4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
588 - foo isn't visible as an individually mountable
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
605 See Documentation/s390/CommonIO for details.
608 Keep all clocks already enabled by bootloader on,
609 even if no driver has claimed them. This is useful
610 for debug and development, but should not be
611 needed on a platform with proper driver support.
612 For more information, see Documentation/clk.txt.
614 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
616 Forces specified clocksource (if available) to be used
617 when calculating gettimeofday(). If specified
618 clocksource is not available, it defaults to PIT.
619 Format: { pit | tsc | cyclone | pmtmr }
621 clocksource= Override the default clocksource
623 Override the default clocksource and use the clocksource
624 with the name specified.
625 Some clocksource names to choose from, depending on
627 [all] jiffies (this is the base, fallback clocksource)
629 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
630 pxa_timer,timer3,32k_counter,timer0_1
632 [X86-32] pit,hpet,tsc;
633 scx200_hrt on Geode; cyclone on IBM x440
641 clearcpuid=BITNUM [X86]
642 Disable CPUID feature X for the kernel. See
643 arch/x86/include/asm/cpufeature.h for the valid bit
644 numbers. Note the Linux specific bits are not necessarily
645 stable over kernel options, but the vendor specific
647 Also note that user programs calling CPUID directly
648 or using the feature without checking anything
649 will still see it. This just prevents it from
650 being used by the kernel or shown in /proc/cpuinfo.
651 Also note the kernel might malfunction if you disable
654 cma=nn[MG]@[start[MG][-end[MG]]]
656 Sets the size of kernel global memory area for
657 contiguous memory allocations and optionally the
658 placement constraint by the physical address range of
659 memory allocations. For more information, see
660 include/linux/dma-contiguous.h
662 cmo_free_hint= [PPC] Format: { yes | no }
663 Specify whether pages are marked as being inactive
664 when they are freed. This is used in CMO environments
665 to determine OS memory pressure for page stealing by
669 coherent_pool=nn[KMG] [ARM,KNL]
670 Sets the size of memory pool for coherent, atomic dma
671 allocations, by default set to 256K.
673 code_bytes [X86] How many bytes of object code to print
678 com20020= [HW,NET] ARCnet - COM20020 chipset
680 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
682 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
686 ARCnet - COM90xx chipset (memory-mapped buffers)
687 Format: <io>[,<irq>[,<memstart>]]
689 condev= [HW,S390] console device
692 console= [KNL] Output console device and options.
694 tty<n> Use the virtual console device <n>.
698 Use the specified serial port. The options are of
699 the form "bbbbpnf", where "bbbb" is the baud rate,
700 "p" is parity ("n", "o", or "e"), "n" is number of
701 bits, and "f" is flow control ("r" for RTS or
702 omit it). Default is "9600n8".
704 See Documentation/serial-console.txt for more
706 Documentation/networking/netconsole.txt for an
709 uart[8250],io,<addr>[,options]
710 uart[8250],mmio,<addr>[,options]
711 Start an early, polled-mode console on the 8250/16550
712 UART at the specified I/O port or MMIO address,
713 switching to the matching ttyS device later. The
714 options are the same as for ttyS, above.
715 hvc<n> Use the hypervisor console device <n>. This is for
716 both Xen and PowerPC hypervisors.
718 If the device connected to the port is not a TTY but a braille
719 device, prepend "brl," before the device type, for instance
721 For now, only VisioBraille is supported.
723 consoleblank= [KNL] The console blank (screen saver) timeout in
724 seconds. Defaults to 10*60 = 10mins. A value of 0
725 disables the blank timer.
728 [KNL] Change the default value for
729 /proc/<pid>/coredump_filter.
730 See also Documentation/filesystems/proc.txt.
732 cpuidle.off=1 [CPU_IDLE]
733 disable the cpuidle sub-system
735 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
737 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
739 crashkernel=size[KMG][@offset[KMG]]
740 [KNL] Using kexec, Linux can switch to a 'crash kernel'
741 upon panic. This parameter reserves the physical
742 memory region [offset, offset + size] for that kernel
743 image. If '@offset' is omitted, then a suitable offset
744 is selected automatically. Check
745 Documentation/kdump/kdump.txt for further details.
747 crashkernel=range1:size1[,range2:size2,...][@offset]
748 [KNL] Same as above, but depends on the memory
749 in the running system. The syntax of range is
750 start-[end] where start and end are both
751 a memory unit (amount[KMG]). See also
752 Documentation/kdump/kdump.txt for an example.
754 crashkernel=size[KMG],high
755 [KNL, x86_64] range could be above 4G. Allow kernel
756 to allocate physical memory region from top, so could
757 be above 4G if system have more than 4G ram installed.
758 Otherwise memory region will be allocated below 4G, if
760 It will be ignored if crashkernel=X is specified.
761 crashkernel=size[KMG],low
762 [KNL, x86_64] range under 4G. When crashkernel=X,high
763 is passed, kernel could allocate physical memory region
764 above 4G, that cause second kernel crash on system
765 that require some amount of low memory, e.g. swiotlb
766 requires at least 64M+32K low memory. Kernel would
767 try to allocate 72M below 4G automatically.
768 This one let user to specify own low range under 4G
769 for second kernel instead.
770 0: to disable low allocation.
771 It will be ignored when crashkernel=X,high is not used
772 or memory reserved is below 4G.
777 cs89x0_media= [HW,NET]
778 Format: { rj45 | aui | bnc }
781 See header of drivers/s390/block/dasd_devmap.c.
783 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
784 (one device per port)
785 Format: <port#>,<type>
786 See also Documentation/input/joystick-parport.txt
788 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
789 time. See Documentation/dynamic-debug-howto.txt for
790 details. Deprecated, see dyndbg.
792 debug [KNL] Enable kernel debugging (events log level).
795 [KNL] verbose self-tests
797 Print debugging info while doing the locking API
799 We default to 0 (no extra messages), setting it to
800 1 will print _a lot_ more information - normally
801 only useful to kernel developers.
803 debug_objects [KNL] Enable object debugging
806 [KNL] Disable object debugging
808 debug_guardpage_minorder=
809 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
810 parameter allows control of the order of pages that will
811 be intentionally kept free (and hence protected) by the
812 buddy allocator. Bigger value increase the probability
813 of catching random memory corruption, but reduce the
814 amount of memory for normal system use. The maximum
815 possible value is MAX_ORDER/2. Setting this parameter
816 to 1 or 2 should be enough to identify most random
817 memory corruption problems caused by bugs in kernel or
818 driver code when a CPU writes to (or reads from) a
819 random memory location. Note that there exists a class
820 of memory corruptions problems caused by buggy H/W or
821 F/W or by drivers badly programing DMA (basically when
822 memory is written at bus level and the CPU MMU is
823 bypassed) which are not detectable by
824 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
825 tracking down these problems.
827 debugpat [X86] Enable PAT debugging
829 decnet.addr= [HW,NET]
830 Format: <area>[,<node>]
831 See also Documentation/networking/decnet.txt.
834 [same as hugepagesz=] The size of the default
835 HugeTLB page size. This is the size represented by
836 the legacy /proc/ hugepages APIs, used for SHM, and
837 default size when mounting hugetlbfs filesystems.
838 Defaults to the default architecture's huge page size
842 Set number of hash buckets for dentry cache.
845 See Documentation/networking/ipv6.txt.
847 disable_cpu_apicid= [X86,APIC,SMP]
849 The number of initial APIC ID for the
850 corresponding CPU to be disabled at boot,
851 mostly used for the kdump 2nd kernel to
852 disable BSP to wake up multiple CPUs without
853 causing system reset or hang due to sending
856 disable_ddw [PPC/PSERIES]
857 Disable Dynamic DMA Window support. Use this if
858 to workaround buggy firmware.
861 See Documentation/networking/ipv6.txt.
863 disable_mtrr_cleanup [X86]
864 The kernel tries to adjust MTRR layout from continuous
865 to discrete, to make X server driver able to add WB
866 entry later. This parameter disables that.
868 disable_mtrr_trim [X86, Intel and AMD only]
869 By default the kernel will trim any uncacheable
870 memory out of your available memory pool based on
871 MTRR settings. This parameter disables that behavior,
872 possibly causing your machine to run very slowly.
874 disable_timer_pin_1 [X86]
875 Disable PIN 1 of APIC timer
876 Can be useful to work around chipset bugs.
878 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
879 this option disables the debugging code at boot.
881 dma_debug_entries=<number>
882 This option allows to tune the number of preallocated
883 entries for DMA-API debugging code. One entry is
884 required per DMA-API allocation. Use this if the
885 DMA-API debugging code disables itself because the
886 architectural default is too low.
888 dma_debug_driver=<driver_name>
889 With this option the DMA-API debugging driver
890 filter feature can be enabled at boot time. Just
891 pass the driver to filter for as the parameter.
892 The filter can be disabled or changed to another
893 driver later using sysfs.
895 drm_kms_helper.edid_firmware=[<connector>:]<file>
896 Broken monitors, graphic adapters and KVMs may
897 send no or incorrect EDID data sets. This parameter
898 allows to specify an EDID data set in the
899 /lib/firmware directory that is used instead.
900 Generic built-in EDID data sets are used, if one of
901 edid/1024x768.bin, edid/1280x1024.bin,
902 edid/1680x1050.bin, or edid/1920x1080.bin is given
903 and no file with the same name exists. Details and
904 instructions how to build your own EDID data are
905 available in Documentation/EDID/HOWTO.txt. An EDID
906 data set will only be used for a particular connector,
907 if its name and a colon are prepended to the EDID
912 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
913 module.dyndbg[="val"]
914 Enable debug messages at boot time. See
915 Documentation/dynamic-debug-howto.txt for details.
917 early_ioremap_debug [KNL]
918 Enable debug messages in early_ioremap support. This
919 is useful for tracking down temporary early mappings
920 which are not unmapped.
922 earlycon= [KNL] Output early console device and options.
925 Start an early, polled-mode console on a cadence serial
926 port at the specified address. The cadence serial port
927 must already be setup and configured. Options are not
930 uart[8250],io,<addr>[,options]
931 uart[8250],mmio,<addr>[,options]
932 uart[8250],mmio32,<addr>[,options]
933 Start an early, polled-mode console on the 8250/16550
934 UART at the specified I/O port or MMIO address.
935 MMIO inter-register address stride is either 8-bit
936 (mmio) or 32-bit (mmio32).
937 The options are the same as for ttyS, above.
940 Start an early, polled-mode console on a pl011 serial
941 port at the specified address. The pl011 serial port
942 must already be setup and configured. Options are not
946 Start an early, polled-mode console on an msm serial
947 port at the specified address. The serial port
948 must already be setup and configured. Options are not
952 Start an early, polled-mode console on an msm serial
953 dm port at the specified address. The serial port
954 must already be setup and configured. Options are not
957 smh Use ARM semihosting calls for early console.
959 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
963 earlyprintk=serial[,ttySn[,baudrate]]
964 earlyprintk=serial[,0x...[,baudrate]]
965 earlyprintk=ttySn[,baudrate]
966 earlyprintk=dbgp[debugController#]
968 earlyprintk is useful when the kernel crashes before
969 the normal console is initialized. It is not enabled by
970 default because it has some cosmetic problems.
972 Append ",keep" to not disable it when the real console
975 Only one of vga, efi, serial, or usb debug port can
978 Currently only ttyS0 and ttyS1 may be specified by
979 name. Other I/O ports may be explicitly specified
980 on some architectures (x86 and arm at least) by
981 replacing ttySn with an I/O port address, like this:
982 earlyprintk=serial,0x1008,115200
983 You can find the port for a given device in
984 /proc/tty/driver/serial:
985 2: uart:ST16650V2 port:00001008 irq:18 ...
987 Interaction with the standard serial driver is not
990 The VGA and EFI output is eventually overwritten by
993 The xen output can only be used by Xen PV guests.
995 edac_report= [HW,EDAC] Control how to report EDAC event
996 Format: {"on" | "off" | "force"}
997 on: enable EDAC to report H/W event. May be overridden
998 by other higher priority error reporting module.
999 off: disable H/W event reporting through EDAC.
1000 force: enforce the use of EDAC to report H/W event.
1003 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1006 This is designed to be used in conjunction with
1007 the boot argument: earlyprintk=vga
1010 Format: {"off" | "on" | "skip[mbr]"}
1013 Format: { "old_map" }
1014 old_map [X86-64]: switch to the old ioremap-based EFI
1015 runtime services mapping. 32-bit still uses this one by
1018 efi_no_storage_paranoia [EFI; X86]
1019 Using this parameter you can use more than 50% of
1020 your efi variable storage. Use this parameter only if
1021 you are really sure that your UEFI does sane gc and
1022 fulfills the spec otherwise your board may brick.
