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
1089 iomem= Disable strict checking of access to MMIO memory
1090 strict regions from userspace.
1105 group_mf [x86, IA-64]
1108 io7= [HW] IO7 for Marvel based alpha systems
1109 See comment before marvel_specify_io7 in
1110 arch/alpha/kernel/core_marvel.c.
1112 io_delay= [X86] I/O delay method
1114 Standard port 0x80 based delay
1116 Alternate port 0xed based delay (needed on some systems)
1118 Simple two microseconds delay
1123 See Documentation/filesystems/nfs/nfsroot.txt.
1125 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1126 See comment before ip2_setup() in
1127 drivers/char/ip2/ip2base.c.
1130 When an interrupt is not handled search all handlers
1131 for it. Intended to get systems with badly broken
1135 When an interrupt is not handled search all handlers
1136 for it. Also check all handlers each timer
1137 interrupt. Intended to get systems with badly broken
1141 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1143 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1145 <cpu number>,...,<cpu number>
1147 <cpu number>-<cpu number>
1148 (must be a positive range in ascending order)
1150 <cpu number>,...,<cpu number>-<cpu number>
1152 This option can be used to specify one or more CPUs
1153 to isolate from the general SMP balancing and scheduling
1154 algorithms. You can move a process onto or off an
1155 "isolated" CPU via the CPU affinity syscalls or cpuset.
1156 <cpu number> begins at 0 and the maximum value is
1157 "number of CPUs in system - 1".
1159 This option is the preferred way to isolate CPUs. The
1160 alternative -- manually setting the CPU mask of all
1161 tasks in the system -- can cause problems and
1162 suboptimal load balancer performance.
1166 js= [HW,JOY] Analog joystick
1167 See Documentation/input/joystick.txt.
1171 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1172 specifies the amount of memory usable by the kernel
1173 for non-movable allocations. The requested amount is
1174 spread evenly throughout all nodes in the system. The
1175 remaining memory in each node is used for Movable
1176 pages. In the event, a node is too small to have both
1177 kernelcore and Movable pages, kernelcore pages will
1178 take priority and other nodes will have a larger number
1179 of kernelcore pages. The Movable zone is used for the
1180 allocation of pages that may be reclaimed or moved
1181 by the page migration subsystem. This means that
1182 HugeTLB pages may not be allocated from this zone.
1183 Note that allocations like PTEs-from-HighMem still
1184 use the HighMem zone if it exists, and the Normal
1185 zone if it does not.
1187 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1188 Format: <Controller#>[,poll interval]
1189 The controller # is the number of the ehci usb debug
1190 port as it is probed via PCI. The poll interval is
1191 optional and is the number seconds in between
1192 each poll cycle to the debug port in case you need
1193 the functionality for interrupting the kernel with
1194 gdb or control-c on the dbgp connection. When
1195 not using this parameter you use sysrq-g to break into
1196 the kernel debugger.
1198 kgdboc= [KGDB,HW] kgdb over consoles.
1199 Requires a tty driver that supports console polling,
1200 or a supported polling keyboard driver (non-usb).
1201 Serial only format: <serial_device>[,baud]
1202 keyboard only format: kbd
1203 keyboard and serial format: kbd,<serial_device>[,baud]
1204 Optional Kernel mode setting:
1205 kms, kbd format: kms,kbd
1206 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1208 kgdbwait [KGDB] Stop kernel execution and enter the
1209 kernel debugger at the earliest opportunity.
1211 kmac= [MIPS] korina ethernet MAC address.
1212 Configure the RouterBoard 532 series on-chip
1213 Ethernet adapter MAC address.
1215 kmemleak= [KNL] Boot-time kmemleak enable/disable
1216 Valid arguments: on, off
1219 kstack=N [X86] Print N words from the kernel stack
1222 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1223 Default is 0 (don't ignore, but inject #GP)
1225 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1229 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1230 Default is 1 (enabled)
1232 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1234 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1236 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1237 (virtualized MMU) support on capable Intel chips.
1238 Default is 1 (enabled)
1240 kvm-intel.emulate_invalid_guest_state=
1241 [KVM,Intel] Enable emulation of invalid guest states
1242 Default is 0 (disabled)
1244 kvm-intel.flexpriority=
1245 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1246 Default is 1 (enabled)
1249 [KVM,Intel] Enable VMX nesting (nVMX).
1250 Default is 0 (disabled)
1252 kvm-intel.unrestricted_guest=
1253 [KVM,Intel] Disable unrestricted guest feature
1254 (virtualized real and unpaged mode) on capable
1255 Intel chips. Default is 1 (enabled)
1257 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1258 feature (tagged TLBs) on capable Intel chips.
1259 Default is 1 (enabled)
1265 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1268 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1271 libata.dma= [LIBATA] DMA control
1272 libata.dma=0 Disable all PATA and SATA DMA
1273 libata.dma=1 PATA and SATA Disk DMA only
1274 libata.dma=2 ATAPI (CDROM) DMA only
1275 libata.dma=4 Compact Flash DMA only
1276 Combinations also work, so libata.dma=3 enables DMA
1277 for disks and CDROMs, but not CFs.
1279 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1280 libata.ignore_hpa=0 keep BIOS limits (default)
1281 libata.ignore_hpa=1 ignore limits, using full disk
1283 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1287 libata.force= [LIBATA] Force configurations. The format is comma
1288 separated list of "[ID:]VAL" where ID is
1289 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1290 matching port, link or device. Basically, it matches
1291 the ATA ID string printed on console by libata. If
1292 the whole ID part is omitted, the last PORT and DEVICE
1293 values are used. If ID hasn't been specified yet, the
1294 configuration applies to all ports, links and devices.
1296 If only DEVICE is omitted, the parameter applies to
1297 the port and all links and devices behind it. DEVICE
1298 number of 0 either selects the first device or the
1299 first fan-out link behind PMP device. It does not
1300 select the host link. DEVICE number of 15 selects the
1301 host link and device attached to it.
1303 The VAL specifies the configuration to force. As long
1304 as there's no ambiguity shortcut notation is allowed.
1305 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1306 The following configurations can be forced.
1308 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1309 Any ID with matching PORT is used.
1311 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1313 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1314 udma[/][16,25,33,44,66,100,133] notation is also
1317 * [no]ncq: Turn on or off NCQ.
1319 * nohrst, nosrst, norst: suppress hard, soft
1322 * dump_id: dump IDENTIFY data.
1324 If there are multiple matching configurations changing
1325 the same attribute, the last one is used.
1327 memblock=debug [KNL] Enable memblock debug messages.
1329 load_ramdisk= [RAM] List of ramdisks to load from floppy
1330 See Documentation/blockdev/ramdisk.txt.
1332 lockd.nlm_grace_period=P [NFS] Assign grace period.
1335 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1338 lockd.nlm_timeout=T [NFS] Assign timeout value.
1341 lockd.nlm_udpport=M [NFS] Assign UDP port.
1344 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1347 loglevel= All Kernel Messages with a loglevel smaller than the
1348 console loglevel will be printed to the console. It can
1349 also be changed with klogd or other programs. The
1350 loglevels are defined as follows:
1352 0 (KERN_EMERG) system is unusable
1353 1 (KERN_ALERT) action must be taken immediately
1354 2 (KERN_CRIT) critical conditions
1355 3 (KERN_ERR) error conditions
1356 4 (KERN_WARNING) warning conditions
1357 5 (KERN_NOTICE) normal but significant condition
1358 6 (KERN_INFO) informational
1359 7 (KERN_DEBUG) debug-level messages
1361 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1362 in bytes. n must be a power of two. The default
1363 size is set in the kernel config file.
1365 logo.nologo [FB] Disables display of the built-in Linux logo.
1366 This may be used to provide more screen space for
1367 kernel log messages and is useful when debugging
1368 kernel boot problems.
1370 lp=0 [LP] Specify parallel ports to use, e.g,
1371 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1372 lp=reset first parallel port). 'lp=0' disables the
1373 lp=auto printer driver. 'lp=reset' (which can be
1374 specified in addition to the ports) causes
1375 attached printers to be reset. Using
1376 lp=port1,port2,... specifies the parallel ports
1377 to associate lp devices with, starting with
1378 lp0. A port specification may be 'none' to skip
1379 that lp device, or a parport name such as
1380 'parport0'. Specifying 'lp=auto' instead of a
1381 port specification list means that device IDs
1382 from each port should be examined, to see if
1383 an IEEE 1284-compliant printer is attached; if
1384 so, the driver will manage that printer.
1385 See also header of drivers/char/lp.c.
1388 Sets loops_per_jiffy to given constant, thus avoiding
1389 time-consuming boot-time autodetection (up to 250 ms per
1390 CPU). 0 enables autodetection (default). To determine
1391 the correct value for your kernel, boot with normal
1392 autodetection and see what value is printed. Note that
1393 on SMP systems the preset will be applied to all CPUs,
1394 which is likely to cause problems if your CPUs need
1395 significantly divergent settings. An incorrect value
1396 will cause delays in the kernel to be wrong, leading to
1397 unpredictable I/O errors and other breakage. Although
1398 unlikely, in the extreme case this might damage your
1402 Format: <io>,<irq>,<dma>
1404 machvec= [IA-64] Force the use of a particular machine-vector
1405 (machvec) in a generic kernel.
1406 Example: machvec=hpzx1_swiotlb
1408 machtype= [Loongson] Share the same kernel image file between different
1410 Example: machtype=lemote-yeeloong-2f-7inch
1412 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1413 than or equal to this physical address is ignored.
1415 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1416 should make use of. maxcpus=n : n >= 0 limits the
1417 kernel to using 'n' processors. n=0 is a special case,
1418 it is equivalent to "nosmp", which also disables
1421 max_loop= [LOOP] The number of loop block devices that get
1422 (loop.max_loop) unconditionally pre-created at init time. The default
1423 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1424 of statically allocating a predefined number, loop
1425 devices can be requested on-demand with the
1426 /dev/loop-control interface.
1430 mce [X86-32] Machine Check Exception
1432 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1434 md= [HW] RAID subsystems devices and level
1435 See Documentation/md.txt.
1438 Format: <first>,<last>
1439 Specifies range of consoles to be captured by the MDA.
1441 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1442 Amount of memory to be used when the kernel is not able
1443 to see the whole system memory or for test.
1444 [X86-32] Use together with memmap= to avoid physical
1445 address space collisions. Without memmap= PCI devices
1446 could be placed at addresses belonging to unused RAM.
1448 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1452 [KNL,SH] Allow user to override the default size for
1453 per-device physically contiguous DMA buffers.
1455 memmap=exactmap [KNL,X86] Enable setting of an exact
1456 E820 memory map, as specified by the user.
1457 Such memmap=exactmap lines can be constructed based on
1458 BIOS output or other requirements. See the memmap=nn@ss
1461 memmap=nn[KMG]@ss[KMG]
1462 [KNL] Force usage of a specific region of memory
1463 Region of memory to be used, from ss to ss+nn.
1465 memmap=nn[KMG]#ss[KMG]
1466 [KNL,ACPI] Mark specific memory as ACPI data.
1467 Region of memory to be used, from ss to ss+nn.
1469 memmap=nn[KMG]$ss[KMG]
1470 [KNL,ACPI] Mark specific memory as reserved.
1471 Region of memory to be used, from ss to ss+nn.
1472 Example: Exclude memory from 0x18690000-0x1869ffff
1473 memmap=64K$0x18690000
1475 memmap=0x10000$0x18690000
1477 memory_corruption_check=0/1 [X86]
1478 Some BIOSes seem to corrupt the first 64k of
1479 memory when doing things like suspend/resume.
1480 Setting this option will scan the memory
1481 looking for corruption. Enabling this will
1482 both detect corruption and prevent the kernel
1483 from using the memory being corrupted.
1484 However, its intended as a diagnostic tool; if
1485 repeatable BIOS-originated corruption always
1486 affects the same memory, you can use memmap=
1487 to prevent the kernel from using that memory.
1489 memory_corruption_check_size=size [X86]
1490 By default it checks for corruption in the low
1491 64k, making this memory unavailable for normal
1492 use. Use this parameter to scan for
1493 corruption in more or less memory.
1495 memory_corruption_check_period=seconds [X86]
1496 By default it checks for corruption every 60
1497 seconds. Use this parameter to check at some
1498 other rate. 0 disables periodic checking.
1500 memtest= [KNL,X86] Enable memtest
1502 default : 0 <disable>
1503 Specifies the number of memtest passes to be
1504 performed. Each pass selects another test
1505 pattern from a given set of patterns. Memtest
1506 fills the memory with this pattern, validates
1507 memory contents and reserves bad memory
1508 regions that are detected.
1510 meye.*= [HW] Set MotionEye Camera parameters
1511 See Documentation/video4linux/meye.txt.
1513 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1514 Multi-Function General Purpose Timers on AMD Geode
1517 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1518 the BIOS has incorrectly applied a workaround. TinyBIOS
1519 version 0.98 is known to be affected, 0.99 fixes the
1520 problem by letting the user disable the workaround.
1524 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1525 physical address is ignored.
1527 mini2440= [ARM,HW,KNL]
1528 Format:[0..2][b][c][t]
1530 MINI2440 configuration specification:
1531 0 - The attached screen is the 3.5" TFT
1532 1 - The attached screen is the 7" TFT
1533 2 - The VGA Shield is attached (1024x768)
1534 Leaving out the screen size parameter will not load
1535 the TFT driver, and the framebuffer will be left
1537 b - Enable backlight. The TFT backlight pin will be
1538 linked to the kernel VESA blanking code and a GPIO
1539 LED. This parameter is not necessary when using the
1541 c - Enable the s3c camera interface.
1542 t - Reserved for enabling touchscreen support. The
1543 touchscreen support is not enabled in the mainstream
1544 kernel as of 2.6.30, a preliminary port can be found
1545 in the "bleeding edge" mini2440 support kernel at
1546 http://repo.or.cz/w/linux-2.6/mini2440.git
1549 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1550 parameter allows control of the logging verbosity for
1551 the additional memory initialisation checks. A value
1552 of 0 disables mminit logging and a level of 4 will
1553 log everything. Information is printed at KERN_DEBUG
1554 so loglevel=8 may also need to be specified.
1557 [MOUSE] Maximum time between finger touching and
1558 leaving touchpad surface for touch to be considered
1559 a tap and be reported as a left button click (for
1560 touchpads working in absolute mode only).
