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 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
216 Format: <irq>,<irq>...
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
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.
233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
236 acpi_serialize [HW,ACPI] force serialization of AML methods
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 old_ordering, s4_nonvs, sci_force_enable }
245 See Documentation/power/video.txt for information on
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
257 sci_force_enable causes the kernel to set SCI_EN directly
258 on resume from S1/S3 (which is against the ACPI spec,
259 but some broken systems don't work without it).
261 acpi_use_timer_override [HW,ACPI]
262 Use timer override. For some broken Nvidia NF5 boards
263 that require a timer override, but don't have HPET
265 acpi_enforce_resources= [ACPI]
266 { strict | lax | no }
267 Check for resource conflicts between native drivers
268 and ACPI OperationRegions (SystemIO and SystemMemory
269 only). IO ports and memory declared in ACPI might be
270 used by the ACPI subsystem in arbitrary AML code and
271 can interfere with legacy drivers.
272 strict (default): access to resources claimed by ACPI
273 is denied; legacy drivers trying to access reserved
274 resources will fail to bind to device using them.
275 lax: access to resources claimed by ACPI is allowed;
276 legacy drivers trying to access reserved resources
277 will bind successfully but a warning message is logged.
278 no: ACPI OperationRegions are not marked as reserved,
279 no further checks are performed.
282 Format: <io>,<irq>,<dma>,<dma2>,<type>
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
288 See header of drivers/scsi/advansys.c.
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/scsi/aha152x.txt.
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
310 See Documentation/scsi/aic7xxx.txt.
313 See Documentation/scsi/aic79xx.txt.
316 Allow the default userspace alignment fault handler
317 behaviour to be specified. Bit 0 enables warnings,
318 bit 1 enables fixups, and bit 2 sends a segfault.
320 amd_iommu= [HW,X86-84]
321 Pass parameters to the AMD IOMMU driver in the system.
323 fullflush - enable flushing of IO/TLB entries when
324 they are unmapped. Otherwise they are
325 flushed before they will be reused, which
328 amijoy.map= [HW,JOY] Amiga joystick support
329 Map of devices attached to JOY0DAT and JOY1DAT
331 See also Documentation/kernel/input/joystick.txt
333 analog.map= [HW,JOY] Analog joystick and gamepad support
334 Specifies type or capabilities of an analog joystick
335 connected to one of 16 gameports
336 Format: <type1>,<type2>,..<type16>
339 Power management functions (SPARCstation-4/5 + deriv.)
341 Disable APC CPU standby support. SPARCstation-Fox does
342 not play well with APC CPU idle - disable it if you have
343 APC and your system crashes randomly.
345 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
346 Change the output verbosity whilst booting
347 Format: { quiet (default) | verbose | debug }
348 Change the amount of debugging information output
349 when initialising the APIC and IO-APIC components.
352 See Documentation/networking/ipv6.txt.
354 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
355 Limit apic dumping. The parameter defines the maximal
356 number of local apics being dumped. Also it is possible
357 to set it to "all" by meaning -- no limit here.
358 Format: { 1 (default) | 2 | ... | all }.
359 The parameter valid if only apic=debug or
360 apic=verbose is specified.
361 Example: apic=debug show_lapic=all
363 apm= [APM] Advanced Power Management
364 See header of arch/x86/kernel/apm_32.c.
366 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
367 Format: <io>,<irq>,<nodeID>
371 atarimouse= [HW,MOUSE] Atari Mouse
373 atascsi= [HW,SCSI] Atari SCSI
375 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
376 EzKey and similar keyboards
378 atkbd.reset= [HW] Reset keyboard during initialization
380 atkbd.set= [HW] Select keyboard code set
381 Format: <int> (2 = AT (default), 3 = PS/2)
383 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
386 atkbd.softraw= [HW] Choose between synthetic and real raw mode
387 Format: <bool> (0 = real, 1 = synthetic (default))
389 atkbd.softrepeat= [HW]
390 Use software keyboard repeat
394 baycom_epp= [HW,AX25]
397 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
399 See header of drivers/net/hamradio/baycom_par.c.
401 baycom_ser_fdx= [HW,AX25]
402 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
403 Format: <io>,<irq>,<mode>[,<baud>]
404 See header of drivers/net/hamradio/baycom_ser_fdx.c.
406 baycom_ser_hdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
408 Format: <io>,<irq>,<mode>
409 See header of drivers/net/hamradio/baycom_ser_hdx.c.
411 boot_delay= Milliseconds to delay each printk during boot.
412 Values larger than 10 seconds (10000) are changed to
416 bootmem_debug [KNL] Enable bootmem allocator debug messages.
418 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
419 bttv.radio= Most important insmod options are available as
421 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
422 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
425 See drivers/scsi/BusLogic.c, comment before function
426 BusLogic_ParseDriverOptions().
428 c101= [NET] Moxa C101 synchronous serial card
430 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
431 Sometimes CPU hardware bugs make them report the cache
432 size incorrectly. The kernel will attempt work arounds
433 to fix known problems, but for some CPUs it is not
434 possible to determine what the correct size should be.
435 This option provides an override for these situations.
438 [SECURITY] Disable capabilities. This would normally
439 be used only if an alternative security model is to be
440 configured. Potentially dangerous and should only be
441 used if you are entirely sure of the consequences.
443 ccw_timeout_log [S390]
444 See Documentation/s390/CommonIO for details.
446 cgroup_disable= [KNL] Disable a particular controller
447 Format: {name of the controller(s) to disable}
448 {Currently supported controllers - "memory"}
450 checkreqprot [SELINUX] Set initial checkreqprot flag value.
451 Format: { "0" | "1" }
452 See security/selinux/Kconfig help text.
453 0 -- check protection applied by kernel (includes
454 any implied execute protection).
455 1 -- check protection requested by application.
456 Default value is set via a kernel config option.
457 Value can be changed at runtime via
458 /selinux/checkreqprot.
461 See Documentation/s390/CommonIO for details.
463 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
465 Forces specified clocksource (if available) to be used
466 when calculating gettimeofday(). If specified
467 clocksource is not available, it defaults to PIT.
468 Format: { pit | tsc | cyclone | pmtmr }
470 clocksource= [GENERIC_TIME] Override the default clocksource
472 Override the default clocksource and use the clocksource
473 with the name specified.
474 Some clocksource names to choose from, depending on
476 [all] jiffies (this is the base, fallback clocksource)
478 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
479 pxa_timer,timer3,32k_counter,timer0_1
481 [X86-32] pit,hpet,tsc,vmi-timer;
482 scx200_hrt on Geode; cyclone on IBM x440
490 clearcpuid=BITNUM [X86]
491 Disable CPUID feature X for the kernel. See
492 arch/x86/include/asm/cpufeature.h for the valid bit
493 numbers. Note the Linux specific bits are not necessarily
494 stable over kernel options, but the vendor specific
496 Also note that user programs calling CPUID directly
497 or using the feature without checking anything
498 will still see it. This just prevents it from
499 being used by the kernel or shown in /proc/cpuinfo.
500 Also note the kernel might malfunction if you disable
503 cmo_free_hint= [PPC] Format: { yes | no }
504 Specify whether pages are marked as being inactive
505 when they are freed. This is used in CMO environments
506 to determine OS memory pressure for page stealing by
510 code_bytes [X86] How many bytes of object code to print
515 com20020= [HW,NET] ARCnet - COM20020 chipset
517 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
519 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
523 ARCnet - COM90xx chipset (memory-mapped buffers)
524 Format: <io>[,<irq>[,<memstart>]]
526 condev= [HW,S390] console device
529 console= [KNL] Output console device and options.
531 tty<n> Use the virtual console device <n>.
535 Use the specified serial port. The options are of
536 the form "bbbbpnf", where "bbbb" is the baud rate,
537 "p" is parity ("n", "o", or "e"), "n" is number of
538 bits, and "f" is flow control ("r" for RTS or
539 omit it). Default is "9600n8".
541 See Documentation/serial-console.txt for more
543 Documentation/networking/netconsole.txt for an
546 uart[8250],io,<addr>[,options]
547 uart[8250],mmio,<addr>[,options]
548 Start an early, polled-mode console on the 8250/16550
549 UART at the specified I/O port or MMIO address,
550 switching to the matching ttyS device later. The
551 options are the same as for ttyS, above.
553 If the device connected to the port is not a TTY but a braille
554 device, prepend "brl," before the device type, for instance
556 For now, only VisioBraille is supported.
558 consoleblank= [KNL] The console blank (screen saver) timeout in
559 seconds. Defaults to 10*60 = 10mins. A value of 0
560 disables the blank timer.
563 [KNL] Change the default value for
564 /proc/<pid>/coredump_filter.
565 See also Documentation/filesystems/proc.txt.
567 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
569 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
571 crashkernel=nn[KMG]@ss[KMG]
572 [KNL] Reserve a chunk of physical memory to
573 hold a kernel to switch to with kexec on panic.
575 crashkernel=range1:size1[,range2:size2,...][@offset]
576 [KNL] Same as above, but depends on the memory
577 in the running system. The syntax of range is
578 start-[end] where start and end are both
579 a memory unit (amount[KMG]). See also
580 Documentation/kdump/kdump.txt for a example.
585 cs89x0_media= [HW,NET]
586 Format: { rj45 | aui | bnc }
589 See header of drivers/s390/block/dasd_devmap.c.
591 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
592 (one device per port)
593 Format: <port#>,<type>
594 See also Documentation/input/joystick-parport.txt
596 debug [KNL] Enable kernel debugging (events log level).
599 [KNL] verbose self-tests
601 Print debugging info while doing the locking API
603 We default to 0 (no extra messages), setting it to
604 1 will print _a lot_ more information - normally
605 only useful to kernel developers.
607 debug_objects [KNL] Enable object debugging
610 [KNL] Disable object debugging
612 debugpat [X86] Enable PAT debugging
614 decnet.addr= [HW,NET]
615 Format: <area>[,<node>]
616 See also Documentation/networking/decnet.txt.
619 [same as hugepagesz=] The size of the default
620 HugeTLB page size. This is the size represented by
621 the legacy /proc/ hugepages APIs, used for SHM, and
622 default size when mounting hugetlbfs filesystems.
623 Defaults to the default architecture's huge page size
627 Set number of hash buckets for dentry cache.
630 IO parameters + enable/disable command.
632 digiepca= [HW,SERIAL]
633 See drivers/char/README.epca and
634 Documentation/serial/digiepca.txt.
637 See Documentation/networking/ipv6.txt.
640 See Documentation/networking/ipv6.txt.
642 disable_mtrr_cleanup [X86]
643 The kernel tries to adjust MTRR layout from continuous
644 to discrete, to make X server driver able to add WB
645 entry later. This parameter disables that.
647 disable_mtrr_trim [X86, Intel and AMD only]
648 By default the kernel will trim any uncacheable
649 memory out of your available memory pool based on
650 MTRR settings. This parameter disables that behavior,
651 possibly causing your machine to run very slowly.
653 disable_timer_pin_1 [X86]
654 Disable PIN 1 of APIC timer
655 Can be useful to work around chipset bugs.
657 dmasound= [HW,OSS] Sound subsystem buffers
659 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
660 this option disables the debugging code at boot.
662 dma_debug_entries=<number>
663 This option allows to tune the number of preallocated
664 entries for DMA-API debugging code. One entry is
665 required per DMA-API allocation. Use this if the
666 DMA-API debugging code disables itself because the
667 architectural default is too low.
669 dma_debug_driver=<driver_name>
670 With this option the DMA-API debugging driver
671 filter feature can be enabled at boot time. Just
672 pass the driver to filter for as the parameter.
673 The filter can be disabled or changed to another
674 driver later using sysfs.
680 dynamic_printk Enables pr_debug()/dev_dbg() calls if
681 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
682 These can also be switched on/off via
683 <debugfs>/dynamic_printk/modules
685 earlycon= [KNL] Output early console device and options.
686 uart[8250],io,<addr>[,options]
687 uart[8250],mmio,<addr>[,options]
688 Start an early, polled-mode console on the 8250/16550
689 UART at the specified I/O port or MMIO address.
690 The options are the same as for ttyS, above.
692 earlyprintk= [X86,SH,BLACKFIN]
694 earlyprintk=serial[,ttySn[,baudrate]]
695 earlyprintk=ttySn[,baudrate]
696 earlyprintk=dbgp[debugController#]
698 Append ",keep" to not disable it when the real console
701 Only vga or serial or usb debug port at a time.
703 Currently only ttyS0 and ttyS1 are supported.
705 Interaction with the standard serial driver is not
708 The VGA output is eventually overwritten by the real
714 Format: {"off" | "on" | "skip[mbr]"}
716 eisa_irq_edge= [PARISC,HW]
717 See header of drivers/parisc/eisa.c.
720 See comment before function elanfreq_setup() in
721 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
724 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
725 See Documentation/block/as-iosched.txt and
726 Documentation/block/deadline-iosched.txt for details.
728 elfcorehdr= [IA64,PPC,SH,X86]
729 Specifies physical address of start of kernel core
730 image elf header. Generally kexec loader will
731 pass this option to capture kernel.
732 See Documentation/kdump/kdump.txt for details.
734 enable_mtrr_cleanup [X86]
735 The kernel tries to adjust MTRR layout from continuous
736 to discrete, to make X server driver able to add WB
737 entry later. This parameter enables that.
739 enable_timer_pin_1 [X86]
740 Enable PIN 1 of APIC timer
741 Can be useful to work around chipset bugs
742 (in particular on some ATI chipsets).
743 The kernel tries to set a reasonable default.
745 enforcing [SELINUX] Set initial enforcing status.
747 See security/selinux/Kconfig help text.
748 0 -- permissive (log only, no denials).
749 1 -- enforcing (deny and log).
751 Value can be changed at runtime via /selinux/enforce.
753 ether= [HW,NET] Ethernet cards parameters
754 This option is obsoleted by the "netdev=" option, which
755 has equivalent usage. See its documentation for details.
757 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
762 fail_make_request=[KNL]
763 General fault injection mechanism.
764 Format: <interval>,<probability>,<space>,<times>
765 See also /Documentation/fault-injection/.
768 See header of drivers/scsi/fd_mcs.c.
771 See header of drivers/scsi/fdomain.c.
774 See Documentation/blockdev/floppy.txt.
776 force_pal_cache_flush
777 [IA-64] Avoid check_sal_cache_flush which may hang on
778 buggy SAL_CACHE_FLUSH implementations. Using this
779 parameter will force ia64_sal_cache_flush to call
780 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
783 [FTRACE] will set and start the specified tracer
784 as early as possible in order to facilitate early
787 ftrace_dump_on_oops[=orig_cpu]
788 [FTRACE] will dump the trace buffers on oops.
789 If no parameter is passed, ftrace will dump
790 buffers of all CPUs, but if you pass orig_cpu, it will
791 dump only the buffer of the CPU that triggered the
794 ftrace_filter=[function-list]
795 [FTRACE] Limit the functions traced by the function
796 tracer at boot up. function-list is a comma separated
797 list of functions. This list can be changed at run
798 time by the set_ftrace_filter file in the debugfs
801 ftrace_notrace=[function-list]
802 [FTRACE] Do not trace the functions specified in
803 function-list. This list can be changed at run time
804 by the set_ftrace_notrace file in the debugfs
807 ftrace_graph_filter=[function-list]
808 [FTRACE] Limit the top level callers functions traced
809 by the function graph tracer at boot up.
810 function-list is a comma separated list of functions
811 that can be changed at run time by the
812 set_graph_function file in the debugfs tracing directory.
815 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
816 support via parallel port (up to 5 devices per port)
817 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
818 See also Documentation/input/joystick-parport.txt
822 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
826 gcov_persist= [GCOV] When non-zero (default), profiling data for
827 kernel modules is saved and remains accessible via
828 debugfs, even when the module is unloaded/reloaded.
829 When zero, profiling data is discarded and associated
830 debugfs files are removed at module unload time.
833 See header of drivers/scsi/gdth.c.
835 gpt [EFI] Forces disk with valid GPT signature but
836 invalid Protective MBR to be treated as GPT.
840 hashdist= [KNL,NUMA] Large hashes allocated during boot
841 are distributed across NUMA nodes. Defaults on
842 for 64bit NUMA, off otherwise.
843 Format: 0 | 1 (for off | on)
845 hcl= [IA-64] SGI's Hardware Graph compatibility layer
847 hd= [EIDE] (E)IDE hard drive subsystem geometry
848 Format: <cyl>,<head>,<sect>
850 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
851 size of <nn>. This works even on boxes that have no
852 highmem otherwise. This also works to reduce highmem
853 size on bigger boxes.
855 highres= [KNL] Enable/disable high resolution timer mode.
856 Valid parameters: "on", "off"
860 See Documentation/isdn/README.HiSax.
864 hpet= [X86-32,HPET] option to control HPET usage
865 Format: { enable (default) | disable | force |
867 disable: disable HPET and use PIT instead
868 force: allow force enabled of undocumented chips (ICH4,
870 verbose: show contents of HPET registers during setup
872 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
873 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
874 On x86-64 and powerpc, this option can be specified
875 multiple times interleaved with hugepages= to reserve
876 huge pages of different sizes. Valid pages sizes on
877 x86-64 are 2M (when the CPU supports "pse") and 1G
878 (when the CPU supports the "pdpe1gb" cpuinfo flag)
879 Note that 1GB pages can only be allocated at boot time
880 using hugepages= and not freed afterwards.
882 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
883 terminal devices. Valid values: 0..8
884 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
885 If specified, z/VM IUCV HVC accepts connections
886 from listed z/VM user IDs only.
888 i2c_bus= [HW] Override the default board specific I2C bus speed
889 or register an additional I2C bus that is not
890 registered from board initialization code.
894 i8042.debug [HW] Toggle i8042 debug mode
895 i8042.direct [HW] Put keyboard port into non-translated mode
896 i8042.dumbkbd [HW] Pretend that controller can only read data from
897 keyboard and cannot control its state
898 (Don't attempt to blink the leds)
899 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
900 i8042.nokbd [HW] Don't check/create keyboard port
901 i8042.noloop [HW] Disable the AUX Loopback command while probing
903 i8042.nomux [HW] Don't check presence of an active multiplexing
905 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
908 [HW] Frequency with which keyboard LEDs should blink
909 when kernel panics (default is 0.5 sec)
910 i8042.reset [HW] Reset the controller during init and cleanup
911 i8042.unlock [HW] Unlock (ignore) the keylock
915 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
916 indicates that the driver is running on unsupported
918 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
919 does not match list of supported models.
