kernel-parameters.txt 108 KB

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  1. Kernel Parameters
  2. ~~~~~~~~~~~~~~~~~
  3. The following is a consolidated list of the kernel parameters as implemented
  4. (mostly) by the __setup() macro and sorted into English Dictionary order
  5. (defined as ignoring all punctuation and sorting digits before letters in a
  6. case insensitive manner), and with descriptions where known.
  7. Module parameters for loadable modules are specified only as the
  8. parameter name with optional '=' and value as appropriate, such as:
  9. modprobe usbcore blinkenlights=1
  10. Module parameters for modules that are built into the kernel image
  11. are specified on the kernel command line with the module name plus
  12. '.' plus parameter name, with '=' and value if appropriate, such as:
  13. usbcore.blinkenlights=1
  14. Hyphens (dashes) and underscores are equivalent in parameter names, so
  15. log_buf_len=1M print-fatal-signals=1
  16. can also be entered as
  17. log-buf-len=1M print_fatal_signals=1
  18. This document may not be entirely up to date and comprehensive. The command
  19. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  20. module. Loadable modules, after being loaded into the running kernel, also
  21. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  22. parameters may be changed at runtime by the command
  23. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  24. The parameters listed below are only valid if certain kernel build options were
  25. enabled and if respective hardware is present. The text in square brackets at
  26. the beginning of each description states the restrictions within which a
  27. parameter is applicable:
  28. ACPI ACPI support is enabled.
  29. AGP AGP (Accelerated Graphics Port) is enabled.
  30. ALSA ALSA sound support is enabled.
  31. APIC APIC support is enabled.
  32. APM Advanced Power Management support is enabled.
  33. ARM ARM architecture is enabled.
  34. AVR32 AVR32 architecture is enabled.
  35. AX25 Appropriate AX.25 support is enabled.
  36. BLACKFIN Blackfin architecture is enabled.
  37. DRM Direct Rendering Management support is enabled.
  38. DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  39. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  40. EFI EFI Partitioning (GPT) is enabled
  41. EIDE EIDE/ATAPI support is enabled.
  42. EVM Extended Verification Module
  43. FB The frame buffer device is enabled.
  44. FTRACE Function tracing enabled.
  45. GCOV GCOV profiling is enabled.
  46. HW Appropriate hardware is enabled.
  47. IA-64 IA-64 architecture is enabled.
  48. IMA Integrity measurement architecture is enabled.
  49. IOSCHED More than one I/O scheduler is enabled.
  50. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  51. IPV6 IPv6 support is enabled.
  52. ISAPNP ISA PnP code is enabled.
  53. ISDN Appropriate ISDN support is enabled.
  54. JOY Appropriate joystick support is enabled.
  55. KGDB Kernel debugger support is enabled.
  56. KVM Kernel Virtual Machine support is enabled.
  57. LIBATA Libata driver is enabled
  58. LP Printer support is enabled.
  59. LOOP Loopback device support is enabled.
  60. M68k M68k architecture is enabled.
  61. These options have more detailed description inside of
  62. Documentation/m68k/kernel-options.txt.
  63. MDA MDA console support is enabled.
  64. MIPS MIPS architecture is enabled.
  65. MOUSE Appropriate mouse support is enabled.
  66. MSI Message Signaled Interrupts (PCI).
  67. MTD MTD (Memory Technology Device) support is enabled.
  68. NET Appropriate network support is enabled.
  69. NUMA NUMA support is enabled.
  70. NFS Appropriate NFS support is enabled.
  71. OSS OSS sound support is enabled.
  72. PV_OPS A paravirtualized kernel is enabled.
  73. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  74. PARISC The PA-RISC architecture is enabled.
  75. PCI PCI bus support is enabled.
  76. PCIE PCI Express support is enabled.
  77. PCMCIA The PCMCIA subsystem is enabled.
  78. PNP Plug & Play support is enabled.
  79. PPC PowerPC architecture is enabled.
  80. PPT Parallel port support is enabled.
  81. PS2 Appropriate PS/2 support is enabled.
  82. RAM RAM disk support is enabled.
  83. S390 S390 architecture is enabled.
  84. SCSI Appropriate SCSI support is enabled.
  85. A lot of drivers have their options described inside
  86. the Documentation/scsi/ sub-directory.
  87. SECURITY Different security models are enabled.
  88. SELINUX SELinux support is enabled.
  89. APPARMOR AppArmor support is enabled.
  90. SERIAL Serial support is enabled.
  91. SH SuperH architecture is enabled.
  92. SMP The kernel is an SMP kernel.
  93. SPARC Sparc architecture is enabled.
  94. SWSUSP Software suspend (hibernation) is enabled.
  95. SUSPEND System suspend states are enabled.
  96. TPM TPM drivers are enabled.
  97. TS Appropriate touchscreen support is enabled.
  98. UMS USB Mass Storage support is enabled.
  99. USB USB support is enabled.
  100. USBHID USB Human Interface Device support is enabled.
  101. V4L Video For Linux support is enabled.
  102. VMMIO Driver for memory mapped virtio devices is enabled.
  103. VGA The VGA console has been enabled.
  104. VT Virtual terminal support is enabled.
  105. WDT Watchdog support is enabled.
  106. XT IBM PC/XT MFM hard disk support is enabled.
  107. X86-32 X86-32, aka i386 architecture is enabled.
  108. X86-64 X86-64 architecture is enabled.
  109. More X86-64 boot options can be found in
  110. Documentation/x86/x86_64/boot-options.txt .
  111. X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
  112. XEN Xen support is enabled
  113. In addition, the following text indicates that the option:
  114. BUGS= Relates to possible processor bugs on the said processor.
  115. KNL Is a kernel start-up parameter.
  116. BOOT Is a boot loader parameter.
  117. Parameters denoted with BOOT are actually interpreted by the boot
  118. loader, and have no meaning to the kernel directly.
  119. Do not modify the syntax of boot loader parameters without extreme
  120. need or coordination with <Documentation/x86/boot.txt>.
  121. There are also arch-specific kernel-parameters not documented here.
  122. See for example <Documentation/x86/x86_64/boot-options.txt>.
  123. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  124. a trailing = on the name of any parameter states that that parameter will
  125. be entered as an environment variable, whereas its absence indicates that
  126. it will appear as a kernel argument readable via /proc/cmdline by programs
  127. running once the system is up.
  128. The number of kernel parameters is not limited, but the length of the
  129. complete command line (parameters including spaces etc.) is limited to
  130. a fixed number of characters. This limit depends on the architecture
  131. and is between 256 and 4096 characters. It is defined in the file
  132. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  133. Finally, the [KMG] suffix is commonly described after a number of kernel
  134. parameter values. These 'K', 'M', and 'G' letters represent the _binary_
  135. multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
  136. bytes respectively. Such letter suffixes can also be entirely omitted.
  137. acpi= [HW,ACPI,X86]
  138. Advanced Configuration and Power Interface
  139. Format: { force | off | strict | noirq | rsdt }
  140. force -- enable ACPI if default was off
  141. off -- disable ACPI if default was on
  142. noirq -- do not use ACPI for IRQ routing
  143. strict -- Be less tolerant of platforms that are not
  144. strictly ACPI specification compliant.
  145. rsdt -- prefer RSDT over (default) XSDT
  146. copy_dsdt -- copy DSDT to memory
  147. See also Documentation/power/runtime_pm.txt, pci=noacpi
  148. acpi_rsdp= [ACPI,EFI,KEXEC]
  149. Pass the RSDP address to the kernel, mostly used
  150. on machines running EFI runtime service to boot the
  151. second kernel for kdump.
  152. acpi_apic_instance= [ACPI, IOAPIC]
  153. Format: <int>
  154. 2: use 2nd APIC table, if available
  155. 1,0: use 1st APIC table
  156. default: 0
  157. acpi_backlight= [HW,ACPI]
  158. acpi_backlight=vendor
  159. acpi_backlight=video
  160. If set to vendor, prefer vendor specific driver
  161. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  162. of the ACPI video.ko driver.
  163. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  164. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  165. Format: <int>
  166. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  167. debug output. Bits in debug_layer correspond to a
  168. _COMPONENT in an ACPI source file, e.g.,
  169. #define _COMPONENT ACPI_PCI_COMPONENT
  170. Bits in debug_level correspond to a level in
  171. ACPI_DEBUG_PRINT statements, e.g.,
  172. ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
  173. The debug_level mask defaults to "info". See
  174. Documentation/acpi/debug.txt for more information about
  175. debug layers and levels.
  176. Enable processor driver info messages:
  177. acpi.debug_layer=0x20000000
  178. Enable PCI/PCI interrupt routing info messages:
  179. acpi.debug_layer=0x400000
  180. Enable AML "Debug" output, i.e., stores to the Debug
  181. object while interpreting AML:
  182. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  183. Enable all messages related to ACPI hardware:
  184. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  185. Some values produce so much output that the system is
  186. unusable. The "log_buf_len" parameter may be useful
  187. if you need to capture more output.
  188. acpi_irq_balance [HW,ACPI]
  189. ACPI will balance active IRQs
  190. default in APIC mode
  191. acpi_irq_nobalance [HW,ACPI]
  192. ACPI will not move active IRQs (default)
  193. default in PIC mode
  194. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  195. Format: <irq>,<irq>...
  196. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  197. use by PCI
  198. Format: <irq>,<irq>...
  199. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  200. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  201. Format: To spoof as Windows 98: ="Microsoft Windows"
  202. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  203. acpi_osi="string1" # add string1 -- only one string
  204. acpi_osi="!string2" # remove built-in string2
  205. acpi_osi= # disable all strings
  206. acpi_pm_good [X86]
  207. Override the pmtimer bug detection: force the kernel
  208. to assume that this machine's pmtimer latches its value
  209. and always returns good values.
  210. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  211. Format: { level | edge | high | low }
  212. acpi_serialize [HW,ACPI] force serialization of AML methods
  213. acpi_skip_timer_override [HW,ACPI]
  214. Recognize and ignore IRQ0/pin2 Interrupt Override.
  215. For broken nForce2 BIOS resulting in XT-PIC timer.
  216. acpi_sleep= [HW,ACPI] Sleep options
  217. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
  218. old_ordering, nonvs, sci_force_enable }
  219. See Documentation/power/video.txt for information on
  220. s3_bios and s3_mode.
  221. s3_beep is for debugging; it makes the PC's speaker beep
  222. as soon as the kernel's real-mode entry point is called.
  223. s4_nohwsig prevents ACPI hardware signature from being
  224. used during resume from hibernation.
  225. old_ordering causes the ACPI 1.0 ordering of the _PTS
  226. control method, with respect to putting devices into
  227. low power states, to be enforced (the ACPI 2.0 ordering
  228. of _PTS is used by default).
  229. nonvs prevents the kernel from saving/restoring the
  230. ACPI NVS memory during suspend/hibernation and resume.
  231. sci_force_enable causes the kernel to set SCI_EN directly
  232. on resume from S1/S3 (which is against the ACPI spec,
  233. but some broken systems don't work without it).
  234. acpi_use_timer_override [HW,ACPI]
  235. Use timer override. For some broken Nvidia NF5 boards
  236. that require a timer override, but don't have HPET
  237. acpi_enforce_resources= [ACPI]
  238. { strict | lax | no }
  239. Check for resource conflicts between native drivers
  240. and ACPI OperationRegions (SystemIO and SystemMemory
  241. only). IO ports and memory declared in ACPI might be
  242. used by the ACPI subsystem in arbitrary AML code and
  243. can interfere with legacy drivers.
  244. strict (default): access to resources claimed by ACPI
  245. is denied; legacy drivers trying to access reserved
  246. resources will fail to bind to device using them.
  247. lax: access to resources claimed by ACPI is allowed;
  248. legacy drivers trying to access reserved resources
  249. will bind successfully but a warning message is logged.
  250. no: ACPI OperationRegions are not marked as reserved,
  251. no further checks are performed.
  252. add_efi_memmap [EFI; X86] Include EFI memory map in
  253. kernel's map of available physical RAM.
  254. agp= [AGP]
  255. { off | try_unsupported }
  256. off: disable AGP support
  257. try_unsupported: try to drive unsupported chipsets
  258. (may crash computer or cause data corruption)
  259. ALSA [HW,ALSA]
  260. See Documentation/sound/alsa/alsa-parameters.txt
  261. alignment= [KNL,ARM]
  262. Allow the default userspace alignment fault handler
  263. behaviour to be specified. Bit 0 enables warnings,
  264. bit 1 enables fixups, and bit 2 sends a segfault.
  265. align_va_addr= [X86-64]
  266. Align virtual addresses by clearing slice [14:12] when
  267. allocating a VMA at process creation time. This option
  268. gives you up to 3% performance improvement on AMD F15h
  269. machines (where it is enabled by default) for a
  270. CPU-intensive style benchmark, and it can vary highly in
  271. a microbenchmark depending on workload and compiler.
  272. 32: only for 32-bit processes
  273. 64: only for 64-bit processes
  274. on: enable for both 32- and 64-bit processes
  275. off: disable for both 32- and 64-bit processes
  276. amd_iommu= [HW,X86-64]
  277. Pass parameters to the AMD IOMMU driver in the system.
  278. Possible values are:
  279. fullflush - enable flushing of IO/TLB entries when
  280. they are unmapped. Otherwise they are
  281. flushed before they will be reused, which
  282. is a lot of faster
  283. off - do not initialize any AMD IOMMU found in
  284. the system
  285. force_isolation - Force device isolation for all
  286. devices. The IOMMU driver is not
  287. allowed anymore to lift isolation
  288. requirements as needed. This option
  289. does not override iommu=pt
  290. amd_iommu_dump= [HW,X86-64]
  291. Enable AMD IOMMU driver option to dump the ACPI table
  292. for AMD IOMMU. With this option enabled, AMD IOMMU
  293. driver will print ACPI tables for AMD IOMMU during
  294. IOMMU initialization.
  295. amijoy.map= [HW,JOY] Amiga joystick support
  296. Map of devices attached to JOY0DAT and JOY1DAT
  297. Format: <a>,<b>
  298. See also Documentation/input/joystick.txt
  299. analog.map= [HW,JOY] Analog joystick and gamepad support
  300. Specifies type or capabilities of an analog joystick
  301. connected to one of 16 gameports
  302. Format: <type1>,<type2>,..<type16>
  303. apc= [HW,SPARC]
  304. Power management functions (SPARCstation-4/5 + deriv.)
  305. Format: noidle
  306. Disable APC CPU standby support. SPARCstation-Fox does
  307. not play well with APC CPU idle - disable it if you have
  308. APC and your system crashes randomly.
  309. apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
  310. Change the output verbosity whilst booting
  311. Format: { quiet (default) | verbose | debug }
  312. Change the amount of debugging information output
  313. when initialising the APIC and IO-APIC components.
  314. autoconf= [IPV6]
  315. See Documentation/networking/ipv6.txt.
  316. show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
  317. Limit apic dumping. The parameter defines the maximal
  318. number of local apics being dumped. Also it is possible
  319. to set it to "all" by meaning -- no limit here.
  320. Format: { 1 (default) | 2 | ... | all }.
  321. The parameter valid if only apic=debug or
  322. apic=verbose is specified.
  323. Example: apic=debug show_lapic=all
  324. apm= [APM] Advanced Power Management
  325. See header of arch/x86/kernel/apm_32.c.
  326. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  327. Format: <io>,<irq>,<nodeID>
  328. ataflop= [HW,M68k]
  329. atarimouse= [HW,MOUSE] Atari Mouse
  330. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  331. EzKey and similar keyboards
  332. atkbd.reset= [HW] Reset keyboard during initialization
  333. atkbd.set= [HW] Select keyboard code set
  334. Format: <int> (2 = AT (default), 3 = PS/2)
  335. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  336. keyboards
  337. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  338. Format: <bool> (0 = real, 1 = synthetic (default))
  339. atkbd.softrepeat= [HW]
  340. Use software keyboard repeat
  341. baycom_epp= [HW,AX25]
  342. Format: <io>,<mode>
  343. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  344. Format: <io>,<mode>
  345. See header of drivers/net/hamradio/baycom_par.c.
  346. baycom_ser_fdx= [HW,AX25]
  347. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  348. Format: <io>,<irq>,<mode>[,<baud>]
  349. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  350. baycom_ser_hdx= [HW,AX25]
  351. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  352. Format: <io>,<irq>,<mode>
  353. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  354. boot_delay= Milliseconds to delay each printk during boot.
  355. Values larger than 10 seconds (10000) are changed to
  356. no delay (0).
  357. Format: integer
  358. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  359. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  360. bttv.radio= Most important insmod options are available as
  361. kernel args too.
  362. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  363. bttv.tuner=
  364. bulk_remove=off [PPC] This parameter disables the use of the pSeries
  365. firmware feature for flushing multiple hpte entries
  366. at a time.
  367. c101= [NET] Moxa C101 synchronous serial card
  368. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  369. Sometimes CPU hardware bugs make them report the cache
  370. size incorrectly. The kernel will attempt work arounds
  371. to fix known problems, but for some CPUs it is not
  372. possible to determine what the correct size should be.
  373. This option provides an override for these situations.
  374. capability.disable=
  375. [SECURITY] Disable capabilities. This would normally
  376. be used only if an alternative security model is to be
  377. configured. Potentially dangerous and should only be
  378. used if you are entirely sure of the consequences.
  379. ccw_timeout_log [S390]
  380. See Documentation/s390/CommonIO for details.
  381. cgroup_disable= [KNL] Disable a particular controller
  382. Format: {name of the controller(s) to disable}
  383. {Currently supported controllers - "memory"}
  384. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  385. Format: { "0" | "1" }
  386. See security/selinux/Kconfig help text.
  387. 0 -- check protection applied by kernel (includes
  388. any implied execute protection).
  389. 1 -- check protection requested by application.
  390. Default value is set via a kernel config option.
  391. Value can be changed at runtime via
  392. /selinux/checkreqprot.
  393. cio_ignore= [S390]
  394. See Documentation/s390/CommonIO for details.
  395. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  396. [Deprecated]
  397. Forces specified clocksource (if available) to be used
  398. when calculating gettimeofday(). If specified
  399. clocksource is not available, it defaults to PIT.
  400. Format: { pit | tsc | cyclone | pmtmr }
  401. clocksource= Override the default clocksource
  402. Format: <string>
  403. Override the default clocksource and use the clocksource
  404. with the name specified.
  405. Some clocksource names to choose from, depending on
  406. the platform:
  407. [all] jiffies (this is the base, fallback clocksource)
  408. [ACPI] acpi_pm
  409. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  410. pxa_timer,timer3,32k_counter,timer0_1
  411. [AVR32] avr32
  412. [X86-32] pit,hpet,tsc;
  413. scx200_hrt on Geode; cyclone on IBM x440
  414. [MIPS] MIPS
  415. [PARISC] cr16
  416. [S390] tod
  417. [SH] SuperH
  418. [SPARC64] tick
  419. [X86-64] hpet,tsc
  420. clearcpuid=BITNUM [X86]
  421. Disable CPUID feature X for the kernel. See
  422. arch/x86/include/asm/cpufeature.h for the valid bit
  423. numbers. Note the Linux specific bits are not necessarily
  424. stable over kernel options, but the vendor specific
  425. ones should be.
  426. Also note that user programs calling CPUID directly
  427. or using the feature without checking anything
  428. will still see it. This just prevents it from
  429. being used by the kernel or shown in /proc/cpuinfo.
  430. Also note the kernel might malfunction if you disable
  431. some critical bits.
  432. cma=nn[MG] [ARM,KNL]
  433. Sets the size of kernel global memory area for contiguous
  434. memory allocations. For more information, see
  435. include/linux/dma-contiguous.h
  436. cmo_free_hint= [PPC] Format: { yes | no }
  437. Specify whether pages are marked as being inactive
  438. when they are freed. This is used in CMO environments
  439. to determine OS memory pressure for page stealing by
  440. a hypervisor.
  441. Default: yes
  442. coherent_pool=nn[KMG] [ARM,KNL]
  443. Sets the size of memory pool for coherent, atomic dma
  444. allocations, by default set to 256K.
  445. code_bytes [X86] How many bytes of object code to print
  446. in an oops report.
  447. Range: 0 - 8192
  448. Default: 64
  449. com20020= [HW,NET] ARCnet - COM20020 chipset
  450. Format:
  451. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  452. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  453. Format: <io>[,<irq>]
  454. com90xx= [HW,NET]
  455. ARCnet - COM90xx chipset (memory-mapped buffers)
  456. Format: <io>[,<irq>[,<memstart>]]
  457. condev= [HW,S390] console device
  458. conmode=
  459. console= [KNL] Output console device and options.
  460. tty<n> Use the virtual console device <n>.
  461. ttyS<n>[,options]
  462. ttyUSB0[,options]
  463. Use the specified serial port. The options are of
  464. the form "bbbbpnf", where "bbbb" is the baud rate,
  465. "p" is parity ("n", "o", or "e"), "n" is number of
  466. bits, and "f" is flow control ("r" for RTS or
  467. omit it). Default is "9600n8".
  468. See Documentation/serial-console.txt for more
  469. information. See
  470. Documentation/networking/netconsole.txt for an
  471. alternative.
  472. uart[8250],io,<addr>[,options]
  473. uart[8250],mmio,<addr>[,options]
  474. Start an early, polled-mode console on the 8250/16550
  475. UART at the specified I/O port or MMIO address,
  476. switching to the matching ttyS device later. The
  477. options are the same as for ttyS, above.
  478. If the device connected to the port is not a TTY but a braille
  479. device, prepend "brl," before the device type, for instance
  480. console=brl,ttyS0
  481. For now, only VisioBraille is supported.
  482. consoleblank= [KNL] The console blank (screen saver) timeout in
  483. seconds. Defaults to 10*60 = 10mins. A value of 0
  484. disables the blank timer.
  485. coredump_filter=
  486. [KNL] Change the default value for
  487. /proc/<pid>/coredump_filter.
  488. See also Documentation/filesystems/proc.txt.
  489. cpuidle.off=1 [CPU_IDLE]
  490. disable the cpuidle sub-system
  491. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  492. Format:
  493. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  494. crashkernel=size[KMG][@offset[KMG]]
  495. [KNL] Using kexec, Linux can switch to a 'crash kernel'
  496. upon panic. This parameter reserves the physical
  497. memory region [offset, offset + size] for that kernel
  498. image. If '@offset' is omitted, then a suitable offset
  499. is selected automatically. Check
  500. Documentation/kdump/kdump.txt for further details.
  501. crashkernel=range1:size1[,range2:size2,...][@offset]
  502. [KNL] Same as above, but depends on the memory
  503. in the running system. The syntax of range is
  504. start-[end] where start and end are both
  505. a memory unit (amount[KMG]). See also
  506. Documentation/kdump/kdump.txt for an example.
  507. cs89x0_dma= [HW,NET]
  508. Format: <dma>
  509. cs89x0_media= [HW,NET]
  510. Format: { rj45 | aui | bnc }
  511. dasd= [HW,NET]
  512. See header of drivers/s390/block/dasd_devmap.c.
  513. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  514. (one device per port)
  515. Format: <port#>,<type>
  516. See also Documentation/input/joystick-parport.txt
  517. ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
  518. time. See Documentation/dynamic-debug-howto.txt for
  519. details. Deprecated, see dyndbg.
  520. debug [KNL] Enable kernel debugging (events log level).
  521. debug_locks_verbose=
  522. [KNL] verbose self-tests
  523. Format=<0|1>
  524. Print debugging info while doing the locking API
  525. self-tests.
  526. We default to 0 (no extra messages), setting it to
  527. 1 will print _a lot_ more information - normally
  528. only useful to kernel developers.
  529. debug_objects [KNL] Enable object debugging
  530. no_debug_objects
  531. [KNL] Disable object debugging
  532. debug_guardpage_minorder=
  533. [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
  534. parameter allows control of the order of pages that will
  535. be intentionally kept free (and hence protected) by the
  536. buddy allocator. Bigger value increase the probability
  537. of catching random memory corruption, but reduce the
  538. amount of memory for normal system use. The maximum
  539. possible value is MAX_ORDER/2. Setting this parameter
  540. to 1 or 2 should be enough to identify most random
  541. memory corruption problems caused by bugs in kernel or
  542. driver code when a CPU writes to (or reads from) a
  543. random memory location. Note that there exists a class
  544. of memory corruptions problems caused by buggy H/W or
  545. F/W or by drivers badly programing DMA (basically when
  546. memory is written at bus level and the CPU MMU is
  547. bypassed) which are not detectable by
  548. CONFIG_DEBUG_PAGEALLOC, hence this option will not help
  549. tracking down these problems.
  550. debugpat [X86] Enable PAT debugging
  551. decnet.addr= [HW,NET]
  552. Format: <area>[,<node>]
  553. See also Documentation/networking/decnet.txt.
  554. default_hugepagesz=
  555. [same as hugepagesz=] The size of the default
  556. HugeTLB page size. This is the size represented by
  557. the legacy /proc/ hugepages APIs, used for SHM, and
  558. default size when mounting hugetlbfs filesystems.
  559. Defaults to the default architecture's huge page size
  560. if not specified.
  561. dhash_entries= [KNL]
  562. Set number of hash buckets for dentry cache.
  563. digi= [HW,SERIAL]
  564. IO parameters + enable/disable command.
  565. digiepca= [HW,SERIAL]
  566. See drivers/char/README.epca and
  567. Documentation/serial/digiepca.txt.
  568. disable= [IPV6]
  569. See Documentation/networking/ipv6.txt.
  570. disable_ddw [PPC/PSERIES]
  571. Disable Dynamic DMA Window support. Use this if
  572. to workaround buggy firmware.
  573. disable_ipv6= [IPV6]
  574. See Documentation/networking/ipv6.txt.
  575. disable_mtrr_cleanup [X86]
  576. The kernel tries to adjust MTRR layout from continuous
  577. to discrete, to make X server driver able to add WB
  578. entry later. This parameter disables that.
  579. disable_mtrr_trim [X86, Intel and AMD only]
  580. By default the kernel will trim any uncacheable
  581. memory out of your available memory pool based on
  582. MTRR settings. This parameter disables that behavior,
  583. possibly causing your machine to run very slowly.
  584. disable_timer_pin_1 [X86]
  585. Disable PIN 1 of APIC timer
  586. Can be useful to work around chipset bugs.
  587. dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
  588. this option disables the debugging code at boot.
  589. dma_debug_entries=<number>
  590. This option allows to tune the number of preallocated
  591. entries for DMA-API debugging code. One entry is
  592. required per DMA-API allocation. Use this if the
  593. DMA-API debugging code disables itself because the
  594. architectural default is too low.
  595. dma_debug_driver=<driver_name>
  596. With this option the DMA-API debugging driver
  597. filter feature can be enabled at boot time. Just
  598. pass the driver to filter for as the parameter.
  599. The filter can be disabled or changed to another
  600. driver later using sysfs.
  601. drm_kms_helper.edid_firmware=[<connector>:]<file>
  602. Broken monitors, graphic adapters and KVMs may
  603. send no or incorrect EDID data sets. This parameter
  604. allows to specify an EDID data set in the
  605. /lib/firmware directory that is used instead.
  606. Generic built-in EDID data sets are used, if one of
  607. edid/1024x768.bin, edid/1280x1024.bin,
  608. edid/1680x1050.bin, or edid/1920x1080.bin is given
  609. and no file with the same name exists. Details and
  610. instructions how to build your own EDID data are
  611. available in Documentation/EDID/HOWTO.txt. An EDID
  612. data set will only be used for a particular connector,
  613. if its name and a colon are prepended to the EDID
  614. name.
  615. dscc4.setup= [NET]
  616. dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
  617. module.dyndbg[="val"]
  618. Enable debug messages at boot time. See
  619. Documentation/dynamic-debug-howto.txt for details.
  620. earlycon= [KNL] Output early console device and options.
  621. uart[8250],io,<addr>[,options]
  622. uart[8250],mmio,<addr>[,options]
  623. uart[8250],mmio32,<addr>[,options]
  624. Start an early, polled-mode console on the 8250/16550
  625. UART at the specified I/O port or MMIO address.
  626. MMIO inter-register address stride is either 8-bit
  627. (mmio) or 32-bit (mmio32).
  628. The options are the same as for ttyS, above.
  629. earlyprintk= [X86,SH,BLACKFIN]
  630. earlyprintk=vga
  631. earlyprintk=serial[,ttySn[,baudrate]]
  632. earlyprintk=ttySn[,baudrate]
  633. earlyprintk=dbgp[debugController#]
  634. Append ",keep" to not disable it when the real console
  635. takes over.
  636. Only vga or serial or usb debug port at a time.
  637. Currently only ttyS0 and ttyS1 are supported.
  638. Interaction with the standard serial driver is not
  639. very good.
  640. The VGA output is eventually overwritten by the real
  641. console.
  642. ekgdboc= [X86,KGDB] Allow early kernel console debugging
  643. ekgdboc=kbd
  644. This is designed to be used in conjunction with
  645. the boot argument: earlyprintk=vga
  646. edd= [EDD]
  647. Format: {"off" | "on" | "skip[mbr]"}
  648. eisa_irq_edge= [PARISC,HW]
  649. See header of drivers/parisc/eisa.c.
  650. elanfreq= [X86-32]
  651. See comment before function elanfreq_setup() in
  652. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  653. elevator= [IOSCHED]
  654. Format: {"cfq" | "deadline" | "noop"}
  655. See Documentation/block/cfq-iosched.txt and
  656. Documentation/block/deadline-iosched.txt for details.
  657. elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
  658. Specifies physical address of start of kernel core
  659. image elf header and optionally the size. Generally
  660. kexec loader will pass this option to capture kernel.
  661. See Documentation/kdump/kdump.txt for details.
  662. enable_mtrr_cleanup [X86]
  663. The kernel tries to adjust MTRR layout from continuous
  664. to discrete, to make X server driver able to add WB
  665. entry later. This parameter enables that.
  666. enable_timer_pin_1 [X86]
  667. Enable PIN 1 of APIC timer
  668. Can be useful to work around chipset bugs
  669. (in particular on some ATI chipsets).
  670. The kernel tries to set a reasonable default.
  671. enforcing [SELINUX] Set initial enforcing status.
  672. Format: {"0" | "1"}
  673. See security/selinux/Kconfig help text.
  674. 0 -- permissive (log only, no denials).
  675. 1 -- enforcing (deny and log).
  676. Default value is 0.
  677. Value can be changed at runtime via /selinux/enforce.
  678. erst_disable [ACPI]
  679. Disable Error Record Serialization Table (ERST)
  680. support.
  681. ether= [HW,NET] Ethernet cards parameters
  682. This option is obsoleted by the "netdev=" option, which
  683. has equivalent usage. See its documentation for details.
  684. evm= [EVM]
  685. Format: { "fix" }
  686. Permit 'security.evm' to be updated regardless of
  687. current integrity status.
  688. failslab=
  689. fail_page_alloc=
  690. fail_make_request=[KNL]
  691. General fault injection mechanism.
  692. Format: <interval>,<probability>,<space>,<times>
  693. See also Documentation/fault-injection/.
  694. floppy= [HW]
  695. See Documentation/blockdev/floppy.txt.
  696. force_pal_cache_flush
  697. [IA-64] Avoid check_sal_cache_flush which may hang on
  698. buggy SAL_CACHE_FLUSH implementations. Using this
  699. parameter will force ia64_sal_cache_flush to call
  700. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  701. ftrace=[tracer]
  702. [FTRACE] will set and start the specified tracer
  703. as early as possible in order to facilitate early
  704. boot debugging.
  705. ftrace_dump_on_oops[=orig_cpu]
  706. [FTRACE] will dump the trace buffers on oops.
  707. If no parameter is passed, ftrace will dump
  708. buffers of all CPUs, but if you pass orig_cpu, it will
  709. dump only the buffer of the CPU that triggered the
  710. oops.
  711. ftrace_filter=[function-list]
  712. [FTRACE] Limit the functions traced by the function
  713. tracer at boot up. function-list is a comma separated
  714. list of functions. This list can be changed at run
  715. time by the set_ftrace_filter file in the debugfs
  716. tracing directory.
  717. ftrace_notrace=[function-list]
  718. [FTRACE] Do not trace the functions specified in
  719. function-list. This list can be changed at run time
  720. by the set_ftrace_notrace file in the debugfs
  721. tracing directory.
  722. ftrace_graph_filter=[function-list]
  723. [FTRACE] Limit the top level callers functions traced
  724. by the function graph tracer at boot up.
  725. function-list is a comma separated list of functions
  726. that can be changed at run time by the
  727. set_graph_function file in the debugfs tracing directory.
  728. gamecon.map[2|3]=
  729. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  730. support via parallel port (up to 5 devices per port)
  731. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  732. See also Documentation/input/joystick-parport.txt
  733. gamma= [HW,DRM]
  734. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  735. Format: off | on
  736. default: on
  737. gcov_persist= [GCOV] When non-zero (default), profiling data for
  738. kernel modules is saved and remains accessible via
  739. debugfs, even when the module is unloaded/reloaded.
  740. When zero, profiling data is discarded and associated
  741. debugfs files are removed at module unload time.
  742. gpt [EFI] Forces disk with valid GPT signature but
  743. invalid Protective MBR to be treated as GPT.
  744. hashdist= [KNL,NUMA] Large hashes allocated during boot
  745. are distributed across NUMA nodes. Defaults on
  746. for 64-bit NUMA, off otherwise.
  747. Format: 0 | 1 (for off | on)
  748. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  749. hd= [EIDE] (E)IDE hard drive subsystem geometry
  750. Format: <cyl>,<head>,<sect>
  751. hest_disable [ACPI]
  752. Disable Hardware Error Source Table (HEST) support;
  753. corresponding firmware-first mode error processing
  754. logic will be disabled.
  755. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  756. size of <nn>. This works even on boxes that have no
  757. highmem otherwise. This also works to reduce highmem
  758. size on bigger boxes.
  759. highres= [KNL] Enable/disable high resolution timer mode.
  760. Valid parameters: "on", "off"
  761. Default: "on"
  762. hisax= [HW,ISDN]
  763. See Documentation/isdn/README.HiSax.
  764. hlt [BUGS=ARM,SH]
  765. hpet= [X86-32,HPET] option to control HPET usage
  766. Format: { enable (default) | disable | force |
  767. verbose }
  768. disable: disable HPET and use PIT instead
  769. force: allow force enabled of undocumented chips (ICH4,
  770. VIA, nVidia)
  771. verbose: show contents of HPET registers during setup
  772. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  773. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  774. On x86-64 and powerpc, this option can be specified
  775. multiple times interleaved with hugepages= to reserve
  776. huge pages of different sizes. Valid pages sizes on
  777. x86-64 are 2M (when the CPU supports "pse") and 1G
  778. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  779. Note that 1GB pages can only be allocated at boot time
  780. using hugepages= and not freed afterwards.
  781. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
  782. terminal devices. Valid values: 0..8
  783. hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
  784. If specified, z/VM IUCV HVC accepts connections
  785. from listed z/VM user IDs only.
  786. keep_bootcon [KNL]
  787. Do not unregister boot console at start. This is only
  788. useful for debugging when something happens in the window
  789. between unregistering the boot console and initializing
  790. the real console.
  791. i2c_bus= [HW] Override the default board specific I2C bus speed
  792. or register an additional I2C bus that is not
  793. registered from board initialization code.
  794. Format:
  795. <bus_id>,<clkrate>
  796. i8042.debug [HW] Toggle i8042 debug mode
  797. i8042.direct [HW] Put keyboard port into non-translated mode
  798. i8042.dumbkbd [HW] Pretend that controller can only read data from
  799. keyboard and cannot control its state
  800. (Don't attempt to blink the leds)
  801. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  802. i8042.nokbd [HW] Don't check/create keyboard port
  803. i8042.noloop [HW] Disable the AUX Loopback command while probing
  804. for the AUX port
  805. i8042.nomux [HW] Don't check presence of an active multiplexing
  806. controller
  807. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  808. controllers
  809. i8042.notimeout [HW] Ignore timeout condition signalled by controller
  810. i8042.reset [HW] Reset the controller during init and cleanup
  811. i8042.unlock [HW] Unlock (ignore) the keylock
  812. i810= [HW,DRM]
  813. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  814. indicates that the driver is running on unsupported
  815. hardware.
  816. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  817. does not match list of supported models.
  818. i8k.power_status
  819. [HW] Report power status in /proc/i8k
  820. (disabled by default)
  821. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  822. capability is set.
  823. i915.invert_brightness=
  824. [DRM] Invert the sense of the variable that is used to
  825. set the brightness of the panel backlight. Normally a
  826. brightness value of 0 indicates backlight switched off,
  827. and the maximum of the brightness value sets the backlight
  828. to maximum brightness. If this parameter is set to 0
  829. (default) and the machine requires it, or this parameter
  830. is set to 1, a brightness value of 0 sets the backlight
  831. to maximum brightness, and the maximum of the brightness
  832. value switches the backlight off.
  833. -1 -- never invert brightness
  834. 0 -- machine default
  835. 1 -- force brightness inversion
  836. icn= [HW,ISDN]
  837. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  838. ide-core.nodma= [HW] (E)IDE subsystem
  839. Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
  840. .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
  841. .cdrom .chs .ignore_cable are additional options
  842. See Documentation/ide/ide.txt.
  843. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  844. Claim all unknown PCI IDE storage controllers.
  845. idle= [X86]
  846. Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
  847. Poll forces a polling idle loop that can slightly
  848. improve the performance of waking up a idle CPU, but
  849. will use a lot of power and make the system run hot.
  850. Not recommended.
  851. idle=mwait: On systems which support MONITOR/MWAIT but
  852. the kernel chose to not use it because it doesn't save
  853. as much power as a normal idle loop, use the
  854. MONITOR/MWAIT idle loop anyways. Performance should be
  855. the same as idle=poll.
  856. idle=halt: Halt is forced to be used for CPU idle.
  857. In such case C2/C3 won't be used again.
  858. idle=nomwait: Disable mwait for CPU C-states
  859. ignore_loglevel [KNL]
  860. Ignore loglevel setting - this will print /all/
  861. kernel messages to the console. Useful for debugging.
  862. We also add it as printk module parameter, so users
  863. could change it dynamically, usually by
  864. /sys/module/printk/parameters/ignore_loglevel.
  865. ihash_entries= [KNL]
  866. Set number of hash buckets for inode cache.
  867. ima_appraise= [IMA] appraise integrity measurements
  868. Format: { "off" | "enforce" | "fix" }
  869. default: "enforce"
  870. ima_appraise_tcb [IMA]
  871. The builtin appraise policy appraises all files
  872. owned by uid=0.
  873. ima_audit= [IMA]
  874. Format: { "0" | "1" }
  875. 0 -- integrity auditing messages. (Default)
  876. 1 -- enable informational integrity auditing messages.
  877. ima_hash= [IMA]
  878. Format: { "sha1" | "md5" }
  879. default: "sha1"
  880. ima_tcb [IMA]
  881. Load a policy which meets the needs of the Trusted
  882. Computing Base. This means IMA will measure all
  883. programs exec'd, files mmap'd for exec, and all files
  884. opened for read by uid=0.
  885. init= [KNL]
  886. Format: <full_path>
  887. Run specified binary instead of /sbin/init as init
  888. process.
  889. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  890. for working out where the kernel is dying during
  891. startup.
  892. initrd= [BOOT] Specify the location of the initial ramdisk
  893. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  894. Format: <irq>
  895. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  896. on
  897. Enable intel iommu driver.
  898. off
  899. Disable intel iommu driver.
  900. igfx_off [Default Off]
  901. By default, gfx is mapped as normal device. If a gfx
  902. device has a dedicated DMAR unit, the DMAR unit is
  903. bypassed by not enabling DMAR with this option. In
  904. this case, gfx device will use physical address for
  905. DMA.
  906. forcedac [x86_64]
  907. With this option iommu will not optimize to look
  908. for io virtual address below 32-bit forcing dual
  909. address cycle on pci bus for cards supporting greater
  910. than 32-bit addressing. The default is to look
  911. for translation below 32-bit and if not available
  912. then look in the higher range.
  913. strict [Default Off]
  914. With this option on every unmap_single operation will
  915. result in a hardware IOTLB flush operation as opposed
  916. to batching them for performance.
  917. sp_off [Default Off]
  918. By default, super page will be supported if Intel IOMMU
  919. has the capability. With this option, super page will
  920. not be supported.
  921. intel_idle.max_cstate= [KNL,HW,ACPI,X86]
  922. 0 disables intel_idle and fall back on acpi_idle.
  923. 1 to 6 specify maximum depth of C-state.
  924. intremap= [X86-64, Intel-IOMMU]
  925. on enable Interrupt Remapping (default)
  926. off disable Interrupt Remapping
  927. nosid disable Source ID checking
  928. no_x2apic_optout
  929. BIOS x2APIC opt-out request will be ignored
  930. iomem= Disable strict checking of access to MMIO memory
  931. strict regions from userspace.
  932. relaxed
  933. iommu= [x86]
  934. off
  935. force
  936. noforce
  937. biomerge
  938. panic
  939. nopanic
  940. merge
  941. nomerge
  942. forcesac
  943. soft
  944. pt [x86, IA-64]
  945. io7= [HW] IO7 for Marvel based alpha systems
  946. See comment before marvel_specify_io7 in
  947. arch/alpha/kernel/core_marvel.c.
  948. io_delay= [X86] I/O delay method
  949. 0x80
  950. Standard port 0x80 based delay
  951. 0xed
  952. Alternate port 0xed based delay (needed on some systems)
  953. udelay
  954. Simple two microseconds delay
  955. none
  956. No delay
  957. ip= [IP_PNP]
  958. See Documentation/filesystems/nfs/nfsroot.txt.
  959. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  960. See comment before ip2_setup() in
  961. drivers/char/ip2/ip2base.c.
  962. irqfixup [HW]
  963. When an interrupt is not handled search all handlers
  964. for it. Intended to get systems with badly broken
  965. firmware running.
  966. irqpoll [HW]
  967. When an interrupt is not handled search all handlers
  968. for it. Also check all handlers each timer
  969. interrupt. Intended to get systems with badly broken
  970. firmware running.
  971. isapnp= [ISAPNP]
  972. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  973. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  974. Format:
  975. <cpu number>,...,<cpu number>
  976. or
  977. <cpu number>-<cpu number>
  978. (must be a positive range in ascending order)
  979. or a mixture
  980. <cpu number>,...,<cpu number>-<cpu number>
  981. This option can be used to specify one or more CPUs
  982. to isolate from the general SMP balancing and scheduling
  983. algorithms. You can move a process onto or off an
  984. "isolated" CPU via the CPU affinity syscalls or cpuset.
  985. <cpu number> begins at 0 and the maximum value is
  986. "number of CPUs in system - 1".
  987. This option is the preferred way to isolate CPUs. The
  988. alternative -- manually setting the CPU mask of all
  989. tasks in the system -- can cause problems and
  990. suboptimal load balancer performance.
  991. iucv= [HW,NET]
  992. js= [HW,JOY] Analog joystick
  993. See Documentation/input/joystick.txt.
  994. keepinitrd [HW,ARM]
  995. kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  996. specifies the amount of memory usable by the kernel
  997. for non-movable allocations. The requested amount is
  998. spread evenly throughout all nodes in the system. The
  999. remaining memory in each node is used for Movable
  1000. pages. In the event, a node is too small to have both
  1001. kernelcore and Movable pages, kernelcore pages will
  1002. take priority and other nodes will have a larger number
  1003. of kernelcore pages. The Movable zone is used for the
  1004. allocation of pages that may be reclaimed or moved
  1005. by the page migration subsystem. This means that
  1006. HugeTLB pages may not be allocated from this zone.
  1007. Note that allocations like PTEs-from-HighMem still
  1008. use the HighMem zone if it exists, and the Normal
  1009. zone if it does not.
  1010. kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
  1011. Format: <Controller#>[,poll interval]
  1012. The controller # is the number of the ehci usb debug
  1013. port as it is probed via PCI. The poll interval is
  1014. optional and is the number seconds in between
  1015. each poll cycle to the debug port in case you need
  1016. the functionality for interrupting the kernel with
  1017. gdb or control-c on the dbgp connection. When
  1018. not using this parameter you use sysrq-g to break into
  1019. the kernel debugger.
  1020. kgdboc= [KGDB,HW] kgdb over consoles.
  1021. Requires a tty driver that supports console polling,
  1022. or a supported polling keyboard driver (non-usb).
  1023. Serial only format: <serial_device>[,baud]
  1024. keyboard only format: kbd
  1025. keyboard and serial format: kbd,<serial_device>[,baud]
  1026. Optional Kernel mode setting:
  1027. kms, kbd format: kms,kbd
  1028. kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
  1029. kgdbwait [KGDB] Stop kernel execution and enter the
  1030. kernel debugger at the earliest opportunity.
  1031. kmac= [MIPS] korina ethernet MAC address.
  1032. Configure the RouterBoard 532 series on-chip
  1033. Ethernet adapter MAC address.
  1034. kmemleak= [KNL] Boot-time kmemleak enable/disable
  1035. Valid arguments: on, off
  1036. Default: on
  1037. kstack=N [X86] Print N words from the kernel stack
  1038. in oops dumps.
  1039. kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
  1040. Default is 0 (don't ignore, but inject #GP)
  1041. kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
  1042. KVM MMU at runtime.
  1043. Default is 0 (off)
  1044. kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
  1045. Default is 1 (enabled)
  1046. kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
  1047. for all guests.
  1048. Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
  1049. kvm-intel.ept= [KVM,Intel] Disable extended page tables
  1050. (virtualized MMU) support on capable Intel chips.
  1051. Default is 1 (enabled)
  1052. kvm-intel.emulate_invalid_guest_state=
  1053. [KVM,Intel] Enable emulation of invalid guest states
  1054. Default is 0 (disabled)
  1055. kvm-intel.flexpriority=
  1056. [KVM,Intel] Disable FlexPriority feature (TPR shadow).
  1057. Default is 1 (enabled)
  1058. kvm-intel.nested=
  1059. [KVM,Intel] Enable VMX nesting (nVMX).
  1060. Default is 0 (disabled)
  1061. kvm-intel.unrestricted_guest=
  1062. [KVM,Intel] Disable unrestricted guest feature
  1063. (virtualized real and unpaged mode) on capable
  1064. Intel chips. Default is 1 (enabled)
  1065. kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
  1066. feature (tagged TLBs) on capable Intel chips.
  1067. Default is 1 (enabled)
  1068. l2cr= [PPC]
  1069. l3cr= [PPC]
  1070. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  1071. disabled it.
  1072. lapic_timer_c2_ok [X86,APIC] trust the local apic timer
  1073. in C2 power state.
  1074. libata.dma= [LIBATA] DMA control
  1075. libata.dma=0 Disable all PATA and SATA DMA
  1076. libata.dma=1 PATA and SATA Disk DMA only
  1077. libata.dma=2 ATAPI (CDROM) DMA only
  1078. libata.dma=4 Compact Flash DMA only
  1079. Combinations also work, so libata.dma=3 enables DMA
  1080. for disks and CDROMs, but not CFs.
  1081. libata.ignore_hpa= [LIBATA] Ignore HPA limit
  1082. libata.ignore_hpa=0 keep BIOS limits (default)
  1083. libata.ignore_hpa=1 ignore limits, using full disk
  1084. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  1085. when set.
  1086. Format: <int>
  1087. libata.force= [LIBATA] Force configurations. The format is comma
  1088. separated list of "[ID:]VAL" where ID is
  1089. PORT[.DEVICE]. PORT and DEVICE are decimal numbers
  1090. matching port, link or device. Basically, it matches
  1091. the ATA ID string printed on console by libata. If
  1092. the whole ID part is omitted, the last PORT and DEVICE
  1093. values are used. If ID hasn't been specified yet, the
  1094. configuration applies to all ports, links and devices.
  1095. If only DEVICE is omitted, the parameter applies to
  1096. the port and all links and devices behind it. DEVICE
  1097. number of 0 either selects the first device or the
  1098. first fan-out link behind PMP device. It does not
  1099. select the host link. DEVICE number of 15 selects the
  1100. host link and device attached to it.
  1101. The VAL specifies the configuration to force. As long
  1102. as there's no ambiguity shortcut notation is allowed.
  1103. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  1104. The following configurations can be forced.
  1105. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  1106. Any ID with matching PORT is used.
  1107. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  1108. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  1109. udma[/][16,25,33,44,66,100,133] notation is also
  1110. allowed.
  1111. * [no]ncq: Turn on or off NCQ.
  1112. * nohrst, nosrst, norst: suppress hard, soft
  1113. and both resets.
  1114. * rstonce: only attempt one reset during
  1115. hot-unplug link recovery
  1116. * dump_id: dump IDENTIFY data.
  1117. If there are multiple matching configurations changing
  1118. the same attribute, the last one is used.
  1119. memblock=debug [KNL] Enable memblock debug messages.
  1120. load_ramdisk= [RAM] List of ramdisks to load from floppy
  1121. See Documentation/blockdev/ramdisk.txt.
  1122. lockd.nlm_grace_period=P [NFS] Assign grace period.
  1123. Format: <integer>
  1124. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  1125. Format: <integer>
  1126. lockd.nlm_timeout=T [NFS] Assign timeout value.
  1127. Format: <integer>
  1128. lockd.nlm_udpport=M [NFS] Assign UDP port.
  1129. Format: <integer>
  1130. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  1131. Format: <irq>
  1132. loglevel= All Kernel Messages with a loglevel smaller than the
  1133. console loglevel will be printed to the console. It can
  1134. also be changed with klogd or other programs. The
  1135. loglevels are defined as follows:
  1136. 0 (KERN_EMERG) system is unusable
  1137. 1 (KERN_ALERT) action must be taken immediately
  1138. 2 (KERN_CRIT) critical conditions
  1139. 3 (KERN_ERR) error conditions
  1140. 4 (KERN_WARNING) warning conditions
  1141. 5 (KERN_NOTICE) normal but significant condition
  1142. 6 (KERN_INFO) informational
  1143. 7 (KERN_DEBUG) debug-level messages
  1144. log_buf_len=n[KMG] Sets the size of the printk ring buffer,
  1145. in bytes. n must be a power of two. The default
  1146. size is set in the kernel config file.
  1147. logo.nologo [FB] Disables display of the built-in Linux logo.
  1148. This may be used to provide more screen space for
  1149. kernel log messages and is useful when debugging
  1150. kernel boot problems.
  1151. lp=0 [LP] Specify parallel ports to use, e.g,
  1152. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  1153. lp=reset first parallel port). 'lp=0' disables the
  1154. lp=auto printer driver. 'lp=reset' (which can be
  1155. specified in addition to the ports) causes
  1156. attached printers to be reset. Using
  1157. lp=port1,port2,... specifies the parallel ports
  1158. to associate lp devices with, starting with
  1159. lp0. A port specification may be 'none' to skip
  1160. that lp device, or a parport name such as
  1161. 'parport0'. Specifying 'lp=auto' instead of a
  1162. port specification list means that device IDs
  1163. from each port should be examined, to see if
  1164. an IEEE 1284-compliant printer is attached; if
  1165. so, the driver will manage that printer.
  1166. See also header of drivers/char/lp.c.
  1167. lpj=n [KNL]
  1168. Sets loops_per_jiffy to given constant, thus avoiding
  1169. time-consuming boot-time autodetection (up to 250 ms per
  1170. CPU). 0 enables autodetection (default). To determine
  1171. the correct value for your kernel, boot with normal
  1172. autodetection and see what value is printed. Note that
  1173. on SMP systems the preset will be applied to all CPUs,
  1174. which is likely to cause problems if your CPUs need
  1175. significantly divergent settings. An incorrect value
  1176. will cause delays in the kernel to be wrong, leading to
  1177. unpredictable I/O errors and other breakage. Although
  1178. unlikely, in the extreme case this might damage your
  1179. hardware.
  1180. ltpc= [NET]
  1181. Format: <io>,<irq>,<dma>
  1182. machvec= [IA-64] Force the use of a particular machine-vector
  1183. (machvec) in a generic kernel.
  1184. Example: machvec=hpzx1_swiotlb
  1185. machtype= [Loongson] Share the same kernel image file between different
  1186. yeeloong laptop.
  1187. Example: machtype=lemote-yeeloong-2f-7inch
  1188. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
  1189. than or equal to this physical address is ignored.
  1190. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  1191. should make use of. maxcpus=n : n >= 0 limits the
  1192. kernel to using 'n' processors. n=0 is a special case,
  1193. it is equivalent to "nosmp", which also disables
  1194. the IO APIC.
  1195. max_loop= [LOOP] The number of loop block devices that get
  1196. (loop.max_loop) unconditionally pre-created at init time. The default
  1197. number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
  1198. of statically allocating a predefined number, loop
  1199. devices can be requested on-demand with the
  1200. /dev/loop-control interface.
  1201. mce [X86-32] Machine Check Exception
  1202. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  1203. md= [HW] RAID subsystems devices and level
  1204. See Documentation/md.txt.
  1205. mdacon= [MDA]
  1206. Format: <first>,<last>
  1207. Specifies range of consoles to be captured by the MDA.
  1208. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  1209. Amount of memory to be used when the kernel is not able
  1210. to see the whole system memory or for test.
  1211. [X86-32] Use together with memmap= to avoid physical
  1212. address space collisions. Without memmap= PCI devices
  1213. could be placed at addresses belonging to unused RAM.
  1214. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1215. memory.
  1216. memchunk=nn[KMG]
  1217. [KNL,SH] Allow user to override the default size for
  1218. per-device physically contiguous DMA buffers.
  1219. memmap=exactmap [KNL,X86] Enable setting of an exact
  1220. E820 memory map, as specified by the user.
  1221. Such memmap=exactmap lines can be constructed based on
  1222. BIOS output or other requirements. See the memmap=nn@ss
  1223. option description.
  1224. memmap=nn[KMG]@ss[KMG]
  1225. [KNL] Force usage of a specific region of memory
  1226. Region of memory to be used, from ss to ss+nn.
  1227. memmap=nn[KMG]#ss[KMG]
  1228. [KNL,ACPI] Mark specific memory as ACPI data.
  1229. Region of memory to be used, from ss to ss+nn.
  1230. memmap=nn[KMG]$ss[KMG]
  1231. [KNL,ACPI] Mark specific memory as reserved.
  1232. Region of memory to be used, from ss to ss+nn.
  1233. Example: Exclude memory from 0x18690000-0x1869ffff
  1234. memmap=64K$0x18690000
  1235. or
  1236. memmap=0x10000$0x18690000
  1237. memory_corruption_check=0/1 [X86]
  1238. Some BIOSes seem to corrupt the first 64k of
  1239. memory when doing things like suspend/resume.
  1240. Setting this option will scan the memory
  1241. looking for corruption. Enabling this will
  1242. both detect corruption and prevent the kernel
  1243. from using the memory being corrupted.
  1244. However, its intended as a diagnostic tool; if
  1245. repeatable BIOS-originated corruption always
  1246. affects the same memory, you can use memmap=
  1247. to prevent the kernel from using that memory.
  1248. memory_corruption_check_size=size [X86]
  1249. By default it checks for corruption in the low
  1250. 64k, making this memory unavailable for normal
  1251. use. Use this parameter to scan for
  1252. corruption in more or less memory.
  1253. memory_corruption_check_period=seconds [X86]
  1254. By default it checks for corruption every 60
  1255. seconds. Use this parameter to check at some
  1256. other rate. 0 disables periodic checking.
  1257. memtest= [KNL,X86] Enable memtest
  1258. Format: <integer>
  1259. default : 0 <disable>
  1260. Specifies the number of memtest passes to be
  1261. performed. Each pass selects another test
  1262. pattern from a given set of patterns. Memtest
  1263. fills the memory with this pattern, validates
  1264. memory contents and reserves bad memory
  1265. regions that are detected.
  1266. meye.*= [HW] Set MotionEye Camera parameters
  1267. See Documentation/video4linux/meye.txt.
  1268. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1269. Multi-Function General Purpose Timers on AMD Geode
  1270. platforms.
  1271. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1272. the BIOS has incorrectly applied a workaround. TinyBIOS
  1273. version 0.98 is known to be affected, 0.99 fixes the
  1274. problem by letting the user disable the workaround.
  1275. mga= [HW,DRM]
  1276. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1277. physical address is ignored.
  1278. mini2440= [ARM,HW,KNL]
  1279. Format:[0..2][b][c][t]
  1280. Default: "0tb"
  1281. MINI2440 configuration specification:
  1282. 0 - The attached screen is the 3.5" TFT
  1283. 1 - The attached screen is the 7" TFT
  1284. 2 - The VGA Shield is attached (1024x768)
  1285. Leaving out the screen size parameter will not load
  1286. the TFT driver, and the framebuffer will be left
  1287. unconfigured.
  1288. b - Enable backlight. The TFT backlight pin will be
  1289. linked to the kernel VESA blanking code and a GPIO
  1290. LED. This parameter is not necessary when using the
  1291. VGA shield.
  1292. c - Enable the s3c camera interface.
  1293. t - Reserved for enabling touchscreen support. The
  1294. touchscreen support is not enabled in the mainstream
  1295. kernel as of 2.6.30, a preliminary port can be found
  1296. in the "bleeding edge" mini2440 support kernel at
  1297. http://repo.or.cz/w/linux-2.6/mini2440.git
  1298. mminit_loglevel=
  1299. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1300. parameter allows control of the logging verbosity for
  1301. the additional memory initialisation checks. A value
  1302. of 0 disables mminit logging and a level of 4 will
  1303. log everything. Information is printed at KERN_DEBUG
  1304. so loglevel=8 may also need to be specified.
  1305. module.sig_enforce
  1306. [KNL] When CONFIG_MODULE_SIG is set, this means that
  1307. modules without (valid) signatures will fail to load.
  1308. Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
  1309. is always true, so this option does nothing.
  1310. mousedev.tap_time=
  1311. [MOUSE] Maximum time between finger touching and
  1312. leaving touchpad surface for touch to be considered
  1313. a tap and be reported as a left button click (for
  1314. touchpads working in absolute mode only).
  1315. Format: <msecs>
  1316. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1317. reporting absolute coordinates, such as tablets
  1318. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1319. reporting absolute coordinates, such as tablets
  1320. movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  1321. is similar to kernelcore except it specifies the
  1322. amount of memory used for migratable allocations.
  1323. If both kernelcore and movablecore is specified,
  1324. then kernelcore will be at *least* the specified
  1325. value but may be more. If movablecore on its own
  1326. is specified, the administrator must be careful
  1327. that the amount of memory usable for all allocations
  1328. is not too small.
  1329. MTD_Partition= [MTD]
  1330. Format: <name>,<region-number>,<size>,<offset>
  1331. MTD_Region= [MTD] Format:
  1332. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1333. mtdparts= [MTD]
  1334. See drivers/mtd/cmdlinepart.c.
  1335. multitce=off [PPC] This parameter disables the use of the pSeries
  1336. firmware feature for updating multiple TCE entries
  1337. at a time.
  1338. onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
  1339. Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
  1340. boundary - index of last SLC block on Flex-OneNAND.
  1341. The remaining blocks are configured as MLC blocks.
  1342. lock - Configure if Flex-OneNAND boundary should be locked.
  1343. Once locked, the boundary cannot be changed.
  1344. 1 indicates lock status, 0 indicates unlock status.
  1345. mtdset= [ARM]
  1346. ARM/S3C2412 JIVE boot control
  1347. See arch/arm/mach-s3c2412/mach-jive.c
  1348. mtouchusb.raw_coordinates=
  1349. [HW] Make the MicroTouch USB driver use raw coordinates
  1350. ('y', default) or cooked coordinates ('n')
  1351. mtrr_chunk_size=nn[KMG] [X86]
  1352. used for mtrr cleanup. It is largest continuous chunk
  1353. that could hold holes aka. UC entries.
  1354. mtrr_gran_size=nn[KMG] [X86]
  1355. Used for mtrr cleanup. It is granularity of mtrr block.
  1356. Default is 1.
  1357. Large value could prevent small alignment from
  1358. using up MTRRs.
  1359. mtrr_spare_reg_nr=n [X86]
  1360. Format: <integer>
  1361. Range: 0,7 : spare reg number
  1362. Default : 1
  1363. Used for mtrr cleanup. It is spare mtrr entries number.
  1364. Set to 2 or more if your graphical card needs more.
  1365. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1366. netdev= [NET] Network devices parameters
  1367. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1368. Note that mem_start is often overloaded to mean
  1369. something different and driver-specific.
  1370. This usage is only documented in each driver source
  1371. file if at all.
  1372. nf_conntrack.acct=
  1373. [NETFILTER] Enable connection tracking flow accounting
  1374. 0 to disable accounting
  1375. 1 to enable accounting
  1376. Default value is 0.
  1377. nfsaddrs= [NFS] Deprecated. Use ip= instead.
  1378. See Documentation/filesystems/nfs/nfsroot.txt.
  1379. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1380. See Documentation/filesystems/nfs/nfsroot.txt.
  1381. nfsrootdebug [NFS] enable nfsroot debugging messages.
  1382. See Documentation/filesystems/nfs/nfsroot.txt.
  1383. nfs.callback_tcpport=
  1384. [NFS] set the TCP port on which the NFSv4 callback
  1385. channel should listen.
  1386. nfs.cache_getent=
  1387. [NFS] sets the pathname to the program which is used
  1388. to update the NFS client cache entries.
  1389. nfs.cache_getent_timeout=
  1390. [NFS] sets the timeout after which an attempt to
  1391. update a cache entry is deemed to have failed.
  1392. nfs.idmap_cache_timeout=
  1393. [NFS] set the maximum lifetime for idmapper cache
  1394. entries.
  1395. nfs.enable_ino64=
  1396. [NFS] enable 64-bit inode numbers.
  1397. If zero, the NFS client will fake up a 32-bit inode
  1398. number for the readdir() and stat() syscalls instead
  1399. of returning the full 64-bit number.
  1400. The default is to return 64-bit inode numbers.
  1401. nfs.max_session_slots=
  1402. [NFSv4.1] Sets the maximum number of session slots
  1403. the client will attempt to negotiate with the server.
  1404. This limits the number of simultaneous RPC requests
  1405. that the client can send to the NFSv4.1 server.
  1406. Note that there is little point in setting this
  1407. value higher than the max_tcp_slot_table_limit.
  1408. nfs.nfs4_disable_idmapping=
  1409. [NFSv4] When set to the default of '1', this option
  1410. ensures that both the RPC level authentication
  1411. scheme and the NFS level operations agree to use
  1412. numeric uids/gids if the mount is using the
  1413. 'sec=sys' security flavour. In effect it is
  1414. disabling idmapping, which can make migration from
  1415. legacy NFSv2/v3 systems to NFSv4 easier.
  1416. Servers that do not support this mode of operation
  1417. will be autodetected by the client, and it will fall
  1418. back to using the idmapper.
  1419. To turn off this behaviour, set the value to '0'.
  1420. nfs.nfs4_unique_id=
  1421. [NFS4] Specify an additional fixed unique ident-
  1422. ification string that NFSv4 clients can insert into
  1423. their nfs_client_id4 string. This is typically a
  1424. UUID that is generated at system install time.
  1425. nfs.send_implementation_id =
  1426. [NFSv4.1] Send client implementation identification
  1427. information in exchange_id requests.
  1428. If zero, no implementation identification information
  1429. will be sent.
  1430. The default is to send the implementation identification
  1431. information.
  1432. nfsd.nfs4_disable_idmapping=
  1433. [NFSv4] When set to the default of '1', the NFSv4
  1434. server will return only numeric uids and gids to
  1435. clients using auth_sys, and will accept numeric uids
  1436. and gids from such clients. This is intended to ease
  1437. migration from NFSv2/v3.
  1438. objlayoutdriver.osd_login_prog=
  1439. [NFS] [OBJLAYOUT] sets the pathname to the program which
  1440. is used to automatically discover and login into new
  1441. osd-targets. Please see:
  1442. Documentation/filesystems/pnfs.txt for more explanations
  1443. nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
  1444. when a NMI is triggered.
  1445. Format: [state][,regs][,debounce][,die]
  1446. nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
  1447. Format: [panic,][nopanic,][num]
  1448. Valid num: 0
  1449. 0 - turn nmi_watchdog off
  1450. When panic is specified, panic when an NMI watchdog
  1451. timeout occurs (or 'nopanic' to override the opposite
  1452. default).
  1453. This is useful when you use a panic=... timeout and
  1454. need the box quickly up again.
  1455. netpoll.carrier_timeout=
  1456. [NET] Specifies amount of time (in seconds) that
  1457. netpoll should wait for a carrier. By default netpoll
  1458. waits 4 seconds.
  1459. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1460. emulation library even if a 387 maths coprocessor
  1461. is present.
  1462. no_console_suspend
  1463. [HW] Never suspend the console
  1464. Disable suspending of consoles during suspend and
  1465. hibernate operations. Once disabled, debugging
  1466. messages can reach various consoles while the rest
  1467. of the system is being put to sleep (ie, while
  1468. debugging driver suspend/resume hooks). This may
  1469. not work reliably with all consoles, but is known
  1470. to work with serial and VGA consoles.
  1471. To facilitate more flexible debugging, we also add
  1472. console_suspend, a printk module parameter to control
  1473. it. Users could use console_suspend (usually
  1474. /sys/module/printk/parameters/console_suspend) to
  1475. turn on/off it dynamically.
  1476. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1477. caches in the slab allocator. Saves per-node memory,
  1478. but will impact performance.
  1479. noalign [KNL,ARM]
  1480. noapic [SMP,APIC] Tells the kernel to not make use of any
  1481. IOAPICs that may be present in the system.
  1482. noautogroup Disable scheduler automatic task group creation.
  1483. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1484. on "Classic" PPC cores.
  1485. nocache [ARM]
  1486. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1487. nodelayacct [KNL] Disable per-task delay accounting
  1488. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1489. nodsp [SH] Disable hardware DSP at boot time.
  1490. noefi [X86] Disable EFI runtime services support.
  1491. noexec [IA-64]
  1492. noexec [X86]
  1493. On X86-32 available only on PAE configured kernels.
  1494. noexec=on: enable non-executable mappings (default)
  1495. noexec=off: disable non-executable mappings
  1496. nosmap [X86]
  1497. Disable SMAP (Supervisor Mode Access Prevention)
  1498. even if it is supported by processor.
  1499. nosmep [X86]
  1500. Disable SMEP (Supervisor Mode Execution Prevention)
  1501. even if it is supported by processor.
  1502. noexec32 [X86-64]
  1503. This affects only 32-bit executables.
  1504. noexec32=on: enable non-executable mappings (default)
  1505. read doesn't imply executable mappings
  1506. noexec32=off: disable non-executable mappings
  1507. read implies executable mappings
  1508. nofpu [SH] Disable hardware FPU at boot time.
  1509. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1510. register save and restore. The kernel will only save
  1511. legacy floating-point registers on task switch.
  1512. noxsave [BUGS=X86] Disables x86 extended register state save
  1513. and restore using xsave. The kernel will fallback to
  1514. enabling legacy floating-point and sse state.
  1515. eagerfpu= [X86]
  1516. on enable eager fpu restore
  1517. off disable eager fpu restore
  1518. auto selects the default scheme, which automatically
  1519. enables eagerfpu restore for xsaveopt.
  1520. nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
  1521. wfi(ARM) instruction doesn't work correctly and not to
  1522. use it. This is also useful when using JTAG debugger.
  1523. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1524. instruction doesn't work correctly and not to
  1525. use it.
  1526. no_file_caps Tells the kernel not to honor file capabilities. The
  1527. only way then for a file to be executed with privilege
  1528. is to be setuid root or executed by root.
  1529. nohalt [IA-64] Tells the kernel not to use the power saving
  1530. function PAL_HALT_LIGHT when idle. This increases
  1531. power-consumption. On the positive side, it reduces
  1532. interrupt wake-up latency, which may improve performance
  1533. in certain environments such as networked servers or
  1534. real-time systems.
  1535. nohz= [KNL] Boottime enable/disable dynamic ticks
  1536. Valid arguments: on, off
  1537. Default: on
  1538. noiotrap [SH] Disables trapped I/O port accesses.
  1539. noirqdebug [X86-32] Disables the code which attempts to detect and
  1540. disable unhandled interrupt sources.
  1541. no_timer_check [X86,APIC] Disables the code which tests for
  1542. broken timer IRQ sources.
  1543. noisapnp [ISAPNP] Disables ISA PnP code.
  1544. noinitrd [RAM] Tells the kernel not to load any configured
  1545. initial RAM disk.
  1546. nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
  1547. remapping.
  1548. [Deprecated - use intremap=off]
  1549. nointroute [IA-64]
  1550. nojitter [IA-64] Disables jitter checking for ITC timers.
  1551. no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
  1552. no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
  1553. fault handling.
  1554. no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
  1555. steal time is computed, but won't influence scheduler
  1556. behaviour
  1557. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1558. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1559. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1560. lowmem mapping on PPC40x.
  1561. nomca [IA-64] Disable machine check abort handling
  1562. nomce [X86-32] Machine Check Exception
  1563. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1564. Timer usage (for AMD Geode machines).
  1565. nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
  1566. shutdown the other cpus. Instead use the REBOOT_VECTOR
  1567. irq.
  1568. nomodule Disable module load
  1569. nopat [X86] Disable PAT (page attribute table extension of
  1570. pagetables) support.
  1571. norandmaps Don't use address space randomization. Equivalent to
  1572. echo 0 > /proc/sys/kernel/randomize_va_space
  1573. noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
  1574. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1575. with UP alternatives
  1576. noresidual [PPC] Don't use residual data on PReP machines.
  1577. nordrand [X86] Disable the direct use of the RDRAND
  1578. instruction even if it is supported by the
  1579. processor. RDRAND is still available to user
  1580. space applications.
  1581. noresume [SWSUSP] Disables resume and restores original swap
  1582. space.
  1583. no-scroll [VGA] Disables scrollback.
  1584. This is required for the Braillex ib80-piezo Braille
  1585. reader made by F.H. Papenmeier (Germany).
  1586. nosbagart [IA-64]
  1587. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1588. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1589. and disable the IO APIC. legacy for "maxcpus=0".
  1590. nosoftlockup [KNL] Disable the soft-lockup detector.
  1591. nosync [HW,M68K] Disables sync negotiation for all devices.
  1592. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1593. nousb [USB] Disable the USB subsystem
  1594. nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
  1595. nowb [ARM]
  1596. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1597. nptcg= [IA-64] Override max number of concurrent global TLB
  1598. purges which is reported from either PAL_VM_SUMMARY or
  1599. SAL PALO.
  1600. nr_cpus= [SMP] Maximum number of processors that an SMP kernel
  1601. could support. nr_cpus=n : n >= 1 limits the kernel to
  1602. supporting 'n' processors. Later in runtime you can not
  1603. use hotplug cpu feature to put more cpu back to online.
  1604. just like you compile the kernel NR_CPUS=n
  1605. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1606. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1607. one of ['zone', 'node', 'default'] can be specified
  1608. This can be set from sysctl after boot.
  1609. See Documentation/sysctl/vm.txt for details.
  1610. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
  1611. See Documentation/debugging-via-ohci1394.txt for more
  1612. info.
  1613. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1614. Rather than timing out after 20 ms if an EC
  1615. command is not properly ACKed, override the length
  1616. of the timeout. We have interrupts disabled while
  1617. waiting for the ACK, so if this is set too high
  1618. interrupts *may* be lost!
  1619. omap_mux= [OMAP] Override bootloader pin multiplexing.
  1620. Format: <mux_mode0.mode_name=value>...
  1621. For example, to override I2C bus2:
  1622. omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
  1623. oprofile.timer= [HW]
  1624. Use timer interrupt instead of performance counters
  1625. oprofile.cpu_type= Force an oprofile cpu type
  1626. This might be useful if you have an older oprofile
  1627. userland or if you want common events.
  1628. Format: { arch_perfmon }
  1629. arch_perfmon: [X86] Force use of architectural
  1630. perfmon on Intel CPUs instead of the
  1631. CPU specific event set.
  1632. timer: [X86] Force use of architectural NMI
  1633. timer mode (see also oprofile.timer
  1634. for generic hr timer mode)
  1635. [s390] Force legacy basic mode sampling
  1636. (report cpu_type "timer")
  1637. oops=panic Always panic on oopses. Default is to just kill the
  1638. process, but there is a small probability of
  1639. deadlocking the machine.
  1640. This will also cause panics on machine check exceptions.
  1641. Useful together with panic=30 to trigger a reboot.
  1642. OSS [HW,OSS]
  1643. See Documentation/sound/oss/oss-parameters.txt
  1644. panic= [KNL] Kernel behaviour on panic: delay <timeout>
  1645. timeout > 0: seconds before rebooting
  1646. timeout = 0: wait forever
  1647. timeout < 0: reboot immediately
  1648. Format: <timeout>
  1649. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1650. connected to, default is 0.
  1651. Format: <parport#>
  1652. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1653. 0 for XT, 1 for AT (default is AT).
  1654. Format: <mode>
  1655. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1656. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1657. Use 'auto' to force the driver to use any
  1658. IRQ/DMA settings detected (the default is to
  1659. ignore detected IRQ/DMA settings because of
  1660. possible conflicts). You can specify the base
  1661. address, IRQ, and DMA settings; IRQ and DMA
  1662. should be numbers, or 'auto' (for using detected
  1663. settings on that particular port), or 'nofifo'
  1664. (to avoid using a FIFO even if it is detected).
  1665. Parallel ports are assigned in the order they
  1666. are specified on the command line, starting
  1667. with parport0.
  1668. parport_init_mode= [HW,PPT]
  1669. Configure VIA parallel port to operate in
  1670. a specific mode. This is necessary on Pegasos
  1671. computer where firmware has no options for setting
  1672. up parallel port mode and sets it to spp.
  1673. Currently this function knows 686a and 8231 chips.
  1674. Format: [spp|ps2|epp|ecp|ecpepp]
  1675. pause_on_oops=
  1676. Halt all CPUs after the first oops has been printed for
  1677. the specified number of seconds. This is to be used if
  1678. your oopses keep scrolling off the screen.
  1679. pcbit= [HW,ISDN]
  1680. pcd. [PARIDE]
  1681. See header of drivers/block/paride/pcd.c.
  1682. See also Documentation/blockdev/paride.txt.
  1683. pci=option[,option...] [PCI] various PCI subsystem options:
  1684. earlydump [X86] dump PCI config space before the kernel
  1685. changes anything
  1686. off [X86] don't probe for the PCI bus
  1687. bios [X86-32] force use of PCI BIOS, don't access
  1688. the hardware directly. Use this if your machine
  1689. has a non-standard PCI host bridge.
  1690. nobios [X86-32] disallow use of PCI BIOS, only direct
  1691. hardware access methods are allowed. Use this
  1692. if you experience crashes upon bootup and you
  1693. suspect they are caused by the BIOS.
  1694. conf1 [X86] Force use of PCI Configuration
  1695. Mechanism 1.
  1696. conf2 [X86] Force use of PCI Configuration
  1697. Mechanism 2.
  1698. noaer [PCIE] If the PCIEAER kernel config parameter is
  1699. enabled, this kernel boot option can be used to
  1700. disable the use of PCIE advanced error reporting.
  1701. nodomains [PCI] Disable support for multiple PCI
  1702. root domains (aka PCI segments, in ACPI-speak).
  1703. nommconf [X86] Disable use of MMCONFIG for PCI
  1704. Configuration
  1705. check_enable_amd_mmconf [X86] check for and enable
  1706. properly configured MMIO access to PCI
  1707. config space on AMD family 10h CPU
  1708. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1709. enabled, this kernel boot option can be used to
  1710. disable the use of MSI interrupts system-wide.
  1711. noioapicquirk [APIC] Disable all boot interrupt quirks.
  1712. Safety option to keep boot IRQs enabled. This
  1713. should never be necessary.
  1714. ioapicreroute [APIC] Enable rerouting of boot IRQs to the
  1715. primary IO-APIC for bridges that cannot disable
  1716. boot IRQs. This fixes a source of spurious IRQs
  1717. when the system masks IRQs.
  1718. noioapicreroute [APIC] Disable workaround that uses the
  1719. boot IRQ equivalent of an IRQ that connects to
  1720. a chipset where boot IRQs cannot be disabled.
  1721. The opposite of ioapicreroute.
  1722. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1723. routing table. These calls are known to be buggy
  1724. on several machines and they hang the machine
  1725. when used, but on other computers it's the only
  1726. way to get the interrupt routing table. Try
  1727. this option if the kernel is unable to allocate
  1728. IRQs or discover secondary PCI buses on your
  1729. motherboard.
  1730. rom [X86] Assign address space to expansion ROMs.
  1731. Use with caution as certain devices share
  1732. address decoders between ROMs and other
  1733. resources.
  1734. norom [X86] Do not assign address space to
  1735. expansion ROMs that do not already have
  1736. BIOS assigned address ranges.
  1737. nobar [X86] Do not assign address space to the
  1738. BARs that weren't assigned by the BIOS.
  1739. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1740. assigned automatically to PCI devices. You can
  1741. make the kernel exclude IRQs of your ISA cards
  1742. this way.
  1743. pirqaddr=0xAAAAA [X86] Specify the physical address
  1744. of the PIRQ table (normally generated
  1745. by the BIOS) if it is outside the
  1746. F0000h-100000h range.
  1747. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1748. useful if the kernel is unable to find your
  1749. secondary buses and you want to tell it
  1750. explicitly which ones they are.
  1751. assign-busses [X86] Always assign all PCI bus
  1752. numbers ourselves, overriding
  1753. whatever the firmware may have done.
  1754. usepirqmask [X86] Honor the possible IRQ mask stored
  1755. in the BIOS $PIR table. This is needed on
  1756. some systems with broken BIOSes, notably
  1757. some HP Pavilion N5400 and Omnibook XE3
  1758. notebooks. This will have no effect if ACPI
  1759. IRQ routing is enabled.
  1760. noacpi [X86] Do not use ACPI for IRQ routing
  1761. or for PCI scanning.
  1762. use_crs [X86] Use PCI host bridge window information
  1763. from ACPI. On BIOSes from 2008 or later, this
  1764. is enabled by default. If you need to use this,
  1765. please report a bug.
  1766. nocrs [X86] Ignore PCI host bridge windows from ACPI.
  1767. If you need to use this, please report a bug.
  1768. routeirq Do IRQ routing for all PCI devices.
  1769. This is normally done in pci_enable_device(),
  1770. so this option is a temporary workaround
  1771. for broken drivers that don't call it.
  1772. skip_isa_align [X86] do not align io start addr, so can
  1773. handle more pci cards
  1774. firmware [ARM] Do not re-enumerate the bus but instead
  1775. just use the configuration from the
  1776. bootloader. This is currently used on
  1777. IXP2000 systems where the bus has to be
  1778. configured a certain way for adjunct CPUs.
  1779. noearly [X86] Don't do any early type 1 scanning.
  1780. This might help on some broken boards which
  1781. machine check when some devices' config space
  1782. is read. But various workarounds are disabled
  1783. and some IOMMU drivers will not work.
  1784. bfsort Sort PCI devices into breadth-first order.
  1785. This sorting is done to get a device
  1786. order compatible with older (<= 2.4) kernels.
  1787. nobfsort Don't sort PCI devices into breadth-first order.
  1788. cbiosize=nn[KMG] The fixed amount of bus space which is
  1789. reserved for the CardBus bridge's IO window.
  1790. The default value is 256 bytes.
  1791. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1792. reserved for the CardBus bridge's memory
  1793. window. The default value is 64 megabytes.
  1794. resource_alignment=
  1795. Format:
  1796. [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
  1797. Specifies alignment and device to reassign
  1798. aligned memory resources.
  1799. If <order of align> is not specified,
  1800. PAGE_SIZE is used as alignment.
  1801. PCI-PCI bridge can be specified, if resource
  1802. windows need to be expanded.
  1803. ecrc= Enable/disable PCIe ECRC (transaction layer
  1804. end-to-end CRC checking).
  1805. bios: Use BIOS/firmware settings. This is the
  1806. the default.
  1807. off: Turn ECRC off
  1808. on: Turn ECRC on.
  1809. realloc= Enable/disable reallocating PCI bridge resources
  1810. if allocations done by BIOS are too small to
  1811. accommodate resources required by all child
  1812. devices.
  1813. off: Turn realloc off
  1814. on: Turn realloc on
  1815. realloc same as realloc=on
  1816. noari do not use PCIe ARI.
  1817. pcie_scan_all Scan all possible PCIe devices. Otherwise we
  1818. only look for one device below a PCIe downstream
  1819. port.
  1820. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1821. Management.
  1822. off Disable ASPM.
  1823. force Enable ASPM even on devices that claim not to support it.
  1824. WARNING: Forcing ASPM on may cause system lockups.
  1825. pcie_hp= [PCIE] PCI Express Hotplug driver options:
  1826. nomsi Do not use MSI for PCI Express Native Hotplug (this
  1827. makes all PCIe ports use INTx for hotplug services).
  1828. pcie_ports= [PCIE] PCIe ports handling:
  1829. auto Ask the BIOS whether or not to use native PCIe services
  1830. associated with PCIe ports (PME, hot-plug, AER). Use
  1831. them only if that is allowed by the BIOS.
  1832. native Use native PCIe services associated with PCIe ports
  1833. unconditionally.
  1834. compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
  1835. ports driver.
  1836. pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
  1837. nomsi Do not use MSI for native PCIe PME signaling (this makes
  1838. all PCIe root ports use INTx for all services).
  1839. pcmv= [HW,PCMCIA] BadgePAD 4
  1840. pd. [PARIDE]
  1841. See Documentation/blockdev/paride.txt.
  1842. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1843. boot time.
  1844. Format: { 0 | 1 }
  1845. See arch/parisc/kernel/pdc_chassis.c
  1846. percpu_alloc= Select which percpu first chunk allocator to use.
  1847. Currently supported values are "embed" and "page".
  1848. Archs may support subset or none of the selections.
  1849. See comments in mm/percpu.c for details on each
  1850. allocator. This parameter is primarily for debugging
  1851. and performance comparison.
  1852. pf. [PARIDE]
  1853. See Documentation/blockdev/paride.txt.
  1854. pg. [PARIDE]
  1855. See Documentation/blockdev/paride.txt.
  1856. pirq= [SMP,APIC] Manual mp-table setup
  1857. See Documentation/x86/i386/IO-APIC.txt.
  1858. plip= [PPT,NET] Parallel port network link
  1859. Format: { parport<nr> | timid | 0 }
  1860. See also Documentation/parport.txt.
  1861. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1862. Override pmtimer IOPort with a hex value.
  1863. e.g. pmtmr=0x508
  1864. pnp.debug=1 [PNP]
  1865. Enable PNP debug messages (depends on the
  1866. CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
  1867. via /sys/module/pnp/parameters/debug. We always show
  1868. current resource usage; turning this on also shows
  1869. possible settings and some assignment information.
  1870. pnpacpi= [ACPI]
  1871. { off }
  1872. pnpbios= [ISAPNP]
  1873. { on | off | curr | res | no-curr | no-res }
  1874. pnp_reserve_irq=
  1875. [ISAPNP] Exclude IRQs for the autoconfiguration
  1876. pnp_reserve_dma=
  1877. [ISAPNP] Exclude DMAs for the autoconfiguration
  1878. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1879. Ranges are in pairs (I/O port base and size).
  1880. pnp_reserve_mem=
  1881. [ISAPNP] Exclude memory regions for the
  1882. autoconfiguration.
  1883. Ranges are in pairs (memory base and size).
  1884. ports= [IP_VS_FTP] IPVS ftp helper module
  1885. Default is 21.
  1886. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  1887. may be specified.
  1888. Format: <port>,<port>....
  1889. print-fatal-signals=
  1890. [KNL] debug: print fatal signals
  1891. If enabled, warn about various signal handling
  1892. related application anomalies: too many signals,
  1893. too many POSIX.1 timers, fatal signals causing a
  1894. coredump - etc.
  1895. If you hit the warning due to signal overflow,
  1896. you might want to try "ulimit -i unlimited".
  1897. default: off.
  1898. printk.always_kmsg_dump=
  1899. Trigger kmsg_dump for cases other than kernel oops or
  1900. panics
  1901. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1902. default: disabled
  1903. printk.time= Show timing data prefixed to each printk message line
  1904. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1905. processor.max_cstate= [HW,ACPI]
  1906. Limit processor to maximum C-state
  1907. max_cstate=9 overrides any DMI blacklist limit.
  1908. processor.nocst [HW,ACPI]
  1909. Ignore the _CST method to determine C-states,
  1910. instead using the legacy FADT method
  1911. profile= [KNL] Enable kernel profiling via /proc/profile
  1912. Format: [schedule,]<number>
  1913. Param: "schedule" - profile schedule points.
  1914. Param: <number> - step/bucket size as a power of 2 for
  1915. statistical time based profiling.
  1916. Param: "sleep" - profile D-state sleeping (millisecs).
  1917. Requires CONFIG_SCHEDSTATS
  1918. Param: "kvm" - profile VM exits.
  1919. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1920. before loading.
  1921. See Documentation/blockdev/ramdisk.txt.
  1922. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1923. probe for; one of (bare|imps|exps|lifebook|any).
  1924. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1925. per second.
  1926. psmouse.resetafter= [HW,MOUSE]
  1927. Try to reset the device after so many bad packets
  1928. (0 = never).
  1929. psmouse.resolution=
  1930. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1931. psmouse.smartscroll=
  1932. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1933. 0 = disabled, 1 = enabled (default).
  1934. pstore.backend= Specify the name of the pstore backend to use
  1935. pt. [PARIDE]
  1936. See Documentation/blockdev/paride.txt.
  1937. pty.legacy_count=
  1938. [KNL] Number of legacy pty's. Overwrites compiled-in
  1939. default number.
  1940. quiet [KNL] Disable most log messages
  1941. r128= [HW,DRM]
  1942. raid= [HW,RAID]
  1943. See Documentation/md.txt.
  1944. ramdisk_blocksize= [RAM]
  1945. See Documentation/blockdev/ramdisk.txt.
  1946. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1947. See Documentation/blockdev/ramdisk.txt.
  1948. rcutree.blimit= [KNL,BOOT]
  1949. Set maximum number of finished RCU callbacks to process
  1950. in one batch.
  1951. rcutree.fanout_leaf= [KNL,BOOT]
  1952. Increase the number of CPUs assigned to each
  1953. leaf rcu_node structure. Useful for very large
  1954. systems.
  1955. rcutree.qhimark= [KNL,BOOT]
  1956. Set threshold of queued
  1957. RCU callbacks over which batch limiting is disabled.
  1958. rcutree.qlowmark= [KNL,BOOT]
  1959. Set threshold of queued RCU callbacks below which
  1960. batch limiting is re-enabled.
  1961. rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
  1962. Suppress RCU CPU stall warning messages.
  1963. rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
  1964. Set timeout for RCU CPU stall warning messages.
  1965. rcutree.jiffies_till_first_fqs= [KNL,BOOT]
  1966. Set delay from grace-period initialization to
  1967. first attempt to force quiescent states.
  1968. Units are jiffies, minimum value is zero,
  1969. and maximum value is HZ.
  1970. rcutree.jiffies_till_next_fqs= [KNL,BOOT]
  1971. Set delay between subsequent attempts to force
  1972. quiescent states. Units are jiffies, minimum
  1973. value is one, and maximum value is HZ.
  1974. rcutorture.fqs_duration= [KNL,BOOT]
  1975. Set duration of force_quiescent_state bursts.
  1976. rcutorture.fqs_holdoff= [KNL,BOOT]
  1977. Set holdoff time within force_quiescent_state bursts.
  1978. rcutorture.fqs_stutter= [KNL,BOOT]
  1979. Set wait time between force_quiescent_state bursts.
  1980. rcutorture.irqreader= [KNL,BOOT]
  1981. Test RCU readers from irq handlers.
  1982. rcutorture.n_barrier_cbs= [KNL,BOOT]
  1983. Set callbacks/threads for rcu_barrier() testing.
  1984. rcutorture.nfakewriters= [KNL,BOOT]
  1985. Set number of concurrent RCU writers. These just
  1986. stress RCU, they don't participate in the actual
  1987. test, hence the "fake".
  1988. rcutorture.nreaders= [KNL,BOOT]
  1989. Set number of RCU readers.
  1990. rcutorture.onoff_holdoff= [KNL,BOOT]
  1991. Set time (s) after boot for CPU-hotplug testing.
  1992. rcutorture.onoff_interval= [KNL,BOOT]
  1993. Set time (s) between CPU-hotplug operations, or
  1994. zero to disable CPU-hotplug testing.
  1995. rcutorture.shuffle_interval= [KNL,BOOT]
  1996. Set task-shuffle interval (s). Shuffling tasks
  1997. allows some CPUs to go into dyntick-idle mode
  1998. during the rcutorture test.
  1999. rcutorture.shutdown_secs= [KNL,BOOT]
  2000. Set time (s) after boot system shutdown. This
  2001. is useful for hands-off automated testing.
  2002. rcutorture.stall_cpu= [KNL,BOOT]
  2003. Duration of CPU stall (s) to test RCU CPU stall
  2004. warnings, zero to disable.
  2005. rcutorture.stall_cpu_holdoff= [KNL,BOOT]
  2006. Time to wait (s) after boot before inducing stall.
  2007. rcutorture.stat_interval= [KNL,BOOT]
  2008. Time (s) between statistics printk()s.
  2009. rcutorture.stutter= [KNL,BOOT]
  2010. Time (s) to stutter testing, for example, specifying
  2011. five seconds causes the test to run for five seconds,
  2012. wait for five seconds, and so on. This tests RCU's
  2013. ability to transition abruptly to and from idle.
  2014. rcutorture.test_boost= [KNL,BOOT]
  2015. Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
  2016. "Maybe" means test if the RCU implementation
  2017. under test support RCU priority boosting.
  2018. rcutorture.test_boost_duration= [KNL,BOOT]
  2019. Duration (s) of each individual boost test.
  2020. rcutorture.test_boost_interval= [KNL,BOOT]
  2021. Interval (s) between each boost test.
  2022. rcutorture.test_no_idle_hz= [KNL,BOOT]
  2023. Test RCU's dyntick-idle handling. See also the
  2024. rcutorture.shuffle_interval parameter.
  2025. rcutorture.torture_type= [KNL,BOOT]
  2026. Specify the RCU implementation to test.
  2027. rcutorture.verbose= [KNL,BOOT]
  2028. Enable additional printk() statements.
  2029. rdinit= [KNL]
  2030. Format: <full_path>
  2031. Run specified binary instead of /init from the ramdisk,
  2032. used for early userspace startup. See initrd.
  2033. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  2034. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  2035. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  2036. relax_domain_level=
  2037. [KNL, SMP] Set scheduler's default relax_domain_level.
  2038. See Documentation/cgroups/cpusets.txt.
  2039. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  2040. reservetop= [X86-32]
  2041. Format: nn[KMG]
  2042. Reserves a hole at the top of the kernel virtual
  2043. address space.
  2044. reservelow= [X86]
  2045. Format: nn[K]
  2046. Set the amount of memory to reserve for BIOS at
  2047. the bottom of the address space.
  2048. reset_devices [KNL] Force drivers to reset the underlying device
  2049. during initialization.
  2050. resume= [SWSUSP]
  2051. Specify the partition device for software suspend
  2052. Format:
  2053. {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
  2054. resume_offset= [SWSUSP]
  2055. Specify the offset from the beginning of the partition
  2056. given by "resume=" at which the swap header is located,
  2057. in <PAGE_SIZE> units (needed only for swap files).
  2058. See Documentation/power/swsusp-and-swap-files.txt
  2059. resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
  2060. read the resume files
  2061. resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
  2062. Useful for devices that are detected asynchronously
  2063. (e.g. USB and MMC devices).
  2064. hibernate= [HIBERNATION]
  2065. noresume Don't check if there's a hibernation image
  2066. present during boot.
  2067. nocompress Don't compress/decompress hibernation images.
  2068. retain_initrd [RAM] Keep initrd memory after extraction
  2069. rhash_entries= [KNL,NET]
  2070. Set number of hash buckets for route cache
  2071. riscom8= [HW,SERIAL]
  2072. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  2073. ro [KNL] Mount root device read-only on boot
  2074. root= [KNL] Root filesystem
  2075. See name_to_dev_t comment in init/do_mounts.c.
  2076. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  2077. mount the root filesystem
  2078. rootflags= [KNL] Set root filesystem mount option string
  2079. rootfstype= [KNL] Set root filesystem type
  2080. rootwait [KNL] Wait (indefinitely) for root device to show up.
  2081. Useful for devices that are detected asynchronously
  2082. (e.g. USB and MMC devices).
  2083. rw [KNL] Mount root device read-write on boot
  2084. S [KNL] Run init in single mode
  2085. sa1100ir [NET]
  2086. See drivers/net/irda/sa1100_ir.c.
  2087. sbni= [NET] Granch SBNI12 leased line adapter
  2088. sched_debug [KNL] Enables verbose scheduler debug messages.
  2089. skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
  2090. xtime_lock contention on larger systems, and/or RCU lock
  2091. contention on all systems with CONFIG_MAXSMP set.
  2092. Format: { "0" | "1" }
  2093. 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
  2094. 1 -- enable.
  2095. Note: increases power consumption, thus should only be
  2096. enabled if running jitter sensitive (HPC/RT) workloads.
  2097. security= [SECURITY] Choose a security module to enable at boot.
  2098. If this boot parameter is not specified, only the first
  2099. security module asking for security registration will be
  2100. loaded. An invalid security module name will be treated
  2101. as if no module has been chosen.
  2102. selinux= [SELINUX] Disable or enable SELinux at boot time.
  2103. Format: { "0" | "1" }
  2104. See security/selinux/Kconfig help text.
  2105. 0 -- disable.
  2106. 1 -- enable.
  2107. Default value is set via kernel config option.
  2108. If enabled at boot time, /selinux/disable can be used
  2109. later to disable prior to initial policy load.
  2110. apparmor= [APPARMOR] Disable or enable AppArmor at boot time
  2111. Format: { "0" | "1" }
  2112. See security/apparmor/Kconfig help text
  2113. 0 -- disable.
  2114. 1 -- enable.
  2115. Default value is set via kernel config option.
  2116. serialnumber [BUGS=X86-32]
  2117. shapers= [NET]
  2118. Maximal number of shapers.
  2119. show_msr= [x86] show boot-time MSR settings
  2120. Format: { <integer> }
  2121. Show boot-time (BIOS-initialized) MSR settings.
  2122. The parameter means the number of CPUs to show,
  2123. for example 1 means boot CPU only.
  2124. simeth= [IA-64]
  2125. simscsi=
  2126. slram= [HW,MTD]
  2127. slab_max_order= [MM, SLAB]
  2128. Determines the maximum allowed order for slabs.
  2129. A high setting may cause OOMs due to memory
  2130. fragmentation. Defaults to 1 for systems with
  2131. more than 32MB of RAM, 0 otherwise.
  2132. slub_debug[=options[,slabs]] [MM, SLUB]
  2133. Enabling slub_debug allows one to determine the
  2134. culprit if slab objects become corrupted. Enabling
  2135. slub_debug can create guard zones around objects and
  2136. may poison objects when not in use. Also tracks the
  2137. last alloc / free. For more information see
  2138. Documentation/vm/slub.txt.
  2139. slub_max_order= [MM, SLUB]
  2140. Determines the maximum allowed order for slabs.
  2141. A high setting may cause OOMs due to memory
  2142. fragmentation. For more information see
  2143. Documentation/vm/slub.txt.
  2144. slub_min_objects= [MM, SLUB]
  2145. The minimum number of objects per slab. SLUB will
  2146. increase the slab order up to slub_max_order to
  2147. generate a sufficiently large slab able to contain
  2148. the number of objects indicated. The higher the number
  2149. of objects the smaller the overhead of tracking slabs
  2150. and the less frequently locks need to be acquired.
  2151. For more information see Documentation/vm/slub.txt.
  2152. slub_min_order= [MM, SLUB]
  2153. Determines the minimum page order for slabs. Must be
  2154. lower than slub_max_order.
  2155. For more information see Documentation/vm/slub.txt.
  2156. slub_nomerge [MM, SLUB]
  2157. Disable merging of slabs with similar size. May be
  2158. necessary if there is some reason to distinguish
  2159. allocs to different slabs. Debug options disable
  2160. merging on their own.
  2161. For more information see Documentation/vm/slub.txt.
  2162. smart2= [HW]
  2163. Format: <io1>[,<io2>[,...,<io8>]]
  2164. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  2165. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  2166. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  2167. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  2168. smsc-ircc2.ircc_irq= [HW] IRQ line
  2169. smsc-ircc2.ircc_dma= [HW] DMA channel
  2170. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  2171. 0: Toshiba Satellite 1800 (GP data pin select)
  2172. 1: Fast pin select (default)
  2173. 2: ATC IRMode
  2174. softlockup_panic=
  2175. [KNL] Should the soft-lockup detector generate panics.
  2176. Format: <integer>
  2177. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  2178. See Documentation/laptops/sonypi.txt
  2179. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  2180. See Documentation/serial/specialix.txt.
  2181. spia_io_base= [HW,MTD]
  2182. spia_fio_base=
  2183. spia_pedr=
  2184. spia_peddr=
  2185. stacktrace [FTRACE]
  2186. Enabled the stack tracer on boot up.
  2187. stacktrace_filter=[function-list]
  2188. [FTRACE] Limit the functions that the stack tracer
  2189. will trace at boot up. function-list is a comma separated
  2190. list of functions. This list can be changed at run
  2191. time by the stack_trace_filter file in the debugfs
  2192. tracing directory. Note, this enables stack tracing
  2193. and the stacktrace above is not needed.
  2194. sti= [PARISC,HW]
  2195. Format: <num>
  2196. Set the STI (builtin display/keyboard on the HP-PARISC
  2197. machines) console (graphic card) which should be used
  2198. as the initial boot-console.
  2199. See also comment in drivers/video/console/sticore.c.
  2200. sti_font= [HW]
  2201. See comment in drivers/video/console/sticore.c.
  2202. stifb= [HW]
  2203. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  2204. sunrpc.min_resvport=
  2205. sunrpc.max_resvport=
  2206. [NFS,SUNRPC]
  2207. SunRPC servers often require that client requests
  2208. originate from a privileged port (i.e. a port in the
  2209. range 0 < portnr < 1024).
  2210. An administrator who wishes to reserve some of these
  2211. ports for other uses may adjust the range that the
  2212. kernel's sunrpc client considers to be privileged
  2213. using these two parameters to set the minimum and
  2214. maximum port values.
  2215. sunrpc.pool_mode=
  2216. [NFS]
  2217. Control how the NFS server code allocates CPUs to
  2218. service thread pools. Depending on how many NICs
  2219. you have and where their interrupts are bound, this
  2220. option will affect which CPUs will do NFS serving.
  2221. Note: this parameter cannot be changed while the
  2222. NFS server is running.
  2223. auto the server chooses an appropriate mode
  2224. automatically using heuristics
  2225. global a single global pool contains all CPUs
  2226. percpu one pool for each CPU
  2227. pernode one pool for each NUMA node (equivalent
  2228. to global on non-NUMA machines)
  2229. sunrpc.tcp_slot_table_entries=
  2230. sunrpc.udp_slot_table_entries=
  2231. [NFS,SUNRPC]
  2232. Sets the upper limit on the number of simultaneous
  2233. RPC calls that can be sent from the client to a
  2234. server. Increasing these values may allow you to
  2235. improve throughput, but will also increase the
  2236. amount of memory reserved for use by the client.
  2237. swapaccount[=0|1]
  2238. [KNL] Enable accounting of swap in memory resource
  2239. controller if no parameter or 1 is given or disable
  2240. it if 0 is given (See Documentation/cgroups/memory.txt)
  2241. swiotlb= [IA-64] Number of I/O TLB slabs
  2242. switches= [HW,M68k]
  2243. sysfs.deprecated=0|1 [KNL]
  2244. Enable/disable old style sysfs layout for old udev
  2245. on older distributions. When this option is enabled
  2246. very new udev will not work anymore. When this option
  2247. is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
  2248. in older udev will not work anymore.
  2249. Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
  2250. the kernel configuration.
  2251. sysrq_always_enabled
  2252. [KNL]
  2253. Ignore sysrq setting - this boot parameter will
  2254. neutralize any effect of /proc/sys/kernel/sysrq.
  2255. Useful for debugging.
  2256. tdfx= [HW,DRM]
  2257. test_suspend= [SUSPEND]
  2258. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  2259. standby suspend) as the system sleep state to briefly
  2260. enter during system startup. The system is woken from
  2261. this state using a wakeup-capable RTC alarm.
  2262. thash_entries= [KNL,NET]
  2263. Set number of hash buckets for TCP connection
  2264. thermal.act= [HW,ACPI]
  2265. -1: disable all active trip points in all thermal zones
  2266. <degrees C>: override all lowest active trip points
  2267. thermal.crt= [HW,ACPI]
  2268. -1: disable all critical trip points in all thermal zones
  2269. <degrees C>: override all critical trip points
  2270. thermal.nocrt= [HW,ACPI]
  2271. Set to disable actions on ACPI thermal zone
  2272. critical and hot trip points.
  2273. thermal.off= [HW,ACPI]
  2274. 1: disable ACPI thermal control
  2275. thermal.psv= [HW,ACPI]
  2276. -1: disable all passive trip points
  2277. <degrees C>: override all passive trip points to this
  2278. value
  2279. thermal.tzp= [HW,ACPI]
  2280. Specify global default ACPI thermal zone polling rate
  2281. <deci-seconds>: poll all this frequency
  2282. 0: no polling (default)
  2283. threadirqs [KNL]
  2284. Force threading of all interrupt handlers except those
  2285. marked explicitly IRQF_NO_THREAD.
  2286. topology= [S390]
  2287. Format: {off | on}
  2288. Specify if the kernel should make use of the cpu
  2289. topology information if the hardware supports this.
  2290. The scheduler will make use of this information and
  2291. e.g. base its process migration decisions on it.
  2292. Default is on.
  2293. tp720= [HW,PS2]
  2294. tpm_suspend_pcr=[HW,TPM]
  2295. Format: integer pcr id
  2296. Specify that at suspend time, the tpm driver
  2297. should extend the specified pcr with zeros,
  2298. as a workaround for some chips which fail to
  2299. flush the last written pcr on TPM_SaveState.
  2300. This will guarantee that all the other pcrs
  2301. are saved.
  2302. trace_buf_size=nn[KMG]
  2303. [FTRACE] will set tracing buffer size.
  2304. trace_event=[event-list]
  2305. [FTRACE] Set and start specified trace events in order
  2306. to facilitate early boot debugging.
  2307. See also Documentation/trace/events.txt
  2308. transparent_hugepage=
  2309. [KNL]
  2310. Format: [always|madvise|never]
  2311. Can be used to control the default behavior of the system
  2312. with respect to transparent hugepages.
  2313. See Documentation/vm/transhuge.txt for more details.
  2314. tsc= Disable clocksource stability checks for TSC.
  2315. Format: <string>
  2316. [x86] reliable: mark tsc clocksource as reliable, this
  2317. disables clocksource verification at runtime, as well
  2318. as the stability checks done at bootup. Used to enable
  2319. high-resolution timer mode on older hardware, and in
  2320. virtualized environment.
  2321. [x86] noirqtime: Do not use TSC to do irq accounting.
  2322. Used to run time disable IRQ_TIME_ACCOUNTING on any
  2323. platforms where RDTSC is slow and this accounting
  2324. can add overhead.
  2325. turbografx.map[2|3]= [HW,JOY]
  2326. TurboGraFX parallel port interface
  2327. Format:
  2328. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  2329. See also Documentation/input/joystick-parport.txt
  2330. udbg-immortal [PPC] When debugging early kernel crashes that
  2331. happen after console_init() and before a proper
  2332. console driver takes over, this boot options might
  2333. help "seeing" what's going on.
  2334. uhash_entries= [KNL,NET]
  2335. Set number of hash buckets for UDP/UDP-Lite connections
  2336. uhci-hcd.ignore_oc=
  2337. [USB] Ignore overcurrent events (default N).
  2338. Some badly-designed motherboards generate lots of
  2339. bogus events, for ports that aren't wired to
  2340. anything. Set this parameter to avoid log spamming.
  2341. Note that genuine overcurrent events won't be
  2342. reported either.
  2343. unknown_nmi_panic
  2344. [X86] Cause panic on unknown NMI.
  2345. usbcore.authorized_default=
  2346. [USB] Default USB device authorization:
  2347. (default -1 = authorized except for wireless USB,
  2348. 0 = not authorized, 1 = authorized)
  2349. usbcore.autosuspend=
  2350. [USB] The autosuspend time delay (in seconds) used
  2351. for newly-detected USB devices (default 2). This
  2352. is the time required before an idle device will be
  2353. autosuspended. Devices for which the delay is set
  2354. to a negative value won't be autosuspended at all.
  2355. usbcore.usbfs_snoop=
  2356. [USB] Set to log all usbfs traffic (default 0 = off).
  2357. usbcore.blinkenlights=
  2358. [USB] Set to cycle leds on hubs (default 0 = off).
  2359. usbcore.old_scheme_first=
  2360. [USB] Start with the old device initialization
  2361. scheme (default 0 = off).
  2362. usbcore.usbfs_memory_mb=
  2363. [USB] Memory limit (in MB) for buffers allocated by
  2364. usbfs (default = 16, 0 = max = 2047).
  2365. usbcore.use_both_schemes=
  2366. [USB] Try the other device initialization scheme
  2367. if the first one fails (default 1 = enabled).
  2368. usbcore.initial_descriptor_timeout=
  2369. [USB] Specifies timeout for the initial 64-byte
  2370. USB_REQ_GET_DESCRIPTOR request in milliseconds
  2371. (default 5000 = 5.0 seconds).
  2372. usbhid.mousepoll=
  2373. [USBHID] The interval which mice are to be polled at.
  2374. usb-storage.delay_use=
  2375. [UMS] The delay in seconds before a new device is
  2376. scanned for Logical Units (default 5).
  2377. usb-storage.quirks=
  2378. [UMS] A list of quirks entries to supplement or
  2379. override the built-in unusual_devs list. List
  2380. entries are separated by commas. Each entry has
  2381. the form VID:PID:Flags where VID and PID are Vendor
  2382. and Product ID values (4-digit hex numbers) and
  2383. Flags is a set of characters, each corresponding
  2384. to a common usb-storage quirk flag as follows:
  2385. a = SANE_SENSE (collect more than 18 bytes
  2386. of sense data);
  2387. b = BAD_SENSE (don't collect more than 18
  2388. bytes of sense data);
  2389. c = FIX_CAPACITY (decrease the reported
  2390. device capacity by one sector);
  2391. d = NO_READ_DISC_INFO (don't use
  2392. READ_DISC_INFO command);
  2393. e = NO_READ_CAPACITY_16 (don't use
  2394. READ_CAPACITY_16 command);
  2395. h = CAPACITY_HEURISTICS (decrease the
  2396. reported device capacity by one
  2397. sector if the number is odd);
  2398. i = IGNORE_DEVICE (don't bind to this
  2399. device);
  2400. l = NOT_LOCKABLE (don't try to lock and
  2401. unlock ejectable media);
  2402. m = MAX_SECTORS_64 (don't transfer more
  2403. than 64 sectors = 32 KB at a time);
  2404. n = INITIAL_READ10 (force a retry of the
  2405. initial READ(10) command);
  2406. o = CAPACITY_OK (accept the capacity
  2407. reported by the device);
  2408. p = WRITE_CACHE (the device cache is ON
  2409. by default);
  2410. r = IGNORE_RESIDUE (the device reports
  2411. bogus residue values);
  2412. s = SINGLE_LUN (the device has only one
  2413. Logical Unit);
  2414. w = NO_WP_DETECT (don't test whether the
  2415. medium is write-protected).
  2416. Example: quirks=0419:aaf5:rl,0421:0433:rc
  2417. user_debug= [KNL,ARM]
  2418. Format: <int>
  2419. See arch/arm/Kconfig.debug help text.
  2420. 1 - undefined instruction events
  2421. 2 - system calls
  2422. 4 - invalid data aborts
  2423. 8 - SIGSEGV faults
  2424. 16 - SIGBUS faults
  2425. Example: user_debug=31
  2426. userpte=
  2427. [X86] Flags controlling user PTE allocations.
  2428. nohigh = do not allocate PTE pages in
  2429. HIGHMEM regardless of setting
  2430. of CONFIG_HIGHPTE.
  2431. vdso= [X86,SH]
  2432. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  2433. vdso=1: enable VDSO (default)
  2434. vdso=0: disable VDSO mapping
  2435. vdso32= [X86]
  2436. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  2437. vdso32=1: enable 32-bit VDSO (default)
  2438. vdso32=0: disable 32-bit VDSO mapping
  2439. vector= [IA-64,SMP]
  2440. vector=percpu: enable percpu vector domain
  2441. video= [FB] Frame buffer configuration
  2442. See Documentation/fb/modedb.txt.
  2443. virtio_mmio.device=
  2444. [VMMIO] Memory mapped virtio (platform) device.
  2445. <size>@<baseaddr>:<irq>[:<id>]
  2446. where:
  2447. <size> := size (can use standard suffixes
  2448. like K, M and G)
  2449. <baseaddr> := physical base address
  2450. <irq> := interrupt number (as passed to
  2451. request_irq())
  2452. <id> := (optional) platform device id
  2453. example:
  2454. virtio_mmio.device=1K@0x100b0000:48:7
  2455. Can be used multiple times for multiple devices.
  2456. vga= [BOOT,X86-32] Select a particular video mode
  2457. See Documentation/x86/boot.txt and
  2458. Documentation/svga.txt.
  2459. Use vga=ask for menu.
  2460. This is actually a boot loader parameter; the value is
  2461. passed to the kernel using a special protocol.
  2462. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  2463. size of <nn>. This can be used to increase the
  2464. minimum size (128MB on x86). It can also be used to
  2465. decrease the size and leave more room for directly
  2466. mapped kernel RAM.
  2467. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  2468. Format: <command>
  2469. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  2470. Format: <command>
  2471. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  2472. Format: <command>
  2473. vsyscall= [X86-64]
  2474. Controls the behavior of vsyscalls (i.e. calls to
  2475. fixed addresses of 0xffffffffff600x00 from legacy
  2476. code). Most statically-linked binaries and older
  2477. versions of glibc use these calls. Because these
  2478. functions are at fixed addresses, they make nice
  2479. targets for exploits that can control RIP.
  2480. emulate [default] Vsyscalls turn into traps and are
  2481. emulated reasonably safely.
  2482. native Vsyscalls are native syscall instructions.
  2483. This is a little bit faster than trapping
  2484. and makes a few dynamic recompilers work
  2485. better than they would in emulation mode.
  2486. It also makes exploits much easier to write.
  2487. none Vsyscalls don't work at all. This makes
  2488. them quite hard to use for exploits but
  2489. might break your system.
  2490. vt.cur_default= [VT] Default cursor shape.
  2491. Format: 0xCCBBAA, where AA, BB, and CC are the same as
  2492. the parameters of the <Esc>[?A;B;Cc escape sequence;
  2493. see VGA-softcursor.txt. Default: 2 = underline.
  2494. vt.default_blu= [VT]
  2495. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  2496. Change the default blue palette of the console.
  2497. This is a 16-member array composed of values
  2498. ranging from 0-255.
  2499. vt.default_grn= [VT]
  2500. Format: <green0>,<green1>,<green2>,...,<green15>
  2501. Change the default green palette of the console.
  2502. This is a 16-member array composed of values
  2503. ranging from 0-255.
  2504. vt.default_red= [VT]
  2505. Format: <red0>,<red1>,<red2>,...,<red15>
  2506. Change the default red palette of the console.
  2507. This is a 16-member array composed of values
  2508. ranging from 0-255.
  2509. vt.default_utf8=
  2510. [VT]
  2511. Format=<0|1>
  2512. Set system-wide default UTF-8 mode for all tty's.
  2513. Default is 1, i.e. UTF-8 mode is enabled for all
  2514. newly opened terminals.
  2515. vt.global_cursor_default=
  2516. [VT]
  2517. Format=<-1|0|1>
  2518. Set system-wide default for whether a cursor
  2519. is shown on new VTs. Default is -1,
  2520. i.e. cursors will be created by default unless
  2521. overridden by individual drivers. 0 will hide
  2522. cursors, 1 will display them.
  2523. watchdog timers [HW,WDT] For information on watchdog timers,
  2524. see Documentation/watchdog/watchdog-parameters.txt
  2525. or other driver-specific files in the
  2526. Documentation/watchdog/ directory.
  2527. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  2528. default x2apic cluster mode on platforms
  2529. supporting x2apic.
  2530. x86_mrst_timer= [X86-32,APBT]
  2531. Choose timer option for x86 Moorestown MID platform.
  2532. Two valid options are apbt timer only and lapic timer
  2533. plus one apbt timer for broadcast timer.
  2534. x86_mrst_timer=apbt_only | lapic_and_apbt
  2535. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  2536. xd_geo= See header of drivers/block/xd.c.
  2537. xen_emul_unplug= [HW,X86,XEN]
  2538. Unplug Xen emulated devices
  2539. Format: [unplug0,][unplug1]
  2540. ide-disks -- unplug primary master IDE devices
  2541. aux-ide-disks -- unplug non-primary-master IDE devices
  2542. nics -- unplug network devices
  2543. all -- unplug all emulated devices (NICs and IDE disks)
  2544. unnecessary -- unplugging emulated devices is
  2545. unnecessary even if the host did not respond to
  2546. the unplug protocol
  2547. never -- do not unplug even if version check succeeds
  2548. xirc2ps_cs= [NET,PCMCIA]
  2549. Format:
  2550. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  2551. ______________________________________________________________________
  2552. TODO:
  2553. Add more DRM drivers.