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 intremap= [X86-64, Intel-IOMMU]
1451 on enable Interrupt Remapping (default)
1452 off disable Interrupt Remapping
1453 nosid disable Source ID checking
1455 BIOS x2APIC opt-out request will be ignored
1457 iomem= Disable strict checking of access to MMIO memory
1458 strict regions from userspace.
1475 io7= [HW] IO7 for Marvel based alpha systems
1476 See comment before marvel_specify_io7 in
1477 arch/alpha/kernel/core_marvel.c.
1479 io_delay= [X86] I/O delay method
1481 Standard port 0x80 based delay
1483 Alternate port 0xed based delay (needed on some systems)
1485 Simple two microseconds delay
1490 See Documentation/filesystems/nfs/nfsroot.txt.
1493 When an interrupt is not handled search all handlers
1494 for it. Intended to get systems with badly broken
1498 When an interrupt is not handled search all handlers
1499 for it. Also check all handlers each timer
1500 interrupt. Intended to get systems with badly broken
1504 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1506 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1508 <cpu number>,...,<cpu number>
1510 <cpu number>-<cpu number>
1511 (must be a positive range in ascending order)
1513 <cpu number>,...,<cpu number>-<cpu number>
1515 This option can be used to specify one or more CPUs
1516 to isolate from the general SMP balancing and scheduling
1517 algorithms. You can move a process onto or off an
1518 "isolated" CPU via the CPU affinity syscalls or cpuset.
1519 <cpu number> begins at 0 and the maximum value is
1520 "number of CPUs in system - 1".
1522 This option is the preferred way to isolate CPUs. The
1523 alternative -- manually setting the CPU mask of all
1524 tasks in the system -- can cause problems and
1525 suboptimal load balancer performance.
1529 ivrs_ioapic [HW,X86_64]
1530 Provide an override to the IOAPIC-ID<->DEVICE-ID
1531 mapping provided in the IVRS ACPI table. For
1532 example, to map IOAPIC-ID decimal 10 to
1533 PCI device 00:14.0 write the parameter as:
1534 ivrs_ioapic[10]=00:14.0
1536 ivrs_hpet [HW,X86_64]
1537 Provide an override to the HPET-ID<->DEVICE-ID
1538 mapping provided in the IVRS ACPI table. For
1539 example, to map HPET-ID decimal 0 to
1540 PCI device 00:14.0 write the parameter as:
1541 ivrs_hpet[0]=00:14.0
1543 js= [HW,JOY] Analog joystick
1544 See Documentation/input/joystick.txt.
1547 Enable/disable kernel and module base offset ASLR
1548 (Address Space Layout Randomization) if built into
1549 the kernel. When CONFIG_HIBERNATION is selected,
1550 kASLR is disabled by default. When kASLR is enabled,
1551 hibernation will be disabled.
1555 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1556 specifies the amount of memory usable by the kernel
1557 for non-movable allocations. The requested amount is
1558 spread evenly throughout all nodes in the system. The
1559 remaining memory in each node is used for Movable
1560 pages. In the event, a node is too small to have both
1561 kernelcore and Movable pages, kernelcore pages will
1562 take priority and other nodes will have a larger number
1563 of Movable pages. The Movable zone is used for the
1564 allocation of pages that may be reclaimed or moved
1565 by the page migration subsystem. This means that
1566 HugeTLB pages may not be allocated from this zone.
1567 Note that allocations like PTEs-from-HighMem still
1568 use the HighMem zone if it exists, and the Normal
1569 zone if it does not.
1571 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1572 Format: <Controller#>[,poll interval]
1573 The controller # is the number of the ehci usb debug
1574 port as it is probed via PCI. The poll interval is
1575 optional and is the number seconds in between
1576 each poll cycle to the debug port in case you need
1577 the functionality for interrupting the kernel with
1578 gdb or control-c on the dbgp connection. When
1579 not using this parameter you use sysrq-g to break into
1580 the kernel debugger.
1582 kgdboc= [KGDB,HW] kgdb over consoles.
1583 Requires a tty driver that supports console polling,
1584 or a supported polling keyboard driver (non-usb).
1585 Serial only format: <serial_device>[,baud]
1586 keyboard only format: kbd
1587 keyboard and serial format: kbd,<serial_device>[,baud]
1588 Optional Kernel mode setting:
1589 kms, kbd format: kms,kbd
1590 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1592 kgdbwait [KGDB] Stop kernel execution and enter the
1593 kernel debugger at the earliest opportunity.
1595 kmac= [MIPS] korina ethernet MAC address.
1596 Configure the RouterBoard 532 series on-chip
1597 Ethernet adapter MAC address.
1599 kmemleak= [KNL] Boot-time kmemleak enable/disable
1600 Valid arguments: on, off
1602 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1605 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1606 Valid arguments: 0, 1, 2
1607 kmemcheck=0 (disabled)
1608 kmemcheck=1 (enabled)
1609 kmemcheck=2 (one-shot mode)
1610 Default: 2 (one-shot mode)
1612 kstack=N [X86] Print N words from the kernel stack
1615 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1616 Default is 0 (don't ignore, but inject #GP)
1618 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1622 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1623 Default is 1 (enabled)
1625 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1627 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1629 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1630 (virtualized MMU) support on capable Intel chips.
1631 Default is 1 (enabled)
1633 kvm-intel.emulate_invalid_guest_state=
1634 [KVM,Intel] Enable emulation of invalid guest states
1635 Default is 0 (disabled)
1637 kvm-intel.flexpriority=
1638 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1639 Default is 1 (enabled)
1642 [KVM,Intel] Enable VMX nesting (nVMX).
1643 Default is 0 (disabled)
1645 kvm-intel.unrestricted_guest=
1646 [KVM,Intel] Disable unrestricted guest feature
1647 (virtualized real and unpaged mode) on capable
1648 Intel chips. Default is 1 (enabled)
1650 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1651 feature (tagged TLBs) on capable Intel chips.
1652 Default is 1 (enabled)
1658 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1661 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1662 value for LAPIC timer one-shot implementation. Default
1663 back to the programmable timer unit in the LAPIC.
1665 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1668 libata.dma= [LIBATA] DMA control
1669 libata.dma=0 Disable all PATA and SATA DMA
1670 libata.dma=1 PATA and SATA Disk DMA only
1671 libata.dma=2 ATAPI (CDROM) DMA only
1672 libata.dma=4 Compact Flash DMA only
1673 Combinations also work, so libata.dma=3 enables DMA
1674 for disks and CDROMs, but not CFs.
1676 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1677 libata.ignore_hpa=0 keep BIOS limits (default)
1678 libata.ignore_hpa=1 ignore limits, using full disk
1680 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1684 libata.force= [LIBATA] Force configurations. The format is comma
1685 separated list of "[ID:]VAL" where ID is
1686 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1687 matching port, link or device. Basically, it matches
1688 the ATA ID string printed on console by libata. If
1689 the whole ID part is omitted, the last PORT and DEVICE
1690 values are used. If ID hasn't been specified yet, the
1691 configuration applies to all ports, links and devices.
1693 If only DEVICE is omitted, the parameter applies to
1694 the port and all links and devices behind it. DEVICE
1695 number of 0 either selects the first device or the
1696 first fan-out link behind PMP device. It does not
1697 select the host link. DEVICE number of 15 selects the
1698 host link and device attached to it.
1700 The VAL specifies the configuration to force. As long
1701 as there's no ambiguity shortcut notation is allowed.
1702 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1703 The following configurations can be forced.
1705 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1706 Any ID with matching PORT is used.
1708 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1710 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1711 udma[/][16,25,33,44,66,100,133] notation is also
1714 * [no]ncq: Turn on or off NCQ.
1716 * nohrst, nosrst, norst: suppress hard, soft
1719 * rstonce: only attempt one reset during
1720 hot-unplug link recovery
1722 * dump_id: dump IDENTIFY data.
1724 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1726 * disable: Disable this device.
1728 If there are multiple matching configurations changing
1729 the same attribute, the last one is used.
1731 memblock=debug [KNL] Enable memblock debug messages.
1733 load_ramdisk= [RAM] List of ramdisks to load from floppy
1734 See Documentation/blockdev/ramdisk.txt.
1736 lockd.nlm_grace_period=P [NFS] Assign grace period.
1739 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1742 lockd.nlm_timeout=T [NFS] Assign timeout value.
1745 lockd.nlm_udpport=M [NFS] Assign UDP port.
1748 locktorture.nreaders_stress= [KNL]
1749 Set the number of locking read-acquisition kthreads.
1750 Defaults to being automatically set based on the
1751 number of online CPUs.
1753 locktorture.nwriters_stress= [KNL]
1754 Set the number of locking write-acquisition kthreads.
1756 locktorture.onoff_holdoff= [KNL]
1757 Set time (s) after boot for CPU-hotplug testing.
1759 locktorture.onoff_interval= [KNL]
1760 Set time (s) between CPU-hotplug operations, or
1761 zero to disable CPU-hotplug testing.
1763 locktorture.shuffle_interval= [KNL]
1764 Set task-shuffle interval (jiffies). Shuffling
1765 tasks allows some CPUs to go into dyntick-idle
1766 mode during the locktorture test.
1768 locktorture.shutdown_secs= [KNL]
1769 Set time (s) after boot system shutdown. This
1770 is useful for hands-off automated testing.
1772 locktorture.stat_interval= [KNL]
1773 Time (s) between statistics printk()s.
1775 locktorture.stutter= [KNL]
1776 Time (s) to stutter testing, for example,
1777 specifying five seconds causes the test to run for
1778 five seconds, wait for five seconds, and so on.
1779 This tests the locking primitive's ability to
1780 transition abruptly to and from idle.
