4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Finally, the [KMG] suffix is commonly described after a number of kernel
148 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150 bytes respectively. Such letter suffixes can also be entirely omitted.
154 Advanced Configuration and Power Interface
155 Format: { force | off | strict | noirq | rsdt }
156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
159 strict -- Be less tolerant of platforms that are not
160 strictly ACPI specification compliant.
161 rsdt -- prefer RSDT over (default) XSDT
162 copy_dsdt -- copy DSDT to memory
164 See also Documentation/power/pm.txt, pci=noacpi
166 acpi_rsdp= [ACPI,EFI,KEXEC]
167 Pass the RSDP address to the kernel, mostly used
168 on machines running EFI runtime service to boot the
169 second kernel for kdump.
171 acpi_apic_instance= [ACPI, IOAPIC]
173 2: use 2nd APIC table, if available
174 1,0: use 1st APIC table
177 acpi_backlight= [HW,ACPI]
178 acpi_backlight=vendor
180 If set to vendor, prefer vendor specific driver
181 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
182 of the ACPI video.ko driver.
184 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
185 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
187 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
188 debug output. Bits in debug_layer correspond to a
189 _COMPONENT in an ACPI source file, e.g.,
190 #define _COMPONENT ACPI_PCI_COMPONENT
191 Bits in debug_level correspond to a level in
192 ACPI_DEBUG_PRINT statements, e.g.,
193 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
194 The debug_level mask defaults to "info". See
195 Documentation/acpi/debug.txt for more information about
196 debug layers and levels.
198 Enable processor driver info messages:
199 acpi.debug_layer=0x20000000
200 Enable PCI/PCI interrupt routing info messages:
201 acpi.debug_layer=0x400000
202 Enable AML "Debug" output, i.e., stores to the Debug
203 object while interpreting AML:
204 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
205 Enable all messages related to ACPI hardware:
206 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
208 Some values produce so much output that the system is
209 unusable. The "log_buf_len" parameter may be useful
210 if you need to capture more output.
212 acpi_irq_balance [HW,ACPI]
213 ACPI will balance active IRQs
216 acpi_irq_nobalance [HW,ACPI]
217 ACPI will not move active IRQs (default)
220 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
221 Format: <irq>,<irq>...
223 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
225 Format: <irq>,<irq>...
227 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
229 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
230 Format: To spoof as Windows 98: ="Microsoft Windows"
232 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
233 acpi_osi="string1" # add string1 -- only one string
234 acpi_osi="!string2" # remove built-in string2
235 acpi_osi= # disable all strings
238 Override the pmtimer bug detection: force the kernel
239 to assume that this machine's pmtimer latches its value
240 and always returns good values.
242 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
243 Format: { level | edge | high | low }
245 acpi_serialize [HW,ACPI] force serialization of AML methods
247 acpi_skip_timer_override [HW,ACPI]
248 Recognize and ignore IRQ0/pin2 Interrupt Override.
249 For broken nForce2 BIOS resulting in XT-PIC timer.
251 acpi_sleep= [HW,ACPI] Sleep options
252 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
253 old_ordering, nonvs, sci_force_enable }
254 See Documentation/power/video.txt for information on
256 s3_beep is for debugging; it makes the PC's speaker beep
257 as soon as the kernel's real-mode entry point is called.
258 s4_nohwsig prevents ACPI hardware signature from being
259 used during resume from hibernation.
260 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with respect to putting devices into
262 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by default).
264 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken systems don't work without it).
270 acpi_use_timer_override [HW,ACPI]
271 Use timer override. For some broken Nvidia NF5 boards
272 that require a timer override, but don't have HPET
274 acpi_enforce_resources= [ACPI]
275 { strict | lax | no }
276 Check for resource conflicts between native drivers
277 and ACPI OperationRegions (SystemIO and SystemMemory
278 only). IO ports and memory declared in ACPI might be
279 used by the ACPI subsystem in arbitrary AML code and
280 can interfere with legacy drivers.
281 strict (default): access to resources claimed by ACPI
282 is denied; legacy drivers trying to access reserved
283 resources will fail to bind to device using them.
284 lax: access to resources claimed by ACPI is allowed;
285 legacy drivers trying to access reserved resources
286 will bind successfully but a warning message is logged.
287 no: ACPI OperationRegions are not marked as reserved,
288 no further checks are performed.
290 add_efi_memmap [EFI; X86] Include EFI memory map in
291 kernel's map of available physical RAM.
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
300 See Documentation/sound/alsa/alsa-parameters.txt
303 Allow the default userspace alignment fault handler
304 behaviour to be specified. Bit 0 enables warnings,
305 bit 1 enables fixups, and bit 2 sends a segfault.
307 amd_iommu= [HW,X86-84]
308 Pass parameters to the AMD IOMMU driver in the system.
310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
314 off - do not initialize any AMD IOMMU found in
317 amijoy.map= [HW,JOY] Amiga joystick support
318 Map of devices attached to JOY0DAT and JOY1DAT
320 See also Documentation/kernel/input/joystick.txt
322 analog.map= [HW,JOY] Analog joystick and gamepad support
323 Specifies type or capabilities of an analog joystick
324 connected to one of 16 gameports
325 Format: <type1>,<type2>,..<type16>
328 Power management functions (SPARCstation-4/5 + deriv.)
330 Disable APC CPU standby support. SPARCstation-Fox does
331 not play well with APC CPU idle - disable it if you have
332 APC and your system crashes randomly.
334 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
335 Change the output verbosity whilst booting
336 Format: { quiet (default) | verbose | debug }
337 Change the amount of debugging information output
338 when initialising the APIC and IO-APIC components.
341 See Documentation/networking/ipv6.txt.
343 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
344 Limit apic dumping. The parameter defines the maximal
345 number of local apics being dumped. Also it is possible
346 to set it to "all" by meaning -- no limit here.
347 Format: { 1 (default) | 2 | ... | all }.
348 The parameter valid if only apic=debug or
349 apic=verbose is specified.
350 Example: apic=debug show_lapic=all
352 apm= [APM] Advanced Power Management
353 See header of arch/x86/kernel/apm_32.c.
355 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
356 Format: <io>,<irq>,<nodeID>
360 atarimouse= [HW,MOUSE] Atari Mouse
362 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
363 EzKey and similar keyboards
365 atkbd.reset= [HW] Reset keyboard during initialization
367 atkbd.set= [HW] Select keyboard code set
368 Format: <int> (2 = AT (default), 3 = PS/2)
370 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
373 atkbd.softraw= [HW] Choose between synthetic and real raw mode
374 Format: <bool> (0 = real, 1 = synthetic (default))
376 atkbd.softrepeat= [HW]
377 Use software keyboard repeat
381 baycom_epp= [HW,AX25]
384 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
386 See header of drivers/net/hamradio/baycom_par.c.
388 baycom_ser_fdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
390 Format: <io>,<irq>,<mode>[,<baud>]
391 See header of drivers/net/hamradio/baycom_ser_fdx.c.
393 baycom_ser_hdx= [HW,AX25]
394 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
395 Format: <io>,<irq>,<mode>
396 See header of drivers/net/hamradio/baycom_ser_hdx.c.
398 boot_delay= Milliseconds to delay each printk during boot.
399 Values larger than 10 seconds (10000) are changed to
403 bootmem_debug [KNL] Enable bootmem allocator debug messages.
405 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
406 bttv.radio= Most important insmod options are available as
408 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
409 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
411 bulk_remove=off [PPC] This parameter disables the use of the pSeries
412 firmware feature for flushing multiple hpte entries
415 c101= [NET] Moxa C101 synchronous serial card
417 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
418 Sometimes CPU hardware bugs make them report the cache
419 size incorrectly. The kernel will attempt work arounds
420 to fix known problems, but for some CPUs it is not
421 possible to determine what the correct size should be.
422 This option provides an override for these situations.
425 [SECURITY] Disable capabilities. This would normally
426 be used only if an alternative security model is to be
427 configured. Potentially dangerous and should only be
428 used if you are entirely sure of the consequences.
430 ccw_timeout_log [S390]
431 See Documentation/s390/CommonIO for details.
433 cgroup_disable= [KNL] Disable a particular controller
434 Format: {name of the controller(s) to disable}
435 {Currently supported controllers - "memory"}
437 checkreqprot [SELINUX] Set initial checkreqprot flag value.
438 Format: { "0" | "1" }
439 See security/selinux/Kconfig help text.
440 0 -- check protection applied by kernel (includes
441 any implied execute protection).
442 1 -- check protection requested by application.
443 Default value is set via a kernel config option.
444 Value can be changed at runtime via
445 /selinux/checkreqprot.
448 See Documentation/s390/CommonIO for details.
450 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
452 Forces specified clocksource (if available) to be used
453 when calculating gettimeofday(). If specified
454 clocksource is not available, it defaults to PIT.
455 Format: { pit | tsc | cyclone | pmtmr }
457 clocksource= Override the default clocksource
459 Override the default clocksource and use the clocksource
460 with the name specified.
461 Some clocksource names to choose from, depending on
463 [all] jiffies (this is the base, fallback clocksource)
465 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
466 pxa_timer,timer3,32k_counter,timer0_1
468 [X86-32] pit,hpet,tsc;
469 scx200_hrt on Geode; cyclone on IBM x440
477 clearcpuid=BITNUM [X86]
478 Disable CPUID feature X for the kernel. See
479 arch/x86/include/asm/cpufeature.h for the valid bit
480 numbers. Note the Linux specific bits are not necessarily
481 stable over kernel options, but the vendor specific
483 Also note that user programs calling CPUID directly
484 or using the feature without checking anything
485 will still see it. This just prevents it from
486 being used by the kernel or shown in /proc/cpuinfo.
