasonable default.
253 disable_timer_pin_1 [i386,x86-64]
254 Disable PIN 1 of APIC timer
255 Can be useful to work around chipset bugs.
258 Format: <io>,<irq>,<dma>,<dma2>,<type>
261 See header of drivers/scsi/advansys.c.
263 advwdt= [HW,WDT] Advantech WDT
264 Format: <iostart>,<iostop>
266 aedsp16= [HW,OSS] Audio Excel DSP 16
267 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
268 See also header of sound/oss/aedsp16.c.
271 See Documentation/scsi/aha152x.txt.
274 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
277 See Documentation/scsi/aic7xxx.txt.
280 See Documentation/scsi/aic79xx.txt.
282 amijoy.map= [HW,JOY] Amiga joystick support
283 Map of devices attached to JOY0DAT and JOY1DAT
285 See also Documentation/kernel/input/joystick.txt
287 analog.map= [HW,JOY] Analog joystick and gamepad support
288 Specifies type or capabilities of an analog joystick
289 connected to one of 16 gameports
290 Format: <type1>,<type2>,..<type16>
293 Power management functions (SPARCstation-4/5 + deriv.)
295 Disable APC CPU standby support. SPARCstation-Fox does
296 not play well with APC CPU idle - disable it if you have
297 APC and your system crashes randomly.
299 apic= [APIC,i386] Advanced Programmable Interrupt Controller
300 Change the output verbosity whilst booting
301 Format: { quiet (default) | verbose | debug }
302 Change the amount of debugging information output
303 when initialising the APIC and IO-APIC components.
305 apm= [APM] Advanced Power Management
306 See header of arch/i386/kernel/apm.c.
308 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
309 Format: <io>,<irq>,<nodeID>
313 atarimouse= [HW,MOUSE] Atari Mouse
315 atascsi= [HW,SCSI] Atari SCSI
317 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
318 EzKey and similar keyboards
320 atkbd.reset= [HW] Reset keyboard during initialization
322 atkbd.set= [HW] Select keyboard code set
323 Format: <int> (2 = AT (default), 3 = PS/2)
325 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
328 atkbd.softraw= [HW] Choose between synthetic and real raw mode
329 Format: <bool> (0 = real, 1 = synthetic (default))
331 atkbd.softrepeat= [HW]
332 Use software keyboard repeat
336 baycom_epp= [HW,AX25]
339 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
341 See header of drivers/net/hamradio/baycom_par.c.
343 baycom_ser_fdx= [HW,AX25]
344 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
345 Format: <io>,<irq>,<mode>[,<baud>]
346 See header of drivers/net/hamradio/baycom_ser_fdx.c.
348 baycom_ser_hdx= [HW,AX25]
349 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
350 Format: <io>,<irq>,<mode>
351 See header of drivers/net/hamradio/baycom_ser_hdx.c.
353 boot_delay= Milliseconds to delay each printk during boot.
354 Values larger than 10 seconds (10000) are changed to
358 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
359 bttv.radio= Most important insmod options are available as
361 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
362 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
365 See drivers/scsi/BusLogic.c, comment before function
366 BusLogic_ParseDriverOptions().
368 c101= [NET] Moxa C101 synchronous serial card
370 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
371 Sometimes CPU hardware bugs make them report the cache
372 size incorrectly. The kernel will attempt work arounds
373 to fix known problems, but for some CPUs it is not
374 possible to determine what the correct size should be.
375 This option provides an override for these situations.
378 [SECURITY] Disable capabilities. This would normally
379 be used only if an alternative security model is to be
380 configured. Potentially dangerous and should only be
381 used if you are entirely sure of the consequences.
383 ccw_timeout_log [S390]
384 See Documentation/s390/CommonIO for details.
386 checkreqprot [SELINUX] Set initial checkreqprot flag value.
387 Format: { "0" | "1" }
388 See security/selinux/Kconfig help text.
389 0 -- check protection applied by kernel (includes
390 any implied execute protection).
391 1 -- check protection requested by application.
392 Default value is set via a kernel config option.
393 Value can be changed at runtime via
394 /selinux/checkreqprot.
397 See Documentation/s390/CommonIO for details.
400 See Documentation/s390/CommonIO for details.
402 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
404 Forces specified clocksource (if available) to be used
405 when calculating gettimeofday(). If specified
406 clocksource is not available, it defaults to PIT.
407 Format: { pit | tsc | cyclone | pmtmr }
409 clocksource= [GENERIC_TIME] Override the default clocksource
411 Override the default clocksource and use the clocksource
412 with the name specified.
413 Some clocksource names to choose from, depending on
415 [all] jiffies (this is the base, fallback clocksource)
417 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
418 pxa_timer,timer3,32k_counter,timer0_1
420 [X86-32] pit,hpet,tsc,vmi-timer;
421 scx200_hrt on Geode; cyclone on IBM x440
429 clearcpuid=BITNUM [X86]
430 Disable CPUID feature X for the kernel. See
431 include/asm-x86/cpufeature.h for the valid bit numbers.
432 Note the Linux specific bits are not necessarily
433 stable over kernel options, but the vendor specific
435 Also note that user programs calling CPUID directly
436 or using the feature without checking anything
437 will still see it. This just prevents it from
438 being used by the kernel or shown in /proc/cpuinfo.
439 Also note the kernel might malfunction if you disable
442 code_bytes [IA32/X86_64] How many bytes of object code to print
449 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
450 over the 8254 in addition to over the IO-APIC. The
451 kernel tries to set a sensible default.
453 hpet= [X86-32,HPET] option to control HPET usage
454 Format: { enable (default) | disable | force }
455 disable: disable HPET and use PIT instead
456 force: allow force enabled of undocumented chips (ICH4,
459 com20020= [HW,NET] ARCnet - COM20020 chipset
461 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
463 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
467 ARCnet - COM90xx chipset (memory-mapped buffers)
468 Format: <io>[,<irq>[,<memstart>]]
470 condev= [HW,S390] console device
473 console= [KNL] Output console device and options.
475 tty<n> Use the virtual console device <n>.
479 Use the specified serial port. The options are of
480 the form "bbbbpnf", where "bbbb" is the baud rate,
481 "p" is parity ("n", "o", or "e"), "n" is number of
482 bits, and "f" is flow control ("r" for RTS or
483 omit it). Default is "9600n8".
