4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend is enabled.
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
99 X86-32 X86-32, aka i386 architecture is enabled.
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
104 In addition, the following text indicates that the option:
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode }
151 See Documentation/power/video.txt
153 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
154 Format: { level | edge | high | low }
156 acpi_irq_balance [HW,ACPI]
157 ACPI will balance active IRQs
160 acpi_irq_nobalance [HW,ACPI]
161 ACPI will not move active IRQs (default)
164 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
166 Format: <irq>,<irq>...
168 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
169 Format: <irq>,<irq>...
171 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
173 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
174 Format: To spoof as Windows 98: ="Microsoft Windows"
176 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
177 acpi_osi="string1" # add string1 -- only one string
178 acpi_osi="!string2" # remove built-in string2
179 acpi_osi= # disable all strings
181 acpi_serialize [HW,ACPI] force serialization of AML methods
183 acpi_skip_timer_override [HW,ACPI]
184 Recognize and ignore IRQ0/pin2 Interrupt Override.
185 For broken nForce2 BIOS resulting in XT-PIC timer.
186 acpi_use_timer_override [HW,ACPI}
187 Use timer override. For some broken Nvidia NF5 boards
188 that require a timer override, but don't have
191 acpi.debug_layer= [HW,ACPI]
193 Each bit of the <int> indicates an ACPI debug layer,
194 1: enable, 0: disable. It is useful for boot time
195 debugging. After system has booted up, it can be set
196 via /sys/module/acpi/parameters/debug_layer.
197 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
198 Available bits (add the numbers together) to enable debug output
199 for specific parts of the ACPI subsystem:
200 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
201 0x10 namespace 0x20 parser 0x40 dispatcher
202 0x80 executer 0x100 resources 0x200 acpica debugger
203 0x400 os services 0x800 acpica disassembler.
204 The number can be in decimal or prefixed with 0x in hex.
205 Warning: Many of these options can produce a lot of
206 output and make your system unusable. Be very careful.
208 acpi.debug_level= [HW,ACPI]
210 Each bit of the <int> indicates an ACPI debug level,
211 1: enable, 0: disable. It is useful for boot time
212 debugging. After system has booted up, it can be set
213 via /sys/module/acpi/parameters/debug_level.
214 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
215 Available bits (add the numbers together) to enable different
216 debug output levels of the ACPI subsystem:
217 0x01 error 0x02 warn 0x04 init 0x08 debug object
218 0x10 info 0x20 init names 0x40 parse 0x80 load
219 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
220 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
221 0x10000 resources 0x20000 user requests 0x40000 package.
222 The number can be in decimal or prefixed with 0x in hex.
223 Warning: Many of these options can produce a lot of
224 output and make your system unusable. Be very careful.
226 acpi_pm_good [X86-32,X86-64]
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
232 { off | try_unsupported }
233 off: disable AGP support
234 try_unsupported: try to drive unsupported chipsets
235 (may crash computer or cause data corruption)
237 enable_timer_pin_1 [i386,x86-64]
238 Enable PIN 1 of APIC timer
239 Can be useful to work around chipset bugs
240 (in particular on some ATI chipsets).
241 The kernel tries to set a reasonable default.
243 disable_timer_pin_1 [i386,x86-64]
244 Disable PIN 1 of APIC timer
245 Can be useful to work around chipset bugs.
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
251 See header of drivers/scsi/advansys.c.
253 advwdt= [HW,WDT] Advantech WDT
254 Format: <iostart>,<iostop>
256 aedsp16= [HW,OSS] Audio Excel DSP 16
257 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
258 See also header of sound/oss/aedsp16.c.
261 See Documentation/scsi/aha152x.txt.
264 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267 See Documentation/scsi/aic7xxx.txt.
270 See Documentation/scsi/aic79xx.txt.
272 amijoy.map= [HW,JOY] Amiga joystick support
273 Map of devices attached to JOY0DAT and JOY1DAT
275 See also Documentation/kernel/input/joystick.txt
277 analog.map= [HW,JOY] Analog joystick and gamepad support
278 Specifies type or capabilities of an analog joystick
279 connected to one of 16 gameports
280 Format: <type1>,<type2>,..<type16>
283 Power management functions (SPARCstation-4/5 + deriv.)
285 Disable APC CPU standby support. SPARCstation-Fox does
286 not play well with APC CPU idle - disable it if you have
287 APC and your system crashes randomly.
289 apic= [APIC,i386] Advanced Programmable Interrupt Controller
290 Change the output verbosity whilst booting
291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
298 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
299 Format: <io>,<irq>,<nodeID>
303 atarimouse= [HW,MOUSE] Atari Mouse
305 atascsi= [HW,SCSI] Atari SCSI
307 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
308 EzKey and similar keyboards
310 atkbd.reset= [HW] Reset keyboard during initialization
312 atkbd.set= [HW] Select keyboard code set
313 Format: <int> (2 = AT (default), 3 = PS/2)
315 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 atkbd.softraw= [HW] Choose between synthetic and real raw mode
319 Format: <bool> (0 = real, 1 = synthetic (default))
321 atkbd.softrepeat= [HW]
322 Use software keyboard repeat
326 baycom_epp= [HW,AX25]
329 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
331 See header of drivers/net/hamradio/baycom_par.c.
333 baycom_ser_fdx= [HW,AX25]
334 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
335 Format: <io>,<irq>,<mode>[,<baud>]
336 See header of drivers/net/hamradio/baycom_ser_fdx.c.
338 baycom_ser_hdx= [HW,AX25]
339 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
340 Format: <io>,<irq>,<mode>
341 See header of drivers/net/hamradio/baycom_ser_hdx.c.
343 boot_delay= Milliseconds to delay each printk during boot.
344 Values larger than 10 seconds (10000) are changed to
348 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
349 bttv.radio= Most important insmod options are available as
351 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
352 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355 See drivers/scsi/BusLogic.c, comment before function
356 BusLogic_ParseDriverOptions().
358 c101= [NET] Moxa C101 synchronous serial card
360 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
361 Sometimes CPU hardware bugs make them report the cache
362 size incorrectly. The kernel will attempt work arounds
363 to fix known problems, but for some CPUs it is not
364 possible to determine what the correct size should be.
365 This option provides an override for these situations.
368 [SECURITY] Disable capabilities. This would normally
369 be used only if an alternative security model is to be
370 configured. Potentially dangerous and should only be
371 used if you are entirely sure of the consequences.
