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 ISAPNP ISA PnP code is enabled.
58 ISDN Appropriate ISDN support is enabled.
59 JOY Appropriate joystick support is enabled.
60 LIBATA Libata driver is enabled
61 LP Printer support is enabled.
62 LOOP Loopback device support is enabled.
63 M68k M68k architecture is enabled.
64 These options have more detailed description inside of
65 Documentation/m68k/kernel-options.txt.
66 MCA MCA bus support is enabled.
67 MDA MDA console support is enabled.
68 MOUSE Appropriate mouse support is enabled.
69 MSI Message Signaled Interrupts (PCI).
70 MTD MTD (Memory Technology Device) support is enabled.
71 NET Appropriate network support is enabled.
72 NUMA NUMA support is enabled.
73 GENERIC_TIME The generic timeofday code is enabled.
74 NFS Appropriate NFS support is enabled.
75 OSS OSS sound support is enabled.
76 PV_OPS A paravirtualized kernel is enabled.
77 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
78 PARISC The PA-RISC architecture is enabled.
79 PCI PCI bus support is enabled.
80 PCIE PCI Express support is enabled.
81 PCMCIA The PCMCIA subsystem is enabled.
82 PNP Plug & Play support is enabled.
83 PPC PowerPC architecture is enabled.
84 PPT Parallel port support is enabled.
85 PS2 Appropriate PS/2 support is enabled.
86 RAM RAM disk support is enabled.
87 ROOTPLUG The example Root Plug LSM is enabled.
88 S390 S390 architecture is enabled.
89 SCSI Appropriate SCSI support is enabled.
90 A lot of drivers has their options described inside of
92 SECURITY Different security models are enabled.
93 SELINUX SELinux support is enabled.
94 SERIAL Serial support is enabled.
95 SH SuperH architecture is enabled.
96 SMP The kernel is an SMP kernel.
97 SPARC Sparc architecture is enabled.
98 SWSUSP Software suspend (hibernation) is enabled.
99 SUSPEND System suspend states are enabled.
100 FTRACE Function tracing enabled.
101 TS Appropriate touchscreen support is enabled.
102 UMS USB Mass Storage support is enabled.
103 USB USB support is enabled.
104 USBHID USB Human Interface Device support is enabled.
105 V4L Video For Linux support is enabled.
106 VGA The VGA console has been enabled.
107 VT Virtual terminal support is enabled.
108 WDT Watchdog support is enabled.
109 XT IBM PC/XT MFM hard disk support is enabled.
110 X86-32 X86-32, aka i386 architecture is enabled.
111 X86-64 X86-64 architecture is enabled.
112 More X86-64 boot options can be found in
113 Documentation/x86/x86_64/boot-options.txt .
114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
116 In addition, the following text indicates that the option:
118 BUGS= Relates to possible processor bugs on the said processor.
119 KNL Is a kernel start-up parameter.
120 BOOT Is a boot loader parameter.
122 Parameters denoted with BOOT are actually interpreted by the boot
123 loader, and have no meaning to the kernel directly.
124 Do not modify the syntax of boot loader parameters without extreme
125 need or coordination with <Documentation/x86/boot.txt>.
127 There are also arch-specific kernel-parameters not documented here.
128 See for example <Documentation/x86/x86_64/boot-options.txt>.
130 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
131 a trailing = on the name of any parameter states that that parameter will
132 be entered as an environment variable, whereas its absence indicates that
133 it will appear as a kernel argument readable via /proc/cmdline by programs
134 running once the system is up.
136 The number of kernel parameters is not limited, but the length of the
137 complete command line (parameters including spaces etc.) is limited to
138 a fixed number of characters. This limit depends on the architecture
139 and is between 256 and 4096 characters. It is defined in the file
140 ./include/asm/setup.h as COMMAND_LINE_SIZE.
144 Advanced Configuration and Power Interface
145 Format: { force | off | ht | strict | noirq | rsdt }
146 force -- enable ACPI if default was off
147 off -- disable ACPI if default was on
148 noirq -- do not use ACPI for IRQ routing
149 ht -- run only enough ACPI to enable Hyper Threading
150 strict -- Be less tolerant of platforms that are not
151 strictly ACPI specification compliant.
152 rsdt -- prefer RSDT over (default) XSDT
154 See also Documentation/power/pm.txt, pci=noacpi
156 acpi_apic_instance= [ACPI, IOAPIC]
158 2: use 2nd APIC table, if available
159 1,0: use 1st APIC table
162 acpi_backlight= [HW,ACPI]
163 acpi_backlight=vendor
165 If set to vendor, prefer vendor specific driver
166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
167 of the ACPI video.ko driver.
169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
173 debug output. Bits in debug_layer correspond to a
174 _COMPONENT in an ACPI source file, e.g.,
175 #define _COMPONENT ACPI_PCI_COMPONENT
176 Bits in debug_level correspond to a level in
177 ACPI_DEBUG_PRINT statements, e.g.,
178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
179 The debug_level mask defaults to "info". See
180 Documentation/acpi/debug.txt for more information about
181 debug layers and levels.
183 Enable processor driver info messages:
184 acpi.debug_layer=0x20000000
185 Enable PCI/PCI interrupt routing info messages:
186 acpi.debug_layer=0x400000
187 Enable AML "Debug" output, i.e., stores to the Debug
188 object while interpreting AML:
189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
190 Enable all messages related to ACPI hardware:
191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
193 Some values produce so much output that the system is
194 unusable. The "log_buf_len" parameter may be useful
195 if you need to capture more output.
197 acpi_display_output= [HW,ACPI]
198 acpi_display_output=vendor
199 acpi_display_output=video
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 Format: <irq>,<irq>...
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
232 acpi.power_nocheck= [HW,ACPI]
233 Format: 1/0 enable/disable the check of power state.
234 On some bogus BIOS the _PSC object/_STA object of
235 power resource can't return the correct device power
236 state. In such case it is unneccessary to check its
237 power state again in power transition.
238 1 : disable the power state check
240 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
241 Format: { level | edge | high | low }
243 acpi_serialize [HW,ACPI] force serialization of AML methods
245 acpi_skip_timer_override [HW,ACPI]
246 Recognize and ignore IRQ0/pin2 Interrupt Override.
247 For broken nForce2 BIOS resulting in XT-PIC timer.
249 acpi_sleep= [HW,ACPI] Sleep options
250 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
251 old_ordering, s4_nonvs }
252 See Documentation/power/video.txt for information on
254 s3_beep is for debugging; it makes the PC's speaker beep
255 as soon as the kernel's real-mode entry point is called.
256 s4_nohwsig prevents ACPI hardware signature from being
257 used during resume from hibernation.
258 old_ordering causes the ACPI 1.0 ordering of the _PTS
259 control method, with respect to putting devices into
260 low power states, to be enforced (the ACPI 2.0 ordering
261 of _PTS is used by default).
262 s4_nonvs prevents the kernel from saving/restoring the
263 ACPI NVS memory during hibernation.
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.
319 amd_iommu= [HW,X86-84]
320 Pass parameters to the AMD IOMMU driver in the system.
322 isolate - enable device isolation (each device, as far
323 as possible, will get its own protection
325 share - put every device behind one IOMMU into the
326 same protection domain
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
332 amijoy.map= [HW,JOY] Amiga joystick support
333 Map of devices attached to JOY0DAT and JOY1DAT
335 See also Documentation/kernel/input/joystick.txt
337 analog.map= [HW,JOY] Analog joystick and gamepad support
338 Specifies type or capabilities of an analog joystick
339 connected to one of 16 gameports
340 Format: <type1>,<type2>,..<type16>
343 Power management functions (SPARCstation-4/5 + deriv.)
345 Disable APC CPU standby support. SPARCstation-Fox does
346 not play well with APC CPU idle - disable it if you have
347 APC and your system crashes randomly.
349 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
350 Change the output verbosity whilst booting
351 Format: { quiet (default) | verbose | debug }
352 Change the amount of debugging information output
353 when initialising the APIC and IO-APIC components.
355 apm= [APM] Advanced Power Management
356 See header of arch/x86/kernel/apm_32.c.
358 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
359 Format: <io>,<irq>,<nodeID>
363 atarimouse= [HW,MOUSE] Atari Mouse
365 atascsi= [HW,SCSI] Atari SCSI
367 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
368 EzKey and similar keyboards
370 atkbd.reset= [HW] Reset keyboard during initialization
372 atkbd.set= [HW] Select keyboard code set
373 Format: <int> (2 = AT (default), 3 = PS/2)
375 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
378 atkbd.softraw= [HW] Choose between synthetic and real raw mode
379 Format: <bool> (0 = real, 1 = synthetic (default))
381 atkbd.softrepeat= [HW]
382 Use software keyboard repeat
386 baycom_epp= [HW,AX25]
389 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
391 See header of drivers/net/hamradio/baycom_par.c.
393 baycom_ser_fdx= [HW,AX25]
394 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
395 Format: <io>,<irq>,<mode>[,<baud>]
396 See header of drivers/net/hamradio/baycom_ser_fdx.c.
398 baycom_ser_hdx= [HW,AX25]
399 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
400 Format: <io>,<irq>,<mode>
401 See header of drivers/net/hamradio/baycom_ser_hdx.c.
403 boot_delay= Milliseconds to delay each printk during boot.