485 See Documentation/serial-console.txt for more
487 Documentation/networking/netconsole.txt for an
490 uart[8250],io,<addr>[,options]
491 uart[8250],mmio,<addr>[,options]
492 Start an early, polled-mode console on the 8250/16550
493 UART at the specified I/O port or MMIO address,
494 switching to the matching ttyS device later. The
495 options are the same as for ttyS, above.
497 earlycon= [KNL] Output early console device and options.
498 uart[8250],io,<addr>[,options]
499 uart[8250],mmio,<addr>[,options]
500 Start an early, polled-mode console on the 8250/16550
501 UART at the specified I/O port or MMIO address.
502 The options are the same as for ttyS, above.
505 [HW] Never suspend the console
506 Disable suspending of consoles during suspend and
507 hibernate operations. Once disabled, debugging
508 messages can reach various consoles while the rest
509 of the system is being put to sleep (ie, while
510 debugging driver suspend/resume hooks). This may
511 not work reliably with all consoles, but is known
512 to work with serial and VGA consoles.
514 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
516 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
518 crashkernel=nn[KMG]@ss[KMG]
519 [KNL] Reserve a chunk of physical memory to
520 hold a kernel to switch to with kexec on panic.
522 crashkernel=range1:size1[,range2:size2,...][@offset]
523 [KNL] Same as above, but depends on the memory
524 in the running system. The syntax of range is
525 start-[end] where start and end are both
526 a memory unit (amount[KMG]). See also
527 Documentation/kdump/kdump.txt for a example.
530 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
535 cs89x0_media= [HW,NET]
536 Format: { rj45 | aui | bnc }
539 See header of drivers/s390/block/dasd_devmap.c.
541 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
542 (one device per port)
543 Format: <port#>,<type>
544 See also Documentation/input/joystick-parport.txt
546 debug [KNL] Enable kernel debugging (events log level).
549 [KNL] verbose self-tests
551 Print debugging info while doing the locking API
553 We default to 0 (no extra messages), setting it to
554 1 will print _a lot_ more information - normally
555 only useful to kernel developers.
557 decnet.addr= [HW,NET]
558 Format: <area>[,<node>]
559 See also Documentation/networking/decnet.txt.
562 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
563 Change the default blue palette of the console.
564 This is a 16-member array composed of values
568 Format: <green0>,<green1>,<green2>,...,<green15>
569 Change the default green palette of the console.
570 This is a 16-member array composed of values
574 Format: <red0>,<red1>,<red2>,...,<red15>
575 Change the default red palette of the console.
576 This is a 16-member array composed of values
582 Set system-wide default UTF-8 mode for all tty's.
583 Default is 1, i.e. UTF-8 mode is enabled for all
584 newly opened terminals.
587 Set number of hash buckets for dentry cache.
590 IO parameters + enable/disable command.
592 digiepca= [HW,SERIAL]
593 See drivers/char/README.epca and
594 Documentation/digiepca.txt.
596 disable_mtrr_trim [X86, Intel and AMD only]
597 By default the kernel will trim any uncacheable
598 memory out of your available memory pool based on
599 MTRR settings. This parameter disables that behavior,
600 possibly causing your machine to run very slowly.
602 dmasound= [HW,OSS] Sound subsystem buffers
608 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
610 earlyprintk=serial[,ttySn[,baudrate]]
612 Append ",keep" to not disable it when the real console
615 Only vga or serial at a time, not both.
617 Currently only ttyS0 and ttyS1 are supported.
619 Interaction with the standard serial driver is not
622 The VGA output is eventually overwritten by the real
628 Format: {"of[f]" | "sk[ipmbr]"}
629 See comment in arch/i386/boot/edd.S
631 eisa_irq_edge= [PARISC,HW]
632 See header of drivers/parisc/eisa.c.
635 See comment before function elanfreq_setup() in
636 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
639 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
640 See Documentation/block/as-iosched.txt and
641 Documentation/block/deadline-iosched.txt for details.
643 elfcorehdr= [X86-32, X86_64]
644 Specifies physical address of start of kernel core
645 image elf header. Generally kexec loader will
646 pass this option to capture kernel.
647 See Documentation/kdump/kdump.txt for details.
649 enforcing [SELINUX] Set initial enforcing status.
651 See security/selinux/Kconfig help text.
652 0 -- permissive (log only, no denials).
653 1 -- enforcing (deny and log).
655 Value can be changed at runtime via /selinux/enforce.
658 Format: <spdif>,[<nomix>,[<amplifier>]]
659 See also header of sound/oss/es1371.c.
661 ether= [HW,NET] Ethernet cards parameters
662 This option is obsoleted by the "netdev=" option, which
663 has equivalent usage. See its documentation for details.
665 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
670 fail_make_request=[KNL]
671 General fault injection mechanism.
672 Format: <interval>,<probability>,<space>,<times>
673 See also /Documentation/fault-injection/.
676 See header of drivers/scsi/fd_mcs.c.
679 See header of drivers/scsi/fdomain.c.
682 See Documentation/floppy.txt.
685 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
686 support via parallel port (up to 5 devices per port)
687 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
688 See also Documentation/input/joystick-parport.txt
692 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
697 See header of drivers/scsi/gdth.c.
699 gpt [EFI] Forces disk with valid GPT signature but
700 invalid Protective MBR to be treated as GPT.
704 hashdist= [KNL,NUMA] Large hashes allocated during boot
705 are distributed across NUMA nodes. Defaults on
706 for IA-64, off otherwise.
707 Format: 0 | 1 (for off | on)
709 hcl= [IA-64] SGI's Hardware Graph compatibility layer
711 hd= [EIDE] (E)IDE hard drive subsystem geometry
712 Format: <cyl>,<head>,<sect>
714 hd?= [HW] (E)IDE subsystem
715 hd?lun= See Documentation/ide/ide.txt.
717 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
718 size of <nn>. This works even on boxes that have no
719 highmem otherwise. This also works to reduce highmem
720 size on bigger boxes.
722 highres= [KNL] Enable/disable high resolution timer mode.