487 Also note the kernel might malfunction if you disable
490 cmo_free_hint= [PPC] Format: { yes | no }
491 Specify whether pages are marked as being inactive
492 when they are freed. This is used in CMO environments
493 to determine OS memory pressure for page stealing by
497 code_bytes [X86] How many bytes of object code to print
502 com20020= [HW,NET] ARCnet - COM20020 chipset
504 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
506 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
510 ARCnet - COM90xx chipset (memory-mapped buffers)
511 Format: <io>[,<irq>[,<memstart>]]
513 condev= [HW,S390] console device
516 console= [KNL] Output console device and options.
518 tty<n> Use the virtual console device <n>.
522 Use the specified serial port. The options are of
523 the form "bbbbpnf", where "bbbb" is the baud rate,
524 "p" is parity ("n", "o", or "e"), "n" is number of
525 bits, and "f" is flow control ("r" for RTS or
526 omit it). Default is "9600n8".
528 See Documentation/serial-console.txt for more
530 Documentation/networking/netconsole.txt for an
533 uart[8250],io,<addr>[,options]
534 uart[8250],mmio,<addr>[,options]
535 Start an early, polled-mode console on the 8250/16550
536 UART at the specified I/O port or MMIO address,
537 switching to the matching ttyS device later. The
538 options are the same as for ttyS, above.
540 If the device connected to the port is not a TTY but a braille
541 device, prepend "brl," before the device type, for instance
543 For now, only VisioBraille is supported.
545 consoleblank= [KNL] The console blank (screen saver) timeout in
546 seconds. Defaults to 10*60 = 10mins. A value of 0
547 disables the blank timer.
550 [KNL] Change the default value for
551 /proc/<pid>/coredump_filter.
552 See also Documentation/filesystems/proc.txt.
554 cpuidle.off=1 [CPU_IDLE]
555 disable the cpuidle sub-system
557 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
559 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
561 crashkernel=size[KMG][@offset[KMG]]
562 [KNL] Using kexec, Linux can switch to a 'crash kernel'
563 upon panic. This parameter reserves the physical
564 memory region [offset, offset + size] for that kernel
565 image. If '@offset' is omitted, then a suitable offset
566 is selected automatically. Check
567 Documentation/kdump/kdump.txt for further details.
569 crashkernel=range1:size1[,range2:size2,...][@offset]
570 [KNL] Same as above, but depends on the memory
571 in the running system. The syntax of range is
572 start-[end] where start and end are both
573 a memory unit (amount[KMG]). See also
574 Documentation/kdump/kdump.txt for an example.
579 cs89x0_media= [HW,NET]
580 Format: { rj45 | aui | bnc }
583 See header of drivers/s390/block/dasd_devmap.c.
585 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
586 (one device per port)
587 Format: <port#>,<type>
588 See also Documentation/input/joystick-parport.txt
590 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
591 time. See Documentation/dynamic-debug-howto.txt for
594 debug [KNL] Enable kernel debugging (events log level).
597 [KNL] verbose self-tests
599 Print debugging info while doing the locking API
601 We default to 0 (no extra messages), setting it to
602 1 will print _a lot_ more information - normally
603 only useful to kernel developers.
605 debug_objects [KNL] Enable object debugging
608 [KNL] Disable object debugging
610 debugpat [X86] Enable PAT debugging
612 decnet.addr= [HW,NET]
613 Format: <area>[,<node>]
614 See also Documentation/networking/decnet.txt.
617 [same as hugepagesz=] The size of the default
618 HugeTLB page size. This is the size represented by
619 the legacy /proc/ hugepages APIs, used for SHM, and
620 default size when mounting hugetlbfs filesystems.
621 Defaults to the default architecture's huge page size
625 Set number of hash buckets for dentry cache.
628 IO parameters + enable/disable command.
630 digiepca= [HW,SERIAL]
631 See drivers/char/README.epca and
632 Documentation/serial/digiepca.txt.
635 See Documentation/networking/ipv6.txt.
637 disable_ddw [PPC/PSERIES]
638 Disable Dynamic DMA Window support. Use this if
639 to workaround buggy firmware.
642 See Documentation/networking/ipv6.txt.
644 disable_mtrr_cleanup [X86]
645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
647 entry later. This parameter disables that.
649 disable_mtrr_trim [X86, Intel and AMD only]
650 By default the kernel will trim any uncacheable
651 memory out of your available memory pool based on
652 MTRR settings. This parameter disables that behavior,
653 possibly causing your machine to run very slowly.
655 disable_timer_pin_1 [X86]
656 Disable PIN 1 of APIC timer
657 Can be useful to work around chipset bugs.
659 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
660 this option disables the debugging code at boot.
662 dma_debug_entries=<number>
663 This option allows to tune the number of preallocated
664 entries for DMA-API debugging code. One entry is
665 required per DMA-API allocation. Use this if the
666 DMA-API debugging code disables itself because the
667 architectural default is too low.
669 dma_debug_driver=<driver_name>
670 With this option the DMA-API debugging driver
671 filter feature can be enabled at boot time. Just
672 pass the driver to filter for as the parameter.
673 The filter can be disabled or changed to another
674 driver later using sysfs.
678 earlycon= [KNL] Output early console device and options.
679 uart[8250],io,<addr>[,options]
680 uart[8250],mmio,<addr>[,options]
681 uart[8250],mmio32,<addr>[,options]
682 Start an early, polled-mode console on the 8250/16550
683 UART at the specified I/O port or MMIO address.
684 MMIO inter-register address stride is either 8bit (mmio)
686 The options are the same as for ttyS, above.
688 earlyprintk= [X86,SH,BLACKFIN]
690 earlyprintk=serial[,ttySn[,baudrate]]
691 earlyprintk=ttySn[,baudrate]
692 earlyprintk=dbgp[debugController#]
694 Append ",keep" to not disable it when the real console
697 Only vga or serial or usb debug port at a time.
699 Currently only ttyS0 and ttyS1 are supported.
701 Interaction with the standard serial driver is not
704 The VGA output is eventually overwritten by the real
707 ekgdboc= [X86,KGDB] Allow early kernel console debugging
710 This is designed to be used in conjunction with
711 the boot argument: earlyprintk=vga
714 Format: {"off" | "on" | "skip[mbr]"}
716 eisa_irq_edge= [PARISC,HW]
717 See header of drivers/parisc/eisa.c.
720 See comment before function elanfreq_setup() in
721 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
724 Format: {"cfq" | "deadline" | "noop"}
725 See Documentation/block/as-iosched.txt and
726 Documentation/block/deadline-iosched.txt for details.
728 elfcorehdr= [IA64,PPC,SH,X86]
729 Specifies physical address of start of kernel core
730 image elf header. Generally kexec loader will
731 pass this option to capture kernel.
732 See Documentation/kdump/kdump.txt for details.
734 enable_mtrr_cleanup [X86]
735 The kernel tries to adjust MTRR layout from continuous
736 to discrete, to make X server driver able to add WB
737 entry later. This parameter enables that.
739 enable_timer_pin_1 [X86]
740 Enable PIN 1 of APIC timer
741 Can be useful to work around chipset bugs
742 (in particular on some ATI chipsets).
743 The kernel tries to set a reasonable default.
745 enforcing [SELINUX] Set initial enforcing status.
747 See security/selinux/Kconfig help text.
748 0 -- permissive (log only, no denials).
749 1 -- enforcing (deny and log).
751 Value can be changed at runtime via /selinux/enforce.
754 Disable Error Record Serialization Table (ERST)
757 ether= [HW,NET] Ethernet cards parameters
758 This option is obsoleted by the "netdev=" option, which
759 has equivalent usage. See its documentation for details.
763 fail_make_request=[KNL]
764 General fault injection mechanism.
765 Format: <interval>,<probability>,<space>,<times>
766 See also /Documentation/fault-injection/.
769 See Documentation/blockdev/floppy.txt.
771 force_pal_cache_flush
772 [IA-64] Avoid check_sal_cache_flush which may hang on
773 buggy SAL_CACHE_FLUSH implementations. Using this
774 parameter will force ia64_sal_cache_flush to call
775 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
778 [FTRACE] will set and start the specified tracer
779 as early as possible in order to facilitate early
782 ftrace_dump_on_oops[=orig_cpu]
783 [FTRACE] will dump the trace buffers on oops.
784 If no parameter is passed, ftrace will dump
785 buffers of all CPUs, but if you pass orig_cpu, it will
786 dump only the buffer of the CPU that triggered the
789 ftrace_filter=[function-list]
790 [FTRACE] Limit the functions traced by the function
791 tracer at boot up. function-list is a comma separated
792 list of functions. This list can be changed at run
793 time by the set_ftrace_filter file in the debugfs
796 ftrace_notrace=[function-list]
797 [FTRACE] Do not trace the functions specified in
798 function-list. This list can be changed at run time
799 by the set_ftrace_notrace file in the debugfs
802 ftrace_graph_filter=[function-list]
803 [FTRACE] Limit the top level callers functions traced
804 by the function graph tracer at boot up.
805 function-list is a comma separated list of functions
806 that can be changed at run time by the
807 set_graph_function file in the debugfs tracing directory.
810 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
811 support via parallel port (up to 5 devices per port)
812 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
813 See also Documentation/input/joystick-parport.txt
817 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
821 gcov_persist= [GCOV] When non-zero (default), profiling data for
822 kernel modules is saved and remains accessible via
823 debugfs, even when the module is unloaded/reloaded.
824 When zero, profiling data is discarded and associated
825 debugfs files are removed at module unload time.
827 gpt [EFI] Forces disk with valid GPT signature but
828 invalid Protective MBR to be treated as GPT.
830 hashdist= [KNL,NUMA] Large hashes allocated during boot
831 are distributed across NUMA nodes. Defaults on
832 for 64bit NUMA, off otherwise.
