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
634 Sets the size of kernel global memory area for contiguous
635 memory allocations. For more information, see
636 include/linux/dma-contiguous.h
638 cmo_free_hint= [PPC] Format: { yes | no }
639 Specify whether pages are marked as being inactive
640 when they are freed. This is used in CMO environments
641 to determine OS memory pressure for page stealing by
645 coherent_pool=nn[KMG] [ARM,KNL]
646 Sets the size of memory pool for coherent, atomic dma
647 allocations, by default set to 256K.
649 code_bytes [X86] How many bytes of object code to print
654 com20020= [HW,NET] ARCnet - COM20020 chipset
656 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
658 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
662 ARCnet - COM90xx chipset (memory-mapped buffers)
663 Format: <io>[,<irq>[,<memstart>]]
665 condev= [HW,S390] console device
668 console= [KNL] Output console device and options.
670 tty<n> Use the virtual console device <n>.
674 Use the specified serial port. The options are of
675 the form "bbbbpnf", where "bbbb" is the baud rate,
676 "p" is parity ("n", "o", or "e"), "n" is number of
677 bits, and "f" is flow control ("r" for RTS or
678 omit it). Default is "9600n8".
680 See Documentation/serial-console.txt for more
682 Documentation/networking/netconsole.txt for an
685 uart[8250],io,<addr>[,options]
686 uart[8250],mmio,<addr>[,options]
687 Start an early, polled-mode console on the 8250/16550
688 UART at the specified I/O port or MMIO address,
689 switching to the matching ttyS device later. The
690 options are the same as for ttyS, above.
691 hvc<n> Use the hypervisor console device <n>. This is for
692 both Xen and PowerPC hypervisors.
694 If the device connected to the port is not a TTY but a braille
695 device, prepend "brl," before the device type, for instance
697 For now, only VisioBraille is supported.
699 consoleblank= [KNL] The console blank (screen saver) timeout in
700 seconds. Defaults to 10*60 = 10mins. A value of 0
701 disables the blank timer.
704 [KNL] Change the default value for
705 /proc/<pid>/coredump_filter.
706 See also Documentation/filesystems/proc.txt.
708 cpuidle.off=1 [CPU_IDLE]
709 disable the cpuidle sub-system
711 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
713 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
715 crashkernel=size[KMG][@offset[KMG]]
716 [KNL] Using kexec, Linux can switch to a 'crash kernel'
717 upon panic. This parameter reserves the physical
718 memory region [offset, offset + size] for that kernel
719 image. If '@offset' is omitted, then a suitable offset
720 is selected automatically. Check
721 Documentation/kdump/kdump.txt for further details.
723 crashkernel=range1:size1[,range2:size2,...][@offset]
724 [KNL] Same as above, but depends on the memory
725 in the running system. The syntax of range is
726 start-[end] where start and end are both
727 a memory unit (amount[KMG]). See also
728 Documentation/kdump/kdump.txt for an example.
730 crashkernel=size[KMG],high
731 [KNL, x86_64] range could be above 4G. Allow kernel
732 to allocate physical memory region from top, so could
733 be above 4G if system have more than 4G ram installed.
734 Otherwise memory region will be allocated below 4G, if
736 It will be ignored if crashkernel=X is specified.
737 crashkernel=size[KMG],low
738 [KNL, x86_64] range under 4G. When crashkernel=X,high
739 is passed, kernel could allocate physical memory region
740 above 4G, that cause second kernel crash on system
741 that require some amount of low memory, e.g. swiotlb
742 requires at least 64M+32K low memory. Kernel would
743 try to allocate 72M below 4G automatically.
744 This one let user to specify own low range under 4G
745 for second kernel instead.
746 0: to disable low allocation.
747 It will be ignored when crashkernel=X,high is not used
748 or memory reserved is below 4G.
753 cs89x0_media= [HW,NET]
754 Format: { rj45 | aui | bnc }
757 See header of drivers/s390/block/dasd_devmap.c.
759 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
760 (one device per port)
761 Format: <port#>,<type>
762 See also Documentation/input/joystick-parport.txt
764 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
765 time. See Documentation/dynamic-debug-howto.txt for
766 details. Deprecated, see dyndbg.
768 debug [KNL] Enable kernel debugging (events log level).
771 [KNL] verbose self-tests
773 Print debugging info while doing the locking API
775 We default to 0 (no extra messages), setting it to
776 1 will print _a lot_ more information - normally
777 only useful to kernel developers.
779 debug_objects [KNL] Enable object debugging
782 [KNL] Disable object debugging
784 debug_guardpage_minorder=
785 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
786 parameter allows control of the order of pages that will
787 be intentionally kept free (and hence protected) by the
788 buddy allocator. Bigger value increase the probability
789 of catching random memory corruption, but reduce the
790 amount of memory for normal system use. The maximum
791 possible value is MAX_ORDER/2. Setting this parameter
792 to 1 or 2 should be enough to identify most random
793 memory corruption problems caused by bugs in kernel or
794 driver code when a CPU writes to (or reads from) a
795 random memory location. Note that there exists a class
796 of memory corruptions problems caused by buggy H/W or
797 F/W or by drivers badly programing DMA (basically when
798 memory is written at bus level and the CPU MMU is
799 bypassed) which are not detectable by
800 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
801 tracking down these problems.
803 debugpat [X86] Enable PAT debugging
805 decnet.addr= [HW,NET]
806 Format: <area>[,<node>]
807 See also Documentation/networking/decnet.txt.
810 [same as hugepagesz=] The size of the default
811 HugeTLB page size. This is the size represented by
812 the legacy /proc/ hugepages APIs, used for SHM, and
813 default size when mounting hugetlbfs filesystems.
814 Defaults to the default architecture's huge page size
818 Set number of hash buckets for dentry cache.
821 See Documentation/networking/ipv6.txt.
823 disable_cpu_apicid= [X86,APIC,SMP]
825 The number of initial APIC ID for the
826 corresponding CPU to be disabled at boot,
827 mostly used for the kdump 2nd kernel to
828 disable BSP to wake up multiple CPUs without
829 causing system reset or hang due to sending
832 disable_ddw [PPC/PSERIES]
833 Disable Dynamic DMA Window support. Use this if
834 to workaround buggy firmware.
837 See Documentation/networking/ipv6.txt.
839 disable_mtrr_cleanup [X86]
840 The kernel tries to adjust MTRR layout from continuous
841 to discrete, to make X server driver able to add WB
842 entry later. This parameter disables that.
844 disable_mtrr_trim [X86, Intel and AMD only]
845 By default the kernel will trim any uncacheable
846 memory out of your available memory pool based on
847 MTRR settings. This parameter disables that behavior,
848 possibly causing your machine to run very slowly.
850 disable_timer_pin_1 [X86]
851 Disable PIN 1 of APIC timer
852 Can be useful to work around chipset bugs.
854 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
855 this option disables the debugging code at boot.
857 dma_debug_entries=<number>
858 This option allows to tune the number of preallocated
859 entries for DMA-API debugging code. One entry is
860 required per DMA-API allocation. Use this if the
861 DMA-API debugging code disables itself because the
862 architectural default is too low.
864 dma_debug_driver=<driver_name>
865 With this option the DMA-API debugging driver
866 filter feature can be enabled at boot time. Just
867 pass the driver to filter for as the parameter.
868 The filter can be disabled or changed to another
869 driver later using sysfs.
871 drm_kms_helper.edid_firmware=[<connector>:]<file>
872 Broken monitors, graphic adapters and KVMs may
873 send no or incorrect EDID data sets. This parameter
874 allows to specify an EDID data set in the
875 /lib/firmware directory that is used instead.
876 Generic built-in EDID data sets are used, if one of
877 edid/1024x768.bin, edid/1280x1024.bin,
878 edid/1680x1050.bin, or edid/1920x1080.bin is given
879 and no file with the same name exists. Details and
880 instructions how to build your own EDID data are
881 available in Documentation/EDID/HOWTO.txt. An EDID
882 data set will only be used for a particular connector,
883 if its name and a colon are prepended to the EDID
888 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
889 module.dyndbg[="val"]
890 Enable debug messages at boot time. See
891 Documentation/dynamic-debug-howto.txt for details.
893 early_ioremap_debug [KNL]
894 Enable debug messages in early_ioremap support. This
895 is useful for tracking down temporary early mappings
896 which are not unmapped.
898 earlycon= [KNL] Output early console device and options.
900 uart[8250],io,<addr>[,options]
901 uart[8250],mmio,<addr>[,options]
902 uart[8250],mmio32,<addr>[,options]
903 Start an early, polled-mode console on the 8250/16550
904 UART at the specified I/O port or MMIO address.
905 MMIO inter-register address stride is either 8-bit
906 (mmio) or 32-bit (mmio32).
907 The options are the same as for ttyS, above.
910 Start an early, polled-mode console on a pl011 serial
911 port at the specified address. The pl011 serial port
912 must already be setup and configured. Options are not
915 smh Use ARM semihosting calls for early console.
917 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
921 earlyprintk=serial[,ttySn[,baudrate]]
922 earlyprintk=serial[,0x...[,baudrate]]
923 earlyprintk=ttySn[,baudrate]
924 earlyprintk=dbgp[debugController#]
926 earlyprintk is useful when the kernel crashes before
927 the normal console is initialized. It is not enabled by
928 default because it has some cosmetic problems.
930 Append ",keep" to not disable it when the real console
933 Only one of vga, efi, serial, or usb debug port can
936 Currently only ttyS0 and ttyS1 may be specified by
937 name. Other I/O ports may be explicitly specified
938 on some architectures (x86 and arm at least) by
939 replacing ttySn with an I/O port address, like this:
940 earlyprintk=serial,0x1008,115200
941 You can find the port for a given device in
942 /proc/tty/driver/serial:
943 2: uart:ST16650V2 port:00001008 irq:18 ...
945 Interaction with the standard serial driver is not
948 The VGA and EFI output is eventually overwritten by
951 The xen output can only be used by Xen PV guests.
953 edac_report= [HW,EDAC] Control how to report EDAC event
954 Format: {"on" | "off" | "force"}
955 on: enable EDAC to report H/W event. May be overridden
956 by other higher priority error reporting module.
957 off: disable H/W event reporting through EDAC.
958 force: enforce the use of EDAC to report H/W event.
961 ekgdboc= [X86,KGDB] Allow early kernel console debugging
964 This is designed to be used in conjunction with
965 the boot argument: earlyprintk=vga
968 Format: {"off" | "on" | "skip[mbr]"}
971 Format: { "old_map" }
972 old_map [X86-64]: switch to the old ioremap-based EFI
973 runtime services mapping. 32-bit still uses this one by
976 efi_no_storage_paranoia [EFI; X86]
977 Using this parameter you can use more than 50% of
978 your efi variable storage. Use this parameter only if
979 you are really sure that your UEFI does sane gc and
980 fulfills the spec otherwise your board may brick.
982 eisa_irq_edge= [PARISC,HW]
983 See header of drivers/parisc/eisa.c.
986 See comment before function elanfreq_setup() in
987 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
990 Format: {"cfq" | "deadline" | "noop"}
991 See Documentation/block/cfq-iosched.txt and
992 Documentation/block/deadline-iosched.txt for details.
994 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
995 Specifies physical address of start of kernel core
996 image elf header and optionally the size. Generally
997 kexec loader will pass this option to capture kernel.
998 See Documentation/kdump/kdump.txt for details.
1000 enable_mtrr_cleanup [X86]
1001 The kernel tries to adjust MTRR layout from continuous
1002 to discrete, to make X server driver able to add WB
1003 entry later. This parameter enables that.
1005 enable_timer_pin_1 [X86]
1006 Enable PIN 1 of APIC timer
1007 Can be useful to work around chipset bugs
1008 (in particular on some ATI chipsets).
1009 The kernel tries to set a reasonable default.
1011 enforcing [SELINUX] Set initial enforcing status.