723 Valid parameters: "on", "off"
727 See Documentation/isdn/README.HiSax.
729 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
730 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
732 i8042.direct [HW] Put keyboard port into non-translated mode
733 i8042.dumbkbd [HW] Pretend that controller can only read data from
734 keyboard and cannot control its state
735 (Don't attempt to blink the leds)
736 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
737 i8042.nokbd [HW] Don't check/create keyboard port
738 i8042.noloop [HW] Disable the AUX Loopback command while probing
740 i8042.nomux [HW] Don't check presence of an active multiplexing
742 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
745 [HW] Frequency with which keyboard LEDs should blink
746 when kernel panics (default is 0.5 sec)
747 i8042.reset [HW] Reset the controller during init and cleanup
748 i8042.unlock [HW] Unlock (ignore) the keylock
752 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
753 indicates that the driver is running on unsupported
755 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
756 does not match list of supported models.
758 [HW] Report power status in /proc/i8k
759 (disabled by default)
760 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
763 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
764 See Documentation/mca.txt.
767 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
769 ide= [HW] (E)IDE subsystem
770 Format: ide=nodma or ide=doubler or ide=reverse
771 See Documentation/ide/ide.txt.
773 ide?= [HW] (E)IDE subsystem
774 Format: ide?=noprobe or chipset specific parameters.
775 See Documentation/ide/ide.txt.
777 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
778 See Documentation/ide/ide.txt.
781 Format: idle=poll or idle=mwait
782 Poll forces a polling idle loop that can slightly improves the performance
783 of waking up a idle CPU, but will use a lot of power and make the system
784 run hot. Not recommended.
785 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
786 to not use it because it doesn't save as much power as a normal idle
787 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
790 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
791 Claim all unknown PCI IDE storage controllers.
793 ignore_loglevel [KNL]
794 Ignore loglevel setting - this will print /all/
795 kernel messages to the console. Useful for debugging.
798 Set number of hash buckets for inode cache.
801 See header of drivers/scsi/in2000.c.
805 Run specified binary instead of /sbin/init as init
808 initcall_debug [KNL] Trace initcalls as they are executed. Useful
809 for working out where the kernel is dying during
812 initrd= [BOOT] Specify the location of the initial ramdisk
814 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
819 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
821 Disable intel iommu driver.
822 igfx_off [Default Off]
823 By default, gfx is mapped as normal device. If a gfx
824 device has a dedicated DMAR unit, the DMAR unit is
825 bypassed by not enabling DMAR with this option. In
826 this case, gfx device will use physical address for
829 With this option iommu will not optimize to look
830 for io virtual address below 32 bit forcing dual
831 address cycle on pci bus for cards supporting greater
832 than 32 bit addressing. The default is to look
833 for translation below 32 bit and if not available
834 then look in the higher range.
836 io_delay= [X86-32,X86-64] I/O delay method
838 Standard port 0x80 based delay
840 Alternate port 0xed based delay (needed on some systems)
842 Simple two microseconds delay
846 io7= [HW] IO7 for Marvel based alpha systems
847 See comment before marvel_specify_io7 in
848 arch/alpha/kernel/core_marvel.c.
851 See Documentation/nfsroot.txt.
853 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
854 See comment before ip2_setup() in
855 drivers/char/ip2/ip2base.c.
857 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
858 See header of drivers/scsi/ips.c.
860 ports= [IP_VS_FTP] IPVS ftp helper module
862 Up to 8 (IP_VS_APP_MAX_PORTS) ports
864 Format: <port>,<port>....
867 When an interrupt is not handled search all handlers
868 for it. Intended to get systems with badly broken
872 When an interrupt is not handled search all handlers
873 for it. Also check all handlers each timer
874 interrupt. Intended to get systems with badly broken
878 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
880 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
882 <cpu number>,...,<cpu number>
884 <cpu number>-<cpu number> (must be a positive range in ascending order)
886 <cpu number>,...,<cpu number>-<cpu number>
887 This option can be used to specify one or more CPUs
888 to isolate from the general SMP balancing and scheduling
889 algorithms. The only way to move a process onto or off
890 an "isolated" CPU is via the CPU affinity syscalls.
891 <cpu number> begins at 0 and the maximum value is
892 "number of CPUs in system - 1".
894 This option is the preferred way to isolate CPUs. The
895 alternative -- manually setting the CPU mask of all
896 tasks in the system -- can cause problems and
897 suboptimal load balancer performance.
901 js= [HW,JOY] Analog joystick
902 See Documentation/input/joystick.txt.
904 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
905 specifies the amount of memory usable by the kernel
906 for non-movable allocations. The requested amount is
907 spread evenly throughout all nodes in the system. The
908 remaining memory in each node is used for Movable
909 pages. In the event, a node is too small to have both
910 kernelcore and Movable pages, kernelcore pages will
911 take priority and other nodes will have a larger number
912 of kernelcore pages. The Movable zone is used for the
913 allocation of pages that may be reclaimed or moved
914 by the page migration subsystem. This means that
915 HugeTLB pages may not be allocated from this zone.
916 Note that allocations like PTEs-from-HighMem still
917 use the HighMem zone if it exists, and the Normal
920 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
921 is similar to kernelcore except it specifies the
922 amount of memory used for migratable allocations.
923 If both kernelcore and movablecore is specified,
924 then kernelcore will be at *least* the specified
925 value but may be more. If movablecore on its own
926 is specified, the administrator must be careful
927 that the amount of memory usable for all allocations
932 kstack=N [X86-32,X86-64] Print N words from the kernel stack
937 lapic [X86-32,APIC] Enable the local APIC even if BIOS
940 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
943 libata.dma= [LIBATA] DMA control
944 libata.dma=0 Disable all PATA and SATA DMA
945 libata.dma=1 PATA and SATA Disk DMA only
946 libata.dma=2 ATAPI (CDROM) DMA only
947 libata.dma=4 Compact Flash DMA only
948 Combinations also work, so libata.dma=3 enables DMA
949 for disks and CDROMs, but not CFs.
951 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
955 libata.force= [LIBATA] Force configurations. The format is comma
956 separated list of "[ID:]VAL" where ID is
957 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
958 matching port, link or device. Basically, it matches
959 the ATA ID string printed on console by libata. If
960 the whole ID part is omitted, the last PORT and DEVICE
961 values are used. If ID hasn't been specified yet, the
962 configuration applies to all ports, links and devices.
964 If only DEVICE is omitted, the parameter applies to
965 the port and all links and devices behind it. DEVICE
966 number of 0 either selects the first device or the
967 first fan-out link behind PMP device. It does not
968 select the host link. DEVICE number of 15 selects the
969 host link and device attached to it.
971 The VAL specifies the configuration to force. As long
972 as there's no ambiguity shortcut notation is allowed.