404 Values larger than 10 seconds (10000) are changed to
408 bootmem_debug [KNL] Enable bootmem allocator debug messages.
410 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
411 bttv.radio= Most important insmod options are available as
413 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
414 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
417 See drivers/scsi/BusLogic.c, comment before function
418 BusLogic_ParseDriverOptions().
420 c101= [NET] Moxa C101 synchronous serial card
422 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
423 Sometimes CPU hardware bugs make them report the cache
424 size incorrectly. The kernel will attempt work arounds
425 to fix known problems, but for some CPUs it is not
426 possible to determine what the correct size should be.
427 This option provides an override for these situations.
430 [SECURITY] Disable capabilities. This would normally
431 be used only if an alternative security model is to be
432 configured. Potentially dangerous and should only be
433 used if you are entirely sure of the consequences.
435 ccw_timeout_log [S390]
436 See Documentation/s390/CommonIO for details.
438 cgroup_disable= [KNL] Disable a particular controller
439 Format: {name of the controller(s) to disable}
440 {Currently supported controllers - "memory"}
442 checkreqprot [SELINUX] Set initial checkreqprot flag value.
443 Format: { "0" | "1" }
444 See security/selinux/Kconfig help text.
445 0 -- check protection applied by kernel (includes
446 any implied execute protection).
447 1 -- check protection requested by application.
448 Default value is set via a kernel config option.
449 Value can be changed at runtime via
450 /selinux/checkreqprot.
453 See Documentation/s390/CommonIO for details.
455 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
457 Forces specified clocksource (if available) to be used
458 when calculating gettimeofday(). If specified
459 clocksource is not available, it defaults to PIT.
460 Format: { pit | tsc | cyclone | pmtmr }
462 clocksource= [GENERIC_TIME] Override the default clocksource
464 Override the default clocksource and use the clocksource
465 with the name specified.
466 Some clocksource names to choose from, depending on
468 [all] jiffies (this is the base, fallback clocksource)
470 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
471 pxa_timer,timer3,32k_counter,timer0_1
473 [X86-32] pit,hpet,tsc,vmi-timer;
474 scx200_hrt on Geode; cyclone on IBM x440
482 clearcpuid=BITNUM [X86]
483 Disable CPUID feature X for the kernel. See
484 arch/x86/include/asm/cpufeature.h for the valid bit
485 numbers. Note the Linux specific bits are not necessarily
486 stable over kernel options, but the vendor specific
488 Also note that user programs calling CPUID directly
489 or using the feature without checking anything
490 will still see it. This just prevents it from
491 being used by the kernel or shown in /proc/cpuinfo.
492 Also note the kernel might malfunction if you disable
495 cmo_free_hint= [PPC] Format: { yes | no }
496 Specify whether pages are marked as being inactive
497 when they are freed. This is used in CMO environments
498 to determine OS memory pressure for page stealing by
502 code_bytes [X86] How many bytes of object code to print
507 com20020= [HW,NET] ARCnet - COM20020 chipset
509 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
511 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
515 ARCnet - COM90xx chipset (memory-mapped buffers)
516 Format: <io>[,<irq>[,<memstart>]]
518 condev= [HW,S390] console device
521 console= [KNL] Output console device and options.
523 tty<n> Use the virtual console device <n>.
527 Use the specified serial port. The options are of
528 the form "bbbbpnf", where "bbbb" is the baud rate,
529 "p" is parity ("n", "o", or "e"), "n" is number of
530 bits, and "f" is flow control ("r" for RTS or
531 omit it). Default is "9600n8".
533 See Documentation/serial-console.txt for more
535 Documentation/networking/netconsole.txt for an
538 uart[8250],io,<addr>[,options]
539 uart[8250],mmio,<addr>[,options]
540 Start an early, polled-mode console on the 8250/16550
541 UART at the specified I/O port or MMIO address,
542 switching to the matching ttyS device later. The
543 options are the same as for ttyS, above.
545 If the device connected to the port is not a TTY but a braille
546 device, prepend "brl," before the device type, for instance
548 For now, only VisioBraille is supported.
550 consoleblank= [KNL] The console blank (screen saver) timeout in
551 seconds. Defaults to 10*60 = 10mins. A value of 0
552 disables the blank timer.
555 [KNL] Change the default value for
556 /proc/<pid>/coredump_filter.
557 See also Documentation/filesystems/proc.txt.
559 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
561 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
563 crashkernel=nn[KMG]@ss[KMG]
564 [KNL] Reserve a chunk of physical memory to
565 hold a kernel to switch to with kexec on panic.
567 crashkernel=range1:size1[,range2:size2,...][@offset]
568 [KNL] Same as above, but depends on the memory
569 in the running system. The syntax of range is
570 start-[end] where start and end are both
571 a memory unit (amount[KMG]). See also
572 Documentation/kdump/kdump.txt for a example.
577 cs89x0_media= [HW,NET]
578 Format: { rj45 | aui | bnc }
581 See header of drivers/s390/block/dasd_devmap.c.
583 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
584 (one device per port)
585 Format: <port#>,<type>
586 See also Documentation/input/joystick-parport.txt
588 debug [KNL] Enable kernel debugging (events log level).
591 [KNL] verbose self-tests
593 Print debugging info while doing the locking API
595 We default to 0 (no extra messages), setting it to
596 1 will print _a lot_ more information - normally
597 only useful to kernel developers.
599 debug_objects [KNL] Enable object debugging
602 [KNL] Disable object debugging
604 debugpat [X86] Enable PAT debugging
606 decnet.addr= [HW,NET]
607 Format: <area>[,<node>]
608 See also Documentation/networking/decnet.txt.
611 [same as hugepagesz=] The size of the default
612 HugeTLB page size. This is the size represented by
613 the legacy /proc/ hugepages APIs, used for SHM, and
614 default size when mounting hugetlbfs filesystems.
615 Defaults to the default architecture's huge page size
619 Set number of hash buckets for dentry cache.
622 IO parameters + enable/disable command.
624 digiepca= [HW,SERIAL]
625 See drivers/char/README.epca and
626 Documentation/serial/digiepca.txt.
628 disable_mtrr_cleanup [X86]
629 The kernel tries to adjust MTRR layout from continuous
630 to discrete, to make X server driver able to add WB
631 entry later. This parameter disables that.
633 disable_mtrr_trim [X86, Intel and AMD only]
634 By default the kernel will trim any uncacheable
635 memory out of your available memory pool based on
636 MTRR settings. This parameter disables that behavior,
637 possibly causing your machine to run very slowly.
639 disable_timer_pin_1 [X86]
640 Disable PIN 1 of APIC timer
641 Can be useful to work around chipset bugs.
643 dmasound= [HW,OSS] Sound subsystem buffers
645 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
646 this option disables the debugging code at boot.
648 dma_debug_entries=<number>
649 This option allows to tune the number of preallocated
650 entries for DMA-API debugging code. One entry is
651 required per DMA-API allocation. Use this if the
652 DMA-API debugging code disables itself because the
653 architectural default is too low.
655 dma_debug_driver=<driver_name>
656 With this option the DMA-API debugging driver
657 filter feature can be enabled at boot time. Just
658 pass the driver to filter for as the parameter.
659 The filter can be disabled or changed to another
660 driver later using sysfs.
666 dynamic_printk Enables pr_debug()/dev_dbg() calls if
667 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
668 These can also be switched on/off via
669 <debugfs>/dynamic_printk/modules
671 earlycon= [KNL] Output early console device and options.
672 uart[8250],io,<addr>[,options]
673 uart[8250],mmio,<addr>[,options]
674 Start an early, polled-mode console on the 8250/16550
675 UART at the specified I/O port or MMIO address.
676 The options are the same as for ttyS, above.
678 earlyprintk= [X86,SH,BLACKFIN]
680 earlyprintk=serial[,ttySn[,baudrate]]
683 Append ",keep" to not disable it when the real console
686 Only vga or serial or usb debug port at a time.
688 Currently only ttyS0 and ttyS1 are supported.
690 Interaction with the standard serial driver is not
693 The VGA output is eventually overwritten by the real
699 Format: {"off" | "on" | "skip[mbr]"}
701 eisa_irq_edge= [PARISC,HW]
702 See header of drivers/parisc/eisa.c.
705 See comment before function elanfreq_setup() in
706 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
709 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
710 See Documentation/block/as-iosched.txt and
711 Documentation/block/deadline-iosched.txt for details.
713 elfcorehdr= [IA64,PPC,SH,X86]
714 Specifies physical address of start of kernel core
715 image elf header. Generally kexec loader will
716 pass this option to capture kernel.
717 See Documentation/kdump/kdump.txt for details.
719 enable_mtrr_cleanup [X86]
720 The kernel tries to adjust MTRR layout from continuous
721 to discrete, to make X server driver able to add WB
722 entry later. This parameter enables that.
724 enable_timer_pin_1 [X86]
725 Enable PIN 1 of APIC timer
726 Can be useful to work around chipset bugs
727 (in particular on some ATI chipsets).
