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.
401 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
403 Forces specified clocksource (if available) to be used
404 when calculating gettimeofday(). If specified
405 clocksource is not available, it defaults to PIT.
406 Format: { pit | tsc | cyclone | pmtmr }
408 clocksource= [GENERIC_TIME] Override the default clocksource
410 Override the default clocksource and use the clocksource
411 with the name specified.
412 Some clocksource names to choose from, depending on
414 [all] jiffies (this is the base, fallback clocksource)
416 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
417 pxa_timer,timer3,32k_counter,timer0_1
419 [X86-32] pit,hpet,tsc,vmi-timer;
420 scx200_hrt on Geode; cyclone on IBM x440
428 clearcpuid=BITNUM [X86]
429 Disable CPUID feature X for the kernel. See
430 include/asm-x86/cpufeature.h for the valid bit numbers.
431 Note the Linux specific bits are not necessarily
432 stable over kernel options, but the vendor specific
434 Also note that user programs calling CPUID directly
435 or using the feature without checking anything
436 will still see it. This just prevents it from
437 being used by the kernel or shown in /proc/cpuinfo.
438 Also note the kernel might malfunction if you disable
441 code_bytes [IA32/X86_64] How many bytes of object code to print
448 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
449 over the 8254 in addition to over the IO-APIC. The
450 kernel tries to set a sensible default.
452 hpet= [X86-32,HPET] option to control HPET usage
453 Format: { enable (default) | disable | force }
454 disable: disable HPET and use PIT instead
455 force: allow force enabled of undocumented chips (ICH4,
458 com20020= [HW,NET] ARCnet - COM20020 chipset
460 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
462 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
466 ARCnet - COM90xx chipset (memory-mapped buffers)
467 Format: <io>[,<irq>[,<memstart>]]
469 condev= [HW,S390] console device
472 console= [KNL] Output console device and options.
474 tty<n> Use the virtual console device <n>.
478 Use the specified serial port. The options are of
479 the form "bbbbpnf", where "bbbb" is the baud rate,
480 "p" is parity ("n", "o", or "e"), "n" is number of
481 bits, and "f" is flow control ("r" for RTS or
482 omit it). Default is "9600n8".
484 See Documentation/serial-console.txt for more
486 Documentation/networking/netconsole.txt for an
489 uart[8250],io,<addr>[,options]
490 uart[8250],mmio,<addr>[,options]
491 Start an early, polled-mode console on the 8250/16550
492 UART at the specified I/O port or MMIO address,
493 switching to the matching ttyS device later. The
494 options are the same as for ttyS, above.
496 If the device connected to the port is not a TTY but a braille
497 device, prepend "brl," before the device type, for instance
499 For now, only VisioBraille is supported.
501 earlycon= [KNL] Output early console device and options.
502 uart[8250],io,<addr>[,options]
503 uart[8250],mmio,<addr>[,options]
504 Start an early, polled-mode console on the 8250/16550
505 UART at the specified I/O port or MMIO address.
506 The options are the same as for ttyS, above.
509 [HW] Never suspend the console
510 Disable suspending of consoles during suspend and
511 hibernate operations. Once disabled, debugging
512 messages can reach various consoles while the rest
513 of the system is being put to sleep (ie, while
514 debugging driver suspend/resume hooks). This may
515 not work reliably with all consoles, but is known
516 to work with serial and VGA consoles.
518 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
520 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
522 crashkernel=nn[KMG]@ss[KMG]
523 [KNL] Reserve a chunk of physical memory to
524 hold a kernel to switch to with kexec on panic.
526 crashkernel=range1:size1[,range2:size2,...][@offset]
527 [KNL] Same as above, but depends on the memory
528 in the running system. The syntax of range is
529 start-[end] where start and end are both
530 a memory unit (amount[KMG]). See also
531 Documentation/kdump/kdump.txt for a example.
534 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
539 cs89x0_media= [HW,NET]
540 Format: { rj45 | aui | bnc }
543 See header of drivers/s390/block/dasd_devmap.c.
545 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
546 (one device per port)
547 Format: <port#>,<type>
548 See also Documentation/input/joystick-parport.txt
550 debug [KNL] Enable kernel debugging (events log level).
553 [KNL] verbose self-tests
555 Print debugging info while doing the locking API
557 We default to 0 (no extra messages), setting it to
558 1 will print _a lot_ more information - normally
559 only useful to kernel developers.
561 debug_objects [KNL] Enable object debugging
563 decnet.addr= [HW,NET]
564 Format: <area>[,<node>]
565 See also Documentation/networking/decnet.txt.
568 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
569 Change the default blue palette of the console.
570 This is a 16-member array composed of values
574 Format: <green0>,<green1>,<green2>,...,<green15>
575 Change the default green palette of the console.
576 This is a 16-member array composed of values
580 Format: <red0>,<red1>,<red2>,...,<red15>
581 Change the default red palette of the console.
582 This is a 16-member array composed of values
588 Set system-wide default UTF-8 mode for all tty's.
589 Default is 1, i.e. UTF-8 mode is enabled for all
590 newly opened terminals.
593 Set number of hash buckets for dentry cache.
596 IO parameters + enable/disable command.
598 digiepca= [HW,SERIAL]
599 See drivers/char/README.epca and
600 Documentation/digiepca.txt.
602 disable_mtrr_trim [X86, Intel and AMD only]
603 By default the kernel will trim any uncacheable
604 memory out of your available memory pool based on
605 MTRR settings. This parameter disables that behavior,
606 possibly causing your machine to run very slowly.
608 dmasound= [HW,OSS] Sound subsystem buffers
614 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
616 earlyprintk=serial[,ttySn[,baudrate]]
618 Append ",keep" to not disable it when the real console
621 Only vga or serial at a time, not both.
623 Currently only ttyS0 and ttyS1 are supported.
625 Interaction with the standard serial driver is not
628 The VGA output is eventually overwritten by the real
634 Format: {"off" | "on" | "skip[mbr]"}
636 eisa_irq_edge= [PARISC,HW]
637 See header of drivers/parisc/eisa.c.
640 See comment before function elanfreq_setup() in
641 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
644 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
645 See Documentation/block/as-iosched.txt and
646 Documentation/block/deadline-iosched.txt for details.
648 elfcorehdr= [X86-32, X86_64]
649 Specifies physical address of start of kernel core
650 image elf header. Generally kexec loader will
651 pass this option to capture kernel.