833 Format: 0 | 1 (for off | on)
835 hcl= [IA-64] SGI's Hardware Graph compatibility layer
837 hd= [EIDE] (E)IDE hard drive subsystem geometry
838 Format: <cyl>,<head>,<sect>
841 Disable Hardware Error Source Table (HEST) support;
842 corresponding firmware-first mode error processing
843 logic will be disabled.
845 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
846 size of <nn>. This works even on boxes that have no
847 highmem otherwise. This also works to reduce highmem
848 size on bigger boxes.
850 highres= [KNL] Enable/disable high resolution timer mode.
851 Valid parameters: "on", "off"
855 See Documentation/isdn/README.HiSax.
859 hpet= [X86-32,HPET] option to control HPET usage
860 Format: { enable (default) | disable | force |
862 disable: disable HPET and use PIT instead
863 force: allow force enabled of undocumented chips (ICH4,
865 verbose: show contents of HPET registers during setup
867 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
868 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
869 On x86-64 and powerpc, this option can be specified
870 multiple times interleaved with hugepages= to reserve
871 huge pages of different sizes. Valid pages sizes on
872 x86-64 are 2M (when the CPU supports "pse") and 1G
873 (when the CPU supports the "pdpe1gb" cpuinfo flag)
874 Note that 1GB pages can only be allocated at boot time
875 using hugepages= and not freed afterwards.
877 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
878 terminal devices. Valid values: 0..8
879 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
880 If specified, z/VM IUCV HVC accepts connections
881 from listed z/VM user IDs only.
884 Do not unregister boot console at start. This is only
885 useful for debugging when something happens in the window
886 between unregistering the boot console and initializing
889 i2c_bus= [HW] Override the default board specific I2C bus speed
890 or register an additional I2C bus that is not
891 registered from board initialization code.
895 i8042.debug [HW] Toggle i8042 debug mode
896 i8042.direct [HW] Put keyboard port into non-translated mode
897 i8042.dumbkbd [HW] Pretend that controller can only read data from
898 keyboard and cannot control its state
899 (Don't attempt to blink the leds)
900 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
901 i8042.nokbd [HW] Don't check/create keyboard port
902 i8042.noloop [HW] Disable the AUX Loopback command while probing
904 i8042.nomux [HW] Don't check presence of an active multiplexing
906 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
908 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
909 i8042.reset [HW] Reset the controller during init and cleanup
910 i8042.unlock [HW] Unlock (ignore) the keylock
914 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
915 indicates that the driver is running on unsupported
917 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
918 does not match list of supported models.
920 [HW] Report power status in /proc/i8k
921 (disabled by default)
922 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
926 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
928 ide-core.nodma= [HW] (E)IDE subsystem
929 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
930 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
931 .cdrom .chs .ignore_cable are additional options
932 See Documentation/ide/ide.txt.
934 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
935 Claim all unknown PCI IDE storage controllers.
938 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
939 Poll forces a polling idle loop that can slightly
940 improve the performance of waking up a idle CPU, but
941 will use a lot of power and make the system run hot.
943 idle=mwait: On systems which support MONITOR/MWAIT but
944 the kernel chose to not use it because it doesn't save
945 as much power as a normal idle loop, use the
946 MONITOR/MWAIT idle loop anyways. Performance should be
947 the same as idle=poll.
948 idle=halt: Halt is forced to be used for CPU idle.
949 In such case C2/C3 won't be used again.
950 idle=nomwait: Disable mwait for CPU C-states
952 ignore_loglevel [KNL]
953 Ignore loglevel setting - this will print /all/
954 kernel messages to the console. Useful for debugging.
957 Set number of hash buckets for inode cache.
960 Format: { "0" | "1" }
961 0 -- integrity auditing messages. (Default)
962 1 -- enable informational integrity auditing messages.
965 Format: { "sha1" | "md5" }
969 Load a policy which meets the needs of the Trusted
970 Computing Base. This means IMA will measure all
971 programs exec'd, files mmap'd for exec, and all files
972 opened for read by uid=0.
976 Run specified binary instead of /sbin/init as init
979 initcall_debug [KNL] Trace initcalls as they are executed. Useful
980 for working out where the kernel is dying during
983 initrd= [BOOT] Specify the location of the initial ramdisk
985 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
988 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
990 Enable intel iommu driver.
992 Disable intel iommu driver.
993 igfx_off [Default Off]
994 By default, gfx is mapped as normal device. If a gfx
995 device has a dedicated DMAR unit, the DMAR unit is
996 bypassed by not enabling DMAR with this option. In
997 this case, gfx device will use physical address for
1000 With this option iommu will not optimize to look
1001 for io virtual address below 32 bit forcing dual
1002 address cycle on pci bus for cards supporting greater
1003 than 32 bit addressing. The default is to look
1004 for translation below 32 bit and if not available
1005 then look in the higher range.
1006 strict [Default Off]
1007 With this option on every unmap_single operation will
1008 result in a hardware IOTLB flush operation as opposed
1009 to batching them for performance.
1010 sp_off [Default Off]
1011 By default, super page will be supported if Intel IOMMU
1012 has the capability. With this option, super page will
1014 intremap= [X86-64, Intel-IOMMU]
1015 Format: { on (default) | off | nosid }
1016 on enable Interrupt Remapping (default)
1017 off disable Interrupt Remapping
1018 nosid disable Source ID checking
1022 iomem= Disable strict checking of access to MMIO memory
1023 strict regions from userspace.
1039 io7= [HW] IO7 for Marvel based alpha systems
1040 See comment before marvel_specify_io7 in
1041 arch/alpha/kernel/core_marvel.c.
1043 io_delay= [X86] I/O delay method
1045 Standard port 0x80 based delay
1047 Alternate port 0xed based delay (needed on some systems)
1049 Simple two microseconds delay
1054 See Documentation/filesystems/nfs/nfsroot.txt.
1056 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1057 See comment before ip2_setup() in
1058 drivers/char/ip2/ip2base.c.
1061 When an interrupt is not handled search all handlers
1062 for it. Intended to get systems with badly broken
1066 When an interrupt is not handled search all handlers
1067 for it. Also check all handlers each timer
1068 interrupt. Intended to get systems with badly broken
1072 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1074 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1076 <cpu number>,...,<cpu number>
1078 <cpu number>-<cpu number>
1079 (must be a positive range in ascending order)
1081 <cpu number>,...,<cpu number>-<cpu number>
1083 This option can be used to specify one or more CPUs
1084 to isolate from the general SMP balancing and scheduling
1085 algorithms. You can move a process onto or off an
1086 "isolated" CPU via the CPU affinity syscalls or cpuset.
1087 <cpu number> begins at 0 and the maximum value is
1088 "number of CPUs in system - 1".
1090 This option is the preferred way to isolate CPUs. The
1091 alternative -- manually setting the CPU mask of all
1092 tasks in the system -- can cause problems and
1093 suboptimal load balancer performance.
1097 js= [HW,JOY] Analog joystick
1098 See Documentation/input/joystick.txt.
1102 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1103 specifies the amount of memory usable by the kernel
1104 for non-movable allocations. The requested amount is
1105 spread evenly throughout all nodes in the system. The
1106 remaining memory in each node is used for Movable
1107 pages. In the event, a node is too small to have both
1108 kernelcore and Movable pages, kernelcore pages will
1109 take priority and other nodes will have a larger number
1110 of kernelcore pages. The Movable zone is used for the
1111 allocation of pages that may be reclaimed or moved
1112 by the page migration subsystem. This means that
1113 HugeTLB pages may not be allocated from this zone.
1114 Note that allocations like PTEs-from-HighMem still
1115 use the HighMem zone if it exists, and the Normal
1116 zone if it does not.
1118 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1119 Format: <Controller#>[,poll interval]
1120 The controller # is the number of the ehci usb debug
1121 port as it is probed via PCI. The poll interval is
1122 optional and is the number seconds in between
1123 each poll cycle to the debug port in case you need
1124 the functionality for interrupting the kernel with
1125 gdb or control-c on the dbgp connection. When
1126 not using this parameter you use sysrq-g to break into
1127 the kernel debugger.
1129 kgdboc= [KGDB,HW] kgdb over consoles.
1130 Requires a tty driver that supports console polling,
1131 or a supported polling keyboard driver (non-usb).
1132 Serial only format: <serial_device>[,baud]
1133 keyboard only format: kbd
1134 keyboard and serial format: kbd,<serial_device>[,baud]
1135 Optional Kernel mode setting:
1136 kms, kbd format: kms,kbd
1137 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1139 kgdbwait [KGDB] Stop kernel execution and enter the
1140 kernel debugger at the earliest opportunity.
1142 kmac= [MIPS] korina ethernet MAC address.
1143 Configure the RouterBoard 532 series on-chip
1144 Ethernet adapter MAC address.
1146 kmemleak= [KNL] Boot-time kmemleak enable/disable
1147 Valid arguments: on, off
1150 kstack=N [X86] Print N words from the kernel stack
1153 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1154 Default is 0 (don't ignore, but inject #GP)
1156 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1157 Default is 1 (enabled)
1159 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1163 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1164 Default is 1 (enabled)
1166 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1168 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1170 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1171 (virtualized MMU) support on capable Intel chips.
1172 Default is 1 (enabled)
1174 kvm-intel.emulate_invalid_guest_state=
1175 [KVM,Intel] Enable emulation of invalid guest states
1176 Default is 0 (disabled)
1178 kvm-intel.flexpriority=
1179 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1180 Default is 1 (enabled)
1182 kvm-intel.unrestricted_guest=
1183 [KVM,Intel] Disable unrestricted guest feature
1184 (virtualized real and unpaged mode) on capable
1185 Intel chips. Default is 1 (enabled)
1187 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1188 feature (tagged TLBs) on capable Intel chips.
