4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend is enabled.
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
99 X86-32 X86-32, aka i386 architecture is enabled.
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
104 In addition, the following text indicates that the option:
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode }
151 See Documentation/power/video.txt
153 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
154 Format: { level | edge | high | low }
156 acpi_irq_balance [HW,ACPI]
157 ACPI will balance active IRQs
160 acpi_irq_nobalance [HW,ACPI]
161 ACPI will not move active IRQs (default)
164 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
166 Format: <irq>,<irq>...
168 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
169 Format: <irq>,<irq>...
171 acpi_new_pts_ordering [HW,ACPI]
172 Enforce the ACPI 2.0 ordering of the _PTS control
173 method wrt putting devices into low power states
174 default: pre ACPI 2.0 ordering of _PTS
176 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
178 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
179 Format: To spoof as Windows 98: ="Microsoft Windows"
181 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
182 acpi_osi="string1" # add string1 -- only one string
183 acpi_osi="!string2" # remove built-in string2
184 acpi_osi= # disable all strings
186 acpi_serialize [HW,ACPI] force serialization of AML methods
188 acpi_skip_timer_override [HW,ACPI]
189 Recognize and ignore IRQ0/pin2 Interrupt Override.
190 For broken nForce2 BIOS resulting in XT-PIC timer.
191 acpi_use_timer_override [HW,ACPI}
192 Use timer override. For some broken Nvidia NF5 boards
193 that require a timer override, but don't have
196 acpi.debug_layer= [HW,ACPI]
198 Each bit of the <int> indicates an ACPI debug layer,
199 1: enable, 0: disable. It is useful for boot time
200 debugging. After system has booted up, it can be set
201 via /sys/module/acpi/parameters/debug_layer.
202 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
203 Available bits (add the numbers together) to enable debug output
204 for specific parts of the ACPI subsystem:
205 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
206 0x10 namespace 0x20 parser 0x40 dispatcher
207 0x80 executer 0x100 resources 0x200 acpica debugger
208 0x400 os services 0x800 acpica disassembler.
209 The number can be in decimal or prefixed with 0x in hex.
210 Warning: Many of these options can produce a lot of
211 output and make your system unusable. Be very careful.
213 acpi.debug_level= [HW,ACPI]
215 Each bit of the <int> indicates an ACPI debug level,
216 1: enable, 0: disable. It is useful for boot time
217 debugging. After system has booted up, it can be set
218 via /sys/module/acpi/parameters/debug_level.
219 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
220 Available bits (add the numbers together) to enable different
221 debug output levels of the ACPI subsystem:
222 0x01 error 0x02 warn 0x04 init 0x08 debug object
223 0x10 info 0x20 init names 0x40 parse 0x80 load
224 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
225 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
226 0x10000 resources 0x20000 user requests 0x40000 package.
227 The number can be in decimal or prefixed with 0x in hex.
228 Warning: Many of these options can produce a lot of
229 output and make your system unusable. Be very careful.
231 acpi_pm_good [X86-32,X86-64]
232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
237 { off | try_unsupported }
238 off: disable AGP support
239 try_unsupported: try to drive unsupported chipsets
240 (may crash computer or cause data corruption)
242 enable_timer_pin_1 [i386,x86-64]
243 Enable PIN 1 of APIC timer
244 Can be useful to work around chipset bugs
245 (in particular on some ATI chipsets).
246 The kernel tries to set a reasonable default.
248 disable_timer_pin_1 [i386,x86-64]
249 Disable PIN 1 of APIC timer
250 Can be useful to work around chipset bugs.
253 Format: <io>,<irq>,<dma>,<dma2>,<type>
256 See header of drivers/scsi/advansys.c.
258 advwdt= [HW,WDT] Advantech WDT
259 Format: <iostart>,<iostop>
261 aedsp16= [HW,OSS] Audio Excel DSP 16
262 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
263 See also header of sound/oss/aedsp16.c.
266 See Documentation/scsi/aha152x.txt.
269 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
272 See Documentation/scsi/aic7xxx.txt.
275 See Documentation/scsi/aic79xx.txt.
277 amijoy.map= [HW,JOY] Amiga joystick support
278 Map of devices attached to JOY0DAT and JOY1DAT
280 See also Documentation/kernel/input/joystick.txt
282 analog.map= [HW,JOY] Analog joystick and gamepad support
283 Specifies type or capabilities of an analog joystick
284 connected to one of 16 gameports
285 Format: <type1>,<type2>,..<type16>
288 Power management functions (SPARCstation-4/5 + deriv.)
290 Disable APC CPU standby support. SPARCstation-Fox does
291 not play well with APC CPU idle - disable it if you have
292 APC and your system crashes randomly.
294 apic= [APIC,i386] Advanced Programmable Interrupt Controller
295 Change the output verbosity whilst booting
296 Format: { quiet (default) | verbose | debug }
297 Change the amount of debugging information output
298 when initialising the APIC and IO-APIC components.
300 apm= [APM] Advanced Power Management
301 See header of arch/i386/kernel/apm.c.
303 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
304 Format: <io>,<irq>,<nodeID>
308 atarimouse= [HW,MOUSE] Atari Mouse
310 atascsi= [HW,SCSI] Atari SCSI
312 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
313 EzKey and similar keyboards
315 atkbd.reset= [HW] Reset keyboard during initialization
317 atkbd.set= [HW] Select keyboard code set
318 Format: <int> (2 = AT (default), 3 = PS/2)
320 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
323 atkbd.softraw= [HW] Choose between synthetic and real raw mode
324 Format: <bool> (0 = real, 1 = synthetic (default))
326 atkbd.softrepeat= [HW]
327 Use software keyboard repeat
331 baycom_epp= [HW,AX25]
334 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
336 See header of drivers/net/hamradio/baycom_par.c.
338 baycom_ser_fdx= [HW,AX25]
339 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
340 Format: <io>,<irq>,<mode>[,<baud>]
341 See header of drivers/net/hamradio/baycom_ser_fdx.c.
343 baycom_ser_hdx= [HW,AX25]
344 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
345 Format: <io>,<irq>,<mode>
346 See header of drivers/net/hamradio/baycom_ser_hdx.c.
348 boot_delay= Milliseconds to delay each printk during boot.
349 Values larger than 10 seconds (10000) are changed to
353 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
354 bttv.radio= Most important insmod options are available as
356 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
357 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
360 See drivers/scsi/BusLogic.c, comment before function
361 BusLogic_ParseDriverOptions().
363 c101= [NET] Moxa C101 synchronous serial card
365 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
366 Sometimes CPU hardware bugs make them report the cache
367 size incorrectly. The kernel will attempt work arounds
368 to fix known problems, but for some CPUs it is not
369 possible to determine what the correct size should be.