1782 locktorture.torture_runnable= [BOOT]
1783 Start locktorture running at boot time.
1785 locktorture.torture_type= [KNL]
1786 Specify the locking implementation to test.
1788 locktorture.verbose= [KNL]
1789 Enable additional printk() statements.
1791 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1794 loglevel= All Kernel Messages with a loglevel smaller than the
1795 console loglevel will be printed to the console. It can
1796 also be changed with klogd or other programs. The
1797 loglevels are defined as follows:
1799 0 (KERN_EMERG) system is unusable
1800 1 (KERN_ALERT) action must be taken immediately
1801 2 (KERN_CRIT) critical conditions
1802 3 (KERN_ERR) error conditions
1803 4 (KERN_WARNING) warning conditions
1804 5 (KERN_NOTICE) normal but significant condition
1805 6 (KERN_INFO) informational
1806 7 (KERN_DEBUG) debug-level messages
1808 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1809 in bytes. n must be a power of two and greater
1810 than the minimal size. The minimal size is defined
1811 by LOG_BUF_SHIFT kernel config parameter. There is
1812 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1813 that allows to increase the default size depending on
1814 the number of CPUs. See init/Kconfig for more details.
1816 logo.nologo [FB] Disables display of the built-in Linux logo.
1817 This may be used to provide more screen space for
1818 kernel log messages and is useful when debugging
1819 kernel boot problems.
1821 lp=0 [LP] Specify parallel ports to use, e.g,
1822 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1823 lp=reset first parallel port). 'lp=0' disables the
1824 lp=auto printer driver. 'lp=reset' (which can be
1825 specified in addition to the ports) causes
1826 attached printers to be reset. Using
1827 lp=port1,port2,... specifies the parallel ports
1828 to associate lp devices with, starting with
1829 lp0. A port specification may be 'none' to skip
1830 that lp device, or a parport name such as
1831 'parport0'. Specifying 'lp=auto' instead of a
1832 port specification list means that device IDs
1833 from each port should be examined, to see if
1834 an IEEE 1284-compliant printer is attached; if
1835 so, the driver will manage that printer.
1836 See also header of drivers/char/lp.c.
1839 Sets loops_per_jiffy to given constant, thus avoiding
1840 time-consuming boot-time autodetection (up to 250 ms per
1841 CPU). 0 enables autodetection (default). To determine
1842 the correct value for your kernel, boot with normal
1843 autodetection and see what value is printed. Note that
1844 on SMP systems the preset will be applied to all CPUs,
1845 which is likely to cause problems if your CPUs need
1846 significantly divergent settings. An incorrect value
1847 will cause delays in the kernel to be wrong, leading to
1848 unpredictable I/O errors and other breakage. Although
1849 unlikely, in the extreme case this might damage your
1853 Format: <io>,<irq>,<dma>
1855 machvec= [IA-64] Force the use of a particular machine-vector
1856 (machvec) in a generic kernel.
1857 Example: machvec=hpzx1_swiotlb
1859 machtype= [Loongson] Share the same kernel image file between different
1861 Example: machtype=lemote-yeeloong-2f-7inch
1863 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1864 than or equal to this physical address is ignored.
1866 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1867 should make use of. maxcpus=n : n >= 0 limits the
1868 kernel to using 'n' processors. n=0 is a special case,
1869 it is equivalent to "nosmp", which also disables
1872 max_loop= [LOOP] The number of loop block devices that get
1873 (loop.max_loop) unconditionally pre-created at init time. The default
1874 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1875 of statically allocating a predefined number, loop
1876 devices can be requested on-demand with the
1877 /dev/loop-control interface.
1879 mce [X86-32] Machine Check Exception
1881 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1883 md= [HW] RAID subsystems devices and level
1884 See Documentation/md.txt.
1887 Format: <first>,<last>
1888 Specifies range of consoles to be captured by the MDA.
1890 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1891 Amount of memory to be used when the kernel is not able
1892 to see the whole system memory or for test.
1893 [X86] Work as limiting max address. Use together
1894 with memmap= to avoid physical address space collisions.
1895 Without memmap= PCI devices could be placed at addresses
1896 belonging to unused RAM.
1898 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1902 [KNL,SH] Allow user to override the default size for
1903 per-device physically contiguous DMA buffers.
1905 memmap=exactmap [KNL,X86] Enable setting of an exact
1906 E820 memory map, as specified by the user.
1907 Such memmap=exactmap lines can be constructed based on
1908 BIOS output or other requirements. See the memmap=nn@ss
1911 memmap=nn[KMG]@ss[KMG]
1912 [KNL] Force usage of a specific region of memory.
1913 Region of memory to be used is from ss to ss+nn.
1915 memmap=nn[KMG]#ss[KMG]
1916 [KNL,ACPI] Mark specific memory as ACPI data.
1917 Region of memory to be marked is from ss to ss+nn.
1919 memmap=nn[KMG]$ss[KMG]
1920 [KNL,ACPI] Mark specific memory as reserved.
1921 Region of memory to be reserved is from ss to ss+nn.
1922 Example: Exclude memory from 0x18690000-0x1869ffff
1923 memmap=64K$0x18690000
1925 memmap=0x10000$0x18690000
1927 memory_corruption_check=0/1 [X86]
1928 Some BIOSes seem to corrupt the first 64k of
1929 memory when doing things like suspend/resume.
1930 Setting this option will scan the memory
1931 looking for corruption. Enabling this will
1932 both detect corruption and prevent the kernel
1933 from using the memory being corrupted.
1934 However, its intended as a diagnostic tool; if
1935 repeatable BIOS-originated corruption always
1936 affects the same memory, you can use memmap=
1937 to prevent the kernel from using that memory.
1939 memory_corruption_check_size=size [X86]
1940 By default it checks for corruption in the low
1941 64k, making this memory unavailable for normal
1942 use. Use this parameter to scan for
1943 corruption in more or less memory.
1945 memory_corruption_check_period=seconds [X86]
1946 By default it checks for corruption every 60
1947 seconds. Use this parameter to check at some
1948 other rate. 0 disables periodic checking.
1950 memtest= [KNL,X86] Enable memtest
1952 default : 0 <disable>
1953 Specifies the number of memtest passes to be
1954 performed. Each pass selects another test
1955 pattern from a given set of patterns. Memtest
1956 fills the memory with this pattern, validates
1957 memory contents and reserves bad memory
1958 regions that are detected.
1960 meye.*= [HW] Set MotionEye Camera parameters
1961 See Documentation/video4linux/meye.txt.
1963 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1964 Multi-Function General Purpose Timers on AMD Geode
1967 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1968 the BIOS has incorrectly applied a workaround. TinyBIOS
1969 version 0.98 is known to be affected, 0.99 fixes the
1970 problem by letting the user disable the workaround.
1974 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1975 physical address is ignored.
1977 mini2440= [ARM,HW,KNL]
1978 Format:[0..2][b][c][t]
1980 MINI2440 configuration specification:
1981 0 - The attached screen is the 3.5" TFT
1982 1 - The attached screen is the 7" TFT
1983 2 - The VGA Shield is attached (1024x768)
1984 Leaving out the screen size parameter will not load
1985 the TFT driver, and the framebuffer will be left
1987 b - Enable backlight. The TFT backlight pin will be
1988 linked to the kernel VESA blanking code and a GPIO
1989 LED. This parameter is not necessary when using the
1991 c - Enable the s3c camera interface.
1992 t - Reserved for enabling touchscreen support. The
1993 touchscreen support is not enabled in the mainstream
1994 kernel as of 2.6.30, a preliminary port can be found
1995 in the "bleeding edge" mini2440 support kernel at
1996 http://repo.or.cz/w/linux-2.6/mini2440.git
1999 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2000 parameter allows control of the logging verbosity for
2001 the additional memory initialisation checks. A value
2002 of 0 disables mminit logging and a level of 4 will
2003 log everything. Information is printed at KERN_DEBUG
2004 so loglevel=8 may also need to be specified.
2007 [KNL] When CONFIG_MODULE_SIG is set, this means that
2008 modules without (valid) signatures will fail to load.
2009 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2010 is always true, so this option does nothing.
2013 [MOUSE] Maximum time between finger touching and
2014 leaving touchpad surface for touch to be considered
2015 a tap and be reported as a left button click (for
2016 touchpads working in absolute mode only).
2018 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2019 reporting absolute coordinates, such as tablets
2020 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2021 reporting absolute coordinates, such as tablets
2023 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2024 is similar to kernelcore except it specifies the
2025 amount of memory used for migratable allocations.
2026 If both kernelcore and movablecore is specified,
2027 then kernelcore will be at *least* the specified
2028 value but may be more. If movablecore on its own
2029 is specified, the administrator must be careful
2030 that the amount of memory usable for all allocations
2033 movable_node [KNL,X86] Boot-time switch to enable the effects
2034 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2036 MTD_Partition= [MTD]
2037 Format: <name>,<region-number>,<size>,<offset>
2039 MTD_Region= [MTD] Format:
2040 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2043 See drivers/mtd/cmdlinepart.c.
2045 multitce=off [PPC] This parameter disables the use of the pSeries
2046 firmware feature for updating multiple TCE entries
2049 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2051 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2053 boundary - index of last SLC block on Flex-OneNAND.
2054 The remaining blocks are configured as MLC blocks.
2055 lock - Configure if Flex-OneNAND boundary should be locked.
2056 Once locked, the boundary cannot be changed.
2057 1 indicates lock status, 0 indicates unlock status.
2060 ARM/S3C2412 JIVE boot control
2062 See arch/arm/mach-s3c2412/mach-jive.c
2064 mtouchusb.raw_coordinates=
2065 [HW] Make the MicroTouch USB driver use raw coordinates
2066 ('y', default) or cooked coordinates ('n')
2068 mtrr_chunk_size=nn[KMG] [X86]
2069 used for mtrr cleanup. It is largest continuous chunk
2070 that could hold holes aka. UC entries.
