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 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_force_table_verification [HW,ACPI]
218 Enable table checksum verification during early stage.
219 By default, this is disabled due to x86 early mapping
222 acpi_irq_balance [HW,ACPI]
223 ACPI will balance active IRQs
226 acpi_irq_nobalance [HW,ACPI]
227 ACPI will not move active IRQs (default)
230 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
231 Format: <irq>,<irq>...
233 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
235 Format: <irq>,<irq>...
237 acpi_no_auto_serialize [HW,ACPI]
238 Disable auto-serialization of AML methods
239 AML control methods that contain the opcodes to create
240 named objects will be marked as "Serialized" by the
241 auto-serialization feature.
242 This feature is enabled by default.
243 This option allows to turn off the feature.
245 acpi_no_static_ssdt [HW,ACPI]
246 Disable installation of static SSDTs at early boot time
247 By default, SSDTs contained in the RSDT/XSDT will be
248 installed automatically and they will appear under
249 /sys/firmware/acpi/tables.
250 This option turns off this feature.
251 Note that specifying this option does not affect
252 dynamic table installation which will install SSDT
253 tables to /sys/firmware/acpi/tables/dynamic.
255 acpica_no_return_repair [HW, ACPI]
256 Disable AML predefined validation mechanism
257 This mechanism can repair the evaluation result to make
258 the return objects more ACPI specification compliant.
259 This option is useful for developers to identify the
260 root cause of an AML interpreter issue when the issue
261 has something to do with the repair mechanism.
263 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
264 Format: To spoof as Windows 98: ="Microsoft Windows"
266 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
267 acpi_osi="string1" # add string1
268 acpi_osi="!string2" # remove string2
269 acpi_osi=!* # remove all strings
270 acpi_osi=! # disable all built-in OS vendor
272 acpi_osi= # disable all strings
274 'acpi_osi=!' can be used in combination with single or
275 multiple 'acpi_osi="string1"' to support specific OS
276 vendor string(s). Note that such command can only
277 affect the default state of the OS vendor strings, thus
278 it cannot affect the default state of the feature group
279 strings and the current state of the OS vendor strings,
280 specifying it multiple times through kernel command line
281 is meaningless. This command is useful when one do not
282 care about the state of the feature group strings which
283 should be controlled by the OSPM.
285 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
286 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
287 can make '_OSI("Windows 2000")' TRUE.
289 'acpi_osi=' cannot be used in combination with other
290 'acpi_osi=' command lines, the _OSI method will not
291 exist in the ACPI namespace. NOTE that such command can
292 only affect the _OSI support state, thus specifying it
293 multiple times through kernel command line is also
296 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
299 'acpi_osi=!*' can be used in combination with single or
300 multiple 'acpi_osi="string1"' to support specific
301 string(s). Note that such command can affect the
302 current state of both the OS vendor strings and the
303 feature group strings, thus specifying it multiple times
304 through kernel command line is meaningful. But it may
305 still not able to affect the final state of a string if
306 there are quirks related to this string. This command
307 is useful when one want to control the state of the
308 feature group strings to debug BIOS issues related to
311 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
312 '_OSI("Module Device")' FALSE.
313 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
314 '_OSI("Module Device")' TRUE.
315 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
317 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
319 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
320 they all will make '_OSI("Windows 2000")' TRUE.
323 Override the pmtimer bug detection: force the kernel
324 to assume that this machine's pmtimer latches its value
325 and always returns good values.
327 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
328 Format: { level | edge | high | low }
330 acpi_skip_timer_override [HW,ACPI]
331 Recognize and ignore IRQ0/pin2 Interrupt Override.
332 For broken nForce2 BIOS resulting in XT-PIC timer.
334 acpi_sleep= [HW,ACPI] Sleep options
335 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
336 old_ordering, nonvs, sci_force_enable }
337 See Documentation/power/video.txt for information on
339 s3_beep is for debugging; it makes the PC's speaker beep
340 as soon as the kernel's real-mode entry point is called.
341 s4_nohwsig prevents ACPI hardware signature from being
342 used during resume from hibernation.
343 old_ordering causes the ACPI 1.0 ordering of the _PTS
344 control method, with respect to putting devices into
345 low power states, to be enforced (the ACPI 2.0 ordering
346 of _PTS is used by default).
347 nonvs prevents the kernel from saving/restoring the
348 ACPI NVS memory during suspend/hibernation and resume.
349 sci_force_enable causes the kernel to set SCI_EN directly
350 on resume from S1/S3 (which is against the ACPI spec,
351 but some broken systems don't work without it).
353 acpi_use_timer_override [HW,ACPI]
354 Use timer override. For some broken Nvidia NF5 boards
355 that require a timer override, but don't have HPET
357 acpi_enforce_resources= [ACPI]
358 { strict | lax | no }
359 Check for resource conflicts between native drivers
360 and ACPI OperationRegions (SystemIO and SystemMemory
361 only). IO ports and memory declared in ACPI might be
362 used by the ACPI subsystem in arbitrary AML code and
363 can interfere with legacy drivers.
364 strict (default): access to resources claimed by ACPI
365 is denied; legacy drivers trying to access reserved
366 resources will fail to bind to device using them.
367 lax: access to resources claimed by ACPI is allowed;
368 legacy drivers trying to access reserved resources
369 will bind successfully but a warning message is logged.
370 no: ACPI OperationRegions are not marked as reserved,
371 no further checks are performed.
373 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
376 add_efi_memmap [EFI; X86] Include EFI memory map in
377 kernel's map of available physical RAM.
380 { off | try_unsupported }
381 off: disable AGP support
382 try_unsupported: try to drive unsupported chipsets
383 (may crash computer or cause data corruption)
386 See Documentation/sound/alsa/alsa-parameters.txt
389 Allow the default userspace alignment fault handler
390 behaviour to be specified. Bit 0 enables warnings,
391 bit 1 enables fixups, and bit 2 sends a segfault.
393 align_va_addr= [X86-64]
394 Align virtual addresses by clearing slice [14:12] when
395 allocating a VMA at process creation time. This option
396 gives you up to 3% performance improvement on AMD F15h
397 machines (where it is enabled by default) for a
398 CPU-intensive style benchmark, and it can vary highly in
399 a microbenchmark depending on workload and compiler.
401 32: only for 32-bit processes
402 64: only for 64-bit processes
403 on: enable for both 32- and 64-bit processes
404 off: disable for both 32- and 64-bit processes
406 alloc_snapshot [FTRACE]
407 Allocate the ftrace snapshot buffer on boot up when the
408 main buffer is allocated. This is handy if debugging
409 and you need to use tracing_snapshot() on boot up, and
410 do not want to use tracing_snapshot_alloc() as it needs
411 to be done where GFP_KERNEL allocations are allowed.
413 amd_iommu= [HW,X86-64]
414 Pass parameters to the AMD IOMMU driver in the system.
416 fullflush - enable flushing of IO/TLB entries when
417 they are unmapped. Otherwise they are
418 flushed before they will be reused, which
420 off - do not initialize any AMD IOMMU found in
422 force_isolation - Force device isolation for all
423 devices. The IOMMU driver is not
424 allowed anymore to lift isolation
425 requirements as needed. This option
426 does not override iommu=pt
428 amd_iommu_dump= [HW,X86-64]
429 Enable AMD IOMMU driver option to dump the ACPI table
430 for AMD IOMMU. With this option enabled, AMD IOMMU
431 driver will print ACPI tables for AMD IOMMU during
432 IOMMU initialization.
434 amijoy.map= [HW,JOY] Amiga joystick support
435 Map of devices attached to JOY0DAT and JOY1DAT
437 See also Documentation/input/joystick.txt
439 analog.map= [HW,JOY] Analog joystick and gamepad support
440 Specifies type or capabilities of an analog joystick
441 connected to one of 16 gameports
442 Format: <type1>,<type2>,..<type16>
445 Power management functions (SPARCstation-4/5 + deriv.)
447 Disable APC CPU standby support. SPARCstation-Fox does
448 not play well with APC CPU idle - disable it if you have
449 APC and your system crashes randomly.
451 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
452 Change the output verbosity whilst booting
453 Format: { quiet (default) | verbose | debug }
454 Change the amount of debugging information output
455 when initialising the APIC and IO-APIC components.
458 See Documentation/networking/ipv6.txt.
460 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
461 Limit apic dumping. The parameter defines the maximal
462 number of local apics being dumped. Also it is possible
463 to set it to "all" by meaning -- no limit here.
464 Format: { 1 (default) | 2 | ... | all }.
465 The parameter valid if only apic=debug or
466 apic=verbose is specified.
467 Example: apic=debug show_lapic=all
469 apm= [APM] Advanced Power Management
470 See header of arch/x86/kernel/apm_32.c.
472 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
473 Format: <io>,<irq>,<nodeID>
477 atarimouse= [HW,MOUSE] Atari Mouse
479 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
480 EzKey and similar keyboards
482 atkbd.reset= [HW] Reset keyboard during initialization
484 atkbd.set= [HW] Select keyboard code set
485 Format: <int> (2 = AT (default), 3 = PS/2)
487 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
490 atkbd.softraw= [HW] Choose between synthetic and real raw mode
491 Format: <bool> (0 = real, 1 = synthetic (default))
493 atkbd.softrepeat= [HW]
494 Use software keyboard repeat
496 audit= [KNL] Enable the audit sub-system
497 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
498 0 - kernel audit is disabled and can not be enabled
499 until the next reboot
500 unset - kernel audit is initialized but disabled and
501 will be fully enabled by the userspace auditd.
502 1 - kernel audit is initialized and partially enabled,
503 storing at most audit_backlog_limit messages in
504 RAM until it is fully enabled by the userspace
508 audit_backlog_limit= [KNL] Set the audit queue size limit.
509 Format: <int> (must be >=0)
512 baycom_epp= [HW,AX25]
515 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
517 See header of drivers/net/hamradio/baycom_par.c.
519 baycom_ser_fdx= [HW,AX25]
520 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
521 Format: <io>,<irq>,<mode>[,<baud>]
522 See header of drivers/net/hamradio/baycom_ser_fdx.c.
524 baycom_ser_hdx= [HW,AX25]
525 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
526 Format: <io>,<irq>,<mode>
527 See header of drivers/net/hamradio/baycom_ser_hdx.c.
529 blkdevparts= Manual partition parsing of block device(s) for
530 embedded devices based on command line input.
531 See Documentation/block/cmdline-partition.txt
533 boot_delay= Milliseconds to delay each printk during boot.
534 Values larger than 10 seconds (10000) are changed to
538 bootmem_debug [KNL] Enable bootmem allocator debug messages.
540 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
541 bttv.radio= Most important insmod options are available as
543 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
546 bulk_remove=off [PPC] This parameter disables the use of the pSeries
547 firmware feature for flushing multiple hpte entries
550 c101= [NET] Moxa C101 synchronous serial card
552 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
553 Sometimes CPU hardware bugs make them report the cache
554 size incorrectly. The kernel will attempt work arounds
555 to fix known problems, but for some CPUs it is not
556 possible to determine what the correct size should be.
557 This option provides an override for these situations.
559 ccw_timeout_log [S390]
560 See Documentation/s390/CommonIO for details.
562 cgroup_disable= [KNL] Disable a particular controller
563 Format: {name of the controller(s) to disable}
564 The effects of cgroup_disable=foo are:
565 - foo isn't auto-mounted if you mount all cgroups in
567 - foo isn't visible as an individually mountable
569 {Currently only "memory" controller deal with this and
570 cut the overhead, others just disable the usage. So
571 only cgroup_disable=memory is actually worthy}
573 checkreqprot [SELINUX] Set initial checkreqprot flag value.
574 Format: { "0" | "1" }
575 See security/selinux/Kconfig help text.
576 0 -- check protection applied by kernel (includes
577 any implied execute protection).
578 1 -- check protection requested by application.
579 Default value is set via a kernel config option.
580 Value can be changed at runtime via
581 /selinux/checkreqprot.
584 See Documentation/s390/CommonIO for details.
587 Keep all clocks already enabled by bootloader on,
588 even if no driver has claimed them. This is useful
589 for debug and development, but should not be
590 needed on a platform with proper driver support.
591 For more information, see Documentation/clk.txt.
593 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
595 Forces specified clocksource (if available) to be used
596 when calculating gettimeofday(). If specified
597 clocksource is not available, it defaults to PIT.
598 Format: { pit | tsc | cyclone | pmtmr }
600 clocksource= Override the default clocksource
602 Override the default clocksource and use the clocksource
603 with the name specified.
604 Some clocksource names to choose from, depending on
606 [all] jiffies (this is the base, fallback clocksource)
608 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
609 pxa_timer,timer3,32k_counter,timer0_1
611 [X86-32] pit,hpet,tsc;
612 scx200_hrt on Geode; cyclone on IBM x440
620 clearcpuid=BITNUM [X86]
621 Disable CPUID feature X for the kernel. See
622 arch/x86/include/asm/cpufeature.h for the valid bit
623 numbers. Note the Linux specific bits are not necessarily
624 stable over kernel options, but the vendor specific
626 Also note that user programs calling CPUID directly
627 or using the feature without checking anything
628 will still see it. This just prevents it from
629 being used by the kernel or shown in /proc/cpuinfo.
