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 uart[8250],mmio32,<addr>[,options]
717 uart[8250],0x<addr>[,options]
718 Start an early, polled-mode console on the 8250/16550
719 UART at the specified I/O port or MMIO address,
720 switching to the matching ttyS device later.
721 MMIO inter-register address stride is either 8-bit
722 (mmio) or 32-bit (mmio32).
723 If none of [io|mmio|mmio32], <addr> is assumed to be
724 equivalent to 'mmio'. 'options' are specified in the
725 same format described for ttyS above; if unspecified,
726 the h/w is not re-initialized.
728 hvc<n> Use the hypervisor console device <n>. This is for
729 both Xen and PowerPC hypervisors.
731 If the device connected to the port is not a TTY but a braille
732 device, prepend "brl," before the device type, for instance
734 For now, only VisioBraille is supported.
736 consoleblank= [KNL] The console blank (screen saver) timeout in
737 seconds. Defaults to 10*60 = 10mins. A value of 0
738 disables the blank timer.
741 [KNL] Change the default value for
742 /proc/<pid>/coredump_filter.
743 See also Documentation/filesystems/proc.txt.
745 cpuidle.off=1 [CPU_IDLE]
746 disable the cpuidle sub-system
748 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
750 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
752 crashkernel=size[KMG][@offset[KMG]]
753 [KNL] Using kexec, Linux can switch to a 'crash kernel'
754 upon panic. This parameter reserves the physical
755 memory region [offset, offset + size] for that kernel
756 image. If '@offset' is omitted, then a suitable offset
757 is selected automatically. Check
758 Documentation/kdump/kdump.txt for further details.
760 crashkernel=range1:size1[,range2:size2,...][@offset]
761 [KNL] Same as above, but depends on the memory
762 in the running system. The syntax of range is
763 start-[end] where start and end are both
764 a memory unit (amount[KMG]). See also
765 Documentation/kdump/kdump.txt for an example.
767 crashkernel=size[KMG],high
768 [KNL, x86_64] range could be above 4G. Allow kernel
769 to allocate physical memory region from top, so could
770 be above 4G if system have more than 4G ram installed.
771 Otherwise memory region will be allocated below 4G, if
773 It will be ignored if crashkernel=X is specified.
774 crashkernel=size[KMG],low
775 [KNL, x86_64] range under 4G. When crashkernel=X,high
776 is passed, kernel could allocate physical memory region
777 above 4G, that cause second kernel crash on system
778 that require some amount of low memory, e.g. swiotlb
779 requires at least 64M+32K low memory. Kernel would
780 try to allocate 72M below 4G automatically.
781 This one let user to specify own low range under 4G
782 for second kernel instead.
783 0: to disable low allocation.
784 It will be ignored when crashkernel=X,high is not used
785 or memory reserved is below 4G.
790 cs89x0_media= [HW,NET]
791 Format: { rj45 | aui | bnc }
794 See header of drivers/s390/block/dasd_devmap.c.
796 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
797 (one device per port)
798 Format: <port#>,<type>
799 See also Documentation/input/joystick-parport.txt
801 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
802 time. See Documentation/dynamic-debug-howto.txt for
803 details. Deprecated, see dyndbg.
805 debug [KNL] Enable kernel debugging (events log level).
808 [KNL] verbose self-tests
810 Print debugging info while doing the locking API
812 We default to 0 (no extra messages), setting it to
813 1 will print _a lot_ more information - normally
814 only useful to kernel developers.
816 debug_objects [KNL] Enable object debugging
819 [KNL] Disable object debugging
821 debug_guardpage_minorder=
822 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
823 parameter allows control of the order of pages that will
824 be intentionally kept free (and hence protected) by the
825 buddy allocator. Bigger value increase the probability
826 of catching random memory corruption, but reduce the
827 amount of memory for normal system use. The maximum
828 possible value is MAX_ORDER/2. Setting this parameter
829 to 1 or 2 should be enough to identify most random
830 memory corruption problems caused by bugs in kernel or
831 driver code when a CPU writes to (or reads from) a
832 random memory location. Note that there exists a class
833 of memory corruptions problems caused by buggy H/W or
834 F/W or by drivers badly programing DMA (basically when
835 memory is written at bus level and the CPU MMU is
836 bypassed) which are not detectable by
837 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
838 tracking down these problems.
841 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
842 parameter enables the feature at boot time. In
843 default, it is disabled. We can avoid allocating huge
844 chunk of memory for debug pagealloc if we don't enable
845 it at boot time and the system will work mostly same
846 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
847 on: enable the feature
849 debugpat [X86] Enable PAT debugging
851 decnet.addr= [HW,NET]
852 Format: <area>[,<node>]
853 See also Documentation/networking/decnet.txt.
856 [same as hugepagesz=] The size of the default
857 HugeTLB page size. This is the size represented by
858 the legacy /proc/ hugepages APIs, used for SHM, and
859 default size when mounting hugetlbfs filesystems.
860 Defaults to the default architecture's huge page size
864 Set number of hash buckets for dentry cache.
867 See Documentation/networking/ipv6.txt.
869 disable_cpu_apicid= [X86,APIC,SMP]
871 The number of initial APIC ID for the
872 corresponding CPU to be disabled at boot,
873 mostly used for the kdump 2nd kernel to
874 disable BSP to wake up multiple CPUs without
875 causing system reset or hang due to sending
878 disable_ddw [PPC/PSERIES]
879 Disable Dynamic DMA Window support. Use this if
880 to workaround buggy firmware.
883 See Documentation/networking/ipv6.txt.
885 disable_mtrr_cleanup [X86]
886 The kernel tries to adjust MTRR layout from continuous
887 to discrete, to make X server driver able to add WB
888 entry later. This parameter disables that.
890 disable_mtrr_trim [X86, Intel and AMD only]
891 By default the kernel will trim any uncacheable
892 memory out of your available memory pool based on
893 MTRR settings. This parameter disables that behavior,
894 possibly causing your machine to run very slowly.
896 disable_timer_pin_1 [X86]
897 Disable PIN 1 of APIC timer
898 Can be useful to work around chipset bugs.
900 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
901 this option disables the debugging code at boot.
903 dma_debug_entries=<number>
904 This option allows to tune the number of preallocated
905 entries for DMA-API debugging code. One entry is
906 required per DMA-API allocation. Use this if the
907 DMA-API debugging code disables itself because the
908 architectural default is too low.
910 dma_debug_driver=<driver_name>
911 With this option the DMA-API debugging driver
912 filter feature can be enabled at boot time. Just
913 pass the driver to filter for as the parameter.
914 The filter can be disabled or changed to another
915 driver later using sysfs.
917 drm_kms_helper.edid_firmware=[<connector>:]<file>
918 Broken monitors, graphic adapters and KVMs may
919 send no or incorrect EDID data sets. This parameter
920 allows to specify an EDID data set in the
921 /lib/firmware directory that is used instead.
922 Generic built-in EDID data sets are used, if one of
923 edid/1024x768.bin, edid/1280x1024.bin,
924 edid/1680x1050.bin, or edid/1920x1080.bin is given
925 and no file with the same name exists. Details and
926 instructions how to build your own EDID data are
927 available in Documentation/EDID/HOWTO.txt. An EDID
928 data set will only be used for a particular connector,
929 if its name and a colon are prepended to the EDID
934 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
935 module.dyndbg[="val"]
936 Enable debug messages at boot time. See
937 Documentation/dynamic-debug-howto.txt for details.
940 on enable eager fpu restore
941 off disable eager fpu restore
942 auto selects the default scheme, which automatically
943 enables eagerfpu restore for xsaveopt.
945 early_ioremap_debug [KNL]
946 Enable debug messages in early_ioremap support. This
947 is useful for tracking down temporary early mappings
948 which are not unmapped.
950 earlycon= [KNL] Output early console device and options.
953 Start an early, polled-mode console on a cadence serial
954 port at the specified address. The cadence serial port
955 must already be setup and configured. Options are not
958 uart[8250],io,<addr>[,options]
959 uart[8250],mmio,<addr>[,options]
960 uart[8250],mmio32,<addr>[,options]
961 uart[8250],0x<addr>[,options]
962 Start an early, polled-mode console on the 8250/16550
963 UART at the specified I/O port or MMIO address.
964 MMIO inter-register address stride is either 8-bit
965 (mmio) or 32-bit (mmio32).
966 If none of [io|mmio|mmio32], <addr> is assumed to be
967 equivalent to 'mmio'. 'options' are specified in the
968 same format described for "console=ttyS<n>"; if
969 unspecified, the h/w is not initialized.
972 Start an early, polled-mode console on a pl011 serial
973 port at the specified address. The pl011 serial port
974 must already be setup and configured. Options are not
978 Start an early, polled-mode console on an msm serial
979 port at the specified address. The serial port
980 must already be setup and configured. Options are not
984 Start an early, polled-mode console on an msm serial
985 dm port at the specified address. The serial port
986 must already be setup and configured. Options are not
989 smh Use ARM semihosting calls for early console.
997 Use early console provided by serial driver available
998 on Samsung SoCs, requires selecting proper type and
999 a correct base address of the selected UART port. The
1000 serial port must already be setup and configured.
1001 Options are not yet supported.
1003 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1007 earlyprintk=serial[,ttySn[,baudrate]]
1008 earlyprintk=serial[,0x...[,baudrate]]
1009 earlyprintk=ttySn[,baudrate]
1010 earlyprintk=dbgp[debugController#]
1012 earlyprintk is useful when the kernel crashes before
1013 the normal console is initialized. It is not enabled by
1014 default because it has some cosmetic problems.
1016 Append ",keep" to not disable it when the real console
1019 Only one of vga, efi, serial, or usb debug port can
1022 Currently only ttyS0 and ttyS1 may be specified by
1023 name. Other I/O ports may be explicitly specified
1024 on some architectures (x86 and arm at least) by
1025 replacing ttySn with an I/O port address, like this:
1026 earlyprintk=serial,0x1008,115200
1027 You can find the port for a given device in
1028 /proc/tty/driver/serial:
1029 2: uart:ST16650V2 port:00001008 irq:18 ...
1031 Interaction with the standard serial driver is not
1034 The VGA and EFI output is eventually overwritten by
1037 The xen output can only be used by Xen PV guests.
1039 edac_report= [HW,EDAC] Control how to report EDAC event
1040 Format: {"on" | "off" | "force"}
1041 on: enable EDAC to report H/W event. May be overridden
1042 by other higher priority error reporting module.
1043 off: disable H/W event reporting through EDAC.
1044 force: enforce the use of EDAC to report H/W event.
1047 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1050 This is designed to be used in conjunction with
1051 the boot argument: earlyprintk=vga
1054 Format: {"off" | "on" | "skip[mbr]"}
1057 Format: { "old_map", "nochunk", "noruntime", "debug" }
1058 old_map [X86-64]: switch to the old ioremap-based EFI
1059 runtime services mapping. 32-bit still uses this one by
1061 nochunk: disable reading files in "chunks" in the EFI
1062 boot stub, as chunking can cause problems with some
1063 firmware implementations.
1064 noruntime : disable EFI runtime services support
1065 debug: enable misc debug output
1067 efi_no_storage_paranoia [EFI; X86]
1068 Using this parameter you can use more than 50% of
1069 your efi variable storage. Use this parameter only if
1070 you are really sure that your UEFI does sane gc and
1071 fulfills the spec otherwise your board may brick.
1073 eisa_irq_edge= [PARISC,HW]
1074 See header of drivers/parisc/eisa.c.
1077 See comment before function elanfreq_setup() in
1078 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1081 Format: {"cfq" | "deadline" | "noop"}
1082 See Documentation/block/cfq-iosched.txt and
1083 Documentation/block/deadline-iosched.txt for details.
1085 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1086 Specifies physical address of start of kernel core
1087 image elf header and optionally the size. Generally
1088 kexec loader will pass this option to capture kernel.
1089 See Documentation/kdump/kdump.txt for details.
1091 enable_mtrr_cleanup [X86]
1092 The kernel tries to adjust MTRR layout from continuous
1093 to discrete, to make X server driver able to add WB
1094 entry later. This parameter enables that.
1096 enable_timer_pin_1 [X86]
1097 Enable PIN 1 of APIC timer
1098 Can be useful to work around chipset bugs
1099 (in particular on some ATI chipsets).
1100 The kernel tries to set a reasonable default.
1102 enforcing [SELINUX] Set initial enforcing status.
1104 See security/selinux/Kconfig help text.
1105 0 -- permissive (log only, no denials).
1106 1 -- enforcing (deny and log).
1108 Value can be changed at runtime via /selinux/enforce.
1111 Disable Error Record Serialization Table (ERST)
1114 ether= [HW,NET] Ethernet cards parameters
1115 This option is obsoleted by the "netdev=" option, which
1116 has equivalent usage. See its documentation for details.
1120 Permit 'security.evm' to be updated regardless of
1121 current integrity status.
1125 fail_make_request=[KNL]
1126 General fault injection mechanism.
1127 Format: <interval>,<probability>,<space>,<times>
1128 See also Documentation/fault-injection/.
1131 See Documentation/blockdev/floppy.txt.
1133 force_pal_cache_flush
1134 [IA-64] Avoid check_sal_cache_flush which may hang on
1135 buggy SAL_CACHE_FLUSH implementations. Using this
1136 parameter will force ia64_sal_cache_flush to call
1137 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1140 Forcefully enable Physical Address Extension (PAE).
