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.
689 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
691 i8042.direct [HW] Put keyboard port into non-translated mode
692 i8042.dumbkbd [HW] Pretend that controller can only read data from
693 keyboard and cannot control its state
694 (Don't attempt to blink the leds)
695 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
696 i8042.nokbd [HW] Don't check/create keyboard port
697 i8042.nomux [HW] Don't check presence of an active multiplexing
699 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
702 [HW] Frequency with which keyboard LEDs should blink
703 when kernel panics (default is 0.5 sec)
704 i8042.reset [HW] Reset the controller during init and cleanup
705 i8042.unlock [HW] Unlock (ignore) the keylock
709 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
710 indicates that the driver is running on unsupported
712 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
713 does not match list of supported models.
715 [HW] Report power status in /proc/i8k
716 (disabled by default)
717 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
720 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
721 See Documentation/mca.txt.
724 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
726 ide= [HW] (E)IDE subsystem
727 Format: ide=nodma or ide=doubler or ide=reverse
728 See Documentation/ide.txt.
730 ide?= [HW] (E)IDE subsystem
731 Format: ide?=noprobe or chipset specific parameters.
732 See Documentation/ide.txt.
734 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
735 See Documentation/ide.txt.
738 Format: idle=poll or idle=mwait
739 Poll forces a polling idle loop that can slightly improves the performance
740 of waking up a idle CPU, but will use a lot of power and make the system
741 run hot. Not recommended.
742 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
743 to not use it because it doesn't save as much power as a normal idle
744 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
747 ignore_loglevel [KNL]
748 Ignore loglevel setting - this will print /all/
749 kernel messages to the console. Useful for debugging.
752 Set number of hash buckets for inode cache.
755 See header of drivers/scsi/in2000.c.
759 Run specified binary instead of /sbin/init as init
762 initcall_debug [KNL] Trace initcalls as they are executed. Useful
763 for working out where the kernel is dying during
766 initrd= [BOOT] Specify the location of the initial ramdisk
768 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
773 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
775 Disable intel iommu driver.
776 igfx_off [Default Off]
777 By default, gfx is mapped as normal device. If a gfx
778 device has a dedicated DMAR unit, the DMAR unit is
779 bypassed by not enabling DMAR with this option. In
780 this case, gfx device will use physical address for
783 With this option iommu will not optimize to look
784 for io virtual address below 32 bit forcing dual
785 address cycle on pci bus for cards supporting greater
786 than 32 bit addressing. The default is to look
787 for translation below 32 bit and if not available
788 then look in the higher range.
790 io7= [HW] IO7 for Marvel based alpha systems
791 See comment before marvel_specify_io7 in
792 arch/alpha/kernel/core_marvel.c.
795 See Documentation/nfsroot.txt.
797 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
798 See comment before ip2_setup() in
799 drivers/char/ip2/ip2base.c.
801 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
802 See header of drivers/scsi/ips.c.
804 ports= [IP_VS_FTP] IPVS ftp helper module
806 Up to 8 (IP_VS_APP_MAX_PORTS) ports
808 Format: <port>,<port>....
811 When an interrupt is not handled search all handlers
812 for it. Intended to get systems with badly broken
816 When an interrupt is not handled search all handlers
817 for it. Also check all handlers each timer
818 interrupt. Intended to get systems with badly broken
822 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
824 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
826 <cpu number>,...,<cpu number>
828 <cpu number>-<cpu number> (must be a positive range in ascending order)
830 <cpu number>,...,<cpu number>-<cpu number>
831 This option can be used to specify one or more CPUs
832 to isolate from the general SMP balancing and scheduling
833 algorithms. The only way to move a process onto or off
834 an "isolated" CPU is via the CPU affinity syscalls.
835 <cpu number> begins at 0 and the maximum value is
836 "number of CPUs in system - 1".
838 This option is the preferred way to isolate CPUs. The
839 alternative -- manually setting the CPU mask of all
840 tasks in the system -- can cause problems and
841 suboptimal load balancer performance.
845 js= [HW,JOY] Analog joystick
846 See Documentation/input/joystick.txt.
848 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
849 specifies the amount of memory usable by the kernel
850 for non-movable allocations. The requested amount is
851 spread evenly throughout all nodes in the system. The
852 remaining memory in each node is used for Movable
853 pages. In the event, a node is too small to have both
854 kernelcore and Movable pages, kernelcore pages will
855 take priority and other nodes will have a larger number
856 of kernelcore pages. The Movable zone is used for the
857 allocation of pages that may be reclaimed or moved
858 by the page migration subsystem. This means that
859 HugeTLB pages may not be allocated from this zone.
860 Note that allocations like PTEs-from-HighMem still
861 use the HighMem zone if it exists, and the Normal
864 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
865 is similar to kernelcore except it specifies the
866 amount of memory used for migratable allocations.