630 Also note the kernel might malfunction if you disable
633 cma=nn[MG]@[start[MG][-end[MG]]]
635 Sets the size of kernel global memory area for
636 contiguous memory allocations and optionally the
637 placement constraint by the physical address range of
638 memory allocations. For more information, see
639 include/linux/dma-contiguous.h
641 cmo_free_hint= [PPC] Format: { yes | no }
642 Specify whether pages are marked as being inactive
643 when they are freed. This is used in CMO environments
644 to determine OS memory pressure for page stealing by
648 coherent_pool=nn[KMG] [ARM,KNL]
649 Sets the size of memory pool for coherent, atomic dma
650 allocations, by default set to 256K.
652 code_bytes [X86] How many bytes of object code to print
657 com20020= [HW,NET] ARCnet - COM20020 chipset
659 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
661 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
665 ARCnet - COM90xx chipset (memory-mapped buffers)
666 Format: <io>[,<irq>[,<memstart>]]
668 condev= [HW,S390] console device
671 console= [KNL] Output console device and options.
673 tty<n> Use the virtual console device <n>.
677 Use the specified serial port. The options are of
678 the form "bbbbpnf", where "bbbb" is the baud rate,
679 "p" is parity ("n", "o", or "e"), "n" is number of
680 bits, and "f" is flow control ("r" for RTS or
681 omit it). Default is "9600n8".
683 See Documentation/serial-console.txt for more
685 Documentation/networking/netconsole.txt for an
688 uart[8250],io,<addr>[,options]
689 uart[8250],mmio,<addr>[,options]
690 Start an early, polled-mode console on the 8250/16550
691 UART at the specified I/O port or MMIO address,
692 switching to the matching ttyS device later. The
693 options are the same as for ttyS, above.
694 hvc<n> Use the hypervisor console device <n>. This is for
695 both Xen and PowerPC hypervisors.
697 If the device connected to the port is not a TTY but a braille
698 device, prepend "brl," before the device type, for instance
700 For now, only VisioBraille is supported.
702 consoleblank= [KNL] The console blank (screen saver) timeout in
703 seconds. Defaults to 10*60 = 10mins. A value of 0
704 disables the blank timer.
707 [KNL] Change the default value for
708 /proc/<pid>/coredump_filter.
709 See also Documentation/filesystems/proc.txt.
711 cpuidle.off=1 [CPU_IDLE]
712 disable the cpuidle sub-system
714 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
716 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
718 crashkernel=size[KMG][@offset[KMG]]
719 [KNL] Using kexec, Linux can switch to a 'crash kernel'
720 upon panic. This parameter reserves the physical
721 memory region [offset, offset + size] for that kernel
722 image. If '@offset' is omitted, then a suitable offset
723 is selected automatically. Check
724 Documentation/kdump/kdump.txt for further details.
726 crashkernel=range1:size1[,range2:size2,...][@offset]
727 [KNL] Same as above, but depends on the memory
728 in the running system. The syntax of range is
729 start-[end] where start and end are both
730 a memory unit (amount[KMG]). See also
731 Documentation/kdump/kdump.txt for an example.
733 crashkernel=size[KMG],high
734 [KNL, x86_64] range could be above 4G. Allow kernel
735 to allocate physical memory region from top, so could
736 be above 4G if system have more than 4G ram installed.
737 Otherwise memory region will be allocated below 4G, if
739 It will be ignored if crashkernel=X is specified.
740 crashkernel=size[KMG],low
741 [KNL, x86_64] range under 4G. When crashkernel=X,high
742 is passed, kernel could allocate physical memory region
743 above 4G, that cause second kernel crash on system
744 that require some amount of low memory, e.g. swiotlb
745 requires at least 64M+32K low memory. Kernel would
746 try to allocate 72M below 4G automatically.
747 This one let user to specify own low range under 4G
748 for second kernel instead.
749 0: to disable low allocation.
750 It will be ignored when crashkernel=X,high is not used
751 or memory reserved is below 4G.
756 cs89x0_media= [HW,NET]
757 Format: { rj45 | aui | bnc }
760 See header of drivers/s390/block/dasd_devmap.c.
762 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
763 (one device per port)
764 Format: <port#>,<type>
765 See also Documentation/input/joystick-parport.txt
767 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
768 time. See Documentation/dynamic-debug-howto.txt for
769 details. Deprecated, see dyndbg.
771 debug [KNL] Enable kernel debugging (events log level).
774 [KNL] verbose self-tests
776 Print debugging info while doing the locking API
778 We default to 0 (no extra messages), setting it to
779 1 will print _a lot_ more information - normally
780 only useful to kernel developers.
782 debug_objects [KNL] Enable object debugging
785 [KNL] Disable object debugging
787 debug_guardpage_minorder=
788 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
789 parameter allows control of the order of pages that will
790 be intentionally kept free (and hence protected) by the
791 buddy allocator. Bigger value increase the probability
792 of catching random memory corruption, but reduce the
793 amount of memory for normal system use. The maximum
794 possible value is MAX_ORDER/2. Setting this parameter
795 to 1 or 2 should be enough to identify most random
796 memory corruption problems caused by bugs in kernel or
797 driver code when a CPU writes to (or reads from) a
798 random memory location. Note that there exists a class
799 of memory corruptions problems caused by buggy H/W or
800 F/W or by drivers badly programing DMA (basically when
801 memory is written at bus level and the CPU MMU is
802 bypassed) which are not detectable by
803 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
804 tracking down these problems.
806 debugpat [X86] Enable PAT debugging
808 decnet.addr= [HW,NET]
809 Format: <area>[,<node>]
810 See also Documentation/networking/decnet.txt.
813 [same as hugepagesz=] The size of the default
814 HugeTLB page size. This is the size represented by
815 the legacy /proc/ hugepages APIs, used for SHM, and
816 default size when mounting hugetlbfs filesystems.
817 Defaults to the default architecture's huge page size
821 Set number of hash buckets for dentry cache.
824 See Documentation/networking/ipv6.txt.
826 disable_cpu_apicid= [X86,APIC,SMP]
828 The number of initial APIC ID for the
829 corresponding CPU to be disabled at boot,
830 mostly used for the kdump 2nd kernel to
831 disable BSP to wake up multiple CPUs without
832 causing system reset or hang due to sending
835 disable_ddw [PPC/PSERIES]
836 Disable Dynamic DMA Window support. Use this if
837 to workaround buggy firmware.
840 See Documentation/networking/ipv6.txt.
842 disable_mtrr_cleanup [X86]
843 The kernel tries to adjust MTRR layout from continuous
844 to discrete, to make X server driver able to add WB
845 entry later. This parameter disables that.
847 disable_mtrr_trim [X86, Intel and AMD only]
848 By default the kernel will trim any uncacheable
849 memory out of your available memory pool based on
850 MTRR settings. This parameter disables that behavior,
851 possibly causing your machine to run very slowly.
853 disable_timer_pin_1 [X86]
854 Disable PIN 1 of APIC timer
855 Can be useful to work around chipset bugs.
857 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
858 this option disables the debugging code at boot.
860 dma_debug_entries=<number>
861 This option allows to tune the number of preallocated
862 entries for DMA-API debugging code. One entry is
863 required per DMA-API allocation. Use this if the
864 DMA-API debugging code disables itself because the
865 architectural default is too low.
867 dma_debug_driver=<driver_name>
868 With this option the DMA-API debugging driver
869 filter feature can be enabled at boot time. Just
870 pass the driver to filter for as the parameter.
871 The filter can be disabled or changed to another
872 driver later using sysfs.
874 drm_kms_helper.edid_firmware=[<connector>:]<file>
875 Broken monitors, graphic adapters and KVMs may
876 send no or incorrect EDID data sets. This parameter
877 allows to specify an EDID data set in the
878 /lib/firmware directory that is used instead.
879 Generic built-in EDID data sets are used, if one of
880 edid/1024x768.bin, edid/1280x1024.bin,
881 edid/1680x1050.bin, or edid/1920x1080.bin is given
882 and no file with the same name exists. Details and
883 instructions how to build your own EDID data are
884 available in Documentation/EDID/HOWTO.txt. An EDID
885 data set will only be used for a particular connector,
886 if its name and a colon are prepended to the EDID
891 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
892 module.dyndbg[="val"]
893 Enable debug messages at boot time. See
894 Documentation/dynamic-debug-howto.txt for details.
896 early_ioremap_debug [KNL]
897 Enable debug messages in early_ioremap support. This
898 is useful for tracking down temporary early mappings
899 which are not unmapped.
901 earlycon= [KNL] Output early console device and options.
903 uart[8250],io,<addr>[,options]
904 uart[8250],mmio,<addr>[,options]
905 uart[8250],mmio32,<addr>[,options]
906 Start an early, polled-mode console on the 8250/16550
907 UART at the specified I/O port or MMIO address.
908 MMIO inter-register address stride is either 8-bit
909 (mmio) or 32-bit (mmio32).
910 The options are the same as for ttyS, above.
913 Start an early, polled-mode console on a pl011 serial
914 port at the specified address. The pl011 serial port
915 must already be setup and configured. Options are not
918 smh Use ARM semihosting calls for early console.
920 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
924 earlyprintk=serial[,ttySn[,baudrate]]
925 earlyprintk=serial[,0x...[,baudrate]]
926 earlyprintk=ttySn[,baudrate]
927 earlyprintk=dbgp[debugController#]
929 earlyprintk is useful when the kernel crashes before
930 the normal console is initialized. It is not enabled by
931 default because it has some cosmetic problems.
933 Append ",keep" to not disable it when the real console
936 Only one of vga, efi, serial, or usb debug port can
939 Currently only ttyS0 and ttyS1 may be specified by
940 name. Other I/O ports may be explicitly specified
941 on some architectures (x86 and arm at least) by
942 replacing ttySn with an I/O port address, like this:
943 earlyprintk=serial,0x1008,115200
944 You can find the port for a given device in
945 /proc/tty/driver/serial:
946 2: uart:ST16650V2 port:00001008 irq:18 ...
948 Interaction with the standard serial driver is not
951 The VGA and EFI output is eventually overwritten by
954 The xen output can only be used by Xen PV guests.
956 edac_report= [HW,EDAC] Control how to report EDAC event
957 Format: {"on" | "off" | "force"}
958 on: enable EDAC to report H/W event. May be overridden
959 by other higher priority error reporting module.
960 off: disable H/W event reporting through EDAC.
961 force: enforce the use of EDAC to report H/W event.
964 ekgdboc= [X86,KGDB] Allow early kernel console debugging
967 This is designed to be used in conjunction with
968 the boot argument: earlyprintk=vga
971 Format: {"off" | "on" | "skip[mbr]"}
974 Format: { "old_map" }
975 old_map [X86-64]: switch to the old ioremap-based EFI
976 runtime services mapping. 32-bit still uses this one by
979 efi_no_storage_paranoia [EFI; X86]
980 Using this parameter you can use more than 50% of
981 your efi variable storage. Use this parameter only if
982 you are really sure that your UEFI does sane gc and
983 fulfills the spec otherwise your board may brick.
985 eisa_irq_edge= [PARISC,HW]
986 See header of drivers/parisc/eisa.c.
989 See comment before function elanfreq_setup() in
990 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
993 Format: {"cfq" | "deadline" | "noop"}
994 See Documentation/block/cfq-iosched.txt and
995 Documentation/block/deadline-iosched.txt for details.
997 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
998 Specifies physical address of start of kernel core
999 image elf header and optionally the size. Generally
1000 kexec loader will pass this option to capture kernel.
1001 See Documentation/kdump/kdump.txt for details.
1003 enable_mtrr_cleanup [X86]
1004 The kernel tries to adjust MTRR layout from continuous
1005 to discrete, to make X server driver able to add WB
1006 entry later. This parameter enables that.
1008 enable_timer_pin_1 [X86]
1009 Enable PIN 1 of APIC timer
1010 Can be useful to work around chipset bugs
1011 (in particular on some ATI chipsets).
1012 The kernel tries to set a reasonable default.
1014 enforcing [SELINUX] Set initial enforcing status.
1016 See security/selinux/Kconfig help text.
1017 0 -- permissive (log only, no denials).
1018 1 -- enforcing (deny and log).
1020 Value can be changed at runtime via /selinux/enforce.
1023 Disable Error Record Serialization Table (ERST)
1026 ether= [HW,NET] Ethernet cards parameters
1027 This option is obsoleted by the "netdev=" option, which
1028 has equivalent usage. See its documentation for details.
1032 Permit 'security.evm' to be updated regardless of
1033 current integrity status.
1037 fail_make_request=[KNL]
1038 General fault injection mechanism.
1039 Format: <interval>,<probability>,<space>,<times>
1040 See also Documentation/fault-injection/.
1043 See Documentation/blockdev/floppy.txt.
1045 force_pal_cache_flush
1046 [IA-64] Avoid check_sal_cache_flush which may hang on
1047 buggy SAL_CACHE_FLUSH implementations. Using this
1048 parameter will force ia64_sal_cache_flush to call
1049 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1052 Forcefully enable Physical Address Extension (PAE).
1053 Many Pentium M systems disable PAE but may have a
1054 functionally usable PAE implementation.
1055 Warning: use of this parameter will taint the kernel
1056 and may cause unknown problems.
1059 [FTRACE] will set and start the specified tracer
1060 as early as possible in order to facilitate early
1063 ftrace_dump_on_oops[=orig_cpu]
1064 [FTRACE] will dump the trace buffers on oops.
1065 If no parameter is passed, ftrace will dump
1066 buffers of all CPUs, but if you pass orig_cpu, it will
1067 dump only the buffer of the CPU that triggered the
1070 ftrace_filter=[function-list]
1071 [FTRACE] Limit the functions traced by the function
1072 tracer at boot up. function-list is a comma separated
1073 list of functions. This list can be changed at run
1074 time by the set_ftrace_filter file in the debugfs
1077 ftrace_notrace=[function-list]
1078 [FTRACE] Do not trace the functions specified in
1079 function-list. This list can be changed at run time
1080 by the set_ftrace_notrace file in the debugfs
1083 ftrace_graph_filter=[function-list]
1084 [FTRACE] Limit the top level callers functions traced
1085 by the function graph tracer at boot up.
1086 function-list is a comma separated list of functions
1087 that can be changed at run time by the
1088 set_graph_function file in the debugfs tracing directory.
1091 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1092 support via parallel port (up to 5 devices per port)
1093 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1094 See also Documentation/input/joystick-parport.txt
1098 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1102 gcov_persist= [GCOV] When non-zero (default), profiling data for
1103 kernel modules is saved and remains accessible via
1104 debugfs, even when the module is unloaded/reloaded.
1105 When zero, profiling data is discarded and associated
1106 debugfs files are removed at module unload time.
1108 gpt [EFI] Forces disk with valid GPT signature but
1109 invalid Protective MBR to be treated as GPT. If the
1110 primary GPT is corrupted, it enables the backup/alternate
1111 GPT to be used instead.
1113 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1114 the "Enable 0" bit of the configuration register.
1117 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1118 the "Enable 0" bit of the configuration register.
1121 grcan.select= [HW] Select which physical interface to use.
1124 grcan.txsize= [HW] Sets the size of the tx buffer.
1125 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1127 grcan.rxsize= [HW] Sets the size of the rx buffer.
1128 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1131 hashdist= [KNL,NUMA] Large hashes allocated during boot
1132 are distributed across NUMA nodes. Defaults on
1133 for 64-bit NUMA, off otherwise.
1134 Format: 0 | 1 (for off | on)
1136 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1138 hd= [EIDE] (E)IDE hard drive subsystem geometry
1139 Format: <cyl>,<head>,<sect>
1142 Disable Hardware Error Source Table (HEST) support;
1143 corresponding firmware-first mode error processing
1144 logic will be disabled.
1146 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1147 size of <nn>. This works even on boxes that have no
1148 highmem otherwise. This also works to reduce highmem
1149 size on bigger boxes.
1151 highres= [KNL] Enable/disable high resolution timer mode.
1152 Valid parameters: "on", "off"
1156 See Documentation/isdn/README.HiSax.
1160 hpet= [X86-32,HPET] option to control HPET usage
1161 Format: { enable (default) | disable | force |
1163 disable: disable HPET and use PIT instead
1164 force: allow force enabled of undocumented chips (ICH4,
1166 verbose: show contents of HPET registers during setup
1168 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1169 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1171 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1172 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1173 On x86-64 and powerpc, this option can be specified
1174 multiple times interleaved with hugepages= to reserve
1175 huge pages of different sizes. Valid pages sizes on
1176 x86-64 are 2M (when the CPU supports "pse") and 1G
1177 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1178 Note that 1GB pages can only be allocated at boot time
1179 using hugepages= and not freed afterwards.
1181 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1182 terminal devices. Valid values: 0..8
1183 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1184 If specified, z/VM IUCV HVC accepts connections
1185 from listed z/VM user IDs only.
1187 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1188 hardware thread id mappings.
1189 Format: <cpu>:<hwthread>
1192 Do not unregister boot console at start. This is only
1193 useful for debugging when something happens in the window
1194 between unregistering the boot console and initializing
1197 i2c_bus= [HW] Override the default board specific I2C bus speed
1198 or register an additional I2C bus that is not
1199 registered from board initialization code.
1203 i8042.debug [HW] Toggle i8042 debug mode
1204 i8042.direct [HW] Put keyboard port into non-translated mode
1205 i8042.dumbkbd [HW] Pretend that controller can only read data from
1206 keyboard and cannot control its state
1207 (Don't attempt to blink the leds)
1208 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1209 i8042.nokbd [HW] Don't check/create keyboard port
1210 i8042.noloop [HW] Disable the AUX Loopback command while probing
1212 i8042.nomux [HW] Don't check presence of an active multiplexing
1214 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1216 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1217 i8042.reset [HW] Reset the controller during init and cleanup
1218 i8042.unlock [HW] Unlock (ignore) the keylock
1222 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1223 indicates that the driver is running on unsupported
1225 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1226 does not match list of supported models.
1228 [HW] Report power status in /proc/i8k
1229 (disabled by default)
1230 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1233 i915.invert_brightness=
1234 [DRM] Invert the sense of the variable that is used to
1235 set the brightness of the panel backlight. Normally a
1236 brightness value of 0 indicates backlight switched off,
1237 and the maximum of the brightness value sets the backlight
1238 to maximum brightness. If this parameter is set to 0
1239 (default) and the machine requires it, or this parameter
1240 is set to 1, a brightness value of 0 sets the backlight
1241 to maximum brightness, and the maximum of the brightness
1242 value switches the backlight off.
1243 -1 -- never invert brightness
1244 0 -- machine default
1245 1 -- force brightness inversion
1248 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1250 ide-core.nodma= [HW] (E)IDE subsystem
1251 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1252 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1253 .cdrom .chs .ignore_cable are additional options
1254 See Documentation/ide/ide.txt.
1256 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1257 Claim all unknown PCI IDE storage controllers.
1260 Format: idle=poll, idle=halt, idle=nomwait
1261 Poll forces a polling idle loop that can slightly
1262 improve the performance of waking up a idle CPU, but
1263 will use a lot of power and make the system run hot.
1265 idle=halt: Halt is forced to be used for CPU idle.
1266 In such case C2/C3 won't be used again.
1267 idle=nomwait: Disable mwait for CPU C-states
1269 ignore_loglevel [KNL]
1270 Ignore loglevel setting - this will print /all/
1271 kernel messages to the console. Useful for debugging.
1272 We also add it as printk module parameter, so users
1273 could change it dynamically, usually by
1274 /sys/module/printk/parameters/ignore_loglevel.
1276 ihash_entries= [KNL]
1277 Set number of hash buckets for inode cache.
1279 ima_appraise= [IMA] appraise integrity measurements
1280 Format: { "off" | "enforce" | "fix" }
1283 ima_appraise_tcb [IMA]
1284 The builtin appraise policy appraises all files
1288 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1292 The list of supported hash algorithms is defined
1293 in crypto/hash_info.h.
1296 Load a policy which meets the needs of the Trusted
1297 Computing Base. This means IMA will measure all
1298 programs exec'd, files mmap'd for exec, and all files
1299 opened for read by uid=0.
1302 Select one of defined IMA measurements template formats.
1303 Formats: { "ima" | "ima-ng" }
1308 Run specified binary instead of /sbin/init as init
1311 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1312 for working out where the kernel is dying during
1315 initrd= [BOOT] Specify the location of the initial ramdisk
1317 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1320 int_pln_enable [x86] Enable power limit notification interrupt
1322 integrity_audit=[IMA]
1323 Format: { "0" | "1" }
1324 0 -- basic integrity auditing messages. (Default)
1325 1 -- additional integrity auditing messages.
1327 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1329 Enable intel iommu driver.
1331 Disable intel iommu driver.
1332 igfx_off [Default Off]
1333 By default, gfx is mapped as normal device. If a gfx
1334 device has a dedicated DMAR unit, the DMAR unit is
1335 bypassed by not enabling DMAR with this option. In
1336 this case, gfx device will use physical address for
1339 With this option iommu will not optimize to look
1340 for io virtual address below 32-bit forcing dual
1341 address cycle on pci bus for cards supporting greater
1342 than 32-bit addressing. The default is to look
1343 for translation below 32-bit and if not available
1344 then look in the higher range.
1345 strict [Default Off]
1346 With this option on every unmap_single operation will
1347 result in a hardware IOTLB flush operation as opposed
1348 to batching them for performance.
1349 sp_off [Default Off]
1350 By default, super page will be supported if Intel IOMMU
1351 has the capability. With this option, super page will
1354 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1355 0 disables intel_idle and fall back on acpi_idle.
1356 1 to 6 specify maximum depth of C-state.
1360 Do not enable intel_pstate as the default
1361 scaling driver for the supported processors
1363 intremap= [X86-64, Intel-IOMMU]
1364 on enable Interrupt Remapping (default)
1365 off disable Interrupt Remapping
1366 nosid disable Source ID checking
1368 BIOS x2APIC opt-out request will be ignored
1370 iomem= Disable strict checking of access to MMIO memory
1371 strict regions from userspace.
1388 io7= [HW] IO7 for Marvel based alpha systems
1389 See comment before marvel_specify_io7 in
1390 arch/alpha/kernel/core_marvel.c.
1392 io_delay= [X86] I/O delay method
1394 Standard port 0x80 based delay
1396 Alternate port 0xed based delay (needed on some systems)
1398 Simple two microseconds delay
1403 See Documentation/filesystems/nfs/nfsroot.txt.
1405 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1406 See comment before ip2_setup() in
1407 drivers/char/ip2/ip2base.c.
1410 When an interrupt is not handled search all handlers
1411 for it. Intended to get systems with badly broken
1415 When an interrupt is not handled search all handlers
1416 for it. Also check all handlers each timer
1417 interrupt. Intended to get systems with badly broken
1421 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1423 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1425 <cpu number>,...,<cpu number>
1427 <cpu number>-<cpu number>
1428 (must be a positive range in ascending order)
1430 <cpu number>,...,<cpu number>-<cpu number>
1432 This option can be used to specify one or more CPUs
1433 to isolate from the general SMP balancing and scheduling
1434 algorithms. You can move a process onto or off an
1435 "isolated" CPU via the CPU affinity syscalls or cpuset.
1436 <cpu number> begins at 0 and the maximum value is
1437 "number of CPUs in system - 1".
1439 This option is the preferred way to isolate CPUs. The
1440 alternative -- manually setting the CPU mask of all
1441 tasks in the system -- can cause problems and
1442 suboptimal load balancer performance.
1446 ivrs_ioapic [HW,X86_64]
1447 Provide an override to the IOAPIC-ID<->DEVICE-ID
1448 mapping provided in the IVRS ACPI table. For
1449 example, to map IOAPIC-ID decimal 10 to
1450 PCI device 00:14.0 write the parameter as:
1451 ivrs_ioapic[10]=00:14.0
1453 ivrs_hpet [HW,X86_64]
1454 Provide an override to the HPET-ID<->DEVICE-ID
1455 mapping provided in the IVRS ACPI table. For
1456 example, to map HPET-ID decimal 0 to
1457 PCI device 00:14.0 write the parameter as:
1458 ivrs_hpet[0]=00:14.0
1460 js= [HW,JOY] Analog joystick
1461 See Documentation/input/joystick.txt.
1465 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1466 specifies the amount of memory usable by the kernel
1467 for non-movable allocations. The requested amount is
1468 spread evenly throughout all nodes in the system. The
1469 remaining memory in each node is used for Movable
1470 pages. In the event, a node is too small to have both
1471 kernelcore and Movable pages, kernelcore pages will
1472 take priority and other nodes will have a larger number
1473 of Movable pages. The Movable zone is used for the
1474 allocation of pages that may be reclaimed or moved
1475 by the page migration subsystem. This means that
1476 HugeTLB pages may not be allocated from this zone.
1477 Note that allocations like PTEs-from-HighMem still
1478 use the HighMem zone if it exists, and the Normal
1479 zone if it does not.
1481 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1482 Format: <Controller#>[,poll interval]
1483 The controller # is the number of the ehci usb debug
1484 port as it is probed via PCI. The poll interval is
1485 optional and is the number seconds in between
1486 each poll cycle to the debug port in case you need
1487 the functionality for interrupting the kernel with
1488 gdb or control-c on the dbgp connection. When
1489 not using this parameter you use sysrq-g to break into
1490 the kernel debugger.
1492 kgdboc= [KGDB,HW] kgdb over consoles.
1493 Requires a tty driver that supports console polling,
1494 or a supported polling keyboard driver (non-usb).
1495 Serial only format: <serial_device>[,baud]
1496 keyboard only format: kbd
1497 keyboard and serial format: kbd,<serial_device>[,baud]
1498 Optional Kernel mode setting:
1499 kms, kbd format: kms,kbd
1500 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1502 kgdbwait [KGDB] Stop kernel execution and enter the
1503 kernel debugger at the earliest opportunity.
1505 kmac= [MIPS] korina ethernet MAC address.
1506 Configure the RouterBoard 532 series on-chip
1507 Ethernet adapter MAC address.
1509 kmemleak= [KNL] Boot-time kmemleak enable/disable
1510 Valid arguments: on, off
1513 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1514 Valid arguments: 0, 1, 2
1515 kmemcheck=0 (disabled)
1516 kmemcheck=1 (enabled)
1517 kmemcheck=2 (one-shot mode)
1518 Default: 2 (one-shot mode)
1520 kstack=N [X86] Print N words from the kernel stack
1523 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1524 Default is 0 (don't ignore, but inject #GP)
1526 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1530 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1531 Default is 1 (enabled)
1533 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1535 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1537 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1538 (virtualized MMU) support on capable Intel chips.
1539 Default is 1 (enabled)
1541 kvm-intel.emulate_invalid_guest_state=
1542 [KVM,Intel] Enable emulation of invalid guest states
1543 Default is 0 (disabled)
1545 kvm-intel.flexpriority=
1546 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1547 Default is 1 (enabled)
1550 [KVM,Intel] Enable VMX nesting (nVMX).
1551 Default is 0 (disabled)
1553 kvm-intel.unrestricted_guest=
1554 [KVM,Intel] Disable unrestricted guest feature
1555 (virtualized real and unpaged mode) on capable
1556 Intel chips. Default is 1 (enabled)
1558 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1559 feature (tagged TLBs) on capable Intel chips.
1560 Default is 1 (enabled)
1566 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1569 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1570 value for LAPIC timer one-shot implementation. Default
1571 back to the programmable timer unit in the LAPIC.
1573 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1576 libata.dma= [LIBATA] DMA control
1577 libata.dma=0 Disable all PATA and SATA DMA
1578 libata.dma=1 PATA and SATA Disk DMA only
1579 libata.dma=2 ATAPI (CDROM) DMA only
1580 libata.dma=4 Compact Flash DMA only
1581 Combinations also work, so libata.dma=3 enables DMA
1582 for disks and CDROMs, but not CFs.
1584 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1585 libata.ignore_hpa=0 keep BIOS limits (default)
1586 libata.ignore_hpa=1 ignore limits, using full disk
1588 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1592 libata.force= [LIBATA] Force configurations. The format is comma
1593 separated list of "[ID:]VAL" where ID is
1594 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1595 matching port, link or device. Basically, it matches
1596 the ATA ID string printed on console by libata. If
1597 the whole ID part is omitted, the last PORT and DEVICE
1598 values are used. If ID hasn't been specified yet, the
1599 configuration applies to all ports, links and devices.
1601 If only DEVICE is omitted, the parameter applies to
1602 the port and all links and devices behind it. DEVICE
1603 number of 0 either selects the first device or the
1604 first fan-out link behind PMP device. It does not
1605 select the host link. DEVICE number of 15 selects the
1606 host link and device attached to it.
1608 The VAL specifies the configuration to force. As long
1609 as there's no ambiguity shortcut notation is allowed.
1610 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1611 The following configurations can be forced.
1613 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1614 Any ID with matching PORT is used.
1616 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1618 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1619 udma[/][16,25,33,44,66,100,133] notation is also
1622 * [no]ncq: Turn on or off NCQ.
1624 * nohrst, nosrst, norst: suppress hard, soft
1627 * rstonce: only attempt one reset during
1628 hot-unplug link recovery
1630 * dump_id: dump IDENTIFY data.
1632 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1634 * disable: Disable this device.
1636 If there are multiple matching configurations changing
1637 the same attribute, the last one is used.
1639 memblock=debug [KNL] Enable memblock debug messages.
1641 load_ramdisk= [RAM] List of ramdisks to load from floppy
1642 See Documentation/blockdev/ramdisk.txt.
1644 lockd.nlm_grace_period=P [NFS] Assign grace period.
1647 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1650 lockd.nlm_timeout=T [NFS] Assign timeout value.
1653 lockd.nlm_udpport=M [NFS] Assign UDP port.
1656 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1659 loglevel= All Kernel Messages with a loglevel smaller than the
1660 console loglevel will be printed to the console. It can
1661 also be changed with klogd or other programs. The
1662 loglevels are defined as follows:
1664 0 (KERN_EMERG) system is unusable
1665 1 (KERN_ALERT) action must be taken immediately
1666 2 (KERN_CRIT) critical conditions
1667 3 (KERN_ERR) error conditions
1668 4 (KERN_WARNING) warning conditions
1669 5 (KERN_NOTICE) normal but significant condition
1670 6 (KERN_INFO) informational
1671 7 (KERN_DEBUG) debug-level messages
1673 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1674 in bytes. n must be a power of two. The default
1675 size is set in the kernel config file.
1677 logo.nologo [FB] Disables display of the built-in Linux logo.
1678 This may be used to provide more screen space for
1679 kernel log messages and is useful when debugging
1680 kernel boot problems.
1682 lp=0 [LP] Specify parallel ports to use, e.g,
1683 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1684 lp=reset first parallel port). 'lp=0' disables the
1685 lp=auto printer driver. 'lp=reset' (which can be
1686 specified in addition to the ports) causes
1687 attached printers to be reset. Using
1688 lp=port1,port2,... specifies the parallel ports
1689 to associate lp devices with, starting with
1690 lp0. A port specification may be 'none' to skip
1691 that lp device, or a parport name such as
1692 'parport0'. Specifying 'lp=auto' instead of a
1693 port specification list means that device IDs
1694 from each port should be examined, to see if
1695 an IEEE 1284-compliant printer is attached; if
1696 so, the driver will manage that printer.
1697 See also header of drivers/char/lp.c.
1700 Sets loops_per_jiffy to given constant, thus avoiding
1701 time-consuming boot-time autodetection (up to 250 ms per
1702 CPU). 0 enables autodetection (default). To determine
1703 the correct value for your kernel, boot with normal
1704 autodetection and see what value is printed. Note that
1705 on SMP systems the preset will be applied to all CPUs,
1706 which is likely to cause problems if your CPUs need
1707 significantly divergent settings. An incorrect value
1708 will cause delays in the kernel to be wrong, leading to
1709 unpredictable I/O errors and other breakage. Although
1710 unlikely, in the extreme case this might damage your
1714 Format: <io>,<irq>,<dma>
1716 machvec= [IA-64] Force the use of a particular machine-vector
1717 (machvec) in a generic kernel.
1718 Example: machvec=hpzx1_swiotlb
1720 machtype= [Loongson] Share the same kernel image file between different
1722 Example: machtype=lemote-yeeloong-2f-7inch
1724 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1725 than or equal to this physical address is ignored.
1727 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1728 should make use of. maxcpus=n : n >= 0 limits the
1729 kernel to using 'n' processors. n=0 is a special case,
1730 it is equivalent to "nosmp", which also disables
1733 max_loop= [LOOP] The number of loop block devices that get
1734 (loop.max_loop) unconditionally pre-created at init time. The default
1735 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1736 of statically allocating a predefined number, loop
1737 devices can be requested on-demand with the
1738 /dev/loop-control interface.
1740 mce [X86-32] Machine Check Exception
1742 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1744 md= [HW] RAID subsystems devices and level
1745 See Documentation/md.txt.
1748 Format: <first>,<last>
1749 Specifies range of consoles to be captured by the MDA.
1751 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1752 Amount of memory to be used when the kernel is not able
1753 to see the whole system memory or for test.
1754 [X86] Work as limiting max address. Use together
1755 with memmap= to avoid physical address space collisions.
1756 Without memmap= PCI devices could be placed at addresses
1757 belonging to unused RAM.
1759 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1763 [KNL,SH] Allow user to override the default size for
1764 per-device physically contiguous DMA buffers.
1766 memmap=exactmap [KNL,X86] Enable setting of an exact
1767 E820 memory map, as specified by the user.
1768 Such memmap=exactmap lines can be constructed based on
1769 BIOS output or other requirements. See the memmap=nn@ss
1772 memmap=nn[KMG]@ss[KMG]
1773 [KNL] Force usage of a specific region of memory.
1774 Region of memory to be used is from ss to ss+nn.
1776 memmap=nn[KMG]#ss[KMG]
1777 [KNL,ACPI] Mark specific memory as ACPI data.
1778 Region of memory to be marked is from ss to ss+nn.
1780 memmap=nn[KMG]$ss[KMG]
1781 [KNL,ACPI] Mark specific memory as reserved.
1782 Region of memory to be reserved is from ss to ss+nn.
1783 Example: Exclude memory from 0x18690000-0x1869ffff
1784 memmap=64K$0x18690000
1786 memmap=0x10000$0x18690000
1788 memory_corruption_check=0/1 [X86]
1789 Some BIOSes seem to corrupt the first 64k of
1790 memory when doing things like suspend/resume.
1791 Setting this option will scan the memory
1792 looking for corruption. Enabling this will
1793 both detect corruption and prevent the kernel
1794 from using the memory being corrupted.
1795 However, its intended as a diagnostic tool; if
1796 repeatable BIOS-originated corruption always
1797 affects the same memory, you can use memmap=
1798 to prevent the kernel from using that memory.
1800 memory_corruption_check_size=size [X86]
1801 By default it checks for corruption in the low
1802 64k, making this memory unavailable for normal
1803 use. Use this parameter to scan for
1804 corruption in more or less memory.
1806 memory_corruption_check_period=seconds [X86]
1807 By default it checks for corruption every 60
1808 seconds. Use this parameter to check at some
1809 other rate. 0 disables periodic checking.
1811 memtest= [KNL,X86] Enable memtest
1813 default : 0 <disable>
1814 Specifies the number of memtest passes to be
1815 performed. Each pass selects another test
1816 pattern from a given set of patterns. Memtest
1817 fills the memory with this pattern, validates
1818 memory contents and reserves bad memory
1819 regions that are detected.
1821 meye.*= [HW] Set MotionEye Camera parameters
1822 See Documentation/video4linux/meye.txt.
1824 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1825 Multi-Function General Purpose Timers on AMD Geode
1828 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1829 the BIOS has incorrectly applied a workaround. TinyBIOS
1830 version 0.98 is known to be affected, 0.99 fixes the
1831 problem by letting the user disable the workaround.
1835 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1836 physical address is ignored.
1838 mini2440= [ARM,HW,KNL]
1839 Format:[0..2][b][c][t]
1841 MINI2440 configuration specification:
1842 0 - The attached screen is the 3.5" TFT
1843 1 - The attached screen is the 7" TFT
1844 2 - The VGA Shield is attached (1024x768)
1845 Leaving out the screen size parameter will not load
1846 the TFT driver, and the framebuffer will be left
1848 b - Enable backlight. The TFT backlight pin will be
1849 linked to the kernel VESA blanking code and a GPIO
1850 LED. This parameter is not necessary when using the
1852 c - Enable the s3c camera interface.
1853 t - Reserved for enabling touchscreen support. The
1854 touchscreen support is not enabled in the mainstream
1855 kernel as of 2.6.30, a preliminary port can be found
1856 in the "bleeding edge" mini2440 support kernel at
1857 http://repo.or.cz/w/linux-2.6/mini2440.git
1860 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1861 parameter allows control of the logging verbosity for
1862 the additional memory initialisation checks. A value
1863 of 0 disables mminit logging and a level of 4 will
1864 log everything. Information is printed at KERN_DEBUG
1865 so loglevel=8 may also need to be specified.
1868 [KNL] When CONFIG_MODULE_SIG is set, this means that
1869 modules without (valid) signatures will fail to load.
1870 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1871 is always true, so this option does nothing.
1874 [MOUSE] Maximum time between finger touching and
1875 leaving touchpad surface for touch to be considered
1876 a tap and be reported as a left button click (for
1877 touchpads working in absolute mode only).
1879 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1880 reporting absolute coordinates, such as tablets
1881 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1882 reporting absolute coordinates, such as tablets
1884 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1885 is similar to kernelcore except it specifies the
1886 amount of memory used for migratable allocations.
1887 If both kernelcore and movablecore is specified,
1888 then kernelcore will be at *least* the specified
1889 value but may be more. If movablecore on its own
1890 is specified, the administrator must be careful
1891 that the amount of memory usable for all allocations
1894 movable_node [KNL,X86] Boot-time switch to enable the effects
1895 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1897 MTD_Partition= [MTD]
1898 Format: <name>,<region-number>,<size>,<offset>
1900 MTD_Region= [MTD] Format:
1901 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1904 See drivers/mtd/cmdlinepart.c.
1906 multitce=off [PPC] This parameter disables the use of the pSeries
1907 firmware feature for updating multiple TCE entries
1910 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1912 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1914 boundary - index of last SLC block on Flex-OneNAND.
1915 The remaining blocks are configured as MLC blocks.
1916 lock - Configure if Flex-OneNAND boundary should be locked.
1917 Once locked, the boundary cannot be changed.
1918 1 indicates lock status, 0 indicates unlock status.
1921 ARM/S3C2412 JIVE boot control
1923 See arch/arm/mach-s3c2412/mach-jive.c
1925 mtouchusb.raw_coordinates=
1926 [HW] Make the MicroTouch USB driver use raw coordinates
1927 ('y', default) or cooked coordinates ('n')
1929 mtrr_chunk_size=nn[KMG] [X86]
1930 used for mtrr cleanup. It is largest continuous chunk
1931 that could hold holes aka. UC entries.
1933 mtrr_gran_size=nn[KMG] [X86]
1934 Used for mtrr cleanup. It is granularity of mtrr block.
1936 Large value could prevent small alignment from
1939 mtrr_spare_reg_nr=n [X86]
1941 Range: 0,7 : spare reg number
1943 Used for mtrr cleanup. It is spare mtrr entries number.
1944 Set to 2 or more if your graphical card needs more.
1946 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1948 netdev= [NET] Network devices parameters
1949 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1950 Note that mem_start is often overloaded to mean
1951 something different and driver-specific.
1952 This usage is only documented in each driver source
1956 [NETFILTER] Enable connection tracking flow accounting
1957 0 to disable accounting
1958 1 to enable accounting
1961 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1962 See Documentation/filesystems/nfs/nfsroot.txt.
1964 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1965 See Documentation/filesystems/nfs/nfsroot.txt.
1967 nfsrootdebug [NFS] enable nfsroot debugging messages.
1968 See Documentation/filesystems/nfs/nfsroot.txt.
1970 nfs.callback_tcpport=
1971 [NFS] set the TCP port on which the NFSv4 callback
1972 channel should listen.
1975 [NFS] sets the pathname to the program which is used
1976 to update the NFS client cache entries.
1978 nfs.cache_getent_timeout=
1979 [NFS] sets the timeout after which an attempt to
1980 update a cache entry is deemed to have failed.
1982 nfs.idmap_cache_timeout=
1983 [NFS] set the maximum lifetime for idmapper cache
1987 [NFS] enable 64-bit inode numbers.
1988 If zero, the NFS client will fake up a 32-bit inode
1989 number for the readdir() and stat() syscalls instead
1990 of returning the full 64-bit number.
1991 The default is to return 64-bit inode numbers.
1993 nfs.max_session_slots=
1994 [NFSv4.1] Sets the maximum number of session slots
1995 the client will attempt to negotiate with the server.
1996 This limits the number of simultaneous RPC requests
1997 that the client can send to the NFSv4.1 server.
1998 Note that there is little point in setting this
1999 value higher than the max_tcp_slot_table_limit.
2001 nfs.nfs4_disable_idmapping=
2002 [NFSv4] When set to the default of '1', this option
2003 ensures that both the RPC level authentication
2004 scheme and the NFS level operations agree to use
2005 numeric uids/gids if the mount is using the
2006 'sec=sys' security flavour. In effect it is
2007 disabling idmapping, which can make migration from
2008 legacy NFSv2/v3 systems to NFSv4 easier.
2009 Servers that do not support this mode of operation
2010 will be autodetected by the client, and it will fall
2011 back to using the idmapper.
2012 To turn off this behaviour, set the value to '0'.
2014 [NFS4] Specify an additional fixed unique ident-
2015 ification string that NFSv4 clients can insert into
2016 their nfs_client_id4 string. This is typically a
2017 UUID that is generated at system install time.
2019 nfs.send_implementation_id =
2020 [NFSv4.1] Send client implementation identification
2021 information in exchange_id requests.
2022 If zero, no implementation identification information
2024 The default is to send the implementation identification
2027 nfs.recover_lost_locks =
2028 [NFSv4] Attempt to recover locks that were lost due
2029 to a lease timeout on the server. Please note that
2030 doing this risks data corruption, since there are
2031 no guarantees that the file will remain unchanged
2032 after the locks are lost.
2033 If you want to enable the kernel legacy behaviour of
2034 attempting to recover these locks, then set this
2036 The default parameter value of '0' causes the kernel
2037 not to attempt recovery of lost locks.
2039 nfsd.nfs4_disable_idmapping=
2040 [NFSv4] When set to the default of '1', the NFSv4
2041 server will return only numeric uids and gids to
2042 clients using auth_sys, and will accept numeric uids
2043 and gids from such clients. This is intended to ease
2044 migration from NFSv2/v3.
2046 objlayoutdriver.osd_login_prog=
2047 [NFS] [OBJLAYOUT] sets the pathname to the program which
2048 is used to automatically discover and login into new
2049 osd-targets. Please see:
2050 Documentation/filesystems/pnfs.txt for more explanations
2052 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2053 when a NMI is triggered.
2054 Format: [state][,regs][,debounce][,die]
2056 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2057 Format: [panic,][nopanic,][num]
2059 0 - turn nmi_watchdog off
2060 When panic is specified, panic when an NMI watchdog
2061 timeout occurs (or 'nopanic' to override the opposite
2063 This is useful when you use a panic=... timeout and
2064 need the box quickly up again.
2066 netpoll.carrier_timeout=
2067 [NET] Specifies amount of time (in seconds) that
2068 netpoll should wait for a carrier. By default netpoll
2071 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2072 emulation library even if a 387 maths coprocessor
2076 [HW] Never suspend the console
2077 Disable suspending of consoles during suspend and
2078 hibernate operations. Once disabled, debugging
2079 messages can reach various consoles while the rest
2080 of the system is being put to sleep (ie, while
2081 debugging driver suspend/resume hooks). This may
2082 not work reliably with all consoles, but is known
2083 to work with serial and VGA consoles.
2084 To facilitate more flexible debugging, we also add
2085 console_suspend, a printk module parameter to control
2086 it. Users could use console_suspend (usually
2087 /sys/module/printk/parameters/console_suspend) to
2088 turn on/off it dynamically.
2090 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2091 caches in the slab allocator. Saves per-node memory,
2092 but will impact performance.
2096 noapic [SMP,APIC] Tells the kernel to not make use of any
2097 IOAPICs that may be present in the system.
2100 Disable kernel and module base offset ASLR (Address
2101 Space Layout Randomization) if built into the kernel.
2103 noautogroup Disable scheduler automatic task group creation.
2105 nobats [PPC] Do not use BATs for mapping kernel lowmem
2106 on "Classic" PPC cores.
2110 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2112 nodelayacct [KNL] Disable per-task delay accounting
2114 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2116 nodsp [SH] Disable hardware DSP at boot time.
2118 noefi [X86] Disable EFI runtime services support.
2123 On X86-32 available only on PAE configured kernels.
2124 noexec=on: enable non-executable mappings (default)
2125 noexec=off: disable non-executable mappings
2128 Disable SMAP (Supervisor Mode Access Prevention)
2129 even if it is supported by processor.
2132 Disable SMEP (Supervisor Mode Execution Prevention)
2133 even if it is supported by processor.
2136 This affects only 32-bit executables.
2137 noexec32=on: enable non-executable mappings (default)
2138 read doesn't imply executable mappings
2139 noexec32=off: disable non-executable mappings
2140 read implies executable mappings
2142 nofpu [SH] Disable hardware FPU at boot time.
2144 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2145 register save and restore. The kernel will only save
2146 legacy floating-point registers on task switch.
2148 noxsave [BUGS=X86] Disables x86 extended register state save
2149 and restore using xsave. The kernel will fallback to
2150 enabling legacy floating-point and sse state.
2153 on enable eager fpu restore
2154 off disable eager fpu restore
2155 auto selects the default scheme, which automatically
2156 enables eagerfpu restore for xsaveopt.
2158 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2159 wfi(ARM) instruction doesn't work correctly and not to
2160 use it. This is also useful when using JTAG debugger.
2162 no_file_caps Tells the kernel not to honor file capabilities. The
2163 only way then for a file to be executed with privilege
2164 is to be setuid root or executed by root.
2166 nohalt [IA-64] Tells the kernel not to use the power saving
2167 function PAL_HALT_LIGHT when idle. This increases
2168 power-consumption. On the positive side, it reduces
2169 interrupt wake-up latency, which may improve performance
2170 in certain environments such as networked servers or
2173 nohz= [KNL] Boottime enable/disable dynamic ticks
2174 Valid arguments: on, off
2177 nohz_full= [KNL,BOOT]
2178 In kernels built with CONFIG_NO_HZ_FULL=y, set
2179 the specified list of CPUs whose tick will be stopped
2180 whenever possible. The boot CPU will be forced outside
2181 the range to maintain the timekeeping.
2182 The CPUs in this range must also be included in the
2185 noiotrap [SH] Disables trapped I/O port accesses.
2187 noirqdebug [X86-32] Disables the code which attempts to detect and
2188 disable unhandled interrupt sources.
2190 no_timer_check [X86,APIC] Disables the code which tests for
2191 broken timer IRQ sources.
2193 noisapnp [ISAPNP] Disables ISA PnP code.
2195 noinitrd [RAM] Tells the kernel not to load any configured
2198 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2200 [Deprecated - use intremap=off]
2204 nojitter [IA-64] Disables jitter checking for ITC timers.
2206 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2208 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2211 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2212 steal time is computed, but won't influence scheduler
2215 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2217 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2219 noltlbs [PPC] Do not use large page/tlb entries for kernel
2220 lowmem mapping on PPC40x.
2222 nomca [IA-64] Disable machine check abort handling
2224 nomce [X86-32] Machine Check Exception
2226 nomfgpt [X86-32] Disable Multi-Function General Purpose
2227 Timer usage (for AMD Geode machines).
2229 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2230 shutdown the other cpus. Instead use the REBOOT_VECTOR
2233 nomodule Disable module load
2235 nopat [X86] Disable PAT (page attribute table extension of
2236 pagetables) support.
2238 norandmaps Don't use address space randomization. Equivalent to
2239 echo 0 > /proc/sys/kernel/randomize_va_space
2241 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2243 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2244 with UP alternatives
2246 nordrand [X86] Disable kernel use of the RDRAND and
2247 RDSEED instructions even if they are supported
2248 by the processor. RDRAND and RDSEED are still
2249 available to user space applications.
2251 noresume [SWSUSP] Disables resume and restores original swap
2254 no-scroll [VGA] Disables scrollback.
2255 This is required for the Braillex ib80-piezo Braille
2256 reader made by F.H. Papenmeier (Germany).
2260 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2262 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2263 and disable the IO APIC. legacy for "maxcpus=0".
2265 nosoftlockup [KNL] Disable the soft-lockup detector.
2267 nosync [HW,M68K] Disables sync negotiation for all devices.
2269 notsc [BUGS=X86-32] Disable Time Stamp Counter
2271 nousb [USB] Disable the USB subsystem
2273 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2277 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2279 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2280 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2281 Some features depend on CPU0. Known dependencies are:
2282 1. Resume from suspend/hibernate depends on CPU0.
2283 Suspend/hibernate will fail if CPU0 is offline and you
2284 need to online CPU0 before suspend/hibernate.
2285 2. PIC interrupts also depend on CPU0. CPU0 can't be
2286 removed if a PIC interrupt is detected.
2287 It's said poweroff/reboot may depend on CPU0 on some
2288 machines although I haven't seen such issues so far
2289 after CPU0 is offline on a few tested machines.
2290 If the dependencies are under your control, you can
2291 turn on cpu0_hotplug.
2293 nptcg= [IA-64] Override max number of concurrent global TLB
2294 purges which is reported from either PAL_VM_SUMMARY or
2297 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2298 could support. nr_cpus=n : n >= 1 limits the kernel to
2299 supporting 'n' processors. Later in runtime you can not
2300 use hotplug cpu feature to put more cpu back to online.
2301 just like you compile the kernel NR_CPUS=n
2303 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2305 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2306 Allowed values are enable and disable
2308 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2309 one of ['zone', 'node', 'default'] can be specified
2310 This can be set from sysctl after boot.
2311 See Documentation/sysctl/vm.txt for details.
2313 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2314 See Documentation/debugging-via-ohci1394.txt for more
2317 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2318 Rather than timing out after 20 ms if an EC
2319 command is not properly ACKed, override the length
2320 of the timeout. We have interrupts disabled while
2321 waiting for the ACK, so if this is set too high
2322 interrupts *may* be lost!
2324 omap_mux= [OMAP] Override bootloader pin multiplexing.
2325 Format: <mux_mode0.mode_name=value>...
2326 For example, to override I2C bus2:
2327 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2329 oprofile.timer= [HW]
2330 Use timer interrupt instead of performance counters
2332 oprofile.cpu_type= Force an oprofile cpu type
2333 This might be useful if you have an older oprofile
2334 userland or if you want common events.
2335 Format: { arch_perfmon }
2336 arch_perfmon: [X86] Force use of architectural
2337 perfmon on Intel CPUs instead of the
2338 CPU specific event set.
2339 timer: [X86] Force use of architectural NMI
2340 timer mode (see also oprofile.timer
2341 for generic hr timer mode)
2342 [s390] Force legacy basic mode sampling
2343 (report cpu_type "timer")
2345 oops=panic Always panic on oopses. Default is to just kill the
2346 process, but there is a small probability of
2347 deadlocking the machine.
2348 This will also cause panics on machine check exceptions.
2349 Useful together with panic=30 to trigger a reboot.
2352 See Documentation/sound/oss/oss-parameters.txt
2354 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2355 timeout > 0: seconds before rebooting
2356 timeout = 0: wait forever
2357 timeout < 0: reboot immediately
2360 parkbd.port= [HW] Parallel port number the keyboard adapter is
2361 connected to, default is 0.
2363 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2364 0 for XT, 1 for AT (default is AT).
2367 parport= [HW,PPT] Specify parallel ports. 0 disables.
2368 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2369 Use 'auto' to force the driver to use any
2370 IRQ/DMA settings detected (the default is to
2371 ignore detected IRQ/DMA settings because of
2372 possible conflicts). You can specify the base
2373 address, IRQ, and DMA settings; IRQ and DMA
2374 should be numbers, or 'auto' (for using detected
2375 settings on that particular port), or 'nofifo'
2376 (to avoid using a FIFO even if it is detected).
2377 Parallel ports are assigned in the order they
2378 are specified on the command line, starting
2381 parport_init_mode= [HW,PPT]
2382 Configure VIA parallel port to operate in
2383 a specific mode. This is necessary on Pegasos
2384 computer where firmware has no options for setting
2385 up parallel port mode and sets it to spp.
2386 Currently this function knows 686a and 8231 chips.
2387 Format: [spp|ps2|epp|ecp|ecpepp]
2390 Halt all CPUs after the first oops has been printed for
2391 the specified number of seconds. This is to be used if
2392 your oopses keep scrolling off the screen.
2397 See header of drivers/block/paride/pcd.c.
2398 See also Documentation/blockdev/paride.txt.
2400 pci=option[,option...] [PCI] various PCI subsystem options:
2401 earlydump [X86] dump PCI config space before the kernel
2403 off [X86] don't probe for the PCI bus
2404 bios [X86-32] force use of PCI BIOS, don't access
2405 the hardware directly. Use this if your machine
2406 has a non-standard PCI host bridge.
2407 nobios [X86-32] disallow use of PCI BIOS, only direct
2408 hardware access methods are allowed. Use this
2409 if you experience crashes upon bootup and you
2410 suspect they are caused by the BIOS.
2411 conf1 [X86] Force use of PCI Configuration
2413 conf2 [X86] Force use of PCI Configuration
2415 noaer [PCIE] If the PCIEAER kernel config parameter is
2416 enabled, this kernel boot option can be used to
2417 disable the use of PCIE advanced error reporting.
2418 nodomains [PCI] Disable support for multiple PCI
2419 root domains (aka PCI segments, in ACPI-speak).
2420 nommconf [X86] Disable use of MMCONFIG for PCI
2422 check_enable_amd_mmconf [X86] check for and enable
2423 properly configured MMIO access to PCI
2424 config space on AMD family 10h CPU
2425 nomsi [MSI] If the PCI_MSI kernel config parameter is
2426 enabled, this kernel boot option can be used to
2427 disable the use of MSI interrupts system-wide.
2428 noioapicquirk [APIC] Disable all boot interrupt quirks.
2429 Safety option to keep boot IRQs enabled. This
2430 should never be necessary.
2431 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2432 primary IO-APIC for bridges that cannot disable
2433 boot IRQs. This fixes a source of spurious IRQs
2434 when the system masks IRQs.
2435 noioapicreroute [APIC] Disable workaround that uses the
2436 boot IRQ equivalent of an IRQ that connects to
2437 a chipset where boot IRQs cannot be disabled.
2438 The opposite of ioapicreroute.
2439 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2440 routing table. These calls are known to be buggy
2441 on several machines and they hang the machine
2442 when used, but on other computers it's the only
2443 way to get the interrupt routing table. Try
2444 this option if the kernel is unable to allocate
2445 IRQs or discover secondary PCI buses on your
2447 rom [X86] Assign address space to expansion ROMs.
2448 Use with caution as certain devices share
2449 address decoders between ROMs and other
2451 norom [X86] Do not assign address space to
2452 expansion ROMs that do not already have
2453 BIOS assigned address ranges.
2454 nobar [X86] Do not assign address space to the
2455 BARs that weren't assigned by the BIOS.
2456 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2457 assigned automatically to PCI devices. You can
2458 make the kernel exclude IRQs of your ISA cards
2460 pirqaddr=0xAAAAA [X86] Specify the physical address
2461 of the PIRQ table (normally generated
2462 by the BIOS) if it is outside the
2463 F0000h-100000h range.
2464 lastbus=N [X86] Scan all buses thru bus #N. Can be
2465 useful if the kernel is unable to find your
2466 secondary buses and you want to tell it
2467 explicitly which ones they are.
2468 assign-busses [X86] Always assign all PCI bus
2469 numbers ourselves, overriding
2470 whatever the firmware may have done.
2471 usepirqmask [X86] Honor the possible IRQ mask stored
2472 in the BIOS $PIR table. This is needed on
2473 some systems with broken BIOSes, notably
2474 some HP Pavilion N5400 and Omnibook XE3
2475 notebooks. This will have no effect if ACPI
2476 IRQ routing is enabled.
2477 noacpi [X86] Do not use ACPI for IRQ routing
2478 or for PCI scanning.
2479 use_crs [X86] Use PCI host bridge window information
2480 from ACPI. On BIOSes from 2008 or later, this
2481 is enabled by default. If you need to use this,
2482 please report a bug.
2483 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2484 If you need to use this, please report a bug.
2485 routeirq Do IRQ routing for all PCI devices.
2486 This is normally done in pci_enable_device(),
2487 so this option is a temporary workaround
2488 for broken drivers that don't call it.
2489 skip_isa_align [X86] do not align io start addr, so can
2490 handle more pci cards
2491 firmware [ARM] Do not re-enumerate the bus but instead
2492 just use the configuration from the
2493 bootloader. This is currently used on
2494 IXP2000 systems where the bus has to be
2495 configured a certain way for adjunct CPUs.
2496 noearly [X86] Don't do any early type 1 scanning.
2497 This might help on some broken boards which
2498 machine check when some devices' config space
2499 is read. But various workarounds are disabled
2500 and some IOMMU drivers will not work.
2501 bfsort Sort PCI devices into breadth-first order.
2502 This sorting is done to get a device
2503 order compatible with older (<= 2.4) kernels.
2504 nobfsort Don't sort PCI devices into breadth-first order.
2505 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2506 tuning and use the BIOS-configured MPS defaults.
2507 pcie_bus_safe Set every device's MPS to the largest value
2508 supported by all devices below the root complex.
2509 pcie_bus_perf Set device MPS to the largest allowable MPS
2510 based on its parent bus. Also set MRRS (Max
2511 Read Request Size) to the largest supported
2512 value (no larger than the MPS that the device
2513 or bus can support) for best performance.
2514 pcie_bus_peer2peer Set every device's MPS to 128B, which
2515 every device is guaranteed to support. This
2516 configuration allows peer-to-peer DMA between
2517 any pair of devices, possibly at the cost of
2518 reduced performance. This also guarantees
2519 that hot-added devices will work.
2520 cbiosize=nn[KMG] The fixed amount of bus space which is
2521 reserved for the CardBus bridge's IO window.
2522 The default value is 256 bytes.
2523 cbmemsize=nn[KMG] The fixed amount of bus space which is
2524 reserved for the CardBus bridge's memory
2525 window. The default value is 64 megabytes.
2528 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2529 Specifies alignment and device to reassign
2530 aligned memory resources.
2531 If <order of align> is not specified,
2532 PAGE_SIZE is used as alignment.
2533 PCI-PCI bridge can be specified, if resource
2534 windows need to be expanded.
2535 ecrc= Enable/disable PCIe ECRC (transaction layer
2536 end-to-end CRC checking).
2537 bios: Use BIOS/firmware settings. This is the
2541 hpiosize=nn[KMG] The fixed amount of bus space which is
2542 reserved for hotplug bridge's IO window.
2543 Default size is 256 bytes.
2544 hpmemsize=nn[KMG] The fixed amount of bus space which is
2545 reserved for hotplug bridge's memory window.
2546 Default size is 2 megabytes.
2547 realloc= Enable/disable reallocating PCI bridge resources
2548 if allocations done by BIOS are too small to
2549 accommodate resources required by all child
2551 off: Turn realloc off
2553 realloc same as realloc=on
2554 noari do not use PCIe ARI.
2555 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2556 only look for one device below a PCIe downstream
2559 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2562 force Enable ASPM even on devices that claim not to support it.
2563 WARNING: Forcing ASPM on may cause system lockups.
2565 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2566 nomsi Do not use MSI for PCI Express Native Hotplug (this
2567 makes all PCIe ports use INTx for hotplug services).
2569 pcie_ports= [PCIE] PCIe ports handling:
2570 auto Ask the BIOS whether or not to use native PCIe services
2571 associated with PCIe ports (PME, hot-plug, AER). Use
2572 them only if that is allowed by the BIOS.
2573 native Use native PCIe services associated with PCIe ports
2575 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2578 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2579 nomsi Do not use MSI for native PCIe PME signaling (this makes
2580 all PCIe root ports use INTx for all services).
2582 pcmv= [HW,PCMCIA] BadgePAD 4
2586 Keep all power-domains already enabled by bootloader on,
2587 even if no driver has claimed them. This is useful
2588 for debug and development, but should not be
2589 needed on a platform with proper driver support.
2592 See Documentation/blockdev/paride.txt.
2594 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2597 See arch/parisc/kernel/pdc_chassis.c
2599 percpu_alloc= Select which percpu first chunk allocator to use.
2600 Currently supported values are "embed" and "page".
2601 Archs may support subset or none of the selections.
2602 See comments in mm/percpu.c for details on each
2603 allocator. This parameter is primarily for debugging
2604 and performance comparison.
2607 See Documentation/blockdev/paride.txt.
2610 See Documentation/blockdev/paride.txt.
2612 pirq= [SMP,APIC] Manual mp-table setup
2613 See Documentation/x86/i386/IO-APIC.txt.
2615 plip= [PPT,NET] Parallel port network link
2616 Format: { parport<nr> | timid | 0 }
2617 See also Documentation/parport.txt.
2619 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2620 Override pmtimer IOPort with a hex value.
2624 Enable PNP debug messages (depends on the
2625 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2626 via /sys/module/pnp/parameters/debug. We always show
2627 current resource usage; turning this on also shows
2628 possible settings and some assignment information.
2634 { on | off | curr | res | no-curr | no-res }
2637 [ISAPNP] Exclude IRQs for the autoconfiguration
2640 [ISAPNP] Exclude DMAs for the autoconfiguration
2642 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2643 Ranges are in pairs (I/O port base and size).
2646 [ISAPNP] Exclude memory regions for the
2648 Ranges are in pairs (memory base and size).
2650 ports= [IP_VS_FTP] IPVS ftp helper module
2652 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2654 Format: <port>,<port>....
2656 print-fatal-signals=
2657 [KNL] debug: print fatal signals
2659 If enabled, warn about various signal handling
2660 related application anomalies: too many signals,
2661 too many POSIX.1 timers, fatal signals causing a
2664 If you hit the warning due to signal overflow,
2665 you might want to try "ulimit -i unlimited".
2669 printk.always_kmsg_dump=
2670 Trigger kmsg_dump for cases other than kernel oops or
2672 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2675 printk.time= Show timing data prefixed to each printk message line
2676 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2678 processor.max_cstate= [HW,ACPI]
2679 Limit processor to maximum C-state
2680 max_cstate=9 overrides any DMI blacklist limit.
2682 processor.nocst [HW,ACPI]
2683 Ignore the _CST method to determine C-states,
2684 instead using the legacy FADT method
2686 profile= [KNL] Enable kernel profiling via /proc/profile
2687 Format: [schedule,]<number>
2688 Param: "schedule" - profile schedule points.
2689 Param: <number> - step/bucket size as a power of 2 for
2690 statistical time based profiling.
2691 Param: "sleep" - profile D-state sleeping (millisecs).
2692 Requires CONFIG_SCHEDSTATS
2693 Param: "kvm" - profile VM exits.
2695 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2697 See Documentation/blockdev/ramdisk.txt.
2699 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2700 probe for; one of (bare|imps|exps|lifebook|any).
2701 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2703 psmouse.resetafter= [HW,MOUSE]
2704 Try to reset the device after so many bad packets
2707 [HW,MOUSE] Set desired mouse resolution, in dpi.
2708 psmouse.smartscroll=
2709 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2710 0 = disabled, 1 = enabled (default).
2712 pstore.backend= Specify the name of the pstore backend to use
2715 See Documentation/blockdev/paride.txt.
2718 [KNL] Number of legacy pty's. Overwrites compiled-in
2721 quiet [KNL] Disable most log messages
2726 See Documentation/md.txt.
2728 ramdisk_blocksize= [RAM]
2729 See Documentation/blockdev/ramdisk.txt.
2731 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2732 See Documentation/blockdev/ramdisk.txt.
2735 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2736 the specified list of CPUs to be no-callback CPUs.
2737 Invocation of these CPUs' RCU callbacks will
2738 be offloaded to "rcuox/N" kthreads created for
2739 that purpose, where "x" is "b" for RCU-bh, "p"
2740 for RCU-preempt, and "s" for RCU-sched, and "N"
2741 is the CPU number. This reduces OS jitter on the
2742 offloaded CPUs, which can be useful for HPC and
2743 real-time workloads. It can also improve energy
2744 efficiency for asymmetric multiprocessors.
2747 Rather than requiring that offloaded CPUs
2748 (specified by rcu_nocbs= above) explicitly
2749 awaken the corresponding "rcuoN" kthreads,
2750 make these kthreads poll for callbacks.
2751 This improves the real-time response for the
2752 offloaded CPUs by relieving them of the need to
2753 wake up the corresponding kthread, but degrades
2754 energy efficiency by requiring that the kthreads
2755 periodically wake up to do the polling.
2757 rcutree.blimit= [KNL]
2758 Set maximum number of finished RCU callbacks to
2759 process in one batch.
2761 rcutree.rcu_fanout_leaf= [KNL]
2762 Increase the number of CPUs assigned to each
2763 leaf rcu_node structure. Useful for very large
2766 rcutree.jiffies_till_first_fqs= [KNL]
2767 Set delay from grace-period initialization to
2768 first attempt to force quiescent states.
2769 Units are jiffies, minimum value is zero,
2770 and maximum value is HZ.
2772 rcutree.jiffies_till_next_fqs= [KNL]
2773 Set delay between subsequent attempts to force
2774 quiescent states. Units are jiffies, minimum
2775 value is one, and maximum value is HZ.
2777 rcutree.qhimark= [KNL]
2778 Set threshold of queued RCU callbacks beyond which
2779 batch limiting is disabled.
2781 rcutree.qlowmark= [KNL]
2782 Set threshold of queued RCU callbacks below which
2783 batch limiting is re-enabled.
2785 rcutree.rcu_idle_gp_delay= [KNL]
2786 Set wakeup interval for idle CPUs that have
2787 RCU callbacks (RCU_FAST_NO_HZ=y).
2789 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2790 Set wakeup interval for idle CPUs that have
2791 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2792 Lazy RCU callbacks are those which RCU can
2793 prove do nothing more than free memory.
2795 rcutorture.fqs_duration= [KNL]
2796 Set duration of force_quiescent_state bursts.
2798 rcutorture.fqs_holdoff= [KNL]
2799 Set holdoff time within force_quiescent_state bursts.
2801 rcutorture.fqs_stutter= [KNL]
2802 Set wait time between force_quiescent_state bursts.
2804 rcutorture.gp_exp= [KNL]
2805 Use expedited update-side primitives.
2807 rcutorture.gp_normal= [KNL]
2808 Use normal (non-expedited) update-side primitives.
2809 If both gp_exp and gp_normal are set, do both.
2810 If neither gp_exp nor gp_normal are set, still
2813 rcutorture.n_barrier_cbs= [KNL]
2814 Set callbacks/threads for rcu_barrier() testing.
2816 rcutorture.nfakewriters= [KNL]
2817 Set number of concurrent RCU writers. These just
2818 stress RCU, they don't participate in the actual
2819 test, hence the "fake".
2821 rcutorture.nreaders= [KNL]
2822 Set number of RCU readers.
2824 rcutorture.object_debug= [KNL]
2825 Enable debug-object double-call_rcu() testing.
2827 rcutorture.onoff_holdoff= [KNL]
2828 Set time (s) after boot for CPU-hotplug testing.
2830 rcutorture.onoff_interval= [KNL]
2831 Set time (s) between CPU-hotplug operations, or
2832 zero to disable CPU-hotplug testing.
2834 rcutorture.rcutorture_runnable= [BOOT]
2835 Start rcutorture running at boot time.
2837 rcutorture.shuffle_interval= [KNL]
2838 Set task-shuffle interval (s). Shuffling tasks
2839 allows some CPUs to go into dyntick-idle mode
2840 during the rcutorture test.
2842 rcutorture.shutdown_secs= [KNL]
2843 Set time (s) after boot system shutdown. This
2844 is useful for hands-off automated testing.
2846 rcutorture.stall_cpu= [KNL]
2847 Duration of CPU stall (s) to test RCU CPU stall
2848 warnings, zero to disable.
2850 rcutorture.stall_cpu_holdoff= [KNL]
2851 Time to wait (s) after boot before inducing stall.
2853 rcutorture.stat_interval= [KNL]
2854 Time (s) between statistics printk()s.
2856 rcutorture.stutter= [KNL]
2857 Time (s) to stutter testing, for example, specifying
2858 five seconds causes the test to run for five seconds,
2859 wait for five seconds, and so on. This tests RCU's
2860 ability to transition abruptly to and from idle.
2862 rcutorture.test_boost= [KNL]
2863 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2864 "Maybe" means test if the RCU implementation
2865 under test support RCU priority boosting.
2867 rcutorture.test_boost_duration= [KNL]
2868 Duration (s) of each individual boost test.
2870 rcutorture.test_boost_interval= [KNL]
2871 Interval (s) between each boost test.
2873 rcutorture.test_no_idle_hz= [KNL]
2874 Test RCU's dyntick-idle handling. See also the
2875 rcutorture.shuffle_interval parameter.
2877 rcutorture.torture_type= [KNL]
2878 Specify the RCU implementation to test.
2880 rcutorture.verbose= [KNL]
2881 Enable additional printk() statements.
2883 rcupdate.rcu_expedited= [KNL]
2884 Use expedited grace-period primitives, for
2885 example, synchronize_rcu_expedited() instead
2886 of synchronize_rcu(). This reduces latency,
2887 but can increase CPU utilization, degrade
2888 real-time latency, and degrade energy efficiency.
2890 rcupdate.rcu_cpu_stall_suppress= [KNL]
2891 Suppress RCU CPU stall warning messages.
2893 rcupdate.rcu_cpu_stall_timeout= [KNL]
2894 Set timeout for RCU CPU stall warning messages.
2898 Run specified binary instead of /init from the ramdisk,
2899 used for early userspace startup. See initrd.
2902 Format (x86 or x86_64):
2903 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2905 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2907 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2908 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2909 reboot_force is either force or not specified,
2910 reboot_cpu is s[mp]#### with #### being the processor
2911 to be used for rebooting.
2914 [KNL, SMP] Set scheduler's default relax_domain_level.
2915 See Documentation/cgroups/cpusets.txt.
2917 relative_sleep_states=
2918 [SUSPEND] Use sleep state labeling where the deepest
2919 state available other than hibernation is always "mem".
2920 Format: { "0" | "1" }
2921 0 -- Traditional sleep state labels.
2922 1 -- Relative sleep state labels.
2924 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2926 reservetop= [X86-32]
2928 Reserves a hole at the top of the kernel virtual
2933 Set the amount of memory to reserve for BIOS at
2934 the bottom of the address space.
2936 reset_devices [KNL] Force drivers to reset the underlying device
2937 during initialization.
2940 Specify the partition device for software suspend
2942 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2944 resume_offset= [SWSUSP]
2945 Specify the offset from the beginning of the partition
2946 given by "resume=" at which the swap header is located,
2947 in <PAGE_SIZE> units (needed only for swap files).
2948 See Documentation/power/swsusp-and-swap-files.txt
2950 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2951 read the resume files
2953 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2954 Useful for devices that are detected asynchronously
2955 (e.g. USB and MMC devices).
2957 hibernate= [HIBERNATION]
2958 noresume Don't check if there's a hibernation image
2959 present during boot.
2960 nocompress Don't compress/decompress hibernation images.
2962 retain_initrd [RAM] Keep initrd memory after extraction
2964 rhash_entries= [KNL,NET]
2965 Set number of hash buckets for route cache
2967 ro [KNL] Mount root device read-only on boot
2969 root= [KNL] Root filesystem
2970 See name_to_dev_t comment in init/do_mounts.c.
2972 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2973 mount the root filesystem
2975 rootflags= [KNL] Set root filesystem mount option string
2977 rootfstype= [KNL] Set root filesystem type
2979 rootwait [KNL] Wait (indefinitely) for root device to show up.
2980 Useful for devices that are detected asynchronously
2981 (e.g. USB and MMC devices).
2983 rproc_mem=nn[KMG][@address]
2984 [KNL,ARM,CMA] Remoteproc physical memory block.
2985 Memory area to be used by remote processor image,
2988 rw [KNL] Mount root device read-write on boot
2990 S [KNL] Run init in single mode
2993 See drivers/net/irda/sa1100_ir.c.
2995 sbni= [NET] Granch SBNI12 leased line adapter
2997 sched_debug [KNL] Enables verbose scheduler debug messages.
2999 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3000 xtime_lock contention on larger systems, and/or RCU lock
3001 contention on all systems with CONFIG_MAXSMP set.
3002 Format: { "0" | "1" }
3003 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3005 Note: increases power consumption, thus should only be
3006 enabled if running jitter sensitive (HPC/RT) workloads.
3008 security= [SECURITY] Choose a security module to enable at boot.
3009 If this boot parameter is not specified, only the first
3010 security module asking for security registration will be
3011 loaded. An invalid security module name will be treated
3012 as if no module has been chosen.
3014 selinux= [SELINUX] Disable or enable SELinux at boot time.
3015 Format: { "0" | "1" }
3016 See security/selinux/Kconfig help text.
3019 Default value is set via kernel config option.
3020 If enabled at boot time, /selinux/disable can be used
3021 later to disable prior to initial policy load.
3023 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3024 Format: { "0" | "1" }
3025 See security/apparmor/Kconfig help text
3028 Default value is set via kernel config option.
3030 serialnumber [BUGS=X86-32]
3033 Maximal number of shapers.
3035 show_msr= [x86] show boot-time MSR settings
3036 Format: { <integer> }
3037 Show boot-time (BIOS-initialized) MSR settings.
3038 The parameter means the number of CPUs to show,
3039 for example 1 means boot CPU only.
3046 slab_max_order= [MM, SLAB]
3047 Determines the maximum allowed order for slabs.
3048 A high setting may cause OOMs due to memory
3049 fragmentation. Defaults to 1 for systems with
3050 more than 32MB of RAM, 0 otherwise.
3052 slub_debug[=options[,slabs]] [MM, SLUB]
3053 Enabling slub_debug allows one to determine the
3054 culprit if slab objects become corrupted. Enabling
3055 slub_debug can create guard zones around objects and
3056 may poison objects when not in use. Also tracks the
3057 last alloc / free. For more information see
3058 Documentation/vm/slub.txt.
3060 slub_max_order= [MM, SLUB]
3061 Determines the maximum allowed order for slabs.
3062 A high setting may cause OOMs due to memory
3063 fragmentation. For more information see
3064 Documentation/vm/slub.txt.
3066 slub_min_objects= [MM, SLUB]
3067 The minimum number of objects per slab. SLUB will
3068 increase the slab order up to slub_max_order to
3069 generate a sufficiently large slab able to contain
3070 the number of objects indicated. The higher the number
3071 of objects the smaller the overhead of tracking slabs
3072 and the less frequently locks need to be acquired.
3073 For more information see Documentation/vm/slub.txt.
3075 slub_min_order= [MM, SLUB]
3076 Determines the minimum page order for slabs. Must be
3077 lower than slub_max_order.
3078 For more information see Documentation/vm/slub.txt.
3080 slub_nomerge [MM, SLUB]
3081 Disable merging of slabs with similar size. May be
3082 necessary if there is some reason to distinguish
3083 allocs to different slabs. Debug options disable
3084 merging on their own.
3085 For more information see Documentation/vm/slub.txt.
3088 Format: <io1>[,<io2>[,...,<io8>]]
3090 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3091 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3092 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3093 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3094 smsc-ircc2.ircc_irq= [HW] IRQ line
3095 smsc-ircc2.ircc_dma= [HW] DMA channel
3096 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3097 0: Toshiba Satellite 1800 (GP data pin select)
3098 1: Fast pin select (default)
3102 [KNL] Should the soft-lockup detector generate panics.
3105 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3106 See Documentation/laptops/sonypi.txt
3108 spia_io_base= [HW,MTD]
3114 Enabled the stack tracer on boot up.
3116 stacktrace_filter=[function-list]
3117 [FTRACE] Limit the functions that the stack tracer
3118 will trace at boot up. function-list is a comma separated
3119 list of functions. This list can be changed at run
3120 time by the stack_trace_filter file in the debugfs
3121 tracing directory. Note, this enables stack tracing
3122 and the stacktrace above is not needed.
3126 Set the STI (builtin display/keyboard on the HP-PARISC
3127 machines) console (graphic card) which should be used
3128 as the initial boot-console.
3129 See also comment in drivers/video/console/sticore.c.
3132 See comment in drivers/video/console/sticore.c.
3135 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3137 sunrpc.min_resvport=
3138 sunrpc.max_resvport=
3140 SunRPC servers often require that client requests
3141 originate from a privileged port (i.e. a port in the
3142 range 0 < portnr < 1024).
3143 An administrator who wishes to reserve some of these
3144 ports for other uses may adjust the range that the
3145 kernel's sunrpc client considers to be privileged
3146 using these two parameters to set the minimum and
3147 maximum port values.
3151 Control how the NFS server code allocates CPUs to
3152 service thread pools. Depending on how many NICs
3153 you have and where their interrupts are bound, this
3154 option will affect which CPUs will do NFS serving.
3155 Note: this parameter cannot be changed while the
3156 NFS server is running.
3158 auto the server chooses an appropriate mode
3159 automatically using heuristics
3160 global a single global pool contains all CPUs
3161 percpu one pool for each CPU
3162 pernode one pool for each NUMA node (equivalent
3163 to global on non-NUMA machines)
3165 sunrpc.tcp_slot_table_entries=
3166 sunrpc.udp_slot_table_entries=
3168 Sets the upper limit on the number of simultaneous
3169 RPC calls that can be sent from the client to a
3170 server. Increasing these values may allow you to
3171 improve throughput, but will also increase the
3172 amount of memory reserved for use by the client.
3175 [KNL] Enable accounting of swap in memory resource
3176 controller if no parameter or 1 is given or disable
3177 it if 0 is given (See Documentation/cgroups/memory.txt)
3179 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3180 Format: { <int> | force }
3181 <int> -- Number of I/O TLB slabs
3182 force -- force using of bounce buffers even if they
3183 wouldn't be automatically used by the kernel
3187 sysfs.deprecated=0|1 [KNL]
3188 Enable/disable old style sysfs layout for old udev
3189 on older distributions. When this option is enabled
3190 very new udev will not work anymore. When this option
3191 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3192 in older udev will not work anymore.
3193 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3194 the kernel configuration.
3196 sysrq_always_enabled
3198 Ignore sysrq setting - this boot parameter will
3199 neutralize any effect of /proc/sys/kernel/sysrq.
3200 Useful for debugging.
3204 test_suspend= [SUSPEND]
3205 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3206 standby suspend) as the system sleep state to briefly
3207 enter during system startup. The system is woken from
3208 this state using a wakeup-capable RTC alarm.
3210 thash_entries= [KNL,NET]
3211 Set number of hash buckets for TCP connection
3213 thermal.act= [HW,ACPI]
3214 -1: disable all active trip points in all thermal zones
3215 <degrees C>: override all lowest active trip points
3217 thermal.crt= [HW,ACPI]
3218 -1: disable all critical trip points in all thermal zones
3219 <degrees C>: override all critical trip points
3221 thermal.nocrt= [HW,ACPI]
3222 Set to disable actions on ACPI thermal zone
3223 critical and hot trip points.
3225 thermal.off= [HW,ACPI]
3226 1: disable ACPI thermal control
3228 thermal.psv= [HW,ACPI]
3229 -1: disable all passive trip points
3230 <degrees C>: override all passive trip points to this
3233 thermal.tzp= [HW,ACPI]
3234 Specify global default ACPI thermal zone polling rate
3235 <deci-seconds>: poll all this frequency
3236 0: no polling (default)
3239 Force threading of all interrupt handlers except those
3240 marked explicitly IRQF_NO_THREAD.
3243 Enable the Transcendent memory driver if built-in.
3245 tmem.cleancache=0|1 [KNL, XEN]
3246 Default is on (1). Disable the usage of the cleancache
3247 API to send anonymous pages to the hypervisor.
3249 tmem.frontswap=0|1 [KNL, XEN]
3250 Default is on (1). Disable the usage of the frontswap
3251 API to send swap pages to the hypervisor. If disabled
3252 the selfballooning and selfshrinking are force disabled.
3254 tmem.selfballooning=0|1 [KNL, XEN]
3255 Default is on (1). Disable the driving of swap pages
3258 tmem.selfshrinking=0|1 [KNL, XEN]
3259 Default is on (1). Partial swapoff that immediately
3260 transfers pages from Xen hypervisor back to the
3261 kernel based on different criteria.
3265 Specify if the kernel should make use of the cpu
3266 topology information if the hardware supports this.
3267 The scheduler will make use of this information and
3268 e.g. base its process migration decisions on it.
3273 tpm_suspend_pcr=[HW,TPM]
3274 Format: integer pcr id
3275 Specify that at suspend time, the tpm driver
3276 should extend the specified pcr with zeros,
3277 as a workaround for some chips which fail to
3278 flush the last written pcr on TPM_SaveState.
3279 This will guarantee that all the other pcrs
3282 trace_buf_size=nn[KMG]
3283 [FTRACE] will set tracing buffer size.
3285 trace_event=[event-list]
3286 [FTRACE] Set and start specified trace events in order
3287 to facilitate early boot debugging.
3288 See also Documentation/trace/events.txt
3290 trace_options=[option-list]
3291 [FTRACE] Enable or disable tracer options at boot.
3292 The option-list is a comma delimited list of options
3293 that can be enabled or disabled just as if you were
3294 to echo the option name into
3296 /sys/kernel/debug/tracing/trace_options
3298 For example, to enable stacktrace option (to dump the
3299 stack trace of each event), add to the command line:
3301 trace_options=stacktrace
3303 See also Documentation/trace/ftrace.txt "trace options"
3307 [FTRACE] enable this option to disable tracing when a
3308 warning is hit. This turns off "tracing_on". Tracing can
3309 be enabled again by echoing '1' into the "tracing_on"
3310 file located in /sys/kernel/debug/tracing/
3312 This option is useful, as it disables the trace before
3313 the WARNING dump is called, which prevents the trace to
3314 be filled with content caused by the warning output.
3316 This option can also be set at run time via the sysctl
3317 option: kernel/traceoff_on_warning
3319 transparent_hugepage=
3321 Format: [always|madvise|never]
3322 Can be used to control the default behavior of the system
3323 with respect to transparent hugepages.
3324 See Documentation/vm/transhuge.txt for more details.
3326 tsc= Disable clocksource stability checks for TSC.
3328 [x86] reliable: mark tsc clocksource as reliable, this
3329 disables clocksource verification at runtime, as well
3330 as the stability checks done at bootup. Used to enable
3331 high-resolution timer mode on older hardware, and in
3332 virtualized environment.
3333 [x86] noirqtime: Do not use TSC to do irq accounting.
3334 Used to run time disable IRQ_TIME_ACCOUNTING on any
3335 platforms where RDTSC is slow and this accounting
3338 turbografx.map[2|3]= [HW,JOY]
3339 TurboGraFX parallel port interface
3341 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3342 See also Documentation/input/joystick-parport.txt
3344 udbg-immortal [PPC] When debugging early kernel crashes that
3345 happen after console_init() and before a proper
3346 console driver takes over, this boot options might
3347 help "seeing" what's going on.
3349 uhash_entries= [KNL,NET]
3350 Set number of hash buckets for UDP/UDP-Lite connections
3353 [USB] Ignore overcurrent events (default N).
3354 Some badly-designed motherboards generate lots of
3355 bogus events, for ports that aren't wired to
3356 anything. Set this parameter to avoid log spamming.
3357 Note that genuine overcurrent events won't be
3361 [X86] Cause panic on unknown NMI.
3363 usbcore.authorized_default=
3364 [USB] Default USB device authorization:
3365 (default -1 = authorized except for wireless USB,
3366 0 = not authorized, 1 = authorized)
3368 usbcore.autosuspend=
3369 [USB] The autosuspend time delay (in seconds) used
3370 for newly-detected USB devices (default 2). This
3371 is the time required before an idle device will be
3372 autosuspended. Devices for which the delay is set
3373 to a negative value won't be autosuspended at all.
3375 usbcore.usbfs_snoop=
3376 [USB] Set to log all usbfs traffic (default 0 = off).
3378 usbcore.blinkenlights=
3379 [USB] Set to cycle leds on hubs (default 0 = off).
3381 usbcore.old_scheme_first=
3382 [USB] Start with the old device initialization
3383 scheme (default 0 = off).
3385 usbcore.usbfs_memory_mb=
3386 [USB] Memory limit (in MB) for buffers allocated by
3387 usbfs (default = 16, 0 = max = 2047).
3389 usbcore.use_both_schemes=
3390 [USB] Try the other device initialization scheme
3391 if the first one fails (default 1 = enabled).
3393 usbcore.initial_descriptor_timeout=
3394 [USB] Specifies timeout for the initial 64-byte
3395 USB_REQ_GET_DESCRIPTOR request in milliseconds
3396 (default 5000 = 5.0 seconds).
3399 [USBHID] The interval which mice are to be polled at.
3401 usb-storage.delay_use=
3402 [UMS] The delay in seconds before a new device is
3403 scanned for Logical Units (default 5).
3406 [UMS] A list of quirks entries to supplement or
3407 override the built-in unusual_devs list. List
3408 entries are separated by commas. Each entry has
3409 the form VID:PID:Flags where VID and PID are Vendor
3410 and Product ID values (4-digit hex numbers) and
3411 Flags is a set of characters, each corresponding
3412 to a common usb-storage quirk flag as follows:
3413 a = SANE_SENSE (collect more than 18 bytes
3415 b = BAD_SENSE (don't collect more than 18
3416 bytes of sense data);
3417 c = FIX_CAPACITY (decrease the reported
3418 device capacity by one sector);
3419 d = NO_READ_DISC_INFO (don't use
3420 READ_DISC_INFO command);
3421 e = NO_READ_CAPACITY_16 (don't use
3422 READ_CAPACITY_16 command);
3423 h = CAPACITY_HEURISTICS (decrease the
3424 reported device capacity by one
3425 sector if the number is odd);
3426 i = IGNORE_DEVICE (don't bind to this
3428 l = NOT_LOCKABLE (don't try to lock and
3429 unlock ejectable media);
3430 m = MAX_SECTORS_64 (don't transfer more
3431 than 64 sectors = 32 KB at a time);
3432 n = INITIAL_READ10 (force a retry of the
3433 initial READ(10) command);
3434 o = CAPACITY_OK (accept the capacity
3435 reported by the device);
3436 p = WRITE_CACHE (the device cache is ON
3438 r = IGNORE_RESIDUE (the device reports
3439 bogus residue values);
3440 s = SINGLE_LUN (the device has only one
3442 w = NO_WP_DETECT (don't test whether the
3443 medium is write-protected).
3444 Example: quirks=0419:aaf5:rl,0421:0433:rc
3446 user_debug= [KNL,ARM]
3448 See arch/arm/Kconfig.debug help text.
3449 1 - undefined instruction events
3451 4 - invalid data aborts
3454 Example: user_debug=31
3457 [X86] Flags controlling user PTE allocations.
3459 nohigh = do not allocate PTE pages in
3460 HIGHMEM regardless of setting
3464 On X86_32, this is an alias for vdso32=. Otherwise:
3466 vdso=1: enable VDSO (the default)
3467 vdso=0: disable VDSO mapping
3469 vdso32= [X86] Control the 32-bit vDSO
3470 vdso32=1: enable 32-bit VDSO
3471 vdso32=0 or vdso32=2: disable 32-bit VDSO
3473 See the help text for CONFIG_COMPAT_VDSO for more
3474 details. If CONFIG_COMPAT_VDSO is set, the default is
3475 vdso32=0; otherwise, the default is vdso32=1.
3477 For compatibility with older kernels, vdso32=2 is an
3480 Try vdso32=0 if you encounter an error that says:
3481 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3484 vector=percpu: enable percpu vector domain
3486 video= [FB] Frame buffer configuration
3487 See Documentation/fb/modedb.txt.
3489 video.brightness_switch_enabled= [0,1]
3490 If set to 1, on receiving an ACPI notify event
3491 generated by hotkey, video driver will adjust brightness
3492 level and then send out the event to user space through
3493 the allocated input device; If set to 0, video driver
3494 will only send out the event without touching backlight
3499 [VMMIO] Memory mapped virtio (platform) device.
3501 <size>@<baseaddr>:<irq>[:<id>]
3503 <size> := size (can use standard suffixes
3505 <baseaddr> := physical base address
3506 <irq> := interrupt number (as passed to
3508 <id> := (optional) platform device id
3510 virtio_mmio.device=1K@0x100b0000:48:7
3512 Can be used multiple times for multiple devices.
3514 vga= [BOOT,X86-32] Select a particular video mode
3515 See Documentation/x86/boot.txt and
3516 Documentation/svga.txt.
3517 Use vga=ask for menu.
3518 This is actually a boot loader parameter; the value is
3519 passed to the kernel using a special protocol.
3521 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3522 size of <nn>. This can be used to increase the
3523 minimum size (128MB on x86). It can also be used to
3524 decrease the size and leave more room for directly
3527 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3530 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3533 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3537 Controls the behavior of vsyscalls (i.e. calls to
3538 fixed addresses of 0xffffffffff600x00 from legacy
3539 code). Most statically-linked binaries and older
3540 versions of glibc use these calls. Because these
3541 functions are at fixed addresses, they make nice
3542 targets for exploits that can control RIP.
3544 emulate [default] Vsyscalls turn into traps and are
3545 emulated reasonably safely.
3547 native Vsyscalls are native syscall instructions.
3548 This is a little bit faster than trapping
3549 and makes a few dynamic recompilers work
3550 better than they would in emulation mode.
3551 It also makes exploits much easier to write.
3553 none Vsyscalls don't work at all. This makes
3554 them quite hard to use for exploits but
3555 might break your system.
3557 vt.color= [VT] Default text color.
3558 Format: 0xYX, X = foreground, Y = background.
3559 Default: 0x07 = light gray on black.
3561 vt.cur_default= [VT] Default cursor shape.
3562 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3563 the parameters of the <Esc>[?A;B;Cc escape sequence;
3564 see VGA-softcursor.txt. Default: 2 = underline.
3566 vt.default_blu= [VT]
3567 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3568 Change the default blue palette of the console.
3569 This is a 16-member array composed of values
3572 vt.default_grn= [VT]
3573 Format: <green0>,<green1>,<green2>,...,<green15>
3574 Change the default green palette of the console.
3575 This is a 16-member array composed of values
3578 vt.default_red= [VT]
3579 Format: <red0>,<red1>,<red2>,...,<red15>
3580 Change the default red palette of the console.
3581 This is a 16-member array composed of values
3587 Set system-wide default UTF-8 mode for all tty's.
3588 Default is 1, i.e. UTF-8 mode is enabled for all
3589 newly opened terminals.
3591 vt.global_cursor_default=
3594 Set system-wide default for whether a cursor
3595 is shown on new VTs. Default is -1,
3596 i.e. cursors will be created by default unless
3597 overridden by individual drivers. 0 will hide
3598 cursors, 1 will display them.
3600 vt.italic= [VT] Default color for italic text; 0-15.
3603 vt.underline= [VT] Default color for underlined text; 0-15.
3606 watchdog timers [HW,WDT] For information on watchdog timers,
3607 see Documentation/watchdog/watchdog-parameters.txt
3608 or other driver-specific files in the
3609 Documentation/watchdog/ directory.
3611 workqueue.disable_numa
3612 By default, all work items queued to unbound
3613 workqueues are affine to the NUMA nodes they're
3614 issued on, which results in better behavior in
3615 general. If NUMA affinity needs to be disabled for
3616 whatever reason, this option can be used. Note
3617 that this also can be controlled per-workqueue for
3618 workqueues visible under /sys/bus/workqueue/.
3620 workqueue.power_efficient
3621 Per-cpu workqueues are generally preferred because
3622 they show better performance thanks to cache
3623 locality; unfortunately, per-cpu workqueues tend to
3624 be more power hungry than unbound workqueues.
3626 Enabling this makes the per-cpu workqueues which
3627 were observed to contribute significantly to power
3628 consumption unbound, leading to measurably lower
3629 power usage at the cost of small performance
3632 The default value of this parameter is determined by
3633 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3635 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3636 default x2apic cluster mode on platforms
3639 x86_intel_mid_timer= [X86-32,APBT]
3640 Choose timer option for x86 Intel MID platform.
3641 Two valid options are apbt timer only and lapic timer
3642 plus one apbt timer for broadcast timer.
3643 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3645 xen_emul_unplug= [HW,X86,XEN]
3646 Unplug Xen emulated devices
3647 Format: [unplug0,][unplug1]
3648 ide-disks -- unplug primary master IDE devices
3649 aux-ide-disks -- unplug non-primary-master IDE devices
3650 nics -- unplug network devices
3651 all -- unplug all emulated devices (NICs and IDE disks)
3652 unnecessary -- unplugging emulated devices is
3653 unnecessary even if the host did not respond to
3655 never -- do not unplug even if version check succeeds
3657 xen_nopvspin [X86,XEN]
3658 Disables the ticketlock slowpath using Xen PV
3661 xirc2ps_cs= [NET,PCMCIA]
3663 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3665 ______________________________________________________________________
3669 Add more DRM drivers.