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.
226 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
228 acpi_pm_good [X86-32,X86-64]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
243 The kernel tries to set a reasonable default.
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
253 See header of drivers/scsi/advansys.c.
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
263 See Documentation/scsi/aha152x.txt.
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
269 See Documentation/scsi/aic7xxx.txt.
272 See Documentation/scsi/aic79xx.txt.
274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
277 See also Documentation/kernel/input/joystick.txt
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
285 Power management functions (SPARCstation-4/5 + deriv.)
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
303 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
304 Format: <io>,<irq>,<nodeID>
308 atarimouse= [HW,MOUSE] Atari Mouse
310 atascsi= [HW,SCSI] Atari SCSI
312 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
313 EzKey and similar keyboards
315 atkbd.reset= [HW] Reset keyboard during initialization
317 atkbd.set= [HW] Select keyboard code set
318 Format: <int> (2 = AT (default), 3 = PS/2)
320 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
323 atkbd.softraw= [HW] Choose between synthetic and real raw mode
324 Format: <bool> (0 = real, 1 = synthetic (default))
326 atkbd.softrepeat= [HW]
327 Use software keyboard repeat
331 baycom_epp= [HW,AX25]
334 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
336 See header of drivers/net/hamradio/baycom_par.c.
338 baycom_ser_fdx= [HW,AX25]
339 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
340 Format: <io>,<irq>,<mode>[,<baud>]
341 See header of drivers/net/hamradio/baycom_ser_fdx.c.
343 baycom_ser_hdx= [HW,AX25]
344 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
345 Format: <io>,<irq>,<mode>
346 See header of drivers/net/hamradio/baycom_ser_hdx.c.
348 blkmtd_device= [HW,MTD]
354 boot_delay= Milliseconds to delay each printk during boot.
355 Values larger than 10 seconds (10000) are changed to
359 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
360 bttv.radio= Most important insmod options are available as
362 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
363 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
366 See drivers/scsi/BusLogic.c, comment before function
367 BusLogic_ParseDriverOptions().
369 c101= [NET] Moxa C101 synchronous serial card
371 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
372 Sometimes CPU hardware bugs make them report the cache
373 size incorrectly. The kernel will attempt work arounds
374 to fix known problems, but for some CPUs it is not
375 possible to determine what the correct size should be.
376 This option provides an override for these situations.
379 [SECURITY] Disable capabilities. This would normally
380 be used only if an alternative security model is to be
381 configured. Potentially dangerous and should only be
382 used if you are entirely sure of the consequences.
384 chandev= [HW,NET] Generic channel device initialisation
386 checkreqprot [SELINUX] Set initial checkreqprot flag value.
387 Format: { "0" | "1" }
388 See security/selinux/Kconfig help text.
389 0 -- check protection applied by kernel (includes
390 any implied execute protection).
391 1 -- check protection requested by application.
392 Default value is set via a kernel config option.
393 Value can be changed at runtime via
394 /selinux/checkreqprot.
396 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
398 Forces specified clocksource (if available) to be used
399 when calculating gettimeofday(). If specified
400 clocksource is not available, it defaults to PIT.
401 Format: { pit | tsc | cyclone | pmtmr }
403 clocksource= [GENERIC_TIME] Override the default clocksource
405 Override the default clocksource and use the clocksource
406 with the name specified.
407 Some clocksource names to choose from, depending on
409 [all] jiffies (this is the base, fallback clocksource)
411 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
412 pxa_timer,timer3,32k_counter,timer0_1
414 [X86-32] pit,hpet,tsc,vmi-timer;
415 scx200_hrt on Geode; cyclone on IBM x440
423 code_bytes [IA32] How many bytes of object code to print in an
430 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
431 over the 8254 in addition to over the IO-APIC. The
432 kernel tries to set a sensible default.
434 hpet= [X86-32,HPET] option to control HPET usage
435 Format: { enable (default) | disable | force }
436 disable: disable HPET and use PIT instead
437 force: allow force enabled of undocumented chips (ICH4, VIA)
439 com20020= [HW,NET] ARCnet - COM20020 chipset
441 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
443 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
447 ARCnet - COM90xx chipset (memory-mapped buffers)
448 Format: <io>[,<irq>[,<memstart>]]
450 condev= [HW,S390] console device
453 console= [KNL] Output console device and options.
455 tty<n> Use the virtual console device <n>.
459 Use the specified serial port. The options are of
460 the form "bbbbpnf", where "bbbb" is the baud rate,
461 "p" is parity ("n", "o", or "e"), "n" is number of
462 bits, and "f" is flow control ("r" for RTS or
463 omit it). Default is "9600n8".