1189 Default is 1 (enabled)
1195 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1198 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1201 libata.dma= [LIBATA] DMA control
1202 libata.dma=0 Disable all PATA and SATA DMA
1203 libata.dma=1 PATA and SATA Disk DMA only
1204 libata.dma=2 ATAPI (CDROM) DMA only
1205 libata.dma=4 Compact Flash DMA only
1206 Combinations also work, so libata.dma=3 enables DMA
1207 for disks and CDROMs, but not CFs.
1209 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1210 libata.ignore_hpa=0 keep BIOS limits (default)
1211 libata.ignore_hpa=1 ignore limits, using full disk
1213 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1217 libata.force= [LIBATA] Force configurations. The format is comma
1218 separated list of "[ID:]VAL" where ID is
1219 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1220 matching port, link or device. Basically, it matches
1221 the ATA ID string printed on console by libata. If
1222 the whole ID part is omitted, the last PORT and DEVICE
1223 values are used. If ID hasn't been specified yet, the
1224 configuration applies to all ports, links and devices.
1226 If only DEVICE is omitted, the parameter applies to
1227 the port and all links and devices behind it. DEVICE
1228 number of 0 either selects the first device or the
1229 first fan-out link behind PMP device. It does not
1230 select the host link. DEVICE number of 15 selects the
1231 host link and device attached to it.
1233 The VAL specifies the configuration to force. As long
1234 as there's no ambiguity shortcut notation is allowed.
1235 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1236 The following configurations can be forced.
1238 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1239 Any ID with matching PORT is used.
1241 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1243 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1244 udma[/][16,25,33,44,66,100,133] notation is also
1247 * [no]ncq: Turn on or off NCQ.
1249 * nohrst, nosrst, norst: suppress hard, soft
1252 * dump_id: dump IDENTIFY data.
1254 If there are multiple matching configurations changing
1255 the same attribute, the last one is used.
1257 memblock=debug [KNL] Enable memblock debug messages.
1259 load_ramdisk= [RAM] List of ramdisks to load from floppy
1260 See Documentation/blockdev/ramdisk.txt.
1262 lockd.nlm_grace_period=P [NFS] Assign grace period.
1265 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1268 lockd.nlm_timeout=T [NFS] Assign timeout value.
1271 lockd.nlm_udpport=M [NFS] Assign UDP port.
1274 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1277 loglevel= All Kernel Messages with a loglevel smaller than the
1278 console loglevel will be printed to the console. It can
1279 also be changed with klogd or other programs. The
1280 loglevels are defined as follows:
1282 0 (KERN_EMERG) system is unusable
1283 1 (KERN_ALERT) action must be taken immediately
1284 2 (KERN_CRIT) critical conditions
1285 3 (KERN_ERR) error conditions
1286 4 (KERN_WARNING) warning conditions
1287 5 (KERN_NOTICE) normal but significant condition
1288 6 (KERN_INFO) informational
1289 7 (KERN_DEBUG) debug-level messages
1291 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1292 in bytes. n must be a power of two. The default
1293 size is set in the kernel config file.
1295 logo.nologo [FB] Disables display of the built-in Linux logo.
1296 This may be used to provide more screen space for
1297 kernel log messages and is useful when debugging
1298 kernel boot problems.
1300 lp=0 [LP] Specify parallel ports to use, e.g,
1301 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1302 lp=reset first parallel port). 'lp=0' disables the
1303 lp=auto printer driver. 'lp=reset' (which can be
1304 specified in addition to the ports) causes
1305 attached printers to be reset. Using
1306 lp=port1,port2,... specifies the parallel ports
1307 to associate lp devices with, starting with
1308 lp0. A port specification may be 'none' to skip
1309 that lp device, or a parport name such as
1310 'parport0'. Specifying 'lp=auto' instead of a
1311 port specification list means that device IDs
1312 from each port should be examined, to see if
1313 an IEEE 1284-compliant printer is attached; if
1314 so, the driver will manage that printer.
1315 See also header of drivers/char/lp.c.
1318 Sets loops_per_jiffy to given constant, thus avoiding
1319 time-consuming boot-time autodetection (up to 250 ms per
1320 CPU). 0 enables autodetection (default). To determine
1321 the correct value for your kernel, boot with normal
1322 autodetection and see what value is printed. Note that
1323 on SMP systems the preset will be applied to all CPUs,
1324 which is likely to cause problems if your CPUs need
1325 significantly divergent settings. An incorrect value
1326 will cause delays in the kernel to be wrong, leading to
1327 unpredictable I/O errors and other breakage. Although
1328 unlikely, in the extreme case this might damage your
1332 Format: <io>,<irq>,<dma>
1334 machvec= [IA64] Force the use of a particular machine-vector
1335 (machvec) in a generic kernel.
1336 Example: machvec=hpzx1_swiotlb
1338 machtype= [Loongson] Share the same kernel image file between different
1340 Example: machtype=lemote-yeeloong-2f-7inch
1342 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1343 than or equal to this physical address is ignored.
1345 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1346 should make use of. maxcpus=n : n >= 0 limits the
1347 kernel to using 'n' processors. n=0 is a special case,
1348 it is equivalent to "nosmp", which also disables
1351 max_loop= [LOOP] Maximum number of loopback devices that can
1357 mce [X86-32] Machine Check Exception
1359 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1361 md= [HW] RAID subsystems devices and level
1362 See Documentation/md.txt.
1365 Format: <first>,<last>
1366 Specifies range of consoles to be captured by the MDA.
1368 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1369 Amount of memory to be used when the kernel is not able
1370 to see the whole system memory or for test.
1371 [X86-32] Use together with memmap= to avoid physical
1372 address space collisions. Without memmap= PCI devices
1373 could be placed at addresses belonging to unused RAM.
1375 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1379 [KNL,SH] Allow user to override the default size for
1380 per-device physically contiguous DMA buffers.
1382 memmap=exactmap [KNL,X86] Enable setting of an exact
1383 E820 memory map, as specified by the user.
1384 Such memmap=exactmap lines can be constructed based on
1385 BIOS output or other requirements. See the memmap=nn@ss
1388 memmap=nn[KMG]@ss[KMG]
1389 [KNL] Force usage of a specific region of memory
1390 Region of memory to be used, from ss to ss+nn.
1392 memmap=nn[KMG]#ss[KMG]
1393 [KNL,ACPI] Mark specific memory as ACPI data.
1394 Region of memory to be used, from ss to ss+nn.
1396 memmap=nn[KMG]$ss[KMG]
1397 [KNL,ACPI] Mark specific memory as reserved.
1398 Region of memory to be used, from ss to ss+nn.
1399 Example: Exclude memory from 0x18690000-0x1869ffff
1400 memmap=64K$0x18690000
1402 memmap=0x10000$0x18690000
1404 memory_corruption_check=0/1 [X86]
1405 Some BIOSes seem to corrupt the first 64k of
1406 memory when doing things like suspend/resume.
1407 Setting this option will scan the memory
1408 looking for corruption. Enabling this will
1409 both detect corruption and prevent the kernel
1410 from using the memory being corrupted.
1411 However, its intended as a diagnostic tool; if
1412 repeatable BIOS-originated corruption always
1413 affects the same memory, you can use memmap=
1414 to prevent the kernel from using that memory.
1416 memory_corruption_check_size=size [X86]
1417 By default it checks for corruption in the low
1418 64k, making this memory unavailable for normal
1419 use. Use this parameter to scan for
1420 corruption in more or less memory.
1422 memory_corruption_check_period=seconds [X86]
1423 By default it checks for corruption every 60
1424 seconds. Use this parameter to check at some
1425 other rate. 0 disables periodic checking.
1427 memtest= [KNL,X86] Enable memtest
1429 default : 0 <disable>
1430 Specifies the number of memtest passes to be
1431 performed. Each pass selects another test
1432 pattern from a given set of patterns. Memtest
1433 fills the memory with this pattern, validates
1434 memory contents and reserves bad memory
1435 regions that are detected.
1437 meye.*= [HW] Set MotionEye Camera parameters
1438 See Documentation/video4linux/meye.txt.
1440 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1441 Multi-Function General Purpose Timers on AMD Geode
1444 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1445 the BIOS has incorrectly applied a workaround. TinyBIOS
1446 version 0.98 is known to be affected, 0.99 fixes the
1447 problem by letting the user disable the workaround.
1451 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1452 physical address is ignored.
1454 mini2440= [ARM,HW,KNL]
1455 Format:[0..2][b][c][t]
1457 MINI2440 configuration specification:
1458 0 - The attached screen is the 3.5" TFT
1459 1 - The attached screen is the 7" TFT
1460 2 - The VGA Shield is attached (1024x768)
1461 Leaving out the screen size parameter will not load
1462 the TFT driver, and the framebuffer will be left
1464 b - Enable backlight. The TFT backlight pin will be
1465 linked to the kernel VESA blanking code and a GPIO
1466 LED. This parameter is not necessary when using the
1468 c - Enable the s3c camera interface.
1469 t - Reserved for enabling touchscreen support. The
1470 touchscreen support is not enabled in the mainstream
1471 kernel as of 2.6.30, a preliminary port can be found
1472 in the "bleeding edge" mini2440 support kernel at
1473 http://repo.or.cz/w/linux-2.6/mini2440.git
1476 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1477 parameter allows control of the logging verbosity for
1478 the additional memory initialisation checks. A value
1479 of 0 disables mminit logging and a level of 4 will
1480 log everything. Information is printed at KERN_DEBUG
1481 so loglevel=8 may also need to be specified.
1484 [MOUSE] Maximum time between finger touching and
1485 leaving touchpad surface for touch to be considered
1486 a tap and be reported as a left button click (for
1487 touchpads working in absolute mode only).
