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" }
1019 old_map [X86-64]: switch to the old ioremap-based EFI
1020 runtime services mapping. 32-bit still uses this one by
1023 efi_no_storage_paranoia [EFI; X86]
1024 Using this parameter you can use more than 50% of
1025 your efi variable storage. Use this parameter only if
1026 you are really sure that your UEFI does sane gc and
1027 fulfills the spec otherwise your board may brick.
1029 eisa_irq_edge= [PARISC,HW]
1030 See header of drivers/parisc/eisa.c.
1033 See comment before function elanfreq_setup() in
1034 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1037 Format: {"cfq" | "deadline" | "noop"}
1038 See Documentation/block/cfq-iosched.txt and
1039 Documentation/block/deadline-iosched.txt for details.
1041 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1042 Specifies physical address of start of kernel core
1043 image elf header and optionally the size. Generally
1044 kexec loader will pass this option to capture kernel.
1045 See Documentation/kdump/kdump.txt for details.
1047 enable_mtrr_cleanup [X86]
1048 The kernel tries to adjust MTRR layout from continuous
1049 to discrete, to make X server driver able to add WB
1050 entry later. This parameter enables that.
1052 enable_timer_pin_1 [X86]
1053 Enable PIN 1 of APIC timer
1054 Can be useful to work around chipset bugs
1055 (in particular on some ATI chipsets).
1056 The kernel tries to set a reasonable default.
1058 enforcing [SELINUX] Set initial enforcing status.
1060 See security/selinux/Kconfig help text.
1061 0 -- permissive (log only, no denials).
1062 1 -- enforcing (deny and log).
1064 Value can be changed at runtime via /selinux/enforce.
1067 Disable Error Record Serialization Table (ERST)
1070 ether= [HW,NET] Ethernet cards parameters
1071 This option is obsoleted by the "netdev=" option, which
1072 has equivalent usage. See its documentation for details.
1076 Permit 'security.evm' to be updated regardless of
1077 current integrity status.
1081 fail_make_request=[KNL]
1082 General fault injection mechanism.
1083 Format: <interval>,<probability>,<space>,<times>
1084 See also Documentation/fault-injection/.
1087 See Documentation/blockdev/floppy.txt.
1089 force_pal_cache_flush
1090 [IA-64] Avoid check_sal_cache_flush which may hang on
1091 buggy SAL_CACHE_FLUSH implementations. Using this
1092 parameter will force ia64_sal_cache_flush to call
1093 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1096 Forcefully enable Physical Address Extension (PAE).
1097 Many Pentium M systems disable PAE but may have a
1098 functionally usable PAE implementation.
1099 Warning: use of this parameter will taint the kernel
1100 and may cause unknown problems.
1103 [FTRACE] will set and start the specified tracer
1104 as early as possible in order to facilitate early
1107 ftrace_dump_on_oops[=orig_cpu]
1108 [FTRACE] will dump the trace buffers on oops.
1109 If no parameter is passed, ftrace will dump
1110 buffers of all CPUs, but if you pass orig_cpu, it will
1111 dump only the buffer of the CPU that triggered the
1114 ftrace_filter=[function-list]
1115 [FTRACE] Limit the functions traced by the function
1116 tracer at boot up. function-list is a comma separated
1117 list of functions. This list can be changed at run
1118 time by the set_ftrace_filter file in the debugfs
1121 ftrace_notrace=[function-list]
1122 [FTRACE] Do not trace the functions specified in
1123 function-list. This list can be changed at run time
1124 by the set_ftrace_notrace file in the debugfs
1127 ftrace_graph_filter=[function-list]
1128 [FTRACE] Limit the top level callers functions traced
1129 by the function graph tracer at boot up.
1130 function-list is a comma separated list of functions
1131 that can be changed at run time by the
1132 set_graph_function file in the debugfs tracing directory.
1134 ftrace_graph_notrace=[function-list]
1135 [FTRACE] Do not trace from the functions specified in
1136 function-list. This list is a comma separated list of
1137 functions that can be changed at run time by the
1138 set_graph_notrace file in the debugfs tracing directory.
1141 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1142 support via parallel port (up to 5 devices per port)
1143 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1144 See also Documentation/input/joystick-parport.txt
1148 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1152 gcov_persist= [GCOV] When non-zero (default), profiling data for
1153 kernel modules is saved and remains accessible via
1154 debugfs, even when the module is unloaded/reloaded.
1155 When zero, profiling data is discarded and associated
1156 debugfs files are removed at module unload time.
1158 gpt [EFI] Forces disk with valid GPT signature but
1159 invalid Protective MBR to be treated as GPT. If the
1160 primary GPT is corrupted, it enables the backup/alternate
1161 GPT to be used instead.
1163 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1164 the "Enable 0" bit of the configuration register.
1167 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1168 the "Enable 0" bit of the configuration register.
1171 grcan.select= [HW] Select which physical interface to use.
1174 grcan.txsize= [HW] Sets the size of the tx buffer.
1175 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1177 grcan.rxsize= [HW] Sets the size of the rx buffer.
1178 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1181 hashdist= [KNL,NUMA] Large hashes allocated during boot
1182 are distributed across NUMA nodes. Defaults on
1183 for 64-bit NUMA, off otherwise.
1184 Format: 0 | 1 (for off | on)
1186 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1188 hd= [EIDE] (E)IDE hard drive subsystem geometry
1189 Format: <cyl>,<head>,<sect>
1192 Disable Hardware Error Source Table (HEST) support;
1193 corresponding firmware-first mode error processing
1194 logic will be disabled.
1196 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1197 size of <nn>. This works even on boxes that have no
1198 highmem otherwise. This also works to reduce highmem
1199 size on bigger boxes.
1201 highres= [KNL] Enable/disable high resolution timer mode.
1202 Valid parameters: "on", "off"
1206 See Documentation/isdn/README.HiSax.
1210 hpet= [X86-32,HPET] option to control HPET usage
1211 Format: { enable (default) | disable | force |
1213 disable: disable HPET and use PIT instead
1214 force: allow force enabled of undocumented chips (ICH4,
1216 verbose: show contents of HPET registers during setup
1218 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1219 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1221 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1222 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1223 On x86-64 and powerpc, this option can be specified
1224 multiple times interleaved with hugepages= to reserve
1225 huge pages of different sizes. Valid pages sizes on
1226 x86-64 are 2M (when the CPU supports "pse") and 1G
1227 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1228 Note that 1GB pages can only be allocated at boot time
1229 using hugepages= and not freed afterwards.
1231 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1232 terminal devices. Valid values: 0..8
1233 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1234 If specified, z/VM IUCV HVC accepts connections
1235 from listed z/VM user IDs only.
1237 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1238 hardware thread id mappings.
1239 Format: <cpu>:<hwthread>
1242 Do not unregister boot console at start. This is only
1243 useful for debugging when something happens in the window
1244 between unregistering the boot console and initializing
1247 i2c_bus= [HW] Override the default board specific I2C bus speed
1248 or register an additional I2C bus that is not
1249 registered from board initialization code.
1253 i8042.debug [HW] Toggle i8042 debug mode
1254 i8042.direct [HW] Put keyboard port into non-translated mode
1255 i8042.dumbkbd [HW] Pretend that controller can only read data from
1256 keyboard and cannot control its state
1257 (Don't attempt to blink the leds)
1258 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1259 i8042.nokbd [HW] Don't check/create keyboard port
1260 i8042.noloop [HW] Disable the AUX Loopback command while probing
1262 i8042.nomux [HW] Don't check presence of an active multiplexing
1263 controller. Default: true.
1264 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1266 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1267 i8042.reset [HW] Reset the controller during init and cleanup
1268 i8042.unlock [HW] Unlock (ignore) the keylock
1272 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1273 indicates that the driver is running on unsupported
1275 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1276 does not match list of supported models.
1278 [HW] Report power status in /proc/i8k
1279 (disabled by default)
1280 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1283 i915.invert_brightness=
1284 [DRM] Invert the sense of the variable that is used to
1285 set the brightness of the panel backlight. Normally a
1286 brightness value of 0 indicates backlight switched off,
1287 and the maximum of the brightness value sets the backlight
1288 to maximum brightness. If this parameter is set to 0
1289 (default) and the machine requires it, or this parameter
1290 is set to 1, a brightness value of 0 sets the backlight
1291 to maximum brightness, and the maximum of the brightness
1292 value switches the backlight off.
1293 -1 -- never invert brightness
1294 0 -- machine default
1295 1 -- force brightness inversion
1298 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1300 ide-core.nodma= [HW] (E)IDE subsystem
1301 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1302 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1303 .cdrom .chs .ignore_cable are additional options
1304 See Documentation/ide/ide.txt.
1306 ide-generic.probe-mask= [HW] (E)IDE subsystem
1308 Probe mask for legacy ISA IDE ports. Depending on
1309 platform up to 6 ports are supported, enabled by
1310 setting corresponding bits in the mask to 1. The
1311 default value is 0x0, which has a special meaning.
1312 On systems that have PCI, it triggers scanning the
1313 PCI bus for the first and the second port, which
1314 are then probed. On systems without PCI the value
1315 of 0x0 enables probing the two first ports as if it
1318 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1319 Claim all unknown PCI IDE storage controllers.
1322 Format: idle=poll, idle=halt, idle=nomwait
1323 Poll forces a polling idle loop that can slightly
1324 improve the performance of waking up a idle CPU, but
1325 will use a lot of power and make the system run hot.
1327 idle=halt: Halt is forced to be used for CPU idle.
1328 In such case C2/C3 won't be used again.
1329 idle=nomwait: Disable mwait for CPU C-states
1331 ignore_loglevel [KNL]
1332 Ignore loglevel setting - this will print /all/
1333 kernel messages to the console. Useful for debugging.
1334 We also add it as printk module parameter, so users
1335 could change it dynamically, usually by
1336 /sys/module/printk/parameters/ignore_loglevel.
1338 ihash_entries= [KNL]
1339 Set number of hash buckets for inode cache.
1341 ima_appraise= [IMA] appraise integrity measurements
1342 Format: { "off" | "enforce" | "fix" | "log" }
1345 ima_appraise_tcb [IMA]
1346 The builtin appraise policy appraises all files
1350 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1354 The list of supported hash algorithms is defined
1355 in crypto/hash_info.h.
1358 Load a policy which meets the needs of the Trusted
1359 Computing Base. This means IMA will measure all
1360 programs exec'd, files mmap'd for exec, and all files
1361 opened for read by uid=0.
1364 Select one of defined IMA measurements template formats.
1365 Formats: { "ima" | "ima-ng" }
1368 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1369 Format: <min_file_size>
1370 Set the minimal file size for using asynchronous hash.
1371 If left unspecified, ahash usage is disabled.
1373 ahash performance varies for different data sizes on
1374 different crypto accelerators. This option can be used
1375 to achieve the best performance for a particular HW.
1377 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1379 Set hashing buffer size. Default: 4k.
1381 ahash performance varies for different chunk sizes on
1382 different crypto accelerators. This option can be used
1383 to achieve best performance for particular HW.
1387 Run specified binary instead of /sbin/init as init
1390 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1391 for working out where the kernel is dying during
1394 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1395 initcall functions. Useful for debugging built-in
1396 modules and initcalls.
