4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend is enabled.
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
99 X86-32 X86-32, aka i386 architecture is enabled.
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
104 In addition, the following text indicates that the option:
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/power/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
156 Format: { level | edge | high | low }
158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
168 Format: <irq>,<irq>...
170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
171 Format: <irq>,<irq>...
173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
183 acpi_serialize [HW,ACPI] force serialization of AML methods
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
193 acpi.debug_layer= [HW,ACPI]
195 Each bit of the <int> indicates an ACPI debug layer,
196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
210 acpi.debug_level= [HW,ACPI]
212 Each bit of the <int> indicates an ACPI debug level,
213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
228 acpi_pm_good [X86-32,X86-64]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
243 The kernel tries to set a reasonable default.
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
253 See header of drivers/scsi/advansys.c.
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
263 See Documentation/scsi/aha152x.txt.
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
269 See Documentation/scsi/aic7xxx.txt.
272 See Documentation/scsi/aic79xx.txt.
274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
277 See also Documentation/kernel/input/joystick.txt
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
285 Power management functions (SPARCstation-4/5 + deriv.)
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
305 atarimouse= [HW,MOUSE] Atari Mouse
307 atascsi= [HW,SCSI] Atari SCSI
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
312 atkbd.reset= [HW] Reset keyboard during initialization
314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
328 baycom_epp= [HW,AX25]
331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
333 See header of drivers/net/hamradio/baycom_par.c.
335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
370 [SECURITY] Disable capabilities. This would normally
371 be used only if an alternative security model is to be
372 configured. Potentially dangerous and should only be
373 used if you are entirely sure of the consequences.
375 ccw_timeout_log [S390]
376 See Documentation/s390/CommonIO for details.
378 cgroup_disable= [KNL] Disable a particular controller
379 Format: {name of the controller(s) to disable}
380 {Currently supported controllers - "memory"}
382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
389 Value can be changed at runtime via
390 /selinux/checkreqprot.
393 See Documentation/s390/CommonIO for details.
396 See Documentation/s390/CommonIO for details.
398 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
400 Forces specified clocksource (if available) to be used
401 when calculating gettimeofday(). If specified
402 clocksource is not available, it defaults to PIT.
403 Format: { pit | tsc | cyclone | pmtmr }
405 clocksource= [GENERIC_TIME] Override the default clocksource
407 Override the default clocksource and use the clocksource
408 with the name specified.
409 Some clocksource names to choose from, depending on
411 [all] jiffies (this is the base, fallback clocksource)
413 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
414 pxa_timer,timer3,32k_counter,timer0_1
416 [X86-32] pit,hpet,tsc,vmi-timer;
417 scx200_hrt on Geode; cyclone on IBM x440
425 clearcpuid=BITNUM [X86]
426 Disable CPUID feature X for the kernel. See
427 include/asm-x86/cpufeature.h for the valid bit numbers.
428 Note the Linux specific bits are not necessarily
429 stable over kernel options, but the vendor specific
431 Also note that user programs calling CPUID directly
432 or using the feature without checking anything
433 will still see it. This just prevents it from
434 being used by the kernel or shown in /proc/cpuinfo.
435 Also note the kernel might malfunction if you disable
438 code_bytes [IA32/X86_64] How many bytes of object code to print
445 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
446 over the 8254 in addition to over the IO-APIC. The
447 kernel tries to set a sensible default.
449 hpet= [X86-32,HPET] option to control HPET usage
450 Format: { enable (default) | disable | force }
451 disable: disable HPET and use PIT instead
452 force: allow force enabled of undocumented chips (ICH4,
455 com20020= [HW,NET] ARCnet - COM20020 chipset
457 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
459 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
463 ARCnet - COM90xx chipset (memory-mapped buffers)
464 Format: <io>[,<irq>[,<memstart>]]
466 condev= [HW,S390] console device
469 console= [KNL] Output console device and options.
471 tty<n> Use the virtual console device <n>.
475 Use the specified serial port. The options are of
476 the form "bbbbpnf", where "bbbb" is the baud rate,
477 "p" is parity ("n", "o", or "e"), "n" is number of
478 bits, and "f" is flow control ("r" for RTS or
479 omit it). Default is "9600n8".
481 See Documentation/serial-console.txt for more
483 Documentation/networking/netconsole.txt for an
486 uart[8250],io,<addr>[,options]
487 uart[8250],mmio,<addr>[,options]
488 Start an early, polled-mode console on the 8250/16550
489 UART at the specified I/O port or MMIO address,
490 switching to the matching ttyS device later. The
491 options are the same as for ttyS, above.
493 earlycon= [KNL] Output early console device and options.
494 uart[8250],io,<addr>[,options]
495 uart[8250],mmio,<addr>[,options]
496 Start an early, polled-mode console on the 8250/16550
497 UART at the specified I/O port or MMIO address.
498 The options are the same as for ttyS, above.
501 [HW] Never suspend the console
502 Disable suspending of consoles during suspend and
503 hibernate operations. Once disabled, debugging
504 messages can reach various consoles while the rest
505 of the system is being put to sleep (ie, while
506 debugging driver suspend/resume hooks). This may
507 not work reliably with all consoles, but is known
508 to work with serial and VGA consoles.
510 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
512 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
514 crashkernel=nn[KMG]@ss[KMG]
515 [KNL] Reserve a chunk of physical memory to
516 hold a kernel to switch to with kexec on panic.
518 crashkernel=range1:size1[,range2:size2,...][@offset]
519 [KNL] Same as above, but depends on the memory
520 in the running system. The syntax of range is
521 start-[end] where start and end are both
522 a memory unit (amount[KMG]). See also
523 Documentation/kdump/kdump.txt for a example.
526 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
531 cs89x0_media= [HW,NET]
532 Format: { rj45 | aui | bnc }
535 See header of drivers/s390/block/dasd_devmap.c.
537 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
538 (one device per port)
539 Format: <port#>,<type>
540 See also Documentation/input/joystick-parport.txt
542 debug [KNL] Enable kernel debugging (events log level).
545 [KNL] verbose self-tests
547 Print debugging info while doing the locking API
549 We default to 0 (no extra messages), setting it to
550 1 will print _a lot_ more information - normally
551 only useful to kernel developers.
553 decnet.addr= [HW,NET]
554 Format: <area>[,<node>]
555 See also Documentation/networking/decnet.txt.
558 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
559 Change the default blue palette of the console.
560 This is a 16-member array composed of values
564 Format: <green0>,<green1>,<green2>,...,<green15>
565 Change the default green palette of the console.
566 This is a 16-member array composed of values
570 Format: <red0>,<red1>,<red2>,...,<red15>
571 Change the default red palette of the console.
572 This is a 16-member array composed of values
578 Set system-wide default UTF-8 mode for all tty's.
579 Default is 1, i.e. UTF-8 mode is enabled for all
580 newly opened terminals.
583 Set number of hash buckets for dentry cache.
586 IO parameters + enable/disable command.
588 digiepca= [HW,SERIAL]
589 See drivers/char/README.epca and
590 Documentation/digiepca.txt.
592 disable_mtrr_trim [X86, Intel and AMD only]
593 By default the kernel will trim any uncacheable
594 memory out of your available memory pool based on
595 MTRR settings. This parameter disables that behavior,
596 possibly causing your machine to run very slowly.
598 dmasound= [HW,OSS] Sound subsystem buffers
604 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
606 earlyprintk=serial[,ttySn[,baudrate]]
608 Append ",keep" to not disable it when the real console
611 Only vga or serial at a time, not both.
613 Currently only ttyS0 and ttyS1 are supported.
615 Interaction with the standard serial driver is not
618 The VGA output is eventually overwritten by the real
624 Format: {"of[f]" | "sk[ipmbr]"}
625 See comment in arch/i386/boot/edd.S
627 eisa_irq_edge= [PARISC,HW]
628 See header of drivers/parisc/eisa.c.
631 See comment before function elanfreq_setup() in
632 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
635 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
636 See Documentation/block/as-iosched.txt and
637 Documentation/block/deadline-iosched.txt for details.
639 elfcorehdr= [X86-32, X86_64]
640 Specifies physical address of start of kernel core
641 image elf header. Generally kexec loader will
642 pass this option to capture kernel.
643 See Documentation/kdump/kdump.txt for details.
645 enforcing [SELINUX] Set initial enforcing status.
647 See security/selinux/Kconfig help text.
648 0 -- permissive (log only, no denials).
649 1 -- enforcing (deny and log).
651 Value can be changed at runtime via /selinux/enforce.
654 Format: <spdif>,[<nomix>,[<amplifier>]]
655 See also header of sound/oss/es1371.c.
657 ether= [HW,NET] Ethernet cards parameters
658 This option is obsoleted by the "netdev=" option, which
659 has equivalent usage. See its documentation for details.
661 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
666 fail_make_request=[KNL]
667 General fault injection mechanism.
668 Format: <interval>,<probability>,<space>,<times>
669 See also /Documentation/fault-injection/.
672 See header of drivers/scsi/fd_mcs.c.
675 See header of drivers/scsi/fdomain.c.
678 See Documentation/floppy.txt.
681 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
682 support via parallel port (up to 5 devices per port)
683 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
684 See also Documentation/input/joystick-parport.txt
688 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
693 See header of drivers/scsi/gdth.c.
695 gpt [EFI] Forces disk with valid GPT signature but
696 invalid Protective MBR to be treated as GPT.
700 hashdist= [KNL,NUMA] Large hashes allocated during boot
701 are distributed across NUMA nodes. Defaults on
702 for IA-64, off otherwise.
703 Format: 0 | 1 (for off | on)
705 hcl= [IA-64] SGI's Hardware Graph compatibility layer
707 hd= [EIDE] (E)IDE hard drive subsystem geometry
708 Format: <cyl>,<head>,<sect>
710 hd?= [HW] (E)IDE subsystem
711 hd?lun= See Documentation/ide/ide.txt.
713 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
714 size of <nn>. This works even on boxes that have no
715 highmem otherwise. This also works to reduce highmem
716 size on bigger boxes.
718 highres= [KNL] Enable/disable high resolution timer mode.
719 Valid parameters: "on", "off"
723 See Documentation/isdn/README.HiSax.
725 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
726 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
728 i8042.direct [HW] Put keyboard port into non-translated mode
729 i8042.dumbkbd [HW] Pretend that controller can only read data from
730 keyboard and cannot control its state
731 (Don't attempt to blink the leds)
732 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
733 i8042.nokbd [HW] Don't check/create keyboard port
734 i8042.noloop [HW] Disable the AUX Loopback command while probing
736 i8042.nomux [HW] Don't check presence of an active multiplexing
738 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
741 [HW] Frequency with which keyboard LEDs should blink
742 when kernel panics (default is 0.5 sec)
743 i8042.reset [HW] Reset the controller during init and cleanup
744 i8042.unlock [HW] Unlock (ignore) the keylock
748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
749 indicates that the driver is running on unsupported
751 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
752 does not match list of supported models.
754 [HW] Report power status in /proc/i8k
755 (disabled by default)
756 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
759 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
760 See Documentation/mca.txt.
763 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
765 ide= [HW] (E)IDE subsystem
766 Format: ide=nodma or ide=doubler or ide=reverse
767 See Documentation/ide/ide.txt.
769 ide?= [HW] (E)IDE subsystem
770 Format: ide?=noprobe or chipset specific parameters.
771 See Documentation/ide/ide.txt.
773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
774 See Documentation/ide/ide.txt.
777 Format: idle=poll or idle=mwait
778 Poll forces a polling idle loop that can slightly improves the performance
779 of waking up a idle CPU, but will use a lot of power and make the system
780 run hot. Not recommended.
781 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
782 to not use it because it doesn't save as much power as a normal idle
783 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
787 Claim all unknown PCI IDE storage controllers.
789 ignore_loglevel [KNL]
790 Ignore loglevel setting - this will print /all/
791 kernel messages to the console. Useful for debugging.
