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 EVM Extended Verification Module
52 FB The frame buffer device is enabled.
53 GCOV GCOV profiling is enabled.
54 HW Appropriate hardware is enabled.
55 IA-64 IA-64 architecture is enabled.
56 IMA Integrity measurement architecture is enabled.
57 IOSCHED More than one I/O scheduler is enabled.
58 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
59 IPV6 IPv6 support is enabled.
60 ISAPNP ISA PnP code is enabled.
61 ISDN Appropriate ISDN support is enabled.
62 JOY Appropriate joystick support is enabled.
63 KGDB Kernel debugger support is enabled.
64 KVM Kernel Virtual Machine support is enabled.
65 LIBATA Libata driver is enabled
66 LP Printer support is enabled.
67 LOOP Loopback device support is enabled.
68 M68k M68k architecture is enabled.
69 These options have more detailed description inside of
70 Documentation/m68k/kernel-options.txt.
71 MCA MCA bus support is enabled.
72 MDA MDA console support is enabled.
73 MOUSE Appropriate mouse support is enabled.
74 MSI Message Signaled Interrupts (PCI).
75 MTD MTD (Memory Technology Device) support is enabled.
76 NET Appropriate network support is enabled.
77 NUMA NUMA support is enabled.
78 NFS Appropriate NFS support is enabled.
79 OSS OSS sound support is enabled.
80 PV_OPS A paravirtualized kernel is enabled.
81 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
82 PARISC The PA-RISC architecture is enabled.
83 PCI PCI bus support is enabled.
84 PCIE PCI Express support is enabled.
85 PCMCIA The PCMCIA subsystem is enabled.
86 PNP Plug & Play support is enabled.
87 PPC PowerPC architecture is enabled.
88 PPT Parallel port support is enabled.
89 PS2 Appropriate PS/2 support is enabled.
90 RAM RAM disk support is enabled.
91 S390 S390 architecture is enabled.
92 SCSI Appropriate SCSI support is enabled.
93 A lot of drivers have their options described inside
94 the Documentation/scsi/ sub-directory.
95 SECURITY Different security models are enabled.
96 SELINUX SELinux support is enabled.
97 APPARMOR AppArmor support is enabled.
98 SERIAL Serial support is enabled.
99 SH SuperH architecture is enabled.
100 SMP The kernel is an SMP kernel.
101 SPARC Sparc architecture is enabled.
102 SWSUSP Software suspend (hibernation) is enabled.
103 SUSPEND System suspend states are enabled.
104 FTRACE Function tracing enabled.
105 TPM TPM drivers are enabled.
106 TS Appropriate touchscreen support is enabled.
107 UMS USB Mass Storage support is enabled.
108 USB USB support is enabled.
109 USBHID USB Human Interface Device support is enabled.
110 V4L Video For Linux support is enabled.
111 VGA The VGA console has been enabled.
112 VT Virtual terminal support is enabled.
113 WDT Watchdog support is enabled.
114 XT IBM PC/XT MFM hard disk support is enabled.
115 X86-32 X86-32, aka i386 architecture is enabled.
116 X86-64 X86-64 architecture is enabled.
117 More X86-64 boot options can be found in
118 Documentation/x86/x86_64/boot-options.txt .
119 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
120 XEN Xen support is enabled
122 In addition, the following text indicates that the option:
124 BUGS= Relates to possible processor bugs on the said processor.
125 KNL Is a kernel start-up parameter.
126 BOOT Is a boot loader parameter.
128 Parameters denoted with BOOT are actually interpreted by the boot
129 loader, and have no meaning to the kernel directly.
130 Do not modify the syntax of boot loader parameters without extreme
131 need or coordination with <Documentation/x86/boot.txt>.
133 There are also arch-specific kernel-parameters not documented here.
134 See for example <Documentation/x86/x86_64/boot-options.txt>.
136 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
137 a trailing = on the name of any parameter states that that parameter will
138 be entered as an environment variable, whereas its absence indicates that
139 it will appear as a kernel argument readable via /proc/cmdline by programs
140 running once the system is up.
142 The number of kernel parameters is not limited, but the length of the
143 complete command line (parameters including spaces etc.) is limited to
144 a fixed number of characters. This limit depends on the architecture
145 and is between 256 and 4096 characters. It is defined in the file
146 ./include/asm/setup.h as COMMAND_LINE_SIZE.
148 Finally, the [KMG] suffix is commonly described after a number of kernel
149 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
150 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
151 bytes respectively. Such letter suffixes can also be entirely omitted.
155 Advanced Configuration and Power Interface
156 Format: { force | off | strict | noirq | rsdt }
157 force -- enable ACPI if default was off
158 off -- disable ACPI if default was on
159 noirq -- do not use ACPI for IRQ routing
160 strict -- Be less tolerant of platforms that are not
161 strictly ACPI specification compliant.
162 rsdt -- prefer RSDT over (default) XSDT
163 copy_dsdt -- copy DSDT to memory
165 See also Documentation/power/pm.txt, pci=noacpi
167 acpi_rsdp= [ACPI,EFI,KEXEC]
168 Pass the RSDP address to the kernel, mostly used
169 on machines running EFI runtime service to boot the
170 second kernel for kdump.
172 acpi_apic_instance= [ACPI, IOAPIC]
174 2: use 2nd APIC table, if available
175 1,0: use 1st APIC table
178 acpi_backlight= [HW,ACPI]
179 acpi_backlight=vendor
181 If set to vendor, prefer vendor specific driver
182 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
183 of the ACPI video.ko driver.
185 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
186 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
188 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
189 debug output. Bits in debug_layer correspond to a
190 _COMPONENT in an ACPI source file, e.g.,
191 #define _COMPONENT ACPI_PCI_COMPONENT
192 Bits in debug_level correspond to a level in
193 ACPI_DEBUG_PRINT statements, e.g.,
194 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
195 The debug_level mask defaults to "info". See
196 Documentation/acpi/debug.txt for more information about
197 debug layers and levels.
199 Enable processor driver info messages:
200 acpi.debug_layer=0x20000000
201 Enable PCI/PCI interrupt routing info messages:
202 acpi.debug_layer=0x400000
203 Enable AML "Debug" output, i.e., stores to the Debug
204 object while interpreting AML:
205 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
206 Enable all messages related to ACPI hardware:
207 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
209 Some values produce so much output that the system is
210 unusable. The "log_buf_len" parameter may be useful
211 if you need to capture more output.
213 acpi_irq_balance [HW,ACPI]
214 ACPI will balance active IRQs
217 acpi_irq_nobalance [HW,ACPI]
218 ACPI will not move active IRQs (default)
221 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
222 Format: <irq>,<irq>...
224 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
226 Format: <irq>,<irq>...
228 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
230 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
231 Format: To spoof as Windows 98: ="Microsoft Windows"
233 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
234 acpi_osi="string1" # add string1 -- only one string
235 acpi_osi="!string2" # remove built-in string2
236 acpi_osi= # disable all strings
239 Override the pmtimer bug detection: force the kernel
240 to assume that this machine's pmtimer latches its value
241 and always returns good values.
243 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
244 Format: { level | edge | high | low }
246 acpi_serialize [HW,ACPI] force serialization of AML methods
248 acpi_skip_timer_override [HW,ACPI]
249 Recognize and ignore IRQ0/pin2 Interrupt Override.
250 For broken nForce2 BIOS resulting in XT-PIC timer.
252 acpi_sleep= [HW,ACPI] Sleep options
253 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
254 old_ordering, nonvs, sci_force_enable }
255 See Documentation/power/video.txt for information on
257 s3_beep is for debugging; it makes the PC's speaker beep
258 as soon as the kernel's real-mode entry point is called.
259 s4_nohwsig prevents ACPI hardware signature from being
260 used during resume from hibernation.
261 old_ordering causes the ACPI 1.0 ordering of the _PTS
262 control method, with respect to putting devices into
263 low power states, to be enforced (the ACPI 2.0 ordering
264 of _PTS is used by default).
265 nonvs prevents the kernel from saving/restoring the
266 ACPI NVS memory during suspend/hibernation and resume.
267 sci_force_enable causes the kernel to set SCI_EN directly
268 on resume from S1/S3 (which is against the ACPI spec,
269 but some broken systems don't work without it).
271 acpi_use_timer_override [HW,ACPI]
272 Use timer override. For some broken Nvidia NF5 boards
273 that require a timer override, but don't have HPET
275 acpi_enforce_resources= [ACPI]
276 { strict | lax | no }
277 Check for resource conflicts between native drivers
278 and ACPI OperationRegions (SystemIO and SystemMemory
279 only). IO ports and memory declared in ACPI might be
280 used by the ACPI subsystem in arbitrary AML code and
281 can interfere with legacy drivers.
282 strict (default): access to resources claimed by ACPI
283 is denied; legacy drivers trying to access reserved
284 resources will fail to bind to device using them.
285 lax: access to resources claimed by ACPI is allowed;
286 legacy drivers trying to access reserved resources
287 will bind successfully but a warning message is logged.
288 no: ACPI OperationRegions are not marked as reserved,
289 no further checks are performed.
291 add_efi_memmap [EFI; X86] Include EFI memory map in
292 kernel's map of available physical RAM.
295 { off | try_unsupported }
296 off: disable AGP support
297 try_unsupported: try to drive unsupported chipsets
298 (may crash computer or cause data corruption)
301 See Documentation/sound/alsa/alsa-parameters.txt
304 Allow the default userspace alignment fault handler
305 behaviour to be specified. Bit 0 enables warnings,
306 bit 1 enables fixups, and bit 2 sends a segfault.
308 amd_iommu= [HW,X86-84]
309 Pass parameters to the AMD IOMMU driver in the system.
311 fullflush - enable flushing of IO/TLB entries when
312 they are unmapped. Otherwise they are
313 flushed before they will be reused, which
315 off - do not initialize any AMD IOMMU found in
318 amijoy.map= [HW,JOY] Amiga joystick support
319 Map of devices attached to JOY0DAT and JOY1DAT
321 See also Documentation/kernel/input/joystick.txt
323 analog.map= [HW,JOY] Analog joystick and gamepad support
324 Specifies type or capabilities of an analog joystick
325 connected to one of 16 gameports
326 Format: <type1>,<type2>,..<type16>
329 Power management functions (SPARCstation-4/5 + deriv.)
331 Disable APC CPU standby support. SPARCstation-Fox does
332 not play well with APC CPU idle - disable it if you have
333 APC and your system crashes randomly.
335 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
336 Change the output verbosity whilst booting
337 Format: { quiet (default) | verbose | debug }
338 Change the amount of debugging information output
339 when initialising the APIC and IO-APIC components.
342 See Documentation/networking/ipv6.txt.
344 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
345 Limit apic dumping. The parameter defines the maximal
346 number of local apics being dumped. Also it is possible
347 to set it to "all" by meaning -- no limit here.
348 Format: { 1 (default) | 2 | ... | all }.
349 The parameter valid if only apic=debug or
350 apic=verbose is specified.
351 Example: apic=debug show_lapic=all
353 apm= [APM] Advanced Power Management
354 See header of arch/x86/kernel/apm_32.c.
356 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
357 Format: <io>,<irq>,<nodeID>
361 atarimouse= [HW,MOUSE] Atari Mouse
363 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
364 EzKey and similar keyboards
366 atkbd.reset= [HW] Reset keyboard during initialization
368 atkbd.set= [HW] Select keyboard code set
369 Format: <int> (2 = AT (default), 3 = PS/2)
371 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
374 atkbd.softraw= [HW] Choose between synthetic and real raw mode
375 Format: <bool> (0 = real, 1 = synthetic (default))
377 atkbd.softrepeat= [HW]
378 Use software keyboard repeat
382 baycom_epp= [HW,AX25]
385 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
387 See header of drivers/net/hamradio/baycom_par.c.
389 baycom_ser_fdx= [HW,AX25]
390 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
391 Format: <io>,<irq>,<mode>[,<baud>]
392 See header of drivers/net/hamradio/baycom_ser_fdx.c.
394 baycom_ser_hdx= [HW,AX25]
395 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
396 Format: <io>,<irq>,<mode>
397 See header of drivers/net/hamradio/baycom_ser_hdx.c.
399 boot_delay= Milliseconds to delay each printk during boot.
400 Values larger than 10 seconds (10000) are changed to
404 bootmem_debug [KNL] Enable bootmem allocator debug messages.
406 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
407 bttv.radio= Most important insmod options are available as
409 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
410 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
412 bulk_remove=off [PPC] This parameter disables the use of the pSeries
413 firmware feature for flushing multiple hpte entries
416 c101= [NET] Moxa C101 synchronous serial card
418 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
419 Sometimes CPU hardware bugs make them report the cache
420 size incorrectly. The kernel will attempt work arounds
421 to fix known problems, but for some CPUs it is not
422 possible to determine what the correct size should be.
423 This option provides an override for these situations.
426 [SECURITY] Disable capabilities. This would normally
427 be used only if an alternative security model is to be
428 configured. Potentially dangerous and should only be
429 used if you are entirely sure of the consequences.
431 ccw_timeout_log [S390]
432 See Documentation/s390/CommonIO for details.
434 cgroup_disable= [KNL] Disable a particular controller
435 Format: {name of the controller(s) to disable}
436 {Currently supported controllers - "memory"}
438 checkreqprot [SELINUX] Set initial checkreqprot flag value.
439 Format: { "0" | "1" }
440 See security/selinux/Kconfig help text.
441 0 -- check protection applied by kernel (includes
442 any implied execute protection).
443 1 -- check protection requested by application.
444 Default value is set via a kernel config option.
445 Value can be changed at runtime via
446 /selinux/checkreqprot.
449 See Documentation/s390/CommonIO for details.
451 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
453 Forces specified clocksource (if available) to be used
454 when calculating gettimeofday(). If specified
455 clocksource is not available, it defaults to PIT.
456 Format: { pit | tsc | cyclone | pmtmr }
458 clocksource= Override the default clocksource
460 Override the default clocksource and use the clocksource
461 with the name specified.
462 Some clocksource names to choose from, depending on
464 [all] jiffies (this is the base, fallback clocksource)
466 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
467 pxa_timer,timer3,32k_counter,timer0_1
469 [X86-32] pit,hpet,tsc;
470 scx200_hrt on Geode; cyclone on IBM x440
478 clearcpuid=BITNUM [X86]
479 Disable CPUID feature X for the kernel. See
480 arch/x86/include/asm/cpufeature.h for the valid bit
481 numbers. Note the Linux specific bits are not necessarily
482 stable over kernel options, but the vendor specific
484 Also note that user programs calling CPUID directly
485 or using the feature without checking anything
486 will still see it. This just prevents it from
487 being used by the kernel or shown in /proc/cpuinfo.
488 Also note the kernel might malfunction if you disable
491 cmo_free_hint= [PPC] Format: { yes | no }
492 Specify whether pages are marked as being inactive
493 when they are freed. This is used in CMO environments
494 to determine OS memory pressure for page stealing by
498 code_bytes [X86] How many bytes of object code to print
503 com20020= [HW,NET] ARCnet - COM20020 chipset
505 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
507 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
511 ARCnet - COM90xx chipset (memory-mapped buffers)
512 Format: <io>[,<irq>[,<memstart>]]
514 condev= [HW,S390] console device
517 console= [KNL] Output console device and options.
519 tty<n> Use the virtual console device <n>.
523 Use the specified serial port. The options are of
524 the form "bbbbpnf", where "bbbb" is the baud rate,
525 "p" is parity ("n", "o", or "e"), "n" is number of
526 bits, and "f" is flow control ("r" for RTS or
527 omit it). Default is "9600n8".
529 See Documentation/serial-console.txt for more
531 Documentation/networking/netconsole.txt for an
534 uart[8250],io,<addr>[,options]
535 uart[8250],mmio,<addr>[,options]
536 Start an early, polled-mode console on the 8250/16550
537 UART at the specified I/O port or MMIO address,
538 switching to the matching ttyS device later. The
539 options are the same as for ttyS, above.
541 If the device connected to the port is not a TTY but a braille
542 device, prepend "brl," before the device type, for instance
544 For now, only VisioBraille is supported.
546 consoleblank= [KNL] The console blank (screen saver) timeout in
547 seconds. Defaults to 10*60 = 10mins. A value of 0
548 disables the blank timer.
551 [KNL] Change the default value for
552 /proc/<pid>/coredump_filter.
553 See also Documentation/filesystems/proc.txt.
555 cpuidle.off=1 [CPU_IDLE]
556 disable the cpuidle sub-system
558 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
560 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
562 crashkernel=size[KMG][@offset[KMG]]
563 [KNL] Using kexec, Linux can switch to a 'crash kernel'
564 upon panic. This parameter reserves the physical
565 memory region [offset, offset + size] for that kernel
566 image. If '@offset' is omitted, then a suitable offset
567 is selected automatically. Check
568 Documentation/kdump/kdump.txt for further details.
570 crashkernel=range1:size1[,range2:size2,...][@offset]
571 [KNL] Same as above, but depends on the memory
572 in the running system. The syntax of range is
573 start-[end] where start and end are both
574 a memory unit (amount[KMG]). See also
575 Documentation/kdump/kdump.txt for an example.
580 cs89x0_media= [HW,NET]
581 Format: { rj45 | aui | bnc }
584 See header of drivers/s390/block/dasd_devmap.c.
586 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
587 (one device per port)
588 Format: <port#>,<type>
589 See also Documentation/input/joystick-parport.txt
591 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
592 time. See Documentation/dynamic-debug-howto.txt for
595 debug [KNL] Enable kernel debugging (events log level).
598 [KNL] verbose self-tests
600 Print debugging info while doing the locking API
602 We default to 0 (no extra messages), setting it to
603 1 will print _a lot_ more information - normally
604 only useful to kernel developers.
606 debug_objects [KNL] Enable object debugging
609 [KNL] Disable object debugging
611 debugpat [X86] Enable PAT debugging
613 decnet.addr= [HW,NET]
614 Format: <area>[,<node>]
615 See also Documentation/networking/decnet.txt.
618 [same as hugepagesz=] The size of the default
619 HugeTLB page size. This is the size represented by
620 the legacy /proc/ hugepages APIs, used for SHM, and
621 default size when mounting hugetlbfs filesystems.
622 Defaults to the default architecture's huge page size
626 Set number of hash buckets for dentry cache.
629 IO parameters + enable/disable command.
631 digiepca= [HW,SERIAL]
632 See drivers/char/README.epca and
633 Documentation/serial/digiepca.txt.
636 See Documentation/networking/ipv6.txt.
638 disable_ddw [PPC/PSERIES]
639 Disable Dynamic DMA Window support. Use this if
640 to workaround buggy firmware.
643 See Documentation/networking/ipv6.txt.
645 disable_mtrr_cleanup [X86]
646 The kernel tries to adjust MTRR layout from continuous
647 to discrete, to make X server driver able to add WB
648 entry later. This parameter disables that.
650 disable_mtrr_trim [X86, Intel and AMD only]
651 By default the kernel will trim any uncacheable
652 memory out of your available memory pool based on
653 MTRR settings. This parameter disables that behavior,
654 possibly causing your machine to run very slowly.
656 disable_timer_pin_1 [X86]
657 Disable PIN 1 of APIC timer
658 Can be useful to work around chipset bugs.
660 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
661 this option disables the debugging code at boot.
663 dma_debug_entries=<number>
664 This option allows to tune the number of preallocated
665 entries for DMA-API debugging code. One entry is
666 required per DMA-API allocation. Use this if the
667 DMA-API debugging code disables itself because the
668 architectural default is too low.
670 dma_debug_driver=<driver_name>
671 With this option the DMA-API debugging driver
672 filter feature can be enabled at boot time. Just
673 pass the driver to filter for as the parameter.
674 The filter can be disabled or changed to another
675 driver later using sysfs.
679 earlycon= [KNL] Output early console device and options.
