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.
369 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
395 Value can be changed at runtime via
396 /selinux/checkreqprot.
399 See Documentation/s390/CommonIO for details.
402 See Documentation/s390/CommonIO for details.
404 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
406 Forces specified clocksource (if available) to be used
407 when calculating gettimeofday(). If specified
408 clocksource is not available, it defaults to PIT.
409 Format: { pit | tsc | cyclone | pmtmr }
411 clocksource= [GENERIC_TIME] Override the default clocksource
413 Override the default clocksource and use the clocksource
414 with the name specified.
415 Some clocksource names to choose from, depending on
417 [all] jiffies (this is the base, fallback clocksource)
419 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
420 pxa_timer,timer3,32k_counter,timer0_1
422 [X86-32] pit,hpet,tsc,vmi-timer;
423 scx200_hrt on Geode; cyclone on IBM x440
431 clearcpuid=BITNUM [X86]
432 Disable CPUID feature X for the kernel. See
433 include/asm-x86/cpufeature.h for the valid bit numbers.
434 Note the Linux specific bits are not necessarily
435 stable over kernel options, but the vendor specific
437 Also note that user programs calling CPUID directly
438 or using the feature without checking anything
439 will still see it. This just prevents it from
440 being used by the kernel or shown in /proc/cpuinfo.
441 Also note the kernel might malfunction if you disable
444 code_bytes [IA32/X86_64] How many bytes of object code to print
451 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
452 over the 8254 in addition to over the IO-APIC. The
453 kernel tries to set a sensible default.
455 hpet= [X86-32,HPET] option to control HPET usage
456 Format: { enable (default) | disable | force }
457 disable: disable HPET and use PIT instead
458 force: allow force enabled of undocumented chips (ICH4,
461 com20020= [HW,NET] ARCnet - COM20020 chipset
463 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
465 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
469 ARCnet - COM90xx chipset (memory-mapped buffers)
470 Format: <io>[,<irq>[,<memstart>]]
472 condev= [HW,S390] console device
475 console= [KNL] Output console device and options.
477 tty<n> Use the virtual console device <n>.
481 Use the specified serial port. The options are of
482 the form "bbbbpnf", where "bbbb" is the baud rate,
483 "p" is parity ("n", "o", or "e"), "n" is number of
484 bits, and "f" is flow control ("r" for RTS or
485 omit it). Default is "9600n8".
487 See Documentation/serial-console.txt for more
489 Documentation/networking/netconsole.txt for an
492 uart[8250],io,<addr>[,options]
493 uart[8250],mmio,<addr>[,options]
494 Start an early, polled-mode console on the 8250/16550
495 UART at the specified I/O port or MMIO address,
496 switching to the matching ttyS device later. The
497 options are the same as for ttyS, above.
499 If the device connected to the port is not a TTY but a braille
500 device, prepend "brl," before the device type, for instance
502 For now, only VisioBraille is supported.
504 earlycon= [KNL] Output early console device and options.
505 uart[8250],io,<addr>[,options]
506 uart[8250],mmio,<addr>[,options]
507 Start an early, polled-mode console on the 8250/16550
508 UART at the specified I/O port or MMIO address.
509 The options are the same as for ttyS, above.
512 [HW] Never suspend the console
513 Disable suspending of consoles during suspend and
514 hibernate operations. Once disabled, debugging
515 messages can reach various consoles while the rest
516 of the system is being put to sleep (ie, while
517 debugging driver suspend/resume hooks). This may
518 not work reliably with all consoles, but is known
519 to work with serial and VGA consoles.
521 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
523 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
525 crashkernel=nn[KMG]@ss[KMG]
526 [KNL] Reserve a chunk of physical memory to
527 hold a kernel to switch to with kexec on panic.
529 crashkernel=range1:size1[,range2:size2,...][@offset]
530 [KNL] Same as above, but depends on the memory
531 in the running system. The syntax of range is
532 start-[end] where start and end are both
533 a memory unit (amount[KMG]). See also
534 Documentation/kdump/kdump.txt for a example.
537 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
542 cs89x0_media= [HW,NET]
543 Format: { rj45 | aui | bnc }
546 See header of drivers/s390/block/dasd_devmap.c.
548 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
549 (one device per port)
550 Format: <port#>,<type>
551 See also Documentation/input/joystick-parport.txt
553 debug [KNL] Enable kernel debugging (events log level).
556 [KNL] verbose self-tests
558 Print debugging info while doing the locking API
560 We default to 0 (no extra messages), setting it to
561 1 will print _a lot_ more information - normally
562 only useful to kernel developers.
564 debug_objects [KNL] Enable object debugging
566 decnet.addr= [HW,NET]
567 Format: <area>[,<node>]
568 See also Documentation/networking/decnet.txt.
571 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
572 Change the default blue palette of the console.
573 This is a 16-member array composed of values
577 Format: <green0>,<green1>,<green2>,...,<green15>
578 Change the default green palette of the console.
579 This is a 16-member array composed of values
583 Format: <red0>,<red1>,<red2>,...,<red15>
584 Change the default red palette of the console.
585 This is a 16-member array composed of values
591 Set system-wide default UTF-8 mode for all tty's.
592 Default is 1, i.e. UTF-8 mode is enabled for all
593 newly opened terminals.
596 Set number of hash buckets for dentry cache.
599 IO parameters + enable/disable command.
601 digiepca= [HW,SERIAL]
602 See drivers/char/README.epca and
603 Documentation/digiepca.txt.
605 disable_mtrr_trim [X86, Intel and AMD only]
606 By default the kernel will trim any uncacheable
607 memory out of your available memory pool based on
608 MTRR settings. This parameter disables that behavior,
609 possibly causing your machine to run very slowly.