370 This option provides an override for these situations.
373 [SECURITY] Disable capabilities. This would normally
374 be used only if an alternative security model is to be
375 configured. Potentially dangerous and should only be
376 used if you are entirely sure of the consequences.
378 ccw_timeout_log [S390]
379 See Documentation/s390/CommonIO for details.
381 checkreqprot [SELINUX] Set initial checkreqprot flag value.
382 Format: { "0" | "1" }
383 See security/selinux/Kconfig help text.
384 0 -- check protection applied by kernel (includes
385 any implied execute protection).
386 1 -- check protection requested by application.
387 Default value is set via a kernel config option.
388 Value can be changed at runtime via
389 /selinux/checkreqprot.
392 See Documentation/s390/CommonIO for details.
395 See Documentation/s390/CommonIO for details.
397 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
399 Forces specified clocksource (if available) to be used
400 when calculating gettimeofday(). If specified
401 clocksource is not available, it defaults to PIT.
402 Format: { pit | tsc | cyclone | pmtmr }
404 clocksource= [GENERIC_TIME] Override the default clocksource
406 Override the default clocksource and use the clocksource
407 with the name specified.
408 Some clocksource names to choose from, depending on
410 [all] jiffies (this is the base, fallback clocksource)
412 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
413 pxa_timer,timer3,32k_counter,timer0_1
415 [X86-32] pit,hpet,tsc,vmi-timer;
416 scx200_hrt on Geode; cyclone on IBM x440
424 clearcpuid=BITNUM [X86]
425 Disable CPUID feature X for the kernel. See
426 include/asm-x86/cpufeature.h for the valid bit numbers.
427 Note the Linux specific bits are not necessarily
428 stable over kernel options, but the vendor specific
430 Also note that user programs calling CPUID directly
431 or using the feature without checking anything
432 will still see it. This just prevents it from
433 being used by the kernel or shown in /proc/cpuinfo.
434 Also note the kernel might malfunction if you disable
437 code_bytes [IA32/X86_64] How many bytes of object code to print
444 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
445 over the 8254 in addition to over the IO-APIC. The
446 kernel tries to set a sensible default.
448 hpet= [X86-32,HPET] option to control HPET usage
449 Format: { enable (default) | disable | force }
450 disable: disable HPET and use PIT instead
451 force: allow force enabled of undocumented chips (ICH4,
454 com20020= [HW,NET] ARCnet - COM20020 chipset
456 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
458 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
462 ARCnet - COM90xx chipset (memory-mapped buffers)
463 Format: <io>[,<irq>[,<memstart>]]
465 condev= [HW,S390] console device
468 console= [KNL] Output console device and options.
470 tty<n> Use the virtual console device <n>.
474 Use the specified serial port. The options are of
475 the form "bbbbpnf", where "bbbb" is the baud rate,
476 "p" is parity ("n", "o", or "e"), "n" is number of
477 bits, and "f" is flow control ("r" for RTS or
478 omit it). Default is "9600n8".
480 See Documentation/serial-console.txt for more
482 Documentation/networking/netconsole.txt for an
485 uart[8250],io,<addr>[,options]
486 uart[8250],mmio,<addr>[,options]
487 Start an early, polled-mode console on the 8250/16550
488 UART at the specified I/O port or MMIO address,
489 switching to the matching ttyS device later. The
490 options are the same as for ttyS, above.
492 earlycon= [KNL] Output early console device and options.
493 uart[8250],io,<addr>[,options]
494 uart[8250],mmio,<addr>[,options]
495 Start an early, polled-mode console on the 8250/16550
496 UART at the specified I/O port or MMIO address.
497 The options are the same as for ttyS, above.
500 [HW] Never suspend the console
501 Disable suspending of consoles during suspend and
502 hibernate operations. Once disabled, debugging
503 messages can reach various consoles while the rest
504 of the system is being put to sleep (ie, while
505 debugging driver suspend/resume hooks). This may
506 not work reliably with all consoles, but is known
507 to work with serial and VGA consoles.
509 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
511 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
513 crashkernel=nn[KMG]@ss[KMG]
514 [KNL] Reserve a chunk of physical memory to
515 hold a kernel to switch to with kexec on panic.
517 crashkernel=range1:size1[,range2:size2,...][@offset]
518 [KNL] Same as above, but depends on the memory
519 in the running system. The syntax of range is
520 start-[end] where start and end are both
521 a memory unit (amount[KMG]). See also
522 Documentation/kdump/kdump.txt for a example.
525 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
530 cs89x0_media= [HW,NET]
531 Format: { rj45 | aui | bnc }
534 See header of drivers/s390/block/dasd_devmap.c.
536 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
537 (one device per port)
538 Format: <port#>,<type>
539 See also Documentation/input/joystick-parport.txt
541 debug [KNL] Enable kernel debugging (events log level).
544 [KNL] verbose self-tests
546 Print debugging info while doing the locking API
548 We default to 0 (no extra messages), setting it to
549 1 will print _a lot_ more information - normally
550 only useful to kernel developers.
552 decnet.addr= [HW,NET]
553 Format: <area>[,<node>]
554 See also Documentation/networking/decnet.txt.
557 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
558 Change the default blue palette of the console.
559 This is a 16-member array composed of values
563 Format: <green0>,<green1>,<green2>,...,<green15>
564 Change the default green palette of the console.
565 This is a 16-member array composed of values
569 Format: <red0>,<red1>,<red2>,...,<red15>
570 Change the default red palette of the console.
571 This is a 16-member array composed of values
577 Set system-wide default UTF-8 mode for all tty's.
578 Default is 1, i.e. UTF-8 mode is enabled for all
579 newly opened terminals.
582 Set number of hash buckets for dentry cache.
585 IO parameters + enable/disable command.
587 digiepca= [HW,SERIAL]
588 See drivers/char/README.epca and
589 Documentation/digiepca.txt.
591 disable_mtrr_trim [X86, Intel and AMD only]
592 By default the kernel will trim any uncacheable
593 memory out of your available memory pool based on
594 MTRR settings. This parameter disables that behavior,
595 possibly causing your machine to run very slowly.
597 dmasound= [HW,OSS] Sound subsystem buffers
603 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
605 earlyprintk=serial[,ttySn[,baudrate]]
607 Append ",keep" to not disable it when the real console
610 Only vga or serial at a time, not both.
612 Currently only ttyS0 and ttyS1 are supported.
614 Interaction with the standard serial driver is not
617 The VGA output is eventually overwritten by the real
623 Format: {"of[f]" | "sk[ipmbr]"}
624 See comment in arch/i386/boot/edd.S
626 eisa_irq_edge= [PARISC,HW]
627 See header of drivers/parisc/eisa.c.
630 See comment before function elanfreq_setup() in
631 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
634 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
635 See Documentation/block/as-iosched.txt and
636 Documentation/block/deadline-iosched.txt for details.
638 elfcorehdr= [X86-32, X86_64]
639 Specifies physical address of start of kernel core
640 image elf header. Generally kexec loader will
641 pass this option to capture kernel.
642 See Documentation/kdump/kdump.txt for details.
644 enforcing [SELINUX] Set initial enforcing status.
646 See security/selinux/Kconfig help text.
647 0 -- permissive (log only, no denials).
648 1 -- enforcing (deny and log).
650 Value can be changed at runtime via /selinux/enforce.
653 Format: <spdif>,[<nomix>,[<amplifier>]]
654 See also header of sound/oss/es1371.c.
656 ether= [HW,NET] Ethernet cards parameters
657 This option is obsoleted by the "netdev=" option, which
658 has equivalent usage. See its documentation for details.
660 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
665 fail_make_request=[KNL]
666 General fault injection mechanism.
667 Format: <interval>,<probability>,<space>,<times>
668 See also /Documentation/fault-injection/.
671 See header of drivers/scsi/fd_mcs.c.
674 See header of drivers/scsi/fdomain.c.
677 See Documentation/floppy.txt.
680 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
681 support via parallel port (up to 5 devices per port)
682 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
683 See also Documentation/input/joystick-parport.txt
687 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
692 See header of drivers/scsi/gdth.c.
694 gpt [EFI] Forces disk with valid GPT signature but
695 invalid Protective MBR to be treated as GPT.
699 hashdist= [KNL,NUMA] Large hashes allocated during boot
700 are distributed across NUMA nodes. Defaults on
701 for IA-64, off otherwise.
702 Format: 0 | 1 (for off | on)
704 hcl= [IA-64] SGI's Hardware Graph compatibility layer
706 hd= [EIDE] (E)IDE hard drive subsystem geometry
707 Format: <cyl>,<head>,<sect>
709 hd?= [HW] (E)IDE subsystem
710 hd?lun= See Documentation/ide.txt.
712 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
713 size of <nn>. This works even on boxes that have no
714 highmem otherwise. This also works to reduce highmem
715 size on bigger boxes.
717 highres= [KNL] Enable/disable high resolution timer mode.
718 Valid parameters: "on", "off"
722 See Documentation/isdn/README.HiSax.
724 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
725 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
727 i8042.direct [HW] Put keyboard port into non-translated mode
728 i8042.dumbkbd [HW] Pretend that controller can only read data from
729 keyboard and cannot control its state
730 (Don't attempt to blink the leds)
731 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
732 i8042.nokbd [HW] Don't check/create keyboard port
733 i8042.nomux [HW] Don't check presence of an active multiplexing
735 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
738 [HW] Frequency with which keyboard LEDs should blink
739 when kernel panics (default is 0.5 sec)
740 i8042.reset [HW] Reset the controller during init and cleanup
741 i8042.unlock [HW] Unlock (ignore) the keylock
745 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
746 indicates that the driver is running on unsupported
748 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
749 does not match list of supported models.
751 [HW] Report power status in /proc/i8k
752 (disabled by default)
753 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
756 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
757 See Documentation/mca.txt.
760 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
762 ide= [HW] (E)IDE subsystem
763 Format: ide=nodma or ide=doubler or ide=reverse
764 See Documentation/ide.txt.
766 ide?= [HW] (E)IDE subsystem
767 Format: ide?=noprobe or chipset specific parameters.
768 See Documentation/ide.txt.
770 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
771 See Documentation/ide.txt.
774 Format: idle=poll or idle=mwait
775 Poll forces a polling idle loop that can slightly improves the performance
776 of waking up a idle CPU, but will use a lot of power and make the system
777 run hot. Not recommended.
778 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
779 to not use it because it doesn't save as much power as a normal idle
780 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
783 ignore_loglevel [KNL]
784 Ignore loglevel setting - this will print /all/
785 kernel messages to the console. Useful for debugging.
788 Set number of hash buckets for inode cache.
791 See header of drivers/scsi/in2000.c.
795 Run specified binary instead of /sbin/init as init
798 initcall_debug [KNL] Trace initcalls as they are executed. Useful
799 for working out where the kernel is dying during
802 initrd= [BOOT] Specify the location of the initial ramdisk
804 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
809 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
811 Disable intel iommu driver.
812 igfx_off [Default Off]
813 By default, gfx is mapped as normal device. If a gfx
814 device has a dedicated DMAR unit, the DMAR unit is
815 bypassed by not enabling DMAR with this option. In
816 this case, gfx device will use physical address for
819 With this option iommu will not optimize to look
820 for io virtual address below 32 bit forcing dual
821 address cycle on pci bus for cards supporting greater
822 than 32 bit addressing. The default is to look
823 for translation below 32 bit and if not available
824 then look in the higher range.
826 io_delay= [X86-32,X86-64] I/O delay method
828 Standard port 0x80 based delay
830 Alternate port 0xed based delay (needed on some systems)
832 Simple two microseconds delay
836 io7= [HW] IO7 for Marvel based alpha systems
837 See comment before marvel_specify_io7 in
838 arch/alpha/kernel/core_marvel.c.
841 See Documentation/nfsroot.txt.
843 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
844 See comment before ip2_setup() in
845 drivers/char/ip2/ip2base.c.
847 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
848 See header of drivers/scsi/ips.c.
850 ports= [IP_VS_FTP] IPVS ftp helper module
852 Up to 8 (IP_VS_APP_MAX_PORTS) ports
854 Format: <port>,<port>....
857 When an interrupt is not handled search all handlers
858 for it. Intended to get systems with badly broken
862 When an interrupt is not handled search all handlers
863 for it. Also check all handlers each timer
864 interrupt. Intended to get systems with badly broken
868 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
870 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
872 <cpu number>,...,<cpu number>
874 <cpu number>-<cpu number> (must be a positive range in ascending order)
876 <cpu number>,...,<cpu number>-<cpu number>
877 This option can be used to specify one or more CPUs
878 to isolate from the general SMP balancing and scheduling
879 algorithms. The only way to move a process onto or off
880 an "isolated" CPU is via the CPU affinity syscalls.
881 <cpu number> begins at 0 and the maximum value is
882 "number of CPUs in system - 1".
884 This option is the preferred way to isolate CPUs. The
885 alternative -- manually setting the CPU mask of all
886 tasks in the system -- can cause problems and
887 suboptimal load balancer performance.