921 [HW] Report power status in /proc/i8k
922 (disabled by default)
923 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
926 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
927 See Documentation/mca.txt.
930 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
932 ide-core.nodma= [HW] (E)IDE subsystem
933 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
934 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
935 .cdrom .chs .ignore_cable are additional options
936 See Documentation/ide/ide.txt.
938 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
939 Claim all unknown PCI IDE storage controllers.
942 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
943 Poll forces a polling idle loop that can slightly
944 improve the performance of waking up a idle CPU, but
945 will use a lot of power and make the system run hot.
947 idle=mwait: On systems which support MONITOR/MWAIT but
948 the kernel chose to not use it because it doesn't save
949 as much power as a normal idle loop, use the
950 MONITOR/MWAIT idle loop anyways. Performance should be
951 the same as idle=poll.
952 idle=halt: Halt is forced to be used for CPU idle.
953 In such case C2/C3 won't be used again.
954 idle=nomwait: Disable mwait for CPU C-states
956 ignore_loglevel [KNL]
957 Ignore loglevel setting - this will print /all/
958 kernel messages to the console. Useful for debugging.
961 Set number of hash buckets for inode cache.
964 Format: { "0" | "1" }
965 0 -- integrity auditing messages. (Default)
966 1 -- enable informational integrity auditing messages.
969 Format: { "sha1" | "md5" }
973 Load a policy which meets the needs of the Trusted
974 Computing Base. This means IMA will measure all
975 programs exec'd, files mmap'd for exec, and all files
976 opened for read by uid=0.
979 See header of drivers/scsi/in2000.c.
983 Run specified binary instead of /sbin/init as init
986 initcall_debug [KNL] Trace initcalls as they are executed. Useful
987 for working out where the kernel is dying during
990 initrd= [BOOT] Specify the location of the initial ramdisk
992 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
995 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
997 Enable intel iommu driver.
999 Disable intel iommu driver.
1000 igfx_off [Default Off]
1001 By default, gfx is mapped as normal device. If a gfx
1002 device has a dedicated DMAR unit, the DMAR unit is
1003 bypassed by not enabling DMAR with this option. In
1004 this case, gfx device will use physical address for
1007 With this option iommu will not optimize to look
1008 for io virtual address below 32 bit forcing dual
1009 address cycle on pci bus for cards supporting greater
1010 than 32 bit addressing. The default is to look
1011 for translation below 32 bit and if not available
1012 then look in the higher range.
1013 strict [Default Off]
1014 With this option on every unmap_single operation will
1015 result in a hardware IOTLB flush operation as opposed
1016 to batching them for performance.
1020 iomem= Disable strict checking of access to MMIO memory
1021 strict regions from userspace.
1037 io7= [HW] IO7 for Marvel based alpha systems
1038 See comment before marvel_specify_io7 in
1039 arch/alpha/kernel/core_marvel.c.
1041 io_delay= [X86] I/O delay method
1043 Standard port 0x80 based delay
1045 Alternate port 0xed based delay (needed on some systems)
1047 Simple two microseconds delay
1052 See Documentation/filesystems/nfs/nfsroot.txt.
1054 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1055 See comment before ip2_setup() in
1056 drivers/char/ip2/ip2base.c.
1058 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1059 See header of drivers/scsi/ips.c.
1062 When an interrupt is not handled search all handlers
1063 for it. Intended to get systems with badly broken
1067 When an interrupt is not handled search all handlers
1068 for it. Also check all handlers each timer
1069 interrupt. Intended to get systems with badly broken
1073 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1075 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1077 <cpu number>,...,<cpu number>
1079 <cpu number>-<cpu number>
1080 (must be a positive range in ascending order)
1082 <cpu number>,...,<cpu number>-<cpu number>
1084 This option can be used to specify one or more CPUs
1085 to isolate from the general SMP balancing and scheduling
1086 algorithms. You can move a process onto or off an
1087 "isolated" CPU via the CPU affinity syscalls or cpuset.
1088 <cpu number> begins at 0 and the maximum value is
1089 "number of CPUs in system - 1".
1091 This option is the preferred way to isolate CPUs. The
1092 alternative -- manually setting the CPU mask of all
1093 tasks in the system -- can cause problems and
1094 suboptimal load balancer performance.
1098 js= [HW,JOY] Analog joystick
1099 See Documentation/input/joystick.txt.
1103 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1104 specifies the amount of memory usable by the kernel
1105 for non-movable allocations. The requested amount is
1106 spread evenly throughout all nodes in the system. The
1107 remaining memory in each node is used for Movable
1108 pages. In the event, a node is too small to have both
1109 kernelcore and Movable pages, kernelcore pages will
1110 take priority and other nodes will have a larger number
1111 of kernelcore pages. The Movable zone is used for the
1112 allocation of pages that may be reclaimed or moved
1113 by the page migration subsystem. This means that
1114 HugeTLB pages may not be allocated from this zone.
1115 Note that allocations like PTEs-from-HighMem still
1116 use the HighMem zone if it exists, and the Normal
1117 zone if it does not.
1119 kgdboc= [HW] kgdb over consoles.
1120 Requires a tty driver that supports console polling.
1121 (only serial supported for now)
1122 Format: <serial_device>[,baud]
1124 kmac= [MIPS] korina ethernet MAC address.
1125 Configure the RouterBoard 532 series on-chip
1126 Ethernet adapter MAC address.
1128 kmemleak= [KNL] Boot-time kmemleak enable/disable
1129 Valid arguments: on, off
1132 kstack=N [X86] Print N words from the kernel stack
1135 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1136 Default is 0 (don't ignore, but inject #GP)
1138 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1139 Default is 1 (enabled)
1141 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1144 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1146 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1148 kvm-intel.bypass_guest_pf=
1149 [KVM,Intel] Disables bypassing of guest page faults
1150 on Intel chips. Default is 1 (enabled)
1152 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1153 (virtualized MMU) support on capable Intel chips.
1154 Default is 1 (enabled)
1156 kvm-intel.emulate_invalid_guest_state=
1157 [KVM,Intel] Enable emulation of invalid guest states
1158 Default is 0 (disabled)
1160 kvm-intel.flexpriority=
1161 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1162 Default is 1 (enabled)
1164 kvm-intel.unrestricted_guest=
1165 [KVM,Intel] Disable unrestricted guest feature
1166 (virtualized real and unpaged mode) on capable
1167 Intel chips. Default is 1 (enabled)
1169 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1170 feature (tagged TLBs) on capable Intel chips.
1171 Default is 1 (enabled)
1177 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1180 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1183 libata.dma= [LIBATA] DMA control
1184 libata.dma=0 Disable all PATA and SATA DMA
1185 libata.dma=1 PATA and SATA Disk DMA only
1186 libata.dma=2 ATAPI (CDROM) DMA only
1187 libata.dma=4 Compact Flash DMA only
1188 Combinations also work, so libata.dma=3 enables DMA
1189 for disks and CDROMs, but not CFs.
1191 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1192 libata.ignore_hpa=0 keep BIOS limits (default)
1193 libata.ignore_hpa=1 ignore limits, using full disk
1195 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1199 libata.force= [LIBATA] Force configurations. The format is comma
1200 separated list of "[ID:]VAL" where ID is
1201 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1202 matching port, link or device. Basically, it matches
1203 the ATA ID string printed on console by libata. If
1204 the whole ID part is omitted, the last PORT and DEVICE
1205 values are used. If ID hasn't been specified yet, the
1206 configuration applies to all ports, links and devices.
1208 If only DEVICE is omitted, the parameter applies to
1209 the port and all links and devices behind it. DEVICE
1210 number of 0 either selects the first device or the
1211 first fan-out link behind PMP device. It does not
1212 select the host link. DEVICE number of 15 selects the
1213 host link and device attached to it.
1215 The VAL specifies the configuration to force. As long
1216 as there's no ambiguity shortcut notation is allowed.
1217 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1218 The following configurations can be forced.
1220 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1221 Any ID with matching PORT is used.
1223 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1225 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1226 udma[/][16,25,33,44,66,100,133] notation is also
1229 * [no]ncq: Turn on or off NCQ.
1231 * nohrst, nosrst, norst: suppress hard, soft
1234 If there are multiple matching configurations changing
1235 the same attribute, the last one is used.
1237 lmb=debug [KNL] Enable lmb debug messages.
1239 load_ramdisk= [RAM] List of ramdisks to load from floppy
1240 See Documentation/blockdev/ramdisk.txt.
1242 lockd.nlm_grace_period=P [NFS] Assign grace period.
1245 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1248 lockd.nlm_timeout=T [NFS] Assign timeout value.
1251 lockd.nlm_udpport=M [NFS] Assign UDP port.
1254 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1257 loglevel= All Kernel Messages with a loglevel smaller than the
1258 console loglevel will be printed to the console. It can
1259 also be changed with klogd or other programs. The
1260 loglevels are defined as follows:
1262 0 (KERN_EMERG) system is unusable
1263 1 (KERN_ALERT) action must be taken immediately
1264 2 (KERN_CRIT) critical conditions
1265 3 (KERN_ERR) error conditions
1266 4 (KERN_WARNING) warning conditions
1267 5 (KERN_NOTICE) normal but significant condition
1268 6 (KERN_INFO) informational
1269 7 (KERN_DEBUG) debug-level messages
1271 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1272 Format: { n | nk | nM }
1273 n must be a power of two. The default size
1274 is set in the kernel config file.
