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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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 FB The frame buffer device is enabled.
53 FTRACE Function tracing enabled.
54 GCOV GCOV profiling is enabled.
55 HW Appropriate hardware is enabled.
56 IA-64 IA-64 architecture is enabled.
57 IMA Integrity measurement architecture is enabled.
58 IOSCHED More than one I/O scheduler is enabled.
59 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
60 IPV6 IPv6 support is enabled.
61 ISAPNP ISA PnP code is enabled.
62 ISDN Appropriate ISDN support is enabled.
63 JOY Appropriate joystick support is enabled.
64 KGDB Kernel debugger support is enabled.
65 KVM Kernel Virtual Machine support is enabled.
66 LIBATA Libata driver is enabled
67 LP Printer support is enabled.
68 LOOP Loopback device support is enabled.
69 M68k M68k architecture is enabled.
70 These options have more detailed description inside of
71 Documentation/m68k/kernel-options.txt.
72 MCA MCA bus support is enabled.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VGA The VGA console has been enabled.
113 VT Virtual terminal support is enabled.
114 WDT Watchdog support is enabled.
115 XT IBM PC/XT MFM hard disk support is enabled.
116 X86-32 X86-32, aka i386 architecture is enabled.
117 X86-64 X86-64 architecture is enabled.
118 More X86-64 boot options can be found in
119 Documentation/x86/x86_64/boot-options.txt .
120 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
121 XEN Xen support is enabled
123 In addition, the following text indicates that the option:
125 BUGS= Relates to possible processor bugs on the said processor.
126 KNL Is a kernel start-up parameter.
127 BOOT Is a boot loader parameter.
129 Parameters denoted with BOOT are actually interpreted by the boot
130 loader, and have no meaning to the kernel directly.
131 Do not modify the syntax of boot loader parameters without extreme
132 need or coordination with <Documentation/x86/boot.txt>.
134 There are also arch-specific kernel-parameters not documented here.
135 See for example <Documentation/x86/x86_64/boot-options.txt>.
137 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
138 a trailing = on the name of any parameter states that that parameter will
139 be entered as an environment variable, whereas its absence indicates that
140 it will appear as a kernel argument readable via /proc/cmdline by programs
141 running once the system is up.
143 The number of kernel parameters is not limited, but the length of the
144 complete command line (parameters including spaces etc.) is limited to
145 a fixed number of characters. This limit depends on the architecture
146 and is between 256 and 4096 characters. It is defined in the file
147 ./include/asm/setup.h as COMMAND_LINE_SIZE.
149 Finally, the [KMG] suffix is commonly described after a number of kernel
150 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
151 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
152 bytes respectively. Such letter suffixes can also be entirely omitted.
155 acpi= [HW,ACPI,X86]
156 Advanced Configuration and Power Interface
157 Format: { force | off | strict | noirq | rsdt }
158 force -- enable ACPI if default was off
159 off -- disable ACPI if default was on
160 noirq -- do not use ACPI for IRQ routing
161 strict -- Be less tolerant of platforms that are not
162 strictly ACPI specification compliant.
163 rsdt -- prefer RSDT over (default) XSDT
164 copy_dsdt -- copy DSDT to memory
166 See also Documentation/power/pm.txt, pci=noacpi
168 acpi_rsdp= [ACPI,EFI,KEXEC]
169 Pass the RSDP address to the kernel, mostly used
170 on machines running EFI runtime service to boot the
171 second kernel for kdump.
173 acpi_apic_instance= [ACPI, IOAPIC]
174 Format: <int>
175 2: use 2nd APIC table, if available
176 1,0: use 1st APIC table
177 default: 0
179 acpi_backlight= [HW,ACPI]
180 acpi_backlight=vendor
181 acpi_backlight=video
182 If set to vendor, prefer vendor specific driver
183 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
184 of the ACPI video.ko driver.
186 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
187 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
188 Format: <int>
189 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
190 debug output. Bits in debug_layer correspond to a
191 _COMPONENT in an ACPI source file, e.g.,
192 #define _COMPONENT ACPI_PCI_COMPONENT
193 Bits in debug_level correspond to a level in
194 ACPI_DEBUG_PRINT statements, e.g.,
195 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
196 The debug_level mask defaults to "info". See
197 Documentation/acpi/debug.txt for more information about
198 debug layers and levels.
200 Enable processor driver info messages:
201 acpi.debug_layer=0x20000000
202 Enable PCI/PCI interrupt routing info messages:
203 acpi.debug_layer=0x400000
204 Enable AML "Debug" output, i.e., stores to the Debug
205 object while interpreting AML:
206 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
207 Enable all messages related to ACPI hardware:
208 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
210 Some values produce so much output that the system is
211 unusable. The "log_buf_len" parameter may be useful
212 if you need to capture more output.
214 acpi_irq_balance [HW,ACPI]
215 ACPI will balance active IRQs
216 default in APIC mode
218 acpi_irq_nobalance [HW,ACPI]
219 ACPI will not move active IRQs (default)
220 default in PIC mode
222 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
223 Format: <irq>,<irq>...
225 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
226 use by PCI
227 Format: <irq>,<irq>...
229 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
231 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
232 Format: To spoof as Windows 98: ="Microsoft Windows"
234 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
235 acpi_osi="string1" # add string1 -- only one string
236 acpi_osi="!string2" # remove built-in string2
237 acpi_osi= # disable all strings
239 acpi_pm_good [X86]
240 Override the pmtimer bug detection: force the kernel
241 to assume that this machine's pmtimer latches its value
242 and always returns good values.
244 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
245 Format: { level | edge | high | low }
247 acpi_serialize [HW,ACPI] force serialization of AML methods
249 acpi_skip_timer_override [HW,ACPI]
250 Recognize and ignore IRQ0/pin2 Interrupt Override.
251 For broken nForce2 BIOS resulting in XT-PIC timer.
253 acpi_sleep= [HW,ACPI] Sleep options
254 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
255 old_ordering, nonvs, sci_force_enable }
256 See Documentation/power/video.txt for information on
257 s3_bios and s3_mode.
258 s3_beep is for debugging; it makes the PC's speaker beep
259 as soon as the kernel's real-mode entry point is called.
260 s4_nohwsig prevents ACPI hardware signature from being
261 used during resume from hibernation.
262 old_ordering causes the ACPI 1.0 ordering of the _PTS
263 control method, with respect to putting devices into
264 low power states, to be enforced (the ACPI 2.0 ordering
265 of _PTS is used by default).
266 nonvs prevents the kernel from saving/restoring the
267 ACPI NVS memory during suspend/hibernation and resume.
268 sci_force_enable causes the kernel to set SCI_EN directly
269 on resume from S1/S3 (which is against the ACPI spec,
270 but some broken systems don't work without it).
272 acpi_use_timer_override [HW,ACPI]
273 Use timer override. For some broken Nvidia NF5 boards
274 that require a timer override, but don't have HPET
276 acpi_enforce_resources= [ACPI]
277 { strict | lax | no }
278 Check for resource conflicts between native drivers
279 and ACPI OperationRegions (SystemIO and SystemMemory
280 only). IO ports and memory declared in ACPI might be
281 used by the ACPI subsystem in arbitrary AML code and
282 can interfere with legacy drivers.
283 strict (default): access to resources claimed by ACPI
284 is denied; legacy drivers trying to access reserved
285 resources will fail to bind to device using them.
286 lax: access to resources claimed by ACPI is allowed;
287 legacy drivers trying to access reserved resources
288 will bind successfully but a warning message is logged.
289 no: ACPI OperationRegions are not marked as reserved,
290 no further checks are performed.
292 add_efi_memmap [EFI; X86] Include EFI memory map in
293 kernel's map of available physical RAM.
295 agp= [AGP]
296 { off | try_unsupported }
297 off: disable AGP support
298 try_unsupported: try to drive unsupported chipsets
299 (may crash computer or cause data corruption)
301 ALSA [HW,ALSA]
302 See Documentation/sound/alsa/alsa-parameters.txt
304 alignment= [KNL,ARM]
305 Allow the default userspace alignment fault handler
306 behaviour to be specified. Bit 0 enables warnings,
307 bit 1 enables fixups, and bit 2 sends a segfault.
309 amd_iommu= [HW,X86-84]
310 Pass parameters to the AMD IOMMU driver in the system.
311 Possible values are:
312 fullflush - enable flushing of IO/TLB entries when
313 they are unmapped. Otherwise they are
314 flushed before they will be reused, which
315 is a lot of faster
316 off - do not initialize any AMD IOMMU found in
317 the system
319 amijoy.map= [HW,JOY] Amiga joystick support
320 Map of devices attached to JOY0DAT and JOY1DAT
321 Format: <a>,<b>
322 See also Documentation/kernel/input/joystick.txt
324 analog.map= [HW,JOY] Analog joystick and gamepad support
325 Specifies type or capabilities of an analog joystick
326 connected to one of 16 gameports
327 Format: <type1>,<type2>,..<type16>
329 apc= [HW,SPARC]
330 Power management functions (SPARCstation-4/5 + deriv.)
331 Format: noidle
332 Disable APC CPU standby support. SPARCstation-Fox does
333 not play well with APC CPU idle - disable it if you have
334 APC and your system crashes randomly.
336 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
337 Change the output verbosity whilst booting
338 Format: { quiet (default) | verbose | debug }
339 Change the amount of debugging information output
340 when initialising the APIC and IO-APIC components.
342 autoconf= [IPV6]
343 See Documentation/networking/ipv6.txt.
345 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
346 Limit apic dumping. The parameter defines the maximal
347 number of local apics being dumped. Also it is possible
348 to set it to "all" by meaning -- no limit here.
349 Format: { 1 (default) | 2 | ... | all }.
350 The parameter valid if only apic=debug or
351 apic=verbose is specified.
352 Example: apic=debug show_lapic=all
354 apm= [APM] Advanced Power Management
355 See header of arch/x86/kernel/apm_32.c.
357 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
358 Format: <io>,<irq>,<nodeID>
360 ataflop= [HW,M68k]
362 atarimouse= [HW,MOUSE] Atari Mouse
364 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
365 EzKey and similar keyboards
367 atkbd.reset= [HW] Reset keyboard during initialization
369 atkbd.set= [HW] Select keyboard code set
370 Format: <int> (2 = AT (default), 3 = PS/2)
372 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
373 keyboards
375 atkbd.softraw= [HW] Choose between synthetic and real raw mode
376 Format: <bool> (0 = real, 1 = synthetic (default))
378 atkbd.softrepeat= [HW]
379 Use software keyboard repeat
381 autotest [IA-64]
383 baycom_epp= [HW,AX25]
384 Format: <io>,<mode>
386 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
387 Format: <io>,<mode>
388 See header of drivers/net/hamradio/baycom_par.c.
390 baycom_ser_fdx= [HW,AX25]
391 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
392 Format: <io>,<irq>,<mode>[,<baud>]
393 See header of drivers/net/hamradio/baycom_ser_fdx.c.
395 baycom_ser_hdx= [HW,AX25]
396 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
397 Format: <io>,<irq>,<mode>
398 See header of drivers/net/hamradio/baycom_ser_hdx.c.
400 boot_delay= Milliseconds to delay each printk during boot.
401 Values larger than 10 seconds (10000) are changed to
402 no delay (0).
403 Format: integer
405 bootmem_debug [KNL] Enable bootmem allocator debug messages.
407 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
408 bttv.radio= Most important insmod options are available as
409 kernel args too.
