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 Prevents the clock framework from automatically gating
609 clocks that have not been explicitly enabled by a Linux
610 device driver but are enabled in hardware at reset or
611 by the bootloader/firmware. Note that this does not
612 force such clocks to be always-on nor does it reserve
613 those clocks in any way. This parameter is useful for
614 debug and development, but should not be needed on a
615 platform with proper driver support. For more
616 information, see Documentation/clk.txt.
618 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
620 Forces specified clocksource (if available) to be used
621 when calculating gettimeofday(). If specified
622 clocksource is not available, it defaults to PIT.
623 Format: { pit | tsc | cyclone | pmtmr }
625 clocksource= Override the default clocksource
627 Override the default clocksource and use the clocksource
628 with the name specified.
629 Some clocksource names to choose from, depending on
631 [all] jiffies (this is the base, fallback clocksource)
633 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634 pxa_timer,timer3,32k_counter,timer0_1
636 [X86-32] pit,hpet,tsc;
637 scx200_hrt on Geode; cyclone on IBM x440
645 clearcpuid=BITNUM [X86]
646 Disable CPUID feature X for the kernel. See
647 arch/x86/include/asm/cpufeature.h for the valid bit
648 numbers. Note the Linux specific bits are not necessarily
649 stable over kernel options, but the vendor specific
651 Also note that user programs calling CPUID directly
652 or using the feature without checking anything
653 will still see it. This just prevents it from
654 being used by the kernel or shown in /proc/cpuinfo.
655 Also note the kernel might malfunction if you disable
658 cma=nn[MG]@[start[MG][-end[MG]]]
660 Sets the size of kernel global memory area for
661 contiguous memory allocations and optionally the
662 placement constraint by the physical address range of
663 memory allocations. A value of 0 disables CMA
664 altogether. For more information, see
665 include/linux/dma-contiguous.h
667 cmo_free_hint= [PPC] Format: { yes | no }
668 Specify whether pages are marked as being inactive
669 when they are freed. This is used in CMO environments
670 to determine OS memory pressure for page stealing by
674 coherent_pool=nn[KMG] [ARM,KNL]
675 Sets the size of memory pool for coherent, atomic dma
676 allocations, by default set to 256K.
678 code_bytes [X86] How many bytes of object code to print
683 com20020= [HW,NET] ARCnet - COM20020 chipset
685 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
687 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
691 ARCnet - COM90xx chipset (memory-mapped buffers)
692 Format: <io>[,<irq>[,<memstart>]]
694 condev= [HW,S390] console device
697 console= [KNL] Output console device and options.
699 tty<n> Use the virtual console device <n>.
703 Use the specified serial port. The options are of
704 the form "bbbbpnf", where "bbbb" is the baud rate,
705 "p" is parity ("n", "o", or "e"), "n" is number of
706 bits, and "f" is flow control ("r" for RTS or
707 omit it). Default is "9600n8".
709 See Documentation/serial-console.txt for more
711 Documentation/networking/netconsole.txt for an
714 uart[8250],io,<addr>[,options]
715 uart[8250],mmio,<addr>[,options]
716 Start an early, polled-mode console on the 8250/16550
717 UART at the specified I/O port or MMIO address,
718 switching to the matching ttyS device later. The
719 options are the same as for ttyS, above.
720 hvc<n> Use the hypervisor console device <n>. This is for
721 both Xen and PowerPC hypervisors.
723 If the device connected to the port is not a TTY but a braille
724 device, prepend "brl," before the device type, for instance
726 For now, only VisioBraille is supported.
728 consoleblank= [KNL] The console blank (screen saver) timeout in
729 seconds. Defaults to 10*60 = 10mins. A value of 0
730 disables the blank timer.
733 [KNL] Change the default value for
734 /proc/<pid>/coredump_filter.
735 See also Documentation/filesystems/proc.txt.
737 cpuidle.off=1 [CPU_IDLE]
738 disable the cpuidle sub-system
740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
742 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
744 crashkernel=size[KMG][@offset[KMG]]
745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
746 upon panic. This parameter reserves the physical
747 memory region [offset, offset + size] for that kernel
748 image. If '@offset' is omitted, then a suitable offset
749 is selected automatically. Check
750 Documentation/kdump/kdump.txt for further details.
752 crashkernel=range1:size1[,range2:size2,...][@offset]
753 [KNL] Same as above, but depends on the memory
754 in the running system. The syntax of range is
755 start-[end] where start and end are both
756 a memory unit (amount[KMG]). See also
757 Documentation/kdump/kdump.txt for an example.
759 crashkernel=size[KMG],high
760 [KNL, x86_64] range could be above 4G. Allow kernel
761 to allocate physical memory region from top, so could
762 be above 4G if system have more than 4G ram installed.
763 Otherwise memory region will be allocated below 4G, if
765 It will be ignored if crashkernel=X is specified.
766 crashkernel=size[KMG],low
767 [KNL, x86_64] range under 4G. When crashkernel=X,high
768 is passed, kernel could allocate physical memory region
769 above 4G, that cause second kernel crash on system
770 that require some amount of low memory, e.g. swiotlb
771 requires at least 64M+32K low memory. Kernel would
772 try to allocate 72M below 4G automatically.
773 This one let user to specify own low range under 4G
774 for second kernel instead.
775 0: to disable low allocation.
776 It will be ignored when crashkernel=X,high is not used
777 or memory reserved is below 4G.
782 cs89x0_media= [HW,NET]
783 Format: { rj45 | aui | bnc }
786 See header of drivers/s390/block/dasd_devmap.c.
788 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
789 (one device per port)
790 Format: <port#>,<type>
791 See also Documentation/input/joystick-parport.txt
793 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794 time. See Documentation/dynamic-debug-howto.txt for
795 details. Deprecated, see dyndbg.
797 debug [KNL] Enable kernel debugging (events log level).
800 [KNL] verbose self-tests
802 Print debugging info while doing the locking API
804 We default to 0 (no extra messages), setting it to
805 1 will print _a lot_ more information - normally
806 only useful to kernel developers.
808 debug_objects [KNL] Enable object debugging
811 [KNL] Disable object debugging
813 debug_guardpage_minorder=
814 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815 parameter allows control of the order of pages that will
816 be intentionally kept free (and hence protected) by the
817 buddy allocator. Bigger value increase the probability
818 of catching random memory corruption, but reduce the
819 amount of memory for normal system use. The maximum
820 possible value is MAX_ORDER/2. Setting this parameter
821 to 1 or 2 should be enough to identify most random
822 memory corruption problems caused by bugs in kernel or
823 driver code when a CPU writes to (or reads from) a
824 random memory location. Note that there exists a class
825 of memory corruptions problems caused by buggy H/W or
826 F/W or by drivers badly programing DMA (basically when
827 memory is written at bus level and the CPU MMU is
828 bypassed) which are not detectable by
829 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830 tracking down these problems.
832 debugpat [X86] Enable PAT debugging
834 decnet.addr= [HW,NET]
835 Format: <area>[,<node>]
836 See also Documentation/networking/decnet.txt.
839 [same as hugepagesz=] The size of the default
840 HugeTLB page size. This is the size represented by
841 the legacy /proc/ hugepages APIs, used for SHM, and
842 default size when mounting hugetlbfs filesystems.
843 Defaults to the default architecture's huge page size
847 Set number of hash buckets for dentry cache.
850 See Documentation/networking/ipv6.txt.
852 disable_cpu_apicid= [X86,APIC,SMP]
854 The number of initial APIC ID for the
855 corresponding CPU to be disabled at boot,
856 mostly used for the kdump 2nd kernel to
857 disable BSP to wake up multiple CPUs without
858 causing system reset or hang due to sending
861 disable_ddw [PPC/PSERIES]
862 Disable Dynamic DMA Window support. Use this if
863 to workaround buggy firmware.
866 See Documentation/networking/ipv6.txt.
868 disable_mtrr_cleanup [X86]
869 The kernel tries to adjust MTRR layout from continuous
870 to discrete, to make X server driver able to add WB
871 entry later. This parameter disables that.
873 disable_mtrr_trim [X86, Intel and AMD only]
874 By default the kernel will trim any uncacheable
875 memory out of your available memory pool based on
876 MTRR settings. This parameter disables that behavior,
877 possibly causing your machine to run very slowly.
879 disable_timer_pin_1 [X86]
880 Disable PIN 1 of APIC timer
881 Can be useful to work around chipset bugs.
883 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
884 this option disables the debugging code at boot.
886 dma_debug_entries=<number>
887 This option allows to tune the number of preallocated
888 entries for DMA-API debugging code. One entry is
889 required per DMA-API allocation. Use this if the
890 DMA-API debugging code disables itself because the
891 architectural default is too low.
893 dma_debug_driver=<driver_name>
894 With this option the DMA-API debugging driver
895 filter feature can be enabled at boot time. Just
896 pass the driver to filter for as the parameter.
897 The filter can be disabled or changed to another
898 driver later using sysfs.
900 drm_kms_helper.edid_firmware=[<connector>:]<file>
901 Broken monitors, graphic adapters and KVMs may
902 send no or incorrect EDID data sets. This parameter
903 allows to specify an EDID data set in the
904 /lib/firmware directory that is used instead.
905 Generic built-in EDID data sets are used, if one of
906 edid/1024x768.bin, edid/1280x1024.bin,
907 edid/1680x1050.bin, or edid/1920x1080.bin is given
908 and no file with the same name exists. Details and
909 instructions how to build your own EDID data are
910 available in Documentation/EDID/HOWTO.txt. An EDID
911 data set will only be used for a particular connector,
912 if its name and a colon are prepended to the EDID
917 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
918 module.dyndbg[="val"]
919 Enable debug messages at boot time. See
920 Documentation/dynamic-debug-howto.txt for details.
922 early_ioremap_debug [KNL]
923 Enable debug messages in early_ioremap support. This
924 is useful for tracking down temporary early mappings
925 which are not unmapped.
927 earlycon= [KNL] Output early console device and options.
930 Start an early, polled-mode console on a cadence serial
931 port at the specified address. The cadence serial port
932 must already be setup and configured. Options are not
935 uart[8250],io,<addr>[,options]
936 uart[8250],mmio,<addr>[,options]
937 uart[8250],mmio32,<addr>[,options]
938 Start an early, polled-mode console on the 8250/16550
939 UART at the specified I/O port or MMIO address.
940 MMIO inter-register address stride is either 8-bit
941 (mmio) or 32-bit (mmio32).
942 The options are the same as for ttyS, above.
945 Start an early, polled-mode console on a pl011 serial
946 port at the specified address. The pl011 serial port
947 must already be setup and configured. Options are not
951 Start an early, polled-mode console on an msm serial
952 port at the specified address. The serial port
953 must already be setup and configured. Options are not
957 Start an early, polled-mode console on an msm serial
958 dm port at the specified address. The serial port
959 must already be setup and configured. Options are not
962 smh Use ARM semihosting calls for early console.
964 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
968 earlyprintk=serial[,ttySn[,baudrate]]
969 earlyprintk=serial[,0x...[,baudrate]]
970 earlyprintk=ttySn[,baudrate]
971 earlyprintk=dbgp[debugController#]
973 earlyprintk is useful when the kernel crashes before
974 the normal console is initialized. It is not enabled by
975 default because it has some cosmetic problems.
977 Append ",keep" to not disable it when the real console
980 Only one of vga, efi, serial, or usb debug port can
983 Currently only ttyS0 and ttyS1 may be specified by
984 name. Other I/O ports may be explicitly specified
985 on some architectures (x86 and arm at least) by
986 replacing ttySn with an I/O port address, like this:
987 earlyprintk=serial,0x1008,115200
988 You can find the port for a given device in
989 /proc/tty/driver/serial:
990 2: uart:ST16650V2 port:00001008 irq:18 ...
992 Interaction with the standard serial driver is not
995 The VGA and EFI output is eventually overwritten by
998 The xen output can only be used by Xen PV guests.
1000 edac_report= [HW,EDAC] Control how to report EDAC event
1001 Format: {"on" | "off" | "force"}
1002 on: enable EDAC to report H/W event. May be overridden
1003 by other higher priority error reporting module.
1004 off: disable H/W event reporting through EDAC.
1005 force: enforce the use of EDAC to report H/W event.
1008 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1011 This is designed to be used in conjunction with
1012 the boot argument: earlyprintk=vga
1015 Format: {"off" | "on" | "skip[mbr]"}
1018 Format: { "old_map", "nochunk", "noruntime" }
1019 old_map [X86-64]: switch to the old ioremap-based EFI
1020 runtime services mapping. 32-bit still uses this one by
1022 nochunk: disable reading files in "chunks" in the EFI
1023 boot stub, as chunking can cause problems with some
1024 firmware implementations.
1025 noruntime : disable EFI runtime services support
1027 efi_no_storage_paranoia [EFI; X86]
1028 Using this parameter you can use more than 50% of
1029 your efi variable storage. Use this parameter only if
1030 you are really sure that your UEFI does sane gc and
1031 fulfills the spec otherwise your board may brick.
1033 eisa_irq_edge= [PARISC,HW]
1034 See header of drivers/parisc/eisa.c.
1037 See comment before function elanfreq_setup() in
1038 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1041 Format: {"cfq" | "deadline" | "noop"}
1042 See Documentation/block/cfq-iosched.txt and
1043 Documentation/block/deadline-iosched.txt for details.
1045 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1046 Specifies physical address of start of kernel core
1047 image elf header and optionally the size. Generally
1048 kexec loader will pass this option to capture kernel.
1049 See Documentation/kdump/kdump.txt for details.
1051 enable_mtrr_cleanup [X86]
1052 The kernel tries to adjust MTRR layout from continuous
1053 to discrete, to make X server driver able to add WB
1054 entry later. This parameter enables that.
1056 enable_timer_pin_1 [X86]
1057 Enable PIN 1 of APIC timer
1058 Can be useful to work around chipset bugs
1059 (in particular on some ATI chipsets).
1060 The kernel tries to set a reasonable default.
1062 enforcing [SELINUX] Set initial enforcing status.
1064 See security/selinux/Kconfig help text.
1065 0 -- permissive (log only, no denials).
1066 1 -- enforcing (deny and log).
1068 Value can be changed at runtime via /selinux/enforce.
1071 Disable Error Record Serialization Table (ERST)
1074 ether= [HW,NET] Ethernet cards parameters
1075 This option is obsoleted by the "netdev=" option, which
1076 has equivalent usage. See its documentation for details.
1080 Permit 'security.evm' to be updated regardless of
1081 current integrity status.
1085 fail_make_request=[KNL]
1086 General fault injection mechanism.
1087 Format: <interval>,<probability>,<space>,<times>
1088 See also Documentation/fault-injection/.
1091 See Documentation/blockdev/floppy.txt.
1093 force_pal_cache_flush
1094 [IA-64] Avoid check_sal_cache_flush which may hang on
1095 buggy SAL_CACHE_FLUSH implementations. Using this
1096 parameter will force ia64_sal_cache_flush to call
1097 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1100 Forcefully enable Physical Address Extension (PAE).
1101 Many Pentium M systems disable PAE but may have a
1102 functionally usable PAE implementation.
1103 Warning: use of this parameter will taint the kernel
1104 and may cause unknown problems.
1107 [FTRACE] will set and start the specified tracer
1108 as early as possible in order to facilitate early
1111 ftrace_dump_on_oops[=orig_cpu]
1112 [FTRACE] will dump the trace buffers on oops.
1113 If no parameter is passed, ftrace will dump
1114 buffers of all CPUs, but if you pass orig_cpu, it will
1115 dump only the buffer of the CPU that triggered the
1118 ftrace_filter=[function-list]
1119 [FTRACE] Limit the functions traced by the function
1120 tracer at boot up. function-list is a comma separated
1121 list of functions. This list can be changed at run
1122 time by the set_ftrace_filter file in the debugfs
1125 ftrace_notrace=[function-list]
1126 [FTRACE] Do not trace the functions specified in
1127 function-list. This list can be changed at run time
1128 by the set_ftrace_notrace file in the debugfs
1131 ftrace_graph_filter=[function-list]
1132 [FTRACE] Limit the top level callers functions traced
1133 by the function graph tracer at boot up.
1134 function-list is a comma separated list of functions
1135 that can be changed at run time by the
1136 set_graph_function file in the debugfs tracing directory.
1138 ftrace_graph_notrace=[function-list]
1139 [FTRACE] Do not trace from the functions specified in
1140 function-list. This list is a comma separated list of
1141 functions that can be changed at run time by the
1142 set_graph_notrace file in the debugfs tracing directory.
1145 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1146 support via parallel port (up to 5 devices per port)
1147 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1148 See also Documentation/input/joystick-parport.txt
1152 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1156 gcov_persist= [GCOV] When non-zero (default), profiling data for
1157 kernel modules is saved and remains accessible via
1158 debugfs, even when the module is unloaded/reloaded.
1159 When zero, profiling data is discarded and associated
1160 debugfs files are removed at module unload time.
1162 gpt [EFI] Forces disk with valid GPT signature but
1163 invalid Protective MBR to be treated as GPT. If the
1164 primary GPT is corrupted, it enables the backup/alternate
1165 GPT to be used instead.
1167 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1168 the "Enable 0" bit of the configuration register.
1171 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1172 the "Enable 0" bit of the configuration register.
1175 grcan.select= [HW] Select which physical interface to use.
1178 grcan.txsize= [HW] Sets the size of the tx buffer.
1179 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1181 grcan.rxsize= [HW] Sets the size of the rx buffer.
1182 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1185 hashdist= [KNL,NUMA] Large hashes allocated during boot
1186 are distributed across NUMA nodes. Defaults on
1187 for 64-bit NUMA, off otherwise.
1188 Format: 0 | 1 (for off | on)
1190 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1192 hd= [EIDE] (E)IDE hard drive subsystem geometry
1193 Format: <cyl>,<head>,<sect>
1196 Disable Hardware Error Source Table (HEST) support;
1197 corresponding firmware-first mode error processing
1198 logic will be disabled.
1200 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1201 size of <nn>. This works even on boxes that have no
1202 highmem otherwise. This also works to reduce highmem
1203 size on bigger boxes.
1205 highres= [KNL] Enable/disable high resolution timer mode.
1206 Valid parameters: "on", "off"
1210 See Documentation/isdn/README.HiSax.
1214 hpet= [X86-32,HPET] option to control HPET usage
1215 Format: { enable (default) | disable | force |
1217 disable: disable HPET and use PIT instead
1218 force: allow force enabled of undocumented chips (ICH4,
1220 verbose: show contents of HPET registers during setup
1222 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1223 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1225 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1226 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1227 On x86-64 and powerpc, this option can be specified
1228 multiple times interleaved with hugepages= to reserve
1229 huge pages of different sizes. Valid pages sizes on
1230 x86-64 are 2M (when the CPU supports "pse") and 1G
1231 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1232 Note that 1GB pages can only be allocated at boot time
1233 using hugepages= and not freed afterwards.
1235 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1236 terminal devices. Valid values: 0..8
1237 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1238 If specified, z/VM IUCV HVC accepts connections
1239 from listed z/VM user IDs only.
1241 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1242 hardware thread id mappings.
1243 Format: <cpu>:<hwthread>
1246 Do not unregister boot console at start. This is only
1247 useful for debugging when something happens in the window
1248 between unregistering the boot console and initializing
1251 i2c_bus= [HW] Override the default board specific I2C bus speed
1252 or register an additional I2C bus that is not
1253 registered from board initialization code.
1257 i8042.debug [HW] Toggle i8042 debug mode
1258 i8042.direct [HW] Put keyboard port into non-translated mode
1259 i8042.dumbkbd [HW] Pretend that controller can only read data from
1260 keyboard and cannot control its state
1261 (Don't attempt to blink the leds)
1262 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1263 i8042.nokbd [HW] Don't check/create keyboard port
1264 i8042.noloop [HW] Disable the AUX Loopback command while probing
1266 i8042.nomux [HW] Don't check presence of an active multiplexing
1268 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1270 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1271 i8042.reset [HW] Reset the controller during init and cleanup
1272 i8042.unlock [HW] Unlock (ignore) the keylock
1276 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1277 indicates that the driver is running on unsupported
1279 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1280 does not match list of supported models.
1282 [HW] Report power status in /proc/i8k
1283 (disabled by default)
1284 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1287 i915.invert_brightness=
1288 [DRM] Invert the sense of the variable that is used to
1289 set the brightness of the panel backlight. Normally a
1290 brightness value of 0 indicates backlight switched off,
1291 and the maximum of the brightness value sets the backlight
1292 to maximum brightness. If this parameter is set to 0
1293 (default) and the machine requires it, or this parameter
1294 is set to 1, a brightness value of 0 sets the backlight
1295 to maximum brightness, and the maximum of the brightness
1296 value switches the backlight off.
1297 -1 -- never invert brightness
1298 0 -- machine default
1299 1 -- force brightness inversion
1302 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1304 ide-core.nodma= [HW] (E)IDE subsystem
1305 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1306 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1307 .cdrom .chs .ignore_cable are additional options
1308 See Documentation/ide/ide.txt.
1310 ide-generic.probe-mask= [HW] (E)IDE subsystem
1312 Probe mask for legacy ISA IDE ports. Depending on
1313 platform up to 6 ports are supported, enabled by
1314 setting corresponding bits in the mask to 1. The
1315 default value is 0x0, which has a special meaning.
1316 On systems that have PCI, it triggers scanning the
1317 PCI bus for the first and the second port, which
1318 are then probed. On systems without PCI the value
1319 of 0x0 enables probing the two first ports as if it
1322 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1323 Claim all unknown PCI IDE storage controllers.
1326 Format: idle=poll, idle=halt, idle=nomwait
1327 Poll forces a polling idle loop that can slightly
1328 improve the performance of waking up a idle CPU, but
1329 will use a lot of power and make the system run hot.
1331 idle=halt: Halt is forced to be used for CPU idle.
1332 In such case C2/C3 won't be used again.
1333 idle=nomwait: Disable mwait for CPU C-states
1335 ignore_loglevel [KNL]
1336 Ignore loglevel setting - this will print /all/
1337 kernel messages to the console. Useful for debugging.
1338 We also add it as printk module parameter, so users
1339 could change it dynamically, usually by
1340 /sys/module/printk/parameters/ignore_loglevel.
1342 ihash_entries= [KNL]
1343 Set number of hash buckets for inode cache.
1345 ima_appraise= [IMA] appraise integrity measurements
1346 Format: { "off" | "enforce" | "fix" | "log" }
1349 ima_appraise_tcb [IMA]
1350 The builtin appraise policy appraises all files
1354 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1358 The list of supported hash algorithms is defined
1359 in crypto/hash_info.h.
1362 Load a policy which meets the needs of the Trusted
1363 Computing Base. This means IMA will measure all
1364 programs exec'd, files mmap'd for exec, and all files
1365 opened for read by uid=0.
1368 Select one of defined IMA measurements template formats.
1369 Formats: { "ima" | "ima-ng" }
1372 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1373 Format: <min_file_size>
1374 Set the minimal file size for using asynchronous hash.
1375 If left unspecified, ahash usage is disabled.
1377 ahash performance varies for different data sizes on
1378 different crypto accelerators. This option can be used
1379 to achieve the best performance for a particular HW.
1381 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1383 Set hashing buffer size. Default: 4k.
1385 ahash performance varies for different chunk sizes on
1386 different crypto accelerators. This option can be used
1387 to achieve best performance for particular HW.
1391 Run specified binary instead of /sbin/init as init
1394 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1395 for working out where the kernel is dying during
1398 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1399 initcall functions. Useful for debugging built-in
1400 modules and initcalls.
1402 initrd= [BOOT] Specify the location of the initial ramdisk
1404 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1407 int_pln_enable [x86] Enable power limit notification interrupt
1409 integrity_audit=[IMA]
1410 Format: { "0" | "1" }
1411 0 -- basic integrity auditing messages. (Default)
1412 1 -- additional integrity auditing messages.
1414 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1416 Enable intel iommu driver.
1418 Disable intel iommu driver.
1419 igfx_off [Default Off]
1420 By default, gfx is mapped as normal device. If a gfx
1421 device has a dedicated DMAR unit, the DMAR unit is
1422 bypassed by not enabling DMAR with this option. In
1423 this case, gfx device will use physical address for
1426 With this option iommu will not optimize to look
1427 for io virtual address below 32-bit forcing dual
1428 address cycle on pci bus for cards supporting greater
1429 than 32-bit addressing. The default is to look
1430 for translation below 32-bit and if not available
1431 then look in the higher range.
1432 strict [Default Off]
1433 With this option on every unmap_single operation will
1434 result in a hardware IOTLB flush operation as opposed
1435 to batching them for performance.
1436 sp_off [Default Off]
1437 By default, super page will be supported if Intel IOMMU
1438 has the capability. With this option, super page will
1441 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1442 0 disables intel_idle and fall back on acpi_idle.
1443 1 to 6 specify maximum depth of C-state.
1447 Do not enable intel_pstate as the default
1448 scaling driver for the supported processors
1450 Do not enable hardware P state control (HWP)
1453 intremap= [X86-64, Intel-IOMMU]
1454 on enable Interrupt Remapping (default)
1455 off disable Interrupt Remapping
1456 nosid disable Source ID checking
1458 BIOS x2APIC opt-out request will be ignored
1460 iomem= Disable strict checking of access to MMIO memory
1461 strict regions from userspace.
1478 io7= [HW] IO7 for Marvel based alpha systems
1479 See comment before marvel_specify_io7 in
1480 arch/alpha/kernel/core_marvel.c.
1482 io_delay= [X86] I/O delay method
1484 Standard port 0x80 based delay
1486 Alternate port 0xed based delay (needed on some systems)
1488 Simple two microseconds delay
1493 See Documentation/filesystems/nfs/nfsroot.txt.
1496 When an interrupt is not handled search all handlers
1497 for it. Intended to get systems with badly broken
1501 When an interrupt is not handled search all handlers
1502 for it. Also check all handlers each timer
1503 interrupt. Intended to get systems with badly broken
1507 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1509 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1511 <cpu number>,...,<cpu number>
1513 <cpu number>-<cpu number>
1514 (must be a positive range in ascending order)
1516 <cpu number>,...,<cpu number>-<cpu number>
1518 This option can be used to specify one or more CPUs
1519 to isolate from the general SMP balancing and scheduling
1520 algorithms. You can move a process onto or off an
1521 "isolated" CPU via the CPU affinity syscalls or cpuset.
1522 <cpu number> begins at 0 and the maximum value is
1523 "number of CPUs in system - 1".
1525 This option is the preferred way to isolate CPUs. The
1526 alternative -- manually setting the CPU mask of all
1527 tasks in the system -- can cause problems and
1528 suboptimal load balancer performance.
1532 ivrs_ioapic [HW,X86_64]
1533 Provide an override to the IOAPIC-ID<->DEVICE-ID
1534 mapping provided in the IVRS ACPI table. For
1535 example, to map IOAPIC-ID decimal 10 to
1536 PCI device 00:14.0 write the parameter as:
1537 ivrs_ioapic[10]=00:14.0
1539 ivrs_hpet [HW,X86_64]
1540 Provide an override to the HPET-ID<->DEVICE-ID
1541 mapping provided in the IVRS ACPI table. For
1542 example, to map HPET-ID decimal 0 to
1543 PCI device 00:14.0 write the parameter as:
1544 ivrs_hpet[0]=00:14.0
1546 js= [HW,JOY] Analog joystick
1547 See Documentation/input/joystick.txt.
1550 Enable/disable kernel and module base offset ASLR
1551 (Address Space Layout Randomization) if built into
1552 the kernel. When CONFIG_HIBERNATION is selected,
1553 kASLR is disabled by default. When kASLR is enabled,
1554 hibernation will be disabled.
1558 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1559 specifies the amount of memory usable by the kernel
1560 for non-movable allocations. The requested amount is
1561 spread evenly throughout all nodes in the system. The
1562 remaining memory in each node is used for Movable
1563 pages. In the event, a node is too small to have both
1564 kernelcore and Movable pages, kernelcore pages will
1565 take priority and other nodes will have a larger number
1566 of Movable pages. The Movable zone is used for the
1567 allocation of pages that may be reclaimed or moved
1568 by the page migration subsystem. This means that
1569 HugeTLB pages may not be allocated from this zone.
1570 Note that allocations like PTEs-from-HighMem still
1571 use the HighMem zone if it exists, and the Normal
1572 zone if it does not.
1574 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1575 Format: <Controller#>[,poll interval]
1576 The controller # is the number of the ehci usb debug
1577 port as it is probed via PCI. The poll interval is
1578 optional and is the number seconds in between
1579 each poll cycle to the debug port in case you need
1580 the functionality for interrupting the kernel with
1581 gdb or control-c on the dbgp connection. When
1582 not using this parameter you use sysrq-g to break into
1583 the kernel debugger.
1585 kgdboc= [KGDB,HW] kgdb over consoles.
1586 Requires a tty driver that supports console polling,
1587 or a supported polling keyboard driver (non-usb).
1588 Serial only format: <serial_device>[,baud]
1589 keyboard only format: kbd
1590 keyboard and serial format: kbd,<serial_device>[,baud]
1591 Optional Kernel mode setting:
1592 kms, kbd format: kms,kbd
1593 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1595 kgdbwait [KGDB] Stop kernel execution and enter the
1596 kernel debugger at the earliest opportunity.
1598 kmac= [MIPS] korina ethernet MAC address.
1599 Configure the RouterBoard 532 series on-chip
1600 Ethernet adapter MAC address.
1602 kmemleak= [KNL] Boot-time kmemleak enable/disable
1603 Valid arguments: on, off
1605 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1608 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1609 Valid arguments: 0, 1, 2
1610 kmemcheck=0 (disabled)
1611 kmemcheck=1 (enabled)
1612 kmemcheck=2 (one-shot mode)
1613 Default: 2 (one-shot mode)
1615 kstack=N [X86] Print N words from the kernel stack
1618 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1619 Default is 0 (don't ignore, but inject #GP)
1621 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1625 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1626 Default is 1 (enabled)
1628 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1630 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1632 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1633 (virtualized MMU) support on capable Intel chips.
1634 Default is 1 (enabled)
1636 kvm-intel.emulate_invalid_guest_state=
1637 [KVM,Intel] Enable emulation of invalid guest states
1638 Default is 0 (disabled)
1640 kvm-intel.flexpriority=
1641 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1642 Default is 1 (enabled)
1645 [KVM,Intel] Enable VMX nesting (nVMX).
1646 Default is 0 (disabled)
1648 kvm-intel.unrestricted_guest=
1649 [KVM,Intel] Disable unrestricted guest feature
1650 (virtualized real and unpaged mode) on capable
1651 Intel chips. Default is 1 (enabled)
1653 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1654 feature (tagged TLBs) on capable Intel chips.
1655 Default is 1 (enabled)
1661 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1664 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1665 value for LAPIC timer one-shot implementation. Default
1666 back to the programmable timer unit in the LAPIC.
1668 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1671 libata.dma= [LIBATA] DMA control
1672 libata.dma=0 Disable all PATA and SATA DMA
1673 libata.dma=1 PATA and SATA Disk DMA only
1674 libata.dma=2 ATAPI (CDROM) DMA only
1675 libata.dma=4 Compact Flash DMA only
1676 Combinations also work, so libata.dma=3 enables DMA
1677 for disks and CDROMs, but not CFs.
1679 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1680 libata.ignore_hpa=0 keep BIOS limits (default)
1681 libata.ignore_hpa=1 ignore limits, using full disk
1683 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1687 libata.force= [LIBATA] Force configurations. The format is comma
1688 separated list of "[ID:]VAL" where ID is
1689 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1690 matching port, link or device. Basically, it matches
1691 the ATA ID string printed on console by libata. If
1692 the whole ID part is omitted, the last PORT and DEVICE
1693 values are used. If ID hasn't been specified yet, the
1694 configuration applies to all ports, links and devices.
1696 If only DEVICE is omitted, the parameter applies to
1697 the port and all links and devices behind it. DEVICE
1698 number of 0 either selects the first device or the
1699 first fan-out link behind PMP device. It does not
1700 select the host link. DEVICE number of 15 selects the
1701 host link and device attached to it.
1703 The VAL specifies the configuration to force. As long
1704 as there's no ambiguity shortcut notation is allowed.
1705 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1706 The following configurations can be forced.
1708 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1709 Any ID with matching PORT is used.
1711 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1713 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1714 udma[/][16,25,33,44,66,100,133] notation is also
1717 * [no]ncq: Turn on or off NCQ.
1719 * nohrst, nosrst, norst: suppress hard, soft
1722 * rstonce: only attempt one reset during
1723 hot-unplug link recovery
1725 * dump_id: dump IDENTIFY data.
1727 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1729 * disable: Disable this device.
1731 If there are multiple matching configurations changing
1732 the same attribute, the last one is used.
1734 memblock=debug [KNL] Enable memblock debug messages.
1736 load_ramdisk= [RAM] List of ramdisks to load from floppy
1737 See Documentation/blockdev/ramdisk.txt.
1739 lockd.nlm_grace_period=P [NFS] Assign grace period.
1742 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1745 lockd.nlm_timeout=T [NFS] Assign timeout value.
1748 lockd.nlm_udpport=M [NFS] Assign UDP port.
1751 locktorture.nreaders_stress= [KNL]
1752 Set the number of locking read-acquisition kthreads.
1753 Defaults to being automatically set based on the
1754 number of online CPUs.
1756 locktorture.nwriters_stress= [KNL]
1757 Set the number of locking write-acquisition kthreads.
1759 locktorture.onoff_holdoff= [KNL]
1760 Set time (s) after boot for CPU-hotplug testing.
1762 locktorture.onoff_interval= [KNL]
1763 Set time (s) between CPU-hotplug operations, or
1764 zero to disable CPU-hotplug testing.
1766 locktorture.shuffle_interval= [KNL]
1767 Set task-shuffle interval (jiffies). Shuffling
1768 tasks allows some CPUs to go into dyntick-idle
1769 mode during the locktorture test.
1771 locktorture.shutdown_secs= [KNL]
1772 Set time (s) after boot system shutdown. This
1773 is useful for hands-off automated testing.
1775 locktorture.stat_interval= [KNL]
1776 Time (s) between statistics printk()s.
1778 locktorture.stutter= [KNL]
1779 Time (s) to stutter testing, for example,
1780 specifying five seconds causes the test to run for
1781 five seconds, wait for five seconds, and so on.
1782 This tests the locking primitive's ability to
1783 transition abruptly to and from idle.
1785 locktorture.torture_runnable= [BOOT]
1786 Start locktorture running at boot time.
1788 locktorture.torture_type= [KNL]
1789 Specify the locking implementation to test.
1791 locktorture.verbose= [KNL]
1792 Enable additional printk() statements.
1794 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1797 loglevel= All Kernel Messages with a loglevel smaller than the
1798 console loglevel will be printed to the console. It can
1799 also be changed with klogd or other programs. The
1800 loglevels are defined as follows:
1802 0 (KERN_EMERG) system is unusable
1803 1 (KERN_ALERT) action must be taken immediately
1804 2 (KERN_CRIT) critical conditions
1805 3 (KERN_ERR) error conditions
1806 4 (KERN_WARNING) warning conditions
1807 5 (KERN_NOTICE) normal but significant condition
1808 6 (KERN_INFO) informational
1809 7 (KERN_DEBUG) debug-level messages
1811 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1812 in bytes. n must be a power of two and greater
1813 than the minimal size. The minimal size is defined
1814 by LOG_BUF_SHIFT kernel config parameter. There is
1815 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1816 that allows to increase the default size depending on
1817 the number of CPUs. See init/Kconfig for more details.
1819 logo.nologo [FB] Disables display of the built-in Linux logo.
1820 This may be used to provide more screen space for
1821 kernel log messages and is useful when debugging
1822 kernel boot problems.
1824 lp=0 [LP] Specify parallel ports to use, e.g,
1825 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1826 lp=reset first parallel port). 'lp=0' disables the
1827 lp=auto printer driver. 'lp=reset' (which can be
1828 specified in addition to the ports) causes
1829 attached printers to be reset. Using
1830 lp=port1,port2,... specifies the parallel ports
1831 to associate lp devices with, starting with
1832 lp0. A port specification may be 'none' to skip
1833 that lp device, or a parport name such as
1834 'parport0'. Specifying 'lp=auto' instead of a
1835 port specification list means that device IDs
1836 from each port should be examined, to see if
1837 an IEEE 1284-compliant printer is attached; if
1838 so, the driver will manage that printer.
1839 See also header of drivers/char/lp.c.
1842 Sets loops_per_jiffy to given constant, thus avoiding
1843 time-consuming boot-time autodetection (up to 250 ms per
1844 CPU). 0 enables autodetection (default). To determine
1845 the correct value for your kernel, boot with normal
1846 autodetection and see what value is printed. Note that
1847 on SMP systems the preset will be applied to all CPUs,
1848 which is likely to cause problems if your CPUs need
1849 significantly divergent settings. An incorrect value
1850 will cause delays in the kernel to be wrong, leading to
1851 unpredictable I/O errors and other breakage. Although
1852 unlikely, in the extreme case this might damage your
1856 Format: <io>,<irq>,<dma>
1858 machvec= [IA-64] Force the use of a particular machine-vector
1859 (machvec) in a generic kernel.
1860 Example: machvec=hpzx1_swiotlb
1862 machtype= [Loongson] Share the same kernel image file between different
1864 Example: machtype=lemote-yeeloong-2f-7inch
1866 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1867 than or equal to this physical address is ignored.
1869 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1870 should make use of. maxcpus=n : n >= 0 limits the
1871 kernel to using 'n' processors. n=0 is a special case,
1872 it is equivalent to "nosmp", which also disables
1875 max_loop= [LOOP] The number of loop block devices that get
1876 (loop.max_loop) unconditionally pre-created at init time. The default
1877 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1878 of statically allocating a predefined number, loop
1879 devices can be requested on-demand with the
1880 /dev/loop-control interface.
1882 mce [X86-32] Machine Check Exception
1884 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1886 md= [HW] RAID subsystems devices and level
1887 See Documentation/md.txt.
1890 Format: <first>,<last>
1891 Specifies range of consoles to be captured by the MDA.
1893 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1894 Amount of memory to be used when the kernel is not able
1895 to see the whole system memory or for test.
1896 [X86] Work as limiting max address. Use together
1897 with memmap= to avoid physical address space collisions.
1898 Without memmap= PCI devices could be placed at addresses
1899 belonging to unused RAM.
1901 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1905 [KNL,SH] Allow user to override the default size for
1906 per-device physically contiguous DMA buffers.
1908 memmap=exactmap [KNL,X86] Enable setting of an exact
1909 E820 memory map, as specified by the user.
1910 Such memmap=exactmap lines can be constructed based on
1911 BIOS output or other requirements. See the memmap=nn@ss
1914 memmap=nn[KMG]@ss[KMG]
1915 [KNL] Force usage of a specific region of memory.
1916 Region of memory to be used is from ss to ss+nn.
1918 memmap=nn[KMG]#ss[KMG]
1919 [KNL,ACPI] Mark specific memory as ACPI data.
1920 Region of memory to be marked is from ss to ss+nn.
1922 memmap=nn[KMG]$ss[KMG]
1923 [KNL,ACPI] Mark specific memory as reserved.
1924 Region of memory to be reserved is from ss to ss+nn.
1925 Example: Exclude memory from 0x18690000-0x1869ffff
1926 memmap=64K$0x18690000
1928 memmap=0x10000$0x18690000
1930 memory_corruption_check=0/1 [X86]
1931 Some BIOSes seem to corrupt the first 64k of
1932 memory when doing things like suspend/resume.
1933 Setting this option will scan the memory
1934 looking for corruption. Enabling this will
1935 both detect corruption and prevent the kernel
1936 from using the memory being corrupted.
1937 However, its intended as a diagnostic tool; if
1938 repeatable BIOS-originated corruption always
1939 affects the same memory, you can use memmap=
1940 to prevent the kernel from using that memory.
1942 memory_corruption_check_size=size [X86]
1943 By default it checks for corruption in the low
1944 64k, making this memory unavailable for normal
1945 use. Use this parameter to scan for
1946 corruption in more or less memory.
1948 memory_corruption_check_period=seconds [X86]
1949 By default it checks for corruption every 60
1950 seconds. Use this parameter to check at some
1951 other rate. 0 disables periodic checking.
1953 memtest= [KNL,X86] Enable memtest
1955 default : 0 <disable>
1956 Specifies the number of memtest passes to be
1957 performed. Each pass selects another test
1958 pattern from a given set of patterns. Memtest
1959 fills the memory with this pattern, validates
1960 memory contents and reserves bad memory
1961 regions that are detected.
1963 meye.*= [HW] Set MotionEye Camera parameters
1964 See Documentation/video4linux/meye.txt.
1966 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1967 Multi-Function General Purpose Timers on AMD Geode
1970 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1971 the BIOS has incorrectly applied a workaround. TinyBIOS
1972 version 0.98 is known to be affected, 0.99 fixes the
1973 problem by letting the user disable the workaround.
1977 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1978 physical address is ignored.
1980 mini2440= [ARM,HW,KNL]
1981 Format:[0..2][b][c][t]
1983 MINI2440 configuration specification:
1984 0 - The attached screen is the 3.5" TFT
1985 1 - The attached screen is the 7" TFT
1986 2 - The VGA Shield is attached (1024x768)
1987 Leaving out the screen size parameter will not load
1988 the TFT driver, and the framebuffer will be left
1990 b - Enable backlight. The TFT backlight pin will be
1991 linked to the kernel VESA blanking code and a GPIO
1992 LED. This parameter is not necessary when using the
1994 c - Enable the s3c camera interface.
1995 t - Reserved for enabling touchscreen support. The
1996 touchscreen support is not enabled in the mainstream
1997 kernel as of 2.6.30, a preliminary port can be found
1998 in the "bleeding edge" mini2440 support kernel at
1999 http://repo.or.cz/w/linux-2.6/mini2440.git
2002 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2003 parameter allows control of the logging verbosity for
2004 the additional memory initialisation checks. A value
2005 of 0 disables mminit logging and a level of 4 will
2006 log everything. Information is printed at KERN_DEBUG
2007 so loglevel=8 may also need to be specified.
2010 [KNL] When CONFIG_MODULE_SIG is set, this means that
2011 modules without (valid) signatures will fail to load.
2012 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2013 is always true, so this option does nothing.
2016 [MOUSE] Maximum time between finger touching and
2017 leaving touchpad surface for touch to be considered
2018 a tap and be reported as a left button click (for
2019 touchpads working in absolute mode only).
2021 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2022 reporting absolute coordinates, such as tablets
2023 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2024 reporting absolute coordinates, such as tablets
2026 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2027 is similar to kernelcore except it specifies the
2028 amount of memory used for migratable allocations.
2029 If both kernelcore and movablecore is specified,
2030 then kernelcore will be at *least* the specified
2031 value but may be more. If movablecore on its own
2032 is specified, the administrator must be careful
2033 that the amount of memory usable for all allocations
2036 movable_node [KNL,X86] Boot-time switch to enable the effects
2037 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2039 MTD_Partition= [MTD]
2040 Format: <name>,<region-number>,<size>,<offset>
2042 MTD_Region= [MTD] Format:
2043 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2046 See drivers/mtd/cmdlinepart.c.
2048 multitce=off [PPC] This parameter disables the use of the pSeries
2049 firmware feature for updating multiple TCE entries
2052 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2054 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2056 boundary - index of last SLC block on Flex-OneNAND.
2057 The remaining blocks are configured as MLC blocks.
2058 lock - Configure if Flex-OneNAND boundary should be locked.
2059 Once locked, the boundary cannot be changed.
2060 1 indicates lock status, 0 indicates unlock status.
2063 ARM/S3C2412 JIVE boot control
2065 See arch/arm/mach-s3c2412/mach-jive.c
2067 mtouchusb.raw_coordinates=
2068 [HW] Make the MicroTouch USB driver use raw coordinates
2069 ('y', default) or cooked coordinates ('n')
2071 mtrr_chunk_size=nn[KMG] [X86]
2072 used for mtrr cleanup. It is largest continuous chunk
2073 that could hold holes aka. UC entries.
2075 mtrr_gran_size=nn[KMG] [X86]
2076 Used for mtrr cleanup. It is granularity of mtrr block.
2078 Large value could prevent small alignment from
2081 mtrr_spare_reg_nr=n [X86]
2083 Range: 0,7 : spare reg number
2085 Used for mtrr cleanup. It is spare mtrr entries number.
2086 Set to 2 or more if your graphical card needs more.
2088 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2090 netdev= [NET] Network devices parameters
2091 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2092 Note that mem_start is often overloaded to mean
2093 something different and driver-specific.
2094 This usage is only documented in each driver source
2098 [NETFILTER] Enable connection tracking flow accounting
2099 0 to disable accounting
2100 1 to enable accounting
2103 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2104 See Documentation/filesystems/nfs/nfsroot.txt.
2106 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2107 See Documentation/filesystems/nfs/nfsroot.txt.
2109 nfsrootdebug [NFS] enable nfsroot debugging messages.
2110 See Documentation/filesystems/nfs/nfsroot.txt.
2112 nfs.callback_tcpport=
2113 [NFS] set the TCP port on which the NFSv4 callback
2114 channel should listen.
2117 [NFS] sets the pathname to the program which is used
2118 to update the NFS client cache entries.
2120 nfs.cache_getent_timeout=
2121 [NFS] sets the timeout after which an attempt to
2122 update a cache entry is deemed to have failed.
2124 nfs.idmap_cache_timeout=
2125 [NFS] set the maximum lifetime for idmapper cache
2129 [NFS] enable 64-bit inode numbers.
2130 If zero, the NFS client will fake up a 32-bit inode
2131 number for the readdir() and stat() syscalls instead
2132 of returning the full 64-bit number.
2133 The default is to return 64-bit inode numbers.
2135 nfs.max_session_slots=
2136 [NFSv4.1] Sets the maximum number of session slots
2137 the client will attempt to negotiate with the server.
2138 This limits the number of simultaneous RPC requests
2139 that the client can send to the NFSv4.1 server.
2140 Note that there is little point in setting this
2141 value higher than the max_tcp_slot_table_limit.
2143 nfs.nfs4_disable_idmapping=
2144 [NFSv4] When set to the default of '1', this option
2145 ensures that both the RPC level authentication
2146 scheme and the NFS level operations agree to use
2147 numeric uids/gids if the mount is using the
2148 'sec=sys' security flavour. In effect it is
2149 disabling idmapping, which can make migration from
2150 legacy NFSv2/v3 systems to NFSv4 easier.
2151 Servers that do not support this mode of operation
2152 will be autodetected by the client, and it will fall
2153 back to using the idmapper.
2154 To turn off this behaviour, set the value to '0'.
2156 [NFS4] Specify an additional fixed unique ident-
2157 ification string that NFSv4 clients can insert into
2158 their nfs_client_id4 string. This is typically a
2159 UUID that is generated at system install time.
2161 nfs.send_implementation_id =
2162 [NFSv4.1] Send client implementation identification
2163 information in exchange_id requests.
2164 If zero, no implementation identification information
2166 The default is to send the implementation identification
2169 nfs.recover_lost_locks =
2170 [NFSv4] Attempt to recover locks that were lost due
2171 to a lease timeout on the server. Please note that
2172 doing this risks data corruption, since there are
2173 no guarantees that the file will remain unchanged
2174 after the locks are lost.
2175 If you want to enable the kernel legacy behaviour of
2176 attempting to recover these locks, then set this
2178 The default parameter value of '0' causes the kernel
2179 not to attempt recovery of lost locks.
2181 nfsd.nfs4_disable_idmapping=
2182 [NFSv4] When set to the default of '1', the NFSv4
2183 server will return only numeric uids and gids to
2184 clients using auth_sys, and will accept numeric uids
2185 and gids from such clients. This is intended to ease
2186 migration from NFSv2/v3.
2188 objlayoutdriver.osd_login_prog=
2189 [NFS] [OBJLAYOUT] sets the pathname to the program which
2190 is used to automatically discover and login into new
2191 osd-targets. Please see:
2192 Documentation/filesystems/pnfs.txt for more explanations
2194 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2195 when a NMI is triggered.
2196 Format: [state][,regs][,debounce][,die]
2198 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2199 Format: [panic,][nopanic,][num]
2201 0 - turn nmi_watchdog off
2202 When panic is specified, panic when an NMI watchdog
2203 timeout occurs (or 'nopanic' to override the opposite
2205 This is useful when you use a panic=... timeout and
2206 need the box quickly up again.
2208 netpoll.carrier_timeout=
2209 [NET] Specifies amount of time (in seconds) that
2210 netpoll should wait for a carrier. By default netpoll
2213 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2214 emulation library even if a 387 maths coprocessor
2218 [HW] Never suspend the console
2219 Disable suspending of consoles during suspend and
2220 hibernate operations. Once disabled, debugging
2221 messages can reach various consoles while the rest
2222 of the system is being put to sleep (ie, while
2223 debugging driver suspend/resume hooks). This may
2224 not work reliably with all consoles, but is known
2225 to work with serial and VGA consoles.
2226 To facilitate more flexible debugging, we also add
2227 console_suspend, a printk module parameter to control
2228 it. Users could use console_suspend (usually
2229 /sys/module/printk/parameters/console_suspend) to
2230 turn on/off it dynamically.
2232 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2233 caches in the slab allocator. Saves per-node memory,
2234 but will impact performance.
2238 noapic [SMP,APIC] Tells the kernel to not make use of any
2239 IOAPICs that may be present in the system.
2241 noautogroup Disable scheduler automatic task group creation.
2243 nobats [PPC] Do not use BATs for mapping kernel lowmem
2244 on "Classic" PPC cores.
2248 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2250 nodelayacct [KNL] Disable per-task delay accounting
2252 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2254 nodsp [SH] Disable hardware DSP at boot time.
2256 noefi Disable EFI runtime services support.
2261 On X86-32 available only on PAE configured kernels.
2262 noexec=on: enable non-executable mappings (default)
2263 noexec=off: disable non-executable mappings
2266 Disable SMAP (Supervisor Mode Access Prevention)
2267 even if it is supported by processor.
2270 Disable SMEP (Supervisor Mode Execution Prevention)
2271 even if it is supported by processor.
2274 This affects only 32-bit executables.
2275 noexec32=on: enable non-executable mappings (default)
2276 read doesn't imply executable mappings
2277 noexec32=off: disable non-executable mappings
2278 read implies executable mappings
2280 nofpu [SH] Disable hardware FPU at boot time.
2282 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2283 register save and restore. The kernel will only save
2284 legacy floating-point registers on task switch.
2286 noxsave [BUGS=X86] Disables x86 extended register state save
2287 and restore using xsave. The kernel will fallback to
2288 enabling legacy floating-point and sse state.
2290 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2291 register states. The kernel will fall back to use
2292 xsave to save the states. By using this parameter,
2293 performance of saving the states is degraded because
2294 xsave doesn't support modified optimization while
2295 xsaveopt supports it on xsaveopt enabled systems.
2297 noxsaves [X86] Disables xsaves and xrstors used in saving and
2298 restoring x86 extended register state in compacted
2299 form of xsave area. The kernel will fall back to use
2300 xsaveopt and xrstor to save and restore the states
2301 in standard form of xsave area. By using this
2302 parameter, xsave area per process might occupy more
2303 memory on xsaves enabled systems.
2306 on enable eager fpu restore
2307 off disable eager fpu restore
2308 auto selects the default scheme, which automatically
2309 enables eagerfpu restore for xsaveopt.
2311 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2312 wfi(ARM) instruction doesn't work correctly and not to
2313 use it. This is also useful when using JTAG debugger.
2315 no_file_caps Tells the kernel not to honor file capabilities. The
2316 only way then for a file to be executed with privilege
2317 is to be setuid root or executed by root.
2319 nohalt [IA-64] Tells the kernel not to use the power saving
2320 function PAL_HALT_LIGHT when idle. This increases
2321 power-consumption. On the positive side, it reduces
2322 interrupt wake-up latency, which may improve performance
2323 in certain environments such as networked servers or
2326 nohibernate [HIBERNATION] Disable hibernation and resume.
2328 nohz= [KNL] Boottime enable/disable dynamic ticks
2329 Valid arguments: on, off
2332 nohz_full= [KNL,BOOT]
2333 In kernels built with CONFIG_NO_HZ_FULL=y, set
2334 the specified list of CPUs whose tick will be stopped
2335 whenever possible. The boot CPU will be forced outside
2336 the range to maintain the timekeeping.
2337 The CPUs in this range must also be included in the
2340 noiotrap [SH] Disables trapped I/O port accesses.
2342 noirqdebug [X86-32] Disables the code which attempts to detect and
2343 disable unhandled interrupt sources.
2345 no_timer_check [X86,APIC] Disables the code which tests for
2346 broken timer IRQ sources.
2348 noisapnp [ISAPNP] Disables ISA PnP code.
2350 noinitrd [RAM] Tells the kernel not to load any configured
2353 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2355 [Deprecated - use intremap=off]
2359 nojitter [IA-64] Disables jitter checking for ITC timers.
2361 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2363 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2366 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2367 steal time is computed, but won't influence scheduler
2370 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2372 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2374 noltlbs [PPC] Do not use large page/tlb entries for kernel
2375 lowmem mapping on PPC40x.
2377 nomca [IA-64] Disable machine check abort handling
2379 nomce [X86-32] Machine Check Exception
2381 nomfgpt [X86-32] Disable Multi-Function General Purpose
2382 Timer usage (for AMD Geode machines).
2384 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2385 shutdown the other cpus. Instead use the REBOOT_VECTOR
2388 nomodule Disable module load
2390 nopat [X86] Disable PAT (page attribute table extension of
2391 pagetables) support.
2393 norandmaps Don't use address space randomization. Equivalent to
2394 echo 0 > /proc/sys/kernel/randomize_va_space
2396 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2398 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2399 with UP alternatives
2401 nordrand [X86] Disable kernel use of the RDRAND and
2402 RDSEED instructions even if they are supported
2403 by the processor. RDRAND and RDSEED are still
2404 available to user space applications.
2406 noresume [SWSUSP] Disables resume and restores original swap
2409 no-scroll [VGA] Disables scrollback.
2410 This is required for the Braillex ib80-piezo Braille
2411 reader made by F.H. Papenmeier (Germany).
2415 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2417 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2418 and disable the IO APIC. legacy for "maxcpus=0".
2420 nosoftlockup [KNL] Disable the soft-lockup detector.
2422 nosync [HW,M68K] Disables sync negotiation for all devices.
2424 notsc [BUGS=X86-32] Disable Time Stamp Counter
2426 nousb [USB] Disable the USB subsystem
2428 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2432 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2434 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2435 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2436 Some features depend on CPU0. Known dependencies are:
2437 1. Resume from suspend/hibernate depends on CPU0.
2438 Suspend/hibernate will fail if CPU0 is offline and you
2439 need to online CPU0 before suspend/hibernate.
2440 2. PIC interrupts also depend on CPU0. CPU0 can't be
2441 removed if a PIC interrupt is detected.
2442 It's said poweroff/reboot may depend on CPU0 on some
2443 machines although I haven't seen such issues so far
2444 after CPU0 is offline on a few tested machines.
2445 If the dependencies are under your control, you can
2446 turn on cpu0_hotplug.
2448 nptcg= [IA-64] Override max number of concurrent global TLB
2449 purges which is reported from either PAL_VM_SUMMARY or
2452 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2453 could support. nr_cpus=n : n >= 1 limits the kernel to
2454 supporting 'n' processors. Later in runtime you can not
2455 use hotplug cpu feature to put more cpu back to online.
2456 just like you compile the kernel NR_CPUS=n
2458 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2460 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2461 Allowed values are enable and disable
2463 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2464 one of ['zone', 'node', 'default'] can be specified
2465 This can be set from sysctl after boot.
2466 See Documentation/sysctl/vm.txt for details.
2468 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2469 See Documentation/debugging-via-ohci1394.txt for more
2472 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2473 Rather than timing out after 20 ms if an EC
2474 command is not properly ACKed, override the length
2475 of the timeout. We have interrupts disabled while
2476 waiting for the ACK, so if this is set too high
2477 interrupts *may* be lost!
2479 omap_mux= [OMAP] Override bootloader pin multiplexing.
2480 Format: <mux_mode0.mode_name=value>...
2481 For example, to override I2C bus2:
2482 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2484 oprofile.timer= [HW]
2485 Use timer interrupt instead of performance counters
2487 oprofile.cpu_type= Force an oprofile cpu type
2488 This might be useful if you have an older oprofile
2489 userland or if you want common events.
2490 Format: { arch_perfmon }
2491 arch_perfmon: [X86] Force use of architectural
2492 perfmon on Intel CPUs instead of the
2493 CPU specific event set.
2494 timer: [X86] Force use of architectural NMI
2495 timer mode (see also oprofile.timer
2496 for generic hr timer mode)
2497 [s390] Force legacy basic mode sampling
2498 (report cpu_type "timer")
2500 oops=panic Always panic on oopses. Default is to just kill the
2501 process, but there is a small probability of
2502 deadlocking the machine.
2503 This will also cause panics on machine check exceptions.
2504 Useful together with panic=30 to trigger a reboot.
2507 See Documentation/sound/oss/oss-parameters.txt
2509 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2510 timeout > 0: seconds before rebooting
2511 timeout = 0: wait forever
2512 timeout < 0: reboot immediately
2515 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2518 crash_kexec_post_notifiers
2519 Run kdump after running panic-notifiers and dumping
2520 kmsg. This only for the users who doubt kdump always
2521 succeeds in any situation.
2522 Note that this also increases risks of kdump failure,
2523 because some panic notifiers can make the crashed
2524 kernel more unstable.
2526 parkbd.port= [HW] Parallel port number the keyboard adapter is
2527 connected to, default is 0.
2529 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2530 0 for XT, 1 for AT (default is AT).
2533 parport= [HW,PPT] Specify parallel ports. 0 disables.
2534 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2535 Use 'auto' to force the driver to use any
2536 IRQ/DMA settings detected (the default is to
2537 ignore detected IRQ/DMA settings because of
2538 possible conflicts). You can specify the base
2539 address, IRQ, and DMA settings; IRQ and DMA
2540 should be numbers, or 'auto' (for using detected
2541 settings on that particular port), or 'nofifo'
2542 (to avoid using a FIFO even if it is detected).
2543 Parallel ports are assigned in the order they
2544 are specified on the command line, starting
2547 parport_init_mode= [HW,PPT]
2548 Configure VIA parallel port to operate in
2549 a specific mode. This is necessary on Pegasos
2550 computer where firmware has no options for setting
2551 up parallel port mode and sets it to spp.
2552 Currently this function knows 686a and 8231 chips.
2553 Format: [spp|ps2|epp|ecp|ecpepp]
2556 Halt all CPUs after the first oops has been printed for
2557 the specified number of seconds. This is to be used if
2558 your oopses keep scrolling off the screen.
2563 See header of drivers/block/paride/pcd.c.
2564 See also Documentation/blockdev/paride.txt.
2566 pci=option[,option...] [PCI] various PCI subsystem options:
2567 earlydump [X86] dump PCI config space before the kernel
2569 off [X86] don't probe for the PCI bus
2570 bios [X86-32] force use of PCI BIOS, don't access
2571 the hardware directly. Use this if your machine
2572 has a non-standard PCI host bridge.
2573 nobios [X86-32] disallow use of PCI BIOS, only direct
2574 hardware access methods are allowed. Use this
2575 if you experience crashes upon bootup and you
2576 suspect they are caused by the BIOS.
2577 conf1 [X86] Force use of PCI Configuration
2579 conf2 [X86] Force use of PCI Configuration
2581 noaer [PCIE] If the PCIEAER kernel config parameter is
2582 enabled, this kernel boot option can be used to
2583 disable the use of PCIE advanced error reporting.
2584 nodomains [PCI] Disable support for multiple PCI
2585 root domains (aka PCI segments, in ACPI-speak).
2586 nommconf [X86] Disable use of MMCONFIG for PCI
2588 check_enable_amd_mmconf [X86] check for and enable
2589 properly configured MMIO access to PCI
2590 config space on AMD family 10h CPU
2591 nomsi [MSI] If the PCI_MSI kernel config parameter is
2592 enabled, this kernel boot option can be used to
2593 disable the use of MSI interrupts system-wide.
2594 noioapicquirk [APIC] Disable all boot interrupt quirks.
2595 Safety option to keep boot IRQs enabled. This
2596 should never be necessary.
2597 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2598 primary IO-APIC for bridges that cannot disable
2599 boot IRQs. This fixes a source of spurious IRQs
2600 when the system masks IRQs.
2601 noioapicreroute [APIC] Disable workaround that uses the
2602 boot IRQ equivalent of an IRQ that connects to
2603 a chipset where boot IRQs cannot be disabled.
2604 The opposite of ioapicreroute.
2605 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2606 routing table. These calls are known to be buggy
2607 on several machines and they hang the machine
2608 when used, but on other computers it's the only
2609 way to get the interrupt routing table. Try
2610 this option if the kernel is unable to allocate
2611 IRQs or discover secondary PCI buses on your
2613 rom [X86] Assign address space to expansion ROMs.
2614 Use with caution as certain devices share
2615 address decoders between ROMs and other
2617 norom [X86] Do not assign address space to
2618 expansion ROMs that do not already have
2619 BIOS assigned address ranges.
2620 nobar [X86] Do not assign address space to the
2621 BARs that weren't assigned by the BIOS.
2622 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2623 assigned automatically to PCI devices. You can
2624 make the kernel exclude IRQs of your ISA cards
2626 pirqaddr=0xAAAAA [X86] Specify the physical address
2627 of the PIRQ table (normally generated
2628 by the BIOS) if it is outside the
2629 F0000h-100000h range.
2630 lastbus=N [X86] Scan all buses thru bus #N. Can be
2631 useful if the kernel is unable to find your
2632 secondary buses and you want to tell it
2633 explicitly which ones they are.
2634 assign-busses [X86] Always assign all PCI bus
2635 numbers ourselves, overriding
2636 whatever the firmware may have done.
2637 usepirqmask [X86] Honor the possible IRQ mask stored
2638 in the BIOS $PIR table. This is needed on
2639 some systems with broken BIOSes, notably
2640 some HP Pavilion N5400 and Omnibook XE3
2641 notebooks. This will have no effect if ACPI
2642 IRQ routing is enabled.
2643 noacpi [X86] Do not use ACPI for IRQ routing
2644 or for PCI scanning.
2645 use_crs [X86] Use PCI host bridge window information
2646 from ACPI. On BIOSes from 2008 or later, this
2647 is enabled by default. If you need to use this,
2648 please report a bug.
2649 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2650 If you need to use this, please report a bug.
2651 routeirq Do IRQ routing for all PCI devices.
2652 This is normally done in pci_enable_device(),
2653 so this option is a temporary workaround
2654 for broken drivers that don't call it.
2655 skip_isa_align [X86] do not align io start addr, so can
2656 handle more pci cards
2657 firmware [ARM] Do not re-enumerate the bus but instead
2658 just use the configuration from the
2659 bootloader. This is currently used on
2660 IXP2000 systems where the bus has to be
2661 configured a certain way for adjunct CPUs.
2662 noearly [X86] Don't do any early type 1 scanning.
2663 This might help on some broken boards which
2664 machine check when some devices' config space
2665 is read. But various workarounds are disabled
2666 and some IOMMU drivers will not work.
2667 bfsort Sort PCI devices into breadth-first order.
2668 This sorting is done to get a device
2669 order compatible with older (<= 2.4) kernels.
2670 nobfsort Don't sort PCI devices into breadth-first order.
2671 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2672 tuning and use the BIOS-configured MPS defaults.
2673 pcie_bus_safe Set every device's MPS to the largest value
2674 supported by all devices below the root complex.
2675 pcie_bus_perf Set device MPS to the largest allowable MPS
2676 based on its parent bus. Also set MRRS (Max
2677 Read Request Size) to the largest supported
2678 value (no larger than the MPS that the device
2679 or bus can support) for best performance.
2680 pcie_bus_peer2peer Set every device's MPS to 128B, which
2681 every device is guaranteed to support. This
2682 configuration allows peer-to-peer DMA between
2683 any pair of devices, possibly at the cost of
2684 reduced performance. This also guarantees
2685 that hot-added devices will work.
2686 cbiosize=nn[KMG] The fixed amount of bus space which is
2687 reserved for the CardBus bridge's IO window.
2688 The default value is 256 bytes.
2689 cbmemsize=nn[KMG] The fixed amount of bus space which is
2690 reserved for the CardBus bridge's memory
2691 window. The default value is 64 megabytes.
2694 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2695 Specifies alignment and device to reassign
2696 aligned memory resources.
2697 If <order of align> is not specified,
2698 PAGE_SIZE is used as alignment.
2699 PCI-PCI bridge can be specified, if resource
2700 windows need to be expanded.
2701 ecrc= Enable/disable PCIe ECRC (transaction layer
2702 end-to-end CRC checking).
2703 bios: Use BIOS/firmware settings. This is the
2707 hpiosize=nn[KMG] The fixed amount of bus space which is
2708 reserved for hotplug bridge's IO window.
2709 Default size is 256 bytes.
2710 hpmemsize=nn[KMG] The fixed amount of bus space which is
2711 reserved for hotplug bridge's memory window.
2712 Default size is 2 megabytes.
2713 realloc= Enable/disable reallocating PCI bridge resources
2714 if allocations done by BIOS are too small to
2715 accommodate resources required by all child
2717 off: Turn realloc off
2719 realloc same as realloc=on
2720 noari do not use PCIe ARI.
2721 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2722 only look for one device below a PCIe downstream
2725 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2728 force Enable ASPM even on devices that claim not to support it.
2729 WARNING: Forcing ASPM on may cause system lockups.
2731 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2732 nomsi Do not use MSI for PCI Express Native Hotplug (this
2733 makes all PCIe ports use INTx for hotplug services).
2735 pcie_ports= [PCIE] PCIe ports handling:
2736 auto Ask the BIOS whether or not to use native PCIe services
2737 associated with PCIe ports (PME, hot-plug, AER). Use
2738 them only if that is allowed by the BIOS.
2739 native Use native PCIe services associated with PCIe ports
2741 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2744 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2745 nomsi Do not use MSI for native PCIe PME signaling (this makes
2746 all PCIe root ports use INTx for all services).
2748 pcmv= [HW,PCMCIA] BadgePAD 4
2752 Keep all power-domains already enabled by bootloader on,
2753 even if no driver has claimed them. This is useful
2754 for debug and development, but should not be
2755 needed on a platform with proper driver support.
2758 See Documentation/blockdev/paride.txt.
2760 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2763 See arch/parisc/kernel/pdc_chassis.c
2765 percpu_alloc= Select which percpu first chunk allocator to use.
2766 Currently supported values are "embed" and "page".
2767 Archs may support subset or none of the selections.
2768 See comments in mm/percpu.c for details on each
2769 allocator. This parameter is primarily for debugging
2770 and performance comparison.
2773 See Documentation/blockdev/paride.txt.
2776 See Documentation/blockdev/paride.txt.
2778 pirq= [SMP,APIC] Manual mp-table setup
2779 See Documentation/x86/i386/IO-APIC.txt.
2781 plip= [PPT,NET] Parallel port network link
2782 Format: { parport<nr> | timid | 0 }
2783 See also Documentation/parport.txt.
2785 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2786 Override pmtimer IOPort with a hex value.
2790 Enable PNP debug messages (depends on the
2791 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2792 via /sys/module/pnp/parameters/debug. We always show
2793 current resource usage; turning this on also shows
2794 possible settings and some assignment information.
2800 { on | off | curr | res | no-curr | no-res }
2803 [ISAPNP] Exclude IRQs for the autoconfiguration
2806 [ISAPNP] Exclude DMAs for the autoconfiguration
2808 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2809 Ranges are in pairs (I/O port base and size).
2812 [ISAPNP] Exclude memory regions for the
2814 Ranges are in pairs (memory base and size).
2816 ports= [IP_VS_FTP] IPVS ftp helper module
2818 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2820 Format: <port>,<port>....
2822 print-fatal-signals=
2823 [KNL] debug: print fatal signals
2825 If enabled, warn about various signal handling
2826 related application anomalies: too many signals,
2827 too many POSIX.1 timers, fatal signals causing a
2830 If you hit the warning due to signal overflow,
2831 you might want to try "ulimit -i unlimited".
2835 printk.always_kmsg_dump=
2836 Trigger kmsg_dump for cases other than kernel oops or
2838 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2841 printk.time= Show timing data prefixed to each printk message line
2842 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2844 processor.max_cstate= [HW,ACPI]
2845 Limit processor to maximum C-state
2846 max_cstate=9 overrides any DMI blacklist limit.
2848 processor.nocst [HW,ACPI]
2849 Ignore the _CST method to determine C-states,
2850 instead using the legacy FADT method
2852 profile= [KNL] Enable kernel profiling via /proc/profile
2853 Format: [schedule,]<number>
2854 Param: "schedule" - profile schedule points.
2855 Param: <number> - step/bucket size as a power of 2 for
2856 statistical time based profiling.
2857 Param: "sleep" - profile D-state sleeping (millisecs).
2858 Requires CONFIG_SCHEDSTATS
2859 Param: "kvm" - profile VM exits.
2861 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2863 See Documentation/blockdev/ramdisk.txt.
2865 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2866 probe for; one of (bare|imps|exps|lifebook|any).
2867 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2869 psmouse.resetafter= [HW,MOUSE]
2870 Try to reset the device after so many bad packets
2873 [HW,MOUSE] Set desired mouse resolution, in dpi.
2874 psmouse.smartscroll=
2875 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2876 0 = disabled, 1 = enabled (default).
2878 pstore.backend= Specify the name of the pstore backend to use
2881 See Documentation/blockdev/paride.txt.
2884 [KNL] Number of legacy pty's. Overwrites compiled-in
2887 quiet [KNL] Disable most log messages
2892 See Documentation/md.txt.
2894 ramdisk_blocksize= [RAM]
2895 See Documentation/blockdev/ramdisk.txt.
2897 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2898 See Documentation/blockdev/ramdisk.txt.
2901 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2902 the specified list of CPUs to be no-callback CPUs.
2903 Invocation of these CPUs' RCU callbacks will
2904 be offloaded to "rcuox/N" kthreads created for
2905 that purpose, where "x" is "b" for RCU-bh, "p"
2906 for RCU-preempt, and "s" for RCU-sched, and "N"
2907 is the CPU number. This reduces OS jitter on the
2908 offloaded CPUs, which can be useful for HPC and
2909 real-time workloads. It can also improve energy
2910 efficiency for asymmetric multiprocessors.
2913 Rather than requiring that offloaded CPUs
2914 (specified by rcu_nocbs= above) explicitly
2915 awaken the corresponding "rcuoN" kthreads,
2916 make these kthreads poll for callbacks.
2917 This improves the real-time response for the
2918 offloaded CPUs by relieving them of the need to
2919 wake up the corresponding kthread, but degrades
2920 energy efficiency by requiring that the kthreads
2921 periodically wake up to do the polling.
2923 rcutree.blimit= [KNL]
2924 Set maximum number of finished RCU callbacks to
2925 process in one batch.
2927 rcutree.rcu_fanout_leaf= [KNL]
2928 Increase the number of CPUs assigned to each
2929 leaf rcu_node structure. Useful for very large
2932 rcutree.jiffies_till_sched_qs= [KNL]
2933 Set required age in jiffies for a
2934 given grace period before RCU starts
2935 soliciting quiescent-state help from
2936 rcu_note_context_switch().
2938 rcutree.jiffies_till_first_fqs= [KNL]
2939 Set delay from grace-period initialization to
2940 first attempt to force quiescent states.
2941 Units are jiffies, minimum value is zero,
2942 and maximum value is HZ.
2944 rcutree.jiffies_till_next_fqs= [KNL]
2945 Set delay between subsequent attempts to force
2946 quiescent states. Units are jiffies, minimum
2947 value is one, and maximum value is HZ.
2949 rcutree.kthread_prio= [KNL,BOOT]
2950 Set the SCHED_FIFO priority of the RCU
2951 per-CPU kthreads (rcuc/N). This value is also
2952 used for the priority of the RCU boost threads
2953 (rcub/N). Valid values are 1-99 and the default
2954 is 1 (the least-favored priority).
2956 rcutree.rcu_nocb_leader_stride= [KNL]
2957 Set the number of NOCB kthread groups, which
2958 defaults to the square root of the number of
2959 CPUs. Larger numbers reduces the wakeup overhead
2960 on the per-CPU grace-period kthreads, but increases
2961 that same overhead on each group's leader.
2963 rcutree.qhimark= [KNL]
2964 Set threshold of queued RCU callbacks beyond which
2965 batch limiting is disabled.
2967 rcutree.qlowmark= [KNL]
2968 Set threshold of queued RCU callbacks below which
2969 batch limiting is re-enabled.
2971 rcutree.rcu_idle_gp_delay= [KNL]
2972 Set wakeup interval for idle CPUs that have
2973 RCU callbacks (RCU_FAST_NO_HZ=y).
2975 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2976 Set wakeup interval for idle CPUs that have
2977 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2978 Lazy RCU callbacks are those which RCU can
2979 prove do nothing more than free memory.
2981 rcutorture.cbflood_inter_holdoff= [KNL]
2982 Set holdoff time (jiffies) between successive
2983 callback-flood tests.
2985 rcutorture.cbflood_intra_holdoff= [KNL]
2986 Set holdoff time (jiffies) between successive
2987 bursts of callbacks within a given callback-flood
2990 rcutorture.cbflood_n_burst= [KNL]
2991 Set the number of bursts making up a given
2992 callback-flood test. Set this to zero to
2993 disable callback-flood testing.
2995 rcutorture.cbflood_n_per_burst= [KNL]
2996 Set the number of callbacks to be registered
2997 in a given burst of a callback-flood test.
2999 rcutorture.fqs_duration= [KNL]
3000 Set duration of force_quiescent_state bursts.
3002 rcutorture.fqs_holdoff= [KNL]
3003 Set holdoff time within force_quiescent_state bursts.
3005 rcutorture.fqs_stutter= [KNL]
3006 Set wait time between force_quiescent_state bursts.
3008 rcutorture.gp_exp= [KNL]
3009 Use expedited update-side primitives.
3011 rcutorture.gp_normal= [KNL]
3012 Use normal (non-expedited) update-side primitives.
3013 If both gp_exp and gp_normal are set, do both.
3014 If neither gp_exp nor gp_normal are set, still
3017 rcutorture.n_barrier_cbs= [KNL]
3018 Set callbacks/threads for rcu_barrier() testing.
3020 rcutorture.nfakewriters= [KNL]
3021 Set number of concurrent RCU writers. These just
3022 stress RCU, they don't participate in the actual
3023 test, hence the "fake".
3025 rcutorture.nreaders= [KNL]
3026 Set number of RCU readers.
3028 rcutorture.object_debug= [KNL]
3029 Enable debug-object double-call_rcu() testing.
3031 rcutorture.onoff_holdoff= [KNL]
3032 Set time (s) after boot for CPU-hotplug testing.
3034 rcutorture.onoff_interval= [KNL]
3035 Set time (s) between CPU-hotplug operations, or
3036 zero to disable CPU-hotplug testing.
3038 rcutorture.torture_runnable= [BOOT]
3039 Start rcutorture running at boot time.
3041 rcutorture.shuffle_interval= [KNL]
3042 Set task-shuffle interval (s). Shuffling tasks
3043 allows some CPUs to go into dyntick-idle mode
3044 during the rcutorture test.
3046 rcutorture.shutdown_secs= [KNL]
3047 Set time (s) after boot system shutdown. This
3048 is useful for hands-off automated testing.
3050 rcutorture.stall_cpu= [KNL]
3051 Duration of CPU stall (s) to test RCU CPU stall
3052 warnings, zero to disable.
3054 rcutorture.stall_cpu_holdoff= [KNL]
3055 Time to wait (s) after boot before inducing stall.
3057 rcutorture.stat_interval= [KNL]
3058 Time (s) between statistics printk()s.
3060 rcutorture.stutter= [KNL]
3061 Time (s) to stutter testing, for example, specifying
3062 five seconds causes the test to run for five seconds,
3063 wait for five seconds, and so on. This tests RCU's
3064 ability to transition abruptly to and from idle.
3066 rcutorture.test_boost= [KNL]
3067 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3068 "Maybe" means test if the RCU implementation
3069 under test support RCU priority boosting.
3071 rcutorture.test_boost_duration= [KNL]
3072 Duration (s) of each individual boost test.
3074 rcutorture.test_boost_interval= [KNL]
3075 Interval (s) between each boost test.
3077 rcutorture.test_no_idle_hz= [KNL]
3078 Test RCU's dyntick-idle handling. See also the
3079 rcutorture.shuffle_interval parameter.
3081 rcutorture.torture_type= [KNL]
3082 Specify the RCU implementation to test.
3084 rcutorture.verbose= [KNL]
3085 Enable additional printk() statements.
3087 rcupdate.rcu_expedited= [KNL]
3088 Use expedited grace-period primitives, for
3089 example, synchronize_rcu_expedited() instead
3090 of synchronize_rcu(). This reduces latency,
3091 but can increase CPU utilization, degrade
3092 real-time latency, and degrade energy efficiency.
3094 rcupdate.rcu_cpu_stall_suppress= [KNL]
3095 Suppress RCU CPU stall warning messages.
3097 rcupdate.rcu_cpu_stall_timeout= [KNL]
3098 Set timeout for RCU CPU stall warning messages.
3100 rcupdate.rcu_task_stall_timeout= [KNL]
3101 Set timeout in jiffies for RCU task stall warning
3102 messages. Disable with a value less than or equal
3105 rcupdate.rcu_self_test= [KNL]
3106 Run the RCU early boot self tests
3108 rcupdate.rcu_self_test_bh= [KNL]
3109 Run the RCU bh early boot self tests
3111 rcupdate.rcu_self_test_sched= [KNL]
3112 Run the RCU sched early boot self tests
3116 Run specified binary instead of /init from the ramdisk,
3117 used for early userspace startup. See initrd.
3120 Format (x86 or x86_64):
3121 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3123 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3125 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3126 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3127 reboot_force is either force or not specified,
3128 reboot_cpu is s[mp]#### with #### being the processor
3129 to be used for rebooting.
3132 [KNL, SMP] Set scheduler's default relax_domain_level.
3133 See Documentation/cgroups/cpusets.txt.
3135 relative_sleep_states=
3136 [SUSPEND] Use sleep state labeling where the deepest
3137 state available other than hibernation is always "mem".
3138 Format: { "0" | "1" }
3139 0 -- Traditional sleep state labels.
3140 1 -- Relative sleep state labels.
3142 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3144 reservetop= [X86-32]
3146 Reserves a hole at the top of the kernel virtual
3151 Set the amount of memory to reserve for BIOS at
3152 the bottom of the address space.
3154 reset_devices [KNL] Force drivers to reset the underlying device
3155 during initialization.
3158 Specify the partition device for software suspend
3160 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3162 resume_offset= [SWSUSP]
3163 Specify the offset from the beginning of the partition
3164 given by "resume=" at which the swap header is located,
3165 in <PAGE_SIZE> units (needed only for swap files).
3166 See Documentation/power/swsusp-and-swap-files.txt
3168 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3169 read the resume files
3171 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3172 Useful for devices that are detected asynchronously
3173 (e.g. USB and MMC devices).
3175 hibernate= [HIBERNATION]
3176 noresume Don't check if there's a hibernation image
3177 present during boot.
3178 nocompress Don't compress/decompress hibernation images.
3179 no Disable hibernation and resume.
3181 retain_initrd [RAM] Keep initrd memory after extraction
3183 rfkill.default_state=
3184 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3185 etc. communication is blocked by default.
3188 rfkill.master_switch_mode=
3189 0 The "airplane mode" button does nothing.
3190 1 The "airplane mode" button toggles between everything
3191 blocked and the previous configuration.
3192 2 The "airplane mode" button toggles between everything
3193 blocked and everything unblocked.
3195 rhash_entries= [KNL,NET]
3196 Set number of hash buckets for route cache
3198 ro [KNL] Mount root device read-only on boot
3200 root= [KNL] Root filesystem
3201 See name_to_dev_t comment in init/do_mounts.c.
3203 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3204 mount the root filesystem
3206 rootflags= [KNL] Set root filesystem mount option string
3208 rootfstype= [KNL] Set root filesystem type
3210 rootwait [KNL] Wait (indefinitely) for root device to show up.
3211 Useful for devices that are detected asynchronously
3212 (e.g. USB and MMC devices).
3214 rproc_mem=nn[KMG][@address]
3215 [KNL,ARM,CMA] Remoteproc physical memory block.
3216 Memory area to be used by remote processor image,
3219 rw [KNL] Mount root device read-write on boot
3221 S [KNL] Run init in single mode
3223 s390_iommu= [HW,S390]
3224 Set s390 IOTLB flushing mode
3226 With strict flushing every unmap operation will result in
3227 an IOTLB flush. Default is lazy flushing before reuse,
3231 See drivers/net/irda/sa1100_ir.c.
3233 sbni= [NET] Granch SBNI12 leased line adapter
3235 sched_debug [KNL] Enables verbose scheduler debug messages.
3237 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3238 xtime_lock contention on larger systems, and/or RCU lock
3239 contention on all systems with CONFIG_MAXSMP set.
3240 Format: { "0" | "1" }
3241 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3243 Note: increases power consumption, thus should only be
3244 enabled if running jitter sensitive (HPC/RT) workloads.
3246 security= [SECURITY] Choose a security module to enable at boot.
3247 If this boot parameter is not specified, only the first
3248 security module asking for security registration will be
3249 loaded. An invalid security module name will be treated
3250 as if no module has been chosen.
3252 selinux= [SELINUX] Disable or enable SELinux at boot time.
3253 Format: { "0" | "1" }
3254 See security/selinux/Kconfig help text.
3257 Default value is set via kernel config option.
3258 If enabled at boot time, /selinux/disable can be used
3259 later to disable prior to initial policy load.
3261 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3262 Format: { "0" | "1" }
3263 See security/apparmor/Kconfig help text
3266 Default value is set via kernel config option.
3268 serialnumber [BUGS=X86-32]
3271 Maximal number of shapers.
3273 show_msr= [x86] show boot-time MSR settings
3274 Format: { <integer> }
3275 Show boot-time (BIOS-initialized) MSR settings.
3276 The parameter means the number of CPUs to show,
3277 for example 1 means boot CPU only.
3285 Disable merging of slabs with similar size. May be
3286 necessary if there is some reason to distinguish
3287 allocs to different slabs. Debug options disable
3288 merging on their own.
3289 For more information see Documentation/vm/slub.txt.
3291 slab_max_order= [MM, SLAB]
3292 Determines the maximum allowed order for slabs.
3293 A high setting may cause OOMs due to memory
3294 fragmentation. Defaults to 1 for systems with
3295 more than 32MB of RAM, 0 otherwise.
3297 slub_debug[=options[,slabs]] [MM, SLUB]
3298 Enabling slub_debug allows one to determine the
3299 culprit if slab objects become corrupted. Enabling
3300 slub_debug can create guard zones around objects and
3301 may poison objects when not in use. Also tracks the
3302 last alloc / free. For more information see
3303 Documentation/vm/slub.txt.
3305 slub_max_order= [MM, SLUB]
3306 Determines the maximum allowed order for slabs.
3307 A high setting may cause OOMs due to memory
3308 fragmentation. For more information see
3309 Documentation/vm/slub.txt.
3311 slub_min_objects= [MM, SLUB]
3312 The minimum number of objects per slab. SLUB will
3313 increase the slab order up to slub_max_order to
3314 generate a sufficiently large slab able to contain
3315 the number of objects indicated. The higher the number
3316 of objects the smaller the overhead of tracking slabs
3317 and the less frequently locks need to be acquired.
3318 For more information see Documentation/vm/slub.txt.
3320 slub_min_order= [MM, SLUB]
3321 Determines the minimum page order for slabs. Must be
3322 lower than slub_max_order.
3323 For more information see Documentation/vm/slub.txt.
3325 slub_nomerge [MM, SLUB]
3326 Same with slab_nomerge. This is supported for legacy.
3327 See slab_nomerge for more information.
3330 Format: <io1>[,<io2>[,...,<io8>]]
3332 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3333 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3334 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3335 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3336 smsc-ircc2.ircc_irq= [HW] IRQ line
3337 smsc-ircc2.ircc_dma= [HW] DMA channel
3338 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3339 0: Toshiba Satellite 1800 (GP data pin select)
3340 1: Fast pin select (default)
3344 [KNL] Should the soft-lockup detector generate panics.
3347 softlockup_all_cpu_backtrace=
3348 [KNL] Should the soft-lockup detector generate
3349 backtraces on all cpus.
3352 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3353 See Documentation/laptops/sonypi.txt
3355 spia_io_base= [HW,MTD]
3361 Enabled the stack tracer on boot up.
3363 stacktrace_filter=[function-list]
3364 [FTRACE] Limit the functions that the stack tracer
3365 will trace at boot up. function-list is a comma separated
3366 list of functions. This list can be changed at run
3367 time by the stack_trace_filter file in the debugfs
3368 tracing directory. Note, this enables stack tracing
3369 and the stacktrace above is not needed.
3373 Set the STI (builtin display/keyboard on the HP-PARISC
3374 machines) console (graphic card) which should be used
3375 as the initial boot-console.
3376 See also comment in drivers/video/console/sticore.c.
3379 See comment in drivers/video/console/sticore.c.
3382 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3384 sunrpc.min_resvport=
3385 sunrpc.max_resvport=
3387 SunRPC servers often require that client requests
3388 originate from a privileged port (i.e. a port in the
3389 range 0 < portnr < 1024).
3390 An administrator who wishes to reserve some of these
3391 ports for other uses may adjust the range that the
3392 kernel's sunrpc client considers to be privileged
3393 using these two parameters to set the minimum and
3394 maximum port values.
3398 Control how the NFS server code allocates CPUs to
3399 service thread pools. Depending on how many NICs
3400 you have and where their interrupts are bound, this
3401 option will affect which CPUs will do NFS serving.
3402 Note: this parameter cannot be changed while the
3403 NFS server is running.
3405 auto the server chooses an appropriate mode
3406 automatically using heuristics
3407 global a single global pool contains all CPUs
3408 percpu one pool for each CPU
3409 pernode one pool for each NUMA node (equivalent
3410 to global on non-NUMA machines)
3412 sunrpc.tcp_slot_table_entries=
3413 sunrpc.udp_slot_table_entries=
3415 Sets the upper limit on the number of simultaneous
3416 RPC calls that can be sent from the client to a
3417 server. Increasing these values may allow you to
3418 improve throughput, but will also increase the
3419 amount of memory reserved for use by the client.
3422 [KNL] Enable accounting of swap in memory resource
3423 controller if no parameter or 1 is given or disable
3424 it if 0 is given (See Documentation/cgroups/memory.txt)
3426 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3427 Format: { <int> | force }
3428 <int> -- Number of I/O TLB slabs
3429 force -- force using of bounce buffers even if they
3430 wouldn't be automatically used by the kernel
3434 sysfs.deprecated=0|1 [KNL]
3435 Enable/disable old style sysfs layout for old udev
3436 on older distributions. When this option is enabled
3437 very new udev will not work anymore. When this option
3438 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3439 in older udev will not work anymore.
3440 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3441 the kernel configuration.
3443 sysrq_always_enabled
3445 Ignore sysrq setting - this boot parameter will
3446 neutralize any effect of /proc/sys/kernel/sysrq.
3447 Useful for debugging.
3451 test_suspend= [SUSPEND][,N]
3452 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3453 standby suspend) or "freeze" (for suspend type freeze)
3454 as the system sleep state during system startup with
3455 the optional capability to repeat N number of times.
3456 The system is woken from this state using a
3457 wakeup-capable RTC alarm.
3459 thash_entries= [KNL,NET]
3460 Set number of hash buckets for TCP connection
3462 thermal.act= [HW,ACPI]
3463 -1: disable all active trip points in all thermal zones
3464 <degrees C>: override all lowest active trip points
3466 thermal.crt= [HW,ACPI]
3467 -1: disable all critical trip points in all thermal zones
3468 <degrees C>: override all critical trip points
3470 thermal.nocrt= [HW,ACPI]
3471 Set to disable actions on ACPI thermal zone
3472 critical and hot trip points.
3474 thermal.off= [HW,ACPI]
3475 1: disable ACPI thermal control
3477 thermal.psv= [HW,ACPI]
3478 -1: disable all passive trip points
3479 <degrees C>: override all passive trip points to this
3482 thermal.tzp= [HW,ACPI]
3483 Specify global default ACPI thermal zone polling rate
3484 <deci-seconds>: poll all this frequency
3485 0: no polling (default)
3488 Force threading of all interrupt handlers except those
3489 marked explicitly IRQF_NO_THREAD.
3492 Enable the Transcendent memory driver if built-in.
3494 tmem.cleancache=0|1 [KNL, XEN]
3495 Default is on (1). Disable the usage of the cleancache
3496 API to send anonymous pages to the hypervisor.
3498 tmem.frontswap=0|1 [KNL, XEN]
3499 Default is on (1). Disable the usage of the frontswap
3500 API to send swap pages to the hypervisor. If disabled
3501 the selfballooning and selfshrinking are force disabled.
3503 tmem.selfballooning=0|1 [KNL, XEN]
3504 Default is on (1). Disable the driving of swap pages
3507 tmem.selfshrinking=0|1 [KNL, XEN]
3508 Default is on (1). Partial swapoff that immediately
3509 transfers pages from Xen hypervisor back to the
3510 kernel based on different criteria.
3514 Specify if the kernel should make use of the cpu
3515 topology information if the hardware supports this.
3516 The scheduler will make use of this information and
3517 e.g. base its process migration decisions on it.
3520 topology_updates= [KNL, PPC, NUMA]
3522 Specify if the kernel should ignore (off)
3523 topology updates sent by the hypervisor to this
3528 tpm_suspend_pcr=[HW,TPM]
3529 Format: integer pcr id
3530 Specify that at suspend time, the tpm driver
3531 should extend the specified pcr with zeros,
3532 as a workaround for some chips which fail to
3533 flush the last written pcr on TPM_SaveState.
3534 This will guarantee that all the other pcrs
3537 trace_buf_size=nn[KMG]
3538 [FTRACE] will set tracing buffer size on each cpu.
3540 trace_event=[event-list]
3541 [FTRACE] Set and start specified trace events in order
3542 to facilitate early boot debugging.
3543 See also Documentation/trace/events.txt
3545 trace_options=[option-list]
3546 [FTRACE] Enable or disable tracer options at boot.
3547 The option-list is a comma delimited list of options
3548 that can be enabled or disabled just as if you were
3549 to echo the option name into
3551 /sys/kernel/debug/tracing/trace_options
3553 For example, to enable stacktrace option (to dump the
3554 stack trace of each event), add to the command line:
3556 trace_options=stacktrace
3558 See also Documentation/trace/ftrace.txt "trace options"
3562 [FTRACE] enable this option to disable tracing when a
3563 warning is hit. This turns off "tracing_on". Tracing can
3564 be enabled again by echoing '1' into the "tracing_on"
3565 file located in /sys/kernel/debug/tracing/
3567 This option is useful, as it disables the trace before
3568 the WARNING dump is called, which prevents the trace to
3569 be filled with content caused by the warning output.
3571 This option can also be set at run time via the sysctl
3572 option: kernel/traceoff_on_warning
3574 transparent_hugepage=
3576 Format: [always|madvise|never]
3577 Can be used to control the default behavior of the system
3578 with respect to transparent hugepages.
3579 See Documentation/vm/transhuge.txt for more details.
3581 tsc= Disable clocksource stability checks for TSC.
3583 [x86] reliable: mark tsc clocksource as reliable, this
3584 disables clocksource verification at runtime, as well
3585 as the stability checks done at bootup. Used to enable
3586 high-resolution timer mode on older hardware, and in
3587 virtualized environment.
3588 [x86] noirqtime: Do not use TSC to do irq accounting.
3589 Used to run time disable IRQ_TIME_ACCOUNTING on any
3590 platforms where RDTSC is slow and this accounting
3593 turbografx.map[2|3]= [HW,JOY]
3594 TurboGraFX parallel port interface
3596 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3597 See also Documentation/input/joystick-parport.txt
3599 udbg-immortal [PPC] When debugging early kernel crashes that
3600 happen after console_init() and before a proper
3601 console driver takes over, this boot options might
3602 help "seeing" what's going on.
3604 uhash_entries= [KNL,NET]
3605 Set number of hash buckets for UDP/UDP-Lite connections
3608 [USB] Ignore overcurrent events (default N).
3609 Some badly-designed motherboards generate lots of
3610 bogus events, for ports that aren't wired to
3611 anything. Set this parameter to avoid log spamming.
3612 Note that genuine overcurrent events won't be
3616 [X86] Cause panic on unknown NMI.
3618 usbcore.authorized_default=
3619 [USB] Default USB device authorization:
3620 (default -1 = authorized except for wireless USB,
3621 0 = not authorized, 1 = authorized)
3623 usbcore.autosuspend=
3624 [USB] The autosuspend time delay (in seconds) used
3625 for newly-detected USB devices (default 2). This
3626 is the time required before an idle device will be
3627 autosuspended. Devices for which the delay is set
3628 to a negative value won't be autosuspended at all.
3630 usbcore.usbfs_snoop=
3631 [USB] Set to log all usbfs traffic (default 0 = off).
3633 usbcore.blinkenlights=
3634 [USB] Set to cycle leds on hubs (default 0 = off).
3636 usbcore.old_scheme_first=
3637 [USB] Start with the old device initialization
3638 scheme (default 0 = off).
3640 usbcore.usbfs_memory_mb=
3641 [USB] Memory limit (in MB) for buffers allocated by
3642 usbfs (default = 16, 0 = max = 2047).
3644 usbcore.use_both_schemes=
3645 [USB] Try the other device initialization scheme
3646 if the first one fails (default 1 = enabled).
3648 usbcore.initial_descriptor_timeout=
3649 [USB] Specifies timeout for the initial 64-byte
3650 USB_REQ_GET_DESCRIPTOR request in milliseconds
3651 (default 5000 = 5.0 seconds).
3654 [USBHID] The interval which mice are to be polled at.
3656 usb-storage.delay_use=
3657 [UMS] The delay in seconds before a new device is
3658 scanned for Logical Units (default 1).
3661 [UMS] A list of quirks entries to supplement or
3662 override the built-in unusual_devs list. List
3663 entries are separated by commas. Each entry has
3664 the form VID:PID:Flags where VID and PID are Vendor
3665 and Product ID values (4-digit hex numbers) and
3666 Flags is a set of characters, each corresponding
3667 to a common usb-storage quirk flag as follows:
3668 a = SANE_SENSE (collect more than 18 bytes
3670 b = BAD_SENSE (don't collect more than 18
3671 bytes of sense data);
3672 c = FIX_CAPACITY (decrease the reported
3673 device capacity by one sector);
3674 d = NO_READ_DISC_INFO (don't use
3675 READ_DISC_INFO command);
3676 e = NO_READ_CAPACITY_16 (don't use
3677 READ_CAPACITY_16 command);
3678 f = NO_REPORT_OPCODES (don't use report opcodes
3680 h = CAPACITY_HEURISTICS (decrease the
3681 reported device capacity by one
3682 sector if the number is odd);
3683 i = IGNORE_DEVICE (don't bind to this
3685 l = NOT_LOCKABLE (don't try to lock and
3686 unlock ejectable media);
3687 m = MAX_SECTORS_64 (don't transfer more
3688 than 64 sectors = 32 KB at a time);
3689 n = INITIAL_READ10 (force a retry of the
3690 initial READ(10) command);
3691 o = CAPACITY_OK (accept the capacity
3692 reported by the device);
3693 p = WRITE_CACHE (the device cache is ON
3695 r = IGNORE_RESIDUE (the device reports
3696 bogus residue values);
3697 s = SINGLE_LUN (the device has only one
3699 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3700 commands, uas only);
3701 u = IGNORE_UAS (don't bind to the uas driver);
3702 w = NO_WP_DETECT (don't test whether the
3703 medium is write-protected).
3704 Example: quirks=0419:aaf5:rl,0421:0433:rc
3706 user_debug= [KNL,ARM]
3708 See arch/arm/Kconfig.debug help text.
3709 1 - undefined instruction events
3711 4 - invalid data aborts
3714 Example: user_debug=31
3717 [X86] Flags controlling user PTE allocations.
3719 nohigh = do not allocate PTE pages in
3720 HIGHMEM regardless of setting
3724 On X86_32, this is an alias for vdso32=. Otherwise:
3726 vdso=1: enable VDSO (the default)
3727 vdso=0: disable VDSO mapping
3729 vdso32= [X86] Control the 32-bit vDSO
3730 vdso32=1: enable 32-bit VDSO
3731 vdso32=0 or vdso32=2: disable 32-bit VDSO
3733 See the help text for CONFIG_COMPAT_VDSO for more
3734 details. If CONFIG_COMPAT_VDSO is set, the default is
3735 vdso32=0; otherwise, the default is vdso32=1.
3737 For compatibility with older kernels, vdso32=2 is an
3740 Try vdso32=0 if you encounter an error that says:
3741 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3744 vector=percpu: enable percpu vector domain
3746 video= [FB] Frame buffer configuration
3747 See Documentation/fb/modedb.txt.
3749 video.brightness_switch_enabled= [0,1]
3750 If set to 1, on receiving an ACPI notify event
3751 generated by hotkey, video driver will adjust brightness
3752 level and then send out the event to user space through
3753 the allocated input device; If set to 0, video driver
3754 will only send out the event without touching backlight
3759 [VMMIO] Memory mapped virtio (platform) device.
3761 <size>@<baseaddr>:<irq>[:<id>]
3763 <size> := size (can use standard suffixes
3765 <baseaddr> := physical base address
3766 <irq> := interrupt number (as passed to
3768 <id> := (optional) platform device id
3770 virtio_mmio.device=1K@0x100b0000:48:7
3772 Can be used multiple times for multiple devices.
3774 vga= [BOOT,X86-32] Select a particular video mode
3775 See Documentation/x86/boot.txt and
3776 Documentation/svga.txt.
3777 Use vga=ask for menu.
3778 This is actually a boot loader parameter; the value is
3779 passed to the kernel using a special protocol.
3781 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3782 size of <nn>. This can be used to increase the
3783 minimum size (128MB on x86). It can also be used to
3784 decrease the size and leave more room for directly
3787 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3790 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3793 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3797 Controls the behavior of vsyscalls (i.e. calls to
3798 fixed addresses of 0xffffffffff600x00 from legacy
3799 code). Most statically-linked binaries and older
3800 versions of glibc use these calls. Because these
3801 functions are at fixed addresses, they make nice
3802 targets for exploits that can control RIP.
3804 emulate [default] Vsyscalls turn into traps and are
3805 emulated reasonably safely.
3807 native Vsyscalls are native syscall instructions.
3808 This is a little bit faster than trapping
3809 and makes a few dynamic recompilers work
3810 better than they would in emulation mode.
3811 It also makes exploits much easier to write.
3813 none Vsyscalls don't work at all. This makes
3814 them quite hard to use for exploits but
3815 might break your system.
3817 vt.color= [VT] Default text color.
3818 Format: 0xYX, X = foreground, Y = background.
3819 Default: 0x07 = light gray on black.
3821 vt.cur_default= [VT] Default cursor shape.
3822 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3823 the parameters of the <Esc>[?A;B;Cc escape sequence;
3824 see VGA-softcursor.txt. Default: 2 = underline.
3826 vt.default_blu= [VT]
3827 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3828 Change the default blue palette of the console.
3829 This is a 16-member array composed of values
3832 vt.default_grn= [VT]
3833 Format: <green0>,<green1>,<green2>,...,<green15>
3834 Change the default green palette of the console.
3835 This is a 16-member array composed of values
3838 vt.default_red= [VT]
3839 Format: <red0>,<red1>,<red2>,...,<red15>
3840 Change the default red palette of the console.
3841 This is a 16-member array composed of values
3847 Set system-wide default UTF-8 mode for all tty's.
3848 Default is 1, i.e. UTF-8 mode is enabled for all
3849 newly opened terminals.
3851 vt.global_cursor_default=
3854 Set system-wide default for whether a cursor
3855 is shown on new VTs. Default is -1,
3856 i.e. cursors will be created by default unless
3857 overridden by individual drivers. 0 will hide
3858 cursors, 1 will display them.
3860 vt.italic= [VT] Default color for italic text; 0-15.
3863 vt.underline= [VT] Default color for underlined text; 0-15.
3866 watchdog timers [HW,WDT] For information on watchdog timers,
3867 see Documentation/watchdog/watchdog-parameters.txt
3868 or other driver-specific files in the
3869 Documentation/watchdog/ directory.
3871 workqueue.disable_numa
3872 By default, all work items queued to unbound
3873 workqueues are affine to the NUMA nodes they're
3874 issued on, which results in better behavior in
3875 general. If NUMA affinity needs to be disabled for
3876 whatever reason, this option can be used. Note
3877 that this also can be controlled per-workqueue for
3878 workqueues visible under /sys/bus/workqueue/.
3880 workqueue.power_efficient
3881 Per-cpu workqueues are generally preferred because
3882 they show better performance thanks to cache
3883 locality; unfortunately, per-cpu workqueues tend to
3884 be more power hungry than unbound workqueues.
3886 Enabling this makes the per-cpu workqueues which
3887 were observed to contribute significantly to power
3888 consumption unbound, leading to measurably lower
3889 power usage at the cost of small performance
3892 The default value of this parameter is determined by
3893 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3895 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3896 default x2apic cluster mode on platforms
3899 x86_intel_mid_timer= [X86-32,APBT]
3900 Choose timer option for x86 Intel MID platform.
3901 Two valid options are apbt timer only and lapic timer
3902 plus one apbt timer for broadcast timer.
3903 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3905 xen_emul_unplug= [HW,X86,XEN]
3906 Unplug Xen emulated devices
3907 Format: [unplug0,][unplug1]
3908 ide-disks -- unplug primary master IDE devices
3909 aux-ide-disks -- unplug non-primary-master IDE devices
3910 nics -- unplug network devices
3911 all -- unplug all emulated devices (NICs and IDE disks)
3912 unnecessary -- unplugging emulated devices is
3913 unnecessary even if the host did not respond to
3915 never -- do not unplug even if version check succeeds
3917 xen_nopvspin [X86,XEN]
3918 Disables the ticketlock slowpath using Xen PV
3922 Disables the PV optimizations forcing the HVM guest to
3923 run as generic HVM guest with no PV drivers.
3925 xirc2ps_cs= [NET,PCMCIA]
3927 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3929 ______________________________________________________________________
3933 Add more DRM drivers.
projects / cascardo / linux.git / blob