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 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amijoy.map= [HW,JOY] Amiga joystick support
339 Map of devices attached to JOY0DAT and JOY1DAT
341 See also Documentation/input/joystick.txt
343 analog.map= [HW,JOY] Analog joystick and gamepad support
344 Specifies type or capabilities of an analog joystick
345 connected to one of 16 gameports
346 Format: <type1>,<type2>,..<type16>
349 Power management functions (SPARCstation-4/5 + deriv.)
351 Disable APC CPU standby support. SPARCstation-Fox does
352 not play well with APC CPU idle - disable it if you have
353 APC and your system crashes randomly.
355 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
356 Change the output verbosity whilst booting
357 Format: { quiet (default) | verbose | debug }
358 Change the amount of debugging information output
359 when initialising the APIC and IO-APIC components.
362 See Documentation/networking/ipv6.txt.
364 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
365 Limit apic dumping. The parameter defines the maximal
366 number of local apics being dumped. Also it is possible
367 to set it to "all" by meaning -- no limit here.
368 Format: { 1 (default) | 2 | ... | all }.
369 The parameter valid if only apic=debug or
370 apic=verbose is specified.
371 Example: apic=debug show_lapic=all
373 apm= [APM] Advanced Power Management
374 See header of arch/x86/kernel/apm_32.c.
376 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
377 Format: <io>,<irq>,<nodeID>
381 atarimouse= [HW,MOUSE] Atari Mouse
383 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
384 EzKey and similar keyboards
386 atkbd.reset= [HW] Reset keyboard during initialization
388 atkbd.set= [HW] Select keyboard code set
389 Format: <int> (2 = AT (default), 3 = PS/2)
391 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
394 atkbd.softraw= [HW] Choose between synthetic and real raw mode
395 Format: <bool> (0 = real, 1 = synthetic (default))
397 atkbd.softrepeat= [HW]
398 Use software keyboard repeat
402 baycom_epp= [HW,AX25]
405 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
407 See header of drivers/net/hamradio/baycom_par.c.
409 baycom_ser_fdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
411 Format: <io>,<irq>,<mode>[,<baud>]
412 See header of drivers/net/hamradio/baycom_ser_fdx.c.
414 baycom_ser_hdx= [HW,AX25]
415 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
416 Format: <io>,<irq>,<mode>
417 See header of drivers/net/hamradio/baycom_ser_hdx.c.
419 boot_delay= Milliseconds to delay each printk during boot.
420 Values larger than 10 seconds (10000) are changed to
424 bootmem_debug [KNL] Enable bootmem allocator debug messages.
426 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
427 bttv.radio= Most important insmod options are available as
429 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
432 bulk_remove=off [PPC] This parameter disables the use of the pSeries
433 firmware feature for flushing multiple hpte entries
436 c101= [NET] Moxa C101 synchronous serial card
438 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
439 Sometimes CPU hardware bugs make them report the cache
440 size incorrectly. The kernel will attempt work arounds
441 to fix known problems, but for some CPUs it is not
442 possible to determine what the correct size should be.
443 This option provides an override for these situations.
446 [SECURITY] Disable capabilities. This would normally
447 be used only if an alternative security model is to be
448 configured. Potentially dangerous and should only be
449 used if you are entirely sure of the consequences.
451 ccw_timeout_log [S390]
452 See Documentation/s390/CommonIO for details.
454 cgroup_disable= [KNL] Disable a particular controller
455 Format: {name of the controller(s) to disable}
456 {Currently supported controllers - "memory"}
458 checkreqprot [SELINUX] Set initial checkreqprot flag value.
459 Format: { "0" | "1" }
460 See security/selinux/Kconfig help text.
461 0 -- check protection applied by kernel (includes
462 any implied execute protection).
463 1 -- check protection requested by application.
464 Default value is set via a kernel config option.
465 Value can be changed at runtime via
466 /selinux/checkreqprot.
469 See Documentation/s390/CommonIO for details.
471 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
473 Forces specified clocksource (if available) to be used
474 when calculating gettimeofday(). If specified
475 clocksource is not available, it defaults to PIT.
476 Format: { pit | tsc | cyclone | pmtmr }
478 clocksource= Override the default clocksource
480 Override the default clocksource and use the clocksource
481 with the name specified.
482 Some clocksource names to choose from, depending on
484 [all] jiffies (this is the base, fallback clocksource)
486 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
487 pxa_timer,timer3,32k_counter,timer0_1
489 [X86-32] pit,hpet,tsc;
490 scx200_hrt on Geode; cyclone on IBM x440
498 clearcpuid=BITNUM [X86]
499 Disable CPUID feature X for the kernel. See
500 arch/x86/include/asm/cpufeature.h for the valid bit
501 numbers. Note the Linux specific bits are not necessarily
502 stable over kernel options, but the vendor specific
504 Also note that user programs calling CPUID directly
505 or using the feature without checking anything
506 will still see it. This just prevents it from
507 being used by the kernel or shown in /proc/cpuinfo.
508 Also note the kernel might malfunction if you disable
511 cmo_free_hint= [PPC] Format: { yes | no }
512 Specify whether pages are marked as being inactive
513 when they are freed. This is used in CMO environments
514 to determine OS memory pressure for page stealing by
518 code_bytes [X86] How many bytes of object code to print
523 hpet64 [X86-64,HPET] enable 64-bit mode of the HPET timer (bnc#456700)
525 com20020= [HW,NET] ARCnet - COM20020 chipset
527 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
529 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
533 ARCnet - COM90xx chipset (memory-mapped buffers)
534 Format: <io>[,<irq>[,<memstart>]]
536 condev= [HW,S390] console device
539 console= [KNL] Output console device and options.
541 tty<n> Use the virtual console device <n>.
545 Use the specified serial port. The options are of
546 the form "bbbbpnf", where "bbbb" is the baud rate,
547 "p" is parity ("n", "o", or "e"), "n" is number of
548 bits, and "f" is flow control ("r" for RTS or
549 omit it). Default is "9600n8".
551 See Documentation/serial-console.txt for more
553 Documentation/networking/netconsole.txt for an
556 uart[8250],io,<addr>[,options]
557 uart[8250],mmio,<addr>[,options]
558 Start an early, polled-mode console on the 8250/16550
559 UART at the specified I/O port or MMIO address,
560 switching to the matching ttyS device later. The
561 options are the same as for ttyS, above.
563 If the device connected to the port is not a TTY but a braille
564 device, prepend "brl," before the device type, for instance
566 For now, only VisioBraille is supported.
568 consoleblank= [KNL] The console blank (screen saver) timeout in
569 seconds. Defaults to 10*60 = 10mins. A value of 0
570 disables the blank timer.
573 [KNL] Change the default value for
574 /proc/<pid>/coredump_filter.
575 See also Documentation/filesystems/proc.txt.
577 cpuidle.off=1 [CPU_IDLE]
578 disable the cpuidle sub-system
580 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
582 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
584 crashkernel=size[KMG][@offset[KMG]]
585 [KNL] Using kexec, Linux can switch to a 'crash kernel'
586 upon panic. This parameter reserves the physical
587 memory region [offset, offset + size] for that kernel
588 image. If '@offset' is omitted, then a suitable offset
589 is selected automatically. Check
590 Documentation/kdump/kdump.txt for further details.
592 crashkernel=range1:size1[,range2:size2,...][@offset]
593 [KNL] Same as above, but depends on the memory
594 in the running system. The syntax of range is
595 start-[end] where start and end are both
596 a memory unit (amount[KMG]). See also
597 Documentation/kdump/kdump.txt for an example.
602 cs89x0_media= [HW,NET]
603 Format: { rj45 | aui | bnc }
606 See header of drivers/s390/block/dasd_devmap.c.
608 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
609 (one device per port)
610 Format: <port#>,<type>
611 See also Documentation/input/joystick-parport.txt
613 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
614 time. See Documentation/dynamic-debug-howto.txt for
617 debug [KNL] Enable kernel debugging (events log level).
620 [KNL] verbose self-tests
622 Print debugging info while doing the locking API
624 We default to 0 (no extra messages), setting it to
625 1 will print _a lot_ more information - normally
626 only useful to kernel developers.
628 debug_objects [KNL] Enable object debugging
631 [KNL] Disable object debugging
633 debug_guardpage_minorder=
634 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
635 parameter allows control of the order of pages that will
636 be intentionally kept free (and hence protected) by the
637 buddy allocator. Bigger value increase the probability
638 of catching random memory corruption, but reduce the
639 amount of memory for normal system use. The maximum
640 possible value is MAX_ORDER/2. Setting this parameter
641 to 1 or 2 should be enough to identify most random
642 memory corruption problems caused by bugs in kernel or
643 driver code when a CPU writes to (or reads from) a
644 random memory location. Note that there exists a class
645 of memory corruptions problems caused by buggy H/W or
646 F/W or by drivers badly programing DMA (basically when
647 memory is written at bus level and the CPU MMU is
648 bypassed) which are not detectable by
649 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
650 tracking down these problems.
652 debugpat [X86] Enable PAT debugging
654 decnet.addr= [HW,NET]
655 Format: <area>[,<node>]
656 See also Documentation/networking/decnet.txt.
659 [same as hugepagesz=] The size of the default
660 HugeTLB page size. This is the size represented by
661 the legacy /proc/ hugepages APIs, used for SHM, and
662 default size when mounting hugetlbfs filesystems.
663 Defaults to the default architecture's huge page size
667 Set number of hash buckets for dentry cache.
670 IO parameters + enable/disable command.
672 digiepca= [HW,SERIAL]
673 See drivers/char/README.epca and
674 Documentation/serial/digiepca.txt.
677 See Documentation/networking/ipv6.txt.
679 disable_ddw [PPC/PSERIES]
680 Disable Dynamic DMA Window support. Use this if
681 to workaround buggy firmware.
684 See Documentation/networking/ipv6.txt.
686 disable_mtrr_cleanup [X86]
687 The kernel tries to adjust MTRR layout from continuous
688 to discrete, to make X server driver able to add WB
689 entry later. This parameter disables that.
691 disable_mtrr_trim [X86, Intel and AMD only]
692 By default the kernel will trim any uncacheable
693 memory out of your available memory pool based on
694 MTRR settings. This parameter disables that behavior,
695 possibly causing your machine to run very slowly.
