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 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
47 EFI EFI Partitioning (GPT) is enabled
48 EIDE EIDE/ATAPI support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
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.
149 Advanced Configuration and Power Interface
150 Format: { force | off | strict | noirq | rsdt }
151 force -- enable ACPI if default was off
152 off -- disable ACPI if default was on
153 noirq -- do not use ACPI for IRQ routing
154 strict -- Be less tolerant of platforms that are not
155 strictly ACPI specification compliant.
156 rsdt -- prefer RSDT over (default) XSDT
157 copy_dsdt -- copy DSDT to memory
159 See also Documentation/power/pm.txt, pci=noacpi
161 acpi_apic_instance= [ACPI, IOAPIC]
163 2: use 2nd APIC table, if available
164 1,0: use 1st APIC table
167 acpi_backlight= [HW,ACPI]
168 acpi_backlight=vendor
170 If set to vendor, prefer vendor specific driver
171 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
172 of the ACPI video.ko driver.
174 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
175 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
177 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
178 debug output. Bits in debug_layer correspond to a
179 _COMPONENT in an ACPI source file, e.g.,
180 #define _COMPONENT ACPI_PCI_COMPONENT
181 Bits in debug_level correspond to a level in
182 ACPI_DEBUG_PRINT statements, e.g.,
183 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
184 The debug_level mask defaults to "info". See
185 Documentation/acpi/debug.txt for more information about
186 debug layers and levels.
188 Enable processor driver info messages:
189 acpi.debug_layer=0x20000000
190 Enable PCI/PCI interrupt routing info messages:
191 acpi.debug_layer=0x400000
192 Enable AML "Debug" output, i.e., stores to the Debug
193 object while interpreting AML:
194 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
195 Enable all messages related to ACPI hardware:
196 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
198 Some values produce so much output that the system is
199 unusable. The "log_buf_len" parameter may be useful
200 if you need to capture more output.
202 acpi_display_output= [HW,ACPI]
203 acpi_display_output=vendor
204 acpi_display_output=video
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
220 Format: <irq>,<irq>...
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
240 acpi_serialize [HW,ACPI] force serialization of AML methods
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248 old_ordering, s4_nonvs, sci_force_enable }
249 See Documentation/power/video.txt for information on
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
295 See Documentation/sound/alsa/alsa-parameters.txt
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
309 off - do not initialize any AMD IOMMU found in
312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
315 See also Documentation/kernel/input/joystick.txt
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
323 Power management functions (SPARCstation-4/5 + deriv.)
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
330 Change the output verbosity whilst booting
331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
336 See Documentation/networking/ipv6.txt.
338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
347 apm= [APM] Advanced Power Management
348 See header of arch/x86/kernel/apm_32.c.
350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
355 atarimouse= [HW,MOUSE] Atari Mouse
357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
360 atkbd.reset= [HW] Reset keyboard during initialization
362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
376 baycom_epp= [HW,AX25]
379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
381 See header of drivers/net/hamradio/baycom_par.c.
383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401 bttv.radio= Most important insmod options are available as
403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
406 c101= [NET] Moxa C101 synchronous serial card
408 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
409 Sometimes CPU hardware bugs make them report the cache
410 size incorrectly. The kernel will attempt work arounds
411 to fix known problems, but for some CPUs it is not
412 possible to determine what the correct size should be.
413 This option provides an override for these situations.
416 [SECURITY] Disable capabilities. This would normally
417 be used only if an alternative security model is to be
418 configured. Potentially dangerous and should only be
419 used if you are entirely sure of the consequences.
421 ccw_timeout_log [S390]
422 See Documentation/s390/CommonIO for details.
424 cgroup_disable= [KNL] Disable a particular controller
425 Format: {name of the controller(s) to disable}
426 {Currently supported controllers - "memory"}
428 checkreqprot [SELINUX] Set initial checkreqprot flag value.
429 Format: { "0" | "1" }
430 See security/selinux/Kconfig help text.
431 0 -- check protection applied by kernel (includes
432 any implied execute protection).
433 1 -- check protection requested by application.
434 Default value is set via a kernel config option.
435 Value can be changed at runtime via
436 /selinux/checkreqprot.
439 See Documentation/s390/CommonIO for details.
441 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
443 Forces specified clocksource (if available) to be used
444 when calculating gettimeofday(). If specified
445 clocksource is not available, it defaults to PIT.
446 Format: { pit | tsc | cyclone | pmtmr }
448 clocksource= Override the default clocksource
450 Override the default clocksource and use the clocksource
451 with the name specified.
452 Some clocksource names to choose from, depending on
454 [all] jiffies (this is the base, fallback clocksource)
456 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
457 pxa_timer,timer3,32k_counter,timer0_1
459 [X86-32] pit,hpet,tsc;
460 scx200_hrt on Geode; cyclone on IBM x440
468 clearcpuid=BITNUM [X86]
469 Disable CPUID feature X for the kernel. See
470 arch/x86/include/asm/cpufeature.h for the valid bit
471 numbers. Note the Linux specific bits are not necessarily
472 stable over kernel options, but the vendor specific
474 Also note that user programs calling CPUID directly
475 or using the feature without checking anything
476 will still see it. This just prevents it from
477 being used by the kernel or shown in /proc/cpuinfo.
478 Also note the kernel might malfunction if you disable
481 cmo_free_hint= [PPC] Format: { yes | no }
482 Specify whether pages are marked as being inactive
483 when they are freed. This is used in CMO environments
484 to determine OS memory pressure for page stealing by
488 code_bytes [X86] How many bytes of object code to print
493 com20020= [HW,NET] ARCnet - COM20020 chipset
495 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
497 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
501 ARCnet - COM90xx chipset (memory-mapped buffers)
502 Format: <io>[,<irq>[,<memstart>]]
504 condev= [HW,S390] console device
507 console= [KNL] Output console device and options.
509 tty<n> Use the virtual console device <n>.
513 Use the specified serial port. The options are of
514 the form "bbbbpnf", where "bbbb" is the baud rate,
515 "p" is parity ("n", "o", or "e"), "n" is number of
516 bits, and "f" is flow control ("r" for RTS or
517 omit it). Default is "9600n8".
519 See Documentation/serial-console.txt for more
521 Documentation/networking/netconsole.txt for an
524 uart[8250],io,<addr>[,options]
525 uart[8250],mmio,<addr>[,options]
526 Start an early, polled-mode console on the 8250/16550
527 UART at the specified I/O port or MMIO address,
528 switching to the matching ttyS device later. The
529 options are the same as for ttyS, above.
531 If the device connected to the port is not a TTY but a braille
532 device, prepend "brl," before the device type, for instance
534 For now, only VisioBraille is supported.
536 consoleblank= [KNL] The console blank (screen saver) timeout in
537 seconds. Defaults to 10*60 = 10mins. A value of 0
538 disables the blank timer.
541 [KNL] Change the default value for
542 /proc/<pid>/coredump_filter.
543 See also Documentation/filesystems/proc.txt.
545 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
547 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
549 crashkernel=nn[KMG]@ss[KMG]
550 [KNL] Reserve a chunk of physical memory to
551 hold a kernel to switch to with kexec on panic.
553 crashkernel=range1:size1[,range2:size2,...][@offset]
554 [KNL] Same as above, but depends on the memory
555 in the running system. The syntax of range is
556 start-[end] where start and end are both
557 a memory unit (amount[KMG]). See also
558 Documentation/kdump/kdump.txt for a example.
563 cs89x0_media= [HW,NET]
564 Format: { rj45 | aui | bnc }
567 See header of drivers/s390/block/dasd_devmap.c.
569 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
570 (one device per port)
571 Format: <port#>,<type>
572 See also Documentation/input/joystick-parport.txt
574 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
575 time. See Documentation/dynamic-debug-howto.txt for
578 debug [KNL] Enable kernel debugging (events log level).
581 [KNL] verbose self-tests
583 Print debugging info while doing the locking API
585 We default to 0 (no extra messages), setting it to
586 1 will print _a lot_ more information - normally
587 only useful to kernel developers.
589 debug_objects [KNL] Enable object debugging
592 [KNL] Disable object debugging
594 debugpat [X86] Enable PAT debugging
596 decnet.addr= [HW,NET]
597 Format: <area>[,<node>]
598 See also Documentation/networking/decnet.txt.
601 [same as hugepagesz=] The size of the default
602 HugeTLB page size. This is the size represented by
603 the legacy /proc/ hugepages APIs, used for SHM, and
604 default size when mounting hugetlbfs filesystems.
605 Defaults to the default architecture's huge page size
609 Set number of hash buckets for dentry cache.
612 IO parameters + enable/disable command.
614 digiepca= [HW,SERIAL]
615 See drivers/char/README.epca and
616 Documentation/serial/digiepca.txt.
619 See Documentation/networking/ipv6.txt.
622 See Documentation/networking/ipv6.txt.
624 disable_mtrr_cleanup [X86]
625 The kernel tries to adjust MTRR layout from continuous
626 to discrete, to make X server driver able to add WB
627 entry later. This parameter disables that.