1489 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1490 reporting absolute coordinates, such as tablets
1491 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1492 reporting absolute coordinates, such as tablets
1494 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1495 is similar to kernelcore except it specifies the
1496 amount of memory used for migratable allocations.
1497 If both kernelcore and movablecore is specified,
1498 then kernelcore will be at *least* the specified
1499 value but may be more. If movablecore on its own
1500 is specified, the administrator must be careful
1501 that the amount of memory usable for all allocations
1504 MTD_Partition= [MTD]
1505 Format: <name>,<region-number>,<size>,<offset>
1507 MTD_Region= [MTD] Format:
1508 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1511 See drivers/mtd/cmdlinepart.c.
1513 multitce=off [PPC] This parameter disables the use of the pSeries
1514 firmware feature for updating multiple TCE entries
1517 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1519 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1521 boundary - index of last SLC block on Flex-OneNAND.
1522 The remaining blocks are configured as MLC blocks.
1523 lock - Configure if Flex-OneNAND boundary should be locked.
1524 Once locked, the boundary cannot be changed.
1525 1 indicates lock status, 0 indicates unlock status.
1528 ARM/S3C2412 JIVE boot control
1530 See arch/arm/mach-s3c2412/mach-jive.c
1532 mtouchusb.raw_coordinates=
1533 [HW] Make the MicroTouch USB driver use raw coordinates
1534 ('y', default) or cooked coordinates ('n')
1536 mtrr_chunk_size=nn[KMG] [X86]
1537 used for mtrr cleanup. It is largest continuous chunk
1538 that could hold holes aka. UC entries.
1540 mtrr_gran_size=nn[KMG] [X86]
1541 Used for mtrr cleanup. It is granularity of mtrr block.
1543 Large value could prevent small alignment from
1546 mtrr_spare_reg_nr=n [X86]
1548 Range: 0,7 : spare reg number
1550 Used for mtrr cleanup. It is spare mtrr entries number.
1551 Set to 2 or more if your graphical card needs more.
1553 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1555 netdev= [NET] Network devices parameters
1556 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1557 Note that mem_start is often overloaded to mean
1558 something different and driver-specific.
1559 This usage is only documented in each driver source
1563 [NETFILTER] Enable connection tracking flow accounting
1564 0 to disable accounting
1565 1 to enable accounting
1568 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1569 See Documentation/filesystems/nfs/nfsroot.txt.
1571 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1572 See Documentation/filesystems/nfs/nfsroot.txt.
1574 nfsrootdebug [NFS] enable nfsroot debugging messages.
1575 See Documentation/filesystems/nfs/nfsroot.txt.
1577 nfs.callback_tcpport=
1578 [NFS] set the TCP port on which the NFSv4 callback
1579 channel should listen.
1582 [NFS] sets the pathname to the program which is used
1583 to update the NFS client cache entries.
1585 nfs.cache_getent_timeout=
1586 [NFS] sets the timeout after which an attempt to
1587 update a cache entry is deemed to have failed.
1589 nfs.idmap_cache_timeout=
1590 [NFS] set the maximum lifetime for idmapper cache
1594 [NFS] enable 64-bit inode numbers.
1595 If zero, the NFS client will fake up a 32-bit inode
1596 number for the readdir() and stat() syscalls instead
1597 of returning the full 64-bit number.
1598 The default is to return 64-bit inode numbers.
1600 nfs.nfs4_disable_idmapping=
1601 [NFSv4] When set, this option disables the NFSv4
1602 idmapper on the client, but only if the mount
1603 is using the 'sec=sys' security flavour. This may
1604 make migration from legacy NFSv2/v3 systems easier
1605 provided that the server has the appropriate support.
1606 The default is to always enable NFSv4 idmapping.
1608 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1609 when a NMI is triggered.
1610 Format: [state][,regs][,debounce][,die]
1612 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1613 Format: [panic,][nopanic,][num]
1615 0 - turn nmi_watchdog off
1616 When panic is specified, panic when an NMI watchdog
1617 timeout occurs (or 'nopanic' to override the opposite
1619 This is useful when you use a panic=... timeout and
1620 need the box quickly up again.
1622 netpoll.carrier_timeout=
1623 [NET] Specifies amount of time (in seconds) that
1624 netpoll should wait for a carrier. By default netpoll
1627 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1628 emulation library even if a 387 maths coprocessor
1632 [HW] Never suspend the console
1633 Disable suspending of consoles during suspend and
1634 hibernate operations. Once disabled, debugging
1635 messages can reach various consoles while the rest
1636 of the system is being put to sleep (ie, while
1637 debugging driver suspend/resume hooks). This may
1638 not work reliably with all consoles, but is known
1639 to work with serial and VGA consoles.
1641 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1642 caches in the slab allocator. Saves per-node memory,
1643 but will impact performance.
1647 noapic [SMP,APIC] Tells the kernel to not make use of any
1648 IOAPICs that may be present in the system.
1650 noautogroup Disable scheduler automatic task group creation.
1652 nobats [PPC] Do not use BATs for mapping kernel lowmem
1653 on "Classic" PPC cores.
1657 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1659 nodelayacct [KNL] Disable per-task delay accounting
1661 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1663 nodsp [SH] Disable hardware DSP at boot time.
1665 noefi [X86] Disable EFI runtime services support.
1670 On X86-32 available only on PAE configured kernels.
1671 noexec=on: enable non-executable mappings (default)
1672 noexec=off: disable non-executable mappings
1675 Disable SMEP (Supervisor Mode Execution Protection)
1676 even if it is supported by processor.
1679 This affects only 32-bit executables.
1680 noexec32=on: enable non-executable mappings (default)
1681 read doesn't imply executable mappings
1682 noexec32=off: disable non-executable mappings
1683 read implies executable mappings
1685 nofpu [SH] Disable hardware FPU at boot time.
1687 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1688 register save and restore. The kernel will only save
1689 legacy floating-point registers on task switch.
1691 noxsave [BUGS=X86] Disables x86 extended register state save
1692 and restore using xsave. The kernel will fallback to
1693 enabling legacy floating-point and sse state.
1695 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1696 wfi(ARM) instruction doesn't work correctly and not to
1697 use it. This is also useful when using JTAG debugger.
1699 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1700 instruction doesn't work correctly and not to
1703 no_file_caps Tells the kernel not to honor file capabilities. The
1704 only way then for a file to be executed with privilege
1705 is to be setuid root or executed by root.
1707 nohalt [IA-64] Tells the kernel not to use the power saving
1708 function PAL_HALT_LIGHT when idle. This increases
1709 power-consumption. On the positive side, it reduces
1710 interrupt wake-up latency, which may improve performance
1711 in certain environments such as networked servers or
1714 nohz= [KNL] Boottime enable/disable dynamic ticks
1715 Valid arguments: on, off
1718 noiotrap [SH] Disables trapped I/O port accesses.
1720 noirqdebug [X86-32] Disables the code which attempts to detect and
1721 disable unhandled interrupt sources.
1723 no_timer_check [X86,APIC] Disables the code which tests for
1724 broken timer IRQ sources.
1726 noisapnp [ISAPNP] Disables ISA PnP code.
1728 noinitrd [RAM] Tells the kernel not to load any configured
1731 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1733 [Deprecated - use intremap=off]
1737 nojitter [IA64] Disables jitter checking for ITC timers.
1739 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1741 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1744 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1745 steal time is computed, but won't influence scheduler
1748 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1750 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1752 noltlbs [PPC] Do not use large page/tlb entries for kernel
1753 lowmem mapping on PPC40x.
1755 nomca [IA-64] Disable machine check abort handling
1757 nomce [X86-32] Machine Check Exception
1759 nomfgpt [X86-32] Disable Multi-Function General Purpose
1760 Timer usage (for AMD Geode machines).
1762 nopat [X86] Disable PAT (page attribute table extension of
1763 pagetables) support.
1765 norandmaps Don't use address space randomization. Equivalent to
1766 echo 0 > /proc/sys/kernel/randomize_va_space
1768 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1770 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1771 with UP alternatives
1773 noresidual [PPC] Don't use residual data on PReP machines.
1775 noresume [SWSUSP] Disables resume and restores original swap
1778 no-scroll [VGA] Disables scrollback.
1779 This is required for the Braillex ib80-piezo Braille
1780 reader made by F.H. Papenmeier (Germany).
1784 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1786 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1787 and disable the IO APIC. legacy for "maxcpus=0".
1789 nosoftlockup [KNL] Disable the soft-lockup detector.
1791 nosync [HW,M68K] Disables sync negotiation for all devices.
1793 notsc [BUGS=X86-32] Disable Time Stamp Counter
1795 nousb [USB] Disable the USB subsystem
1797 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1801 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1803 nptcg= [IA64] Override max number of concurrent global TLB
1804 purges which is reported from either PAL_VM_SUMMARY or
1807 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1808 could support. nr_cpus=n : n >= 1 limits the kernel to
1809 supporting 'n' processors. Later in runtime you can not
1810 use hotplug cpu feature to put more cpu back to online.
1811 just like you compile the kernel NR_CPUS=n
1813 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1815 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1816 one of ['zone', 'node', 'default'] can be specified
1817 This can be set from sysctl after boot.
1818 See Documentation/sysctl/vm.txt for details.
1820 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1821 See Documentation/debugging-via-ohci1394.txt for more
1824 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1825 Rather than timing out after 20 ms if an EC
1826 command is not properly ACKed, override the length
1827 of the timeout. We have interrupts disabled while
1828 waiting for the ACK, so if this is set too high
1829 interrupts *may* be lost!
1831 omap_mux= [OMAP] Override bootloader pin multiplexing.