973 For example, both 1.5 and 1.5G would work for 1.5Gbps.
974 The following configurations can be forced.
976 * Cable type: 40c, 80c, short40c, unk, ign or sata.
977 Any ID with matching PORT is used.
979 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
981 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
982 udma[/][16,25,33,44,66,100,133] notation is also
985 * [no]ncq: Turn on or off NCQ.
987 If there are multiple matching configurations changing
988 the same attribute, the last one is used.
990 load_ramdisk= [RAM] List of ramdisks to load from floppy
991 See Documentation/ramdisk.txt.
993 lockd.nlm_grace_period=P [NFS] Assign grace period.
996 lockd.nlm_tcpport=N [NFS] Assign TCP port.
999 lockd.nlm_timeout=T [NFS] Assign timeout value.
1002 lockd.nlm_udpport=M [NFS] Assign UDP port.
1005 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1008 loglevel= All Kernel Messages with a loglevel smaller than the
1009 console loglevel will be printed to the console. It can
1010 also be changed with klogd or other programs. The
1011 loglevels are defined as follows:
1013 0 (KERN_EMERG) system is unusable
1014 1 (KERN_ALERT) action must be taken immediately
1015 2 (KERN_CRIT) critical conditions
1016 3 (KERN_ERR) error conditions
1017 4 (KERN_WARNING) warning conditions
1018 5 (KERN_NOTICE) normal but significant condition
1019 6 (KERN_INFO) informational
1020 7 (KERN_DEBUG) debug-level messages
1022 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1023 Format: { n | nk | nM }
1024 n must be a power of two. The default size
1025 is set in the kernel config file.
1027 logo.nologo [FB] Disables display of the built-in Linux logo.
1028 This may be used to provide more screen space for
1029 kernel log messages and is useful when debugging
1030 kernel boot problems.
1032 lp=0 [LP] Specify parallel ports to use, e.g,
1033 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1034 lp=reset first parallel port). 'lp=0' disables the
1035 lp=auto printer driver. 'lp=reset' (which can be
1036 specified in addition to the ports) causes
1037 attached printers to be reset. Using
1038 lp=port1,port2,... specifies the parallel ports
1039 to associate lp devices with, starting with
1040 lp0. A port specification may be 'none' to skip
1041 that lp device, or a parport name such as
1042 'parport0'. Specifying 'lp=auto' instead of a
1043 port specification list means that device IDs
1044 from each port should be examined, to see if
1045 an IEEE 1284-compliant printer is attached; if
1046 so, the driver will manage that printer.
1047 See also header of drivers/char/lp.c.
1050 Sets loops_per_jiffy to given constant, thus avoiding
1051 time-consuming boot-time autodetection (up to 250 ms per
1052 CPU). 0 enables autodetection (default). To determine
1053 the correct value for your kernel, boot with normal
1054 autodetection and see what value is printed. Note that
1055 on SMP systems the preset will be applied to all CPUs,
1056 which is likely to cause problems if your CPUs need
1057 significantly divergent settings. An incorrect value
1058 will cause delays in the kernel to be wrong, leading to
1059 unpredictable I/O errors and other breakage. Although
1060 unlikely, in the extreme case this might damage your
1064 Format: <io>,<irq>,<dma>
1066 mac5380= [HW,SCSI] Format:
1067 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1069 mac53c9x= [HW,SCSI] Format:
1070 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1072 machvec= [IA64] Force the use of a particular machine-vector
1073 (machvec) in a generic kernel.
1074 Example: machvec=hpzx1_swiotlb
1076 max_loop= [LOOP] Maximum number of loopback devices that can
1080 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1081 should make use of. maxcpus=n : n >= 0 limits the
1082 kernel to using 'n' processors. n=0 is a special case,
1083 it is equivalent to "nosmp", which also disables
1086 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1087 equal to this physical address is ignored.
1089 max_luns= [SCSI] Maximum number of LUNs to probe.
1090 Should be between 1 and 2^32-1.
1093 [SCSI] Maximum number of LUNs received.
1094 Should be between 1 and 16384.
1098 mce [X86-32] Machine Check Exception
1100 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1102 md= [HW] RAID subsystems devices and level
1103 See Documentation/md.txt.
1106 Format: <first>,<last>
1107 Specifies range of consoles to be captured by the MDA.
1109 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1110 Amount of memory to be used when the kernel is not able
1111 to see the whole system memory or for test.
1112 [X86-32] Use together with memmap= to avoid physical
1113 address space collisions. Without memmap= PCI devices
1114 could be placed at addresses belonging to unused RAM.
1116 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1119 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1120 E820 memory map, as specified by the user.
1121 Such memmap=exactmap lines can be constructed based on
1122 BIOS output or other requirements. See the memmap=nn@ss
1125 memmap=nn[KMG]@ss[KMG]
1126 [KNL] Force usage of a specific region of memory
1127 Region of memory to be used, from ss to ss+nn.
1129 memmap=nn[KMG]#ss[KMG]
1130 [KNL,ACPI] Mark specific memory as ACPI data.
1131 Region of memory to be used, from ss to ss+nn.
1133 memmap=nn[KMG]$ss[KMG]
1134 [KNL,ACPI] Mark specific memory as reserved.
1135 Region of memory to be used, from ss to ss+nn.
1137 meye.*= [HW] Set MotionEye Camera parameters
1138 See Documentation/video4linux/meye.txt.
1140 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1141 Multi-Function General Purpose Timers on AMD Geode
1144 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1145 the BIOS has incorrectly applied a workaround. TinyBIOS
1146 version 0.98 is known to be affected, 0.99 fixes the
1147 problem by letting the user disable the workaround.
1152 [MOUSE] Maximum time between finger touching and
1153 leaving touchpad surface for touch to be considered
1154 a tap and be reported as a left button click (for
1155 touchpads working in absolute mode only).
1157 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1158 reporting absolute coordinates, such as tablets
1159 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1160 reporting absolute coordinates, such as tablets
1165 MTD_Partition= [MTD]
1166 Format: <name>,<region-number>,<size>,<offset>
1168 MTD_Region= [MTD] Format:
1169 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1172 See drivers/mtd/cmdlinepart.c.
1174 mtouchusb.raw_coordinates=
1175 [HW] Make the MicroTouch USB driver use raw coordinates
1176 ('y', default) or cooked coordinates ('n')
1178 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1181 See header of drivers/scsi/NCR_D700.c.