794 Set number of hash buckets for inode cache.
797 See header of drivers/scsi/in2000.c.
801 Run specified binary instead of /sbin/init as init
804 initcall_debug [KNL] Trace initcalls as they are executed. Useful
805 for working out where the kernel is dying during
808 initrd= [BOOT] Specify the location of the initial ramdisk
810 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
815 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
817 Disable intel iommu driver.
818 igfx_off [Default Off]
819 By default, gfx is mapped as normal device. If a gfx
820 device has a dedicated DMAR unit, the DMAR unit is
821 bypassed by not enabling DMAR with this option. In
822 this case, gfx device will use physical address for
825 With this option iommu will not optimize to look
826 for io virtual address below 32 bit forcing dual
827 address cycle on pci bus for cards supporting greater
828 than 32 bit addressing. The default is to look
829 for translation below 32 bit and if not available
830 then look in the higher range.
832 io_delay= [X86-32,X86-64] I/O delay method
834 Standard port 0x80 based delay
836 Alternate port 0xed based delay (needed on some systems)
838 Simple two microseconds delay
842 io7= [HW] IO7 for Marvel based alpha systems
843 See comment before marvel_specify_io7 in
844 arch/alpha/kernel/core_marvel.c.
847 See Documentation/nfsroot.txt.
849 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
850 See comment before ip2_setup() in
851 drivers/char/ip2/ip2base.c.
853 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
854 See header of drivers/scsi/ips.c.
856 ports= [IP_VS_FTP] IPVS ftp helper module
858 Up to 8 (IP_VS_APP_MAX_PORTS) ports
860 Format: <port>,<port>....
863 When an interrupt is not handled search all handlers
864 for it. Intended to get systems with badly broken
868 When an interrupt is not handled search all handlers
869 for it. Also check all handlers each timer
870 interrupt. Intended to get systems with badly broken
874 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
876 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
878 <cpu number>,...,<cpu number>
880 <cpu number>-<cpu number> (must be a positive range in ascending order)
882 <cpu number>,...,<cpu number>-<cpu number>
883 This option can be used to specify one or more CPUs
884 to isolate from the general SMP balancing and scheduling
885 algorithms. The only way to move a process onto or off
886 an "isolated" CPU is via the CPU affinity syscalls.
887 <cpu number> begins at 0 and the maximum value is
888 "number of CPUs in system - 1".
890 This option is the preferred way to isolate CPUs. The
891 alternative -- manually setting the CPU mask of all
892 tasks in the system -- can cause problems and
893 suboptimal load balancer performance.
897 js= [HW,JOY] Analog joystick
898 See Documentation/input/joystick.txt.
900 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
901 specifies the amount of memory usable by the kernel
902 for non-movable allocations. The requested amount is
903 spread evenly throughout all nodes in the system. The
904 remaining memory in each node is used for Movable
905 pages. In the event, a node is too small to have both
906 kernelcore and Movable pages, kernelcore pages will
907 take priority and other nodes will have a larger number
908 of kernelcore pages. The Movable zone is used for the
909 allocation of pages that may be reclaimed or moved
910 by the page migration subsystem. This means that
911 HugeTLB pages may not be allocated from this zone.
912 Note that allocations like PTEs-from-HighMem still
913 use the HighMem zone if it exists, and the Normal
916 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
917 is similar to kernelcore except it specifies the
918 amount of memory used for migratable allocations.
919 If both kernelcore and movablecore is specified,
920 then kernelcore will be at *least* the specified
921 value but may be more. If movablecore on its own
922 is specified, the administrator must be careful
923 that the amount of memory usable for all allocations
928 kstack=N [X86-32,X86-64] Print N words from the kernel stack
933 lapic [X86-32,APIC] Enable the local APIC even if BIOS
936 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
939 libata.dma= [LIBATA] DMA control
940 libata.dma=0 Disable all PATA and SATA DMA
941 libata.dma=1 PATA and SATA Disk DMA only
942 libata.dma=2 ATAPI (CDROM) DMA only
943 libata.dma=4 Compact Flash DMA only
944 Combinations also work, so libata.dma=3 enables DMA
945 for disks and CDROMs, but not CFs.
947 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
951 libata.force= [LIBATA] Force configurations. The format is comma
952 separated list of "[ID:]VAL" where ID is
953 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
954 matching port, link or device. Basically, it matches
955 the ATA ID string printed on console by libata. If
956 the whole ID part is omitted, the last PORT and DEVICE
957 values are used. If ID hasn't been specified yet, the
958 configuration applies to all ports, links and devices.
960 If only DEVICE is omitted, the parameter applies to
961 the port and all links and devices behind it. DEVICE
962 number of 0 either selects the first device or the
963 first fan-out link behind PMP device. It does not
964 select the host link. DEVICE number of 15 selects the
965 host link and device attached to it.
967 The VAL specifies the configuration to force. As long
968 as there's no ambiguity shortcut notation is allowed.
969 For example, both 1.5 and 1.5G would work for 1.5Gbps.
970 The following configurations can be forced.
972 * Cable type: 40c, 80c, short40c, unk, ign or sata.
973 Any ID with matching PORT is used.
975 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
977 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
978 udma[/][16,25,33,44,66,100,133] notation is also
981 * [no]ncq: Turn on or off NCQ.
983 If there are multiple matching configurations changing
984 the same attribute, the last one is used.
986 load_ramdisk= [RAM] List of ramdisks to load from floppy
987 See Documentation/ramdisk.txt.
989 lockd.nlm_grace_period=P [NFS] Assign grace period.
992 lockd.nlm_tcpport=N [NFS] Assign TCP port.
995 lockd.nlm_timeout=T [NFS] Assign timeout value.
998 lockd.nlm_udpport=M [NFS] Assign UDP port.
1001 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1004 loglevel= All Kernel Messages with a loglevel smaller than the
1005 console loglevel will be printed to the console. It can
1006 also be changed with klogd or other programs. The
1007 loglevels are defined as follows:
1009 0 (KERN_EMERG) system is unusable
1010 1 (KERN_ALERT) action must be taken immediately
1011 2 (KERN_CRIT) critical conditions
1012 3 (KERN_ERR) error conditions
1013 4 (KERN_WARNING) warning conditions
1014 5 (KERN_NOTICE) normal but significant condition
1015 6 (KERN_INFO) informational
1016 7 (KERN_DEBUG) debug-level messages
1018 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1019 Format: { n | nk | nM }
1020 n must be a power of two. The default size
1021 is set in the kernel config file.