1832 Format: <mux_mode0.mode_name=value>...
1833 For example, to override I2C bus2:
1834 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1836 oprofile.timer= [HW]
1837 Use timer interrupt instead of performance counters
1839 oprofile.cpu_type= Force an oprofile cpu type
1840 This might be useful if you have an older oprofile
1841 userland or if you want common events.
1842 Format: { arch_perfmon }
1843 arch_perfmon: [X86] Force use of architectural
1844 perfmon on Intel CPUs instead of the
1845 CPU specific event set.
1847 oops=panic Always panic on oopses. Default is to just kill the
1848 process, but there is a small probability of
1849 deadlocking the machine.
1850 This will also cause panics on machine check exceptions.
1851 Useful together with panic=30 to trigger a reboot.
1854 See Documentation/sound/oss/oss-parameters.txt
1856 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1857 timeout > 0: seconds before rebooting
1858 timeout = 0: wait forever
1859 timeout < 0: reboot immediately
1862 parkbd.port= [HW] Parallel port number the keyboard adapter is
1863 connected to, default is 0.
1865 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1866 0 for XT, 1 for AT (default is AT).
1869 parport= [HW,PPT] Specify parallel ports. 0 disables.
1870 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1871 Use 'auto' to force the driver to use any
1872 IRQ/DMA settings detected (the default is to
1873 ignore detected IRQ/DMA settings because of
1874 possible conflicts). You can specify the base
1875 address, IRQ, and DMA settings; IRQ and DMA
1876 should be numbers, or 'auto' (for using detected
1877 settings on that particular port), or 'nofifo'
1878 (to avoid using a FIFO even if it is detected).
1879 Parallel ports are assigned in the order they
1880 are specified on the command line, starting
1883 parport_init_mode= [HW,PPT]
1884 Configure VIA parallel port to operate in
1885 a specific mode. This is necessary on Pegasos
1886 computer where firmware has no options for setting
1887 up parallel port mode and sets it to spp.
1888 Currently this function knows 686a and 8231 chips.
1889 Format: [spp|ps2|epp|ecp|ecpepp]
1892 Halt all CPUs after the first oops has been printed for
1893 the specified number of seconds. This is to be used if
1894 your oopses keep scrolling off the screen.
1899 See header of drivers/block/paride/pcd.c.
1900 See also Documentation/blockdev/paride.txt.
1902 pci=option[,option...] [PCI] various PCI subsystem options:
1903 earlydump [X86] dump PCI config space before the kernel
1905 off [X86] don't probe for the PCI bus
1906 bios [X86-32] force use of PCI BIOS, don't access
1907 the hardware directly. Use this if your machine
1908 has a non-standard PCI host bridge.
1909 nobios [X86-32] disallow use of PCI BIOS, only direct
1910 hardware access methods are allowed. Use this
1911 if you experience crashes upon bootup and you
1912 suspect they are caused by the BIOS.
1913 conf1 [X86] Force use of PCI Configuration
1915 conf2 [X86] Force use of PCI Configuration
1917 noaer [PCIE] If the PCIEAER kernel config parameter is
1918 enabled, this kernel boot option can be used to
1919 disable the use of PCIE advanced error reporting.
1920 nodomains [PCI] Disable support for multiple PCI
1921 root domains (aka PCI segments, in ACPI-speak).
1922 nommconf [X86] Disable use of MMCONFIG for PCI
1924 check_enable_amd_mmconf [X86] check for and enable
1925 properly configured MMIO access to PCI
1926 config space on AMD family 10h CPU
1927 nomsi [MSI] If the PCI_MSI kernel config parameter is
1928 enabled, this kernel boot option can be used to
1929 disable the use of MSI interrupts system-wide.
1930 noioapicquirk [APIC] Disable all boot interrupt quirks.
1931 Safety option to keep boot IRQs enabled. This
1932 should never be necessary.
1933 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1934 primary IO-APIC for bridges that cannot disable
1935 boot IRQs. This fixes a source of spurious IRQs
1936 when the system masks IRQs.
1937 noioapicreroute [APIC] Disable workaround that uses the
1938 boot IRQ equivalent of an IRQ that connects to
1939 a chipset where boot IRQs cannot be disabled.
1940 The opposite of ioapicreroute.
1941 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1942 routing table. These calls are known to be buggy
1943 on several machines and they hang the machine
1944 when used, but on other computers it's the only
1945 way to get the interrupt routing table. Try
1946 this option if the kernel is unable to allocate
1947 IRQs or discover secondary PCI buses on your
1949 rom [X86] Assign address space to expansion ROMs.
1950 Use with caution as certain devices share
1951 address decoders between ROMs and other
1953 norom [X86] Do not assign address space to
1954 expansion ROMs that do not already have
1955 BIOS assigned address ranges.
1956 nobar [X86] Do not assign address space to the
1957 BARs that weren't assigned by the BIOS.
1958 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1959 assigned automatically to PCI devices. You can
1960 make the kernel exclude IRQs of your ISA cards
1962 pirqaddr=0xAAAAA [X86] Specify the physical address
1963 of the PIRQ table (normally generated
1964 by the BIOS) if it is outside the
1965 F0000h-100000h range.
1966 lastbus=N [X86] Scan all buses thru bus #N. Can be
1967 useful if the kernel is unable to find your
1968 secondary buses and you want to tell it
1969 explicitly which ones they are.
1970 assign-busses [X86] Always assign all PCI bus
1971 numbers ourselves, overriding
1972 whatever the firmware may have done.
1973 usepirqmask [X86] Honor the possible IRQ mask stored
1974 in the BIOS $PIR table. This is needed on
1975 some systems with broken BIOSes, notably
1976 some HP Pavilion N5400 and Omnibook XE3
1977 notebooks. This will have no effect if ACPI
1978 IRQ routing is enabled.
1979 noacpi [X86] Do not use ACPI for IRQ routing
1980 or for PCI scanning.
1981 use_crs [X86] Use PCI host bridge window information
1982 from ACPI. On BIOSes from 2008 or later, this
1983 is enabled by default. If you need to use this,
1984 please report a bug.
1985 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1986 If you need to use this, please report a bug.
1987 routeirq Do IRQ routing for all PCI devices.
1988 This is normally done in pci_enable_device(),
1989 so this option is a temporary workaround
1990 for broken drivers that don't call it.
1991 skip_isa_align [X86] do not align io start addr, so can
1992 handle more pci cards
1993 firmware [ARM] Do not re-enumerate the bus but instead
1994 just use the configuration from the
1995 bootloader. This is currently used on
1996 IXP2000 systems where the bus has to be
1997 configured a certain way for adjunct CPUs.
1998 noearly [X86] Don't do any early type 1 scanning.
1999 This might help on some broken boards which
2000 machine check when some devices' config space
2001 is read. But various workarounds are disabled
2002 and some IOMMU drivers will not work.
2003 bfsort Sort PCI devices into breadth-first order.
2004 This sorting is done to get a device
2005 order compatible with older (<= 2.4) kernels.
2006 nobfsort Don't sort PCI devices into breadth-first order.
2007 cbiosize=nn[KMG] The fixed amount of bus space which is
2008 reserved for the CardBus bridge's IO window.
2009 The default value is 256 bytes.
2010 cbmemsize=nn[KMG] The fixed amount of bus space which is
2011 reserved for the CardBus bridge's memory
2012 window. The default value is 64 megabytes.
2015 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2016 Specifies alignment and device to reassign
2017 aligned memory resources.
2018 If <order of align> is not specified,
2019 PAGE_SIZE is used as alignment.
2020 PCI-PCI bridge can be specified, if resource
2021 windows need to be expanded.
2022 ecrc= Enable/disable PCIe ECRC (transaction layer
2023 end-to-end CRC checking).
2024 bios: Use BIOS/firmware settings. This is the
2028 realloc reallocate PCI resources if allocations done by BIOS
2031 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2034 force Enable ASPM even on devices that claim not to support it.
2035 WARNING: Forcing ASPM on may cause system lockups.
2037 pcie_ports= [PCIE] PCIe ports handling:
2038 auto Ask the BIOS whether or not to use native PCIe services
2039 associated with PCIe ports (PME, hot-plug, AER). Use
2040 them only if that is allowed by the BIOS.
2041 native Use native PCIe services associated with PCIe ports
2043 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2046 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2047 nomsi Do not use MSI for native PCIe PME signaling (this makes
2048 all PCIe root ports use INTx for all services).
2050 pcmv= [HW,PCMCIA] BadgePAD 4
2053 See Documentation/blockdev/paride.txt.
2055 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2058 See arch/parisc/kernel/pdc_chassis.c
2060 percpu_alloc= Select which percpu first chunk allocator to use.
2061 Currently supported values are "embed" and "page".
2062 Archs may support subset or none of the selections.
2063 See comments in mm/percpu.c for details on each
2064 allocator. This parameter is primarily for debugging
2065 and performance comparison.
2068 See Documentation/blockdev/paride.txt.
2071 See Documentation/blockdev/paride.txt.
2073 pirq= [SMP,APIC] Manual mp-table setup
2074 See Documentation/x86/i386/IO-APIC.txt.
2076 plip= [PPT,NET] Parallel port network link
2077 Format: { parport<nr> | timid | 0 }
2078 See also Documentation/parport.txt.
2080 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2081 Override pmtimer IOPort with a hex value.
2085 Enable PNP debug messages. This depends on the
2086 CONFIG_PNP_DEBUG_MESSAGES option.
2092 { on | off | curr | res | no-curr | no-res }
2095 [ISAPNP] Exclude IRQs for the autoconfiguration
2098 [ISAPNP] Exclude DMAs for the autoconfiguration
2100 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2101 Ranges are in pairs (I/O port base and size).
2104 [ISAPNP] Exclude memory regions for the
2106 Ranges are in pairs (memory base and size).
2108 ports= [IP_VS_FTP] IPVS ftp helper module
2110 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2112 Format: <port>,<port>....
