4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DM Device mapper support is enabled.
48 DRM Direct Rendering Management support is enabled.
49 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
50 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
51 EFI EFI Partitioning (GPT) is enabled
52 EIDE EIDE/ATAPI support is enabled.
53 EVM Extended Verification Module
54 FB The frame buffer device is enabled.
55 FTRACE Function tracing enabled.
56 GCOV GCOV profiling is enabled.
57 HW Appropriate hardware is enabled.
58 IA-64 IA-64 architecture is enabled.
59 IMA Integrity measurement architecture is enabled.
60 IOSCHED More than one I/O scheduler is enabled.
61 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
62 IPV6 IPv6 support is enabled.
63 ISAPNP ISA PnP code is enabled.
64 ISDN Appropriate ISDN support is enabled.
65 JOY Appropriate joystick support is enabled.
66 KGDB Kernel debugger support is enabled.
67 KVM Kernel Virtual Machine support is enabled.
68 LIBATA Libata driver is enabled
69 LP Printer support is enabled.
70 LOOP Loopback device support is enabled.
71 M68k M68k architecture is enabled.
72 These options have more detailed description inside of
73 Documentation/m68k/kernel-options.txt.
74 MCA MCA bus support is enabled.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VGA The VGA console has been enabled.
115 VT Virtual terminal support is enabled.
116 WDT Watchdog support is enabled.
117 XT IBM PC/XT MFM hard disk support is enabled.
118 X86-32 X86-32, aka i386 architecture is enabled.
119 X86-64 X86-64 architecture is enabled.
120 More X86-64 boot options can be found in
121 Documentation/x86/x86_64/boot-options.txt .
122 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
123 XEN Xen support is enabled
125 In addition, the following text indicates that the option:
127 BUGS= Relates to possible processor bugs on the said processor.
128 KNL Is a kernel start-up parameter.
129 BOOT Is a boot loader parameter.
131 Parameters denoted with BOOT are actually interpreted by the boot
132 loader, and have no meaning to the kernel directly.
133 Do not modify the syntax of boot loader parameters without extreme
134 need or coordination with <Documentation/x86/boot.txt>.
136 There are also arch-specific kernel-parameters not documented here.
137 See for example <Documentation/x86/x86_64/boot-options.txt>.
139 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
140 a trailing = on the name of any parameter states that that parameter will
141 be entered as an environment variable, whereas its absence indicates that
142 it will appear as a kernel argument readable via /proc/cmdline by programs
143 running once the system is up.
145 The number of kernel parameters is not limited, but the length of the
146 complete command line (parameters including spaces etc.) is limited to
147 a fixed number of characters. This limit depends on the architecture
148 and is between 256 and 4096 characters. It is defined in the file
149 ./include/asm/setup.h as COMMAND_LINE_SIZE.
151 Finally, the [KMG] suffix is commonly described after a number of kernel
152 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
153 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
154 bytes respectively. Such letter suffixes can also be entirely omitted.
158 Advanced Configuration and Power Interface
159 Format: { force | off | strict | noirq | rsdt }
160 force -- enable ACPI if default was off
161 off -- disable ACPI if default was on
162 noirq -- do not use ACPI for IRQ routing
163 strict -- Be less tolerant of platforms that are not
164 strictly ACPI specification compliant.
165 rsdt -- prefer RSDT over (default) XSDT
166 copy_dsdt -- copy DSDT to memory
168 See also Documentation/power/runtime_pm.txt, pci=noacpi
170 acpi_rsdp= [ACPI,EFI,KEXEC]
171 Pass the RSDP address to the kernel, mostly used
172 on machines running EFI runtime service to boot the
173 second kernel for kdump.
175 acpi_apic_instance= [ACPI, IOAPIC]
177 2: use 2nd APIC table, if available
178 1,0: use 1st APIC table
181 acpi_backlight= [HW,ACPI]
182 acpi_backlight=vendor
184 If set to vendor, prefer vendor specific driver
185 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
186 of the ACPI video.ko driver.
188 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
189 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
191 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
192 debug output. Bits in debug_layer correspond to a
193 _COMPONENT in an ACPI source file, e.g.,
194 #define _COMPONENT ACPI_PCI_COMPONENT
195 Bits in debug_level correspond to a level in
196 ACPI_DEBUG_PRINT statements, e.g.,
197 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
198 The debug_level mask defaults to "info". See
199 Documentation/acpi/debug.txt for more information about
200 debug layers and levels.
202 Enable processor driver info messages:
203 acpi.debug_layer=0x20000000
204 Enable PCI/PCI interrupt routing info messages:
205 acpi.debug_layer=0x400000
206 Enable AML "Debug" output, i.e., stores to the Debug
207 object while interpreting AML:
208 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
209 Enable all messages related to ACPI hardware:
210 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212 Some values produce so much output that the system is
213 unusable. The "log_buf_len" parameter may be useful
214 if you need to capture more output.
216 acpi_irq_balance [HW,ACPI]
217 ACPI will balance active IRQs
220 acpi_irq_nobalance [HW,ACPI]
221 ACPI will not move active IRQs (default)
224 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
225 Format: <irq>,<irq>...
227 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 Format: <irq>,<irq>...
231 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
234 Format: To spoof as Windows 98: ="Microsoft Windows"
236 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
237 acpi_osi="string1" # add string1 -- only one string
238 acpi_osi="!string2" # remove built-in string2
239 acpi_osi= # disable all strings
242 Override the pmtimer bug detection: force the kernel
243 to assume that this machine's pmtimer latches its value
244 and always returns good values.
246 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
247 Format: { level | edge | high | low }
249 acpi_serialize [HW,ACPI] force serialization of AML methods
251 acpi_skip_timer_override [HW,ACPI]
252 Recognize and ignore IRQ0/pin2 Interrupt Override.
253 For broken nForce2 BIOS resulting in XT-PIC timer.
255 acpi_sleep= [HW,ACPI] Sleep options
256 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
257 old_ordering, nonvs, sci_force_enable }
258 See Documentation/power/video.txt for information on
260 s3_beep is for debugging; it makes the PC's speaker beep
261 as soon as the kernel's real-mode entry point is called.
262 s4_nohwsig prevents ACPI hardware signature from being
263 used during resume from hibernation.
264 old_ordering causes the ACPI 1.0 ordering of the _PTS
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
267 of _PTS is used by default).
268 nonvs prevents the kernel from saving/restoring the
269 ACPI NVS memory during suspend/hibernation and resume.
270 sci_force_enable causes the kernel to set SCI_EN directly
271 on resume from S1/S3 (which is against the ACPI spec,
272 but some broken systems don't work without it).
274 acpi_use_timer_override [HW,ACPI]
275 Use timer override. For some broken Nvidia NF5 boards
276 that require a timer override, but don't have HPET
278 acpi_enforce_resources= [ACPI]
279 { strict | lax | no }
280 Check for resource conflicts between native drivers
281 and ACPI OperationRegions (SystemIO and SystemMemory
282 only). IO ports and memory declared in ACPI might be
283 used by the ACPI subsystem in arbitrary AML code and
284 can interfere with legacy drivers.
285 strict (default): access to resources claimed by ACPI
286 is denied; legacy drivers trying to access reserved
287 resources will fail to bind to device using them.
288 lax: access to resources claimed by ACPI is allowed;
289 legacy drivers trying to access reserved resources
290 will bind successfully but a warning message is logged.
291 no: ACPI OperationRegions are not marked as reserved,
292 no further checks are performed.
294 add_efi_memmap [EFI; X86] Include EFI memory map in
295 kernel's map of available physical RAM.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/sound/alsa/alsa-parameters.txt
307 Allow the default userspace alignment fault handler
308 behaviour to be specified. Bit 0 enables warnings,
309 bit 1 enables fixups, and bit 2 sends a segfault.
311 align_va_addr= [X86-64]
312 Align virtual addresses by clearing slice [14:12] when
313 allocating a VMA at process creation time. This option
314 gives you up to 3% performance improvement on AMD F15h
315 machines (where it is enabled by default) for a
316 CPU-intensive style benchmark, and it can vary highly in
317 a microbenchmark depending on workload and compiler.
319 32: only for 32-bit processes
320 64: only for 64-bit processes
321 on: enable for both 32- and 64-bit processes
322 off: disable for both 32- and 64-bit processes
324 amd_iommu= [HW,X86-64]
325 Pass parameters to the AMD IOMMU driver in the system.
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
331 off - do not initialize any AMD IOMMU found in
333 force_isolation - Force device isolation for all
334 devices. The IOMMU driver is not
335 allowed anymore to lift isolation
336 requirements as needed. This option
337 does not override iommu=pt
339 amijoy.map= [HW,JOY] Amiga joystick support
340 Map of devices attached to JOY0DAT and JOY1DAT
342 See also Documentation/input/joystick.txt
344 analog.map= [HW,JOY] Analog joystick and gamepad support
345 Specifies type or capabilities of an analog joystick
346 connected to one of 16 gameports
347 Format: <type1>,<type2>,..<type16>
350 Power management functions (SPARCstation-4/5 + deriv.)
352 Disable APC CPU standby support. SPARCstation-Fox does
353 not play well with APC CPU idle - disable it if you have
354 APC and your system crashes randomly.
356 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
357 Change the output verbosity whilst booting
358 Format: { quiet (default) | verbose | debug }
359 Change the amount of debugging information output
360 when initialising the APIC and IO-APIC components.
363 See Documentation/networking/ipv6.txt.
365 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
366 Limit apic dumping. The parameter defines the maximal
367 number of local apics being dumped. Also it is possible
368 to set it to "all" by meaning -- no limit here.
369 Format: { 1 (default) | 2 | ... | all }.
370 The parameter valid if only apic=debug or
371 apic=verbose is specified.
372 Example: apic=debug show_lapic=all
374 apm= [APM] Advanced Power Management
375 See header of arch/x86/kernel/apm_32.c.
377 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
378 Format: <io>,<irq>,<nodeID>
382 atarimouse= [HW,MOUSE] Atari Mouse
384 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
385 EzKey and similar keyboards
387 atkbd.reset= [HW] Reset keyboard during initialization
389 atkbd.set= [HW] Select keyboard code set
390 Format: <int> (2 = AT (default), 3 = PS/2)
392 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
395 atkbd.softraw= [HW] Choose between synthetic and real raw mode
396 Format: <bool> (0 = real, 1 = synthetic (default))
398 atkbd.softrepeat= [HW]
399 Use software keyboard repeat
403 baycom_epp= [HW,AX25]
406 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
408 See header of drivers/net/hamradio/baycom_par.c.
410 baycom_ser_fdx= [HW,AX25]
411 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
412 Format: <io>,<irq>,<mode>[,<baud>]
413 See header of drivers/net/hamradio/baycom_ser_fdx.c.
415 baycom_ser_hdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
417 Format: <io>,<irq>,<mode>
418 See header of drivers/net/hamradio/baycom_ser_hdx.c.
420 boot_delay= Milliseconds to delay each printk during boot.
421 Values larger than 10 seconds (10000) are changed to
425 bootmem_debug [KNL] Enable bootmem allocator debug messages.
427 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
428 bttv.radio= Most important insmod options are available as
430 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
433 bulk_remove=off [PPC] This parameter disables the use of the pSeries
434 firmware feature for flushing multiple hpte entries
437 c101= [NET] Moxa C101 synchronous serial card
439 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
440 Sometimes CPU hardware bugs make them report the cache
441 size incorrectly. The kernel will attempt work arounds
442 to fix known problems, but for some CPUs it is not
443 possible to determine what the correct size should be.
444 This option provides an override for these situations.
447 [SECURITY] Disable capabilities. This would normally
448 be used only if an alternative security model is to be
449 configured. Potentially dangerous and should only be
450 used if you are entirely sure of the consequences.
452 ccw_timeout_log [S390]
453 See Documentation/s390/CommonIO for details.
455 cgroup_disable= [KNL] Disable a particular controller
456 Format: {name of the controller(s) to disable}
457 {Currently supported controllers - "memory"}
459 checkreqprot [SELINUX] Set initial checkreqprot flag value.
460 Format: { "0" | "1" }
461 See security/selinux/Kconfig help text.
462 0 -- check protection applied by kernel (includes
463 any implied execute protection).
464 1 -- check protection requested by application.
465 Default value is set via a kernel config option.
466 Value can be changed at runtime via
467 /selinux/checkreqprot.
470 See Documentation/s390/CommonIO for details.
472 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
474 Forces specified clocksource (if available) to be used
475 when calculating gettimeofday(). If specified
476 clocksource is not available, it defaults to PIT.
477 Format: { pit | tsc | cyclone | pmtmr }
479 clocksource= Override the default clocksource
481 Override the default clocksource and use the clocksource
482 with the name specified.
483 Some clocksource names to choose from, depending on
485 [all] jiffies (this is the base, fallback clocksource)
487 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
488 pxa_timer,timer3,32k_counter,timer0_1
490 [X86-32] pit,hpet,tsc;
491 scx200_hrt on Geode; cyclone on IBM x440
499 clearcpuid=BITNUM [X86]
500 Disable CPUID feature X for the kernel. See
501 arch/x86/include/asm/cpufeature.h for the valid bit
502 numbers. Note the Linux specific bits are not necessarily
503 stable over kernel options, but the vendor specific
505 Also note that user programs calling CPUID directly
506 or using the feature without checking anything
507 will still see it. This just prevents it from
508 being used by the kernel or shown in /proc/cpuinfo.
509 Also note the kernel might malfunction if you disable
513 Sets the size of kernel global memory area for contiguous
514 memory allocations. For more information, see
515 include/linux/dma-contiguous.h
517 cmo_free_hint= [PPC] Format: { yes | no }
518 Specify whether pages are marked as being inactive
519 when they are freed. This is used in CMO environments
520 to determine OS memory pressure for page stealing by
524 coherent_pool=nn[KMG] [ARM,KNL]
525 Sets the size of memory pool for coherent, atomic dma
528 code_bytes [X86] How many bytes of object code to print
533 com20020= [HW,NET] ARCnet - COM20020 chipset
535 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
537 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
541 ARCnet - COM90xx chipset (memory-mapped buffers)
542 Format: <io>[,<irq>[,<memstart>]]
544 condev= [HW,S390] console device
547 console= [KNL] Output console device and options.
549 tty<n> Use the virtual console device <n>.
553 Use the specified serial port. The options are of
554 the form "bbbbpnf", where "bbbb" is the baud rate,
555 "p" is parity ("n", "o", or "e"), "n" is number of
556 bits, and "f" is flow control ("r" for RTS or
557 omit it). Default is "9600n8".
559 See Documentation/serial-console.txt for more
561 Documentation/networking/netconsole.txt for an
564 uart[8250],io,<addr>[,options]
565 uart[8250],mmio,<addr>[,options]
566 Start an early, polled-mode console on the 8250/16550
567 UART at the specified I/O port or MMIO address,
568 switching to the matching ttyS device later. The
569 options are the same as for ttyS, above.
571 If the device connected to the port is not a TTY but a braille
572 device, prepend "brl," before the device type, for instance
574 For now, only VisioBraille is supported.
576 consoleblank= [KNL] The console blank (screen saver) timeout in
577 seconds. Defaults to 10*60 = 10mins. A value of 0
578 disables the blank timer.
581 [KNL] Change the default value for
582 /proc/<pid>/coredump_filter.
583 See also Documentation/filesystems/proc.txt.
585 cpuidle.off=1 [CPU_IDLE]
586 disable the cpuidle sub-system
588 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
590 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
592 crashkernel=size[KMG][@offset[KMG]]
593 [KNL] Using kexec, Linux can switch to a 'crash kernel'
594 upon panic. This parameter reserves the physical
595 memory region [offset, offset + size] for that kernel
596 image. If '@offset' is omitted, then a suitable offset
597 is selected automatically. Check
598 Documentation/kdump/kdump.txt for further details.
600 crashkernel=range1:size1[,range2:size2,...][@offset]
601 [KNL] Same as above, but depends on the memory
602 in the running system. The syntax of range is
603 start-[end] where start and end are both
604 a memory unit (amount[KMG]). See also
605 Documentation/kdump/kdump.txt for an example.
607 cros_shared_mem=[ARM]
608 Format: <hex integer>
609 Base address of the ChromeOS shared memory window,
610 aligned at megabyte boundary, window size is fixed at
616 cs89x0_media= [HW,NET]
617 Format: { rj45 | aui | bnc }
620 See header of drivers/s390/block/dasd_devmap.c.
622 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
623 (one device per port)
624 Format: <port#>,<type>
625 See also Documentation/input/joystick-parport.txt
627 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
628 time. See Documentation/dynamic-debug-howto.txt for
631 debug [KNL] Enable kernel debugging (events log level).
634 [KNL] verbose self-tests
636 Print debugging info while doing the locking API
638 We default to 0 (no extra messages), setting it to
639 1 will print _a lot_ more information - normally
640 only useful to kernel developers.
642 debug_objects [KNL] Enable object debugging
645 [KNL] Disable object debugging
647 debug_guardpage_minorder=
648 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
649 parameter allows control of the order of pages that will
650 be intentionally kept free (and hence protected) by the
651 buddy allocator. Bigger value increase the probability
652 of catching random memory corruption, but reduce the
653 amount of memory for normal system use. The maximum
654 possible value is MAX_ORDER/2. Setting this parameter
655 to 1 or 2 should be enough to identify most random
656 memory corruption problems caused by bugs in kernel or
657 driver code when a CPU writes to (or reads from) a
658 random memory location. Note that there exists a class
659 of memory corruptions problems caused by buggy H/W or
660 F/W or by drivers badly programing DMA (basically when
661 memory is written at bus level and the CPU MMU is
662 bypassed) which are not detectable by
663 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
664 tracking down these problems.
666 debugpat [X86] Enable PAT debugging
668 decnet.addr= [HW,NET]
669 Format: <area>[,<node>]
670 See also Documentation/networking/decnet.txt.
673 [same as hugepagesz=] The size of the default
674 HugeTLB page size. This is the size represented by
675 the legacy /proc/ hugepages APIs, used for SHM, and
676 default size when mounting hugetlbfs filesystems.
677 Defaults to the default architecture's huge page size
681 Set number of hash buckets for dentry cache.
684 IO parameters + enable/disable command.
686 digiepca= [HW,SERIAL]
687 See drivers/char/README.epca and
688 Documentation/serial/digiepca.txt.
691 See Documentation/networking/ipv6.txt.
693 disable_ddw [PPC/PSERIES]
694 Disable Dynamic DMA Window support. Use this if
695 to workaround buggy firmware.
698 See Documentation/networking/ipv6.txt.
700 disable_mtrr_cleanup [X86]
701 The kernel tries to adjust MTRR layout from continuous
702 to discrete, to make X server driver able to add WB
703 entry later. This parameter disables that.
705 disable_mtrr_trim [X86, Intel and AMD only]
706 By default the kernel will trim any uncacheable
707 memory out of your available memory pool based on
708 MTRR settings. This parameter disables that behavior,
709 possibly causing your machine to run very slowly.
711 disable_timer_pin_1 [X86]
712 Disable PIN 1 of APIC timer
713 Can be useful to work around chipset bugs.
715 dm= [DM] Allows early creation of a device-mapper device.
716 See Documentation/device-mapper/boot.txt.
718 dmasound= [HW,OSS] Sound subsystem buffers
720 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
721 this option disables the debugging code at boot.
723 dma_debug_entries=<number>
724 This option allows to tune the number of preallocated
725 entries for DMA-API debugging code. One entry is
726 required per DMA-API allocation. Use this if the
727 DMA-API debugging code disables itself because the
728 architectural default is too low.
730 dma_debug_driver=<driver_name>
731 With this option the DMA-API debugging driver
732 filter feature can be enabled at boot time. Just
733 pass the driver to filter for as the parameter.
734 The filter can be disabled or changed to another
735 driver later using sysfs.
737 drm_kms_helper.edid_firmware=[<connector>:]<file>
738 Broken monitors, graphic adapters and KVMs may
739 send no or incorrect EDID data sets. This parameter
740 allows to specify an EDID data set in the
741 /lib/firmware directory that is used instead.
742 Generic built-in EDID data sets are used, if one of
743 edid/1024x768.bin, edid/1280x1024.bin,
744 edid/1680x1050.bin, or edid/1920x1080.bin is given
745 and no file with the same name exists. Details and
746 instructions how to build your own EDID data are
747 available in Documentation/EDID/HOWTO.txt. An EDID
748 data set will only be used for a particular connector,
749 if its name and a colon are prepended to the EDID
754 earlycon= [KNL] Output early console device and options.
755 uart[8250],io,<addr>[,options]
756 uart[8250],mmio,<addr>[,options]
757 uart[8250],mmio32,<addr>[,options]
758 Start an early, polled-mode console on the 8250/16550
759 UART at the specified I/O port or MMIO address.
760 MMIO inter-register address stride is either 8-bit
761 (mmio) or 32-bit (mmio32).
762 The options are the same as for ttyS, above.
764 earlyprintk= [X86,SH,BLACKFIN]
766 earlyprintk=serial[,ttySn[,baudrate]]
767 earlyprintk=ttySn[,baudrate]
768 earlyprintk=dbgp[debugController#]
770 Append ",keep" to not disable it when the real console
773 Only vga or serial or usb debug port at a time.
775 Currently only ttyS0 and ttyS1 are supported.
777 Interaction with the standard serial driver is not
780 The VGA output is eventually overwritten by the real
783 ekgdboc= [X86,KGDB] Allow early kernel console debugging
786 This is designed to be used in conjunction with
787 the boot argument: earlyprintk=vga
790 Format: {"off" | "on" | "skip[mbr]"}
792 eisa_irq_edge= [PARISC,HW]
793 See header of drivers/parisc/eisa.c.
796 See comment before function elanfreq_setup() in
797 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
800 Format: {"cfq" | "deadline" | "noop"}
801 See Documentation/block/cfq-iosched.txt and
802 Documentation/block/deadline-iosched.txt for details.
804 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
805 Specifies physical address of start of kernel core
806 image elf header and optionally the size. Generally
807 kexec loader will pass this option to capture kernel.
808 See Documentation/kdump/kdump.txt for details.
810 enable_mtrr_cleanup [X86]
811 The kernel tries to adjust MTRR layout from continuous
812 to discrete, to make X server driver able to add WB
813 entry later. This parameter enables that.
815 enable_timer_pin_1 [X86]
816 Enable PIN 1 of APIC timer
817 Can be useful to work around chipset bugs
818 (in particular on some ATI chipsets).
819 The kernel tries to set a reasonable default.
821 enforcing [SELINUX] Set initial enforcing status.
823 See security/selinux/Kconfig help text.
824 0 -- permissive (log only, no denials).
825 1 -- enforcing (deny and log).
827 Value can be changed at runtime via /selinux/enforce.
830 Disable Error Record Serialization Table (ERST)
833 ether= [HW,NET] Ethernet cards parameters
834 This option is obsoleted by the "netdev=" option, which
835 has equivalent usage. See its documentation for details.
839 Permit 'security.evm' to be updated regardless of
840 current integrity status.
844 fail_make_request=[KNL]
845 General fault injection mechanism.
846 Format: <interval>,<probability>,<space>,<times>
847 See also Documentation/fault-injection/.
850 See Documentation/blockdev/floppy.txt.
852 force_pal_cache_flush
853 [IA-64] Avoid check_sal_cache_flush which may hang on
854 buggy SAL_CACHE_FLUSH implementations. Using this
855 parameter will force ia64_sal_cache_flush to call
856 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
859 [FTRACE] will set and start the specified tracer
860 as early as possible in order to facilitate early
863 ftrace_dump_on_oops[=orig_cpu]
864 [FTRACE] will dump the trace buffers on oops.
865 If no parameter is passed, ftrace will dump
866 buffers of all CPUs, but if you pass orig_cpu, it will
867 dump only the buffer of the CPU that triggered the
870 ftrace_filter=[function-list]
871 [FTRACE] Limit the functions traced by the function
872 tracer at boot up. function-list is a comma separated
873 list of functions. This list can be changed at run
874 time by the set_ftrace_filter file in the debugfs
877 ftrace_notrace=[function-list]
878 [FTRACE] Do not trace the functions specified in
879 function-list. This list can be changed at run time
880 by the set_ftrace_notrace file in the debugfs
883 ftrace_graph_filter=[function-list]
884 [FTRACE] Limit the top level callers functions traced
885 by the function graph tracer at boot up.
886 function-list is a comma separated list of functions
887 that can be changed at run time by the
888 set_graph_function file in the debugfs tracing directory.
891 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
892 support via parallel port (up to 5 devices per port)
893 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
894 See also Documentation/input/joystick-parport.txt
898 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
902 gcov_persist= [GCOV] When non-zero (default), profiling data for
903 kernel modules is saved and remains accessible via
904 debugfs, even when the module is unloaded/reloaded.
905 When zero, profiling data is discarded and associated
906 debugfs files are removed at module unload time.
908 gpt [EFI] Forces disk with valid GPT signature but
909 invalid Protective MBR to be treated as GPT.
911 hashdist= [KNL,NUMA] Large hashes allocated during boot
912 are distributed across NUMA nodes. Defaults on
913 for 64-bit NUMA, off otherwise.
914 Format: 0 | 1 (for off | on)
916 hcl= [IA-64] SGI's Hardware Graph compatibility layer
918 hd= [EIDE] (E)IDE hard drive subsystem geometry
919 Format: <cyl>,<head>,<sect>
922 Disable Hardware Error Source Table (HEST) support;
923 corresponding firmware-first mode error processing
924 logic will be disabled.
926 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
927 size of <nn>. This works even on boxes that have no
928 highmem otherwise. This also works to reduce highmem
929 size on bigger boxes.
931 highres= [KNL] Enable/disable high resolution timer mode.
932 Valid parameters: "on", "off"
936 See Documentation/isdn/README.HiSax.
940 hpet= [X86-32,HPET] option to control HPET usage
941 Format: { enable (default) | disable | force |
943 disable: disable HPET and use PIT instead
944 force: allow force enabled of undocumented chips (ICH4,
946 verbose: show contents of HPET registers during setup
948 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
949 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
950 On x86-64 and powerpc, this option can be specified
951 multiple times interleaved with hugepages= to reserve
952 huge pages of different sizes. Valid pages sizes on
953 x86-64 are 2M (when the CPU supports "pse") and 1G
954 (when the CPU supports the "pdpe1gb" cpuinfo flag)
955 Note that 1GB pages can only be allocated at boot time
956 using hugepages= and not freed afterwards.
958 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
959 terminal devices. Valid values: 0..8
960 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
961 If specified, z/VM IUCV HVC accepts connections
962 from listed z/VM user IDs only.
965 Do not unregister boot console at start. This is only
966 useful for debugging when something happens in the window
967 between unregistering the boot console and initializing
970 i2c_bus= [HW] Override the default board specific I2C bus speed
971 or register an additional I2C bus that is not
972 registered from board initialization code.
976 i8042.debug [HW] Toggle i8042 debug mode
977 i8042.direct [HW] Put keyboard port into non-translated mode
978 i8042.dumbkbd [HW] Pretend that controller can only read data from
979 keyboard and cannot control its state
980 (Don't attempt to blink the leds)
981 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
982 i8042.nokbd [HW] Don't check/create keyboard port
983 i8042.noloop [HW] Disable the AUX Loopback command while probing
985 i8042.nomux [HW] Don't check presence of an active multiplexing
987 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
989 i8042.notimeout [HW] Ignore timeout condition signalled by controller
990 i8042.reset [HW] Reset the controller during init and cleanup
991 i8042.unlock [HW] Unlock (ignore) the keylock
995 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
996 indicates that the driver is running on unsupported
998 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
999 does not match list of supported models.
1001 [HW] Report power status in /proc/i8k
1002 (disabled by default)
1003 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1007 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1009 ide-core.nodma= [HW] (E)IDE subsystem
1010 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1011 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1012 .cdrom .chs .ignore_cable are additional options
1013 See Documentation/ide/ide.txt.
1015 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1016 Claim all unknown PCI IDE storage controllers.
1019 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1020 Poll forces a polling idle loop that can slightly
1021 improve the performance of waking up a idle CPU, but
1022 will use a lot of power and make the system run hot.
1024 idle=mwait: On systems which support MONITOR/MWAIT but
1025 the kernel chose to not use it because it doesn't save
1026 as much power as a normal idle loop, use the
1027 MONITOR/MWAIT idle loop anyways. Performance should be
1028 the same as idle=poll.
1029 idle=halt: Halt is forced to be used for CPU idle.
1030 In such case C2/C3 won't be used again.
1031 idle=nomwait: Disable mwait for CPU C-states
1033 ignore_loglevel [KNL]
1034 Ignore loglevel setting - this will print /all/
1035 kernel messages to the console. Useful for debugging.
1036 We also add it as printk module parameter, so users
1037 could change it dynamically, usually by
1038 /sys/module/printk/parameters/ignore_loglevel.
1040 ihash_entries= [KNL]
1041 Set number of hash buckets for inode cache.
1044 Format: { "0" | "1" }
1045 0 -- integrity auditing messages. (Default)
1046 1 -- enable informational integrity auditing messages.
1049 Format: { "sha1" | "md5" }
1053 Load a policy which meets the needs of the Trusted
1054 Computing Base. This means IMA will measure all
1055 programs exec'd, files mmap'd for exec, and all files
1056 opened for read by uid=0.
1060 Run specified binary instead of /sbin/init as init
1063 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1064 for working out where the kernel is dying during
1067 initrd= [BOOT] Specify the location of the initial ramdisk
1069 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1072 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1074 Enable intel iommu driver.
1076 Disable intel iommu driver.
1077 igfx_off [Default Off]
1078 By default, gfx is mapped as normal device. If a gfx
1079 device has a dedicated DMAR unit, the DMAR unit is
1080 bypassed by not enabling DMAR with this option. In
1081 this case, gfx device will use physical address for
1084 With this option iommu will not optimize to look
1085 for io virtual address below 32-bit forcing dual
1086 address cycle on pci bus for cards supporting greater
1087 than 32-bit addressing. The default is to look
1088 for translation below 32-bit and if not available
1089 then look in the higher range.
1090 strict [Default Off]
1091 With this option on every unmap_single operation will
1092 result in a hardware IOTLB flush operation as opposed
1093 to batching them for performance.
1094 sp_off [Default Off]
1095 By default, super page will be supported if Intel IOMMU
1096 has the capability. With this option, super page will
1099 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1100 0 disables intel_idle and fall back on acpi_idle.
1101 1 to 6 specify maximum depth of C-state.
1103 intremap= [X86-64, Intel-IOMMU]
1104 on enable Interrupt Remapping (default)
1105 off disable Interrupt Remapping
1106 nosid disable Source ID checking
1108 BIOS x2APIC opt-out request will be ignored
1110 iomem= Disable strict checking of access to MMIO memory
1111 strict regions from userspace.
1126 group_mf [x86, IA-64]
1129 io7= [HW] IO7 for Marvel based alpha systems
1130 See comment before marvel_specify_io7 in
1131 arch/alpha/kernel/core_marvel.c.
1133 io_delay= [X86] I/O delay method
1135 Standard port 0x80 based delay
1137 Alternate port 0xed based delay (needed on some systems)
1139 Simple two microseconds delay
1144 See Documentation/filesystems/nfs/nfsroot.txt.
1146 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1147 See comment before ip2_setup() in
1148 drivers/char/ip2/ip2base.c.
1151 When an interrupt is not handled search all handlers
1152 for it. Intended to get systems with badly broken
1156 When an interrupt is not handled search all handlers
1157 for it. Also check all handlers each timer
1158 interrupt. Intended to get systems with badly broken
1162 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1164 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1166 <cpu number>,...,<cpu number>
1168 <cpu number>-<cpu number>
1169 (must be a positive range in ascending order)
1171 <cpu number>,...,<cpu number>-<cpu number>
1173 This option can be used to specify one or more CPUs
1174 to isolate from the general SMP balancing and scheduling
1175 algorithms. You can move a process onto or off an
1176 "isolated" CPU via the CPU affinity syscalls or cpuset.
1177 <cpu number> begins at 0 and the maximum value is
1178 "number of CPUs in system - 1".
1180 This option is the preferred way to isolate CPUs. The
1181 alternative -- manually setting the CPU mask of all
1182 tasks in the system -- can cause problems and
1183 suboptimal load balancer performance.
1187 js= [HW,JOY] Analog joystick
1188 See Documentation/input/joystick.txt.
1192 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1193 specifies the amount of memory usable by the kernel
1194 for non-movable allocations. The requested amount is
1195 spread evenly throughout all nodes in the system. The
1196 remaining memory in each node is used for Movable
1197 pages. In the event, a node is too small to have both
1198 kernelcore and Movable pages, kernelcore pages will
1199 take priority and other nodes will have a larger number
1200 of kernelcore pages. The Movable zone is used for the
1201 allocation of pages that may be reclaimed or moved
1202 by the page migration subsystem. This means that
1203 HugeTLB pages may not be allocated from this zone.
1204 Note that allocations like PTEs-from-HighMem still
1205 use the HighMem zone if it exists, and the Normal
1206 zone if it does not.
1208 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1209 Format: <Controller#>[,poll interval]
1210 The controller # is the number of the ehci usb debug
1211 port as it is probed via PCI. The poll interval is
1212 optional and is the number seconds in between
1213 each poll cycle to the debug port in case you need
1214 the functionality for interrupting the kernel with
1215 gdb or control-c on the dbgp connection. When
1216 not using this parameter you use sysrq-g to break into
1217 the kernel debugger.
1219 kgdboc= [KGDB,HW] kgdb over consoles.
1220 Requires a tty driver that supports console polling,
1221 or a supported polling keyboard driver (non-usb).
1222 Serial only format: <serial_device>[,baud]
1223 keyboard only format: kbd
1224 keyboard and serial format: kbd,<serial_device>[,baud]
1225 Optional Kernel mode setting:
1226 kms, kbd format: kms,kbd
1227 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1229 kgdbwait [KGDB] Stop kernel execution and enter the
1230 kernel debugger at the earliest opportunity.
1232 kmac= [MIPS] korina ethernet MAC address.
1233 Configure the RouterBoard 532 series on-chip
1234 Ethernet adapter MAC address.
1236 kmemleak= [KNL] Boot-time kmemleak enable/disable
1237 Valid arguments: on, off
1240 kstack=N [X86] Print N words from the kernel stack
1243 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1244 Default is 0 (don't ignore, but inject #GP)
1246 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1250 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1251 Default is 1 (enabled)
1253 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1255 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1257 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1258 (virtualized MMU) support on capable Intel chips.
1259 Default is 1 (enabled)
1261 kvm-intel.emulate_invalid_guest_state=
1262 [KVM,Intel] Enable emulation of invalid guest states
1263 Default is 0 (disabled)
1265 kvm-intel.flexpriority=
1266 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1267 Default is 1 (enabled)
1270 [KVM,Intel] Enable VMX nesting (nVMX).
1271 Default is 0 (disabled)
1273 kvm-intel.unrestricted_guest=
1274 [KVM,Intel] Disable unrestricted guest feature
1275 (virtualized real and unpaged mode) on capable
1276 Intel chips. Default is 1 (enabled)
1278 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1279 feature (tagged TLBs) on capable Intel chips.
1280 Default is 1 (enabled)
1286 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1289 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1292 libata.dma= [LIBATA] DMA control
1293 libata.dma=0 Disable all PATA and SATA DMA
1294 libata.dma=1 PATA and SATA Disk DMA only
1295 libata.dma=2 ATAPI (CDROM) DMA only
1296 libata.dma=4 Compact Flash DMA only
1297 Combinations also work, so libata.dma=3 enables DMA
1298 for disks and CDROMs, but not CFs.
1300 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1301 libata.ignore_hpa=0 keep BIOS limits (default)
1302 libata.ignore_hpa=1 ignore limits, using full disk
1304 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1308 libata.force= [LIBATA] Force configurations. The format is comma
1309 separated list of "[ID:]VAL" where ID is
1310 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1311 matching port, link or device. Basically, it matches
1312 the ATA ID string printed on console by libata. If
1313 the whole ID part is omitted, the last PORT and DEVICE
1314 values are used. If ID hasn't been specified yet, the
1315 configuration applies to all ports, links and devices.
1317 If only DEVICE is omitted, the parameter applies to
1318 the port and all links and devices behind it. DEVICE
1319 number of 0 either selects the first device or the
1320 first fan-out link behind PMP device. It does not
1321 select the host link. DEVICE number of 15 selects the
1322 host link and device attached to it.
1324 The VAL specifies the configuration to force. As long
1325 as there's no ambiguity shortcut notation is allowed.
1326 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1327 The following configurations can be forced.
1329 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1330 Any ID with matching PORT is used.
1332 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1334 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1335 udma[/][16,25,33,44,66,100,133] notation is also
1338 * [no]ncq: Turn on or off NCQ.
1340 * nohrst, nosrst, norst: suppress hard, soft
1343 * dump_id: dump IDENTIFY data.
1345 If there are multiple matching configurations changing
1346 the same attribute, the last one is used.
1348 memblock=debug [KNL] Enable memblock debug messages.
1350 load_ramdisk= [RAM] List of ramdisks to load from floppy
1351 See Documentation/blockdev/ramdisk.txt.
1353 lockd.nlm_grace_period=P [NFS] Assign grace period.
1356 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1359 lockd.nlm_timeout=T [NFS] Assign timeout value.
1362 lockd.nlm_udpport=M [NFS] Assign UDP port.
1365 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1368 loglevel= All Kernel Messages with a loglevel smaller than the
1369 console loglevel will be printed to the console. It can
1370 also be changed with klogd or other programs. The
1371 loglevels are defined as follows:
1373 0 (KERN_EMERG) system is unusable
1374 1 (KERN_ALERT) action must be taken immediately
1375 2 (KERN_CRIT) critical conditions
1376 3 (KERN_ERR) error conditions
1377 4 (KERN_WARNING) warning conditions
1378 5 (KERN_NOTICE) normal but significant condition
1379 6 (KERN_INFO) informational
1380 7 (KERN_DEBUG) debug-level messages
1382 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1383 in bytes. n must be a power of two. The default
1384 size is set in the kernel config file.
1386 logo.nologo [FB] Disables display of the built-in Linux logo.
1387 This may be used to provide more screen space for
1388 kernel log messages and is useful when debugging
1389 kernel boot problems.
1391 lp=0 [LP] Specify parallel ports to use, e.g,
1392 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1393 lp=reset first parallel port). 'lp=0' disables the
1394 lp=auto printer driver. 'lp=reset' (which can be
1395 specified in addition to the ports) causes
1396 attached printers to be reset. Using
1397 lp=port1,port2,... specifies the parallel ports
1398 to associate lp devices with, starting with
1399 lp0. A port specification may be 'none' to skip
1400 that lp device, or a parport name such as
1401 'parport0'. Specifying 'lp=auto' instead of a
1402 port specification list means that device IDs
1403 from each port should be examined, to see if
1404 an IEEE 1284-compliant printer is attached; if
1405 so, the driver will manage that printer.
1406 See also header of drivers/char/lp.c.
1409 Sets loops_per_jiffy to given constant, thus avoiding
1410 time-consuming boot-time autodetection (up to 250 ms per
1411 CPU). 0 enables autodetection (default). To determine
1412 the correct value for your kernel, boot with normal
1413 autodetection and see what value is printed. Note that
1414 on SMP systems the preset will be applied to all CPUs,
1415 which is likely to cause problems if your CPUs need
1416 significantly divergent settings. An incorrect value
1417 will cause delays in the kernel to be wrong, leading to
1418 unpredictable I/O errors and other breakage. Although
1419 unlikely, in the extreme case this might damage your
1423 Format: <io>,<irq>,<dma>
1425 machvec= [IA-64] Force the use of a particular machine-vector
1426 (machvec) in a generic kernel.
1427 Example: machvec=hpzx1_swiotlb
1429 machtype= [Loongson] Share the same kernel image file between different
1431 Example: machtype=lemote-yeeloong-2f-7inch
1433 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1434 than or equal to this physical address is ignored.
1436 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1437 should make use of. maxcpus=n : n >= 0 limits the
1438 kernel to using 'n' processors. n=0 is a special case,
1439 it is equivalent to "nosmp", which also disables
1442 max_loop= [LOOP] The number of loop block devices that get
1443 (loop.max_loop) unconditionally pre-created at init time. The default
1444 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1445 of statically allocating a predefined number, loop
1446 devices can be requested on-demand with the
1447 /dev/loop-control interface.
1451 mce [X86-32] Machine Check Exception
1453 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1455 md= [HW] RAID subsystems devices and level
1456 See Documentation/md.txt.
1459 Format: <first>,<last>
1460 Specifies range of consoles to be captured by the MDA.
1462 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1463 Amount of memory to be used when the kernel is not able
1464 to see the whole system memory or for test.
1465 [X86-32] Use together with memmap= to avoid physical
1466 address space collisions. Without memmap= PCI devices
1467 could be placed at addresses belonging to unused RAM.
1469 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1473 [KNL,SH] Allow user to override the default size for
1474 per-device physically contiguous DMA buffers.
1476 memmap=exactmap [KNL,X86] Enable setting of an exact
1477 E820 memory map, as specified by the user.
1478 Such memmap=exactmap lines can be constructed based on
1479 BIOS output or other requirements. See the memmap=nn@ss
1482 memmap=nn[KMG]@ss[KMG]
1483 [KNL] Force usage of a specific region of memory
1484 Region of memory to be used, from ss to ss+nn.
1486 memmap=nn[KMG]#ss[KMG]
1487 [KNL,ACPI] Mark specific memory as ACPI data.
1488 Region of memory to be used, from ss to ss+nn.
1490 memmap=nn[KMG]$ss[KMG]
1491 [KNL,ACPI] Mark specific memory as reserved.
1492 Region of memory to be used, from ss to ss+nn.
1493 Example: Exclude memory from 0x18690000-0x1869ffff
1494 memmap=64K$0x18690000
1496 memmap=0x10000$0x18690000
1498 memory_corruption_check=0/1 [X86]
1499 Some BIOSes seem to corrupt the first 64k of
1500 memory when doing things like suspend/resume.
1501 Setting this option will scan the memory
1502 looking for corruption. Enabling this will
1503 both detect corruption and prevent the kernel
1504 from using the memory being corrupted.
1505 However, its intended as a diagnostic tool; if
1506 repeatable BIOS-originated corruption always
1507 affects the same memory, you can use memmap=
1508 to prevent the kernel from using that memory.
1510 memory_corruption_check_size=size [X86]
1511 By default it checks for corruption in the low
1512 64k, making this memory unavailable for normal
1513 use. Use this parameter to scan for
1514 corruption in more or less memory.
1516 memory_corruption_check_period=seconds [X86]
1517 By default it checks for corruption every 60
1518 seconds. Use this parameter to check at some
1519 other rate. 0 disables periodic checking.
1521 memtest= [KNL,X86] Enable memtest
1523 default : 0 <disable>
1524 Specifies the number of memtest passes to be
1525 performed. Each pass selects another test
1526 pattern from a given set of patterns. Memtest
1527 fills the memory with this pattern, validates
1528 memory contents and reserves bad memory
1529 regions that are detected.
1531 meye.*= [HW] Set MotionEye Camera parameters
1532 See Documentation/video4linux/meye.txt.
1534 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1535 Multi-Function General Purpose Timers on AMD Geode
1538 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1539 the BIOS has incorrectly applied a workaround. TinyBIOS
1540 version 0.98 is known to be affected, 0.99 fixes the
1541 problem by letting the user disable the workaround.
1545 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1546 physical address is ignored.
1548 mini2440= [ARM,HW,KNL]
1549 Format:[0..2][b][c][t]
1551 MINI2440 configuration specification:
1552 0 - The attached screen is the 3.5" TFT
1553 1 - The attached screen is the 7" TFT
1554 2 - The VGA Shield is attached (1024x768)
1555 Leaving out the screen size parameter will not load
1556 the TFT driver, and the framebuffer will be left
1558 b - Enable backlight. The TFT backlight pin will be
1559 linked to the kernel VESA blanking code and a GPIO
1560 LED. This parameter is not necessary when using the
1562 c - Enable the s3c camera interface.
1563 t - Reserved for enabling touchscreen support. The
1564 touchscreen support is not enabled in the mainstream
1565 kernel as of 2.6.30, a preliminary port can be found
1566 in the "bleeding edge" mini2440 support kernel at
1567 http://repo.or.cz/w/linux-2.6/mini2440.git
1570 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1571 parameter allows control of the logging verbosity for
1572 the additional memory initialisation checks. A value
1573 of 0 disables mminit logging and a level of 4 will
1574 log everything. Information is printed at KERN_DEBUG
1575 so loglevel=8 may also need to be specified.
1578 [MOUSE] Maximum time between finger touching and
1579 leaving touchpad surface for touch to be considered
1580 a tap and be reported as a left button click (for
1581 touchpads working in absolute mode only).
1583 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1584 reporting absolute coordinates, such as tablets
1585 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1586 reporting absolute coordinates, such as tablets
1588 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1589 is similar to kernelcore except it specifies the
1590 amount of memory used for migratable allocations.
1591 If both kernelcore and movablecore is specified,
1592 then kernelcore will be at *least* the specified
1593 value but may be more. If movablecore on its own
1594 is specified, the administrator must be careful
1595 that the amount of memory usable for all allocations
1598 MTD_Partition= [MTD]
1599 Format: <name>,<region-number>,<size>,<offset>
1601 MTD_Region= [MTD] Format:
1602 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1605 See drivers/mtd/cmdlinepart.c.
1607 multitce=off [PPC] This parameter disables the use of the pSeries
1608 firmware feature for updating multiple TCE entries
1611 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1613 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1615 boundary - index of last SLC block on Flex-OneNAND.
1616 The remaining blocks are configured as MLC blocks.
1617 lock - Configure if Flex-OneNAND boundary should be locked.
1618 Once locked, the boundary cannot be changed.
1619 1 indicates lock status, 0 indicates unlock status.
1622 ARM/S3C2412 JIVE boot control
1624 See arch/arm/mach-s3c2412/mach-jive.c
1626 mtouchusb.raw_coordinates=
1627 [HW] Make the MicroTouch USB driver use raw coordinates
1628 ('y', default) or cooked coordinates ('n')
1630 mtrr_chunk_size=nn[KMG] [X86]
1631 used for mtrr cleanup. It is largest continuous chunk
1632 that could hold holes aka. UC entries.
1634 mtrr_gran_size=nn[KMG] [X86]
1635 Used for mtrr cleanup. It is granularity of mtrr block.
1637 Large value could prevent small alignment from
1640 mtrr_spare_reg_nr=n [X86]
1642 Range: 0,7 : spare reg number
1644 Used for mtrr cleanup. It is spare mtrr entries number.
1645 Set to 2 or more if your graphical card needs more.
1647 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1649 netdev= [NET] Network devices parameters
1650 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1651 Note that mem_start is often overloaded to mean
1652 something different and driver-specific.
1653 This usage is only documented in each driver source
1657 [NETFILTER] Enable connection tracking flow accounting
1658 0 to disable accounting
1659 1 to enable accounting
1662 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1663 See Documentation/filesystems/nfs/nfsroot.txt.
1665 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1666 See Documentation/filesystems/nfs/nfsroot.txt.
1668 nfsrootdebug [NFS] enable nfsroot debugging messages.
1669 See Documentation/filesystems/nfs/nfsroot.txt.
1671 nfs.callback_tcpport=
1672 [NFS] set the TCP port on which the NFSv4 callback
1673 channel should listen.
1676 [NFS] sets the pathname to the program which is used
1677 to update the NFS client cache entries.
1679 nfs.cache_getent_timeout=
1680 [NFS] sets the timeout after which an attempt to
1681 update a cache entry is deemed to have failed.
1683 nfs.idmap_cache_timeout=
1684 [NFS] set the maximum lifetime for idmapper cache
1688 [NFS] enable 64-bit inode numbers.
1689 If zero, the NFS client will fake up a 32-bit inode
1690 number for the readdir() and stat() syscalls instead
1691 of returning the full 64-bit number.
1692 The default is to return 64-bit inode numbers.
1694 nfs.max_session_slots=
1695 [NFSv4.1] Sets the maximum number of session slots
1696 the client will attempt to negotiate with the server.
1697 This limits the number of simultaneous RPC requests
1698 that the client can send to the NFSv4.1 server.
1699 Note that there is little point in setting this
1700 value higher than the max_tcp_slot_table_limit.
1702 nfs.nfs4_disable_idmapping=
1703 [NFSv4] When set to the default of '1', this option
1704 ensures that both the RPC level authentication
1705 scheme and the NFS level operations agree to use
1706 numeric uids/gids if the mount is using the
1707 'sec=sys' security flavour. In effect it is
1708 disabling idmapping, which can make migration from
1709 legacy NFSv2/v3 systems to NFSv4 easier.
1710 Servers that do not support this mode of operation
1711 will be autodetected by the client, and it will fall
1712 back to using the idmapper.
1713 To turn off this behaviour, set the value to '0'.
1715 nfs.send_implementation_id =
1716 [NFSv4.1] Send client implementation identification
1717 information in exchange_id requests.
1718 If zero, no implementation identification information
1720 The default is to send the implementation identification
1723 nfsd.nfs4_disable_idmapping=
1724 [NFSv4] When set to the default of '1', the NFSv4
1725 server will return only numeric uids and gids to
1726 clients using auth_sys, and will accept numeric uids
1727 and gids from such clients. This is intended to ease
1728 migration from NFSv2/v3.
1730 objlayoutdriver.osd_login_prog=
1731 [NFS] [OBJLAYOUT] sets the pathname to the program which
1732 is used to automatically discover and login into new
1733 osd-targets. Please see:
1734 Documentation/filesystems/pnfs.txt for more explanations
1736 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1737 when a NMI is triggered.
1738 Format: [state][,regs][,debounce][,die]
1740 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1741 Format: [panic,][nopanic,][num]
1743 0 - turn nmi_watchdog off
1744 When panic is specified, panic when an NMI watchdog
1745 timeout occurs (or 'nopanic' to override the opposite
1747 This is useful when you use a panic=... timeout and
1748 need the box quickly up again.
1750 netpoll.carrier_timeout=
1751 [NET] Specifies amount of time (in seconds) that
1752 netpoll should wait for a carrier. By default netpoll
1755 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1756 emulation library even if a 387 maths coprocessor
1760 [HW] Never suspend the console
1761 Disable suspending of consoles during suspend and
1762 hibernate operations. Once disabled, debugging
1763 messages can reach various consoles while the rest
1764 of the system is being put to sleep (ie, while
1765 debugging driver suspend/resume hooks). This may
1766 not work reliably with all consoles, but is known
1767 to work with serial and VGA consoles.
1768 To facilitate more flexible debugging, we also add
1769 console_suspend, a printk module parameter to control
1770 it. Users could use console_suspend (usually
1771 /sys/module/printk/parameters/console_suspend) to
1772 turn on/off it dynamically.
1774 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1775 caches in the slab allocator. Saves per-node memory,
1776 but will impact performance.
1780 noapic [SMP,APIC] Tells the kernel to not make use of any
1781 IOAPICs that may be present in the system.
1783 noautogroup Disable scheduler automatic task group creation.
1785 nobats [PPC] Do not use BATs for mapping kernel lowmem
1786 on "Classic" PPC cores.
1790 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1792 nodelayacct [KNL] Disable per-task delay accounting
1794 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1796 nodsp [SH] Disable hardware DSP at boot time.
1798 noefi [X86] Disable EFI runtime services support.
1803 On X86-32 available only on PAE configured kernels.
1804 noexec=on: enable non-executable mappings (default)
1805 noexec=off: disable non-executable mappings
1808 Disable SMEP (Supervisor Mode Execution Protection)
1809 even if it is supported by processor.
1812 This affects only 32-bit executables.
1813 noexec32=on: enable non-executable mappings (default)
1814 read doesn't imply executable mappings
1815 noexec32=off: disable non-executable mappings
1816 read implies executable mappings
1818 nofpu [SH] Disable hardware FPU at boot time.
1820 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1821 register save and restore. The kernel will only save
1822 legacy floating-point registers on task switch.
1824 noxsave [BUGS=X86] Disables x86 extended register state save
1825 and restore using xsave. The kernel will fallback to
1826 enabling legacy floating-point and sse state.
1828 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1829 wfi(ARM) instruction doesn't work correctly and not to
1830 use it. This is also useful when using JTAG debugger.
1832 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1833 instruction doesn't work correctly and not to
1836 no_file_caps Tells the kernel not to honor file capabilities. The
1837 only way then for a file to be executed with privilege
1838 is to be setuid root or executed by root.
1840 nohalt [IA-64] Tells the kernel not to use the power saving
1841 function PAL_HALT_LIGHT when idle. This increases
1842 power-consumption. On the positive side, it reduces
1843 interrupt wake-up latency, which may improve performance
1844 in certain environments such as networked servers or
1847 nohz= [KNL] Boottime enable/disable dynamic ticks
1848 Valid arguments: on, off
1851 noiotrap [SH] Disables trapped I/O port accesses.
1853 noirqdebug [X86-32] Disables the code which attempts to detect and
1854 disable unhandled interrupt sources.
1856 no_timer_check [X86,APIC] Disables the code which tests for
1857 broken timer IRQ sources.
1859 noisapnp [ISAPNP] Disables ISA PnP code.
1861 noinitrd [RAM] Tells the kernel not to load any configured
1864 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1866 [Deprecated - use intremap=off]
1870 nojitter [IA-64] Disables jitter checking for ITC timers.
1872 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1874 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1877 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1878 steal time is computed, but won't influence scheduler
1881 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1883 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1885 noltlbs [PPC] Do not use large page/tlb entries for kernel
1886 lowmem mapping on PPC40x.
1888 nomca [IA-64] Disable machine check abort handling
1890 nomce [X86-32] Machine Check Exception
1892 nomfgpt [X86-32] Disable Multi-Function General Purpose
1893 Timer usage (for AMD Geode machines).
1895 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1896 shutdown the other cpus. Instead use the REBOOT_VECTOR
1899 nomodule Disable module load
1901 nopat [X86] Disable PAT (page attribute table extension of
1902 pagetables) support.
1904 norandmaps Don't use address space randomization. Equivalent to
1905 echo 0 > /proc/sys/kernel/randomize_va_space
1907 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1909 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1910 with UP alternatives
1912 noresidual [PPC] Don't use residual data on PReP machines.
1914 nordrand [X86] Disable the direct use of the RDRAND
1915 instruction even if it is supported by the
1916 processor. RDRAND is still available to user
1919 noresume [SWSUSP] Disables resume and restores original swap
1922 no-scroll [VGA] Disables scrollback.
1923 This is required for the Braillex ib80-piezo Braille
1924 reader made by F.H. Papenmeier (Germany).
1928 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1930 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1931 and disable the IO APIC. legacy for "maxcpus=0".
1933 nosoftlockup [KNL] Disable the soft-lockup detector.
1935 nosync [HW,M68K] Disables sync negotiation for all devices.
1937 notsc [BUGS=X86-32] Disable Time Stamp Counter
1939 nousb [USB] Disable the USB subsystem
1941 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1945 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1947 nptcg= [IA-64] Override max number of concurrent global TLB
1948 purges which is reported from either PAL_VM_SUMMARY or
1951 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1952 could support. nr_cpus=n : n >= 1 limits the kernel to
1953 supporting 'n' processors. Later in runtime you can not
1954 use hotplug cpu feature to put more cpu back to online.
1955 just like you compile the kernel NR_CPUS=n
1957 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1959 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1960 one of ['zone', 'node', 'default'] can be specified
1961 This can be set from sysctl after boot.
1962 See Documentation/sysctl/vm.txt for details.
1964 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1965 See Documentation/debugging-via-ohci1394.txt for more
1968 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1969 Rather than timing out after 20 ms if an EC
1970 command is not properly ACKed, override the length
1971 of the timeout. We have interrupts disabled while
1972 waiting for the ACK, so if this is set too high
1973 interrupts *may* be lost!
1975 omap_mux= [OMAP] Override bootloader pin multiplexing.
1976 Format: <mux_mode0.mode_name=value>...
1977 For example, to override I2C bus2:
1978 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1980 oprofile.timer= [HW]
1981 Use timer interrupt instead of performance counters
1983 oprofile.cpu_type= Force an oprofile cpu type
1984 This might be useful if you have an older oprofile
1985 userland or if you want common events.
1986 Format: { arch_perfmon }
1987 arch_perfmon: [X86] Force use of architectural
1988 perfmon on Intel CPUs instead of the
1989 CPU specific event set.
1990 timer: [X86] Force use of architectural NMI
1991 timer mode (see also oprofile.timer
1992 for generic hr timer mode)
1993 [s390] Force legacy basic mode sampling
1994 (report cpu_type "timer")
1996 oops=panic Always panic on oopses. Default is to just kill the
1997 process, but there is a small probability of
1998 deadlocking the machine.
1999 This will also cause panics on machine check exceptions.
2000 Useful together with panic=30 to trigger a reboot.
2003 See Documentation/sound/oss/oss-parameters.txt
2005 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2006 timeout > 0: seconds before rebooting
2007 timeout = 0: wait forever
2008 timeout < 0: reboot immediately
2011 parkbd.port= [HW] Parallel port number the keyboard adapter is
2012 connected to, default is 0.
2014 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2015 0 for XT, 1 for AT (default is AT).
2018 parport= [HW,PPT] Specify parallel ports. 0 disables.
2019 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2020 Use 'auto' to force the driver to use any
2021 IRQ/DMA settings detected (the default is to
2022 ignore detected IRQ/DMA settings because of
2023 possible conflicts). You can specify the base
2024 address, IRQ, and DMA settings; IRQ and DMA
2025 should be numbers, or 'auto' (for using detected
2026 settings on that particular port), or 'nofifo'
2027 (to avoid using a FIFO even if it is detected).
2028 Parallel ports are assigned in the order they
2029 are specified on the command line, starting
2032 parport_init_mode= [HW,PPT]
2033 Configure VIA parallel port to operate in
2034 a specific mode. This is necessary on Pegasos
2035 computer where firmware has no options for setting
2036 up parallel port mode and sets it to spp.
2037 Currently this function knows 686a and 8231 chips.
2038 Format: [spp|ps2|epp|ecp|ecpepp]
2041 Halt all CPUs after the first oops has been printed for
2042 the specified number of seconds. This is to be used if
2043 your oopses keep scrolling off the screen.
2048 See header of drivers/block/paride/pcd.c.
2049 See also Documentation/blockdev/paride.txt.
2051 pci=option[,option...] [PCI] various PCI subsystem options:
2052 earlydump [X86] dump PCI config space before the kernel
2054 off [X86] don't probe for the PCI bus
2055 bios [X86-32] force use of PCI BIOS, don't access
2056 the hardware directly. Use this if your machine
2057 has a non-standard PCI host bridge.
2058 nobios [X86-32] disallow use of PCI BIOS, only direct
2059 hardware access methods are allowed. Use this
2060 if you experience crashes upon bootup and you
2061 suspect they are caused by the BIOS.
2062 conf1 [X86] Force use of PCI Configuration
2064 conf2 [X86] Force use of PCI Configuration
2066 noaer [PCIE] If the PCIEAER kernel config parameter is
2067 enabled, this kernel boot option can be used to
2068 disable the use of PCIE advanced error reporting.
2069 nodomains [PCI] Disable support for multiple PCI
2070 root domains (aka PCI segments, in ACPI-speak).
2071 nommconf [X86] Disable use of MMCONFIG for PCI
2073 check_enable_amd_mmconf [X86] check for and enable
2074 properly configured MMIO access to PCI
2075 config space on AMD family 10h CPU
2076 nomsi [MSI] If the PCI_MSI kernel config parameter is
2077 enabled, this kernel boot option can be used to
2078 disable the use of MSI interrupts system-wide.
2079 noioapicquirk [APIC] Disable all boot interrupt quirks.
2080 Safety option to keep boot IRQs enabled. This
2081 should never be necessary.
2082 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2083 primary IO-APIC for bridges that cannot disable
2084 boot IRQs. This fixes a source of spurious IRQs
2085 when the system masks IRQs.
2086 noioapicreroute [APIC] Disable workaround that uses the
2087 boot IRQ equivalent of an IRQ that connects to
2088 a chipset where boot IRQs cannot be disabled.
2089 The opposite of ioapicreroute.
2090 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2091 routing table. These calls are known to be buggy
2092 on several machines and they hang the machine
2093 when used, but on other computers it's the only
2094 way to get the interrupt routing table. Try
2095 this option if the kernel is unable to allocate
2096 IRQs or discover secondary PCI buses on your
2098 rom [X86] Assign address space to expansion ROMs.
2099 Use with caution as certain devices share
2100 address decoders between ROMs and other
2102 norom [X86] Do not assign address space to
2103 expansion ROMs that do not already have
2104 BIOS assigned address ranges.
2105 nobar [X86] Do not assign address space to the
2106 BARs that weren't assigned by the BIOS.
2107 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2108 assigned automatically to PCI devices. You can
2109 make the kernel exclude IRQs of your ISA cards
2111 pirqaddr=0xAAAAA [X86] Specify the physical address
2112 of the PIRQ table (normally generated
2113 by the BIOS) if it is outside the
2114 F0000h-100000h range.
2115 lastbus=N [X86] Scan all buses thru bus #N. Can be
2116 useful if the kernel is unable to find your
2117 secondary buses and you want to tell it
2118 explicitly which ones they are.
2119 assign-busses [X86] Always assign all PCI bus
2120 numbers ourselves, overriding
2121 whatever the firmware may have done.
2122 usepirqmask [X86] Honor the possible IRQ mask stored
2123 in the BIOS $PIR table. This is needed on
2124 some systems with broken BIOSes, notably
2125 some HP Pavilion N5400 and Omnibook XE3
2126 notebooks. This will have no effect if ACPI
2127 IRQ routing is enabled.
2128 noacpi [X86] Do not use ACPI for IRQ routing
2129 or for PCI scanning.
2130 use_crs [X86] Use PCI host bridge window information
2131 from ACPI. On BIOSes from 2008 or later, this
2132 is enabled by default. If you need to use this,
2133 please report a bug.
2134 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2135 If you need to use this, please report a bug.
2136 routeirq Do IRQ routing for all PCI devices.
2137 This is normally done in pci_enable_device(),
2138 so this option is a temporary workaround
2139 for broken drivers that don't call it.
2140 skip_isa_align [X86] do not align io start addr, so can
2141 handle more pci cards
2142 firmware [ARM] Do not re-enumerate the bus but instead
2143 just use the configuration from the
2144 bootloader. This is currently used on
2145 IXP2000 systems where the bus has to be
2146 configured a certain way for adjunct CPUs.
2147 noearly [X86] Don't do any early type 1 scanning.
2148 This might help on some broken boards which
2149 machine check when some devices' config space
2150 is read. But various workarounds are disabled
2151 and some IOMMU drivers will not work.
2152 bfsort Sort PCI devices into breadth-first order.
2153 This sorting is done to get a device
2154 order compatible with older (<= 2.4) kernels.
2155 nobfsort Don't sort PCI devices into breadth-first order.
2156 cbiosize=nn[KMG] The fixed amount of bus space which is
2157 reserved for the CardBus bridge's IO window.
2158 The default value is 256 bytes.
2159 cbmemsize=nn[KMG] The fixed amount of bus space which is
2160 reserved for the CardBus bridge's memory
2161 window. The default value is 64 megabytes.
2164 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2165 Specifies alignment and device to reassign
2166 aligned memory resources.
2167 If <order of align> is not specified,
2168 PAGE_SIZE is used as alignment.
2169 PCI-PCI bridge can be specified, if resource
2170 windows need to be expanded.
2171 ecrc= Enable/disable PCIe ECRC (transaction layer
2172 end-to-end CRC checking).
2173 bios: Use BIOS/firmware settings. This is the
2177 realloc= Enable/disable reallocating PCI bridge resources
2178 if allocations done by BIOS are too small to
2179 accommodate resources required by all child
2181 off: Turn realloc off
2183 realloc same as realloc=on
2184 noari do not use PCIe ARI.
2186 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2189 force Enable ASPM even on devices that claim not to support it.
2190 WARNING: Forcing ASPM on may cause system lockups.
2192 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2193 nomsi Do not use MSI for PCI Express Native Hotplug (this
2194 makes all PCIe ports use INTx for hotplug services).
2196 pcie_ports= [PCIE] PCIe ports handling:
2197 auto Ask the BIOS whether or not to use native PCIe services
2198 associated with PCIe ports (PME, hot-plug, AER). Use
2199 them only if that is allowed by the BIOS.
2200 native Use native PCIe services associated with PCIe ports
2202 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2205 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2206 nomsi Do not use MSI for native PCIe PME signaling (this makes
2207 all PCIe root ports use INTx for all services).
2209 pcmv= [HW,PCMCIA] BadgePAD 4
2212 See Documentation/blockdev/paride.txt.
2214 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2217 See arch/parisc/kernel/pdc_chassis.c
2219 percpu_alloc= Select which percpu first chunk allocator to use.
2220 Currently supported values are "embed" and "page".
2221 Archs may support subset or none of the selections.
2222 See comments in mm/percpu.c for details on each
2223 allocator. This parameter is primarily for debugging
2224 and performance comparison.
2227 See Documentation/blockdev/paride.txt.
2230 See Documentation/blockdev/paride.txt.
2232 pirq= [SMP,APIC] Manual mp-table setup
2233 See Documentation/x86/i386/IO-APIC.txt.
2235 plip= [PPT,NET] Parallel port network link
2236 Format: { parport<nr> | timid | 0 }
2237 See also Documentation/parport.txt.
2239 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2240 Override pmtimer IOPort with a hex value.
2244 Enable PNP debug messages (depends on the
2245 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2246 via /sys/module/pnp/parameters/debug. We always show
2247 current resource usage; turning this on also shows
2248 possible settings and some assignment information.
2254 { on | off | curr | res | no-curr | no-res }
2257 [ISAPNP] Exclude IRQs for the autoconfiguration
2260 [ISAPNP] Exclude DMAs for the autoconfiguration
2262 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2263 Ranges are in pairs (I/O port base and size).
2266 [ISAPNP] Exclude memory regions for the
2268 Ranges are in pairs (memory base and size).
2270 ports= [IP_VS_FTP] IPVS ftp helper module
2272 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2274 Format: <port>,<port>....
2276 print-fatal-signals=
2277 [KNL] debug: print fatal signals
2279 If enabled, warn about various signal handling
2280 related application anomalies: too many signals,
2281 too many POSIX.1 timers, fatal signals causing a
2284 If you hit the warning due to signal overflow,
2285 you might want to try "ulimit -i unlimited".
2289 printk.always_kmsg_dump=
2290 Trigger kmsg_dump for cases other than kernel oops or
2292 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2295 printk.time= Show timing data prefixed to each printk message line
2296 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2298 processor.max_cstate= [HW,ACPI]
2299 Limit processor to maximum C-state
2300 max_cstate=9 overrides any DMI blacklist limit.
2302 processor.nocst [HW,ACPI]
2303 Ignore the _CST method to determine C-states,
2304 instead using the legacy FADT method
2306 profile= [KNL] Enable kernel profiling via /proc/profile
2307 Format: [schedule,]<number>
2308 Param: "schedule" - profile schedule points.
2309 Param: <number> - step/bucket size as a power of 2 for
2310 statistical time based profiling.
2311 Param: "sleep" - profile D-state sleeping (millisecs).
2312 Requires CONFIG_SCHEDSTATS
2313 Param: "kvm" - profile VM exits.
2315 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2317 See Documentation/blockdev/ramdisk.txt.
2319 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2320 probe for; one of (bare|imps|exps|lifebook|any).
2321 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2323 psmouse.resetafter= [HW,MOUSE]
2324 Try to reset the device after so many bad packets
2327 [HW,MOUSE] Set desired mouse resolution, in dpi.
2328 psmouse.smartscroll=
2329 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2330 0 = disabled, 1 = enabled (default).
2332 pstore.backend= Specify the name of the pstore backend to use
2335 See Documentation/blockdev/paride.txt.
2338 [KNL] Number of legacy pty's. Overwrites compiled-in
2341 quiet [KNL] Disable most log messages
2346 See Documentation/md.txt.
2348 ramdisk_blocksize= [RAM]
2349 See Documentation/blockdev/ramdisk.txt.
2351 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2352 See Documentation/blockdev/ramdisk.txt.
2354 rcupdate.blimit= [KNL,BOOT]
2355 Set maximum number of finished RCU callbacks to process
2358 rcupdate.qhimark= [KNL,BOOT]
2359 Set threshold of queued
2360 RCU callbacks over which batch limiting is disabled.
2362 rcupdate.qlowmark= [KNL,BOOT]
2363 Set threshold of queued RCU callbacks below which
2364 batch limiting is re-enabled.
2368 Run specified binary instead of /init from the ramdisk,
2369 used for early userspace startup. See initrd.
2371 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2372 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2373 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2376 [KNL, SMP] Set scheduler's default relax_domain_level.
2377 See Documentation/cgroups/cpusets.txt.
2379 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2381 reservetop= [X86-32]
2383 Reserves a hole at the top of the kernel virtual
2388 Set the amount of memory to reserve for BIOS at
2389 the bottom of the address space.
2391 reset_devices [KNL] Force drivers to reset the underlying device
2392 during initialization.
2395 Specify the partition device for software suspend
2397 resume_offset= [SWSUSP]
2398 Specify the offset from the beginning of the partition
2399 given by "resume=" at which the swap header is located,
2400 in <PAGE_SIZE> units (needed only for swap files).
2401 See Documentation/power/swsusp-and-swap-files.txt
2403 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2404 read the resume files
2406 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2407 Useful for devices that are detected asynchronously
2408 (e.g. USB and MMC devices).
2410 hibernate= [HIBERNATION]
2411 noresume Don't check if there's a hibernation image
2412 present during boot.
2413 nocompress Don't compress/decompress hibernation images.
2415 retain_initrd [RAM] Keep initrd memory after extraction
2417 rhash_entries= [KNL,NET]
2418 Set number of hash buckets for route cache
2420 riscom8= [HW,SERIAL]
2421 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2423 ro [KNL] Mount root device read-only on boot
2425 root= [KNL] Root filesystem
2426 See name_to_dev_t comment in init/do_mounts.c.
2428 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2429 mount the root filesystem
2431 rootflags= [KNL] Set root filesystem mount option string
2433 rootfstype= [KNL] Set root filesystem type
2435 rootwait [KNL] Wait (indefinitely) for root device to show up.
2436 Useful for devices that are detected asynchronously
2437 (e.g. USB and MMC devices).
2439 rw [KNL] Mount root device read-write on boot
2441 S [KNL] Run init in single mode
2444 See drivers/net/irda/sa1100_ir.c.
2446 sbni= [NET] Granch SBNI12 leased line adapter
2448 sched_debug [KNL] Enables verbose scheduler debug messages.
2450 security= [SECURITY] Choose a security module to enable at boot.
2451 If this boot parameter is not specified, only the first
2452 security module asking for security registration will be
2453 loaded. An invalid security module name will be treated
2454 as if no module has been chosen.
2456 selinux= [SELINUX] Disable or enable SELinux at boot time.
2457 Format: { "0" | "1" }
2458 See security/selinux/Kconfig help text.
2461 Default value is set via kernel config option.
2462 If enabled at boot time, /selinux/disable can be used
2463 later to disable prior to initial policy load.
2465 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2466 Format: { "0" | "1" }
2467 See security/apparmor/Kconfig help text
2470 Default value is set via kernel config option.
2472 serialnumber [BUGS=X86-32]
2475 Maximal number of shapers.
2477 show_msr= [x86] show boot-time MSR settings
2478 Format: { <integer> }
2479 Show boot-time (BIOS-initialized) MSR settings.
2480 The parameter means the number of CPUs to show,
2481 for example 1 means boot CPU only.
2488 slab_max_order= [MM, SLAB]
2489 Determines the maximum allowed order for slabs.
2490 A high setting may cause OOMs due to memory
2491 fragmentation. Defaults to 1 for systems with
2492 more than 32MB of RAM, 0 otherwise.
2494 slub_debug[=options[,slabs]] [MM, SLUB]
2495 Enabling slub_debug allows one to determine the
2496 culprit if slab objects become corrupted. Enabling
2497 slub_debug can create guard zones around objects and
2498 may poison objects when not in use. Also tracks the
2499 last alloc / free. For more information see
2500 Documentation/vm/slub.txt.
2502 slub_max_order= [MM, SLUB]
2503 Determines the maximum allowed order for slabs.
2504 A high setting may cause OOMs due to memory
2505 fragmentation. For more information see
2506 Documentation/vm/slub.txt.
2508 slub_min_objects= [MM, SLUB]
2509 The minimum number of objects per slab. SLUB will
2510 increase the slab order up to slub_max_order to
2511 generate a sufficiently large slab able to contain
2512 the number of objects indicated. The higher the number
2513 of objects the smaller the overhead of tracking slabs
2514 and the less frequently locks need to be acquired.
2515 For more information see Documentation/vm/slub.txt.
2517 slub_min_order= [MM, SLUB]
2518 Determines the minimum page order for slabs. Must be
2519 lower than slub_max_order.
2520 For more information see Documentation/vm/slub.txt.
2522 slub_nomerge [MM, SLUB]
2523 Disable merging of slabs with similar size. May be
2524 necessary if there is some reason to distinguish
2525 allocs to different slabs. Debug options disable
2526 merging on their own.
2527 For more information see Documentation/vm/slub.txt.
2530 Format: <io1>[,<io2>[,...,<io8>]]
2532 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2533 attempt to substitute SMP alternatives once at boot.
2535 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2536 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2537 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2538 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2539 smsc-ircc2.ircc_irq= [HW] IRQ line
2540 smsc-ircc2.ircc_dma= [HW] DMA channel
2541 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2542 0: Toshiba Satellite 1800 (GP data pin select)
2543 1: Fast pin select (default)
2547 [KNL] Should the soft-lockup detector generate panics.
2550 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2551 See Documentation/laptops/sonypi.txt
2553 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2554 See Documentation/serial/specialix.txt.
2556 spia_io_base= [HW,MTD]
2562 Enabled the stack tracer on boot up.
2564 stacktrace_filter=[function-list]
2565 [FTRACE] Limit the functions that the stack tracer
2566 will trace at boot up. function-list is a comma separated
2567 list of functions. This list can be changed at run
2568 time by the stack_trace_filter file in the debugfs
2569 tracing directory. Note, this enables stack tracing
2570 and the stacktrace above is not needed.
2574 Set the STI (builtin display/keyboard on the HP-PARISC
2575 machines) console (graphic card) which should be used
2576 as the initial boot-console.
2577 See also comment in drivers/video/console/sticore.c.
2580 See comment in drivers/video/console/sticore.c.
2583 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2585 sunrpc.min_resvport=
2586 sunrpc.max_resvport=
2588 SunRPC servers often require that client requests
2589 originate from a privileged port (i.e. a port in the
2590 range 0 < portnr < 1024).
2591 An administrator who wishes to reserve some of these
2592 ports for other uses may adjust the range that the
2593 kernel's sunrpc client considers to be privileged
2594 using these two parameters to set the minimum and
2595 maximum port values.
2599 Control how the NFS server code allocates CPUs to
2600 service thread pools. Depending on how many NICs
2601 you have and where their interrupts are bound, this
2602 option will affect which CPUs will do NFS serving.
2603 Note: this parameter cannot be changed while the
2604 NFS server is running.
2606 auto the server chooses an appropriate mode
2607 automatically using heuristics
2608 global a single global pool contains all CPUs
2609 percpu one pool for each CPU
2610 pernode one pool for each NUMA node (equivalent
2611 to global on non-NUMA machines)
2613 sunrpc.tcp_slot_table_entries=
2614 sunrpc.udp_slot_table_entries=
2616 Sets the upper limit on the number of simultaneous
2617 RPC calls that can be sent from the client to a
2618 server. Increasing these values may allow you to
2619 improve throughput, but will also increase the
2620 amount of memory reserved for use by the client.
2623 [KNL] Enable accounting of swap in memory resource
2624 controller if no parameter or 1 is given or disable
2625 it if 0 is given (See Documentation/cgroups/memory.txt)
2627 swiotlb= [IA-64] Number of I/O TLB slabs
2631 sysfs.deprecated=0|1 [KNL]
2632 Enable/disable old style sysfs layout for old udev
2633 on older distributions. When this option is enabled
2634 very new udev will not work anymore. When this option
2635 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2636 in older udev will not work anymore.
2637 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2638 the kernel configuration.
2640 sysrq_always_enabled
2642 Ignore sysrq setting - this boot parameter will
2643 neutralize any effect of /proc/sys/kernel/sysrq.
2644 Useful for debugging.
2648 test_suspend= [SUSPEND]
2649 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2650 standby suspend) as the system sleep state to briefly
2651 enter during system startup. The system is woken from
2652 this state using a wakeup-capable RTC alarm.
2654 thash_entries= [KNL,NET]
2655 Set number of hash buckets for TCP connection
2657 thermal.act= [HW,ACPI]
2658 -1: disable all active trip points in all thermal zones
2659 <degrees C>: override all lowest active trip points
2661 thermal.crt= [HW,ACPI]
2662 -1: disable all critical trip points in all thermal zones
2663 <degrees C>: override all critical trip points
2665 thermal.nocrt= [HW,ACPI]
2666 Set to disable actions on ACPI thermal zone
2667 critical and hot trip points.
2669 thermal.off= [HW,ACPI]
2670 1: disable ACPI thermal control
2672 thermal.psv= [HW,ACPI]
2673 -1: disable all passive trip points
2674 <degrees C>: override all passive trip points to this
2677 thermal.tzp= [HW,ACPI]
2678 Specify global default ACPI thermal zone polling rate
2679 <deci-seconds>: poll all this frequency
2680 0: no polling (default)
2683 Force threading of all interrupt handlers except those
2684 marked explicitly IRQF_NO_THREAD.
2688 Specify if the kernel should make use of the cpu
2689 topology information if the hardware supports this.
2690 The scheduler will make use of this information and
2691 e.g. base its process migration decisions on it.
2696 tpm_suspend_pcr=[HW,TPM]
2697 Format: integer pcr id
2698 Specify that at suspend time, the tpm driver
2699 should extend the specified pcr with zeros,
2700 as a workaround for some chips which fail to
2701 flush the last written pcr on TPM_SaveState.
2702 This will guarantee that all the other pcrs
2705 trace_buf_size=nn[KMG]
2706 [FTRACE] will set tracing buffer size.
2708 trace_event=[event-list]
2709 [FTRACE] Set and start specified trace events in order
2710 to facilitate early boot debugging.
2711 See also Documentation/trace/events.txt
2713 transparent_hugepage=
2715 Format: [always|madvise|never]
2716 Can be used to control the default behavior of the system
2717 with respect to transparent hugepages.
2718 See Documentation/vm/transhuge.txt for more details.
2720 tsc= Disable clocksource stability checks for TSC.
2722 [x86] reliable: mark tsc clocksource as reliable, this
2723 disables clocksource verification at runtime, as well
2724 as the stability checks done at bootup. Used to enable
2725 high-resolution timer mode on older hardware, and in
2726 virtualized environment.
2727 [x86] noirqtime: Do not use TSC to do irq accounting.
2728 Used to run time disable IRQ_TIME_ACCOUNTING on any
2729 platforms where RDTSC is slow and this accounting
2732 turbografx.map[2|3]= [HW,JOY]
2733 TurboGraFX parallel port interface
2735 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2736 See also Documentation/input/joystick-parport.txt
2738 udbg-immortal [PPC] When debugging early kernel crashes that
2739 happen after console_init() and before a proper
2740 console driver takes over, this boot options might
2741 help "seeing" what's going on.
2743 uhash_entries= [KNL,NET]
2744 Set number of hash buckets for UDP/UDP-Lite connections
2747 [USB] Ignore overcurrent events (default N).
2748 Some badly-designed motherboards generate lots of
2749 bogus events, for ports that aren't wired to
2750 anything. Set this parameter to avoid log spamming.
2751 Note that genuine overcurrent events won't be
2755 [X86] Cause panic on unknown NMI.
2757 usbcore.authorized_default=
2758 [USB] Default USB device authorization:
2759 (default -1 = authorized except for wireless USB,
2760 0 = not authorized, 1 = authorized)
2762 usbcore.autosuspend=
2763 [USB] The autosuspend time delay (in seconds) used
2764 for newly-detected USB devices (default 2). This
2765 is the time required before an idle device will be
2766 autosuspended. Devices for which the delay is set
2767 to a negative value won't be autosuspended at all.
2769 usbcore.usbfs_snoop=
2770 [USB] Set to log all usbfs traffic (default 0 = off).
2772 usbcore.blinkenlights=
2773 [USB] Set to cycle leds on hubs (default 0 = off).
2775 usbcore.old_scheme_first=
2776 [USB] Start with the old device initialization
2777 scheme (default 0 = off).
2779 usbcore.usbfs_memory_mb=
2780 [USB] Memory limit (in MB) for buffers allocated by
2781 usbfs (default = 16, 0 = max = 2047).
2783 usbcore.use_both_schemes=
2784 [USB] Try the other device initialization scheme
2785 if the first one fails (default 1 = enabled).
2787 usbcore.initial_descriptor_timeout=
2788 [USB] Specifies timeout for the initial 64-byte
2789 USB_REQ_GET_DESCRIPTOR request in milliseconds
2790 (default 5000 = 5.0 seconds).
2793 [USBHID] The interval which mice are to be polled at.
2795 usb-storage.delay_use=
2796 [UMS] The delay in seconds before a new device is
2797 scanned for Logical Units (default 5).
2800 [UMS] A list of quirks entries to supplement or
2801 override the built-in unusual_devs list. List
2802 entries are separated by commas. Each entry has
2803 the form VID:PID:Flags where VID and PID are Vendor
2804 and Product ID values (4-digit hex numbers) and
2805 Flags is a set of characters, each corresponding
2806 to a common usb-storage quirk flag as follows:
2807 a = SANE_SENSE (collect more than 18 bytes
2809 b = BAD_SENSE (don't collect more than 18
2810 bytes of sense data);
2811 c = FIX_CAPACITY (decrease the reported
2812 device capacity by one sector);
2813 d = NO_READ_DISC_INFO (don't use
2814 READ_DISC_INFO command);
2815 e = NO_READ_CAPACITY_16 (don't use
2816 READ_CAPACITY_16 command);
2817 h = CAPACITY_HEURISTICS (decrease the
2818 reported device capacity by one
2819 sector if the number is odd);
2820 i = IGNORE_DEVICE (don't bind to this
2822 l = NOT_LOCKABLE (don't try to lock and
2823 unlock ejectable media);
2824 m = MAX_SECTORS_64 (don't transfer more
2825 than 64 sectors = 32 KB at a time);
2826 n = INITIAL_READ10 (force a retry of the
2827 initial READ(10) command);
2828 o = CAPACITY_OK (accept the capacity
2829 reported by the device);
2830 r = IGNORE_RESIDUE (the device reports
2831 bogus residue values);
2832 s = SINGLE_LUN (the device has only one
2834 w = NO_WP_DETECT (don't test whether the
2835 medium is write-protected).
2836 Example: quirks=0419:aaf5:rl,0421:0433:rc
2838 user_debug= [KNL,ARM]
2840 See arch/arm/Kconfig.debug help text.
2841 1 - undefined instruction events
2843 4 - invalid data aborts
2846 Example: user_debug=31
2849 [X86] Flags controlling user PTE allocations.
2851 nohigh = do not allocate PTE pages in
2852 HIGHMEM regardless of setting
2856 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2857 vdso=1: enable VDSO (default)
2858 vdso=0: disable VDSO mapping
2861 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2862 vdso32=1: enable 32-bit VDSO (default)
2863 vdso32=0: disable 32-bit VDSO mapping
2866 vector=percpu: enable percpu vector domain
2868 video= [FB] Frame buffer configuration
2869 See Documentation/fb/modedb.txt.
2871 vga= [BOOT,X86-32] Select a particular video mode
2872 See Documentation/x86/boot.txt and
2873 Documentation/svga.txt.
2874 Use vga=ask for menu.
2875 This is actually a boot loader parameter; the value is
2876 passed to the kernel using a special protocol.
2878 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2879 size of <nn>. This can be used to increase the
2880 minimum size (128MB on x86). It can also be used to
2881 decrease the size and leave more room for directly
2884 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2887 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2890 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2894 Controls the behavior of vsyscalls (i.e. calls to
2895 fixed addresses of 0xffffffffff600x00 from legacy
2896 code). Most statically-linked binaries and older
2897 versions of glibc use these calls. Because these
2898 functions are at fixed addresses, they make nice
2899 targets for exploits that can control RIP.
2901 emulate [default] Vsyscalls turn into traps and are
2902 emulated reasonably safely.
2904 native Vsyscalls are native syscall instructions.
2905 This is a little bit faster than trapping
2906 and makes a few dynamic recompilers work
2907 better than they would in emulation mode.
2908 It also makes exploits much easier to write.
2910 none Vsyscalls don't work at all. This makes
2911 them quite hard to use for exploits but
2912 might break your system.
2914 vt.cur_default= [VT] Default cursor shape.
2915 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2916 the parameters of the <Esc>[?A;B;Cc escape sequence;
2917 see VGA-softcursor.txt. Default: 2 = underline.
2919 vt.default_blu= [VT]
2920 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2921 Change the default blue palette of the console.
2922 This is a 16-member array composed of values
2925 vt.default_grn= [VT]
2926 Format: <green0>,<green1>,<green2>,...,<green15>
2927 Change the default green palette of the console.
2928 This is a 16-member array composed of values
2931 vt.default_red= [VT]
2932 Format: <red0>,<red1>,<red2>,...,<red15>
2933 Change the default red palette of the console.
2934 This is a 16-member array composed of values
2940 Set system-wide default UTF-8 mode for all tty's.
2941 Default is 1, i.e. UTF-8 mode is enabled for all
2942 newly opened terminals.
2944 vt.global_cursor_default=
2947 Set system-wide default for whether a cursor
2948 is shown on new VTs. Default is -1,
2949 i.e. cursors will be created by default unless
2950 overridden by individual drivers. 0 will hide
2951 cursors, 1 will display them.
2953 watchdog timers [HW,WDT] For information on watchdog timers,
2954 see Documentation/watchdog/watchdog-parameters.txt
2955 or other driver-specific files in the
2956 Documentation/watchdog/ directory.
2958 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2959 default x2apic cluster mode on platforms
2962 x86_mrst_timer= [X86-32,APBT]
2963 Choose timer option for x86 Moorestown MID platform.
2964 Two valid options are apbt timer only and lapic timer
2965 plus one apbt timer for broadcast timer.
2966 x86_mrst_timer=apbt_only | lapic_and_apbt
2968 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2969 xd_geo= See header of drivers/block/xd.c.
2971 xen_emul_unplug= [HW,X86,XEN]
2972 Unplug Xen emulated devices
2973 Format: [unplug0,][unplug1]
2974 ide-disks -- unplug primary master IDE devices
2975 aux-ide-disks -- unplug non-primary-master IDE devices
2976 nics -- unplug network devices
2977 all -- unplug all emulated devices (NICs and IDE disks)
2978 unnecessary -- unplugging emulated devices is
2979 unnecessary even if the host did not respond to
2981 never -- do not unplug even if version check succeeds
2983 xirc2ps_cs= [NET,PCMCIA]
2985 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2987 ______________________________________________________________________
2991 Add more DRM drivers.
projects / cascardo / linux.git / blob