611 dmasound= [HW,OSS] Sound subsystem buffers
617 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
619 earlyprintk=serial[,ttySn[,baudrate]]
621 Append ",keep" to not disable it when the real console
624 Only vga or serial at a time, not both.
626 Currently only ttyS0 and ttyS1 are supported.
628 Interaction with the standard serial driver is not
631 The VGA output is eventually overwritten by the real
637 Format: {"off" | "on" | "skip[mbr]"}
639 eisa_irq_edge= [PARISC,HW]
640 See header of drivers/parisc/eisa.c.
643 See comment before function elanfreq_setup() in
644 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
647 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
648 See Documentation/block/as-iosched.txt and
649 Documentation/block/deadline-iosched.txt for details.
651 elfcorehdr= [X86-32, X86_64]
652 Specifies physical address of start of kernel core
653 image elf header. Generally kexec loader will
654 pass this option to capture kernel.
655 See Documentation/kdump/kdump.txt for details.
657 enforcing [SELINUX] Set initial enforcing status.
659 See security/selinux/Kconfig help text.
660 0 -- permissive (log only, no denials).
661 1 -- enforcing (deny and log).
663 Value can be changed at runtime via /selinux/enforce.
666 Format: <spdif>,[<nomix>,[<amplifier>]]
667 See also header of sound/oss/es1371.c.
669 ether= [HW,NET] Ethernet cards parameters
670 This option is obsoleted by the "netdev=" option, which
671 has equivalent usage. See its documentation for details.
673 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
678 fail_make_request=[KNL]
679 General fault injection mechanism.
680 Format: <interval>,<probability>,<space>,<times>
681 See also /Documentation/fault-injection/.
684 See header of drivers/scsi/fd_mcs.c.
687 See header of drivers/scsi/fdomain.c.
690 See Documentation/floppy.txt.
693 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
694 support via parallel port (up to 5 devices per port)
695 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
696 See also Documentation/input/joystick-parport.txt
700 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
705 See header of drivers/scsi/gdth.c.
707 gpt [EFI] Forces disk with valid GPT signature but
708 invalid Protective MBR to be treated as GPT.
712 hashdist= [KNL,NUMA] Large hashes allocated during boot
713 are distributed across NUMA nodes. Defaults on
714 for IA-64, off otherwise.
715 Format: 0 | 1 (for off | on)
717 hcl= [IA-64] SGI's Hardware Graph compatibility layer
719 hd= [EIDE] (E)IDE hard drive subsystem geometry
720 Format: <cyl>,<head>,<sect>
722 hd?= [HW] (E)IDE subsystem
723 hd?lun= See Documentation/ide/ide.txt.
725 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
726 size of <nn>. This works even on boxes that have no
727 highmem otherwise. This also works to reduce highmem
728 size on bigger boxes.
730 highres= [KNL] Enable/disable high resolution timer mode.
731 Valid parameters: "on", "off"
735 See Documentation/isdn/README.HiSax.
737 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
738 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
740 i8042.direct [HW] Put keyboard port into non-translated mode
741 i8042.dumbkbd [HW] Pretend that controller can only read data from
742 keyboard and cannot control its state
743 (Don't attempt to blink the leds)
744 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
745 i8042.nokbd [HW] Don't check/create keyboard port
746 i8042.noloop [HW] Disable the AUX Loopback command while probing
748 i8042.nomux [HW] Don't check presence of an active multiplexing
750 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
753 [HW] Frequency with which keyboard LEDs should blink
754 when kernel panics (default is 0.5 sec)
755 i8042.reset [HW] Reset the controller during init and cleanup
756 i8042.unlock [HW] Unlock (ignore) the keylock
760 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
761 indicates that the driver is running on unsupported
763 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
764 does not match list of supported models.
766 [HW] Report power status in /proc/i8k
767 (disabled by default)
768 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
771 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
772 See Documentation/mca.txt.
775 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
777 ide= [HW] (E)IDE subsystem
778 Format: ide=nodma or ide=doubler
779 See Documentation/ide/ide.txt.
781 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
782 See Documentation/ide/ide.txt.
785 Format: idle=poll or idle=mwait
786 Poll forces a polling idle loop that can slightly improves the performance
787 of waking up a idle CPU, but will use a lot of power and make the system
788 run hot. Not recommended.
789 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
790 to not use it because it doesn't save as much power as a normal idle
791 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
794 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
795 Claim all unknown PCI IDE storage controllers.
797 ignore_loglevel [KNL]
798 Ignore loglevel setting - this will print /all/
799 kernel messages to the console. Useful for debugging.
802 Set number of hash buckets for inode cache.
805 See header of drivers/scsi/in2000.c.
809 Run specified binary instead of /sbin/init as init
812 initcall_debug [KNL] Trace initcalls as they are executed. Useful
813 for working out where the kernel is dying during
816 initrd= [BOOT] Specify the location of the initial ramdisk
818 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
836 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
838 Disable intel iommu driver.
839 igfx_off [Default Off]
840 By default, gfx is mapped as normal device. If a gfx
841 device has a dedicated DMAR unit, the DMAR unit is
842 bypassed by not enabling DMAR with this option. In
843 this case, gfx device will use physical address for
846 With this option iommu will not optimize to look
847 for io virtual address below 32 bit forcing dual
848 address cycle on pci bus for cards supporting greater
849 than 32 bit addressing. The default is to look
850 for translation below 32 bit and if not available
851 then look in the higher range.
853 With this option on every unmap_single operation will
854 result in a hardware IOTLB flush operation as opposed
855 to batching them for performance.
857 io_delay= [X86-32,X86-64] I/O delay method
859 Standard port 0x80 based delay
861 Alternate port 0xed based delay (needed on some systems)
863 Simple two microseconds delay
867 io7= [HW] IO7 for Marvel based alpha systems
868 See comment before marvel_specify_io7 in
869 arch/alpha/kernel/core_marvel.c.
872 See Documentation/filesystems/nfsroot.txt.
874 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
875 See comment before ip2_setup() in
876 drivers/char/ip2/ip2base.c.