2114 print-fatal-signals=
2115 [KNL] debug: print fatal signals
2117 If enabled, warn about various signal handling
2118 related application anomalies: too many signals,
2119 too many POSIX.1 timers, fatal signals causing a
2122 If you hit the warning due to signal overflow,
2123 you might want to try "ulimit -i unlimited".
2127 printk.time= Show timing data prefixed to each printk message line
2128 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2130 processor.max_cstate= [HW,ACPI]
2131 Limit processor to maximum C-state
2132 max_cstate=9 overrides any DMI blacklist limit.
2134 processor.nocst [HW,ACPI]
2135 Ignore the _CST method to determine C-states,
2136 instead using the legacy FADT method
2138 profile= [KNL] Enable kernel profiling via /proc/profile
2139 Format: [schedule,]<number>
2140 Param: "schedule" - profile schedule points.
2141 Param: <number> - step/bucket size as a power of 2 for
2142 statistical time based profiling.
2143 Param: "sleep" - profile D-state sleeping (millisecs).
2144 Requires CONFIG_SCHEDSTATS
2145 Param: "kvm" - profile VM exits.
2147 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2149 See Documentation/blockdev/ramdisk.txt.
2151 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2152 probe for; one of (bare|imps|exps|lifebook|any).
2153 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2155 psmouse.resetafter= [HW,MOUSE]
2156 Try to reset the device after so many bad packets
2159 [HW,MOUSE] Set desired mouse resolution, in dpi.
2160 psmouse.smartscroll=
2161 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2162 0 = disabled, 1 = enabled (default).
2164 pstore.backend= Specify the name of the pstore backend to use
2167 See Documentation/blockdev/paride.txt.
2170 [KNL] Number of legacy pty's. Overwrites compiled-in
2173 quiet [KNL] Disable most log messages
2178 See Documentation/md.txt.
2180 ramdisk_blocksize= [RAM]
2181 See Documentation/blockdev/ramdisk.txt.
2183 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2184 See Documentation/blockdev/ramdisk.txt.
2186 rcupdate.blimit= [KNL,BOOT]
2187 Set maximum number of finished RCU callbacks to process
2190 rcupdate.qhimark= [KNL,BOOT]
2191 Set threshold of queued
2192 RCU callbacks over which batch limiting is disabled.
2194 rcupdate.qlowmark= [KNL,BOOT]
2195 Set threshold of queued RCU callbacks below which
2196 batch limiting is re-enabled.
2200 Run specified binary instead of /init from the ramdisk,
2201 used for early userspace startup. See initrd.
2203 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2204 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2205 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2208 [KNL, SMP] Set scheduler's default relax_domain_level.
2209 See Documentation/cgroups/cpusets.txt.
2211 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2213 reservetop= [X86-32]
2215 Reserves a hole at the top of the kernel virtual
2220 Set the amount of memory to reserve for BIOS at
2221 the bottom of the address space.
2223 reset_devices [KNL] Force drivers to reset the underlying device
2224 during initialization.
2227 Specify the partition device for software suspend
2229 resume_offset= [SWSUSP]
2230 Specify the offset from the beginning of the partition
2231 given by "resume=" at which the swap header is located,
2232 in <PAGE_SIZE> units (needed only for swap files).
2233 See Documentation/power/swsusp-and-swap-files.txt
2235 hibernate= [HIBERNATION]
2236 noresume Don't check if there's a hibernation image
2237 present during boot.
2238 nocompress Don't compress/decompress hibernation images.
2240 retain_initrd [RAM] Keep initrd memory after extraction
2242 rhash_entries= [KNL,NET]
2243 Set number of hash buckets for route cache
2245 riscom8= [HW,SERIAL]
2246 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2248 ro [KNL] Mount root device read-only on boot
2250 root= [KNL] Root filesystem
2251 See name_to_dev_t comment in init/do_mounts.c.
2253 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2254 mount the root filesystem
2256 rootflags= [KNL] Set root filesystem mount option string
2258 rootfstype= [KNL] Set root filesystem type
2260 rootwait [KNL] Wait (indefinitely) for root device to show up.
2261 Useful for devices that are detected asynchronously
2262 (e.g. USB and MMC devices).
2264 rw [KNL] Mount root device read-write on boot
2266 S [KNL] Run init in single mode
2269 See drivers/net/irda/sa1100_ir.c.
2271 sbni= [NET] Granch SBNI12 leased line adapter
2273 sched_debug [KNL] Enables verbose scheduler debug messages.
2275 security= [SECURITY] Choose a security module to enable at boot.
2276 If this boot parameter is not specified, only the first
2277 security module asking for security registration will be
2278 loaded. An invalid security module name will be treated
2279 as if no module has been chosen.
2281 selinux= [SELINUX] Disable or enable SELinux at boot time.
2282 Format: { "0" | "1" }
2283 See security/selinux/Kconfig help text.
2286 Default value is set via kernel config option.
2287 If enabled at boot time, /selinux/disable can be used
2288 later to disable prior to initial policy load.
2290 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2291 Format: { "0" | "1" }
2292 See security/apparmor/Kconfig help text
2295 Default value is set via kernel config option.
2297 serialnumber [BUGS=X86-32]
2300 Maximal number of shapers.
2302 show_msr= [x86] show boot-time MSR settings
2303 Format: { <integer> }
2304 Show boot-time (BIOS-initialized) MSR settings.
2305 The parameter means the number of CPUs to show,
2306 for example 1 means boot CPU only.
2313 slub_debug[=options[,slabs]] [MM, SLUB]
2314 Enabling slub_debug allows one to determine the
2315 culprit if slab objects become corrupted. Enabling
2316 slub_debug can create guard zones around objects and
2317 may poison objects when not in use. Also tracks the
2318 last alloc / free. For more information see
2319 Documentation/vm/slub.txt.
2321 slub_max_order= [MM, SLUB]
2322 Determines the maximum allowed order for slabs.
2323 A high setting may cause OOMs due to memory
2324 fragmentation. For more information see
2325 Documentation/vm/slub.txt.
2327 slub_min_objects= [MM, SLUB]
2328 The minimum number of objects per slab. SLUB will
2329 increase the slab order up to slub_max_order to
2330 generate a sufficiently large slab able to contain
2331 the number of objects indicated. The higher the number
2332 of objects the smaller the overhead of tracking slabs
2333 and the less frequently locks need to be acquired.
2334 For more information see Documentation/vm/slub.txt.
2336 slub_min_order= [MM, SLUB]
2337 Determines the mininum page order for slabs. Must be
2338 lower than slub_max_order.
2339 For more information see Documentation/vm/slub.txt.
2341 slub_nomerge [MM, SLUB]
2342 Disable merging of slabs with similar size. May be
2343 necessary if there is some reason to distinguish
2344 allocs to different slabs. Debug options disable
2345 merging on their own.
2346 For more information see Documentation/vm/slub.txt.
2349 Format: <io1>[,<io2>[,...,<io8>]]
2351 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2352 attempt to substitute SMP alternatives once at boot.
2354 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2355 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2356 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2357 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2358 smsc-ircc2.ircc_irq= [HW] IRQ line
2359 smsc-ircc2.ircc_dma= [HW] DMA channel
2360 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2361 0: Toshiba Satellite 1800 (GP data pin select)
2362 1: Fast pin select (default)
2366 [KNL] Should the soft-lockup detector generate panics.
2369 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2370 See Documentation/sonypi.txt
2372 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2373 See Documentation/serial/specialix.txt.
2375 spia_io_base= [HW,MTD]
2381 Enabled the stack tracer on boot up.
2385 Set the STI (builtin display/keyboard on the HP-PARISC
2386 machines) console (graphic card) which should be used
2387 as the initial boot-console.
2388 See also comment in drivers/video/console/sticore.c.
2391 See comment in drivers/video/console/sticore.c.
2394 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2396 sunrpc.min_resvport=
2397 sunrpc.max_resvport=
2399 SunRPC servers often require that client requests
2400 originate from a privileged port (i.e. a port in the
2401 range 0 < portnr < 1024).
2402 An administrator who wishes to reserve some of these
2403 ports for other uses may adjust the range that the
2404 kernel's sunrpc client considers to be privileged
2405 using these two parameters to set the minimum and
2406 maximum port values.
2410 Control how the NFS server code allocates CPUs to
2411 service thread pools. Depending on how many NICs
2412 you have and where their interrupts are bound, this
2413 option will affect which CPUs will do NFS serving.
2414 Note: this parameter cannot be changed while the
2415 NFS server is running.
2417 auto the server chooses an appropriate mode
2418 automatically using heuristics
2419 global a single global pool contains all CPUs
2420 percpu one pool for each CPU
2421 pernode one pool for each NUMA node (equivalent
2422 to global on non-NUMA machines)
2424 sunrpc.tcp_slot_table_entries=
2425 sunrpc.udp_slot_table_entries=
2427 Sets the upper limit on the number of simultaneous
2428 RPC calls that can be sent from the client to a
2429 server. Increasing these values may allow you to
2430 improve throughput, but will also increase the
2431 amount of memory reserved for use by the client.
2434 [KNL] Enable accounting of swap in memory resource
2435 controller if no parameter or 1 is given or disable
2436 it if 0 is given (See Documentation/cgroups/memory.txt)
2438 swiotlb= [IA-64] Number of I/O TLB slabs
2442 sysfs.deprecated=0|1 [KNL]
2443 Enable/disable old style sysfs layout for old udev
2444 on older distributions. When this option is enabled
2445 very new udev will not work anymore. When this option
2446 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2447 in older udev will not work anymore.
2448 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2449 the kernel configuration.
2451 sysrq_always_enabled
2453 Ignore sysrq setting - this boot parameter will
2454 neutralize any effect of /proc/sys/kernel/sysrq.
