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_apic_instance= [ACPI, IOAPIC]
168 2: use 2nd APIC table, if available
169 1,0: use 1st APIC table
172 acpi_backlight= [HW,ACPI]
173 acpi_backlight=vendor
175 If set to vendor, prefer vendor specific driver
176 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
177 of the ACPI video.ko driver.
179 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
180 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
182 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
183 debug output. Bits in debug_layer correspond to a
184 _COMPONENT in an ACPI source file, e.g.,
185 #define _COMPONENT ACPI_PCI_COMPONENT
186 Bits in debug_level correspond to a level in
187 ACPI_DEBUG_PRINT statements, e.g.,
188 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
189 The debug_level mask defaults to "info". See
190 Documentation/acpi/debug.txt for more information about
191 debug layers and levels.
193 Enable processor driver info messages:
194 acpi.debug_layer=0x20000000
195 Enable PCI/PCI interrupt routing info messages:
196 acpi.debug_layer=0x400000
197 Enable AML "Debug" output, i.e., stores to the Debug
198 object while interpreting AML:
199 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
200 Enable all messages related to ACPI hardware:
201 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
203 Some values produce so much output that the system is
204 unusable. The "log_buf_len" parameter may be useful
205 if you need to capture more output.
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, 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 bulk_remove=off [PPC] This parameter disables the use of the pSeries
407 firmware feature for flushing multiple hpte entries
410 c101= [NET] Moxa C101 synchronous serial card
412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
420 [SECURITY] Disable capabilities. This would normally
421 be used only if an alternative security model is to be
422 configured. Potentially dangerous and should only be
423 used if you are entirely sure of the consequences.
425 ccw_timeout_log [S390]
426 See Documentation/s390/CommonIO for details.
428 cgroup_disable= [KNL] Disable a particular controller
429 Format: {name of the controller(s) to disable}
430 {Currently supported controllers - "memory"}
432 checkreqprot [SELINUX] Set initial checkreqprot flag value.
433 Format: { "0" | "1" }
434 See security/selinux/Kconfig help text.
435 0 -- check protection applied by kernel (includes
436 any implied execute protection).
437 1 -- check protection requested by application.
438 Default value is set via a kernel config option.
439 Value can be changed at runtime via
440 /selinux/checkreqprot.
443 See Documentation/s390/CommonIO for details.
445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
447 Forces specified clocksource (if available) to be used
448 when calculating gettimeofday(). If specified
449 clocksource is not available, it defaults to PIT.
450 Format: { pit | tsc | cyclone | pmtmr }
452 clocksource= Override the default clocksource
454 Override the default clocksource and use the clocksource
455 with the name specified.
456 Some clocksource names to choose from, depending on
458 [all] jiffies (this is the base, fallback clocksource)
460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461 pxa_timer,timer3,32k_counter,timer0_1
463 [X86-32] pit,hpet,tsc;
464 scx200_hrt on Geode; cyclone on IBM x440
472 clearcpuid=BITNUM [X86]
473 Disable CPUID feature X for the kernel. See
474 arch/x86/include/asm/cpufeature.h for the valid bit
475 numbers. Note the Linux specific bits are not necessarily
476 stable over kernel options, but the vendor specific
478 Also note that user programs calling CPUID directly
479 or using the feature without checking anything
480 will still see it. This just prevents it from
481 being used by the kernel or shown in /proc/cpuinfo.
482 Also note the kernel might malfunction if you disable
485 cmo_free_hint= [PPC] Format: { yes | no }
486 Specify whether pages are marked as being inactive
487 when they are freed. This is used in CMO environments
488 to determine OS memory pressure for page stealing by
492 code_bytes [X86] How many bytes of object code to print
497 com20020= [HW,NET] ARCnet - COM20020 chipset
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
525 Documentation/networking/netconsole.txt for an
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
538 For now, only VisioBraille is supported.
540 consoleblank= [KNL] The console blank (screen saver) timeout in
541 seconds. Defaults to 10*60 = 10mins. A value of 0
542 disables the blank timer.
545 [KNL] Change the default value for
546 /proc/<pid>/coredump_filter.
547 See also Documentation/filesystems/proc.txt.
549 cpuidle.off=1 [CPU_IDLE]
550 disable the cpuidle sub-system
552 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
554 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
556 crashkernel=size[KMG][@offset[KMG]]
557 [KNL] Using kexec, Linux can switch to a 'crash kernel'
558 upon panic. This parameter reserves the physical
559 memory region [offset, offset + size] for that kernel
560 image. If '@offset' is omitted, then a suitable offset
561 is selected automatically. Check
562 Documentation/kdump/kdump.txt for further details.
564 crashkernel=range1:size1[,range2:size2,...][@offset]
565 [KNL] Same as above, but depends on the memory
566 in the running system. The syntax of range is
567 start-[end] where start and end are both
568 a memory unit (amount[KMG]). See also
569 Documentation/kdump/kdump.txt for an example.
574 cs89x0_media= [HW,NET]
575 Format: { rj45 | aui | bnc }
578 See header of drivers/s390/block/dasd_devmap.c.
580 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
581 (one device per port)
582 Format: <port#>,<type>
583 See also Documentation/input/joystick-parport.txt
585 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
586 time. See Documentation/dynamic-debug-howto.txt for
589 debug [KNL] Enable kernel debugging (events log level).
592 [KNL] verbose self-tests
594 Print debugging info while doing the locking API
596 We default to 0 (no extra messages), setting it to
597 1 will print _a lot_ more information - normally
598 only useful to kernel developers.
600 debug_objects [KNL] Enable object debugging
603 [KNL] Disable object debugging
605 debugpat [X86] Enable PAT debugging
607 decnet.addr= [HW,NET]
608 Format: <area>[,<node>]
609 See also Documentation/networking/decnet.txt.
612 [same as hugepagesz=] The size of the default
613 HugeTLB page size. This is the size represented by
614 the legacy /proc/ hugepages APIs, used for SHM, and
615 default size when mounting hugetlbfs filesystems.
616 Defaults to the default architecture's huge page size
620 Set number of hash buckets for dentry cache.
623 IO parameters + enable/disable command.
625 digiepca= [HW,SERIAL]
626 See drivers/char/README.epca and
627 Documentation/serial/digiepca.txt.
630 See Documentation/networking/ipv6.txt.
632 disable_ddw [PPC/PSERIES]
633 Disable Dynamic DMA Window support. Use this if
634 to workaround buggy firmware.
637 See Documentation/networking/ipv6.txt.
639 disable_mtrr_cleanup [X86]
640 The kernel tries to adjust MTRR layout from continuous
641 to discrete, to make X server driver able to add WB
642 entry later. This parameter disables that.
644 disable_mtrr_trim [X86, Intel and AMD only]
645 By default the kernel will trim any uncacheable
646 memory out of your available memory pool based on
647 MTRR settings. This parameter disables that behavior,
648 possibly causing your machine to run very slowly.
650 disable_timer_pin_1 [X86]
651 Disable PIN 1 of APIC timer
652 Can be useful to work around chipset bugs.
654 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
655 this option disables the debugging code at boot.
657 dma_debug_entries=<number>
658 This option allows to tune the number of preallocated
659 entries for DMA-API debugging code. One entry is
660 required per DMA-API allocation. Use this if the
661 DMA-API debugging code disables itself because the
662 architectural default is too low.
664 dma_debug_driver=<driver_name>
665 With this option the DMA-API debugging driver
666 filter feature can be enabled at boot time. Just
667 pass the driver to filter for as the parameter.
668 The filter can be disabled or changed to another
669 driver later using sysfs.
673 earlycon= [KNL] Output early console device and options.
674 uart[8250],io,<addr>[,options]
675 uart[8250],mmio,<addr>[,options]
676 uart[8250],mmio32,<addr>[,options]
677 Start an early, polled-mode console on the 8250/16550
678 UART at the specified I/O port or MMIO address.
679 MMIO inter-register address stride is either 8bit (mmio)
681 The options are the same as for ttyS, above.
683 earlyprintk= [X86,SH,BLACKFIN]
685 earlyprintk=serial[,ttySn[,baudrate]]
686 earlyprintk=ttySn[,baudrate]
687 earlyprintk=dbgp[debugController#]
689 Append ",keep" to not disable it when the real console
692 Only vga or serial or usb debug port at a time.
694 Currently only ttyS0 and ttyS1 are supported.
696 Interaction with the standard serial driver is not
699 The VGA output is eventually overwritten by the real
702 ekgdboc= [X86,KGDB] Allow early kernel console debugging
705 This is designed to be used in conjunction with
706 the boot argument: earlyprintk=vga
709 Format: {"off" | "on" | "skip[mbr]"}
711 eisa_irq_edge= [PARISC,HW]
712 See header of drivers/parisc/eisa.c.
715 See comment before function elanfreq_setup() in
716 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
719 Format: {"cfq" | "deadline" | "noop"}
720 See Documentation/block/as-iosched.txt and
721 Documentation/block/deadline-iosched.txt for details.
723 elfcorehdr= [IA64,PPC,SH,X86]
724 Specifies physical address of start of kernel core
725 image elf header. Generally kexec loader will
726 pass this option to capture kernel.