891 js= [HW,JOY] Analog joystick
892 See Documentation/input/joystick.txt.
894 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
895 specifies the amount of memory usable by the kernel
896 for non-movable allocations. The requested amount is
897 spread evenly throughout all nodes in the system. The
898 remaining memory in each node is used for Movable
899 pages. In the event, a node is too small to have both
900 kernelcore and Movable pages, kernelcore pages will
901 take priority and other nodes will have a larger number
902 of kernelcore pages. The Movable zone is used for the
903 allocation of pages that may be reclaimed or moved
904 by the page migration subsystem. This means that
905 HugeTLB pages may not be allocated from this zone.
906 Note that allocations like PTEs-from-HighMem still
907 use the HighMem zone if it exists, and the Normal
910 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
911 is similar to kernelcore except it specifies the
912 amount of memory used for migratable allocations.
913 If both kernelcore and movablecore is specified,
914 then kernelcore will be at *least* the specified
915 value but may be more. If movablecore on its own
916 is specified, the administrator must be careful
917 that the amount of memory usable for all allocations
922 kstack=N [X86-32,X86-64] Print N words from the kernel stack
927 lapic [X86-32,APIC] Enable the local APIC even if BIOS
930 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
933 libata.dma= [LIBATA] DMA control
934 libata.dma=0 Disable all PATA and SATA DMA
935 libata.dma=1 PATA and SATA Disk DMA only
936 libata.dma=2 ATAPI (CDROM) DMA only
937 libata.dma=4 Compact Flash DMA only
938 Combinations also work, so libata.dma=3 enables DMA
939 for disks and CDROMs, but not CFs.
941 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
945 load_ramdisk= [RAM] List of ramdisks to load from floppy
946 See Documentation/ramdisk.txt.
948 lockd.nlm_grace_period=P [NFS] Assign grace period.
951 lockd.nlm_tcpport=N [NFS] Assign TCP port.
954 lockd.nlm_timeout=T [NFS] Assign timeout value.
957 lockd.nlm_udpport=M [NFS] Assign UDP port.
960 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
963 loglevel= All Kernel Messages with a loglevel smaller than the
964 console loglevel will be printed to the console. It can
965 also be changed with klogd or other programs. The
966 loglevels are defined as follows:
968 0 (KERN_EMERG) system is unusable
969 1 (KERN_ALERT) action must be taken immediately
970 2 (KERN_CRIT) critical conditions
971 3 (KERN_ERR) error conditions
972 4 (KERN_WARNING) warning conditions
973 5 (KERN_NOTICE) normal but significant condition
974 6 (KERN_INFO) informational
975 7 (KERN_DEBUG) debug-level messages
977 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
978 Format: { n | nk | nM }
979 n must be a power of two. The default size
980 is set in the kernel config file.
982 logo.nologo [FB] Disables display of the built-in Linux logo.
983 This may be used to provide more screen space for
984 kernel log messages and is useful when debugging
985 kernel boot problems.
987 lp=0 [LP] Specify parallel ports to use, e.g,
988 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
989 lp=reset first parallel port). 'lp=0' disables the
990 lp=auto printer driver. 'lp=reset' (which can be
991 specified in addition to the ports) causes
992 attached printers to be reset. Using
993 lp=port1,port2,... specifies the parallel ports
994 to associate lp devices with, starting with
995 lp0. A port specification may be 'none' to skip
996 that lp device, or a parport name such as
997 'parport0'. Specifying 'lp=auto' instead of a
998 port specification list means that device IDs
999 from each port should be examined, to see if
1000 an IEEE 1284-compliant printer is attached; if
1001 so, the driver will manage that printer.
1002 See also header of drivers/char/lp.c.
1005 Sets loops_per_jiffy to given constant, thus avoiding
1006 time-consuming boot-time autodetection (up to 250 ms per
1007 CPU). 0 enables autodetection (default). To determine
1008 the correct value for your kernel, boot with normal
1009 autodetection and see what value is printed. Note that
1010 on SMP systems the preset will be applied to all CPUs,
1011 which is likely to cause problems if your CPUs need
1012 significantly divergent settings. An incorrect value
1013 will cause delays in the kernel to be wrong, leading to
1014 unpredictable I/O errors and other breakage. Although
1015 unlikely, in the extreme case this might damage your
1019 Format: <io>,<irq>,<dma>
1021 mac5380= [HW,SCSI] Format:
1022 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1024 mac53c9x= [HW,SCSI] Format:
1025 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1027 machvec= [IA64] Force the use of a particular machine-vector
1028 (machvec) in a generic kernel.
1029 Example: machvec=hpzx1_swiotlb
1031 max_loop= [LOOP] Maximum number of loopback devices that can
1035 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1036 should make use of. maxcpus=n : n >= 0 limits the
1037 kernel to using 'n' processors. n=0 is a special case,
1038 it is equivalent to "nosmp", which also disables
1041 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1042 equal to this physical address is ignored.
1044 max_luns= [SCSI] Maximum number of LUNs to probe.
1045 Should be between 1 and 2^32-1.
1048 [SCSI] Maximum number of LUNs received.
1049 Should be between 1 and 16384.
1051 mca-pentium [BUGS=X86-32]
1055 mce [X86-32] Machine Check Exception
1057 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1059 md= [HW] RAID subsystems devices and level
1060 See Documentation/md.txt.
1063 Format: <first>,<last>
1064 Specifies range of consoles to be captured by the MDA.
1066 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1067 Amount of memory to be used when the kernel is not able
1068 to see the whole system memory or for test.
1069 [X86-32] Use together with memmap= to avoid physical
1070 address space collisions. Without memmap= PCI devices
1071 could be placed at addresses belonging to unused RAM.
1073 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1076 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1077 E820 memory map, as specified by the user.
1078 Such memmap=exactmap lines can be constructed based on
1079 BIOS output or other requirements. See the memmap=nn@ss
1082 memmap=nn[KMG]@ss[KMG]
1083 [KNL] Force usage of a specific region of memory
1084 Region of memory to be used, from ss to ss+nn.
1086 memmap=nn[KMG]#ss[KMG]
1087 [KNL,ACPI] Mark specific memory as ACPI data.
1088 Region of memory to be used, from ss to ss+nn.
1090 memmap=nn[KMG]$ss[KMG]
1091 [KNL,ACPI] Mark specific memory as reserved.
1092 Region of memory to be used, from ss to ss+nn.
1094 meye.*= [HW] Set MotionEye Camera parameters
1095 See Documentation/video4linux/meye.txt.
1097 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1098 Multi-Function General Purpose Timers on AMD Geode
1101 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1102 the BIOS has incorrectly applied a workaround. TinyBIOS
1103 version 0.98 is known to be affected, 0.99 fixes the
1104 problem by letting the user disable the workaround.