2455 Useful for debugging.
2459 test_suspend= [SUSPEND]
2460 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2461 standby suspend) as the system sleep state to briefly
2462 enter during system startup. The system is woken from
2463 this state using a wakeup-capable RTC alarm.
2465 thash_entries= [KNL,NET]
2466 Set number of hash buckets for TCP connection
2468 thermal.act= [HW,ACPI]
2469 -1: disable all active trip points in all thermal zones
2470 <degrees C>: override all lowest active trip points
2472 thermal.crt= [HW,ACPI]
2473 -1: disable all critical trip points in all thermal zones
2474 <degrees C>: override all critical trip points
2476 thermal.nocrt= [HW,ACPI]
2477 Set to disable actions on ACPI thermal zone
2478 critical and hot trip points.
2480 thermal.off= [HW,ACPI]
2481 1: disable ACPI thermal control
2483 thermal.psv= [HW,ACPI]
2484 -1: disable all passive trip points
2485 <degrees C>: override all passive trip points to this
2488 thermal.tzp= [HW,ACPI]
2489 Specify global default ACPI thermal zone polling rate
2490 <deci-seconds>: poll all this frequency
2491 0: no polling (default)
2494 Force threading of all interrupt handlers except those
2495 marked explicitely IRQF_NO_THREAD.
2499 Specify if the kernel should make use of the cpu
2500 topology information if the hardware supports this.
2501 The scheduler will make use of this information and
2502 e.g. base its process migration decisions on it.
2507 tpm_suspend_pcr=[HW,TPM]
2508 Format: integer pcr id
2509 Specify that at suspend time, the tpm driver
2510 should extend the specified pcr with zeros,
2511 as a workaround for some chips which fail to
2512 flush the last written pcr on TPM_SaveState.
2513 This will guarantee that all the other pcrs
2516 trace_buf_size=nn[KMG]
2517 [FTRACE] will set tracing buffer size.
2519 trace_event=[event-list]
2520 [FTRACE] Set and start specified trace events in order
2521 to facilitate early boot debugging.
2522 See also Documentation/trace/events.txt
2524 tsc= Disable clocksource stability checks for TSC.
2526 [x86] reliable: mark tsc clocksource as reliable, this
2527 disables clocksource verification at runtime, as well
2528 as the stability checks done at bootup. Used to enable
2529 high-resolution timer mode on older hardware, and in
2530 virtualized environment.
2531 [x86] noirqtime: Do not use TSC to do irq accounting.
2532 Used to run time disable IRQ_TIME_ACCOUNTING on any
2533 platforms where RDTSC is slow and this accounting
2536 turbografx.map[2|3]= [HW,JOY]
2537 TurboGraFX parallel port interface
2539 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2540 See also Documentation/input/joystick-parport.txt
2542 udbg-immortal [PPC] When debugging early kernel crashes that
2543 happen after console_init() and before a proper
2544 console driver takes over, this boot options might
2545 help "seeing" what's going on.
2547 uhash_entries= [KNL,NET]
2548 Set number of hash buckets for UDP/UDP-Lite connections
2551 [USB] Ignore overcurrent events (default N).
2552 Some badly-designed motherboards generate lots of
2553 bogus events, for ports that aren't wired to
2554 anything. Set this parameter to avoid log spamming.
2555 Note that genuine overcurrent events won't be
2559 [X86] Cause panic on unknown NMI.
2561 usbcore.authorized_default=
2562 [USB] Default USB device authorization:
2563 (default -1 = authorized except for wireless USB,
2564 0 = not authorized, 1 = authorized)
2566 usbcore.autosuspend=
2567 [USB] The autosuspend time delay (in seconds) used
2568 for newly-detected USB devices (default 2). This
2569 is the time required before an idle device will be
2570 autosuspended. Devices for which the delay is set
2571 to a negative value won't be autosuspended at all.
2573 usbcore.usbfs_snoop=
2574 [USB] Set to log all usbfs traffic (default 0 = off).
2576 usbcore.blinkenlights=
2577 [USB] Set to cycle leds on hubs (default 0 = off).
2579 usbcore.old_scheme_first=
2580 [USB] Start with the old device initialization
2581 scheme (default 0 = off).
2583 usbcore.use_both_schemes=
2584 [USB] Try the other device initialization scheme
2585 if the first one fails (default 1 = enabled).
2587 usbcore.initial_descriptor_timeout=
2588 [USB] Specifies timeout for the initial 64-byte
2589 USB_REQ_GET_DESCRIPTOR request in milliseconds
2590 (default 5000 = 5.0 seconds).
2593 [USBHID] The interval which mice are to be polled at.
2595 usb-storage.delay_use=
2596 [UMS] The delay in seconds before a new device is
2597 scanned for Logical Units (default 5).
2600 [UMS] A list of quirks entries to supplement or
2601 override the built-in unusual_devs list. List
2602 entries are separated by commas. Each entry has
2603 the form VID:PID:Flags where VID and PID are Vendor
2604 and Product ID values (4-digit hex numbers) and
2605 Flags is a set of characters, each corresponding
2606 to a common usb-storage quirk flag as follows:
2607 a = SANE_SENSE (collect more than 18 bytes
2609 b = BAD_SENSE (don't collect more than 18
2610 bytes of sense data);
2611 c = FIX_CAPACITY (decrease the reported
2612 device capacity by one sector);
2613 d = NO_READ_DISC_INFO (don't use
2614 READ_DISC_INFO command);
2615 e = NO_READ_CAPACITY_16 (don't use
2616 READ_CAPACITY_16 command);
2617 h = CAPACITY_HEURISTICS (decrease the
2618 reported device capacity by one
2619 sector if the number is odd);
2620 i = IGNORE_DEVICE (don't bind to this
2622 l = NOT_LOCKABLE (don't try to lock and
2623 unlock ejectable media);
2624 m = MAX_SECTORS_64 (don't transfer more
2625 than 64 sectors = 32 KB at a time);
2626 n = INITIAL_READ10 (force a retry of the
2627 initial READ(10) command);
2628 o = CAPACITY_OK (accept the capacity
2629 reported by the device);
2630 r = IGNORE_RESIDUE (the device reports
2631 bogus residue values);
2632 s = SINGLE_LUN (the device has only one
2634 w = NO_WP_DETECT (don't test whether the
2635 medium is write-protected).
2636 Example: quirks=0419:aaf5:rl,0421:0433:rc
2639 [X86] Flags controlling user PTE allocations.
2641 nohigh = do not allocate PTE pages in
2642 HIGHMEM regardless of setting
2646 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2647 vdso=1: enable VDSO (default)
2648 vdso=0: disable VDSO mapping
2651 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2652 vdso32=1: enable 32-bit VDSO (default)
2653 vdso32=0: disable 32-bit VDSO mapping
2656 vector=percpu: enable percpu vector domain
2658 video= [FB] Frame buffer configuration
2659 See Documentation/fb/modedb.txt.
2661 vga= [BOOT,X86-32] Select a particular video mode
2662 See Documentation/x86/boot.txt and
2663 Documentation/svga.txt.
2664 Use vga=ask for menu.
2665 This is actually a boot loader parameter; the value is
2666 passed to the kernel using a special protocol.
2668 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2669 size of <nn>. This can be used to increase the
2670 minimum size (128MB on x86). It can also be used to
2671 decrease the size and leave more room for directly
2674 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2677 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2680 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2683 vt.cur_default= [VT] Default cursor shape.
2684 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2685 the parameters of the <Esc>[?A;B;Cc escape sequence;
2686 see VGA-softcursor.txt. Default: 2 = underline.
2688 vt.default_blu= [VT]
2689 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2690 Change the default blue palette of the console.
2691 This is a 16-member array composed of values
2694 vt.default_grn= [VT]
2695 Format: <green0>,<green1>,<green2>,...,<green15>
2696 Change the default green palette of the console.
2697 This is a 16-member array composed of values
2700 vt.default_red= [VT]
2701 Format: <red0>,<red1>,<red2>,...,<red15>
2702 Change the default red palette of the console.
2703 This is a 16-member array composed of values
2709 Set system-wide default UTF-8 mode for all tty's.
2710 Default is 1, i.e. UTF-8 mode is enabled for all
2711 newly opened terminals.
2713 vt.global_cursor_default=
2716 Set system-wide default for whether a cursor
2717 is shown on new VTs. Default is -1,
2718 i.e. cursors will be created by default unless
2719 overridden by individual drivers. 0 will hide
2720 cursors, 1 will display them.
2722 watchdog timers [HW,WDT] For information on watchdog timers,
2723 see Documentation/watchdog/watchdog-parameters.txt
2724 or other driver-specific files in the
2725 Documentation/watchdog/ directory.
2727 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2728 default x2apic cluster mode on platforms
2731 x86_mrst_timer= [X86-32,APBT]
2732 Choose timer option for x86 Moorestown MID platform.
2733 Two valid options are apbt timer only and lapic timer
2734 plus one apbt timer for broadcast timer.
2735 x86_mrst_timer=apbt_only | lapic_and_apbt
2737 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2738 xd_geo= See header of drivers/block/xd.c.
2740 xen_emul_unplug= [HW,X86,XEN]
2741 Unplug Xen emulated devices
2742 Format: [unplug0,][unplug1]
2743 ide-disks -- unplug primary master IDE devices
2744 aux-ide-disks -- unplug non-primary-master IDE devices
2745 nics -- unplug network devices
2746 all -- unplug all emulated devices (NICs and IDE disks)
2747 unnecessary -- unplugging emulated devices is
2748 unnecessary even if the host did not respond to
2750 never -- do not unplug even if version check succeeds
2752 xirc2ps_cs= [NET,PCMCIA]
2754 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2756 ______________________________________________________________________
2760 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob