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 AX25 Appropriate AX.25 support is enabled.
38 BLACKFIN Blackfin architecture is enabled.
39 DRM Direct Rendering Management support is enabled.
40 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
41 EFI EFI Partitioning (GPT) is enabled
42 EIDE EIDE/ATAPI support is enabled.
43 FB The frame buffer device is enabled.
44 HW Appropriate hardware is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LIBATA Libata driver is enabled
52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
60 MSI Message Signaled Interrupts (PCI).
61 MTD MTD (Memory Technology Device) support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
64 GENERIC_TIME The generic timeofday code is enabled.
65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PV_OPS A paravirtualized kernel is enabled.
68 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
69 PARISC The PA-RISC architecture is enabled.
70 PCI PCI bus support is enabled.
71 PCIE PCI Express support is enabled.
72 PCMCIA The PCMCIA subsystem is enabled.
73 PNP Plug & Play support is enabled.
74 PPC PowerPC architecture is enabled.
75 PPT Parallel port support is enabled.
76 PS2 Appropriate PS/2 support is enabled.
77 RAM RAM disk support is enabled.
78 ROOTPLUG The example Root Plug LSM is enabled.
79 S390 S390 architecture is enabled.
80 SCSI Appropriate SCSI support is enabled.
81 A lot of drivers has their options described inside of
83 SECURITY Different security models are enabled.
84 SELINUX SELinux support is enabled.
85 SERIAL Serial support is enabled.
86 SH SuperH architecture is enabled.
87 SMP The kernel is an SMP kernel.
88 SPARC Sparc architecture is enabled.
89 SWSUSP Software suspend is enabled.
90 TS Appropriate touchscreen support is enabled.
91 USB USB support is enabled.
92 USBHID USB Human Interface Device support is enabled.
93 V4L Video For Linux support is enabled.
94 VGA The VGA console has been enabled.
95 VT Virtual terminal support is enabled.
96 WDT Watchdog support is enabled.
97 XT IBM PC/XT MFM hard disk support is enabled.
98 X86-32 X86-32, aka i386 architecture is enabled.
99 X86-64 X86-64 architecture is enabled.
100 More X86-64 boot options can be found in
101 Documentation/x86_64/boot-options.txt .
103 In addition, the following text indicates that the option:
105 BUGS= Relates to possible processor bugs on the said processor.
106 KNL Is a kernel start-up parameter.
107 BOOT Is a boot loader parameter.
109 Parameters denoted with BOOT are actually interpreted by the boot
110 loader, and have no meaning to the kernel directly.
111 Do not modify the syntax of boot loader parameters without extreme
112 need or coordination with <Documentation/i386/boot.txt>.
114 There are also arch-specific kernel-parameters not documented here.
115 See for example <Documentation/x86_64/boot-options.txt>.
117 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
118 a trailing = on the name of any parameter states that that parameter will
119 be entered as an environment variable, whereas its absence indicates that
120 it will appear as a kernel argument readable via /proc/cmdline by programs
121 running once the system is up.
123 The number of kernel parameters is not limited, but the length of the
124 complete command line (parameters including spaces etc.) is limited to
125 a fixed number of characters. This limit depends on the architecture
126 and is between 256 and 4096 characters. It is defined in the file
127 ./include/asm/setup.h as COMMAND_LINE_SIZE.
130 acpi= [HW,ACPI,X86-64,i386]
131 Advanced Configuration and Power Interface
132 Format: { force | off | ht | strict | noirq }
133 force -- enable ACPI if default was off
134 off -- disable ACPI if default was on
135 noirq -- do not use ACPI for IRQ routing
136 ht -- run only enough ACPI to enable Hyper Threading
137 strict -- Be less tolerant of platforms that are not
138 strictly ACPI specification compliant.
140 See also Documentation/pm.txt, pci=noacpi
142 acpi_apic_instance= [ACPI, IOAPIC]
144 2: use 2nd APIC table, if available
145 1,0: use 1st APIC table
148 acpi_sleep= [HW,ACPI] Sleep options
149 Format: { s3_bios, s3_mode }
150 See Documentation/power/video.txt
152 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
153 Format: { level | edge | high | low }
155 acpi_irq_balance [HW,ACPI]
156 ACPI will balance active IRQs
159 acpi_irq_nobalance [HW,ACPI]
160 ACPI will not move active IRQs (default)
163 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
165 Format: <irq>,<irq>...
167 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
168 Format: <irq>,<irq>...
170 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
172 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
173 Format: To spoof as Windows 98: ="Microsoft Windows"
175 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
176 acpi_osi="string1" # add string1 -- only one string
177 acpi_osi="!string2" # remove built-in string2
178 acpi_osi= # disable all strings
180 acpi_serialize [HW,ACPI] force serialization of AML methods
182 acpi_skip_timer_override [HW,ACPI]
183 Recognize and ignore IRQ0/pin2 Interrupt Override.
184 For broken nForce2 BIOS resulting in XT-PIC timer.
185 acpi_use_timer_override [HW,ACPI}
186 Use timer override. For some broken Nvidia NF5 boards
187 that require a timer override, but don't have
190 acpi.debug_layer= [HW,ACPI]
192 Each bit of the <int> indicates an ACPI debug layer,
193 1: enable, 0: disable. It is useful for boot time
194 debugging. After system has booted up, it can be set
195 via /sys/module/acpi/parameters/debug_layer.
196 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
197 Available bits (add the numbers together) to enable debug output
198 for specific parts of the ACPI subsystem:
199 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
200 0x10 namespace 0x20 parser 0x40 dispatcher
201 0x80 executer 0x100 resources 0x200 acpica debugger
202 0x400 os services 0x800 acpica disassembler.
203 The number can be in decimal or prefixed with 0x in hex.
204 Warning: Many of these options can produce a lot of
205 output and make your system unusable. Be very careful.
207 acpi.debug_level= [HW,ACPI]
209 Each bit of the <int> indicates an ACPI debug level,
210 1: enable, 0: disable. It is useful for boot time
211 debugging. After system has booted up, it can be set
212 via /sys/module/acpi/parameters/debug_level.
213 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
214 Available bits (add the numbers together) to enable different
215 debug output levels of the ACPI subsystem:
216 0x01 error 0x02 warn 0x04 init 0x08 debug object
217 0x10 info 0x20 init names 0x40 parse 0x80 load
218 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
219 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
220 0x10000 resources 0x20000 user requests 0x40000 package.
221 The number can be in decimal or prefixed with 0x in hex.
222 Warning: Many of these options can produce a lot of
223 output and make your system unusable. Be very careful.
225 acpi_pm_good [X86-32,X86-64]
226 Override the pmtimer bug detection: force the kernel
227 to assume that this machine's pmtimer latches its value
228 and always returns good values.