697 disable_timer_pin_1 [X86]
698 Disable PIN 1 of APIC timer
699 Can be useful to work around chipset bugs.
701 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
702 this option disables the debugging code at boot.
704 dma_debug_entries=<number>
705 This option allows to tune the number of preallocated
706 entries for DMA-API debugging code. One entry is
707 required per DMA-API allocation. Use this if the
708 DMA-API debugging code disables itself because the
709 architectural default is too low.
711 dma_debug_driver=<driver_name>
712 With this option the DMA-API debugging driver
713 filter feature can be enabled at boot time. Just
714 pass the driver to filter for as the parameter.
715 The filter can be disabled or changed to another
716 driver later using sysfs.
718 drm_kms_helper.edid_firmware=[<connector>:]<file>
719 Broken monitors, graphic adapters and KVMs may
720 send no or incorrect EDID data sets. This parameter
721 allows to specify an EDID data set in the
722 /lib/firmware directory that is used instead.
723 Generic built-in EDID data sets are used, if one of
724 edid/1024x768.bin, edid/1280x1024.bin,
725 edid/1680x1050.bin, or edid/1920x1080.bin is given
726 and no file with the same name exists. Details and
727 instructions how to build your own EDID data are
728 available in Documentation/EDID/HOWTO.txt. An EDID
729 data set will only be used for a particular connector,
730 if its name and a colon are prepended to the EDID
735 earlycon= [KNL] Output early console device and options.
736 uart[8250],io,<addr>[,options]
737 uart[8250],mmio,<addr>[,options]
738 uart[8250],mmio32,<addr>[,options]
739 Start an early, polled-mode console on the 8250/16550
740 UART at the specified I/O port or MMIO address.
741 MMIO inter-register address stride is either 8-bit
742 (mmio) or 32-bit (mmio32).
743 The options are the same as for ttyS, above.
745 earlyprintk= [X86,SH,BLACKFIN]
747 earlyprintk=serial[,ttySn[,baudrate]]
748 earlyprintk=ttySn[,baudrate]
749 earlyprintk=dbgp[debugController#]
751 Append ",keep" to not disable it when the real console
754 Only vga or serial or usb debug port at a time.
756 Currently only ttyS0 and ttyS1 are supported.
758 Interaction with the standard serial driver is not
761 The VGA output is eventually overwritten by the real
764 ekgdboc= [X86,KGDB] Allow early kernel console debugging
767 This is designed to be used in conjunction with
768 the boot argument: earlyprintk=vga
771 Format: {"off" | "on" | "skip[mbr]"}
773 eisa_irq_edge= [PARISC,HW]
774 See header of drivers/parisc/eisa.c.
777 See comment before function elanfreq_setup() in
778 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
781 Format: {"cfq" | "deadline" | "noop"}
782 See Documentation/block/cfq-iosched.txt and
783 Documentation/block/deadline-iosched.txt for details.
785 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
786 Specifies physical address of start of kernel core
787 image elf header and optionally the size. Generally
788 kexec loader will pass this option to capture kernel.
789 See Documentation/kdump/kdump.txt for details.
791 enable_mtrr_cleanup [X86]
792 The kernel tries to adjust MTRR layout from continuous
793 to discrete, to make X server driver able to add WB
794 entry later. This parameter enables that.
796 enable_timer_pin_1 [X86]
797 Enable PIN 1 of APIC timer
798 Can be useful to work around chipset bugs
799 (in particular on some ATI chipsets).
800 The kernel tries to set a reasonable default.
802 enforcing [SELINUX] Set initial enforcing status.
804 See security/selinux/Kconfig help text.
805 0 -- permissive (log only, no denials).
806 1 -- enforcing (deny and log).
808 Value can be changed at runtime via /selinux/enforce.
811 Disable Error Record Serialization Table (ERST)
814 ether= [HW,NET] Ethernet cards parameters
815 This option is obsoleted by the "netdev=" option, which
816 has equivalent usage. See its documentation for details.
820 Permit 'security.evm' to be updated regardless of
821 current integrity status.
825 fail_make_request=[KNL]
826 General fault injection mechanism.
827 Format: <interval>,<probability>,<space>,<times>
828 See also Documentation/fault-injection/.
831 See Documentation/blockdev/floppy.txt.
833 force_pal_cache_flush
834 [IA-64] Avoid check_sal_cache_flush which may hang on
835 buggy SAL_CACHE_FLUSH implementations. Using this
836 parameter will force ia64_sal_cache_flush to call
837 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
840 [FTRACE] will set and start the specified tracer
841 as early as possible in order to facilitate early
844 ftrace_dump_on_oops[=orig_cpu]
845 [FTRACE] will dump the trace buffers on oops.
846 If no parameter is passed, ftrace will dump
847 buffers of all CPUs, but if you pass orig_cpu, it will
848 dump only the buffer of the CPU that triggered the
851 ftrace_filter=[function-list]
852 [FTRACE] Limit the functions traced by the function
853 tracer at boot up. function-list is a comma separated
854 list of functions. This list can be changed at run
855 time by the set_ftrace_filter file in the debugfs
858 ftrace_notrace=[function-list]
859 [FTRACE] Do not trace the functions specified in
860 function-list. This list can be changed at run time
861 by the set_ftrace_notrace file in the debugfs
864 ftrace_graph_filter=[function-list]
865 [FTRACE] Limit the top level callers functions traced
866 by the function graph tracer at boot up.
867 function-list is a comma separated list of functions
868 that can be changed at run time by the
869 set_graph_function file in the debugfs tracing directory.
872 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
873 support via parallel port (up to 5 devices per port)
874 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
875 See also Documentation/input/joystick-parport.txt
879 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
883 gcov_persist= [GCOV] When non-zero (default), profiling data for
884 kernel modules is saved and remains accessible via
885 debugfs, even when the module is unloaded/reloaded.
886 When zero, profiling data is discarded and associated
887 debugfs files are removed at module unload time.
889 gpt [EFI] Forces disk with valid GPT signature but
890 invalid Protective MBR to be treated as GPT.
892 guestdev= [PCI,ACPI,XEN]
893 Format: {<device path>|<sbdf>}][,{<device path>|<sbdf>}[,...]]
894 Format of device path: <hid>[:<uid>]-<dev>.<func>[-<dev>.<func>[,...]][+iomul]
895 Format of sbdf: [<segment>:]<bus>:<dev>.<func>[+iomul]
896 Specifies PCI device for guest domain.
897 If PCI-PCI bridge is specified, all PCI devices
898 behind PCI-PCI bridge are reserved.
899 +iomul means that this PCI function will share
900 IO ports with other +iomul functions under same
901 switch. NOTE: if +iomul is specfied, all the functions
902 of the device will share IO ports.
904 guestiomuldev= [PCI,ACPI,XEN]
905 Format: [sbd][,<sbd>][,...]
906 Format of sbdf: [<segment>:]<bus>:<dev>
907 Note: function shouldn't be specified.
908 Specifies PCI device for IO port multiplexing driver.
910 hashdist= [KNL,NUMA] Large hashes allocated during boot
911 are distributed across NUMA nodes. Defaults on
912 for 64-bit NUMA, off otherwise.
913 Format: 0 | 1 (for off | on)
915 hcl= [IA-64] SGI's Hardware Graph compatibility layer
917 hd= [EIDE] (E)IDE hard drive subsystem geometry
918 Format: <cyl>,<head>,<sect>
921 Disable Hardware Error Source Table (HEST) support;
922 corresponding firmware-first mode error processing
923 logic will be disabled.
925 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
926 size of <nn>. This works even on boxes that have no
927 highmem otherwise. This also works to reduce highmem
928 size on bigger boxes.
930 highres= [KNL] Enable/disable high resolution timer mode.
931 Valid parameters: "on", "off"
935 See Documentation/isdn/README.HiSax.
939 hpet= [X86-32,HPET] option to control HPET usage
940 Format: { enable (default) | disable | force |
942 disable: disable HPET and use PIT instead
943 force: allow force enabled of undocumented chips (ICH4,
945 verbose: show contents of HPET registers during setup
947 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
948 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
949 On x86-64 and powerpc, this option can be specified
950 multiple times interleaved with hugepages= to reserve
951 huge pages of different sizes. Valid pages sizes on
952 x86-64 are 2M (when the CPU supports "pse") and 1G
953 (when the CPU supports the "pdpe1gb" cpuinfo flag)
954 Note that 1GB pages can only be allocated at boot time
955 using hugepages= and not freed afterwards.
957 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
958 terminal devices. Valid values: 0..8
959 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
960 If specified, z/VM IUCV HVC accepts connections
961 from listed z/VM user IDs only.
964 Do not unregister boot console at start. This is only
965 useful for debugging when something happens in the window
966 between unregistering the boot console and initializing
969 i2c_bus= [HW] Override the default board specific I2C bus speed
970 or register an additional I2C bus that is not
971 registered from board initialization code.
975 i8042.debug [HW] Toggle i8042 debug mode
976 i8042.direct [HW] Put keyboard port into non-translated mode
977 i8042.dumbkbd [HW] Pretend that controller can only read data from
978 keyboard and cannot control its state
979 (Don't attempt to blink the leds)
980 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
981 i8042.nokbd [HW] Don't check/create keyboard port
982 i8042.noloop [HW] Disable the AUX Loopback command while probing
984 i8042.nomux [HW] Don't check presence of an active multiplexing
986 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
988 i8042.notimeout [HW] Ignore timeout condition signalled by controller
989 i8042.reset [HW] Reset the controller during init and cleanup
990 i8042.unlock [HW] Unlock (ignore) the keylock
994 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
995 indicates that the driver is running on unsupported
997 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
998 does not match list of supported models.
1000 [HW] Report power status in /proc/i8k
1001 (disabled by default)
1002 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1006 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1008 ide-core.nodma= [HW] (E)IDE subsystem
1009 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1010 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1011 .cdrom .chs .ignore_cable are additional options
1012 See Documentation/ide/ide.txt.
1014 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1015 Claim all unknown PCI IDE storage controllers.
1018 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1019 Poll forces a polling idle loop that can slightly
1020 improve the performance of waking up a idle CPU, but
1021 will use a lot of power and make the system run hot.
1023 idle=mwait: On systems which support MONITOR/MWAIT but
1024 the kernel chose to not use it because it doesn't save
1025 as much power as a normal idle loop, use the
1026 MONITOR/MWAIT idle loop anyways. Performance should be
1027 the same as idle=poll.
1028 idle=halt: Halt is forced to be used for CPU idle.
1029 In such case C2/C3 won't be used again.
1030 idle=nomwait: Disable mwait for CPU C-states
1032 ignore_loglevel [KNL]
1033 Ignore loglevel setting - this will print /all/
1034 kernel messages to the console. Useful for debugging.
1035 We also add it as printk module parameter, so users
1036 could change it dynamically, usually by
1037 /sys/module/printk/parameters/ignore_loglevel.
1039 ihash_entries= [KNL]
1040 Set number of hash buckets for inode cache.
1043 Format: { "0" | "1" }
1044 0 -- integrity auditing messages. (Default)
1045 1 -- enable informational integrity auditing messages.
1048 Format: { "sha1" | "md5" }
1052 Load a policy which meets the needs of the Trusted
1053 Computing Base. This means IMA will measure all
1054 programs exec'd, files mmap'd for exec, and all files
1055 opened for read by uid=0.
1059 Run specified binary instead of /sbin/init as init
1062 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1063 for working out where the kernel is dying during
1066 initrd= [BOOT] Specify the location of the initial ramdisk
1068 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1071 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1073 Enable intel iommu driver.
1075 Disable intel iommu driver.
1076 igfx_off [Default Off]
1077 By default, gfx is mapped as normal device. If a gfx
1078 device has a dedicated DMAR unit, the DMAR unit is
1079 bypassed by not enabling DMAR with this option. In
1080 this case, gfx device will use physical address for
1083 With this option iommu will not optimize to look
1084 for io virtual address below 32-bit forcing dual
1085 address cycle on pci bus for cards supporting greater
1086 than 32-bit addressing. The default is to look
1087 for translation below 32-bit and if not available
1088 then look in the higher range.
1089 strict [Default Off]
1090 With this option on every unmap_single operation will
1091 result in a hardware IOTLB flush operation as opposed
1092 to batching them for performance.
1093 sp_off [Default Off]
1094 By default, super page will be supported if Intel IOMMU
1095 has the capability. With this option, super page will
1098 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1099 0 disables intel_idle and fall back on acpi_idle.
1100 1 to 6 specify maximum depth of C-state.
1102 intremap= [X86-64, Intel-IOMMU]
1103 on enable Interrupt Remapping (default)
1104 off disable Interrupt Remapping
1105 nosid disable Source ID checking
1107 BIOS x2APIC opt-out request will be ignored
1109 iomem= Disable strict checking of access to MMIO memory
1110 strict regions from userspace.
1125 group_mf [x86, IA-64]
1128 io7= [HW] IO7 for Marvel based alpha systems
1129 See comment before marvel_specify_io7 in
1130 arch/alpha/kernel/core_marvel.c.
1132 io_delay= [X86] I/O delay method
1134 Standard port 0x80 based delay
1136 Alternate port 0xed based delay (needed on some systems)
1138 Simple two microseconds delay
1143 See Documentation/filesystems/nfs/nfsroot.txt.
1145 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1146 See comment before ip2_setup() in
1147 drivers/char/ip2/ip2base.c.
1150 When an interrupt is not handled search all handlers
1151 for it. Intended to get systems with badly broken
1155 When an interrupt is not handled search all handlers
1156 for it. Also check all handlers each timer
1157 interrupt. Intended to get systems with badly broken
1161 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1163 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1165 <cpu number>,...,<cpu number>
1167 <cpu number>-<cpu number>
1168 (must be a positive range in ascending order)
1170 <cpu number>,...,<cpu number>-<cpu number>
1172 This option can be used to specify one or more CPUs
1173 to isolate from the general SMP balancing and scheduling
1174 algorithms. You can move a process onto or off an
1175 "isolated" CPU via the CPU affinity syscalls or cpuset.
1176 <cpu number> begins at 0 and the maximum value is
1177 "number of CPUs in system - 1".
1179 This option is the preferred way to isolate CPUs. The
1180 alternative -- manually setting the CPU mask of all
1181 tasks in the system -- can cause problems and
1182 suboptimal load balancer performance.
1186 js= [HW,JOY] Analog joystick
1187 See Documentation/input/joystick.txt.
1191 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1192 specifies the amount of memory usable by the kernel
1193 for non-movable allocations. The requested amount is
1194 spread evenly throughout all nodes in the system. The
1195 remaining memory in each node is used for Movable
1196 pages. In the event, a node is too small to have both
1197 kernelcore and Movable pages, kernelcore pages will
1198 take priority and other nodes will have a larger number
1199 of kernelcore pages. The Movable zone is used for the
1200 allocation of pages that may be reclaimed or moved
1201 by the page migration subsystem. This means that
1202 HugeTLB pages may not be allocated from this zone.
1203 Note that allocations like PTEs-from-HighMem still
1204 use the HighMem zone if it exists, and the Normal
1205 zone if it does not.
1207 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1208 Format: <Controller#>[,poll interval]
1209 The controller # is the number of the ehci usb debug
1210 port as it is probed via PCI. The poll interval is
1211 optional and is the number seconds in between
1212 each poll cycle to the debug port in case you need
1213 the functionality for interrupting the kernel with
1214 gdb or control-c on the dbgp connection. When
1215 not using this parameter you use sysrq-g to break into
1216 the kernel debugger.
1218 kgdboc= [KGDB,HW] kgdb over consoles.
1219 Requires a tty driver that supports console polling,
1220 or a supported polling keyboard driver (non-usb).
1221 Serial only format: <serial_device>[,baud]
1222 keyboard only format: kbd
1223 keyboard and serial format: kbd,<serial_device>[,baud]
1224 Optional Kernel mode setting:
1225 kms, kbd format: kms,kbd
1226 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1228 kgdbwait [KGDB] Stop kernel execution and enter the
1229 kernel debugger at the earliest opportunity.
1231 kmac= [MIPS] korina ethernet MAC address.
1232 Configure the RouterBoard 532 series on-chip
1233 Ethernet adapter MAC address.
1235 kmemleak= [KNL] Boot-time kmemleak enable/disable
1236 Valid arguments: on, off
1239 kstack=N [X86] Print N words from the kernel stack
1242 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1243 Default is 0 (don't ignore, but inject #GP)
1245 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1249 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1250 Default is 1 (enabled)
1252 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1254 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1256 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1257 (virtualized MMU) support on capable Intel chips.
1258 Default is 1 (enabled)
1260 kvm-intel.emulate_invalid_guest_state=
1261 [KVM,Intel] Enable emulation of invalid guest states
1262 Default is 0 (disabled)
1264 kvm-intel.flexpriority=
1265 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1266 Default is 1 (enabled)
1269 [KVM,Intel] Enable VMX nesting (nVMX).
1270 Default is 0 (disabled)
1272 kvm-intel.unrestricted_guest=
1273 [KVM,Intel] Disable unrestricted guest feature
1274 (virtualized real and unpaged mode) on capable
1275 Intel chips. Default is 1 (enabled)
1277 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1278 feature (tagged TLBs) on capable Intel chips.
1279 Default is 1 (enabled)
1285 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1288 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1291 libata.dma= [LIBATA] DMA control
1292 libata.dma=0 Disable all PATA and SATA DMA
1293 libata.dma=1 PATA and SATA Disk DMA only
1294 libata.dma=2 ATAPI (CDROM) DMA only
1295 libata.dma=4 Compact Flash DMA only
1296 Combinations also work, so libata.dma=3 enables DMA
1297 for disks and CDROMs, but not CFs.
1299 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1300 libata.ignore_hpa=0 keep BIOS limits (default)
1301 libata.ignore_hpa=1 ignore limits, using full disk
1303 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1307 libata.force= [LIBATA] Force configurations. The format is comma
1308 separated list of "[ID:]VAL" where ID is
1309 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1310 matching port, link or device. Basically, it matches
1311 the ATA ID string printed on console by libata. If
1312 the whole ID part is omitted, the last PORT and DEVICE
1313 values are used. If ID hasn't been specified yet, the
1314 configuration applies to all ports, links and devices.
1316 If only DEVICE is omitted, the parameter applies to
1317 the port and all links and devices behind it. DEVICE
1318 number of 0 either selects the first device or the
1319 first fan-out link behind PMP device. It does not
1320 select the host link. DEVICE number of 15 selects the
1321 host link and device attached to it.
1323 The VAL specifies the configuration to force. As long
1324 as there's no ambiguity shortcut notation is allowed.
1325 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1326 The following configurations can be forced.
1328 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1329 Any ID with matching PORT is used.
1331 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1333 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1334 udma[/][16,25,33,44,66,100,133] notation is also
1337 * [no]ncq: Turn on or off NCQ.
1339 * nohrst, nosrst, norst: suppress hard, soft
1342 * dump_id: dump IDENTIFY data.
1344 If there are multiple matching configurations changing
1345 the same attribute, the last one is used.
1347 memblock=debug [KNL] Enable memblock debug messages.
1349 load_ramdisk= [RAM] List of ramdisks to load from floppy
1350 See Documentation/blockdev/ramdisk.txt.
1352 lockd.nlm_grace_period=P [NFS] Assign grace period.
1355 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1358 lockd.nlm_timeout=T [NFS] Assign timeout value.
1361 lockd.nlm_udpport=M [NFS] Assign UDP port.
1364 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1367 loglevel= All Kernel Messages with a loglevel smaller than the
1368 console loglevel will be printed to the console. It can
1369 also be changed with klogd or other programs. The
1370 loglevels are defined as follows:
1372 0 (KERN_EMERG) system is unusable
1373 1 (KERN_ALERT) action must be taken immediately
1374 2 (KERN_CRIT) critical conditions
1375 3 (KERN_ERR) error conditions
1376 4 (KERN_WARNING) warning conditions
1377 5 (KERN_NOTICE) normal but significant condition
1378 6 (KERN_INFO) informational
1379 7 (KERN_DEBUG) debug-level messages
1381 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1382 in bytes. n must be a power of two. The default
1383 size is set in the kernel config file.
1385 logo.nologo [FB] Disables display of the built-in Linux logo.
1386 This may be used to provide more screen space for
1387 kernel log messages and is useful when debugging
1388 kernel boot problems.
1390 lp=0 [LP] Specify parallel ports to use, e.g,
1391 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1392 lp=reset first parallel port). 'lp=0' disables the
1393 lp=auto printer driver. 'lp=reset' (which can be
1394 specified in addition to the ports) causes
1395 attached printers to be reset. Using
1396 lp=port1,port2,... specifies the parallel ports
1397 to associate lp devices with, starting with
1398 lp0. A port specification may be 'none' to skip
1399 that lp device, or a parport name such as
1400 'parport0'. Specifying 'lp=auto' instead of a
1401 port specification list means that device IDs
1402 from each port should be examined, to see if
1403 an IEEE 1284-compliant printer is attached; if
1404 so, the driver will manage that printer.
1405 See also header of drivers/char/lp.c.
1408 Sets loops_per_jiffy to given constant, thus avoiding
1409 time-consuming boot-time autodetection (up to 250 ms per
1410 CPU). 0 enables autodetection (default). To determine
1411 the correct value for your kernel, boot with normal
1412 autodetection and see what value is printed. Note that
1413 on SMP systems the preset will be applied to all CPUs,
1414 which is likely to cause problems if your CPUs need
1415 significantly divergent settings. An incorrect value
1416 will cause delays in the kernel to be wrong, leading to
1417 unpredictable I/O errors and other breakage. Although
1418 unlikely, in the extreme case this might damage your
1422 Format: <io>,<irq>,<dma>
1424 machvec= [IA-64] Force the use of a particular machine-vector
1425 (machvec) in a generic kernel.
1426 Example: machvec=hpzx1_swiotlb
1428 machtype= [Loongson] Share the same kernel image file between different
1430 Example: machtype=lemote-yeeloong-2f-7inch
1432 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1433 than or equal to this physical address is ignored.
1435 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1436 should make use of. maxcpus=n : n >= 0 limits the
1437 kernel to using 'n' processors. n=0 is a special case,
1438 it is equivalent to "nosmp", which also disables
1441 max_loop= [LOOP] The number of loop block devices that get
1442 (loop.max_loop) unconditionally pre-created at init time. The default
1443 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1444 of statically allocating a predefined number, loop
1445 devices can be requested on-demand with the
1446 /dev/loop-control interface.
1450 mce [X86-32] Machine Check Exception
1452 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1454 md= [HW] RAID subsystems devices and level
1455 See Documentation/md.txt.
1458 Format: <first>,<last>
1459 Specifies range of consoles to be captured by the MDA.
1461 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1462 Amount of memory to be used when the kernel is not able
1463 to see the whole system memory or for test.
1464 [X86-32] Use together with memmap= to avoid physical
1465 address space collisions. Without memmap= PCI devices
1466 could be placed at addresses belonging to unused RAM.
1468 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1472 [KNL,SH] Allow user to override the default size for
1473 per-device physically contiguous DMA buffers.
1475 memmap=exactmap [KNL,X86] Enable setting of an exact
1476 E820 memory map, as specified by the user.
1477 Such memmap=exactmap lines can be constructed based on
1478 BIOS output or other requirements. See the memmap=nn@ss
1481 memmap=nn[KMG]@ss[KMG]
1482 [KNL] Force usage of a specific region of memory
1483 Region of memory to be used, from ss to ss+nn.
1485 memmap=nn[KMG]#ss[KMG]
1486 [KNL,ACPI] Mark specific memory as ACPI data.
1487 Region of memory to be used, from ss to ss+nn.
1489 memmap=nn[KMG]$ss[KMG]
1490 [KNL,ACPI] Mark specific memory as reserved.
1491 Region of memory to be used, from ss to ss+nn.
1492 Example: Exclude memory from 0x18690000-0x1869ffff
1493 memmap=64K$0x18690000
1495 memmap=0x10000$0x18690000
1497 memory_corruption_check=0/1 [X86]
1498 Some BIOSes seem to corrupt the first 64k of
1499 memory when doing things like suspend/resume.
1500 Setting this option will scan the memory
1501 looking for corruption. Enabling this will
1502 both detect corruption and prevent the kernel
1503 from using the memory being corrupted.
1504 However, its intended as a diagnostic tool; if
1505 repeatable BIOS-originated corruption always
1506 affects the same memory, you can use memmap=
1507 to prevent the kernel from using that memory.
1509 memory_corruption_check_size=size [X86]
1510 By default it checks for corruption in the low
1511 64k, making this memory unavailable for normal
1512 use. Use this parameter to scan for
1513 corruption in more or less memory.
1515 memory_corruption_check_period=seconds [X86]
1516 By default it checks for corruption every 60
1517 seconds. Use this parameter to check at some
1518 other rate. 0 disables periodic checking.
1520 memtest= [KNL,X86] Enable memtest
1522 default : 0 <disable>
1523 Specifies the number of memtest passes to be
1524 performed. Each pass selects another test
1525 pattern from a given set of patterns. Memtest
1526 fills the memory with this pattern, validates
1527 memory contents and reserves bad memory
1528 regions that are detected.
1530 meye.*= [HW] Set MotionEye Camera parameters
1531 See Documentation/video4linux/meye.txt.
1533 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1534 Multi-Function General Purpose Timers on AMD Geode
1537 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1538 the BIOS has incorrectly applied a workaround. TinyBIOS
1539 version 0.98 is known to be affected, 0.99 fixes the
1540 problem by letting the user disable the workaround.
1544 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1545 physical address is ignored.
1547 mini2440= [ARM,HW,KNL]
1548 Format:[0..2][b][c][t]
1550 MINI2440 configuration specification:
1551 0 - The attached screen is the 3.5" TFT
1552 1 - The attached screen is the 7" TFT
1553 2 - The VGA Shield is attached (1024x768)
1554 Leaving out the screen size parameter will not load
1555 the TFT driver, and the framebuffer will be left
1557 b - Enable backlight. The TFT backlight pin will be
1558 linked to the kernel VESA blanking code and a GPIO
1559 LED. This parameter is not necessary when using the
1561 c - Enable the s3c camera interface.
1562 t - Reserved for enabling touchscreen support. The
1563 touchscreen support is not enabled in the mainstream
1564 kernel as of 2.6.30, a preliminary port can be found
1565 in the "bleeding edge" mini2440 support kernel at
1566 http://repo.or.cz/w/linux-2.6/mini2440.git
1569 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1570 parameter allows control of the logging verbosity for
1571 the additional memory initialisation checks. A value
1572 of 0 disables mminit logging and a level of 4 will
1573 log everything. Information is printed at KERN_DEBUG
1574 so loglevel=8 may also need to be specified.
1577 [MOUSE] Maximum time between finger touching and
1578 leaving touchpad surface for touch to be considered
1579 a tap and be reported as a left button click (for
1580 touchpads working in absolute mode only).
1582 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1583 reporting absolute coordinates, such as tablets
1584 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1585 reporting absolute coordinates, such as tablets
1587 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1588 is similar to kernelcore except it specifies the
1589 amount of memory used for migratable allocations.
1590 If both kernelcore and movablecore is specified,
1591 then kernelcore will be at *least* the specified
1592 value but may be more. If movablecore on its own
1593 is specified, the administrator must be careful
1594 that the amount of memory usable for all allocations
1597 MTD_Partition= [MTD]
1598 Format: <name>,<region-number>,<size>,<offset>
1600 MTD_Region= [MTD] Format:
1601 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1604 See drivers/mtd/cmdlinepart.c.
1606 multitce=off [PPC] This parameter disables the use of the pSeries
1607 firmware feature for updating multiple TCE entries
1610 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1612 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1614 boundary - index of last SLC block on Flex-OneNAND.
1615 The remaining blocks are configured as MLC blocks.
1616 lock - Configure if Flex-OneNAND boundary should be locked.
1617 Once locked, the boundary cannot be changed.
1618 1 indicates lock status, 0 indicates unlock status.
1621 ARM/S3C2412 JIVE boot control
1623 See arch/arm/mach-s3c2412/mach-jive.c
1625 mtouchusb.raw_coordinates=
1626 [HW] Make the MicroTouch USB driver use raw coordinates
1627 ('y', default) or cooked coordinates ('n')
1629 mtrr_chunk_size=nn[KMG] [X86]
1630 used for mtrr cleanup. It is largest continuous chunk
1631 that could hold holes aka. UC entries.
1633 mtrr_gran_size=nn[KMG] [X86]
1634 Used for mtrr cleanup. It is granularity of mtrr block.
1636 Large value could prevent small alignment from
1639 mtrr_spare_reg_nr=n [X86]
1641 Range: 0,7 : spare reg number
1643 Used for mtrr cleanup. It is spare mtrr entries number.
1644 Set to 2 or more if your graphical card needs more.
1646 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1648 netdev= [NET] Network devices parameters
1649 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1650 Note that mem_start is often overloaded to mean
1651 something different and driver-specific.
1652 This usage is only documented in each driver source
1656 [NETFILTER] Enable connection tracking flow accounting
1657 0 to disable accounting
1658 1 to enable accounting
1661 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1662 See Documentation/filesystems/nfs/nfsroot.txt.
1664 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1665 See Documentation/filesystems/nfs/nfsroot.txt.
1667 nfsrootdebug [NFS] enable nfsroot debugging messages.
1668 See Documentation/filesystems/nfs/nfsroot.txt.
1670 nfs.callback_tcpport=
1671 [NFS] set the TCP port on which the NFSv4 callback
1672 channel should listen.
1675 [NFS] sets the pathname to the program which is used
1676 to update the NFS client cache entries.
1678 nfs.cache_getent_timeout=
1679 [NFS] sets the timeout after which an attempt to
1680 update a cache entry is deemed to have failed.
1682 nfs.idmap_cache_timeout=
1683 [NFS] set the maximum lifetime for idmapper cache
1687 [NFS] enable 64-bit inode numbers.
1688 If zero, the NFS client will fake up a 32-bit inode
1689 number for the readdir() and stat() syscalls instead
1690 of returning the full 64-bit number.
1691 The default is to return 64-bit inode numbers.
1693 nfs.max_session_slots=
1694 [NFSv4.1] Sets the maximum number of session slots
1695 the client will attempt to negotiate with the server.
1696 This limits the number of simultaneous RPC requests
1697 that the client can send to the NFSv4.1 server.
1698 Note that there is little point in setting this
1699 value higher than the max_tcp_slot_table_limit.
1701 nfs.nfs4_disable_idmapping=
1702 [NFSv4] When set to the default of '1', this option
1703 ensures that both the RPC level authentication
1704 scheme and the NFS level operations agree to use
1705 numeric uids/gids if the mount is using the
1706 'sec=sys' security flavour. In effect it is
1707 disabling idmapping, which can make migration from
1708 legacy NFSv2/v3 systems to NFSv4 easier.
1709 Servers that do not support this mode of operation
1710 will be autodetected by the client, and it will fall
1711 back to using the idmapper.
1712 To turn off this behaviour, set the value to '0'.
1714 nfs.send_implementation_id =
1715 [NFSv4.1] Send client implementation identification
1716 information in exchange_id requests.
1717 If zero, no implementation identification information
1719 The default is to send the implementation identification
1722 nfsd.nfs4_disable_idmapping=
1723 [NFSv4] When set to the default of '1', the NFSv4
1724 server will return only numeric uids and gids to
1725 clients using auth_sys, and will accept numeric uids
1726 and gids from such clients. This is intended to ease
1727 migration from NFSv2/v3.
1729 objlayoutdriver.osd_login_prog=
1730 [NFS] [OBJLAYOUT] sets the pathname to the program which
1731 is used to automatically discover and login into new
1732 osd-targets. Please see:
1733 Documentation/filesystems/pnfs.txt for more explanations
1735 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1736 when a NMI is triggered.
1737 Format: [state][,regs][,debounce][,die]
1739 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1740 Format: [panic,][nopanic,][num]
1742 0 - turn nmi_watchdog off
1743 When panic is specified, panic when an NMI watchdog
1744 timeout occurs (or 'nopanic' to override the opposite
1746 This is useful when you use a panic=... timeout and
1747 need the box quickly up again.
1749 netpoll.carrier_timeout=
1750 [NET] Specifies amount of time (in seconds) that
1751 netpoll should wait for a carrier. By default netpoll
1754 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1755 emulation library even if a 387 maths coprocessor
1759 [HW] Never suspend the console
1760 Disable suspending of consoles during suspend and
1761 hibernate operations. Once disabled, debugging
1762 messages can reach various consoles while the rest
1763 of the system is being put to sleep (ie, while
1764 debugging driver suspend/resume hooks). This may
1765 not work reliably with all consoles, but is known
1766 to work with serial and VGA consoles.
1767 To facilitate more flexible debugging, we also add
1768 console_suspend, a printk module parameter to control
1769 it. Users could use console_suspend (usually
1770 /sys/module/printk/parameters/console_suspend) to
1771 turn on/off it dynamically.
1773 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1774 caches in the slab allocator. Saves per-node memory,
1775 but will impact performance.
1779 noapic [SMP,APIC] Tells the kernel to not make use of any
1780 IOAPICs that may be present in the system.
1782 noautogroup Disable scheduler automatic task group creation.
1784 nobats [PPC] Do not use BATs for mapping kernel lowmem
1785 on "Classic" PPC cores.
1789 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1791 nodelayacct [KNL] Disable per-task delay accounting
1793 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1795 nodsp [SH] Disable hardware DSP at boot time.
1797 noefi [X86] Disable EFI runtime services support.
1802 On X86-32 available only on PAE configured kernels.
1803 noexec=on: enable non-executable mappings (default)
1804 noexec=off: disable non-executable mappings
1807 Disable SMEP (Supervisor Mode Execution Protection)
1808 even if it is supported by processor.
1811 This affects only 32-bit executables.
1812 noexec32=on: enable non-executable mappings (default)
1813 read doesn't imply executable mappings
1814 noexec32=off: disable non-executable mappings
1815 read implies executable mappings
1817 nofpu [SH] Disable hardware FPU at boot time.
1819 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1820 register save and restore. The kernel will only save
1821 legacy floating-point registers on task switch.
1823 noxsave [BUGS=X86] Disables x86 extended register state save
1824 and restore using xsave. The kernel will fallback to
1825 enabling legacy floating-point and sse state.
1827 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1828 wfi(ARM) instruction doesn't work correctly and not to
1829 use it. This is also useful when using JTAG debugger.
1831 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1832 instruction doesn't work correctly and not to
1835 no_file_caps Tells the kernel not to honor file capabilities. The
1836 only way then for a file to be executed with privilege
1837 is to be setuid root or executed by root.
1839 nohalt [IA-64] Tells the kernel not to use the power saving
1840 function PAL_HALT_LIGHT when idle. This increases
1841 power-consumption. On the positive side, it reduces
1842 interrupt wake-up latency, which may improve performance
1843 in certain environments such as networked servers or
1846 nohz= [KNL] Boottime enable/disable dynamic ticks
1847 Valid arguments: on, off
1850 noiotrap [SH] Disables trapped I/O port accesses.
1852 noirqdebug [X86-32] Disables the code which attempts to detect and
1853 disable unhandled interrupt sources.
1855 no_timer_check [X86,APIC] Disables the code which tests for
1856 broken timer IRQ sources.
1858 noisapnp [ISAPNP] Disables ISA PnP code.
1860 noinitrd [RAM] Tells the kernel not to load any configured
1863 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1865 [Deprecated - use intremap=off]
1869 nojitter [IA-64] Disables jitter checking for ITC timers.
1871 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1873 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1876 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1877 steal time is computed, but won't influence scheduler
1880 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1882 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1884 noltlbs [PPC] Do not use large page/tlb entries for kernel
1885 lowmem mapping on PPC40x.
1887 nomca [IA-64] Disable machine check abort handling
1889 nomce [X86-32] Machine Check Exception
1891 nomfgpt [X86-32] Disable Multi-Function General Purpose
1892 Timer usage (for AMD Geode machines).
1894 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1895 shutdown the other cpus. Instead use the REBOOT_VECTOR
1898 nomodule Disable module load
1900 nopat [X86] Disable PAT (page attribute table extension of
1901 pagetables) support.
1903 norandmaps Don't use address space randomization. Equivalent to
1904 echo 0 > /proc/sys/kernel/randomize_va_space
1906 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1908 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1909 with UP alternatives
1911 noresidual [PPC] Don't use residual data on PReP machines.
1913 nordrand [X86] Disable the direct use of the RDRAND
1914 instruction even if it is supported by the
1915 processor. RDRAND is still available to user
1918 noresume [SWSUSP] Disables resume and restores original swap
1921 no-scroll [VGA] Disables scrollback.
1922 This is required for the Braillex ib80-piezo Braille
1923 reader made by F.H. Papenmeier (Germany).
1927 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1929 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1930 and disable the IO APIC. legacy for "maxcpus=0".
1932 nosoftlockup [KNL] Disable the soft-lockup detector.
1934 nosync [HW,M68K] Disables sync negotiation for all devices.
1936 notsc [BUGS=X86-32] Disable Time Stamp Counter
1938 nousb [USB] Disable the USB subsystem
1940 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1944 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1946 nptcg= [IA-64] Override max number of concurrent global TLB
1947 purges which is reported from either PAL_VM_SUMMARY or
1950 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1951 could support. nr_cpus=n : n >= 1 limits the kernel to
1952 supporting 'n' processors. Later in runtime you can not
1953 use hotplug cpu feature to put more cpu back to online.
1954 just like you compile the kernel NR_CPUS=n
1956 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1958 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1959 one of ['zone', 'node', 'default'] can be specified
1960 This can be set from sysctl after boot.
1961 See Documentation/sysctl/vm.txt for details.
1963 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1964 See Documentation/debugging-via-ohci1394.txt for more
1967 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1968 Rather than timing out after 20 ms if an EC
1969 command is not properly ACKed, override the length
1970 of the timeout. We have interrupts disabled while
1971 waiting for the ACK, so if this is set too high
1972 interrupts *may* be lost!
1974 omap_mux= [OMAP] Override bootloader pin multiplexing.
1975 Format: <mux_mode0.mode_name=value>...
1976 For example, to override I2C bus2:
1977 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1979 oprofile.timer= [HW]
1980 Use timer interrupt instead of performance counters
1982 oprofile.cpu_type= Force an oprofile cpu type
1983 This might be useful if you have an older oprofile
1984 userland or if you want common events.
1985 Format: { arch_perfmon }
1986 arch_perfmon: [X86] Force use of architectural
1987 perfmon on Intel CPUs instead of the
1988 CPU specific event set.
1989 timer: [X86] Force use of architectural NMI
1990 timer mode (see also oprofile.timer
1991 for generic hr timer mode)
1992 [s390] Force legacy basic mode sampling
1993 (report cpu_type "timer")
1995 oops=panic Always panic on oopses. Default is to just kill the
1996 process, but there is a small probability of
1997 deadlocking the machine.
1998 This will also cause panics on machine check exceptions.
1999 Useful together with panic=30 to trigger a reboot.
2002 See Documentation/sound/oss/oss-parameters.txt
2004 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2005 timeout > 0: seconds before rebooting
2006 timeout = 0: wait forever
2007 timeout < 0: reboot immediately
2010 parkbd.port= [HW] Parallel port number the keyboard adapter is
2011 connected to, default is 0.
2013 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2014 0 for XT, 1 for AT (default is AT).
2017 parport= [HW,PPT] Specify parallel ports. 0 disables.
2018 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2019 Use 'auto' to force the driver to use any
2020 IRQ/DMA settings detected (the default is to
2021 ignore detected IRQ/DMA settings because of
2022 possible conflicts). You can specify the base
2023 address, IRQ, and DMA settings; IRQ and DMA
2024 should be numbers, or 'auto' (for using detected
2025 settings on that particular port), or 'nofifo'
2026 (to avoid using a FIFO even if it is detected).
2027 Parallel ports are assigned in the order they
2028 are specified on the command line, starting
2031 parport_init_mode= [HW,PPT]
2032 Configure VIA parallel port to operate in
2033 a specific mode. This is necessary on Pegasos
2034 computer where firmware has no options for setting
2035 up parallel port mode and sets it to spp.
2036 Currently this function knows 686a and 8231 chips.
2037 Format: [spp|ps2|epp|ecp|ecpepp]
2040 Halt all CPUs after the first oops has been printed for
2041 the specified number of seconds. This is to be used if
2042 your oopses keep scrolling off the screen.
2047 See header of drivers/block/paride/pcd.c.
2048 See also Documentation/blockdev/paride.txt.
2050 pci=option[,option...] [PCI] various PCI subsystem options:
2051 earlydump [X86] dump PCI config space before the kernel
2053 off [X86] don't probe for the PCI bus
2054 bios [X86-32] force use of PCI BIOS, don't access
2055 the hardware directly. Use this if your machine
2056 has a non-standard PCI host bridge.
2057 nobios [X86-32] disallow use of PCI BIOS, only direct
2058 hardware access methods are allowed. Use this
2059 if you experience crashes upon bootup and you
2060 suspect they are caused by the BIOS.
2061 conf1 [X86] Force use of PCI Configuration
2063 conf2 [X86] Force use of PCI Configuration
2065 noaer [PCIE] If the PCIEAER kernel config parameter is
2066 enabled, this kernel boot option can be used to
2067 disable the use of PCIE advanced error reporting.
2068 nodomains [PCI] Disable support for multiple PCI
2069 root domains (aka PCI segments, in ACPI-speak).
2070 nommconf [X86] Disable use of MMCONFIG for PCI
2072 check_enable_amd_mmconf [X86] check for and enable
2073 properly configured MMIO access to PCI
2074 config space on AMD family 10h CPU
2075 nomsi [MSI] If the PCI_MSI kernel config parameter is
2076 enabled, this kernel boot option can be used to
2077 disable the use of MSI interrupts system-wide.
2078 noioapicquirk [APIC] Disable all boot interrupt quirks.
2079 Safety option to keep boot IRQs enabled. This
2080 should never be necessary.
2081 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2082 primary IO-APIC for bridges that cannot disable
2083 boot IRQs. This fixes a source of spurious IRQs
2084 when the system masks IRQs.
2085 noioapicreroute [APIC] Disable workaround that uses the
2086 boot IRQ equivalent of an IRQ that connects to
2087 a chipset where boot IRQs cannot be disabled.
2088 The opposite of ioapicreroute.
2089 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2090 routing table. These calls are known to be buggy
2091 on several machines and they hang the machine
2092 when used, but on other computers it's the only
2093 way to get the interrupt routing table. Try
2094 this option if the kernel is unable to allocate
2095 IRQs or discover secondary PCI buses on your
2097 rom [X86] Assign address space to expansion ROMs.
2098 Use with caution as certain devices share
2099 address decoders between ROMs and other
2101 norom [X86] Do not assign address space to
2102 expansion ROMs that do not already have
2103 BIOS assigned address ranges.
2104 nobar [X86] Do not assign address space to the
2105 BARs that weren't assigned by the BIOS.
2106 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2107 assigned automatically to PCI devices. You can
2108 make the kernel exclude IRQs of your ISA cards
2110 pirqaddr=0xAAAAA [X86] Specify the physical address
2111 of the PIRQ table (normally generated
2112 by the BIOS) if it is outside the
2113 F0000h-100000h range.
2114 lastbus=N [X86] Scan all buses thru bus #N. Can be
2115 useful if the kernel is unable to find your
2116 secondary buses and you want to tell it
2117 explicitly which ones they are.
2118 assign-busses [X86] Always assign all PCI bus
2119 numbers ourselves, overriding
2120 whatever the firmware may have done.
2121 usepirqmask [X86] Honor the possible IRQ mask stored
2122 in the BIOS $PIR table. This is needed on
2123 some systems with broken BIOSes, notably
2124 some HP Pavilion N5400 and Omnibook XE3
2125 notebooks. This will have no effect if ACPI
2126 IRQ routing is enabled.
2127 noacpi [X86] Do not use ACPI for IRQ routing
2128 or for PCI scanning.
2129 use_crs [X86] Use PCI host bridge window information
2130 from ACPI. On BIOSes from 2008 or later, this
2131 is enabled by default. If you need to use this,
2132 please report a bug.
2133 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2134 If you need to use this, please report a bug.
2135 routeirq Do IRQ routing for all PCI devices.
2136 This is normally done in pci_enable_device(),
2137 so this option is a temporary workaround
2138 for broken drivers that don't call it.
2139 skip_isa_align [X86] do not align io start addr, so can
2140 handle more pci cards
2141 firmware [ARM] Do not re-enumerate the bus but instead
2142 just use the configuration from the
2143 bootloader. This is currently used on
2144 IXP2000 systems where the bus has to be
2145 configured a certain way for adjunct CPUs.
2146 noearly [X86] Don't do any early type 1 scanning.
2147 This might help on some broken boards which
2148 machine check when some devices' config space
2149 is read. But various workarounds are disabled
2150 and some IOMMU drivers will not work.
2151 bfsort Sort PCI devices into breadth-first order.
2152 This sorting is done to get a device
2153 order compatible with older (<= 2.4) kernels.
2154 nobfsort Don't sort PCI devices into breadth-first order.
2155 cbiosize=nn[KMG] The fixed amount of bus space which is
2156 reserved for the CardBus bridge's IO window.
2157 The default value is 256 bytes.
2158 cbmemsize=nn[KMG] The fixed amount of bus space which is
2159 reserved for the CardBus bridge's memory
2160 window. The default value is 64 megabytes.
2163 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2164 Specifies alignment and device to reassign
2165 aligned memory resources.
2166 If <order of align> is not specified,
2167 PAGE_SIZE is used as alignment.
2168 PCI-PCI bridge can be specified, if resource
2169 windows need to be expanded.
2170 ecrc= Enable/disable PCIe ECRC (transaction layer
2171 end-to-end CRC checking).
2172 bios: Use BIOS/firmware settings. This is the
2176 realloc= Enable/disable reallocating PCI bridge resources
2177 if allocations done by BIOS are too small to
2178 accommodate resources required by all child
2180 off: Turn realloc off
2182 realloc same as realloc=on
2183 noari do not use PCIe ARI.
2186 Format: [<sbdf>[+IO<size>][+MEM<size>]][,<sbdf>...]
2187 Format of sbdf: [<segment>:]<bus>:<dev>.<func>
2188 Specifies the least reserved io size or memory size
2189 which is assigned to PCI bridge even when no child
2190 pci device exists. This is useful with PCI hotplug.
2192 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2195 force Enable ASPM even on devices that claim not to support it.
2196 WARNING: Forcing ASPM on may cause system lockups.
2198 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2199 nomsi Do not use MSI for PCI Express Native Hotplug (this
2200 makes all PCIe ports use INTx for hotplug services).
2202 pcie_ports= [PCIE] PCIe ports handling:
2203 auto Ask the BIOS whether or not to use native PCIe services
2204 associated with PCIe ports (PME, hot-plug, AER). Use
2205 them only if that is allowed by the BIOS.
2206 native Use native PCIe services associated with PCIe ports
2208 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2211 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2212 nomsi Do not use MSI for native PCIe PME signaling (this makes
2213 all PCIe root ports use INTx for all services).
2215 pcmv= [HW,PCMCIA] BadgePAD 4
2218 See Documentation/blockdev/paride.txt.
2220 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2223 See arch/parisc/kernel/pdc_chassis.c
2225 percpu_alloc= Select which percpu first chunk allocator to use.
2226 Currently supported values are "embed" and "page".
2227 Archs may support subset or none of the selections.
2228 See comments in mm/percpu.c for details on each
2229 allocator. This parameter is primarily for debugging
2230 and performance comparison.
2233 See Documentation/blockdev/paride.txt.
2236 See Documentation/blockdev/paride.txt.
2238 pirq= [SMP,APIC] Manual mp-table setup
2239 See Documentation/x86/i386/IO-APIC.txt.
2241 plip= [PPT,NET] Parallel port network link
2242 Format: { parport<nr> | timid | 0 }
2243 See also Documentation/parport.txt.
2245 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2246 Override pmtimer IOPort with a hex value.
2250 Enable PNP debug messages (depends on the
2251 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2252 via /sys/module/pnp/parameters/debug. We always show
2253 current resource usage; turning this on also shows
2254 possible settings and some assignment information.
2260 { on | off | curr | res | no-curr | no-res }
2263 [ISAPNP] Exclude IRQs for the autoconfiguration
2266 [ISAPNP] Exclude DMAs for the autoconfiguration
2268 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2269 Ranges are in pairs (I/O port base and size).
2272 [ISAPNP] Exclude memory regions for the
2274 Ranges are in pairs (memory base and size).
2276 ports= [IP_VS_FTP] IPVS ftp helper module
2278 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2280 Format: <port>,<port>....
2282 print-fatal-signals=
2283 [KNL] debug: print fatal signals
2285 If enabled, warn about various signal handling
2286 related application anomalies: too many signals,
2287 too many POSIX.1 timers, fatal signals causing a
2290 If you hit the warning due to signal overflow,
2291 you might want to try "ulimit -i unlimited".
2295 printk.always_kmsg_dump=
2296 Trigger kmsg_dump for cases other than kernel oops or
2298 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2301 printk.time= Show timing data prefixed to each printk message line
2302 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2304 processor.max_cstate= [HW,ACPI]
2305 Limit processor to maximum C-state
2306 max_cstate=9 overrides any DMI blacklist limit.
2308 processor.nocst [HW,ACPI]
2309 Ignore the _CST method to determine C-states,
2310 instead using the legacy FADT method
2312 profile= [KNL] Enable kernel profiling via /proc/profile
2313 Format: [schedule,]<number>
2314 Param: "schedule" - profile schedule points.
2315 Param: <number> - step/bucket size as a power of 2 for
2316 statistical time based profiling.
2317 Param: "sleep" - profile D-state sleeping (millisecs).
2318 Requires CONFIG_SCHEDSTATS
2319 Param: "kvm" - profile VM exits.
2321 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2323 See Documentation/blockdev/ramdisk.txt.
2325 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2326 probe for; one of (bare|imps|exps|lifebook|any).
2327 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2329 psmouse.resetafter= [HW,MOUSE]
2330 Try to reset the device after so many bad packets
2333 [HW,MOUSE] Set desired mouse resolution, in dpi.
2334 psmouse.smartscroll=
2335 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2336 0 = disabled, 1 = enabled (default).
2338 pstore.backend= Specify the name of the pstore backend to use
2341 See Documentation/blockdev/paride.txt.
2344 [KNL] Number of legacy pty's. Overwrites compiled-in
2347 quiet [KNL] Disable most log messages
2352 See Documentation/md.txt.
2354 ramdisk_blocksize= [RAM]
2355 See Documentation/blockdev/ramdisk.txt.
2357 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2358 See Documentation/blockdev/ramdisk.txt.
2360 rcupdate.blimit= [KNL,BOOT]
2361 Set maximum number of finished RCU callbacks to process
2364 rcupdate.qhimark= [KNL,BOOT]
2365 Set threshold of queued
2366 RCU callbacks over which batch limiting is disabled.
2368 rcupdate.qlowmark= [KNL,BOOT]
2369 Set threshold of queued RCU callbacks below which
2370 batch limiting is re-enabled.
2374 Run specified binary instead of /init from the ramdisk,
2375 used for early userspace startup. See initrd.
2377 reassign_resources [PCI,ACPI,XEN]
2378 Use guestdev= parameter to reassign device's
2379 resources, or specify =all here.
2381 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2382 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2383 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2386 [KNL, SMP] Set scheduler's default relax_domain_level.
2387 See Documentation/cgroups/cpusets.txt.
2389 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2391 reservetop= [X86-32]
2393 Reserves a hole at the top of the kernel virtual
2398 Set the amount of memory to reserve for BIOS at
2399 the bottom of the address space.
2401 reset_devices [KNL] Force drivers to reset the underlying device
2402 during initialization.
2405 Specify the partition device for software suspend
2407 resume_offset= [SWSUSP]
2408 Specify the offset from the beginning of the partition
2409 given by "resume=" at which the swap header is located,
2410 in <PAGE_SIZE> units (needed only for swap files).
2411 See Documentation/power/swsusp-and-swap-files.txt
2413 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2414 read the resume files
2416 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2417 Useful for devices that are detected asynchronously
2418 (e.g. USB and MMC devices).
2420 hibernate= [HIBERNATION]
2421 noresume Don't check if there's a hibernation image
2422 present during boot.
2423 nocompress Don't compress/decompress hibernation images.
2425 retain_initrd [RAM] Keep initrd memory after extraction
2427 rhash_entries= [KNL,NET]
2428 Set number of hash buckets for route cache
2430 riscom8= [HW,SERIAL]
2431 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2433 ro [KNL] Mount root device read-only on boot
2435 root= [KNL] Root filesystem
2436 See name_to_dev_t comment in init/do_mounts.c.
2438 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2439 mount the root filesystem
2441 rootflags= [KNL] Set root filesystem mount option string
2443 rootfstype= [KNL] Set root filesystem type
2445 rootwait [KNL] Wait (indefinitely) for root device to show up.
2446 Useful for devices that are detected asynchronously
2447 (e.g. USB and MMC devices).
2449 rw [KNL] Mount root device read-write on boot
2451 S [KNL] Run init in single mode
2454 See drivers/net/irda/sa1100_ir.c.
2456 sbni= [NET] Granch SBNI12 leased line adapter
2458 sched_debug [KNL] Enables verbose scheduler debug messages.
2460 security= [SECURITY] Choose a security module to enable at boot.
2461 If this boot parameter is not specified, only the first
2462 security module asking for security registration will be
2463 loaded. An invalid security module name will be treated
2464 as if no module has been chosen.
2466 selinux= [SELINUX] Disable or enable SELinux at boot time.
2467 Format: { "0" | "1" }
2468 See security/selinux/Kconfig help text.
2471 Default value is set via kernel config option.
2472 If enabled at boot time, /selinux/disable can be used
2473 later to disable prior to initial policy load.
2475 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2476 Format: { "0" | "1" }
2477 See security/apparmor/Kconfig help text
2480 Default value is set via kernel config option.
2482 serialnumber [BUGS=X86-32]
2485 Maximal number of shapers.
2487 show_msr= [x86] show boot-time MSR settings
2488 Format: { <integer> }
2489 Show boot-time (BIOS-initialized) MSR settings.
2490 The parameter means the number of CPUs to show,
2491 for example 1 means boot CPU only.
2498 slab_max_order= [MM, SLAB]
2499 Determines the maximum allowed order for slabs.
2500 A high setting may cause OOMs due to memory
2501 fragmentation. Defaults to 1 for systems with
2502 more than 32MB of RAM, 0 otherwise.
2504 slub_debug[=options[,slabs]] [MM, SLUB]
2505 Enabling slub_debug allows one to determine the
2506 culprit if slab objects become corrupted. Enabling
2507 slub_debug can create guard zones around objects and
2508 may poison objects when not in use. Also tracks the
2509 last alloc / free. For more information see
2510 Documentation/vm/slub.txt.
2512 slub_max_order= [MM, SLUB]
2513 Determines the maximum allowed order for slabs.
2514 A high setting may cause OOMs due to memory
2515 fragmentation. For more information see
2516 Documentation/vm/slub.txt.
2518 slub_min_objects= [MM, SLUB]
2519 The minimum number of objects per slab. SLUB will
2520 increase the slab order up to slub_max_order to
2521 generate a sufficiently large slab able to contain
2522 the number of objects indicated. The higher the number
2523 of objects the smaller the overhead of tracking slabs
2524 and the less frequently locks need to be acquired.
2525 For more information see Documentation/vm/slub.txt.
2527 slub_min_order= [MM, SLUB]
2528 Determines the minimum page order for slabs. Must be
2529 lower than slub_max_order.
2530 For more information see Documentation/vm/slub.txt.
2532 slub_nomerge [MM, SLUB]
2533 Disable merging of slabs with similar size. May be
2534 necessary if there is some reason to distinguish
2535 allocs to different slabs. Debug options disable
2536 merging on their own.
2537 For more information see Documentation/vm/slub.txt.
2540 Format: <io1>[,<io2>[,...,<io8>]]
2542 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2543 attempt to substitute SMP alternatives once at boot.
2545 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2546 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2547 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2548 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2549 smsc-ircc2.ircc_irq= [HW] IRQ line
2550 smsc-ircc2.ircc_dma= [HW] DMA channel
2551 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2552 0: Toshiba Satellite 1800 (GP data pin select)
2553 1: Fast pin select (default)
2557 [KNL] Should the soft-lockup detector generate panics.
2560 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2561 See Documentation/laptops/sonypi.txt
2563 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2564 See Documentation/serial/specialix.txt.
2566 spia_io_base= [HW,MTD]
2572 Enabled the stack tracer on boot up.
2574 stacktrace_filter=[function-list]
2575 [FTRACE] Limit the functions that the stack tracer
2576 will trace at boot up. function-list is a comma separated
2577 list of functions. This list can be changed at run
2578 time by the stack_trace_filter file in the debugfs
2579 tracing directory. Note, this enables stack tracing
2580 and the stacktrace above is not needed.
2584 Set the STI (builtin display/keyboard on the HP-PARISC
2585 machines) console (graphic card) which should be used
2586 as the initial boot-console.
2587 See also comment in drivers/video/console/sticore.c.
2590 See comment in drivers/video/console/sticore.c.
2593 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2595 sunrpc.min_resvport=
2596 sunrpc.max_resvport=
2598 SunRPC servers often require that client requests
2599 originate from a privileged port (i.e. a port in the
2600 range 0 < portnr < 1024).
2601 An administrator who wishes to reserve some of these
2602 ports for other uses may adjust the range that the
2603 kernel's sunrpc client considers to be privileged
2604 using these two parameters to set the minimum and
2605 maximum port values.
2609 Control how the NFS server code allocates CPUs to
2610 service thread pools. Depending on how many NICs
2611 you have and where their interrupts are bound, this
2612 option will affect which CPUs will do NFS serving.
2613 Note: this parameter cannot be changed while the
2614 NFS server is running.
2616 auto the server chooses an appropriate mode
2617 automatically using heuristics
2618 global a single global pool contains all CPUs
2619 percpu one pool for each CPU
2620 pernode one pool for each NUMA node (equivalent
2621 to global on non-NUMA machines)
2623 sunrpc.tcp_slot_table_entries=
2624 sunrpc.udp_slot_table_entries=
2626 Sets the upper limit on the number of simultaneous
2627 RPC calls that can be sent from the client to a
2628 server. Increasing these values may allow you to
2629 improve throughput, but will also increase the
2630 amount of memory reserved for use by the client.
2633 [KNL] Enable accounting of swap in memory resource
2634 controller if no parameter or 1 is given or disable
2635 it if 0 is given (See Documentation/cgroups/memory.txt)
2637 swiotlb= [IA-64] Number of I/O TLB slabs
2641 sysfs.deprecated=0|1 [KNL]
2642 Enable/disable old style sysfs layout for old udev
2643 on older distributions. When this option is enabled
2644 very new udev will not work anymore. When this option
2645 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2646 in older udev will not work anymore.
2647 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2648 the kernel configuration.
2650 sysrq_always_enabled
2652 Ignore sysrq setting - this boot parameter will
2653 neutralize any effect of /proc/sys/kernel/sysrq.
2654 Useful for debugging.
2658 test_suspend= [SUSPEND]
2659 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2660 standby suspend) as the system sleep state to briefly
2661 enter during system startup. The system is woken from
2662 this state using a wakeup-capable RTC alarm.
2664 thash_entries= [KNL,NET]
2665 Set number of hash buckets for TCP connection
2667 thermal.act= [HW,ACPI]
2668 -1: disable all active trip points in all thermal zones
2669 <degrees C>: override all lowest active trip points
2671 thermal.crt= [HW,ACPI]
2672 -1: disable all critical trip points in all thermal zones
2673 <degrees C>: override all critical trip points
2675 thermal.nocrt= [HW,ACPI]
2676 Set to disable actions on ACPI thermal zone
2677 critical and hot trip points.
2679 thermal.off= [HW,ACPI]
2680 1: disable ACPI thermal control
2682 thermal.psv= [HW,ACPI]
2683 -1: disable all passive trip points
2684 <degrees C>: override all passive trip points to this
2687 thermal.tzp= [HW,ACPI]
2688 Specify global default ACPI thermal zone polling rate
2689 <deci-seconds>: poll all this frequency
2690 0: no polling (default)
2693 Force threading of all interrupt handlers except those
2694 marked explicitly IRQF_NO_THREAD.
2698 Specify if the kernel should make use of the cpu
2699 topology information if the hardware supports this.
2700 The scheduler will make use of this information and
2701 e.g. base its process migration decisions on it.
2706 tpm_suspend_pcr=[HW,TPM]
2707 Format: integer pcr id
2708 Specify that at suspend time, the tpm driver
2709 should extend the specified pcr with zeros,
2710 as a workaround for some chips which fail to
2711 flush the last written pcr on TPM_SaveState.
2712 This will guarantee that all the other pcrs
2715 trace_buf_size=nn[KMG]
2716 [FTRACE] will set tracing buffer size.
2718 trace_event=[event-list]
2719 [FTRACE] Set and start specified trace events in order
2720 to facilitate early boot debugging.
2721 See also Documentation/trace/events.txt
2723 transparent_hugepage=
2725 Format: [always|madvise|never]
2726 Can be used to control the default behavior of the system
2727 with respect to transparent hugepages.
2728 See Documentation/vm/transhuge.txt for more details.
2730 tsc= Disable clocksource stability checks for TSC.
2732 [x86] reliable: mark tsc clocksource as reliable, this
2733 disables clocksource verification at runtime, as well
2734 as the stability checks done at bootup. Used to enable
2735 high-resolution timer mode on older hardware, and in
2736 virtualized environment.
2737 [x86] noirqtime: Do not use TSC to do irq accounting.
2738 Used to run time disable IRQ_TIME_ACCOUNTING on any
2739 platforms where RDTSC is slow and this accounting
2742 turbografx.map[2|3]= [HW,JOY]
2743 TurboGraFX parallel port interface
2745 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2746 See also Documentation/input/joystick-parport.txt
2748 udbg-immortal [PPC] When debugging early kernel crashes that
2749 happen after console_init() and before a proper
2750 console driver takes over, this boot options might
2751 help "seeing" what's going on.
2753 uhash_entries= [KNL,NET]
2754 Set number of hash buckets for UDP/UDP-Lite connections
2757 [USB] Ignore overcurrent events (default N).
2758 Some badly-designed motherboards generate lots of
2759 bogus events, for ports that aren't wired to
2760 anything. Set this parameter to avoid log spamming.
2761 Note that genuine overcurrent events won't be
2765 [X86] Cause panic on unknown NMI.
2767 unsupported Allow loading of unsupported kernel modules:
2768 0 = only allow supported modules,
2769 1 = warn when loading unsupported modules,
2772 CONFIG_ENTERPRISE_SUPPORT must be enabled for this
2775 usbcore.authorized_default=
2776 [USB] Default USB device authorization:
2777 (default -1 = authorized except for wireless USB,
2778 0 = not authorized, 1 = authorized)
2780 usbcore.autosuspend=
2781 [USB] The autosuspend time delay (in seconds) used
2782 for newly-detected USB devices (default 2). This
2783 is the time required before an idle device will be
2784 autosuspended. Devices for which the delay is set
2785 to a negative value won't be autosuspended at all.
2787 usbcore.usbfs_snoop=
2788 [USB] Set to log all usbfs traffic (default 0 = off).
2790 usbcore.blinkenlights=
2791 [USB] Set to cycle leds on hubs (default 0 = off).
2793 usbcore.old_scheme_first=
2794 [USB] Start with the old device initialization
2795 scheme (default 0 = off).
2797 usbcore.usbfs_memory_mb=
2798 [USB] Memory limit (in MB) for buffers allocated by
2799 usbfs (default = 16, 0 = max = 2047).
2801 usbcore.use_both_schemes=
2802 [USB] Try the other device initialization scheme
2803 if the first one fails (default 1 = enabled).
2805 usbcore.initial_descriptor_timeout=
2806 [USB] Specifies timeout for the initial 64-byte
2807 USB_REQ_GET_DESCRIPTOR request in milliseconds
2808 (default 5000 = 5.0 seconds).
2811 [USBHID] The interval which mice are to be polled at.
2813 usb-storage.delay_use=
2814 [UMS] The delay in seconds before a new device is
2815 scanned for Logical Units (default 5).
2818 [UMS] A list of quirks entries to supplement or
2819 override the built-in unusual_devs list. List
2820 entries are separated by commas. Each entry has
2821 the form VID:PID:Flags where VID and PID are Vendor
2822 and Product ID values (4-digit hex numbers) and
2823 Flags is a set of characters, each corresponding
2824 to a common usb-storage quirk flag as follows:
2825 a = SANE_SENSE (collect more than 18 bytes
2827 b = BAD_SENSE (don't collect more than 18
2828 bytes of sense data);
2829 c = FIX_CAPACITY (decrease the reported
2830 device capacity by one sector);
2831 d = NO_READ_DISC_INFO (don't use
2832 READ_DISC_INFO command);
2833 e = NO_READ_CAPACITY_16 (don't use
2834 READ_CAPACITY_16 command);
2835 h = CAPACITY_HEURISTICS (decrease the
2836 reported device capacity by one
2837 sector if the number is odd);
2838 i = IGNORE_DEVICE (don't bind to this
2840 l = NOT_LOCKABLE (don't try to lock and
2841 unlock ejectable media);
2842 m = MAX_SECTORS_64 (don't transfer more
2843 than 64 sectors = 32 KB at a time);
2844 n = INITIAL_READ10 (force a retry of the
2845 initial READ(10) command);
2846 o = CAPACITY_OK (accept the capacity
2847 reported by the device);
2848 r = IGNORE_RESIDUE (the device reports
2849 bogus residue values);
2850 s = SINGLE_LUN (the device has only one
2852 w = NO_WP_DETECT (don't test whether the
2853 medium is write-protected).
2854 Example: quirks=0419:aaf5:rl,0421:0433:rc
2856 user_debug= [KNL,ARM]
2858 See arch/arm/Kconfig.debug help text.
2859 1 - undefined instruction events
2861 4 - invalid data aborts
2864 Example: user_debug=31
2867 [X86] Flags controlling user PTE allocations.
2869 nohigh = do not allocate PTE pages in
2870 HIGHMEM regardless of setting
2874 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2875 vdso=1: enable VDSO (default)
2876 vdso=0: disable VDSO mapping
2879 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2880 vdso32=1: enable 32-bit VDSO (default)
2881 vdso32=0: disable 32-bit VDSO mapping
2884 vector=percpu: enable percpu vector domain
2886 video= [FB] Frame buffer configuration
2887 See Documentation/fb/modedb.txt.
2889 vga= [BOOT,X86-32] Select a particular video mode
2890 See Documentation/x86/boot.txt and
2891 Documentation/svga.txt.
2892 Use vga=ask for menu.
2893 This is actually a boot loader parameter; the value is
2894 passed to the kernel using a special protocol.
2896 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2897 size of <nn>. This can be used to increase the
2898 minimum size (128MB on x86). It can also be used to
2899 decrease the size and leave more room for directly
2902 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2905 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2908 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2912 Controls the behavior of vsyscalls (i.e. calls to
2913 fixed addresses of 0xffffffffff600x00 from legacy
2914 code). Most statically-linked binaries and older
2915 versions of glibc use these calls. Because these
2916 functions are at fixed addresses, they make nice
2917 targets for exploits that can control RIP.
2919 emulate [default] Vsyscalls turn into traps and are
2920 emulated reasonably safely.
2922 native Vsyscalls are native syscall instructions.
2923 This is a little bit faster than trapping
2924 and makes a few dynamic recompilers work
2925 better than they would in emulation mode.
2926 It also makes exploits much easier to write.
2928 none Vsyscalls don't work at all. This makes
2929 them quite hard to use for exploits but
2930 might break your system.
2932 vt.cur_default= [VT] Default cursor shape.
2933 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2934 the parameters of the <Esc>[?A;B;Cc escape sequence;
2935 see VGA-softcursor.txt. Default: 2 = underline.
2937 vt.default_blu= [VT]
2938 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2939 Change the default blue palette of the console.
2940 This is a 16-member array composed of values
2943 vt.default_grn= [VT]
2944 Format: <green0>,<green1>,<green2>,...,<green15>
2945 Change the default green palette of the console.
2946 This is a 16-member array composed of values
2949 vt.default_red= [VT]
2950 Format: <red0>,<red1>,<red2>,...,<red15>
2951 Change the default red palette of the console.
2952 This is a 16-member array composed of values
2958 Set system-wide default UTF-8 mode for all tty's.
2959 Default is 1, i.e. UTF-8 mode is enabled for all
2960 newly opened terminals.
2962 vt.global_cursor_default=
2965 Set system-wide default for whether a cursor
2966 is shown on new VTs. Default is -1,
2967 i.e. cursors will be created by default unless
2968 overridden by individual drivers. 0 will hide
2969 cursors, 1 will display them.
2971 watchdog timers [HW,WDT] For information on watchdog timers,
2972 see Documentation/watchdog/watchdog-parameters.txt
2973 or other driver-specific files in the
2974 Documentation/watchdog/ directory.
2976 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2977 default x2apic cluster mode on platforms
2980 x86_mrst_timer= [X86-32,APBT]
2981 Choose timer option for x86 Moorestown MID platform.
2982 Two valid options are apbt timer only and lapic timer
2983 plus one apbt timer for broadcast timer.
2984 x86_mrst_timer=apbt_only | lapic_and_apbt
2986 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2987 xd_geo= See header of drivers/block/xd.c.
2989 xen_emul_unplug= [HW,X86,XEN]
2990 Unplug Xen emulated devices
2991 Format: [unplug0,][unplug1]
2992 ide-disks -- unplug primary master IDE devices
2993 aux-ide-disks -- unplug non-primary-master IDE devices
2994 nics -- unplug network devices
2995 all -- unplug all emulated devices (NICs and IDE disks)
2996 unnecessary -- unplugging emulated devices is
2997 unnecessary even if the host did not respond to
2999 never -- do not unplug even if version check succeeds
3001 xirc2ps_cs= [NET,PCMCIA]
3003 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3005 ______________________________________________________________________
3009 Add more DRM drivers.
projects / linux-flexiantxendom0-3.2.10.git / blob