1109 [MOUSE] Maximum time between finger touching and
1110 leaving touchpad surface for touch to be considered
1111 a tap and be reported as a left button click (for
1112 touchpads working in absolute mode only).
1114 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1115 reporting absolute coordinates, such as tablets
1116 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1117 reporting absolute coordinates, such as tablets
1122 MTD_Partition= [MTD]
1123 Format: <name>,<region-number>,<size>,<offset>
1125 MTD_Region= [MTD] Format:
1126 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1129 See drivers/mtd/cmdlinepart.c.
1131 mtouchusb.raw_coordinates=
1132 [HW] Make the MicroTouch USB driver use raw coordinates
1133 ('y', default) or cooked coordinates ('n')
1135 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1138 See header of drivers/scsi/NCR_D700.c.
1142 ncr53c400= [HW,SCSI]
1144 ncr53c400a= [HW,SCSI]
1146 ncr53c406a= [HW,SCSI]
1148 ncr53c8xx= [HW,SCSI]
1150 netdev= [NET] Network devices parameters
1151 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1152 Note that mem_start is often overloaded to mean
1153 something different and driver-specific.
1154 This usage is only documented in each driver source
1158 See Documentation/nfsroot.txt.
1160 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1161 See Documentation/nfsroot.txt.
1163 nfs.callback_tcpport=
1164 [NFS] set the TCP port on which the NFSv4 callback
1165 channel should listen.
1167 nfs.idmap_cache_timeout=
1168 [NFS] set the maximum lifetime for idmapper cache
1172 [NFS] enable 64-bit inode numbers.
1173 If zero, the NFS client will fake up a 32-bit inode
1174 number for the readdir() and stat() syscalls instead
1175 of returning the full 64-bit number.
1176 The default is to return 64-bit inode numbers.
1178 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1179 when a NMI is triggered.
1180 Format: [state][,regs][,debounce][,die]
1182 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1184 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1185 emulation library even if a 387 maths coprocessor
1188 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1189 caches in the slab allocator. Saves per-node memory,
1190 but will impact performance.
1194 noapic [SMP,APIC] Tells the kernel to not make use of any
1195 IOAPICs that may be present in the system.
1197 nobats [PPC] Do not use BATs for mapping kernel lowmem
1198 on "Classic" PPC cores.
1202 nodelayacct [KNL] Disable per-task delay accounting
1204 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1206 noefi [X86-32,X86-64] Disable EFI runtime services support.
1210 noexec [X86-32,X86-64]
1211 noexec=on: enable non-executable mappings (default)
1212 noexec=off: disable nn-executable mappings
1214 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1215 register save and restore. The kernel will only save
1216 legacy floating-point registers on task switch.
1218 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1222 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1223 instruction doesn't work correctly and not to
1226 nohalt [IA-64] Tells the kernel not to use the power saving
1227 function PAL_HALT_LIGHT when idle. This increases
1228 power-consumption. On the positive side, it reduces
1229 interrupt wake-up latency, which may improve performance
1230 in certain environments such as networked servers or
1233 nohz= [KNL] Boottime enable/disable dynamic ticks
1234 Valid arguments: on, off
1237 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1239 noirqdebug [X86-32] Disables the code which attempts to detect and
1240 disable unhandled interrupt sources.
1242 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1243 broken timer IRQ sources.
1245 noisapnp [ISAPNP] Disables ISA PnP code.
1247 noinitrd [RAM] Tells the kernel not to load any configured
1252 nojitter [IA64] Disables jitter checking for ITC timers.
1254 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1256 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1258 noltlbs [PPC] Do not use large page/tlb entries for kernel
1259 lowmem mapping on PPC40x.
1261 nomca [IA-64] Disable machine check abort handling
1263 nomce [X86-32] Machine Check Exception
1265 nomfgpt [X86-32] Disable Multi-Function General Purpose
1266 Timer usage (for AMD Geode machines).
1268 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1270 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1271 with UP alternatives
1273 noresidual [PPC] Don't use residual data on PReP machines.
1275 noresume [SWSUSP] Disables resume and restores original swap
1278 no-scroll [VGA] Disables scrollback.
1279 This is required for the Braillex ib80-piezo Braille
1280 reader made by F.H. Papenmeier (Germany).
1284 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1286 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1287 and disable the IO APIC. legacy for "maxcpus=0".
1289 nosoftlockup [KNL] Disable the soft-lockup detector.
1291 nosync [HW,M68K] Disables sync negotiation for all devices.
1293 notsc [BUGS=X86-32] Disable Time Stamp Counter
1295 nousb [USB] Disable the USB subsystem
1299 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1300 one of ['zone', 'node', 'default'] can be specified
1301 This can be set from sysctl after boot.
1302 See Documentation/sysctl/vm.txt for details.
1304 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1309 oprofile.timer= [HW]
1310 Use timer interrupt instead of performance counters
1312 osst= [HW,SCSI] SCSI Tape Driver
1313 Format: <buffer_size>,<write_threshold>
1314 See also Documentation/scsi/st.txt.
1316 panic= [KNL] Kernel behaviour on panic
1319 parkbd.port= [HW] Parallel port number the keyboard adapter is
1320 connected to, default is 0.
1322 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1323 0 for XT, 1 for AT (default is AT).
1326 parport= [HW,PPT] Specify parallel ports. 0 disables.
1327 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1328 Use 'auto' to force the driver to use any
1329 IRQ/DMA settings detected (the default is to
1330 ignore detected IRQ/DMA settings because of
1331 possible conflicts). You can specify the base
1332 address, IRQ, and DMA settings; IRQ and DMA
1333 should be numbers, or 'auto' (for using detected
1334 settings on that particular port), or 'nofifo'
1335 (to avoid using a FIFO even if it is detected).
1336 Parallel ports are assigned in the order they
1337 are specified on the command line, starting
1340 parport_init_mode= [HW,PPT]
1341 Configure VIA parallel port to operate in
1342 a specific mode. This is necessary on Pegasos
1343 computer where firmware has no options for setting
1344 up parallel port mode and sets it to spp.
1345 Currently this function knows 686a and 8231 chips.
1346 Format: [spp|ps2|epp|ecp|ecpepp]
1348 pas2= [HW,OSS] Format:
1349 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1352 See header of drivers/scsi/pas16.c.
1355 Halt all CPUs after the first oops has been printed for
1356 the specified number of seconds. This is to be used if
1357 your oopses keep scrolling off the screen.