727 See Documentation/kdump/kdump.txt for details.
729 enable_mtrr_cleanup [X86]
730 The kernel tries to adjust MTRR layout from continuous
731 to discrete, to make X server driver able to add WB
732 entry later. This parameter enables that.
734 enable_timer_pin_1 [X86]
735 Enable PIN 1 of APIC timer
736 Can be useful to work around chipset bugs
737 (in particular on some ATI chipsets).
738 The kernel tries to set a reasonable default.
740 enforcing [SELINUX] Set initial enforcing status.
742 See security/selinux/Kconfig help text.
743 0 -- permissive (log only, no denials).
744 1 -- enforcing (deny and log).
746 Value can be changed at runtime via /selinux/enforce.
749 Disable Error Record Serialization Table (ERST)
752 ether= [HW,NET] Ethernet cards parameters
753 This option is obsoleted by the "netdev=" option, which
754 has equivalent usage. See its documentation for details.
758 fail_make_request=[KNL]
759 General fault injection mechanism.
760 Format: <interval>,<probability>,<space>,<times>
761 See also /Documentation/fault-injection/.
764 See Documentation/blockdev/floppy.txt.
766 force_pal_cache_flush
767 [IA-64] Avoid check_sal_cache_flush which may hang on
768 buggy SAL_CACHE_FLUSH implementations. Using this
769 parameter will force ia64_sal_cache_flush to call
770 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
773 [FTRACE] will set and start the specified tracer
774 as early as possible in order to facilitate early
777 ftrace_dump_on_oops[=orig_cpu]
778 [FTRACE] will dump the trace buffers on oops.
779 If no parameter is passed, ftrace will dump
780 buffers of all CPUs, but if you pass orig_cpu, it will
781 dump only the buffer of the CPU that triggered the
784 ftrace_filter=[function-list]
785 [FTRACE] Limit the functions traced by the function
786 tracer at boot up. function-list is a comma separated
787 list of functions. This list can be changed at run
788 time by the set_ftrace_filter file in the debugfs
791 ftrace_notrace=[function-list]
792 [FTRACE] Do not trace the functions specified in
793 function-list. This list can be changed at run time
794 by the set_ftrace_notrace file in the debugfs
797 ftrace_graph_filter=[function-list]
798 [FTRACE] Limit the top level callers functions traced
799 by the function graph tracer at boot up.
800 function-list is a comma separated list of functions
801 that can be changed at run time by the
802 set_graph_function file in the debugfs tracing directory.
805 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
806 support via parallel port (up to 5 devices per port)
807 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
808 See also Documentation/input/joystick-parport.txt
812 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
816 gcov_persist= [GCOV] When non-zero (default), profiling data for
817 kernel modules is saved and remains accessible via
818 debugfs, even when the module is unloaded/reloaded.
819 When zero, profiling data is discarded and associated
820 debugfs files are removed at module unload time.
822 gpt [EFI] Forces disk with valid GPT signature but
823 invalid Protective MBR to be treated as GPT.
825 hashdist= [KNL,NUMA] Large hashes allocated during boot
826 are distributed across NUMA nodes. Defaults on
827 for 64bit NUMA, off otherwise.
828 Format: 0 | 1 (for off | on)
830 hcl= [IA-64] SGI's Hardware Graph compatibility layer
832 hd= [EIDE] (E)IDE hard drive subsystem geometry
833 Format: <cyl>,<head>,<sect>
836 Disable Hardware Error Source Table (HEST) support;
837 corresponding firmware-first mode error processing
838 logic will be disabled.
840 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
841 size of <nn>. This works even on boxes that have no
842 highmem otherwise. This also works to reduce highmem
843 size on bigger boxes.
845 highres= [KNL] Enable/disable high resolution timer mode.
846 Valid parameters: "on", "off"
850 See Documentation/isdn/README.HiSax.
854 hpet= [X86-32,HPET] option to control HPET usage
855 Format: { enable (default) | disable | force |
857 disable: disable HPET and use PIT instead
858 force: allow force enabled of undocumented chips (ICH4,
860 verbose: show contents of HPET registers during setup
862 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
863 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
864 On x86-64 and powerpc, this option can be specified
865 multiple times interleaved with hugepages= to reserve
866 huge pages of different sizes. Valid pages sizes on
867 x86-64 are 2M (when the CPU supports "pse") and 1G
868 (when the CPU supports the "pdpe1gb" cpuinfo flag)
869 Note that 1GB pages can only be allocated at boot time
870 using hugepages= and not freed afterwards.
872 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
873 terminal devices. Valid values: 0..8
874 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
875 If specified, z/VM IUCV HVC accepts connections
876 from listed z/VM user IDs only.
879 Do not unregister boot console at start. This is only
880 useful for debugging when something happens in the window
881 between unregistering the boot console and initializing
884 i2c_bus= [HW] Override the default board specific I2C bus speed
885 or register an additional I2C bus that is not
886 registered from board initialization code.
890 i8042.debug [HW] Toggle i8042 debug mode
891 i8042.direct [HW] Put keyboard port into non-translated mode
892 i8042.dumbkbd [HW] Pretend that controller can only read data from
893 keyboard and cannot control its state
894 (Don't attempt to blink the leds)
895 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
896 i8042.nokbd [HW] Don't check/create keyboard port
897 i8042.noloop [HW] Disable the AUX Loopback command while probing
899 i8042.nomux [HW] Don't check presence of an active multiplexing
901 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
903 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
904 i8042.reset [HW] Reset the controller during init and cleanup
905 i8042.unlock [HW] Unlock (ignore) the keylock
909 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
910 indicates that the driver is running on unsupported
912 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
913 does not match list of supported models.
915 [HW] Report power status in /proc/i8k
916 (disabled by default)
917 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
921 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
923 ide-core.nodma= [HW] (E)IDE subsystem
924 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
925 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
926 .cdrom .chs .ignore_cable are additional options
927 See Documentation/ide/ide.txt.
929 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
930 Claim all unknown PCI IDE storage controllers.
933 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
934 Poll forces a polling idle loop that can slightly
935 improve the performance of waking up a idle CPU, but
936 will use a lot of power and make the system run hot.
938 idle=mwait: On systems which support MONITOR/MWAIT but
939 the kernel chose to not use it because it doesn't save
940 as much power as a normal idle loop, use the
941 MONITOR/MWAIT idle loop anyways. Performance should be
942 the same as idle=poll.
943 idle=halt: Halt is forced to be used for CPU idle.
944 In such case C2/C3 won't be used again.
945 idle=nomwait: Disable mwait for CPU C-states
947 ignore_loglevel [KNL]
948 Ignore loglevel setting - this will print /all/
949 kernel messages to the console. Useful for debugging.
952 Set number of hash buckets for inode cache.
955 Format: { "0" | "1" }
956 0 -- integrity auditing messages. (Default)
957 1 -- enable informational integrity auditing messages.
960 Format: { "sha1" | "md5" }
964 Load a policy which meets the needs of the Trusted
965 Computing Base. This means IMA will measure all
966 programs exec'd, files mmap'd for exec, and all files
967 opened for read by uid=0.
971 Run specified binary instead of /sbin/init as init
974 initcall_debug [KNL] Trace initcalls as they are executed. Useful
975 for working out where the kernel is dying during
978 initrd= [BOOT] Specify the location of the initial ramdisk
980 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
983 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
985 Enable intel iommu driver.
987 Disable intel iommu driver.
988 igfx_off [Default Off]
989 By default, gfx is mapped as normal device. If a gfx
990 device has a dedicated DMAR unit, the DMAR unit is
991 bypassed by not enabling DMAR with this option. In
992 this case, gfx device will use physical address for
995 With this option iommu will not optimize to look
996 for io virtual address below 32 bit forcing dual
997 address cycle on pci bus for cards supporting greater
998 than 32 bit addressing. The default is to look
999 for translation below 32 bit and if not available
1000 then look in the higher range.
1001 strict [Default Off]
1002 With this option on every unmap_single operation will
1003 result in a hardware IOTLB flush operation as opposed
1004 to batching them for performance.
1005 sp_off [Default Off]
1006 By default, super page will be supported if Intel IOMMU
1007 has the capability. With this option, super page will
1009 intremap= [X86-64, Intel-IOMMU]
1010 Format: { on (default) | off | nosid }
1011 on enable Interrupt Remapping (default)
1012 off disable Interrupt Remapping
1013 nosid disable Source ID checking
1017 iomem= Disable strict checking of access to MMIO memory
1018 strict regions from userspace.
1034 io7= [HW] IO7 for Marvel based alpha systems
1035 See comment before marvel_specify_io7 in
1036 arch/alpha/kernel/core_marvel.c.
1038 io_delay= [X86] I/O delay method
1040 Standard port 0x80 based delay
1042 Alternate port 0xed based delay (needed on some systems)
1044 Simple two microseconds delay
1049 See Documentation/filesystems/nfs/nfsroot.txt.
1051 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1052 See comment before ip2_setup() in
1053 drivers/char/ip2/ip2base.c.
1056 When an interrupt is not handled search all handlers
1057 for it. Intended to get systems with badly broken
1061 When an interrupt is not handled search all handlers
1062 for it. Also check all handlers each timer
1063 interrupt. Intended to get systems with badly broken
1067 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1069 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1071 <cpu number>,...,<cpu number>
1073 <cpu number>-<cpu number>
1074 (must be a positive range in ascending order)
1076 <cpu number>,...,<cpu number>-<cpu number>
1078 This option can be used to specify one or more CPUs
1079 to isolate from the general SMP balancing and scheduling
1080 algorithms. You can move a process onto or off an
1081 "isolated" CPU via the CPU affinity syscalls or cpuset.
1082 <cpu number> begins at 0 and the maximum value is
1083 "number of CPUs in system - 1".
1085 This option is the preferred way to isolate CPUs. The
1086 alternative -- manually setting the CPU mask of all
1087 tasks in the system -- can cause problems and
1088 suboptimal load balancer performance.
1092 js= [HW,JOY] Analog joystick
1093 See Documentation/input/joystick.txt.
1097 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1098 specifies the amount of memory usable by the kernel
1099 for non-movable allocations. The requested amount is
1100 spread evenly throughout all nodes in the system. The
1101 remaining memory in each node is used for Movable
1102 pages. In the event, a node is too small to have both
1103 kernelcore and Movable pages, kernelcore pages will
1104 take priority and other nodes will have a larger number
1105 of kernelcore pages. The Movable zone is used for the
1106 allocation of pages that may be reclaimed or moved
1107 by the page migration subsystem. This means that
1108 HugeTLB pages may not be allocated from this zone.
1109 Note that allocations like PTEs-from-HighMem still
1110 use the HighMem zone if it exists, and the Normal
1111 zone if it does not.
1113 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1114 Format: <Controller#>[,poll interval]
1115 The controller # is the number of the ehci usb debug
1116 port as it is probed via PCI. The poll interval is
1117 optional and is the number seconds in between
1118 each poll cycle to the debug port in case you need
1119 the functionality for interrupting the kernel with
1120 gdb or control-c on the dbgp connection. When
1121 not using this parameter you use sysrq-g to break into
1122 the kernel debugger.
1124 kgdboc= [KGDB,HW] kgdb over consoles.
1125 Requires a tty driver that supports console polling,
1126 or a supported polling keyboard driver (non-usb).
1127 Serial only format: <serial_device>[,baud]
1128 keyboard only format: kbd
1129 keyboard and serial format: kbd,<serial_device>[,baud]
1130 Optional Kernel mode setting:
1131 kms, kbd format: kms,kbd
1132 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1134 kgdbwait [KGDB] Stop kernel execution and enter the
1135 kernel debugger at the earliest opportunity.
1137 kmac= [MIPS] korina ethernet MAC address.
1138 Configure the RouterBoard 532 series on-chip
1139 Ethernet adapter MAC address.
1141 kmemleak= [KNL] Boot-time kmemleak enable/disable
1142 Valid arguments: on, off
1145 kstack=N [X86] Print N words from the kernel stack
1148 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1149 Default is 0 (don't ignore, but inject #GP)
1151 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1152 Default is 1 (enabled)
1154 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1158 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1159 Default is 1 (enabled)
1161 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1163 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1165 kvm-intel.bypass_guest_pf=
1166 [KVM,Intel] Disables bypassing of guest page faults
1167 on Intel chips. Default is 1 (enabled)
1169 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1170 (virtualized MMU) support on capable Intel chips.
1171 Default is 1 (enabled)
1173 kvm-intel.emulate_invalid_guest_state=
1174 [KVM,Intel] Enable emulation of invalid guest states
1175 Default is 0 (disabled)
1177 kvm-intel.flexpriority=
1178 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1179 Default is 1 (enabled)
1181 kvm-intel.unrestricted_guest=
1182 [KVM,Intel] Disable unrestricted guest feature
1183 (virtualized real and unpaged mode) on capable
1184 Intel chips. Default is 1 (enabled)
1186 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1187 feature (tagged TLBs) on capable Intel chips.
1188 Default is 1 (enabled)
1194 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1197 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1200 libata.dma= [LIBATA] DMA control
1201 libata.dma=0 Disable all PATA and SATA DMA
1202 libata.dma=1 PATA and SATA Disk DMA only
1203 libata.dma=2 ATAPI (CDROM) DMA only
1204 libata.dma=4 Compact Flash DMA only
1205 Combinations also work, so libata.dma=3 enables DMA
1206 for disks and CDROMs, but not CFs.
1208 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1209 libata.ignore_hpa=0 keep BIOS limits (default)
1210 libata.ignore_hpa=1 ignore limits, using full disk
1212 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1216 libata.force= [LIBATA] Force configurations. The format is comma
1217 separated list of "[ID:]VAL" where ID is
1218 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1219 matching port, link or device. Basically, it matches
1220 the ATA ID string printed on console by libata. If
1221 the whole ID part is omitted, the last PORT and DEVICE
1222 values are used. If ID hasn't been specified yet, the
1223 configuration applies to all ports, links and devices.
1225 If only DEVICE is omitted, the parameter applies to
1226 the port and all links and devices behind it. DEVICE
1227 number of 0 either selects the first device or the
1228 first fan-out link behind PMP device. It does not
1229 select the host link. DEVICE number of 15 selects the
1230 host link and device attached to it.
1232 The VAL specifies the configuration to force. As long
1233 as there's no ambiguity shortcut notation is allowed.
1234 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1235 The following configurations can be forced.
1237 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1238 Any ID with matching PORT is used.
1240 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1242 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1243 udma[/][16,25,33,44,66,100,133] notation is also
1246 * [no]ncq: Turn on or off NCQ.
1248 * nohrst, nosrst, norst: suppress hard, soft
1251 * dump_id: dump IDENTIFY data.
1253 If there are multiple matching configurations changing
1254 the same attribute, the last one is used.
1256 memblock=debug [KNL] Enable memblock debug messages.
1258 load_ramdisk= [RAM] List of ramdisks to load from floppy
1259 See Documentation/blockdev/ramdisk.txt.
1261 lockd.nlm_grace_period=P [NFS] Assign grace period.
1264 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1267 lockd.nlm_timeout=T [NFS] Assign timeout value.
1270 lockd.nlm_udpport=M [NFS] Assign UDP port.
1273 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1276 loglevel= All Kernel Messages with a loglevel smaller than the
1277 console loglevel will be printed to the console. It can
1278 also be changed with klogd or other programs. The
1279 loglevels are defined as follows:
1281 0 (KERN_EMERG) system is unusable
1282 1 (KERN_ALERT) action must be taken immediately
1283 2 (KERN_CRIT) critical conditions
1284 3 (KERN_ERR) error conditions
1285 4 (KERN_WARNING) warning conditions
1286 5 (KERN_NOTICE) normal but significant condition
1287 6 (KERN_INFO) informational
1288 7 (KERN_DEBUG) debug-level messages
1290 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1291 in bytes. n must be a power of two. The default
1292 size is set in the kernel config file.
1294 logo.nologo [FB] Disables display of the built-in Linux logo.
1295 This may be used to provide more screen space for
1296 kernel log messages and is useful when debugging
1297 kernel boot problems.
1299 lp=0 [LP] Specify parallel ports to use, e.g,
1300 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1301 lp=reset first parallel port). 'lp=0' disables the
1302 lp=auto printer driver. 'lp=reset' (which can be
1303 specified in addition to the ports) causes
1304 attached printers to be reset. Using
1305 lp=port1,port2,... specifies the parallel ports
1306 to associate lp devices with, starting with
1307 lp0. A port specification may be 'none' to skip
1308 that lp device, or a parport name such as
1309 'parport0'. Specifying 'lp=auto' instead of a
1310 port specification list means that device IDs
1311 from each port should be examined, to see if
1312 an IEEE 1284-compliant printer is attached; if
1313 so, the driver will manage that printer.
