4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
203 acpi_early_pdc_eval [HW,ACPI] Evaluate processor _PDC methods
204 early. Needed on some platforms to properly
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
220 Format: <irq>,<irq>...
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
240 acpi_serialize [HW,ACPI] force serialization of AML methods
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248 old_ordering, s4_nonvs, sci_force_enable }
249 See Documentation/power/video.txt for information on
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
259 s4_nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during hibernation.
261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
286 Format: <io>,<irq>,<dma>,<dma2>,<type>
288 add_efi_memmap [EFI; X86] Include EFI memory map in
289 kernel's map of available physical RAM.
292 See header of drivers/scsi/advansys.c.
294 advwdt= [HW,WDT] Advantech WDT
295 Format: <iostart>,<iostop>
297 aedsp16= [HW,OSS] Audio Excel DSP 16
298 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
299 See also header of sound/oss/aedsp16.c.
302 { off | try_unsupported }
303 off: disable AGP support
304 try_unsupported: try to drive unsupported chipsets
305 (may crash computer or cause data corruption)
308 See Documentation/scsi/aha152x.txt.
311 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
314 See Documentation/scsi/aic7xxx.txt.
317 See Documentation/scsi/aic79xx.txt.
320 Allow the default userspace alignment fault handler
321 behaviour to be specified. Bit 0 enables warnings,
322 bit 1 enables fixups, and bit 2 sends a segfault.
324 amd_iommu= [HW,X86-84]
325 Pass parameters to the AMD IOMMU driver in the system.
327 isolate - enable device isolation (each device, as far
328 as possible, will get its own protection
330 share - put every device behind one IOMMU into the
331 same protection domain
332 fullflush - enable flushing of IO/TLB entries when
333 they are unmapped. Otherwise they are
334 flushed before they will be reused, which
337 amijoy.map= [HW,JOY] Amiga joystick support
338 Map of devices attached to JOY0DAT and JOY1DAT
340 See also Documentation/kernel/input/joystick.txt
342 analog.map= [HW,JOY] Analog joystick and gamepad support
343 Specifies type or capabilities of an analog joystick
344 connected to one of 16 gameports
345 Format: <type1>,<type2>,..<type16>
348 Power management functions (SPARCstation-4/5 + deriv.)
350 Disable APC CPU standby support. SPARCstation-Fox does
351 not play well with APC CPU idle - disable it if you have
352 APC and your system crashes randomly.
354 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
355 Change the output verbosity whilst booting
356 Format: { quiet (default) | verbose | debug }
357 Change the amount of debugging information output
358 when initialising the APIC and IO-APIC components.
361 See Documentation/networking/ipv6.txt.
363 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
364 Limit apic dumping. The parameter defines the maximal
365 number of local apics being dumped. Also it is possible
366 to set it to "all" by meaning -- no limit here.
367 Format: { 1 (default) | 2 | ... | all }.
368 The parameter valid if only apic=debug or
369 apic=verbose is specified.
370 Example: apic=debug show_lapic=all
372 apm= [APM] Advanced Power Management
373 See header of arch/x86/kernel/apm_32.c.
375 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
376 Format: <io>,<irq>,<nodeID>
380 atarimouse= [HW,MOUSE] Atari Mouse
382 atascsi= [HW,SCSI] Atari SCSI
384 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
385 EzKey and similar keyboards
387 atkbd.reset= [HW] Reset keyboard during initialization
389 atkbd.set= [HW] Select keyboard code set
390 Format: <int> (2 = AT (default), 3 = PS/2)
392 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
395 atkbd.softraw= [HW] Choose between synthetic and real raw mode
396 Format: <bool> (0 = real, 1 = synthetic (default))
398 atkbd.softrepeat= [HW]
399 Use software keyboard repeat
403 baycom_epp= [HW,AX25]
406 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
408 See header of drivers/net/hamradio/baycom_par.c.
410 baycom_ser_fdx= [HW,AX25]
411 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
412 Format: <io>,<irq>,<mode>[,<baud>]
413 See header of drivers/net/hamradio/baycom_ser_fdx.c.
415 baycom_ser_hdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
417 Format: <io>,<irq>,<mode>
418 See header of drivers/net/hamradio/baycom_ser_hdx.c.
420 boot_delay= Milliseconds to delay each printk during boot.
421 Values larger than 10 seconds (10000) are changed to
425 bootmem_debug [KNL] Enable bootmem allocator debug messages.
427 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
428 bttv.radio= Most important insmod options are available as
430 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
431 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
434 See drivers/scsi/BusLogic.c, comment before function
435 BusLogic_ParseDriverOptions().
437 c101= [NET] Moxa C101 synchronous serial card
439 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
440 Sometimes CPU hardware bugs make them report the cache
441 size incorrectly. The kernel will attempt work arounds
442 to fix known problems, but for some CPUs it is not
443 possible to determine what the correct size should be.
444 This option provides an override for these situations.
447 [SECURITY] Disable capabilities. This would normally
448 be used only if an alternative security model is to be
449 configured. Potentially dangerous and should only be
450 used if you are entirely sure of the consequences.
452 ccw_timeout_log [S390]
453 See Documentation/s390/CommonIO for details.
455 cgroup_disable= [KNL] Disable a particular controller
456 Format: {name of the controller(s) to disable}
457 {Currently supported controllers - "memory"}
459 checkreqprot [SELINUX] Set initial checkreqprot flag value.
460 Format: { "0" | "1" }
461 See security/selinux/Kconfig help text.
462 0 -- check protection applied by kernel (includes
463 any implied execute protection).
464 1 -- check protection requested by application.
465 Default value is set via a kernel config option.
466 Value can be changed at runtime via
467 /selinux/checkreqprot.
470 See Documentation/s390/CommonIO for details.
472 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
474 Forces specified clocksource (if available) to be used
475 when calculating gettimeofday(). If specified
476 clocksource is not available, it defaults to PIT.
477 Format: { pit | tsc | cyclone | pmtmr }
479 clocksource= [GENERIC_TIME] Override the default clocksource
481 Override the default clocksource and use the clocksource
482 with the name specified.
483 Some clocksource names to choose from, depending on
485 [all] jiffies (this is the base, fallback clocksource)
487 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
488 pxa_timer,timer3,32k_counter,timer0_1
490 [X86-32] pit,hpet,tsc,vmi-timer;
491 scx200_hrt on Geode; cyclone on IBM x440
499 clearcpuid=BITNUM [X86]
500 Disable CPUID feature X for the kernel. See
501 arch/x86/include/asm/cpufeature.h for the valid bit
502 numbers. Note the Linux specific bits are not necessarily
503 stable over kernel options, but the vendor specific
505 Also note that user programs calling CPUID directly
506 or using the feature without checking anything
507 will still see it. This just prevents it from
508 being used by the kernel or shown in /proc/cpuinfo.
509 Also note the kernel might malfunction if you disable
512 cmo_free_hint= [PPC] Format: { yes | no }
513 Specify whether pages are marked as being inactive
514 when they are freed. This is used in CMO environments
515 to determine OS memory pressure for page stealing by
519 code_bytes [X86] How many bytes of object code to print
524 com20020= [HW,NET] ARCnet - COM20020 chipset
526 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
528 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
532 ARCnet - COM90xx chipset (memory-mapped buffers)
533 Format: <io>[,<irq>[,<memstart>]]
535 condev= [HW,S390] console device
538 console= [KNL] Output console device and options.
540 tty<n> Use the virtual console device <n>.
544 Use the specified serial port. The options are of
545 the form "bbbbpnf", where "bbbb" is the baud rate,
546 "p" is parity ("n", "o", or "e"), "n" is number of
547 bits, and "f" is flow control ("r" for RTS or
548 omit it). Default is "9600n8".
550 See Documentation/serial-console.txt for more
552 Documentation/networking/netconsole.txt for an
555 uart[8250],io,<addr>[,options]
556 uart[8250],mmio,<addr>[,options]
557 Start an early, polled-mode console on the 8250/16550
558 UART at the specified I/O port or MMIO address,
559 switching to the matching ttyS device later. The
560 options are the same as for ttyS, above.