728 The kernel tries to set a reasonable default.
730 enforcing [SELINUX] Set initial enforcing status.
732 See security/selinux/Kconfig help text.
733 0 -- permissive (log only, no denials).
734 1 -- enforcing (deny and log).
736 Value can be changed at runtime via /selinux/enforce.
738 ether= [HW,NET] Ethernet cards parameters
739 This option is obsoleted by the "netdev=" option, which
740 has equivalent usage. See its documentation for details.
742 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
747 fail_make_request=[KNL]
748 General fault injection mechanism.
749 Format: <interval>,<probability>,<space>,<times>
750 See also /Documentation/fault-injection/.
753 See header of drivers/scsi/fd_mcs.c.
756 See header of drivers/scsi/fdomain.c.
759 See Documentation/blockdev/floppy.txt.
761 force_pal_cache_flush
762 [IA-64] Avoid check_sal_cache_flush which may hang on
763 buggy SAL_CACHE_FLUSH implementations. Using this
764 parameter will force ia64_sal_cache_flush to call
765 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
768 [FTRACE] will set and start the specified tracer
769 as early as possible in order to facilitate early
773 [FTRACE] will dump the trace buffers on oops.
775 ftrace_filter=[function-list]
776 [FTRACE] Limit the functions traced by the function
777 tracer at boot up. function-list is a comma separated
778 list of functions. This list can be changed at run
779 time by the set_ftrace_filter file in the debugfs
782 ftrace_notrace=[function-list]
783 [FTRACE] Do not trace the functions specified in
784 function-list. This list can be changed at run time
785 by the set_ftrace_notrace file in the debugfs
789 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
790 support via parallel port (up to 5 devices per port)
791 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
792 See also Documentation/input/joystick-parport.txt
796 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
800 gcov_persist= [GCOV] When non-zero (default), profiling data for
801 kernel modules is saved and remains accessible via
802 debugfs, even when the module is unloaded/reloaded.
803 When zero, profiling data is discarded and associated
804 debugfs files are removed at module unload time.
807 See header of drivers/scsi/gdth.c.
809 gpt [EFI] Forces disk with valid GPT signature but
810 invalid Protective MBR to be treated as GPT.
814 hashdist= [KNL,NUMA] Large hashes allocated during boot
815 are distributed across NUMA nodes. Defaults on
816 for 64bit NUMA, off otherwise.
817 Format: 0 | 1 (for off | on)
819 hcl= [IA-64] SGI's Hardware Graph compatibility layer
821 hd= [EIDE] (E)IDE hard drive subsystem geometry
822 Format: <cyl>,<head>,<sect>
824 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
825 size of <nn>. This works even on boxes that have no
826 highmem otherwise. This also works to reduce highmem
827 size on bigger boxes.
829 highres= [KNL] Enable/disable high resolution timer mode.
830 Valid parameters: "on", "off"
834 See Documentation/isdn/README.HiSax.
838 hpet= [X86-32,HPET] option to control HPET usage
839 Format: { enable (default) | disable | force |
841 disable: disable HPET and use PIT instead
842 force: allow force enabled of undocumented chips (ICH4,
844 verbose: show contents of HPET registers during setup
846 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
847 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
848 On x86-64 and powerpc, this option can be specified
849 multiple times interleaved with hugepages= to reserve
850 huge pages of different sizes. Valid pages sizes on
851 x86-64 are 2M (when the CPU supports "pse") and 1G
852 (when the CPU supports the "pdpe1gb" cpuinfo flag)
853 Note that 1GB pages can only be allocated at boot time
854 using hugepages= and not freed afterwards.
856 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
857 terminal devices. Valid values: 0..8
858 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
859 If specified, z/VM IUCV HVC accepts connections
860 from listed z/VM user IDs only.
862 i2c_bus= [HW] Override the default board specific I2C bus speed
863 or register an additional I2C bus that is not
864 registered from board initialization code.
868 i8042.debug [HW] Toggle i8042 debug mode
869 i8042.direct [HW] Put keyboard port into non-translated mode
870 i8042.dumbkbd [HW] Pretend that controller can only read data from
871 keyboard and cannot control its state
872 (Don't attempt to blink the leds)
873 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
874 i8042.nokbd [HW] Don't check/create keyboard port
875 i8042.noloop [HW] Disable the AUX Loopback command while probing
877 i8042.nomux [HW] Don't check presence of an active multiplexing
879 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
882 [HW] Frequency with which keyboard LEDs should blink
883 when kernel panics (default is 0.5 sec)
884 i8042.reset [HW] Reset the controller during init and cleanup
885 i8042.unlock [HW] Unlock (ignore) the keylock
889 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
890 indicates that the driver is running on unsupported
892 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
893 does not match list of supported models.
895 [HW] Report power status in /proc/i8k
896 (disabled by default)
897 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
900 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
901 See Documentation/mca.txt.
904 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
906 ide-core.nodma= [HW] (E)IDE subsystem
907 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
908 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
909 .cdrom .chs .ignore_cable are additional options
910 See Documentation/ide/ide.txt.
912 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
913 Claim all unknown PCI IDE storage controllers.
916 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
917 Poll forces a polling idle loop that can slightly
918 improve the performance of waking up a idle CPU, but
919 will use a lot of power and make the system run hot.
921 idle=mwait: On systems which support MONITOR/MWAIT but
922 the kernel chose to not use it because it doesn't save
923 as much power as a normal idle loop, use the
924 MONITOR/MWAIT idle loop anyways. Performance should be
925 the same as idle=poll.
926 idle=halt: Halt is forced to be used for CPU idle.
927 In such case C2/C3 won't be used again.
928 idle=nomwait: Disable mwait for CPU C-states
930 ignore_loglevel [KNL]
931 Ignore loglevel setting - this will print /all/
932 kernel messages to the console. Useful for debugging.
935 Set number of hash buckets for inode cache.
938 Format: { "0" | "1" }
939 0 -- integrity auditing messages. (Default)
940 1 -- enable informational integrity auditing messages.
943 Formt: { "sha1" | "md5" }
947 Load a policy which meets the needs of the Trusted
948 Computing Base. This means IMA will measure all
949 programs exec'd, files mmap'd for exec, and all files
950 opened for read by uid=0.
953 See header of drivers/scsi/in2000.c.
957 Run specified binary instead of /sbin/init as init
960 initcall_debug [KNL] Trace initcalls as they are executed. Useful
961 for working out where the kernel is dying during
964 initrd= [BOOT] Specify the location of the initial ramdisk
966 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
969 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
971 Enable intel iommu driver.
973 Disable intel iommu driver.
974 igfx_off [Default Off]
975 By default, gfx is mapped as normal device. If a gfx
976 device has a dedicated DMAR unit, the DMAR unit is
977 bypassed by not enabling DMAR with this option. In
978 this case, gfx device will use physical address for
981 With this option iommu will not optimize to look
982 for io virtual address below 32 bit forcing dual
983 address cycle on pci bus for cards supporting greater
984 than 32 bit addressing. The default is to look
985 for translation below 32 bit and if not available
986 then look in the higher range.
988 With this option on every unmap_single operation will
989 result in a hardware IOTLB flush operation as opposed
990 to batching them for performance.
994 iomem= Disable strict checking of access to MMIO memory
995 strict regions from userspace.
1010 io7= [HW] IO7 for Marvel based alpha systems
1011 See comment before marvel_specify_io7 in
1012 arch/alpha/kernel/core_marvel.c.
1014 io_delay= [X86] I/O delay method
1016 Standard port 0x80 based delay
1018 Alternate port 0xed based delay (needed on some systems)
1020 Simple two microseconds delay
1025 See Documentation/filesystems/nfsroot.txt.
1027 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1028 See comment before ip2_setup() in
1029 drivers/char/ip2/ip2base.c.
1031 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1032 See header of drivers/scsi/ips.c.
1035 When an interrupt is not handled search all handlers
1036 for it. Intended to get systems with badly broken
1040 When an interrupt is not handled search all handlers
1041 for it. Also check all handlers each timer
1042 interrupt. Intended to get systems with badly broken
1046 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1048 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1050 <cpu number>,...,<cpu number>
1052 <cpu number>-<cpu number>
1053 (must be a positive range in ascending order)
1055 <cpu number>,...,<cpu number>-<cpu number>
1057 This option can be used to specify one or more CPUs
1058 to isolate from the general SMP balancing and scheduling
1059 algorithms. You can move a process onto or off an
1060 "isolated" CPU via the CPU affinity syscalls or cpuset.
1061 <cpu number> begins at 0 and the maximum value is
1062 "number of CPUs in system - 1".
1064 This option is the preferred way to isolate CPUs. The
1065 alternative -- manually setting the CPU mask of all
1066 tasks in the system -- can cause problems and
1067 suboptimal load balancer performance.
1071 js= [HW,JOY] Analog joystick
1072 See Documentation/input/joystick.txt.
1076 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1077 specifies the amount of memory usable by the kernel
1078 for non-movable allocations. The requested amount is
1079 spread evenly throughout all nodes in the system. The
1080 remaining memory in each node is used for Movable
1081 pages. In the event, a node is too small to have both
1082 kernelcore and Movable pages, kernelcore pages will
1083 take priority and other nodes will have a larger number
1084 of kernelcore pages. The Movable zone is used for the
1085 allocation of pages that may be reclaimed or moved
1086 by the page migration subsystem. This means that
1087 HugeTLB pages may not be allocated from this zone.
1088 Note that allocations like PTEs-from-HighMem still
1089 use the HighMem zone if it exists, and the Normal
1090 zone if it does not.
1092 kgdboc= [HW] kgdb over consoles.
1093 Requires a tty driver that supports console polling.
1094 (only serial supported for now)
1095 Format: <serial_device>[,baud]
1097 kmac= [MIPS] korina ethernet MAC address.
1098 Configure the RouterBoard 532 series on-chip
1099 Ethernet adapter MAC address.
1101 kmemleak= [KNL] Boot-time kmemleak enable/disable
1102 Valid arguments: on, off
1105 kstack=N [X86] Print N words from the kernel stack
1112 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1115 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1118 libata.dma= [LIBATA] DMA control
1119 libata.dma=0 Disable all PATA and SATA DMA
1120 libata.dma=1 PATA and SATA Disk DMA only
1121 libata.dma=2 ATAPI (CDROM) DMA only
1122 libata.dma=4 Compact Flash DMA only
1123 Combinations also work, so libata.dma=3 enables DMA
1124 for disks and CDROMs, but not CFs.
1126 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1130 libata.force= [LIBATA] Force configurations. The format is comma
1131 separated list of "[ID:]VAL" where ID is
1132 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1133 matching port, link or device. Basically, it matches
1134 the ATA ID string printed on console by libata. If
1135 the whole ID part is omitted, the last PORT and DEVICE
1136 values are used. If ID hasn't been specified yet, the
1137 configuration applies to all ports, links and devices.
1139 If only DEVICE is omitted, the parameter applies to
1140 the port and all links and devices behind it. DEVICE
1141 number of 0 either selects the first device or the
1142 first fan-out link behind PMP device. It does not
1143 select the host link. DEVICE number of 15 selects the
1144 host link and device attached to it.
1146 The VAL specifies the configuration to force. As long
1147 as there's no ambiguity shortcut notation is allowed.
1148 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1149 The following configurations can be forced.
1151 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1152 Any ID with matching PORT is used.
1154 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1156 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1157 udma[/][16,25,33,44,66,100,133] notation is also
1160 * [no]ncq: Turn on or off NCQ.
1162 * nohrst, nosrst, norst: suppress hard, soft
1165 If there are multiple matching configurations changing
1166 the same attribute, the last one is used.
1168 lmb=debug [KNL] Enable lmb debug messages.
1170 load_ramdisk= [RAM] List of ramdisks to load from floppy
1171 See Documentation/blockdev/ramdisk.txt.
1173 lockd.nlm_grace_period=P [NFS] Assign grace period.
1176 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1179 lockd.nlm_timeout=T [NFS] Assign timeout value.
1182 lockd.nlm_udpport=M [NFS] Assign UDP port.
1185 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1188 loglevel= All Kernel Messages with a loglevel smaller than the
1189 console loglevel will be printed to the console. It can
1190 also be changed with klogd or other programs. The
1191 loglevels are defined as follows:
1193 0 (KERN_EMERG) system is unusable
1194 1 (KERN_ALERT) action must be taken immediately
1195 2 (KERN_CRIT) critical conditions
1196 3 (KERN_ERR) error conditions
1197 4 (KERN_WARNING) warning conditions
1198 5 (KERN_NOTICE) normal but significant condition
1199 6 (KERN_INFO) informational
1200 7 (KERN_DEBUG) debug-level messages
1202 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1203 Format: { n | nk | nM }
1204 n must be a power of two. The default size
1205 is set in the kernel config file.
1207 logo.nologo [FB] Disables display of the built-in Linux logo.
1208 This may be used to provide more screen space for
1209 kernel log messages and is useful when debugging
1210 kernel boot problems.
1212 lp=0 [LP] Specify parallel ports to use, e.g,
1213 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1214 lp=reset first parallel port). 'lp=0' disables the
1215 lp=auto printer driver. 'lp=reset' (which can be
1216 specified in addition to the ports) causes
1217 attached printers to be reset. Using
1218 lp=port1,port2,... specifies the parallel ports
1219 to associate lp devices with, starting with
1220 lp0. A port specification may be 'none' to skip
1221 that lp device, or a parport name such as
1222 'parport0'. Specifying 'lp=auto' instead of a
1223 port specification list means that device IDs
1224 from each port should be examined, to see if
1225 an IEEE 1284-compliant printer is attached; if
1226 so, the driver will manage that printer.
1227 See also header of drivers/char/lp.c.
1230 Sets loops_per_jiffy to given constant, thus avoiding
1231 time-consuming boot-time autodetection (up to 250 ms per
1232 CPU). 0 enables autodetection (default). To determine
1233 the correct value for your kernel, boot with normal
1234 autodetection and see what value is printed. Note that
1235 on SMP systems the preset will be applied to all CPUs,
1236 which is likely to cause problems if your CPUs need
1237 significantly divergent settings. An incorrect value
1238 will cause delays in the kernel to be wrong, leading to
1239 unpredictable I/O errors and other breakage. Although
1240 unlikely, in the extreme case this might damage your
1244 Format: <io>,<irq>,<dma>
1246 mac5380= [HW,SCSI] Format:
1247 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1249 machvec= [IA64] Force the use of a particular machine-vector
1250 (machvec) in a generic kernel.
1251 Example: machvec=hpzx1_swiotlb
1253 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1254 than or equal to this physical address is ignored.
1256 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1257 should make use of. maxcpus=n : n >= 0 limits the
1258 kernel to using 'n' processors. n=0 is a special case,
1259 it is equivalent to "nosmp", which also disables
1262 max_loop= [LOOP] Maximum number of loopback devices that can
1266 max_luns= [SCSI] Maximum number of LUNs to probe.
1267 Should be between 1 and 2^32-1.
1270 [SCSI] Maximum number of LUNs received.
1271 Should be between 1 and 16384.
1275 mce [X86-32] Machine Check Exception
1277 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1279 md= [HW] RAID subsystems devices and level
1280 See Documentation/md.txt.
1283 Format: <first>,<last>
1284 Specifies range of consoles to be captured by the MDA.
1286 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1287 Amount of memory to be used when the kernel is not able
1288 to see the whole system memory or for test.
1289 [X86-32] Use together with memmap= to avoid physical
1290 address space collisions. Without memmap= PCI devices
1291 could be placed at addresses belonging to unused RAM.
1293 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1297 [KNL,SH] Allow user to override the default size for
1298 per-device physically contiguous DMA buffers.
1300 memmap=exactmap [KNL,X86] Enable setting of an exact
1301 E820 memory map, as specified by the user.
1302 Such memmap=exactmap lines can be constructed based on
1303 BIOS output or other requirements. See the memmap=nn@ss
1306 memmap=nn[KMG]@ss[KMG]
1307 [KNL] Force usage of a specific region of memory
1308 Region of memory to be used, from ss to ss+nn.
1310 memmap=nn[KMG]#ss[KMG]
1311 [KNL,ACPI] Mark specific memory as ACPI data.
1312 Region of memory to be used, from ss to ss+nn.
1314 memmap=nn[KMG]$ss[KMG]
1315 [KNL,ACPI] Mark specific memory as reserved.
1316 Region of memory to be used, from ss to ss+nn.
1317 Example: Exclude memory from 0x18690000-0x1869ffff
1318 memmap=64K$0x18690000
1320 memmap=0x10000$0x18690000
1322 memory_corruption_check=0/1 [X86]
1323 Some BIOSes seem to corrupt the first 64k of
1324 memory when doing things like suspend/resume.
1325 Setting this option will scan the memory
1326 looking for corruption. Enabling this will
1327 both detect corruption and prevent the kernel
1328 from using the memory being corrupted.
1329 However, its intended as a diagnostic tool; if
1330 repeatable BIOS-originated corruption always
1331 affects the same memory, you can use memmap=
1332 to prevent the kernel from using that memory.
1334 memory_corruption_check_size=size [X86]
1335 By default it checks for corruption in the low
1336 64k, making this memory unavailable for normal
1337 use. Use this parameter to scan for
1338 corruption in more or less memory.
1340 memory_corruption_check_period=seconds [X86]
1341 By default it checks for corruption every 60
1342 seconds. Use this parameter to check at some
1343 other rate. 0 disables periodic checking.
1345 memtest= [KNL,X86] Enable memtest
1347 default : 0 <disable>
1348 Specifies the number of memtest passes to be
1349 performed. Each pass selects another test
1350 pattern from a given set of patterns. Memtest
1351 fills the memory with this pattern, validates
1352 memory contents and reserves bad memory
1353 regions that are detected.
1355 meye.*= [HW] Set MotionEye Camera parameters
1356 See Documentation/video4linux/meye.txt.
1358 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1359 Multi-Function General Purpose Timers on AMD Geode
1362 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1363 the BIOS has incorrectly applied a workaround. TinyBIOS
1364 version 0.98 is known to be affected, 0.99 fixes the
1365 problem by letting the user disable the workaround.
1369 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1370 physical address is ignored.
1373 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1374 parameter allows control of the logging verbosity for
1375 the additional memory initialisation checks. A value
1376 of 0 disables mminit logging and a level of 4 will
1377 log everything. Information is printed at KERN_DEBUG
1378 so loglevel=8 may also need to be specified.
1381 [MOUSE] Maximum time between finger touching and
1382 leaving touchpad surface for touch to be considered
1383 a tap and be reported as a left button click (for
1384 touchpads working in absolute mode only).
1386 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1387 reporting absolute coordinates, such as tablets
1388 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1389 reporting absolute coordinates, such as tablets
1391 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1392 is similar to kernelcore except it specifies the
1393 amount of memory used for migratable allocations.
1394 If both kernelcore and movablecore is specified,
1395 then kernelcore will be at *least* the specified
1396 value but may be more. If movablecore on its own
1397 is specified, the administrator must be careful
1398 that the amount of memory usable for all allocations
1404 MTD_Partition= [MTD]
1405 Format: <name>,<region-number>,<size>,<offset>
1407 MTD_Region= [MTD] Format:
1408 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1411 See drivers/mtd/cmdlinepart.c.
1414 ARM/S3C2412 JIVE boot control
1416 See arch/arm/mach-s3c2412/mach-jive.c
1418 mtouchusb.raw_coordinates=
1419 [HW] Make the MicroTouch USB driver use raw coordinates
1420 ('y', default) or cooked coordinates ('n')
1422 mtrr_chunk_size=nn[KMG] [X86]
1423 used for mtrr cleanup. It is largest continuous chunk
1424 that could hold holes aka. UC entries.
1426 mtrr_gran_size=nn[KMG] [X86]
1427 Used for mtrr cleanup. It is granularity of mtrr block.
1429 Large value could prevent small alignment from
1432 mtrr_spare_reg_nr=n [X86]
1434 Range: 0,7 : spare reg number
1436 Used for mtrr cleanup. It is spare mtrr entries number.
1437 Set to 2 or more if your graphical card needs more.
1439 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1442 See header of drivers/scsi/NCR_D700.c.
1446 ncr53c400= [HW,SCSI]
1448 ncr53c400a= [HW,SCSI]
1450 ncr53c406a= [HW,SCSI]
1452 ncr53c8xx= [HW,SCSI]
1454 netdev= [NET] Network devices parameters
1455 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1456 Note that mem_start is often overloaded to mean
1457 something different and driver-specific.
1458 This usage is only documented in each driver source
1462 [NETFILTER] Enable connection tracking flow accounting
1463 0 to disable accounting
1464 1 to enable accounting
1465 Default value depends on CONFIG_NF_CT_ACCT that is
1466 going to be removed in 2.6.29.
1469 See Documentation/filesystems/nfsroot.txt.
1471 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1472 See Documentation/filesystems/nfsroot.txt.
1474 nfs.callback_tcpport=
1475 [NFS] set the TCP port on which the NFSv4 callback
1476 channel should listen.
1478 nfs.idmap_cache_timeout=
1479 [NFS] set the maximum lifetime for idmapper cache
1483 [NFS] enable 64-bit inode numbers.
1484 If zero, the NFS client will fake up a 32-bit inode
1485 number for the readdir() and stat() syscalls instead
1486 of returning the full 64-bit number.
1487 The default is to return 64-bit inode numbers.
1489 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1490 when a NMI is triggered.
1491 Format: [state][,regs][,debounce][,die]
1493 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1494 Format: [panic,][num]
1496 0 - turn nmi_watchdog off
1497 1 - use the IO-APIC timer for the NMI watchdog
1498 2 - use the local APIC for the NMI watchdog using
1499 a performance counter. Note: This will use one
1500 performance counter and the local APIC's performance
1502 When panic is specified, panic when an NMI watchdog
1504 This is useful when you use a panic=... timeout and
1505 need the box quickly up again.
1506 Instead of 1 and 2 it is possible to use the following
1507 symbolic names: lapic and ioapic
1508 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1510 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1511 emulation library even if a 387 maths coprocessor
1515 [HW] Never suspend the console
1516 Disable suspending of consoles during suspend and
1517 hibernate operations. Once disabled, debugging
1518 messages can reach various consoles while the rest
1519 of the system is being put to sleep (ie, while
1520 debugging driver suspend/resume hooks). This may
1521 not work reliably with all consoles, but is known
1522 to work with serial and VGA consoles.
1524 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1525 caches in the slab allocator. Saves per-node memory,
1526 but will impact performance.
1530 noapic [SMP,APIC] Tells the kernel to not make use of any
1531 IOAPICs that may be present in the system.
1533 nobats [PPC] Do not use BATs for mapping kernel lowmem
1534 on "Classic" PPC cores.
1538 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1540 nodelayacct [KNL] Disable per-task delay accounting
1542 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1544 nodsp [SH] Disable hardware DSP at boot time.
1546 noefi [X86] Disable EFI runtime services support.
1551 On X86-32 available only on PAE configured kernels.
1552 noexec=on: enable non-executable mappings (default)
1553 noexec=off: disable non-executable mappings
1556 This affects only 32-bit executables.
1557 noexec32=on: enable non-executable mappings (default)
1558 read doesn't imply executable mappings
1559 noexec32=off: disable non-executable mappings
1560 read implies executable mappings
1562 nofpu [SH] Disable hardware FPU at boot time.
1564 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1565 register save and restore. The kernel will only save
1566 legacy floating-point registers on task switch.
1568 noxsave [BUGS=X86] Disables x86 extended register state save
1569 and restore using xsave. The kernel will fallback to
1570 enabling legacy floating-point and sse state.
1572 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1573 wfi(ARM) instruction doesn't work correctly and not to
1574 use it. This is also useful when using JTAG debugger.
1576 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1577 instruction doesn't work correctly and not to
1580 no_file_caps Tells the kernel not to honor file capabilities. The
1581 only way then for a file to be executed with privilege
1582 is to be setuid root or executed by root.
1584 nohalt [IA-64] Tells the kernel not to use the power saving
1585 function PAL_HALT_LIGHT when idle. This increases
1586 power-consumption. On the positive side, it reduces
1587 interrupt wake-up latency, which may improve performance
1588 in certain environments such as networked servers or
1591 nohz= [KNL] Boottime enable/disable dynamic ticks
1592 Valid arguments: on, off
1595 noiotrap [SH] Disables trapped I/O port accesses.
1597 noirqdebug [X86-32] Disables the code which attempts to detect and
1598 disable unhandled interrupt sources.
1600 no_timer_check [X86,APIC] Disables the code which tests for
1601 broken timer IRQ sources.
1603 noisapnp [ISAPNP] Disables ISA PnP code.
1605 noinitrd [RAM] Tells the kernel not to load any configured
1608 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1613 nojitter [IA64] Disables jitter checking for ITC timers.
1615 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1617 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1619 noltlbs [PPC] Do not use large page/tlb entries for kernel
1620 lowmem mapping on PPC40x.
1622 nomca [IA-64] Disable machine check abort handling
1624 nomce [X86-32] Machine Check Exception
1626 nomfgpt [X86-32] Disable Multi-Function General Purpose
1627 Timer usage (for AMD Geode machines).
1629 norandmaps Don't use address space randomization. Equivalent to
1630 echo 0 > /proc/sys/kernel/randomize_va_space
1632 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1634 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1635 with UP alternatives
1637 noresidual [PPC] Don't use residual data on PReP machines.
1639 noresume [SWSUSP] Disables resume and restores original swap
1642 no-scroll [VGA] Disables scrollback.
1643 This is required for the Braillex ib80-piezo Braille
1644 reader made by F.H. Papenmeier (Germany).
1648 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1650 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1651 and disable the IO APIC. legacy for "maxcpus=0".
1653 nosoftlockup [KNL] Disable the soft-lockup detector.
1655 noswapaccount [KNL] Disable accounting of swap in memory resource
1656 controller. (See Documentation/cgroups/memory.txt)
1658 nosync [HW,M68K] Disables sync negotiation for all devices.
1660 notsc [BUGS=X86-32] Disable Time Stamp Counter
1662 nousb [USB] Disable the USB subsystem
1666 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1668 nptcg= [IA64] Override max number of concurrent global TLB
1669 purges which is reported from either PAL_VM_SUMMARY or
1672 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1674 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1675 one of ['zone', 'node', 'default'] can be specified
1676 This can be set from sysctl after boot.
1677 See Documentation/sysctl/vm.txt for details.
1679 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1680 See Documentation/debugging-via-ohci1394.txt for more
1683 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1684 Rather than timing out after 20 ms if an EC
1685 command is not properly ACKed, override the length
1686 of the timeout. We have interrupts disabled while
1687 waiting for the ACK, so if this is set too high
1688 interrupts *may* be lost!