629 disable_mtrr_trim [X86, Intel and AMD only]
630 By default the kernel will trim any uncacheable
631 memory out of your available memory pool based on
632 MTRR settings. This parameter disables that behavior,
633 possibly causing your machine to run very slowly.
635 disable_timer_pin_1 [X86]
636 Disable PIN 1 of APIC timer
637 Can be useful to work around chipset bugs.
639 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
640 this option disables the debugging code at boot.
642 dma_debug_entries=<number>
643 This option allows to tune the number of preallocated
644 entries for DMA-API debugging code. One entry is
645 required per DMA-API allocation. Use this if the
646 DMA-API debugging code disables itself because the
647 architectural default is too low.
649 dma_debug_driver=<driver_name>
650 With this option the DMA-API debugging driver
651 filter feature can be enabled at boot time. Just
652 pass the driver to filter for as the parameter.
653 The filter can be disabled or changed to another
654 driver later using sysfs.
658 dynamic_printk Enables pr_debug()/dev_dbg() calls if
659 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
660 These can also be switched on/off via
661 <debugfs>/dynamic_printk/modules
663 earlycon= [KNL] Output early console device and options.
664 uart[8250],io,<addr>[,options]
665 uart[8250],mmio,<addr>[,options]
666 uart[8250],mmio32,<addr>[,options]
667 Start an early, polled-mode console on the 8250/16550
668 UART at the specified I/O port or MMIO address.
669 MMIO inter-register address stride is either 8bit (mmio)
671 The options are the same as for ttyS, above.
673 earlyprintk= [X86,SH,BLACKFIN]
675 earlyprintk=serial[,ttySn[,baudrate]]
676 earlyprintk=ttySn[,baudrate]
677 earlyprintk=dbgp[debugController#]
679 Append ",keep" to not disable it when the real console
682 Only vga or serial or usb debug port at a time.
684 Currently only ttyS0 and ttyS1 are supported.
686 Interaction with the standard serial driver is not
689 The VGA output is eventually overwritten by the real
692 ekgdboc= [X86,KGDB] Allow early kernel console debugging
695 This is desgined to be used in conjunction with
696 the boot argument: earlyprintk=vga
699 Format: {"off" | "on" | "skip[mbr]"}
701 eisa_irq_edge= [PARISC,HW]
702 See header of drivers/parisc/eisa.c.
705 See comment before function elanfreq_setup() in
706 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
709 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
710 See Documentation/block/as-iosched.txt and
711 Documentation/block/deadline-iosched.txt for details.
713 elfcorehdr= [IA64,PPC,SH,X86]
714 Specifies physical address of start of kernel core
715 image elf header. Generally kexec loader will
716 pass this option to capture kernel.
717 See Documentation/kdump/kdump.txt for details.
719 enable_mtrr_cleanup [X86]
720 The kernel tries to adjust MTRR layout from continuous
721 to discrete, to make X server driver able to add WB
722 entry later. This parameter enables that.
724 enable_timer_pin_1 [X86]
725 Enable PIN 1 of APIC timer
726 Can be useful to work around chipset bugs
727 (in particular on some ATI chipsets).
728 The kernel tries to set a reasonable default.
730 enforcing [SELINUX] Set initial enforcing status.
732 See security/selinux/Kconfig help text.
733 0 -- permissive (log only, no denials).
734 1 -- enforcing (deny and log).
736 Value can be changed at runtime via /selinux/enforce.
739 Disable Error Record Serialization Table (ERST)
742 ether= [HW,NET] Ethernet cards parameters
743 This option is obsoleted by the "netdev=" option, which
744 has equivalent usage. See its documentation for details.
748 fail_make_request=[KNL]
749 General fault injection mechanism.
750 Format: <interval>,<probability>,<space>,<times>
751 See also /Documentation/fault-injection/.
754 See Documentation/blockdev/floppy.txt.
756 force_pal_cache_flush
757 [IA-64] Avoid check_sal_cache_flush which may hang on
758 buggy SAL_CACHE_FLUSH implementations. Using this
759 parameter will force ia64_sal_cache_flush to call
760 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
763 [FTRACE] will set and start the specified tracer
764 as early as possible in order to facilitate early
767 ftrace_dump_on_oops[=orig_cpu]
768 [FTRACE] will dump the trace buffers on oops.
769 If no parameter is passed, ftrace will dump
770 buffers of all CPUs, but if you pass orig_cpu, it will
771 dump only the buffer of the CPU that triggered the
774 ftrace_filter=[function-list]
775 [FTRACE] Limit the functions traced by the function
776 tracer at boot up. function-list is a comma separated
777 list of functions. This list can be changed at run
778 time by the set_ftrace_filter file in the debugfs
781 ftrace_notrace=[function-list]
782 [FTRACE] Do not trace the functions specified in
783 function-list. This list can be changed at run time
784 by the set_ftrace_notrace file in the debugfs
787 ftrace_graph_filter=[function-list]
788 [FTRACE] Limit the top level callers functions traced
789 by the function graph tracer at boot up.
790 function-list is a comma separated list of functions
791 that can be changed at run time by the
792 set_graph_function file in the debugfs tracing directory.
795 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
796 support via parallel port (up to 5 devices per port)
797 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
798 See also Documentation/input/joystick-parport.txt
802 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
806 gcov_persist= [GCOV] When non-zero (default), profiling data for
807 kernel modules is saved and remains accessible via
808 debugfs, even when the module is unloaded/reloaded.
809 When zero, profiling data is discarded and associated
810 debugfs files are removed at module unload time.
812 gpt [EFI] Forces disk with valid GPT signature but
813 invalid Protective MBR to be treated as GPT.
815 hashdist= [KNL,NUMA] Large hashes allocated during boot
816 are distributed across NUMA nodes. Defaults on
817 for 64bit NUMA, off otherwise.
818 Format: 0 | 1 (for off | on)
820 hcl= [IA-64] SGI's Hardware Graph compatibility layer
822 hd= [EIDE] (E)IDE hard drive subsystem geometry
823 Format: <cyl>,<head>,<sect>
826 Disable Hardware Error Source Table (HEST) support;
827 corresponding firmware-first mode error processing
828 logic will be disabled.
830 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
831 size of <nn>. This works even on boxes that have no
832 highmem otherwise. This also works to reduce highmem
833 size on bigger boxes.
835 highres= [KNL] Enable/disable high resolution timer mode.
836 Valid parameters: "on", "off"
840 See Documentation/isdn/README.HiSax.
844 hpet= [X86-32,HPET] option to control HPET usage
845 Format: { enable (default) | disable | force |
847 disable: disable HPET and use PIT instead
848 force: allow force enabled of undocumented chips (ICH4,
850 verbose: show contents of HPET registers during setup
852 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
853 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
854 On x86-64 and powerpc, this option can be specified
855 multiple times interleaved with hugepages= to reserve
856 huge pages of different sizes. Valid pages sizes on
857 x86-64 are 2M (when the CPU supports "pse") and 1G
858 (when the CPU supports the "pdpe1gb" cpuinfo flag)
859 Note that 1GB pages can only be allocated at boot time
860 using hugepages= and not freed afterwards.
862 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
863 terminal devices. Valid values: 0..8
864 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
865 If specified, z/VM IUCV HVC accepts connections
866 from listed z/VM user IDs only.
868 i2c_bus= [HW] Override the default board specific I2C bus speed
869 or register an additional I2C bus that is not
870 registered from board initialization code.
874 i8042.debug [HW] Toggle i8042 debug mode
875 i8042.direct [HW] Put keyboard port into non-translated mode
876 i8042.dumbkbd [HW] Pretend that controller can only read data from
877 keyboard and cannot control its state
878 (Don't attempt to blink the leds)
879 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
880 i8042.nokbd [HW] Don't check/create keyboard port
881 i8042.noloop [HW] Disable the AUX Loopback command while probing
883 i8042.nomux [HW] Don't check presence of an active multiplexing
885 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
887 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
888 i8042.reset [HW] Reset the controller during init and cleanup
889 i8042.unlock [HW] Unlock (ignore) the keylock
893 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
894 indicates that the driver is running on unsupported
896 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
897 does not match list of supported models.
899 [HW] Report power status in /proc/i8k
900 (disabled by default)
901 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
905 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
907 ide-core.nodma= [HW] (E)IDE subsystem
908 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
909 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
910 .cdrom .chs .ignore_cable are additional options
911 See Documentation/ide/ide.txt.
913 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
914 Claim all unknown PCI IDE storage controllers.
917 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
918 Poll forces a polling idle loop that can slightly
919 improve the performance of waking up a idle CPU, but
920 will use a lot of power and make the system run hot.
922 idle=mwait: On systems which support MONITOR/MWAIT but
923 the kernel chose to not use it because it doesn't save
924 as much power as a normal idle loop, use the
925 MONITOR/MWAIT idle loop anyways. Performance should be
926 the same as idle=poll.
927 idle=halt: Halt is forced to be used for CPU idle.
928 In such case C2/C3 won't be used again.
929 idle=nomwait: Disable mwait for CPU C-states
931 ignore_loglevel [KNL]
932 Ignore loglevel setting - this will print /all/
933 kernel messages to the console. Useful for debugging.
936 Set number of hash buckets for inode cache.
939 Format: { "0" | "1" }
940 0 -- integrity auditing messages. (Default)
941 1 -- enable informational integrity auditing messages.
944 Format: { "sha1" | "md5" }
948 Load a policy which meets the needs of the Trusted
949 Computing Base. This means IMA will measure all
950 programs exec'd, files mmap'd for exec, and all files
951 opened for read by uid=0.
955 Run specified binary instead of /sbin/init as init
958 initcall_debug [KNL] Trace initcalls as they are executed. Useful
959 for working out where the kernel is dying during
962 initrd= [BOOT] Specify the location of the initial ramdisk
964 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
967 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
969 Enable intel iommu driver.
971 Disable intel iommu driver.
972 igfx_off [Default Off]
973 By default, gfx is mapped as normal device. If a gfx
974 device has a dedicated DMAR unit, the DMAR unit is
975 bypassed by not enabling DMAR with this option. In
976 this case, gfx device will use physical address for
979 With this option iommu will not optimize to look
980 for io virtual address below 32 bit forcing dual
981 address cycle on pci bus for cards supporting greater
982 than 32 bit addressing. The default is to look
983 for translation below 32 bit and if not available
984 then look in the higher range.
986 With this option on every unmap_single operation will
987 result in a hardware IOTLB flush operation as opposed
988 to batching them for performance.
990 intremap= [X86-64, Intel-IOMMU]
991 Format: { on (default) | off | nosid }
992 on enable Interrupt Remapping (default)
993 off disable Interrupt Remapping
994 nosid disable Source ID checking
998 iomem= Disable strict checking of access to MMIO memory
999 strict regions from userspace.
1015 io7= [HW] IO7 for Marvel based alpha systems
1016 See comment before marvel_specify_io7 in
1017 arch/alpha/kernel/core_marvel.c.
1019 io_delay= [X86] I/O delay method
1021 Standard port 0x80 based delay
1023 Alternate port 0xed based delay (needed on some systems)
1025 Simple two microseconds delay
1030 See Documentation/filesystems/nfs/nfsroot.txt.
1032 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1033 See comment before ip2_setup() in
1034 drivers/char/ip2/ip2base.c.
1037 When an interrupt is not handled search all handlers
1038 for it. Intended to get systems with badly broken
1042 When an interrupt is not handled search all handlers
1043 for it. Also check all handlers each timer
1044 interrupt. Intended to get systems with badly broken
1048 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1050 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1052 <cpu number>,...,<cpu number>
1054 <cpu number>-<cpu number>
1055 (must be a positive range in ascending order)
1057 <cpu number>,...,<cpu number>-<cpu number>
1059 This option can be used to specify one or more CPUs
1060 to isolate from the general SMP balancing and scheduling
1061 algorithms. You can move a process onto or off an
1062 "isolated" CPU via the CPU affinity syscalls or cpuset.
1063 <cpu number> begins at 0 and the maximum value is
1064 "number of CPUs in system - 1".
1066 This option is the preferred way to isolate CPUs. The
1067 alternative -- manually setting the CPU mask of all
1068 tasks in the system -- can cause problems and
1069 suboptimal load balancer performance.
1073 js= [HW,JOY] Analog joystick
1074 See Documentation/input/joystick.txt.
1078 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1079 specifies the amount of memory usable by the kernel
1080 for non-movable allocations. The requested amount is
1081 spread evenly throughout all nodes in the system. The
1082 remaining memory in each node is used for Movable
1083 pages. In the event, a node is too small to have both
1084 kernelcore and Movable pages, kernelcore pages will
1085 take priority and other nodes will have a larger number
1086 of kernelcore pages. The Movable zone is used for the
1087 allocation of pages that may be reclaimed or moved
1088 by the page migration subsystem. This means that
1089 HugeTLB pages may not be allocated from this zone.
1090 Note that allocations like PTEs-from-HighMem still
1091 use the HighMem zone if it exists, and the Normal
1092 zone if it does not.
1094 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1095 Format: <Controller#>[,poll interval]
1096 The controller # is the number of the ehci usb debug
1097 port as it is probed via PCI. The poll interval is
1098 optional and is the number seconds in between
1099 each poll cycle to the debug port in case you need
1100 the functionality for interrupting the kernel with
1101 gdb or control-c on the dbgp connection. When
1102 not using this parameter you use sysrq-g to break into
1103 the kernel debugger.
1105 kgdboc= [KGDB,HW] kgdb over consoles.
1106 Requires a tty driver that supports console polling,
1107 or a supported polling keyboard driver (non-usb).
1108 Serial only format: <serial_device>[,baud]
1109 keyboard only format: kbd
1110 keyboard and serial format: kbd,<serial_device>[,baud]
1111 Optional Kernel mode setting:
1112 kms, kbd format: kms,kbd
1113 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1115 kgdbwait [KGDB] Stop kernel execution and enter the
1116 kernel debugger at the earliest opportunity.
1118 kmac= [MIPS] korina ethernet MAC address.
1119 Configure the RouterBoard 532 series on-chip
1120 Ethernet adapter MAC address.
1122 kmemleak= [KNL] Boot-time kmemleak enable/disable
1123 Valid arguments: on, off
1126 kstack=N [X86] Print N words from the kernel stack
1129 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1130 Default is 0 (don't ignore, but inject #GP)
1132 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1133 Default is 1 (enabled)
1135 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1139 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1140 Default is 1 (enabled)
1142 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1144 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1146 kvm-intel.bypass_guest_pf=
1147 [KVM,Intel] Disables bypassing of guest page faults
1148 on Intel chips. Default is 1 (enabled)
1150 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1151 (virtualized MMU) support on capable Intel chips.
1152 Default is 1 (enabled)
1154 kvm-intel.emulate_invalid_guest_state=
1155 [KVM,Intel] Enable emulation of invalid guest states
1156 Default is 0 (disabled)
1158 kvm-intel.flexpriority=
1159 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1160 Default is 1 (enabled)
1162 kvm-intel.unrestricted_guest=
1163 [KVM,Intel] Disable unrestricted guest feature
1164 (virtualized real and unpaged mode) on capable
1165 Intel chips. Default is 1 (enabled)
1167 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1168 feature (tagged TLBs) on capable Intel chips.
1169 Default is 1 (enabled)
1175 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1178 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1181 libata.dma= [LIBATA] DMA control
1182 libata.dma=0 Disable all PATA and SATA DMA
1183 libata.dma=1 PATA and SATA Disk DMA only
1184 libata.dma=2 ATAPI (CDROM) DMA only
1185 libata.dma=4 Compact Flash DMA only
1186 Combinations also work, so libata.dma=3 enables DMA
1187 for disks and CDROMs, but not CFs.
1189 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1190 libata.ignore_hpa=0 keep BIOS limits (default)
1191 libata.ignore_hpa=1 ignore limits, using full disk
1193 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1197 libata.force= [LIBATA] Force configurations. The format is comma
1198 separated list of "[ID:]VAL" where ID is
1199 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1200 matching port, link or device. Basically, it matches
1201 the ATA ID string printed on console by libata. If
1202 the whole ID part is omitted, the last PORT and DEVICE
1203 values are used. If ID hasn't been specified yet, the
1204 configuration applies to all ports, links and devices.
1206 If only DEVICE is omitted, the parameter applies to
1207 the port and all links and devices behind it. DEVICE
1208 number of 0 either selects the first device or the
1209 first fan-out link behind PMP device. It does not
1210 select the host link. DEVICE number of 15 selects the
1211 host link and device attached to it.
1213 The VAL specifies the configuration to force. As long
1214 as there's no ambiguity shortcut notation is allowed.
1215 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1216 The following configurations can be forced.
1218 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1219 Any ID with matching PORT is used.
1221 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1223 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1224 udma[/][16,25,33,44,66,100,133] notation is also
1227 * [no]ncq: Turn on or off NCQ.
1229 * nohrst, nosrst, norst: suppress hard, soft
1232 * dump_id: dump IDENTIFY data.
1234 If there are multiple matching configurations changing
1235 the same attribute, the last one is used.
1237 memblock=debug [KNL] Enable memblock debug messages.
1239 load_ramdisk= [RAM] List of ramdisks to load from floppy
1240 See Documentation/blockdev/ramdisk.txt.
1242 lockd.nlm_grace_period=P [NFS] Assign grace period.
1245 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1248 lockd.nlm_timeout=T [NFS] Assign timeout value.
1251 lockd.nlm_udpport=M [NFS] Assign UDP port.
1254 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1257 loglevel= All Kernel Messages with a loglevel smaller than the
1258 console loglevel will be printed to the console. It can
1259 also be changed with klogd or other programs. The
1260 loglevels are defined as follows:
1262 0 (KERN_EMERG) system is unusable
1263 1 (KERN_ALERT) action must be taken immediately
1264 2 (KERN_CRIT) critical conditions
1265 3 (KERN_ERR) error conditions
1266 4 (KERN_WARNING) warning conditions
1267 5 (KERN_NOTICE) normal but significant condition
1268 6 (KERN_INFO) informational
1269 7 (KERN_DEBUG) debug-level messages
1271 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1272 Format: { n | nk | nM }
1273 n must be a power of two. The default size
1274 is set in the kernel config file.
1276 logo.nologo [FB] Disables display of the built-in Linux logo.
1277 This may be used to provide more screen space for
1278 kernel log messages and is useful when debugging
1279 kernel boot problems.
1281 lp=0 [LP] Specify parallel ports to use, e.g,
1282 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1283 lp=reset first parallel port). 'lp=0' disables the
1284 lp=auto printer driver. 'lp=reset' (which can be
1285 specified in addition to the ports) causes
1286 attached printers to be reset. Using
1287 lp=port1,port2,... specifies the parallel ports
1288 to associate lp devices with, starting with
1289 lp0. A port specification may be 'none' to skip
1290 that lp device, or a parport name such as
1291 'parport0'. Specifying 'lp=auto' instead of a
1292 port specification list means that device IDs
1293 from each port should be examined, to see if
1294 an IEEE 1284-compliant printer is attached; if
1295 so, the driver will manage that printer.
1296 See also header of drivers/char/lp.c.
1299 Sets loops_per_jiffy to given constant, thus avoiding
1300 time-consuming boot-time autodetection (up to 250 ms per
1301 CPU). 0 enables autodetection (default). To determine
1302 the correct value for your kernel, boot with normal
1303 autodetection and see what value is printed. Note that
1304 on SMP systems the preset will be applied to all CPUs,
1305 which is likely to cause problems if your CPUs need
1306 significantly divergent settings. An incorrect value
1307 will cause delays in the kernel to be wrong, leading to
1308 unpredictable I/O errors and other breakage. Although
1309 unlikely, in the extreme case this might damage your
1313 Format: <io>,<irq>,<dma>
1315 machvec= [IA64] Force the use of a particular machine-vector
1316 (machvec) in a generic kernel.
1317 Example: machvec=hpzx1_swiotlb
1319 machtype= [Loongson] Share the same kernel image file between different
1321 Example: machtype=lemote-yeeloong-2f-7inch
1323 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1324 than or equal to this physical address is ignored.
1326 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1327 should make use of. maxcpus=n : n >= 0 limits the
1328 kernel to using 'n' processors. n=0 is a special case,
1329 it is equivalent to "nosmp", which also disables
1332 max_loop= [LOOP] Maximum number of loopback devices that can
1338 mce [X86-32] Machine Check Exception
1340 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1342 md= [HW] RAID subsystems devices and level
1343 See Documentation/md.txt.
1346 Format: <first>,<last>
1347 Specifies range of consoles to be captured by the MDA.
1349 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1350 Amount of memory to be used when the kernel is not able
1351 to see the whole system memory or for test.
1352 [X86-32] Use together with memmap= to avoid physical
1353 address space collisions. Without memmap= PCI devices
1354 could be placed at addresses belonging to unused RAM.
1356 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1360 [KNL,SH] Allow user to override the default size for
1361 per-device physically contiguous DMA buffers.
1363 memmap=exactmap [KNL,X86] Enable setting of an exact
1364 E820 memory map, as specified by the user.
1365 Such memmap=exactmap lines can be constructed based on
1366 BIOS output or other requirements. See the memmap=nn@ss
1369 memmap=nn[KMG]@ss[KMG]
1370 [KNL] Force usage of a specific region of memory
1371 Region of memory to be used, from ss to ss+nn.
1373 memmap=nn[KMG]#ss[KMG]
1374 [KNL,ACPI] Mark specific memory as ACPI data.
1375 Region of memory to be used, from ss to ss+nn.
1377 memmap=nn[KMG]$ss[KMG]
1378 [KNL,ACPI] Mark specific memory as reserved.
1379 Region of memory to be used, from ss to ss+nn.
1380 Example: Exclude memory from 0x18690000-0x1869ffff
1381 memmap=64K$0x18690000
1383 memmap=0x10000$0x18690000
1385 memory_corruption_check=0/1 [X86]
1386 Some BIOSes seem to corrupt the first 64k of
1387 memory when doing things like suspend/resume.
1388 Setting this option will scan the memory
1389 looking for corruption. Enabling this will
1390 both detect corruption and prevent the kernel
1391 from using the memory being corrupted.
1392 However, its intended as a diagnostic tool; if
1393 repeatable BIOS-originated corruption always
1394 affects the same memory, you can use memmap=
1395 to prevent the kernel from using that memory.
1397 memory_corruption_check_size=size [X86]
1398 By default it checks for corruption in the low
1399 64k, making this memory unavailable for normal
1400 use. Use this parameter to scan for
1401 corruption in more or less memory.
1403 memory_corruption_check_period=seconds [X86]
1404 By default it checks for corruption every 60
1405 seconds. Use this parameter to check at some
1406 other rate. 0 disables periodic checking.
1408 memtest= [KNL,X86] Enable memtest
1410 default : 0 <disable>
1411 Specifies the number of memtest passes to be
1412 performed. Each pass selects another test
1413 pattern from a given set of patterns. Memtest
1414 fills the memory with this pattern, validates
1415 memory contents and reserves bad memory
1416 regions that are detected.
1418 meye.*= [HW] Set MotionEye Camera parameters
1419 See Documentation/video4linux/meye.txt.
1421 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1422 Multi-Function General Purpose Timers on AMD Geode
1425 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1426 the BIOS has incorrectly applied a workaround. TinyBIOS
1427 version 0.98 is known to be affected, 0.99 fixes the
1428 problem by letting the user disable the workaround.
1432 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1433 physical address is ignored.
1435 mini2440= [ARM,HW,KNL]
1436 Format:[0..2][b][c][t]
1438 MINI2440 configuration specification:
1439 0 - The attached screen is the 3.5" TFT
1440 1 - The attached screen is the 7" TFT
1441 2 - The VGA Shield is attached (1024x768)
1442 Leaving out the screen size parameter will not load
1443 the TFT driver, and the framebuffer will be left
1445 b - Enable backlight. The TFT backlight pin will be
1446 linked to the kernel VESA blanking code and a GPIO
1447 LED. This parameter is not necessary when using the
1449 c - Enable the s3c camera interface.
1450 t - Reserved for enabling touchscreen support. The
1451 touchscreen support is not enabled in the mainstream
1452 kernel as of 2.6.30, a preliminary port can be found
1453 in the "bleeding edge" mini2440 support kernel at
1454 http://repo.or.cz/w/linux-2.6/mini2440.git
1457 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1458 parameter allows control of the logging verbosity for
1459 the additional memory initialisation checks. A value
1460 of 0 disables mminit logging and a level of 4 will
1461 log everything. Information is printed at KERN_DEBUG
1462 so loglevel=8 may also need to be specified.
1465 [MOUSE] Maximum time between finger touching and
1466 leaving touchpad surface for touch to be considered
1467 a tap and be reported as a left button click (for
1468 touchpads working in absolute mode only).
1470 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1471 reporting absolute coordinates, such as tablets
1472 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1473 reporting absolute coordinates, such as tablets
1475 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1476 is similar to kernelcore except it specifies the
1477 amount of memory used for migratable allocations.
1478 If both kernelcore and movablecore is specified,
1479 then kernelcore will be at *least* the specified
1480 value but may be more. If movablecore on its own
1481 is specified, the administrator must be careful
1482 that the amount of memory usable for all allocations
1485 MTD_Partition= [MTD]
1486 Format: <name>,<region-number>,<size>,<offset>
1488 MTD_Region= [MTD] Format:
1489 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1492 See drivers/mtd/cmdlinepart.c.
1494 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1496 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1498 boundary - index of last SLC block on Flex-OneNAND.
1499 The remaining blocks are configured as MLC blocks.
1500 lock - Configure if Flex-OneNAND boundary should be locked.
1501 Once locked, the boundary cannot be changed.
1502 1 indicates lock status, 0 indicates unlock status.
1505 ARM/S3C2412 JIVE boot control
1507 See arch/arm/mach-s3c2412/mach-jive.c
1509 mtouchusb.raw_coordinates=
1510 [HW] Make the MicroTouch USB driver use raw coordinates
1511 ('y', default) or cooked coordinates ('n')
1513 mtrr_chunk_size=nn[KMG] [X86]
1514 used for mtrr cleanup. It is largest continuous chunk
1515 that could hold holes aka. UC entries.
1517 mtrr_gran_size=nn[KMG] [X86]
1518 Used for mtrr cleanup. It is granularity of mtrr block.
1520 Large value could prevent small alignment from
1523 mtrr_spare_reg_nr=n [X86]
1525 Range: 0,7 : spare reg number
1527 Used for mtrr cleanup. It is spare mtrr entries number.
1528 Set to 2 or more if your graphical card needs more.
1530 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1532 netdev= [NET] Network devices parameters
1533 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1534 Note that mem_start is often overloaded to mean
1535 something different and driver-specific.
1536 This usage is only documented in each driver source
1540 [NETFILTER] Enable connection tracking flow accounting
1541 0 to disable accounting
1542 1 to enable accounting
1545 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1546 See Documentation/filesystems/nfs/nfsroot.txt.
1548 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1549 See Documentation/filesystems/nfs/nfsroot.txt.
1551 nfsrootdebug [NFS] enable nfsroot debugging messages.
1552 See Documentation/filesystems/nfs/nfsroot.txt.
1554 nfs.callback_tcpport=
1555 [NFS] set the TCP port on which the NFSv4 callback
1556 channel should listen.
1559 [NFS] sets the pathname to the program which is used
1560 to update the NFS client cache entries.
1562 nfs.cache_getent_timeout=
1563 [NFS] sets the timeout after which an attempt to
1564 update a cache entry is deemed to have failed.
1566 nfs.idmap_cache_timeout=
1567 [NFS] set the maximum lifetime for idmapper cache
1571 [NFS] enable 64-bit inode numbers.
1572 If zero, the NFS client will fake up a 32-bit inode
1573 number for the readdir() and stat() syscalls instead
1574 of returning the full 64-bit number.
1575 The default is to return 64-bit inode numbers.
1577 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1578 when a NMI is triggered.
1579 Format: [state][,regs][,debounce][,die]
1581 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1582 Format: [panic,][num]
1584 0 - turn nmi_watchdog off
1585 1 - use the IO-APIC timer for the NMI watchdog
1586 2 - use the local APIC for the NMI watchdog using
1587 a performance counter. Note: This will use one
1588 performance counter and the local APIC's performance
1590 When panic is specified, panic when an NMI watchdog
1592 This is useful when you use a panic=... timeout and
1593 need the box quickly up again.
1594 Instead of 1 and 2 it is possible to use the following
1595 symbolic names: lapic and ioapic
1596 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1598 netpoll.carrier_timeout=
1599 [NET] Specifies amount of time (in seconds) that
1600 netpoll should wait for a carrier. By default netpoll
1603 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1604 emulation library even if a 387 maths coprocessor
1608 [HW] Never suspend the console
1609 Disable suspending of consoles during suspend and
1610 hibernate operations. Once disabled, debugging
1611 messages can reach various consoles while the rest
1612 of the system is being put to sleep (ie, while
1613 debugging driver suspend/resume hooks). This may
1614 not work reliably with all consoles, but is known
1615 to work with serial and VGA consoles.
1617 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1618 caches in the slab allocator. Saves per-node memory,
1619 but will impact performance.
1623 noapic [SMP,APIC] Tells the kernel to not make use of any
1624 IOAPICs that may be present in the system.
1626 nobats [PPC] Do not use BATs for mapping kernel lowmem
1627 on "Classic" PPC cores.
1631 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1633 nodelayacct [KNL] Disable per-task delay accounting
1635 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1637 nodsp [SH] Disable hardware DSP at boot time.
1639 noefi [X86] Disable EFI runtime services support.
1644 On X86-32 available only on PAE configured kernels.
1645 noexec=on: enable non-executable mappings (default)
1646 noexec=off: disable non-executable mappings
1649 This affects only 32-bit executables.
1650 noexec32=on: enable non-executable mappings (default)
1651 read doesn't imply executable mappings
1652 noexec32=off: disable non-executable mappings
1653 read implies executable mappings
1655 nofpu [SH] Disable hardware FPU at boot time.
1657 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1658 register save and restore. The kernel will only save
1659 legacy floating-point registers on task switch.
1661 noxsave [BUGS=X86] Disables x86 extended register state save
1662 and restore using xsave. The kernel will fallback to
1663 enabling legacy floating-point and sse state.
1665 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1666 wfi(ARM) instruction doesn't work correctly and not to
1667 use it. This is also useful when using JTAG debugger.
1669 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1670 instruction doesn't work correctly and not to
1673 no_file_caps Tells the kernel not to honor file capabilities. The
1674 only way then for a file to be executed with privilege
1675 is to be setuid root or executed by root.
1677 nohalt [IA-64] Tells the kernel not to use the power saving
1678 function PAL_HALT_LIGHT when idle. This increases
1679 power-consumption. On the positive side, it reduces
1680 interrupt wake-up latency, which may improve performance
1681 in certain environments such as networked servers or
1684 nohz= [KNL] Boottime enable/disable dynamic ticks
1685 Valid arguments: on, off
1688 noiotrap [SH] Disables trapped I/O port accesses.
1690 noirqdebug [X86-32] Disables the code which attempts to detect and
1691 disable unhandled interrupt sources.
1693 no_timer_check [X86,APIC] Disables the code which tests for
1694 broken timer IRQ sources.
1696 noisapnp [ISAPNP] Disables ISA PnP code.
1698 noinitrd [RAM] Tells the kernel not to load any configured
1701 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1703 [Deprecated - use intremap=off]
1707 nojitter [IA64] Disables jitter checking for ITC timers.
1709 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1711 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1713 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1715 noltlbs [PPC] Do not use large page/tlb entries for kernel
1716 lowmem mapping on PPC40x.
1718 nomca [IA-64] Disable machine check abort handling
1720 nomce [X86-32] Machine Check Exception
1722 nomfgpt [X86-32] Disable Multi-Function General Purpose
1723 Timer usage (for AMD Geode machines).
1725 nopat [X86] Disable PAT (page attribute table extension of
1726 pagetables) support.
1728 norandmaps Don't use address space randomization. Equivalent to
1729 echo 0 > /proc/sys/kernel/randomize_va_space
1731 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1733 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1734 with UP alternatives
1736 noresidual [PPC] Don't use residual data on PReP machines.
1738 noresume [SWSUSP] Disables resume and restores original swap
1741 no-scroll [VGA] Disables scrollback.
1742 This is required for the Braillex ib80-piezo Braille
1743 reader made by F.H. Papenmeier (Germany).
1747 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1749 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1750 and disable the IO APIC. legacy for "maxcpus=0".
1752 nosoftlockup [KNL] Disable the soft-lockup detector.
1754 noswapaccount [KNL] Disable accounting of swap in memory resource
1755 controller. (See Documentation/cgroups/memory.txt)
1757 nosync [HW,M68K] Disables sync negotiation for all devices.
1759 notsc [BUGS=X86-32] Disable Time Stamp Counter
1761 nousb [USB] Disable the USB subsystem
1763 nowatchdog [KNL] Disable the lockup detector.
1767 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1769 nptcg= [IA64] Override max number of concurrent global TLB
1770 purges which is reported from either PAL_VM_SUMMARY or
1773 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1774 could support. nr_cpus=n : n >= 1 limits the kernel to
1775 supporting 'n' processors. Later in runtime you can not
1776 use hotplug cpu feature to put more cpu back to online.
1777 just like you compile the kernel NR_CPUS=n
1779 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1781 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1782 one of ['zone', 'node', 'default'] can be specified
1783 This can be set from sysctl after boot.
1784 See Documentation/sysctl/vm.txt for details.
1786 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1787 See Documentation/debugging-via-ohci1394.txt for more
1790 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1791 Rather than timing out after 20 ms if an EC
1792 command is not properly ACKed, override the length
1793 of the timeout. We have interrupts disabled while
1794 waiting for the ACK, so if this is set too high
1795 interrupts *may* be lost!
1797 omap_mux= [OMAP] Override bootloader pin multiplexing.
1798 Format: <mux_mode0.mode_name=value>...
1799 For example, to override I2C bus2:
1800 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1802 oprofile.timer= [HW]
1803 Use timer interrupt instead of performance counters
1805 oprofile.cpu_type= Force an oprofile cpu type
1806 This might be useful if you have an older oprofile
1807 userland or if you want common events.
1808 Format: { arch_perfmon }
1809 arch_perfmon: [X86] Force use of architectural
1810 perfmon on Intel CPUs instead of the
1811 CPU specific event set.
1814 See Documentation/sound/oss/oss-parameters.txt
1816 panic= [KNL] Kernel behaviour on panic
1819 parkbd.port= [HW] Parallel port number the keyboard adapter is
1820 connected to, default is 0.
1822 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1823 0 for XT, 1 for AT (default is AT).
1826 parport= [HW,PPT] Specify parallel ports. 0 disables.
1827 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1828 Use 'auto' to force the driver to use any
1829 IRQ/DMA settings detected (the default is to
1830 ignore detected IRQ/DMA settings because of
1831 possible conflicts). You can specify the base
1832 address, IRQ, and DMA settings; IRQ and DMA
1833 should be numbers, or 'auto' (for using detected
1834 settings on that particular port), or 'nofifo'
1835 (to avoid using a FIFO even if it is detected).
1836 Parallel ports are assigned in the order they
1837 are specified on the command line, starting
1840 parport_init_mode= [HW,PPT]
1841 Configure VIA parallel port to operate in
1842 a specific mode. This is necessary on Pegasos
1843 computer where firmware has no options for setting
1844 up parallel port mode and sets it to spp.
1845 Currently this function knows 686a and 8231 chips.
1846 Format: [spp|ps2|epp|ecp|ecpepp]
1849 Halt all CPUs after the first oops has been printed for
1850 the specified number of seconds. This is to be used if
1851 your oopses keep scrolling off the screen.
1856 See header of drivers/block/paride/pcd.c.
1857 See also Documentation/blockdev/paride.txt.
1859 pci=option[,option...] [PCI] various PCI subsystem options:
1860 earlydump [X86] dump PCI config space before the kernel
1862 off [X86] don't probe for the PCI bus
1863 bios [X86-32] force use of PCI BIOS, don't access
1864 the hardware directly. Use this if your machine
1865 has a non-standard PCI host bridge.
1866 nobios [X86-32] disallow use of PCI BIOS, only direct
1867 hardware access methods are allowed. Use this
1868 if you experience crashes upon bootup and you
1869 suspect they are caused by the BIOS.
1870 conf1 [X86] Force use of PCI Configuration
1872 conf2 [X86] Force use of PCI Configuration
1874 noaer [PCIE] If the PCIEAER kernel config parameter is
1875 enabled, this kernel boot option can be used to
1876 disable the use of PCIE advanced error reporting.
1877 nodomains [PCI] Disable support for multiple PCI
1878 root domains (aka PCI segments, in ACPI-speak).
1879 nommconf [X86] Disable use of MMCONFIG for PCI
1881 check_enable_amd_mmconf [X86] check for and enable
1882 properly configured MMIO access to PCI
1883 config space on AMD family 10h CPU
1884 nomsi [MSI] If the PCI_MSI kernel config parameter is
1885 enabled, this kernel boot option can be used to
1886 disable the use of MSI interrupts system-wide.
1887 noioapicquirk [APIC] Disable all boot interrupt quirks.
1888 Safety option to keep boot IRQs enabled. This
1889 should never be necessary.
1890 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1891 primary IO-APIC for bridges that cannot disable
1892 boot IRQs. This fixes a source of spurious IRQs
1893 when the system masks IRQs.
1894 noioapicreroute [APIC] Disable workaround that uses the
1895 boot IRQ equivalent of an IRQ that connects to
1896 a chipset where boot IRQs cannot be disabled.
1897 The opposite of ioapicreroute.
1898 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1899 routing table. These calls are known to be buggy
1900 on several machines and they hang the machine
1901 when used, but on other computers it's the only
1902 way to get the interrupt routing table. Try
1903 this option if the kernel is unable to allocate
1904 IRQs or discover secondary PCI buses on your
1906 rom [X86] Assign address space to expansion ROMs.
1907 Use with caution as certain devices share
1908 address decoders between ROMs and other
1910 norom [X86] Do not assign address space to
1911 expansion ROMs that do not already have
1912 BIOS assigned address ranges.
1913 nobar [X86] Do not assign address space to the
1914 BARs that weren't assigned by the BIOS.
1915 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1916 assigned automatically to PCI devices. You can
1917 make the kernel exclude IRQs of your ISA cards
1919 pirqaddr=0xAAAAA [X86] Specify the physical address
1920 of the PIRQ table (normally generated
1921 by the BIOS) if it is outside the
1922 F0000h-100000h range.
1923 lastbus=N [X86] Scan all buses thru bus #N. Can be
1924 useful if the kernel is unable to find your
1925 secondary buses and you want to tell it
1926 explicitly which ones they are.
1927 assign-busses [X86] Always assign all PCI bus
1928 numbers ourselves, overriding
1929 whatever the firmware may have done.
1930 usepirqmask [X86] Honor the possible IRQ mask stored
1931 in the BIOS $PIR table. This is needed on
1932 some systems with broken BIOSes, notably
1933 some HP Pavilion N5400 and Omnibook XE3
1934 notebooks. This will have no effect if ACPI
1935 IRQ routing is enabled.
1936 noacpi [X86] Do not use ACPI for IRQ routing
1937 or for PCI scanning.
1938 use_crs [X86] Use PCI host bridge window information
1939 from ACPI. On BIOSes from 2008 or later, this
1940 is enabled by default. If you need to use this,
1941 please report a bug.
1942 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1943 If you need to use this, please report a bug.
1944 routeirq Do IRQ routing for all PCI devices.
1945 This is normally done in pci_enable_device(),
1946 so this option is a temporary workaround
1947 for broken drivers that don't call it.
1948 skip_isa_align [X86] do not align io start addr, so can
1949 handle more pci cards
1950 firmware [ARM] Do not re-enumerate the bus but instead
1951 just use the configuration from the
1952 bootloader. This is currently used on
1953 IXP2000 systems where the bus has to be
1954 configured a certain way for adjunct CPUs.
1955 noearly [X86] Don't do any early type 1 scanning.
1956 This might help on some broken boards which
1957 machine check when some devices' config space
1958 is read. But various workarounds are disabled
1959 and some IOMMU drivers will not work.
1960 bfsort Sort PCI devices into breadth-first order.
1961 This sorting is done to get a device
1962 order compatible with older (<= 2.4) kernels.
1963 nobfsort Don't sort PCI devices into breadth-first order.
1964 cbiosize=nn[KMG] The fixed amount of bus space which is
1965 reserved for the CardBus bridge's IO window.
1966 The default value is 256 bytes.
1967 cbmemsize=nn[KMG] The fixed amount of bus space which is
1968 reserved for the CardBus bridge's memory
1969 window. The default value is 64 megabytes.
1972 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1973 Specifies alignment and device to reassign
1974 aligned memory resources.
1975 If <order of align> is not specified,
1976 PAGE_SIZE is used as alignment.
1977 PCI-PCI bridge can be specified, if resource
1978 windows need to be expanded.
1979 ecrc= Enable/disable PCIe ECRC (transaction layer
1980 end-to-end CRC checking).
1981 bios: Use BIOS/firmware settings. This is the
1986 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1989 force Enable ASPM even on devices that claim not to support it.
1990 WARNING: Forcing ASPM on may cause system lockups.
1992 pcie_ports= [PCIE] PCIe ports handling:
1993 auto Ask the BIOS whether or not to use native PCIe services
1994 associated with PCIe ports (PME, hot-plug, AER). Use
1995 them only if that is allowed by the BIOS.
1996 native Use native PCIe services associated with PCIe ports
1998 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2001 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2002 nomsi Do not use MSI for native PCIe PME signaling (this makes
2003 all PCIe root ports use INTx for all services).
2005 pcmv= [HW,PCMCIA] BadgePAD 4
2008 See Documentation/blockdev/paride.txt.
2010 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2013 See arch/parisc/kernel/pdc_chassis.c
2015 percpu_alloc= Select which percpu first chunk allocator to use.
2016 Currently supported values are "embed" and "page".
2017 Archs may support subset or none of the selections.
2018 See comments in mm/percpu.c for details on each
2019 allocator. This parameter is primarily for debugging
2020 and performance comparison.
2023 See Documentation/blockdev/paride.txt.
2026 See Documentation/blockdev/paride.txt.
2028 pirq= [SMP,APIC] Manual mp-table setup
2029 See Documentation/x86/i386/IO-APIC.txt.
2031 plip= [PPT,NET] Parallel port network link
2032 Format: { parport<nr> | timid | 0 }
2033 See also Documentation/parport.txt.
2035 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2036 Override pmtimer IOPort with a hex value.
2040 Enable PNP debug messages. This depends on the
2041 CONFIG_PNP_DEBUG_MESSAGES option.
2047 { on | off | curr | res | no-curr | no-res }
2050 [ISAPNP] Exclude IRQs for the autoconfiguration
2053 [ISAPNP] Exclude DMAs for the autoconfiguration
2055 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2056 Ranges are in pairs (I/O port base and size).
2059 [ISAPNP] Exclude memory regions for the
2061 Ranges are in pairs (memory base and size).
2063 ports= [IP_VS_FTP] IPVS ftp helper module
2065 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2067 Format: <port>,<port>....
2069 print-fatal-signals=
2070 [KNL] debug: print fatal signals
2072 If enabled, warn about various signal handling
2073 related application anomalies: too many signals,
2074 too many POSIX.1 timers, fatal signals causing a
2077 If you hit the warning due to signal overflow,
2078 you might want to try "ulimit -i unlimited".
2082 printk.time= Show timing data prefixed to each printk message line
2083 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2085 processor.max_cstate= [HW,ACPI]
2086 Limit processor to maximum C-state
2087 max_cstate=9 overrides any DMI blacklist limit.