1024 eisa_irq_edge= [PARISC,HW]
1025 See header of drivers/parisc/eisa.c.
1028 See comment before function elanfreq_setup() in
1029 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1032 Format: {"cfq" | "deadline" | "noop"}
1033 See Documentation/block/cfq-iosched.txt and
1034 Documentation/block/deadline-iosched.txt for details.
1036 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1037 Specifies physical address of start of kernel core
1038 image elf header and optionally the size. Generally
1039 kexec loader will pass this option to capture kernel.
1040 See Documentation/kdump/kdump.txt for details.
1042 enable_mtrr_cleanup [X86]
1043 The kernel tries to adjust MTRR layout from continuous
1044 to discrete, to make X server driver able to add WB
1045 entry later. This parameter enables that.
1047 enable_timer_pin_1 [X86]
1048 Enable PIN 1 of APIC timer
1049 Can be useful to work around chipset bugs
1050 (in particular on some ATI chipsets).
1051 The kernel tries to set a reasonable default.
1053 enforcing [SELINUX] Set initial enforcing status.
1055 See security/selinux/Kconfig help text.
1056 0 -- permissive (log only, no denials).
1057 1 -- enforcing (deny and log).
1059 Value can be changed at runtime via /selinux/enforce.
1062 Disable Error Record Serialization Table (ERST)
1065 ether= [HW,NET] Ethernet cards parameters
1066 This option is obsoleted by the "netdev=" option, which
1067 has equivalent usage. See its documentation for details.
1071 Permit 'security.evm' to be updated regardless of
1072 current integrity status.
1076 fail_make_request=[KNL]
1077 General fault injection mechanism.
1078 Format: <interval>,<probability>,<space>,<times>
1079 See also Documentation/fault-injection/.
1082 See Documentation/blockdev/floppy.txt.
1084 force_pal_cache_flush
1085 [IA-64] Avoid check_sal_cache_flush which may hang on
1086 buggy SAL_CACHE_FLUSH implementations. Using this
1087 parameter will force ia64_sal_cache_flush to call
1088 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1091 Forcefully enable Physical Address Extension (PAE).
1092 Many Pentium M systems disable PAE but may have a
1093 functionally usable PAE implementation.
1094 Warning: use of this parameter will taint the kernel
1095 and may cause unknown problems.
1098 [FTRACE] will set and start the specified tracer
1099 as early as possible in order to facilitate early
1102 ftrace_dump_on_oops[=orig_cpu]
1103 [FTRACE] will dump the trace buffers on oops.
1104 If no parameter is passed, ftrace will dump
1105 buffers of all CPUs, but if you pass orig_cpu, it will
1106 dump only the buffer of the CPU that triggered the
1109 ftrace_filter=[function-list]
1110 [FTRACE] Limit the functions traced by the function
1111 tracer at boot up. function-list is a comma separated
1112 list of functions. This list can be changed at run
1113 time by the set_ftrace_filter file in the debugfs
1116 ftrace_notrace=[function-list]
1117 [FTRACE] Do not trace the functions specified in
1118 function-list. This list can be changed at run time
1119 by the set_ftrace_notrace file in the debugfs
1122 ftrace_graph_filter=[function-list]
1123 [FTRACE] Limit the top level callers functions traced
1124 by the function graph tracer at boot up.
1125 function-list is a comma separated list of functions
1126 that can be changed at run time by the
1127 set_graph_function file in the debugfs tracing directory.
1129 ftrace_graph_notrace=[function-list]
1130 [FTRACE] Do not trace from the functions specified in
1131 function-list. This list is a comma separated list of
1132 functions that can be changed at run time by the
1133 set_graph_notrace file in the debugfs tracing directory.
1136 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1137 support via parallel port (up to 5 devices per port)
1138 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1139 See also Documentation/input/joystick-parport.txt
1143 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1147 gcov_persist= [GCOV] When non-zero (default), profiling data for
1148 kernel modules is saved and remains accessible via
1149 debugfs, even when the module is unloaded/reloaded.
1150 When zero, profiling data is discarded and associated
1151 debugfs files are removed at module unload time.
1153 gpt [EFI] Forces disk with valid GPT signature but
1154 invalid Protective MBR to be treated as GPT. If the
1155 primary GPT is corrupted, it enables the backup/alternate
1156 GPT to be used instead.
1158 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1159 the "Enable 0" bit of the configuration register.
1162 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1163 the "Enable 0" bit of the configuration register.
1166 grcan.select= [HW] Select which physical interface to use.
1169 grcan.txsize= [HW] Sets the size of the tx buffer.
1170 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1172 grcan.rxsize= [HW] Sets the size of the rx buffer.
1173 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1176 hashdist= [KNL,NUMA] Large hashes allocated during boot
1177 are distributed across NUMA nodes. Defaults on
1178 for 64-bit NUMA, off otherwise.
1179 Format: 0 | 1 (for off | on)
1181 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1183 hd= [EIDE] (E)IDE hard drive subsystem geometry
1184 Format: <cyl>,<head>,<sect>
1187 Disable Hardware Error Source Table (HEST) support;
1188 corresponding firmware-first mode error processing
1189 logic will be disabled.
1191 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1192 size of <nn>. This works even on boxes that have no
1193 highmem otherwise. This also works to reduce highmem
1194 size on bigger boxes.
1196 highres= [KNL] Enable/disable high resolution timer mode.
1197 Valid parameters: "on", "off"
1201 See Documentation/isdn/README.HiSax.
1205 hpet= [X86-32,HPET] option to control HPET usage
1206 Format: { enable (default) | disable | force |
1208 disable: disable HPET and use PIT instead
1209 force: allow force enabled of undocumented chips (ICH4,
1211 verbose: show contents of HPET registers during setup
1213 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1214 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1216 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1217 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1218 On x86-64 and powerpc, this option can be specified
1219 multiple times interleaved with hugepages= to reserve
1220 huge pages of different sizes. Valid pages sizes on
1221 x86-64 are 2M (when the CPU supports "pse") and 1G
1222 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1223 Note that 1GB pages can only be allocated at boot time
1224 using hugepages= and not freed afterwards.
1226 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1227 terminal devices. Valid values: 0..8
1228 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1229 If specified, z/VM IUCV HVC accepts connections
1230 from listed z/VM user IDs only.
1232 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1233 hardware thread id mappings.
1234 Format: <cpu>:<hwthread>
1237 Do not unregister boot console at start. This is only
1238 useful for debugging when something happens in the window
1239 between unregistering the boot console and initializing
1242 i2c_bus= [HW] Override the default board specific I2C bus speed
1243 or register an additional I2C bus that is not
1244 registered from board initialization code.
1248 i8042.debug [HW] Toggle i8042 debug mode
1249 i8042.direct [HW] Put keyboard port into non-translated mode
1250 i8042.dumbkbd [HW] Pretend that controller can only read data from
1251 keyboard and cannot control its state
1252 (Don't attempt to blink the leds)
1253 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1254 i8042.nokbd [HW] Don't check/create keyboard port
1255 i8042.noloop [HW] Disable the AUX Loopback command while probing
1257 i8042.nomux [HW] Don't check presence of an active multiplexing
1259 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1261 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1262 i8042.reset [HW] Reset the controller during init and cleanup
1263 i8042.unlock [HW] Unlock (ignore) the keylock
1267 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1268 indicates that the driver is running on unsupported
1270 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1271 does not match list of supported models.
1273 [HW] Report power status in /proc/i8k
1274 (disabled by default)
1275 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1278 i915.invert_brightness=
1279 [DRM] Invert the sense of the variable that is used to
1280 set the brightness of the panel backlight. Normally a
1281 brightness value of 0 indicates backlight switched off,
1282 and the maximum of the brightness value sets the backlight
1283 to maximum brightness. If this parameter is set to 0
1284 (default) and the machine requires it, or this parameter
1285 is set to 1, a brightness value of 0 sets the backlight
1286 to maximum brightness, and the maximum of the brightness
1287 value switches the backlight off.
1288 -1 -- never invert brightness
1289 0 -- machine default
1290 1 -- force brightness inversion
1293 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1295 ide-core.nodma= [HW] (E)IDE subsystem
1296 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1297 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1298 .cdrom .chs .ignore_cable are additional options
1299 See Documentation/ide/ide.txt.
1301 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1302 Claim all unknown PCI IDE storage controllers.
1305 Format: idle=poll, idle=halt, idle=nomwait
1306 Poll forces a polling idle loop that can slightly
1307 improve the performance of waking up a idle CPU, but
1308 will use a lot of power and make the system run hot.
1310 idle=halt: Halt is forced to be used for CPU idle.
1311 In such case C2/C3 won't be used again.
1312 idle=nomwait: Disable mwait for CPU C-states
1314 ignore_loglevel [KNL]
1315 Ignore loglevel setting - this will print /all/
1316 kernel messages to the console. Useful for debugging.
1317 We also add it as printk module parameter, so users
1318 could change it dynamically, usually by
1319 /sys/module/printk/parameters/ignore_loglevel.
1321 ihash_entries= [KNL]
1322 Set number of hash buckets for inode cache.
1324 ima_appraise= [IMA] appraise integrity measurements
1325 Format: { "off" | "enforce" | "fix" }
1328 ima_appraise_tcb [IMA]
1329 The builtin appraise policy appraises all files
1333 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1337 The list of supported hash algorithms is defined
1338 in crypto/hash_info.h.
1341 Load a policy which meets the needs of the Trusted
1342 Computing Base. This means IMA will measure all
1343 programs exec'd, files mmap'd for exec, and all files
1344 opened for read by uid=0.
1347 Select one of defined IMA measurements template formats.
1348 Formats: { "ima" | "ima-ng" }
1351 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1352 Format: <min_file_size>
1353 Set the minimal file size for using asynchronous hash.
1354 If left unspecified, ahash usage is disabled.
1356 ahash performance varies for different data sizes on
1357 different crypto accelerators. This option can be used
1358 to achieve the best performance for a particular HW.
1360 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1362 Set hashing buffer size. Default: 4k.
1364 ahash performance varies for different chunk sizes on
1365 different crypto accelerators. This option can be used
1366 to achieve best performance for particular HW.
1370 Run specified binary instead of /sbin/init as init
1373 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1374 for working out where the kernel is dying during
1377 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1378 initcall functions. Useful for debugging built-in
1379 modules and initcalls.
1381 initrd= [BOOT] Specify the location of the initial ramdisk
1383 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1386 int_pln_enable [x86] Enable power limit notification interrupt
1388 integrity_audit=[IMA]
1389 Format: { "0" | "1" }
1390 0 -- basic integrity auditing messages. (Default)
1391 1 -- additional integrity auditing messages.
1393 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1395 Enable intel iommu driver.
1397 Disable intel iommu driver.
1398 igfx_off [Default Off]
1399 By default, gfx is mapped as normal device. If a gfx
1400 device has a dedicated DMAR unit, the DMAR unit is
1401 bypassed by not enabling DMAR with this option. In
1402 this case, gfx device will use physical address for
1405 With this option iommu will not optimize to look
1406 for io virtual address below 32-bit forcing dual
1407 address cycle on pci bus for cards supporting greater
1408 than 32-bit addressing. The default is to look
1409 for translation below 32-bit and if not available
1410 then look in the higher range.
1411 strict [Default Off]
1412 With this option on every unmap_single operation will
1413 result in a hardware IOTLB flush operation as opposed
1414 to batching them for performance.
1415 sp_off [Default Off]
1416 By default, super page will be supported if Intel IOMMU
1417 has the capability. With this option, super page will
1420 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1421 0 disables intel_idle and fall back on acpi_idle.
1422 1 to 6 specify maximum depth of C-state.
1426 Do not enable intel_pstate as the default
1427 scaling driver for the supported processors
1429 intremap= [X86-64, Intel-IOMMU]
1430 on enable Interrupt Remapping (default)
1431 off disable Interrupt Remapping
1432 nosid disable Source ID checking
1434 BIOS x2APIC opt-out request will be ignored
1436 iomem= Disable strict checking of access to MMIO memory
1437 strict regions from userspace.
1454 io7= [HW] IO7 for Marvel based alpha systems
1455 See comment before marvel_specify_io7 in
1456 arch/alpha/kernel/core_marvel.c.
1458 io_delay= [X86] I/O delay method
1460 Standard port 0x80 based delay
1462 Alternate port 0xed based delay (needed on some systems)
1464 Simple two microseconds delay
1469 See Documentation/filesystems/nfs/nfsroot.txt.
1472 When an interrupt is not handled search all handlers
1473 for it. Intended to get systems with badly broken
1477 When an interrupt is not handled search all handlers
1478 for it. Also check all handlers each timer
1479 interrupt. Intended to get systems with badly broken
1483 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1485 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1487 <cpu number>,...,<cpu number>
1489 <cpu number>-<cpu number>
1490 (must be a positive range in ascending order)
1492 <cpu number>,...,<cpu number>-<cpu number>
1494 This option can be used to specify one or more CPUs
1495 to isolate from the general SMP balancing and scheduling
1496 algorithms. You can move a process onto or off an
1497 "isolated" CPU via the CPU affinity syscalls or cpuset.
1498 <cpu number> begins at 0 and the maximum value is
1499 "number of CPUs in system - 1".
1501 This option is the preferred way to isolate CPUs. The
1502 alternative -- manually setting the CPU mask of all
1503 tasks in the system -- can cause problems and
1504 suboptimal load balancer performance.
1508 ivrs_ioapic [HW,X86_64]
1509 Provide an override to the IOAPIC-ID<->DEVICE-ID
1510 mapping provided in the IVRS ACPI table. For
1511 example, to map IOAPIC-ID decimal 10 to
1512 PCI device 00:14.0 write the parameter as:
1513 ivrs_ioapic[10]=00:14.0
1515 ivrs_hpet [HW,X86_64]
1516 Provide an override to the HPET-ID<->DEVICE-ID
1517 mapping provided in the IVRS ACPI table. For
1518 example, to map HPET-ID decimal 0 to
1519 PCI device 00:14.0 write the parameter as:
1520 ivrs_hpet[0]=00:14.0
1522 js= [HW,JOY] Analog joystick
1523 See Documentation/input/joystick.txt.
1526 Enable/disable kernel and module base offset ASLR
1527 (Address Space Layout Randomization) if built into
1528 the kernel. When CONFIG_HIBERNATION is selected,
1529 kASLR is disabled by default. When kASLR is enabled,
1530 hibernation will be disabled.
1534 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1535 specifies the amount of memory usable by the kernel
1536 for non-movable allocations. The requested amount is
1537 spread evenly throughout all nodes in the system. The
1538 remaining memory in each node is used for Movable
1539 pages. In the event, a node is too small to have both
1540 kernelcore and Movable pages, kernelcore pages will
1541 take priority and other nodes will have a larger number
1542 of Movable pages. The Movable zone is used for the
1543 allocation of pages that may be reclaimed or moved
1544 by the page migration subsystem. This means that
1545 HugeTLB pages may not be allocated from this zone.
1546 Note that allocations like PTEs-from-HighMem still
1547 use the HighMem zone if it exists, and the Normal
1548 zone if it does not.
1550 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1551 Format: <Controller#>[,poll interval]
1552 The controller # is the number of the ehci usb debug
1553 port as it is probed via PCI. The poll interval is
1554 optional and is the number seconds in between
1555 each poll cycle to the debug port in case you need
1556 the functionality for interrupting the kernel with
1557 gdb or control-c on the dbgp connection. When
1558 not using this parameter you use sysrq-g to break into
1559 the kernel debugger.
1561 kgdboc= [KGDB,HW] kgdb over consoles.
1562 Requires a tty driver that supports console polling,
1563 or a supported polling keyboard driver (non-usb).
1564 Serial only format: <serial_device>[,baud]
1565 keyboard only format: kbd
1566 keyboard and serial format: kbd,<serial_device>[,baud]
1567 Optional Kernel mode setting:
1568 kms, kbd format: kms,kbd
1569 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1571 kgdbwait [KGDB] Stop kernel execution and enter the
1572 kernel debugger at the earliest opportunity.
1574 kmac= [MIPS] korina ethernet MAC address.
1575 Configure the RouterBoard 532 series on-chip
1576 Ethernet adapter MAC address.
1578 kmemleak= [KNL] Boot-time kmemleak enable/disable
1579 Valid arguments: on, off
1582 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1583 Valid arguments: 0, 1, 2
1584 kmemcheck=0 (disabled)
1585 kmemcheck=1 (enabled)
1586 kmemcheck=2 (one-shot mode)
1587 Default: 2 (one-shot mode)
1589 kstack=N [X86] Print N words from the kernel stack
1592 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1593 Default is 0 (don't ignore, but inject #GP)
1595 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1599 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1600 Default is 1 (enabled)
1602 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1604 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1606 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1607 (virtualized MMU) support on capable Intel chips.
1608 Default is 1 (enabled)
1610 kvm-intel.emulate_invalid_guest_state=
1611 [KVM,Intel] Enable emulation of invalid guest states
1612 Default is 0 (disabled)
1614 kvm-intel.flexpriority=
1615 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1616 Default is 1 (enabled)
1619 [KVM,Intel] Enable VMX nesting (nVMX).
1620 Default is 0 (disabled)
1622 kvm-intel.unrestricted_guest=
1623 [KVM,Intel] Disable unrestricted guest feature
1624 (virtualized real and unpaged mode) on capable
1625 Intel chips. Default is 1 (enabled)
1627 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1628 feature (tagged TLBs) on capable Intel chips.
1629 Default is 1 (enabled)
1635 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1638 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1639 value for LAPIC timer one-shot implementation. Default
1640 back to the programmable timer unit in the LAPIC.
1642 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1645 libata.dma= [LIBATA] DMA control
1646 libata.dma=0 Disable all PATA and SATA DMA
1647 libata.dma=1 PATA and SATA Disk DMA only
1648 libata.dma=2 ATAPI (CDROM) DMA only
1649 libata.dma=4 Compact Flash DMA only
1650 Combinations also work, so libata.dma=3 enables DMA
1651 for disks and CDROMs, but not CFs.
1653 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1654 libata.ignore_hpa=0 keep BIOS limits (default)
1655 libata.ignore_hpa=1 ignore limits, using full disk
1657 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1661 libata.force= [LIBATA] Force configurations. The format is comma
1662 separated list of "[ID:]VAL" where ID is
1663 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1664 matching port, link or device. Basically, it matches
1665 the ATA ID string printed on console by libata. If
1666 the whole ID part is omitted, the last PORT and DEVICE
1667 values are used. If ID hasn't been specified yet, the
1668 configuration applies to all ports, links and devices.
1670 If only DEVICE is omitted, the parameter applies to
1671 the port and all links and devices behind it. DEVICE
1672 number of 0 either selects the first device or the
1673 first fan-out link behind PMP device. It does not
1674 select the host link. DEVICE number of 15 selects the
1675 host link and device attached to it.
1677 The VAL specifies the configuration to force. As long
1678 as there's no ambiguity shortcut notation is allowed.
1679 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1680 The following configurations can be forced.
1682 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1683 Any ID with matching PORT is used.
1685 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1687 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1688 udma[/][16,25,33,44,66,100,133] notation is also
1691 * [no]ncq: Turn on or off NCQ.
1693 * nohrst, nosrst, norst: suppress hard, soft
1696 * rstonce: only attempt one reset during
1697 hot-unplug link recovery
1699 * dump_id: dump IDENTIFY data.
1701 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1703 * disable: Disable this device.
1705 If there are multiple matching configurations changing
1706 the same attribute, the last one is used.
1708 memblock=debug [KNL] Enable memblock debug messages.
1710 load_ramdisk= [RAM] List of ramdisks to load from floppy
1711 See Documentation/blockdev/ramdisk.txt.
1713 lockd.nlm_grace_period=P [NFS] Assign grace period.
1716 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1719 lockd.nlm_timeout=T [NFS] Assign timeout value.
1722 lockd.nlm_udpport=M [NFS] Assign UDP port.
1725 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1728 loglevel= All Kernel Messages with a loglevel smaller than the
1729 console loglevel will be printed to the console. It can
1730 also be changed with klogd or other programs. The
1731 loglevels are defined as follows:
1733 0 (KERN_EMERG) system is unusable
1734 1 (KERN_ALERT) action must be taken immediately
1735 2 (KERN_CRIT) critical conditions
1736 3 (KERN_ERR) error conditions
1737 4 (KERN_WARNING) warning conditions
1738 5 (KERN_NOTICE) normal but significant condition
1739 6 (KERN_INFO) informational
1740 7 (KERN_DEBUG) debug-level messages
1742 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1743 in bytes. n must be a power of two and greater
1744 than the minimal size. The minimal size is defined
1745 by LOG_BUF_SHIFT kernel config parameter. There is
1746 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1747 that allows to increase the default size depending on
1748 the number of CPUs. See init/Kconfig for more details.
1750 logo.nologo [FB] Disables display of the built-in Linux logo.
1751 This may be used to provide more screen space for
1752 kernel log messages and is useful when debugging
1753 kernel boot problems.
1755 lp=0 [LP] Specify parallel ports to use, e.g,
1756 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1757 lp=reset first parallel port). 'lp=0' disables the
1758 lp=auto printer driver. 'lp=reset' (which can be
1759 specified in addition to the ports) causes
1760 attached printers to be reset. Using
1761 lp=port1,port2,... specifies the parallel ports
1762 to associate lp devices with, starting with
1763 lp0. A port specification may be 'none' to skip
1764 that lp device, or a parport name such as
1765 'parport0'. Specifying 'lp=auto' instead of a
1766 port specification list means that device IDs
1767 from each port should be examined, to see if
1768 an IEEE 1284-compliant printer is attached; if
1769 so, the driver will manage that printer.
1770 See also header of drivers/char/lp.c.
1773 Sets loops_per_jiffy to given constant, thus avoiding
1774 time-consuming boot-time autodetection (up to 250 ms per
1775 CPU). 0 enables autodetection (default). To determine
1776 the correct value for your kernel, boot with normal
1777 autodetection and see what value is printed. Note that
1778 on SMP systems the preset will be applied to all CPUs,
1779 which is likely to cause problems if your CPUs need
1780 significantly divergent settings. An incorrect value
1781 will cause delays in the kernel to be wrong, leading to
1782 unpredictable I/O errors and other breakage. Although
1783 unlikely, in the extreme case this might damage your
1787 Format: <io>,<irq>,<dma>
1789 machvec= [IA-64] Force the use of a particular machine-vector
1790 (machvec) in a generic kernel.
1791 Example: machvec=hpzx1_swiotlb
1793 machtype= [Loongson] Share the same kernel image file between different
1795 Example: machtype=lemote-yeeloong-2f-7inch
1797 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1798 than or equal to this physical address is ignored.
1800 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1801 should make use of. maxcpus=n : n >= 0 limits the
1802 kernel to using 'n' processors. n=0 is a special case,
1803 it is equivalent to "nosmp", which also disables
1806 max_loop= [LOOP] The number of loop block devices that get
1807 (loop.max_loop) unconditionally pre-created at init time. The default
1808 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1809 of statically allocating a predefined number, loop
1810 devices can be requested on-demand with the
1811 /dev/loop-control interface.
1813 mce [X86-32] Machine Check Exception
1815 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1817 md= [HW] RAID subsystems devices and level
1818 See Documentation/md.txt.
1821 Format: <first>,<last>
1822 Specifies range of consoles to be captured by the MDA.
1824 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1825 Amount of memory to be used when the kernel is not able
1826 to see the whole system memory or for test.
1827 [X86] Work as limiting max address. Use together
1828 with memmap= to avoid physical address space collisions.
1829 Without memmap= PCI devices could be placed at addresses
1830 belonging to unused RAM.
1832 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1836 [KNL,SH] Allow user to override the default size for
1837 per-device physically contiguous DMA buffers.
1839 memmap=exactmap [KNL,X86] Enable setting of an exact
1840 E820 memory map, as specified by the user.
1841 Such memmap=exactmap lines can be constructed based on
1842 BIOS output or other requirements. See the memmap=nn@ss
1845 memmap=nn[KMG]@ss[KMG]
1846 [KNL] Force usage of a specific region of memory.
1847 Region of memory to be used is from ss to ss+nn.
1849 memmap=nn[KMG]#ss[KMG]
1850 [KNL,ACPI] Mark specific memory as ACPI data.
1851 Region of memory to be marked is from ss to ss+nn.
1853 memmap=nn[KMG]$ss[KMG]
1854 [KNL,ACPI] Mark specific memory as reserved.
1855 Region of memory to be reserved is from ss to ss+nn.
1856 Example: Exclude memory from 0x18690000-0x1869ffff
1857 memmap=64K$0x18690000
1859 memmap=0x10000$0x18690000
1861 memory_corruption_check=0/1 [X86]
1862 Some BIOSes seem to corrupt the first 64k of
1863 memory when doing things like suspend/resume.
1864 Setting this option will scan the memory
1865 looking for corruption. Enabling this will
1866 both detect corruption and prevent the kernel
1867 from using the memory being corrupted.
1868 However, its intended as a diagnostic tool; if
1869 repeatable BIOS-originated corruption always
1870 affects the same memory, you can use memmap=
1871 to prevent the kernel from using that memory.
1873 memory_corruption_check_size=size [X86]
1874 By default it checks for corruption in the low
1875 64k, making this memory unavailable for normal
1876 use. Use this parameter to scan for
1877 corruption in more or less memory.
1879 memory_corruption_check_period=seconds [X86]
1880 By default it checks for corruption every 60
1881 seconds. Use this parameter to check at some
1882 other rate. 0 disables periodic checking.
1884 memtest= [KNL,X86] Enable memtest
1886 default : 0 <disable>
1887 Specifies the number of memtest passes to be
1888 performed. Each pass selects another test
1889 pattern from a given set of patterns. Memtest
1890 fills the memory with this pattern, validates
1891 memory contents and reserves bad memory
1892 regions that are detected.
1894 meye.*= [HW] Set MotionEye Camera parameters
1895 See Documentation/video4linux/meye.txt.
1897 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1898 Multi-Function General Purpose Timers on AMD Geode
1901 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1902 the BIOS has incorrectly applied a workaround. TinyBIOS
1903 version 0.98 is known to be affected, 0.99 fixes the
1904 problem by letting the user disable the workaround.
1908 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1909 physical address is ignored.
1911 mini2440= [ARM,HW,KNL]
1912 Format:[0..2][b][c][t]
1914 MINI2440 configuration specification:
1915 0 - The attached screen is the 3.5" TFT
1916 1 - The attached screen is the 7" TFT
1917 2 - The VGA Shield is attached (1024x768)
1918 Leaving out the screen size parameter will not load
1919 the TFT driver, and the framebuffer will be left
1921 b - Enable backlight. The TFT backlight pin will be
1922 linked to the kernel VESA blanking code and a GPIO
1923 LED. This parameter is not necessary when using the
1925 c - Enable the s3c camera interface.
1926 t - Reserved for enabling touchscreen support. The
1927 touchscreen support is not enabled in the mainstream
1928 kernel as of 2.6.30, a preliminary port can be found
1929 in the "bleeding edge" mini2440 support kernel at
1930 http://repo.or.cz/w/linux-2.6/mini2440.git
1933 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1934 parameter allows control of the logging verbosity for
1935 the additional memory initialisation checks. A value
1936 of 0 disables mminit logging and a level of 4 will
1937 log everything. Information is printed at KERN_DEBUG
1938 so loglevel=8 may also need to be specified.
1941 [KNL] When CONFIG_MODULE_SIG is set, this means that
1942 modules without (valid) signatures will fail to load.
1943 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1944 is always true, so this option does nothing.
1947 [MOUSE] Maximum time between finger touching and
1948 leaving touchpad surface for touch to be considered
1949 a tap and be reported as a left button click (for
1950 touchpads working in absolute mode only).
1952 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1953 reporting absolute coordinates, such as tablets
1954 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1955 reporting absolute coordinates, such as tablets
1957 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1958 is similar to kernelcore except it specifies the
1959 amount of memory used for migratable allocations.
1960 If both kernelcore and movablecore is specified,
1961 then kernelcore will be at *least* the specified
1962 value but may be more. If movablecore on its own
1963 is specified, the administrator must be careful
1964 that the amount of memory usable for all allocations
1967 movable_node [KNL,X86] Boot-time switch to enable the effects
1968 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1970 MTD_Partition= [MTD]
1971 Format: <name>,<region-number>,<size>,<offset>
1973 MTD_Region= [MTD] Format:
1974 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1977 See drivers/mtd/cmdlinepart.c.
1979 multitce=off [PPC] This parameter disables the use of the pSeries
1980 firmware feature for updating multiple TCE entries
1983 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1985 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1987 boundary - index of last SLC block on Flex-OneNAND.
1988 The remaining blocks are configured as MLC blocks.
1989 lock - Configure if Flex-OneNAND boundary should be locked.
1990 Once locked, the boundary cannot be changed.
1991 1 indicates lock status, 0 indicates unlock status.
1994 ARM/S3C2412 JIVE boot control
1996 See arch/arm/mach-s3c2412/mach-jive.c
1998 mtouchusb.raw_coordinates=
1999 [HW] Make the MicroTouch USB driver use raw coordinates
2000 ('y', default) or cooked coordinates ('n')
2002 mtrr_chunk_size=nn[KMG] [X86]
2003 used for mtrr cleanup. It is largest continuous chunk
2004 that could hold holes aka. UC entries.
2006 mtrr_gran_size=nn[KMG] [X86]
2007 Used for mtrr cleanup. It is granularity of mtrr block.
2009 Large value could prevent small alignment from
2012 mtrr_spare_reg_nr=n [X86]
2014 Range: 0,7 : spare reg number
2016 Used for mtrr cleanup. It is spare mtrr entries number.
2017 Set to 2 or more if your graphical card needs more.
2019 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2021 netdev= [NET] Network devices parameters
2022 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2023 Note that mem_start is often overloaded to mean
2024 something different and driver-specific.
2025 This usage is only documented in each driver source
2029 [NETFILTER] Enable connection tracking flow accounting
2030 0 to disable accounting
2031 1 to enable accounting
2034 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2035 See Documentation/filesystems/nfs/nfsroot.txt.
2037 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2038 See Documentation/filesystems/nfs/nfsroot.txt.
2040 nfsrootdebug [NFS] enable nfsroot debugging messages.
2041 See Documentation/filesystems/nfs/nfsroot.txt.
2043 nfs.callback_tcpport=
2044 [NFS] set the TCP port on which the NFSv4 callback
2045 channel should listen.
2048 [NFS] sets the pathname to the program which is used
2049 to update the NFS client cache entries.
2051 nfs.cache_getent_timeout=
2052 [NFS] sets the timeout after which an attempt to
2053 update a cache entry is deemed to have failed.
2055 nfs.idmap_cache_timeout=
2056 [NFS] set the maximum lifetime for idmapper cache
2060 [NFS] enable 64-bit inode numbers.
2061 If zero, the NFS client will fake up a 32-bit inode
2062 number for the readdir() and stat() syscalls instead
2063 of returning the full 64-bit number.
2064 The default is to return 64-bit inode numbers.
2066 nfs.max_session_slots=
2067 [NFSv4.1] Sets the maximum number of session slots
2068 the client will attempt to negotiate with the server.
2069 This limits the number of simultaneous RPC requests
2070 that the client can send to the NFSv4.1 server.
2071 Note that there is little point in setting this
2072 value higher than the max_tcp_slot_table_limit.
2074 nfs.nfs4_disable_idmapping=
2075 [NFSv4] When set to the default of '1', this option
2076 ensures that both the RPC level authentication
2077 scheme and the NFS level operations agree to use
2078 numeric uids/gids if the mount is using the
2079 'sec=sys' security flavour. In effect it is
2080 disabling idmapping, which can make migration from
2081 legacy NFSv2/v3 systems to NFSv4 easier.
2082 Servers that do not support this mode of operation
2083 will be autodetected by the client, and it will fall
2084 back to using the idmapper.
2085 To turn off this behaviour, set the value to '0'.
2087 [NFS4] Specify an additional fixed unique ident-
2088 ification string that NFSv4 clients can insert into
2089 their nfs_client_id4 string. This is typically a
2090 UUID that is generated at system install time.
2092 nfs.send_implementation_id =
2093 [NFSv4.1] Send client implementation identification
2094 information in exchange_id requests.
2095 If zero, no implementation identification information
2097 The default is to send the implementation identification
2100 nfs.recover_lost_locks =
2101 [NFSv4] Attempt to recover locks that were lost due
2102 to a lease timeout on the server. Please note that
2103 doing this risks data corruption, since there are
2104 no guarantees that the file will remain unchanged
2105 after the locks are lost.
2106 If you want to enable the kernel legacy behaviour of
2107 attempting to recover these locks, then set this
2109 The default parameter value of '0' causes the kernel
2110 not to attempt recovery of lost locks.
2112 nfsd.nfs4_disable_idmapping=
2113 [NFSv4] When set to the default of '1', the NFSv4
2114 server will return only numeric uids and gids to
2115 clients using auth_sys, and will accept numeric uids
2116 and gids from such clients. This is intended to ease
2117 migration from NFSv2/v3.
2119 objlayoutdriver.osd_login_prog=
2120 [NFS] [OBJLAYOUT] sets the pathname to the program which
2121 is used to automatically discover and login into new
2122 osd-targets. Please see:
2123 Documentation/filesystems/pnfs.txt for more explanations
2125 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2126 when a NMI is triggered.
2127 Format: [state][,regs][,debounce][,die]
2129 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2130 Format: [panic,][nopanic,][num]
2132 0 - turn nmi_watchdog off
2133 When panic is specified, panic when an NMI watchdog
2134 timeout occurs (or 'nopanic' to override the opposite
2136 This is useful when you use a panic=... timeout and
2137 need the box quickly up again.
2139 netpoll.carrier_timeout=
2140 [NET] Specifies amount of time (in seconds) that
2141 netpoll should wait for a carrier. By default netpoll
2144 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2145 emulation library even if a 387 maths coprocessor
2149 [HW] Never suspend the console
2150 Disable suspending of consoles during suspend and
2151 hibernate operations. Once disabled, debugging
2152 messages can reach various consoles while the rest
2153 of the system is being put to sleep (ie, while
2154 debugging driver suspend/resume hooks). This may
2155 not work reliably with all consoles, but is known
2156 to work with serial and VGA consoles.
2157 To facilitate more flexible debugging, we also add
2158 console_suspend, a printk module parameter to control
2159 it. Users could use console_suspend (usually
2160 /sys/module/printk/parameters/console_suspend) to
2161 turn on/off it dynamically.
2163 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2164 caches in the slab allocator. Saves per-node memory,
2165 but will impact performance.
2169 noapic [SMP,APIC] Tells the kernel to not make use of any
2170 IOAPICs that may be present in the system.
2172 noautogroup Disable scheduler automatic task group creation.
2174 nobats [PPC] Do not use BATs for mapping kernel lowmem
2175 on "Classic" PPC cores.
2179 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2181 nodelayacct [KNL] Disable per-task delay accounting
2183 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2185 nodsp [SH] Disable hardware DSP at boot time.
2187 noefi [X86] Disable EFI runtime services support.
2192 On X86-32 available only on PAE configured kernels.
2193 noexec=on: enable non-executable mappings (default)
2194 noexec=off: disable non-executable mappings
2197 Disable SMAP (Supervisor Mode Access Prevention)
2198 even if it is supported by processor.
2201 Disable SMEP (Supervisor Mode Execution Prevention)
2202 even if it is supported by processor.
2205 This affects only 32-bit executables.
2206 noexec32=on: enable non-executable mappings (default)
2207 read doesn't imply executable mappings
2208 noexec32=off: disable non-executable mappings
2209 read implies executable mappings
2211 nofpu [SH] Disable hardware FPU at boot time.
2213 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2214 register save and restore. The kernel will only save
2215 legacy floating-point registers on task switch.
2217 noxsave [BUGS=X86] Disables x86 extended register state save
2218 and restore using xsave. The kernel will fallback to
2219 enabling legacy floating-point and sse state.
2221 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2222 register states. The kernel will fall back to use
2223 xsave to save the states. By using this parameter,
2224 performance of saving the states is degraded because
2225 xsave doesn't support modified optimization while
2226 xsaveopt supports it on xsaveopt enabled systems.
2228 noxsaves [X86] Disables xsaves and xrstors used in saving and
2229 restoring x86 extended register state in compacted
2230 form of xsave area. The kernel will fall back to use
2231 xsaveopt and xrstor to save and restore the states
2232 in standard form of xsave area. By using this
2233 parameter, xsave area per process might occupy more
2234 memory on xsaves enabled systems.
2237 on enable eager fpu restore
2238 off disable eager fpu restore
2239 auto selects the default scheme, which automatically
2240 enables eagerfpu restore for xsaveopt.
2242 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2243 wfi(ARM) instruction doesn't work correctly and not to
2244 use it. This is also useful when using JTAG debugger.
2246 no_file_caps Tells the kernel not to honor file capabilities. The
2247 only way then for a file to be executed with privilege
2248 is to be setuid root or executed by root.
2250 nohalt [IA-64] Tells the kernel not to use the power saving
2251 function PAL_HALT_LIGHT when idle. This increases
2252 power-consumption. On the positive side, it reduces
2253 interrupt wake-up latency, which may improve performance
2254 in certain environments such as networked servers or
2257 nohibernate [HIBERNATION] Disable hibernation and resume.
2259 nohz= [KNL] Boottime enable/disable dynamic ticks
2260 Valid arguments: on, off
2263 nohz_full= [KNL,BOOT]
2264 In kernels built with CONFIG_NO_HZ_FULL=y, set
2265 the specified list of CPUs whose tick will be stopped
2266 whenever possible. The boot CPU will be forced outside
2267 the range to maintain the timekeeping.
2268 The CPUs in this range must also be included in the
2271 noiotrap [SH] Disables trapped I/O port accesses.
2273 noirqdebug [X86-32] Disables the code which attempts to detect and
2274 disable unhandled interrupt sources.
2276 no_timer_check [X86,APIC] Disables the code which tests for
2277 broken timer IRQ sources.
2279 noisapnp [ISAPNP] Disables ISA PnP code.
2281 noinitrd [RAM] Tells the kernel not to load any configured
2284 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2286 [Deprecated - use intremap=off]
2290 nojitter [IA-64] Disables jitter checking for ITC timers.
2292 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2294 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2297 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2298 steal time is computed, but won't influence scheduler
2301 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2303 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2305 noltlbs [PPC] Do not use large page/tlb entries for kernel
2306 lowmem mapping on PPC40x.
2308 nomca [IA-64] Disable machine check abort handling
2310 nomce [X86-32] Machine Check Exception
2312 nomfgpt [X86-32] Disable Multi-Function General Purpose
2313 Timer usage (for AMD Geode machines).
2315 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2316 shutdown the other cpus. Instead use the REBOOT_VECTOR
2319 nomodule Disable module load
2321 nopat [X86] Disable PAT (page attribute table extension of
2322 pagetables) support.
2324 norandmaps Don't use address space randomization. Equivalent to
2325 echo 0 > /proc/sys/kernel/randomize_va_space
2327 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2329 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2330 with UP alternatives
2332 nordrand [X86] Disable kernel use of the RDRAND and
2333 RDSEED instructions even if they are supported
2334 by the processor. RDRAND and RDSEED are still
2335 available to user space applications.
2337 noresume [SWSUSP] Disables resume and restores original swap
2340 no-scroll [VGA] Disables scrollback.
2341 This is required for the Braillex ib80-piezo Braille
2342 reader made by F.H. Papenmeier (Germany).
2346 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2348 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2349 and disable the IO APIC. legacy for "maxcpus=0".
2351 nosoftlockup [KNL] Disable the soft-lockup detector.
2353 nosync [HW,M68K] Disables sync negotiation for all devices.
2355 notsc [BUGS=X86-32] Disable Time Stamp Counter
2357 nousb [USB] Disable the USB subsystem
2359 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2363 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2365 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2366 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2367 Some features depend on CPU0. Known dependencies are:
2368 1. Resume from suspend/hibernate depends on CPU0.
2369 Suspend/hibernate will fail if CPU0 is offline and you
2370 need to online CPU0 before suspend/hibernate.
2371 2. PIC interrupts also depend on CPU0. CPU0 can't be
2372 removed if a PIC interrupt is detected.
2373 It's said poweroff/reboot may depend on CPU0 on some
2374 machines although I haven't seen such issues so far
2375 after CPU0 is offline on a few tested machines.
2376 If the dependencies are under your control, you can
2377 turn on cpu0_hotplug.
2379 nptcg= [IA-64] Override max number of concurrent global TLB
2380 purges which is reported from either PAL_VM_SUMMARY or
2383 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2384 could support. nr_cpus=n : n >= 1 limits the kernel to
2385 supporting 'n' processors. Later in runtime you can not
2386 use hotplug cpu feature to put more cpu back to online.
2387 just like you compile the kernel NR_CPUS=n
2389 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2391 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2392 Allowed values are enable and disable
2394 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2395 one of ['zone', 'node', 'default'] can be specified
2396 This can be set from sysctl after boot.
2397 See Documentation/sysctl/vm.txt for details.
2399 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2400 See Documentation/debugging-via-ohci1394.txt for more
2403 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2404 Rather than timing out after 20 ms if an EC
2405 command is not properly ACKed, override the length
2406 of the timeout. We have interrupts disabled while
2407 waiting for the ACK, so if this is set too high
2408 interrupts *may* be lost!
2410 omap_mux= [OMAP] Override bootloader pin multiplexing.
2411 Format: <mux_mode0.mode_name=value>...
2412 For example, to override I2C bus2:
2413 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2415 oprofile.timer= [HW]
2416 Use timer interrupt instead of performance counters
2418 oprofile.cpu_type= Force an oprofile cpu type
2419 This might be useful if you have an older oprofile
2420 userland or if you want common events.
2421 Format: { arch_perfmon }
2422 arch_perfmon: [X86] Force use of architectural
2423 perfmon on Intel CPUs instead of the
2424 CPU specific event set.
2425 timer: [X86] Force use of architectural NMI
2426 timer mode (see also oprofile.timer
2427 for generic hr timer mode)
2428 [s390] Force legacy basic mode sampling
2429 (report cpu_type "timer")
2431 oops=panic Always panic on oopses. Default is to just kill the
2432 process, but there is a small probability of
2433 deadlocking the machine.
2434 This will also cause panics on machine check exceptions.
2435 Useful together with panic=30 to trigger a reboot.
2438 See Documentation/sound/oss/oss-parameters.txt
2440 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2441 timeout > 0: seconds before rebooting
2442 timeout = 0: wait forever
2443 timeout < 0: reboot immediately
2446 crash_kexec_post_notifiers
2447 Run kdump after running panic-notifiers and dumping
2448 kmsg. This only for the users who doubt kdump always
2449 succeeds in any situation.
2450 Note that this also increases risks of kdump failure,
2451 because some panic notifiers can make the crashed
2452 kernel more unstable.
2454 parkbd.port= [HW] Parallel port number the keyboard adapter is
2455 connected to, default is 0.
2457 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2458 0 for XT, 1 for AT (default is AT).
2461 parport= [HW,PPT] Specify parallel ports. 0 disables.
2462 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2463 Use 'auto' to force the driver to use any
2464 IRQ/DMA settings detected (the default is to
2465 ignore detected IRQ/DMA settings because of
2466 possible conflicts). You can specify the base
2467 address, IRQ, and DMA settings; IRQ and DMA
2468 should be numbers, or 'auto' (for using detected
2469 settings on that particular port), or 'nofifo'
2470 (to avoid using a FIFO even if it is detected).
2471 Parallel ports are assigned in the order they
2472 are specified on the command line, starting
2475 parport_init_mode= [HW,PPT]
2476 Configure VIA parallel port to operate in
2477 a specific mode. This is necessary on Pegasos
2478 computer where firmware has no options for setting
2479 up parallel port mode and sets it to spp.
2480 Currently this function knows 686a and 8231 chips.
2481 Format: [spp|ps2|epp|ecp|ecpepp]
2484 Halt all CPUs after the first oops has been printed for
2485 the specified number of seconds. This is to be used if
2486 your oopses keep scrolling off the screen.
2491 See header of drivers/block/paride/pcd.c.
2492 See also Documentation/blockdev/paride.txt.
2494 pci=option[,option...] [PCI] various PCI subsystem options:
2495 earlydump [X86] dump PCI config space before the kernel
2497 off [X86] don't probe for the PCI bus
2498 bios [X86-32] force use of PCI BIOS, don't access
2499 the hardware directly. Use this if your machine
2500 has a non-standard PCI host bridge.
2501 nobios [X86-32] disallow use of PCI BIOS, only direct
2502 hardware access methods are allowed. Use this
2503 if you experience crashes upon bootup and you
2504 suspect they are caused by the BIOS.
2505 conf1 [X86] Force use of PCI Configuration
2507 conf2 [X86] Force use of PCI Configuration
2509 noaer [PCIE] If the PCIEAER kernel config parameter is
2510 enabled, this kernel boot option can be used to
2511 disable the use of PCIE advanced error reporting.
2512 nodomains [PCI] Disable support for multiple PCI
2513 root domains (aka PCI segments, in ACPI-speak).
2514 nommconf [X86] Disable use of MMCONFIG for PCI
2516 check_enable_amd_mmconf [X86] check for and enable
2517 properly configured MMIO access to PCI
2518 config space on AMD family 10h CPU
2519 nomsi [MSI] If the PCI_MSI kernel config parameter is
2520 enabled, this kernel boot option can be used to
2521 disable the use of MSI interrupts system-wide.
2522 noioapicquirk [APIC] Disable all boot interrupt quirks.
2523 Safety option to keep boot IRQs enabled. This
2524 should never be necessary.
2525 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2526 primary IO-APIC for bridges that cannot disable
2527 boot IRQs. This fixes a source of spurious IRQs
2528 when the system masks IRQs.
2529 noioapicreroute [APIC] Disable workaround that uses the
2530 boot IRQ equivalent of an IRQ that connects to
2531 a chipset where boot IRQs cannot be disabled.
2532 The opposite of ioapicreroute.
2533 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2534 routing table. These calls are known to be buggy
2535 on several machines and they hang the machine
2536 when used, but on other computers it's the only
2537 way to get the interrupt routing table. Try
2538 this option if the kernel is unable to allocate
2539 IRQs or discover secondary PCI buses on your
2541 rom [X86] Assign address space to expansion ROMs.
2542 Use with caution as certain devices share
2543 address decoders between ROMs and other
2545 norom [X86] Do not assign address space to
2546 expansion ROMs that do not already have
2547 BIOS assigned address ranges.
2548 nobar [X86] Do not assign address space to the
2549 BARs that weren't assigned by the BIOS.
2550 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2551 assigned automatically to PCI devices. You can
2552 make the kernel exclude IRQs of your ISA cards
2554 pirqaddr=0xAAAAA [X86] Specify the physical address
2555 of the PIRQ table (normally generated
2556 by the BIOS) if it is outside the
2557 F0000h-100000h range.
2558 lastbus=N [X86] Scan all buses thru bus #N. Can be
2559 useful if the kernel is unable to find your
2560 secondary buses and you want to tell it
2561 explicitly which ones they are.
2562 assign-busses [X86] Always assign all PCI bus
2563 numbers ourselves, overriding
2564 whatever the firmware may have done.
2565 usepirqmask [X86] Honor the possible IRQ mask stored
2566 in the BIOS $PIR table. This is needed on
2567 some systems with broken BIOSes, notably
2568 some HP Pavilion N5400 and Omnibook XE3
2569 notebooks. This will have no effect if ACPI
2570 IRQ routing is enabled.
2571 noacpi [X86] Do not use ACPI for IRQ routing
2572 or for PCI scanning.
2573 use_crs [X86] Use PCI host bridge window information
2574 from ACPI. On BIOSes from 2008 or later, this
2575 is enabled by default. If you need to use this,
2576 please report a bug.
2577 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2578 If you need to use this, please report a bug.
2579 routeirq Do IRQ routing for all PCI devices.
2580 This is normally done in pci_enable_device(),
2581 so this option is a temporary workaround
2582 for broken drivers that don't call it.
2583 skip_isa_align [X86] do not align io start addr, so can
2584 handle more pci cards
2585 firmware [ARM] Do not re-enumerate the bus but instead
2586 just use the configuration from the
2587 bootloader. This is currently used on
2588 IXP2000 systems where the bus has to be
2589 configured a certain way for adjunct CPUs.
2590 noearly [X86] Don't do any early type 1 scanning.
2591 This might help on some broken boards which
2592 machine check when some devices' config space
2593 is read. But various workarounds are disabled
2594 and some IOMMU drivers will not work.
2595 bfsort Sort PCI devices into breadth-first order.
2596 This sorting is done to get a device
2597 order compatible with older (<= 2.4) kernels.
2598 nobfsort Don't sort PCI devices into breadth-first order.
2599 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2600 tuning and use the BIOS-configured MPS defaults.
2601 pcie_bus_safe Set every device's MPS to the largest value
2602 supported by all devices below the root complex.
2603 pcie_bus_perf Set device MPS to the largest allowable MPS
2604 based on its parent bus. Also set MRRS (Max
2605 Read Request Size) to the largest supported
2606 value (no larger than the MPS that the device
2607 or bus can support) for best performance.
2608 pcie_bus_peer2peer Set every device's MPS to 128B, which
2609 every device is guaranteed to support. This
2610 configuration allows peer-to-peer DMA between
2611 any pair of devices, possibly at the cost of
2612 reduced performance. This also guarantees
2613 that hot-added devices will work.
2614 cbiosize=nn[KMG] The fixed amount of bus space which is
2615 reserved for the CardBus bridge's IO window.
2616 The default value is 256 bytes.
2617 cbmemsize=nn[KMG] The fixed amount of bus space which is
2618 reserved for the CardBus bridge's memory
2619 window. The default value is 64 megabytes.
2622 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2623 Specifies alignment and device to reassign
2624 aligned memory resources.
2625 If <order of align> is not specified,
2626 PAGE_SIZE is used as alignment.
2627 PCI-PCI bridge can be specified, if resource
2628 windows need to be expanded.
2629 ecrc= Enable/disable PCIe ECRC (transaction layer
2630 end-to-end CRC checking).
2631 bios: Use BIOS/firmware settings. This is the
2635 hpiosize=nn[KMG] The fixed amount of bus space which is
2636 reserved for hotplug bridge's IO window.
2637 Default size is 256 bytes.
2638 hpmemsize=nn[KMG] The fixed amount of bus space which is
2639 reserved for hotplug bridge's memory window.
2640 Default size is 2 megabytes.
2641 realloc= Enable/disable reallocating PCI bridge resources
2642 if allocations done by BIOS are too small to
2643 accommodate resources required by all child
2645 off: Turn realloc off
2647 realloc same as realloc=on
2648 noari do not use PCIe ARI.
2649 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2650 only look for one device below a PCIe downstream
2653 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2656 force Enable ASPM even on devices that claim not to support it.
2657 WARNING: Forcing ASPM on may cause system lockups.
2659 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2660 nomsi Do not use MSI for PCI Express Native Hotplug (this
2661 makes all PCIe ports use INTx for hotplug services).
2663 pcie_ports= [PCIE] PCIe ports handling:
2664 auto Ask the BIOS whether or not to use native PCIe services
2665 associated with PCIe ports (PME, hot-plug, AER). Use
2666 them only if that is allowed by the BIOS.
2667 native Use native PCIe services associated with PCIe ports
2669 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2672 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2673 nomsi Do not use MSI for native PCIe PME signaling (this makes
2674 all PCIe root ports use INTx for all services).
2676 pcmv= [HW,PCMCIA] BadgePAD 4
2680 Keep all power-domains already enabled by bootloader on,
2681 even if no driver has claimed them. This is useful
2682 for debug and development, but should not be
2683 needed on a platform with proper driver support.
2686 See Documentation/blockdev/paride.txt.
2688 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2691 See arch/parisc/kernel/pdc_chassis.c
2693 percpu_alloc= Select which percpu first chunk allocator to use.
2694 Currently supported values are "embed" and "page".
2695 Archs may support subset or none of the selections.
2696 See comments in mm/percpu.c for details on each
2697 allocator. This parameter is primarily for debugging
2698 and performance comparison.
2701 See Documentation/blockdev/paride.txt.
2704 See Documentation/blockdev/paride.txt.
2706 pirq= [SMP,APIC] Manual mp-table setup
2707 See Documentation/x86/i386/IO-APIC.txt.
2709 plip= [PPT,NET] Parallel port network link
2710 Format: { parport<nr> | timid | 0 }
2711 See also Documentation/parport.txt.
2713 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2714 Override pmtimer IOPort with a hex value.
2718 Enable PNP debug messages (depends on the
2719 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2720 via /sys/module/pnp/parameters/debug. We always show
2721 current resource usage; turning this on also shows
2722 possible settings and some assignment information.
2728 { on | off | curr | res | no-curr | no-res }
2731 [ISAPNP] Exclude IRQs for the autoconfiguration
2734 [ISAPNP] Exclude DMAs for the autoconfiguration
2736 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2737 Ranges are in pairs (I/O port base and size).
2740 [ISAPNP] Exclude memory regions for the
2742 Ranges are in pairs (memory base and size).
2744 ports= [IP_VS_FTP] IPVS ftp helper module
2746 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2748 Format: <port>,<port>....
2750 print-fatal-signals=
2751 [KNL] debug: print fatal signals
2753 If enabled, warn about various signal handling
2754 related application anomalies: too many signals,
2755 too many POSIX.1 timers, fatal signals causing a
2758 If you hit the warning due to signal overflow,
2759 you might want to try "ulimit -i unlimited".
2763 printk.always_kmsg_dump=
2764 Trigger kmsg_dump for cases other than kernel oops or
2766 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2769 printk.time= Show timing data prefixed to each printk message line
2770 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2772 processor.max_cstate= [HW,ACPI]
2773 Limit processor to maximum C-state
2774 max_cstate=9 overrides any DMI blacklist limit.
2776 processor.nocst [HW,ACPI]
2777 Ignore the _CST method to determine C-states,
2778 instead using the legacy FADT method
2780 profile= [KNL] Enable kernel profiling via /proc/profile
2781 Format: [schedule,]<number>
2782 Param: "schedule" - profile schedule points.
2783 Param: <number> - step/bucket size as a power of 2 for
2784 statistical time based profiling.
2785 Param: "sleep" - profile D-state sleeping (millisecs).
2786 Requires CONFIG_SCHEDSTATS
2787 Param: "kvm" - profile VM exits.
2789 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2791 See Documentation/blockdev/ramdisk.txt.
2793 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2794 probe for; one of (bare|imps|exps|lifebook|any).
2795 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2797 psmouse.resetafter= [HW,MOUSE]
2798 Try to reset the device after so many bad packets
2801 [HW,MOUSE] Set desired mouse resolution, in dpi.
2802 psmouse.smartscroll=
2803 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2804 0 = disabled, 1 = enabled (default).
2806 pstore.backend= Specify the name of the pstore backend to use
2809 See Documentation/blockdev/paride.txt.
2812 [KNL] Number of legacy pty's. Overwrites compiled-in
2815 quiet [KNL] Disable most log messages
2820 See Documentation/md.txt.
2822 ramdisk_blocksize= [RAM]
2823 See Documentation/blockdev/ramdisk.txt.
2825 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2826 See Documentation/blockdev/ramdisk.txt.
2829 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2830 the specified list of CPUs to be no-callback CPUs.
2831 Invocation of these CPUs' RCU callbacks will
2832 be offloaded to "rcuox/N" kthreads created for
2833 that purpose, where "x" is "b" for RCU-bh, "p"
2834 for RCU-preempt, and "s" for RCU-sched, and "N"
2835 is the CPU number. This reduces OS jitter on the
2836 offloaded CPUs, which can be useful for HPC and
2837 real-time workloads. It can also improve energy
2838 efficiency for asymmetric multiprocessors.
2841 Rather than requiring that offloaded CPUs
2842 (specified by rcu_nocbs= above) explicitly
2843 awaken the corresponding "rcuoN" kthreads,
2844 make these kthreads poll for callbacks.
2845 This improves the real-time response for the
2846 offloaded CPUs by relieving them of the need to
2847 wake up the corresponding kthread, but degrades
2848 energy efficiency by requiring that the kthreads
2849 periodically wake up to do the polling.
2851 rcutree.blimit= [KNL]
2852 Set maximum number of finished RCU callbacks to
2853 process in one batch.
2855 rcutree.rcu_fanout_leaf= [KNL]
2856 Increase the number of CPUs assigned to each
2857 leaf rcu_node structure. Useful for very large
2860 rcutree.jiffies_till_sched_qs= [KNL]
2861 Set required age in jiffies for a
2862 given grace period before RCU starts
2863 soliciting quiescent-state help from
2864 rcu_note_context_switch().
2866 rcutree.jiffies_till_first_fqs= [KNL]
2867 Set delay from grace-period initialization to
2868 first attempt to force quiescent states.
2869 Units are jiffies, minimum value is zero,
2870 and maximum value is HZ.
2872 rcutree.jiffies_till_next_fqs= [KNL]
2873 Set delay between subsequent attempts to force
2874 quiescent states. Units are jiffies, minimum
2875 value is one, and maximum value is HZ.
2877 rcutree.rcu_nocb_leader_stride= [KNL]
2878 Set the number of NOCB kthread groups, which
2879 defaults to the square root of the number of
2880 CPUs. Larger numbers reduces the wakeup overhead
2881 on the per-CPU grace-period kthreads, but increases
2882 that same overhead on each group's leader.
2884 rcutree.qhimark= [KNL]
2885 Set threshold of queued RCU callbacks beyond which
2886 batch limiting is disabled.
2888 rcutree.qlowmark= [KNL]
2889 Set threshold of queued RCU callbacks below which
2890 batch limiting is re-enabled.
2892 rcutree.rcu_idle_gp_delay= [KNL]
2893 Set wakeup interval for idle CPUs that have
2894 RCU callbacks (RCU_FAST_NO_HZ=y).
2896 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2897 Set wakeup interval for idle CPUs that have
2898 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2899 Lazy RCU callbacks are those which RCU can
2900 prove do nothing more than free memory.
2902 rcutorture.fqs_duration= [KNL]
2903 Set duration of force_quiescent_state bursts.
2905 rcutorture.fqs_holdoff= [KNL]
2906 Set holdoff time within force_quiescent_state bursts.
2908 rcutorture.fqs_stutter= [KNL]
2909 Set wait time between force_quiescent_state bursts.
2911 rcutorture.gp_exp= [KNL]
2912 Use expedited update-side primitives.
2914 rcutorture.gp_normal= [KNL]
2915 Use normal (non-expedited) update-side primitives.
2916 If both gp_exp and gp_normal are set, do both.
2917 If neither gp_exp nor gp_normal are set, still
2920 rcutorture.n_barrier_cbs= [KNL]
2921 Set callbacks/threads for rcu_barrier() testing.
2923 rcutorture.nfakewriters= [KNL]
2924 Set number of concurrent RCU writers. These just
2925 stress RCU, they don't participate in the actual
2926 test, hence the "fake".
2928 rcutorture.nreaders= [KNL]
2929 Set number of RCU readers.
2931 rcutorture.object_debug= [KNL]
2932 Enable debug-object double-call_rcu() testing.
2934 rcutorture.onoff_holdoff= [KNL]
2935 Set time (s) after boot for CPU-hotplug testing.
2937 rcutorture.onoff_interval= [KNL]
2938 Set time (s) between CPU-hotplug operations, or
2939 zero to disable CPU-hotplug testing.
2941 rcutorture.rcutorture_runnable= [BOOT]
2942 Start rcutorture running at boot time.
2944 rcutorture.shuffle_interval= [KNL]
2945 Set task-shuffle interval (s). Shuffling tasks
2946 allows some CPUs to go into dyntick-idle mode
2947 during the rcutorture test.
2949 rcutorture.shutdown_secs= [KNL]
2950 Set time (s) after boot system shutdown. This
2951 is useful for hands-off automated testing.
2953 rcutorture.stall_cpu= [KNL]
2954 Duration of CPU stall (s) to test RCU CPU stall
2955 warnings, zero to disable.
2957 rcutorture.stall_cpu_holdoff= [KNL]
2958 Time to wait (s) after boot before inducing stall.
2960 rcutorture.stat_interval= [KNL]
2961 Time (s) between statistics printk()s.
2963 rcutorture.stutter= [KNL]
2964 Time (s) to stutter testing, for example, specifying
2965 five seconds causes the test to run for five seconds,
2966 wait for five seconds, and so on. This tests RCU's
2967 ability to transition abruptly to and from idle.
2969 rcutorture.test_boost= [KNL]
2970 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2971 "Maybe" means test if the RCU implementation
2972 under test support RCU priority boosting.
2974 rcutorture.test_boost_duration= [KNL]
2975 Duration (s) of each individual boost test.
2977 rcutorture.test_boost_interval= [KNL]
2978 Interval (s) between each boost test.
2980 rcutorture.test_no_idle_hz= [KNL]
2981 Test RCU's dyntick-idle handling. See also the
2982 rcutorture.shuffle_interval parameter.
2984 rcutorture.torture_type= [KNL]
2985 Specify the RCU implementation to test.
2987 rcutorture.verbose= [KNL]
2988 Enable additional printk() statements.
2990 rcupdate.rcu_expedited= [KNL]
2991 Use expedited grace-period primitives, for
2992 example, synchronize_rcu_expedited() instead
2993 of synchronize_rcu(). This reduces latency,
2994 but can increase CPU utilization, degrade
2995 real-time latency, and degrade energy efficiency.
2997 rcupdate.rcu_cpu_stall_suppress= [KNL]
2998 Suppress RCU CPU stall warning messages.
3000 rcupdate.rcu_cpu_stall_timeout= [KNL]
3001 Set timeout for RCU CPU stall warning messages.
3005 Run specified binary instead of /init from the ramdisk,
3006 used for early userspace startup. See initrd.
3009 Format (x86 or x86_64):
3010 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3012 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3014 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3015 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3016 reboot_force is either force or not specified,
3017 reboot_cpu is s[mp]#### with #### being the processor
3018 to be used for rebooting.
3021 [KNL, SMP] Set scheduler's default relax_domain_level.
3022 See Documentation/cgroups/cpusets.txt.
3024 relative_sleep_states=
3025 [SUSPEND] Use sleep state labeling where the deepest
3026 state available other than hibernation is always "mem".
3027 Format: { "0" | "1" }
3028 0 -- Traditional sleep state labels.
3029 1 -- Relative sleep state labels.
3031 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3033 reservetop= [X86-32]
3035 Reserves a hole at the top of the kernel virtual
3040 Set the amount of memory to reserve for BIOS at
3041 the bottom of the address space.
3043 reset_devices [KNL] Force drivers to reset the underlying device
3044 during initialization.
3047 Specify the partition device for software suspend
3049 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3051 resume_offset= [SWSUSP]
3052 Specify the offset from the beginning of the partition
3053 given by "resume=" at which the swap header is located,
3054 in <PAGE_SIZE> units (needed only for swap files).
3055 See Documentation/power/swsusp-and-swap-files.txt
3057 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3058 read the resume files
3060 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3061 Useful for devices that are detected asynchronously
3062 (e.g. USB and MMC devices).
3064 hibernate= [HIBERNATION]
3065 noresume Don't check if there's a hibernation image
3066 present during boot.
3067 nocompress Don't compress/decompress hibernation images.
3068 no Disable hibernation and resume.
3070 retain_initrd [RAM] Keep initrd memory after extraction
3072 rhash_entries= [KNL,NET]
3073 Set number of hash buckets for route cache
3075 ro [KNL] Mount root device read-only on boot
3077 root= [KNL] Root filesystem
3078 See name_to_dev_t comment in init/do_mounts.c.
3080 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3081 mount the root filesystem
3083 rootflags= [KNL] Set root filesystem mount option string
3085 rootfstype= [KNL] Set root filesystem type
3087 rootwait [KNL] Wait (indefinitely) for root device to show up.
3088 Useful for devices that are detected asynchronously
3089 (e.g. USB and MMC devices).
3091 rproc_mem=nn[KMG][@address]
3092 [KNL,ARM,CMA] Remoteproc physical memory block.
3093 Memory area to be used by remote processor image,
3096 rw [KNL] Mount root device read-write on boot
3098 S [KNL] Run init in single mode
3100 s390_iommu= [HW,S390]
3101 Set s390 IOTLB flushing mode
3103 With strict flushing every unmap operation will result in
3104 an IOTLB flush. Default is lazy flushing before reuse,
3108 See drivers/net/irda/sa1100_ir.c.
3110 sbni= [NET] Granch SBNI12 leased line adapter
3112 sched_debug [KNL] Enables verbose scheduler debug messages.
3114 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3115 xtime_lock contention on larger systems, and/or RCU lock
3116 contention on all systems with CONFIG_MAXSMP set.
3117 Format: { "0" | "1" }
3118 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3120 Note: increases power consumption, thus should only be
3121 enabled if running jitter sensitive (HPC/RT) workloads.
3123 security= [SECURITY] Choose a security module to enable at boot.
3124 If this boot parameter is not specified, only the first
3125 security module asking for security registration will be
3126 loaded. An invalid security module name will be treated
3127 as if no module has been chosen.
3129 selinux= [SELINUX] Disable or enable SELinux at boot time.
3130 Format: { "0" | "1" }
3131 See security/selinux/Kconfig help text.
3134 Default value is set via kernel config option.
3135 If enabled at boot time, /selinux/disable can be used
3136 later to disable prior to initial policy load.
3138 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3139 Format: { "0" | "1" }
3140 See security/apparmor/Kconfig help text
3143 Default value is set via kernel config option.
3145 serialnumber [BUGS=X86-32]
3148 Maximal number of shapers.
3150 show_msr= [x86] show boot-time MSR settings
3151 Format: { <integer> }
3152 Show boot-time (BIOS-initialized) MSR settings.
3153 The parameter means the number of CPUs to show,
3154 for example 1 means boot CPU only.
3161 slab_max_order= [MM, SLAB]
3162 Determines the maximum allowed order for slabs.
3163 A high setting may cause OOMs due to memory
3164 fragmentation. Defaults to 1 for systems with
3165 more than 32MB of RAM, 0 otherwise.
3167 slub_debug[=options[,slabs]] [MM, SLUB]
3168 Enabling slub_debug allows one to determine the
3169 culprit if slab objects become corrupted. Enabling
3170 slub_debug can create guard zones around objects and
3171 may poison objects when not in use. Also tracks the
3172 last alloc / free. For more information see
3173 Documentation/vm/slub.txt.
3175 slub_max_order= [MM, SLUB]
3176 Determines the maximum allowed order for slabs.
3177 A high setting may cause OOMs due to memory
3178 fragmentation. For more information see
3179 Documentation/vm/slub.txt.
3181 slub_min_objects= [MM, SLUB]
3182 The minimum number of objects per slab. SLUB will
3183 increase the slab order up to slub_max_order to
3184 generate a sufficiently large slab able to contain
3185 the number of objects indicated. The higher the number
3186 of objects the smaller the overhead of tracking slabs
3187 and the less frequently locks need to be acquired.
3188 For more information see Documentation/vm/slub.txt.
3190 slub_min_order= [MM, SLUB]
3191 Determines the minimum page order for slabs. Must be
3192 lower than slub_max_order.
3193 For more information see Documentation/vm/slub.txt.
3195 slub_nomerge [MM, SLUB]
3196 Disable merging of slabs with similar size. May be
3197 necessary if there is some reason to distinguish
3198 allocs to different slabs. Debug options disable
3199 merging on their own.
3200 For more information see Documentation/vm/slub.txt.
3203 Format: <io1>[,<io2>[,...,<io8>]]
3205 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3206 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3207 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3208 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3209 smsc-ircc2.ircc_irq= [HW] IRQ line
3210 smsc-ircc2.ircc_dma= [HW] DMA channel
3211 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3212 0: Toshiba Satellite 1800 (GP data pin select)
3213 1: Fast pin select (default)
3217 [KNL] Should the soft-lockup detector generate panics.
3220 softlockup_all_cpu_backtrace=
3221 [KNL] Should the soft-lockup detector generate
3222 backtraces on all cpus.
3225 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3226 See Documentation/laptops/sonypi.txt
3228 spia_io_base= [HW,MTD]
3234 Enabled the stack tracer on boot up.
3236 stacktrace_filter=[function-list]
3237 [FTRACE] Limit the functions that the stack tracer
3238 will trace at boot up. function-list is a comma separated
3239 list of functions. This list can be changed at run
3240 time by the stack_trace_filter file in the debugfs
3241 tracing directory. Note, this enables stack tracing
3242 and the stacktrace above is not needed.
3246 Set the STI (builtin display/keyboard on the HP-PARISC
3247 machines) console (graphic card) which should be used
3248 as the initial boot-console.
3249 See also comment in drivers/video/console/sticore.c.
3252 See comment in drivers/video/console/sticore.c.
3255 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3257 sunrpc.min_resvport=
3258 sunrpc.max_resvport=
3260 SunRPC servers often require that client requests
3261 originate from a privileged port (i.e. a port in the
3262 range 0 < portnr < 1024).
3263 An administrator who wishes to reserve some of these
3264 ports for other uses may adjust the range that the
3265 kernel's sunrpc client considers to be privileged
3266 using these two parameters to set the minimum and
3267 maximum port values.
3271 Control how the NFS server code allocates CPUs to
3272 service thread pools. Depending on how many NICs
3273 you have and where their interrupts are bound, this
3274 option will affect which CPUs will do NFS serving.
3275 Note: this parameter cannot be changed while the
3276 NFS server is running.
3278 auto the server chooses an appropriate mode
3279 automatically using heuristics
3280 global a single global pool contains all CPUs
3281 percpu one pool for each CPU
3282 pernode one pool for each NUMA node (equivalent
3283 to global on non-NUMA machines)
3285 sunrpc.tcp_slot_table_entries=
3286 sunrpc.udp_slot_table_entries=
3288 Sets the upper limit on the number of simultaneous
3289 RPC calls that can be sent from the client to a
3290 server. Increasing these values may allow you to
3291 improve throughput, but will also increase the
3292 amount of memory reserved for use by the client.
3295 [KNL] Enable accounting of swap in memory resource
3296 controller if no parameter or 1 is given or disable
3297 it if 0 is given (See Documentation/cgroups/memory.txt)
3299 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3300 Format: { <int> | force }
3301 <int> -- Number of I/O TLB slabs
3302 force -- force using of bounce buffers even if they
3303 wouldn't be automatically used by the kernel
3307 sysfs.deprecated=0|1 [KNL]
3308 Enable/disable old style sysfs layout for old udev
3309 on older distributions. When this option is enabled
3310 very new udev will not work anymore. When this option
3311 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3312 in older udev will not work anymore.
3313 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3314 the kernel configuration.
3316 sysrq_always_enabled
3318 Ignore sysrq setting - this boot parameter will
3319 neutralize any effect of /proc/sys/kernel/sysrq.
3320 Useful for debugging.
3324 test_suspend= [SUSPEND]
3325 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3326 standby suspend) as the system sleep state to briefly
3327 enter during system startup. The system is woken from
3328 this state using a wakeup-capable RTC alarm.
3330 thash_entries= [KNL,NET]
3331 Set number of hash buckets for TCP connection
3333 thermal.act= [HW,ACPI]
3334 -1: disable all active trip points in all thermal zones
3335 <degrees C>: override all lowest active trip points
3337 thermal.crt= [HW,ACPI]
3338 -1: disable all critical trip points in all thermal zones
3339 <degrees C>: override all critical trip points
3341 thermal.nocrt= [HW,ACPI]
3342 Set to disable actions on ACPI thermal zone
3343 critical and hot trip points.
3345 thermal.off= [HW,ACPI]
3346 1: disable ACPI thermal control
3348 thermal.psv= [HW,ACPI]
3349 -1: disable all passive trip points
3350 <degrees C>: override all passive trip points to this
3353 thermal.tzp= [HW,ACPI]
3354 Specify global default ACPI thermal zone polling rate
3355 <deci-seconds>: poll all this frequency
3356 0: no polling (default)
3359 Force threading of all interrupt handlers except those
3360 marked explicitly IRQF_NO_THREAD.
3363 Enable the Transcendent memory driver if built-in.
3365 tmem.cleancache=0|1 [KNL, XEN]
3366 Default is on (1). Disable the usage of the cleancache
3367 API to send anonymous pages to the hypervisor.
3369 tmem.frontswap=0|1 [KNL, XEN]
3370 Default is on (1). Disable the usage of the frontswap
3371 API to send swap pages to the hypervisor. If disabled
3372 the selfballooning and selfshrinking are force disabled.
3374 tmem.selfballooning=0|1 [KNL, XEN]
3375 Default is on (1). Disable the driving of swap pages
3378 tmem.selfshrinking=0|1 [KNL, XEN]
3379 Default is on (1). Partial swapoff that immediately
3380 transfers pages from Xen hypervisor back to the
3381 kernel based on different criteria.
3385 Specify if the kernel should make use of the cpu
3386 topology information if the hardware supports this.
3387 The scheduler will make use of this information and
3388 e.g. base its process migration decisions on it.
3393 tpm_suspend_pcr=[HW,TPM]
3394 Format: integer pcr id
3395 Specify that at suspend time, the tpm driver
3396 should extend the specified pcr with zeros,
3397 as a workaround for some chips which fail to
3398 flush the last written pcr on TPM_SaveState.
3399 This will guarantee that all the other pcrs
3402 trace_buf_size=nn[KMG]
3403 [FTRACE] will set tracing buffer size.
3405 trace_event=[event-list]
3406 [FTRACE] Set and start specified trace events in order
3407 to facilitate early boot debugging.
3408 See also Documentation/trace/events.txt
3410 trace_options=[option-list]
3411 [FTRACE] Enable or disable tracer options at boot.
3412 The option-list is a comma delimited list of options
3413 that can be enabled or disabled just as if you were
3414 to echo the option name into
3416 /sys/kernel/debug/tracing/trace_options
3418 For example, to enable stacktrace option (to dump the
3419 stack trace of each event), add to the command line:
3421 trace_options=stacktrace
3423 See also Documentation/trace/ftrace.txt "trace options"
3427 [FTRACE] enable this option to disable tracing when a
3428 warning is hit. This turns off "tracing_on". Tracing can
3429 be enabled again by echoing '1' into the "tracing_on"
3430 file located in /sys/kernel/debug/tracing/
3432 This option is useful, as it disables the trace before
3433 the WARNING dump is called, which prevents the trace to
3434 be filled with content caused by the warning output.
3436 This option can also be set at run time via the sysctl
3437 option: kernel/traceoff_on_warning
3439 transparent_hugepage=
3441 Format: [always|madvise|never]
3442 Can be used to control the default behavior of the system
3443 with respect to transparent hugepages.
3444 See Documentation/vm/transhuge.txt for more details.
3446 tsc= Disable clocksource stability checks for TSC.
3448 [x86] reliable: mark tsc clocksource as reliable, this
3449 disables clocksource verification at runtime, as well
3450 as the stability checks done at bootup. Used to enable
3451 high-resolution timer mode on older hardware, and in
3452 virtualized environment.
3453 [x86] noirqtime: Do not use TSC to do irq accounting.
3454 Used to run time disable IRQ_TIME_ACCOUNTING on any
3455 platforms where RDTSC is slow and this accounting
3458 turbografx.map[2|3]= [HW,JOY]
3459 TurboGraFX parallel port interface
3461 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3462 See also Documentation/input/joystick-parport.txt
3464 udbg-immortal [PPC] When debugging early kernel crashes that
3465 happen after console_init() and before a proper
3466 console driver takes over, this boot options might
3467 help "seeing" what's going on.
3469 uhash_entries= [KNL,NET]
3470 Set number of hash buckets for UDP/UDP-Lite connections
3473 [USB] Ignore overcurrent events (default N).
3474 Some badly-designed motherboards generate lots of
3475 bogus events, for ports that aren't wired to
3476 anything. Set this parameter to avoid log spamming.
3477 Note that genuine overcurrent events won't be
3481 [X86] Cause panic on unknown NMI.
3483 usbcore.authorized_default=
3484 [USB] Default USB device authorization:
3485 (default -1 = authorized except for wireless USB,
3486 0 = not authorized, 1 = authorized)
3488 usbcore.autosuspend=
3489 [USB] The autosuspend time delay (in seconds) used
3490 for newly-detected USB devices (default 2). This
3491 is the time required before an idle device will be
3492 autosuspended. Devices for which the delay is set
3493 to a negative value won't be autosuspended at all.
3495 usbcore.usbfs_snoop=
3496 [USB] Set to log all usbfs traffic (default 0 = off).
3498 usbcore.blinkenlights=
3499 [USB] Set to cycle leds on hubs (default 0 = off).
3501 usbcore.old_scheme_first=
3502 [USB] Start with the old device initialization
3503 scheme (default 0 = off).
3505 usbcore.usbfs_memory_mb=
3506 [USB] Memory limit (in MB) for buffers allocated by
3507 usbfs (default = 16, 0 = max = 2047).
3509 usbcore.use_both_schemes=
3510 [USB] Try the other device initialization scheme
3511 if the first one fails (default 1 = enabled).
3513 usbcore.initial_descriptor_timeout=
3514 [USB] Specifies timeout for the initial 64-byte
3515 USB_REQ_GET_DESCRIPTOR request in milliseconds
3516 (default 5000 = 5.0 seconds).
3519 [USBHID] The interval which mice are to be polled at.
3521 usb-storage.delay_use=
3522 [UMS] The delay in seconds before a new device is
3523 scanned for Logical Units (default 5).
3526 [UMS] A list of quirks entries to supplement or
3527 override the built-in unusual_devs list. List
3528 entries are separated by commas. Each entry has
3529 the form VID:PID:Flags where VID and PID are Vendor
3530 and Product ID values (4-digit hex numbers) and
3531 Flags is a set of characters, each corresponding
3532 to a common usb-storage quirk flag as follows:
3533 a = SANE_SENSE (collect more than 18 bytes
3535 b = BAD_SENSE (don't collect more than 18
3536 bytes of sense data);
3537 c = FIX_CAPACITY (decrease the reported
3538 device capacity by one sector);
3539 d = NO_READ_DISC_INFO (don't use
3540 READ_DISC_INFO command);
3541 e = NO_READ_CAPACITY_16 (don't use
3542 READ_CAPACITY_16 command);
3543 f = NO_REPORT_OPCODES (don't use report opcodes
3545 h = CAPACITY_HEURISTICS (decrease the
3546 reported device capacity by one
3547 sector if the number is odd);
3548 i = IGNORE_DEVICE (don't bind to this
3550 l = NOT_LOCKABLE (don't try to lock and
3551 unlock ejectable media);
3552 m = MAX_SECTORS_64 (don't transfer more
3553 than 64 sectors = 32 KB at a time);
3554 n = INITIAL_READ10 (force a retry of the
3555 initial READ(10) command);
3556 o = CAPACITY_OK (accept the capacity
3557 reported by the device);
3558 p = WRITE_CACHE (the device cache is ON
3560 r = IGNORE_RESIDUE (the device reports
3561 bogus residue values);
3562 s = SINGLE_LUN (the device has only one
3564 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3565 commands, uas only);
3566 u = IGNORE_UAS (don't bind to the uas driver);
3567 w = NO_WP_DETECT (don't test whether the
3568 medium is write-protected).
3569 Example: quirks=0419:aaf5:rl,0421:0433:rc
3571 user_debug= [KNL,ARM]
3573 See arch/arm/Kconfig.debug help text.
3574 1 - undefined instruction events
3576 4 - invalid data aborts
3579 Example: user_debug=31
3582 [X86] Flags controlling user PTE allocations.
3584 nohigh = do not allocate PTE pages in
3585 HIGHMEM regardless of setting
3589 On X86_32, this is an alias for vdso32=. Otherwise:
3591 vdso=1: enable VDSO (the default)
3592 vdso=0: disable VDSO mapping
3594 vdso32= [X86] Control the 32-bit vDSO
3595 vdso32=1: enable 32-bit VDSO
3596 vdso32=0 or vdso32=2: disable 32-bit VDSO
3598 See the help text for CONFIG_COMPAT_VDSO for more
3599 details. If CONFIG_COMPAT_VDSO is set, the default is
3600 vdso32=0; otherwise, the default is vdso32=1.
3602 For compatibility with older kernels, vdso32=2 is an
3605 Try vdso32=0 if you encounter an error that says:
3606 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3609 vector=percpu: enable percpu vector domain
3611 video= [FB] Frame buffer configuration
3612 See Documentation/fb/modedb.txt.
3614 video.brightness_switch_enabled= [0,1]
3615 If set to 1, on receiving an ACPI notify event
3616 generated by hotkey, video driver will adjust brightness
3617 level and then send out the event to user space through
3618 the allocated input device; If set to 0, video driver
3619 will only send out the event without touching backlight
3624 [VMMIO] Memory mapped virtio (platform) device.
3626 <size>@<baseaddr>:<irq>[:<id>]
3628 <size> := size (can use standard suffixes
3630 <baseaddr> := physical base address
3631 <irq> := interrupt number (as passed to
3633 <id> := (optional) platform device id
3635 virtio_mmio.device=1K@0x100b0000:48:7
3637 Can be used multiple times for multiple devices.
3639 vga= [BOOT,X86-32] Select a particular video mode
3640 See Documentation/x86/boot.txt and
3641 Documentation/svga.txt.
3642 Use vga=ask for menu.
3643 This is actually a boot loader parameter; the value is
3644 passed to the kernel using a special protocol.
3646 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3647 size of <nn>. This can be used to increase the
3648 minimum size (128MB on x86). It can also be used to
3649 decrease the size and leave more room for directly
3652 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3655 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3658 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3662 Controls the behavior of vsyscalls (i.e. calls to
3663 fixed addresses of 0xffffffffff600x00 from legacy
3664 code). Most statically-linked binaries and older
3665 versions of glibc use these calls. Because these
3666 functions are at fixed addresses, they make nice
3667 targets for exploits that can control RIP.
3669 emulate [default] Vsyscalls turn into traps and are
3670 emulated reasonably safely.
3672 native Vsyscalls are native syscall instructions.
3673 This is a little bit faster than trapping
3674 and makes a few dynamic recompilers work
3675 better than they would in emulation mode.
3676 It also makes exploits much easier to write.
3678 none Vsyscalls don't work at all. This makes
3679 them quite hard to use for exploits but
3680 might break your system.
3682 vt.color= [VT] Default text color.
3683 Format: 0xYX, X = foreground, Y = background.
3684 Default: 0x07 = light gray on black.
3686 vt.cur_default= [VT] Default cursor shape.
3687 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3688 the parameters of the <Esc>[?A;B;Cc escape sequence;
3689 see VGA-softcursor.txt. Default: 2 = underline.
3691 vt.default_blu= [VT]
3692 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3693 Change the default blue palette of the console.
3694 This is a 16-member array composed of values
3697 vt.default_grn= [VT]
3698 Format: <green0>,<green1>,<green2>,...,<green15>
3699 Change the default green palette of the console.
3700 This is a 16-member array composed of values
3703 vt.default_red= [VT]
3704 Format: <red0>,<red1>,<red2>,...,<red15>
3705 Change the default red palette of the console.
3706 This is a 16-member array composed of values
3712 Set system-wide default UTF-8 mode for all tty's.
3713 Default is 1, i.e. UTF-8 mode is enabled for all
3714 newly opened terminals.
3716 vt.global_cursor_default=
3719 Set system-wide default for whether a cursor
3720 is shown on new VTs. Default is -1,
3721 i.e. cursors will be created by default unless
3722 overridden by individual drivers. 0 will hide
3723 cursors, 1 will display them.
3725 vt.italic= [VT] Default color for italic text; 0-15.
3728 vt.underline= [VT] Default color for underlined text; 0-15.
3731 watchdog timers [HW,WDT] For information on watchdog timers,
3732 see Documentation/watchdog/watchdog-parameters.txt
3733 or other driver-specific files in the
3734 Documentation/watchdog/ directory.
3736 workqueue.disable_numa
3737 By default, all work items queued to unbound
3738 workqueues are affine to the NUMA nodes they're
3739 issued on, which results in better behavior in
3740 general. If NUMA affinity needs to be disabled for
3741 whatever reason, this option can be used. Note
3742 that this also can be controlled per-workqueue for
3743 workqueues visible under /sys/bus/workqueue/.
3745 workqueue.power_efficient
3746 Per-cpu workqueues are generally preferred because
3747 they show better performance thanks to cache
3748 locality; unfortunately, per-cpu workqueues tend to
3749 be more power hungry than unbound workqueues.
3751 Enabling this makes the per-cpu workqueues which
3752 were observed to contribute significantly to power
3753 consumption unbound, leading to measurably lower
3754 power usage at the cost of small performance
3757 The default value of this parameter is determined by
3758 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3760 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3761 default x2apic cluster mode on platforms
3764 x86_intel_mid_timer= [X86-32,APBT]
3765 Choose timer option for x86 Intel MID platform.
3766 Two valid options are apbt timer only and lapic timer
3767 plus one apbt timer for broadcast timer.
3768 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3770 xen_emul_unplug= [HW,X86,XEN]
3771 Unplug Xen emulated devices
3772 Format: [unplug0,][unplug1]
3773 ide-disks -- unplug primary master IDE devices
3774 aux-ide-disks -- unplug non-primary-master IDE devices
3775 nics -- unplug network devices
3776 all -- unplug all emulated devices (NICs and IDE disks)
3777 unnecessary -- unplugging emulated devices is
3778 unnecessary even if the host did not respond to
3780 never -- do not unplug even if version check succeeds
3782 xen_nopvspin [X86,XEN]
3783 Disables the ticketlock slowpath using Xen PV
3787 Disables the PV optimizations forcing the HVM guest to
3788 run as generic HVM guest with no PV drivers.
3790 xirc2ps_cs= [NET,PCMCIA]
3792 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3794 ______________________________________________________________________
3798 Add more DRM drivers.
git.openpandora.org / pandora-kernel.git / blob