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.
716 drm_kms_helper.edid_firmware=[<connector>:]<file>
717 Broken monitors, graphic adapters and KVMs may
718 send no or incorrect EDID data sets. This parameter
719 allows to specify an EDID data set in the
720 /lib/firmware directory that is used instead.
721 Generic built-in EDID data sets are used, if one of
722 edid/1024x768.bin, edid/1280x1024.bin,
723 edid/1680x1050.bin, or edid/1920x1080.bin is given
724 and no file with the same name exists. Details and
725 instructions how to build your own EDID data are
726 available in Documentation/EDID/HOWTO.txt. An EDID
727 data set will only be used for a particular connector,
728 if its name and a colon are prepended to the EDID
733 earlycon= [KNL] Output early console device and options.
734 uart[8250],io,<addr>[,options]
735 uart[8250],mmio,<addr>[,options]
736 uart[8250],mmio32,<addr>[,options]
737 Start an early, polled-mode console on the 8250/16550
738 UART at the specified I/O port or MMIO address.
739 MMIO inter-register address stride is either 8-bit
740 (mmio) or 32-bit (mmio32).
741 The options are the same as for ttyS, above.
743 earlyprintk= [X86,SH,BLACKFIN]
745 earlyprintk=serial[,ttySn[,baudrate]]
746 earlyprintk=ttySn[,baudrate]
747 earlyprintk=dbgp[debugController#]
749 Append ",keep" to not disable it when the real console
752 Only vga or serial or usb debug port at a time.
754 Currently only ttyS0 and ttyS1 are supported.
756 Interaction with the standard serial driver is not
759 The VGA output is eventually overwritten by the real
762 ekgdboc= [X86,KGDB] Allow early kernel console debugging
765 This is designed to be used in conjunction with
766 the boot argument: earlyprintk=vga
769 Format: {"off" | "on" | "skip[mbr]"}
771 eisa_irq_edge= [PARISC,HW]
772 See header of drivers/parisc/eisa.c.
775 See comment before function elanfreq_setup() in
776 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
779 Format: {"cfq" | "deadline" | "noop"}
780 See Documentation/block/cfq-iosched.txt and
781 Documentation/block/deadline-iosched.txt for details.
783 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
784 Specifies physical address of start of kernel core
785 image elf header and optionally the size. Generally
786 kexec loader will pass this option to capture kernel.
787 See Documentation/kdump/kdump.txt for details.
789 enable_mtrr_cleanup [X86]
790 The kernel tries to adjust MTRR layout from continuous
791 to discrete, to make X server driver able to add WB
792 entry later. This parameter enables that.
794 enable_timer_pin_1 [X86]
795 Enable PIN 1 of APIC timer
796 Can be useful to work around chipset bugs
797 (in particular on some ATI chipsets).
798 The kernel tries to set a reasonable default.
800 enforcing [SELINUX] Set initial enforcing status.
802 See security/selinux/Kconfig help text.
803 0 -- permissive (log only, no denials).
804 1 -- enforcing (deny and log).
806 Value can be changed at runtime via /selinux/enforce.
809 Disable Error Record Serialization Table (ERST)
812 ether= [HW,NET] Ethernet cards parameters
813 This option is obsoleted by the "netdev=" option, which
814 has equivalent usage. See its documentation for details.
818 Permit 'security.evm' to be updated regardless of
819 current integrity status.
823 fail_make_request=[KNL]
824 General fault injection mechanism.
825 Format: <interval>,<probability>,<space>,<times>
826 See also Documentation/fault-injection/.
829 See Documentation/blockdev/floppy.txt.
831 force_pal_cache_flush
832 [IA-64] Avoid check_sal_cache_flush which may hang on
833 buggy SAL_CACHE_FLUSH implementations. Using this
834 parameter will force ia64_sal_cache_flush to call
835 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
838 [FTRACE] will set and start the specified tracer
839 as early as possible in order to facilitate early
842 ftrace_dump_on_oops[=orig_cpu]
843 [FTRACE] will dump the trace buffers on oops.
844 If no parameter is passed, ftrace will dump
845 buffers of all CPUs, but if you pass orig_cpu, it will
846 dump only the buffer of the CPU that triggered the
849 ftrace_filter=[function-list]
850 [FTRACE] Limit the functions traced by the function
851 tracer at boot up. function-list is a comma separated
852 list of functions. This list can be changed at run
853 time by the set_ftrace_filter file in the debugfs
856 ftrace_notrace=[function-list]
857 [FTRACE] Do not trace the functions specified in
858 function-list. This list can be changed at run time
859 by the set_ftrace_notrace file in the debugfs
862 ftrace_graph_filter=[function-list]
863 [FTRACE] Limit the top level callers functions traced
864 by the function graph tracer at boot up.
865 function-list is a comma separated list of functions
866 that can be changed at run time by the
867 set_graph_function file in the debugfs tracing directory.
870 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
871 support via parallel port (up to 5 devices per port)
872 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
873 See also Documentation/input/joystick-parport.txt
877 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
881 gcov_persist= [GCOV] When non-zero (default), profiling data for
882 kernel modules is saved and remains accessible via
883 debugfs, even when the module is unloaded/reloaded.
884 When zero, profiling data is discarded and associated
885 debugfs files are removed at module unload time.
887 gpt [EFI] Forces disk with valid GPT signature but
888 invalid Protective MBR to be treated as GPT.
890 hashdist= [KNL,NUMA] Large hashes allocated during boot
891 are distributed across NUMA nodes. Defaults on
892 for 64-bit NUMA, off otherwise.
893 Format: 0 | 1 (for off | on)
895 hcl= [IA-64] SGI's Hardware Graph compatibility layer
897 hd= [EIDE] (E)IDE hard drive subsystem geometry
898 Format: <cyl>,<head>,<sect>
901 Disable Hardware Error Source Table (HEST) support;
902 corresponding firmware-first mode error processing
903 logic will be disabled.
905 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
906 size of <nn>. This works even on boxes that have no
907 highmem otherwise. This also works to reduce highmem
908 size on bigger boxes.
910 highres= [KNL] Enable/disable high resolution timer mode.
911 Valid parameters: "on", "off"
915 See Documentation/isdn/README.HiSax.
919 hpet= [X86-32,HPET] option to control HPET usage
920 Format: { enable (default) | disable | force |
922 disable: disable HPET and use PIT instead
923 force: allow force enabled of undocumented chips (ICH4,
925 verbose: show contents of HPET registers during setup
927 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
928 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
929 On x86-64 and powerpc, this option can be specified
930 multiple times interleaved with hugepages= to reserve
931 huge pages of different sizes. Valid pages sizes on
932 x86-64 are 2M (when the CPU supports "pse") and 1G
933 (when the CPU supports the "pdpe1gb" cpuinfo flag)
934 Note that 1GB pages can only be allocated at boot time
935 using hugepages= and not freed afterwards.
937 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
938 terminal devices. Valid values: 0..8
939 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
940 If specified, z/VM IUCV HVC accepts connections
941 from listed z/VM user IDs only.
944 Do not unregister boot console at start. This is only
945 useful for debugging when something happens in the window
946 between unregistering the boot console and initializing
949 i2c_bus= [HW] Override the default board specific I2C bus speed
950 or register an additional I2C bus that is not
951 registered from board initialization code.
955 i8042.debug [HW] Toggle i8042 debug mode
956 i8042.direct [HW] Put keyboard port into non-translated mode
957 i8042.dumbkbd [HW] Pretend that controller can only read data from
958 keyboard and cannot control its state
959 (Don't attempt to blink the leds)
960 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
961 i8042.nokbd [HW] Don't check/create keyboard port
962 i8042.noloop [HW] Disable the AUX Loopback command while probing
964 i8042.nomux [HW] Don't check presence of an active multiplexing
966 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
968 i8042.notimeout [HW] Ignore timeout condition signalled by controller
969 i8042.reset [HW] Reset the controller during init and cleanup
970 i8042.unlock [HW] Unlock (ignore) the keylock
974 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
975 indicates that the driver is running on unsupported
977 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
978 does not match list of supported models.
980 [HW] Report power status in /proc/i8k
981 (disabled by default)
982 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
986 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
988 ide-core.nodma= [HW] (E)IDE subsystem
989 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
990 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
991 .cdrom .chs .ignore_cable are additional options
992 See Documentation/ide/ide.txt.
994 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
995 Claim all unknown PCI IDE storage controllers.
998 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
999 Poll forces a polling idle loop that can slightly
1000 improve the performance of waking up a idle CPU, but
1001 will use a lot of power and make the system run hot.
1003 idle=mwait: On systems which support MONITOR/MWAIT but
1004 the kernel chose to not use it because it doesn't save
1005 as much power as a normal idle loop, use the
1006 MONITOR/MWAIT idle loop anyways. Performance should be
1007 the same as idle=poll.
1008 idle=halt: Halt is forced to be used for CPU idle.
1009 In such case C2/C3 won't be used again.
1010 idle=nomwait: Disable mwait for CPU C-states
1012 ignore_loglevel [KNL]
1013 Ignore loglevel setting - this will print /all/
1014 kernel messages to the console. Useful for debugging.
1015 We also add it as printk module parameter, so users
1016 could change it dynamically, usually by
1017 /sys/module/printk/parameters/ignore_loglevel.
1019 ihash_entries= [KNL]
1020 Set number of hash buckets for inode cache.
1023 Format: { "0" | "1" }
1024 0 -- integrity auditing messages. (Default)
1025 1 -- enable informational integrity auditing messages.
1028 Format: { "sha1" | "md5" }
1032 Load a policy which meets the needs of the Trusted
1033 Computing Base. This means IMA will measure all
1034 programs exec'd, files mmap'd for exec, and all files
1035 opened for read by uid=0.
1039 Run specified binary instead of /sbin/init as init
1042 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1043 for working out where the kernel is dying during
1046 initrd= [BOOT] Specify the location of the initial ramdisk
1048 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1051 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1053 Enable intel iommu driver.
1055 Disable intel iommu driver.
1056 igfx_off [Default Off]
1057 By default, gfx is mapped as normal device. If a gfx
1058 device has a dedicated DMAR unit, the DMAR unit is
1059 bypassed by not enabling DMAR with this option. In
1060 this case, gfx device will use physical address for
1063 With this option iommu will not optimize to look
1064 for io virtual address below 32-bit forcing dual
1065 address cycle on pci bus for cards supporting greater
1066 than 32-bit addressing. The default is to look
1067 for translation below 32-bit and if not available
1068 then look in the higher range.
1069 strict [Default Off]
1070 With this option on every unmap_single operation will
1071 result in a hardware IOTLB flush operation as opposed
1072 to batching them for performance.
1073 sp_off [Default Off]
1074 By default, super page will be supported if Intel IOMMU
1075 has the capability. With this option, super page will
1078 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1079 0 disables intel_idle and fall back on acpi_idle.
1080 1 to 6 specify maximum depth of C-state.
1082 intremap= [X86-64, Intel-IOMMU]
1083 on enable Interrupt Remapping (default)
1084 off disable Interrupt Remapping
1085 nosid disable Source ID checking
1087 BIOS x2APIC opt-out request will be ignored
1091 iomem= Disable strict checking of access to MMIO memory
1092 strict regions from userspace.
1107 group_mf [x86, IA-64]
1110 io7= [HW] IO7 for Marvel based alpha systems
1111 See comment before marvel_specify_io7 in
1112 arch/alpha/kernel/core_marvel.c.
1114 io_delay= [X86] I/O delay method
1116 Standard port 0x80 based delay
1118 Alternate port 0xed based delay (needed on some systems)
1120 Simple two microseconds delay
1125 See Documentation/filesystems/nfs/nfsroot.txt.
1127 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1128 See comment before ip2_setup() in
1129 drivers/char/ip2/ip2base.c.
1132 When an interrupt is not handled search all handlers
1133 for it. Intended to get systems with badly broken
1137 When an interrupt is not handled search all handlers
1138 for it. Also check all handlers each timer
1139 interrupt. Intended to get systems with badly broken
1143 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1145 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1147 <cpu number>,...,<cpu number>
1149 <cpu number>-<cpu number>
1150 (must be a positive range in ascending order)
1152 <cpu number>,...,<cpu number>-<cpu number>
1154 This option can be used to specify one or more CPUs
1155 to isolate from the general SMP balancing and scheduling
1156 algorithms. You can move a process onto or off an
1157 "isolated" CPU via the CPU affinity syscalls or cpuset.
1158 <cpu number> begins at 0 and the maximum value is
1159 "number of CPUs in system - 1".
1161 This option is the preferred way to isolate CPUs. The
1162 alternative -- manually setting the CPU mask of all
1163 tasks in the system -- can cause problems and
1164 suboptimal load balancer performance.
1168 js= [HW,JOY] Analog joystick
1169 See Documentation/input/joystick.txt.
1173 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1174 specifies the amount of memory usable by the kernel
1175 for non-movable allocations. The requested amount is
1176 spread evenly throughout all nodes in the system. The
1177 remaining memory in each node is used for Movable
1178 pages. In the event, a node is too small to have both
1179 kernelcore and Movable pages, kernelcore pages will
1180 take priority and other nodes will have a larger number
1181 of kernelcore pages. The Movable zone is used for the
1182 allocation of pages that may be reclaimed or moved
1183 by the page migration subsystem. This means that
1184 HugeTLB pages may not be allocated from this zone.
1185 Note that allocations like PTEs-from-HighMem still
1186 use the HighMem zone if it exists, and the Normal
1187 zone if it does not.
1189 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1190 Format: <Controller#>[,poll interval]
1191 The controller # is the number of the ehci usb debug
1192 port as it is probed via PCI. The poll interval is
1193 optional and is the number seconds in between
1194 each poll cycle to the debug port in case you need
1195 the functionality for interrupting the kernel with
1196 gdb or control-c on the dbgp connection. When
1197 not using this parameter you use sysrq-g to break into
1198 the kernel debugger.
1200 kgdboc= [KGDB,HW] kgdb over consoles.
1201 Requires a tty driver that supports console polling,
1202 or a supported polling keyboard driver (non-usb).
1203 Serial only format: <serial_device>[,baud]
1204 keyboard only format: kbd
1205 keyboard and serial format: kbd,<serial_device>[,baud]
1206 Optional Kernel mode setting:
1207 kms, kbd format: kms,kbd
1208 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1210 kgdbwait [KGDB] Stop kernel execution and enter the
1211 kernel debugger at the earliest opportunity.
1213 kmac= [MIPS] korina ethernet MAC address.
1214 Configure the RouterBoard 532 series on-chip
1215 Ethernet adapter MAC address.
1217 kmemleak= [KNL] Boot-time kmemleak enable/disable
1218 Valid arguments: on, off
1221 kstack=N [X86] Print N words from the kernel stack
1224 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1225 Default is 0 (don't ignore, but inject #GP)
1227 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1231 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1232 Default is 1 (enabled)
1234 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1236 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1238 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1239 (virtualized MMU) support on capable Intel chips.
1240 Default is 1 (enabled)
1242 kvm-intel.emulate_invalid_guest_state=
1243 [KVM,Intel] Enable emulation of invalid guest states
1244 Default is 0 (disabled)
1246 kvm-intel.flexpriority=
1247 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1248 Default is 1 (enabled)
1251 [KVM,Intel] Enable VMX nesting (nVMX).
1252 Default is 0 (disabled)
1254 kvm-intel.unrestricted_guest=
1255 [KVM,Intel] Disable unrestricted guest feature
1256 (virtualized real and unpaged mode) on capable
1257 Intel chips. Default is 1 (enabled)
1259 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1260 feature (tagged TLBs) on capable Intel chips.
1261 Default is 1 (enabled)
1267 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1270 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1273 libata.dma= [LIBATA] DMA control
1274 libata.dma=0 Disable all PATA and SATA DMA
1275 libata.dma=1 PATA and SATA Disk DMA only
1276 libata.dma=2 ATAPI (CDROM) DMA only
1277 libata.dma=4 Compact Flash DMA only
1278 Combinations also work, so libata.dma=3 enables DMA
1279 for disks and CDROMs, but not CFs.
1281 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1282 libata.ignore_hpa=0 keep BIOS limits (default)
1283 libata.ignore_hpa=1 ignore limits, using full disk
1285 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1289 libata.force= [LIBATA] Force configurations. The format is comma
1290 separated list of "[ID:]VAL" where ID is
1291 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1292 matching port, link or device. Basically, it matches
1293 the ATA ID string printed on console by libata. If
1294 the whole ID part is omitted, the last PORT and DEVICE
1295 values are used. If ID hasn't been specified yet, the
1296 configuration applies to all ports, links and devices.
1298 If only DEVICE is omitted, the parameter applies to
1299 the port and all links and devices behind it. DEVICE
1300 number of 0 either selects the first device or the
1301 first fan-out link behind PMP device. It does not
1302 select the host link. DEVICE number of 15 selects the
1303 host link and device attached to it.
1305 The VAL specifies the configuration to force. As long
1306 as there's no ambiguity shortcut notation is allowed.
1307 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1308 The following configurations can be forced.
1310 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1311 Any ID with matching PORT is used.
1313 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1315 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1316 udma[/][16,25,33,44,66,100,133] notation is also
1319 * [no]ncq: Turn on or off NCQ.
1321 * nohrst, nosrst, norst: suppress hard, soft
1324 * dump_id: dump IDENTIFY data.
1326 If there are multiple matching configurations changing
1327 the same attribute, the last one is used.
1329 memblock=debug [KNL] Enable memblock debug messages.
1331 load_ramdisk= [RAM] List of ramdisks to load from floppy
1332 See Documentation/blockdev/ramdisk.txt.
1334 lockd.nlm_grace_period=P [NFS] Assign grace period.
1337 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1340 lockd.nlm_timeout=T [NFS] Assign timeout value.
1343 lockd.nlm_udpport=M [NFS] Assign UDP port.
1346 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1349 loglevel= All Kernel Messages with a loglevel smaller than the
1350 console loglevel will be printed to the console. It can
1351 also be changed with klogd or other programs. The
1352 loglevels are defined as follows:
1354 0 (KERN_EMERG) system is unusable
1355 1 (KERN_ALERT) action must be taken immediately
1356 2 (KERN_CRIT) critical conditions
1357 3 (KERN_ERR) error conditions
1358 4 (KERN_WARNING) warning conditions
1359 5 (KERN_NOTICE) normal but significant condition
1360 6 (KERN_INFO) informational
1361 7 (KERN_DEBUG) debug-level messages
1363 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1364 in bytes. n must be a power of two. The default
1365 size is set in the kernel config file.
1367 logo.nologo [FB] Disables display of the built-in Linux logo.
1368 This may be used to provide more screen space for
1369 kernel log messages and is useful when debugging
1370 kernel boot problems.
1372 lp=0 [LP] Specify parallel ports to use, e.g,
1373 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1374 lp=reset first parallel port). 'lp=0' disables the
1375 lp=auto printer driver. 'lp=reset' (which can be
1376 specified in addition to the ports) causes
1377 attached printers to be reset. Using
1378 lp=port1,port2,... specifies the parallel ports
1379 to associate lp devices with, starting with
1380 lp0. A port specification may be 'none' to skip
1381 that lp device, or a parport name such as
1382 'parport0'. Specifying 'lp=auto' instead of a
1383 port specification list means that device IDs
1384 from each port should be examined, to see if
1385 an IEEE 1284-compliant printer is attached; if
1386 so, the driver will manage that printer.
1387 See also header of drivers/char/lp.c.
1390 Sets loops_per_jiffy to given constant, thus avoiding
1391 time-consuming boot-time autodetection (up to 250 ms per
1392 CPU). 0 enables autodetection (default). To determine
1393 the correct value for your kernel, boot with normal
1394 autodetection and see what value is printed. Note that
1395 on SMP systems the preset will be applied to all CPUs,
1396 which is likely to cause problems if your CPUs need
1397 significantly divergent settings. An incorrect value
1398 will cause delays in the kernel to be wrong, leading to
1399 unpredictable I/O errors and other breakage. Although
1400 unlikely, in the extreme case this might damage your
1404 Format: <io>,<irq>,<dma>
1406 machvec= [IA-64] Force the use of a particular machine-vector
1407 (machvec) in a generic kernel.
1408 Example: machvec=hpzx1_swiotlb
1410 machtype= [Loongson] Share the same kernel image file between different
1412 Example: machtype=lemote-yeeloong-2f-7inch
1414 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1415 than or equal to this physical address is ignored.
1417 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1418 should make use of. maxcpus=n : n >= 0 limits the
1419 kernel to using 'n' processors. n=0 is a special case,
1420 it is equivalent to "nosmp", which also disables
1423 max_loop= [LOOP] The number of loop block devices that get
1424 (loop.max_loop) unconditionally pre-created at init time. The default
1425 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1426 of statically allocating a predefined number, loop
1427 devices can be requested on-demand with the
1428 /dev/loop-control interface.
1432 mce [X86-32] Machine Check Exception
1434 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1436 md= [HW] RAID subsystems devices and level
1437 See Documentation/md.txt.
1440 Format: <first>,<last>
1441 Specifies range of consoles to be captured by the MDA.
1443 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1444 Amount of memory to be used when the kernel is not able
1445 to see the whole system memory or for test.
1446 [X86-32] Use together with memmap= to avoid physical
1447 address space collisions. Without memmap= PCI devices
1448 could be placed at addresses belonging to unused RAM.
1450 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1454 [KNL,SH] Allow user to override the default size for
1455 per-device physically contiguous DMA buffers.
1457 memmap=exactmap [KNL,X86] Enable setting of an exact
1458 E820 memory map, as specified by the user.
1459 Such memmap=exactmap lines can be constructed based on
1460 BIOS output or other requirements. See the memmap=nn@ss
1463 memmap=nn[KMG]@ss[KMG]
1464 [KNL] Force usage of a specific region of memory
1465 Region of memory to be used, from ss to ss+nn.
1467 memmap=nn[KMG]#ss[KMG]
1468 [KNL,ACPI] Mark specific memory as ACPI data.
1469 Region of memory to be used, from ss to ss+nn.
1471 memmap=nn[KMG]$ss[KMG]
1472 [KNL,ACPI] Mark specific memory as reserved.
1473 Region of memory to be used, from ss to ss+nn.
1474 Example: Exclude memory from 0x18690000-0x1869ffff
1475 memmap=64K$0x18690000
1477 memmap=0x10000$0x18690000
1479 memory_corruption_check=0/1 [X86]
1480 Some BIOSes seem to corrupt the first 64k of
1481 memory when doing things like suspend/resume.
1482 Setting this option will scan the memory
1483 looking for corruption. Enabling this will
1484 both detect corruption and prevent the kernel
1485 from using the memory being corrupted.
1486 However, its intended as a diagnostic tool; if
1487 repeatable BIOS-originated corruption always
1488 affects the same memory, you can use memmap=
1489 to prevent the kernel from using that memory.
1491 memory_corruption_check_size=size [X86]
1492 By default it checks for corruption in the low
1493 64k, making this memory unavailable for normal
1494 use. Use this parameter to scan for
1495 corruption in more or less memory.
1497 memory_corruption_check_period=seconds [X86]
1498 By default it checks for corruption every 60
1499 seconds. Use this parameter to check at some
1500 other rate. 0 disables periodic checking.
1502 memtest= [KNL,X86] Enable memtest
1504 default : 0 <disable>
1505 Specifies the number of memtest passes to be
1506 performed. Each pass selects another test
1507 pattern from a given set of patterns. Memtest
1508 fills the memory with this pattern, validates
1509 memory contents and reserves bad memory
1510 regions that are detected.
1512 meye.*= [HW] Set MotionEye Camera parameters
1513 See Documentation/video4linux/meye.txt.
1515 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1516 Multi-Function General Purpose Timers on AMD Geode
1519 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1520 the BIOS has incorrectly applied a workaround. TinyBIOS
1521 version 0.98 is known to be affected, 0.99 fixes the
1522 problem by letting the user disable the workaround.
1526 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1527 physical address is ignored.
1529 mini2440= [ARM,HW,KNL]
1530 Format:[0..2][b][c][t]
1532 MINI2440 configuration specification:
1533 0 - The attached screen is the 3.5" TFT
1534 1 - The attached screen is the 7" TFT
1535 2 - The VGA Shield is attached (1024x768)
1536 Leaving out the screen size parameter will not load
1537 the TFT driver, and the framebuffer will be left
1539 b - Enable backlight. The TFT backlight pin will be
1540 linked to the kernel VESA blanking code and a GPIO
1541 LED. This parameter is not necessary when using the
1543 c - Enable the s3c camera interface.
1544 t - Reserved for enabling touchscreen support. The
1545 touchscreen support is not enabled in the mainstream
1546 kernel as of 2.6.30, a preliminary port can be found
1547 in the "bleeding edge" mini2440 support kernel at
1548 http://repo.or.cz/w/linux-2.6/mini2440.git
1551 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1552 parameter allows control of the logging verbosity for
1553 the additional memory initialisation checks. A value
1554 of 0 disables mminit logging and a level of 4 will
1555 log everything. Information is printed at KERN_DEBUG
1556 so loglevel=8 may also need to be specified.
1559 [MOUSE] Maximum time between finger touching and
1560 leaving touchpad surface for touch to be considered
1561 a tap and be reported as a left button click (for
1562 touchpads working in absolute mode only).
1564 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1565 reporting absolute coordinates, such as tablets
1566 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1567 reporting absolute coordinates, such as tablets
1569 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1570 is similar to kernelcore except it specifies the
1571 amount of memory used for migratable allocations.
1572 If both kernelcore and movablecore is specified,
1573 then kernelcore will be at *least* the specified
1574 value but may be more. If movablecore on its own
1575 is specified, the administrator must be careful
1576 that the amount of memory usable for all allocations
1579 MTD_Partition= [MTD]
1580 Format: <name>,<region-number>,<size>,<offset>
1582 MTD_Region= [MTD] Format:
1583 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1586 See drivers/mtd/cmdlinepart.c.
1588 multitce=off [PPC] This parameter disables the use of the pSeries
1589 firmware feature for updating multiple TCE entries
1592 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1594 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1596 boundary - index of last SLC block on Flex-OneNAND.
1597 The remaining blocks are configured as MLC blocks.
1598 lock - Configure if Flex-OneNAND boundary should be locked.
1599 Once locked, the boundary cannot be changed.
1600 1 indicates lock status, 0 indicates unlock status.
1603 ARM/S3C2412 JIVE boot control
1605 See arch/arm/mach-s3c2412/mach-jive.c
1607 mtouchusb.raw_coordinates=
1608 [HW] Make the MicroTouch USB driver use raw coordinates
1609 ('y', default) or cooked coordinates ('n')
1611 mtrr_chunk_size=nn[KMG] [X86]
1612 used for mtrr cleanup. It is largest continuous chunk
1613 that could hold holes aka. UC entries.
1615 mtrr_gran_size=nn[KMG] [X86]
1616 Used for mtrr cleanup. It is granularity of mtrr block.
1618 Large value could prevent small alignment from
1621 mtrr_spare_reg_nr=n [X86]
1623 Range: 0,7 : spare reg number
1625 Used for mtrr cleanup. It is spare mtrr entries number.
1626 Set to 2 or more if your graphical card needs more.
1628 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1630 netdev= [NET] Network devices parameters
1631 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1632 Note that mem_start is often overloaded to mean
1633 something different and driver-specific.
1634 This usage is only documented in each driver source
1638 [NETFILTER] Enable connection tracking flow accounting
1639 0 to disable accounting
1640 1 to enable accounting
1643 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1644 See Documentation/filesystems/nfs/nfsroot.txt.
1646 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1647 See Documentation/filesystems/nfs/nfsroot.txt.
1649 nfsrootdebug [NFS] enable nfsroot debugging messages.
1650 See Documentation/filesystems/nfs/nfsroot.txt.
1652 nfs.callback_tcpport=
1653 [NFS] set the TCP port on which the NFSv4 callback
1654 channel should listen.
1657 [NFS] sets the pathname to the program which is used
1658 to update the NFS client cache entries.
1660 nfs.cache_getent_timeout=
1661 [NFS] sets the timeout after which an attempt to
1662 update a cache entry is deemed to have failed.
1664 nfs.idmap_cache_timeout=
1665 [NFS] set the maximum lifetime for idmapper cache
1669 [NFS] enable 64-bit inode numbers.
1670 If zero, the NFS client will fake up a 32-bit inode
1671 number for the readdir() and stat() syscalls instead
1672 of returning the full 64-bit number.
1673 The default is to return 64-bit inode numbers.
1675 nfs.max_session_slots=
1676 [NFSv4.1] Sets the maximum number of session slots
1677 the client will attempt to negotiate with the server.
1678 This limits the number of simultaneous RPC requests
1679 that the client can send to the NFSv4.1 server.
1680 Note that there is little point in setting this
1681 value higher than the max_tcp_slot_table_limit.
1683 nfs.nfs4_disable_idmapping=
1684 [NFSv4] When set to the default of '1', this option
1685 ensures that both the RPC level authentication
1686 scheme and the NFS level operations agree to use
1687 numeric uids/gids if the mount is using the
1688 'sec=sys' security flavour. In effect it is
1689 disabling idmapping, which can make migration from
1690 legacy NFSv2/v3 systems to NFSv4 easier.
1691 Servers that do not support this mode of operation
1692 will be autodetected by the client, and it will fall
1693 back to using the idmapper.
1694 To turn off this behaviour, set the value to '0'.
1696 nfs.send_implementation_id =
1697 [NFSv4.1] Send client implementation identification
1698 information in exchange_id requests.
1699 If zero, no implementation identification information
1701 The default is to send the implementation identification
1705 objlayoutdriver.osd_login_prog=
1706 [NFS] [OBJLAYOUT] sets the pathname to the program which
1707 is used to automatically discover and login into new
1708 osd-targets. Please see:
1709 Documentation/filesystems/pnfs.txt for more explanations
1711 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1712 when a NMI is triggered.
1713 Format: [state][,regs][,debounce][,die]
1715 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1716 Format: [panic,][nopanic,][num]
1718 0 - turn nmi_watchdog off
1719 When panic is specified, panic when an NMI watchdog
1720 timeout occurs (or 'nopanic' to override the opposite
1722 This is useful when you use a panic=... timeout and
1723 need the box quickly up again.
1725 netpoll.carrier_timeout=
1726 [NET] Specifies amount of time (in seconds) that
1727 netpoll should wait for a carrier. By default netpoll
1730 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1731 emulation library even if a 387 maths coprocessor
1735 [HW] Never suspend the console
1736 Disable suspending of consoles during suspend and
1737 hibernate operations. Once disabled, debugging
1738 messages can reach various consoles while the rest
1739 of the system is being put to sleep (ie, while
1740 debugging driver suspend/resume hooks). This may
1741 not work reliably with all consoles, but is known
1742 to work with serial and VGA consoles.
1743 To facilitate more flexible debugging, we also add
1744 console_suspend, a printk module parameter to control
1745 it. Users could use console_suspend (usually
1746 /sys/module/printk/parameters/console_suspend) to
1747 turn on/off it dynamically.
1749 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1750 caches in the slab allocator. Saves per-node memory,
1751 but will impact performance.
1755 noapic [SMP,APIC] Tells the kernel to not make use of any
1756 IOAPICs that may be present in the system.
1758 noautogroup Disable scheduler automatic task group creation.
1760 nobats [PPC] Do not use BATs for mapping kernel lowmem
1761 on "Classic" PPC cores.
1765 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1767 nodelayacct [KNL] Disable per-task delay accounting
1769 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1771 nodsp [SH] Disable hardware DSP at boot time.
1773 noefi [X86] Disable EFI runtime services support.
1778 On X86-32 available only on PAE configured kernels.
1779 noexec=on: enable non-executable mappings (default)
1780 noexec=off: disable non-executable mappings
1783 Disable SMEP (Supervisor Mode Execution Protection)
1784 even if it is supported by processor.
1787 This affects only 32-bit executables.
1788 noexec32=on: enable non-executable mappings (default)
1789 read doesn't imply executable mappings
1790 noexec32=off: disable non-executable mappings
1791 read implies executable mappings
1793 nofpu [SH] Disable hardware FPU at boot time.
1795 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1796 register save and restore. The kernel will only save
1797 legacy floating-point registers on task switch.
1799 noxsave [BUGS=X86] Disables x86 extended register state save
1800 and restore using xsave. The kernel will fallback to
1801 enabling legacy floating-point and sse state.
1803 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1804 wfi(ARM) instruction doesn't work correctly and not to
1805 use it. This is also useful when using JTAG debugger.
1807 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1808 instruction doesn't work correctly and not to
1811 no_file_caps Tells the kernel not to honor file capabilities. The
1812 only way then for a file to be executed with privilege
1813 is to be setuid root or executed by root.
1815 nohalt [IA-64] Tells the kernel not to use the power saving
1816 function PAL_HALT_LIGHT when idle. This increases
1817 power-consumption. On the positive side, it reduces
1818 interrupt wake-up latency, which may improve performance
1819 in certain environments such as networked servers or
1822 nohz= [KNL] Boottime enable/disable dynamic ticks
1823 Valid arguments: on, off
1826 noiotrap [SH] Disables trapped I/O port accesses.
1828 noirqdebug [X86-32] Disables the code which attempts to detect and
1829 disable unhandled interrupt sources.
1831 no_timer_check [X86,APIC] Disables the code which tests for
1832 broken timer IRQ sources.
1834 noisapnp [ISAPNP] Disables ISA PnP code.
1836 noinitrd [RAM] Tells the kernel not to load any configured
1839 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1841 [Deprecated - use intremap=off]
1845 nojitter [IA-64] Disables jitter checking for ITC timers.
1847 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1849 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1852 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1853 steal time is computed, but won't influence scheduler
1856 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1858 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1860 noltlbs [PPC] Do not use large page/tlb entries for kernel
1861 lowmem mapping on PPC40x.
1863 nomca [IA-64] Disable machine check abort handling
1865 nomce [X86-32] Machine Check Exception
1867 nomfgpt [X86-32] Disable Multi-Function General Purpose
1868 Timer usage (for AMD Geode machines).
1870 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1871 shutdown the other cpus. Instead use the REBOOT_VECTOR
1874 nopat [X86] Disable PAT (page attribute table extension of
1875 pagetables) support.
1877 norandmaps Don't use address space randomization. Equivalent to
1878 echo 0 > /proc/sys/kernel/randomize_va_space
1880 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1882 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1883 with UP alternatives
1885 noresidual [PPC] Don't use residual data on PReP machines.
1887 nordrand [X86] Disable the direct use of the RDRAND
1888 instruction even if it is supported by the
1889 processor. RDRAND is still available to user
1892 noresume [SWSUSP] Disables resume and restores original swap
1895 no-scroll [VGA] Disables scrollback.
1896 This is required for the Braillex ib80-piezo Braille
1897 reader made by F.H. Papenmeier (Germany).
1901 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1903 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1904 and disable the IO APIC. legacy for "maxcpus=0".
1906 nosoftlockup [KNL] Disable the soft-lockup detector.
1908 nosync [HW,M68K] Disables sync negotiation for all devices.
1910 notsc [BUGS=X86-32] Disable Time Stamp Counter
1912 nousb [USB] Disable the USB subsystem
1914 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1918 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1920 nptcg= [IA-64] Override max number of concurrent global TLB
1921 purges which is reported from either PAL_VM_SUMMARY or
1924 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1925 could support. nr_cpus=n : n >= 1 limits the kernel to
1926 supporting 'n' processors. Later in runtime you can not
1927 use hotplug cpu feature to put more cpu back to online.
1928 just like you compile the kernel NR_CPUS=n
1930 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1932 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1933 one of ['zone', 'node', 'default'] can be specified
1934 This can be set from sysctl after boot.
1935 See Documentation/sysctl/vm.txt for details.
1937 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1938 See Documentation/debugging-via-ohci1394.txt for more
1941 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1942 Rather than timing out after 20 ms if an EC
1943 command is not properly ACKed, override the length
1944 of the timeout. We have interrupts disabled while
1945 waiting for the ACK, so if this is set too high
1946 interrupts *may* be lost!
1948 omap_mux= [OMAP] Override bootloader pin multiplexing.
1949 Format: <mux_mode0.mode_name=value>...
1950 For example, to override I2C bus2:
1951 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1953 oprofile.timer= [HW]
1954 Use timer interrupt instead of performance counters
1956 oprofile.cpu_type= Force an oprofile cpu type
1957 This might be useful if you have an older oprofile
1958 userland or if you want common events.
1959 Format: { arch_perfmon }
1960 arch_perfmon: [X86] Force use of architectural
1961 perfmon on Intel CPUs instead of the
1962 CPU specific event set.
1963 timer: [X86] Force use of architectural NMI
1964 timer mode (see also oprofile.timer
1965 for generic hr timer mode)
1966 [s390] Force legacy basic mode sampling
1967 (report cpu_type "timer")
1969 oops=panic Always panic on oopses. Default is to just kill the
1970 process, but there is a small probability of
1971 deadlocking the machine.
1972 This will also cause panics on machine check exceptions.
1973 Useful together with panic=30 to trigger a reboot.
1976 See Documentation/sound/oss/oss-parameters.txt
1978 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1979 timeout > 0: seconds before rebooting
1980 timeout = 0: wait forever
1981 timeout < 0: reboot immediately
1984 parkbd.port= [HW] Parallel port number the keyboard adapter is
1985 connected to, default is 0.
1987 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1988 0 for XT, 1 for AT (default is AT).
1991 parport= [HW,PPT] Specify parallel ports. 0 disables.
1992 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1993 Use 'auto' to force the driver to use any
1994 IRQ/DMA settings detected (the default is to
1995 ignore detected IRQ/DMA settings because of
1996 possible conflicts). You can specify the base
1997 address, IRQ, and DMA settings; IRQ and DMA
1998 should be numbers, or 'auto' (for using detected
1999 settings on that particular port), or 'nofifo'
2000 (to avoid using a FIFO even if it is detected).
2001 Parallel ports are assigned in the order they
2002 are specified on the command line, starting
2005 parport_init_mode= [HW,PPT]
2006 Configure VIA parallel port to operate in
2007 a specific mode. This is necessary on Pegasos
2008 computer where firmware has no options for setting
2009 up parallel port mode and sets it to spp.
2010 Currently this function knows 686a and 8231 chips.
2011 Format: [spp|ps2|epp|ecp|ecpepp]
2014 Halt all CPUs after the first oops has been printed for
2015 the specified number of seconds. This is to be used if
2016 your oopses keep scrolling off the screen.
2021 See header of drivers/block/paride/pcd.c.
2022 See also Documentation/blockdev/paride.txt.
2024 pci=option[,option...] [PCI] various PCI subsystem options:
2025 earlydump [X86] dump PCI config space before the kernel
2027 off [X86] don't probe for the PCI bus
2028 bios [X86-32] force use of PCI BIOS, don't access
2029 the hardware directly. Use this if your machine
2030 has a non-standard PCI host bridge.
2031 nobios [X86-32] disallow use of PCI BIOS, only direct
2032 hardware access methods are allowed. Use this
2033 if you experience crashes upon bootup and you
2034 suspect they are caused by the BIOS.
2035 conf1 [X86] Force use of PCI Configuration
2037 conf2 [X86] Force use of PCI Configuration
2039 noaer [PCIE] If the PCIEAER kernel config parameter is
2040 enabled, this kernel boot option can be used to
2041 disable the use of PCIE advanced error reporting.
2042 nodomains [PCI] Disable support for multiple PCI
2043 root domains (aka PCI segments, in ACPI-speak).
2044 nommconf [X86] Disable use of MMCONFIG for PCI
2046 check_enable_amd_mmconf [X86] check for and enable
2047 properly configured MMIO access to PCI
2048 config space on AMD family 10h CPU
2049 nomsi [MSI] If the PCI_MSI kernel config parameter is
2050 enabled, this kernel boot option can be used to
2051 disable the use of MSI interrupts system-wide.
2052 noioapicquirk [APIC] Disable all boot interrupt quirks.
2053 Safety option to keep boot IRQs enabled. This
2054 should never be necessary.
2055 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2056 primary IO-APIC for bridges that cannot disable
2057 boot IRQs. This fixes a source of spurious IRQs
2058 when the system masks IRQs.
2059 noioapicreroute [APIC] Disable workaround that uses the
2060 boot IRQ equivalent of an IRQ that connects to
2061 a chipset where boot IRQs cannot be disabled.
2062 The opposite of ioapicreroute.
2063 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2064 routing table. These calls are known to be buggy
2065 on several machines and they hang the machine
2066 when used, but on other computers it's the only
2067 way to get the interrupt routing table. Try
2068 this option if the kernel is unable to allocate
2069 IRQs or discover secondary PCI buses on your
2071 rom [X86] Assign address space to expansion ROMs.
2072 Use with caution as certain devices share
2073 address decoders between ROMs and other
2075 norom [X86] Do not assign address space to
2076 expansion ROMs that do not already have
2077 BIOS assigned address ranges.
2078 nobar [X86] Do not assign address space to the
2079 BARs that weren't assigned by the BIOS.
2080 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2081 assigned automatically to PCI devices. You can
2082 make the kernel exclude IRQs of your ISA cards
2084 pirqaddr=0xAAAAA [X86] Specify the physical address
2085 of the PIRQ table (normally generated
2086 by the BIOS) if it is outside the
2087 F0000h-100000h range.
2088 lastbus=N [X86] Scan all buses thru bus #N. Can be
2089 useful if the kernel is unable to find your
2090 secondary buses and you want to tell it
2091 explicitly which ones they are.
2092 assign-busses [X86] Always assign all PCI bus
2093 numbers ourselves, overriding
2094 whatever the firmware may have done.
2095 usepirqmask [X86] Honor the possible IRQ mask stored
2096 in the BIOS $PIR table. This is needed on
2097 some systems with broken BIOSes, notably
2098 some HP Pavilion N5400 and Omnibook XE3
2099 notebooks. This will have no effect if ACPI
2100 IRQ routing is enabled.
2101 noacpi [X86] Do not use ACPI for IRQ routing
2102 or for PCI scanning.
2103 use_crs [X86] Use PCI host bridge window information
2104 from ACPI. On BIOSes from 2008 or later, this
2105 is enabled by default. If you need to use this,
2106 please report a bug.
2107 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2108 If you need to use this, please report a bug.
2109 routeirq Do IRQ routing for all PCI devices.
2110 This is normally done in pci_enable_device(),
2111 so this option is a temporary workaround
2112 for broken drivers that don't call it.
2113 skip_isa_align [X86] do not align io start addr, so can
2114 handle more pci cards
2115 firmware [ARM] Do not re-enumerate the bus but instead
2116 just use the configuration from the
2117 bootloader. This is currently used on
2118 IXP2000 systems where the bus has to be
2119 configured a certain way for adjunct CPUs.
2120 noearly [X86] Don't do any early type 1 scanning.
2121 This might help on some broken boards which
2122 machine check when some devices' config space
2123 is read. But various workarounds are disabled
2124 and some IOMMU drivers will not work.
2125 bfsort Sort PCI devices into breadth-first order.
2126 This sorting is done to get a device
2127 order compatible with older (<= 2.4) kernels.
2128 nobfsort Don't sort PCI devices into breadth-first order.
2129 cbiosize=nn[KMG] The fixed amount of bus space which is
2130 reserved for the CardBus bridge's IO window.
2131 The default value is 256 bytes.
2132 cbmemsize=nn[KMG] The fixed amount of bus space which is
2133 reserved for the CardBus bridge's memory
2134 window. The default value is 64 megabytes.
2137 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2138 Specifies alignment and device to reassign
2139 aligned memory resources.
2140 If <order of align> is not specified,
2141 PAGE_SIZE is used as alignment.
2142 PCI-PCI bridge can be specified, if resource
2143 windows need to be expanded.
2144 ecrc= Enable/disable PCIe ECRC (transaction layer
2145 end-to-end CRC checking).
2146 bios: Use BIOS/firmware settings. This is the
2150 realloc reallocate PCI resources if allocations done by BIOS
2153 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2156 force Enable ASPM even on devices that claim not to support it.
2157 WARNING: Forcing ASPM on may cause system lockups.
2159 pcie_ports= [PCIE] PCIe ports handling:
2160 auto Ask the BIOS whether or not to use native PCIe services
2161 associated with PCIe ports (PME, hot-plug, AER). Use
2162 them only if that is allowed by the BIOS.
2163 native Use native PCIe services associated with PCIe ports
2165 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2168 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2169 nomsi Do not use MSI for native PCIe PME signaling (this makes
2170 all PCIe root ports use INTx for all services).
2172 pcmv= [HW,PCMCIA] BadgePAD 4
2175 See Documentation/blockdev/paride.txt.
2177 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2180 See arch/parisc/kernel/pdc_chassis.c
2182 percpu_alloc= Select which percpu first chunk allocator to use.
2183 Currently supported values are "embed" and "page".
2184 Archs may support subset or none of the selections.
2185 See comments in mm/percpu.c for details on each
2186 allocator. This parameter is primarily for debugging
2187 and performance comparison.
2190 See Documentation/blockdev/paride.txt.
2193 See Documentation/blockdev/paride.txt.
2195 pirq= [SMP,APIC] Manual mp-table setup
2196 See Documentation/x86/i386/IO-APIC.txt.
2198 plip= [PPT,NET] Parallel port network link
2199 Format: { parport<nr> | timid | 0 }
2200 See also Documentation/parport.txt.
2202 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2203 Override pmtimer IOPort with a hex value.
2207 Enable PNP debug messages (depends on the
2208 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2209 via /sys/module/pnp/parameters/debug. We always show
2210 current resource usage; turning this on also shows
2211 possible settings and some assignment information.
2217 { on | off | curr | res | no-curr | no-res }
2220 [ISAPNP] Exclude IRQs for the autoconfiguration
2223 [ISAPNP] Exclude DMAs for the autoconfiguration
2225 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2226 Ranges are in pairs (I/O port base and size).
2229 [ISAPNP] Exclude memory regions for the
2231 Ranges are in pairs (memory base and size).
2233 ports= [IP_VS_FTP] IPVS ftp helper module
2235 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2237 Format: <port>,<port>....
2239 print-fatal-signals=
2240 [KNL] debug: print fatal signals
2242 If enabled, warn about various signal handling
2243 related application anomalies: too many signals,
2244 too many POSIX.1 timers, fatal signals causing a
2247 If you hit the warning due to signal overflow,
2248 you might want to try "ulimit -i unlimited".
2252 printk.always_kmsg_dump=
2253 Trigger kmsg_dump for cases other than kernel oops or
2255 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2258 printk.time= Show timing data prefixed to each printk message line
2259 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2261 processor.max_cstate= [HW,ACPI]
2262 Limit processor to maximum C-state
2263 max_cstate=9 overrides any DMI blacklist limit.
2265 processor.nocst [HW,ACPI]
2266 Ignore the _CST method to determine C-states,
2267 instead using the legacy FADT method
2269 profile= [KNL] Enable kernel profiling via /proc/profile
2270 Format: [schedule,]<number>
2271 Param: "schedule" - profile schedule points.
2272 Param: <number> - step/bucket size as a power of 2 for
2273 statistical time based profiling.
2274 Param: "sleep" - profile D-state sleeping (millisecs).
2275 Requires CONFIG_SCHEDSTATS
2276 Param: "kvm" - profile VM exits.
2278 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2280 See Documentation/blockdev/ramdisk.txt.
2282 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2283 probe for; one of (bare|imps|exps|lifebook|any).
2284 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2286 psmouse.resetafter= [HW,MOUSE]
2287 Try to reset the device after so many bad packets
2290 [HW,MOUSE] Set desired mouse resolution, in dpi.
2291 psmouse.smartscroll=
2292 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2293 0 = disabled, 1 = enabled (default).
2295 pstore.backend= Specify the name of the pstore backend to use
2298 See Documentation/blockdev/paride.txt.
2301 [KNL] Number of legacy pty's. Overwrites compiled-in
2304 quiet [KNL] Disable most log messages
2309 See Documentation/md.txt.
2311 ramdisk_blocksize= [RAM]
2312 See Documentation/blockdev/ramdisk.txt.
2314 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2315 See Documentation/blockdev/ramdisk.txt.
2317 rcupdate.blimit= [KNL,BOOT]
2318 Set maximum number of finished RCU callbacks to process
2321 rcupdate.qhimark= [KNL,BOOT]
2322 Set threshold of queued
2323 RCU callbacks over which batch limiting is disabled.
2325 rcupdate.qlowmark= [KNL,BOOT]
2326 Set threshold of queued RCU callbacks below which
2327 batch limiting is re-enabled.
2331 Run specified binary instead of /init from the ramdisk,
2332 used for early userspace startup. See initrd.
2334 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2335 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2336 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2339 [KNL, SMP] Set scheduler's default relax_domain_level.
2340 See Documentation/cgroups/cpusets.txt.
2342 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2344 reservetop= [X86-32]
2346 Reserves a hole at the top of the kernel virtual
2351 Set the amount of memory to reserve for BIOS at
2352 the bottom of the address space.
2354 reset_devices [KNL] Force drivers to reset the underlying device
2355 during initialization.
2358 Specify the partition device for software suspend
2360 resume_offset= [SWSUSP]
2361 Specify the offset from the beginning of the partition
2362 given by "resume=" at which the swap header is located,
2363 in <PAGE_SIZE> units (needed only for swap files).
2364 See Documentation/power/swsusp-and-swap-files.txt
2366 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2367 read the resume files
2369 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2370 Useful for devices that are detected asynchronously
2371 (e.g. USB and MMC devices).
2373 hibernate= [HIBERNATION]
2374 noresume Don't check if there's a hibernation image
2375 present during boot.
2376 nocompress Don't compress/decompress hibernation images.
2378 retain_initrd [RAM] Keep initrd memory after extraction
2380 rhash_entries= [KNL,NET]
2381 Set number of hash buckets for route cache
2383 riscom8= [HW,SERIAL]
2384 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2386 ro [KNL] Mount root device read-only on boot
2388 root= [KNL] Root filesystem
2389 See name_to_dev_t comment in init/do_mounts.c.
2391 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2392 mount the root filesystem
2394 rootflags= [KNL] Set root filesystem mount option string
2396 rootfstype= [KNL] Set root filesystem type
2398 rootwait [KNL] Wait (indefinitely) for root device to show up.
2399 Useful for devices that are detected asynchronously
2400 (e.g. USB and MMC devices).
2402 rw [KNL] Mount root device read-write on boot
2404 S [KNL] Run init in single mode
2407 See drivers/net/irda/sa1100_ir.c.
2409 sbni= [NET] Granch SBNI12 leased line adapter
2411 sched_debug [KNL] Enables verbose scheduler debug messages.
2413 security= [SECURITY] Choose a security module to enable at boot.
2414 If this boot parameter is not specified, only the first
2415 security module asking for security registration will be
2416 loaded. An invalid security module name will be treated
2417 as if no module has been chosen.
2419 selinux= [SELINUX] Disable or enable SELinux at boot time.
2420 Format: { "0" | "1" }
2421 See security/selinux/Kconfig help text.
2424 Default value is set via kernel config option.
2425 If enabled at boot time, /selinux/disable can be used
2426 later to disable prior to initial policy load.
2428 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2429 Format: { "0" | "1" }
2430 See security/apparmor/Kconfig help text
2433 Default value is set via kernel config option.
2435 serialnumber [BUGS=X86-32]
2438 Maximal number of shapers.
2440 show_msr= [x86] show boot-time MSR settings
2441 Format: { <integer> }
2442 Show boot-time (BIOS-initialized) MSR settings.
2443 The parameter means the number of CPUs to show,
2444 for example 1 means boot CPU only.
2451 slab_max_order= [MM, SLAB]
2452 Determines the maximum allowed order for slabs.
2453 A high setting may cause OOMs due to memory
2454 fragmentation. Defaults to 1 for systems with
2455 more than 32MB of RAM, 0 otherwise.
2457 slub_debug[=options[,slabs]] [MM, SLUB]
2458 Enabling slub_debug allows one to determine the
2459 culprit if slab objects become corrupted. Enabling
2460 slub_debug can create guard zones around objects and
2461 may poison objects when not in use. Also tracks the
2462 last alloc / free. For more information see
2463 Documentation/vm/slub.txt.
2465 slub_max_order= [MM, SLUB]
2466 Determines the maximum allowed order for slabs.
2467 A high setting may cause OOMs due to memory
2468 fragmentation. For more information see
2469 Documentation/vm/slub.txt.
2471 slub_min_objects= [MM, SLUB]
2472 The minimum number of objects per slab. SLUB will
2473 increase the slab order up to slub_max_order to
2474 generate a sufficiently large slab able to contain
2475 the number of objects indicated. The higher the number
2476 of objects the smaller the overhead of tracking slabs
2477 and the less frequently locks need to be acquired.
2478 For more information see Documentation/vm/slub.txt.
2480 slub_min_order= [MM, SLUB]
2481 Determines the minimum page order for slabs. Must be
2482 lower than slub_max_order.
2483 For more information see Documentation/vm/slub.txt.
2485 slub_nomerge [MM, SLUB]
2486 Disable merging of slabs with similar size. May be
2487 necessary if there is some reason to distinguish
2488 allocs to different slabs. Debug options disable
2489 merging on their own.
2490 For more information see Documentation/vm/slub.txt.
2493 Format: <io1>[,<io2>[,...,<io8>]]
2495 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2496 attempt to substitute SMP alternatives once at boot.
2498 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2499 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2500 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2501 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2502 smsc-ircc2.ircc_irq= [HW] IRQ line
2503 smsc-ircc2.ircc_dma= [HW] DMA channel
2504 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2505 0: Toshiba Satellite 1800 (GP data pin select)
2506 1: Fast pin select (default)
2510 [KNL] Should the soft-lockup detector generate panics.
2513 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2514 See Documentation/laptops/sonypi.txt
2516 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2517 See Documentation/serial/specialix.txt.
2519 spia_io_base= [HW,MTD]
2525 Enabled the stack tracer on boot up.
2527 stacktrace_filter=[function-list]
2528 [FTRACE] Limit the functions that the stack tracer
2529 will trace at boot up. function-list is a comma separated
2530 list of functions. This list can be changed at run
2531 time by the stack_trace_filter file in the debugfs
2532 tracing directory. Note, this enables stack tracing
2533 and the stacktrace above is not needed.
2537 Set the STI (builtin display/keyboard on the HP-PARISC
2538 machines) console (graphic card) which should be used
2539 as the initial boot-console.
2540 See also comment in drivers/video/console/sticore.c.
2543 See comment in drivers/video/console/sticore.c.
2546 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2548 sunrpc.min_resvport=
2549 sunrpc.max_resvport=
2551 SunRPC servers often require that client requests
2552 originate from a privileged port (i.e. a port in the
2553 range 0 < portnr < 1024).
2554 An administrator who wishes to reserve some of these
2555 ports for other uses may adjust the range that the
2556 kernel's sunrpc client considers to be privileged
2557 using these two parameters to set the minimum and
2558 maximum port values.
2562 Control how the NFS server code allocates CPUs to
2563 service thread pools. Depending on how many NICs
2564 you have and where their interrupts are bound, this
2565 option will affect which CPUs will do NFS serving.
2566 Note: this parameter cannot be changed while the
2567 NFS server is running.
2569 auto the server chooses an appropriate mode
2570 automatically using heuristics
2571 global a single global pool contains all CPUs
2572 percpu one pool for each CPU
2573 pernode one pool for each NUMA node (equivalent
2574 to global on non-NUMA machines)
2576 sunrpc.tcp_slot_table_entries=
2577 sunrpc.udp_slot_table_entries=
2579 Sets the upper limit on the number of simultaneous
2580 RPC calls that can be sent from the client to a
2581 server. Increasing these values may allow you to
2582 improve throughput, but will also increase the
2583 amount of memory reserved for use by the client.
2586 [KNL] Enable accounting of swap in memory resource
2587 controller if no parameter or 1 is given or disable
2588 it if 0 is given (See Documentation/cgroups/memory.txt)
2590 swiotlb= [IA-64] Number of I/O TLB slabs
2594 sysfs.deprecated=0|1 [KNL]
2595 Enable/disable old style sysfs layout for old udev
2596 on older distributions. When this option is enabled
2597 very new udev will not work anymore. When this option
2598 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2599 in older udev will not work anymore.
2600 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2601 the kernel configuration.
2603 sysrq_always_enabled
2605 Ignore sysrq setting - this boot parameter will
2606 neutralize any effect of /proc/sys/kernel/sysrq.
2607 Useful for debugging.
2611 test_suspend= [SUSPEND]
2612 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2613 standby suspend) as the system sleep state to briefly
2614 enter during system startup. The system is woken from
2615 this state using a wakeup-capable RTC alarm.
2617 thash_entries= [KNL,NET]
2618 Set number of hash buckets for TCP connection
2620 thermal.act= [HW,ACPI]
2621 -1: disable all active trip points in all thermal zones
2622 <degrees C>: override all lowest active trip points
2624 thermal.crt= [HW,ACPI]
2625 -1: disable all critical trip points in all thermal zones
2626 <degrees C>: override all critical trip points
2628 thermal.nocrt= [HW,ACPI]
2629 Set to disable actions on ACPI thermal zone
2630 critical and hot trip points.
2632 thermal.off= [HW,ACPI]
2633 1: disable ACPI thermal control
2635 thermal.psv= [HW,ACPI]
2636 -1: disable all passive trip points
2637 <degrees C>: override all passive trip points to this
2640 thermal.tzp= [HW,ACPI]
2641 Specify global default ACPI thermal zone polling rate
2642 <deci-seconds>: poll all this frequency
2643 0: no polling (default)
2646 Force threading of all interrupt handlers except those
2647 marked explicitly IRQF_NO_THREAD.
2651 Specify if the kernel should make use of the cpu
2652 topology information if the hardware supports this.
2653 The scheduler will make use of this information and
2654 e.g. base its process migration decisions on it.
2659 tpm_suspend_pcr=[HW,TPM]
2660 Format: integer pcr id
2661 Specify that at suspend time, the tpm driver
2662 should extend the specified pcr with zeros,
2663 as a workaround for some chips which fail to
2664 flush the last written pcr on TPM_SaveState.
2665 This will guarantee that all the other pcrs
2668 trace_buf_size=nn[KMG]
2669 [FTRACE] will set tracing buffer size.
2671 trace_event=[event-list]
2672 [FTRACE] Set and start specified trace events in order
2673 to facilitate early boot debugging.
2674 See also Documentation/trace/events.txt
2676 transparent_hugepage=
2678 Format: [always|madvise|never]
2679 Can be used to control the default behavior of the system
2680 with respect to transparent hugepages.
2681 See Documentation/vm/transhuge.txt for more details.
2683 tsc= Disable clocksource stability checks for TSC.
2685 [x86] reliable: mark tsc clocksource as reliable, this
2686 disables clocksource verification at runtime, as well
2687 as the stability checks done at bootup. Used to enable
2688 high-resolution timer mode on older hardware, and in
2689 virtualized environment.
2690 [x86] noirqtime: Do not use TSC to do irq accounting.
2691 Used to run time disable IRQ_TIME_ACCOUNTING on any
2692 platforms where RDTSC is slow and this accounting
2695 turbografx.map[2|3]= [HW,JOY]
2696 TurboGraFX parallel port interface
2698 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2699 See also Documentation/input/joystick-parport.txt
2701 udbg-immortal [PPC] When debugging early kernel crashes that
2702 happen after console_init() and before a proper
2703 console driver takes over, this boot options might
2704 help "seeing" what's going on.
2706 uhash_entries= [KNL,NET]
2707 Set number of hash buckets for UDP/UDP-Lite connections
2710 [USB] Ignore overcurrent events (default N).
2711 Some badly-designed motherboards generate lots of
2712 bogus events, for ports that aren't wired to
2713 anything. Set this parameter to avoid log spamming.
2714 Note that genuine overcurrent events won't be
2718 [X86] Cause panic on unknown NMI.
2720 usbcore.authorized_default=
2721 [USB] Default USB device authorization:
2722 (default -1 = authorized except for wireless USB,
2723 0 = not authorized, 1 = authorized)
2725 usbcore.autosuspend=
2726 [USB] The autosuspend time delay (in seconds) used
2727 for newly-detected USB devices (default 2). This
2728 is the time required before an idle device will be
2729 autosuspended. Devices for which the delay is set
2730 to a negative value won't be autosuspended at all.
2732 usbcore.usbfs_snoop=
2733 [USB] Set to log all usbfs traffic (default 0 = off).
2735 usbcore.blinkenlights=
2736 [USB] Set to cycle leds on hubs (default 0 = off).
2738 usbcore.old_scheme_first=
2739 [USB] Start with the old device initialization
2740 scheme (default 0 = off).
2742 usbcore.usbfs_memory_mb=
2743 [USB] Memory limit (in MB) for buffers allocated by
2744 usbfs (default = 16, 0 = max = 2047).
2746 usbcore.use_both_schemes=
2747 [USB] Try the other device initialization scheme
2748 if the first one fails (default 1 = enabled).
2750 usbcore.initial_descriptor_timeout=
2751 [USB] Specifies timeout for the initial 64-byte
2752 USB_REQ_GET_DESCRIPTOR request in milliseconds
2753 (default 5000 = 5.0 seconds).
2756 [USBHID] The interval which mice are to be polled at.
2758 usb-storage.delay_use=
2759 [UMS] The delay in seconds before a new device is
2760 scanned for Logical Units (default 5).
2763 [UMS] A list of quirks entries to supplement or
2764 override the built-in unusual_devs list. List
2765 entries are separated by commas. Each entry has
2766 the form VID:PID:Flags where VID and PID are Vendor
2767 and Product ID values (4-digit hex numbers) and
2768 Flags is a set of characters, each corresponding
2769 to a common usb-storage quirk flag as follows:
2770 a = SANE_SENSE (collect more than 18 bytes
2772 b = BAD_SENSE (don't collect more than 18
2773 bytes of sense data);
2774 c = FIX_CAPACITY (decrease the reported
2775 device capacity by one sector);
2776 d = NO_READ_DISC_INFO (don't use
2777 READ_DISC_INFO command);
2778 e = NO_READ_CAPACITY_16 (don't use
2779 READ_CAPACITY_16 command);
2780 h = CAPACITY_HEURISTICS (decrease the
2781 reported device capacity by one
2782 sector if the number is odd);
2783 i = IGNORE_DEVICE (don't bind to this
2785 l = NOT_LOCKABLE (don't try to lock and
2786 unlock ejectable media);
2787 m = MAX_SECTORS_64 (don't transfer more
2788 than 64 sectors = 32 KB at a time);
2789 n = INITIAL_READ10 (force a retry of the
2790 initial READ(10) command);
2791 o = CAPACITY_OK (accept the capacity
2792 reported by the device);
2793 r = IGNORE_RESIDUE (the device reports
2794 bogus residue values);
2795 s = SINGLE_LUN (the device has only one
2797 w = NO_WP_DETECT (don't test whether the
2798 medium is write-protected).
2799 Example: quirks=0419:aaf5:rl,0421:0433:rc
2801 user_debug= [KNL,ARM]
2803 See arch/arm/Kconfig.debug help text.
2804 1 - undefined instruction events
2806 4 - invalid data aborts
2809 Example: user_debug=31
2812 [X86] Flags controlling user PTE allocations.
2814 nohigh = do not allocate PTE pages in
2815 HIGHMEM regardless of setting
2819 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2820 vdso=1: enable VDSO (default)
2821 vdso=0: disable VDSO mapping
2824 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2825 vdso32=1: enable 32-bit VDSO (default)
2826 vdso32=0: disable 32-bit VDSO mapping
2829 vector=percpu: enable percpu vector domain
2831 video= [FB] Frame buffer configuration
2832 See Documentation/fb/modedb.txt.
2834 vga= [BOOT,X86-32] Select a particular video mode
2835 See Documentation/x86/boot.txt and
2836 Documentation/svga.txt.
2837 Use vga=ask for menu.
2838 This is actually a boot loader parameter; the value is
2839 passed to the kernel using a special protocol.
2841 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2842 size of <nn>. This can be used to increase the
2843 minimum size (128MB on x86). It can also be used to
2844 decrease the size and leave more room for directly
2847 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2850 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2853 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2857 Controls the behavior of vsyscalls (i.e. calls to
2858 fixed addresses of 0xffffffffff600x00 from legacy
2859 code). Most statically-linked binaries and older
2860 versions of glibc use these calls. Because these
2861 functions are at fixed addresses, they make nice
2862 targets for exploits that can control RIP.
2864 emulate [default] Vsyscalls turn into traps and are
2865 emulated reasonably safely.
2867 native Vsyscalls are native syscall instructions.
2868 This is a little bit faster than trapping
2869 and makes a few dynamic recompilers work
2870 better than they would in emulation mode.
2871 It also makes exploits much easier to write.
2873 none Vsyscalls don't work at all. This makes
2874 them quite hard to use for exploits but
2875 might break your system.
2877 vt.cur_default= [VT] Default cursor shape.
2878 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2879 the parameters of the <Esc>[?A;B;Cc escape sequence;
2880 see VGA-softcursor.txt. Default: 2 = underline.
2882 vt.default_blu= [VT]
2883 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2884 Change the default blue palette of the console.
2885 This is a 16-member array composed of values
2888 vt.default_grn= [VT]
2889 Format: <green0>,<green1>,<green2>,...,<green15>
2890 Change the default green palette of the console.
2891 This is a 16-member array composed of values
2894 vt.default_red= [VT]
2895 Format: <red0>,<red1>,<red2>,...,<red15>
2896 Change the default red palette of the console.
2897 This is a 16-member array composed of values
2903 Set system-wide default UTF-8 mode for all tty's.
2904 Default is 1, i.e. UTF-8 mode is enabled for all
2905 newly opened terminals.
2907 vt.global_cursor_default=
2910 Set system-wide default for whether a cursor
2911 is shown on new VTs. Default is -1,
2912 i.e. cursors will be created by default unless
2913 overridden by individual drivers. 0 will hide
2914 cursors, 1 will display them.
2916 watchdog timers [HW,WDT] For information on watchdog timers,
2917 see Documentation/watchdog/watchdog-parameters.txt
2918 or other driver-specific files in the
2919 Documentation/watchdog/ directory.
2921 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2922 default x2apic cluster mode on platforms
2925 x86_mrst_timer= [X86-32,APBT]
2926 Choose timer option for x86 Moorestown MID platform.
2927 Two valid options are apbt timer only and lapic timer
2928 plus one apbt timer for broadcast timer.
2929 x86_mrst_timer=apbt_only | lapic_and_apbt
2931 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2932 xd_geo= See header of drivers/block/xd.c.
2934 xen_emul_unplug= [HW,X86,XEN]
2935 Unplug Xen emulated devices
2936 Format: [unplug0,][unplug1]
2937 ide-disks -- unplug primary master IDE devices
2938 aux-ide-disks -- unplug non-primary-master IDE devices
2939 nics -- unplug network devices
2940 all -- unplug all emulated devices (NICs and IDE disks)
2941 unnecessary -- unplugging emulated devices is
2942 unnecessary even if the host did not respond to
2944 never -- do not unplug even if version check succeeds
2946 xirc2ps_cs= [NET,PCMCIA]
2948 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2950 ______________________________________________________________________
2954 Add more DRM drivers.
projects / ~andy / linux / blob