2089 processor.nocst [HW,ACPI]
2090 Ignore the _CST method to determine C-states,
2091 instead using the legacy FADT method
2093 profile= [KNL] Enable kernel profiling via /proc/profile
2094 Format: [schedule,]<number>
2095 Param: "schedule" - profile schedule points.
2096 Param: <number> - step/bucket size as a power of 2 for
2097 statistical time based profiling.
2098 Param: "sleep" - profile D-state sleeping (millisecs).
2099 Requires CONFIG_SCHEDSTATS
2100 Param: "kvm" - profile VM exits.
2102 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2104 See Documentation/blockdev/ramdisk.txt.
2106 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2107 probe for; one of (bare|imps|exps|lifebook|any).
2108 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2110 psmouse.resetafter= [HW,MOUSE]
2111 Try to reset the device after so many bad packets
2114 [HW,MOUSE] Set desired mouse resolution, in dpi.
2115 psmouse.smartscroll=
2116 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2117 0 = disabled, 1 = enabled (default).
2120 See Documentation/blockdev/paride.txt.
2123 [KNL] Number of legacy pty's. Overwrites compiled-in
2126 quiet [KNL] Disable most log messages
2131 See Documentation/md.txt.
2133 ramdisk_blocksize= [RAM]
2134 See Documentation/blockdev/ramdisk.txt.
2136 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2137 See Documentation/blockdev/ramdisk.txt.
2139 rcupdate.blimit= [KNL,BOOT]
2140 Set maximum number of finished RCU callbacks to process
2143 rcupdate.qhimark= [KNL,BOOT]
2144 Set threshold of queued
2145 RCU callbacks over which batch limiting is disabled.
2147 rcupdate.qlowmark= [KNL,BOOT]
2148 Set threshold of queued RCU callbacks below which
2149 batch limiting is re-enabled.
2153 Run specified binary instead of /init from the ramdisk,
2154 used for early userspace startup. See initrd.
2156 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2157 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2158 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2161 [KNL, SMP] Set scheduler's default relax_domain_level.
2162 See Documentation/cgroups/cpusets.txt.
2164 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2166 reservetop= [X86-32]
2168 Reserves a hole at the top of the kernel virtual
2173 Set the amount of memory to reserve for BIOS at
2174 the bottom of the address space.
2176 reset_devices [KNL] Force drivers to reset the underlying device
2177 during initialization.
2179 resource_alloc_from_bottom
2180 Allocate new resources from the beginning of available
2181 space, not the end. If you need to use this, please
2185 Specify the partition device for software suspend
2187 resume_offset= [SWSUSP]
2188 Specify the offset from the beginning of the partition
2189 given by "resume=" at which the swap header is located,
2190 in <PAGE_SIZE> units (needed only for swap files).
2191 See Documentation/power/swsusp-and-swap-files.txt
2193 hibernate= [HIBERNATION]
2194 noresume Don't check if there's a hibernation image
2195 present during boot.
2196 nocompress Don't compress/decompress hibernation images.
2198 retain_initrd [RAM] Keep initrd memory after extraction
2200 rhash_entries= [KNL,NET]
2201 Set number of hash buckets for route cache
2203 riscom8= [HW,SERIAL]
2204 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2206 ro [KNL] Mount root device read-only on boot
2208 root= [KNL] Root filesystem
2210 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2211 mount the root filesystem
2213 rootflags= [KNL] Set root filesystem mount option string
2215 rootfstype= [KNL] Set root filesystem type
2217 rootwait [KNL] Wait (indefinitely) for root device to show up.
2218 Useful for devices that are detected asynchronously
2219 (e.g. USB and MMC devices).
2221 rw [KNL] Mount root device read-write on boot
2223 S [KNL] Run init in single mode
2226 See drivers/net/irda/sa1100_ir.c.
2228 sbni= [NET] Granch SBNI12 leased line adapter
2230 sched_debug [KNL] Enables verbose scheduler debug messages.
2232 security= [SECURITY] Choose a security module to enable at boot.
2233 If this boot parameter is not specified, only the first
2234 security module asking for security registration will be
2235 loaded. An invalid security module name will be treated
2236 as if no module has been chosen.
2238 selinux= [SELINUX] Disable or enable SELinux at boot time.
2239 Format: { "0" | "1" }
2240 See security/selinux/Kconfig help text.
2243 Default value is set via kernel config option.
2244 If enabled at boot time, /selinux/disable can be used
2245 later to disable prior to initial policy load.
2247 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2248 Format: { "0" | "1" }
2249 See security/apparmor/Kconfig help text
2252 Default value is set via kernel config option.
2254 serialnumber [BUGS=X86-32]
2257 Maximal number of shapers.
2259 show_msr= [x86] show boot-time MSR settings
2260 Format: { <integer> }
2261 Show boot-time (BIOS-initialized) MSR settings.
2262 The parameter means the number of CPUs to show,
2263 for example 1 means boot CPU only.
2270 slub_debug[=options[,slabs]] [MM, SLUB]
2271 Enabling slub_debug allows one to determine the
2272 culprit if slab objects become corrupted. Enabling
2273 slub_debug can create guard zones around objects and
2274 may poison objects when not in use. Also tracks the
2275 last alloc / free. For more information see
2276 Documentation/vm/slub.txt.
2278 slub_max_order= [MM, SLUB]
2279 Determines the maximum allowed order for slabs.
2280 A high setting may cause OOMs due to memory
2281 fragmentation. For more information see
2282 Documentation/vm/slub.txt.
2284 slub_min_objects= [MM, SLUB]
2285 The minimum number of objects per slab. SLUB will
2286 increase the slab order up to slub_max_order to
2287 generate a sufficiently large slab able to contain
2288 the number of objects indicated. The higher the number
2289 of objects the smaller the overhead of tracking slabs
2290 and the less frequently locks need to be acquired.
2291 For more information see Documentation/vm/slub.txt.
2293 slub_min_order= [MM, SLUB]
2294 Determines the mininum page order for slabs. Must be
2295 lower than slub_max_order.
2296 For more information see Documentation/vm/slub.txt.
2298 slub_nomerge [MM, SLUB]
2299 Disable merging of slabs with similar size. May be
2300 necessary if there is some reason to distinguish
2301 allocs to different slabs. Debug options disable
2302 merging on their own.
2303 For more information see Documentation/vm/slub.txt.
2306 Format: <io1>[,<io2>[,...,<io8>]]
2308 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2309 attempt to substitute SMP alternatives once at boot.
2311 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2312 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2313 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2314 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2315 smsc-ircc2.ircc_irq= [HW] IRQ line
2316 smsc-ircc2.ircc_dma= [HW] DMA channel
2317 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2318 0: Toshiba Satellite 1800 (GP data pin select)
2319 1: Fast pin select (default)
2323 [KNL] Should the soft-lockup detector generate panics.
2325 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2326 See Documentation/sonypi.txt
2328 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2329 See Documentation/serial/specialix.txt.
2331 spia_io_base= [HW,MTD]
2337 Enabled the stack tracer on boot up.
2341 Set the STI (builtin display/keyboard on the HP-PARISC
2342 machines) console (graphic card) which should be used
2343 as the initial boot-console.
2344 See also comment in drivers/video/console/sticore.c.
2347 See comment in drivers/video/console/sticore.c.
2350 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2352 sunrpc.min_resvport=
2353 sunrpc.max_resvport=
2355 SunRPC servers often require that client requests
2356 originate from a privileged port (i.e. a port in the
2357 range 0 < portnr < 1024).
2358 An administrator who wishes to reserve some of these
2359 ports for other uses may adjust the range that the
2360 kernel's sunrpc client considers to be privileged
2361 using these two parameters to set the minimum and
2362 maximum port values.
2366 Control how the NFS server code allocates CPUs to
2367 service thread pools. Depending on how many NICs
2368 you have and where their interrupts are bound, this
2369 option will affect which CPUs will do NFS serving.
2370 Note: this parameter cannot be changed while the
2371 NFS server is running.
2373 auto the server chooses an appropriate mode
2374 automatically using heuristics
2375 global a single global pool contains all CPUs
2376 percpu one pool for each CPU
2377 pernode one pool for each NUMA node (equivalent
2378 to global on non-NUMA machines)
2380 sunrpc.tcp_slot_table_entries=
2381 sunrpc.udp_slot_table_entries=
2383 Sets the upper limit on the number of simultaneous
2384 RPC calls that can be sent from the client to a
2385 server. Increasing these values may allow you to
2386 improve throughput, but will also increase the
2387 amount of memory reserved for use by the client.
2389 swiotlb= [IA-64] Number of I/O TLB slabs
2393 sysfs.deprecated=0|1 [KNL]
2394 Enable/disable old style sysfs layout for old udev
2395 on older distributions. When this option is enabled
2396 very new udev will not work anymore. When this option
2397 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2398 in older udev will not work anymore.
2399 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2400 the kernel configuration.
2402 sysrq_always_enabled
2404 Ignore sysrq setting - this boot parameter will
2405 neutralize any effect of /proc/sys/kernel/sysrq.
