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 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VGA The VGA console has been enabled.
113 VT Virtual terminal support is enabled.
114 WDT Watchdog support is enabled.
115 XT IBM PC/XT MFM hard disk support is enabled.
116 X86-32 X86-32, aka i386 architecture is enabled.
117 X86-64 X86-64 architecture is enabled.
118 More X86-64 boot options can be found in
119 Documentation/x86/x86_64/boot-options.txt .
120 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
121 XEN Xen support is enabled
123 In addition, the following text indicates that the option:
125 BUGS= Relates to possible processor bugs on the said processor.
126 KNL Is a kernel start-up parameter.
127 BOOT Is a boot loader parameter.
129 Parameters denoted with BOOT are actually interpreted by the boot
130 loader, and have no meaning to the kernel directly.
131 Do not modify the syntax of boot loader parameters without extreme
132 need or coordination with <Documentation/x86/boot.txt>.
134 There are also arch-specific kernel-parameters not documented here.
135 See for example <Documentation/x86/x86_64/boot-options.txt>.
137 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
138 a trailing = on the name of any parameter states that that parameter will
139 be entered as an environment variable, whereas its absence indicates that
140 it will appear as a kernel argument readable via /proc/cmdline by programs
141 running once the system is up.
143 The number of kernel parameters is not limited, but the length of the
144 complete command line (parameters including spaces etc.) is limited to
145 a fixed number of characters. This limit depends on the architecture
146 and is between 256 and 4096 characters. It is defined in the file
147 ./include/asm/setup.h as COMMAND_LINE_SIZE.
149 Finally, the [KMG] suffix is commonly described after a number of kernel
150 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
151 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
152 bytes respectively. Such letter suffixes can also be entirely omitted.
156 Advanced Configuration and Power Interface
157 Format: { force | off | strict | noirq | rsdt }
158 force -- enable ACPI if default was off
159 off -- disable ACPI if default was on
160 noirq -- do not use ACPI for IRQ routing
161 strict -- Be less tolerant of platforms that are not
162 strictly ACPI specification compliant.
163 rsdt -- prefer RSDT over (default) XSDT
164 copy_dsdt -- copy DSDT to memory
166 See also Documentation/power/runtime_pm.txt, pci=noacpi
168 acpi_rsdp= [ACPI,EFI,KEXEC]
169 Pass the RSDP address to the kernel, mostly used
170 on machines running EFI runtime service to boot the
171 second kernel for kdump.
173 acpi_apic_instance= [ACPI, IOAPIC]
175 2: use 2nd APIC table, if available
176 1,0: use 1st APIC table
179 acpi_backlight= [HW,ACPI]
180 acpi_backlight=vendor
182 If set to vendor, prefer vendor specific driver
183 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
184 of the ACPI video.ko driver.
186 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
187 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
189 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
190 debug output. Bits in debug_layer correspond to a
191 _COMPONENT in an ACPI source file, e.g.,
192 #define _COMPONENT ACPI_PCI_COMPONENT
193 Bits in debug_level correspond to a level in
194 ACPI_DEBUG_PRINT statements, e.g.,
195 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
196 The debug_level mask defaults to "info". See
197 Documentation/acpi/debug.txt for more information about
198 debug layers and levels.
200 Enable processor driver info messages:
201 acpi.debug_layer=0x20000000
202 Enable PCI/PCI interrupt routing info messages:
203 acpi.debug_layer=0x400000
204 Enable AML "Debug" output, i.e., stores to the Debug
205 object while interpreting AML:
206 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
207 Enable all messages related to ACPI hardware:
208 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
210 Some values produce so much output that the system is
211 unusable. The "log_buf_len" parameter may be useful
212 if you need to capture more output.
214 acpi_irq_balance [HW,ACPI]
215 ACPI will balance active IRQs
218 acpi_irq_nobalance [HW,ACPI]
219 ACPI will not move active IRQs (default)
222 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
223 Format: <irq>,<irq>...
225 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
227 Format: <irq>,<irq>...
229 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
231 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
232 Format: To spoof as Windows 98: ="Microsoft Windows"
234 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
235 acpi_osi="string1" # add string1 -- only one string
236 acpi_osi="!string2" # remove built-in string2
237 acpi_osi= # disable all strings
240 Override the pmtimer bug detection: force the kernel
241 to assume that this machine's pmtimer latches its value
242 and always returns good values.
244 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
245 Format: { level | edge | high | low }
247 acpi_serialize [HW,ACPI] force serialization of AML methods
249 acpi_skip_timer_override [HW,ACPI]
250 Recognize and ignore IRQ0/pin2 Interrupt Override.
251 For broken nForce2 BIOS resulting in XT-PIC timer.
253 acpi_sleep= [HW,ACPI] Sleep options
254 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
255 old_ordering, nonvs, sci_force_enable }
256 See Documentation/power/video.txt for information on
258 s3_beep is for debugging; it makes the PC's speaker beep
259 as soon as the kernel's real-mode entry point is called.
260 s4_nohwsig prevents ACPI hardware signature from being
261 used during resume from hibernation.
262 old_ordering causes the ACPI 1.0 ordering of the _PTS
263 control method, with respect to putting devices into
264 low power states, to be enforced (the ACPI 2.0 ordering
265 of _PTS is used by default).
266 nonvs prevents the kernel from saving/restoring the
267 ACPI NVS memory during suspend/hibernation and resume.
268 sci_force_enable causes the kernel to set SCI_EN directly
269 on resume from S1/S3 (which is against the ACPI spec,
270 but some broken systems don't work without it).
272 acpi_use_timer_override [HW,ACPI]
273 Use timer override. For some broken Nvidia NF5 boards
274 that require a timer override, but don't have HPET
276 acpi_enforce_resources= [ACPI]
277 { strict | lax | no }
278 Check for resource conflicts between native drivers
279 and ACPI OperationRegions (SystemIO and SystemMemory
280 only). IO ports and memory declared in ACPI might be
281 used by the ACPI subsystem in arbitrary AML code and
282 can interfere with legacy drivers.
283 strict (default): access to resources claimed by ACPI
284 is denied; legacy drivers trying to access reserved
285 resources will fail to bind to device using them.
286 lax: access to resources claimed by ACPI is allowed;
287 legacy drivers trying to access reserved resources
288 will bind successfully but a warning message is logged.
289 no: ACPI OperationRegions are not marked as reserved,
290 no further checks are performed.
292 add_efi_memmap [EFI; X86] Include EFI memory map in
293 kernel's map of available physical RAM.
296 { off | try_unsupported }
297 off: disable AGP support
298 try_unsupported: try to drive unsupported chipsets
299 (may crash computer or cause data corruption)
302 See Documentation/sound/alsa/alsa-parameters.txt
305 Allow the default userspace alignment fault handler
306 behaviour to be specified. Bit 0 enables warnings,
307 bit 1 enables fixups, and bit 2 sends a segfault.
309 align_va_addr= [X86-64]
310 Align virtual addresses by clearing slice [14:12] when
311 allocating a VMA at process creation time. This option
312 gives you up to 3% performance improvement on AMD F15h
313 machines (where it is enabled by default) for a
314 CPU-intensive style benchmark, and it can vary highly in
315 a microbenchmark depending on workload and compiler.
317 32: only for 32-bit processes
318 64: only for 64-bit processes
319 on: enable for both 32- and 64-bit processes
320 off: disable for both 32- and 64-bit processes
322 amd_iommu= [HW,X86-64]
323 Pass parameters to the AMD IOMMU driver in the system.
325 fullflush - enable flushing of IO/TLB entries when
326 they are unmapped. Otherwise they are
327 flushed before they will be reused, which
329 off - do not initialize any AMD IOMMU found in
331 force_isolation - Force device isolation for all
332 devices. The IOMMU driver is not
333 allowed anymore to lift isolation
334 requirements as needed. This option
335 does not override iommu=pt
337 amijoy.map= [HW,JOY] Amiga joystick support
338 Map of devices attached to JOY0DAT and JOY1DAT
340 See also Documentation/input/joystick.txt
342 analog.map= [HW,JOY] Analog joystick and gamepad support
343 Specifies type or capabilities of an analog joystick
344 connected to one of 16 gameports
345 Format: <type1>,<type2>,..<type16>
348 Power management functions (SPARCstation-4/5 + deriv.)
350 Disable APC CPU standby support. SPARCstation-Fox does
351 not play well with APC CPU idle - disable it if you have
352 APC and your system crashes randomly.
354 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
355 Change the output verbosity whilst booting
356 Format: { quiet (default) | verbose | debug }
357 Change the amount of debugging information output
358 when initialising the APIC and IO-APIC components.
361 See Documentation/networking/ipv6.txt.
363 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
364 Limit apic dumping. The parameter defines the maximal
365 number of local apics being dumped. Also it is possible
366 to set it to "all" by meaning -- no limit here.
367 Format: { 1 (default) | 2 | ... | all }.
368 The parameter valid if only apic=debug or
369 apic=verbose is specified.
370 Example: apic=debug show_lapic=all
372 apm= [APM] Advanced Power Management
373 See header of arch/x86/kernel/apm_32.c.
375 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
376 Format: <io>,<irq>,<nodeID>
380 atarimouse= [HW,MOUSE] Atari Mouse
382 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
383 EzKey and similar keyboards
385 atkbd.reset= [HW] Reset keyboard during initialization
387 atkbd.set= [HW] Select keyboard code set
388 Format: <int> (2 = AT (default), 3 = PS/2)
390 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
393 atkbd.softraw= [HW] Choose between synthetic and real raw mode
394 Format: <bool> (0 = real, 1 = synthetic (default))
396 atkbd.softrepeat= [HW]
397 Use software keyboard repeat
401 baycom_epp= [HW,AX25]
404 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
406 See header of drivers/net/hamradio/baycom_par.c.
408 baycom_ser_fdx= [HW,AX25]
409 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
410 Format: <io>,<irq>,<mode>[,<baud>]
411 See header of drivers/net/hamradio/baycom_ser_fdx.c.
413 baycom_ser_hdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
415 Format: <io>,<irq>,<mode>
416 See header of drivers/net/hamradio/baycom_ser_hdx.c.
418 boot_delay= Milliseconds to delay each printk during boot.
419 Values larger than 10 seconds (10000) are changed to
423 bootmem_debug [KNL] Enable bootmem allocator debug messages.
425 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
426 bttv.radio= Most important insmod options are available as
428 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
431 bulk_remove=off [PPC] This parameter disables the use of the pSeries
432 firmware feature for flushing multiple hpte entries
435 c101= [NET] Moxa C101 synchronous serial card
437 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
438 Sometimes CPU hardware bugs make them report the cache
439 size incorrectly. The kernel will attempt work arounds
440 to fix known problems, but for some CPUs it is not
441 possible to determine what the correct size should be.
442 This option provides an override for these situations.
445 [SECURITY] Disable capabilities. This would normally
446 be used only if an alternative security model is to be
447 configured. Potentially dangerous and should only be
448 used if you are entirely sure of the consequences.
450 ccw_timeout_log [S390]
451 See Documentation/s390/CommonIO for details.
453 cgroup_disable= [KNL] Disable a particular controller
454 Format: {name of the controller(s) to disable}
455 {Currently supported controllers - "memory"}
457 checkreqprot [SELINUX] Set initial checkreqprot flag value.
458 Format: { "0" | "1" }
459 See security/selinux/Kconfig help text.
460 0 -- check protection applied by kernel (includes
461 any implied execute protection).
462 1 -- check protection requested by application.
463 Default value is set via a kernel config option.
464 Value can be changed at runtime via
465 /selinux/checkreqprot.
468 See Documentation/s390/CommonIO for details.
470 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
472 Forces specified clocksource (if available) to be used
473 when calculating gettimeofday(). If specified
474 clocksource is not available, it defaults to PIT.
475 Format: { pit | tsc | cyclone | pmtmr }
477 clocksource= Override the default clocksource
479 Override the default clocksource and use the clocksource
480 with the name specified.
481 Some clocksource names to choose from, depending on
483 [all] jiffies (this is the base, fallback clocksource)
485 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
486 pxa_timer,timer3,32k_counter,timer0_1
488 [X86-32] pit,hpet,tsc;
489 scx200_hrt on Geode; cyclone on IBM x440
497 clearcpuid=BITNUM [X86]
498 Disable CPUID feature X for the kernel. See
499 arch/x86/include/asm/cpufeature.h for the valid bit
500 numbers. Note the Linux specific bits are not necessarily
501 stable over kernel options, but the vendor specific
503 Also note that user programs calling CPUID directly
504 or using the feature without checking anything
505 will still see it. This just prevents it from
506 being used by the kernel or shown in /proc/cpuinfo.
507 Also note the kernel might malfunction if you disable
510 cmo_free_hint= [PPC] Format: { yes | no }
511 Specify whether pages are marked as being inactive
512 when they are freed. This is used in CMO environments
513 to determine OS memory pressure for page stealing by
517 code_bytes [X86] How many bytes of object code to print
522 com20020= [HW,NET] ARCnet - COM20020 chipset
524 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
526 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
530 ARCnet - COM90xx chipset (memory-mapped buffers)
531 Format: <io>[,<irq>[,<memstart>]]
533 condev= [HW,S390] console device
536 console= [KNL] Output console device and options.
538 tty<n> Use the virtual console device <n>.
542 Use the specified serial port. The options are of
543 the form "bbbbpnf", where "bbbb" is the baud rate,
544 "p" is parity ("n", "o", or "e"), "n" is number of
545 bits, and "f" is flow control ("r" for RTS or
546 omit it). Default is "9600n8".
548 See Documentation/serial-console.txt for more
550 Documentation/networking/netconsole.txt for an
553 uart[8250],io,<addr>[,options]
554 uart[8250],mmio,<addr>[,options]
555 Start an early, polled-mode console on the 8250/16550
556 UART at the specified I/O port or MMIO address,
557 switching to the matching ttyS device later. The
558 options are the same as for ttyS, above.
560 If the device connected to the port is not a TTY but a braille
561 device, prepend "brl," before the device type, for instance
563 For now, only VisioBraille is supported.
565 consoleblank= [KNL] The console blank (screen saver) timeout in
566 seconds. Defaults to 10*60 = 10mins. A value of 0
567 disables the blank timer.
570 [KNL] Change the default value for
571 /proc/<pid>/coredump_filter.
572 See also Documentation/filesystems/proc.txt.
574 cpuidle.off=1 [CPU_IDLE]
575 disable the cpuidle sub-system
577 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
579 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
581 crashkernel=size[KMG][@offset[KMG]]
582 [KNL] Using kexec, Linux can switch to a 'crash kernel'
583 upon panic. This parameter reserves the physical
584 memory region [offset, offset + size] for that kernel
585 image. If '@offset' is omitted, then a suitable offset
586 is selected automatically. Check
587 Documentation/kdump/kdump.txt for further details.
589 crashkernel=range1:size1[,range2:size2,...][@offset]
590 [KNL] Same as above, but depends on the memory
591 in the running system. The syntax of range is
592 start-[end] where start and end are both
593 a memory unit (amount[KMG]). See also
594 Documentation/kdump/kdump.txt for an example.
599 cs89x0_media= [HW,NET]
600 Format: { rj45 | aui | bnc }
603 See header of drivers/s390/block/dasd_devmap.c.
605 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
606 (one device per port)
607 Format: <port#>,<type>
608 See also Documentation/input/joystick-parport.txt
610 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
611 time. See Documentation/dynamic-debug-howto.txt for
614 debug [KNL] Enable kernel debugging (events log level).
617 [KNL] verbose self-tests
619 Print debugging info while doing the locking API
621 We default to 0 (no extra messages), setting it to
622 1 will print _a lot_ more information - normally
623 only useful to kernel developers.
625 debug_objects [KNL] Enable object debugging
628 [KNL] Disable object debugging
630 debug_guardpage_minorder=
631 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
632 parameter allows control of the order of pages that will
633 be intentionally kept free (and hence protected) by the
634 buddy allocator. Bigger value increase the probability
635 of catching random memory corruption, but reduce the
636 amount of memory for normal system use. The maximum
637 possible value is MAX_ORDER/2. Setting this parameter
638 to 1 or 2 should be enough to identify most random
639 memory corruption problems caused by bugs in kernel or
640 driver code when a CPU writes to (or reads from) a
641 random memory location. Note that there exists a class
642 of memory corruptions problems caused by buggy H/W or
643 F/W or by drivers badly programing DMA (basically when
644 memory is written at bus level and the CPU MMU is
645 bypassed) which are not detectable by
646 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
647 tracking down these problems.
649 debugpat [X86] Enable PAT debugging
651 decnet.addr= [HW,NET]
652 Format: <area>[,<node>]
653 See also Documentation/networking/decnet.txt.
656 [same as hugepagesz=] The size of the default
657 HugeTLB page size. This is the size represented by
658 the legacy /proc/ hugepages APIs, used for SHM, and
659 default size when mounting hugetlbfs filesystems.
660 Defaults to the default architecture's huge page size
664 Set number of hash buckets for dentry cache.
667 IO parameters + enable/disable command.
669 digiepca= [HW,SERIAL]
670 See drivers/char/README.epca and
671 Documentation/serial/digiepca.txt.
674 See Documentation/networking/ipv6.txt.
676 disable_ddw [PPC/PSERIES]
677 Disable Dynamic DMA Window support. Use this if
678 to workaround buggy firmware.
681 See Documentation/networking/ipv6.txt.
683 disable_mtrr_cleanup [X86]
684 The kernel tries to adjust MTRR layout from continuous
685 to discrete, to make X server driver able to add WB
686 entry later. This parameter disables that.
688 disable_mtrr_trim [X86, Intel and AMD only]
689 By default the kernel will trim any uncacheable
690 memory out of your available memory pool based on
691 MTRR settings. This parameter disables that behavior,
692 possibly causing your machine to run very slowly.
694 disable_timer_pin_1 [X86]
695 Disable PIN 1 of APIC timer
696 Can be useful to work around chipset bugs.
698 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
699 this option disables the debugging code at boot.
701 dma_debug_entries=<number>
702 This option allows to tune the number of preallocated
703 entries for DMA-API debugging code. One entry is
704 required per DMA-API allocation. Use this if the
705 DMA-API debugging code disables itself because the
706 architectural default is too low.
708 dma_debug_driver=<driver_name>
709 With this option the DMA-API debugging driver
710 filter feature can be enabled at boot time. Just
711 pass the driver to filter for as the parameter.
712 The filter can be disabled or changed to another
713 driver later using sysfs.
715 drm_kms_helper.edid_firmware=[<connector>:]<file>
716 Broken monitors, graphic adapters and KVMs may
717 send no or incorrect EDID data sets. This parameter
718 allows to specify an EDID data set in the
719 /lib/firmware directory that is used instead.
720 Generic built-in EDID data sets are used, if one of
721 edid/1024x768.bin, edid/1280x1024.bin,
722 edid/1680x1050.bin, or edid/1920x1080.bin is given
723 and no file with the same name exists. Details and
724 instructions how to build your own EDID data are
725 available in Documentation/EDID/HOWTO.txt. An EDID
726 data set will only be used for a particular connector,
727 if its name and a colon are prepended to the EDID
732 earlycon= [KNL] Output early console device and options.
733 uart[8250],io,<addr>[,options]
734 uart[8250],mmio,<addr>[,options]
735 uart[8250],mmio32,<addr>[,options]
736 Start an early, polled-mode console on the 8250/16550
737 UART at the specified I/O port or MMIO address.
738 MMIO inter-register address stride is either 8-bit
739 (mmio) or 32-bit (mmio32).
740 The options are the same as for ttyS, above.
742 earlyprintk= [X86,SH,BLACKFIN]
744 earlyprintk=serial[,ttySn[,baudrate]]
745 earlyprintk=ttySn[,baudrate]
746 earlyprintk=dbgp[debugController#]
748 Append ",keep" to not disable it when the real console
751 Only vga or serial or usb debug port at a time.
753 Currently only ttyS0 and ttyS1 are supported.
755 Interaction with the standard serial driver is not
758 The VGA output is eventually overwritten by the real
761 ekgdboc= [X86,KGDB] Allow early kernel console debugging
764 This is designed to be used in conjunction with
765 the boot argument: earlyprintk=vga
768 Format: {"off" | "on" | "skip[mbr]"}
770 eisa_irq_edge= [PARISC,HW]
771 See header of drivers/parisc/eisa.c.
774 See comment before function elanfreq_setup() in
775 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
778 Format: {"cfq" | "deadline" | "noop"}
779 See Documentation/block/cfq-iosched.txt and
780 Documentation/block/deadline-iosched.txt for details.
782 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
783 Specifies physical address of start of kernel core
784 image elf header and optionally the size. Generally
785 kexec loader will pass this option to capture kernel.
786 See Documentation/kdump/kdump.txt for details.
788 enable_mtrr_cleanup [X86]
789 The kernel tries to adjust MTRR layout from continuous
790 to discrete, to make X server driver able to add WB
791 entry later. This parameter enables that.
793 enable_timer_pin_1 [X86]
794 Enable PIN 1 of APIC timer
795 Can be useful to work around chipset bugs
796 (in particular on some ATI chipsets).
797 The kernel tries to set a reasonable default.
799 enforcing [SELINUX] Set initial enforcing status.
801 See security/selinux/Kconfig help text.
802 0 -- permissive (log only, no denials).
803 1 -- enforcing (deny and log).
805 Value can be changed at runtime via /selinux/enforce.
808 Disable Error Record Serialization Table (ERST)
811 ether= [HW,NET] Ethernet cards parameters
812 This option is obsoleted by the "netdev=" option, which
813 has equivalent usage. See its documentation for details.
817 Permit 'security.evm' to be updated regardless of
818 current integrity status.
822 fail_make_request=[KNL]
823 General fault injection mechanism.
824 Format: <interval>,<probability>,<space>,<times>
825 See also Documentation/fault-injection/.
828 See Documentation/blockdev/floppy.txt.
830 force_pal_cache_flush
831 [IA-64] Avoid check_sal_cache_flush which may hang on
832 buggy SAL_CACHE_FLUSH implementations. Using this
833 parameter will force ia64_sal_cache_flush to call
834 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
837 [FTRACE] will set and start the specified tracer
838 as early as possible in order to facilitate early
841 ftrace_dump_on_oops[=orig_cpu]
842 [FTRACE] will dump the trace buffers on oops.
843 If no parameter is passed, ftrace will dump
844 buffers of all CPUs, but if you pass orig_cpu, it will
845 dump only the buffer of the CPU that triggered the
848 ftrace_filter=[function-list]
849 [FTRACE] Limit the functions traced by the function
850 tracer at boot up. function-list is a comma separated
851 list of functions. This list can be changed at run
852 time by the set_ftrace_filter file in the debugfs
855 ftrace_notrace=[function-list]
856 [FTRACE] Do not trace the functions specified in
857 function-list. This list can be changed at run time
858 by the set_ftrace_notrace file in the debugfs
861 ftrace_graph_filter=[function-list]
862 [FTRACE] Limit the top level callers functions traced
863 by the function graph tracer at boot up.
864 function-list is a comma separated list of functions
865 that can be changed at run time by the
866 set_graph_function file in the debugfs tracing directory.
869 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
870 support via parallel port (up to 5 devices per port)
871 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
872 See also Documentation/input/joystick-parport.txt
876 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
880 gcov_persist= [GCOV] When non-zero (default), profiling data for
881 kernel modules is saved and remains accessible via
882 debugfs, even when the module is unloaded/reloaded.
883 When zero, profiling data is discarded and associated
884 debugfs files are removed at module unload time.
886 gpt [EFI] Forces disk with valid GPT signature but
887 invalid Protective MBR to be treated as GPT.
889 hashdist= [KNL,NUMA] Large hashes allocated during boot
890 are distributed across NUMA nodes. Defaults on
891 for 64-bit NUMA, off otherwise.
892 Format: 0 | 1 (for off | on)
894 hcl= [IA-64] SGI's Hardware Graph compatibility layer
896 hd= [EIDE] (E)IDE hard drive subsystem geometry
897 Format: <cyl>,<head>,<sect>
900 Disable Hardware Error Source Table (HEST) support;
901 corresponding firmware-first mode error processing
902 logic will be disabled.
904 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
905 size of <nn>. This works even on boxes that have no
906 highmem otherwise. This also works to reduce highmem
907 size on bigger boxes.
909 highres= [KNL] Enable/disable high resolution timer mode.
910 Valid parameters: "on", "off"
914 See Documentation/isdn/README.HiSax.
918 hpet= [X86-32,HPET] option to control HPET usage
919 Format: { enable (default) | disable | force |
921 disable: disable HPET and use PIT instead
922 force: allow force enabled of undocumented chips (ICH4,
924 verbose: show contents of HPET registers during setup
926 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
927 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
928 On x86-64 and powerpc, this option can be specified
929 multiple times interleaved with hugepages= to reserve
930 huge pages of different sizes. Valid pages sizes on
931 x86-64 are 2M (when the CPU supports "pse") and 1G
932 (when the CPU supports the "pdpe1gb" cpuinfo flag)
933 Note that 1GB pages can only be allocated at boot time
934 using hugepages= and not freed afterwards.
936 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
937 terminal devices. Valid values: 0..8
938 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
939 If specified, z/VM IUCV HVC accepts connections
940 from listed z/VM user IDs only.
943 Do not unregister boot console at start. This is only
944 useful for debugging when something happens in the window
945 between unregistering the boot console and initializing
948 i2c_bus= [HW] Override the default board specific I2C bus speed
949 or register an additional I2C bus that is not
950 registered from board initialization code.
954 i8042.debug [HW] Toggle i8042 debug mode
955 i8042.direct [HW] Put keyboard port into non-translated mode
956 i8042.dumbkbd [HW] Pretend that controller can only read data from
957 keyboard and cannot control its state
958 (Don't attempt to blink the leds)
959 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
960 i8042.nokbd [HW] Don't check/create keyboard port
961 i8042.noloop [HW] Disable the AUX Loopback command while probing
963 i8042.nomux [HW] Don't check presence of an active multiplexing
965 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
967 i8042.notimeout [HW] Ignore timeout condition signalled by controller
968 i8042.reset [HW] Reset the controller during init and cleanup
969 i8042.unlock [HW] Unlock (ignore) the keylock
973 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
974 indicates that the driver is running on unsupported
976 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
977 does not match list of supported models.
979 [HW] Report power status in /proc/i8k
980 (disabled by default)
981 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
985 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
987 ide-core.nodma= [HW] (E)IDE subsystem
988 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
989 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
990 .cdrom .chs .ignore_cable are additional options
991 See Documentation/ide/ide.txt.
993 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
994 Claim all unknown PCI IDE storage controllers.
997 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
998 Poll forces a polling idle loop that can slightly
999 improve the performance of waking up a idle CPU, but
1000 will use a lot of power and make the system run hot.
1002 idle=mwait: On systems which support MONITOR/MWAIT but
1003 the kernel chose to not use it because it doesn't save
1004 as much power as a normal idle loop, use the
1005 MONITOR/MWAIT idle loop anyways. Performance should be
1006 the same as idle=poll.
1007 idle=halt: Halt is forced to be used for CPU idle.
1008 In such case C2/C3 won't be used again.
1009 idle=nomwait: Disable mwait for CPU C-states
1011 ignore_loglevel [KNL]
1012 Ignore loglevel setting - this will print /all/
1013 kernel messages to the console. Useful for debugging.
1014 We also add it as printk module parameter, so users
1015 could change it dynamically, usually by
1016 /sys/module/printk/parameters/ignore_loglevel.
1018 ihash_entries= [KNL]
1019 Set number of hash buckets for inode cache.
1022 Format: { "0" | "1" }
1023 0 -- integrity auditing messages. (Default)
1024 1 -- enable informational integrity auditing messages.
1027 Format: { "sha1" | "md5" }
1031 Load a policy which meets the needs of the Trusted
1032 Computing Base. This means IMA will measure all
1033 programs exec'd, files mmap'd for exec, and all files
1034 opened for read by uid=0.
1038 Run specified binary instead of /sbin/init as init
1041 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1042 for working out where the kernel is dying during
1045 initrd= [BOOT] Specify the location of the initial ramdisk
1047 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1050 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1052 Enable intel iommu driver.
1054 Disable intel iommu driver.
1055 igfx_off [Default Off]
1056 By default, gfx is mapped as normal device. If a gfx
1057 device has a dedicated DMAR unit, the DMAR unit is
1058 bypassed by not enabling DMAR with this option. In
1059 this case, gfx device will use physical address for
1062 With this option iommu will not optimize to look
1063 for io virtual address below 32-bit forcing dual
1064 address cycle on pci bus for cards supporting greater
1065 than 32-bit addressing. The default is to look
1066 for translation below 32-bit and if not available
1067 then look in the higher range.
1068 strict [Default Off]
1069 With this option on every unmap_single operation will
1070 result in a hardware IOTLB flush operation as opposed
1071 to batching them for performance.
1072 sp_off [Default Off]
1073 By default, super page will be supported if Intel IOMMU
1074 has the capability. With this option, super page will
1077 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1078 0 disables intel_idle and fall back on acpi_idle.
1079 1 to 6 specify maximum depth of C-state.
1081 intremap= [X86-64, Intel-IOMMU]
1082 on enable Interrupt Remapping (default)
1083 off disable Interrupt Remapping
1084 nosid disable Source ID checking
1086 BIOS x2APIC opt-out request will be ignored
1088 iomem= Disable strict checking of access to MMIO memory
1089 strict regions from userspace.
1104 group_mf [x86, IA-64]
1107 io7= [HW] IO7 for Marvel based alpha systems
1108 See comment before marvel_specify_io7 in
1109 arch/alpha/kernel/core_marvel.c.
1111 io_delay= [X86] I/O delay method
1113 Standard port 0x80 based delay
1115 Alternate port 0xed based delay (needed on some systems)
1117 Simple two microseconds delay
1122 See Documentation/filesystems/nfs/nfsroot.txt.
1124 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1125 See comment before ip2_setup() in
1126 drivers/char/ip2/ip2base.c.
1129 When an interrupt is not handled search all handlers
1130 for it. Intended to get systems with badly broken
1134 When an interrupt is not handled search all handlers
1135 for it. Also check all handlers each timer
1136 interrupt. Intended to get systems with badly broken
1140 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1142 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1144 <cpu number>,...,<cpu number>
1146 <cpu number>-<cpu number>
1147 (must be a positive range in ascending order)
1149 <cpu number>,...,<cpu number>-<cpu number>
1151 This option can be used to specify one or more CPUs
1152 to isolate from the general SMP balancing and scheduling
1153 algorithms. You can move a process onto or off an
1154 "isolated" CPU via the CPU affinity syscalls or cpuset.
1155 <cpu number> begins at 0 and the maximum value is
1156 "number of CPUs in system - 1".
1158 This option is the preferred way to isolate CPUs. The
1159 alternative -- manually setting the CPU mask of all
1160 tasks in the system -- can cause problems and
1161 suboptimal load balancer performance.
1165 js= [HW,JOY] Analog joystick
1166 See Documentation/input/joystick.txt.
1170 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1171 specifies the amount of memory usable by the kernel
1172 for non-movable allocations. The requested amount is
1173 spread evenly throughout all nodes in the system. The
1174 remaining memory in each node is used for Movable
1175 pages. In the event, a node is too small to have both
1176 kernelcore and Movable pages, kernelcore pages will
1177 take priority and other nodes will have a larger number
1178 of kernelcore pages. The Movable zone is used for the
1179 allocation of pages that may be reclaimed or moved
1180 by the page migration subsystem. This means that
1181 HugeTLB pages may not be allocated from this zone.
1182 Note that allocations like PTEs-from-HighMem still
1183 use the HighMem zone if it exists, and the Normal
1184 zone if it does not.
1186 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1187 Format: <Controller#>[,poll interval]
1188 The controller # is the number of the ehci usb debug
1189 port as it is probed via PCI. The poll interval is
1190 optional and is the number seconds in between
1191 each poll cycle to the debug port in case you need
1192 the functionality for interrupting the kernel with
1193 gdb or control-c on the dbgp connection. When
1194 not using this parameter you use sysrq-g to break into
1195 the kernel debugger.
1197 kgdboc= [KGDB,HW] kgdb over consoles.
1198 Requires a tty driver that supports console polling,
1199 or a supported polling keyboard driver (non-usb).
1200 Serial only format: <serial_device>[,baud]
1201 keyboard only format: kbd
1202 keyboard and serial format: kbd,<serial_device>[,baud]
1203 Optional Kernel mode setting:
1204 kms, kbd format: kms,kbd
1205 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1207 kgdbwait [KGDB] Stop kernel execution and enter the
1208 kernel debugger at the earliest opportunity.
1210 kmac= [MIPS] korina ethernet MAC address.
1211 Configure the RouterBoard 532 series on-chip
1212 Ethernet adapter MAC address.
1214 kmemleak= [KNL] Boot-time kmemleak enable/disable
1215 Valid arguments: on, off
1218 kstack=N [X86] Print N words from the kernel stack
1221 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1222 Default is 0 (don't ignore, but inject #GP)
1224 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1228 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1229 Default is 1 (enabled)
1231 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1233 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1235 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1236 (virtualized MMU) support on capable Intel chips.
1237 Default is 1 (enabled)
1239 kvm-intel.emulate_invalid_guest_state=
1240 [KVM,Intel] Enable emulation of invalid guest states
1241 Default is 0 (disabled)
1243 kvm-intel.flexpriority=
1244 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1245 Default is 1 (enabled)
1248 [KVM,Intel] Enable VMX nesting (nVMX).
1249 Default is 0 (disabled)
1251 kvm-intel.unrestricted_guest=
1252 [KVM,Intel] Disable unrestricted guest feature
1253 (virtualized real and unpaged mode) on capable
1254 Intel chips. Default is 1 (enabled)
1256 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1257 feature (tagged TLBs) on capable Intel chips.
1258 Default is 1 (enabled)
1264 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1267 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1270 libata.dma= [LIBATA] DMA control
1271 libata.dma=0 Disable all PATA and SATA DMA
1272 libata.dma=1 PATA and SATA Disk DMA only
1273 libata.dma=2 ATAPI (CDROM) DMA only
1274 libata.dma=4 Compact Flash DMA only
1275 Combinations also work, so libata.dma=3 enables DMA
1276 for disks and CDROMs, but not CFs.
1278 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1279 libata.ignore_hpa=0 keep BIOS limits (default)
1280 libata.ignore_hpa=1 ignore limits, using full disk
1282 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1286 libata.force= [LIBATA] Force configurations. The format is comma
1287 separated list of "[ID:]VAL" where ID is
1288 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1289 matching port, link or device. Basically, it matches
1290 the ATA ID string printed on console by libata. If
1291 the whole ID part is omitted, the last PORT and DEVICE
1292 values are used. If ID hasn't been specified yet, the
1293 configuration applies to all ports, links and devices.
1295 If only DEVICE is omitted, the parameter applies to
1296 the port and all links and devices behind it. DEVICE
1297 number of 0 either selects the first device or the
1298 first fan-out link behind PMP device. It does not
1299 select the host link. DEVICE number of 15 selects the
1300 host link and device attached to it.
1302 The VAL specifies the configuration to force. As long
1303 as there's no ambiguity shortcut notation is allowed.
1304 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1305 The following configurations can be forced.
1307 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1308 Any ID with matching PORT is used.
1310 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1312 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1313 udma[/][16,25,33,44,66,100,133] notation is also
1316 * [no]ncq: Turn on or off NCQ.
1318 * nohrst, nosrst, norst: suppress hard, soft
1321 * dump_id: dump IDENTIFY data.
1323 If there are multiple matching configurations changing
1324 the same attribute, the last one is used.
1326 memblock=debug [KNL] Enable memblock debug messages.
1328 load_ramdisk= [RAM] List of ramdisks to load from floppy
1329 See Documentation/blockdev/ramdisk.txt.
1331 lockd.nlm_grace_period=P [NFS] Assign grace period.
1334 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1337 lockd.nlm_timeout=T [NFS] Assign timeout value.
1340 lockd.nlm_udpport=M [NFS] Assign UDP port.
1343 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1346 loglevel= All Kernel Messages with a loglevel smaller than the
1347 console loglevel will be printed to the console. It can
1348 also be changed with klogd or other programs. The
1349 loglevels are defined as follows:
1351 0 (KERN_EMERG) system is unusable
1352 1 (KERN_ALERT) action must be taken immediately
1353 2 (KERN_CRIT) critical conditions
1354 3 (KERN_ERR) error conditions
1355 4 (KERN_WARNING) warning conditions
1356 5 (KERN_NOTICE) normal but significant condition
1357 6 (KERN_INFO) informational
1358 7 (KERN_DEBUG) debug-level messages
1360 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1361 in bytes. n must be a power of two. The default
1362 size is set in the kernel config file.
1364 logo.nologo [FB] Disables display of the built-in Linux logo.
1365 This may be used to provide more screen space for
1366 kernel log messages and is useful when debugging
1367 kernel boot problems.
1369 lp=0 [LP] Specify parallel ports to use, e.g,
1370 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1371 lp=reset first parallel port). 'lp=0' disables the
1372 lp=auto printer driver. 'lp=reset' (which can be
1373 specified in addition to the ports) causes
1374 attached printers to be reset. Using
1375 lp=port1,port2,... specifies the parallel ports
1376 to associate lp devices with, starting with
1377 lp0. A port specification may be 'none' to skip
1378 that lp device, or a parport name such as
1379 'parport0'. Specifying 'lp=auto' instead of a
1380 port specification list means that device IDs
1381 from each port should be examined, to see if
1382 an IEEE 1284-compliant printer is attached; if
1383 so, the driver will manage that printer.
1384 See also header of drivers/char/lp.c.
1387 Sets loops_per_jiffy to given constant, thus avoiding
1388 time-consuming boot-time autodetection (up to 250 ms per
1389 CPU). 0 enables autodetection (default). To determine
1390 the correct value for your kernel, boot with normal
1391 autodetection and see what value is printed. Note that
1392 on SMP systems the preset will be applied to all CPUs,
1393 which is likely to cause problems if your CPUs need
1394 significantly divergent settings. An incorrect value
1395 will cause delays in the kernel to be wrong, leading to
1396 unpredictable I/O errors and other breakage. Although
1397 unlikely, in the extreme case this might damage your
1401 Format: <io>,<irq>,<dma>
1403 machvec= [IA-64] Force the use of a particular machine-vector
1404 (machvec) in a generic kernel.
1405 Example: machvec=hpzx1_swiotlb
1407 machtype= [Loongson] Share the same kernel image file between different
1409 Example: machtype=lemote-yeeloong-2f-7inch
1411 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1412 than or equal to this physical address is ignored.
1414 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1415 should make use of. maxcpus=n : n >= 0 limits the
1416 kernel to using 'n' processors. n=0 is a special case,
1417 it is equivalent to "nosmp", which also disables
1420 max_loop= [LOOP] The number of loop block devices that get
1421 (loop.max_loop) unconditionally pre-created at init time. The default
1422 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1423 of statically allocating a predefined number, loop
1424 devices can be requested on-demand with the
1425 /dev/loop-control interface.
1429 mce [X86-32] Machine Check Exception
1431 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1433 md= [HW] RAID subsystems devices and level
1434 See Documentation/md.txt.
1437 Format: <first>,<last>
1438 Specifies range of consoles to be captured by the MDA.
1440 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1441 Amount of memory to be used when the kernel is not able
1442 to see the whole system memory or for test.
1443 [X86-32] Use together with memmap= to avoid physical
1444 address space collisions. Without memmap= PCI devices
1445 could be placed at addresses belonging to unused RAM.
1447 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1451 [KNL,SH] Allow user to override the default size for
1452 per-device physically contiguous DMA buffers.
1454 memmap=exactmap [KNL,X86] Enable setting of an exact
1455 E820 memory map, as specified by the user.
1456 Such memmap=exactmap lines can be constructed based on
1457 BIOS output or other requirements. See the memmap=nn@ss
1460 memmap=nn[KMG]@ss[KMG]
1461 [KNL] Force usage of a specific region of memory
1462 Region of memory to be used, from ss to ss+nn.
1464 memmap=nn[KMG]#ss[KMG]
1465 [KNL,ACPI] Mark specific memory as ACPI data.
1466 Region of memory to be used, from ss to ss+nn.
1468 memmap=nn[KMG]$ss[KMG]
1469 [KNL,ACPI] Mark specific memory as reserved.
1470 Region of memory to be used, from ss to ss+nn.
1471 Example: Exclude memory from 0x18690000-0x1869ffff
1472 memmap=64K$0x18690000
1474 memmap=0x10000$0x18690000
1476 memory_corruption_check=0/1 [X86]
1477 Some BIOSes seem to corrupt the first 64k of
1478 memory when doing things like suspend/resume.
1479 Setting this option will scan the memory
1480 looking for corruption. Enabling this will
1481 both detect corruption and prevent the kernel
1482 from using the memory being corrupted.
1483 However, its intended as a diagnostic tool; if
1484 repeatable BIOS-originated corruption always
1485 affects the same memory, you can use memmap=
1486 to prevent the kernel from using that memory.
1488 memory_corruption_check_size=size [X86]
1489 By default it checks for corruption in the low
1490 64k, making this memory unavailable for normal
1491 use. Use this parameter to scan for
1492 corruption in more or less memory.
1494 memory_corruption_check_period=seconds [X86]
1495 By default it checks for corruption every 60
1496 seconds. Use this parameter to check at some
1497 other rate. 0 disables periodic checking.
1499 memtest= [KNL,X86] Enable memtest
1501 default : 0 <disable>
1502 Specifies the number of memtest passes to be
1503 performed. Each pass selects another test
1504 pattern from a given set of patterns. Memtest
1505 fills the memory with this pattern, validates
1506 memory contents and reserves bad memory
1507 regions that are detected.
1509 meye.*= [HW] Set MotionEye Camera parameters
1510 See Documentation/video4linux/meye.txt.
1512 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1513 Multi-Function General Purpose Timers on AMD Geode
1516 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1517 the BIOS has incorrectly applied a workaround. TinyBIOS
1518 version 0.98 is known to be affected, 0.99 fixes the
1519 problem by letting the user disable the workaround.
1523 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1524 physical address is ignored.
1526 mini2440= [ARM,HW,KNL]
1527 Format:[0..2][b][c][t]
1529 MINI2440 configuration specification:
1530 0 - The attached screen is the 3.5" TFT
1531 1 - The attached screen is the 7" TFT
1532 2 - The VGA Shield is attached (1024x768)
1533 Leaving out the screen size parameter will not load
1534 the TFT driver, and the framebuffer will be left
1536 b - Enable backlight. The TFT backlight pin will be
1537 linked to the kernel VESA blanking code and a GPIO
1538 LED. This parameter is not necessary when using the
1540 c - Enable the s3c camera interface.
1541 t - Reserved for enabling touchscreen support. The
1542 touchscreen support is not enabled in the mainstream
1543 kernel as of 2.6.30, a preliminary port can be found
1544 in the "bleeding edge" mini2440 support kernel at
1545 http://repo.or.cz/w/linux-2.6/mini2440.git
1548 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1549 parameter allows control of the logging verbosity for
1550 the additional memory initialisation checks. A value
1551 of 0 disables mminit logging and a level of 4 will
1552 log everything. Information is printed at KERN_DEBUG
1553 so loglevel=8 may also need to be specified.
1556 [MOUSE] Maximum time between finger touching and
1557 leaving touchpad surface for touch to be considered
1558 a tap and be reported as a left button click (for
1559 touchpads working in absolute mode only).
1561 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1562 reporting absolute coordinates, such as tablets
1563 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1564 reporting absolute coordinates, such as tablets
1566 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1567 is similar to kernelcore except it specifies the
1568 amount of memory used for migratable allocations.
1569 If both kernelcore and movablecore is specified,
1570 then kernelcore will be at *least* the specified
1571 value but may be more. If movablecore on its own
1572 is specified, the administrator must be careful
1573 that the amount of memory usable for all allocations
1576 MTD_Partition= [MTD]
1577 Format: <name>,<region-number>,<size>,<offset>
1579 MTD_Region= [MTD] Format:
1580 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1583 See drivers/mtd/cmdlinepart.c.
1585 multitce=off [PPC] This parameter disables the use of the pSeries
1586 firmware feature for updating multiple TCE entries
1589 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1591 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1593 boundary - index of last SLC block on Flex-OneNAND.
1594 The remaining blocks are configured as MLC blocks.
1595 lock - Configure if Flex-OneNAND boundary should be locked.
1596 Once locked, the boundary cannot be changed.
1597 1 indicates lock status, 0 indicates unlock status.
1600 ARM/S3C2412 JIVE boot control
1602 See arch/arm/mach-s3c2412/mach-jive.c
1604 mtouchusb.raw_coordinates=
1605 [HW] Make the MicroTouch USB driver use raw coordinates
1606 ('y', default) or cooked coordinates ('n')
1608 mtrr_chunk_size=nn[KMG] [X86]
1609 used for mtrr cleanup. It is largest continuous chunk
1610 that could hold holes aka. UC entries.
1612 mtrr_gran_size=nn[KMG] [X86]
1613 Used for mtrr cleanup. It is granularity of mtrr block.
1615 Large value could prevent small alignment from
1618 mtrr_spare_reg_nr=n [X86]
1620 Range: 0,7 : spare reg number
1622 Used for mtrr cleanup. It is spare mtrr entries number.
1623 Set to 2 or more if your graphical card needs more.
1625 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1627 netdev= [NET] Network devices parameters
1628 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1629 Note that mem_start is often overloaded to mean
1630 something different and driver-specific.
1631 This usage is only documented in each driver source
1635 [NETFILTER] Enable connection tracking flow accounting
1636 0 to disable accounting
1637 1 to enable accounting
1640 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1641 See Documentation/filesystems/nfs/nfsroot.txt.
1643 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1644 See Documentation/filesystems/nfs/nfsroot.txt.
1646 nfsrootdebug [NFS] enable nfsroot debugging messages.
1647 See Documentation/filesystems/nfs/nfsroot.txt.
1649 nfs.callback_tcpport=
1650 [NFS] set the TCP port on which the NFSv4 callback
1651 channel should listen.
1654 [NFS] sets the pathname to the program which is used
1655 to update the NFS client cache entries.
1657 nfs.cache_getent_timeout=
1658 [NFS] sets the timeout after which an attempt to
1659 update a cache entry is deemed to have failed.
1661 nfs.idmap_cache_timeout=
1662 [NFS] set the maximum lifetime for idmapper cache
1666 [NFS] enable 64-bit inode numbers.
1667 If zero, the NFS client will fake up a 32-bit inode
1668 number for the readdir() and stat() syscalls instead
1669 of returning the full 64-bit number.
1670 The default is to return 64-bit inode numbers.
1672 nfs.max_session_slots=
1673 [NFSv4.1] Sets the maximum number of session slots
1674 the client will attempt to negotiate with the server.
1675 This limits the number of simultaneous RPC requests
1676 that the client can send to the NFSv4.1 server.
1677 Note that there is little point in setting this
1678 value higher than the max_tcp_slot_table_limit.
1680 nfs.nfs4_disable_idmapping=
1681 [NFSv4] When set to the default of '1', this option
1682 ensures that both the RPC level authentication
1683 scheme and the NFS level operations agree to use
1684 numeric uids/gids if the mount is using the
1685 'sec=sys' security flavour. In effect it is
1686 disabling idmapping, which can make migration from
1687 legacy NFSv2/v3 systems to NFSv4 easier.
1688 Servers that do not support this mode of operation
1689 will be autodetected by the client, and it will fall
1690 back to using the idmapper.
1691 To turn off this behaviour, set the value to '0'.
1693 nfs.send_implementation_id =
1694 [NFSv4.1] Send client implementation identification
1695 information in exchange_id requests.
1696 If zero, no implementation identification information
1698 The default is to send the implementation identification
1701 nfsd.nfs4_disable_idmapping=
1702 [NFSv4] When set to the default of '1', the NFSv4
1703 server will return only numeric uids and gids to
1704 clients using auth_sys, and will accept numeric uids
1705 and gids from such clients. This is intended to ease
1706 migration from NFSv2/v3.
1708 objlayoutdriver.osd_login_prog=
1709 [NFS] [OBJLAYOUT] sets the pathname to the program which
1710 is used to automatically discover and login into new
1711 osd-targets. Please see:
1712 Documentation/filesystems/pnfs.txt for more explanations
1714 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1715 when a NMI is triggered.
1716 Format: [state][,regs][,debounce][,die]
1718 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1719 Format: [panic,][nopanic,][num]
1721 0 - turn nmi_watchdog off
1722 When panic is specified, panic when an NMI watchdog
1723 timeout occurs (or 'nopanic' to override the opposite
1725 This is useful when you use a panic=... timeout and
1726 need the box quickly up again.
1728 netpoll.carrier_timeout=
1729 [NET] Specifies amount of time (in seconds) that
1730 netpoll should wait for a carrier. By default netpoll
1733 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1734 emulation library even if a 387 maths coprocessor
1738 [HW] Never suspend the console
1739 Disable suspending of consoles during suspend and
1740 hibernate operations. Once disabled, debugging
1741 messages can reach various consoles while the rest
1742 of the system is being put to sleep (ie, while
1743 debugging driver suspend/resume hooks). This may
1744 not work reliably with all consoles, but is known
1745 to work with serial and VGA consoles.
1746 To facilitate more flexible debugging, we also add
1747 console_suspend, a printk module parameter to control
1748 it. Users could use console_suspend (usually
1749 /sys/module/printk/parameters/console_suspend) to
1750 turn on/off it dynamically.
1752 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1753 caches in the slab allocator. Saves per-node memory,
1754 but will impact performance.
1758 noapic [SMP,APIC] Tells the kernel to not make use of any
1759 IOAPICs that may be present in the system.
1761 noautogroup Disable scheduler automatic task group creation.
1763 nobats [PPC] Do not use BATs for mapping kernel lowmem
1764 on "Classic" PPC cores.
1768 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1770 nodelayacct [KNL] Disable per-task delay accounting
1772 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1774 nodsp [SH] Disable hardware DSP at boot time.
1776 noefi [X86] Disable EFI runtime services support.
1781 On X86-32 available only on PAE configured kernels.
1782 noexec=on: enable non-executable mappings (default)
1783 noexec=off: disable non-executable mappings
1786 Disable SMEP (Supervisor Mode Execution Protection)
1787 even if it is supported by processor.
1790 This affects only 32-bit executables.
1791 noexec32=on: enable non-executable mappings (default)
1792 read doesn't imply executable mappings
1793 noexec32=off: disable non-executable mappings
1794 read implies executable mappings
1796 nofpu [SH] Disable hardware FPU at boot time.
1798 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1799 register save and restore. The kernel will only save
1800 legacy floating-point registers on task switch.
1802 noxsave [BUGS=X86] Disables x86 extended register state save
1803 and restore using xsave. The kernel will fallback to
1804 enabling legacy floating-point and sse state.
1806 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1807 wfi(ARM) instruction doesn't work correctly and not to
1808 use it. This is also useful when using JTAG debugger.
1810 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1811 instruction doesn't work correctly and not to
1814 no_file_caps Tells the kernel not to honor file capabilities. The
1815 only way then for a file to be executed with privilege
1816 is to be setuid root or executed by root.
1818 nohalt [IA-64] Tells the kernel not to use the power saving
1819 function PAL_HALT_LIGHT when idle. This increases
1820 power-consumption. On the positive side, it reduces
1821 interrupt wake-up latency, which may improve performance
1822 in certain environments such as networked servers or
1825 nohz= [KNL] Boottime enable/disable dynamic ticks
1826 Valid arguments: on, off
1829 noiotrap [SH] Disables trapped I/O port accesses.
1831 noirqdebug [X86-32] Disables the code which attempts to detect and
1832 disable unhandled interrupt sources.
1834 no_timer_check [X86,APIC] Disables the code which tests for
1835 broken timer IRQ sources.
1837 noisapnp [ISAPNP] Disables ISA PnP code.
1839 noinitrd [RAM] Tells the kernel not to load any configured
1842 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1844 [Deprecated - use intremap=off]
1848 nojitter [IA-64] Disables jitter checking for ITC timers.
1850 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1852 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1855 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1856 steal time is computed, but won't influence scheduler
1859 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1861 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1863 noltlbs [PPC] Do not use large page/tlb entries for kernel
1864 lowmem mapping on PPC40x.
1866 nomca [IA-64] Disable machine check abort handling
1868 nomce [X86-32] Machine Check Exception
1870 nomfgpt [X86-32] Disable Multi-Function General Purpose
1871 Timer usage (for AMD Geode machines).
1873 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1874 shutdown the other cpus. Instead use the REBOOT_VECTOR
1877 nomodule Disable module load
1879 nopat [X86] Disable PAT (page attribute table extension of
1880 pagetables) support.
1882 norandmaps Don't use address space randomization. Equivalent to
1883 echo 0 > /proc/sys/kernel/randomize_va_space
1885 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1887 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1888 with UP alternatives
1890 noresidual [PPC] Don't use residual data on PReP machines.
1892 nordrand [X86] Disable the direct use of the RDRAND
1893 instruction even if it is supported by the
1894 processor. RDRAND is still available to user
1897 noresume [SWSUSP] Disables resume and restores original swap
1900 no-scroll [VGA] Disables scrollback.
1901 This is required for the Braillex ib80-piezo Braille
1902 reader made by F.H. Papenmeier (Germany).
1906 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1908 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1909 and disable the IO APIC. legacy for "maxcpus=0".
1911 nosoftlockup [KNL] Disable the soft-lockup detector.
1913 nosync [HW,M68K] Disables sync negotiation for all devices.
1915 notsc [BUGS=X86-32] Disable Time Stamp Counter
1917 nousb [USB] Disable the USB subsystem
1919 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1923 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1925 nptcg= [IA-64] Override max number of concurrent global TLB
1926 purges which is reported from either PAL_VM_SUMMARY or
1929 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1930 could support. nr_cpus=n : n >= 1 limits the kernel to
1931 supporting 'n' processors. Later in runtime you can not
1932 use hotplug cpu feature to put more cpu back to online.
1933 just like you compile the kernel NR_CPUS=n
1935 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1937 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1938 one of ['zone', 'node', 'default'] can be specified
1939 This can be set from sysctl after boot.
1940 See Documentation/sysctl/vm.txt for details.
1942 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1943 See Documentation/debugging-via-ohci1394.txt for more
1946 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1947 Rather than timing out after 20 ms if an EC
1948 command is not properly ACKed, override the length
1949 of the timeout. We have interrupts disabled while
1950 waiting for the ACK, so if this is set too high
1951 interrupts *may* be lost!
1953 omap_mux= [OMAP] Override bootloader pin multiplexing.
1954 Format: <mux_mode0.mode_name=value>...
1955 For example, to override I2C bus2:
1956 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1958 oprofile.timer= [HW]
1959 Use timer interrupt instead of performance counters
1961 oprofile.cpu_type= Force an oprofile cpu type
1962 This might be useful if you have an older oprofile
1963 userland or if you want common events.
1964 Format: { arch_perfmon }
1965 arch_perfmon: [X86] Force use of architectural
1966 perfmon on Intel CPUs instead of the
1967 CPU specific event set.
1968 timer: [X86] Force use of architectural NMI
1969 timer mode (see also oprofile.timer
1970 for generic hr timer mode)
1971 [s390] Force legacy basic mode sampling
1972 (report cpu_type "timer")
1974 oops=panic Always panic on oopses. Default is to just kill the
1975 process, but there is a small probability of
1976 deadlocking the machine.
1977 This will also cause panics on machine check exceptions.
1978 Useful together with panic=30 to trigger a reboot.
1981 See Documentation/sound/oss/oss-parameters.txt
1983 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1984 timeout > 0: seconds before rebooting
1985 timeout = 0: wait forever
1986 timeout < 0: reboot immediately
1989 parkbd.port= [HW] Parallel port number the keyboard adapter is
1990 connected to, default is 0.
1992 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1993 0 for XT, 1 for AT (default is AT).
1996 parport= [HW,PPT] Specify parallel ports. 0 disables.
1997 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1998 Use 'auto' to force the driver to use any
1999 IRQ/DMA settings detected (the default is to
2000 ignore detected IRQ/DMA settings because of
2001 possible conflicts). You can specify the base
2002 address, IRQ, and DMA settings; IRQ and DMA
2003 should be numbers, or 'auto' (for using detected
2004 settings on that particular port), or 'nofifo'
2005 (to avoid using a FIFO even if it is detected).
2006 Parallel ports are assigned in the order they
2007 are specified on the command line, starting
2010 parport_init_mode= [HW,PPT]
2011 Configure VIA parallel port to operate in
2012 a specific mode. This is necessary on Pegasos
2013 computer where firmware has no options for setting
2014 up parallel port mode and sets it to spp.
2015 Currently this function knows 686a and 8231 chips.
2016 Format: [spp|ps2|epp|ecp|ecpepp]
2019 Halt all CPUs after the first oops has been printed for
2020 the specified number of seconds. This is to be used if
2021 your oopses keep scrolling off the screen.
2026 See header of drivers/block/paride/pcd.c.
2027 See also Documentation/blockdev/paride.txt.
2029 pci=option[,option...] [PCI] various PCI subsystem options:
2030 earlydump [X86] dump PCI config space before the kernel
2032 off [X86] don't probe for the PCI bus
2033 bios [X86-32] force use of PCI BIOS, don't access
2034 the hardware directly. Use this if your machine
2035 has a non-standard PCI host bridge.
2036 nobios [X86-32] disallow use of PCI BIOS, only direct
2037 hardware access methods are allowed. Use this
2038 if you experience crashes upon bootup and you
2039 suspect they are caused by the BIOS.
2040 conf1 [X86] Force use of PCI Configuration
2042 conf2 [X86] Force use of PCI Configuration
2044 noaer [PCIE] If the PCIEAER kernel config parameter is
2045 enabled, this kernel boot option can be used to
2046 disable the use of PCIE advanced error reporting.
2047 nodomains [PCI] Disable support for multiple PCI
2048 root domains (aka PCI segments, in ACPI-speak).
2049 nommconf [X86] Disable use of MMCONFIG for PCI
2051 check_enable_amd_mmconf [X86] check for and enable
2052 properly configured MMIO access to PCI
2053 config space on AMD family 10h CPU
2054 nomsi [MSI] If the PCI_MSI kernel config parameter is
2055 enabled, this kernel boot option can be used to
2056 disable the use of MSI interrupts system-wide.
2057 noioapicquirk [APIC] Disable all boot interrupt quirks.
2058 Safety option to keep boot IRQs enabled. This
2059 should never be necessary.
2060 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2061 primary IO-APIC for bridges that cannot disable
2062 boot IRQs. This fixes a source of spurious IRQs
2063 when the system masks IRQs.
2064 noioapicreroute [APIC] Disable workaround that uses the
2065 boot IRQ equivalent of an IRQ that connects to
2066 a chipset where boot IRQs cannot be disabled.
2067 The opposite of ioapicreroute.
2068 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2069 routing table. These calls are known to be buggy
2070 on several machines and they hang the machine
2071 when used, but on other computers it's the only
2072 way to get the interrupt routing table. Try
2073 this option if the kernel is unable to allocate
2074 IRQs or discover secondary PCI buses on your
2076 rom [X86] Assign address space to expansion ROMs.
2077 Use with caution as certain devices share
2078 address decoders between ROMs and other
2080 norom [X86] Do not assign address space to
2081 expansion ROMs that do not already have
2082 BIOS assigned address ranges.
2083 nobar [X86] Do not assign address space to the
2084 BARs that weren't assigned by the BIOS.
2085 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2086 assigned automatically to PCI devices. You can
2087 make the kernel exclude IRQs of your ISA cards
2089 pirqaddr=0xAAAAA [X86] Specify the physical address
2090 of the PIRQ table (normally generated
2091 by the BIOS) if it is outside the
2092 F0000h-100000h range.
2093 lastbus=N [X86] Scan all buses thru bus #N. Can be
2094 useful if the kernel is unable to find your
2095 secondary buses and you want to tell it
2096 explicitly which ones they are.
2097 assign-busses [X86] Always assign all PCI bus
2098 numbers ourselves, overriding
2099 whatever the firmware may have done.
2100 usepirqmask [X86] Honor the possible IRQ mask stored
2101 in the BIOS $PIR table. This is needed on
2102 some systems with broken BIOSes, notably
2103 some HP Pavilion N5400 and Omnibook XE3
2104 notebooks. This will have no effect if ACPI
2105 IRQ routing is enabled.
2106 noacpi [X86] Do not use ACPI for IRQ routing
2107 or for PCI scanning.
2108 use_crs [X86] Use PCI host bridge window information
2109 from ACPI. On BIOSes from 2008 or later, this
2110 is enabled by default. If you need to use this,
2111 please report a bug.
2112 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2113 If you need to use this, please report a bug.
2114 routeirq Do IRQ routing for all PCI devices.
2115 This is normally done in pci_enable_device(),
2116 so this option is a temporary workaround
2117 for broken drivers that don't call it.
2118 skip_isa_align [X86] do not align io start addr, so can
2119 handle more pci cards
2120 firmware [ARM] Do not re-enumerate the bus but instead
2121 just use the configuration from the
2122 bootloader. This is currently used on
2123 IXP2000 systems where the bus has to be
2124 configured a certain way for adjunct CPUs.
2125 noearly [X86] Don't do any early type 1 scanning.
2126 This might help on some broken boards which
2127 machine check when some devices' config space
2128 is read. But various workarounds are disabled
2129 and some IOMMU drivers will not work.
2130 bfsort Sort PCI devices into breadth-first order.
2131 This sorting is done to get a device
2132 order compatible with older (<= 2.4) kernels.
2133 nobfsort Don't sort PCI devices into breadth-first order.
2134 cbiosize=nn[KMG] The fixed amount of bus space which is
2135 reserved for the CardBus bridge's IO window.
2136 The default value is 256 bytes.
2137 cbmemsize=nn[KMG] The fixed amount of bus space which is
2138 reserved for the CardBus bridge's memory
2139 window. The default value is 64 megabytes.
2142 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2143 Specifies alignment and device to reassign
2144 aligned memory resources.
2145 If <order of align> is not specified,
2146 PAGE_SIZE is used as alignment.
2147 PCI-PCI bridge can be specified, if resource
2148 windows need to be expanded.
2149 ecrc= Enable/disable PCIe ECRC (transaction layer
2150 end-to-end CRC checking).
2151 bios: Use BIOS/firmware settings. This is the
2155 realloc= Enable/disable reallocating PCI bridge resources
2156 if allocations done by BIOS are too small to
2157 accommodate resources required by all child
2159 off: Turn realloc off
2161 realloc same as realloc=on
2162 noari do not use PCIe ARI.
2164 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2167 force Enable ASPM even on devices that claim not to support it.
2168 WARNING: Forcing ASPM on may cause system lockups.
2170 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2171 nomsi Do not use MSI for PCI Express Native Hotplug (this
2172 makes all PCIe ports use INTx for hotplug services).
2174 pcie_ports= [PCIE] PCIe ports handling:
2175 auto Ask the BIOS whether or not to use native PCIe services
2176 associated with PCIe ports (PME, hot-plug, AER). Use
2177 them only if that is allowed by the BIOS.
2178 native Use native PCIe services associated with PCIe ports
2180 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2183 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2184 nomsi Do not use MSI for native PCIe PME signaling (this makes
2185 all PCIe root ports use INTx for all services).
2187 pcmv= [HW,PCMCIA] BadgePAD 4
2190 See Documentation/blockdev/paride.txt.
2192 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2195 See arch/parisc/kernel/pdc_chassis.c
2197 percpu_alloc= Select which percpu first chunk allocator to use.
2198 Currently supported values are "embed" and "page".
2199 Archs may support subset or none of the selections.
2200 See comments in mm/percpu.c for details on each
2201 allocator. This parameter is primarily for debugging
2202 and performance comparison.
2205 See Documentation/blockdev/paride.txt.
2208 See Documentation/blockdev/paride.txt.
2210 pirq= [SMP,APIC] Manual mp-table setup
2211 See Documentation/x86/i386/IO-APIC.txt.
2213 plip= [PPT,NET] Parallel port network link
2214 Format: { parport<nr> | timid | 0 }
2215 See also Documentation/parport.txt.
2217 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2218 Override pmtimer IOPort with a hex value.
2222 Enable PNP debug messages (depends on the
2223 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2224 via /sys/module/pnp/parameters/debug. We always show
2225 current resource usage; turning this on also shows
2226 possible settings and some assignment information.
2232 { on | off | curr | res | no-curr | no-res }
2235 [ISAPNP] Exclude IRQs for the autoconfiguration
2238 [ISAPNP] Exclude DMAs for the autoconfiguration
2240 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2241 Ranges are in pairs (I/O port base and size).
2244 [ISAPNP] Exclude memory regions for the
2246 Ranges are in pairs (memory base and size).
2248 ports= [IP_VS_FTP] IPVS ftp helper module
2250 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2252 Format: <port>,<port>....
2254 print-fatal-signals=
2255 [KNL] debug: print fatal signals
2257 If enabled, warn about various signal handling
2258 related application anomalies: too many signals,
2259 too many POSIX.1 timers, fatal signals causing a
2262 If you hit the warning due to signal overflow,
2263 you might want to try "ulimit -i unlimited".
2267 printk.always_kmsg_dump=
2268 Trigger kmsg_dump for cases other than kernel oops or
2270 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2273 printk.time= Show timing data prefixed to each printk message line
2274 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2276 processor.max_cstate= [HW,ACPI]
2277 Limit processor to maximum C-state
2278 max_cstate=9 overrides any DMI blacklist limit.
2280 processor.nocst [HW,ACPI]
2281 Ignore the _CST method to determine C-states,
2282 instead using the legacy FADT method
2284 profile= [KNL] Enable kernel profiling via /proc/profile
2285 Format: [schedule,]<number>
2286 Param: "schedule" - profile schedule points.
2287 Param: <number> - step/bucket size as a power of 2 for
2288 statistical time based profiling.
2289 Param: "sleep" - profile D-state sleeping (millisecs).
2290 Requires CONFIG_SCHEDSTATS
2291 Param: "kvm" - profile VM exits.
2293 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2295 See Documentation/blockdev/ramdisk.txt.
2297 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2298 probe for; one of (bare|imps|exps|lifebook|any).
2299 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2301 psmouse.resetafter= [HW,MOUSE]
2302 Try to reset the device after so many bad packets
2305 [HW,MOUSE] Set desired mouse resolution, in dpi.
2306 psmouse.smartscroll=
2307 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2308 0 = disabled, 1 = enabled (default).
2310 pstore.backend= Specify the name of the pstore backend to use
2313 See Documentation/blockdev/paride.txt.
2316 [KNL] Number of legacy pty's. Overwrites compiled-in
2319 quiet [KNL] Disable most log messages
2324 See Documentation/md.txt.
2326 ramdisk_blocksize= [RAM]
2327 See Documentation/blockdev/ramdisk.txt.
2329 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2330 See Documentation/blockdev/ramdisk.txt.
2332 rcupdate.blimit= [KNL,BOOT]
2333 Set maximum number of finished RCU callbacks to process
2336 rcupdate.qhimark= [KNL,BOOT]
2337 Set threshold of queued
2338 RCU callbacks over which batch limiting is disabled.
2340 rcupdate.qlowmark= [KNL,BOOT]
2341 Set threshold of queued RCU callbacks below which
2342 batch limiting is re-enabled.
2346 Run specified binary instead of /init from the ramdisk,
2347 used for early userspace startup. See initrd.
2349 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2350 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2351 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2354 [KNL, SMP] Set scheduler's default relax_domain_level.
2355 See Documentation/cgroups/cpusets.txt.
2357 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2359 reservetop= [X86-32]
2361 Reserves a hole at the top of the kernel virtual
2366 Set the amount of memory to reserve for BIOS at
2367 the bottom of the address space.
2369 reset_devices [KNL] Force drivers to reset the underlying device
2370 during initialization.
2373 Specify the partition device for software suspend
2375 resume_offset= [SWSUSP]
2376 Specify the offset from the beginning of the partition
2377 given by "resume=" at which the swap header is located,
2378 in <PAGE_SIZE> units (needed only for swap files).
2379 See Documentation/power/swsusp-and-swap-files.txt
2381 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2382 read the resume files
2384 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2385 Useful for devices that are detected asynchronously
2386 (e.g. USB and MMC devices).
2388 hibernate= [HIBERNATION]
2389 noresume Don't check if there's a hibernation image
2390 present during boot.
2391 nocompress Don't compress/decompress hibernation images.
2393 retain_initrd [RAM] Keep initrd memory after extraction
2395 rhash_entries= [KNL,NET]
2396 Set number of hash buckets for route cache
2398 riscom8= [HW,SERIAL]
2399 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2401 ro [KNL] Mount root device read-only on boot
2403 root= [KNL] Root filesystem
2404 See name_to_dev_t comment in init/do_mounts.c.
2406 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2407 mount the root filesystem
2409 rootflags= [KNL] Set root filesystem mount option string
2411 rootfstype= [KNL] Set root filesystem type
2413 rootwait [KNL] Wait (indefinitely) for root device to show up.
2414 Useful for devices that are detected asynchronously
2415 (e.g. USB and MMC devices).
2417 rw [KNL] Mount root device read-write on boot
2419 S [KNL] Run init in single mode
2422 See drivers/net/irda/sa1100_ir.c.
2424 sbni= [NET] Granch SBNI12 leased line adapter
2426 sched_debug [KNL] Enables verbose scheduler debug messages.
2428 security= [SECURITY] Choose a security module to enable at boot.
2429 If this boot parameter is not specified, only the first
2430 security module asking for security registration will be
2431 loaded. An invalid security module name will be treated
2432 as if no module has been chosen.
2434 selinux= [SELINUX] Disable or enable SELinux at boot time.
2435 Format: { "0" | "1" }
2436 See security/selinux/Kconfig help text.
2439 Default value is set via kernel config option.
2440 If enabled at boot time, /selinux/disable can be used
2441 later to disable prior to initial policy load.
2443 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2444 Format: { "0" | "1" }
2445 See security/apparmor/Kconfig help text
2448 Default value is set via kernel config option.
2450 serialnumber [BUGS=X86-32]
2453 Maximal number of shapers.
2455 show_msr= [x86] show boot-time MSR settings
2456 Format: { <integer> }
2457 Show boot-time (BIOS-initialized) MSR settings.
2458 The parameter means the number of CPUs to show,
2459 for example 1 means boot CPU only.
2466 slab_max_order= [MM, SLAB]
2467 Determines the maximum allowed order for slabs.
2468 A high setting may cause OOMs due to memory
2469 fragmentation. Defaults to 1 for systems with
2470 more than 32MB of RAM, 0 otherwise.
2472 slub_debug[=options[,slabs]] [MM, SLUB]
2473 Enabling slub_debug allows one to determine the
2474 culprit if slab objects become corrupted. Enabling
2475 slub_debug can create guard zones around objects and
2476 may poison objects when not in use. Also tracks the
2477 last alloc / free. For more information see
2478 Documentation/vm/slub.txt.
2480 slub_max_order= [MM, SLUB]
2481 Determines the maximum allowed order for slabs.
2482 A high setting may cause OOMs due to memory
2483 fragmentation. For more information see
2484 Documentation/vm/slub.txt.
2486 slub_min_objects= [MM, SLUB]
2487 The minimum number of objects per slab. SLUB will
2488 increase the slab order up to slub_max_order to
2489 generate a sufficiently large slab able to contain
2490 the number of objects indicated. The higher the number
2491 of objects the smaller the overhead of tracking slabs
2492 and the less frequently locks need to be acquired.
2493 For more information see Documentation/vm/slub.txt.
2495 slub_min_order= [MM, SLUB]
2496 Determines the minimum page order for slabs. Must be
2497 lower than slub_max_order.
2498 For more information see Documentation/vm/slub.txt.
2500 slub_nomerge [MM, SLUB]
2501 Disable merging of slabs with similar size. May be
2502 necessary if there is some reason to distinguish
2503 allocs to different slabs. Debug options disable
2504 merging on their own.
2505 For more information see Documentation/vm/slub.txt.
2508 Format: <io1>[,<io2>[,...,<io8>]]
2510 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2511 attempt to substitute SMP alternatives once at boot.
2513 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2514 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2515 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2516 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2517 smsc-ircc2.ircc_irq= [HW] IRQ line
2518 smsc-ircc2.ircc_dma= [HW] DMA channel
2519 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2520 0: Toshiba Satellite 1800 (GP data pin select)
2521 1: Fast pin select (default)
2525 [KNL] Should the soft-lockup detector generate panics.
2528 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2529 See Documentation/laptops/sonypi.txt
2531 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2532 See Documentation/serial/specialix.txt.
2534 spia_io_base= [HW,MTD]
2540 Enabled the stack tracer on boot up.
2542 stacktrace_filter=[function-list]
2543 [FTRACE] Limit the functions that the stack tracer
2544 will trace at boot up. function-list is a comma separated
2545 list of functions. This list can be changed at run
2546 time by the stack_trace_filter file in the debugfs
2547 tracing directory. Note, this enables stack tracing
2548 and the stacktrace above is not needed.
2552 Set the STI (builtin display/keyboard on the HP-PARISC
2553 machines) console (graphic card) which should be used
2554 as the initial boot-console.
2555 See also comment in drivers/video/console/sticore.c.
2558 See comment in drivers/video/console/sticore.c.
2561 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2563 sunrpc.min_resvport=
2564 sunrpc.max_resvport=
2566 SunRPC servers often require that client requests
2567 originate from a privileged port (i.e. a port in the
2568 range 0 < portnr < 1024).
2569 An administrator who wishes to reserve some of these
2570 ports for other uses may adjust the range that the
2571 kernel's sunrpc client considers to be privileged
2572 using these two parameters to set the minimum and
2573 maximum port values.
2577 Control how the NFS server code allocates CPUs to
2578 service thread pools. Depending on how many NICs
2579 you have and where their interrupts are bound, this
2580 option will affect which CPUs will do NFS serving.
2581 Note: this parameter cannot be changed while the
2582 NFS server is running.
2584 auto the server chooses an appropriate mode
2585 automatically using heuristics
2586 global a single global pool contains all CPUs
2587 percpu one pool for each CPU
2588 pernode one pool for each NUMA node (equivalent
2589 to global on non-NUMA machines)
2591 sunrpc.tcp_slot_table_entries=
2592 sunrpc.udp_slot_table_entries=
2594 Sets the upper limit on the number of simultaneous
2595 RPC calls that can be sent from the client to a
2596 server. Increasing these values may allow you to
2597 improve throughput, but will also increase the
2598 amount of memory reserved for use by the client.
2601 [KNL] Enable accounting of swap in memory resource
2602 controller if no parameter or 1 is given or disable
2603 it if 0 is given (See Documentation/cgroups/memory.txt)
2605 swiotlb= [IA-64] Number of I/O TLB slabs
2609 sysfs.deprecated=0|1 [KNL]
2610 Enable/disable old style sysfs layout for old udev
2611 on older distributions. When this option is enabled
2612 very new udev will not work anymore. When this option
2613 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2614 in older udev will not work anymore.
2615 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2616 the kernel configuration.
2618 sysrq_always_enabled
2620 Ignore sysrq setting - this boot parameter will
2621 neutralize any effect of /proc/sys/kernel/sysrq.
2622 Useful for debugging.
2626 test_suspend= [SUSPEND]
2627 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2628 standby suspend) as the system sleep state to briefly
2629 enter during system startup. The system is woken from
2630 this state using a wakeup-capable RTC alarm.
2632 thash_entries= [KNL,NET]
2633 Set number of hash buckets for TCP connection
2635 thermal.act= [HW,ACPI]
2636 -1: disable all active trip points in all thermal zones
2637 <degrees C>: override all lowest active trip points
2639 thermal.crt= [HW,ACPI]
2640 -1: disable all critical trip points in all thermal zones
2641 <degrees C>: override all critical trip points
2643 thermal.nocrt= [HW,ACPI]
2644 Set to disable actions on ACPI thermal zone
2645 critical and hot trip points.
2647 thermal.off= [HW,ACPI]
2648 1: disable ACPI thermal control
2650 thermal.psv= [HW,ACPI]
2651 -1: disable all passive trip points
2652 <degrees C>: override all passive trip points to this
2655 thermal.tzp= [HW,ACPI]
2656 Specify global default ACPI thermal zone polling rate
2657 <deci-seconds>: poll all this frequency
2658 0: no polling (default)
2661 Force threading of all interrupt handlers except those
2662 marked explicitly IRQF_NO_THREAD.
2666 Specify if the kernel should make use of the cpu
2667 topology information if the hardware supports this.
2668 The scheduler will make use of this information and
2669 e.g. base its process migration decisions on it.
2674 tpm_suspend_pcr=[HW,TPM]
2675 Format: integer pcr id
2676 Specify that at suspend time, the tpm driver
2677 should extend the specified pcr with zeros,
2678 as a workaround for some chips which fail to
2679 flush the last written pcr on TPM_SaveState.
2680 This will guarantee that all the other pcrs
2683 trace_buf_size=nn[KMG]
2684 [FTRACE] will set tracing buffer size.
2686 trace_event=[event-list]
2687 [FTRACE] Set and start specified trace events in order
2688 to facilitate early boot debugging.
2689 See also Documentation/trace/events.txt
2691 transparent_hugepage=
2693 Format: [always|madvise|never]
2694 Can be used to control the default behavior of the system
2695 with respect to transparent hugepages.
2696 See Documentation/vm/transhuge.txt for more details.
2698 tsc= Disable clocksource stability checks for TSC.
2700 [x86] reliable: mark tsc clocksource as reliable, this
2701 disables clocksource verification at runtime, as well
2702 as the stability checks done at bootup. Used to enable
2703 high-resolution timer mode on older hardware, and in
2704 virtualized environment.
2705 [x86] noirqtime: Do not use TSC to do irq accounting.
2706 Used to run time disable IRQ_TIME_ACCOUNTING on any
2707 platforms where RDTSC is slow and this accounting
2710 turbografx.map[2|3]= [HW,JOY]
2711 TurboGraFX parallel port interface
2713 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2714 See also Documentation/input/joystick-parport.txt
2716 udbg-immortal [PPC] When debugging early kernel crashes that
2717 happen after console_init() and before a proper
2718 console driver takes over, this boot options might
2719 help "seeing" what's going on.
2721 uhash_entries= [KNL,NET]
2722 Set number of hash buckets for UDP/UDP-Lite connections
2725 [USB] Ignore overcurrent events (default N).
2726 Some badly-designed motherboards generate lots of
2727 bogus events, for ports that aren't wired to
2728 anything. Set this parameter to avoid log spamming.
2729 Note that genuine overcurrent events won't be
2733 [X86] Cause panic on unknown NMI.
2735 usbcore.authorized_default=
2736 [USB] Default USB device authorization:
2737 (default -1 = authorized except for wireless USB,
2738 0 = not authorized, 1 = authorized)
2740 usbcore.autosuspend=
2741 [USB] The autosuspend time delay (in seconds) used
2742 for newly-detected USB devices (default 2). This
2743 is the time required before an idle device will be
2744 autosuspended. Devices for which the delay is set
2745 to a negative value won't be autosuspended at all.
2747 usbcore.usbfs_snoop=
2748 [USB] Set to log all usbfs traffic (default 0 = off).
2750 usbcore.blinkenlights=
2751 [USB] Set to cycle leds on hubs (default 0 = off).
2753 usbcore.old_scheme_first=
2754 [USB] Start with the old device initialization
2755 scheme (default 0 = off).
2757 usbcore.usbfs_memory_mb=
2758 [USB] Memory limit (in MB) for buffers allocated by
2759 usbfs (default = 16, 0 = max = 2047).
2761 usbcore.use_both_schemes=
2762 [USB] Try the other device initialization scheme
2763 if the first one fails (default 1 = enabled).
2765 usbcore.initial_descriptor_timeout=
2766 [USB] Specifies timeout for the initial 64-byte
2767 USB_REQ_GET_DESCRIPTOR request in milliseconds
2768 (default 5000 = 5.0 seconds).
2771 [USBHID] The interval which mice are to be polled at.
2773 usb-storage.delay_use=
2774 [UMS] The delay in seconds before a new device is
2775 scanned for Logical Units (default 5).
2778 [UMS] A list of quirks entries to supplement or
2779 override the built-in unusual_devs list. List
2780 entries are separated by commas. Each entry has
2781 the form VID:PID:Flags where VID and PID are Vendor
2782 and Product ID values (4-digit hex numbers) and
2783 Flags is a set of characters, each corresponding
2784 to a common usb-storage quirk flag as follows:
2785 a = SANE_SENSE (collect more than 18 bytes
2787 b = BAD_SENSE (don't collect more than 18
2788 bytes of sense data);
2789 c = FIX_CAPACITY (decrease the reported
2790 device capacity by one sector);
2791 d = NO_READ_DISC_INFO (don't use
2792 READ_DISC_INFO command);
2793 e = NO_READ_CAPACITY_16 (don't use
2794 READ_CAPACITY_16 command);
2795 h = CAPACITY_HEURISTICS (decrease the
2796 reported device capacity by one
2797 sector if the number is odd);
2798 i = IGNORE_DEVICE (don't bind to this
2800 l = NOT_LOCKABLE (don't try to lock and
2801 unlock ejectable media);
2802 m = MAX_SECTORS_64 (don't transfer more
2803 than 64 sectors = 32 KB at a time);
2804 n = INITIAL_READ10 (force a retry of the
2805 initial READ(10) command);
2806 o = CAPACITY_OK (accept the capacity
2807 reported by the device);
2808 r = IGNORE_RESIDUE (the device reports
2809 bogus residue values);
2810 s = SINGLE_LUN (the device has only one
2812 w = NO_WP_DETECT (don't test whether the
2813 medium is write-protected).
2814 Example: quirks=0419:aaf5:rl,0421:0433:rc
2816 user_debug= [KNL,ARM]
2818 See arch/arm/Kconfig.debug help text.
2819 1 - undefined instruction events
2821 4 - invalid data aborts
2824 Example: user_debug=31
2827 [X86] Flags controlling user PTE allocations.
2829 nohigh = do not allocate PTE pages in
2830 HIGHMEM regardless of setting
2834 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2835 vdso=1: enable VDSO (default)
2836 vdso=0: disable VDSO mapping
2839 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2840 vdso32=1: enable 32-bit VDSO (default)
2841 vdso32=0: disable 32-bit VDSO mapping
2844 vector=percpu: enable percpu vector domain
2846 video= [FB] Frame buffer configuration
2847 See Documentation/fb/modedb.txt.
2849 vga= [BOOT,X86-32] Select a particular video mode
2850 See Documentation/x86/boot.txt and
2851 Documentation/svga.txt.
2852 Use vga=ask for menu.
2853 This is actually a boot loader parameter; the value is
2854 passed to the kernel using a special protocol.
2856 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2857 size of <nn>. This can be used to increase the
2858 minimum size (128MB on x86). It can also be used to
2859 decrease the size and leave more room for directly
2862 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2865 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2868 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2872 Controls the behavior of vsyscalls (i.e. calls to
2873 fixed addresses of 0xffffffffff600x00 from legacy
2874 code). Most statically-linked binaries and older
2875 versions of glibc use these calls. Because these
2876 functions are at fixed addresses, they make nice
2877 targets for exploits that can control RIP.
2879 emulate [default] Vsyscalls turn into traps and are
2880 emulated reasonably safely.
2882 native Vsyscalls are native syscall instructions.
2883 This is a little bit faster than trapping
2884 and makes a few dynamic recompilers work
2885 better than they would in emulation mode.
2886 It also makes exploits much easier to write.
2888 none Vsyscalls don't work at all. This makes
2889 them quite hard to use for exploits but
2890 might break your system.
2892 vt.cur_default= [VT] Default cursor shape.
2893 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2894 the parameters of the <Esc>[?A;B;Cc escape sequence;
2895 see VGA-softcursor.txt. Default: 2 = underline.
2897 vt.default_blu= [VT]
2898 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2899 Change the default blue palette of the console.
2900 This is a 16-member array composed of values
2903 vt.default_grn= [VT]
2904 Format: <green0>,<green1>,<green2>,...,<green15>
2905 Change the default green palette of the console.
2906 This is a 16-member array composed of values
2909 vt.default_red= [VT]
2910 Format: <red0>,<red1>,<red2>,...,<red15>
2911 Change the default red palette of the console.
2912 This is a 16-member array composed of values
2918 Set system-wide default UTF-8 mode for all tty's.
2919 Default is 1, i.e. UTF-8 mode is enabled for all
2920 newly opened terminals.
2922 vt.global_cursor_default=
2925 Set system-wide default for whether a cursor
2926 is shown on new VTs. Default is -1,
2927 i.e. cursors will be created by default unless
2928 overridden by individual drivers. 0 will hide
2929 cursors, 1 will display them.
2931 watchdog timers [HW,WDT] For information on watchdog timers,
2932 see Documentation/watchdog/watchdog-parameters.txt
2933 or other driver-specific files in the
2934 Documentation/watchdog/ directory.
2936 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2937 default x2apic cluster mode on platforms
2940 x86_mrst_timer= [X86-32,APBT]
2941 Choose timer option for x86 Moorestown MID platform.
2942 Two valid options are apbt timer only and lapic timer
2943 plus one apbt timer for broadcast timer.
2944 x86_mrst_timer=apbt_only | lapic_and_apbt
2946 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2947 xd_geo= See header of drivers/block/xd.c.
2949 xen_emul_unplug= [HW,X86,XEN]
2950 Unplug Xen emulated devices
2951 Format: [unplug0,][unplug1]
2952 ide-disks -- unplug primary master IDE devices
2953 aux-ide-disks -- unplug non-primary-master IDE devices
2954 nics -- unplug network devices
2955 all -- unplug all emulated devices (NICs and IDE disks)
2956 unnecessary -- unplugging emulated devices is
2957 unnecessary even if the host did not respond to
2959 never -- do not unplug even if version check succeeds
2961 xirc2ps_cs= [NET,PCMCIA]
2963 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2965 ______________________________________________________________________
2969 Add more DRM drivers.
projects / mirror_ubuntu-artful-kernel.git / blob