1141 Many Pentium M systems disable PAE but may have a
1142 functionally usable PAE implementation.
1143 Warning: use of this parameter will taint the kernel
1144 and may cause unknown problems.
1147 [FTRACE] will set and start the specified tracer
1148 as early as possible in order to facilitate early
1151 ftrace_dump_on_oops[=orig_cpu]
1152 [FTRACE] will dump the trace buffers on oops.
1153 If no parameter is passed, ftrace will dump
1154 buffers of all CPUs, but if you pass orig_cpu, it will
1155 dump only the buffer of the CPU that triggered the
1158 ftrace_filter=[function-list]
1159 [FTRACE] Limit the functions traced by the function
1160 tracer at boot up. function-list is a comma separated
1161 list of functions. This list can be changed at run
1162 time by the set_ftrace_filter file in the debugfs
1165 ftrace_notrace=[function-list]
1166 [FTRACE] Do not trace the functions specified in
1167 function-list. This list can be changed at run time
1168 by the set_ftrace_notrace file in the debugfs
1171 ftrace_graph_filter=[function-list]
1172 [FTRACE] Limit the top level callers functions traced
1173 by the function graph tracer at boot up.
1174 function-list is a comma separated list of functions
1175 that can be changed at run time by the
1176 set_graph_function file in the debugfs tracing directory.
1178 ftrace_graph_notrace=[function-list]
1179 [FTRACE] Do not trace from the functions specified in
1180 function-list. This list is a comma separated list of
1181 functions that can be changed at run time by the
1182 set_graph_notrace file in the debugfs tracing directory.
1185 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1186 support via parallel port (up to 5 devices per port)
1187 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1188 See also Documentation/input/joystick-parport.txt
1192 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1196 gcov_persist= [GCOV] When non-zero (default), profiling data for
1197 kernel modules is saved and remains accessible via
1198 debugfs, even when the module is unloaded/reloaded.
1199 When zero, profiling data is discarded and associated
1200 debugfs files are removed at module unload time.
1202 gpt [EFI] Forces disk with valid GPT signature but
1203 invalid Protective MBR to be treated as GPT. If the
1204 primary GPT is corrupted, it enables the backup/alternate
1205 GPT to be used instead.
1207 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1208 the "Enable 0" bit of the configuration register.
1211 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1212 the "Enable 0" bit of the configuration register.
1215 grcan.select= [HW] Select which physical interface to use.
1218 grcan.txsize= [HW] Sets the size of the tx buffer.
1219 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1221 grcan.rxsize= [HW] Sets the size of the rx buffer.
1222 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1225 hashdist= [KNL,NUMA] Large hashes allocated during boot
1226 are distributed across NUMA nodes. Defaults on
1227 for 64-bit NUMA, off otherwise.
1228 Format: 0 | 1 (for off | on)
1230 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1232 hd= [EIDE] (E)IDE hard drive subsystem geometry
1233 Format: <cyl>,<head>,<sect>
1236 Disable Hardware Error Source Table (HEST) support;
1237 corresponding firmware-first mode error processing
1238 logic will be disabled.
1240 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1241 size of <nn>. This works even on boxes that have no
1242 highmem otherwise. This also works to reduce highmem
1243 size on bigger boxes.
1245 highres= [KNL] Enable/disable high resolution timer mode.
1246 Valid parameters: "on", "off"
1250 See Documentation/isdn/README.HiSax.
1254 hpet= [X86-32,HPET] option to control HPET usage
1255 Format: { enable (default) | disable | force |
1257 disable: disable HPET and use PIT instead
1258 force: allow force enabled of undocumented chips (ICH4,
1260 verbose: show contents of HPET registers during setup
1262 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1263 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1265 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1266 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1267 On x86-64 and powerpc, this option can be specified
1268 multiple times interleaved with hugepages= to reserve
1269 huge pages of different sizes. Valid pages sizes on
1270 x86-64 are 2M (when the CPU supports "pse") and 1G
1271 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1273 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1274 terminal devices. Valid values: 0..8
1275 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1276 If specified, z/VM IUCV HVC accepts connections
1277 from listed z/VM user IDs only.
1279 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1280 hardware thread id mappings.
1281 Format: <cpu>:<hwthread>
1284 Do not unregister boot console at start. This is only
1285 useful for debugging when something happens in the window
1286 between unregistering the boot console and initializing
1289 i2c_bus= [HW] Override the default board specific I2C bus speed
1290 or register an additional I2C bus that is not
1291 registered from board initialization code.
1295 i8042.debug [HW] Toggle i8042 debug mode
1296 i8042.direct [HW] Put keyboard port into non-translated mode
1297 i8042.dumbkbd [HW] Pretend that controller can only read data from
1298 keyboard and cannot control its state
1299 (Don't attempt to blink the leds)
1300 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1301 i8042.nokbd [HW] Don't check/create keyboard port
1302 i8042.noloop [HW] Disable the AUX Loopback command while probing
1304 i8042.nomux [HW] Don't check presence of an active multiplexing
1306 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1308 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1309 i8042.reset [HW] Reset the controller during init and cleanup
1310 i8042.unlock [HW] Unlock (ignore) the keylock
1311 i8042.kbdreset [HW] Reset device connected to KBD port
1315 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1316 indicates that the driver is running on unsupported
1318 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1319 does not match list of supported models.
1321 [HW] Report power status in /proc/i8k
1322 (disabled by default)
1323 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1326 i915.invert_brightness=
1327 [DRM] Invert the sense of the variable that is used to
1328 set the brightness of the panel backlight. Normally a
1329 brightness value of 0 indicates backlight switched off,
1330 and the maximum of the brightness value sets the backlight
1331 to maximum brightness. If this parameter is set to 0
1332 (default) and the machine requires it, or this parameter
1333 is set to 1, a brightness value of 0 sets the backlight
1334 to maximum brightness, and the maximum of the brightness
1335 value switches the backlight off.
1336 -1 -- never invert brightness
1337 0 -- machine default
1338 1 -- force brightness inversion
1341 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1343 ide-core.nodma= [HW] (E)IDE subsystem
1344 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1345 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1346 .cdrom .chs .ignore_cable are additional options
1347 See Documentation/ide/ide.txt.
1349 ide-generic.probe-mask= [HW] (E)IDE subsystem
1351 Probe mask for legacy ISA IDE ports. Depending on
1352 platform up to 6 ports are supported, enabled by
1353 setting corresponding bits in the mask to 1. The
1354 default value is 0x0, which has a special meaning.
1355 On systems that have PCI, it triggers scanning the
1356 PCI bus for the first and the second port, which
1357 are then probed. On systems without PCI the value
1358 of 0x0 enables probing the two first ports as if it
1361 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1362 Claim all unknown PCI IDE storage controllers.
1365 Format: idle=poll, idle=halt, idle=nomwait
1366 Poll forces a polling idle loop that can slightly
1367 improve the performance of waking up a idle CPU, but
1368 will use a lot of power and make the system run hot.
1370 idle=halt: Halt is forced to be used for CPU idle.
1371 In such case C2/C3 won't be used again.
1372 idle=nomwait: Disable mwait for CPU C-states
1374 ignore_loglevel [KNL]
1375 Ignore loglevel setting - this will print /all/
1376 kernel messages to the console. Useful for debugging.
1377 We also add it as printk module parameter, so users
1378 could change it dynamically, usually by
1379 /sys/module/printk/parameters/ignore_loglevel.
1381 ihash_entries= [KNL]
1382 Set number of hash buckets for inode cache.
1384 ima_appraise= [IMA] appraise integrity measurements
1385 Format: { "off" | "enforce" | "fix" | "log" }
1388 ima_appraise_tcb [IMA]
1389 The builtin appraise policy appraises all files
1393 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1397 The list of supported hash algorithms is defined
1398 in crypto/hash_info.h.
1401 Load a policy which meets the needs of the Trusted
1402 Computing Base. This means IMA will measure all
1403 programs exec'd, files mmap'd for exec, and all files
1404 opened for read by uid=0.
1407 Select one of defined IMA measurements template formats.
1408 Formats: { "ima" | "ima-ng" }
1412 [IMA] Define a custom template format.
1413 Format: { "field1|...|fieldN" }
1415 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1416 Format: <min_file_size>
1417 Set the minimal file size for using asynchronous hash.
1418 If left unspecified, ahash usage is disabled.
1420 ahash performance varies for different data sizes on
1421 different crypto accelerators. This option can be used
1422 to achieve the best performance for a particular HW.
1424 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1426 Set hashing buffer size. Default: 4k.
1428 ahash performance varies for different chunk sizes on
1429 different crypto accelerators. This option can be used
1430 to achieve best performance for particular HW.
1434 Run specified binary instead of /sbin/init as init
1437 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1438 for working out where the kernel is dying during
1441 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1442 initcall functions. Useful for debugging built-in
1443 modules and initcalls.
1445 initrd= [BOOT] Specify the location of the initial ramdisk
1447 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1450 int_pln_enable [x86] Enable power limit notification interrupt
1452 integrity_audit=[IMA]
1453 Format: { "0" | "1" }
1454 0 -- basic integrity auditing messages. (Default)
1455 1 -- additional integrity auditing messages.
1457 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1459 Enable intel iommu driver.
1461 Disable intel iommu driver.
1462 igfx_off [Default Off]
1463 By default, gfx is mapped as normal device. If a gfx
1464 device has a dedicated DMAR unit, the DMAR unit is
1465 bypassed by not enabling DMAR with this option. In
1466 this case, gfx device will use physical address for
1469 With this option iommu will not optimize to look
1470 for io virtual address below 32-bit forcing dual
1471 address cycle on pci bus for cards supporting greater
1472 than 32-bit addressing. The default is to look
1473 for translation below 32-bit and if not available
1474 then look in the higher range.
1475 strict [Default Off]
1476 With this option on every unmap_single operation will
1477 result in a hardware IOTLB flush operation as opposed
1478 to batching them for performance.
1479 sp_off [Default Off]
1480 By default, super page will be supported if Intel IOMMU
1481 has the capability. With this option, super page will
1484 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1485 0 disables intel_idle and fall back on acpi_idle.
1486 1 to 6 specify maximum depth of C-state.
1490 Do not enable intel_pstate as the default
1491 scaling driver for the supported processors
1493 Enable intel_pstate on systems that prohibit it by default
1494 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1495 instead of acpi-cpufreq may disable platform features, such
1496 as thermal controls and power capping, that rely on ACPI
1497 P-States information being indicated to OSPM and therefore
1498 should be used with caution. This option does not work with
1499 processors that aren't supported by the intel_pstate driver
1500 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1502 Do not enable hardware P state control (HWP)
1505 Only load intel_pstate on systems which support
1506 hardware P state control (HWP) if available.
1508 intremap= [X86-64, Intel-IOMMU]
1509 on enable Interrupt Remapping (default)
1510 off disable Interrupt Remapping
1511 nosid disable Source ID checking
1513 BIOS x2APIC opt-out request will be ignored
1515 iomem= Disable strict checking of access to MMIO memory
1516 strict regions from userspace.
1531 nobypass [PPC/POWERNV]
1532 Disable IOMMU bypass, using IOMMU for PCI devices.
1535 io7= [HW] IO7 for Marvel based alpha systems
1536 See comment before marvel_specify_io7 in
1537 arch/alpha/kernel/core_marvel.c.
1539 io_delay= [X86] I/O delay method
1541 Standard port 0x80 based delay
1543 Alternate port 0xed based delay (needed on some systems)
1545 Simple two microseconds delay
1550 See Documentation/filesystems/nfs/nfsroot.txt.
1553 When an interrupt is not handled search all handlers
1554 for it. Intended to get systems with badly broken
1558 When an interrupt is not handled search all handlers
1559 for it. Also check all handlers each timer
1560 interrupt. Intended to get systems with badly broken
1564 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1566 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1568 <cpu number>,...,<cpu number>
1570 <cpu number>-<cpu number>
1571 (must be a positive range in ascending order)
1573 <cpu number>,...,<cpu number>-<cpu number>
1575 This option can be used to specify one or more CPUs
1576 to isolate from the general SMP balancing and scheduling
1577 algorithms. You can move a process onto or off an
1578 "isolated" CPU via the CPU affinity syscalls or cpuset.
1579 <cpu number> begins at 0 and the maximum value is
1580 "number of CPUs in system - 1".
1582 This option is the preferred way to isolate CPUs. The
1583 alternative -- manually setting the CPU mask of all
1584 tasks in the system -- can cause problems and
1585 suboptimal load balancer performance.
1589 ivrs_ioapic [HW,X86_64]
1590 Provide an override to the IOAPIC-ID<->DEVICE-ID
1591 mapping provided in the IVRS ACPI table. For
1592 example, to map IOAPIC-ID decimal 10 to
1593 PCI device 00:14.0 write the parameter as:
1594 ivrs_ioapic[10]=00:14.0
1596 ivrs_hpet [HW,X86_64]
1597 Provide an override to the HPET-ID<->DEVICE-ID
1598 mapping provided in the IVRS ACPI table. For
1599 example, to map HPET-ID decimal 0 to
1600 PCI device 00:14.0 write the parameter as:
1601 ivrs_hpet[0]=00:14.0
1603 js= [HW,JOY] Analog joystick
1604 See Documentation/input/joystick.txt.
1607 Enable/disable kernel and module base offset ASLR
1608 (Address Space Layout Randomization) if built into
1609 the kernel. When CONFIG_HIBERNATION is selected,
1610 kASLR is disabled by default. When kASLR is enabled,
1611 hibernation will be disabled.
1615 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1616 specifies the amount of memory usable by the kernel
1617 for non-movable allocations. The requested amount is
1618 spread evenly throughout all nodes in the system. The
1619 remaining memory in each node is used for Movable
1620 pages. In the event, a node is too small to have both
1621 kernelcore and Movable pages, kernelcore pages will
1622 take priority and other nodes will have a larger number
1623 of Movable pages. The Movable zone is used for the
1624 allocation of pages that may be reclaimed or moved
1625 by the page migration subsystem. This means that
1626 HugeTLB pages may not be allocated from this zone.
1627 Note that allocations like PTEs-from-HighMem still
1628 use the HighMem zone if it exists, and the Normal
1629 zone if it does not.
1631 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1632 Format: <Controller#>[,poll interval]
1633 The controller # is the number of the ehci usb debug
1634 port as it is probed via PCI. The poll interval is
1635 optional and is the number seconds in between
1636 each poll cycle to the debug port in case you need
1637 the functionality for interrupting the kernel with
1638 gdb or control-c on the dbgp connection. When
1639 not using this parameter you use sysrq-g to break into
1640 the kernel debugger.
1642 kgdboc= [KGDB,HW] kgdb over consoles.
1643 Requires a tty driver that supports console polling,
1644 or a supported polling keyboard driver (non-usb).
1645 Serial only format: <serial_device>[,baud]
1646 keyboard only format: kbd
1647 keyboard and serial format: kbd,<serial_device>[,baud]
1648 Optional Kernel mode setting:
1649 kms, kbd format: kms,kbd
1650 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1652 kgdbwait [KGDB] Stop kernel execution and enter the
1653 kernel debugger at the earliest opportunity.
1655 kmac= [MIPS] korina ethernet MAC address.
1656 Configure the RouterBoard 532 series on-chip
1657 Ethernet adapter MAC address.
1659 kmemleak= [KNL] Boot-time kmemleak enable/disable
1660 Valid arguments: on, off
1662 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1665 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1666 Valid arguments: 0, 1, 2
1667 kmemcheck=0 (disabled)
1668 kmemcheck=1 (enabled)
1669 kmemcheck=2 (one-shot mode)
1670 Default: 2 (one-shot mode)
1672 kstack=N [X86] Print N words from the kernel stack
1675 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1676 Default is 0 (don't ignore, but inject #GP)
1678 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1682 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1683 Default is 1 (enabled)
1685 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1687 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1689 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1690 (virtualized MMU) support on capable Intel chips.
1691 Default is 1 (enabled)
1693 kvm-intel.emulate_invalid_guest_state=
1694 [KVM,Intel] Enable emulation of invalid guest states
1695 Default is 0 (disabled)
1697 kvm-intel.flexpriority=
1698 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1699 Default is 1 (enabled)
1702 [KVM,Intel] Enable VMX nesting (nVMX).
1703 Default is 0 (disabled)
1705 kvm-intel.unrestricted_guest=
1706 [KVM,Intel] Disable unrestricted guest feature
1707 (virtualized real and unpaged mode) on capable
1708 Intel chips. Default is 1 (enabled)
1710 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1711 feature (tagged TLBs) on capable Intel chips.
1712 Default is 1 (enabled)
1718 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1721 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1722 value for LAPIC timer one-shot implementation. Default
1723 back to the programmable timer unit in the LAPIC.
1725 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1728 libata.dma= [LIBATA] DMA control
1729 libata.dma=0 Disable all PATA and SATA DMA
1730 libata.dma=1 PATA and SATA Disk DMA only
1731 libata.dma=2 ATAPI (CDROM) DMA only
1732 libata.dma=4 Compact Flash DMA only
1733 Combinations also work, so libata.dma=3 enables DMA
1734 for disks and CDROMs, but not CFs.
1736 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1737 libata.ignore_hpa=0 keep BIOS limits (default)
1738 libata.ignore_hpa=1 ignore limits, using full disk
1740 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1744 libata.force= [LIBATA] Force configurations. The format is comma
1745 separated list of "[ID:]VAL" where ID is
1746 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1747 matching port, link or device. Basically, it matches
1748 the ATA ID string printed on console by libata. If
1749 the whole ID part is omitted, the last PORT and DEVICE
1750 values are used. If ID hasn't been specified yet, the
1751 configuration applies to all ports, links and devices.
1753 If only DEVICE is omitted, the parameter applies to
1754 the port and all links and devices behind it. DEVICE
1755 number of 0 either selects the first device or the
1756 first fan-out link behind PMP device. It does not
1757 select the host link. DEVICE number of 15 selects the
1758 host link and device attached to it.
1760 The VAL specifies the configuration to force. As long
1761 as there's no ambiguity shortcut notation is allowed.
1762 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1763 The following configurations can be forced.
1765 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1766 Any ID with matching PORT is used.
1768 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1770 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1771 udma[/][16,25,33,44,66,100,133] notation is also
1774 * [no]ncq: Turn on or off NCQ.
1776 * nohrst, nosrst, norst: suppress hard, soft
1779 * rstonce: only attempt one reset during
1780 hot-unplug link recovery
1782 * dump_id: dump IDENTIFY data.
1784 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1786 * disable: Disable this device.
1788 If there are multiple matching configurations changing
1789 the same attribute, the last one is used.
1791 memblock=debug [KNL] Enable memblock debug messages.
1793 load_ramdisk= [RAM] List of ramdisks to load from floppy
1794 See Documentation/blockdev/ramdisk.txt.
1796 lockd.nlm_grace_period=P [NFS] Assign grace period.
1799 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1802 lockd.nlm_timeout=T [NFS] Assign timeout value.
1805 lockd.nlm_udpport=M [NFS] Assign UDP port.
1808 locktorture.nreaders_stress= [KNL]
1809 Set the number of locking read-acquisition kthreads.
1810 Defaults to being automatically set based on the
1811 number of online CPUs.
1813 locktorture.nwriters_stress= [KNL]
1814 Set the number of locking write-acquisition kthreads.
1816 locktorture.onoff_holdoff= [KNL]
1817 Set time (s) after boot for CPU-hotplug testing.
1819 locktorture.onoff_interval= [KNL]
1820 Set time (s) between CPU-hotplug operations, or
1821 zero to disable CPU-hotplug testing.
1823 locktorture.shuffle_interval= [KNL]
1824 Set task-shuffle interval (jiffies). Shuffling
1825 tasks allows some CPUs to go into dyntick-idle
1826 mode during the locktorture test.
1828 locktorture.shutdown_secs= [KNL]
1829 Set time (s) after boot system shutdown. This
1830 is useful for hands-off automated testing.
1832 locktorture.stat_interval= [KNL]
1833 Time (s) between statistics printk()s.
1835 locktorture.stutter= [KNL]
1836 Time (s) to stutter testing, for example,
1837 specifying five seconds causes the test to run for
1838 five seconds, wait for five seconds, and so on.
1839 This tests the locking primitive's ability to
1840 transition abruptly to and from idle.
1842 locktorture.torture_runnable= [BOOT]
1843 Start locktorture running at boot time.
1845 locktorture.torture_type= [KNL]
1846 Specify the locking implementation to test.
1848 locktorture.verbose= [KNL]
1849 Enable additional printk() statements.
1851 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1854 loglevel= All Kernel Messages with a loglevel smaller than the
1855 console loglevel will be printed to the console. It can
1856 also be changed with klogd or other programs. The
1857 loglevels are defined as follows:
1859 0 (KERN_EMERG) system is unusable
1860 1 (KERN_ALERT) action must be taken immediately
1861 2 (KERN_CRIT) critical conditions
1862 3 (KERN_ERR) error conditions
1863 4 (KERN_WARNING) warning conditions
1864 5 (KERN_NOTICE) normal but significant condition
1865 6 (KERN_INFO) informational
1866 7 (KERN_DEBUG) debug-level messages
1868 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1869 in bytes. n must be a power of two and greater
1870 than the minimal size. The minimal size is defined
1871 by LOG_BUF_SHIFT kernel config parameter. There is
1872 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1873 that allows to increase the default size depending on
1874 the number of CPUs. See init/Kconfig for more details.
1876 logo.nologo [FB] Disables display of the built-in Linux logo.
1877 This may be used to provide more screen space for
1878 kernel log messages and is useful when debugging
1879 kernel boot problems.
1881 lp=0 [LP] Specify parallel ports to use, e.g,
1882 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1883 lp=reset first parallel port). 'lp=0' disables the
1884 lp=auto printer driver. 'lp=reset' (which can be
1885 specified in addition to the ports) causes
1886 attached printers to be reset. Using
1887 lp=port1,port2,... specifies the parallel ports
1888 to associate lp devices with, starting with
1889 lp0. A port specification may be 'none' to skip
1890 that lp device, or a parport name such as
1891 'parport0'. Specifying 'lp=auto' instead of a
1892 port specification list means that device IDs
1893 from each port should be examined, to see if
1894 an IEEE 1284-compliant printer is attached; if
1895 so, the driver will manage that printer.
1896 See also header of drivers/char/lp.c.
1899 Sets loops_per_jiffy to given constant, thus avoiding
1900 time-consuming boot-time autodetection (up to 250 ms per
1901 CPU). 0 enables autodetection (default). To determine
1902 the correct value for your kernel, boot with normal
1903 autodetection and see what value is printed. Note that
1904 on SMP systems the preset will be applied to all CPUs,
1905 which is likely to cause problems if your CPUs need
1906 significantly divergent settings. An incorrect value
1907 will cause delays in the kernel to be wrong, leading to
1908 unpredictable I/O errors and other breakage. Although
1909 unlikely, in the extreme case this might damage your
1913 Format: <io>,<irq>,<dma>
1915 machvec= [IA-64] Force the use of a particular machine-vector
1916 (machvec) in a generic kernel.
1917 Example: machvec=hpzx1_swiotlb
1919 machtype= [Loongson] Share the same kernel image file between different
1921 Example: machtype=lemote-yeeloong-2f-7inch
1923 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1924 than or equal to this physical address is ignored.
1926 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1927 should make use of. maxcpus=n : n >= 0 limits the
1928 kernel to using 'n' processors. n=0 is a special case,
1929 it is equivalent to "nosmp", which also disables
1932 max_loop= [LOOP] The number of loop block devices that get
1933 (loop.max_loop) unconditionally pre-created at init time. The default
1934 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1935 of statically allocating a predefined number, loop
1936 devices can be requested on-demand with the
1937 /dev/loop-control interface.
1939 mce [X86-32] Machine Check Exception
1941 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1943 md= [HW] RAID subsystems devices and level
1944 See Documentation/md.txt.
1947 Format: <first>,<last>
1948 Specifies range of consoles to be captured by the MDA.
1950 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1951 Amount of memory to be used when the kernel is not able
1952 to see the whole system memory or for test.
1953 [X86] Work as limiting max address. Use together
1954 with memmap= to avoid physical address space collisions.
1955 Without memmap= PCI devices could be placed at addresses
1956 belonging to unused RAM.
1958 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1962 [KNL,SH] Allow user to override the default size for
1963 per-device physically contiguous DMA buffers.
1965 memmap=exactmap [KNL,X86] Enable setting of an exact
1966 E820 memory map, as specified by the user.
1967 Such memmap=exactmap lines can be constructed based on
1968 BIOS output or other requirements. See the memmap=nn@ss
1971 memmap=nn[KMG]@ss[KMG]
1972 [KNL] Force usage of a specific region of memory.
1973 Region of memory to be used is from ss to ss+nn.
1975 memmap=nn[KMG]#ss[KMG]
1976 [KNL,ACPI] Mark specific memory as ACPI data.
1977 Region of memory to be marked is from ss to ss+nn.
1979 memmap=nn[KMG]$ss[KMG]
1980 [KNL,ACPI] Mark specific memory as reserved.
1981 Region of memory to be reserved is from ss to ss+nn.
1982 Example: Exclude memory from 0x18690000-0x1869ffff
1983 memmap=64K$0x18690000
1985 memmap=0x10000$0x18690000
1987 memmap=nn[KMG]!ss[KMG]
1988 [KNL,X86] Mark specific memory as protected.
1989 Region of memory to be used, from ss to ss+nn.
1990 The memory region may be marked as e820 type 12 (0xc)
1991 and is NVDIMM or ADR memory.
1993 memory_corruption_check=0/1 [X86]
1994 Some BIOSes seem to corrupt the first 64k of
1995 memory when doing things like suspend/resume.
1996 Setting this option will scan the memory
1997 looking for corruption. Enabling this will
1998 both detect corruption and prevent the kernel
1999 from using the memory being corrupted.