652 See Documentation/kdump/kdump.txt for details.
654 enforcing [SELINUX] Set initial enforcing status.
656 See security/selinux/Kconfig help text.
657 0 -- permissive (log only, no denials).
658 1 -- enforcing (deny and log).
660 Value can be changed at runtime via /selinux/enforce.
663 Format: <spdif>,[<nomix>,[<amplifier>]]
664 See also header of sound/oss/es1371.c.
666 ether= [HW,NET] Ethernet cards parameters
667 This option is obsoleted by the "netdev=" option, which
668 has equivalent usage. See its documentation for details.
670 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
675 fail_make_request=[KNL]
676 General fault injection mechanism.
677 Format: <interval>,<probability>,<space>,<times>
678 See also /Documentation/fault-injection/.
681 See header of drivers/scsi/fd_mcs.c.
684 See header of drivers/scsi/fdomain.c.
687 See Documentation/floppy.txt.
689 force_pal_cache_flush
690 [IA-64] Avoid check_sal_cache_flush which may hang on
691 buggy SAL_CACHE_FLUSH implementations. Using this
692 parameter will force ia64_sal_cache_flush to call
693 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
696 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
697 support via parallel port (up to 5 devices per port)
698 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
699 See also Documentation/input/joystick-parport.txt
703 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
708 See header of drivers/scsi/gdth.c.
710 gpt [EFI] Forces disk with valid GPT signature but
711 invalid Protective MBR to be treated as GPT.
715 hashdist= [KNL,NUMA] Large hashes allocated during boot
716 are distributed across NUMA nodes. Defaults on
717 for IA-64, off otherwise.
718 Format: 0 | 1 (for off | on)
720 hcl= [IA-64] SGI's Hardware Graph compatibility layer
722 hd= [EIDE] (E)IDE hard drive subsystem geometry
723 Format: <cyl>,<head>,<sect>
725 hd?= [HW] (E)IDE subsystem
726 hd?lun= See Documentation/ide/ide.txt.
728 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
729 size of <nn>. This works even on boxes that have no
730 highmem otherwise. This also works to reduce highmem
731 size on bigger boxes.
733 highres= [KNL] Enable/disable high resolution timer mode.
734 Valid parameters: "on", "off"
738 See Documentation/isdn/README.HiSax.
740 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
741 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
743 i8042.direct [HW] Put keyboard port into non-translated mode
744 i8042.dumbkbd [HW] Pretend that controller can only read data from
745 keyboard and cannot control its state
746 (Don't attempt to blink the leds)
747 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
748 i8042.nokbd [HW] Don't check/create keyboard port
749 i8042.noloop [HW] Disable the AUX Loopback command while probing
751 i8042.nomux [HW] Don't check presence of an active multiplexing
753 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
756 [HW] Frequency with which keyboard LEDs should blink
757 when kernel panics (default is 0.5 sec)
758 i8042.reset [HW] Reset the controller during init and cleanup
759 i8042.unlock [HW] Unlock (ignore) the keylock
763 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
764 indicates that the driver is running on unsupported
766 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
767 does not match list of supported models.
769 [HW] Report power status in /proc/i8k
770 (disabled by default)
771 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
774 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
775 See Documentation/mca.txt.
778 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
780 ide= [HW] (E)IDE subsystem
781 Format: ide=nodma or ide=doubler
782 See Documentation/ide/ide.txt.
784 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
785 See Documentation/ide/ide.txt.
788 Format: idle=poll or idle=mwait
789 Poll forces a polling idle loop that can slightly improves the performance
790 of waking up a idle CPU, but will use a lot of power and make the system
791 run hot. Not recommended.
792 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
793 to not use it because it doesn't save as much power as a normal idle
794 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
797 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
798 Claim all unknown PCI IDE storage controllers.
800 ignore_loglevel [KNL]
801 Ignore loglevel setting - this will print /all/
802 kernel messages to the console. Useful for debugging.
805 Set number of hash buckets for inode cache.
808 See header of drivers/scsi/in2000.c.
812 Run specified binary instead of /sbin/init as init
815 initcall_debug [KNL] Trace initcalls as they are executed. Useful
816 for working out where the kernel is dying during
819 initrd= [BOOT] Specify the location of the initial ramdisk
821 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
839 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
841 Disable intel iommu driver.
842 igfx_off [Default Off]
843 By default, gfx is mapped as normal device. If a gfx
844 device has a dedicated DMAR unit, the DMAR unit is
845 bypassed by not enabling DMAR with this option. In
846 this case, gfx device will use physical address for
849 With this option iommu will not optimize to look
850 for io virtual address below 32 bit forcing dual
851 address cycle on pci bus for cards supporting greater
852 than 32 bit addressing. The default is to look
853 for translation below 32 bit and if not available
854 then look in the higher range.
856 With this option on every unmap_single operation will
857 result in a hardware IOTLB flush operation as opposed
858 to batching them for performance.
860 io_delay= [X86-32,X86-64] I/O delay method
862 Standard port 0x80 based delay
864 Alternate port 0xed based delay (needed on some systems)
866 Simple two microseconds delay
870 io7= [HW] IO7 for Marvel based alpha systems
871 See comment before marvel_specify_io7 in
872 arch/alpha/kernel/core_marvel.c.
875 See Documentation/filesystems/nfsroot.txt.
877 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
878 See comment before ip2_setup() in
879 drivers/char/ip2/ip2base.c.