1562 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1563 reporting absolute coordinates, such as tablets
1564 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1565 reporting absolute coordinates, such as tablets
1567 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1568 is similar to kernelcore except it specifies the
1569 amount of memory used for migratable allocations.
1570 If both kernelcore and movablecore is specified,
1571 then kernelcore will be at *least* the specified
1572 value but may be more. If movablecore on its own
1573 is specified, the administrator must be careful
1574 that the amount of memory usable for all allocations
1577 MTD_Partition= [MTD]
1578 Format: <name>,<region-number>,<size>,<offset>
1580 MTD_Region= [MTD] Format:
1581 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1584 See drivers/mtd/cmdlinepart.c.
1586 multitce=off [PPC] This parameter disables the use of the pSeries
1587 firmware feature for updating multiple TCE entries
1590 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1592 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1594 boundary - index of last SLC block on Flex-OneNAND.
1595 The remaining blocks are configured as MLC blocks.
1596 lock - Configure if Flex-OneNAND boundary should be locked.
1597 Once locked, the boundary cannot be changed.
1598 1 indicates lock status, 0 indicates unlock status.
1601 ARM/S3C2412 JIVE boot control
1603 See arch/arm/mach-s3c2412/mach-jive.c
1605 mtouchusb.raw_coordinates=
1606 [HW] Make the MicroTouch USB driver use raw coordinates
1607 ('y', default) or cooked coordinates ('n')
1609 mtrr_chunk_size=nn[KMG] [X86]
1610 used for mtrr cleanup. It is largest continuous chunk
1611 that could hold holes aka. UC entries.
1613 mtrr_gran_size=nn[KMG] [X86]
1614 Used for mtrr cleanup. It is granularity of mtrr block.
1616 Large value could prevent small alignment from
1619 mtrr_spare_reg_nr=n [X86]
1621 Range: 0,7 : spare reg number
1623 Used for mtrr cleanup. It is spare mtrr entries number.
1624 Set to 2 or more if your graphical card needs more.
1626 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1628 netdev= [NET] Network devices parameters
1629 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1630 Note that mem_start is often overloaded to mean
1631 something different and driver-specific.
1632 This usage is only documented in each driver source
1636 [NETFILTER] Enable connection tracking flow accounting
1637 0 to disable accounting
1638 1 to enable accounting
1641 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1642 See Documentation/filesystems/nfs/nfsroot.txt.
1644 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1645 See Documentation/filesystems/nfs/nfsroot.txt.
1647 nfsrootdebug [NFS] enable nfsroot debugging messages.
1648 See Documentation/filesystems/nfs/nfsroot.txt.
1650 nfs.callback_tcpport=
1651 [NFS] set the TCP port on which the NFSv4 callback
1652 channel should listen.
1655 [NFS] sets the pathname to the program which is used
1656 to update the NFS client cache entries.
1658 nfs.cache_getent_timeout=
1659 [NFS] sets the timeout after which an attempt to
1660 update a cache entry is deemed to have failed.
1662 nfs.idmap_cache_timeout=
1663 [NFS] set the maximum lifetime for idmapper cache
1667 [NFS] enable 64-bit inode numbers.
1668 If zero, the NFS client will fake up a 32-bit inode
1669 number for the readdir() and stat() syscalls instead
1670 of returning the full 64-bit number.
1671 The default is to return 64-bit inode numbers.
1673 nfs.max_session_slots=
1674 [NFSv4.1] Sets the maximum number of session slots
1675 the client will attempt to negotiate with the server.
1676 This limits the number of simultaneous RPC requests
1677 that the client can send to the NFSv4.1 server.
1678 Note that there is little point in setting this
1679 value higher than the max_tcp_slot_table_limit.
1681 nfs.nfs4_disable_idmapping=
1682 [NFSv4] When set to the default of '1', this option
1683 ensures that both the RPC level authentication
1684 scheme and the NFS level operations agree to use
1685 numeric uids/gids if the mount is using the
1686 'sec=sys' security flavour. In effect it is
1687 disabling idmapping, which can make migration from
1688 legacy NFSv2/v3 systems to NFSv4 easier.
1689 Servers that do not support this mode of operation
1690 will be autodetected by the client, and it will fall
1691 back to using the idmapper.
1692 To turn off this behaviour, set the value to '0'.
1694 nfs.send_implementation_id =
1695 [NFSv4.1] Send client implementation identification
1696 information in exchange_id requests.
1697 If zero, no implementation identification information
1699 The default is to send the implementation identification
1703 objlayoutdriver.osd_login_prog=
1704 [NFS] [OBJLAYOUT] sets the pathname to the program which
1705 is used to automatically discover and login into new
1706 osd-targets. Please see:
1707 Documentation/filesystems/pnfs.txt for more explanations
1709 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1710 when a NMI is triggered.
1711 Format: [state][,regs][,debounce][,die]
1713 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1714 Format: [panic,][nopanic,][num]
1716 0 - turn nmi_watchdog off
1717 When panic is specified, panic when an NMI watchdog
1718 timeout occurs (or 'nopanic' to override the opposite
1720 This is useful when you use a panic=... timeout and
1721 need the box quickly up again.
1723 netpoll.carrier_timeout=
1724 [NET] Specifies amount of time (in seconds) that
1725 netpoll should wait for a carrier. By default netpoll
1728 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1729 emulation library even if a 387 maths coprocessor
1733 [HW] Never suspend the console
1734 Disable suspending of consoles during suspend and
1735 hibernate operations. Once disabled, debugging
1736 messages can reach various consoles while the rest
1737 of the system is being put to sleep (ie, while
1738 debugging driver suspend/resume hooks). This may
1739 not work reliably with all consoles, but is known
1740 to work with serial and VGA consoles.
1741 To facilitate more flexible debugging, we also add
1742 console_suspend, a printk module parameter to control
1743 it. Users could use console_suspend (usually
1744 /sys/module/printk/parameters/console_suspend) to
1745 turn on/off it dynamically.
1747 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1748 caches in the slab allocator. Saves per-node memory,
1749 but will impact performance.
1753 noapic [SMP,APIC] Tells the kernel to not make use of any
1754 IOAPICs that may be present in the system.
1756 noautogroup Disable scheduler automatic task group creation.
1758 nobats [PPC] Do not use BATs for mapping kernel lowmem
1759 on "Classic" PPC cores.
1763 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1765 nodelayacct [KNL] Disable per-task delay accounting
1767 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1769 nodsp [SH] Disable hardware DSP at boot time.
1771 noefi [X86] Disable EFI runtime services support.
1776 On X86-32 available only on PAE configured kernels.
1777 noexec=on: enable non-executable mappings (default)
1778 noexec=off: disable non-executable mappings
1781 Disable SMEP (Supervisor Mode Execution Protection)
1782 even if it is supported by processor.
1785 This affects only 32-bit executables.
1786 noexec32=on: enable non-executable mappings (default)
1787 read doesn't imply executable mappings
1788 noexec32=off: disable non-executable mappings
1789 read implies executable mappings
1791 nofpu [SH] Disable hardware FPU at boot time.
1793 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1794 register save and restore. The kernel will only save
1795 legacy floating-point registers on task switch.
1797 noxsave [BUGS=X86] Disables x86 extended register state save
1798 and restore using xsave. The kernel will fallback to
1799 enabling legacy floating-point and sse state.
1801 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1802 wfi(ARM) instruction doesn't work correctly and not to
1803 use it. This is also useful when using JTAG debugger.
1805 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1806 instruction doesn't work correctly and not to
1809 no_file_caps Tells the kernel not to honor file capabilities. The
1810 only way then for a file to be executed with privilege
1811 is to be setuid root or executed by root.
1813 nohalt [IA-64] Tells the kernel not to use the power saving
1814 function PAL_HALT_LIGHT when idle. This increases
1815 power-consumption. On the positive side, it reduces
1816 interrupt wake-up latency, which may improve performance
1817 in certain environments such as networked servers or
1820 nohz= [KNL] Boottime enable/disable dynamic ticks
1821 Valid arguments: on, off
1824 noiotrap [SH] Disables trapped I/O port accesses.
1826 noirqdebug [X86-32] Disables the code which attempts to detect and
1827 disable unhandled interrupt sources.
1829 no_timer_check [X86,APIC] Disables the code which tests for
1830 broken timer IRQ sources.
1832 noisapnp [ISAPNP] Disables ISA PnP code.
1834 noinitrd [RAM] Tells the kernel not to load any configured
1837 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1839 [Deprecated - use intremap=off]
1843 nojitter [IA-64] Disables jitter checking for ITC timers.
1845 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1847 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1850 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1851 steal time is computed, but won't influence scheduler
1854 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1856 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1858 noltlbs [PPC] Do not use large page/tlb entries for kernel
1859 lowmem mapping on PPC40x.
1861 nomca [IA-64] Disable machine check abort handling
1863 nomce [X86-32] Machine Check Exception
1865 nomfgpt [X86-32] Disable Multi-Function General Purpose
1866 Timer usage (for AMD Geode machines).
1868 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1869 shutdown the other cpus. Instead use the REBOOT_VECTOR
1872 nopat [X86] Disable PAT (page attribute table extension of
1873 pagetables) support.
1875 norandmaps Don't use address space randomization. Equivalent to
1876 echo 0 > /proc/sys/kernel/randomize_va_space
1878 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1880 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1881 with UP alternatives
1883 noresidual [PPC] Don't use residual data on PReP machines.
1885 nordrand [X86] Disable the direct use of the RDRAND
1886 instruction even if it is supported by the
1887 processor. RDRAND is still available to user
1890 noresume [SWSUSP] Disables resume and restores original swap
1893 no-scroll [VGA] Disables scrollback.
1894 This is required for the Braillex ib80-piezo Braille
1895 reader made by F.H. Papenmeier (Germany).
1899 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1901 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1902 and disable the IO APIC. legacy for "maxcpus=0".
1904 nosoftlockup [KNL] Disable the soft-lockup detector.
1906 nosync [HW,M68K] Disables sync negotiation for all devices.
1908 notsc [BUGS=X86-32] Disable Time Stamp Counter
1910 nousb [USB] Disable the USB subsystem
1912 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1916 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1918 nptcg= [IA-64] Override max number of concurrent global TLB
1919 purges which is reported from either PAL_VM_SUMMARY or
1922 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1923 could support. nr_cpus=n : n >= 1 limits the kernel to
1924 supporting 'n' processors. Later in runtime you can not
1925 use hotplug cpu feature to put more cpu back to online.
1926 just like you compile the kernel NR_CPUS=n
1928 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1930 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1931 one of ['zone', 'node', 'default'] can be specified
1932 This can be set from sysctl after boot.
1933 See Documentation/sysctl/vm.txt for details.
1935 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1936 See Documentation/debugging-via-ohci1394.txt for more
1939 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1940 Rather than timing out after 20 ms if an EC
1941 command is not properly ACKed, override the length
1942 of the timeout. We have interrupts disabled while
1943 waiting for the ACK, so if this is set too high
1944 interrupts *may* be lost!
1946 omap_mux= [OMAP] Override bootloader pin multiplexing.
1947 Format: <mux_mode0.mode_name=value>...
1948 For example, to override I2C bus2:
1949 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1951 oprofile.timer= [HW]
1952 Use timer interrupt instead of performance counters
1954 oprofile.cpu_type= Force an oprofile cpu type
1955 This might be useful if you have an older oprofile
1956 userland or if you want common events.
1957 Format: { arch_perfmon }
1958 arch_perfmon: [X86] Force use of architectural
1959 perfmon on Intel CPUs instead of the
1960 CPU specific event set.
1961 timer: [X86] Force use of architectural NMI
1962 timer mode (see also oprofile.timer
1963 for generic hr timer mode)
1964 [s390] Force legacy basic mode sampling
1965 (report cpu_type "timer")
1967 oops=panic Always panic on oopses. Default is to just kill the
1968 process, but there is a small probability of
1969 deadlocking the machine.
1970 This will also cause panics on machine check exceptions.
1971 Useful together with panic=30 to trigger a reboot.
1974 See Documentation/sound/oss/oss-parameters.txt
1976 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1977 timeout > 0: seconds before rebooting
1978 timeout = 0: wait forever
1979 timeout < 0: reboot immediately
1982 parkbd.port= [HW] Parallel port number the keyboard adapter is
1983 connected to, default is 0.
1985 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1986 0 for XT, 1 for AT (default is AT).
1989 parport= [HW,PPT] Specify parallel ports. 0 disables.
1990 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1991 Use 'auto' to force the driver to use any
1992 IRQ/DMA settings detected (the default is to
1993 ignore detected IRQ/DMA settings because of
1994 possible conflicts). You can specify the base
1995 address, IRQ, and DMA settings; IRQ and DMA
1996 should be numbers, or 'auto' (for using detected
1997 settings on that particular port), or 'nofifo'
1998 (to avoid using a FIFO even if it is detected).
1999 Parallel ports are assigned in the order they
2000 are specified on the command line, starting
2003 parport_init_mode= [HW,PPT]
2004 Configure VIA parallel port to operate in
2005 a specific mode. This is necessary on Pegasos
2006 computer where firmware has no options for setting
2007 up parallel port mode and sets it to spp.
2008 Currently this function knows 686a and 8231 chips.
2009 Format: [spp|ps2|epp|ecp|ecpepp]
2012 Halt all CPUs after the first oops has been printed for
2013 the specified number of seconds. This is to be used if
2014 your oopses keep scrolling off the screen.
2019 See header of drivers/block/paride/pcd.c.
2020 See also Documentation/blockdev/paride.txt.
2022 pci=option[,option...] [PCI] various PCI subsystem options:
2023 earlydump [X86] dump PCI config space before the kernel
2025 off [X86] don't probe for the PCI bus
2026 bios [X86-32] force use of PCI BIOS, don't access
2027 the hardware directly. Use this if your machine
2028 has a non-standard PCI host bridge.
2029 nobios [X86-32] disallow use of PCI BIOS, only direct
2030 hardware access methods are allowed. Use this
2031 if you experience crashes upon bootup and you
2032 suspect they are caused by the BIOS.
2033 conf1 [X86] Force use of PCI Configuration
2035 conf2 [X86] Force use of PCI Configuration
2037 noaer [PCIE] If the PCIEAER kernel config parameter is
2038 enabled, this kernel boot option can be used to
2039 disable the use of PCIE advanced error reporting.
2040 nodomains [PCI] Disable support for multiple PCI
2041 root domains (aka PCI segments, in ACPI-speak).
2042 nommconf [X86] Disable use of MMCONFIG for PCI
2044 check_enable_amd_mmconf [X86] check for and enable
2045 properly configured MMIO access to PCI
2046 config space on AMD family 10h CPU
2047 nomsi [MSI] If the PCI_MSI kernel config parameter is
2048 enabled, this kernel boot option can be used to
2049 disable the use of MSI interrupts system-wide.
2050 noioapicquirk [APIC] Disable all boot interrupt quirks.
2051 Safety option to keep boot IRQs enabled. This
2052 should never be necessary.
2053 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2054 primary IO-APIC for bridges that cannot disable
2055 boot IRQs. This fixes a source of spurious IRQs
2056 when the system masks IRQs.
2057 noioapicreroute [APIC] Disable workaround that uses the
2058 boot IRQ equivalent of an IRQ that connects to
2059 a chipset where boot IRQs cannot be disabled.
2060 The opposite of ioapicreroute.
2061 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2062 routing table. These calls are known to be buggy
2063 on several machines and they hang the machine
2064 when used, but on other computers it's the only
2065 way to get the interrupt routing table. Try
2066 this option if the kernel is unable to allocate
2067 IRQs or discover secondary PCI buses on your
2069 rom [X86] Assign address space to expansion ROMs.
2070 Use with caution as certain devices share
2071 address decoders between ROMs and other
2073 norom [X86] Do not assign address space to
2074 expansion ROMs that do not already have
2075 BIOS assigned address ranges.
2076 nobar [X86] Do not assign address space to the
2077 BARs that weren't assigned by the BIOS.
2078 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2079 assigned automatically to PCI devices. You can
2080 make the kernel exclude IRQs of your ISA cards
2082 pirqaddr=0xAAAAA [X86] Specify the physical address
2083 of the PIRQ table (normally generated
2084 by the BIOS) if it is outside the
2085 F0000h-100000h range.
2086 lastbus=N [X86] Scan all buses thru bus #N. Can be
2087 useful if the kernel is unable to find your
2088 secondary buses and you want to tell it
2089 explicitly which ones they are.
2090 assign-busses [X86] Always assign all PCI bus
2091 numbers ourselves, overriding
2092 whatever the firmware may have done.
2093 usepirqmask [X86] Honor the possible IRQ mask stored
2094 in the BIOS $PIR table. This is needed on
2095 some systems with broken BIOSes, notably
2096 some HP Pavilion N5400 and Omnibook XE3
2097 notebooks. This will have no effect if ACPI
2098 IRQ routing is enabled.
2099 noacpi [X86] Do not use ACPI for IRQ routing
2100 or for PCI scanning.
2101 use_crs [X86] Use PCI host bridge window information
2102 from ACPI. On BIOSes from 2008 or later, this
2103 is enabled by default. If you need to use this,
2104 please report a bug.
2105 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2106 If you need to use this, please report a bug.
2107 routeirq Do IRQ routing for all PCI devices.
2108 This is normally done in pci_enable_device(),
2109 so this option is a temporary workaround
2110 for broken drivers that don't call it.
2111 skip_isa_align [X86] do not align io start addr, so can
2112 handle more pci cards
2113 firmware [ARM] Do not re-enumerate the bus but instead
2114 just use the configuration from the
2115 bootloader. This is currently used on
2116 IXP2000 systems where the bus has to be
2117 configured a certain way for adjunct CPUs.
2118 noearly [X86] Don't do any early type 1 scanning.
2119 This might help on some broken boards which
2120 machine check when some devices' config space
2121 is read. But various workarounds are disabled
2122 and some IOMMU drivers will not work.
2123 bfsort Sort PCI devices into breadth-first order.
2124 This sorting is done to get a device
2125 order compatible with older (<= 2.4) kernels.
2126 nobfsort Don't sort PCI devices into breadth-first order.
2127 cbiosize=nn[KMG] The fixed amount of bus space which is
2128 reserved for the CardBus bridge's IO window.
2129 The default value is 256 bytes.
2130 cbmemsize=nn[KMG] The fixed amount of bus space which is
2131 reserved for the CardBus bridge's memory
2132 window. The default value is 64 megabytes.
2135 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2136 Specifies alignment and device to reassign
2137 aligned memory resources.
2138 If <order of align> is not specified,
2139 PAGE_SIZE is used as alignment.
2140 PCI-PCI bridge can be specified, if resource
2141 windows need to be expanded.
2142 ecrc= Enable/disable PCIe ECRC (transaction layer
2143 end-to-end CRC checking).
2144 bios: Use BIOS/firmware settings. This is the
2148 realloc= Enable/disable reallocating PCI bridge resources
2149 if allocations done by BIOS are too small to
2150 accommodate resources required by all child
2152 off: Turn realloc off
2154 realloc same as realloc=on
2155 noari do not use PCIe ARI.
2157 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2160 force Enable ASPM even on devices that claim not to support it.
2161 WARNING: Forcing ASPM on may cause system lockups.
2163 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2164 nomsi Do not use MSI for PCI Express Native Hotplug (this
2165 makes all PCIe ports use INTx for hotplug services).
2167 pcie_ports= [PCIE] PCIe ports handling:
2168 auto Ask the BIOS whether or not to use native PCIe services
2169 associated with PCIe ports (PME, hot-plug, AER). Use
2170 them only if that is allowed by the BIOS.
2171 native Use native PCIe services associated with PCIe ports
2173 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2176 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2177 nomsi Do not use MSI for native PCIe PME signaling (this makes
2178 all PCIe root ports use INTx for all services).
2180 pcmv= [HW,PCMCIA] BadgePAD 4
2183 See Documentation/blockdev/paride.txt.
2185 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2188 See arch/parisc/kernel/pdc_chassis.c
2190 percpu_alloc= Select which percpu first chunk allocator to use.
2191 Currently supported values are "embed" and "page".
2192 Archs may support subset or none of the selections.
2193 See comments in mm/percpu.c for details on each
2194 allocator. This parameter is primarily for debugging
2195 and performance comparison.
2198 See Documentation/blockdev/paride.txt.
2201 See Documentation/blockdev/paride.txt.
2203 pirq= [SMP,APIC] Manual mp-table setup
2204 See Documentation/x86/i386/IO-APIC.txt.
2206 plip= [PPT,NET] Parallel port network link
2207 Format: { parport<nr> | timid | 0 }
2208 See also Documentation/parport.txt.
2210 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2211 Override pmtimer IOPort with a hex value.
2215 Enable PNP debug messages (depends on the
2216 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2217 via /sys/module/pnp/parameters/debug. We always show
2218 current resource usage; turning this on also shows
2219 possible settings and some assignment information.
2225 { on | off | curr | res | no-curr | no-res }
2228 [ISAPNP] Exclude IRQs for the autoconfiguration
2231 [ISAPNP] Exclude DMAs for the autoconfiguration
2233 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2234 Ranges are in pairs (I/O port base and size).
2237 [ISAPNP] Exclude memory regions for the
2239 Ranges are in pairs (memory base and size).
2241 ports= [IP_VS_FTP] IPVS ftp helper module
2243 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2245 Format: <port>,<port>....
2247 print-fatal-signals=
2248 [KNL] debug: print fatal signals
2250 If enabled, warn about various signal handling
2251 related application anomalies: too many signals,
2252 too many POSIX.1 timers, fatal signals causing a
2255 If you hit the warning due to signal overflow,
2256 you might want to try "ulimit -i unlimited".
2260 printk.always_kmsg_dump=
2261 Trigger kmsg_dump for cases other than kernel oops or
2263 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2266 printk.time= Show timing data prefixed to each printk message line
2267 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2269 processor.max_cstate= [HW,ACPI]
2270 Limit processor to maximum C-state
2271 max_cstate=9 overrides any DMI blacklist limit.
2273 processor.nocst [HW,ACPI]
2274 Ignore the _CST method to determine C-states,
2275 instead using the legacy FADT method
2277 profile= [KNL] Enable kernel profiling via /proc/profile
2278 Format: [schedule,]<number>
2279 Param: "schedule" - profile schedule points.
2280 Param: <number> - step/bucket size as a power of 2 for
2281 statistical time based profiling.
2282 Param: "sleep" - profile D-state sleeping (millisecs).
2283 Requires CONFIG_SCHEDSTATS
2284 Param: "kvm" - profile VM exits.
2286 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2288 See Documentation/blockdev/ramdisk.txt.
2290 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2291 probe for; one of (bare|imps|exps|lifebook|any).
2292 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2294 psmouse.resetafter= [HW,MOUSE]
2295 Try to reset the device after so many bad packets
2298 [HW,MOUSE] Set desired mouse resolution, in dpi.
2299 psmouse.smartscroll=
2300 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2301 0 = disabled, 1 = enabled (default).
2303 pstore.backend= Specify the name of the pstore backend to use
2306 See Documentation/blockdev/paride.txt.
2309 [KNL] Number of legacy pty's. Overwrites compiled-in
2312 quiet [KNL] Disable most log messages
2317 See Documentation/md.txt.
2319 ramdisk_blocksize= [RAM]
2320 See Documentation/blockdev/ramdisk.txt.
2322 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2323 See Documentation/blockdev/ramdisk.txt.
2325 rcupdate.blimit= [KNL,BOOT]
2326 Set maximum number of finished RCU callbacks to process
2329 rcupdate.qhimark= [KNL,BOOT]
2330 Set threshold of queued
2331 RCU callbacks over which batch limiting is disabled.
2333 rcupdate.qlowmark= [KNL,BOOT]
2334 Set threshold of queued RCU callbacks below which
2335 batch limiting is re-enabled.
2339 Run specified binary instead of /init from the ramdisk,
2340 used for early userspace startup. See initrd.
2342 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2343 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2344 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2347 [KNL, SMP] Set scheduler's default relax_domain_level.
2348 See Documentation/cgroups/cpusets.txt.
2350 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2352 reservetop= [X86-32]
2354 Reserves a hole at the top of the kernel virtual
2359 Set the amount of memory to reserve for BIOS at
2360 the bottom of the address space.
2362 reset_devices [KNL] Force drivers to reset the underlying device
2363 during initialization.
2366 Specify the partition device for software suspend
2368 resume_offset= [SWSUSP]
2369 Specify the offset from the beginning of the partition
2370 given by "resume=" at which the swap header is located,
2371 in <PAGE_SIZE> units (needed only for swap files).
2372 See Documentation/power/swsusp-and-swap-files.txt
2374 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2375 read the resume files
2377 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2378 Useful for devices that are detected asynchronously
2379 (e.g. USB and MMC devices).
2381 hibernate= [HIBERNATION]
2382 noresume Don't check if there's a hibernation image
2383 present during boot.
2384 nocompress Don't compress/decompress hibernation images.
2386 retain_initrd [RAM] Keep initrd memory after extraction
2388 rhash_entries= [KNL,NET]
2389 Set number of hash buckets for route cache
2391 riscom8= [HW,SERIAL]
2392 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2394 ro [KNL] Mount root device read-only on boot
2396 root= [KNL] Root filesystem
2397 See name_to_dev_t comment in init/do_mounts.c.
2399 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2400 mount the root filesystem
2402 rootflags= [KNL] Set root filesystem mount option string
2404 rootfstype= [KNL] Set root filesystem type
2406 rootwait [KNL] Wait (indefinitely) for root device to show up.
2407 Useful for devices that are detected asynchronously
2408 (e.g. USB and MMC devices).
2410 rw [KNL] Mount root device read-write on boot
2412 S [KNL] Run init in single mode
2415 See drivers/net/irda/sa1100_ir.c.
2417 sbni= [NET] Granch SBNI12 leased line adapter
2419 sched_debug [KNL] Enables verbose scheduler debug messages.
2421 security= [SECURITY] Choose a security module to enable at boot.
2422 If this boot parameter is not specified, only the first
2423 security module asking for security registration will be
2424 loaded. An invalid security module name will be treated
2425 as if no module has been chosen.
2427 selinux= [SELINUX] Disable or enable SELinux at boot time.
2428 Format: { "0" | "1" }
2429 See security/selinux/Kconfig help text.
2432 Default value is set via kernel config option.
2433 If enabled at boot time, /selinux/disable can be used
2434 later to disable prior to initial policy load.
2436 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2437 Format: { "0" | "1" }
2438 See security/apparmor/Kconfig help text
2441 Default value is set via kernel config option.
2443 serialnumber [BUGS=X86-32]
2446 Maximal number of shapers.
2448 show_msr= [x86] show boot-time MSR settings
2449 Format: { <integer> }
2450 Show boot-time (BIOS-initialized) MSR settings.
2451 The parameter means the number of CPUs to show,
2452 for example 1 means boot CPU only.
2459 slab_max_order= [MM, SLAB]
2460 Determines the maximum allowed order for slabs.
2461 A high setting may cause OOMs due to memory
2462 fragmentation. Defaults to 1 for systems with
2463 more than 32MB of RAM, 0 otherwise.
2465 slub_debug[=options[,slabs]] [MM, SLUB]
2466 Enabling slub_debug allows one to determine the
2467 culprit if slab objects become corrupted. Enabling
2468 slub_debug can create guard zones around objects and
2469 may poison objects when not in use. Also tracks the
2470 last alloc / free. For more information see
2471 Documentation/vm/slub.txt.
2473 slub_max_order= [MM, SLUB]
2474 Determines the maximum allowed order for slabs.
2475 A high setting may cause OOMs due to memory
2476 fragmentation. For more information see
2477 Documentation/vm/slub.txt.
2479 slub_min_objects= [MM, SLUB]
2480 The minimum number of objects per slab. SLUB will
2481 increase the slab order up to slub_max_order to
2482 generate a sufficiently large slab able to contain
2483 the number of objects indicated. The higher the number
2484 of objects the smaller the overhead of tracking slabs
2485 and the less frequently locks need to be acquired.
2486 For more information see Documentation/vm/slub.txt.
2488 slub_min_order= [MM, SLUB]
2489 Determines the minimum page order for slabs. Must be
2490 lower than slub_max_order.
2491 For more information see Documentation/vm/slub.txt.
2493 slub_nomerge [MM, SLUB]
2494 Disable merging of slabs with similar size. May be
2495 necessary if there is some reason to distinguish
2496 allocs to different slabs. Debug options disable
2497 merging on their own.
2498 For more information see Documentation/vm/slub.txt.
2501 Format: <io1>[,<io2>[,...,<io8>]]
2503 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2504 attempt to substitute SMP alternatives once at boot.
2506 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2507 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2508 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2509 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2510 smsc-ircc2.ircc_irq= [HW] IRQ line
2511 smsc-ircc2.ircc_dma= [HW] DMA channel
2512 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2513 0: Toshiba Satellite 1800 (GP data pin select)
2514 1: Fast pin select (default)
2518 [KNL] Should the soft-lockup detector generate panics.
2521 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2522 See Documentation/laptops/sonypi.txt
2524 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2525 See Documentation/serial/specialix.txt.
2527 spia_io_base= [HW,MTD]
2533 Enabled the stack tracer on boot up.
2535 stacktrace_filter=[function-list]
2536 [FTRACE] Limit the functions that the stack tracer
2537 will trace at boot up. function-list is a comma separated
2538 list of functions. This list can be changed at run
2539 time by the stack_trace_filter file in the debugfs
2540 tracing directory. Note, this enables stack tracing
2541 and the stacktrace above is not needed.
2545 Set the STI (builtin display/keyboard on the HP-PARISC
2546 machines) console (graphic card) which should be used
2547 as the initial boot-console.
2548 See also comment in drivers/video/console/sticore.c.
2551 See comment in drivers/video/console/sticore.c.
2554 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2556 sunrpc.min_resvport=
2557 sunrpc.max_resvport=
2559 SunRPC servers often require that client requests
2560 originate from a privileged port (i.e. a port in the
2561 range 0 < portnr < 1024).
2562 An administrator who wishes to reserve some of these
2563 ports for other uses may adjust the range that the
2564 kernel's sunrpc client considers to be privileged
2565 using these two parameters to set the minimum and
2566 maximum port values.
2570 Control how the NFS server code allocates CPUs to
2571 service thread pools. Depending on how many NICs
2572 you have and where their interrupts are bound, this
2573 option will affect which CPUs will do NFS serving.
2574 Note: this parameter cannot be changed while the
2575 NFS server is running.
2577 auto the server chooses an appropriate mode
2578 automatically using heuristics
2579 global a single global pool contains all CPUs
2580 percpu one pool for each CPU
2581 pernode one pool for each NUMA node (equivalent
2582 to global on non-NUMA machines)
2584 sunrpc.tcp_slot_table_entries=
2585 sunrpc.udp_slot_table_entries=
2587 Sets the upper limit on the number of simultaneous
2588 RPC calls that can be sent from the client to a
2589 server. Increasing these values may allow you to
2590 improve throughput, but will also increase the
2591 amount of memory reserved for use by the client.
2594 [KNL] Enable accounting of swap in memory resource
2595 controller if no parameter or 1 is given or disable
2596 it if 0 is given (See Documentation/cgroups/memory.txt)
2598 swiotlb= [IA-64] Number of I/O TLB slabs
2602 sysfs.deprecated=0|1 [KNL]
2603 Enable/disable old style sysfs layout for old udev
2604 on older distributions. When this option is enabled
2605 very new udev will not work anymore. When this option
2606 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2607 in older udev will not work anymore.
2608 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2609 the kernel configuration.
2611 sysrq_always_enabled
2613 Ignore sysrq setting - this boot parameter will
2614 neutralize any effect of /proc/sys/kernel/sysrq.
2615 Useful for debugging.
2619 test_suspend= [SUSPEND]
2620 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2621 standby suspend) as the system sleep state to briefly
2622 enter during system startup. The system is woken from
2623 this state using a wakeup-capable RTC alarm.
2625 thash_entries= [KNL,NET]
2626 Set number of hash buckets for TCP connection
2628 thermal.act= [HW,ACPI]
2629 -1: disable all active trip points in all thermal zones
2630 <degrees C>: override all lowest active trip points
2632 thermal.crt= [HW,ACPI]
2633 -1: disable all critical trip points in all thermal zones
2634 <degrees C>: override all critical trip points
2636 thermal.nocrt= [HW,ACPI]
2637 Set to disable actions on ACPI thermal zone
2638 critical and hot trip points.
2640 thermal.off= [HW,ACPI]
2641 1: disable ACPI thermal control
2643 thermal.psv= [HW,ACPI]
2644 -1: disable all passive trip points
2645 <degrees C>: override all passive trip points to this
2648 thermal.tzp= [HW,ACPI]
2649 Specify global default ACPI thermal zone polling rate
2650 <deci-seconds>: poll all this frequency
2651 0: no polling (default)
2654 Force threading of all interrupt handlers except those
2655 marked explicitly IRQF_NO_THREAD.
2659 Specify if the kernel should make use of the cpu
2660 topology information if the hardware supports this.
2661 The scheduler will make use of this information and
2662 e.g. base its process migration decisions on it.
2667 tpm_suspend_pcr=[HW,TPM]
2668 Format: integer pcr id
2669 Specify that at suspend time, the tpm driver
2670 should extend the specified pcr with zeros,
2671 as a workaround for some chips which fail to
2672 flush the last written pcr on TPM_SaveState.
2673 This will guarantee that all the other pcrs
2676 trace_buf_size=nn[KMG]
2677 [FTRACE] will set tracing buffer size.
2679 trace_event=[event-list]
2680 [FTRACE] Set and start specified trace events in order
2681 to facilitate early boot debugging.
2682 See also Documentation/trace/events.txt
2684 transparent_hugepage=
2686 Format: [always|madvise|never]
2687 Can be used to control the default behavior of the system
2688 with respect to transparent hugepages.
2689 See Documentation/vm/transhuge.txt for more details.
2691 tsc= Disable clocksource stability checks for TSC.
2693 [x86] reliable: mark tsc clocksource as reliable, this
2694 disables clocksource verification at runtime, as well
2695 as the stability checks done at bootup. Used to enable
2696 high-resolution timer mode on older hardware, and in
2697 virtualized environment.
2698 [x86] noirqtime: Do not use TSC to do irq accounting.
2699 Used to run time disable IRQ_TIME_ACCOUNTING on any
2700 platforms where RDTSC is slow and this accounting
2703 turbografx.map[2|3]= [HW,JOY]
2704 TurboGraFX parallel port interface
2706 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2707 See also Documentation/input/joystick-parport.txt
2709 udbg-immortal [PPC] When debugging early kernel crashes that
2710 happen after console_init() and before a proper
2711 console driver takes over, this boot options might
2712 help "seeing" what's going on.
2714 uhash_entries= [KNL,NET]
2715 Set number of hash buckets for UDP/UDP-Lite connections
2718 [USB] Ignore overcurrent events (default N).
2719 Some badly-designed motherboards generate lots of
2720 bogus events, for ports that aren't wired to
2721 anything. Set this parameter to avoid log spamming.
2722 Note that genuine overcurrent events won't be
2726 [X86] Cause panic on unknown NMI.
2728 usbcore.authorized_default=
2729 [USB] Default USB device authorization:
2730 (default -1 = authorized except for wireless USB,
2731 0 = not authorized, 1 = authorized)
2733 usbcore.autosuspend=
2734 [USB] The autosuspend time delay (in seconds) used
2735 for newly-detected USB devices (default 2). This
2736 is the time required before an idle device will be
2737 autosuspended. Devices for which the delay is set
2738 to a negative value won't be autosuspended at all.