562 If the device connected to the port is not a TTY but a braille
563 device, prepend "brl," before the device type, for instance
565 For now, only VisioBraille is supported.
567 consoleblank= [KNL] The console blank (screen saver) timeout in
568 seconds. Defaults to 10*60 = 10mins. A value of 0
569 disables the blank timer.
572 [KNL] Change the default value for
573 /proc/<pid>/coredump_filter.
574 See also Documentation/filesystems/proc.txt.
576 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
578 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
580 crashkernel=nn[KMG]@ss[KMG]
581 [KNL] Reserve a chunk of physical memory to
582 hold a kernel to switch to with kexec on panic.
584 crashkernel=range1:size1[,range2:size2,...][@offset]
585 [KNL] Same as above, but depends on the memory
586 in the running system. The syntax of range is
587 start-[end] where start and end are both
588 a memory unit (amount[KMG]). See also
589 Documentation/kdump/kdump.txt for a example.
594 cs89x0_media= [HW,NET]
595 Format: { rj45 | aui | bnc }
598 See header of drivers/s390/block/dasd_devmap.c.
600 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
601 (one device per port)
602 Format: <port#>,<type>
603 See also Documentation/input/joystick-parport.txt
605 debug [KNL] Enable kernel debugging (events log level).
608 [KNL] verbose self-tests
610 Print debugging info while doing the locking API
612 We default to 0 (no extra messages), setting it to
613 1 will print _a lot_ more information - normally
614 only useful to kernel developers.
616 debug_objects [KNL] Enable object debugging
619 [KNL] Disable object debugging
621 debugpat [X86] Enable PAT debugging
623 decnet.addr= [HW,NET]
624 Format: <area>[,<node>]
625 See also Documentation/networking/decnet.txt.
628 [same as hugepagesz=] The size of the default
629 HugeTLB page size. This is the size represented by
630 the legacy /proc/ hugepages APIs, used for SHM, and
631 default size when mounting hugetlbfs filesystems.
632 Defaults to the default architecture's huge page size
636 Set number of hash buckets for dentry cache.
639 IO parameters + enable/disable command.
641 digiepca= [HW,SERIAL]
642 See drivers/char/README.epca and
643 Documentation/serial/digiepca.txt.
646 See Documentation/networking/ipv6.txt.
649 See Documentation/networking/ipv6.txt.
651 disable_mtrr_cleanup [X86]
652 The kernel tries to adjust MTRR layout from continuous
653 to discrete, to make X server driver able to add WB
654 entry later. This parameter disables that.
656 disable_mtrr_trim [X86, Intel and AMD only]
657 By default the kernel will trim any uncacheable
658 memory out of your available memory pool based on
659 MTRR settings. This parameter disables that behavior,
660 possibly causing your machine to run very slowly.
662 disable_timer_pin_1 [X86]
663 Disable PIN 1 of APIC timer
664 Can be useful to work around chipset bugs.
666 dmasound= [HW,OSS] Sound subsystem buffers
668 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
669 this option disables the debugging code at boot.
671 dma_debug_entries=<number>
672 This option allows to tune the number of preallocated
673 entries for DMA-API debugging code. One entry is
674 required per DMA-API allocation. Use this if the
675 DMA-API debugging code disables itself because the
676 architectural default is too low.
678 dma_debug_driver=<driver_name>
679 With this option the DMA-API debugging driver
680 filter feature can be enabled at boot time. Just
681 pass the driver to filter for as the parameter.
682 The filter can be disabled or changed to another
683 driver later using sysfs.
689 dynamic_printk Enables pr_debug()/dev_dbg() calls if
690 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
691 These can also be switched on/off via
692 <debugfs>/dynamic_printk/modules
694 earlycon= [KNL] Output early console device and options.
695 uart[8250],io,<addr>[,options]
696 uart[8250],mmio,<addr>[,options]
697 Start an early, polled-mode console on the 8250/16550
698 UART at the specified I/O port or MMIO address.
699 The options are the same as for ttyS, above.
701 earlyprintk= [X86,SH,BLACKFIN]
703 earlyprintk=serial[,ttySn[,baudrate]]
704 earlyprintk=ttySn[,baudrate]
705 earlyprintk=dbgp[debugController#]
707 Append ",keep" to not disable it when the real console
710 Only vga or serial or usb debug port at a time.
712 Currently only ttyS0 and ttyS1 are supported.
714 Interaction with the standard serial driver is not
717 The VGA output is eventually overwritten by the real
723 Format: {"off" | "on" | "skip[mbr]"}
725 eisa_irq_edge= [PARISC,HW]
726 See header of drivers/parisc/eisa.c.
729 See comment before function elanfreq_setup() in
730 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
733 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
734 See Documentation/block/as-iosched.txt and
735 Documentation/block/deadline-iosched.txt for details.
737 elfcorehdr= [IA64,PPC,SH,X86]
738 Specifies physical address of start of kernel core
739 image elf header. Generally kexec loader will
740 pass this option to capture kernel.
741 See Documentation/kdump/kdump.txt for details.
743 enable_mtrr_cleanup [X86]
744 The kernel tries to adjust MTRR layout from continuous
745 to discrete, to make X server driver able to add WB
746 entry later. This parameter enables that.
748 enable_timer_pin_1 [X86]
749 Enable PIN 1 of APIC timer
750 Can be useful to work around chipset bugs
751 (in particular on some ATI chipsets).
752 The kernel tries to set a reasonable default.
754 enforcing [SELINUX] Set initial enforcing status.
756 See security/selinux/Kconfig help text.
757 0 -- permissive (log only, no denials).
758 1 -- enforcing (deny and log).
760 Value can be changed at runtime via /selinux/enforce.
762 ether= [HW,NET] Ethernet cards parameters
763 This option is obsoleted by the "netdev=" option, which
764 has equivalent usage. See its documentation for details.
766 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
771 fail_make_request=[KNL]
772 General fault injection mechanism.
773 Format: <interval>,<probability>,<space>,<times>
774 See also /Documentation/fault-injection/.
777 See header of drivers/scsi/fd_mcs.c.
780 See header of drivers/scsi/fdomain.c.
783 See Documentation/blockdev/floppy.txt.
785 force_pal_cache_flush
786 [IA-64] Avoid check_sal_cache_flush which may hang on
787 buggy SAL_CACHE_FLUSH implementations. Using this
788 parameter will force ia64_sal_cache_flush to call
789 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
792 [FTRACE] will set and start the specified tracer
793 as early as possible in order to facilitate early
797 [FTRACE] will dump the trace buffers on oops.
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= [HW] kgdb over consoles.
1125 Requires a tty driver that supports console polling.
1126 (only serial supported for now)
1127 Format: <serial_device>[,baud]
1129 kmac= [MIPS] korina ethernet MAC address.
1130 Configure the RouterBoard 532 series on-chip
1131 Ethernet adapter MAC address.
1133 kmemleak= [KNL] Boot-time kmemleak enable/disable
1134 Valid arguments: on, off
1137 kstack=N [X86] Print N words from the kernel stack
1140 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1141 Default is 0 (don't ignore, but inject #GP)
1143 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1144 Default is 1 (enabled)
1146 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1149 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1151 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1153 kvm-intel.bypass_guest_pf=
1154 [KVM,Intel] Disables bypassing of guest page faults
1155 on Intel chips. Default is 1 (enabled)
1157 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1158 (virtualized MMU) support on capable Intel chips.
1159 Default is 1 (enabled)
1161 kvm-intel.emulate_invalid_guest_state=
1162 [KVM,Intel] Enable emulation of invalid guest states
1163 Default is 0 (disabled)
1165 kvm-intel.flexpriority=
1166 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1167 Default is 1 (enabled)
1169 kvm-intel.unrestricted_guest=
1170 [KVM,Intel] Disable unrestricted guest feature
1171 (virtualized real and unpaged mode) on capable
1172 Intel chips. Default is 1 (enabled)
1174 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1175 feature (tagged TLBs) on capable Intel chips.
1176 Default is 1 (enabled)
1182 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1185 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1188 libata.dma= [LIBATA] DMA control
1189 libata.dma=0 Disable all PATA and SATA DMA
1190 libata.dma=1 PATA and SATA Disk DMA only
1191 libata.dma=2 ATAPI (CDROM) DMA only
1192 libata.dma=4 Compact Flash DMA only
1193 Combinations also work, so libata.dma=3 enables DMA
1194 for disks and CDROMs, but not CFs.
1196 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1197 libata.ignore_hpa=0 keep BIOS limits (default)
1198 libata.ignore_hpa=1 ignore limits, using full disk
1200 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1204 libata.force= [LIBATA] Force configurations. The format is comma
1205 separated list of "[ID:]VAL" where ID is
1206 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1207 matching port, link or device. Basically, it matches
1208 the ATA ID string printed on console by libata. If
1209 the whole ID part is omitted, the last PORT and DEVICE
1210 values are used. If ID hasn't been specified yet, the
1211 configuration applies to all ports, links and devices.
1213 If only DEVICE is omitted, the parameter applies to
1214 the port and all links and devices behind it. DEVICE
1215 number of 0 either selects the first device or the
1216 first fan-out link behind PMP device. It does not
1217 select the host link. DEVICE number of 15 selects the
1218 host link and device attached to it.
1220 The VAL specifies the configuration to force. As long
1221 as there's no ambiguity shortcut notation is allowed.
1222 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1223 The following configurations can be forced.
1225 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1226 Any ID with matching PORT is used.
1228 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1230 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1231 udma[/][16,25,33,44,66,100,133] notation is also
1234 * [no]ncq: Turn on or off NCQ.
1236 * nohrst, nosrst, norst: suppress hard, soft
1239 If there are multiple matching configurations changing
1240 the same attribute, the last one is used.
1242 lmb=debug [KNL] Enable lmb debug messages.
1244 load_ramdisk= [RAM] List of ramdisks to load from floppy
1245 See Documentation/blockdev/ramdisk.txt.
1247 lockd.nlm_grace_period=P [NFS] Assign grace period.
1250 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1253 lockd.nlm_timeout=T [NFS] Assign timeout value.
1256 lockd.nlm_udpport=M [NFS] Assign UDP port.
1259 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1262 loglevel= All Kernel Messages with a loglevel smaller than the
1263 console loglevel will be printed to the console. It can
1264 also be changed with klogd or other programs. The
1265 loglevels are defined as follows:
1267 0 (KERN_EMERG) system is unusable
1268 1 (KERN_ALERT) action must be taken immediately
1269 2 (KERN_CRIT) critical conditions
1270 3 (KERN_ERR) error conditions
1271 4 (KERN_WARNING) warning conditions
1272 5 (KERN_NOTICE) normal but significant condition
1273 6 (KERN_INFO) informational
1274 7 (KERN_DEBUG) debug-level messages
1276 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1277 Format: { n | nk | nM }
1278 n must be a power of two. The default size
1279 is set in the kernel config file.
1281 logo.nologo [FB] Disables display of the built-in Linux logo.
1282 This may be used to provide more screen space for
1283 kernel log messages and is useful when debugging
1284 kernel boot problems.
1286 lp=0 [LP] Specify parallel ports to use, e.g,
1287 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1288 lp=reset first parallel port). 'lp=0' disables the
1289 lp=auto printer driver. 'lp=reset' (which can be
1290 specified in addition to the ports) causes
1291 attached printers to be reset. Using
1292 lp=port1,port2,... specifies the parallel ports
1293 to associate lp devices with, starting with
1294 lp0. A port specification may be 'none' to skip
1295 that lp device, or a parport name such as
1296 'parport0'. Specifying 'lp=auto' instead of a
1297 port specification list means that device IDs
1298 from each port should be examined, to see if
1299 an IEEE 1284-compliant printer is attached; if
1300 so, the driver will manage that printer.
1301 See also header of drivers/char/lp.c.
1304 Sets loops_per_jiffy to given constant, thus avoiding
1305 time-consuming boot-time autodetection (up to 250 ms per
1306 CPU). 0 enables autodetection (default). To determine
1307 the correct value for your kernel, boot with normal
1308 autodetection and see what value is printed. Note that
1309 on SMP systems the preset will be applied to all CPUs,
1310 which is likely to cause problems if your CPUs need
1311 significantly divergent settings. An incorrect value
1312 will cause delays in the kernel to be wrong, leading to
1313 unpredictable I/O errors and other breakage. Although
1314 unlikely, in the extreme case this might damage your
1318 Format: <io>,<irq>,<dma>
1320 mac5380= [HW,SCSI] Format:
1321 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1323 machvec= [IA64] Force the use of a particular machine-vector
1324 (machvec) in a generic kernel.
1325 Example: machvec=hpzx1_swiotlb
1327 machtype= [Loongson] Share the same kernel image file between different
1329 Example: machtype=lemote-yeeloong-2f-7inch
1331 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1332 than or equal to this physical address is ignored.
1334 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1335 should make use of. maxcpus=n : n >= 0 limits the
1336 kernel to using 'n' processors. n=0 is a special case,
1337 it is equivalent to "nosmp", which also disables
1340 max_loop= [LOOP] Maximum number of loopback devices that can
1344 max_luns= [SCSI] Maximum number of LUNs to probe.
1345 Should be between 1 and 2^32-1.
1348 [SCSI] Maximum number of LUNs received.
1349 Should be between 1 and 16384.
1353 mce [X86-32] Machine Check Exception
1355 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1357 md= [HW] RAID subsystems devices and level
1358 See Documentation/md.txt.
1361 Format: <first>,<last>
1362 Specifies range of consoles to be captured by the MDA.
1364 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1365 Amount of memory to be used when the kernel is not able
1366 to see the whole system memory or for test.
1367 [X86-32] Use together with memmap= to avoid physical
1368 address space collisions. Without memmap= PCI devices
1369 could be placed at addresses belonging to unused RAM.
1371 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1375 [KNL,SH] Allow user to override the default size for
1376 per-device physically contiguous DMA buffers.
1378 memmap=exactmap [KNL,X86] Enable setting of an exact
1379 E820 memory map, as specified by the user.
1380 Such memmap=exactmap lines can be constructed based on
1381 BIOS output or other requirements. See the memmap=nn@ss
1384 memmap=nn[KMG]@ss[KMG]
1385 [KNL] Force usage of a specific region of memory
1386 Region of memory to be used, from ss to ss+nn.
1388 memmap=nn[KMG]#ss[KMG]
1389 [KNL,ACPI] Mark specific memory as ACPI data.
1390 Region of memory to be used, from ss to ss+nn.
1392 memmap=nn[KMG]$ss[KMG]
1393 [KNL,ACPI] Mark specific memory as reserved.
1394 Region of memory to be used, from ss to ss+nn.
1395 Example: Exclude memory from 0x18690000-0x1869ffff
1396 memmap=64K$0x18690000
1398 memmap=0x10000$0x18690000
1400 memory_corruption_check=0/1 [X86]
1401 Some BIOSes seem to corrupt the first 64k of
1402 memory when doing things like suspend/resume.
1403 Setting this option will scan the memory
1404 looking for corruption. Enabling this will
1405 both detect corruption and prevent the kernel
1406 from using the memory being corrupted.
1407 However, its intended as a diagnostic tool; if
1408 repeatable BIOS-originated corruption always
1409 affects the same memory, you can use memmap=
1410 to prevent the kernel from using that memory.
1412 memory_corruption_check_size=size [X86]
1413 By default it checks for corruption in the low
1414 64k, making this memory unavailable for normal
1415 use. Use this parameter to scan for
1416 corruption in more or less memory.
1418 memory_corruption_check_period=seconds [X86]
1419 By default it checks for corruption every 60
1420 seconds. Use this parameter to check at some
1421 other rate. 0 disables periodic checking.
1423 memtest= [KNL,X86] Enable memtest
1425 default : 0 <disable>
1426 Specifies the number of memtest passes to be
1427 performed. Each pass selects another test
1428 pattern from a given set of patterns. Memtest
1429 fills the memory with this pattern, validates
1430 memory contents and reserves bad memory
1431 regions that are detected.
1433 meye.*= [HW] Set MotionEye Camera parameters
1434 See Documentation/video4linux/meye.txt.
1436 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1437 Multi-Function General Purpose Timers on AMD Geode
1440 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1441 the BIOS has incorrectly applied a workaround. TinyBIOS
1442 version 0.98 is known to be affected, 0.99 fixes the
1443 problem by letting the user disable the workaround.
1447 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1448 physical address is ignored.
1450 mini2440= [ARM,HW,KNL]
1451 Format:[0..2][b][c][t]
1453 MINI2440 configuration specification:
1454 0 - The attached screen is the 3.5" TFT
1455 1 - The attached screen is the 7" TFT
1456 2 - The VGA Shield is attached (1024x768)
1457 Leaving out the screen size parameter will not load
1458 the TFT driver, and the framebuffer will be left
1460 b - Enable backlight. The TFT backlight pin will be
1461 linked to the kernel VESA blanking code and a GPIO
1462 LED. This parameter is not necessary when using the
1464 c - Enable the s3c camera interface.
1465 t - Reserved for enabling touchscreen support. The
1466 touchscreen support is not enabled in the mainstream
1467 kernel as of 2.6.30, a preliminary port can be found
1468 in the "bleeding edge" mini2440 support kernel at
1469 http://repo.or.cz/w/linux-2.6/mini2440.git
1472 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1473 parameter allows control of the logging verbosity for
1474 the additional memory initialisation checks. A value
1475 of 0 disables mminit logging and a level of 4 will
1476 log everything. Information is printed at KERN_DEBUG
1477 so loglevel=8 may also need to be specified.
1480 [MOUSE] Maximum time between finger touching and
1481 leaving touchpad surface for touch to be considered
1482 a tap and be reported as a left button click (for
1483 touchpads working in absolute mode only).
1485 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1486 reporting absolute coordinates, such as tablets
1487 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1488 reporting absolute coordinates, such as tablets
1490 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1491 is similar to kernelcore except it specifies the
1492 amount of memory used for migratable allocations.
1493 If both kernelcore and movablecore is specified,
1494 then kernelcore will be at *least* the specified
1495 value but may be more. If movablecore on its own
1496 is specified, the administrator must be careful
1497 that the amount of memory usable for all allocations
1503 MTD_Partition= [MTD]
1504 Format: <name>,<region-number>,<size>,<offset>
1506 MTD_Region= [MTD] Format:
1507 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1510 See drivers/mtd/cmdlinepart.c.
1512 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1514 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1516 boundary - index of last SLC block on Flex-OneNAND.
1517 The remaining blocks are configured as MLC blocks.
1518 lock - Configure if Flex-OneNAND boundary should be locked.
1519 Once locked, the boundary cannot be changed.
1520 1 indicates lock status, 0 indicates unlock status.
1523 ARM/S3C2412 JIVE boot control
1525 See arch/arm/mach-s3c2412/mach-jive.c
1527 mtouchusb.raw_coordinates=
1528 [HW] Make the MicroTouch USB driver use raw coordinates
1529 ('y', default) or cooked coordinates ('n')
1531 mtrr_chunk_size=nn[KMG] [X86]
1532 used for mtrr cleanup. It is largest continuous chunk
1533 that could hold holes aka. UC entries.
1535 mtrr_gran_size=nn[KMG] [X86]
1536 Used for mtrr cleanup. It is granularity of mtrr block.
1538 Large value could prevent small alignment from
1541 mtrr_spare_reg_nr=n [X86]
1543 Range: 0,7 : spare reg number
1545 Used for mtrr cleanup. It is spare mtrr entries number.
1546 Set to 2 or more if your graphical card needs more.
1548 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1551 See header of drivers/scsi/NCR_D700.c.
1555 ncr53c400= [HW,SCSI]
1557 ncr53c400a= [HW,SCSI]
1559 ncr53c406a= [HW,SCSI]
1561 ncr53c8xx= [HW,SCSI]
1563 netdev= [NET] Network devices parameters
1564 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1565 Note that mem_start is often overloaded to mean
1566 something different and driver-specific.
1567 This usage is only documented in each driver source
1571 [NETFILTER] Enable connection tracking flow accounting
1572 0 to disable accounting
1573 1 to enable accounting
1574 Default value depends on CONFIG_NF_CT_ACCT that is
1575 going to be removed in 2.6.29.
1578 See Documentation/filesystems/nfs/nfsroot.txt.
1580 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1581 See Documentation/filesystems/nfs/nfsroot.txt.
1583 nfs.callback_tcpport=
1584 [NFS] set the TCP port on which the NFSv4 callback
1585 channel should listen.
1588 [NFS] sets the pathname to the program which is used
1589 to update the NFS client cache entries.
1591 nfs.cache_getent_timeout=
1592 [NFS] sets the timeout after which an attempt to
1593 update a cache entry is deemed to have failed.
1595 nfs.idmap_cache_timeout=
1596 [NFS] set the maximum lifetime for idmapper cache
1600 [NFS] enable 64-bit inode numbers.
1601 If zero, the NFS client will fake up a 32-bit inode
1602 number for the readdir() and stat() syscalls instead
1603 of returning the full 64-bit number.
1604 The default is to return 64-bit inode numbers.
1606 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1607 when a NMI is triggered.
1608 Format: [state][,regs][,debounce][,die]
1610 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1611 Format: [panic,][num]
1613 0 - turn nmi_watchdog off
1614 1 - use the IO-APIC timer for the NMI watchdog
1615 2 - use the local APIC for the NMI watchdog using
1616 a performance counter. Note: This will use one
1617 performance counter and the local APIC's performance
1619 When panic is specified, panic when an NMI watchdog
1621 This is useful when you use a panic=... timeout and
1622 need the box quickly up again.
1623 Instead of 1 and 2 it is possible to use the following
1624 symbolic names: lapic and ioapic
1625 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1627 netpoll.carrier_timeout=
1628 [NET] Specifies amount of time (in seconds) that
1629 netpoll should wait for a carrier. By default netpoll
1632 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1633 emulation library even if a 387 maths coprocessor
1637 [HW] Never suspend the console
1638 Disable suspending of consoles during suspend and
1639 hibernate operations. Once disabled, debugging
1640 messages can reach various consoles while the rest
1641 of the system is being put to sleep (ie, while
1642 debugging driver suspend/resume hooks). This may
1643 not work reliably with all consoles, but is known
1644 to work with serial and VGA consoles.
1646 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1647 caches in the slab allocator. Saves per-node memory,
1648 but will impact performance.
1652 noapic [SMP,APIC] Tells the kernel to not make use of any
1653 IOAPICs that may be present in the system.
1655 nobats [PPC] Do not use BATs for mapping kernel lowmem
1656 on "Classic" PPC cores.
1660 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1662 nodelayacct [KNL] Disable per-task delay accounting
1664 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1666 nodsp [SH] Disable hardware DSP at boot time.
1668 noefi [X86] Disable EFI runtime services support.
1673 On X86-32 available only on PAE configured kernels.
1674 noexec=on: enable non-executable mappings (default)
1675 noexec=off: disable non-executable mappings
1678 This affects only 32-bit executables.
1679 noexec32=on: enable non-executable mappings (default)
1680 read doesn't imply executable mappings
1681 noexec32=off: disable non-executable mappings
1682 read implies executable mappings
1684 nofpu [SH] Disable hardware FPU at boot time.
1686 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1687 register save and restore. The kernel will only save
1688 legacy floating-point registers on task switch.
1690 noxsave [BUGS=X86] Disables x86 extended register state save
1691 and restore using xsave. The kernel will fallback to
1692 enabling legacy floating-point and sse state.
1694 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1695 wfi(ARM) instruction doesn't work correctly and not to
1696 use it. This is also useful when using JTAG debugger.
1698 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1699 instruction doesn't work correctly and not to
1702 no_file_caps Tells the kernel not to honor file capabilities. The
1703 only way then for a file to be executed with privilege
1704 is to be setuid root or executed by root.
1706 nohalt [IA-64] Tells the kernel not to use the power saving
1707 function PAL_HALT_LIGHT when idle. This increases
1708 power-consumption. On the positive side, it reduces
1709 interrupt wake-up latency, which may improve performance
1710 in certain environments such as networked servers or
1713 nohz= [KNL] Boottime enable/disable dynamic ticks
1714 Valid arguments: on, off
1717 noiotrap [SH] Disables trapped I/O port accesses.
1719 noirqdebug [X86-32] Disables the code which attempts to detect and
1720 disable unhandled interrupt sources.
1722 no_timer_check [X86,APIC] Disables the code which tests for
1723 broken timer IRQ sources.
1725 noisapnp [ISAPNP] Disables ISA PnP code.
1727 noinitrd [RAM] Tells the kernel not to load any configured
1730 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1735 nojitter [IA64] Disables jitter checking for ITC timers.
1737 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1739 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1741 noltlbs [PPC] Do not use large page/tlb entries for kernel
1742 lowmem mapping on PPC40x.
1744 nomca [IA-64] Disable machine check abort handling
1746 nomce [X86-32] Machine Check Exception
1748 nomfgpt [X86-32] Disable Multi-Function General Purpose
1749 Timer usage (for AMD Geode machines).
1751 nopat [X86] Disable PAT (page attribute table extension of
1752 pagetables) support.
1754 norandmaps Don't use address space randomization. Equivalent to
1755 echo 0 > /proc/sys/kernel/randomize_va_space
1757 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1759 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1760 with UP alternatives
1762 noresidual [PPC] Don't use residual data on PReP machines.
1764 noresume [SWSUSP] Disables resume and restores original swap
1767 no-scroll [VGA] Disables scrollback.
1768 This is required for the Braillex ib80-piezo Braille
1769 reader made by F.H. Papenmeier (Germany).
1773 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1775 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1776 and disable the IO APIC. legacy for "maxcpus=0".
1778 nosoftlockup [KNL] Disable the soft-lockup detector.
1780 noswapaccount [KNL] Disable accounting of swap in memory resource
1781 controller. (See Documentation/cgroups/memory.txt)
1783 nosync [HW,M68K] Disables sync negotiation for all devices.
1785 notsc [BUGS=X86-32] Disable Time Stamp Counter
1787 nousb [USB] Disable the USB subsystem
1791 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1793 nptcg= [IA64] Override max number of concurrent global TLB
1794 purges which is reported from either PAL_VM_SUMMARY or
1797 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1799 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1800 one of ['zone', 'node', 'default'] can be specified
1801 This can be set from sysctl after boot.
1802 See Documentation/sysctl/vm.txt for details.
1804 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1805 See Documentation/debugging-via-ohci1394.txt for more
1808 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1809 Rather than timing out after 20 ms if an EC
1810 command is not properly ACKed, override the length
1811 of the timeout. We have interrupts disabled while
1812 waiting for the ACK, so if this is set too high
1813 interrupts *may* be lost!
1815 omap_mux= [OMAP] Override bootloader pin multiplexing.
1816 Format: <mux_mode0.mode_name=value>...
1817 For example, to override I2C bus2:
1818 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1823 oprofile.timer= [HW]
1824 Use timer interrupt instead of performance counters
1826 oprofile.cpu_type= Force an oprofile cpu type
1827 This might be useful if you have an older oprofile
1828 userland or if you want common events.
1829 Format: { arch_perfmon }
1830 arch_perfmon: [X86] Force use of architectural
1831 perfmon on Intel CPUs instead of the
1832 CPU specific event set.
1834 osst= [HW,SCSI] SCSI Tape Driver
1835 Format: <buffer_size>,<write_threshold>
1836 See also Documentation/scsi/st.txt.
1838 panic= [KNL] Kernel behaviour on panic
1841 parkbd.port= [HW] Parallel port number the keyboard adapter is
1842 connected to, default is 0.
1844 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1845 0 for XT, 1 for AT (default is AT).
1848 parport= [HW,PPT] Specify parallel ports. 0 disables.
1849 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1850 Use 'auto' to force the driver to use any
1851 IRQ/DMA settings detected (the default is to
1852 ignore detected IRQ/DMA settings because of
1853 possible conflicts). You can specify the base
1854 address, IRQ, and DMA settings; IRQ and DMA
1855 should be numbers, or 'auto' (for using detected
1856 settings on that particular port), or 'nofifo'
1857 (to avoid using a FIFO even if it is detected).
1858 Parallel ports are assigned in the order they
1859 are specified on the command line, starting
1862 parport_init_mode= [HW,PPT]
1863 Configure VIA parallel port to operate in
1864 a specific mode. This is necessary on Pegasos
1865 computer where firmware has no options for setting
1866 up parallel port mode and sets it to spp.
1867 Currently this function knows 686a and 8231 chips.
1868 Format: [spp|ps2|epp|ecp|ecpepp]
1870 pas2= [HW,OSS] Format:
1871 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1874 See header of drivers/scsi/pas16.c.
1877 Halt all CPUs after the first oops has been printed for
1878 the specified number of seconds. This is to be used if
1879 your oopses keep scrolling off the screen.
1884 See header of drivers/block/paride/pcd.c.
1885 See also Documentation/blockdev/paride.txt.
1887 pci=option[,option...] [PCI] various PCI subsystem options:
1888 earlydump [X86] dump PCI config space before the kernel
1890 off [X86] don't probe for the PCI bus
1891 bios [X86-32] force use of PCI BIOS, don't access
1892 the hardware directly. Use this if your machine
1893 has a non-standard PCI host bridge.
1894 nobios [X86-32] disallow use of PCI BIOS, only direct
1895 hardware access methods are allowed. Use this
1896 if you experience crashes upon bootup and you
1897 suspect they are caused by the BIOS.
1898 conf1 [X86] Force use of PCI Configuration
1900 conf2 [X86] Force use of PCI Configuration
1902 noaer [PCIE] If the PCIEAER kernel config parameter is
1903 enabled, this kernel boot option can be used to
1904 disable the use of PCIE advanced error reporting.
1905 nodomains [PCI] Disable support for multiple PCI
1906 root domains (aka PCI segments, in ACPI-speak).
1907 nommconf [X86] Disable use of MMCONFIG for PCI
1909 check_enable_amd_mmconf [X86] check for and enable
1910 properly configured MMIO access to PCI
1911 config space on AMD family 10h CPU
1912 nomsi [MSI] If the PCI_MSI kernel config parameter is
1913 enabled, this kernel boot option can be used to
1914 disable the use of MSI interrupts system-wide.
1915 noioapicquirk [APIC] Disable all boot interrupt quirks.
1916 Safety option to keep boot IRQs enabled. This
1917 should never be necessary.
1918 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1919 primary IO-APIC for bridges that cannot disable
1920 boot IRQs. This fixes a source of spurious IRQs
1921 when the system masks IRQs.
1922 noioapicreroute [APIC] Disable workaround that uses the
1923 boot IRQ equivalent of an IRQ that connects to
1924 a chipset where boot IRQs cannot be disabled.
1925 The opposite of ioapicreroute.
1926 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1927 routing table. These calls are known to be buggy
1928 on several machines and they hang the machine
1929 when used, but on other computers it's the only
1930 way to get the interrupt routing table. Try
1931 this option if the kernel is unable to allocate
1932 IRQs or discover secondary PCI buses on your
1934 rom [X86] Assign address space to expansion ROMs.
1935 Use with caution as certain devices share
1936 address decoders between ROMs and other
1938 norom [X86] Do not assign address space to
1939 expansion ROMs that do not already have
1940 BIOS assigned address ranges.
1941 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1942 assigned automatically to PCI devices. You can
1943 make the kernel exclude IRQs of your ISA cards
1945 pirqaddr=0xAAAAA [X86] Specify the physical address
1946 of the PIRQ table (normally generated
1947 by the BIOS) if it is outside the
1948 F0000h-100000h range.
1949 lastbus=N [X86] Scan all buses thru bus #N. Can be
1950 useful if the kernel is unable to find your
1951 secondary buses and you want to tell it
1952 explicitly which ones they are.
1953 assign-busses [X86] Always assign all PCI bus
1954 numbers ourselves, overriding
1955 whatever the firmware may have done.
1956 usepirqmask [X86] Honor the possible IRQ mask stored
1957 in the BIOS $PIR table. This is needed on
1958 some systems with broken BIOSes, notably
1959 some HP Pavilion N5400 and Omnibook XE3
1960 notebooks. This will have no effect if ACPI
1961 IRQ routing is enabled.
1962 noacpi [X86] Do not use ACPI for IRQ routing
1963 or for PCI scanning.
1964 use_crs [X86] Use PCI host bridge window information
1965 from ACPI. On BIOSes from 2008 or later, this
1966 is enabled by default. If you need to use this,
1967 please report a bug.
1968 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1969 If you need to use this, please report a bug.
1970 routeirq Do IRQ routing for all PCI devices.
1971 This is normally done in pci_enable_device(),
1972 so this option is a temporary workaround
1973 for broken drivers that don't call it.
1974 skip_isa_align [X86] do not align io start addr, so can
1975 handle more pci cards
1976 firmware [ARM] Do not re-enumerate the bus but instead
1977 just use the configuration from the
1978 bootloader. This is currently used on
1979 IXP2000 systems where the bus has to be
1980 configured a certain way for adjunct CPUs.
1981 noearly [X86] Don't do any early type 1 scanning.
1982 This might help on some broken boards which
1983 machine check when some devices' config space
1984 is read. But various workarounds are disabled
1985 and some IOMMU drivers will not work.
1986 bfsort Sort PCI devices into breadth-first order.
1987 This sorting is done to get a device
1988 order compatible with older (<= 2.4) kernels.
1989 nobfsort Don't sort PCI devices into breadth-first order.
1990 cbiosize=nn[KMG] The fixed amount of bus space which is
1991 reserved for the CardBus bridge's IO window.
1992 The default value is 256 bytes.
1993 cbmemsize=nn[KMG] The fixed amount of bus space which is
1994 reserved for the CardBus bridge's memory
1995 window. The default value is 64 megabytes.
1998 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1999 Specifies alignment and device to reassign
2000 aligned memory resources.
2001 If <order of align> is not specified,
2002 PAGE_SIZE is used as alignment.
2003 PCI-PCI bridge can be specified, if resource
2004 windows need to be expanded.
2005 ecrc= Enable/disable PCIe ECRC (transaction layer
2006 end-to-end CRC checking).
2007 bios: Use BIOS/firmware settings. This is the
2012 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2015 force Enable ASPM even on devices that claim not to support it.
2016 WARNING: Forcing ASPM on may cause system lockups.
2018 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2019 off Do not use native PCIe PME signaling.
2020 force Use native PCIe PME signaling even if the BIOS refuses
2021 to allow the kernel to control the relevant PCIe config
2023 nomsi Do not use MSI for native PCIe PME signaling (this makes
2024 all PCIe root ports use INTx for everything).
2026 pcmv= [HW,PCMCIA] BadgePAD 4
2029 See Documentation/blockdev/paride.txt.
2031 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2034 See arch/parisc/kernel/pdc_chassis.c
2036 percpu_alloc= Select which percpu first chunk allocator to use.
2037 Currently supported values are "embed" and "page".
2038 Archs may support subset or none of the selections.
2039 See comments in mm/percpu.c for details on each
2040 allocator. This parameter is primarily for debugging
2041 and performance comparison.
2044 See Documentation/blockdev/paride.txt.
2047 See Documentation/blockdev/paride.txt.
2049 pirq= [SMP,APIC] Manual mp-table setup
2050 See Documentation/x86/i386/IO-APIC.txt.
2052 plip= [PPT,NET] Parallel port network link
2053 Format: { parport<nr> | timid | 0 }
2054 See also Documentation/parport.txt.
2056 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2057 Override pmtimer IOPort with a hex value.
2061 Enable PNP debug messages. This depends on the
2062 CONFIG_PNP_DEBUG_MESSAGES option.
2068 { on | off | curr | res | no-curr | no-res }
2071 [ISAPNP] Exclude IRQs for the autoconfiguration
2074 [ISAPNP] Exclude DMAs for the autoconfiguration
2076 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2077 Ranges are in pairs (I/O port base and size).
2080 [ISAPNP] Exclude memory regions for the
2082 Ranges are in pairs (memory base and size).
2084 ports= [IP_VS_FTP] IPVS ftp helper module
2086 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2088 Format: <port>,<port>....
2090 print-fatal-signals=
2091 [KNL] debug: print fatal signals
2093 If enabled, warn about various signal handling
2094 related application anomalies: too many signals,
2095 too many POSIX.1 timers, fatal signals causing a
2098 If you hit the warning due to signal overflow,
2099 you might want to try "ulimit -i unlimited".
2103 printk.time= Show timing data prefixed to each printk message line
2104 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2106 processor.max_cstate= [HW,ACPI]
2107 Limit processor to maximum C-state
2108 max_cstate=9 overrides any DMI blacklist limit.
2110 processor.nocst [HW,ACPI]
2111 Ignore the _CST method to determine C-states,
2112 instead using the legacy FADT method
2114 profile= [KNL] Enable kernel profiling via /proc/profile
2115 Format: [schedule,]<number>
2116 Param: "schedule" - profile schedule points.
2117 Param: <number> - step/bucket size as a power of 2 for
2118 statistical time based profiling.
2119 Param: "sleep" - profile D-state sleeping (millisecs).
2120 Requires CONFIG_SCHEDSTATS
2121 Param: "kvm" - profile VM exits.
2123 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2125 See Documentation/blockdev/ramdisk.txt.
2127 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2128 probe for; one of (bare|imps|exps|lifebook|any).
2129 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2131 psmouse.resetafter= [HW,MOUSE]
2132 Try to reset the device after so many bad packets
2135 [HW,MOUSE] Set desired mouse resolution, in dpi.
2136 psmouse.smartscroll=
2137 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2138 0 = disabled, 1 = enabled (default).
2140 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2142 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2145 See Documentation/blockdev/paride.txt.
2148 [KNL] Number of legacy pty's. Overwrites compiled-in
2151 quiet [KNL] Disable most log messages
2156 See Documentation/md.txt.
2158 ramdisk_blocksize= [RAM]
2159 See Documentation/blockdev/ramdisk.txt.
2161 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2162 See Documentation/blockdev/ramdisk.txt.
2164 rcupdate.blimit= [KNL,BOOT]
2165 Set maximum number of finished RCU callbacks to process
2168 rcupdate.qhimark= [KNL,BOOT]
2169 Set threshold of queued
2170 RCU callbacks over which batch limiting is disabled.
2172 rcupdate.qlowmark= [KNL,BOOT]
2173 Set threshold of queued RCU callbacks below which
2174 batch limiting is re-enabled.
2178 Run specified binary instead of /init from the ramdisk,
2179 used for early userspace startup. See initrd.
2181 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2182 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2183 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2186 [KNL, SMP] Set scheduler's default relax_domain_level.
2187 See Documentation/cgroups/cpusets.txt.
2189 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2191 reservetop= [X86-32]
2193 Reserves a hole at the top of the kernel virtual
2196 reset_devices [KNL] Force drivers to reset the underlying device
2197 during initialization.
2200 Specify the partition device for software suspend
2202 resume_offset= [SWSUSP]
2203 Specify the offset from the beginning of the partition
2204 given by "resume=" at which the swap header is located,
2205 in <PAGE_SIZE> units (needed only for swap files).
2206 See Documentation/power/swsusp-and-swap-files.txt
2208 retain_initrd [RAM] Keep initrd memory after extraction
2210 rhash_entries= [KNL,NET]
2211 Set number of hash buckets for route cache
2213 riscom8= [HW,SERIAL]
2214 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2216 ro [KNL] Mount root device read-only on boot
2218 root= [KNL] Root filesystem
2220 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2221 mount the root filesystem
2223 rootflags= [KNL] Set root filesystem mount option string
2225 rootfstype= [KNL] Set root filesystem type
2227 rootwait [KNL] Wait (indefinitely) for root device to show up.
2228 Useful for devices that are detected asynchronously
2229 (e.g. USB and MMC devices).
2231 rw [KNL] Mount root device read-write on boot
2233 S [KNL] Run init in single mode
2236 See drivers/net/irda/sa1100_ir.c.
2238 sbni= [NET] Granch SBNI12 leased line adapter
2240 sched_debug [KNL] Enables verbose scheduler debug messages.
2242 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2243 Format: <io>[,<timeout>[,<isapnp>]]
2245 scsi_debug_*= [SCSI]
2246 See drivers/scsi/scsi_debug.c.
2248 scsi_default_dev_flags=
2249 [SCSI] SCSI default device flags
2252 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2253 Format: <vendor>:<model>:<flags>
2254 (flags are integer value)
2256 scsi_logging_level= [SCSI] a bit mask of logging levels
2257 See drivers/scsi/scsi_logging.h for bits. Also
2258 settable via sysctl at dev.scsi.logging_level
2259 (/proc/sys/dev/scsi/logging_level).
2260 There is also a nice 'scsi_logging_level' script in the
2261 S390-tools package, available for download at
2262 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2264 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2265 discovered. async scans them in kernel threads,
2266 allowing boot to proceed. none ignores them, expecting
2267 user space to do the scan.
2269 security= [SECURITY] Choose a security module to enable at boot.
2270 If this boot parameter is not specified, only the first
2271 security module asking for security registration will be
2272 loaded. An invalid security module name will be treated
2273 as if no module has been chosen.
2275 selinux= [SELINUX] Disable or enable SELinux at boot time.
2276 Format: { "0" | "1" }
2277 See security/selinux/Kconfig help text.
2280 Default value is set via kernel config option.
2281 If enabled at boot time, /selinux/disable can be used
2282 later to disable prior to initial policy load.
2284 serialnumber [BUGS=X86-32]
2287 Maximal number of shapers.
2289 show_msr= [x86] show boot-time MSR settings
2290 Format: { <integer> }
2291 Show boot-time (BIOS-initialized) MSR settings.
2292 The parameter means the number of CPUs to show,
2293 for example 1 means boot CPU only.
2296 See header of drivers/scsi/sim710.c.
2303 slub_debug[=options[,slabs]] [MM, SLUB]
2304 Enabling slub_debug allows one to determine the
2305 culprit if slab objects become corrupted. Enabling
2306 slub_debug can create guard zones around objects and
2307 may poison objects when not in use. Also tracks the
2308 last alloc / free. For more information see
2309 Documentation/vm/slub.txt.
2311 slub_max_order= [MM, SLUB]
2312 Determines the maximum allowed order for slabs.
2313 A high setting may cause OOMs due to memory
2314 fragmentation. For more information see
2315 Documentation/vm/slub.txt.
2317 slub_min_objects= [MM, SLUB]
2318 The minimum number of objects per slab. SLUB will
2319 increase the slab order up to slub_max_order to
2320 generate a sufficiently large slab able to contain
2321 the number of objects indicated. The higher the number
2322 of objects the smaller the overhead of tracking slabs
2323 and the less frequently locks need to be acquired.
2324 For more information see Documentation/vm/slub.txt.
2326 slub_min_order= [MM, SLUB]
2327 Determines the mininum page order for slabs. Must be
2328 lower than slub_max_order.
2329 For more information see Documentation/vm/slub.txt.
2331 slub_nomerge [MM, SLUB]
2332 Disable merging of slabs with similar size. May be
2333 necessary if there is some reason to distinguish
2334 allocs to different slabs. Debug options disable
2335 merging on their own.
2336 For more information see Documentation/vm/slub.txt.
2339 Format: <io1>[,<io2>[,...,<io8>]]
2341 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2342 attempt to substitute SMP alternatives once at boot.
2344 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2345 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2346 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2347 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2348 smsc-ircc2.ircc_irq= [HW] IRQ line
2349 smsc-ircc2.ircc_dma= [HW] DMA channel
2350 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2351 0: Toshiba Satellite 1800 (GP data pin select)
2352 1: Fast pin select (default)
2355 snd-ad1816a= [HW,ALSA]
2357 snd-ad1848= [HW,ALSA]
2359 snd-ali5451= [HW,ALSA]
2361 snd-als100= [HW,ALSA]
2363 snd-als4000= [HW,ALSA]
2365 snd-azt2320= [HW,ALSA]
2367 snd-cmi8330= [HW,ALSA]
2369 snd-cmipci= [HW,ALSA]
2371 snd-cs4231= [HW,ALSA]
2373 snd-cs4232= [HW,ALSA]
2375 snd-cs4236= [HW,ALSA]
2377 snd-cs4281= [HW,ALSA]
2379 snd-cs46xx= [HW,ALSA]
2381 snd-dt019x= [HW,ALSA]
2383 snd-dummy= [HW,ALSA]
2385 snd-emu10k1= [HW,ALSA]
2387 snd-ens1370= [HW,ALSA]
2389 snd-ens1371= [HW,ALSA]
2391 snd-es968= [HW,ALSA]
2393 snd-es1688= [HW,ALSA]
2395 snd-es18xx= [HW,ALSA]
2397 snd-es1938= [HW,ALSA]
2399 snd-es1968= [HW,ALSA]
2401 snd-fm801= [HW,ALSA]
2403 snd-gusclassic= [HW,ALSA]
2405 snd-gusextreme= [HW,ALSA]
2407 snd-gusmax= [HW,ALSA]
2411 snd-ice1712= [HW,ALSA]
2413 snd-intel8x0= [HW,ALSA]
2415 snd-interwave= [HW,ALSA]
2420 snd-korg1212= [HW,ALSA]
2422 snd-maestro3= [HW,ALSA]
2424 snd-mpu401= [HW,ALSA]
2426 snd-mtpav= [HW,ALSA]
2428 snd-nm256= [HW,ALSA]
2430 snd-opl3sa2= [HW,ALSA]
2438 snd-opti93x= [HW,ALSA]
2442 snd-rme32= [HW,ALSA]
2444 snd-rme96= [HW,ALSA]
2446 snd-rme9652= [HW,ALSA]
2452 snd-sbawe= [HW,ALSA]
2454 snd-serial= [HW,ALSA]
2456 snd-sgalaxy= [HW,ALSA]
2458 snd-sonicvibes= [HW,ALSA]
2463 snd-sun-cs4231= [HW,ALSA]
2465 snd-trident= [HW,ALSA]
2467 snd-usb-audio= [HW,ALSA,USB]
2469 snd-via82xx= [HW,ALSA]
2471 snd-virmidi= [HW,ALSA]
2473 snd-wavefront= [HW,ALSA]
2475 snd-ymfpci= [HW,ALSA]
2478 [KNL] Should the soft-lockup detector generate panics.
2480 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2481 See Documentation/sonypi.txt
2483 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2484 See Documentation/serial/specialix.txt.
2486 spia_io_base= [HW,MTD]
2492 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2494 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2495 See Documentation/scsi/st.txt.
2498 Enabled the stack tracer on boot up.
2502 Set the STI (builtin display/keyboard on the HP-PARISC
2503 machines) console (graphic card) which should be used
2504 as the initial boot-console.
2505 See also comment in drivers/video/console/sticore.c.
2508 See comment in drivers/video/console/sticore.c.
2511 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2513 sunrpc.min_resvport=
2514 sunrpc.max_resvport=
2516 SunRPC servers often require that client requests
2517 originate from a privileged port (i.e. a port in the
2518 range 0 < portnr < 1024).
2519 An administrator who wishes to reserve some of these
2520 ports for other uses may adjust the range that the
2521 kernel's sunrpc client considers to be privileged
2522 using these two parameters to set the minimum and
2523 maximum port values.
2527 Control how the NFS server code allocates CPUs to
2528 service thread pools. Depending on how many NICs
2529 you have and where their interrupts are bound, this
2530 option will affect which CPUs will do NFS serving.
2531 Note: this parameter cannot be changed while the
2532 NFS server is running.
2534 auto the server chooses an appropriate mode
2535 automatically using heuristics
2536 global a single global pool contains all CPUs
2537 percpu one pool for each CPU
2538 pernode one pool for each NUMA node (equivalent
2539 to global on non-NUMA machines)
2541 sunrpc.tcp_slot_table_entries=
2542 sunrpc.udp_slot_table_entries=
2544 Sets the upper limit on the number of simultaneous
2545 RPC calls that can be sent from the client to a
2546 server. Increasing these values may allow you to
2547 improve throughput, but will also increase the
2548 amount of memory reserved for use by the client.
2550 swiotlb= [IA-64] Number of I/O TLB slabs
2554 sym53c416= [HW,SCSI]
2555 See header of drivers/scsi/sym53c416.c.
2557 sysrq_always_enabled
2559 Ignore sysrq setting - this boot parameter will
2560 neutralize any effect of /proc/sys/kernel/sysrq.
2561 Useful for debugging.
2564 See header of drivers/scsi/t128.c.
2568 test_suspend= [SUSPEND]
2569 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2570 standby suspend) as the system sleep state to briefly
2571 enter during system startup. The system is woken from
2572 this state using a wakeup-capable RTC alarm.
2574 thash_entries= [KNL,NET]
2575 Set number of hash buckets for TCP connection
2577 thermal.act= [HW,ACPI]
2578 -1: disable all active trip points in all thermal zones
2579 <degrees C>: override all lowest active trip points
2581 thermal.crt= [HW,ACPI]
2582 -1: disable all critical trip points in all thermal zones
2583 <degrees C>: override all critical trip points
2585 thermal.nocrt= [HW,ACPI]
2586 Set to disable actions on ACPI thermal zone
2587 critical and hot trip points.
2589 thermal.off= [HW,ACPI]
2590 1: disable ACPI thermal control
2592 thermal.psv= [HW,ACPI]
2593 -1: disable all passive trip points
2594 <degrees C>: override all passive trip points to this
2597 thermal.tzp= [HW,ACPI]
2598 Specify global default ACPI thermal zone polling rate
2599 <deci-seconds>: poll all this frequency
2600 0: no polling (default)
2603 See comment before function dc390_setup() in
2604 drivers/scsi/tmscsim.c.
2608 Specify if the kernel should make use of the cpu
2609 topology informations if the hardware supports these.
2610 The scheduler will make use of these informations and
2611 e.g. base its process migration decisions on it.
2616 trace_buf_size=nn[KMG]
2617 [FTRACE] will set tracing buffer size.
2619 trace_event=[event-list]
2620 [FTRACE] Set and start specified trace events in order
2621 to facilitate early boot debugging.
2622 See also Documentation/trace/events.txt
2624 trix= [HW,OSS] MediaTrix AudioTrix Pro
2626 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2628 tsc= Disable clocksource-must-verify flag for TSC.
2630 [x86] reliable: mark tsc clocksource as reliable, this
2631 disables clocksource verification at runtime.
2632 Used to enable high-resolution timer mode on older
2633 hardware, and in virtualized environment.
2635 turbografx.map[2|3]= [HW,JOY]
2636 TurboGraFX parallel port interface
2638 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2639 See also Documentation/input/joystick-parport.txt
2641 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2642 See header of drivers/scsi/u14-34f.c.
2650 uhash_entries= [KNL,NET]
2651 Set number of hash buckets for UDP/UDP-Lite connections
2654 [USB] Ignore overcurrent events (default N).
2655 Some badly-designed motherboards generate lots of
2656 bogus events, for ports that aren't wired to
2657 anything. Set this parameter to avoid log spamming.
2658 Note that genuine overcurrent events won't be
2663 Set unknown_nmi_panic=1 early on boot.
2665 usbcore.autosuspend=
2666 [USB] The autosuspend time delay (in seconds) used
2667 for newly-detected USB devices (default 2). This
2668 is the time required before an idle device will be
2669 autosuspended. Devices for which the delay is set
2670 to a negative value won't be autosuspended at all.
2672 usbcore.usbfs_snoop=
2673 [USB] Set to log all usbfs traffic (default 0 = off).
2675 usbcore.blinkenlights=
2676 [USB] Set to cycle leds on hubs (default 0 = off).
2678 usbcore.old_scheme_first=
2679 [USB] Start with the old device initialization
2680 scheme (default 0 = off).
2682 usbcore.use_both_schemes=
2683 [USB] Try the other device initialization scheme
2684 if the first one fails (default 1 = enabled).
2686 usbcore.initial_descriptor_timeout=
2687 [USB] Specifies timeout for the initial 64-byte
2688 USB_REQ_GET_DESCRIPTOR request in milliseconds
2689 (default 5000 = 5.0 seconds).
2692 [USBHID] The interval which mice are to be polled at.
2694 usb-storage.delay_use=
2695 [UMS] The delay in seconds before a new device is
2696 scanned for Logical Units (default 5).
2699 [UMS] A list of quirks entries to supplement or
2700 override the built-in unusual_devs list. List
2701 entries are separated by commas. Each entry has
2702 the form VID:PID:Flags where VID and PID are Vendor
2703 and Product ID values (4-digit hex numbers) and
2704 Flags is a set of characters, each corresponding
2705 to a common usb-storage quirk flag as follows:
2706 a = SANE_SENSE (collect more than 18 bytes
2708 b = BAD_SENSE (don't collect more than 18
2709 bytes of sense data);
2710 c = FIX_CAPACITY (decrease the reported
2711 device capacity by one sector);
2712 h = CAPACITY_HEURISTICS (decrease the
2713 reported device capacity by one
2714 sector if the number is odd);
2715 i = IGNORE_DEVICE (don't bind to this
2717 l = NOT_LOCKABLE (don't try to lock and
2718 unlock ejectable media);
2719 m = MAX_SECTORS_64 (don't transfer more
2720 than 64 sectors = 32 KB at a time);
2721 o = CAPACITY_OK (accept the capacity
2722 reported by the device);
2723 r = IGNORE_RESIDUE (the device reports
2724 bogus residue values);
2725 s = SINGLE_LUN (the device has only one
2727 w = NO_WP_DETECT (don't test whether the
2728 medium is write-protected).
2729 Example: quirks=0419:aaf5:rl,0421:0433:rc
2732 [X86] Flags controlling user PTE allocations.
2734 nohigh = do not allocate PTE pages in
2735 HIGHMEM regardless of setting
2739 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2740 vdso=1: enable VDSO (default)
2741 vdso=0: disable VDSO mapping
2744 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2745 vdso32=1: enable 32-bit VDSO (default)
2746 vdso32=0: disable 32-bit VDSO mapping
2749 vector=percpu: enable percpu vector domain
2751 video= [FB] Frame buffer configuration
2752 See Documentation/fb/modedb.txt.
2754 vga= [BOOT,X86-32] Select a particular video mode
2755 See Documentation/x86/boot.txt and
2756 Documentation/svga.txt.
2757 Use vga=ask for menu.
2758 This is actually a boot loader parameter; the value is
2759 passed to the kernel using a special protocol.
2761 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2762 size of <nn>. This can be used to increase the
2763 minimum size (128MB on x86). It can also be used to
2764 decrease the size and leave more room for directly
2767 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2770 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2773 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2776 vt.cur_default= [VT] Default cursor shape.
2777 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2778 the parameters of the <Esc>[?A;B;Cc escape sequence;
2779 see VGA-softcursor.txt. Default: 2 = underline.
2781 vt.default_blu= [VT]
2782 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2783 Change the default blue palette of the console.
2784 This is a 16-member array composed of values
2787 vt.default_grn= [VT]
2788 Format: <green0>,<green1>,<green2>,...,<green15>
2789 Change the default green palette of the console.
2790 This is a 16-member array composed of values
2793 vt.default_red= [VT]
2794 Format: <red0>,<red1>,<red2>,...,<red15>
2795 Change the default red palette of the console.
2796 This is a 16-member array composed of values
2802 Set system-wide default UTF-8 mode for all tty's.
2803 Default is 1, i.e. UTF-8 mode is enabled for all
2804 newly opened terminals.
2806 vt.global_cursor_default=
2809 Set system-wide default for whether a cursor
2810 is shown on new VTs. Default is -1,
2811 i.e. cursors will be created by default unless
2812 overridden by individual drivers. 0 will hide
2813 cursors, 1 will display them.
2815 waveartist= [HW,OSS]
2816 Format: <io>,<irq>,<dma>,<dma2>
2819 See header of drivers/scsi/wd33c93.c.
2822 See header of drivers/scsi/wd7000.c.
2825 See Documentation/watchdog/wdt.txt.
2827 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2828 default x2apic cluster mode on platforms
2831 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2832 xd_geo= See header of drivers/block/xd.c.
2834 xirc2ps_cs= [NET,PCMCIA]
2836 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2838 ______________________________________________________________________
2842 Add documentation for ALSA options.
2843 Add more DRM drivers.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob