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
716 ekgdboc= [X86,KGDB] Allow early kernel console debugging
719 This is desgined to be used in conjunction with
720 the boot argument: earlyprintk=vga
725 Format: {"off" | "on" | "skip[mbr]"}
727 eisa_irq_edge= [PARISC,HW]
728 See header of drivers/parisc/eisa.c.
731 See comment before function elanfreq_setup() in
732 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
735 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
736 See Documentation/block/as-iosched.txt and
737 Documentation/block/deadline-iosched.txt for details.
739 elfcorehdr= [IA64,PPC,SH,X86]
740 Specifies physical address of start of kernel core
741 image elf header. Generally kexec loader will
742 pass this option to capture kernel.
743 See Documentation/kdump/kdump.txt for details.
745 enable_mtrr_cleanup [X86]
746 The kernel tries to adjust MTRR layout from continuous
747 to discrete, to make X server driver able to add WB
748 entry later. This parameter enables that.
750 enable_timer_pin_1 [X86]
751 Enable PIN 1 of APIC timer
752 Can be useful to work around chipset bugs
753 (in particular on some ATI chipsets).
754 The kernel tries to set a reasonable default.
756 enforcing [SELINUX] Set initial enforcing status.
758 See security/selinux/Kconfig help text.
759 0 -- permissive (log only, no denials).
760 1 -- enforcing (deny and log).
762 Value can be changed at runtime via /selinux/enforce.
764 ether= [HW,NET] Ethernet cards parameters
765 This option is obsoleted by the "netdev=" option, which
766 has equivalent usage. See its documentation for details.
768 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
773 fail_make_request=[KNL]
774 General fault injection mechanism.
775 Format: <interval>,<probability>,<space>,<times>
776 See also /Documentation/fault-injection/.
779 See header of drivers/scsi/fd_mcs.c.
782 See header of drivers/scsi/fdomain.c.
785 See Documentation/blockdev/floppy.txt.
787 force_pal_cache_flush
788 [IA-64] Avoid check_sal_cache_flush which may hang on
789 buggy SAL_CACHE_FLUSH implementations. Using this
790 parameter will force ia64_sal_cache_flush to call
791 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
794 [FTRACE] will set and start the specified tracer
795 as early as possible in order to facilitate early
798 ftrace_dump_on_oops[=orig_cpu]
799 [FTRACE] will dump the trace buffers on oops.
800 If no parameter is passed, ftrace will dump
801 buffers of all CPUs, but if you pass orig_cpu, it will
802 dump only the buffer of the CPU that triggered the
805 ftrace_filter=[function-list]
806 [FTRACE] Limit the functions traced by the function
807 tracer at boot up. function-list is a comma separated
808 list of functions. This list can be changed at run
809 time by the set_ftrace_filter file in the debugfs
812 ftrace_notrace=[function-list]
813 [FTRACE] Do not trace the functions specified in
814 function-list. This list can be changed at run time
815 by the set_ftrace_notrace file in the debugfs
818 ftrace_graph_filter=[function-list]
819 [FTRACE] Limit the top level callers functions traced
820 by the function graph tracer at boot up.
821 function-list is a comma separated list of functions
822 that can be changed at run time by the
823 set_graph_function file in the debugfs tracing directory.
826 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
827 support via parallel port (up to 5 devices per port)
828 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
829 See also Documentation/input/joystick-parport.txt
833 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
837 gcov_persist= [GCOV] When non-zero (default), profiling data for
838 kernel modules is saved and remains accessible via
839 debugfs, even when the module is unloaded/reloaded.
840 When zero, profiling data is discarded and associated
841 debugfs files are removed at module unload time.
844 See header of drivers/scsi/gdth.c.
846 gpt [EFI] Forces disk with valid GPT signature but
847 invalid Protective MBR to be treated as GPT.
851 hashdist= [KNL,NUMA] Large hashes allocated during boot
852 are distributed across NUMA nodes. Defaults on
853 for 64bit NUMA, off otherwise.
854 Format: 0 | 1 (for off | on)
856 hcl= [IA-64] SGI's Hardware Graph compatibility layer
858 hd= [EIDE] (E)IDE hard drive subsystem geometry
859 Format: <cyl>,<head>,<sect>
861 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
862 size of <nn>. This works even on boxes that have no
863 highmem otherwise. This also works to reduce highmem
864 size on bigger boxes.
866 highres= [KNL] Enable/disable high resolution timer mode.
867 Valid parameters: "on", "off"
871 See Documentation/isdn/README.HiSax.
875 hpet= [X86-32,HPET] option to control HPET usage
876 Format: { enable (default) | disable | force |
878 disable: disable HPET and use PIT instead
879 force: allow force enabled of undocumented chips (ICH4,
881 verbose: show contents of HPET registers during setup
883 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
884 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
885 On x86-64 and powerpc, this option can be specified
886 multiple times interleaved with hugepages= to reserve
887 huge pages of different sizes. Valid pages sizes on
888 x86-64 are 2M (when the CPU supports "pse") and 1G
889 (when the CPU supports the "pdpe1gb" cpuinfo flag)
890 Note that 1GB pages can only be allocated at boot time
891 using hugepages= and not freed afterwards.
893 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
894 terminal devices. Valid values: 0..8
895 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
896 If specified, z/VM IUCV HVC accepts connections
897 from listed z/VM user IDs only.
899 i2c_bus= [HW] Override the default board specific I2C bus speed
900 or register an additional I2C bus that is not
901 registered from board initialization code.
905 i8042.debug [HW] Toggle i8042 debug mode
906 i8042.direct [HW] Put keyboard port into non-translated mode
907 i8042.dumbkbd [HW] Pretend that controller can only read data from
908 keyboard and cannot control its state
909 (Don't attempt to blink the leds)
910 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
911 i8042.nokbd [HW] Don't check/create keyboard port
912 i8042.noloop [HW] Disable the AUX Loopback command while probing
914 i8042.nomux [HW] Don't check presence of an active multiplexing
916 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
919 [HW] Frequency with which keyboard LEDs should blink
920 when kernel panics (default is 0.5 sec)
921 i8042.reset [HW] Reset the controller during init and cleanup
922 i8042.unlock [HW] Unlock (ignore) the keylock
926 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
927 indicates that the driver is running on unsupported
929 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
930 does not match list of supported models.
932 [HW] Report power status in /proc/i8k
933 (disabled by default)
934 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
937 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
938 See Documentation/mca.txt.
941 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
943 ide-core.nodma= [HW] (E)IDE subsystem
944 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
945 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
946 .cdrom .chs .ignore_cable are additional options
947 See Documentation/ide/ide.txt.
949 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
950 Claim all unknown PCI IDE storage controllers.
953 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
954 Poll forces a polling idle loop that can slightly
955 improve the performance of waking up a idle CPU, but
956 will use a lot of power and make the system run hot.
958 idle=mwait: On systems which support MONITOR/MWAIT but
959 the kernel chose to not use it because it doesn't save
960 as much power as a normal idle loop, use the
961 MONITOR/MWAIT idle loop anyways. Performance should be
962 the same as idle=poll.
963 idle=halt: Halt is forced to be used for CPU idle.
964 In such case C2/C3 won't be used again.
965 idle=nomwait: Disable mwait for CPU C-states
967 ignore_loglevel [KNL]
968 Ignore loglevel setting - this will print /all/
969 kernel messages to the console. Useful for debugging.
972 Set number of hash buckets for inode cache.
975 Format: { "0" | "1" }
976 0 -- integrity auditing messages. (Default)
977 1 -- enable informational integrity auditing messages.
980 Format: { "sha1" | "md5" }
984 Load a policy which meets the needs of the Trusted
985 Computing Base. This means IMA will measure all
986 programs exec'd, files mmap'd for exec, and all files
987 opened for read by uid=0.