1314 See also header of drivers/char/lp.c.
1317 Sets loops_per_jiffy to given constant, thus avoiding
1318 time-consuming boot-time autodetection (up to 250 ms per
1319 CPU). 0 enables autodetection (default). To determine
1320 the correct value for your kernel, boot with normal
1321 autodetection and see what value is printed. Note that
1322 on SMP systems the preset will be applied to all CPUs,
1323 which is likely to cause problems if your CPUs need
1324 significantly divergent settings. An incorrect value
1325 will cause delays in the kernel to be wrong, leading to
1326 unpredictable I/O errors and other breakage. Although
1327 unlikely, in the extreme case this might damage your
1331 Format: <io>,<irq>,<dma>
1333 machvec= [IA64] Force the use of a particular machine-vector
1334 (machvec) in a generic kernel.
1335 Example: machvec=hpzx1_swiotlb
1337 machtype= [Loongson] Share the same kernel image file between different
1339 Example: machtype=lemote-yeeloong-2f-7inch
1341 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1342 than or equal to this physical address is ignored.
1344 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1345 should make use of. maxcpus=n : n >= 0 limits the
1346 kernel to using 'n' processors. n=0 is a special case,
1347 it is equivalent to "nosmp", which also disables
1350 max_loop= [LOOP] Maximum number of loopback devices that can
1356 mce [X86-32] Machine Check Exception
1358 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1360 md= [HW] RAID subsystems devices and level
1361 See Documentation/md.txt.
1364 Format: <first>,<last>
1365 Specifies range of consoles to be captured by the MDA.
1367 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1368 Amount of memory to be used when the kernel is not able
1369 to see the whole system memory or for test.
1370 [X86-32] Use together with memmap= to avoid physical
1371 address space collisions. Without memmap= PCI devices
1372 could be placed at addresses belonging to unused RAM.
1374 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1378 [KNL,SH] Allow user to override the default size for
1379 per-device physically contiguous DMA buffers.
1381 memmap=exactmap [KNL,X86] Enable setting of an exact
1382 E820 memory map, as specified by the user.
1383 Such memmap=exactmap lines can be constructed based on
1384 BIOS output or other requirements. See the memmap=nn@ss
1387 memmap=nn[KMG]@ss[KMG]
1388 [KNL] Force usage of a specific region of memory
1389 Region of memory to be used, from ss to ss+nn.
1391 memmap=nn[KMG]#ss[KMG]
1392 [KNL,ACPI] Mark specific memory as ACPI data.
1393 Region of memory to be used, from ss to ss+nn.
1395 memmap=nn[KMG]$ss[KMG]
1396 [KNL,ACPI] Mark specific memory as reserved.
1397 Region of memory to be used, from ss to ss+nn.
1398 Example: Exclude memory from 0x18690000-0x1869ffff
1399 memmap=64K$0x18690000
1401 memmap=0x10000$0x18690000
1403 memory_corruption_check=0/1 [X86]
1404 Some BIOSes seem to corrupt the first 64k of
1405 memory when doing things like suspend/resume.
1406 Setting this option will scan the memory
1407 looking for corruption. Enabling this will
1408 both detect corruption and prevent the kernel
1409 from using the memory being corrupted.
1410 However, its intended as a diagnostic tool; if
1411 repeatable BIOS-originated corruption always
1412 affects the same memory, you can use memmap=
1413 to prevent the kernel from using that memory.
1415 memory_corruption_check_size=size [X86]
1416 By default it checks for corruption in the low
1417 64k, making this memory unavailable for normal
1418 use. Use this parameter to scan for
1419 corruption in more or less memory.
1421 memory_corruption_check_period=seconds [X86]
1422 By default it checks for corruption every 60
1423 seconds. Use this parameter to check at some
1424 other rate. 0 disables periodic checking.
1426 memtest= [KNL,X86] Enable memtest
1428 default : 0 <disable>
1429 Specifies the number of memtest passes to be
1430 performed. Each pass selects another test
1431 pattern from a given set of patterns. Memtest
1432 fills the memory with this pattern, validates
1433 memory contents and reserves bad memory
1434 regions that are detected.
1436 meye.*= [HW] Set MotionEye Camera parameters
1437 See Documentation/video4linux/meye.txt.
1439 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1440 Multi-Function General Purpose Timers on AMD Geode
1443 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1444 the BIOS has incorrectly applied a workaround. TinyBIOS
1445 version 0.98 is known to be affected, 0.99 fixes the
1446 problem by letting the user disable the workaround.
1450 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1451 physical address is ignored.
1453 mini2440= [ARM,HW,KNL]
1454 Format:[0..2][b][c][t]
1456 MINI2440 configuration specification:
1457 0 - The attached screen is the 3.5" TFT
1458 1 - The attached screen is the 7" TFT
1459 2 - The VGA Shield is attached (1024x768)
1460 Leaving out the screen size parameter will not load
1461 the TFT driver, and the framebuffer will be left
1463 b - Enable backlight. The TFT backlight pin will be
1464 linked to the kernel VESA blanking code and a GPIO
1465 LED. This parameter is not necessary when using the
1467 c - Enable the s3c camera interface.
1468 t - Reserved for enabling touchscreen support. The
1469 touchscreen support is not enabled in the mainstream
1470 kernel as of 2.6.30, a preliminary port can be found
1471 in the "bleeding edge" mini2440 support kernel at
1472 http://repo.or.cz/w/linux-2.6/mini2440.git
1475 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1476 parameter allows control of the logging verbosity for
1477 the additional memory initialisation checks. A value
1478 of 0 disables mminit logging and a level of 4 will
1479 log everything. Information is printed at KERN_DEBUG
1480 so loglevel=8 may also need to be specified.
1483 [MOUSE] Maximum time between finger touching and
1484 leaving touchpad surface for touch to be considered
1485 a tap and be reported as a left button click (for
1486 touchpads working in absolute mode only).
1488 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1489 reporting absolute coordinates, such as tablets
1490 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1491 reporting absolute coordinates, such as tablets
1493 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1494 is similar to kernelcore except it specifies the
1495 amount of memory used for migratable allocations.
1496 If both kernelcore and movablecore is specified,
1497 then kernelcore will be at *least* the specified
1498 value but may be more. If movablecore on its own
1499 is specified, the administrator must be careful
1500 that the amount of memory usable for all allocations
1503 MTD_Partition= [MTD]
1504 Format: <name>,<region-number>,<size>,<offset>
1506 MTD_Region= [MTD] Format:
1507 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1510 See drivers/mtd/cmdlinepart.c.
1512 multitce=off [PPC] This parameter disables the use of the pSeries
1513 firmware feature for updating multiple TCE entries
1516 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1518 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1520 boundary - index of last SLC block on Flex-OneNAND.
1521 The remaining blocks are configured as MLC blocks.
1522 lock - Configure if Flex-OneNAND boundary should be locked.
1523 Once locked, the boundary cannot be changed.
1524 1 indicates lock status, 0 indicates unlock status.
1527 ARM/S3C2412 JIVE boot control
1529 See arch/arm/mach-s3c2412/mach-jive.c
1531 mtouchusb.raw_coordinates=
1532 [HW] Make the MicroTouch USB driver use raw coordinates
1533 ('y', default) or cooked coordinates ('n')
1535 mtrr_chunk_size=nn[KMG] [X86]
1536 used for mtrr cleanup. It is largest continuous chunk
1537 that could hold holes aka. UC entries.
1539 mtrr_gran_size=nn[KMG] [X86]
1540 Used for mtrr cleanup. It is granularity of mtrr block.
1542 Large value could prevent small alignment from
1545 mtrr_spare_reg_nr=n [X86]
1547 Range: 0,7 : spare reg number
1549 Used for mtrr cleanup. It is spare mtrr entries number.
1550 Set to 2 or more if your graphical card needs more.
1552 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1554 netdev= [NET] Network devices parameters
1555 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1556 Note that mem_start is often overloaded to mean
1557 something different and driver-specific.
1558 This usage is only documented in each driver source
1562 [NETFILTER] Enable connection tracking flow accounting
1563 0 to disable accounting
1564 1 to enable accounting
1567 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1568 See Documentation/filesystems/nfs/nfsroot.txt.
1570 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1571 See Documentation/filesystems/nfs/nfsroot.txt.
1573 nfsrootdebug [NFS] enable nfsroot debugging messages.
1574 See Documentation/filesystems/nfs/nfsroot.txt.
1576 nfs.callback_tcpport=
1577 [NFS] set the TCP port on which the NFSv4 callback
1578 channel should listen.
1581 [NFS] sets the pathname to the program which is used
1582 to update the NFS client cache entries.
1584 nfs.cache_getent_timeout=
1585 [NFS] sets the timeout after which an attempt to
1586 update a cache entry is deemed to have failed.
1588 nfs.idmap_cache_timeout=
1589 [NFS] set the maximum lifetime for idmapper cache
1593 [NFS] enable 64-bit inode numbers.
1594 If zero, the NFS client will fake up a 32-bit inode
1595 number for the readdir() and stat() syscalls instead
1596 of returning the full 64-bit number.
