kernel-parameters.txt 75 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. This document may not be entirely up to date and comprehensive. The command
  15. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  16. module. Loadable modules, after being loaded into the running kernel, also
  17. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  18. parameters may be changed at runtime by the command
  19. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  20. The parameters listed below are only valid if certain kernel build options were
  21. enabled and if respective hardware is present. The text in square brackets at
  22. the beginning of each description states the restrictions within which a
  23. parameter is applicable:
  24. ACPI ACPI support is enabled.
  25. AGP AGP (Accelerated Graphics Port) is enabled.
  26. ALSA ALSA sound support is enabled.
  27. APIC APIC support is enabled.
  28. APM Advanced Power Management support is enabled.
  29. AVR32 AVR32 architecture is enabled.
  30. AX25 Appropriate AX.25 support is enabled.
  31. BLACKFIN Blackfin architecture is enabled.
  32. DRM Direct Rendering Management support is enabled.
  33. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  34. EFI EFI Partitioning (GPT) is enabled
  35. EIDE EIDE/ATAPI support is enabled.
  36. FB The frame buffer device is enabled.
  37. HW Appropriate hardware is enabled.
  38. IA-64 IA-64 architecture is enabled.
  39. IOSCHED More than one I/O scheduler is enabled.
  40. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  41. ISAPNP ISA PnP code is enabled.
  42. ISDN Appropriate ISDN support is enabled.
  43. JOY Appropriate joystick support is enabled.
  44. LIBATA Libata driver is enabled
  45. LP Printer support is enabled.
  46. LOOP Loopback device support is enabled.
  47. M68k M68k architecture is enabled.
  48. These options have more detailed description inside of
  49. Documentation/m68k/kernel-options.txt.
  50. MCA MCA bus support is enabled.
  51. MDA MDA console support is enabled.
  52. MOUSE Appropriate mouse support is enabled.
  53. MSI Message Signaled Interrupts (PCI).
  54. MTD MTD (Memory Technology Device) support is enabled.
  55. NET Appropriate network support is enabled.
  56. NUMA NUMA support is enabled.
  57. GENERIC_TIME The generic timeofday code is enabled.
  58. NFS Appropriate NFS support is enabled.
  59. OSS OSS sound support is enabled.
  60. PV_OPS A paravirtualized kernel is enabled.
  61. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  62. PARISC The PA-RISC architecture is enabled.
  63. PCI PCI bus support is enabled.
  64. PCIE PCI Express support is enabled.
  65. PCMCIA The PCMCIA subsystem is enabled.
  66. PNP Plug & Play support is enabled.
  67. PPC PowerPC architecture is enabled.
  68. PPT Parallel port support is enabled.
  69. PS2 Appropriate PS/2 support is enabled.
  70. RAM RAM disk support is enabled.
  71. ROOTPLUG The example Root Plug LSM is enabled.
  72. S390 S390 architecture is enabled.
  73. SCSI Appropriate SCSI support is enabled.
  74. A lot of drivers has their options described inside of
  75. Documentation/scsi/.
  76. SECURITY Different security models are enabled.
  77. SELINUX SELinux support is enabled.
  78. SERIAL Serial support is enabled.
  79. SH SuperH architecture is enabled.
  80. SMP The kernel is an SMP kernel.
  81. SPARC Sparc architecture is enabled.
  82. SWSUSP Software suspend (hibernation) is enabled.
  83. SUSPEND System suspend states are enabled.
  84. TS Appropriate touchscreen support is enabled.
  85. USB USB support is enabled.
  86. USBHID USB Human Interface Device support is enabled.
  87. V4L Video For Linux support is enabled.
  88. VGA The VGA console has been enabled.
  89. VT Virtual terminal support is enabled.
  90. WDT Watchdog support is enabled.
  91. XT IBM PC/XT MFM hard disk support is enabled.
  92. X86-32 X86-32, aka i386 architecture is enabled.
  93. X86-64 X86-64 architecture is enabled.
  94. More X86-64 boot options can be found in
  95. Documentation/x86/x86_64/boot-options.txt .
  96. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  97. In addition, the following text indicates that the option:
  98. BUGS= Relates to possible processor bugs on the said processor.
  99. KNL Is a kernel start-up parameter.
  100. BOOT Is a boot loader parameter.
  101. Parameters denoted with BOOT are actually interpreted by the boot
  102. loader, and have no meaning to the kernel directly.
  103. Do not modify the syntax of boot loader parameters without extreme
  104. need or coordination with <Documentation/x86/i386/boot.txt>.
  105. There are also arch-specific kernel-parameters not documented here.
  106. See for example <Documentation/x86/x86_64/boot-options.txt>.
  107. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  108. a trailing = on the name of any parameter states that that parameter will
  109. be entered as an environment variable, whereas its absence indicates that
  110. it will appear as a kernel argument readable via /proc/cmdline by programs
  111. running once the system is up.
  112. The number of kernel parameters is not limited, but the length of the
  113. complete command line (parameters including spaces etc.) is limited to
  114. a fixed number of characters. This limit depends on the architecture
  115. and is between 256 and 4096 characters. It is defined in the file
  116. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  117. acpi= [HW,ACPI,X86-64,i386]
  118. Advanced Configuration and Power Interface
  119. Format: { force | off | ht | strict | noirq }
  120. force -- enable ACPI if default was off
  121. off -- disable ACPI if default was on
  122. noirq -- do not use ACPI for IRQ routing
  123. ht -- run only enough ACPI to enable Hyper Threading
  124. strict -- Be less tolerant of platforms that are not
  125. strictly ACPI specification compliant.
  126. See also Documentation/power/pm.txt, pci=noacpi
  127. acpi_apic_instance= [ACPI, IOAPIC]
  128. Format: <int>
  129. 2: use 2nd APIC table, if available
  130. 1,0: use 1st APIC table
  131. default: 0
  132. acpi_sleep= [HW,ACPI] Sleep options
  133. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
  134. See Documentation/power/video.txt for s3_bios and s3_mode.
  135. s3_beep is for debugging; it makes the PC's speaker beep
  136. as soon as the kernel's real-mode entry point is called.
  137. s4_nohwsig prevents ACPI hardware signature from being
  138. used during resume from hibernation.
  139. old_ordering causes the ACPI 1.0 ordering of the _PTS
  140. control method, wrt putting devices into low power
  141. states, to be enforced (the ACPI 2.0 ordering of _PTS is
  142. used by default).
  143. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  144. Format: { level | edge | high | low }
  145. acpi_irq_balance [HW,ACPI]
  146. ACPI will balance active IRQs
  147. default in APIC mode
  148. acpi_irq_nobalance [HW,ACPI]
  149. ACPI will not move active IRQs (default)
  150. default in PIC mode
  151. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  152. use by PCI
  153. Format: <irq>,<irq>...
  154. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  155. Format: <irq>,<irq>...
  156. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  157. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  158. Format: To spoof as Windows 98: ="Microsoft Windows"
  159. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  160. acpi_osi="string1" # add string1 -- only one string
  161. acpi_osi="!string2" # remove built-in string2
  162. acpi_osi= # disable all strings
  163. acpi_serialize [HW,ACPI] force serialization of AML methods
  164. acpi_skip_timer_override [HW,ACPI]
  165. Recognize and ignore IRQ0/pin2 Interrupt Override.
  166. For broken nForce2 BIOS resulting in XT-PIC timer.
  167. acpi_use_timer_override [HW,ACPI}
  168. Use timer override. For some broken Nvidia NF5 boards
  169. that require a timer override, but don't have
  170. HPET
  171. acpi.debug_layer= [HW,ACPI]
  172. Format: <int>
  173. Each bit of the <int> indicates an ACPI debug layer,
  174. 1: enable, 0: disable. It is useful for boot time
  175. debugging. After system has booted up, it can be set
  176. via /sys/module/acpi/parameters/debug_layer.
  177. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  178. Available bits (add the numbers together) to enable debug output
  179. for specific parts of the ACPI subsystem:
  180. 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
  181. 0x10 namespace 0x20 parser 0x40 dispatcher
  182. 0x80 executer 0x100 resources 0x200 acpica debugger
  183. 0x400 os services 0x800 acpica disassembler.
  184. The number can be in decimal or prefixed with 0x in hex.
  185. Warning: Many of these options can produce a lot of
  186. output and make your system unusable. Be very careful.
  187. acpi.debug_level= [HW,ACPI]
  188. Format: <int>
  189. Each bit of the <int> indicates an ACPI debug level,
  190. which corresponds to the level in an ACPI_DEBUG_PRINT
  191. statement. After system has booted up, this mask
  192. can be set via /sys/module/acpi/parameters/debug_level.
  193. CONFIG_ACPI_DEBUG must be enabled for this to produce
  194. any output. The number can be in decimal or prefixed
  195. with 0x in hex. Some of these options produce so much
  196. output that the system is unusable.
  197. The following global components are defined by the
  198. ACPI CA:
  199. 0x01 error
  200. 0x02 warn
  201. 0x04 init
  202. 0x08 debug object
  203. 0x10 info
  204. 0x20 init names
  205. 0x40 parse
  206. 0x80 load
  207. 0x100 dispatch
  208. 0x200 execute
  209. 0x400 names
  210. 0x800 operation region
  211. 0x1000 bfield
  212. 0x2000 tables
  213. 0x4000 values
  214. 0x8000 objects
  215. 0x10000 resources
  216. 0x20000 user requests
  217. 0x40000 package
  218. The number can be in decimal or prefixed with 0x in hex.
  219. Warning: Many of these options can produce a lot of
  220. output and make your system unusable. Be very careful.
  221. acpi.power_nocheck= [HW,ACPI]
  222. Format: 1/0 enable/disable the check of power state.
  223. On some bogus BIOS the _PSC object/_STA object of
  224. power resource can't return the correct device power
  225. state. In such case it is unneccessary to check its
  226. power state again in power transition.
  227. 1 : disable the power state check
  228. acpi_pm_good [X86-32,X86-64]
  229. Override the pmtimer bug detection: force the kernel
  230. to assume that this machine's pmtimer latches its value
  231. and always returns good values.
  232. agp= [AGP]
  233. { off | try_unsupported }
  234. off: disable AGP support
  235. try_unsupported: try to drive unsupported chipsets
  236. (may crash computer or cause data corruption)
  237. enable_timer_pin_1 [i386,x86-64]
  238. Enable PIN 1 of APIC timer
  239. Can be useful to work around chipset bugs
  240. (in particular on some ATI chipsets).
  241. The kernel tries to set a reasonable default.
  242. disable_timer_pin_1 [i386,x86-64]
  243. Disable PIN 1 of APIC timer
  244. Can be useful to work around chipset bugs.
  245. ad1848= [HW,OSS]
  246. Format: <io>,<irq>,<dma>,<dma2>,<type>
  247. advansys= [HW,SCSI]
  248. See header of drivers/scsi/advansys.c.
  249. advwdt= [HW,WDT] Advantech WDT
  250. Format: <iostart>,<iostop>
  251. aedsp16= [HW,OSS] Audio Excel DSP 16
  252. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  253. See also header of sound/oss/aedsp16.c.
  254. aha152x= [HW,SCSI]
  255. See Documentation/scsi/aha152x.txt.
  256. aha1542= [HW,SCSI]
  257. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  258. aic7xxx= [HW,SCSI]
  259. See Documentation/scsi/aic7xxx.txt.
  260. aic79xx= [HW,SCSI]
  261. See Documentation/scsi/aic79xx.txt.
  262. amd_iommu= [HW,X86-84]
  263. Pass parameters to the AMD IOMMU driver in the system.
  264. Possible values are:
  265. isolate - enable device isolation (each device, as far
  266. as possible, will get its own protection
  267. domain)
  268. fullflush - enable flushing of IO/TLB entries when
  269. they are unmapped. Otherwise they are
  270. flushed before they will be reused, which
  271. is a lot of faster
  272. amd_iommu_size= [HW,X86-64]
  273. Define the size of the aperture for the AMD IOMMU
  274. driver. Possible values are:
  275. '32M', '64M' (default), '128M', '256M', '512M', '1G'
  276. amijoy.map= [HW,JOY] Amiga joystick support
  277. Map of devices attached to JOY0DAT and JOY1DAT
  278. Format: <a>,<b>
  279. See also Documentation/kernel/input/joystick.txt
  280. analog.map= [HW,JOY] Analog joystick and gamepad support
  281. Specifies type or capabilities of an analog joystick
  282. connected to one of 16 gameports
  283. Format: <type1>,<type2>,..<type16>
  284. apc= [HW,SPARC]
  285. Power management functions (SPARCstation-4/5 + deriv.)
  286. Format: noidle
  287. Disable APC CPU standby support. SPARCstation-Fox does
  288. not play well with APC CPU idle - disable it if you have
  289. APC and your system crashes randomly.
  290. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  291. Change the output verbosity whilst booting
  292. Format: { quiet (default) | verbose | debug }
  293. Change the amount of debugging information output
  294. when initialising the APIC and IO-APIC components.
  295. apm= [APM] Advanced Power Management
  296. See header of arch/x86/kernel/apm_32.c.
  297. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  298. Format: <io>,<irq>,<nodeID>
  299. ataflop= [HW,M68k]
  300. atarimouse= [HW,MOUSE] Atari Mouse
  301. atascsi= [HW,SCSI] Atari SCSI
  302. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  303. EzKey and similar keyboards
  304. atkbd.reset= [HW] Reset keyboard during initialization
  305. atkbd.set= [HW] Select keyboard code set
  306. Format: <int> (2 = AT (default), 3 = PS/2)
  307. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  308. keyboards
  309. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  310. Format: <bool> (0 = real, 1 = synthetic (default))
  311. atkbd.softrepeat= [HW]
  312. Use software keyboard repeat
  313. autotest [IA64]
  314. baycom_epp= [HW,AX25]
  315. Format: <io>,<mode>
  316. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  317. Format: <io>,<mode>
  318. See header of drivers/net/hamradio/baycom_par.c.
  319. baycom_ser_fdx= [HW,AX25]
  320. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  321. Format: <io>,<irq>,<mode>[,<baud>]
  322. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  323. baycom_ser_hdx= [HW,AX25]
  324. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  325. Format: <io>,<irq>,<mode>
  326. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  327. boot_delay= Milliseconds to delay each printk during boot.
  328. Values larger than 10 seconds (10000) are changed to
  329. no delay (0).
  330. Format: integer
  331. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  332. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  333. bttv.radio= Most important insmod options are available as
  334. kernel args too.
  335. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  336. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  337. BusLogic= [HW,SCSI]
  338. See drivers/scsi/BusLogic.c, comment before function
  339. BusLogic_ParseDriverOptions().
  340. c101= [NET] Moxa C101 synchronous serial card
  341. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  342. Sometimes CPU hardware bugs make them report the cache
  343. size incorrectly. The kernel will attempt work arounds
  344. to fix known problems, but for some CPUs it is not
  345. possible to determine what the correct size should be.
  346. This option provides an override for these situations.
  347. security= [SECURITY] Choose a security module to enable at boot.
  348. If this boot parameter is not specified, only the first
  349. security module asking for security registration will be
  350. loaded. An invalid security module name will be treated
  351. as if no module has been chosen.
  352. capability.disable=
  353. [SECURITY] Disable capabilities. This would normally
  354. be used only if an alternative security model is to be
  355. configured. Potentially dangerous and should only be
  356. used if you are entirely sure of the consequences.
  357. ccw_timeout_log [S390]
  358. See Documentation/s390/CommonIO for details.
  359. cgroup_disable= [KNL] Disable a particular controller
  360. Format: {name of the controller(s) to disable}
  361. {Currently supported controllers - "memory"}
  362. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  363. Format: { "0" | "1" }
  364. See security/selinux/Kconfig help text.
  365. 0 -- check protection applied by kernel (includes
  366. any implied execute protection).
  367. 1 -- check protection requested by application.
  368. Default value is set via a kernel config option.
  369. Value can be changed at runtime via
  370. /selinux/checkreqprot.
  371. cio_ignore= [S390]
  372. See Documentation/s390/CommonIO for details.
  373. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  374. [Deprecated]
  375. Forces specified clocksource (if available) to be used
  376. when calculating gettimeofday(). If specified
  377. clocksource is not available, it defaults to PIT.
  378. Format: { pit | tsc | cyclone | pmtmr }
  379. clocksource= [GENERIC_TIME] Override the default clocksource
  380. Format: <string>
  381. Override the default clocksource and use the clocksource
  382. with the name specified.
  383. Some clocksource names to choose from, depending on
  384. the platform:
  385. [all] jiffies (this is the base, fallback clocksource)
  386. [ACPI] acpi_pm
  387. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  388. pxa_timer,timer3,32k_counter,timer0_1
  389. [AVR32] avr32
  390. [X86-32] pit,hpet,tsc,vmi-timer;
  391. scx200_hrt on Geode; cyclone on IBM x440
  392. [MIPS] MIPS
  393. [PARISC] cr16
  394. [S390] tod
  395. [SH] SuperH
  396. [SPARC64] tick
  397. [X86-64] hpet,tsc
  398. clearcpuid=BITNUM [X86]
  399. Disable CPUID feature X for the kernel. See
  400. include/asm-x86/cpufeature.h for the valid bit numbers.
  401. Note the Linux specific bits are not necessarily
  402. stable over kernel options, but the vendor specific
  403. ones should be.
  404. Also note that user programs calling CPUID directly
  405. or using the feature without checking anything
  406. will still see it. This just prevents it from
  407. being used by the kernel or shown in /proc/cpuinfo.
  408. Also note the kernel might malfunction if you disable
  409. some critical bits.
  410. code_bytes [IA32/X86_64] How many bytes of object code to print
  411. in an oops report.
  412. Range: 0 - 8192
  413. Default: 64
  414. hpet= [X86-32,HPET] option to control HPET usage
  415. Format: { enable (default) | disable | force }
  416. disable: disable HPET and use PIT instead
  417. force: allow force enabled of undocumented chips (ICH4,
  418. VIA, nVidia)
  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. earlycon= [KNL] Output early console device and options.
  453. uart[8250],io,<addr>[,options]
  454. uart[8250],mmio,<addr>[,options]
  455. Start an early, polled-mode console on the 8250/16550
  456. UART at the specified I/O port or MMIO address.
  457. The options are the same as for ttyS, above.
  458. no_console_suspend
  459. [HW] Never suspend the console
  460. Disable suspending of consoles during suspend and
  461. hibernate operations. Once disabled, debugging
  462. messages can reach various consoles while the rest
  463. of the system is being put to sleep (ie, while
  464. debugging driver suspend/resume hooks). This may
  465. not work reliably with all consoles, but is known
  466. to work with serial and VGA consoles.
  467. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  468. Format:
  469. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  470. crashkernel=nn[KMG]@ss[KMG]
  471. [KNL] Reserve a chunk of physical memory to
  472. hold a kernel to switch to with kexec on panic.
  473. crashkernel=range1:size1[,range2:size2,...][@offset]
  474. [KNL] Same as above, but depends on the memory
  475. in the running system. The syntax of range is
  476. start-[end] where start and end are both
  477. a memory unit (amount[KMG]). See also
  478. Documentation/kdump/kdump.txt for a example.
  479. cs4232= [HW,OSS]
  480. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  481. cs89x0_dma= [HW,NET]
  482. Format: <dma>
  483. cs89x0_media= [HW,NET]
  484. Format: { rj45 | aui | bnc }
  485. dasd= [HW,NET]
  486. See header of drivers/s390/block/dasd_devmap.c.
  487. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  488. (one device per port)
  489. Format: <port#>,<type>
  490. See also Documentation/input/joystick-parport.txt
  491. debug [KNL] Enable kernel debugging (events log level).
  492. debug_locks_verbose=
  493. [KNL] verbose self-tests
  494. Format=<0|1>
  495. Print debugging info while doing the locking API
  496. self-tests.
  497. We default to 0 (no extra messages), setting it to
  498. 1 will print _a lot_ more information - normally
  499. only useful to kernel developers.
  500. debug_objects [KNL] Enable object debugging
  501. debugpat [X86] Enable PAT debugging
  502. decnet.addr= [HW,NET]
  503. Format: <area>[,<node>]
  504. See also Documentation/networking/decnet.txt.
  505. vt.default_blu= [VT]
  506. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  507. Change the default blue palette of the console.
  508. This is a 16-member array composed of values
  509. ranging from 0-255.
  510. vt.default_grn= [VT]
  511. Format: <green0>,<green1>,<green2>,...,<green15>
  512. Change the default green palette of the console.
  513. This is a 16-member array composed of values
  514. ranging from 0-255.
  515. vt.default_red= [VT]
  516. Format: <red0>,<red1>,<red2>,...,<red15>
  517. Change the default red palette of the console.
  518. This is a 16-member array composed of values
  519. ranging from 0-255.
  520. vt.default_utf8=
  521. [VT]
  522. Format=<0|1>
  523. Set system-wide default UTF-8 mode for all tty's.
  524. Default is 1, i.e. UTF-8 mode is enabled for all
  525. newly opened terminals.
  526. dhash_entries= [KNL]
  527. Set number of hash buckets for dentry cache.
  528. digi= [HW,SERIAL]
  529. IO parameters + enable/disable command.
  530. digiepca= [HW,SERIAL]
  531. See drivers/char/README.epca and
  532. Documentation/digiepca.txt.
  533. disable_mtrr_cleanup [X86]
  534. enable_mtrr_cleanup [X86]
  535. The kernel tries to adjust MTRR layout from continuous
  536. to discrete, to make X server driver able to add WB
  537. entry later. This parameter enables/disables that.
  538. mtrr_chunk_size=nn[KMG] [X86]
  539. used for mtrr cleanup. It is largest continous chunk
  540. that could hold holes aka. UC entries.
  541. mtrr_gran_size=nn[KMG] [X86]
  542. Used for mtrr cleanup. It is granularity of mtrr block.
  543. Default is 1.
  544. Large value could prevent small alignment from
  545. using up MTRRs.
  546. mtrr_spare_reg_nr=n [X86]
  547. Format: <integer>
  548. Range: 0,7 : spare reg number
  549. Default : 1
  550. Used for mtrr cleanup. It is spare mtrr entries number.
  551. Set to 2 or more if your graphical card needs more.
  552. disable_mtrr_trim [X86, Intel and AMD only]
  553. By default the kernel will trim any uncacheable
  554. memory out of your available memory pool based on
  555. MTRR settings. This parameter disables that behavior,
  556. possibly causing your machine to run very slowly.
  557. dmasound= [HW,OSS] Sound subsystem buffers
  558. dscc4.setup= [NET]
  559. dtc3181e= [HW,SCSI]
  560. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  561. earlyprintk=vga
  562. earlyprintk=serial[,ttySn[,baudrate]]
  563. earlyprintk=dbgp
  564. Append ",keep" to not disable it when the real console
  565. takes over.
  566. Only vga or serial or usb debug port at a time.
  567. Currently only ttyS0 and ttyS1 are supported.
  568. Interaction with the standard serial driver is not
  569. very good.
  570. The VGA output is eventually overwritten by the real
  571. console.
  572. eata= [HW,SCSI]
  573. edd= [EDD]
  574. Format: {"off" | "on" | "skip[mbr]"}
  575. eisa_irq_edge= [PARISC,HW]
  576. See header of drivers/parisc/eisa.c.
  577. elanfreq= [X86-32]
  578. See comment before function elanfreq_setup() in
  579. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  580. elevator= [IOSCHED]
  581. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  582. See Documentation/block/as-iosched.txt and
  583. Documentation/block/deadline-iosched.txt for details.
  584. elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
  585. Specifies physical address of start of kernel core
  586. image elf header. Generally kexec loader will
  587. pass this option to capture kernel.
  588. See Documentation/kdump/kdump.txt for details.
  589. enforcing [SELINUX] Set initial enforcing status.
  590. Format: {"0" | "1"}
  591. See security/selinux/Kconfig help text.
  592. 0 -- permissive (log only, no denials).
  593. 1 -- enforcing (deny and log).
  594. Default value is 0.
  595. Value can be changed at runtime via /selinux/enforce.
  596. es1371= [HW,OSS]
  597. Format: <spdif>,[<nomix>,[<amplifier>]]
  598. See also header of sound/oss/es1371.c.
  599. ether= [HW,NET] Ethernet cards parameters
  600. This option is obsoleted by the "netdev=" option, which
  601. has equivalent usage. See its documentation for details.
  602. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  603. Format: <io>[,<irq>]
  604. failslab=
  605. fail_page_alloc=
  606. fail_make_request=[KNL]
  607. General fault injection mechanism.
  608. Format: <interval>,<probability>,<space>,<times>
  609. See also /Documentation/fault-injection/.
  610. fd_mcs= [HW,SCSI]
  611. See header of drivers/scsi/fd_mcs.c.
  612. fdomain= [HW,SCSI]
  613. See header of drivers/scsi/fdomain.c.
  614. floppy= [HW]
  615. See Documentation/floppy.txt.
  616. force_pal_cache_flush
  617. [IA-64] Avoid check_sal_cache_flush which may hang on
  618. buggy SAL_CACHE_FLUSH implementations. Using this
  619. parameter will force ia64_sal_cache_flush to call
  620. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  621. gamecon.map[2|3]=
  622. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  623. support via parallel port (up to 5 devices per port)
  624. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  625. See also Documentation/input/joystick-parport.txt
  626. gamma= [HW,DRM]
  627. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  628. Format: off | on
  629. default: on
  630. gdth= [HW,SCSI]
  631. See header of drivers/scsi/gdth.c.
  632. gpt [EFI] Forces disk with valid GPT signature but
  633. invalid Protective MBR to be treated as GPT.
  634. gvp11= [HW,SCSI]
  635. hashdist= [KNL,NUMA] Large hashes allocated during boot
  636. are distributed across NUMA nodes. Defaults on
  637. for IA-64, off otherwise.
  638. Format: 0 | 1 (for off | on)
  639. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  640. hd= [EIDE] (E)IDE hard drive subsystem geometry
  641. Format: <cyl>,<head>,<sect>
  642. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  643. size of <nn>. This works even on boxes that have no
  644. highmem otherwise. This also works to reduce highmem
  645. size on bigger boxes.
  646. highres= [KNL] Enable/disable high resolution timer mode.
  647. Valid parameters: "on", "off"
  648. Default: "on"
  649. hisax= [HW,ISDN]
  650. See Documentation/isdn/README.HiSax.
  651. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  652. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  653. On x86-64 and powerpc, this option can be specified
  654. multiple times interleaved with hugepages= to reserve
  655. huge pages of different sizes. Valid pages sizes on
  656. x86-64 are 2M (when the CPU supports "pse") and 1G
  657. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  658. Note that 1GB pages can only be allocated at boot time
  659. using hugepages= and not freed afterwards.
  660. default_hugepagesz=
  661. [same as hugepagesz=] The size of the default
  662. HugeTLB page size. This is the size represented by
  663. the legacy /proc/ hugepages APIs, used for SHM, and
  664. default size when mounting hugetlbfs filesystems.
  665. Defaults to the default architecture's huge page size
  666. if not specified.
  667. hlt [BUGS=ARM,SH]
  668. i8042.debug [HW] Toggle i8042 debug mode
  669. i8042.direct [HW] Put keyboard port into non-translated mode
  670. i8042.dumbkbd [HW] Pretend that controller can only read data from
  671. keyboard and cannot control its state
  672. (Don't attempt to blink the leds)
  673. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  674. i8042.nokbd [HW] Don't check/create keyboard port
  675. i8042.noloop [HW] Disable the AUX Loopback command while probing
  676. for the AUX port
  677. i8042.nomux [HW] Don't check presence of an active multiplexing
  678. controller
  679. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  680. controllers
  681. i8042.panicblink=
  682. [HW] Frequency with which keyboard LEDs should blink
  683. when kernel panics (default is 0.5 sec)
  684. i8042.reset [HW] Reset the controller during init and cleanup
  685. i8042.unlock [HW] Unlock (ignore) the keylock
  686. i810= [HW,DRM]
  687. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  688. indicates that the driver is running on unsupported
  689. hardware.
  690. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  691. does not match list of supported models.
  692. i8k.power_status
  693. [HW] Report power status in /proc/i8k
  694. (disabled by default)
  695. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  696. capability is set.
  697. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  698. See Documentation/mca.txt.
  699. icn= [HW,ISDN]
  700. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  701. ide= [HW] (E)IDE subsystem
  702. Format: ide=nodma or ide=doubler
  703. See Documentation/ide/ide.txt.
  704. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  705. See Documentation/ide/ide.txt.
  706. idle= [X86]
  707. Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
  708. Poll forces a polling idle loop that can slightly improves the performance
  709. of waking up a idle CPU, but will use a lot of power and make the system
  710. run hot. Not recommended.
  711. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  712. to not use it because it doesn't save as much power as a normal idle
  713. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  714. as idle=poll.
  715. idle=halt. Halt is forced to be used for CPU idle.
  716. In such case C2/C3 won't be used again.
  717. idle=nomwait. Disable mwait for CPU C-states
  718. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  719. Claim all unknown PCI IDE storage controllers.
  720. ignore_loglevel [KNL]
  721. Ignore loglevel setting - this will print /all/
  722. kernel messages to the console. Useful for debugging.
  723. ihash_entries= [KNL]
  724. Set number of hash buckets for inode cache.
  725. in2000= [HW,SCSI]
  726. See header of drivers/scsi/in2000.c.
  727. init= [KNL]
  728. Format: <full_path>
  729. Run specified binary instead of /sbin/init as init
  730. process.
  731. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  732. for working out where the kernel is dying during
  733. startup.
  734. initrd= [BOOT] Specify the location of the initial ramdisk
  735. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  736. Format: <irq>
  737. inttest= [IA64]
  738. iommu= [x86]
  739. off
  740. force
  741. noforce
  742. biomerge
  743. panic
  744. nopanic
  745. merge
  746. nomerge
  747. forcesac
  748. soft
  749. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  750. off
  751. Disable intel iommu driver.
  752. igfx_off [Default Off]
  753. By default, gfx is mapped as normal device. If a gfx
  754. device has a dedicated DMAR unit, the DMAR unit is
  755. bypassed by not enabling DMAR with this option. In
  756. this case, gfx device will use physical address for
  757. DMA.
  758. forcedac [x86_64]
  759. With this option iommu will not optimize to look
  760. for io virtual address below 32 bit forcing dual
  761. address cycle on pci bus for cards supporting greater
  762. than 32 bit addressing. The default is to look
  763. for translation below 32 bit and if not available
  764. then look in the higher range.
  765. strict [Default Off]
  766. With this option on every unmap_single operation will
  767. result in a hardware IOTLB flush operation as opposed
  768. to batching them for performance.
  769. io_delay= [X86-32,X86-64] I/O delay method
  770. 0x80
  771. Standard port 0x80 based delay
  772. 0xed
  773. Alternate port 0xed based delay (needed on some systems)
  774. udelay
  775. Simple two microseconds delay
  776. none
  777. No delay
  778. io7= [HW] IO7 for Marvel based alpha systems
  779. See comment before marvel_specify_io7 in
  780. arch/alpha/kernel/core_marvel.c.
  781. ip= [IP_PNP]
  782. See Documentation/filesystems/nfsroot.txt.
  783. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  784. See comment before ip2_setup() in
  785. drivers/char/ip2/ip2base.c.
  786. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  787. See header of drivers/scsi/ips.c.
  788. ports= [IP_VS_FTP] IPVS ftp helper module
  789. Default is 21.
  790. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  791. may be specified.
  792. Format: <port>,<port>....
  793. irqfixup [HW]
  794. When an interrupt is not handled search all handlers
  795. for it. Intended to get systems with badly broken
  796. firmware running.
  797. irqpoll [HW]
  798. When an interrupt is not handled search all handlers
  799. for it. Also check all handlers each timer
  800. interrupt. Intended to get systems with badly broken
  801. firmware running.
  802. isapnp= [ISAPNP]
  803. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  804. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  805. Format:
  806. <cpu number>,...,<cpu number>
  807. or
  808. <cpu number>-<cpu number> (must be a positive range in ascending order)
  809. or a mixture
  810. <cpu number>,...,<cpu number>-<cpu number>
  811. This option can be used to specify one or more CPUs
  812. to isolate from the general SMP balancing and scheduling
  813. algorithms. The only way to move a process onto or off
  814. an "isolated" CPU is via the CPU affinity syscalls.
  815. <cpu number> begins at 0 and the maximum value is
  816. "number of CPUs in system - 1".
  817. This option is the preferred way to isolate CPUs. The
  818. alternative -- manually setting the CPU mask of all
  819. tasks in the system -- can cause problems and
  820. suboptimal load balancer performance.
  821. iucv= [HW,NET]
  822. js= [HW,JOY] Analog joystick
  823. See Documentation/input/joystick.txt.
  824. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  825. specifies the amount of memory usable by the kernel
  826. for non-movable allocations. The requested amount is
  827. spread evenly throughout all nodes in the system. The
  828. remaining memory in each node is used for Movable
  829. pages. In the event, a node is too small to have both
  830. kernelcore and Movable pages, kernelcore pages will
  831. take priority and other nodes will have a larger number
  832. of kernelcore pages. The Movable zone is used for the
  833. allocation of pages that may be reclaimed or moved
  834. by the page migration subsystem. This means that
  835. HugeTLB pages may not be allocated from this zone.
  836. Note that allocations like PTEs-from-HighMem still
  837. use the HighMem zone if it exists, and the Normal
  838. zone if it does not.
  839. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  840. is similar to kernelcore except it specifies the
  841. amount of memory used for migratable allocations.
  842. If both kernelcore and movablecore is specified,
  843. then kernelcore will be at *least* the specified
  844. value but may be more. If movablecore on its own
  845. is specified, the administrator must be careful
  846. that the amount of memory usable for all allocations
  847. is not too small.
  848. keepinitrd [HW,ARM]
  849. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  850. in oops dumps.
  851. kgdboc= [HW] kgdb over consoles.
  852. Requires a tty driver that supports console polling.
  853. (only serial suported for now)
  854. Format: <serial_device>[,baud]
  855. kmac= [MIPS] korina ethernet MAC address.
  856. Configure the RouterBoard 532 series on-chip
  857. Ethernet adapter MAC address.
  858. l2cr= [PPC]
  859. l3cr= [PPC]
  860. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  861. disabled it.
  862. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  863. C2 power state.
  864. libata.dma= [LIBATA] DMA control
  865. libata.dma=0 Disable all PATA and SATA DMA
  866. libata.dma=1 PATA and SATA Disk DMA only
  867. libata.dma=2 ATAPI (CDROM) DMA only
  868. libata.dma=4 Compact Flash DMA only
  869. Combinations also work, so libata.dma=3 enables DMA
  870. for disks and CDROMs, but not CFs.
  871. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  872. when set.
  873. Format: <int>
  874. libata.force= [LIBATA] Force configurations. The format is comma
  875. separated list of "[ID:]VAL" where ID is
  876. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  877. matching port, link or device. Basically, it matches
  878. the ATA ID string printed on console by libata. If
  879. the whole ID part is omitted, the last PORT and DEVICE
  880. values are used. If ID hasn't been specified yet, the
  881. configuration applies to all ports, links and devices.
  882. If only DEVICE is omitted, the parameter applies to
  883. the port and all links and devices behind it. DEVICE
  884. number of 0 either selects the first device or the
  885. first fan-out link behind PMP device. It does not
  886. select the host link. DEVICE number of 15 selects the
  887. host link and device attached to it.
  888. The VAL specifies the configuration to force. As long
  889. as there's no ambiguity shortcut notation is allowed.
  890. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  891. The following configurations can be forced.
  892. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  893. Any ID with matching PORT is used.
  894. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  895. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  896. udma[/][16,25,33,44,66,100,133] notation is also
  897. allowed.
  898. * [no]ncq: Turn on or off NCQ.
  899. * nohrst, nosrst, norst: suppress hard, soft
  900. and both resets.
  901. If there are multiple matching configurations changing
  902. the same attribute, the last one is used.
  903. load_ramdisk= [RAM] List of ramdisks to load from floppy
  904. See Documentation/ramdisk.txt.
  905. lockd.nlm_grace_period=P [NFS] Assign grace period.
  906. Format: <integer>
  907. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  908. Format: <integer>
  909. lockd.nlm_timeout=T [NFS] Assign timeout value.
  910. Format: <integer>
  911. lockd.nlm_udpport=M [NFS] Assign UDP port.
  912. Format: <integer>
  913. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  914. Format: <irq>
  915. loglevel= All Kernel Messages with a loglevel smaller than the
  916. console loglevel will be printed to the console. It can
  917. also be changed with klogd or other programs. The
  918. loglevels are defined as follows:
  919. 0 (KERN_EMERG) system is unusable
  920. 1 (KERN_ALERT) action must be taken immediately
  921. 2 (KERN_CRIT) critical conditions
  922. 3 (KERN_ERR) error conditions
  923. 4 (KERN_WARNING) warning conditions
  924. 5 (KERN_NOTICE) normal but significant condition
  925. 6 (KERN_INFO) informational
  926. 7 (KERN_DEBUG) debug-level messages
  927. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  928. Format: { n | nk | nM }
  929. n must be a power of two. The default size
  930. is set in the kernel config file.
  931. logo.nologo [FB] Disables display of the built-in Linux logo.
  932. This may be used to provide more screen space for
  933. kernel log messages and is useful when debugging
  934. kernel boot problems.
  935. lp=0 [LP] Specify parallel ports to use, e.g,
  936. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  937. lp=reset first parallel port). 'lp=0' disables the
  938. lp=auto printer driver. 'lp=reset' (which can be
  939. specified in addition to the ports) causes
  940. attached printers to be reset. Using
  941. lp=port1,port2,... specifies the parallel ports
  942. to associate lp devices with, starting with
  943. lp0. A port specification may be 'none' to skip
  944. that lp device, or a parport name such as
  945. 'parport0'. Specifying 'lp=auto' instead of a
  946. port specification list means that device IDs
  947. from each port should be examined, to see if
  948. an IEEE 1284-compliant printer is attached; if
  949. so, the driver will manage that printer.
  950. See also header of drivers/char/lp.c.
  951. lpj=n [KNL]
  952. Sets loops_per_jiffy to given constant, thus avoiding
  953. time-consuming boot-time autodetection (up to 250 ms per
  954. CPU). 0 enables autodetection (default). To determine
  955. the correct value for your kernel, boot with normal
  956. autodetection and see what value is printed. Note that
  957. on SMP systems the preset will be applied to all CPUs,
  958. which is likely to cause problems if your CPUs need
  959. significantly divergent settings. An incorrect value
  960. will cause delays in the kernel to be wrong, leading to
  961. unpredictable I/O errors and other breakage. Although
  962. unlikely, in the extreme case this might damage your
  963. hardware.
  964. ltpc= [NET]
  965. Format: <io>,<irq>,<dma>
  966. mac5380= [HW,SCSI] Format:
  967. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  968. machvec= [IA64] Force the use of a particular machine-vector
  969. (machvec) in a generic kernel.
  970. Example: machvec=hpzx1_swiotlb
  971. max_loop= [LOOP] Maximum number of loopback devices that can
  972. be mounted
  973. Format: <1-256>
  974. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  975. should make use of. maxcpus=n : n >= 0 limits the
  976. kernel to using 'n' processors. n=0 is a special case,
  977. it is equivalent to "nosmp", which also disables
  978. the IO APIC.
  979. max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
  980. equal to this physical address is ignored.
  981. max_luns= [SCSI] Maximum number of LUNs to probe.
  982. Should be between 1 and 2^32-1.
  983. max_report_luns=
  984. [SCSI] Maximum number of LUNs received.
  985. Should be between 1 and 16384.
  986. mcatest= [IA-64]
  987. mce [X86-32] Machine Check Exception
  988. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  989. md= [HW] RAID subsystems devices and level
  990. See Documentation/md.txt.
  991. mdacon= [MDA]
  992. Format: <first>,<last>
  993. Specifies range of consoles to be captured by the MDA.
  994. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  995. Amount of memory to be used when the kernel is not able
  996. to see the whole system memory or for test.
  997. [X86-32] Use together with memmap= to avoid physical
  998. address space collisions. Without memmap= PCI devices
  999. could be placed at addresses belonging to unused RAM.
  1000. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1001. memory.
  1002. memchunk=nn[KMG]
  1003. [KNL,SH] Allow user to override the default size for
  1004. per-device physically contiguous DMA buffers.
  1005. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  1006. E820 memory map, as specified by the user.
  1007. Such memmap=exactmap lines can be constructed based on
  1008. BIOS output or other requirements. See the memmap=nn@ss
  1009. option description.
  1010. memmap=nn[KMG]@ss[KMG]
  1011. [KNL] Force usage of a specific region of memory
  1012. Region of memory to be used, from ss to ss+nn.
  1013. memmap=nn[KMG]#ss[KMG]
  1014. [KNL,ACPI] Mark specific memory as ACPI data.
  1015. Region of memory to be used, from ss to ss+nn.
  1016. memmap=nn[KMG]$ss[KMG]
  1017. [KNL,ACPI] Mark specific memory as reserved.
  1018. Region of memory to be used, from ss to ss+nn.
  1019. Example: Exclude memory from 0x18690000-0x1869ffff
  1020. memmap=64K$0x18690000
  1021. or
  1022. memmap=0x10000$0x18690000
  1023. memory_corruption_check=0/1 [X86]
  1024. Some BIOSes seem to corrupt the first 64k of
  1025. memory when doing things like suspend/resume.
  1026. Setting this option will scan the memory
  1027. looking for corruption. Enabling this will
  1028. both detect corruption and prevent the kernel
  1029. from using the memory being corrupted.
  1030. However, its intended as a diagnostic tool; if
  1031. repeatable BIOS-originated corruption always
  1032. affects the same memory, you can use memmap=
  1033. to prevent the kernel from using that memory.
  1034. memory_corruption_check_size=size [X86]
  1035. By default it checks for corruption in the low
  1036. 64k, making this memory unavailable for normal
  1037. use. Use this parameter to scan for
  1038. corruption in more or less memory.
  1039. memory_corruption_check_period=seconds [X86]
  1040. By default it checks for corruption every 60
  1041. seconds. Use this parameter to check at some
  1042. other rate. 0 disables periodic checking.
  1043. memtest= [KNL,X86] Enable memtest
  1044. Format: <integer>
  1045. range: 0,4 : pattern number
  1046. default : 0 <disable>
  1047. meye.*= [HW] Set MotionEye Camera parameters
  1048. See Documentation/video4linux/meye.txt.
  1049. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1050. Multi-Function General Purpose Timers on AMD Geode
  1051. platforms.
  1052. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1053. the BIOS has incorrectly applied a workaround. TinyBIOS
  1054. version 0.98 is known to be affected, 0.99 fixes the
  1055. problem by letting the user disable the workaround.
  1056. mga= [HW,DRM]
  1057. mminit_loglevel=
  1058. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1059. parameter allows control of the logging verbosity for
  1060. the additional memory initialisation checks. A value
  1061. of 0 disables mminit logging and a level of 4 will
  1062. log everything. Information is printed at KERN_DEBUG
  1063. so loglevel=8 may also need to be specified.
  1064. mousedev.tap_time=
  1065. [MOUSE] Maximum time between finger touching and
  1066. leaving touchpad surface for touch to be considered
  1067. a tap and be reported as a left button click (for
  1068. touchpads working in absolute mode only).
  1069. Format: <msecs>
  1070. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1071. reporting absolute coordinates, such as tablets
  1072. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1073. reporting absolute coordinates, such as tablets
  1074. mpu401= [HW,OSS]
  1075. Format: <io>,<irq>
  1076. MTD_Partition= [MTD]
  1077. Format: <name>,<region-number>,<size>,<offset>
  1078. MTD_Region= [MTD] Format:
  1079. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1080. mtdparts= [MTD]
  1081. See drivers/mtd/cmdlinepart.c.
  1082. mtdset= [ARM]
  1083. ARM/S3C2412 JIVE boot control
  1084. See arch/arm/mach-s3c2412/mach-jive.c
  1085. mtouchusb.raw_coordinates=
  1086. [HW] Make the MicroTouch USB driver use raw coordinates
  1087. ('y', default) or cooked coordinates ('n')
  1088. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1089. NCR_D700= [HW,SCSI]
  1090. See header of drivers/scsi/NCR_D700.c.
  1091. ncr5380= [HW,SCSI]
  1092. ncr53c400= [HW,SCSI]
  1093. ncr53c400a= [HW,SCSI]
  1094. ncr53c406a= [HW,SCSI]
  1095. ncr53c8xx= [HW,SCSI]
  1096. netdev= [NET] Network devices parameters
  1097. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1098. Note that mem_start is often overloaded to mean
  1099. something different and driver-specific.
  1100. This usage is only documented in each driver source
  1101. file if at all.
  1102. nf_conntrack.acct=
  1103. [NETFILTER] Enable connection tracking flow accounting
  1104. 0 to disable accounting
  1105. 1 to enable accounting
  1106. Default value depends on CONFIG_NF_CT_ACCT that is
  1107. going to be removed in 2.6.29.
  1108. nfsaddrs= [NFS]
  1109. See Documentation/filesystems/nfsroot.txt.
  1110. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1111. See Documentation/filesystems/nfsroot.txt.
  1112. nfs.callback_tcpport=
  1113. [NFS] set the TCP port on which the NFSv4 callback
  1114. channel should listen.
  1115. nfs.idmap_cache_timeout=
  1116. [NFS] set the maximum lifetime for idmapper cache
  1117. entries.
  1118. nfs.enable_ino64=
  1119. [NFS] enable 64-bit inode numbers.
  1120. If zero, the NFS client will fake up a 32-bit inode
  1121. number for the readdir() and stat() syscalls instead
  1122. of returning the full 64-bit number.
  1123. The default is to return 64-bit inode numbers.
  1124. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1125. when a NMI is triggered.
  1126. Format: [state][,regs][,debounce][,die]
  1127. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  1128. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1129. emulation library even if a 387 maths coprocessor
  1130. is present.
  1131. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1132. caches in the slab allocator. Saves per-node memory,
  1133. but will impact performance.
  1134. noalign [KNL,ARM]
  1135. noapic [SMP,APIC] Tells the kernel to not make use of any
  1136. IOAPICs that may be present in the system.
  1137. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1138. on "Classic" PPC cores.
  1139. nocache [ARM]
  1140. nodelayacct [KNL] Disable per-task delay accounting
  1141. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1142. nodsp [SH] Disable hardware DSP at boot time.
  1143. noefi [X86-32,X86-64] Disable EFI runtime services support.
  1144. noexec [IA-64]
  1145. noexec [X86-32,X86-64]
  1146. On X86-32 available only on PAE configured kernels.
  1147. noexec=on: enable non-executable mappings (default)
  1148. noexec=off: disable non-executable mappings
  1149. noexec32 [X86-64]
  1150. This affects only 32-bit executables.
  1151. noexec32=on: enable non-executable mappings (default)
  1152. read doesn't imply executable mappings
  1153. noexec32=off: disable non-executable mappings
  1154. read implies executable mappings
  1155. nofpu [SH] Disable hardware FPU at boot time.
  1156. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1157. register save and restore. The kernel will only save
  1158. legacy floating-point registers on task switch.
  1159. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1160. nohlt [BUGS=ARM,SH]
  1161. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1162. instruction doesn't work correctly and not to
  1163. use it.
  1164. nohalt [IA-64] Tells the kernel not to use the power saving
  1165. function PAL_HALT_LIGHT when idle. This increases
  1166. power-consumption. On the positive side, it reduces
  1167. interrupt wake-up latency, which may improve performance
  1168. in certain environments such as networked servers or
  1169. real-time systems.
  1170. nohz= [KNL] Boottime enable/disable dynamic ticks
  1171. Valid arguments: on, off
  1172. Default: on
  1173. noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
  1174. noirqdebug [X86-32] Disables the code which attempts to detect and
  1175. disable unhandled interrupt sources.
  1176. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1177. broken timer IRQ sources.
  1178. noisapnp [ISAPNP] Disables ISA PnP code.
  1179. noinitrd [RAM] Tells the kernel not to load any configured
  1180. initial RAM disk.
  1181. nointroute [IA-64]
  1182. nojitter [IA64] Disables jitter checking for ITC timers.
  1183. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1184. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1185. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1186. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  1187. default x2apic cluster mode on platforms
  1188. supporting x2apic.
  1189. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1190. lowmem mapping on PPC40x.
  1191. nomca [IA-64] Disable machine check abort handling
  1192. nomce [X86-32] Machine Check Exception
  1193. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1194. Timer usage (for AMD Geode machines).
  1195. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1196. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1197. with UP alternatives
  1198. noresidual [PPC] Don't use residual data on PReP machines.
  1199. noresume [SWSUSP] Disables resume and restores original swap
  1200. space.
  1201. no-scroll [VGA] Disables scrollback.
  1202. This is required for the Braillex ib80-piezo Braille
  1203. reader made by F.H. Papenmeier (Germany).
  1204. nosbagart [IA-64]
  1205. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1206. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1207. and disable the IO APIC. legacy for "maxcpus=0".
  1208. nosoftlockup [KNL] Disable the soft-lockup detector.
  1209. nosync [HW,M68K] Disables sync negotiation for all devices.
  1210. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1211. nousb [USB] Disable the USB subsystem
  1212. nowb [ARM]
  1213. nptcg= [IA64] Override max number of concurrent global TLB
  1214. purges which is reported from either PAL_VM_SUMMARY or
  1215. SAL PALO.
  1216. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1217. one of ['zone', 'node', 'default'] can be specified
  1218. This can be set from sysctl after boot.
  1219. See Documentation/sysctl/vm.txt for details.
  1220. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1221. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1222. Rather than timing out after 20 ms if an EC
  1223. command is not properly ACKed, override the length
  1224. of the timeout. We have interrupts disabled while
  1225. waiting for the ACK, so if this is set too high
  1226. interrupts *may* be lost!
  1227. opl3= [HW,OSS]
  1228. Format: <io>
  1229. oprofile.timer= [HW]
  1230. Use timer interrupt instead of performance counters
  1231. osst= [HW,SCSI] SCSI Tape Driver
  1232. Format: <buffer_size>,<write_threshold>
  1233. See also Documentation/scsi/st.txt.
  1234. panic= [KNL] Kernel behaviour on panic
  1235. Format: <timeout>
  1236. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1237. connected to, default is 0.
  1238. Format: <parport#>
  1239. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1240. 0 for XT, 1 for AT (default is AT).
  1241. Format: <mode>
  1242. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1243. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1244. Use 'auto' to force the driver to use any
  1245. IRQ/DMA settings detected (the default is to
  1246. ignore detected IRQ/DMA settings because of
  1247. possible conflicts). You can specify the base
  1248. address, IRQ, and DMA settings; IRQ and DMA
  1249. should be numbers, or 'auto' (for using detected
  1250. settings on that particular port), or 'nofifo'
  1251. (to avoid using a FIFO even if it is detected).
  1252. Parallel ports are assigned in the order they
  1253. are specified on the command line, starting
  1254. with parport0.
  1255. parport_init_mode= [HW,PPT]
  1256. Configure VIA parallel port to operate in
  1257. a specific mode. This is necessary on Pegasos
  1258. computer where firmware has no options for setting
  1259. up parallel port mode and sets it to spp.
  1260. Currently this function knows 686a and 8231 chips.
  1261. Format: [spp|ps2|epp|ecp|ecpepp]
  1262. pas2= [HW,OSS] Format:
  1263. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1264. pas16= [HW,SCSI]
  1265. See header of drivers/scsi/pas16.c.
  1266. pause_on_oops=
  1267. Halt all CPUs after the first oops has been printed for
  1268. the specified number of seconds. This is to be used if
  1269. your oopses keep scrolling off the screen.
  1270. pcbit= [HW,ISDN]
  1271. pcd. [PARIDE]
  1272. See header of drivers/block/paride/pcd.c.
  1273. See also Documentation/paride.txt.
  1274. pci=option[,option...] [PCI] various PCI subsystem options:
  1275. off [X86] don't probe for the PCI bus
  1276. bios [X86-32] force use of PCI BIOS, don't access
  1277. the hardware directly. Use this if your machine
  1278. has a non-standard PCI host bridge.
  1279. nobios [X86-32] disallow use of PCI BIOS, only direct
  1280. hardware access methods are allowed. Use this
  1281. if you experience crashes upon bootup and you
  1282. suspect they are caused by the BIOS.
  1283. conf1 [X86] Force use of PCI Configuration
  1284. Mechanism 1.
  1285. conf2 [X86] Force use of PCI Configuration
  1286. Mechanism 2.
  1287. noaer [PCIE] If the PCIEAER kernel config parameter is
  1288. enabled, this kernel boot option can be used to
  1289. disable the use of PCIE advanced error reporting.
  1290. nodomains [PCI] Disable support for multiple PCI
  1291. root domains (aka PCI segments, in ACPI-speak).
  1292. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1293. Configuration
  1294. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1295. enabled, this kernel boot option can be used to
  1296. disable the use of MSI interrupts system-wide.
  1297. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1298. routing table. These calls are known to be buggy
  1299. on several machines and they hang the machine
  1300. when used, but on other computers it's the only
  1301. way to get the interrupt routing table. Try
  1302. this option if the kernel is unable to allocate
  1303. IRQs or discover secondary PCI buses on your
  1304. motherboard.
  1305. rom [X86] Assign address space to expansion ROMs.
  1306. Use with caution as certain devices share
  1307. address decoders between ROMs and other
  1308. resources.
  1309. norom [X86] Do not assign address space to
  1310. expansion ROMs that do not already have
  1311. BIOS assigned address ranges.
  1312. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1313. assigned automatically to PCI devices. You can
  1314. make the kernel exclude IRQs of your ISA cards
  1315. this way.
  1316. pirqaddr=0xAAAAA [X86] Specify the physical address
  1317. of the PIRQ table (normally generated
  1318. by the BIOS) if it is outside the
  1319. F0000h-100000h range.
  1320. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1321. useful if the kernel is unable to find your
  1322. secondary buses and you want to tell it
  1323. explicitly which ones they are.
  1324. assign-busses [X86] Always assign all PCI bus
  1325. numbers ourselves, overriding
  1326. whatever the firmware may have done.
  1327. usepirqmask [X86] Honor the possible IRQ mask stored
  1328. in the BIOS $PIR table. This is needed on
  1329. some systems with broken BIOSes, notably
  1330. some HP Pavilion N5400 and Omnibook XE3
  1331. notebooks. This will have no effect if ACPI
  1332. IRQ routing is enabled.
  1333. noacpi [X86] Do not use ACPI for IRQ routing
  1334. or for PCI scanning.
  1335. use_crs [X86] Use _CRS for PCI resource
  1336. allocation.
  1337. routeirq Do IRQ routing for all PCI devices.
  1338. This is normally done in pci_enable_device(),
  1339. so this option is a temporary workaround
  1340. for broken drivers that don't call it.
  1341. skip_isa_align [X86] do not align io start addr, so can
  1342. handle more pci cards
  1343. firmware [ARM] Do not re-enumerate the bus but instead
  1344. just use the configuration from the
  1345. bootloader. This is currently used on
  1346. IXP2000 systems where the bus has to be
  1347. configured a certain way for adjunct CPUs.
  1348. noearly [X86] Don't do any early type 1 scanning.
  1349. This might help on some broken boards which
  1350. machine check when some devices' config space
  1351. is read. But various workarounds are disabled
  1352. and some IOMMU drivers will not work.
  1353. bfsort Sort PCI devices into breadth-first order.
  1354. This sorting is done to get a device
  1355. order compatible with older (<= 2.4) kernels.
  1356. nobfsort Don't sort PCI devices into breadth-first order.
  1357. cbiosize=nn[KMG] The fixed amount of bus space which is
  1358. reserved for the CardBus bridge's IO window.
  1359. The default value is 256 bytes.
  1360. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1361. reserved for the CardBus bridge's memory
  1362. window. The default value is 64 megabytes.
  1363. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1364. Management.
  1365. off Disable ASPM.
  1366. force Enable ASPM even on devices that claim not to support it.
  1367. WARNING: Forcing ASPM on may cause system lockups.
  1368. pcmv= [HW,PCMCIA] BadgePAD 4
  1369. pd. [PARIDE]
  1370. See Documentation/paride.txt.
  1371. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1372. boot time.
  1373. Format: { 0 | 1 }
  1374. See arch/parisc/kernel/pdc_chassis.c
  1375. pf. [PARIDE]
  1376. See Documentation/paride.txt.
  1377. pg. [PARIDE]
  1378. See Documentation/paride.txt.
  1379. pirq= [SMP,APIC] Manual mp-table setup
  1380. See Documentation/x86/i386/IO-APIC.txt.
  1381. plip= [PPT,NET] Parallel port network link
  1382. Format: { parport<nr> | timid | 0 }
  1383. See also Documentation/parport.txt.
  1384. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1385. Override pmtimer IOPort with a hex value.
  1386. e.g. pmtmr=0x508
  1387. pnp.debug [PNP]
  1388. Enable PNP debug messages. This depends on the
  1389. CONFIG_PNP_DEBUG_MESSAGES option.
  1390. pnpacpi= [ACPI]
  1391. { off }
  1392. pnpbios= [ISAPNP]
  1393. { on | off | curr | res | no-curr | no-res }
  1394. pnp_reserve_irq=
  1395. [ISAPNP] Exclude IRQs for the autoconfiguration
  1396. pnp_reserve_dma=
  1397. [ISAPNP] Exclude DMAs for the autoconfiguration
  1398. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1399. Ranges are in pairs (I/O port base and size).
  1400. pnp_reserve_mem=
  1401. [ISAPNP] Exclude memory regions for the
  1402. autoconfiguration.
  1403. Ranges are in pairs (memory base and size).
  1404. dynamic_printk
  1405. Enables pr_debug()/dev_dbg() calls if
  1406. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
  1407. be switched on/off via <debugfs>/dynamic_printk/modules
  1408. print-fatal-signals=
  1409. [KNL] debug: print fatal signals
  1410. print-fatal-signals=1: print segfault info to
  1411. the kernel console.
  1412. default: off.
  1413. printk.time= Show timing data prefixed to each printk message line
  1414. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1415. profile= [KNL] Enable kernel profiling via /proc/profile
  1416. Format: [schedule,]<number>
  1417. Param: "schedule" - profile schedule points.
  1418. Param: <number> - step/bucket size as a power of 2 for
  1419. statistical time based profiling.
  1420. Param: "sleep" - profile D-state sleeping (millisecs).
  1421. Requires CONFIG_SCHEDSTATS
  1422. Param: "kvm" - profile VM exits.
  1423. processor.max_cstate= [HW,ACPI]
  1424. Limit processor to maximum C-state
  1425. max_cstate=9 overrides any DMI blacklist limit.
  1426. processor.nocst [HW,ACPI]
  1427. Ignore the _CST method to determine C-states,
  1428. instead using the legacy FADT method
  1429. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1430. before loading.
  1431. See Documentation/ramdisk.txt.
  1432. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1433. probe for; one of (bare|imps|exps|lifebook|any).
  1434. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1435. per second.
  1436. psmouse.resetafter= [HW,MOUSE]
  1437. Try to reset the device after so many bad packets
  1438. (0 = never).
  1439. psmouse.resolution=
  1440. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1441. psmouse.smartscroll=
  1442. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1443. 0 = disabled, 1 = enabled (default).
  1444. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1445. Format:
  1446. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1447. pt. [PARIDE]
  1448. See Documentation/paride.txt.
  1449. pty.legacy_count=
  1450. [KNL] Number of legacy pty's. Overwrites compiled-in
  1451. default number.
  1452. quiet [KNL] Disable most log messages
  1453. r128= [HW,DRM]
  1454. raid= [HW,RAID]
  1455. See Documentation/md.txt.
  1456. ramdisk_blocksize= [RAM]
  1457. See Documentation/ramdisk.txt.
  1458. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1459. See Documentation/ramdisk.txt.
  1460. rcupdate.blimit= [KNL,BOOT]
  1461. Set maximum number of finished RCU callbacks to process
  1462. in one batch.
  1463. rcupdate.qhimark= [KNL,BOOT]
  1464. Set threshold of queued
  1465. RCU callbacks over which batch limiting is disabled.
  1466. rcupdate.qlowmark= [KNL,BOOT]
  1467. Set threshold of queued RCU callbacks below which
  1468. batch limiting is re-enabled.
  1469. rdinit= [KNL]
  1470. Format: <full_path>
  1471. Run specified binary instead of /init from the ramdisk,
  1472. used for early userspace startup. See initrd.
  1473. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1474. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1475. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1476. relax_domain_level=
  1477. [KNL, SMP] Set scheduler's default relax_domain_level.
  1478. See Documentation/cpusets.txt.
  1479. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1480. reservetop= [X86-32]
  1481. Format: nn[KMG]
  1482. Reserves a hole at the top of the kernel virtual
  1483. address space.
  1484. reset_devices [KNL] Force drivers to reset the underlying device
  1485. during initialization.
  1486. resume= [SWSUSP]
  1487. Specify the partition device for software suspend
  1488. resume_offset= [SWSUSP]
  1489. Specify the offset from the beginning of the partition
  1490. given by "resume=" at which the swap header is located,
  1491. in <PAGE_SIZE> units (needed only for swap files).
  1492. See Documentation/power/swsusp-and-swap-files.txt
  1493. retain_initrd [RAM] Keep initrd memory after extraction
  1494. rhash_entries= [KNL,NET]
  1495. Set number of hash buckets for route cache
  1496. riscom8= [HW,SERIAL]
  1497. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1498. ro [KNL] Mount root device read-only on boot
  1499. root= [KNL] Root filesystem
  1500. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1501. mount the root filesystem
  1502. rootflags= [KNL] Set root filesystem mount option string
  1503. rootfstype= [KNL] Set root filesystem type
  1504. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1505. Useful for devices that are detected asynchronously
  1506. (e.g. USB and MMC devices).
  1507. root_plug.vendor_id=
  1508. [ROOTPLUG] Override the default vendor ID
  1509. root_plug.product_id=
  1510. [ROOTPLUG] Override the default product ID
  1511. root_plug.debug=
  1512. [ROOTPLUG] Enable debugging output
  1513. rw [KNL] Mount root device read-write on boot
  1514. S [KNL] Run init in single mode
  1515. sa1100ir [NET]
  1516. See drivers/net/irda/sa1100_ir.c.
  1517. sbni= [NET] Granch SBNI12 leased line adapter
  1518. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1519. Format: <io>[,<timeout>[,<isapnp>]]
  1520. scsi_debug_*= [SCSI]
  1521. See drivers/scsi/scsi_debug.c.
  1522. scsi_default_dev_flags=
  1523. [SCSI] SCSI default device flags
  1524. Format: <integer>
  1525. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1526. Format: <vendor>:<model>:<flags>
  1527. (flags are integer value)
  1528. scsi_logging_level= [SCSI] a bit mask of logging levels
  1529. See drivers/scsi/scsi_logging.h for bits. Also
  1530. settable via sysctl at dev.scsi.logging_level
  1531. (/proc/sys/dev/scsi/logging_level).
  1532. There is also a nice 'scsi_logging_level' script in the
  1533. S390-tools package, available for download at
  1534. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1535. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1536. discovered. async scans them in kernel threads,
  1537. allowing boot to proceed. none ignores them, expecting
  1538. user space to do the scan.
  1539. selinux [SELINUX] Disable or enable SELinux at boot time.
  1540. Format: { "0" | "1" }
  1541. See security/selinux/Kconfig help text.
  1542. 0 -- disable.
  1543. 1 -- enable.
  1544. Default value is set via kernel config option.
  1545. If enabled at boot time, /selinux/disable can be used
  1546. later to disable prior to initial policy load.
  1547. selinux_compat_net =
  1548. [SELINUX] Set initial selinux_compat_net flag value.
  1549. Format: { "0" | "1" }
  1550. 0 -- use new secmark-based packet controls
  1551. 1 -- use legacy packet controls
  1552. Default value is 0 (preferred).
  1553. Value can be changed at runtime via
  1554. /selinux/compat_net.
  1555. serialnumber [BUGS=X86-32]
  1556. shapers= [NET]
  1557. Maximal number of shapers.
  1558. show_msr= [x86] show boot-time MSR settings
  1559. Format: { <integer> }
  1560. Show boot-time (BIOS-initialized) MSR settings.
  1561. The parameter means the number of CPUs to show,
  1562. for example 1 means boot CPU only.
  1563. sim710= [SCSI,HW]
  1564. See header of drivers/scsi/sim710.c.
  1565. simeth= [IA-64]
  1566. simscsi=
  1567. slram= [HW,MTD]
  1568. slub_debug[=options[,slabs]] [MM, SLUB]
  1569. Enabling slub_debug allows one to determine the
  1570. culprit if slab objects become corrupted. Enabling
  1571. slub_debug can create guard zones around objects and
  1572. may poison objects when not in use. Also tracks the
  1573. last alloc / free. For more information see
  1574. Documentation/vm/slub.txt.
  1575. slub_max_order= [MM, SLUB]
  1576. Determines the maximum allowed order for slabs.
  1577. A high setting may cause OOMs due to memory
  1578. fragmentation. For more information see
  1579. Documentation/vm/slub.txt.
  1580. slub_min_objects= [MM, SLUB]
  1581. The minimum number of objects per slab. SLUB will
  1582. increase the slab order up to slub_max_order to
  1583. generate a sufficiently large slab able to contain
  1584. the number of objects indicated. The higher the number
  1585. of objects the smaller the overhead of tracking slabs
  1586. and the less frequently locks need to be acquired.
  1587. For more information see Documentation/vm/slub.txt.
  1588. slub_min_order= [MM, SLUB]
  1589. Determines the mininum page order for slabs. Must be
  1590. lower than slub_max_order.
  1591. For more information see Documentation/vm/slub.txt.
  1592. slub_nomerge [MM, SLUB]
  1593. Disable merging of slabs with similar size. May be
  1594. necessary if there is some reason to distinguish
  1595. allocs to different slabs. Debug options disable
  1596. merging on their own.
  1597. For more information see Documentation/vm/slub.txt.
  1598. smart2= [HW]
  1599. Format: <io1>[,<io2>[,...,<io8>]]
  1600. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1601. attempt to substitute SMP alternatives once at boot.
  1602. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1603. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1604. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1605. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1606. smsc-ircc2.ircc_irq= [HW] IRQ line
  1607. smsc-ircc2.ircc_dma= [HW] DMA channel
  1608. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1609. 0: Toshiba Satellite 1800 (GP data pin select)
  1610. 1: Fast pin select (default)
  1611. 2: ATC IRMode
  1612. snd-ad1816a= [HW,ALSA]
  1613. snd-ad1848= [HW,ALSA]
  1614. snd-ali5451= [HW,ALSA]
  1615. snd-als100= [HW,ALSA]
  1616. snd-als4000= [HW,ALSA]
  1617. snd-azt2320= [HW,ALSA]
  1618. snd-cmi8330= [HW,ALSA]
  1619. snd-cmipci= [HW,ALSA]
  1620. snd-cs4231= [HW,ALSA]
  1621. snd-cs4232= [HW,ALSA]
  1622. snd-cs4236= [HW,ALSA]
  1623. snd-cs4281= [HW,ALSA]
  1624. snd-cs46xx= [HW,ALSA]
  1625. snd-dt019x= [HW,ALSA]
  1626. snd-dummy= [HW,ALSA]
  1627. snd-emu10k1= [HW,ALSA]
  1628. snd-ens1370= [HW,ALSA]
  1629. snd-ens1371= [HW,ALSA]
  1630. snd-es968= [HW,ALSA]
  1631. snd-es1688= [HW,ALSA]
  1632. snd-es18xx= [HW,ALSA]
  1633. snd-es1938= [HW,ALSA]
  1634. snd-es1968= [HW,ALSA]
  1635. snd-fm801= [HW,ALSA]
  1636. snd-gusclassic= [HW,ALSA]
  1637. snd-gusextreme= [HW,ALSA]
  1638. snd-gusmax= [HW,ALSA]
  1639. snd-hdsp= [HW,ALSA]
  1640. snd-ice1712= [HW,ALSA]
  1641. snd-intel8x0= [HW,ALSA]
  1642. snd-interwave= [HW,ALSA]
  1643. snd-interwave-stb=
  1644. [HW,ALSA]
  1645. snd-korg1212= [HW,ALSA]
  1646. snd-maestro3= [HW,ALSA]
  1647. snd-mpu401= [HW,ALSA]
  1648. snd-mtpav= [HW,ALSA]
  1649. snd-nm256= [HW,ALSA]
  1650. snd-opl3sa2= [HW,ALSA]
  1651. snd-opti92x-ad1848=
  1652. [HW,ALSA]
  1653. snd-opti92x-cs4231=
  1654. [HW,ALSA]
  1655. snd-opti93x= [HW,ALSA]
  1656. snd-pmac= [HW,ALSA]
  1657. snd-rme32= [HW,ALSA]
  1658. snd-rme96= [HW,ALSA]
  1659. snd-rme9652= [HW,ALSA]
  1660. snd-sb8= [HW,ALSA]
  1661. snd-sb16= [HW,ALSA]
  1662. snd-sbawe= [HW,ALSA]
  1663. snd-serial= [HW,ALSA]
  1664. snd-sgalaxy= [HW,ALSA]
  1665. snd-sonicvibes= [HW,ALSA]
  1666. snd-sun-amd7930=
  1667. [HW,ALSA]
  1668. snd-sun-cs4231= [HW,ALSA]
  1669. snd-trident= [HW,ALSA]
  1670. snd-usb-audio= [HW,ALSA,USB]
  1671. snd-via82xx= [HW,ALSA]
  1672. snd-virmidi= [HW,ALSA]
  1673. snd-wavefront= [HW,ALSA]
  1674. snd-ymfpci= [HW,ALSA]
  1675. softlockup_panic=
  1676. [KNL] Should the soft-lockup detector generate panics.
  1677. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1678. See Documentation/sonypi.txt
  1679. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1680. See Documentation/specialix.txt.
  1681. spia_io_base= [HW,MTD]
  1682. spia_fio_base=
  1683. spia_pedr=
  1684. spia_peddr=
  1685. sscape= [HW,OSS]
  1686. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1687. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1688. See Documentation/scsi/st.txt.
  1689. sti= [PARISC,HW]
  1690. Format: <num>
  1691. Set the STI (builtin display/keyboard on the HP-PARISC
  1692. machines) console (graphic card) which should be used
  1693. as the initial boot-console.
  1694. See also comment in drivers/video/console/sticore.c.
  1695. sti_font= [HW]
  1696. See comment in drivers/video/console/sticore.c.
  1697. stifb= [HW]
  1698. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1699. sunrpc.pool_mode=
  1700. [NFS]
  1701. Control how the NFS server code allocates CPUs to
  1702. service thread pools. Depending on how many NICs
  1703. you have and where their interrupts are bound, this
  1704. option will affect which CPUs will do NFS serving.
  1705. Note: this parameter cannot be changed while the
  1706. NFS server is running.
  1707. auto the server chooses an appropriate mode
  1708. automatically using heuristics
  1709. global a single global pool contains all CPUs
  1710. percpu one pool for each CPU
  1711. pernode one pool for each NUMA node (equivalent
  1712. to global on non-NUMA machines)
  1713. swiotlb= [IA-64] Number of I/O TLB slabs
  1714. switches= [HW,M68k]
  1715. sym53c416= [HW,SCSI]
  1716. See header of drivers/scsi/sym53c416.c.
  1717. sysrq_always_enabled
  1718. [KNL]
  1719. Ignore sysrq setting - this boot parameter will
  1720. neutralize any effect of /proc/sys/kernel/sysrq.
  1721. Useful for debugging.
  1722. t128= [HW,SCSI]
  1723. See header of drivers/scsi/t128.c.
  1724. tdfx= [HW,DRM]
  1725. test_suspend= [SUSPEND]
  1726. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1727. standby suspend) as the system sleep state to briefly
  1728. enter during system startup. The system is woken from
  1729. this state using a wakeup-capable RTC alarm.
  1730. thash_entries= [KNL,NET]
  1731. Set number of hash buckets for TCP connection
  1732. thermal.act= [HW,ACPI]
  1733. -1: disable all active trip points in all thermal zones
  1734. <degrees C>: override all lowest active trip points
  1735. thermal.crt= [HW,ACPI]
  1736. -1: disable all critical trip points in all thermal zones
  1737. <degrees C>: override all critical trip points
  1738. thermal.nocrt= [HW,ACPI]
  1739. Set to disable actions on ACPI thermal zone
  1740. critical and hot trip points.
  1741. thermal.off= [HW,ACPI]
  1742. 1: disable ACPI thermal control
  1743. thermal.psv= [HW,ACPI]
  1744. -1: disable all passive trip points
  1745. <degrees C>: override all passive trip points to this value
  1746. thermal.tzp= [HW,ACPI]
  1747. Specify global default ACPI thermal zone polling rate
  1748. <deci-seconds>: poll all this frequency
  1749. 0: no polling (default)
  1750. tmscsim= [HW,SCSI]
  1751. See comment before function dc390_setup() in
  1752. drivers/scsi/tmscsim.c.
  1753. tp720= [HW,PS2]
  1754. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1755. Format:
  1756. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1757. turbografx.map[2|3]= [HW,JOY]
  1758. TurboGraFX parallel port interface
  1759. Format:
  1760. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1761. See also Documentation/input/joystick-parport.txt
  1762. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1763. See header of drivers/scsi/u14-34f.c.
  1764. uart401= [HW,OSS]
  1765. Format: <io>,<irq>
  1766. uart6850= [HW,OSS]
  1767. Format: <io>,<irq>
  1768. uhci-hcd.ignore_oc=
  1769. [USB] Ignore overcurrent events (default N).
  1770. Some badly-designed motherboards generate lots of
  1771. bogus events, for ports that aren't wired to
  1772. anything. Set this parameter to avoid log spamming.
  1773. Note that genuine overcurrent events won't be
  1774. reported either.
  1775. unknown_nmi_panic
  1776. [X86-32,X86-64]
  1777. Set unknown_nmi_panic=1 early on boot.
  1778. usbcore.autosuspend=
  1779. [USB] The autosuspend time delay (in seconds) used
  1780. for newly-detected USB devices (default 2). This
  1781. is the time required before an idle device will be
  1782. autosuspended. Devices for which the delay is set
  1783. to a negative value won't be autosuspended at all.
  1784. usbcore.usbfs_snoop=
  1785. [USB] Set to log all usbfs traffic (default 0 = off).
  1786. usbcore.blinkenlights=
  1787. [USB] Set to cycle leds on hubs (default 0 = off).
  1788. usbcore.old_scheme_first=
  1789. [USB] Start with the old device initialization
  1790. scheme (default 0 = off).
  1791. usbcore.use_both_schemes=
  1792. [USB] Try the other device initialization scheme
  1793. if the first one fails (default 1 = enabled).
  1794. usbcore.initial_descriptor_timeout=
  1795. [USB] Specifies timeout for the initial 64-byte
  1796. USB_REQ_GET_DESCRIPTOR request in milliseconds
  1797. (default 5000 = 5.0 seconds).
  1798. usbhid.mousepoll=
  1799. [USBHID] The interval which mice are to be polled at.
  1800. add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
  1801. kernel's map of available physical RAM.
  1802. vdso= [X86-32,SH,x86-64]
  1803. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1804. vdso=1: enable VDSO (default)
  1805. vdso=0: disable VDSO mapping
  1806. vdso32= [X86-32,X86-64]
  1807. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1808. vdso32=1: enable 32-bit VDSO (default)
  1809. vdso32=0: disable 32-bit VDSO mapping
  1810. vector= [IA-64,SMP]
  1811. vector=percpu: enable percpu vector domain
  1812. video= [FB] Frame buffer configuration
  1813. See Documentation/fb/modedb.txt.
  1814. vga= [BOOT,X86-32] Select a particular video mode
  1815. See Documentation/x86/i386/boot.txt and
  1816. Documentation/svga.txt.
  1817. Use vga=ask for menu.
  1818. This is actually a boot loader parameter; the value is
  1819. passed to the kernel using a special protocol.
  1820. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1821. size of <nn>. This can be used to increase the
  1822. minimum size (128MB on x86). It can also be used to
  1823. decrease the size and leave more room for directly
  1824. mapped kernel RAM.
  1825. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1826. Format: <command>
  1827. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1828. Format: <command>
  1829. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1830. Format: <command>
  1831. waveartist= [HW,OSS]
  1832. Format: <io>,<irq>,<dma>,<dma2>
  1833. wd33c93= [HW,SCSI]
  1834. See header of drivers/scsi/wd33c93.c.
  1835. wd7000= [HW,SCSI]
  1836. See header of drivers/scsi/wd7000.c.
  1837. wdt= [WDT] Watchdog
  1838. See Documentation/watchdog/wdt.txt.
  1839. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1840. xd_geo= See header of drivers/block/xd.c.
  1841. xirc2ps_cs= [NET,PCMCIA]
  1842. Format:
  1843. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1844. norandmaps Don't use address space randomization
  1845. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1846. ______________________________________________________________________
  1847. TODO:
  1848. Add documentation for ALSA options.
  1849. Add more DRM drivers.