4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KGDB Kernel debugger support is enabled.
62 KVM Kernel Virtual Machine support is enabled.
63 LIBATA Libata driver is enabled
64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
72 MSI Message Signaled Interrupts (PCI).
73 MTD MTD (Memory Technology Device) support is enabled.
74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
76 GENERIC_TIME The generic timeofday code is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers has their options described inside of
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 SERIAL Serial support is enabled.
97 SH SuperH architecture is enabled.
98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
102 FTRACE Function tracing enabled.
103 TPM TPM drivers are enabled.
104 TS Appropriate touchscreen support is enabled.
105 UMS USB Mass Storage support is enabled.
106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
113 X86-32 X86-32, aka i386 architecture is enabled.
114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
116 Documentation/x86/x86_64/boot-options.txt .
117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 In addition, the following text indicates that the option:
121 BUGS= Relates to possible processor bugs on the said processor.
122 KNL Is a kernel start-up parameter.
123 BOOT Is a boot loader parameter.
125 Parameters denoted with BOOT are actually interpreted by the boot
126 loader, and have no meaning to the kernel directly.
127 Do not modify the syntax of boot loader parameters without extreme
128 need or coordination with <Documentation/x86/boot.txt>.
130 There are also arch-specific kernel-parameters not documented here.
131 See for example <Documentation/x86/x86_64/boot-options.txt>.
133 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
134 a trailing = on the name of any parameter states that that parameter will
135 be entered as an environment variable, whereas its absence indicates that
136 it will appear as a kernel argument readable via /proc/cmdline by programs
137 running once the system is up.
139 The number of kernel parameters is not limited, but the length of the
140 complete command line (parameters including spaces etc.) is limited to
141 a fixed number of characters. This limit depends on the architecture
142 and is between 256 and 4096 characters. It is defined in the file
143 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Advanced Configuration and Power Interface
148 Format: { force | off | strict | noirq | rsdt }
149 force -- enable ACPI if default was off
150 off -- disable ACPI if default was on
151 noirq -- do not use ACPI for IRQ routing
152 strict -- Be less tolerant of platforms that are not
153 strictly ACPI specification compliant.
154 rsdt -- prefer RSDT over (default) XSDT
155 copy_dsdt -- copy DSDT to memory
157 See also Documentation/power/pm.txt, pci=noacpi
159 acpi_apic_instance= [ACPI, IOAPIC]
161 2: use 2nd APIC table, if available
162 1,0: use 1st APIC table
165 acpi_backlight= [HW,ACPI]
166 acpi_backlight=vendor
168 If set to vendor, prefer vendor specific driver
169 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
170 of the ACPI video.ko driver.
172 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
173 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
175 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
176 debug output. Bits in debug_layer correspond to a
177 _COMPONENT in an ACPI source file, e.g.,
178 #define _COMPONENT ACPI_PCI_COMPONENT
179 Bits in debug_level correspond to a level in
180 ACPI_DEBUG_PRINT statements, e.g.,
181 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
182 The debug_level mask defaults to "info". See
183 Documentation/acpi/debug.txt for more information about
184 debug layers and levels.
186 Enable processor driver info messages:
187 acpi.debug_layer=0x20000000
188 Enable PCI/PCI interrupt routing info messages:
189 acpi.debug_layer=0x400000
190 Enable AML "Debug" output, i.e., stores to the Debug
191 object while interpreting AML:
192 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
193 Enable all messages related to ACPI hardware:
194 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
196 Some values produce so much output that the system is
197 unusable. The "log_buf_len" parameter may be useful
198 if you need to capture more output.
200 acpi_display_output= [HW,ACPI]
201 acpi_display_output=vendor
202 acpi_display_output=video
205 acpi_irq_balance [HW,ACPI]
206 ACPI will balance active IRQs
209 acpi_irq_nobalance [HW,ACPI]
210 ACPI will not move active IRQs (default)
213 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
214 Format: <irq>,<irq>...
216 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
218 Format: <irq>,<irq>...
220 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
222 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
223 Format: To spoof as Windows 98: ="Microsoft Windows"
225 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
226 acpi_osi="string1" # add string1 -- only one string
227 acpi_osi="!string2" # remove built-in string2
228 acpi_osi= # disable all strings
231 Override the pmtimer bug detection: force the kernel
232 to assume that this machine's pmtimer latches its value
233 and always returns good values.
235 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge | high | low }
238 acpi_serialize [HW,ACPI] force serialization of AML methods
240 acpi_skip_timer_override [HW,ACPI]
241 Recognize and ignore IRQ0/pin2 Interrupt Override.
242 For broken nForce2 BIOS resulting in XT-PIC timer.
244 acpi_sleep= [HW,ACPI] Sleep options
245 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
246 old_ordering, s4_nonvs, sci_force_enable }
247 See Documentation/power/video.txt for information on
249 s3_beep is for debugging; it makes the PC's speaker beep
250 as soon as the kernel's real-mode entry point is called.
251 s4_nohwsig prevents ACPI hardware signature from being
252 used during resume from hibernation.
253 old_ordering causes the ACPI 1.0 ordering of the _PTS
254 control method, with respect to putting devices into
255 low power states, to be enforced (the ACPI 2.0 ordering
256 of _PTS is used by default).
257 nonvs prevents the kernel from saving/restoring the
258 ACPI NVS memory during suspend/hibernation and resume.
259 sci_force_enable causes the kernel to set SCI_EN directly
260 on resume from S1/S3 (which is against the ACPI spec,
261 but some broken systems don't work without it).
263 acpi_use_timer_override [HW,ACPI]
264 Use timer override. For some broken Nvidia NF5 boards
265 that require a timer override, but don't have HPET
267 acpi_enforce_resources= [ACPI]
268 { strict | lax | no }
269 Check for resource conflicts between native drivers
270 and ACPI OperationRegions (SystemIO and SystemMemory
271 only). IO ports and memory declared in ACPI might be
272 used by the ACPI subsystem in arbitrary AML code and
273 can interfere with legacy drivers.
274 strict (default): access to resources claimed by ACPI
275 is denied; legacy drivers trying to access reserved
276 resources will fail to bind to device using them.
277 lax: access to resources claimed by ACPI is allowed;
278 legacy drivers trying to access reserved resources
279 will bind successfully but a warning message is logged.
280 no: ACPI OperationRegions are not marked as reserved,
281 no further checks are performed.
283 add_efi_memmap [EFI; X86] Include EFI memory map in
284 kernel's map of available physical RAM.
287 See header of drivers/scsi/advansys.c.
290 { off | try_unsupported }
291 off: disable AGP support
292 try_unsupported: try to drive unsupported chipsets
293 (may crash computer or cause data corruption)
296 See Documentation/scsi/aha152x.txt.
299 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
302 See Documentation/scsi/aic7xxx.txt.
305 See Documentation/scsi/aic79xx.txt.
308 See Documentation/sound/alsa/alsa-parameters.txt
311 Allow the default userspace alignment fault handler
312 behaviour to be specified. Bit 0 enables warnings,
313 bit 1 enables fixups, and bit 2 sends a segfault.
315 amd_iommu= [HW,X86-84]
316 Pass parameters to the AMD IOMMU driver in the system.
318 fullflush - enable flushing of IO/TLB entries when
319 they are unmapped. Otherwise they are
320 flushed before they will be reused, which
322 off - do not initialize any AMD IOMMU found in
325 amijoy.map= [HW,JOY] Amiga joystick support
326 Map of devices attached to JOY0DAT and JOY1DAT
328 See also Documentation/kernel/input/joystick.txt
330 analog.map= [HW,JOY] Analog joystick and gamepad support
331 Specifies type or capabilities of an analog joystick
332 connected to one of 16 gameports
333 Format: <type1>,<type2>,..<type16>
336 Power management functions (SPARCstation-4/5 + deriv.)
338 Disable APC CPU standby support. SPARCstation-Fox does
339 not play well with APC CPU idle - disable it if you have
340 APC and your system crashes randomly.
342 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
343 Change the output verbosity whilst booting
344 Format: { quiet (default) | verbose | debug }
345 Change the amount of debugging information output
346 when initialising the APIC and IO-APIC components.
349 See Documentation/networking/ipv6.txt.
351 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
352 Limit apic dumping. The parameter defines the maximal
353 number of local apics being dumped. Also it is possible
354 to set it to "all" by meaning -- no limit here.
355 Format: { 1 (default) | 2 | ... | all }.
356 The parameter valid if only apic=debug or
357 apic=verbose is specified.
358 Example: apic=debug show_lapic=all
360 apm= [APM] Advanced Power Management
361 See header of arch/x86/kernel/apm_32.c.
363 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
364 Format: <io>,<irq>,<nodeID>
368 atarimouse= [HW,MOUSE] Atari Mouse
370 atascsi= [HW,SCSI] Atari SCSI
372 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
373 EzKey and similar keyboards
375 atkbd.reset= [HW] Reset keyboard during initialization
377 atkbd.set= [HW] Select keyboard code set
378 Format: <int> (2 = AT (default), 3 = PS/2)
380 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
383 atkbd.softraw= [HW] Choose between synthetic and real raw mode
384 Format: <bool> (0 = real, 1 = synthetic (default))
386 atkbd.softrepeat= [HW]
387 Use software keyboard repeat
391 baycom_epp= [HW,AX25]
394 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
396 See header of drivers/net/hamradio/baycom_par.c.
398 baycom_ser_fdx= [HW,AX25]
399 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
400 Format: <io>,<irq>,<mode>[,<baud>]
401 See header of drivers/net/hamradio/baycom_ser_fdx.c.
403 baycom_ser_hdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
405 Format: <io>,<irq>,<mode>
406 See header of drivers/net/hamradio/baycom_ser_hdx.c.
408 boot_delay= Milliseconds to delay each printk during boot.
409 Values larger than 10 seconds (10000) are changed to
413 bootmem_debug [KNL] Enable bootmem allocator debug messages.