465 See Documentation/serial-console.txt for more
467 Documentation/networking/netconsole.txt for an
470 uart[8250],io,<addr>[,options]
471 uart[8250],mmio,<addr>[,options]
472 Start an early, polled-mode console on the 8250/16550
473 UART at the specified I/O port or MMIO address,
474 switching to the matching ttyS device later. The
475 options are the same as for ttyS, above.
477 earlycon= [KNL] Output early console device and options.
478 uart[8250],io,<addr>[,options]
479 uart[8250],mmio,<addr>[,options]
480 Start an early, polled-mode console on the 8250/16550
481 UART at the specified I/O port or MMIO address.
482 The options are the same as for ttyS, above.
485 [HW] Never suspend the console
486 Disable suspending of consoles during suspend and
487 hibernate operations. Once disabled, debugging
488 messages can reach various consoles while the rest
489 of the system is being put to sleep (ie, while
490 debugging driver suspend/resume hooks). This may
491 not work reliably with all consoles, but is known
492 to work with serial and VGA consoles.
494 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
496 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
498 crashkernel=nn[KMG]@ss[KMG]
499 [KNL] Reserve a chunk of physical memory to
500 hold a kernel to switch to with kexec on panic.
502 crashkernel=range1:size1[,range2:size2,...][@offset]
503 [KNL] Same as above, but depends on the memory
504 in the running system. The syntax of range is
505 start-[end] where start and end are both
506 a memory unit (amount[KMG]). See also
507 Documentation/kdump/kdump.txt for a example.
510 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
515 cs89x0_media= [HW,NET]
516 Format: { rj45 | aui | bnc }
518 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
521 See header of drivers/s390/block/dasd_devmap.c.
523 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
524 (one device per port)
525 Format: <port#>,<type>
526 See also Documentation/input/joystick-parport.txt
528 debug [KNL] Enable kernel debugging (events log level).
531 [KNL] verbose self-tests
533 Print debugging info while doing the locking API
535 We default to 0 (no extra messages), setting it to
536 1 will print _a lot_ more information - normally
537 only useful to kernel developers.
540 Format: <area>[,<node>]
541 See also Documentation/networking/decnet.txt.
544 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
545 Change the default blue palette of the console.
546 This is a 16-member array composed of values
550 Format: <green0>,<green1>,<green2>,...,<green15>
551 Change the default green palette of the console.
552 This is a 16-member array composed of values
556 Format: <red0>,<red1>,<red2>,...,<red15>
557 Change the default red palette of the console.
558 This is a 16-member array composed of values
563 Set system-wide default UTF-8 mode for all tty's.
564 Default is 0 and by setting to 1, it enables UTF-8
565 mode for all newly opened or allocated terminals.
568 Set number of hash buckets for dentry cache.
571 IO parameters + enable/disable command.
573 digiepca= [HW,SERIAL]
574 See drivers/char/README.epca and
575 Documentation/digiepca.txt.
577 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
579 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
581 dmasound= [HW,OSS] Sound subsystem buffers
587 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
589 earlyprintk=serial[,ttySn[,baudrate]]
591 Append ",keep" to not disable it when the real console
594 Only vga or serial at a time, not both.
596 Currently only ttyS0 and ttyS1 are supported.
598 Interaction with the standard serial driver is not
601 The VGA output is eventually overwritten by the real
606 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
609 non-0: interrupt mode (default)
616 Format: {"of[f]" | "sk[ipmbr]"}
617 See comment in arch/i386/boot/edd.S
620 Format: <id>,<membase>,<irq>
622 eisa_irq_edge= [PARISC,HW]
623 See header of drivers/parisc/eisa.c.
626 See comment before function elanfreq_setup() in
627 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
630 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
631 See Documentation/block/as-iosched.txt and
632 Documentation/block/deadline-iosched.txt for details.
634 elfcorehdr= [X86-32, X86_64]
635 Specifies physical address of start of kernel core
636 image elf header. Generally kexec loader will
637 pass this option to capture kernel.
638 See Documentation/kdump/kdump.txt for details.
640 enforcing [SELINUX] Set initial enforcing status.
642 See security/selinux/Kconfig help text.
643 0 -- permissive (log only, no denials).
644 1 -- enforcing (deny and log).
646 Value can be changed at runtime via /selinux/enforce.
649 Format: <spdif>,[<nomix>,[<amplifier>]]
650 See also header of sound/oss/es1371.c.
652 ether= [HW,NET] Ethernet cards parameters
653 This option is obsoleted by the "netdev=" option, which
654 has equivalent usage. See its documentation for details.
656 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
661 fail_make_request=[KNL]
662 General fault injection mechanism.
663 Format: <interval>,<probability>,<space>,<times>
664 See also /Documentation/fault-injection/.
667 See header of drivers/scsi/fd_mcs.c.
670 See header of drivers/scsi/fdomain.c.
673 See Documentation/floppy.txt.
676 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
677 support via parallel port (up to 5 devices per port)
678 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
679 See also Documentation/input/joystick-parport.txt
684 See header of drivers/scsi/gdth.c.
686 gpt [EFI] Forces disk with valid GPT signature but
687 invalid Protective MBR to be treated as GPT.
691 hashdist= [KNL,NUMA] Large hashes allocated during boot
692 are distributed across NUMA nodes. Defaults on
693 for IA-64, off otherwise.
694 Format: 0 | 1 (for off | on)
696 hcl= [IA-64] SGI's Hardware Graph compatibility layer
698 hd= [EIDE] (E)IDE hard drive subsystem geometry
699 Format: <cyl>,<head>,<sect>
701 hd?= [HW] (E)IDE subsystem
702 hd?lun= See Documentation/ide.txt.
704 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
705 size of <nn>. This works even on boxes that have no
706 highmem otherwise. This also works to reduce highmem
707 size on bigger boxes.
709 highres= [KNL] Enable/disable high resolution timer mode.
710 Valid parameters: "on", "off"
714 See Documentation/isdn/README.HiSax.
716 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
718 i8042.direct [HW] Put keyboard port into non-translated mode
719 i8042.dumbkbd [HW] Pretend that controller can only read data from
720 keyboard and cannot control its state
721 (Don't attempt to blink the leds)
722 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
723 i8042.nokbd [HW] Don't check/create keyboard port
724 i8042.nomux [HW] Don't check presence of an active multiplexing
726 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
729 [HW] Frequency with which keyboard LEDs should blink
730 when kernel panics (default is 0.5 sec)
731 i8042.reset [HW] Reset the controller during init and cleanup
732 i8042.unlock [HW] Unlock (ignore) the keylock
736 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
737 indicates that the driver is running on unsupported
739 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
740 does not match list of supported models.
742 [HW] Report power status in /proc/i8k
743 (disabled by default)
744 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
747 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
748 See Documentation/mca.txt.
751 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
753 ide= [HW] (E)IDE subsystem
754 Format: ide=nodma or ide=doubler or ide=reverse
755 See Documentation/ide.txt.
757 ide?= [HW] (E)IDE subsystem
758 Format: ide?=noprobe or chipset specific parameters.
759 See Documentation/ide.txt.
761 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
762 See Documentation/ide.txt.
765 Format: idle=poll or idle=mwait
766 Poll forces a polling idle loop that can slightly improves the performance
767 of waking up a idle CPU, but will use a lot of power and make the system
768 run hot. Not recommended.
769 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
770 to not use it because it doesn't save as much power as a normal idle
771 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
774 ignore_loglevel [KNL]
775 Ignore loglevel setting - this will print /all/
776 kernel messages to the console. Useful for debugging.
779 Set number of hash buckets for inode cache.
782 See header of drivers/scsi/in2000.c.
786 Run specified binary instead of /sbin/init as init
789 initcall_debug [KNL] Trace initcalls as they are executed. Useful
790 for working out where the kernel is dying during
793 initrd= [BOOT] Specify the location of the initial ramdisk
795 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
800 io7= [HW] IO7 for Marvel based alpha systems
801 See comment before marvel_specify_io7 in
802 arch/alpha/kernel/core_marvel.c.
805 See Documentation/nfsroot.txt.
807 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
808 See comment before ip2_setup() in
809 drivers/char/ip2/ip2base.c.
811 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
812 See header of drivers/scsi/ips.c.
814 ports= [IP_VS_FTP] IPVS ftp helper module
816 Up to 8 (IP_VS_APP_MAX_PORTS) ports
818 Format: <port>,<port>....
821 When an interrupt is not handled search all handlers
822 for it. Intended to get systems with badly broken
826 When an interrupt is not handled search all handlers
827 for it. Also check all handlers each timer
828 interrupt. Intended to get systems with badly broken
832 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
834 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
836 <cpu number>,...,<cpu number>
838 <cpu number>-<cpu number> (must be a positive range in ascending order)
840 <cpu number>,...,<cpu number>-<cpu number>
841 This option can be used to specify one or more CPUs
842 to isolate from the general SMP balancing and scheduling
843 algorithms. The only way to move a process onto or off
844 an "isolated" CPU is via the CPU affinity syscalls.