878 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
879 See header of drivers/scsi/ips.c.
881 ports= [IP_VS_FTP] IPVS ftp helper module
883 Up to 8 (IP_VS_APP_MAX_PORTS) ports
885 Format: <port>,<port>....
888 When an interrupt is not handled search all handlers
889 for it. Intended to get systems with badly broken
893 When an interrupt is not handled search all handlers
894 for it. Also check all handlers each timer
895 interrupt. Intended to get systems with badly broken
899 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
901 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
903 <cpu number>,...,<cpu number>
905 <cpu number>-<cpu number> (must be a positive range in ascending order)
907 <cpu number>,...,<cpu number>-<cpu number>
908 This option can be used to specify one or more CPUs
909 to isolate from the general SMP balancing and scheduling
910 algorithms. The only way to move a process onto or off
911 an "isolated" CPU is via the CPU affinity syscalls.
912 <cpu number> begins at 0 and the maximum value is
913 "number of CPUs in system - 1".
915 This option is the preferred way to isolate CPUs. The
916 alternative -- manually setting the CPU mask of all
917 tasks in the system -- can cause problems and
918 suboptimal load balancer performance.
922 js= [HW,JOY] Analog joystick
923 See Documentation/input/joystick.txt.
925 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
926 specifies the amount of memory usable by the kernel
927 for non-movable allocations. The requested amount is
928 spread evenly throughout all nodes in the system. The
929 remaining memory in each node is used for Movable
930 pages. In the event, a node is too small to have both
931 kernelcore and Movable pages, kernelcore pages will
932 take priority and other nodes will have a larger number
933 of kernelcore pages. The Movable zone is used for the
934 allocation of pages that may be reclaimed or moved
935 by the page migration subsystem. This means that
936 HugeTLB pages may not be allocated from this zone.
937 Note that allocations like PTEs-from-HighMem still
938 use the HighMem zone if it exists, and the Normal
941 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
942 is similar to kernelcore except it specifies the
943 amount of memory used for migratable allocations.
944 If both kernelcore and movablecore is specified,
945 then kernelcore will be at *least* the specified
946 value but may be more. If movablecore on its own
947 is specified, the administrator must be careful
948 that the amount of memory usable for all allocations
953 kstack=N [X86-32,X86-64] Print N words from the kernel stack
956 kgdboc= [HW] kgdb over consoles.
957 Requires a tty driver that supports console polling.
958 (only serial suported for now)
959 Format: <serial_device>[,baud]
965 lapic [X86-32,APIC] Enable the local APIC even if BIOS
968 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
971 libata.dma= [LIBATA] DMA control
972 libata.dma=0 Disable all PATA and SATA DMA
973 libata.dma=1 PATA and SATA Disk DMA only
974 libata.dma=2 ATAPI (CDROM) DMA only
975 libata.dma=4 Compact Flash DMA only
976 Combinations also work, so libata.dma=3 enables DMA
977 for disks and CDROMs, but not CFs.
979 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
983 libata.force= [LIBATA] Force configurations. The format is comma
984 separated list of "[ID:]VAL" where ID is
985 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
986 matching port, link or device. Basically, it matches
987 the ATA ID string printed on console by libata. If
988 the whole ID part is omitted, the last PORT and DEVICE
989 values are used. If ID hasn't been specified yet, the
990 configuration applies to all ports, links and devices.
992 If only DEVICE is omitted, the parameter applies to
993 the port and all links and devices behind it. DEVICE
994 number of 0 either selects the first device or the
995 first fan-out link behind PMP device. It does not
996 select the host link. DEVICE number of 15 selects the
997 host link and device attached to it.
999 The VAL specifies the configuration to force. As long
1000 as there's no ambiguity shortcut notation is allowed.
1001 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1002 The following configurations can be forced.
1004 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1005 Any ID with matching PORT is used.
1007 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1009 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1010 udma[/][16,25,33,44,66,100,133] notation is also
1013 * [no]ncq: Turn on or off NCQ.
1015 If there are multiple matching configurations changing
1016 the same attribute, the last one is used.
1018 load_ramdisk= [RAM] List of ramdisks to load from floppy
1019 See Documentation/ramdisk.txt.
1021 lockd.nlm_grace_period=P [NFS] Assign grace period.
1024 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1027 lockd.nlm_timeout=T [NFS] Assign timeout value.
1030 lockd.nlm_udpport=M [NFS] Assign UDP port.
1033 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1036 loglevel= All Kernel Messages with a loglevel smaller than the
1037 console loglevel will be printed to the console. It can
1038 also be changed with klogd or other programs. The
1039 loglevels are defined as follows:
1041 0 (KERN_EMERG) system is unusable
1042 1 (KERN_ALERT) action must be taken immediately
1043 2 (KERN_CRIT) critical conditions
1044 3 (KERN_ERR) error conditions
1045 4 (KERN_WARNING) warning conditions
1046 5 (KERN_NOTICE) normal but significant condition
1047 6 (KERN_INFO) informational
1048 7 (KERN_DEBUG) debug-level messages
1050 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1051 Format: { n | nk | nM }
1052 n must be a power of two. The default size
1053 is set in the kernel config file.
1055 logo.nologo [FB] Disables display of the built-in Linux logo.
1056 This may be used to provide more screen space for
1057 kernel log messages and is useful when debugging
1058 kernel boot problems.
1060 lp=0 [LP] Specify parallel ports to use, e.g,
1061 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1062 lp=reset first parallel port). 'lp=0' disables the
1063 lp=auto printer driver. 'lp=reset' (which can be
1064 specified in addition to the ports) causes
1065 attached printers to be reset. Using
1066 lp=port1,port2,... specifies the parallel ports
1067 to associate lp devices with, starting with
1068 lp0. A port specification may be 'none' to skip
1069 that lp device, or a parport name such as
1070 'parport0'. Specifying 'lp=auto' instead of a
1071 port specification list means that device IDs
1072 from each port should be examined, to see if
1073 an IEEE 1284-compliant printer is attached; if
1074 so, the driver will manage that printer.