1185 ncr53c400= [HW,SCSI]
1187 ncr53c400a= [HW,SCSI]
1189 ncr53c406a= [HW,SCSI]
1191 ncr53c8xx= [HW,SCSI]
1193 netdev= [NET] Network devices parameters
1194 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1195 Note that mem_start is often overloaded to mean
1196 something different and driver-specific.
1197 This usage is only documented in each driver source
1201 See Documentation/nfsroot.txt.
1203 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1204 See Documentation/nfsroot.txt.
1206 nfs.callback_tcpport=
1207 [NFS] set the TCP port on which the NFSv4 callback
1208 channel should listen.
1210 nfs.idmap_cache_timeout=
1211 [NFS] set the maximum lifetime for idmapper cache
1215 [NFS] enable 64-bit inode numbers.
1216 If zero, the NFS client will fake up a 32-bit inode
1217 number for the readdir() and stat() syscalls instead
1218 of returning the full 64-bit number.
1219 The default is to return 64-bit inode numbers.
1221 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1222 when a NMI is triggered.
1223 Format: [state][,regs][,debounce][,die]
1225 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1227 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1228 emulation library even if a 387 maths coprocessor
1231 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1232 caches in the slab allocator. Saves per-node memory,
1233 but will impact performance.
1237 noapic [SMP,APIC] Tells the kernel to not make use of any
1238 IOAPICs that may be present in the system.
1240 nobats [PPC] Do not use BATs for mapping kernel lowmem
1241 on "Classic" PPC cores.
1245 nodelayacct [KNL] Disable per-task delay accounting
1247 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1249 noefi [X86-32,X86-64] Disable EFI runtime services support.
1253 noexec [X86-32,X86-64]
1254 noexec=on: enable non-executable mappings (default)
1255 noexec=off: disable nn-executable mappings
1257 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1258 register save and restore. The kernel will only save
1259 legacy floating-point registers on task switch.
1261 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1265 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1266 instruction doesn't work correctly and not to
1269 nohalt [IA-64] Tells the kernel not to use the power saving
1270 function PAL_HALT_LIGHT when idle. This increases
1271 power-consumption. On the positive side, it reduces
1272 interrupt wake-up latency, which may improve performance
1273 in certain environments such as networked servers or
1276 nohz= [KNL] Boottime enable/disable dynamic ticks
1277 Valid arguments: on, off
1280 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1282 noirqdebug [X86-32] Disables the code which attempts to detect and
1283 disable unhandled interrupt sources.
1285 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1286 broken timer IRQ sources.
1288 noisapnp [ISAPNP] Disables ISA PnP code.
1290 noinitrd [RAM] Tells the kernel not to load any configured
1295 nojitter [IA64] Disables jitter checking for ITC timers.
1297 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1299 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1301 noltlbs [PPC] Do not use large page/tlb entries for kernel
1302 lowmem mapping on PPC40x.
1304 nomca [IA-64] Disable machine check abort handling
1306 nomce [X86-32] Machine Check Exception
1308 nomfgpt [X86-32] Disable Multi-Function General Purpose
1309 Timer usage (for AMD Geode machines).
1311 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1313 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1314 with UP alternatives
1316 noresidual [PPC] Don't use residual data on PReP machines.
1318 noresume [SWSUSP] Disables resume and restores original swap
1321 no-scroll [VGA] Disables scrollback.
1322 This is required for the Braillex ib80-piezo Braille
1323 reader made by F.H. Papenmeier (Germany).
1327 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1329 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1330 and disable the IO APIC. legacy for "maxcpus=0".
1332 nosoftlockup [KNL] Disable the soft-lockup detector.
1334 nosync [HW,M68K] Disables sync negotiation for all devices.
1336 notsc [BUGS=X86-32] Disable Time Stamp Counter
1338 nousb [USB] Disable the USB subsystem
1342 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1343 one of ['zone', 'node', 'default'] can be specified
1344 This can be set from sysctl after boot.
1345 See Documentation/sysctl/vm.txt for details.
1347 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1352 oprofile.timer= [HW]
1353 Use timer interrupt instead of performance counters
1355 osst= [HW,SCSI] SCSI Tape Driver
1356 Format: <buffer_size>,<write_threshold>
1357 See also Documentation/scsi/st.txt.
1359 panic= [KNL] Kernel behaviour on panic
1362 parkbd.port= [HW] Parallel port number the keyboard adapter is
1363 connected to, default is 0.
1365 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1366 0 for XT, 1 for AT (default is AT).
1369 parport= [HW,PPT] Specify parallel ports. 0 disables.
1370 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1371 Use 'auto' to force the driver to use any
1372 IRQ/DMA settings detected (the default is to
1373 ignore detected IRQ/DMA settings because of
1374 possible conflicts). You can specify the base
1375 address, IRQ, and DMA settings; IRQ and DMA
1376 should be numbers, or 'auto' (for using detected
1377 settings on that particular port), or 'nofifo'
1378 (to avoid using a FIFO even if it is detected).
1379 Parallel ports are assigned in the order they
1380 are specified on the command line, starting
1383 parport_init_mode= [HW,PPT]
1384 Configure VIA parallel port to operate in
1385 a specific mode. This is necessary on Pegasos
1386 computer where firmware has no options for setting
1387 up parallel port mode and sets it to spp.
1388 Currently this function knows 686a and 8231 chips.
1389 Format: [spp|ps2|epp|ecp|ecpepp]
1391 pas2= [HW,OSS] Format:
1392 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1395 See header of drivers/scsi/pas16.c.
1398 Halt all CPUs after the first oops has been printed for
1399 the specified number of seconds. This is to be used if
1400 your oopses keep scrolling off the screen.
1405 See header of drivers/block/paride/pcd.c.
1406 See also Documentation/paride.txt.
1408 pci=option[,option...] [PCI] various PCI subsystem options:
1409 off [X86-32] don't probe for the PCI bus
1410 bios [X86-32] force use of PCI BIOS, don't access
1411 the hardware directly. Use this if your machine
1412 has a non-standard PCI host bridge.
1413 nobios [X86-32] disallow use of PCI BIOS, only direct
1414 hardware access methods are allowed. Use this
1415 if you experience crashes upon bootup and you
1416 suspect they are caused by the BIOS.
1417 conf1 [X86-32] Force use of PCI Configuration
1419 conf2 [X86-32] Force use of PCI Configuration
1421 noaer [PCIE] If the PCIEAER kernel config parameter is
1422 enabled, this kernel boot option can be used to
1423 disable the use of PCIE advanced error reporting.