680 uart[8250],io,<addr>[,options]
681 uart[8250],mmio,<addr>[,options]
682 uart[8250],mmio32,<addr>[,options]
683 Start an early, polled-mode console on the 8250/16550
684 UART at the specified I/O port or MMIO address.
685 MMIO inter-register address stride is either 8bit (mmio)
687 The options are the same as for ttyS, above.
689 earlyprintk= [X86,SH,BLACKFIN]
691 earlyprintk=serial[,ttySn[,baudrate]]
692 earlyprintk=ttySn[,baudrate]
693 earlyprintk=dbgp[debugController#]
695 Append ",keep" to not disable it when the real console
698 Only vga or serial or usb debug port at a time.
700 Currently only ttyS0 and ttyS1 are supported.
702 Interaction with the standard serial driver is not
705 The VGA output is eventually overwritten by the real
708 ekgdboc= [X86,KGDB] Allow early kernel console debugging
711 This is designed to be used in conjunction with
712 the boot argument: earlyprintk=vga
715 Format: {"off" | "on" | "skip[mbr]"}
717 eisa_irq_edge= [PARISC,HW]
718 See header of drivers/parisc/eisa.c.
721 See comment before function elanfreq_setup() in
722 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
725 Format: {"cfq" | "deadline" | "noop"}
726 See Documentation/block/as-iosched.txt and
727 Documentation/block/deadline-iosched.txt for details.
729 elfcorehdr= [IA64,PPC,SH,X86]
730 Specifies physical address of start of kernel core
731 image elf header. Generally kexec loader will
732 pass this option to capture kernel.
733 See Documentation/kdump/kdump.txt for details.
735 enable_mtrr_cleanup [X86]
736 The kernel tries to adjust MTRR layout from continuous
737 to discrete, to make X server driver able to add WB
738 entry later. This parameter enables that.
740 enable_timer_pin_1 [X86]
741 Enable PIN 1 of APIC timer
742 Can be useful to work around chipset bugs
743 (in particular on some ATI chipsets).
744 The kernel tries to set a reasonable default.
746 enforcing [SELINUX] Set initial enforcing status.
748 See security/selinux/Kconfig help text.
749 0 -- permissive (log only, no denials).
750 1 -- enforcing (deny and log).
752 Value can be changed at runtime via /selinux/enforce.
755 Disable Error Record Serialization Table (ERST)
758 ether= [HW,NET] Ethernet cards parameters
759 This option is obsoleted by the "netdev=" option, which
760 has equivalent usage. See its documentation for details.
764 Permit 'security.evm' to be updated regardless of
765 current integrity status.
769 fail_make_request=[KNL]
770 General fault injection mechanism.
771 Format: <interval>,<probability>,<space>,<times>
772 See also /Documentation/fault-injection/.
775 See Documentation/blockdev/floppy.txt.
777 force_pal_cache_flush
778 [IA-64] Avoid check_sal_cache_flush which may hang on
779 buggy SAL_CACHE_FLUSH implementations. Using this
780 parameter will force ia64_sal_cache_flush to call
781 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
784 [FTRACE] will set and start the specified tracer
785 as early as possible in order to facilitate early
788 ftrace_dump_on_oops[=orig_cpu]
789 [FTRACE] will dump the trace buffers on oops.
790 If no parameter is passed, ftrace will dump
791 buffers of all CPUs, but if you pass orig_cpu, it will
792 dump only the buffer of the CPU that triggered the
795 ftrace_filter=[function-list]
796 [FTRACE] Limit the functions traced by the function
797 tracer at boot up. function-list is a comma separated
798 list of functions. This list can be changed at run
799 time by the set_ftrace_filter file in the debugfs
802 ftrace_notrace=[function-list]
803 [FTRACE] Do not trace the functions specified in
804 function-list. This list can be changed at run time
805 by the set_ftrace_notrace file in the debugfs
808 ftrace_graph_filter=[function-list]
809 [FTRACE] Limit the top level callers functions traced
810 by the function graph tracer at boot up.
811 function-list is a comma separated list of functions
812 that can be changed at run time by the
813 set_graph_function file in the debugfs tracing directory.
816 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
817 support via parallel port (up to 5 devices per port)
818 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
819 See also Documentation/input/joystick-parport.txt
823 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
827 gcov_persist= [GCOV] When non-zero (default), profiling data for
828 kernel modules is saved and remains accessible via
829 debugfs, even when the module is unloaded/reloaded.
830 When zero, profiling data is discarded and associated
831 debugfs files are removed at module unload time.
833 gpt [EFI] Forces disk with valid GPT signature but
834 invalid Protective MBR to be treated as GPT.
836 hashdist= [KNL,NUMA] Large hashes allocated during boot
837 are distributed across NUMA nodes. Defaults on
838 for 64bit NUMA, off otherwise.
839 Format: 0 | 1 (for off | on)
841 hcl= [IA-64] SGI's Hardware Graph compatibility layer
843 hd= [EIDE] (E)IDE hard drive subsystem geometry
844 Format: <cyl>,<head>,<sect>
847 Disable Hardware Error Source Table (HEST) support;
848 corresponding firmware-first mode error processing
849 logic will be disabled.
851 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
852 size of <nn>. This works even on boxes that have no
853 highmem otherwise. This also works to reduce highmem
854 size on bigger boxes.
856 highres= [KNL] Enable/disable high resolution timer mode.
857 Valid parameters: "on", "off"
861 See Documentation/isdn/README.HiSax.
865 hpet= [X86-32,HPET] option to control HPET usage
866 Format: { enable (default) | disable | force |
868 disable: disable HPET and use PIT instead
869 force: allow force enabled of undocumented chips (ICH4,
871 verbose: show contents of HPET registers during setup
873 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
874 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
875 On x86-64 and powerpc, this option can be specified
876 multiple times interleaved with hugepages= to reserve
877 huge pages of different sizes. Valid pages sizes on
878 x86-64 are 2M (when the CPU supports "pse") and 1G
879 (when the CPU supports the "pdpe1gb" cpuinfo flag)
880 Note that 1GB pages can only be allocated at boot time
881 using hugepages= and not freed afterwards.
883 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
884 terminal devices. Valid values: 0..8
885 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
886 If specified, z/VM IUCV HVC accepts connections
887 from listed z/VM user IDs only.
890 Do not unregister boot console at start. This is only
891 useful for debugging when something happens in the window
892 between unregistering the boot console and initializing
895 i2c_bus= [HW] Override the default board specific I2C bus speed
896 or register an additional I2C bus that is not
897 registered from board initialization code.
901 i8042.debug [HW] Toggle i8042 debug mode
902 i8042.direct [HW] Put keyboard port into non-translated mode
903 i8042.dumbkbd [HW] Pretend that controller can only read data from
904 keyboard and cannot control its state
905 (Don't attempt to blink the leds)
906 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
907 i8042.nokbd [HW] Don't check/create keyboard port
908 i8042.noloop [HW] Disable the AUX Loopback command while probing
910 i8042.nomux [HW] Don't check presence of an active multiplexing
912 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
914 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
915 i8042.reset [HW] Reset the controller during init and cleanup
916 i8042.unlock [HW] Unlock (ignore) the keylock
920 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
921 indicates that the driver is running on unsupported
923 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
924 does not match list of supported models.
926 [HW] Report power status in /proc/i8k
927 (disabled by default)
928 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
932 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
934 ide-core.nodma= [HW] (E)IDE subsystem
935 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
936 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
937 .cdrom .chs .ignore_cable are additional options
938 See Documentation/ide/ide.txt.
940 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
941 Claim all unknown PCI IDE storage controllers.
944 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
945 Poll forces a polling idle loop that can slightly
946 improve the performance of waking up a idle CPU, but
947 will use a lot of power and make the system run hot.
949 idle=mwait: On systems which support MONITOR/MWAIT but
950 the kernel chose to not use it because it doesn't save
951 as much power as a normal idle loop, use the
952 MONITOR/MWAIT idle loop anyways. Performance should be
953 the same as idle=poll.
954 idle=halt: Halt is forced to be used for CPU idle.
955 In such case C2/C3 won't be used again.
956 idle=nomwait: Disable mwait for CPU C-states
958 ignore_loglevel [KNL]
959 Ignore loglevel setting - this will print /all/
960 kernel messages to the console. Useful for debugging.
963 Set number of hash buckets for inode cache.
966 Format: { "0" | "1" }
967 0 -- integrity auditing messages. (Default)
968 1 -- enable informational integrity auditing messages.
971 Format: { "sha1" | "md5" }
975 Load a policy which meets the needs of the Trusted
976 Computing Base. This means IMA will measure all
977 programs exec'd, files mmap'd for exec, and all files
978 opened for read by uid=0.
982 Run specified binary instead of /sbin/init as init
985 initcall_debug [KNL] Trace initcalls as they are executed. Useful
986 for working out where the kernel is dying during
989 initrd= [BOOT] Specify the location of the initial ramdisk
991 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
994 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
996 Enable intel iommu driver.
998 Disable intel iommu driver.
999 igfx_off [Default Off]
1000 By default, gfx is mapped as normal device. If a gfx
1001 device has a dedicated DMAR unit, the DMAR unit is
1002 bypassed by not enabling DMAR with this option. In
1003 this case, gfx device will use physical address for
1006 With this option iommu will not optimize to look
1007 for io virtual address below 32 bit forcing dual
1008 address cycle on pci bus for cards supporting greater
1009 than 32 bit addressing. The default is to look
1010 for translation below 32 bit and if not available
1011 then look in the higher range.
1012 strict [Default Off]
1013 With this option on every unmap_single operation will
1014 result in a hardware IOTLB flush operation as opposed
1015 to batching them for performance.
1016 sp_off [Default Off]
1017 By default, super page will be supported if Intel IOMMU
1018 has the capability. With this option, super page will
1020 intremap= [X86-64, Intel-IOMMU]
1021 Format: { on (default) | off | nosid }
1022 on enable Interrupt Remapping (default)
1023 off disable Interrupt Remapping
1024 nosid disable Source ID checking
1028 iomem= Disable strict checking of access to MMIO memory
1029 strict regions from userspace.
1045 io7= [HW] IO7 for Marvel based alpha systems
1046 See comment before marvel_specify_io7 in
1047 arch/alpha/kernel/core_marvel.c.
1049 io_delay= [X86] I/O delay method
1051 Standard port 0x80 based delay
1053 Alternate port 0xed based delay (needed on some systems)
1055 Simple two microseconds delay
1060 See Documentation/filesystems/nfs/nfsroot.txt.
1062 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1063 See comment before ip2_setup() in
1064 drivers/char/ip2/ip2base.c.
1067 When an interrupt is not handled search all handlers
1068 for it. Intended to get systems with badly broken
1072 When an interrupt is not handled search all handlers
1073 for it. Also check all handlers each timer
1074 interrupt. Intended to get systems with badly broken
1078 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1080 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1082 <cpu number>,...,<cpu number>
1084 <cpu number>-<cpu number>
1085 (must be a positive range in ascending order)
1087 <cpu number>,...,<cpu number>-<cpu number>
1089 This option can be used to specify one or more CPUs
1090 to isolate from the general SMP balancing and scheduling
1091 algorithms. You can move a process onto or off an
1092 "isolated" CPU via the CPU affinity syscalls or cpuset.