415 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
416 bttv.radio= Most important insmod options are available as
418 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
419 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
422 See drivers/scsi/BusLogic.c, comment before function
423 BusLogic_ParseDriverOptions().
425 c101= [NET] Moxa C101 synchronous serial card
427 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
428 Sometimes CPU hardware bugs make them report the cache
429 size incorrectly. The kernel will attempt work arounds
430 to fix known problems, but for some CPUs it is not
431 possible to determine what the correct size should be.
432 This option provides an override for these situations.
435 [SECURITY] Disable capabilities. This would normally
436 be used only if an alternative security model is to be
437 configured. Potentially dangerous and should only be
438 used if you are entirely sure of the consequences.
440 ccw_timeout_log [S390]
441 See Documentation/s390/CommonIO for details.
443 cgroup_disable= [KNL] Disable a particular controller
444 Format: {name of the controller(s) to disable}
445 {Currently supported controllers - "memory"}
447 checkreqprot [SELINUX] Set initial checkreqprot flag value.
448 Format: { "0" | "1" }
449 See security/selinux/Kconfig help text.
450 0 -- check protection applied by kernel (includes
451 any implied execute protection).
452 1 -- check protection requested by application.
453 Default value is set via a kernel config option.
454 Value can be changed at runtime via
455 /selinux/checkreqprot.
458 See Documentation/s390/CommonIO for details.
460 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
462 Forces specified clocksource (if available) to be used
463 when calculating gettimeofday(). If specified
464 clocksource is not available, it defaults to PIT.
465 Format: { pit | tsc | cyclone | pmtmr }
467 clocksource= [GENERIC_TIME] Override the default clocksource
469 Override the default clocksource and use the clocksource
470 with the name specified.
471 Some clocksource names to choose from, depending on
473 [all] jiffies (this is the base, fallback clocksource)
475 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
476 pxa_timer,timer3,32k_counter,timer0_1
478 [X86-32] pit,hpet,tsc,vmi-timer;
479 scx200_hrt on Geode; cyclone on IBM x440
487 clearcpuid=BITNUM [X86]
488 Disable CPUID feature X for the kernel. See
489 arch/x86/include/asm/cpufeature.h for the valid bit
490 numbers. Note the Linux specific bits are not necessarily
491 stable over kernel options, but the vendor specific
493 Also note that user programs calling CPUID directly
494 or using the feature without checking anything
495 will still see it. This just prevents it from
496 being used by the kernel or shown in /proc/cpuinfo.
497 Also note the kernel might malfunction if you disable
500 cmo_free_hint= [PPC] Format: { yes | no }
501 Specify whether pages are marked as being inactive
502 when they are freed. This is used in CMO environments
503 to determine OS memory pressure for page stealing by
507 code_bytes [X86] How many bytes of object code to print
512 com20020= [HW,NET] ARCnet - COM20020 chipset
514 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
516 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
520 ARCnet - COM90xx chipset (memory-mapped buffers)
521 Format: <io>[,<irq>[,<memstart>]]
523 condev= [HW,S390] console device
526 console= [KNL] Output console device and options.
528 tty<n> Use the virtual console device <n>.
532 Use the specified serial port. The options are of
533 the form "bbbbpnf", where "bbbb" is the baud rate,
534 "p" is parity ("n", "o", or "e"), "n" is number of
535 bits, and "f" is flow control ("r" for RTS or
536 omit it). Default is "9600n8".
538 See Documentation/serial-console.txt for more
540 Documentation/networking/netconsole.txt for an
543 uart[8250],io,<addr>[,options]
544 uart[8250],mmio,<addr>[,options]
545 Start an early, polled-mode console on the 8250/16550
546 UART at the specified I/O port or MMIO address,
547 switching to the matching ttyS device later. The
548 options are the same as for ttyS, above.
550 If the device connected to the port is not a TTY but a braille
551 device, prepend "brl," before the device type, for instance
553 For now, only VisioBraille is supported.
555 consoleblank= [KNL] The console blank (screen saver) timeout in
556 seconds. Defaults to 10*60 = 10mins. A value of 0
557 disables the blank timer.
560 [KNL] Change the default value for
561 /proc/<pid>/coredump_filter.
562 See also Documentation/filesystems/proc.txt.
564 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
566 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
568 crashkernel=nn[KMG]@ss[KMG]
569 [KNL] Reserve a chunk of physical memory to
570 hold a kernel to switch to with kexec on panic.
572 crashkernel=range1:size1[,range2:size2,...][@offset]
573 [KNL] Same as above, but depends on the memory
574 in the running system. The syntax of range is
575 start-[end] where start and end are both
576 a memory unit (amount[KMG]). See also
577 Documentation/kdump/kdump.txt for a example.
582 cs89x0_media= [HW,NET]
583 Format: { rj45 | aui | bnc }
586 See header of drivers/s390/block/dasd_devmap.c.
588 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
589 (one device per port)
590 Format: <port#>,<type>
591 See also Documentation/input/joystick-parport.txt
593 debug [KNL] Enable kernel debugging (events log level).
596 [KNL] verbose self-tests
598 Print debugging info while doing the locking API
600 We default to 0 (no extra messages), setting it to
601 1 will print _a lot_ more information - normally
602 only useful to kernel developers.
604 debug_objects [KNL] Enable object debugging
607 [KNL] Disable object debugging
609 debugpat [X86] Enable PAT debugging
611 decnet.addr= [HW,NET]
612 Format: <area>[,<node>]
613 See also Documentation/networking/decnet.txt.
616 [same as hugepagesz=] The size of the default
617 HugeTLB page size. This is the size represented by
618 the legacy /proc/ hugepages APIs, used for SHM, and
619 default size when mounting hugetlbfs filesystems.
620 Defaults to the default architecture's huge page size
624 Set number of hash buckets for dentry cache.
627 IO parameters + enable/disable command.
629 digiepca= [HW,SERIAL]
630 See drivers/char/README.epca and
631 Documentation/serial/digiepca.txt.
634 See Documentation/networking/ipv6.txt.
637 See Documentation/networking/ipv6.txt.
639 disable_mtrr_cleanup [X86]
640 The kernel tries to adjust MTRR layout from continuous
641 to discrete, to make X server driver able to add WB
642 entry later. This parameter disables that.
644 disable_mtrr_trim [X86, Intel and AMD only]
645 By default the kernel will trim any uncacheable
646 memory out of your available memory pool based on
647 MTRR settings. This parameter disables that behavior,
648 possibly causing your machine to run very slowly.
650 disable_timer_pin_1 [X86]
651 Disable PIN 1 of APIC timer
652 Can be useful to work around chipset bugs.
654 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
655 this option disables the debugging code at boot.
657 dma_debug_entries=<number>
658 This option allows to tune the number of preallocated
659 entries for DMA-API debugging code. One entry is
660 required per DMA-API allocation. Use this if the
661 DMA-API debugging code disables itself because the
662 architectural default is too low.
664 dma_debug_driver=<driver_name>
665 With this option the DMA-API debugging driver
666 filter feature can be enabled at boot time. Just
667 pass the driver to filter for as the parameter.
668 The filter can be disabled or changed to another
669 driver later using sysfs.
675 dynamic_printk Enables pr_debug()/dev_dbg() calls if
676 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
677 These can also be switched on/off via
678 <debugfs>/dynamic_printk/modules
680 earlycon= [KNL] Output early console device and options.
681 uart[8250],io,<addr>[,options]
682 uart[8250],mmio,<addr>[,options]
683 Start an early, polled-mode console on the 8250/16550
684 UART at the specified I/O port or MMIO address.
685 The options are the same as for ttyS, above.
687 earlyprintk= [X86,SH,BLACKFIN]
689 earlyprintk=serial[,ttySn[,baudrate]]
690 earlyprintk=ttySn[,baudrate]
691 earlyprintk=dbgp[debugController#]
693 Append ",keep" to not disable it when the real console
696 Only vga or serial or usb debug port at a time.
698 Currently only ttyS0 and ttyS1 are supported.
700 Interaction with the standard serial driver is not
703 The VGA output is eventually overwritten by the real
706 ekgdboc= [X86,KGDB] Allow early kernel console debugging
709 This is desgined to be used in conjunction with
710 the boot argument: earlyprintk=vga
715 Format: {"off" | "on" | "skip[mbr]"}
717 eisa_irq_edge= [PARISC,HW]
718 See header of drivers/parisc/eisa.c.
721 See comment before function elanfreq_setup() in
722 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
725 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
726 See Documentation/block/as-iosched.txt and
727 Documentation/block/deadline-iosched.txt for details.
729 elfcorehdr= [IA64,PPC,SH,X86]
730 Specifies physical address of start of kernel core
731 image elf header. Generally kexec loader will
732 pass this option to capture kernel.
733 See Documentation/kdump/kdump.txt for details.
735 enable_mtrr_cleanup [X86]
736 The kernel tries to adjust MTRR layout from continuous
737 to discrete, to make X server driver able to add WB
738 entry later. This parameter enables that.
740 enable_timer_pin_1 [X86]
741 Enable PIN 1 of APIC timer
742 Can be useful to work around chipset bugs
743 (in particular on some ATI chipsets).
744 The kernel tries to set a reasonable default.
746 enforcing [SELINUX] Set initial enforcing status.
748 See security/selinux/Kconfig help text.
749 0 -- permissive (log only, no denials).
750 1 -- enforcing (deny and log).
752 Value can be changed at runtime via /selinux/enforce.
755 Disable Error Record Serialization Table (ERST)
758 ether= [HW,NET] Ethernet cards parameters
759 This option is obsoleted by the "netdev=" option, which
760 has equivalent usage. See its documentation for details.