867 If both kernelcore and movablecore is specified,
868 then kernelcore will be at *least* the specified
869 value but may be more. If movablecore on its own
870 is specified, the administrator must be careful
871 that the amount of memory usable for all allocations
876 kstack=N [X86-32,X86-64] Print N words from the kernel stack
881 lapic [X86-32,APIC] Enable the local APIC even if BIOS
884 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
887 libata.dma= [LIBATA] DMA control
888 libata.dma=0 Disable all PATA and SATA DMA
889 libata.dma=1 PATA and SATA Disk DMA only
890 libata.dma=2 ATAPI (CDROM) DMA only
891 libata.dma=4 Compact Flash DMA only
892 Combinations also work, so libata.dma=3 enables DMA
893 for disks and CDROMs, but not CFs.
895 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
899 load_ramdisk= [RAM] List of ramdisks to load from floppy
900 See Documentation/ramdisk.txt.
902 lockd.nlm_grace_period=P [NFS] Assign grace period.
905 lockd.nlm_tcpport=N [NFS] Assign TCP port.
908 lockd.nlm_timeout=T [NFS] Assign timeout value.
911 lockd.nlm_udpport=M [NFS] Assign UDP port.
914 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
917 loglevel= All Kernel Messages with a loglevel smaller than the
918 console loglevel will be printed to the console. It can
919 also be changed with klogd or other programs. The
920 loglevels are defined as follows:
922 0 (KERN_EMERG) system is unusable
923 1 (KERN_ALERT) action must be taken immediately
924 2 (KERN_CRIT) critical conditions
925 3 (KERN_ERR) error conditions
926 4 (KERN_WARNING) warning conditions
927 5 (KERN_NOTICE) normal but significant condition
928 6 (KERN_INFO) informational
929 7 (KERN_DEBUG) debug-level messages
931 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
932 Format: { n | nk | nM }
933 n must be a power of two. The default size
934 is set in the kernel config file.
936 logo.nologo [FB] Disables display of the built-in Linux logo.
937 This may be used to provide more screen space for
938 kernel log messages and is useful when debugging
939 kernel boot problems.
941 lp=0 [LP] Specify parallel ports to use, e.g,
942 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
943 lp=reset first parallel port). 'lp=0' disables the
944 lp=auto printer driver. 'lp=reset' (which can be
945 specified in addition to the ports) causes
946 attached printers to be reset. Using
947 lp=port1,port2,... specifies the parallel ports
948 to associate lp devices with, starting with
949 lp0. A port specification may be 'none' to skip
950 that lp device, or a parport name such as
951 'parport0'. Specifying 'lp=auto' instead of a
952 port specification list means that device IDs
953 from each port should be examined, to see if
954 an IEEE 1284-compliant printer is attached; if
955 so, the driver will manage that printer.
956 See also header of drivers/char/lp.c.
959 Sets loops_per_jiffy to given constant, thus avoiding
960 time-consuming boot-time autodetection (up to 250 ms per
961 CPU). 0 enables autodetection (default). To determine
962 the correct value for your kernel, boot with normal
963 autodetection and see what value is printed. Note that
964 on SMP systems the preset will be applied to all CPUs,
965 which is likely to cause problems if your CPUs need
966 significantly divergent settings. An incorrect value
967 will cause delays in the kernel to be wrong, leading to
968 unpredictable I/O errors and other breakage. Although
969 unlikely, in the extreme case this might damage your
973 Format: <io>,<irq>,<dma>
975 mac5380= [HW,SCSI] Format:
976 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
978 mac53c9x= [HW,SCSI] Format:
979 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
981 machvec= [IA64] Force the use of a particular machine-vector
982 (machvec) in a generic kernel.
983 Example: machvec=hpzx1_swiotlb
985 max_loop= [LOOP] Maximum number of loopback devices that can
989 maxcpus= [SMP] Maximum number of processors that an SMP kernel
990 should make use of. maxcpus=n : n >= 0 limits the
991 kernel to using 'n' processors. n=0 is a special case,
992 it is equivalent to "nosmp", which also disables
995 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
996 equal to this physical address is ignored.
998 max_luns= [SCSI] Maximum number of LUNs to probe.
999 Should be between 1 and 2^32-1.
1002 [SCSI] Maximum number of LUNs received.