1597 The default is to return 64-bit inode numbers.
1599 nfs.nfs4_disable_idmapping=
1600 [NFSv4] When set, this option disables the NFSv4
1601 idmapper on the client, but only if the mount
1602 is using the 'sec=sys' security flavour. This may
1603 make migration from legacy NFSv2/v3 systems easier
1604 provided that the server has the appropriate support.
1605 The default is to always enable NFSv4 idmapping.
1607 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1608 when a NMI is triggered.
1609 Format: [state][,regs][,debounce][,die]
1611 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1612 Format: [panic,][nopanic,][num]
1614 0 - turn nmi_watchdog off
1615 When panic is specified, panic when an NMI watchdog
1616 timeout occurs (or 'nopanic' to override the opposite
1618 This is useful when you use a panic=... timeout and
1619 need the box quickly up again.
1621 netpoll.carrier_timeout=
1622 [NET] Specifies amount of time (in seconds) that
1623 netpoll should wait for a carrier. By default netpoll
1626 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1627 emulation library even if a 387 maths coprocessor
1631 [HW] Never suspend the console
1632 Disable suspending of consoles during suspend and
1633 hibernate operations. Once disabled, debugging
1634 messages can reach various consoles while the rest
1635 of the system is being put to sleep (ie, while
1636 debugging driver suspend/resume hooks). This may
1637 not work reliably with all consoles, but is known
1638 to work with serial and VGA consoles.
1640 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1641 caches in the slab allocator. Saves per-node memory,
1642 but will impact performance.
1646 noapic [SMP,APIC] Tells the kernel to not make use of any
1647 IOAPICs that may be present in the system.
1649 noautogroup Disable scheduler automatic task group creation.
1651 nobats [PPC] Do not use BATs for mapping kernel lowmem
1652 on "Classic" PPC cores.
1656 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1658 nodelayacct [KNL] Disable per-task delay accounting
1660 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1662 nodsp [SH] Disable hardware DSP at boot time.
1664 noefi [X86] Disable EFI runtime services support.
1669 On X86-32 available only on PAE configured kernels.
1670 noexec=on: enable non-executable mappings (default)
1671 noexec=off: disable non-executable mappings
1674 Disable SMEP (Supervisor Mode Execution Protection)
1675 even if it is supported by processor.
1678 This affects only 32-bit executables.
1679 noexec32=on: enable non-executable mappings (default)
1680 read doesn't imply executable mappings
1681 noexec32=off: disable non-executable mappings
1682 read implies executable mappings
1684 nofpu [SH] Disable hardware FPU at boot time.
1686 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1687 register save and restore. The kernel will only save
1688 legacy floating-point registers on task switch.
1690 noxsave [BUGS=X86] Disables x86 extended register state save
1691 and restore using xsave. The kernel will fallback to
1692 enabling legacy floating-point and sse state.
1694 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1695 wfi(ARM) instruction doesn't work correctly and not to
1696 use it. This is also useful when using JTAG debugger.
1698 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1699 instruction doesn't work correctly and not to
1702 no_file_caps Tells the kernel not to honor file capabilities. The
1703 only way then for a file to be executed with privilege
1704 is to be setuid root or executed by root.
1706 nohalt [IA-64] Tells the kernel not to use the power saving
1707 function PAL_HALT_LIGHT when idle. This increases
1708 power-consumption. On the positive side, it reduces
1709 interrupt wake-up latency, which may improve performance
1710 in certain environments such as networked servers or
1713 nohz= [KNL] Boottime enable/disable dynamic ticks
1714 Valid arguments: on, off
1717 noiotrap [SH] Disables trapped I/O port accesses.
1719 noirqdebug [X86-32] Disables the code which attempts to detect and
1720 disable unhandled interrupt sources.
1722 no_timer_check [X86,APIC] Disables the code which tests for
1723 broken timer IRQ sources.
1725 noisapnp [ISAPNP] Disables ISA PnP code.
1727 noinitrd [RAM] Tells the kernel not to load any configured
1730 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1732 [Deprecated - use intremap=off]
1736 nojitter [IA64] Disables jitter checking for ITC timers.
1738 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1740 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1743 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1745 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1747 noltlbs [PPC] Do not use large page/tlb entries for kernel
1748 lowmem mapping on PPC40x.
1750 nomca [IA-64] Disable machine check abort handling
1752 nomce [X86-32] Machine Check Exception
1754 nomfgpt [X86-32] Disable Multi-Function General Purpose
1755 Timer usage (for AMD Geode machines).
1757 nopat [X86] Disable PAT (page attribute table extension of
1758 pagetables) support.
1760 norandmaps Don't use address space randomization. Equivalent to
1761 echo 0 > /proc/sys/kernel/randomize_va_space
1763 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1765 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1766 with UP alternatives
1768 noresidual [PPC] Don't use residual data on PReP machines.
1770 noresume [SWSUSP] Disables resume and restores original swap
1773 no-scroll [VGA] Disables scrollback.
1774 This is required for the Braillex ib80-piezo Braille
1775 reader made by F.H. Papenmeier (Germany).
1779 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1781 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1782 and disable the IO APIC. legacy for "maxcpus=0".
1784 nosoftlockup [KNL] Disable the soft-lockup detector.
1786 nosync [HW,M68K] Disables sync negotiation for all devices.
1788 notsc [BUGS=X86-32] Disable Time Stamp Counter
1790 nousb [USB] Disable the USB subsystem
1792 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1796 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1798 nptcg= [IA64] Override max number of concurrent global TLB
1799 purges which is reported from either PAL_VM_SUMMARY or
1802 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1803 could support. nr_cpus=n : n >= 1 limits the kernel to
1804 supporting 'n' processors. Later in runtime you can not
1805 use hotplug cpu feature to put more cpu back to online.
1806 just like you compile the kernel NR_CPUS=n
1808 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1810 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1811 one of ['zone', 'node', 'default'] can be specified
1812 This can be set from sysctl after boot.
1813 See Documentation/sysctl/vm.txt for details.
1815 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1816 See Documentation/debugging-via-ohci1394.txt for more
1819 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1820 Rather than timing out after 20 ms if an EC
1821 command is not properly ACKed, override the length
1822 of the timeout. We have interrupts disabled while
1823 waiting for the ACK, so if this is set too high
1824 interrupts *may* be lost!
1826 omap_mux= [OMAP] Override bootloader pin multiplexing.
1827 Format: <mux_mode0.mode_name=value>...
1828 For example, to override I2C bus2:
1829 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1831 oprofile.timer= [HW]
1832 Use timer interrupt instead of performance counters
1834 oprofile.cpu_type= Force an oprofile cpu type
1835 This might be useful if you have an older oprofile
1836 userland or if you want common events.
1837 Format: { arch_perfmon }
1838 arch_perfmon: [X86] Force use of architectural
1839 perfmon on Intel CPUs instead of the
1840 CPU specific event set.
1842 oops=panic Always panic on oopses. Default is to just kill the
1843 process, but there is a small probability of
1844 deadlocking the machine.
1845 This will also cause panics on machine check exceptions.
1846 Useful together with panic=30 to trigger a reboot.
1849 See Documentation/sound/oss/oss-parameters.txt
1851 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1852 seconds before rebooting
1855 parkbd.port= [HW] Parallel port number the keyboard adapter is
1856 connected to, default is 0.
1858 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1859 0 for XT, 1 for AT (default is AT).
1862 parport= [HW,PPT] Specify parallel ports. 0 disables.
1863 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1864 Use 'auto' to force the driver to use any
1865 IRQ/DMA settings detected (the default is to
1866 ignore detected IRQ/DMA settings because of
1867 possible conflicts). You can specify the base
1868 address, IRQ, and DMA settings; IRQ and DMA
1869 should be numbers, or 'auto' (for using detected
1870 settings on that particular port), or 'nofifo'
1871 (to avoid using a FIFO even if it is detected).
1872 Parallel ports are assigned in the order they
1873 are specified on the command line, starting
1876 parport_init_mode= [HW,PPT]
1877 Configure VIA parallel port to operate in
1878 a specific mode. This is necessary on Pegasos
1879 computer where firmware has no options for setting
1880 up parallel port mode and sets it to spp.
1881 Currently this function knows 686a and 8231 chips.
1882 Format: [spp|ps2|epp|ecp|ecpepp]
1885 Halt all CPUs after the first oops has been printed for
1886 the specified number of seconds. This is to be used if
1887 your oopses keep scrolling off the screen.
1892 See header of drivers/block/paride/pcd.c.
1893 See also Documentation/blockdev/paride.txt.
1895 pci=option[,option...] [PCI] various PCI subsystem options:
1896 earlydump [X86] dump PCI config space before the kernel
1898 off [X86] don't probe for the PCI bus
1899 bios [X86-32] force use of PCI BIOS, don't access
1900 the hardware directly. Use this if your machine
1901 has a non-standard PCI host bridge.