1023 logo.nologo [FB] Disables display of the built-in Linux logo.
1024 This may be used to provide more screen space for
1025 kernel log messages and is useful when debugging
1026 kernel boot problems.
1028 lp=0 [LP] Specify parallel ports to use, e.g,
1029 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1030 lp=reset first parallel port). 'lp=0' disables the
1031 lp=auto printer driver. 'lp=reset' (which can be
1032 specified in addition to the ports) causes
1033 attached printers to be reset. Using
1034 lp=port1,port2,... specifies the parallel ports
1035 to associate lp devices with, starting with
1036 lp0. A port specification may be 'none' to skip
1037 that lp device, or a parport name such as
1038 'parport0'. Specifying 'lp=auto' instead of a
1039 port specification list means that device IDs
1040 from each port should be examined, to see if
1041 an IEEE 1284-compliant printer is attached; if
1042 so, the driver will manage that printer.
1043 See also header of drivers/char/lp.c.
1046 Sets loops_per_jiffy to given constant, thus avoiding
1047 time-consuming boot-time autodetection (up to 250 ms per
1048 CPU). 0 enables autodetection (default). To determine
1049 the correct value for your kernel, boot with normal
1050 autodetection and see what value is printed. Note that
1051 on SMP systems the preset will be applied to all CPUs,
1052 which is likely to cause problems if your CPUs need
1053 significantly divergent settings. An incorrect value
1054 will cause delays in the kernel to be wrong, leading to
1055 unpredictable I/O errors and other breakage. Although
1056 unlikely, in the extreme case this might damage your
1060 Format: <io>,<irq>,<dma>
1062 mac5380= [HW,SCSI] Format:
1063 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1065 mac53c9x= [HW,SCSI] Format:
1066 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1068 machvec= [IA64] Force the use of a particular machine-vector
1069 (machvec) in a generic kernel.
1070 Example: machvec=hpzx1_swiotlb
1072 max_loop= [LOOP] Maximum number of loopback devices that can
1076 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1077 should make use of. maxcpus=n : n >= 0 limits the
1078 kernel to using 'n' processors. n=0 is a special case,
1079 it is equivalent to "nosmp", which also disables
1082 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1083 equal to this physical address is ignored.
1085 max_luns= [SCSI] Maximum number of LUNs to probe.
1086 Should be between 1 and 2^32-1.
1089 [SCSI] Maximum number of LUNs received.
1090 Should be between 1 and 16384.
1094 mce [X86-32] Machine Check Exception
1096 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1098 md= [HW] RAID subsystems devices and level
1099 See Documentation/md.txt.
1102 Format: <first>,<last>
1103 Specifies range of consoles to be captured by the MDA.
1105 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1106 Amount of memory to be used when the kernel is not able
1107 to see the whole system memory or for test.
1108 [X86-32] Use together with memmap= to avoid physical
1109 address space collisions. Without memmap= PCI devices
1110 could be placed at addresses belonging to unused RAM.
1112 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1115 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1116 E820 memory map, as specified by the user.
1117 Such memmap=exactmap lines can be constructed based on
1118 BIOS output or other requirements. See the memmap=nn@ss
1121 memmap=nn[KMG]@ss[KMG]
1122 [KNL] Force usage of a specific region of memory
1123 Region of memory to be used, from ss to ss+nn.
1125 memmap=nn[KMG]#ss[KMG]
1126 [KNL,ACPI] Mark specific memory as ACPI data.
1127 Region of memory to be used, from ss to ss+nn.
1129 memmap=nn[KMG]$ss[KMG]
1130 [KNL,ACPI] Mark specific memory as reserved.
1131 Region of memory to be used, from ss to ss+nn.
1132 Example: Exclude memory from 0x18690000-0x1869ffff
1133 memmap=64K$0x18690000
1135 memmap=0x10000$0x18690000
1137 meye.*= [HW] Set MotionEye Camera parameters
1138 See Documentation/video4linux/meye.txt.
1140 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1141 Multi-Function General Purpose Timers on AMD Geode
1144 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1145 the BIOS has incorrectly applied a workaround. TinyBIOS
1146 version 0.98 is known to be affected, 0.99 fixes the
1147 problem by letting the user disable the workaround.
1152 [MOUSE] Maximum time between finger touching and
1153 leaving touchpad surface for touch to be considered
1154 a tap and be reported as a left button click (for
1155 touchpads working in absolute mode only).
1157 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1158 reporting absolute coordinates, such as tablets
1159 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1160 reporting absolute coordinates, such as tablets
1165 MTD_Partition= [MTD]
1166 Format: <name>,<region-number>,<size>,<offset>
1168 MTD_Region= [MTD] Format:
1169 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1172 See drivers/mtd/cmdlinepart.c.
1174 mtouchusb.raw_coordinates=
1175 [HW] Make the MicroTouch USB driver use raw coordinates
1176 ('y', default) or cooked coordinates ('n')
1178 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1181 See header of drivers/scsi/NCR_D700.c.
1185 ncr53c400= [HW,SCSI]
1187 ncr53c400a= [HW,SCSI]
1189 ncr53c406a= [HW,SCSI]
1191 ncr53c8xx= [HW,SCSI]
1193 netdev= [NET] Network devices parameters
1194 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1195 Note that mem_start is often overloaded to mean
1196 something different and driver-specific.
1197 This usage is only documented in each driver source
1201 See Documentation/nfsroot.txt.
1203 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1204 See Documentation/nfsroot.txt.
1206 nfs.callback_tcpport=
1207 [NFS] set the TCP port on which the NFSv4 callback
1208 channel should listen.
1210 nfs.idmap_cache_timeout=
1211 [NFS] set the maximum lifetime for idmapper cache
1215 [NFS] enable 64-bit inode numbers.
1216 If zero, the NFS client will fake up a 32-bit inode
1217 number for the readdir() and stat() syscalls instead
1218 of returning the full 64-bit number.
1219 The default is to return 64-bit inode numbers.
1221 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1222 when a NMI is triggered.