373 checkreqprot [SELINUX] Set initial checkreqprot flag value.
374 Format: { "0" | "1" }
375 See security/selinux/Kconfig help text.
376 0 -- check protection applied by kernel (includes
377 any implied execute protection).
378 1 -- check protection requested by application.
379 Default value is set via a kernel config option.
380 Value can be changed at runtime via
381 /selinux/checkreqprot.
384 See Documentation/s390/CommonIO for details.
387 See Documentation/s390/CommonIO for details.
389 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
391 Forces specified clocksource (if available) to be used
392 when calculating gettimeofday(). If specified
393 clocksource is not available, it defaults to PIT.
394 Format: { pit | tsc | cyclone | pmtmr }
396 clocksource= [GENERIC_TIME] Override the default clocksource
398 Override the default clocksource and use the clocksource
399 with the name specified.
400 Some clocksource names to choose from, depending on
402 [all] jiffies (this is the base, fallback clocksource)
404 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
405 pxa_timer,timer3,32k_counter,timer0_1
407 [X86-32] pit,hpet,tsc,vmi-timer;
408 scx200_hrt on Geode; cyclone on IBM x440
416 code_bytes [IA32] How many bytes of object code to print in an
423 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
424 over the 8254 in addition to over the IO-APIC. The
425 kernel tries to set a sensible default.
427 hpet= [X86-32,HPET] option to control HPET usage
428 Format: { enable (default) | disable | force }
429 disable: disable HPET and use PIT instead
430 force: allow force enabled of undocumented chips (ICH4,
433 com20020= [HW,NET] ARCnet - COM20020 chipset
435 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
437 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
441 ARCnet - COM90xx chipset (memory-mapped buffers)
442 Format: <io>[,<irq>[,<memstart>]]
444 condev= [HW,S390] console device
447 console= [KNL] Output console device and options.
449 tty<n> Use the virtual console device <n>.
453 Use the specified serial port. The options are of
454 the form "bbbbpnf", where "bbbb" is the baud rate,
455 "p" is parity ("n", "o", or "e"), "n" is number of
456 bits, and "f" is flow control ("r" for RTS or
457 omit it). Default is "9600n8".
459 See Documentation/serial-console.txt for more
461 Documentation/networking/netconsole.txt for an
464 uart[8250],io,<addr>[,options]
465 uart[8250],mmio,<addr>[,options]
466 Start an early, polled-mode console on the 8250/16550
467 UART at the specified I/O port or MMIO address,
468 switching to the matching ttyS device later. The
469 options are the same as for ttyS, above.
471 earlycon= [KNL] Output early console device and options.
472 uart[8250],io,<addr>[,options]
473 uart[8250],mmio,<addr>[,options]
474 Start an early, polled-mode console on the 8250/16550
475 UART at the specified I/O port or MMIO address.
476 The options are the same as for ttyS, above.
479 [HW] Never suspend the console
480 Disable suspending of consoles during suspend and
481 hibernate operations. Once disabled, debugging
482 messages can reach various consoles while the rest
483 of the system is being put to sleep (ie, while
484 debugging driver suspend/resume hooks). This may
485 not work reliably with all consoles, but is known
486 to work with serial and VGA consoles.
488 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
490 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
492 crashkernel=nn[KMG]@ss[KMG]
493 [KNL] Reserve a chunk of physical memory to
494 hold a kernel to switch to with kexec on panic.
496 crashkernel=range1:size1[,range2:size2,...][@offset]
497 [KNL] Same as above, but depends on the memory
498 in the running system. The syntax of range is
499 start-[end] where start and end are both
500 a memory unit (amount[KMG]). See also
501 Documentation/kdump/kdump.txt for a example.
504 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
509 cs89x0_media= [HW,NET]
510 Format: { rj45 | aui | bnc }
513 See header of drivers/s390/block/dasd_devmap.c.
515 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
516 (one device per port)
517 Format: <port#>,<type>
518 See also Documentation/input/joystick-parport.txt
520 debug [KNL] Enable kernel debugging (events log level).
523 [KNL] verbose self-tests
525 Print debugging info while doing the locking API
527 We default to 0 (no extra messages), setting it to
528 1 will print _a lot_ more information - normally
529 only useful to kernel developers.
532 Format: <area>[,<node>]
533 See also Documentation/networking/decnet.txt.
536 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
537 Change the default blue palette of the console.
538 This is a 16-member array composed of values
542 Format: <green0>,<green1>,<green2>,...,<green15>
543 Change the default green palette of the console.
544 This is a 16-member array composed of values
548 Format: <red0>,<red1>,<red2>,...,<red15>
549 Change the default red palette of the console.
550 This is a 16-member array composed of values
556 Set system-wide default UTF-8 mode for all tty's.
557 Default is 1, i.e. UTF-8 mode is enabled for all
558 newly opened terminals.
561 Set number of hash buckets for dentry cache.
564 IO parameters + enable/disable command.
566 digiepca= [HW,SERIAL]
567 See drivers/char/README.epca and
568 Documentation/digiepca.txt.
570 dmasound= [HW,OSS] Sound subsystem buffers
576 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
578 earlyprintk=serial[,ttySn[,baudrate]]
580 Append ",keep" to not disable it when the real console
583 Only vga or serial at a time, not both.
585 Currently only ttyS0 and ttyS1 are supported.
587 Interaction with the standard serial driver is not
590 The VGA output is eventually overwritten by the real
596 Format: {"of[f]" | "sk[ipmbr]"}
597 See comment in arch/i386/boot/edd.S
599 eisa_irq_edge= [PARISC,HW]
600 See header of drivers/parisc/eisa.c.
603 See comment before function elanfreq_setup() in
604 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
607 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
608 See Documentation/block/as-iosched.txt and
609 Documentation/block/deadline-iosched.txt for details.
611 elfcorehdr= [X86-32, X86_64]
612 Specifies physical address of start of kernel core
613 image elf header. Generally kexec loader will
614 pass this option to capture kernel.
615 See Documentation/kdump/kdump.txt for details.
617 enforcing [SELINUX] Set initial enforcing status.
619 See security/selinux/Kconfig help text.
620 0 -- permissive (log only, no denials).
621 1 -- enforcing (deny and log).