1902 nobios [X86-32] disallow use of PCI BIOS, only direct
1903 hardware access methods are allowed. Use this
1904 if you experience crashes upon bootup and you
1905 suspect they are caused by the BIOS.
1906 conf1 [X86] Force use of PCI Configuration
1908 conf2 [X86] Force use of PCI Configuration
1910 noaer [PCIE] If the PCIEAER kernel config parameter is
1911 enabled, this kernel boot option can be used to
1912 disable the use of PCIE advanced error reporting.
1913 nodomains [PCI] Disable support for multiple PCI
1914 root domains (aka PCI segments, in ACPI-speak).
1915 nommconf [X86] Disable use of MMCONFIG for PCI
1917 check_enable_amd_mmconf [X86] check for and enable
1918 properly configured MMIO access to PCI
1919 config space on AMD family 10h CPU
1920 nomsi [MSI] If the PCI_MSI kernel config parameter is
1921 enabled, this kernel boot option can be used to
1922 disable the use of MSI interrupts system-wide.
1923 noioapicquirk [APIC] Disable all boot interrupt quirks.
1924 Safety option to keep boot IRQs enabled. This
1925 should never be necessary.
1926 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1927 primary IO-APIC for bridges that cannot disable
1928 boot IRQs. This fixes a source of spurious IRQs
1929 when the system masks IRQs.
1930 noioapicreroute [APIC] Disable workaround that uses the
1931 boot IRQ equivalent of an IRQ that connects to
1932 a chipset where boot IRQs cannot be disabled.
1933 The opposite of ioapicreroute.
1934 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1935 routing table. These calls are known to be buggy
1936 on several machines and they hang the machine
1937 when used, but on other computers it's the only
1938 way to get the interrupt routing table. Try
1939 this option if the kernel is unable to allocate
1940 IRQs or discover secondary PCI buses on your
1942 rom [X86] Assign address space to expansion ROMs.
1943 Use with caution as certain devices share
1944 address decoders between ROMs and other
1946 norom [X86] Do not assign address space to
1947 expansion ROMs that do not already have
1948 BIOS assigned address ranges.
1949 nobar [X86] Do not assign address space to the
1950 BARs that weren't assigned by the BIOS.
1951 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1952 assigned automatically to PCI devices. You can
1953 make the kernel exclude IRQs of your ISA cards
1955 pirqaddr=0xAAAAA [X86] Specify the physical address
1956 of the PIRQ table (normally generated
1957 by the BIOS) if it is outside the
1958 F0000h-100000h range.
1959 lastbus=N [X86] Scan all buses thru bus #N. Can be
1960 useful if the kernel is unable to find your
1961 secondary buses and you want to tell it
1962 explicitly which ones they are.
1963 assign-busses [X86] Always assign all PCI bus
1964 numbers ourselves, overriding
1965 whatever the firmware may have done.
1966 usepirqmask [X86] Honor the possible IRQ mask stored
1967 in the BIOS $PIR table. This is needed on
1968 some systems with broken BIOSes, notably
1969 some HP Pavilion N5400 and Omnibook XE3
1970 notebooks. This will have no effect if ACPI
1971 IRQ routing is enabled.
1972 noacpi [X86] Do not use ACPI for IRQ routing
1973 or for PCI scanning.
1974 use_crs [X86] Use PCI host bridge window information
1975 from ACPI. On BIOSes from 2008 or later, this
1976 is enabled by default. If you need to use this,
1977 please report a bug.
1978 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1979 If you need to use this, please report a bug.
1980 routeirq Do IRQ routing for all PCI devices.
1981 This is normally done in pci_enable_device(),
1982 so this option is a temporary workaround
1983 for broken drivers that don't call it.
1984 skip_isa_align [X86] do not align io start addr, so can
1985 handle more pci cards
1986 firmware [ARM] Do not re-enumerate the bus but instead
1987 just use the configuration from the
1988 bootloader. This is currently used on
1989 IXP2000 systems where the bus has to be
1990 configured a certain way for adjunct CPUs.
1991 noearly [X86] Don't do any early type 1 scanning.
1992 This might help on some broken boards which
1993 machine check when some devices' config space
1994 is read. But various workarounds are disabled
1995 and some IOMMU drivers will not work.
1996 bfsort Sort PCI devices into breadth-first order.
1997 This sorting is done to get a device
1998 order compatible with older (<= 2.4) kernels.
1999 nobfsort Don't sort PCI devices into breadth-first order.
2000 cbiosize=nn[KMG] The fixed amount of bus space which is
2001 reserved for the CardBus bridge's IO window.
2002 The default value is 256 bytes.
2003 cbmemsize=nn[KMG] The fixed amount of bus space which is
2004 reserved for the CardBus bridge's memory
2005 window. The default value is 64 megabytes.
2008 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2009 Specifies alignment and device to reassign
2010 aligned memory resources.
2011 If <order of align> is not specified,
2012 PAGE_SIZE is used as alignment.
2013 PCI-PCI bridge can be specified, if resource
2014 windows need to be expanded.
2015 ecrc= Enable/disable PCIe ECRC (transaction layer
2016 end-to-end CRC checking).
2017 bios: Use BIOS/firmware settings. This is the
2021 realloc reallocate PCI resources if allocations done by BIOS
2024 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2027 force Enable ASPM even on devices that claim not to support it.
2028 WARNING: Forcing ASPM on may cause system lockups.
2030 pcie_ports= [PCIE] PCIe ports handling:
2031 auto Ask the BIOS whether or not to use native PCIe services
2032 associated with PCIe ports (PME, hot-plug, AER). Use
2033 them only if that is allowed by the BIOS.
2034 native Use native PCIe services associated with PCIe ports
2036 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2039 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2040 nomsi Do not use MSI for native PCIe PME signaling (this makes
2041 all PCIe root ports use INTx for all services).
2043 pcmv= [HW,PCMCIA] BadgePAD 4
2046 See Documentation/blockdev/paride.txt.
2048 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2051 See arch/parisc/kernel/pdc_chassis.c
2053 percpu_alloc= Select which percpu first chunk allocator to use.
2054 Currently supported values are "embed" and "page".
2055 Archs may support subset or none of the selections.
2056 See comments in mm/percpu.c for details on each
2057 allocator. This parameter is primarily for debugging
2058 and performance comparison.
2061 See Documentation/blockdev/paride.txt.
2064 See Documentation/blockdev/paride.txt.
2066 pirq= [SMP,APIC] Manual mp-table setup
2067 See Documentation/x86/i386/IO-APIC.txt.
2069 plip= [PPT,NET] Parallel port network link
2070 Format: { parport<nr> | timid | 0 }
2071 See also Documentation/parport.txt.
2073 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2074 Override pmtimer IOPort with a hex value.
2078 Enable PNP debug messages. This depends on the
2079 CONFIG_PNP_DEBUG_MESSAGES option.
2085 { on | off | curr | res | no-curr | no-res }
2088 [ISAPNP] Exclude IRQs for the autoconfiguration
2091 [ISAPNP] Exclude DMAs for the autoconfiguration
2093 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2094 Ranges are in pairs (I/O port base and size).
2097 [ISAPNP] Exclude memory regions for the
2099 Ranges are in pairs (memory base and size).
2101 ports= [IP_VS_FTP] IPVS ftp helper module
2103 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2105 Format: <port>,<port>....
2107 print-fatal-signals=
2108 [KNL] debug: print fatal signals
2110 If enabled, warn about various signal handling
2111 related application anomalies: too many signals,
2112 too many POSIX.1 timers, fatal signals causing a
2115 If you hit the warning due to signal overflow,
2116 you might want to try "ulimit -i unlimited".
2120 printk.time= Show timing data prefixed to each printk message line
2121 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2123 processor.max_cstate= [HW,ACPI]
2124 Limit processor to maximum C-state
2125 max_cstate=9 overrides any DMI blacklist limit.
2127 processor.nocst [HW,ACPI]
2128 Ignore the _CST method to determine C-states,
2129 instead using the legacy FADT method
2131 profile= [KNL] Enable kernel profiling via /proc/profile
2132 Format: [schedule,]<number>
2133 Param: "schedule" - profile schedule points.
2134 Param: <number> - step/bucket size as a power of 2 for
2135 statistical time based profiling.
2136 Param: "sleep" - profile D-state sleeping (millisecs).
2137 Requires CONFIG_SCHEDSTATS
2138 Param: "kvm" - profile VM exits.
2140 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2142 See Documentation/blockdev/ramdisk.txt.
2144 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2145 probe for; one of (bare|imps|exps|lifebook|any).
2146 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2148 psmouse.resetafter= [HW,MOUSE]
2149 Try to reset the device after so many bad packets
2152 [HW,MOUSE] Set desired mouse resolution, in dpi.