1075 See also header of drivers/char/lp.c.
1078 Sets loops_per_jiffy to given constant, thus avoiding
1079 time-consuming boot-time autodetection (up to 250 ms per
1080 CPU). 0 enables autodetection (default). To determine
1081 the correct value for your kernel, boot with normal
1082 autodetection and see what value is printed. Note that
1083 on SMP systems the preset will be applied to all CPUs,
1084 which is likely to cause problems if your CPUs need
1085 significantly divergent settings. An incorrect value
1086 will cause delays in the kernel to be wrong, leading to
1087 unpredictable I/O errors and other breakage. Although
1088 unlikely, in the extreme case this might damage your
1092 Format: <io>,<irq>,<dma>
1094 mac5380= [HW,SCSI] Format:
1095 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1097 machvec= [IA64] Force the use of a particular machine-vector
1098 (machvec) in a generic kernel.
1099 Example: machvec=hpzx1_swiotlb
1101 max_loop= [LOOP] Maximum number of loopback devices that can
1105 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1106 should make use of. maxcpus=n : n >= 0 limits the
1107 kernel to using 'n' processors. n=0 is a special case,
1108 it is equivalent to "nosmp", which also disables
1111 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1112 equal to this physical address is ignored.
1114 max_luns= [SCSI] Maximum number of LUNs to probe.
1115 Should be between 1 and 2^32-1.
1118 [SCSI] Maximum number of LUNs received.
1119 Should be between 1 and 16384.
1123 mce [X86-32] Machine Check Exception
1125 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1127 md= [HW] RAID subsystems devices and level
1128 See Documentation/md.txt.
1131 Format: <first>,<last>
1132 Specifies range of consoles to be captured by the MDA.
1134 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1135 Amount of memory to be used when the kernel is not able
1136 to see the whole system memory or for test.
1137 [X86-32] Use together with memmap= to avoid physical
1138 address space collisions. Without memmap= PCI devices
1139 could be placed at addresses belonging to unused RAM.
1141 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1144 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1145 E820 memory map, as specified by the user.
1146 Such memmap=exactmap lines can be constructed based on
1147 BIOS output or other requirements. See the memmap=nn@ss
1150 memmap=nn[KMG]@ss[KMG]
1151 [KNL] Force usage of a specific region of memory
1152 Region of memory to be used, from ss to ss+nn.
1154 memmap=nn[KMG]#ss[KMG]
1155 [KNL,ACPI] Mark specific memory as ACPI data.
1156 Region of memory to be used, from ss to ss+nn.
1158 memmap=nn[KMG]$ss[KMG]
1159 [KNL,ACPI] Mark specific memory as reserved.
1160 Region of memory to be used, from ss to ss+nn.
1161 Example: Exclude memory from 0x18690000-0x1869ffff
1162 memmap=64K$0x18690000
1164 memmap=0x10000$0x18690000
1166 memtest= [KNL,X86_64] Enable memtest
1168 range: 0,4 : pattern number
1169 default : 0 <disable>
1171 meye.*= [HW] Set MotionEye Camera parameters
1172 See Documentation/video4linux/meye.txt.
1174 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1175 Multi-Function General Purpose Timers on AMD Geode
1178 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1179 the BIOS has incorrectly applied a workaround. TinyBIOS
1180 version 0.98 is known to be affected, 0.99 fixes the
1181 problem by letting the user disable the workaround.
1186 [MOUSE] Maximum time between finger touching and
1187 leaving touchpad surface for touch to be considered
1188 a tap and be reported as a left button click (for
1189 touchpads working in absolute mode only).
1191 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1192 reporting absolute coordinates, such as tablets
1193 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1194 reporting absolute coordinates, such as tablets
1199 MTD_Partition= [MTD]
1200 Format: <name>,<region-number>,<size>,<offset>
1202 MTD_Region= [MTD] Format:
1203 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1206 See drivers/mtd/cmdlinepart.c.
1208 mtouchusb.raw_coordinates=
1209 [HW] Make the MicroTouch USB driver use raw coordinates
1210 ('y', default) or cooked coordinates ('n')
1212 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1215 See header of drivers/scsi/NCR_D700.c.
1219 ncr53c400= [HW,SCSI]
1221 ncr53c400a= [HW,SCSI]
1223 ncr53c406a= [HW,SCSI]
1225 ncr53c8xx= [HW,SCSI]
1227 netdev= [NET] Network devices parameters
1228 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1229 Note that mem_start is often overloaded to mean
1230 something different and driver-specific.
1231 This usage is only documented in each driver source
1235 See Documentation/filesystems/nfsroot.txt.
1237 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1238 See Documentation/filesystems/nfsroot.txt.
1240 nfs.callback_tcpport=
1241 [NFS] set the TCP port on which the NFSv4 callback
1242 channel should listen.
1244 nfs.idmap_cache_timeout=
1245 [NFS] set the maximum lifetime for idmapper cache
1249 [NFS] enable 64-bit inode numbers.
1250 If zero, the NFS client will fake up a 32-bit inode
1251 number for the readdir() and stat() syscalls instead
1252 of returning the full 64-bit number.
1253 The default is to return 64-bit inode numbers.
1255 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1256 when a NMI is triggered.
1257 Format: [state][,regs][,debounce][,die]
1259 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1261 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1262 emulation library even if a 387 maths coprocessor
1265 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1266 caches in the slab allocator. Saves per-node memory,
1267 but will impact performance.
1271 noapic [SMP,APIC] Tells the kernel to not make use of any
1272 IOAPICs that may be present in the system.
1274 nobats [PPC] Do not use BATs for mapping kernel lowmem
1275 on "Classic" PPC cores.
1279 nodelayacct [KNL] Disable per-task delay accounting
1281 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1283 noefi [X86-32,X86-64] Disable EFI runtime services support.
1287 noexec [X86-32,X86-64]
1288 On X86-32 available only on PAE configured kernels.
1289 noexec=on: enable non-executable mappings (default)
1290 noexec=off: disable non-executable mappings
1293 This affects only 32-bit executables.
1294 noexec32=on: enable non-executable mappings (default)
1295 read doesn't imply executable mappings
1296 noexec32=off: disable non-executable mappings
1297 read implies executable mappings
1299 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1300 register save and restore. The kernel will only save
1301 legacy floating-point registers on task switch.