1276 logo.nologo [FB] Disables display of the built-in Linux logo.
1277 This may be used to provide more screen space for
1278 kernel log messages and is useful when debugging
1279 kernel boot problems.
1281 lp=0 [LP] Specify parallel ports to use, e.g,
1282 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1283 lp=reset first parallel port). 'lp=0' disables the
1284 lp=auto printer driver. 'lp=reset' (which can be
1285 specified in addition to the ports) causes
1286 attached printers to be reset. Using
1287 lp=port1,port2,... specifies the parallel ports
1288 to associate lp devices with, starting with
1289 lp0. A port specification may be 'none' to skip
1290 that lp device, or a parport name such as
1291 'parport0'. Specifying 'lp=auto' instead of a
1292 port specification list means that device IDs
1293 from each port should be examined, to see if
1294 an IEEE 1284-compliant printer is attached; if
1295 so, the driver will manage that printer.
1296 See also header of drivers/char/lp.c.
1299 Sets loops_per_jiffy to given constant, thus avoiding
1300 time-consuming boot-time autodetection (up to 250 ms per
1301 CPU). 0 enables autodetection (default). To determine
1302 the correct value for your kernel, boot with normal
1303 autodetection and see what value is printed. Note that
1304 on SMP systems the preset will be applied to all CPUs,
1305 which is likely to cause problems if your CPUs need
1306 significantly divergent settings. An incorrect value
1307 will cause delays in the kernel to be wrong, leading to
1308 unpredictable I/O errors and other breakage. Although
1309 unlikely, in the extreme case this might damage your
1313 Format: <io>,<irq>,<dma>
1315 mac5380= [HW,SCSI] Format:
1316 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1318 machvec= [IA64] Force the use of a particular machine-vector
1319 (machvec) in a generic kernel.
1320 Example: machvec=hpzx1_swiotlb
1322 machtype= [Loongson] Share the same kernel image file between different
1324 Example: machtype=lemote-yeeloong-2f-7inch
1326 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1327 than or equal to this physical address is ignored.
1329 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1330 should make use of. maxcpus=n : n >= 0 limits the
1331 kernel to using 'n' processors. n=0 is a special case,
1332 it is equivalent to "nosmp", which also disables
1335 max_loop= [LOOP] Maximum number of loopback devices that can
1339 max_luns= [SCSI] Maximum number of LUNs to probe.
1340 Should be between 1 and 2^32-1.
1343 [SCSI] Maximum number of LUNs received.
1344 Should be between 1 and 16384.
1348 mce [X86-32] Machine Check Exception
1350 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1352 md= [HW] RAID subsystems devices and level
1353 See Documentation/md.txt.
1356 Format: <first>,<last>
1357 Specifies range of consoles to be captured by the MDA.
1359 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1360 Amount of memory to be used when the kernel is not able
1361 to see the whole system memory or for test.
1362 [X86-32] Use together with memmap= to avoid physical
1363 address space collisions. Without memmap= PCI devices
1364 could be placed at addresses belonging to unused RAM.
1366 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1370 [KNL,SH] Allow user to override the default size for
1371 per-device physically contiguous DMA buffers.
1373 memmap=exactmap [KNL,X86] Enable setting of an exact
1374 E820 memory map, as specified by the user.
1375 Such memmap=exactmap lines can be constructed based on
1376 BIOS output or other requirements. See the memmap=nn@ss
1379 memmap=nn[KMG]@ss[KMG]
1380 [KNL] Force usage of a specific region of memory
1381 Region of memory to be used, from ss to ss+nn.
1383 memmap=nn[KMG]#ss[KMG]
1384 [KNL,ACPI] Mark specific memory as ACPI data.
1385 Region of memory to be used, from ss to ss+nn.
1387 memmap=nn[KMG]$ss[KMG]
1388 [KNL,ACPI] Mark specific memory as reserved.
1389 Region of memory to be used, from ss to ss+nn.
1390 Example: Exclude memory from 0x18690000-0x1869ffff
1391 memmap=64K$0x18690000
1393 memmap=0x10000$0x18690000
1395 memory_corruption_check=0/1 [X86]
1396 Some BIOSes seem to corrupt the first 64k of
1397 memory when doing things like suspend/resume.
1398 Setting this option will scan the memory
1399 looking for corruption. Enabling this will
1400 both detect corruption and prevent the kernel
1401 from using the memory being corrupted.
1402 However, its intended as a diagnostic tool; if
1403 repeatable BIOS-originated corruption always
1404 affects the same memory, you can use memmap=
1405 to prevent the kernel from using that memory.
1407 memory_corruption_check_size=size [X86]
1408 By default it checks for corruption in the low
1409 64k, making this memory unavailable for normal
1410 use. Use this parameter to scan for
1411 corruption in more or less memory.
1413 memory_corruption_check_period=seconds [X86]
1414 By default it checks for corruption every 60
1415 seconds. Use this parameter to check at some
1416 other rate. 0 disables periodic checking.
1418 memtest= [KNL,X86] Enable memtest
1420 default : 0 <disable>
1421 Specifies the number of memtest passes to be
1422 performed. Each pass selects another test
1423 pattern from a given set of patterns. Memtest
1424 fills the memory with this pattern, validates
1425 memory contents and reserves bad memory
1426 regions that are detected.
1428 meye.*= [HW] Set MotionEye Camera parameters
1429 See Documentation/video4linux/meye.txt.
1431 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1432 Multi-Function General Purpose Timers on AMD Geode
1435 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1436 the BIOS has incorrectly applied a workaround. TinyBIOS
1437 version 0.98 is known to be affected, 0.99 fixes the
1438 problem by letting the user disable the workaround.
1442 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1443 physical address is ignored.
1445 mini2440= [ARM,HW,KNL]
1446 Format:[0..2][b][c][t]
1448 MINI2440 configuration specification:
1449 0 - The attached screen is the 3.5" TFT
1450 1 - The attached screen is the 7" TFT
1451 2 - The VGA Shield is attached (1024x768)
1452 Leaving out the screen size parameter will not load
1453 the TFT driver, and the framebuffer will be left
1455 b - Enable backlight. The TFT backlight pin will be
1456 linked to the kernel VESA blanking code and a GPIO
1457 LED. This parameter is not necessary when using the
1459 c - Enable the s3c camera interface.
1460 t - Reserved for enabling touchscreen support. The
1461 touchscreen support is not enabled in the mainstream
1462 kernel as of 2.6.30, a preliminary port can be found
1463 in the "bleeding edge" mini2440 support kernel at
1464 http://repo.or.cz/w/linux-2.6/mini2440.git
1467 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1468 parameter allows control of the logging verbosity for
1469 the additional memory initialisation checks. A value
1470 of 0 disables mminit logging and a level of 4 will
1471 log everything. Information is printed at KERN_DEBUG
1472 so loglevel=8 may also need to be specified.
1475 [MOUSE] Maximum time between finger touching and
1476 leaving touchpad surface for touch to be considered
1477 a tap and be reported as a left button click (for
1478 touchpads working in absolute mode only).
1480 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1481 reporting absolute coordinates, such as tablets
1482 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1483 reporting absolute coordinates, such as tablets
1485 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1486 is similar to kernelcore except it specifies the
1487 amount of memory used for migratable allocations.
1488 If both kernelcore and movablecore is specified,
1489 then kernelcore will be at *least* the specified
1490 value but may be more. If movablecore on its own
1491 is specified, the administrator must be careful
1492 that the amount of memory usable for all allocations
1498 MTD_Partition= [MTD]
1499 Format: <name>,<region-number>,<size>,<offset>
1501 MTD_Region= [MTD] Format:
1502 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1505 See drivers/mtd/cmdlinepart.c.
1507 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1509 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1511 boundary - index of last SLC block on Flex-OneNAND.
1512 The remaining blocks are configured as MLC blocks.
1513 lock - Configure if Flex-OneNAND boundary should be locked.
1514 Once locked, the boundary cannot be changed.
1515 1 indicates lock status, 0 indicates unlock status.
1518 ARM/S3C2412 JIVE boot control
1520 See arch/arm/mach-s3c2412/mach-jive.c
1522 mtouchusb.raw_coordinates=
1523 [HW] Make the MicroTouch USB driver use raw coordinates
1524 ('y', default) or cooked coordinates ('n')
1526 mtrr_chunk_size=nn[KMG] [X86]
1527 used for mtrr cleanup. It is largest continuous chunk
1528 that could hold holes aka. UC entries.
1530 mtrr_gran_size=nn[KMG] [X86]
1531 Used for mtrr cleanup. It is granularity of mtrr block.
1533 Large value could prevent small alignment from
1536 mtrr_spare_reg_nr=n [X86]
1538 Range: 0,7 : spare reg number
1540 Used for mtrr cleanup. It is spare mtrr entries number.
1541 Set to 2 or more if your graphical card needs more.
1543 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1546 See header of drivers/scsi/NCR_D700.c.
1550 ncr53c400= [HW,SCSI]
1552 ncr53c400a= [HW,SCSI]
1554 ncr53c406a= [HW,SCSI]
1556 ncr53c8xx= [HW,SCSI]
1558 netdev= [NET] Network devices parameters
1559 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1560 Note that mem_start is often overloaded to mean
1561 something different and driver-specific.