1223 Format: [state][,regs][,debounce][,die]
1225 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1227 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1228 emulation library even if a 387 maths coprocessor
1231 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1232 caches in the slab allocator. Saves per-node memory,
1233 but will impact performance.
1237 noapic [SMP,APIC] Tells the kernel to not make use of any
1238 IOAPICs that may be present in the system.
1240 nobats [PPC] Do not use BATs for mapping kernel lowmem
1241 on "Classic" PPC cores.
1245 nodelayacct [KNL] Disable per-task delay accounting
1247 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1249 noefi [X86-32,X86-64] Disable EFI runtime services support.
1253 noexec [X86-32,X86-64]
1254 noexec=on: enable non-executable mappings (default)
1255 noexec=off: disable nn-executable mappings
1257 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1258 register save and restore. The kernel will only save
1259 legacy floating-point registers on task switch.
1261 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1265 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1266 instruction doesn't work correctly and not to
1269 nohalt [IA-64] Tells the kernel not to use the power saving
1270 function PAL_HALT_LIGHT when idle. This increases
1271 power-consumption. On the positive side, it reduces
1272 interrupt wake-up latency, which may improve performance
1273 in certain environments such as networked servers or
1276 nohz= [KNL] Boottime enable/disable dynamic ticks
1277 Valid arguments: on, off
1280 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1282 noirqdebug [X86-32] Disables the code which attempts to detect and
1283 disable unhandled interrupt sources.
1285 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1286 broken timer IRQ sources.
1288 noisapnp [ISAPNP] Disables ISA PnP code.
1290 noinitrd [RAM] Tells the kernel not to load any configured
1295 nojitter [IA64] Disables jitter checking for ITC timers.
1297 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1299 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1301 noltlbs [PPC] Do not use large page/tlb entries for kernel
1302 lowmem mapping on PPC40x.
1304 nomca [IA-64] Disable machine check abort handling
1306 nomce [X86-32] Machine Check Exception
1308 nomfgpt [X86-32] Disable Multi-Function General Purpose
1309 Timer usage (for AMD Geode machines).
1311 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1313 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1314 with UP alternatives
1316 noresidual [PPC] Don't use residual data on PReP machines.
1318 noresume [SWSUSP] Disables resume and restores original swap
1321 no-scroll [VGA] Disables scrollback.
1322 This is required for the Braillex ib80-piezo Braille
1323 reader made by F.H. Papenmeier (Germany).
1327 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1329 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1330 and disable the IO APIC. legacy for "maxcpus=0".
1332 nosoftlockup [KNL] Disable the soft-lockup detector.
1334 nosync [HW,M68K] Disables sync negotiation for all devices.
1336 notsc [BUGS=X86-32] Disable Time Stamp Counter
1338 nousb [USB] Disable the USB subsystem
1342 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1343 one of ['zone', 'node', 'default'] can be specified
1344 This can be set from sysctl after boot.
1345 See Documentation/sysctl/vm.txt for details.
1347 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1352 oprofile.timer= [HW]
1353 Use timer interrupt instead of performance counters
1355 osst= [HW,SCSI] SCSI Tape Driver
1356 Format: <buffer_size>,<write_threshold>
1357 See also Documentation/scsi/st.txt.
1359 panic= [KNL] Kernel behaviour on panic
1362 parkbd.port= [HW] Parallel port number the keyboard adapter is
1363 connected to, default is 0.
1365 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1366 0 for XT, 1 for AT (default is AT).
1369 parport= [HW,PPT] Specify parallel ports. 0 disables.
1370 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1371 Use 'auto' to force the driver to use any
1372 IRQ/DMA settings detected (the default is to
1373 ignore detected IRQ/DMA settings because of
1374 possible conflicts). You can specify the base
1375 address, IRQ, and DMA settings; IRQ and DMA
1376 should be numbers, or 'auto' (for using detected
1377 settings on that particular port), or 'nofifo'
1378 (to avoid using a FIFO even if it is detected).
1379 Parallel ports are assigned in the order they
1380 are specified on the command line, starting
1383 parport_init_mode= [HW,PPT]
1384 Configure VIA parallel port to operate in
1385 a specific mode. This is necessary on Pegasos
1386 computer where firmware has no options for setting
1387 up parallel port mode and sets it to spp.
1388 Currently this function knows 686a and 8231 chips.
1389 Format: [spp|ps2|epp|ecp|ecpepp]
1391 pas2= [HW,OSS] Format:
1392 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1395 See header of drivers/scsi/pas16.c.
1398 Halt all CPUs after the first oops has been printed for
1399 the specified number of seconds. This is to be used if
1400 your oopses keep scrolling off the screen.
1405 See header of drivers/block/paride/pcd.c.
1406 See also Documentation/paride.txt.
1408 pci=option[,option...] [PCI] various PCI subsystem options:
1409 off [X86-32] don't probe for the PCI bus
1410 bios [X86-32] force use of PCI BIOS, don't access
1411 the hardware directly. Use this if your machine
1412 has a non-standard PCI host bridge.
1413 nobios [X86-32] disallow use of PCI BIOS, only direct
1414 hardware access methods are allowed. Use this
1415 if you experience crashes upon bootup and you
1416 suspect they are caused by the BIOS.
1417 conf1 [X86-32] Force use of PCI Configuration
1419 conf2 [X86-32] Force use of PCI Configuration
1421 noaer [PCIE] If the PCIEAER kernel config parameter is
1422 enabled, this kernel boot option can be used to
1423 disable the use of PCIE advanced error reporting.
1424 nodomains [PCI] Disable support for multiple PCI
1425 root domains (aka PCI segments, in ACPI-speak).
1426 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1428 nomsi [MSI] If the PCI_MSI kernel config parameter is
1429 enabled, this kernel boot option can be used to
1430 disable the use of MSI interrupts system-wide.
1431 nosort [X86-32] Don't sort PCI devices according to
1432 order given by the PCI BIOS. This sorting is
1433 done to get a device order compatible with
1435 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1436 routing table. These calls are known to be buggy
1437 on several machines and they hang the machine
1438 when used, but on other computers it's the only
1439 way to get the interrupt routing table. Try
1440 this option if the kernel is unable to allocate
1441 IRQs or discover secondary PCI buses on your
1443 rom [X86-32] Assign address space to expansion ROMs.
