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 KGDB Kernel debugger support is enabled.
62 KVM Kernel Virtual Machine support is enabled.
63 LIBATA Libata driver is enabled
64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
72 MSI Message Signaled Interrupts (PCI).
73 MTD MTD (Memory Technology Device) support is enabled.
74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
76 GENERIC_TIME The generic timeofday code is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers has their options described inside of
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 SERIAL Serial support is enabled.
97 SH SuperH architecture is enabled.
98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
102 FTRACE Function tracing enabled.
103 TPM TPM drivers are enabled.
104 TS Appropriate touchscreen support is enabled.
105 UMS USB Mass Storage support is enabled.
106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
113 X86-32 X86-32, aka i386 architecture is enabled.
114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
116 Documentation/x86/x86_64/boot-options.txt .
117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 In addition, the following text indicates that the option:
121 BUGS= Relates to possible processor bugs on the said processor.
122 KNL Is a kernel start-up parameter.
123 BOOT Is a boot loader parameter.
125 Parameters denoted with BOOT are actually interpreted by the boot
126 loader, and have no meaning to the kernel directly.
127 Do not modify the syntax of boot loader parameters without extreme
128 need or coordination with <Documentation/x86/boot.txt>.
130 There are also arch-specific kernel-parameters not documented here.
131 See for example <Documentation/x86/x86_64/boot-options.txt>.
133 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
134 a trailing = on the name of any parameter states that that parameter will
135 be entered as an environment variable, whereas its absence indicates that
136 it will appear as a kernel argument readable via /proc/cmdline by programs
137 running once the system is up.
139 The number of kernel parameters is not limited, but the length of the
140 complete command line (parameters including spaces etc.) is limited to
141 a fixed number of characters. This limit depends on the architecture
142 and is between 256 and 4096 characters. It is defined in the file
143 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Advanced Configuration and Power Interface
148 Format: { force | off | ht | strict | noirq | rsdt }
149 force -- enable ACPI if default was off
150 off -- disable ACPI if default was on
151 noirq -- do not use ACPI for IRQ routing
152 ht -- run only enough ACPI to enable Hyper Threading
153 strict -- Be less tolerant of platforms that are not
154 strictly ACPI specification compliant.
155 rsdt -- prefer RSDT over (default) XSDT
156 copy_dsdt -- copy DSDT to memory
158 See also Documentation/power/pm.txt, pci=noacpi
160 acpi_apic_instance= [ACPI, IOAPIC]
162 2: use 2nd APIC table, if available
163 1,0: use 1st APIC table
166 acpi_backlight= [HW,ACPI]
167 acpi_backlight=vendor
169 If set to vendor, prefer vendor specific driver
170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
171 of the ACPI video.ko driver.
173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
177 debug output. Bits in debug_layer correspond to a
178 _COMPONENT in an ACPI source file, e.g.,
179 #define _COMPONENT ACPI_PCI_COMPONENT
180 Bits in debug_level correspond to a level in
181 ACPI_DEBUG_PRINT statements, e.g.,
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
183 The debug_level mask defaults to "info". See
184 Documentation/acpi/debug.txt for more information about
185 debug layers and levels.
187 Enable processor driver info messages:
188 acpi.debug_layer=0x20000000
189 Enable PCI/PCI interrupt routing info messages:
190 acpi.debug_layer=0x400000
191 Enable AML "Debug" output, i.e., stores to the Debug
192 object while interpreting AML:
193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
194 Enable all messages related to ACPI hardware:
195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197 Some values produce so much output that the system is
198 unusable. The "log_buf_len" parameter may be useful
199 if you need to capture more output.
201 acpi_display_output= [HW,ACPI]
202 acpi_display_output=vendor
203 acpi_display_output=video
206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 Format: <irq>,<irq>...
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
239 acpi_serialize [HW,ACPI] force serialization of AML methods
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
247 old_ordering, s4_nonvs, sci_force_enable }
248 See Documentation/power/video.txt for information on
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
258 s4_nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during hibernation.
260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
287 add_efi_memmap [EFI; X86] Include EFI memory map in
288 kernel's map of available physical RAM.
291 See header of drivers/scsi/advansys.c.
293 advwdt= [HW,WDT] Advantech WDT
294 Format: <iostart>,<iostop>
296 aedsp16= [HW,OSS] Audio Excel DSP 16
297 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
298 See also header of sound/oss/aedsp16.c.
301 { off | try_unsupported }
302 off: disable AGP support
303 try_unsupported: try to drive unsupported chipsets
304 (may crash computer or cause data corruption)
307 See Documentation/scsi/aha152x.txt.
310 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
313 See Documentation/scsi/aic7xxx.txt.
316 See Documentation/scsi/aic79xx.txt.
319 Allow the default userspace alignment fault handler
320 behaviour to be specified. Bit 0 enables warnings,
321 bit 1 enables fixups, and bit 2 sends a segfault.
323 amd_iommu= [HW,X86-84]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
333 amijoy.map= [HW,JOY] Amiga joystick support
334 Map of devices attached to JOY0DAT and JOY1DAT
336 See also Documentation/kernel/input/joystick.txt
338 analog.map= [HW,JOY] Analog joystick and gamepad support
339 Specifies type or capabilities of an analog joystick
340 connected to one of 16 gameports
341 Format: <type1>,<type2>,..<type16>
344 Power management functions (SPARCstation-4/5 + deriv.)
346 Disable APC CPU standby support. SPARCstation-Fox does
347 not play well with APC CPU idle - disable it if you have
348 APC and your system crashes randomly.
350 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
351 Change the output verbosity whilst booting
352 Format: { quiet (default) | verbose | debug }
353 Change the amount of debugging information output
354 when initialising the APIC and IO-APIC components.
357 See Documentation/networking/ipv6.txt.
359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
360 Limit apic dumping. The parameter defines the maximal
361 number of local apics being dumped. Also it is possible
362 to set it to "all" by meaning -- no limit here.
363 Format: { 1 (default) | 2 | ... | all }.
364 The parameter valid if only apic=debug or
365 apic=verbose is specified.
366 Example: apic=debug show_lapic=all
368 apm= [APM] Advanced Power Management
369 See header of arch/x86/kernel/apm_32.c.
371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
372 Format: <io>,<irq>,<nodeID>
376 atarimouse= [HW,MOUSE] Atari Mouse
378 atascsi= [HW,SCSI] Atari SCSI
380 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
381 EzKey and similar keyboards
383 atkbd.reset= [HW] Reset keyboard during initialization
385 atkbd.set= [HW] Select keyboard code set
386 Format: <int> (2 = AT (default), 3 = PS/2)
388 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
391 atkbd.softraw= [HW] Choose between synthetic and real raw mode
392 Format: <bool> (0 = real, 1 = synthetic (default))
394 atkbd.softrepeat= [HW]
395 Use software keyboard repeat
399 baycom_epp= [HW,AX25]
402 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
404 See header of drivers/net/hamradio/baycom_par.c.
406 baycom_ser_fdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
408 Format: <io>,<irq>,<mode>[,<baud>]
409 See header of drivers/net/hamradio/baycom_ser_fdx.c.
411 baycom_ser_hdx= [HW,AX25]
412 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
413 Format: <io>,<irq>,<mode>
414 See header of drivers/net/hamradio/baycom_ser_hdx.c.
416 boot_delay= Milliseconds to delay each printk during boot.
417 Values larger than 10 seconds (10000) are changed to
421 bootmem_debug [KNL] Enable bootmem allocator debug messages.
423 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
424 bttv.radio= Most important insmod options are available as
426 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
427 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
430 See drivers/scsi/BusLogic.c, comment before function
431 BusLogic_ParseDriverOptions().
433 c101= [NET] Moxa C101 synchronous serial card
435 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
436 Sometimes CPU hardware bugs make them report the cache
437 size incorrectly. The kernel will attempt work arounds
438 to fix known problems, but for some CPUs it is not
439 possible to determine what the correct size should be.
440 This option provides an override for these situations.
443 [SECURITY] Disable capabilities. This would normally
444 be used only if an alternative security model is to be
445 configured. Potentially dangerous and should only be
446 used if you are entirely sure of the consequences.
448 ccw_timeout_log [S390]
449 See Documentation/s390/CommonIO for details.
451 cgroup_disable= [KNL] Disable a particular controller
452 Format: {name of the controller(s) to disable}
453 {Currently supported controllers - "memory"}
455 checkreqprot [SELINUX] Set initial checkreqprot flag value.
456 Format: { "0" | "1" }
457 See security/selinux/Kconfig help text.
458 0 -- check protection applied by kernel (includes
459 any implied execute protection).
460 1 -- check protection requested by application.
461 Default value is set via a kernel config option.
462 Value can be changed at runtime via
463 /selinux/checkreqprot.
466 See Documentation/s390/CommonIO for details.
468 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
470 Forces specified clocksource (if available) to be used
471 when calculating gettimeofday(). If specified
472 clocksource is not available, it defaults to PIT.
473 Format: { pit | tsc | cyclone | pmtmr }
475 clocksource= [GENERIC_TIME] Override the default clocksource
477 Override the default clocksource and use the clocksource
478 with the name specified.
479 Some clocksource names to choose from, depending on
481 [all] jiffies (this is the base, fallback clocksource)
483 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
484 pxa_timer,timer3,32k_counter,timer0_1
486 [X86-32] pit,hpet,tsc,vmi-timer;
487 scx200_hrt on Geode; cyclone on IBM x440
495 clearcpuid=BITNUM [X86]
496 Disable CPUID feature X for the kernel. See
497 arch/x86/include/asm/cpufeature.h for the valid bit
498 numbers. Note the Linux specific bits are not necessarily
499 stable over kernel options, but the vendor specific
501 Also note that user programs calling CPUID directly
502 or using the feature without checking anything
503 will still see it. This just prevents it from
504 being used by the kernel or shown in /proc/cpuinfo.
505 Also note the kernel might malfunction if you disable
508 cmo_free_hint= [PPC] Format: { yes | no }
509 Specify whether pages are marked as being inactive
510 when they are freed. This is used in CMO environments
511 to determine OS memory pressure for page stealing by
515 code_bytes [X86] How many bytes of object code to print
520 com20020= [HW,NET] ARCnet - COM20020 chipset
522 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
524 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
528 ARCnet - COM90xx chipset (memory-mapped buffers)
529 Format: <io>[,<irq>[,<memstart>]]
531 condev= [HW,S390] console device
534 console= [KNL] Output console device and options.
536 tty<n> Use the virtual console device <n>.
540 Use the specified serial port. The options are of
541 the form "bbbbpnf", where "bbbb" is the baud rate,
542 "p" is parity ("n", "o", or "e"), "n" is number of
543 bits, and "f" is flow control ("r" for RTS or
544 omit it). Default is "9600n8".
546 See Documentation/serial-console.txt for more
548 Documentation/networking/netconsole.txt for an
551 uart[8250],io,<addr>[,options]
552 uart[8250],mmio,<addr>[,options]
553 Start an early, polled-mode console on the 8250/16550
554 UART at the specified I/O port or MMIO address,
555 switching to the matching ttyS device later. The
556 options are the same as for ttyS, above.
558 If the device connected to the port is not a TTY but a braille
559 device, prepend "brl," before the device type, for instance
561 For now, only VisioBraille is supported.
563 consoleblank= [KNL] The console blank (screen saver) timeout in
564 seconds. Defaults to 10*60 = 10mins. A value of 0
565 disables the blank timer.
568 [KNL] Change the default value for
569 /proc/<pid>/coredump_filter.
570 See also Documentation/filesystems/proc.txt.
572 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
574 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
576 crashkernel=nn[KMG]@ss[KMG]
577 [KNL] Reserve a chunk of physical memory to
578 hold a kernel to switch to with kexec on panic.
580 crashkernel=range1:size1[,range2:size2,...][@offset]
581 [KNL] Same as above, but depends on the memory
582 in the running system. The syntax of range is
583 start-[end] where start and end are both
584 a memory unit (amount[KMG]). See also
585 Documentation/kdump/kdump.txt for a example.
590 cs89x0_media= [HW,NET]
591 Format: { rj45 | aui | bnc }
594 See header of drivers/s390/block/dasd_devmap.c.
596 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
597 (one device per port)
598 Format: <port#>,<type>
599 See also Documentation/input/joystick-parport.txt
601 debug [KNL] Enable kernel debugging (events log level).
604 [KNL] verbose self-tests
606 Print debugging info while doing the locking API
608 We default to 0 (no extra messages), setting it to
609 1 will print _a lot_ more information - normally
610 only useful to kernel developers.
612 debug_objects [KNL] Enable object debugging
615 [KNL] Disable object debugging
617 debugpat [X86] Enable PAT debugging
619 decnet.addr= [HW,NET]
620 Format: <area>[,<node>]
621 See also Documentation/networking/decnet.txt.
624 [same as hugepagesz=] The size of the default
625 HugeTLB page size. This is the size represented by
626 the legacy /proc/ hugepages APIs, used for SHM, and
627 default size when mounting hugetlbfs filesystems.
628 Defaults to the default architecture's huge page size
632 Set number of hash buckets for dentry cache.
635 IO parameters + enable/disable command.
637 digiepca= [HW,SERIAL]
638 See drivers/char/README.epca and
639 Documentation/serial/digiepca.txt.
642 See Documentation/networking/ipv6.txt.
645 See Documentation/networking/ipv6.txt.
647 disable_mtrr_cleanup [X86]
648 The kernel tries to adjust MTRR layout from continuous
649 to discrete, to make X server driver able to add WB
650 entry later. This parameter disables that.
652 disable_mtrr_trim [X86, Intel and AMD only]
653 By default the kernel will trim any uncacheable
654 memory out of your available memory pool based on
655 MTRR settings. This parameter disables that behavior,
656 possibly causing your machine to run very slowly.
658 disable_timer_pin_1 [X86]
659 Disable PIN 1 of APIC timer
660 Can be useful to work around chipset bugs.
662 dmasound= [HW,OSS] Sound subsystem buffers
664 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
665 this option disables the debugging code at boot.
667 dma_debug_entries=<number>
668 This option allows to tune the number of preallocated
669 entries for DMA-API debugging code. One entry is
670 required per DMA-API allocation. Use this if the
671 DMA-API debugging code disables itself because the
672 architectural default is too low.
674 dma_debug_driver=<driver_name>
675 With this option the DMA-API debugging driver
676 filter feature can be enabled at boot time. Just
677 pass the driver to filter for as the parameter.
678 The filter can be disabled or changed to another
679 driver later using sysfs.
685 dynamic_printk Enables pr_debug()/dev_dbg() calls if
686 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
687 These can also be switched on/off via
688 <debugfs>/dynamic_printk/modules
690 earlycon= [KNL] Output early console device and options.
691 uart[8250],io,<addr>[,options]
692 uart[8250],mmio,<addr>[,options]
693 Start an early, polled-mode console on the 8250/16550
694 UART at the specified I/O port or MMIO address.
695 The options are the same as for ttyS, above.
697 earlyprintk= [X86,SH,BLACKFIN]
699 earlyprintk=serial[,ttySn[,baudrate]]
700 earlyprintk=ttySn[,baudrate]
701 earlyprintk=dbgp[debugController#]
703 Append ",keep" to not disable it when the real console
706 Only vga or serial or usb debug port at a time.
708 Currently only ttyS0 and ttyS1 are supported.
710 Interaction with the standard serial driver is not
713 The VGA output is eventually overwritten by the real
719 Format: {"off" | "on" | "skip[mbr]"}
721 eisa_irq_edge= [PARISC,HW]
722 See header of drivers/parisc/eisa.c.
725 See comment before function elanfreq_setup() in
726 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
729 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
730 See Documentation/block/as-iosched.txt and
731 Documentation/block/deadline-iosched.txt for details.
733 elfcorehdr= [IA64,PPC,SH,X86]
734 Specifies physical address of start of kernel core
735 image elf header. Generally kexec loader will
736 pass this option to capture kernel.
737 See Documentation/kdump/kdump.txt for details.
739 enable_mtrr_cleanup [X86]
740 The kernel tries to adjust MTRR layout from continuous
741 to discrete, to make X server driver able to add WB
742 entry later. This parameter enables that.
744 enable_timer_pin_1 [X86]
745 Enable PIN 1 of APIC timer
746 Can be useful to work around chipset bugs
747 (in particular on some ATI chipsets).
748 The kernel tries to set a reasonable default.
750 enforcing [SELINUX] Set initial enforcing status.
752 See security/selinux/Kconfig help text.
753 0 -- permissive (log only, no denials).
754 1 -- enforcing (deny and log).
756 Value can be changed at runtime via /selinux/enforce.
758 ether= [HW,NET] Ethernet cards parameters
759 This option is obsoleted by the "netdev=" option, which
760 has equivalent usage. See its documentation for details.
762 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
767 fail_make_request=[KNL]
768 General fault injection mechanism.
769 Format: <interval>,<probability>,<space>,<times>
770 See also /Documentation/fault-injection/.
773 See header of drivers/scsi/fd_mcs.c.
776 See header of drivers/scsi/fdomain.c.
779 See Documentation/blockdev/floppy.txt.
781 force_pal_cache_flush
782 [IA-64] Avoid check_sal_cache_flush which may hang on
783 buggy SAL_CACHE_FLUSH implementations. Using this
784 parameter will force ia64_sal_cache_flush to call
785 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
788 [FTRACE] will set and start the specified tracer
789 as early as possible in order to facilitate early
792 ftrace_dump_on_oops[=orig_cpu]
793 [FTRACE] will dump the trace buffers on oops.
794 If no parameter is passed, ftrace will dump
795 buffers of all CPUs, but if you pass orig_cpu, it will
796 dump only the buffer of the CPU that triggered the
799 ftrace_filter=[function-list]
800 [FTRACE] Limit the functions traced by the function
801 tracer at boot up. function-list is a comma separated
802 list of functions. This list can be changed at run
803 time by the set_ftrace_filter file in the debugfs
806 ftrace_notrace=[function-list]
807 [FTRACE] Do not trace the functions specified in
808 function-list. This list can be changed at run time
809 by the set_ftrace_notrace file in the debugfs
812 ftrace_graph_filter=[function-list]
813 [FTRACE] Limit the top level callers functions traced
814 by the function graph tracer at boot up.
815 function-list is a comma separated list of functions
816 that can be changed at run time by the
817 set_graph_function file in the debugfs tracing directory.
820 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
821 support via parallel port (up to 5 devices per port)
822 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
823 See also Documentation/input/joystick-parport.txt
827 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
831 gcov_persist= [GCOV] When non-zero (default), profiling data for
832 kernel modules is saved and remains accessible via
833 debugfs, even when the module is unloaded/reloaded.
834 When zero, profiling data is discarded and associated
835 debugfs files are removed at module unload time.
838 See header of drivers/scsi/gdth.c.
840 gpt [EFI] Forces disk with valid GPT signature but
841 invalid Protective MBR to be treated as GPT.
845 hashdist= [KNL,NUMA] Large hashes allocated during boot
846 are distributed across NUMA nodes. Defaults on
847 for 64bit NUMA, off otherwise.
848 Format: 0 | 1 (for off | on)
850 hcl= [IA-64] SGI's Hardware Graph compatibility layer
852 hd= [EIDE] (E)IDE hard drive subsystem geometry
853 Format: <cyl>,<head>,<sect>
855 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
856 size of <nn>. This works even on boxes that have no
857 highmem otherwise. This also works to reduce highmem
858 size on bigger boxes.