881 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
882 See header of drivers/scsi/ips.c.
884 ports= [IP_VS_FTP] IPVS ftp helper module
886 Up to 8 (IP_VS_APP_MAX_PORTS) ports
888 Format: <port>,<port>....
891 When an interrupt is not handled search all handlers
892 for it. Intended to get systems with badly broken
896 When an interrupt is not handled search all handlers
897 for it. Also check all handlers each timer
898 interrupt. Intended to get systems with badly broken
902 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
904 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
906 <cpu number>,...,<cpu number>
908 <cpu number>-<cpu number> (must be a positive range in ascending order)
910 <cpu number>,...,<cpu number>-<cpu number>
911 This option can be used to specify one or more CPUs
912 to isolate from the general SMP balancing and scheduling
913 algorithms. The only way to move a process onto or off
914 an "isolated" CPU is via the CPU affinity syscalls.
915 <cpu number> begins at 0 and the maximum value is
916 "number of CPUs in system - 1".
918 This option is the preferred way to isolate CPUs. The
919 alternative -- manually setting the CPU mask of all
920 tasks in the system -- can cause problems and
921 suboptimal load balancer performance.
925 js= [HW,JOY] Analog joystick
926 See Documentation/input/joystick.txt.
928 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
929 specifies the amount of memory usable by the kernel
930 for non-movable allocations. The requested amount is
931 spread evenly throughout all nodes in the system. The
932 remaining memory in each node is used for Movable
933 pages. In the event, a node is too small to have both
934 kernelcore and Movable pages, kernelcore pages will
935 take priority and other nodes will have a larger number
936 of kernelcore pages. The Movable zone is used for the
937 allocation of pages that may be reclaimed or moved
938 by the page migration subsystem. This means that
939 HugeTLB pages may not be allocated from this zone.
940 Note that allocations like PTEs-from-HighMem still
941 use the HighMem zone if it exists, and the Normal
944 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
945 is similar to kernelcore except it specifies the
946 amount of memory used for migratable allocations.
947 If both kernelcore and movablecore is specified,
948 then kernelcore will be at *least* the specified
949 value but may be more. If movablecore on its own
950 is specified, the administrator must be careful
951 that the amount of memory usable for all allocations
956 kstack=N [X86-32,X86-64] Print N words from the kernel stack
959 kgdboc= [HW] kgdb over consoles.
960 Requires a tty driver that supports console polling.
961 (only serial suported for now)
962 Format: <serial_device>[,baud]
968 lapic [X86-32,APIC] Enable the local APIC even if BIOS
971 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
974 libata.dma= [LIBATA] DMA control
975 libata.dma=0 Disable all PATA and SATA DMA
976 libata.dma=1 PATA and SATA Disk DMA only
977 libata.dma=2 ATAPI (CDROM) DMA only
978 libata.dma=4 Compact Flash DMA only
979 Combinations also work, so libata.dma=3 enables DMA
980 for disks and CDROMs, but not CFs.
982 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
986 libata.force= [LIBATA] Force configurations. The format is comma
987 separated list of "[ID:]VAL" where ID is
988 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
989 matching port, link or device. Basically, it matches
990 the ATA ID string printed on console by libata. If
991 the whole ID part is omitted, the last PORT and DEVICE
992 values are used. If ID hasn't been specified yet, the
993 configuration applies to all ports, links and devices.
995 If only DEVICE is omitted, the parameter applies to
996 the port and all links and devices behind it. DEVICE
997 number of 0 either selects the first device or the
998 first fan-out link behind PMP device. It does not
999 select the host link. DEVICE number of 15 selects the
1000 host link and device attached to it.
1002 The VAL specifies the configuration to force. As long
1003 as there's no ambiguity shortcut notation is allowed.
1004 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1005 The following configurations can be forced.
1007 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1008 Any ID with matching PORT is used.
1010 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1012 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1013 udma[/][16,25,33,44,66,100,133] notation is also
1016 * [no]ncq: Turn on or off NCQ.
1018 If there are multiple matching configurations changing
1019 the same attribute, the last one is used.
1021 load_ramdisk= [RAM] List of ramdisks to load from floppy
1022 See Documentation/ramdisk.txt.
1024 lockd.nlm_grace_period=P [NFS] Assign grace period.
1027 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1030 lockd.nlm_timeout=T [NFS] Assign timeout value.
1033 lockd.nlm_udpport=M [NFS] Assign UDP port.
1036 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1039 loglevel= All Kernel Messages with a loglevel smaller than the
1040 console loglevel will be printed to the console. It can
1041 also be changed with klogd or other programs. The
1042 loglevels are defined as follows:
1044 0 (KERN_EMERG) system is unusable
1045 1 (KERN_ALERT) action must be taken immediately
1046 2 (KERN_CRIT) critical conditions
1047 3 (KERN_ERR) error conditions
1048 4 (KERN_WARNING) warning conditions
1049 5 (KERN_NOTICE) normal but significant condition
1050 6 (KERN_INFO) informational
1051 7 (KERN_DEBUG) debug-level messages
1053 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1054 Format: { n | nk | nM }
1055 n must be a power of two. The default size
1056 is set in the kernel config file.
1058 logo.nologo [FB] Disables display of the built-in Linux logo.
1059 This may be used to provide more screen space for
1060 kernel log messages and is useful when debugging
1061 kernel boot problems.
1063 lp=0 [LP] Specify parallel ports to use, e.g,
1064 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1065 lp=reset first parallel port). 'lp=0' disables the
1066 lp=auto printer driver. 'lp=reset' (which can be
1067 specified in addition to the ports) causes
1068 attached printers to be reset. Using
1069 lp=port1,port2,... specifies the parallel ports
1070 to associate lp devices with, starting with
1071 lp0. A port specification may be 'none' to skip
1072 that lp device, or a parport name such as
1073 'parport0'. Specifying 'lp=auto' instead of a
1074 port specification list means that device IDs
1075 from each port should be examined, to see if
1076 an IEEE 1284-compliant printer is attached; if
1077 so, the driver will manage that printer.
1078 See also header of drivers/char/lp.c.
1081 Sets loops_per_jiffy to given constant, thus avoiding
1082 time-consuming boot-time autodetection (up to 250 ms per
1083 CPU). 0 enables autodetection (default). To determine
1084 the correct value for your kernel, boot with normal
1085 autodetection and see what value is printed. Note that
1086 on SMP systems the preset will be applied to all CPUs,
1087 which is likely to cause problems if your CPUs need
1088 significantly divergent settings. An incorrect value
1089 will cause delays in the kernel to be wrong, leading to
1090 unpredictable I/O errors and other breakage. Although
1091 unlikely, in the extreme case this might damage your
1095 Format: <io>,<irq>,<dma>
1097 mac5380= [HW,SCSI] Format:
1098 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1100 machvec= [IA64] Force the use of a particular machine-vector
1101 (machvec) in a generic kernel.
1102 Example: machvec=hpzx1_swiotlb
1104 max_loop= [LOOP] Maximum number of loopback devices that can
1108 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1109 should make use of. maxcpus=n : n >= 0 limits the
1110 kernel to using 'n' processors. n=0 is a special case,
1111 it is equivalent to "nosmp", which also disables
1114 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1115 equal to this physical address is ignored.
1117 max_luns= [SCSI] Maximum number of LUNs to probe.
1118 Should be between 1 and 2^32-1.
1121 [SCSI] Maximum number of LUNs received.
1122 Should be between 1 and 16384.
1126 mce [X86-32] Machine Check Exception
1128 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1130 md= [HW] RAID subsystems devices and level
1131 See Documentation/md.txt.
1134 Format: <first>,<last>
1135 Specifies range of consoles to be captured by the MDA.
1137 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1138 Amount of memory to be used when the kernel is not able
1139 to see the whole system memory or for test.
1140 [X86-32] Use together with memmap= to avoid physical
1141 address space collisions. Without memmap= PCI devices
1142 could be placed at addresses belonging to unused RAM.
1144 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1147 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1148 E820 memory map, as specified by the user.
1149 Such memmap=exactmap lines can be constructed based on
1150 BIOS output or other requirements. See the memmap=nn@ss
1153 memmap=nn[KMG]@ss[KMG]
1154 [KNL] Force usage of a specific region of memory
1155 Region of memory to be used, from ss to ss+nn.
1157 memmap=nn[KMG]#ss[KMG]
1158 [KNL,ACPI] Mark specific memory as ACPI data.
1159 Region of memory to be used, from ss to ss+nn.
1161 memmap=nn[KMG]$ss[KMG]
1162 [KNL,ACPI] Mark specific memory as reserved.
1163 Region of memory to be used, from ss to ss+nn.
1164 Example: Exclude memory from 0x18690000-0x1869ffff
1165 memmap=64K$0x18690000
1167 memmap=0x10000$0x18690000
1169 memtest= [KNL,X86_64] Enable memtest
1171 range: 0,4 : pattern number
1172 default : 0 <disable>
1174 meye.*= [HW] Set MotionEye Camera parameters
1175 See Documentation/video4linux/meye.txt.
1177 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1178 Multi-Function General Purpose Timers on AMD Geode
1181 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1182 the BIOS has incorrectly applied a workaround. TinyBIOS
1183 version 0.98 is known to be affected, 0.99 fixes the
1184 problem by letting the user disable the workaround.
1189 [MOUSE] Maximum time between finger touching and
1190 leaving touchpad surface for touch to be considered
1191 a tap and be reported as a left button click (for
1192 touchpads working in absolute mode only).
1194 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1195 reporting absolute coordinates, such as tablets
1196 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1197 reporting absolute coordinates, such as tablets
1202 MTD_Partition= [MTD]
1203 Format: <name>,<region-number>,<size>,<offset>
1205 MTD_Region= [MTD] Format:
1206 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1209 See drivers/mtd/cmdlinepart.c.
1211 mtouchusb.raw_coordinates=
1212 [HW] Make the MicroTouch USB driver use raw coordinates
1213 ('y', default) or cooked coordinates ('n')
1215 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1218 See header of drivers/scsi/NCR_D700.c.
1222 ncr53c400= [HW,SCSI]
1224 ncr53c400a= [HW,SCSI]
1226 ncr53c406a= [HW,SCSI]
1228 ncr53c8xx= [HW,SCSI]
1230 netdev= [NET] Network devices parameters
1231 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1232 Note that mem_start is often overloaded to mean
1233 something different and driver-specific.
1234 This usage is only documented in each driver source
1238 See Documentation/filesystems/nfsroot.txt.
1240 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1241 See Documentation/filesystems/nfsroot.txt.
1243 nfs.callback_tcpport=
1244 [NFS] set the TCP port on which the NFSv4 callback
1245 channel should listen.
1247 nfs.idmap_cache_timeout=
1248 [NFS] set the maximum lifetime for idmapper cache
1252 [NFS] enable 64-bit inode numbers.
1253 If zero, the NFS client will fake up a 32-bit inode
1254 number for the readdir() and stat() syscalls instead
1255 of returning the full 64-bit number.
1256 The default is to return 64-bit inode numbers.
1258 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1259 when a NMI is triggered.
1260 Format: [state][,regs][,debounce][,die]
1262 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1264 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1265 emulation library even if a 387 maths coprocessor
1268 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1269 caches in the slab allocator. Saves per-node memory,
1270 but will impact performance.
1274 noapic [SMP,APIC] Tells the kernel to not make use of any
1275 IOAPICs that may be present in the system.
1277 nobats [PPC] Do not use BATs for mapping kernel lowmem
1278 on "Classic" PPC cores.
1282 nodelayacct [KNL] Disable per-task delay accounting
1284 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1286 noefi [X86-32,X86-64] Disable EFI runtime services support.
1290 noexec [X86-32,X86-64]
1291 On X86-32 available only on PAE configured kernels.
1292 noexec=on: enable non-executable mappings (default)
1293 noexec=off: disable non-executable mappings
1296 This affects only 32-bit executables.
1297 noexec32=on: enable non-executable mappings (default)
1298 read doesn't imply executable mappings
1299 noexec32=off: disable non-executable mappings
1300 read implies executable mappings
1302 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1303 register save and restore. The kernel will only save
1304 legacy floating-point registers on task switch.
1306 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1310 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1311 instruction doesn't work correctly and not to
1314 nohalt [IA-64] Tells the kernel not to use the power saving
1315 function PAL_HALT_LIGHT when idle. This increases
1316 power-consumption. On the positive side, it reduces
1317 interrupt wake-up latency, which may improve performance
1318 in certain environments such as networked servers or
1321 nohz= [KNL] Boottime enable/disable dynamic ticks
1322 Valid arguments: on, off
1325 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1327 noirqdebug [X86-32] Disables the code which attempts to detect and
1328 disable unhandled interrupt sources.
1330 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1331 broken timer IRQ sources.
1333 noisapnp [ISAPNP] Disables ISA PnP code.
1335 noinitrd [RAM] Tells the kernel not to load any configured
1340 nojitter [IA64] Disables jitter checking for ITC timers.
1342 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1344 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1346 noltlbs [PPC] Do not use large page/tlb entries for kernel
1347 lowmem mapping on PPC40x.
1349 nomca [IA-64] Disable machine check abort handling
1351 nomce [X86-32] Machine Check Exception
1353 nomfgpt [X86-32] Disable Multi-Function General Purpose
1354 Timer usage (for AMD Geode machines).
1356 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1358 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1359 with UP alternatives
1361 noresidual [PPC] Don't use residual data on PReP machines.
1363 noresume [SWSUSP] Disables resume and restores original swap
1366 no-scroll [VGA] Disables scrollback.
1367 This is required for the Braillex ib80-piezo Braille
1368 reader made by F.H. Papenmeier (Germany).
1372 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1374 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1375 and disable the IO APIC. legacy for "maxcpus=0".
1377 nosoftlockup [KNL] Disable the soft-lockup detector.
1379 nosync [HW,M68K] Disables sync negotiation for all devices.
1381 notsc [BUGS=X86-32] Disable Time Stamp Counter
1383 nousb [USB] Disable the USB subsystem
1387 nptcg= [IA64] Override max number of concurrent global TLB
1388 purges which is reported from either PAL_VM_SUMMARY or
1391 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1392 one of ['zone', 'node', 'default'] can be specified
1393 This can be set from sysctl after boot.
1394 See Documentation/sysctl/vm.txt for details.
1396 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1398 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1399 Rather than timing out after 20 ms if an EC
1400 command is not properly ACKed, override the length
1401 of the timeout. We have interrupts disabled while
1402 waiting for the ACK, so if this is set too high
1403 interrupts *may* be lost!
1408 oprofile.timer= [HW]
1409 Use timer interrupt instead of performance counters
1411 osst= [HW,SCSI] SCSI Tape Driver
1412 Format: <buffer_size>,<write_threshold>
1413 See also Documentation/scsi/st.txt.
1415 panic= [KNL] Kernel behaviour on panic
1418 parkbd.port= [HW] Parallel port number the keyboard adapter is
1419 connected to, default is 0.
1421 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1422 0 for XT, 1 for AT (default is AT).
1425 parport= [HW,PPT] Specify parallel ports. 0 disables.
1426 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1427 Use 'auto' to force the driver to use any
1428 IRQ/DMA settings detected (the default is to
1429 ignore detected IRQ/DMA settings because of
1430 possible conflicts). You can specify the base
1431 address, IRQ, and DMA settings; IRQ and DMA
1432 should be numbers, or 'auto' (for using detected
1433 settings on that particular port), or 'nofifo'
1434 (to avoid using a FIFO even if it is detected).
1435 Parallel ports are assigned in the order they
1436 are specified on the command line, starting
1439 parport_init_mode= [HW,PPT]
1440 Configure VIA parallel port to operate in
1441 a specific mode. This is necessary on Pegasos
1442 computer where firmware has no options for setting
1443 up parallel port mode and sets it to spp.
1444 Currently this function knows 686a and 8231 chips.
1445 Format: [spp|ps2|epp|ecp|ecpepp]
1447 pas2= [HW,OSS] Format:
1448 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1451 See header of drivers/scsi/pas16.c.
1454 Halt all CPUs after the first oops has been printed for
1455 the specified number of seconds. This is to be used if
1456 your oopses keep scrolling off the screen.
1461 See header of drivers/block/paride/pcd.c.
1462 See also Documentation/paride.txt.
1464 pci=option[,option...] [PCI] various PCI subsystem options:
1465 off [X86-32] don't probe for the PCI bus
1466 bios [X86-32] force use of PCI BIOS, don't access
1467 the hardware directly. Use this if your machine
1468 has a non-standard PCI host bridge.
1469 nobios [X86-32] disallow use of PCI BIOS, only direct
1470 hardware access methods are allowed. Use this
1471 if you experience crashes upon bootup and you
1472 suspect they are caused by the BIOS.
1473 conf1 [X86-32] Force use of PCI Configuration
1475 conf2 [X86-32] Force use of PCI Configuration
1477 noaer [PCIE] If the PCIEAER kernel config parameter is
1478 enabled, this kernel boot option can be used to
1479 disable the use of PCIE advanced error reporting.
1480 nodomains [PCI] Disable support for multiple PCI
1481 root domains (aka PCI segments, in ACPI-speak).
1482 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1484 nomsi [MSI] If the PCI_MSI kernel config parameter is
1485 enabled, this kernel boot option can be used to
1486 disable the use of MSI interrupts system-wide.
1487 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1488 routing table. These calls are known to be buggy
1489 on several machines and they hang the machine
1490 when used, but on other computers it's the only
1491 way to get the interrupt routing table. Try
1492 this option if the kernel is unable to allocate
1493 IRQs or discover secondary PCI buses on your
1495 rom [X86-32] Assign address space to expansion ROMs.
1496 Use with caution as certain devices share
1497 address decoders between ROMs and other
1499 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1500 assigned automatically to PCI devices. You can
1501 make the kernel exclude IRQs of your ISA cards
1503 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1504 of the PIRQ table (normally generated
1505 by the BIOS) if it is outside the
1506 F0000h-100000h range.
1507 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1508 useful if the kernel is unable to find your
1509 secondary buses and you want to tell it
1510 explicitly which ones they are.
1511 assign-busses [X86-32] Always assign all PCI bus
1512 numbers ourselves, overriding
1513 whatever the firmware may have done.
1514 usepirqmask [X86-32] Honor the possible IRQ mask stored
1515 in the BIOS $PIR table. This is needed on
1516 some systems with broken BIOSes, notably
1517 some HP Pavilion N5400 and Omnibook XE3
1518 notebooks. This will have no effect if ACPI
1519 IRQ routing is enabled.
1520 noacpi [X86-32] Do not use ACPI for IRQ routing
1521 or for PCI scanning.
1522 use_crs [X86-32] Use _CRS for PCI resource
1524 routeirq Do IRQ routing for all PCI devices.
1525 This is normally done in pci_enable_device(),
1526 so this option is a temporary workaround
1527 for broken drivers that don't call it.
1528 skip_isa_align [X86] do not align io start addr, so can
1529 handle more pci cards
1530 firmware [ARM] Do not re-enumerate the bus but instead
1531 just use the configuration from the
1532 bootloader. This is currently used on
1533 IXP2000 systems where the bus has to be
1534 configured a certain way for adjunct CPUs.
1535 noearly [X86] Don't do any early type 1 scanning.
1536 This might help on some broken boards which
1537 machine check when some devices' config space
1538 is read. But various workarounds are disabled
1539 and some IOMMU drivers will not work.
1540 bfsort Sort PCI devices into breadth-first order.
1541 This sorting is done to get a device
1542 order compatible with older (<= 2.4) kernels.
1543 nobfsort Don't sort PCI devices into breadth-first order.
1544 cbiosize=nn[KMG] The fixed amount of bus space which is
1545 reserved for the CardBus bridge's IO window.
1546 The default value is 256 bytes.
1547 cbmemsize=nn[KMG] The fixed amount of bus space which is
1548 reserved for the CardBus bridge's memory
1549 window. The default value is 64 megabytes.
1551 pcmv= [HW,PCMCIA] BadgePAD 4
1554 See Documentation/paride.txt.
1556 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1559 See arch/parisc/kernel/pdc_chassis.c
1562 See Documentation/paride.txt.
1565 See Documentation/paride.txt.
1567 pirq= [SMP,APIC] Manual mp-table setup
1568 See Documentation/i386/IO-APIC.txt.
1570 plip= [PPT,NET] Parallel port network link
1571 Format: { parport<nr> | timid | 0 }
1572 See also Documentation/parport.txt.
1578 { on | off | curr | res | no-curr | no-res }
1581 [ISAPNP] Exclude IRQs for the autoconfiguration
1584 [ISAPNP] Exclude DMAs for the autoconfiguration
1586 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1587 Ranges are in pairs (I/O port base and size).
1590 [ISAPNP] Exclude memory regions for the
1592 Ranges are in pairs (memory base and size).
1594 print-fatal-signals=
1595 [KNL] debug: print fatal signals
1596 print-fatal-signals=1: print segfault info to
1600 printk.time= Show timing data prefixed to each printk message line
1601 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1603 profile= [KNL] Enable kernel profiling via /proc/profile
1604 Format: [schedule,]<number>
1605 Param: "schedule" - profile schedule points.
1606 Param: <number> - step/bucket size as a power of 2 for
1607 statistical time based profiling.
1608 Param: "sleep" - profile D-state sleeping (millisecs).
1609 Requires CONFIG_SCHEDSTATS
1610 Param: "kvm" - profile VM exits.
1612 processor.max_cstate= [HW,ACPI]
1613 Limit processor to maximum C-state
1614 max_cstate=9 overrides any DMI blacklist limit.
1616 processor.nocst [HW,ACPI]
1617 Ignore the _CST method to determine C-states,
1618 instead using the legacy FADT method
1620 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1622 See Documentation/ramdisk.txt.
1624 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1625 probe for; one of (bare|imps|exps|lifebook|any).
1626 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1628 psmouse.resetafter= [HW,MOUSE]
1629 Try to reset the device after so many bad packets
1632 [HW,MOUSE] Set desired mouse resolution, in dpi.
1633 psmouse.smartscroll=
1634 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1635 0 = disabled, 1 = enabled (default).
1637 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1639 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1642 See Documentation/paride.txt.
1645 [KNL] Number of legacy pty's. Overwrites compiled-in
1648 quiet [KNL] Disable most log messages
1653 See Documentation/md.txt.
1655 ramdisk_blocksize= [RAM]
1656 See Documentation/ramdisk.txt.
1658 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1659 See Documentation/ramdisk.txt.
1661 rcupdate.blimit= [KNL,BOOT]
1662 Set maximum number of finished RCU callbacks to process
1665 rcupdate.qhimark= [KNL,BOOT]
1666 Set threshold of queued
1667 RCU callbacks over which batch limiting is disabled.
1669 rcupdate.qlowmark= [KNL,BOOT]
1670 Set threshold of queued RCU callbacks below which
1671 batch limiting is re-enabled.
1675 Run specified binary instead of /init from the ramdisk,
1676 used for early userspace startup. See initrd.
1678 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1679 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1680 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1682 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1684 reservetop= [X86-32]
1686 Reserves a hole at the top of the kernel virtual
1689 reset_devices [KNL] Force drivers to reset the underlying device
1690 during initialization.
1693 Specify the partition device for software suspend
1695 resume_offset= [SWSUSP]
1696 Specify the offset from the beginning of the partition
1697 given by "resume=" at which the swap header is located,
1698 in <PAGE_SIZE> units (needed only for swap files).
1699 See Documentation/power/swsusp-and-swap-files.txt
1701 retain_initrd [RAM] Keep initrd memory after extraction
1703 rhash_entries= [KNL,NET]
1704 Set number of hash buckets for route cache
1706 riscom8= [HW,SERIAL]
1707 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1709 ro [KNL] Mount root device read-only on boot
1711 root= [KNL] Root filesystem
1713 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1714 mount the root filesystem
1716 rootflags= [KNL] Set root filesystem mount option string
1718 rootfstype= [KNL] Set root filesystem type
1720 rootwait [KNL] Wait (indefinitely) for root device to show up.
1721 Useful for devices that are detected asynchronously
1722 (e.g. USB and MMC devices).
1724 root_plug.vendor_id=
1725 [ROOTPLUG] Override the default vendor ID
1727 root_plug.product_id=
1728 [ROOTPLUG] Override the default product ID
1731 [ROOTPLUG] Enable debugging output
1733 rw [KNL] Mount root device read-write on boot
1735 S [KNL] Run init in single mode
1738 See drivers/net/irda/sa1100_ir.c.
1740 sbni= [NET] Granch SBNI12 leased line adapter
1742 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1743 Format: <io>[,<timeout>[,<isapnp>]]
1745 scsi_debug_*= [SCSI]
1746 See drivers/scsi/scsi_debug.c.
1748 scsi_default_dev_flags=
1749 [SCSI] SCSI default device flags
1752 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1753 Format: <vendor>:<model>:<flags>
1754 (flags are integer value)
1756 scsi_logging_level= [SCSI] a bit mask of logging levels
1757 See drivers/scsi/scsi_logging.h for bits. Also
1758 settable via sysctl at dev.scsi.logging_level
1759 (/proc/sys/dev/scsi/logging_level).
1760 There is also a nice 'scsi_logging_level' script in the
1761 S390-tools package, available for download at
1762 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1764 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1765 discovered. async scans them in kernel threads,
1766 allowing boot to proceed. none ignores them, expecting
1767 user space to do the scan.
1769 selinux [SELINUX] Disable or enable SELinux at boot time.
1770 Format: { "0" | "1" }
1771 See security/selinux/Kconfig help text.
1774 Default value is set via kernel config option.
1775 If enabled at boot time, /selinux/disable can be used
1776 later to disable prior to initial policy load.
1778 selinux_compat_net =
1779 [SELINUX] Set initial selinux_compat_net flag value.
1780 Format: { "0" | "1" }
1781 0 -- use new secmark-based packet controls
1782 1 -- use legacy packet controls
1783 Default value is 0 (preferred).
1784 Value can be changed at runtime via
1785 /selinux/compat_net.
1787 serialnumber [BUGS=X86-32]
1790 Maximal number of shapers.
1793 See header of drivers/scsi/sim710.c.
1800 slub_debug[=options[,slabs]] [MM, SLUB]
1801 Enabling slub_debug allows one to determine the
1802 culprit if slab objects become corrupted. Enabling
1803 slub_debug can create guard zones around objects and
1804 may poison objects when not in use. Also tracks the
1805 last alloc / free. For more information see
1806 Documentation/vm/slub.txt.
1808 slub_max_order= [MM, SLUB]
1809 Determines the maximum allowed order for slabs.
1810 A high setting may cause OOMs due to memory
1811 fragmentation. For more information see
1812 Documentation/vm/slub.txt.
1814 slub_min_objects= [MM, SLUB]
1815 The minimum number of objects per slab. SLUB will
1816 increase the slab order up to slub_max_order to
1817 generate a sufficiently large slab able to contain
1818 the number of objects indicated. The higher the number
1819 of objects the smaller the overhead of tracking slabs
1820 and the less frequently locks need to be acquired.
1821 For more information see Documentation/vm/slub.txt.
1823 slub_min_order= [MM, SLUB]
1824 Determines the mininum page order for slabs. Must be
1825 lower than slub_max_order.
1826 For more information see Documentation/vm/slub.txt.
1828 slub_nomerge [MM, SLUB]
1829 Disable merging of slabs with similar size. May be
1830 necessary if there is some reason to distinguish
1831 allocs to different slabs. Debug options disable
1832 merging on their own.
1833 For more information see Documentation/vm/slub.txt.
1836 Format: <io1>[,<io2>[,...,<io8>]]
1838 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1839 attempt to substitute SMP alternatives once at boot.
1841 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1842 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1843 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1844 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1845 smsc-ircc2.ircc_irq= [HW] IRQ line
1846 smsc-ircc2.ircc_dma= [HW] DMA channel
1847 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1848 0: Toshiba Satellite 1800 (GP data pin select)
1849 1: Fast pin select (default)
1852 snd-ad1816a= [HW,ALSA]
1854 snd-ad1848= [HW,ALSA]
1856 snd-ali5451= [HW,ALSA]
1858 snd-als100= [HW,ALSA]
1860 snd-als4000= [HW,ALSA]
1862 snd-azt2320= [HW,ALSA]
1864 snd-cmi8330= [HW,ALSA]
1866 snd-cmipci= [HW,ALSA]
1868 snd-cs4231= [HW,ALSA]
1870 snd-cs4232= [HW,ALSA]
1872 snd-cs4236= [HW,ALSA]
1874 snd-cs4281= [HW,ALSA]
1876 snd-cs46xx= [HW,ALSA]
1878 snd-dt019x= [HW,ALSA]
1880 snd-dummy= [HW,ALSA]
1882 snd-emu10k1= [HW,ALSA]
1884 snd-ens1370= [HW,ALSA]
1886 snd-ens1371= [HW,ALSA]
1888 snd-es968= [HW,ALSA]
1890 snd-es1688= [HW,ALSA]
1892 snd-es18xx= [HW,ALSA]
1894 snd-es1938= [HW,ALSA]
1896 snd-es1968= [HW,ALSA]
1898 snd-fm801= [HW,ALSA]
1900 snd-gusclassic= [HW,ALSA]
1902 snd-gusextreme= [HW,ALSA]
1904 snd-gusmax= [HW,ALSA]
1908 snd-ice1712= [HW,ALSA]
1910 snd-intel8x0= [HW,ALSA]
1912 snd-interwave= [HW,ALSA]
1917 snd-korg1212= [HW,ALSA]
1919 snd-maestro3= [HW,ALSA]
1921 snd-mpu401= [HW,ALSA]
1923 snd-mtpav= [HW,ALSA]
1925 snd-nm256= [HW,ALSA]
1927 snd-opl3sa2= [HW,ALSA]
1935 snd-opti93x= [HW,ALSA]
1939 snd-rme32= [HW,ALSA]
1941 snd-rme96= [HW,ALSA]
1943 snd-rme9652= [HW,ALSA]
1949 snd-sbawe= [HW,ALSA]
1951 snd-serial= [HW,ALSA]
1953 snd-sgalaxy= [HW,ALSA]
1955 snd-sonicvibes= [HW,ALSA]
1960 snd-sun-cs4231= [HW,ALSA]
1962 snd-trident= [HW,ALSA]
1964 snd-usb-audio= [HW,ALSA,USB]
1966 snd-via82xx= [HW,ALSA]
1968 snd-virmidi= [HW,ALSA]
1970 snd-wavefront= [HW,ALSA]
1972 snd-ymfpci= [HW,ALSA]
1974 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1975 See Documentation/sonypi.txt
1977 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1978 See Documentation/specialix.txt.