1362 See header of drivers/block/paride/pcd.c.
1363 See also Documentation/paride.txt.
1365 pci=option[,option...] [PCI] various PCI subsystem options:
1366 off [X86-32] don't probe for the PCI bus
1367 bios [X86-32] force use of PCI BIOS, don't access
1368 the hardware directly. Use this if your machine
1369 has a non-standard PCI host bridge.
1370 nobios [X86-32] disallow use of PCI BIOS, only direct
1371 hardware access methods are allowed. Use this
1372 if you experience crashes upon bootup and you
1373 suspect they are caused by the BIOS.
1374 conf1 [X86-32] Force use of PCI Configuration
1376 conf2 [X86-32] Force use of PCI Configuration
1378 noaer [PCIE] If the PCIEAER kernel config parameter is
1379 enabled, this kernel boot option can be used to
1380 disable the use of PCIE advanced error reporting.
1381 nodomains [PCI] Disable support for multiple PCI
1382 root domains (aka PCI segments, in ACPI-speak).
1383 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1385 nomsi [MSI] If the PCI_MSI kernel config parameter is
1386 enabled, this kernel boot option can be used to
1387 disable the use of MSI interrupts system-wide.
1388 nosort [X86-32] Don't sort PCI devices according to
1389 order given by the PCI BIOS. This sorting is
1390 done to get a device order compatible with
1392 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1393 routing table. These calls are known to be buggy
1394 on several machines and they hang the machine
1395 when used, but on other computers it's the only
1396 way to get the interrupt routing table. Try
1397 this option if the kernel is unable to allocate
1398 IRQs or discover secondary PCI buses on your
1400 rom [X86-32] Assign address space to expansion ROMs.
1401 Use with caution as certain devices share
1402 address decoders between ROMs and other
1404 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1405 assigned automatically to PCI devices. You can
1406 make the kernel exclude IRQs of your ISA cards
1408 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1409 of the PIRQ table (normally generated
1410 by the BIOS) if it is outside the
1411 F0000h-100000h range.
1412 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1413 useful if the kernel is unable to find your
1414 secondary buses and you want to tell it
1415 explicitly which ones they are.
1416 assign-busses [X86-32] Always assign all PCI bus
1417 numbers ourselves, overriding
1418 whatever the firmware may have done.
1419 usepirqmask [X86-32] Honor the possible IRQ mask stored
1420 in the BIOS $PIR table. This is needed on
1421 some systems with broken BIOSes, notably
1422 some HP Pavilion N5400 and Omnibook XE3
1423 notebooks. This will have no effect if ACPI
1424 IRQ routing is enabled.
1425 noacpi [X86-32] Do not use ACPI for IRQ routing
1426 or for PCI scanning.
1427 use_crs [X86-32] Use _CRS for PCI resource
1429 routeirq Do IRQ routing for all PCI devices.
1430 This is normally done in pci_enable_device(),
1431 so this option is a temporary workaround
1432 for broken drivers that don't call it.
1433 firmware [ARM] Do not re-enumerate the bus but instead
1434 just use the configuration from the
1435 bootloader. This is currently used on
1436 IXP2000 systems where the bus has to be
1437 configured a certain way for adjunct CPUs.
1438 noearly [X86] Don't do any early type 1 scanning.
1439 This might help on some broken boards which
1440 machine check when some devices' config space
1441 is read. But various workarounds are disabled
1442 and some IOMMU drivers will not work.
1443 bfsort Sort PCI devices into breadth-first order.
1444 This sorting is done to get a device
1445 order compatible with older (<= 2.4) kernels.
1446 nobfsort Don't sort PCI devices into breadth-first order.
1447 cbiosize=nn[KMG] The fixed amount of bus space which is
1448 reserved for the CardBus bridge's IO window.
1449 The default value is 256 bytes.
1450 cbmemsize=nn[KMG] The fixed amount of bus space which is
1451 reserved for the CardBus bridge's memory
1452 window. The default value is 64 megabytes.
1454 pcmv= [HW,PCMCIA] BadgePAD 4
1457 See Documentation/paride.txt.
1459 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1462 See arch/parisc/kernel/pdc_chassis.c
1465 See Documentation/paride.txt.
1468 See Documentation/paride.txt.
1470 pirq= [SMP,APIC] Manual mp-table setup
1471 See Documentation/i386/IO-APIC.txt.
1473 plip= [PPT,NET] Parallel port network link
1474 Format: { parport<nr> | timid | 0 }
1475 See also Documentation/parport.txt.
1481 { on | off | curr | res | no-curr | no-res }
1484 [ISAPNP] Exclude IRQs for the autoconfiguration
1487 [ISAPNP] Exclude DMAs for the autoconfiguration
1489 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1490 Ranges are in pairs (I/O port base and size).
1493 [ISAPNP] Exclude memory regions for the
1495 Ranges are in pairs (memory base and size).
1497 print-fatal-signals=
1498 [KNL] debug: print fatal signals
1499 print-fatal-signals=1: print segfault info to
1503 printk.time= Show timing data prefixed to each printk message line
1504 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1506 profile= [KNL] Enable kernel profiling via /proc/profile
1507 Format: [schedule,]<number>
1508 Param: "schedule" - profile schedule points.
1509 Param: <number> - step/bucket size as a power of 2 for
1510 statistical time based profiling.
1511 Param: "sleep" - profile D-state sleeping (millisecs).
1512 Requires CONFIG_SCHEDSTATS
1513 Param: "kvm" - profile VM exits.
1515 processor.max_cstate= [HW,ACPI]
1516 Limit processor to maximum C-state
1517 max_cstate=9 overrides any DMI blacklist limit.
1519 processor.nocst [HW,ACPI]
1520 Ignore the _CST method to determine C-states,
1521 instead using the legacy FADT method
1523 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1525 See Documentation/ramdisk.txt.
1527 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1528 probe for; one of (bare|imps|exps|lifebook|any).
1529 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1531 psmouse.resetafter= [HW,MOUSE]
1532 Try to reset the device after so many bad packets
1535 [HW,MOUSE] Set desired mouse resolution, in dpi.
1536 psmouse.smartscroll=
1537 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1538 0 = disabled, 1 = enabled (default).
1540 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1542 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1545 See Documentation/paride.txt.
1548 [KNL] Number of legacy pty's. Overwrites compiled-in
1551 quiet [KNL] Disable most log messages
1556 See Documentation/md.txt.
1558 ramdisk_blocksize= [RAM]
1559 See Documentation/ramdisk.txt.
1561 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1562 See Documentation/ramdisk.txt.
1564 rcupdate.blimit= [KNL,BOOT]
1565 Set maximum number of finished RCU callbacks to process
1568 rcupdate.qhimark= [KNL,BOOT]
1569 Set threshold of queued
1570 RCU callbacks over which batch limiting is disabled.
1572 rcupdate.qlowmark= [KNL,BOOT]
1573 Set threshold of queued RCU callbacks below which
1574 batch limiting is re-enabled.