860 highres= [KNL] Enable/disable high resolution timer mode.
861 Valid parameters: "on", "off"
865 See Documentation/isdn/README.HiSax.
869 hpet= [X86-32,HPET] option to control HPET usage
870 Format: { enable (default) | disable | force |
872 disable: disable HPET and use PIT instead
873 force: allow force enabled of undocumented chips (ICH4,
875 verbose: show contents of HPET registers during setup
877 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
878 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
879 On x86-64 and powerpc, this option can be specified
880 multiple times interleaved with hugepages= to reserve
881 huge pages of different sizes. Valid pages sizes on
882 x86-64 are 2M (when the CPU supports "pse") and 1G
883 (when the CPU supports the "pdpe1gb" cpuinfo flag)
884 Note that 1GB pages can only be allocated at boot time
885 using hugepages= and not freed afterwards.
887 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
888 terminal devices. Valid values: 0..8
889 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
890 If specified, z/VM IUCV HVC accepts connections
891 from listed z/VM user IDs only.
893 i2c_bus= [HW] Override the default board specific I2C bus speed
894 or register an additional I2C bus that is not
895 registered from board initialization code.
899 i8042.debug [HW] Toggle i8042 debug mode
900 i8042.direct [HW] Put keyboard port into non-translated mode
901 i8042.dumbkbd [HW] Pretend that controller can only read data from
902 keyboard and cannot control its state
903 (Don't attempt to blink the leds)
904 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
905 i8042.nokbd [HW] Don't check/create keyboard port
906 i8042.noloop [HW] Disable the AUX Loopback command while probing
908 i8042.nomux [HW] Don't check presence of an active multiplexing
910 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
913 [HW] Frequency with which keyboard LEDs should blink
914 when kernel panics (default is 0.5 sec)
915 i8042.reset [HW] Reset the controller during init and cleanup
916 i8042.unlock [HW] Unlock (ignore) the keylock
920 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
921 indicates that the driver is running on unsupported
923 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
924 does not match list of supported models.
926 [HW] Report power status in /proc/i8k
927 (disabled by default)
928 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
931 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
932 See Documentation/mca.txt.
935 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
937 ide-core.nodma= [HW] (E)IDE subsystem
938 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
939 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
940 .cdrom .chs .ignore_cable are additional options
941 See Documentation/ide/ide.txt.
943 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
944 Claim all unknown PCI IDE storage controllers.
947 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
948 Poll forces a polling idle loop that can slightly
949 improve the performance of waking up a idle CPU, but
950 will use a lot of power and make the system run hot.
952 idle=mwait: On systems which support MONITOR/MWAIT but
953 the kernel chose to not use it because it doesn't save
954 as much power as a normal idle loop, use the
955 MONITOR/MWAIT idle loop anyways. Performance should be
956 the same as idle=poll.
957 idle=halt: Halt is forced to be used for CPU idle.
958 In such case C2/C3 won't be used again.
959 idle=nomwait: Disable mwait for CPU C-states
961 ignore_loglevel [KNL]
962 Ignore loglevel setting - this will print /all/
963 kernel messages to the console. Useful for debugging.
966 Set number of hash buckets for inode cache.
969 Format: { "0" | "1" }
970 0 -- integrity auditing messages. (Default)
971 1 -- enable informational integrity auditing messages.
974 Format: { "sha1" | "md5" }
978 Load a policy which meets the needs of the Trusted
979 Computing Base. This means IMA will measure all
980 programs exec'd, files mmap'd for exec, and all files
981 opened for read by uid=0.
984 See header of drivers/scsi/in2000.c.
988 Run specified binary instead of /sbin/init as init
991 initcall_debug [KNL] Trace initcalls as they are executed. Useful
992 for working out where the kernel is dying during
995 initrd= [BOOT] Specify the location of the initial ramdisk
997 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1000 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1002 Enable intel iommu driver.
1004 Disable intel iommu driver.
1005 igfx_off [Default Off]
1006 By default, gfx is mapped as normal device. If a gfx
1007 device has a dedicated DMAR unit, the DMAR unit is
1008 bypassed by not enabling DMAR with this option. In
1009 this case, gfx device will use physical address for
1012 With this option iommu will not optimize to look
1013 for io virtual address below 32 bit forcing dual
1014 address cycle on pci bus for cards supporting greater
1015 than 32 bit addressing. The default is to look
1016 for translation below 32 bit and if not available
1017 then look in the higher range.
1018 strict [Default Off]
1019 With this option on every unmap_single operation will
1020 result in a hardware IOTLB flush operation as opposed
1021 to batching them for performance.
1025 iomem= Disable strict checking of access to MMIO memory
1026 strict regions from userspace.
1042 io7= [HW] IO7 for Marvel based alpha systems
1043 See comment before marvel_specify_io7 in
1044 arch/alpha/kernel/core_marvel.c.
1046 io_delay= [X86] I/O delay method
1048 Standard port 0x80 based delay
1050 Alternate port 0xed based delay (needed on some systems)
1052 Simple two microseconds delay
1057 See Documentation/filesystems/nfs/nfsroot.txt.
1059 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1060 See comment before ip2_setup() in
1061 drivers/char/ip2/ip2base.c.
1063 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1064 See header of drivers/scsi/ips.c.
1067 When an interrupt is not handled search all handlers
1068 for it. Intended to get systems with badly broken
1072 When an interrupt is not handled search all handlers
1073 for it. Also check all handlers each timer
1074 interrupt. Intended to get systems with badly broken
1078 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1080 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1082 <cpu number>,...,<cpu number>
1084 <cpu number>-<cpu number>
1085 (must be a positive range in ascending order)
1087 <cpu number>,...,<cpu number>-<cpu number>
1089 This option can be used to specify one or more CPUs
1090 to isolate from the general SMP balancing and scheduling
1091 algorithms. You can move a process onto or off an
1092 "isolated" CPU via the CPU affinity syscalls or cpuset.
1093 <cpu number> begins at 0 and the maximum value is
1094 "number of CPUs in system - 1".
1096 This option is the preferred way to isolate CPUs. The
1097 alternative -- manually setting the CPU mask of all
1098 tasks in the system -- can cause problems and
1099 suboptimal load balancer performance.
1103 js= [HW,JOY] Analog joystick
1104 See Documentation/input/joystick.txt.
1108 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1109 specifies the amount of memory usable by the kernel
1110 for non-movable allocations. The requested amount is
1111 spread evenly throughout all nodes in the system. The
1112 remaining memory in each node is used for Movable
1113 pages. In the event, a node is too small to have both
1114 kernelcore and Movable pages, kernelcore pages will
1115 take priority and other nodes will have a larger number
1116 of kernelcore pages. The Movable zone is used for the
1117 allocation of pages that may be reclaimed or moved
1118 by the page migration subsystem. This means that
1119 HugeTLB pages may not be allocated from this zone.
1120 Note that allocations like PTEs-from-HighMem still
1121 use the HighMem zone if it exists, and the Normal
1122 zone if it does not.
1124 kgdboc= [KGDB,HW] kgdb over consoles.
1125 Requires a tty driver that supports console polling,
1126 or a supported polling keyboard driver (non-usb).
1127 Serial only format: <serial_device>[,baud]
1128 keyboard only format: kbd
1129 keyboard and serial format: kbd,<serial_device>[,baud]
1131 kgdbwait [KGDB] Stop kernel execution and enter the
1132 kernel debugger at the earliest opportunity.
1134 kmac= [MIPS] korina ethernet MAC address.
1135 Configure the RouterBoard 532 series on-chip
1136 Ethernet adapter MAC address.
1138 kmemleak= [KNL] Boot-time kmemleak enable/disable
1139 Valid arguments: on, off
1142 kstack=N [X86] Print N words from the kernel stack
1145 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1146 Default is 0 (don't ignore, but inject #GP)
1148 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1149 Default is 1 (enabled)
1151 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1154 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1156 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1158 kvm-intel.bypass_guest_pf=
1159 [KVM,Intel] Disables bypassing of guest page faults
1160 on Intel chips. Default is 1 (enabled)
1162 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1163 (virtualized MMU) support on capable Intel chips.
1164 Default is 1 (enabled)
1166 kvm-intel.emulate_invalid_guest_state=
1167 [KVM,Intel] Enable emulation of invalid guest states
1168 Default is 0 (disabled)
1170 kvm-intel.flexpriority=
1171 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1172 Default is 1 (enabled)
1174 kvm-intel.unrestricted_guest=
1175 [KVM,Intel] Disable unrestricted guest feature
1176 (virtualized real and unpaged mode) on capable
1177 Intel chips. Default is 1 (enabled)
1179 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1180 feature (tagged TLBs) on capable Intel chips.
1181 Default is 1 (enabled)
1187 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1190 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1193 libata.dma= [LIBATA] DMA control
1194 libata.dma=0 Disable all PATA and SATA DMA
1195 libata.dma=1 PATA and SATA Disk DMA only
1196 libata.dma=2 ATAPI (CDROM) DMA only
1197 libata.dma=4 Compact Flash DMA only
1198 Combinations also work, so libata.dma=3 enables DMA
1199 for disks and CDROMs, but not CFs.
1201 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1202 libata.ignore_hpa=0 keep BIOS limits (default)
1203 libata.ignore_hpa=1 ignore limits, using full disk
1205 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1209 libata.force= [LIBATA] Force configurations. The format is comma
1210 separated list of "[ID:]VAL" where ID is
1211 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1212 matching port, link or device. Basically, it matches
1213 the ATA ID string printed on console by libata. If
1214 the whole ID part is omitted, the last PORT and DEVICE
1215 values are used. If ID hasn't been specified yet, the
1216 configuration applies to all ports, links and devices.