1003 Should be between 1 and 16384.
1005 mca-pentium [BUGS=X86-32]
1009 mce [X86-32] Machine Check Exception
1011 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1013 md= [HW] RAID subsystems devices and level
1014 See Documentation/md.txt.
1017 Format: <first>,<last>
1018 Specifies range of consoles to be captured by the MDA.
1020 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1021 Amount of memory to be used when the kernel is not able
1022 to see the whole system memory or for test.
1023 [X86-32] Use together with memmap= to avoid physical
1024 address space collisions. Without memmap= PCI devices
1025 could be placed at addresses belonging to unused RAM.
1027 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1030 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1031 E820 memory map, as specified by the user.
1032 Such memmap=exactmap lines can be constructed based on
1033 BIOS output or other requirements. See the memmap=nn@ss
1036 memmap=nn[KMG]@ss[KMG]
1037 [KNL] Force usage of a specific region of memory
1038 Region of memory to be used, from ss to ss+nn.
1040 memmap=nn[KMG]#ss[KMG]
1041 [KNL,ACPI] Mark specific memory as ACPI data.
1042 Region of memory to be used, from ss to ss+nn.
1044 memmap=nn[KMG]$ss[KMG]
1045 [KNL,ACPI] Mark specific memory as reserved.
1046 Region of memory to be used, from ss to ss+nn.
1048 meye.*= [HW] Set MotionEye Camera parameters
1049 See Documentation/video4linux/meye.txt.
1051 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1052 Multi-Function General Purpose Timers on AMD Geode
1058 [MOUSE] Maximum time between finger touching and
1059 leaving touchpad surface for touch to be considered
1060 a tap and be reported as a left button click (for
1061 touchpads working in absolute mode only).
1063 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1064 reporting absolute coordinates, such as tablets
1065 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1066 reporting absolute coordinates, such as tablets
1071 MTD_Partition= [MTD]
1072 Format: <name>,<region-number>,<size>,<offset>
1074 MTD_Region= [MTD] Format:
1075 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1078 See drivers/mtd/cmdlinepart.c.
1080 mtouchusb.raw_coordinates=
1081 [HW] Make the MicroTouch USB driver use raw coordinates
1082 ('y', default) or cooked coordinates ('n')
1084 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1087 See header of drivers/scsi/NCR_D700.c.
1091 ncr53c400= [HW,SCSI]
1093 ncr53c400a= [HW,SCSI]
1095 ncr53c406a= [HW,SCSI]
1097 ncr53c8xx= [HW,SCSI]
1099 netdev= [NET] Network devices parameters
1100 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1101 Note that mem_start is often overloaded to mean
1102 something different and driver-specific.
1103 This usage is only documented in each driver source
1107 See Documentation/nfsroot.txt.
1109 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1110 See Documentation/nfsroot.txt.
1112 nfs.callback_tcpport=
1113 [NFS] set the TCP port on which the NFSv4 callback
1114 channel should listen.
1116 nfs.idmap_cache_timeout=
1117 [NFS] set the maximum lifetime for idmapper cache
1121 [NFS] enable 64-bit inode numbers.
1122 If zero, the NFS client will fake up a 32-bit inode
1123 number for the readdir() and stat() syscalls instead
1124 of returning the full 64-bit number.
1125 The default is to return 64-bit inode numbers.
1127 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1129 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1130 emulation library even if a 387 maths coprocessor
1133 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1134 caches in the slab allocator. Saves per-node memory,
1135 but will impact performance.
1139 noapic [SMP,APIC] Tells the kernel to not make use of any
1140 IOAPICs that may be present in the system.
1142 nobats [PPC] Do not use BATs for mapping kernel lowmem
1143 on "Classic" PPC cores.
1147 nodelayacct [KNL] Disable per-task delay accounting
1149 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1153 noexec [X86-32,X86-64]
1154 noexec=on: enable non-executable mappings (default)
1155 noexec=off: disable nn-executable mappings
1157 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1158 register save and restore. The kernel will only save
1159 legacy floating-point registers on task switch.
1163 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1164 instruction doesn't work correctly and not to
1167 nohalt [IA-64] Tells the kernel not to use the power saving
1168 function PAL_HALT_LIGHT when idle. This increases
1169 power-consumption. On the positive side, it reduces
1170 interrupt wake-up latency, which may improve performance
1171 in certain environments such as networked servers or
1174 nohz= [KNL] Boottime enable/disable dynamic ticks
1175 Valid arguments: on, off
1178 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1180 noirqdebug [X86-32] Disables the code which attempts to detect and
1181 disable unhandled interrupt sources.