845 <cpu number> begins at 0 and the maximum value is
846 "number of CPUs in system - 1".
848 This option is the preferred way to isolate CPUs. The
849 alternative -- manually setting the CPU mask of all
850 tasks in the system -- can cause problems and
851 suboptimal load balancer performance.
855 js= [HW,JOY] Analog joystick
856 See Documentation/input/joystick.txt.
858 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
859 specifies the amount of memory usable by the kernel
860 for non-movable allocations. The requested amount is
861 spread evenly throughout all nodes in the system. The
862 remaining memory in each node is used for Movable
863 pages. In the event, a node is too small to have both
864 kernelcore and Movable pages, kernelcore pages will
865 take priority and other nodes will have a larger number
866 of kernelcore pages. The Movable zone is used for the
867 allocation of pages that may be reclaimed or moved
868 by the page migration subsystem. This means that
869 HugeTLB pages may not be allocated from this zone.
870 Note that allocations like PTEs-from-HighMem still
871 use the HighMem zone if it exists, and the Normal
874 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
875 is similar to kernelcore except it specifies the
876 amount of memory used for migratable allocations.
877 If both kernelcore and movablecore is specified,
878 then kernelcore will be at *least* the specified
879 value but may be more. If movablecore on its own
880 is specified, the administrator must be careful
881 that the amount of memory usable for all allocations
886 kstack=N [X86-32,X86-64] Print N words from the kernel stack
891 lapic [X86-32,APIC] Enable the local APIC even if BIOS
894 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
897 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
898 Format: addr:<io>,irq:<irq>
900 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
904 load_ramdisk= [RAM] List of ramdisks to load from floppy
905 See Documentation/ramdisk.txt.
907 lockd.nlm_grace_period=P [NFS] Assign grace period.
910 lockd.nlm_tcpport=N [NFS] Assign TCP port.
913 lockd.nlm_timeout=T [NFS] Assign timeout value.
916 lockd.nlm_udpport=M [NFS] Assign UDP port.
919 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
922 loglevel= All Kernel Messages with a loglevel smaller than the
923 console loglevel will be printed to the console. It can
924 also be changed with klogd or other programs. The
925 loglevels are defined as follows:
927 0 (KERN_EMERG) system is unusable
928 1 (KERN_ALERT) action must be taken immediately
929 2 (KERN_CRIT) critical conditions
930 3 (KERN_ERR) error conditions
931 4 (KERN_WARNING) warning conditions
932 5 (KERN_NOTICE) normal but significant condition
933 6 (KERN_INFO) informational
934 7 (KERN_DEBUG) debug-level messages
936 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
937 Format: { n | nk | nM }
938 n must be a power of two. The default size
939 is set in the kernel config file.
941 logo.nologo [FB] Disables display of the built-in Linux logo.
942 This may be used to provide more screen space for
943 kernel log messages and is useful when debugging
944 kernel boot problems.
946 lp=0 [LP] Specify parallel ports to use, e.g,
947 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
948 lp=reset first parallel port). 'lp=0' disables the
949 lp=auto printer driver. 'lp=reset' (which can be
950 specified in addition to the ports) causes
951 attached printers to be reset. Using
952 lp=port1,port2,... specifies the parallel ports
953 to associate lp devices with, starting with
954 lp0. A port specification may be 'none' to skip
955 that lp device, or a parport name such as
956 'parport0'. Specifying 'lp=auto' instead of a
957 port specification list means that device IDs
958 from each port should be examined, to see if
959 an IEEE 1284-compliant printer is attached; if
960 so, the driver will manage that printer.
961 See also header of drivers/char/lp.c.
964 Sets loops_per_jiffy to given constant, thus avoiding
965 time-consuming boot-time autodetection (up to 250 ms per
966 CPU). 0 enables autodetection (default). To determine
967 the correct value for your kernel, boot with normal
968 autodetection and see what value is printed. Note that
969 on SMP systems the preset will be applied to all CPUs,
970 which is likely to cause problems if your CPUs need
971 significantly divergent settings. An incorrect value
972 will cause delays in the kernel to be wrong, leading to
973 unpredictable I/O errors and other breakage. Although
974 unlikely, in the extreme case this might damage your
978 Format: <io>,<irq>,<dma>
980 mac5380= [HW,SCSI] Format:
981 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
983 mac53c9x= [HW,SCSI] Format:
984 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
986 machvec= [IA64] Force the use of a particular machine-vector
987 (machvec) in a generic kernel.