1218 If only DEVICE is omitted, the parameter applies to
1219 the port and all links and devices behind it. DEVICE
1220 number of 0 either selects the first device or the
1221 first fan-out link behind PMP device. It does not
1222 select the host link. DEVICE number of 15 selects the
1223 host link and device attached to it.
1225 The VAL specifies the configuration to force. As long
1226 as there's no ambiguity shortcut notation is allowed.
1227 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1228 The following configurations can be forced.
1230 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1231 Any ID with matching PORT is used.
1233 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1235 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1236 udma[/][16,25,33,44,66,100,133] notation is also
1239 * [no]ncq: Turn on or off NCQ.
1241 * nohrst, nosrst, norst: suppress hard, soft
1244 If there are multiple matching configurations changing
1245 the same attribute, the last one is used.
1247 lmb=debug [KNL] Enable lmb debug messages.
1249 load_ramdisk= [RAM] List of ramdisks to load from floppy
1250 See Documentation/blockdev/ramdisk.txt.
1252 lockd.nlm_grace_period=P [NFS] Assign grace period.
1255 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1258 lockd.nlm_timeout=T [NFS] Assign timeout value.
1261 lockd.nlm_udpport=M [NFS] Assign UDP port.
1264 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1267 loglevel= All Kernel Messages with a loglevel smaller than the
1268 console loglevel will be printed to the console. It can
1269 also be changed with klogd or other programs. The
1270 loglevels are defined as follows:
1272 0 (KERN_EMERG) system is unusable
1273 1 (KERN_ALERT) action must be taken immediately
1274 2 (KERN_CRIT) critical conditions
1275 3 (KERN_ERR) error conditions
1276 4 (KERN_WARNING) warning conditions
1277 5 (KERN_NOTICE) normal but significant condition
1278 6 (KERN_INFO) informational
1279 7 (KERN_DEBUG) debug-level messages
1281 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1282 Format: { n | nk | nM }
1283 n must be a power of two. The default size
1284 is set in the kernel config file.
1286 logo.nologo [FB] Disables display of the built-in Linux logo.
1287 This may be used to provide more screen space for
1288 kernel log messages and is useful when debugging
1289 kernel boot problems.
1291 lp=0 [LP] Specify parallel ports to use, e.g,
1292 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1293 lp=reset first parallel port). 'lp=0' disables the
1294 lp=auto printer driver. 'lp=reset' (which can be
1295 specified in addition to the ports) causes
1296 attached printers to be reset. Using
1297 lp=port1,port2,... specifies the parallel ports
1298 to associate lp devices with, starting with
1299 lp0. A port specification may be 'none' to skip
1300 that lp device, or a parport name such as
1301 'parport0'. Specifying 'lp=auto' instead of a
1302 port specification list means that device IDs
1303 from each port should be examined, to see if
1304 an IEEE 1284-compliant printer is attached; if
1305 so, the driver will manage that printer.
1306 See also header of drivers/char/lp.c.
1309 Sets loops_per_jiffy to given constant, thus avoiding
1310 time-consuming boot-time autodetection (up to 250 ms per
1311 CPU). 0 enables autodetection (default). To determine
1312 the correct value for your kernel, boot with normal
1313 autodetection and see what value is printed. Note that
1314 on SMP systems the preset will be applied to all CPUs,
1315 which is likely to cause problems if your CPUs need
1316 significantly divergent settings. An incorrect value
1317 will cause delays in the kernel to be wrong, leading to
1318 unpredictable I/O errors and other breakage. Although
1319 unlikely, in the extreme case this might damage your
1323 Format: <io>,<irq>,<dma>
1325 mac5380= [HW,SCSI] Format:
1326 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1328 machvec= [IA64] Force the use of a particular machine-vector
1329 (machvec) in a generic kernel.
1330 Example: machvec=hpzx1_swiotlb
1332 machtype= [Loongson] Share the same kernel image file between different
1334 Example: machtype=lemote-yeeloong-2f-7inch
1336 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1337 than or equal to this physical address is ignored.
1339 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1340 should make use of. maxcpus=n : n >= 0 limits the
1341 kernel to using 'n' processors. n=0 is a special case,
1342 it is equivalent to "nosmp", which also disables
1345 max_loop= [LOOP] Maximum number of loopback devices that can
1349 max_luns= [SCSI] Maximum number of LUNs to probe.
1350 Should be between 1 and 2^32-1.
1353 [SCSI] Maximum number of LUNs received.
1354 Should be between 1 and 16384.
1358 mce [X86-32] Machine Check Exception
1360 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1362 md= [HW] RAID subsystems devices and level
1363 See Documentation/md.txt.
1366 Format: <first>,<last>
1367 Specifies range of consoles to be captured by the MDA.
1369 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1370 Amount of memory to be used when the kernel is not able
1371 to see the whole system memory or for test.
1372 [X86-32] Use together with memmap= to avoid physical
1373 address space collisions. Without memmap= PCI devices
1374 could be placed at addresses belonging to unused RAM.
1376 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1380 [KNL,SH] Allow user to override the default size for
1381 per-device physically contiguous DMA buffers.
1383 memmap=exactmap [KNL,X86] Enable setting of an exact
1384 E820 memory map, as specified by the user.
1385 Such memmap=exactmap lines can be constructed based on
1386 BIOS output or other requirements. See the memmap=nn@ss
1389 memmap=nn[KMG]@ss[KMG]
1390 [KNL] Force usage of a specific region of memory
1391 Region of memory to be used, from ss to ss+nn.
1393 memmap=nn[KMG]#ss[KMG]
1394 [KNL,ACPI] Mark specific memory as ACPI data.
1395 Region of memory to be used, from ss to ss+nn.
1397 memmap=nn[KMG]$ss[KMG]
1398 [KNL,ACPI] Mark specific memory as reserved.
1399 Region of memory to be used, from ss to ss+nn.
1400 Example: Exclude memory from 0x18690000-0x1869ffff
1401 memmap=64K$0x18690000
1403 memmap=0x10000$0x18690000
1405 memory_corruption_check=0/1 [X86]
1406 Some BIOSes seem to corrupt the first 64k of
1407 memory when doing things like suspend/resume.
1408 Setting this option will scan the memory
1409 looking for corruption. Enabling this will
1410 both detect corruption and prevent the kernel
1411 from using the memory being corrupted.
1412 However, its intended as a diagnostic tool; if
1413 repeatable BIOS-originated corruption always
1414 affects the same memory, you can use memmap=
1415 to prevent the kernel from using that memory.
1417 memory_corruption_check_size=size [X86]
1418 By default it checks for corruption in the low
1419 64k, making this memory unavailable for normal
1420 use. Use this parameter to scan for
1421 corruption in more or less memory.
1423 memory_corruption_check_period=seconds [X86]
1424 By default it checks for corruption every 60
1425 seconds. Use this parameter to check at some
1426 other rate. 0 disables periodic checking.
1428 memtest= [KNL,X86] Enable memtest
1430 default : 0 <disable>
1431 Specifies the number of memtest passes to be
1432 performed. Each pass selects another test
1433 pattern from a given set of patterns. Memtest
1434 fills the memory with this pattern, validates
1435 memory contents and reserves bad memory
1436 regions that are detected.
1438 meye.*= [HW] Set MotionEye Camera parameters
1439 See Documentation/video4linux/meye.txt.
1441 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1442 Multi-Function General Purpose Timers on AMD Geode
1445 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1446 the BIOS has incorrectly applied a workaround. TinyBIOS
1447 version 0.98 is known to be affected, 0.99 fixes the
1448 problem by letting the user disable the workaround.
1452 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1453 physical address is ignored.
1455 mini2440= [ARM,HW,KNL]
1456 Format:[0..2][b][c][t]
1458 MINI2440 configuration specification:
1459 0 - The attached screen is the 3.5" TFT
1460 1 - The attached screen is the 7" TFT
1461 2 - The VGA Shield is attached (1024x768)
1462 Leaving out the screen size parameter will not load
1463 the TFT driver, and the framebuffer will be left
1465 b - Enable backlight. The TFT backlight pin will be
1466 linked to the kernel VESA blanking code and a GPIO
1467 LED. This parameter is not necessary when using the
1469 c - Enable the s3c camera interface.
1470 t - Reserved for enabling touchscreen support. The
1471 touchscreen support is not enabled in the mainstream
1472 kernel as of 2.6.30, a preliminary port can be found
1473 in the "bleeding edge" mini2440 support kernel at
1474 http://repo.or.cz/w/linux-2.6/mini2440.git
1477 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1478 parameter allows control of the logging verbosity for
1479 the additional memory initialisation checks. A value
1480 of 0 disables mminit logging and a level of 4 will
1481 log everything. Information is printed at KERN_DEBUG
1482 so loglevel=8 may also need to be specified.
1485 [MOUSE] Maximum time between finger touching and
1486 leaving touchpad surface for touch to be considered
1487 a tap and be reported as a left button click (for
1488 touchpads working in absolute mode only).
1490 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1491 reporting absolute coordinates, such as tablets
1492 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1493 reporting absolute coordinates, such as tablets
1495 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1496 is similar to kernelcore except it specifies the
1497 amount of memory used for migratable allocations.
1498 If both kernelcore and movablecore is specified,
1499 then kernelcore will be at *least* the specified
1500 value but may be more. If movablecore on its own
1501 is specified, the administrator must be careful
1502 that the amount of memory usable for all allocations
1508 MTD_Partition= [MTD]
1509 Format: <name>,<region-number>,<size>,<offset>
1511 MTD_Region= [MTD] Format:
1512 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1515 See drivers/mtd/cmdlinepart.c.
1517 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1519 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1521 boundary - index of last SLC block on Flex-OneNAND.
1522 The remaining blocks are configured as MLC blocks.
1523 lock - Configure if Flex-OneNAND boundary should be locked.
