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/power/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, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
156 Format: { level | edge | high | low }
158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
168 Format: <irq>,<irq>...
170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
171 Format: <irq>,<irq>...
173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
183 acpi_serialize [HW,ACPI] force serialization of AML methods
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
193 acpi.debug_layer= [HW,ACPI]
195 Each bit of the <int> indicates an ACPI debug layer,
196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
210 acpi.debug_level= [HW,ACPI]
212 Each bit of the <int> indicates an ACPI debug level,
213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
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.
300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
305 atarimouse= [HW,MOUSE] Atari Mouse
307 atascsi= [HW,SCSI] Atari SCSI
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
312 atkbd.reset= [HW] Reset keyboard during initialization
314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
328 baycom_epp= [HW,AX25]
331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
333 See header of drivers/net/hamradio/baycom_par.c.
335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
370 [SECURITY] Disable capabilities. This would normally
371 be used only if an alternative security model is to be
372 configured. Potentially dangerous and should only be
373 used if you are entirely sure of the consequences.
375 ccw_timeout_log [S390]
376 See Documentation/s390/CommonIO for details.
378 cgroup_disable= [KNL] Disable a particular controller
379 Format: {name of the controller(s) to disable}
380 {Currently supported controllers - "memory"}
382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
389 Value can be changed at runtime via
390 /selinux/checkreqprot.
393 See Documentation/s390/CommonIO for details.
396 See Documentation/s390/CommonIO for details.
398 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
400 Forces specified clocksource (if available) to be used
401 when calculating gettimeofday(). If specified
402 clocksource is not available, it defaults to PIT.
403 Format: { pit | tsc | cyclone | pmtmr }
405 clocksource= [GENERIC_TIME] Override the default clocksource
407 Override the default clocksource and use the clocksource
408 with the name specified.
409 Some clocksource names to choose from, depending on
411 [all] jiffies (this is the base, fallback clocksource)
413 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
414 pxa_timer,timer3,32k_counter,timer0_1
416 [X86-32] pit,hpet,tsc,vmi-timer;
417 scx200_hrt on Geode; cyclone on IBM x440
425 clearcpuid=BITNUM [X86]
426 Disable CPUID feature X for the kernel. See
427 include/asm-x86/cpufeature.h for the valid bit numbers.
428 Note the Linux specific bits are not necessarily
429 stable over kernel options, but the vendor specific
431 Also note that user programs calling CPUID directly
432 or using the feature without checking anything
433 will still see it. This just prevents it from
434 being used by the kernel or shown in /proc/cpuinfo.
435 Also note the kernel might malfunction if you disable
438 code_bytes [IA32/X86_64] How many bytes of object code to print
445 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
446 over the 8254 in addition to over the IO-APIC. The
447 kernel tries to set a sensible default.
449 hpet= [X86-32,HPET] option to control HPET usage
450 Format: { enable (default) | disable | force }
451 disable: disable HPET and use PIT instead
452 force: allow force enabled of undocumented chips (ICH4,
455 com20020= [HW,NET] ARCnet - COM20020 chipset
457 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
459 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
463 ARCnet - COM90xx chipset (memory-mapped buffers)
464 Format: <io>[,<irq>[,<memstart>]]
466 condev= [HW,S390] console device
469 console= [KNL] Output console device and options.
471 tty<n> Use the virtual console device <n>.
475 Use the specified serial port. The options are of
476 the form "bbbbpnf", where "bbbb" is the baud rate,
477 "p" is parity ("n", "o", or "e"), "n" is number of
478 bits, and "f" is flow control ("r" for RTS or
479 omit it). Default is "9600n8".
481 See Documentation/serial-console.txt for more
483 Documentation/networking/netconsole.txt for an
486 uart[8250],io,<addr>[,options]
487 uart[8250],mmio,<addr>[,options]
488 Start an early, polled-mode console on the 8250/16550
489 UART at the specified I/O port or MMIO address,
490 switching to the matching ttyS device later. The
491 options are the same as for ttyS, above.
493 earlycon= [KNL] Output early console device and options.
494 uart[8250],io,<addr>[,options]
495 uart[8250],mmio,<addr>[,options]
496 Start an early, polled-mode console on the 8250/16550
497 UART at the specified I/O port or MMIO address.
498 The options are the same as for ttyS, above.
501 [HW] Never suspend the console
502 Disable suspending of consoles during suspend and
503 hibernate operations. Once disabled, debugging
504 messages can reach various consoles while the rest
505 of the system is being put to sleep (ie, while
506 debugging driver suspend/resume hooks). This may
507 not work reliably with all consoles, but is known
508 to work with serial and VGA consoles.
510 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
512 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
514 crashkernel=nn[KMG]@ss[KMG]
515 [KNL] Reserve a chunk of physical memory to
516 hold a kernel to switch to with kexec on panic.
518 crashkernel=range1:size1[,range2:size2,...][@offset]
519 [KNL] Same as above, but depends on the memory
520 in the running system. The syntax of range is
521 start-[end] where start and end are both
522 a memory unit (amount[KMG]). See also
523 Documentation/kdump/kdump.txt for a example.
526 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
531 cs89x0_media= [HW,NET]
532 Format: { rj45 | aui | bnc }
535 See header of drivers/s390/block/dasd_devmap.c.
537 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
538 (one device per port)
539 Format: <port#>,<type>
540 See also Documentation/input/joystick-parport.txt
542 debug [KNL] Enable kernel debugging (events log level).
545 [KNL] verbose self-tests
547 Print debugging info while doing the locking API
549 We default to 0 (no extra messages), setting it to
550 1 will print _a lot_ more information - normally
551 only useful to kernel developers.
553 decnet.addr= [HW,NET]
554 Format: <area>[,<node>]
555 See also Documentation/networking/decnet.txt.
558 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
559 Change the default blue palette of the console.
560 This is a 16-member array composed of values
564 Format: <green0>,<green1>,<green2>,...,<green15>
565 Change the default green palette of the console.
566 This is a 16-member array composed of values
570 Format: <red0>,<red1>,<red2>,...,<red15>
571 Change the default red palette of the console.
572 This is a 16-member array composed of values
578 Set system-wide default UTF-8 mode for all tty's.
579 Default is 1, i.e. UTF-8 mode is enabled for all
580 newly opened terminals.