990 See header of drivers/scsi/in2000.c.
994 Run specified binary instead of /sbin/init as init
997 initcall_debug [KNL] Trace initcalls as they are executed. Useful
998 for working out where the kernel is dying during
1001 initrd= [BOOT] Specify the location of the initial ramdisk
1003 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1006 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1008 Enable intel iommu driver.
1010 Disable intel iommu driver.
1011 igfx_off [Default Off]
1012 By default, gfx is mapped as normal device. If a gfx
1013 device has a dedicated DMAR unit, the DMAR unit is
1014 bypassed by not enabling DMAR with this option. In
1015 this case, gfx device will use physical address for
1018 With this option iommu will not optimize to look
1019 for io virtual address below 32 bit forcing dual
1020 address cycle on pci bus for cards supporting greater
1021 than 32 bit addressing. The default is to look
1022 for translation below 32 bit and if not available
1023 then look in the higher range.
1024 strict [Default Off]
1025 With this option on every unmap_single operation will
1026 result in a hardware IOTLB flush operation as opposed
1027 to batching them for performance.
1031 iomem= Disable strict checking of access to MMIO memory
1032 strict regions from userspace.
1048 io7= [HW] IO7 for Marvel based alpha systems
1049 See comment before marvel_specify_io7 in
1050 arch/alpha/kernel/core_marvel.c.
1052 io_delay= [X86] I/O delay method
1054 Standard port 0x80 based delay
1056 Alternate port 0xed based delay (needed on some systems)
1058 Simple two microseconds delay
1063 See Documentation/filesystems/nfs/nfsroot.txt.
1065 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1066 See comment before ip2_setup() in
1067 drivers/char/ip2/ip2base.c.
1069 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1070 See header of drivers/scsi/ips.c.
1073 When an interrupt is not handled search all handlers
1074 for it. Intended to get systems with badly broken
1078 When an interrupt is not handled search all handlers
1079 for it. Also check all handlers each timer
1080 interrupt. Intended to get systems with badly broken
1084 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1086 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1088 <cpu number>,...,<cpu number>
1090 <cpu number>-<cpu number>
1091 (must be a positive range in ascending order)
1093 <cpu number>,...,<cpu number>-<cpu number>
1095 This option can be used to specify one or more CPUs
1096 to isolate from the general SMP balancing and scheduling
1097 algorithms. You can move a process onto or off an
1098 "isolated" CPU via the CPU affinity syscalls or cpuset.
1099 <cpu number> begins at 0 and the maximum value is
1100 "number of CPUs in system - 1".
1102 This option is the preferred way to isolate CPUs. The
1103 alternative -- manually setting the CPU mask of all
1104 tasks in the system -- can cause problems and
1105 suboptimal load balancer performance.
1109 js= [HW,JOY] Analog joystick
1110 See Documentation/input/joystick.txt.
1114 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1115 specifies the amount of memory usable by the kernel
1116 for non-movable allocations. The requested amount is
1117 spread evenly throughout all nodes in the system. The
1118 remaining memory in each node is used for Movable
1119 pages. In the event, a node is too small to have both
1120 kernelcore and Movable pages, kernelcore pages will
1121 take priority and other nodes will have a larger number
1122 of kernelcore pages. The Movable zone is used for the
1123 allocation of pages that may be reclaimed or moved
1124 by the page migration subsystem. This means that
1125 HugeTLB pages may not be allocated from this zone.
1126 Note that allocations like PTEs-from-HighMem still
1127 use the HighMem zone if it exists, and the Normal
1128 zone if it does not.
1130 kgdboc= [KGDB,HW] kgdb over consoles.
1131 Requires a tty driver that supports console polling,
1132 or a supported polling keyboard driver (non-usb).
1133 Serial only format: <serial_device>[,baud]
1134 keyboard only format: kbd
1135 keyboard and serial format: kbd,<serial_device>[,baud]
1137 kgdbwait [KGDB] Stop kernel execution and enter the
1138 kernel debugger at the earliest opportunity.
1140 kmac= [MIPS] korina ethernet MAC address.
1141 Configure the RouterBoard 532 series on-chip
1142 Ethernet adapter MAC address.
1144 kmemleak= [KNL] Boot-time kmemleak enable/disable
1145 Valid arguments: on, off
1148 kstack=N [X86] Print N words from the kernel stack
1151 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1152 Default is 0 (don't ignore, but inject #GP)
1154 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1155 Default is 1 (enabled)
1157 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1160 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1162 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1164 kvm-intel.bypass_guest_pf=
1165 [KVM,Intel] Disables bypassing of guest page faults
1166 on Intel chips. Default is 1 (enabled)
1168 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1169 (virtualized MMU) support on capable Intel chips.
1170 Default is 1 (enabled)
1172 kvm-intel.emulate_invalid_guest_state=
1173 [KVM,Intel] Enable emulation of invalid guest states
1174 Default is 0 (disabled)
1176 kvm-intel.flexpriority=
1177 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1178 Default is 1 (enabled)
1180 kvm-intel.unrestricted_guest=
1181 [KVM,Intel] Disable unrestricted guest feature
1182 (virtualized real and unpaged mode) on capable
1183 Intel chips. Default is 1 (enabled)
1185 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1186 feature (tagged TLBs) on capable Intel chips.
1187 Default is 1 (enabled)
1193 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1196 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1199 libata.dma= [LIBATA] DMA control
1200 libata.dma=0 Disable all PATA and SATA DMA
1201 libata.dma=1 PATA and SATA Disk DMA only
1202 libata.dma=2 ATAPI (CDROM) DMA only
1203 libata.dma=4 Compact Flash DMA only
1204 Combinations also work, so libata.dma=3 enables DMA
1205 for disks and CDROMs, but not CFs.
1207 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1208 libata.ignore_hpa=0 keep BIOS limits (default)
1209 libata.ignore_hpa=1 ignore limits, using full disk
1211 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1215 libata.force= [LIBATA] Force configurations. The format is comma
1216 separated list of "[ID:]VAL" where ID is
1217 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1218 matching port, link or device. Basically, it matches
1219 the ATA ID string printed on console by libata. If
1220 the whole ID part is omitted, the last PORT and DEVICE
1221 values are used. If ID hasn't been specified yet, the
1222 configuration applies to all ports, links and devices.
1224 If only DEVICE is omitted, the parameter applies to
1225 the port and all links and devices behind it. DEVICE
1226 number of 0 either selects the first device or the
1227 first fan-out link behind PMP device. It does not
1228 select the host link. DEVICE number of 15 selects the
1229 host link and device attached to it.
1231 The VAL specifies the configuration to force. As long
1232 as there's no ambiguity shortcut notation is allowed.
1233 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1234 The following configurations can be forced.
1236 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1237 Any ID with matching PORT is used.
1239 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1241 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1242 udma[/][16,25,33,44,66,100,133] notation is also
1245 * [no]ncq: Turn on or off NCQ.
1247 * nohrst, nosrst, norst: suppress hard, soft
1250 If there are multiple matching configurations changing
1251 the same attribute, the last one is used.
1253 lmb=debug [KNL] Enable lmb debug messages.
1255 load_ramdisk= [RAM] List of ramdisks to load from floppy
1256 See Documentation/blockdev/ramdisk.txt.
1258 lockd.nlm_grace_period=P [NFS] Assign grace period.
1261 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1264 lockd.nlm_timeout=T [NFS] Assign timeout value.
1267 lockd.nlm_udpport=M [NFS] Assign UDP port.
1270 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1273 loglevel= All Kernel Messages with a loglevel smaller than the
1274 console loglevel will be printed to the console. It can
1275 also be changed with klogd or other programs. The
1276 loglevels are defined as follows:
1278 0 (KERN_EMERG) system is unusable
1279 1 (KERN_ALERT) action must be taken immediately
1280 2 (KERN_CRIT) critical conditions
1281 3 (KERN_ERR) error conditions
1282 4 (KERN_WARNING) warning conditions
1283 5 (KERN_NOTICE) normal but significant condition
1284 6 (KERN_INFO) informational
1285 7 (KERN_DEBUG) debug-level messages
1287 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1288 Format: { n | nk | nM }
1289 n must be a power of two. The default size
1290 is set in the kernel config file.