1398 initrd= [BOOT] Specify the location of the initial ramdisk
1400 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1403 int_pln_enable [x86] Enable power limit notification interrupt
1405 integrity_audit=[IMA]
1406 Format: { "0" | "1" }
1407 0 -- basic integrity auditing messages. (Default)
1408 1 -- additional integrity auditing messages.
1410 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1412 Enable intel iommu driver.
1414 Disable intel iommu driver.
1415 igfx_off [Default Off]
1416 By default, gfx is mapped as normal device. If a gfx
1417 device has a dedicated DMAR unit, the DMAR unit is
1418 bypassed by not enabling DMAR with this option. In
1419 this case, gfx device will use physical address for
1422 With this option iommu will not optimize to look
1423 for io virtual address below 32-bit forcing dual
1424 address cycle on pci bus for cards supporting greater
1425 than 32-bit addressing. The default is to look
1426 for translation below 32-bit and if not available
1427 then look in the higher range.
1428 strict [Default Off]
1429 With this option on every unmap_single operation will
1430 result in a hardware IOTLB flush operation as opposed
1431 to batching them for performance.
1432 sp_off [Default Off]
1433 By default, super page will be supported if Intel IOMMU
1434 has the capability. With this option, super page will
1437 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1438 0 disables intel_idle and fall back on acpi_idle.
1439 1 to 6 specify maximum depth of C-state.
1443 Do not enable intel_pstate as the default
1444 scaling driver for the supported processors
1446 intremap= [X86-64, Intel-IOMMU]
1447 on enable Interrupt Remapping (default)
1448 off disable Interrupt Remapping
1449 nosid disable Source ID checking
1451 BIOS x2APIC opt-out request will be ignored
1453 iomem= Disable strict checking of access to MMIO memory
1454 strict regions from userspace.
1471 io7= [HW] IO7 for Marvel based alpha systems
1472 See comment before marvel_specify_io7 in
1473 arch/alpha/kernel/core_marvel.c.
1475 io_delay= [X86] I/O delay method
1477 Standard port 0x80 based delay
1479 Alternate port 0xed based delay (needed on some systems)
1481 Simple two microseconds delay
1486 See Documentation/filesystems/nfs/nfsroot.txt.
1489 When an interrupt is not handled search all handlers
1490 for it. Intended to get systems with badly broken
1494 When an interrupt is not handled search all handlers
1495 for it. Also check all handlers each timer
1496 interrupt. Intended to get systems with badly broken
1500 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1502 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1504 <cpu number>,...,<cpu number>
1506 <cpu number>-<cpu number>
1507 (must be a positive range in ascending order)
1509 <cpu number>,...,<cpu number>-<cpu number>
1511 This option can be used to specify one or more CPUs
1512 to isolate from the general SMP balancing and scheduling
1513 algorithms. You can move a process onto or off an
1514 "isolated" CPU via the CPU affinity syscalls or cpuset.
1515 <cpu number> begins at 0 and the maximum value is
1516 "number of CPUs in system - 1".
1518 This option is the preferred way to isolate CPUs. The
1519 alternative -- manually setting the CPU mask of all
1520 tasks in the system -- can cause problems and
1521 suboptimal load balancer performance.
1525 ivrs_ioapic [HW,X86_64]
1526 Provide an override to the IOAPIC-ID<->DEVICE-ID
1527 mapping provided in the IVRS ACPI table. For
1528 example, to map IOAPIC-ID decimal 10 to
1529 PCI device 00:14.0 write the parameter as:
1530 ivrs_ioapic[10]=00:14.0
1532 ivrs_hpet [HW,X86_64]
1533 Provide an override to the HPET-ID<->DEVICE-ID
1534 mapping provided in the IVRS ACPI table. For
1535 example, to map HPET-ID decimal 0 to
1536 PCI device 00:14.0 write the parameter as:
1537 ivrs_hpet[0]=00:14.0
1539 js= [HW,JOY] Analog joystick
1540 See Documentation/input/joystick.txt.
1543 Enable/disable kernel and module base offset ASLR
1544 (Address Space Layout Randomization) if built into
1545 the kernel. When CONFIG_HIBERNATION is selected,
1546 kASLR is disabled by default. When kASLR is enabled,
1547 hibernation will be disabled.
1551 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1552 specifies the amount of memory usable by the kernel
1553 for non-movable allocations. The requested amount is
1554 spread evenly throughout all nodes in the system. The
1555 remaining memory in each node is used for Movable
1556 pages. In the event, a node is too small to have both
1557 kernelcore and Movable pages, kernelcore pages will
1558 take priority and other nodes will have a larger number
1559 of Movable pages. The Movable zone is used for the
1560 allocation of pages that may be reclaimed or moved
1561 by the page migration subsystem. This means that
1562 HugeTLB pages may not be allocated from this zone.
1563 Note that allocations like PTEs-from-HighMem still
1564 use the HighMem zone if it exists, and the Normal
1565 zone if it does not.
1567 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1568 Format: <Controller#>[,poll interval]
1569 The controller # is the number of the ehci usb debug
1570 port as it is probed via PCI. The poll interval is
1571 optional and is the number seconds in between
1572 each poll cycle to the debug port in case you need
1573 the functionality for interrupting the kernel with
1574 gdb or control-c on the dbgp connection. When
1575 not using this parameter you use sysrq-g to break into
1576 the kernel debugger.
1578 kgdboc= [KGDB,HW] kgdb over consoles.
1579 Requires a tty driver that supports console polling,
1580 or a supported polling keyboard driver (non-usb).
1581 Serial only format: <serial_device>[,baud]
1582 keyboard only format: kbd
1583 keyboard and serial format: kbd,<serial_device>[,baud]
1584 Optional Kernel mode setting:
1585 kms, kbd format: kms,kbd
1586 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1588 kgdbwait [KGDB] Stop kernel execution and enter the
1589 kernel debugger at the earliest opportunity.
1591 kmac= [MIPS] korina ethernet MAC address.
1592 Configure the RouterBoard 532 series on-chip
1593 Ethernet adapter MAC address.
1595 kmemleak= [KNL] Boot-time kmemleak enable/disable
1596 Valid arguments: on, off
1598 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1601 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1602 Valid arguments: 0, 1, 2
1603 kmemcheck=0 (disabled)
1604 kmemcheck=1 (enabled)
1605 kmemcheck=2 (one-shot mode)
1606 Default: 2 (one-shot mode)
1608 kstack=N [X86] Print N words from the kernel stack
1611 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1612 Default is 0 (don't ignore, but inject #GP)
1614 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1618 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1619 Default is 1 (enabled)
1621 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1623 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1625 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1626 (virtualized MMU) support on capable Intel chips.
1627 Default is 1 (enabled)
1629 kvm-intel.emulate_invalid_guest_state=
1630 [KVM,Intel] Enable emulation of invalid guest states
1631 Default is 0 (disabled)
1633 kvm-intel.flexpriority=
1634 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1635 Default is 1 (enabled)
1638 [KVM,Intel] Enable VMX nesting (nVMX).
1639 Default is 0 (disabled)
1641 kvm-intel.unrestricted_guest=
1642 [KVM,Intel] Disable unrestricted guest feature
1643 (virtualized real and unpaged mode) on capable
1644 Intel chips. Default is 1 (enabled)
1646 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1647 feature (tagged TLBs) on capable Intel chips.
1648 Default is 1 (enabled)
1654 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1657 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1658 value for LAPIC timer one-shot implementation. Default
1659 back to the programmable timer unit in the LAPIC.
1661 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1664 libata.dma= [LIBATA] DMA control
1665 libata.dma=0 Disable all PATA and SATA DMA
1666 libata.dma=1 PATA and SATA Disk DMA only
1667 libata.dma=2 ATAPI (CDROM) DMA only
1668 libata.dma=4 Compact Flash DMA only
1669 Combinations also work, so libata.dma=3 enables DMA
1670 for disks and CDROMs, but not CFs.
1672 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1673 libata.ignore_hpa=0 keep BIOS limits (default)
1674 libata.ignore_hpa=1 ignore limits, using full disk
1676 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1680 libata.force= [LIBATA] Force configurations. The format is comma
1681 separated list of "[ID:]VAL" where ID is
1682 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1683 matching port, link or device. Basically, it matches
1684 the ATA ID string printed on console by libata. If
1685 the whole ID part is omitted, the last PORT and DEVICE
1686 values are used. If ID hasn't been specified yet, the
1687 configuration applies to all ports, links and devices.
1689 If only DEVICE is omitted, the parameter applies to
1690 the port and all links and devices behind it. DEVICE
1691 number of 0 either selects the first device or the
1692 first fan-out link behind PMP device. It does not
1693 select the host link. DEVICE number of 15 selects the
1694 host link and device attached to it.
1696 The VAL specifies the configuration to force. As long
1697 as there's no ambiguity shortcut notation is allowed.
1698 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1699 The following configurations can be forced.
1701 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1702 Any ID with matching PORT is used.
1704 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1706 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1707 udma[/][16,25,33,44,66,100,133] notation is also
1710 * [no]ncq: Turn on or off NCQ.
1712 * nohrst, nosrst, norst: suppress hard, soft
1715 * rstonce: only attempt one reset during
1716 hot-unplug link recovery
1718 * dump_id: dump IDENTIFY data.
1720 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1722 * disable: Disable this device.
1724 If there are multiple matching configurations changing
1725 the same attribute, the last one is used.
1727 memblock=debug [KNL] Enable memblock debug messages.
1729 load_ramdisk= [RAM] List of ramdisks to load from floppy
1730 See Documentation/blockdev/ramdisk.txt.
1732 lockd.nlm_grace_period=P [NFS] Assign grace period.
1735 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1738 lockd.nlm_timeout=T [NFS] Assign timeout value.
1741 lockd.nlm_udpport=M [NFS] Assign UDP port.
1744 locktorture.nreaders_stress= [KNL]
1745 Set the number of locking read-acquisition kthreads.
1746 Defaults to being automatically set based on the
1747 number of online CPUs.
1749 locktorture.nwriters_stress= [KNL]
1750 Set the number of locking write-acquisition kthreads.
1752 locktorture.onoff_holdoff= [KNL]
1753 Set time (s) after boot for CPU-hotplug testing.
1755 locktorture.onoff_interval= [KNL]
1756 Set time (s) between CPU-hotplug operations, or
1757 zero to disable CPU-hotplug testing.
1759 locktorture.shuffle_interval= [KNL]
1760 Set task-shuffle interval (jiffies). Shuffling
1761 tasks allows some CPUs to go into dyntick-idle
1762 mode during the locktorture test.
1764 locktorture.shutdown_secs= [KNL]
1765 Set time (s) after boot system shutdown. This
1766 is useful for hands-off automated testing.
1768 locktorture.stat_interval= [KNL]
1769 Time (s) between statistics printk()s.
1771 locktorture.stutter= [KNL]
1772 Time (s) to stutter testing, for example,
1773 specifying five seconds causes the test to run for
1774 five seconds, wait for five seconds, and so on.
1775 This tests the locking primitive's ability to
1776 transition abruptly to and from idle.
