4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amijoy.map= [HW,JOY] Amiga joystick support
339 Map of devices attached to JOY0DAT and JOY1DAT
341 See also Documentation/input/joystick.txt
343 analog.map= [HW,JOY] Analog joystick and gamepad support
344 Specifies type or capabilities of an analog joystick
345 connected to one of 16 gameports
346 Format: <type1>,<type2>,..<type16>
349 Power management functions (SPARCstation-4/5 + deriv.)
351 Disable APC CPU standby support. SPARCstation-Fox does
352 not play well with APC CPU idle - disable it if you have
353 APC and your system crashes randomly.
355 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
356 Change the output verbosity whilst booting
357 Format: { quiet (default) | verbose | debug }
358 Change the amount of debugging information output
359 when initialising the APIC and IO-APIC components.
362 See Documentation/networking/ipv6.txt.
364 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
365 Limit apic dumping. The parameter defines the maximal
366 number of local apics being dumped. Also it is possible
367 to set it to "all" by meaning -- no limit here.
368 Format: { 1 (default) | 2 | ... | all }.
369 The parameter valid if only apic=debug or
370 apic=verbose is specified.
371 Example: apic=debug show_lapic=all
373 apm= [APM] Advanced Power Management
374 See header of arch/x86/kernel/apm_32.c.
376 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
377 Format: <io>,<irq>,<nodeID>
381 atarimouse= [HW,MOUSE] Atari Mouse
383 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
384 EzKey and similar keyboards
386 atkbd.reset= [HW] Reset keyboard during initialization
388 atkbd.set= [HW] Select keyboard code set
389 Format: <int> (2 = AT (default), 3 = PS/2)
391 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
394 atkbd.softraw= [HW] Choose between synthetic and real raw mode
395 Format: <bool> (0 = real, 1 = synthetic (default))
397 atkbd.softrepeat= [HW]
398 Use software keyboard repeat
402 baycom_epp= [HW,AX25]
405 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
407 See header of drivers/net/hamradio/baycom_par.c.
409 baycom_ser_fdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
411 Format: <io>,<irq>,<mode>[,<baud>]
412 See header of drivers/net/hamradio/baycom_ser_fdx.c.
414 baycom_ser_hdx= [HW,AX25]
415 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
416 Format: <io>,<irq>,<mode>
417 See header of drivers/net/hamradio/baycom_ser_hdx.c.
419 boot_delay= Milliseconds to delay each printk during boot.
420 Values larger than 10 seconds (10000) are changed to
424 bootmem_debug [KNL] Enable bootmem allocator debug messages.
426 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
427 bttv.radio= Most important insmod options are available as
429 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
432 bulk_remove=off [PPC] This parameter disables the use of the pSeries
433 firmware feature for flushing multiple hpte entries
436 c101= [NET] Moxa C101 synchronous serial card
438 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
439 Sometimes CPU hardware bugs make them report the cache
440 size incorrectly. The kernel will attempt work arounds
441 to fix known problems, but for some CPUs it is not
442 possible to determine what the correct size should be.
443 This option provides an override for these situations.
446 [SECURITY] Disable capabilities. This would normally
447 be used only if an alternative security model is to be
448 configured. Potentially dangerous and should only be
449 used if you are entirely sure of the consequences.
451 ccw_timeout_log [S390]
452 See Documentation/s390/CommonIO for details.
454 cgroup_disable= [KNL] Disable a particular controller
455 Format: {name of the controller(s) to disable}
456 {Currently supported controllers - "memory"}
458 checkreqprot [SELINUX] Set initial checkreqprot flag value.
459 Format: { "0" | "1" }
460 See security/selinux/Kconfig help text.
461 0 -- check protection applied by kernel (includes
462 any implied execute protection).
463 1 -- check protection requested by application.
464 Default value is set via a kernel config option.
465 Value can be changed at runtime via
466 /selinux/checkreqprot.
469 See Documentation/s390/CommonIO for details.
471 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
473 Forces specified clocksource (if available) to be used
474 when calculating gettimeofday(). If specified
475 clocksource is not available, it defaults to PIT.
476 Format: { pit | tsc | cyclone | pmtmr }
478 clocksource= Override the default clocksource
480 Override the default clocksource and use the clocksource
481 with the name specified.
482 Some clocksource names to choose from, depending on
484 [all] jiffies (this is the base, fallback clocksource)
486 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
487 pxa_timer,timer3,32k_counter,timer0_1
489 [X86-32] pit,hpet,tsc;
490 scx200_hrt on Geode; cyclone on IBM x440
498 clearcpuid=BITNUM [X86]
499 Disable CPUID feature X for the kernel. See
500 arch/x86/include/asm/cpufeature.h for the valid bit
501 numbers. Note the Linux specific bits are not necessarily
502 stable over kernel options, but the vendor specific
504 Also note that user programs calling CPUID directly
505 or using the feature without checking anything
506 will still see it. This just prevents it from
507 being used by the kernel or shown in /proc/cpuinfo.
508 Also note the kernel might malfunction if you disable
511 cmo_free_hint= [PPC] Format: { yes | no }
512 Specify whether pages are marked as being inactive
513 when they are freed. This is used in CMO environments
514 to determine OS memory pressure for page stealing by
518 code_bytes [X86] How many bytes of object code to print
523 com20020= [HW,NET] ARCnet - COM20020 chipset
525 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
527 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
531 ARCnet - COM90xx chipset (memory-mapped buffers)
532 Format: <io>[,<irq>[,<memstart>]]
534 condev= [HW,S390] console device
537 console= [KNL] Output console device and options.
539 tty<n> Use the virtual console device <n>.
543 Use the specified serial port. The options are of
544 the form "bbbbpnf", where "bbbb" is the baud rate,
545 "p" is parity ("n", "o", or "e"), "n" is number of
546 bits, and "f" is flow control ("r" for RTS or
547 omit it). Default is "9600n8".
549 See Documentation/serial-console.txt for more
551 Documentation/networking/netconsole.txt for an
554 uart[8250],io,<addr>[,options]
555 uart[8250],mmio,<addr>[,options]
556 Start an early, polled-mode console on the 8250/16550
557 UART at the specified I/O port or MMIO address,
558 switching to the matching ttyS device later. The
559 options are the same as for ttyS, above.
561 If the device connected to the port is not a TTY but a braille
562 device, prepend "brl," before the device type, for instance
564 For now, only VisioBraille is supported.
566 consoleblank= [KNL] The console blank (screen saver) timeout in
567 seconds. Defaults to 10*60 = 10mins. A value of 0
568 disables the blank timer.
571 [KNL] Change the default value for
572 /proc/<pid>/coredump_filter.
573 See also Documentation/filesystems/proc.txt.
575 cpuidle.off=1 [CPU_IDLE]
576 disable the cpuidle sub-system
578 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
580 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
582 crashkernel=size[KMG][@offset[KMG]]
583 [KNL] Using kexec, Linux can switch to a 'crash kernel'
584 upon panic. This parameter reserves the physical
585 memory region [offset, offset + size] for that kernel
586 image. If '@offset' is omitted, then a suitable offset
587 is selected automatically. Check
588 Documentation/kdump/kdump.txt for further details.
590 crashkernel=range1:size1[,range2:size2,...][@offset]
591 [KNL] Same as above, but depends on the memory
592 in the running system. The syntax of range is
593 start-[end] where start and end are both
594 a memory unit (amount[KMG]). See also
595 Documentation/kdump/kdump.txt for an example.
600 cs89x0_media= [HW,NET]
601 Format: { rj45 | aui | bnc }
604 See header of drivers/s390/block/dasd_devmap.c.
606 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
607 (one device per port)
608 Format: <port#>,<type>
609 See also Documentation/input/joystick-parport.txt
611 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
612 time. See Documentation/dynamic-debug-howto.txt for
615 debug [KNL] Enable kernel debugging (events log level).
618 [KNL] verbose self-tests
620 Print debugging info while doing the locking API
622 We default to 0 (no extra messages), setting it to
623 1 will print _a lot_ more information - normally
624 only useful to kernel developers.
626 debug_objects [KNL] Enable object debugging
629 [KNL] Disable object debugging
631 debug_guardpage_minorder=
632 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
633 parameter allows control of the order of pages that will
634 be intentionally kept free (and hence protected) by the
635 buddy allocator. Bigger value increase the probability
636 of catching random memory corruption, but reduce the
637 amount of memory for normal system use. The maximum
638 possible value is MAX_ORDER/2. Setting this parameter
639 to 1 or 2 should be enough to identify most random
640 memory corruption problems caused by bugs in kernel or
641 driver code when a CPU writes to (or reads from) a
642 random memory location. Note that there exists a class
643 of memory corruptions problems caused by buggy H/W or
644 F/W or by drivers badly programing DMA (basically when
645 memory is written at bus level and the CPU MMU is
646 bypassed) which are not detectable by
647 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
648 tracking down these problems.
650 debugpat [X86] Enable PAT debugging
652 decnet.addr= [HW,NET]
653 Format: <area>[,<node>]
654 See also Documentation/networking/decnet.txt.
657 [same as hugepagesz=] The size of the default
658 HugeTLB page size. This is the size represented by
659 the legacy /proc/ hugepages APIs, used for SHM, and
660 default size when mounting hugetlbfs filesystems.
661 Defaults to the default architecture's huge page size
665 Set number of hash buckets for dentry cache.
668 IO parameters + enable/disable command.
670 digiepca= [HW,SERIAL]
671 See drivers/char/README.epca and
672 Documentation/serial/digiepca.txt.
675 See Documentation/networking/ipv6.txt.
677 disable_ddw [PPC/PSERIES]
678 Disable Dynamic DMA Window support. Use this if
679 to workaround buggy firmware.
682 See Documentation/networking/ipv6.txt.
684 disable_mtrr_cleanup [X86]
685 The kernel tries to adjust MTRR layout from continuous
686 to discrete, to make X server driver able to add WB
687 entry later. This parameter disables that.
689 disable_mtrr_trim [X86, Intel and AMD only]
690 By default the kernel will trim any uncacheable
691 memory out of your available memory pool based on
692 MTRR settings. This parameter disables that behavior,
693 possibly causing your machine to run very slowly.
695 disable_timer_pin_1 [X86]
696 Disable PIN 1 of APIC timer
697 Can be useful to work around chipset bugs.
699 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
700 this option disables the debugging code at boot.
702 dma_debug_entries=<number>
703 This option allows to tune the number of preallocated
704 entries for DMA-API debugging code. One entry is
705 required per DMA-API allocation. Use this if the
706 DMA-API debugging code disables itself because the
707 architectural default is too low.
709 dma_debug_driver=<driver_name>
710 With this option the DMA-API debugging driver
711 filter feature can be enabled at boot time. Just
712 pass the driver to filter for as the parameter.
713 The filter can be disabled or changed to another
714 driver later using sysfs.
718 earlycon= [KNL] Output early console device and options.
719 uart[8250],io,<addr>[,options]
720 uart[8250],mmio,<addr>[,options]
721 uart[8250],mmio32,<addr>[,options]
722 Start an early, polled-mode console on the 8250/16550
723 UART at the specified I/O port or MMIO address.
724 MMIO inter-register address stride is either 8-bit
725 (mmio) or 32-bit (mmio32).
726 The options are the same as for ttyS, above.
728 earlyprintk= [X86,SH,BLACKFIN]
730 earlyprintk=serial[,ttySn[,baudrate]]
731 earlyprintk=ttySn[,baudrate]
732 earlyprintk=dbgp[debugController#]
734 Append ",keep" to not disable it when the real console
737 Only vga or serial or usb debug port at a time.
739 Currently only ttyS0 and ttyS1 are supported.
741 Interaction with the standard serial driver is not
744 The VGA output is eventually overwritten by the real
747 ekgdboc= [X86,KGDB] Allow early kernel console debugging
750 This is designed to be used in conjunction with
751 the boot argument: earlyprintk=vga
754 Format: {"off" | "on" | "skip[mbr]"}
756 eisa_irq_edge= [PARISC,HW]
757 See header of drivers/parisc/eisa.c.
760 See comment before function elanfreq_setup() in
761 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
764 Format: {"cfq" | "deadline" | "noop"}
765 See Documentation/block/cfq-iosched.txt and
766 Documentation/block/deadline-iosched.txt for details.
768 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
769 Specifies physical address of start of kernel core
770 image elf header and optionally the size. Generally
771 kexec loader will pass this option to capture kernel.
772 See Documentation/kdump/kdump.txt for details.
774 enable_mtrr_cleanup [X86]
775 The kernel tries to adjust MTRR layout from continuous
776 to discrete, to make X server driver able to add WB
777 entry later. This parameter enables that.
779 enable_timer_pin_1 [X86]
780 Enable PIN 1 of APIC timer
781 Can be useful to work around chipset bugs
782 (in particular on some ATI chipsets).
783 The kernel tries to set a reasonable default.
785 enforcing [SELINUX] Set initial enforcing status.
787 See security/selinux/Kconfig help text.
788 0 -- permissive (log only, no denials).
789 1 -- enforcing (deny and log).
791 Value can be changed at runtime via /selinux/enforce.
794 Disable Error Record Serialization Table (ERST)
797 ether= [HW,NET] Ethernet cards parameters
798 This option is obsoleted by the "netdev=" option, which
799 has equivalent usage. See its documentation for details.
803 Permit 'security.evm' to be updated regardless of
804 current integrity status.
808 fail_make_request=[KNL]
809 General fault injection mechanism.
810 Format: <interval>,<probability>,<space>,<times>
811 See also Documentation/fault-injection/.
814 See Documentation/blockdev/floppy.txt.
816 force_pal_cache_flush
817 [IA-64] Avoid check_sal_cache_flush which may hang on
818 buggy SAL_CACHE_FLUSH implementations. Using this
819 parameter will force ia64_sal_cache_flush to call
820 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
823 [FTRACE] will set and start the specified tracer
824 as early as possible in order to facilitate early
827 ftrace_dump_on_oops[=orig_cpu]
828 [FTRACE] will dump the trace buffers on oops.
829 If no parameter is passed, ftrace will dump
830 buffers of all CPUs, but if you pass orig_cpu, it will
831 dump only the buffer of the CPU that triggered the
834 ftrace_filter=[function-list]
835 [FTRACE] Limit the functions traced by the function
836 tracer at boot up. function-list is a comma separated
837 list of functions. This list can be changed at run
838 time by the set_ftrace_filter file in the debugfs
841 ftrace_notrace=[function-list]
842 [FTRACE] Do not trace the functions specified in
843 function-list. This list can be changed at run time
844 by the set_ftrace_notrace file in the debugfs
847 ftrace_graph_filter=[function-list]
848 [FTRACE] Limit the top level callers functions traced
849 by the function graph tracer at boot up.
850 function-list is a comma separated list of functions
851 that can be changed at run time by the
852 set_graph_function file in the debugfs tracing directory.
855 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
856 support via parallel port (up to 5 devices per port)
857 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
858 See also Documentation/input/joystick-parport.txt
862 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
866 gcov_persist= [GCOV] When non-zero (default), profiling data for
867 kernel modules is saved and remains accessible via
868 debugfs, even when the module is unloaded/reloaded.
869 When zero, profiling data is discarded and associated
870 debugfs files are removed at module unload time.
872 gpt [EFI] Forces disk with valid GPT signature but
873 invalid Protective MBR to be treated as GPT.
875 hashdist= [KNL,NUMA] Large hashes allocated during boot
876 are distributed across NUMA nodes. Defaults on
877 for 64-bit NUMA, off otherwise.
878 Format: 0 | 1 (for off | on)
880 hcl= [IA-64] SGI's Hardware Graph compatibility layer
882 hd= [EIDE] (E)IDE hard drive subsystem geometry
883 Format: <cyl>,<head>,<sect>
886 Disable Hardware Error Source Table (HEST) support;
887 corresponding firmware-first mode error processing
888 logic will be disabled.
890 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
891 size of <nn>. This works even on boxes that have no
892 highmem otherwise. This also works to reduce highmem
893 size on bigger boxes.
895 highres= [KNL] Enable/disable high resolution timer mode.
896 Valid parameters: "on", "off"
900 See Documentation/isdn/README.HiSax.
904 hpet= [X86-32,HPET] option to control HPET usage
905 Format: { enable (default) | disable | force |
907 disable: disable HPET and use PIT instead
908 force: allow force enabled of undocumented chips (ICH4,
910 verbose: show contents of HPET registers during setup
912 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
913 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
914 On x86-64 and powerpc, this option can be specified
915 multiple times interleaved with hugepages= to reserve
916 huge pages of different sizes. Valid pages sizes on
917 x86-64 are 2M (when the CPU supports "pse") and 1G
918 (when the CPU supports the "pdpe1gb" cpuinfo flag)
919 Note that 1GB pages can only be allocated at boot time
920 using hugepages= and not freed afterwards.
922 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
923 terminal devices. Valid values: 0..8
924 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
925 If specified, z/VM IUCV HVC accepts connections
926 from listed z/VM user IDs only.
929 Do not unregister boot console at start. This is only
930 useful for debugging when something happens in the window
931 between unregistering the boot console and initializing
934 i2c_bus= [HW] Override the default board specific I2C bus speed
935 or register an additional I2C bus that is not
936 registered from board initialization code.
940 i8042.debug [HW] Toggle i8042 debug mode
941 i8042.direct [HW] Put keyboard port into non-translated mode
942 i8042.dumbkbd [HW] Pretend that controller can only read data from
943 keyboard and cannot control its state
944 (Don't attempt to blink the leds)
945 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
946 i8042.nokbd [HW] Don't check/create keyboard port
947 i8042.noloop [HW] Disable the AUX Loopback command while probing
949 i8042.nomux [HW] Don't check presence of an active multiplexing
951 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
953 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
954 i8042.reset [HW] Reset the controller during init and cleanup
955 i8042.unlock [HW] Unlock (ignore) the keylock
959 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
960 indicates that the driver is running on unsupported
962 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
963 does not match list of supported models.
965 [HW] Report power status in /proc/i8k
966 (disabled by default)
967 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
970 i915.invert_brightness
971 [DRM] Invert the sense of the variable that is used to
972 set the brightness of the panel backlight. Normally a
973 value of 0 indicates backlight switched off, and the
974 maximum value sets the backlight to maximum brightness.
975 If this parameter is specified, a value of 0 sets the
976 backlight to maximum brightness, and the maximum value
977 switches the backlight off.
980 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
982 ide-core.nodma= [HW] (E)IDE subsystem
983 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
984 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
985 .cdrom .chs .ignore_cable are additional options
986 See Documentation/ide/ide.txt.
988 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
989 Claim all unknown PCI IDE storage controllers.
992 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
993 Poll forces a polling idle loop that can slightly
994 improve the performance of waking up a idle CPU, but
995 will use a lot of power and make the system run hot.
997 idle=mwait: On systems which support MONITOR/MWAIT but
998 the kernel chose to not use it because it doesn't save
999 as much power as a normal idle loop, use the
1000 MONITOR/MWAIT idle loop anyways. Performance should be
1001 the same as idle=poll.
1002 idle=halt: Halt is forced to be used for CPU idle.
1003 In such case C2/C3 won't be used again.
1004 idle=nomwait: Disable mwait for CPU C-states
1006 ignore_loglevel [KNL]
1007 Ignore loglevel setting - this will print /all/
1008 kernel messages to the console. Useful for debugging.
1009 We also add it as printk module parameter, so users
1010 could change it dynamically, usually by
1011 /sys/module/printk/parameters/ignore_loglevel.
1013 ihash_entries= [KNL]
1014 Set number of hash buckets for inode cache.
1017 Format: { "0" | "1" }
1018 0 -- integrity auditing messages. (Default)
1019 1 -- enable informational integrity auditing messages.
1022 Format: { "sha1" | "md5" }
1026 Load a policy which meets the needs of the Trusted
1027 Computing Base. This means IMA will measure all
1028 programs exec'd, files mmap'd for exec, and all files
1029 opened for read by uid=0.
1033 Run specified binary instead of /sbin/init as init
1036 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1037 for working out where the kernel is dying during
1040 initrd= [BOOT] Specify the location of the initial ramdisk
1042 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1045 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1047 Enable intel iommu driver.
1049 Disable intel iommu driver.
1050 igfx_off [Default Off]
1051 By default, gfx is mapped as normal device. If a gfx
1052 device has a dedicated DMAR unit, the DMAR unit is
1053 bypassed by not enabling DMAR with this option. In
1054 this case, gfx device will use physical address for
1057 With this option iommu will not optimize to look
1058 for io virtual address below 32-bit forcing dual
1059 address cycle on pci bus for cards supporting greater
1060 than 32-bit addressing. The default is to look
1061 for translation below 32-bit and if not available
1062 then look in the higher range.
1063 strict [Default Off]
1064 With this option on every unmap_single operation will
1065 result in a hardware IOTLB flush operation as opposed
1066 to batching them for performance.
1067 sp_off [Default Off]
1068 By default, super page will be supported if Intel IOMMU
1069 has the capability. With this option, super page will
1072 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1073 0 disables intel_idle and fall back on acpi_idle.
1074 1 to 6 specify maximum depth of C-state.
1076 intremap= [X86-64, Intel-IOMMU]
1077 on enable Interrupt Remapping (default)
1078 off disable Interrupt Remapping
1079 nosid disable Source ID checking
1081 BIOS x2APIC opt-out request will be ignored
1085 iomem= Disable strict checking of access to MMIO memory
1086 strict regions from userspace.
1101 group_mf [x86, IA-64]
1104 io7= [HW] IO7 for Marvel based alpha systems
1105 See comment before marvel_specify_io7 in
1106 arch/alpha/kernel/core_marvel.c.
1108 io_delay= [X86] I/O delay method
1110 Standard port 0x80 based delay
1112 Alternate port 0xed based delay (needed on some systems)
1114 Simple two microseconds delay
1119 See Documentation/filesystems/nfs/nfsroot.txt.
1121 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1122 See comment before ip2_setup() in
1123 drivers/char/ip2/ip2base.c.
1126 When an interrupt is not handled search all handlers
1127 for it. Intended to get systems with badly broken
1131 When an interrupt is not handled search all handlers
1132 for it. Also check all handlers each timer
1133 interrupt. Intended to get systems with badly broken
1137 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1139 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1141 <cpu number>,...,<cpu number>
1143 <cpu number>-<cpu number>
1144 (must be a positive range in ascending order)
1146 <cpu number>,...,<cpu number>-<cpu number>
1148 This option can be used to specify one or more CPUs
1149 to isolate from the general SMP balancing and scheduling
1150 algorithms. You can move a process onto or off an
1151 "isolated" CPU via the CPU affinity syscalls or cpuset.
1152 <cpu number> begins at 0 and the maximum value is
1153 "number of CPUs in system - 1".
1155 This option is the preferred way to isolate CPUs. The
1156 alternative -- manually setting the CPU mask of all
1157 tasks in the system -- can cause problems and
1158 suboptimal load balancer performance.
1162 js= [HW,JOY] Analog joystick
1163 See Documentation/input/joystick.txt.
1167 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1168 specifies the amount of memory usable by the kernel
1169 for non-movable allocations. The requested amount is
1170 spread evenly throughout all nodes in the system. The
1171 remaining memory in each node is used for Movable
1172 pages. In the event, a node is too small to have both
1173 kernelcore and Movable pages, kernelcore pages will
1174 take priority and other nodes will have a larger number
1175 of kernelcore pages. The Movable zone is used for the
1176 allocation of pages that may be reclaimed or moved
1177 by the page migration subsystem. This means that
1178 HugeTLB pages may not be allocated from this zone.
1179 Note that allocations like PTEs-from-HighMem still
1180 use the HighMem zone if it exists, and the Normal
1181 zone if it does not.
1183 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1184 Format: <Controller#>[,poll interval]
1185 The controller # is the number of the ehci usb debug
1186 port as it is probed via PCI. The poll interval is
1187 optional and is the number seconds in between
1188 each poll cycle to the debug port in case you need
1189 the functionality for interrupting the kernel with
1190 gdb or control-c on the dbgp connection. When
1191 not using this parameter you use sysrq-g to break into
1192 the kernel debugger.
1194 kgdboc= [KGDB,HW] kgdb over consoles.
1195 Requires a tty driver that supports console polling,
1196 or a supported polling keyboard driver (non-usb).
1197 Serial only format: <serial_device>[,baud]
1198 keyboard only format: kbd
1199 keyboard and serial format: kbd,<serial_device>[,baud]
1200 Optional Kernel mode setting:
1201 kms, kbd format: kms,kbd
1202 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1204 kgdbwait [KGDB] Stop kernel execution and enter the
1205 kernel debugger at the earliest opportunity.
1207 kmac= [MIPS] korina ethernet MAC address.
1208 Configure the RouterBoard 532 series on-chip
1209 Ethernet adapter MAC address.
1211 kmemleak= [KNL] Boot-time kmemleak enable/disable
1212 Valid arguments: on, off
1215 kstack=N [X86] Print N words from the kernel stack
1218 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1219 Default is 0 (don't ignore, but inject #GP)
1221 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1225 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1226 Default is 1 (enabled)
1228 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1230 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1232 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1233 (virtualized MMU) support on capable Intel chips.
1234 Default is 1 (enabled)
1236 kvm-intel.emulate_invalid_guest_state=
1237 [KVM,Intel] Enable emulation of invalid guest states
1238 Default is 0 (disabled)
1240 kvm-intel.flexpriority=
1241 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1242 Default is 1 (enabled)
1245 [KVM,Intel] Enable VMX nesting (nVMX).
1246 Default is 0 (disabled)
1248 kvm-intel.unrestricted_guest=
1249 [KVM,Intel] Disable unrestricted guest feature
1250 (virtualized real and unpaged mode) on capable
1251 Intel chips. Default is 1 (enabled)
1253 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1254 feature (tagged TLBs) on capable Intel chips.
1255 Default is 1 (enabled)
1261 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1264 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1267 libata.dma= [LIBATA] DMA control
1268 libata.dma=0 Disable all PATA and SATA DMA
1269 libata.dma=1 PATA and SATA Disk DMA only
1270 libata.dma=2 ATAPI (CDROM) DMA only
1271 libata.dma=4 Compact Flash DMA only
1272 Combinations also work, so libata.dma=3 enables DMA
1273 for disks and CDROMs, but not CFs.
1275 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1276 libata.ignore_hpa=0 keep BIOS limits (default)
1277 libata.ignore_hpa=1 ignore limits, using full disk
1279 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1283 libata.force= [LIBATA] Force configurations. The format is comma
1284 separated list of "[ID:]VAL" where ID is
1285 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1286 matching port, link or device. Basically, it matches
1287 the ATA ID string printed on console by libata. If
1288 the whole ID part is omitted, the last PORT and DEVICE
1289 values are used. If ID hasn't been specified yet, the
1290 configuration applies to all ports, links and devices.
1292 If only DEVICE is omitted, the parameter applies to
1293 the port and all links and devices behind it. DEVICE
1294 number of 0 either selects the first device or the
1295 first fan-out link behind PMP device. It does not
1296 select the host link. DEVICE number of 15 selects the
1297 host link and device attached to it.
1299 The VAL specifies the configuration to force. As long
1300 as there's no ambiguity shortcut notation is allowed.
1301 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1302 The following configurations can be forced.
1304 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1305 Any ID with matching PORT is used.
1307 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1309 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1310 udma[/][16,25,33,44,66,100,133] notation is also
1313 * [no]ncq: Turn on or off NCQ.
1315 * nohrst, nosrst, norst: suppress hard, soft
1318 * dump_id: dump IDENTIFY data.
1320 If there are multiple matching configurations changing
1321 the same attribute, the last one is used.
1323 memblock=debug [KNL] Enable memblock debug messages.
1325 load_ramdisk= [RAM] List of ramdisks to load from floppy
1326 See Documentation/blockdev/ramdisk.txt.
1328 lockd.nlm_grace_period=P [NFS] Assign grace period.
1331 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1334 lockd.nlm_timeout=T [NFS] Assign timeout value.
1337 lockd.nlm_udpport=M [NFS] Assign UDP port.
1340 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1343 loglevel= All Kernel Messages with a loglevel smaller than the
1344 console loglevel will be printed to the console. It can
1345 also be changed with klogd or other programs. The
1346 loglevels are defined as follows:
1348 0 (KERN_EMERG) system is unusable
1349 1 (KERN_ALERT) action must be taken immediately
1350 2 (KERN_CRIT) critical conditions
1351 3 (KERN_ERR) error conditions
1352 4 (KERN_WARNING) warning conditions
1353 5 (KERN_NOTICE) normal but significant condition
1354 6 (KERN_INFO) informational
1355 7 (KERN_DEBUG) debug-level messages
1357 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1358 in bytes. n must be a power of two. The default
1359 size is set in the kernel config file.
1361 logo.nologo [FB] Disables display of the built-in Linux logo.
1362 This may be used to provide more screen space for
1363 kernel log messages and is useful when debugging
1364 kernel boot problems.
1366 lp=0 [LP] Specify parallel ports to use, e.g,
1367 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1368 lp=reset first parallel port). 'lp=0' disables the
1369 lp=auto printer driver. 'lp=reset' (which can be
1370 specified in addition to the ports) causes
1371 attached printers to be reset. Using
1372 lp=port1,port2,... specifies the parallel ports
1373 to associate lp devices with, starting with
1374 lp0. A port specification may be 'none' to skip
1375 that lp device, or a parport name such as
1376 'parport0'. Specifying 'lp=auto' instead of a
1377 port specification list means that device IDs
1378 from each port should be examined, to see if
1379 an IEEE 1284-compliant printer is attached; if
1380 so, the driver will manage that printer.
1381 See also header of drivers/char/lp.c.
1384 Sets loops_per_jiffy to given constant, thus avoiding
1385 time-consuming boot-time autodetection (up to 250 ms per
1386 CPU). 0 enables autodetection (default). To determine
1387 the correct value for your kernel, boot with normal
1388 autodetection and see what value is printed. Note that
1389 on SMP systems the preset will be applied to all CPUs,
1390 which is likely to cause problems if your CPUs need
1391 significantly divergent settings. An incorrect value
1392 will cause delays in the kernel to be wrong, leading to
1393 unpredictable I/O errors and other breakage. Although
1394 unlikely, in the extreme case this might damage your
1398 Format: <io>,<irq>,<dma>
1400 machvec= [IA-64] Force the use of a particular machine-vector
1401 (machvec) in a generic kernel.
1402 Example: machvec=hpzx1_swiotlb
1404 machtype= [Loongson] Share the same kernel image file between different
1406 Example: machtype=lemote-yeeloong-2f-7inch
1408 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1409 than or equal to this physical address is ignored.
1411 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1412 should make use of. maxcpus=n : n >= 0 limits the
1413 kernel to using 'n' processors. n=0 is a special case,
1414 it is equivalent to "nosmp", which also disables
1417 max_loop= [LOOP] The number of loop block devices that get
1418 (loop.max_loop) unconditionally pre-created at init time. The default
1419 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1420 of statically allocating a predefined number, loop
1421 devices can be requested on-demand with the
1422 /dev/loop-control interface.
1426 mce [X86-32] Machine Check Exception
1428 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1430 md= [HW] RAID subsystems devices and level
1431 See Documentation/md.txt.
1434 Format: <first>,<last>
1435 Specifies range of consoles to be captured by the MDA.
1437 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1438 Amount of memory to be used when the kernel is not able
1439 to see the whole system memory or for test.
1440 [X86-32] Use together with memmap= to avoid physical
1441 address space collisions. Without memmap= PCI devices
1442 could be placed at addresses belonging to unused RAM.
1444 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1448 [KNL,SH] Allow user to override the default size for
1449 per-device physically contiguous DMA buffers.
1451 memmap=exactmap [KNL,X86] Enable setting of an exact
1452 E820 memory map, as specified by the user.
1453 Such memmap=exactmap lines can be constructed based on
1454 BIOS output or other requirements. See the memmap=nn@ss
1457 memmap=nn[KMG]@ss[KMG]
1458 [KNL] Force usage of a specific region of memory
1459 Region of memory to be used, from ss to ss+nn.
1461 memmap=nn[KMG]#ss[KMG]
1462 [KNL,ACPI] Mark specific memory as ACPI data.
1463 Region of memory to be used, from ss to ss+nn.
1465 memmap=nn[KMG]$ss[KMG]
1466 [KNL,ACPI] Mark specific memory as reserved.
1467 Region of memory to be used, from ss to ss+nn.
1468 Example: Exclude memory from 0x18690000-0x1869ffff
1469 memmap=64K$0x18690000
1471 memmap=0x10000$0x18690000
1473 memory_corruption_check=0/1 [X86]
1474 Some BIOSes seem to corrupt the first 64k of
1475 memory when doing things like suspend/resume.
1476 Setting this option will scan the memory
1477 looking for corruption. Enabling this will
1478 both detect corruption and prevent the kernel
1479 from using the memory being corrupted.
1480 However, its intended as a diagnostic tool; if
1481 repeatable BIOS-originated corruption always
1482 affects the same memory, you can use memmap=
1483 to prevent the kernel from using that memory.
1485 memory_corruption_check_size=size [X86]
1486 By default it checks for corruption in the low
1487 64k, making this memory unavailable for normal
1488 use. Use this parameter to scan for
1489 corruption in more or less memory.
1491 memory_corruption_check_period=seconds [X86]
1492 By default it checks for corruption every 60
1493 seconds. Use this parameter to check at some
1494 other rate. 0 disables periodic checking.
1496 memtest= [KNL,X86] Enable memtest
1498 default : 0 <disable>
1499 Specifies the number of memtest passes to be
1500 performed. Each pass selects another test
1501 pattern from a given set of patterns. Memtest
1502 fills the memory with this pattern, validates
1503 memory contents and reserves bad memory
1504 regions that are detected.
1506 meye.*= [HW] Set MotionEye Camera parameters
1507 See Documentation/video4linux/meye.txt.
1509 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1510 Multi-Function General Purpose Timers on AMD Geode
1513 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1514 the BIOS has incorrectly applied a workaround. TinyBIOS
1515 version 0.98 is known to be affected, 0.99 fixes the
1516 problem by letting the user disable the workaround.
1520 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1521 physical address is ignored.
1523 mini2440= [ARM,HW,KNL]
1524 Format:[0..2][b][c][t]
1526 MINI2440 configuration specification:
1527 0 - The attached screen is the 3.5" TFT
1528 1 - The attached screen is the 7" TFT
1529 2 - The VGA Shield is attached (1024x768)
1530 Leaving out the screen size parameter will not load
1531 the TFT driver, and the framebuffer will be left
1533 b - Enable backlight. The TFT backlight pin will be
1534 linked to the kernel VESA blanking code and a GPIO
1535 LED. This parameter is not necessary when using the
1537 c - Enable the s3c camera interface.
1538 t - Reserved for enabling touchscreen support. The
1539 touchscreen support is not enabled in the mainstream
1540 kernel as of 2.6.30, a preliminary port can be found
1541 in the "bleeding edge" mini2440 support kernel at
1542 http://repo.or.cz/w/linux-2.6/mini2440.git
1545 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1546 parameter allows control of the logging verbosity for
1547 the additional memory initialisation checks. A value
1548 of 0 disables mminit logging and a level of 4 will
1549 log everything. Information is printed at KERN_DEBUG
1550 so loglevel=8 may also need to be specified.
1553 [MOUSE] Maximum time between finger touching and
1554 leaving touchpad surface for touch to be considered
1555 a tap and be reported as a left button click (for
1556 touchpads working in absolute mode only).
1558 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1559 reporting absolute coordinates, such as tablets
1560 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1561 reporting absolute coordinates, such as tablets
1563 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1564 is similar to kernelcore except it specifies the
1565 amount of memory used for migratable allocations.
1566 If both kernelcore and movablecore is specified,
1567 then kernelcore will be at *least* the specified
1568 value but may be more. If movablecore on its own
1569 is specified, the administrator must be careful
1570 that the amount of memory usable for all allocations
1573 MTD_Partition= [MTD]
1574 Format: <name>,<region-number>,<size>,<offset>
1576 MTD_Region= [MTD] Format:
1577 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1580 See drivers/mtd/cmdlinepart.c.
1582 multitce=off [PPC] This parameter disables the use of the pSeries
1583 firmware feature for updating multiple TCE entries
1586 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1588 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1590 boundary - index of last SLC block on Flex-OneNAND.
1591 The remaining blocks are configured as MLC blocks.
1592 lock - Configure if Flex-OneNAND boundary should be locked.
1593 Once locked, the boundary cannot be changed.
1594 1 indicates lock status, 0 indicates unlock status.
1597 ARM/S3C2412 JIVE boot control
1599 See arch/arm/mach-s3c2412/mach-jive.c
1601 mtouchusb.raw_coordinates=
1602 [HW] Make the MicroTouch USB driver use raw coordinates
1603 ('y', default) or cooked coordinates ('n')
1605 mtrr_chunk_size=nn[KMG] [X86]
1606 used for mtrr cleanup. It is largest continuous chunk
1607 that could hold holes aka. UC entries.
1609 mtrr_gran_size=nn[KMG] [X86]
1610 Used for mtrr cleanup. It is granularity of mtrr block.
1612 Large value could prevent small alignment from
1615 mtrr_spare_reg_nr=n [X86]
1617 Range: 0,7 : spare reg number
1619 Used for mtrr cleanup. It is spare mtrr entries number.
1620 Set to 2 or more if your graphical card needs more.
1622 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1624 netdev= [NET] Network devices parameters
1625 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1626 Note that mem_start is often overloaded to mean
1627 something different and driver-specific.
1628 This usage is only documented in each driver source
1632 [NETFILTER] Enable connection tracking flow accounting
1633 0 to disable accounting
1634 1 to enable accounting
1637 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1638 See Documentation/filesystems/nfs/nfsroot.txt.
1640 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1641 See Documentation/filesystems/nfs/nfsroot.txt.
1643 nfsrootdebug [NFS] enable nfsroot debugging messages.
1644 See Documentation/filesystems/nfs/nfsroot.txt.
1646 nfs.callback_tcpport=
1647 [NFS] set the TCP port on which the NFSv4 callback
1648 channel should listen.
1651 [NFS] sets the pathname to the program which is used
1652 to update the NFS client cache entries.
1654 nfs.cache_getent_timeout=
1655 [NFS] sets the timeout after which an attempt to
1656 update a cache entry is deemed to have failed.
1658 nfs.idmap_cache_timeout=
1659 [NFS] set the maximum lifetime for idmapper cache
1663 [NFS] enable 64-bit inode numbers.
1664 If zero, the NFS client will fake up a 32-bit inode
1665 number for the readdir() and stat() syscalls instead
1666 of returning the full 64-bit number.
1667 The default is to return 64-bit inode numbers.
1669 nfs.nfs4_disable_idmapping=
1670 [NFSv4] When set to the default of '1', this option
1671 ensures that both the RPC level authentication
1672 scheme and the NFS level operations agree to use
1673 numeric uids/gids if the mount is using the
1674 'sec=sys' security flavour. In effect it is
1675 disabling idmapping, which can make migration from
1676 legacy NFSv2/v3 systems to NFSv4 easier.
1677 Servers that do not support this mode of operation
1678 will be autodetected by the client, and it will fall
1679 back to using the idmapper.
1680 To turn off this behaviour, set the value to '0'.
1682 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1683 when a NMI is triggered.
1684 Format: [state][,regs][,debounce][,die]
1686 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1687 Format: [panic,][nopanic,][num]
1689 0 - turn nmi_watchdog off
1690 When panic is specified, panic when an NMI watchdog
1691 timeout occurs (or 'nopanic' to override the opposite
1693 This is useful when you use a panic=... timeout and
1694 need the box quickly up again.
1696 netpoll.carrier_timeout=
1697 [NET] Specifies amount of time (in seconds) that
1698 netpoll should wait for a carrier. By default netpoll
1701 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1702 emulation library even if a 387 maths coprocessor
1706 [HW] Never suspend the console
1707 Disable suspending of consoles during suspend and
1708 hibernate operations. Once disabled, debugging
1709 messages can reach various consoles while the rest
1710 of the system is being put to sleep (ie, while
1711 debugging driver suspend/resume hooks). This may
1712 not work reliably with all consoles, but is known
1713 to work with serial and VGA consoles.
1714 To facilitate more flexible debugging, we also add
1715 console_suspend, a printk module parameter to control
1716 it. Users could use console_suspend (usually
1717 /sys/module/printk/parameters/console_suspend) to
1718 turn on/off it dynamically.
1720 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1721 caches in the slab allocator. Saves per-node memory,
1722 but will impact performance.
1726 noapic [SMP,APIC] Tells the kernel to not make use of any
1727 IOAPICs that may be present in the system.
1729 noautogroup Disable scheduler automatic task group creation.
1731 nobats [PPC] Do not use BATs for mapping kernel lowmem
1732 on "Classic" PPC cores.
1736 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1738 nodelayacct [KNL] Disable per-task delay accounting
1740 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1742 nodsp [SH] Disable hardware DSP at boot time.
1744 noefi [X86] Disable EFI runtime services support.
1749 On X86-32 available only on PAE configured kernels.
1750 noexec=on: enable non-executable mappings (default)
1751 noexec=off: disable non-executable mappings
1754 Disable SMEP (Supervisor Mode Execution Protection)
1755 even if it is supported by processor.
1758 This affects only 32-bit executables.
1759 noexec32=on: enable non-executable mappings (default)
1760 read doesn't imply executable mappings
1761 noexec32=off: disable non-executable mappings
1762 read implies executable mappings
1764 nofpu [SH] Disable hardware FPU at boot time.
1766 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1767 register save and restore. The kernel will only save
1768 legacy floating-point registers on task switch.
1770 noxsave [BUGS=X86] Disables x86 extended register state save
1771 and restore using xsave. The kernel will fallback to
1772 enabling legacy floating-point and sse state.
1774 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1775 wfi(ARM) instruction doesn't work correctly and not to
1776 use it. This is also useful when using JTAG debugger.
1778 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1779 instruction doesn't work correctly and not to
1782 no_file_caps Tells the kernel not to honor file capabilities. The
1783 only way then for a file to be executed with privilege
1784 is to be setuid root or executed by root.
1786 nohalt [IA-64] Tells the kernel not to use the power saving
1787 function PAL_HALT_LIGHT when idle. This increases
1788 power-consumption. On the positive side, it reduces
1789 interrupt wake-up latency, which may improve performance
1790 in certain environments such as networked servers or
1793 nohz= [KNL] Boottime enable/disable dynamic ticks
1794 Valid arguments: on, off
1797 noiotrap [SH] Disables trapped I/O port accesses.
1799 noirqdebug [X86-32] Disables the code which attempts to detect and
1800 disable unhandled interrupt sources.
1802 no_timer_check [X86,APIC] Disables the code which tests for
1803 broken timer IRQ sources.
1805 noisapnp [ISAPNP] Disables ISA PnP code.
1807 noinitrd [RAM] Tells the kernel not to load any configured
1810 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1812 [Deprecated - use intremap=off]
1816 nojitter [IA-64] Disables jitter checking for ITC timers.
1818 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1820 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1823 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1824 steal time is computed, but won't influence scheduler
1827 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1829 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1831 noltlbs [PPC] Do not use large page/tlb entries for kernel
1832 lowmem mapping on PPC40x.
1834 nomca [IA-64] Disable machine check abort handling
1836 nomce [X86-32] Machine Check Exception
1838 nomfgpt [X86-32] Disable Multi-Function General Purpose
1839 Timer usage (for AMD Geode machines).
1841 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1842 shutdown the other cpus. Instead use the REBOOT_VECTOR
1845 nopat [X86] Disable PAT (page attribute table extension of
1846 pagetables) support.
1848 norandmaps Don't use address space randomization. Equivalent to
1849 echo 0 > /proc/sys/kernel/randomize_va_space
1851 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1853 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1854 with UP alternatives
1856 noresidual [PPC] Don't use residual data on PReP machines.
1858 nordrand [X86] Disable the direct use of the RDRAND
1859 instruction even if it is supported by the
1860 processor. RDRAND is still available to user
1863 noresume [SWSUSP] Disables resume and restores original swap
1866 no-scroll [VGA] Disables scrollback.
1867 This is required for the Braillex ib80-piezo Braille
1868 reader made by F.H. Papenmeier (Germany).
1872 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1874 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1875 and disable the IO APIC. legacy for "maxcpus=0".
1877 nosoftlockup [KNL] Disable the soft-lockup detector.
1879 nosync [HW,M68K] Disables sync negotiation for all devices.
1881 notsc [BUGS=X86-32] Disable Time Stamp Counter
1883 nousb [USB] Disable the USB subsystem
1885 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1889 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1891 nptcg= [IA-64] Override max number of concurrent global TLB
1892 purges which is reported from either PAL_VM_SUMMARY or
1895 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1896 could support. nr_cpus=n : n >= 1 limits the kernel to
1897 supporting 'n' processors. Later in runtime you can not
1898 use hotplug cpu feature to put more cpu back to online.
1899 just like you compile the kernel NR_CPUS=n
1901 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1903 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1904 one of ['zone', 'node', 'default'] can be specified
1905 This can be set from sysctl after boot.
1906 See Documentation/sysctl/vm.txt for details.
1908 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1909 See Documentation/debugging-via-ohci1394.txt for more
1912 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1913 Rather than timing out after 20 ms if an EC
1914 command is not properly ACKed, override the length
1915 of the timeout. We have interrupts disabled while
1916 waiting for the ACK, so if this is set too high
1917 interrupts *may* be lost!
1919 omap_mux= [OMAP] Override bootloader pin multiplexing.
1920 Format: <mux_mode0.mode_name=value>...
1921 For example, to override I2C bus2:
1922 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1924 oprofile.timer= [HW]
1925 Use timer interrupt instead of performance counters
1927 oprofile.cpu_type= Force an oprofile cpu type
1928 This might be useful if you have an older oprofile
1929 userland or if you want common events.
1930 Format: { arch_perfmon }
1931 arch_perfmon: [X86] Force use of architectural
1932 perfmon on Intel CPUs instead of the
1933 CPU specific event set.
1934 timer: [X86] Force use of architectural NMI
1935 timer mode (see also oprofile.timer
1936 for generic hr timer mode)
1937 [s390] Force legacy basic mode sampling
1938 (report cpu_type "timer")
1940 oops=panic Always panic on oopses. Default is to just kill the
1941 process, but there is a small probability of
1942 deadlocking the machine.
1943 This will also cause panics on machine check exceptions.
1944 Useful together with panic=30 to trigger a reboot.
1947 See Documentation/sound/oss/oss-parameters.txt
1949 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1950 timeout > 0: seconds before rebooting
1951 timeout = 0: wait forever
1952 timeout < 0: reboot immediately
1955 parkbd.port= [HW] Parallel port number the keyboard adapter is
1956 connected to, default is 0.
1958 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1959 0 for XT, 1 for AT (default is AT).
1962 parport= [HW,PPT] Specify parallel ports. 0 disables.
1963 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1964 Use 'auto' to force the driver to use any
1965 IRQ/DMA settings detected (the default is to
1966 ignore detected IRQ/DMA settings because of
1967 possible conflicts). You can specify the base
1968 address, IRQ, and DMA settings; IRQ and DMA
1969 should be numbers, or 'auto' (for using detected
1970 settings on that particular port), or 'nofifo'
1971 (to avoid using a FIFO even if it is detected).
1972 Parallel ports are assigned in the order they
1973 are specified on the command line, starting
1976 parport_init_mode= [HW,PPT]
1977 Configure VIA parallel port to operate in
1978 a specific mode. This is necessary on Pegasos
1979 computer where firmware has no options for setting
1980 up parallel port mode and sets it to spp.
1981 Currently this function knows 686a and 8231 chips.
1982 Format: [spp|ps2|epp|ecp|ecpepp]
1985 Halt all CPUs after the first oops has been printed for
1986 the specified number of seconds. This is to be used if
1987 your oopses keep scrolling off the screen.
1992 See header of drivers/block/paride/pcd.c.
1993 See also Documentation/blockdev/paride.txt.
1995 pci=option[,option...] [PCI] various PCI subsystem options:
1996 earlydump [X86] dump PCI config space before the kernel
1998 off [X86] don't probe for the PCI bus
1999 bios [X86-32] force use of PCI BIOS, don't access
2000 the hardware directly. Use this if your machine
2001 has a non-standard PCI host bridge.
2002 nobios [X86-32] disallow use of PCI BIOS, only direct
2003 hardware access methods are allowed. Use this
2004 if you experience crashes upon bootup and you
2005 suspect they are caused by the BIOS.
2006 conf1 [X86] Force use of PCI Configuration
2008 conf2 [X86] Force use of PCI Configuration
2010 noaer [PCIE] If the PCIEAER kernel config parameter is
2011 enabled, this kernel boot option can be used to
2012 disable the use of PCIE advanced error reporting.
2013 nodomains [PCI] Disable support for multiple PCI
2014 root domains (aka PCI segments, in ACPI-speak).
2015 nommconf [X86] Disable use of MMCONFIG for PCI
2017 check_enable_amd_mmconf [X86] check for and enable
2018 properly configured MMIO access to PCI
2019 config space on AMD family 10h CPU
2020 nomsi [MSI] If the PCI_MSI kernel config parameter is
2021 enabled, this kernel boot option can be used to
2022 disable the use of MSI interrupts system-wide.
2023 noioapicquirk [APIC] Disable all boot interrupt quirks.
2024 Safety option to keep boot IRQs enabled. This
2025 should never be necessary.
2026 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2027 primary IO-APIC for bridges that cannot disable
2028 boot IRQs. This fixes a source of spurious IRQs
2029 when the system masks IRQs.
2030 noioapicreroute [APIC] Disable workaround that uses the
2031 boot IRQ equivalent of an IRQ that connects to
2032 a chipset where boot IRQs cannot be disabled.
2033 The opposite of ioapicreroute.
2034 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2035 routing table. These calls are known to be buggy
2036 on several machines and they hang the machine
2037 when used, but on other computers it's the only
2038 way to get the interrupt routing table. Try
2039 this option if the kernel is unable to allocate
2040 IRQs or discover secondary PCI buses on your
2042 rom [X86] Assign address space to expansion ROMs.
2043 Use with caution as certain devices share
2044 address decoders between ROMs and other
2046 norom [X86] Do not assign address space to
2047 expansion ROMs that do not already have
2048 BIOS assigned address ranges.
2049 nobar [X86] Do not assign address space to the
2050 BARs that weren't assigned by the BIOS.
2051 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2052 assigned automatically to PCI devices. You can
2053 make the kernel exclude IRQs of your ISA cards
2055 pirqaddr=0xAAAAA [X86] Specify the physical address
2056 of the PIRQ table (normally generated
2057 by the BIOS) if it is outside the
2058 F0000h-100000h range.
2059 lastbus=N [X86] Scan all buses thru bus #N. Can be
2060 useful if the kernel is unable to find your
2061 secondary buses and you want to tell it
2062 explicitly which ones they are.
2063 assign-busses [X86] Always assign all PCI bus
2064 numbers ourselves, overriding
2065 whatever the firmware may have done.
2066 usepirqmask [X86] Honor the possible IRQ mask stored
2067 in the BIOS $PIR table. This is needed on
2068 some systems with broken BIOSes, notably
2069 some HP Pavilion N5400 and Omnibook XE3
2070 notebooks. This will have no effect if ACPI
2071 IRQ routing is enabled.
2072 noacpi [X86] Do not use ACPI for IRQ routing
2073 or for PCI scanning.
2074 use_crs [X86] Use PCI host bridge window information
2075 from ACPI. On BIOSes from 2008 or later, this
2076 is enabled by default. If you need to use this,
2077 please report a bug.
2078 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2079 If you need to use this, please report a bug.
2080 routeirq Do IRQ routing for all PCI devices.
2081 This is normally done in pci_enable_device(),
2082 so this option is a temporary workaround
2083 for broken drivers that don't call it.
2084 skip_isa_align [X86] do not align io start addr, so can
2085 handle more pci cards
2086 firmware [ARM] Do not re-enumerate the bus but instead
2087 just use the configuration from the
2088 bootloader. This is currently used on
2089 IXP2000 systems where the bus has to be
2090 configured a certain way for adjunct CPUs.
2091 noearly [X86] Don't do any early type 1 scanning.
2092 This might help on some broken boards which
2093 machine check when some devices' config space
2094 is read. But various workarounds are disabled
2095 and some IOMMU drivers will not work.
2096 bfsort Sort PCI devices into breadth-first order.
2097 This sorting is done to get a device
2098 order compatible with older (<= 2.4) kernels.
2099 nobfsort Don't sort PCI devices into breadth-first order.
2100 cbiosize=nn[KMG] The fixed amount of bus space which is
2101 reserved for the CardBus bridge's IO window.
2102 The default value is 256 bytes.
2103 cbmemsize=nn[KMG] The fixed amount of bus space which is
2104 reserved for the CardBus bridge's memory
2105 window. The default value is 64 megabytes.
2108 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2109 Specifies alignment and device to reassign
2110 aligned memory resources.
2111 If <order of align> is not specified,
2112 PAGE_SIZE is used as alignment.
2113 PCI-PCI bridge can be specified, if resource
2114 windows need to be expanded.
2115 ecrc= Enable/disable PCIe ECRC (transaction layer
2116 end-to-end CRC checking).
2117 bios: Use BIOS/firmware settings. This is the
2121 realloc reallocate PCI resources if allocations done by BIOS
2124 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2127 force Enable ASPM even on devices that claim not to support it.
2128 WARNING: Forcing ASPM on may cause system lockups.
2130 pcie_ports= [PCIE] PCIe ports handling:
2131 auto Ask the BIOS whether or not to use native PCIe services
2132 associated with PCIe ports (PME, hot-plug, AER). Use
2133 them only if that is allowed by the BIOS.
2134 native Use native PCIe services associated with PCIe ports
2136 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2139 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2140 nomsi Do not use MSI for native PCIe PME signaling (this makes
2141 all PCIe root ports use INTx for all services).
2143 pcmv= [HW,PCMCIA] BadgePAD 4
2146 See Documentation/blockdev/paride.txt.
2148 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2151 See arch/parisc/kernel/pdc_chassis.c
2153 percpu_alloc= Select which percpu first chunk allocator to use.
2154 Currently supported values are "embed" and "page".
2155 Archs may support subset or none of the selections.
2156 See comments in mm/percpu.c for details on each
2157 allocator. This parameter is primarily for debugging
2158 and performance comparison.
2161 See Documentation/blockdev/paride.txt.
2164 See Documentation/blockdev/paride.txt.
2166 pirq= [SMP,APIC] Manual mp-table setup
2167 See Documentation/x86/i386/IO-APIC.txt.
2169 plip= [PPT,NET] Parallel port network link
2170 Format: { parport<nr> | timid | 0 }
2171 See also Documentation/parport.txt.
2173 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2174 Override pmtimer IOPort with a hex value.
2178 Enable PNP debug messages (depends on the
2179 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2180 via /sys/module/pnp/parameters/debug. We always show
2181 current resource usage; turning this on also shows
2182 possible settings and some assignment information.
2188 { on | off | curr | res | no-curr | no-res }
2191 [ISAPNP] Exclude IRQs for the autoconfiguration
2194 [ISAPNP] Exclude DMAs for the autoconfiguration
2196 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2197 Ranges are in pairs (I/O port base and size).
2200 [ISAPNP] Exclude memory regions for the
2202 Ranges are in pairs (memory base and size).
2204 ports= [IP_VS_FTP] IPVS ftp helper module
2206 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2208 Format: <port>,<port>....
2210 print-fatal-signals=
2211 [KNL] debug: print fatal signals
2213 If enabled, warn about various signal handling
2214 related application anomalies: too many signals,
2215 too many POSIX.1 timers, fatal signals causing a
2218 If you hit the warning due to signal overflow,
2219 you might want to try "ulimit -i unlimited".
2223 printk.time= Show timing data prefixed to each printk message line
2224 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2226 processor.max_cstate= [HW,ACPI]
2227 Limit processor to maximum C-state
2228 max_cstate=9 overrides any DMI blacklist limit.
2230 processor.nocst [HW,ACPI]
2231 Ignore the _CST method to determine C-states,
2232 instead using the legacy FADT method
2234 profile= [KNL] Enable kernel profiling via /proc/profile
2235 Format: [schedule,]<number>
2236 Param: "schedule" - profile schedule points.
2237 Param: <number> - step/bucket size as a power of 2 for
2238 statistical time based profiling.
2239 Param: "sleep" - profile D-state sleeping (millisecs).
2240 Requires CONFIG_SCHEDSTATS
2241 Param: "kvm" - profile VM exits.
2243 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2245 See Documentation/blockdev/ramdisk.txt.
2247 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2248 probe for; one of (bare|imps|exps|lifebook|any).
2249 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2251 psmouse.resetafter= [HW,MOUSE]
2252 Try to reset the device after so many bad packets
2255 [HW,MOUSE] Set desired mouse resolution, in dpi.
2256 psmouse.smartscroll=
2257 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2258 0 = disabled, 1 = enabled (default).
2260 pstore.backend= Specify the name of the pstore backend to use
2263 See Documentation/blockdev/paride.txt.
2266 [KNL] Number of legacy pty's. Overwrites compiled-in
2269 quiet [KNL] Disable most log messages
2274 See Documentation/md.txt.
2276 ramdisk_blocksize= [RAM]
2277 See Documentation/blockdev/ramdisk.txt.
2279 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2280 See Documentation/blockdev/ramdisk.txt.
2282 rcupdate.blimit= [KNL,BOOT]
2283 Set maximum number of finished RCU callbacks to process
2286 rcupdate.qhimark= [KNL,BOOT]
2287 Set threshold of queued
2288 RCU callbacks over which batch limiting is disabled.
2290 rcupdate.qlowmark= [KNL,BOOT]
2291 Set threshold of queued RCU callbacks below which
2292 batch limiting is re-enabled.
2296 Run specified binary instead of /init from the ramdisk,
2297 used for early userspace startup. See initrd.
2299 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2300 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2301 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2304 [KNL, SMP] Set scheduler's default relax_domain_level.
2305 See Documentation/cgroups/cpusets.txt.
2307 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2309 reservetop= [X86-32]
2311 Reserves a hole at the top of the kernel virtual
2316 Set the amount of memory to reserve for BIOS at
2317 the bottom of the address space.
2319 reset_devices [KNL] Force drivers to reset the underlying device
2320 during initialization.
2323 Specify the partition device for software suspend
2325 resume_offset= [SWSUSP]
2326 Specify the offset from the beginning of the partition
2327 given by "resume=" at which the swap header is located,
2328 in <PAGE_SIZE> units (needed only for swap files).
2329 See Documentation/power/swsusp-and-swap-files.txt
2331 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2332 read the resume files
2334 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2335 Useful for devices that are detected asynchronously
2336 (e.g. USB and MMC devices).
2338 hibernate= [HIBERNATION]
2339 noresume Don't check if there's a hibernation image
2340 present during boot.
2341 nocompress Don't compress/decompress hibernation images.
2343 retain_initrd [RAM] Keep initrd memory after extraction
2345 rhash_entries= [KNL,NET]
2346 Set number of hash buckets for route cache
2348 riscom8= [HW,SERIAL]
2349 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2351 ro [KNL] Mount root device read-only on boot
2353 root= [KNL] Root filesystem
2354 See name_to_dev_t comment in init/do_mounts.c.
2356 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2357 mount the root filesystem
2359 rootflags= [KNL] Set root filesystem mount option string
2361 rootfstype= [KNL] Set root filesystem type
2363 rootwait [KNL] Wait (indefinitely) for root device to show up.
2364 Useful for devices that are detected asynchronously
2365 (e.g. USB and MMC devices).
2367 rw [KNL] Mount root device read-write on boot
2369 S [KNL] Run init in single mode
2372 See drivers/net/irda/sa1100_ir.c.
2374 sbni= [NET] Granch SBNI12 leased line adapter
2376 sched_debug [KNL] Enables verbose scheduler debug messages.
2378 security= [SECURITY] Choose a security module to enable at boot.
2379 If this boot parameter is not specified, only the first
2380 security module asking for security registration will be
2381 loaded. An invalid security module name will be treated
2382 as if no module has been chosen.
2384 selinux= [SELINUX] Disable or enable SELinux at boot time.
2385 Format: { "0" | "1" }
2386 See security/selinux/Kconfig help text.
2389 Default value is set via kernel config option.
2390 If enabled at boot time, /selinux/disable can be used
2391 later to disable prior to initial policy load.
2393 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2394 Format: { "0" | "1" }
2395 See security/apparmor/Kconfig help text
2398 Default value is set via kernel config option.
2400 serialnumber [BUGS=X86-32]
2403 Maximal number of shapers.
2405 show_msr= [x86] show boot-time MSR settings
2406 Format: { <integer> }
2407 Show boot-time (BIOS-initialized) MSR settings.
2408 The parameter means the number of CPUs to show,
2409 for example 1 means boot CPU only.
2416 slab_max_order= [MM, SLAB]
2417 Determines the maximum allowed order for slabs.
2418 A high setting may cause OOMs due to memory
2419 fragmentation. Defaults to 1 for systems with
2420 more than 32MB of RAM, 0 otherwise.
2422 slub_debug[=options[,slabs]] [MM, SLUB]
2423 Enabling slub_debug allows one to determine the
2424 culprit if slab objects become corrupted. Enabling
2425 slub_debug can create guard zones around objects and
2426 may poison objects when not in use. Also tracks the
2427 last alloc / free. For more information see
2428 Documentation/vm/slub.txt.
2430 slub_max_order= [MM, SLUB]
2431 Determines the maximum allowed order for slabs.
2432 A high setting may cause OOMs due to memory
2433 fragmentation. For more information see
2434 Documentation/vm/slub.txt.
2436 slub_min_objects= [MM, SLUB]
2437 The minimum number of objects per slab. SLUB will
2438 increase the slab order up to slub_max_order to
2439 generate a sufficiently large slab able to contain
2440 the number of objects indicated. The higher the number
2441 of objects the smaller the overhead of tracking slabs
2442 and the less frequently locks need to be acquired.
2443 For more information see Documentation/vm/slub.txt.
2445 slub_min_order= [MM, SLUB]
2446 Determines the mininum page order for slabs. Must be
2447 lower than slub_max_order.
2448 For more information see Documentation/vm/slub.txt.
2450 slub_nomerge [MM, SLUB]
2451 Disable merging of slabs with similar size. May be
2452 necessary if there is some reason to distinguish
2453 allocs to different slabs. Debug options disable
2454 merging on their own.
2455 For more information see Documentation/vm/slub.txt.
2458 Format: <io1>[,<io2>[,...,<io8>]]
2460 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2461 attempt to substitute SMP alternatives once at boot.
2463 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2464 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2465 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2466 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2467 smsc-ircc2.ircc_irq= [HW] IRQ line
2468 smsc-ircc2.ircc_dma= [HW] DMA channel
2469 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2470 0: Toshiba Satellite 1800 (GP data pin select)
2471 1: Fast pin select (default)
2475 [KNL] Should the soft-lockup detector generate panics.
2478 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2479 See Documentation/laptops/sonypi.txt
2481 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2482 See Documentation/serial/specialix.txt.
2484 spia_io_base= [HW,MTD]
2490 Enabled the stack tracer on boot up.
2492 stacktrace_filter=[function-list]
2493 [FTRACE] Limit the functions that the stack tracer
2494 will trace at boot up. function-list is a comma separated
2495 list of functions. This list can be changed at run
2496 time by the stack_trace_filter file in the debugfs
2497 tracing directory. Note, this enables stack tracing
2498 and the stacktrace above is not needed.
2502 Set the STI (builtin display/keyboard on the HP-PARISC
2503 machines) console (graphic card) which should be used
2504 as the initial boot-console.
2505 See also comment in drivers/video/console/sticore.c.
2508 See comment in drivers/video/console/sticore.c.
2511 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2513 sunrpc.min_resvport=
2514 sunrpc.max_resvport=
2516 SunRPC servers often require that client requests
2517 originate from a privileged port (i.e. a port in the
2518 range 0 < portnr < 1024).
2519 An administrator who wishes to reserve some of these
2520 ports for other uses may adjust the range that the
2521 kernel's sunrpc client considers to be privileged
2522 using these two parameters to set the minimum and
2523 maximum port values.
2527 Control how the NFS server code allocates CPUs to
2528 service thread pools. Depending on how many NICs
2529 you have and where their interrupts are bound, this
2530 option will affect which CPUs will do NFS serving.
2531 Note: this parameter cannot be changed while the
2532 NFS server is running.
2534 auto the server chooses an appropriate mode
2535 automatically using heuristics
2536 global a single global pool contains all CPUs
2537 percpu one pool for each CPU
2538 pernode one pool for each NUMA node (equivalent
2539 to global on non-NUMA machines)
2541 sunrpc.tcp_slot_table_entries=
2542 sunrpc.udp_slot_table_entries=
2544 Sets the upper limit on the number of simultaneous
2545 RPC calls that can be sent from the client to a
2546 server. Increasing these values may allow you to
2547 improve throughput, but will also increase the
2548 amount of memory reserved for use by the client.
2551 [KNL] Enable accounting of swap in memory resource
2552 controller if no parameter or 1 is given or disable
2553 it if 0 is given (See Documentation/cgroups/memory.txt)
2555 swiotlb= [IA-64] Number of I/O TLB slabs
2559 sysfs.deprecated=0|1 [KNL]
2560 Enable/disable old style sysfs layout for old udev
2561 on older distributions. When this option is enabled
2562 very new udev will not work anymore. When this option
2563 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2564 in older udev will not work anymore.
2565 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2566 the kernel configuration.
2568 sysrq_always_enabled
2570 Ignore sysrq setting - this boot parameter will
2571 neutralize any effect of /proc/sys/kernel/sysrq.
2572 Useful for debugging.
2576 test_suspend= [SUSPEND]
2577 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2578 standby suspend) as the system sleep state to briefly
2579 enter during system startup. The system is woken from
2580 this state using a wakeup-capable RTC alarm.
2582 thash_entries= [KNL,NET]
2583 Set number of hash buckets for TCP connection
2585 thermal.act= [HW,ACPI]
2586 -1: disable all active trip points in all thermal zones
2587 <degrees C>: override all lowest active trip points
2589 thermal.crt= [HW,ACPI]
2590 -1: disable all critical trip points in all thermal zones
2591 <degrees C>: override all critical trip points
2593 thermal.nocrt= [HW,ACPI]
2594 Set to disable actions on ACPI thermal zone
2595 critical and hot trip points.
2597 thermal.off= [HW,ACPI]
2598 1: disable ACPI thermal control
2600 thermal.psv= [HW,ACPI]
2601 -1: disable all passive trip points
2602 <degrees C>: override all passive trip points to this
2605 thermal.tzp= [HW,ACPI]
2606 Specify global default ACPI thermal zone polling rate
2607 <deci-seconds>: poll all this frequency
2608 0: no polling (default)
2611 Force threading of all interrupt handlers except those
2612 marked explicitely IRQF_NO_THREAD.
2616 Specify if the kernel should make use of the cpu
2617 topology information if the hardware supports this.
2618 The scheduler will make use of this information and
2619 e.g. base its process migration decisions on it.
2624 tpm_suspend_pcr=[HW,TPM]
2625 Format: integer pcr id
2626 Specify that at suspend time, the tpm driver
2627 should extend the specified pcr with zeros,
2628 as a workaround for some chips which fail to
2629 flush the last written pcr on TPM_SaveState.
2630 This will guarantee that all the other pcrs
2633 trace_buf_size=nn[KMG]
2634 [FTRACE] will set tracing buffer size.
2636 trace_event=[event-list]
2637 [FTRACE] Set and start specified trace events in order
2638 to facilitate early boot debugging.
2639 See also Documentation/trace/events.txt
2641 tsc= Disable clocksource stability checks for TSC.
2643 [x86] reliable: mark tsc clocksource as reliable, this
2644 disables clocksource verification at runtime, as well
2645 as the stability checks done at bootup. Used to enable
2646 high-resolution timer mode on older hardware, and in
2647 virtualized environment.
2648 [x86] noirqtime: Do not use TSC to do irq accounting.
2649 Used to run time disable IRQ_TIME_ACCOUNTING on any
2650 platforms where RDTSC is slow and this accounting
2653 turbografx.map[2|3]= [HW,JOY]
2654 TurboGraFX parallel port interface
2656 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2657 See also Documentation/input/joystick-parport.txt
2659 udbg-immortal [PPC] When debugging early kernel crashes that
2660 happen after console_init() and before a proper
2661 console driver takes over, this boot options might
2662 help "seeing" what's going on.
2664 uhash_entries= [KNL,NET]
2665 Set number of hash buckets for UDP/UDP-Lite connections
2668 [USB] Ignore overcurrent events (default N).
2669 Some badly-designed motherboards generate lots of
2670 bogus events, for ports that aren't wired to
2671 anything. Set this parameter to avoid log spamming.
2672 Note that genuine overcurrent events won't be
2676 [X86] Cause panic on unknown NMI.
2678 usbcore.authorized_default=
2679 [USB] Default USB device authorization:
2680 (default -1 = authorized except for wireless USB,
2681 0 = not authorized, 1 = authorized)
2683 usbcore.autosuspend=
2684 [USB] The autosuspend time delay (in seconds) used
2685 for newly-detected USB devices (default 2). This
2686 is the time required before an idle device will be
2687 autosuspended. Devices for which the delay is set
2688 to a negative value won't be autosuspended at all.
2690 usbcore.usbfs_snoop=
2691 [USB] Set to log all usbfs traffic (default 0 = off).
2693 usbcore.blinkenlights=
2694 [USB] Set to cycle leds on hubs (default 0 = off).
2696 usbcore.old_scheme_first=
2697 [USB] Start with the old device initialization
2698 scheme (default 0 = off).
2700 usbcore.usbfs_memory_mb=
2701 [USB] Memory limit (in MB) for buffers allocated by
2702 usbfs (default = 16, 0 = max = 2047).
2704 usbcore.use_both_schemes=
2705 [USB] Try the other device initialization scheme
2706 if the first one fails (default 1 = enabled).
2708 usbcore.initial_descriptor_timeout=
2709 [USB] Specifies timeout for the initial 64-byte
2710 USB_REQ_GET_DESCRIPTOR request in milliseconds
2711 (default 5000 = 5.0 seconds).
2714 [USBHID] The interval which mice are to be polled at.
2716 usb-storage.delay_use=
2717 [UMS] The delay in seconds before a new device is
2718 scanned for Logical Units (default 5).
2721 [UMS] A list of quirks entries to supplement or
2722 override the built-in unusual_devs list. List
2723 entries are separated by commas. Each entry has
2724 the form VID:PID:Flags where VID and PID are Vendor
2725 and Product ID values (4-digit hex numbers) and
2726 Flags is a set of characters, each corresponding
2727 to a common usb-storage quirk flag as follows:
2728 a = SANE_SENSE (collect more than 18 bytes
2730 b = BAD_SENSE (don't collect more than 18
2731 bytes of sense data);
2732 c = FIX_CAPACITY (decrease the reported
2733 device capacity by one sector);
2734 d = NO_READ_DISC_INFO (don't use
2735 READ_DISC_INFO command);
2736 e = NO_READ_CAPACITY_16 (don't use
2737 READ_CAPACITY_16 command);
2738 h = CAPACITY_HEURISTICS (decrease the
2739 reported device capacity by one
2740 sector if the number is odd);
2741 i = IGNORE_DEVICE (don't bind to this
2743 l = NOT_LOCKABLE (don't try to lock and
2744 unlock ejectable media);
2745 m = MAX_SECTORS_64 (don't transfer more
2746 than 64 sectors = 32 KB at a time);
2747 n = INITIAL_READ10 (force a retry of the
2748 initial READ(10) command);
2749 o = CAPACITY_OK (accept the capacity
2750 reported by the device);
2751 r = IGNORE_RESIDUE (the device reports
2752 bogus residue values);
2753 s = SINGLE_LUN (the device has only one
2755 w = NO_WP_DETECT (don't test whether the
2756 medium is write-protected).
2757 Example: quirks=0419:aaf5:rl,0421:0433:rc
2759 user_debug= [KNL,ARM]
2761 See arch/arm/Kconfig.debug help text.
2762 1 - undefined instruction events
2764 4 - invalid data aborts
2767 Example: user_debug=31
2770 [X86] Flags controlling user PTE allocations.
2772 nohigh = do not allocate PTE pages in
2773 HIGHMEM regardless of setting
2777 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2778 vdso=1: enable VDSO (default)
2779 vdso=0: disable VDSO mapping
2782 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2783 vdso32=1: enable 32-bit VDSO (default)
2784 vdso32=0: disable 32-bit VDSO mapping
2787 vector=percpu: enable percpu vector domain
2789 video= [FB] Frame buffer configuration
2790 See Documentation/fb/modedb.txt.
2792 vga= [BOOT,X86-32] Select a particular video mode
2793 See Documentation/x86/boot.txt and
2794 Documentation/svga.txt.
2795 Use vga=ask for menu.
2796 This is actually a boot loader parameter; the value is
2797 passed to the kernel using a special protocol.
2799 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2800 size of <nn>. This can be used to increase the
2801 minimum size (128MB on x86). It can also be used to
2802 decrease the size and leave more room for directly
2805 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2808 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2811 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2815 Controls the behavior of vsyscalls (i.e. calls to
2816 fixed addresses of 0xffffffffff600x00 from legacy
2817 code). Most statically-linked binaries and older
2818 versions of glibc use these calls. Because these
2819 functions are at fixed addresses, they make nice
2820 targets for exploits that can control RIP.
2822 emulate [default] Vsyscalls turn into traps and are
2823 emulated reasonably safely.
2825 native Vsyscalls are native syscall instructions.
2826 This is a little bit faster than trapping
2827 and makes a few dynamic recompilers work
2828 better than they would in emulation mode.
2829 It also makes exploits much easier to write.
2831 none Vsyscalls don't work at all. This makes
2832 them quite hard to use for exploits but
2833 might break your system.
2835 vt.cur_default= [VT] Default cursor shape.
2836 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2837 the parameters of the <Esc>[?A;B;Cc escape sequence;
2838 see VGA-softcursor.txt. Default: 2 = underline.
2840 vt.default_blu= [VT]
2841 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2842 Change the default blue palette of the console.
2843 This is a 16-member array composed of values
2846 vt.default_grn= [VT]
2847 Format: <green0>,<green1>,<green2>,...,<green15>
2848 Change the default green palette of the console.
2849 This is a 16-member array composed of values
2852 vt.default_red= [VT]
2853 Format: <red0>,<red1>,<red2>,...,<red15>
2854 Change the default red palette of the console.
2855 This is a 16-member array composed of values
2861 Set system-wide default UTF-8 mode for all tty's.
2862 Default is 1, i.e. UTF-8 mode is enabled for all
2863 newly opened terminals.
2865 vt.global_cursor_default=
2868 Set system-wide default for whether a cursor
2869 is shown on new VTs. Default is -1,
2870 i.e. cursors will be created by default unless
2871 overridden by individual drivers. 0 will hide
2872 cursors, 1 will display them.
2874 watchdog timers [HW,WDT] For information on watchdog timers,
2875 see Documentation/watchdog/watchdog-parameters.txt
2876 or other driver-specific files in the
2877 Documentation/watchdog/ directory.
2879 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2880 default x2apic cluster mode on platforms
2883 x86_mrst_timer= [X86-32,APBT]
2884 Choose timer option for x86 Moorestown MID platform.
2885 Two valid options are apbt timer only and lapic timer
2886 plus one apbt timer for broadcast timer.
2887 x86_mrst_timer=apbt_only | lapic_and_apbt
2889 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2890 xd_geo= See header of drivers/block/xd.c.
2892 xen_emul_unplug= [HW,X86,XEN]
2893 Unplug Xen emulated devices
2894 Format: [unplug0,][unplug1]
2895 ide-disks -- unplug primary master IDE devices
2896 aux-ide-disks -- unplug non-primary-master IDE devices
2897 nics -- unplug network devices
2898 all -- unplug all emulated devices (NICs and IDE disks)
2899 unnecessary -- unplugging emulated devices is
2900 unnecessary even if the host did not respond to
2902 never -- do not unplug even if version check succeeds
2904 xirc2ps_cs= [NET,PCMCIA]
2906 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2908 ______________________________________________________________________
2912 Add more DRM drivers.
projects / mirror_ubuntu-artful-kernel.git / blob