1424 nodomains [PCI] Disable support for multiple PCI
1425 root domains (aka PCI segments, in ACPI-speak).
1426 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1428 nomsi [MSI] If the PCI_MSI kernel config parameter is
1429 enabled, this kernel boot option can be used to
1430 disable the use of MSI interrupts system-wide.
1431 nosort [X86-32] Don't sort PCI devices according to
1432 order given by the PCI BIOS. This sorting is
1433 done to get a device order compatible with
1435 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1436 routing table. These calls are known to be buggy
1437 on several machines and they hang the machine
1438 when used, but on other computers it's the only
1439 way to get the interrupt routing table. Try
1440 this option if the kernel is unable to allocate
1441 IRQs or discover secondary PCI buses on your
1443 rom [X86-32] Assign address space to expansion ROMs.
1444 Use with caution as certain devices share
1445 address decoders between ROMs and other
1447 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1448 assigned automatically to PCI devices. You can
1449 make the kernel exclude IRQs of your ISA cards
1451 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1452 of the PIRQ table (normally generated
1453 by the BIOS) if it is outside the
1454 F0000h-100000h range.
1455 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1456 useful if the kernel is unable to find your
1457 secondary buses and you want to tell it
1458 explicitly which ones they are.
1459 assign-busses [X86-32] Always assign all PCI bus
1460 numbers ourselves, overriding
1461 whatever the firmware may have done.
1462 usepirqmask [X86-32] Honor the possible IRQ mask stored
1463 in the BIOS $PIR table. This is needed on
1464 some systems with broken BIOSes, notably
1465 some HP Pavilion N5400 and Omnibook XE3
1466 notebooks. This will have no effect if ACPI
1467 IRQ routing is enabled.
1468 noacpi [X86-32] Do not use ACPI for IRQ routing
1469 or for PCI scanning.
1470 use_crs [X86-32] Use _CRS for PCI resource
1472 routeirq Do IRQ routing for all PCI devices.
1473 This is normally done in pci_enable_device(),
1474 so this option is a temporary workaround
1475 for broken drivers that don't call it.
1476 firmware [ARM] Do not re-enumerate the bus but instead
1477 just use the configuration from the
1478 bootloader. This is currently used on
1479 IXP2000 systems where the bus has to be
1480 configured a certain way for adjunct CPUs.
1481 noearly [X86] Don't do any early type 1 scanning.
1482 This might help on some broken boards which
1483 machine check when some devices' config space
1484 is read. But various workarounds are disabled
1485 and some IOMMU drivers will not work.
1486 bfsort Sort PCI devices into breadth-first order.
1487 This sorting is done to get a device
1488 order compatible with older (<= 2.4) kernels.
1489 nobfsort Don't sort PCI devices into breadth-first order.
1490 cbiosize=nn[KMG] The fixed amount of bus space which is
1491 reserved for the CardBus bridge's IO window.
1492 The default value is 256 bytes.
1493 cbmemsize=nn[KMG] The fixed amount of bus space which is
1494 reserved for the CardBus bridge's memory
1495 window. The default value is 64 megabytes.
1497 pcmv= [HW,PCMCIA] BadgePAD 4
1500 See Documentation/paride.txt.
1502 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1505 See arch/parisc/kernel/pdc_chassis.c
1508 See Documentation/paride.txt.
1511 See Documentation/paride.txt.
1513 pirq= [SMP,APIC] Manual mp-table setup
1514 See Documentation/i386/IO-APIC.txt.
1516 plip= [PPT,NET] Parallel port network link
1517 Format: { parport<nr> | timid | 0 }
1518 See also Documentation/parport.txt.
1524 { on | off | curr | res | no-curr | no-res }
1527 [ISAPNP] Exclude IRQs for the autoconfiguration
1530 [ISAPNP] Exclude DMAs for the autoconfiguration
1532 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1533 Ranges are in pairs (I/O port base and size).
1536 [ISAPNP] Exclude memory regions for the
1538 Ranges are in pairs (memory base and size).
1540 print-fatal-signals=
1541 [KNL] debug: print fatal signals
1542 print-fatal-signals=1: print segfault info to
1546 printk.time= Show timing data prefixed to each printk message line
1547 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1549 profile= [KNL] Enable kernel profiling via /proc/profile
1550 Format: [schedule,]<number>
1551 Param: "schedule" - profile schedule points.
1552 Param: <number> - step/bucket size as a power of 2 for
1553 statistical time based profiling.
1554 Param: "sleep" - profile D-state sleeping (millisecs).
1555 Requires CONFIG_SCHEDSTATS
1556 Param: "kvm" - profile VM exits.
1558 processor.max_cstate= [HW,ACPI]
1559 Limit processor to maximum C-state
1560 max_cstate=9 overrides any DMI blacklist limit.
1562 processor.nocst [HW,ACPI]
1563 Ignore the _CST method to determine C-states,
1564 instead using the legacy FADT method
1566 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1568 See Documentation/ramdisk.txt.
1570 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1571 probe for; one of (bare|imps|exps|lifebook|any).
1572 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1574 psmouse.resetafter= [HW,MOUSE]
1575 Try to reset the device after so many bad packets
1578 [HW,MOUSE] Set desired mouse resolution, in dpi.
1579 psmouse.smartscroll=
1580 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1581 0 = disabled, 1 = enabled (default).
1583 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1585 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1588 See Documentation/paride.txt.
1591 [KNL] Number of legacy pty's. Overwrites compiled-in
1594 quiet [KNL] Disable most log messages
1599 See Documentation/md.txt.
1601 ramdisk_blocksize= [RAM]
1602 See Documentation/ramdisk.txt.
1604 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1605 See Documentation/ramdisk.txt.
1607 rcupdate.blimit= [KNL,BOOT]
1608 Set maximum number of finished RCU callbacks to process
1611 rcupdate.qhimark= [KNL,BOOT]
1612 Set threshold of queued
1613 RCU callbacks over which batch limiting is disabled.
1615 rcupdate.qlowmark= [KNL,BOOT]
1616 Set threshold of queued RCU callbacks below which
1617 batch limiting is re-enabled.
1621 Run specified binary instead of /init from the ramdisk,
1622 used for early userspace startup. See initrd.
1624 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1625 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1626 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1628 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1630 reservetop= [X86-32]
1632 Reserves a hole at the top of the kernel virtual
1635 reset_devices [KNL] Force drivers to reset the underlying device
1636 during initialization.