2072 mtrr_gran_size=nn[KMG] [X86]
2073 Used for mtrr cleanup. It is granularity of mtrr block.
2075 Large value could prevent small alignment from
2078 mtrr_spare_reg_nr=n [X86]
2080 Range: 0,7 : spare reg number
2082 Used for mtrr cleanup. It is spare mtrr entries number.
2083 Set to 2 or more if your graphical card needs more.
2085 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2087 netdev= [NET] Network devices parameters
2088 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2089 Note that mem_start is often overloaded to mean
2090 something different and driver-specific.
2091 This usage is only documented in each driver source
2095 [NETFILTER] Enable connection tracking flow accounting
2096 0 to disable accounting
2097 1 to enable accounting
2100 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2101 See Documentation/filesystems/nfs/nfsroot.txt.
2103 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2104 See Documentation/filesystems/nfs/nfsroot.txt.
2106 nfsrootdebug [NFS] enable nfsroot debugging messages.
2107 See Documentation/filesystems/nfs/nfsroot.txt.
2109 nfs.callback_tcpport=
2110 [NFS] set the TCP port on which the NFSv4 callback
2111 channel should listen.
2114 [NFS] sets the pathname to the program which is used
2115 to update the NFS client cache entries.
2117 nfs.cache_getent_timeout=
2118 [NFS] sets the timeout after which an attempt to
2119 update a cache entry is deemed to have failed.
2121 nfs.idmap_cache_timeout=
2122 [NFS] set the maximum lifetime for idmapper cache
2126 [NFS] enable 64-bit inode numbers.
2127 If zero, the NFS client will fake up a 32-bit inode
2128 number for the readdir() and stat() syscalls instead
2129 of returning the full 64-bit number.
2130 The default is to return 64-bit inode numbers.
2132 nfs.max_session_slots=
2133 [NFSv4.1] Sets the maximum number of session slots
2134 the client will attempt to negotiate with the server.
2135 This limits the number of simultaneous RPC requests
2136 that the client can send to the NFSv4.1 server.
2137 Note that there is little point in setting this
2138 value higher than the max_tcp_slot_table_limit.
2140 nfs.nfs4_disable_idmapping=
2141 [NFSv4] When set to the default of '1', this option
2142 ensures that both the RPC level authentication
2143 scheme and the NFS level operations agree to use
2144 numeric uids/gids if the mount is using the
2145 'sec=sys' security flavour. In effect it is
2146 disabling idmapping, which can make migration from
2147 legacy NFSv2/v3 systems to NFSv4 easier.
2148 Servers that do not support this mode of operation
2149 will be autodetected by the client, and it will fall
2150 back to using the idmapper.
2151 To turn off this behaviour, set the value to '0'.
2153 [NFS4] Specify an additional fixed unique ident-
2154 ification string that NFSv4 clients can insert into
2155 their nfs_client_id4 string. This is typically a
2156 UUID that is generated at system install time.
2158 nfs.send_implementation_id =
2159 [NFSv4.1] Send client implementation identification
2160 information in exchange_id requests.
2161 If zero, no implementation identification information
2163 The default is to send the implementation identification
2166 nfs.recover_lost_locks =
2167 [NFSv4] Attempt to recover locks that were lost due
2168 to a lease timeout on the server. Please note that
2169 doing this risks data corruption, since there are
2170 no guarantees that the file will remain unchanged
2171 after the locks are lost.
2172 If you want to enable the kernel legacy behaviour of
2173 attempting to recover these locks, then set this
2175 The default parameter value of '0' causes the kernel
2176 not to attempt recovery of lost locks.
2178 nfsd.nfs4_disable_idmapping=
2179 [NFSv4] When set to the default of '1', the NFSv4
2180 server will return only numeric uids and gids to
2181 clients using auth_sys, and will accept numeric uids
2182 and gids from such clients. This is intended to ease
2183 migration from NFSv2/v3.
2185 objlayoutdriver.osd_login_prog=
2186 [NFS] [OBJLAYOUT] sets the pathname to the program which
2187 is used to automatically discover and login into new
2188 osd-targets. Please see:
2189 Documentation/filesystems/pnfs.txt for more explanations
2191 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2192 when a NMI is triggered.
2193 Format: [state][,regs][,debounce][,die]
2195 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2196 Format: [panic,][nopanic,][num]
2198 0 - turn nmi_watchdog off
2199 When panic is specified, panic when an NMI watchdog
2200 timeout occurs (or 'nopanic' to override the opposite
2202 This is useful when you use a panic=... timeout and
2203 need the box quickly up again.
2205 netpoll.carrier_timeout=
2206 [NET] Specifies amount of time (in seconds) that
2207 netpoll should wait for a carrier. By default netpoll
2210 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2211 emulation library even if a 387 maths coprocessor
2215 [HW] Never suspend the console
2216 Disable suspending of consoles during suspend and
2217 hibernate operations. Once disabled, debugging
2218 messages can reach various consoles while the rest
2219 of the system is being put to sleep (ie, while
2220 debugging driver suspend/resume hooks). This may
2221 not work reliably with all consoles, but is known
2222 to work with serial and VGA consoles.
2223 To facilitate more flexible debugging, we also add
2224 console_suspend, a printk module parameter to control
2225 it. Users could use console_suspend (usually
2226 /sys/module/printk/parameters/console_suspend) to
2227 turn on/off it dynamically.
2229 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2230 caches in the slab allocator. Saves per-node memory,
2231 but will impact performance.
2235 noapic [SMP,APIC] Tells the kernel to not make use of any
2236 IOAPICs that may be present in the system.
2238 noautogroup Disable scheduler automatic task group creation.
2240 nobats [PPC] Do not use BATs for mapping kernel lowmem
2241 on "Classic" PPC cores.
2245 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2247 nodelayacct [KNL] Disable per-task delay accounting
2249 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2251 nodsp [SH] Disable hardware DSP at boot time.
2253 noefi Disable EFI runtime services support.
2258 On X86-32 available only on PAE configured kernels.
2259 noexec=on: enable non-executable mappings (default)
2260 noexec=off: disable non-executable mappings
2263 Disable SMAP (Supervisor Mode Access Prevention)
2264 even if it is supported by processor.
2267 Disable SMEP (Supervisor Mode Execution Prevention)
2268 even if it is supported by processor.
2271 This affects only 32-bit executables.
2272 noexec32=on: enable non-executable mappings (default)
2273 read doesn't imply executable mappings
2274 noexec32=off: disable non-executable mappings
2275 read implies executable mappings
2277 nofpu [SH] Disable hardware FPU at boot time.
2279 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2280 register save and restore. The kernel will only save
2281 legacy floating-point registers on task switch.
2283 noxsave [BUGS=X86] Disables x86 extended register state save
2284 and restore using xsave. The kernel will fallback to
2285 enabling legacy floating-point and sse state.
2287 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2288 register states. The kernel will fall back to use
2289 xsave to save the states. By using this parameter,
2290 performance of saving the states is degraded because
2291 xsave doesn't support modified optimization while
2292 xsaveopt supports it on xsaveopt enabled systems.
2294 noxsaves [X86] Disables xsaves and xrstors used in saving and
2295 restoring x86 extended register state in compacted
2296 form of xsave area. The kernel will fall back to use
2297 xsaveopt and xrstor to save and restore the states
2298 in standard form of xsave area. By using this
2299 parameter, xsave area per process might occupy more
2300 memory on xsaves enabled systems.
2303 on enable eager fpu restore
2304 off disable eager fpu restore
2305 auto selects the default scheme, which automatically
2306 enables eagerfpu restore for xsaveopt.
2308 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2309 wfi(ARM) instruction doesn't work correctly and not to
2310 use it. This is also useful when using JTAG debugger.
2312 no_file_caps Tells the kernel not to honor file capabilities. The
2313 only way then for a file to be executed with privilege
2314 is to be setuid root or executed by root.
2316 nohalt [IA-64] Tells the kernel not to use the power saving
2317 function PAL_HALT_LIGHT when idle. This increases
2318 power-consumption. On the positive side, it reduces
2319 interrupt wake-up latency, which may improve performance
2320 in certain environments such as networked servers or
2323 nohibernate [HIBERNATION] Disable hibernation and resume.
2325 nohz= [KNL] Boottime enable/disable dynamic ticks
2326 Valid arguments: on, off
2329 nohz_full= [KNL,BOOT]
2330 In kernels built with CONFIG_NO_HZ_FULL=y, set
2331 the specified list of CPUs whose tick will be stopped
2332 whenever possible. The boot CPU will be forced outside
2333 the range to maintain the timekeeping.
2334 The CPUs in this range must also be included in the
2337 noiotrap [SH] Disables trapped I/O port accesses.
2339 noirqdebug [X86-32] Disables the code which attempts to detect and
2340 disable unhandled interrupt sources.
2342 no_timer_check [X86,APIC] Disables the code which tests for
2343 broken timer IRQ sources.
2345 noisapnp [ISAPNP] Disables ISA PnP code.
2347 noinitrd [RAM] Tells the kernel not to load any configured
2350 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2352 [Deprecated - use intremap=off]
2356 nojitter [IA-64] Disables jitter checking for ITC timers.
2358 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2360 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2363 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2364 steal time is computed, but won't influence scheduler
2367 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2369 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2371 noltlbs [PPC] Do not use large page/tlb entries for kernel
2372 lowmem mapping on PPC40x.
2374 nomca [IA-64] Disable machine check abort handling
2376 nomce [X86-32] Machine Check Exception
2378 nomfgpt [X86-32] Disable Multi-Function General Purpose
2379 Timer usage (for AMD Geode machines).
2381 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2382 shutdown the other cpus. Instead use the REBOOT_VECTOR
2385 nomodule Disable module load
2387 nopat [X86] Disable PAT (page attribute table extension of
2388 pagetables) support.