2153 psmouse.smartscroll=
2154 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2155 0 = disabled, 1 = enabled (default).
2158 See Documentation/blockdev/paride.txt.
2161 [KNL] Number of legacy pty's. Overwrites compiled-in
2164 quiet [KNL] Disable most log messages
2169 See Documentation/md.txt.
2171 ramdisk_blocksize= [RAM]
2172 See Documentation/blockdev/ramdisk.txt.
2174 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2175 See Documentation/blockdev/ramdisk.txt.
2177 rcupdate.blimit= [KNL,BOOT]
2178 Set maximum number of finished RCU callbacks to process
2181 rcupdate.qhimark= [KNL,BOOT]
2182 Set threshold of queued
2183 RCU callbacks over which batch limiting is disabled.
2185 rcupdate.qlowmark= [KNL,BOOT]
2186 Set threshold of queued RCU callbacks below which
2187 batch limiting is re-enabled.
2191 Run specified binary instead of /init from the ramdisk,
2192 used for early userspace startup. See initrd.
2194 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2195 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2196 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2199 [KNL, SMP] Set scheduler's default relax_domain_level.
2200 See Documentation/cgroups/cpusets.txt.
2202 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2204 reservetop= [X86-32]
2206 Reserves a hole at the top of the kernel virtual
2211 Set the amount of memory to reserve for BIOS at
2212 the bottom of the address space.
2214 reset_devices [KNL] Force drivers to reset the underlying device
2215 during initialization.
2218 Specify the partition device for software suspend
2220 resume_offset= [SWSUSP]
2221 Specify the offset from the beginning of the partition
2222 given by "resume=" at which the swap header is located,
2223 in <PAGE_SIZE> units (needed only for swap files).
2224 See Documentation/power/swsusp-and-swap-files.txt
2226 hibernate= [HIBERNATION]
2227 noresume Don't check if there's a hibernation image
2228 present during boot.
2229 nocompress Don't compress/decompress hibernation images.
2231 retain_initrd [RAM] Keep initrd memory after extraction
2233 rhash_entries= [KNL,NET]
2234 Set number of hash buckets for route cache
2236 riscom8= [HW,SERIAL]
2237 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2239 ro [KNL] Mount root device read-only on boot
2241 root= [KNL] Root filesystem
2243 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2244 mount the root filesystem
2246 rootflags= [KNL] Set root filesystem mount option string
2248 rootfstype= [KNL] Set root filesystem type
2250 rootwait [KNL] Wait (indefinitely) for root device to show up.
2251 Useful for devices that are detected asynchronously
2252 (e.g. USB and MMC devices).
2254 rw [KNL] Mount root device read-write on boot
2256 S [KNL] Run init in single mode
2259 See drivers/net/irda/sa1100_ir.c.
2261 sbni= [NET] Granch SBNI12 leased line adapter
2263 sched_debug [KNL] Enables verbose scheduler debug messages.
2265 security= [SECURITY] Choose a security module to enable at boot.
2266 If this boot parameter is not specified, only the first
2267 security module asking for security registration will be
2268 loaded. An invalid security module name will be treated
2269 as if no module has been chosen.
2271 selinux= [SELINUX] Disable or enable SELinux at boot time.
2272 Format: { "0" | "1" }
2273 See security/selinux/Kconfig help text.
2276 Default value is set via kernel config option.
2277 If enabled at boot time, /selinux/disable can be used
2278 later to disable prior to initial policy load.
2280 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2281 Format: { "0" | "1" }
2282 See security/apparmor/Kconfig help text
2285 Default value is set via kernel config option.
2287 serialnumber [BUGS=X86-32]
2290 Maximal number of shapers.
2292 show_msr= [x86] show boot-time MSR settings
2293 Format: { <integer> }
2294 Show boot-time (BIOS-initialized) MSR settings.
2295 The parameter means the number of CPUs to show,
2296 for example 1 means boot CPU only.
2303 slub_debug[=options[,slabs]] [MM, SLUB]
2304 Enabling slub_debug allows one to determine the
2305 culprit if slab objects become corrupted. Enabling
2306 slub_debug can create guard zones around objects and
2307 may poison objects when not in use. Also tracks the
2308 last alloc / free. For more information see
2309 Documentation/vm/slub.txt.
2311 slub_max_order= [MM, SLUB]
2312 Determines the maximum allowed order for slabs.
2313 A high setting may cause OOMs due to memory
2314 fragmentation. For more information see
2315 Documentation/vm/slub.txt.
2317 slub_min_objects= [MM, SLUB]
2318 The minimum number of objects per slab. SLUB will
2319 increase the slab order up to slub_max_order to
2320 generate a sufficiently large slab able to contain
2321 the number of objects indicated. The higher the number
2322 of objects the smaller the overhead of tracking slabs
2323 and the less frequently locks need to be acquired.
2324 For more information see Documentation/vm/slub.txt.
2326 slub_min_order= [MM, SLUB]
2327 Determines the mininum page order for slabs. Must be
2328 lower than slub_max_order.
2329 For more information see Documentation/vm/slub.txt.
2331 slub_nomerge [MM, SLUB]
2332 Disable merging of slabs with similar size. May be
2333 necessary if there is some reason to distinguish
2334 allocs to different slabs. Debug options disable
2335 merging on their own.
2336 For more information see Documentation/vm/slub.txt.
2339 Format: <io1>[,<io2>[,...,<io8>]]
2341 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2342 attempt to substitute SMP alternatives once at boot.
2344 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2345 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2346 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2347 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2348 smsc-ircc2.ircc_irq= [HW] IRQ line
2349 smsc-ircc2.ircc_dma= [HW] DMA channel
2350 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2351 0: Toshiba Satellite 1800 (GP data pin select)
2352 1: Fast pin select (default)
2356 [KNL] Should the soft-lockup detector generate panics.
2359 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2360 See Documentation/sonypi.txt
2362 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2363 See Documentation/serial/specialix.txt.
2365 spia_io_base= [HW,MTD]
2371 Enabled the stack tracer on boot up.
2375 Set the STI (builtin display/keyboard on the HP-PARISC
2376 machines) console (graphic card) which should be used
2377 as the initial boot-console.
2378 See also comment in drivers/video/console/sticore.c.
2381 See comment in drivers/video/console/sticore.c.
2384 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2386 sunrpc.min_resvport=
2387 sunrpc.max_resvport=
2389 SunRPC servers often require that client requests
2390 originate from a privileged port (i.e. a port in the
2391 range 0 < portnr < 1024).
2392 An administrator who wishes to reserve some of these
2393 ports for other uses may adjust the range that the
2394 kernel's sunrpc client considers to be privileged
2395 using these two parameters to set the minimum and
2396 maximum port values.
2400 Control how the NFS server code allocates CPUs to
2401 service thread pools. Depending on how many NICs
2402 you have and where their interrupts are bound, this
2403 option will affect which CPUs will do NFS serving.
2404 Note: this parameter cannot be changed while the
2405 NFS server is running.
2407 auto the server chooses an appropriate mode
2408 automatically using heuristics
2409 global a single global pool contains all CPUs
2410 percpu one pool for each CPU
2411 pernode one pool for each NUMA node (equivalent
2412 to global on non-NUMA machines)
2414 sunrpc.tcp_slot_table_entries=
2415 sunrpc.udp_slot_table_entries=
2417 Sets the upper limit on the number of simultaneous
2418 RPC calls that can be sent from the client to a
2419 server. Increasing these values may allow you to
2420 improve throughput, but will also increase the
2421 amount of memory reserved for use by the client.
2424 [KNL] Enable accounting of swap in memory resource
2425 controller if no parameter or 1 is given or disable
2426 it if 0 is given (See Documentation/cgroups/memory.txt)
2428 swiotlb= [IA-64] Number of I/O TLB slabs
2432 sysfs.deprecated=0|1 [KNL]
2433 Enable/disable old style sysfs layout for old udev
2434 on older distributions. When this option is enabled
2435 very new udev will not work anymore. When this option
2436 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2437 in older udev will not work anymore.
2438 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2439 the kernel configuration.
2441 sysrq_always_enabled
2443 Ignore sysrq setting - this boot parameter will
2444 neutralize any effect of /proc/sys/kernel/sysrq.
2445 Useful for debugging.
2449 test_suspend= [SUSPEND]
2450 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2451 standby suspend) as the system sleep state to briefly
2452 enter during system startup. The system is woken from
2453 this state using a wakeup-capable RTC alarm.
2455 thash_entries= [KNL,NET]
2456 Set number of hash buckets for TCP connection
2458 thermal.act= [HW,ACPI]
2459 -1: disable all active trip points in all thermal zones
2460 <degrees C>: override all lowest active trip points
2462 thermal.crt= [HW,ACPI]
2463 -1: disable all critical trip points in all thermal zones
2464 <degrees C>: override all critical trip points
2466 thermal.nocrt= [HW,ACPI]
2467 Set to disable actions on ACPI thermal zone
2468 critical and hot trip points.