1303 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1307 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1308 instruction doesn't work correctly and not to
1311 nohalt [IA-64] Tells the kernel not to use the power saving
1312 function PAL_HALT_LIGHT when idle. This increases
1313 power-consumption. On the positive side, it reduces
1314 interrupt wake-up latency, which may improve performance
1315 in certain environments such as networked servers or
1318 nohz= [KNL] Boottime enable/disable dynamic ticks
1319 Valid arguments: on, off
1322 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1324 noirqdebug [X86-32] Disables the code which attempts to detect and
1325 disable unhandled interrupt sources.
1327 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1328 broken timer IRQ sources.
1330 noisapnp [ISAPNP] Disables ISA PnP code.
1332 noinitrd [RAM] Tells the kernel not to load any configured
1337 nojitter [IA64] Disables jitter checking for ITC timers.
1339 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1341 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1343 noltlbs [PPC] Do not use large page/tlb entries for kernel
1344 lowmem mapping on PPC40x.
1346 nomca [IA-64] Disable machine check abort handling
1348 nomce [X86-32] Machine Check Exception
1350 nomfgpt [X86-32] Disable Multi-Function General Purpose
1351 Timer usage (for AMD Geode machines).
1353 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1355 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1356 with UP alternatives
1358 noresidual [PPC] Don't use residual data on PReP machines.
1360 noresume [SWSUSP] Disables resume and restores original swap
1363 no-scroll [VGA] Disables scrollback.
1364 This is required for the Braillex ib80-piezo Braille
1365 reader made by F.H. Papenmeier (Germany).
1369 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1371 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1372 and disable the IO APIC. legacy for "maxcpus=0".
1374 nosoftlockup [KNL] Disable the soft-lockup detector.
1376 nosync [HW,M68K] Disables sync negotiation for all devices.
1378 notsc [BUGS=X86-32] Disable Time Stamp Counter
1380 nousb [USB] Disable the USB subsystem
1384 nptcg= [IA64] Override max number of concurrent global TLB
1385 purges which is reported from either PAL_VM_SUMMARY or
1388 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1389 one of ['zone', 'node', 'default'] can be specified
1390 This can be set from sysctl after boot.
1391 See Documentation/sysctl/vm.txt for details.
1393 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1395 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1396 Rather than timing out after 20 ms if an EC
1397 command is not properly ACKed, override the length
1398 of the timeout. We have interrupts disabled while
1399 waiting for the ACK, so if this is set too high
1400 interrupts *may* be lost!
1405 oprofile.timer= [HW]
1406 Use timer interrupt instead of performance counters
1408 osst= [HW,SCSI] SCSI Tape Driver
1409 Format: <buffer_size>,<write_threshold>
1410 See also Documentation/scsi/st.txt.
1412 panic= [KNL] Kernel behaviour on panic
1415 parkbd.port= [HW] Parallel port number the keyboard adapter is
1416 connected to, default is 0.
1418 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1419 0 for XT, 1 for AT (default is AT).
1422 parport= [HW,PPT] Specify parallel ports. 0 disables.
1423 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1424 Use 'auto' to force the driver to use any
1425 IRQ/DMA settings detected (the default is to
1426 ignore detected IRQ/DMA settings because of
1427 possible conflicts). You can specify the base
1428 address, IRQ, and DMA settings; IRQ and DMA
1429 should be numbers, or 'auto' (for using detected
1430 settings on that particular port), or 'nofifo'
1431 (to avoid using a FIFO even if it is detected).
1432 Parallel ports are assigned in the order they
1433 are specified on the command line, starting
1436 parport_init_mode= [HW,PPT]
1437 Configure VIA parallel port to operate in
1438 a specific mode. This is necessary on Pegasos
1439 computer where firmware has no options for setting
1440 up parallel port mode and sets it to spp.
1441 Currently this function knows 686a and 8231 chips.
1442 Format: [spp|ps2|epp|ecp|ecpepp]
1444 pas2= [HW,OSS] Format:
1445 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1448 See header of drivers/scsi/pas16.c.
1451 Halt all CPUs after the first oops has been printed for
1452 the specified number of seconds. This is to be used if
1453 your oopses keep scrolling off the screen.
1458 See header of drivers/block/paride/pcd.c.
1459 See also Documentation/paride.txt.
1461 pci=option[,option...] [PCI] various PCI subsystem options:
1462 off [X86-32] don't probe for the PCI bus
1463 bios [X86-32] force use of PCI BIOS, don't access
1464 the hardware directly. Use this if your machine
1465 has a non-standard PCI host bridge.
1466 nobios [X86-32] disallow use of PCI BIOS, only direct
1467 hardware access methods are allowed. Use this
1468 if you experience crashes upon bootup and you
1469 suspect they are caused by the BIOS.
1470 conf1 [X86-32] Force use of PCI Configuration
1472 conf2 [X86-32] Force use of PCI Configuration
1474 noaer [PCIE] If the PCIEAER kernel config parameter is
1475 enabled, this kernel boot option can be used to
1476 disable the use of PCIE advanced error reporting.
1477 nodomains [PCI] Disable support for multiple PCI
1478 root domains (aka PCI segments, in ACPI-speak).
1479 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1481 nomsi [MSI] If the PCI_MSI kernel config parameter is
1482 enabled, this kernel boot option can be used to
1483 disable the use of MSI interrupts system-wide.
1484 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1485 routing table. These calls are known to be buggy
1486 on several machines and they hang the machine
1487 when used, but on other computers it's the only
1488 way to get the interrupt routing table. Try
1489 this option if the kernel is unable to allocate
1490 IRQs or discover secondary PCI buses on your
1492 rom [X86-32] Assign address space to expansion ROMs.
1493 Use with caution as certain devices share
1494 address decoders between ROMs and other
1496 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1497 assigned automatically to PCI devices. You can
1498 make the kernel exclude IRQs of your ISA cards
1500 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1501 of the PIRQ table (normally generated
1502 by the BIOS) if it is outside the
1503 F0000h-100000h range.
1504 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1505 useful if the kernel is unable to find your
1506 secondary buses and you want to tell it
1507 explicitly which ones they are.