1778 locktorture.torture_runnable= [BOOT]
1779 Start locktorture running at boot time.
1781 locktorture.torture_type= [KNL]
1782 Specify the locking implementation to test.
1784 locktorture.verbose= [KNL]
1785 Enable additional printk() statements.
1787 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1790 loglevel= All Kernel Messages with a loglevel smaller than the
1791 console loglevel will be printed to the console. It can
1792 also be changed with klogd or other programs. The
1793 loglevels are defined as follows:
1795 0 (KERN_EMERG) system is unusable
1796 1 (KERN_ALERT) action must be taken immediately
1797 2 (KERN_CRIT) critical conditions
1798 3 (KERN_ERR) error conditions
1799 4 (KERN_WARNING) warning conditions
1800 5 (KERN_NOTICE) normal but significant condition
1801 6 (KERN_INFO) informational
1802 7 (KERN_DEBUG) debug-level messages
1804 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1805 in bytes. n must be a power of two and greater
1806 than the minimal size. The minimal size is defined
1807 by LOG_BUF_SHIFT kernel config parameter. There is
1808 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1809 that allows to increase the default size depending on
1810 the number of CPUs. See init/Kconfig for more details.
1812 logo.nologo [FB] Disables display of the built-in Linux logo.
1813 This may be used to provide more screen space for
1814 kernel log messages and is useful when debugging
1815 kernel boot problems.
1817 lp=0 [LP] Specify parallel ports to use, e.g,
1818 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1819 lp=reset first parallel port). 'lp=0' disables the
1820 lp=auto printer driver. 'lp=reset' (which can be
1821 specified in addition to the ports) causes
1822 attached printers to be reset. Using
1823 lp=port1,port2,... specifies the parallel ports
1824 to associate lp devices with, starting with
1825 lp0. A port specification may be 'none' to skip
1826 that lp device, or a parport name such as
1827 'parport0'. Specifying 'lp=auto' instead of a
1828 port specification list means that device IDs
1829 from each port should be examined, to see if
1830 an IEEE 1284-compliant printer is attached; if
1831 so, the driver will manage that printer.
1832 See also header of drivers/char/lp.c.
1835 Sets loops_per_jiffy to given constant, thus avoiding
1836 time-consuming boot-time autodetection (up to 250 ms per
1837 CPU). 0 enables autodetection (default). To determine
1838 the correct value for your kernel, boot with normal
1839 autodetection and see what value is printed. Note that
1840 on SMP systems the preset will be applied to all CPUs,
1841 which is likely to cause problems if your CPUs need
1842 significantly divergent settings. An incorrect value
1843 will cause delays in the kernel to be wrong, leading to
1844 unpredictable I/O errors and other breakage. Although
1845 unlikely, in the extreme case this might damage your
1849 Format: <io>,<irq>,<dma>
1851 machvec= [IA-64] Force the use of a particular machine-vector
1852 (machvec) in a generic kernel.
1853 Example: machvec=hpzx1_swiotlb
1855 machtype= [Loongson] Share the same kernel image file between different
1857 Example: machtype=lemote-yeeloong-2f-7inch
1859 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1860 than or equal to this physical address is ignored.
1862 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1863 should make use of. maxcpus=n : n >= 0 limits the
1864 kernel to using 'n' processors. n=0 is a special case,
1865 it is equivalent to "nosmp", which also disables
1868 max_loop= [LOOP] The number of loop block devices that get
1869 (loop.max_loop) unconditionally pre-created at init time. The default
1870 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1871 of statically allocating a predefined number, loop
1872 devices can be requested on-demand with the
1873 /dev/loop-control interface.
1875 mce [X86-32] Machine Check Exception
1877 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1879 md= [HW] RAID subsystems devices and level
1880 See Documentation/md.txt.
1883 Format: <first>,<last>
1884 Specifies range of consoles to be captured by the MDA.
1886 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1887 Amount of memory to be used when the kernel is not able
1888 to see the whole system memory or for test.
1889 [X86] Work as limiting max address. Use together
1890 with memmap= to avoid physical address space collisions.
1891 Without memmap= PCI devices could be placed at addresses
1892 belonging to unused RAM.
1894 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1898 [KNL,SH] Allow user to override the default size for
1899 per-device physically contiguous DMA buffers.
1901 memmap=exactmap [KNL,X86] Enable setting of an exact
1902 E820 memory map, as specified by the user.
1903 Such memmap=exactmap lines can be constructed based on
1904 BIOS output or other requirements. See the memmap=nn@ss
1907 memmap=nn[KMG]@ss[KMG]
1908 [KNL] Force usage of a specific region of memory.
1909 Region of memory to be used is from ss to ss+nn.
1911 memmap=nn[KMG]#ss[KMG]
1912 [KNL,ACPI] Mark specific memory as ACPI data.
1913 Region of memory to be marked is from ss to ss+nn.
1915 memmap=nn[KMG]$ss[KMG]
1916 [KNL,ACPI] Mark specific memory as reserved.
1917 Region of memory to be reserved is from ss to ss+nn.
1918 Example: Exclude memory from 0x18690000-0x1869ffff
1919 memmap=64K$0x18690000
1921 memmap=0x10000$0x18690000
1923 memory_corruption_check=0/1 [X86]
1924 Some BIOSes seem to corrupt the first 64k of
1925 memory when doing things like suspend/resume.
1926 Setting this option will scan the memory
1927 looking for corruption. Enabling this will
1928 both detect corruption and prevent the kernel
1929 from using the memory being corrupted.
1930 However, its intended as a diagnostic tool; if
1931 repeatable BIOS-originated corruption always
1932 affects the same memory, you can use memmap=
1933 to prevent the kernel from using that memory.
1935 memory_corruption_check_size=size [X86]
1936 By default it checks for corruption in the low
1937 64k, making this memory unavailable for normal
1938 use. Use this parameter to scan for
1939 corruption in more or less memory.
1941 memory_corruption_check_period=seconds [X86]
1942 By default it checks for corruption every 60
1943 seconds. Use this parameter to check at some
1944 other rate. 0 disables periodic checking.
1946 memtest= [KNL,X86] Enable memtest
1948 default : 0 <disable>
1949 Specifies the number of memtest passes to be
1950 performed. Each pass selects another test
1951 pattern from a given set of patterns. Memtest
1952 fills the memory with this pattern, validates
1953 memory contents and reserves bad memory
1954 regions that are detected.
1956 meye.*= [HW] Set MotionEye Camera parameters
1957 See Documentation/video4linux/meye.txt.
1959 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1960 Multi-Function General Purpose Timers on AMD Geode
1963 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1964 the BIOS has incorrectly applied a workaround. TinyBIOS
1965 version 0.98 is known to be affected, 0.99 fixes the
1966 problem by letting the user disable the workaround.
1970 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1971 physical address is ignored.
1973 mini2440= [ARM,HW,KNL]
1974 Format:[0..2][b][c][t]
1976 MINI2440 configuration specification:
1977 0 - The attached screen is the 3.5" TFT
1978 1 - The attached screen is the 7" TFT
1979 2 - The VGA Shield is attached (1024x768)
1980 Leaving out the screen size parameter will not load
1981 the TFT driver, and the framebuffer will be left
1983 b - Enable backlight. The TFT backlight pin will be
1984 linked to the kernel VESA blanking code and a GPIO
1985 LED. This parameter is not necessary when using the
1987 c - Enable the s3c camera interface.
1988 t - Reserved for enabling touchscreen support. The
1989 touchscreen support is not enabled in the mainstream
1990 kernel as of 2.6.30, a preliminary port can be found
1991 in the "bleeding edge" mini2440 support kernel at
1992 http://repo.or.cz/w/linux-2.6/mini2440.git
1995 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1996 parameter allows control of the logging verbosity for
1997 the additional memory initialisation checks. A value
1998 of 0 disables mminit logging and a level of 4 will
1999 log everything. Information is printed at KERN_DEBUG
2000 so loglevel=8 may also need to be specified.
2003 [KNL] When CONFIG_MODULE_SIG is set, this means that
2004 modules without (valid) signatures will fail to load.
2005 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2006 is always true, so this option does nothing.
2009 [MOUSE] Maximum time between finger touching and
2010 leaving touchpad surface for touch to be considered
2011 a tap and be reported as a left button click (for
2012 touchpads working in absolute mode only).
2014 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2015 reporting absolute coordinates, such as tablets
2016 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2017 reporting absolute coordinates, such as tablets
2019 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2020 is similar to kernelcore except it specifies the
2021 amount of memory used for migratable allocations.
2022 If both kernelcore and movablecore is specified,
2023 then kernelcore will be at *least* the specified
2024 value but may be more. If movablecore on its own
2025 is specified, the administrator must be careful
2026 that the amount of memory usable for all allocations
2029 movable_node [KNL,X86] Boot-time switch to enable the effects
2030 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2032 MTD_Partition= [MTD]
2033 Format: <name>,<region-number>,<size>,<offset>
2035 MTD_Region= [MTD] Format:
2036 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2039 See drivers/mtd/cmdlinepart.c.
2041 multitce=off [PPC] This parameter disables the use of the pSeries
2042 firmware feature for updating multiple TCE entries
2045 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2047 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2049 boundary - index of last SLC block on Flex-OneNAND.
2050 The remaining blocks are configured as MLC blocks.
2051 lock - Configure if Flex-OneNAND boundary should be locked.
2052 Once locked, the boundary cannot be changed.
2053 1 indicates lock status, 0 indicates unlock status.
2056 ARM/S3C2412 JIVE boot control
2058 See arch/arm/mach-s3c2412/mach-jive.c
2060 mtouchusb.raw_coordinates=
2061 [HW] Make the MicroTouch USB driver use raw coordinates
2062 ('y', default) or cooked coordinates ('n')
2064 mtrr_chunk_size=nn[KMG] [X86]
2065 used for mtrr cleanup. It is largest continuous chunk
2066 that could hold holes aka. UC entries.
2068 mtrr_gran_size=nn[KMG] [X86]
2069 Used for mtrr cleanup. It is granularity of mtrr block.
2071 Large value could prevent small alignment from
2074 mtrr_spare_reg_nr=n [X86]
2076 Range: 0,7 : spare reg number
2078 Used for mtrr cleanup. It is spare mtrr entries number.
2079 Set to 2 or more if your graphical card needs more.
2081 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2083 netdev= [NET] Network devices parameters
2084 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2085 Note that mem_start is often overloaded to mean
2086 something different and driver-specific.
2087 This usage is only documented in each driver source
2091 [NETFILTER] Enable connection tracking flow accounting
2092 0 to disable accounting
2093 1 to enable accounting
2096 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2097 See Documentation/filesystems/nfs/nfsroot.txt.
2099 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2100 See Documentation/filesystems/nfs/nfsroot.txt.
2102 nfsrootdebug [NFS] enable nfsroot debugging messages.
2103 See Documentation/filesystems/nfs/nfsroot.txt.
2105 nfs.callback_tcpport=
2106 [NFS] set the TCP port on which the NFSv4 callback
2107 channel should listen.
2110 [NFS] sets the pathname to the program which is used
2111 to update the NFS client cache entries.
2113 nfs.cache_getent_timeout=
2114 [NFS] sets the timeout after which an attempt to
2115 update a cache entry is deemed to have failed.
2117 nfs.idmap_cache_timeout=
2118 [NFS] set the maximum lifetime for idmapper cache
2122 [NFS] enable 64-bit inode numbers.
2123 If zero, the NFS client will fake up a 32-bit inode
2124 number for the readdir() and stat() syscalls instead
2125 of returning the full 64-bit number.
2126 The default is to return 64-bit inode numbers.
2128 nfs.max_session_slots=
2129 [NFSv4.1] Sets the maximum number of session slots
2130 the client will attempt to negotiate with the server.
2131 This limits the number of simultaneous RPC requests
2132 that the client can send to the NFSv4.1 server.