1578 Run specified binary instead of /init from the ramdisk,
1579 used for early userspace startup. See initrd.
1581 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1582 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1583 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1585 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1587 reservetop= [X86-32]
1589 Reserves a hole at the top of the kernel virtual
1592 reset_devices [KNL] Force drivers to reset the underlying device
1593 during initialization.
1596 Specify the partition device for software suspend
1598 resume_offset= [SWSUSP]
1599 Specify the offset from the beginning of the partition
1600 given by "resume=" at which the swap header is located,
1601 in <PAGE_SIZE> units (needed only for swap files).
1602 See Documentation/power/swsusp-and-swap-files.txt
1604 retain_initrd [RAM] Keep initrd memory after extraction
1606 rhash_entries= [KNL,NET]
1607 Set number of hash buckets for route cache
1609 riscom8= [HW,SERIAL]
1610 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1612 ro [KNL] Mount root device read-only on boot
1614 root= [KNL] Root filesystem
1616 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1617 mount the root filesystem
1619 rootflags= [KNL] Set root filesystem mount option string
1621 rootfstype= [KNL] Set root filesystem type
1623 rootwait [KNL] Wait (indefinitely) for root device to show up.
1624 Useful for devices that are detected asynchronously
1625 (e.g. USB and MMC devices).
1627 root_plug.vendor_id=
1628 [ROOTPLUG] Override the default vendor ID
1630 root_plug.product_id=
1631 [ROOTPLUG] Override the default product ID
1634 [ROOTPLUG] Enable debugging output
1636 rw [KNL] Mount root device read-write on boot
1638 S [KNL] Run init in single mode
1641 See drivers/net/irda/sa1100_ir.c.
1643 sbni= [NET] Granch SBNI12 leased line adapter
1645 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1646 Format: <io>[,<timeout>[,<isapnp>]]
1648 scsi_debug_*= [SCSI]
1649 See drivers/scsi/scsi_debug.c.
1651 scsi_default_dev_flags=
1652 [SCSI] SCSI default device flags
1655 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1656 Format: <vendor>:<model>:<flags>
1657 (flags are integer value)
1659 scsi_logging_level= [SCSI] a bit mask of logging levels
1660 See drivers/scsi/scsi_logging.h for bits. Also
1661 settable via sysctl at dev.scsi.logging_level
1662 (/proc/sys/dev/scsi/logging_level).
1663 There is also a nice 'scsi_logging_level' script in the
1664 S390-tools package, available for download at
1665 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1667 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1668 discovered. async scans them in kernel threads,
1669 allowing boot to proceed. none ignores them, expecting
1670 user space to do the scan.
1672 selinux [SELINUX] Disable or enable SELinux at boot time.
1673 Format: { "0" | "1" }
1674 See security/selinux/Kconfig help text.
1677 Default value is set via kernel config option.
1678 If enabled at boot time, /selinux/disable can be used
1679 later to disable prior to initial policy load.
1681 selinux_compat_net =
1682 [SELINUX] Set initial selinux_compat_net flag value.
1683 Format: { "0" | "1" }
1684 0 -- use new secmark-based packet controls
1685 1 -- use legacy packet controls
1686 Default value is 0 (preferred).
1687 Value can be changed at runtime via
1688 /selinux/compat_net.
1690 serialnumber [BUGS=X86-32]
1693 Maximal number of shapers.
1696 See header of drivers/scsi/sim710.c.
1703 slub_debug[=options[,slabs]] [MM, SLUB]
1704 Enabling slub_debug allows one to determine the
1705 culprit if slab objects become corrupted. Enabling
1706 slub_debug can create guard zones around objects and
1707 may poison objects when not in use. Also tracks the
1708 last alloc / free. For more information see
1709 Documentation/vm/slub.txt.
1711 slub_max_order= [MM, SLUB]
1712 Determines the maximum allowed order for slabs.
1713 A high setting may cause OOMs due to memory
1714 fragmentation. For more information see
1715 Documentation/vm/slub.txt.
1717 slub_min_objects= [MM, SLUB]
1718 The minimum number of objects per slab. SLUB will
1719 increase the slab order up to slub_max_order to
1720 generate a sufficiently large slab able to contain
1721 the number of objects indicated. The higher the number
1722 of objects the smaller the overhead of tracking slabs
1723 and the less frequently locks need to be acquired.
1724 For more information see Documentation/vm/slub.txt.
1726 slub_min_order= [MM, SLUB]
1727 Determines the mininum page order for slabs. Must be
1728 lower than slub_max_order.
1729 For more information see Documentation/vm/slub.txt.
1731 slub_nomerge [MM, SLUB]
1732 Disable merging of slabs with similar size. May be
1733 necessary if there is some reason to distinguish
1734 allocs to different slabs. Debug options disable
1735 merging on their own.
1736 For more information see Documentation/vm/slub.txt.
1739 Format: <io1>[,<io2>[,...,<io8>]]
1741 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1742 attempt to substitute SMP alternatives once at boot.
1744 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1745 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1746 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1747 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1748 smsc-ircc2.ircc_irq= [HW] IRQ line
1749 smsc-ircc2.ircc_dma= [HW] DMA channel
1750 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1751 0: Toshiba Satellite 1800 (GP data pin select)
1752 1: Fast pin select (default)
1755 snd-ad1816a= [HW,ALSA]
1757 snd-ad1848= [HW,ALSA]
1759 snd-ali5451= [HW,ALSA]
1761 snd-als100= [HW,ALSA]
1763 snd-als4000= [HW,ALSA]
1765 snd-azt2320= [HW,ALSA]
1767 snd-cmi8330= [HW,ALSA]
1769 snd-cmipci= [HW,ALSA]
1771 snd-cs4231= [HW,ALSA]
1773 snd-cs4232= [HW,ALSA]
1775 snd-cs4236= [HW,ALSA]
1777 snd-cs4281= [HW,ALSA]
1779 snd-cs46xx= [HW,ALSA]
1781 snd-dt019x= [HW,ALSA]
1783 snd-dummy= [HW,ALSA]
1785 snd-emu10k1= [HW,ALSA]
1787 snd-ens1370= [HW,ALSA]
1789 snd-ens1371= [HW,ALSA]
1791 snd-es968= [HW,ALSA]
1793 snd-es1688= [HW,ALSA]
1795 snd-es18xx= [HW,ALSA]
1797 snd-es1938= [HW,ALSA]
1799 snd-es1968= [HW,ALSA]
1801 snd-fm801= [HW,ALSA]
1803 snd-gusclassic= [HW,ALSA]
1805 snd-gusextreme= [HW,ALSA]
1807 snd-gusmax= [HW,ALSA]
1811 snd-ice1712= [HW,ALSA]
1813 snd-intel8x0= [HW,ALSA]
1815 snd-interwave= [HW,ALSA]
1820 snd-korg1212= [HW,ALSA]
1822 snd-maestro3= [HW,ALSA]
1824 snd-mpu401= [HW,ALSA]
1826 snd-mtpav= [HW,ALSA]
1828 snd-nm256= [HW,ALSA]
1830 snd-opl3sa2= [HW,ALSA]
1838 snd-opti93x= [HW,ALSA]
1842 snd-rme32= [HW,ALSA]
1844 snd-rme96= [HW,ALSA]
1846 snd-rme9652= [HW,ALSA]
1852 snd-sbawe= [HW,ALSA]
1854 snd-serial= [HW,ALSA]
1856 snd-sgalaxy= [HW,ALSA]
1858 snd-sonicvibes= [HW,ALSA]
1863 snd-sun-cs4231= [HW,ALSA]
1865 snd-trident= [HW,ALSA]
1867 snd-usb-audio= [HW,ALSA,USB]
1869 snd-via82xx= [HW,ALSA]
1871 snd-virmidi= [HW,ALSA]
1873 snd-wavefront= [HW,ALSA]
1875 snd-ymfpci= [HW,ALSA]
1877 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1878 See Documentation/sonypi.txt
1880 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1881 See Documentation/specialix.txt.
1883 spia_io_base= [HW,MTD]
1889 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1891 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1892 See Documentation/scsi/st.txt.
1896 Set the STI (builtin display/keyboard on the HP-PARISC
1897 machines) console (graphic card) which should be used
1898 as the initial boot-console.
1899 See also comment in drivers/video/console/sticore.c.
1902 See comment in drivers/video/console/sticore.c.
1905 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1909 Control how the NFS server code allocates CPUs to
1910 service thread pools. Depending on how many NICs
1911 you have and where their interrupts are bound, this
1912 option will affect which CPUs will do NFS serving.
1913 Note: this parameter cannot be changed while the
1914 NFS server is running.
1916 auto the server chooses an appropriate mode
1917 automatically using heuristics
1918 global a single global pool contains all CPUs
1919 percpu one pool for each CPU
1920 pernode one pool for each NUMA node (equivalent
1921 to global on non-NUMA machines)
1923 swiotlb= [IA-64] Number of I/O TLB slabs
1927 sym53c416= [HW,SCSI]
1928 See header of drivers/scsi/sym53c416.c.
1930 sysrq_always_enabled
1932 Ignore sysrq setting - this boot parameter will
1933 neutralize any effect of /proc/sys/kernel/sysrq.
1934 Useful for debugging.
1937 See header of drivers/scsi/t128.c.
1941 thash_entries= [KNL,NET]
1942 Set number of hash buckets for TCP connection
1944 thermal.act= [HW,ACPI]
1945 -1: disable all active trip points in all thermal zones
1946 <degrees C>: override all lowest active trip points
1948 thermal.crt= [HW,ACPI]
1949 -1: disable all critical trip points in all thermal zones
1950 <degrees C>: lower all critical trip points
1952 thermal.nocrt= [HW,ACPI]
1953 Set to disable actions on ACPI thermal zone
1954 critical and hot trip points.
1956 thermal.off= [HW,ACPI]
1957 1: disable ACPI thermal control
1959 thermal.psv= [HW,ACPI]
1960 -1: disable all passive trip points
1961 <degrees C>: override all passive trip points to this value
1963 thermal.tzp= [HW,ACPI]
1964 Specify global default ACPI thermal zone polling rate
1965 <deci-seconds>: poll all this frequency
1966 0: no polling (default)
1968 time Show timing data prefixed to each printk message line
1969 [deprecated, see 'printk.time']
1971 tipar.timeout= [HW,PPT]
1972 Set communications timeout in tenths of a second
1975 tipar.delay= [HW,PPT]
1976 Set inter-bit delay in microseconds (default 10).
1979 See comment before function dc390_setup() in
1980 drivers/scsi/tmscsim.c.
1984 trix= [HW,OSS] MediaTrix AudioTrix Pro
1986 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1988 turbografx.map[2|3]= [HW,JOY]
1989 TurboGraFX parallel port interface
1991 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1992 See also Documentation/input/joystick-parport.txt
1994 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1995 See header of drivers/scsi/u14-34f.c.
2004 [USB] Ignore overcurrent events (default N).
2005 Some badly-designed motherboards generate lots of
2006 bogus events, for ports that aren't wired to
2007 anything. Set this parameter to avoid log spamming.
2008 Note that genuine overcurrent events won't be
2011 usbcore.autosuspend=
2012 [USB] The autosuspend time delay (in seconds) used
2013 for newly-detected USB devices (default 2). This
2014 is the time required before an idle device will be
2015 autosuspended. Devices for which the delay is set
2016 to a negative value won't be autosuspended at all.
2019 [USBHID] The interval which mice are to be polled at.
2021 vdso= [X86-32,SH,x86-64]
2022 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2023 vdso=1: enable VDSO (default)
2024 vdso=0: disable VDSO mapping
2026 vdso32= [X86-32,X86-64]
2027 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2028 vdso32=1: enable 32-bit VDSO (default)
2029 vdso32=0: disable 32-bit VDSO mapping
2032 vector=percpu: enable percpu vector domain
2034 video= [FB] Frame buffer configuration
2035 See Documentation/fb/modedb.txt.
2037 vga= [BOOT,X86-32] Select a particular video mode
2038 See Documentation/i386/boot.txt and
2039 Documentation/svga.txt.
2040 Use vga=ask for menu.
2041 This is actually a boot loader parameter; the value is
2042 passed to the kernel using a special protocol.
2044 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2045 size of <nn>. This can be used to increase the
2046 minimum size (128MB on x86). It can also be used to
2047 decrease the size and leave more room for directly
2050 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2053 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2056 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2059 waveartist= [HW,OSS]
2060 Format: <io>,<irq>,<dma>,<dma2>
2063 See header of drivers/scsi/wd33c93.c.
2066 See header of drivers/scsi/wd7000.c.
2069 See Documentation/watchdog/wdt.txt.
2071 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2072 xd_geo= See header of drivers/block/xd.c.
2074 xirc2ps_cs= [NET,PCMCIA]
2076 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2078 norandmaps Don't use address space randomization
2079 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2081 ______________________________________________________________________
2085 Add documentation for ALSA options.
2086 Add more DRM drivers.