623 Value can be changed at runtime via /selinux/enforce.
626 Format: <spdif>,[<nomix>,[<amplifier>]]
627 See also header of sound/oss/es1371.c.
629 ether= [HW,NET] Ethernet cards parameters
630 This option is obsoleted by the "netdev=" option, which
631 has equivalent usage. See its documentation for details.
633 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
638 fail_make_request=[KNL]
639 General fault injection mechanism.
640 Format: <interval>,<probability>,<space>,<times>
641 See also /Documentation/fault-injection/.
644 See header of drivers/scsi/fd_mcs.c.
647 See header of drivers/scsi/fdomain.c.
650 See Documentation/floppy.txt.
653 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
654 support via parallel port (up to 5 devices per port)
655 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
656 See also Documentation/input/joystick-parport.txt
661 See header of drivers/scsi/gdth.c.
663 gpt [EFI] Forces disk with valid GPT signature but
664 invalid Protective MBR to be treated as GPT.
668 hashdist= [KNL,NUMA] Large hashes allocated during boot
669 are distributed across NUMA nodes. Defaults on
670 for IA-64, off otherwise.
671 Format: 0 | 1 (for off | on)
673 hcl= [IA-64] SGI's Hardware Graph compatibility layer
675 hd= [EIDE] (E)IDE hard drive subsystem geometry
676 Format: <cyl>,<head>,<sect>
678 hd?= [HW] (E)IDE subsystem
679 hd?lun= See Documentation/ide.txt.
681 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
682 size of <nn>. This works even on boxes that have no
683 highmem otherwise. This also works to reduce highmem
684 size on bigger boxes.
686 highres= [KNL] Enable/disable high resolution timer mode.
687 Valid parameters: "on", "off"
691 See Documentation/isdn/README.HiSax.
693 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
695 i8042.direct [HW] Put keyboard port into non-translated mode
696 i8042.dumbkbd [HW] Pretend that controller can only read data from
697 keyboard and cannot control its state
698 (Don't attempt to blink the leds)
699 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
700 i8042.nokbd [HW] Don't check/create keyboard port
701 i8042.nomux [HW] Don't check presence of an active multiplexing
703 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
706 [HW] Frequency with which keyboard LEDs should blink
707 when kernel panics (default is 0.5 sec)
708 i8042.reset [HW] Reset the controller during init and cleanup
709 i8042.unlock [HW] Unlock (ignore) the keylock
713 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
714 indicates that the driver is running on unsupported
716 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
717 does not match list of supported models.
719 [HW] Report power status in /proc/i8k
720 (disabled by default)
721 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
724 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
725 See Documentation/mca.txt.
728 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
730 ide= [HW] (E)IDE subsystem
731 Format: ide=nodma or ide=doubler or ide=reverse
732 See Documentation/ide.txt.
734 ide?= [HW] (E)IDE subsystem
735 Format: ide?=noprobe or chipset specific parameters.
736 See Documentation/ide.txt.
738 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
739 See Documentation/ide.txt.
742 Format: idle=poll or idle=mwait
743 Poll forces a polling idle loop that can slightly improves the performance
744 of waking up a idle CPU, but will use a lot of power and make the system
745 run hot. Not recommended.
746 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
747 to not use it because it doesn't save as much power as a normal idle
748 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
751 ignore_loglevel [KNL]
752 Ignore loglevel setting - this will print /all/
753 kernel messages to the console. Useful for debugging.
756 Set number of hash buckets for inode cache.
759 See header of drivers/scsi/in2000.c.
763 Run specified binary instead of /sbin/init as init
766 initcall_debug [KNL] Trace initcalls as they are executed. Useful
767 for working out where the kernel is dying during
770 initrd= [BOOT] Specify the location of the initial ramdisk
772 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
777 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
779 Disable intel iommu driver.
780 igfx_off [Default Off]
781 By default, gfx is mapped as normal device. If a gfx
782 device has a dedicated DMAR unit, the DMAR unit is
783 bypassed by not enabling DMAR with this option. In
784 this case, gfx device will use physical address for
787 With this option iommu will not optimize to look
788 for io virtual address below 32 bit forcing dual
789 address cycle on pci bus for cards supporting greater
790 than 32 bit addressing. The default is to look
791 for translation below 32 bit and if not available
792 then look in the higher range.
794 io7= [HW] IO7 for Marvel based alpha systems
795 See comment before marvel_specify_io7 in
796 arch/alpha/kernel/core_marvel.c.
799 See Documentation/nfsroot.txt.
801 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
802 See comment before ip2_setup() in
803 drivers/char/ip2/ip2base.c.
805 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
806 See header of drivers/scsi/ips.c.
808 ports= [IP_VS_FTP] IPVS ftp helper module
810 Up to 8 (IP_VS_APP_MAX_PORTS) ports
812 Format: <port>,<port>....
815 When an interrupt is not handled search all handlers
816 for it. Intended to get systems with badly broken
820 When an interrupt is not handled search all handlers
821 for it. Also check all handlers each timer
822 interrupt. Intended to get systems with badly broken
826 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
828 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
830 <cpu number>,...,<cpu number>
832 <cpu number>-<cpu number> (must be a positive range in ascending order)
834 <cpu number>,...,<cpu number>-<cpu number>
835 This option can be used to specify one or more CPUs
836 to isolate from the general SMP balancing and scheduling
837 algorithms. The only way to move a process onto or off
838 an "isolated" CPU is via the CPU affinity syscalls.
839 <cpu number> begins at 0 and the maximum value is
840 "number of CPUs in system - 1".
842 This option is the preferred way to isolate CPUs. The
843 alternative -- manually setting the CPU mask of all
844 tasks in the system -- can cause problems and
845 suboptimal load balancer performance.
849 js= [HW,JOY] Analog joystick
850 See Documentation/input/joystick.txt.
852 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
853 specifies the amount of memory usable by the kernel
854 for non-movable allocations. The requested amount is
855 spread evenly throughout all nodes in the system. The
856 remaining memory in each node is used for Movable
857 pages. In the event, a node is too small to have both
858 kernelcore and Movable pages, kernelcore pages will
859 take priority and other nodes will have a larger number
860 of kernelcore pages. The Movable zone is used for the
861 allocation of pages that may be reclaimed or moved
862 by the page migration subsystem. This means that
863 HugeTLB pages may not be allocated from this zone.
864 Note that allocations like PTEs-from-HighMem still
865 use the HighMem zone if it exists, and the Normal
868 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
869 is similar to kernelcore except it specifies the
870 amount of memory used for migratable allocations.