2470 thermal.off= [HW,ACPI]
2471 1: disable ACPI thermal control
2473 thermal.psv= [HW,ACPI]
2474 -1: disable all passive trip points
2475 <degrees C>: override all passive trip points to this
2478 thermal.tzp= [HW,ACPI]
2479 Specify global default ACPI thermal zone polling rate
2480 <deci-seconds>: poll all this frequency
2481 0: no polling (default)
2484 Force threading of all interrupt handlers except those
2485 marked explicitely IRQF_NO_THREAD.
2489 Specify if the kernel should make use of the cpu
2490 topology information if the hardware supports this.
2491 The scheduler will make use of this information and
2492 e.g. base its process migration decisions on it.
2497 tpm_suspend_pcr=[HW,TPM]
2498 Format: integer pcr id
2499 Specify that at suspend time, the tpm driver
2500 should extend the specified pcr with zeros,
2501 as a workaround for some chips which fail to
2502 flush the last written pcr on TPM_SaveState.
2503 This will guarantee that all the other pcrs
2506 trace_buf_size=nn[KMG]
2507 [FTRACE] will set tracing buffer size.
2509 trace_event=[event-list]
2510 [FTRACE] Set and start specified trace events in order
2511 to facilitate early boot debugging.
2512 See also Documentation/trace/events.txt
2514 tsc= Disable clocksource stability checks for TSC.
2516 [x86] reliable: mark tsc clocksource as reliable, this
2517 disables clocksource verification at runtime, as well
2518 as the stability checks done at bootup. Used to enable
2519 high-resolution timer mode on older hardware, and in
2520 virtualized environment.
2521 [x86] noirqtime: Do not use TSC to do irq accounting.
2522 Used to run time disable IRQ_TIME_ACCOUNTING on any
2523 platforms where RDTSC is slow and this accounting
2526 turbografx.map[2|3]= [HW,JOY]
2527 TurboGraFX parallel port interface
2529 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2530 See also Documentation/input/joystick-parport.txt
2532 uhash_entries= [KNL,NET]
2533 Set number of hash buckets for UDP/UDP-Lite connections
2536 [USB] Ignore overcurrent events (default N).
2537 Some badly-designed motherboards generate lots of
2538 bogus events, for ports that aren't wired to
2539 anything. Set this parameter to avoid log spamming.
2540 Note that genuine overcurrent events won't be
2544 [X86] Cause panic on unknown NMI.
2546 usbcore.autosuspend=
2547 [USB] The autosuspend time delay (in seconds) used
2548 for newly-detected USB devices (default 2). This
2549 is the time required before an idle device will be
2550 autosuspended. Devices for which the delay is set
2551 to a negative value won't be autosuspended at all.
2553 usbcore.usbfs_snoop=
2554 [USB] Set to log all usbfs traffic (default 0 = off).
2556 usbcore.blinkenlights=
2557 [USB] Set to cycle leds on hubs (default 0 = off).
2559 usbcore.old_scheme_first=
2560 [USB] Start with the old device initialization
2561 scheme (default 0 = off).
2563 usbcore.use_both_schemes=
2564 [USB] Try the other device initialization scheme
2565 if the first one fails (default 1 = enabled).
2567 usbcore.initial_descriptor_timeout=
2568 [USB] Specifies timeout for the initial 64-byte
2569 USB_REQ_GET_DESCRIPTOR request in milliseconds
2570 (default 5000 = 5.0 seconds).
2573 [USBHID] The interval which mice are to be polled at.
2575 usb-storage.delay_use=
2576 [UMS] The delay in seconds before a new device is
2577 scanned for Logical Units (default 5).
2580 [UMS] A list of quirks entries to supplement or
2581 override the built-in unusual_devs list. List
2582 entries are separated by commas. Each entry has
2583 the form VID:PID:Flags where VID and PID are Vendor
2584 and Product ID values (4-digit hex numbers) and
2585 Flags is a set of characters, each corresponding
2586 to a common usb-storage quirk flag as follows:
2587 a = SANE_SENSE (collect more than 18 bytes
2589 b = BAD_SENSE (don't collect more than 18
2590 bytes of sense data);
2591 c = FIX_CAPACITY (decrease the reported
2592 device capacity by one sector);
2593 d = NO_READ_DISC_INFO (don't use
2594 READ_DISC_INFO command);
2595 e = NO_READ_CAPACITY_16 (don't use
2596 READ_CAPACITY_16 command);
2597 h = CAPACITY_HEURISTICS (decrease the
2598 reported device capacity by one
2599 sector if the number is odd);
2600 i = IGNORE_DEVICE (don't bind to this
2602 l = NOT_LOCKABLE (don't try to lock and
2603 unlock ejectable media);
2604 m = MAX_SECTORS_64 (don't transfer more
2605 than 64 sectors = 32 KB at a time);
2606 n = INITIAL_READ10 (force a retry of the
2607 initial READ(10) command);
2608 o = CAPACITY_OK (accept the capacity
2609 reported by the device);
2610 r = IGNORE_RESIDUE (the device reports
2611 bogus residue values);
2612 s = SINGLE_LUN (the device has only one
2614 w = NO_WP_DETECT (don't test whether the
2615 medium is write-protected).
2616 Example: quirks=0419:aaf5:rl,0421:0433:rc
2619 [X86] Flags controlling user PTE allocations.
2621 nohigh = do not allocate PTE pages in
2622 HIGHMEM regardless of setting
2626 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2627 vdso=1: enable VDSO (default)
2628 vdso=0: disable VDSO mapping
2631 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2632 vdso32=1: enable 32-bit VDSO (default)
2633 vdso32=0: disable 32-bit VDSO mapping
2636 vector=percpu: enable percpu vector domain
2638 video= [FB] Frame buffer configuration
2639 See Documentation/fb/modedb.txt.
2641 vga= [BOOT,X86-32] Select a particular video mode
2642 See Documentation/x86/boot.txt and
2643 Documentation/svga.txt.
2644 Use vga=ask for menu.
2645 This is actually a boot loader parameter; the value is
2646 passed to the kernel using a special protocol.
2648 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2649 size of <nn>. This can be used to increase the
2650 minimum size (128MB on x86). It can also be used to
2651 decrease the size and leave more room for directly
2654 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2657 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2660 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2663 vt.cur_default= [VT] Default cursor shape.
2664 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2665 the parameters of the <Esc>[?A;B;Cc escape sequence;
2666 see VGA-softcursor.txt. Default: 2 = underline.
2668 vt.default_blu= [VT]
2669 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2670 Change the default blue palette of the console.
2671 This is a 16-member array composed of values
2674 vt.default_grn= [VT]
2675 Format: <green0>,<green1>,<green2>,...,<green15>
2676 Change the default green palette of the console.
2677 This is a 16-member array composed of values
2680 vt.default_red= [VT]
2681 Format: <red0>,<red1>,<red2>,...,<red15>
2682 Change the default red palette of the console.
2683 This is a 16-member array composed of values
2689 Set system-wide default UTF-8 mode for all tty's.
2690 Default is 1, i.e. UTF-8 mode is enabled for all
2691 newly opened terminals.
2693 vt.global_cursor_default=
2696 Set system-wide default for whether a cursor
2697 is shown on new VTs. Default is -1,
2698 i.e. cursors will be created by default unless
2699 overridden by individual drivers. 0 will hide
2700 cursors, 1 will display them.
2702 watchdog timers [HW,WDT] For information on watchdog timers,
2703 see Documentation/watchdog/watchdog-parameters.txt
2704 or other driver-specific files in the
2705 Documentation/watchdog/ directory.
2707 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2708 default x2apic cluster mode on platforms
2711 x86_mrst_timer= [X86-32,APBT]
2712 Choose timer option for x86 Moorestown MID platform.
2713 Two valid options are apbt timer only and lapic timer
2714 plus one apbt timer for broadcast timer.
2715 x86_mrst_timer=apbt_only | lapic_and_apbt
2717 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2718 xd_geo= See header of drivers/block/xd.c.
2720 xen_emul_unplug= [HW,X86,XEN]
2721 Unplug Xen emulated devices
2722 Format: [unplug0,][unplug1]
2723 ide-disks -- unplug primary master IDE devices
2724 aux-ide-disks -- unplug non-primary-master IDE devices
2725 nics -- unplug network devices
2726 all -- unplug all emulated devices (NICs and IDE disks)
2727 unnecessary -- unplugging emulated devices is
2728 unnecessary even if the host did not respond to
2730 never -- do not unplug even if version check succeeds
2732 xirc2ps_cs= [NET,PCMCIA]
2734 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2736 ______________________________________________________________________
2740 Add more DRM drivers.
git.openpandora.org / pandora-kernel.git / blob