1980 spia_io_base= [HW,MTD]
1986 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1988 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1989 See Documentation/scsi/st.txt.
1993 Set the STI (builtin display/keyboard on the HP-PARISC
1994 machines) console (graphic card) which should be used
1995 as the initial boot-console.
1996 See also comment in drivers/video/console/sticore.c.
1999 See comment in drivers/video/console/sticore.c.
2002 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2006 Control how the NFS server code allocates CPUs to
2007 service thread pools. Depending on how many NICs
2008 you have and where their interrupts are bound, this
2009 option will affect which CPUs will do NFS serving.
2010 Note: this parameter cannot be changed while the
2011 NFS server is running.
2013 auto the server chooses an appropriate mode
2014 automatically using heuristics
2015 global a single global pool contains all CPUs
2016 percpu one pool for each CPU
2017 pernode one pool for each NUMA node (equivalent
2018 to global on non-NUMA machines)
2020 swiotlb= [IA-64] Number of I/O TLB slabs
2024 sym53c416= [HW,SCSI]
2025 See header of drivers/scsi/sym53c416.c.
2027 sysrq_always_enabled
2029 Ignore sysrq setting - this boot parameter will
2030 neutralize any effect of /proc/sys/kernel/sysrq.
2031 Useful for debugging.
2034 See header of drivers/scsi/t128.c.
2038 thash_entries= [KNL,NET]
2039 Set number of hash buckets for TCP connection
2041 thermal.act= [HW,ACPI]
2042 -1: disable all active trip points in all thermal zones
2043 <degrees C>: override all lowest active trip points
2045 thermal.crt= [HW,ACPI]
2046 -1: disable all critical trip points in all thermal zones
2047 <degrees C>: lower all critical trip points
2049 thermal.nocrt= [HW,ACPI]
2050 Set to disable actions on ACPI thermal zone
2051 critical and hot trip points.
2053 thermal.off= [HW,ACPI]
2054 1: disable ACPI thermal control
2056 thermal.psv= [HW,ACPI]
2057 -1: disable all passive trip points
2058 <degrees C>: override all passive trip points to this value
2060 thermal.tzp= [HW,ACPI]
2061 Specify global default ACPI thermal zone polling rate
2062 <deci-seconds>: poll all this frequency
2063 0: no polling (default)
2065 tipar.timeout= [HW,PPT]
2066 Set communications timeout in tenths of a second
2069 tipar.delay= [HW,PPT]
2070 Set inter-bit delay in microseconds (default 10).
2073 See comment before function dc390_setup() in
2074 drivers/scsi/tmscsim.c.
2078 trix= [HW,OSS] MediaTrix AudioTrix Pro
2080 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2082 turbografx.map[2|3]= [HW,JOY]
2083 TurboGraFX parallel port interface
2085 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2086 See also Documentation/input/joystick-parport.txt
2088 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2089 See header of drivers/scsi/u14-34f.c.
2098 [USB] Ignore overcurrent events (default N).
2099 Some badly-designed motherboards generate lots of
2100 bogus events, for ports that aren't wired to
2101 anything. Set this parameter to avoid log spamming.
2102 Note that genuine overcurrent events won't be
2105 usbcore.autosuspend=
2106 [USB] The autosuspend time delay (in seconds) used
2107 for newly-detected USB devices (default 2). This
2108 is the time required before an idle device will be
2109 autosuspended. Devices for which the delay is set
2110 to a negative value won't be autosuspended at all.
2113 [USBHID] The interval which mice are to be polled at.
2115 vdso= [X86-32,SH,x86-64]
2116 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2117 vdso=1: enable VDSO (default)
2118 vdso=0: disable VDSO mapping
2120 vdso32= [X86-32,X86-64]
2121 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2122 vdso32=1: enable 32-bit VDSO (default)
2123 vdso32=0: disable 32-bit VDSO mapping
2126 vector=percpu: enable percpu vector domain
2128 video= [FB] Frame buffer configuration
2129 See Documentation/fb/modedb.txt.
2131 vga= [BOOT,X86-32] Select a particular video mode
2132 See Documentation/i386/boot.txt and
2133 Documentation/svga.txt.
2134 Use vga=ask for menu.
2135 This is actually a boot loader parameter; the value is
2136 passed to the kernel using a special protocol.
2138 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2139 size of <nn>. This can be used to increase the
2140 minimum size (128MB on x86). It can also be used to
2141 decrease the size and leave more room for directly
2144 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2147 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2150 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2153 waveartist= [HW,OSS]
2154 Format: <io>,<irq>,<dma>,<dma2>
2157 See header of drivers/scsi/wd33c93.c.
2160 See header of drivers/scsi/wd7000.c.
2163 See Documentation/watchdog/wdt.txt.
2165 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2166 xd_geo= See header of drivers/block/xd.c.
2168 xirc2ps_cs= [NET,PCMCIA]
2170 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2172 norandmaps Don't use address space randomization
2173 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2175 ______________________________________________________________________
2179 Add documentation for ALSA options.
2180 Add more DRM drivers.
projects / linux-2.6 / blob