1093 <cpu number> begins at 0 and the maximum value is
1094 "number of CPUs in system - 1".
1096 This option is the preferred way to isolate CPUs. The
1097 alternative -- manually setting the CPU mask of all
1098 tasks in the system -- can cause problems and
1099 suboptimal load balancer performance.
1103 js= [HW,JOY] Analog joystick
1104 See Documentation/input/joystick.txt.
1108 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1109 specifies the amount of memory usable by the kernel
1110 for non-movable allocations. The requested amount is
1111 spread evenly throughout all nodes in the system. The
1112 remaining memory in each node is used for Movable
1113 pages. In the event, a node is too small to have both
1114 kernelcore and Movable pages, kernelcore pages will
1115 take priority and other nodes will have a larger number
1116 of kernelcore pages. The Movable zone is used for the
1117 allocation of pages that may be reclaimed or moved
1118 by the page migration subsystem. This means that
1119 HugeTLB pages may not be allocated from this zone.
1120 Note that allocations like PTEs-from-HighMem still
1121 use the HighMem zone if it exists, and the Normal
1122 zone if it does not.
1124 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1125 Format: <Controller#>[,poll interval]
1126 The controller # is the number of the ehci usb debug
1127 port as it is probed via PCI. The poll interval is
1128 optional and is the number seconds in between
1129 each poll cycle to the debug port in case you need
1130 the functionality for interrupting the kernel with
1131 gdb or control-c on the dbgp connection. When
1132 not using this parameter you use sysrq-g to break into
1133 the kernel debugger.
1135 kgdboc= [KGDB,HW] kgdb over consoles.
1136 Requires a tty driver that supports console polling,
1137 or a supported polling keyboard driver (non-usb).
1138 Serial only format: <serial_device>[,baud]
1139 keyboard only format: kbd
1140 keyboard and serial format: kbd,<serial_device>[,baud]
1141 Optional Kernel mode setting:
1142 kms, kbd format: kms,kbd
1143 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1145 kgdbwait [KGDB] Stop kernel execution and enter the
1146 kernel debugger at the earliest opportunity.
1148 kmac= [MIPS] korina ethernet MAC address.
1149 Configure the RouterBoard 532 series on-chip
1150 Ethernet adapter MAC address.
1152 kmemleak= [KNL] Boot-time kmemleak enable/disable
1153 Valid arguments: on, off
1156 kstack=N [X86] Print N words from the kernel stack
1159 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1160 Default is 0 (don't ignore, but inject #GP)
1162 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1163 Default is 1 (enabled)
1165 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1169 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1170 Default is 1 (enabled)
1172 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1174 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1176 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1177 (virtualized MMU) support on capable Intel chips.
1178 Default is 1 (enabled)
1180 kvm-intel.emulate_invalid_guest_state=
1181 [KVM,Intel] Enable emulation of invalid guest states
1182 Default is 0 (disabled)
1184 kvm-intel.flexpriority=
1185 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1186 Default is 1 (enabled)
1188 kvm-intel.unrestricted_guest=
1189 [KVM,Intel] Disable unrestricted guest feature
1190 (virtualized real and unpaged mode) on capable
1191 Intel chips. Default is 1 (enabled)
1193 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1194 feature (tagged TLBs) on capable Intel chips.
1195 Default is 1 (enabled)
1201 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1204 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1207 libata.dma= [LIBATA] DMA control
1208 libata.dma=0 Disable all PATA and SATA DMA
1209 libata.dma=1 PATA and SATA Disk DMA only
1210 libata.dma=2 ATAPI (CDROM) DMA only
1211 libata.dma=4 Compact Flash DMA only
1212 Combinations also work, so libata.dma=3 enables DMA
1213 for disks and CDROMs, but not CFs.
1215 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1216 libata.ignore_hpa=0 keep BIOS limits (default)
1217 libata.ignore_hpa=1 ignore limits, using full disk
1219 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1223 libata.force= [LIBATA] Force configurations. The format is comma
1224 separated list of "[ID:]VAL" where ID is
1225 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1226 matching port, link or device. Basically, it matches
1227 the ATA ID string printed on console by libata. If
1228 the whole ID part is omitted, the last PORT and DEVICE
1229 values are used. If ID hasn't been specified yet, the
1230 configuration applies to all ports, links and devices.
1232 If only DEVICE is omitted, the parameter applies to
1233 the port and all links and devices behind it. DEVICE
1234 number of 0 either selects the first device or the
1235 first fan-out link behind PMP device. It does not
1236 select the host link. DEVICE number of 15 selects the
1237 host link and device attached to it.
1239 The VAL specifies the configuration to force. As long
1240 as there's no ambiguity shortcut notation is allowed.
1241 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1242 The following configurations can be forced.
1244 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1245 Any ID with matching PORT is used.
1247 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1249 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1250 udma[/][16,25,33,44,66,100,133] notation is also
1253 * [no]ncq: Turn on or off NCQ.
1255 * nohrst, nosrst, norst: suppress hard, soft
1258 * dump_id: dump IDENTIFY data.
1260 If there are multiple matching configurations changing
1261 the same attribute, the last one is used.
1263 memblock=debug [KNL] Enable memblock debug messages.
1265 load_ramdisk= [RAM] List of ramdisks to load from floppy
1266 See Documentation/blockdev/ramdisk.txt.
1268 lockd.nlm_grace_period=P [NFS] Assign grace period.
1271 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1274 lockd.nlm_timeout=T [NFS] Assign timeout value.
1277 lockd.nlm_udpport=M [NFS] Assign UDP port.
1280 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1283 loglevel= All Kernel Messages with a loglevel smaller than the
1284 console loglevel will be printed to the console. It can
1285 also be changed with klogd or other programs. The
1286 loglevels are defined as follows:
1288 0 (KERN_EMERG) system is unusable
1289 1 (KERN_ALERT) action must be taken immediately
1290 2 (KERN_CRIT) critical conditions
1291 3 (KERN_ERR) error conditions
1292 4 (KERN_WARNING) warning conditions
1293 5 (KERN_NOTICE) normal but significant condition
1294 6 (KERN_INFO) informational
1295 7 (KERN_DEBUG) debug-level messages
1297 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1298 in bytes. n must be a power of two. The default
1299 size is set in the kernel config file.
1301 logo.nologo [FB] Disables display of the built-in Linux logo.
1302 This may be used to provide more screen space for
1303 kernel log messages and is useful when debugging
1304 kernel boot problems.
1306 lp=0 [LP] Specify parallel ports to use, e.g,
1307 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1308 lp=reset first parallel port). 'lp=0' disables the
1309 lp=auto printer driver. 'lp=reset' (which can be
1310 specified in addition to the ports) causes
1311 attached printers to be reset. Using
1312 lp=port1,port2,... specifies the parallel ports
1313 to associate lp devices with, starting with
1314 lp0. A port specification may be 'none' to skip
1315 that lp device, or a parport name such as
1316 'parport0'. Specifying 'lp=auto' instead of a
1317 port specification list means that device IDs
1318 from each port should be examined, to see if
1319 an IEEE 1284-compliant printer is attached; if
1320 so, the driver will manage that printer.
1321 See also header of drivers/char/lp.c.
1324 Sets loops_per_jiffy to given constant, thus avoiding
1325 time-consuming boot-time autodetection (up to 250 ms per
1326 CPU). 0 enables autodetection (default). To determine
1327 the correct value for your kernel, boot with normal
1328 autodetection and see what value is printed. Note that
1329 on SMP systems the preset will be applied to all CPUs,
1330 which is likely to cause problems if your CPUs need
1331 significantly divergent settings. An incorrect value
1332 will cause delays in the kernel to be wrong, leading to
1333 unpredictable I/O errors and other breakage. Although
1334 unlikely, in the extreme case this might damage your
1338 Format: <io>,<irq>,<dma>
1340 machvec= [IA64] Force the use of a particular machine-vector
1341 (machvec) in a generic kernel.
1342 Example: machvec=hpzx1_swiotlb
1344 machtype= [Loongson] Share the same kernel image file between different
1346 Example: machtype=lemote-yeeloong-2f-7inch
1348 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1349 than or equal to this physical address is ignored.
1351 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1352 should make use of. maxcpus=n : n >= 0 limits the
1353 kernel to using 'n' processors. n=0 is a special case,
1354 it is equivalent to "nosmp", which also disables
1357 max_loop= [LOOP] Maximum number of loopback devices that can
1363 mce [X86-32] Machine Check Exception
1365 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1367 md= [HW] RAID subsystems devices and level
1368 See Documentation/md.txt.
1371 Format: <first>,<last>
1372 Specifies range of consoles to be captured by the MDA.
1374 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1375 Amount of memory to be used when the kernel is not able
1376 to see the whole system memory or for test.
1377 [X86-32] Use together with memmap= to avoid physical
1378 address space collisions. Without memmap= PCI devices
1379 could be placed at addresses belonging to unused RAM.
1381 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1385 [KNL,SH] Allow user to override the default size for
1386 per-device physically contiguous DMA buffers.
1388 memmap=exactmap [KNL,X86] Enable setting of an exact
1389 E820 memory map, as specified by the user.
1390 Such memmap=exactmap lines can be constructed based on
1391 BIOS output or other requirements. See the memmap=nn@ss
1394 memmap=nn[KMG]@ss[KMG]
1395 [KNL] Force usage of a specific region of memory
1396 Region of memory to be used, from ss to ss+nn.
1398 memmap=nn[KMG]#ss[KMG]
1399 [KNL,ACPI] Mark specific memory as ACPI data.
1400 Region of memory to be used, from ss to ss+nn.
1402 memmap=nn[KMG]$ss[KMG]
1403 [KNL,ACPI] Mark specific memory as reserved.
1404 Region of memory to be used, from ss to ss+nn.
1405 Example: Exclude memory from 0x18690000-0x1869ffff
1406 memmap=64K$0x18690000
1408 memmap=0x10000$0x18690000
1410 memory_corruption_check=0/1 [X86]
1411 Some BIOSes seem to corrupt the first 64k of
1412 memory when doing things like suspend/resume.
1413 Setting this option will scan the memory
1414 looking for corruption. Enabling this will
1415 both detect corruption and prevent the kernel
1416 from using the memory being corrupted.
1417 However, its intended as a diagnostic tool; if
1418 repeatable BIOS-originated corruption always
1419 affects the same memory, you can use memmap=
1420 to prevent the kernel from using that memory.
1422 memory_corruption_check_size=size [X86]
1423 By default it checks for corruption in the low
1424 64k, making this memory unavailable for normal
1425 use. Use this parameter to scan for
1426 corruption in more or less memory.
1428 memory_corruption_check_period=seconds [X86]
1429 By default it checks for corruption every 60
1430 seconds. Use this parameter to check at some
1431 other rate. 0 disables periodic checking.
1433 memtest= [KNL,X86] Enable memtest
1435 default : 0 <disable>
1436 Specifies the number of memtest passes to be
1437 performed. Each pass selects another test
1438 pattern from a given set of patterns. Memtest
1439 fills the memory with this pattern, validates
1440 memory contents and reserves bad memory
1441 regions that are detected.
1443 meye.*= [HW] Set MotionEye Camera parameters
1444 See Documentation/video4linux/meye.txt.
1446 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1447 Multi-Function General Purpose Timers on AMD Geode
1450 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1451 the BIOS has incorrectly applied a workaround. TinyBIOS
1452 version 0.98 is known to be affected, 0.99 fixes the
1453 problem by letting the user disable the workaround.
1457 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1458 physical address is ignored.
1460 mini2440= [ARM,HW,KNL]
1461 Format:[0..2][b][c][t]
1463 MINI2440 configuration specification:
1464 0 - The attached screen is the 3.5" TFT
1465 1 - The attached screen is the 7" TFT
1466 2 - The VGA Shield is attached (1024x768)
1467 Leaving out the screen size parameter will not load
1468 the TFT driver, and the framebuffer will be left
1470 b - Enable backlight. The TFT backlight pin will be
1471 linked to the kernel VESA blanking code and a GPIO
1472 LED. This parameter is not necessary when using the
1474 c - Enable the s3c camera interface.
1475 t - Reserved for enabling touchscreen support. The
1476 touchscreen support is not enabled in the mainstream
1477 kernel as of 2.6.30, a preliminary port can be found
1478 in the "bleeding edge" mini2440 support kernel at
1479 http://repo.or.cz/w/linux-2.6/mini2440.git
1482 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1483 parameter allows control of the logging verbosity for
1484 the additional memory initialisation checks. A value
1485 of 0 disables mminit logging and a level of 4 will
1486 log everything. Information is printed at KERN_DEBUG
1487 so loglevel=8 may also need to be specified.
1490 [MOUSE] Maximum time between finger touching and
1491 leaving touchpad surface for touch to be considered
1492 a tap and be reported as a left button click (for
1493 touchpads working in absolute mode only).
1495 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1496 reporting absolute coordinates, such as tablets
1497 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1498 reporting absolute coordinates, such as tablets
1500 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1501 is similar to kernelcore except it specifies the
1502 amount of memory used for migratable allocations.
1503 If both kernelcore and movablecore is specified,
1504 then kernelcore will be at *least* the specified
1505 value but may be more. If movablecore on its own
1506 is specified, the administrator must be careful
1507 that the amount of memory usable for all allocations
1510 MTD_Partition= [MTD]
1511 Format: <name>,<region-number>,<size>,<offset>
1513 MTD_Region= [MTD] Format:
1514 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1517 See drivers/mtd/cmdlinepart.c.
1519 multitce=off [PPC] This parameter disables the use of the pSeries
1520 firmware feature for updating multiple TCE entries
1523 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1525 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1527 boundary - index of last SLC block on Flex-OneNAND.
1528 The remaining blocks are configured as MLC blocks.
1529 lock - Configure if Flex-OneNAND boundary should be locked.
1530 Once locked, the boundary cannot be changed.
1531 1 indicates lock status, 0 indicates unlock status.
1534 ARM/S3C2412 JIVE boot control
1536 See arch/arm/mach-s3c2412/mach-jive.c
1538 mtouchusb.raw_coordinates=
1539 [HW] Make the MicroTouch USB driver use raw coordinates
1540 ('y', default) or cooked coordinates ('n')
1542 mtrr_chunk_size=nn[KMG] [X86]
1543 used for mtrr cleanup. It is largest continuous chunk
1544 that could hold holes aka. UC entries.
1546 mtrr_gran_size=nn[KMG] [X86]
1547 Used for mtrr cleanup. It is granularity of mtrr block.
1549 Large value could prevent small alignment from
1552 mtrr_spare_reg_nr=n [X86]
1554 Range: 0,7 : spare reg number
1556 Used for mtrr cleanup. It is spare mtrr entries number.
1557 Set to 2 or more if your graphical card needs more.
1559 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1561 netdev= [NET] Network devices parameters
1562 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1563 Note that mem_start is often overloaded to mean
1564 something different and driver-specific.
1565 This usage is only documented in each driver source
1569 [NETFILTER] Enable connection tracking flow accounting
1570 0 to disable accounting
1571 1 to enable accounting
1574 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1575 See Documentation/filesystems/nfs/nfsroot.txt.
1577 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1578 See Documentation/filesystems/nfs/nfsroot.txt.
1580 nfsrootdebug [NFS] enable nfsroot debugging messages.
1581 See Documentation/filesystems/nfs/nfsroot.txt.
1583 nfs.callback_tcpport=
1584 [NFS] set the TCP port on which the NFSv4 callback
1585 channel should listen.
1588 [NFS] sets the pathname to the program which is used
1589 to update the NFS client cache entries.
1591 nfs.cache_getent_timeout=
1592 [NFS] sets the timeout after which an attempt to
1593 update a cache entry is deemed to have failed.
1595 nfs.idmap_cache_timeout=
1596 [NFS] set the maximum lifetime for idmapper cache
1600 [NFS] enable 64-bit inode numbers.
1601 If zero, the NFS client will fake up a 32-bit inode
1602 number for the readdir() and stat() syscalls instead
1603 of returning the full 64-bit number.
1604 The default is to return 64-bit inode numbers.
1606 nfs.nfs4_disable_idmapping=
1607 [NFSv4] When set, this option disables the NFSv4
1608 idmapper on the client, but only if the mount
1609 is using the 'sec=sys' security flavour. This may
1610 make migration from legacy NFSv2/v3 systems easier
1611 provided that the server has the appropriate support.
1612 The default is to always enable NFSv4 idmapping.
1614 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1615 when a NMI is triggered.
1616 Format: [state][,regs][,debounce][,die]
1618 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1619 Format: [panic,][nopanic,][num]
1621 0 - turn nmi_watchdog off
1622 When panic is specified, panic when an NMI watchdog
1623 timeout occurs (or 'nopanic' to override the opposite
1625 This is useful when you use a panic=... timeout and
1626 need the box quickly up again.
1628 netpoll.carrier_timeout=
1629 [NET] Specifies amount of time (in seconds) that
1630 netpoll should wait for a carrier. By default netpoll
1633 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1634 emulation library even if a 387 maths coprocessor
1638 [HW] Never suspend the console
1639 Disable suspending of consoles during suspend and
1640 hibernate operations. Once disabled, debugging
1641 messages can reach various consoles while the rest
1642 of the system is being put to sleep (ie, while
1643 debugging driver suspend/resume hooks). This may
1644 not work reliably with all consoles, but is known
1645 to work with serial and VGA consoles.
1647 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1648 caches in the slab allocator. Saves per-node memory,
1649 but will impact performance.
1653 noapic [SMP,APIC] Tells the kernel to not make use of any
1654 IOAPICs that may be present in the system.
1656 noautogroup Disable scheduler automatic task group creation.
1658 nobats [PPC] Do not use BATs for mapping kernel lowmem
1659 on "Classic" PPC cores.
1663 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1665 nodelayacct [KNL] Disable per-task delay accounting
1667 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1669 nodsp [SH] Disable hardware DSP at boot time.
1671 noefi [X86] Disable EFI runtime services support.
1676 On X86-32 available only on PAE configured kernels.
1677 noexec=on: enable non-executable mappings (default)
1678 noexec=off: disable non-executable mappings
1681 Disable SMEP (Supervisor Mode Execution Protection)
1682 even if it is supported by processor.
1685 This affects only 32-bit executables.
1686 noexec32=on: enable non-executable mappings (default)
1687 read doesn't imply executable mappings
1688 noexec32=off: disable non-executable mappings
1689 read implies executable mappings
1691 nofpu [SH] Disable hardware FPU at boot time.
1693 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1694 register save and restore. The kernel will only save
1695 legacy floating-point registers on task switch.
1697 noxsave [BUGS=X86] Disables x86 extended register state save
1698 and restore using xsave. The kernel will fallback to
1699 enabling legacy floating-point and sse state.
1701 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1702 wfi(ARM) instruction doesn't work correctly and not to
1703 use it. This is also useful when using JTAG debugger.
1705 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1706 instruction doesn't work correctly and not to
1709 no_file_caps Tells the kernel not to honor file capabilities. The
1710 only way then for a file to be executed with privilege
1711 is to be setuid root or executed by root.
1713 nohalt [IA-64] Tells the kernel not to use the power saving
1714 function PAL_HALT_LIGHT when idle. This increases
1715 power-consumption. On the positive side, it reduces
1716 interrupt wake-up latency, which may improve performance
1717 in certain environments such as networked servers or
1720 nohz= [KNL] Boottime enable/disable dynamic ticks
1721 Valid arguments: on, off
1724 noiotrap [SH] Disables trapped I/O port accesses.
1726 noirqdebug [X86-32] Disables the code which attempts to detect and
1727 disable unhandled interrupt sources.
1729 no_timer_check [X86,APIC] Disables the code which tests for
1730 broken timer IRQ sources.
1732 noisapnp [ISAPNP] Disables ISA PnP code.
1734 noinitrd [RAM] Tells the kernel not to load any configured
1737 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1739 [Deprecated - use intremap=off]
1743 nojitter [IA64] Disables jitter checking for ITC timers.
1745 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1747 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1750 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1751 steal time is computed, but won't influence scheduler
1754 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1756 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1758 noltlbs [PPC] Do not use large page/tlb entries for kernel
1759 lowmem mapping on PPC40x.
1761 nomca [IA-64] Disable machine check abort handling
1763 nomce [X86-32] Machine Check Exception
1765 nomfgpt [X86-32] Disable Multi-Function General Purpose
1766 Timer usage (for AMD Geode machines).
1768 nopat [X86] Disable PAT (page attribute table extension of
1769 pagetables) support.
1771 norandmaps Don't use address space randomization. Equivalent to
1772 echo 0 > /proc/sys/kernel/randomize_va_space
1774 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1776 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1777 with UP alternatives
1779 noresidual [PPC] Don't use residual data on PReP machines.
1781 noresume [SWSUSP] Disables resume and restores original swap
1784 no-scroll [VGA] Disables scrollback.
1785 This is required for the Braillex ib80-piezo Braille
1786 reader made by F.H. Papenmeier (Germany).
1790 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1792 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1793 and disable the IO APIC. legacy for "maxcpus=0".
1795 nosoftlockup [KNL] Disable the soft-lockup detector.
1797 nosync [HW,M68K] Disables sync negotiation for all devices.
1799 notsc [BUGS=X86-32] Disable Time Stamp Counter
1801 nousb [USB] Disable the USB subsystem
1803 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1807 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1809 nptcg= [IA64] Override max number of concurrent global TLB
1810 purges which is reported from either PAL_VM_SUMMARY or
1813 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1814 could support. nr_cpus=n : n >= 1 limits the kernel to
1815 supporting 'n' processors. Later in runtime you can not
1816 use hotplug cpu feature to put more cpu back to online.
1817 just like you compile the kernel NR_CPUS=n
1819 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1821 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1822 one of ['zone', 'node', 'default'] can be specified
1823 This can be set from sysctl after boot.
1824 See Documentation/sysctl/vm.txt for details.
1826 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1827 See Documentation/debugging-via-ohci1394.txt for more
1830 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1831 Rather than timing out after 20 ms if an EC
1832 command is not properly ACKed, override the length
1833 of the timeout. We have interrupts disabled while
1834 waiting for the ACK, so if this is set too high
1835 interrupts *may* be lost!
1837 omap_mux= [OMAP] Override bootloader pin multiplexing.
1838 Format: <mux_mode0.mode_name=value>...
1839 For example, to override I2C bus2:
1840 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1842 oprofile.timer= [HW]
1843 Use timer interrupt instead of performance counters
1845 oprofile.cpu_type= Force an oprofile cpu type
1846 This might be useful if you have an older oprofile
1847 userland or if you want common events.
1848 Format: { arch_perfmon }
1849 arch_perfmon: [X86] Force use of architectural
1850 perfmon on Intel CPUs instead of the
1851 CPU specific event set.
1853 oops=panic Always panic on oopses. Default is to just kill the
1854 process, but there is a small probability of
1855 deadlocking the machine.
1856 This will also cause panics on machine check exceptions.
1857 Useful together with panic=30 to trigger a reboot.
1860 See Documentation/sound/oss/oss-parameters.txt
1862 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1863 timeout > 0: seconds before rebooting
1864 timeout = 0: wait forever
1865 timeout < 0: reboot immediately
1868 parkbd.port= [HW] Parallel port number the keyboard adapter is
1869 connected to, default is 0.
1871 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1872 0 for XT, 1 for AT (default is AT).
1875 parport= [HW,PPT] Specify parallel ports. 0 disables.
1876 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1877 Use 'auto' to force the driver to use any
1878 IRQ/DMA settings detected (the default is to
1879 ignore detected IRQ/DMA settings because of
1880 possible conflicts). You can specify the base
1881 address, IRQ, and DMA settings; IRQ and DMA
1882 should be numbers, or 'auto' (for using detected
1883 settings on that particular port), or 'nofifo'
1884 (to avoid using a FIFO even if it is detected).
1885 Parallel ports are assigned in the order they
1886 are specified on the command line, starting
1889 parport_init_mode= [HW,PPT]
1890 Configure VIA parallel port to operate in
1891 a specific mode. This is necessary on Pegasos
1892 computer where firmware has no options for setting
1893 up parallel port mode and sets it to spp.
1894 Currently this function knows 686a and 8231 chips.
1895 Format: [spp|ps2|epp|ecp|ecpepp]
1898 Halt all CPUs after the first oops has been printed for
1899 the specified number of seconds. This is to be used if
1900 your oopses keep scrolling off the screen.
1905 See header of drivers/block/paride/pcd.c.
1906 See also Documentation/blockdev/paride.txt.
1908 pci=option[,option...] [PCI] various PCI subsystem options:
1909 earlydump [X86] dump PCI config space before the kernel
1911 off [X86] don't probe for the PCI bus
1912 bios [X86-32] force use of PCI BIOS, don't access
1913 the hardware directly. Use this if your machine
1914 has a non-standard PCI host bridge.
1915 nobios [X86-32] disallow use of PCI BIOS, only direct
1916 hardware access methods are allowed. Use this
1917 if you experience crashes upon bootup and you
1918 suspect they are caused by the BIOS.
1919 conf1 [X86] Force use of PCI Configuration
1921 conf2 [X86] Force use of PCI Configuration
1923 noaer [PCIE] If the PCIEAER kernel config parameter is
1924 enabled, this kernel boot option can be used to
1925 disable the use of PCIE advanced error reporting.
1926 nodomains [PCI] Disable support for multiple PCI
1927 root domains (aka PCI segments, in ACPI-speak).
1928 nommconf [X86] Disable use of MMCONFIG for PCI
1930 check_enable_amd_mmconf [X86] check for and enable
1931 properly configured MMIO access to PCI
1932 config space on AMD family 10h CPU
1933 nomsi [MSI] If the PCI_MSI kernel config parameter is
1934 enabled, this kernel boot option can be used to
1935 disable the use of MSI interrupts system-wide.
1936 noioapicquirk [APIC] Disable all boot interrupt quirks.
1937 Safety option to keep boot IRQs enabled. This
1938 should never be necessary.
1939 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1940 primary IO-APIC for bridges that cannot disable
1941 boot IRQs. This fixes a source of spurious IRQs
1942 when the system masks IRQs.
1943 noioapicreroute [APIC] Disable workaround that uses the
1944 boot IRQ equivalent of an IRQ that connects to
1945 a chipset where boot IRQs cannot be disabled.
1946 The opposite of ioapicreroute.
1947 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1948 routing table. These calls are known to be buggy
1949 on several machines and they hang the machine
1950 when used, but on other computers it's the only
1951 way to get the interrupt routing table. Try
1952 this option if the kernel is unable to allocate
1953 IRQs or discover secondary PCI buses on your
1955 rom [X86] Assign address space to expansion ROMs.
1956 Use with caution as certain devices share
1957 address decoders between ROMs and other
1959 norom [X86] Do not assign address space to
1960 expansion ROMs that do not already have
1961 BIOS assigned address ranges.
1962 nobar [X86] Do not assign address space to the
1963 BARs that weren't assigned by the BIOS.
1964 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1965 assigned automatically to PCI devices. You can
1966 make the kernel exclude IRQs of your ISA cards
1968 pirqaddr=0xAAAAA [X86] Specify the physical address
1969 of the PIRQ table (normally generated
1970 by the BIOS) if it is outside the
1971 F0000h-100000h range.
1972 lastbus=N [X86] Scan all buses thru bus #N. Can be
1973 useful if the kernel is unable to find your
1974 secondary buses and you want to tell it
1975 explicitly which ones they are.
1976 assign-busses [X86] Always assign all PCI bus
1977 numbers ourselves, overriding
1978 whatever the firmware may have done.
1979 usepirqmask [X86] Honor the possible IRQ mask stored
1980 in the BIOS $PIR table. This is needed on
1981 some systems with broken BIOSes, notably
1982 some HP Pavilion N5400 and Omnibook XE3
1983 notebooks. This will have no effect if ACPI
1984 IRQ routing is enabled.
1985 noacpi [X86] Do not use ACPI for IRQ routing
1986 or for PCI scanning.
1987 use_crs [X86] Use PCI host bridge window information
1988 from ACPI. On BIOSes from 2008 or later, this
1989 is enabled by default. If you need to use this,
1990 please report a bug.
1991 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1992 If you need to use this, please report a bug.
1993 routeirq Do IRQ routing for all PCI devices.
1994 This is normally done in pci_enable_device(),
1995 so this option is a temporary workaround
1996 for broken drivers that don't call it.
1997 skip_isa_align [X86] do not align io start addr, so can
1998 handle more pci cards
1999 firmware [ARM] Do not re-enumerate the bus but instead
2000 just use the configuration from the
2001 bootloader. This is currently used on
2002 IXP2000 systems where the bus has to be
2003 configured a certain way for adjunct CPUs.
2004 noearly [X86] Don't do any early type 1 scanning.
2005 This might help on some broken boards which
2006 machine check when some devices' config space
2007 is read. But various workarounds are disabled
2008 and some IOMMU drivers will not work.
2009 bfsort Sort PCI devices into breadth-first order.
2010 This sorting is done to get a device
2011 order compatible with older (<= 2.4) kernels.
2012 nobfsort Don't sort PCI devices into breadth-first order.
2013 cbiosize=nn[KMG] The fixed amount of bus space which is
2014 reserved for the CardBus bridge's IO window.
2015 The default value is 256 bytes.
2016 cbmemsize=nn[KMG] The fixed amount of bus space which is
2017 reserved for the CardBus bridge's memory
2018 window. The default value is 64 megabytes.
2021 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2022 Specifies alignment and device to reassign
2023 aligned memory resources.
2024 If <order of align> is not specified,
2025 PAGE_SIZE is used as alignment.
2026 PCI-PCI bridge can be specified, if resource
2027 windows need to be expanded.
2028 ecrc= Enable/disable PCIe ECRC (transaction layer
2029 end-to-end CRC checking).
2030 bios: Use BIOS/firmware settings. This is the
2034 realloc reallocate PCI resources if allocations done by BIOS
2037 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2040 force Enable ASPM even on devices that claim not to support it.
2041 WARNING: Forcing ASPM on may cause system lockups.
2043 pcie_ports= [PCIE] PCIe ports handling:
2044 auto Ask the BIOS whether or not to use native PCIe services
2045 associated with PCIe ports (PME, hot-plug, AER). Use
2046 them only if that is allowed by the BIOS.
2047 native Use native PCIe services associated with PCIe ports
2049 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2052 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2053 nomsi Do not use MSI for native PCIe PME signaling (this makes
2054 all PCIe root ports use INTx for all services).
2056 pcmv= [HW,PCMCIA] BadgePAD 4
2059 See Documentation/blockdev/paride.txt.
2061 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2064 See arch/parisc/kernel/pdc_chassis.c
2066 percpu_alloc= Select which percpu first chunk allocator to use.
2067 Currently supported values are "embed" and "page".
2068 Archs may support subset or none of the selections.
2069 See comments in mm/percpu.c for details on each
2070 allocator. This parameter is primarily for debugging
2071 and performance comparison.
2074 See Documentation/blockdev/paride.txt.
2077 See Documentation/blockdev/paride.txt.
2079 pirq= [SMP,APIC] Manual mp-table setup
2080 See Documentation/x86/i386/IO-APIC.txt.
2082 plip= [PPT,NET] Parallel port network link
2083 Format: { parport<nr> | timid | 0 }
2084 See also Documentation/parport.txt.
2086 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2087 Override pmtimer IOPort with a hex value.
2091 Enable PNP debug messages. This depends on the
2092 CONFIG_PNP_DEBUG_MESSAGES option.
2098 { on | off | curr | res | no-curr | no-res }
2101 [ISAPNP] Exclude IRQs for the autoconfiguration
2104 [ISAPNP] Exclude DMAs for the autoconfiguration
2106 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2107 Ranges are in pairs (I/O port base and size).
2110 [ISAPNP] Exclude memory regions for the
2112 Ranges are in pairs (memory base and size).
2114 ports= [IP_VS_FTP] IPVS ftp helper module
2116 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2118 Format: <port>,<port>....
2120 print-fatal-signals=
2121 [KNL] debug: print fatal signals
2123 If enabled, warn about various signal handling
2124 related application anomalies: too many signals,
2125 too many POSIX.1 timers, fatal signals causing a
2128 If you hit the warning due to signal overflow,
2129 you might want to try "ulimit -i unlimited".
2133 printk.time= Show timing data prefixed to each printk message line
2134 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2136 processor.max_cstate= [HW,ACPI]
2137 Limit processor to maximum C-state
2138 max_cstate=9 overrides any DMI blacklist limit.
2140 processor.nocst [HW,ACPI]
2141 Ignore the _CST method to determine C-states,
2142 instead using the legacy FADT method
2144 profile= [KNL] Enable kernel profiling via /proc/profile
2145 Format: [schedule,]<number>
2146 Param: "schedule" - profile schedule points.
2147 Param: <number> - step/bucket size as a power of 2 for
2148 statistical time based profiling.
2149 Param: "sleep" - profile D-state sleeping (millisecs).
2150 Requires CONFIG_SCHEDSTATS
2151 Param: "kvm" - profile VM exits.
2153 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2155 See Documentation/blockdev/ramdisk.txt.
2157 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2158 probe for; one of (bare|imps|exps|lifebook|any).
2159 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2161 psmouse.resetafter= [HW,MOUSE]
2162 Try to reset the device after so many bad packets
2165 [HW,MOUSE] Set desired mouse resolution, in dpi.
2166 psmouse.smartscroll=
2167 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2168 0 = disabled, 1 = enabled (default).
2170 pstore.backend= Specify the name of the pstore backend to use
2173 See Documentation/blockdev/paride.txt.
2176 [KNL] Number of legacy pty's. Overwrites compiled-in
2179 quiet [KNL] Disable most log messages
2184 See Documentation/md.txt.
2186 ramdisk_blocksize= [RAM]
2187 See Documentation/blockdev/ramdisk.txt.
2189 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2190 See Documentation/blockdev/ramdisk.txt.
2192 rcupdate.blimit= [KNL,BOOT]
2193 Set maximum number of finished RCU callbacks to process
2196 rcupdate.qhimark= [KNL,BOOT]
2197 Set threshold of queued
2198 RCU callbacks over which batch limiting is disabled.
2200 rcupdate.qlowmark= [KNL,BOOT]
2201 Set threshold of queued RCU callbacks below which
2202 batch limiting is re-enabled.
2206 Run specified binary instead of /init from the ramdisk,
2207 used for early userspace startup. See initrd.
2209 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2210 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2211 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2214 [KNL, SMP] Set scheduler's default relax_domain_level.
2215 See Documentation/cgroups/cpusets.txt.
2217 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2219 reservetop= [X86-32]
2221 Reserves a hole at the top of the kernel virtual
2226 Set the amount of memory to reserve for BIOS at
2227 the bottom of the address space.
2229 reset_devices [KNL] Force drivers to reset the underlying device
2230 during initialization.
2233 Specify the partition device for software suspend
2235 resume_offset= [SWSUSP]
2236 Specify the offset from the beginning of the partition
2237 given by "resume=" at which the swap header is located,
2238 in <PAGE_SIZE> units (needed only for swap files).
2239 See Documentation/power/swsusp-and-swap-files.txt
2241 hibernate= [HIBERNATION]
2242 noresume Don't check if there's a hibernation image
2243 present during boot.
2244 nocompress Don't compress/decompress hibernation images.
2246 retain_initrd [RAM] Keep initrd memory after extraction
2248 rhash_entries= [KNL,NET]
2249 Set number of hash buckets for route cache
2251 riscom8= [HW,SERIAL]
2252 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2254 ro [KNL] Mount root device read-only on boot
2256 root= [KNL] Root filesystem
2257 See name_to_dev_t comment in init/do_mounts.c.
2259 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2260 mount the root filesystem
2262 rootflags= [KNL] Set root filesystem mount option string
2264 rootfstype= [KNL] Set root filesystem type
2266 rootwait [KNL] Wait (indefinitely) for root device to show up.
2267 Useful for devices that are detected asynchronously
2268 (e.g. USB and MMC devices).
2270 rw [KNL] Mount root device read-write on boot
2272 S [KNL] Run init in single mode
2275 See drivers/net/irda/sa1100_ir.c.
2277 sbni= [NET] Granch SBNI12 leased line adapter
2279 sched_debug [KNL] Enables verbose scheduler debug messages.
2281 security= [SECURITY] Choose a security module to enable at boot.
2282 If this boot parameter is not specified, only the first
2283 security module asking for security registration will be
2284 loaded. An invalid security module name will be treated
2285 as if no module has been chosen.
2287 selinux= [SELINUX] Disable or enable SELinux at boot time.
2288 Format: { "0" | "1" }
2289 See security/selinux/Kconfig help text.
2292 Default value is set via kernel config option.
2293 If enabled at boot time, /selinux/disable can be used
2294 later to disable prior to initial policy load.
2296 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2297 Format: { "0" | "1" }
2298 See security/apparmor/Kconfig help text
2301 Default value is set via kernel config option.
2303 serialnumber [BUGS=X86-32]
2306 Maximal number of shapers.
2308 show_msr= [x86] show boot-time MSR settings
2309 Format: { <integer> }
2310 Show boot-time (BIOS-initialized) MSR settings.
2311 The parameter means the number of CPUs to show,
2312 for example 1 means boot CPU only.
2319 slub_debug[=options[,slabs]] [MM, SLUB]
2320 Enabling slub_debug allows one to determine the
2321 culprit if slab objects become corrupted. Enabling
2322 slub_debug can create guard zones around objects and
2323 may poison objects when not in use. Also tracks the
2324 last alloc / free. For more information see
2325 Documentation/vm/slub.txt.
2327 slub_max_order= [MM, SLUB]
2328 Determines the maximum allowed order for slabs.
2329 A high setting may cause OOMs due to memory
2330 fragmentation. For more information see
2331 Documentation/vm/slub.txt.
2333 slub_min_objects= [MM, SLUB]
2334 The minimum number of objects per slab. SLUB will
2335 increase the slab order up to slub_max_order to
2336 generate a sufficiently large slab able to contain
2337 the number of objects indicated. The higher the number
2338 of objects the smaller the overhead of tracking slabs
2339 and the less frequently locks need to be acquired.
2340 For more information see Documentation/vm/slub.txt.
2342 slub_min_order= [MM, SLUB]
2343 Determines the mininum page order for slabs. Must be
2344 lower than slub_max_order.
2345 For more information see Documentation/vm/slub.txt.
2347 slub_nomerge [MM, SLUB]
2348 Disable merging of slabs with similar size. May be
2349 necessary if there is some reason to distinguish
2350 allocs to different slabs. Debug options disable
2351 merging on their own.
2352 For more information see Documentation/vm/slub.txt.
2355 Format: <io1>[,<io2>[,...,<io8>]]
2357 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2358 attempt to substitute SMP alternatives once at boot.
2360 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2361 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2362 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2363 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2364 smsc-ircc2.ircc_irq= [HW] IRQ line
2365 smsc-ircc2.ircc_dma= [HW] DMA channel
2366 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2367 0: Toshiba Satellite 1800 (GP data pin select)
2368 1: Fast pin select (default)
2372 [KNL] Should the soft-lockup detector generate panics.
2375 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2376 See Documentation/sonypi.txt
2378 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2379 See Documentation/serial/specialix.txt.
2381 spia_io_base= [HW,MTD]
2387 Enabled the stack tracer on boot up.
2391 Set the STI (builtin display/keyboard on the HP-PARISC
2392 machines) console (graphic card) which should be used
2393 as the initial boot-console.
2394 See also comment in drivers/video/console/sticore.c.
2397 See comment in drivers/video/console/sticore.c.
2400 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2402 sunrpc.min_resvport=
2403 sunrpc.max_resvport=
2405 SunRPC servers often require that client requests
2406 originate from a privileged port (i.e. a port in the
2407 range 0 < portnr < 1024).
2408 An administrator who wishes to reserve some of these
2409 ports for other uses may adjust the range that the
2410 kernel's sunrpc client considers to be privileged
2411 using these two parameters to set the minimum and
2412 maximum port values.
2416 Control how the NFS server code allocates CPUs to
2417 service thread pools. Depending on how many NICs
2418 you have and where their interrupts are bound, this
2419 option will affect which CPUs will do NFS serving.
2420 Note: this parameter cannot be changed while the
2421 NFS server is running.
2423 auto the server chooses an appropriate mode
2424 automatically using heuristics
2425 global a single global pool contains all CPUs
2426 percpu one pool for each CPU
2427 pernode one pool for each NUMA node (equivalent
2428 to global on non-NUMA machines)
2430 sunrpc.tcp_slot_table_entries=
2431 sunrpc.udp_slot_table_entries=
2433 Sets the upper limit on the number of simultaneous
2434 RPC calls that can be sent from the client to a
2435 server. Increasing these values may allow you to
2436 improve throughput, but will also increase the
2437 amount of memory reserved for use by the client.
2440 [KNL] Enable accounting of swap in memory resource
2441 controller if no parameter or 1 is given or disable
2442 it if 0 is given (See Documentation/cgroups/memory.txt)
2444 swiotlb= [IA-64] Number of I/O TLB slabs
2448 sysfs.deprecated=0|1 [KNL]
2449 Enable/disable old style sysfs layout for old udev
2450 on older distributions. When this option is enabled
2451 very new udev will not work anymore. When this option
2452 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2453 in older udev will not work anymore.
2454 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2455 the kernel configuration.
2457 sysrq_always_enabled
2459 Ignore sysrq setting - this boot parameter will
2460 neutralize any effect of /proc/sys/kernel/sysrq.
2461 Useful for debugging.
2465 test_suspend= [SUSPEND]
2466 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2467 standby suspend) as the system sleep state to briefly
2468 enter during system startup. The system is woken from
2469 this state using a wakeup-capable RTC alarm.
2471 thash_entries= [KNL,NET]
2472 Set number of hash buckets for TCP connection
2474 thermal.act= [HW,ACPI]
2475 -1: disable all active trip points in all thermal zones
2476 <degrees C>: override all lowest active trip points
2478 thermal.crt= [HW,ACPI]
2479 -1: disable all critical trip points in all thermal zones
2480 <degrees C>: override all critical trip points
2482 thermal.nocrt= [HW,ACPI]
2483 Set to disable actions on ACPI thermal zone
2484 critical and hot trip points.
2486 thermal.off= [HW,ACPI]
2487 1: disable ACPI thermal control
2489 thermal.psv= [HW,ACPI]
2490 -1: disable all passive trip points
2491 <degrees C>: override all passive trip points to this
2494 thermal.tzp= [HW,ACPI]
2495 Specify global default ACPI thermal zone polling rate
2496 <deci-seconds>: poll all this frequency
2497 0: no polling (default)
2500 Force threading of all interrupt handlers except those
2501 marked explicitely IRQF_NO_THREAD.
2505 Specify if the kernel should make use of the cpu
2506 topology information if the hardware supports this.
2507 The scheduler will make use of this information and
2508 e.g. base its process migration decisions on it.
2513 tpm_suspend_pcr=[HW,TPM]
2514 Format: integer pcr id
2515 Specify that at suspend time, the tpm driver
2516 should extend the specified pcr with zeros,
2517 as a workaround for some chips which fail to
2518 flush the last written pcr on TPM_SaveState.
2519 This will guarantee that all the other pcrs
2522 trace_buf_size=nn[KMG]
2523 [FTRACE] will set tracing buffer size.
2525 trace_event=[event-list]
2526 [FTRACE] Set and start specified trace events in order
2527 to facilitate early boot debugging.
2528 See also Documentation/trace/events.txt
2530 tsc= Disable clocksource stability checks for TSC.
2532 [x86] reliable: mark tsc clocksource as reliable, this
2533 disables clocksource verification at runtime, as well
2534 as the stability checks done at bootup. Used to enable
2535 high-resolution timer mode on older hardware, and in
2536 virtualized environment.
2537 [x86] noirqtime: Do not use TSC to do irq accounting.
2538 Used to run time disable IRQ_TIME_ACCOUNTING on any
2539 platforms where RDTSC is slow and this accounting
2542 turbografx.map[2|3]= [HW,JOY]
2543 TurboGraFX parallel port interface
2545 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2546 See also Documentation/input/joystick-parport.txt
2548 udbg-immortal [PPC] When debugging early kernel crashes that
2549 happen after console_init() and before a proper
2550 console driver takes over, this boot options might
2551 help "seeing" what's going on.
2553 uhash_entries= [KNL,NET]
2554 Set number of hash buckets for UDP/UDP-Lite connections
2557 [USB] Ignore overcurrent events (default N).
2558 Some badly-designed motherboards generate lots of
2559 bogus events, for ports that aren't wired to
2560 anything. Set this parameter to avoid log spamming.
2561 Note that genuine overcurrent events won't be
2565 [X86] Cause panic on unknown NMI.
2567 usbcore.authorized_default=
2568 [USB] Default USB device authorization:
2569 (default -1 = authorized except for wireless USB,
2570 0 = not authorized, 1 = authorized)
2572 usbcore.autosuspend=
2573 [USB] The autosuspend time delay (in seconds) used
2574 for newly-detected USB devices (default 2). This
2575 is the time required before an idle device will be
2576 autosuspended. Devices for which the delay is set
2577 to a negative value won't be autosuspended at all.
2579 usbcore.usbfs_snoop=
2580 [USB] Set to log all usbfs traffic (default 0 = off).
2582 usbcore.blinkenlights=
2583 [USB] Set to cycle leds on hubs (default 0 = off).
2585 usbcore.old_scheme_first=
2586 [USB] Start with the old device initialization
2587 scheme (default 0 = off).
2589 usbcore.use_both_schemes=
2590 [USB] Try the other device initialization scheme
2591 if the first one fails (default 1 = enabled).
2593 usbcore.initial_descriptor_timeout=
2594 [USB] Specifies timeout for the initial 64-byte
2595 USB_REQ_GET_DESCRIPTOR request in milliseconds
2596 (default 5000 = 5.0 seconds).
2599 [USBHID] The interval which mice are to be polled at.
2601 usb-storage.delay_use=
2602 [UMS] The delay in seconds before a new device is
2603 scanned for Logical Units (default 5).
2606 [UMS] A list of quirks entries to supplement or
2607 override the built-in unusual_devs list. List
2608 entries are separated by commas. Each entry has
2609 the form VID:PID:Flags where VID and PID are Vendor
2610 and Product ID values (4-digit hex numbers) and
2611 Flags is a set of characters, each corresponding
2612 to a common usb-storage quirk flag as follows:
2613 a = SANE_SENSE (collect more than 18 bytes
2615 b = BAD_SENSE (don't collect more than 18
2616 bytes of sense data);
2617 c = FIX_CAPACITY (decrease the reported
2618 device capacity by one sector);
2619 d = NO_READ_DISC_INFO (don't use
2620 READ_DISC_INFO command);
2621 e = NO_READ_CAPACITY_16 (don't use
2622 READ_CAPACITY_16 command);
2623 h = CAPACITY_HEURISTICS (decrease the
2624 reported device capacity by one
2625 sector if the number is odd);
2626 i = IGNORE_DEVICE (don't bind to this
2628 l = NOT_LOCKABLE (don't try to lock and
2629 unlock ejectable media);
2630 m = MAX_SECTORS_64 (don't transfer more
2631 than 64 sectors = 32 KB at a time);
2632 n = INITIAL_READ10 (force a retry of the
2633 initial READ(10) command);
2634 o = CAPACITY_OK (accept the capacity
2635 reported by the device);
2636 r = IGNORE_RESIDUE (the device reports
2637 bogus residue values);
2638 s = SINGLE_LUN (the device has only one
2640 w = NO_WP_DETECT (don't test whether the
2641 medium is write-protected).
2642 Example: quirks=0419:aaf5:rl,0421:0433:rc
2645 [X86] Flags controlling user PTE allocations.
2647 nohigh = do not allocate PTE pages in
2648 HIGHMEM regardless of setting
2652 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2653 vdso=1: enable VDSO (default)
2654 vdso=0: disable VDSO mapping
2657 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2658 vdso32=1: enable 32-bit VDSO (default)
2659 vdso32=0: disable 32-bit VDSO mapping
2662 vector=percpu: enable percpu vector domain
2664 video= [FB] Frame buffer configuration
2665 See Documentation/fb/modedb.txt.
2667 vga= [BOOT,X86-32] Select a particular video mode
2668 See Documentation/x86/boot.txt and
2669 Documentation/svga.txt.
2670 Use vga=ask for menu.
2671 This is actually a boot loader parameter; the value is
2672 passed to the kernel using a special protocol.
2674 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2675 size of <nn>. This can be used to increase the
2676 minimum size (128MB on x86). It can also be used to
2677 decrease the size and leave more room for directly
2680 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2683 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2686 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2689 vt.cur_default= [VT] Default cursor shape.
2690 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2691 the parameters of the <Esc>[?A;B;Cc escape sequence;
2692 see VGA-softcursor.txt. Default: 2 = underline.
2694 vt.default_blu= [VT]
2695 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2696 Change the default blue palette of the console.
2697 This is a 16-member array composed of values
2700 vt.default_grn= [VT]
2701 Format: <green0>,<green1>,<green2>,...,<green15>
2702 Change the default green palette of the console.
2703 This is a 16-member array composed of values
2706 vt.default_red= [VT]
2707 Format: <red0>,<red1>,<red2>,...,<red15>
2708 Change the default red palette of the console.
2709 This is a 16-member array composed of values
2715 Set system-wide default UTF-8 mode for all tty's.
2716 Default is 1, i.e. UTF-8 mode is enabled for all
2717 newly opened terminals.
2719 vt.global_cursor_default=
2722 Set system-wide default for whether a cursor
2723 is shown on new VTs. Default is -1,
2724 i.e. cursors will be created by default unless
2725 overridden by individual drivers. 0 will hide
2726 cursors, 1 will display them.
2728 watchdog timers [HW,WDT] For information on watchdog timers,
2729 see Documentation/watchdog/watchdog-parameters.txt
2730 or other driver-specific files in the
2731 Documentation/watchdog/ directory.
2733 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2734 default x2apic cluster mode on platforms
2737 x86_mrst_timer= [X86-32,APBT]
2738 Choose timer option for x86 Moorestown MID platform.
2739 Two valid options are apbt timer only and lapic timer
2740 plus one apbt timer for broadcast timer.
2741 x86_mrst_timer=apbt_only | lapic_and_apbt
2743 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2744 xd_geo= See header of drivers/block/xd.c.
2746 xen_emul_unplug= [HW,X86,XEN]
2747 Unplug Xen emulated devices
2748 Format: [unplug0,][unplug1]
2749 ide-disks -- unplug primary master IDE devices
2750 aux-ide-disks -- unplug non-primary-master IDE devices
2751 nics -- unplug network devices
2752 all -- unplug all emulated devices (NICs and IDE disks)
2753 unnecessary -- unplugging emulated devices is
2754 unnecessary even if the host did not respond to
2756 never -- do not unplug even if version check succeeds
2758 xirc2ps_cs= [NET,PCMCIA]
2760 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2762 ______________________________________________________________________
2766 Add more DRM drivers.
projects / platform / adaptation / renesas_rcar / renesas_kernel.git / blob