583 Set number of hash buckets for dentry cache.
586 IO parameters + enable/disable command.
588 digiepca= [HW,SERIAL]
589 See drivers/char/README.epca and
590 Documentation/digiepca.txt.
592 disable_mtrr_trim [X86, Intel and AMD only]
593 By default the kernel will trim any uncacheable
594 memory out of your available memory pool based on
595 MTRR settings. This parameter disables that behavior,
596 possibly causing your machine to run very slowly.
598 dmasound= [HW,OSS] Sound subsystem buffers
604 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
606 earlyprintk=serial[,ttySn[,baudrate]]
608 Append ",keep" to not disable it when the real console
611 Only vga or serial at a time, not both.
613 Currently only ttyS0 and ttyS1 are supported.
615 Interaction with the standard serial driver is not
618 The VGA output is eventually overwritten by the real
624 Format: {"of[f]" | "sk[ipmbr]"}
625 See comment in arch/i386/boot/edd.S
627 eisa_irq_edge= [PARISC,HW]
628 See header of drivers/parisc/eisa.c.
631 See comment before function elanfreq_setup() in
632 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
635 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
636 See Documentation/block/as-iosched.txt and
637 Documentation/block/deadline-iosched.txt for details.
639 elfcorehdr= [X86-32, X86_64]
640 Specifies physical address of start of kernel core
641 image elf header. Generally kexec loader will
642 pass this option to capture kernel.
643 See Documentation/kdump/kdump.txt for details.
645 enforcing [SELINUX] Set initial enforcing status.
647 See security/selinux/Kconfig help text.
648 0 -- permissive (log only, no denials).
649 1 -- enforcing (deny and log).
651 Value can be changed at runtime via /selinux/enforce.
654 Format: <spdif>,[<nomix>,[<amplifier>]]
655 See also header of sound/oss/es1371.c.
657 ether= [HW,NET] Ethernet cards parameters
658 This option is obsoleted by the "netdev=" option, which
659 has equivalent usage. See its documentation for details.
661 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
666 fail_make_request=[KNL]
667 General fault injection mechanism.
668 Format: <interval>,<probability>,<space>,<times>
669 See also /Documentation/fault-injection/.
672 See header of drivers/scsi/fd_mcs.c.
675 See header of drivers/scsi/fdomain.c.
678 See Documentation/floppy.txt.
681 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
682 support via parallel port (up to 5 devices per port)
683 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
684 See also Documentation/input/joystick-parport.txt
688 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
693 See header of drivers/scsi/gdth.c.
695 gpt [EFI] Forces disk with valid GPT signature but
696 invalid Protective MBR to be treated as GPT.
700 hashdist= [KNL,NUMA] Large hashes allocated during boot
701 are distributed across NUMA nodes. Defaults on
702 for IA-64, off otherwise.
703 Format: 0 | 1 (for off | on)
705 hcl= [IA-64] SGI's Hardware Graph compatibility layer
707 hd= [EIDE] (E)IDE hard drive subsystem geometry
708 Format: <cyl>,<head>,<sect>
710 hd?= [HW] (E)IDE subsystem
711 hd?lun= See Documentation/ide/ide.txt.
713 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
714 size of <nn>. This works even on boxes that have no
715 highmem otherwise. This also works to reduce highmem
716 size on bigger boxes.
718 highres= [KNL] Enable/disable high resolution timer mode.
719 Valid parameters: "on", "off"
723 See Documentation/isdn/README.HiSax.
725 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
726 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
728 i8042.direct [HW] Put keyboard port into non-translated mode
729 i8042.dumbkbd [HW] Pretend that controller can only read data from
730 keyboard and cannot control its state
731 (Don't attempt to blink the leds)
732 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
733 i8042.nokbd [HW] Don't check/create keyboard port
734 i8042.noloop [HW] Disable the AUX Loopback command while probing
736 i8042.nomux [HW] Don't check presence of an active multiplexing
738 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
741 [HW] Frequency with which keyboard LEDs should blink
742 when kernel panics (default is 0.5 sec)
743 i8042.reset [HW] Reset the controller during init and cleanup
744 i8042.unlock [HW] Unlock (ignore) the keylock
748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
749 indicates that the driver is running on unsupported
751 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
752 does not match list of supported models.
754 [HW] Report power status in /proc/i8k
755 (disabled by default)
756 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
759 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
760 See Documentation/mca.txt.
763 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
765 ide= [HW] (E)IDE subsystem
766 Format: ide=nodma or ide=doubler
767 See Documentation/ide/ide.txt.
769 ide?= [HW] (E)IDE subsystem
770 Format: ide?=ata66 or chipset specific parameters.
771 See Documentation/ide/ide.txt.
773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
774 See Documentation/ide/ide.txt.
777 Format: idle=poll or idle=mwait
778 Poll forces a polling idle loop that can slightly improves the performance
779 of waking up a idle CPU, but will use a lot of power and make the system
780 run hot. Not recommended.
781 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
782 to not use it because it doesn't save as much power as a normal idle
783 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
787 Claim all unknown PCI IDE storage controllers.
789 ignore_loglevel [KNL]
790 Ignore loglevel setting - this will print /all/
791 kernel messages to the console. Useful for debugging.
794 Set number of hash buckets for inode cache.
797 See header of drivers/scsi/in2000.c.
801 Run specified binary instead of /sbin/init as init
804 initcall_debug [KNL] Trace initcalls as they are executed. Useful
805 for working out where the kernel is dying during
808 initrd= [BOOT] Specify the location of the initial ramdisk
810 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
828 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
830 Disable intel iommu driver.
831 igfx_off [Default Off]
832 By default, gfx is mapped as normal device. If a gfx
833 device has a dedicated DMAR unit, the DMAR unit is
834 bypassed by not enabling DMAR with this option. In
835 this case, gfx device will use physical address for
838 With this option iommu will not optimize to look
839 for io virtual address below 32 bit forcing dual
840 address cycle on pci bus for cards supporting greater
841 than 32 bit addressing. The default is to look
842 for translation below 32 bit and if not available
843 then look in the higher range.