2133 Note that there is little point in setting this
2134 value higher than the max_tcp_slot_table_limit.
2136 nfs.nfs4_disable_idmapping=
2137 [NFSv4] When set to the default of '1', this option
2138 ensures that both the RPC level authentication
2139 scheme and the NFS level operations agree to use
2140 numeric uids/gids if the mount is using the
2141 'sec=sys' security flavour. In effect it is
2142 disabling idmapping, which can make migration from
2143 legacy NFSv2/v3 systems to NFSv4 easier.
2144 Servers that do not support this mode of operation
2145 will be autodetected by the client, and it will fall
2146 back to using the idmapper.
2147 To turn off this behaviour, set the value to '0'.
2149 [NFS4] Specify an additional fixed unique ident-
2150 ification string that NFSv4 clients can insert into
2151 their nfs_client_id4 string. This is typically a
2152 UUID that is generated at system install time.
2154 nfs.send_implementation_id =
2155 [NFSv4.1] Send client implementation identification
2156 information in exchange_id requests.
2157 If zero, no implementation identification information
2159 The default is to send the implementation identification
2162 nfs.recover_lost_locks =
2163 [NFSv4] Attempt to recover locks that were lost due
2164 to a lease timeout on the server. Please note that
2165 doing this risks data corruption, since there are
2166 no guarantees that the file will remain unchanged
2167 after the locks are lost.
2168 If you want to enable the kernel legacy behaviour of
2169 attempting to recover these locks, then set this
2171 The default parameter value of '0' causes the kernel
2172 not to attempt recovery of lost locks.
2174 nfsd.nfs4_disable_idmapping=
2175 [NFSv4] When set to the default of '1', the NFSv4
2176 server will return only numeric uids and gids to
2177 clients using auth_sys, and will accept numeric uids
2178 and gids from such clients. This is intended to ease
2179 migration from NFSv2/v3.
2181 objlayoutdriver.osd_login_prog=
2182 [NFS] [OBJLAYOUT] sets the pathname to the program which
2183 is used to automatically discover and login into new
2184 osd-targets. Please see:
2185 Documentation/filesystems/pnfs.txt for more explanations
2187 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2188 when a NMI is triggered.
2189 Format: [state][,regs][,debounce][,die]
2191 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2192 Format: [panic,][nopanic,][num]
2194 0 - turn nmi_watchdog off
2195 When panic is specified, panic when an NMI watchdog
2196 timeout occurs (or 'nopanic' to override the opposite
2198 This is useful when you use a panic=... timeout and
2199 need the box quickly up again.
2201 netpoll.carrier_timeout=
2202 [NET] Specifies amount of time (in seconds) that
2203 netpoll should wait for a carrier. By default netpoll
2206 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2207 emulation library even if a 387 maths coprocessor
2211 [HW] Never suspend the console
2212 Disable suspending of consoles during suspend and
2213 hibernate operations. Once disabled, debugging
2214 messages can reach various consoles while the rest
2215 of the system is being put to sleep (ie, while
2216 debugging driver suspend/resume hooks). This may
2217 not work reliably with all consoles, but is known
2218 to work with serial and VGA consoles.
2219 To facilitate more flexible debugging, we also add
2220 console_suspend, a printk module parameter to control
2221 it. Users could use console_suspend (usually
2222 /sys/module/printk/parameters/console_suspend) to
2223 turn on/off it dynamically.
2225 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2226 caches in the slab allocator. Saves per-node memory,
2227 but will impact performance.
2231 noapic [SMP,APIC] Tells the kernel to not make use of any
2232 IOAPICs that may be present in the system.
2234 noautogroup Disable scheduler automatic task group creation.
2236 nobats [PPC] Do not use BATs for mapping kernel lowmem
2237 on "Classic" PPC cores.
2241 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2243 nodelayacct [KNL] Disable per-task delay accounting
2245 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2247 nodsp [SH] Disable hardware DSP at boot time.
2249 noefi [X86] Disable EFI runtime services support.
2254 On X86-32 available only on PAE configured kernels.
2255 noexec=on: enable non-executable mappings (default)
2256 noexec=off: disable non-executable mappings
2259 Disable SMAP (Supervisor Mode Access Prevention)
2260 even if it is supported by processor.
2263 Disable SMEP (Supervisor Mode Execution Prevention)
2264 even if it is supported by processor.
2267 This affects only 32-bit executables.
2268 noexec32=on: enable non-executable mappings (default)
2269 read doesn't imply executable mappings
2270 noexec32=off: disable non-executable mappings
2271 read implies executable mappings
2273 nofpu [SH] Disable hardware FPU at boot time.
2275 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2276 register save and restore. The kernel will only save
2277 legacy floating-point registers on task switch.
2279 noxsave [BUGS=X86] Disables x86 extended register state save
2280 and restore using xsave. The kernel will fallback to
2281 enabling legacy floating-point and sse state.
2283 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2284 register states. The kernel will fall back to use
2285 xsave to save the states. By using this parameter,
2286 performance of saving the states is degraded because
2287 xsave doesn't support modified optimization while
2288 xsaveopt supports it on xsaveopt enabled systems.
2290 noxsaves [X86] Disables xsaves and xrstors used in saving and
2291 restoring x86 extended register state in compacted
2292 form of xsave area. The kernel will fall back to use
2293 xsaveopt and xrstor to save and restore the states
2294 in standard form of xsave area. By using this
2295 parameter, xsave area per process might occupy more
2296 memory on xsaves enabled systems.
2299 on enable eager fpu restore
2300 off disable eager fpu restore
2301 auto selects the default scheme, which automatically
2302 enables eagerfpu restore for xsaveopt.
2304 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2305 wfi(ARM) instruction doesn't work correctly and not to
2306 use it. This is also useful when using JTAG debugger.
2308 no_file_caps Tells the kernel not to honor file capabilities. The
2309 only way then for a file to be executed with privilege
2310 is to be setuid root or executed by root.
2312 nohalt [IA-64] Tells the kernel not to use the power saving
2313 function PAL_HALT_LIGHT when idle. This increases
2314 power-consumption. On the positive side, it reduces
2315 interrupt wake-up latency, which may improve performance
2316 in certain environments such as networked servers or
2319 nohibernate [HIBERNATION] Disable hibernation and resume.
2321 nohz= [KNL] Boottime enable/disable dynamic ticks
2322 Valid arguments: on, off
2325 nohz_full= [KNL,BOOT]
2326 In kernels built with CONFIG_NO_HZ_FULL=y, set
2327 the specified list of CPUs whose tick will be stopped
2328 whenever possible. The boot CPU will be forced outside
2329 the range to maintain the timekeeping.
2330 The CPUs in this range must also be included in the
2333 noiotrap [SH] Disables trapped I/O port accesses.
2335 noirqdebug [X86-32] Disables the code which attempts to detect and
2336 disable unhandled interrupt sources.
2338 no_timer_check [X86,APIC] Disables the code which tests for
2339 broken timer IRQ sources.
2341 noisapnp [ISAPNP] Disables ISA PnP code.
2343 noinitrd [RAM] Tells the kernel not to load any configured
2346 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2348 [Deprecated - use intremap=off]
2352 nojitter [IA-64] Disables jitter checking for ITC timers.
2354 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2356 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2359 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2360 steal time is computed, but won't influence scheduler
2363 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2365 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2367 noltlbs [PPC] Do not use large page/tlb entries for kernel
2368 lowmem mapping on PPC40x.
2370 nomca [IA-64] Disable machine check abort handling
2372 nomce [X86-32] Machine Check Exception
2374 nomfgpt [X86-32] Disable Multi-Function General Purpose
2375 Timer usage (for AMD Geode machines).
2377 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2378 shutdown the other cpus. Instead use the REBOOT_VECTOR
2381 nomodule Disable module load
2383 nopat [X86] Disable PAT (page attribute table extension of
2384 pagetables) support.
2386 norandmaps Don't use address space randomization. Equivalent to
2387 echo 0 > /proc/sys/kernel/randomize_va_space
2389 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2391 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2392 with UP alternatives
2394 nordrand [X86] Disable kernel use of the RDRAND and
2395 RDSEED instructions even if they are supported
2396 by the processor. RDRAND and RDSEED are still
2397 available to user space applications.
2399 noresume [SWSUSP] Disables resume and restores original swap
2402 no-scroll [VGA] Disables scrollback.
2403 This is required for the Braillex ib80-piezo Braille
2404 reader made by F.H. Papenmeier (Germany).
2408 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2410 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2411 and disable the IO APIC. legacy for "maxcpus=0".
2413 nosoftlockup [KNL] Disable the soft-lockup detector.
2415 nosync [HW,M68K] Disables sync negotiation for all devices.
2417 notsc [BUGS=X86-32] Disable Time Stamp Counter
2419 nousb [USB] Disable the USB subsystem
2421 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2425 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2427 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2428 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2429 Some features depend on CPU0. Known dependencies are:
2430 1. Resume from suspend/hibernate depends on CPU0.
2431 Suspend/hibernate will fail if CPU0 is offline and you
2432 need to online CPU0 before suspend/hibernate.
2433 2. PIC interrupts also depend on CPU0. CPU0 can't be
2434 removed if a PIC interrupt is detected.
2435 It's said poweroff/reboot may depend on CPU0 on some
2436 machines although I haven't seen such issues so far
2437 after CPU0 is offline on a few tested machines.
2438 If the dependencies are under your control, you can
2439 turn on cpu0_hotplug.
2441 nptcg= [IA-64] Override max number of concurrent global TLB
2442 purges which is reported from either PAL_VM_SUMMARY or
2445 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2446 could support. nr_cpus=n : n >= 1 limits the kernel to
2447 supporting 'n' processors. Later in runtime you can not
2448 use hotplug cpu feature to put more cpu back to online.
2449 just like you compile the kernel NR_CPUS=n
2451 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2453 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2454 Allowed values are enable and disable
2456 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2457 one of ['zone', 'node', 'default'] can be specified
2458 This can be set from sysctl after boot.
2459 See Documentation/sysctl/vm.txt for details.
2461 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2462 See Documentation/debugging-via-ohci1394.txt for more
2465 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2466 Rather than timing out after 20 ms if an EC
2467 command is not properly ACKed, override the length
2468 of the timeout. We have interrupts disabled while
2469 waiting for the ACK, so if this is set too high
2470 interrupts *may* be lost!
2472 omap_mux= [OMAP] Override bootloader pin multiplexing.
2473 Format: <mux_mode0.mode_name=value>...
2474 For example, to override I2C bus2:
2475 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2477 oprofile.timer= [HW]
2478 Use timer interrupt instead of performance counters
2480 oprofile.cpu_type= Force an oprofile cpu type
2481 This might be useful if you have an older oprofile
2482 userland or if you want common events.
2483 Format: { arch_perfmon }
2484 arch_perfmon: [X86] Force use of architectural
2485 perfmon on Intel CPUs instead of the
2486 CPU specific event set.
2487 timer: [X86] Force use of architectural NMI
2488 timer mode (see also oprofile.timer
2489 for generic hr timer mode)
2490 [s390] Force legacy basic mode sampling
2491 (report cpu_type "timer")
2493 oops=panic Always panic on oopses. Default is to just kill the
2494 process, but there is a small probability of
2495 deadlocking the machine.