1183 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1184 broken timer IRQ sources.
1186 noisapnp [ISAPNP] Disables ISA PnP code.
1188 noinitrd [RAM] Tells the kernel not to load any configured
1193 nojitter [IA64] Disables jitter checking for ITC timers.
1195 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1197 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1199 noltlbs [PPC] Do not use large page/tlb entries for kernel
1200 lowmem mapping on PPC40x.
1202 nomca [IA-64] Disable machine check abort handling
1204 nomce [X86-32] Machine Check Exception
1206 nomfgpt [X86-32] Disable Multi-Function General Purpose
1207 Timer usage (for AMD Geode machines).
1209 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1211 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1212 with UP alternatives
1214 noresidual [PPC] Don't use residual data on PReP machines.
1216 noresume [SWSUSP] Disables resume and restores original swap
1219 no-scroll [VGA] Disables scrollback.
1220 This is required for the Braillex ib80-piezo Braille
1221 reader made by F.H. Papenmeier (Germany).
1225 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1227 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1228 and disable the IO APIC. legacy for "maxcpus=0".
1230 nosoftlockup [KNL] Disable the soft-lockup detector.
1232 nosync [HW,M68K] Disables sync negotiation for all devices.
1234 notsc [BUGS=X86-32] Disable Time Stamp Counter
1236 nousb [USB] Disable the USB subsystem
1240 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1241 one of ['zone', 'node', 'default'] can be specified
1242 This can be set from sysctl after boot.
1243 See Documentation/sysctl/vm.txt for details.
1245 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1250 oprofile.timer= [HW]
1251 Use timer interrupt instead of performance counters
1253 osst= [HW,SCSI] SCSI Tape Driver
1254 Format: <buffer_size>,<write_threshold>
1255 See also Documentation/scsi/st.txt.
1257 panic= [KNL] Kernel behaviour on panic
1260 parkbd.port= [HW] Parallel port number the keyboard adapter is
1261 connected to, default is 0.
1263 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1264 0 for XT, 1 for AT (default is AT).
1267 parport= [HW,PPT] Specify parallel ports. 0 disables.
1268 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1269 Use 'auto' to force the driver to use any
1270 IRQ/DMA settings detected (the default is to
1271 ignore detected IRQ/DMA settings because of
1272 possible conflicts). You can specify the base
1273 address, IRQ, and DMA settings; IRQ and DMA
1274 should be numbers, or 'auto' (for using detected
1275 settings on that particular port), or 'nofifo'
1276 (to avoid using a FIFO even if it is detected).
1277 Parallel ports are assigned in the order they
1278 are specified on the command line, starting
1281 parport_init_mode= [HW,PPT]
1282 Configure VIA parallel port to operate in
1283 a specific mode. This is necessary on Pegasos
1284 computer where firmware has no options for setting
1285 up parallel port mode and sets it to spp.
1286 Currently this function knows 686a and 8231 chips.
1287 Format: [spp|ps2|epp|ecp|ecpepp]
1289 pas2= [HW,OSS] Format:
1290 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1293 See header of drivers/scsi/pas16.c.
1296 Halt all CPUs after the first oops has been printed for
1297 the specified number of seconds. This is to be used if
1298 your oopses keep scrolling off the screen.
1303 See header of drivers/block/paride/pcd.c.
1304 See also Documentation/paride.txt.
1306 pci=option[,option...] [PCI] various PCI subsystem options:
1307 off [X86-32] don't probe for the PCI bus
1308 bios [X86-32] force use of PCI BIOS, don't access
1309 the hardware directly. Use this if your machine
1310 has a non-standard PCI host bridge.
1311 nobios [X86-32] disallow use of PCI BIOS, only direct
1312 hardware access methods are allowed. Use this
1313 if you experience crashes upon bootup and you
1314 suspect they are caused by the BIOS.
1315 conf1 [X86-32] Force use of PCI Configuration
1317 conf2 [X86-32] Force use of PCI Configuration
1319 noaer [PCIE] If the PCIEAER kernel config parameter is
1320 enabled, this kernel boot option can be used to
1321 disable the use of PCIE advanced error reporting.
1322 nodomains [PCI] Disable support for multiple PCI
1323 root domains (aka PCI segments, in ACPI-speak).
1324 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1326 nomsi [MSI] If the PCI_MSI kernel config parameter is
1327 enabled, this kernel boot option can be used to
1328 disable the use of MSI interrupts system-wide.