764 fail_make_request=[KNL]
765 General fault injection mechanism.
766 Format: <interval>,<probability>,<space>,<times>
767 See also /Documentation/fault-injection/.
770 See header of drivers/scsi/fd_mcs.c.
773 See header of drivers/scsi/fdomain.c.
776 See Documentation/blockdev/floppy.txt.
778 force_pal_cache_flush
779 [IA-64] Avoid check_sal_cache_flush which may hang on
780 buggy SAL_CACHE_FLUSH implementations. Using this
781 parameter will force ia64_sal_cache_flush to call
782 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
785 [FTRACE] will set and start the specified tracer
786 as early as possible in order to facilitate early
789 ftrace_dump_on_oops[=orig_cpu]
790 [FTRACE] will dump the trace buffers on oops.
791 If no parameter is passed, ftrace will dump
792 buffers of all CPUs, but if you pass orig_cpu, it will
793 dump only the buffer of the CPU that triggered the
796 ftrace_filter=[function-list]
797 [FTRACE] Limit the functions traced by the function
798 tracer at boot up. function-list is a comma separated
799 list of functions. This list can be changed at run
800 time by the set_ftrace_filter file in the debugfs
803 ftrace_notrace=[function-list]
804 [FTRACE] Do not trace the functions specified in
805 function-list. This list can be changed at run time
806 by the set_ftrace_notrace file in the debugfs
809 ftrace_graph_filter=[function-list]
810 [FTRACE] Limit the top level callers functions traced
811 by the function graph tracer at boot up.
812 function-list is a comma separated list of functions
813 that can be changed at run time by the
814 set_graph_function file in the debugfs tracing directory.
817 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
818 support via parallel port (up to 5 devices per port)
819 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
820 See also Documentation/input/joystick-parport.txt
824 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
828 gcov_persist= [GCOV] When non-zero (default), profiling data for
829 kernel modules is saved and remains accessible via
830 debugfs, even when the module is unloaded/reloaded.
831 When zero, profiling data is discarded and associated
832 debugfs files are removed at module unload time.
835 See header of drivers/scsi/gdth.c.
837 gpt [EFI] Forces disk with valid GPT signature but
838 invalid Protective MBR to be treated as GPT.
842 hashdist= [KNL,NUMA] Large hashes allocated during boot
843 are distributed across NUMA nodes. Defaults on
844 for 64bit NUMA, off otherwise.
845 Format: 0 | 1 (for off | on)
847 hcl= [IA-64] SGI's Hardware Graph compatibility layer
849 hd= [EIDE] (E)IDE hard drive subsystem geometry
850 Format: <cyl>,<head>,<sect>
853 Disable Hardware Error Source Table (HEST) support;
854 corresponding firmware-first mode error processing
855 logic will be disabled.
857 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
858 size of <nn>. This works even on boxes that have no
859 highmem otherwise. This also works to reduce highmem
860 size on bigger boxes.
862 highres= [KNL] Enable/disable high resolution timer mode.
863 Valid parameters: "on", "off"
867 See Documentation/isdn/README.HiSax.
871 hpet= [X86-32,HPET] option to control HPET usage
872 Format: { enable (default) | disable | force |
874 disable: disable HPET and use PIT instead
875 force: allow force enabled of undocumented chips (ICH4,
877 verbose: show contents of HPET registers during setup
879 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
880 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
881 On x86-64 and powerpc, this option can be specified
882 multiple times interleaved with hugepages= to reserve
883 huge pages of different sizes. Valid pages sizes on
884 x86-64 are 2M (when the CPU supports "pse") and 1G
885 (when the CPU supports the "pdpe1gb" cpuinfo flag)
886 Note that 1GB pages can only be allocated at boot time
887 using hugepages= and not freed afterwards.
889 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
890 terminal devices. Valid values: 0..8
891 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
892 If specified, z/VM IUCV HVC accepts connections
893 from listed z/VM user IDs only.
895 i2c_bus= [HW] Override the default board specific I2C bus speed
896 or register an additional I2C bus that is not
897 registered from board initialization code.
901 i8042.debug [HW] Toggle i8042 debug mode
902 i8042.direct [HW] Put keyboard port into non-translated mode
903 i8042.dumbkbd [HW] Pretend that controller can only read data from
904 keyboard and cannot control its state
905 (Don't attempt to blink the leds)
906 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
907 i8042.nokbd [HW] Don't check/create keyboard port
908 i8042.noloop [HW] Disable the AUX Loopback command while probing
910 i8042.nomux [HW] Don't check presence of an active multiplexing
912 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
915 [HW] Frequency with which keyboard LEDs should blink
916 when kernel panics (default is 0.5 sec)
917 i8042.reset [HW] Reset the controller during init and cleanup
918 i8042.unlock [HW] Unlock (ignore) the keylock
922 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
923 indicates that the driver is running on unsupported
925 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
926 does not match list of supported models.
928 [HW] Report power status in /proc/i8k
929 (disabled by default)
930 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
933 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
934 See Documentation/mca.txt.
937 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
939 ide-core.nodma= [HW] (E)IDE subsystem
940 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
941 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
942 .cdrom .chs .ignore_cable are additional options
943 See Documentation/ide/ide.txt.
945 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
946 Claim all unknown PCI IDE storage controllers.
949 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
950 Poll forces a polling idle loop that can slightly
951 improve the performance of waking up a idle CPU, but
952 will use a lot of power and make the system run hot.
954 idle=mwait: On systems which support MONITOR/MWAIT but
955 the kernel chose to not use it because it doesn't save
956 as much power as a normal idle loop, use the
957 MONITOR/MWAIT idle loop anyways. Performance should be
958 the same as idle=poll.
959 idle=halt: Halt is forced to be used for CPU idle.
960 In such case C2/C3 won't be used again.
961 idle=nomwait: Disable mwait for CPU C-states
963 ignore_loglevel [KNL]
964 Ignore loglevel setting - this will print /all/
965 kernel messages to the console. Useful for debugging.
968 Set number of hash buckets for inode cache.
971 Format: { "0" | "1" }
972 0 -- integrity auditing messages. (Default)
973 1 -- enable informational integrity auditing messages.
976 Format: { "sha1" | "md5" }
980 Load a policy which meets the needs of the Trusted
981 Computing Base. This means IMA will measure all
982 programs exec'd, files mmap'd for exec, and all files
983 opened for read by uid=0.
986 See header of drivers/scsi/in2000.c.
990 Run specified binary instead of /sbin/init as init
993 initcall_debug [KNL] Trace initcalls as they are executed. Useful
994 for working out where the kernel is dying during
997 initrd= [BOOT] Specify the location of the initial ramdisk
999 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1002 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1004 Enable intel iommu driver.
1006 Disable intel iommu driver.
1007 igfx_off [Default Off]
1008 By default, gfx is mapped as normal device. If a gfx
1009 device has a dedicated DMAR unit, the DMAR unit is
1010 bypassed by not enabling DMAR with this option. In
1011 this case, gfx device will use physical address for
1014 With this option iommu will not optimize to look
1015 for io virtual address below 32 bit forcing dual
1016 address cycle on pci bus for cards supporting greater
1017 than 32 bit addressing. The default is to look
1018 for translation below 32 bit and if not available
1019 then look in the higher range.
1020 strict [Default Off]
1021 With this option on every unmap_single operation will
1022 result in a hardware IOTLB flush operation as opposed
1023 to batching them for performance.
1027 iomem= Disable strict checking of access to MMIO memory
1028 strict regions from userspace.
1044 io7= [HW] IO7 for Marvel based alpha systems
1045 See comment before marvel_specify_io7 in
1046 arch/alpha/kernel/core_marvel.c.
1048 io_delay= [X86] I/O delay method
1050 Standard port 0x80 based delay
1052 Alternate port 0xed based delay (needed on some systems)
1054 Simple two microseconds delay
1059 See Documentation/filesystems/nfs/nfsroot.txt.
1061 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1062 See comment before ip2_setup() in
1063 drivers/char/ip2/ip2base.c.
1065 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1066 See header of drivers/scsi/ips.c.
1069 When an interrupt is not handled search all handlers
1070 for it. Intended to get systems with badly broken
1074 When an interrupt is not handled search all handlers
1075 for it. Also check all handlers each timer
1076 interrupt. Intended to get systems with badly broken
1080 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1082 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1084 <cpu number>,...,<cpu number>
1086 <cpu number>-<cpu number>
1087 (must be a positive range in ascending order)
1089 <cpu number>,...,<cpu number>-<cpu number>
1091 This option can be used to specify one or more CPUs
1092 to isolate from the general SMP balancing and scheduling
1093 algorithms. You can move a process onto or off an
1094 "isolated" CPU via the CPU affinity syscalls or cpuset.
1095 <cpu number> begins at 0 and the maximum value is
1096 "number of CPUs in system - 1".
1098 This option is the preferred way to isolate CPUs. The
1099 alternative -- manually setting the CPU mask of all
1100 tasks in the system -- can cause problems and
1101 suboptimal load balancer performance.
1105 js= [HW,JOY] Analog joystick
1106 See Documentation/input/joystick.txt.
1110 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1111 specifies the amount of memory usable by the kernel
1112 for non-movable allocations. The requested amount is
1113 spread evenly throughout all nodes in the system. The
1114 remaining memory in each node is used for Movable
1115 pages. In the event, a node is too small to have both
1116 kernelcore and Movable pages, kernelcore pages will
1117 take priority and other nodes will have a larger number
1118 of kernelcore pages. The Movable zone is used for the
1119 allocation of pages that may be reclaimed or moved
1120 by the page migration subsystem. This means that
1121 HugeTLB pages may not be allocated from this zone.
1122 Note that allocations like PTEs-from-HighMem still
1123 use the HighMem zone if it exists, and the Normal
1124 zone if it does not.
1126 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1127 Format: <Controller#>[,poll interval]
1128 The controller # is the number of the ehci usb debug
1129 port as it is probed via PCI. The poll interval is
1130 optional and is the number seconds in between
1131 each poll cycle to the debug port in case you need
1132 the functionality for interrupting the kernel with
1133 gdb or control-c on the dbgp connection. When
1134 not using this parameter you use sysrq-g to break into
1135 the kernel debugger.