2496 This will also cause panics on machine check exceptions.
2497 Useful together with panic=30 to trigger a reboot.
2500 See Documentation/sound/oss/oss-parameters.txt
2502 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2503 timeout > 0: seconds before rebooting
2504 timeout = 0: wait forever
2505 timeout < 0: reboot immediately
2508 crash_kexec_post_notifiers
2509 Run kdump after running panic-notifiers and dumping
2510 kmsg. This only for the users who doubt kdump always
2511 succeeds in any situation.
2512 Note that this also increases risks of kdump failure,
2513 because some panic notifiers can make the crashed
2514 kernel more unstable.
2516 parkbd.port= [HW] Parallel port number the keyboard adapter is
2517 connected to, default is 0.
2519 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2520 0 for XT, 1 for AT (default is AT).
2523 parport= [HW,PPT] Specify parallel ports. 0 disables.
2524 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2525 Use 'auto' to force the driver to use any
2526 IRQ/DMA settings detected (the default is to
2527 ignore detected IRQ/DMA settings because of
2528 possible conflicts). You can specify the base
2529 address, IRQ, and DMA settings; IRQ and DMA
2530 should be numbers, or 'auto' (for using detected
2531 settings on that particular port), or 'nofifo'
2532 (to avoid using a FIFO even if it is detected).
2533 Parallel ports are assigned in the order they
2534 are specified on the command line, starting
2537 parport_init_mode= [HW,PPT]
2538 Configure VIA parallel port to operate in
2539 a specific mode. This is necessary on Pegasos
2540 computer where firmware has no options for setting
2541 up parallel port mode and sets it to spp.
2542 Currently this function knows 686a and 8231 chips.
2543 Format: [spp|ps2|epp|ecp|ecpepp]
2546 Halt all CPUs after the first oops has been printed for
2547 the specified number of seconds. This is to be used if
2548 your oopses keep scrolling off the screen.
2553 See header of drivers/block/paride/pcd.c.
2554 See also Documentation/blockdev/paride.txt.
2556 pci=option[,option...] [PCI] various PCI subsystem options:
2557 earlydump [X86] dump PCI config space before the kernel
2559 off [X86] don't probe for the PCI bus
2560 bios [X86-32] force use of PCI BIOS, don't access
2561 the hardware directly. Use this if your machine
2562 has a non-standard PCI host bridge.
2563 nobios [X86-32] disallow use of PCI BIOS, only direct
2564 hardware access methods are allowed. Use this
2565 if you experience crashes upon bootup and you
2566 suspect they are caused by the BIOS.
2567 conf1 [X86] Force use of PCI Configuration
2569 conf2 [X86] Force use of PCI Configuration
2571 noaer [PCIE] If the PCIEAER kernel config parameter is
2572 enabled, this kernel boot option can be used to
2573 disable the use of PCIE advanced error reporting.
2574 nodomains [PCI] Disable support for multiple PCI
2575 root domains (aka PCI segments, in ACPI-speak).
2576 nommconf [X86] Disable use of MMCONFIG for PCI
2578 check_enable_amd_mmconf [X86] check for and enable
2579 properly configured MMIO access to PCI
2580 config space on AMD family 10h CPU
2581 nomsi [MSI] If the PCI_MSI kernel config parameter is
2582 enabled, this kernel boot option can be used to
2583 disable the use of MSI interrupts system-wide.
2584 noioapicquirk [APIC] Disable all boot interrupt quirks.
2585 Safety option to keep boot IRQs enabled. This
2586 should never be necessary.
2587 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2588 primary IO-APIC for bridges that cannot disable
2589 boot IRQs. This fixes a source of spurious IRQs
2590 when the system masks IRQs.
2591 noioapicreroute [APIC] Disable workaround that uses the
2592 boot IRQ equivalent of an IRQ that connects to
2593 a chipset where boot IRQs cannot be disabled.
2594 The opposite of ioapicreroute.
2595 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2596 routing table. These calls are known to be buggy
2597 on several machines and they hang the machine
2598 when used, but on other computers it's the only
2599 way to get the interrupt routing table. Try
2600 this option if the kernel is unable to allocate
2601 IRQs or discover secondary PCI buses on your
2603 rom [X86] Assign address space to expansion ROMs.
2604 Use with caution as certain devices share
2605 address decoders between ROMs and other
2607 norom [X86] Do not assign address space to
2608 expansion ROMs that do not already have
2609 BIOS assigned address ranges.
2610 nobar [X86] Do not assign address space to the
2611 BARs that weren't assigned by the BIOS.
2612 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2613 assigned automatically to PCI devices. You can
2614 make the kernel exclude IRQs of your ISA cards
2616 pirqaddr=0xAAAAA [X86] Specify the physical address
2617 of the PIRQ table (normally generated
2618 by the BIOS) if it is outside the
2619 F0000h-100000h range.
2620 lastbus=N [X86] Scan all buses thru bus #N. Can be
2621 useful if the kernel is unable to find your
2622 secondary buses and you want to tell it
2623 explicitly which ones they are.
2624 assign-busses [X86] Always assign all PCI bus
2625 numbers ourselves, overriding
2626 whatever the firmware may have done.
2627 usepirqmask [X86] Honor the possible IRQ mask stored
2628 in the BIOS $PIR table. This is needed on
2629 some systems with broken BIOSes, notably
2630 some HP Pavilion N5400 and Omnibook XE3
2631 notebooks. This will have no effect if ACPI
2632 IRQ routing is enabled.
2633 noacpi [X86] Do not use ACPI for IRQ routing
2634 or for PCI scanning.
2635 use_crs [X86] Use PCI host bridge window information
2636 from ACPI. On BIOSes from 2008 or later, this
2637 is enabled by default. If you need to use this,
2638 please report a bug.
2639 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2640 If you need to use this, please report a bug.
2641 routeirq Do IRQ routing for all PCI devices.
2642 This is normally done in pci_enable_device(),
2643 so this option is a temporary workaround
2644 for broken drivers that don't call it.
2645 skip_isa_align [X86] do not align io start addr, so can
2646 handle more pci cards
2647 firmware [ARM] Do not re-enumerate the bus but instead
2648 just use the configuration from the
2649 bootloader. This is currently used on
2650 IXP2000 systems where the bus has to be
2651 configured a certain way for adjunct CPUs.
2652 noearly [X86] Don't do any early type 1 scanning.
2653 This might help on some broken boards which
2654 machine check when some devices' config space
2655 is read. But various workarounds are disabled
2656 and some IOMMU drivers will not work.
2657 bfsort Sort PCI devices into breadth-first order.
2658 This sorting is done to get a device
2659 order compatible with older (<= 2.4) kernels.
2660 nobfsort Don't sort PCI devices into breadth-first order.
2661 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2662 tuning and use the BIOS-configured MPS defaults.
2663 pcie_bus_safe Set every device's MPS to the largest value
2664 supported by all devices below the root complex.
2665 pcie_bus_perf Set device MPS to the largest allowable MPS
2666 based on its parent bus. Also set MRRS (Max
2667 Read Request Size) to the largest supported
2668 value (no larger than the MPS that the device
2669 or bus can support) for best performance.
2670 pcie_bus_peer2peer Set every device's MPS to 128B, which
2671 every device is guaranteed to support. This
2672 configuration allows peer-to-peer DMA between
2673 any pair of devices, possibly at the cost of
2674 reduced performance. This also guarantees
2675 that hot-added devices will work.
2676 cbiosize=nn[KMG] The fixed amount of bus space which is
2677 reserved for the CardBus bridge's IO window.
2678 The default value is 256 bytes.
2679 cbmemsize=nn[KMG] The fixed amount of bus space which is
2680 reserved for the CardBus bridge's memory
2681 window. The default value is 64 megabytes.
2684 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2685 Specifies alignment and device to reassign
2686 aligned memory resources.
2687 If <order of align> is not specified,
2688 PAGE_SIZE is used as alignment.
2689 PCI-PCI bridge can be specified, if resource
2690 windows need to be expanded.
2691 ecrc= Enable/disable PCIe ECRC (transaction layer
2692 end-to-end CRC checking).
2693 bios: Use BIOS/firmware settings. This is the
2697 hpiosize=nn[KMG] The fixed amount of bus space which is
2698 reserved for hotplug bridge's IO window.
2699 Default size is 256 bytes.
2700 hpmemsize=nn[KMG] The fixed amount of bus space which is
2701 reserved for hotplug bridge's memory window.
2702 Default size is 2 megabytes.
2703 realloc= Enable/disable reallocating PCI bridge resources
2704 if allocations done by BIOS are too small to
2705 accommodate resources required by all child
2707 off: Turn realloc off
2709 realloc same as realloc=on
2710 noari do not use PCIe ARI.
2711 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2712 only look for one device below a PCIe downstream
2715 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2718 force Enable ASPM even on devices that claim not to support it.
2719 WARNING: Forcing ASPM on may cause system lockups.
2721 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2722 nomsi Do not use MSI for PCI Express Native Hotplug (this
2723 makes all PCIe ports use INTx for hotplug services).
2725 pcie_ports= [PCIE] PCIe ports handling:
2726 auto Ask the BIOS whether or not to use native PCIe services
2727 associated with PCIe ports (PME, hot-plug, AER). Use
2728 them only if that is allowed by the BIOS.
2729 native Use native PCIe services associated with PCIe ports
2731 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2734 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2735 nomsi Do not use MSI for native PCIe PME signaling (this makes
2736 all PCIe root ports use INTx for all services).
2738 pcmv= [HW,PCMCIA] BadgePAD 4
2742 Keep all power-domains already enabled by bootloader on,
2743 even if no driver has claimed them. This is useful
2744 for debug and development, but should not be
2745 needed on a platform with proper driver support.
2748 See Documentation/blockdev/paride.txt.
2750 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2753 See arch/parisc/kernel/pdc_chassis.c
2755 percpu_alloc= Select which percpu first chunk allocator to use.
2756 Currently supported values are "embed" and "page".
2757 Archs may support subset or none of the selections.
2758 See comments in mm/percpu.c for details on each
2759 allocator. This parameter is primarily for debugging
2760 and performance comparison.
2763 See Documentation/blockdev/paride.txt.
2766 See Documentation/blockdev/paride.txt.
2768 pirq= [SMP,APIC] Manual mp-table setup
2769 See Documentation/x86/i386/IO-APIC.txt.
2771 plip= [PPT,NET] Parallel port network link
2772 Format: { parport<nr> | timid | 0 }
2773 See also Documentation/parport.txt.
2775 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2776 Override pmtimer IOPort with a hex value.
2780 Enable PNP debug messages (depends on the
2781 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2782 via /sys/module/pnp/parameters/debug. We always show
2783 current resource usage; turning this on also shows
2784 possible settings and some assignment information.
2790 { on | off | curr | res | no-curr | no-res }
2793 [ISAPNP] Exclude IRQs for the autoconfiguration
2796 [ISAPNP] Exclude DMAs for the autoconfiguration
2798 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2799 Ranges are in pairs (I/O port base and size).
2802 [ISAPNP] Exclude memory regions for the
2804 Ranges are in pairs (memory base and size).
2806 ports= [IP_VS_FTP] IPVS ftp helper module
2808 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2810 Format: <port>,<port>....
2812 print-fatal-signals=
2813 [KNL] debug: print fatal signals
2815 If enabled, warn about various signal handling
2816 related application anomalies: too many signals,
2817 too many POSIX.1 timers, fatal signals causing a
2820 If you hit the warning due to signal overflow,
2821 you might want to try "ulimit -i unlimited".