2000 However, its intended as a diagnostic tool; if
2001 repeatable BIOS-originated corruption always
2002 affects the same memory, you can use memmap=
2003 to prevent the kernel from using that memory.
2005 memory_corruption_check_size=size [X86]
2006 By default it checks for corruption in the low
2007 64k, making this memory unavailable for normal
2008 use. Use this parameter to scan for
2009 corruption in more or less memory.
2011 memory_corruption_check_period=seconds [X86]
2012 By default it checks for corruption every 60
2013 seconds. Use this parameter to check at some
2014 other rate. 0 disables periodic checking.
2016 memtest= [KNL,X86,ARM] Enable memtest
2018 default : 0 <disable>
2019 Specifies the number of memtest passes to be
2020 performed. Each pass selects another test
2021 pattern from a given set of patterns. Memtest
2022 fills the memory with this pattern, validates
2023 memory contents and reserves bad memory
2024 regions that are detected.
2026 meye.*= [HW] Set MotionEye Camera parameters
2027 See Documentation/video4linux/meye.txt.
2029 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2030 Multi-Function General Purpose Timers on AMD Geode
2033 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2034 the BIOS has incorrectly applied a workaround. TinyBIOS
2035 version 0.98 is known to be affected, 0.99 fixes the
2036 problem by letting the user disable the workaround.
2040 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2041 physical address is ignored.
2043 mini2440= [ARM,HW,KNL]
2044 Format:[0..2][b][c][t]
2046 MINI2440 configuration specification:
2047 0 - The attached screen is the 3.5" TFT
2048 1 - The attached screen is the 7" TFT
2049 2 - The VGA Shield is attached (1024x768)
2050 Leaving out the screen size parameter will not load
2051 the TFT driver, and the framebuffer will be left
2053 b - Enable backlight. The TFT backlight pin will be
2054 linked to the kernel VESA blanking code and a GPIO
2055 LED. This parameter is not necessary when using the
2057 c - Enable the s3c camera interface.
2058 t - Reserved for enabling touchscreen support. The
2059 touchscreen support is not enabled in the mainstream
2060 kernel as of 2.6.30, a preliminary port can be found
2061 in the "bleeding edge" mini2440 support kernel at
2062 http://repo.or.cz/w/linux-2.6/mini2440.git
2065 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2066 parameter allows control of the logging verbosity for
2067 the additional memory initialisation checks. A value
2068 of 0 disables mminit logging and a level of 4 will
2069 log everything. Information is printed at KERN_DEBUG
2070 so loglevel=8 may also need to be specified.
2073 [KNL] When CONFIG_MODULE_SIG is set, this means that
2074 modules without (valid) signatures will fail to load.
2075 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2076 is always true, so this option does nothing.
2079 [MOUSE] Maximum time between finger touching and
2080 leaving touchpad surface for touch to be considered
2081 a tap and be reported as a left button click (for
2082 touchpads working in absolute mode only).
2084 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2085 reporting absolute coordinates, such as tablets
2086 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2087 reporting absolute coordinates, such as tablets
2089 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2090 is similar to kernelcore except it specifies the
2091 amount of memory used for migratable allocations.
2092 If both kernelcore and movablecore is specified,
2093 then kernelcore will be at *least* the specified
2094 value but may be more. If movablecore on its own
2095 is specified, the administrator must be careful
2096 that the amount of memory usable for all allocations
2099 movable_node [KNL,X86] Boot-time switch to enable the effects
2100 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2102 MTD_Partition= [MTD]
2103 Format: <name>,<region-number>,<size>,<offset>
2105 MTD_Region= [MTD] Format:
2106 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2109 See drivers/mtd/cmdlinepart.c.
2111 multitce=off [PPC] This parameter disables the use of the pSeries
2112 firmware feature for updating multiple TCE entries
2115 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2117 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2119 boundary - index of last SLC block on Flex-OneNAND.
2120 The remaining blocks are configured as MLC blocks.
2121 lock - Configure if Flex-OneNAND boundary should be locked.
2122 Once locked, the boundary cannot be changed.
2123 1 indicates lock status, 0 indicates unlock status.
2126 ARM/S3C2412 JIVE boot control
2128 See arch/arm/mach-s3c2412/mach-jive.c
2130 mtouchusb.raw_coordinates=
2131 [HW] Make the MicroTouch USB driver use raw coordinates
2132 ('y', default) or cooked coordinates ('n')
2134 mtrr_chunk_size=nn[KMG] [X86]
2135 used for mtrr cleanup. It is largest continuous chunk
2136 that could hold holes aka. UC entries.
2138 mtrr_gran_size=nn[KMG] [X86]
2139 Used for mtrr cleanup. It is granularity of mtrr block.
2141 Large value could prevent small alignment from
2144 mtrr_spare_reg_nr=n [X86]
2146 Range: 0,7 : spare reg number
2148 Used for mtrr cleanup. It is spare mtrr entries number.
2149 Set to 2 or more if your graphical card needs more.
2151 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2153 netdev= [NET] Network devices parameters
2154 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2155 Note that mem_start is often overloaded to mean
2156 something different and driver-specific.
2157 This usage is only documented in each driver source
2161 [NETFILTER] Enable connection tracking flow accounting
2162 0 to disable accounting
2163 1 to enable accounting
2166 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2167 See Documentation/filesystems/nfs/nfsroot.txt.
2169 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2170 See Documentation/filesystems/nfs/nfsroot.txt.
2172 nfsrootdebug [NFS] enable nfsroot debugging messages.
2173 See Documentation/filesystems/nfs/nfsroot.txt.
2175 nfs.callback_tcpport=
2176 [NFS] set the TCP port on which the NFSv4 callback
2177 channel should listen.
2180 [NFS] sets the pathname to the program which is used
2181 to update the NFS client cache entries.
2183 nfs.cache_getent_timeout=
2184 [NFS] sets the timeout after which an attempt to
2185 update a cache entry is deemed to have failed.
2187 nfs.idmap_cache_timeout=
2188 [NFS] set the maximum lifetime for idmapper cache
2192 [NFS] enable 64-bit inode numbers.
2193 If zero, the NFS client will fake up a 32-bit inode
2194 number for the readdir() and stat() syscalls instead
2195 of returning the full 64-bit number.
2196 The default is to return 64-bit inode numbers.
2198 nfs.max_session_slots=
2199 [NFSv4.1] Sets the maximum number of session slots
2200 the client will attempt to negotiate with the server.
2201 This limits the number of simultaneous RPC requests
2202 that the client can send to the NFSv4.1 server.
2203 Note that there is little point in setting this
2204 value higher than the max_tcp_slot_table_limit.
2206 nfs.nfs4_disable_idmapping=
2207 [NFSv4] When set to the default of '1', this option
2208 ensures that both the RPC level authentication
2209 scheme and the NFS level operations agree to use
2210 numeric uids/gids if the mount is using the
2211 'sec=sys' security flavour. In effect it is
2212 disabling idmapping, which can make migration from
2213 legacy NFSv2/v3 systems to NFSv4 easier.
2214 Servers that do not support this mode of operation
2215 will be autodetected by the client, and it will fall
2216 back to using the idmapper.
2217 To turn off this behaviour, set the value to '0'.
2219 [NFS4] Specify an additional fixed unique ident-
2220 ification string that NFSv4 clients can insert into
2221 their nfs_client_id4 string. This is typically a
2222 UUID that is generated at system install time.
2224 nfs.send_implementation_id =
2225 [NFSv4.1] Send client implementation identification
2226 information in exchange_id requests.
2227 If zero, no implementation identification information
2229 The default is to send the implementation identification
2232 nfs.recover_lost_locks =
2233 [NFSv4] Attempt to recover locks that were lost due
2234 to a lease timeout on the server. Please note that
2235 doing this risks data corruption, since there are
2236 no guarantees that the file will remain unchanged
2237 after the locks are lost.
2238 If you want to enable the kernel legacy behaviour of
2239 attempting to recover these locks, then set this
2241 The default parameter value of '0' causes the kernel
2242 not to attempt recovery of lost locks.
2244 nfsd.nfs4_disable_idmapping=
2245 [NFSv4] When set to the default of '1', the NFSv4
2246 server will return only numeric uids and gids to
2247 clients using auth_sys, and will accept numeric uids
2248 and gids from such clients. This is intended to ease
2249 migration from NFSv2/v3.
2251 objlayoutdriver.osd_login_prog=
2252 [NFS] [OBJLAYOUT] sets the pathname to the program which
2253 is used to automatically discover and login into new
2254 osd-targets. Please see:
2255 Documentation/filesystems/pnfs.txt for more explanations
2257 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2258 when a NMI is triggered.
2259 Format: [state][,regs][,debounce][,die]
2261 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2262 Format: [panic,][nopanic,][num]
2264 0 - turn nmi_watchdog off
2265 1 - turn nmi_watchdog on
2266 When panic is specified, panic when an NMI watchdog
2267 timeout occurs (or 'nopanic' to override the opposite
2269 This is useful when you use a panic=... timeout and
2270 need the box quickly up again.
2272 netpoll.carrier_timeout=
2273 [NET] Specifies amount of time (in seconds) that
2274 netpoll should wait for a carrier. By default netpoll
2277 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2278 emulation library even if a 387 maths coprocessor
2282 [HW] Never suspend the console
2283 Disable suspending of consoles during suspend and
2284 hibernate operations. Once disabled, debugging
2285 messages can reach various consoles while the rest
2286 of the system is being put to sleep (ie, while
2287 debugging driver suspend/resume hooks). This may
2288 not work reliably with all consoles, but is known
2289 to work with serial and VGA consoles.
2290 To facilitate more flexible debugging, we also add
2291 console_suspend, a printk module parameter to control
2292 it. Users could use console_suspend (usually
2293 /sys/module/printk/parameters/console_suspend) to
2294 turn on/off it dynamically.
2296 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2297 caches in the slab allocator. Saves per-node memory,
2298 but will impact performance.
2302 noapic [SMP,APIC] Tells the kernel to not make use of any
2303 IOAPICs that may be present in the system.
2305 noautogroup Disable scheduler automatic task group creation.
2307 nobats [PPC] Do not use BATs for mapping kernel lowmem
2308 on "Classic" PPC cores.
2312 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2314 nodelayacct [KNL] Disable per-task delay accounting
2316 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2318 nodsp [SH] Disable hardware DSP at boot time.
2320 noefi Disable EFI runtime services support.
2325 On X86-32 available only on PAE configured kernels.
2326 noexec=on: enable non-executable mappings (default)
2327 noexec=off: disable non-executable mappings
2330 Disable SMAP (Supervisor Mode Access Prevention)
2331 even if it is supported by processor.
2334 Disable SMEP (Supervisor Mode Execution Prevention)
2335 even if it is supported by processor.
2338 This affects only 32-bit executables.
2339 noexec32=on: enable non-executable mappings (default)
2340 read doesn't imply executable mappings
2341 noexec32=off: disable non-executable mappings
2342 read implies executable mappings
2344 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2346 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2347 register save and restore. The kernel will only save
2348 legacy floating-point registers on task switch.
2350 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2352 noxsave [BUGS=X86] Disables x86 extended register state save
2353 and restore using xsave. The kernel will fallback to
2354 enabling legacy floating-point and sse state.
2356 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2357 register states. The kernel will fall back to use
2358 xsave to save the states. By using this parameter,
2359 performance of saving the states is degraded because
2360 xsave doesn't support modified optimization while
2361 xsaveopt supports it on xsaveopt enabled systems.
2363 noxsaves [X86] Disables xsaves and xrstors used in saving and
2364 restoring x86 extended register state in compacted
2365 form of xsave area. The kernel will fall back to use
2366 xsaveopt and xrstor to save and restore the states
2367 in standard form of xsave area. By using this
2368 parameter, xsave area per process might occupy more
2369 memory on xsaves enabled systems.
2371 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2372 wfi(ARM) instruction doesn't work correctly and not to
2373 use it. This is also useful when using JTAG debugger.
2375 no_file_caps Tells the kernel not to honor file capabilities. The
2376 only way then for a file to be executed with privilege
2377 is to be setuid root or executed by root.
2379 nohalt [IA-64] Tells the kernel not to use the power saving
2380 function PAL_HALT_LIGHT when idle. This increases
2381 power-consumption. On the positive side, it reduces
2382 interrupt wake-up latency, which may improve performance
2383 in certain environments such as networked servers or
2386 nohibernate [HIBERNATION] Disable hibernation and resume.
2388 nohz= [KNL] Boottime enable/disable dynamic ticks
2389 Valid arguments: on, off
2392 nohz_full= [KNL,BOOT]
2393 In kernels built with CONFIG_NO_HZ_FULL=y, set
2394 the specified list of CPUs whose tick will be stopped
2395 whenever possible. The boot CPU will be forced outside
2396 the range to maintain the timekeeping.
2397 The CPUs in this range must also be included in the
2400 noiotrap [SH] Disables trapped I/O port accesses.
2402 noirqdebug [X86-32] Disables the code which attempts to detect and
2403 disable unhandled interrupt sources.
2405 no_timer_check [X86,APIC] Disables the code which tests for
2406 broken timer IRQ sources.
2408 noisapnp [ISAPNP] Disables ISA PnP code.
