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 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support 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 have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Finally, the [KMG] suffix is commonly described after a number of kernel
148 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150 bytes respectively. Such letter suffixes can also be entirely omitted.
154 Advanced Configuration and Power Interface
155 Format: { force | off | strict | noirq | rsdt }
156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
159 strict -- Be less tolerant of platforms that are not
160 strictly ACPI specification compliant.
161 rsdt -- prefer RSDT over (default) XSDT
162 copy_dsdt -- copy DSDT to memory
164 See also Documentation/power/pm.txt, pci=noacpi
166 acpi_rsdp= [ACPI,EFI,KEXEC]
167 Pass the RSDP address to the kernel, mostly used
168 on machines running EFI runtime service to boot the
169 second kernel for kdump.
171 acpi_apic_instance= [ACPI, IOAPIC]
173 2: use 2nd APIC table, if available
174 1,0: use 1st APIC table
177 acpi_backlight= [HW,ACPI]
178 acpi_backlight=vendor
180 If set to vendor, prefer vendor specific driver
181 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
182 of the ACPI video.ko driver.
184 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
185 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
187 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
188 debug output. Bits in debug_layer correspond to a
189 _COMPONENT in an ACPI source file, e.g.,
190 #define _COMPONENT ACPI_PCI_COMPONENT
191 Bits in debug_level correspond to a level in
192 ACPI_DEBUG_PRINT statements, e.g.,
193 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
194 The debug_level mask defaults to "info". See
195 Documentation/acpi/debug.txt for more information about
196 debug layers and levels.
198 Enable processor driver info messages:
199 acpi.debug_layer=0x20000000
200 Enable PCI/PCI interrupt routing info messages:
201 acpi.debug_layer=0x400000
202 Enable AML "Debug" output, i.e., stores to the Debug
203 object while interpreting AML:
204 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
205 Enable all messages related to ACPI hardware:
206 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
208 Some values produce so much output that the system is
209 unusable. The "log_buf_len" parameter may be useful
210 if you need to capture more output.
212 acpi_irq_balance [HW,ACPI]
213 ACPI will balance active IRQs
216 acpi_irq_nobalance [HW,ACPI]
217 ACPI will not move active IRQs (default)
220 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
221 Format: <irq>,<irq>...
223 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
225 Format: <irq>,<irq>...
227 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
229 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
230 Format: To spoof as Windows 98: ="Microsoft Windows"
232 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
233 acpi_osi="string1" # add string1 -- only one string
234 acpi_osi="!string2" # remove built-in string2
235 acpi_osi= # disable all strings
238 Override the pmtimer bug detection: force the kernel
239 to assume that this machine's pmtimer latches its value
240 and always returns good values.
242 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
243 Format: { level | edge | high | low }
245 acpi_serialize [HW,ACPI] force serialization of AML methods
247 acpi_skip_timer_override [HW,ACPI]
248 Recognize and ignore IRQ0/pin2 Interrupt Override.
249 For broken nForce2 BIOS resulting in XT-PIC timer.
251 acpi_sleep= [HW,ACPI] Sleep options
252 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
253 old_ordering, nonvs, sci_force_enable }
254 See Documentation/power/video.txt for information on
256 s3_beep is for debugging; it makes the PC's speaker beep
257 as soon as the kernel's real-mode entry point is called.
258 s4_nohwsig prevents ACPI hardware signature from being
259 used during resume from hibernation.
260 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with respect to putting devices into
262 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by default).
264 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken systems don't work without it).
270 acpi_use_timer_override [HW,ACPI]
271 Use timer override. For some broken Nvidia NF5 boards
272 that require a timer override, but don't have HPET
274 acpi_enforce_resources= [ACPI]
275 { strict | lax | no }
276 Check for resource conflicts between native drivers
277 and ACPI OperationRegions (SystemIO and SystemMemory
278 only). IO ports and memory declared in ACPI might be
279 used by the ACPI subsystem in arbitrary AML code and
280 can interfere with legacy drivers.
281 strict (default): access to resources claimed by ACPI
282 is denied; legacy drivers trying to access reserved
283 resources will fail to bind to device using them.
284 lax: access to resources claimed by ACPI is allowed;
285 legacy drivers trying to access reserved resources
286 will bind successfully but a warning message is logged.
287 no: ACPI OperationRegions are not marked as reserved,
288 no further checks are performed.
290 add_efi_memmap [EFI; X86] Include EFI memory map in
291 kernel's map of available physical RAM.
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
300 See Documentation/sound/alsa/alsa-parameters.txt
303 Allow the default userspace alignment fault handler
304 behaviour to be specified. Bit 0 enables warnings,
305 bit 1 enables fixups, and bit 2 sends a segfault.
307 amd_iommu= [HW,X86-84]
308 Pass parameters to the AMD IOMMU driver in the system.
310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
314 off - do not initialize any AMD IOMMU found in
317 amijoy.map= [HW,JOY] Amiga joystick support
318 Map of devices attached to JOY0DAT and JOY1DAT
320 See also Documentation/kernel/input/joystick.txt
322 analog.map= [HW,JOY] Analog joystick and gamepad support
323 Specifies type or capabilities of an analog joystick
324 connected to one of 16 gameports
325 Format: <type1>,<type2>,..<type16>
328 Power management functions (SPARCstation-4/5 + deriv.)
330 Disable APC CPU standby support. SPARCstation-Fox does
331 not play well with APC CPU idle - disable it if you have
332 APC and your system crashes randomly.
334 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
335 Change the output verbosity whilst booting
336 Format: { quiet (default) | verbose | debug }
337 Change the amount of debugging information output
338 when initialising the APIC and IO-APIC components.
341 See Documentation/networking/ipv6.txt.
343 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
344 Limit apic dumping. The parameter defines the maximal
345 number of local apics being dumped. Also it is possible
346 to set it to "all" by meaning -- no limit here.
347 Format: { 1 (default) | 2 | ... | all }.
348 The parameter valid if only apic=debug or
349 apic=verbose is specified.
350 Example: apic=debug show_lapic=all
352 apm= [APM] Advanced Power Management
353 See header of arch/x86/kernel/apm_32.c.
355 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
356 Format: <io>,<irq>,<nodeID>
360 atarimouse= [HW,MOUSE] Atari Mouse
362 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
363 EzKey and similar keyboards
365 atkbd.reset= [HW] Reset keyboard during initialization
367 atkbd.set= [HW] Select keyboard code set
368 Format: <int> (2 = AT (default), 3 = PS/2)
370 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
373 atkbd.softraw= [HW] Choose between synthetic and real raw mode
374 Format: <bool> (0 = real, 1 = synthetic (default))
376 atkbd.softrepeat= [HW]
377 Use software keyboard repeat
381 baycom_epp= [HW,AX25]
384 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
386 See header of drivers/net/hamradio/baycom_par.c.
388 baycom_ser_fdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
390 Format: <io>,<irq>,<mode>[,<baud>]
391 See header of drivers/net/hamradio/baycom_ser_fdx.c.
393 baycom_ser_hdx= [HW,AX25]
394 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
395 Format: <io>,<irq>,<mode>
396 See header of drivers/net/hamradio/baycom_ser_hdx.c.
398 boot_delay= Milliseconds to delay each printk during boot.
399 Values larger than 10 seconds (10000) are changed to
403 bootmem_debug [KNL] Enable bootmem allocator debug messages.
405 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
406 bttv.radio= Most important insmod options are available as
408 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
409 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
411 bulk_remove=off [PPC] This parameter disables the use of the pSeries
412 firmware feature for flushing multiple hpte entries
415 c101= [NET] Moxa C101 synchronous serial card
417 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
418 Sometimes CPU hardware bugs make them report the cache
419 size incorrectly. The kernel will attempt work arounds
420 to fix known problems, but for some CPUs it is not
421 possible to determine what the correct size should be.
422 This option provides an override for these situations.
425 [SECURITY] Disable capabilities. This would normally
426 be used only if an alternative security model is to be
427 configured. Potentially dangerous and should only be
428 used if you are entirely sure of the consequences.
430 ccw_timeout_log [S390]
431 See Documentation/s390/CommonIO for details.
433 cgroup_disable= [KNL] Disable a particular controller
434 Format: {name of the controller(s) to disable}
435 {Currently supported controllers - "memory"}
437 checkreqprot [SELINUX] Set initial checkreqprot flag value.
438 Format: { "0" | "1" }
439 See security/selinux/Kconfig help text.
440 0 -- check protection applied by kernel (includes
441 any implied execute protection).
442 1 -- check protection requested by application.
443 Default value is set via a kernel config option.
444 Value can be changed at runtime via
445 /selinux/checkreqprot.
448 See Documentation/s390/CommonIO for details.
450 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
452 Forces specified clocksource (if available) to be used
453 when calculating gettimeofday(). If specified
454 clocksource is not available, it defaults to PIT.
455 Format: { pit | tsc | cyclone | pmtmr }
457 clocksource= Override the default clocksource
459 Override the default clocksource and use the clocksource
460 with the name specified.
461 Some clocksource names to choose from, depending on
463 [all] jiffies (this is the base, fallback clocksource)
465 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
466 pxa_timer,timer3,32k_counter,timer0_1
468 [X86-32] pit,hpet,tsc;
469 scx200_hrt on Geode; cyclone on IBM x440
477 clearcpuid=BITNUM [X86]
478 Disable CPUID feature X for the kernel. See
479 arch/x86/include/asm/cpufeature.h for the valid bit
480 numbers. Note the Linux specific bits are not necessarily
481 stable over kernel options, but the vendor specific
483 Also note that user programs calling CPUID directly
484 or using the feature without checking anything
485 will still see it. This just prevents it from
486 being used by the kernel or shown in /proc/cpuinfo.