2825 printk.always_kmsg_dump=
2826 Trigger kmsg_dump for cases other than kernel oops or
2828 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2831 printk.time= Show timing data prefixed to each printk message line
2832 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2834 processor.max_cstate= [HW,ACPI]
2835 Limit processor to maximum C-state
2836 max_cstate=9 overrides any DMI blacklist limit.
2838 processor.nocst [HW,ACPI]
2839 Ignore the _CST method to determine C-states,
2840 instead using the legacy FADT method
2842 profile= [KNL] Enable kernel profiling via /proc/profile
2843 Format: [schedule,]<number>
2844 Param: "schedule" - profile schedule points.
2845 Param: <number> - step/bucket size as a power of 2 for
2846 statistical time based profiling.
2847 Param: "sleep" - profile D-state sleeping (millisecs).
2848 Requires CONFIG_SCHEDSTATS
2849 Param: "kvm" - profile VM exits.
2851 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2853 See Documentation/blockdev/ramdisk.txt.
2855 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2856 probe for; one of (bare|imps|exps|lifebook|any).
2857 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2859 psmouse.resetafter= [HW,MOUSE]
2860 Try to reset the device after so many bad packets
2863 [HW,MOUSE] Set desired mouse resolution, in dpi.
2864 psmouse.smartscroll=
2865 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2866 0 = disabled, 1 = enabled (default).
2868 pstore.backend= Specify the name of the pstore backend to use
2871 See Documentation/blockdev/paride.txt.
2874 [KNL] Number of legacy pty's. Overwrites compiled-in
2877 quiet [KNL] Disable most log messages
2882 See Documentation/md.txt.
2884 ramdisk_blocksize= [RAM]
2885 See Documentation/blockdev/ramdisk.txt.
2887 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2888 See Documentation/blockdev/ramdisk.txt.
2891 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2892 the specified list of CPUs to be no-callback CPUs.
2893 Invocation of these CPUs' RCU callbacks will
2894 be offloaded to "rcuox/N" kthreads created for
2895 that purpose, where "x" is "b" for RCU-bh, "p"
2896 for RCU-preempt, and "s" for RCU-sched, and "N"
2897 is the CPU number. This reduces OS jitter on the
2898 offloaded CPUs, which can be useful for HPC and
2899 real-time workloads. It can also improve energy
2900 efficiency for asymmetric multiprocessors.
2903 Rather than requiring that offloaded CPUs
2904 (specified by rcu_nocbs= above) explicitly
2905 awaken the corresponding "rcuoN" kthreads,
2906 make these kthreads poll for callbacks.
2907 This improves the real-time response for the
2908 offloaded CPUs by relieving them of the need to
2909 wake up the corresponding kthread, but degrades
2910 energy efficiency by requiring that the kthreads
2911 periodically wake up to do the polling.
2913 rcutree.blimit= [KNL]
2914 Set maximum number of finished RCU callbacks to
2915 process in one batch.
2917 rcutree.rcu_fanout_leaf= [KNL]
2918 Increase the number of CPUs assigned to each
2919 leaf rcu_node structure. Useful for very large
2922 rcutree.jiffies_till_sched_qs= [KNL]
2923 Set required age in jiffies for a
2924 given grace period before RCU starts
2925 soliciting quiescent-state help from
2926 rcu_note_context_switch().
2928 rcutree.jiffies_till_first_fqs= [KNL]
2929 Set delay from grace-period initialization to
2930 first attempt to force quiescent states.
2931 Units are jiffies, minimum value is zero,
2932 and maximum value is HZ.
2934 rcutree.jiffies_till_next_fqs= [KNL]
2935 Set delay between subsequent attempts to force
2936 quiescent states. Units are jiffies, minimum
2937 value is one, and maximum value is HZ.
2939 rcutree.rcu_nocb_leader_stride= [KNL]
2940 Set the number of NOCB kthread groups, which
2941 defaults to the square root of the number of
2942 CPUs. Larger numbers reduces the wakeup overhead
2943 on the per-CPU grace-period kthreads, but increases
2944 that same overhead on each group's leader.
2946 rcutree.qhimark= [KNL]
2947 Set threshold of queued RCU callbacks beyond which
2948 batch limiting is disabled.
2950 rcutree.qlowmark= [KNL]
2951 Set threshold of queued RCU callbacks below which
2952 batch limiting is re-enabled.
2954 rcutree.rcu_idle_gp_delay= [KNL]
2955 Set wakeup interval for idle CPUs that have
2956 RCU callbacks (RCU_FAST_NO_HZ=y).
2958 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2959 Set wakeup interval for idle CPUs that have
2960 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2961 Lazy RCU callbacks are those which RCU can
2962 prove do nothing more than free memory.
2964 rcutorture.cbflood_inter_holdoff= [KNL]
2965 Set holdoff time (jiffies) between successive
2966 callback-flood tests.
2968 rcutorture.cbflood_intra_holdoff= [KNL]
2969 Set holdoff time (jiffies) between successive
2970 bursts of callbacks within a given callback-flood
2973 rcutorture.cbflood_n_burst= [KNL]
2974 Set the number of bursts making up a given
2975 callback-flood test. Set this to zero to
2976 disable callback-flood testing.
2978 rcutorture.cbflood_n_per_burst= [KNL]
2979 Set the number of callbacks to be registered
2980 in a given burst of a callback-flood test.
2982 rcutorture.fqs_duration= [KNL]
2983 Set duration of force_quiescent_state bursts.
2985 rcutorture.fqs_holdoff= [KNL]
2986 Set holdoff time within force_quiescent_state bursts.
2988 rcutorture.fqs_stutter= [KNL]
2989 Set wait time between force_quiescent_state bursts.
2991 rcutorture.gp_exp= [KNL]
2992 Use expedited update-side primitives.
2994 rcutorture.gp_normal= [KNL]
2995 Use normal (non-expedited) update-side primitives.
2996 If both gp_exp and gp_normal are set, do both.
2997 If neither gp_exp nor gp_normal are set, still
3000 rcutorture.n_barrier_cbs= [KNL]
3001 Set callbacks/threads for rcu_barrier() testing.
3003 rcutorture.nfakewriters= [KNL]
3004 Set number of concurrent RCU writers. These just
3005 stress RCU, they don't participate in the actual
3006 test, hence the "fake".
3008 rcutorture.nreaders= [KNL]
3009 Set number of RCU readers.
3011 rcutorture.object_debug= [KNL]
3012 Enable debug-object double-call_rcu() testing.
3014 rcutorture.onoff_holdoff= [KNL]
3015 Set time (s) after boot for CPU-hotplug testing.
3017 rcutorture.onoff_interval= [KNL]
3018 Set time (s) between CPU-hotplug operations, or
3019 zero to disable CPU-hotplug testing.
3021 rcutorture.torture_runnable= [BOOT]
3022 Start rcutorture running at boot time.
3024 rcutorture.shuffle_interval= [KNL]
3025 Set task-shuffle interval (s). Shuffling tasks
3026 allows some CPUs to go into dyntick-idle mode
3027 during the rcutorture test.
3029 rcutorture.shutdown_secs= [KNL]
3030 Set time (s) after boot system shutdown. This
3031 is useful for hands-off automated testing.
3033 rcutorture.stall_cpu= [KNL]
3034 Duration of CPU stall (s) to test RCU CPU stall
3035 warnings, zero to disable.
3037 rcutorture.stall_cpu_holdoff= [KNL]
3038 Time to wait (s) after boot before inducing stall.
3040 rcutorture.stat_interval= [KNL]
3041 Time (s) between statistics printk()s.
3043 rcutorture.stutter= [KNL]
3044 Time (s) to stutter testing, for example, specifying
3045 five seconds causes the test to run for five seconds,
3046 wait for five seconds, and so on. This tests RCU's
3047 ability to transition abruptly to and from idle.
3049 rcutorture.test_boost= [KNL]
3050 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3051 "Maybe" means test if the RCU implementation
3052 under test support RCU priority boosting.
3054 rcutorture.test_boost_duration= [KNL]
3055 Duration (s) of each individual boost test.
3057 rcutorture.test_boost_interval= [KNL]
3058 Interval (s) between each boost test.
3060 rcutorture.test_no_idle_hz= [KNL]
3061 Test RCU's dyntick-idle handling. See also the
3062 rcutorture.shuffle_interval parameter.
3064 rcutorture.torture_type= [KNL]
3065 Specify the RCU implementation to test.
3067 rcutorture.verbose= [KNL]
3068 Enable additional printk() statements.
3070 rcupdate.rcu_expedited= [KNL]
3071 Use expedited grace-period primitives, for
3072 example, synchronize_rcu_expedited() instead
3073 of synchronize_rcu(). This reduces latency,
3074 but can increase CPU utilization, degrade
3075 real-time latency, and degrade energy efficiency.
3077 rcupdate.rcu_cpu_stall_suppress= [KNL]
3078 Suppress RCU CPU stall warning messages.
3080 rcupdate.rcu_cpu_stall_timeout= [KNL]
3081 Set timeout for RCU CPU stall warning messages.
3083 rcupdate.rcu_task_stall_timeout= [KNL]
3084 Set timeout in jiffies for RCU task stall warning
3085 messages. Disable with a value less than or equal
3090 Run specified binary instead of /init from the ramdisk,
3091 used for early userspace startup. See initrd.
3094 Format (x86 or x86_64):
3095 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3097 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3099 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3100 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3101 reboot_force is either force or not specified,
3102 reboot_cpu is s[mp]#### with #### being the processor
3103 to be used for rebooting.
3106 [KNL, SMP] Set scheduler's default relax_domain_level.
3107 See Documentation/cgroups/cpusets.txt.
3109 relative_sleep_states=
3110 [SUSPEND] Use sleep state labeling where the deepest
3111 state available other than hibernation is always "mem".
3112 Format: { "0" | "1" }
3113 0 -- Traditional sleep state labels.
3114 1 -- Relative sleep state labels.
3116 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3118 reservetop= [X86-32]
3120 Reserves a hole at the top of the kernel virtual
3125 Set the amount of memory to reserve for BIOS at
3126 the bottom of the address space.
3128 reset_devices [KNL] Force drivers to reset the underlying device
3129 during initialization.
3132 Specify the partition device for software suspend
3134 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3136 resume_offset= [SWSUSP]
3137 Specify the offset from the beginning of the partition
3138 given by "resume=" at which the swap header is located,
3139 in <PAGE_SIZE> units (needed only for swap files).
3140 See Documentation/power/swsusp-and-swap-files.txt
3142 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3143 read the resume files
3145 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3146 Useful for devices that are detected asynchronously
3147 (e.g. USB and MMC devices).
3149 hibernate= [HIBERNATION]
3150 noresume Don't check if there's a hibernation image
3151 present during boot.
3152 nocompress Don't compress/decompress hibernation images.
3153 no Disable hibernation and resume.
3155 retain_initrd [RAM] Keep initrd memory after extraction
3157 rhash_entries= [KNL,NET]
3158 Set number of hash buckets for route cache
3160 ro [KNL] Mount root device read-only on boot
3162 root= [KNL] Root filesystem
3163 See name_to_dev_t comment in init/do_mounts.c.
3165 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3166 mount the root filesystem
3168 rootflags= [KNL] Set root filesystem mount option string
3170 rootfstype= [KNL] Set root filesystem type
3172 rootwait [KNL] Wait (indefinitely) for root device to show up.