1444 Use with caution as certain devices share
1445 address decoders between ROMs and other
1447 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1448 assigned automatically to PCI devices. You can
1449 make the kernel exclude IRQs of your ISA cards
1451 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1452 of the PIRQ table (normally generated
1453 by the BIOS) if it is outside the
1454 F0000h-100000h range.
1455 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1456 useful if the kernel is unable to find your
1457 secondary buses and you want to tell it
1458 explicitly which ones they are.
1459 assign-busses [X86-32] Always assign all PCI bus
1460 numbers ourselves, overriding
1461 whatever the firmware may have done.
1462 usepirqmask [X86-32] Honor the possible IRQ mask stored
1463 in the BIOS $PIR table. This is needed on
1464 some systems with broken BIOSes, notably
1465 some HP Pavilion N5400 and Omnibook XE3
1466 notebooks. This will have no effect if ACPI
1467 IRQ routing is enabled.
1468 noacpi [X86-32] Do not use ACPI for IRQ routing
1469 or for PCI scanning.
1470 use_crs [X86-32] Use _CRS for PCI resource
1472 routeirq Do IRQ routing for all PCI devices.
1473 This is normally done in pci_enable_device(),
1474 so this option is a temporary workaround
1475 for broken drivers that don't call it.
1476 firmware [ARM] Do not re-enumerate the bus but instead
1477 just use the configuration from the
1478 bootloader. This is currently used on
1479 IXP2000 systems where the bus has to be
1480 configured a certain way for adjunct CPUs.
1481 noearly [X86] Don't do any early type 1 scanning.
1482 This might help on some broken boards which
1483 machine check when some devices' config space
1484 is read. But various workarounds are disabled
1485 and some IOMMU drivers will not work.
1486 bfsort Sort PCI devices into breadth-first order.
1487 This sorting is done to get a device
1488 order compatible with older (<= 2.4) kernels.
1489 nobfsort Don't sort PCI devices into breadth-first order.
1490 cbiosize=nn[KMG] The fixed amount of bus space which is
1491 reserved for the CardBus bridge's IO window.
1492 The default value is 256 bytes.
1493 cbmemsize=nn[KMG] The fixed amount of bus space which is
1494 reserved for the CardBus bridge's memory
1495 window. The default value is 64 megabytes.
1497 pcmv= [HW,PCMCIA] BadgePAD 4
1500 See Documentation/paride.txt.
1502 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1505 See arch/parisc/kernel/pdc_chassis.c
1508 See Documentation/paride.txt.
1511 See Documentation/paride.txt.
1513 pirq= [SMP,APIC] Manual mp-table setup
1514 See Documentation/i386/IO-APIC.txt.
1516 plip= [PPT,NET] Parallel port network link
1517 Format: { parport<nr> | timid | 0 }
1518 See also Documentation/parport.txt.
1524 { on | off | curr | res | no-curr | no-res }
1527 [ISAPNP] Exclude IRQs for the autoconfiguration
1530 [ISAPNP] Exclude DMAs for the autoconfiguration
1532 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1533 Ranges are in pairs (I/O port base and size).
1536 [ISAPNP] Exclude memory regions for the
1538 Ranges are in pairs (memory base and size).
1540 print-fatal-signals=
1541 [KNL] debug: print fatal signals
1542 print-fatal-signals=1: print segfault info to
1546 printk.time= Show timing data prefixed to each printk message line
1547 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1549 profile= [KNL] Enable kernel profiling via /proc/profile
1550 Format: [schedule,]<number>
1551 Param: "schedule" - profile schedule points.
1552 Param: <number> - step/bucket size as a power of 2 for
1553 statistical time based profiling.
1554 Param: "sleep" - profile D-state sleeping (millisecs).
1555 Requires CONFIG_SCHEDSTATS
1556 Param: "kvm" - profile VM exits.
1558 processor.max_cstate= [HW,ACPI]
1559 Limit processor to maximum C-state
1560 max_cstate=9 overrides any DMI blacklist limit.
1562 processor.nocst [HW,ACPI]
1563 Ignore the _CST method to determine C-states,
1564 instead using the legacy FADT method
1566 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1568 See Documentation/ramdisk.txt.
1570 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1571 probe for; one of (bare|imps|exps|lifebook|any).
1572 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1574 psmouse.resetafter= [HW,MOUSE]
1575 Try to reset the device after so many bad packets
1578 [HW,MOUSE] Set desired mouse resolution, in dpi.
1579 psmouse.smartscroll=
1580 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1581 0 = disabled, 1 = enabled (default).
1583 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1585 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1588 See Documentation/paride.txt.
1591 [KNL] Number of legacy pty's. Overwrites compiled-in
1594 quiet [KNL] Disable most log messages
1599 See Documentation/md.txt.
1601 ramdisk_blocksize= [RAM]
1602 See Documentation/ramdisk.txt.
1604 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1605 See Documentation/ramdisk.txt.
1607 rcupdate.blimit= [KNL,BOOT]
1608 Set maximum number of finished RCU callbacks to process
1611 rcupdate.qhimark= [KNL,BOOT]
1612 Set threshold of queued
1613 RCU callbacks over which batch limiting is disabled.
1615 rcupdate.qlowmark= [KNL,BOOT]
1616 Set threshold of queued RCU callbacks below which
1617 batch limiting is re-enabled.
1621 Run specified binary instead of /init from the ramdisk,
1622 used for early userspace startup. See initrd.
1624 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1625 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1626 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1628 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1630 reservetop= [X86-32]
1632 Reserves a hole at the top of the kernel virtual
1635 reset_devices [KNL] Force drivers to reset the underlying device
1636 during initialization.
1639 Specify the partition device for software suspend
1641 resume_offset= [SWSUSP]
1642 Specify the offset from the beginning of the partition
1643 given by "resume=" at which the swap header is located,
1644 in <PAGE_SIZE> units (needed only for swap files).