845 io_delay= [X86-32,X86-64] I/O delay method
847 Standard port 0x80 based delay
849 Alternate port 0xed based delay (needed on some systems)
851 Simple two microseconds delay
855 io7= [HW] IO7 for Marvel based alpha systems
856 See comment before marvel_specify_io7 in
857 arch/alpha/kernel/core_marvel.c.
860 See Documentation/filesystems/nfsroot.txt.
862 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
863 See comment before ip2_setup() in
864 drivers/char/ip2/ip2base.c.
866 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
867 See header of drivers/scsi/ips.c.
869 ports= [IP_VS_FTP] IPVS ftp helper module
871 Up to 8 (IP_VS_APP_MAX_PORTS) ports
873 Format: <port>,<port>....
876 When an interrupt is not handled search all handlers
877 for it. Intended to get systems with badly broken
881 When an interrupt is not handled search all handlers
882 for it. Also check all handlers each timer
883 interrupt. Intended to get systems with badly broken
887 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
889 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
891 <cpu number>,...,<cpu number>
893 <cpu number>-<cpu number> (must be a positive range in ascending order)
895 <cpu number>,...,<cpu number>-<cpu number>
896 This option can be used to specify one or more CPUs
897 to isolate from the general SMP balancing and scheduling
898 algorithms. The only way to move a process onto or off
899 an "isolated" CPU is via the CPU affinity syscalls.
900 <cpu number> begins at 0 and the maximum value is
901 "number of CPUs in system - 1".
903 This option is the preferred way to isolate CPUs. The
904 alternative -- manually setting the CPU mask of all
905 tasks in the system -- can cause problems and
906 suboptimal load balancer performance.
910 js= [HW,JOY] Analog joystick
911 See Documentation/input/joystick.txt.
913 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
914 specifies the amount of memory usable by the kernel
915 for non-movable allocations. The requested amount is
916 spread evenly throughout all nodes in the system. The
917 remaining memory in each node is used for Movable
918 pages. In the event, a node is too small to have both
919 kernelcore and Movable pages, kernelcore pages will
920 take priority and other nodes will have a larger number
921 of kernelcore pages. The Movable zone is used for the
922 allocation of pages that may be reclaimed or moved
923 by the page migration subsystem. This means that
924 HugeTLB pages may not be allocated from this zone.
925 Note that allocations like PTEs-from-HighMem still
926 use the HighMem zone if it exists, and the Normal
929 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
930 is similar to kernelcore except it specifies the
931 amount of memory used for migratable allocations.
932 If both kernelcore and movablecore is specified,
933 then kernelcore will be at *least* the specified
934 value but may be more. If movablecore on its own
935 is specified, the administrator must be careful
936 that the amount of memory usable for all allocations
941 kstack=N [X86-32,X86-64] Print N words from the kernel stack
944 kgdboc= [HW] kgdb over consoles.
945 Requires a tty driver that supports console polling.
946 (only serial suported for now)
947 Format: <serial_device>[,baud]
951 lapic [X86-32,APIC] Enable the local APIC even if BIOS
954 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
957 libata.dma= [LIBATA] DMA control
958 libata.dma=0 Disable all PATA and SATA DMA
959 libata.dma=1 PATA and SATA Disk DMA only
960 libata.dma=2 ATAPI (CDROM) DMA only
961 libata.dma=4 Compact Flash DMA only
962 Combinations also work, so libata.dma=3 enables DMA
963 for disks and CDROMs, but not CFs.
965 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
969 libata.force= [LIBATA] Force configurations. The format is comma
970 separated list of "[ID:]VAL" where ID is
971 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
972 matching port, link or device. Basically, it matches
973 the ATA ID string printed on console by libata. If
974 the whole ID part is omitted, the last PORT and DEVICE
975 values are used. If ID hasn't been specified yet, the
976 configuration applies to all ports, links and devices.
978 If only DEVICE is omitted, the parameter applies to
979 the port and all links and devices behind it. DEVICE
980 number of 0 either selects the first device or the
981 first fan-out link behind PMP device. It does not
982 select the host link. DEVICE number of 15 selects the
983 host link and device attached to it.
985 The VAL specifies the configuration to force. As long
986 as there's no ambiguity shortcut notation is allowed.
987 For example, both 1.5 and 1.5G would work for 1.5Gbps.
988 The following configurations can be forced.
990 * Cable type: 40c, 80c, short40c, unk, ign or sata.
991 Any ID with matching PORT is used.
993 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
995 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
996 udma[/][16,25,33,44,66,100,133] notation is also
999 * [no]ncq: Turn on or off NCQ.
1001 If there are multiple matching configurations changing
1002 the same attribute, the last one is used.
1004 load_ramdisk= [RAM] List of ramdisks to load from floppy
1005 See Documentation/ramdisk.txt.
1007 lockd.nlm_grace_period=P [NFS] Assign grace period.
1010 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1013 lockd.nlm_timeout=T [NFS] Assign timeout value.
1016 lockd.nlm_udpport=M [NFS] Assign UDP port.
1019 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1022 loglevel= All Kernel Messages with a loglevel smaller than the
1023 console loglevel will be printed to the console. It can
1024 also be changed with klogd or other programs. The
1025 loglevels are defined as follows:
1027 0 (KERN_EMERG) system is unusable
1028 1 (KERN_ALERT) action must be taken immediately
1029 2 (KERN_CRIT) critical conditions
1030 3 (KERN_ERR) error conditions
1031 4 (KERN_WARNING) warning conditions
1032 5 (KERN_NOTICE) normal but significant condition
1033 6 (KERN_INFO) informational
1034 7 (KERN_DEBUG) debug-level messages
1036 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1037 Format: { n | nk | nM }
1038 n must be a power of two. The default size
1039 is set in the kernel config file.
1041 logo.nologo [FB] Disables display of the built-in Linux logo.
1042 This may be used to provide more screen space for
1043 kernel log messages and is useful when debugging
1044 kernel boot problems.
1046 lp=0 [LP] Specify parallel ports to use, e.g,
1047 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1048 lp=reset first parallel port). 'lp=0' disables the
1049 lp=auto printer driver. 'lp=reset' (which can be
1050 specified in addition to the ports) causes
1051 attached printers to be reset. Using
1052 lp=port1,port2,... specifies the parallel ports
1053 to associate lp devices with, starting with
1054 lp0. A port specification may be 'none' to skip
1055 that lp device, or a parport name such as
1056 'parport0'. Specifying 'lp=auto' instead of a
1057 port specification list means that device IDs
1058 from each port should be examined, to see if
1059 an IEEE 1284-compliant printer is attached; if
1060 so, the driver will manage that printer.
1061 See also header of drivers/char/lp.c.
1064 Sets loops_per_jiffy to given constant, thus avoiding
1065 time-consuming boot-time autodetection (up to 250 ms per
1066 CPU). 0 enables autodetection (default). To determine
1067 the correct value for your kernel, boot with normal
1068 autodetection and see what value is printed. Note that
1069 on SMP systems the preset will be applied to all CPUs,
1070 which is likely to cause problems if your CPUs need
1071 significantly divergent settings. An incorrect value
1072 will cause delays in the kernel to be wrong, leading to
1073 unpredictable I/O errors and other breakage. Although
1074 unlikely, in the extreme case this might damage your
1078 Format: <io>,<irq>,<dma>
1080 mac5380= [HW,SCSI] Format:
1081 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1083 mac53c9x= [HW,SCSI] Format:
1084 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1086 machvec= [IA64] Force the use of a particular machine-vector
1087 (machvec) in a generic kernel.
1088 Example: machvec=hpzx1_swiotlb
1090 max_loop= [LOOP] Maximum number of loopback devices that can
1094 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1095 should make use of. maxcpus=n : n >= 0 limits the
1096 kernel to using 'n' processors. n=0 is a special case,
1097 it is equivalent to "nosmp", which also disables
1100 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1101 equal to this physical address is ignored.
1103 max_luns= [SCSI] Maximum number of LUNs to probe.
1104 Should be between 1 and 2^32-1.
1107 [SCSI] Maximum number of LUNs received.
1108 Should be between 1 and 16384.
1112 mce [X86-32] Machine Check Exception
1114 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1116 md= [HW] RAID subsystems devices and level
1117 See Documentation/md.txt.
1120 Format: <first>,<last>
1121 Specifies range of consoles to be captured by the MDA.
1123 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1124 Amount of memory to be used when the kernel is not able
1125 to see the whole system memory or for test.
1126 [X86-32] Use together with memmap= to avoid physical
1127 address space collisions. Without memmap= PCI devices
1128 could be placed at addresses belonging to unused RAM.
1130 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1133 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1134 E820 memory map, as specified by the user.
1135 Such memmap=exactmap lines can be constructed based on
1136 BIOS output or other requirements. See the memmap=nn@ss
1139 memmap=nn[KMG]@ss[KMG]
1140 [KNL] Force usage of a specific region of memory
1141 Region of memory to be used, from ss to ss+nn.
1143 memmap=nn[KMG]#ss[KMG]
1144 [KNL,ACPI] Mark specific memory as ACPI data.
1145 Region of memory to be used, from ss to ss+nn.
1147 memmap=nn[KMG]$ss[KMG]
1148 [KNL,ACPI] Mark specific memory as reserved.
1149 Region of memory to be used, from ss to ss+nn.
1150 Example: Exclude memory from 0x18690000-0x1869ffff
1151 memmap=64K$0x18690000
1153 memmap=0x10000$0x18690000
1155 memtest= [KNL,X86_64] Enable memtest
1157 range: 0,4 : pattern number
1158 default : 0 <disable>
1160 meye.*= [HW] Set MotionEye Camera parameters
1161 See Documentation/video4linux/meye.txt.
1163 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1164 Multi-Function General Purpose Timers on AMD Geode
1167 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1168 the BIOS has incorrectly applied a workaround. TinyBIOS
1169 version 0.98 is known to be affected, 0.99 fixes the
1170 problem by letting the user disable the workaround.
1175 [MOUSE] Maximum time between finger touching and
1176 leaving touchpad surface for touch to be considered
1177 a tap and be reported as a left button click (for
1178 touchpads working in absolute mode only).
1180 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1181 reporting absolute coordinates, such as tablets
1182 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1183 reporting absolute coordinates, such as tablets
1188 MTD_Partition= [MTD]
1189 Format: <name>,<region-number>,<size>,<offset>
1191 MTD_Region= [MTD] Format:
1192 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1195 See drivers/mtd/cmdlinepart.c.
1197 mtouchusb.raw_coordinates=
1198 [HW] Make the MicroTouch USB driver use raw coordinates
1199 ('y', default) or cooked coordinates ('n')
1201 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1204 See header of drivers/scsi/NCR_D700.c.
1208 ncr53c400= [HW,SCSI]
1210 ncr53c400a= [HW,SCSI]
1212 ncr53c406a= [HW,SCSI]
1214 ncr53c8xx= [HW,SCSI]
1216 netdev= [NET] Network devices parameters
1217 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1218 Note that mem_start is often overloaded to mean
1219 something different and driver-specific.
1220 This usage is only documented in each driver source
1224 See Documentation/filesystems/nfsroot.txt.
1226 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1227 See Documentation/filesystems/nfsroot.txt.
1229 nfs.callback_tcpport=
1230 [NFS] set the TCP port on which the NFSv4 callback
1231 channel should listen.
1233 nfs.idmap_cache_timeout=
1234 [NFS] set the maximum lifetime for idmapper cache
1238 [NFS] enable 64-bit inode numbers.
1239 If zero, the NFS client will fake up a 32-bit inode
1240 number for the readdir() and stat() syscalls instead
1241 of returning the full 64-bit number.
1242 The default is to return 64-bit inode numbers.
1244 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1245 when a NMI is triggered.
1246 Format: [state][,regs][,debounce][,die]
1248 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1250 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1251 emulation library even if a 387 maths coprocessor
1254 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1255 caches in the slab allocator. Saves per-node memory,
1256 but will impact performance.