1329 nosort [X86-32] Don't sort PCI devices according to
1330 order given by the PCI BIOS. This sorting is
1331 done to get a device order compatible with
1333 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1334 routing table. These calls are known to be buggy
1335 on several machines and they hang the machine
1336 when used, but on other computers it's the only
1337 way to get the interrupt routing table. Try
1338 this option if the kernel is unable to allocate
1339 IRQs or discover secondary PCI buses on your
1341 rom [X86-32] Assign address space to expansion ROMs.
1342 Use with caution as certain devices share
1343 address decoders between ROMs and other
1345 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1346 assigned automatically to PCI devices. You can
1347 make the kernel exclude IRQs of your ISA cards
1349 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1350 of the PIRQ table (normally generated
1351 by the BIOS) if it is outside the
1352 F0000h-100000h range.
1353 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1354 useful if the kernel is unable to find your
1355 secondary buses and you want to tell it
1356 explicitly which ones they are.
1357 assign-busses [X86-32] Always assign all PCI bus
1358 numbers ourselves, overriding
1359 whatever the firmware may have done.
1360 usepirqmask [X86-32] Honor the possible IRQ mask stored
1361 in the BIOS $PIR table. This is needed on
1362 some systems with broken BIOSes, notably
1363 some HP Pavilion N5400 and Omnibook XE3
1364 notebooks. This will have no effect if ACPI
1365 IRQ routing is enabled.
1366 noacpi [X86-32] Do not use ACPI for IRQ routing
1367 or for PCI scanning.
1368 use_crs [X86-32] Use _CRS for PCI resource
1370 routeirq Do IRQ routing for all PCI devices.
1371 This is normally done in pci_enable_device(),
1372 so this option is a temporary workaround
1373 for broken drivers that don't call it.
1374 firmware [ARM] Do not re-enumerate the bus but instead
1375 just use the configuration from the
1376 bootloader. This is currently used on
1377 IXP2000 systems where the bus has to be
1378 configured a certain way for adjunct CPUs.
1379 noearly [X86] Don't do any early type 1 scanning.
1380 This might help on some broken boards which
1381 machine check when some devices' config space
1382 is read. But various workarounds are disabled
1383 and some IOMMU drivers will not work.
1384 bfsort Sort PCI devices into breadth-first order.
1385 This sorting is done to get a device
1386 order compatible with older (<= 2.4) kernels.
1387 nobfsort Don't sort PCI devices into breadth-first order.
1388 cbiosize=nn[KMG] The fixed amount of bus space which is
1389 reserved for the CardBus bridge's IO window.
1390 The default value is 256 bytes.
1391 cbmemsize=nn[KMG] The fixed amount of bus space which is
1392 reserved for the CardBus bridge's memory
1393 window. The default value is 64 megabytes.
1395 pcmv= [HW,PCMCIA] BadgePAD 4
1398 See Documentation/paride.txt.
1400 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1403 See arch/parisc/kernel/pdc_chassis.c
1406 See Documentation/paride.txt.
1409 See Documentation/paride.txt.
1411 pirq= [SMP,APIC] Manual mp-table setup
1412 See Documentation/i386/IO-APIC.txt.
1414 plip= [PPT,NET] Parallel port network link
1415 Format: { parport<nr> | timid | 0 }
1416 See also Documentation/parport.txt.
1422 { on | off | curr | res | no-curr | no-res }
1425 [ISAPNP] Exclude IRQs for the autoconfiguration
1428 [ISAPNP] Exclude DMAs for the autoconfiguration
1430 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1431 Ranges are in pairs (I/O port base and size).
1434 [ISAPNP] Exclude memory regions for the
1436 Ranges are in pairs (memory base and size).
1438 print-fatal-signals=
1439 [KNL] debug: print fatal signals
1440 print-fatal-signals=1: print segfault info to
1444 printk.time= Show timing data prefixed to each printk message line
1445 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1447 profile= [KNL] Enable kernel profiling via /proc/profile
1448 Format: [schedule,]<number>
1449 Param: "schedule" - profile schedule points.
1450 Param: <number> - step/bucket size as a power of 2 for
1451 statistical time based profiling.
1452 Param: "sleep" - profile D-state sleeping (millisecs).
1453 Requires CONFIG_SCHEDSTATS
1454 Param: "kvm" - profile VM exits.
1456 processor.max_cstate= [HW,ACPI]
1457 Limit processor to maximum C-state
1458 max_cstate=9 overrides any DMI blacklist limit.
1460 processor.nocst [HW,ACPI]
1461 Ignore the _CST method to determine C-states,
1462 instead using the legacy FADT method
1464 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1466 See Documentation/ramdisk.txt.
1468 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1469 probe for; one of (bare|imps|exps|lifebook|any).