1013 See security/selinux/Kconfig help text.
1014 0 -- permissive (log only, no denials).
1015 1 -- enforcing (deny and log).
1017 Value can be changed at runtime via /selinux/enforce.
1020 Disable Error Record Serialization Table (ERST)
1023 ether= [HW,NET] Ethernet cards parameters
1024 This option is obsoleted by the "netdev=" option, which
1025 has equivalent usage. See its documentation for details.
1029 Permit 'security.evm' to be updated regardless of
1030 current integrity status.
1034 fail_make_request=[KNL]
1035 General fault injection mechanism.
1036 Format: <interval>,<probability>,<space>,<times>
1037 See also Documentation/fault-injection/.
1040 See Documentation/blockdev/floppy.txt.
1042 force_pal_cache_flush
1043 [IA-64] Avoid check_sal_cache_flush which may hang on
1044 buggy SAL_CACHE_FLUSH implementations. Using this
1045 parameter will force ia64_sal_cache_flush to call
1046 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1049 Forcefully enable Physical Address Extension (PAE).
1050 Many Pentium M systems disable PAE but may have a
1051 functionally usable PAE implementation.
1052 Warning: use of this parameter will taint the kernel
1053 and may cause unknown problems.
1056 [FTRACE] will set and start the specified tracer
1057 as early as possible in order to facilitate early
1060 ftrace_dump_on_oops[=orig_cpu]
1061 [FTRACE] will dump the trace buffers on oops.
1062 If no parameter is passed, ftrace will dump
1063 buffers of all CPUs, but if you pass orig_cpu, it will
1064 dump only the buffer of the CPU that triggered the
1067 ftrace_filter=[function-list]
1068 [FTRACE] Limit the functions traced by the function
1069 tracer at boot up. function-list is a comma separated
1070 list of functions. This list can be changed at run
1071 time by the set_ftrace_filter file in the debugfs
1074 ftrace_notrace=[function-list]
1075 [FTRACE] Do not trace the functions specified in
1076 function-list. This list can be changed at run time
1077 by the set_ftrace_notrace file in the debugfs
1080 ftrace_graph_filter=[function-list]
1081 [FTRACE] Limit the top level callers functions traced
1082 by the function graph tracer at boot up.
1083 function-list is a comma separated list of functions
1084 that can be changed at run time by the
1085 set_graph_function file in the debugfs tracing directory.
1088 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1089 support via parallel port (up to 5 devices per port)
1090 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1091 See also Documentation/input/joystick-parport.txt
1095 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1099 gcov_persist= [GCOV] When non-zero (default), profiling data for
1100 kernel modules is saved and remains accessible via
1101 debugfs, even when the module is unloaded/reloaded.
1102 When zero, profiling data is discarded and associated
1103 debugfs files are removed at module unload time.
1105 gpt [EFI] Forces disk with valid GPT signature but
1106 invalid Protective MBR to be treated as GPT. If the
1107 primary GPT is corrupted, it enables the backup/alternate
1108 GPT to be used instead.
1110 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1111 the "Enable 0" bit of the configuration register.
1114 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1115 the "Enable 0" bit of the configuration register.
1118 grcan.select= [HW] Select which physical interface to use.
1121 grcan.txsize= [HW] Sets the size of the tx buffer.
1122 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1124 grcan.rxsize= [HW] Sets the size of the rx buffer.
1125 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1128 hashdist= [KNL,NUMA] Large hashes allocated during boot
1129 are distributed across NUMA nodes. Defaults on
1130 for 64-bit NUMA, off otherwise.
1131 Format: 0 | 1 (for off | on)
1133 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1135 hd= [EIDE] (E)IDE hard drive subsystem geometry
1136 Format: <cyl>,<head>,<sect>
1139 Disable Hardware Error Source Table (HEST) support;
1140 corresponding firmware-first mode error processing
1141 logic will be disabled.
1143 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1144 size of <nn>. This works even on boxes that have no
1145 highmem otherwise. This also works to reduce highmem
1146 size on bigger boxes.
1148 highres= [KNL] Enable/disable high resolution timer mode.
1149 Valid parameters: "on", "off"
1153 See Documentation/isdn/README.HiSax.
1157 hpet= [X86-32,HPET] option to control HPET usage
1158 Format: { enable (default) | disable | force |
1160 disable: disable HPET and use PIT instead
1161 force: allow force enabled of undocumented chips (ICH4,
1163 verbose: show contents of HPET registers during setup
1165 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1166 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1168 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1169 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1170 On x86-64 and powerpc, this option can be specified
1171 multiple times interleaved with hugepages= to reserve
1172 huge pages of different sizes. Valid pages sizes on
1173 x86-64 are 2M (when the CPU supports "pse") and 1G
1174 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1175 Note that 1GB pages can only be allocated at boot time
1176 using hugepages= and not freed afterwards.
1178 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1179 terminal devices. Valid values: 0..8
1180 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1181 If specified, z/VM IUCV HVC accepts connections
1182 from listed z/VM user IDs only.
1184 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1185 hardware thread id mappings.
1186 Format: <cpu>:<hwthread>
1189 Do not unregister boot console at start. This is only
1190 useful for debugging when something happens in the window
1191 between unregistering the boot console and initializing
1194 i2c_bus= [HW] Override the default board specific I2C bus speed
1195 or register an additional I2C bus that is not
1196 registered from board initialization code.
1200 i8042.debug [HW] Toggle i8042 debug mode
1201 i8042.direct [HW] Put keyboard port into non-translated mode
1202 i8042.dumbkbd [HW] Pretend that controller can only read data from
1203 keyboard and cannot control its state
1204 (Don't attempt to blink the leds)
1205 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1206 i8042.nokbd [HW] Don't check/create keyboard port
1207 i8042.noloop [HW] Disable the AUX Loopback command while probing
1209 i8042.nomux [HW] Don't check presence of an active multiplexing
1211 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1213 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1214 i8042.reset [HW] Reset the controller during init and cleanup
1215 i8042.unlock [HW] Unlock (ignore) the keylock
1219 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1220 indicates that the driver is running on unsupported
1222 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1223 does not match list of supported models.
1225 [HW] Report power status in /proc/i8k
1226 (disabled by default)
1227 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1230 i915.invert_brightness=
1231 [DRM] Invert the sense of the variable that is used to
1232 set the brightness of the panel backlight. Normally a
1233 brightness value of 0 indicates backlight switched off,
1234 and the maximum of the brightness value sets the backlight
1235 to maximum brightness. If this parameter is set to 0
1236 (default) and the machine requires it, or this parameter
1237 is set to 1, a brightness value of 0 sets the backlight
1238 to maximum brightness, and the maximum of the brightness
1239 value switches the backlight off.
1240 -1 -- never invert brightness
1241 0 -- machine default
1242 1 -- force brightness inversion
1245 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1247 ide-core.nodma= [HW] (E)IDE subsystem
1248 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1249 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1250 .cdrom .chs .ignore_cable are additional options
1251 See Documentation/ide/ide.txt.
1253 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1254 Claim all unknown PCI IDE storage controllers.
1257 Format: idle=poll, idle=halt, idle=nomwait
1258 Poll forces a polling idle loop that can slightly
1259 improve the performance of waking up a idle CPU, but
1260 will use a lot of power and make the system run hot.
1262 idle=halt: Halt is forced to be used for CPU idle.
1263 In such case C2/C3 won't be used again.
1264 idle=nomwait: Disable mwait for CPU C-states
1266 ignore_loglevel [KNL]
1267 Ignore loglevel setting - this will print /all/
1268 kernel messages to the console. Useful for debugging.
1269 We also add it as printk module parameter, so users
1270 could change it dynamically, usually by
1271 /sys/module/printk/parameters/ignore_loglevel.
1273 ihash_entries= [KNL]
1274 Set number of hash buckets for inode cache.
1276 ima_appraise= [IMA] appraise integrity measurements
1277 Format: { "off" | "enforce" | "fix" }
1280 ima_appraise_tcb [IMA]
1281 The builtin appraise policy appraises all files
1285 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1289 The list of supported hash algorithms is defined
1290 in crypto/hash_info.h.
1293 Load a policy which meets the needs of the Trusted
1294 Computing Base. This means IMA will measure all
1295 programs exec'd, files mmap'd for exec, and all files
1296 opened for read by uid=0.
1299 Select one of defined IMA measurements template formats.
1300 Formats: { "ima" | "ima-ng" }
1305 Run specified binary instead of /sbin/init as init
1308 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1309 for working out where the kernel is dying during
1312 initrd= [BOOT] Specify the location of the initial ramdisk
1314 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1317 int_pln_enable [x86] Enable power limit notification interrupt
1319 integrity_audit=[IMA]
1320 Format: { "0" | "1" }
1321 0 -- basic integrity auditing messages. (Default)
1322 1 -- additional integrity auditing messages.
1324 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1326 Enable intel iommu driver.
1328 Disable intel iommu driver.
1329 igfx_off [Default Off]
1330 By default, gfx is mapped as normal device. If a gfx
1331 device has a dedicated DMAR unit, the DMAR unit is
1332 bypassed by not enabling DMAR with this option. In
1333 this case, gfx device will use physical address for
1336 With this option iommu will not optimize to look
1337 for io virtual address below 32-bit forcing dual
1338 address cycle on pci bus for cards supporting greater
1339 than 32-bit addressing. The default is to look
1340 for translation below 32-bit and if not available
1341 then look in the higher range.
1342 strict [Default Off]
1343 With this option on every unmap_single operation will
1344 result in a hardware IOTLB flush operation as opposed
1345 to batching them for performance.
1346 sp_off [Default Off]
1347 By default, super page will be supported if Intel IOMMU
1348 has the capability. With this option, super page will
1351 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1352 0 disables intel_idle and fall back on acpi_idle.
1353 1 to 6 specify maximum depth of C-state.
1357 Do not enable intel_pstate as the default
1358 scaling driver for the supported processors
1360 intremap= [X86-64, Intel-IOMMU]
1361 on enable Interrupt Remapping (default)
1362 off disable Interrupt Remapping
1363 nosid disable Source ID checking
1365 BIOS x2APIC opt-out request will be ignored
1367 iomem= Disable strict checking of access to MMIO memory
1368 strict regions from userspace.
1385 io7= [HW] IO7 for Marvel based alpha systems
1386 See comment before marvel_specify_io7 in
1387 arch/alpha/kernel/core_marvel.c.
1389 io_delay= [X86] I/O delay method
1391 Standard port 0x80 based delay
1393 Alternate port 0xed based delay (needed on some systems)
1395 Simple two microseconds delay
1400 See Documentation/filesystems/nfs/nfsroot.txt.
1402 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1403 See comment before ip2_setup() in
1404 drivers/char/ip2/ip2base.c.
1407 When an interrupt is not handled search all handlers
1408 for it. Intended to get systems with badly broken
1412 When an interrupt is not handled search all handlers
1413 for it. Also check all handlers each timer
1414 interrupt. Intended to get systems with badly broken
1418 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1420 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1422 <cpu number>,...,<cpu number>
1424 <cpu number>-<cpu number>
1425 (must be a positive range in ascending order)
1427 <cpu number>,...,<cpu number>-<cpu number>
1429 This option can be used to specify one or more CPUs
1430 to isolate from the general SMP balancing and scheduling
1431 algorithms. You can move a process onto or off an
1432 "isolated" CPU via the CPU affinity syscalls or cpuset.
1433 <cpu number> begins at 0 and the maximum value is
1434 "number of CPUs in system - 1".
1436 This option is the preferred way to isolate CPUs. The
1437 alternative -- manually setting the CPU mask of all
1438 tasks in the system -- can cause problems and
1439 suboptimal load balancer performance.
1443 ivrs_ioapic [HW,X86_64]
1444 Provide an override to the IOAPIC-ID<->DEVICE-ID
1445 mapping provided in the IVRS ACPI table. For
1446 example, to map IOAPIC-ID decimal 10 to
1447 PCI device 00:14.0 write the parameter as:
1448 ivrs_ioapic[10]=00:14.0
1450 ivrs_hpet [HW,X86_64]
1451 Provide an override to the HPET-ID<->DEVICE-ID
1452 mapping provided in the IVRS ACPI table. For
1453 example, to map HPET-ID decimal 0 to
1454 PCI device 00:14.0 write the parameter as:
1455 ivrs_hpet[0]=00:14.0
1457 js= [HW,JOY] Analog joystick
1458 See Documentation/input/joystick.txt.
1462 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1463 specifies the amount of memory usable by the kernel
1464 for non-movable allocations. The requested amount is
1465 spread evenly throughout all nodes in the system. The
1466 remaining memory in each node is used for Movable
1467 pages. In the event, a node is too small to have both
1468 kernelcore and Movable pages, kernelcore pages will
1469 take priority and other nodes will have a larger number
1470 of Movable pages. The Movable zone is used for the
1471 allocation of pages that may be reclaimed or moved
1472 by the page migration subsystem. This means that
1473 HugeTLB pages may not be allocated from this zone.
1474 Note that allocations like PTEs-from-HighMem still
1475 use the HighMem zone if it exists, and the Normal
1476 zone if it does not.
1478 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1479 Format: <Controller#>[,poll interval]
1480 The controller # is the number of the ehci usb debug
1481 port as it is probed via PCI. The poll interval is
1482 optional and is the number seconds in between
1483 each poll cycle to the debug port in case you need
1484 the functionality for interrupting the kernel with
1485 gdb or control-c on the dbgp connection. When
1486 not using this parameter you use sysrq-g to break into
1487 the kernel debugger.
1489 kgdboc= [KGDB,HW] kgdb over consoles.
1490 Requires a tty driver that supports console polling,
1491 or a supported polling keyboard driver (non-usb).
1492 Serial only format: <serial_device>[,baud]
1493 keyboard only format: kbd
1494 keyboard and serial format: kbd,<serial_device>[,baud]
1495 Optional Kernel mode setting:
1496 kms, kbd format: kms,kbd
1497 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1499 kgdbwait [KGDB] Stop kernel execution and enter the
1500 kernel debugger at the earliest opportunity.
1502 kmac= [MIPS] korina ethernet MAC address.
1503 Configure the RouterBoard 532 series on-chip
1504 Ethernet adapter MAC address.
1506 kmemleak= [KNL] Boot-time kmemleak enable/disable
1507 Valid arguments: on, off
1510 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1511 Valid arguments: 0, 1, 2
1512 kmemcheck=0 (disabled)
1513 kmemcheck=1 (enabled)
1514 kmemcheck=2 (one-shot mode)
1515 Default: 2 (one-shot mode)
1517 kstack=N [X86] Print N words from the kernel stack
1520 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1521 Default is 0 (don't ignore, but inject #GP)
1523 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1527 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1528 Default is 1 (enabled)
1530 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1532 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1534 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1535 (virtualized MMU) support on capable Intel chips.
1536 Default is 1 (enabled)
1538 kvm-intel.emulate_invalid_guest_state=
1539 [KVM,Intel] Enable emulation of invalid guest states
1540 Default is 0 (disabled)
1542 kvm-intel.flexpriority=
1543 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1544 Default is 1 (enabled)
1547 [KVM,Intel] Enable VMX nesting (nVMX).
1548 Default is 0 (disabled)
1550 kvm-intel.unrestricted_guest=
1551 [KVM,Intel] Disable unrestricted guest feature
1552 (virtualized real and unpaged mode) on capable
1553 Intel chips. Default is 1 (enabled)
1555 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1556 feature (tagged TLBs) on capable Intel chips.
1557 Default is 1 (enabled)
1563 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1566 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1567 value for LAPIC timer one-shot implementation. Default
1568 back to the programmable timer unit in the LAPIC.
1570 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1573 libata.dma= [LIBATA] DMA control
1574 libata.dma=0 Disable all PATA and SATA DMA
1575 libata.dma=1 PATA and SATA Disk DMA only
1576 libata.dma=2 ATAPI (CDROM) DMA only
1577 libata.dma=4 Compact Flash DMA only
1578 Combinations also work, so libata.dma=3 enables DMA
1579 for disks and CDROMs, but not CFs.
1581 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1582 libata.ignore_hpa=0 keep BIOS limits (default)
1583 libata.ignore_hpa=1 ignore limits, using full disk
1585 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1589 libata.force= [LIBATA] Force configurations. The format is comma
1590 separated list of "[ID:]VAL" where ID is
1591 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1592 matching port, link or device. Basically, it matches
1593 the ATA ID string printed on console by libata. If
1594 the whole ID part is omitted, the last PORT and DEVICE
1595 values are used. If ID hasn't been specified yet, the
1596 configuration applies to all ports, links and devices.
1598 If only DEVICE is omitted, the parameter applies to
1599 the port and all links and devices behind it. DEVICE
1600 number of 0 either selects the first device or the
1601 first fan-out link behind PMP device. It does not
1602 select the host link. DEVICE number of 15 selects the
1603 host link and device attached to it.
1605 The VAL specifies the configuration to force. As long
1606 as there's no ambiguity shortcut notation is allowed.
1607 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1608 The following configurations can be forced.
1610 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1611 Any ID with matching PORT is used.
1613 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1615 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1616 udma[/][16,25,33,44,66,100,133] notation is also
1619 * [no]ncq: Turn on or off NCQ.
1621 * nohrst, nosrst, norst: suppress hard, soft
1624 * rstonce: only attempt one reset during
1625 hot-unplug link recovery
1627 * dump_id: dump IDENTIFY data.
1629 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1631 * disable: Disable this device.
1633 If there are multiple matching configurations changing
1634 the same attribute, the last one is used.
1636 memblock=debug [KNL] Enable memblock debug messages.
1638 load_ramdisk= [RAM] List of ramdisks to load from floppy
1639 See Documentation/blockdev/ramdisk.txt.
1641 lockd.nlm_grace_period=P [NFS] Assign grace period.
1644 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1647 lockd.nlm_timeout=T [NFS] Assign timeout value.
1650 lockd.nlm_udpport=M [NFS] Assign UDP port.
1653 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1656 loglevel= All Kernel Messages with a loglevel smaller than the
1657 console loglevel will be printed to the console. It can
1658 also be changed with klogd or other programs. The
1659 loglevels are defined as follows:
1661 0 (KERN_EMERG) system is unusable
1662 1 (KERN_ALERT) action must be taken immediately
1663 2 (KERN_CRIT) critical conditions
1664 3 (KERN_ERR) error conditions
1665 4 (KERN_WARNING) warning conditions
1666 5 (KERN_NOTICE) normal but significant condition
1667 6 (KERN_INFO) informational
1668 7 (KERN_DEBUG) debug-level messages
1670 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1671 in bytes. n must be a power of two. The default
1672 size is set in the kernel config file.
1674 logo.nologo [FB] Disables display of the built-in Linux logo.
1675 This may be used to provide more screen space for
1676 kernel log messages and is useful when debugging
1677 kernel boot problems.
1679 lp=0 [LP] Specify parallel ports to use, e.g,
1680 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1681 lp=reset first parallel port). 'lp=0' disables the
1682 lp=auto printer driver. 'lp=reset' (which can be
1683 specified in addition to the ports) causes
1684 attached printers to be reset. Using
1685 lp=port1,port2,... specifies the parallel ports
1686 to associate lp devices with, starting with
1687 lp0. A port specification may be 'none' to skip
1688 that lp device, or a parport name such as
1689 'parport0'. Specifying 'lp=auto' instead of a
1690 port specification list means that device IDs
1691 from each port should be examined, to see if
1692 an IEEE 1284-compliant printer is attached; if
1693 so, the driver will manage that printer.
1694 See also header of drivers/char/lp.c.
1697 Sets loops_per_jiffy to given constant, thus avoiding
1698 time-consuming boot-time autodetection (up to 250 ms per
1699 CPU). 0 enables autodetection (default). To determine
1700 the correct value for your kernel, boot with normal
1701 autodetection and see what value is printed. Note that
1702 on SMP systems the preset will be applied to all CPUs,
1703 which is likely to cause problems if your CPUs need
1704 significantly divergent settings. An incorrect value
1705 will cause delays in the kernel to be wrong, leading to
1706 unpredictable I/O errors and other breakage. Although
1707 unlikely, in the extreme case this might damage your
1711 Format: <io>,<irq>,<dma>
1713 machvec= [IA-64] Force the use of a particular machine-vector
1714 (machvec) in a generic kernel.
1715 Example: machvec=hpzx1_swiotlb
1717 machtype= [Loongson] Share the same kernel image file between different
1719 Example: machtype=lemote-yeeloong-2f-7inch
1721 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1722 than or equal to this physical address is ignored.
1724 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1725 should make use of. maxcpus=n : n >= 0 limits the
1726 kernel to using 'n' processors. n=0 is a special case,
1727 it is equivalent to "nosmp", which also disables
1730 max_loop= [LOOP] The number of loop block devices that get
1731 (loop.max_loop) unconditionally pre-created at init time. The default
1732 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1733 of statically allocating a predefined number, loop
1734 devices can be requested on-demand with the
1735 /dev/loop-control interface.
1737 mce [X86-32] Machine Check Exception
1739 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1741 md= [HW] RAID subsystems devices and level
1742 See Documentation/md.txt.
1745 Format: <first>,<last>
1746 Specifies range of consoles to be captured by the MDA.
1748 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1749 Amount of memory to be used when the kernel is not able
1750 to see the whole system memory or for test.
1751 [X86] Work as limiting max address. Use together
1752 with memmap= to avoid physical address space collisions.
1753 Without memmap= PCI devices could be placed at addresses
1754 belonging to unused RAM.
1756 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1760 [KNL,SH] Allow user to override the default size for
1761 per-device physically contiguous DMA buffers.
1763 memmap=exactmap [KNL,X86] Enable setting of an exact
1764 E820 memory map, as specified by the user.
1765 Such memmap=exactmap lines can be constructed based on
1766 BIOS output or other requirements. See the memmap=nn@ss
1769 memmap=nn[KMG]@ss[KMG]
1770 [KNL] Force usage of a specific region of memory.
1771 Region of memory to be used is from ss to ss+nn.
1773 memmap=nn[KMG]#ss[KMG]
1774 [KNL,ACPI] Mark specific memory as ACPI data.
1775 Region of memory to be marked is from ss to ss+nn.
1777 memmap=nn[KMG]$ss[KMG]
1778 [KNL,ACPI] Mark specific memory as reserved.
1779 Region of memory to be reserved is from ss to ss+nn.
1780 Example: Exclude memory from 0x18690000-0x1869ffff
1781 memmap=64K$0x18690000
1783 memmap=0x10000$0x18690000
1785 memory_corruption_check=0/1 [X86]
1786 Some BIOSes seem to corrupt the first 64k of
1787 memory when doing things like suspend/resume.
1788 Setting this option will scan the memory
1789 looking for corruption. Enabling this will
1790 both detect corruption and prevent the kernel
1791 from using the memory being corrupted.
1792 However, its intended as a diagnostic tool; if
1793 repeatable BIOS-originated corruption always
1794 affects the same memory, you can use memmap=
1795 to prevent the kernel from using that memory.
1797 memory_corruption_check_size=size [X86]
1798 By default it checks for corruption in the low
1799 64k, making this memory unavailable for normal
1800 use. Use this parameter to scan for
1801 corruption in more or less memory.
1803 memory_corruption_check_period=seconds [X86]
1804 By default it checks for corruption every 60
1805 seconds. Use this parameter to check at some
1806 other rate. 0 disables periodic checking.
1808 memtest= [KNL,X86] Enable memtest
1810 default : 0 <disable>
1811 Specifies the number of memtest passes to be
1812 performed. Each pass selects another test
1813 pattern from a given set of patterns. Memtest
1814 fills the memory with this pattern, validates
1815 memory contents and reserves bad memory
1816 regions that are detected.
1818 meye.*= [HW] Set MotionEye Camera parameters
1819 See Documentation/video4linux/meye.txt.
1821 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1822 Multi-Function General Purpose Timers on AMD Geode
1825 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1826 the BIOS has incorrectly applied a workaround. TinyBIOS
1827 version 0.98 is known to be affected, 0.99 fixes the
1828 problem by letting the user disable the workaround.
1832 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1833 physical address is ignored.
1835 mini2440= [ARM,HW,KNL]
1836 Format:[0..2][b][c][t]
1838 MINI2440 configuration specification:
1839 0 - The attached screen is the 3.5" TFT
1840 1 - The attached screen is the 7" TFT
1841 2 - The VGA Shield is attached (1024x768)
1842 Leaving out the screen size parameter will not load
1843 the TFT driver, and the framebuffer will be left
1845 b - Enable backlight. The TFT backlight pin will be
1846 linked to the kernel VESA blanking code and a GPIO
1847 LED. This parameter is not necessary when using the
1849 c - Enable the s3c camera interface.
1850 t - Reserved for enabling touchscreen support. The
1851 touchscreen support is not enabled in the mainstream
1852 kernel as of 2.6.30, a preliminary port can be found
1853 in the "bleeding edge" mini2440 support kernel at
1854 http://repo.or.cz/w/linux-2.6/mini2440.git
1857 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1858 parameter allows control of the logging verbosity for
1859 the additional memory initialisation checks. A value
1860 of 0 disables mminit logging and a level of 4 will
1861 log everything. Information is printed at KERN_DEBUG
1862 so loglevel=8 may also need to be specified.
1865 [KNL] When CONFIG_MODULE_SIG is set, this means that
1866 modules without (valid) signatures will fail to load.
1867 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1868 is always true, so this option does nothing.
1871 [MOUSE] Maximum time between finger touching and
1872 leaving touchpad surface for touch to be considered
1873 a tap and be reported as a left button click (for
1874 touchpads working in absolute mode only).
1876 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1877 reporting absolute coordinates, such as tablets
1878 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1879 reporting absolute coordinates, such as tablets
1881 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1882 is similar to kernelcore except it specifies the
1883 amount of memory used for migratable allocations.
1884 If both kernelcore and movablecore is specified,
1885 then kernelcore will be at *least* the specified
1886 value but may be more. If movablecore on its own
1887 is specified, the administrator must be careful
1888 that the amount of memory usable for all allocations
1891 movable_node [KNL,X86] Boot-time switch to enable the effects
1892 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1894 MTD_Partition= [MTD]
1895 Format: <name>,<region-number>,<size>,<offset>
1897 MTD_Region= [MTD] Format:
1898 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1901 See drivers/mtd/cmdlinepart.c.
1903 multitce=off [PPC] This parameter disables the use of the pSeries
1904 firmware feature for updating multiple TCE entries
1907 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1909 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1911 boundary - index of last SLC block on Flex-OneNAND.
1912 The remaining blocks are configured as MLC blocks.
1913 lock - Configure if Flex-OneNAND boundary should be locked.
1914 Once locked, the boundary cannot be changed.
1915 1 indicates lock status, 0 indicates unlock status.
1918 ARM/S3C2412 JIVE boot control
1920 See arch/arm/mach-s3c2412/mach-jive.c
1922 mtouchusb.raw_coordinates=
1923 [HW] Make the MicroTouch USB driver use raw coordinates
1924 ('y', default) or cooked coordinates ('n')
1926 mtrr_chunk_size=nn[KMG] [X86]
1927 used for mtrr cleanup. It is largest continuous chunk
1928 that could hold holes aka. UC entries.
1930 mtrr_gran_size=nn[KMG] [X86]
1931 Used for mtrr cleanup. It is granularity of mtrr block.
1933 Large value could prevent small alignment from
1936 mtrr_spare_reg_nr=n [X86]
1938 Range: 0,7 : spare reg number
1940 Used for mtrr cleanup. It is spare mtrr entries number.
1941 Set to 2 or more if your graphical card needs more.
1943 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1945 netdev= [NET] Network devices parameters
1946 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1947 Note that mem_start is often overloaded to mean
1948 something different and driver-specific.
1949 This usage is only documented in each driver source
1953 [NETFILTER] Enable connection tracking flow accounting
1954 0 to disable accounting
1955 1 to enable accounting
1958 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1959 See Documentation/filesystems/nfs/nfsroot.txt.
1961 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1962 See Documentation/filesystems/nfs/nfsroot.txt.
1964 nfsrootdebug [NFS] enable nfsroot debugging messages.
1965 See Documentation/filesystems/nfs/nfsroot.txt.
1967 nfs.callback_tcpport=
1968 [NFS] set the TCP port on which the NFSv4 callback
1969 channel should listen.
1972 [NFS] sets the pathname to the program which is used
1973 to update the NFS client cache entries.
1975 nfs.cache_getent_timeout=
1976 [NFS] sets the timeout after which an attempt to
1977 update a cache entry is deemed to have failed.
1979 nfs.idmap_cache_timeout=
1980 [NFS] set the maximum lifetime for idmapper cache
1984 [NFS] enable 64-bit inode numbers.
1985 If zero, the NFS client will fake up a 32-bit inode
1986 number for the readdir() and stat() syscalls instead
1987 of returning the full 64-bit number.
1988 The default is to return 64-bit inode numbers.
1990 nfs.max_session_slots=
1991 [NFSv4.1] Sets the maximum number of session slots
1992 the client will attempt to negotiate with the server.
1993 This limits the number of simultaneous RPC requests
1994 that the client can send to the NFSv4.1 server.
1995 Note that there is little point in setting this
1996 value higher than the max_tcp_slot_table_limit.
1998 nfs.nfs4_disable_idmapping=
1999 [NFSv4] When set to the default of '1', this option
2000 ensures that both the RPC level authentication
2001 scheme and the NFS level operations agree to use
2002 numeric uids/gids if the mount is using the
2003 'sec=sys' security flavour. In effect it is
2004 disabling idmapping, which can make migration from
2005 legacy NFSv2/v3 systems to NFSv4 easier.
2006 Servers that do not support this mode of operation
2007 will be autodetected by the client, and it will fall
2008 back to using the idmapper.
2009 To turn off this behaviour, set the value to '0'.
2011 [NFS4] Specify an additional fixed unique ident-
2012 ification string that NFSv4 clients can insert into
2013 their nfs_client_id4 string. This is typically a
2014 UUID that is generated at system install time.
2016 nfs.send_implementation_id =
2017 [NFSv4.1] Send client implementation identification
2018 information in exchange_id requests.
2019 If zero, no implementation identification information
2021 The default is to send the implementation identification
2024 nfs.recover_lost_locks =
2025 [NFSv4] Attempt to recover locks that were lost due
2026 to a lease timeout on the server. Please note that
2027 doing this risks data corruption, since there are
2028 no guarantees that the file will remain unchanged
2029 after the locks are lost.
2030 If you want to enable the kernel legacy behaviour of
2031 attempting to recover these locks, then set this
2033 The default parameter value of '0' causes the kernel
2034 not to attempt recovery of lost locks.
2036 nfsd.nfs4_disable_idmapping=
2037 [NFSv4] When set to the default of '1', the NFSv4
2038 server will return only numeric uids and gids to
2039 clients using auth_sys, and will accept numeric uids
2040 and gids from such clients. This is intended to ease
2041 migration from NFSv2/v3.
2043 objlayoutdriver.osd_login_prog=
2044 [NFS] [OBJLAYOUT] sets the pathname to the program which
2045 is used to automatically discover and login into new
2046 osd-targets. Please see:
2047 Documentation/filesystems/pnfs.txt for more explanations
2049 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2050 when a NMI is triggered.
2051 Format: [state][,regs][,debounce][,die]
2053 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2054 Format: [panic,][nopanic,][num]
2056 0 - turn nmi_watchdog off
2057 When panic is specified, panic when an NMI watchdog
2058 timeout occurs (or 'nopanic' to override the opposite
2060 This is useful when you use a panic=... timeout and
2061 need the box quickly up again.
2063 netpoll.carrier_timeout=
2064 [NET] Specifies amount of time (in seconds) that
2065 netpoll should wait for a carrier. By default netpoll
2068 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2069 emulation library even if a 387 maths coprocessor
2073 [HW] Never suspend the console
2074 Disable suspending of consoles during suspend and
2075 hibernate operations. Once disabled, debugging
2076 messages can reach various consoles while the rest
2077 of the system is being put to sleep (ie, while
2078 debugging driver suspend/resume hooks). This may
2079 not work reliably with all consoles, but is known
2080 to work with serial and VGA consoles.
2081 To facilitate more flexible debugging, we also add
2082 console_suspend, a printk module parameter to control
2083 it. Users could use console_suspend (usually
2084 /sys/module/printk/parameters/console_suspend) to
2085 turn on/off it dynamically.
2087 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2088 caches in the slab allocator. Saves per-node memory,
2089 but will impact performance.
2093 noapic [SMP,APIC] Tells the kernel to not make use of any
2094 IOAPICs that may be present in the system.
2097 Disable kernel and module base offset ASLR (Address
2098 Space Layout Randomization) if built into the kernel.
2100 noautogroup Disable scheduler automatic task group creation.
2102 nobats [PPC] Do not use BATs for mapping kernel lowmem
2103 on "Classic" PPC cores.
2107 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2109 nodelayacct [KNL] Disable per-task delay accounting
2111 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2113 nodsp [SH] Disable hardware DSP at boot time.
2115 noefi [X86] Disable EFI runtime services support.
2120 On X86-32 available only on PAE configured kernels.
2121 noexec=on: enable non-executable mappings (default)
2122 noexec=off: disable non-executable mappings
2125 Disable SMAP (Supervisor Mode Access Prevention)
2126 even if it is supported by processor.
2129 Disable SMEP (Supervisor Mode Execution Prevention)
2130 even if it is supported by processor.
2133 This affects only 32-bit executables.
2134 noexec32=on: enable non-executable mappings (default)
2135 read doesn't imply executable mappings
2136 noexec32=off: disable non-executable mappings
2137 read implies executable mappings
2139 nofpu [SH] Disable hardware FPU at boot time.
2141 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2142 register save and restore. The kernel will only save
2143 legacy floating-point registers on task switch.
2145 noxsave [BUGS=X86] Disables x86 extended register state save
2146 and restore using xsave. The kernel will fallback to
2147 enabling legacy floating-point and sse state.
2150 on enable eager fpu restore
2151 off disable eager fpu restore
2152 auto selects the default scheme, which automatically
2153 enables eagerfpu restore for xsaveopt.
2155 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2156 wfi(ARM) instruction doesn't work correctly and not to
2157 use it. This is also useful when using JTAG debugger.
2159 no_file_caps Tells the kernel not to honor file capabilities. The
2160 only way then for a file to be executed with privilege
2161 is to be setuid root or executed by root.
2163 nohalt [IA-64] Tells the kernel not to use the power saving
2164 function PAL_HALT_LIGHT when idle. This increases
2165 power-consumption. On the positive side, it reduces
2166 interrupt wake-up latency, which may improve performance
2167 in certain environments such as networked servers or
2170 nohz= [KNL] Boottime enable/disable dynamic ticks
2171 Valid arguments: on, off
2174 nohz_full= [KNL,BOOT]
2175 In kernels built with CONFIG_NO_HZ_FULL=y, set
2176 the specified list of CPUs whose tick will be stopped
2177 whenever possible. The boot CPU will be forced outside
2178 the range to maintain the timekeeping.
2179 The CPUs in this range must also be included in the
2182 noiotrap [SH] Disables trapped I/O port accesses.
2184 noirqdebug [X86-32] Disables the code which attempts to detect and
2185 disable unhandled interrupt sources.
2187 no_timer_check [X86,APIC] Disables the code which tests for
2188 broken timer IRQ sources.
2190 noisapnp [ISAPNP] Disables ISA PnP code.
2192 noinitrd [RAM] Tells the kernel not to load any configured
2195 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2197 [Deprecated - use intremap=off]
2201 nojitter [IA-64] Disables jitter checking for ITC timers.
2203 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2205 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2208 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2209 steal time is computed, but won't influence scheduler
2212 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2214 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2216 noltlbs [PPC] Do not use large page/tlb entries for kernel
2217 lowmem mapping on PPC40x.
2219 nomca [IA-64] Disable machine check abort handling
2221 nomce [X86-32] Machine Check Exception
2223 nomfgpt [X86-32] Disable Multi-Function General Purpose
2224 Timer usage (for AMD Geode machines).
2226 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2227 shutdown the other cpus. Instead use the REBOOT_VECTOR
2230 nomodule Disable module load
2232 nopat [X86] Disable PAT (page attribute table extension of
2233 pagetables) support.
2235 norandmaps Don't use address space randomization. Equivalent to
2236 echo 0 > /proc/sys/kernel/randomize_va_space
2238 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2240 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2241 with UP alternatives
2243 nordrand [X86] Disable kernel use of the RDRAND and
2244 RDSEED instructions even if they are supported
2245 by the processor. RDRAND and RDSEED are still
2246 available to user space applications.
2248 noresume [SWSUSP] Disables resume and restores original swap
2251 no-scroll [VGA] Disables scrollback.
2252 This is required for the Braillex ib80-piezo Braille
2253 reader made by F.H. Papenmeier (Germany).
2257 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2259 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2260 and disable the IO APIC. legacy for "maxcpus=0".
2262 nosoftlockup [KNL] Disable the soft-lockup detector.
2264 nosync [HW,M68K] Disables sync negotiation for all devices.
2266 notsc [BUGS=X86-32] Disable Time Stamp Counter
2268 nousb [USB] Disable the USB subsystem
2270 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2274 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2276 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2277 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2278 Some features depend on CPU0. Known dependencies are:
2279 1. Resume from suspend/hibernate depends on CPU0.
2280 Suspend/hibernate will fail if CPU0 is offline and you
2281 need to online CPU0 before suspend/hibernate.
2282 2. PIC interrupts also depend on CPU0. CPU0 can't be
2283 removed if a PIC interrupt is detected.
2284 It's said poweroff/reboot may depend on CPU0 on some
2285 machines although I haven't seen such issues so far
2286 after CPU0 is offline on a few tested machines.
2287 If the dependencies are under your control, you can
2288 turn on cpu0_hotplug.
2290 nptcg= [IA-64] Override max number of concurrent global TLB
2291 purges which is reported from either PAL_VM_SUMMARY or
2294 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2295 could support. nr_cpus=n : n >= 1 limits the kernel to
2296 supporting 'n' processors. Later in runtime you can not
2297 use hotplug cpu feature to put more cpu back to online.
2298 just like you compile the kernel NR_CPUS=n
2300 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2302 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2303 Allowed values are enable and disable
2305 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2306 one of ['zone', 'node', 'default'] can be specified
2307 This can be set from sysctl after boot.
2308 See Documentation/sysctl/vm.txt for details.
2310 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2311 See Documentation/debugging-via-ohci1394.txt for more
2314 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2315 Rather than timing out after 20 ms if an EC
2316 command is not properly ACKed, override the length
2317 of the timeout. We have interrupts disabled while
2318 waiting for the ACK, so if this is set too high
2319 interrupts *may* be lost!
2321 omap_mux= [OMAP] Override bootloader pin multiplexing.
2322 Format: <mux_mode0.mode_name=value>...
2323 For example, to override I2C bus2:
2324 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2326 oprofile.timer= [HW]
2327 Use timer interrupt instead of performance counters
2329 oprofile.cpu_type= Force an oprofile cpu type
2330 This might be useful if you have an older oprofile
2331 userland or if you want common events.
2332 Format: { arch_perfmon }
2333 arch_perfmon: [X86] Force use of architectural
2334 perfmon on Intel CPUs instead of the
2335 CPU specific event set.
2336 timer: [X86] Force use of architectural NMI
2337 timer mode (see also oprofile.timer
2338 for generic hr timer mode)
2339 [s390] Force legacy basic mode sampling
2340 (report cpu_type "timer")
2342 oops=panic Always panic on oopses. Default is to just kill the
2343 process, but there is a small probability of
2344 deadlocking the machine.
2345 This will also cause panics on machine check exceptions.
2346 Useful together with panic=30 to trigger a reboot.
2349 See Documentation/sound/oss/oss-parameters.txt
2351 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2352 timeout > 0: seconds before rebooting
2353 timeout = 0: wait forever
2354 timeout < 0: reboot immediately
2357 parkbd.port= [HW] Parallel port number the keyboard adapter is
2358 connected to, default is 0.
2360 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2361 0 for XT, 1 for AT (default is AT).
2364 parport= [HW,PPT] Specify parallel ports. 0 disables.
2365 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2366 Use 'auto' to force the driver to use any
2367 IRQ/DMA settings detected (the default is to
2368 ignore detected IRQ/DMA settings because of
2369 possible conflicts). You can specify the base
2370 address, IRQ, and DMA settings; IRQ and DMA
2371 should be numbers, or 'auto' (for using detected
2372 settings on that particular port), or 'nofifo'
2373 (to avoid using a FIFO even if it is detected).
2374 Parallel ports are assigned in the order they
2375 are specified on the command line, starting
2378 parport_init_mode= [HW,PPT]
2379 Configure VIA parallel port to operate in
2380 a specific mode. This is necessary on Pegasos
2381 computer where firmware has no options for setting
2382 up parallel port mode and sets it to spp.
2383 Currently this function knows 686a and 8231 chips.
2384 Format: [spp|ps2|epp|ecp|ecpepp]
2387 Halt all CPUs after the first oops has been printed for
2388 the specified number of seconds. This is to be used if
2389 your oopses keep scrolling off the screen.
2394 See header of drivers/block/paride/pcd.c.
2395 See also Documentation/blockdev/paride.txt.
2397 pci=option[,option...] [PCI] various PCI subsystem options:
2398 earlydump [X86] dump PCI config space before the kernel
2400 off [X86] don't probe for the PCI bus
2401 bios [X86-32] force use of PCI BIOS, don't access
2402 the hardware directly. Use this if your machine
2403 has a non-standard PCI host bridge.
2404 nobios [X86-32] disallow use of PCI BIOS, only direct
2405 hardware access methods are allowed. Use this
2406 if you experience crashes upon bootup and you
2407 suspect they are caused by the BIOS.
2408 conf1 [X86] Force use of PCI Configuration
2410 conf2 [X86] Force use of PCI Configuration
2412 noaer [PCIE] If the PCIEAER kernel config parameter is
2413 enabled, this kernel boot option can be used to
2414 disable the use of PCIE advanced error reporting.
2415 nodomains [PCI] Disable support for multiple PCI
2416 root domains (aka PCI segments, in ACPI-speak).
2417 nommconf [X86] Disable use of MMCONFIG for PCI
2419 check_enable_amd_mmconf [X86] check for and enable
2420 properly configured MMIO access to PCI
2421 config space on AMD family 10h CPU
2422 nomsi [MSI] If the PCI_MSI kernel config parameter is
2423 enabled, this kernel boot option can be used to
2424 disable the use of MSI interrupts system-wide.
2425 noioapicquirk [APIC] Disable all boot interrupt quirks.
2426 Safety option to keep boot IRQs enabled. This
2427 should never be necessary.
2428 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2429 primary IO-APIC for bridges that cannot disable
2430 boot IRQs. This fixes a source of spurious IRQs
2431 when the system masks IRQs.
2432 noioapicreroute [APIC] Disable workaround that uses the
2433 boot IRQ equivalent of an IRQ that connects to
2434 a chipset where boot IRQs cannot be disabled.
2435 The opposite of ioapicreroute.
2436 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2437 routing table. These calls are known to be buggy
2438 on several machines and they hang the machine
2439 when used, but on other computers it's the only
2440 way to get the interrupt routing table. Try
2441 this option if the kernel is unable to allocate
2442 IRQs or discover secondary PCI buses on your
2444 rom [X86] Assign address space to expansion ROMs.
2445 Use with caution as certain devices share
2446 address decoders between ROMs and other
2448 norom [X86] Do not assign address space to
2449 expansion ROMs that do not already have
2450 BIOS assigned address ranges.
2451 nobar [X86] Do not assign address space to the
2452 BARs that weren't assigned by the BIOS.
2453 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2454 assigned automatically to PCI devices. You can
2455 make the kernel exclude IRQs of your ISA cards
2457 pirqaddr=0xAAAAA [X86] Specify the physical address
2458 of the PIRQ table (normally generated
2459 by the BIOS) if it is outside the
2460 F0000h-100000h range.
2461 lastbus=N [X86] Scan all buses thru bus #N. Can be
2462 useful if the kernel is unable to find your
2463 secondary buses and you want to tell it
2464 explicitly which ones they are.
2465 assign-busses [X86] Always assign all PCI bus
2466 numbers ourselves, overriding
2467 whatever the firmware may have done.
2468 usepirqmask [X86] Honor the possible IRQ mask stored
2469 in the BIOS $PIR table. This is needed on
2470 some systems with broken BIOSes, notably
2471 some HP Pavilion N5400 and Omnibook XE3
2472 notebooks. This will have no effect if ACPI
2473 IRQ routing is enabled.
2474 noacpi [X86] Do not use ACPI for IRQ routing
2475 or for PCI scanning.
2476 use_crs [X86] Use PCI host bridge window information
2477 from ACPI. On BIOSes from 2008 or later, this
2478 is enabled by default. If you need to use this,
2479 please report a bug.
2480 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2481 If you need to use this, please report a bug.
2482 routeirq Do IRQ routing for all PCI devices.
2483 This is normally done in pci_enable_device(),
2484 so this option is a temporary workaround
2485 for broken drivers that don't call it.
2486 skip_isa_align [X86] do not align io start addr, so can
2487 handle more pci cards
2488 firmware [ARM] Do not re-enumerate the bus but instead
2489 just use the configuration from the
2490 bootloader. This is currently used on
2491 IXP2000 systems where the bus has to be
2492 configured a certain way for adjunct CPUs.
2493 noearly [X86] Don't do any early type 1 scanning.
2494 This might help on some broken boards which
2495 machine check when some devices' config space
2496 is read. But various workarounds are disabled
2497 and some IOMMU drivers will not work.
2498 bfsort Sort PCI devices into breadth-first order.
2499 This sorting is done to get a device
2500 order compatible with older (<= 2.4) kernels.
2501 nobfsort Don't sort PCI devices into breadth-first order.
2502 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2503 tuning and use the BIOS-configured MPS defaults.
2504 pcie_bus_safe Set every device's MPS to the largest value
2505 supported by all devices below the root complex.
2506 pcie_bus_perf Set device MPS to the largest allowable MPS
2507 based on its parent bus. Also set MRRS (Max
2508 Read Request Size) to the largest supported
2509 value (no larger than the MPS that the device
2510 or bus can support) for best performance.
2511 pcie_bus_peer2peer Set every device's MPS to 128B, which
2512 every device is guaranteed to support. This
2513 configuration allows peer-to-peer DMA between
2514 any pair of devices, possibly at the cost of
2515 reduced performance. This also guarantees
2516 that hot-added devices will work.
2517 cbiosize=nn[KMG] The fixed amount of bus space which is
2518 reserved for the CardBus bridge's IO window.
2519 The default value is 256 bytes.
2520 cbmemsize=nn[KMG] The fixed amount of bus space which is
2521 reserved for the CardBus bridge's memory
2522 window. The default value is 64 megabytes.
2525 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2526 Specifies alignment and device to reassign
2527 aligned memory resources.
2528 If <order of align> is not specified,
2529 PAGE_SIZE is used as alignment.
2530 PCI-PCI bridge can be specified, if resource
2531 windows need to be expanded.
2532 ecrc= Enable/disable PCIe ECRC (transaction layer
2533 end-to-end CRC checking).
2534 bios: Use BIOS/firmware settings. This is the
2538 hpiosize=nn[KMG] The fixed amount of bus space which is
2539 reserved for hotplug bridge's IO window.
2540 Default size is 256 bytes.
2541 hpmemsize=nn[KMG] The fixed amount of bus space which is
2542 reserved for hotplug bridge's memory window.
2543 Default size is 2 megabytes.
2544 realloc= Enable/disable reallocating PCI bridge resources
2545 if allocations done by BIOS are too small to
2546 accommodate resources required by all child
2548 off: Turn realloc off
2550 realloc same as realloc=on
2551 noari do not use PCIe ARI.
2552 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2553 only look for one device below a PCIe downstream
2556 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2559 force Enable ASPM even on devices that claim not to support it.
2560 WARNING: Forcing ASPM on may cause system lockups.
2562 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2563 nomsi Do not use MSI for PCI Express Native Hotplug (this
2564 makes all PCIe ports use INTx for hotplug services).
2566 pcie_ports= [PCIE] PCIe ports handling:
2567 auto Ask the BIOS whether or not to use native PCIe services
2568 associated with PCIe ports (PME, hot-plug, AER). Use
2569 them only if that is allowed by the BIOS.
2570 native Use native PCIe services associated with PCIe ports
2572 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2575 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2576 nomsi Do not use MSI for native PCIe PME signaling (this makes
2577 all PCIe root ports use INTx for all services).
2579 pcmv= [HW,PCMCIA] BadgePAD 4
2583 Keep all power-domains already enabled by bootloader on,
2584 even if no driver has claimed them. This is useful
2585 for debug and development, but should not be
2586 needed on a platform with proper driver support.
2589 See Documentation/blockdev/paride.txt.
2591 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2594 See arch/parisc/kernel/pdc_chassis.c
2596 percpu_alloc= Select which percpu first chunk allocator to use.
2597 Currently supported values are "embed" and "page".
2598 Archs may support subset or none of the selections.
2599 See comments in mm/percpu.c for details on each
2600 allocator. This parameter is primarily for debugging
2601 and performance comparison.
2604 See Documentation/blockdev/paride.txt.
2607 See Documentation/blockdev/paride.txt.
2609 pirq= [SMP,APIC] Manual mp-table setup
2610 See Documentation/x86/i386/IO-APIC.txt.
2612 plip= [PPT,NET] Parallel port network link
2613 Format: { parport<nr> | timid | 0 }
2614 See also Documentation/parport.txt.
2616 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2617 Override pmtimer IOPort with a hex value.
2621 Enable PNP debug messages (depends on the
2622 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2623 via /sys/module/pnp/parameters/debug. We always show
2624 current resource usage; turning this on also shows
2625 possible settings and some assignment information.
2631 { on | off | curr | res | no-curr | no-res }
2634 [ISAPNP] Exclude IRQs for the autoconfiguration
2637 [ISAPNP] Exclude DMAs for the autoconfiguration
2639 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2640 Ranges are in pairs (I/O port base and size).
2643 [ISAPNP] Exclude memory regions for the
2645 Ranges are in pairs (memory base and size).
2647 ports= [IP_VS_FTP] IPVS ftp helper module
2649 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2651 Format: <port>,<port>....
2653 print-fatal-signals=
2654 [KNL] debug: print fatal signals
2656 If enabled, warn about various signal handling
2657 related application anomalies: too many signals,
2658 too many POSIX.1 timers, fatal signals causing a
2661 If you hit the warning due to signal overflow,
2662 you might want to try "ulimit -i unlimited".
2666 printk.always_kmsg_dump=
2667 Trigger kmsg_dump for cases other than kernel oops or
2669 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2672 printk.time= Show timing data prefixed to each printk message line
2673 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2675 processor.max_cstate= [HW,ACPI]
2676 Limit processor to maximum C-state
2677 max_cstate=9 overrides any DMI blacklist limit.
2679 processor.nocst [HW,ACPI]
2680 Ignore the _CST method to determine C-states,
2681 instead using the legacy FADT method
2683 profile= [KNL] Enable kernel profiling via /proc/profile
2684 Format: [schedule,]<number>
2685 Param: "schedule" - profile schedule points.
2686 Param: <number> - step/bucket size as a power of 2 for
2687 statistical time based profiling.
2688 Param: "sleep" - profile D-state sleeping (millisecs).
2689 Requires CONFIG_SCHEDSTATS
2690 Param: "kvm" - profile VM exits.
2692 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2694 See Documentation/blockdev/ramdisk.txt.
2696 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2697 probe for; one of (bare|imps|exps|lifebook|any).
2698 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2700 psmouse.resetafter= [HW,MOUSE]
2701 Try to reset the device after so many bad packets
2704 [HW,MOUSE] Set desired mouse resolution, in dpi.
2705 psmouse.smartscroll=
2706 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2707 0 = disabled, 1 = enabled (default).
2709 pstore.backend= Specify the name of the pstore backend to use
2712 See Documentation/blockdev/paride.txt.
2715 [KNL] Number of legacy pty's. Overwrites compiled-in
2718 quiet [KNL] Disable most log messages
2723 See Documentation/md.txt.
2725 ramdisk_blocksize= [RAM]
2726 See Documentation/blockdev/ramdisk.txt.
2728 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2729 See Documentation/blockdev/ramdisk.txt.
2732 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2733 the specified list of CPUs to be no-callback CPUs.
2734 Invocation of these CPUs' RCU callbacks will
2735 be offloaded to "rcuox/N" kthreads created for
2736 that purpose, where "x" is "b" for RCU-bh, "p"
2737 for RCU-preempt, and "s" for RCU-sched, and "N"
2738 is the CPU number. This reduces OS jitter on the
2739 offloaded CPUs, which can be useful for HPC and
2740 real-time workloads. It can also improve energy
2741 efficiency for asymmetric multiprocessors.
2744 Rather than requiring that offloaded CPUs
2745 (specified by rcu_nocbs= above) explicitly
2746 awaken the corresponding "rcuoN" kthreads,
2747 make these kthreads poll for callbacks.
2748 This improves the real-time response for the
2749 offloaded CPUs by relieving them of the need to
2750 wake up the corresponding kthread, but degrades
2751 energy efficiency by requiring that the kthreads
2752 periodically wake up to do the polling.
2754 rcutree.blimit= [KNL]
2755 Set maximum number of finished RCU callbacks to
2756 process in one batch.
2758 rcutree.rcu_fanout_leaf= [KNL]
2759 Increase the number of CPUs assigned to each
2760 leaf rcu_node structure. Useful for very large
2763 rcutree.jiffies_till_first_fqs= [KNL]
2764 Set delay from grace-period initialization to
2765 first attempt to force quiescent states.
2766 Units are jiffies, minimum value is zero,
2767 and maximum value is HZ.
2769 rcutree.jiffies_till_next_fqs= [KNL]
2770 Set delay between subsequent attempts to force
2771 quiescent states. Units are jiffies, minimum
2772 value is one, and maximum value is HZ.
2774 rcutree.qhimark= [KNL]
2775 Set threshold of queued RCU callbacks beyond which
2776 batch limiting is disabled.
2778 rcutree.qlowmark= [KNL]
2779 Set threshold of queued RCU callbacks below which
2780 batch limiting is re-enabled.
2782 rcutree.rcu_idle_gp_delay= [KNL]
2783 Set wakeup interval for idle CPUs that have
2784 RCU callbacks (RCU_FAST_NO_HZ=y).
2786 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2787 Set wakeup interval for idle CPUs that have
2788 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2789 Lazy RCU callbacks are those which RCU can
2790 prove do nothing more than free memory.
2792 rcutorture.fqs_duration= [KNL]
2793 Set duration of force_quiescent_state bursts.
2795 rcutorture.fqs_holdoff= [KNL]
2796 Set holdoff time within force_quiescent_state bursts.
2798 rcutorture.fqs_stutter= [KNL]
2799 Set wait time between force_quiescent_state bursts.
2801 rcutorture.gp_exp= [KNL]
2802 Use expedited update-side primitives.
2804 rcutorture.gp_normal= [KNL]
2805 Use normal (non-expedited) update-side primitives.
2806 If both gp_exp and gp_normal are set, do both.
2807 If neither gp_exp nor gp_normal are set, still
2810 rcutorture.n_barrier_cbs= [KNL]
2811 Set callbacks/threads for rcu_barrier() testing.
2813 rcutorture.nfakewriters= [KNL]
2814 Set number of concurrent RCU writers. These just
2815 stress RCU, they don't participate in the actual
2816 test, hence the "fake".
2818 rcutorture.nreaders= [KNL]
2819 Set number of RCU readers.
2821 rcutorture.object_debug= [KNL]
2822 Enable debug-object double-call_rcu() testing.
2824 rcutorture.onoff_holdoff= [KNL]
2825 Set time (s) after boot for CPU-hotplug testing.
2827 rcutorture.onoff_interval= [KNL]
2828 Set time (s) between CPU-hotplug operations, or
2829 zero to disable CPU-hotplug testing.
2831 rcutorture.rcutorture_runnable= [BOOT]
2832 Start rcutorture running at boot time.
2834 rcutorture.shuffle_interval= [KNL]
2835 Set task-shuffle interval (s). Shuffling tasks
2836 allows some CPUs to go into dyntick-idle mode
2837 during the rcutorture test.
2839 rcutorture.shutdown_secs= [KNL]
2840 Set time (s) after boot system shutdown. This
2841 is useful for hands-off automated testing.
2843 rcutorture.stall_cpu= [KNL]
2844 Duration of CPU stall (s) to test RCU CPU stall
2845 warnings, zero to disable.
2847 rcutorture.stall_cpu_holdoff= [KNL]
2848 Time to wait (s) after boot before inducing stall.
2850 rcutorture.stat_interval= [KNL]
2851 Time (s) between statistics printk()s.
2853 rcutorture.stutter= [KNL]
2854 Time (s) to stutter testing, for example, specifying
2855 five seconds causes the test to run for five seconds,
2856 wait for five seconds, and so on. This tests RCU's
2857 ability to transition abruptly to and from idle.
2859 rcutorture.test_boost= [KNL]
2860 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2861 "Maybe" means test if the RCU implementation
2862 under test support RCU priority boosting.
2864 rcutorture.test_boost_duration= [KNL]
2865 Duration (s) of each individual boost test.
2867 rcutorture.test_boost_interval= [KNL]
2868 Interval (s) between each boost test.
2870 rcutorture.test_no_idle_hz= [KNL]
2871 Test RCU's dyntick-idle handling. See also the
2872 rcutorture.shuffle_interval parameter.
2874 rcutorture.torture_type= [KNL]
2875 Specify the RCU implementation to test.
2877 rcutorture.verbose= [KNL]
2878 Enable additional printk() statements.
2880 rcupdate.rcu_expedited= [KNL]
2881 Use expedited grace-period primitives, for
2882 example, synchronize_rcu_expedited() instead
2883 of synchronize_rcu(). This reduces latency,
2884 but can increase CPU utilization, degrade
2885 real-time latency, and degrade energy efficiency.
2887 rcupdate.rcu_cpu_stall_suppress= [KNL]
2888 Suppress RCU CPU stall warning messages.
2890 rcupdate.rcu_cpu_stall_timeout= [KNL]
2891 Set timeout for RCU CPU stall warning messages.
2895 Run specified binary instead of /init from the ramdisk,
2896 used for early userspace startup. See initrd.
2899 Format (x86 or x86_64):
2900 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2902 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2904 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2905 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2906 reboot_force is either force or not specified,
2907 reboot_cpu is s[mp]#### with #### being the processor
2908 to be used for rebooting.
2911 [KNL, SMP] Set scheduler's default relax_domain_level.
2912 See Documentation/cgroups/cpusets.txt.
2914 relative_sleep_states=
2915 [SUSPEND] Use sleep state labeling where the deepest
2916 state available other than hibernation is always "mem".
2917 Format: { "0" | "1" }
2918 0 -- Traditional sleep state labels.
2919 1 -- Relative sleep state labels.
2921 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2923 reservetop= [X86-32]
2925 Reserves a hole at the top of the kernel virtual
2930 Set the amount of memory to reserve for BIOS at
2931 the bottom of the address space.
2933 reset_devices [KNL] Force drivers to reset the underlying device
2934 during initialization.
2937 Specify the partition device for software suspend
2939 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2941 resume_offset= [SWSUSP]
2942 Specify the offset from the beginning of the partition
2943 given by "resume=" at which the swap header is located,
2944 in <PAGE_SIZE> units (needed only for swap files).
2945 See Documentation/power/swsusp-and-swap-files.txt
2947 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2948 read the resume files
2950 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2951 Useful for devices that are detected asynchronously
2952 (e.g. USB and MMC devices).
2954 hibernate= [HIBERNATION]
2955 noresume Don't check if there's a hibernation image
2956 present during boot.
2957 nocompress Don't compress/decompress hibernation images.
2959 retain_initrd [RAM] Keep initrd memory after extraction
2961 rhash_entries= [KNL,NET]
2962 Set number of hash buckets for route cache
2964 ro [KNL] Mount root device read-only on boot
2966 root= [KNL] Root filesystem
2967 See name_to_dev_t comment in init/do_mounts.c.
2969 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2970 mount the root filesystem
2972 rootflags= [KNL] Set root filesystem mount option string
2974 rootfstype= [KNL] Set root filesystem type
2976 rootwait [KNL] Wait (indefinitely) for root device to show up.
2977 Useful for devices that are detected asynchronously
2978 (e.g. USB and MMC devices).
2980 rproc_mem=nn[KMG][@address]
2981 [KNL,ARM,CMA] Remoteproc physical memory block.
2982 Memory area to be used by remote processor image,
2985 rw [KNL] Mount root device read-write on boot
2987 S [KNL] Run init in single mode
2990 See drivers/net/irda/sa1100_ir.c.
2992 sbni= [NET] Granch SBNI12 leased line adapter
2994 sched_debug [KNL] Enables verbose scheduler debug messages.
2996 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2997 xtime_lock contention on larger systems, and/or RCU lock
2998 contention on all systems with CONFIG_MAXSMP set.
2999 Format: { "0" | "1" }
3000 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3002 Note: increases power consumption, thus should only be
3003 enabled if running jitter sensitive (HPC/RT) workloads.
3005 security= [SECURITY] Choose a security module to enable at boot.
3006 If this boot parameter is not specified, only the first
3007 security module asking for security registration will be
3008 loaded. An invalid security module name will be treated
3009 as if no module has been chosen.
3011 selinux= [SELINUX] Disable or enable SELinux at boot time.
3012 Format: { "0" | "1" }
3013 See security/selinux/Kconfig help text.
3016 Default value is set via kernel config option.
3017 If enabled at boot time, /selinux/disable can be used
3018 later to disable prior to initial policy load.
3020 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3021 Format: { "0" | "1" }
3022 See security/apparmor/Kconfig help text
3025 Default value is set via kernel config option.
3027 serialnumber [BUGS=X86-32]
3030 Maximal number of shapers.
3032 show_msr= [x86] show boot-time MSR settings
3033 Format: { <integer> }
3034 Show boot-time (BIOS-initialized) MSR settings.
3035 The parameter means the number of CPUs to show,
3036 for example 1 means boot CPU only.
3043 slab_max_order= [MM, SLAB]
3044 Determines the maximum allowed order for slabs.
3045 A high setting may cause OOMs due to memory
3046 fragmentation. Defaults to 1 for systems with
3047 more than 32MB of RAM, 0 otherwise.
3049 slub_debug[=options[,slabs]] [MM, SLUB]
3050 Enabling slub_debug allows one to determine the
3051 culprit if slab objects become corrupted. Enabling
3052 slub_debug can create guard zones around objects and
3053 may poison objects when not in use. Also tracks the
3054 last alloc / free. For more information see
3055 Documentation/vm/slub.txt.
3057 slub_max_order= [MM, SLUB]
3058 Determines the maximum allowed order for slabs.
3059 A high setting may cause OOMs due to memory
3060 fragmentation. For more information see
3061 Documentation/vm/slub.txt.
3063 slub_min_objects= [MM, SLUB]
3064 The minimum number of objects per slab. SLUB will
3065 increase the slab order up to slub_max_order to
3066 generate a sufficiently large slab able to contain
3067 the number of objects indicated. The higher the number
3068 of objects the smaller the overhead of tracking slabs
3069 and the less frequently locks need to be acquired.
3070 For more information see Documentation/vm/slub.txt.
3072 slub_min_order= [MM, SLUB]
3073 Determines the minimum page order for slabs. Must be
3074 lower than slub_max_order.
3075 For more information see Documentation/vm/slub.txt.
3077 slub_nomerge [MM, SLUB]
3078 Disable merging of slabs with similar size. May be
3079 necessary if there is some reason to distinguish
3080 allocs to different slabs. Debug options disable
3081 merging on their own.
3082 For more information see Documentation/vm/slub.txt.
3085 Format: <io1>[,<io2>[,...,<io8>]]
3087 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3088 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3089 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3090 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3091 smsc-ircc2.ircc_irq= [HW] IRQ line
3092 smsc-ircc2.ircc_dma= [HW] DMA channel
3093 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3094 0: Toshiba Satellite 1800 (GP data pin select)
3095 1: Fast pin select (default)
3099 [KNL] Should the soft-lockup detector generate panics.
3102 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3103 See Documentation/laptops/sonypi.txt
3105 spia_io_base= [HW,MTD]
3111 Enabled the stack tracer on boot up.
3113 stacktrace_filter=[function-list]
3114 [FTRACE] Limit the functions that the stack tracer
3115 will trace at boot up. function-list is a comma separated
3116 list of functions. This list can be changed at run
3117 time by the stack_trace_filter file in the debugfs
3118 tracing directory. Note, this enables stack tracing
3119 and the stacktrace above is not needed.
3123 Set the STI (builtin display/keyboard on the HP-PARISC
3124 machines) console (graphic card) which should be used
3125 as the initial boot-console.
3126 See also comment in drivers/video/console/sticore.c.
3129 See comment in drivers/video/console/sticore.c.
3132 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3134 sunrpc.min_resvport=
3135 sunrpc.max_resvport=
3137 SunRPC servers often require that client requests
3138 originate from a privileged port (i.e. a port in the
3139 range 0 < portnr < 1024).
3140 An administrator who wishes to reserve some of these
3141 ports for other uses may adjust the range that the
3142 kernel's sunrpc client considers to be privileged
3143 using these two parameters to set the minimum and
3144 maximum port values.
3148 Control how the NFS server code allocates CPUs to
3149 service thread pools. Depending on how many NICs
3150 you have and where their interrupts are bound, this
3151 option will affect which CPUs will do NFS serving.
3152 Note: this parameter cannot be changed while the
3153 NFS server is running.
3155 auto the server chooses an appropriate mode
3156 automatically using heuristics
3157 global a single global pool contains all CPUs
3158 percpu one pool for each CPU
3159 pernode one pool for each NUMA node (equivalent
3160 to global on non-NUMA machines)
3162 sunrpc.tcp_slot_table_entries=
3163 sunrpc.udp_slot_table_entries=
3165 Sets the upper limit on the number of simultaneous
3166 RPC calls that can be sent from the client to a
3167 server. Increasing these values may allow you to
3168 improve throughput, but will also increase the
3169 amount of memory reserved for use by the client.
3172 [KNL] Enable accounting of swap in memory resource
3173 controller if no parameter or 1 is given or disable
3174 it if 0 is given (See Documentation/cgroups/memory.txt)
3176 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3177 Format: { <int> | force }
3178 <int> -- Number of I/O TLB slabs
3179 force -- force using of bounce buffers even if they
3180 wouldn't be automatically used by the kernel
3184 sysfs.deprecated=0|1 [KNL]
3185 Enable/disable old style sysfs layout for old udev
3186 on older distributions. When this option is enabled
3187 very new udev will not work anymore. When this option
3188 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3189 in older udev will not work anymore.
3190 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3191 the kernel configuration.
3193 sysrq_always_enabled
3195 Ignore sysrq setting - this boot parameter will
3196 neutralize any effect of /proc/sys/kernel/sysrq.
3197 Useful for debugging.
3201 test_suspend= [SUSPEND]
3202 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3203 standby suspend) as the system sleep state to briefly
3204 enter during system startup. The system is woken from
3205 this state using a wakeup-capable RTC alarm.
3207 thash_entries= [KNL,NET]
3208 Set number of hash buckets for TCP connection
3210 thermal.act= [HW,ACPI]
3211 -1: disable all active trip points in all thermal zones
3212 <degrees C>: override all lowest active trip points
3214 thermal.crt= [HW,ACPI]
3215 -1: disable all critical trip points in all thermal zones
3216 <degrees C>: override all critical trip points
3218 thermal.nocrt= [HW,ACPI]
3219 Set to disable actions on ACPI thermal zone
3220 critical and hot trip points.
3222 thermal.off= [HW,ACPI]
3223 1: disable ACPI thermal control
3225 thermal.psv= [HW,ACPI]
3226 -1: disable all passive trip points
3227 <degrees C>: override all passive trip points to this
3230 thermal.tzp= [HW,ACPI]
3231 Specify global default ACPI thermal zone polling rate
3232 <deci-seconds>: poll all this frequency
3233 0: no polling (default)
3236 Force threading of all interrupt handlers except those
3237 marked explicitly IRQF_NO_THREAD.
3240 Enable the Transcendent memory driver if built-in.
3242 tmem.cleancache=0|1 [KNL, XEN]
3243 Default is on (1). Disable the usage of the cleancache
3244 API to send anonymous pages to the hypervisor.
3246 tmem.frontswap=0|1 [KNL, XEN]
3247 Default is on (1). Disable the usage of the frontswap
3248 API to send swap pages to the hypervisor. If disabled
3249 the selfballooning and selfshrinking are force disabled.
3251 tmem.selfballooning=0|1 [KNL, XEN]
3252 Default is on (1). Disable the driving of swap pages
3255 tmem.selfshrinking=0|1 [KNL, XEN]
3256 Default is on (1). Partial swapoff that immediately
3257 transfers pages from Xen hypervisor back to the
3258 kernel based on different criteria.
3262 Specify if the kernel should make use of the cpu
3263 topology information if the hardware supports this.
3264 The scheduler will make use of this information and
3265 e.g. base its process migration decisions on it.
3270 tpm_suspend_pcr=[HW,TPM]
3271 Format: integer pcr id
3272 Specify that at suspend time, the tpm driver
3273 should extend the specified pcr with zeros,
3274 as a workaround for some chips which fail to
3275 flush the last written pcr on TPM_SaveState.
3276 This will guarantee that all the other pcrs
3279 trace_buf_size=nn[KMG]
3280 [FTRACE] will set tracing buffer size.
3282 trace_event=[event-list]
3283 [FTRACE] Set and start specified trace events in order
3284 to facilitate early boot debugging.
3285 See also Documentation/trace/events.txt
3287 trace_options=[option-list]
3288 [FTRACE] Enable or disable tracer options at boot.
3289 The option-list is a comma delimited list of options
3290 that can be enabled or disabled just as if you were
3291 to echo the option name into
3293 /sys/kernel/debug/tracing/trace_options
3295 For example, to enable stacktrace option (to dump the
3296 stack trace of each event), add to the command line:
3298 trace_options=stacktrace
3300 See also Documentation/trace/ftrace.txt "trace options"
3304 [FTRACE] enable this option to disable tracing when a
3305 warning is hit. This turns off "tracing_on". Tracing can
3306 be enabled again by echoing '1' into the "tracing_on"
3307 file located in /sys/kernel/debug/tracing/
3309 This option is useful, as it disables the trace before
3310 the WARNING dump is called, which prevents the trace to
3311 be filled with content caused by the warning output.
3313 This option can also be set at run time via the sysctl
3314 option: kernel/traceoff_on_warning
3316 transparent_hugepage=
3318 Format: [always|madvise|never]
3319 Can be used to control the default behavior of the system
3320 with respect to transparent hugepages.
3321 See Documentation/vm/transhuge.txt for more details.
3323 tsc= Disable clocksource stability checks for TSC.
3325 [x86] reliable: mark tsc clocksource as reliable, this
3326 disables clocksource verification at runtime, as well
3327 as the stability checks done at bootup. Used to enable
3328 high-resolution timer mode on older hardware, and in
3329 virtualized environment.
3330 [x86] noirqtime: Do not use TSC to do irq accounting.
3331 Used to run time disable IRQ_TIME_ACCOUNTING on any
3332 platforms where RDTSC is slow and this accounting
3335 turbografx.map[2|3]= [HW,JOY]
3336 TurboGraFX parallel port interface
3338 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3339 See also Documentation/input/joystick-parport.txt
3341 udbg-immortal [PPC] When debugging early kernel crashes that
3342 happen after console_init() and before a proper
3343 console driver takes over, this boot options might
3344 help "seeing" what's going on.
3346 uhash_entries= [KNL,NET]
3347 Set number of hash buckets for UDP/UDP-Lite connections
3350 [USB] Ignore overcurrent events (default N).
3351 Some badly-designed motherboards generate lots of
3352 bogus events, for ports that aren't wired to
3353 anything. Set this parameter to avoid log spamming.
3354 Note that genuine overcurrent events won't be
3358 [X86] Cause panic on unknown NMI.
3360 usbcore.authorized_default=
3361 [USB] Default USB device authorization:
3362 (default -1 = authorized except for wireless USB,
3363 0 = not authorized, 1 = authorized)
3365 usbcore.autosuspend=
3366 [USB] The autosuspend time delay (in seconds) used
3367 for newly-detected USB devices (default 2). This
3368 is the time required before an idle device will be
3369 autosuspended. Devices for which the delay is set
3370 to a negative value won't be autosuspended at all.
3372 usbcore.usbfs_snoop=
3373 [USB] Set to log all usbfs traffic (default 0 = off).
3375 usbcore.blinkenlights=
3376 [USB] Set to cycle leds on hubs (default 0 = off).
3378 usbcore.old_scheme_first=
3379 [USB] Start with the old device initialization
3380 scheme (default 0 = off).
3382 usbcore.usbfs_memory_mb=
3383 [USB] Memory limit (in MB) for buffers allocated by
3384 usbfs (default = 16, 0 = max = 2047).
3386 usbcore.use_both_schemes=
3387 [USB] Try the other device initialization scheme
3388 if the first one fails (default 1 = enabled).
3390 usbcore.initial_descriptor_timeout=
3391 [USB] Specifies timeout for the initial 64-byte
3392 USB_REQ_GET_DESCRIPTOR request in milliseconds
3393 (default 5000 = 5.0 seconds).
3396 [USBHID] The interval which mice are to be polled at.
3398 usb-storage.delay_use=
3399 [UMS] The delay in seconds before a new device is
3400 scanned for Logical Units (default 5).
3403 [UMS] A list of quirks entries to supplement or
3404 override the built-in unusual_devs list. List
3405 entries are separated by commas. Each entry has
3406 the form VID:PID:Flags where VID and PID are Vendor
3407 and Product ID values (4-digit hex numbers) and
3408 Flags is a set of characters, each corresponding
3409 to a common usb-storage quirk flag as follows:
3410 a = SANE_SENSE (collect more than 18 bytes
3412 b = BAD_SENSE (don't collect more than 18
3413 bytes of sense data);
3414 c = FIX_CAPACITY (decrease the reported
3415 device capacity by one sector);
3416 d = NO_READ_DISC_INFO (don't use
3417 READ_DISC_INFO command);
3418 e = NO_READ_CAPACITY_16 (don't use
3419 READ_CAPACITY_16 command);
3420 h = CAPACITY_HEURISTICS (decrease the
3421 reported device capacity by one
3422 sector if the number is odd);
3423 i = IGNORE_DEVICE (don't bind to this
3425 l = NOT_LOCKABLE (don't try to lock and
3426 unlock ejectable media);
3427 m = MAX_SECTORS_64 (don't transfer more
3428 than 64 sectors = 32 KB at a time);
3429 n = INITIAL_READ10 (force a retry of the
3430 initial READ(10) command);
3431 o = CAPACITY_OK (accept the capacity
3432 reported by the device);
3433 p = WRITE_CACHE (the device cache is ON
3435 r = IGNORE_RESIDUE (the device reports
3436 bogus residue values);
3437 s = SINGLE_LUN (the device has only one
3439 w = NO_WP_DETECT (don't test whether the
3440 medium is write-protected).
3441 Example: quirks=0419:aaf5:rl,0421:0433:rc
3443 user_debug= [KNL,ARM]
3445 See arch/arm/Kconfig.debug help text.
3446 1 - undefined instruction events
3448 4 - invalid data aborts
3451 Example: user_debug=31
3454 [X86] Flags controlling user PTE allocations.
3456 nohigh = do not allocate PTE pages in
3457 HIGHMEM regardless of setting
3461 On X86_32, this is an alias for vdso32=. Otherwise:
3463 vdso=1: enable VDSO (the default)
3464 vdso=0: disable VDSO mapping
3466 vdso32= [X86] Control the 32-bit vDSO
3467 vdso32=1: enable 32-bit VDSO
3468 vdso32=0 or vdso32=2: disable 32-bit VDSO
3470 See the help text for CONFIG_COMPAT_VDSO for more
3471 details. If CONFIG_COMPAT_VDSO is set, the default is
3472 vdso32=0; otherwise, the default is vdso32=1.
3474 For compatibility with older kernels, vdso32=2 is an
3477 Try vdso32=0 if you encounter an error that says:
3478 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3481 vector=percpu: enable percpu vector domain
3483 video= [FB] Frame buffer configuration
3484 See Documentation/fb/modedb.txt.
3486 video.brightness_switch_enabled= [0,1]
3487 If set to 1, on receiving an ACPI notify event
3488 generated by hotkey, video driver will adjust brightness
3489 level and then send out the event to user space through
3490 the allocated input device; If set to 0, video driver
3491 will only send out the event without touching backlight
3496 [VMMIO] Memory mapped virtio (platform) device.
3498 <size>@<baseaddr>:<irq>[:<id>]
3500 <size> := size (can use standard suffixes
3502 <baseaddr> := physical base address
3503 <irq> := interrupt number (as passed to
3505 <id> := (optional) platform device id
3507 virtio_mmio.device=1K@0x100b0000:48:7
3509 Can be used multiple times for multiple devices.
3511 vga= [BOOT,X86-32] Select a particular video mode
3512 See Documentation/x86/boot.txt and
3513 Documentation/svga.txt.
3514 Use vga=ask for menu.
3515 This is actually a boot loader parameter; the value is
3516 passed to the kernel using a special protocol.
3518 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3519 size of <nn>. This can be used to increase the
3520 minimum size (128MB on x86). It can also be used to
3521 decrease the size and leave more room for directly
3524 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3527 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3530 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3534 Controls the behavior of vsyscalls (i.e. calls to
3535 fixed addresses of 0xffffffffff600x00 from legacy
3536 code). Most statically-linked binaries and older
3537 versions of glibc use these calls. Because these
3538 functions are at fixed addresses, they make nice
3539 targets for exploits that can control RIP.
3541 emulate [default] Vsyscalls turn into traps and are
3542 emulated reasonably safely.
3544 native Vsyscalls are native syscall instructions.
3545 This is a little bit faster than trapping
3546 and makes a few dynamic recompilers work
3547 better than they would in emulation mode.
3548 It also makes exploits much easier to write.
3550 none Vsyscalls don't work at all. This makes
3551 them quite hard to use for exploits but
3552 might break your system.
3554 vt.color= [VT] Default text color.
3555 Format: 0xYX, X = foreground, Y = background.
3556 Default: 0x07 = light gray on black.
3558 vt.cur_default= [VT] Default cursor shape.
3559 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3560 the parameters of the <Esc>[?A;B;Cc escape sequence;
3561 see VGA-softcursor.txt. Default: 2 = underline.
3563 vt.default_blu= [VT]
3564 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3565 Change the default blue palette of the console.
3566 This is a 16-member array composed of values
3569 vt.default_grn= [VT]
3570 Format: <green0>,<green1>,<green2>,...,<green15>
3571 Change the default green palette of the console.
3572 This is a 16-member array composed of values
3575 vt.default_red= [VT]
3576 Format: <red0>,<red1>,<red2>,...,<red15>
3577 Change the default red palette of the console.
3578 This is a 16-member array composed of values
3584 Set system-wide default UTF-8 mode for all tty's.
3585 Default is 1, i.e. UTF-8 mode is enabled for all
3586 newly opened terminals.
3588 vt.global_cursor_default=
3591 Set system-wide default for whether a cursor
3592 is shown on new VTs. Default is -1,
3593 i.e. cursors will be created by default unless
3594 overridden by individual drivers. 0 will hide
3595 cursors, 1 will display them.
3597 vt.italic= [VT] Default color for italic text; 0-15.
3600 vt.underline= [VT] Default color for underlined text; 0-15.
3603 watchdog timers [HW,WDT] For information on watchdog timers,
3604 see Documentation/watchdog/watchdog-parameters.txt
3605 or other driver-specific files in the
3606 Documentation/watchdog/ directory.
3608 workqueue.disable_numa
3609 By default, all work items queued to unbound
3610 workqueues are affine to the NUMA nodes they're
3611 issued on, which results in better behavior in
3612 general. If NUMA affinity needs to be disabled for
3613 whatever reason, this option can be used. Note
3614 that this also can be controlled per-workqueue for
3615 workqueues visible under /sys/bus/workqueue/.
3617 workqueue.power_efficient
3618 Per-cpu workqueues are generally preferred because
3619 they show better performance thanks to cache
3620 locality; unfortunately, per-cpu workqueues tend to
3621 be more power hungry than unbound workqueues.
3623 Enabling this makes the per-cpu workqueues which
3624 were observed to contribute significantly to power
3625 consumption unbound, leading to measurably lower
3626 power usage at the cost of small performance
3629 The default value of this parameter is determined by
3630 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3632 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3633 default x2apic cluster mode on platforms
3636 x86_intel_mid_timer= [X86-32,APBT]
3637 Choose timer option for x86 Intel MID platform.
3638 Two valid options are apbt timer only and lapic timer
3639 plus one apbt timer for broadcast timer.
3640 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3642 xen_emul_unplug= [HW,X86,XEN]
3643 Unplug Xen emulated devices
3644 Format: [unplug0,][unplug1]
3645 ide-disks -- unplug primary master IDE devices
3646 aux-ide-disks -- unplug non-primary-master IDE devices
3647 nics -- unplug network devices
3648 all -- unplug all emulated devices (NICs and IDE disks)
3649 unnecessary -- unplugging emulated devices is
3650 unnecessary even if the host did not respond to
3652 never -- do not unplug even if version check succeeds
3654 xen_nopvspin [X86,XEN]
3655 Disables the ticketlock slowpath using Xen PV
3658 xirc2ps_cs= [NET,PCMCIA]
3660 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3662 ______________________________________________________________________
3666 Add more DRM drivers.
git.openpandora.org / pandora-kernel.git / blob