2410 noinitrd [RAM] Tells the kernel not to load any configured
2413 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2415 [Deprecated - use intremap=off]
2419 nojitter [IA-64] Disables jitter checking for ITC timers.
2421 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2423 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2426 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2427 steal time is computed, but won't influence scheduler
2430 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2432 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2434 noltlbs [PPC] Do not use large page/tlb entries for kernel
2435 lowmem mapping on PPC40x.
2437 nomca [IA-64] Disable machine check abort handling
2439 nomce [X86-32] Machine Check Exception
2441 nomfgpt [X86-32] Disable Multi-Function General Purpose
2442 Timer usage (for AMD Geode machines).
2444 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2445 shutdown the other cpus. Instead use the REBOOT_VECTOR
2448 nomodule Disable module load
2450 nopat [X86] Disable PAT (page attribute table extension of
2451 pagetables) support.
2453 norandmaps Don't use address space randomization. Equivalent to
2454 echo 0 > /proc/sys/kernel/randomize_va_space
2456 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2458 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2459 with UP alternatives
2461 nordrand [X86] Disable kernel use of the RDRAND and
2462 RDSEED instructions even if they are supported
2463 by the processor. RDRAND and RDSEED are still
2464 available to user space applications.
2466 noresume [SWSUSP] Disables resume and restores original swap
2469 no-scroll [VGA] Disables scrollback.
2470 This is required for the Braillex ib80-piezo Braille
2471 reader made by F.H. Papenmeier (Germany).
2475 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2477 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2478 and disable the IO APIC. legacy for "maxcpus=0".
2480 nosoftlockup [KNL] Disable the soft-lockup detector.
2482 nosync [HW,M68K] Disables sync negotiation for all devices.
2484 notsc [BUGS=X86-32] Disable Time Stamp Counter
2486 nousb [USB] Disable the USB subsystem
2488 nowatchdog [KNL] Disable both lockup detectors, i.e.
2489 soft-lockup and NMI watchdog (hard-lockup).
2493 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2495 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2496 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2497 Some features depend on CPU0. Known dependencies are:
2498 1. Resume from suspend/hibernate depends on CPU0.
2499 Suspend/hibernate will fail if CPU0 is offline and you
2500 need to online CPU0 before suspend/hibernate.
2501 2. PIC interrupts also depend on CPU0. CPU0 can't be
2502 removed if a PIC interrupt is detected.
2503 It's said poweroff/reboot may depend on CPU0 on some
2504 machines although I haven't seen such issues so far
2505 after CPU0 is offline on a few tested machines.
2506 If the dependencies are under your control, you can
2507 turn on cpu0_hotplug.
2509 nptcg= [IA-64] Override max number of concurrent global TLB
2510 purges which is reported from either PAL_VM_SUMMARY or
2513 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2514 could support. nr_cpus=n : n >= 1 limits the kernel to
2515 supporting 'n' processors. Later in runtime you can not
2516 use hotplug cpu feature to put more cpu back to online.
2517 just like you compile the kernel NR_CPUS=n
2519 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2521 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2522 Allowed values are enable and disable
2524 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2525 one of ['zone', 'node', 'default'] can be specified
2526 This can be set from sysctl after boot.
2527 See Documentation/sysctl/vm.txt for details.
2529 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2530 See Documentation/debugging-via-ohci1394.txt for more
2533 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2534 Rather than timing out after 20 ms if an EC
2535 command is not properly ACKed, override the length
2536 of the timeout. We have interrupts disabled while
2537 waiting for the ACK, so if this is set too high
2538 interrupts *may* be lost!
2540 omap_mux= [OMAP] Override bootloader pin multiplexing.
2541 Format: <mux_mode0.mode_name=value>...
2542 For example, to override I2C bus2:
2543 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2545 oprofile.timer= [HW]
2546 Use timer interrupt instead of performance counters
2548 oprofile.cpu_type= Force an oprofile cpu type
2549 This might be useful if you have an older oprofile
2550 userland or if you want common events.
2551 Format: { arch_perfmon }
2552 arch_perfmon: [X86] Force use of architectural
2553 perfmon on Intel CPUs instead of the
2554 CPU specific event set.
2555 timer: [X86] Force use of architectural NMI
2556 timer mode (see also oprofile.timer
2557 for generic hr timer mode)
2558 [s390] Force legacy basic mode sampling
2559 (report cpu_type "timer")
2561 oops=panic Always panic on oopses. Default is to just kill the
2562 process, but there is a small probability of
2563 deadlocking the machine.
2564 This will also cause panics on machine check exceptions.
2565 Useful together with panic=30 to trigger a reboot.
2568 See Documentation/sound/oss/oss-parameters.txt
2570 page_owner= [KNL] Boot-time page_owner enabling option.
2571 Storage of the information about who allocated
2572 each page is disabled in default. With this switch,
2574 on: enable the feature
2576 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2577 timeout > 0: seconds before rebooting
2578 timeout = 0: wait forever
2579 timeout < 0: reboot immediately
2582 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2585 crash_kexec_post_notifiers
2586 Run kdump after running panic-notifiers and dumping
2587 kmsg. This only for the users who doubt kdump always
2588 succeeds in any situation.
2589 Note that this also increases risks of kdump failure,
2590 because some panic notifiers can make the crashed
2591 kernel more unstable.
2593 parkbd.port= [HW] Parallel port number the keyboard adapter is
2594 connected to, default is 0.
2596 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2597 0 for XT, 1 for AT (default is AT).
2600 parport= [HW,PPT] Specify parallel ports. 0 disables.
2601 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2602 Use 'auto' to force the driver to use any
2603 IRQ/DMA settings detected (the default is to
2604 ignore detected IRQ/DMA settings because of
2605 possible conflicts). You can specify the base
2606 address, IRQ, and DMA settings; IRQ and DMA
2607 should be numbers, or 'auto' (for using detected
2608 settings on that particular port), or 'nofifo'
2609 (to avoid using a FIFO even if it is detected).
2610 Parallel ports are assigned in the order they
2611 are specified on the command line, starting
2614 parport_init_mode= [HW,PPT]
2615 Configure VIA parallel port to operate in
2616 a specific mode. This is necessary on Pegasos
2617 computer where firmware has no options for setting
2618 up parallel port mode and sets it to spp.
2619 Currently this function knows 686a and 8231 chips.
2620 Format: [spp|ps2|epp|ecp|ecpepp]
2623 Halt all CPUs after the first oops has been printed for
2624 the specified number of seconds. This is to be used if
2625 your oopses keep scrolling off the screen.
2630 See header of drivers/block/paride/pcd.c.
2631 See also Documentation/blockdev/paride.txt.
2633 pci=option[,option...] [PCI] various PCI subsystem options:
2634 earlydump [X86] dump PCI config space before the kernel
2636 off [X86] don't probe for the PCI bus
2637 bios [X86-32] force use of PCI BIOS, don't access
2638 the hardware directly. Use this if your machine
2639 has a non-standard PCI host bridge.
2640 nobios [X86-32] disallow use of PCI BIOS, only direct
2641 hardware access methods are allowed. Use this
2642 if you experience crashes upon bootup and you
2643 suspect they are caused by the BIOS.
2644 conf1 [X86] Force use of PCI Configuration
2646 conf2 [X86] Force use of PCI Configuration
2648 noaer [PCIE] If the PCIEAER kernel config parameter is
2649 enabled, this kernel boot option can be used to
2650 disable the use of PCIE advanced error reporting.
2651 nodomains [PCI] Disable support for multiple PCI
2652 root domains (aka PCI segments, in ACPI-speak).
2653 nommconf [X86] Disable use of MMCONFIG for PCI
2655 check_enable_amd_mmconf [X86] check for and enable
2656 properly configured MMIO access to PCI
2657 config space on AMD family 10h CPU
2658 nomsi [MSI] If the PCI_MSI kernel config parameter is
2659 enabled, this kernel boot option can be used to
2660 disable the use of MSI interrupts system-wide.
2661 noioapicquirk [APIC] Disable all boot interrupt quirks.
2662 Safety option to keep boot IRQs enabled. This
2663 should never be necessary.
2664 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2665 primary IO-APIC for bridges that cannot disable
2666 boot IRQs. This fixes a source of spurious IRQs
2667 when the system masks IRQs.
2668 noioapicreroute [APIC] Disable workaround that uses the
2669 boot IRQ equivalent of an IRQ that connects to
2670 a chipset where boot IRQs cannot be disabled.
2671 The opposite of ioapicreroute.
2672 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2673 routing table. These calls are known to be buggy
2674 on several machines and they hang the machine
2675 when used, but on other computers it's the only
2676 way to get the interrupt routing table. Try
2677 this option if the kernel is unable to allocate
2678 IRQs or discover secondary PCI buses on your
2680 rom [X86] Assign address space to expansion ROMs.
2681 Use with caution as certain devices share
2682 address decoders between ROMs and other
2684 norom [X86] Do not assign address space to
2685 expansion ROMs that do not already have
2686 BIOS assigned address ranges.
2687 nobar [X86] Do not assign address space to the
2688 BARs that weren't assigned by the BIOS.
2689 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2690 assigned automatically to PCI devices. You can
2691 make the kernel exclude IRQs of your ISA cards
2693 pirqaddr=0xAAAAA [X86] Specify the physical address
2694 of the PIRQ table (normally generated
2695 by the BIOS) if it is outside the
2696 F0000h-100000h range.
2697 lastbus=N [X86] Scan all buses thru bus #N. Can be
2698 useful if the kernel is unable to find your
2699 secondary buses and you want to tell it
2700 explicitly which ones they are.
2701 assign-busses [X86] Always assign all PCI bus
2702 numbers ourselves, overriding
2703 whatever the firmware may have done.
2704 usepirqmask [X86] Honor the possible IRQ mask stored
2705 in the BIOS $PIR table. This is needed on
2706 some systems with broken BIOSes, notably
2707 some HP Pavilion N5400 and Omnibook XE3
2708 notebooks. This will have no effect if ACPI
2709 IRQ routing is enabled.
2710 noacpi [X86] Do not use ACPI for IRQ routing
2711 or for PCI scanning.
2712 use_crs [X86] Use PCI host bridge window information
2713 from ACPI. On BIOSes from 2008 or later, this
2714 is enabled by default. If you need to use this,
2715 please report a bug.
2716 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2717 If you need to use this, please report a bug.
2718 routeirq Do IRQ routing for all PCI devices.
2719 This is normally done in pci_enable_device(),
2720 so this option is a temporary workaround
2721 for broken drivers that don't call it.
2722 skip_isa_align [X86] do not align io start addr, so can
2723 handle more pci cards
2724 firmware [ARM] Do not re-enumerate the bus but instead
2725 just use the configuration from the
2726 bootloader. This is currently used on
2727 IXP2000 systems where the bus has to be
2728 configured a certain way for adjunct CPUs.
2729 noearly [X86] Don't do any early type 1 scanning.
2730 This might help on some broken boards which
2731 machine check when some devices' config space
2732 is read. But various workarounds are disabled
2733 and some IOMMU drivers will not work.
2734 bfsort Sort PCI devices into breadth-first order.
2735 This sorting is done to get a device
2736 order compatible with older (<= 2.4) kernels.
2737 nobfsort Don't sort PCI devices into breadth-first order.
2738 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2739 tuning and use the BIOS-configured MPS defaults.
2740 pcie_bus_safe Set every device's MPS to the largest value
2741 supported by all devices below the root complex.
2742 pcie_bus_perf Set device MPS to the largest allowable MPS
2743 based on its parent bus. Also set MRRS (Max
2744 Read Request Size) to the largest supported
2745 value (no larger than the MPS that the device
2746 or bus can support) for best performance.
2747 pcie_bus_peer2peer Set every device's MPS to 128B, which
2748 every device is guaranteed to support. This
2749 configuration allows peer-to-peer DMA between
2750 any pair of devices, possibly at the cost of
2751 reduced performance. This also guarantees
2752 that hot-added devices will work.
2753 cbiosize=nn[KMG] The fixed amount of bus space which is
2754 reserved for the CardBus bridge's IO window.
2755 The default value is 256 bytes.
2756 cbmemsize=nn[KMG] The fixed amount of bus space which is
2757 reserved for the CardBus bridge's memory
2758 window. The default value is 64 megabytes.
2761 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2762 Specifies alignment and device to reassign
2763 aligned memory resources.
2764 If <order of align> is not specified,
2765 PAGE_SIZE is used as alignment.
2766 PCI-PCI bridge can be specified, if resource
2767 windows need to be expanded.
2768 ecrc= Enable/disable PCIe ECRC (transaction layer
2769 end-to-end CRC checking).
2770 bios: Use BIOS/firmware settings. This is the
2774 hpiosize=nn[KMG] The fixed amount of bus space which is
2775 reserved for hotplug bridge's IO window.
2776 Default size is 256 bytes.
2777 hpmemsize=nn[KMG] The fixed amount of bus space which is
2778 reserved for hotplug bridge's memory window.
2779 Default size is 2 megabytes.
2780 realloc= Enable/disable reallocating PCI bridge resources
2781 if allocations done by BIOS are too small to
2782 accommodate resources required by all child
2784 off: Turn realloc off
2786 realloc same as realloc=on
2787 noari do not use PCIe ARI.