871 If both kernelcore and movablecore is specified,
872 then kernelcore will be at *least* the specified
873 value but may be more. If movablecore on its own
874 is specified, the administrator must be careful
875 that the amount of memory usable for all allocations
880 kstack=N [X86-32,X86-64] Print N words from the kernel stack
885 lapic [X86-32,APIC] Enable the local APIC even if BIOS
888 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
891 libata.dma= [LIBATA] DMA control
892 libata.dma=0 Disable all PATA and SATA DMA
893 libata.dma=1 PATA and SATA Disk DMA only
894 libata.dma=2 ATAPI (CDROM) DMA only
895 libata.dma=4 Compact Flash DMA only
896 Combinations also work, so libata.dma=3 enables DMA
897 for disks and CDROMs, but not CFs.
899 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
903 load_ramdisk= [RAM] List of ramdisks to load from floppy
904 See Documentation/ramdisk.txt.
906 lockd.nlm_grace_period=P [NFS] Assign grace period.
909 lockd.nlm_tcpport=N [NFS] Assign TCP port.
912 lockd.nlm_timeout=T [NFS] Assign timeout value.
915 lockd.nlm_udpport=M [NFS] Assign UDP port.
918 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
921 loglevel= All Kernel Messages with a loglevel smaller than the
922 console loglevel will be printed to the console. It can
923 also be changed with klogd or other programs. The
924 loglevels are defined as follows:
926 0 (KERN_EMERG) system is unusable
927 1 (KERN_ALERT) action must be taken immediately
928 2 (KERN_CRIT) critical conditions
929 3 (KERN_ERR) error conditions
930 4 (KERN_WARNING) warning conditions
931 5 (KERN_NOTICE) normal but significant condition
932 6 (KERN_INFO) informational
933 7 (KERN_DEBUG) debug-level messages
935 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
936 Format: { n | nk | nM }
937 n must be a power of two. The default size
938 is set in the kernel config file.
940 logo.nologo [FB] Disables display of the built-in Linux logo.
941 This may be used to provide more screen space for
942 kernel log messages and is useful when debugging
943 kernel boot problems.
945 lp=0 [LP] Specify parallel ports to use, e.g,
946 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
947 lp=reset first parallel port). 'lp=0' disables the
948 lp=auto printer driver. 'lp=reset' (which can be
949 specified in addition to the ports) causes
950 attached printers to be reset. Using
951 lp=port1,port2,... specifies the parallel ports
952 to associate lp devices with, starting with
953 lp0. A port specification may be 'none' to skip
954 that lp device, or a parport name such as
955 'parport0'. Specifying 'lp=auto' instead of a
956 port specification list means that device IDs
957 from each port should be examined, to see if
958 an IEEE 1284-compliant printer is attached; if
959 so, the driver will manage that printer.
960 See also header of drivers/char/lp.c.
963 Sets loops_per_jiffy to given constant, thus avoiding
964 time-consuming boot-time autodetection (up to 250 ms per
965 CPU). 0 enables autodetection (default). To determine
966 the correct value for your kernel, boot with normal
967 autodetection and see what value is printed. Note that
968 on SMP systems the preset will be applied to all CPUs,
969 which is likely to cause problems if your CPUs need
970 significantly divergent settings. An incorrect value
971 will cause delays in the kernel to be wrong, leading to
972 unpredictable I/O errors and other breakage. Although
973 unlikely, in the extreme case this might damage your
977 Format: <io>,<irq>,<dma>
979 mac5380= [HW,SCSI] Format:
980 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
982 mac53c9x= [HW,SCSI] Format:
983 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
985 machvec= [IA64] Force the use of a particular machine-vector
986 (machvec) in a generic kernel.
987 Example: machvec=hpzx1_swiotlb
989 max_loop= [LOOP] Maximum number of loopback devices that can
993 maxcpus= [SMP] Maximum number of processors that an SMP kernel
994 should make use of. maxcpus=n : n >= 0 limits the
995 kernel to using 'n' processors. n=0 is a special case,
996 it is equivalent to "nosmp", which also disables
999 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1000 equal to this physical address is ignored.
1002 max_luns= [SCSI] Maximum number of LUNs to probe.
1003 Should be between 1 and 2^32-1.
1006 [SCSI] Maximum number of LUNs received.
1007 Should be between 1 and 16384.
1009 mca-pentium [BUGS=X86-32]
1013 mce [X86-32] Machine Check Exception
1015 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1017 md= [HW] RAID subsystems devices and level
1018 See Documentation/md.txt.
1021 Format: <first>,<last>
1022 Specifies range of consoles to be captured by the MDA.
1024 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1025 Amount of memory to be used when the kernel is not able
1026 to see the whole system memory or for test.
1027 [X86-32] Use together with memmap= to avoid physical
1028 address space collisions. Without memmap= PCI devices
1029 could be placed at addresses belonging to unused RAM.
1031 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1034 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1035 E820 memory map, as specified by the user.
1036 Such memmap=exactmap lines can be constructed based on
1037 BIOS output or other requirements. See the memmap=nn@ss
1040 memmap=nn[KMG]@ss[KMG]
1041 [KNL] Force usage of a specific region of memory
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 ACPI data.
1046 Region of memory to be used, from ss to ss+nn.
1048 memmap=nn[KMG]$ss[KMG]
1049 [KNL,ACPI] Mark specific memory as reserved.
1050 Region of memory to be used, from ss to ss+nn.
1052 meye.*= [HW] Set MotionEye Camera parameters
1053 See Documentation/video4linux/meye.txt.
1055 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1056 Multi-Function General Purpose Timers on AMD Geode
1062 [MOUSE] Maximum time between finger touching and
1063 leaving touchpad surface for touch to be considered
1064 a tap and be reported as a left button click (for
1065 touchpads working in absolute mode only).
1067 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1068 reporting absolute coordinates, such as tablets
1069 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1070 reporting absolute coordinates, such as tablets
1075 MTD_Partition= [MTD]
1076 Format: <name>,<region-number>,<size>,<offset>
1078 MTD_Region= [MTD] Format:
1079 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1082 See drivers/mtd/cmdlinepart.c.
1084 mtouchusb.raw_coordinates=
1085 [HW] Make the MicroTouch USB driver use raw coordinates
1086 ('y', default) or cooked coordinates ('n')
1088 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1091 See header of drivers/scsi/NCR_D700.c.
1095 ncr53c400= [HW,SCSI]
1097 ncr53c400a= [HW,SCSI]
1099 ncr53c406a= [HW,SCSI]
1101 ncr53c8xx= [HW,SCSI]
1103 netdev= [NET] Network devices parameters
1104 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1105 Note that mem_start is often overloaded to mean
1106 something different and driver-specific.
1107 This usage is only documented in each driver source
1111 See Documentation/nfsroot.txt.
1113 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1114 See Documentation/nfsroot.txt.
1116 nfs.callback_tcpport=
1117 [NFS] set the TCP port on which the NFSv4 callback
1118 channel should listen.
1120 nfs.idmap_cache_timeout=
1121 [NFS] set the maximum lifetime for idmapper cache
1125 [NFS] enable 64-bit inode numbers.
1126 If zero, the NFS client will fake up a 32-bit inode
1127 number for the readdir() and stat() syscalls instead
1128 of returning the full 64-bit number.
1129 The default is to return 64-bit inode numbers.
1131 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1132 when a NMI is triggered.
1133 Format: [state][,regs][,debounce][,die]
1135 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1137 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1138 emulation library even if a 387 maths coprocessor
1141 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1142 caches in the slab allocator. Saves per-node memory,
1143 but will impact performance.
1147 noapic [SMP,APIC] Tells the kernel to not make use of any
1148 IOAPICs that may be present in the system.
1150 nobats [PPC] Do not use BATs for mapping kernel lowmem
1151 on "Classic" PPC cores.
1155 nodelayacct [KNL] Disable per-task delay accounting
1157 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1161 noexec [X86-32,X86-64]
1162 noexec=on: enable non-executable mappings (default)
1163 noexec=off: disable nn-executable mappings
1165 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1166 register save and restore. The kernel will only save
1167 legacy floating-point registers on task switch.
1171 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1172 instruction doesn't work correctly and not to
1175 nohalt [IA-64] Tells the kernel not to use the power saving
1176 function PAL_HALT_LIGHT when idle. This increases
1177 power-consumption. On the positive side, it reduces
1178 interrupt wake-up latency, which may improve performance
1179 in certain environments such as networked servers or
1182 nohz= [KNL] Boottime enable/disable dynamic ticks
1183 Valid arguments: on, off
1186 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1188 noirqdebug [X86-32] Disables the code which attempts to detect and
1189 disable unhandled interrupt sources.
1191 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1192 broken timer IRQ sources.
1194 noisapnp [ISAPNP] Disables ISA PnP code.
1196 noinitrd [RAM] Tells the kernel not to load any configured
1201 nojitter [IA64] Disables jitter checking for ITC timers.
1203 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1205 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1207 noltlbs [PPC] Do not use large page/tlb entries for kernel
1208 lowmem mapping on PPC40x.
1210 nomca [IA-64] Disable machine check abort handling
1212 nomce [X86-32] Machine Check Exception
1214 nomfgpt [X86-32] Disable Multi-Function General Purpose
1215 Timer usage (for AMD Geode machines).
1217 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1219 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1220 with UP alternatives
1222 noresidual [PPC] Don't use residual data on PReP machines.
1224 noresume [SWSUSP] Disables resume and restores original swap
1227 no-scroll [VGA] Disables scrollback.
1228 This is required for the Braillex ib80-piezo Braille
1229 reader made by F.H. Papenmeier (Germany).
1233 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1235 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1236 and disable the IO APIC. legacy for "maxcpus=0".
1238 nosoftlockup [KNL] Disable the soft-lockup detector.
1240 nosync [HW,M68K] Disables sync negotiation for all devices.
1242 notsc [BUGS=X86-32] Disable Time Stamp Counter
1244 nousb [USB] Disable the USB subsystem
1248 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1249 one of ['zone', 'node', 'default'] can be specified
1250 This can be set from sysctl after boot.
1251 See Documentation/sysctl/vm.txt for details.
1253 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1258 oprofile.timer= [HW]
1259 Use timer interrupt instead of performance counters
1261 osst= [HW,SCSI] SCSI Tape Driver
1262 Format: <buffer_size>,<write_threshold>
1263 See also Documentation/scsi/st.txt.
1265 panic= [KNL] Kernel behaviour on panic
1268 parkbd.port= [HW] Parallel port number the keyboard adapter is
1269 connected to, default is 0.
1271 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1272 0 for XT, 1 for AT (default is AT).
1275 parport= [HW,PPT] Specify parallel ports. 0 disables.
1276 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1277 Use 'auto' to force the driver to use any
1278 IRQ/DMA settings detected (the default is to
1279 ignore detected IRQ/DMA settings because of
1280 possible conflicts). You can specify the base
1281 address, IRQ, and DMA settings; IRQ and DMA
1282 should be numbers, or 'auto' (for using detected
1283 settings on that particular port), or 'nofifo'
1284 (to avoid using a FIFO even if it is detected).
1285 Parallel ports are assigned in the order they
1286 are specified on the command line, starting
1289 parport_init_mode= [HW,PPT]
1290 Configure VIA parallel port to operate in
1291 a specific mode. This is necessary on Pegasos
1292 computer where firmware has no options for setting
1293 up parallel port mode and sets it to spp.
1294 Currently this function knows 686a and 8231 chips.
1295 Format: [spp|ps2|epp|ecp|ecpepp]
1297 pas2= [HW,OSS] Format:
1298 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1301 See header of drivers/scsi/pas16.c.
1304 Halt all CPUs after the first oops has been printed for
1305 the specified number of seconds. This is to be used if
1306 your oopses keep scrolling off the screen.
1311 See header of drivers/block/paride/pcd.c.
1312 See also Documentation/paride.txt.
1314 pci=option[,option...] [PCI] various PCI subsystem options:
1315 off [X86-32] don't probe for the PCI bus
1316 bios [X86-32] force use of PCI BIOS, don't access
1317 the hardware directly. Use this if your machine
1318 has a non-standard PCI host bridge.
1319 nobios [X86-32] disallow use of PCI BIOS, only direct
1320 hardware access methods are allowed. Use this
1321 if you experience crashes upon bootup and you
1322 suspect they are caused by the BIOS.
1323 conf1 [X86-32] Force use of PCI Configuration
1325 conf2 [X86-32] Force use of PCI Configuration
1327 noaer [PCIE] If the PCIEAER kernel config parameter is
1328 enabled, this kernel boot option can be used to
1329 disable the use of PCIE advanced error reporting.
1330 nodomains [PCI] Disable support for multiple PCI
1331 root domains (aka PCI segments, in ACPI-speak).
1332 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1334 nomsi [MSI] If the PCI_MSI kernel config parameter is
1335 enabled, this kernel boot option can be used to
1336 disable the use of MSI interrupts system-wide.
1337 nosort [X86-32] Don't sort PCI devices according to
1338 order given by the PCI BIOS. This sorting is
1339 done to get a device order compatible with
1341 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1342 routing table. These calls are known to be buggy
1343 on several machines and they hang the machine
1344 when used, but on other computers it's the only
1345 way to get the interrupt routing table. Try
1346 this option if the kernel is unable to allocate
1347 IRQs or discover secondary PCI buses on your
1349 rom [X86-32] Assign address space to expansion ROMs.
1350 Use with caution as certain devices share
1351 address decoders between ROMs and other
1353 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1354 assigned automatically to PCI devices. You can
1355 make the kernel exclude IRQs of your ISA cards
1357 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1358 of the PIRQ table (normally generated
1359 by the BIOS) if it is outside the
1360 F0000h-100000h range.
1361 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1362 useful if the kernel is unable to find your
1363 secondary buses and you want to tell it
1364 explicitly which ones they are.
1365 assign-busses [X86-32] Always assign all PCI bus
1366 numbers ourselves, overriding
1367 whatever the firmware may have done.
1368 usepirqmask [X86-32] Honor the possible IRQ mask stored
1369 in the BIOS $PIR table. This is needed on
1370 some systems with broken BIOSes, notably
1371 some HP Pavilion N5400 and Omnibook XE3
1372 notebooks. This will have no effect if ACPI
1373 IRQ routing is enabled.
1374 noacpi [X86-32] Do not use ACPI for IRQ routing
1375 or for PCI scanning.
1376 use_crs [X86-32] Use _CRS for PCI resource
1378 routeirq Do IRQ routing for all PCI devices.
1379 This is normally done in pci_enable_device(),
1380 so this option is a temporary workaround
1381 for broken drivers that don't call it.
1382 firmware [ARM] Do not re-enumerate the bus but instead
1383 just use the configuration from the
1384 bootloader. This is currently used on
1385 IXP2000 systems where the bus has to be
1386 configured a certain way for adjunct CPUs.
1387 noearly [X86] Don't do any early type 1 scanning.
1388 This might help on some broken boards which
1389 machine check when some devices' config space
1390 is read. But various workarounds are disabled
1391 and some IOMMU drivers will not work.
1392 bfsort Sort PCI devices into breadth-first order.
1393 This sorting is done to get a device
1394 order compatible with older (<= 2.4) kernels.
1395 nobfsort Don't sort PCI devices into breadth-first order.
1396 cbiosize=nn[KMG] The fixed amount of bus space which is
1397 reserved for the CardBus bridge's IO window.
1398 The default value is 256 bytes.
1399 cbmemsize=nn[KMG] The fixed amount of bus space which is
1400 reserved for the CardBus bridge's memory
1401 window. The default value is 64 megabytes.
1403 pcmv= [HW,PCMCIA] BadgePAD 4
1406 See Documentation/paride.txt.
1408 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1411 See arch/parisc/kernel/pdc_chassis.c
1414 See Documentation/paride.txt.
1417 See Documentation/paride.txt.
1419 pirq= [SMP,APIC] Manual mp-table setup
1420 See Documentation/i386/IO-APIC.txt.
1422 plip= [PPT,NET] Parallel port network link
1423 Format: { parport<nr> | timid | 0 }
1424 See also Documentation/parport.txt.
1430 { on | off | curr | res | no-curr | no-res }
1433 [ISAPNP] Exclude IRQs for the autoconfiguration
1436 [ISAPNP] Exclude DMAs for the autoconfiguration
1438 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1439 Ranges are in pairs (I/O port base and size).
1442 [ISAPNP] Exclude memory regions for the
1444 Ranges are in pairs (memory base and size).
1446 print-fatal-signals=
1447 [KNL] debug: print fatal signals
1448 print-fatal-signals=1: print segfault info to
1452 printk.time= Show timing data prefixed to each printk message line
1453 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1455 profile= [KNL] Enable kernel profiling via /proc/profile
1456 Format: [schedule,]<number>
1457 Param: "schedule" - profile schedule points.
1458 Param: <number> - step/bucket size as a power of 2 for
1459 statistical time based profiling.
1460 Param: "sleep" - profile D-state sleeping (millisecs).
1461 Requires CONFIG_SCHEDSTATS
1462 Param: "kvm" - profile VM exits.
1464 processor.max_cstate= [HW,ACPI]
1465 Limit processor to maximum C-state
1466 max_cstate=9 overrides any DMI blacklist limit.
1468 processor.nocst [HW,ACPI]
1469 Ignore the _CST method to determine C-states,
1470 instead using the legacy FADT method
1472 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1474 See Documentation/ramdisk.txt.
1476 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1477 probe for; one of (bare|imps|exps|lifebook|any).
1478 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1480 psmouse.resetafter= [HW,MOUSE]
1481 Try to reset the device after so many bad packets
1484 [HW,MOUSE] Set desired mouse resolution, in dpi.
1485 psmouse.smartscroll=
1486 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1487 0 = disabled, 1 = enabled (default).
1489 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1491 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1494 See Documentation/paride.txt.
1497 [KNL] Number of legacy pty's. Overwrites compiled-in
1500 quiet [KNL] Disable most log messages
1505 See Documentation/md.txt.
1507 ramdisk_blocksize= [RAM]
1508 See Documentation/ramdisk.txt.
1510 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1511 See Documentation/ramdisk.txt.
1513 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1514 RCU callbacks to process in one batch.
1516 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1517 RCU callbacks over which batch limiting is disabled.
1519 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1520 RCU callbacks below which batch limiting is re-enabled.
1524 Run specified binary instead of /init from the ramdisk,
1525 used for early userspace startup. See initrd.
1527 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1528 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1529 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1531 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1533 reservetop= [X86-32]
1535 Reserves a hole at the top of the kernel virtual
1538 reset_devices [KNL] Force drivers to reset the underlying device
1539 during initialization.
1542 Specify the partition device for software suspend
1544 resume_offset= [SWSUSP]
1545 Specify the offset from the beginning of the partition
1546 given by "resume=" at which the swap header is located,
1547 in <PAGE_SIZE> units (needed only for swap files).
1548 See Documentation/power/swsusp-and-swap-files.txt
1550 retain_initrd [RAM] Keep initrd memory after extraction
1552 rhash_entries= [KNL,NET]
1553 Set number of hash buckets for route cache
1555 riscom8= [HW,SERIAL]
1556 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1558 ro [KNL] Mount root device read-only on boot
1560 root= [KNL] Root filesystem
1562 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1563 mount the root filesystem
1565 rootflags= [KNL] Set root filesystem mount option string
1567 rootfstype= [KNL] Set root filesystem type
1569 rootwait [KNL] Wait (indefinitely) for root device to show up.
1570 Useful for devices that are detected asynchronously
1571 (e.g. USB and MMC devices).
1573 root_plug.vendor_id=
1574 [ROOTPLUG] Override the default vendor ID
1576 root_plug.product_id=
1577 [ROOTPLUG] Override the default product ID
1580 [ROOTPLUG] Enable debugging output
1582 rw [KNL] Mount root device read-write on boot
1584 S [KNL] Run init in single mode
1587 See drivers/net/irda/sa1100_ir.c.
1589 sbni= [NET] Granch SBNI12 leased line adapter
1591 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1592 Format: <io>[,<timeout>[,<isapnp>]]
1594 scsi_debug_*= [SCSI]
1595 See drivers/scsi/scsi_debug.c.
1597 scsi_default_dev_flags=
1598 [SCSI] SCSI default device flags
1601 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1602 Format: <vendor>:<model>:<flags>
1603 (flags are integer value)
1605 scsi_logging_level= [SCSI] a bit mask of logging levels
1606 See drivers/scsi/scsi_logging.h for bits. Also
1607 settable via sysctl at dev.scsi.logging_level
1608 (/proc/sys/dev/scsi/logging_level).
1609 There is also a nice 'scsi_logging_level' script in the
1610 S390-tools package, available for download at
1611 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1613 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1614 discovered. async scans them in kernel threads,
1615 allowing boot to proceed. none ignores them, expecting
1616 user space to do the scan.
1618 selinux [SELINUX] Disable or enable SELinux at boot time.
1619 Format: { "0" | "1" }
1620 See security/selinux/Kconfig help text.
1623 Default value is set via kernel config option.
1624 If enabled at boot time, /selinux/disable can be used
1625 later to disable prior to initial policy load.
1627 selinux_compat_net =
1628 [SELINUX] Set initial selinux_compat_net flag value.
1629 Format: { "0" | "1" }
1630 0 -- use new secmark-based packet controls
1631 1 -- use legacy packet controls
1632 Default value is 0 (preferred).
1633 Value can be changed at runtime via
1634 /selinux/compat_net.
1636 serialnumber [BUGS=X86-32]
1639 Maximal number of shapers.
1642 See header of drivers/scsi/sim710.c.
1649 slub_debug[=options[,slabs]] [MM, SLUB]
1650 Enabling slub_debug allows one to determine the
1651 culprit if slab objects become corrupted. Enabling
1652 slub_debug can create guard zones around objects and
1653 may poison objects when not in use. Also tracks the
1654 last alloc / free. For more information see
1655 Documentation/vm/slub.txt.
1657 slub_max_order= [MM, SLUB]
1658 Determines the maximum allowed order for slabs.
1659 A high setting may cause OOMs due to memory
1660 fragmentation. For more information see
1661 Documentation/vm/slub.txt.
1663 slub_min_objects= [MM, SLUB]
1664 The minimum number of objects per slab. SLUB will
1665 increase the slab order up to slub_max_order to
1666 generate a sufficiently large slab able to contain
1667 the number of objects indicated. The higher the number
1668 of objects the smaller the overhead of tracking slabs
1669 and the less frequently locks need to be acquired.
1670 For more information see Documentation/vm/slub.txt.
1672 slub_min_order= [MM, SLUB]
1673 Determines the mininum page order for slabs. Must be
1674 lower than slub_max_order.
1675 For more information see Documentation/vm/slub.txt.
1677 slub_nomerge [MM, SLUB]
1678 Disable merging of slabs with similar size. May be
1679 necessary if there is some reason to distinguish
1680 allocs to different slabs. Debug options disable
1681 merging on their own.
1682 For more information see Documentation/vm/slub.txt.
1685 Format: <io1>[,<io2>[,...,<io8>]]
1687 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1688 attempt to substitute SMP alternatives once at boot.
1690 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1691 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1692 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1693 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1694 smsc-ircc2.ircc_irq= [HW] IRQ line
1695 smsc-ircc2.ircc_dma= [HW] DMA channel
1696 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1697 0: Toshiba Satellite 1800 (GP data pin select)
1698 1: Fast pin select (default)
1701 snd-ad1816a= [HW,ALSA]
1703 snd-ad1848= [HW,ALSA]
1705 snd-ali5451= [HW,ALSA]
1707 snd-als100= [HW,ALSA]
1709 snd-als4000= [HW,ALSA]
1711 snd-azt2320= [HW,ALSA]
1713 snd-cmi8330= [HW,ALSA]
1715 snd-cmipci= [HW,ALSA]
1717 snd-cs4231= [HW,ALSA]
1719 snd-cs4232= [HW,ALSA]
1721 snd-cs4236= [HW,ALSA]
1723 snd-cs4281= [HW,ALSA]
1725 snd-cs46xx= [HW,ALSA]
1727 snd-dt019x= [HW,ALSA]
1729 snd-dummy= [HW,ALSA]
1731 snd-emu10k1= [HW,ALSA]
1733 snd-ens1370= [HW,ALSA]
1735 snd-ens1371= [HW,ALSA]
1737 snd-es968= [HW,ALSA]
1739 snd-es1688= [HW,ALSA]
1741 snd-es18xx= [HW,ALSA]
1743 snd-es1938= [HW,ALSA]
1745 snd-es1968= [HW,ALSA]
1747 snd-fm801= [HW,ALSA]
1749 snd-gusclassic= [HW,ALSA]
1751 snd-gusextreme= [HW,ALSA]
1753 snd-gusmax= [HW,ALSA]
1757 snd-ice1712= [HW,ALSA]
1759 snd-intel8x0= [HW,ALSA]
1761 snd-interwave= [HW,ALSA]
1766 snd-korg1212= [HW,ALSA]
1768 snd-maestro3= [HW,ALSA]
1770 snd-mpu401= [HW,ALSA]
1772 snd-mtpav= [HW,ALSA]
1774 snd-nm256= [HW,ALSA]
1776 snd-opl3sa2= [HW,ALSA]
1784 snd-opti93x= [HW,ALSA]
1788 snd-rme32= [HW,ALSA]
1790 snd-rme96= [HW,ALSA]
1792 snd-rme9652= [HW,ALSA]
1798 snd-sbawe= [HW,ALSA]
1800 snd-serial= [HW,ALSA]
1802 snd-sgalaxy= [HW,ALSA]
1804 snd-sonicvibes= [HW,ALSA]
1809 snd-sun-cs4231= [HW,ALSA]
1811 snd-trident= [HW,ALSA]
1813 snd-usb-audio= [HW,ALSA,USB]
1815 snd-via82xx= [HW,ALSA]
1817 snd-virmidi= [HW,ALSA]
1819 snd-wavefront= [HW,ALSA]
1821 snd-ymfpci= [HW,ALSA]
1823 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1824 See Documentation/sonypi.txt
1826 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1827 See Documentation/specialix.txt.
1829 spia_io_base= [HW,MTD]
1835 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1837 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1838 See Documentation/scsi/st.txt.
1841 See header of drivers/scsi/seagate.c.
1845 Set the STI (builtin display/keyboard on the HP-PARISC
1846 machines) console (graphic card) which should be used
1847 as the initial boot-console.
1848 See also comment in drivers/video/console/sticore.c.
1851 See comment in drivers/video/console/sticore.c.
1854 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1858 Control how the NFS server code allocates CPUs to
1859 service thread pools. Depending on how many NICs
1860 you have and where their interrupts are bound, this
1861 option will affect which CPUs will do NFS serving.
1862 Note: this parameter cannot be changed while the
1863 NFS server is running.
1865 auto the server chooses an appropriate mode
1866 automatically using heuristics
1867 global a single global pool contains all CPUs
1868 percpu one pool for each CPU
1869 pernode one pool for each NUMA node (equivalent
1870 to global on non-NUMA machines)
1872 swiotlb= [IA-64] Number of I/O TLB slabs
1876 sym53c416= [HW,SCSI]
1877 See header of drivers/scsi/sym53c416.c.
1879 sysrq_always_enabled
1881 Ignore sysrq setting - this boot parameter will
1882 neutralize any effect of /proc/sys/kernel/sysrq.
1883 Useful for debugging.
1886 See header of drivers/scsi/t128.c.
1890 thash_entries= [KNL,NET]
1891 Set number of hash buckets for TCP connection
1893 thermal.act= [HW,ACPI]
1894 -1: disable all active trip points in all thermal zones
1895 <degrees C>: override all lowest active trip points
1897 thermal.crt= [HW,ACPI]
1898 -1: disable all critical trip points in all thermal zones
1899 <degrees C>: lower all critical trip points
1901 thermal.nocrt= [HW,ACPI]
1902 Set to disable actions on ACPI thermal zone
1903 critical and hot trip points.
1905 thermal.off= [HW,ACPI]
1906 1: disable ACPI thermal control
1908 thermal.psv= [HW,ACPI]
1909 -1: disable all passive trip points
1910 <degrees C>: override all passive trip points to this value
1912 thermal.tzp= [HW,ACPI]
1913 Specify global default ACPI thermal zone polling rate
1914 <deci-seconds>: poll all this frequency
1915 0: no polling (default)
1917 time Show timing data prefixed to each printk message line
1918 [deprecated, see 'printk.time']
1920 tipar.timeout= [HW,PPT]
1921 Set communications timeout in tenths of a second
1924 tipar.delay= [HW,PPT]
1925 Set inter-bit delay in microseconds (default 10).
1928 See header of drivers/scsi/seagate.c.
1931 See comment before function dc390_setup() in
1932 drivers/scsi/tmscsim.c.
1936 trix= [HW,OSS] MediaTrix AudioTrix Pro
1938 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1940 turbografx.map[2|3]= [HW,JOY]
1941 TurboGraFX parallel port interface
1943 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1944 See also Documentation/input/joystick-parport.txt
1946 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1947 See header of drivers/scsi/u14-34f.c.
1956 [USB] Ignore overcurrent events (default N).
1957 Some badly-designed motherboards generate lots of
1958 bogus events, for ports that aren't wired to
1959 anything. Set this parameter to avoid log spamming.
1960 Note that genuine overcurrent events won't be
1963 usbcore.autosuspend=
1964 [USB] The autosuspend time delay (in seconds) used
1965 for newly-detected USB devices (default 2). This
1966 is the time required before an idle device will be
1967 autosuspended. Devices for which the delay is set
1968 to a negative value won't be autosuspended at all.
1971 [USBHID] The interval which mice are to be polled at.
1973 vdso= [X86-32,SH,x86-64]
1974 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1975 vdso=1: enable VDSO (default)
1976 vdso=0: disable VDSO mapping
1979 vector=percpu: enable percpu vector domain
1981 video= [FB] Frame buffer configuration
1982 See Documentation/fb/modedb.txt.
1984 vga= [BOOT,X86-32] Select a particular video mode
1985 See Documentation/i386/boot.txt and
1986 Documentation/svga.txt.
1987 Use vga=ask for menu.
1988 This is actually a boot loader parameter; the value is
1989 passed to the kernel using a special protocol.
1991 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1992 size of <nn>. This can be used to increase the
1993 minimum size (128MB on x86). It can also be used to
1994 decrease the size and leave more room for directly
1997 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2000 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2003 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2006 waveartist= [HW,OSS]
2007 Format: <io>,<irq>,<dma>,<dma2>
2010 See header of drivers/scsi/wd33c93.c.
2013 See header of drivers/scsi/wd7000.c.
2016 See Documentation/watchdog/wdt.txt.
2018 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2019 xd_geo= See header of drivers/block/xd.c.
2021 xirc2ps_cs= [NET,PCMCIA]
2023 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2025 norandmaps Don't use address space randomization
2026 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2028 ______________________________________________________________________
2032 Add documentation for ALSA options.
2033 Add more DRM drivers.