487 Also note the kernel might malfunction if you disable
490 cmo_free_hint= [PPC] Format: { yes | no }
491 Specify whether pages are marked as being inactive
492 when they are freed. This is used in CMO environments
493 to determine OS memory pressure for page stealing by
497 code_bytes [X86] How many bytes of object code to print
502 com20020= [HW,NET] ARCnet - COM20020 chipset
504 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
506 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
510 ARCnet - COM90xx chipset (memory-mapped buffers)
511 Format: <io>[,<irq>[,<memstart>]]
513 condev= [HW,S390] console device
516 console= [KNL] Output console device and options.
518 tty<n> Use the virtual console device <n>.
522 Use the specified serial port. The options are of
523 the form "bbbbpnf", where "bbbb" is the baud rate,
524 "p" is parity ("n", "o", or "e"), "n" is number of
525 bits, and "f" is flow control ("r" for RTS or
526 omit it). Default is "9600n8".
528 See Documentation/serial-console.txt for more
530 Documentation/networking/netconsole.txt for an
533 uart[8250],io,<addr>[,options]
534 uart[8250],mmio,<addr>[,options]
535 Start an early, polled-mode console on the 8250/16550
536 UART at the specified I/O port or MMIO address,
537 switching to the matching ttyS device later. The
538 options are the same as for ttyS, above.
540 If the device connected to the port is not a TTY but a braille
541 device, prepend "brl," before the device type, for instance
543 For now, only VisioBraille is supported.
545 consoleblank= [KNL] The console blank (screen saver) timeout in
546 seconds. Defaults to 10*60 = 10mins. A value of 0
547 disables the blank timer.
550 [KNL] Change the default value for
551 /proc/<pid>/coredump_filter.
552 See also Documentation/filesystems/proc.txt.
554 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
556 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
558 crashkernel=size[KMG][@offset[KMG]]
559 [KNL] Using kexec, Linux can switch to a 'crash kernel'
560 upon panic. This parameter reserves the physical
561 memory region [offset, offset + size] for that kernel
562 image. If '@offset' is omitted, then a suitable offset
563 is selected automatically. Check
564 Documentation/kdump/kdump.txt for further details.
566 crashkernel=range1:size1[,range2:size2,...][@offset]
567 [KNL] Same as above, but depends on the memory
568 in the running system. The syntax of range is
569 start-[end] where start and end are both
570 a memory unit (amount[KMG]). See also
571 Documentation/kdump/kdump.txt for an example.
576 cs89x0_media= [HW,NET]
577 Format: { rj45 | aui | bnc }
580 See header of drivers/s390/block/dasd_devmap.c.
582 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
583 (one device per port)
584 Format: <port#>,<type>
585 See also Documentation/input/joystick-parport.txt
587 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
588 time. See Documentation/dynamic-debug-howto.txt for
591 debug [KNL] Enable kernel debugging (events log level).
594 [KNL] verbose self-tests
596 Print debugging info while doing the locking API
598 We default to 0 (no extra messages), setting it to
599 1 will print _a lot_ more information - normally
600 only useful to kernel developers.
602 debug_objects [KNL] Enable object debugging
605 [KNL] Disable object debugging
607 debugpat [X86] Enable PAT debugging
609 decnet.addr= [HW,NET]
610 Format: <area>[,<node>]
611 See also Documentation/networking/decnet.txt.
614 [same as hugepagesz=] The size of the default
615 HugeTLB page size. This is the size represented by
616 the legacy /proc/ hugepages APIs, used for SHM, and
617 default size when mounting hugetlbfs filesystems.
618 Defaults to the default architecture's huge page size
622 Set number of hash buckets for dentry cache.
625 IO parameters + enable/disable command.
627 digiepca= [HW,SERIAL]
628 See drivers/char/README.epca and
629 Documentation/serial/digiepca.txt.
632 See Documentation/networking/ipv6.txt.
634 disable_ddw [PPC/PSERIES]
635 Disable Dynamic DMA Window support. Use this if
636 to workaround buggy firmware.
639 See Documentation/networking/ipv6.txt.
641 disable_mtrr_cleanup [X86]
642 The kernel tries to adjust MTRR layout from continuous
643 to discrete, to make X server driver able to add WB
644 entry later. This parameter disables that.
646 disable_mtrr_trim [X86, Intel and AMD only]
647 By default the kernel will trim any uncacheable
648 memory out of your available memory pool based on
649 MTRR settings. This parameter disables that behavior,
650 possibly causing your machine to run very slowly.
652 disable_timer_pin_1 [X86]
653 Disable PIN 1 of APIC timer
654 Can be useful to work around chipset bugs.
656 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
657 this option disables the debugging code at boot.
659 dma_debug_entries=<number>
660 This option allows to tune the number of preallocated
661 entries for DMA-API debugging code. One entry is
662 required per DMA-API allocation. Use this if the
663 DMA-API debugging code disables itself because the
664 architectural default is too low.
666 dma_debug_driver=<driver_name>
667 With this option the DMA-API debugging driver
668 filter feature can be enabled at boot time. Just
669 pass the driver to filter for as the parameter.
670 The filter can be disabled or changed to another
671 driver later using sysfs.
675 earlycon= [KNL] Output early console device and options.
676 uart[8250],io,<addr>[,options]
677 uart[8250],mmio,<addr>[,options]
678 uart[8250],mmio32,<addr>[,options]
679 Start an early, polled-mode console on the 8250/16550
680 UART at the specified I/O port or MMIO address.
681 MMIO inter-register address stride is either 8bit (mmio)
683 The options are the same as for ttyS, above.
685 earlyprintk= [X86,SH,BLACKFIN]
687 earlyprintk=serial[,ttySn[,baudrate]]
688 earlyprintk=ttySn[,baudrate]
689 earlyprintk=dbgp[debugController#]
691 Append ",keep" to not disable it when the real console
694 Only vga or serial or usb debug port at a time.
696 Currently only ttyS0 and ttyS1 are supported.
698 Interaction with the standard serial driver is not
701 The VGA output is eventually overwritten by the real
704 ekgdboc= [X86,KGDB] Allow early kernel console debugging
707 This is designed to be used in conjunction with
708 the boot argument: earlyprintk=vga
711 Format: {"off" | "on" | "skip[mbr]"}
713 eisa_irq_edge= [PARISC,HW]
714 See header of drivers/parisc/eisa.c.
717 See comment before function elanfreq_setup() in
718 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
721 Format: {"cfq" | "deadline" | "noop"}
722 See Documentation/block/as-iosched.txt and
723 Documentation/block/deadline-iosched.txt for details.
725 elfcorehdr= [IA64,PPC,SH,X86]
726 Specifies physical address of start of kernel core
727 image elf header. Generally kexec loader will
728 pass this option to capture kernel.
729 See Documentation/kdump/kdump.txt for details.
731 enable_mtrr_cleanup [X86]
732 The kernel tries to adjust MTRR layout from continuous
733 to discrete, to make X server driver able to add WB
734 entry later. This parameter enables that.
736 enable_timer_pin_1 [X86]
737 Enable PIN 1 of APIC timer
738 Can be useful to work around chipset bugs
739 (in particular on some ATI chipsets).
740 The kernel tries to set a reasonable default.
742 enforcing [SELINUX] Set initial enforcing status.
744 See security/selinux/Kconfig help text.
745 0 -- permissive (log only, no denials).
746 1 -- enforcing (deny and log).
748 Value can be changed at runtime via /selinux/enforce.
751 Disable Error Record Serialization Table (ERST)
754 ether= [HW,NET] Ethernet cards parameters
755 This option is obsoleted by the "netdev=" option, which
756 has equivalent usage. See its documentation for details.
760 fail_make_request=[KNL]
761 General fault injection mechanism.
762 Format: <interval>,<probability>,<space>,<times>
763 See also /Documentation/fault-injection/.
766 See Documentation/blockdev/floppy.txt.
768 force_pal_cache_flush
769 [IA-64] Avoid check_sal_cache_flush which may hang on
770 buggy SAL_CACHE_FLUSH implementations. Using this
771 parameter will force ia64_sal_cache_flush to call
772 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
775 [FTRACE] will set and start the specified tracer
776 as early as possible in order to facilitate early
779 ftrace_dump_on_oops[=orig_cpu]
780 [FTRACE] will dump the trace buffers on oops.
781 If no parameter is passed, ftrace will dump
782 buffers of all CPUs, but if you pass orig_cpu, it will
783 dump only the buffer of the CPU that triggered the
786 ftrace_filter=[function-list]
787 [FTRACE] Limit the functions traced by the function
788 tracer at boot up. function-list is a comma separated
789 list of functions. This list can be changed at run
790 time by the set_ftrace_filter file in the debugfs
793 ftrace_notrace=[function-list]
794 [FTRACE] Do not trace the functions specified in
795 function-list. This list can be changed at run time
796 by the set_ftrace_notrace file in the debugfs
799 ftrace_graph_filter=[function-list]
800 [FTRACE] Limit the top level callers functions traced
801 by the function graph tracer at boot up.