1524 Once locked, the boundary cannot be changed.
1525 1 indicates lock status, 0 indicates unlock status.
1528 ARM/S3C2412 JIVE boot control
1530 See arch/arm/mach-s3c2412/mach-jive.c
1532 mtouchusb.raw_coordinates=
1533 [HW] Make the MicroTouch USB driver use raw coordinates
1534 ('y', default) or cooked coordinates ('n')
1536 mtrr_chunk_size=nn[KMG] [X86]
1537 used for mtrr cleanup. It is largest continuous chunk
1538 that could hold holes aka. UC entries.
1540 mtrr_gran_size=nn[KMG] [X86]
1541 Used for mtrr cleanup. It is granularity of mtrr block.
1543 Large value could prevent small alignment from
1546 mtrr_spare_reg_nr=n [X86]
1548 Range: 0,7 : spare reg number
1550 Used for mtrr cleanup. It is spare mtrr entries number.
1551 Set to 2 or more if your graphical card needs more.
1553 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1556 See header of drivers/scsi/NCR_D700.c.
1560 ncr53c400= [HW,SCSI]
1562 ncr53c400a= [HW,SCSI]
1564 ncr53c406a= [HW,SCSI]
1566 ncr53c8xx= [HW,SCSI]
1568 netdev= [NET] Network devices parameters
1569 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1570 Note that mem_start is often overloaded to mean
1571 something different and driver-specific.
1572 This usage is only documented in each driver source
1576 [NETFILTER] Enable connection tracking flow accounting
1577 0 to disable accounting
1578 1 to enable accounting
1579 Default value depends on CONFIG_NF_CT_ACCT that is
1580 going to be removed in 2.6.29.
1583 See Documentation/filesystems/nfs/nfsroot.txt.
1585 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1586 See Documentation/filesystems/nfs/nfsroot.txt.
1588 nfs.callback_tcpport=
1589 [NFS] set the TCP port on which the NFSv4 callback
1590 channel should listen.
1593 [NFS] sets the pathname to the program which is used
1594 to update the NFS client cache entries.
1596 nfs.cache_getent_timeout=
1597 [NFS] sets the timeout after which an attempt to
1598 update a cache entry is deemed to have failed.
1600 nfs.idmap_cache_timeout=
1601 [NFS] set the maximum lifetime for idmapper cache
1605 [NFS] enable 64-bit inode numbers.
1606 If zero, the NFS client will fake up a 32-bit inode
1607 number for the readdir() and stat() syscalls instead
1608 of returning the full 64-bit number.
1609 The default is to return 64-bit inode numbers.
1611 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1612 when a NMI is triggered.
1613 Format: [state][,regs][,debounce][,die]
1615 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1616 Format: [panic,][num]
1618 0 - turn nmi_watchdog off
1619 1 - use the IO-APIC timer for the NMI watchdog
1620 2 - use the local APIC for the NMI watchdog using
1621 a performance counter. Note: This will use one
1622 performance counter and the local APIC's performance
1624 When panic is specified, panic when an NMI watchdog
1626 This is useful when you use a panic=... timeout and
1627 need the box quickly up again.
1628 Instead of 1 and 2 it is possible to use the following
1629 symbolic names: lapic and ioapic
1630 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1632 netpoll.carrier_timeout=
1633 [NET] Specifies amount of time (in seconds) that
1634 netpoll should wait for a carrier. By default netpoll
1637 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1638 emulation library even if a 387 maths coprocessor
1642 [HW] Never suspend the console
1643 Disable suspending of consoles during suspend and
1644 hibernate operations. Once disabled, debugging
1645 messages can reach various consoles while the rest
1646 of the system is being put to sleep (ie, while
1647 debugging driver suspend/resume hooks). This may
1648 not work reliably with all consoles, but is known
1649 to work with serial and VGA consoles.
1651 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1652 caches in the slab allocator. Saves per-node memory,
1653 but will impact performance.
1657 noapic [SMP,APIC] Tells the kernel to not make use of any
1658 IOAPICs that may be present in the system.
1660 nobats [PPC] Do not use BATs for mapping kernel lowmem
1661 on "Classic" PPC cores.
1665 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1667 nodelayacct [KNL] Disable per-task delay accounting
1669 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1671 nodsp [SH] Disable hardware DSP at boot time.
1673 noefi [X86] Disable EFI runtime services support.
1678 On X86-32 available only on PAE configured kernels.
1679 noexec=on: enable non-executable mappings (default)
1680 noexec=off: disable non-executable mappings
1683 This affects only 32-bit executables.
1684 noexec32=on: enable non-executable mappings (default)
1685 read doesn't imply executable mappings
1686 noexec32=off: disable non-executable mappings
1687 read implies executable mappings
1689 nofpu [SH] Disable hardware FPU at boot time.
1691 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1692 register save and restore. The kernel will only save
1693 legacy floating-point registers on task switch.
1695 noxsave [BUGS=X86] Disables x86 extended register state save
1696 and restore using xsave. The kernel will fallback to
1697 enabling legacy floating-point and sse state.
1699 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1700 wfi(ARM) instruction doesn't work correctly and not to
1701 use it. This is also useful when using JTAG debugger.
1703 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1704 instruction doesn't work correctly and not to
1707 no_file_caps Tells the kernel not to honor file capabilities. The
1708 only way then for a file to be executed with privilege
1709 is to be setuid root or executed by root.
1711 nohalt [IA-64] Tells the kernel not to use the power saving
1712 function PAL_HALT_LIGHT when idle. This increases
1713 power-consumption. On the positive side, it reduces
1714 interrupt wake-up latency, which may improve performance
1715 in certain environments such as networked servers or
1718 nohz= [KNL] Boottime enable/disable dynamic ticks
1719 Valid arguments: on, off
1722 noiotrap [SH] Disables trapped I/O port accesses.
1724 noirqdebug [X86-32] Disables the code which attempts to detect and
1725 disable unhandled interrupt sources.
1727 no_timer_check [X86,APIC] Disables the code which tests for
1728 broken timer IRQ sources.
1730 noisapnp [ISAPNP] Disables ISA PnP code.
1732 noinitrd [RAM] Tells the kernel not to load any configured
1735 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1740 nojitter [IA64] Disables jitter checking for ITC timers.
1742 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1744 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1746 noltlbs [PPC] Do not use large page/tlb entries for kernel
1747 lowmem mapping on PPC40x.
1749 nomca [IA-64] Disable machine check abort handling
1751 nomce [X86-32] Machine Check Exception
1753 nomfgpt [X86-32] Disable Multi-Function General Purpose
1754 Timer usage (for AMD Geode machines).
1756 nopat [X86] Disable PAT (page attribute table extension of
1757 pagetables) support.
1759 norandmaps Don't use address space randomization. Equivalent to
1760 echo 0 > /proc/sys/kernel/randomize_va_space
1762 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1764 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1765 with UP alternatives
1767 noresidual [PPC] Don't use residual data on PReP machines.
1769 noresume [SWSUSP] Disables resume and restores original swap
1772 no-scroll [VGA] Disables scrollback.
1773 This is required for the Braillex ib80-piezo Braille
1774 reader made by F.H. Papenmeier (Germany).
1778 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1780 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1781 and disable the IO APIC. legacy for "maxcpus=0".
1783 nosoftlockup [KNL] Disable the soft-lockup detector.
1785 noswapaccount [KNL] Disable accounting of swap in memory resource
1786 controller. (See Documentation/cgroups/memory.txt)
1788 nosync [HW,M68K] Disables sync negotiation for all devices.
1790 notsc [BUGS=X86-32] Disable Time Stamp Counter
1792 nousb [USB] Disable the USB subsystem
1796 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1798 nptcg= [IA64] Override max number of concurrent global TLB
1799 purges which is reported from either PAL_VM_SUMMARY or
1802 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1803 could support. nr_cpus=n : n >= 1 limits the kernel to
1804 supporting 'n' processors. Later in runtime you can not
1805 use hotplug cpu feature to put more cpu back to online.
1806 just like you compile the kernel NR_CPUS=n
1808 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1810 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1811 one of ['zone', 'node', 'default'] can be specified
1812 This can be set from sysctl after boot.
1813 See Documentation/sysctl/vm.txt for details.
1815 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1816 See Documentation/debugging-via-ohci1394.txt for more
1819 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1820 Rather than timing out after 20 ms if an EC
1821 command is not properly ACKed, override the length
1822 of the timeout. We have interrupts disabled while
1823 waiting for the ACK, so if this is set too high
1824 interrupts *may* be lost!
1826 omap_mux= [OMAP] Override bootloader pin multiplexing.
1827 Format: <mux_mode0.mode_name=value>...
1828 For example, to override I2C bus2:
1829 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1834 oprofile.timer= [HW]
1835 Use timer interrupt instead of performance counters
1837 oprofile.cpu_type= Force an oprofile cpu type
1838 This might be useful if you have an older oprofile
1839 userland or if you want common events.
1840 Format: { arch_perfmon }
1841 arch_perfmon: [X86] Force use of architectural
1842 perfmon on Intel CPUs instead of the
1843 CPU specific event set.
1845 osst= [HW,SCSI] SCSI Tape Driver
1846 Format: <buffer_size>,<write_threshold>
1847 See also Documentation/scsi/st.txt.
1849 panic= [KNL] Kernel behaviour on panic
1852 parkbd.port= [HW] Parallel port number the keyboard adapter is
1853 connected to, default is 0.
1855 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1856 0 for XT, 1 for AT (default is AT).
1859 parport= [HW,PPT] Specify parallel ports. 0 disables.
1860 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1861 Use 'auto' to force the driver to use any
1862 IRQ/DMA settings detected (the default is to
1863 ignore detected IRQ/DMA settings because of
1864 possible conflicts). You can specify the base
1865 address, IRQ, and DMA settings; IRQ and DMA
1866 should be numbers, or 'auto' (for using detected
1867 settings on that particular port), or 'nofifo'
1868 (to avoid using a FIFO even if it is detected).