988 Example: machvec=hpzx1_swiotlb
990 max_loop= [LOOP] Maximum number of loopback devices that can
994 maxcpus= [SMP] Maximum number of processors that an SMP kernel
995 should make use of. maxcpus=n : n >= 0 limits the
996 kernel to using 'n' processors. n=0 is a special case,
997 it is equivalent to "nosmp", which also disables
1000 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1001 equal to this physical address is ignored.
1003 max_luns= [SCSI] Maximum number of LUNs to probe.
1004 Should be between 1 and 2^32-1.
1007 [SCSI] Maximum number of LUNs received.
1008 Should be between 1 and 16384.
1010 mca-pentium [BUGS=X86-32]
1014 mce [X86-32] Machine Check Exception
1016 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1018 md= [HW] RAID subsystems devices and level
1019 See Documentation/md.txt.
1022 Format: <first>,<last>
1023 Specifies range of consoles to be captured by the MDA.
1025 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1026 Amount of memory to be used when the kernel is not able
1027 to see the whole system memory or for test.
1028 [X86-32] Use together with memmap= to avoid physical
1029 address space collisions. Without memmap= PCI devices
1030 could be placed at addresses belonging to unused RAM.
1032 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1035 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1036 E820 memory map, as specified by the user.
1037 Such memmap=exactmap lines can be constructed based on
1038 BIOS output or other requirements. See the memmap=nn@ss
1041 memmap=nn[KMG]@ss[KMG]
1042 [KNL] Force usage of a specific region of memory
1043 Region of memory to be used, from ss to ss+nn.
1045 memmap=nn[KMG]#ss[KMG]
1046 [KNL,ACPI] Mark specific memory as ACPI data.
1047 Region of memory to be used, from ss to ss+nn.
1049 memmap=nn[KMG]$ss[KMG]
1050 [KNL,ACPI] Mark specific memory as reserved.
1051 Region of memory to be used, from ss to ss+nn.
1053 meye.*= [HW] Set MotionEye Camera parameters
1054 See Documentation/video4linux/meye.txt.
1056 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1057 Multi-Function General Purpose Timers on AMD Geode
1063 [MOUSE] Maximum time between finger touching and
1064 leaving touchpad surface for touch to be considered
1065 a tap and be reported as a left button click (for
1066 touchpads working in absolute mode only).
1068 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1069 reporting absolute coordinates, such as tablets
1070 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1071 reporting absolute coordinates, such as tablets
1076 MTD_Partition= [MTD]
1077 Format: <name>,<region-number>,<size>,<offset>
1079 MTD_Region= [MTD] Format:
1080 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1083 See drivers/mtd/cmdlinepart.c.
1085 mtouchusb.raw_coordinates=
1086 [HW] Make the MicroTouch USB driver use raw coordinates
1087 ('y', default) or cooked coordinates ('n')
1089 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1092 See header of drivers/scsi/NCR_D700.c.
1096 ncr53c400= [HW,SCSI]
1098 ncr53c400a= [HW,SCSI]
1100 ncr53c406a= [HW,SCSI]
1102 ncr53c8xx= [HW,SCSI]
1104 netdev= [NET] Network devices parameters
1105 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1106 Note that mem_start is often overloaded to mean
1107 something different and driver-specific.
1108 This usage is only documented in each driver source
1112 See Documentation/nfsroot.txt.
1114 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1115 See Documentation/nfsroot.txt.
1117 nfs.callback_tcpport=
1118 [NFS] set the TCP port on which the NFSv4 callback
1119 channel should listen.
1121 nfs.idmap_cache_timeout=
1122 [NFS] set the maximum lifetime for idmapper cache
1126 [NFS] enable 64-bit inode numbers.
1127 If zero, the NFS client will fake up a 32-bit inode
1128 number for the readdir() and stat() syscalls instead
1129 of returning the full 64-bit number.
1130 The default is to return 64-bit inode numbers.
1132 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1134 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1135 emulation library even if a 387 maths coprocessor
1138 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1139 caches in the slab allocator. Saves per-node memory,
1140 but will impact performance.
1144 noapic [SMP,APIC] Tells the kernel to not make use of any
1145 IOAPICs that may be present in the system.
1147 noasync [HW,M68K] Disables async and sync negotiation for
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)
1462 processor.max_cstate= [HW,ACPI]
1463 Limit processor to maximum C-state
1464 max_cstate=9 overrides any DMI blacklist limit.
1466 processor.nocst [HW,ACPI]
1467 Ignore the _CST method to determine C-states,
1468 instead using the legacy FADT method
1470 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1472 See Documentation/ramdisk.txt.
1474 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1475 probe for; one of (bare|imps|exps|lifebook|any).
1476 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1478 psmouse.resetafter= [HW,MOUSE]
1479 Try to reset the device after so many bad packets
1482 [HW,MOUSE] Set desired mouse resolution, in dpi.
1483 psmouse.smartscroll=
1484 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1485 0 = disabled, 1 = enabled (default).
1487 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1489 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1492 See Documentation/paride.txt.
1495 [KNL] Number of legacy pty's. Overwrites compiled-in
1498 quiet [KNL] Disable most log messages
1503 See Documentation/md.txt.
1505 ramdisk_blocksize= [RAM]
1506 See Documentation/ramdisk.txt.
1508 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1509 See Documentation/ramdisk.txt.
1511 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1512 RCU callbacks to process in one batch.
1514 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1515 RCU callbacks over which batch limiting is disabled.
1517 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1518 RCU callbacks below which batch limiting is re-enabled.
1522 Run specified binary instead of /init from the ramdisk,
1523 used for early userspace startup. See initrd.
1525 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1526 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1527 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1529 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1531 reservetop= [X86-32]
1533 Reserves a hole at the top of the kernel virtual
1536 reset_devices [KNL] Force drivers to reset the underlying device
1537 during initialization.
1540 Specify the partition device for software suspend
1542 resume_offset= [SWSUSP]
1543 Specify the offset from the beginning of the partition
1544 given by "resume=" at which the swap header is located,
1545 in <PAGE_SIZE> units (needed only for swap files).
1546 See Documentation/power/swsusp-and-swap-files.txt
1548 retain_initrd [RAM] Keep initrd memory after extraction
1550 rhash_entries= [KNL,NET]
1551 Set number of hash buckets for route cache
1553 riscom8= [HW,SERIAL]
1554 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1556 ro [KNL] Mount root device read-only on boot
1558 root= [KNL] Root filesystem
1560 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1561 mount the root filesystem
1563 rootflags= [KNL] Set root filesystem mount option string
1565 rootfstype= [KNL] Set root filesystem type
1567 rootwait [KNL] Wait (indefinitely) for root device to show up.
1568 Useful for devices that are detected asynchronously
1569 (e.g. USB and MMC devices).
1571 root_plug.vendor_id=
1572 [ROOTPLUG] Override the default vendor ID
1574 root_plug.product_id=
1575 [ROOTPLUG] Override the default product ID
1578 [ROOTPLUG] Enable debugging output
1580 rw [KNL] Mount root device read-write on boot
1582 S [KNL] Run init in single mode
1585 See drivers/net/irda/sa1100_ir.c.
1588 Format: <io>,<irq>,<dma>,<dma2>
1590 sbni= [NET] Granch SBNI12 leased line adapter
1592 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1593 Format: <io>[,<timeout>[,<isapnp>]]
1595 scsi_debug_*= [SCSI]
1596 See drivers/scsi/scsi_debug.c.
1598 scsi_default_dev_flags=
1599 [SCSI] SCSI default device flags
1602 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1603 Format: <vendor>:<model>:<flags>
1604 (flags are integer value)
1606 scsi_logging= [SCSI]
1608 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1609 discovered. async scans them in kernel threads,
1610 allowing boot to proceed. none ignores them, expecting
1611 user space to do the scan.
1613 selinux [SELINUX] Disable or enable SELinux at boot time.
1614 Format: { "0" | "1" }
1615 See security/selinux/Kconfig help text.
1618 Default value is set via kernel config option.
1619 If enabled at boot time, /selinux/disable can be used
1620 later to disable prior to initial policy load.
1622 selinux_compat_net =
1623 [SELINUX] Set initial selinux_compat_net flag value.
1624 Format: { "0" | "1" }
1625 0 -- use new secmark-based packet controls
1626 1 -- use legacy packet controls
1627 Default value is 0 (preferred).
1628 Value can be changed at runtime via
1629 /selinux/compat_net.
1631 serialnumber [BUGS=X86-32]
1633 sg_def_reserved_size= [SCSI]
1636 Maximal number of shapers.
1639 See header of drivers/scsi/sim710.c.
1646 slub_debug[=options[,slabs]] [MM, SLUB]
1647 Enabling slub_debug allows one to determine the
1648 culprit if slab objects become corrupted. Enabling
1649 slub_debug can create guard zones around objects and
1650 may poison objects when not in use. Also tracks the
1651 last alloc / free. For more information see
1652 Documentation/vm/slub.txt.
1654 slub_max_order= [MM, SLUB]
1655 Determines the maximum allowed order for slabs.
1656 A high setting may cause OOMs due to memory
1657 fragmentation. For more information see
1658 Documentation/vm/slub.txt.
1660 slub_min_objects= [MM, SLUB]
1661 The minimum number of objects per slab. SLUB will
1662 increase the slab order up to slub_max_order to
1663 generate a sufficiently large slab able to contain
1664 the number of objects indicated. The higher the number
1665 of objects the smaller the overhead of tracking slabs
1666 and the less frequently locks need to be acquired.
1667 For more information see Documentation/vm/slub.txt.
1669 slub_min_order= [MM, SLUB]
1670 Determines the mininum page order for slabs. Must be
1671 lower than slub_max_order.
1672 For more information see Documentation/vm/slub.txt.
1674 slub_nomerge [MM, SLUB]
1675 Disable merging of slabs with similar size. May be
1676 necessary if there is some reason to distinguish
1677 allocs to different slabs. Debug options disable
1678 merging on their own.
1679 For more information see Documentation/vm/slub.txt.
1682 Format: <io1>[,<io2>[,...,<io8>]]
1684 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1685 attempt to substitute SMP alternatives once at boot.
1687 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1688 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1689 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1690 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1691 smsc-ircc2.ircc_irq= [HW] IRQ line
1692 smsc-ircc2.ircc_dma= [HW] DMA channel
1693 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1694 0: Toshiba Satellite 1800 (GP data pin select)
1695 1: Fast pin select (default)
1698 snd-ad1816a= [HW,ALSA]
1700 snd-ad1848= [HW,ALSA]
1702 snd-ali5451= [HW,ALSA]
1704 snd-als100= [HW,ALSA]
1706 snd-als4000= [HW,ALSA]
1708 snd-azt2320= [HW,ALSA]
1710 snd-cmi8330= [HW,ALSA]
1712 snd-cmipci= [HW,ALSA]
1714 snd-cs4231= [HW,ALSA]
1716 snd-cs4232= [HW,ALSA]
1718 snd-cs4236= [HW,ALSA]
1720 snd-cs4281= [HW,ALSA]
1722 snd-cs46xx= [HW,ALSA]
1724 snd-dt019x= [HW,ALSA]
1726 snd-dummy= [HW,ALSA]
1728 snd-emu10k1= [HW,ALSA]
1730 snd-ens1370= [HW,ALSA]
1732 snd-ens1371= [HW,ALSA]
1734 snd-es968= [HW,ALSA]
1736 snd-es1688= [HW,ALSA]
1738 snd-es18xx= [HW,ALSA]
1740 snd-es1938= [HW,ALSA]
1742 snd-es1968= [HW,ALSA]
1744 snd-fm801= [HW,ALSA]
1746 snd-gusclassic= [HW,ALSA]
1748 snd-gusextreme= [HW,ALSA]
1750 snd-gusmax= [HW,ALSA]
1754 snd-ice1712= [HW,ALSA]
1756 snd-intel8x0= [HW,ALSA]
1758 snd-interwave= [HW,ALSA]
1763 snd-korg1212= [HW,ALSA]
1765 snd-maestro3= [HW,ALSA]
1767 snd-mpu401= [HW,ALSA]
1769 snd-mtpav= [HW,ALSA]
1771 snd-nm256= [HW,ALSA]
1773 snd-opl3sa2= [HW,ALSA]
1781 snd-opti93x= [HW,ALSA]
1785 snd-rme32= [HW,ALSA]
1787 snd-rme96= [HW,ALSA]
1789 snd-rme9652= [HW,ALSA]
1795 snd-sbawe= [HW,ALSA]
1797 snd-serial= [HW,ALSA]
1799 snd-sgalaxy= [HW,ALSA]
1801 snd-sonicvibes= [HW,ALSA]
1806 snd-sun-cs4231= [HW,ALSA]
1808 snd-trident= [HW,ALSA]
1810 snd-usb-audio= [HW,ALSA,USB]
1812 snd-via82xx= [HW,ALSA]
1814 snd-virmidi= [HW,ALSA]
1816 snd-wavefront= [HW,ALSA]
1818 snd-ymfpci= [HW,ALSA]
1820 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1821 See Documentation/sonypi.txt
1823 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1824 See Documentation/specialix.txt.
1826 spia_io_base= [HW,MTD]
1832 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1834 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1835 See Documentation/scsi/st.txt.
1838 See header of drivers/scsi/seagate.c.
1842 Set the STI (builtin display/keyboard on the HP-PARISC
1843 machines) console (graphic card) which should be used
1844 as the initial boot-console.
1845 See also comment in drivers/video/console/sticore.c.
1848 See comment in drivers/video/console/sticore.c.
1851 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1855 Control how the NFS server code allocates CPUs to
1856 service thread pools. Depending on how many NICs
1857 you have and where their interrupts are bound, this
1858 option will affect which CPUs will do NFS serving.
1859 Note: this parameter cannot be changed while the
1860 NFS server is running.
1862 auto the server chooses an appropriate mode
1863 automatically using heuristics
1864 global a single global pool contains all CPUs
1865 percpu one pool for each CPU
1866 pernode one pool for each NUMA node (equivalent
1867 to global on non-NUMA machines)
1869 swiotlb= [IA-64] Number of I/O TLB slabs
1873 sym53c416= [HW,SCSI]
1874 See header of drivers/scsi/sym53c416.c.
1876 sysrq_always_enabled
1878 Ignore sysrq setting - this boot parameter will
1879 neutralize any effect of /proc/sys/kernel/sysrq.
1880 Useful for debugging.
1883 See header of drivers/scsi/t128.c.
1887 thash_entries= [KNL,NET]
1888 Set number of hash buckets for TCP connection
1890 thermal.act= [HW,ACPI]
1891 -1: disable all active trip points in all thermal zones
1892 <degrees C>: override all lowest active trip points
1894 thermal.crt= [HW,ACPI]
1895 -1: disable all critical trip points in all thermal zones
1896 <degrees C>: lower all critical trip points
1898 thermal.nocrt= [HW,ACPI]
1899 Set to disable actions on ACPI thermal zone
1900 critical and hot trip points.
1902 thermal.off= [HW,ACPI]
1903 1: disable ACPI thermal control
1905 thermal.psv= [HW,ACPI]
1906 -1: disable all passive trip points
1907 <degrees C>: override all passive trip points to this value
1909 thermal.tzp= [HW,ACPI]
1910 Specify global default ACPI thermal zone polling rate
1911 <deci-seconds>: poll all this frequency
1912 0: no polling (default)
1914 time Show timing data prefixed to each printk message line
1915 [deprecated, see 'printk.time']
1917 tipar.timeout= [HW,PPT]
1918 Set communications timeout in tenths of a second
1921 tipar.delay= [HW,PPT]
1922 Set inter-bit delay in microseconds (default 10).
1925 See header of drivers/scsi/seagate.c.
1928 See comment before function dc390_setup() in
1929 drivers/scsi/tmscsim.c.
1933 trix= [HW,OSS] MediaTrix AudioTrix Pro
1935 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1937 turbografx.map[2|3]= [HW,JOY]
1938 TurboGraFX parallel port interface
1940 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1941 See also Documentation/input/joystick-parport.txt
1943 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1944 See header of drivers/scsi/u14-34f.c.
1953 [USB] Ignore overcurrent events (default N).
1954 Some badly-designed motherboards generate lots of
1955 bogus events, for ports that aren't wired to
1956 anything. Set this parameter to avoid log spamming.
1957 Note that genuine overcurrent events won't be
1960 usbcore.autosuspend=
1961 [USB] The autosuspend time delay (in seconds) used
1962 for newly-detected USB devices (default 2). This
1963 is the time required before an idle device will be
1964 autosuspended. Devices for which the delay is set
1965 to a negative value won't be autosuspended at all.
1968 [USBHID] The interval which mice are to be polled at.
1970 vdso= [X86-32,SH,x86-64]
1971 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1972 vdso=1: enable VDSO (default)
1973 vdso=0: disable VDSO mapping
1976 vector=percpu: enable percpu vector domain
1978 video= [FB] Frame buffer configuration
1979 See Documentation/fb/modedb.txt.
1981 vga= [BOOT,X86-32] Select a particular video mode
1982 See Documentation/i386/boot.txt and
1983 Documentation/svga.txt.
1984 Use vga=ask for menu.
1985 This is actually a boot loader parameter; the value is
1986 passed to the kernel using a special protocol.
1988 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1989 size of <nn>. This can be used to increase the
1990 minimum size (128MB on x86). It can also be used to
1991 decrease the size and leave more room for directly
1994 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1997 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2000 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2003 waveartist= [HW,OSS]
2004 Format: <io>,<irq>,<dma>,<dma2>
2007 See header of drivers/scsi/wd33c93.c.
2010 See header of drivers/scsi/wd7000.c.
2013 See Documentation/watchdog/wdt.txt.
2015 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2016 xd_geo= See header of drivers/block/xd.c.
2018 xirc2ps_cs= [NET,PCMCIA]
2020 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2022 norandmaps Don't use address space randomization
2023 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2025 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
2026 This is useful to get more information why
2027 you got a "dwarf2 unwinder stuck"
2029 ______________________________________________________________________
2033 Add documentation for ALSA options.
2034 Add more DRM drivers.