1639 Specify the partition device for software suspend
1641 resume_offset= [SWSUSP]
1642 Specify the offset from the beginning of the partition
1643 given by "resume=" at which the swap header is located,
1644 in <PAGE_SIZE> units (needed only for swap files).
1645 See Documentation/power/swsusp-and-swap-files.txt
1647 retain_initrd [RAM] Keep initrd memory after extraction
1649 rhash_entries= [KNL,NET]
1650 Set number of hash buckets for route cache
1652 riscom8= [HW,SERIAL]
1653 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1655 ro [KNL] Mount root device read-only on boot
1657 root= [KNL] Root filesystem
1659 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1660 mount the root filesystem
1662 rootflags= [KNL] Set root filesystem mount option string
1664 rootfstype= [KNL] Set root filesystem type
1666 rootwait [KNL] Wait (indefinitely) for root device to show up.
1667 Useful for devices that are detected asynchronously
1668 (e.g. USB and MMC devices).
1670 root_plug.vendor_id=
1671 [ROOTPLUG] Override the default vendor ID
1673 root_plug.product_id=
1674 [ROOTPLUG] Override the default product ID
1677 [ROOTPLUG] Enable debugging output
1679 rw [KNL] Mount root device read-write on boot
1681 S [KNL] Run init in single mode
1684 See drivers/net/irda/sa1100_ir.c.
1686 sbni= [NET] Granch SBNI12 leased line adapter
1688 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1689 Format: <io>[,<timeout>[,<isapnp>]]
1691 scsi_debug_*= [SCSI]
1692 See drivers/scsi/scsi_debug.c.
1694 scsi_default_dev_flags=
1695 [SCSI] SCSI default device flags
1698 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1699 Format: <vendor>:<model>:<flags>
1700 (flags are integer value)
1702 scsi_logging_level= [SCSI] a bit mask of logging levels
1703 See drivers/scsi/scsi_logging.h for bits. Also
1704 settable via sysctl at dev.scsi.logging_level
1705 (/proc/sys/dev/scsi/logging_level).
1706 There is also a nice 'scsi_logging_level' script in the
1707 S390-tools package, available for download at
1708 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1710 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1711 discovered. async scans them in kernel threads,
1712 allowing boot to proceed. none ignores them, expecting
1713 user space to do the scan.
1715 selinux [SELINUX] Disable or enable SELinux at boot time.
1716 Format: { "0" | "1" }
1717 See security/selinux/Kconfig help text.
1720 Default value is set via kernel config option.
1721 If enabled at boot time, /selinux/disable can be used
1722 later to disable prior to initial policy load.
1724 selinux_compat_net =
1725 [SELINUX] Set initial selinux_compat_net flag value.
1726 Format: { "0" | "1" }
1727 0 -- use new secmark-based packet controls
1728 1 -- use legacy packet controls
1729 Default value is 0 (preferred).
1730 Value can be changed at runtime via
1731 /selinux/compat_net.
1733 serialnumber [BUGS=X86-32]
1736 Maximal number of shapers.
1739 See header of drivers/scsi/sim710.c.
1746 slub_debug[=options[,slabs]] [MM, SLUB]
1747 Enabling slub_debug allows one to determine the
1748 culprit if slab objects become corrupted. Enabling
1749 slub_debug can create guard zones around objects and
1750 may poison objects when not in use. Also tracks the
1751 last alloc / free. For more information see
1752 Documentation/vm/slub.txt.
1754 slub_max_order= [MM, SLUB]
1755 Determines the maximum allowed order for slabs.
1756 A high setting may cause OOMs due to memory
1757 fragmentation. For more information see
1758 Documentation/vm/slub.txt.
1760 slub_min_objects= [MM, SLUB]
1761 The minimum number of objects per slab. SLUB will
1762 increase the slab order up to slub_max_order to
1763 generate a sufficiently large slab able to contain
1764 the number of objects indicated. The higher the number
1765 of objects the smaller the overhead of tracking slabs
1766 and the less frequently locks need to be acquired.
1767 For more information see Documentation/vm/slub.txt.
1769 slub_min_order= [MM, SLUB]
1770 Determines the mininum page order for slabs. Must be
1771 lower than slub_max_order.
1772 For more information see Documentation/vm/slub.txt.
1774 slub_nomerge [MM, SLUB]
1775 Disable merging of slabs with similar size. May be
1776 necessary if there is some reason to distinguish
1777 allocs to different slabs. Debug options disable
1778 merging on their own.
1779 For more information see Documentation/vm/slub.txt.
1782 Format: <io1>[,<io2>[,...,<io8>]]
1784 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1785 attempt to substitute SMP alternatives once at boot.
1787 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1788 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1789 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1790 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1791 smsc-ircc2.ircc_irq= [HW] IRQ line
1792 smsc-ircc2.ircc_dma= [HW] DMA channel
1793 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1794 0: Toshiba Satellite 1800 (GP data pin select)
1795 1: Fast pin select (default)
1798 snd-ad1816a= [HW,ALSA]
1800 snd-ad1848= [HW,ALSA]
1802 snd-ali5451= [HW,ALSA]
1804 snd-als100= [HW,ALSA]
1806 snd-als4000= [HW,ALSA]
1808 snd-azt2320= [HW,ALSA]
1810 snd-cmi8330= [HW,ALSA]
1812 snd-cmipci= [HW,ALSA]
1814 snd-cs4231= [HW,ALSA]
1816 snd-cs4232= [HW,ALSA]
1818 snd-cs4236= [HW,ALSA]
1820 snd-cs4281= [HW,ALSA]
1822 snd-cs46xx= [HW,ALSA]
1824 snd-dt019x= [HW,ALSA]
1826 snd-dummy= [HW,ALSA]
1828 snd-emu10k1= [HW,ALSA]
1830 snd-ens1370= [HW,ALSA]
1832 snd-ens1371= [HW,ALSA]
1834 snd-es968= [HW,ALSA]
1836 snd-es1688= [HW,ALSA]
1838 snd-es18xx= [HW,ALSA]
1840 snd-es1938= [HW,ALSA]
1842 snd-es1968= [HW,ALSA]
1844 snd-fm801= [HW,ALSA]
1846 snd-gusclassic= [HW,ALSA]
1848 snd-gusextreme= [HW,ALSA]
1850 snd-gusmax= [HW,ALSA]
1854 snd-ice1712= [HW,ALSA]
1856 snd-intel8x0= [HW,ALSA]
1858 snd-interwave= [HW,ALSA]
1863 snd-korg1212= [HW,ALSA]
1865 snd-maestro3= [HW,ALSA]
1867 snd-mpu401= [HW,ALSA]
1869 snd-mtpav= [HW,ALSA]
1871 snd-nm256= [HW,ALSA]
1873 snd-opl3sa2= [HW,ALSA]
1881 snd-opti93x= [HW,ALSA]
1885 snd-rme32= [HW,ALSA]
1887 snd-rme96= [HW,ALSA]
1889 snd-rme9652= [HW,ALSA]
1895 snd-sbawe= [HW,ALSA]
1897 snd-serial= [HW,ALSA]
1899 snd-sgalaxy= [HW,ALSA]
1901 snd-sonicvibes= [HW,ALSA]
1906 snd-sun-cs4231= [HW,ALSA]
1908 snd-trident= [HW,ALSA]
1910 snd-usb-audio= [HW,ALSA,USB]
1912 snd-via82xx= [HW,ALSA]
1914 snd-virmidi= [HW,ALSA]
1916 snd-wavefront= [HW,ALSA]
1918 snd-ymfpci= [HW,ALSA]
1920 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1921 See Documentation/sonypi.txt
1923 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1924 See Documentation/specialix.txt.