410 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
411 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
413 bulk_remove=off [PPC] This parameter disables the use of the pSeries
414 firmware feature for flushing multiple hpte entries
415 at a time.
417 c101= [NET] Moxa C101 synchronous serial card
419 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
420 Sometimes CPU hardware bugs make them report the cache
421 size incorrectly. The kernel will attempt work arounds
422 to fix known problems, but for some CPUs it is not
423 possible to determine what the correct size should be.
424 This option provides an override for these situations.
426 capability.disable=
427 [SECURITY] Disable capabilities. This would normally
428 be used only if an alternative security model is to be
429 configured. Potentially dangerous and should only be
430 used if you are entirely sure of the consequences.
432 ccw_timeout_log [S390]
433 See Documentation/s390/CommonIO for details.
435 cgroup_disable= [KNL] Disable a particular controller
436 Format: {name of the controller(s) to disable}
437 {Currently supported controllers - "memory"}
439 checkreqprot [SELINUX] Set initial checkreqprot flag value.
440 Format: { "0" | "1" }
441 See security/selinux/Kconfig help text.
442 0 -- check protection applied by kernel (includes
443 any implied execute protection).
444 1 -- check protection requested by application.
445 Default value is set via a kernel config option.
446 Value can be changed at runtime via
447 /selinux/checkreqprot.
449 cio_ignore= [S390]
450 See Documentation/s390/CommonIO for details.
452 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
453 [Deprecated]
454 Forces specified clocksource (if available) to be used
455 when calculating gettimeofday(). If specified
456 clocksource is not available, it defaults to PIT.
457 Format: { pit | tsc | cyclone | pmtmr }
459 clocksource= Override the default clocksource
460 Format: <string>
461 Override the default clocksource and use the clocksource
462 with the name specified.
463 Some clocksource names to choose from, depending on
464 the platform:
465 [all] jiffies (this is the base, fallback clocksource)
466 [ACPI] acpi_pm
467 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
468 pxa_timer,timer3,32k_counter,timer0_1
469 [AVR32] avr32
470 [X86-32] pit,hpet,tsc;
471 scx200_hrt on Geode; cyclone on IBM x440
472 [MIPS] MIPS
473 [PARISC] cr16
474 [S390] tod
475 [SH] SuperH
476 [SPARC64] tick
477 [X86-64] hpet,tsc
479 clearcpuid=BITNUM [X86]
480 Disable CPUID feature X for the kernel. See
481 arch/x86/include/asm/cpufeature.h for the valid bit
482 numbers. Note the Linux specific bits are not necessarily
483 stable over kernel options, but the vendor specific
484 ones should be.
485 Also note that user programs calling CPUID directly
486 or using the feature without checking anything
487 will still see it. This just prevents it from
488 being used by the kernel or shown in /proc/cpuinfo.
489 Also note the kernel might malfunction if you disable
490 some critical bits.
492 cmo_free_hint= [PPC] Format: { yes | no }
493 Specify whether pages are marked as being inactive
494 when they are freed. This is used in CMO environments
495 to determine OS memory pressure for page stealing by
496 a hypervisor.
497 Default: yes
499 code_bytes [X86] How many bytes of object code to print
500 in an oops report.
501 Range: 0 - 8192
502 Default: 64
504 com20020= [HW,NET] ARCnet - COM20020 chipset
505 Format:
506 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
508 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
509 Format: <io>[,<irq>]
511 com90xx= [HW,NET]
512 ARCnet - COM90xx chipset (memory-mapped buffers)
513 Format: <io>[,<irq>[,<memstart>]]
515 condev= [HW,S390] console device
516 conmode=
518 console= [KNL] Output console device and options.
520 tty<n> Use the virtual console device <n>.
522 ttyS<n>[,options]
523 ttyUSB0[,options]
524 Use the specified serial port. The options are of
525 the form "bbbbpnf", where "bbbb" is the baud rate,
526 "p" is parity ("n", "o", or "e"), "n" is number of
527 bits, and "f" is flow control ("r" for RTS or
528 omit it). Default is "9600n8".
530 See Documentation/serial-console.txt for more
531 information. See
532 Documentation/networking/netconsole.txt for an
533 alternative.
535 uart[8250],io,<addr>[,options]
536 uart[8250],mmio,<addr>[,options]
537 Start an early, polled-mode console on the 8250/16550
538 UART at the specified I/O port or MMIO address,
539 switching to the matching ttyS device later. The
540 options are the same as for ttyS, above.
542 If the device connected to the port is not a TTY but a braille
543 device, prepend "brl," before the device type, for instance
544 console=brl,ttyS0
545 For now, only VisioBraille is supported.
547 consoleblank= [KNL] The console blank (screen saver) timeout in
548 seconds. Defaults to 10*60 = 10mins. A value of 0
549 disables the blank timer.
551 coredump_filter=
552 [KNL] Change the default value for
553 /proc/<pid>/coredump_filter.
554 See also Documentation/filesystems/proc.txt.
556 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
557 Format:
558 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
560 crashkernel=size[KMG][@offset[KMG]]
561 [KNL] Using kexec, Linux can switch to a 'crash kernel'
562 upon panic. This parameter reserves the physical
563 memory region [offset, offset + size] for that kernel
564 image. If '@offset' is omitted, then a suitable offset
565 is selected automatically. Check
566 Documentation/kdump/kdump.txt for further details.
568 crashkernel=range1:size1[,range2:size2,...][@offset]
569 [KNL] Same as above, but depends on the memory
570 in the running system. The syntax of range is
571 start-[end] where start and end are both
572 a memory unit (amount[KMG]). See also
573 Documentation/kdump/kdump.txt for an example.
575 cs89x0_dma= [HW,NET]
576 Format: <dma>
578 cs89x0_media= [HW,NET]
579 Format: { rj45 | aui | bnc }
581 dasd= [HW,NET]
582 See header of drivers/s390/block/dasd_devmap.c.
584 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
585 (one device per port)
586 Format: <port#>,<type>
587 See also Documentation/input/joystick-parport.txt
589 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
590 time. See Documentation/dynamic-debug-howto.txt for
591 details.
593 debug [KNL] Enable kernel debugging (events log level).
595 debug_locks_verbose=
596 [KNL] verbose self-tests
597 Format=<0|1>
598 Print debugging info while doing the locking API
599 self-tests.
600 We default to 0 (no extra messages), setting it to
601 1 will print _a lot_ more information - normally
602 only useful to kernel developers.
604 debug_objects [KNL] Enable object debugging
606 no_debug_objects
607 [KNL] Disable object debugging
609 debugpat [X86] Enable PAT debugging
611 decnet.addr= [HW,NET]
612 Format: <area>[,<node>]
613 See also Documentation/networking/decnet.txt.
615 default_hugepagesz=
616 [same as hugepagesz=] The size of the default
617 HugeTLB page size. This is the size represented by
618 the legacy /proc/ hugepages APIs, used for SHM, and
619 default size when mounting hugetlbfs filesystems.
620 Defaults to the default architecture's huge page size
621 if not specified.
623 dhash_entries= [KNL]
624 Set number of hash buckets for dentry cache.
626 digi= [HW,SERIAL]
627 IO parameters + enable/disable command.
629 digiepca= [HW,SERIAL]
630 See drivers/char/README.epca and
631 Documentation/serial/digiepca.txt.
633 disable= [IPV6]
634 See Documentation/networking/ipv6.txt.
636 disable_ddw [PPC/PSERIES]
637 Disable Dynamic DMA Window support. Use this if
638 to workaround buggy firmware.
640 disable_ipv6= [IPV6]
641 See Documentation/networking/ipv6.txt.
643 disable_mtrr_cleanup [X86]
644 The kernel tries to adjust MTRR layout from continuous
645 to discrete, to make X server driver able to add WB
646 entry later. This parameter disables that.
648 disable_mtrr_trim [X86, Intel and AMD only]
649 By default the kernel will trim any uncacheable
650 memory out of your available memory pool based on
651 MTRR settings. This parameter disables that behavior,
652 possibly causing your machine to run very slowly.
654 disable_timer_pin_1 [X86]
655 Disable PIN 1 of APIC timer
656 Can be useful to work around chipset bugs.
658 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
659 this option disables the debugging code at boot.
661 dma_debug_entries=<number>
662 This option allows to tune the number of preallocated
663 entries for DMA-API debugging code. One entry is
664 required per DMA-API allocation. Use this if the
665 DMA-API debugging code disables itself because the
666 architectural default is too low.
668 dma_debug_driver=<driver_name>
669 With this option the DMA-API debugging driver
670 filter feature can be enabled at boot time. Just
671 pass the driver to filter for as the parameter.
672 The filter can be disabled or changed to another
673 driver later using sysfs.
675 dscc4.setup= [NET]
677 earlycon= [KNL] Output early console device and options.
678 uart[8250],io,<addr>[,options]
679 uart[8250],mmio,<addr>[,options]
680 uart[8250],mmio32,<addr>[,options]
681 Start an early, polled-mode console on the 8250/16550
682 UART at the specified I/O port or MMIO address.
683 MMIO inter-register address stride is either 8-bit
684 (mmio) or 32-bit (mmio32).
685 The options are the same as for ttyS, above.
687 earlyprintk= [X86,SH,BLACKFIN]
688 earlyprintk=vga
689 earlyprintk=serial[,ttySn[,baudrate]]
690 earlyprintk=ttySn[,baudrate]
691 earlyprintk=dbgp[debugController#]
693 Append ",keep" to not disable it when the real console
694 takes over.
696 Only vga or serial or usb debug port at a time.
698 Currently only ttyS0 and ttyS1 are supported.
700 Interaction with the standard serial driver is not
701 very good.
703 The VGA output is eventually overwritten by the real
704 console.
706 ekgdboc= [X86,KGDB] Allow early kernel console debugging
707 ekgdboc=kbd
709 This is designed to be used in conjunction with
710 the boot argument: earlyprintk=vga
712 edd= [EDD]
713 Format: {"off" | "on" | "skip[mbr]"}
715 eisa_irq_edge= [PARISC,HW]
716 See header of drivers/parisc/eisa.c.
718 elanfreq= [X86-32]
719 See comment before function elanfreq_setup() in
720 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
722 elevator= [IOSCHED]
723 Format: {"cfq" | "deadline" | "noop"}
724 See Documentation/block/as-iosched.txt and
725 Documentation/block/deadline-iosched.txt for details.
727 elfcorehdr= [IA-64,PPC,SH,X86]
728 Specifies physical address of start of kernel core
729 image elf header. Generally kexec loader will
730 pass this option to capture kernel.
731 See Documentation/kdump/kdump.txt for details.
733 enable_mtrr_cleanup [X86]
734 The kernel tries to adjust MTRR layout from continuous
735 to discrete, to make X server driver able to add WB
736 entry later. This parameter enables that.
738 enable_timer_pin_1 [X86]
739 Enable PIN 1 of APIC timer
740 Can be useful to work around chipset bugs
741 (in particular on some ATI chipsets).
742 The kernel tries to set a reasonable default.
744 enforcing [SELINUX] Set initial enforcing status.
745 Format: {"0" | "1"}
746 See security/selinux/Kconfig help text.
747 0 -- permissive (log only, no denials).
748 1 -- enforcing (deny and log).
749 Default value is 0.
750 Value can be changed at runtime via /selinux/enforce.
752 erst_disable [ACPI]
753 Disable Error Record Serialization Table (ERST)
754 support.
756 ether= [HW,NET] Ethernet cards parameters
757 This option is obsoleted by the "netdev=" option, which
758 has equivalent usage. See its documentation for details.
760 failslab=
761 fail_page_alloc=
762 fail_make_request=[KNL]
763 General fault injection mechanism.
764 Format: <interval>,<probability>,<space>,<times>
765 See also /Documentation/fault-injection/.
767 floppy= [HW]
768 See Documentation/blockdev/floppy.txt.
770 force_pal_cache_flush
771 [IA-64] Avoid check_sal_cache_flush which may hang on
772 buggy SAL_CACHE_FLUSH implementations. Using this
773 parameter will force ia64_sal_cache_flush to call
774 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
776 ftrace=[tracer]
777 [FTRACE] will set and start the specified tracer
778 as early as possible in order to facilitate early
779 boot debugging.
781 ftrace_dump_on_oops[=orig_cpu]
782 [FTRACE] will dump the trace buffers on oops.
783 If no parameter is passed, ftrace will dump
784 buffers of all CPUs, but if you pass orig_cpu, it will
785 dump only the buffer of the CPU that triggered the
786 oops.
788 ftrace_filter=[function-list]
789 [FTRACE] Limit the functions traced by the function
790 tracer at boot up. function-list is a comma separated
791 list of functions. This list can be changed at run
792 time by the set_ftrace_filter file in the debugfs
793 tracing directory.
795 ftrace_notrace=[function-list]
796 [FTRACE] Do not trace the functions specified in
797 function-list. This list can be changed at run time
798 by the set_ftrace_notrace file in the debugfs
799 tracing directory.
801 ftrace_graph_filter=[function-list]
802 [FTRACE] Limit the top level callers functions traced
803 by the function graph tracer at boot up.
804 function-list is a comma separated list of functions
805 that can be changed at run time by the
806 set_graph_function file in the debugfs tracing directory.
808 gamecon.map[2|3]=
809 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
810 support via parallel port (up to 5 devices per port)
811 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
812 See also Documentation/input/joystick-parport.txt
814 gamma= [HW,DRM]
816 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
817 Format: off | on
818 default: on
820 gcov_persist= [GCOV] When non-zero (default), profiling data for
821 kernel modules is saved and remains accessible via
822 debugfs, even when the module is unloaded/reloaded.
823 When zero, profiling data is discarded and associated
824 debugfs files are removed at module unload time.
826 gpt [EFI] Forces disk with valid GPT signature but
827 invalid Protective MBR to be treated as GPT.
829 hashdist= [KNL,NUMA] Large hashes allocated during boot
830 are distributed across NUMA nodes. Defaults on
831 for 64-bit NUMA, off otherwise.
832 Format: 0 | 1 (for off | on)
834 hcl= [IA-64] SGI's Hardware Graph compatibility layer
836 hd= [EIDE] (E)IDE hard drive subsystem geometry
837 Format: <cyl>,<head>,<sect>
839 hest_disable [ACPI]
840 Disable Hardware Error Source Table (HEST) support;
841 corresponding firmware-first mode error processing
842 logic will be disabled.
844 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
845 size of <nn>. This works even on boxes that have no
846 highmem otherwise. This also works to reduce highmem
847 size on bigger boxes.
849 highres= [KNL] Enable/disable high resolution timer mode.
850 Valid parameters: "on", "off"
851 Default: "on"
853 hisax= [HW,ISDN]
854 See Documentation/isdn/README.HiSax.
856 hlt [BUGS=ARM,SH]
858 hpet= [X86-32,HPET] option to control HPET usage
859 Format: { enable (default) | disable | force |
860 verbose }
861 disable: disable HPET and use PIT instead
862 force: allow force enabled of undocumented chips (ICH4,
863 VIA, nVidia)
864 verbose: show contents of HPET registers during setup
866 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
867 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
868 On x86-64 and powerpc, this option can be specified
869 multiple times interleaved with hugepages= to reserve
870 huge pages of different sizes. Valid pages sizes on
871 x86-64 are 2M (when the CPU supports "pse") and 1G
872 (when the CPU supports the "pdpe1gb" cpuinfo flag)
873 Note that 1GB pages can only be allocated at boot time
874 using hugepages= and not freed afterwards.
876 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
877 terminal devices. Valid values: 0..8
878 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
879 If specified, z/VM IUCV HVC accepts connections
880 from listed z/VM user IDs only.
882 keep_bootcon [KNL]
883 Do not unregister boot console at start. This is only
884 useful for debugging when something happens in the window
885 between unregistering the boot console and initializing
886 the real console.
888 i2c_bus= [HW] Override the default board specific I2C bus speed
889 or register an additional I2C bus that is not
890 registered from board initialization code.
891 Format:
892 <bus_id>,<clkrate>
894 i8042.debug [HW] Toggle i8042 debug mode
895 i8042.direct [HW] Put keyboard port into non-translated mode
896 i8042.dumbkbd [HW] Pretend that controller can only read data from
897 keyboard and cannot control its state
898 (Don't attempt to blink the leds)
899 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
900 i8042.nokbd [HW] Don't check/create keyboard port
901 i8042.noloop [HW] Disable the AUX Loopback command while probing
902 for the AUX port
903 i8042.nomux [HW] Don't check presence of an active multiplexing
904 controller
905 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
906 controllers
907 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
908 i8042.reset [HW] Reset the controller during init and cleanup
909 i8042.unlock [HW] Unlock (ignore) the keylock
911 i810= [HW,DRM]
913 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
914 indicates that the driver is running on unsupported
915 hardware.
916 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
917 does not match list of supported models.
918 i8k.power_status
919 [HW] Report power status in /proc/i8k
920 (disabled by default)
921 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
922 capability is set.
924 icn= [HW,ISDN]
925 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
927 ide-core.nodma= [HW] (E)IDE subsystem
928 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
929 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
930 .cdrom .chs .ignore_cable are additional options
931 See Documentation/ide/ide.txt.
933 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
934 Claim all unknown PCI IDE storage controllers.
936 idle= [X86]
937 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
938 Poll forces a polling idle loop that can slightly
939 improve the performance of waking up a idle CPU, but
940 will use a lot of power and make the system run hot.
941 Not recommended.
942 idle=mwait: On systems which support MONITOR/MWAIT but
943 the kernel chose to not use it because it doesn't save
944 as much power as a normal idle loop, use the
945 MONITOR/MWAIT idle loop anyways. Performance should be
946 the same as idle=poll.
947 idle=halt: Halt is forced to be used for CPU idle.
948 In such case C2/C3 won't be used again.
949 idle=nomwait: Disable mwait for CPU C-states
951 ignore_loglevel [KNL]
952 Ignore loglevel setting - this will print /all/
953 kernel messages to the console. Useful for debugging.
955 ihash_entries= [KNL]
956 Set number of hash buckets for inode cache.
958 ima_audit= [IMA]
959 Format: { "0" | "1" }
960 0 -- integrity auditing messages. (Default)
961 1 -- enable informational integrity auditing messages.
963 ima_hash= [IMA]
964 Format: { "sha1" | "md5" }
965 default: "sha1"
967 ima_tcb [IMA]
968 Load a policy which meets the needs of the Trusted
969 Computing Base. This means IMA will measure all
970 programs exec'd, files mmap'd for exec, and all files
971 opened for read by uid=0.
973 init= [KNL]
974 Format: <full_path>
975 Run specified binary instead of /sbin/init as init
976 process.
978 initcall_debug [KNL] Trace initcalls as they are executed. Useful
979 for working out where the kernel is dying during
980 startup.
982 initrd= [BOOT] Specify the location of the initial ramdisk
984 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
985 Format: <irq>
987 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
988 on
989 Enable intel iommu driver.
990 off
991 Disable intel iommu driver.
992 igfx_off [Default Off]
993 By default, gfx is mapped as normal device. If a gfx
994 device has a dedicated DMAR unit, the DMAR unit is
995 bypassed by not enabling DMAR with this option. In
996 this case, gfx device will use physical address for
997 DMA.
998 forcedac [x86_64]
999 With this option iommu will not optimize to look
1000 for io virtual address below 32-bit forcing dual
1001 address cycle on pci bus for cards supporting greater
1002 than 32-bit addressing. The default is to look
1003 for translation below 32-bit and if not available
1004 then look in the higher range.
1005 strict [Default Off]
1006 With this option on every unmap_single operation will
1007 result in a hardware IOTLB flush operation as opposed
1008 to batching them for performance.
1009 sp_off [Default Off]
1010 By default, super page will be supported if Intel IOMMU
1011 has the capability. With this option, super page will
1012 not be supported.
1013 intremap= [X86-64, Intel-IOMMU]
1014 Format: { on (default) | off | nosid }
1015 on enable Interrupt Remapping (default)
1016 off disable Interrupt Remapping
1017 nosid disable Source ID checking
1019 inttest= [IA-64]
1021 iomem= Disable strict checking of access to MMIO memory
1022 strict regions from userspace.
1023 relaxed
1025 iommu= [x86]
1026 off
1027 force
1028 noforce
1029 biomerge
1030 panic
1031 nopanic
1032 merge
1033 nomerge
1034 forcesac
1035 soft
1036 pt [x86, IA-64]
1038 io7= [HW] IO7 for Marvel based alpha systems
1039 See comment before marvel_specify_io7 in
1040 arch/alpha/kernel/core_marvel.c.
1042 io_delay= [X86] I/O delay method
1043 0x80
1044 Standard port 0x80 based delay
1045 0xed
1046 Alternate port 0xed based delay (needed on some systems)
1047 udelay
1048 Simple two microseconds delay
1049 none
1050 No delay
1052 ip= [IP_PNP]
1053 See Documentation/filesystems/nfs/nfsroot.txt.
1055 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1056 See comment before ip2_setup() in
1057 drivers/char/ip2/ip2base.c.
1059 irqfixup [HW]
1060 When an interrupt is not handled search all handlers
1061 for it. Intended to get systems with badly broken
1062 firmware running.
1064 irqpoll [HW]
1065 When an interrupt is not handled search all handlers
1066 for it. Also check all handlers each timer
1067 interrupt. Intended to get systems with badly broken
1068 firmware running.
1070 isapnp= [ISAPNP]
1071 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1073 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1074 Format:
1075 <cpu number>,...,<cpu number>
1076 or
1077 <cpu number>-<cpu number>
1078 (must be a positive range in ascending order)
1079 or a mixture
1080 <cpu number>,...,<cpu number>-<cpu number>
1082 This option can be used to specify one or more CPUs
1083 to isolate from the general SMP balancing and scheduling
1084 algorithms. You can move a process onto or off an
1085 "isolated" CPU via the CPU affinity syscalls or cpuset.
1086 <cpu number> begins at 0 and the maximum value is
1087 "number of CPUs in system - 1".
1089 This option is the preferred way to isolate CPUs. The
1090 alternative -- manually setting the CPU mask of all
1091 tasks in the system -- can cause problems and
1092 suboptimal load balancer performance.
1094 iucv= [HW,NET]
1096 js= [HW,JOY] Analog joystick
1097 See Documentation/input/joystick.txt.
1099 keepinitrd [HW,ARM]
1101 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1102 specifies the amount of memory usable by the kernel
1103 for non-movable allocations. The requested amount is
1104 spread evenly throughout all nodes in the system. The
1105 remaining memory in each node is used for Movable
1106 pages. In the event, a node is too small to have both
1107 kernelcore and Movable pages, kernelcore pages will
1108 take priority and other nodes will have a larger number
1109 of kernelcore pages. The Movable zone is used for the
1110 allocation of pages that may be reclaimed or moved
1111 by the page migration subsystem. This means that
1112 HugeTLB pages may not be allocated from this zone.
1113 Note that allocations like PTEs-from-HighMem still
1114 use the HighMem zone if it exists, and the Normal
1115 zone if it does not.
1117 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1118 Format: <Controller#>[,poll interval]
1119 The controller # is the number of the ehci usb debug
1120 port as it is probed via PCI. The poll interval is
1121 optional and is the number seconds in between
1122 each poll cycle to the debug port in case you need
1123 the functionality for interrupting the kernel with
1124 gdb or control-c on the dbgp connection. When
1125 not using this parameter you use sysrq-g to break into
1126 the kernel debugger.
1128 kgdboc= [KGDB,HW] kgdb over consoles.
1129 Requires a tty driver that supports console polling,
1130 or a supported polling keyboard driver (non-usb).
1131 Serial only format: <serial_device>[,baud]
1132 keyboard only format: kbd
1133 keyboard and serial format: kbd,<serial_device>[,baud]
1134 Optional Kernel mode setting:
1135 kms, kbd format: kms,kbd
1136 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1138 kgdbwait [KGDB] Stop kernel execution and enter the
1139 kernel debugger at the earliest opportunity.
1141 kmac= [MIPS] korina ethernet MAC address.
1142 Configure the RouterBoard 532 series on-chip
1143 Ethernet adapter MAC address.
1145 kmemleak= [KNL] Boot-time kmemleak enable/disable
1146 Valid arguments: on, off
1147 Default: on
1149 kstack=N [X86] Print N words from the kernel stack
1150 in oops dumps.
1152 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1153 Default is 0 (don't ignore, but inject #GP)
1155 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1156 Default is 1 (enabled)
1158 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1159 KVM MMU at runtime.
1160 Default is 0 (off)
1162 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1163 Default is 1 (enabled)
1165 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1166 for all guests.
1167 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1169 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1170 (virtualized MMU) support on capable Intel chips.
1171 Default is 1 (enabled)
1173 kvm-intel.emulate_invalid_guest_state=
1174 [KVM,Intel] Enable emulation of invalid guest states
1175 Default is 0 (disabled)
1177 kvm-intel.flexpriority=
1178 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1179 Default is 1 (enabled)
1181 kvm-intel.unrestricted_guest=
1182 [KVM,Intel] Disable unrestricted guest feature
1183 (virtualized real and unpaged mode) on capable
1184 Intel chips. Default is 1 (enabled)
1186 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1187 feature (tagged TLBs) on capable Intel chips.
1188 Default is 1 (enabled)
1190 l2cr= [PPC]
1192 l3cr= [PPC]
1194 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1195 disabled it.
1197 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1198 in C2 power state.
1200 libata.dma= [LIBATA] DMA control
1201 libata.dma=0 Disable all PATA and SATA DMA
1202 libata.dma=1 PATA and SATA Disk DMA only
1203 libata.dma=2 ATAPI (CDROM) DMA only
1204 libata.dma=4 Compact Flash DMA only
1205 Combinations also work, so libata.dma=3 enables DMA
1206 for disks and CDROMs, but not CFs.
1208 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1209 libata.ignore_hpa=0 keep BIOS limits (default)
1210 libata.ignore_hpa=1 ignore limits, using full disk
1212 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1213 when set.
1214 Format: <int>
1216 libata.force= [LIBATA] Force configurations. The format is comma
1217 separated list of "[ID:]VAL" where ID is
1218 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1219 matching port, link or device. Basically, it matches
1220 the ATA ID string printed on console by libata. If
1221 the whole ID part is omitted, the last PORT and DEVICE
1222 values are used. If ID hasn't been specified yet, the
1223 configuration applies to all ports, links and devices.
1225 If only DEVICE is omitted, the parameter applies to
1226 the port and all links and devices behind it. DEVICE
1227 number of 0 either selects the first device or the
1228 first fan-out link behind PMP device. It does not
1229 select the host link. DEVICE number of 15 selects the
1230 host link and device attached to it.
1232 The VAL specifies the configuration to force. As long
1233 as there's no ambiguity shortcut notation is allowed.
1234 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1235 The following configurations can be forced.
1237 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1238 Any ID with matching PORT is used.
1240 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1242 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1243 udma[/][16,25,33,44,66,100,133] notation is also
1244 allowed.
1246 * [no]ncq: Turn on or off NCQ.
1248 * nohrst, nosrst, norst: suppress hard, soft
1249 and both resets.
1251 * dump_id: dump IDENTIFY data.
1253 If there are multiple matching configurations changing
1254 the same attribute, the last one is used.
1256 memblock=debug [KNL] Enable memblock debug messages.
1258 load_ramdisk= [RAM] List of ramdisks to load from floppy
1259 See Documentation/blockdev/ramdisk.txt.
1261 lockd.nlm_grace_period=P [NFS] Assign grace period.
1262 Format: <integer>
1264 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1265 Format: <integer>
1267 lockd.nlm_timeout=T [NFS] Assign timeout value.
1268 Format: <integer>
1270 lockd.nlm_udpport=M [NFS] Assign UDP port.
1271 Format: <integer>
1273 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1274 Format: <irq>
1276 loglevel= All Kernel Messages with a loglevel smaller than the
1277 console loglevel will be printed to the console. It can
1278 also be changed with klogd or other programs. The
1279 loglevels are defined as follows:
1281 0 (KERN_EMERG) system is unusable
1282 1 (KERN_ALERT) action must be taken immediately
1283 2 (KERN_CRIT) critical conditions
1284 3 (KERN_ERR) error conditions
1285 4 (KERN_WARNING) warning conditions
1286 5 (KERN_NOTICE) normal but significant condition
1287 6 (KERN_INFO) informational
1288 7 (KERN_DEBUG) debug-level messages
1290 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1291 in bytes. n must be a power of two. The default
1292 size is set in the kernel config file.
1294 logo.nologo [FB] Disables display of the built-in Linux logo.
1295 This may be used to provide more screen space for
1296 kernel log messages and is useful when debugging
1297 kernel boot problems.
1299 lp=0 [LP] Specify parallel ports to use, e.g,
1300 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1301 lp=reset first parallel port). 'lp=0' disables the
1302 lp=auto printer driver. 'lp=reset' (which can be
1303 specified in addition to the ports) causes
1304 attached printers to be reset. Using
1305 lp=port1,port2,... specifies the parallel ports
1306 to associate lp devices with, starting with
1307 lp0. A port specification may be 'none' to skip
1308 that lp device, or a parport name such as
1309 'parport0'. Specifying 'lp=auto' instead of a
1310 port specification list means that device IDs
1311 from each port should be examined, to see if
1312 an IEEE 1284-compliant printer is attached; if
1313 so, the driver will manage that printer.
1314 See also header of drivers/char/lp.c.
1316 lpj=n [KNL]
1317 Sets loops_per_jiffy to given constant, thus avoiding
1318 time-consuming boot-time autodetection (up to 250 ms per
1319 CPU). 0 enables autodetection (default). To determine
1320 the correct value for your kernel, boot with normal
1321 autodetection and see what value is printed. Note that
1322 on SMP systems the preset will be applied to all CPUs,
1323 which is likely to cause problems if your CPUs need
1324 significantly divergent settings. An incorrect value
1325 will cause delays in the kernel to be wrong, leading to
1326 unpredictable I/O errors and other breakage. Although
1327 unlikely, in the extreme case this might damage your
1328 hardware.
1330 ltpc= [NET]
1331 Format: <io>,<irq>,<dma>
1333 machvec= [IA-64] Force the use of a particular machine-vector
1334 (machvec) in a generic kernel.
1335 Example: machvec=hpzx1_swiotlb
1337 machtype= [Loongson] Share the same kernel image file between different
1338 yeeloong laptop.
1339 Example: machtype=lemote-yeeloong-2f-7inch
1341 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1342 than or equal to this physical address is ignored.
1344 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1345 should make use of. maxcpus=n : n >= 0 limits the
1346 kernel to using 'n' processors. n=0 is a special case,
1347 it is equivalent to "nosmp", which also disables
1348 the IO APIC.
1350 max_loop= [LOOP] Maximum number of loopback devices that can
1351 be mounted
1352 Format: <1-256>
1354 mcatest= [IA-64]
1356 mce [X86-32] Machine Check Exception
1358 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1360 md= [HW] RAID subsystems devices and level
1361 See Documentation/md.txt.
1363 mdacon= [MDA]
1364 Format: <first>,<last>
1365 Specifies range of consoles to be captured by the MDA.
1367 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1368 Amount of memory to be used when the kernel is not able
1369 to see the whole system memory or for test.
1370 [X86-32] Use together with memmap= to avoid physical
1371 address space collisions. Without memmap= PCI devices
1372 could be placed at addresses belonging to unused RAM.
1374 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1375 memory.
1377 memchunk=nn[KMG]
1378 [KNL,SH] Allow user to override the default size for
1379 per-device physically contiguous DMA buffers.
1381 memmap=exactmap [KNL,X86] Enable setting of an exact
1382 E820 memory map, as specified by the user.
1383 Such memmap=exactmap lines can be constructed based on
1384 BIOS output or other requirements. See the memmap=nn@ss
1385 option description.
1387 memmap=nn[KMG]@ss[KMG]
1388 [KNL] Force usage of a specific region of memory
1389 Region of memory to be used, from ss to ss+nn.
1391 memmap=nn[KMG]#ss[KMG]
1392 [KNL,ACPI] Mark specific memory as ACPI data.
1393 Region of memory to be used, from ss to ss+nn.
1395 memmap=nn[KMG]$ss[KMG]
1396 [KNL,ACPI] Mark specific memory as reserved.
1397 Region of memory to be used, from ss to ss+nn.
1398 Example: Exclude memory from 0x18690000-0x1869ffff
1399 memmap=64K$0x18690000
1400 or
1401 memmap=0x10000$0x18690000
1403 memory_corruption_check=0/1 [X86]
1404 Some BIOSes seem to corrupt the first 64k of
1405 memory when doing things like suspend/resume.
1406 Setting this option will scan the memory
1407 looking for corruption. Enabling this will
1408 both detect corruption and prevent the kernel
1409 from using the memory being corrupted.
1410 However, its intended as a diagnostic tool; if
1411 repeatable BIOS-originated corruption always
1412 affects the same memory, you can use memmap=
1413 to prevent the kernel from using that memory.
1415 memory_corruption_check_size=size [X86]
1416 By default it checks for corruption in the low
1417 64k, making this memory unavailable for normal
1418 use. Use this parameter to scan for
1419 corruption in more or less memory.
1421 memory_corruption_check_period=seconds [X86]
1422 By default it checks for corruption every 60
1423 seconds. Use this parameter to check at some
1424 other rate. 0 disables periodic checking.
1426 memtest= [KNL,X86] Enable memtest
1427 Format: <integer>
1428 default : 0 <disable>
1429 Specifies the number of memtest passes to be
1430 performed. Each pass selects another test
1431 pattern from a given set of patterns. Memtest
1432 fills the memory with this pattern, validates
1433 memory contents and reserves bad memory
1434 regions that are detected.
1436 meye.*= [HW] Set MotionEye Camera parameters
1437 See Documentation/video4linux/meye.txt.
1439 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1440 Multi-Function General Purpose Timers on AMD Geode
1441 platforms.
1443 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1444 the BIOS has incorrectly applied a workaround. TinyBIOS
1445 version 0.98 is known to be affected, 0.99 fixes the
1446 problem by letting the user disable the workaround.
1448 mga= [HW,DRM]
1450 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1451 physical address is ignored.
1453 mini2440= [ARM,HW,KNL]
1454 Format:[0..2][b][c][t]
1455 Default: "0tb"
1456 MINI2440 configuration specification:
1457 0 - The attached screen is the 3.5" TFT
1458 1 - The attached screen is the 7" TFT
1459 2 - The VGA Shield is attached (1024x768)
1460 Leaving out the screen size parameter will not load
1461 the TFT driver, and the framebuffer will be left
1462 unconfigured.
1463 b - Enable backlight. The TFT backlight pin will be
1464 linked to the kernel VESA blanking code and a GPIO
1465 LED. This parameter is not necessary when using the
1466 VGA shield.
1467 c - Enable the s3c camera interface.
1468 t - Reserved for enabling touchscreen support. The
1469 touchscreen support is not enabled in the mainstream
1470 kernel as of 2.6.30, a preliminary port can be found
1471 in the "bleeding edge" mini2440 support kernel at
1472 http://repo.or.cz/w/linux-2.6/mini2440.git
1474 mminit_loglevel=
1475 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1476 parameter allows control of the logging verbosity for
1477 the additional memory initialisation checks. A value
1478 of 0 disables mminit logging and a level of 4 will
1479 log everything. Information is printed at KERN_DEBUG
1480 so loglevel=8 may also need to be specified.
1482 mousedev.tap_time=
1483 [MOUSE] Maximum time between finger touching and
1484 leaving touchpad surface for touch to be considered
1485 a tap and be reported as a left button click (for
1486 touchpads working in absolute mode only).
1487 Format: <msecs>
1488 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1489 reporting absolute coordinates, such as tablets
1490 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1491 reporting absolute coordinates, such as tablets
1493 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1494 is similar to kernelcore except it specifies the
1495 amount of memory used for migratable allocations.
1496 If both kernelcore and movablecore is specified,
1497 then kernelcore will be at *least* the specified
1498 value but may be more. If movablecore on its own
1499 is specified, the administrator must be careful
1500 that the amount of memory usable for all allocations
1501 is not too small.
1503 MTD_Partition= [MTD]
1504 Format: <name>,<region-number>,<size>,<offset>
1506 MTD_Region= [MTD] Format:
1507 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1509 mtdparts= [MTD]
1510 See drivers/mtd/cmdlinepart.c.
1512 multitce=off [PPC] This parameter disables the use of the pSeries
1513 firmware feature for updating multiple TCE entries
1514 at a time.
1516 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1518 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1520 boundary - index of last SLC block on Flex-OneNAND.
1521 The remaining blocks are configured as MLC blocks.
1522 lock - Configure if Flex-OneNAND boundary should be locked.
1523 Once locked, the boundary cannot be changed.
1524 1 indicates lock status, 0 indicates unlock status.
1526 mtdset= [ARM]
1527 ARM/S3C2412 JIVE boot control
1529 See arch/arm/mach-s3c2412/mach-jive.c
1531 mtouchusb.raw_coordinates=
1532 [HW] Make the MicroTouch USB driver use raw coordinates
1533 ('y', default) or cooked coordinates ('n')
1535 mtrr_chunk_size=nn[KMG] [X86]
1536 used for mtrr cleanup. It is largest continuous chunk
1537 that could hold holes aka. UC entries.
1539 mtrr_gran_size=nn[KMG] [X86]
1540 Used for mtrr cleanup. It is granularity of mtrr block.
1541 Default is 1.
1542 Large value could prevent small alignment from
1543 using up MTRRs.
1545 mtrr_spare_reg_nr=n [X86]
1546 Format: <integer>
1547 Range: 0,7 : spare reg number
1548 Default : 1
1549 Used for mtrr cleanup. It is spare mtrr entries number.
1550 Set to 2 or more if your graphical card needs more.
1552 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1554 netdev= [NET] Network devices parameters
1555 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1556 Note that mem_start is often overloaded to mean
1557 something different and driver-specific.
1558 This usage is only documented in each driver source
1559 file if at all.
1561 nf_conntrack.acct=
1562 [NETFILTER] Enable connection tracking flow accounting
1563 0 to disable accounting
1564 1 to enable accounting
1565 Default value is 0.
1567 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1568 See Documentation/filesystems/nfs/nfsroot.txt.
1570 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1571 See Documentation/filesystems/nfs/nfsroot.txt.
1573 nfsrootdebug [NFS] enable nfsroot debugging messages.
1574 See Documentation/filesystems/nfs/nfsroot.txt.
1576 nfs.callback_tcpport=
1577 [NFS] set the TCP port on which the NFSv4 callback
1578 channel should listen.
1580 nfs.cache_getent=
1581 [NFS] sets the pathname to the program which is used
1582 to update the NFS client cache entries.
1584 nfs.cache_getent_timeout=
1585 [NFS] sets the timeout after which an attempt to
1586 update a cache entry is deemed to have failed.
1588 nfs.idmap_cache_timeout=
1589 [NFS] set the maximum lifetime for idmapper cache
1590 entries.
1592 nfs.enable_ino64=
1593 [NFS] enable 64-bit inode numbers.
1594 If zero, the NFS client will fake up a 32-bit inode
1595 number for the readdir() and stat() syscalls instead
1596 of returning the full 64-bit number.
1597 The default is to return 64-bit inode numbers.
1599 nfs.nfs4_disable_idmapping=
1600 [NFSv4] When set, this option disables the NFSv4
1601 idmapper on the client, but only if the mount
1602 is using the 'sec=sys' security flavour. This may
1603 make migration from legacy NFSv2/v3 systems easier
1604 provided that the server has the appropriate support.
1605 The default is to always enable NFSv4 idmapping.
1607 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1608 when a NMI is triggered.
1609 Format: [state][,regs][,debounce][,die]
1611 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1612 Format: [panic,][nopanic,][num]
1613 Valid num: 0
1614 0 - turn nmi_watchdog off
1615 When panic is specified, panic when an NMI watchdog
1616 timeout occurs (or 'nopanic' to override the opposite
1617 default).
1618 This is useful when you use a panic=... timeout and
1619 need the box quickly up again.
1621 netpoll.carrier_timeout=
1622 [NET] Specifies amount of time (in seconds) that
1623 netpoll should wait for a carrier. By default netpoll
1624 waits 4 seconds.
1626 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1627 emulation library even if a 387 maths coprocessor
1628 is present.
1630 no_console_suspend
1631 [HW] Never suspend the console
1632 Disable suspending of consoles during suspend and
1633 hibernate operations. Once disabled, debugging
1634 messages can reach various consoles while the rest
1635 of the system is being put to sleep (ie, while
1636 debugging driver suspend/resume hooks). This may
1637 not work reliably with all consoles, but is known
1638 to work with serial and VGA consoles.
1640 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1641 caches in the slab allocator. Saves per-node memory,
1642 but will impact performance.
1644 noalign [KNL,ARM]
1646 noapic [SMP,APIC] Tells the kernel to not make use of any
1647 IOAPICs that may be present in the system.
1649 noautogroup Disable scheduler automatic task group creation.
1651 nobats [PPC] Do not use BATs for mapping kernel lowmem
1652 on "Classic" PPC cores.
1654 nocache [ARM]
1656 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1658 nodelayacct [KNL] Disable per-task delay accounting
1660 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1662 nodsp [SH] Disable hardware DSP at boot time.
1664 noefi [X86] Disable EFI runtime services support.
1666 noexec [IA-64]
1668 noexec [X86]
1669 On X86-32 available only on PAE configured kernels.
1670 noexec=on: enable non-executable mappings (default)
1671 noexec=off: disable non-executable mappings
1673 nosmep [X86]
1674 Disable SMEP (Supervisor Mode Execution Protection)
1675 even if it is supported by processor.
1677 noexec32 [X86-64]
1678 This affects only 32-bit executables.
1679 noexec32=on: enable non-executable mappings (default)
1680 read doesn't imply executable mappings
1681 noexec32=off: disable non-executable mappings
1682 read implies executable mappings
1684 nofpu [SH] Disable hardware FPU at boot time.
1686 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1687 register save and restore. The kernel will only save
1688 legacy floating-point registers on task switch.
1690 noxsave [BUGS=X86] Disables x86 extended register state save
1691 and restore using xsave. The kernel will fallback to
1692 enabling legacy floating-point and sse state.
1694 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1695 wfi(ARM) instruction doesn't work correctly and not to
1696 use it. This is also useful when using JTAG debugger.
1698 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1699 instruction doesn't work correctly and not to
1700 use it.
1702 no_file_caps Tells the kernel not to honor file capabilities. The
1703 only way then for a file to be executed with privilege
1704 is to be setuid root or executed by root.
1706 nohalt [IA-64] Tells the kernel not to use the power saving
1707 function PAL_HALT_LIGHT when idle. This increases
1708 power-consumption. On the positive side, it reduces
1709 interrupt wake-up latency, which may improve performance
1710 in certain environments such as networked servers or
1711 real-time systems.
1713 nohz= [KNL] Boottime enable/disable dynamic ticks
1714 Valid arguments: on, off
1715 Default: on
1717 noiotrap [SH] Disables trapped I/O port accesses.
1719 noirqdebug [X86-32] Disables the code which attempts to detect and
1720 disable unhandled interrupt sources.
1722 no_timer_check [X86,APIC] Disables the code which tests for
1723 broken timer IRQ sources.
1725 noisapnp [ISAPNP] Disables ISA PnP code.
1727 noinitrd [RAM] Tells the kernel not to load any configured
1728 initial RAM disk.
1730 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1731 remapping.
1732 [Deprecated - use intremap=off]
1734 nointroute [IA-64]
1736 nojitter [IA-64] Disables jitter checking for ITC timers.
1738 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1740 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1741 fault handling.
1743 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1744 steal time is computed, but won't influence scheduler
1745 behaviour
1747 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1749 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1751 noltlbs [PPC] Do not use large page/tlb entries for kernel
1752 lowmem mapping on PPC40x.
1754 nomca [IA-64] Disable machine check abort handling
1756 nomce [X86-32] Machine Check Exception
1758 nomfgpt [X86-32] Disable Multi-Function General Purpose
1759 Timer usage (for AMD Geode machines).
1761 nopat [X86] Disable PAT (page attribute table extension of
1762 pagetables) support.
1764 norandmaps Don't use address space randomization. Equivalent to
1765 echo 0 > /proc/sys/kernel/randomize_va_space
1767 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1769 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1770 with UP alternatives
1772 noresidual [PPC] Don't use residual data on PReP machines.
1774 noresume [SWSUSP] Disables resume and restores original swap
1775 space.
1777 no-scroll [VGA] Disables scrollback.
1778 This is required for the Braillex ib80-piezo Braille
1779 reader made by F.H. Papenmeier (Germany).
1781 nosbagart [IA-64]
1783 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1785 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1786 and disable the IO APIC. legacy for "maxcpus=0".
1788 nosoftlockup [KNL] Disable the soft-lockup detector.
1790 nosync [HW,M68K] Disables sync negotiation for all devices.
1792 notsc [BUGS=X86-32] Disable Time Stamp Counter
1794 nousb [USB] Disable the USB subsystem
1796 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1798 nowb [ARM]
1800 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1802 nptcg= [IA-64] Override max number of concurrent global TLB
1803 purges which is reported from either PAL_VM_SUMMARY or
1804 SAL PALO.
1806 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1807 could support. nr_cpus=n : n >= 1 limits the kernel to
1808 supporting 'n' processors. Later in runtime you can not
1809 use hotplug cpu feature to put more cpu back to online.
1810 just like you compile the kernel NR_CPUS=n
1812 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1814 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1815 one of ['zone', 'node', 'default'] can be specified
1816 This can be set from sysctl after boot.
1817 See Documentation/sysctl/vm.txt for details.
1819 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1820 See Documentation/debugging-via-ohci1394.txt for more
1821 info.
1823 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1824 Rather than timing out after 20 ms if an EC
1825 command is not properly ACKed, override the length
1826 of the timeout. We have interrupts disabled while
1827 waiting for the ACK, so if this is set too high
1828 interrupts *may* be lost!
1830 omap_mux= [OMAP] Override bootloader pin multiplexing.
1831 Format: <mux_mode0.mode_name=value>...
1832 For example, to override I2C bus2:
1833 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1835 oprofile.timer= [HW]
1836 Use timer interrupt instead of performance counters
1838 oprofile.cpu_type= Force an oprofile cpu type
1839 This might be useful if you have an older oprofile
1840 userland or if you want common events.
1841 Format: { arch_perfmon }
1842 arch_perfmon: [X86] Force use of architectural
1843 perfmon on Intel CPUs instead of the
1844 CPU specific event set.
1846 oops=panic Always panic on oopses. Default is to just kill the
1847 process, but there is a small probability of
1848 deadlocking the machine.
1849 This will also cause panics on machine check exceptions.
1850 Useful together with panic=30 to trigger a reboot.
1852 OSS [HW,OSS]
1853 See Documentation/sound/oss/oss-parameters.txt
1855 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1856 timeout > 0: seconds before rebooting
1857 timeout = 0: wait forever
1858 timeout < 0: reboot immediately
1859 Format: <timeout>
1861 parkbd.port= [HW] Parallel port number the keyboard adapter is
1862 connected to, default is 0.
1863 Format: <parport#>
1864 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1865 0 for XT, 1 for AT (default is AT).
1866 Format: <mode>
1868 parport= [HW,PPT] Specify parallel ports. 0 disables.
1869 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1870 Use 'auto' to force the driver to use any
1871 IRQ/DMA settings detected (the default is to
1872 ignore detected IRQ/DMA settings because of
1873 possible conflicts). You can specify the base
1874 address, IRQ, and DMA settings; IRQ and DMA
1875 should be numbers, or 'auto' (for using detected
1876 settings on that particular port), or 'nofifo'
1877 (to avoid using a FIFO even if it is detected).
1878 Parallel ports are assigned in the order they
1879 are specified on the command line, starting
1880 with parport0.
1882 parport_init_mode= [HW,PPT]
1883 Configure VIA parallel port to operate in
1884 a specific mode. This is necessary on Pegasos
1885 computer where firmware has no options for setting
1886 up parallel port mode and sets it to spp.
1887 Currently this function knows 686a and 8231 chips.
1888 Format: [spp|ps2|epp|ecp|ecpepp]
1890 pause_on_oops=
1891 Halt all CPUs after the first oops has been printed for
1892 the specified number of seconds. This is to be used if
1893 your oopses keep scrolling off the screen.
1895 pcbit= [HW,ISDN]
1897 pcd. [PARIDE]
1898 See header of drivers/block/paride/pcd.c.
1899 See also Documentation/blockdev/paride.txt.
1901 pci=option[,option...] [PCI] various PCI subsystem options:
1902 earlydump [X86] dump PCI config space before the kernel
1903 changes anything
1904 off [X86] don't probe for the PCI bus
1905 bios [X86-32] force use of PCI BIOS, don't access
1906 the hardware directly. Use this if your machine
1907 has a non-standard PCI host bridge.
1908 nobios [X86-32] disallow use of PCI BIOS, only direct
1909 hardware access methods are allowed. Use this
1910 if you experience crashes upon bootup and you
1911 suspect they are caused by the BIOS.
1912 conf1 [X86] Force use of PCI Configuration
1913 Mechanism 1.
1914 conf2 [X86] Force use of PCI Configuration
1915 Mechanism 2.
1916 noaer [PCIE] If the PCIEAER kernel config parameter is
1917 enabled, this kernel boot option can be used to
1918 disable the use of PCIE advanced error reporting.
1919 nodomains [PCI] Disable support for multiple PCI
1920 root domains (aka PCI segments, in ACPI-speak).
1921 nommconf [X86] Disable use of MMCONFIG for PCI
1922 Configuration
1923 check_enable_amd_mmconf [X86] check for and enable
1924 properly configured MMIO access to PCI
1925 config space on AMD family 10h CPU
1926 nomsi [MSI] If the PCI_MSI kernel config parameter is
1927 enabled, this kernel boot option can be used to
1928 disable the use of MSI interrupts system-wide.
1929 noioapicquirk [APIC] Disable all boot interrupt quirks.
1930 Safety option to keep boot IRQs enabled. This
1931 should never be necessary.
1932 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1933 primary IO-APIC for bridges that cannot disable
1934 boot IRQs. This fixes a source of spurious IRQs
1935 when the system masks IRQs.
1936 noioapicreroute [APIC] Disable workaround that uses the
1937 boot IRQ equivalent of an IRQ that connects to
1938 a chipset where boot IRQs cannot be disabled.
1939 The opposite of ioapicreroute.
1940 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1941 routing table. These calls are known to be buggy
1942 on several machines and they hang the machine
1943 when used, but on other computers it's the only
1944 way to get the interrupt routing table. Try
1945 this option if the kernel is unable to allocate
1946 IRQs or discover secondary PCI buses on your
1947 motherboard.
1948 rom [X86] Assign address space to expansion ROMs.
1949 Use with caution as certain devices share
1950 address decoders between ROMs and other
1951 resources.
1952 norom [X86] Do not assign address space to
1953 expansion ROMs that do not already have
1954 BIOS assigned address ranges.
1955 nobar [X86] Do not assign address space to the
1956 BARs that weren't assigned by the BIOS.
1957 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1958 assigned automatically to PCI devices. You can
1959 make the kernel exclude IRQs of your ISA cards
1960 this way.
1961 pirqaddr=0xAAAAA [X86] Specify the physical address
1962 of the PIRQ table (normally generated
1963 by the BIOS) if it is outside the
1964 F0000h-100000h range.
1965 lastbus=N [X86] Scan all buses thru bus #N. Can be
1966 useful if the kernel is unable to find your
1967 secondary buses and you want to tell it
1968 explicitly which ones they are.
1969 assign-busses [X86] Always assign all PCI bus
1970 numbers ourselves, overriding
1971 whatever the firmware may have done.
1972 usepirqmask [X86] Honor the possible IRQ mask stored
1973 in the BIOS $PIR table. This is needed on
1974 some systems with broken BIOSes, notably
1975 some HP Pavilion N5400 and Omnibook XE3
1976 notebooks. This will have no effect if ACPI
1977 IRQ routing is enabled.
1978 noacpi [X86] Do not use ACPI for IRQ routing
1979 or for PCI scanning.
1980 use_crs [X86] Use PCI host bridge window information
1981 from ACPI. On BIOSes from 2008 or later, this
1982 is enabled by default. If you need to use this,
1983 please report a bug.
1984 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1985 If you need to use this, please report a bug.
1986 routeirq Do IRQ routing for all PCI devices.
1987 This is normally done in pci_enable_device(),
1988 so this option is a temporary workaround
1989 for broken drivers that don't call it.
1990 skip_isa_align [X86] do not align io start addr, so can
1991 handle more pci cards
1992 firmware [ARM] Do not re-enumerate the bus but instead
1993 just use the configuration from the
1994 bootloader. This is currently used on
1995 IXP2000 systems where the bus has to be
1996 configured a certain way for adjunct CPUs.
1997 noearly [X86] Don't do any early type 1 scanning.
1998 This might help on some broken boards which
1999 machine check when some devices' config space
2000 is read. But various workarounds are disabled
2001 and some IOMMU drivers will not work.
2002 bfsort Sort PCI devices into breadth-first order.
2003 This sorting is done to get a device
2004 order compatible with older (<= 2.4) kernels.
2005 nobfsort Don't sort PCI devices into breadth-first order.
2006 cbiosize=nn[KMG] The fixed amount of bus space which is
2007 reserved for the CardBus bridge's IO window.
2008 The default value is 256 bytes.
2009 cbmemsize=nn[KMG] The fixed amount of bus space which is
2010 reserved for the CardBus bridge's memory
2011 window. The default value is 64 megabytes.
2012 resource_alignment=
2013 Format:
2014 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2015 Specifies alignment and device to reassign
2016 aligned memory resources.
2017 If <order of align> is not specified,
2018 PAGE_SIZE is used as alignment.
2019 PCI-PCI bridge can be specified, if resource
2020 windows need to be expanded.
2021 ecrc= Enable/disable PCIe ECRC (transaction layer
2022 end-to-end CRC checking).
2023 bios: Use BIOS/firmware settings. This is the
2024 the default.
2025 off: Turn ECRC off
2026 on: Turn ECRC on.
2027 realloc reallocate PCI resources if allocations done by BIOS
2028 are erroneous.
2030 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2031 Management.
2032 off Disable ASPM.
2033 force Enable ASPM even on devices that claim not to support it.
2034 WARNING: Forcing ASPM on may cause system lockups.
2036 pcie_ports= [PCIE] PCIe ports handling:
2037 auto Ask the BIOS whether or not to use native PCIe services
2038 associated with PCIe ports (PME, hot-plug, AER). Use
2039 them only if that is allowed by the BIOS.
2040 native Use native PCIe services associated with PCIe ports
2041 unconditionally.
2042 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2043 ports driver.
2045 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2046 nomsi Do not use MSI for native PCIe PME signaling (this makes
2047 all PCIe root ports use INTx for all services).
2049 pcmv= [HW,PCMCIA] BadgePAD 4
2051 pd. [PARIDE]
2052 See Documentation/blockdev/paride.txt.
2054 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2055 boot time.
2056 Format: { 0 | 1 }
2057 See arch/parisc/kernel/pdc_chassis.c
2059 percpu_alloc= Select which percpu first chunk allocator to use.
2060 Currently supported values are "embed" and "page".
2061 Archs may support subset or none of the selections.
2062 See comments in mm/percpu.c for details on each
2063 allocator. This parameter is primarily for debugging
2064 and performance comparison.
2066 pf. [PARIDE]
2067 See Documentation/blockdev/paride.txt.
2069 pg. [PARIDE]
2070 See Documentation/blockdev/paride.txt.
2072 pirq= [SMP,APIC] Manual mp-table setup
2073 See Documentation/x86/i386/IO-APIC.txt.
2075 plip= [PPT,NET] Parallel port network link
2076 Format: { parport<nr> | timid | 0 }
2077 See also Documentation/parport.txt.
2079 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2080 Override pmtimer IOPort with a hex value.
2081 e.g. pmtmr=0x508
2083 pnp.debug [PNP]
2084 Enable PNP debug messages. This depends on the
2085 CONFIG_PNP_DEBUG_MESSAGES option.
2087 pnpacpi= [ACPI]
2088 { off }
2090 pnpbios= [ISAPNP]
2091 { on | off | curr | res | no-curr | no-res }
2093 pnp_reserve_irq=
2094 [ISAPNP] Exclude IRQs for the autoconfiguration
2096 pnp_reserve_dma=
2097 [ISAPNP] Exclude DMAs for the autoconfiguration
2099 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2100 Ranges are in pairs (I/O port base and size).
2102 pnp_reserve_mem=
2103 [ISAPNP] Exclude memory regions for the
2104 autoconfiguration.
2105 Ranges are in pairs (memory base and size).
2107 ports= [IP_VS_FTP] IPVS ftp helper module
2108 Default is 21.
2109 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2110 may be specified.
2111 Format: <port>,<port>....
2113 print-fatal-signals=
2114 [KNL] debug: print fatal signals
2116 If enabled, warn about various signal handling
2117 related application anomalies: too many signals,
2118 too many POSIX.1 timers, fatal signals causing a
2119 coredump - etc.
2121 If you hit the warning due to signal overflow,
2122 you might want to try "ulimit -i unlimited".
2124 default: off.
2126 printk.time= Show timing data prefixed to each printk message line
2127 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2129 processor.max_cstate= [HW,ACPI]
2130 Limit processor to maximum C-state
2131 max_cstate=9 overrides any DMI blacklist limit.
2133 processor.nocst [HW,ACPI]
2134 Ignore the _CST method to determine C-states,
2135 instead using the legacy FADT method
2137 profile= [KNL] Enable kernel profiling via /proc/profile
2138 Format: [schedule,]<number>
2139 Param: "schedule" - profile schedule points.
2140 Param: <number> - step/bucket size as a power of 2 for
2141 statistical time based profiling.
2142 Param: "sleep" - profile D-state sleeping (millisecs).
2143 Requires CONFIG_SCHEDSTATS
2144 Param: "kvm" - profile VM exits.
2146 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2147 before loading.
2148 See Documentation/blockdev/ramdisk.txt.
2150 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2151 probe for; one of (bare|imps|exps|lifebook|any).
2152 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2153 per second.
2154 psmouse.resetafter= [HW,MOUSE]
2155 Try to reset the device after so many bad packets
2156 (0 = never).
2157 psmouse.resolution=
2158 [HW,MOUSE] Set desired mouse resolution, in dpi.
2159 psmouse.smartscroll=
2160 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2161 0 = disabled, 1 = enabled (default).
2163 pstore.backend= Specify the name of the pstore backend to use
2165 pt. [PARIDE]
2166 See Documentation/blockdev/paride.txt.
2168 pty.legacy_count=
2169 [KNL] Number of legacy pty's. Overwrites compiled-in
2170 default number.
2172 quiet [KNL] Disable most log messages
2174 r128= [HW,DRM]
2176 raid= [HW,RAID]
2177 See Documentation/md.txt.
2179 ramdisk_blocksize= [RAM]
2180 See Documentation/blockdev/ramdisk.txt.
2182 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2183 See Documentation/blockdev/ramdisk.txt.
2185 rcupdate.blimit= [KNL,BOOT]
2186 Set maximum number of finished RCU callbacks to process
2187 in one batch.
2189 rcupdate.qhimark= [KNL,BOOT]
2190 Set threshold of queued
2191 RCU callbacks over which batch limiting is disabled.
2193 rcupdate.qlowmark= [KNL,BOOT]
2194 Set threshold of queued RCU callbacks below which
2195 batch limiting is re-enabled.
2197 rdinit= [KNL]
2198 Format: <full_path>
2199 Run specified binary instead of /init from the ramdisk,
2200 used for early userspace startup. See initrd.
2202 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2203 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2204 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2206 relax_domain_level=
2207 [KNL, SMP] Set scheduler's default relax_domain_level.
2208 See Documentation/cgroups/cpusets.txt.
2210 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2212 reservetop= [X86-32]
2213 Format: nn[KMG]
2214 Reserves a hole at the top of the kernel virtual
2215 address space.
2217 reservelow= [X86]
2218 Format: nn[K]
2219 Set the amount of memory to reserve for BIOS at
2220 the bottom of the address space.
2222 reset_devices [KNL] Force drivers to reset the underlying device
2223 during initialization.
2225 resume= [SWSUSP]
2226 Specify the partition device for software suspend
2228 resume_offset= [SWSUSP]
2229 Specify the offset from the beginning of the partition
2230 given by "resume=" at which the swap header is located,
2231 in <PAGE_SIZE> units (needed only for swap files).
2232 See Documentation/power/swsusp-and-swap-files.txt
2234 hibernate= [HIBERNATION]
2235 noresume Don't check if there's a hibernation image
2236 present during boot.
2237 nocompress Don't compress/decompress hibernation images.
2239 retain_initrd [RAM] Keep initrd memory after extraction
2241 rhash_entries= [KNL,NET]
2242 Set number of hash buckets for route cache
2244 riscom8= [HW,SERIAL]
2245 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2247 ro [KNL] Mount root device read-only on boot
2249 root= [KNL] Root filesystem
2250 See name_to_dev_t comment in init/do_mounts.c.
2252 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2253 mount the root filesystem
2255 rootflags= [KNL] Set root filesystem mount option string
2257 rootfstype= [KNL] Set root filesystem type
2259 rootwait [KNL] Wait (indefinitely) for root device to show up.
2260 Useful for devices that are detected asynchronously
2261 (e.g. USB and MMC devices).
2263 rw [KNL] Mount root device read-write on boot
2265 S [KNL] Run init in single mode
2267 sa1100ir [NET]
2268 See drivers/net/irda/sa1100_ir.c.
2270 sbni= [NET] Granch SBNI12 leased line adapter
2272 sched_debug [KNL] Enables verbose scheduler debug messages.
2274 security= [SECURITY] Choose a security module to enable at boot.
2275 If this boot parameter is not specified, only the first
2276 security module asking for security registration will be
2277 loaded. An invalid security module name will be treated
2278 as if no module has been chosen.
2280 selinux= [SELINUX] Disable or enable SELinux at boot time.
2281 Format: { "0" | "1" }
2282 See security/selinux/Kconfig help text.
2283 0 -- disable.
2284 1 -- enable.
2285 Default value is set via kernel config option.
2286 If enabled at boot time, /selinux/disable can be used
2287 later to disable prior to initial policy load.
2289 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2290 Format: { "0" | "1" }
2291 See security/apparmor/Kconfig help text
2292 0 -- disable.
2293 1 -- enable.
2294 Default value is set via kernel config option.
2296 serialnumber [BUGS=X86-32]
2298 shapers= [NET]
2299 Maximal number of shapers.
2301 show_msr= [x86] show boot-time MSR settings
2302 Format: { <integer> }
2303 Show boot-time (BIOS-initialized) MSR settings.
2304 The parameter means the number of CPUs to show,
2305 for example 1 means boot CPU only.
2307 simeth= [IA-64]
2308 simscsi=
2310 slram= [HW,MTD]
2312 slub_debug[=options[,slabs]] [MM, SLUB]
2313 Enabling slub_debug allows one to determine the
2314 culprit if slab objects become corrupted. Enabling
2315 slub_debug can create guard zones around objects and
2316 may poison objects when not in use. Also tracks the
2317 last alloc / free. For more information see
2318 Documentation/vm/slub.txt.
2320 slub_max_order= [MM, SLUB]
2321 Determines the maximum allowed order for slabs.
2322 A high setting may cause OOMs due to memory
2323 fragmentation. For more information see
2324 Documentation/vm/slub.txt.
2326 slub_min_objects= [MM, SLUB]
2327 The minimum number of objects per slab. SLUB will
2328 increase the slab order up to slub_max_order to
2329 generate a sufficiently large slab able to contain
2330 the number of objects indicated. The higher the number
2331 of objects the smaller the overhead of tracking slabs
2332 and the less frequently locks need to be acquired.
2333 For more information see Documentation/vm/slub.txt.
2335 slub_min_order= [MM, SLUB]
2336 Determines the mininum page order for slabs. Must be
2337 lower than slub_max_order.
2338 For more information see Documentation/vm/slub.txt.
2340 slub_nomerge [MM, SLUB]
2341 Disable merging of slabs with similar size. May be
2342 necessary if there is some reason to distinguish
2343 allocs to different slabs. Debug options disable
2344 merging on their own.
2345 For more information see Documentation/vm/slub.txt.
2347 smart2= [HW]
2348 Format: <io1>[,<io2>[,...,<io8>]]
2350 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2351 attempt to substitute SMP alternatives once at boot.
2353 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2354 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2355 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2356 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2357 smsc-ircc2.ircc_irq= [HW] IRQ line
2358 smsc-ircc2.ircc_dma= [HW] DMA channel
2359 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2360 0: Toshiba Satellite 1800 (GP data pin select)
2361 1: Fast pin select (default)
2362 2: ATC IRMode
2364 softlockup_panic=
2365 [KNL] Should the soft-lockup detector generate panics.
2366 Format: <integer>
2368 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2369 See Documentation/sonypi.txt
2371 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2372 See Documentation/serial/specialix.txt.
2374 spia_io_base= [HW,MTD]
2375 spia_fio_base=
2376 spia_pedr=
2377 spia_peddr=
2379 stacktrace [FTRACE]
2380 Enabled the stack tracer on boot up.
2382 sti= [PARISC,HW]
2383 Format: <num>
2384 Set the STI (builtin display/keyboard on the HP-PARISC
2385 machines) console (graphic card) which should be used
2386 as the initial boot-console.
2387 See also comment in drivers/video/console/sticore.c.
2389 sti_font= [HW]
2390 See comment in drivers/video/console/sticore.c.
2392 stifb= [HW]
2393 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2395 sunrpc.min_resvport=
2396 sunrpc.max_resvport=
2397 [NFS,SUNRPC]
2398 SunRPC servers often require that client requests
2399 originate from a privileged port (i.e. a port in the
2400 range 0 < portnr < 1024).
2401 An administrator who wishes to reserve some of these
2402 ports for other uses may adjust the range that the
2403 kernel's sunrpc client considers to be privileged
2404 using these two parameters to set the minimum and
2405 maximum port values.
2407 sunrpc.pool_mode=
2408 [NFS]
2409 Control how the NFS server code allocates CPUs to
2410 service thread pools. Depending on how many NICs
2411 you have and where their interrupts are bound, this
2412 option will affect which CPUs will do NFS serving.
2413 Note: this parameter cannot be changed while the
2414 NFS server is running.
2416 auto the server chooses an appropriate mode
2417 automatically using heuristics
2418 global a single global pool contains all CPUs
2419 percpu one pool for each CPU
2420 pernode one pool for each NUMA node (equivalent
2421 to global on non-NUMA machines)
2423 sunrpc.tcp_slot_table_entries=
2424 sunrpc.udp_slot_table_entries=
2425 [NFS,SUNRPC]
2426 Sets the upper limit on the number of simultaneous
2427 RPC calls that can be sent from the client to a
2428 server. Increasing these values may allow you to
2429 improve throughput, but will also increase the
2430 amount of memory reserved for use by the client.
2432 swapaccount[=0|1]
2433 [KNL] Enable accounting of swap in memory resource
2434 controller if no parameter or 1 is given or disable
2435 it if 0 is given (See Documentation/cgroups/memory.txt)
2437 swiotlb= [IA-64] Number of I/O TLB slabs
2439 switches= [HW,M68k]
2441 sysfs.deprecated=0|1 [KNL]
2442 Enable/disable old style sysfs layout for old udev
2443 on older distributions. When this option is enabled
2444 very new udev will not work anymore. When this option
2445 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2446 in older udev will not work anymore.
2447 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2448 the kernel configuration.
2450 sysrq_always_enabled
2451 [KNL]
2452 Ignore sysrq setting - this boot parameter will
2453 neutralize any effect of /proc/sys/kernel/sysrq.
2454 Useful for debugging.
2456 tdfx= [HW,DRM]
2458 test_suspend= [SUSPEND]
2459 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2460 standby suspend) as the system sleep state to briefly
2461 enter during system startup. The system is woken from
2462 this state using a wakeup-capable RTC alarm.
2464 thash_entries= [KNL,NET]
2465 Set number of hash buckets for TCP connection
2467 thermal.act= [HW,ACPI]
2468 -1: disable all active trip points in all thermal zones
2469 <degrees C>: override all lowest active trip points
2471 thermal.crt= [HW,ACPI]
2472 -1: disable all critical trip points in all thermal zones
2473 <degrees C>: override all critical trip points
2475 thermal.nocrt= [HW,ACPI]
2476 Set to disable actions on ACPI thermal zone
2477 critical and hot trip points.
2479 thermal.off= [HW,ACPI]
2480 1: disable ACPI thermal control
2482 thermal.psv= [HW,ACPI]
2483 -1: disable all passive trip points
2484 <degrees C>: override all passive trip points to this
2485 value
2487 thermal.tzp= [HW,ACPI]
2488 Specify global default ACPI thermal zone polling rate
2489 <deci-seconds>: poll all this frequency
2490 0: no polling (default)
2492 threadirqs [KNL]
2493 Force threading of all interrupt handlers except those
2494 marked explicitely IRQF_NO_THREAD.
2496 topology= [S390]
2497 Format: {off | on}
2498 Specify if the kernel should make use of the cpu
2499 topology information if the hardware supports this.
2500 The scheduler will make use of this information and
2501 e.g. base its process migration decisions on it.
2502 Default is on.
2504 tp720= [HW,PS2]
2506 tpm_suspend_pcr=[HW,TPM]
2507 Format: integer pcr id
2508 Specify that at suspend time, the tpm driver
2509 should extend the specified pcr with zeros,
2510 as a workaround for some chips which fail to
2511 flush the last written pcr on TPM_SaveState.
2512 This will guarantee that all the other pcrs
2513 are saved.
2515 trace_buf_size=nn[KMG]
2516 [FTRACE] will set tracing buffer size.
2518 trace_event=[event-list]
2519 [FTRACE] Set and start specified trace events in order
2520 to facilitate early boot debugging.
2521 See also Documentation/trace/events.txt
2523 tsc= Disable clocksource stability checks for TSC.
2524 Format: <string>
2525 [x86] reliable: mark tsc clocksource as reliable, this
2526 disables clocksource verification at runtime, as well
2527 as the stability checks done at bootup. Used to enable
2528 high-resolution timer mode on older hardware, and in
2529 virtualized environment.
2530 [x86] noirqtime: Do not use TSC to do irq accounting.
2531 Used to run time disable IRQ_TIME_ACCOUNTING on any
2532 platforms where RDTSC is slow and this accounting
2533 can add overhead.
2535 turbografx.map[2|3]= [HW,JOY]
2536 TurboGraFX parallel port interface
2537 Format:
2538 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2539 See also Documentation/input/joystick-parport.txt
2541 udbg-immortal [PPC] When debugging early kernel crashes that
2542 happen after console_init() and before a proper
2543 console driver takes over, this boot options might
2544 help "seeing" what's going on.
2546 uhash_entries= [KNL,NET]
2547 Set number of hash buckets for UDP/UDP-Lite connections
2549 uhci-hcd.ignore_oc=
2550 [USB] Ignore overcurrent events (default N).
2551 Some badly-designed motherboards generate lots of
2552 bogus events, for ports that aren't wired to
2553 anything. Set this parameter to avoid log spamming.
2554 Note that genuine overcurrent events won't be
2555 reported either.
2557 unknown_nmi_panic
2558 [X86] Cause panic on unknown NMI.
2560 usbcore.authorized_default=
2561 [USB] Default USB device authorization:
2562 (default -1 = authorized except for wireless USB,
2563 0 = not authorized, 1 = authorized)
2565 usbcore.autosuspend=
2566 [USB] The autosuspend time delay (in seconds) used
2567 for newly-detected USB devices (default 2). This
2568 is the time required before an idle device will be
2569 autosuspended. Devices for which the delay is set
2570 to a negative value won't be autosuspended at all.
2572 usbcore.usbfs_snoop=
2573 [USB] Set to log all usbfs traffic (default 0 = off).
2575 usbcore.blinkenlights=
2576 [USB] Set to cycle leds on hubs (default 0 = off).
2578 usbcore.old_scheme_first=
2579 [USB] Start with the old device initialization
2580 scheme (default 0 = off).
2582 usbcore.use_both_schemes=
2583 [USB] Try the other device initialization scheme
2584 if the first one fails (default 1 = enabled).
2586 usbcore.initial_descriptor_timeout=
2587 [USB] Specifies timeout for the initial 64-byte
2588 USB_REQ_GET_DESCRIPTOR request in milliseconds
2589 (default 5000 = 5.0 seconds).
2591 usbhid.mousepoll=
2592 [USBHID] The interval which mice are to be polled at.
2594 usb-storage.delay_use=
2595 [UMS] The delay in seconds before a new device is
2596 scanned for Logical Units (default 5).
2598 usb-storage.quirks=
2599 [UMS] A list of quirks entries to supplement or
2600 override the built-in unusual_devs list. List
2601 entries are separated by commas. Each entry has
2602 the form VID:PID:Flags where VID and PID are Vendor
2603 and Product ID values (4-digit hex numbers) and
2604 Flags is a set of characters, each corresponding
2605 to a common usb-storage quirk flag as follows:
2606 a = SANE_SENSE (collect more than 18 bytes
2607 of sense data);
2608 b = BAD_SENSE (don't collect more than 18
2609 bytes of sense data);
2610 c = FIX_CAPACITY (decrease the reported
2611 device capacity by one sector);
2612 d = NO_READ_DISC_INFO (don't use
2613 READ_DISC_INFO command);
2614 e = NO_READ_CAPACITY_16 (don't use
2615 READ_CAPACITY_16 command);
2616 h = CAPACITY_HEURISTICS (decrease the
2617 reported device capacity by one
2618 sector if the number is odd);
2619 i = IGNORE_DEVICE (don't bind to this
2620 device);
2621 l = NOT_LOCKABLE (don't try to lock and
2622 unlock ejectable media);
2623 m = MAX_SECTORS_64 (don't transfer more
2624 than 64 sectors = 32 KB at a time);
2625 n = INITIAL_READ10 (force a retry of the
2626 initial READ(10) command);
2627 o = CAPACITY_OK (accept the capacity
2628 reported by the device);
2629 r = IGNORE_RESIDUE (the device reports
2630 bogus residue values);
2631 s = SINGLE_LUN (the device has only one
2632 Logical Unit);
2633 w = NO_WP_DETECT (don't test whether the
2634 medium is write-protected).
2635 Example: quirks=0419:aaf5:rl,0421:0433:rc
2637 user_debug= [KNL,ARM]
2638 Format: <int>
2639 See arch/arm/Kconfig.debug help text.
2640 1 - undefined instruction events
2641 2 - system calls
2642 4 - invalid data aborts
2643 8 - SIGSEGV faults
2644 16 - SIGBUS faults
2645 Example: user_debug=31
2647 userpte=
2648 [X86] Flags controlling user PTE allocations.
2650 nohigh = do not allocate PTE pages in
2651 HIGHMEM regardless of setting
2652 of CONFIG_HIGHPTE.
2654 vdso= [X86,SH]
2655 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2656 vdso=1: enable VDSO (default)
2657 vdso=0: disable VDSO mapping
2659 vdso32= [X86]
2660 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2661 vdso32=1: enable 32-bit VDSO (default)
2662 vdso32=0: disable 32-bit VDSO mapping
2664 vector= [IA-64,SMP]
2665 vector=percpu: enable percpu vector domain
2667 video= [FB] Frame buffer configuration
2668 See Documentation/fb/modedb.txt.
2670 vga= [BOOT,X86-32] Select a particular video mode
2671 See Documentation/x86/boot.txt and
2672 Documentation/svga.txt.
2673 Use vga=ask for menu.
2674 This is actually a boot loader parameter; the value is
2675 passed to the kernel using a special protocol.
2677 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2678 size of <nn>. This can be used to increase the
2679 minimum size (128MB on x86). It can also be used to
2680 decrease the size and leave more room for directly
2681 mapped kernel RAM.
2683 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2684 Format: <command>
2686 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2687 Format: <command>
2689 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2690 Format: <command>
2692 vt.cur_default= [VT] Default cursor shape.
2693 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2694 the parameters of the <Esc>[?A;B;Cc escape sequence;
2695 see VGA-softcursor.txt. Default: 2 = underline.
2697 vt.default_blu= [VT]
2698 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2699 Change the default blue palette of the console.
2700 This is a 16-member array composed of values
2701 ranging from 0-255.
2703 vt.default_grn= [VT]
2704 Format: <green0>,<green1>,<green2>,...,<green15>
2705 Change the default green palette of the console.
2706 This is a 16-member array composed of values
2707 ranging from 0-255.
2709 vt.default_red= [VT]
2710 Format: <red0>,<red1>,<red2>,...,<red15>
2711 Change the default red palette of the console.
2712 This is a 16-member array composed of values
2713 ranging from 0-255.
2715 vt.default_utf8=
2716 [VT]
2717 Format=<0|1>
2718 Set system-wide default UTF-8 mode for all tty's.
2719 Default is 1, i.e. UTF-8 mode is enabled for all
2720 newly opened terminals.
2722 vt.global_cursor_default=
2723 [VT]
2724 Format=<-1|0|1>
2725 Set system-wide default for whether a cursor
2726 is shown on new VTs. Default is -1,
2727 i.e. cursors will be created by default unless
2728 overridden by individual drivers. 0 will hide
2729 cursors, 1 will display them.
2731 watchdog timers [HW,WDT] For information on watchdog timers,
2732 see Documentation/watchdog/watchdog-parameters.txt
2733 or other driver-specific files in the
2734 Documentation/watchdog/ directory.
2736 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2737 default x2apic cluster mode on platforms
2738 supporting x2apic.
2740 x86_mrst_timer= [X86-32,APBT]
2741 Choose timer option for x86 Moorestown MID platform.
2742 Two valid options are apbt timer only and lapic timer
2743 plus one apbt timer for broadcast timer.
2744 x86_mrst_timer=apbt_only | lapic_and_apbt
2746 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2747 xd_geo= See header of drivers/block/xd.c.
2749 xen_emul_unplug= [HW,X86,XEN]
2750 Unplug Xen emulated devices
2751 Format: [unplug0,][unplug1]
2752 ide-disks -- unplug primary master IDE devices
2753 aux-ide-disks -- unplug non-primary-master IDE devices
2754 nics -- unplug network devices
2755 all -- unplug all emulated devices (NICs and IDE disks)
2756 unnecessary -- unplugging emulated devices is
2757 unnecessary even if the host did not respond to
2758 the unplug protocol
2759 never -- do not unplug even if version check succeeds
2761 xirc2ps_cs= [NET,PCMCIA]
2762 Format:
2763 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2765 ______________________________________________________________________
2767 TODO:
2769 Add more DRM drivers.