1645 See Documentation/power/swsusp-and-swap-files.txt
1647 retain_initrd [RAM] Keep initrd memory after extraction
1649 rhash_entries= [KNL,NET]
1650 Set number of hash buckets for route cache
1652 riscom8= [HW,SERIAL]
1653 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1655 ro [KNL] Mount root device read-only on boot
1657 root= [KNL] Root filesystem
1659 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1660 mount the root filesystem
1662 rootflags= [KNL] Set root filesystem mount option string
1664 rootfstype= [KNL] Set root filesystem type
1666 rootwait [KNL] Wait (indefinitely) for root device to show up.
1667 Useful for devices that are detected asynchronously
1668 (e.g. USB and MMC devices).
1670 root_plug.vendor_id=
1671 [ROOTPLUG] Override the default vendor ID
1673 root_plug.product_id=
1674 [ROOTPLUG] Override the default product ID
1677 [ROOTPLUG] Enable debugging output
1679 rw [KNL] Mount root device read-write on boot
1681 S [KNL] Run init in single mode
1684 See drivers/net/irda/sa1100_ir.c.
1686 sbni= [NET] Granch SBNI12 leased line adapter
1688 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1689 Format: <io>[,<timeout>[,<isapnp>]]
1691 scsi_debug_*= [SCSI]
1692 See drivers/scsi/scsi_debug.c.
1694 scsi_default_dev_flags=
1695 [SCSI] SCSI default device flags
1698 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1699 Format: <vendor>:<model>:<flags>
1700 (flags are integer value)
1702 scsi_logging_level= [SCSI] a bit mask of logging levels
1703 See drivers/scsi/scsi_logging.h for bits. Also
1704 settable via sysctl at dev.scsi.logging_level
1705 (/proc/sys/dev/scsi/logging_level).
1706 There is also a nice 'scsi_logging_level' script in the
1707 S390-tools package, available for download at
1708 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1710 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1711 discovered. async scans them in kernel threads,
1712 allowing boot to proceed. none ignores them, expecting
1713 user space to do the scan.
1715 selinux [SELINUX] Disable or enable SELinux at boot time.
1716 Format: { "0" | "1" }
1717 See security/selinux/Kconfig help text.
1720 Default value is set via kernel config option.
1721 If enabled at boot time, /selinux/disable can be used
1722 later to disable prior to initial policy load.
1724 selinux_compat_net =
1725 [SELINUX] Set initial selinux_compat_net flag value.
1726 Format: { "0" | "1" }
1727 0 -- use new secmark-based packet controls
1728 1 -- use legacy packet controls
1729 Default value is 0 (preferred).
1730 Value can be changed at runtime via
1731 /selinux/compat_net.
1733 serialnumber [BUGS=X86-32]
1736 Maximal number of shapers.
1739 See header of drivers/scsi/sim710.c.
1746 slub_debug[=options[,slabs]] [MM, SLUB]
1747 Enabling slub_debug allows one to determine the
1748 culprit if slab objects become corrupted. Enabling
1749 slub_debug can create guard zones around objects and
1750 may poison objects when not in use. Also tracks the
1751 last alloc / free. For more information see
1752 Documentation/vm/slub.txt.
1754 slub_max_order= [MM, SLUB]
1755 Determines the maximum allowed order for slabs.
1756 A high setting may cause OOMs due to memory
1757 fragmentation. For more information see
1758 Documentation/vm/slub.txt.
1760 slub_min_objects= [MM, SLUB]
1761 The minimum number of objects per slab. SLUB will
1762 increase the slab order up to slub_max_order to
1763 generate a sufficiently large slab able to contain
1764 the number of objects indicated. The higher the number
1765 of objects the smaller the overhead of tracking slabs
1766 and the less frequently locks need to be acquired.
1767 For more information see Documentation/vm/slub.txt.
1769 slub_min_order= [MM, SLUB]
1770 Determines the mininum page order for slabs. Must be
1771 lower than slub_max_order.
1772 For more information see Documentation/vm/slub.txt.
1774 slub_nomerge [MM, SLUB]
1775 Disable merging of slabs with similar size. May be
1776 necessary if there is some reason to distinguish
1777 allocs to different slabs. Debug options disable
1778 merging on their own.
1779 For more information see Documentation/vm/slub.txt.
1782 Format: <io1>[,<io2>[,...,<io8>]]
1784 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1785 attempt to substitute SMP alternatives once at boot.
1787 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1788 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1789 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1790 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1791 smsc-ircc2.ircc_irq= [HW] IRQ line
1792 smsc-ircc2.ircc_dma= [HW] DMA channel
1793 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1794 0: Toshiba Satellite 1800 (GP data pin select)
1795 1: Fast pin select (default)
1798 snd-ad1816a= [HW,ALSA]
1800 snd-ad1848= [HW,ALSA]
1802 snd-ali5451= [HW,ALSA]
1804 snd-als100= [HW,ALSA]
1806 snd-als4000= [HW,ALSA]
1808 snd-azt2320= [HW,ALSA]
1810 snd-cmi8330= [HW,ALSA]
1812 snd-cmipci= [HW,ALSA]
1814 snd-cs4231= [HW,ALSA]
1816 snd-cs4232= [HW,ALSA]
1818 snd-cs4236= [HW,ALSA]
1820 snd-cs4281= [HW,ALSA]
1822 snd-cs46xx= [HW,ALSA]
1824 snd-dt019x= [HW,ALSA]
1826 snd-dummy= [HW,ALSA]
1828 snd-emu10k1= [HW,ALSA]
1830 snd-ens1370= [HW,ALSA]
1832 snd-ens1371= [HW,ALSA]
1834 snd-es968= [HW,ALSA]
1836 snd-es1688= [HW,ALSA]
1838 snd-es18xx= [HW,ALSA]
1840 snd-es1938= [HW,ALSA]
1842 snd-es1968= [HW,ALSA]
1844 snd-fm801= [HW,ALSA]
1846 snd-gusclassic= [HW,ALSA]
1848 snd-gusextreme= [HW,ALSA]
1850 snd-gusmax= [HW,ALSA]
1854 snd-ice1712= [HW,ALSA]
1856 snd-intel8x0= [HW,ALSA]
1858 snd-interwave= [HW,ALSA]
1863 snd-korg1212= [HW,ALSA]
1865 snd-maestro3= [HW,ALSA]
1867 snd-mpu401= [HW,ALSA]
1869 snd-mtpav= [HW,ALSA]
1871 snd-nm256= [HW,ALSA]
1873 snd-opl3sa2= [HW,ALSA]
1881 snd-opti93x= [HW,ALSA]
1885 snd-rme32= [HW,ALSA]
1887 snd-rme96= [HW,ALSA]
1889 snd-rme9652= [HW,ALSA]
1895 snd-sbawe= [HW,ALSA]
1897 snd-serial= [HW,ALSA]
1899 snd-sgalaxy= [HW,ALSA]
1901 snd-sonicvibes= [HW,ALSA]
1906 snd-sun-cs4231= [HW,ALSA]
1908 snd-trident= [HW,ALSA]
1910 snd-usb-audio= [HW,ALSA,USB]
1912 snd-via82xx= [HW,ALSA]
1914 snd-virmidi= [HW,ALSA]
1916 snd-wavefront= [HW,ALSA]
1918 snd-ymfpci= [HW,ALSA]
1920 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1921 See Documentation/sonypi.txt
1923 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1924 See Documentation/specialix.txt.