3173 Useful for devices that are detected asynchronously
3174 (e.g. USB and MMC devices).
3176 rproc_mem=nn[KMG][@address]
3177 [KNL,ARM,CMA] Remoteproc physical memory block.
3178 Memory area to be used by remote processor image,
3181 rw [KNL] Mount root device read-write on boot
3183 S [KNL] Run init in single mode
3185 s390_iommu= [HW,S390]
3186 Set s390 IOTLB flushing mode
3188 With strict flushing every unmap operation will result in
3189 an IOTLB flush. Default is lazy flushing before reuse,
3193 See drivers/net/irda/sa1100_ir.c.
3195 sbni= [NET] Granch SBNI12 leased line adapter
3197 sched_debug [KNL] Enables verbose scheduler debug messages.
3199 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3200 xtime_lock contention on larger systems, and/or RCU lock
3201 contention on all systems with CONFIG_MAXSMP set.
3202 Format: { "0" | "1" }
3203 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3205 Note: increases power consumption, thus should only be
3206 enabled if running jitter sensitive (HPC/RT) workloads.
3208 security= [SECURITY] Choose a security module to enable at boot.
3209 If this boot parameter is not specified, only the first
3210 security module asking for security registration will be
3211 loaded. An invalid security module name will be treated
3212 as if no module has been chosen.
3214 selinux= [SELINUX] Disable or enable SELinux at boot time.
3215 Format: { "0" | "1" }
3216 See security/selinux/Kconfig help text.
3219 Default value is set via kernel config option.
3220 If enabled at boot time, /selinux/disable can be used
3221 later to disable prior to initial policy load.
3223 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3224 Format: { "0" | "1" }
3225 See security/apparmor/Kconfig help text
3228 Default value is set via kernel config option.
3230 serialnumber [BUGS=X86-32]
3233 Maximal number of shapers.
3235 show_msr= [x86] show boot-time MSR settings
3236 Format: { <integer> }
3237 Show boot-time (BIOS-initialized) MSR settings.
3238 The parameter means the number of CPUs to show,
3239 for example 1 means boot CPU only.
3247 Disable merging of slabs with similar size. May be
3248 necessary if there is some reason to distinguish
3249 allocs to different slabs. Debug options disable
3250 merging on their own.
3251 For more information see Documentation/vm/slub.txt.
3253 slab_max_order= [MM, SLAB]
3254 Determines the maximum allowed order for slabs.
3255 A high setting may cause OOMs due to memory
3256 fragmentation. Defaults to 1 for systems with
3257 more than 32MB of RAM, 0 otherwise.
3259 slub_debug[=options[,slabs]] [MM, SLUB]
3260 Enabling slub_debug allows one to determine the
3261 culprit if slab objects become corrupted. Enabling
3262 slub_debug can create guard zones around objects and
3263 may poison objects when not in use. Also tracks the
3264 last alloc / free. For more information see
3265 Documentation/vm/slub.txt.
3267 slub_max_order= [MM, SLUB]
3268 Determines the maximum allowed order for slabs.
3269 A high setting may cause OOMs due to memory
3270 fragmentation. For more information see
3271 Documentation/vm/slub.txt.
3273 slub_min_objects= [MM, SLUB]
3274 The minimum number of objects per slab. SLUB will
3275 increase the slab order up to slub_max_order to
3276 generate a sufficiently large slab able to contain
3277 the number of objects indicated. The higher the number
3278 of objects the smaller the overhead of tracking slabs
3279 and the less frequently locks need to be acquired.
3280 For more information see Documentation/vm/slub.txt.
3282 slub_min_order= [MM, SLUB]
3283 Determines the minimum page order for slabs. Must be
3284 lower than slub_max_order.
3285 For more information see Documentation/vm/slub.txt.
3287 slub_nomerge [MM, SLUB]
3288 Same with slab_nomerge. This is supported for legacy.
3289 See slab_nomerge for more information.
3292 Format: <io1>[,<io2>[,...,<io8>]]
3294 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3295 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3296 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3297 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3298 smsc-ircc2.ircc_irq= [HW] IRQ line
3299 smsc-ircc2.ircc_dma= [HW] DMA channel
3300 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3301 0: Toshiba Satellite 1800 (GP data pin select)
3302 1: Fast pin select (default)
3306 [KNL] Should the soft-lockup detector generate panics.
3309 softlockup_all_cpu_backtrace=
3310 [KNL] Should the soft-lockup detector generate
3311 backtraces on all cpus.
3314 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3315 See Documentation/laptops/sonypi.txt
3317 spia_io_base= [HW,MTD]
3323 Enabled the stack tracer on boot up.
3325 stacktrace_filter=[function-list]
3326 [FTRACE] Limit the functions that the stack tracer
3327 will trace at boot up. function-list is a comma separated
3328 list of functions. This list can be changed at run
3329 time by the stack_trace_filter file in the debugfs
3330 tracing directory. Note, this enables stack tracing
3331 and the stacktrace above is not needed.
3335 Set the STI (builtin display/keyboard on the HP-PARISC
3336 machines) console (graphic card) which should be used
3337 as the initial boot-console.
3338 See also comment in drivers/video/console/sticore.c.
3341 See comment in drivers/video/console/sticore.c.
3344 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3346 sunrpc.min_resvport=
3347 sunrpc.max_resvport=
3349 SunRPC servers often require that client requests
3350 originate from a privileged port (i.e. a port in the
3351 range 0 < portnr < 1024).
3352 An administrator who wishes to reserve some of these
3353 ports for other uses may adjust the range that the
3354 kernel's sunrpc client considers to be privileged
3355 using these two parameters to set the minimum and
3356 maximum port values.
3360 Control how the NFS server code allocates CPUs to
3361 service thread pools. Depending on how many NICs
3362 you have and where their interrupts are bound, this
3363 option will affect which CPUs will do NFS serving.
3364 Note: this parameter cannot be changed while the
3365 NFS server is running.
3367 auto the server chooses an appropriate mode
3368 automatically using heuristics
3369 global a single global pool contains all CPUs
3370 percpu one pool for each CPU
3371 pernode one pool for each NUMA node (equivalent
3372 to global on non-NUMA machines)
3374 sunrpc.tcp_slot_table_entries=
3375 sunrpc.udp_slot_table_entries=
3377 Sets the upper limit on the number of simultaneous
3378 RPC calls that can be sent from the client to a
3379 server. Increasing these values may allow you to
3380 improve throughput, but will also increase the
3381 amount of memory reserved for use by the client.
3384 [KNL] Enable accounting of swap in memory resource
3385 controller if no parameter or 1 is given or disable
3386 it if 0 is given (See Documentation/cgroups/memory.txt)
3388 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3389 Format: { <int> | force }
3390 <int> -- Number of I/O TLB slabs
3391 force -- force using of bounce buffers even if they
3392 wouldn't be automatically used by the kernel
3396 sysfs.deprecated=0|1 [KNL]
3397 Enable/disable old style sysfs layout for old udev
3398 on older distributions. When this option is enabled
3399 very new udev will not work anymore. When this option
3400 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3401 in older udev will not work anymore.
3402 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3403 the kernel configuration.
3405 sysrq_always_enabled
3407 Ignore sysrq setting - this boot parameter will
3408 neutralize any effect of /proc/sys/kernel/sysrq.
3409 Useful for debugging.
3413 test_suspend= [SUSPEND][,N]
3414 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3415 standby suspend) or "freeze" (for suspend type freeze)
3416 as the system sleep state during system startup with
3417 the optional capability to repeat N number of times.
3418 The system is woken from this state using a
3419 wakeup-capable RTC alarm.
3421 thash_entries= [KNL,NET]
3422 Set number of hash buckets for TCP connection
3424 thermal.act= [HW,ACPI]
3425 -1: disable all active trip points in all thermal zones
3426 <degrees C>: override all lowest active trip points
3428 thermal.crt= [HW,ACPI]
3429 -1: disable all critical trip points in all thermal zones
3430 <degrees C>: override all critical trip points
3432 thermal.nocrt= [HW,ACPI]
3433 Set to disable actions on ACPI thermal zone
3434 critical and hot trip points.
3436 thermal.off= [HW,ACPI]
3437 1: disable ACPI thermal control
3439 thermal.psv= [HW,ACPI]
3440 -1: disable all passive trip points
3441 <degrees C>: override all passive trip points to this
3444 thermal.tzp= [HW,ACPI]
3445 Specify global default ACPI thermal zone polling rate
3446 <deci-seconds>: poll all this frequency
3447 0: no polling (default)
3450 Force threading of all interrupt handlers except those
3451 marked explicitly IRQF_NO_THREAD.
3454 Enable the Transcendent memory driver if built-in.
3456 tmem.cleancache=0|1 [KNL, XEN]
3457 Default is on (1). Disable the usage of the cleancache
3458 API to send anonymous pages to the hypervisor.
3460 tmem.frontswap=0|1 [KNL, XEN]
3461 Default is on (1). Disable the usage of the frontswap
3462 API to send swap pages to the hypervisor. If disabled
3463 the selfballooning and selfshrinking are force disabled.
3465 tmem.selfballooning=0|1 [KNL, XEN]
3466 Default is on (1). Disable the driving of swap pages
3469 tmem.selfshrinking=0|1 [KNL, XEN]
3470 Default is on (1). Partial swapoff that immediately
3471 transfers pages from Xen hypervisor back to the
3472 kernel based on different criteria.
3476 Specify if the kernel should make use of the cpu
3477 topology information if the hardware supports this.
3478 The scheduler will make use of this information and
3479 e.g. base its process migration decisions on it.
3484 tpm_suspend_pcr=[HW,TPM]
3485 Format: integer pcr id
3486 Specify that at suspend time, the tpm driver
3487 should extend the specified pcr with zeros,
3488 as a workaround for some chips which fail to
3489 flush the last written pcr on TPM_SaveState.
3490 This will guarantee that all the other pcrs
3493 trace_buf_size=nn[KMG]
3494 [FTRACE] will set tracing buffer size.
3496 trace_event=[event-list]
3497 [FTRACE] Set and start specified trace events in order
3498 to facilitate early boot debugging.
3499 See also Documentation/trace/events.txt
3501 trace_options=[option-list]
3502 [FTRACE] Enable or disable tracer options at boot.
3503 The option-list is a comma delimited list of options
3504 that can be enabled or disabled just as if you were
3505 to echo the option name into
3507 /sys/kernel/debug/tracing/trace_options
3509 For example, to enable stacktrace option (to dump the
3510 stack trace of each event), add to the command line:
3512 trace_options=stacktrace
3514 See also Documentation/trace/ftrace.txt "trace options"
3518 [FTRACE] enable this option to disable tracing when a
3519 warning is hit. This turns off "tracing_on". Tracing can
3520 be enabled again by echoing '1' into the "tracing_on"
3521 file located in /sys/kernel/debug/tracing/
3523 This option is useful, as it disables the trace before
3524 the WARNING dump is called, which prevents the trace to
3525 be filled with content caused by the warning output.
3527 This option can also be set at run time via the sysctl
3528 option: kernel/traceoff_on_warning
3530 transparent_hugepage=
3532 Format: [always|madvise|never]
3533 Can be used to control the default behavior of the system
3534 with respect to transparent hugepages.
3535 See Documentation/vm/transhuge.txt for more details.
3537 tsc= Disable clocksource stability checks for TSC.