1562 This usage is only documented in each driver source
1566 [NETFILTER] Enable connection tracking flow accounting
1567 0 to disable accounting
1568 1 to enable accounting
1569 Default value depends on CONFIG_NF_CT_ACCT that is
1570 going to be removed in 2.6.29.
1573 See Documentation/filesystems/nfs/nfsroot.txt.
1575 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1576 See Documentation/filesystems/nfs/nfsroot.txt.
1578 nfs.callback_tcpport=
1579 [NFS] set the TCP port on which the NFSv4 callback
1580 channel should listen.
1583 [NFS] sets the pathname to the program which is used
1584 to update the NFS client cache entries.
1586 nfs.cache_getent_timeout=
1587 [NFS] sets the timeout after which an attempt to
1588 update a cache entry is deemed to have failed.
1590 nfs.idmap_cache_timeout=
1591 [NFS] set the maximum lifetime for idmapper cache
1595 [NFS] enable 64-bit inode numbers.
1596 If zero, the NFS client will fake up a 32-bit inode
1597 number for the readdir() and stat() syscalls instead
1598 of returning the full 64-bit number.
1599 The default is to return 64-bit inode numbers.
1601 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1602 when a NMI is triggered.
1603 Format: [state][,regs][,debounce][,die]
1605 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1606 Format: [panic,][num]
1608 0 - turn nmi_watchdog off
1609 1 - use the IO-APIC timer for the NMI watchdog
1610 2 - use the local APIC for the NMI watchdog using
1611 a performance counter. Note: This will use one
1612 performance counter and the local APIC's performance
1614 When panic is specified, panic when an NMI watchdog
1616 This is useful when you use a panic=... timeout and
1617 need the box quickly up again.
1618 Instead of 1 and 2 it is possible to use the following
1619 symbolic names: lapic and ioapic
1620 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1622 netpoll.carrier_timeout=
1623 [NET] Specifies amount of time (in seconds) that
1624 netpoll should wait for a carrier. By default netpoll
1627 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1628 emulation library even if a 387 maths coprocessor
1632 [HW] Never suspend the console
1633 Disable suspending of consoles during suspend and
1634 hibernate operations. Once disabled, debugging
1635 messages can reach various consoles while the rest
1636 of the system is being put to sleep (ie, while
1637 debugging driver suspend/resume hooks). This may
1638 not work reliably with all consoles, but is known
1639 to work with serial and VGA consoles.
1641 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1642 caches in the slab allocator. Saves per-node memory,
1643 but will impact performance.
1647 noapic [SMP,APIC] Tells the kernel to not make use of any
1648 IOAPICs that may be present in the system.
1650 nobats [PPC] Do not use BATs for mapping kernel lowmem
1651 on "Classic" PPC cores.
1655 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1657 nodelayacct [KNL] Disable per-task delay accounting
1659 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1661 nodsp [SH] Disable hardware DSP at boot time.
1663 noefi [X86] Disable EFI runtime services support.
1668 On X86-32 available only on PAE configured kernels.
1669 noexec=on: enable non-executable mappings (default)
1670 noexec=off: disable non-executable mappings
1673 This affects only 32-bit executables.
1674 noexec32=on: enable non-executable mappings (default)
1675 read doesn't imply executable mappings
1676 noexec32=off: disable non-executable mappings
1677 read implies executable mappings
1679 nofpu [SH] Disable hardware FPU at boot time.
1681 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1682 register save and restore. The kernel will only save
1683 legacy floating-point registers on task switch.
1685 noxsave [BUGS=X86] Disables x86 extended register state save
1686 and restore using xsave. The kernel will fallback to
1687 enabling legacy floating-point and sse state.
1689 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1690 wfi(ARM) instruction doesn't work correctly and not to
1691 use it. This is also useful when using JTAG debugger.
1693 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1694 instruction doesn't work correctly and not to
1697 no_file_caps Tells the kernel not to honor file capabilities. The
1698 only way then for a file to be executed with privilege
1699 is to be setuid root or executed by root.
1701 nohalt [IA-64] Tells the kernel not to use the power saving
1702 function PAL_HALT_LIGHT when idle. This increases
1703 power-consumption. On the positive side, it reduces
1704 interrupt wake-up latency, which may improve performance
1705 in certain environments such as networked servers or
1708 nohz= [KNL] Boottime enable/disable dynamic ticks
1709 Valid arguments: on, off
1712 noiotrap [SH] Disables trapped I/O port accesses.
1714 noirqdebug [X86-32] Disables the code which attempts to detect and
1715 disable unhandled interrupt sources.
1717 no_timer_check [X86,APIC] Disables the code which tests for
1718 broken timer IRQ sources.
1720 noisapnp [ISAPNP] Disables ISA PnP code.
1722 noinitrd [RAM] Tells the kernel not to load any configured
1725 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1730 nojitter [IA64] Disables jitter checking for ITC timers.
1732 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1734 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1736 noltlbs [PPC] Do not use large page/tlb entries for kernel
1737 lowmem mapping on PPC40x.
1739 nomca [IA-64] Disable machine check abort handling
1741 nomce [X86-32] Machine Check Exception
1743 nomfgpt [X86-32] Disable Multi-Function General Purpose
1744 Timer usage (for AMD Geode machines).
1746 nopat [X86] Disable PAT (page attribute table extension of
1747 pagetables) support.
1749 norandmaps Don't use address space randomization. Equivalent to
1750 echo 0 > /proc/sys/kernel/randomize_va_space
1752 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1754 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1755 with UP alternatives
1757 noresidual [PPC] Don't use residual data on PReP machines.
1759 noresume [SWSUSP] Disables resume and restores original swap
1762 no-scroll [VGA] Disables scrollback.
1763 This is required for the Braillex ib80-piezo Braille
1764 reader made by F.H. Papenmeier (Germany).
1768 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1770 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1771 and disable the IO APIC. legacy for "maxcpus=0".
1773 nosoftlockup [KNL] Disable the soft-lockup detector.
1775 noswapaccount [KNL] Disable accounting of swap in memory resource
1776 controller. (See Documentation/cgroups/memory.txt)
1778 nosync [HW,M68K] Disables sync negotiation for all devices.
1780 notsc [BUGS=X86-32] Disable Time Stamp Counter
1782 nousb [USB] Disable the USB subsystem
1786 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1788 nptcg= [IA64] Override max number of concurrent global TLB
1789 purges which is reported from either PAL_VM_SUMMARY or
1792 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1793 could support. nr_cpus=n : n >= 1 limits the kernel to
1794 supporting 'n' processors. Later in runtime you can not
1795 use hotplug cpu feature to put more cpu back to online.
1796 just like you compile the kernel NR_CPUS=n
1798 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1800 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1801 one of ['zone', 'node', 'default'] can be specified
1802 This can be set from sysctl after boot.
1803 See Documentation/sysctl/vm.txt for details.
1805 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1806 See Documentation/debugging-via-ohci1394.txt for more
1809 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1810 Rather than timing out after 20 ms if an EC
1811 command is not properly ACKed, override the length
1812 of the timeout. We have interrupts disabled while
1813 waiting for the ACK, so if this is set too high
1814 interrupts *may* be lost!
1816 omap_mux= [OMAP] Override bootloader pin multiplexing.
1817 Format: <mux_mode0.mode_name=value>...
1818 For example, to override I2C bus2:
1819 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1824 oprofile.timer= [HW]
1825 Use timer interrupt instead of performance counters
1827 oprofile.cpu_type= Force an oprofile cpu type
1828 This might be useful if you have an older oprofile
1829 userland or if you want common events.
1830 Format: { arch_perfmon }
1831 arch_perfmon: [X86] Force use of architectural
1832 perfmon on Intel CPUs instead of the
1833 CPU specific event set.
1835 osst= [HW,SCSI] SCSI Tape Driver
1836 Format: <buffer_size>,<write_threshold>
1837 See also Documentation/scsi/st.txt.
1839 panic= [KNL] Kernel behaviour on panic
1842 parkbd.port= [HW] Parallel port number the keyboard adapter is
1843 connected to, default is 0.
1845 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1846 0 for XT, 1 for AT (default is AT).
1849 parport= [HW,PPT] Specify parallel ports. 0 disables.
1850 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1851 Use 'auto' to force the driver to use any
1852 IRQ/DMA settings detected (the default is to
1853 ignore detected IRQ/DMA settings because of
1854 possible conflicts). You can specify the base
1855 address, IRQ, and DMA settings; IRQ and DMA
1856 should be numbers, or 'auto' (for using detected
1857 settings on that particular port), or 'nofifo'
1858 (to avoid using a FIFO even if it is detected).
1859 Parallel ports are assigned in the order they
1860 are specified on the command line, starting
1863 parport_init_mode= [HW,PPT]
1864 Configure VIA parallel port to operate in
1865 a specific mode. This is necessary on Pegasos
1866 computer where firmware has no options for setting
1867 up parallel port mode and sets it to spp.
1868 Currently this function knows 686a and 8231 chips.
1869 Format: [spp|ps2|epp|ecp|ecpepp]
1871 pas2= [HW,OSS] Format:
1872 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1875 See header of drivers/scsi/pas16.c.
1878 Halt all CPUs after the first oops has been printed for
1879 the specified number of seconds. This is to be used if
1880 your oopses keep scrolling off the screen.
1885 See header of drivers/block/paride/pcd.c.
1886 See also Documentation/blockdev/paride.txt.
1888 pci=option[,option...] [PCI] various PCI subsystem options:
1889 earlydump [X86] dump PCI config space before the kernel
1891 off [X86] don't probe for the PCI bus
1892 bios [X86-32] force use of PCI BIOS, don't access
1893 the hardware directly. Use this if your machine
1894 has a non-standard PCI host bridge.
1895 nobios [X86-32] disallow use of PCI BIOS, only direct
1896 hardware access methods are allowed. Use this
1897 if you experience crashes upon bootup and you
1898 suspect they are caused by the BIOS.
1899 conf1 [X86] Force use of PCI Configuration
1901 conf2 [X86] Force use of PCI Configuration
1903 noaer [PCIE] If the PCIEAER kernel config parameter is
1904 enabled, this kernel boot option can be used to
1905 disable the use of PCIE advanced error reporting.
1906 nodomains [PCI] Disable support for multiple PCI
1907 root domains (aka PCI segments, in ACPI-speak).
1908 nommconf [X86] Disable use of MMCONFIG for PCI
1910 check_enable_amd_mmconf [X86] check for and enable
1911 properly configured MMIO access to PCI
1912 config space on AMD family 10h CPU
1913 nomsi [MSI] If the PCI_MSI kernel config parameter is
1914 enabled, this kernel boot option can be used to
1915 disable the use of MSI interrupts system-wide.
1916 noioapicquirk [APIC] Disable all boot interrupt quirks.
1917 Safety option to keep boot IRQs enabled. This
1918 should never be necessary.
1919 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1920 primary IO-APIC for bridges that cannot disable
1921 boot IRQs. This fixes a source of spurious IRQs
1922 when the system masks IRQs.
1923 noioapicreroute [APIC] Disable workaround that uses the
1924 boot IRQ equivalent of an IRQ that connects to
1925 a chipset where boot IRQs cannot be disabled.
1926 The opposite of ioapicreroute.
1927 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1928 routing table. These calls are known to be buggy
1929 on several machines and they hang the machine
1930 when used, but on other computers it's the only
1931 way to get the interrupt routing table. Try
1932 this option if the kernel is unable to allocate
1933 IRQs or discover secondary PCI buses on your
1935 rom [X86] Assign address space to expansion ROMs.
1936 Use with caution as certain devices share
1937 address decoders between ROMs and other
1939 norom [X86] Do not assign address space to
1940 expansion ROMs that do not already have
1941 BIOS assigned address ranges.
1942 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1943 assigned automatically to PCI devices. You can
1944 make the kernel exclude IRQs of your ISA cards
1946 pirqaddr=0xAAAAA [X86] Specify the physical address
1947 of the PIRQ table (normally generated
1948 by the BIOS) if it is outside the
1949 F0000h-100000h range.
1950 lastbus=N [X86] Scan all buses thru bus #N. Can be
1951 useful if the kernel is unable to find your
1952 secondary buses and you want to tell it
1953 explicitly which ones they are.
1954 assign-busses [X86] Always assign all PCI bus
1955 numbers ourselves, overriding
1956 whatever the firmware may have done.
1957 usepirqmask [X86] Honor the possible IRQ mask stored
1958 in the BIOS $PIR table. This is needed on
1959 some systems with broken BIOSes, notably
1960 some HP Pavilion N5400 and Omnibook XE3
1961 notebooks. This will have no effect if ACPI
1962 IRQ routing is enabled.
1963 noacpi [X86] Do not use ACPI for IRQ routing
1964 or for PCI scanning.
1965 use_crs [X86] Use PCI host bridge window information
1966 from ACPI. On BIOSes from 2008 or later, this
1967 is enabled by default. If you need to use this,
1968 please report a bug.
1969 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1970 If you need to use this, please report a bug.
1971 routeirq Do IRQ routing for all PCI devices.
1972 This is normally done in pci_enable_device(),
1973 so this option is a temporary workaround
1974 for broken drivers that don't call it.
1975 skip_isa_align [X86] do not align io start addr, so can
1976 handle more pci cards
1977 firmware [ARM] Do not re-enumerate the bus but instead
1978 just use the configuration from the
1979 bootloader. This is currently used on
1980 IXP2000 systems where the bus has to be
1981 configured a certain way for adjunct CPUs.
1982 noearly [X86] Don't do any early type 1 scanning.
1983 This might help on some broken boards which
1984 machine check when some devices' config space
1985 is read. But various workarounds are disabled
1986 and some IOMMU drivers will not work.
1987 bfsort Sort PCI devices into breadth-first order.
1988 This sorting is done to get a device
1989 order compatible with older (<= 2.4) kernels.
1990 nobfsort Don't sort PCI devices into breadth-first order.
1991 cbiosize=nn[KMG] The fixed amount of bus space which is
1992 reserved for the CardBus bridge's IO window.
1993 The default value is 256 bytes.
1994 cbmemsize=nn[KMG] The fixed amount of bus space which is
1995 reserved for the CardBus bridge's memory
1996 window. The default value is 64 megabytes.
1999 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2000 Specifies alignment and device to reassign
2001 aligned memory resources.
2002 If <order of align> is not specified,
2003 PAGE_SIZE is used as alignment.
2004 PCI-PCI bridge can be specified, if resource
2005 windows need to be expanded.
2006 ecrc= Enable/disable PCIe ECRC (transaction layer
2007 end-to-end CRC checking).
2008 bios: Use BIOS/firmware settings. This is the
2013 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2016 force Enable ASPM even on devices that claim not to support it.
2017 WARNING: Forcing ASPM on may cause system lockups.
2019 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2020 off Do not use native PCIe PME signaling.
2021 force Use native PCIe PME signaling even if the BIOS refuses
2022 to allow the kernel to control the relevant PCIe config
2024 nomsi Do not use MSI for native PCIe PME signaling (this makes
2025 all PCIe root ports use INTx for everything).
2027 pcmv= [HW,PCMCIA] BadgePAD 4
2030 See Documentation/blockdev/paride.txt.
2032 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2035 See arch/parisc/kernel/pdc_chassis.c
2037 percpu_alloc= Select which percpu first chunk allocator to use.
2038 Currently supported values are "embed" and "page".
2039 Archs may support subset or none of the selections.
2040 See comments in mm/percpu.c for details on each
2041 allocator. This parameter is primarily for debugging
2042 and performance comparison.
2045 See Documentation/blockdev/paride.txt.
2048 See Documentation/blockdev/paride.txt.
2050 pirq= [SMP,APIC] Manual mp-table setup
2051 See Documentation/x86/i386/IO-APIC.txt.
2053 plip= [PPT,NET] Parallel port network link
2054 Format: { parport<nr> | timid | 0 }
2055 See also Documentation/parport.txt.
2057 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2058 Override pmtimer IOPort with a hex value.
2062 Enable PNP debug messages. This depends on the
2063 CONFIG_PNP_DEBUG_MESSAGES option.
2069 { on | off | curr | res | no-curr | no-res }
2072 [ISAPNP] Exclude IRQs for the autoconfiguration
2075 [ISAPNP] Exclude DMAs for the autoconfiguration
2077 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2078 Ranges are in pairs (I/O port base and size).
2081 [ISAPNP] Exclude memory regions for the
2083 Ranges are in pairs (memory base and size).
2085 ports= [IP_VS_FTP] IPVS ftp helper module
2087 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2089 Format: <port>,<port>....
2091 print-fatal-signals=
2092 [KNL] debug: print fatal signals
2094 If enabled, warn about various signal handling
2095 related application anomalies: too many signals,
2096 too many POSIX.1 timers, fatal signals causing a
2099 If you hit the warning due to signal overflow,
2100 you might want to try "ulimit -i unlimited".
2104 printk.time= Show timing data prefixed to each printk message line
2105 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2107 processor.max_cstate= [HW,ACPI]
2108 Limit processor to maximum C-state
2109 max_cstate=9 overrides any DMI blacklist limit.
2111 processor.nocst [HW,ACPI]
2112 Ignore the _CST method to determine C-states,
2113 instead using the legacy FADT method
2115 profile= [KNL] Enable kernel profiling via /proc/profile
2116 Format: [schedule,]<number>
2117 Param: "schedule" - profile schedule points.
2118 Param: <number> - step/bucket size as a power of 2 for
2119 statistical time based profiling.
2120 Param: "sleep" - profile D-state sleeping (millisecs).
2121 Requires CONFIG_SCHEDSTATS
2122 Param: "kvm" - profile VM exits.
2124 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2126 See Documentation/blockdev/ramdisk.txt.
2128 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2129 probe for; one of (bare|imps|exps|lifebook|any).
2130 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2132 psmouse.resetafter= [HW,MOUSE]
2133 Try to reset the device after so many bad packets
2136 [HW,MOUSE] Set desired mouse resolution, in dpi.
2137 psmouse.smartscroll=
2138 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2139 0 = disabled, 1 = enabled (default).
2141 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2143 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2146 See Documentation/blockdev/paride.txt.
2149 [KNL] Number of legacy pty's. Overwrites compiled-in
2152 quiet [KNL] Disable most log messages
2157 See Documentation/md.txt.
2159 ramdisk_blocksize= [RAM]
2160 See Documentation/blockdev/ramdisk.txt.
2162 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2163 See Documentation/blockdev/ramdisk.txt.
2165 rcupdate.blimit= [KNL,BOOT]
2166 Set maximum number of finished RCU callbacks to process
2169 rcupdate.qhimark= [KNL,BOOT]
2170 Set threshold of queued
2171 RCU callbacks over which batch limiting is disabled.
2173 rcupdate.qlowmark= [KNL,BOOT]
2174 Set threshold of queued RCU callbacks below which
2175 batch limiting is re-enabled.
2179 Run specified binary instead of /init from the ramdisk,
2180 used for early userspace startup. See initrd.
2182 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2183 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2184 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2187 [KNL, SMP] Set scheduler's default relax_domain_level.
2188 See Documentation/cgroups/cpusets.txt.
2190 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2192 reservetop= [X86-32]
2194 Reserves a hole at the top of the kernel virtual
2197 reset_devices [KNL] Force drivers to reset the underlying device
2198 during initialization.
2201 Specify the partition device for software suspend
2203 resume_offset= [SWSUSP]
2204 Specify the offset from the beginning of the partition
2205 given by "resume=" at which the swap header is located,
2206 in <PAGE_SIZE> units (needed only for swap files).
2207 See Documentation/power/swsusp-and-swap-files.txt
2209 retain_initrd [RAM] Keep initrd memory after extraction
2211 rhash_entries= [KNL,NET]
2212 Set number of hash buckets for route cache
2214 riscom8= [HW,SERIAL]
2215 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2217 ro [KNL] Mount root device read-only on boot
2219 root= [KNL] Root filesystem
2221 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2222 mount the root filesystem
2224 rootflags= [KNL] Set root filesystem mount option string
2226 rootfstype= [KNL] Set root filesystem type
2228 rootwait [KNL] Wait (indefinitely) for root device to show up.
2229 Useful for devices that are detected asynchronously
2230 (e.g. USB and MMC devices).
2232 rw [KNL] Mount root device read-write on boot
2234 S [KNL] Run init in single mode
2237 See drivers/net/irda/sa1100_ir.c.
2239 sbni= [NET] Granch SBNI12 leased line adapter
2241 sched_debug [KNL] Enables verbose scheduler debug messages.
2243 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2244 Format: <io>[,<timeout>[,<isapnp>]]
2246 scsi_debug_*= [SCSI]
2247 See drivers/scsi/scsi_debug.c.
2249 scsi_default_dev_flags=
2250 [SCSI] SCSI default device flags
2253 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2254 Format: <vendor>:<model>:<flags>
2255 (flags are integer value)
2257 scsi_logging_level= [SCSI] a bit mask of logging levels
2258 See drivers/scsi/scsi_logging.h for bits. Also
2259 settable via sysctl at dev.scsi.logging_level
2260 (/proc/sys/dev/scsi/logging_level).
2261 There is also a nice 'scsi_logging_level' script in the
2262 S390-tools package, available for download at
2263 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2265 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2266 discovered. async scans them in kernel threads,
2267 allowing boot to proceed. none ignores them, expecting
2268 user space to do the scan.
2270 security= [SECURITY] Choose a security module to enable at boot.
2271 If this boot parameter is not specified, only the first
2272 security module asking for security registration will be
2273 loaded. An invalid security module name will be treated
2274 as if no module has been chosen.
2276 selinux= [SELINUX] Disable or enable SELinux at boot time.
2277 Format: { "0" | "1" }
2278 See security/selinux/Kconfig help text.
2281 Default value is set via kernel config option.
2282 If enabled at boot time, /selinux/disable can be used
2283 later to disable prior to initial policy load.
2285 serialnumber [BUGS=X86-32]
2288 Maximal number of shapers.
2290 show_msr= [x86] show boot-time MSR settings
2291 Format: { <integer> }
2292 Show boot-time (BIOS-initialized) MSR settings.
2293 The parameter means the number of CPUs to show,
2294 for example 1 means boot CPU only.
2297 See header of drivers/scsi/sim710.c.
2304 slub_debug[=options[,slabs]] [MM, SLUB]
2305 Enabling slub_debug allows one to determine the
2306 culprit if slab objects become corrupted. Enabling
2307 slub_debug can create guard zones around objects and
2308 may poison objects when not in use. Also tracks the
2309 last alloc / free. For more information see
2310 Documentation/vm/slub.txt.
2312 slub_max_order= [MM, SLUB]
2313 Determines the maximum allowed order for slabs.
2314 A high setting may cause OOMs due to memory
2315 fragmentation. For more information see
2316 Documentation/vm/slub.txt.
2318 slub_min_objects= [MM, SLUB]
2319 The minimum number of objects per slab. SLUB will
2320 increase the slab order up to slub_max_order to
2321 generate a sufficiently large slab able to contain
2322 the number of objects indicated. The higher the number
2323 of objects the smaller the overhead of tracking slabs
2324 and the less frequently locks need to be acquired.
2325 For more information see Documentation/vm/slub.txt.
2327 slub_min_order= [MM, SLUB]
2328 Determines the mininum page order for slabs. Must be
2329 lower than slub_max_order.
2330 For more information see Documentation/vm/slub.txt.
2332 slub_nomerge [MM, SLUB]
2333 Disable merging of slabs with similar size. May be
2334 necessary if there is some reason to distinguish
2335 allocs to different slabs. Debug options disable
2336 merging on their own.
2337 For more information see Documentation/vm/slub.txt.
2340 Format: <io1>[,<io2>[,...,<io8>]]
2342 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2343 attempt to substitute SMP alternatives once at boot.
2345 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2346 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2347 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2348 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2349 smsc-ircc2.ircc_irq= [HW] IRQ line
2350 smsc-ircc2.ircc_dma= [HW] DMA channel
2351 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2352 0: Toshiba Satellite 1800 (GP data pin select)
2353 1: Fast pin select (default)
2356 snd-ad1816a= [HW,ALSA]
2358 snd-ad1848= [HW,ALSA]
2360 snd-ali5451= [HW,ALSA]
2362 snd-als100= [HW,ALSA]
2364 snd-als4000= [HW,ALSA]
2366 snd-azt2320= [HW,ALSA]
2368 snd-cmi8330= [HW,ALSA]
2370 snd-cmipci= [HW,ALSA]
2372 snd-cs4231= [HW,ALSA]
2374 snd-cs4232= [HW,ALSA]
2376 snd-cs4236= [HW,ALSA]
2378 snd-cs4281= [HW,ALSA]
2380 snd-cs46xx= [HW,ALSA]
2382 snd-dt019x= [HW,ALSA]
2384 snd-dummy= [HW,ALSA]
2386 snd-emu10k1= [HW,ALSA]
2388 snd-ens1370= [HW,ALSA]
2390 snd-ens1371= [HW,ALSA]
2392 snd-es968= [HW,ALSA]
2394 snd-es1688= [HW,ALSA]
2396 snd-es18xx= [HW,ALSA]
2398 snd-es1938= [HW,ALSA]
2400 snd-es1968= [HW,ALSA]
2402 snd-fm801= [HW,ALSA]
2404 snd-gusclassic= [HW,ALSA]
2406 snd-gusextreme= [HW,ALSA]
2408 snd-gusmax= [HW,ALSA]
2412 snd-ice1712= [HW,ALSA]
2414 snd-intel8x0= [HW,ALSA]
2416 snd-interwave= [HW,ALSA]
2421 snd-korg1212= [HW,ALSA]
2423 snd-maestro3= [HW,ALSA]
2425 snd-mpu401= [HW,ALSA]
2427 snd-mtpav= [HW,ALSA]
2429 snd-nm256= [HW,ALSA]
2431 snd-opl3sa2= [HW,ALSA]
2439 snd-opti93x= [HW,ALSA]
2443 snd-rme32= [HW,ALSA]
2445 snd-rme96= [HW,ALSA]
2447 snd-rme9652= [HW,ALSA]
2453 snd-sbawe= [HW,ALSA]
2455 snd-serial= [HW,ALSA]
2457 snd-sgalaxy= [HW,ALSA]
2459 snd-sonicvibes= [HW,ALSA]
2464 snd-sun-cs4231= [HW,ALSA]
2466 snd-trident= [HW,ALSA]
2468 snd-usb-audio= [HW,ALSA,USB]
2470 snd-via82xx= [HW,ALSA]
2472 snd-virmidi= [HW,ALSA]
2474 snd-wavefront= [HW,ALSA]
2476 snd-ymfpci= [HW,ALSA]
2479 [KNL] Should the soft-lockup detector generate panics.
2481 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2482 See Documentation/sonypi.txt
2484 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2485 See Documentation/serial/specialix.txt.
2487 spia_io_base= [HW,MTD]
2493 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2495 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2496 See Documentation/scsi/st.txt.
2499 Enabled the stack tracer on boot up.
2503 Set the STI (builtin display/keyboard on the HP-PARISC
2504 machines) console (graphic card) which should be used
2505 as the initial boot-console.
2506 See also comment in drivers/video/console/sticore.c.
2509 See comment in drivers/video/console/sticore.c.
2512 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2514 sunrpc.min_resvport=
2515 sunrpc.max_resvport=
2517 SunRPC servers often require that client requests
2518 originate from a privileged port (i.e. a port in the
2519 range 0 < portnr < 1024).
2520 An administrator who wishes to reserve some of these
2521 ports for other uses may adjust the range that the
2522 kernel's sunrpc client considers to be privileged
2523 using these two parameters to set the minimum and
2524 maximum port values.
2528 Control how the NFS server code allocates CPUs to
2529 service thread pools. Depending on how many NICs
2530 you have and where their interrupts are bound, this
2531 option will affect which CPUs will do NFS serving.