231 { off | try_unsupported }
232 off: disable AGP support
233 try_unsupported: try to drive unsupported chipsets
234 (may crash computer or cause data corruption)
236 enable_timer_pin_1 [i386,x86-64]
237 Enable PIN 1 of APIC timer
238 Can be useful to work around chipset bugs
239 (in particular on some ATI chipsets).
240 The kernel tries to set a reasonable default.
242 disable_timer_pin_1 [i386,x86-64]
243 Disable PIN 1 of APIC timer
244 Can be useful to work around chipset bugs.
247 Format: <io>,<irq>,<dma>,<dma2>,<type>
250 See header of drivers/scsi/advansys.c.
252 advwdt= [HW,WDT] Advantech WDT
253 Format: <iostart>,<iostop>
255 aedsp16= [HW,OSS] Audio Excel DSP 16
256 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
257 See also header of sound/oss/aedsp16.c.
260 See Documentation/scsi/aha152x.txt.
263 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
266 See Documentation/scsi/aic7xxx.txt.
269 See Documentation/scsi/aic79xx.txt.
271 amijoy.map= [HW,JOY] Amiga joystick support
272 Map of devices attached to JOY0DAT and JOY1DAT
274 See also Documentation/kernel/input/joystick.txt
276 analog.map= [HW,JOY] Analog joystick and gamepad support
277 Specifies type or capabilities of an analog joystick
278 connected to one of 16 gameports
279 Format: <type1>,<type2>,..<type16>
282 Power management functions (SPARCstation-4/5 + deriv.)
284 Disable APC CPU standby support. SPARCstation-Fox does
285 not play well with APC CPU idle - disable it if you have
286 APC and your system crashes randomly.
288 apic= [APIC,i386] Advanced Programmable Interrupt Controller
289 Change the output verbosity whilst booting
290 Format: { quiet (default) | verbose | debug }
291 Change the amount of debugging information output
292 when initialising the APIC and IO-APIC components.
294 apm= [APM] Advanced Power Management
295 See header of arch/i386/kernel/apm.c.
297 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
298 Format: <io>,<irq>,<nodeID>
302 atarimouse= [HW,MOUSE] Atari Mouse
304 atascsi= [HW,SCSI] Atari SCSI
306 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
307 EzKey and similar keyboards
309 atkbd.reset= [HW] Reset keyboard during initialization
311 atkbd.set= [HW] Select keyboard code set
312 Format: <int> (2 = AT (default), 3 = PS/2)
314 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
317 atkbd.softraw= [HW] Choose between synthetic and real raw mode
318 Format: <bool> (0 = real, 1 = synthetic (default))
320 atkbd.softrepeat= [HW]
321 Use software keyboard repeat
325 baycom_epp= [HW,AX25]
328 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
330 See header of drivers/net/hamradio/baycom_par.c.
332 baycom_ser_fdx= [HW,AX25]
333 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
334 Format: <io>,<irq>,<mode>[,<baud>]
335 See header of drivers/net/hamradio/baycom_ser_fdx.c.
337 baycom_ser_hdx= [HW,AX25]
338 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
339 Format: <io>,<irq>,<mode>
340 See header of drivers/net/hamradio/baycom_ser_hdx.c.
342 boot_delay= Milliseconds to delay each printk during boot.
343 Values larger than 10 seconds (10000) are changed to
347 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
348 bttv.radio= Most important insmod options are available as
350 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
351 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
354 See drivers/scsi/BusLogic.c, comment before function
355 BusLogic_ParseDriverOptions().
357 c101= [NET] Moxa C101 synchronous serial card
359 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
360 Sometimes CPU hardware bugs make them report the cache
361 size incorrectly. The kernel will attempt work arounds
362 to fix known problems, but for some CPUs it is not
363 possible to determine what the correct size should be.
364 This option provides an override for these situations.
367 [SECURITY] Disable capabilities. This would normally
368 be used only if an alternative security model is to be
369 configured. Potentially dangerous and should only be
370 used if you are entirely sure of the consequences.
372 chandev= [HW,NET] Generic channel device initialisation
374 checkreqprot [SELINUX] Set initial checkreqprot flag value.
375 Format: { "0" | "1" }
376 See security/selinux/Kconfig help text.
377 0 -- check protection applied by kernel (includes
378 any implied execute protection).
379 1 -- check protection requested by application.
380 Default value is set via a kernel config option.
381 Value can be changed at runtime via
382 /selinux/checkreqprot.
384 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
386 Forces specified clocksource (if available) to be used
387 when calculating gettimeofday(). If specified
388 clocksource is not available, it defaults to PIT.
389 Format: { pit | tsc | cyclone | pmtmr }
391 clocksource= [GENERIC_TIME] Override the default clocksource
393 Override the default clocksource and use the clocksource
394 with the name specified.
395 Some clocksource names to choose from, depending on
397 [all] jiffies (this is the base, fallback clocksource)
399 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
400 pxa_timer,timer3,32k_counter,timer0_1
402 [X86-32] pit,hpet,tsc,vmi-timer;
403 scx200_hrt on Geode; cyclone on IBM x440
411 code_bytes [IA32] How many bytes of object code to print in an
418 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
419 over the 8254 in addition to over the IO-APIC. The
420 kernel tries to set a sensible default.
422 hpet= [X86-32,HPET] option to control HPET usage
423 Format: { enable (default) | disable | force }
424 disable: disable HPET and use PIT instead
425 force: allow force enabled of undocumented chips (ICH4,
428 com20020= [HW,NET] ARCnet - COM20020 chipset
430 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
432 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
436 ARCnet - COM90xx chipset (memory-mapped buffers)
437 Format: <io>[,<irq>[,<memstart>]]
439 condev= [HW,S390] console device
442 console= [KNL] Output console device and options.
444 tty<n> Use the virtual console device <n>.
448 Use the specified serial port. The options are of
449 the form "bbbbpnf", where "bbbb" is the baud rate,
450 "p" is parity ("n", "o", or "e"), "n" is number of
451 bits, and "f" is flow control ("r" for RTS or
452 omit it). Default is "9600n8".
454 See Documentation/serial-console.txt for more
456 Documentation/networking/netconsole.txt for an
459 uart[8250],io,<addr>[,options]
460 uart[8250],mmio,<addr>[,options]
461 Start an early, polled-mode console on the 8250/16550
462 UART at the specified I/O port or MMIO address,
463 switching to the matching ttyS device later. The
464 options are the same as for ttyS, above.
466 earlycon= [KNL] Output early console device and options.
467 uart[8250],io,<addr>[,options]
468 uart[8250],mmio,<addr>[,options]
469 Start an early, polled-mode console on the 8250/16550
470 UART at the specified I/O port or MMIO address.
471 The options are the same as for ttyS, above.
474 [HW] Never suspend the console
475 Disable suspending of consoles during suspend and
476 hibernate operations. Once disabled, debugging
477 messages can reach various consoles while the rest
478 of the system is being put to sleep (ie, while
479 debugging driver suspend/resume hooks). This may
480 not work reliably with all consoles, but is known
481 to work with serial and VGA consoles.
483 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
485 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
487 crashkernel=nn[KMG]@ss[KMG]
488 [KNL] Reserve a chunk of physical memory to
489 hold a kernel to switch to with kexec on panic.
491 crashkernel=range1:size1[,range2:size2,...][@offset]
492 [KNL] Same as above, but depends on the memory
493 in the running system. The syntax of range is
494 start-[end] where start and end are both
495 a memory unit (amount[KMG]). See also
496 Documentation/kdump/kdump.txt for a example.
499 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
504 cs89x0_media= [HW,NET]
505 Format: { rj45 | aui | bnc }
508 See header of drivers/s390/block/dasd_devmap.c.
510 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
511 (one device per port)
512 Format: <port#>,<type>
513 See also Documentation/input/joystick-parport.txt
515 debug [KNL] Enable kernel debugging (events log level).
518 [KNL] verbose self-tests
520 Print debugging info while doing the locking API
522 We default to 0 (no extra messages), setting it to
523 1 will print _a lot_ more information - normally
524 only useful to kernel developers.
527 Format: <area>[,<node>]
528 See also Documentation/networking/decnet.txt.
531 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
532 Change the default blue palette of the console.
533 This is a 16-member array composed of values
537 Format: <green0>,<green1>,<green2>,...,<green15>
538 Change the default green palette of the console.
539 This is a 16-member array composed of values
543 Format: <red0>,<red1>,<red2>,...,<red15>
544 Change the default red palette of the console.
545 This is a 16-member array composed of values
551 Set system-wide default UTF-8 mode for all tty's.
552 Default is 1, i.e. UTF-8 mode is enabled for all
553 newly opened terminals.
556 Set number of hash buckets for dentry cache.
559 IO parameters + enable/disable command.
561 digiepca= [HW,SERIAL]
562 See drivers/char/README.epca and
563 Documentation/digiepca.txt.
565 dmasound= [HW,OSS] Sound subsystem buffers
571 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
573 earlyprintk=serial[,ttySn[,baudrate]]
575 Append ",keep" to not disable it when the real console
578 Only vga or serial at a time, not both.
580 Currently only ttyS0 and ttyS1 are supported.
582 Interaction with the standard serial driver is not
585 The VGA output is eventually overwritten by the real
591 Format: {"of[f]" | "sk[ipmbr]"}
592 See comment in arch/i386/boot/edd.S
594 eisa_irq_edge= [PARISC,HW]
595 See header of drivers/parisc/eisa.c.
598 See comment before function elanfreq_setup() in
599 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
602 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
603 See Documentation/block/as-iosched.txt and
604 Documentation/block/deadline-iosched.txt for details.
606 elfcorehdr= [X86-32, X86_64]
607 Specifies physical address of start of kernel core
608 image elf header. Generally kexec loader will
609 pass this option to capture kernel.
610 See Documentation/kdump/kdump.txt for details.
612 enforcing [SELINUX] Set initial enforcing status.
614 See security/selinux/Kconfig help text.
615 0 -- permissive (log only, no denials).
616 1 -- enforcing (deny and log).
618 Value can be changed at runtime via /selinux/enforce.
621 Format: <spdif>,[<nomix>,[<amplifier>]]
622 See also header of sound/oss/es1371.c.
624 ether= [HW,NET] Ethernet cards parameters
625 This option is obsoleted by the "netdev=" option, which
626 has equivalent usage. See its documentation for details.
628 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
633 fail_make_request=[KNL]
634 General fault injection mechanism.
635 Format: <interval>,<probability>,<space>,<times>
636 See also /Documentation/fault-injection/.
639 See header of drivers/scsi/fd_mcs.c.
642 See header of drivers/scsi/fdomain.c.
645 See Documentation/floppy.txt.
648 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
649 support via parallel port (up to 5 devices per port)
650 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
651 See also Documentation/input/joystick-parport.txt
656 See header of drivers/scsi/gdth.c.
658 gpt [EFI] Forces disk with valid GPT signature but
659 invalid Protective MBR to be treated as GPT.
663 hashdist= [KNL,NUMA] Large hashes allocated during boot
664 are distributed across NUMA nodes. Defaults on
665 for IA-64, off otherwise.
666 Format: 0 | 1 (for off | on)
668 hcl= [IA-64] SGI's Hardware Graph compatibility layer
670 hd= [EIDE] (E)IDE hard drive subsystem geometry
671 Format: <cyl>,<head>,<sect>
673 hd?= [HW] (E)IDE subsystem
674 hd?lun= See Documentation/ide.txt.
676 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
677 size of <nn>. This works even on boxes that have no
678 highmem otherwise. This also works to reduce highmem
679 size on bigger boxes.
681 highres= [KNL] Enable/disable high resolution timer mode.
682 Valid parameters: "on", "off"
686 See Documentation/isdn/README.HiSax.
688 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
690 i8042.direct [HW] Put keyboard port into non-translated mode
691 i8042.dumbkbd [HW] Pretend that controller can only read data from
692 keyboard and cannot control its state
693 (Don't attempt to blink the leds)
694 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
695 i8042.nokbd [HW] Don't check/create keyboard port
696 i8042.nomux [HW] Don't check presence of an active multiplexing
698 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
701 [HW] Frequency with which keyboard LEDs should blink
702 when kernel panics (default is 0.5 sec)
703 i8042.reset [HW] Reset the controller during init and cleanup
704 i8042.unlock [HW] Unlock (ignore) the keylock
708 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
709 indicates that the driver is running on unsupported
711 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
712 does not match list of supported models.
714 [HW] Report power status in /proc/i8k
715 (disabled by default)
716 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
719 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
720 See Documentation/mca.txt.
723 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
725 ide= [HW] (E)IDE subsystem
726 Format: ide=nodma or ide=doubler or ide=reverse
727 See Documentation/ide.txt.
729 ide?= [HW] (E)IDE subsystem
730 Format: ide?=noprobe or chipset specific parameters.
731 See Documentation/ide.txt.
733 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
734 See Documentation/ide.txt.
737 Format: idle=poll or idle=mwait
738 Poll forces a polling idle loop that can slightly improves the performance
739 of waking up a idle CPU, but will use a lot of power and make the system
740 run hot. Not recommended.
741 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
742 to not use it because it doesn't save as much power as a normal idle
743 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
746 ignore_loglevel [KNL]
747 Ignore loglevel setting - this will print /all/
748 kernel messages to the console. Useful for debugging.
751 Set number of hash buckets for inode cache.
754 See header of drivers/scsi/in2000.c.
758 Run specified binary instead of /sbin/init as init
761 initcall_debug [KNL] Trace initcalls as they are executed. Useful
762 for working out where the kernel is dying during
765 initrd= [BOOT] Specify the location of the initial ramdisk
767 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
772 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
774 Disable intel iommu driver.
775 igfx_off [Default Off]
776 By default, gfx is mapped as normal device. If a gfx
777 device has a dedicated DMAR unit, the DMAR unit is
778 bypassed by not enabling DMAR with this option. In
779 this case, gfx device will use physical address for
782 With this option iommu will not optimize to look
783 for io virtual address below 32 bit forcing dual
784 address cycle on pci bus for cards supporting greater
785 than 32 bit addressing. The default is to look
786 for translation below 32 bit and if not available
787 then look in the higher range.
789 io7= [HW] IO7 for Marvel based alpha systems
790 See comment before marvel_specify_io7 in
791 arch/alpha/kernel/core_marvel.c.
794 See Documentation/nfsroot.txt.
796 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
797 See comment before ip2_setup() in
798 drivers/char/ip2/ip2base.c.
800 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
801 See header of drivers/scsi/ips.c.
803 ports= [IP_VS_FTP] IPVS ftp helper module
805 Up to 8 (IP_VS_APP_MAX_PORTS) ports
807 Format: <port>,<port>....
810 When an interrupt is not handled search all handlers
811 for it. Intended to get systems with badly broken
815 When an interrupt is not handled search all handlers
816 for it. Also check all handlers each timer
817 interrupt. Intended to get systems with badly broken
821 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
823 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
825 <cpu number>,...,<cpu number>
827 <cpu number>-<cpu number> (must be a positive range in ascending order)
829 <cpu number>,...,<cpu number>-<cpu number>
830 This option can be used to specify one or more CPUs
831 to isolate from the general SMP balancing and scheduling
832 algorithms. The only way to move a process onto or off
833 an "isolated" CPU is via the CPU affinity syscalls.
834 <cpu number> begins at 0 and the maximum value is
835 "number of CPUs in system - 1".
837 This option is the preferred way to isolate CPUs. The
838 alternative -- manually setting the CPU mask of all
839 tasks in the system -- can cause problems and
840 suboptimal load balancer performance.
844 js= [HW,JOY] Analog joystick
845 See Documentation/input/joystick.txt.
847 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
848 specifies the amount of memory usable by the kernel
849 for non-movable allocations. The requested amount is
850 spread evenly throughout all nodes in the system. The
851 remaining memory in each node is used for Movable
852 pages. In the event, a node is too small to have both
853 kernelcore and Movable pages, kernelcore pages will
854 take priority and other nodes will have a larger number
855 of kernelcore pages. The Movable zone is used for the
856 allocation of pages that may be reclaimed or moved
857 by the page migration subsystem. This means that
858 HugeTLB pages may not be allocated from this zone.
859 Note that allocations like PTEs-from-HighMem still
860 use the HighMem zone if it exists, and the Normal
863 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
864 is similar to kernelcore except it specifies the
865 amount of memory used for migratable allocations.
866 If both kernelcore and movablecore is specified,
867 then kernelcore will be at *least* the specified
868 value but may be more. If movablecore on its own
869 is specified, the administrator must be careful
870 that the amount of memory usable for all allocations
875 kstack=N [X86-32,X86-64] Print N words from the kernel stack
880 lapic [X86-32,APIC] Enable the local APIC even if BIOS
883 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
886 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
890 load_ramdisk= [RAM] List of ramdisks to load from floppy
891 See Documentation/ramdisk.txt.
893 lockd.nlm_grace_period=P [NFS] Assign grace period.
896 lockd.nlm_tcpport=N [NFS] Assign TCP port.
899 lockd.nlm_timeout=T [NFS] Assign timeout value.
902 lockd.nlm_udpport=M [NFS] Assign UDP port.
905 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
908 loglevel= All Kernel Messages with a loglevel smaller than the
909 console loglevel will be printed to the console. It can
910 also be changed with klogd or other programs. The
911 loglevels are defined as follows:
913 0 (KERN_EMERG) system is unusable
914 1 (KERN_ALERT) action must be taken immediately
915 2 (KERN_CRIT) critical conditions
916 3 (KERN_ERR) error conditions
917 4 (KERN_WARNING) warning conditions
918 5 (KERN_NOTICE) normal but significant condition
919 6 (KERN_INFO) informational
920 7 (KERN_DEBUG) debug-level messages
922 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
923 Format: { n | nk | nM }
924 n must be a power of two. The default size
925 is set in the kernel config file.
927 logo.nologo [FB] Disables display of the built-in Linux logo.
928 This may be used to provide more screen space for
929 kernel log messages and is useful when debugging
930 kernel boot problems.
932 lp=0 [LP] Specify parallel ports to use, e.g,
933 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
934 lp=reset first parallel port). 'lp=0' disables the
935 lp=auto printer driver. 'lp=reset' (which can be
936 specified in addition to the ports) causes
937 attached printers to be reset. Using
938 lp=port1,port2,... specifies the parallel ports
939 to associate lp devices with, starting with
940 lp0. A port specification may be 'none' to skip
941 that lp device, or a parport name such as
942 'parport0'. Specifying 'lp=auto' instead of a
943 port specification list means that device IDs
944 from each port should be examined, to see if
945 an IEEE 1284-compliant printer is attached; if
946 so, the driver will manage that printer.
947 See also header of drivers/char/lp.c.
950 Sets loops_per_jiffy to given constant, thus avoiding
951 time-consuming boot-time autodetection (up to 250 ms per
952 CPU). 0 enables autodetection (default). To determine
953 the correct value for your kernel, boot with normal
954 autodetection and see what value is printed. Note that
955 on SMP systems the preset will be applied to all CPUs,
956 which is likely to cause problems if your CPUs need
957 significantly divergent settings. An incorrect value
958 will cause delays in the kernel to be wrong, leading to
959 unpredictable I/O errors and other breakage. Although
960 unlikely, in the extreme case this might damage your
964 Format: <io>,<irq>,<dma>
966 mac5380= [HW,SCSI] Format:
967 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
969 mac53c9x= [HW,SCSI] Format:
970 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
972 machvec= [IA64] Force the use of a particular machine-vector
973 (machvec) in a generic kernel.
974 Example: machvec=hpzx1_swiotlb
976 max_loop= [LOOP] Maximum number of loopback devices that can
980 maxcpus= [SMP] Maximum number of processors that an SMP kernel
981 should make use of. maxcpus=n : n >= 0 limits the
982 kernel to using 'n' processors. n=0 is a special case,
983 it is equivalent to "nosmp", which also disables
986 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
987 equal to this physical address is ignored.
989 max_luns= [SCSI] Maximum number of LUNs to probe.
990 Should be between 1 and 2^32-1.
993 [SCSI] Maximum number of LUNs received.
994 Should be between 1 and 16384.
996 mca-pentium [BUGS=X86-32]
1000 mce [X86-32] Machine Check Exception
1002 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1004 md= [HW] RAID subsystems devices and level
1005 See Documentation/md.txt.
1008 Format: <first>,<last>
1009 Specifies range of consoles to be captured by the MDA.
1011 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1012 Amount of memory to be used when the kernel is not able
1013 to see the whole system memory or for test.
1014 [X86-32] Use together with memmap= to avoid physical
1015 address space collisions. Without memmap= PCI devices
1016 could be placed at addresses belonging to unused RAM.
1018 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1021 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1022 E820 memory map, as specified by the user.
1023 Such memmap=exactmap lines can be constructed based on
1024 BIOS output or other requirements. See the memmap=nn@ss
1027 memmap=nn[KMG]@ss[KMG]
1028 [KNL] Force usage of a specific region of memory
1029 Region of memory to be used, from ss to ss+nn.
1031 memmap=nn[KMG]#ss[KMG]
1032 [KNL,ACPI] Mark specific memory as ACPI data.
1033 Region of memory to be used, from ss to ss+nn.
1035 memmap=nn[KMG]$ss[KMG]
1036 [KNL,ACPI] Mark specific memory as reserved.
1037 Region of memory to be used, from ss to ss+nn.
1039 meye.*= [HW] Set MotionEye Camera parameters
1040 See Documentation/video4linux/meye.txt.
1042 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1043 Multi-Function General Purpose Timers on AMD Geode
1049 [MOUSE] Maximum time between finger touching and
1050 leaving touchpad surface for touch to be considered
1051 a tap and be reported as a left button click (for
1052 touchpads working in absolute mode only).
1054 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1055 reporting absolute coordinates, such as tablets
1056 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1057 reporting absolute coordinates, such as tablets
1062 MTD_Partition= [MTD]
1063 Format: <name>,<region-number>,<size>,<offset>
1065 MTD_Region= [MTD] Format:
1066 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1069 See drivers/mtd/cmdlinepart.c.
1071 mtouchusb.raw_coordinates=
1072 [HW] Make the MicroTouch USB driver use raw coordinates
1073 ('y', default) or cooked coordinates ('n')
1075 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1078 See header of drivers/scsi/NCR_D700.c.
1082 ncr53c400= [HW,SCSI]
1084 ncr53c400a= [HW,SCSI]
1086 ncr53c406a= [HW,SCSI]
1088 ncr53c8xx= [HW,SCSI]
1090 netdev= [NET] Network devices parameters
1091 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1092 Note that mem_start is often overloaded to mean
1093 something different and driver-specific.
1094 This usage is only documented in each driver source
1098 See Documentation/nfsroot.txt.
1100 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1101 See Documentation/nfsroot.txt.
1103 nfs.callback_tcpport=
1104 [NFS] set the TCP port on which the NFSv4 callback
1105 channel should listen.
1107 nfs.idmap_cache_timeout=
1108 [NFS] set the maximum lifetime for idmapper cache
1112 [NFS] enable 64-bit inode numbers.
1113 If zero, the NFS client will fake up a 32-bit inode
1114 number for the readdir() and stat() syscalls instead
1115 of returning the full 64-bit number.
1116 The default is to return 64-bit inode numbers.
1118 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1120 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1121 emulation library even if a 387 maths coprocessor
1124 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1125 caches in the slab allocator. Saves per-node memory,
1126 but will impact performance.
1130 noapic [SMP,APIC] Tells the kernel to not make use of any
1131 IOAPICs that may be present in the system.
1133 nobats [PPC] Do not use BATs for mapping kernel lowmem
1134 on "Classic" PPC cores.
1138 nodelayacct [KNL] Disable per-task delay accounting
1140 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1144 noexec [X86-32,X86-64]
1145 noexec=on: enable non-executable mappings (default)
1146 noexec=off: disable nn-executable mappings
1148 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1149 register save and restore. The kernel will only save
1150 legacy floating-point registers on task switch.
1154 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1155 instruction doesn't work correctly and not to
1158 nohalt [IA-64] Tells the kernel not to use the power saving
1159 function PAL_HALT_LIGHT when idle. This increases
1160 power-consumption. On the positive side, it reduces
1161 interrupt wake-up latency, which may improve performance
1162 in certain environments such as networked servers or
1165 nohz= [KNL] Boottime enable/disable dynamic ticks
1166 Valid arguments: on, off
1169 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1171 noirqdebug [X86-32] Disables the code which attempts to detect and
1172 disable unhandled interrupt sources.
1174 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1175 broken timer IRQ sources.
1177 noisapnp [ISAPNP] Disables ISA PnP code.
1179 noinitrd [RAM] Tells the kernel not to load any configured
1184 nojitter [IA64] Disables jitter checking for ITC timers.
1186 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1188 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1190 noltlbs [PPC] Do not use large page/tlb entries for kernel
1191 lowmem mapping on PPC40x.
1193 nomca [IA-64] Disable machine check abort handling
1195 nomce [X86-32] Machine Check Exception
1197 nomfgpt [X86-32] Disable Multi-Function General Purpose
1198 Timer usage (for AMD Geode machines).
1200 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1202 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1203 with UP alternatives
1205 noresidual [PPC] Don't use residual data on PReP machines.
1207 noresume [SWSUSP] Disables resume and restores original swap
1210 no-scroll [VGA] Disables scrollback.
1211 This is required for the Braillex ib80-piezo Braille
1212 reader made by F.H. Papenmeier (Germany).
1216 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1218 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1219 and disable the IO APIC. legacy for "maxcpus=0".
1221 nosoftlockup [KNL] Disable the soft-lockup detector.
1223 nosync [HW,M68K] Disables sync negotiation for all devices.
1225 notsc [BUGS=X86-32] Disable Time Stamp Counter
1227 nousb [USB] Disable the USB subsystem
1231 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1232 one of ['zone', 'node', 'default'] can be specified
1233 This can be set from sysctl after boot.
1234 See Documentation/sysctl/vm.txt for details.
1236 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1241 oprofile.timer= [HW]
1242 Use timer interrupt instead of performance counters
1244 osst= [HW,SCSI] SCSI Tape Driver
1245 Format: <buffer_size>,<write_threshold>
1246 See also Documentation/scsi/st.txt.
1248 panic= [KNL] Kernel behaviour on panic
1251 parkbd.port= [HW] Parallel port number the keyboard adapter is
1252 connected to, default is 0.
1254 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1255 0 for XT, 1 for AT (default is AT).
1258 parport= [HW,PPT] Specify parallel ports. 0 disables.
1259 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1260 Use 'auto' to force the driver to use any
1261 IRQ/DMA settings detected (the default is to
1262 ignore detected IRQ/DMA settings because of
1263 possible conflicts). You can specify the base
1264 address, IRQ, and DMA settings; IRQ and DMA
1265 should be numbers, or 'auto' (for using detected
1266 settings on that particular port), or 'nofifo'
1267 (to avoid using a FIFO even if it is detected).
1268 Parallel ports are assigned in the order they
1269 are specified on the command line, starting
1272 parport_init_mode= [HW,PPT]
1273 Configure VIA parallel port to operate in
1274 a specific mode. This is necessary on Pegasos
1275 computer where firmware has no options for setting
1276 up parallel port mode and sets it to spp.
1277 Currently this function knows 686a and 8231 chips.
1278 Format: [spp|ps2|epp|ecp|ecpepp]
1280 pas2= [HW,OSS] Format:
1281 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1284 See header of drivers/scsi/pas16.c.
1287 Halt all CPUs after the first oops has been printed for
1288 the specified number of seconds. This is to be used if
1289 your oopses keep scrolling off the screen.
1294 See header of drivers/block/paride/pcd.c.
1295 See also Documentation/paride.txt.
1297 pci=option[,option...] [PCI] various PCI subsystem options:
1298 off [X86-32] don't probe for the PCI bus
1299 bios [X86-32] force use of PCI BIOS, don't access
1300 the hardware directly. Use this if your machine
1301 has a non-standard PCI host bridge.
1302 nobios [X86-32] disallow use of PCI BIOS, only direct
1303 hardware access methods are allowed. Use this
1304 if you experience crashes upon bootup and you
1305 suspect they are caused by the BIOS.
1306 conf1 [X86-32] Force use of PCI Configuration
1308 conf2 [X86-32] Force use of PCI Configuration
1310 noaer [PCIE] If the PCIEAER kernel config parameter is
1311 enabled, this kernel boot option can be used to
1312 disable the use of PCIE advanced error reporting.
1313 nodomains [PCI] Disable support for multiple PCI
1314 root domains (aka PCI segments, in ACPI-speak).
1315 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1317 nomsi [MSI] If the PCI_MSI kernel config parameter is
1318 enabled, this kernel boot option can be used to
1319 disable the use of MSI interrupts system-wide.
1320 nosort [X86-32] Don't sort PCI devices according to
1321 order given by the PCI BIOS. This sorting is
1322 done to get a device order compatible with
1324 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1325 routing table. These calls are known to be buggy
1326 on several machines and they hang the machine
1327 when used, but on other computers it's the only
1328 way to get the interrupt routing table. Try
1329 this option if the kernel is unable to allocate
1330 IRQs or discover secondary PCI buses on your
1332 rom [X86-32] Assign address space to expansion ROMs.
1333 Use with caution as certain devices share
1334 address decoders between ROMs and other
1336 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1337 assigned automatically to PCI devices. You can
1338 make the kernel exclude IRQs of your ISA cards
1340 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1341 of the PIRQ table (normally generated
1342 by the BIOS) if it is outside the
1343 F0000h-100000h range.
1344 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1345 useful if the kernel is unable to find your
1346 secondary buses and you want to tell it
1347 explicitly which ones they are.
1348 assign-busses [X86-32] Always assign all PCI bus
1349 numbers ourselves, overriding
1350 whatever the firmware may have done.
1351 usepirqmask [X86-32] Honor the possible IRQ mask stored
1352 in the BIOS $PIR table. This is needed on
1353 some systems with broken BIOSes, notably
1354 some HP Pavilion N5400 and Omnibook XE3
1355 notebooks. This will have no effect if ACPI
1356 IRQ routing is enabled.
1357 noacpi [X86-32] Do not use ACPI for IRQ routing
1358 or for PCI scanning.
1359 use_crs [X86-32] Use _CRS for PCI resource
1361 routeirq Do IRQ routing for all PCI devices.
1362 This is normally done in pci_enable_device(),
1363 so this option is a temporary workaround
1364 for broken drivers that don't call it.
1365 firmware [ARM] Do not re-enumerate the bus but instead
1366 just use the configuration from the
1367 bootloader. This is currently used on
1368 IXP2000 systems where the bus has to be
1369 configured a certain way for adjunct CPUs.
1370 noearly [X86] Don't do any early type 1 scanning.
1371 This might help on some broken boards which
1372 machine check when some devices' config space
1373 is read. But various workarounds are disabled
1374 and some IOMMU drivers will not work.
1375 bfsort Sort PCI devices into breadth-first order.
1376 This sorting is done to get a device
1377 order compatible with older (<= 2.4) kernels.
1378 nobfsort Don't sort PCI devices into breadth-first order.
1379 cbiosize=nn[KMG] The fixed amount of bus space which is
1380 reserved for the CardBus bridge's IO window.
1381 The default value is 256 bytes.
1382 cbmemsize=nn[KMG] The fixed amount of bus space which is
1383 reserved for the CardBus bridge's memory
1384 window. The default value is 64 megabytes.
1386 pcmv= [HW,PCMCIA] BadgePAD 4
1389 See Documentation/paride.txt.
1391 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1394 See arch/parisc/kernel/pdc_chassis.c
1397 See Documentation/paride.txt.
1400 See Documentation/paride.txt.
1402 pirq= [SMP,APIC] Manual mp-table setup
1403 See Documentation/i386/IO-APIC.txt.
1405 plip= [PPT,NET] Parallel port network link
1406 Format: { parport<nr> | timid | 0 }
1407 See also Documentation/parport.txt.
1413 { on | off | curr | res | no-curr | no-res }
1416 [ISAPNP] Exclude IRQs for the autoconfiguration
1419 [ISAPNP] Exclude DMAs for the autoconfiguration
1421 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1422 Ranges are in pairs (I/O port base and size).
1425 [ISAPNP] Exclude memory regions for the
1427 Ranges are in pairs (memory base and size).
1429 print-fatal-signals=
1430 [KNL] debug: print fatal signals
1431 print-fatal-signals=1: print segfault info to
1435 printk.time= Show timing data prefixed to each printk message line
1436 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1438 profile= [KNL] Enable kernel profiling via /proc/profile
1439 Format: [schedule,]<number>
1440 Param: "schedule" - profile schedule points.
1441 Param: <number> - step/bucket size as a power of 2 for
1442 statistical time based profiling.
1443 Param: "sleep" - profile D-state sleeping (millisecs).
1444 Requires CONFIG_SCHEDSTATS
1445 Param: "kvm" - profile VM exits.
1447 processor.max_cstate= [HW,ACPI]
1448 Limit processor to maximum C-state
1449 max_cstate=9 overrides any DMI blacklist limit.
1451 processor.nocst [HW,ACPI]
1452 Ignore the _CST method to determine C-states,
1453 instead using the legacy FADT method
1455 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1457 See Documentation/ramdisk.txt.
1459 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1460 probe for; one of (bare|imps|exps|lifebook|any).
1461 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1463 psmouse.resetafter= [HW,MOUSE]
1464 Try to reset the device after so many bad packets
1467 [HW,MOUSE] Set desired mouse resolution, in dpi.
1468 psmouse.smartscroll=
1469 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1470 0 = disabled, 1 = enabled (default).
1472 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1474 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1477 See Documentation/paride.txt.
1480 [KNL] Number of legacy pty's. Overwrites compiled-in
1483 quiet [KNL] Disable most log messages
1488 See Documentation/md.txt.
1490 ramdisk_blocksize= [RAM]
1491 See Documentation/ramdisk.txt.
1493 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1494 See Documentation/ramdisk.txt.
1496 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1497 RCU callbacks to process in one batch.
1499 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1500 RCU callbacks over which batch limiting is disabled.
1502 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1503 RCU callbacks below which batch limiting is re-enabled.
1507 Run specified binary instead of /init from the ramdisk,
1508 used for early userspace startup. See initrd.
1510 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1511 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1512 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1514 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1516 reservetop= [X86-32]
1518 Reserves a hole at the top of the kernel virtual
1521 reset_devices [KNL] Force drivers to reset the underlying device
1522 during initialization.
1525 Specify the partition device for software suspend
1527 resume_offset= [SWSUSP]
1528 Specify the offset from the beginning of the partition
1529 given by "resume=" at which the swap header is located,
1530 in <PAGE_SIZE> units (needed only for swap files).
1531 See Documentation/power/swsusp-and-swap-files.txt
1533 retain_initrd [RAM] Keep initrd memory after extraction
1535 rhash_entries= [KNL,NET]
1536 Set number of hash buckets for route cache
1538 riscom8= [HW,SERIAL]
1539 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1541 ro [KNL] Mount root device read-only on boot
1543 root= [KNL] Root filesystem
1545 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1546 mount the root filesystem
1548 rootflags= [KNL] Set root filesystem mount option string
1550 rootfstype= [KNL] Set root filesystem type
1552 rootwait [KNL] Wait (indefinitely) for root device to show up.
1553 Useful for devices that are detected asynchronously
1554 (e.g. USB and MMC devices).
1556 root_plug.vendor_id=
1557 [ROOTPLUG] Override the default vendor ID
1559 root_plug.product_id=
1560 [ROOTPLUG] Override the default product ID
1563 [ROOTPLUG] Enable debugging output
1565 rw [KNL] Mount root device read-write on boot
1567 S [KNL] Run init in single mode
1570 See drivers/net/irda/sa1100_ir.c.
1572 sbni= [NET] Granch SBNI12 leased line adapter
1574 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1575 Format: <io>[,<timeout>[,<isapnp>]]
1577 scsi_debug_*= [SCSI]
1578 See drivers/scsi/scsi_debug.c.
1580 scsi_default_dev_flags=
1581 [SCSI] SCSI default device flags
1584 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1585 Format: <vendor>:<model>:<flags>
1586 (flags are integer value)
1588 scsi_logging= [SCSI]
1590 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1591 discovered. async scans them in kernel threads,
1592 allowing boot to proceed. none ignores them, expecting
1593 user space to do the scan.
1595 selinux [SELINUX] Disable or enable SELinux at boot time.
1596 Format: { "0" | "1" }
1597 See security/selinux/Kconfig help text.
1600 Default value is set via kernel config option.
1601 If enabled at boot time, /selinux/disable can be used
1602 later to disable prior to initial policy load.
1604 selinux_compat_net =
1605 [SELINUX] Set initial selinux_compat_net flag value.
1606 Format: { "0" | "1" }
1607 0 -- use new secmark-based packet controls
1608 1 -- use legacy packet controls
1609 Default value is 0 (preferred).
1610 Value can be changed at runtime via
1611 /selinux/compat_net.
1613 serialnumber [BUGS=X86-32]
1616 Maximal number of shapers.
1619 See header of drivers/scsi/sim710.c.
1626 slub_debug[=options[,slabs]] [MM, SLUB]
1627 Enabling slub_debug allows one to determine the
1628 culprit if slab objects become corrupted. Enabling
1629 slub_debug can create guard zones around objects and
1630 may poison objects when not in use. Also tracks the
1631 last alloc / free. For more information see
1632 Documentation/vm/slub.txt.
1634 slub_max_order= [MM, SLUB]
1635 Determines the maximum allowed order for slabs.
1636 A high setting may cause OOMs due to memory
1637 fragmentation. For more information see
1638 Documentation/vm/slub.txt.
1640 slub_min_objects= [MM, SLUB]
1641 The minimum number of objects per slab. SLUB will
1642 increase the slab order up to slub_max_order to
1643 generate a sufficiently large slab able to contain
1644 the number of objects indicated. The higher the number
1645 of objects the smaller the overhead of tracking slabs
1646 and the less frequently locks need to be acquired.
1647 For more information see Documentation/vm/slub.txt.
1649 slub_min_order= [MM, SLUB]
1650 Determines the mininum page order for slabs. Must be
1651 lower than slub_max_order.
1652 For more information see Documentation/vm/slub.txt.
1654 slub_nomerge [MM, SLUB]
1655 Disable merging of slabs with similar size. May be
1656 necessary if there is some reason to distinguish
1657 allocs to different slabs. Debug options disable
1658 merging on their own.
1659 For more information see Documentation/vm/slub.txt.
1662 Format: <io1>[,<io2>[,...,<io8>]]
1664 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1665 attempt to substitute SMP alternatives once at boot.
1667 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1668 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1669 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1670 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1671 smsc-ircc2.ircc_irq= [HW] IRQ line
1672 smsc-ircc2.ircc_dma= [HW] DMA channel
1673 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1674 0: Toshiba Satellite 1800 (GP data pin select)
1675 1: Fast pin select (default)
1678 snd-ad1816a= [HW,ALSA]
1680 snd-ad1848= [HW,ALSA]
1682 snd-ali5451= [HW,ALSA]
1684 snd-als100= [HW,ALSA]
1686 snd-als4000= [HW,ALSA]
1688 snd-azt2320= [HW,ALSA]
1690 snd-cmi8330= [HW,ALSA]
1692 snd-cmipci= [HW,ALSA]
1694 snd-cs4231= [HW,ALSA]
1696 snd-cs4232= [HW,ALSA]
1698 snd-cs4236= [HW,ALSA]
1700 snd-cs4281= [HW,ALSA]
1702 snd-cs46xx= [HW,ALSA]
1704 snd-dt019x= [HW,ALSA]
1706 snd-dummy= [HW,ALSA]
1708 snd-emu10k1= [HW,ALSA]
1710 snd-ens1370= [HW,ALSA]
1712 snd-ens1371= [HW,ALSA]
1714 snd-es968= [HW,ALSA]
1716 snd-es1688= [HW,ALSA]
1718 snd-es18xx= [HW,ALSA]
1720 snd-es1938= [HW,ALSA]
1722 snd-es1968= [HW,ALSA]
1724 snd-fm801= [HW,ALSA]
1726 snd-gusclassic= [HW,ALSA]
1728 snd-gusextreme= [HW,ALSA]
1730 snd-gusmax= [HW,ALSA]
1734 snd-ice1712= [HW,ALSA]
1736 snd-intel8x0= [HW,ALSA]
1738 snd-interwave= [HW,ALSA]
1743 snd-korg1212= [HW,ALSA]
1745 snd-maestro3= [HW,ALSA]
1747 snd-mpu401= [HW,ALSA]
1749 snd-mtpav= [HW,ALSA]
1751 snd-nm256= [HW,ALSA]
1753 snd-opl3sa2= [HW,ALSA]
1761 snd-opti93x= [HW,ALSA]
1765 snd-rme32= [HW,ALSA]
1767 snd-rme96= [HW,ALSA]
1769 snd-rme9652= [HW,ALSA]
1775 snd-sbawe= [HW,ALSA]
1777 snd-serial= [HW,ALSA]
1779 snd-sgalaxy= [HW,ALSA]
1781 snd-sonicvibes= [HW,ALSA]
1786 snd-sun-cs4231= [HW,ALSA]
1788 snd-trident= [HW,ALSA]
1790 snd-usb-audio= [HW,ALSA,USB]
1792 snd-via82xx= [HW,ALSA]
1794 snd-virmidi= [HW,ALSA]
1796 snd-wavefront= [HW,ALSA]
1798 snd-ymfpci= [HW,ALSA]
1800 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1801 See Documentation/sonypi.txt
1803 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1804 See Documentation/specialix.txt.
1806 spia_io_base= [HW,MTD]
1812 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1814 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1815 See Documentation/scsi/st.txt.
1818 See header of drivers/scsi/seagate.c.
1822 Set the STI (builtin display/keyboard on the HP-PARISC
1823 machines) console (graphic card) which should be used
1824 as the initial boot-console.
1825 See also comment in drivers/video/console/sticore.c.
1828 See comment in drivers/video/console/sticore.c.
1831 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1835 Control how the NFS server code allocates CPUs to
1836 service thread pools. Depending on how many NICs
1837 you have and where their interrupts are bound, this
1838 option will affect which CPUs will do NFS serving.
1839 Note: this parameter cannot be changed while the
1840 NFS server is running.
1842 auto the server chooses an appropriate mode
1843 automatically using heuristics
1844 global a single global pool contains all CPUs
1845 percpu one pool for each CPU
1846 pernode one pool for each NUMA node (equivalent
1847 to global on non-NUMA machines)
1849 swiotlb= [IA-64] Number of I/O TLB slabs
1853 sym53c416= [HW,SCSI]
1854 See header of drivers/scsi/sym53c416.c.
1856 sysrq_always_enabled
1858 Ignore sysrq setting - this boot parameter will
1859 neutralize any effect of /proc/sys/kernel/sysrq.
1860 Useful for debugging.
1863 See header of drivers/scsi/t128.c.
1867 thash_entries= [KNL,NET]
1868 Set number of hash buckets for TCP connection
1870 thermal.act= [HW,ACPI]
1871 -1: disable all active trip points in all thermal zones
1872 <degrees C>: override all lowest active trip points
1874 thermal.crt= [HW,ACPI]
1875 -1: disable all critical trip points in all thermal zones
1876 <degrees C>: lower all critical trip points
1878 thermal.nocrt= [HW,ACPI]
1879 Set to disable actions on ACPI thermal zone
1880 critical and hot trip points.
1882 thermal.off= [HW,ACPI]
1883 1: disable ACPI thermal control
1885 thermal.psv= [HW,ACPI]
1886 -1: disable all passive trip points
1887 <degrees C>: override all passive trip points to this value
1889 thermal.tzp= [HW,ACPI]
1890 Specify global default ACPI thermal zone polling rate
1891 <deci-seconds>: poll all this frequency
1892 0: no polling (default)
1894 time Show timing data prefixed to each printk message line
1895 [deprecated, see 'printk.time']
1897 tipar.timeout= [HW,PPT]
1898 Set communications timeout in tenths of a second
1901 tipar.delay= [HW,PPT]
1902 Set inter-bit delay in microseconds (default 10).
1905 See header of drivers/scsi/seagate.c.
1908 See comment before function dc390_setup() in
1909 drivers/scsi/tmscsim.c.
1913 trix= [HW,OSS] MediaTrix AudioTrix Pro
1915 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1917 turbografx.map[2|3]= [HW,JOY]
1918 TurboGraFX parallel port interface
1920 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1921 See also Documentation/input/joystick-parport.txt
1923 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1924 See header of drivers/scsi/u14-34f.c.
1933 [USB] Ignore overcurrent events (default N).
1934 Some badly-designed motherboards generate lots of
1935 bogus events, for ports that aren't wired to
1936 anything. Set this parameter to avoid log spamming.
1937 Note that genuine overcurrent events won't be
1940 usbcore.autosuspend=
1941 [USB] The autosuspend time delay (in seconds) used
1942 for newly-detected USB devices (default 2). This
1943 is the time required before an idle device will be
1944 autosuspended. Devices for which the delay is set
1945 to a negative value won't be autosuspended at all.
1948 [USBHID] The interval which mice are to be polled at.
1950 vdso= [X86-32,SH,x86-64]
1951 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1952 vdso=1: enable VDSO (default)
1953 vdso=0: disable VDSO mapping
1956 vector=percpu: enable percpu vector domain
1958 video= [FB] Frame buffer configuration
1959 See Documentation/fb/modedb.txt.
1961 vga= [BOOT,X86-32] Select a particular video mode
1962 See Documentation/i386/boot.txt and
1963 Documentation/svga.txt.
1964 Use vga=ask for menu.
1965 This is actually a boot loader parameter; the value is
1966 passed to the kernel using a special protocol.
1968 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1969 size of <nn>. This can be used to increase the
1970 minimum size (128MB on x86). It can also be used to
1971 decrease the size and leave more room for directly
1974 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1977 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1980 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1983 waveartist= [HW,OSS]
1984 Format: <io>,<irq>,<dma>,<dma2>
1987 See header of drivers/scsi/wd33c93.c.
1990 See header of drivers/scsi/wd7000.c.
1993 See Documentation/watchdog/wdt.txt.
1995 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1996 xd_geo= See header of drivers/block/xd.c.
1998 xirc2ps_cs= [NET,PCMCIA]
2000 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2002 norandmaps Don't use address space randomization
2003 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2005 ______________________________________________________________________
2009 Add documentation for ALSA options.
2010 Add more DRM drivers.