3539 [x86] reliable: mark tsc clocksource as reliable, this
3540 disables clocksource verification at runtime, as well
3541 as the stability checks done at bootup. Used to enable
3542 high-resolution timer mode on older hardware, and in
3543 virtualized environment.
3544 [x86] noirqtime: Do not use TSC to do irq accounting.
3545 Used to run time disable IRQ_TIME_ACCOUNTING on any
3546 platforms where RDTSC is slow and this accounting
3549 turbografx.map[2|3]= [HW,JOY]
3550 TurboGraFX parallel port interface
3552 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3553 See also Documentation/input/joystick-parport.txt
3555 udbg-immortal [PPC] When debugging early kernel crashes that
3556 happen after console_init() and before a proper
3557 console driver takes over, this boot options might
3558 help "seeing" what's going on.
3560 uhash_entries= [KNL,NET]
3561 Set number of hash buckets for UDP/UDP-Lite connections
3564 [USB] Ignore overcurrent events (default N).
3565 Some badly-designed motherboards generate lots of
3566 bogus events, for ports that aren't wired to
3567 anything. Set this parameter to avoid log spamming.
3568 Note that genuine overcurrent events won't be
3572 [X86] Cause panic on unknown NMI.
3574 usbcore.authorized_default=
3575 [USB] Default USB device authorization:
3576 (default -1 = authorized except for wireless USB,
3577 0 = not authorized, 1 = authorized)
3579 usbcore.autosuspend=
3580 [USB] The autosuspend time delay (in seconds) used
3581 for newly-detected USB devices (default 2). This
3582 is the time required before an idle device will be
3583 autosuspended. Devices for which the delay is set
3584 to a negative value won't be autosuspended at all.
3586 usbcore.usbfs_snoop=
3587 [USB] Set to log all usbfs traffic (default 0 = off).
3589 usbcore.blinkenlights=
3590 [USB] Set to cycle leds on hubs (default 0 = off).
3592 usbcore.old_scheme_first=
3593 [USB] Start with the old device initialization
3594 scheme (default 0 = off).
3596 usbcore.usbfs_memory_mb=
3597 [USB] Memory limit (in MB) for buffers allocated by
3598 usbfs (default = 16, 0 = max = 2047).
3600 usbcore.use_both_schemes=
3601 [USB] Try the other device initialization scheme
3602 if the first one fails (default 1 = enabled).
3604 usbcore.initial_descriptor_timeout=
3605 [USB] Specifies timeout for the initial 64-byte
3606 USB_REQ_GET_DESCRIPTOR request in milliseconds
3607 (default 5000 = 5.0 seconds).
3610 [USBHID] The interval which mice are to be polled at.
3612 usb-storage.delay_use=
3613 [UMS] The delay in seconds before a new device is
3614 scanned for Logical Units (default 5).
3617 [UMS] A list of quirks entries to supplement or
3618 override the built-in unusual_devs list. List
3619 entries are separated by commas. Each entry has
3620 the form VID:PID:Flags where VID and PID are Vendor
3621 and Product ID values (4-digit hex numbers) and
3622 Flags is a set of characters, each corresponding
3623 to a common usb-storage quirk flag as follows:
3624 a = SANE_SENSE (collect more than 18 bytes
3626 b = BAD_SENSE (don't collect more than 18
3627 bytes of sense data);
3628 c = FIX_CAPACITY (decrease the reported
3629 device capacity by one sector);
3630 d = NO_READ_DISC_INFO (don't use
3631 READ_DISC_INFO command);
3632 e = NO_READ_CAPACITY_16 (don't use
3633 READ_CAPACITY_16 command);
3634 f = NO_REPORT_OPCODES (don't use report opcodes
3636 h = CAPACITY_HEURISTICS (decrease the
3637 reported device capacity by one
3638 sector if the number is odd);
3639 i = IGNORE_DEVICE (don't bind to this
3641 l = NOT_LOCKABLE (don't try to lock and
3642 unlock ejectable media);
3643 m = MAX_SECTORS_64 (don't transfer more
3644 than 64 sectors = 32 KB at a time);
3645 n = INITIAL_READ10 (force a retry of the
3646 initial READ(10) command);
3647 o = CAPACITY_OK (accept the capacity
3648 reported by the device);
3649 p = WRITE_CACHE (the device cache is ON
3651 r = IGNORE_RESIDUE (the device reports
3652 bogus residue values);
3653 s = SINGLE_LUN (the device has only one
3655 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3656 commands, uas only);
3657 u = IGNORE_UAS (don't bind to the uas driver);
3658 w = NO_WP_DETECT (don't test whether the
3659 medium is write-protected).
3660 Example: quirks=0419:aaf5:rl,0421:0433:rc
3662 user_debug= [KNL,ARM]
3664 See arch/arm/Kconfig.debug help text.
3665 1 - undefined instruction events
3667 4 - invalid data aborts
3670 Example: user_debug=31
3673 [X86] Flags controlling user PTE allocations.
3675 nohigh = do not allocate PTE pages in
3676 HIGHMEM regardless of setting
3680 On X86_32, this is an alias for vdso32=. Otherwise:
3682 vdso=1: enable VDSO (the default)
3683 vdso=0: disable VDSO mapping
3685 vdso32= [X86] Control the 32-bit vDSO
3686 vdso32=1: enable 32-bit VDSO
3687 vdso32=0 or vdso32=2: disable 32-bit VDSO
3689 See the help text for CONFIG_COMPAT_VDSO for more
3690 details. If CONFIG_COMPAT_VDSO is set, the default is
3691 vdso32=0; otherwise, the default is vdso32=1.
3693 For compatibility with older kernels, vdso32=2 is an
3696 Try vdso32=0 if you encounter an error that says:
3697 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3700 vector=percpu: enable percpu vector domain
3702 video= [FB] Frame buffer configuration
3703 See Documentation/fb/modedb.txt.
3705 video.brightness_switch_enabled= [0,1]
3706 If set to 1, on receiving an ACPI notify event
3707 generated by hotkey, video driver will adjust brightness
3708 level and then send out the event to user space through
3709 the allocated input device; If set to 0, video driver
3710 will only send out the event without touching backlight
3715 [VMMIO] Memory mapped virtio (platform) device.
3717 <size>@<baseaddr>:<irq>[:<id>]
3719 <size> := size (can use standard suffixes
3721 <baseaddr> := physical base address
3722 <irq> := interrupt number (as passed to
3724 <id> := (optional) platform device id
3726 virtio_mmio.device=1K@0x100b0000:48:7
3728 Can be used multiple times for multiple devices.
3730 vga= [BOOT,X86-32] Select a particular video mode
3731 See Documentation/x86/boot.txt and
3732 Documentation/svga.txt.
3733 Use vga=ask for menu.
3734 This is actually a boot loader parameter; the value is
3735 passed to the kernel using a special protocol.
3737 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3738 size of <nn>. This can be used to increase the
3739 minimum size (128MB on x86). It can also be used to
3740 decrease the size and leave more room for directly
3743 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3746 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3749 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3753 Controls the behavior of vsyscalls (i.e. calls to
3754 fixed addresses of 0xffffffffff600x00 from legacy
3755 code). Most statically-linked binaries and older
3756 versions of glibc use these calls. Because these
3757 functions are at fixed addresses, they make nice
3758 targets for exploits that can control RIP.
3760 emulate [default] Vsyscalls turn into traps and are
3761 emulated reasonably safely.
3763 native Vsyscalls are native syscall instructions.
3764 This is a little bit faster than trapping
3765 and makes a few dynamic recompilers work
3766 better than they would in emulation mode.
3767 It also makes exploits much easier to write.
3769 none Vsyscalls don't work at all. This makes
3770 them quite hard to use for exploits but
3771 might break your system.
3773 vt.color= [VT] Default text color.
3774 Format: 0xYX, X = foreground, Y = background.
3775 Default: 0x07 = light gray on black.
3777 vt.cur_default= [VT] Default cursor shape.
3778 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3779 the parameters of the <Esc>[?A;B;Cc escape sequence;
3780 see VGA-softcursor.txt. Default: 2 = underline.
3782 vt.default_blu= [VT]
3783 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3784 Change the default blue palette of the console.
3785 This is a 16-member array composed of values
3788 vt.default_grn= [VT]
3789 Format: <green0>,<green1>,<green2>,...,<green15>
3790 Change the default green palette of the console.
3791 This is a 16-member array composed of values
3794 vt.default_red= [VT]
3795 Format: <red0>,<red1>,<red2>,...,<red15>
3796 Change the default red palette of the console.
3797 This is a 16-member array composed of values
3803 Set system-wide default UTF-8 mode for all tty's.
3804 Default is 1, i.e. UTF-8 mode is enabled for all
3805 newly opened terminals.
3807 vt.global_cursor_default=
3810 Set system-wide default for whether a cursor
3811 is shown on new VTs. Default is -1,
3812 i.e. cursors will be created by default unless
3813 overridden by individual drivers. 0 will hide
3814 cursors, 1 will display them.
3816 vt.italic= [VT] Default color for italic text; 0-15.
3819 vt.underline= [VT] Default color for underlined text; 0-15.
3822 watchdog timers [HW,WDT] For information on watchdog timers,
3823 see Documentation/watchdog/watchdog-parameters.txt
3824 or other driver-specific files in the
3825 Documentation/watchdog/ directory.
3827 workqueue.disable_numa
3828 By default, all work items queued to unbound
3829 workqueues are affine to the NUMA nodes they're
3830 issued on, which results in better behavior in
3831 general. If NUMA affinity needs to be disabled for
3832 whatever reason, this option can be used. Note
3833 that this also can be controlled per-workqueue for
3834 workqueues visible under /sys/bus/workqueue/.
3836 workqueue.power_efficient
3837 Per-cpu workqueues are generally preferred because
3838 they show better performance thanks to cache
3839 locality; unfortunately, per-cpu workqueues tend to
3840 be more power hungry than unbound workqueues.
3842 Enabling this makes the per-cpu workqueues which
3843 were observed to contribute significantly to power
3844 consumption unbound, leading to measurably lower
3845 power usage at the cost of small performance
3848 The default value of this parameter is determined by
3849 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3851 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3852 default x2apic cluster mode on platforms
3855 x86_intel_mid_timer= [X86-32,APBT]
3856 Choose timer option for x86 Intel MID platform.
3857 Two valid options are apbt timer only and lapic timer
3858 plus one apbt timer for broadcast timer.
3859 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3861 xen_emul_unplug= [HW,X86,XEN]
3862 Unplug Xen emulated devices
3863 Format: [unplug0,][unplug1]
3864 ide-disks -- unplug primary master IDE devices
3865 aux-ide-disks -- unplug non-primary-master IDE devices
3866 nics -- unplug network devices
3867 all -- unplug all emulated devices (NICs and IDE disks)
3868 unnecessary -- unplugging emulated devices is
3869 unnecessary even if the host did not respond to
3871 never -- do not unplug even if version check succeeds
3873 xen_nopvspin [X86,XEN]
3874 Disables the ticketlock slowpath using Xen PV
3878 Disables the PV optimizations forcing the HVM guest to
3879 run as generic HVM guest with no PV drivers.
3881 xirc2ps_cs= [NET,PCMCIA]
3883 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3885 ______________________________________________________________________
3889 Add more DRM drivers.
projects / karo-tx-linux.git / blob