1260 noapic [SMP,APIC] Tells the kernel to not make use of any
1261 IOAPICs that may be present in the system.
1263 nobats [PPC] Do not use BATs for mapping kernel lowmem
1264 on "Classic" PPC cores.
1268 nodelayacct [KNL] Disable per-task delay accounting
1270 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1272 noefi [X86-32,X86-64] Disable EFI runtime services support.
1276 noexec [X86-32,X86-64]
1277 noexec=on: enable non-executable mappings (default)
1278 noexec=off: disable nn-executable mappings
1280 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1281 register save and restore. The kernel will only save
1282 legacy floating-point registers on task switch.
1284 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1288 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1289 instruction doesn't work correctly and not to
1292 nohalt [IA-64] Tells the kernel not to use the power saving
1293 function PAL_HALT_LIGHT when idle. This increases
1294 power-consumption. On the positive side, it reduces
1295 interrupt wake-up latency, which may improve performance
1296 in certain environments such as networked servers or
1299 nohz= [KNL] Boottime enable/disable dynamic ticks
1300 Valid arguments: on, off
1303 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1305 noirqdebug [X86-32] Disables the code which attempts to detect and
1306 disable unhandled interrupt sources.
1308 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1309 broken timer IRQ sources.
1311 noisapnp [ISAPNP] Disables ISA PnP code.
1313 noinitrd [RAM] Tells the kernel not to load any configured
1318 nojitter [IA64] Disables jitter checking for ITC timers.
1320 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1322 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1324 noltlbs [PPC] Do not use large page/tlb entries for kernel
1325 lowmem mapping on PPC40x.
1327 nomca [IA-64] Disable machine check abort handling
1329 nomce [X86-32] Machine Check Exception
1331 nomfgpt [X86-32] Disable Multi-Function General Purpose
1332 Timer usage (for AMD Geode machines).
1334 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1336 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1337 with UP alternatives
1339 noresidual [PPC] Don't use residual data on PReP machines.
1341 noresume [SWSUSP] Disables resume and restores original swap
1344 no-scroll [VGA] Disables scrollback.
1345 This is required for the Braillex ib80-piezo Braille
1346 reader made by F.H. Papenmeier (Germany).
1350 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1352 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1353 and disable the IO APIC. legacy for "maxcpus=0".
1355 nosoftlockup [KNL] Disable the soft-lockup detector.
1357 nosync [HW,M68K] Disables sync negotiation for all devices.
1359 notsc [BUGS=X86-32] Disable Time Stamp Counter
1361 nousb [USB] Disable the USB subsystem
1365 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1366 one of ['zone', 'node', 'default'] can be specified
1367 This can be set from sysctl after boot.
1368 See Documentation/sysctl/vm.txt for details.
1370 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1375 oprofile.timer= [HW]
1376 Use timer interrupt instead of performance counters
1378 osst= [HW,SCSI] SCSI Tape Driver
1379 Format: <buffer_size>,<write_threshold>
1380 See also Documentation/scsi/st.txt.
1382 panic= [KNL] Kernel behaviour on panic
1385 parkbd.port= [HW] Parallel port number the keyboard adapter is
1386 connected to, default is 0.
1388 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1389 0 for XT, 1 for AT (default is AT).
1392 parport= [HW,PPT] Specify parallel ports. 0 disables.
1393 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1394 Use 'auto' to force the driver to use any
1395 IRQ/DMA settings detected (the default is to
1396 ignore detected IRQ/DMA settings because of
1397 possible conflicts). You can specify the base
1398 address, IRQ, and DMA settings; IRQ and DMA
1399 should be numbers, or 'auto' (for using detected
1400 settings on that particular port), or 'nofifo'
1401 (to avoid using a FIFO even if it is detected).
1402 Parallel ports are assigned in the order they
1403 are specified on the command line, starting
1406 parport_init_mode= [HW,PPT]
1407 Configure VIA parallel port to operate in
1408 a specific mode. This is necessary on Pegasos
1409 computer where firmware has no options for setting
1410 up parallel port mode and sets it to spp.
1411 Currently this function knows 686a and 8231 chips.
1412 Format: [spp|ps2|epp|ecp|ecpepp]
1414 pas2= [HW,OSS] Format:
1415 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1418 See header of drivers/scsi/pas16.c.
1421 Halt all CPUs after the first oops has been printed for
1422 the specified number of seconds. This is to be used if
1423 your oopses keep scrolling off the screen.
1428 See header of drivers/block/paride/pcd.c.
1429 See also Documentation/paride.txt.
1431 pci=option[,option...] [PCI] various PCI subsystem options:
1432 off [X86-32] don't probe for the PCI bus
1433 bios [X86-32] force use of PCI BIOS, don't access
1434 the hardware directly. Use this if your machine
1435 has a non-standard PCI host bridge.
1436 nobios [X86-32] disallow use of PCI BIOS, only direct
1437 hardware access methods are allowed. Use this
1438 if you experience crashes upon bootup and you
1439 suspect they are caused by the BIOS.
1440 conf1 [X86-32] Force use of PCI Configuration
1442 conf2 [X86-32] Force use of PCI Configuration
1444 noaer [PCIE] If the PCIEAER kernel config parameter is
1445 enabled, this kernel boot option can be used to
1446 disable the use of PCIE advanced error reporting.
1447 nodomains [PCI] Disable support for multiple PCI
1448 root domains (aka PCI segments, in ACPI-speak).
1449 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1451 nomsi [MSI] If the PCI_MSI kernel config parameter is
1452 enabled, this kernel boot option can be used to
1453 disable the use of MSI interrupts system-wide.
1454 nosort [X86-32] Don't sort PCI devices according to
1455 order given by the PCI BIOS. This sorting is
1456 done to get a device order compatible with
1458 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1459 routing table. These calls are known to be buggy
1460 on several machines and they hang the machine
1461 when used, but on other computers it's the only
1462 way to get the interrupt routing table. Try
1463 this option if the kernel is unable to allocate
1464 IRQs or discover secondary PCI buses on your
1466 rom [X86-32] Assign address space to expansion ROMs.
1467 Use with caution as certain devices share
1468 address decoders between ROMs and other
1470 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1471 assigned automatically to PCI devices. You can
1472 make the kernel exclude IRQs of your ISA cards
1474 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1475 of the PIRQ table (normally generated
1476 by the BIOS) if it is outside the
1477 F0000h-100000h range.
1478 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1479 useful if the kernel is unable to find your
1480 secondary buses and you want to tell it
1481 explicitly which ones they are.
1482 assign-busses [X86-32] Always assign all PCI bus
1483 numbers ourselves, overriding
1484 whatever the firmware may have done.
1485 usepirqmask [X86-32] Honor the possible IRQ mask stored
1486 in the BIOS $PIR table. This is needed on
1487 some systems with broken BIOSes, notably
1488 some HP Pavilion N5400 and Omnibook XE3
1489 notebooks. This will have no effect if ACPI
1490 IRQ routing is enabled.
1491 noacpi [X86-32] Do not use ACPI for IRQ routing
1492 or for PCI scanning.
1493 use_crs [X86-32] Use _CRS for PCI resource
1495 routeirq Do IRQ routing for all PCI devices.
1496 This is normally done in pci_enable_device(),
1497 so this option is a temporary workaround
1498 for broken drivers that don't call it.
1499 firmware [ARM] Do not re-enumerate the bus but instead
1500 just use the configuration from the
1501 bootloader. This is currently used on
1502 IXP2000 systems where the bus has to be
1503 configured a certain way for adjunct CPUs.
1504 noearly [X86] Don't do any early type 1 scanning.
1505 This might help on some broken boards which
1506 machine check when some devices' config space
1507 is read. But various workarounds are disabled
1508 and some IOMMU drivers will not work.
1509 bfsort Sort PCI devices into breadth-first order.
1510 This sorting is done to get a device
1511 order compatible with older (<= 2.4) kernels.
1512 nobfsort Don't sort PCI devices into breadth-first order.
1513 cbiosize=nn[KMG] The fixed amount of bus space which is
1514 reserved for the CardBus bridge's IO window.
1515 The default value is 256 bytes.
1516 cbmemsize=nn[KMG] The fixed amount of bus space which is
1517 reserved for the CardBus bridge's memory
1518 window. The default value is 64 megabytes.
1520 pcmv= [HW,PCMCIA] BadgePAD 4
1523 See Documentation/paride.txt.
1525 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1528 See arch/parisc/kernel/pdc_chassis.c
1531 See Documentation/paride.txt.
1534 See Documentation/paride.txt.
1536 pirq= [SMP,APIC] Manual mp-table setup
1537 See Documentation/i386/IO-APIC.txt.
1539 plip= [PPT,NET] Parallel port network link
1540 Format: { parport<nr> | timid | 0 }
1541 See also Documentation/parport.txt.
1547 { on | off | curr | res | no-curr | no-res }
1550 [ISAPNP] Exclude IRQs for the autoconfiguration
1553 [ISAPNP] Exclude DMAs for the autoconfiguration
1555 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1556 Ranges are in pairs (I/O port base and size).
1559 [ISAPNP] Exclude memory regions for the
1561 Ranges are in pairs (memory base and size).
1563 print-fatal-signals=
1564 [KNL] debug: print fatal signals
1565 print-fatal-signals=1: print segfault info to
1569 printk.time= Show timing data prefixed to each printk message line
1570 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1572 profile= [KNL] Enable kernel profiling via /proc/profile
1573 Format: [schedule,]<number>
1574 Param: "schedule" - profile schedule points.
1575 Param: <number> - step/bucket size as a power of 2 for
1576 statistical time based profiling.
1577 Param: "sleep" - profile D-state sleeping (millisecs).
1578 Requires CONFIG_SCHEDSTATS
1579 Param: "kvm" - profile VM exits.
1581 processor.max_cstate= [HW,ACPI]
1582 Limit processor to maximum C-state
1583 max_cstate=9 overrides any DMI blacklist limit.
1585 processor.nocst [HW,ACPI]
1586 Ignore the _CST method to determine C-states,
1587 instead using the legacy FADT method
1589 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1591 See Documentation/ramdisk.txt.
1593 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1594 probe for; one of (bare|imps|exps|lifebook|any).
1595 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1597 psmouse.resetafter= [HW,MOUSE]
1598 Try to reset the device after so many bad packets
1601 [HW,MOUSE] Set desired mouse resolution, in dpi.
1602 psmouse.smartscroll=
1603 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1604 0 = disabled, 1 = enabled (default).
1606 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1608 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1611 See Documentation/paride.txt.
1614 [KNL] Number of legacy pty's. Overwrites compiled-in
1617 quiet [KNL] Disable most log messages
1622 See Documentation/md.txt.
1624 ramdisk_blocksize= [RAM]
1625 See Documentation/ramdisk.txt.
1627 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1628 See Documentation/ramdisk.txt.
1630 rcupdate.blimit= [KNL,BOOT]
1631 Set maximum number of finished RCU callbacks to process
1634 rcupdate.qhimark= [KNL,BOOT]
1635 Set threshold of queued
1636 RCU callbacks over which batch limiting is disabled.
1638 rcupdate.qlowmark= [KNL,BOOT]
1639 Set threshold of queued RCU callbacks below which
1640 batch limiting is re-enabled.
1644 Run specified binary instead of /init from the ramdisk,
1645 used for early userspace startup. See initrd.
1647 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1648 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1649 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1651 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1653 reservetop= [X86-32]
1655 Reserves a hole at the top of the kernel virtual
1658 reset_devices [KNL] Force drivers to reset the underlying device
1659 during initialization.
1662 Specify the partition device for software suspend
1664 resume_offset= [SWSUSP]
1665 Specify the offset from the beginning of the partition
1666 given by "resume=" at which the swap header is located,
1667 in <PAGE_SIZE> units (needed only for swap files).