1693 oprofile.timer= [HW]
1694 Use timer interrupt instead of performance counters
1696 oprofile.cpu_type= Force an oprofile cpu type
1697 This might be useful if you have an older oprofile
1698 userland or if you want common events.
1699 Format: { archperfmon }
1700 archperfmon: [X86] Force use of architectural
1701 perfmon on Intel CPUs instead of the
1702 CPU specific event set.
1704 osst= [HW,SCSI] SCSI Tape Driver
1705 Format: <buffer_size>,<write_threshold>
1706 See also Documentation/scsi/st.txt.
1708 panic= [KNL] Kernel behaviour on panic
1711 parkbd.port= [HW] Parallel port number the keyboard adapter is
1712 connected to, default is 0.
1714 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1715 0 for XT, 1 for AT (default is AT).
1718 parport= [HW,PPT] Specify parallel ports. 0 disables.
1719 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1720 Use 'auto' to force the driver to use any
1721 IRQ/DMA settings detected (the default is to
1722 ignore detected IRQ/DMA settings because of
1723 possible conflicts). You can specify the base
1724 address, IRQ, and DMA settings; IRQ and DMA
1725 should be numbers, or 'auto' (for using detected
1726 settings on that particular port), or 'nofifo'
1727 (to avoid using a FIFO even if it is detected).
1728 Parallel ports are assigned in the order they
1729 are specified on the command line, starting
1732 parport_init_mode= [HW,PPT]
1733 Configure VIA parallel port to operate in
1734 a specific mode. This is necessary on Pegasos
1735 computer where firmware has no options for setting
1736 up parallel port mode and sets it to spp.
1737 Currently this function knows 686a and 8231 chips.
1738 Format: [spp|ps2|epp|ecp|ecpepp]
1740 pas2= [HW,OSS] Format:
1741 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1744 See header of drivers/scsi/pas16.c.
1747 Halt all CPUs after the first oops has been printed for
1748 the specified number of seconds. This is to be used if
1749 your oopses keep scrolling off the screen.
1754 See header of drivers/block/paride/pcd.c.
1755 See also Documentation/blockdev/paride.txt.
1757 pci=option[,option...] [PCI] various PCI subsystem options:
1758 earlydump [X86] dump PCI config space before the kernel
1760 off [X86] don't probe for the PCI bus
1761 bios [X86-32] force use of PCI BIOS, don't access
1762 the hardware directly. Use this if your machine
1763 has a non-standard PCI host bridge.
1764 nobios [X86-32] disallow use of PCI BIOS, only direct
1765 hardware access methods are allowed. Use this
1766 if you experience crashes upon bootup and you
1767 suspect they are caused by the BIOS.
1768 conf1 [X86] Force use of PCI Configuration
1770 conf2 [X86] Force use of PCI Configuration
1772 noaer [PCIE] If the PCIEAER kernel config parameter is
1773 enabled, this kernel boot option can be used to
1774 disable the use of PCIE advanced error reporting.
1775 nodomains [PCI] Disable support for multiple PCI
1776 root domains (aka PCI segments, in ACPI-speak).
1777 nommconf [X86] Disable use of MMCONFIG for PCI
1779 check_enable_amd_mmconf [X86] check for and enable
1780 properly configured MMIO access to PCI
1781 config space on AMD family 10h CPU
1782 nomsi [MSI] If the PCI_MSI kernel config parameter is
1783 enabled, this kernel boot option can be used to
1784 disable the use of MSI interrupts system-wide.
1785 noioapicquirk [APIC] Disable all boot interrupt quirks.
1786 Safety option to keep boot IRQs enabled. This
1787 should never be necessary.
1788 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1789 primary IO-APIC for bridges that cannot disable
1790 boot IRQs. This fixes a source of spurious IRQs
1791 when the system masks IRQs.
1792 noioapicreroute [APIC] Disable workaround that uses the
1793 boot IRQ equivalent of an IRQ that connects to
1794 a chipset where boot IRQs cannot be disabled.
1795 The opposite of ioapicreroute.
1796 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1797 routing table. These calls are known to be buggy
1798 on several machines and they hang the machine
1799 when used, but on other computers it's the only
1800 way to get the interrupt routing table. Try
1801 this option if the kernel is unable to allocate
1802 IRQs or discover secondary PCI buses on your
1804 rom [X86] Assign address space to expansion ROMs.
1805 Use with caution as certain devices share
1806 address decoders between ROMs and other
1808 norom [X86] Do not assign address space to
1809 expansion ROMs that do not already have
1810 BIOS assigned address ranges.
1811 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1812 assigned automatically to PCI devices. You can
1813 make the kernel exclude IRQs of your ISA cards
1815 pirqaddr=0xAAAAA [X86] Specify the physical address
1816 of the PIRQ table (normally generated
1817 by the BIOS) if it is outside the
1818 F0000h-100000h range.
1819 lastbus=N [X86] Scan all buses thru bus #N. Can be
1820 useful if the kernel is unable to find your
1821 secondary buses and you want to tell it
1822 explicitly which ones they are.
1823 assign-busses [X86] Always assign all PCI bus
1824 numbers ourselves, overriding
1825 whatever the firmware may have done.
1826 usepirqmask [X86] Honor the possible IRQ mask stored
1827 in the BIOS $PIR table. This is needed on
1828 some systems with broken BIOSes, notably
1829 some HP Pavilion N5400 and Omnibook XE3
1830 notebooks. This will have no effect if ACPI
1831 IRQ routing is enabled.
1832 noacpi [X86] Do not use ACPI for IRQ routing
1833 or for PCI scanning.
1834 nocrs [X86] Don't use _CRS for PCI resource
1836 routeirq Do IRQ routing for all PCI devices.
1837 This is normally done in pci_enable_device(),
1838 so this option is a temporary workaround
1839 for broken drivers that don't call it.
1840 skip_isa_align [X86] do not align io start addr, so can
1841 handle more pci cards
1842 firmware [ARM] Do not re-enumerate the bus but instead
1843 just use the configuration from the
1844 bootloader. This is currently used on
1845 IXP2000 systems where the bus has to be
1846 configured a certain way for adjunct CPUs.
1847 noearly [X86] Don't do any early type 1 scanning.
1848 This might help on some broken boards which
1849 machine check when some devices' config space
1850 is read. But various workarounds are disabled
1851 and some IOMMU drivers will not work.
1852 bfsort Sort PCI devices into breadth-first order.
1853 This sorting is done to get a device
1854 order compatible with older (<= 2.4) kernels.
1855 nobfsort Don't sort PCI devices into breadth-first order.
1856 cbiosize=nn[KMG] The fixed amount of bus space which is
1857 reserved for the CardBus bridge's IO window.
1858 The default value is 256 bytes.
1859 cbmemsize=nn[KMG] The fixed amount of bus space which is
1860 reserved for the CardBus bridge's memory
1861 window. The default value is 64 megabytes.
1864 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1865 Specifies alignment and device to reassign
1866 aligned memory resources.
1867 If <order of align> is not specified,
1868 PAGE_SIZE is used as alignment.
1869 PCI-PCI bridge can be specified, if resource
1870 windows need to be expanded.
1871 ecrc= Enable/disable PCIe ECRC (transaction layer
1872 end-to-end CRC checking).
1873 bios: Use BIOS/firmware settings. This is the
1878 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1881 force Enable ASPM even on devices that claim not to support it.
1882 WARNING: Forcing ASPM on may cause system lockups.
1884 pcmv= [HW,PCMCIA] BadgePAD 4
1887 See Documentation/blockdev/paride.txt.
1889 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1892 See arch/parisc/kernel/pdc_chassis.c
1895 See Documentation/blockdev/paride.txt.
1898 See Documentation/blockdev/paride.txt.
1900 pirq= [SMP,APIC] Manual mp-table setup
1901 See Documentation/x86/i386/IO-APIC.txt.
1903 plip= [PPT,NET] Parallel port network link
1904 Format: { parport<nr> | timid | 0 }
1905 See also Documentation/parport.txt.
1907 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1908 Override pmtimer IOPort with a hex value.
1912 Enable PNP debug messages. This depends on the
1913 CONFIG_PNP_DEBUG_MESSAGES option.
1919 { on | off | curr | res | no-curr | no-res }
1922 [ISAPNP] Exclude IRQs for the autoconfiguration
1925 [ISAPNP] Exclude DMAs for the autoconfiguration
1927 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1928 Ranges are in pairs (I/O port base and size).
1931 [ISAPNP] Exclude memory regions for the
1933 Ranges are in pairs (memory base and size).
1935 ports= [IP_VS_FTP] IPVS ftp helper module
1937 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1939 Format: <port>,<port>....
1941 print-fatal-signals=
1942 [KNL] debug: print fatal signals
1943 print-fatal-signals=1: print segfault info to
1947 printk.time= Show timing data prefixed to each printk message line
1948 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1950 processor.max_cstate= [HW,ACPI]
1951 Limit processor to maximum C-state
1952 max_cstate=9 overrides any DMI blacklist limit.
1954 processor.nocst [HW,ACPI]
1955 Ignore the _CST method to determine C-states,
1956 instead using the legacy FADT method
1958 profile= [KNL] Enable kernel profiling via /proc/profile
1959 Format: [schedule,]<number>
1960 Param: "schedule" - profile schedule points.
1961 Param: <number> - step/bucket size as a power of 2 for
1962 statistical time based profiling.
1963 Param: "sleep" - profile D-state sleeping (millisecs).
1964 Requires CONFIG_SCHEDSTATS
1965 Param: "kvm" - profile VM exits.
1967 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1969 See Documentation/blockdev/ramdisk.txt.
1971 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1972 probe for; one of (bare|imps|exps|lifebook|any).
1973 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1975 psmouse.resetafter= [HW,MOUSE]
1976 Try to reset the device after so many bad packets
1979 [HW,MOUSE] Set desired mouse resolution, in dpi.
1980 psmouse.smartscroll=
1981 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1982 0 = disabled, 1 = enabled (default).
1984 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1986 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1989 See Documentation/blockdev/paride.txt.
1992 [KNL] Number of legacy pty's. Overwrites compiled-in
1995 quiet [KNL] Disable most log messages
2000 See Documentation/md.txt.
2002 ramdisk_blocksize= [RAM]
2003 See Documentation/blockdev/ramdisk.txt.
2005 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2006 See Documentation/blockdev/ramdisk.txt.
2008 rcupdate.blimit= [KNL,BOOT]
2009 Set maximum number of finished RCU callbacks to process
2012 rcupdate.qhimark= [KNL,BOOT]
2013 Set threshold of queued
2014 RCU callbacks over which batch limiting is disabled.
2016 rcupdate.qlowmark= [KNL,BOOT]
2017 Set threshold of queued RCU callbacks below which
2018 batch limiting is re-enabled.
2022 Run specified binary instead of /init from the ramdisk,
2023 used for early userspace startup. See initrd.
2025 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2026 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2027 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2030 [KNL, SMP] Set scheduler's default relax_domain_level.
2031 See Documentation/cgroups/cpusets.txt.
2033 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2035 reservetop= [X86-32]
2037 Reserves a hole at the top of the kernel virtual
2040 reset_devices [KNL] Force drivers to reset the underlying device
2041 during initialization.
2044 Specify the partition device for software suspend
2046 resume_offset= [SWSUSP]
2047 Specify the offset from the beginning of the partition
2048 given by "resume=" at which the swap header is located,
2049 in <PAGE_SIZE> units (needed only for swap files).
2050 See Documentation/power/swsusp-and-swap-files.txt
2052 retain_initrd [RAM] Keep initrd memory after extraction
2054 rhash_entries= [KNL,NET]
2055 Set number of hash buckets for route cache
2057 riscom8= [HW,SERIAL]
2058 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2060 ro [KNL] Mount root device read-only on boot
2062 root= [KNL] Root filesystem
2064 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2065 mount the root filesystem
2067 rootflags= [KNL] Set root filesystem mount option string
2069 rootfstype= [KNL] Set root filesystem type
2071 rootwait [KNL] Wait (indefinitely) for root device to show up.
2072 Useful for devices that are detected asynchronously
2073 (e.g. USB and MMC devices).
2075 root_plug.vendor_id=
2076 [ROOTPLUG] Override the default vendor ID
2078 root_plug.product_id=
2079 [ROOTPLUG] Override the default product ID
2082 [ROOTPLUG] Enable debugging output
2084 rw [KNL] Mount root device read-write on boot
2086 S [KNL] Run init in single mode
2089 See drivers/net/irda/sa1100_ir.c.
2091 sbni= [NET] Granch SBNI12 leased line adapter
2093 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2094 Format: <io>[,<timeout>[,<isapnp>]]
2096 scsi_debug_*= [SCSI]
2097 See drivers/scsi/scsi_debug.c.
2099 scsi_default_dev_flags=
2100 [SCSI] SCSI default device flags
2103 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2104 Format: <vendor>:<model>:<flags>
2105 (flags are integer value)
2107 scsi_logging_level= [SCSI] a bit mask of logging levels
2108 See drivers/scsi/scsi_logging.h for bits. Also
2109 settable via sysctl at dev.scsi.logging_level
2110 (/proc/sys/dev/scsi/logging_level).
2111 There is also a nice 'scsi_logging_level' script in the
2112 S390-tools package, available for download at
2113 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2115 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2116 discovered. async scans them in kernel threads,
2117 allowing boot to proceed. none ignores them, expecting
2118 user space to do the scan.
2120 security= [SECURITY] Choose a security module to enable at boot.
2121 If this boot parameter is not specified, only the first
2122 security module asking for security registration will be
2123 loaded. An invalid security module name will be treated
2124 as if no module has been chosen.
2126 selinux= [SELINUX] Disable or enable SELinux at boot time.
2127 Format: { "0" | "1" }
2128 See security/selinux/Kconfig help text.
2131 Default value is set via kernel config option.
2132 If enabled at boot time, /selinux/disable can be used
2133 later to disable prior to initial policy load.
2135 serialnumber [BUGS=X86-32]
2138 Maximal number of shapers.
2140 show_msr= [x86] show boot-time MSR settings
2141 Format: { <integer> }
2142 Show boot-time (BIOS-initialized) MSR settings.
2143 The parameter means the number of CPUs to show,
2144 for example 1 means boot CPU only.
2147 See header of drivers/scsi/sim710.c.
2154 slub_debug[=options[,slabs]] [MM, SLUB]
2155 Enabling slub_debug allows one to determine the
2156 culprit if slab objects become corrupted. Enabling
2157 slub_debug can create guard zones around objects and
2158 may poison objects when not in use. Also tracks the
2159 last alloc / free. For more information see
2160 Documentation/vm/slub.txt.
2162 slub_max_order= [MM, SLUB]
2163 Determines the maximum allowed order for slabs.
2164 A high setting may cause OOMs due to memory
2165 fragmentation. For more information see
2166 Documentation/vm/slub.txt.
2168 slub_min_objects= [MM, SLUB]
2169 The minimum number of objects per slab. SLUB will
2170 increase the slab order up to slub_max_order to
2171 generate a sufficiently large slab able to contain
2172 the number of objects indicated. The higher the number
2173 of objects the smaller the overhead of tracking slabs
2174 and the less frequently locks need to be acquired.
2175 For more information see Documentation/vm/slub.txt.
2177 slub_min_order= [MM, SLUB]
2178 Determines the mininum page order for slabs. Must be
2179 lower than slub_max_order.
2180 For more information see Documentation/vm/slub.txt.
2182 slub_nomerge [MM, SLUB]
2183 Disable merging of slabs with similar size. May be
2184 necessary if there is some reason to distinguish
2185 allocs to different slabs. Debug options disable
2186 merging on their own.
2187 For more information see Documentation/vm/slub.txt.
2190 Format: <io1>[,<io2>[,...,<io8>]]
2192 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2193 attempt to substitute SMP alternatives once at boot.
2195 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2196 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2197 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2198 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2199 smsc-ircc2.ircc_irq= [HW] IRQ line
2200 smsc-ircc2.ircc_dma= [HW] DMA channel
2201 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2202 0: Toshiba Satellite 1800 (GP data pin select)
2203 1: Fast pin select (default)
2206 snd-ad1816a= [HW,ALSA]
2208 snd-ad1848= [HW,ALSA]
2210 snd-ali5451= [HW,ALSA]
2212 snd-als100= [HW,ALSA]
2214 snd-als4000= [HW,ALSA]
2216 snd-azt2320= [HW,ALSA]
2218 snd-cmi8330= [HW,ALSA]
2220 snd-cmipci= [HW,ALSA]
2222 snd-cs4231= [HW,ALSA]
2224 snd-cs4232= [HW,ALSA]
2226 snd-cs4236= [HW,ALSA]
2228 snd-cs4281= [HW,ALSA]
2230 snd-cs46xx= [HW,ALSA]
2232 snd-dt019x= [HW,ALSA]
2234 snd-dummy= [HW,ALSA]
2236 snd-emu10k1= [HW,ALSA]
2238 snd-ens1370= [HW,ALSA]
2240 snd-ens1371= [HW,ALSA]
2242 snd-es968= [HW,ALSA]
2244 snd-es1688= [HW,ALSA]
2246 snd-es18xx= [HW,ALSA]
2248 snd-es1938= [HW,ALSA]
2250 snd-es1968= [HW,ALSA]
2252 snd-fm801= [HW,ALSA]
2254 snd-gusclassic= [HW,ALSA]
2256 snd-gusextreme= [HW,ALSA]
2258 snd-gusmax= [HW,ALSA]
2262 snd-ice1712= [HW,ALSA]
2264 snd-intel8x0= [HW,ALSA]
2266 snd-interwave= [HW,ALSA]
2271 snd-korg1212= [HW,ALSA]
2273 snd-maestro3= [HW,ALSA]
2275 snd-mpu401= [HW,ALSA]
2277 snd-mtpav= [HW,ALSA]
2279 snd-nm256= [HW,ALSA]
2281 snd-opl3sa2= [HW,ALSA]
2289 snd-opti93x= [HW,ALSA]
2293 snd-rme32= [HW,ALSA]
2295 snd-rme96= [HW,ALSA]
2297 snd-rme9652= [HW,ALSA]
2303 snd-sbawe= [HW,ALSA]
2305 snd-serial= [HW,ALSA]
2307 snd-sgalaxy= [HW,ALSA]
2309 snd-sonicvibes= [HW,ALSA]
2314 snd-sun-cs4231= [HW,ALSA]
2316 snd-trident= [HW,ALSA]
2318 snd-usb-audio= [HW,ALSA,USB]
2320 snd-via82xx= [HW,ALSA]
2322 snd-virmidi= [HW,ALSA]
2324 snd-wavefront= [HW,ALSA]
2326 snd-ymfpci= [HW,ALSA]
2329 [KNL] Should the soft-lockup detector generate panics.
2331 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2332 See Documentation/sonypi.txt
2334 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2335 See Documentation/serial/specialix.txt.
2337 spia_io_base= [HW,MTD]
2343 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2345 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2346 See Documentation/scsi/st.txt.
2349 Enabled the stack tracer on boot up.
2353 Set the STI (builtin display/keyboard on the HP-PARISC
2354 machines) console (graphic card) which should be used
2355 as the initial boot-console.
2356 See also comment in drivers/video/console/sticore.c.
2359 See comment in drivers/video/console/sticore.c.
2362 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2366 Control how the NFS server code allocates CPUs to
2367 service thread pools. Depending on how many NICs
2368 you have and where their interrupts are bound, this
2369 option will affect which CPUs will do NFS serving.
2370 Note: this parameter cannot be changed while the
2371 NFS server is running.
2373 auto the server chooses an appropriate mode
2374 automatically using heuristics
2375 global a single global pool contains all CPUs
2376 percpu one pool for each CPU
2377 pernode one pool for each NUMA node (equivalent
2378 to global on non-NUMA machines)
2380 swiotlb= [IA-64] Number of I/O TLB slabs
2384 sym53c416= [HW,SCSI]
2385 See header of drivers/scsi/sym53c416.c.
2387 sysrq_always_enabled
2389 Ignore sysrq setting - this boot parameter will
2390 neutralize any effect of /proc/sys/kernel/sysrq.
2391 Useful for debugging.
2394 See header of drivers/scsi/t128.c.
2398 test_suspend= [SUSPEND]
2399 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2400 standby suspend) as the system sleep state to briefly
2401 enter during system startup. The system is woken from
2402 this state using a wakeup-capable RTC alarm.
2404 thash_entries= [KNL,NET]
2405 Set number of hash buckets for TCP connection
2407 thermal.act= [HW,ACPI]
2408 -1: disable all active trip points in all thermal zones
2409 <degrees C>: override all lowest active trip points
2411 thermal.crt= [HW,ACPI]
2412 -1: disable all critical trip points in all thermal zones
2413 <degrees C>: override all critical trip points
2415 thermal.nocrt= [HW,ACPI]
2416 Set to disable actions on ACPI thermal zone
2417 critical and hot trip points.
2419 thermal.off= [HW,ACPI]
2420 1: disable ACPI thermal control
2422 thermal.psv= [HW,ACPI]
2423 -1: disable all passive trip points
2424 <degrees C>: override all passive trip points to this
2427 thermal.tzp= [HW,ACPI]
2428 Specify global default ACPI thermal zone polling rate
2429 <deci-seconds>: poll all this frequency
2430 0: no polling (default)
2433 See comment before function dc390_setup() in
2434 drivers/scsi/tmscsim.c.
2438 Specify if the kernel should make use of the cpu
2439 topology informations if the hardware supports these.
2440 The scheduler will make use of these informations and
2441 e.g. base its process migration decisions on it.
2446 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2448 trix= [HW,OSS] MediaTrix AudioTrix Pro
2450 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2452 tsc= Disable clocksource-must-verify flag for TSC.
2454 [x86] reliable: mark tsc clocksource as reliable, this
2455 disables clocksource verification at runtime.
2456 Used to enable high-resolution timer mode on older
2457 hardware, and in virtualized environment.
2459 turbografx.map[2|3]= [HW,JOY]
2460 TurboGraFX parallel port interface
2462 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2463 See also Documentation/input/joystick-parport.txt
2465 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2466 See header of drivers/scsi/u14-34f.c.
2475 [USB] Ignore overcurrent events (default N).
2476 Some badly-designed motherboards generate lots of
2477 bogus events, for ports that aren't wired to
2478 anything. Set this parameter to avoid log spamming.
2479 Note that genuine overcurrent events won't be
2484 Set unknown_nmi_panic=1 early on boot.
2486 usbcore.autosuspend=
2487 [USB] The autosuspend time delay (in seconds) used
2488 for newly-detected USB devices (default 2). This
2489 is the time required before an idle device will be
2490 autosuspended. Devices for which the delay is set
2491 to a negative value won't be autosuspended at all.
2493 usbcore.usbfs_snoop=
2494 [USB] Set to log all usbfs traffic (default 0 = off).
2496 usbcore.blinkenlights=
2497 [USB] Set to cycle leds on hubs (default 0 = off).
2499 usbcore.old_scheme_first=
2500 [USB] Start with the old device initialization
2501 scheme (default 0 = off).
2503 usbcore.use_both_schemes=
2504 [USB] Try the other device initialization scheme
2505 if the first one fails (default 1 = enabled).
2507 usbcore.initial_descriptor_timeout=
2508 [USB] Specifies timeout for the initial 64-byte
2509 USB_REQ_GET_DESCRIPTOR request in milliseconds
2510 (default 5000 = 5.0 seconds).
2513 [USBHID] The interval which mice are to be polled at.
2515 usb-storage.delay_use=
2516 [UMS] The delay in seconds before a new device is
2517 scanned for Logical Units (default 5).
2520 [UMS] A list of quirks entries to supplement or
2521 override the built-in unusual_devs list. List
2522 entries are separated by commas. Each entry has
2523 the form VID:PID:Flags where VID and PID are Vendor
2524 and Product ID values (4-digit hex numbers) and
2525 Flags is a set of characters, each corresponding
2526 to a common usb-storage quirk flag as follows:
2527 a = SANE_SENSE (collect more than 18 bytes
2529 c = FIX_CAPACITY (decrease the reported
2530 device capacity by one sector);
2531 h = CAPACITY_HEURISTICS (decrease the
2532 reported device capacity by one
2533 sector if the number is odd);
2534 i = IGNORE_DEVICE (don't bind to this
2536 l = NOT_LOCKABLE (don't try to lock and
2537 unlock ejectable media);
2538 m = MAX_SECTORS_64 (don't transfer more
2539 than 64 sectors = 32 KB at a time);
2540 o = CAPACITY_OK (accept the capacity
2541 reported by the device);
2542 r = IGNORE_RESIDUE (the device reports
2543 bogus residue values);
2544 s = SINGLE_LUN (the device has only one
2546 w = NO_WP_DETECT (don't test whether the
2547 medium is write-protected).
2548 Example: quirks=0419:aaf5:rl,0421:0433:rc
2551 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2552 vdso=1: enable VDSO (default)
2553 vdso=0: disable VDSO mapping
2556 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2557 vdso32=1: enable 32-bit VDSO (default)
2558 vdso32=0: disable 32-bit VDSO mapping
2561 vector=percpu: enable percpu vector domain
2563 video= [FB] Frame buffer configuration
2564 See Documentation/fb/modedb.txt.
2566 vga= [BOOT,X86-32] Select a particular video mode
2567 See Documentation/x86/boot.txt and
2568 Documentation/svga.txt.
2569 Use vga=ask for menu.
2570 This is actually a boot loader parameter; the value is
2571 passed to the kernel using a special protocol.
2573 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2574 size of <nn>. This can be used to increase the
2575 minimum size (128MB on x86). It can also be used to
2576 decrease the size and leave more room for directly
2579 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2582 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2585 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2588 vt.default_blu= [VT]
2589 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2590 Change the default blue palette of the console.
2591 This is a 16-member array composed of values
2594 vt.default_grn= [VT]
2595 Format: <green0>,<green1>,<green2>,...,<green15>
2596 Change the default green palette of the console.
2597 This is a 16-member array composed of values
2600 vt.default_red= [VT]
2601 Format: <red0>,<red1>,<red2>,...,<red15>
2602 Change the default red palette of the console.
2603 This is a 16-member array composed of values
2609 Set system-wide default UTF-8 mode for all tty's.
2610 Default is 1, i.e. UTF-8 mode is enabled for all
2611 newly opened terminals.
2613 waveartist= [HW,OSS]
2614 Format: <io>,<irq>,<dma>,<dma2>
2617 See header of drivers/scsi/wd33c93.c.
2620 See header of drivers/scsi/wd7000.c.
2623 See Documentation/watchdog/wdt.txt.
2625 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2626 default x2apic cluster mode on platforms
2629 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2630 xd_geo= See header of drivers/block/xd.c.
2632 xirc2ps_cs= [NET,PCMCIA]
2634 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2636 ______________________________________________________________________
2640 Add documentation for ALSA options.
2641 Add more DRM drivers.
projects / linux-2.6 / blob