1508 assign-busses [X86-32] Always assign all PCI bus
1509 numbers ourselves, overriding
1510 whatever the firmware may have done.
1511 usepirqmask [X86-32] Honor the possible IRQ mask stored
1512 in the BIOS $PIR table. This is needed on
1513 some systems with broken BIOSes, notably
1514 some HP Pavilion N5400 and Omnibook XE3
1515 notebooks. This will have no effect if ACPI
1516 IRQ routing is enabled.
1517 noacpi [X86-32] Do not use ACPI for IRQ routing
1518 or for PCI scanning.
1519 use_crs [X86-32] Use _CRS for PCI resource
1521 routeirq Do IRQ routing for all PCI devices.
1522 This is normally done in pci_enable_device(),
1523 so this option is a temporary workaround
1524 for broken drivers that don't call it.
1525 skip_isa_align [X86] do not align io start addr, so can
1526 handle more pci cards
1527 firmware [ARM] Do not re-enumerate the bus but instead
1528 just use the configuration from the
1529 bootloader. This is currently used on
1530 IXP2000 systems where the bus has to be
1531 configured a certain way for adjunct CPUs.
1532 noearly [X86] Don't do any early type 1 scanning.
1533 This might help on some broken boards which
1534 machine check when some devices' config space
1535 is read. But various workarounds are disabled
1536 and some IOMMU drivers will not work.
1537 bfsort Sort PCI devices into breadth-first order.
1538 This sorting is done to get a device
1539 order compatible with older (<= 2.4) kernels.
1540 nobfsort Don't sort PCI devices into breadth-first order.
1541 cbiosize=nn[KMG] The fixed amount of bus space which is
1542 reserved for the CardBus bridge's IO window.
1543 The default value is 256 bytes.
1544 cbmemsize=nn[KMG] The fixed amount of bus space which is
1545 reserved for the CardBus bridge's memory
1546 window. The default value is 64 megabytes.
1548 pcmv= [HW,PCMCIA] BadgePAD 4
1551 See Documentation/paride.txt.
1553 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1556 See arch/parisc/kernel/pdc_chassis.c
1559 See Documentation/paride.txt.
1562 See Documentation/paride.txt.
1564 pirq= [SMP,APIC] Manual mp-table setup
1565 See Documentation/i386/IO-APIC.txt.
1567 plip= [PPT,NET] Parallel port network link
1568 Format: { parport<nr> | timid | 0 }
1569 See also Documentation/parport.txt.
1575 { on | off | curr | res | no-curr | no-res }
1578 [ISAPNP] Exclude IRQs for the autoconfiguration
1581 [ISAPNP] Exclude DMAs for the autoconfiguration
1583 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1584 Ranges are in pairs (I/O port base and size).
1587 [ISAPNP] Exclude memory regions for the
1589 Ranges are in pairs (memory base and size).
1591 print-fatal-signals=
1592 [KNL] debug: print fatal signals
1593 print-fatal-signals=1: print segfault info to
1597 printk.time= Show timing data prefixed to each printk message line
1598 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1600 profile= [KNL] Enable kernel profiling via /proc/profile
1601 Format: [schedule,]<number>
1602 Param: "schedule" - profile schedule points.
1603 Param: <number> - step/bucket size as a power of 2 for
1604 statistical time based profiling.
1605 Param: "sleep" - profile D-state sleeping (millisecs).
1606 Requires CONFIG_SCHEDSTATS
1607 Param: "kvm" - profile VM exits.
1609 processor.max_cstate= [HW,ACPI]
1610 Limit processor to maximum C-state
1611 max_cstate=9 overrides any DMI blacklist limit.
1613 processor.nocst [HW,ACPI]
1614 Ignore the _CST method to determine C-states,
1615 instead using the legacy FADT method
1617 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1619 See Documentation/ramdisk.txt.
1621 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1622 probe for; one of (bare|imps|exps|lifebook|any).
1623 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1625 psmouse.resetafter= [HW,MOUSE]
1626 Try to reset the device after so many bad packets
1629 [HW,MOUSE] Set desired mouse resolution, in dpi.
1630 psmouse.smartscroll=
1631 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1632 0 = disabled, 1 = enabled (default).
1634 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1636 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1639 See Documentation/paride.txt.
1642 [KNL] Number of legacy pty's. Overwrites compiled-in
1645 quiet [KNL] Disable most log messages
1650 See Documentation/md.txt.
1652 ramdisk_blocksize= [RAM]
1653 See Documentation/ramdisk.txt.
1655 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1656 See Documentation/ramdisk.txt.
1658 rcupdate.blimit= [KNL,BOOT]
1659 Set maximum number of finished RCU callbacks to process
1662 rcupdate.qhimark= [KNL,BOOT]
1663 Set threshold of queued
1664 RCU callbacks over which batch limiting is disabled.
1666 rcupdate.qlowmark= [KNL,BOOT]
1667 Set threshold of queued RCU callbacks below which
1668 batch limiting is re-enabled.
1672 Run specified binary instead of /init from the ramdisk,
1673 used for early userspace startup. See initrd.
1675 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1676 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1677 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1679 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1681 reservetop= [X86-32]
1683 Reserves a hole at the top of the kernel virtual
1686 reset_devices [KNL] Force drivers to reset the underlying device
1687 during initialization.
1690 Specify the partition device for software suspend
1692 resume_offset= [SWSUSP]
1693 Specify the offset from the beginning of the partition
1694 given by "resume=" at which the swap header is located,
1695 in <PAGE_SIZE> units (needed only for swap files).
1696 See Documentation/power/swsusp-and-swap-files.txt
1698 retain_initrd [RAM] Keep initrd memory after extraction
1700 rhash_entries= [KNL,NET]
1701 Set number of hash buckets for route cache
1703 riscom8= [HW,SERIAL]
1704 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1706 ro [KNL] Mount root device read-only on boot
1708 root= [KNL] Root filesystem
1710 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1711 mount the root filesystem
1713 rootflags= [KNL] Set root filesystem mount option string
1715 rootfstype= [KNL] Set root filesystem type
1717 rootwait [KNL] Wait (indefinitely) for root device to show up.
1718 Useful for devices that are detected asynchronously
1719 (e.g. USB and MMC devices).
1721 root_plug.vendor_id=
1722 [ROOTPLUG] Override the default vendor ID
1724 root_plug.product_id=
1725 [ROOTPLUG] Override the default product ID
1728 [ROOTPLUG] Enable debugging output
1730 rw [KNL] Mount root device read-write on boot
1732 S [KNL] Run init in single mode
1735 See drivers/net/irda/sa1100_ir.c.
1737 sbni= [NET] Granch SBNI12 leased line adapter
1739 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1740 Format: <io>[,<timeout>[,<isapnp>]]
1742 scsi_debug_*= [SCSI]
1743 See drivers/scsi/scsi_debug.c.
1745 scsi_default_dev_flags=
1746 [SCSI] SCSI default device flags
1749 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1750 Format: <vendor>:<model>:<flags>
1751 (flags are integer value)
1753 scsi_logging_level= [SCSI] a bit mask of logging levels
1754 See drivers/scsi/scsi_logging.h for bits. Also
1755 settable via sysctl at dev.scsi.logging_level
1756 (/proc/sys/dev/scsi/logging_level).
1757 There is also a nice 'scsi_logging_level' script in the
1758 S390-tools package, available for download at
1759 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1761 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1762 discovered. async scans them in kernel threads,
1763 allowing boot to proceed. none ignores them, expecting
1764 user space to do the scan.
1766 selinux [SELINUX] Disable or enable SELinux at boot time.
1767 Format: { "0" | "1" }
1768 See security/selinux/Kconfig help text.
1771 Default value is set via kernel config option.
1772 If enabled at boot time, /selinux/disable can be used
1773 later to disable prior to initial policy load.
1775 selinux_compat_net =
1776 [SELINUX] Set initial selinux_compat_net flag value.
1777 Format: { "0" | "1" }
1778 0 -- use new secmark-based packet controls
1779 1 -- use legacy packet controls
1780 Default value is 0 (preferred).
1781 Value can be changed at runtime via
1782 /selinux/compat_net.
1784 serialnumber [BUGS=X86-32]
1787 Maximal number of shapers.
1790 See header of drivers/scsi/sim710.c.
1797 slub_debug[=options[,slabs]] [MM, SLUB]
1798 Enabling slub_debug allows one to determine the
1799 culprit if slab objects become corrupted. Enabling
1800 slub_debug can create guard zones around objects and
1801 may poison objects when not in use. Also tracks the
1802 last alloc / free. For more information see
1803 Documentation/vm/slub.txt.
1805 slub_max_order= [MM, SLUB]
1806 Determines the maximum allowed order for slabs.
1807 A high setting may cause OOMs due to memory
1808 fragmentation. For more information see
1809 Documentation/vm/slub.txt.
1811 slub_min_objects= [MM, SLUB]
1812 The minimum number of objects per slab. SLUB will
1813 increase the slab order up to slub_max_order to
1814 generate a sufficiently large slab able to contain
1815 the number of objects indicated. The higher the number
1816 of objects the smaller the overhead of tracking slabs
1817 and the less frequently locks need to be acquired.
1818 For more information see Documentation/vm/slub.txt.
1820 slub_min_order= [MM, SLUB]
1821 Determines the mininum page order for slabs. Must be
1822 lower than slub_max_order.
1823 For more information see Documentation/vm/slub.txt.
1825 slub_nomerge [MM, SLUB]
1826 Disable merging of slabs with similar size. May be
1827 necessary if there is some reason to distinguish
1828 allocs to different slabs. Debug options disable
1829 merging on their own.
1830 For more information see Documentation/vm/slub.txt.
1833 Format: <io1>[,<io2>[,...,<io8>]]
1835 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1836 attempt to substitute SMP alternatives once at boot.
1838 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1839 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1840 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1841 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1842 smsc-ircc2.ircc_irq= [HW] IRQ line
1843 smsc-ircc2.ircc_dma= [HW] DMA channel
1844 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1845 0: Toshiba Satellite 1800 (GP data pin select)
1846 1: Fast pin select (default)
1849 snd-ad1816a= [HW,ALSA]
1851 snd-ad1848= [HW,ALSA]
1853 snd-ali5451= [HW,ALSA]
1855 snd-als100= [HW,ALSA]
1857 snd-als4000= [HW,ALSA]
1859 snd-azt2320= [HW,ALSA]
1861 snd-cmi8330= [HW,ALSA]
1863 snd-cmipci= [HW,ALSA]
1865 snd-cs4231= [HW,ALSA]
1867 snd-cs4232= [HW,ALSA]
1869 snd-cs4236= [HW,ALSA]
1871 snd-cs4281= [HW,ALSA]
1873 snd-cs46xx= [HW,ALSA]
1875 snd-dt019x= [HW,ALSA]
1877 snd-dummy= [HW,ALSA]
1879 snd-emu10k1= [HW,ALSA]
1881 snd-ens1370= [HW,ALSA]
1883 snd-ens1371= [HW,ALSA]
1885 snd-es968= [HW,ALSA]
1887 snd-es1688= [HW,ALSA]
1889 snd-es18xx= [HW,ALSA]
1891 snd-es1938= [HW,ALSA]
1893 snd-es1968= [HW,ALSA]
1895 snd-fm801= [HW,ALSA]
1897 snd-gusclassic= [HW,ALSA]
1899 snd-gusextreme= [HW,ALSA]
1901 snd-gusmax= [HW,ALSA]
1905 snd-ice1712= [HW,ALSA]
1907 snd-intel8x0= [HW,ALSA]
1909 snd-interwave= [HW,ALSA]
1914 snd-korg1212= [HW,ALSA]
1916 snd-maestro3= [HW,ALSA]
1918 snd-mpu401= [HW,ALSA]
1920 snd-mtpav= [HW,ALSA]
1922 snd-nm256= [HW,ALSA]
1924 snd-opl3sa2= [HW,ALSA]
1932 snd-opti93x= [HW,ALSA]
1936 snd-rme32= [HW,ALSA]
1938 snd-rme96= [HW,ALSA]
1940 snd-rme9652= [HW,ALSA]
1946 snd-sbawe= [HW,ALSA]
1948 snd-serial= [HW,ALSA]
1950 snd-sgalaxy= [HW,ALSA]
1952 snd-sonicvibes= [HW,ALSA]
1957 snd-sun-cs4231= [HW,ALSA]
1959 snd-trident= [HW,ALSA]
1961 snd-usb-audio= [HW,ALSA,USB]
1963 snd-via82xx= [HW,ALSA]
1965 snd-virmidi= [HW,ALSA]
1967 snd-wavefront= [HW,ALSA]
1969 snd-ymfpci= [HW,ALSA]
1971 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1972 See Documentation/sonypi.txt
1974 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1975 See Documentation/specialix.txt.
1977 spia_io_base= [HW,MTD]
1983 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1985 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1986 See Documentation/scsi/st.txt.
1990 Set the STI (builtin display/keyboard on the HP-PARISC
1991 machines) console (graphic card) which should be used
1992 as the initial boot-console.
1993 See also comment in drivers/video/console/sticore.c.
1996 See comment in drivers/video/console/sticore.c.
1999 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2003 Control how the NFS server code allocates CPUs to
2004 service thread pools. Depending on how many NICs
2005 you have and where their interrupts are bound, this
2006 option will affect which CPUs will do NFS serving.
2007 Note: this parameter cannot be changed while the
2008 NFS server is running.
2010 auto the server chooses an appropriate mode
2011 automatically using heuristics
2012 global a single global pool contains all CPUs
2013 percpu one pool for each CPU
2014 pernode one pool for each NUMA node (equivalent
2015 to global on non-NUMA machines)
2017 swiotlb= [IA-64] Number of I/O TLB slabs
2021 sym53c416= [HW,SCSI]
2022 See header of drivers/scsi/sym53c416.c.
2024 sysrq_always_enabled
2026 Ignore sysrq setting - this boot parameter will
2027 neutralize any effect of /proc/sys/kernel/sysrq.
2028 Useful for debugging.
2031 See header of drivers/scsi/t128.c.
2035 thash_entries= [KNL,NET]
2036 Set number of hash buckets for TCP connection
2038 thermal.act= [HW,ACPI]
2039 -1: disable all active trip points in all thermal zones
2040 <degrees C>: override all lowest active trip points
2042 thermal.crt= [HW,ACPI]
2043 -1: disable all critical trip points in all thermal zones
2044 <degrees C>: lower all critical trip points
2046 thermal.nocrt= [HW,ACPI]
2047 Set to disable actions on ACPI thermal zone
2048 critical and hot trip points.
2050 thermal.off= [HW,ACPI]
2051 1: disable ACPI thermal control
2053 thermal.psv= [HW,ACPI]
2054 -1: disable all passive trip points
2055 <degrees C>: override all passive trip points to this value
2057 thermal.tzp= [HW,ACPI]
2058 Specify global default ACPI thermal zone polling rate
2059 <deci-seconds>: poll all this frequency
2060 0: no polling (default)
2062 tipar.timeout= [HW,PPT]
2063 Set communications timeout in tenths of a second
2066 tipar.delay= [HW,PPT]
2067 Set inter-bit delay in microseconds (default 10).
2070 See comment before function dc390_setup() in
2071 drivers/scsi/tmscsim.c.
2075 trix= [HW,OSS] MediaTrix AudioTrix Pro
2077 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2079 turbografx.map[2|3]= [HW,JOY]
2080 TurboGraFX parallel port interface
2082 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2083 See also Documentation/input/joystick-parport.txt
2085 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2086 See header of drivers/scsi/u14-34f.c.
2095 [USB] Ignore overcurrent events (default N).
2096 Some badly-designed motherboards generate lots of
2097 bogus events, for ports that aren't wired to
2098 anything. Set this parameter to avoid log spamming.
2099 Note that genuine overcurrent events won't be
2102 usbcore.autosuspend=
2103 [USB] The autosuspend time delay (in seconds) used
2104 for newly-detected USB devices (default 2). This
2105 is the time required before an idle device will be
2106 autosuspended. Devices for which the delay is set
2107 to a negative value won't be autosuspended at all.
2110 [USBHID] The interval which mice are to be polled at.
2112 vdso= [X86-32,SH,x86-64]
2113 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2114 vdso=1: enable VDSO (default)
2115 vdso=0: disable VDSO mapping
2117 vdso32= [X86-32,X86-64]
2118 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2119 vdso32=1: enable 32-bit VDSO (default)
2120 vdso32=0: disable 32-bit VDSO mapping
2123 vector=percpu: enable percpu vector domain
2125 video= [FB] Frame buffer configuration
2126 See Documentation/fb/modedb.txt.
2128 vga= [BOOT,X86-32] Select a particular video mode
2129 See Documentation/i386/boot.txt and
2130 Documentation/svga.txt.
2131 Use vga=ask for menu.
2132 This is actually a boot loader parameter; the value is
2133 passed to the kernel using a special protocol.
2135 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2136 size of <nn>. This can be used to increase the
2137 minimum size (128MB on x86). It can also be used to
2138 decrease the size and leave more room for directly
2141 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2144 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2147 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2150 waveartist= [HW,OSS]
2151 Format: <io>,<irq>,<dma>,<dma2>
2154 See header of drivers/scsi/wd33c93.c.
2157 See header of drivers/scsi/wd7000.c.
2160 See Documentation/watchdog/wdt.txt.
2162 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2163 xd_geo= See header of drivers/block/xd.c.
2165 xirc2ps_cs= [NET,PCMCIA]
2167 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2169 norandmaps Don't use address space randomization
2170 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2172 ______________________________________________________________________
2176 Add documentation for ALSA options.
2177 Add more DRM drivers.
projects / linux-2.6 / blob