1926 spia_io_base= [HW,MTD]
1932 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1934 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1935 See Documentation/scsi/st.txt.
1939 Set the STI (builtin display/keyboard on the HP-PARISC
1940 machines) console (graphic card) which should be used
1941 as the initial boot-console.
1942 See also comment in drivers/video/console/sticore.c.
1945 See comment in drivers/video/console/sticore.c.
1948 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1952 Control how the NFS server code allocates CPUs to
1953 service thread pools. Depending on how many NICs
1954 you have and where their interrupts are bound, this
1955 option will affect which CPUs will do NFS serving.
1956 Note: this parameter cannot be changed while the
1957 NFS server is running.
1959 auto the server chooses an appropriate mode
1960 automatically using heuristics
1961 global a single global pool contains all CPUs
1962 percpu one pool for each CPU
1963 pernode one pool for each NUMA node (equivalent
1964 to global on non-NUMA machines)
1966 swiotlb= [IA-64] Number of I/O TLB slabs
1970 sym53c416= [HW,SCSI]
1971 See header of drivers/scsi/sym53c416.c.
1973 sysrq_always_enabled
1975 Ignore sysrq setting - this boot parameter will
1976 neutralize any effect of /proc/sys/kernel/sysrq.
1977 Useful for debugging.
1980 See header of drivers/scsi/t128.c.
1984 thash_entries= [KNL,NET]
1985 Set number of hash buckets for TCP connection
1987 thermal.act= [HW,ACPI]
1988 -1: disable all active trip points in all thermal zones
1989 <degrees C>: override all lowest active trip points
1991 thermal.crt= [HW,ACPI]
1992 -1: disable all critical trip points in all thermal zones
1993 <degrees C>: lower all critical trip points
1995 thermal.nocrt= [HW,ACPI]
1996 Set to disable actions on ACPI thermal zone
1997 critical and hot trip points.
1999 thermal.off= [HW,ACPI]
2000 1: disable ACPI thermal control
2002 thermal.psv= [HW,ACPI]
2003 -1: disable all passive trip points
2004 <degrees C>: override all passive trip points to this value
2006 thermal.tzp= [HW,ACPI]
2007 Specify global default ACPI thermal zone polling rate
2008 <deci-seconds>: poll all this frequency
2009 0: no polling (default)
2011 tipar.timeout= [HW,PPT]
2012 Set communications timeout in tenths of a second
2015 tipar.delay= [HW,PPT]
2016 Set inter-bit delay in microseconds (default 10).
2019 See comment before function dc390_setup() in
2020 drivers/scsi/tmscsim.c.
2024 trix= [HW,OSS] MediaTrix AudioTrix Pro
2026 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2028 turbografx.map[2|3]= [HW,JOY]
2029 TurboGraFX parallel port interface
2031 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2032 See also Documentation/input/joystick-parport.txt
2034 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2035 See header of drivers/scsi/u14-34f.c.
2044 [USB] Ignore overcurrent events (default N).
2045 Some badly-designed motherboards generate lots of
2046 bogus events, for ports that aren't wired to
2047 anything. Set this parameter to avoid log spamming.
2048 Note that genuine overcurrent events won't be
2051 usbcore.autosuspend=
2052 [USB] The autosuspend time delay (in seconds) used
2053 for newly-detected USB devices (default 2). This
2054 is the time required before an idle device will be
2055 autosuspended. Devices for which the delay is set
2056 to a negative value won't be autosuspended at all.
2059 [USBHID] The interval which mice are to be polled at.
2061 vdso= [X86-32,SH,x86-64]
2062 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2063 vdso=1: enable VDSO (default)
2064 vdso=0: disable VDSO mapping
2066 vdso32= [X86-32,X86-64]
2067 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2068 vdso32=1: enable 32-bit VDSO (default)
2069 vdso32=0: disable 32-bit VDSO mapping
2072 vector=percpu: enable percpu vector domain
2074 video= [FB] Frame buffer configuration
2075 See Documentation/fb/modedb.txt.
2077 vga= [BOOT,X86-32] Select a particular video mode
2078 See Documentation/i386/boot.txt and
2079 Documentation/svga.txt.
2080 Use vga=ask for menu.
2081 This is actually a boot loader parameter; the value is
2082 passed to the kernel using a special protocol.
2084 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2085 size of <nn>. This can be used to increase the
2086 minimum size (128MB on x86). It can also be used to
2087 decrease the size and leave more room for directly
2090 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2093 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2096 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2099 waveartist= [HW,OSS]
2100 Format: <io>,<irq>,<dma>,<dma2>
2103 See header of drivers/scsi/wd33c93.c.
2106 See header of drivers/scsi/wd7000.c.
2109 See Documentation/watchdog/wdt.txt.
2111 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2112 xd_geo= See header of drivers/block/xd.c.
2114 xirc2ps_cs= [NET,PCMCIA]
2116 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2118 norandmaps Don't use address space randomization
2119 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2121 ______________________________________________________________________
2125 Add documentation for ALSA options.
2126 Add more DRM drivers.
projects / linux-2.6 / blob