1137 kgdboc= [KGDB,HW] kgdb over consoles.
1138 Requires a tty driver that supports console polling,
1139 or a supported polling keyboard driver (non-usb).
1140 Serial only format: <serial_device>[,baud]
1141 keyboard only format: kbd
1142 keyboard and serial format: kbd,<serial_device>[,baud]
1144 kgdbwait [KGDB] Stop kernel execution and enter the
1145 kernel debugger at the earliest opportunity.
1147 kmac= [MIPS] korina ethernet MAC address.
1148 Configure the RouterBoard 532 series on-chip
1149 Ethernet adapter MAC address.
1151 kmemleak= [KNL] Boot-time kmemleak enable/disable
1152 Valid arguments: on, off
1155 kstack=N [X86] Print N words from the kernel stack
1158 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1159 Default is 0 (don't ignore, but inject #GP)
1161 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1162 Default is 1 (enabled)
1164 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1167 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1169 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1171 kvm-intel.bypass_guest_pf=
1172 [KVM,Intel] Disables bypassing of guest page faults
1173 on Intel chips. Default is 1 (enabled)
1175 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1176 (virtualized MMU) support on capable Intel chips.
1177 Default is 1 (enabled)
1179 kvm-intel.emulate_invalid_guest_state=
1180 [KVM,Intel] Enable emulation of invalid guest states
1181 Default is 0 (disabled)
1183 kvm-intel.flexpriority=
1184 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1185 Default is 1 (enabled)
1187 kvm-intel.unrestricted_guest=
1188 [KVM,Intel] Disable unrestricted guest feature
1189 (virtualized real and unpaged mode) on capable
1190 Intel chips. Default is 1 (enabled)
1192 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1193 feature (tagged TLBs) on capable Intel chips.
1194 Default is 1 (enabled)
1200 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1203 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1206 libata.dma= [LIBATA] DMA control
1207 libata.dma=0 Disable all PATA and SATA DMA
1208 libata.dma=1 PATA and SATA Disk DMA only
1209 libata.dma=2 ATAPI (CDROM) DMA only
1210 libata.dma=4 Compact Flash DMA only
1211 Combinations also work, so libata.dma=3 enables DMA
1212 for disks and CDROMs, but not CFs.
1214 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1215 libata.ignore_hpa=0 keep BIOS limits (default)
1216 libata.ignore_hpa=1 ignore limits, using full disk
1218 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1222 libata.force= [LIBATA] Force configurations. The format is comma
1223 separated list of "[ID:]VAL" where ID is
1224 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1225 matching port, link or device. Basically, it matches
1226 the ATA ID string printed on console by libata. If
1227 the whole ID part is omitted, the last PORT and DEVICE
1228 values are used. If ID hasn't been specified yet, the
1229 configuration applies to all ports, links and devices.
1231 If only DEVICE is omitted, the parameter applies to
1232 the port and all links and devices behind it. DEVICE
1233 number of 0 either selects the first device or the
1234 first fan-out link behind PMP device. It does not
1235 select the host link. DEVICE number of 15 selects the
1236 host link and device attached to it.
1238 The VAL specifies the configuration to force. As long
1239 as there's no ambiguity shortcut notation is allowed.
1240 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1241 The following configurations can be forced.
1243 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1244 Any ID with matching PORT is used.
1246 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1248 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1249 udma[/][16,25,33,44,66,100,133] notation is also
1252 * [no]ncq: Turn on or off NCQ.
1254 * nohrst, nosrst, norst: suppress hard, soft
1257 * dump_id: dump IDENTIFY data.
1259 If there are multiple matching configurations changing
1260 the same attribute, the last one is used.
1262 memblock=debug [KNL] Enable memblock debug messages.
1264 load_ramdisk= [RAM] List of ramdisks to load from floppy
1265 See Documentation/blockdev/ramdisk.txt.
1267 lockd.nlm_grace_period=P [NFS] Assign grace period.
1270 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1273 lockd.nlm_timeout=T [NFS] Assign timeout value.
1276 lockd.nlm_udpport=M [NFS] Assign UDP port.
1279 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1282 loglevel= All Kernel Messages with a loglevel smaller than the
1283 console loglevel will be printed to the console. It can
1284 also be changed with klogd or other programs. The
1285 loglevels are defined as follows:
1287 0 (KERN_EMERG) system is unusable
1288 1 (KERN_ALERT) action must be taken immediately
1289 2 (KERN_CRIT) critical conditions
1290 3 (KERN_ERR) error conditions
1291 4 (KERN_WARNING) warning conditions
1292 5 (KERN_NOTICE) normal but significant condition
1293 6 (KERN_INFO) informational
1294 7 (KERN_DEBUG) debug-level messages
1296 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1297 Format: { n | nk | nM }
1298 n must be a power of two. The default size
1299 is set in the kernel config file.
1301 logo.nologo [FB] Disables display of the built-in Linux logo.
1302 This may be used to provide more screen space for
1303 kernel log messages and is useful when debugging
1304 kernel boot problems.
1306 lp=0 [LP] Specify parallel ports to use, e.g,
1307 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1308 lp=reset first parallel port). 'lp=0' disables the
1309 lp=auto printer driver. 'lp=reset' (which can be
1310 specified in addition to the ports) causes
1311 attached printers to be reset. Using
1312 lp=port1,port2,... specifies the parallel ports
1313 to associate lp devices with, starting with
1314 lp0. A port specification may be 'none' to skip
1315 that lp device, or a parport name such as
1316 'parport0'. Specifying 'lp=auto' instead of a
1317 port specification list means that device IDs
1318 from each port should be examined, to see if
1319 an IEEE 1284-compliant printer is attached; if
1320 so, the driver will manage that printer.
1321 See also header of drivers/char/lp.c.
1324 Sets loops_per_jiffy to given constant, thus avoiding
1325 time-consuming boot-time autodetection (up to 250 ms per
1326 CPU). 0 enables autodetection (default). To determine
1327 the correct value for your kernel, boot with normal
1328 autodetection and see what value is printed. Note that
1329 on SMP systems the preset will be applied to all CPUs,
1330 which is likely to cause problems if your CPUs need
1331 significantly divergent settings. An incorrect value
1332 will cause delays in the kernel to be wrong, leading to
1333 unpredictable I/O errors and other breakage. Although
1334 unlikely, in the extreme case this might damage your
1338 Format: <io>,<irq>,<dma>
1340 mac5380= [HW,SCSI] Format:
1341 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1343 machvec= [IA64] Force the use of a particular machine-vector
1344 (machvec) in a generic kernel.
1345 Example: machvec=hpzx1_swiotlb
1347 machtype= [Loongson] Share the same kernel image file between different
1349 Example: machtype=lemote-yeeloong-2f-7inch
1351 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1352 than or equal to this physical address is ignored.
1354 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1355 should make use of. maxcpus=n : n >= 0 limits the
1356 kernel to using 'n' processors. n=0 is a special case,
1357 it is equivalent to "nosmp", which also disables
1360 max_loop= [LOOP] Maximum number of loopback devices that can
1364 max_luns= [SCSI] Maximum number of LUNs to probe.
1365 Should be between 1 and 2^32-1.
1368 [SCSI] Maximum number of LUNs received.
1369 Should be between 1 and 16384.
1373 mce [X86-32] Machine Check Exception
1375 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1377 md= [HW] RAID subsystems devices and level
1378 See Documentation/md.txt.
1381 Format: <first>,<last>
1382 Specifies range of consoles to be captured by the MDA.
1384 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1385 Amount of memory to be used when the kernel is not able
1386 to see the whole system memory or for test.
1387 [X86-32] Use together with memmap= to avoid physical
1388 address space collisions. Without memmap= PCI devices
1389 could be placed at addresses belonging to unused RAM.
1391 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1395 [KNL,SH] Allow user to override the default size for
1396 per-device physically contiguous DMA buffers.
1398 memmap=exactmap [KNL,X86] Enable setting of an exact
1399 E820 memory map, as specified by the user.
1400 Such memmap=exactmap lines can be constructed based on
1401 BIOS output or other requirements. See the memmap=nn@ss
1404 memmap=nn[KMG]@ss[KMG]
1405 [KNL] Force usage of a specific region of memory
1406 Region of memory to be used, from ss to ss+nn.
1408 memmap=nn[KMG]#ss[KMG]
1409 [KNL,ACPI] Mark specific memory as ACPI data.
1410 Region of memory to be used, from ss to ss+nn.
1412 memmap=nn[KMG]$ss[KMG]
1413 [KNL,ACPI] Mark specific memory as reserved.
1414 Region of memory to be used, from ss to ss+nn.
1415 Example: Exclude memory from 0x18690000-0x1869ffff
1416 memmap=64K$0x18690000
1418 memmap=0x10000$0x18690000
1420 memory_corruption_check=0/1 [X86]
1421 Some BIOSes seem to corrupt the first 64k of
1422 memory when doing things like suspend/resume.
1423 Setting this option will scan the memory
1424 looking for corruption. Enabling this will
1425 both detect corruption and prevent the kernel
1426 from using the memory being corrupted.
1427 However, its intended as a diagnostic tool; if
1428 repeatable BIOS-originated corruption always
1429 affects the same memory, you can use memmap=
1430 to prevent the kernel from using that memory.
1432 memory_corruption_check_size=size [X86]
1433 By default it checks for corruption in the low
1434 64k, making this memory unavailable for normal
1435 use. Use this parameter to scan for
1436 corruption in more or less memory.
1438 memory_corruption_check_period=seconds [X86]
1439 By default it checks for corruption every 60
1440 seconds. Use this parameter to check at some
1441 other rate. 0 disables periodic checking.
1443 memtest= [KNL,X86] Enable memtest
1445 default : 0 <disable>
1446 Specifies the number of memtest passes to be
1447 performed. Each pass selects another test
1448 pattern from a given set of patterns. Memtest
1449 fills the memory with this pattern, validates
1450 memory contents and reserves bad memory
1451 regions that are detected.
1453 meye.*= [HW] Set MotionEye Camera parameters
1454 See Documentation/video4linux/meye.txt.
1456 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1457 Multi-Function General Purpose Timers on AMD Geode
1460 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1461 the BIOS has incorrectly applied a workaround. TinyBIOS
1462 version 0.98 is known to be affected, 0.99 fixes the
1463 problem by letting the user disable the workaround.
1467 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1468 physical address is ignored.
1470 mini2440= [ARM,HW,KNL]
1471 Format:[0..2][b][c][t]
1473 MINI2440 configuration specification:
1474 0 - The attached screen is the 3.5" TFT
1475 1 - The attached screen is the 7" TFT
1476 2 - The VGA Shield is attached (1024x768)
1477 Leaving out the screen size parameter will not load
1478 the TFT driver, and the framebuffer will be left
1480 b - Enable backlight. The TFT backlight pin will be
1481 linked to the kernel VESA blanking code and a GPIO
1482 LED. This parameter is not necessary when using the
1484 c - Enable the s3c camera interface.
1485 t - Reserved for enabling touchscreen support. The
1486 touchscreen support is not enabled in the mainstream
1487 kernel as of 2.6.30, a preliminary port can be found
1488 in the "bleeding edge" mini2440 support kernel at
1489 http://repo.or.cz/w/linux-2.6/mini2440.git
1492 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1493 parameter allows control of the logging verbosity for
1494 the additional memory initialisation checks. A value
1495 of 0 disables mminit logging and a level of 4 will
1496 log everything. Information is printed at KERN_DEBUG
1497 so loglevel=8 may also need to be specified.
1500 [MOUSE] Maximum time between finger touching and
1501 leaving touchpad surface for touch to be considered
1502 a tap and be reported as a left button click (for
1503 touchpads working in absolute mode only).
1505 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1506 reporting absolute coordinates, such as tablets
1507 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1508 reporting absolute coordinates, such as tablets
1510 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1511 is similar to kernelcore except it specifies the
1512 amount of memory used for migratable allocations.
1513 If both kernelcore and movablecore is specified,
1514 then kernelcore will be at *least* the specified
1515 value but may be more. If movablecore on its own
1516 is specified, the administrator must be careful
1517 that the amount of memory usable for all allocations
1520 MTD_Partition= [MTD]
1521 Format: <name>,<region-number>,<size>,<offset>
1523 MTD_Region= [MTD] Format:
1524 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1527 See drivers/mtd/cmdlinepart.c.
1529 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1531 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1533 boundary - index of last SLC block on Flex-OneNAND.
1534 The remaining blocks are configured as MLC blocks.
1535 lock - Configure if Flex-OneNAND boundary should be locked.
1536 Once locked, the boundary cannot be changed.
1537 1 indicates lock status, 0 indicates unlock status.
1540 ARM/S3C2412 JIVE boot control
1542 See arch/arm/mach-s3c2412/mach-jive.c
1544 mtouchusb.raw_coordinates=
1545 [HW] Make the MicroTouch USB driver use raw coordinates
1546 ('y', default) or cooked coordinates ('n')
1548 mtrr_chunk_size=nn[KMG] [X86]
1549 used for mtrr cleanup. It is largest continuous chunk
1550 that could hold holes aka. UC entries.
1552 mtrr_gran_size=nn[KMG] [X86]
1553 Used for mtrr cleanup. It is granularity of mtrr block.
1555 Large value could prevent small alignment from
1558 mtrr_spare_reg_nr=n [X86]
1560 Range: 0,7 : spare reg number
1562 Used for mtrr cleanup. It is spare mtrr entries number.
1563 Set to 2 or more if your graphical card needs more.
1565 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1568 See header of drivers/scsi/NCR_D700.c.
1572 ncr53c400= [HW,SCSI]
1574 ncr53c400a= [HW,SCSI]
1576 ncr53c406a= [HW,SCSI]
1578 ncr53c8xx= [HW,SCSI]
1580 netdev= [NET] Network devices parameters
1581 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1582 Note that mem_start is often overloaded to mean
1583 something different and driver-specific.
1584 This usage is only documented in each driver source
1588 [NETFILTER] Enable connection tracking flow accounting
1589 0 to disable accounting
1590 1 to enable accounting
1591 Default value depends on CONFIG_NF_CT_ACCT that is
1592 going to be removed in 2.6.29.
1595 See Documentation/filesystems/nfs/nfsroot.txt.
1597 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1598 See Documentation/filesystems/nfs/nfsroot.txt.
1600 nfs.callback_tcpport=
1601 [NFS] set the TCP port on which the NFSv4 callback
1602 channel should listen.
1605 [NFS] sets the pathname to the program which is used
1606 to update the NFS client cache entries.
1608 nfs.cache_getent_timeout=
1609 [NFS] sets the timeout after which an attempt to
1610 update a cache entry is deemed to have failed.
1612 nfs.idmap_cache_timeout=
1613 [NFS] set the maximum lifetime for idmapper cache
1617 [NFS] enable 64-bit inode numbers.
1618 If zero, the NFS client will fake up a 32-bit inode
1619 number for the readdir() and stat() syscalls instead
1620 of returning the full 64-bit number.
1621 The default is to return 64-bit inode numbers.
1623 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1624 when a NMI is triggered.
1625 Format: [state][,regs][,debounce][,die]
1627 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1628 Format: [panic,][num]
1630 0 - turn nmi_watchdog off
1631 1 - use the IO-APIC timer for the NMI watchdog
1632 2 - use the local APIC for the NMI watchdog using
1633 a performance counter. Note: This will use one
1634 performance counter and the local APIC's performance
1636 When panic is specified, panic when an NMI watchdog
1638 This is useful when you use a panic=... timeout and
1639 need the box quickly up again.
1640 Instead of 1 and 2 it is possible to use the following
1641 symbolic names: lapic and ioapic
1642 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1644 netpoll.carrier_timeout=
1645 [NET] Specifies amount of time (in seconds) that
1646 netpoll should wait for a carrier. By default netpoll
1649 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1650 emulation library even if a 387 maths coprocessor
1654 [HW] Never suspend the console
1655 Disable suspending of consoles during suspend and
1656 hibernate operations. Once disabled, debugging
1657 messages can reach various consoles while the rest
1658 of the system is being put to sleep (ie, while
1659 debugging driver suspend/resume hooks). This may
1660 not work reliably with all consoles, but is known
1661 to work with serial and VGA consoles.
1663 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1664 caches in the slab allocator. Saves per-node memory,
1665 but will impact performance.
1669 noapic [SMP,APIC] Tells the kernel to not make use of any
1670 IOAPICs that may be present in the system.
1672 nobats [PPC] Do not use BATs for mapping kernel lowmem
1673 on "Classic" PPC cores.
1677 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1679 nodelayacct [KNL] Disable per-task delay accounting
1681 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1683 nodsp [SH] Disable hardware DSP at boot time.
1685 noefi [X86] Disable EFI runtime services support.
1690 On X86-32 available only on PAE configured kernels.
1691 noexec=on: enable non-executable mappings (default)
1692 noexec=off: disable non-executable mappings
1695 This affects only 32-bit executables.
1696 noexec32=on: enable non-executable mappings (default)
1697 read doesn't imply executable mappings
1698 noexec32=off: disable non-executable mappings
1699 read implies executable mappings
1701 nofpu [SH] Disable hardware FPU at boot time.
1703 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1704 register save and restore. The kernel will only save
1705 legacy floating-point registers on task switch.
1707 noxsave [BUGS=X86] Disables x86 extended register state save
1708 and restore using xsave. The kernel will fallback to
1709 enabling legacy floating-point and sse state.
1711 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1712 wfi(ARM) instruction doesn't work correctly and not to
1713 use it. This is also useful when using JTAG debugger.
1715 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1716 instruction doesn't work correctly and not to
1719 no_file_caps Tells the kernel not to honor file capabilities. The
1720 only way then for a file to be executed with privilege
1721 is to be setuid root or executed by root.
1723 nohalt [IA-64] Tells the kernel not to use the power saving
1724 function PAL_HALT_LIGHT when idle. This increases
1725 power-consumption. On the positive side, it reduces
1726 interrupt wake-up latency, which may improve performance
1727 in certain environments such as networked servers or
1730 nohz= [KNL] Boottime enable/disable dynamic ticks
1731 Valid arguments: on, off
1734 noiotrap [SH] Disables trapped I/O port accesses.
1736 noirqdebug [X86-32] Disables the code which attempts to detect and
1737 disable unhandled interrupt sources.
1739 no_timer_check [X86,APIC] Disables the code which tests for
1740 broken timer IRQ sources.
1742 noisapnp [ISAPNP] Disables ISA PnP code.
1744 noinitrd [RAM] Tells the kernel not to load any configured
1747 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1752 nojitter [IA64] Disables jitter checking for ITC timers.
1754 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1756 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1758 noltlbs [PPC] Do not use large page/tlb entries for kernel
1759 lowmem mapping on PPC40x.
1761 nomca [IA-64] Disable machine check abort handling
1763 nomce [X86-32] Machine Check Exception
1765 nomfgpt [X86-32] Disable Multi-Function General Purpose
1766 Timer usage (for AMD Geode machines).
1768 nopat [X86] Disable PAT (page attribute table extension of
1769 pagetables) support.
1771 norandmaps Don't use address space randomization. Equivalent to
1772 echo 0 > /proc/sys/kernel/randomize_va_space
1774 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1776 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1777 with UP alternatives
1779 noresidual [PPC] Don't use residual data on PReP machines.
1781 noresume [SWSUSP] Disables resume and restores original swap
1784 no-scroll [VGA] Disables scrollback.
1785 This is required for the Braillex ib80-piezo Braille
1786 reader made by F.H. Papenmeier (Germany).
1790 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1792 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1793 and disable the IO APIC. legacy for "maxcpus=0".
1795 nosoftlockup [KNL] Disable the soft-lockup detector.
1797 noswapaccount [KNL] Disable accounting of swap in memory resource
1798 controller. (See Documentation/cgroups/memory.txt)
1800 nosync [HW,M68K] Disables sync negotiation for all devices.
1802 notsc [BUGS=X86-32] Disable Time Stamp Counter
1804 nousb [USB] Disable the USB subsystem
1808 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1810 nptcg= [IA64] Override max number of concurrent global TLB
1811 purges which is reported from either PAL_VM_SUMMARY or
1814 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1815 could support. nr_cpus=n : n >= 1 limits the kernel to
1816 supporting 'n' processors. Later in runtime you can not
1817 use hotplug cpu feature to put more cpu back to online.
1818 just like you compile the kernel NR_CPUS=n
1820 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1822 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1823 one of ['zone', 'node', 'default'] can be specified
1824 This can be set from sysctl after boot.
1825 See Documentation/sysctl/vm.txt for details.
1827 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1828 See Documentation/debugging-via-ohci1394.txt for more
1831 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1832 Rather than timing out after 20 ms if an EC
1833 command is not properly ACKed, override the length
1834 of the timeout. We have interrupts disabled while
1835 waiting for the ACK, so if this is set too high
1836 interrupts *may* be lost!
1838 omap_mux= [OMAP] Override bootloader pin multiplexing.
1839 Format: <mux_mode0.mode_name=value>...
1840 For example, to override I2C bus2:
1841 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1843 oprofile.timer= [HW]
1844 Use timer interrupt instead of performance counters
1846 oprofile.cpu_type= Force an oprofile cpu type
1847 This might be useful if you have an older oprofile
1848 userland or if you want common events.
1849 Format: { arch_perfmon }
1850 arch_perfmon: [X86] Force use of architectural
1851 perfmon on Intel CPUs instead of the
1852 CPU specific event set.
1855 See Documentation/sound/oss/oss-parameters.txt
1857 osst= [HW,SCSI] SCSI Tape Driver
1858 Format: <buffer_size>,<write_threshold>
1859 See also Documentation/scsi/st.txt.
1861 panic= [KNL] Kernel behaviour on panic
1864 parkbd.port= [HW] Parallel port number the keyboard adapter is
1865 connected to, default is 0.
1867 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1868 0 for XT, 1 for AT (default is AT).
1871 parport= [HW,PPT] Specify parallel ports. 0 disables.
1872 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1873 Use 'auto' to force the driver to use any
1874 IRQ/DMA settings detected (the default is to
1875 ignore detected IRQ/DMA settings because of
1876 possible conflicts). You can specify the base
1877 address, IRQ, and DMA settings; IRQ and DMA
1878 should be numbers, or 'auto' (for using detected
1879 settings on that particular port), or 'nofifo'
1880 (to avoid using a FIFO even if it is detected).
1881 Parallel ports are assigned in the order they
1882 are specified on the command line, starting
1885 parport_init_mode= [HW,PPT]
1886 Configure VIA parallel port to operate in
1887 a specific mode. This is necessary on Pegasos
1888 computer where firmware has no options for setting
1889 up parallel port mode and sets it to spp.
1890 Currently this function knows 686a and 8231 chips.
1891 Format: [spp|ps2|epp|ecp|ecpepp]
1894 See header of drivers/scsi/pas16.c.
1897 Halt all CPUs after the first oops has been printed for
1898 the specified number of seconds. This is to be used if
1899 your oopses keep scrolling off the screen.
1904 See header of drivers/block/paride/pcd.c.
1905 See also Documentation/blockdev/paride.txt.
1907 pci=option[,option...] [PCI] various PCI subsystem options:
1908 earlydump [X86] dump PCI config space before the kernel
1910 off [X86] don't probe for the PCI bus
1911 bios [X86-32] force use of PCI BIOS, don't access
1912 the hardware directly. Use this if your machine
1913 has a non-standard PCI host bridge.
1914 nobios [X86-32] disallow use of PCI BIOS, only direct
1915 hardware access methods are allowed. Use this
1916 if you experience crashes upon bootup and you
1917 suspect they are caused by the BIOS.
1918 conf1 [X86] Force use of PCI Configuration
1920 conf2 [X86] Force use of PCI Configuration
1922 noaer [PCIE] If the PCIEAER kernel config parameter is
1923 enabled, this kernel boot option can be used to
1924 disable the use of PCIE advanced error reporting.
1925 nodomains [PCI] Disable support for multiple PCI
1926 root domains (aka PCI segments, in ACPI-speak).
1927 nommconf [X86] Disable use of MMCONFIG for PCI
1929 check_enable_amd_mmconf [X86] check for and enable
1930 properly configured MMIO access to PCI
1931 config space on AMD family 10h CPU
1932 nomsi [MSI] If the PCI_MSI kernel config parameter is
1933 enabled, this kernel boot option can be used to
1934 disable the use of MSI interrupts system-wide.
1935 noioapicquirk [APIC] Disable all boot interrupt quirks.
1936 Safety option to keep boot IRQs enabled. This
1937 should never be necessary.
1938 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1939 primary IO-APIC for bridges that cannot disable
1940 boot IRQs. This fixes a source of spurious IRQs
1941 when the system masks IRQs.
1942 noioapicreroute [APIC] Disable workaround that uses the
1943 boot IRQ equivalent of an IRQ that connects to
1944 a chipset where boot IRQs cannot be disabled.
1945 The opposite of ioapicreroute.
1946 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1947 routing table. These calls are known to be buggy
1948 on several machines and they hang the machine
1949 when used, but on other computers it's the only
1950 way to get the interrupt routing table. Try
1951 this option if the kernel is unable to allocate
1952 IRQs or discover secondary PCI buses on your
1954 rom [X86] Assign address space to expansion ROMs.
1955 Use with caution as certain devices share
1956 address decoders between ROMs and other
1958 norom [X86] Do not assign address space to
1959 expansion ROMs that do not already have
1960 BIOS assigned address ranges.
1961 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1962 assigned automatically to PCI devices. You can
1963 make the kernel exclude IRQs of your ISA cards
1965 pirqaddr=0xAAAAA [X86] Specify the physical address
1966 of the PIRQ table (normally generated
1967 by the BIOS) if it is outside the
1968 F0000h-100000h range.
1969 lastbus=N [X86] Scan all buses thru bus #N. Can be
1970 useful if the kernel is unable to find your
1971 secondary buses and you want to tell it
1972 explicitly which ones they are.
1973 assign-busses [X86] Always assign all PCI bus
1974 numbers ourselves, overriding
1975 whatever the firmware may have done.
1976 usepirqmask [X86] Honor the possible IRQ mask stored
1977 in the BIOS $PIR table. This is needed on
1978 some systems with broken BIOSes, notably
1979 some HP Pavilion N5400 and Omnibook XE3
1980 notebooks. This will have no effect if ACPI
1981 IRQ routing is enabled.
1982 noacpi [X86] Do not use ACPI for IRQ routing
1983 or for PCI scanning.
1984 use_crs [X86] Use PCI host bridge window information
1985 from ACPI. On BIOSes from 2008 or later, this
1986 is enabled by default. If you need to use this,
1987 please report a bug.
1988 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1989 If you need to use this, please report a bug.
1990 routeirq Do IRQ routing for all PCI devices.
1991 This is normally done in pci_enable_device(),
1992 so this option is a temporary workaround
1993 for broken drivers that don't call it.
1994 skip_isa_align [X86] do not align io start addr, so can
1995 handle more pci cards
1996 firmware [ARM] Do not re-enumerate the bus but instead
1997 just use the configuration from the
1998 bootloader. This is currently used on
1999 IXP2000 systems where the bus has to be
2000 configured a certain way for adjunct CPUs.
2001 noearly [X86] Don't do any early type 1 scanning.
2002 This might help on some broken boards which
2003 machine check when some devices' config space
2004 is read. But various workarounds are disabled
2005 and some IOMMU drivers will not work.
2006 bfsort Sort PCI devices into breadth-first order.
2007 This sorting is done to get a device
2008 order compatible with older (<= 2.4) kernels.
2009 nobfsort Don't sort PCI devices into breadth-first order.
2010 cbiosize=nn[KMG] The fixed amount of bus space which is
2011 reserved for the CardBus bridge's IO window.
2012 The default value is 256 bytes.
2013 cbmemsize=nn[KMG] The fixed amount of bus space which is
2014 reserved for the CardBus bridge's memory
2015 window. The default value is 64 megabytes.
2018 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2019 Specifies alignment and device to reassign
2020 aligned memory resources.
2021 If <order of align> is not specified,
2022 PAGE_SIZE is used as alignment.
2023 PCI-PCI bridge can be specified, if resource
2024 windows need to be expanded.
2025 ecrc= Enable/disable PCIe ECRC (transaction layer
2026 end-to-end CRC checking).
2027 bios: Use BIOS/firmware settings. This is the
2032 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2035 force Enable ASPM even on devices that claim not to support it.
2036 WARNING: Forcing ASPM on may cause system lockups.
2038 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2039 Format: {auto|force}[,nomsi]
2040 auto Use native PCIe PME signaling if the BIOS allows the
2041 kernel to control PCIe config registers of root ports.
2042 force Use native PCIe PME signaling even if the BIOS refuses
2043 to allow the kernel to control the relevant PCIe config
2045 nomsi Do not use MSI for native PCIe PME signaling (this makes
2046 all PCIe root ports use INTx for everything).