1869 Parallel ports are assigned in the order they
1870 are specified on the command line, starting
1873 parport_init_mode= [HW,PPT]
1874 Configure VIA parallel port to operate in
1875 a specific mode. This is necessary on Pegasos
1876 computer where firmware has no options for setting
1877 up parallel port mode and sets it to spp.
1878 Currently this function knows 686a and 8231 chips.
1879 Format: [spp|ps2|epp|ecp|ecpepp]
1881 pas2= [HW,OSS] Format:
1882 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1885 See header of drivers/scsi/pas16.c.
1888 Halt all CPUs after the first oops has been printed for
1889 the specified number of seconds. This is to be used if
1890 your oopses keep scrolling off the screen.
1895 See header of drivers/block/paride/pcd.c.
1896 See also Documentation/blockdev/paride.txt.
1898 pci=option[,option...] [PCI] various PCI subsystem options:
1899 earlydump [X86] dump PCI config space before the kernel
1901 off [X86] don't probe for the PCI bus
1902 bios [X86-32] force use of PCI BIOS, don't access
1903 the hardware directly. Use this if your machine
1904 has a non-standard PCI host bridge.
1905 nobios [X86-32] disallow use of PCI BIOS, only direct
1906 hardware access methods are allowed. Use this
1907 if you experience crashes upon bootup and you
1908 suspect they are caused by the BIOS.
1909 conf1 [X86] Force use of PCI Configuration
1911 conf2 [X86] Force use of PCI Configuration
1913 noaer [PCIE] If the PCIEAER kernel config parameter is
1914 enabled, this kernel boot option can be used to
1915 disable the use of PCIE advanced error reporting.
1916 nodomains [PCI] Disable support for multiple PCI
1917 root domains (aka PCI segments, in ACPI-speak).
1918 nommconf [X86] Disable use of MMCONFIG for PCI
1920 check_enable_amd_mmconf [X86] check for and enable
1921 properly configured MMIO access to PCI
1922 config space on AMD family 10h CPU
1923 nomsi [MSI] If the PCI_MSI kernel config parameter is
1924 enabled, this kernel boot option can be used to
1925 disable the use of MSI interrupts system-wide.
1926 noioapicquirk [APIC] Disable all boot interrupt quirks.
1927 Safety option to keep boot IRQs enabled. This
1928 should never be necessary.
1929 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1930 primary IO-APIC for bridges that cannot disable
1931 boot IRQs. This fixes a source of spurious IRQs
1932 when the system masks IRQs.
1933 noioapicreroute [APIC] Disable workaround that uses the
1934 boot IRQ equivalent of an IRQ that connects to
1935 a chipset where boot IRQs cannot be disabled.
1936 The opposite of ioapicreroute.
1937 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1938 routing table. These calls are known to be buggy
1939 on several machines and they hang the machine
1940 when used, but on other computers it's the only
1941 way to get the interrupt routing table. Try
1942 this option if the kernel is unable to allocate
1943 IRQs or discover secondary PCI buses on your
1945 rom [X86] Assign address space to expansion ROMs.
1946 Use with caution as certain devices share
1947 address decoders between ROMs and other
1949 norom [X86] Do not assign address space to
1950 expansion ROMs that do not already have
1951 BIOS assigned address ranges.
1952 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1953 assigned automatically to PCI devices. You can
1954 make the kernel exclude IRQs of your ISA cards
1956 pirqaddr=0xAAAAA [X86] Specify the physical address
1957 of the PIRQ table (normally generated
1958 by the BIOS) if it is outside the
1959 F0000h-100000h range.
1960 lastbus=N [X86] Scan all buses thru bus #N. Can be
1961 useful if the kernel is unable to find your
1962 secondary buses and you want to tell it
1963 explicitly which ones they are.
1964 assign-busses [X86] Always assign all PCI bus
1965 numbers ourselves, overriding
1966 whatever the firmware may have done.
1967 usepirqmask [X86] Honor the possible IRQ mask stored
1968 in the BIOS $PIR table. This is needed on
1969 some systems with broken BIOSes, notably
1970 some HP Pavilion N5400 and Omnibook XE3
1971 notebooks. This will have no effect if ACPI
1972 IRQ routing is enabled.
1973 noacpi [X86] Do not use ACPI for IRQ routing
1974 or for PCI scanning.
1975 use_crs [X86] Use PCI host bridge window information
1976 from ACPI. On BIOSes from 2008 or later, this
1977 is enabled by default. If you need to use this,
1978 please report a bug.
1979 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1980 If you need to use this, please report a bug.
1981 routeirq Do IRQ routing for all PCI devices.
1982 This is normally done in pci_enable_device(),
1983 so this option is a temporary workaround
1984 for broken drivers that don't call it.
1985 skip_isa_align [X86] do not align io start addr, so can
1986 handle more pci cards
1987 firmware [ARM] Do not re-enumerate the bus but instead
1988 just use the configuration from the
1989 bootloader. This is currently used on
1990 IXP2000 systems where the bus has to be
1991 configured a certain way for adjunct CPUs.
1992 noearly [X86] Don't do any early type 1 scanning.
1993 This might help on some broken boards which
1994 machine check when some devices' config space
1995 is read. But various workarounds are disabled
1996 and some IOMMU drivers will not work.
1997 bfsort Sort PCI devices into breadth-first order.
1998 This sorting is done to get a device
1999 order compatible with older (<= 2.4) kernels.
2000 nobfsort Don't sort PCI devices into breadth-first order.
2001 cbiosize=nn[KMG] The fixed amount of bus space which is
2002 reserved for the CardBus bridge's IO window.
2003 The default value is 256 bytes.
2004 cbmemsize=nn[KMG] The fixed amount of bus space which is
2005 reserved for the CardBus bridge's memory
2006 window. The default value is 64 megabytes.
2009 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2010 Specifies alignment and device to reassign
2011 aligned memory resources.
2012 If <order of align> is not specified,
2013 PAGE_SIZE is used as alignment.
2014 PCI-PCI bridge can be specified, if resource
2015 windows need to be expanded.
2016 ecrc= Enable/disable PCIe ECRC (transaction layer
2017 end-to-end CRC checking).
2018 bios: Use BIOS/firmware settings. This is the
2023 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2026 force Enable ASPM even on devices that claim not to support it.
2027 WARNING: Forcing ASPM on may cause system lockups.
2029 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2030 off Do not use native PCIe PME signaling.
2031 force Use native PCIe PME signaling even if the BIOS refuses
2032 to allow the kernel to control the relevant PCIe config
2034 nomsi Do not use MSI for native PCIe PME signaling (this makes
2035 all PCIe root ports use INTx for everything).
2037 pcmv= [HW,PCMCIA] BadgePAD 4
2040 See Documentation/blockdev/paride.txt.
2042 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2045 See arch/parisc/kernel/pdc_chassis.c
2047 percpu_alloc= Select which percpu first chunk allocator to use.
2048 Currently supported values are "embed" and "page".
2049 Archs may support subset or none of the selections.
2050 See comments in mm/percpu.c for details on each
2051 allocator. This parameter is primarily for debugging
2052 and performance comparison.
2055 See Documentation/blockdev/paride.txt.
2058 See Documentation/blockdev/paride.txt.
2060 pirq= [SMP,APIC] Manual mp-table setup
2061 See Documentation/x86/i386/IO-APIC.txt.
2063 plip= [PPT,NET] Parallel port network link
2064 Format: { parport<nr> | timid | 0 }
2065 See also Documentation/parport.txt.
2067 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2068 Override pmtimer IOPort with a hex value.
2072 Enable PNP debug messages. This depends on the
2073 CONFIG_PNP_DEBUG_MESSAGES option.
2079 { on | off | curr | res | no-curr | no-res }
2082 [ISAPNP] Exclude IRQs for the autoconfiguration
2085 [ISAPNP] Exclude DMAs for the autoconfiguration
2087 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2088 Ranges are in pairs (I/O port base and size).
2091 [ISAPNP] Exclude memory regions for the
2093 Ranges are in pairs (memory base and size).
2095 ports= [IP_VS_FTP] IPVS ftp helper module
2097 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2099 Format: <port>,<port>....
2101 print-fatal-signals=
2102 [KNL] debug: print fatal signals
2104 If enabled, warn about various signal handling
2105 related application anomalies: too many signals,
2106 too many POSIX.1 timers, fatal signals causing a
2109 If you hit the warning due to signal overflow,
2110 you might want to try "ulimit -i unlimited".
2114 printk.time= Show timing data prefixed to each printk message line
2115 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2117 processor.max_cstate= [HW,ACPI]
2118 Limit processor to maximum C-state
2119 max_cstate=9 overrides any DMI blacklist limit.
2121 processor.nocst [HW,ACPI]
2122 Ignore the _CST method to determine C-states,
2123 instead using the legacy FADT method
2125 profile= [KNL] Enable kernel profiling via /proc/profile
2126 Format: [schedule,]<number>
2127 Param: "schedule" - profile schedule points.
2128 Param: <number> - step/bucket size as a power of 2 for
2129 statistical time based profiling.
2130 Param: "sleep" - profile D-state sleeping (millisecs).
2131 Requires CONFIG_SCHEDSTATS
2132 Param: "kvm" - profile VM exits.
2134 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2136 See Documentation/blockdev/ramdisk.txt.
2138 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2139 probe for; one of (bare|imps|exps|lifebook|any).
2140 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2142 psmouse.resetafter= [HW,MOUSE]
2143 Try to reset the device after so many bad packets
2146 [HW,MOUSE] Set desired mouse resolution, in dpi.
2147 psmouse.smartscroll=
2148 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2149 0 = disabled, 1 = enabled (default).
2151 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2153 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2156 See Documentation/blockdev/paride.txt.
2159 [KNL] Number of legacy pty's. Overwrites compiled-in
2162 quiet [KNL] Disable most log messages
2167 See Documentation/md.txt.
2169 ramdisk_blocksize= [RAM]
2170 See Documentation/blockdev/ramdisk.txt.
2172 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2173 See Documentation/blockdev/ramdisk.txt.
2175 rcupdate.blimit= [KNL,BOOT]
2176 Set maximum number of finished RCU callbacks to process
2179 rcupdate.qhimark= [KNL,BOOT]
2180 Set threshold of queued
2181 RCU callbacks over which batch limiting is disabled.
2183 rcupdate.qlowmark= [KNL,BOOT]
2184 Set threshold of queued RCU callbacks below which
2185 batch limiting is re-enabled.
2189 Run specified binary instead of /init from the ramdisk,
2190 used for early userspace startup. See initrd.
2192 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2193 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2194 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2197 [KNL, SMP] Set scheduler's default relax_domain_level.
2198 See Documentation/cgroups/cpusets.txt.
2200 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2202 reservetop= [X86-32]
2204 Reserves a hole at the top of the kernel virtual
2207 reset_devices [KNL] Force drivers to reset the underlying device
2208 during initialization.
2211 Specify the partition device for software suspend
2213 resume_offset= [SWSUSP]
2214 Specify the offset from the beginning of the partition
2215 given by "resume=" at which the swap header is located,
2216 in <PAGE_SIZE> units (needed only for swap files).
2217 See Documentation/power/swsusp-and-swap-files.txt
2219 retain_initrd [RAM] Keep initrd memory after extraction
2221 rhash_entries= [KNL,NET]
2222 Set number of hash buckets for route cache
2224 riscom8= [HW,SERIAL]
2225 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2227 ro [KNL] Mount root device read-only on boot
2229 root= [KNL] Root filesystem
2231 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2232 mount the root filesystem
2234 rootflags= [KNL] Set root filesystem mount option string
2236 rootfstype= [KNL] Set root filesystem type
2238 rootwait [KNL] Wait (indefinitely) for root device to show up.
2239 Useful for devices that are detected asynchronously
2240 (e.g. USB and MMC devices).
2242 rw [KNL] Mount root device read-write on boot
2244 S [KNL] Run init in single mode
2247 See drivers/net/irda/sa1100_ir.c.
2249 sbni= [NET] Granch SBNI12 leased line adapter
2251 sched_debug [KNL] Enables verbose scheduler debug messages.
2253 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2254 Format: <io>[,<timeout>[,<isapnp>]]
2256 scsi_debug_*= [SCSI]
2257 See drivers/scsi/scsi_debug.c.
2259 scsi_default_dev_flags=
2260 [SCSI] SCSI default device flags
2263 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2264 Format: <vendor>:<model>:<flags>
2265 (flags are integer value)
2267 scsi_logging_level= [SCSI] a bit mask of logging levels
2268 See drivers/scsi/scsi_logging.h for bits. Also
2269 settable via sysctl at dev.scsi.logging_level
2270 (/proc/sys/dev/scsi/logging_level).
2271 There is also a nice 'scsi_logging_level' script in the
2272 S390-tools package, available for download at
2273 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2275 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2276 discovered. async scans them in kernel threads,
2277 allowing boot to proceed. none ignores them, expecting
2278 user space to do the scan.
2280 security= [SECURITY] Choose a security module to enable at boot.
2281 If this boot parameter is not specified, only the first
2282 security module asking for security registration will be
2283 loaded. An invalid security module name will be treated
2284 as if no module has been chosen.
2286 selinux= [SELINUX] Disable or enable SELinux at boot time.
2287 Format: { "0" | "1" }
2288 See security/selinux/Kconfig help text.
2291 Default value is set via kernel config option.
2292 If enabled at boot time, /selinux/disable can be used
2293 later to disable prior to initial policy load.
2295 serialnumber [BUGS=X86-32]
2298 Maximal number of shapers.
2300 show_msr= [x86] show boot-time MSR settings
2301 Format: { <integer> }
2302 Show boot-time (BIOS-initialized) MSR settings.
2303 The parameter means the number of CPUs to show,
2304 for example 1 means boot CPU only.
2307 See header of drivers/scsi/sim710.c.
2314 slub_debug[=options[,slabs]] [MM, SLUB]
2315 Enabling slub_debug allows one to determine the
2316 culprit if slab objects become corrupted. Enabling
2317 slub_debug can create guard zones around objects and
2318 may poison objects when not in use. Also tracks the
2319 last alloc / free. For more information see
2320 Documentation/vm/slub.txt.
2322 slub_max_order= [MM, SLUB]
2323 Determines the maximum allowed order for slabs.
2324 A high setting may cause OOMs due to memory
2325 fragmentation. For more information see
2326 Documentation/vm/slub.txt.
2328 slub_min_objects= [MM, SLUB]
2329 The minimum number of objects per slab. SLUB will
2330 increase the slab order up to slub_max_order to
2331 generate a sufficiently large slab able to contain
2332 the number of objects indicated. The higher the number
2333 of objects the smaller the overhead of tracking slabs
2334 and the less frequently locks need to be acquired.
2335 For more information see Documentation/vm/slub.txt.
2337 slub_min_order= [MM, SLUB]
2338 Determines the mininum page order for slabs. Must be
2339 lower than slub_max_order.
2340 For more information see Documentation/vm/slub.txt.
2342 slub_nomerge [MM, SLUB]
2343 Disable merging of slabs with similar size. May be
2344 necessary if there is some reason to distinguish
2345 allocs to different slabs. Debug options disable
2346 merging on their own.
2347 For more information see Documentation/vm/slub.txt.
2350 Format: <io1>[,<io2>[,...,<io8>]]
2352 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2353 attempt to substitute SMP alternatives once at boot.
2355 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2356 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2357 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2358 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2359 smsc-ircc2.ircc_irq= [HW] IRQ line
2360 smsc-ircc2.ircc_dma= [HW] DMA channel
2361 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2362 0: Toshiba Satellite 1800 (GP data pin select)
2363 1: Fast pin select (default)
2366 snd-ad1816a= [HW,ALSA]
2368 snd-ad1848= [HW,ALSA]
2370 snd-ali5451= [HW,ALSA]
2372 snd-als100= [HW,ALSA]
2374 snd-als4000= [HW,ALSA]
2376 snd-azt2320= [HW,ALSA]
2378 snd-cmi8330= [HW,ALSA]
2380 snd-cmipci= [HW,ALSA]
2382 snd-cs4231= [HW,ALSA]
2384 snd-cs4232= [HW,ALSA]
2386 snd-cs4236= [HW,ALSA]
2388 snd-cs4281= [HW,ALSA]
2390 snd-cs46xx= [HW,ALSA]
2392 snd-dt019x= [HW,ALSA]
2394 snd-dummy= [HW,ALSA]
2396 snd-emu10k1= [HW,ALSA]
2398 snd-ens1370= [HW,ALSA]
2400 snd-ens1371= [HW,ALSA]
2402 snd-es968= [HW,ALSA]
2404 snd-es1688= [HW,ALSA]
2406 snd-es18xx= [HW,ALSA]
2408 snd-es1938= [HW,ALSA]
2410 snd-es1968= [HW,ALSA]
2412 snd-fm801= [HW,ALSA]
2414 snd-gusclassic= [HW,ALSA]
2416 snd-gusextreme= [HW,ALSA]
2418 snd-gusmax= [HW,ALSA]
2422 snd-ice1712= [HW,ALSA]
2424 snd-intel8x0= [HW,ALSA]
2426 snd-interwave= [HW,ALSA]
2431 snd-korg1212= [HW,ALSA]
2433 snd-maestro3= [HW,ALSA]
2435 snd-mpu401= [HW,ALSA]
2437 snd-mtpav= [HW,ALSA]
2439 snd-nm256= [HW,ALSA]
2441 snd-opl3sa2= [HW,ALSA]
2449 snd-opti93x= [HW,ALSA]
2453 snd-rme32= [HW,ALSA]
2455 snd-rme96= [HW,ALSA]
2457 snd-rme9652= [HW,ALSA]
2463 snd-sbawe= [HW,ALSA]
2465 snd-serial= [HW,ALSA]
2467 snd-sgalaxy= [HW,ALSA]
2469 snd-sonicvibes= [HW,ALSA]
2474 snd-sun-cs4231= [HW,ALSA]
2476 snd-trident= [HW,ALSA]
2478 snd-usb-audio= [HW,ALSA,USB]
2480 snd-via82xx= [HW,ALSA]
2482 snd-virmidi= [HW,ALSA]
2484 snd-wavefront= [HW,ALSA]
2486 snd-ymfpci= [HW,ALSA]
2489 [KNL] Should the soft-lockup detector generate panics.
2491 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2492 See Documentation/sonypi.txt
2494 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2495 See Documentation/serial/specialix.txt.
2497 spia_io_base= [HW,MTD]
2503 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2505 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2506 See Documentation/scsi/st.txt.
2509 Enabled the stack tracer on boot up.
2513 Set the STI (builtin display/keyboard on the HP-PARISC
2514 machines) console (graphic card) which should be used
2515 as the initial boot-console.
2516 See also comment in drivers/video/console/sticore.c.
2519 See comment in drivers/video/console/sticore.c.
2522 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2524 sunrpc.min_resvport=
2525 sunrpc.max_resvport=
2527 SunRPC servers often require that client requests
2528 originate from a privileged port (i.e. a port in the
2529 range 0 < portnr < 1024).
2530 An administrator who wishes to reserve some of these
2531 ports for other uses may adjust the range that the
2532 kernel's sunrpc client considers to be privileged
2533 using these two parameters to set the minimum and
2534 maximum port values.
2538 Control how the NFS server code allocates CPUs to
2539 service thread pools. Depending on how many NICs
2540 you have and where their interrupts are bound, this
2541 option will affect which CPUs will do NFS serving.
2542 Note: this parameter cannot be changed while the
2543 NFS server is running.
2545 auto the server chooses an appropriate mode
2546 automatically using heuristics
2547 global a single global pool contains all CPUs
2548 percpu one pool for each CPU
2549 pernode one pool for each NUMA node (equivalent
2550 to global on non-NUMA machines)
2552 sunrpc.tcp_slot_table_entries=
2553 sunrpc.udp_slot_table_entries=
2555 Sets the upper limit on the number of simultaneous
2556 RPC calls that can be sent from the client to a
2557 server. Increasing these values may allow you to
2558 improve throughput, but will also increase the
2559 amount of memory reserved for use by the client.
2561 swiotlb= [IA-64] Number of I/O TLB slabs
2565 sym53c416= [HW,SCSI]
2566 See header of drivers/scsi/sym53c416.c.
2568 sysrq_always_enabled
2570 Ignore sysrq setting - this boot parameter will
2571 neutralize any effect of /proc/sys/kernel/sysrq.
2572 Useful for debugging.
2575 See header of drivers/scsi/t128.c.
2579 test_suspend= [SUSPEND]
2580 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2581 standby suspend) as the system sleep state to briefly
2582 enter during system startup. The system is woken from
2583 this state using a wakeup-capable RTC alarm.
2585 thash_entries= [KNL,NET]
2586 Set number of hash buckets for TCP connection
2588 thermal.act= [HW,ACPI]
2589 -1: disable all active trip points in all thermal zones
2590 <degrees C>: override all lowest active trip points
2592 thermal.crt= [HW,ACPI]
2593 -1: disable all critical trip points in all thermal zones
2594 <degrees C>: override all critical trip points
2596 thermal.nocrt= [HW,ACPI]
2597 Set to disable actions on ACPI thermal zone
2598 critical and hot trip points.
2600 thermal.off= [HW,ACPI]
2601 1: disable ACPI thermal control
2603 thermal.psv= [HW,ACPI]
2604 -1: disable all passive trip points
2605 <degrees C>: override all passive trip points to this
2608 thermal.tzp= [HW,ACPI]
2609 Specify global default ACPI thermal zone polling rate
2610 <deci-seconds>: poll all this frequency
2611 0: no polling (default)
2614 See comment before function dc390_setup() in
2615 drivers/scsi/tmscsim.c.
2619 Specify if the kernel should make use of the cpu
2620 topology informations if the hardware supports these.
2621 The scheduler will make use of these informations and
2622 e.g. base its process migration decisions on it.
2627 tpm_suspend_pcr=[HW,TPM]
2628 Format: integer pcr id
2629 Specify that at suspend time, the tpm driver
2630 should extend the specified pcr with zeros,
2631 as a workaround for some chips which fail to
2632 flush the last written pcr on TPM_SaveState.
2633 This will guarantee that all the other pcrs
2636 trace_buf_size=nn[KMG]
2637 [FTRACE] will set tracing buffer size.
2639 trace_event=[event-list]
2640 [FTRACE] Set and start specified trace events in order
2641 to facilitate early boot debugging.
2642 See also Documentation/trace/events.txt
2644 trix= [HW,OSS] MediaTrix AudioTrix Pro
2646 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2648 tsc= Disable clocksource-must-verify flag for TSC.
2650 [x86] reliable: mark tsc clocksource as reliable, this
2651 disables clocksource verification at runtime.
2652 Used to enable high-resolution timer mode on older
2653 hardware, and in virtualized environment.
2655 turbografx.map[2|3]= [HW,JOY]
2656 TurboGraFX parallel port interface
2658 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2659 See also Documentation/input/joystick-parport.txt
2661 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2662 See header of drivers/scsi/u14-34f.c.
2670 uhash_entries= [KNL,NET]
2671 Set number of hash buckets for UDP/UDP-Lite connections
2674 [USB] Ignore overcurrent events (default N).
2675 Some badly-designed motherboards generate lots of
2676 bogus events, for ports that aren't wired to
2677 anything. Set this parameter to avoid log spamming.
2678 Note that genuine overcurrent events won't be
2683 Set unknown_nmi_panic=1 early on boot.
2685 usbcore.autosuspend=
2686 [USB] The autosuspend time delay (in seconds) used
2687 for newly-detected USB devices (default 2). This
2688 is the time required before an idle device will be
2689 autosuspended. Devices for which the delay is set
2690 to a negative value won't be autosuspended at all.
2692 usbcore.usbfs_snoop=
2693 [USB] Set to log all usbfs traffic (default 0 = off).
2695 usbcore.blinkenlights=
2696 [USB] Set to cycle leds on hubs (default 0 = off).
2698 usbcore.old_scheme_first=
2699 [USB] Start with the old device initialization
2700 scheme (default 0 = off).
2702 usbcore.use_both_schemes=
2703 [USB] Try the other device initialization scheme
2704 if the first one fails (default 1 = enabled).
2706 usbcore.initial_descriptor_timeout=
2707 [USB] Specifies timeout for the initial 64-byte
2708 USB_REQ_GET_DESCRIPTOR request in milliseconds
2709 (default 5000 = 5.0 seconds).
2712 [USBHID] The interval which mice are to be polled at.
2714 usb-storage.delay_use=
2715 [UMS] The delay in seconds before a new device is
2716 scanned for Logical Units (default 5).
2719 [UMS] A list of quirks entries to supplement or
2720 override the built-in unusual_devs list. List
2721 entries are separated by commas. Each entry has
2722 the form VID:PID:Flags where VID and PID are Vendor
2723 and Product ID values (4-digit hex numbers) and
2724 Flags is a set of characters, each corresponding
2725 to a common usb-storage quirk flag as follows:
2726 a = SANE_SENSE (collect more than 18 bytes
2728 b = BAD_SENSE (don't collect more than 18
2729 bytes of sense data);
2730 c = FIX_CAPACITY (decrease the reported
2731 device capacity by one sector);
2732 h = CAPACITY_HEURISTICS (decrease the
2733 reported device capacity by one
2734 sector if the number is odd);
2735 i = IGNORE_DEVICE (don't bind to this
2737 l = NOT_LOCKABLE (don't try to lock and
2738 unlock ejectable media);
2739 m = MAX_SECTORS_64 (don't transfer more
2740 than 64 sectors = 32 KB at a time);
2741 o = CAPACITY_OK (accept the capacity
2742 reported by the device);
2743 r = IGNORE_RESIDUE (the device reports
2744 bogus residue values);
2745 s = SINGLE_LUN (the device has only one
2747 w = NO_WP_DETECT (don't test whether the
2748 medium is write-protected).
2749 Example: quirks=0419:aaf5:rl,0421:0433:rc
2752 [X86] Flags controlling user PTE allocations.
2754 nohigh = do not allocate PTE pages in
2755 HIGHMEM regardless of setting
2759 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2760 vdso=1: enable VDSO (default)
2761 vdso=0: disable VDSO mapping
2764 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2765 vdso32=1: enable 32-bit VDSO (default)
2766 vdso32=0: disable 32-bit VDSO mapping
2769 vector=percpu: enable percpu vector domain
2771 video= [FB] Frame buffer configuration
2772 See Documentation/fb/modedb.txt.
2774 vga= [BOOT,X86-32] Select a particular video mode
2775 See Documentation/x86/boot.txt and
2776 Documentation/svga.txt.
2777 Use vga=ask for menu.
2778 This is actually a boot loader parameter; the value is
2779 passed to the kernel using a special protocol.
2781 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2782 size of <nn>. This can be used to increase the
2783 minimum size (128MB on x86). It can also be used to
2784 decrease the size and leave more room for directly
2787 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2790 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2793 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2796 vt.cur_default= [VT] Default cursor shape.
2797 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2798 the parameters of the <Esc>[?A;B;Cc escape sequence;
2799 see VGA-softcursor.txt. Default: 2 = underline.
2801 vt.default_blu= [VT]
2802 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2803 Change the default blue palette of the console.
2804 This is a 16-member array composed of values
2807 vt.default_grn= [VT]
2808 Format: <green0>,<green1>,<green2>,...,<green15>
2809 Change the default green palette of the console.
2810 This is a 16-member array composed of values
2813 vt.default_red= [VT]
2814 Format: <red0>,<red1>,<red2>,...,<red15>
2815 Change the default red palette of the console.
2816 This is a 16-member array composed of values
2822 Set system-wide default UTF-8 mode for all tty's.
2823 Default is 1, i.e. UTF-8 mode is enabled for all
2824 newly opened terminals.
2826 vt.global_cursor_default=
2829 Set system-wide default for whether a cursor
2830 is shown on new VTs. Default is -1,
2831 i.e. cursors will be created by default unless
2832 overridden by individual drivers. 0 will hide
2833 cursors, 1 will display them.
2835 waveartist= [HW,OSS]
2836 Format: <io>,<irq>,<dma>,<dma2>
2839 See header of drivers/scsi/wd33c93.c.
2842 See header of drivers/scsi/wd7000.c.
2845 See Documentation/watchdog/wdt.txt.
2847 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2848 default x2apic cluster mode on platforms
2851 x86_mrst_timer= [X86-32,APBT]
2852 Choose timer option for x86 Moorestown MID platform.
2853 Two valid options are apbt timer only and lapic timer
2854 plus one apbt timer for broadcast timer.
2855 x86_mrst_timer=apbt_only | lapic_and_apbt
2857 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2858 xd_geo= See header of drivers/block/xd.c.
2860 xirc2ps_cs= [NET,PCMCIA]
2862 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2864 ______________________________________________________________________
2868 Add documentation for ALSA options.
2869 Add more DRM drivers.
projects / linux.git / blob