2390 norandmaps Don't use address space randomization. Equivalent to
2391 echo 0 > /proc/sys/kernel/randomize_va_space
2393 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2395 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2396 with UP alternatives
2398 nordrand [X86] Disable kernel use of the RDRAND and
2399 RDSEED instructions even if they are supported
2400 by the processor. RDRAND and RDSEED are still
2401 available to user space applications.
2403 noresume [SWSUSP] Disables resume and restores original swap
2406 no-scroll [VGA] Disables scrollback.
2407 This is required for the Braillex ib80-piezo Braille
2408 reader made by F.H. Papenmeier (Germany).
2412 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2414 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2415 and disable the IO APIC. legacy for "maxcpus=0".
2417 nosoftlockup [KNL] Disable the soft-lockup detector.
2419 nosync [HW,M68K] Disables sync negotiation for all devices.
2421 notsc [BUGS=X86-32] Disable Time Stamp Counter
2423 nousb [USB] Disable the USB subsystem
2425 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2429 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2431 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2432 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2433 Some features depend on CPU0. Known dependencies are:
2434 1. Resume from suspend/hibernate depends on CPU0.
2435 Suspend/hibernate will fail if CPU0 is offline and you
2436 need to online CPU0 before suspend/hibernate.
2437 2. PIC interrupts also depend on CPU0. CPU0 can't be
2438 removed if a PIC interrupt is detected.
2439 It's said poweroff/reboot may depend on CPU0 on some
2440 machines although I haven't seen such issues so far
2441 after CPU0 is offline on a few tested machines.
2442 If the dependencies are under your control, you can
2443 turn on cpu0_hotplug.
2445 nptcg= [IA-64] Override max number of concurrent global TLB
2446 purges which is reported from either PAL_VM_SUMMARY or
2449 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2450 could support. nr_cpus=n : n >= 1 limits the kernel to
2451 supporting 'n' processors. Later in runtime you can not
2452 use hotplug cpu feature to put more cpu back to online.
2453 just like you compile the kernel NR_CPUS=n
2455 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2457 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2458 Allowed values are enable and disable
2460 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2461 one of ['zone', 'node', 'default'] can be specified
2462 This can be set from sysctl after boot.
2463 See Documentation/sysctl/vm.txt for details.
2465 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2466 See Documentation/debugging-via-ohci1394.txt for more
2469 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2470 Rather than timing out after 20 ms if an EC
2471 command is not properly ACKed, override the length
2472 of the timeout. We have interrupts disabled while
2473 waiting for the ACK, so if this is set too high
2474 interrupts *may* be lost!
2476 omap_mux= [OMAP] Override bootloader pin multiplexing.
2477 Format: <mux_mode0.mode_name=value>...
2478 For example, to override I2C bus2:
2479 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2481 oprofile.timer= [HW]
2482 Use timer interrupt instead of performance counters
2484 oprofile.cpu_type= Force an oprofile cpu type
2485 This might be useful if you have an older oprofile
2486 userland or if you want common events.
2487 Format: { arch_perfmon }
2488 arch_perfmon: [X86] Force use of architectural
2489 perfmon on Intel CPUs instead of the
2490 CPU specific event set.
2491 timer: [X86] Force use of architectural NMI
2492 timer mode (see also oprofile.timer
2493 for generic hr timer mode)
2494 [s390] Force legacy basic mode sampling
2495 (report cpu_type "timer")
2497 oops=panic Always panic on oopses. Default is to just kill the
2498 process, but there is a small probability of
2499 deadlocking the machine.
2500 This will also cause panics on machine check exceptions.
2501 Useful together with panic=30 to trigger a reboot.
2504 See Documentation/sound/oss/oss-parameters.txt
2506 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2507 timeout > 0: seconds before rebooting
2508 timeout = 0: wait forever
2509 timeout < 0: reboot immediately
2512 crash_kexec_post_notifiers
2513 Run kdump after running panic-notifiers and dumping
2514 kmsg. This only for the users who doubt kdump always
2515 succeeds in any situation.
2516 Note that this also increases risks of kdump failure,
2517 because some panic notifiers can make the crashed
2518 kernel more unstable.
2520 parkbd.port= [HW] Parallel port number the keyboard adapter is
2521 connected to, default is 0.
2523 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2524 0 for XT, 1 for AT (default is AT).
2527 parport= [HW,PPT] Specify parallel ports. 0 disables.
2528 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2529 Use 'auto' to force the driver to use any
2530 IRQ/DMA settings detected (the default is to
2531 ignore detected IRQ/DMA settings because of
2532 possible conflicts). You can specify the base
2533 address, IRQ, and DMA settings; IRQ and DMA
2534 should be numbers, or 'auto' (for using detected
2535 settings on that particular port), or 'nofifo'
2536 (to avoid using a FIFO even if it is detected).
2537 Parallel ports are assigned in the order they
2538 are specified on the command line, starting
2541 parport_init_mode= [HW,PPT]
2542 Configure VIA parallel port to operate in
2543 a specific mode. This is necessary on Pegasos
2544 computer where firmware has no options for setting
2545 up parallel port mode and sets it to spp.
2546 Currently this function knows 686a and 8231 chips.
2547 Format: [spp|ps2|epp|ecp|ecpepp]
2550 Halt all CPUs after the first oops has been printed for
2551 the specified number of seconds. This is to be used if
2552 your oopses keep scrolling off the screen.
2557 See header of drivers/block/paride/pcd.c.
2558 See also Documentation/blockdev/paride.txt.
2560 pci=option[,option...] [PCI] various PCI subsystem options:
2561 earlydump [X86] dump PCI config space before the kernel
2563 off [X86] don't probe for the PCI bus
2564 bios [X86-32] force use of PCI BIOS, don't access
2565 the hardware directly. Use this if your machine
2566 has a non-standard PCI host bridge.
2567 nobios [X86-32] disallow use of PCI BIOS, only direct
2568 hardware access methods are allowed. Use this
2569 if you experience crashes upon bootup and you
2570 suspect they are caused by the BIOS.
2571 conf1 [X86] Force use of PCI Configuration
2573 conf2 [X86] Force use of PCI Configuration
2575 noaer [PCIE] If the PCIEAER kernel config parameter is
2576 enabled, this kernel boot option can be used to
2577 disable the use of PCIE advanced error reporting.
2578 nodomains [PCI] Disable support for multiple PCI
2579 root domains (aka PCI segments, in ACPI-speak).
2580 nommconf [X86] Disable use of MMCONFIG for PCI
2582 check_enable_amd_mmconf [X86] check for and enable
2583 properly configured MMIO access to PCI
2584 config space on AMD family 10h CPU
2585 nomsi [MSI] If the PCI_MSI kernel config parameter is
2586 enabled, this kernel boot option can be used to
2587 disable the use of MSI interrupts system-wide.
2588 noioapicquirk [APIC] Disable all boot interrupt quirks.
2589 Safety option to keep boot IRQs enabled. This
2590 should never be necessary.
2591 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2592 primary IO-APIC for bridges that cannot disable
2593 boot IRQs. This fixes a source of spurious IRQs
2594 when the system masks IRQs.
2595 noioapicreroute [APIC] Disable workaround that uses the
2596 boot IRQ equivalent of an IRQ that connects to
2597 a chipset where boot IRQs cannot be disabled.
2598 The opposite of ioapicreroute.
2599 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2600 routing table. These calls are known to be buggy
2601 on several machines and they hang the machine
2602 when used, but on other computers it's the only
2603 way to get the interrupt routing table. Try
2604 this option if the kernel is unable to allocate
2605 IRQs or discover secondary PCI buses on your
2607 rom [X86] Assign address space to expansion ROMs.
2608 Use with caution as certain devices share
2609 address decoders between ROMs and other
2611 norom [X86] Do not assign address space to
2612 expansion ROMs that do not already have
2613 BIOS assigned address ranges.
2614 nobar [X86] Do not assign address space to the
2615 BARs that weren't assigned by the BIOS.
2616 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2617 assigned automatically to PCI devices. You can
2618 make the kernel exclude IRQs of your ISA cards
2620 pirqaddr=0xAAAAA [X86] Specify the physical address
2621 of the PIRQ table (normally generated
2622 by the BIOS) if it is outside the
2623 F0000h-100000h range.
2624 lastbus=N [X86] Scan all buses thru bus #N. Can be
2625 useful if the kernel is unable to find your
2626 secondary buses and you want to tell it
2627 explicitly which ones they are.
2628 assign-busses [X86] Always assign all PCI bus
2629 numbers ourselves, overriding
2630 whatever the firmware may have done.
2631 usepirqmask [X86] Honor the possible IRQ mask stored
2632 in the BIOS $PIR table. This is needed on
2633 some systems with broken BIOSes, notably
2634 some HP Pavilion N5400 and Omnibook XE3
2635 notebooks. This will have no effect if ACPI
2636 IRQ routing is enabled.
2637 noacpi [X86] Do not use ACPI for IRQ routing
2638 or for PCI scanning.
2639 use_crs [X86] Use PCI host bridge window information
2640 from ACPI. On BIOSes from 2008 or later, this
2641 is enabled by default. If you need to use this,
2642 please report a bug.
2643 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2644 If you need to use this, please report a bug.
2645 routeirq Do IRQ routing for all PCI devices.
2646 This is normally done in pci_enable_device(),
2647 so this option is a temporary workaround
2648 for broken drivers that don't call it.
2649 skip_isa_align [X86] do not align io start addr, so can
2650 handle more pci cards
2651 firmware [ARM] Do not re-enumerate the bus but instead
2652 just use the configuration from the
2653 bootloader. This is currently used on
2654 IXP2000 systems where the bus has to be
2655 configured a certain way for adjunct CPUs.
2656 noearly [X86] Don't do any early type 1 scanning.
2657 This might help on some broken boards which
2658 machine check when some devices' config space
2659 is read. But various workarounds are disabled
2660 and some IOMMU drivers will not work.
2661 bfsort Sort PCI devices into breadth-first order.
2662 This sorting is done to get a device
2663 order compatible with older (<= 2.4) kernels.
2664 nobfsort Don't sort PCI devices into breadth-first order.
2665 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2666 tuning and use the BIOS-configured MPS defaults.
2667 pcie_bus_safe Set every device's MPS to the largest value
2668 supported by all devices below the root complex.
2669 pcie_bus_perf Set device MPS to the largest allowable MPS
2670 based on its parent bus. Also set MRRS (Max
2671 Read Request Size) to the largest supported
2672 value (no larger than the MPS that the device
2673 or bus can support) for best performance.
2674 pcie_bus_peer2peer Set every device's MPS to 128B, which
2675 every device is guaranteed to support. This
2676 configuration allows peer-to-peer DMA between
2677 any pair of devices, possibly at the cost of
2678 reduced performance. This also guarantees
2679 that hot-added devices will work.
2680 cbiosize=nn[KMG] The fixed amount of bus space which is
2681 reserved for the CardBus bridge's IO window.
2682 The default value is 256 bytes.
2683 cbmemsize=nn[KMG] The fixed amount of bus space which is
2684 reserved for the CardBus bridge's memory
2685 window. The default value is 64 megabytes.
2688 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2689 Specifies alignment and device to reassign
2690 aligned memory resources.
2691 If <order of align> is not specified,
2692 PAGE_SIZE is used as alignment.
2693 PCI-PCI bridge can be specified, if resource
2694 windows need to be expanded.
2695 ecrc= Enable/disable PCIe ECRC (transaction layer
2696 end-to-end CRC checking).
2697 bios: Use BIOS/firmware settings. This is the
2701 hpiosize=nn[KMG] The fixed amount of bus space which is
2702 reserved for hotplug bridge's IO window.
2703 Default size is 256 bytes.
2704 hpmemsize=nn[KMG] The fixed amount of bus space which is
2705 reserved for hotplug bridge's memory window.
2706 Default size is 2 megabytes.
2707 realloc= Enable/disable reallocating PCI bridge resources
2708 if allocations done by BIOS are too small to
2709 accommodate resources required by all child
2711 off: Turn realloc off
2713 realloc same as realloc=on
2714 noari do not use PCIe ARI.
2715 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2716 only look for one device below a PCIe downstream
2719 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2722 force Enable ASPM even on devices that claim not to support it.
2723 WARNING: Forcing ASPM on may cause system lockups.
2725 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2726 nomsi Do not use MSI for PCI Express Native Hotplug (this
2727 makes all PCIe ports use INTx for hotplug services).
2729 pcie_ports= [PCIE] PCIe ports handling:
2730 auto Ask the BIOS whether or not to use native PCIe services
2731 associated with PCIe ports (PME, hot-plug, AER). Use
2732 them only if that is allowed by the BIOS.
2733 native Use native PCIe services associated with PCIe ports
2735 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2738 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2739 nomsi Do not use MSI for native PCIe PME signaling (this makes
2740 all PCIe root ports use INTx for all services).
2742 pcmv= [HW,PCMCIA] BadgePAD 4
2746 Keep all power-domains already enabled by bootloader on,
2747 even if no driver has claimed them. This is useful
2748 for debug and development, but should not be
2749 needed on a platform with proper driver support.
2752 See Documentation/blockdev/paride.txt.
2754 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2757 See arch/parisc/kernel/pdc_chassis.c
2759 percpu_alloc= Select which percpu first chunk allocator to use.
2760 Currently supported values are "embed" and "page".
2761 Archs may support subset or none of the selections.
2762 See comments in mm/percpu.c for details on each
2763 allocator. This parameter is primarily for debugging
2764 and performance comparison.
2767 See Documentation/blockdev/paride.txt.
2770 See Documentation/blockdev/paride.txt.
2772 pirq= [SMP,APIC] Manual mp-table setup
2773 See Documentation/x86/i386/IO-APIC.txt.
2775 plip= [PPT,NET] Parallel port network link
2776 Format: { parport<nr> | timid | 0 }
2777 See also Documentation/parport.txt.
2779 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2780 Override pmtimer IOPort with a hex value.
2784 Enable PNP debug messages (depends on the
2785 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2786 via /sys/module/pnp/parameters/debug. We always show
2787 current resource usage; turning this on also shows
2788 possible settings and some assignment information.
2794 { on | off | curr | res | no-curr | no-res }
2797 [ISAPNP] Exclude IRQs for the autoconfiguration
2800 [ISAPNP] Exclude DMAs for the autoconfiguration
2802 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2803 Ranges are in pairs (I/O port base and size).
2806 [ISAPNP] Exclude memory regions for the
2808 Ranges are in pairs (memory base and size).
2810 ports= [IP_VS_FTP] IPVS ftp helper module
2812 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2814 Format: <port>,<port>....
2816 print-fatal-signals=
2817 [KNL] debug: print fatal signals
2819 If enabled, warn about various signal handling
2820 related application anomalies: too many signals,
2821 too many POSIX.1 timers, fatal signals causing a
2824 If you hit the warning due to signal overflow,
2825 you might want to try "ulimit -i unlimited".
2829 printk.always_kmsg_dump=
2830 Trigger kmsg_dump for cases other than kernel oops or
2832 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2835 printk.time= Show timing data prefixed to each printk message line
2836 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2838 processor.max_cstate= [HW,ACPI]
2839 Limit processor to maximum C-state
2840 max_cstate=9 overrides any DMI blacklist limit.
2842 processor.nocst [HW,ACPI]
2843 Ignore the _CST method to determine C-states,
2844 instead using the legacy FADT method
2846 profile= [KNL] Enable kernel profiling via /proc/profile
2847 Format: [schedule,]<number>
2848 Param: "schedule" - profile schedule points.
2849 Param: <number> - step/bucket size as a power of 2 for
2850 statistical time based profiling.
2851 Param: "sleep" - profile D-state sleeping (millisecs).
2852 Requires CONFIG_SCHEDSTATS
2853 Param: "kvm" - profile VM exits.
2855 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2857 See Documentation/blockdev/ramdisk.txt.
2859 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2860 probe for; one of (bare|imps|exps|lifebook|any).
2861 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2863 psmouse.resetafter= [HW,MOUSE]
2864 Try to reset the device after so many bad packets
2867 [HW,MOUSE] Set desired mouse resolution, in dpi.
2868 psmouse.smartscroll=
2869 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2870 0 = disabled, 1 = enabled (default).
2872 pstore.backend= Specify the name of the pstore backend to use
2875 See Documentation/blockdev/paride.txt.
2878 [KNL] Number of legacy pty's. Overwrites compiled-in
2881 quiet [KNL] Disable most log messages
2886 See Documentation/md.txt.
2888 ramdisk_blocksize= [RAM]
2889 See Documentation/blockdev/ramdisk.txt.
2891 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2892 See Documentation/blockdev/ramdisk.txt.
2895 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2896 the specified list of CPUs to be no-callback CPUs.
2897 Invocation of these CPUs' RCU callbacks will
2898 be offloaded to "rcuox/N" kthreads created for
2899 that purpose, where "x" is "b" for RCU-bh, "p"
2900 for RCU-preempt, and "s" for RCU-sched, and "N"
2901 is the CPU number. This reduces OS jitter on the
2902 offloaded CPUs, which can be useful for HPC and
2903 real-time workloads. It can also improve energy
2904 efficiency for asymmetric multiprocessors.
2907 Rather than requiring that offloaded CPUs
2908 (specified by rcu_nocbs= above) explicitly
2909 awaken the corresponding "rcuoN" kthreads,
2910 make these kthreads poll for callbacks.
2911 This improves the real-time response for the
2912 offloaded CPUs by relieving them of the need to
2913 wake up the corresponding kthread, but degrades
2914 energy efficiency by requiring that the kthreads
2915 periodically wake up to do the polling.
2917 rcutree.blimit= [KNL]
2918 Set maximum number of finished RCU callbacks to
2919 process in one batch.
2921 rcutree.rcu_fanout_leaf= [KNL]
2922 Increase the number of CPUs assigned to each
2923 leaf rcu_node structure. Useful for very large
2926 rcutree.jiffies_till_sched_qs= [KNL]
2927 Set required age in jiffies for a
2928 given grace period before RCU starts
2929 soliciting quiescent-state help from
2930 rcu_note_context_switch().
2932 rcutree.jiffies_till_first_fqs= [KNL]
2933 Set delay from grace-period initialization to
2934 first attempt to force quiescent states.
2935 Units are jiffies, minimum value is zero,
2936 and maximum value is HZ.
2938 rcutree.jiffies_till_next_fqs= [KNL]
2939 Set delay between subsequent attempts to force
2940 quiescent states. Units are jiffies, minimum
2941 value is one, and maximum value is HZ.
2943 rcutree.rcu_nocb_leader_stride= [KNL]
2944 Set the number of NOCB kthread groups, which
2945 defaults to the square root of the number of
2946 CPUs. Larger numbers reduces the wakeup overhead
2947 on the per-CPU grace-period kthreads, but increases
2948 that same overhead on each group's leader.
2950 rcutree.qhimark= [KNL]
2951 Set threshold of queued RCU callbacks beyond which
2952 batch limiting is disabled.
2954 rcutree.qlowmark= [KNL]
2955 Set threshold of queued RCU callbacks below which
2956 batch limiting is re-enabled.
2958 rcutree.rcu_idle_gp_delay= [KNL]
2959 Set wakeup interval for idle CPUs that have
2960 RCU callbacks (RCU_FAST_NO_HZ=y).
2962 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2963 Set wakeup interval for idle CPUs that have
2964 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2965 Lazy RCU callbacks are those which RCU can
2966 prove do nothing more than free memory.
2968 rcutorture.cbflood_inter_holdoff= [KNL]
2969 Set holdoff time (jiffies) between successive
2970 callback-flood tests.
2972 rcutorture.cbflood_intra_holdoff= [KNL]
2973 Set holdoff time (jiffies) between successive
2974 bursts of callbacks within a given callback-flood
2977 rcutorture.cbflood_n_burst= [KNL]
2978 Set the number of bursts making up a given
2979 callback-flood test. Set this to zero to
2980 disable callback-flood testing.
2982 rcutorture.cbflood_n_per_burst= [KNL]
2983 Set the number of callbacks to be registered
2984 in a given burst of a callback-flood test.
2986 rcutorture.fqs_duration= [KNL]
2987 Set duration of force_quiescent_state bursts.
2989 rcutorture.fqs_holdoff= [KNL]
2990 Set holdoff time within force_quiescent_state bursts.
2992 rcutorture.fqs_stutter= [KNL]
2993 Set wait time between force_quiescent_state bursts.
2995 rcutorture.gp_exp= [KNL]
2996 Use expedited update-side primitives.
2998 rcutorture.gp_normal= [KNL]
2999 Use normal (non-expedited) update-side primitives.
3000 If both gp_exp and gp_normal are set, do both.
3001 If neither gp_exp nor gp_normal are set, still
3004 rcutorture.n_barrier_cbs= [KNL]
3005 Set callbacks/threads for rcu_barrier() testing.
3007 rcutorture.nfakewriters= [KNL]
3008 Set number of concurrent RCU writers. These just
3009 stress RCU, they don't participate in the actual
3010 test, hence the "fake".
3012 rcutorture.nreaders= [KNL]
3013 Set number of RCU readers.
3015 rcutorture.object_debug= [KNL]
3016 Enable debug-object double-call_rcu() testing.
3018 rcutorture.onoff_holdoff= [KNL]
3019 Set time (s) after boot for CPU-hotplug testing.
3021 rcutorture.onoff_interval= [KNL]
3022 Set time (s) between CPU-hotplug operations, or
3023 zero to disable CPU-hotplug testing.
3025 rcutorture.torture_runnable= [BOOT]
3026 Start rcutorture running at boot time.
3028 rcutorture.shuffle_interval= [KNL]
3029 Set task-shuffle interval (s). Shuffling tasks
3030 allows some CPUs to go into dyntick-idle mode
3031 during the rcutorture test.
3033 rcutorture.shutdown_secs= [KNL]
3034 Set time (s) after boot system shutdown. This
3035 is useful for hands-off automated testing.
3037 rcutorture.stall_cpu= [KNL]
3038 Duration of CPU stall (s) to test RCU CPU stall
3039 warnings, zero to disable.
3041 rcutorture.stall_cpu_holdoff= [KNL]
3042 Time to wait (s) after boot before inducing stall.
3044 rcutorture.stat_interval= [KNL]
3045 Time (s) between statistics printk()s.
3047 rcutorture.stutter= [KNL]
3048 Time (s) to stutter testing, for example, specifying
3049 five seconds causes the test to run for five seconds,
3050 wait for five seconds, and so on. This tests RCU's
3051 ability to transition abruptly to and from idle.
3053 rcutorture.test_boost= [KNL]
3054 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3055 "Maybe" means test if the RCU implementation
3056 under test support RCU priority boosting.
3058 rcutorture.test_boost_duration= [KNL]
3059 Duration (s) of each individual boost test.
3061 rcutorture.test_boost_interval= [KNL]
3062 Interval (s) between each boost test.
3064 rcutorture.test_no_idle_hz= [KNL]
3065 Test RCU's dyntick-idle handling. See also the
3066 rcutorture.shuffle_interval parameter.
3068 rcutorture.torture_type= [KNL]
3069 Specify the RCU implementation to test.
3071 rcutorture.verbose= [KNL]
3072 Enable additional printk() statements.
3074 rcupdate.rcu_expedited= [KNL]
3075 Use expedited grace-period primitives, for
3076 example, synchronize_rcu_expedited() instead
3077 of synchronize_rcu(). This reduces latency,
3078 but can increase CPU utilization, degrade
3079 real-time latency, and degrade energy efficiency.
3081 rcupdate.rcu_cpu_stall_suppress= [KNL]
3082 Suppress RCU CPU stall warning messages.
3084 rcupdate.rcu_cpu_stall_timeout= [KNL]
3085 Set timeout for RCU CPU stall warning messages.
3087 rcupdate.rcu_task_stall_timeout= [KNL]
3088 Set timeout in jiffies for RCU task stall warning
3089 messages. Disable with a value less than or equal
3094 Run specified binary instead of /init from the ramdisk,
3095 used for early userspace startup. See initrd.
3098 Format (x86 or x86_64):
3099 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3101 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3103 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3104 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3105 reboot_force is either force or not specified,
3106 reboot_cpu is s[mp]#### with #### being the processor
3107 to be used for rebooting.
3110 [KNL, SMP] Set scheduler's default relax_domain_level.
3111 See Documentation/cgroups/cpusets.txt.
3113 relative_sleep_states=
3114 [SUSPEND] Use sleep state labeling where the deepest
3115 state available other than hibernation is always "mem".
3116 Format: { "0" | "1" }
3117 0 -- Traditional sleep state labels.
3118 1 -- Relative sleep state labels.
3120 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3122 reservetop= [X86-32]
3124 Reserves a hole at the top of the kernel virtual
3129 Set the amount of memory to reserve for BIOS at
3130 the bottom of the address space.
3132 reset_devices [KNL] Force drivers to reset the underlying device
3133 during initialization.
3136 Specify the partition device for software suspend
3138 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3140 resume_offset= [SWSUSP]
3141 Specify the offset from the beginning of the partition
3142 given by "resume=" at which the swap header is located,
3143 in <PAGE_SIZE> units (needed only for swap files).
3144 See Documentation/power/swsusp-and-swap-files.txt
3146 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3147 read the resume files
3149 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3150 Useful for devices that are detected asynchronously
3151 (e.g. USB and MMC devices).
3153 hibernate= [HIBERNATION]
3154 noresume Don't check if there's a hibernation image
3155 present during boot.
3156 nocompress Don't compress/decompress hibernation images.
3157 no Disable hibernation and resume.
3159 retain_initrd [RAM] Keep initrd memory after extraction
3161 rhash_entries= [KNL,NET]
3162 Set number of hash buckets for route cache
3164 ro [KNL] Mount root device read-only on boot
3166 root= [KNL] Root filesystem
3167 See name_to_dev_t comment in init/do_mounts.c.
3169 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3170 mount the root filesystem
3172 rootflags= [KNL] Set root filesystem mount option string
3174 rootfstype= [KNL] Set root filesystem type
3176 rootwait [KNL] Wait (indefinitely) for root device to show up.
3177 Useful for devices that are detected asynchronously
3178 (e.g. USB and MMC devices).
3180 rproc_mem=nn[KMG][@address]
3181 [KNL,ARM,CMA] Remoteproc physical memory block.
3182 Memory area to be used by remote processor image,
3185 rw [KNL] Mount root device read-write on boot
3187 S [KNL] Run init in single mode
3189 s390_iommu= [HW,S390]
3190 Set s390 IOTLB flushing mode
3192 With strict flushing every unmap operation will result in
3193 an IOTLB flush. Default is lazy flushing before reuse,
3197 See drivers/net/irda/sa1100_ir.c.
3199 sbni= [NET] Granch SBNI12 leased line adapter
3201 sched_debug [KNL] Enables verbose scheduler debug messages.
3203 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3204 xtime_lock contention on larger systems, and/or RCU lock
3205 contention on all systems with CONFIG_MAXSMP set.
3206 Format: { "0" | "1" }
3207 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3209 Note: increases power consumption, thus should only be
3210 enabled if running jitter sensitive (HPC/RT) workloads.
3212 security= [SECURITY] Choose a security module to enable at boot.
3213 If this boot parameter is not specified, only the first
3214 security module asking for security registration will be
3215 loaded. An invalid security module name will be treated
3216 as if no module has been chosen.
3218 selinux= [SELINUX] Disable or enable SELinux at boot time.
3219 Format: { "0" | "1" }
3220 See security/selinux/Kconfig help text.
3223 Default value is set via kernel config option.
3224 If enabled at boot time, /selinux/disable can be used
3225 later to disable prior to initial policy load.
3227 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3228 Format: { "0" | "1" }
3229 See security/apparmor/Kconfig help text
3232 Default value is set via kernel config option.
3234 serialnumber [BUGS=X86-32]
3237 Maximal number of shapers.
3239 show_msr= [x86] show boot-time MSR settings
3240 Format: { <integer> }
3241 Show boot-time (BIOS-initialized) MSR settings.
3242 The parameter means the number of CPUs to show,
3243 for example 1 means boot CPU only.
3251 Disable merging of slabs with similar size. May be
3252 necessary if there is some reason to distinguish
3253 allocs to different slabs. Debug options disable
3254 merging on their own.
3255 For more information see Documentation/vm/slub.txt.
3257 slab_max_order= [MM, SLAB]
3258 Determines the maximum allowed order for slabs.
3259 A high setting may cause OOMs due to memory
3260 fragmentation. Defaults to 1 for systems with
3261 more than 32MB of RAM, 0 otherwise.
3263 slub_debug[=options[,slabs]] [MM, SLUB]
3264 Enabling slub_debug allows one to determine the
3265 culprit if slab objects become corrupted. Enabling
3266 slub_debug can create guard zones around objects and
3267 may poison objects when not in use. Also tracks the
3268 last alloc / free. For more information see
3269 Documentation/vm/slub.txt.
3271 slub_max_order= [MM, SLUB]
3272 Determines the maximum allowed order for slabs.
3273 A high setting may cause OOMs due to memory
3274 fragmentation. For more information see
3275 Documentation/vm/slub.txt.
3277 slub_min_objects= [MM, SLUB]
3278 The minimum number of objects per slab. SLUB will
3279 increase the slab order up to slub_max_order to
3280 generate a sufficiently large slab able to contain
3281 the number of objects indicated. The higher the number
3282 of objects the smaller the overhead of tracking slabs
3283 and the less frequently locks need to be acquired.
3284 For more information see Documentation/vm/slub.txt.
3286 slub_min_order= [MM, SLUB]
3287 Determines the minimum page order for slabs. Must be
3288 lower than slub_max_order.
3289 For more information see Documentation/vm/slub.txt.
3291 slub_nomerge [MM, SLUB]
3292 Same with slab_nomerge. This is supported for legacy.
3293 See slab_nomerge for more information.
3296 Format: <io1>[,<io2>[,...,<io8>]]
3298 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3299 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3300 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3301 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3302 smsc-ircc2.ircc_irq= [HW] IRQ line
3303 smsc-ircc2.ircc_dma= [HW] DMA channel
3304 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3305 0: Toshiba Satellite 1800 (GP data pin select)
3306 1: Fast pin select (default)
3310 [KNL] Should the soft-lockup detector generate panics.
3313 softlockup_all_cpu_backtrace=
3314 [KNL] Should the soft-lockup detector generate
3315 backtraces on all cpus.
3318 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3319 See Documentation/laptops/sonypi.txt
3321 spia_io_base= [HW,MTD]
3327 Enabled the stack tracer on boot up.
3329 stacktrace_filter=[function-list]
3330 [FTRACE] Limit the functions that the stack tracer
3331 will trace at boot up. function-list is a comma separated
3332 list of functions. This list can be changed at run
3333 time by the stack_trace_filter file in the debugfs
3334 tracing directory. Note, this enables stack tracing
3335 and the stacktrace above is not needed.
3339 Set the STI (builtin display/keyboard on the HP-PARISC
3340 machines) console (graphic card) which should be used
3341 as the initial boot-console.
3342 See also comment in drivers/video/console/sticore.c.
3345 See comment in drivers/video/console/sticore.c.
3348 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3350 sunrpc.min_resvport=
3351 sunrpc.max_resvport=
3353 SunRPC servers often require that client requests
3354 originate from a privileged port (i.e. a port in the
3355 range 0 < portnr < 1024).
3356 An administrator who wishes to reserve some of these
3357 ports for other uses may adjust the range that the
3358 kernel's sunrpc client considers to be privileged
3359 using these two parameters to set the minimum and
3360 maximum port values.
3364 Control how the NFS server code allocates CPUs to
3365 service thread pools. Depending on how many NICs
3366 you have and where their interrupts are bound, this
3367 option will affect which CPUs will do NFS serving.
3368 Note: this parameter cannot be changed while the
3369 NFS server is running.
3371 auto the server chooses an appropriate mode
3372 automatically using heuristics
3373 global a single global pool contains all CPUs
3374 percpu one pool for each CPU
3375 pernode one pool for each NUMA node (equivalent
3376 to global on non-NUMA machines)
3378 sunrpc.tcp_slot_table_entries=
3379 sunrpc.udp_slot_table_entries=
3381 Sets the upper limit on the number of simultaneous
3382 RPC calls that can be sent from the client to a
3383 server. Increasing these values may allow you to
3384 improve throughput, but will also increase the
3385 amount of memory reserved for use by the client.
3388 [KNL] Enable accounting of swap in memory resource
3389 controller if no parameter or 1 is given or disable
3390 it if 0 is given (See Documentation/cgroups/memory.txt)
3392 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3393 Format: { <int> | force }
3394 <int> -- Number of I/O TLB slabs
3395 force -- force using of bounce buffers even if they
3396 wouldn't be automatically used by the kernel
3400 sysfs.deprecated=0|1 [KNL]
3401 Enable/disable old style sysfs layout for old udev
3402 on older distributions. When this option is enabled
3403 very new udev will not work anymore. When this option
3404 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3405 in older udev will not work anymore.
3406 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3407 the kernel configuration.
3409 sysrq_always_enabled
3411 Ignore sysrq setting - this boot parameter will
3412 neutralize any effect of /proc/sys/kernel/sysrq.
3413 Useful for debugging.
3417 test_suspend= [SUSPEND][,N]
3418 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3419 standby suspend) or "freeze" (for suspend type freeze)
3420 as the system sleep state during system startup with
3421 the optional capability to repeat N number of times.
3422 The system is woken from this state using a
3423 wakeup-capable RTC alarm.
3425 thash_entries= [KNL,NET]
3426 Set number of hash buckets for TCP connection
3428 thermal.act= [HW,ACPI]
3429 -1: disable all active trip points in all thermal zones
3430 <degrees C>: override all lowest active trip points
3432 thermal.crt= [HW,ACPI]
3433 -1: disable all critical trip points in all thermal zones
3434 <degrees C>: override all critical trip points
3436 thermal.nocrt= [HW,ACPI]
3437 Set to disable actions on ACPI thermal zone
3438 critical and hot trip points.
3440 thermal.off= [HW,ACPI]
3441 1: disable ACPI thermal control
3443 thermal.psv= [HW,ACPI]
3444 -1: disable all passive trip points
3445 <degrees C>: override all passive trip points to this
3448 thermal.tzp= [HW,ACPI]
3449 Specify global default ACPI thermal zone polling rate
3450 <deci-seconds>: poll all this frequency
3451 0: no polling (default)
3454 Force threading of all interrupt handlers except those
3455 marked explicitly IRQF_NO_THREAD.
3458 Enable the Transcendent memory driver if built-in.
3460 tmem.cleancache=0|1 [KNL, XEN]
3461 Default is on (1). Disable the usage of the cleancache
3462 API to send anonymous pages to the hypervisor.
3464 tmem.frontswap=0|1 [KNL, XEN]
3465 Default is on (1). Disable the usage of the frontswap
3466 API to send swap pages to the hypervisor. If disabled
3467 the selfballooning and selfshrinking are force disabled.
3469 tmem.selfballooning=0|1 [KNL, XEN]
3470 Default is on (1). Disable the driving of swap pages
3473 tmem.selfshrinking=0|1 [KNL, XEN]
3474 Default is on (1). Partial swapoff that immediately
3475 transfers pages from Xen hypervisor back to the
3476 kernel based on different criteria.
3480 Specify if the kernel should make use of the cpu
3481 topology information if the hardware supports this.
3482 The scheduler will make use of this information and
3483 e.g. base its process migration decisions on it.
3486 topology_updates= [KNL, PPC, NUMA]
3488 Specify if the kernel should ignore (off)
3489 topology updates sent by the hypervisor to this
3494 tpm_suspend_pcr=[HW,TPM]
3495 Format: integer pcr id
3496 Specify that at suspend time, the tpm driver
3497 should extend the specified pcr with zeros,
3498 as a workaround for some chips which fail to
3499 flush the last written pcr on TPM_SaveState.
3500 This will guarantee that all the other pcrs
3503 trace_buf_size=nn[KMG]
3504 [FTRACE] will set tracing buffer size.
3506 trace_event=[event-list]
3507 [FTRACE] Set and start specified trace events in order
3508 to facilitate early boot debugging.
3509 See also Documentation/trace/events.txt
3511 trace_options=[option-list]
3512 [FTRACE] Enable or disable tracer options at boot.
3513 The option-list is a comma delimited list of options
3514 that can be enabled or disabled just as if you were
3515 to echo the option name into
3517 /sys/kernel/debug/tracing/trace_options
3519 For example, to enable stacktrace option (to dump the
3520 stack trace of each event), add to the command line:
3522 trace_options=stacktrace
3524 See also Documentation/trace/ftrace.txt "trace options"
3528 [FTRACE] enable this option to disable tracing when a
3529 warning is hit. This turns off "tracing_on". Tracing can
3530 be enabled again by echoing '1' into the "tracing_on"
3531 file located in /sys/kernel/debug/tracing/
3533 This option is useful, as it disables the trace before
3534 the WARNING dump is called, which prevents the trace to
3535 be filled with content caused by the warning output.
3537 This option can also be set at run time via the sysctl
3538 option: kernel/traceoff_on_warning
3540 transparent_hugepage=
3542 Format: [always|madvise|never]
3543 Can be used to control the default behavior of the system
3544 with respect to transparent hugepages.
3545 See Documentation/vm/transhuge.txt for more details.
3547 tsc= Disable clocksource stability checks for TSC.
3549 [x86] reliable: mark tsc clocksource as reliable, this
3550 disables clocksource verification at runtime, as well
3551 as the stability checks done at bootup. Used to enable
3552 high-resolution timer mode on older hardware, and in
3553 virtualized environment.
3554 [x86] noirqtime: Do not use TSC to do irq accounting.
3555 Used to run time disable IRQ_TIME_ACCOUNTING on any
3556 platforms where RDTSC is slow and this accounting
3559 turbografx.map[2|3]= [HW,JOY]
3560 TurboGraFX parallel port interface
3562 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3563 See also Documentation/input/joystick-parport.txt
3565 udbg-immortal [PPC] When debugging early kernel crashes that
3566 happen after console_init() and before a proper
3567 console driver takes over, this boot options might
3568 help "seeing" what's going on.
3570 uhash_entries= [KNL,NET]
3571 Set number of hash buckets for UDP/UDP-Lite connections
3574 [USB] Ignore overcurrent events (default N).
3575 Some badly-designed motherboards generate lots of
3576 bogus events, for ports that aren't wired to
3577 anything. Set this parameter to avoid log spamming.
3578 Note that genuine overcurrent events won't be
3582 [X86] Cause panic on unknown NMI.
3584 usbcore.authorized_default=
3585 [USB] Default USB device authorization:
3586 (default -1 = authorized except for wireless USB,
3587 0 = not authorized, 1 = authorized)
3589 usbcore.autosuspend=
3590 [USB] The autosuspend time delay (in seconds) used
3591 for newly-detected USB devices (default 2). This
3592 is the time required before an idle device will be
3593 autosuspended. Devices for which the delay is set
3594 to a negative value won't be autosuspended at all.
3596 usbcore.usbfs_snoop=
3597 [USB] Set to log all usbfs traffic (default 0 = off).
3599 usbcore.blinkenlights=
3600 [USB] Set to cycle leds on hubs (default 0 = off).
3602 usbcore.old_scheme_first=
3603 [USB] Start with the old device initialization
3604 scheme (default 0 = off).
3606 usbcore.usbfs_memory_mb=
3607 [USB] Memory limit (in MB) for buffers allocated by
3608 usbfs (default = 16, 0 = max = 2047).
3610 usbcore.use_both_schemes=
3611 [USB] Try the other device initialization scheme
3612 if the first one fails (default 1 = enabled).
3614 usbcore.initial_descriptor_timeout=
3615 [USB] Specifies timeout for the initial 64-byte
3616 USB_REQ_GET_DESCRIPTOR request in milliseconds
3617 (default 5000 = 5.0 seconds).
3620 [USBHID] The interval which mice are to be polled at.
3622 usb-storage.delay_use=
3623 [UMS] The delay in seconds before a new device is
3624 scanned for Logical Units (default 5).
3627 [UMS] A list of quirks entries to supplement or
3628 override the built-in unusual_devs list. List
3629 entries are separated by commas. Each entry has
3630 the form VID:PID:Flags where VID and PID are Vendor
3631 and Product ID values (4-digit hex numbers) and
3632 Flags is a set of characters, each corresponding
3633 to a common usb-storage quirk flag as follows:
3634 a = SANE_SENSE (collect more than 18 bytes
3636 b = BAD_SENSE (don't collect more than 18
3637 bytes of sense data);
3638 c = FIX_CAPACITY (decrease the reported
3639 device capacity by one sector);
3640 d = NO_READ_DISC_INFO (don't use
3641 READ_DISC_INFO command);
3642 e = NO_READ_CAPACITY_16 (don't use
3643 READ_CAPACITY_16 command);
3644 f = NO_REPORT_OPCODES (don't use report opcodes
3646 h = CAPACITY_HEURISTICS (decrease the
3647 reported device capacity by one
3648 sector if the number is odd);
3649 i = IGNORE_DEVICE (don't bind to this
3651 l = NOT_LOCKABLE (don't try to lock and
3652 unlock ejectable media);
3653 m = MAX_SECTORS_64 (don't transfer more
3654 than 64 sectors = 32 KB at a time);
3655 n = INITIAL_READ10 (force a retry of the
3656 initial READ(10) command);
3657 o = CAPACITY_OK (accept the capacity
3658 reported by the device);
3659 p = WRITE_CACHE (the device cache is ON
3661 r = IGNORE_RESIDUE (the device reports
3662 bogus residue values);
3663 s = SINGLE_LUN (the device has only one
3665 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3666 commands, uas only);
3667 u = IGNORE_UAS (don't bind to the uas driver);
3668 w = NO_WP_DETECT (don't test whether the
3669 medium is write-protected).
3670 Example: quirks=0419:aaf5:rl,0421:0433:rc
3672 user_debug= [KNL,ARM]
3674 See arch/arm/Kconfig.debug help text.
3675 1 - undefined instruction events
3677 4 - invalid data aborts
3680 Example: user_debug=31
3683 [X86] Flags controlling user PTE allocations.
3685 nohigh = do not allocate PTE pages in
3686 HIGHMEM regardless of setting
3690 On X86_32, this is an alias for vdso32=. Otherwise:
3692 vdso=1: enable VDSO (the default)
3693 vdso=0: disable VDSO mapping
3695 vdso32= [X86] Control the 32-bit vDSO
3696 vdso32=1: enable 32-bit VDSO
3697 vdso32=0 or vdso32=2: disable 32-bit VDSO
3699 See the help text for CONFIG_COMPAT_VDSO for more
3700 details. If CONFIG_COMPAT_VDSO is set, the default is
3701 vdso32=0; otherwise, the default is vdso32=1.
3703 For compatibility with older kernels, vdso32=2 is an
3706 Try vdso32=0 if you encounter an error that says:
3707 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3710 vector=percpu: enable percpu vector domain
3712 video= [FB] Frame buffer configuration
3713 See Documentation/fb/modedb.txt.
3715 video.brightness_switch_enabled= [0,1]
3716 If set to 1, on receiving an ACPI notify event
3717 generated by hotkey, video driver will adjust brightness
3718 level and then send out the event to user space through
3719 the allocated input device; If set to 0, video driver
3720 will only send out the event without touching backlight
3725 [VMMIO] Memory mapped virtio (platform) device.
3727 <size>@<baseaddr>:<irq>[:<id>]
3729 <size> := size (can use standard suffixes
3731 <baseaddr> := physical base address
3732 <irq> := interrupt number (as passed to
3734 <id> := (optional) platform device id
3736 virtio_mmio.device=1K@0x100b0000:48:7
3738 Can be used multiple times for multiple devices.
3740 vga= [BOOT,X86-32] Select a particular video mode
3741 See Documentation/x86/boot.txt and
3742 Documentation/svga.txt.
3743 Use vga=ask for menu.
3744 This is actually a boot loader parameter; the value is
3745 passed to the kernel using a special protocol.
3747 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3748 size of <nn>. This can be used to increase the
3749 minimum size (128MB on x86). It can also be used to
3750 decrease the size and leave more room for directly
3753 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3756 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3759 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3763 Controls the behavior of vsyscalls (i.e. calls to
3764 fixed addresses of 0xffffffffff600x00 from legacy
3765 code). Most statically-linked binaries and older
3766 versions of glibc use these calls. Because these
3767 functions are at fixed addresses, they make nice
3768 targets for exploits that can control RIP.
3770 emulate [default] Vsyscalls turn into traps and are
3771 emulated reasonably safely.
3773 native Vsyscalls are native syscall instructions.
3774 This is a little bit faster than trapping
3775 and makes a few dynamic recompilers work
3776 better than they would in emulation mode.
3777 It also makes exploits much easier to write.
3779 none Vsyscalls don't work at all. This makes
3780 them quite hard to use for exploits but
3781 might break your system.
3783 vt.color= [VT] Default text color.
3784 Format: 0xYX, X = foreground, Y = background.
3785 Default: 0x07 = light gray on black.
3787 vt.cur_default= [VT] Default cursor shape.
3788 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3789 the parameters of the <Esc>[?A;B;Cc escape sequence;
3790 see VGA-softcursor.txt. Default: 2 = underline.
3792 vt.default_blu= [VT]
3793 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3794 Change the default blue palette of the console.
3795 This is a 16-member array composed of values
3798 vt.default_grn= [VT]
3799 Format: <green0>,<green1>,<green2>,...,<green15>
3800 Change the default green palette of the console.
3801 This is a 16-member array composed of values
3804 vt.default_red= [VT]
3805 Format: <red0>,<red1>,<red2>,...,<red15>
3806 Change the default red palette of the console.
3807 This is a 16-member array composed of values
3813 Set system-wide default UTF-8 mode for all tty's.
3814 Default is 1, i.e. UTF-8 mode is enabled for all
3815 newly opened terminals.
3817 vt.global_cursor_default=
3820 Set system-wide default for whether a cursor
3821 is shown on new VTs. Default is -1,
3822 i.e. cursors will be created by default unless
3823 overridden by individual drivers. 0 will hide
3824 cursors, 1 will display them.
3826 vt.italic= [VT] Default color for italic text; 0-15.
3829 vt.underline= [VT] Default color for underlined text; 0-15.
3832 watchdog timers [HW,WDT] For information on watchdog timers,
3833 see Documentation/watchdog/watchdog-parameters.txt
3834 or other driver-specific files in the
3835 Documentation/watchdog/ directory.
3837 workqueue.disable_numa
3838 By default, all work items queued to unbound
3839 workqueues are affine to the NUMA nodes they're
3840 issued on, which results in better behavior in
3841 general. If NUMA affinity needs to be disabled for
3842 whatever reason, this option can be used. Note
3843 that this also can be controlled per-workqueue for
3844 workqueues visible under /sys/bus/workqueue/.
3846 workqueue.power_efficient
3847 Per-cpu workqueues are generally preferred because
3848 they show better performance thanks to cache
3849 locality; unfortunately, per-cpu workqueues tend to
3850 be more power hungry than unbound workqueues.
3852 Enabling this makes the per-cpu workqueues which
3853 were observed to contribute significantly to power
3854 consumption unbound, leading to measurably lower
3855 power usage at the cost of small performance
3858 The default value of this parameter is determined by
3859 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3861 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3862 default x2apic cluster mode on platforms
3865 x86_intel_mid_timer= [X86-32,APBT]
3866 Choose timer option for x86 Intel MID platform.
3867 Two valid options are apbt timer only and lapic timer
3868 plus one apbt timer for broadcast timer.
3869 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3871 xen_emul_unplug= [HW,X86,XEN]
3872 Unplug Xen emulated devices
3873 Format: [unplug0,][unplug1]
3874 ide-disks -- unplug primary master IDE devices
3875 aux-ide-disks -- unplug non-primary-master IDE devices
3876 nics -- unplug network devices
3877 all -- unplug all emulated devices (NICs and IDE disks)
3878 unnecessary -- unplugging emulated devices is
3879 unnecessary even if the host did not respond to
3881 never -- do not unplug even if version check succeeds
3883 xen_nopvspin [X86,XEN]
3884 Disables the ticketlock slowpath using Xen PV
3888 Disables the PV optimizations forcing the HVM guest to
3889 run as generic HVM guest with no PV drivers.
3891 xirc2ps_cs= [NET,PCMCIA]
3893 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3895 ______________________________________________________________________
3899 Add more DRM drivers.
projects / cascardo / linux.git / blob