2406 Useful for debugging.
2410 test_suspend= [SUSPEND]
2411 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2412 standby suspend) as the system sleep state to briefly
2413 enter during system startup. The system is woken from
2414 this state using a wakeup-capable RTC alarm.
2416 thash_entries= [KNL,NET]
2417 Set number of hash buckets for TCP connection
2419 thermal.act= [HW,ACPI]
2420 -1: disable all active trip points in all thermal zones
2421 <degrees C>: override all lowest active trip points
2423 thermal.crt= [HW,ACPI]
2424 -1: disable all critical trip points in all thermal zones
2425 <degrees C>: override all critical trip points
2427 thermal.nocrt= [HW,ACPI]
2428 Set to disable actions on ACPI thermal zone
2429 critical and hot trip points.
2431 thermal.off= [HW,ACPI]
2432 1: disable ACPI thermal control
2434 thermal.psv= [HW,ACPI]
2435 -1: disable all passive trip points
2436 <degrees C>: override all passive trip points to this
2439 thermal.tzp= [HW,ACPI]
2440 Specify global default ACPI thermal zone polling rate
2441 <deci-seconds>: poll all this frequency
2442 0: no polling (default)
2446 Specify if the kernel should make use of the cpu
2447 topology informations if the hardware supports these.
2448 The scheduler will make use of these informations and
2449 e.g. base its process migration decisions on it.
2454 tpm_suspend_pcr=[HW,TPM]
2455 Format: integer pcr id
2456 Specify that at suspend time, the tpm driver
2457 should extend the specified pcr with zeros,
2458 as a workaround for some chips which fail to
2459 flush the last written pcr on TPM_SaveState.
2460 This will guarantee that all the other pcrs
2463 trace_buf_size=nn[KMG]
2464 [FTRACE] will set tracing buffer size.
2466 trace_event=[event-list]
2467 [FTRACE] Set and start specified trace events in order
2468 to facilitate early boot debugging.
2469 See also Documentation/trace/events.txt
2471 tsc= Disable clocksource-must-verify flag for TSC.
2473 [x86] reliable: mark tsc clocksource as reliable, this
2474 disables clocksource verification at runtime.
2475 Used to enable high-resolution timer mode on older
2476 hardware, and in virtualized environment.
2477 [x86] noirqtime: Do not use TSC to do irq accounting.
2478 Used to run time disable IRQ_TIME_ACCOUNTING on any
2479 platforms where RDTSC is slow and this accounting
2482 turbografx.map[2|3]= [HW,JOY]
2483 TurboGraFX parallel port interface
2485 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2486 See also Documentation/input/joystick-parport.txt
2488 uhash_entries= [KNL,NET]
2489 Set number of hash buckets for UDP/UDP-Lite connections
2492 [USB] Ignore overcurrent events (default N).
2493 Some badly-designed motherboards generate lots of
2494 bogus events, for ports that aren't wired to
2495 anything. Set this parameter to avoid log spamming.
2496 Note that genuine overcurrent events won't be
2501 Set unknown_nmi_panic=1 early on boot.
2503 usbcore.autosuspend=
2504 [USB] The autosuspend time delay (in seconds) used
2505 for newly-detected USB devices (default 2). This
2506 is the time required before an idle device will be
2507 autosuspended. Devices for which the delay is set
2508 to a negative value won't be autosuspended at all.
2510 usbcore.usbfs_snoop=
2511 [USB] Set to log all usbfs traffic (default 0 = off).
2513 usbcore.blinkenlights=
2514 [USB] Set to cycle leds on hubs (default 0 = off).
2516 usbcore.old_scheme_first=
2517 [USB] Start with the old device initialization
2518 scheme (default 0 = off).
2520 usbcore.use_both_schemes=
2521 [USB] Try the other device initialization scheme
2522 if the first one fails (default 1 = enabled).
2524 usbcore.initial_descriptor_timeout=
2525 [USB] Specifies timeout for the initial 64-byte
2526 USB_REQ_GET_DESCRIPTOR request in milliseconds
2527 (default 5000 = 5.0 seconds).
2530 [USBHID] The interval which mice are to be polled at.
2532 usb-storage.delay_use=
2533 [UMS] The delay in seconds before a new device is
2534 scanned for Logical Units (default 5).
2537 [UMS] A list of quirks entries to supplement or
2538 override the built-in unusual_devs list. List
2539 entries are separated by commas. Each entry has
2540 the form VID:PID:Flags where VID and PID are Vendor
2541 and Product ID values (4-digit hex numbers) and
2542 Flags is a set of characters, each corresponding
2543 to a common usb-storage quirk flag as follows:
2544 a = SANE_SENSE (collect more than 18 bytes
2546 b = BAD_SENSE (don't collect more than 18
2547 bytes of sense data);
2548 c = FIX_CAPACITY (decrease the reported
2549 device capacity by one sector);
2550 h = CAPACITY_HEURISTICS (decrease the
2551 reported device capacity by one
2552 sector if the number is odd);
2553 i = IGNORE_DEVICE (don't bind to this
2555 l = NOT_LOCKABLE (don't try to lock and
2556 unlock ejectable media);
2557 m = MAX_SECTORS_64 (don't transfer more
2558 than 64 sectors = 32 KB at a time);
2559 o = CAPACITY_OK (accept the capacity
2560 reported by the device);
2561 r = IGNORE_RESIDUE (the device reports
2562 bogus residue values);
2563 s = SINGLE_LUN (the device has only one
2565 w = NO_WP_DETECT (don't test whether the
2566 medium is write-protected).
2567 Example: quirks=0419:aaf5:rl,0421:0433:rc
2570 [X86] Flags controlling user PTE allocations.
2572 nohigh = do not allocate PTE pages in
2573 HIGHMEM regardless of setting
2577 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2578 vdso=1: enable VDSO (default)
2579 vdso=0: disable VDSO mapping
2582 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2583 vdso32=1: enable 32-bit VDSO (default)
2584 vdso32=0: disable 32-bit VDSO mapping
2587 vector=percpu: enable percpu vector domain
2589 video= [FB] Frame buffer configuration
2590 See Documentation/fb/modedb.txt.
2592 vga= [BOOT,X86-32] Select a particular video mode
2593 See Documentation/x86/boot.txt and
2594 Documentation/svga.txt.
2595 Use vga=ask for menu.
2596 This is actually a boot loader parameter; the value is
2597 passed to the kernel using a special protocol.
2599 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2600 size of <nn>. This can be used to increase the
2601 minimum size (128MB on x86). It can also be used to
2602 decrease the size and leave more room for directly
2605 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2608 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2611 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2614 vt.cur_default= [VT] Default cursor shape.
2615 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2616 the parameters of the <Esc>[?A;B;Cc escape sequence;
2617 see VGA-softcursor.txt. Default: 2 = underline.
2619 vt.default_blu= [VT]
2620 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2621 Change the default blue palette of the console.
2622 This is a 16-member array composed of values
2625 vt.default_grn= [VT]
2626 Format: <green0>,<green1>,<green2>,...,<green15>
2627 Change the default green palette of the console.
2628 This is a 16-member array composed of values
2631 vt.default_red= [VT]
2632 Format: <red0>,<red1>,<red2>,...,<red15>
2633 Change the default red palette of the console.
2634 This is a 16-member array composed of values
2640 Set system-wide default UTF-8 mode for all tty's.
2641 Default is 1, i.e. UTF-8 mode is enabled for all
2642 newly opened terminals.
2644 vt.global_cursor_default=
2647 Set system-wide default for whether a cursor
2648 is shown on new VTs. Default is -1,
2649 i.e. cursors will be created by default unless
2650 overridden by individual drivers. 0 will hide
2651 cursors, 1 will display them.
2653 watchdog timers [HW,WDT] For information on watchdog timers,
2654 see Documentation/watchdog/watchdog-parameters.txt
2655 or other driver-specific files in the
2656 Documentation/watchdog/ directory.
2658 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2659 default x2apic cluster mode on platforms
2662 x86_mrst_timer= [X86-32,APBT]
2663 Choose timer option for x86 Moorestown MID platform.
2664 Two valid options are apbt timer only and lapic timer
2665 plus one apbt timer for broadcast timer.
2666 x86_mrst_timer=apbt_only | lapic_and_apbt
2668 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2669 xd_geo= See header of drivers/block/xd.c.
2671 xen_emul_unplug= [HW,X86,XEN]
2672 Unplug Xen emulated devices
2673 Format: [unplug0,][unplug1]
2674 ide-disks -- unplug primary master IDE devices
2675 aux-ide-disks -- unplug non-primary-master IDE devices
2676 nics -- unplug network devices
2677 all -- unplug all emulated devices (NICs and IDE disks)
2678 unnecessary -- unplugging emulated devices is
2679 unnecessary even if the host did not respond to
2681 never -- do not unplug even if version check succeeds
2683 xirc2ps_cs= [NET,PCMCIA]
2685 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2687 ______________________________________________________________________
2691 Add more DRM drivers.
projects / mv-sheeva.git / blob