kernel-parameters.txt 85 KB

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  1. Kernel Parameters
  2. ~~~~~~~~~~~~~~~~~
  3. The following is a consolidated list of the kernel parameters as implemented
  4. (mostly) by the __setup() macro and sorted into English Dictionary order
  5. (defined as ignoring all punctuation and sorting digits before letters in a
  6. case insensitive manner), and with descriptions where known.
  7. Module parameters for loadable modules are specified only as the
  8. parameter name with optional '=' and value as appropriate, such as:
  9. modprobe usbcore blinkenlights=1
  10. Module parameters for modules that are built into the kernel image
  11. are specified on the kernel command line with the module name plus
  12. '.' plus parameter name, with '=' and value if appropriate, such as:
  13. usbcore.blinkenlights=1
  14. Hyphens (dashes) and underscores are equivalent in parameter names, so
  15. log_buf_len=1M print-fatal-signals=1
  16. can also be entered as
  17. log-buf-len=1M print_fatal_signals=1
  18. This document may not be entirely up to date and comprehensive. The command
  19. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  20. module. Loadable modules, after being loaded into the running kernel, also
  21. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  22. parameters may be changed at runtime by the command
  23. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  24. The parameters listed below are only valid if certain kernel build options were
  25. enabled and if respective hardware is present. The text in square brackets at
  26. the beginning of each description states the restrictions within which a
  27. parameter is applicable:
  28. ACPI ACPI support is enabled.
  29. AGP AGP (Accelerated Graphics Port) is enabled.
  30. ALSA ALSA sound support is enabled.
  31. APIC APIC support is enabled.
  32. APM Advanced Power Management support is enabled.
  33. AVR32 AVR32 architecture is enabled.
  34. AX25 Appropriate AX.25 support is enabled.
  35. BLACKFIN Blackfin architecture is enabled.
  36. DRM Direct Rendering Management support is enabled.
  37. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  38. EFI EFI Partitioning (GPT) is enabled
  39. EIDE EIDE/ATAPI support is enabled.
  40. FB The frame buffer device is enabled.
  41. GCOV GCOV profiling is enabled.
  42. HW Appropriate hardware is enabled.
  43. IA-64 IA-64 architecture is enabled.
  44. IMA Integrity measurement architecture is enabled.
  45. IOSCHED More than one I/O scheduler is enabled.
  46. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  47. ISAPNP ISA PnP code is enabled.
  48. ISDN Appropriate ISDN support is enabled.
  49. JOY Appropriate joystick support is enabled.
  50. LIBATA Libata driver is enabled
  51. LP Printer support is enabled.
  52. LOOP Loopback device support is enabled.
  53. M68k M68k architecture is enabled.
  54. These options have more detailed description inside of
  55. Documentation/m68k/kernel-options.txt.
  56. MCA MCA bus support is enabled.
  57. MDA MDA console support is enabled.
  58. MOUSE Appropriate mouse support is enabled.
  59. MSI Message Signaled Interrupts (PCI).
  60. MTD MTD (Memory Technology Device) support is enabled.
  61. NET Appropriate network support is enabled.
  62. NUMA NUMA support is enabled.
  63. GENERIC_TIME The generic timeofday code is enabled.
  64. NFS Appropriate NFS support is enabled.
  65. OSS OSS sound support is enabled.
  66. PV_OPS A paravirtualized kernel is enabled.
  67. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  68. PARISC The PA-RISC architecture is enabled.
  69. PCI PCI bus support is enabled.
  70. PCIE PCI Express support is enabled.
  71. PCMCIA The PCMCIA subsystem is enabled.
  72. PNP Plug & Play support is enabled.
  73. PPC PowerPC architecture is enabled.
  74. PPT Parallel port support is enabled.
  75. PS2 Appropriate PS/2 support is enabled.
  76. RAM RAM disk support is enabled.
  77. ROOTPLUG The example Root Plug LSM is enabled.
  78. S390 S390 architecture is enabled.
  79. SCSI Appropriate SCSI support is enabled.
  80. A lot of drivers has their options described inside of
  81. Documentation/scsi/.
  82. SECURITY Different security models are enabled.
  83. SELINUX SELinux support is enabled.
  84. SERIAL Serial support is enabled.
  85. SH SuperH architecture is enabled.
  86. SMP The kernel is an SMP kernel.
  87. SPARC Sparc architecture is enabled.
  88. SWSUSP Software suspend (hibernation) is enabled.
  89. SUSPEND System suspend states are enabled.
  90. FTRACE Function tracing enabled.
  91. TS Appropriate touchscreen support is enabled.
  92. UMS USB Mass Storage support is enabled.
  93. USB USB support is enabled.
  94. USBHID USB Human Interface Device support is enabled.
  95. V4L Video For Linux support is enabled.
  96. VGA The VGA console has been enabled.
  97. VT Virtual terminal support is enabled.
  98. WDT Watchdog support is enabled.
  99. XT IBM PC/XT MFM hard disk support is enabled.
  100. X86-32 X86-32, aka i386 architecture is enabled.
  101. X86-64 X86-64 architecture is enabled.
  102. More X86-64 boot options can be found in
  103. Documentation/x86/x86_64/boot-options.txt .
  104. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  105. In addition, the following text indicates that the option:
  106. BUGS= Relates to possible processor bugs on the said processor.
  107. KNL Is a kernel start-up parameter.
  108. BOOT Is a boot loader parameter.
  109. Parameters denoted with BOOT are actually interpreted by the boot
  110. loader, and have no meaning to the kernel directly.
  111. Do not modify the syntax of boot loader parameters without extreme
  112. need or coordination with <Documentation/x86/boot.txt>.
  113. There are also arch-specific kernel-parameters not documented here.
  114. See for example <Documentation/x86/x86_64/boot-options.txt>.
  115. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  116. a trailing = on the name of any parameter states that that parameter will
  117. be entered as an environment variable, whereas its absence indicates that
  118. it will appear as a kernel argument readable via /proc/cmdline by programs
  119. running once the system is up.
  120. The number of kernel parameters is not limited, but the length of the
  121. complete command line (parameters including spaces etc.) is limited to
  122. a fixed number of characters. This limit depends on the architecture
  123. and is between 256 and 4096 characters. It is defined in the file
  124. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  125. acpi= [HW,ACPI,X86]
  126. Advanced Configuration and Power Interface
  127. Format: { force | off | ht | strict | noirq | rsdt }
  128. force -- enable ACPI if default was off
  129. off -- disable ACPI if default was on
  130. noirq -- do not use ACPI for IRQ routing
  131. ht -- run only enough ACPI to enable Hyper Threading
  132. strict -- Be less tolerant of platforms that are not
  133. strictly ACPI specification compliant.
  134. rsdt -- prefer RSDT over (default) XSDT
  135. See also Documentation/power/pm.txt, pci=noacpi
  136. acpi_apic_instance= [ACPI, IOAPIC]
  137. Format: <int>
  138. 2: use 2nd APIC table, if available
  139. 1,0: use 1st APIC table
  140. default: 0
  141. acpi_backlight= [HW,ACPI]
  142. acpi_backlight=vendor
  143. acpi_backlight=video
  144. If set to vendor, prefer vendor specific driver
  145. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  146. of the ACPI video.ko driver.
  147. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  148. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  149. Format: <int>
  150. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  151. debug output. Bits in debug_layer correspond to a
  152. _COMPONENT in an ACPI source file, e.g.,
  153. #define _COMPONENT ACPI_PCI_COMPONENT
  154. Bits in debug_level correspond to a level in
  155. ACPI_DEBUG_PRINT statements, e.g.,
  156. ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
  157. The debug_level mask defaults to "info". See
  158. Documentation/acpi/debug.txt for more information about
  159. debug layers and levels.
  160. Enable processor driver info messages:
  161. acpi.debug_layer=0x20000000
  162. Enable PCI/PCI interrupt routing info messages:
  163. acpi.debug_layer=0x400000
  164. Enable AML "Debug" output, i.e., stores to the Debug
  165. object while interpreting AML:
  166. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  167. Enable all messages related to ACPI hardware:
  168. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  169. Some values produce so much output that the system is
  170. unusable. The "log_buf_len" parameter may be useful
  171. if you need to capture more output.
  172. acpi_display_output= [HW,ACPI]
  173. acpi_display_output=vendor
  174. acpi_display_output=video
  175. See above.
  176. acpi_irq_balance [HW,ACPI]
  177. ACPI will balance active IRQs
  178. default in APIC mode
  179. acpi_irq_nobalance [HW,ACPI]
  180. ACPI will not move active IRQs (default)
  181. default in PIC mode
  182. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  183. Format: <irq>,<irq>...
  184. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  185. use by PCI
  186. Format: <irq>,<irq>...
  187. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  188. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  189. Format: To spoof as Windows 98: ="Microsoft Windows"
  190. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  191. acpi_osi="string1" # add string1 -- only one string
  192. acpi_osi="!string2" # remove built-in string2
  193. acpi_osi= # disable all strings
  194. acpi_pm_good [X86]
  195. Override the pmtimer bug detection: force the kernel
  196. to assume that this machine's pmtimer latches its value
  197. and always returns good values.
  198. acpi.power_nocheck= [HW,ACPI]
  199. Format: 1/0 enable/disable the check of power state.
  200. On some bogus BIOS the _PSC object/_STA object of
  201. power resource can't return the correct device power
  202. state. In such case it is unneccessary to check its
  203. power state again in power transition.
  204. 1 : disable the power state check
  205. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  206. Format: { level | edge | high | low }
  207. acpi_serialize [HW,ACPI] force serialization of AML methods
  208. acpi_skip_timer_override [HW,ACPI]
  209. Recognize and ignore IRQ0/pin2 Interrupt Override.
  210. For broken nForce2 BIOS resulting in XT-PIC timer.
  211. acpi_sleep= [HW,ACPI] Sleep options
  212. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
  213. old_ordering, s4_nonvs }
  214. See Documentation/power/video.txt for information on
  215. s3_bios and s3_mode.
  216. s3_beep is for debugging; it makes the PC's speaker beep
  217. as soon as the kernel's real-mode entry point is called.
  218. s4_nohwsig prevents ACPI hardware signature from being
  219. used during resume from hibernation.
  220. old_ordering causes the ACPI 1.0 ordering of the _PTS
  221. control method, with respect to putting devices into
  222. low power states, to be enforced (the ACPI 2.0 ordering
  223. of _PTS is used by default).
  224. s4_nonvs prevents the kernel from saving/restoring the
  225. ACPI NVS memory during hibernation.
  226. acpi_use_timer_override [HW,ACPI]
  227. Use timer override. For some broken Nvidia NF5 boards
  228. that require a timer override, but don't have HPET
  229. acpi_enforce_resources= [ACPI]
  230. { strict | lax | no }
  231. Check for resource conflicts between native drivers
  232. and ACPI OperationRegions (SystemIO and SystemMemory
  233. only). IO ports and memory declared in ACPI might be
  234. used by the ACPI subsystem in arbitrary AML code and
  235. can interfere with legacy drivers.
  236. strict (default): access to resources claimed by ACPI
  237. is denied; legacy drivers trying to access reserved
  238. resources will fail to bind to device using them.
  239. lax: access to resources claimed by ACPI is allowed;
  240. legacy drivers trying to access reserved resources
  241. will bind successfully but a warning message is logged.
  242. no: ACPI OperationRegions are not marked as reserved,
  243. no further checks are performed.
  244. ad1848= [HW,OSS]
  245. Format: <io>,<irq>,<dma>,<dma2>,<type>
  246. add_efi_memmap [EFI; X86] Include EFI memory map in
  247. kernel's map of available physical RAM.
  248. advansys= [HW,SCSI]
  249. See header of drivers/scsi/advansys.c.
  250. advwdt= [HW,WDT] Advantech WDT
  251. Format: <iostart>,<iostop>
  252. aedsp16= [HW,OSS] Audio Excel DSP 16
  253. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  254. See also header of sound/oss/aedsp16.c.
  255. agp= [AGP]
  256. { off | try_unsupported }
  257. off: disable AGP support
  258. try_unsupported: try to drive unsupported chipsets
  259. (may crash computer or cause data corruption)
  260. aha152x= [HW,SCSI]
  261. See Documentation/scsi/aha152x.txt.
  262. aha1542= [HW,SCSI]
  263. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  264. aic7xxx= [HW,SCSI]
  265. See Documentation/scsi/aic7xxx.txt.
  266. aic79xx= [HW,SCSI]
  267. See Documentation/scsi/aic79xx.txt.
  268. amd_iommu= [HW,X86-84]
  269. Pass parameters to the AMD IOMMU driver in the system.
  270. Possible values are:
  271. isolate - enable device isolation (each device, as far
  272. as possible, will get its own protection
  273. domain) [default]
  274. share - put every device behind one IOMMU into the
  275. same protection domain
  276. fullflush - enable flushing of IO/TLB entries when
  277. they are unmapped. Otherwise they are
  278. flushed before they will be reused, which
  279. is a lot of faster
  280. amijoy.map= [HW,JOY] Amiga joystick support
  281. Map of devices attached to JOY0DAT and JOY1DAT
  282. Format: <a>,<b>
  283. See also Documentation/kernel/input/joystick.txt
  284. analog.map= [HW,JOY] Analog joystick and gamepad support
  285. Specifies type or capabilities of an analog joystick
  286. connected to one of 16 gameports
  287. Format: <type1>,<type2>,..<type16>
  288. apc= [HW,SPARC]
  289. Power management functions (SPARCstation-4/5 + deriv.)
  290. Format: noidle
  291. Disable APC CPU standby support. SPARCstation-Fox does
  292. not play well with APC CPU idle - disable it if you have
  293. APC and your system crashes randomly.
  294. apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
  295. Change the output verbosity whilst booting
  296. Format: { quiet (default) | verbose | debug }
  297. Change the amount of debugging information output
  298. when initialising the APIC and IO-APIC components.
  299. apm= [APM] Advanced Power Management
  300. See header of arch/x86/kernel/apm_32.c.
  301. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  302. Format: <io>,<irq>,<nodeID>
  303. ataflop= [HW,M68k]
  304. atarimouse= [HW,MOUSE] Atari Mouse
  305. atascsi= [HW,SCSI] Atari SCSI
  306. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  307. EzKey and similar keyboards
  308. atkbd.reset= [HW] Reset keyboard during initialization
  309. atkbd.set= [HW] Select keyboard code set
  310. Format: <int> (2 = AT (default), 3 = PS/2)
  311. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  312. keyboards
  313. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  314. Format: <bool> (0 = real, 1 = synthetic (default))
  315. atkbd.softrepeat= [HW]
  316. Use software keyboard repeat
  317. autotest [IA64]
  318. baycom_epp= [HW,AX25]
  319. Format: <io>,<mode>
  320. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  321. Format: <io>,<mode>
  322. See header of drivers/net/hamradio/baycom_par.c.
  323. baycom_ser_fdx= [HW,AX25]
  324. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  325. Format: <io>,<irq>,<mode>[,<baud>]
  326. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  327. baycom_ser_hdx= [HW,AX25]
  328. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  329. Format: <io>,<irq>,<mode>
  330. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  331. boot_delay= Milliseconds to delay each printk during boot.
  332. Values larger than 10 seconds (10000) are changed to
  333. no delay (0).
  334. Format: integer
  335. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  336. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  337. bttv.radio= Most important insmod options are available as
  338. kernel args too.
  339. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  340. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  341. BusLogic= [HW,SCSI]
  342. See drivers/scsi/BusLogic.c, comment before function
  343. BusLogic_ParseDriverOptions().
  344. c101= [NET] Moxa C101 synchronous serial card
  345. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  346. Sometimes CPU hardware bugs make them report the cache
  347. size incorrectly. The kernel will attempt work arounds
  348. to fix known problems, but for some CPUs it is not
  349. possible to determine what the correct size should be.
  350. This option provides an override for these situations.
  351. capability.disable=
  352. [SECURITY] Disable capabilities. This would normally
  353. be used only if an alternative security model is to be
  354. configured. Potentially dangerous and should only be
  355. used if you are entirely sure of the consequences.
  356. ccw_timeout_log [S390]
  357. See Documentation/s390/CommonIO for details.
  358. cgroup_disable= [KNL] Disable a particular controller
  359. Format: {name of the controller(s) to disable}
  360. {Currently supported controllers - "memory"}
  361. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  362. Format: { "0" | "1" }
  363. See security/selinux/Kconfig help text.
  364. 0 -- check protection applied by kernel (includes
  365. any implied execute protection).
  366. 1 -- check protection requested by application.
  367. Default value is set via a kernel config option.
  368. Value can be changed at runtime via
  369. /selinux/checkreqprot.
  370. cio_ignore= [S390]
  371. See Documentation/s390/CommonIO for details.
  372. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  373. [Deprecated]
  374. Forces specified clocksource (if available) to be used
  375. when calculating gettimeofday(). If specified
  376. clocksource is not available, it defaults to PIT.
  377. Format: { pit | tsc | cyclone | pmtmr }
  378. clocksource= [GENERIC_TIME] Override the default clocksource
  379. Format: <string>
  380. Override the default clocksource and use the clocksource
  381. with the name specified.
  382. Some clocksource names to choose from, depending on
  383. the platform:
  384. [all] jiffies (this is the base, fallback clocksource)
  385. [ACPI] acpi_pm
  386. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  387. pxa_timer,timer3,32k_counter,timer0_1
  388. [AVR32] avr32
  389. [X86-32] pit,hpet,tsc,vmi-timer;
  390. scx200_hrt on Geode; cyclone on IBM x440
  391. [MIPS] MIPS
  392. [PARISC] cr16
  393. [S390] tod
  394. [SH] SuperH
  395. [SPARC64] tick
  396. [X86-64] hpet,tsc
  397. clearcpuid=BITNUM [X86]
  398. Disable CPUID feature X for the kernel. See
  399. arch/x86/include/asm/cpufeature.h for the valid bit
  400. numbers. Note the Linux specific bits are not necessarily
  401. stable over kernel options, but the vendor specific
  402. ones should be.
  403. Also note that user programs calling CPUID directly
  404. or using the feature without checking anything
  405. will still see it. This just prevents it from
  406. being used by the kernel or shown in /proc/cpuinfo.
  407. Also note the kernel might malfunction if you disable
  408. some critical bits.
  409. cmo_free_hint= [PPC] Format: { yes | no }
  410. Specify whether pages are marked as being inactive
  411. when they are freed. This is used in CMO environments
  412. to determine OS memory pressure for page stealing by
  413. a hypervisor.
  414. Default: yes
  415. code_bytes [X86] How many bytes of object code to print
  416. in an oops report.
  417. Range: 0 - 8192
  418. Default: 64
  419. com20020= [HW,NET] ARCnet - COM20020 chipset
  420. Format:
  421. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  422. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  423. Format: <io>[,<irq>]
  424. com90xx= [HW,NET]
  425. ARCnet - COM90xx chipset (memory-mapped buffers)
  426. Format: <io>[,<irq>[,<memstart>]]
  427. condev= [HW,S390] console device
  428. conmode=
  429. console= [KNL] Output console device and options.
  430. tty<n> Use the virtual console device <n>.
  431. ttyS<n>[,options]
  432. ttyUSB0[,options]
  433. Use the specified serial port. The options are of
  434. the form "bbbbpnf", where "bbbb" is the baud rate,
  435. "p" is parity ("n", "o", or "e"), "n" is number of
  436. bits, and "f" is flow control ("r" for RTS or
  437. omit it). Default is "9600n8".
  438. See Documentation/serial-console.txt for more
  439. information. See
  440. Documentation/networking/netconsole.txt for an
  441. alternative.
  442. uart[8250],io,<addr>[,options]
  443. uart[8250],mmio,<addr>[,options]
  444. Start an early, polled-mode console on the 8250/16550
  445. UART at the specified I/O port or MMIO address,
  446. switching to the matching ttyS device later. The
  447. options are the same as for ttyS, above.
  448. If the device connected to the port is not a TTY but a braille
  449. device, prepend "brl," before the device type, for instance
  450. console=brl,ttyS0
  451. For now, only VisioBraille is supported.
  452. consoleblank= [KNL] The console blank (screen saver) timeout in
  453. seconds. Defaults to 10*60 = 10mins. A value of 0
  454. disables the blank timer.
  455. coredump_filter=
  456. [KNL] Change the default value for
  457. /proc/<pid>/coredump_filter.
  458. See also Documentation/filesystems/proc.txt.
  459. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  460. Format:
  461. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  462. crashkernel=nn[KMG]@ss[KMG]
  463. [KNL] Reserve a chunk of physical memory to
  464. hold a kernel to switch to with kexec on panic.
  465. crashkernel=range1:size1[,range2:size2,...][@offset]
  466. [KNL] Same as above, but depends on the memory
  467. in the running system. The syntax of range is
  468. start-[end] where start and end are both
  469. a memory unit (amount[KMG]). See also
  470. Documentation/kdump/kdump.txt for a example.
  471. cs89x0_dma= [HW,NET]
  472. Format: <dma>
  473. cs89x0_media= [HW,NET]
  474. Format: { rj45 | aui | bnc }
  475. dasd= [HW,NET]
  476. See header of drivers/s390/block/dasd_devmap.c.
  477. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  478. (one device per port)
  479. Format: <port#>,<type>
  480. See also Documentation/input/joystick-parport.txt
  481. debug [KNL] Enable kernel debugging (events log level).
  482. debug_locks_verbose=
  483. [KNL] verbose self-tests
  484. Format=<0|1>
  485. Print debugging info while doing the locking API
  486. self-tests.
  487. We default to 0 (no extra messages), setting it to
  488. 1 will print _a lot_ more information - normally
  489. only useful to kernel developers.
  490. debug_objects [KNL] Enable object debugging
  491. no_debug_objects
  492. [KNL] Disable object debugging
  493. debugpat [X86] Enable PAT debugging
  494. decnet.addr= [HW,NET]
  495. Format: <area>[,<node>]
  496. See also Documentation/networking/decnet.txt.
  497. default_hugepagesz=
  498. [same as hugepagesz=] The size of the default
  499. HugeTLB page size. This is the size represented by
  500. the legacy /proc/ hugepages APIs, used for SHM, and
  501. default size when mounting hugetlbfs filesystems.
  502. Defaults to the default architecture's huge page size
  503. if not specified.
  504. dhash_entries= [KNL]
  505. Set number of hash buckets for dentry cache.
  506. digi= [HW,SERIAL]
  507. IO parameters + enable/disable command.
  508. digiepca= [HW,SERIAL]
  509. See drivers/char/README.epca and
  510. Documentation/serial/digiepca.txt.
  511. disable_mtrr_cleanup [X86]
  512. The kernel tries to adjust MTRR layout from continuous
  513. to discrete, to make X server driver able to add WB
  514. entry later. This parameter disables that.
  515. disable_mtrr_trim [X86, Intel and AMD only]
  516. By default the kernel will trim any uncacheable
  517. memory out of your available memory pool based on
  518. MTRR settings. This parameter disables that behavior,
  519. possibly causing your machine to run very slowly.
  520. disable_timer_pin_1 [X86]
  521. Disable PIN 1 of APIC timer
  522. Can be useful to work around chipset bugs.
  523. dmasound= [HW,OSS] Sound subsystem buffers
  524. dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
  525. this option disables the debugging code at boot.
  526. dma_debug_entries=<number>
  527. This option allows to tune the number of preallocated
  528. entries for DMA-API debugging code. One entry is
  529. required per DMA-API allocation. Use this if the
  530. DMA-API debugging code disables itself because the
  531. architectural default is too low.
  532. dma_debug_driver=<driver_name>
  533. With this option the DMA-API debugging driver
  534. filter feature can be enabled at boot time. Just
  535. pass the driver to filter for as the parameter.
  536. The filter can be disabled or changed to another
  537. driver later using sysfs.
  538. dscc4.setup= [NET]
  539. dtc3181e= [HW,SCSI]
  540. dynamic_printk Enables pr_debug()/dev_dbg() calls if
  541. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
  542. These can also be switched on/off via
  543. <debugfs>/dynamic_printk/modules
  544. earlycon= [KNL] Output early console device and options.
  545. uart[8250],io,<addr>[,options]
  546. uart[8250],mmio,<addr>[,options]
  547. Start an early, polled-mode console on the 8250/16550
  548. UART at the specified I/O port or MMIO address.
  549. The options are the same as for ttyS, above.
  550. earlyprintk= [X86,SH,BLACKFIN]
  551. earlyprintk=vga
  552. earlyprintk=serial[,ttySn[,baudrate]]
  553. earlyprintk=dbgp
  554. Append ",keep" to not disable it when the real console
  555. takes over.
  556. Only vga or serial or usb debug port at a time.
  557. Currently only ttyS0 and ttyS1 are supported.
  558. Interaction with the standard serial driver is not
  559. very good.
  560. The VGA output is eventually overwritten by the real
  561. console.
  562. eata= [HW,SCSI]
  563. edd= [EDD]
  564. Format: {"off" | "on" | "skip[mbr]"}
  565. eisa_irq_edge= [PARISC,HW]
  566. See header of drivers/parisc/eisa.c.
  567. elanfreq= [X86-32]
  568. See comment before function elanfreq_setup() in
  569. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  570. elevator= [IOSCHED]
  571. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  572. See Documentation/block/as-iosched.txt and
  573. Documentation/block/deadline-iosched.txt for details.
  574. elfcorehdr= [IA64,PPC,SH,X86]
  575. Specifies physical address of start of kernel core
  576. image elf header. Generally kexec loader will
  577. pass this option to capture kernel.
  578. See Documentation/kdump/kdump.txt for details.
  579. enable_mtrr_cleanup [X86]
  580. The kernel tries to adjust MTRR layout from continuous
  581. to discrete, to make X server driver able to add WB
  582. entry later. This parameter enables that.
  583. enable_timer_pin_1 [X86]
  584. Enable PIN 1 of APIC timer
  585. Can be useful to work around chipset bugs
  586. (in particular on some ATI chipsets).
  587. The kernel tries to set a reasonable default.
  588. enforcing [SELINUX] Set initial enforcing status.
  589. Format: {"0" | "1"}
  590. See security/selinux/Kconfig help text.
  591. 0 -- permissive (log only, no denials).
  592. 1 -- enforcing (deny and log).
  593. Default value is 0.
  594. Value can be changed at runtime via /selinux/enforce.
  595. ether= [HW,NET] Ethernet cards parameters
  596. This option is obsoleted by the "netdev=" option, which
  597. has equivalent usage. See its documentation for details.
  598. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  599. Format: <io>[,<irq>]
  600. failslab=
  601. fail_page_alloc=
  602. fail_make_request=[KNL]
  603. General fault injection mechanism.
  604. Format: <interval>,<probability>,<space>,<times>
  605. See also /Documentation/fault-injection/.
  606. fd_mcs= [HW,SCSI]
  607. See header of drivers/scsi/fd_mcs.c.
  608. fdomain= [HW,SCSI]
  609. See header of drivers/scsi/fdomain.c.
  610. floppy= [HW]
  611. See Documentation/blockdev/floppy.txt.
  612. force_pal_cache_flush
  613. [IA-64] Avoid check_sal_cache_flush which may hang on
  614. buggy SAL_CACHE_FLUSH implementations. Using this
  615. parameter will force ia64_sal_cache_flush to call
  616. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  617. ftrace=[tracer]
  618. [FTRACE] will set and start the specified tracer
  619. as early as possible in order to facilitate early
  620. boot debugging.
  621. ftrace_dump_on_oops
  622. [FTRACE] will dump the trace buffers on oops.
  623. ftrace_filter=[function-list]
  624. [FTRACE] Limit the functions traced by the function
  625. tracer at boot up. function-list is a comma separated
  626. list of functions. This list can be changed at run
  627. time by the set_ftrace_filter file in the debugfs
  628. tracing directory.
  629. ftrace_notrace=[function-list]
  630. [FTRACE] Do not trace the functions specified in
  631. function-list. This list can be changed at run time
  632. by the set_ftrace_notrace file in the debugfs
  633. tracing directory.
  634. gamecon.map[2|3]=
  635. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  636. support via parallel port (up to 5 devices per port)
  637. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  638. See also Documentation/input/joystick-parport.txt
  639. gamma= [HW,DRM]
  640. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  641. Format: off | on
  642. default: on
  643. gcov_persist= [GCOV] When non-zero (default), profiling data for
  644. kernel modules is saved and remains accessible via
  645. debugfs, even when the module is unloaded/reloaded.
  646. When zero, profiling data is discarded and associated
  647. debugfs files are removed at module unload time.
  648. gdth= [HW,SCSI]
  649. See header of drivers/scsi/gdth.c.
  650. gpt [EFI] Forces disk with valid GPT signature but
  651. invalid Protective MBR to be treated as GPT.
  652. gvp11= [HW,SCSI]
  653. hashdist= [KNL,NUMA] Large hashes allocated during boot
  654. are distributed across NUMA nodes. Defaults on
  655. for 64bit NUMA, off otherwise.
  656. Format: 0 | 1 (for off | on)
  657. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  658. hd= [EIDE] (E)IDE hard drive subsystem geometry
  659. Format: <cyl>,<head>,<sect>
  660. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  661. size of <nn>. This works even on boxes that have no
  662. highmem otherwise. This also works to reduce highmem
  663. size on bigger boxes.
  664. highres= [KNL] Enable/disable high resolution timer mode.
  665. Valid parameters: "on", "off"
  666. Default: "on"
  667. hisax= [HW,ISDN]
  668. See Documentation/isdn/README.HiSax.
  669. hlt [BUGS=ARM,SH]
  670. hpet= [X86-32,HPET] option to control HPET usage
  671. Format: { enable (default) | disable | force |
  672. verbose }
  673. disable: disable HPET and use PIT instead
  674. force: allow force enabled of undocumented chips (ICH4,
  675. VIA, nVidia)
  676. verbose: show contents of HPET registers during setup
  677. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  678. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  679. On x86-64 and powerpc, this option can be specified
  680. multiple times interleaved with hugepages= to reserve
  681. huge pages of different sizes. Valid pages sizes on
  682. x86-64 are 2M (when the CPU supports "pse") and 1G
  683. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  684. Note that 1GB pages can only be allocated at boot time
  685. using hugepages= and not freed afterwards.
  686. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
  687. terminal devices. Valid values: 0..8
  688. hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
  689. If specified, z/VM IUCV HVC accepts connections
  690. from listed z/VM user IDs only.
  691. i2c_bus= [HW] Override the default board specific I2C bus speed
  692. or register an additional I2C bus that is not
  693. registered from board initialization code.
  694. Format:
  695. <bus_id>,<clkrate>
  696. i8042.debug [HW] Toggle i8042 debug mode
  697. i8042.direct [HW] Put keyboard port into non-translated mode
  698. i8042.dumbkbd [HW] Pretend that controller can only read data from
  699. keyboard and cannot control its state
  700. (Don't attempt to blink the leds)
  701. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  702. i8042.nokbd [HW] Don't check/create keyboard port
  703. i8042.noloop [HW] Disable the AUX Loopback command while probing
  704. for the AUX port
  705. i8042.nomux [HW] Don't check presence of an active multiplexing
  706. controller
  707. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  708. controllers
  709. i8042.panicblink=
  710. [HW] Frequency with which keyboard LEDs should blink
  711. when kernel panics (default is 0.5 sec)
  712. i8042.reset [HW] Reset the controller during init and cleanup
  713. i8042.unlock [HW] Unlock (ignore) the keylock
  714. i810= [HW,DRM]
  715. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  716. indicates that the driver is running on unsupported
  717. hardware.
  718. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  719. does not match list of supported models.
  720. i8k.power_status
  721. [HW] Report power status in /proc/i8k
  722. (disabled by default)
  723. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  724. capability is set.
  725. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  726. See Documentation/mca.txt.
  727. icn= [HW,ISDN]
  728. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  729. ide-core.nodma= [HW] (E)IDE subsystem
  730. Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
  731. .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
  732. .cdrom .chs .ignore_cable are additional options
  733. See Documentation/ide/ide.txt.
  734. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  735. Claim all unknown PCI IDE storage controllers.
  736. idle= [X86]
  737. Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
  738. Poll forces a polling idle loop that can slightly
  739. improve the performance of waking up a idle CPU, but
  740. will use a lot of power and make the system run hot.
  741. Not recommended.
  742. idle=mwait: On systems which support MONITOR/MWAIT but
  743. the kernel chose to not use it because it doesn't save
  744. as much power as a normal idle loop, use the
  745. MONITOR/MWAIT idle loop anyways. Performance should be
  746. the same as idle=poll.
  747. idle=halt: Halt is forced to be used for CPU idle.
  748. In such case C2/C3 won't be used again.
  749. idle=nomwait: Disable mwait for CPU C-states
  750. ignore_loglevel [KNL]
  751. Ignore loglevel setting - this will print /all/
  752. kernel messages to the console. Useful for debugging.
  753. ihash_entries= [KNL]
  754. Set number of hash buckets for inode cache.
  755. ima_audit= [IMA]
  756. Format: { "0" | "1" }
  757. 0 -- integrity auditing messages. (Default)
  758. 1 -- enable informational integrity auditing messages.
  759. ima_hash= [IMA]
  760. Formt: { "sha1" | "md5" }
  761. default: "sha1"
  762. ima_tcb [IMA]
  763. Load a policy which meets the needs of the Trusted
  764. Computing Base. This means IMA will measure all
  765. programs exec'd, files mmap'd for exec, and all files
  766. opened for read by uid=0.
  767. in2000= [HW,SCSI]
  768. See header of drivers/scsi/in2000.c.
  769. init= [KNL]
  770. Format: <full_path>
  771. Run specified binary instead of /sbin/init as init
  772. process.
  773. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  774. for working out where the kernel is dying during
  775. startup.
  776. initrd= [BOOT] Specify the location of the initial ramdisk
  777. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  778. Format: <irq>
  779. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  780. on
  781. Enable intel iommu driver.
  782. off
  783. Disable intel iommu driver.
  784. igfx_off [Default Off]
  785. By default, gfx is mapped as normal device. If a gfx
  786. device has a dedicated DMAR unit, the DMAR unit is
  787. bypassed by not enabling DMAR with this option. In
  788. this case, gfx device will use physical address for
  789. DMA.
  790. forcedac [x86_64]
  791. With this option iommu will not optimize to look
  792. for io virtual address below 32 bit forcing dual
  793. address cycle on pci bus for cards supporting greater
  794. than 32 bit addressing. The default is to look
  795. for translation below 32 bit and if not available
  796. then look in the higher range.
  797. strict [Default Off]
  798. With this option on every unmap_single operation will
  799. result in a hardware IOTLB flush operation as opposed
  800. to batching them for performance.
  801. inttest= [IA64]
  802. iomem= Disable strict checking of access to MMIO memory
  803. strict regions from userspace.
  804. relaxed
  805. iommu= [x86]
  806. off
  807. force
  808. noforce
  809. biomerge
  810. panic
  811. nopanic
  812. merge
  813. nomerge
  814. forcesac
  815. soft
  816. io7= [HW] IO7 for Marvel based alpha systems
  817. See comment before marvel_specify_io7 in
  818. arch/alpha/kernel/core_marvel.c.
  819. io_delay= [X86] I/O delay method
  820. 0x80
  821. Standard port 0x80 based delay
  822. 0xed
  823. Alternate port 0xed based delay (needed on some systems)
  824. udelay
  825. Simple two microseconds delay
  826. none
  827. No delay
  828. ip= [IP_PNP]
  829. See Documentation/filesystems/nfsroot.txt.
  830. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  831. See comment before ip2_setup() in
  832. drivers/char/ip2/ip2base.c.
  833. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  834. See header of drivers/scsi/ips.c.
  835. irqfixup [HW]
  836. When an interrupt is not handled search all handlers
  837. for it. Intended to get systems with badly broken
  838. firmware running.
  839. irqpoll [HW]
  840. When an interrupt is not handled search all handlers
  841. for it. Also check all handlers each timer
  842. interrupt. Intended to get systems with badly broken
  843. firmware running.
  844. isapnp= [ISAPNP]
  845. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  846. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  847. Format:
  848. <cpu number>,...,<cpu number>
  849. or
  850. <cpu number>-<cpu number>
  851. (must be a positive range in ascending order)
  852. or a mixture
  853. <cpu number>,...,<cpu number>-<cpu number>
  854. This option can be used to specify one or more CPUs
  855. to isolate from the general SMP balancing and scheduling
  856. algorithms. You can move a process onto or off an
  857. "isolated" CPU via the CPU affinity syscalls or cpuset.
  858. <cpu number> begins at 0 and the maximum value is
  859. "number of CPUs in system - 1".
  860. This option is the preferred way to isolate CPUs. The
  861. alternative -- manually setting the CPU mask of all
  862. tasks in the system -- can cause problems and
  863. suboptimal load balancer performance.
  864. iucv= [HW,NET]
  865. js= [HW,JOY] Analog joystick
  866. See Documentation/input/joystick.txt.
  867. keepinitrd [HW,ARM]
  868. kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  869. specifies the amount of memory usable by the kernel
  870. for non-movable allocations. The requested amount is
  871. spread evenly throughout all nodes in the system. The
  872. remaining memory in each node is used for Movable
  873. pages. In the event, a node is too small to have both
  874. kernelcore and Movable pages, kernelcore pages will
  875. take priority and other nodes will have a larger number
  876. of kernelcore pages. The Movable zone is used for the
  877. allocation of pages that may be reclaimed or moved
  878. by the page migration subsystem. This means that
  879. HugeTLB pages may not be allocated from this zone.
  880. Note that allocations like PTEs-from-HighMem still
  881. use the HighMem zone if it exists, and the Normal
  882. zone if it does not.
  883. kgdboc= [HW] kgdb over consoles.
  884. Requires a tty driver that supports console polling.
  885. (only serial supported for now)
  886. Format: <serial_device>[,baud]
  887. kmac= [MIPS] korina ethernet MAC address.
  888. Configure the RouterBoard 532 series on-chip
  889. Ethernet adapter MAC address.
  890. kmemleak= [KNL] Boot-time kmemleak enable/disable
  891. Valid arguments: on, off
  892. Default: on
  893. kstack=N [X86] Print N words from the kernel stack
  894. in oops dumps.
  895. l2cr= [PPC]
  896. l3cr= [PPC]
  897. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  898. disabled it.
  899. lapic_timer_c2_ok [X86,APIC] trust the local apic timer
  900. in C2 power state.
  901. libata.dma= [LIBATA] DMA control
  902. libata.dma=0 Disable all PATA and SATA DMA
  903. libata.dma=1 PATA and SATA Disk DMA only
  904. libata.dma=2 ATAPI (CDROM) DMA only
  905. libata.dma=4 Compact Flash DMA only
  906. Combinations also work, so libata.dma=3 enables DMA
  907. for disks and CDROMs, but not CFs.
  908. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  909. when set.
  910. Format: <int>
  911. libata.force= [LIBATA] Force configurations. The format is comma
  912. separated list of "[ID:]VAL" where ID is
  913. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  914. matching port, link or device. Basically, it matches
  915. the ATA ID string printed on console by libata. If
  916. the whole ID part is omitted, the last PORT and DEVICE
  917. values are used. If ID hasn't been specified yet, the
  918. configuration applies to all ports, links and devices.
  919. If only DEVICE is omitted, the parameter applies to
  920. the port and all links and devices behind it. DEVICE
  921. number of 0 either selects the first device or the
  922. first fan-out link behind PMP device. It does not
  923. select the host link. DEVICE number of 15 selects the
  924. host link and device attached to it.
  925. The VAL specifies the configuration to force. As long
  926. as there's no ambiguity shortcut notation is allowed.
  927. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  928. The following configurations can be forced.
  929. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  930. Any ID with matching PORT is used.
  931. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  932. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  933. udma[/][16,25,33,44,66,100,133] notation is also
  934. allowed.
  935. * [no]ncq: Turn on or off NCQ.
  936. * nohrst, nosrst, norst: suppress hard, soft
  937. and both resets.
  938. If there are multiple matching configurations changing
  939. the same attribute, the last one is used.
  940. lmb=debug [KNL] Enable lmb debug messages.
  941. load_ramdisk= [RAM] List of ramdisks to load from floppy
  942. See Documentation/blockdev/ramdisk.txt.
  943. lockd.nlm_grace_period=P [NFS] Assign grace period.
  944. Format: <integer>
  945. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  946. Format: <integer>
  947. lockd.nlm_timeout=T [NFS] Assign timeout value.
  948. Format: <integer>
  949. lockd.nlm_udpport=M [NFS] Assign UDP port.
  950. Format: <integer>
  951. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  952. Format: <irq>
  953. loglevel= All Kernel Messages with a loglevel smaller than the
  954. console loglevel will be printed to the console. It can
  955. also be changed with klogd or other programs. The
  956. loglevels are defined as follows:
  957. 0 (KERN_EMERG) system is unusable
  958. 1 (KERN_ALERT) action must be taken immediately
  959. 2 (KERN_CRIT) critical conditions
  960. 3 (KERN_ERR) error conditions
  961. 4 (KERN_WARNING) warning conditions
  962. 5 (KERN_NOTICE) normal but significant condition
  963. 6 (KERN_INFO) informational
  964. 7 (KERN_DEBUG) debug-level messages
  965. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  966. Format: { n | nk | nM }
  967. n must be a power of two. The default size
  968. is set in the kernel config file.
  969. logo.nologo [FB] Disables display of the built-in Linux logo.
  970. This may be used to provide more screen space for
  971. kernel log messages and is useful when debugging
  972. kernel boot problems.
  973. lp=0 [LP] Specify parallel ports to use, e.g,
  974. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  975. lp=reset first parallel port). 'lp=0' disables the
  976. lp=auto printer driver. 'lp=reset' (which can be
  977. specified in addition to the ports) causes
  978. attached printers to be reset. Using
  979. lp=port1,port2,... specifies the parallel ports
  980. to associate lp devices with, starting with
  981. lp0. A port specification may be 'none' to skip
  982. that lp device, or a parport name such as
  983. 'parport0'. Specifying 'lp=auto' instead of a
  984. port specification list means that device IDs
  985. from each port should be examined, to see if
  986. an IEEE 1284-compliant printer is attached; if
  987. so, the driver will manage that printer.
  988. See also header of drivers/char/lp.c.
  989. lpj=n [KNL]
  990. Sets loops_per_jiffy to given constant, thus avoiding
  991. time-consuming boot-time autodetection (up to 250 ms per
  992. CPU). 0 enables autodetection (default). To determine
  993. the correct value for your kernel, boot with normal
  994. autodetection and see what value is printed. Note that
  995. on SMP systems the preset will be applied to all CPUs,
  996. which is likely to cause problems if your CPUs need
  997. significantly divergent settings. An incorrect value
  998. will cause delays in the kernel to be wrong, leading to
  999. unpredictable I/O errors and other breakage. Although
  1000. unlikely, in the extreme case this might damage your
  1001. hardware.
  1002. ltpc= [NET]
  1003. Format: <io>,<irq>,<dma>
  1004. mac5380= [HW,SCSI] Format:
  1005. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  1006. machvec= [IA64] Force the use of a particular machine-vector
  1007. (machvec) in a generic kernel.
  1008. Example: machvec=hpzx1_swiotlb
  1009. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
  1010. than or equal to this physical address is ignored.
  1011. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  1012. should make use of. maxcpus=n : n >= 0 limits the
  1013. kernel to using 'n' processors. n=0 is a special case,
  1014. it is equivalent to "nosmp", which also disables
  1015. the IO APIC.
  1016. max_loop= [LOOP] Maximum number of loopback devices that can
  1017. be mounted
  1018. Format: <1-256>
  1019. max_luns= [SCSI] Maximum number of LUNs to probe.
  1020. Should be between 1 and 2^32-1.
  1021. max_report_luns=
  1022. [SCSI] Maximum number of LUNs received.
  1023. Should be between 1 and 16384.
  1024. mcatest= [IA-64]
  1025. mce [X86-32] Machine Check Exception
  1026. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  1027. md= [HW] RAID subsystems devices and level
  1028. See Documentation/md.txt.
  1029. mdacon= [MDA]
  1030. Format: <first>,<last>
  1031. Specifies range of consoles to be captured by the MDA.
  1032. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  1033. Amount of memory to be used when the kernel is not able
  1034. to see the whole system memory or for test.
  1035. [X86-32] Use together with memmap= to avoid physical
  1036. address space collisions. Without memmap= PCI devices
  1037. could be placed at addresses belonging to unused RAM.
  1038. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1039. memory.
  1040. memchunk=nn[KMG]
  1041. [KNL,SH] Allow user to override the default size for
  1042. per-device physically contiguous DMA buffers.
  1043. memmap=exactmap [KNL,X86] Enable setting of an exact
  1044. E820 memory map, as specified by the user.
  1045. Such memmap=exactmap lines can be constructed based on
  1046. BIOS output or other requirements. See the memmap=nn@ss
  1047. option description.
  1048. memmap=nn[KMG]@ss[KMG]
  1049. [KNL] Force usage of a specific region of memory
  1050. Region of memory to be used, from ss to ss+nn.
  1051. memmap=nn[KMG]#ss[KMG]
  1052. [KNL,ACPI] Mark specific memory as ACPI data.
  1053. Region of memory to be used, from ss to ss+nn.
  1054. memmap=nn[KMG]$ss[KMG]
  1055. [KNL,ACPI] Mark specific memory as reserved.
  1056. Region of memory to be used, from ss to ss+nn.
  1057. Example: Exclude memory from 0x18690000-0x1869ffff
  1058. memmap=64K$0x18690000
  1059. or
  1060. memmap=0x10000$0x18690000
  1061. memory_corruption_check=0/1 [X86]
  1062. Some BIOSes seem to corrupt the first 64k of
  1063. memory when doing things like suspend/resume.
  1064. Setting this option will scan the memory
  1065. looking for corruption. Enabling this will
  1066. both detect corruption and prevent the kernel
  1067. from using the memory being corrupted.
  1068. However, its intended as a diagnostic tool; if
  1069. repeatable BIOS-originated corruption always
  1070. affects the same memory, you can use memmap=
  1071. to prevent the kernel from using that memory.
  1072. memory_corruption_check_size=size [X86]
  1073. By default it checks for corruption in the low
  1074. 64k, making this memory unavailable for normal
  1075. use. Use this parameter to scan for
  1076. corruption in more or less memory.
  1077. memory_corruption_check_period=seconds [X86]
  1078. By default it checks for corruption every 60
  1079. seconds. Use this parameter to check at some
  1080. other rate. 0 disables periodic checking.
  1081. memtest= [KNL,X86] Enable memtest
  1082. Format: <integer>
  1083. default : 0 <disable>
  1084. Specifies the number of memtest passes to be
  1085. performed. Each pass selects another test
  1086. pattern from a given set of patterns. Memtest
  1087. fills the memory with this pattern, validates
  1088. memory contents and reserves bad memory
  1089. regions that are detected.
  1090. meye.*= [HW] Set MotionEye Camera parameters
  1091. See Documentation/video4linux/meye.txt.
  1092. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1093. Multi-Function General Purpose Timers on AMD Geode
  1094. platforms.
  1095. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1096. the BIOS has incorrectly applied a workaround. TinyBIOS
  1097. version 0.98 is known to be affected, 0.99 fixes the
  1098. problem by letting the user disable the workaround.
  1099. mga= [HW,DRM]
  1100. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1101. physical address is ignored.
  1102. mini2440= [ARM,HW,KNL]
  1103. Format:[0..2][b][c][t]
  1104. Default: "0tb"
  1105. MINI2440 configuration specification:
  1106. 0 - The attached screen is the 3.5" TFT
  1107. 1 - The attached screen is the 7" TFT
  1108. 2 - The VGA Shield is attached (1024x768)
  1109. Leaving out the screen size parameter will not load
  1110. the TFT driver, and the framebuffer will be left
  1111. unconfigured.
  1112. b - Enable backlight. The TFT backlight pin will be
  1113. linked to the kernel VESA blanking code and a GPIO
  1114. LED. This parameter is not necessary when using the
  1115. VGA shield.
  1116. c - Enable the s3c camera interface.
  1117. t - Reserved for enabling touchscreen support. The
  1118. touchscreen support is not enabled in the mainstream
  1119. kernel as of 2.6.30, a preliminary port can be found
  1120. in the "bleeding edge" mini2440 support kernel at
  1121. http://repo.or.cz/w/linux-2.6/mini2440.git
  1122. mminit_loglevel=
  1123. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1124. parameter allows control of the logging verbosity for
  1125. the additional memory initialisation checks. A value
  1126. of 0 disables mminit logging and a level of 4 will
  1127. log everything. Information is printed at KERN_DEBUG
  1128. so loglevel=8 may also need to be specified.
  1129. mousedev.tap_time=
  1130. [MOUSE] Maximum time between finger touching and
  1131. leaving touchpad surface for touch to be considered
  1132. a tap and be reported as a left button click (for
  1133. touchpads working in absolute mode only).
  1134. Format: <msecs>
  1135. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1136. reporting absolute coordinates, such as tablets
  1137. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1138. reporting absolute coordinates, such as tablets
  1139. movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  1140. is similar to kernelcore except it specifies the
  1141. amount of memory used for migratable allocations.
  1142. If both kernelcore and movablecore is specified,
  1143. then kernelcore will be at *least* the specified
  1144. value but may be more. If movablecore on its own
  1145. is specified, the administrator must be careful
  1146. that the amount of memory usable for all allocations
  1147. is not too small.
  1148. mpu401= [HW,OSS]
  1149. Format: <io>,<irq>
  1150. MTD_Partition= [MTD]
  1151. Format: <name>,<region-number>,<size>,<offset>
  1152. MTD_Region= [MTD] Format:
  1153. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1154. mtdparts= [MTD]
  1155. See drivers/mtd/cmdlinepart.c.
  1156. mtdset= [ARM]
  1157. ARM/S3C2412 JIVE boot control
  1158. See arch/arm/mach-s3c2412/mach-jive.c
  1159. mtouchusb.raw_coordinates=
  1160. [HW] Make the MicroTouch USB driver use raw coordinates
  1161. ('y', default) or cooked coordinates ('n')
  1162. mtrr_chunk_size=nn[KMG] [X86]
  1163. used for mtrr cleanup. It is largest continuous chunk
  1164. that could hold holes aka. UC entries.
  1165. mtrr_gran_size=nn[KMG] [X86]
  1166. Used for mtrr cleanup. It is granularity of mtrr block.
  1167. Default is 1.
  1168. Large value could prevent small alignment from
  1169. using up MTRRs.
  1170. mtrr_spare_reg_nr=n [X86]
  1171. Format: <integer>
  1172. Range: 0,7 : spare reg number
  1173. Default : 1
  1174. Used for mtrr cleanup. It is spare mtrr entries number.
  1175. Set to 2 or more if your graphical card needs more.
  1176. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1177. NCR_D700= [HW,SCSI]
  1178. See header of drivers/scsi/NCR_D700.c.
  1179. ncr5380= [HW,SCSI]
  1180. ncr53c400= [HW,SCSI]
  1181. ncr53c400a= [HW,SCSI]
  1182. ncr53c406a= [HW,SCSI]
  1183. ncr53c8xx= [HW,SCSI]
  1184. netdev= [NET] Network devices parameters
  1185. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1186. Note that mem_start is often overloaded to mean
  1187. something different and driver-specific.
  1188. This usage is only documented in each driver source
  1189. file if at all.
  1190. nf_conntrack.acct=
  1191. [NETFILTER] Enable connection tracking flow accounting
  1192. 0 to disable accounting
  1193. 1 to enable accounting
  1194. Default value depends on CONFIG_NF_CT_ACCT that is
  1195. going to be removed in 2.6.29.
  1196. nfsaddrs= [NFS]
  1197. See Documentation/filesystems/nfsroot.txt.
  1198. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1199. See Documentation/filesystems/nfsroot.txt.
  1200. nfs.callback_tcpport=
  1201. [NFS] set the TCP port on which the NFSv4 callback
  1202. channel should listen.
  1203. nfs.idmap_cache_timeout=
  1204. [NFS] set the maximum lifetime for idmapper cache
  1205. entries.
  1206. nfs.enable_ino64=
  1207. [NFS] enable 64-bit inode numbers.
  1208. If zero, the NFS client will fake up a 32-bit inode
  1209. number for the readdir() and stat() syscalls instead
  1210. of returning the full 64-bit number.
  1211. The default is to return 64-bit inode numbers.
  1212. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1213. when a NMI is triggered.
  1214. Format: [state][,regs][,debounce][,die]
  1215. nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
  1216. Format: [panic,][num]
  1217. Valid num: 0,1,2
  1218. 0 - turn nmi_watchdog off
  1219. 1 - use the IO-APIC timer for the NMI watchdog
  1220. 2 - use the local APIC for the NMI watchdog using
  1221. a performance counter. Note: This will use one
  1222. performance counter and the local APIC's performance
  1223. vector.
  1224. When panic is specified, panic when an NMI watchdog
  1225. timeout occurs.
  1226. This is useful when you use a panic=... timeout and
  1227. need the box quickly up again.
  1228. Instead of 1 and 2 it is possible to use the following
  1229. symbolic names: lapic and ioapic
  1230. Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
  1231. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1232. emulation library even if a 387 maths coprocessor
  1233. is present.
  1234. no_console_suspend
  1235. [HW] Never suspend the console
  1236. Disable suspending of consoles during suspend and
  1237. hibernate operations. Once disabled, debugging
  1238. messages can reach various consoles while the rest
  1239. of the system is being put to sleep (ie, while
  1240. debugging driver suspend/resume hooks). This may
  1241. not work reliably with all consoles, but is known
  1242. to work with serial and VGA consoles.
  1243. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1244. caches in the slab allocator. Saves per-node memory,
  1245. but will impact performance.
  1246. noalign [KNL,ARM]
  1247. noapic [SMP,APIC] Tells the kernel to not make use of any
  1248. IOAPICs that may be present in the system.
  1249. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1250. on "Classic" PPC cores.
  1251. nocache [ARM]
  1252. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1253. nodelayacct [KNL] Disable per-task delay accounting
  1254. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1255. nodsp [SH] Disable hardware DSP at boot time.
  1256. noefi [X86] Disable EFI runtime services support.
  1257. noexec [IA-64]
  1258. noexec [X86]
  1259. On X86-32 available only on PAE configured kernels.
  1260. noexec=on: enable non-executable mappings (default)
  1261. noexec=off: disable non-executable mappings
  1262. noexec32 [X86-64]
  1263. This affects only 32-bit executables.
  1264. noexec32=on: enable non-executable mappings (default)
  1265. read doesn't imply executable mappings
  1266. noexec32=off: disable non-executable mappings
  1267. read implies executable mappings
  1268. nofpu [SH] Disable hardware FPU at boot time.
  1269. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1270. register save and restore. The kernel will only save
  1271. legacy floating-point registers on task switch.
  1272. noxsave [BUGS=X86] Disables x86 extended register state save
  1273. and restore using xsave. The kernel will fallback to
  1274. enabling legacy floating-point and sse state.
  1275. nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
  1276. wfi(ARM) instruction doesn't work correctly and not to
  1277. use it. This is also useful when using JTAG debugger.
  1278. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1279. instruction doesn't work correctly and not to
  1280. use it.
  1281. no_file_caps Tells the kernel not to honor file capabilities. The
  1282. only way then for a file to be executed with privilege
  1283. is to be setuid root or executed by root.
  1284. nohalt [IA-64] Tells the kernel not to use the power saving
  1285. function PAL_HALT_LIGHT when idle. This increases
  1286. power-consumption. On the positive side, it reduces
  1287. interrupt wake-up latency, which may improve performance
  1288. in certain environments such as networked servers or
  1289. real-time systems.
  1290. nohz= [KNL] Boottime enable/disable dynamic ticks
  1291. Valid arguments: on, off
  1292. Default: on
  1293. noiotrap [SH] Disables trapped I/O port accesses.
  1294. noirqdebug [X86-32] Disables the code which attempts to detect and
  1295. disable unhandled interrupt sources.
  1296. no_timer_check [X86,APIC] Disables the code which tests for
  1297. broken timer IRQ sources.
  1298. noisapnp [ISAPNP] Disables ISA PnP code.
  1299. noinitrd [RAM] Tells the kernel not to load any configured
  1300. initial RAM disk.
  1301. nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
  1302. remapping.
  1303. nointroute [IA-64]
  1304. nojitter [IA64] Disables jitter checking for ITC timers.
  1305. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1306. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1307. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1308. lowmem mapping on PPC40x.
  1309. nomca [IA-64] Disable machine check abort handling
  1310. nomce [X86-32] Machine Check Exception
  1311. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1312. Timer usage (for AMD Geode machines).
  1313. norandmaps Don't use address space randomization. Equivalent to
  1314. echo 0 > /proc/sys/kernel/randomize_va_space
  1315. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1316. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1317. with UP alternatives
  1318. noresidual [PPC] Don't use residual data on PReP machines.
  1319. noresume [SWSUSP] Disables resume and restores original swap
  1320. space.
  1321. no-scroll [VGA] Disables scrollback.
  1322. This is required for the Braillex ib80-piezo Braille
  1323. reader made by F.H. Papenmeier (Germany).
  1324. nosbagart [IA-64]
  1325. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1326. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1327. and disable the IO APIC. legacy for "maxcpus=0".
  1328. nosoftlockup [KNL] Disable the soft-lockup detector.
  1329. noswapaccount [KNL] Disable accounting of swap in memory resource
  1330. controller. (See Documentation/cgroups/memory.txt)
  1331. nosync [HW,M68K] Disables sync negotiation for all devices.
  1332. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1333. nousb [USB] Disable the USB subsystem
  1334. nowb [ARM]
  1335. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1336. nptcg= [IA64] Override max number of concurrent global TLB
  1337. purges which is reported from either PAL_VM_SUMMARY or
  1338. SAL PALO.
  1339. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1340. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1341. one of ['zone', 'node', 'default'] can be specified
  1342. This can be set from sysctl after boot.
  1343. See Documentation/sysctl/vm.txt for details.
  1344. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
  1345. See Documentation/debugging-via-ohci1394.txt for more
  1346. info.
  1347. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1348. Rather than timing out after 20 ms if an EC
  1349. command is not properly ACKed, override the length
  1350. of the timeout. We have interrupts disabled while
  1351. waiting for the ACK, so if this is set too high
  1352. interrupts *may* be lost!
  1353. opl3= [HW,OSS]
  1354. Format: <io>
  1355. oprofile.timer= [HW]
  1356. Use timer interrupt instead of performance counters
  1357. oprofile.cpu_type= Force an oprofile cpu type
  1358. This might be useful if you have an older oprofile
  1359. userland or if you want common events.
  1360. Format: { archperfmon }
  1361. archperfmon: [X86] Force use of architectural
  1362. perfmon on Intel CPUs instead of the
  1363. CPU specific event set.
  1364. osst= [HW,SCSI] SCSI Tape Driver
  1365. Format: <buffer_size>,<write_threshold>
  1366. See also Documentation/scsi/st.txt.
  1367. panic= [KNL] Kernel behaviour on panic
  1368. Format: <timeout>
  1369. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1370. connected to, default is 0.
  1371. Format: <parport#>
  1372. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1373. 0 for XT, 1 for AT (default is AT).
  1374. Format: <mode>
  1375. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1376. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1377. Use 'auto' to force the driver to use any
  1378. IRQ/DMA settings detected (the default is to
  1379. ignore detected IRQ/DMA settings because of
  1380. possible conflicts). You can specify the base
  1381. address, IRQ, and DMA settings; IRQ and DMA
  1382. should be numbers, or 'auto' (for using detected
  1383. settings on that particular port), or 'nofifo'
  1384. (to avoid using a FIFO even if it is detected).
  1385. Parallel ports are assigned in the order they
  1386. are specified on the command line, starting
  1387. with parport0.
  1388. parport_init_mode= [HW,PPT]
  1389. Configure VIA parallel port to operate in
  1390. a specific mode. This is necessary on Pegasos
  1391. computer where firmware has no options for setting
  1392. up parallel port mode and sets it to spp.
  1393. Currently this function knows 686a and 8231 chips.
  1394. Format: [spp|ps2|epp|ecp|ecpepp]
  1395. pas2= [HW,OSS] Format:
  1396. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1397. pas16= [HW,SCSI]
  1398. See header of drivers/scsi/pas16.c.
  1399. pause_on_oops=
  1400. Halt all CPUs after the first oops has been printed for
  1401. the specified number of seconds. This is to be used if
  1402. your oopses keep scrolling off the screen.
  1403. pcbit= [HW,ISDN]
  1404. pcd. [PARIDE]
  1405. See header of drivers/block/paride/pcd.c.
  1406. See also Documentation/blockdev/paride.txt.
  1407. pci=option[,option...] [PCI] various PCI subsystem options:
  1408. earlydump [X86] dump PCI config space before the kernel
  1409. changes anything
  1410. off [X86] don't probe for the PCI bus
  1411. bios [X86-32] force use of PCI BIOS, don't access
  1412. the hardware directly. Use this if your machine
  1413. has a non-standard PCI host bridge.
  1414. nobios [X86-32] disallow use of PCI BIOS, only direct
  1415. hardware access methods are allowed. Use this
  1416. if you experience crashes upon bootup and you
  1417. suspect they are caused by the BIOS.
  1418. conf1 [X86] Force use of PCI Configuration
  1419. Mechanism 1.
  1420. conf2 [X86] Force use of PCI Configuration
  1421. Mechanism 2.
  1422. noaer [PCIE] If the PCIEAER kernel config parameter is
  1423. enabled, this kernel boot option can be used to
  1424. disable the use of PCIE advanced error reporting.
  1425. nodomains [PCI] Disable support for multiple PCI
  1426. root domains (aka PCI segments, in ACPI-speak).
  1427. nommconf [X86] Disable use of MMCONFIG for PCI
  1428. Configuration
  1429. check_enable_amd_mmconf [X86] check for and enable
  1430. properly configured MMIO access to PCI
  1431. config space on AMD family 10h CPU
  1432. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1433. enabled, this kernel boot option can be used to
  1434. disable the use of MSI interrupts system-wide.
  1435. noioapicquirk [APIC] Disable all boot interrupt quirks.
  1436. Safety option to keep boot IRQs enabled. This
  1437. should never be necessary.
  1438. ioapicreroute [APIC] Enable rerouting of boot IRQs to the
  1439. primary IO-APIC for bridges that cannot disable
  1440. boot IRQs. This fixes a source of spurious IRQs
  1441. when the system masks IRQs.
  1442. noioapicreroute [APIC] Disable workaround that uses the
  1443. boot IRQ equivalent of an IRQ that connects to
  1444. a chipset where boot IRQs cannot be disabled.
  1445. The opposite of ioapicreroute.
  1446. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1447. routing table. These calls are known to be buggy
  1448. on several machines and they hang the machine
  1449. when used, but on other computers it's the only
  1450. way to get the interrupt routing table. Try
  1451. this option if the kernel is unable to allocate
  1452. IRQs or discover secondary PCI buses on your
  1453. motherboard.
  1454. rom [X86] Assign address space to expansion ROMs.
  1455. Use with caution as certain devices share
  1456. address decoders between ROMs and other
  1457. resources.
  1458. norom [X86] Do not assign address space to
  1459. expansion ROMs that do not already have
  1460. BIOS assigned address ranges.
  1461. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1462. assigned automatically to PCI devices. You can
  1463. make the kernel exclude IRQs of your ISA cards
  1464. this way.
  1465. pirqaddr=0xAAAAA [X86] Specify the physical address
  1466. of the PIRQ table (normally generated
  1467. by the BIOS) if it is outside the
  1468. F0000h-100000h range.
  1469. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1470. useful if the kernel is unable to find your
  1471. secondary buses and you want to tell it
  1472. explicitly which ones they are.
  1473. assign-busses [X86] Always assign all PCI bus
  1474. numbers ourselves, overriding
  1475. whatever the firmware may have done.
  1476. usepirqmask [X86] Honor the possible IRQ mask stored
  1477. in the BIOS $PIR table. This is needed on
  1478. some systems with broken BIOSes, notably
  1479. some HP Pavilion N5400 and Omnibook XE3
  1480. notebooks. This will have no effect if ACPI
  1481. IRQ routing is enabled.
  1482. noacpi [X86] Do not use ACPI for IRQ routing
  1483. or for PCI scanning.
  1484. nocrs [X86] Don't use _CRS for PCI resource
  1485. allocation.
  1486. routeirq Do IRQ routing for all PCI devices.
  1487. This is normally done in pci_enable_device(),
  1488. so this option is a temporary workaround
  1489. for broken drivers that don't call it.
  1490. skip_isa_align [X86] do not align io start addr, so can
  1491. handle more pci cards
  1492. firmware [ARM] Do not re-enumerate the bus but instead
  1493. just use the configuration from the
  1494. bootloader. This is currently used on
  1495. IXP2000 systems where the bus has to be
  1496. configured a certain way for adjunct CPUs.
  1497. noearly [X86] Don't do any early type 1 scanning.
  1498. This might help on some broken boards which
  1499. machine check when some devices' config space
  1500. is read. But various workarounds are disabled
  1501. and some IOMMU drivers will not work.
  1502. bfsort Sort PCI devices into breadth-first order.
  1503. This sorting is done to get a device
  1504. order compatible with older (<= 2.4) kernels.
  1505. nobfsort Don't sort PCI devices into breadth-first order.
  1506. cbiosize=nn[KMG] The fixed amount of bus space which is
  1507. reserved for the CardBus bridge's IO window.
  1508. The default value is 256 bytes.
  1509. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1510. reserved for the CardBus bridge's memory
  1511. window. The default value is 64 megabytes.
  1512. resource_alignment=
  1513. Format:
  1514. [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
  1515. Specifies alignment and device to reassign
  1516. aligned memory resources.
  1517. If <order of align> is not specified,
  1518. PAGE_SIZE is used as alignment.
  1519. PCI-PCI bridge can be specified, if resource
  1520. windows need to be expanded.
  1521. ecrc= Enable/disable PCIe ECRC (transaction layer
  1522. end-to-end CRC checking).
  1523. bios: Use BIOS/firmware settings. This is the
  1524. the default.
  1525. off: Turn ECRC off
  1526. on: Turn ECRC on.
  1527. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1528. Management.
  1529. off Disable ASPM.
  1530. force Enable ASPM even on devices that claim not to support it.
  1531. WARNING: Forcing ASPM on may cause system lockups.
  1532. pcmv= [HW,PCMCIA] BadgePAD 4
  1533. pd. [PARIDE]
  1534. See Documentation/blockdev/paride.txt.
  1535. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1536. boot time.
  1537. Format: { 0 | 1 }
  1538. See arch/parisc/kernel/pdc_chassis.c
  1539. pf. [PARIDE]
  1540. See Documentation/blockdev/paride.txt.
  1541. pg. [PARIDE]
  1542. See Documentation/blockdev/paride.txt.
  1543. pirq= [SMP,APIC] Manual mp-table setup
  1544. See Documentation/x86/i386/IO-APIC.txt.
  1545. plip= [PPT,NET] Parallel port network link
  1546. Format: { parport<nr> | timid | 0 }
  1547. See also Documentation/parport.txt.
  1548. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1549. Override pmtimer IOPort with a hex value.
  1550. e.g. pmtmr=0x508
  1551. pnp.debug [PNP]
  1552. Enable PNP debug messages. This depends on the
  1553. CONFIG_PNP_DEBUG_MESSAGES option.
  1554. pnpacpi= [ACPI]
  1555. { off }
  1556. pnpbios= [ISAPNP]
  1557. { on | off | curr | res | no-curr | no-res }
  1558. pnp_reserve_irq=
  1559. [ISAPNP] Exclude IRQs for the autoconfiguration
  1560. pnp_reserve_dma=
  1561. [ISAPNP] Exclude DMAs for the autoconfiguration
  1562. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1563. Ranges are in pairs (I/O port base and size).
  1564. pnp_reserve_mem=
  1565. [ISAPNP] Exclude memory regions for the
  1566. autoconfiguration.
  1567. Ranges are in pairs (memory base and size).
  1568. ports= [IP_VS_FTP] IPVS ftp helper module
  1569. Default is 21.
  1570. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  1571. may be specified.
  1572. Format: <port>,<port>....
  1573. print-fatal-signals=
  1574. [KNL] debug: print fatal signals
  1575. print-fatal-signals=1: print segfault info to
  1576. the kernel console.
  1577. default: off.
  1578. printk.time= Show timing data prefixed to each printk message line
  1579. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1580. processor.max_cstate= [HW,ACPI]
  1581. Limit processor to maximum C-state
  1582. max_cstate=9 overrides any DMI blacklist limit.
  1583. processor.nocst [HW,ACPI]
  1584. Ignore the _CST method to determine C-states,
  1585. instead using the legacy FADT method
  1586. profile= [KNL] Enable kernel profiling via /proc/profile
  1587. Format: [schedule,]<number>
  1588. Param: "schedule" - profile schedule points.
  1589. Param: <number> - step/bucket size as a power of 2 for
  1590. statistical time based profiling.
  1591. Param: "sleep" - profile D-state sleeping (millisecs).
  1592. Requires CONFIG_SCHEDSTATS
  1593. Param: "kvm" - profile VM exits.
  1594. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1595. before loading.
  1596. See Documentation/blockdev/ramdisk.txt.
  1597. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1598. probe for; one of (bare|imps|exps|lifebook|any).
  1599. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1600. per second.
  1601. psmouse.resetafter= [HW,MOUSE]
  1602. Try to reset the device after so many bad packets
  1603. (0 = never).
  1604. psmouse.resolution=
  1605. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1606. psmouse.smartscroll=
  1607. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1608. 0 = disabled, 1 = enabled (default).
  1609. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1610. Format:
  1611. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1612. pt. [PARIDE]
  1613. See Documentation/blockdev/paride.txt.
  1614. pty.legacy_count=
  1615. [KNL] Number of legacy pty's. Overwrites compiled-in
  1616. default number.
  1617. quiet [KNL] Disable most log messages
  1618. r128= [HW,DRM]
  1619. raid= [HW,RAID]
  1620. See Documentation/md.txt.
  1621. ramdisk_blocksize= [RAM]
  1622. See Documentation/blockdev/ramdisk.txt.
  1623. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1624. See Documentation/blockdev/ramdisk.txt.
  1625. rcupdate.blimit= [KNL,BOOT]
  1626. Set maximum number of finished RCU callbacks to process
  1627. in one batch.
  1628. rcupdate.qhimark= [KNL,BOOT]
  1629. Set threshold of queued
  1630. RCU callbacks over which batch limiting is disabled.
  1631. rcupdate.qlowmark= [KNL,BOOT]
  1632. Set threshold of queued RCU callbacks below which
  1633. batch limiting is re-enabled.
  1634. rdinit= [KNL]
  1635. Format: <full_path>
  1636. Run specified binary instead of /init from the ramdisk,
  1637. used for early userspace startup. See initrd.
  1638. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1639. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1640. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1641. relax_domain_level=
  1642. [KNL, SMP] Set scheduler's default relax_domain_level.
  1643. See Documentation/cgroups/cpusets.txt.
  1644. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1645. reservetop= [X86-32]
  1646. Format: nn[KMG]
  1647. Reserves a hole at the top of the kernel virtual
  1648. address space.
  1649. reset_devices [KNL] Force drivers to reset the underlying device
  1650. during initialization.
  1651. resume= [SWSUSP]
  1652. Specify the partition device for software suspend
  1653. resume_offset= [SWSUSP]
  1654. Specify the offset from the beginning of the partition
  1655. given by "resume=" at which the swap header is located,
  1656. in <PAGE_SIZE> units (needed only for swap files).
  1657. See Documentation/power/swsusp-and-swap-files.txt
  1658. retain_initrd [RAM] Keep initrd memory after extraction
  1659. rhash_entries= [KNL,NET]
  1660. Set number of hash buckets for route cache
  1661. riscom8= [HW,SERIAL]
  1662. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1663. ro [KNL] Mount root device read-only on boot
  1664. root= [KNL] Root filesystem
  1665. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1666. mount the root filesystem
  1667. rootflags= [KNL] Set root filesystem mount option string
  1668. rootfstype= [KNL] Set root filesystem type
  1669. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1670. Useful for devices that are detected asynchronously
  1671. (e.g. USB and MMC devices).
  1672. root_plug.vendor_id=
  1673. [ROOTPLUG] Override the default vendor ID
  1674. root_plug.product_id=
  1675. [ROOTPLUG] Override the default product ID
  1676. root_plug.debug=
  1677. [ROOTPLUG] Enable debugging output
  1678. rw [KNL] Mount root device read-write on boot
  1679. S [KNL] Run init in single mode
  1680. sa1100ir [NET]
  1681. See drivers/net/irda/sa1100_ir.c.
  1682. sbni= [NET] Granch SBNI12 leased line adapter
  1683. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1684. Format: <io>[,<timeout>[,<isapnp>]]
  1685. scsi_debug_*= [SCSI]
  1686. See drivers/scsi/scsi_debug.c.
  1687. scsi_default_dev_flags=
  1688. [SCSI] SCSI default device flags
  1689. Format: <integer>
  1690. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1691. Format: <vendor>:<model>:<flags>
  1692. (flags are integer value)
  1693. scsi_logging_level= [SCSI] a bit mask of logging levels
  1694. See drivers/scsi/scsi_logging.h for bits. Also
  1695. settable via sysctl at dev.scsi.logging_level
  1696. (/proc/sys/dev/scsi/logging_level).
  1697. There is also a nice 'scsi_logging_level' script in the
  1698. S390-tools package, available for download at
  1699. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1700. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1701. discovered. async scans them in kernel threads,
  1702. allowing boot to proceed. none ignores them, expecting
  1703. user space to do the scan.
  1704. security= [SECURITY] Choose a security module to enable at boot.
  1705. If this boot parameter is not specified, only the first
  1706. security module asking for security registration will be
  1707. loaded. An invalid security module name will be treated
  1708. as if no module has been chosen.
  1709. selinux= [SELINUX] Disable or enable SELinux at boot time.
  1710. Format: { "0" | "1" }
  1711. See security/selinux/Kconfig help text.
  1712. 0 -- disable.
  1713. 1 -- enable.
  1714. Default value is set via kernel config option.
  1715. If enabled at boot time, /selinux/disable can be used
  1716. later to disable prior to initial policy load.
  1717. serialnumber [BUGS=X86-32]
  1718. shapers= [NET]
  1719. Maximal number of shapers.
  1720. show_msr= [x86] show boot-time MSR settings
  1721. Format: { <integer> }
  1722. Show boot-time (BIOS-initialized) MSR settings.
  1723. The parameter means the number of CPUs to show,
  1724. for example 1 means boot CPU only.
  1725. sim710= [SCSI,HW]
  1726. See header of drivers/scsi/sim710.c.
  1727. simeth= [IA-64]
  1728. simscsi=
  1729. slram= [HW,MTD]
  1730. slub_debug[=options[,slabs]] [MM, SLUB]
  1731. Enabling slub_debug allows one to determine the
  1732. culprit if slab objects become corrupted. Enabling
  1733. slub_debug can create guard zones around objects and
  1734. may poison objects when not in use. Also tracks the
  1735. last alloc / free. For more information see
  1736. Documentation/vm/slub.txt.
  1737. slub_max_order= [MM, SLUB]
  1738. Determines the maximum allowed order for slabs.
  1739. A high setting may cause OOMs due to memory
  1740. fragmentation. For more information see
  1741. Documentation/vm/slub.txt.
  1742. slub_min_objects= [MM, SLUB]
  1743. The minimum number of objects per slab. SLUB will
  1744. increase the slab order up to slub_max_order to
  1745. generate a sufficiently large slab able to contain
  1746. the number of objects indicated. The higher the number
  1747. of objects the smaller the overhead of tracking slabs
  1748. and the less frequently locks need to be acquired.
  1749. For more information see Documentation/vm/slub.txt.
  1750. slub_min_order= [MM, SLUB]
  1751. Determines the mininum page order for slabs. Must be
  1752. lower than slub_max_order.
  1753. For more information see Documentation/vm/slub.txt.
  1754. slub_nomerge [MM, SLUB]
  1755. Disable merging of slabs with similar size. May be
  1756. necessary if there is some reason to distinguish
  1757. allocs to different slabs. Debug options disable
  1758. merging on their own.
  1759. For more information see Documentation/vm/slub.txt.
  1760. smart2= [HW]
  1761. Format: <io1>[,<io2>[,...,<io8>]]
  1762. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1763. attempt to substitute SMP alternatives once at boot.
  1764. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1765. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1766. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1767. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1768. smsc-ircc2.ircc_irq= [HW] IRQ line
  1769. smsc-ircc2.ircc_dma= [HW] DMA channel
  1770. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1771. 0: Toshiba Satellite 1800 (GP data pin select)
  1772. 1: Fast pin select (default)
  1773. 2: ATC IRMode
  1774. snd-ad1816a= [HW,ALSA]
  1775. snd-ad1848= [HW,ALSA]
  1776. snd-ali5451= [HW,ALSA]
  1777. snd-als100= [HW,ALSA]
  1778. snd-als4000= [HW,ALSA]
  1779. snd-azt2320= [HW,ALSA]
  1780. snd-cmi8330= [HW,ALSA]
  1781. snd-cmipci= [HW,ALSA]
  1782. snd-cs4231= [HW,ALSA]
  1783. snd-cs4232= [HW,ALSA]
  1784. snd-cs4236= [HW,ALSA]
  1785. snd-cs4281= [HW,ALSA]
  1786. snd-cs46xx= [HW,ALSA]
  1787. snd-dt019x= [HW,ALSA]
  1788. snd-dummy= [HW,ALSA]
  1789. snd-emu10k1= [HW,ALSA]
  1790. snd-ens1370= [HW,ALSA]
  1791. snd-ens1371= [HW,ALSA]
  1792. snd-es968= [HW,ALSA]
  1793. snd-es1688= [HW,ALSA]
  1794. snd-es18xx= [HW,ALSA]
  1795. snd-es1938= [HW,ALSA]
  1796. snd-es1968= [HW,ALSA]
  1797. snd-fm801= [HW,ALSA]
  1798. snd-gusclassic= [HW,ALSA]
  1799. snd-gusextreme= [HW,ALSA]
  1800. snd-gusmax= [HW,ALSA]
  1801. snd-hdsp= [HW,ALSA]
  1802. snd-ice1712= [HW,ALSA]
  1803. snd-intel8x0= [HW,ALSA]
  1804. snd-interwave= [HW,ALSA]
  1805. snd-interwave-stb=
  1806. [HW,ALSA]
  1807. snd-korg1212= [HW,ALSA]
  1808. snd-maestro3= [HW,ALSA]
  1809. snd-mpu401= [HW,ALSA]
  1810. snd-mtpav= [HW,ALSA]
  1811. snd-nm256= [HW,ALSA]
  1812. snd-opl3sa2= [HW,ALSA]
  1813. snd-opti92x-ad1848=
  1814. [HW,ALSA]
  1815. snd-opti92x-cs4231=
  1816. [HW,ALSA]
  1817. snd-opti93x= [HW,ALSA]
  1818. snd-pmac= [HW,ALSA]
  1819. snd-rme32= [HW,ALSA]
  1820. snd-rme96= [HW,ALSA]
  1821. snd-rme9652= [HW,ALSA]
  1822. snd-sb8= [HW,ALSA]
  1823. snd-sb16= [HW,ALSA]
  1824. snd-sbawe= [HW,ALSA]
  1825. snd-serial= [HW,ALSA]
  1826. snd-sgalaxy= [HW,ALSA]
  1827. snd-sonicvibes= [HW,ALSA]
  1828. snd-sun-amd7930=
  1829. [HW,ALSA]
  1830. snd-sun-cs4231= [HW,ALSA]
  1831. snd-trident= [HW,ALSA]
  1832. snd-usb-audio= [HW,ALSA,USB]
  1833. snd-via82xx= [HW,ALSA]
  1834. snd-virmidi= [HW,ALSA]
  1835. snd-wavefront= [HW,ALSA]
  1836. snd-ymfpci= [HW,ALSA]
  1837. softlockup_panic=
  1838. [KNL] Should the soft-lockup detector generate panics.
  1839. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1840. See Documentation/sonypi.txt
  1841. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1842. See Documentation/serial/specialix.txt.
  1843. spia_io_base= [HW,MTD]
  1844. spia_fio_base=
  1845. spia_pedr=
  1846. spia_peddr=
  1847. sscape= [HW,OSS]
  1848. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1849. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1850. See Documentation/scsi/st.txt.
  1851. stacktrace [FTRACE]
  1852. Enabled the stack tracer on boot up.
  1853. sti= [PARISC,HW]
  1854. Format: <num>
  1855. Set the STI (builtin display/keyboard on the HP-PARISC
  1856. machines) console (graphic card) which should be used
  1857. as the initial boot-console.
  1858. See also comment in drivers/video/console/sticore.c.
  1859. sti_font= [HW]
  1860. See comment in drivers/video/console/sticore.c.
  1861. stifb= [HW]
  1862. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1863. sunrpc.pool_mode=
  1864. [NFS]
  1865. Control how the NFS server code allocates CPUs to
  1866. service thread pools. Depending on how many NICs
  1867. you have and where their interrupts are bound, this
  1868. option will affect which CPUs will do NFS serving.
  1869. Note: this parameter cannot be changed while the
  1870. NFS server is running.
  1871. auto the server chooses an appropriate mode
  1872. automatically using heuristics
  1873. global a single global pool contains all CPUs
  1874. percpu one pool for each CPU
  1875. pernode one pool for each NUMA node (equivalent
  1876. to global on non-NUMA machines)
  1877. swiotlb= [IA-64] Number of I/O TLB slabs
  1878. switches= [HW,M68k]
  1879. sym53c416= [HW,SCSI]
  1880. See header of drivers/scsi/sym53c416.c.
  1881. sysrq_always_enabled
  1882. [KNL]
  1883. Ignore sysrq setting - this boot parameter will
  1884. neutralize any effect of /proc/sys/kernel/sysrq.
  1885. Useful for debugging.
  1886. t128= [HW,SCSI]
  1887. See header of drivers/scsi/t128.c.
  1888. tdfx= [HW,DRM]
  1889. test_suspend= [SUSPEND]
  1890. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1891. standby suspend) as the system sleep state to briefly
  1892. enter during system startup. The system is woken from
  1893. this state using a wakeup-capable RTC alarm.
  1894. thash_entries= [KNL,NET]
  1895. Set number of hash buckets for TCP connection
  1896. thermal.act= [HW,ACPI]
  1897. -1: disable all active trip points in all thermal zones
  1898. <degrees C>: override all lowest active trip points
  1899. thermal.crt= [HW,ACPI]
  1900. -1: disable all critical trip points in all thermal zones
  1901. <degrees C>: override all critical trip points
  1902. thermal.nocrt= [HW,ACPI]
  1903. Set to disable actions on ACPI thermal zone
  1904. critical and hot trip points.
  1905. thermal.off= [HW,ACPI]
  1906. 1: disable ACPI thermal control
  1907. thermal.psv= [HW,ACPI]
  1908. -1: disable all passive trip points
  1909. <degrees C>: override all passive trip points to this
  1910. value
  1911. thermal.tzp= [HW,ACPI]
  1912. Specify global default ACPI thermal zone polling rate
  1913. <deci-seconds>: poll all this frequency
  1914. 0: no polling (default)
  1915. tmscsim= [HW,SCSI]
  1916. See comment before function dc390_setup() in
  1917. drivers/scsi/tmscsim.c.
  1918. topology= [S390]
  1919. Format: {off | on}
  1920. Specify if the kernel should make use of the cpu
  1921. topology informations if the hardware supports these.
  1922. The scheduler will make use of these informations and
  1923. e.g. base its process migration decisions on it.
  1924. Default is off.
  1925. tp720= [HW,PS2]
  1926. trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
  1927. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1928. Format:
  1929. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1930. tsc= Disable clocksource-must-verify flag for TSC.
  1931. Format: <string>
  1932. [x86] reliable: mark tsc clocksource as reliable, this
  1933. disables clocksource verification at runtime.
  1934. Used to enable high-resolution timer mode on older
  1935. hardware, and in virtualized environment.
  1936. turbografx.map[2|3]= [HW,JOY]
  1937. TurboGraFX parallel port interface
  1938. Format:
  1939. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1940. See also Documentation/input/joystick-parport.txt
  1941. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1942. See header of drivers/scsi/u14-34f.c.
  1943. uart401= [HW,OSS]
  1944. Format: <io>,<irq>
  1945. uart6850= [HW,OSS]
  1946. Format: <io>,<irq>
  1947. uhci-hcd.ignore_oc=
  1948. [USB] Ignore overcurrent events (default N).
  1949. Some badly-designed motherboards generate lots of
  1950. bogus events, for ports that aren't wired to
  1951. anything. Set this parameter to avoid log spamming.
  1952. Note that genuine overcurrent events won't be
  1953. reported either.
  1954. unknown_nmi_panic
  1955. [X86]
  1956. Set unknown_nmi_panic=1 early on boot.
  1957. usbcore.autosuspend=
  1958. [USB] The autosuspend time delay (in seconds) used
  1959. for newly-detected USB devices (default 2). This
  1960. is the time required before an idle device will be
  1961. autosuspended. Devices for which the delay is set
  1962. to a negative value won't be autosuspended at all.
  1963. usbcore.usbfs_snoop=
  1964. [USB] Set to log all usbfs traffic (default 0 = off).
  1965. usbcore.blinkenlights=
  1966. [USB] Set to cycle leds on hubs (default 0 = off).
  1967. usbcore.old_scheme_first=
  1968. [USB] Start with the old device initialization
  1969. scheme (default 0 = off).
  1970. usbcore.use_both_schemes=
  1971. [USB] Try the other device initialization scheme
  1972. if the first one fails (default 1 = enabled).
  1973. usbcore.initial_descriptor_timeout=
  1974. [USB] Specifies timeout for the initial 64-byte
  1975. USB_REQ_GET_DESCRIPTOR request in milliseconds
  1976. (default 5000 = 5.0 seconds).
  1977. usbhid.mousepoll=
  1978. [USBHID] The interval which mice are to be polled at.
  1979. usb-storage.delay_use=
  1980. [UMS] The delay in seconds before a new device is
  1981. scanned for Logical Units (default 5).
  1982. usb-storage.quirks=
  1983. [UMS] A list of quirks entries to supplement or
  1984. override the built-in unusual_devs list. List
  1985. entries are separated by commas. Each entry has
  1986. the form VID:PID:Flags where VID and PID are Vendor
  1987. and Product ID values (4-digit hex numbers) and
  1988. Flags is a set of characters, each corresponding
  1989. to a common usb-storage quirk flag as follows:
  1990. a = SANE_SENSE (collect more than 18 bytes
  1991. of sense data);
  1992. c = FIX_CAPACITY (decrease the reported
  1993. device capacity by one sector);
  1994. h = CAPACITY_HEURISTICS (decrease the
  1995. reported device capacity by one
  1996. sector if the number is odd);
  1997. i = IGNORE_DEVICE (don't bind to this
  1998. device);
  1999. l = NOT_LOCKABLE (don't try to lock and
  2000. unlock ejectable media);
  2001. m = MAX_SECTORS_64 (don't transfer more
  2002. than 64 sectors = 32 KB at a time);
  2003. o = CAPACITY_OK (accept the capacity
  2004. reported by the device);
  2005. r = IGNORE_RESIDUE (the device reports
  2006. bogus residue values);
  2007. s = SINGLE_LUN (the device has only one
  2008. Logical Unit);
  2009. w = NO_WP_DETECT (don't test whether the
  2010. medium is write-protected).
  2011. Example: quirks=0419:aaf5:rl,0421:0433:rc
  2012. vdso= [X86,SH]
  2013. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  2014. vdso=1: enable VDSO (default)
  2015. vdso=0: disable VDSO mapping
  2016. vdso32= [X86]
  2017. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  2018. vdso32=1: enable 32-bit VDSO (default)
  2019. vdso32=0: disable 32-bit VDSO mapping
  2020. vector= [IA-64,SMP]
  2021. vector=percpu: enable percpu vector domain
  2022. video= [FB] Frame buffer configuration
  2023. See Documentation/fb/modedb.txt.
  2024. vga= [BOOT,X86-32] Select a particular video mode
  2025. See Documentation/x86/boot.txt and
  2026. Documentation/svga.txt.
  2027. Use vga=ask for menu.
  2028. This is actually a boot loader parameter; the value is
  2029. passed to the kernel using a special protocol.
  2030. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  2031. size of <nn>. This can be used to increase the
  2032. minimum size (128MB on x86). It can also be used to
  2033. decrease the size and leave more room for directly
  2034. mapped kernel RAM.
  2035. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  2036. Format: <command>
  2037. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  2038. Format: <command>
  2039. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  2040. Format: <command>
  2041. vt.default_blu= [VT]
  2042. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  2043. Change the default blue palette of the console.
  2044. This is a 16-member array composed of values
  2045. ranging from 0-255.
  2046. vt.default_grn= [VT]
  2047. Format: <green0>,<green1>,<green2>,...,<green15>
  2048. Change the default green palette of the console.
  2049. This is a 16-member array composed of values
  2050. ranging from 0-255.
  2051. vt.default_red= [VT]
  2052. Format: <red0>,<red1>,<red2>,...,<red15>
  2053. Change the default red palette of the console.
  2054. This is a 16-member array composed of values
  2055. ranging from 0-255.
  2056. vt.default_utf8=
  2057. [VT]
  2058. Format=<0|1>
  2059. Set system-wide default UTF-8 mode for all tty's.
  2060. Default is 1, i.e. UTF-8 mode is enabled for all
  2061. newly opened terminals.
  2062. waveartist= [HW,OSS]
  2063. Format: <io>,<irq>,<dma>,<dma2>
  2064. wd33c93= [HW,SCSI]
  2065. See header of drivers/scsi/wd33c93.c.
  2066. wd7000= [HW,SCSI]
  2067. See header of drivers/scsi/wd7000.c.
  2068. wdt= [WDT] Watchdog
  2069. See Documentation/watchdog/wdt.txt.
  2070. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  2071. default x2apic cluster mode on platforms
  2072. supporting x2apic.
  2073. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  2074. xd_geo= See header of drivers/block/xd.c.
  2075. xirc2ps_cs= [NET,PCMCIA]
  2076. Format:
  2077. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  2078. ______________________________________________________________________
  2079. TODO:
  2080. Add documentation for ALSA options.
  2081. Add more DRM drivers.