1292 logo.nologo [FB] Disables display of the built-in Linux logo.
1293 This may be used to provide more screen space for
1294 kernel log messages and is useful when debugging
1295 kernel boot problems.
1297 lp=0 [LP] Specify parallel ports to use, e.g,
1298 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1299 lp=reset first parallel port). 'lp=0' disables the
1300 lp=auto printer driver. 'lp=reset' (which can be
1301 specified in addition to the ports) causes
1302 attached printers to be reset. Using
1303 lp=port1,port2,... specifies the parallel ports
1304 to associate lp devices with, starting with
1305 lp0. A port specification may be 'none' to skip
1306 that lp device, or a parport name such as
1307 'parport0'. Specifying 'lp=auto' instead of a
1308 port specification list means that device IDs
1309 from each port should be examined, to see if
1310 an IEEE 1284-compliant printer is attached; if
1311 so, the driver will manage that printer.
1312 See also header of drivers/char/lp.c.
1315 Sets loops_per_jiffy to given constant, thus avoiding
1316 time-consuming boot-time autodetection (up to 250 ms per
1317 CPU). 0 enables autodetection (default). To determine
1318 the correct value for your kernel, boot with normal
1319 autodetection and see what value is printed. Note that
1320 on SMP systems the preset will be applied to all CPUs,
1321 which is likely to cause problems if your CPUs need
1322 significantly divergent settings. An incorrect value
1323 will cause delays in the kernel to be wrong, leading to
1324 unpredictable I/O errors and other breakage. Although
1325 unlikely, in the extreme case this might damage your
1329 Format: <io>,<irq>,<dma>
1331 mac5380= [HW,SCSI] Format:
1332 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1334 machvec= [IA64] Force the use of a particular machine-vector
1335 (machvec) in a generic kernel.
1336 Example: machvec=hpzx1_swiotlb
1338 machtype= [Loongson] Share the same kernel image file between different
1340 Example: machtype=lemote-yeeloong-2f-7inch
1342 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1343 than or equal to this physical address is ignored.
1345 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1346 should make use of. maxcpus=n : n >= 0 limits the
1347 kernel to using 'n' processors. n=0 is a special case,
1348 it is equivalent to "nosmp", which also disables
1351 max_loop= [LOOP] Maximum number of loopback devices that can
1355 max_luns= [SCSI] Maximum number of LUNs to probe.
1356 Should be between 1 and 2^32-1.
1359 [SCSI] Maximum number of LUNs received.
1360 Should be between 1 and 16384.
1364 mce [X86-32] Machine Check Exception
1366 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1368 md= [HW] RAID subsystems devices and level
1369 See Documentation/md.txt.
1372 Format: <first>,<last>
1373 Specifies range of consoles to be captured by the MDA.
1375 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1376 Amount of memory to be used when the kernel is not able
1377 to see the whole system memory or for test.
1378 [X86-32] Use together with memmap= to avoid physical
1379 address space collisions. Without memmap= PCI devices
1380 could be placed at addresses belonging to unused RAM.
1382 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1386 [KNL,SH] Allow user to override the default size for
1387 per-device physically contiguous DMA buffers.
1389 memmap=exactmap [KNL,X86] Enable setting of an exact
1390 E820 memory map, as specified by the user.
1391 Such memmap=exactmap lines can be constructed based on
1392 BIOS output or other requirements. See the memmap=nn@ss
1395 memmap=nn[KMG]@ss[KMG]
1396 [KNL] Force usage of a specific region of memory
1397 Region of memory to be used, from ss to ss+nn.
1399 memmap=nn[KMG]#ss[KMG]
1400 [KNL,ACPI] Mark specific memory as ACPI data.
1401 Region of memory to be used, from ss to ss+nn.
1403 memmap=nn[KMG]$ss[KMG]
1404 [KNL,ACPI] Mark specific memory as reserved.
1405 Region of memory to be used, from ss to ss+nn.
1406 Example: Exclude memory from 0x18690000-0x1869ffff
1407 memmap=64K$0x18690000
1409 memmap=0x10000$0x18690000
1411 memory_corruption_check=0/1 [X86]
1412 Some BIOSes seem to corrupt the first 64k of
1413 memory when doing things like suspend/resume.
1414 Setting this option will scan the memory
1415 looking for corruption. Enabling this will
1416 both detect corruption and prevent the kernel
1417 from using the memory being corrupted.
1418 However, its intended as a diagnostic tool; if
1419 repeatable BIOS-originated corruption always
1420 affects the same memory, you can use memmap=
1421 to prevent the kernel from using that memory.
1423 memory_corruption_check_size=size [X86]
1424 By default it checks for corruption in the low
1425 64k, making this memory unavailable for normal
1426 use. Use this parameter to scan for
1427 corruption in more or less memory.
1429 memory_corruption_check_period=seconds [X86]
1430 By default it checks for corruption every 60
1431 seconds. Use this parameter to check at some
1432 other rate. 0 disables periodic checking.
1434 memtest= [KNL,X86] Enable memtest
1436 default : 0 <disable>
1437 Specifies the number of memtest passes to be
1438 performed. Each pass selects another test
1439 pattern from a given set of patterns. Memtest
1440 fills the memory with this pattern, validates
1441 memory contents and reserves bad memory
1442 regions that are detected.
1444 meye.*= [HW] Set MotionEye Camera parameters
1445 See Documentation/video4linux/meye.txt.
1447 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1448 Multi-Function General Purpose Timers on AMD Geode
1451 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1452 the BIOS has incorrectly applied a workaround. TinyBIOS
1453 version 0.98 is known to be affected, 0.99 fixes the
1454 problem by letting the user disable the workaround.
1458 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1459 physical address is ignored.
1461 mini2440= [ARM,HW,KNL]
1462 Format:[0..2][b][c][t]
1464 MINI2440 configuration specification:
1465 0 - The attached screen is the 3.5" TFT
1466 1 - The attached screen is the 7" TFT
1467 2 - The VGA Shield is attached (1024x768)
1468 Leaving out the screen size parameter will not load
1469 the TFT driver, and the framebuffer will be left
1471 b - Enable backlight. The TFT backlight pin will be
1472 linked to the kernel VESA blanking code and a GPIO
1473 LED. This parameter is not necessary when using the
1475 c - Enable the s3c camera interface.
1476 t - Reserved for enabling touchscreen support. The
1477 touchscreen support is not enabled in the mainstream
1478 kernel as of 2.6.30, a preliminary port can be found
1479 in the "bleeding edge" mini2440 support kernel at
1480 http://repo.or.cz/w/linux-2.6/mini2440.git
1483 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1484 parameter allows control of the logging verbosity for
1485 the additional memory initialisation checks. A value
1486 of 0 disables mminit logging and a level of 4 will
1487 log everything. Information is printed at KERN_DEBUG
1488 so loglevel=8 may also need to be specified.
1491 [MOUSE] Maximum time between finger touching and
1492 leaving touchpad surface for touch to be considered
1493 a tap and be reported as a left button click (for
1494 touchpads working in absolute mode only).
1496 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1497 reporting absolute coordinates, such as tablets
1498 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1499 reporting absolute coordinates, such as tablets
1501 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1502 is similar to kernelcore except it specifies the
1503 amount of memory used for migratable allocations.
1504 If both kernelcore and movablecore is specified,
1505 then kernelcore will be at *least* the specified
1506 value but may be more. If movablecore on its own
1507 is specified, the administrator must be careful
1508 that the amount of memory usable for all allocations
1514 MTD_Partition= [MTD]
1515 Format: <name>,<region-number>,<size>,<offset>
1517 MTD_Region= [MTD] Format:
1518 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1521 See drivers/mtd/cmdlinepart.c.
1523 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1525 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1527 boundary - index of last SLC block on Flex-OneNAND.
1528 The remaining blocks are configured as MLC blocks.
1529 lock - Configure if Flex-OneNAND boundary should be locked.
1530 Once locked, the boundary cannot be changed.
1531 1 indicates lock status, 0 indicates unlock status.
1534 ARM/S3C2412 JIVE boot control
1536 See arch/arm/mach-s3c2412/mach-jive.c
1538 mtouchusb.raw_coordinates=
1539 [HW] Make the MicroTouch USB driver use raw coordinates
1540 ('y', default) or cooked coordinates ('n')
1542 mtrr_chunk_size=nn[KMG] [X86]
1543 used for mtrr cleanup. It is largest continuous chunk
1544 that could hold holes aka. UC entries.
1546 mtrr_gran_size=nn[KMG] [X86]
1547 Used for mtrr cleanup. It is granularity of mtrr block.
1549 Large value could prevent small alignment from
1552 mtrr_spare_reg_nr=n [X86]
1554 Range: 0,7 : spare reg number
1556 Used for mtrr cleanup. It is spare mtrr entries number.
1557 Set to 2 or more if your graphical card needs more.
1559 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1562 See header of drivers/scsi/NCR_D700.c.
1566 ncr53c400= [HW,SCSI]
1568 ncr53c400a= [HW,SCSI]
1570 ncr53c406a= [HW,SCSI]
1572 ncr53c8xx= [HW,SCSI]
1574 netdev= [NET] Network devices parameters
1575 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1576 Note that mem_start is often overloaded to mean
1577 something different and driver-specific.
1578 This usage is only documented in each driver source
1582 [NETFILTER] Enable connection tracking flow accounting
1583 0 to disable accounting
1584 1 to enable accounting
1585 Default value depends on CONFIG_NF_CT_ACCT that is
1586 going to be removed in 2.6.29.
1589 See Documentation/filesystems/nfs/nfsroot.txt.
1591 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1592 See Documentation/filesystems/nfs/nfsroot.txt.
1594 nfs.callback_tcpport=
1595 [NFS] set the TCP port on which the NFSv4 callback
1596 channel should listen.
1599 [NFS] sets the pathname to the program which is used
1600 to update the NFS client cache entries.
1602 nfs.cache_getent_timeout=
1603 [NFS] sets the timeout after which an attempt to
1604 update a cache entry is deemed to have failed.
1606 nfs.idmap_cache_timeout=
1607 [NFS] set the maximum lifetime for idmapper cache
1611 [NFS] enable 64-bit inode numbers.
1612 If zero, the NFS client will fake up a 32-bit inode
1613 number for the readdir() and stat() syscalls instead
1614 of returning the full 64-bit number.
1615 The default is to return 64-bit inode numbers.
1617 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1618 when a NMI is triggered.
1619 Format: [state][,regs][,debounce][,die]
1621 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1622 Format: [panic,][num]
1624 0 - turn nmi_watchdog off
1625 1 - use the IO-APIC timer for the NMI watchdog
1626 2 - use the local APIC for the NMI watchdog using
1627 a performance counter. Note: This will use one
1628 performance counter and the local APIC's performance
1630 When panic is specified, panic when an NMI watchdog
1632 This is useful when you use a panic=... timeout and
1633 need the box quickly up again.
1634 Instead of 1 and 2 it is possible to use the following
1635 symbolic names: lapic and ioapic
1636 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1638 netpoll.carrier_timeout=
1639 [NET] Specifies amount of time (in seconds) that
1640 netpoll should wait for a carrier. By default netpoll
1643 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1644 emulation library even if a 387 maths coprocessor
1648 [HW] Never suspend the console
1649 Disable suspending of consoles during suspend and
1650 hibernate operations. Once disabled, debugging
1651 messages can reach various consoles while the rest
1652 of the system is being put to sleep (ie, while
1653 debugging driver suspend/resume hooks). This may
1654 not work reliably with all consoles, but is known
1655 to work with serial and VGA consoles.
1657 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1658 caches in the slab allocator. Saves per-node memory,
1659 but will impact performance.
1663 noapic [SMP,APIC] Tells the kernel to not make use of any
1664 IOAPICs that may be present in the system.
1666 nobats [PPC] Do not use BATs for mapping kernel lowmem
1667 on "Classic" PPC cores.
1671 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1673 nodelayacct [KNL] Disable per-task delay accounting
1675 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1677 nodsp [SH] Disable hardware DSP at boot time.
1679 noefi [X86] Disable EFI runtime services support.
1684 On X86-32 available only on PAE configured kernels.
1685 noexec=on: enable non-executable mappings (default)
1686 noexec=off: disable non-executable mappings
1689 This affects only 32-bit executables.
1690 noexec32=on: enable non-executable mappings (default)
1691 read doesn't imply executable mappings
1692 noexec32=off: disable non-executable mappings
1693 read implies executable mappings
1695 nofpu [SH] Disable hardware FPU at boot time.
1697 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1698 register save and restore. The kernel will only save
1699 legacy floating-point registers on task switch.
1701 noxsave [BUGS=X86] Disables x86 extended register state save
1702 and restore using xsave. The kernel will fallback to
1703 enabling legacy floating-point and sse state.
1705 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1706 wfi(ARM) instruction doesn't work correctly and not to
1707 use it. This is also useful when using JTAG debugger.
1709 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1710 instruction doesn't work correctly and not to
1713 no_file_caps Tells the kernel not to honor file capabilities. The
1714 only way then for a file to be executed with privilege
1715 is to be setuid root or executed by root.
1717 nohalt [IA-64] Tells the kernel not to use the power saving
1718 function PAL_HALT_LIGHT when idle. This increases
1719 power-consumption. On the positive side, it reduces
1720 interrupt wake-up latency, which may improve performance
1721 in certain environments such as networked servers or
1724 nohz= [KNL] Boottime enable/disable dynamic ticks
1725 Valid arguments: on, off
1728 noiotrap [SH] Disables trapped I/O port accesses.
1730 noirqdebug [X86-32] Disables the code which attempts to detect and
1731 disable unhandled interrupt sources.
1733 no_timer_check [X86,APIC] Disables the code which tests for
1734 broken timer IRQ sources.
1736 noisapnp [ISAPNP] Disables ISA PnP code.
1738 noinitrd [RAM] Tells the kernel not to load any configured
1741 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1746 nojitter [IA64] Disables jitter checking for ITC timers.
1748 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1750 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1752 noltlbs [PPC] Do not use large page/tlb entries for kernel
1753 lowmem mapping on PPC40x.
1755 nomca [IA-64] Disable machine check abort handling
1757 nomce [X86-32] Machine Check Exception
1759 nomfgpt [X86-32] Disable Multi-Function General Purpose
1760 Timer usage (for AMD Geode machines).
1762 nopat [X86] Disable PAT (page attribute table extension of
1763 pagetables) support.
1765 norandmaps Don't use address space randomization. Equivalent to
1766 echo 0 > /proc/sys/kernel/randomize_va_space
1768 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1770 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1771 with UP alternatives
1773 noresidual [PPC] Don't use residual data on PReP machines.
1775 noresume [SWSUSP] Disables resume and restores original swap
1778 no-scroll [VGA] Disables scrollback.
1779 This is required for the Braillex ib80-piezo Braille
1780 reader made by F.H. Papenmeier (Germany).
1784 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1786 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1787 and disable the IO APIC. legacy for "maxcpus=0".
1789 nosoftlockup [KNL] Disable the soft-lockup detector.
1791 noswapaccount [KNL] Disable accounting of swap in memory resource
1792 controller. (See Documentation/cgroups/memory.txt)
1794 nosync [HW,M68K] Disables sync negotiation for all devices.
1796 notsc [BUGS=X86-32] Disable Time Stamp Counter
1798 nousb [USB] Disable the USB subsystem
1802 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1804 nptcg= [IA64] Override max number of concurrent global TLB
1805 purges which is reported from either PAL_VM_SUMMARY or
1808 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1809 could support. nr_cpus=n : n >= 1 limits the kernel to
1810 supporting 'n' processors. Later in runtime you can not
1811 use hotplug cpu feature to put more cpu back to online.
1812 just like you compile the kernel NR_CPUS=n
1814 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1816 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1817 one of ['zone', 'node', 'default'] can be specified
1818 This can be set from sysctl after boot.
1819 See Documentation/sysctl/vm.txt for details.
1821 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1822 See Documentation/debugging-via-ohci1394.txt for more
1825 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1826 Rather than timing out after 20 ms if an EC
1827 command is not properly ACKed, override the length
1828 of the timeout. We have interrupts disabled while
1829 waiting for the ACK, so if this is set too high
1830 interrupts *may* be lost!
1832 omap_mux= [OMAP] Override bootloader pin multiplexing.
1833 Format: <mux_mode0.mode_name=value>...
1834 For example, to override I2C bus2:
1835 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1840 oprofile.timer= [HW]
1841 Use timer interrupt instead of performance counters
1843 oprofile.cpu_type= Force an oprofile cpu type
1844 This might be useful if you have an older oprofile
1845 userland or if you want common events.
1846 Format: { arch_perfmon }
1847 arch_perfmon: [X86] Force use of architectural
1848 perfmon on Intel CPUs instead of the
1849 CPU specific event set.
1851 osst= [HW,SCSI] SCSI Tape Driver
1852 Format: <buffer_size>,<write_threshold>
1853 See also Documentation/scsi/st.txt.
1855 panic= [KNL] Kernel behaviour on panic
1858 parkbd.port= [HW] Parallel port number the keyboard adapter is
1859 connected to, default is 0.
1861 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1862 0 for XT, 1 for AT (default is AT).
1865 parport= [HW,PPT] Specify parallel ports. 0 disables.
1866 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1867 Use 'auto' to force the driver to use any
1868 IRQ/DMA settings detected (the default is to
1869 ignore detected IRQ/DMA settings because of
1870 possible conflicts). You can specify the base
1871 address, IRQ, and DMA settings; IRQ and DMA
1872 should be numbers, or 'auto' (for using detected
1873 settings on that particular port), or 'nofifo'
1874 (to avoid using a FIFO even if it is detected).
1875 Parallel ports are assigned in the order they
1876 are specified on the command line, starting
1879 parport_init_mode= [HW,PPT]
1880 Configure VIA parallel port to operate in
1881 a specific mode. This is necessary on Pegasos
1882 computer where firmware has no options for setting
1883 up parallel port mode and sets it to spp.
1884 Currently this function knows 686a and 8231 chips.
1885 Format: [spp|ps2|epp|ecp|ecpepp]
1887 pas2= [HW,OSS] Format:
1888 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1891 See header of drivers/scsi/pas16.c.
1894 Halt all CPUs after the first oops has been printed for
1895 the specified number of seconds. This is to be used if
1896 your oopses keep scrolling off the screen.
1901 See header of drivers/block/paride/pcd.c.
1902 See also Documentation/blockdev/paride.txt.
1904 pci=option[,option...] [PCI] various PCI subsystem options:
1905 earlydump [X86] dump PCI config space before the kernel
1907 off [X86] don't probe for the PCI bus
1908 bios [X86-32] force use of PCI BIOS, don't access
1909 the hardware directly. Use this if your machine
1910 has a non-standard PCI host bridge.
1911 nobios [X86-32] disallow use of PCI BIOS, only direct
1912 hardware access methods are allowed. Use this
1913 if you experience crashes upon bootup and you
1914 suspect they are caused by the BIOS.
1915 conf1 [X86] Force use of PCI Configuration
1917 conf2 [X86] Force use of PCI Configuration
1919 noaer [PCIE] If the PCIEAER kernel config parameter is
1920 enabled, this kernel boot option can be used to
1921 disable the use of PCIE advanced error reporting.
1922 nodomains [PCI] Disable support for multiple PCI
1923 root domains (aka PCI segments, in ACPI-speak).
1924 nommconf [X86] Disable use of MMCONFIG for PCI
1926 check_enable_amd_mmconf [X86] check for and enable
1927 properly configured MMIO access to PCI
1928 config space on AMD family 10h CPU
1929 nomsi [MSI] If the PCI_MSI kernel config parameter is
1930 enabled, this kernel boot option can be used to
1931 disable the use of MSI interrupts system-wide.
1932 noioapicquirk [APIC] Disable all boot interrupt quirks.
1933 Safety option to keep boot IRQs enabled. This
1934 should never be necessary.
1935 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1936 primary IO-APIC for bridges that cannot disable
1937 boot IRQs. This fixes a source of spurious IRQs
1938 when the system masks IRQs.
1939 noioapicreroute [APIC] Disable workaround that uses the
1940 boot IRQ equivalent of an IRQ that connects to
1941 a chipset where boot IRQs cannot be disabled.
1942 The opposite of ioapicreroute.
1943 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1944 routing table. These calls are known to be buggy
1945 on several machines and they hang the machine
1946 when used, but on other computers it's the only
1947 way to get the interrupt routing table. Try
1948 this option if the kernel is unable to allocate
1949 IRQs or discover secondary PCI buses on your
1951 rom [X86] Assign address space to expansion ROMs.
1952 Use with caution as certain devices share
1953 address decoders between ROMs and other
1955 norom [X86] Do not assign address space to
1956 expansion ROMs that do not already have
1957 BIOS assigned address ranges.
1958 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1959 assigned automatically to PCI devices. You can
1960 make the kernel exclude IRQs of your ISA cards
1962 pirqaddr=0xAAAAA [X86] Specify the physical address
1963 of the PIRQ table (normally generated
1964 by the BIOS) if it is outside the
1965 F0000h-100000h range.
1966 lastbus=N [X86] Scan all buses thru bus #N. Can be
1967 useful if the kernel is unable to find your
1968 secondary buses and you want to tell it
1969 explicitly which ones they are.
1970 assign-busses [X86] Always assign all PCI bus
1971 numbers ourselves, overriding
1972 whatever the firmware may have done.
1973 usepirqmask [X86] Honor the possible IRQ mask stored
1974 in the BIOS $PIR table. This is needed on
1975 some systems with broken BIOSes, notably
1976 some HP Pavilion N5400 and Omnibook XE3
1977 notebooks. This will have no effect if ACPI
1978 IRQ routing is enabled.
1979 noacpi [X86] Do not use ACPI for IRQ routing
1980 or for PCI scanning.
1981 use_crs [X86] Use PCI host bridge window information
1982 from ACPI. On BIOSes from 2008 or later, this
1983 is enabled by default. If you need to use this,
1984 please report a bug.
1985 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1986 If you need to use this, please report a bug.
1987 routeirq Do IRQ routing for all PCI devices.
1988 This is normally done in pci_enable_device(),
1989 so this option is a temporary workaround
1990 for broken drivers that don't call it.
1991 skip_isa_align [X86] do not align io start addr, so can
1992 handle more pci cards
1993 firmware [ARM] Do not re-enumerate the bus but instead
1994 just use the configuration from the
1995 bootloader. This is currently used on
1996 IXP2000 systems where the bus has to be
1997 configured a certain way for adjunct CPUs.
1998 noearly [X86] Don't do any early type 1 scanning.
1999 This might help on some broken boards which
2000 machine check when some devices' config space
2001 is read. But various workarounds are disabled
2002 and some IOMMU drivers will not work.
2003 bfsort Sort PCI devices into breadth-first order.
2004 This sorting is done to get a device
2005 order compatible with older (<= 2.4) kernels.
2006 nobfsort Don't sort PCI devices into breadth-first order.
2007 cbiosize=nn[KMG] The fixed amount of bus space which is
2008 reserved for the CardBus bridge's IO window.
2009 The default value is 256 bytes.
2010 cbmemsize=nn[KMG] The fixed amount of bus space which is
2011 reserved for the CardBus bridge's memory
2012 window. The default value is 64 megabytes.
2015 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2016 Specifies alignment and device to reassign
2017 aligned memory resources.
2018 If <order of align> is not specified,
2019 PAGE_SIZE is used as alignment.
2020 PCI-PCI bridge can be specified, if resource
2021 windows need to be expanded.
2022 ecrc= Enable/disable PCIe ECRC (transaction layer
2023 end-to-end CRC checking).
2024 bios: Use BIOS/firmware settings. This is the
2029 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2032 force Enable ASPM even on devices that claim not to support it.
2033 WARNING: Forcing ASPM on may cause system lockups.
2035 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2036 off Do not use native PCIe PME signaling.
2037 force Use native PCIe PME signaling even if the BIOS refuses
2038 to allow the kernel to control the relevant PCIe config
2040 nomsi Do not use MSI for native PCIe PME signaling (this makes
2041 all PCIe root ports use INTx for everything).
2043 pcmv= [HW,PCMCIA] BadgePAD 4
2046 See Documentation/blockdev/paride.txt.
2048 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2051 See arch/parisc/kernel/pdc_chassis.c
2053 percpu_alloc= Select which percpu first chunk allocator to use.
2054 Currently supported values are "embed" and "page".
2055 Archs may support subset or none of the selections.
2056 See comments in mm/percpu.c for details on each
2057 allocator. This parameter is primarily for debugging
2058 and performance comparison.
2061 See Documentation/blockdev/paride.txt.
2064 See Documentation/blockdev/paride.txt.
2066 pirq= [SMP,APIC] Manual mp-table setup
2067 See Documentation/x86/i386/IO-APIC.txt.
2069 plip= [PPT,NET] Parallel port network link
2070 Format: { parport<nr> | timid | 0 }
2071 See also Documentation/parport.txt.
2073 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2074 Override pmtimer IOPort with a hex value.
2078 Enable PNP debug messages. This depends on the
2079 CONFIG_PNP_DEBUG_MESSAGES option.
2085 { on | off | curr | res | no-curr | no-res }
2088 [ISAPNP] Exclude IRQs for the autoconfiguration
2091 [ISAPNP] Exclude DMAs for the autoconfiguration
2093 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2094 Ranges are in pairs (I/O port base and size).
2097 [ISAPNP] Exclude memory regions for the
2099 Ranges are in pairs (memory base and size).
2101 ports= [IP_VS_FTP] IPVS ftp helper module
2103 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2105 Format: <port>,<port>....
2107 print-fatal-signals=
2108 [KNL] debug: print fatal signals
2110 If enabled, warn about various signal handling
2111 related application anomalies: too many signals,
2112 too many POSIX.1 timers, fatal signals causing a
2115 If you hit the warning due to signal overflow,
2116 you might want to try "ulimit -i unlimited".
2120 printk.time= Show timing data prefixed to each printk message line
2121 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2123 processor.max_cstate= [HW,ACPI]
2124 Limit processor to maximum C-state
2125 max_cstate=9 overrides any DMI blacklist limit.
2127 processor.nocst [HW,ACPI]
2128 Ignore the _CST method to determine C-states,
2129 instead using the legacy FADT method
2131 profile= [KNL] Enable kernel profiling via /proc/profile
2132 Format: [schedule,]<number>
2133 Param: "schedule" - profile schedule points.
2134 Param: <number> - step/bucket size as a power of 2 for
2135 statistical time based profiling.
2136 Param: "sleep" - profile D-state sleeping (millisecs).
2137 Requires CONFIG_SCHEDSTATS
2138 Param: "kvm" - profile VM exits.
2140 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2142 See Documentation/blockdev/ramdisk.txt.
2144 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2145 probe for; one of (bare|imps|exps|lifebook|any).
2146 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2148 psmouse.resetafter= [HW,MOUSE]
2149 Try to reset the device after so many bad packets
2152 [HW,MOUSE] Set desired mouse resolution, in dpi.
2153 psmouse.smartscroll=
2154 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2155 0 = disabled, 1 = enabled (default).
2157 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2159 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2162 See Documentation/blockdev/paride.txt.
2165 [KNL] Number of legacy pty's. Overwrites compiled-in
2168 quiet [KNL] Disable most log messages
2173 See Documentation/md.txt.
2175 ramdisk_blocksize= [RAM]
2176 See Documentation/blockdev/ramdisk.txt.
2178 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2179 See Documentation/blockdev/ramdisk.txt.
2181 rcupdate.blimit= [KNL,BOOT]
2182 Set maximum number of finished RCU callbacks to process
2185 rcupdate.qhimark= [KNL,BOOT]
2186 Set threshold of queued
2187 RCU callbacks over which batch limiting is disabled.
2189 rcupdate.qlowmark= [KNL,BOOT]
2190 Set threshold of queued RCU callbacks below which
2191 batch limiting is re-enabled.
2195 Run specified binary instead of /init from the ramdisk,
2196 used for early userspace startup. See initrd.
2198 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2199 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2200 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2203 [KNL, SMP] Set scheduler's default relax_domain_level.
2204 See Documentation/cgroups/cpusets.txt.
2206 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2208 reservetop= [X86-32]
2210 Reserves a hole at the top of the kernel virtual
2213 reset_devices [KNL] Force drivers to reset the underlying device
2214 during initialization.
2217 Specify the partition device for software suspend
2219 resume_offset= [SWSUSP]
2220 Specify the offset from the beginning of the partition
2221 given by "resume=" at which the swap header is located,
2222 in <PAGE_SIZE> units (needed only for swap files).
2223 See Documentation/power/swsusp-and-swap-files.txt
2225 retain_initrd [RAM] Keep initrd memory after extraction
2227 rhash_entries= [KNL,NET]
2228 Set number of hash buckets for route cache
2230 riscom8= [HW,SERIAL]
2231 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2233 ro [KNL] Mount root device read-only on boot
2235 root= [KNL] Root filesystem
2237 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2238 mount the root filesystem
2240 rootflags= [KNL] Set root filesystem mount option string
2242 rootfstype= [KNL] Set root filesystem type
2244 rootwait [KNL] Wait (indefinitely) for root device to show up.
2245 Useful for devices that are detected asynchronously
2246 (e.g. USB and MMC devices).
2248 rw [KNL] Mount root device read-write on boot
2250 S [KNL] Run init in single mode
2253 See drivers/net/irda/sa1100_ir.c.
2255 sbni= [NET] Granch SBNI12 leased line adapter
2257 sched_debug [KNL] Enables verbose scheduler debug messages.
2259 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2260 Format: <io>[,<timeout>[,<isapnp>]]
2262 scsi_debug_*= [SCSI]
2263 See drivers/scsi/scsi_debug.c.
2265 scsi_default_dev_flags=
2266 [SCSI] SCSI default device flags
2269 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2270 Format: <vendor>:<model>:<flags>
2271 (flags are integer value)
2273 scsi_logging_level= [SCSI] a bit mask of logging levels
2274 See drivers/scsi/scsi_logging.h for bits. Also
2275 settable via sysctl at dev.scsi.logging_level
2276 (/proc/sys/dev/scsi/logging_level).
2277 There is also a nice 'scsi_logging_level' script in the
2278 S390-tools package, available for download at
2279 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2281 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2282 discovered. async scans them in kernel threads,
2283 allowing boot to proceed. none ignores them, expecting
2284 user space to do the scan.
2286 security= [SECURITY] Choose a security module to enable at boot.
2287 If this boot parameter is not specified, only the first
2288 security module asking for security registration will be
2289 loaded. An invalid security module name will be treated
2290 as if no module has been chosen.
2292 selinux= [SELINUX] Disable or enable SELinux at boot time.
2293 Format: { "0" | "1" }
2294 See security/selinux/Kconfig help text.
2297 Default value is set via kernel config option.
2298 If enabled at boot time, /selinux/disable can be used
2299 later to disable prior to initial policy load.
2301 serialnumber [BUGS=X86-32]
2304 Maximal number of shapers.
2306 show_msr= [x86] show boot-time MSR settings
2307 Format: { <integer> }
2308 Show boot-time (BIOS-initialized) MSR settings.
2309 The parameter means the number of CPUs to show,
2310 for example 1 means boot CPU only.
2313 See header of drivers/scsi/sim710.c.
2320 slub_debug[=options[,slabs]] [MM, SLUB]
2321 Enabling slub_debug allows one to determine the
2322 culprit if slab objects become corrupted. Enabling
2323 slub_debug can create guard zones around objects and
2324 may poison objects when not in use. Also tracks the
2325 last alloc / free. For more information see
2326 Documentation/vm/slub.txt.
2328 slub_max_order= [MM, SLUB]
2329 Determines the maximum allowed order for slabs.
2330 A high setting may cause OOMs due to memory
2331 fragmentation. For more information see
2332 Documentation/vm/slub.txt.
2334 slub_min_objects= [MM, SLUB]
2335 The minimum number of objects per slab. SLUB will
2336 increase the slab order up to slub_max_order to
2337 generate a sufficiently large slab able to contain
2338 the number of objects indicated. The higher the number
2339 of objects the smaller the overhead of tracking slabs
2340 and the less frequently locks need to be acquired.
2341 For more information see Documentation/vm/slub.txt.
2343 slub_min_order= [MM, SLUB]
2344 Determines the mininum page order for slabs. Must be
2345 lower than slub_max_order.
2346 For more information see Documentation/vm/slub.txt.
2348 slub_nomerge [MM, SLUB]
2349 Disable merging of slabs with similar size. May be
2350 necessary if there is some reason to distinguish
2351 allocs to different slabs. Debug options disable
2352 merging on their own.
2353 For more information see Documentation/vm/slub.txt.
2356 Format: <io1>[,<io2>[,...,<io8>]]
2358 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2359 attempt to substitute SMP alternatives once at boot.
2361 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2362 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2363 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2364 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2365 smsc-ircc2.ircc_irq= [HW] IRQ line
2366 smsc-ircc2.ircc_dma= [HW] DMA channel
2367 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2368 0: Toshiba Satellite 1800 (GP data pin select)
2369 1: Fast pin select (default)
2372 snd-ad1816a= [HW,ALSA]
2374 snd-ad1848= [HW,ALSA]
2376 snd-ali5451= [HW,ALSA]
2378 snd-als100= [HW,ALSA]
2380 snd-als4000= [HW,ALSA]
2382 snd-azt2320= [HW,ALSA]
2384 snd-cmi8330= [HW,ALSA]
2386 snd-cmipci= [HW,ALSA]
2388 snd-cs4231= [HW,ALSA]
2390 snd-cs4232= [HW,ALSA]
2392 snd-cs4236= [HW,ALSA]
2394 snd-cs4281= [HW,ALSA]
2396 snd-cs46xx= [HW,ALSA]
2398 snd-dt019x= [HW,ALSA]
2400 snd-dummy= [HW,ALSA]
2402 snd-emu10k1= [HW,ALSA]
2404 snd-ens1370= [HW,ALSA]
2406 snd-ens1371= [HW,ALSA]
2408 snd-es968= [HW,ALSA]
2410 snd-es1688= [HW,ALSA]
2412 snd-es18xx= [HW,ALSA]
2414 snd-es1938= [HW,ALSA]
2416 snd-es1968= [HW,ALSA]
2418 snd-fm801= [HW,ALSA]
2420 snd-gusclassic= [HW,ALSA]
2422 snd-gusextreme= [HW,ALSA]
2424 snd-gusmax= [HW,ALSA]
2428 snd-ice1712= [HW,ALSA]
2430 snd-intel8x0= [HW,ALSA]
2432 snd-interwave= [HW,ALSA]
2437 snd-korg1212= [HW,ALSA]
2439 snd-maestro3= [HW,ALSA]
2441 snd-mpu401= [HW,ALSA]
2443 snd-mtpav= [HW,ALSA]
2445 snd-nm256= [HW,ALSA]
2447 snd-opl3sa2= [HW,ALSA]
2455 snd-opti93x= [HW,ALSA]
2459 snd-rme32= [HW,ALSA]
2461 snd-rme96= [HW,ALSA]
2463 snd-rme9652= [HW,ALSA]
2469 snd-sbawe= [HW,ALSA]
2471 snd-serial= [HW,ALSA]
2473 snd-sgalaxy= [HW,ALSA]
2475 snd-sonicvibes= [HW,ALSA]
2480 snd-sun-cs4231= [HW,ALSA]
2482 snd-trident= [HW,ALSA]
2484 snd-usb-audio= [HW,ALSA,USB]
2486 snd-via82xx= [HW,ALSA]
2488 snd-virmidi= [HW,ALSA]
2490 snd-wavefront= [HW,ALSA]
2492 snd-ymfpci= [HW,ALSA]
2495 [KNL] Should the soft-lockup detector generate panics.
2497 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2498 See Documentation/sonypi.txt
2500 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2501 See Documentation/serial/specialix.txt.
2503 spia_io_base= [HW,MTD]
2509 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2511 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2512 See Documentation/scsi/st.txt.
2515 Enabled the stack tracer on boot up.
2519 Set the STI (builtin display/keyboard on the HP-PARISC
2520 machines) console (graphic card) which should be used
2521 as the initial boot-console.
2522 See also comment in drivers/video/console/sticore.c.
2525 See comment in drivers/video/console/sticore.c.
2528 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2530 sunrpc.min_resvport=
2531 sunrpc.max_resvport=
2533 SunRPC servers often require that client requests
2534 originate from a privileged port (i.e. a port in the
2535 range 0 < portnr < 1024).
2536 An administrator who wishes to reserve some of these
2537 ports for other uses may adjust the range that the
2538 kernel's sunrpc client considers to be privileged
2539 using these two parameters to set the minimum and
2540 maximum port values.
2544 Control how the NFS server code allocates CPUs to
2545 service thread pools. Depending on how many NICs
2546 you have and where their interrupts are bound, this
2547 option will affect which CPUs will do NFS serving.
2548 Note: this parameter cannot be changed while the
2549 NFS server is running.
2551 auto the server chooses an appropriate mode
2552 automatically using heuristics
2553 global a single global pool contains all CPUs
2554 percpu one pool for each CPU
2555 pernode one pool for each NUMA node (equivalent
2556 to global on non-NUMA machines)
2558 sunrpc.tcp_slot_table_entries=
2559 sunrpc.udp_slot_table_entries=
2561 Sets the upper limit on the number of simultaneous
2562 RPC calls that can be sent from the client to a
2563 server. Increasing these values may allow you to
2564 improve throughput, but will also increase the
2565 amount of memory reserved for use by the client.
2567 swiotlb= [IA-64] Number of I/O TLB slabs
2571 sym53c416= [HW,SCSI]
2572 See header of drivers/scsi/sym53c416.c.
2574 sysrq_always_enabled
2576 Ignore sysrq setting - this boot parameter will
2577 neutralize any effect of /proc/sys/kernel/sysrq.
2578 Useful for debugging.
2581 See header of drivers/scsi/t128.c.
2585 test_suspend= [SUSPEND]
2586 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2587 standby suspend) as the system sleep state to briefly
2588 enter during system startup. The system is woken from
2589 this state using a wakeup-capable RTC alarm.
2591 thash_entries= [KNL,NET]
2592 Set number of hash buckets for TCP connection
2594 thermal.act= [HW,ACPI]
2595 -1: disable all active trip points in all thermal zones
2596 <degrees C>: override all lowest active trip points
2598 thermal.crt= [HW,ACPI]
2599 -1: disable all critical trip points in all thermal zones
2600 <degrees C>: override all critical trip points
2602 thermal.nocrt= [HW,ACPI]
2603 Set to disable actions on ACPI thermal zone
2604 critical and hot trip points.
2606 thermal.off= [HW,ACPI]
2607 1: disable ACPI thermal control
2609 thermal.psv= [HW,ACPI]
2610 -1: disable all passive trip points
2611 <degrees C>: override all passive trip points to this
2614 thermal.tzp= [HW,ACPI]
2615 Specify global default ACPI thermal zone polling rate
2616 <deci-seconds>: poll all this frequency
2617 0: no polling (default)
2620 See comment before function dc390_setup() in
2621 drivers/scsi/tmscsim.c.
2625 Specify if the kernel should make use of the cpu
2626 topology informations if the hardware supports these.
2627 The scheduler will make use of these informations and
2628 e.g. base its process migration decisions on it.
2633 tpm_suspend_pcr=[HW,TPM]
2634 Format: integer pcr id
2635 Specify that at suspend time, the tpm driver
2636 should extend the specified pcr with zeros,
2637 as a workaround for some chips which fail to
2638 flush the last written pcr on TPM_SaveState.
2639 This will guarantee that all the other pcrs
2642 trace_buf_size=nn[KMG]
2643 [FTRACE] will set tracing buffer size.
2645 trace_event=[event-list]
2646 [FTRACE] Set and start specified trace events in order
2647 to facilitate early boot debugging.
2648 See also Documentation/trace/events.txt
2650 trix= [HW,OSS] MediaTrix AudioTrix Pro
2652 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2654 tsc= Disable clocksource-must-verify flag for TSC.
2656 [x86] reliable: mark tsc clocksource as reliable, this
2657 disables clocksource verification at runtime.
2658 Used to enable high-resolution timer mode on older
2659 hardware, and in virtualized environment.
2661 turbografx.map[2|3]= [HW,JOY]
2662 TurboGraFX parallel port interface
2664 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2665 See also Documentation/input/joystick-parport.txt
2667 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2668 See header of drivers/scsi/u14-34f.c.
2676 uhash_entries= [KNL,NET]
2677 Set number of hash buckets for UDP/UDP-Lite connections
2680 [USB] Ignore overcurrent events (default N).
2681 Some badly-designed motherboards generate lots of
2682 bogus events, for ports that aren't wired to
2683 anything. Set this parameter to avoid log spamming.
2684 Note that genuine overcurrent events won't be
2689 Set unknown_nmi_panic=1 early on boot.
2691 usbcore.autosuspend=
2692 [USB] The autosuspend time delay (in seconds) used
2693 for newly-detected USB devices (default 2). This
2694 is the time required before an idle device will be
2695 autosuspended. Devices for which the delay is set
2696 to a negative value won't be autosuspended at all.
2698 usbcore.usbfs_snoop=
2699 [USB] Set to log all usbfs traffic (default 0 = off).
2701 usbcore.blinkenlights=
2702 [USB] Set to cycle leds on hubs (default 0 = off).
2704 usbcore.old_scheme_first=
2705 [USB] Start with the old device initialization
2706 scheme (default 0 = off).
2708 usbcore.use_both_schemes=
2709 [USB] Try the other device initialization scheme
2710 if the first one fails (default 1 = enabled).
2712 usbcore.initial_descriptor_timeout=
2713 [USB] Specifies timeout for the initial 64-byte
2714 USB_REQ_GET_DESCRIPTOR request in milliseconds
2715 (default 5000 = 5.0 seconds).
2718 [USBHID] The interval which mice are to be polled at.
2720 usb-storage.delay_use=
2721 [UMS] The delay in seconds before a new device is
2722 scanned for Logical Units (default 5).
2725 [UMS] A list of quirks entries to supplement or
2726 override the built-in unusual_devs list. List
2727 entries are separated by commas. Each entry has
2728 the form VID:PID:Flags where VID and PID are Vendor
2729 and Product ID values (4-digit hex numbers) and
2730 Flags is a set of characters, each corresponding
2731 to a common usb-storage quirk flag as follows:
2732 a = SANE_SENSE (collect more than 18 bytes
2734 b = BAD_SENSE (don't collect more than 18
2735 bytes of sense data);
2736 c = FIX_CAPACITY (decrease the reported
2737 device capacity by one sector);
2738 h = CAPACITY_HEURISTICS (decrease the
2739 reported device capacity by one
2740 sector if the number is odd);
2741 i = IGNORE_DEVICE (don't bind to this
2743 l = NOT_LOCKABLE (don't try to lock and
2744 unlock ejectable media);
2745 m = MAX_SECTORS_64 (don't transfer more
2746 than 64 sectors = 32 KB at a time);
2747 o = CAPACITY_OK (accept the capacity
2748 reported by the device);
2749 r = IGNORE_RESIDUE (the device reports
2750 bogus residue values);
2751 s = SINGLE_LUN (the device has only one
2753 w = NO_WP_DETECT (don't test whether the
2754 medium is write-protected).
2755 Example: quirks=0419:aaf5:rl,0421:0433:rc
2758 [X86] Flags controlling user PTE allocations.
2760 nohigh = do not allocate PTE pages in
2761 HIGHMEM regardless of setting
2765 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2766 vdso=1: enable VDSO (default)
2767 vdso=0: disable VDSO mapping
2770 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2771 vdso32=1: enable 32-bit VDSO (default)
2772 vdso32=0: disable 32-bit VDSO mapping
2775 vector=percpu: enable percpu vector domain
2777 video= [FB] Frame buffer configuration
2778 See Documentation/fb/modedb.txt.
2780 vga= [BOOT,X86-32] Select a particular video mode
2781 See Documentation/x86/boot.txt and
2782 Documentation/svga.txt.
2783 Use vga=ask for menu.
2784 This is actually a boot loader parameter; the value is
2785 passed to the kernel using a special protocol.
2787 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2788 size of <nn>. This can be used to increase the
2789 minimum size (128MB on x86). It can also be used to
2790 decrease the size and leave more room for directly
2793 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2796 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2799 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2802 vt.cur_default= [VT] Default cursor shape.
2803 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2804 the parameters of the <Esc>[?A;B;Cc escape sequence;
2805 see VGA-softcursor.txt. Default: 2 = underline.
2807 vt.default_blu= [VT]
2808 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2809 Change the default blue palette of the console.
2810 This is a 16-member array composed of values
2813 vt.default_grn= [VT]
2814 Format: <green0>,<green1>,<green2>,...,<green15>
2815 Change the default green palette of the console.
2816 This is a 16-member array composed of values
2819 vt.default_red= [VT]
2820 Format: <red0>,<red1>,<red2>,...,<red15>
2821 Change the default red palette of the console.
2822 This is a 16-member array composed of values
2828 Set system-wide default UTF-8 mode for all tty's.
2829 Default is 1, i.e. UTF-8 mode is enabled for all
2830 newly opened terminals.
2832 vt.global_cursor_default=
2835 Set system-wide default for whether a cursor
2836 is shown on new VTs. Default is -1,
2837 i.e. cursors will be created by default unless
2838 overridden by individual drivers. 0 will hide
2839 cursors, 1 will display them.
2841 waveartist= [HW,OSS]
2842 Format: <io>,<irq>,<dma>,<dma2>
2845 See header of drivers/scsi/wd33c93.c.
2848 See header of drivers/scsi/wd7000.c.
2851 See Documentation/watchdog/wdt.txt.
2853 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2854 default x2apic cluster mode on platforms
2857 x86_mrst_timer= [X86-32,APBT]
2858 Choose timer option for x86 Moorestown MID platform.
2859 Two valid options are apbt timer only and lapic timer
2860 plus one apbt timer for broadcast timer.
2861 x86_mrst_timer=apbt_only | lapic_and_apbt
2863 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2864 xd_geo= See header of drivers/block/xd.c.
2866 xirc2ps_cs= [NET,PCMCIA]
2868 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2870 ______________________________________________________________________
2874 Add documentation for ALSA options.
2875 Add more DRM drivers.
git.openpandora.org / pandora-kernel.git / blob