1470 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1472 psmouse.resetafter= [HW,MOUSE]
1473 Try to reset the device after so many bad packets
1476 [HW,MOUSE] Set desired mouse resolution, in dpi.
1477 psmouse.smartscroll=
1478 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1479 0 = disabled, 1 = enabled (default).
1481 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1483 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1486 See Documentation/paride.txt.
1489 [KNL] Number of legacy pty's. Overwrites compiled-in
1492 quiet [KNL] Disable most log messages
1497 See Documentation/md.txt.
1499 ramdisk_blocksize= [RAM]
1500 See Documentation/ramdisk.txt.
1502 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1503 See Documentation/ramdisk.txt.
1505 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1506 RCU callbacks to process in one batch.
1508 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1509 RCU callbacks over which batch limiting is disabled.
1511 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1512 RCU callbacks below which batch limiting is re-enabled.
1516 Run specified binary instead of /init from the ramdisk,
1517 used for early userspace startup. See initrd.
1519 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1520 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1521 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1523 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1525 reservetop= [X86-32]
1527 Reserves a hole at the top of the kernel virtual
1530 reset_devices [KNL] Force drivers to reset the underlying device
1531 during initialization.
1534 Specify the partition device for software suspend
1536 resume_offset= [SWSUSP]
1537 Specify the offset from the beginning of the partition
1538 given by "resume=" at which the swap header is located,
1539 in <PAGE_SIZE> units (needed only for swap files).
1540 See Documentation/power/swsusp-and-swap-files.txt
1542 retain_initrd [RAM] Keep initrd memory after extraction
1544 rhash_entries= [KNL,NET]
1545 Set number of hash buckets for route cache
1547 riscom8= [HW,SERIAL]
1548 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1550 ro [KNL] Mount root device read-only on boot
1552 root= [KNL] Root filesystem
1554 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1555 mount the root filesystem
1557 rootflags= [KNL] Set root filesystem mount option string
1559 rootfstype= [KNL] Set root filesystem type
1561 rootwait [KNL] Wait (indefinitely) for root device to show up.
1562 Useful for devices that are detected asynchronously
1563 (e.g. USB and MMC devices).
1565 root_plug.vendor_id=
1566 [ROOTPLUG] Override the default vendor ID
1568 root_plug.product_id=
1569 [ROOTPLUG] Override the default product ID
1572 [ROOTPLUG] Enable debugging output
1574 rw [KNL] Mount root device read-write on boot
1576 S [KNL] Run init in single mode
1579 See drivers/net/irda/sa1100_ir.c.
1581 sbni= [NET] Granch SBNI12 leased line adapter
1583 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1584 Format: <io>[,<timeout>[,<isapnp>]]
1586 scsi_debug_*= [SCSI]
1587 See drivers/scsi/scsi_debug.c.
1589 scsi_default_dev_flags=
1590 [SCSI] SCSI default device flags
1593 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1594 Format: <vendor>:<model>:<flags>
1595 (flags are integer value)
1597 scsi_logging= [SCSI]
1599 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1600 discovered. async scans them in kernel threads,
1601 allowing boot to proceed. none ignores them, expecting
1602 user space to do the scan.
1604 selinux [SELINUX] Disable or enable SELinux at boot time.
1605 Format: { "0" | "1" }
1606 See security/selinux/Kconfig help text.
1609 Default value is set via kernel config option.
1610 If enabled at boot time, /selinux/disable can be used
1611 later to disable prior to initial policy load.
1613 selinux_compat_net =
1614 [SELINUX] Set initial selinux_compat_net flag value.
1615 Format: { "0" | "1" }
1616 0 -- use new secmark-based packet controls
1617 1 -- use legacy packet controls
1618 Default value is 0 (preferred).
1619 Value can be changed at runtime via
1620 /selinux/compat_net.
1622 serialnumber [BUGS=X86-32]
1625 Maximal number of shapers.
1628 See header of drivers/scsi/sim710.c.
1635 slub_debug[=options[,slabs]] [MM, SLUB]
1636 Enabling slub_debug allows one to determine the
1637 culprit if slab objects become corrupted. Enabling
1638 slub_debug can create guard zones around objects and
1639 may poison objects when not in use. Also tracks the
1640 last alloc / free. For more information see
1641 Documentation/vm/slub.txt.
1643 slub_max_order= [MM, SLUB]
1644 Determines the maximum allowed order for slabs.
1645 A high setting may cause OOMs due to memory
1646 fragmentation. For more information see
1647 Documentation/vm/slub.txt.
1649 slub_min_objects= [MM, SLUB]
1650 The minimum number of objects per slab. SLUB will
1651 increase the slab order up to slub_max_order to
1652 generate a sufficiently large slab able to contain
1653 the number of objects indicated. The higher the number
1654 of objects the smaller the overhead of tracking slabs
1655 and the less frequently locks need to be acquired.
1656 For more information see Documentation/vm/slub.txt.
1658 slub_min_order= [MM, SLUB]
1659 Determines the mininum page order for slabs. Must be
1660 lower than slub_max_order.
1661 For more information see Documentation/vm/slub.txt.
1663 slub_nomerge [MM, SLUB]
1664 Disable merging of slabs with similar size. May be
1665 necessary if there is some reason to distinguish
1666 allocs to different slabs. Debug options disable
1667 merging on their own.
1668 For more information see Documentation/vm/slub.txt.
1671 Format: <io1>[,<io2>[,...,<io8>]]
1673 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1674 attempt to substitute SMP alternatives once at boot.
1676 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1677 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1678 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1679 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1680 smsc-ircc2.ircc_irq= [HW] IRQ line
1681 smsc-ircc2.ircc_dma= [HW] DMA channel
1682 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1683 0: Toshiba Satellite 1800 (GP data pin select)
1684 1: Fast pin select (default)
1687 snd-ad1816a= [HW,ALSA]
1689 snd-ad1848= [HW,ALSA]
1691 snd-ali5451= [HW,ALSA]
1693 snd-als100= [HW,ALSA]
1695 snd-als4000= [HW,ALSA]
1697 snd-azt2320= [HW,ALSA]
1699 snd-cmi8330= [HW,ALSA]
1701 snd-cmipci= [HW,ALSA]
1703 snd-cs4231= [HW,ALSA]
1705 snd-cs4232= [HW,ALSA]
1707 snd-cs4236= [HW,ALSA]
1709 snd-cs4281= [HW,ALSA]
1711 snd-cs46xx= [HW,ALSA]
1713 snd-dt019x= [HW,ALSA]
1715 snd-dummy= [HW,ALSA]
1717 snd-emu10k1= [HW,ALSA]
1719 snd-ens1370= [HW,ALSA]
1721 snd-ens1371= [HW,ALSA]
1723 snd-es968= [HW,ALSA]
1725 snd-es1688= [HW,ALSA]
1727 snd-es18xx= [HW,ALSA]
1729 snd-es1938= [HW,ALSA]
1731 snd-es1968= [HW,ALSA]
1733 snd-fm801= [HW,ALSA]
1735 snd-gusclassic= [HW,ALSA]
1737 snd-gusextreme= [HW,ALSA]
1739 snd-gusmax= [HW,ALSA]
1743 snd-ice1712= [HW,ALSA]
1745 snd-intel8x0= [HW,ALSA]
1747 snd-interwave= [HW,ALSA]
1752 snd-korg1212= [HW,ALSA]
1754 snd-maestro3= [HW,ALSA]
1756 snd-mpu401= [HW,ALSA]
1758 snd-mtpav= [HW,ALSA]
1760 snd-nm256= [HW,ALSA]
1762 snd-opl3sa2= [HW,ALSA]
1770 snd-opti93x= [HW,ALSA]
1774 snd-rme32= [HW,ALSA]
1776 snd-rme96= [HW,ALSA]
1778 snd-rme9652= [HW,ALSA]
1784 snd-sbawe= [HW,ALSA]
1786 snd-serial= [HW,ALSA]
1788 snd-sgalaxy= [HW,ALSA]
1790 snd-sonicvibes= [HW,ALSA]
1795 snd-sun-cs4231= [HW,ALSA]
1797 snd-trident= [HW,ALSA]
1799 snd-usb-audio= [HW,ALSA,USB]
1801 snd-via82xx= [HW,ALSA]
1803 snd-virmidi= [HW,ALSA]
1805 snd-wavefront= [HW,ALSA]
1807 snd-ymfpci= [HW,ALSA]
1809 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1810 See Documentation/sonypi.txt
1812 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1813 See Documentation/specialix.txt.
1815 spia_io_base= [HW,MTD]
1821 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1823 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1824 See Documentation/scsi/st.txt.
1827 See header of drivers/scsi/seagate.c.
1831 Set the STI (builtin display/keyboard on the HP-PARISC
1832 machines) console (graphic card) which should be used
1833 as the initial boot-console.
1834 See also comment in drivers/video/console/sticore.c.
1837 See comment in drivers/video/console/sticore.c.
1840 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1844 Control how the NFS server code allocates CPUs to
1845 service thread pools. Depending on how many NICs
1846 you have and where their interrupts are bound, this
1847 option will affect which CPUs will do NFS serving.
1848 Note: this parameter cannot be changed while the
1849 NFS server is running.
1851 auto the server chooses an appropriate mode
1852 automatically using heuristics
1853 global a single global pool contains all CPUs
1854 percpu one pool for each CPU
1855 pernode one pool for each NUMA node (equivalent
1856 to global on non-NUMA machines)
1858 swiotlb= [IA-64] Number of I/O TLB slabs
1862 sym53c416= [HW,SCSI]
1863 See header of drivers/scsi/sym53c416.c.
1865 sysrq_always_enabled
1867 Ignore sysrq setting - this boot parameter will
1868 neutralize any effect of /proc/sys/kernel/sysrq.
1869 Useful for debugging.
1872 See header of drivers/scsi/t128.c.
1876 thash_entries= [KNL,NET]
1877 Set number of hash buckets for TCP connection
1879 thermal.act= [HW,ACPI]
1880 -1: disable all active trip points in all thermal zones
1881 <degrees C>: override all lowest active trip points
1883 thermal.crt= [HW,ACPI]
1884 -1: disable all critical trip points in all thermal zones
1885 <degrees C>: lower all critical trip points
1887 thermal.nocrt= [HW,ACPI]
1888 Set to disable actions on ACPI thermal zone
1889 critical and hot trip points.
1891 thermal.off= [HW,ACPI]
1892 1: disable ACPI thermal control
1894 thermal.psv= [HW,ACPI]
1895 -1: disable all passive trip points
1896 <degrees C>: override all passive trip points to this value
1898 thermal.tzp= [HW,ACPI]
1899 Specify global default ACPI thermal zone polling rate
1900 <deci-seconds>: poll all this frequency
1901 0: no polling (default)
1903 time Show timing data prefixed to each printk message line
1904 [deprecated, see 'printk.time']
1906 tipar.timeout= [HW,PPT]
1907 Set communications timeout in tenths of a second
1910 tipar.delay= [HW,PPT]
1911 Set inter-bit delay in microseconds (default 10).
1914 See header of drivers/scsi/seagate.c.
1917 See comment before function dc390_setup() in
1918 drivers/scsi/tmscsim.c.
1922 trix= [HW,OSS] MediaTrix AudioTrix Pro
1924 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1926 turbografx.map[2|3]= [HW,JOY]
1927 TurboGraFX parallel port interface
1929 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1930 See also Documentation/input/joystick-parport.txt
1932 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1933 See header of drivers/scsi/u14-34f.c.
1942 [USB] Ignore overcurrent events (default N).
1943 Some badly-designed motherboards generate lots of
1944 bogus events, for ports that aren't wired to
1945 anything. Set this parameter to avoid log spamming.
1946 Note that genuine overcurrent events won't be
1949 usbcore.autosuspend=
1950 [USB] The autosuspend time delay (in seconds) used
1951 for newly-detected USB devices (default 2). This
1952 is the time required before an idle device will be
1953 autosuspended. Devices for which the delay is set
1954 to a negative value won't be autosuspended at all.
1957 [USBHID] The interval which mice are to be polled at.
1959 vdso= [X86-32,SH,x86-64]
1960 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1961 vdso=1: enable VDSO (default)
1962 vdso=0: disable VDSO mapping
1965 vector=percpu: enable percpu vector domain
1967 video= [FB] Frame buffer configuration
1968 See Documentation/fb/modedb.txt.
1970 vga= [BOOT,X86-32] Select a particular video mode
1971 See Documentation/i386/boot.txt and
1972 Documentation/svga.txt.
1973 Use vga=ask for menu.
1974 This is actually a boot loader parameter; the value is
1975 passed to the kernel using a special protocol.
1977 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1978 size of <nn>. This can be used to increase the
1979 minimum size (128MB on x86). It can also be used to
1980 decrease the size and leave more room for directly
1983 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1986 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1989 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1992 waveartist= [HW,OSS]
1993 Format: <io>,<irq>,<dma>,<dma2>
1996 See header of drivers/scsi/wd33c93.c.
1999 See header of drivers/scsi/wd7000.c.
2002 See Documentation/watchdog/wdt.txt.
2004 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2005 xd_geo= See header of drivers/block/xd.c.
2007 xirc2ps_cs= [NET,PCMCIA]
2009 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2011 norandmaps Don't use address space randomization
2012 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2014 ______________________________________________________________________
2018 Add documentation for ALSA options.
2019 Add more DRM drivers.