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 DM Device mapper support is enabled.
48 DRM Direct Rendering Management support is enabled.
49 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
50 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
51 EFI EFI Partitioning (GPT) is enabled
52 EIDE EIDE/ATAPI support is enabled.
53 EVM Extended Verification Module
54 FB The frame buffer device is enabled.
55 FTRACE Function tracing enabled.
56 GCOV GCOV profiling is enabled.
57 HW Appropriate hardware is enabled.
58 IA-64 IA-64 architecture is enabled.
59 IMA Integrity measurement architecture is enabled.
60 IOSCHED More than one I/O scheduler is enabled.
61 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
62 IPV6 IPv6 support is enabled.
63 ISAPNP ISA PnP code is enabled.
64 ISDN Appropriate ISDN support is enabled.
65 JOY Appropriate joystick support is enabled.
66 KGDB Kernel debugger support is enabled.
67 KVM Kernel Virtual Machine support is enabled.
68 LIBATA Libata driver is enabled
69 LP Printer support is enabled.
70 LOOP Loopback device support is enabled.
71 M68k M68k architecture is enabled.
72 These options have more detailed description inside of
73 Documentation/m68k/kernel-options.txt.
74 MCA MCA bus support is enabled.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VGA The VGA console has been enabled.
115 VT Virtual terminal support is enabled.
116 WDT Watchdog support is enabled.
117 XT IBM PC/XT MFM hard disk support is enabled.
118 X86-32 X86-32, aka i386 architecture is enabled.
119 X86-64 X86-64 architecture is enabled.
120 More X86-64 boot options can be found in
121 Documentation/x86/x86_64/boot-options.txt .
122 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
123 XEN Xen support is enabled
125 In addition, the following text indicates that the option:
127 BUGS= Relates to possible processor bugs on the said processor.
128 KNL Is a kernel start-up parameter.
129 BOOT Is a boot loader parameter.
131 Parameters denoted with BOOT are actually interpreted by the boot
132 loader, and have no meaning to the kernel directly.
133 Do not modify the syntax of boot loader parameters without extreme
134 need or coordination with <Documentation/x86/boot.txt>.
136 There are also arch-specific kernel-parameters not documented here.
137 See for example <Documentation/x86/x86_64/boot-options.txt>.
139 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
140 a trailing = on the name of any parameter states that that parameter will
141 be entered as an environment variable, whereas its absence indicates that
142 it will appear as a kernel argument readable via /proc/cmdline by programs
143 running once the system is up.
145 The number of kernel parameters is not limited, but the length of the
146 complete command line (parameters including spaces etc.) is limited to
147 a fixed number of characters. This limit depends on the architecture
148 and is between 256 and 4096 characters. It is defined in the file
149 ./include/asm/setup.h as COMMAND_LINE_SIZE.
151 Finally, the [KMG] suffix is commonly described after a number of kernel
152 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
153 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
154 bytes respectively. Such letter suffixes can also be entirely omitted.
158 Advanced Configuration and Power Interface
159 Format: { force | off | strict | noirq | rsdt }
160 force -- enable ACPI if default was off
161 off -- disable ACPI if default was on
162 noirq -- do not use ACPI for IRQ routing
163 strict -- Be less tolerant of platforms that are not
164 strictly ACPI specification compliant.
165 rsdt -- prefer RSDT over (default) XSDT
166 copy_dsdt -- copy DSDT to memory
168 See also Documentation/power/runtime_pm.txt, pci=noacpi
170 acpi_rsdp= [ACPI,EFI,KEXEC]
171 Pass the RSDP address to the kernel, mostly used
172 on machines running EFI runtime service to boot the
173 second kernel for kdump.
175 acpi_apic_instance= [ACPI, IOAPIC]
177 2: use 2nd APIC table, if available
178 1,0: use 1st APIC table
181 acpi_backlight= [HW,ACPI]
182 acpi_backlight=vendor
184 If set to vendor, prefer vendor specific driver
185 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
186 of the ACPI video.ko driver.
188 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
189 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
191 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
192 debug output. Bits in debug_layer correspond to a
193 _COMPONENT in an ACPI source file, e.g.,
194 #define _COMPONENT ACPI_PCI_COMPONENT
195 Bits in debug_level correspond to a level in
196 ACPI_DEBUG_PRINT statements, e.g.,
197 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
198 The debug_level mask defaults to "info". See
199 Documentation/acpi/debug.txt for more information about
200 debug layers and levels.
202 Enable processor driver info messages:
203 acpi.debug_layer=0x20000000
204 Enable PCI/PCI interrupt routing info messages:
205 acpi.debug_layer=0x400000
206 Enable AML "Debug" output, i.e., stores to the Debug
207 object while interpreting AML:
208 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
209 Enable all messages related to ACPI hardware:
210 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212 Some values produce so much output that the system is
213 unusable. The "log_buf_len" parameter may be useful
214 if you need to capture more output.
216 acpi_irq_balance [HW,ACPI]
217 ACPI will balance active IRQs
220 acpi_irq_nobalance [HW,ACPI]
221 ACPI will not move active IRQs (default)
224 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
225 Format: <irq>,<irq>...
227 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 Format: <irq>,<irq>...
231 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
234 Format: To spoof as Windows 98: ="Microsoft Windows"
236 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
237 acpi_osi="string1" # add string1 -- only one string
238 acpi_osi="!string2" # remove built-in string2
239 acpi_osi= # disable all strings
242 Override the pmtimer bug detection: force the kernel
243 to assume that this machine's pmtimer latches its value
244 and always returns good values.
246 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
247 Format: { level | edge | high | low }
249 acpi_serialize [HW,ACPI] force serialization of AML methods
251 acpi_skip_timer_override [HW,ACPI]
252 Recognize and ignore IRQ0/pin2 Interrupt Override.
253 For broken nForce2 BIOS resulting in XT-PIC timer.
255 acpi_sleep= [HW,ACPI] Sleep options
256 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
257 old_ordering, nonvs, sci_force_enable }
258 See Documentation/power/video.txt for information on
260 s3_beep is for debugging; it makes the PC's speaker beep
261 as soon as the kernel's real-mode entry point is called.
262 s4_nohwsig prevents ACPI hardware signature from being
263 used during resume from hibernation.
264 old_ordering causes the ACPI 1.0 ordering of the _PTS
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
267 of _PTS is used by default).
268 nonvs prevents the kernel from saving/restoring the
269 ACPI NVS memory during suspend/hibernation and resume.
270 sci_force_enable causes the kernel to set SCI_EN directly
271 on resume from S1/S3 (which is against the ACPI spec,
272 but some broken systems don't work without it).
274 acpi_use_timer_override [HW,ACPI]
275 Use timer override. For some broken Nvidia NF5 boards
276 that require a timer override, but don't have HPET
278 acpi_enforce_resources= [ACPI]
279 { strict | lax | no }
280 Check for resource conflicts between native drivers
281 and ACPI OperationRegions (SystemIO and SystemMemory
282 only). IO ports and memory declared in ACPI might be
283 used by the ACPI subsystem in arbitrary AML code and
284 can interfere with legacy drivers.
285 strict (default): access to resources claimed by ACPI
286 is denied; legacy drivers trying to access reserved
287 resources will fail to bind to device using them.
288 lax: access to resources claimed by ACPI is allowed;
289 legacy drivers trying to access reserved resources
290 will bind successfully but a warning message is logged.
291 no: ACPI OperationRegions are not marked as reserved,
292 no further checks are performed.
294 add_efi_memmap [EFI; X86] Include EFI memory map in
295 kernel's map of available physical RAM.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/sound/alsa/alsa-parameters.txt
307 Allow the default userspace alignment fault handler
308 behaviour to be specified. Bit 0 enables warnings,
309 bit 1 enables fixups, and bit 2 sends a segfault.
311 align_va_addr= [X86-64]
312 Align virtual addresses by clearing slice [14:12] when
313 allocating a VMA at process creation time. This option
314 gives you up to 3% performance improvement on AMD F15h
315 machines (where it is enabled by default) for a
316 CPU-intensive style benchmark, and it can vary highly in
317 a microbenchmark depending on workload and compiler.
319 32: only for 32-bit processes
320 64: only for 64-bit processes
321 on: enable for both 32- and 64-bit processes
322 off: disable for both 32- and 64-bit processes
324 amd_iommu= [HW,X86-64]
325 Pass parameters to the AMD IOMMU driver in the system.
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
331 off - do not initialize any AMD IOMMU found in
333 force_isolation - Force device isolation for all
334 devices. The IOMMU driver is not
335 allowed anymore to lift isolation
336 requirements as needed. This option
337 does not override iommu=pt
339 amijoy.map= [HW,JOY] Amiga joystick support
340 Map of devices attached to JOY0DAT and JOY1DAT
342 See also Documentation/input/joystick.txt
344 analog.map= [HW,JOY] Analog joystick and gamepad support
345 Specifies type or capabilities of an analog joystick
346 connected to one of 16 gameports
347 Format: <type1>,<type2>,..<type16>
350 Power management functions (SPARCstation-4/5 + deriv.)
352 Disable APC CPU standby support. SPARCstation-Fox does
353 not play well with APC CPU idle - disable it if you have
354 APC and your system crashes randomly.
356 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
357 Change the output verbosity whilst booting
358 Format: { quiet (default) | verbose | debug }
359 Change the amount of debugging information output
360 when initialising the APIC and IO-APIC components.
363 See Documentation/networking/ipv6.txt.
365 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
366 Limit apic dumping. The parameter defines the maximal
367 number of local apics being dumped. Also it is possible
368 to set it to "all" by meaning -- no limit here.
369 Format: { 1 (default) | 2 | ... | all }.
370 The parameter valid if only apic=debug or
371 apic=verbose is specified.
372 Example: apic=debug show_lapic=all
374 apm= [APM] Advanced Power Management
375 See header of arch/x86/kernel/apm_32.c.
377 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
378 Format: <io>,<irq>,<nodeID>
382 atarimouse= [HW,MOUSE] Atari Mouse
384 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
385 EzKey and similar keyboards
387 atkbd.reset= [HW] Reset keyboard during initialization
389 atkbd.set= [HW] Select keyboard code set
390 Format: <int> (2 = AT (default), 3 = PS/2)
392 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
395 atkbd.softraw= [HW] Choose between synthetic and real raw mode
396 Format: <bool> (0 = real, 1 = synthetic (default))
398 atkbd.softrepeat= [HW]
399 Use software keyboard repeat
403 baycom_epp= [HW,AX25]
406 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
408 See header of drivers/net/hamradio/baycom_par.c.
410 baycom_ser_fdx= [HW,AX25]
411 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
412 Format: <io>,<irq>,<mode>[,<baud>]
413 See header of drivers/net/hamradio/baycom_ser_fdx.c.
415 baycom_ser_hdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
417 Format: <io>,<irq>,<mode>
418 See header of drivers/net/hamradio/baycom_ser_hdx.c.
420 boot_delay= Milliseconds to delay each printk during boot.
421 Values larger than 10 seconds (10000) are changed to
425 bootmem_debug [KNL] Enable bootmem allocator debug messages.
427 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
428 bttv.radio= Most important insmod options are available as
430 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
433 bulk_remove=off [PPC] This parameter disables the use of the pSeries
434 firmware feature for flushing multiple hpte entries
437 c101= [NET] Moxa C101 synchronous serial card
439 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
440 Sometimes CPU hardware bugs make them report the cache
441 size incorrectly. The kernel will attempt work arounds
442 to fix known problems, but for some CPUs it is not
443 possible to determine what the correct size should be.
444 This option provides an override for these situations.
447 [SECURITY] Disable capabilities. This would normally
448 be used only if an alternative security model is to be
449 configured. Potentially dangerous and should only be
450 used if you are entirely sure of the consequences.
452 ccw_timeout_log [S390]
453 See Documentation/s390/CommonIO for details.
455 cgroup_disable= [KNL] Disable a particular controller
456 Format: {name of the controller(s) to disable}
457 {Currently supported controllers - "memory"}
459 checkreqprot [SELINUX] Set initial checkreqprot flag value.
460 Format: { "0" | "1" }
461 See security/selinux/Kconfig help text.
462 0 -- check protection applied by kernel (includes
463 any implied execute protection).
464 1 -- check protection requested by application.
465 Default value is set via a kernel config option.
466 Value can be changed at runtime via
467 /selinux/checkreqprot.
470 See Documentation/s390/CommonIO for details.
472 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
474 Forces specified clocksource (if available) to be used
475 when calculating gettimeofday(). If specified
476 clocksource is not available, it defaults to PIT.
477 Format: { pit | tsc | cyclone | pmtmr }
479 clocksource= Override the default clocksource
481 Override the default clocksource and use the clocksource
482 with the name specified.
483 Some clocksource names to choose from, depending on
485 [all] jiffies (this is the base, fallback clocksource)
487 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
488 pxa_timer,timer3,32k_counter,timer0_1
490 [X86-32] pit,hpet,tsc;
491 scx200_hrt on Geode; cyclone on IBM x440
499 clearcpuid=BITNUM [X86]
500 Disable CPUID feature X for the kernel. See
501 arch/x86/include/asm/cpufeature.h for the valid bit
502 numbers. Note the Linux specific bits are not necessarily
503 stable over kernel options, but the vendor specific
505 Also note that user programs calling CPUID directly
506 or using the feature without checking anything
507 will still see it. This just prevents it from
508 being used by the kernel or shown in /proc/cpuinfo.
509 Also note the kernel might malfunction if you disable
512 cmo_free_hint= [PPC] Format: { yes | no }
513 Specify whether pages are marked as being inactive
514 when they are freed. This is used in CMO environments
515 to determine OS memory pressure for page stealing by
519 code_bytes [X86] How many bytes of object code to print
524 com20020= [HW,NET] ARCnet - COM20020 chipset
526 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
528 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
532 ARCnet - COM90xx chipset (memory-mapped buffers)
533 Format: <io>[,<irq>[,<memstart>]]
535 condev= [HW,S390] console device
538 console= [KNL] Output console device and options.
540 tty<n> Use the virtual console device <n>.
544 Use the specified serial port. The options are of
545 the form "bbbbpnf", where "bbbb" is the baud rate,
546 "p" is parity ("n", "o", or "e"), "n" is number of
547 bits, and "f" is flow control ("r" for RTS or
548 omit it). Default is "9600n8".
550 See Documentation/serial-console.txt for more
552 Documentation/networking/netconsole.txt for an
555 uart[8250],io,<addr>[,options]
556 uart[8250],mmio,<addr>[,options]
557 Start an early, polled-mode console on the 8250/16550
558 UART at the specified I/O port or MMIO address,
559 switching to the matching ttyS device later. The
560 options are the same as for ttyS, above.
562 If the device connected to the port is not a TTY but a braille
563 device, prepend "brl," before the device type, for instance
565 For now, only VisioBraille is supported.
567 consoleblank= [KNL] The console blank (screen saver) timeout in
568 seconds. Defaults to 10*60 = 10mins. A value of 0
569 disables the blank timer.
572 [KNL] Change the default value for
573 /proc/<pid>/coredump_filter.
574 See also Documentation/filesystems/proc.txt.
576 cpuidle.off=1 [CPU_IDLE]
577 disable the cpuidle sub-system
579 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
581 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
583 crashkernel=size[KMG][@offset[KMG]]
584 [KNL] Using kexec, Linux can switch to a 'crash kernel'
585 upon panic. This parameter reserves the physical
586 memory region [offset, offset + size] for that kernel
587 image. If '@offset' is omitted, then a suitable offset
588 is selected automatically. Check
589 Documentation/kdump/kdump.txt for further details.
591 crashkernel=range1:size1[,range2:size2,...][@offset]
592 [KNL] Same as above, but depends on the memory
593 in the running system. The syntax of range is
594 start-[end] where start and end are both
595 a memory unit (amount[KMG]). See also
596 Documentation/kdump/kdump.txt for an example.
598 cros_shared_mem=[ARM]
599 Format: <hex integer>
600 Base address of the ChromeOS shared memory window,
601 aligned at megabyte boundary, window size is fixed at
607 cs89x0_media= [HW,NET]
608 Format: { rj45 | aui | bnc }
611 See header of drivers/s390/block/dasd_devmap.c.
613 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
614 (one device per port)
615 Format: <port#>,<type>
616 See also Documentation/input/joystick-parport.txt
618 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
619 time. See Documentation/dynamic-debug-howto.txt for
622 debug [KNL] Enable kernel debugging (events log level).
625 [KNL] verbose self-tests
627 Print debugging info while doing the locking API
629 We default to 0 (no extra messages), setting it to
630 1 will print _a lot_ more information - normally
631 only useful to kernel developers.
633 debug_objects [KNL] Enable object debugging
636 [KNL] Disable object debugging
638 debug_guardpage_minorder=
639 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
640 parameter allows control of the order of pages that will
641 be intentionally kept free (and hence protected) by the
642 buddy allocator. Bigger value increase the probability
643 of catching random memory corruption, but reduce the
644 amount of memory for normal system use. The maximum
645 possible value is MAX_ORDER/2. Setting this parameter
646 to 1 or 2 should be enough to identify most random
647 memory corruption problems caused by bugs in kernel or
648 driver code when a CPU writes to (or reads from) a
649 random memory location. Note that there exists a class
650 of memory corruptions problems caused by buggy H/W or
651 F/W or by drivers badly programing DMA (basically when
652 memory is written at bus level and the CPU MMU is
653 bypassed) which are not detectable by
654 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
655 tracking down these problems.
657 debugpat [X86] Enable PAT debugging
659 decnet.addr= [HW,NET]
660 Format: <area>[,<node>]
661 See also Documentation/networking/decnet.txt.
664 [same as hugepagesz=] The size of the default
665 HugeTLB page size. This is the size represented by
666 the legacy /proc/ hugepages APIs, used for SHM, and
667 default size when mounting hugetlbfs filesystems.
668 Defaults to the default architecture's huge page size
672 Set number of hash buckets for dentry cache.
675 IO parameters + enable/disable command.
677 digiepca= [HW,SERIAL]
678 See drivers/char/README.epca and
679 Documentation/serial/digiepca.txt.
682 See Documentation/networking/ipv6.txt.
684 disable_ddw [PPC/PSERIES]
685 Disable Dynamic DMA Window support. Use this if
686 to workaround buggy firmware.
689 See Documentation/networking/ipv6.txt.
691 disable_mtrr_cleanup [X86]
692 The kernel tries to adjust MTRR layout from continuous
693 to discrete, to make X server driver able to add WB
694 entry later. This parameter disables that.
696 disable_mtrr_trim [X86, Intel and AMD only]
697 By default the kernel will trim any uncacheable
698 memory out of your available memory pool based on
699 MTRR settings. This parameter disables that behavior,
700 possibly causing your machine to run very slowly.
702 disable_timer_pin_1 [X86]
703 Disable PIN 1 of APIC timer
704 Can be useful to work around chipset bugs.
706 dm= [DM] Allows early creation of a device-mapper device.
707 See Documentation/device-mapper/boot.txt.
709 dmasound= [HW,OSS] Sound subsystem buffers
711 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
712 this option disables the debugging code at boot.
714 dma_debug_entries=<number>
715 This option allows to tune the number of preallocated
716 entries for DMA-API debugging code. One entry is
717 required per DMA-API allocation. Use this if the
718 DMA-API debugging code disables itself because the
719 architectural default is too low.
721 dma_debug_driver=<driver_name>
722 With this option the DMA-API debugging driver
723 filter feature can be enabled at boot time. Just
724 pass the driver to filter for as the parameter.
725 The filter can be disabled or changed to another
726 driver later using sysfs.
728 drm_kms_helper.edid_firmware=[<connector>:]<file>
729 Broken monitors, graphic adapters and KVMs may
730 send no or incorrect EDID data sets. This parameter
731 allows to specify an EDID data set in the
732 /lib/firmware directory that is used instead.
733 Generic built-in EDID data sets are used, if one of
734 edid/1024x768.bin, edid/1280x1024.bin,
735 edid/1680x1050.bin, or edid/1920x1080.bin is given
736 and no file with the same name exists. Details and
737 instructions how to build your own EDID data are
738 available in Documentation/EDID/HOWTO.txt. An EDID
739 data set will only be used for a particular connector,
740 if its name and a colon are prepended to the EDID
745 earlycon= [KNL] Output early console device and options.
746 uart[8250],io,<addr>[,options]
747 uart[8250],mmio,<addr>[,options]
748 uart[8250],mmio32,<addr>[,options]
749 Start an early, polled-mode console on the 8250/16550
750 UART at the specified I/O port or MMIO address.
751 MMIO inter-register address stride is either 8-bit
752 (mmio) or 32-bit (mmio32).
753 The options are the same as for ttyS, above.
755 earlyprintk= [X86,SH,BLACKFIN]
757 earlyprintk=serial[,ttySn[,baudrate]]
758 earlyprintk=ttySn[,baudrate]
759 earlyprintk=dbgp[debugController#]
761 Append ",keep" to not disable it when the real console
764 Only vga or serial or usb debug port at a time.
766 Currently only ttyS0 and ttyS1 are supported.
768 Interaction with the standard serial driver is not
771 The VGA output is eventually overwritten by the real
774 ekgdboc= [X86,KGDB] Allow early kernel console debugging
777 This is designed to be used in conjunction with
778 the boot argument: earlyprintk=vga
781 Format: {"off" | "on" | "skip[mbr]"}
783 eisa_irq_edge= [PARISC,HW]
784 See header of drivers/parisc/eisa.c.
787 See comment before function elanfreq_setup() in
788 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
791 Format: {"cfq" | "deadline" | "noop"}
792 See Documentation/block/cfq-iosched.txt and
793 Documentation/block/deadline-iosched.txt for details.
795 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
796 Specifies physical address of start of kernel core
797 image elf header and optionally the size. Generally
798 kexec loader will pass this option to capture kernel.
799 See Documentation/kdump/kdump.txt for details.
801 enable_mtrr_cleanup [X86]
802 The kernel tries to adjust MTRR layout from continuous
803 to discrete, to make X server driver able to add WB
804 entry later. This parameter enables that.
806 enable_timer_pin_1 [X86]
807 Enable PIN 1 of APIC timer
808 Can be useful to work around chipset bugs
809 (in particular on some ATI chipsets).
810 The kernel tries to set a reasonable default.
812 enforcing [SELINUX] Set initial enforcing status.
814 See security/selinux/Kconfig help text.
815 0 -- permissive (log only, no denials).
816 1 -- enforcing (deny and log).
818 Value can be changed at runtime via /selinux/enforce.
821 Disable Error Record Serialization Table (ERST)
824 ether= [HW,NET] Ethernet cards parameters
825 This option is obsoleted by the "netdev=" option, which
826 has equivalent usage. See its documentation for details.
830 Permit 'security.evm' to be updated regardless of
831 current integrity status.
835 fail_make_request=[KNL]
836 General fault injection mechanism.
837 Format: <interval>,<probability>,<space>,<times>
838 See also Documentation/fault-injection/.
841 See Documentation/blockdev/floppy.txt.
843 force_pal_cache_flush
844 [IA-64] Avoid check_sal_cache_flush which may hang on
845 buggy SAL_CACHE_FLUSH implementations. Using this
846 parameter will force ia64_sal_cache_flush to call
847 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
850 [FTRACE] will set and start the specified tracer
851 as early as possible in order to facilitate early
854 ftrace_dump_on_oops[=orig_cpu]
855 [FTRACE] will dump the trace buffers on oops.
856 If no parameter is passed, ftrace will dump
857 buffers of all CPUs, but if you pass orig_cpu, it will
858 dump only the buffer of the CPU that triggered the
861 ftrace_filter=[function-list]
862 [FTRACE] Limit the functions traced by the function
863 tracer at boot up. function-list is a comma separated
864 list of functions. This list can be changed at run
865 time by the set_ftrace_filter file in the debugfs
868 ftrace_notrace=[function-list]
869 [FTRACE] Do not trace the functions specified in
870 function-list. This list can be changed at run time
871 by the set_ftrace_notrace file in the debugfs
874 ftrace_graph_filter=[function-list]
875 [FTRACE] Limit the top level callers functions traced
876 by the function graph tracer at boot up.
877 function-list is a comma separated list of functions
878 that can be changed at run time by the
879 set_graph_function file in the debugfs tracing directory.
882 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
883 support via parallel port (up to 5 devices per port)
884 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
885 See also Documentation/input/joystick-parport.txt
889 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
893 gcov_persist= [GCOV] When non-zero (default), profiling data for
894 kernel modules is saved and remains accessible via
895 debugfs, even when the module is unloaded/reloaded.
896 When zero, profiling data is discarded and associated
897 debugfs files are removed at module unload time.
899 gpt [EFI] Forces disk with valid GPT signature but
900 invalid Protective MBR to be treated as GPT.
902 hashdist= [KNL,NUMA] Large hashes allocated during boot
903 are distributed across NUMA nodes. Defaults on
904 for 64-bit NUMA, off otherwise.
905 Format: 0 | 1 (for off | on)
907 hcl= [IA-64] SGI's Hardware Graph compatibility layer
909 hd= [EIDE] (E)IDE hard drive subsystem geometry
910 Format: <cyl>,<head>,<sect>
913 Disable Hardware Error Source Table (HEST) support;
914 corresponding firmware-first mode error processing
915 logic will be disabled.
917 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
918 size of <nn>. This works even on boxes that have no
919 highmem otherwise. This also works to reduce highmem
920 size on bigger boxes.
922 highres= [KNL] Enable/disable high resolution timer mode.
923 Valid parameters: "on", "off"
927 See Documentation/isdn/README.HiSax.
931 hpet= [X86-32,HPET] option to control HPET usage
932 Format: { enable (default) | disable | force |
934 disable: disable HPET and use PIT instead
935 force: allow force enabled of undocumented chips (ICH4,
937 verbose: show contents of HPET registers during setup
939 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
940 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
941 On x86-64 and powerpc, this option can be specified
942 multiple times interleaved with hugepages= to reserve
943 huge pages of different sizes. Valid pages sizes on
944 x86-64 are 2M (when the CPU supports "pse") and 1G
945 (when the CPU supports the "pdpe1gb" cpuinfo flag)
946 Note that 1GB pages can only be allocated at boot time
947 using hugepages= and not freed afterwards.
949 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
950 terminal devices. Valid values: 0..8
951 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
952 If specified, z/VM IUCV HVC accepts connections
953 from listed z/VM user IDs only.
956 Do not unregister boot console at start. This is only
957 useful for debugging when something happens in the window
958 between unregistering the boot console and initializing
961 i2c_bus= [HW] Override the default board specific I2C bus speed
962 or register an additional I2C bus that is not
963 registered from board initialization code.
967 i8042.debug [HW] Toggle i8042 debug mode
968 i8042.direct [HW] Put keyboard port into non-translated mode
969 i8042.dumbkbd [HW] Pretend that controller can only read data from
970 keyboard and cannot control its state
971 (Don't attempt to blink the leds)
972 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
973 i8042.nokbd [HW] Don't check/create keyboard port
974 i8042.noloop [HW] Disable the AUX Loopback command while probing
976 i8042.nomux [HW] Don't check presence of an active multiplexing
978 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
980 i8042.notimeout [HW] Ignore timeout condition signalled by controller
981 i8042.reset [HW] Reset the controller during init and cleanup
982 i8042.unlock [HW] Unlock (ignore) the keylock
986 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
987 indicates that the driver is running on unsupported
989 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
990 does not match list of supported models.
992 [HW] Report power status in /proc/i8k
993 (disabled by default)
994 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
998 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1000 ide-core.nodma= [HW] (E)IDE subsystem
1001 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1002 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1003 .cdrom .chs .ignore_cable are additional options
1004 See Documentation/ide/ide.txt.
1006 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1007 Claim all unknown PCI IDE storage controllers.
1010 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1011 Poll forces a polling idle loop that can slightly
1012 improve the performance of waking up a idle CPU, but
1013 will use a lot of power and make the system run hot.
1015 idle=mwait: On systems which support MONITOR/MWAIT but
1016 the kernel chose to not use it because it doesn't save
1017 as much power as a normal idle loop, use the
1018 MONITOR/MWAIT idle loop anyways. Performance should be
1019 the same as idle=poll.
1020 idle=halt: Halt is forced to be used for CPU idle.
1021 In such case C2/C3 won't be used again.
1022 idle=nomwait: Disable mwait for CPU C-states
1024 ignore_loglevel [KNL]
1025 Ignore loglevel setting - this will print /all/
1026 kernel messages to the console. Useful for debugging.
1027 We also add it as printk module parameter, so users
1028 could change it dynamically, usually by
1029 /sys/module/printk/parameters/ignore_loglevel.
1031 ihash_entries= [KNL]
1032 Set number of hash buckets for inode cache.
1035 Format: { "0" | "1" }
1036 0 -- integrity auditing messages. (Default)
1037 1 -- enable informational integrity auditing messages.
1040 Format: { "sha1" | "md5" }
1044 Load a policy which meets the needs of the Trusted
1045 Computing Base. This means IMA will measure all
1046 programs exec'd, files mmap'd for exec, and all files
1047 opened for read by uid=0.
1051 Run specified binary instead of /sbin/init as init
1054 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1055 for working out where the kernel is dying during
1058 initrd= [BOOT] Specify the location of the initial ramdisk
1060 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1063 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1065 Enable intel iommu driver.
1067 Disable intel iommu driver.
1068 igfx_off [Default Off]
1069 By default, gfx is mapped as normal device. If a gfx
1070 device has a dedicated DMAR unit, the DMAR unit is
1071 bypassed by not enabling DMAR with this option. In
1072 this case, gfx device will use physical address for
1075 With this option iommu will not optimize to look
1076 for io virtual address below 32-bit forcing dual
1077 address cycle on pci bus for cards supporting greater
1078 than 32-bit addressing. The default is to look
1079 for translation below 32-bit and if not available
1080 then look in the higher range.
1081 strict [Default Off]
1082 With this option on every unmap_single operation will
1083 result in a hardware IOTLB flush operation as opposed
1084 to batching them for performance.
1085 sp_off [Default Off]
1086 By default, super page will be supported if Intel IOMMU
1087 has the capability. With this option, super page will
1090 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1091 0 disables intel_idle and fall back on acpi_idle.
1092 1 to 6 specify maximum depth of C-state.
1094 intremap= [X86-64, Intel-IOMMU]
1095 on enable Interrupt Remapping (default)
1096 off disable Interrupt Remapping
1097 nosid disable Source ID checking
1099 BIOS x2APIC opt-out request will be ignored
1101 iomem= Disable strict checking of access to MMIO memory
1102 strict regions from userspace.
1117 group_mf [x86, IA-64]
1120 io7= [HW] IO7 for Marvel based alpha systems
1121 See comment before marvel_specify_io7 in
1122 arch/alpha/kernel/core_marvel.c.
1124 io_delay= [X86] I/O delay method
1126 Standard port 0x80 based delay
1128 Alternate port 0xed based delay (needed on some systems)
1130 Simple two microseconds delay
1135 See Documentation/filesystems/nfs/nfsroot.txt.
1137 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1138 See comment before ip2_setup() in
1139 drivers/char/ip2/ip2base.c.
1142 When an interrupt is not handled search all handlers
1143 for it. Intended to get systems with badly broken
1147 When an interrupt is not handled search all handlers
1148 for it. Also check all handlers each timer
1149 interrupt. Intended to get systems with badly broken
1153 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1155 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1157 <cpu number>,...,<cpu number>
1159 <cpu number>-<cpu number>
1160 (must be a positive range in ascending order)
1162 <cpu number>,...,<cpu number>-<cpu number>
1164 This option can be used to specify one or more CPUs
1165 to isolate from the general SMP balancing and scheduling
1166 algorithms. You can move a process onto or off an
1167 "isolated" CPU via the CPU affinity syscalls or cpuset.
1168 <cpu number> begins at 0 and the maximum value is
1169 "number of CPUs in system - 1".
1171 This option is the preferred way to isolate CPUs. The
1172 alternative -- manually setting the CPU mask of all
1173 tasks in the system -- can cause problems and
1174 suboptimal load balancer performance.
1178 js= [HW,JOY] Analog joystick
1179 See Documentation/input/joystick.txt.
1183 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1184 specifies the amount of memory usable by the kernel
1185 for non-movable allocations. The requested amount is
1186 spread evenly throughout all nodes in the system. The
1187 remaining memory in each node is used for Movable
1188 pages. In the event, a node is too small to have both
1189 kernelcore and Movable pages, kernelcore pages will
1190 take priority and other nodes will have a larger number
1191 of kernelcore pages. The Movable zone is used for the
1192 allocation of pages that may be reclaimed or moved
1193 by the page migration subsystem. This means that
1194 HugeTLB pages may not be allocated from this zone.
1195 Note that allocations like PTEs-from-HighMem still
1196 use the HighMem zone if it exists, and the Normal
1197 zone if it does not.
1199 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1200 Format: <Controller#>[,poll interval]
1201 The controller # is the number of the ehci usb debug
1202 port as it is probed via PCI. The poll interval is
1203 optional and is the number seconds in between
1204 each poll cycle to the debug port in case you need
1205 the functionality for interrupting the kernel with
1206 gdb or control-c on the dbgp connection. When
1207 not using this parameter you use sysrq-g to break into
1208 the kernel debugger.
1210 kgdboc= [KGDB,HW] kgdb over consoles.
1211 Requires a tty driver that supports console polling,
1212 or a supported polling keyboard driver (non-usb).
1213 Serial only format: <serial_device>[,baud]
1214 keyboard only format: kbd
1215 keyboard and serial format: kbd,<serial_device>[,baud]
1216 Optional Kernel mode setting:
1217 kms, kbd format: kms,kbd
1218 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1220 kgdbwait [KGDB] Stop kernel execution and enter the
1221 kernel debugger at the earliest opportunity.
1223 kmac= [MIPS] korina ethernet MAC address.
1224 Configure the RouterBoard 532 series on-chip
1225 Ethernet adapter MAC address.
1227 kmemleak= [KNL] Boot-time kmemleak enable/disable
1228 Valid arguments: on, off
1231 kstack=N [X86] Print N words from the kernel stack
1234 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1235 Default is 0 (don't ignore, but inject #GP)
1237 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1241 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1242 Default is 1 (enabled)
1244 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1246 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1248 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1249 (virtualized MMU) support on capable Intel chips.
1250 Default is 1 (enabled)
1252 kvm-intel.emulate_invalid_guest_state=
1253 [KVM,Intel] Enable emulation of invalid guest states
1254 Default is 0 (disabled)
1256 kvm-intel.flexpriority=
1257 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1258 Default is 1 (enabled)
1261 [KVM,Intel] Enable VMX nesting (nVMX).
1262 Default is 0 (disabled)
1264 kvm-intel.unrestricted_guest=
1265 [KVM,Intel] Disable unrestricted guest feature
1266 (virtualized real and unpaged mode) on capable
1267 Intel chips. Default is 1 (enabled)
1269 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1270 feature (tagged TLBs) on capable Intel chips.
1271 Default is 1 (enabled)
1277 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1280 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1283 libata.dma= [LIBATA] DMA control
1284 libata.dma=0 Disable all PATA and SATA DMA
1285 libata.dma=1 PATA and SATA Disk DMA only
1286 libata.dma=2 ATAPI (CDROM) DMA only
1287 libata.dma=4 Compact Flash DMA only
1288 Combinations also work, so libata.dma=3 enables DMA
1289 for disks and CDROMs, but not CFs.
1291 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1292 libata.ignore_hpa=0 keep BIOS limits (default)
1293 libata.ignore_hpa=1 ignore limits, using full disk
1295 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1299 libata.force= [LIBATA] Force configurations. The format is comma
1300 separated list of "[ID:]VAL" where ID is
1301 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1302 matching port, link or device. Basically, it matches
1303 the ATA ID string printed on console by libata. If
1304 the whole ID part is omitted, the last PORT and DEVICE
1305 values are used. If ID hasn't been specified yet, the
1306 configuration applies to all ports, links and devices.
1308 If only DEVICE is omitted, the parameter applies to
1309 the port and all links and devices behind it. DEVICE
1310 number of 0 either selects the first device or the
1311 first fan-out link behind PMP device. It does not
1312 select the host link. DEVICE number of 15 selects the
1313 host link and device attached to it.
1315 The VAL specifies the configuration to force. As long
1316 as there's no ambiguity shortcut notation is allowed.
1317 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1318 The following configurations can be forced.
1320 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1321 Any ID with matching PORT is used.
1323 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1325 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1326 udma[/][16,25,33,44,66,100,133] notation is also
1329 * [no]ncq: Turn on or off NCQ.
1331 * nohrst, nosrst, norst: suppress hard, soft
1334 * dump_id: dump IDENTIFY data.
1336 If there are multiple matching configurations changing
1337 the same attribute, the last one is used.
1339 memblock=debug [KNL] Enable memblock debug messages.
1341 load_ramdisk= [RAM] List of ramdisks to load from floppy
1342 See Documentation/blockdev/ramdisk.txt.
1344 lockd.nlm_grace_period=P [NFS] Assign grace period.
1347 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1350 lockd.nlm_timeout=T [NFS] Assign timeout value.
1353 lockd.nlm_udpport=M [NFS] Assign UDP port.
1356 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1359 loglevel= All Kernel Messages with a loglevel smaller than the
1360 console loglevel will be printed to the console. It can
1361 also be changed with klogd or other programs. The
1362 loglevels are defined as follows:
1364 0 (KERN_EMERG) system is unusable
1365 1 (KERN_ALERT) action must be taken immediately
1366 2 (KERN_CRIT) critical conditions
1367 3 (KERN_ERR) error conditions
1368 4 (KERN_WARNING) warning conditions
1369 5 (KERN_NOTICE) normal but significant condition
1370 6 (KERN_INFO) informational
1371 7 (KERN_DEBUG) debug-level messages
1373 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1374 in bytes. n must be a power of two. The default
1375 size is set in the kernel config file.
1377 logo.nologo [FB] Disables display of the built-in Linux logo.
1378 This may be used to provide more screen space for
1379 kernel log messages and is useful when debugging
1380 kernel boot problems.
1382 lp=0 [LP] Specify parallel ports to use, e.g,
1383 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1384 lp=reset first parallel port). 'lp=0' disables the
1385 lp=auto printer driver. 'lp=reset' (which can be
1386 specified in addition to the ports) causes
1387 attached printers to be reset. Using
1388 lp=port1,port2,... specifies the parallel ports
1389 to associate lp devices with, starting with
1390 lp0. A port specification may be 'none' to skip
1391 that lp device, or a parport name such as
1392 'parport0'. Specifying 'lp=auto' instead of a
1393 port specification list means that device IDs
1394 from each port should be examined, to see if
1395 an IEEE 1284-compliant printer is attached; if
1396 so, the driver will manage that printer.
1397 See also header of drivers/char/lp.c.
1400 Sets loops_per_jiffy to given constant, thus avoiding
1401 time-consuming boot-time autodetection (up to 250 ms per
1402 CPU). 0 enables autodetection (default). To determine
1403 the correct value for your kernel, boot with normal
1404 autodetection and see what value is printed. Note that
1405 on SMP systems the preset will be applied to all CPUs,
1406 which is likely to cause problems if your CPUs need
1407 significantly divergent settings. An incorrect value
1408 will cause delays in the kernel to be wrong, leading to
1409 unpredictable I/O errors and other breakage. Although
1410 unlikely, in the extreme case this might damage your
1414 Format: <io>,<irq>,<dma>
1416 machvec= [IA-64] Force the use of a particular machine-vector
1417 (machvec) in a generic kernel.
1418 Example: machvec=hpzx1_swiotlb
1420 machtype= [Loongson] Share the same kernel image file between different
1422 Example: machtype=lemote-yeeloong-2f-7inch
1424 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1425 than or equal to this physical address is ignored.
1427 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1428 should make use of. maxcpus=n : n >= 0 limits the
1429 kernel to using 'n' processors. n=0 is a special case,
1430 it is equivalent to "nosmp", which also disables
1433 max_loop= [LOOP] The number of loop block devices that get
1434 (loop.max_loop) unconditionally pre-created at init time. The default
1435 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1436 of statically allocating a predefined number, loop
1437 devices can be requested on-demand with the
1438 /dev/loop-control interface.
1442 mce [X86-32] Machine Check Exception
1444 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1446 md= [HW] RAID subsystems devices and level
1447 See Documentation/md.txt.
1450 Format: <first>,<last>
1451 Specifies range of consoles to be captured by the MDA.
1453 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1454 Amount of memory to be used when the kernel is not able
1455 to see the whole system memory or for test.
1456 [X86-32] Use together with memmap= to avoid physical
1457 address space collisions. Without memmap= PCI devices
1458 could be placed at addresses belonging to unused RAM.
1460 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1464 [KNL,SH] Allow user to override the default size for
1465 per-device physically contiguous DMA buffers.
1467 memmap=exactmap [KNL,X86] Enable setting of an exact
1468 E820 memory map, as specified by the user.
1469 Such memmap=exactmap lines can be constructed based on
1470 BIOS output or other requirements. See the memmap=nn@ss
1473 memmap=nn[KMG]@ss[KMG]
1474 [KNL] Force usage of a specific region of memory
1475 Region of memory to be used, from ss to ss+nn.
1477 memmap=nn[KMG]#ss[KMG]
1478 [KNL,ACPI] Mark specific memory as ACPI data.
1479 Region of memory to be used, from ss to ss+nn.
1481 memmap=nn[KMG]$ss[KMG]
1482 [KNL,ACPI] Mark specific memory as reserved.
1483 Region of memory to be used, from ss to ss+nn.
1484 Example: Exclude memory from 0x18690000-0x1869ffff
1485 memmap=64K$0x18690000
1487 memmap=0x10000$0x18690000
1489 memory_corruption_check=0/1 [X86]
1490 Some BIOSes seem to corrupt the first 64k of
1491 memory when doing things like suspend/resume.
1492 Setting this option will scan the memory
1493 looking for corruption. Enabling this will
1494 both detect corruption and prevent the kernel
1495 from using the memory being corrupted.
1496 However, its intended as a diagnostic tool; if
1497 repeatable BIOS-originated corruption always
1498 affects the same memory, you can use memmap=
1499 to prevent the kernel from using that memory.
1501 memory_corruption_check_size=size [X86]
1502 By default it checks for corruption in the low
1503 64k, making this memory unavailable for normal
1504 use. Use this parameter to scan for
1505 corruption in more or less memory.
1507 memory_corruption_check_period=seconds [X86]
1508 By default it checks for corruption every 60
1509 seconds. Use this parameter to check at some
1510 other rate. 0 disables periodic checking.
1512 memtest= [KNL,X86] Enable memtest
1514 default : 0 <disable>
1515 Specifies the number of memtest passes to be
1516 performed. Each pass selects another test
1517 pattern from a given set of patterns. Memtest
1518 fills the memory with this pattern, validates
1519 memory contents and reserves bad memory
1520 regions that are detected.
1522 meye.*= [HW] Set MotionEye Camera parameters
1523 See Documentation/video4linux/meye.txt.
1525 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1526 Multi-Function General Purpose Timers on AMD Geode
1529 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1530 the BIOS has incorrectly applied a workaround. TinyBIOS
1531 version 0.98 is known to be affected, 0.99 fixes the
1532 problem by letting the user disable the workaround.
1536 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1537 physical address is ignored.
1539 mini2440= [ARM,HW,KNL]
1540 Format:[0..2][b][c][t]
1542 MINI2440 configuration specification:
1543 0 - The attached screen is the 3.5" TFT
1544 1 - The attached screen is the 7" TFT
1545 2 - The VGA Shield is attached (1024x768)
1546 Leaving out the screen size parameter will not load
1547 the TFT driver, and the framebuffer will be left
1549 b - Enable backlight. The TFT backlight pin will be
1550 linked to the kernel VESA blanking code and a GPIO
1551 LED. This parameter is not necessary when using the
1553 c - Enable the s3c camera interface.
1554 t - Reserved for enabling touchscreen support. The
1555 touchscreen support is not enabled in the mainstream
1556 kernel as of 2.6.30, a preliminary port can be found
1557 in the "bleeding edge" mini2440 support kernel at
1558 http://repo.or.cz/w/linux-2.6/mini2440.git
1561 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1562 parameter allows control of the logging verbosity for
1563 the additional memory initialisation checks. A value
1564 of 0 disables mminit logging and a level of 4 will
1565 log everything. Information is printed at KERN_DEBUG
1566 so loglevel=8 may also need to be specified.
1569 [MOUSE] Maximum time between finger touching and
1570 leaving touchpad surface for touch to be considered
1571 a tap and be reported as a left button click (for
1572 touchpads working in absolute mode only).
1574 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1575 reporting absolute coordinates, such as tablets
1576 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1577 reporting absolute coordinates, such as tablets
1579 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1580 is similar to kernelcore except it specifies the
1581 amount of memory used for migratable allocations.
1582 If both kernelcore and movablecore is specified,
1583 then kernelcore will be at *least* the specified
1584 value but may be more. If movablecore on its own
1585 is specified, the administrator must be careful
1586 that the amount of memory usable for all allocations
1589 MTD_Partition= [MTD]
1590 Format: <name>,<region-number>,<size>,<offset>
1592 MTD_Region= [MTD] Format:
1593 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1596 See drivers/mtd/cmdlinepart.c.
1598 multitce=off [PPC] This parameter disables the use of the pSeries
1599 firmware feature for updating multiple TCE entries
1602 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1604 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1606 boundary - index of last SLC block on Flex-OneNAND.
1607 The remaining blocks are configured as MLC blocks.
1608 lock - Configure if Flex-OneNAND boundary should be locked.
1609 Once locked, the boundary cannot be changed.
1610 1 indicates lock status, 0 indicates unlock status.
1613 ARM/S3C2412 JIVE boot control
1615 See arch/arm/mach-s3c2412/mach-jive.c
1617 mtouchusb.raw_coordinates=
1618 [HW] Make the MicroTouch USB driver use raw coordinates
1619 ('y', default) or cooked coordinates ('n')
1621 mtrr_chunk_size=nn[KMG] [X86]
1622 used for mtrr cleanup. It is largest continuous chunk
1623 that could hold holes aka. UC entries.
1625 mtrr_gran_size=nn[KMG] [X86]
1626 Used for mtrr cleanup. It is granularity of mtrr block.
1628 Large value could prevent small alignment from
1631 mtrr_spare_reg_nr=n [X86]
1633 Range: 0,7 : spare reg number
1635 Used for mtrr cleanup. It is spare mtrr entries number.
1636 Set to 2 or more if your graphical card needs more.
1638 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1640 netdev= [NET] Network devices parameters
1641 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1642 Note that mem_start is often overloaded to mean
1643 something different and driver-specific.
1644 This usage is only documented in each driver source
1648 [NETFILTER] Enable connection tracking flow accounting
1649 0 to disable accounting
1650 1 to enable accounting
1653 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1654 See Documentation/filesystems/nfs/nfsroot.txt.
1656 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1657 See Documentation/filesystems/nfs/nfsroot.txt.
1659 nfsrootdebug [NFS] enable nfsroot debugging messages.
1660 See Documentation/filesystems/nfs/nfsroot.txt.
1662 nfs.callback_tcpport=
1663 [NFS] set the TCP port on which the NFSv4 callback
1664 channel should listen.
1667 [NFS] sets the pathname to the program which is used
1668 to update the NFS client cache entries.
1670 nfs.cache_getent_timeout=
1671 [NFS] sets the timeout after which an attempt to
1672 update a cache entry is deemed to have failed.
1674 nfs.idmap_cache_timeout=
1675 [NFS] set the maximum lifetime for idmapper cache
1679 [NFS] enable 64-bit inode numbers.
1680 If zero, the NFS client will fake up a 32-bit inode
1681 number for the readdir() and stat() syscalls instead
1682 of returning the full 64-bit number.
1683 The default is to return 64-bit inode numbers.
1685 nfs.max_session_slots=
1686 [NFSv4.1] Sets the maximum number of session slots
1687 the client will attempt to negotiate with the server.
1688 This limits the number of simultaneous RPC requests
1689 that the client can send to the NFSv4.1 server.
1690 Note that there is little point in setting this
1691 value higher than the max_tcp_slot_table_limit.
1693 nfs.nfs4_disable_idmapping=
1694 [NFSv4] When set to the default of '1', this option
1695 ensures that both the RPC level authentication
1696 scheme and the NFS level operations agree to use
1697 numeric uids/gids if the mount is using the
1698 'sec=sys' security flavour. In effect it is
1699 disabling idmapping, which can make migration from
1700 legacy NFSv2/v3 systems to NFSv4 easier.
1701 Servers that do not support this mode of operation
1702 will be autodetected by the client, and it will fall
1703 back to using the idmapper.
1704 To turn off this behaviour, set the value to '0'.
1706 nfs.send_implementation_id =
1707 [NFSv4.1] Send client implementation identification
1708 information in exchange_id requests.
1709 If zero, no implementation identification information
1711 The default is to send the implementation identification
1714 nfsd.nfs4_disable_idmapping=
1715 [NFSv4] When set to the default of '1', the NFSv4
1716 server will return only numeric uids and gids to
1717 clients using auth_sys, and will accept numeric uids
1718 and gids from such clients. This is intended to ease
1719 migration from NFSv2/v3.
1721 objlayoutdriver.osd_login_prog=
1722 [NFS] [OBJLAYOUT] sets the pathname to the program which
1723 is used to automatically discover and login into new
1724 osd-targets. Please see:
1725 Documentation/filesystems/pnfs.txt for more explanations
1727 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1728 when a NMI is triggered.
1729 Format: [state][,regs][,debounce][,die]
1731 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1732 Format: [panic,][nopanic,][num]
1734 0 - turn nmi_watchdog off
1735 When panic is specified, panic when an NMI watchdog
1736 timeout occurs (or 'nopanic' to override the opposite
1738 This is useful when you use a panic=... timeout and
1739 need the box quickly up again.
1741 netpoll.carrier_timeout=
1742 [NET] Specifies amount of time (in seconds) that
1743 netpoll should wait for a carrier. By default netpoll
1746 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1747 emulation library even if a 387 maths coprocessor
1751 [HW] Never suspend the console
1752 Disable suspending of consoles during suspend and
1753 hibernate operations. Once disabled, debugging
1754 messages can reach various consoles while the rest
1755 of the system is being put to sleep (ie, while
1756 debugging driver suspend/resume hooks). This may
1757 not work reliably with all consoles, but is known
1758 to work with serial and VGA consoles.
1759 To facilitate more flexible debugging, we also add
1760 console_suspend, a printk module parameter to control
1761 it. Users could use console_suspend (usually
1762 /sys/module/printk/parameters/console_suspend) to
1763 turn on/off it dynamically.
1765 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1766 caches in the slab allocator. Saves per-node memory,
1767 but will impact performance.
1771 noapic [SMP,APIC] Tells the kernel to not make use of any
1772 IOAPICs that may be present in the system.
1774 noautogroup Disable scheduler automatic task group creation.
1776 nobats [PPC] Do not use BATs for mapping kernel lowmem
1777 on "Classic" PPC cores.
1781 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1783 nodelayacct [KNL] Disable per-task delay accounting
1785 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1787 nodsp [SH] Disable hardware DSP at boot time.
1789 noefi [X86] Disable EFI runtime services support.
1794 On X86-32 available only on PAE configured kernels.
1795 noexec=on: enable non-executable mappings (default)
1796 noexec=off: disable non-executable mappings
1799 Disable SMEP (Supervisor Mode Execution Protection)
1800 even if it is supported by processor.
1803 This affects only 32-bit executables.
1804 noexec32=on: enable non-executable mappings (default)
1805 read doesn't imply executable mappings
1806 noexec32=off: disable non-executable mappings
1807 read implies executable mappings
1809 nofpu [SH] Disable hardware FPU at boot time.
1811 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1812 register save and restore. The kernel will only save
1813 legacy floating-point registers on task switch.
1815 noxsave [BUGS=X86] Disables x86 extended register state save
1816 and restore using xsave. The kernel will fallback to
1817 enabling legacy floating-point and sse state.
1819 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1820 wfi(ARM) instruction doesn't work correctly and not to
1821 use it. This is also useful when using JTAG debugger.
1823 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1824 instruction doesn't work correctly and not to
1827 no_file_caps Tells the kernel not to honor file capabilities. The
1828 only way then for a file to be executed with privilege
1829 is to be setuid root or executed by root.
1831 nohalt [IA-64] Tells the kernel not to use the power saving
1832 function PAL_HALT_LIGHT when idle. This increases
1833 power-consumption. On the positive side, it reduces
1834 interrupt wake-up latency, which may improve performance
1835 in certain environments such as networked servers or
1838 nohz= [KNL] Boottime enable/disable dynamic ticks
1839 Valid arguments: on, off
1842 noiotrap [SH] Disables trapped I/O port accesses.
1844 noirqdebug [X86-32] Disables the code which attempts to detect and
1845 disable unhandled interrupt sources.
1847 no_timer_check [X86,APIC] Disables the code which tests for
1848 broken timer IRQ sources.
1850 noisapnp [ISAPNP] Disables ISA PnP code.
1852 noinitrd [RAM] Tells the kernel not to load any configured
1855 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1857 [Deprecated - use intremap=off]
1861 nojitter [IA-64] Disables jitter checking for ITC timers.
1863 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1865 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1868 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1869 steal time is computed, but won't influence scheduler
1872 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1874 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1876 noltlbs [PPC] Do not use large page/tlb entries for kernel
1877 lowmem mapping on PPC40x.
1879 nomca [IA-64] Disable machine check abort handling
1881 nomce [X86-32] Machine Check Exception
1883 nomfgpt [X86-32] Disable Multi-Function General Purpose
1884 Timer usage (for AMD Geode machines).
1886 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1887 shutdown the other cpus. Instead use the REBOOT_VECTOR
1890 nomodule Disable module load
1892 nopat [X86] Disable PAT (page attribute table extension of
1893 pagetables) support.
1895 norandmaps Don't use address space randomization. Equivalent to
1896 echo 0 > /proc/sys/kernel/randomize_va_space
1898 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1900 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1901 with UP alternatives
1903 noresidual [PPC] Don't use residual data on PReP machines.
1905 nordrand [X86] Disable the direct use of the RDRAND
1906 instruction even if it is supported by the
1907 processor. RDRAND is still available to user
1910 noresume [SWSUSP] Disables resume and restores original swap
1913 no-scroll [VGA] Disables scrollback.
1914 This is required for the Braillex ib80-piezo Braille
1915 reader made by F.H. Papenmeier (Germany).
1919 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1921 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1922 and disable the IO APIC. legacy for "maxcpus=0".
1924 nosoftlockup [KNL] Disable the soft-lockup detector.
1926 nosync [HW,M68K] Disables sync negotiation for all devices.
1928 notsc [BUGS=X86-32] Disable Time Stamp Counter
1930 nousb [USB] Disable the USB subsystem
1932 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1936 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1938 nptcg= [IA-64] Override max number of concurrent global TLB
1939 purges which is reported from either PAL_VM_SUMMARY or
1942 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1943 could support. nr_cpus=n : n >= 1 limits the kernel to
1944 supporting 'n' processors. Later in runtime you can not
1945 use hotplug cpu feature to put more cpu back to online.
1946 just like you compile the kernel NR_CPUS=n
1948 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1950 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1951 one of ['zone', 'node', 'default'] can be specified
1952 This can be set from sysctl after boot.
1953 See Documentation/sysctl/vm.txt for details.
1955 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1956 See Documentation/debugging-via-ohci1394.txt for more
1959 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1960 Rather than timing out after 20 ms if an EC
1961 command is not properly ACKed, override the length
1962 of the timeout. We have interrupts disabled while
1963 waiting for the ACK, so if this is set too high
1964 interrupts *may* be lost!
1966 omap_mux= [OMAP] Override bootloader pin multiplexing.
1967 Format: <mux_mode0.mode_name=value>...
1968 For example, to override I2C bus2:
1969 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1971 oprofile.timer= [HW]
1972 Use timer interrupt instead of performance counters
1974 oprofile.cpu_type= Force an oprofile cpu type
1975 This might be useful if you have an older oprofile
1976 userland or if you want common events.
1977 Format: { arch_perfmon }
1978 arch_perfmon: [X86] Force use of architectural
1979 perfmon on Intel CPUs instead of the
1980 CPU specific event set.
1981 timer: [X86] Force use of architectural NMI
1982 timer mode (see also oprofile.timer
1983 for generic hr timer mode)
1984 [s390] Force legacy basic mode sampling
1985 (report cpu_type "timer")
1987 oops=panic Always panic on oopses. Default is to just kill the
1988 process, but there is a small probability of
1989 deadlocking the machine.
1990 This will also cause panics on machine check exceptions.
1991 Useful together with panic=30 to trigger a reboot.
1994 See Documentation/sound/oss/oss-parameters.txt
1996 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1997 timeout > 0: seconds before rebooting
1998 timeout = 0: wait forever
1999 timeout < 0: reboot immediately
2002 parkbd.port= [HW] Parallel port number the keyboard adapter is
2003 connected to, default is 0.
2005 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2006 0 for XT, 1 for AT (default is AT).
2009 parport= [HW,PPT] Specify parallel ports. 0 disables.
2010 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2011 Use 'auto' to force the driver to use any
2012 IRQ/DMA settings detected (the default is to
2013 ignore detected IRQ/DMA settings because of
2014 possible conflicts). You can specify the base
2015 address, IRQ, and DMA settings; IRQ and DMA
2016 should be numbers, or 'auto' (for using detected
2017 settings on that particular port), or 'nofifo'
2018 (to avoid using a FIFO even if it is detected).
2019 Parallel ports are assigned in the order they
2020 are specified on the command line, starting
2023 parport_init_mode= [HW,PPT]
2024 Configure VIA parallel port to operate in
2025 a specific mode. This is necessary on Pegasos
2026 computer where firmware has no options for setting
2027 up parallel port mode and sets it to spp.
2028 Currently this function knows 686a and 8231 chips.
2029 Format: [spp|ps2|epp|ecp|ecpepp]
2032 Halt all CPUs after the first oops has been printed for
2033 the specified number of seconds. This is to be used if
2034 your oopses keep scrolling off the screen.
2039 See header of drivers/block/paride/pcd.c.
2040 See also Documentation/blockdev/paride.txt.
2042 pci=option[,option...] [PCI] various PCI subsystem options:
2043 earlydump [X86] dump PCI config space before the kernel
2045 off [X86] don't probe for the PCI bus
2046 bios [X86-32] force use of PCI BIOS, don't access
2047 the hardware directly. Use this if your machine
2048 has a non-standard PCI host bridge.
2049 nobios [X86-32] disallow use of PCI BIOS, only direct
2050 hardware access methods are allowed. Use this
2051 if you experience crashes upon bootup and you
2052 suspect they are caused by the BIOS.
2053 conf1 [X86] Force use of PCI Configuration
2055 conf2 [X86] Force use of PCI Configuration
2057 noaer [PCIE] If the PCIEAER kernel config parameter is
2058 enabled, this kernel boot option can be used to
2059 disable the use of PCIE advanced error reporting.
2060 nodomains [PCI] Disable support for multiple PCI
2061 root domains (aka PCI segments, in ACPI-speak).
2062 nommconf [X86] Disable use of MMCONFIG for PCI
2064 check_enable_amd_mmconf [X86] check for and enable
2065 properly configured MMIO access to PCI
2066 config space on AMD family 10h CPU
2067 nomsi [MSI] If the PCI_MSI kernel config parameter is
2068 enabled, this kernel boot option can be used to
2069 disable the use of MSI interrupts system-wide.
2070 noioapicquirk [APIC] Disable all boot interrupt quirks.
2071 Safety option to keep boot IRQs enabled. This
2072 should never be necessary.
2073 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2074 primary IO-APIC for bridges that cannot disable
2075 boot IRQs. This fixes a source of spurious IRQs
2076 when the system masks IRQs.
2077 noioapicreroute [APIC] Disable workaround that uses the
2078 boot IRQ equivalent of an IRQ that connects to
2079 a chipset where boot IRQs cannot be disabled.
2080 The opposite of ioapicreroute.
2081 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2082 routing table. These calls are known to be buggy
2083 on several machines and they hang the machine
2084 when used, but on other computers it's the only
2085 way to get the interrupt routing table. Try
2086 this option if the kernel is unable to allocate
2087 IRQs or discover secondary PCI buses on your
2089 rom [X86] Assign address space to expansion ROMs.
2090 Use with caution as certain devices share
2091 address decoders between ROMs and other
2093 norom [X86] Do not assign address space to
2094 expansion ROMs that do not already have
2095 BIOS assigned address ranges.
2096 nobar [X86] Do not assign address space to the
2097 BARs that weren't assigned by the BIOS.
2098 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2099 assigned automatically to PCI devices. You can
2100 make the kernel exclude IRQs of your ISA cards
2102 pirqaddr=0xAAAAA [X86] Specify the physical address
2103 of the PIRQ table (normally generated
2104 by the BIOS) if it is outside the
2105 F0000h-100000h range.
2106 lastbus=N [X86] Scan all buses thru bus #N. Can be
2107 useful if the kernel is unable to find your
2108 secondary buses and you want to tell it
2109 explicitly which ones they are.
2110 assign-busses [X86] Always assign all PCI bus
2111 numbers ourselves, overriding
2112 whatever the firmware may have done.
2113 usepirqmask [X86] Honor the possible IRQ mask stored
2114 in the BIOS $PIR table. This is needed on
2115 some systems with broken BIOSes, notably
2116 some HP Pavilion N5400 and Omnibook XE3
2117 notebooks. This will have no effect if ACPI
2118 IRQ routing is enabled.
2119 noacpi [X86] Do not use ACPI for IRQ routing
2120 or for PCI scanning.
2121 use_crs [X86] Use PCI host bridge window information
2122 from ACPI. On BIOSes from 2008 or later, this
2123 is enabled by default. If you need to use this,
2124 please report a bug.
2125 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2126 If you need to use this, please report a bug.
2127 routeirq Do IRQ routing for all PCI devices.
2128 This is normally done in pci_enable_device(),
2129 so this option is a temporary workaround
2130 for broken drivers that don't call it.
2131 skip_isa_align [X86] do not align io start addr, so can
2132 handle more pci cards
2133 firmware [ARM] Do not re-enumerate the bus but instead
2134 just use the configuration from the
2135 bootloader. This is currently used on
2136 IXP2000 systems where the bus has to be
2137 configured a certain way for adjunct CPUs.
2138 noearly [X86] Don't do any early type 1 scanning.
2139 This might help on some broken boards which
2140 machine check when some devices' config space
2141 is read. But various workarounds are disabled
2142 and some IOMMU drivers will not work.
2143 bfsort Sort PCI devices into breadth-first order.
2144 This sorting is done to get a device
2145 order compatible with older (<= 2.4) kernels.
2146 nobfsort Don't sort PCI devices into breadth-first order.
2147 cbiosize=nn[KMG] The fixed amount of bus space which is
2148 reserved for the CardBus bridge's IO window.
2149 The default value is 256 bytes.
2150 cbmemsize=nn[KMG] The fixed amount of bus space which is
2151 reserved for the CardBus bridge's memory
2152 window. The default value is 64 megabytes.
2155 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2156 Specifies alignment and device to reassign
2157 aligned memory resources.
2158 If <order of align> is not specified,
2159 PAGE_SIZE is used as alignment.
2160 PCI-PCI bridge can be specified, if resource
2161 windows need to be expanded.
2162 ecrc= Enable/disable PCIe ECRC (transaction layer
2163 end-to-end CRC checking).
2164 bios: Use BIOS/firmware settings. This is the
2168 realloc= Enable/disable reallocating PCI bridge resources
2169 if allocations done by BIOS are too small to
2170 accommodate resources required by all child
2172 off: Turn realloc off
2174 realloc same as realloc=on
2175 noari do not use PCIe ARI.
2177 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2180 force Enable ASPM even on devices that claim not to support it.
2181 WARNING: Forcing ASPM on may cause system lockups.
2183 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2184 nomsi Do not use MSI for PCI Express Native Hotplug (this
2185 makes all PCIe ports use INTx for hotplug services).
2187 pcie_ports= [PCIE] PCIe ports handling:
2188 auto Ask the BIOS whether or not to use native PCIe services
2189 associated with PCIe ports (PME, hot-plug, AER). Use
2190 them only if that is allowed by the BIOS.
2191 native Use native PCIe services associated with PCIe ports
2193 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2196 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2197 nomsi Do not use MSI for native PCIe PME signaling (this makes
2198 all PCIe root ports use INTx for all services).
2200 pcmv= [HW,PCMCIA] BadgePAD 4
2203 See Documentation/blockdev/paride.txt.
2205 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2208 See arch/parisc/kernel/pdc_chassis.c
2210 percpu_alloc= Select which percpu first chunk allocator to use.
2211 Currently supported values are "embed" and "page".
2212 Archs may support subset or none of the selections.
2213 See comments in mm/percpu.c for details on each
2214 allocator. This parameter is primarily for debugging
2215 and performance comparison.
2218 See Documentation/blockdev/paride.txt.
2221 See Documentation/blockdev/paride.txt.
2223 pirq= [SMP,APIC] Manual mp-table setup
2224 See Documentation/x86/i386/IO-APIC.txt.
2226 plip= [PPT,NET] Parallel port network link
2227 Format: { parport<nr> | timid | 0 }
2228 See also Documentation/parport.txt.
2230 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2231 Override pmtimer IOPort with a hex value.
2235 Enable PNP debug messages (depends on the
2236 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2237 via /sys/module/pnp/parameters/debug. We always show
2238 current resource usage; turning this on also shows
2239 possible settings and some assignment information.
2245 { on | off | curr | res | no-curr | no-res }
2248 [ISAPNP] Exclude IRQs for the autoconfiguration
2251 [ISAPNP] Exclude DMAs for the autoconfiguration
2253 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2254 Ranges are in pairs (I/O port base and size).
2257 [ISAPNP] Exclude memory regions for the
2259 Ranges are in pairs (memory base and size).
2261 ports= [IP_VS_FTP] IPVS ftp helper module
2263 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2265 Format: <port>,<port>....
2267 print-fatal-signals=
2268 [KNL] debug: print fatal signals
2270 If enabled, warn about various signal handling
2271 related application anomalies: too many signals,
2272 too many POSIX.1 timers, fatal signals causing a
2275 If you hit the warning due to signal overflow,
2276 you might want to try "ulimit -i unlimited".
2280 printk.always_kmsg_dump=
2281 Trigger kmsg_dump for cases other than kernel oops or
2283 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2286 printk.time= Show timing data prefixed to each printk message line
2287 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2289 processor.max_cstate= [HW,ACPI]
2290 Limit processor to maximum C-state
2291 max_cstate=9 overrides any DMI blacklist limit.
2293 processor.nocst [HW,ACPI]
2294 Ignore the _CST method to determine C-states,
2295 instead using the legacy FADT method
2297 profile= [KNL] Enable kernel profiling via /proc/profile
2298 Format: [schedule,]<number>
2299 Param: "schedule" - profile schedule points.
2300 Param: <number> - step/bucket size as a power of 2 for
2301 statistical time based profiling.
2302 Param: "sleep" - profile D-state sleeping (millisecs).
2303 Requires CONFIG_SCHEDSTATS
2304 Param: "kvm" - profile VM exits.
2306 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2308 See Documentation/blockdev/ramdisk.txt.
2310 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2311 probe for; one of (bare|imps|exps|lifebook|any).
2312 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2314 psmouse.resetafter= [HW,MOUSE]
2315 Try to reset the device after so many bad packets
2318 [HW,MOUSE] Set desired mouse resolution, in dpi.
2319 psmouse.smartscroll=
2320 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2321 0 = disabled, 1 = enabled (default).
2323 pstore.backend= Specify the name of the pstore backend to use
2326 See Documentation/blockdev/paride.txt.
2329 [KNL] Number of legacy pty's. Overwrites compiled-in
2332 quiet [KNL] Disable most log messages
2337 See Documentation/md.txt.
2339 ramdisk_blocksize= [RAM]
2340 See Documentation/blockdev/ramdisk.txt.
2342 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2343 See Documentation/blockdev/ramdisk.txt.
2345 rcupdate.blimit= [KNL,BOOT]
2346 Set maximum number of finished RCU callbacks to process
2349 rcupdate.qhimark= [KNL,BOOT]
2350 Set threshold of queued
2351 RCU callbacks over which batch limiting is disabled.
2353 rcupdate.qlowmark= [KNL,BOOT]
2354 Set threshold of queued RCU callbacks below which
2355 batch limiting is re-enabled.
2359 Run specified binary instead of /init from the ramdisk,
2360 used for early userspace startup. See initrd.
2362 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2363 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2364 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2367 [KNL, SMP] Set scheduler's default relax_domain_level.
2368 See Documentation/cgroups/cpusets.txt.
2370 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2372 reservetop= [X86-32]
2374 Reserves a hole at the top of the kernel virtual
2379 Set the amount of memory to reserve for BIOS at
2380 the bottom of the address space.
2382 reset_devices [KNL] Force drivers to reset the underlying device
2383 during initialization.
2386 Specify the partition device for software suspend
2388 resume_offset= [SWSUSP]
2389 Specify the offset from the beginning of the partition
2390 given by "resume=" at which the swap header is located,
2391 in <PAGE_SIZE> units (needed only for swap files).
2392 See Documentation/power/swsusp-and-swap-files.txt
2394 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2395 read the resume files
2397 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2398 Useful for devices that are detected asynchronously
2399 (e.g. USB and MMC devices).
2401 hibernate= [HIBERNATION]
2402 noresume Don't check if there's a hibernation image
2403 present during boot.
2404 nocompress Don't compress/decompress hibernation images.
2406 retain_initrd [RAM] Keep initrd memory after extraction
2408 rhash_entries= [KNL,NET]
2409 Set number of hash buckets for route cache
2411 riscom8= [HW,SERIAL]
2412 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2414 ro [KNL] Mount root device read-only on boot
2416 root= [KNL] Root filesystem
2417 See name_to_dev_t comment in init/do_mounts.c.
2419 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2420 mount the root filesystem
2422 rootflags= [KNL] Set root filesystem mount option string
2424 rootfstype= [KNL] Set root filesystem type
2426 rootwait [KNL] Wait (indefinitely) for root device to show up.
2427 Useful for devices that are detected asynchronously
2428 (e.g. USB and MMC devices).
2430 rw [KNL] Mount root device read-write on boot
2432 S [KNL] Run init in single mode
2435 See drivers/net/irda/sa1100_ir.c.
2437 sbni= [NET] Granch SBNI12 leased line adapter
2439 sched_debug [KNL] Enables verbose scheduler debug messages.
2441 security= [SECURITY] Choose a security module to enable at boot.
2442 If this boot parameter is not specified, only the first
2443 security module asking for security registration will be
2444 loaded. An invalid security module name will be treated
2445 as if no module has been chosen.
2447 selinux= [SELINUX] Disable or enable SELinux at boot time.
2448 Format: { "0" | "1" }
2449 See security/selinux/Kconfig help text.
2452 Default value is set via kernel config option.
2453 If enabled at boot time, /selinux/disable can be used
2454 later to disable prior to initial policy load.
2456 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2457 Format: { "0" | "1" }
2458 See security/apparmor/Kconfig help text
2461 Default value is set via kernel config option.
2463 serialnumber [BUGS=X86-32]
2466 Maximal number of shapers.
2468 show_msr= [x86] show boot-time MSR settings
2469 Format: { <integer> }
2470 Show boot-time (BIOS-initialized) MSR settings.
2471 The parameter means the number of CPUs to show,
2472 for example 1 means boot CPU only.
2479 slab_max_order= [MM, SLAB]
2480 Determines the maximum allowed order for slabs.
2481 A high setting may cause OOMs due to memory
2482 fragmentation. Defaults to 1 for systems with
2483 more than 32MB of RAM, 0 otherwise.
2485 slub_debug[=options[,slabs]] [MM, SLUB]
2486 Enabling slub_debug allows one to determine the
2487 culprit if slab objects become corrupted. Enabling
2488 slub_debug can create guard zones around objects and
2489 may poison objects when not in use. Also tracks the
2490 last alloc / free. For more information see
2491 Documentation/vm/slub.txt.
2493 slub_max_order= [MM, SLUB]
2494 Determines the maximum allowed order for slabs.
2495 A high setting may cause OOMs due to memory
2496 fragmentation. For more information see
2497 Documentation/vm/slub.txt.
2499 slub_min_objects= [MM, SLUB]
2500 The minimum number of objects per slab. SLUB will
2501 increase the slab order up to slub_max_order to
2502 generate a sufficiently large slab able to contain
2503 the number of objects indicated. The higher the number
2504 of objects the smaller the overhead of tracking slabs
2505 and the less frequently locks need to be acquired.
2506 For more information see Documentation/vm/slub.txt.
2508 slub_min_order= [MM, SLUB]
2509 Determines the minimum page order for slabs. Must be
2510 lower than slub_max_order.
2511 For more information see Documentation/vm/slub.txt.
2513 slub_nomerge [MM, SLUB]
2514 Disable merging of slabs with similar size. May be
2515 necessary if there is some reason to distinguish
2516 allocs to different slabs. Debug options disable
2517 merging on their own.
2518 For more information see Documentation/vm/slub.txt.
2521 Format: <io1>[,<io2>[,...,<io8>]]
2523 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2524 attempt to substitute SMP alternatives once at boot.
2526 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2527 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2528 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2529 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2530 smsc-ircc2.ircc_irq= [HW] IRQ line
2531 smsc-ircc2.ircc_dma= [HW] DMA channel
2532 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2533 0: Toshiba Satellite 1800 (GP data pin select)
2534 1: Fast pin select (default)
2538 [KNL] Should the soft-lockup detector generate panics.
2541 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2542 See Documentation/laptops/sonypi.txt
2544 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2545 See Documentation/serial/specialix.txt.
2547 spia_io_base= [HW,MTD]
2553 Enabled the stack tracer on boot up.
2555 stacktrace_filter=[function-list]
2556 [FTRACE] Limit the functions that the stack tracer
2557 will trace at boot up. function-list is a comma separated
2558 list of functions. This list can be changed at run
2559 time by the stack_trace_filter file in the debugfs
2560 tracing directory. Note, this enables stack tracing
2561 and the stacktrace above is not needed.
2565 Set the STI (builtin display/keyboard on the HP-PARISC
2566 machines) console (graphic card) which should be used
2567 as the initial boot-console.
2568 See also comment in drivers/video/console/sticore.c.
2571 See comment in drivers/video/console/sticore.c.
2574 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2576 sunrpc.min_resvport=
2577 sunrpc.max_resvport=
2579 SunRPC servers often require that client requests
2580 originate from a privileged port (i.e. a port in the
2581 range 0 < portnr < 1024).
2582 An administrator who wishes to reserve some of these
2583 ports for other uses may adjust the range that the
2584 kernel's sunrpc client considers to be privileged
2585 using these two parameters to set the minimum and
2586 maximum port values.
2590 Control how the NFS server code allocates CPUs to
2591 service thread pools. Depending on how many NICs
2592 you have and where their interrupts are bound, this
2593 option will affect which CPUs will do NFS serving.
2594 Note: this parameter cannot be changed while the
2595 NFS server is running.
2597 auto the server chooses an appropriate mode
2598 automatically using heuristics
2599 global a single global pool contains all CPUs
2600 percpu one pool for each CPU
2601 pernode one pool for each NUMA node (equivalent
2602 to global on non-NUMA machines)
2604 sunrpc.tcp_slot_table_entries=
2605 sunrpc.udp_slot_table_entries=
2607 Sets the upper limit on the number of simultaneous
2608 RPC calls that can be sent from the client to a
2609 server. Increasing these values may allow you to
2610 improve throughput, but will also increase the
2611 amount of memory reserved for use by the client.
2614 [KNL] Enable accounting of swap in memory resource
2615 controller if no parameter or 1 is given or disable
2616 it if 0 is given (See Documentation/cgroups/memory.txt)
2618 swiotlb= [IA-64] Number of I/O TLB slabs
2622 sysfs.deprecated=0|1 [KNL]
2623 Enable/disable old style sysfs layout for old udev
2624 on older distributions. When this option is enabled
2625 very new udev will not work anymore. When this option
2626 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2627 in older udev will not work anymore.
2628 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2629 the kernel configuration.
2631 sysrq_always_enabled
2633 Ignore sysrq setting - this boot parameter will
2634 neutralize any effect of /proc/sys/kernel/sysrq.
2635 Useful for debugging.
2639 test_suspend= [SUSPEND]
2640 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2641 standby suspend) as the system sleep state to briefly
2642 enter during system startup. The system is woken from
2643 this state using a wakeup-capable RTC alarm.
2645 thash_entries= [KNL,NET]
2646 Set number of hash buckets for TCP connection
2648 thermal.act= [HW,ACPI]
2649 -1: disable all active trip points in all thermal zones
2650 <degrees C>: override all lowest active trip points
2652 thermal.crt= [HW,ACPI]
2653 -1: disable all critical trip points in all thermal zones
2654 <degrees C>: override all critical trip points
2656 thermal.nocrt= [HW,ACPI]
2657 Set to disable actions on ACPI thermal zone
2658 critical and hot trip points.
2660 thermal.off= [HW,ACPI]
2661 1: disable ACPI thermal control
2663 thermal.psv= [HW,ACPI]
2664 -1: disable all passive trip points
2665 <degrees C>: override all passive trip points to this
2668 thermal.tzp= [HW,ACPI]
2669 Specify global default ACPI thermal zone polling rate
2670 <deci-seconds>: poll all this frequency
2671 0: no polling (default)
2674 Force threading of all interrupt handlers except those
2675 marked explicitly IRQF_NO_THREAD.
2679 Specify if the kernel should make use of the cpu
2680 topology information if the hardware supports this.
2681 The scheduler will make use of this information and
2682 e.g. base its process migration decisions on it.
2687 tpm_suspend_pcr=[HW,TPM]
2688 Format: integer pcr id
2689 Specify that at suspend time, the tpm driver
2690 should extend the specified pcr with zeros,
2691 as a workaround for some chips which fail to
2692 flush the last written pcr on TPM_SaveState.
2693 This will guarantee that all the other pcrs
2696 trace_buf_size=nn[KMG]
2697 [FTRACE] will set tracing buffer size.
2699 trace_event=[event-list]
2700 [FTRACE] Set and start specified trace events in order
2701 to facilitate early boot debugging.
2702 See also Documentation/trace/events.txt
2704 transparent_hugepage=
2706 Format: [always|madvise|never]
2707 Can be used to control the default behavior of the system
2708 with respect to transparent hugepages.
2709 See Documentation/vm/transhuge.txt for more details.
2711 tsc= Disable clocksource stability checks for TSC.
2713 [x86] reliable: mark tsc clocksource as reliable, this
2714 disables clocksource verification at runtime, as well
2715 as the stability checks done at bootup. Used to enable
2716 high-resolution timer mode on older hardware, and in
2717 virtualized environment.
2718 [x86] noirqtime: Do not use TSC to do irq accounting.
2719 Used to run time disable IRQ_TIME_ACCOUNTING on any
2720 platforms where RDTSC is slow and this accounting
2723 turbografx.map[2|3]= [HW,JOY]
2724 TurboGraFX parallel port interface
2726 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2727 See also Documentation/input/joystick-parport.txt
2729 udbg-immortal [PPC] When debugging early kernel crashes that
2730 happen after console_init() and before a proper
2731 console driver takes over, this boot options might
2732 help "seeing" what's going on.
2734 uhash_entries= [KNL,NET]
2735 Set number of hash buckets for UDP/UDP-Lite connections
2738 [USB] Ignore overcurrent events (default N).
2739 Some badly-designed motherboards generate lots of
2740 bogus events, for ports that aren't wired to
2741 anything. Set this parameter to avoid log spamming.
2742 Note that genuine overcurrent events won't be
2746 [X86] Cause panic on unknown NMI.
2748 usbcore.authorized_default=
2749 [USB] Default USB device authorization:
2750 (default -1 = authorized except for wireless USB,
2751 0 = not authorized, 1 = authorized)
2753 usbcore.autosuspend=
2754 [USB] The autosuspend time delay (in seconds) used
2755 for newly-detected USB devices (default 2). This
2756 is the time required before an idle device will be
2757 autosuspended. Devices for which the delay is set
2758 to a negative value won't be autosuspended at all.
2760 usbcore.usbfs_snoop=
2761 [USB] Set to log all usbfs traffic (default 0 = off).
2763 usbcore.blinkenlights=
2764 [USB] Set to cycle leds on hubs (default 0 = off).
2766 usbcore.old_scheme_first=
2767 [USB] Start with the old device initialization
2768 scheme (default 0 = off).
2770 usbcore.usbfs_memory_mb=
2771 [USB] Memory limit (in MB) for buffers allocated by
2772 usbfs (default = 16, 0 = max = 2047).
2774 usbcore.use_both_schemes=
2775 [USB] Try the other device initialization scheme
2776 if the first one fails (default 1 = enabled).
2778 usbcore.initial_descriptor_timeout=
2779 [USB] Specifies timeout for the initial 64-byte
2780 USB_REQ_GET_DESCRIPTOR request in milliseconds
2781 (default 5000 = 5.0 seconds).
2784 [USBHID] The interval which mice are to be polled at.
2786 usb-storage.delay_use=
2787 [UMS] The delay in seconds before a new device is
2788 scanned for Logical Units (default 5).
2791 [UMS] A list of quirks entries to supplement or
2792 override the built-in unusual_devs list. List
2793 entries are separated by commas. Each entry has
2794 the form VID:PID:Flags where VID and PID are Vendor
2795 and Product ID values (4-digit hex numbers) and
2796 Flags is a set of characters, each corresponding
2797 to a common usb-storage quirk flag as follows:
2798 a = SANE_SENSE (collect more than 18 bytes
2800 b = BAD_SENSE (don't collect more than 18
2801 bytes of sense data);
2802 c = FIX_CAPACITY (decrease the reported
2803 device capacity by one sector);
2804 d = NO_READ_DISC_INFO (don't use
2805 READ_DISC_INFO command);
2806 e = NO_READ_CAPACITY_16 (don't use
2807 READ_CAPACITY_16 command);
2808 h = CAPACITY_HEURISTICS (decrease the
2809 reported device capacity by one
2810 sector if the number is odd);
2811 i = IGNORE_DEVICE (don't bind to this
2813 l = NOT_LOCKABLE (don't try to lock and
2814 unlock ejectable media);
2815 m = MAX_SECTORS_64 (don't transfer more
2816 than 64 sectors = 32 KB at a time);
2817 n = INITIAL_READ10 (force a retry of the
2818 initial READ(10) command);
2819 o = CAPACITY_OK (accept the capacity
2820 reported by the device);
2821 r = IGNORE_RESIDUE (the device reports
2822 bogus residue values);
2823 s = SINGLE_LUN (the device has only one
2825 w = NO_WP_DETECT (don't test whether the
2826 medium is write-protected).
2827 Example: quirks=0419:aaf5:rl,0421:0433:rc
2829 user_debug= [KNL,ARM]
2831 See arch/arm/Kconfig.debug help text.
2832 1 - undefined instruction events
2834 4 - invalid data aborts
2837 Example: user_debug=31
2840 [X86] Flags controlling user PTE allocations.
2842 nohigh = do not allocate PTE pages in
2843 HIGHMEM regardless of setting
2847 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2848 vdso=1: enable VDSO (default)
2849 vdso=0: disable VDSO mapping
2852 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2853 vdso32=1: enable 32-bit VDSO (default)
2854 vdso32=0: disable 32-bit VDSO mapping
2857 vector=percpu: enable percpu vector domain
2859 video= [FB] Frame buffer configuration
2860 See Documentation/fb/modedb.txt.
2862 vga= [BOOT,X86-32] Select a particular video mode
2863 See Documentation/x86/boot.txt and
2864 Documentation/svga.txt.
2865 Use vga=ask for menu.
2866 This is actually a boot loader parameter; the value is
2867 passed to the kernel using a special protocol.
2869 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2870 size of <nn>. This can be used to increase the
2871 minimum size (128MB on x86). It can also be used to
2872 decrease the size and leave more room for directly
2875 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2878 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2881 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2885 Controls the behavior of vsyscalls (i.e. calls to
2886 fixed addresses of 0xffffffffff600x00 from legacy
2887 code). Most statically-linked binaries and older
2888 versions of glibc use these calls. Because these
2889 functions are at fixed addresses, they make nice
2890 targets for exploits that can control RIP.
2892 emulate [default] Vsyscalls turn into traps and are
2893 emulated reasonably safely.
2895 native Vsyscalls are native syscall instructions.
2896 This is a little bit faster than trapping
2897 and makes a few dynamic recompilers work
2898 better than they would in emulation mode.
2899 It also makes exploits much easier to write.
2901 none Vsyscalls don't work at all. This makes
2902 them quite hard to use for exploits but
2903 might break your system.
2905 vt.cur_default= [VT] Default cursor shape.
2906 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2907 the parameters of the <Esc>[?A;B;Cc escape sequence;
2908 see VGA-softcursor.txt. Default: 2 = underline.
2910 vt.default_blu= [VT]
2911 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2912 Change the default blue palette of the console.
2913 This is a 16-member array composed of values
2916 vt.default_grn= [VT]
2917 Format: <green0>,<green1>,<green2>,...,<green15>
2918 Change the default green palette of the console.
2919 This is a 16-member array composed of values
2922 vt.default_red= [VT]
2923 Format: <red0>,<red1>,<red2>,...,<red15>
2924 Change the default red palette of the console.
2925 This is a 16-member array composed of values
2931 Set system-wide default UTF-8 mode for all tty's.
2932 Default is 1, i.e. UTF-8 mode is enabled for all
2933 newly opened terminals.
2935 vt.global_cursor_default=
2938 Set system-wide default for whether a cursor
2939 is shown on new VTs. Default is -1,
2940 i.e. cursors will be created by default unless
2941 overridden by individual drivers. 0 will hide
2942 cursors, 1 will display them.
2944 watchdog timers [HW,WDT] For information on watchdog timers,
2945 see Documentation/watchdog/watchdog-parameters.txt
2946 or other driver-specific files in the
2947 Documentation/watchdog/ directory.
2949 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2950 default x2apic cluster mode on platforms
2953 x86_mrst_timer= [X86-32,APBT]
2954 Choose timer option for x86 Moorestown MID platform.
2955 Two valid options are apbt timer only and lapic timer
2956 plus one apbt timer for broadcast timer.
2957 x86_mrst_timer=apbt_only | lapic_and_apbt
2959 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2960 xd_geo= See header of drivers/block/xd.c.
2962 xen_emul_unplug= [HW,X86,XEN]
2963 Unplug Xen emulated devices
2964 Format: [unplug0,][unplug1]
2965 ide-disks -- unplug primary master IDE devices
2966 aux-ide-disks -- unplug non-primary-master IDE devices
2967 nics -- unplug network devices
2968 all -- unplug all emulated devices (NICs and IDE disks)
2969 unnecessary -- unplugging emulated devices is
2970 unnecessary even if the host did not respond to
2972 never -- do not unplug even if version check succeeds
2974 xirc2ps_cs= [NET,PCMCIA]
2976 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2978 ______________________________________________________________________
2982 Add more DRM drivers.
projects / cascardo / linux.git / blob