2048 pcmv= [HW,PCMCIA] BadgePAD 4
2051 See Documentation/blockdev/paride.txt.
2053 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2056 See arch/parisc/kernel/pdc_chassis.c
2058 percpu_alloc= Select which percpu first chunk allocator to use.
2059 Currently supported values are "embed" and "page".
2060 Archs may support subset or none of the selections.
2061 See comments in mm/percpu.c for details on each
2062 allocator. This parameter is primarily for debugging
2063 and performance comparison.
2066 See Documentation/blockdev/paride.txt.
2069 See Documentation/blockdev/paride.txt.
2071 pirq= [SMP,APIC] Manual mp-table setup
2072 See Documentation/x86/i386/IO-APIC.txt.
2074 plip= [PPT,NET] Parallel port network link
2075 Format: { parport<nr> | timid | 0 }
2076 See also Documentation/parport.txt.
2078 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2079 Override pmtimer IOPort with a hex value.
2083 Enable PNP debug messages. This depends on the
2084 CONFIG_PNP_DEBUG_MESSAGES option.
2090 { on | off | curr | res | no-curr | no-res }
2093 [ISAPNP] Exclude IRQs for the autoconfiguration
2096 [ISAPNP] Exclude DMAs for the autoconfiguration
2098 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2099 Ranges are in pairs (I/O port base and size).
2102 [ISAPNP] Exclude memory regions for the
2104 Ranges are in pairs (memory base and size).
2106 ports= [IP_VS_FTP] IPVS ftp helper module
2108 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2110 Format: <port>,<port>....
2112 print-fatal-signals=
2113 [KNL] debug: print fatal signals
2115 If enabled, warn about various signal handling
2116 related application anomalies: too many signals,
2117 too many POSIX.1 timers, fatal signals causing a
2120 If you hit the warning due to signal overflow,
2121 you might want to try "ulimit -i unlimited".
2125 printk.time= Show timing data prefixed to each printk message line
2126 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2128 processor.max_cstate= [HW,ACPI]
2129 Limit processor to maximum C-state
2130 max_cstate=9 overrides any DMI blacklist limit.
2132 processor.nocst [HW,ACPI]
2133 Ignore the _CST method to determine C-states,
2134 instead using the legacy FADT method
2136 profile= [KNL] Enable kernel profiling via /proc/profile
2137 Format: [schedule,]<number>
2138 Param: "schedule" - profile schedule points.
2139 Param: <number> - step/bucket size as a power of 2 for
2140 statistical time based profiling.
2141 Param: "sleep" - profile D-state sleeping (millisecs).
2142 Requires CONFIG_SCHEDSTATS
2143 Param: "kvm" - profile VM exits.
2145 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2147 See Documentation/blockdev/ramdisk.txt.
2149 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2150 probe for; one of (bare|imps|exps|lifebook|any).
2151 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2153 psmouse.resetafter= [HW,MOUSE]
2154 Try to reset the device after so many bad packets
2157 [HW,MOUSE] Set desired mouse resolution, in dpi.
2158 psmouse.smartscroll=
2159 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2160 0 = disabled, 1 = enabled (default).
2163 See Documentation/blockdev/paride.txt.
2166 [KNL] Number of legacy pty's. Overwrites compiled-in
2169 quiet [KNL] Disable most log messages
2174 See Documentation/md.txt.
2176 ramdisk_blocksize= [RAM]
2177 See Documentation/blockdev/ramdisk.txt.
2179 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2180 See Documentation/blockdev/ramdisk.txt.
2182 rcupdate.blimit= [KNL,BOOT]
2183 Set maximum number of finished RCU callbacks to process
2186 rcupdate.qhimark= [KNL,BOOT]
2187 Set threshold of queued
2188 RCU callbacks over which batch limiting is disabled.
2190 rcupdate.qlowmark= [KNL,BOOT]
2191 Set threshold of queued RCU callbacks below which
2192 batch limiting is re-enabled.
2196 Run specified binary instead of /init from the ramdisk,
2197 used for early userspace startup. See initrd.
2199 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2200 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2201 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2204 [KNL, SMP] Set scheduler's default relax_domain_level.
2205 See Documentation/cgroups/cpusets.txt.
2207 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2209 reservetop= [X86-32]
2211 Reserves a hole at the top of the kernel virtual
2214 reset_devices [KNL] Force drivers to reset the underlying device
2215 during initialization.
2218 Specify the partition device for software suspend
2220 resume_offset= [SWSUSP]
2221 Specify the offset from the beginning of the partition
2222 given by "resume=" at which the swap header is located,
2223 in <PAGE_SIZE> units (needed only for swap files).
2224 See Documentation/power/swsusp-and-swap-files.txt
2226 retain_initrd [RAM] Keep initrd memory after extraction
2228 rhash_entries= [KNL,NET]
2229 Set number of hash buckets for route cache
2231 riscom8= [HW,SERIAL]
2232 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2234 ro [KNL] Mount root device read-only on boot
2236 root= [KNL] Root filesystem
2238 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2239 mount the root filesystem
2241 rootflags= [KNL] Set root filesystem mount option string
2243 rootfstype= [KNL] Set root filesystem type
2245 rootwait [KNL] Wait (indefinitely) for root device to show up.
2246 Useful for devices that are detected asynchronously
2247 (e.g. USB and MMC devices).
2249 rw [KNL] Mount root device read-write on boot
2251 S [KNL] Run init in single mode
2254 See drivers/net/irda/sa1100_ir.c.
2256 sbni= [NET] Granch SBNI12 leased line adapter
2258 sched_debug [KNL] Enables verbose scheduler debug messages.
2260 scsi_debug_*= [SCSI]
2261 See drivers/scsi/scsi_debug.c.
2263 scsi_default_dev_flags=
2264 [SCSI] SCSI default device flags
2267 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2268 Format: <vendor>:<model>:<flags>
2269 (flags are integer value)
2271 scsi_logging_level= [SCSI] a bit mask of logging levels
2272 See drivers/scsi/scsi_logging.h for bits. Also
2273 settable via sysctl at dev.scsi.logging_level
2274 (/proc/sys/dev/scsi/logging_level).
2275 There is also a nice 'scsi_logging_level' script in the
2276 S390-tools package, available for download at
2277 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2279 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2280 discovered. async scans them in kernel threads,
2281 allowing boot to proceed. none ignores them, expecting
2282 user space to do the scan.
2284 security= [SECURITY] Choose a security module to enable at boot.
2285 If this boot parameter is not specified, only the first
2286 security module asking for security registration will be
2287 loaded. An invalid security module name will be treated
2288 as if no module has been chosen.
2290 selinux= [SELINUX] Disable or enable SELinux at boot time.
2291 Format: { "0" | "1" }
2292 See security/selinux/Kconfig help text.
2295 Default value is set via kernel config option.
2296 If enabled at boot time, /selinux/disable can be used
2297 later to disable prior to initial policy load.
2299 serialnumber [BUGS=X86-32]
2302 Maximal number of shapers.
2304 show_msr= [x86] show boot-time MSR settings
2305 Format: { <integer> }
2306 Show boot-time (BIOS-initialized) MSR settings.
2307 The parameter means the number of CPUs to show,
2308 for example 1 means boot CPU only.
2311 See header of drivers/scsi/sim710.c.
2318 slub_debug[=options[,slabs]] [MM, SLUB]
2319 Enabling slub_debug allows one to determine the
2320 culprit if slab objects become corrupted. Enabling
2321 slub_debug can create guard zones around objects and
2322 may poison objects when not in use. Also tracks the
2323 last alloc / free. For more information see
2324 Documentation/vm/slub.txt.
2326 slub_max_order= [MM, SLUB]
2327 Determines the maximum allowed order for slabs.
2328 A high setting may cause OOMs due to memory
2329 fragmentation. For more information see
2330 Documentation/vm/slub.txt.
2332 slub_min_objects= [MM, SLUB]
2333 The minimum number of objects per slab. SLUB will
2334 increase the slab order up to slub_max_order to
2335 generate a sufficiently large slab able to contain
2336 the number of objects indicated. The higher the number
2337 of objects the smaller the overhead of tracking slabs
2338 and the less frequently locks need to be acquired.
2339 For more information see Documentation/vm/slub.txt.
2341 slub_min_order= [MM, SLUB]
2342 Determines the mininum page order for slabs. Must be
2343 lower than slub_max_order.
2344 For more information see Documentation/vm/slub.txt.
2346 slub_nomerge [MM, SLUB]
2347 Disable merging of slabs with similar size. May be
2348 necessary if there is some reason to distinguish
2349 allocs to different slabs. Debug options disable
2350 merging on their own.
2351 For more information see Documentation/vm/slub.txt.
2354 Format: <io1>[,<io2>[,...,<io8>]]
2356 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2357 attempt to substitute SMP alternatives once at boot.
2359 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2360 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2361 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2362 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2363 smsc-ircc2.ircc_irq= [HW] IRQ line
2364 smsc-ircc2.ircc_dma= [HW] DMA channel
2365 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2366 0: Toshiba Satellite 1800 (GP data pin select)
2367 1: Fast pin select (default)
2371 [KNL] Should the soft-lockup detector generate panics.
2373 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2374 See Documentation/sonypi.txt
2376 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2377 See Documentation/serial/specialix.txt.
2379 spia_io_base= [HW,MTD]
2384 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2385 See Documentation/scsi/st.txt.
2388 Enabled the stack tracer on boot up.
2392 Set the STI (builtin display/keyboard on the HP-PARISC
2393 machines) console (graphic card) which should be used
2394 as the initial boot-console.
2395 See also comment in drivers/video/console/sticore.c.
2398 See comment in drivers/video/console/sticore.c.
2401 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2403 sunrpc.min_resvport=
2404 sunrpc.max_resvport=
2406 SunRPC servers often require that client requests
2407 originate from a privileged port (i.e. a port in the
2408 range 0 < portnr < 1024).
2409 An administrator who wishes to reserve some of these
2410 ports for other uses may adjust the range that the
2411 kernel's sunrpc client considers to be privileged
2412 using these two parameters to set the minimum and
2413 maximum port values.
2417 Control how the NFS server code allocates CPUs to
2418 service thread pools. Depending on how many NICs
2419 you have and where their interrupts are bound, this
2420 option will affect which CPUs will do NFS serving.
2421 Note: this parameter cannot be changed while the
2422 NFS server is running.
2424 auto the server chooses an appropriate mode
2425 automatically using heuristics
2426 global a single global pool contains all CPUs
2427 percpu one pool for each CPU
2428 pernode one pool for each NUMA node (equivalent
2429 to global on non-NUMA machines)
2431 sunrpc.tcp_slot_table_entries=
2432 sunrpc.udp_slot_table_entries=
2434 Sets the upper limit on the number of simultaneous
2435 RPC calls that can be sent from the client to a
2436 server. Increasing these values may allow you to
2437 improve throughput, but will also increase the
2438 amount of memory reserved for use by the client.
2440 swiotlb= [IA-64] Number of I/O TLB slabs
2444 sym53c416= [HW,SCSI]
2445 See header of drivers/scsi/sym53c416.c.
2447 sysrq_always_enabled
2449 Ignore sysrq setting - this boot parameter will
2450 neutralize any effect of /proc/sys/kernel/sysrq.
2451 Useful for debugging.
2454 See header of drivers/scsi/t128.c.
2458 test_suspend= [SUSPEND]
2459 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2460 standby suspend) as the system sleep state to briefly
2461 enter during system startup. The system is woken from
2462 this state using a wakeup-capable RTC alarm.
2464 thash_entries= [KNL,NET]
2465 Set number of hash buckets for TCP connection
2467 thermal.act= [HW,ACPI]
2468 -1: disable all active trip points in all thermal zones
2469 <degrees C>: override all lowest active trip points
2471 thermal.crt= [HW,ACPI]
2472 -1: disable all critical trip points in all thermal zones
2473 <degrees C>: override all critical trip points
2475 thermal.nocrt= [HW,ACPI]
2476 Set to disable actions on ACPI thermal zone
2477 critical and hot trip points.
2479 thermal.off= [HW,ACPI]
2480 1: disable ACPI thermal control
2482 thermal.psv= [HW,ACPI]
2483 -1: disable all passive trip points
2484 <degrees C>: override all passive trip points to this
2487 thermal.tzp= [HW,ACPI]
2488 Specify global default ACPI thermal zone polling rate
2489 <deci-seconds>: poll all this frequency
2490 0: no polling (default)
2493 See comment before function dc390_setup() in
2494 drivers/scsi/tmscsim.c.
2498 Specify if the kernel should make use of the cpu
2499 topology informations if the hardware supports these.
2500 The scheduler will make use of these informations and
2501 e.g. base its process migration decisions on it.
2506 tpm_suspend_pcr=[HW,TPM]
2507 Format: integer pcr id
2508 Specify that at suspend time, the tpm driver
2509 should extend the specified pcr with zeros,
2510 as a workaround for some chips which fail to
2511 flush the last written pcr on TPM_SaveState.
2512 This will guarantee that all the other pcrs
2515 trace_buf_size=nn[KMG]
2516 [FTRACE] will set tracing buffer size.
2518 trace_event=[event-list]
2519 [FTRACE] Set and start specified trace events in order
2520 to facilitate early boot debugging.
2521 See also Documentation/trace/events.txt
2523 tsc= Disable clocksource-must-verify flag for TSC.
2525 [x86] reliable: mark tsc clocksource as reliable, this
2526 disables clocksource verification at runtime.
2527 Used to enable high-resolution timer mode on older
2528 hardware, and in virtualized environment.
2530 turbografx.map[2|3]= [HW,JOY]
2531 TurboGraFX parallel port interface
2533 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2534 See also Documentation/input/joystick-parport.txt
2536 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2537 See header of drivers/scsi/u14-34f.c.
2539 uhash_entries= [KNL,NET]
2540 Set number of hash buckets for UDP/UDP-Lite connections
2543 [USB] Ignore overcurrent events (default N).
2544 Some badly-designed motherboards generate lots of
2545 bogus events, for ports that aren't wired to
2546 anything. Set this parameter to avoid log spamming.
2547 Note that genuine overcurrent events won't be
2552 Set unknown_nmi_panic=1 early on boot.
2554 usbcore.autosuspend=
2555 [USB] The autosuspend time delay (in seconds) used
2556 for newly-detected USB devices (default 2). This
2557 is the time required before an idle device will be
2558 autosuspended. Devices for which the delay is set
2559 to a negative value won't be autosuspended at all.
2561 usbcore.usbfs_snoop=
2562 [USB] Set to log all usbfs traffic (default 0 = off).
2564 usbcore.blinkenlights=
2565 [USB] Set to cycle leds on hubs (default 0 = off).
2567 usbcore.old_scheme_first=
2568 [USB] Start with the old device initialization
2569 scheme (default 0 = off).
2571 usbcore.use_both_schemes=
2572 [USB] Try the other device initialization scheme
2573 if the first one fails (default 1 = enabled).
2575 usbcore.initial_descriptor_timeout=
2576 [USB] Specifies timeout for the initial 64-byte
2577 USB_REQ_GET_DESCRIPTOR request in milliseconds
2578 (default 5000 = 5.0 seconds).
2581 [USBHID] The interval which mice are to be polled at.
2583 usb-storage.delay_use=
2584 [UMS] The delay in seconds before a new device is
2585 scanned for Logical Units (default 5).
2588 [UMS] A list of quirks entries to supplement or
2589 override the built-in unusual_devs list. List
2590 entries are separated by commas. Each entry has
2591 the form VID:PID:Flags where VID and PID are Vendor
2592 and Product ID values (4-digit hex numbers) and
2593 Flags is a set of characters, each corresponding
2594 to a common usb-storage quirk flag as follows:
2595 a = SANE_SENSE (collect more than 18 bytes
2597 b = BAD_SENSE (don't collect more than 18
2598 bytes of sense data);
2599 c = FIX_CAPACITY (decrease the reported
2600 device capacity by one sector);
2601 h = CAPACITY_HEURISTICS (decrease the
2602 reported device capacity by one
2603 sector if the number is odd);
2604 i = IGNORE_DEVICE (don't bind to this
2606 l = NOT_LOCKABLE (don't try to lock and
2607 unlock ejectable media);
2608 m = MAX_SECTORS_64 (don't transfer more
2609 than 64 sectors = 32 KB at a time);
2610 o = CAPACITY_OK (accept the capacity
2611 reported by the device);
2612 r = IGNORE_RESIDUE (the device reports
2613 bogus residue values);
2614 s = SINGLE_LUN (the device has only one
2616 w = NO_WP_DETECT (don't test whether the
2617 medium is write-protected).
2618 Example: quirks=0419:aaf5:rl,0421:0433:rc
2621 [X86] Flags controlling user PTE allocations.
2623 nohigh = do not allocate PTE pages in
2624 HIGHMEM regardless of setting
2628 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2629 vdso=1: enable VDSO (default)
2630 vdso=0: disable VDSO mapping
2633 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2634 vdso32=1: enable 32-bit VDSO (default)
2635 vdso32=0: disable 32-bit VDSO mapping
2638 vector=percpu: enable percpu vector domain
2640 video= [FB] Frame buffer configuration
2641 See Documentation/fb/modedb.txt.
2643 vga= [BOOT,X86-32] Select a particular video mode
2644 See Documentation/x86/boot.txt and
2645 Documentation/svga.txt.
2646 Use vga=ask for menu.
2647 This is actually a boot loader parameter; the value is
2648 passed to the kernel using a special protocol.
2650 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2651 size of <nn>. This can be used to increase the
2652 minimum size (128MB on x86). It can also be used to
2653 decrease the size and leave more room for directly
2656 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2659 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2662 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2665 vt.cur_default= [VT] Default cursor shape.
2666 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2667 the parameters of the <Esc>[?A;B;Cc escape sequence;
2668 see VGA-softcursor.txt. Default: 2 = underline.
2670 vt.default_blu= [VT]
2671 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2672 Change the default blue palette of the console.
2673 This is a 16-member array composed of values
2676 vt.default_grn= [VT]
2677 Format: <green0>,<green1>,<green2>,...,<green15>
2678 Change the default green palette of the console.
2679 This is a 16-member array composed of values
2682 vt.default_red= [VT]
2683 Format: <red0>,<red1>,<red2>,...,<red15>
2684 Change the default red palette of the console.
2685 This is a 16-member array composed of values
2691 Set system-wide default UTF-8 mode for all tty's.
2692 Default is 1, i.e. UTF-8 mode is enabled for all
2693 newly opened terminals.
2695 vt.global_cursor_default=
2698 Set system-wide default for whether a cursor
2699 is shown on new VTs. Default is -1,
2700 i.e. cursors will be created by default unless
2701 overridden by individual drivers. 0 will hide
2702 cursors, 1 will display them.
2705 See header of drivers/scsi/wd33c93.c.
2708 See header of drivers/scsi/wd7000.c.
2710 watchdog timers [HW,WDT] For information on watchdog timers,
2711 see Documentation/watchdog/watchdog-parameters.txt
2712 or other driver-specific files in the
2713 Documentation/watchdog/ directory.
2715 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2716 default x2apic cluster mode on platforms
2719 x86_mrst_timer= [X86-32,APBT]
2720 Choose timer option for x86 Moorestown MID platform.
2721 Two valid options are apbt timer only and lapic timer
2722 plus one apbt timer for broadcast timer.
2723 x86_mrst_timer=apbt_only | lapic_and_apbt
2725 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2726 xd_geo= See header of drivers/block/xd.c.
2728 xirc2ps_cs= [NET,PCMCIA]
2730 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2732 ______________________________________________________________________
2736 Add more DRM drivers.