1668 See Documentation/power/swsusp-and-swap-files.txt
1670 retain_initrd [RAM] Keep initrd memory after extraction
1672 rhash_entries= [KNL,NET]
1673 Set number of hash buckets for route cache
1675 riscom8= [HW,SERIAL]
1676 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1678 ro [KNL] Mount root device read-only on boot
1680 root= [KNL] Root filesystem
1682 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1683 mount the root filesystem
1685 rootflags= [KNL] Set root filesystem mount option string
1687 rootfstype= [KNL] Set root filesystem type
1689 rootwait [KNL] Wait (indefinitely) for root device to show up.
1690 Useful for devices that are detected asynchronously
1691 (e.g. USB and MMC devices).
1693 root_plug.vendor_id=
1694 [ROOTPLUG] Override the default vendor ID
1696 root_plug.product_id=
1697 [ROOTPLUG] Override the default product ID
1700 [ROOTPLUG] Enable debugging output
1702 rw [KNL] Mount root device read-write on boot
1704 S [KNL] Run init in single mode
1707 See drivers/net/irda/sa1100_ir.c.
1709 sbni= [NET] Granch SBNI12 leased line adapter
1711 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1712 Format: <io>[,<timeout>[,<isapnp>]]
1714 scsi_debug_*= [SCSI]
1715 See drivers/scsi/scsi_debug.c.
1717 scsi_default_dev_flags=
1718 [SCSI] SCSI default device flags
1721 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1722 Format: <vendor>:<model>:<flags>
1723 (flags are integer value)
1725 scsi_logging_level= [SCSI] a bit mask of logging levels
1726 See drivers/scsi/scsi_logging.h for bits. Also
1727 settable via sysctl at dev.scsi.logging_level
1728 (/proc/sys/dev/scsi/logging_level).
1729 There is also a nice 'scsi_logging_level' script in the
1730 S390-tools package, available for download at
1731 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1733 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1734 discovered. async scans them in kernel threads,
1735 allowing boot to proceed. none ignores them, expecting
1736 user space to do the scan.
1738 selinux [SELINUX] Disable or enable SELinux at boot time.
1739 Format: { "0" | "1" }
1740 See security/selinux/Kconfig help text.
1743 Default value is set via kernel config option.
1744 If enabled at boot time, /selinux/disable can be used
1745 later to disable prior to initial policy load.
1747 selinux_compat_net =
1748 [SELINUX] Set initial selinux_compat_net flag value.
1749 Format: { "0" | "1" }
1750 0 -- use new secmark-based packet controls
1751 1 -- use legacy packet controls
1752 Default value is 0 (preferred).
1753 Value can be changed at runtime via
1754 /selinux/compat_net.
1756 serialnumber [BUGS=X86-32]
1759 Maximal number of shapers.
1762 See header of drivers/scsi/sim710.c.
1769 slub_debug[=options[,slabs]] [MM, SLUB]
1770 Enabling slub_debug allows one to determine the
1771 culprit if slab objects become corrupted. Enabling
1772 slub_debug can create guard zones around objects and
1773 may poison objects when not in use. Also tracks the
1774 last alloc / free. For more information see
1775 Documentation/vm/slub.txt.
1777 slub_max_order= [MM, SLUB]
1778 Determines the maximum allowed order for slabs.
1779 A high setting may cause OOMs due to memory
1780 fragmentation. For more information see
1781 Documentation/vm/slub.txt.
1783 slub_min_objects= [MM, SLUB]
1784 The minimum number of objects per slab. SLUB will
1785 increase the slab order up to slub_max_order to
1786 generate a sufficiently large slab able to contain
1787 the number of objects indicated. The higher the number
1788 of objects the smaller the overhead of tracking slabs
1789 and the less frequently locks need to be acquired.
1790 For more information see Documentation/vm/slub.txt.
1792 slub_min_order= [MM, SLUB]
1793 Determines the mininum page order for slabs. Must be
1794 lower than slub_max_order.
1795 For more information see Documentation/vm/slub.txt.
1797 slub_nomerge [MM, SLUB]
1798 Disable merging of slabs with similar size. May be
1799 necessary if there is some reason to distinguish
1800 allocs to different slabs. Debug options disable
1801 merging on their own.
1802 For more information see Documentation/vm/slub.txt.
1805 Format: <io1>[,<io2>[,...,<io8>]]
1807 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1808 attempt to substitute SMP alternatives once at boot.
1810 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1811 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1812 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1813 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1814 smsc-ircc2.ircc_irq= [HW] IRQ line
1815 smsc-ircc2.ircc_dma= [HW] DMA channel
1816 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1817 0: Toshiba Satellite 1800 (GP data pin select)
1818 1: Fast pin select (default)
1821 snd-ad1816a= [HW,ALSA]
1823 snd-ad1848= [HW,ALSA]
1825 snd-ali5451= [HW,ALSA]
1827 snd-als100= [HW,ALSA]
1829 snd-als4000= [HW,ALSA]
1831 snd-azt2320= [HW,ALSA]
1833 snd-cmi8330= [HW,ALSA]
1835 snd-cmipci= [HW,ALSA]
1837 snd-cs4231= [HW,ALSA]
1839 snd-cs4232= [HW,ALSA]
1841 snd-cs4236= [HW,ALSA]
1843 snd-cs4281= [HW,ALSA]
1845 snd-cs46xx= [HW,ALSA]
1847 snd-dt019x= [HW,ALSA]
1849 snd-dummy= [HW,ALSA]
1851 snd-emu10k1= [HW,ALSA]
1853 snd-ens1370= [HW,ALSA]
1855 snd-ens1371= [HW,ALSA]
1857 snd-es968= [HW,ALSA]
1859 snd-es1688= [HW,ALSA]
1861 snd-es18xx= [HW,ALSA]
1863 snd-es1938= [HW,ALSA]
1865 snd-es1968= [HW,ALSA]
1867 snd-fm801= [HW,ALSA]
1869 snd-gusclassic= [HW,ALSA]
1871 snd-gusextreme= [HW,ALSA]
1873 snd-gusmax= [HW,ALSA]
1877 snd-ice1712= [HW,ALSA]
1879 snd-intel8x0= [HW,ALSA]
1881 snd-interwave= [HW,ALSA]
1886 snd-korg1212= [HW,ALSA]
1888 snd-maestro3= [HW,ALSA]
1890 snd-mpu401= [HW,ALSA]
1892 snd-mtpav= [HW,ALSA]
1894 snd-nm256= [HW,ALSA]
1896 snd-opl3sa2= [HW,ALSA]
1904 snd-opti93x= [HW,ALSA]
1908 snd-rme32= [HW,ALSA]
1910 snd-rme96= [HW,ALSA]
1912 snd-rme9652= [HW,ALSA]
1918 snd-sbawe= [HW,ALSA]
1920 snd-serial= [HW,ALSA]
1922 snd-sgalaxy= [HW,ALSA]
1924 snd-sonicvibes= [HW,ALSA]
1929 snd-sun-cs4231= [HW,ALSA]
1931 snd-trident= [HW,ALSA]
1933 snd-usb-audio= [HW,ALSA,USB]
1935 snd-via82xx= [HW,ALSA]
1937 snd-virmidi= [HW,ALSA]
1939 snd-wavefront= [HW,ALSA]
1941 snd-ymfpci= [HW,ALSA]
1943 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1944 See Documentation/sonypi.txt
1946 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1947 See Documentation/specialix.txt.