1926 spia_io_base= [HW,MTD]
1932 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1934 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1935 See Documentation/scsi/st.txt.
1939 Set the STI (builtin display/keyboard on the HP-PARISC
1940 machines) console (graphic card) which should be used
1941 as the initial boot-console.
1942 See also comment in drivers/video/console/sticore.c.
1945 See comment in drivers/video/console/sticore.c.
1948 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1952 Control how the NFS server code allocates CPUs to
1953 service thread pools. Depending on how many NICs
1954 you have and where their interrupts are bound, this
1955 option will affect which CPUs will do NFS serving.
1956 Note: this parameter cannot be changed while the
1957 NFS server is running.
1959 auto the server chooses an appropriate mode
1960 automatically using heuristics
1961 global a single global pool contains all CPUs
1962 percpu one pool for each CPU
1963 pernode one pool for each NUMA node (equivalent
1964 to global on non-NUMA machines)
1966 swiotlb= [IA-64] Number of I/O TLB slabs
1970 sym53c416= [HW,SCSI]
1971 See header of drivers/scsi/sym53c416.c.
1973 sysrq_always_enabled
1975 Ignore sysrq setting - this boot parameter will
1976 neutralize any effect of /proc/sys/kernel/sysrq.
1977 Useful for debugging.
1980 See header of drivers/scsi/t128.c.
1984 thash_entries= [KNL,NET]
1985 Set number of hash buckets for TCP connection
1987 thermal.act= [HW,ACPI]
1988 -1: disable all active trip points in all thermal zones
1989 <degrees C>: override all lowest active trip points
1991 thermal.crt= [HW,ACPI]
1992 -1: disable all critical trip points in all thermal zones
1993 <degrees C>: lower all critical trip points
1995 thermal.nocrt= [HW,ACPI]
1996 Set to disable actions on ACPI thermal zone
1997 critical and hot trip points.
1999 thermal.off= [HW,ACPI]
2000 1: disable ACPI thermal control
2002 thermal.psv= [HW,ACPI]
2003 -1: disable all passive trip points
2004 <degrees C>: override all passive trip points to this value
2006 thermal.tzp= [HW,ACPI]
2007 Specify global default ACPI thermal zone polling rate
2008 <deci-seconds>: poll all this frequency
2009 0: no polling (default)
2011 tipar.timeout= [HW,PPT]
2012 Set communications timeout in tenths of a second
2015 tipar.delay= [HW,PPT]
2016 Set inter-bit delay in microseconds (default 10).
2019 See comment before function dc390_setup() in
2020 drivers/scsi/tmscsim.c.
2024 trix= [HW,OSS] MediaTrix AudioTrix Pro
2026 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2028 turbografx.map[2|3]= [HW,JOY]
2029 TurboGraFX parallel port interface
2031 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2032 See also Documentation/input/joystick-parport.txt
2034 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2035 See header of drivers/scsi/u14-34f.c.
2044 [USB] Ignore overcurrent events (default N).
2045 Some badly-designed motherboards generate lots of
2046 bogus events, for ports that aren't wired to
2047 anything. Set this parameter to avoid log spamming.
2048 Note that genuine overcurrent events won't be
2051 usbcore.autosuspend=
2052 [USB] The autosuspend time delay (in seconds) used
2053 for newly-detected USB devices (default 2). This
2054 is the time required before an idle device will be
2055 autosuspended. Devices for which the delay is set
2056 to a negative value won't be autosuspended at all.
2059 [USBHID] The interval which mice are to be polled at.
2061 vdso= [X86-32,SH,x86-64]
2062 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2063 vdso=1: enable VDSO (default)
2064 vdso=0: disable VDSO mapping
2066 vdso32= [X86-32,X86-64]
2067 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2068 vdso32=1: enable 32-bit VDSO (default)
2069 vdso32=0: disable 32-bit VDSO mapping
2072 vector=percpu: enable percpu vector domain
2074 video= [FB] Frame buffer configuration
2075 See Documentation/fb/modedb.txt.
2077 vga= [BOOT,X86-32] Select a particular video mode
2078 See Documentation/i386/boot.txt and
2079 Documentation/svga.txt.
2080 Use vga=ask for menu.
2081 This is actually a boot loader parameter; the value is
2082 passed to the kernel using a special protocol.
2084 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2085 size of <nn>. This can be used to increase the
2086 minimum size (128MB on x86). It can also be used to
2087 decrease the size and leave more room for directly
2090 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2093 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2096 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2099 waveartist= [HW,OSS]
2100 Format: <io>,<irq>,<dma>,<dma2>
2103 See header of drivers/scsi/wd33c93.c.
2106 See header of drivers/scsi/wd7000.c.
2109 See Documentation/watchdog/wdt.txt.
2111 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2112 xd_geo= See header of drivers/block/xd.c.
2114 xirc2ps_cs= [NET,PCMCIA]
2116 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2118 norandmaps Don't use address space randomization
2119 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2121 ______________________________________________________________________
2125 Add documentation for ALSA options.
2126 Add more DRM drivers.