2740 usbcore.usbfs_snoop=
2741 [USB] Set to log all usbfs traffic (default 0 = off).
2743 usbcore.blinkenlights=
2744 [USB] Set to cycle leds on hubs (default 0 = off).
2746 usbcore.old_scheme_first=
2747 [USB] Start with the old device initialization
2748 scheme (default 0 = off).
2750 usbcore.usbfs_memory_mb=
2751 [USB] Memory limit (in MB) for buffers allocated by
2752 usbfs (default = 16, 0 = max = 2047).
2754 usbcore.use_both_schemes=
2755 [USB] Try the other device initialization scheme
2756 if the first one fails (default 1 = enabled).
2758 usbcore.initial_descriptor_timeout=
2759 [USB] Specifies timeout for the initial 64-byte
2760 USB_REQ_GET_DESCRIPTOR request in milliseconds
2761 (default 5000 = 5.0 seconds).
2764 [USBHID] The interval which mice are to be polled at.
2766 usb-storage.delay_use=
2767 [UMS] The delay in seconds before a new device is
2768 scanned for Logical Units (default 5).
2771 [UMS] A list of quirks entries to supplement or
2772 override the built-in unusual_devs list. List
2773 entries are separated by commas. Each entry has
2774 the form VID:PID:Flags where VID and PID are Vendor
2775 and Product ID values (4-digit hex numbers) and
2776 Flags is a set of characters, each corresponding
2777 to a common usb-storage quirk flag as follows:
2778 a = SANE_SENSE (collect more than 18 bytes
2780 b = BAD_SENSE (don't collect more than 18
2781 bytes of sense data);
2782 c = FIX_CAPACITY (decrease the reported
2783 device capacity by one sector);
2784 d = NO_READ_DISC_INFO (don't use
2785 READ_DISC_INFO command);
2786 e = NO_READ_CAPACITY_16 (don't use
2787 READ_CAPACITY_16 command);
2788 h = CAPACITY_HEURISTICS (decrease the
2789 reported device capacity by one
2790 sector if the number is odd);
2791 i = IGNORE_DEVICE (don't bind to this
2793 l = NOT_LOCKABLE (don't try to lock and
2794 unlock ejectable media);
2795 m = MAX_SECTORS_64 (don't transfer more
2796 than 64 sectors = 32 KB at a time);
2797 n = INITIAL_READ10 (force a retry of the
2798 initial READ(10) command);
2799 o = CAPACITY_OK (accept the capacity
2800 reported by the device);
2801 r = IGNORE_RESIDUE (the device reports
2802 bogus residue values);
2803 s = SINGLE_LUN (the device has only one
2805 w = NO_WP_DETECT (don't test whether the
2806 medium is write-protected).
2807 Example: quirks=0419:aaf5:rl,0421:0433:rc
2809 user_debug= [KNL,ARM]
2811 See arch/arm/Kconfig.debug help text.
2812 1 - undefined instruction events
2814 4 - invalid data aborts
2817 Example: user_debug=31
2820 [X86] Flags controlling user PTE allocations.
2822 nohigh = do not allocate PTE pages in
2823 HIGHMEM regardless of setting
2827 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2828 vdso=1: enable VDSO (default)
2829 vdso=0: disable VDSO mapping
2832 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2833 vdso32=1: enable 32-bit VDSO (default)
2834 vdso32=0: disable 32-bit VDSO mapping
2837 vector=percpu: enable percpu vector domain
2839 video= [FB] Frame buffer configuration
2840 See Documentation/fb/modedb.txt.
2842 vga= [BOOT,X86-32] Select a particular video mode
2843 See Documentation/x86/boot.txt and
2844 Documentation/svga.txt.
2845 Use vga=ask for menu.
2846 This is actually a boot loader parameter; the value is
2847 passed to the kernel using a special protocol.
2849 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2850 size of <nn>. This can be used to increase the
2851 minimum size (128MB on x86). It can also be used to
2852 decrease the size and leave more room for directly
2855 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2858 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2861 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2865 Controls the behavior of vsyscalls (i.e. calls to
2866 fixed addresses of 0xffffffffff600x00 from legacy
2867 code). Most statically-linked binaries and older
2868 versions of glibc use these calls. Because these
2869 functions are at fixed addresses, they make nice
2870 targets for exploits that can control RIP.
2872 emulate [default] Vsyscalls turn into traps and are
2873 emulated reasonably safely.
2875 native Vsyscalls are native syscall instructions.
2876 This is a little bit faster than trapping
2877 and makes a few dynamic recompilers work
2878 better than they would in emulation mode.
2879 It also makes exploits much easier to write.
2881 none Vsyscalls don't work at all. This makes
2882 them quite hard to use for exploits but
2883 might break your system.
2885 vt.cur_default= [VT] Default cursor shape.
2886 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2887 the parameters of the <Esc>[?A;B;Cc escape sequence;
2888 see VGA-softcursor.txt. Default: 2 = underline.
2890 vt.default_blu= [VT]
2891 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2892 Change the default blue palette of the console.
2893 This is a 16-member array composed of values
2896 vt.default_grn= [VT]
2897 Format: <green0>,<green1>,<green2>,...,<green15>
2898 Change the default green palette of the console.
2899 This is a 16-member array composed of values
2902 vt.default_red= [VT]
2903 Format: <red0>,<red1>,<red2>,...,<red15>
2904 Change the default red palette of the console.
2905 This is a 16-member array composed of values
2911 Set system-wide default UTF-8 mode for all tty's.
2912 Default is 1, i.e. UTF-8 mode is enabled for all
2913 newly opened terminals.
2915 vt.global_cursor_default=
2918 Set system-wide default for whether a cursor
2919 is shown on new VTs. Default is -1,
2920 i.e. cursors will be created by default unless
2921 overridden by individual drivers. 0 will hide
2922 cursors, 1 will display them.
2924 watchdog timers [HW,WDT] For information on watchdog timers,
2925 see Documentation/watchdog/watchdog-parameters.txt
2926 or other driver-specific files in the
2927 Documentation/watchdog/ directory.
2929 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2930 default x2apic cluster mode on platforms
2933 x86_mrst_timer= [X86-32,APBT]
2934 Choose timer option for x86 Moorestown MID platform.
2935 Two valid options are apbt timer only and lapic timer
2936 plus one apbt timer for broadcast timer.
2937 x86_mrst_timer=apbt_only | lapic_and_apbt
2939 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2940 xd_geo= See header of drivers/block/xd.c.
2942 xen_emul_unplug= [HW,X86,XEN]
2943 Unplug Xen emulated devices
2944 Format: [unplug0,][unplug1]
2945 ide-disks -- unplug primary master IDE devices
2946 aux-ide-disks -- unplug non-primary-master IDE devices
2947 nics -- unplug network devices
2948 all -- unplug all emulated devices (NICs and IDE disks)
2949 unnecessary -- unplugging emulated devices is
2950 unnecessary even if the host did not respond to
2952 never -- do not unplug even if version check succeeds
2954 xirc2ps_cs= [NET,PCMCIA]
2956 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2958 ______________________________________________________________________
2962 Add more DRM drivers.
projects / mirror_ubuntu-zesty-kernel.git / blob