2788 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2789 only look for one device below a PCIe downstream
2792 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2795 force Enable ASPM even on devices that claim not to support it.
2796 WARNING: Forcing ASPM on may cause system lockups.
2798 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2799 nomsi Do not use MSI for PCI Express Native Hotplug (this
2800 makes all PCIe ports use INTx for hotplug services).
2802 pcie_ports= [PCIE] PCIe ports handling:
2803 auto Ask the BIOS whether or not to use native PCIe services
2804 associated with PCIe ports (PME, hot-plug, AER). Use
2805 them only if that is allowed by the BIOS.
2806 native Use native PCIe services associated with PCIe ports
2808 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2811 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2812 nomsi Do not use MSI for native PCIe PME signaling (this makes
2813 all PCIe root ports use INTx for all services).
2815 pcmv= [HW,PCMCIA] BadgePAD 4
2819 Keep all power-domains already enabled by bootloader on,
2820 even if no driver has claimed them. This is useful
2821 for debug and development, but should not be
2822 needed on a platform with proper driver support.
2825 See Documentation/blockdev/paride.txt.
2827 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2830 See arch/parisc/kernel/pdc_chassis.c
2832 percpu_alloc= Select which percpu first chunk allocator to use.
2833 Currently supported values are "embed" and "page".
2834 Archs may support subset or none of the selections.
2835 See comments in mm/percpu.c for details on each
2836 allocator. This parameter is primarily for debugging
2837 and performance comparison.
2840 See Documentation/blockdev/paride.txt.
2843 See Documentation/blockdev/paride.txt.
2845 pirq= [SMP,APIC] Manual mp-table setup
2846 See Documentation/x86/i386/IO-APIC.txt.
2848 plip= [PPT,NET] Parallel port network link
2849 Format: { parport<nr> | timid | 0 }
2850 See also Documentation/parport.txt.
2852 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2853 Override pmtimer IOPort with a hex value.
2857 Enable PNP debug messages (depends on the
2858 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2859 via /sys/module/pnp/parameters/debug. We always show
2860 current resource usage; turning this on also shows
2861 possible settings and some assignment information.
2867 { on | off | curr | res | no-curr | no-res }
2870 [ISAPNP] Exclude IRQs for the autoconfiguration
2873 [ISAPNP] Exclude DMAs for the autoconfiguration
2875 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2876 Ranges are in pairs (I/O port base and size).
2879 [ISAPNP] Exclude memory regions for the
2881 Ranges are in pairs (memory base and size).
2883 ports= [IP_VS_FTP] IPVS ftp helper module
2885 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2887 Format: <port>,<port>....
2889 print-fatal-signals=
2890 [KNL] debug: print fatal signals
2892 If enabled, warn about various signal handling
2893 related application anomalies: too many signals,
2894 too many POSIX.1 timers, fatal signals causing a
2897 If you hit the warning due to signal overflow,
2898 you might want to try "ulimit -i unlimited".
2902 printk.always_kmsg_dump=
2903 Trigger kmsg_dump for cases other than kernel oops or
2905 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2908 printk.time= Show timing data prefixed to each printk message line
2909 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2911 processor.max_cstate= [HW,ACPI]
2912 Limit processor to maximum C-state
2913 max_cstate=9 overrides any DMI blacklist limit.
2915 processor.nocst [HW,ACPI]
2916 Ignore the _CST method to determine C-states,
2917 instead using the legacy FADT method
2919 profile= [KNL] Enable kernel profiling via /proc/profile
2920 Format: [schedule,]<number>
2921 Param: "schedule" - profile schedule points.
2922 Param: <number> - step/bucket size as a power of 2 for
2923 statistical time based profiling.
2924 Param: "sleep" - profile D-state sleeping (millisecs).
2925 Requires CONFIG_SCHEDSTATS
2926 Param: "kvm" - profile VM exits.
2928 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2930 See Documentation/blockdev/ramdisk.txt.
2932 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2933 probe for; one of (bare|imps|exps|lifebook|any).
2934 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2936 psmouse.resetafter= [HW,MOUSE]
2937 Try to reset the device after so many bad packets
2940 [HW,MOUSE] Set desired mouse resolution, in dpi.
2941 psmouse.smartscroll=
2942 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2943 0 = disabled, 1 = enabled (default).
2945 pstore.backend= Specify the name of the pstore backend to use
2948 See Documentation/blockdev/paride.txt.
2951 [KNL] Number of legacy pty's. Overwrites compiled-in
2954 quiet [KNL] Disable most log messages
2959 See Documentation/md.txt.
2961 ramdisk_blocksize= [RAM]
2962 See Documentation/blockdev/ramdisk.txt.
2964 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2965 See Documentation/blockdev/ramdisk.txt.
2968 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2969 the specified list of CPUs to be no-callback CPUs.
2970 Invocation of these CPUs' RCU callbacks will
2971 be offloaded to "rcuox/N" kthreads created for
2972 that purpose, where "x" is "b" for RCU-bh, "p"
2973 for RCU-preempt, and "s" for RCU-sched, and "N"
2974 is the CPU number. This reduces OS jitter on the
2975 offloaded CPUs, which can be useful for HPC and
2976 real-time workloads. It can also improve energy
2977 efficiency for asymmetric multiprocessors.
2980 Rather than requiring that offloaded CPUs
2981 (specified by rcu_nocbs= above) explicitly
2982 awaken the corresponding "rcuoN" kthreads,
2983 make these kthreads poll for callbacks.
2984 This improves the real-time response for the
2985 offloaded CPUs by relieving them of the need to
2986 wake up the corresponding kthread, but degrades
2987 energy efficiency by requiring that the kthreads
2988 periodically wake up to do the polling.
2990 rcutree.blimit= [KNL]
2991 Set maximum number of finished RCU callbacks to
2992 process in one batch.
2994 rcutree.gp_init_delay= [KNL]
2995 Set the number of jiffies to delay each step of
2996 RCU grace-period initialization. This only has
2997 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
3000 rcutree.rcu_fanout_leaf= [KNL]
3001 Increase the number of CPUs assigned to each
3002 leaf rcu_node structure. Useful for very large
3005 rcutree.jiffies_till_sched_qs= [KNL]
3006 Set required age in jiffies for a
3007 given grace period before RCU starts
3008 soliciting quiescent-state help from
3009 rcu_note_context_switch().
3011 rcutree.jiffies_till_first_fqs= [KNL]
3012 Set delay from grace-period initialization to
3013 first attempt to force quiescent states.
3014 Units are jiffies, minimum value is zero,
3015 and maximum value is HZ.
3017 rcutree.jiffies_till_next_fqs= [KNL]
3018 Set delay between subsequent attempts to force
3019 quiescent states. Units are jiffies, minimum
3020 value is one, and maximum value is HZ.
3022 rcutree.kthread_prio= [KNL,BOOT]
3023 Set the SCHED_FIFO priority of the RCU per-CPU
3024 kthreads (rcuc/N). This value is also used for
3025 the priority of the RCU boost threads (rcub/N)
3026 and for the RCU grace-period kthreads (rcu_bh,
3027 rcu_preempt, and rcu_sched). If RCU_BOOST is
3028 set, valid values are 1-99 and the default is 1
3029 (the least-favored priority). Otherwise, when
3030 RCU_BOOST is not set, valid values are 0-99 and
3031 the default is zero (non-realtime operation).
3033 rcutree.rcu_nocb_leader_stride= [KNL]
3034 Set the number of NOCB kthread groups, which
3035 defaults to the square root of the number of
3036 CPUs. Larger numbers reduces the wakeup overhead
3037 on the per-CPU grace-period kthreads, but increases
3038 that same overhead on each group's leader.
3040 rcutree.qhimark= [KNL]
3041 Set threshold of queued RCU callbacks beyond which
3042 batch limiting is disabled.
3044 rcutree.qlowmark= [KNL]
3045 Set threshold of queued RCU callbacks below which
3046 batch limiting is re-enabled.
3048 rcutree.rcu_idle_gp_delay= [KNL]
3049 Set wakeup interval for idle CPUs that have
3050 RCU callbacks (RCU_FAST_NO_HZ=y).
3052 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3053 Set wakeup interval for idle CPUs that have
3054 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3055 Lazy RCU callbacks are those which RCU can
3056 prove do nothing more than free memory.
3058 rcutorture.cbflood_inter_holdoff= [KNL]
3059 Set holdoff time (jiffies) between successive
3060 callback-flood tests.
3062 rcutorture.cbflood_intra_holdoff= [KNL]
3063 Set holdoff time (jiffies) between successive
3064 bursts of callbacks within a given callback-flood
3067 rcutorture.cbflood_n_burst= [KNL]
3068 Set the number of bursts making up a given
3069 callback-flood test. Set this to zero to
3070 disable callback-flood testing.
3072 rcutorture.cbflood_n_per_burst= [KNL]
3073 Set the number of callbacks to be registered
3074 in a given burst of a callback-flood test.
3076 rcutorture.fqs_duration= [KNL]
3077 Set duration of force_quiescent_state bursts.
3079 rcutorture.fqs_holdoff= [KNL]
3080 Set holdoff time within force_quiescent_state bursts.
3082 rcutorture.fqs_stutter= [KNL]
3083 Set wait time between force_quiescent_state bursts.
3085 rcutorture.gp_exp= [KNL]
3086 Use expedited update-side primitives.
3088 rcutorture.gp_normal= [KNL]
3089 Use normal (non-expedited) update-side primitives.
3090 If both gp_exp and gp_normal are set, do both.
3091 If neither gp_exp nor gp_normal are set, still
3094 rcutorture.n_barrier_cbs= [KNL]
3095 Set callbacks/threads for rcu_barrier() testing.
3097 rcutorture.nfakewriters= [KNL]
3098 Set number of concurrent RCU writers. These just
3099 stress RCU, they don't participate in the actual
3100 test, hence the "fake".
3102 rcutorture.nreaders= [KNL]
3103 Set number of RCU readers.
3105 rcutorture.object_debug= [KNL]
3106 Enable debug-object double-call_rcu() testing.
3108 rcutorture.onoff_holdoff= [KNL]
3109 Set time (s) after boot for CPU-hotplug testing.
3111 rcutorture.onoff_interval= [KNL]
3112 Set time (s) between CPU-hotplug operations, or
3113 zero to disable CPU-hotplug testing.
3115 rcutorture.torture_runnable= [BOOT]
3116 Start rcutorture running at boot time.
3118 rcutorture.shuffle_interval= [KNL]
3119 Set task-shuffle interval (s). Shuffling tasks
3120 allows some CPUs to go into dyntick-idle mode
3121 during the rcutorture test.
3123 rcutorture.shutdown_secs= [KNL]
3124 Set time (s) after boot system shutdown. This
3125 is useful for hands-off automated testing.
3127 rcutorture.stall_cpu= [KNL]
3128 Duration of CPU stall (s) to test RCU CPU stall
3129 warnings, zero to disable.
3131 rcutorture.stall_cpu_holdoff= [KNL]
3132 Time to wait (s) after boot before inducing stall.
3134 rcutorture.stat_interval= [KNL]
3135 Time (s) between statistics printk()s.
3137 rcutorture.stutter= [KNL]
3138 Time (s) to stutter testing, for example, specifying
3139 five seconds causes the test to run for five seconds,
3140 wait for five seconds, and so on. This tests RCU's
3141 ability to transition abruptly to and from idle.
3143 rcutorture.test_boost= [KNL]
3144 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3145 "Maybe" means test if the RCU implementation
3146 under test support RCU priority boosting.
3148 rcutorture.test_boost_duration= [KNL]
3149 Duration (s) of each individual boost test.
3151 rcutorture.test_boost_interval= [KNL]
3152 Interval (s) between each boost test.
3154 rcutorture.test_no_idle_hz= [KNL]
3155 Test RCU's dyntick-idle handling. See also the
3156 rcutorture.shuffle_interval parameter.
3158 rcutorture.torture_type= [KNL]
3159 Specify the RCU implementation to test.
3161 rcutorture.verbose= [KNL]
3162 Enable additional printk() statements.
3164 rcupdate.rcu_expedited= [KNL]
3165 Use expedited grace-period primitives, for
3166 example, synchronize_rcu_expedited() instead
3167 of synchronize_rcu(). This reduces latency,
3168 but can increase CPU utilization, degrade
3169 real-time latency, and degrade energy efficiency.
3171 rcupdate.rcu_cpu_stall_suppress= [KNL]
3172 Suppress RCU CPU stall warning messages.
3174 rcupdate.rcu_cpu_stall_timeout= [KNL]
3175 Set timeout for RCU CPU stall warning messages.
3177 rcupdate.rcu_task_stall_timeout= [KNL]
3178 Set timeout in jiffies for RCU task stall warning
3179 messages. Disable with a value less than or equal
3182 rcupdate.rcu_self_test= [KNL]
3183 Run the RCU early boot self tests
3185 rcupdate.rcu_self_test_bh= [KNL]
3186 Run the RCU bh early boot self tests
3188 rcupdate.rcu_self_test_sched= [KNL]
3189 Run the RCU sched early boot self tests
3193 Run specified binary instead of /init from the ramdisk,
3194 used for early userspace startup. See initrd.
3197 Format (x86 or x86_64):
3198 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3200 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3202 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3203 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3204 reboot_force is either force or not specified,
3205 reboot_cpu is s[mp]#### with #### being the processor
3206 to be used for rebooting.
3209 [KNL, SMP] Set scheduler's default relax_domain_level.
3210 See Documentation/cgroups/cpusets.txt.
3212 relative_sleep_states=
3213 [SUSPEND] Use sleep state labeling where the deepest
3214 state available other than hibernation is always "mem".
3215 Format: { "0" | "1" }
3216 0 -- Traditional sleep state labels.
3217 1 -- Relative sleep state labels.
3219 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3221 reservetop= [X86-32]
3223 Reserves a hole at the top of the kernel virtual
3228 Set the amount of memory to reserve for BIOS at
3229 the bottom of the address space.
3231 reset_devices [KNL] Force drivers to reset the underlying device
3232 during initialization.
3235 Specify the partition device for software suspend
3237 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3239 resume_offset= [SWSUSP]
3240 Specify the offset from the beginning of the partition
3241 given by "resume=" at which the swap header is located,
3242 in <PAGE_SIZE> units (needed only for swap files).
3243 See Documentation/power/swsusp-and-swap-files.txt
3245 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3246 read the resume files
3248 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3249 Useful for devices that are detected asynchronously
3250 (e.g. USB and MMC devices).
3252 hibernate= [HIBERNATION]
3253 noresume Don't check if there's a hibernation image
3254 present during boot.
3255 nocompress Don't compress/decompress hibernation images.
3256 no Disable hibernation and resume.
3258 retain_initrd [RAM] Keep initrd memory after extraction
3260 rfkill.default_state=
3261 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3262 etc. communication is blocked by default.
3265 rfkill.master_switch_mode=
3266 0 The "airplane mode" button does nothing.
3267 1 The "airplane mode" button toggles between everything
3268 blocked and the previous configuration.
3269 2 The "airplane mode" button toggles between everything
3270 blocked and everything unblocked.
3272 rhash_entries= [KNL,NET]
3273 Set number of hash buckets for route cache
3275 ro [KNL] Mount root device read-only on boot
3277 root= [KNL] Root filesystem
3278 See name_to_dev_t comment in init/do_mounts.c.
3280 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3281 mount the root filesystem
3283 rootflags= [KNL] Set root filesystem mount option string
3285 rootfstype= [KNL] Set root filesystem type
3287 rootwait [KNL] Wait (indefinitely) for root device to show up.
3288 Useful for devices that are detected asynchronously
3289 (e.g. USB and MMC devices).
3291 rproc_mem=nn[KMG][@address]
3292 [KNL,ARM,CMA] Remoteproc physical memory block.
3293 Memory area to be used by remote processor image,
3296 rw [KNL] Mount root device read-write on boot
3298 S [KNL] Run init in single mode
3300 s390_iommu= [HW,S390]
3301 Set s390 IOTLB flushing mode
3303 With strict flushing every unmap operation will result in
3304 an IOTLB flush. Default is lazy flushing before reuse,
3308 See drivers/net/irda/sa1100_ir.c.
3310 sbni= [NET] Granch SBNI12 leased line adapter
3312 sched_debug [KNL] Enables verbose scheduler debug messages.
3314 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3315 xtime_lock contention on larger systems, and/or RCU lock
3316 contention on all systems with CONFIG_MAXSMP set.
3317 Format: { "0" | "1" }
3318 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3320 Note: increases power consumption, thus should only be
3321 enabled if running jitter sensitive (HPC/RT) workloads.
3323 security= [SECURITY] Choose a security module to enable at boot.
3324 If this boot parameter is not specified, only the first
3325 security module asking for security registration will be
3326 loaded. An invalid security module name will be treated
3327 as if no module has been chosen.
3329 selinux= [SELINUX] Disable or enable SELinux at boot time.
3330 Format: { "0" | "1" }
3331 See security/selinux/Kconfig help text.
3334 Default value is set via kernel config option.
3335 If enabled at boot time, /selinux/disable can be used
3336 later to disable prior to initial policy load.
3338 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3339 Format: { "0" | "1" }
3340 See security/apparmor/Kconfig help text
3343 Default value is set via kernel config option.
3345 serialnumber [BUGS=X86-32]
3348 Maximal number of shapers.
3350 show_msr= [x86] show boot-time MSR settings
3351 Format: { <integer> }
3352 Show boot-time (BIOS-initialized) MSR settings.
3353 The parameter means the number of CPUs to show,
3354 for example 1 means boot CPU only.
3362 Disable merging of slabs with similar size. May be
3363 necessary if there is some reason to distinguish
3364 allocs to different slabs. Debug options disable
3365 merging on their own.
3366 For more information see Documentation/vm/slub.txt.
3368 slab_max_order= [MM, SLAB]
3369 Determines the maximum allowed order for slabs.
3370 A high setting may cause OOMs due to memory
3371 fragmentation. Defaults to 1 for systems with
3372 more than 32MB of RAM, 0 otherwise.
3374 slub_debug[=options[,slabs]] [MM, SLUB]
3375 Enabling slub_debug allows one to determine the
3376 culprit if slab objects become corrupted. Enabling
3377 slub_debug can create guard zones around objects and
3378 may poison objects when not in use. Also tracks the
3379 last alloc / free. For more information see
3380 Documentation/vm/slub.txt.
3382 slub_max_order= [MM, SLUB]
3383 Determines the maximum allowed order for slabs.
3384 A high setting may cause OOMs due to memory
3385 fragmentation. For more information see
3386 Documentation/vm/slub.txt.
3388 slub_min_objects= [MM, SLUB]
3389 The minimum number of objects per slab. SLUB will
3390 increase the slab order up to slub_max_order to
3391 generate a sufficiently large slab able to contain
3392 the number of objects indicated. The higher the number
3393 of objects the smaller the overhead of tracking slabs
3394 and the less frequently locks need to be acquired.
3395 For more information see Documentation/vm/slub.txt.
3397 slub_min_order= [MM, SLUB]
3398 Determines the minimum page order for slabs. Must be
3399 lower than slub_max_order.
3400 For more information see Documentation/vm/slub.txt.
3402 slub_nomerge [MM, SLUB]
3403 Same with slab_nomerge. This is supported for legacy.
3404 See slab_nomerge for more information.
3407 Format: <io1>[,<io2>[,...,<io8>]]
3409 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3410 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3411 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3412 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3413 smsc-ircc2.ircc_irq= [HW] IRQ line
3414 smsc-ircc2.ircc_dma= [HW] DMA channel
3415 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3416 0: Toshiba Satellite 1800 (GP data pin select)
3417 1: Fast pin select (default)
3421 [KNL] Should the soft-lockup detector generate panics.
3424 softlockup_all_cpu_backtrace=
3425 [KNL] Should the soft-lockup detector generate
3426 backtraces on all cpus.
3429 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3430 See Documentation/laptops/sonypi.txt
3432 spia_io_base= [HW,MTD]
3438 Enabled the stack tracer on boot up.
3440 stacktrace_filter=[function-list]
3441 [FTRACE] Limit the functions that the stack tracer
3442 will trace at boot up. function-list is a comma separated
3443 list of functions. This list can be changed at run
3444 time by the stack_trace_filter file in the debugfs
3445 tracing directory. Note, this enables stack tracing
3446 and the stacktrace above is not needed.
3450 Set the STI (builtin display/keyboard on the HP-PARISC
3451 machines) console (graphic card) which should be used
3452 as the initial boot-console.
3453 See also comment in drivers/video/console/sticore.c.
3456 See comment in drivers/video/console/sticore.c.
3459 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3461 sunrpc.min_resvport=
3462 sunrpc.max_resvport=
3464 SunRPC servers often require that client requests
3465 originate from a privileged port (i.e. a port in the
3466 range 0 < portnr < 1024).
3467 An administrator who wishes to reserve some of these
3468 ports for other uses may adjust the range that the
3469 kernel's sunrpc client considers to be privileged
3470 using these two parameters to set the minimum and
3471 maximum port values.
3475 Control how the NFS server code allocates CPUs to
3476 service thread pools. Depending on how many NICs
3477 you have and where their interrupts are bound, this
3478 option will affect which CPUs will do NFS serving.
3479 Note: this parameter cannot be changed while the
3480 NFS server is running.
3482 auto the server chooses an appropriate mode
3483 automatically using heuristics
3484 global a single global pool contains all CPUs
3485 percpu one pool for each CPU
3486 pernode one pool for each NUMA node (equivalent
3487 to global on non-NUMA machines)
3489 sunrpc.tcp_slot_table_entries=
3490 sunrpc.udp_slot_table_entries=
3492 Sets the upper limit on the number of simultaneous
3493 RPC calls that can be sent from the client to a
3494 server. Increasing these values may allow you to
3495 improve throughput, but will also increase the
3496 amount of memory reserved for use by the client.
3498 suspend.pm_test_delay=
3500 Sets the number of seconds to remain in a suspend test
3501 mode before resuming the system (see
3502 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3503 is set. Default value is 5.
3506 [KNL] Enable accounting of swap in memory resource
3507 controller if no parameter or 1 is given or disable
3508 it if 0 is given (See Documentation/cgroups/memory.txt)
3510 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3511 Format: { <int> | force }
3512 <int> -- Number of I/O TLB slabs
3513 force -- force using of bounce buffers even if they
3514 wouldn't be automatically used by the kernel
3518 sysfs.deprecated=0|1 [KNL]
3519 Enable/disable old style sysfs layout for old udev
3520 on older distributions. When this option is enabled
3521 very new udev will not work anymore. When this option
3522 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3523 in older udev will not work anymore.
3524 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3525 the kernel configuration.
3527 sysrq_always_enabled
3529 Ignore sysrq setting - this boot parameter will
3530 neutralize any effect of /proc/sys/kernel/sysrq.
3531 Useful for debugging.
3533 tcpmhash_entries= [KNL,NET]
3534 Set the number of tcp_metrics_hash slots.
3535 Default value is 8192 or 16384 depending on total
3536 ram pages. This is used to specify the TCP metrics
3537 cache size. See Documentation/networking/ip-sysctl.txt
3538 "tcp_no_metrics_save" section for more details.
3542 test_suspend= [SUSPEND][,N]
3543 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3544 standby suspend) or "freeze" (for suspend type freeze)
3545 as the system sleep state during system startup with
3546 the optional capability to repeat N number of times.
3547 The system is woken from this state using a
3548 wakeup-capable RTC alarm.
3550 thash_entries= [KNL,NET]
3551 Set number of hash buckets for TCP connection
3553 thermal.act= [HW,ACPI]
3554 -1: disable all active trip points in all thermal zones
3555 <degrees C>: override all lowest active trip points
3557 thermal.crt= [HW,ACPI]
3558 -1: disable all critical trip points in all thermal zones
3559 <degrees C>: override all critical trip points
3561 thermal.nocrt= [HW,ACPI]
3562 Set to disable actions on ACPI thermal zone
3563 critical and hot trip points.
3565 thermal.off= [HW,ACPI]
3566 1: disable ACPI thermal control
3568 thermal.psv= [HW,ACPI]
3569 -1: disable all passive trip points
3570 <degrees C>: override all passive trip points to this
3573 thermal.tzp= [HW,ACPI]
3574 Specify global default ACPI thermal zone polling rate
3575 <deci-seconds>: poll all this frequency
3576 0: no polling (default)
3579 Force threading of all interrupt handlers except those
3580 marked explicitly IRQF_NO_THREAD.
3583 Enable the Transcendent memory driver if built-in.
3585 tmem.cleancache=0|1 [KNL, XEN]
3586 Default is on (1). Disable the usage of the cleancache
3587 API to send anonymous pages to the hypervisor.
3589 tmem.frontswap=0|1 [KNL, XEN]
3590 Default is on (1). Disable the usage of the frontswap
3591 API to send swap pages to the hypervisor. If disabled
3592 the selfballooning and selfshrinking are force disabled.
3594 tmem.selfballooning=0|1 [KNL, XEN]
3595 Default is on (1). Disable the driving of swap pages
3598 tmem.selfshrinking=0|1 [KNL, XEN]
3599 Default is on (1). Partial swapoff that immediately
3600 transfers pages from Xen hypervisor back to the
3601 kernel based on different criteria.
3605 Specify if the kernel should make use of the cpu
3606 topology information if the hardware supports this.
3607 The scheduler will make use of this information and
3608 e.g. base its process migration decisions on it.
3611 topology_updates= [KNL, PPC, NUMA]
3613 Specify if the kernel should ignore (off)
3614 topology updates sent by the hypervisor to this
3619 tpm_suspend_pcr=[HW,TPM]
3620 Format: integer pcr id
3621 Specify that at suspend time, the tpm driver
3622 should extend the specified pcr with zeros,
3623 as a workaround for some chips which fail to
3624 flush the last written pcr on TPM_SaveState.
3625 This will guarantee that all the other pcrs
3628 trace_buf_size=nn[KMG]
3629 [FTRACE] will set tracing buffer size on each cpu.
3631 trace_event=[event-list]
3632 [FTRACE] Set and start specified trace events in order
3633 to facilitate early boot debugging.
3634 See also Documentation/trace/events.txt
3636 trace_options=[option-list]
3637 [FTRACE] Enable or disable tracer options at boot.
3638 The option-list is a comma delimited list of options
3639 that can be enabled or disabled just as if you were
3640 to echo the option name into
3642 /sys/kernel/debug/tracing/trace_options
3644 For example, to enable stacktrace option (to dump the
3645 stack trace of each event), add to the command line:
3647 trace_options=stacktrace
3649 See also Documentation/trace/ftrace.txt "trace options"
3653 Have the tracepoints sent to printk as well as the
3654 tracing ring buffer. This is useful for early boot up
3655 where the system hangs or reboots and does not give the
3656 option for reading the tracing buffer or performing a
3657 ftrace_dump_on_oops.
3659 To turn off having tracepoints sent to printk,
3660 echo 0 > /proc/sys/kernel/tracepoint_printk
3661 Note, echoing 1 into this file without the
3662 tracepoint_printk kernel cmdline option has no effect.
3666 Having tracepoints sent to printk() and activating high
3667 frequency tracepoints such as irq or sched, can cause
3668 the system to live lock.
3671 [FTRACE] enable this option to disable tracing when a
3672 warning is hit. This turns off "tracing_on". Tracing can
3673 be enabled again by echoing '1' into the "tracing_on"
3674 file located in /sys/kernel/debug/tracing/
3676 This option is useful, as it disables the trace before
3677 the WARNING dump is called, which prevents the trace to
3678 be filled with content caused by the warning output.
3680 This option can also be set at run time via the sysctl
3681 option: kernel/traceoff_on_warning
3683 transparent_hugepage=
3685 Format: [always|madvise|never]
3686 Can be used to control the default behavior of the system
3687 with respect to transparent hugepages.
3688 See Documentation/vm/transhuge.txt for more details.
3690 tsc= Disable clocksource stability checks for TSC.
3692 [x86] reliable: mark tsc clocksource as reliable, this
3693 disables clocksource verification at runtime, as well
3694 as the stability checks done at bootup. Used to enable
3695 high-resolution timer mode on older hardware, and in
3696 virtualized environment.
3697 [x86] noirqtime: Do not use TSC to do irq accounting.
3698 Used to run time disable IRQ_TIME_ACCOUNTING on any
3699 platforms where RDTSC is slow and this accounting
3702 turbografx.map[2|3]= [HW,JOY]
3703 TurboGraFX parallel port interface
3705 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3706 See also Documentation/input/joystick-parport.txt
3708 udbg-immortal [PPC] When debugging early kernel crashes that
3709 happen after console_init() and before a proper
3710 console driver takes over, this boot options might
3711 help "seeing" what's going on.
3713 uhash_entries= [KNL,NET]
3714 Set number of hash buckets for UDP/UDP-Lite connections
3717 [USB] Ignore overcurrent events (default N).
3718 Some badly-designed motherboards generate lots of
3719 bogus events, for ports that aren't wired to
3720 anything. Set this parameter to avoid log spamming.
3721 Note that genuine overcurrent events won't be
3725 [X86] Cause panic on unknown NMI.
3727 usbcore.authorized_default=
3728 [USB] Default USB device authorization:
3729 (default -1 = authorized except for wireless USB,
3730 0 = not authorized, 1 = authorized)
3732 usbcore.autosuspend=
3733 [USB] The autosuspend time delay (in seconds) used
3734 for newly-detected USB devices (default 2). This
3735 is the time required before an idle device will be
3736 autosuspended. Devices for which the delay is set
3737 to a negative value won't be autosuspended at all.
3739 usbcore.usbfs_snoop=
3740 [USB] Set to log all usbfs traffic (default 0 = off).
3742 usbcore.blinkenlights=
3743 [USB] Set to cycle leds on hubs (default 0 = off).
3745 usbcore.old_scheme_first=
3746 [USB] Start with the old device initialization
3747 scheme (default 0 = off).
3749 usbcore.usbfs_memory_mb=
3750 [USB] Memory limit (in MB) for buffers allocated by
3751 usbfs (default = 16, 0 = max = 2047).
3753 usbcore.use_both_schemes=
3754 [USB] Try the other device initialization scheme
3755 if the first one fails (default 1 = enabled).
3757 usbcore.initial_descriptor_timeout=
3758 [USB] Specifies timeout for the initial 64-byte
3759 USB_REQ_GET_DESCRIPTOR request in milliseconds
3760 (default 5000 = 5.0 seconds).
3763 [USBHID] The interval which mice are to be polled at.
3765 usb-storage.delay_use=
3766 [UMS] The delay in seconds before a new device is
3767 scanned for Logical Units (default 1).
3770 [UMS] A list of quirks entries to supplement or
3771 override the built-in unusual_devs list. List
3772 entries are separated by commas. Each entry has
3773 the form VID:PID:Flags where VID and PID are Vendor
3774 and Product ID values (4-digit hex numbers) and
3775 Flags is a set of characters, each corresponding
3776 to a common usb-storage quirk flag as follows:
3777 a = SANE_SENSE (collect more than 18 bytes
3779 b = BAD_SENSE (don't collect more than 18
3780 bytes of sense data);
3781 c = FIX_CAPACITY (decrease the reported
3782 device capacity by one sector);
3783 d = NO_READ_DISC_INFO (don't use
3784 READ_DISC_INFO command);
3785 e = NO_READ_CAPACITY_16 (don't use
3786 READ_CAPACITY_16 command);
3787 f = NO_REPORT_OPCODES (don't use report opcodes
3789 h = CAPACITY_HEURISTICS (decrease the
3790 reported device capacity by one
3791 sector if the number is odd);
3792 i = IGNORE_DEVICE (don't bind to this
3794 l = NOT_LOCKABLE (don't try to lock and
3795 unlock ejectable media);
3796 m = MAX_SECTORS_64 (don't transfer more
3797 than 64 sectors = 32 KB at a time);
3798 n = INITIAL_READ10 (force a retry of the
3799 initial READ(10) command);
3800 o = CAPACITY_OK (accept the capacity
3801 reported by the device);
3802 p = WRITE_CACHE (the device cache is ON
3804 r = IGNORE_RESIDUE (the device reports
3805 bogus residue values);
3806 s = SINGLE_LUN (the device has only one
3808 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3809 commands, uas only);
3810 u = IGNORE_UAS (don't bind to the uas driver);
3811 w = NO_WP_DETECT (don't test whether the
3812 medium is write-protected).
3813 Example: quirks=0419:aaf5:rl,0421:0433:rc
3815 user_debug= [KNL,ARM]
3817 See arch/arm/Kconfig.debug help text.
3818 1 - undefined instruction events
3820 4 - invalid data aborts
3823 Example: user_debug=31
3826 [X86] Flags controlling user PTE allocations.
3828 nohigh = do not allocate PTE pages in
3829 HIGHMEM regardless of setting
3833 On X86_32, this is an alias for vdso32=. Otherwise:
3835 vdso=1: enable VDSO (the default)
3836 vdso=0: disable VDSO mapping
3838 vdso32= [X86] Control the 32-bit vDSO
3839 vdso32=1: enable 32-bit VDSO
3840 vdso32=0 or vdso32=2: disable 32-bit VDSO
3842 See the help text for CONFIG_COMPAT_VDSO for more
3843 details. If CONFIG_COMPAT_VDSO is set, the default is
3844 vdso32=0; otherwise, the default is vdso32=1.
3846 For compatibility with older kernels, vdso32=2 is an
3849 Try vdso32=0 if you encounter an error that says:
3850 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3853 vector=percpu: enable percpu vector domain
3855 video= [FB] Frame buffer configuration
3856 See Documentation/fb/modedb.txt.
3858 video.brightness_switch_enabled= [0,1]
3859 If set to 1, on receiving an ACPI notify event
3860 generated by hotkey, video driver will adjust brightness
3861 level and then send out the event to user space through
3862 the allocated input device; If set to 0, video driver
3863 will only send out the event without touching backlight
3868 [VMMIO] Memory mapped virtio (platform) device.
3870 <size>@<baseaddr>:<irq>[:<id>]
3872 <size> := size (can use standard suffixes
3874 <baseaddr> := physical base address
3875 <irq> := interrupt number (as passed to
3877 <id> := (optional) platform device id
3879 virtio_mmio.device=1K@0x100b0000:48:7
3881 Can be used multiple times for multiple devices.
3883 vga= [BOOT,X86-32] Select a particular video mode
3884 See Documentation/x86/boot.txt and
3885 Documentation/svga.txt.
3886 Use vga=ask for menu.
3887 This is actually a boot loader parameter; the value is
3888 passed to the kernel using a special protocol.
3890 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3891 size of <nn>. This can be used to increase the
3892 minimum size (128MB on x86). It can also be used to
3893 decrease the size and leave more room for directly
3896 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3899 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3902 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3906 Controls the behavior of vsyscalls (i.e. calls to
3907 fixed addresses of 0xffffffffff600x00 from legacy
3908 code). Most statically-linked binaries and older
3909 versions of glibc use these calls. Because these
3910 functions are at fixed addresses, they make nice
3911 targets for exploits that can control RIP.
3913 emulate [default] Vsyscalls turn into traps and are
3914 emulated reasonably safely.
3916 native Vsyscalls are native syscall instructions.
3917 This is a little bit faster than trapping
3918 and makes a few dynamic recompilers work
3919 better than they would in emulation mode.
3920 It also makes exploits much easier to write.
3922 none Vsyscalls don't work at all. This makes
3923 them quite hard to use for exploits but
3924 might break your system.
3926 vt.color= [VT] Default text color.
3927 Format: 0xYX, X = foreground, Y = background.
3928 Default: 0x07 = light gray on black.
3930 vt.cur_default= [VT] Default cursor shape.
3931 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3932 the parameters of the <Esc>[?A;B;Cc escape sequence;
3933 see VGA-softcursor.txt. Default: 2 = underline.
3935 vt.default_blu= [VT]
3936 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3937 Change the default blue palette of the console.
3938 This is a 16-member array composed of values
3941 vt.default_grn= [VT]
3942 Format: <green0>,<green1>,<green2>,...,<green15>
3943 Change the default green palette of the console.
3944 This is a 16-member array composed of values
3947 vt.default_red= [VT]
3948 Format: <red0>,<red1>,<red2>,...,<red15>
3949 Change the default red palette of the console.
3950 This is a 16-member array composed of values
3956 Set system-wide default UTF-8 mode for all tty's.
3957 Default is 1, i.e. UTF-8 mode is enabled for all
3958 newly opened terminals.
3960 vt.global_cursor_default=
3963 Set system-wide default for whether a cursor
3964 is shown on new VTs. Default is -1,
3965 i.e. cursors will be created by default unless
3966 overridden by individual drivers. 0 will hide
3967 cursors, 1 will display them.
3969 vt.italic= [VT] Default color for italic text; 0-15.
3972 vt.underline= [VT] Default color for underlined text; 0-15.
3975 watchdog timers [HW,WDT] For information on watchdog timers,
3976 see Documentation/watchdog/watchdog-parameters.txt
3977 or other driver-specific files in the
3978 Documentation/watchdog/ directory.
3980 workqueue.disable_numa
3981 By default, all work items queued to unbound
3982 workqueues are affine to the NUMA nodes they're
3983 issued on, which results in better behavior in
3984 general. If NUMA affinity needs to be disabled for
3985 whatever reason, this option can be used. Note
3986 that this also can be controlled per-workqueue for
3987 workqueues visible under /sys/bus/workqueue/.
3989 workqueue.power_efficient
3990 Per-cpu workqueues are generally preferred because
3991 they show better performance thanks to cache
3992 locality; unfortunately, per-cpu workqueues tend to
3993 be more power hungry than unbound workqueues.
3995 Enabling this makes the per-cpu workqueues which
3996 were observed to contribute significantly to power
3997 consumption unbound, leading to measurably lower
3998 power usage at the cost of small performance
4001 The default value of this parameter is determined by
4002 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4004 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4005 default x2apic cluster mode on platforms
4008 x86_intel_mid_timer= [X86-32,APBT]
4009 Choose timer option for x86 Intel MID platform.
4010 Two valid options are apbt timer only and lapic timer
4011 plus one apbt timer for broadcast timer.
4012 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4014 xen_emul_unplug= [HW,X86,XEN]
4015 Unplug Xen emulated devices
4016 Format: [unplug0,][unplug1]
4017 ide-disks -- unplug primary master IDE devices
4018 aux-ide-disks -- unplug non-primary-master IDE devices
4019 nics -- unplug network devices
4020 all -- unplug all emulated devices (NICs and IDE disks)
4021 unnecessary -- unplugging emulated devices is
4022 unnecessary even if the host did not respond to
4024 never -- do not unplug even if version check succeeds
4026 xen_nopvspin [X86,XEN]
4027 Disables the ticketlock slowpath using Xen PV
4031 Disables the PV optimizations forcing the HVM guest to
4032 run as generic HVM guest with no PV drivers.
4034 xirc2ps_cs= [NET,PCMCIA]
4036 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4038 ______________________________________________________________________
4042 Add more DRM drivers.
projects / linux-2.6-microblaze.git / blob