1949 spia_io_base= [HW,MTD]
1955 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1957 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1958 See Documentation/scsi/st.txt.
1962 Set the STI (builtin display/keyboard on the HP-PARISC
1963 machines) console (graphic card) which should be used
1964 as the initial boot-console.
1965 See also comment in drivers/video/console/sticore.c.
1968 See comment in drivers/video/console/sticore.c.
1971 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1975 Control how the NFS server code allocates CPUs to
1976 service thread pools. Depending on how many NICs
1977 you have and where their interrupts are bound, this
1978 option will affect which CPUs will do NFS serving.
1979 Note: this parameter cannot be changed while the
1980 NFS server is running.
1982 auto the server chooses an appropriate mode
1983 automatically using heuristics
1984 global a single global pool contains all CPUs
1985 percpu one pool for each CPU
1986 pernode one pool for each NUMA node (equivalent
1987 to global on non-NUMA machines)
1989 swiotlb= [IA-64] Number of I/O TLB slabs
1993 sym53c416= [HW,SCSI]
1994 See header of drivers/scsi/sym53c416.c.
1996 sysrq_always_enabled
1998 Ignore sysrq setting - this boot parameter will
1999 neutralize any effect of /proc/sys/kernel/sysrq.
2000 Useful for debugging.
2003 See header of drivers/scsi/t128.c.
2007 thash_entries= [KNL,NET]
2008 Set number of hash buckets for TCP connection
2010 thermal.act= [HW,ACPI]
2011 -1: disable all active trip points in all thermal zones
2012 <degrees C>: override all lowest active trip points
2014 thermal.crt= [HW,ACPI]
2015 -1: disable all critical trip points in all thermal zones
2016 <degrees C>: lower all critical trip points
2018 thermal.nocrt= [HW,ACPI]
2019 Set to disable actions on ACPI thermal zone
2020 critical and hot trip points.
2022 thermal.off= [HW,ACPI]
2023 1: disable ACPI thermal control
2025 thermal.psv= [HW,ACPI]
2026 -1: disable all passive trip points
2027 <degrees C>: override all passive trip points to this value
2029 thermal.tzp= [HW,ACPI]
2030 Specify global default ACPI thermal zone polling rate
2031 <deci-seconds>: poll all this frequency
2032 0: no polling (default)
2034 tipar.timeout= [HW,PPT]
2035 Set communications timeout in tenths of a second
2038 tipar.delay= [HW,PPT]
2039 Set inter-bit delay in microseconds (default 10).
2042 See comment before function dc390_setup() in
2043 drivers/scsi/tmscsim.c.
2047 trix= [HW,OSS] MediaTrix AudioTrix Pro
2049 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2051 turbografx.map[2|3]= [HW,JOY]
2052 TurboGraFX parallel port interface
2054 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2055 See also Documentation/input/joystick-parport.txt
2057 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2058 See header of drivers/scsi/u14-34f.c.
2067 [USB] Ignore overcurrent events (default N).
2068 Some badly-designed motherboards generate lots of
2069 bogus events, for ports that aren't wired to
2070 anything. Set this parameter to avoid log spamming.
2071 Note that genuine overcurrent events won't be
2074 usbcore.autosuspend=
2075 [USB] The autosuspend time delay (in seconds) used
2076 for newly-detected USB devices (default 2). This
2077 is the time required before an idle device will be
2078 autosuspended. Devices for which the delay is set
2079 to a negative value won't be autosuspended at all.
2082 [USBHID] The interval which mice are to be polled at.
2084 vdso= [X86-32,SH,x86-64]
2085 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2086 vdso=1: enable VDSO (default)
2087 vdso=0: disable VDSO mapping
2089 vdso32= [X86-32,X86-64]
2090 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2091 vdso32=1: enable 32-bit VDSO (default)
2092 vdso32=0: disable 32-bit VDSO mapping
2095 vector=percpu: enable percpu vector domain
2097 video= [FB] Frame buffer configuration
2098 See Documentation/fb/modedb.txt.
2100 vga= [BOOT,X86-32] Select a particular video mode
2101 See Documentation/i386/boot.txt and
2102 Documentation/svga.txt.
2103 Use vga=ask for menu.
2104 This is actually a boot loader parameter; the value is
2105 passed to the kernel using a special protocol.
2107 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2108 size of <nn>. This can be used to increase the
2109 minimum size (128MB on x86). It can also be used to
2110 decrease the size and leave more room for directly
2113 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2116 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2119 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2122 waveartist= [HW,OSS]
2123 Format: <io>,<irq>,<dma>,<dma2>
2126 See header of drivers/scsi/wd33c93.c.
2129 See header of drivers/scsi/wd7000.c.
2132 See Documentation/watchdog/wdt.txt.
2134 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2135 xd_geo= See header of drivers/block/xd.c.
2137 xirc2ps_cs= [NET,PCMCIA]
2139 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2141 norandmaps Don't use address space randomization
2142 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2144 ______________________________________________________________________
2148 Add documentation for ALSA options.
2149 Add more DRM drivers.