2532 Note: this parameter cannot be changed while the
2533 NFS server is running.
2535 auto the server chooses an appropriate mode
2536 automatically using heuristics
2537 global a single global pool contains all CPUs
2538 percpu one pool for each CPU
2539 pernode one pool for each NUMA node (equivalent
2540 to global on non-NUMA machines)
2542 sunrpc.tcp_slot_table_entries=
2543 sunrpc.udp_slot_table_entries=
2545 Sets the upper limit on the number of simultaneous
2546 RPC calls that can be sent from the client to a
2547 server. Increasing these values may allow you to
2548 improve throughput, but will also increase the
2549 amount of memory reserved for use by the client.
2551 swiotlb= [IA-64] Number of I/O TLB slabs
2555 sym53c416= [HW,SCSI]
2556 See header of drivers/scsi/sym53c416.c.
2558 sysrq_always_enabled
2560 Ignore sysrq setting - this boot parameter will
2561 neutralize any effect of /proc/sys/kernel/sysrq.
2562 Useful for debugging.
2565 See header of drivers/scsi/t128.c.
2569 test_suspend= [SUSPEND]
2570 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2571 standby suspend) as the system sleep state to briefly
2572 enter during system startup. The system is woken from
2573 this state using a wakeup-capable RTC alarm.
2575 thash_entries= [KNL,NET]
2576 Set number of hash buckets for TCP connection
2578 thermal.act= [HW,ACPI]
2579 -1: disable all active trip points in all thermal zones
2580 <degrees C>: override all lowest active trip points
2582 thermal.crt= [HW,ACPI]
2583 -1: disable all critical trip points in all thermal zones
2584 <degrees C>: override all critical trip points
2586 thermal.nocrt= [HW,ACPI]
2587 Set to disable actions on ACPI thermal zone
2588 critical and hot trip points.
2590 thermal.off= [HW,ACPI]
2591 1: disable ACPI thermal control
2593 thermal.psv= [HW,ACPI]
2594 -1: disable all passive trip points
2595 <degrees C>: override all passive trip points to this
2598 thermal.tzp= [HW,ACPI]
2599 Specify global default ACPI thermal zone polling rate
2600 <deci-seconds>: poll all this frequency
2601 0: no polling (default)
2604 See comment before function dc390_setup() in
2605 drivers/scsi/tmscsim.c.
2609 Specify if the kernel should make use of the cpu
2610 topology informations if the hardware supports these.
2611 The scheduler will make use of these informations and
2612 e.g. base its process migration decisions on it.
2617 trace_buf_size=nn[KMG]
2618 [FTRACE] will set tracing buffer size.
2620 trace_event=[event-list]
2621 [FTRACE] Set and start specified trace events in order
2622 to facilitate early boot debugging.
2623 See also Documentation/trace/events.txt
2625 trix= [HW,OSS] MediaTrix AudioTrix Pro
2627 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2629 tsc= Disable clocksource-must-verify flag for TSC.
2631 [x86] reliable: mark tsc clocksource as reliable, this
2632 disables clocksource verification at runtime.
2633 Used to enable high-resolution timer mode on older
2634 hardware, and in virtualized environment.
2636 turbografx.map[2|3]= [HW,JOY]
2637 TurboGraFX parallel port interface
2639 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2640 See also Documentation/input/joystick-parport.txt
2642 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2643 See header of drivers/scsi/u14-34f.c.
2651 uhash_entries= [KNL,NET]
2652 Set number of hash buckets for UDP/UDP-Lite connections
2655 [USB] Ignore overcurrent events (default N).
2656 Some badly-designed motherboards generate lots of
2657 bogus events, for ports that aren't wired to
2658 anything. Set this parameter to avoid log spamming.
2659 Note that genuine overcurrent events won't be
2664 Set unknown_nmi_panic=1 early on boot.
2666 usbcore.autosuspend=
2667 [USB] The autosuspend time delay (in seconds) used
2668 for newly-detected USB devices (default 2). This
2669 is the time required before an idle device will be
2670 autosuspended. Devices for which the delay is set
2671 to a negative value won't be autosuspended at all.
2673 usbcore.usbfs_snoop=
2674 [USB] Set to log all usbfs traffic (default 0 = off).
2676 usbcore.blinkenlights=
2677 [USB] Set to cycle leds on hubs (default 0 = off).
2679 usbcore.old_scheme_first=
2680 [USB] Start with the old device initialization
2681 scheme (default 0 = off).
2683 usbcore.use_both_schemes=
2684 [USB] Try the other device initialization scheme
2685 if the first one fails (default 1 = enabled).
2687 usbcore.initial_descriptor_timeout=
2688 [USB] Specifies timeout for the initial 64-byte
2689 USB_REQ_GET_DESCRIPTOR request in milliseconds
2690 (default 5000 = 5.0 seconds).
2693 [USBHID] The interval which mice are to be polled at.
2695 usb-storage.delay_use=
2696 [UMS] The delay in seconds before a new device is
2697 scanned for Logical Units (default 5).
2700 [UMS] A list of quirks entries to supplement or
2701 override the built-in unusual_devs list. List
2702 entries are separated by commas. Each entry has
2703 the form VID:PID:Flags where VID and PID are Vendor
2704 and Product ID values (4-digit hex numbers) and
2705 Flags is a set of characters, each corresponding
2706 to a common usb-storage quirk flag as follows:
2707 a = SANE_SENSE (collect more than 18 bytes
2709 b = BAD_SENSE (don't collect more than 18
2710 bytes of sense data);
2711 c = FIX_CAPACITY (decrease the reported
2712 device capacity by one sector);
2713 h = CAPACITY_HEURISTICS (decrease the
2714 reported device capacity by one
2715 sector if the number is odd);
2716 i = IGNORE_DEVICE (don't bind to this
2718 l = NOT_LOCKABLE (don't try to lock and
2719 unlock ejectable media);
2720 m = MAX_SECTORS_64 (don't transfer more
2721 than 64 sectors = 32 KB at a time);
2722 o = CAPACITY_OK (accept the capacity
2723 reported by the device);
2724 r = IGNORE_RESIDUE (the device reports
2725 bogus residue values);
2726 s = SINGLE_LUN (the device has only one
2728 w = NO_WP_DETECT (don't test whether the
2729 medium is write-protected).
2730 Example: quirks=0419:aaf5:rl,0421:0433:rc
2733 [X86] Flags controlling user PTE allocations.
2735 nohigh = do not allocate PTE pages in
2736 HIGHMEM regardless of setting
2740 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2741 vdso=1: enable VDSO (default)
2742 vdso=0: disable VDSO mapping
2745 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2746 vdso32=1: enable 32-bit VDSO (default)
2747 vdso32=0: disable 32-bit VDSO mapping
2750 vector=percpu: enable percpu vector domain
2752 video= [FB] Frame buffer configuration
2753 See Documentation/fb/modedb.txt.
2755 vga= [BOOT,X86-32] Select a particular video mode
2756 See Documentation/x86/boot.txt and
2757 Documentation/svga.txt.
2758 Use vga=ask for menu.
2759 This is actually a boot loader parameter; the value is
2760 passed to the kernel using a special protocol.
2762 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2763 size of <nn>. This can be used to increase the
2764 minimum size (128MB on x86). It can also be used to
2765 decrease the size and leave more room for directly
2768 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2771 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2774 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2777 vt.cur_default= [VT] Default cursor shape.
2778 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2779 the parameters of the <Esc>[?A;B;Cc escape sequence;
2780 see VGA-softcursor.txt. Default: 2 = underline.
2782 vt.default_blu= [VT]
2783 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2784 Change the default blue palette of the console.
2785 This is a 16-member array composed of values
2788 vt.default_grn= [VT]
2789 Format: <green0>,<green1>,<green2>,...,<green15>
2790 Change the default green palette of the console.
2791 This is a 16-member array composed of values
2794 vt.default_red= [VT]
2795 Format: <red0>,<red1>,<red2>,...,<red15>
2796 Change the default red palette of the console.
2797 This is a 16-member array composed of values
2803 Set system-wide default UTF-8 mode for all tty's.
2804 Default is 1, i.e. UTF-8 mode is enabled for all
2805 newly opened terminals.
2807 vt.global_cursor_default=
2810 Set system-wide default for whether a cursor
2811 is shown on new VTs. Default is -1,
2812 i.e. cursors will be created by default unless
2813 overridden by individual drivers. 0 will hide
2814 cursors, 1 will display them.
2816 waveartist= [HW,OSS]
2817 Format: <io>,<irq>,<dma>,<dma2>
2820 See header of drivers/scsi/wd33c93.c.
2823 See header of drivers/scsi/wd7000.c.
2826 See Documentation/watchdog/wdt.txt.
2828 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2829 default x2apic cluster mode on platforms
2832 x86_mrst_timer= [X86-32,APBT]
2833 Choose timer option for x86 Moorestown MID platform.
2834 Two valid options are apbt timer only and lapic timer
2835 plus one apbt timer for broadcast timer.
2836 x86_mrst_timer=apbt_only | lapic_and_apbt
2838 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2839 xd_geo= See header of drivers/block/xd.c.
2841 xirc2ps_cs= [NET,PCMCIA]
2843 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2845 ______________________________________________________________________
2849 Add documentation for ALSA options.
2850 Add more DRM drivers.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob