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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. DM Device mapper support is enabled.
  37. DRM Direct Rendering Management support is enabled.
  38. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  39. EFI EFI Partitioning (GPT) is enabled
  40. EIDE EIDE/ATAPI support is enabled.
  41. FB The frame buffer device is enabled.
  42. GCOV GCOV profiling is enabled.
  43. HW Appropriate hardware is enabled.
  44. IA-64 IA-64 architecture is enabled.
  45. IMA Integrity measurement architecture is enabled.
  46. IOSCHED More than one I/O scheduler is enabled.
  47. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  48. ISAPNP ISA PnP code is enabled.
  49. ISDN Appropriate ISDN support is enabled.
  50. JOY Appropriate joystick support is enabled.
  51. KVM Kernel Virtual Machine support is enabled.
  52. LIBATA Libata driver is enabled
  53. LP Printer support is enabled.
  54. LOOP Loopback device support is enabled.
  55. M68k M68k architecture is enabled.
  56. These options have more detailed description inside of
  57. Documentation/m68k/kernel-options.txt.
  58. MCA MCA bus support is enabled.
  59. MDA MDA console support is enabled.
  60. MOUSE Appropriate mouse support is enabled.
  61. MSI Message Signaled Interrupts (PCI).
  62. MTD MTD (Memory Technology Device) support is enabled.
  63. NET Appropriate network support is enabled.
  64. NUMA NUMA support is enabled.
  65. GENERIC_TIME The generic timeofday code is enabled.
  66. NFS Appropriate NFS support is enabled.
  67. OSS OSS sound support is enabled.
  68. PV_OPS A paravirtualized kernel is enabled.
  69. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  70. PARISC The PA-RISC architecture is enabled.
  71. PCI PCI bus support is enabled.
  72. PCIE PCI Express support is enabled.
  73. PCMCIA The PCMCIA subsystem is enabled.
  74. PNP Plug & Play support is enabled.
  75. PPC PowerPC architecture is enabled.
  76. PPT Parallel port support is enabled.
  77. PS2 Appropriate PS/2 support is enabled.
  78. RAM RAM disk support is enabled.
  79. ROOTPLUG The example Root Plug LSM is enabled.
  80. S390 S390 architecture is enabled.
  81. SCSI Appropriate SCSI support is enabled.
  82. A lot of drivers has their options described inside of
  83. Documentation/scsi/.
  84. SECURITY Different security models are enabled.
  85. SELINUX SELinux support is enabled.
  86. SERIAL Serial support is enabled.
  87. SH SuperH architecture is enabled.
  88. SMP The kernel is an SMP kernel.
  89. SPARC Sparc architecture is enabled.
  90. SWSUSP Software suspend (hibernation) is enabled.
  91. SUSPEND System suspend states are enabled.
  92. FTRACE Function tracing enabled.
  93. TS Appropriate touchscreen support is enabled.
  94. UMS USB Mass Storage support is enabled.
  95. USB USB support is enabled.
  96. USBHID USB Human Interface Device support is enabled.
  97. V4L Video For Linux support is enabled.
  98. VGA The VGA console has been enabled.
  99. VT Virtual terminal support is enabled.
  100. WDT Watchdog support is enabled.
  101. XT IBM PC/XT MFM hard disk support is enabled.
  102. X86-32 X86-32, aka i386 architecture is enabled.
  103. X86-64 X86-64 architecture is enabled.
  104. More X86-64 boot options can be found in
  105. Documentation/x86/x86_64/boot-options.txt .
  106. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  107. In addition, the following text indicates that the option:
  108. BUGS= Relates to possible processor bugs on the said processor.
  109. KNL Is a kernel start-up parameter.
  110. BOOT Is a boot loader parameter.
  111. Parameters denoted with BOOT are actually interpreted by the boot
  112. loader, and have no meaning to the kernel directly.
  113. Do not modify the syntax of boot loader parameters without extreme
  114. need or coordination with <Documentation/x86/boot.txt>.
  115. There are also arch-specific kernel-parameters not documented here.
  116. See for example <Documentation/x86/x86_64/boot-options.txt>.
  117. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  118. a trailing = on the name of any parameter states that that parameter will
  119. be entered as an environment variable, whereas its absence indicates that
  120. it will appear as a kernel argument readable via /proc/cmdline by programs
  121. running once the system is up.
  122. The number of kernel parameters is not limited, but the length of the
  123. complete command line (parameters including spaces etc.) is limited to
  124. a fixed number of characters. This limit depends on the architecture
  125. and is between 256 and 4096 characters. It is defined in the file
  126. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  127. acpi= [HW,ACPI,X86]
  128. Advanced Configuration and Power Interface
  129. Format: { force | off | ht | strict | noirq | rsdt }
  130. force -- enable ACPI if default was off
  131. off -- disable ACPI if default was on
  132. noirq -- do not use ACPI for IRQ routing
  133. ht -- run only enough ACPI to enable Hyper Threading
  134. strict -- Be less tolerant of platforms that are not
  135. strictly ACPI specification compliant.
  136. rsdt -- prefer RSDT over (default) XSDT
  137. See also Documentation/power/pm.txt, pci=noacpi
  138. acpi_apic_instance= [ACPI, IOAPIC]
  139. Format: <int>
  140. 2: use 2nd APIC table, if available
  141. 1,0: use 1st APIC table
  142. default: 0
  143. acpi_backlight= [HW,ACPI]
  144. acpi_backlight=vendor
  145. acpi_backlight=video
  146. If set to vendor, prefer vendor specific driver
  147. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  148. of the ACPI video.ko driver.
  149. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  150. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  151. Format: <int>
  152. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  153. debug output. Bits in debug_layer correspond to a
  154. _COMPONENT in an ACPI source file, e.g.,
  156. Bits in debug_level correspond to a level in
  157. ACPI_DEBUG_PRINT statements, e.g.,
  159. The debug_level mask defaults to "info". See
  160. Documentation/acpi/debug.txt for more information about
  161. debug layers and levels.
  162. Enable processor driver info messages:
  163. acpi.debug_layer=0x20000000
  164. Enable PCI/PCI interrupt routing info messages:
  165. acpi.debug_layer=0x400000
  166. Enable AML "Debug" output, i.e., stores to the Debug
  167. object while interpreting AML:
  168. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  169. Enable all messages related to ACPI hardware:
  170. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  171. Some values produce so much output that the system is
  172. unusable. The "log_buf_len" parameter may be useful
  173. if you need to capture more output.
  174. acpi_display_output= [HW,ACPI]
  175. acpi_display_output=vendor
  176. acpi_display_output=video
  177. See above.
  178. acpi_irq_balance [HW,ACPI]
  179. ACPI will balance active IRQs
  180. default in APIC mode
  181. acpi_irq_nobalance [HW,ACPI]
  182. ACPI will not move active IRQs (default)
  183. default in PIC mode
  184. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  185. Format: <irq>,<irq>...
  186. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  187. use by PCI
  188. Format: <irq>,<irq>...
  189. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  190. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  191. Format: To spoof as Windows 98: ="Microsoft Windows"
  192. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  193. acpi_osi="string1" # add string1 -- only one string
  194. acpi_osi="!string2" # remove built-in string2
  195. acpi_osi= # disable all strings
  196. acpi_pm_good [X86]
  197. Override the pmtimer bug detection: force the kernel
  198. to assume that this machine's pmtimer latches its value
  199. and always returns good values.
  200. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  201. Format: { level | edge | high | low }
  202. acpi_serialize [HW,ACPI] force serialization of AML methods
  203. acpi_skip_timer_override [HW,ACPI]
  204. Recognize and ignore IRQ0/pin2 Interrupt Override.
  205. For broken nForce2 BIOS resulting in XT-PIC timer.
  206. acpi_sleep= [HW,ACPI] Sleep options
  207. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
  208. old_ordering, s4_nonvs, sci_force_enable }
  209. See Documentation/power/video.txt for information on
  210. s3_bios and s3_mode.
  211. s3_beep is for debugging; it makes the PC's speaker beep
  212. as soon as the kernel's real-mode entry point is called.
  213. s4_nohwsig prevents ACPI hardware signature from being
  214. used during resume from hibernation.
  215. old_ordering causes the ACPI 1.0 ordering of the _PTS
  216. control method, with respect to putting devices into
  217. low power states, to be enforced (the ACPI 2.0 ordering
  218. of _PTS is used by default).
  219. s4_nonvs prevents the kernel from saving/restoring the
  220. ACPI NVS memory during hibernation.
  221. sci_force_enable causes the kernel to set SCI_EN directly
  222. on resume from S1/S3 (which is against the ACPI spec,
  223. but some broken systems don't work without it).
  224. acpi_use_timer_override [HW,ACPI]
  225. Use timer override. For some broken Nvidia NF5 boards
  226. that require a timer override, but don't have HPET
  227. acpi_enforce_resources= [ACPI]
  228. { strict | lax | no }
  229. Check for resource conflicts between native drivers
  230. and ACPI OperationRegions (SystemIO and SystemMemory
  231. only). IO ports and memory declared in ACPI might be
  232. used by the ACPI subsystem in arbitrary AML code and
  233. can interfere with legacy drivers.
  234. strict (default): access to resources claimed by ACPI
  235. is denied; legacy drivers trying to access reserved
  236. resources will fail to bind to device using them.
  237. lax: access to resources claimed by ACPI is allowed;
  238. legacy drivers trying to access reserved resources
  239. will bind successfully but a warning message is logged.
  240. no: ACPI OperationRegions are not marked as reserved,
  241. no further checks are performed.
  242. ad1848= [HW,OSS]
  243. Format: <io>,<irq>,<dma>,<dma2>,<type>
  244. add_efi_memmap [EFI; X86] Include EFI memory map in
  245. kernel's map of available physical RAM.
  246. advansys= [HW,SCSI]
  247. See header of drivers/scsi/advansys.c.
  248. advwdt= [HW,WDT] Advantech WDT
  249. Format: <iostart>,<iostop>
  250. aedsp16= [HW,OSS] Audio Excel DSP 16
  251. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  252. See also header of sound/oss/aedsp16.c.
  253. agp= [AGP]
  254. { off | try_unsupported }
  255. off: disable AGP support
  256. try_unsupported: try to drive unsupported chipsets
  257. (may crash computer or cause data corruption)
  258. aha152x= [HW,SCSI]
  259. See Documentation/scsi/aha152x.txt.
  260. aha1542= [HW,SCSI]
  261. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  262. aic7xxx= [HW,SCSI]
  263. See Documentation/scsi/aic7xxx.txt.
  264. aic79xx= [HW,SCSI]
  265. See Documentation/scsi/aic79xx.txt.
  266. amd_iommu= [HW,X86-84]
  267. Pass parameters to the AMD IOMMU driver in the system.
  268. Possible values are:
  269. isolate - enable device isolation (each device, as far
  270. as possible, will get its own protection
  271. domain) [default]
  272. share - put every device behind one IOMMU into the
  273. same protection domain
  274. fullflush - enable flushing of IO/TLB entries when
  275. they are unmapped. Otherwise they are
  276. flushed before they will be reused, which
  277. is a lot of faster
  278. [HW,JOY] Amiga joystick support
  279. Map of devices attached to JOY0DAT and JOY1DAT
  280. Format: <a>,<b>
  281. See also Documentation/kernel/input/joystick.txt
  282. [HW,JOY] Analog joystick and gamepad support
  283. Specifies type or capabilities of an analog joystick
  284. connected to one of 16 gameports
  285. Format: <type1>,<type2>,..<type16>
  286. apc= [HW,SPARC]
  287. Power management functions (SPARCstation-4/5 + deriv.)
  288. Format: noidle
  289. Disable APC CPU standby support. SPARCstation-Fox does
  290. not play well with APC CPU idle - disable it if you have
  291. APC and your system crashes randomly.
  292. apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
  293. Change the output verbosity whilst booting
  294. Format: { quiet (default) | verbose | debug }
  295. Change the amount of debugging information output
  296. when initialising the APIC and IO-APIC components.
  297. apm= [APM] Advanced Power Management
  298. See header of arch/x86/kernel/apm_32.c.
  299. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  300. Format: <io>,<irq>,<nodeID>
  301. ataflop= [HW,M68k]
  302. atarimouse= [HW,MOUSE] Atari Mouse
  303. atascsi= [HW,SCSI] Atari SCSI
  304. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  305. EzKey and similar keyboards
  306. atkbd.reset= [HW] Reset keyboard during initialization
  307. atkbd.set= [HW] Select keyboard code set
  308. Format: <int> (2 = AT (default), 3 = PS/2)
  309. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  310. keyboards
  311. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  312. Format: <bool> (0 = real, 1 = synthetic (default))
  313. atkbd.softrepeat= [HW]
  314. Use software keyboard repeat
  315. autotest [IA64]
  316. baycom_epp= [HW,AX25]
  317. Format: <io>,<mode>
  318. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  319. Format: <io>,<mode>
  320. See header of drivers/net/hamradio/baycom_par.c.
  321. baycom_ser_fdx= [HW,AX25]
  322. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  323. Format: <io>,<irq>,<mode>[,<baud>]
  324. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  325. baycom_ser_hdx= [HW,AX25]
  326. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  327. Format: <io>,<irq>,<mode>
  328. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  329. boot_delay= Milliseconds to delay each printk during boot.
  330. Values larger than 10 seconds (10000) are changed to
  331. no delay (0).
  332. Format: integer
  333. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  334. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  335. Most important insmod options are available as
  336. kernel args too.
  337. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  338. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  339. BusLogic= [HW,SCSI]
  340. See drivers/scsi/BusLogic.c, comment before function
  341. BusLogic_ParseDriverOptions().
  342. c101= [NET] Moxa C101 synchronous serial card
  343. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  344. Sometimes CPU hardware bugs make them report the cache
  345. size incorrectly. The kernel will attempt work arounds
  346. to fix known problems, but for some CPUs it is not
  347. possible to determine what the correct size should be.
  348. This option provides an override for these situations.
  349. capability.disable=
  350. [SECURITY] Disable capabilities. This would normally
  351. be used only if an alternative security model is to be
  352. configured. Potentially dangerous and should only be
  353. used if you are entirely sure of the consequences.
  354. ccw_timeout_log [S390]
  355. See Documentation/s390/CommonIO for details.
  356. cgroup_disable= [KNL] Disable a particular controller
  357. Format: {name of the controller(s) to disable}
  358. {Currently supported controllers - "memory"}
  359. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  360. Format: { "0" | "1" }
  361. See security/selinux/Kconfig help text.
  362. 0 -- check protection applied by kernel (includes
  363. any implied execute protection).
  364. 1 -- check protection requested by application.
  365. Default value is set via a kernel config option.
  366. Value can be changed at runtime via
  367. /selinux/checkreqprot.
  368. cio_ignore= [S390]
  369. See Documentation/s390/CommonIO for details.
  370. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  371. [Deprecated]
  372. Forces specified clocksource (if available) to be used
  373. when calculating gettimeofday(). If specified
  374. clocksource is not available, it defaults to PIT.
  375. Format: { pit | tsc | cyclone | pmtmr }
  376. clocksource= [GENERIC_TIME] Override the default clocksource
  377. Format: <string>
  378. Override the default clocksource and use the clocksource
  379. with the name specified.
  380. Some clocksource names to choose from, depending on
  381. the platform:
  382. [all] jiffies (this is the base, fallback clocksource)
  383. [ACPI] acpi_pm
  384. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  385. pxa_timer,timer3,32k_counter,timer0_1
  386. [AVR32] avr32
  387. [X86-32] pit,hpet,tsc,vmi-timer;
  388. scx200_hrt on Geode; cyclone on IBM x440
  389. [MIPS] MIPS
  390. [PARISC] cr16
  391. [S390] tod
  392. [SH] SuperH
  393. [SPARC64] tick
  394. [X86-64] hpet,tsc
  395. clearcpuid=BITNUM [X86]
  396. Disable CPUID feature X for the kernel. See
  397. arch/x86/include/asm/cpufeature.h for the valid bit
  398. numbers. Note the Linux specific bits are not necessarily
  399. stable over kernel options, but the vendor specific
  400. ones should be.
  401. Also note that user programs calling CPUID directly
  402. or using the feature without checking anything
  403. will still see it. This just prevents it from
  404. being used by the kernel or shown in /proc/cpuinfo.
  405. Also note the kernel might malfunction if you disable
  406. some critical bits.
  407. cmo_free_hint= [PPC] Format: { yes | no }
  408. Specify whether pages are marked as being inactive
  409. when they are freed. This is used in CMO environments
  410. to determine OS memory pressure for page stealing by
  411. a hypervisor.
  412. Default: yes
  413. code_bytes [X86] How many bytes of object code to print
  414. in an oops report.
  415. Range: 0 - 8192
  416. Default: 64
  417. com20020= [HW,NET] ARCnet - COM20020 chipset
  418. Format:
  419. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  420. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  421. Format: <io>[,<irq>]
  422. com90xx= [HW,NET]
  423. ARCnet - COM90xx chipset (memory-mapped buffers)
  424. Format: <io>[,<irq>[,<memstart>]]
  425. condev= [HW,S390] console device
  426. conmode=
  427. console= [KNL] Output console device and options.
  428. tty<n> Use the virtual console device <n>.
  429. ttyS<n>[,options]
  430. ttyUSB0[,options]
  431. Use the specified serial port. The options are of
  432. the form "bbbbpnf", where "bbbb" is the baud rate,
  433. "p" is parity ("n", "o", or "e"), "n" is number of
  434. bits, and "f" is flow control ("r" for RTS or
  435. omit it). Default is "9600n8".
  436. See Documentation/serial-console.txt for more
  437. information. See
  438. Documentation/networking/netconsole.txt for an
  439. alternative.
  440. uart[8250],io,<addr>[,options]
  441. uart[8250],mmio,<addr>[,options]
  442. Start an early, polled-mode console on the 8250/16550
  443. UART at the specified I/O port or MMIO address,
  444. switching to the matching ttyS device later. The
  445. options are the same as for ttyS, above.
  446. If the device connected to the port is not a TTY but a braille
  447. device, prepend "brl," before the device type, for instance
  448. console=brl,ttyS0
  449. For now, only VisioBraille is supported.
  450. consoleblank= [KNL] The console blank (screen saver) timeout in
  451. seconds. Defaults to 10*60 = 10mins. A value of 0
  452. disables the blank timer.
  453. coredump_filter=
  454. [KNL] Change the default value for
  455. /proc/<pid>/coredump_filter.
  456. See also Documentation/filesystems/proc.txt.
  457. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  458. Format:
  459. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  460. crashkernel=nn[KMG]@ss[KMG]
  461. [KNL] Reserve a chunk of physical memory to
  462. hold a kernel to switch to with kexec on panic.
  463. crashkernel=range1:size1[,range2:size2,...][@offset]
  464. [KNL] Same as above, but depends on the memory
  465. in the running system. The syntax of range is
  466. start-[end] where start and end are both
  467. a memory unit (amount[KMG]). See also
  468. Documentation/kdump/kdump.txt for a example.
  469. cs89x0_dma= [HW,NET]
  470. Format: <dma>
  471. cs89x0_media= [HW,NET]
  472. Format: { rj45 | aui | bnc }
  473. dasd= [HW,NET]
  474. See header of drivers/s390/block/dasd_devmap.c.
  475.[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  476. (one device per port)
  477. Format: <port#>,<type>
  478. See also Documentation/input/joystick-parport.txt
  479. debug [KNL] Enable kernel debugging (events log level).
  480. debug_locks_verbose=
  481. [KNL] verbose self-tests
  482. Format=<0|1>
  483. Print debugging info while doing the locking API
  484. self-tests.
  485. We default to 0 (no extra messages), setting it to
  486. 1 will print _a lot_ more information - normally
  487. only useful to kernel developers.
  488. debug_objects [KNL] Enable object debugging
  489. no_debug_objects
  490. [KNL] Disable object debugging
  491. debugpat [X86] Enable PAT debugging
  492. decnet.addr= [HW,NET]
  493. Format: <area>[,<node>]
  494. See also Documentation/networking/decnet.txt.
  495. default_hugepagesz=
  496. [same as hugepagesz=] The size of the default
  497. HugeTLB page size. This is the size represented by
  498. the legacy /proc/ hugepages APIs, used for SHM, and
  499. default size when mounting hugetlbfs filesystems.
  500. Defaults to the default architecture's huge page size
  501. if not specified.
  502. dhash_entries= [KNL]
  503. Set number of hash buckets for dentry cache.
  504. digi= [HW,SERIAL]
  505. IO parameters + enable/disable command.
  506. digiepca= [HW,SERIAL]
  507. See drivers/char/README.epca and
  508. Documentation/serial/digiepca.txt.
  509. disable_mtrr_cleanup [X86]
  510. The kernel tries to adjust MTRR layout from continuous
  511. to discrete, to make X server driver able to add WB
  512. entry later. This parameter disables that.
  513. disable_mtrr_trim [X86, Intel and AMD only]
  514. By default the kernel will trim any uncacheable
  515. memory out of your available memory pool based on
  516. MTRR settings. This parameter disables that behavior,
  517. possibly causing your machine to run very slowly.
  518. disable_timer_pin_1 [X86]
  519. Disable PIN 1 of APIC timer
  520. Can be useful to work around chipset bugs.
  521. dm= [DM] Allows early creation of a device-mapper device.
  522. See Documentation/device-mapper/boot.txt.
  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=ttySn[,baudrate]
  554. earlyprintk=dbgp[debugController#]
  555. Append ",keep" to not disable it when the real console
  556. takes over.
  557. Only vga or serial or usb debug port at a time.
  558. Currently only ttyS0 and ttyS1 are supported.
  559. Interaction with the standard serial driver is not
  560. very good.
  561. The VGA output is eventually overwritten by the real
  562. console.
  563. eata= [HW,SCSI]
  564. edd= [EDD]
  565. Format: {"off" | "on" | "skip[mbr]"}
  566. eisa_irq_edge= [PARISC,HW]
  567. See header of drivers/parisc/eisa.c.
  568. elanfreq= [X86-32]
  569. See comment before function elanfreq_setup() in
  570. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  571. elevator= [IOSCHED]
  572. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  573. See Documentation/block/as-iosched.txt and
  574. Documentation/block/deadline-iosched.txt for details.
  575. elfcorehdr= [IA64,PPC,SH,X86]
  576. Specifies physical address of start of kernel core
  577. image elf header. Generally kexec loader will
  578. pass this option to capture kernel.
  579. See Documentation/kdump/kdump.txt for details.
  580. enable_mtrr_cleanup [X86]
  581. The kernel tries to adjust MTRR layout from continuous
  582. to discrete, to make X server driver able to add WB
  583. entry later. This parameter enables that.
  584. enable_timer_pin_1 [X86]
  585. Enable PIN 1 of APIC timer
  586. Can be useful to work around chipset bugs
  587. (in particular on some ATI chipsets).
  588. The kernel tries to set a reasonable default.
  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. ether= [HW,NET] Ethernet cards parameters
  597. This option is obsoleted by the "netdev=" option, which
  598. has equivalent usage. See its documentation for details.
  599. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  600. Format: <io>[,<irq>]
  601. failslab=
  602. fail_page_alloc=
  603. fail_make_request=[KNL]
  604. General fault injection mechanism.
  605. Format: <interval>,<probability>,<space>,<times>
  606. See also /Documentation/fault-injection/.
  607. fd_mcs= [HW,SCSI]
  608. See header of drivers/scsi/fd_mcs.c.
  609. fdomain= [HW,SCSI]
  610. See header of drivers/scsi/fdomain.c.
  611. floppy= [HW]
  612. See Documentation/blockdev/floppy.txt.
  613. force_pal_cache_flush
  614. [IA-64] Avoid check_sal_cache_flush which may hang on
  615. buggy SAL_CACHE_FLUSH implementations. Using this
  616. parameter will force ia64_sal_cache_flush to call
  617. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  618. ftrace=[tracer]
  619. [FTRACE] will set and start the specified tracer
  620. as early as possible in order to facilitate early
  621. boot debugging.
  622. ftrace_dump_on_oops
  623. [FTRACE] will dump the trace buffers on oops.
  624. ftrace_filter=[function-list]
  625. [FTRACE] Limit the functions traced by the function
  626. tracer at boot up. function-list is a comma separated
  627. list of functions. This list can be changed at run
  628. time by the set_ftrace_filter file in the debugfs
  629. tracing directory.
  630. ftrace_notrace=[function-list]
  631. [FTRACE] Do not trace the functions specified in
  632. function-list. This list can be changed at run time
  633. by the set_ftrace_notrace file in the debugfs
  634. tracing directory.
  636. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  637. support via parallel port (up to 5 devices per port)
  638. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  639. See also Documentation/input/joystick-parport.txt
  640. gamma= [HW,DRM]
  641. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  642. Format: off | on
  643. default: on
  644. gcov_persist= [GCOV] When non-zero (default), profiling data for
  645. kernel modules is saved and remains accessible via
  646. debugfs, even when the module is unloaded/reloaded.
  647. When zero, profiling data is discarded and associated
  648. debugfs files are removed at module unload time.
  649. gdth= [HW,SCSI]
  650. See header of drivers/scsi/gdth.c.
  651. gpt [EFI] Forces disk with valid GPT signature but
  652. invalid Protective MBR to be treated as GPT.
  653. gvp11= [HW,SCSI]
  654. hashdist= [KNL,NUMA] Large hashes allocated during boot
  655. are distributed across NUMA nodes. Defaults on
  656. for 64bit NUMA, off otherwise.
  657. Format: 0 | 1 (for off | on)
  658. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  659. hd= [EIDE] (E)IDE hard drive subsystem geometry
  660. Format: <cyl>,<head>,<sect>
  661. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  662. size of <nn>. This works even on boxes that have no
  663. highmem otherwise. This also works to reduce highmem
  664. size on bigger boxes.
  665. highres= [KNL] Enable/disable high resolution timer mode.
  666. Valid parameters: "on", "off"
  667. Default: "on"
  668. hisax= [HW,ISDN]
  669. See Documentation/isdn/README.HiSax.
  670. hlt [BUGS=ARM,SH]
  671. hpet= [X86-32,HPET] option to control HPET usage
  672. Format: { enable (default) | disable | force |
  673. verbose }
  674. disable: disable HPET and use PIT instead
  675. force: allow force enabled of undocumented chips (ICH4,
  676. VIA, nVidia)
  677. verbose: show contents of HPET registers during setup
  678. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  679. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  680. On x86-64 and powerpc, this option can be specified
  681. multiple times interleaved with hugepages= to reserve
  682. huge pages of different sizes. Valid pages sizes on
  683. x86-64 are 2M (when the CPU supports "pse") and 1G
  684. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  685. Note that 1GB pages can only be allocated at boot time
  686. using hugepages= and not freed afterwards.
  687. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
  688. terminal devices. Valid values: 0..8
  689. hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
  690. If specified, z/VM IUCV HVC accepts connections
  691. from listed z/VM user IDs only.
  692. i2c_bus= [HW] Override the default board specific I2C bus speed
  693. or register an additional I2C bus that is not
  694. registered from board initialization code.
  695. Format:
  696. <bus_id>,<clkrate>
  697. i8042.debug [HW] Toggle i8042 debug mode
  698. [HW] Put keyboard port into non-translated mode
  699. i8042.dumbkbd [HW] Pretend that controller can only read data from
  700. keyboard and cannot control its state
  701. (Don't attempt to blink the leds)
  702. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  703. i8042.nokbd [HW] Don't check/create keyboard port
  704. i8042.noloop [HW] Disable the AUX Loopback command while probing
  705. for the AUX port
  706. i8042.nomux [HW] Don't check presence of an active multiplexing
  707. controller
  708. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  709. controllers
  710. i8042.panicblink=
  711. [HW] Frequency with which keyboard LEDs should blink
  712. when kernel panics (default is 0.5 sec)
  713. i8042.reset [HW] Reset the controller during init and cleanup
  714. i8042.unlock [HW] Unlock (ignore) the keylock
  715. i810= [HW,DRM]
  716. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  717. indicates that the driver is running on unsupported
  718. hardware.
  719. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  720. does not match list of supported models.
  721. i8k.power_status
  722. [HW] Report power status in /proc/i8k
  723. (disabled by default)
  724. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  725. capability is set.
  726. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  727. See Documentation/mca.txt.
  728. icn= [HW,ISDN]
  729. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  730. ide-core.nodma= [HW] (E)IDE subsystem
  731. Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
  732. .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
  733. .cdrom .chs .ignore_cable are additional options
  734. See Documentation/ide/ide.txt.
  735. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  736. Claim all unknown PCI IDE storage controllers.
  737. idle= [X86]
  738. Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
  739. Poll forces a polling idle loop that can slightly
  740. improve the performance of waking up a idle CPU, but
  741. will use a lot of power and make the system run hot.
  742. Not recommended.
  743. idle=mwait: On systems which support MONITOR/MWAIT but
  744. the kernel chose to not use it because it doesn't save
  745. as much power as a normal idle loop, use the
  746. MONITOR/MWAIT idle loop anyways. Performance should be
  747. the same as idle=poll.
  748. idle=halt: Halt is forced to be used for CPU idle.
  749. In such case C2/C3 won't be used again.
  750. idle=nomwait: Disable mwait for CPU C-states
  751. ignore_loglevel [KNL]
  752. Ignore loglevel setting - this will print /all/
  753. kernel messages to the console. Useful for debugging.
  754. ihash_entries= [KNL]
  755. Set number of hash buckets for inode cache.
  756. ima_audit= [IMA]
  757. Format: { "0" | "1" }
  758. 0 -- integrity auditing messages. (Default)
  759. 1 -- enable informational integrity auditing messages.
  760. ima_hash= [IMA]
  761. Format: { "sha1" | "md5" }
  762. default: "sha1"
  763. ima_tcb [IMA]
  764. Load a policy which meets the needs of the Trusted
  765. Computing Base. This means IMA will measure all
  766. programs exec'd, files mmap'd for exec, and all files
  767. opened for read by uid=0.
  768. in2000= [HW,SCSI]
  769. See header of drivers/scsi/in2000.c.
  770. init= [KNL]
  771. Format: <full_path>
  772. Run specified binary instead of /sbin/init as init
  773. process.
  774. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  775. for working out where the kernel is dying during
  776. startup.
  777. initrd= [BOOT] Specify the location of the initial ramdisk
  778. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  779. Format: <irq>
  780. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  781. on
  782. Enable intel iommu driver.
  783. off
  784. Disable intel iommu driver.
  785. igfx_off [Default Off]
  786. By default, gfx is mapped as normal device. If a gfx
  787. device has a dedicated DMAR unit, the DMAR unit is
  788. bypassed by not enabling DMAR with this option. In
  789. this case, gfx device will use physical address for
  790. DMA.
  791. forcedac [x86_64]
  792. With this option iommu will not optimize to look
  793. for io virtual address below 32 bit forcing dual
  794. address cycle on pci bus for cards supporting greater
  795. than 32 bit addressing. The default is to look
  796. for translation below 32 bit and if not available
  797. then look in the higher range.
  798. strict [Default Off]
  799. With this option on every unmap_single operation will
  800. result in a hardware IOTLB flush operation as opposed
  801. to batching them for performance.
  802. inttest= [IA64]
  803. iomem= Disable strict checking of access to MMIO memory
  804. strict regions from userspace.
  805. relaxed
  806. iommu= [x86]
  807. off
  808. force
  809. noforce
  810. biomerge
  811. panic
  812. nopanic
  813. merge
  814. nomerge
  815. forcesac
  816. soft
  817. pt [x86, IA64]
  818. io7= [HW] IO7 for Marvel based alpha systems
  819. See comment before marvel_specify_io7 in
  820. arch/alpha/kernel/core_marvel.c.
  821. io_delay= [X86] I/O delay method
  822. 0x80
  823. Standard port 0x80 based delay
  824. 0xed
  825. Alternate port 0xed based delay (needed on some systems)
  826. udelay
  827. Simple two microseconds delay
  828. none
  829. No delay
  830. ip= [IP_PNP]
  831. See Documentation/filesystems/nfsroot.txt.
  832. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  833. See comment before ip2_setup() in
  834. drivers/char/ip2/ip2base.c.
  835. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  836. See header of drivers/scsi/ips.c.
  837. irqfixup [HW]
  838. When an interrupt is not handled search all handlers
  839. for it. Intended to get systems with badly broken
  840. firmware running.
  841. irqpoll [HW]
  842. When an interrupt is not handled search all handlers
  843. for it. Also check all handlers each timer
  844. interrupt. Intended to get systems with badly broken
  845. firmware running.
  846. isapnp= [ISAPNP]
  847. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  848. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  849. Format:
  850. <cpu number>,...,<cpu number>
  851. or
  852. <cpu number>-<cpu number>
  853. (must be a positive range in ascending order)
  854. or a mixture
  855. <cpu number>,...,<cpu number>-<cpu number>
  856. This option can be used to specify one or more CPUs
  857. to isolate from the general SMP balancing and scheduling
  858. algorithms. You can move a process onto or off an
  859. "isolated" CPU via the CPU affinity syscalls or cpuset.
  860. <cpu number> begins at 0 and the maximum value is
  861. "number of CPUs in system - 1".
  862. This option is the preferred way to isolate CPUs. The
  863. alternative -- manually setting the CPU mask of all
  864. tasks in the system -- can cause problems and
  865. suboptimal load balancer performance.
  866. iucv= [HW,NET]
  867. js= [HW,JOY] Analog joystick
  868. See Documentation/input/joystick.txt.
  869. keepinitrd [HW,ARM]
  870. kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  871. specifies the amount of memory usable by the kernel
  872. for non-movable allocations. The requested amount is
  873. spread evenly throughout all nodes in the system. The
  874. remaining memory in each node is used for Movable
  875. pages. In the event, a node is too small to have both
  876. kernelcore and Movable pages, kernelcore pages will
  877. take priority and other nodes will have a larger number
  878. of kernelcore pages. The Movable zone is used for the
  879. allocation of pages that may be reclaimed or moved
  880. by the page migration subsystem. This means that
  881. HugeTLB pages may not be allocated from this zone.
  882. Note that allocations like PTEs-from-HighMem still
  883. use the HighMem zone if it exists, and the Normal
  884. zone if it does not.
  885. kgdboc= [HW] kgdb over consoles.
  886. Requires a tty driver that supports console polling.
  887. (only serial supported for now)
  888. Format: <serial_device>[,baud]
  889. kmac= [MIPS] korina ethernet MAC address.
  890. Configure the RouterBoard 532 series on-chip
  891. Ethernet adapter MAC address.
  892. kmemleak= [KNL] Boot-time kmemleak enable/disable
  893. Valid arguments: on, off
  894. Default: on
  895. kstack=N [X86] Print N words from the kernel stack
  896. in oops dumps.
  897. kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
  898. Default is 0 (don't ignore, but inject #GP)
  899. kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
  900. Default is 1 (enabled)
  901. kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
  902. Default is 0 (off)
  903. kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
  904. for all guests.
  905. Default is 1 (enabled) if in 64bit or 32bit-PAE mode
  906. kvm-intel.bypass_guest_pf=
  907. [KVM,Intel] Disables bypassing of guest page faults
  908. on Intel chips. Default is 1 (enabled)
  909. kvm-intel.ept= [KVM,Intel] Disable extended page tables
  910. (virtualized MMU) support on capable Intel chips.
  911. Default is 1 (enabled)
  912. kvm-intel.emulate_invalid_guest_state=
  913. [KVM,Intel] Enable emulation of invalid guest states
  914. Default is 0 (disabled)
  915. kvm-intel.flexpriority=
  916. [KVM,Intel] Disable FlexPriority feature (TPR shadow).
  917. Default is 1 (enabled)
  918. kvm-intel.unrestricted_guest=
  919. [KVM,Intel] Disable unrestricted guest feature
  920. (virtualized real and unpaged mode) on capable
  921. Intel chips. Default is 1 (enabled)
  922. kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
  923. feature (tagged TLBs) on capable Intel chips.
  924. Default is 1 (enabled)
  925. l2cr= [PPC]
  926. l3cr= [PPC]
  927. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  928. disabled it.
  929. lapic_timer_c2_ok [X86,APIC] trust the local apic timer
  930. in C2 power state.
  931. libata.dma= [LIBATA] DMA control
  932. libata.dma=0 Disable all PATA and SATA DMA
  933. libata.dma=1 PATA and SATA Disk DMA only
  934. libata.dma=2 ATAPI (CDROM) DMA only
  935. libata.dma=4 Compact Flash DMA only
  936. Combinations also work, so libata.dma=3 enables DMA
  937. for disks and CDROMs, but not CFs.
  938. libata.ignore_hpa= [LIBATA] Ignore HPA limit
  939. libata.ignore_hpa=0 keep BIOS limits (default)
  940. libata.ignore_hpa=1 ignore limits, using full disk
  941. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  942. when set.
  943. Format: <int>
  944. libata.force= [LIBATA] Force configurations. The format is comma
  945. separated list of "[ID:]VAL" where ID is
  946. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  947. matching port, link or device. Basically, it matches
  948. the ATA ID string printed on console by libata. If
  949. the whole ID part is omitted, the last PORT and DEVICE
  950. values are used. If ID hasn't been specified yet, the
  951. configuration applies to all ports, links and devices.
  952. If only DEVICE is omitted, the parameter applies to
  953. the port and all links and devices behind it. DEVICE
  954. number of 0 either selects the first device or the
  955. first fan-out link behind PMP device. It does not
  956. select the host link. DEVICE number of 15 selects the
  957. host link and device attached to it.
  958. The VAL specifies the configuration to force. As long
  959. as there's no ambiguity shortcut notation is allowed.
  960. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  961. The following configurations can be forced.
  962. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  963. Any ID with matching PORT is used.
  964. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  965. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  966. udma[/][16,25,33,44,66,100,133] notation is also
  967. allowed.
  968. * [no]ncq: Turn on or off NCQ.
  969. * nohrst, nosrst, norst: suppress hard, soft
  970. and both resets.
  971. If there are multiple matching configurations changing
  972. the same attribute, the last one is used.
  973. lmb=debug [KNL] Enable lmb debug messages.
  974. load_ramdisk= [RAM] List of ramdisks to load from floppy
  975. See Documentation/blockdev/ramdisk.txt.
  976. lockd.nlm_grace_period=P [NFS] Assign grace period.
  977. Format: <integer>
  978. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  979. Format: <integer>
  980. lockd.nlm_timeout=T [NFS] Assign timeout value.
  981. Format: <integer>
  982. lockd.nlm_udpport=M [NFS] Assign UDP port.
  983. Format: <integer>
  984. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  985. Format: <irq>
  986. loglevel= All Kernel Messages with a loglevel smaller than the
  987. console loglevel will be printed to the console. It can
  988. also be changed with klogd or other programs. The
  989. loglevels are defined as follows:
  990. 0 (KERN_EMERG) system is unusable
  991. 1 (KERN_ALERT) action must be taken immediately
  992. 2 (KERN_CRIT) critical conditions
  993. 3 (KERN_ERR) error conditions
  994. 4 (KERN_WARNING) warning conditions
  995. 5 (KERN_NOTICE) normal but significant condition
  996. 6 (KERN_INFO) informational
  997. 7 (KERN_DEBUG) debug-level messages
  998. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  999. Format: { n | nk | nM }
  1000. n must be a power of two. The default size
  1001. is set in the kernel config file.
  1002. logo.nologo [FB] Disables display of the built-in Linux logo.
  1003. This may be used to provide more screen space for
  1004. kernel log messages and is useful when debugging
  1005. kernel boot problems.
  1006. lp=0 [LP] Specify parallel ports to use, e.g,
  1007. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  1008. lp=reset first parallel port). 'lp=0' disables the
  1009. lp=auto printer driver. 'lp=reset' (which can be
  1010. specified in addition to the ports) causes
  1011. attached printers to be reset. Using
  1012. lp=port1,port2,... specifies the parallel ports
  1013. to associate lp devices with, starting with
  1014. lp0. A port specification may be 'none' to skip
  1015. that lp device, or a parport name such as
  1016. 'parport0'. Specifying 'lp=auto' instead of a
  1017. port specification list means that device IDs
  1018. from each port should be examined, to see if
  1019. an IEEE 1284-compliant printer is attached; if
  1020. so, the driver will manage that printer.
  1021. See also header of drivers/char/lp.c.
  1022. lpj=n [KNL]
  1023. Sets loops_per_jiffy to given constant, thus avoiding
  1024. time-consuming boot-time autodetection (up to 250 ms per
  1025. CPU). 0 enables autodetection (default). To determine
  1026. the correct value for your kernel, boot with normal
  1027. autodetection and see what value is printed. Note that
  1028. on SMP systems the preset will be applied to all CPUs,
  1029. which is likely to cause problems if your CPUs need
  1030. significantly divergent settings. An incorrect value
  1031. will cause delays in the kernel to be wrong, leading to
  1032. unpredictable I/O errors and other breakage. Although
  1033. unlikely, in the extreme case this might damage your
  1034. hardware.
  1035. ltpc= [NET]
  1036. Format: <io>,<irq>,<dma>
  1037. mac5380= [HW,SCSI] Format:
  1038. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  1039. machvec= [IA64] Force the use of a particular machine-vector
  1040. (machvec) in a generic kernel.
  1041. Example: machvec=hpzx1_swiotlb
  1042. machtype= [Loongson] Share the same kernel image file between different
  1043. yeeloong laptop.
  1044. Example: machtype=lemote-yeeloong-2f-7inch
  1045. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
  1046. than or equal to this physical address is ignored.
  1047. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  1048. should make use of. maxcpus=n : n >= 0 limits the
  1049. kernel to using 'n' processors. n=0 is a special case,
  1050. it is equivalent to "nosmp", which also disables
  1051. the IO APIC.
  1052. max_loop= [LOOP] Maximum number of loopback devices that can
  1053. be mounted
  1054. Format: <1-256>
  1055. max_luns= [SCSI] Maximum number of LUNs to probe.
  1056. Should be between 1 and 2^32-1.
  1057. max_report_luns=
  1058. [SCSI] Maximum number of LUNs received.
  1059. Should be between 1 and 16384.
  1060. mcatest= [IA-64]
  1061. mce [X86-32] Machine Check Exception
  1062. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  1063. md= [HW] RAID subsystems devices and level
  1064. See Documentation/md.txt.
  1065. mdacon= [MDA]
  1066. Format: <first>,<last>
  1067. Specifies range of consoles to be captured by the MDA.
  1068. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  1069. Amount of memory to be used when the kernel is not able
  1070. to see the whole system memory or for test.
  1071. [X86-32] Use together with memmap= to avoid physical
  1072. address space collisions. Without memmap= PCI devices
  1073. could be placed at addresses belonging to unused RAM.
  1074. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1075. memory.
  1076. memchunk=nn[KMG]
  1077. [KNL,SH] Allow user to override the default size for
  1078. per-device physically contiguous DMA buffers.
  1079. memmap=exactmap [KNL,X86] Enable setting of an exact
  1080. E820 memory map, as specified by the user.
  1081. Such memmap=exactmap lines can be constructed based on
  1082. BIOS output or other requirements. See the memmap=nn@ss
  1083. option description.
  1084. memmap=nn[KMG]@ss[KMG]
  1085. [KNL] Force usage of a specific region of memory
  1086. Region of memory to be used, from ss to ss+nn.
  1087. memmap=nn[KMG]#ss[KMG]
  1088. [KNL,ACPI] Mark specific memory as ACPI data.
  1089. Region of memory to be used, from ss to ss+nn.
  1090. memmap=nn[KMG]$ss[KMG]
  1091. [KNL,ACPI] Mark specific memory as reserved.
  1092. Region of memory to be used, from ss to ss+nn.
  1093. Example: Exclude memory from 0x18690000-0x1869ffff
  1094. memmap=64K$0x18690000
  1095. or
  1096. memmap=0x10000$0x18690000
  1097. memory_corruption_check=0/1 [X86]
  1098. Some BIOSes seem to corrupt the first 64k of
  1099. memory when doing things like suspend/resume.
  1100. Setting this option will scan the memory
  1101. looking for corruption. Enabling this will
  1102. both detect corruption and prevent the kernel
  1103. from using the memory being corrupted.
  1104. However, its intended as a diagnostic tool; if
  1105. repeatable BIOS-originated corruption always
  1106. affects the same memory, you can use memmap=
  1107. to prevent the kernel from using that memory.
  1108. memory_corruption_check_size=size [X86]
  1109. By default it checks for corruption in the low
  1110. 64k, making this memory unavailable for normal
  1111. use. Use this parameter to scan for
  1112. corruption in more or less memory.
  1113. memory_corruption_check_period=seconds [X86]
  1114. By default it checks for corruption every 60
  1115. seconds. Use this parameter to check at some
  1116. other rate. 0 disables periodic checking.
  1117. memtest= [KNL,X86] Enable memtest
  1118. Format: <integer>
  1119. default : 0 <disable>
  1120. Specifies the number of memtest passes to be
  1121. performed. Each pass selects another test
  1122. pattern from a given set of patterns. Memtest
  1123. fills the memory with this pattern, validates
  1124. memory contents and reserves bad memory
  1125. regions that are detected.
  1126. meye.*= [HW] Set MotionEye Camera parameters
  1127. See Documentation/video4linux/meye.txt.
  1128. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1129. Multi-Function General Purpose Timers on AMD Geode
  1130. platforms.
  1131. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1132. the BIOS has incorrectly applied a workaround. TinyBIOS
  1133. version 0.98 is known to be affected, 0.99 fixes the
  1134. problem by letting the user disable the workaround.
  1135. mga= [HW,DRM]
  1136. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1137. physical address is ignored.
  1138. mini2440= [ARM,HW,KNL]
  1139. Format:[0..2][b][c][t]
  1140. Default: "0tb"
  1141. MINI2440 configuration specification:
  1142. 0 - The attached screen is the 3.5" TFT
  1143. 1 - The attached screen is the 7" TFT
  1144. 2 - The VGA Shield is attached (1024x768)
  1145. Leaving out the screen size parameter will not load
  1146. the TFT driver, and the framebuffer will be left
  1147. unconfigured.
  1148. b - Enable backlight. The TFT backlight pin will be
  1149. linked to the kernel VESA blanking code and a GPIO
  1150. LED. This parameter is not necessary when using the
  1151. VGA shield.
  1152. c - Enable the s3c camera interface.
  1153. t - Reserved for enabling touchscreen support. The
  1154. touchscreen support is not enabled in the mainstream
  1155. kernel as of 2.6.30, a preliminary port can be found
  1156. in the "bleeding edge" mini2440 support kernel at
  1158. mminit_loglevel=
  1159. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1160. parameter allows control of the logging verbosity for
  1161. the additional memory initialisation checks. A value
  1162. of 0 disables mminit logging and a level of 4 will
  1163. log everything. Information is printed at KERN_DEBUG
  1164. so loglevel=8 may also need to be specified.
  1165. mousedev.tap_time=
  1166. [MOUSE] Maximum time between finger touching and
  1167. leaving touchpad surface for touch to be considered
  1168. a tap and be reported as a left button click (for
  1169. touchpads working in absolute mode only).
  1170. Format: <msecs>
  1171. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1172. reporting absolute coordinates, such as tablets
  1173. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1174. reporting absolute coordinates, such as tablets
  1175. movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  1176. is similar to kernelcore except it specifies the
  1177. amount of memory used for migratable allocations.
  1178. If both kernelcore and movablecore is specified,
  1179. then kernelcore will be at *least* the specified
  1180. value but may be more. If movablecore on its own
  1181. is specified, the administrator must be careful
  1182. that the amount of memory usable for all allocations
  1183. is not too small.
  1184. mpu401= [HW,OSS]
  1185. Format: <io>,<irq>
  1186. MTD_Partition= [MTD]
  1187. Format: <name>,<region-number>,<size>,<offset>
  1188. MTD_Region= [MTD] Format:
  1189. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1190. mtdparts= [MTD]
  1191. See drivers/mtd/cmdlinepart.c.
  1192. onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
  1193. Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
  1194. boundary - index of last SLC block on Flex-OneNAND.
  1195. The remaining blocks are configured as MLC blocks.
  1196. lock - Configure if Flex-OneNAND boundary should be locked.
  1197. Once locked, the boundary cannot be changed.
  1198. 1 indicates lock status, 0 indicates unlock status.
  1199. mtdset= [ARM]
  1200. ARM/S3C2412 JIVE boot control
  1201. See arch/arm/mach-s3c2412/mach-jive.c
  1202. mtouchusb.raw_coordinates=
  1203. [HW] Make the MicroTouch USB driver use raw coordinates
  1204. ('y', default) or cooked coordinates ('n')
  1205. mtrr_chunk_size=nn[KMG] [X86]
  1206. used for mtrr cleanup. It is largest continuous chunk
  1207. that could hold holes aka. UC entries.
  1208. mtrr_gran_size=nn[KMG] [X86]
  1209. Used for mtrr cleanup. It is granularity of mtrr block.
  1210. Default is 1.
  1211. Large value could prevent small alignment from
  1212. using up MTRRs.
  1213. mtrr_spare_reg_nr=n [X86]
  1214. Format: <integer>
  1215. Range: 0,7 : spare reg number
  1216. Default : 1
  1217. Used for mtrr cleanup. It is spare mtrr entries number.
  1218. Set to 2 or more if your graphical card needs more.
  1219. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1220. NCR_D700= [HW,SCSI]
  1221. See header of drivers/scsi/NCR_D700.c.
  1222. ncr5380= [HW,SCSI]
  1223. ncr53c400= [HW,SCSI]
  1224. ncr53c400a= [HW,SCSI]
  1225. ncr53c406a= [HW,SCSI]
  1226. ncr53c8xx= [HW,SCSI]
  1227. netdev= [NET] Network devices parameters
  1228. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1229. Note that mem_start is often overloaded to mean
  1230. something different and driver-specific.
  1231. This usage is only documented in each driver source
  1232. file if at all.
  1233. nf_conntrack.acct=
  1234. [NETFILTER] Enable connection tracking flow accounting
  1235. 0 to disable accounting
  1236. 1 to enable accounting
  1237. Default value depends on CONFIG_NF_CT_ACCT that is
  1238. going to be removed in 2.6.29.
  1239. nfsaddrs= [NFS]
  1240. See Documentation/filesystems/nfsroot.txt.
  1241. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1242. See Documentation/filesystems/nfsroot.txt.
  1243. nfs.callback_tcpport=
  1244. [NFS] set the TCP port on which the NFSv4 callback
  1245. channel should listen.
  1246. nfs.cache_getent=
  1247. [NFS] sets the pathname to the program which is used
  1248. to update the NFS client cache entries.
  1249. nfs.cache_getent_timeout=
  1250. [NFS] sets the timeout after which an attempt to
  1251. update a cache entry is deemed to have failed.
  1252. nfs.idmap_cache_timeout=
  1253. [NFS] set the maximum lifetime for idmapper cache
  1254. entries.
  1255. nfs.enable_ino64=
  1256. [NFS] enable 64-bit inode numbers.
  1257. If zero, the NFS client will fake up a 32-bit inode
  1258. number for the readdir() and stat() syscalls instead
  1259. of returning the full 64-bit number.
  1260. The default is to return 64-bit inode numbers.
  1261. nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
  1262. when a NMI is triggered.
  1263. Format: [state][,regs][,debounce][,die]
  1264. nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
  1265. Format: [panic,][num]
  1266. Valid num: 0,1,2
  1267. 0 - turn nmi_watchdog off
  1268. 1 - use the IO-APIC timer for the NMI watchdog
  1269. 2 - use the local APIC for the NMI watchdog using
  1270. a performance counter. Note: This will use one
  1271. performance counter and the local APIC's performance
  1272. vector.
  1273. When panic is specified, panic when an NMI watchdog
  1274. timeout occurs.
  1275. This is useful when you use a panic=... timeout and
  1276. need the box quickly up again.
  1277. Instead of 1 and 2 it is possible to use the following
  1278. symbolic names: lapic and ioapic
  1279. Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
  1280. netpoll.carrier_timeout=
  1281. [NET] Specifies amount of time (in seconds) that
  1282. netpoll should wait for a carrier. By default netpoll
  1283. waits 4 seconds.
  1284. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1285. emulation library even if a 387 maths coprocessor
  1286. is present.
  1287. no_console_suspend
  1288. [HW] Never suspend the console
  1289. Disable suspending of consoles during suspend and
  1290. hibernate operations. Once disabled, debugging
  1291. messages can reach various consoles while the rest
  1292. of the system is being put to sleep (ie, while
  1293. debugging driver suspend/resume hooks). This may
  1294. not work reliably with all consoles, but is known
  1295. to work with serial and VGA consoles.
  1296. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1297. caches in the slab allocator. Saves per-node memory,
  1298. but will impact performance.
  1299. noalign [KNL,ARM]
  1300. noapic [SMP,APIC] Tells the kernel to not make use of any
  1301. IOAPICs that may be present in the system.
  1302. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1303. on "Classic" PPC cores.
  1304. nocache [ARM]
  1305. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1306. nodelayacct [KNL] Disable per-task delay accounting
  1307. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1308. nodsp [SH] Disable hardware DSP at boot time.
  1309. noefi [X86] Disable EFI runtime services support.
  1310. noexec [IA-64]
  1311. noexec [X86]
  1312. On X86-32 available only on PAE configured kernels.
  1313. noexec=on: enable non-executable mappings (default)
  1314. noexec=off: disable non-executable mappings
  1315. noexec32 [X86-64]
  1316. This affects only 32-bit executables.
  1317. noexec32=on: enable non-executable mappings (default)
  1318. read doesn't imply executable mappings
  1319. noexec32=off: disable non-executable mappings
  1320. read implies executable mappings
  1321. nofpu [SH] Disable hardware FPU at boot time.
  1322. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1323. register save and restore. The kernel will only save
  1324. legacy floating-point registers on task switch.
  1325. noxsave [BUGS=X86] Disables x86 extended register state save
  1326. and restore using xsave. The kernel will fallback to
  1327. enabling legacy floating-point and sse state.
  1328. nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
  1329. wfi(ARM) instruction doesn't work correctly and not to
  1330. use it. This is also useful when using JTAG debugger.
  1331. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1332. instruction doesn't work correctly and not to
  1333. use it.
  1334. no_file_caps Tells the kernel not to honor file capabilities. The
  1335. only way then for a file to be executed with privilege
  1336. is to be setuid root or executed by root.
  1337. nohalt [IA-64] Tells the kernel not to use the power saving
  1338. function PAL_HALT_LIGHT when idle. This increases
  1339. power-consumption. On the positive side, it reduces
  1340. interrupt wake-up latency, which may improve performance
  1341. in certain environments such as networked servers or
  1342. real-time systems.
  1343. nohz= [KNL] Boottime enable/disable dynamic ticks
  1344. Valid arguments: on, off
  1345. Default: on
  1346. noiotrap [SH] Disables trapped I/O port accesses.
  1347. noirqdebug [X86-32] Disables the code which attempts to detect and
  1348. disable unhandled interrupt sources.
  1349. no_timer_check [X86,APIC] Disables the code which tests for
  1350. broken timer IRQ sources.
  1351. noisapnp [ISAPNP] Disables ISA PnP code.
  1352. noinitrd [RAM] Tells the kernel not to load any configured
  1353. initial RAM disk.
  1354. nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
  1355. remapping.
  1356. nointroute [IA-64]
  1357. nojitter [IA64] Disables jitter checking for ITC timers.
  1358. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1359. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1360. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1361. lowmem mapping on PPC40x.
  1362. nomca [IA-64] Disable machine check abort handling
  1363. nomce [X86-32] Machine Check Exception
  1364. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1365. Timer usage (for AMD Geode machines).
  1366. norandmaps Don't use address space randomization. Equivalent to
  1367. echo 0 > /proc/sys/kernel/randomize_va_space
  1368. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1369. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1370. with UP alternatives
  1371. noresidual [PPC] Don't use residual data on PReP machines.
  1372. noresume [SWSUSP] Disables resume and restores original swap
  1373. space.
  1374. no-scroll [VGA] Disables scrollback.
  1375. This is required for the Braillex ib80-piezo Braille
  1376. reader made by F.H. Papenmeier (Germany).
  1377. nosbagart [IA-64]
  1378. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1379. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1380. and disable the IO APIC. legacy for "maxcpus=0".
  1381. nosoftlockup [KNL] Disable the soft-lockup detector.
  1382. noswapaccount [KNL] Disable accounting of swap in memory resource
  1383. controller. (See Documentation/cgroups/memory.txt)
  1384. nosync [HW,M68K] Disables sync negotiation for all devices.
  1385. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1386. nousb [USB] Disable the USB subsystem
  1387. nowb [ARM]
  1388. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1389. nptcg= [IA64] Override max number of concurrent global TLB
  1390. purges which is reported from either PAL_VM_SUMMARY or
  1391. SAL PALO.
  1392. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1393. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1394. one of ['zone', 'node', 'default'] can be specified
  1395. This can be set from sysctl after boot.
  1396. See Documentation/sysctl/vm.txt for details.
  1397. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
  1398. See Documentation/debugging-via-ohci1394.txt for more
  1399. info.
  1400. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1401. Rather than timing out after 20 ms if an EC
  1402. command is not properly ACKed, override the length
  1403. of the timeout. We have interrupts disabled while
  1404. waiting for the ACK, so if this is set too high
  1405. interrupts *may* be lost!
  1406. opl3= [HW,OSS]
  1407. Format: <io>
  1408. oprofile.timer= [HW]
  1409. Use timer interrupt instead of performance counters
  1410. oprofile.cpu_type= Force an oprofile cpu type
  1411. This might be useful if you have an older oprofile
  1412. userland or if you want common events.
  1413. Format: { arch_perfmon }
  1414. arch_perfmon: [X86] Force use of architectural
  1415. perfmon on Intel CPUs instead of the
  1416. CPU specific event set.
  1417. osst= [HW,SCSI] SCSI Tape Driver
  1418. Format: <buffer_size>,<write_threshold>
  1419. See also Documentation/scsi/st.txt.
  1420. panic= [KNL] Kernel behaviour on panic
  1421. Format: <timeout>
  1422. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1423. connected to, default is 0.
  1424. Format: <parport#>
  1425. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1426. 0 for XT, 1 for AT (default is AT).
  1427. Format: <mode>
  1428. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1429. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1430. Use 'auto' to force the driver to use any
  1431. IRQ/DMA settings detected (the default is to
  1432. ignore detected IRQ/DMA settings because of
  1433. possible conflicts). You can specify the base
  1434. address, IRQ, and DMA settings; IRQ and DMA
  1435. should be numbers, or 'auto' (for using detected
  1436. settings on that particular port), or 'nofifo'
  1437. (to avoid using a FIFO even if it is detected).
  1438. Parallel ports are assigned in the order they
  1439. are specified on the command line, starting
  1440. with parport0.
  1441. parport_init_mode= [HW,PPT]
  1442. Configure VIA parallel port to operate in
  1443. a specific mode. This is necessary on Pegasos
  1444. computer where firmware has no options for setting
  1445. up parallel port mode and sets it to spp.
  1446. Currently this function knows 686a and 8231 chips.
  1447. Format: [spp|ps2|epp|ecp|ecpepp]
  1448. pas2= [HW,OSS] Format:
  1449. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1450. pas16= [HW,SCSI]
  1451. See header of drivers/scsi/pas16.c.
  1452. pause_on_oops=
  1453. Halt all CPUs after the first oops has been printed for
  1454. the specified number of seconds. This is to be used if
  1455. your oopses keep scrolling off the screen.
  1456. pcbit= [HW,ISDN]
  1457. pcd. [PARIDE]
  1458. See header of drivers/block/paride/pcd.c.
  1459. See also Documentation/blockdev/paride.txt.
  1460. pci=option[,option...] [PCI] various PCI subsystem options:
  1461. earlydump [X86] dump PCI config space before the kernel
  1462. changes anything
  1463. off [X86] don't probe for the PCI bus
  1464. bios [X86-32] force use of PCI BIOS, don't access
  1465. the hardware directly. Use this if your machine
  1466. has a non-standard PCI host bridge.
  1467. nobios [X86-32] disallow use of PCI BIOS, only direct
  1468. hardware access methods are allowed. Use this
  1469. if you experience crashes upon bootup and you
  1470. suspect they are caused by the BIOS.
  1471. conf1 [X86] Force use of PCI Configuration
  1472. Mechanism 1.
  1473. conf2 [X86] Force use of PCI Configuration
  1474. Mechanism 2.
  1475. noaer [PCIE] If the PCIEAER kernel config parameter is
  1476. enabled, this kernel boot option can be used to
  1477. disable the use of PCIE advanced error reporting.
  1478. nodomains [PCI] Disable support for multiple PCI
  1479. root domains (aka PCI segments, in ACPI-speak).
  1480. nommconf [X86] Disable use of MMCONFIG for PCI
  1481. Configuration
  1482. check_enable_amd_mmconf [X86] check for and enable
  1483. properly configured MMIO access to PCI
  1484. config space on AMD family 10h CPU
  1485. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1486. enabled, this kernel boot option can be used to
  1487. disable the use of MSI interrupts system-wide.
  1488. noioapicquirk [APIC] Disable all boot interrupt quirks.
  1489. Safety option to keep boot IRQs enabled. This
  1490. should never be necessary.
  1491. ioapicreroute [APIC] Enable rerouting of boot IRQs to the
  1492. primary IO-APIC for bridges that cannot disable
  1493. boot IRQs. This fixes a source of spurious IRQs
  1494. when the system masks IRQs.
  1495. noioapicreroute [APIC] Disable workaround that uses the
  1496. boot IRQ equivalent of an IRQ that connects to
  1497. a chipset where boot IRQs cannot be disabled.
  1498. The opposite of ioapicreroute.
  1499. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1500. routing table. These calls are known to be buggy
  1501. on several machines and they hang the machine
  1502. when used, but on other computers it's the only
  1503. way to get the interrupt routing table. Try
  1504. this option if the kernel is unable to allocate
  1505. IRQs or discover secondary PCI buses on your
  1506. motherboard.
  1507. rom [X86] Assign address space to expansion ROMs.
  1508. Use with caution as certain devices share
  1509. address decoders between ROMs and other
  1510. resources.
  1511. norom [X86] Do not assign address space to
  1512. expansion ROMs that do not already have
  1513. BIOS assigned address ranges.
  1514. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1515. assigned automatically to PCI devices. You can
  1516. make the kernel exclude IRQs of your ISA cards
  1517. this way.
  1518. pirqaddr=0xAAAAA [X86] Specify the physical address
  1519. of the PIRQ table (normally generated
  1520. by the BIOS) if it is outside the
  1521. F0000h-100000h range.
  1522. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1523. useful if the kernel is unable to find your
  1524. secondary buses and you want to tell it
  1525. explicitly which ones they are.
  1526. assign-busses [X86] Always assign all PCI bus
  1527. numbers ourselves, overriding
  1528. whatever the firmware may have done.
  1529. usepirqmask [X86] Honor the possible IRQ mask stored
  1530. in the BIOS $PIR table. This is needed on
  1531. some systems with broken BIOSes, notably
  1532. some HP Pavilion N5400 and Omnibook XE3
  1533. notebooks. This will have no effect if ACPI
  1534. IRQ routing is enabled.
  1535. noacpi [X86] Do not use ACPI for IRQ routing
  1536. or for PCI scanning.
  1537. use_crs [X86] Use _CRS for PCI resource
  1538. allocation.
  1539. routeirq Do IRQ routing for all PCI devices.
  1540. This is normally done in pci_enable_device(),
  1541. so this option is a temporary workaround
  1542. for broken drivers that don't call it.
  1543. skip_isa_align [X86] do not align io start addr, so can
  1544. handle more pci cards
  1545. firmware [ARM] Do not re-enumerate the bus but instead
  1546. just use the configuration from the
  1547. bootloader. This is currently used on
  1548. IXP2000 systems where the bus has to be
  1549. configured a certain way for adjunct CPUs.
  1550. noearly [X86] Don't do any early type 1 scanning.
  1551. This might help on some broken boards which
  1552. machine check when some devices' config space
  1553. is read. But various workarounds are disabled
  1554. and some IOMMU drivers will not work.
  1555. bfsort Sort PCI devices into breadth-first order.
  1556. This sorting is done to get a device
  1557. order compatible with older (<= 2.4) kernels.
  1558. nobfsort Don't sort PCI devices into breadth-first order.
  1559. cbiosize=nn[KMG] The fixed amount of bus space which is
  1560. reserved for the CardBus bridge's IO window.
  1561. The default value is 256 bytes.
  1562. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1563. reserved for the CardBus bridge's memory
  1564. window. The default value is 64 megabytes.
  1565. resource_alignment=
  1566. Format:
  1567. [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
  1568. Specifies alignment and device to reassign
  1569. aligned memory resources.
  1570. If <order of align> is not specified,
  1571. PAGE_SIZE is used as alignment.
  1572. PCI-PCI bridge can be specified, if resource
  1573. windows need to be expanded.
  1574. ecrc= Enable/disable PCIe ECRC (transaction layer
  1575. end-to-end CRC checking).
  1576. bios: Use BIOS/firmware settings. This is the
  1577. the default.
  1578. off: Turn ECRC off
  1579. on: Turn ECRC on.
  1580. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1581. Management.
  1582. off Disable ASPM.
  1583. force Enable ASPM even on devices that claim not to support it.
  1584. WARNING: Forcing ASPM on may cause system lockups.
  1585. pcmv= [HW,PCMCIA] BadgePAD 4
  1586. pd. [PARIDE]
  1587. See Documentation/blockdev/paride.txt.
  1588. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1589. boot time.
  1590. Format: { 0 | 1 }
  1591. See arch/parisc/kernel/pdc_chassis.c
  1592. percpu_alloc= Select which percpu first chunk allocator to use.
  1593. Currently supported values are "embed" and "page".
  1594. Archs may support subset or none of the selections.
  1595. See comments in mm/percpu.c for details on each
  1596. allocator. This parameter is primarily for debugging
  1597. and performance comparison.
  1598. pf. [PARIDE]
  1599. See Documentation/blockdev/paride.txt.
  1600. pg. [PARIDE]
  1601. See Documentation/blockdev/paride.txt.
  1602. pirq= [SMP,APIC] Manual mp-table setup
  1603. See Documentation/x86/i386/IO-APIC.txt.
  1604. plip= [PPT,NET] Parallel port network link
  1605. Format: { parport<nr> | timid | 0 }
  1606. See also Documentation/parport.txt.
  1607. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1608. Override pmtimer IOPort with a hex value.
  1609. e.g. pmtmr=0x508
  1610. pnp.debug [PNP]
  1611. Enable PNP debug messages. This depends on the
  1613. pnpacpi= [ACPI]
  1614. { off }
  1615. pnpbios= [ISAPNP]
  1616. { on | off | curr | res | no-curr | no-res }
  1617. pnp_reserve_irq=
  1618. [ISAPNP] Exclude IRQs for the autoconfiguration
  1619. pnp_reserve_dma=
  1620. [ISAPNP] Exclude DMAs for the autoconfiguration
  1621. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1622. Ranges are in pairs (I/O port base and size).
  1623. pnp_reserve_mem=
  1624. [ISAPNP] Exclude memory regions for the
  1625. autoconfiguration.
  1626. Ranges are in pairs (memory base and size).
  1627. ports= [IP_VS_FTP] IPVS ftp helper module
  1628. Default is 21.
  1629. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  1630. may be specified.
  1631. Format: <port>,<port>....
  1632. print-fatal-signals=
  1633. [KNL] debug: print fatal signals
  1634. print-fatal-signals=1: print segfault info to
  1635. the kernel console.
  1636. default: off.
  1637. printk.time= Show timing data prefixed to each printk message line
  1638. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1639. processor.max_cstate= [HW,ACPI]
  1640. Limit processor to maximum C-state
  1641. max_cstate=9 overrides any DMI blacklist limit.
  1642. processor.nocst [HW,ACPI]
  1643. Ignore the _CST method to determine C-states,
  1644. instead using the legacy FADT method
  1645. profile= [KNL] Enable kernel profiling via /proc/profile
  1646. Format: [schedule,]<number>
  1647. Param: "schedule" - profile schedule points.
  1648. Param: <number> - step/bucket size as a power of 2 for
  1649. statistical time based profiling.
  1650. Param: "sleep" - profile D-state sleeping (millisecs).
  1651. Requires CONFIG_SCHEDSTATS
  1652. Param: "kvm" - profile VM exits.
  1653. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1654. before loading.
  1655. See Documentation/blockdev/ramdisk.txt.
  1656. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1657. probe for; one of (bare|imps|exps|lifebook|any).
  1658. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1659. per second.
  1660. psmouse.resetafter= [HW,MOUSE]
  1661. Try to reset the device after so many bad packets
  1662. (0 = never).
  1663. psmouse.resolution=
  1664. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1665. psmouse.smartscroll=
  1666. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1667. 0 = disabled, 1 = enabled (default).
  1668. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1669. Format:
  1670. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1671. pt. [PARIDE]
  1672. See Documentation/blockdev/paride.txt.
  1673. pty.legacy_count=
  1674. [KNL] Number of legacy pty's. Overwrites compiled-in
  1675. default number.
  1676. quiet [KNL] Disable most log messages
  1677. r128= [HW,DRM]
  1678. raid= [HW,RAID]
  1679. See Documentation/md.txt.
  1680. ramdisk_blocksize= [RAM]
  1681. See Documentation/blockdev/ramdisk.txt.
  1682. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1683. See Documentation/blockdev/ramdisk.txt.
  1684. rcupdate.blimit= [KNL,BOOT]
  1685. Set maximum number of finished RCU callbacks to process
  1686. in one batch.
  1687. rcupdate.qhimark= [KNL,BOOT]
  1688. Set threshold of queued
  1689. RCU callbacks over which batch limiting is disabled.
  1690. rcupdate.qlowmark= [KNL,BOOT]
  1691. Set threshold of queued RCU callbacks below which
  1692. batch limiting is re-enabled.
  1693. rdinit= [KNL]
  1694. Format: <full_path>
  1695. Run specified binary instead of /init from the ramdisk,
  1696. used for early userspace startup. See initrd.
  1697. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1698. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1699. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1700. relax_domain_level=
  1701. [KNL, SMP] Set scheduler's default relax_domain_level.
  1702. See Documentation/cgroups/cpusets.txt.
  1703. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1704. reservetop= [X86-32]
  1705. Format: nn[KMG]
  1706. Reserves a hole at the top of the kernel virtual
  1707. address space.
  1708. reset_devices [KNL] Force drivers to reset the underlying device
  1709. during initialization.
  1710. resume= [SWSUSP]
  1711. Specify the partition device for software suspend
  1712. resume_offset= [SWSUSP]
  1713. Specify the offset from the beginning of the partition
  1714. given by "resume=" at which the swap header is located,
  1715. in <PAGE_SIZE> units (needed only for swap files).
  1716. See Documentation/power/swsusp-and-swap-files.txt
  1717. retain_initrd [RAM] Keep initrd memory after extraction
  1718. rhash_entries= [KNL,NET]
  1719. Set number of hash buckets for route cache
  1720. riscom8= [HW,SERIAL]
  1721. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1722. ro [KNL] Mount root device read-only on boot
  1723. root= [KNL] Root filesystem
  1724. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1725. mount the root filesystem
  1726. rootflags= [KNL] Set root filesystem mount option string
  1727. rootfstype= [KNL] Set root filesystem type
  1728. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1729. Useful for devices that are detected asynchronously
  1730. (e.g. USB and MMC devices).
  1731. root_plug.vendor_id=
  1732. [ROOTPLUG] Override the default vendor ID
  1733. root_plug.product_id=
  1734. [ROOTPLUG] Override the default product ID
  1735. root_plug.debug=
  1736. [ROOTPLUG] Enable debugging output
  1737. rw [KNL] Mount root device read-write on boot
  1738. S [KNL] Run init in single mode
  1739. sa1100ir [NET]
  1740. See drivers/net/irda/sa1100_ir.c.
  1741. sbni= [NET] Granch SBNI12 leased line adapter
  1742. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1743. Format: <io>[,<timeout>[,<isapnp>]]
  1744. scsi_debug_*= [SCSI]
  1745. See drivers/scsi/scsi_debug.c.
  1746. scsi_default_dev_flags=
  1747. [SCSI] SCSI default device flags
  1748. Format: <integer>
  1749. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1750. Format: <vendor>:<model>:<flags>
  1751. (flags are integer value)
  1752. scsi_logging_level= [SCSI] a bit mask of logging levels
  1753. See drivers/scsi/scsi_logging.h for bits. Also
  1754. settable via sysctl at dev.scsi.logging_level
  1755. (/proc/sys/dev/scsi/logging_level).
  1756. There is also a nice 'scsi_logging_level' script in the
  1757. S390-tools package, available for download at
  1759. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1760. discovered. async scans them in kernel threads,
  1761. allowing boot to proceed. none ignores them, expecting
  1762. user space to do the scan.
  1763. security= [SECURITY] Choose a security module to enable at boot.
  1764. If this boot parameter is not specified, only the first
  1765. security module asking for security registration will be
  1766. loaded. An invalid security module name will be treated
  1767. as if no module has been chosen.
  1768. selinux= [SELINUX] Disable or enable SELinux at boot time.
  1769. Format: { "0" | "1" }
  1770. See security/selinux/Kconfig help text.
  1771. 0 -- disable.
  1772. 1 -- enable.
  1773. Default value is set via kernel config option.
  1774. If enabled at boot time, /selinux/disable can be used
  1775. later to disable prior to initial policy load.
  1776. serialnumber [BUGS=X86-32]
  1777. shapers= [NET]
  1778. Maximal number of shapers.
  1779. show_msr= [x86] show boot-time MSR settings
  1780. Format: { <integer> }
  1781. Show boot-time (BIOS-initialized) MSR settings.
  1782. The parameter means the number of CPUs to show,
  1783. for example 1 means boot CPU only.
  1784. sim710= [SCSI,HW]
  1785. See header of drivers/scsi/sim710.c.
  1786. simeth= [IA-64]
  1787. simscsi=
  1788. slram= [HW,MTD]
  1789. slub_debug[=options[,slabs]] [MM, SLUB]
  1790. Enabling slub_debug allows one to determine the
  1791. culprit if slab objects become corrupted. Enabling
  1792. slub_debug can create guard zones around objects and
  1793. may poison objects when not in use. Also tracks the
  1794. last alloc / free. For more information see
  1795. Documentation/vm/slub.txt.
  1796. slub_max_order= [MM, SLUB]
  1797. Determines the maximum allowed order for slabs.
  1798. A high setting may cause OOMs due to memory
  1799. fragmentation. For more information see
  1800. Documentation/vm/slub.txt.
  1801. slub_min_objects= [MM, SLUB]
  1802. The minimum number of objects per slab. SLUB will
  1803. increase the slab order up to slub_max_order to
  1804. generate a sufficiently large slab able to contain
  1805. the number of objects indicated. The higher the number
  1806. of objects the smaller the overhead of tracking slabs
  1807. and the less frequently locks need to be acquired.
  1808. For more information see Documentation/vm/slub.txt.
  1809. slub_min_order= [MM, SLUB]
  1810. Determines the mininum page order for slabs. Must be
  1811. lower than slub_max_order.
  1812. For more information see Documentation/vm/slub.txt.
  1813. slub_nomerge [MM, SLUB]
  1814. Disable merging of slabs with similar size. May be
  1815. necessary if there is some reason to distinguish
  1816. allocs to different slabs. Debug options disable
  1817. merging on their own.
  1818. For more information see Documentation/vm/slub.txt.
  1819. smart2= [HW]
  1820. Format: <io1>[,<io2>[,...,<io8>]]
  1821. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1822. attempt to substitute SMP alternatives once at boot.
  1823. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1824. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1825. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1826. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1827. smsc-ircc2.ircc_irq= [HW] IRQ line
  1828. smsc-ircc2.ircc_dma= [HW] DMA channel
  1829. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1830. 0: Toshiba Satellite 1800 (GP data pin select)
  1831. 1: Fast pin select (default)
  1832. 2: ATC IRMode
  1833. snd-ad1816a= [HW,ALSA]
  1834. snd-ad1848= [HW,ALSA]
  1835. snd-ali5451= [HW,ALSA]
  1836. snd-als100= [HW,ALSA]
  1837. snd-als4000= [HW,ALSA]
  1838. snd-azt2320= [HW,ALSA]
  1839. snd-cmi8330= [HW,ALSA]
  1840. snd-cmipci= [HW,ALSA]
  1841. snd-cs4231= [HW,ALSA]
  1842. snd-cs4232= [HW,ALSA]
  1843. snd-cs4236= [HW,ALSA]
  1844. snd-cs4281= [HW,ALSA]
  1845. snd-cs46xx= [HW,ALSA]
  1846. snd-dt019x= [HW,ALSA]
  1847. snd-dummy= [HW,ALSA]
  1848. snd-emu10k1= [HW,ALSA]
  1849. snd-ens1370= [HW,ALSA]
  1850. snd-ens1371= [HW,ALSA]
  1851. snd-es968= [HW,ALSA]
  1852. snd-es1688= [HW,ALSA]
  1853. snd-es18xx= [HW,ALSA]
  1854. snd-es1938= [HW,ALSA]
  1855. snd-es1968= [HW,ALSA]
  1856. snd-fm801= [HW,ALSA]
  1857. snd-gusclassic= [HW,ALSA]
  1858. snd-gusextreme= [HW,ALSA]
  1859. snd-gusmax= [HW,ALSA]
  1860. snd-hdsp= [HW,ALSA]
  1861. snd-ice1712= [HW,ALSA]
  1862. snd-intel8x0= [HW,ALSA]
  1863. snd-interwave= [HW,ALSA]
  1864. snd-interwave-stb=
  1865. [HW,ALSA]
  1866. snd-korg1212= [HW,ALSA]
  1867. snd-maestro3= [HW,ALSA]
  1868. snd-mpu401= [HW,ALSA]
  1869. snd-mtpav= [HW,ALSA]
  1870. snd-nm256= [HW,ALSA]
  1871. snd-opl3sa2= [HW,ALSA]
  1872. snd-opti92x-ad1848=
  1873. [HW,ALSA]
  1874. snd-opti92x-cs4231=
  1875. [HW,ALSA]
  1876. snd-opti93x= [HW,ALSA]
  1877. snd-pmac= [HW,ALSA]
  1878. snd-rme32= [HW,ALSA]
  1879. snd-rme96= [HW,ALSA]
  1880. snd-rme9652= [HW,ALSA]
  1881. snd-sb8= [HW,ALSA]
  1882. snd-sb16= [HW,ALSA]
  1883. snd-sbawe= [HW,ALSA]
  1884. snd-serial= [HW,ALSA]
  1885. snd-sgalaxy= [HW,ALSA]
  1886. snd-sonicvibes= [HW,ALSA]
  1887. snd-sun-amd7930=
  1888. [HW,ALSA]
  1889. snd-sun-cs4231= [HW,ALSA]
  1890. snd-trident= [HW,ALSA]
  1891. snd-usb-audio= [HW,ALSA,USB]
  1892. snd-via82xx= [HW,ALSA]
  1893. snd-virmidi= [HW,ALSA]
  1894. snd-wavefront= [HW,ALSA]
  1895. snd-ymfpci= [HW,ALSA]
  1896. softlockup_panic=
  1897. [KNL] Should the soft-lockup detector generate panics.
  1898. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1899. See Documentation/sonypi.txt
  1900. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1901. See Documentation/serial/specialix.txt.
  1902. spia_io_base= [HW,MTD]
  1903. spia_fio_base=
  1904. spia_pedr=
  1905. spia_peddr=
  1906. sscape= [HW,OSS]
  1907. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1908. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1909. See Documentation/scsi/st.txt.
  1910. stacktrace [FTRACE]
  1911. Enabled the stack tracer on boot up.
  1912. sti= [PARISC,HW]
  1913. Format: <num>
  1914. Set the STI (builtin display/keyboard on the HP-PARISC
  1915. machines) console (graphic card) which should be used
  1916. as the initial boot-console.
  1917. See also comment in drivers/video/console/sticore.c.
  1918. sti_font= [HW]
  1919. See comment in drivers/video/console/sticore.c.
  1920. stifb= [HW]
  1921. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1922. sunrpc.min_resvport=
  1923. sunrpc.max_resvport=
  1924. [NFS,SUNRPC]
  1925. SunRPC servers often require that client requests
  1926. originate from a privileged port (i.e. a port in the
  1927. range 0 < portnr < 1024).
  1928. An administrator who wishes to reserve some of these
  1929. ports for other uses may adjust the range that the
  1930. kernel's sunrpc client considers to be privileged
  1931. using these two parameters to set the minimum and
  1932. maximum port values.
  1933. sunrpc.pool_mode=
  1934. [NFS]
  1935. Control how the NFS server code allocates CPUs to
  1936. service thread pools. Depending on how many NICs
  1937. you have and where their interrupts are bound, this
  1938. option will affect which CPUs will do NFS serving.
  1939. Note: this parameter cannot be changed while the
  1940. NFS server is running.
  1941. auto the server chooses an appropriate mode
  1942. automatically using heuristics
  1943. global a single global pool contains all CPUs
  1944. percpu one pool for each CPU
  1945. pernode one pool for each NUMA node (equivalent
  1946. to global on non-NUMA machines)
  1947. sunrpc.tcp_slot_table_entries=
  1948. sunrpc.udp_slot_table_entries=
  1949. [NFS,SUNRPC]
  1950. Sets the upper limit on the number of simultaneous
  1951. RPC calls that can be sent from the client to a
  1952. server. Increasing these values may allow you to
  1953. improve throughput, but will also increase the
  1954. amount of memory reserved for use by the client.
  1955. swiotlb= [IA-64] Number of I/O TLB slabs
  1956. switches= [HW,M68k]
  1957. sym53c416= [HW,SCSI]
  1958. See header of drivers/scsi/sym53c416.c.
  1959. sysrq_always_enabled
  1960. [KNL]
  1961. Ignore sysrq setting - this boot parameter will
  1962. neutralize any effect of /proc/sys/kernel/sysrq.
  1963. Useful for debugging.
  1964. t128= [HW,SCSI]
  1965. See header of drivers/scsi/t128.c.
  1966. tdfx= [HW,DRM]
  1967. test_suspend= [SUSPEND]
  1968. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1969. standby suspend) as the system sleep state to briefly
  1970. enter during system startup. The system is woken from
  1971. this state using a wakeup-capable RTC alarm.
  1972. thash_entries= [KNL,NET]
  1973. Set number of hash buckets for TCP connection
  1974. thermal.act= [HW,ACPI]
  1975. -1: disable all active trip points in all thermal zones
  1976. <degrees C>: override all lowest active trip points
  1977. thermal.crt= [HW,ACPI]
  1978. -1: disable all critical trip points in all thermal zones
  1979. <degrees C>: override all critical trip points
  1980. thermal.nocrt= [HW,ACPI]
  1981. Set to disable actions on ACPI thermal zone
  1982. critical and hot trip points.
  1983. [HW,ACPI]
  1984. 1: disable ACPI thermal control
  1985. thermal.psv= [HW,ACPI]
  1986. -1: disable all passive trip points
  1987. <degrees C>: override all passive trip points to this
  1988. value
  1989. thermal.tzp= [HW,ACPI]
  1990. Specify global default ACPI thermal zone polling rate
  1991. <deci-seconds>: poll all this frequency
  1992. 0: no polling (default)
  1993. tmscsim= [HW,SCSI]
  1994. See comment before function dc390_setup() in
  1995. drivers/scsi/tmscsim.c.
  1996. topology= [S390]
  1997. Format: {off | on}
  1998. Specify if the kernel should make use of the cpu
  1999. topology informations if the hardware supports these.
  2000. The scheduler will make use of these informations and
  2001. e.g. base its process migration decisions on it.
  2002. Default is off.
  2003. tp720= [HW,PS2]
  2004. trace_buf_size=nn[KMG]
  2005. [FTRACE] will set tracing buffer size.
  2006. trace_event=[event-list]
  2007. [FTRACE] Set and start specified trace events in order
  2008. to facilitate early boot debugging.
  2009. See also Documentation/trace/events.txt
  2010. trix= [HW,OSS] MediaTrix AudioTrix Pro
  2011. Format:
  2012. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  2013. tsc= Disable clocksource-must-verify flag for TSC.
  2014. Format: <string>
  2015. [x86] reliable: mark tsc clocksource as reliable, this
  2016. disables clocksource verification at runtime.
  2017. Used to enable high-resolution timer mode on older
  2018. hardware, and in virtualized environment.
  2019.[2|3]= [HW,JOY]
  2020. TurboGraFX parallel port interface
  2021. Format:
  2022. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  2023. See also Documentation/input/joystick-parport.txt
  2024. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  2025. See header of drivers/scsi/u14-34f.c.
  2026. uart401= [HW,OSS]
  2027. Format: <io>,<irq>
  2028. uart6850= [HW,OSS]
  2029. Format: <io>,<irq>
  2030. uhci-hcd.ignore_oc=
  2031. [USB] Ignore overcurrent events (default N).
  2032. Some badly-designed motherboards generate lots of
  2033. bogus events, for ports that aren't wired to
  2034. anything. Set this parameter to avoid log spamming.
  2035. Note that genuine overcurrent events won't be
  2036. reported either.
  2037. unknown_nmi_panic
  2038. [X86]
  2039. Set unknown_nmi_panic=1 early on boot.
  2040. usbcore.autosuspend=
  2041. [USB] The autosuspend time delay (in seconds) used
  2042. for newly-detected USB devices (default 2). This
  2043. is the time required before an idle device will be
  2044. autosuspended. Devices for which the delay is set
  2045. to a negative value won't be autosuspended at all.
  2046. usbcore.usbfs_snoop=
  2047. [USB] Set to log all usbfs traffic (default 0 = off).
  2048. usbcore.blinkenlights=
  2049. [USB] Set to cycle leds on hubs (default 0 = off).
  2050. usbcore.old_scheme_first=
  2051. [USB] Start with the old device initialization
  2052. scheme (default 0 = off).
  2053. usbcore.use_both_schemes=
  2054. [USB] Try the other device initialization scheme
  2055. if the first one fails (default 1 = enabled).
  2056. usbcore.initial_descriptor_timeout=
  2057. [USB] Specifies timeout for the initial 64-byte
  2058. USB_REQ_GET_DESCRIPTOR request in milliseconds
  2059. (default 5000 = 5.0 seconds).
  2060. usbhid.mousepoll=
  2061. [USBHID] The interval which mice are to be polled at.
  2062. usb-storage.delay_use=
  2063. [UMS] The delay in seconds before a new device is
  2064. scanned for Logical Units (default 5).
  2065. usb-storage.quirks=
  2066. [UMS] A list of quirks entries to supplement or
  2067. override the built-in unusual_devs list. List
  2068. entries are separated by commas. Each entry has
  2069. the form VID:PID:Flags where VID and PID are Vendor
  2070. and Product ID values (4-digit hex numbers) and
  2071. Flags is a set of characters, each corresponding
  2072. to a common usb-storage quirk flag as follows:
  2073. a = SANE_SENSE (collect more than 18 bytes
  2074. of sense data);
  2075. b = BAD_SENSE (don't collect more than 18
  2076. bytes of sense data);
  2077. c = FIX_CAPACITY (decrease the reported
  2078. device capacity by one sector);
  2079. h = CAPACITY_HEURISTICS (decrease the
  2080. reported device capacity by one
  2081. sector if the number is odd);
  2082. i = IGNORE_DEVICE (don't bind to this
  2083. device);
  2084. l = NOT_LOCKABLE (don't try to lock and
  2085. unlock ejectable media);
  2086. m = MAX_SECTORS_64 (don't transfer more
  2087. than 64 sectors = 32 KB at a time);
  2088. o = CAPACITY_OK (accept the capacity
  2089. reported by the device);
  2090. r = IGNORE_RESIDUE (the device reports
  2091. bogus residue values);
  2092. s = SINGLE_LUN (the device has only one
  2093. Logical Unit);
  2094. w = NO_WP_DETECT (don't test whether the
  2095. medium is write-protected).
  2096. Example: quirks=0419:aaf5:rl,0421:0433:rc
  2097. userpte=
  2098. [X86] Flags controlling user PTE allocations.
  2099. nohigh = do not allocate PTE pages in
  2100. HIGHMEM regardless of setting
  2101. of CONFIG_HIGHPTE.
  2102. vdso= [X86,SH]
  2103. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  2104. vdso=1: enable VDSO (default)
  2105. vdso=0: disable VDSO mapping
  2106. vdso32= [X86]
  2107. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  2108. vdso32=1: enable 32-bit VDSO (default)
  2109. vdso32=0: disable 32-bit VDSO mapping
  2110. vector= [IA-64,SMP]
  2111. vector=percpu: enable percpu vector domain
  2112. video= [FB] Frame buffer configuration
  2113. See Documentation/fb/modedb.txt.
  2114. vga= [BOOT,X86-32] Select a particular video mode
  2115. See Documentation/x86/boot.txt and
  2116. Documentation/svga.txt.
  2117. Use vga=ask for menu.
  2118. This is actually a boot loader parameter; the value is
  2119. passed to the kernel using a special protocol.
  2120. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  2121. size of <nn>. This can be used to increase the
  2122. minimum size (128MB on x86). It can also be used to
  2123. decrease the size and leave more room for directly
  2124. mapped kernel RAM.
  2125. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  2126. Format: <command>
  2127. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  2128. Format: <command>
  2129. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  2130. Format: <command>
  2131. vt.default_blu= [VT]
  2132. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  2133. Change the default blue palette of the console.
  2134. This is a 16-member array composed of values
  2135. ranging from 0-255.
  2136. vt.default_grn= [VT]
  2137. Format: <green0>,<green1>,<green2>,...,<green15>
  2138. Change the default green palette of the console.
  2139. This is a 16-member array composed of values
  2140. ranging from 0-255.
  2141. vt.default_red= [VT]
  2142. Format: <red0>,<red1>,<red2>,...,<red15>
  2143. Change the default red palette of the console.
  2144. This is a 16-member array composed of values
  2145. ranging from 0-255.
  2146. vt.default_utf8=
  2147. [VT]
  2148. Format=<0|1>
  2149. Set system-wide default UTF-8 mode for all tty's.
  2150. Default is 1, i.e. UTF-8 mode is enabled for all
  2151. newly opened terminals.
  2152. waveartist= [HW,OSS]
  2153. Format: <io>,<irq>,<dma>,<dma2>
  2154. wd33c93= [HW,SCSI]
  2155. See header of drivers/scsi/wd33c93.c.
  2156. wd7000= [HW,SCSI]
  2157. See header of drivers/scsi/wd7000.c.
  2158. wdt= [WDT] Watchdog
  2159. See Documentation/watchdog/wdt.txt.
  2160. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  2161. default x2apic cluster mode on platforms
  2162. supporting x2apic.
  2163. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  2164. xd_geo= See header of drivers/block/xd.c.
  2165. xirc2ps_cs= [NET,PCMCIA]
  2166. Format:
  2167. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  2168. ______________________________________________________________________
  2169. TODO:
  2170. Add documentation for ALSA options.
  2171. Add more DRM drivers.