802 function-list is a comma separated list of functions
803 that can be changed at run time by the
804 set_graph_function file in the debugfs tracing directory.
807 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
808 support via parallel port (up to 5 devices per port)
809 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
810 See also Documentation/input/joystick-parport.txt
814 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
818 gcov_persist= [GCOV] When non-zero (default), profiling data for
819 kernel modules is saved and remains accessible via
820 debugfs, even when the module is unloaded/reloaded.
821 When zero, profiling data is discarded and associated
822 debugfs files are removed at module unload time.
824 gpt [EFI] Forces disk with valid GPT signature but
825 invalid Protective MBR to be treated as GPT.
827 hashdist= [KNL,NUMA] Large hashes allocated during boot
828 are distributed across NUMA nodes. Defaults on
829 for 64bit NUMA, off otherwise.
830 Format: 0 | 1 (for off | on)
832 hcl= [IA-64] SGI's Hardware Graph compatibility layer
834 hd= [EIDE] (E)IDE hard drive subsystem geometry
835 Format: <cyl>,<head>,<sect>
838 Disable Hardware Error Source Table (HEST) support;
839 corresponding firmware-first mode error processing
840 logic will be disabled.
842 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
843 size of <nn>. This works even on boxes that have no
844 highmem otherwise. This also works to reduce highmem
845 size on bigger boxes.
847 highres= [KNL] Enable/disable high resolution timer mode.
848 Valid parameters: "on", "off"
852 See Documentation/isdn/README.HiSax.
856 hpet= [X86-32,HPET] option to control HPET usage
857 Format: { enable (default) | disable | force |
859 disable: disable HPET and use PIT instead
860 force: allow force enabled of undocumented chips (ICH4,
862 verbose: show contents of HPET registers during setup
864 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
865 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
866 On x86-64 and powerpc, this option can be specified
867 multiple times interleaved with hugepages= to reserve
868 huge pages of different sizes. Valid pages sizes on
869 x86-64 are 2M (when the CPU supports "pse") and 1G
870 (when the CPU supports the "pdpe1gb" cpuinfo flag)
871 Note that 1GB pages can only be allocated at boot time
872 using hugepages= and not freed afterwards.
874 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
875 terminal devices. Valid values: 0..8
876 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
877 If specified, z/VM IUCV HVC accepts connections
878 from listed z/VM user IDs only.
881 Do not unregister boot console at start. This is only
882 useful for debugging when something happens in the window
883 between unregistering the boot console and initializing
886 i2c_bus= [HW] Override the default board specific I2C bus speed
887 or register an additional I2C bus that is not
888 registered from board initialization code.
892 i8042.debug [HW] Toggle i8042 debug mode
893 i8042.direct [HW] Put keyboard port into non-translated mode
894 i8042.dumbkbd [HW] Pretend that controller can only read data from
895 keyboard and cannot control its state
896 (Don't attempt to blink the leds)
897 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
898 i8042.nokbd [HW] Don't check/create keyboard port
899 i8042.noloop [HW] Disable the AUX Loopback command while probing
901 i8042.nomux [HW] Don't check presence of an active multiplexing
903 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
905 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
906 i8042.reset [HW] Reset the controller during init and cleanup
907 i8042.unlock [HW] Unlock (ignore) the keylock
911 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
912 indicates that the driver is running on unsupported
914 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
915 does not match list of supported models.
917 [HW] Report power status in /proc/i8k
918 (disabled by default)
919 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
923 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
925 ide-core.nodma= [HW] (E)IDE subsystem
926 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
927 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
928 .cdrom .chs .ignore_cable are additional options
929 See Documentation/ide/ide.txt.
931 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
932 Claim all unknown PCI IDE storage controllers.
935 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
936 Poll forces a polling idle loop that can slightly
937 improve the performance of waking up a idle CPU, but
938 will use a lot of power and make the system run hot.
940 idle=mwait: On systems which support MONITOR/MWAIT but
941 the kernel chose to not use it because it doesn't save
942 as much power as a normal idle loop, use the
943 MONITOR/MWAIT idle loop anyways. Performance should be
944 the same as idle=poll.
945 idle=halt: Halt is forced to be used for CPU idle.
946 In such case C2/C3 won't be used again.
947 idle=nomwait: Disable mwait for CPU C-states
949 ignore_loglevel [KNL]
950 Ignore loglevel setting - this will print /all/
951 kernel messages to the console. Useful for debugging.
954 Set number of hash buckets for inode cache.
957 Format: { "0" | "1" }
958 0 -- integrity auditing messages. (Default)
959 1 -- enable informational integrity auditing messages.
962 Format: { "sha1" | "md5" }
966 Load a policy which meets the needs of the Trusted
967 Computing Base. This means IMA will measure all
968 programs exec'd, files mmap'd for exec, and all files
969 opened for read by uid=0.
973 Run specified binary instead of /sbin/init as init
976 initcall_debug [KNL] Trace initcalls as they are executed. Useful
977 for working out where the kernel is dying during
980 initrd= [BOOT] Specify the location of the initial ramdisk
982 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
985 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
987 Enable intel iommu driver.
989 Disable intel iommu driver.
990 igfx_off [Default Off]
991 By default, gfx is mapped as normal device. If a gfx
992 device has a dedicated DMAR unit, the DMAR unit is
993 bypassed by not enabling DMAR with this option. In
994 this case, gfx device will use physical address for
997 With this option iommu will not optimize to look
998 for io virtual address below 32 bit forcing dual
999 address cycle on pci bus for cards supporting greater
1000 than 32 bit addressing. The default is to look
1001 for translation below 32 bit and if not available
1002 then look in the higher range.
1003 strict [Default Off]
1004 With this option on every unmap_single operation will
1005 result in a hardware IOTLB flush operation as opposed
1006 to batching them for performance.
1007 sp_off [Default Off]
1008 By default, super page will be supported if Intel IOMMU
1009 has the capability. With this option, super page will
1011 intremap= [X86-64, Intel-IOMMU]
1012 Format: { on (default) | off | nosid }
1013 on enable Interrupt Remapping (default)
1014 off disable Interrupt Remapping
1015 nosid disable Source ID checking
1019 iomem= Disable strict checking of access to MMIO memory
1020 strict regions from userspace.
1036 io7= [HW] IO7 for Marvel based alpha systems
1037 See comment before marvel_specify_io7 in
1038 arch/alpha/kernel/core_marvel.c.
1040 io_delay= [X86] I/O delay method
1042 Standard port 0x80 based delay
1044 Alternate port 0xed based delay (needed on some systems)
1046 Simple two microseconds delay
1051 See Documentation/filesystems/nfs/nfsroot.txt.
1053 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1054 See comment before ip2_setup() in
1055 drivers/char/ip2/ip2base.c.
1058 When an interrupt is not handled search all handlers
1059 for it. Intended to get systems with badly broken
1063 When an interrupt is not handled search all handlers
1064 for it. Also check all handlers each timer
1065 interrupt. Intended to get systems with badly broken
1069 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1071 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1073 <cpu number>,...,<cpu number>
1075 <cpu number>-<cpu number>
1076 (must be a positive range in ascending order)
1078 <cpu number>,...,<cpu number>-<cpu number>
1080 This option can be used to specify one or more CPUs
1081 to isolate from the general SMP balancing and scheduling
1082 algorithms. You can move a process onto or off an
1083 "isolated" CPU via the CPU affinity syscalls or cpuset.
1084 <cpu number> begins at 0 and the maximum value is
1085 "number of CPUs in system - 1".
1087 This option is the preferred way to isolate CPUs. The
1088 alternative -- manually setting the CPU mask of all
1089 tasks in the system -- can cause problems and
1090 suboptimal load balancer performance.
1094 js= [HW,JOY] Analog joystick
1095 See Documentation/input/joystick.txt.
1099 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1100 specifies the amount of memory usable by the kernel
1101 for non-movable allocations. The requested amount is
1102 spread evenly throughout all nodes in the system. The
1103 remaining memory in each node is used for Movable
1104 pages. In the event, a node is too small to have both
1105 kernelcore and Movable pages, kernelcore pages will
1106 take priority and other nodes will have a larger number
1107 of kernelcore pages. The Movable zone is used for the
1108 allocation of pages that may be reclaimed or moved
1109 by the page migration subsystem. This means that
1110 HugeTLB pages may not be allocated from this zone.
1111 Note that allocations like PTEs-from-HighMem still
1112 use the HighMem zone if it exists, and the Normal
1113 zone if it does not.
1115 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1116 Format: <Controller#>[,poll interval]
1117 The controller # is the number of the ehci usb debug
1118 port as it is probed via PCI. The poll interval is
1119 optional and is the number seconds in between
1120 each poll cycle to the debug port in case you need
1121 the functionality for interrupting the kernel with
1122 gdb or control-c on the dbgp connection. When
1123 not using this parameter you use sysrq-g to break into
1124 the kernel debugger.
1126 kgdboc= [KGDB,HW] kgdb over consoles.
1127 Requires a tty driver that supports console polling,
1128 or a supported polling keyboard driver (non-usb).
1129 Serial only format: <serial_device>[,baud]
1130 keyboard only format: kbd
1131 keyboard and serial format: kbd,<serial_device>[,baud]
1132 Optional Kernel mode setting:
1133 kms, kbd format: kms,kbd
1134 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1136 kgdbwait [KGDB] Stop kernel execution and enter the
1137 kernel debugger at the earliest opportunity.
1139 kmac= [MIPS] korina ethernet MAC address.
1140 Configure the RouterBoard 532 series on-chip
1141 Ethernet adapter MAC address.
1143 kmemleak= [KNL] Boot-time kmemleak enable/disable
1144 Valid arguments: on, off
1147 kstack=N [X86] Print N words from the kernel stack
1150 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1151 Default is 0 (don't ignore, but inject #GP)
1153 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1154 Default is 1 (enabled)
1156 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1160 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1161 Default is 1 (enabled)
1163 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1165 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1167 kvm-intel.bypass_guest_pf=
1168 [KVM,Intel] Disables bypassing of guest page faults
1169 on Intel chips. Default is 1 (enabled)
1171 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1172 (virtualized MMU) support on capable Intel chips.
1173 Default is 1 (enabled)
1175 kvm-intel.emulate_invalid_guest_state=
1176 [KVM,Intel] Enable emulation of invalid guest states
1177 Default is 0 (disabled)
1179 kvm-intel.flexpriority=
1180 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1181 Default is 1 (enabled)
1183 kvm-intel.unrestricted_guest=
1184 [KVM,Intel] Disable unrestricted guest feature
1185 (virtualized real and unpaged mode) on capable
1186 Intel chips. Default is 1 (enabled)
1188 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1189 feature (tagged TLBs) on capable Intel chips.
1190 Default is 1 (enabled)
1196 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1199 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1202 libata.dma= [LIBATA] DMA control
1203 libata.dma=0 Disable all PATA and SATA DMA
1204 libata.dma=1 PATA and SATA Disk DMA only
1205 libata.dma=2 ATAPI (CDROM) DMA only
1206 libata.dma=4 Compact Flash DMA only
1207 Combinations also work, so libata.dma=3 enables DMA
1208 for disks and CDROMs, but not CFs.
1210 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1211 libata.ignore_hpa=0 keep BIOS limits (default)
1212 libata.ignore_hpa=1 ignore limits, using full disk
1214 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1218 libata.force= [LIBATA] Force configurations. The format is comma
1219 separated list of "[ID:]VAL" where ID is
1220 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1221 matching port, link or device. Basically, it matches
1222 the ATA ID string printed on console by libata. If
1223 the whole ID part is omitted, the last PORT and DEVICE
1224 values are used. If ID hasn't been specified yet, the
1225 configuration applies to all ports, links and devices.
1227 If only DEVICE is omitted, the parameter applies to
1228 the port and all links and devices behind it. DEVICE
1229 number of 0 either selects the first device or the
1230 first fan-out link behind PMP device. It does not
1231 select the host link. DEVICE number of 15 selects the
1232 host link and device attached to it.
1234 The VAL specifies the configuration to force. As long
1235 as there's no ambiguity shortcut notation is allowed.
1236 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1237 The following configurations can be forced.
1239 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1240 Any ID with matching PORT is used.
1242 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1244 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1245 udma[/][16,25,33,44,66,100,133] notation is also
1248 * [no]ncq: Turn on or off NCQ.
1250 * nohrst, nosrst, norst: suppress hard, soft
1253 * dump_id: dump IDENTIFY data.
1255 If there are multiple matching configurations changing
1256 the same attribute, the last one is used.
1258 memblock=debug [KNL] Enable memblock debug messages.
1260 load_ramdisk= [RAM] List of ramdisks to load from floppy
1261 See Documentation/blockdev/ramdisk.txt.
1263 lockd.nlm_grace_period=P [NFS] Assign grace period.
1266 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1269 lockd.nlm_timeout=T [NFS] Assign timeout value.
1272 lockd.nlm_udpport=M [NFS] Assign UDP port.
1275 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1278 loglevel= All Kernel Messages with a loglevel smaller than the
1279 console loglevel will be printed to the console. It can
1280 also be changed with klogd or other programs. The
1281 loglevels are defined as follows:
1283 0 (KERN_EMERG) system is unusable
1284 1 (KERN_ALERT) action must be taken immediately
1285 2 (KERN_CRIT) critical conditions
1286 3 (KERN_ERR) error conditions
1287 4 (KERN_WARNING) warning conditions
1288 5 (KERN_NOTICE) normal but significant condition
1289 6 (KERN_INFO) informational
1290 7 (KERN_DEBUG) debug-level messages
1292 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1293 in bytes. n must be a power of two. The default
1294 size is set in the kernel config file.
1296 logo.nologo [FB] Disables display of the built-in Linux logo.
1297 This may be used to provide more screen space for
1298 kernel log messages and is useful when debugging
1299 kernel boot problems.
1301 lp=0 [LP] Specify parallel ports to use, e.g,
1302 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1303 lp=reset first parallel port). 'lp=0' disables the
1304 lp=auto printer driver. 'lp=reset' (which can be
1305 specified in addition to the ports) causes
1306 attached printers to be reset. Using
1307 lp=port1,port2,... specifies the parallel ports
1308 to associate lp devices with, starting with
1309 lp0. A port specification may be 'none' to skip
1310 that lp device, or a parport name such as
1311 'parport0'. Specifying 'lp=auto' instead of a
1312 port specification list means that device IDs
1313 from each port should be examined, to see if
1314 an IEEE 1284-compliant printer is attached; if
1315 so, the driver will manage that printer.
1316 See also header of drivers/char/lp.c.
1319 Sets loops_per_jiffy to given constant, thus avoiding
1320 time-consuming boot-time autodetection (up to 250 ms per
1321 CPU). 0 enables autodetection (default). To determine
1322 the correct value for your kernel, boot with normal
1323 autodetection and see what value is printed. Note that
1324 on SMP systems the preset will be applied to all CPUs,
1325 which is likely to cause problems if your CPUs need
1326 significantly divergent settings. An incorrect value
1327 will cause delays in the kernel to be wrong, leading to
1328 unpredictable I/O errors and other breakage. Although
1329 unlikely, in the extreme case this might damage your
1333 Format: <io>,<irq>,<dma>
1335 machvec= [IA64] Force the use of a particular machine-vector
1336 (machvec) in a generic kernel.
1337 Example: machvec=hpzx1_swiotlb
1339 machtype= [Loongson] Share the same kernel image file between different
1341 Example: machtype=lemote-yeeloong-2f-7inch
1343 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1344 than or equal to this physical address is ignored.
1346 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1347 should make use of. maxcpus=n : n >= 0 limits the
1348 kernel to using 'n' processors. n=0 is a special case,
1349 it is equivalent to "nosmp", which also disables
1352 max_loop= [LOOP] Maximum number of loopback devices that can
1358 mce [X86-32] Machine Check Exception
1360 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1362 md= [HW] RAID subsystems devices and level
1363 See Documentation/md.txt.
1366 Format: <first>,<last>
1367 Specifies range of consoles to be captured by the MDA.
1369 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1370 Amount of memory to be used when the kernel is not able
1371 to see the whole system memory or for test.
1372 [X86-32] Use together with memmap= to avoid physical
1373 address space collisions. Without memmap= PCI devices
1374 could be placed at addresses belonging to unused RAM.
1376 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1380 [KNL,SH] Allow user to override the default size for
1381 per-device physically contiguous DMA buffers.
1383 memmap=exactmap [KNL,X86] Enable setting of an exact
1384 E820 memory map, as specified by the user.
1385 Such memmap=exactmap lines can be constructed based on
1386 BIOS output or other requirements. See the memmap=nn@ss
1389 memmap=nn[KMG]@ss[KMG]
1390 [KNL] Force usage of a specific region of memory
1391 Region of memory to be used, from ss to ss+nn.
1393 memmap=nn[KMG]#ss[KMG]
1394 [KNL,ACPI] Mark specific memory as ACPI data.
1395 Region of memory to be used, from ss to ss+nn.
1397 memmap=nn[KMG]$ss[KMG]
1398 [KNL,ACPI] Mark specific memory as reserved.
1399 Region of memory to be used, from ss to ss+nn.
1400 Example: Exclude memory from 0x18690000-0x1869ffff
1401 memmap=64K$0x18690000
1403 memmap=0x10000$0x18690000
1405 memory_corruption_check=0/1 [X86]
1406 Some BIOSes seem to corrupt the first 64k of
1407 memory when doing things like suspend/resume.
1408 Setting this option will scan the memory
1409 looking for corruption. Enabling this will
1410 both detect corruption and prevent the kernel
1411 from using the memory being corrupted.
1412 However, its intended as a diagnostic tool; if
1413 repeatable BIOS-originated corruption always
1414 affects the same memory, you can use memmap=
1415 to prevent the kernel from using that memory.
1417 memory_corruption_check_size=size [X86]
1418 By default it checks for corruption in the low
1419 64k, making this memory unavailable for normal
1420 use. Use this parameter to scan for
1421 corruption in more or less memory.
1423 memory_corruption_check_period=seconds [X86]
1424 By default it checks for corruption every 60
1425 seconds. Use this parameter to check at some
1426 other rate. 0 disables periodic checking.
1428 memtest= [KNL,X86] Enable memtest
1430 default : 0 <disable>
1431 Specifies the number of memtest passes to be
1432 performed. Each pass selects another test
1433 pattern from a given set of patterns. Memtest
1434 fills the memory with this pattern, validates
1435 memory contents and reserves bad memory
1436 regions that are detected.
1438 meye.*= [HW] Set MotionEye Camera parameters
1439 See Documentation/video4linux/meye.txt.
1441 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1442 Multi-Function General Purpose Timers on AMD Geode
1445 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1446 the BIOS has incorrectly applied a workaround. TinyBIOS
1447 version 0.98 is known to be affected, 0.99 fixes the
1448 problem by letting the user disable the workaround.
1452 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1453 physical address is ignored.
1455 mini2440= [ARM,HW,KNL]
1456 Format:[0..2][b][c][t]
1458 MINI2440 configuration specification:
1459 0 - The attached screen is the 3.5" TFT
1460 1 - The attached screen is the 7" TFT
1461 2 - The VGA Shield is attached (1024x768)
1462 Leaving out the screen size parameter will not load
1463 the TFT driver, and the framebuffer will be left
1465 b - Enable backlight. The TFT backlight pin will be
1466 linked to the kernel VESA blanking code and a GPIO
1467 LED. This parameter is not necessary when using the
1469 c - Enable the s3c camera interface.
1470 t - Reserved for enabling touchscreen support. The
1471 touchscreen support is not enabled in the mainstream
1472 kernel as of 2.6.30, a preliminary port can be found
1473 in the "bleeding edge" mini2440 support kernel at
1474 http://repo.or.cz/w/linux-2.6/mini2440.git
1477 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1478 parameter allows control of the logging verbosity for
1479 the additional memory initialisation checks. A value
1480 of 0 disables mminit logging and a level of 4 will
1481 log everything. Information is printed at KERN_DEBUG
1482 so loglevel=8 may also need to be specified.
1485 [MOUSE] Maximum time between finger touching and
1486 leaving touchpad surface for touch to be considered
1487 a tap and be reported as a left button click (for
1488 touchpads working in absolute mode only).
1490 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1491 reporting absolute coordinates, such as tablets
1492 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1493 reporting absolute coordinates, such as tablets
1495 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1496 is similar to kernelcore except it specifies the
1497 amount of memory used for migratable allocations.
1498 If both kernelcore and movablecore is specified,
1499 then kernelcore will be at *least* the specified
1500 value but may be more. If movablecore on its own
1501 is specified, the administrator must be careful
1502 that the amount of memory usable for all allocations
1505 MTD_Partition= [MTD]
1506 Format: <name>,<region-number>,<size>,<offset>
1508 MTD_Region= [MTD] Format:
1509 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1512 See drivers/mtd/cmdlinepart.c.
1514 multitce=off [PPC] This parameter disables the use of the pSeries
1515 firmware feature for updating multiple TCE entries
1518 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1520 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1522 boundary - index of last SLC block on Flex-OneNAND.
1523 The remaining blocks are configured as MLC blocks.
1524 lock - Configure if Flex-OneNAND boundary should be locked.
1525 Once locked, the boundary cannot be changed.
1526 1 indicates lock status, 0 indicates unlock status.
1529 ARM/S3C2412 JIVE boot control
1531 See arch/arm/mach-s3c2412/mach-jive.c
1533 mtouchusb.raw_coordinates=
1534 [HW] Make the MicroTouch USB driver use raw coordinates
1535 ('y', default) or cooked coordinates ('n')
1537 mtrr_chunk_size=nn[KMG] [X86]
1538 used for mtrr cleanup. It is largest continuous chunk
1539 that could hold holes aka. UC entries.
1541 mtrr_gran_size=nn[KMG] [X86]
1542 Used for mtrr cleanup. It is granularity of mtrr block.
1544 Large value could prevent small alignment from
1547 mtrr_spare_reg_nr=n [X86]
1549 Range: 0,7 : spare reg number
1551 Used for mtrr cleanup. It is spare mtrr entries number.
1552 Set to 2 or more if your graphical card needs more.
1554 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1556 netdev= [NET] Network devices parameters
1557 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1558 Note that mem_start is often overloaded to mean
1559 something different and driver-specific.
1560 This usage is only documented in each driver source
1564 [NETFILTER] Enable connection tracking flow accounting
1565 0 to disable accounting
1566 1 to enable accounting
1569 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1570 See Documentation/filesystems/nfs/nfsroot.txt.
1572 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1573 See Documentation/filesystems/nfs/nfsroot.txt.
1575 nfsrootdebug [NFS] enable nfsroot debugging messages.
1576 See Documentation/filesystems/nfs/nfsroot.txt.
1578 nfs.callback_tcpport=
1579 [NFS] set the TCP port on which the NFSv4 callback
1580 channel should listen.
1583 [NFS] sets the pathname to the program which is used
1584 to update the NFS client cache entries.
1586 nfs.cache_getent_timeout=
1587 [NFS] sets the timeout after which an attempt to
1588 update a cache entry is deemed to have failed.
1590 nfs.idmap_cache_timeout=
1591 [NFS] set the maximum lifetime for idmapper cache
1595 [NFS] enable 64-bit inode numbers.
1596 If zero, the NFS client will fake up a 32-bit inode
1597 number for the readdir() and stat() syscalls instead
1598 of returning the full 64-bit number.
1599 The default is to return 64-bit inode numbers.
1601 nfs.nfs4_disable_idmapping=
1602 [NFSv4] When set, this option disables the NFSv4
1603 idmapper on the client, but only if the mount
1604 is using the 'sec=sys' security flavour. This may
1605 make migration from legacy NFSv2/v3 systems easier
1606 provided that the server has the appropriate support.
1607 The default is to always enable NFSv4 idmapping.
1609 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1610 when a NMI is triggered.
1611 Format: [state][,regs][,debounce][,die]
1613 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1614 Format: [panic,][nopanic,][num]
1616 0 - turn nmi_watchdog off
1617 When panic is specified, panic when an NMI watchdog
1618 timeout occurs (or 'nopanic' to override the opposite
1620 This is useful when you use a panic=... timeout and
1621 need the box quickly up again.
1623 netpoll.carrier_timeout=
1624 [NET] Specifies amount of time (in seconds) that
1625 netpoll should wait for a carrier. By default netpoll
1628 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1629 emulation library even if a 387 maths coprocessor
1633 [HW] Never suspend the console
1634 Disable suspending of consoles during suspend and
1635 hibernate operations. Once disabled, debugging
1636 messages can reach various consoles while the rest
1637 of the system is being put to sleep (ie, while
1638 debugging driver suspend/resume hooks). This may
1639 not work reliably with all consoles, but is known
1640 to work with serial and VGA consoles.
1642 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1643 caches in the slab allocator. Saves per-node memory,
1644 but will impact performance.
1648 noapic [SMP,APIC] Tells the kernel to not make use of any
1649 IOAPICs that may be present in the system.
1651 noautogroup Disable scheduler automatic task group creation.
1653 nobats [PPC] Do not use BATs for mapping kernel lowmem
1654 on "Classic" PPC cores.
1658 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1660 nodelayacct [KNL] Disable per-task delay accounting
1662 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1664 nodsp [SH] Disable hardware DSP at boot time.
1666 noefi [X86] Disable EFI runtime services support.
1671 On X86-32 available only on PAE configured kernels.
1672 noexec=on: enable non-executable mappings (default)
1673 noexec=off: disable non-executable mappings
1676 Disable SMEP (Supervisor Mode Execution Protection)
1677 even if it is supported by processor.
1680 This affects only 32-bit executables.
1681 noexec32=on: enable non-executable mappings (default)
1682 read doesn't imply executable mappings
1683 noexec32=off: disable non-executable mappings
1684 read implies executable mappings
1686 nofpu [SH] Disable hardware FPU at boot time.
1688 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1689 register save and restore. The kernel will only save
1690 legacy floating-point registers on task switch.
1692 noxsave [BUGS=X86] Disables x86 extended register state save
1693 and restore using xsave. The kernel will fallback to
1694 enabling legacy floating-point and sse state.
1696 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1697 wfi(ARM) instruction doesn't work correctly and not to
1698 use it. This is also useful when using JTAG debugger.
1700 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1701 instruction doesn't work correctly and not to
1704 no_file_caps Tells the kernel not to honor file capabilities. The
1705 only way then for a file to be executed with privilege
1706 is to be setuid root or executed by root.
1708 nohalt [IA-64] Tells the kernel not to use the power saving
1709 function PAL_HALT_LIGHT when idle. This increases
1710 power-consumption. On the positive side, it reduces
1711 interrupt wake-up latency, which may improve performance
1712 in certain environments such as networked servers or
1715 nohz= [KNL] Boottime enable/disable dynamic ticks
1716 Valid arguments: on, off
1719 noiotrap [SH] Disables trapped I/O port accesses.
1721 noirqdebug [X86-32] Disables the code which attempts to detect and
1722 disable unhandled interrupt sources.
1724 no_timer_check [X86,APIC] Disables the code which tests for
1725 broken timer IRQ sources.
1727 noisapnp [ISAPNP] Disables ISA PnP code.
1729 noinitrd [RAM] Tells the kernel not to load any configured
1732 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1734 [Deprecated - use intremap=off]
1738 nojitter [IA64] Disables jitter checking for ITC timers.
1740 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1742 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1745 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1747 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1749 noltlbs [PPC] Do not use large page/tlb entries for kernel
1750 lowmem mapping on PPC40x.
1752 nomca [IA-64] Disable machine check abort handling
1754 nomce [X86-32] Machine Check Exception
1756 nomfgpt [X86-32] Disable Multi-Function General Purpose
1757 Timer usage (for AMD Geode machines).
1759 nopat [X86] Disable PAT (page attribute table extension of
1760 pagetables) support.
1762 norandmaps Don't use address space randomization. Equivalent to
1763 echo 0 > /proc/sys/kernel/randomize_va_space
1765 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1767 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1768 with UP alternatives
1770 noresidual [PPC] Don't use residual data on PReP machines.
1772 noresume [SWSUSP] Disables resume and restores original swap
1775 no-scroll [VGA] Disables scrollback.
1776 This is required for the Braillex ib80-piezo Braille
1777 reader made by F.H. Papenmeier (Germany).
1781 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1783 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1784 and disable the IO APIC. legacy for "maxcpus=0".
1786 nosoftlockup [KNL] Disable the soft-lockup detector.
1788 nosync [HW,M68K] Disables sync negotiation for all devices.
1790 notsc [BUGS=X86-32] Disable Time Stamp Counter
1792 nousb [USB] Disable the USB subsystem
1794 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1798 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1800 nptcg= [IA64] Override max number of concurrent global TLB
1801 purges which is reported from either PAL_VM_SUMMARY or
1804 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1805 could support. nr_cpus=n : n >= 1 limits the kernel to
1806 supporting 'n' processors. Later in runtime you can not
1807 use hotplug cpu feature to put more cpu back to online.
1808 just like you compile the kernel NR_CPUS=n
1810 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1812 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1813 one of ['zone', 'node', 'default'] can be specified
1814 This can be set from sysctl after boot.
1815 See Documentation/sysctl/vm.txt for details.
1817 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1818 See Documentation/debugging-via-ohci1394.txt for more
1821 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1822 Rather than timing out after 20 ms if an EC
1823 command is not properly ACKed, override the length
1824 of the timeout. We have interrupts disabled while
1825 waiting for the ACK, so if this is set too high
1826 interrupts *may* be lost!
1828 omap_mux= [OMAP] Override bootloader pin multiplexing.
1829 Format: <mux_mode0.mode_name=value>...
1830 For example, to override I2C bus2:
1831 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1833 oprofile.timer= [HW]
1834 Use timer interrupt instead of performance counters
1836 oprofile.cpu_type= Force an oprofile cpu type
1837 This might be useful if you have an older oprofile
1838 userland or if you want common events.
1839 Format: { arch_perfmon }
1840 arch_perfmon: [X86] Force use of architectural
1841 perfmon on Intel CPUs instead of the
1842 CPU specific event set.
1844 oops=panic Always panic on oopses. Default is to just kill the
1845 process, but there is a small probability of
1846 deadlocking the machine.
1847 This will also cause panics on machine check exceptions.
1848 Useful together with panic=30 to trigger a reboot.
1851 See Documentation/sound/oss/oss-parameters.txt
1853 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1854 seconds before rebooting
1857 parkbd.port= [HW] Parallel port number the keyboard adapter is
1858 connected to, default is 0.
1860 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1861 0 for XT, 1 for AT (default is AT).
1864 parport= [HW,PPT] Specify parallel ports. 0 disables.
1865 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1866 Use 'auto' to force the driver to use any
1867 IRQ/DMA settings detected (the default is to
1868 ignore detected IRQ/DMA settings because of
1869 possible conflicts). You can specify the base
1870 address, IRQ, and DMA settings; IRQ and DMA
1871 should be numbers, or 'auto' (for using detected
1872 settings on that particular port), or 'nofifo'
1873 (to avoid using a FIFO even if it is detected).
1874 Parallel ports are assigned in the order they
1875 are specified on the command line, starting
1878 parport_init_mode= [HW,PPT]
1879 Configure VIA parallel port to operate in
1880 a specific mode. This is necessary on Pegasos
1881 computer where firmware has no options for setting
1882 up parallel port mode and sets it to spp.
1883 Currently this function knows 686a and 8231 chips.
1884 Format: [spp|ps2|epp|ecp|ecpepp]
1887 Halt all CPUs after the first oops has been printed for
1888 the specified number of seconds. This is to be used if
1889 your oopses keep scrolling off the screen.
1894 See header of drivers/block/paride/pcd.c.
1895 See also Documentation/blockdev/paride.txt.
1897 pci=option[,option...] [PCI] various PCI subsystem options:
1898 earlydump [X86] dump PCI config space before the kernel
1900 off [X86] don't probe for the PCI bus
1901 bios [X86-32] force use of PCI BIOS, don't access
1902 the hardware directly. Use this if your machine
1903 has a non-standard PCI host bridge.
1904 nobios [X86-32] disallow use of PCI BIOS, only direct
1905 hardware access methods are allowed. Use this
1906 if you experience crashes upon bootup and you
1907 suspect they are caused by the BIOS.
1908 conf1 [X86] Force use of PCI Configuration
1910 conf2 [X86] Force use of PCI Configuration
1912 noaer [PCIE] If the PCIEAER kernel config parameter is
1913 enabled, this kernel boot option can be used to
1914 disable the use of PCIE advanced error reporting.
1915 nodomains [PCI] Disable support for multiple PCI
1916 root domains (aka PCI segments, in ACPI-speak).
1917 nommconf [X86] Disable use of MMCONFIG for PCI
1919 check_enable_amd_mmconf [X86] check for and enable
1920 properly configured MMIO access to PCI
1921 config space on AMD family 10h CPU
1922 nomsi [MSI] If the PCI_MSI kernel config parameter is
1923 enabled, this kernel boot option can be used to
1924 disable the use of MSI interrupts system-wide.
1925 noioapicquirk [APIC] Disable all boot interrupt quirks.
1926 Safety option to keep boot IRQs enabled. This
1927 should never be necessary.
1928 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1929 primary IO-APIC for bridges that cannot disable
1930 boot IRQs. This fixes a source of spurious IRQs
1931 when the system masks IRQs.
1932 noioapicreroute [APIC] Disable workaround that uses the
1933 boot IRQ equivalent of an IRQ that connects to
1934 a chipset where boot IRQs cannot be disabled.
1935 The opposite of ioapicreroute.
1936 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1937 routing table. These calls are known to be buggy
1938 on several machines and they hang the machine
1939 when used, but on other computers it's the only
1940 way to get the interrupt routing table. Try
1941 this option if the kernel is unable to allocate
1942 IRQs or discover secondary PCI buses on your
1944 rom [X86] Assign address space to expansion ROMs.
1945 Use with caution as certain devices share
1946 address decoders between ROMs and other
1948 norom [X86] Do not assign address space to
1949 expansion ROMs that do not already have
1950 BIOS assigned address ranges.
1951 nobar [X86] Do not assign address space to the
1952 BARs that weren't assigned by the BIOS.
1953 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1954 assigned automatically to PCI devices. You can
1955 make the kernel exclude IRQs of your ISA cards
1957 pirqaddr=0xAAAAA [X86] Specify the physical address
1958 of the PIRQ table (normally generated
1959 by the BIOS) if it is outside the
1960 F0000h-100000h range.
1961 lastbus=N [X86] Scan all buses thru bus #N. Can be
1962 useful if the kernel is unable to find your
1963 secondary buses and you want to tell it
1964 explicitly which ones they are.
1965 assign-busses [X86] Always assign all PCI bus
1966 numbers ourselves, overriding
1967 whatever the firmware may have done.
1968 usepirqmask [X86] Honor the possible IRQ mask stored
1969 in the BIOS $PIR table. This is needed on
1970 some systems with broken BIOSes, notably
1971 some HP Pavilion N5400 and Omnibook XE3
1972 notebooks. This will have no effect if ACPI
1973 IRQ routing is enabled.
1974 noacpi [X86] Do not use ACPI for IRQ routing
1975 or for PCI scanning.
1976 use_crs [X86] Use PCI host bridge window information
1977 from ACPI. On BIOSes from 2008 or later, this
1978 is enabled by default. If you need to use this,
1979 please report a bug.
1980 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1981 If you need to use this, please report a bug.
1982 routeirq Do IRQ routing for all PCI devices.
1983 This is normally done in pci_enable_device(),
1984 so this option is a temporary workaround
1985 for broken drivers that don't call it.
1986 skip_isa_align [X86] do not align io start addr, so can
1987 handle more pci cards
1988 firmware [ARM] Do not re-enumerate the bus but instead
1989 just use the configuration from the
1990 bootloader. This is currently used on
1991 IXP2000 systems where the bus has to be
1992 configured a certain way for adjunct CPUs.
1993 noearly [X86] Don't do any early type 1 scanning.
1994 This might help on some broken boards which
1995 machine check when some devices' config space
1996 is read. But various workarounds are disabled
1997 and some IOMMU drivers will not work.
1998 bfsort Sort PCI devices into breadth-first order.
1999 This sorting is done to get a device
2000 order compatible with older (<= 2.4) kernels.
2001 nobfsort Don't sort PCI devices into breadth-first order.
2002 cbiosize=nn[KMG] The fixed amount of bus space which is
2003 reserved for the CardBus bridge's IO window.
2004 The default value is 256 bytes.
2005 cbmemsize=nn[KMG] The fixed amount of bus space which is
2006 reserved for the CardBus bridge's memory
2007 window. The default value is 64 megabytes.
2010 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2011 Specifies alignment and device to reassign
2012 aligned memory resources.
2013 If <order of align> is not specified,
2014 PAGE_SIZE is used as alignment.
2015 PCI-PCI bridge can be specified, if resource
2016 windows need to be expanded.
2017 ecrc= Enable/disable PCIe ECRC (transaction layer
2018 end-to-end CRC checking).
2019 bios: Use BIOS/firmware settings. This is the
2023 realloc reallocate PCI resources if allocations done by BIOS
2026 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2029 force Enable ASPM even on devices that claim not to support it.
2030 WARNING: Forcing ASPM on may cause system lockups.
2032 pcie_ports= [PCIE] PCIe ports handling:
2033 auto Ask the BIOS whether or not to use native PCIe services
2034 associated with PCIe ports (PME, hot-plug, AER). Use
2035 them only if that is allowed by the BIOS.
2036 native Use native PCIe services associated with PCIe ports
2038 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2041 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2042 nomsi Do not use MSI for native PCIe PME signaling (this makes
2043 all PCIe root ports use INTx for all services).
2045 pcmv= [HW,PCMCIA] BadgePAD 4
2048 See Documentation/blockdev/paride.txt.
2050 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2053 See arch/parisc/kernel/pdc_chassis.c
2055 percpu_alloc= Select which percpu first chunk allocator to use.
2056 Currently supported values are "embed" and "page".
2057 Archs may support subset or none of the selections.
2058 See comments in mm/percpu.c for details on each
2059 allocator. This parameter is primarily for debugging
2060 and performance comparison.
2063 See Documentation/blockdev/paride.txt.
2066 See Documentation/blockdev/paride.txt.
2068 pirq= [SMP,APIC] Manual mp-table setup
2069 See Documentation/x86/i386/IO-APIC.txt.
2071 plip= [PPT,NET] Parallel port network link
2072 Format: { parport<nr> | timid | 0 }
2073 See also Documentation/parport.txt.
2075 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2076 Override pmtimer IOPort with a hex value.
2080 Enable PNP debug messages. This depends on the
2081 CONFIG_PNP_DEBUG_MESSAGES option.
2087 { on | off | curr | res | no-curr | no-res }
2090 [ISAPNP] Exclude IRQs for the autoconfiguration
2093 [ISAPNP] Exclude DMAs for the autoconfiguration
2095 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2096 Ranges are in pairs (I/O port base and size).
2099 [ISAPNP] Exclude memory regions for the
2101 Ranges are in pairs (memory base and size).
2103 ports= [IP_VS_FTP] IPVS ftp helper module
2105 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2107 Format: <port>,<port>....
2109 print-fatal-signals=
2110 [KNL] debug: print fatal signals
2112 If enabled, warn about various signal handling
2113 related application anomalies: too many signals,
2114 too many POSIX.1 timers, fatal signals causing a
2117 If you hit the warning due to signal overflow,
2118 you might want to try "ulimit -i unlimited".
2122 printk.time= Show timing data prefixed to each printk message line
2123 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2125 processor.max_cstate= [HW,ACPI]
2126 Limit processor to maximum C-state
2127 max_cstate=9 overrides any DMI blacklist limit.
2129 processor.nocst [HW,ACPI]
2130 Ignore the _CST method to determine C-states,
2131 instead using the legacy FADT method
2133 profile= [KNL] Enable kernel profiling via /proc/profile
2134 Format: [schedule,]<number>
2135 Param: "schedule" - profile schedule points.
2136 Param: <number> - step/bucket size as a power of 2 for
2137 statistical time based profiling.
2138 Param: "sleep" - profile D-state sleeping (millisecs).
2139 Requires CONFIG_SCHEDSTATS
2140 Param: "kvm" - profile VM exits.
2142 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2144 See Documentation/blockdev/ramdisk.txt.
2146 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2147 probe for; one of (bare|imps|exps|lifebook|any).
2148 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2150 psmouse.resetafter= [HW,MOUSE]
2151 Try to reset the device after so many bad packets
2154 [HW,MOUSE] Set desired mouse resolution, in dpi.
2155 psmouse.smartscroll=
2156 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2157 0 = disabled, 1 = enabled (default).
2160 See Documentation/blockdev/paride.txt.
2163 [KNL] Number of legacy pty's. Overwrites compiled-in
2166 quiet [KNL] Disable most log messages
2171 See Documentation/md.txt.
2173 ramdisk_blocksize= [RAM]
2174 See Documentation/blockdev/ramdisk.txt.
2176 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2177 See Documentation/blockdev/ramdisk.txt.
2179 rcupdate.blimit= [KNL,BOOT]
2180 Set maximum number of finished RCU callbacks to process
2183 rcupdate.qhimark= [KNL,BOOT]
2184 Set threshold of queued
2185 RCU callbacks over which batch limiting is disabled.
2187 rcupdate.qlowmark= [KNL,BOOT]
2188 Set threshold of queued RCU callbacks below which
2189 batch limiting is re-enabled.
2193 Run specified binary instead of /init from the ramdisk,
2194 used for early userspace startup. See initrd.
2196 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2197 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2198 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2201 [KNL, SMP] Set scheduler's default relax_domain_level.
2202 See Documentation/cgroups/cpusets.txt.
2204 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2206 reservetop= [X86-32]
2208 Reserves a hole at the top of the kernel virtual
2213 Set the amount of memory to reserve for BIOS at
2214 the bottom of the address space.
2216 reset_devices [KNL] Force drivers to reset the underlying device
2217 during initialization.
2220 Specify the partition device for software suspend
2222 resume_offset= [SWSUSP]
2223 Specify the offset from the beginning of the partition
2224 given by "resume=" at which the swap header is located,
2225 in <PAGE_SIZE> units (needed only for swap files).
2226 See Documentation/power/swsusp-and-swap-files.txt
2228 hibernate= [HIBERNATION]
2229 noresume Don't check if there's a hibernation image
2230 present during boot.
2231 nocompress Don't compress/decompress hibernation images.
2233 retain_initrd [RAM] Keep initrd memory after extraction
2235 rhash_entries= [KNL,NET]
2236 Set number of hash buckets for route cache
2238 riscom8= [HW,SERIAL]
2239 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2241 ro [KNL] Mount root device read-only on boot
2243 root= [KNL] Root filesystem
2245 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2246 mount the root filesystem
2248 rootflags= [KNL] Set root filesystem mount option string
2250 rootfstype= [KNL] Set root filesystem type
2252 rootwait [KNL] Wait (indefinitely) for root device to show up.
2253 Useful for devices that are detected asynchronously
2254 (e.g. USB and MMC devices).
2256 rw [KNL] Mount root device read-write on boot
2258 S [KNL] Run init in single mode
2261 See drivers/net/irda/sa1100_ir.c.
2263 sbni= [NET] Granch SBNI12 leased line adapter
2265 sched_debug [KNL] Enables verbose scheduler debug messages.
2267 security= [SECURITY] Choose a security module to enable at boot.
2268 If this boot parameter is not specified, only the first
2269 security module asking for security registration will be
2270 loaded. An invalid security module name will be treated
2271 as if no module has been chosen.
2273 selinux= [SELINUX] Disable or enable SELinux at boot time.
2274 Format: { "0" | "1" }
2275 See security/selinux/Kconfig help text.
2278 Default value is set via kernel config option.
2279 If enabled at boot time, /selinux/disable can be used
2280 later to disable prior to initial policy load.
2282 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2283 Format: { "0" | "1" }
2284 See security/apparmor/Kconfig help text
2287 Default value is set via kernel config option.
2289 serialnumber [BUGS=X86-32]
2292 Maximal number of shapers.
2294 show_msr= [x86] show boot-time MSR settings
2295 Format: { <integer> }
2296 Show boot-time (BIOS-initialized) MSR settings.
2297 The parameter means the number of CPUs to show,
2298 for example 1 means boot CPU only.
2305 slub_debug[=options[,slabs]] [MM, SLUB]
2306 Enabling slub_debug allows one to determine the
2307 culprit if slab objects become corrupted. Enabling
2308 slub_debug can create guard zones around objects and
2309 may poison objects when not in use. Also tracks the
2310 last alloc / free. For more information see
2311 Documentation/vm/slub.txt.
2313 slub_max_order= [MM, SLUB]
2314 Determines the maximum allowed order for slabs.
2315 A high setting may cause OOMs due to memory
2316 fragmentation. For more information see
2317 Documentation/vm/slub.txt.
2319 slub_min_objects= [MM, SLUB]
2320 The minimum number of objects per slab. SLUB will
2321 increase the slab order up to slub_max_order to
2322 generate a sufficiently large slab able to contain
2323 the number of objects indicated. The higher the number
2324 of objects the smaller the overhead of tracking slabs
2325 and the less frequently locks need to be acquired.
2326 For more information see Documentation/vm/slub.txt.
2328 slub_min_order= [MM, SLUB]
2329 Determines the mininum page order for slabs. Must be
2330 lower than slub_max_order.
2331 For more information see Documentation/vm/slub.txt.
2333 slub_nomerge [MM, SLUB]
2334 Disable merging of slabs with similar size. May be
2335 necessary if there is some reason to distinguish
2336 allocs to different slabs. Debug options disable
2337 merging on their own.
2338 For more information see Documentation/vm/slub.txt.
2341 Format: <io1>[,<io2>[,...,<io8>]]
2343 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2344 attempt to substitute SMP alternatives once at boot.
2346 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2347 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2348 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2349 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2350 smsc-ircc2.ircc_irq= [HW] IRQ line
2351 smsc-ircc2.ircc_dma= [HW] DMA channel
2352 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2353 0: Toshiba Satellite 1800 (GP data pin select)
2354 1: Fast pin select (default)
2358 [KNL] Should the soft-lockup detector generate panics.
2361 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2362 See Documentation/sonypi.txt
2364 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2365 See Documentation/serial/specialix.txt.
2367 spia_io_base= [HW,MTD]
2373 Enabled the stack tracer on boot up.
2377 Set the STI (builtin display/keyboard on the HP-PARISC
2378 machines) console (graphic card) which should be used
2379 as the initial boot-console.
2380 See also comment in drivers/video/console/sticore.c.
2383 See comment in drivers/video/console/sticore.c.
2386 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2388 sunrpc.min_resvport=
2389 sunrpc.max_resvport=
2391 SunRPC servers often require that client requests
2392 originate from a privileged port (i.e. a port in the
2393 range 0 < portnr < 1024).
2394 An administrator who wishes to reserve some of these
2395 ports for other uses may adjust the range that the
2396 kernel's sunrpc client considers to be privileged
2397 using these two parameters to set the minimum and
2398 maximum port values.
2402 Control how the NFS server code allocates CPUs to
2403 service thread pools. Depending on how many NICs
2404 you have and where their interrupts are bound, this
2405 option will affect which CPUs will do NFS serving.
2406 Note: this parameter cannot be changed while the
2407 NFS server is running.
2409 auto the server chooses an appropriate mode
2410 automatically using heuristics
2411 global a single global pool contains all CPUs
2412 percpu one pool for each CPU
2413 pernode one pool for each NUMA node (equivalent
2414 to global on non-NUMA machines)
2416 sunrpc.tcp_slot_table_entries=
2417 sunrpc.udp_slot_table_entries=
2419 Sets the upper limit on the number of simultaneous
2420 RPC calls that can be sent from the client to a
2421 server. Increasing these values may allow you to
2422 improve throughput, but will also increase the
2423 amount of memory reserved for use by the client.
2426 [KNL] Enable accounting of swap in memory resource
2427 controller if no parameter or 1 is given or disable
2428 it if 0 is given (See Documentation/cgroups/memory.txt)
2430 swiotlb= [IA-64] Number of I/O TLB slabs
2434 sysfs.deprecated=0|1 [KNL]
2435 Enable/disable old style sysfs layout for old udev
2436 on older distributions. When this option is enabled
2437 very new udev will not work anymore. When this option
2438 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2439 in older udev will not work anymore.
2440 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2441 the kernel configuration.
2443 sysrq_always_enabled
2445 Ignore sysrq setting - this boot parameter will
2446 neutralize any effect of /proc/sys/kernel/sysrq.
2447 Useful for debugging.
2451 test_suspend= [SUSPEND]
2452 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2453 standby suspend) as the system sleep state to briefly
2454 enter during system startup. The system is woken from
2455 this state using a wakeup-capable RTC alarm.
2457 thash_entries= [KNL,NET]
2458 Set number of hash buckets for TCP connection
2460 thermal.act= [HW,ACPI]
2461 -1: disable all active trip points in all thermal zones
2462 <degrees C>: override all lowest active trip points
2464 thermal.crt= [HW,ACPI]
2465 -1: disable all critical trip points in all thermal zones
2466 <degrees C>: override all critical trip points
2468 thermal.nocrt= [HW,ACPI]
2469 Set to disable actions on ACPI thermal zone
2470 critical and hot trip points.
2472 thermal.off= [HW,ACPI]
2473 1: disable ACPI thermal control
2475 thermal.psv= [HW,ACPI]
2476 -1: disable all passive trip points
2477 <degrees C>: override all passive trip points to this
2480 thermal.tzp= [HW,ACPI]
2481 Specify global default ACPI thermal zone polling rate
2482 <deci-seconds>: poll all this frequency
2483 0: no polling (default)
2486 Force threading of all interrupt handlers except those
2487 marked explicitely IRQF_NO_THREAD.
2491 Specify if the kernel should make use of the cpu
2492 topology information if the hardware supports this.
2493 The scheduler will make use of this information and
2494 e.g. base its process migration decisions on it.
2499 tpm_suspend_pcr=[HW,TPM]
2500 Format: integer pcr id
2501 Specify that at suspend time, the tpm driver
2502 should extend the specified pcr with zeros,
2503 as a workaround for some chips which fail to
2504 flush the last written pcr on TPM_SaveState.
2505 This will guarantee that all the other pcrs
2508 trace_buf_size=nn[KMG]
2509 [FTRACE] will set tracing buffer size.
2511 trace_event=[event-list]
2512 [FTRACE] Set and start specified trace events in order
2513 to facilitate early boot debugging.
2514 See also Documentation/trace/events.txt
2516 tsc= Disable clocksource stability checks for TSC.
2518 [x86] reliable: mark tsc clocksource as reliable, this
2519 disables clocksource verification at runtime, as well
2520 as the stability checks done at bootup. Used to enable
2521 high-resolution timer mode on older hardware, and in
2522 virtualized environment.
2523 [x86] noirqtime: Do not use TSC to do irq accounting.
2524 Used to run time disable IRQ_TIME_ACCOUNTING on any
2525 platforms where RDTSC is slow and this accounting
2528 turbografx.map[2|3]= [HW,JOY]
2529 TurboGraFX parallel port interface
2531 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2532 See also Documentation/input/joystick-parport.txt
2534 uhash_entries= [KNL,NET]
2535 Set number of hash buckets for UDP/UDP-Lite connections
2538 [USB] Ignore overcurrent events (default N).
2539 Some badly-designed motherboards generate lots of
2540 bogus events, for ports that aren't wired to
2541 anything. Set this parameter to avoid log spamming.
2542 Note that genuine overcurrent events won't be
2546 [X86] Cause panic on unknown NMI.
2548 usbcore.autosuspend=
2549 [USB] The autosuspend time delay (in seconds) used
2550 for newly-detected USB devices (default 2). This
2551 is the time required before an idle device will be
2552 autosuspended. Devices for which the delay is set
2553 to a negative value won't be autosuspended at all.
2555 usbcore.usbfs_snoop=
2556 [USB] Set to log all usbfs traffic (default 0 = off).
2558 usbcore.blinkenlights=
2559 [USB] Set to cycle leds on hubs (default 0 = off).
2561 usbcore.old_scheme_first=
2562 [USB] Start with the old device initialization
2563 scheme (default 0 = off).
2565 usbcore.use_both_schemes=
2566 [USB] Try the other device initialization scheme
2567 if the first one fails (default 1 = enabled).
2569 usbcore.initial_descriptor_timeout=
2570 [USB] Specifies timeout for the initial 64-byte
2571 USB_REQ_GET_DESCRIPTOR request in milliseconds
2572 (default 5000 = 5.0 seconds).
2575 [USBHID] The interval which mice are to be polled at.
2577 usb-storage.delay_use=
2578 [UMS] The delay in seconds before a new device is
2579 scanned for Logical Units (default 5).
2582 [UMS] A list of quirks entries to supplement or
2583 override the built-in unusual_devs list. List
2584 entries are separated by commas. Each entry has
2585 the form VID:PID:Flags where VID and PID are Vendor
2586 and Product ID values (4-digit hex numbers) and
2587 Flags is a set of characters, each corresponding
2588 to a common usb-storage quirk flag as follows:
2589 a = SANE_SENSE (collect more than 18 bytes
2591 b = BAD_SENSE (don't collect more than 18
2592 bytes of sense data);
2593 c = FIX_CAPACITY (decrease the reported
2594 device capacity by one sector);
2595 d = NO_READ_DISC_INFO (don't use
2596 READ_DISC_INFO command);
2597 e = NO_READ_CAPACITY_16 (don't use
2598 READ_CAPACITY_16 command);
2599 h = CAPACITY_HEURISTICS (decrease the
2600 reported device capacity by one
2601 sector if the number is odd);
2602 i = IGNORE_DEVICE (don't bind to this
2604 l = NOT_LOCKABLE (don't try to lock and
2605 unlock ejectable media);
2606 m = MAX_SECTORS_64 (don't transfer more
2607 than 64 sectors = 32 KB at a time);
2608 n = INITIAL_READ10 (force a retry of the
2609 initial READ(10) command);
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.
2704 watchdog timers [HW,WDT] For information on watchdog timers,
2705 see Documentation/watchdog/watchdog-parameters.txt
2706 or other driver-specific files in the
2707 Documentation/watchdog/ directory.
2709 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2710 default x2apic cluster mode on platforms
2713 x86_mrst_timer= [X86-32,APBT]
2714 Choose timer option for x86 Moorestown MID platform.
2715 Two valid options are apbt timer only and lapic timer
2716 plus one apbt timer for broadcast timer.
2717 x86_mrst_timer=apbt_only | lapic_and_apbt
2719 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2720 xd_geo= See header of drivers/block/xd.c.
2722 xen_emul_unplug= [HW,X86,XEN]
2723 Unplug Xen emulated devices
2724 Format: [unplug0,][unplug1]
2725 ide-disks -- unplug primary master IDE devices
2726 aux-ide-disks -- unplug non-primary-master IDE devices
2727 nics -- unplug network devices
2728 all -- unplug all emulated devices (NICs and IDE disks)
2729 unnecessary -- unplugging emulated devices is
2730 unnecessary even if the host did not respond to
2732 never -- do not unplug even if version check succeeds
2734 xirc2ps_cs= [NET,PCMCIA]
2736 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2738 ______________________________________________________________________
2742 Add more DRM drivers.
git.openpandora.org / pandora-kernel.git / blob