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.
168 acpi= [HW,ACPI,X86,ARM64]
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
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_rsdp= [ACPI,EFI,KEXEC]
183 Pass the RSDP address to the kernel, mostly used
184 on machines running EFI runtime service to boot the
185 second kernel for kdump.
187 acpi_apic_instance= [ACPI, IOAPIC]
189 2: use 2nd APIC table, if available
190 1,0: use 1st APIC table
193 acpi_backlight= [HW,ACPI]
194 acpi_backlight=vendor
196 If set to vendor, prefer vendor specific driver
197 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
198 of the ACPI video.ko driver.
200 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
201 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
203 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
204 debug output. Bits in debug_layer correspond to a
205 _COMPONENT in an ACPI source file, e.g.,
206 #define _COMPONENT ACPI_PCI_COMPONENT
207 Bits in debug_level correspond to a level in
208 ACPI_DEBUG_PRINT statements, e.g.,
209 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
210 The debug_level mask defaults to "info". See
211 Documentation/acpi/debug.txt for more information about
212 debug layers and levels.
214 Enable processor driver info messages:
215 acpi.debug_layer=0x20000000
216 Enable PCI/PCI interrupt routing info messages:
217 acpi.debug_layer=0x400000
218 Enable AML "Debug" output, i.e., stores to the Debug
219 object while interpreting AML:
220 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
221 Enable all messages related to ACPI hardware:
222 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
224 Some values produce so much output that the system is
225 unusable. The "log_buf_len" parameter may be useful
226 if you need to capture more output.
228 acpi_force_table_verification [HW,ACPI]
229 Enable table checksum verification during early stage.
230 By default, this is disabled due to x86 early mapping
233 acpi_irq_balance [HW,ACPI]
234 ACPI will balance active IRQs
237 acpi_irq_nobalance [HW,ACPI]
238 ACPI will not move active IRQs (default)
241 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
242 Format: <irq>,<irq>...
244 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
246 Format: <irq>,<irq>...
248 acpi_no_auto_serialize [HW,ACPI]
249 Disable auto-serialization of AML methods
250 AML control methods that contain the opcodes to create
251 named objects will be marked as "Serialized" by the
252 auto-serialization feature.
253 This feature is enabled by default.
254 This option allows to turn off the feature.
256 acpi_no_static_ssdt [HW,ACPI]
257 Disable installation of static SSDTs at early boot time
258 By default, SSDTs contained in the RSDT/XSDT will be
259 installed automatically and they will appear under
260 /sys/firmware/acpi/tables.
261 This option turns off this feature.
262 Note that specifying this option does not affect
263 dynamic table installation which will install SSDT
264 tables to /sys/firmware/acpi/tables/dynamic.
266 acpica_no_return_repair [HW, ACPI]
267 Disable AML predefined validation mechanism
268 This mechanism can repair the evaluation result to make
269 the return objects more ACPI specification compliant.
270 This option is useful for developers to identify the
271 root cause of an AML interpreter issue when the issue
272 has something to do with the repair mechanism.
274 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
275 Format: To spoof as Windows 98: ="Microsoft Windows"
277 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
278 acpi_osi="string1" # add string1
279 acpi_osi="!string2" # remove string2
280 acpi_osi=!* # remove all strings
281 acpi_osi=! # disable all built-in OS vendor
283 acpi_osi= # disable all strings
285 'acpi_osi=!' can be used in combination with single or
286 multiple 'acpi_osi="string1"' to support specific OS
287 vendor string(s). Note that such command can only
288 affect the default state of the OS vendor strings, thus
289 it cannot affect the default state of the feature group
290 strings and the current state of the OS vendor strings,
291 specifying it multiple times through kernel command line
292 is meaningless. This command is useful when one do not
293 care about the state of the feature group strings which
294 should be controlled by the OSPM.
296 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
297 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
298 can make '_OSI("Windows 2000")' TRUE.
300 'acpi_osi=' cannot be used in combination with other
301 'acpi_osi=' command lines, the _OSI method will not
302 exist in the ACPI namespace. NOTE that such command can
303 only affect the _OSI support state, thus specifying it
304 multiple times through kernel command line is also
307 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
310 'acpi_osi=!*' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific
312 string(s). Note that such command can affect the
313 current state of both the OS vendor strings and the
314 feature group strings, thus specifying it multiple times
315 through kernel command line is meaningful. But it may
316 still not able to affect the final state of a string if
317 there are quirks related to this string. This command
318 is useful when one want to control the state of the
319 feature group strings to debug BIOS issues related to
322 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
323 '_OSI("Module Device")' FALSE.
324 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
325 '_OSI("Module Device")' TRUE.
326 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
328 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
330 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
331 they all will make '_OSI("Windows 2000")' TRUE.
334 Override the pmtimer bug detection: force the kernel
335 to assume that this machine's pmtimer latches its value
336 and always returns good values.
338 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
339 Format: { level | edge | high | low }
341 acpi_skip_timer_override [HW,ACPI]
342 Recognize and ignore IRQ0/pin2 Interrupt Override.
343 For broken nForce2 BIOS resulting in XT-PIC timer.
345 acpi_sleep= [HW,ACPI] Sleep options
346 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
347 old_ordering, nonvs, sci_force_enable }
348 See Documentation/power/video.txt for information on
350 s3_beep is for debugging; it makes the PC's speaker beep
351 as soon as the kernel's real-mode entry point is called.
352 s4_nohwsig prevents ACPI hardware signature from being
353 used during resume from hibernation.
354 old_ordering causes the ACPI 1.0 ordering of the _PTS
355 control method, with respect to putting devices into
356 low power states, to be enforced (the ACPI 2.0 ordering
357 of _PTS is used by default).
358 nonvs prevents the kernel from saving/restoring the
359 ACPI NVS memory during suspend/hibernation and resume.
360 sci_force_enable causes the kernel to set SCI_EN directly
361 on resume from S1/S3 (which is against the ACPI spec,
362 but some broken systems don't work without it).
364 acpi_use_timer_override [HW,ACPI]
365 Use timer override. For some broken Nvidia NF5 boards
366 that require a timer override, but don't have HPET
368 acpi_enforce_resources= [ACPI]
369 { strict | lax | no }
370 Check for resource conflicts between native drivers
371 and ACPI OperationRegions (SystemIO and SystemMemory
372 only). IO ports and memory declared in ACPI might be
373 used by the ACPI subsystem in arbitrary AML code and
374 can interfere with legacy drivers.
375 strict (default): access to resources claimed by ACPI
376 is denied; legacy drivers trying to access reserved
377 resources will fail to bind to device using them.
378 lax: access to resources claimed by ACPI is allowed;
379 legacy drivers trying to access reserved resources
380 will bind successfully but a warning message is logged.
381 no: ACPI OperationRegions are not marked as reserved,
382 no further checks are performed.
384 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
387 add_efi_memmap [EFI; X86] Include EFI memory map in
388 kernel's map of available physical RAM.
391 { off | try_unsupported }
392 off: disable AGP support
393 try_unsupported: try to drive unsupported chipsets
394 (may crash computer or cause data corruption)
397 See Documentation/sound/alsa/alsa-parameters.txt
400 Allow the default userspace alignment fault handler
401 behaviour to be specified. Bit 0 enables warnings,
402 bit 1 enables fixups, and bit 2 sends a segfault.
404 align_va_addr= [X86-64]
405 Align virtual addresses by clearing slice [14:12] when
406 allocating a VMA at process creation time. This option
407 gives you up to 3% performance improvement on AMD F15h
408 machines (where it is enabled by default) for a
409 CPU-intensive style benchmark, and it can vary highly in
410 a microbenchmark depending on workload and compiler.
412 32: only for 32-bit processes
413 64: only for 64-bit processes
414 on: enable for both 32- and 64-bit processes
415 off: disable for both 32- and 64-bit processes
417 alloc_snapshot [FTRACE]
418 Allocate the ftrace snapshot buffer on boot up when the
419 main buffer is allocated. This is handy if debugging
420 and you need to use tracing_snapshot() on boot up, and
421 do not want to use tracing_snapshot_alloc() as it needs
422 to be done where GFP_KERNEL allocations are allowed.
424 amd_iommu= [HW,X86-64]
425 Pass parameters to the AMD IOMMU driver in the system.
427 fullflush - enable flushing of IO/TLB entries when
428 they are unmapped. Otherwise they are
429 flushed before they will be reused, which
431 off - do not initialize any AMD IOMMU found in
433 force_isolation - Force device isolation for all
434 devices. The IOMMU driver is not
435 allowed anymore to lift isolation
436 requirements as needed. This option
437 does not override iommu=pt
439 amd_iommu_dump= [HW,X86-64]
440 Enable AMD IOMMU driver option to dump the ACPI table
441 for AMD IOMMU. With this option enabled, AMD IOMMU
442 driver will print ACPI tables for AMD IOMMU during
443 IOMMU initialization.
445 amijoy.map= [HW,JOY] Amiga joystick support
446 Map of devices attached to JOY0DAT and JOY1DAT
448 See also Documentation/input/joystick.txt
450 analog.map= [HW,JOY] Analog joystick and gamepad support
451 Specifies type or capabilities of an analog joystick
452 connected to one of 16 gameports
453 Format: <type1>,<type2>,..<type16>
456 Power management functions (SPARCstation-4/5 + deriv.)
458 Disable APC CPU standby support. SPARCstation-Fox does
459 not play well with APC CPU idle - disable it if you have
460 APC and your system crashes randomly.
462 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
463 Change the output verbosity whilst booting
464 Format: { quiet (default) | verbose | debug }
465 Change the amount of debugging information output
466 when initialising the APIC and IO-APIC components.
469 See Documentation/networking/ipv6.txt.
471 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
472 Limit apic dumping. The parameter defines the maximal
473 number of local apics being dumped. Also it is possible
474 to set it to "all" by meaning -- no limit here.
475 Format: { 1 (default) | 2 | ... | all }.
476 The parameter valid if only apic=debug or
477 apic=verbose is specified.
478 Example: apic=debug show_lapic=all
480 apm= [APM] Advanced Power Management
481 See header of arch/x86/kernel/apm_32.c.
483 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484 Format: <io>,<irq>,<nodeID>
488 atarimouse= [HW,MOUSE] Atari Mouse
490 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
491 EzKey and similar keyboards
493 atkbd.reset= [HW] Reset keyboard during initialization
495 atkbd.set= [HW] Select keyboard code set
496 Format: <int> (2 = AT (default), 3 = PS/2)
498 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
501 atkbd.softraw= [HW] Choose between synthetic and real raw mode
502 Format: <bool> (0 = real, 1 = synthetic (default))
504 atkbd.softrepeat= [HW]
505 Use software keyboard repeat
507 audit= [KNL] Enable the audit sub-system
508 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
509 0 - kernel audit is disabled and can not be enabled
510 until the next reboot
511 unset - kernel audit is initialized but disabled and
512 will be fully enabled by the userspace auditd.
513 1 - kernel audit is initialized and partially enabled,
514 storing at most audit_backlog_limit messages in
515 RAM until it is fully enabled by the userspace
519 audit_backlog_limit= [KNL] Set the audit queue size limit.
520 Format: <int> (must be >=0)
523 baycom_epp= [HW,AX25]
526 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
528 See header of drivers/net/hamradio/baycom_par.c.
530 baycom_ser_fdx= [HW,AX25]
531 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
532 Format: <io>,<irq>,<mode>[,<baud>]
533 See header of drivers/net/hamradio/baycom_ser_fdx.c.
535 baycom_ser_hdx= [HW,AX25]
536 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
537 Format: <io>,<irq>,<mode>
538 See header of drivers/net/hamradio/baycom_ser_hdx.c.
540 blkdevparts= Manual partition parsing of block device(s) for
541 embedded devices based on command line input.
542 See Documentation/block/cmdline-partition.txt
544 boot_delay= Milliseconds to delay each printk during boot.
545 Values larger than 10 seconds (10000) are changed to
549 bootmem_debug [KNL] Enable bootmem allocator debug messages.
551 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
552 bttv.radio= Most important insmod options are available as
554 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
557 bulk_remove=off [PPC] This parameter disables the use of the pSeries
558 firmware feature for flushing multiple hpte entries
561 c101= [NET] Moxa C101 synchronous serial card
563 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
564 Sometimes CPU hardware bugs make them report the cache
565 size incorrectly. The kernel will attempt work arounds
566 to fix known problems, but for some CPUs it is not
567 possible to determine what the correct size should be.
568 This option provides an override for these situations.
570 ca_keys= [KEYS] This parameter identifies a specific key(s) on
571 the system trusted keyring to be used for certificate
573 format: { id:<keyid> | builtin }
575 cca= [MIPS] Override the kernel pages' cache coherency
576 algorithm. Accepted values range from 0 to 7
577 inclusive. See arch/mips/include/asm/pgtable-bits.h
578 for platform specific values (SB1, Loongson3 and
581 ccw_timeout_log [S390]
582 See Documentation/s390/CommonIO for details.
584 cgroup_disable= [KNL] Disable a particular controller
585 Format: {name of the controller(s) to disable}
586 The effects of cgroup_disable=foo are:
587 - foo isn't auto-mounted if you mount all cgroups in
589 - foo isn't visible as an individually mountable
591 {Currently only "memory" controller deal with this and
592 cut the overhead, others just disable the usage. So
593 only cgroup_disable=memory is actually worthy}
595 checkreqprot [SELINUX] Set initial checkreqprot flag value.
596 Format: { "0" | "1" }
597 See security/selinux/Kconfig help text.
598 0 -- check protection applied by kernel (includes
599 any implied execute protection).
600 1 -- check protection requested by application.
601 Default value is set via a kernel config option.
602 Value can be changed at runtime via
603 /selinux/checkreqprot.
606 See Documentation/s390/CommonIO for details.
609 Prevents the clock framework from automatically gating
610 clocks that have not been explicitly enabled by a Linux
611 device driver but are enabled in hardware at reset or
612 by the bootloader/firmware. Note that this does not
613 force such clocks to be always-on nor does it reserve
614 those clocks in any way. This parameter is useful for
615 debug and development, but should not be needed on a
616 platform with proper driver support. For more
617 information, see Documentation/clk.txt.
619 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
621 Forces specified clocksource (if available) to be used
622 when calculating gettimeofday(). If specified
623 clocksource is not available, it defaults to PIT.
624 Format: { pit | tsc | cyclone | pmtmr }
626 clocksource= Override the default clocksource
628 Override the default clocksource and use the clocksource
629 with the name specified.
630 Some clocksource names to choose from, depending on
632 [all] jiffies (this is the base, fallback clocksource)
634 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635 pxa_timer,timer3,32k_counter,timer0_1
637 [X86-32] pit,hpet,tsc;
638 scx200_hrt on Geode; cyclone on IBM x440
646 clearcpuid=BITNUM [X86]
647 Disable CPUID feature X for the kernel. See
648 arch/x86/include/asm/cpufeature.h for the valid bit
649 numbers. Note the Linux specific bits are not necessarily
650 stable over kernel options, but the vendor specific
652 Also note that user programs calling CPUID directly
653 or using the feature without checking anything
654 will still see it. This just prevents it from
655 being used by the kernel or shown in /proc/cpuinfo.
656 Also note the kernel might malfunction if you disable
659 cma=nn[MG]@[start[MG][-end[MG]]]
661 Sets the size of kernel global memory area for
662 contiguous memory allocations and optionally the
663 placement constraint by the physical address range of
664 memory allocations. A value of 0 disables CMA
665 altogether. For more information, see
666 include/linux/dma-contiguous.h
668 cmo_free_hint= [PPC] Format: { yes | no }
669 Specify whether pages are marked as being inactive
670 when they are freed. This is used in CMO environments
671 to determine OS memory pressure for page stealing by
675 coherent_pool=nn[KMG] [ARM,KNL]
676 Sets the size of memory pool for coherent, atomic dma
677 allocations, by default set to 256K.
679 code_bytes [X86] How many bytes of object code to print
684 com20020= [HW,NET] ARCnet - COM20020 chipset
686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
692 ARCnet - COM90xx chipset (memory-mapped buffers)
693 Format: <io>[,<irq>[,<memstart>]]
695 condev= [HW,S390] console device
698 console= [KNL] Output console device and options.
700 tty<n> Use the virtual console device <n>.
704 Use the specified serial port. The options are of
705 the form "bbbbpnf", where "bbbb" is the baud rate,
706 "p" is parity ("n", "o", or "e"), "n" is number of
707 bits, and "f" is flow control ("r" for RTS or
708 omit it). Default is "9600n8".
710 See Documentation/serial-console.txt for more
712 Documentation/networking/netconsole.txt for an
715 uart[8250],io,<addr>[,options]
716 uart[8250],mmio,<addr>[,options]
717 Start an early, polled-mode console on the 8250/16550
718 UART at the specified I/O port or MMIO address,
719 switching to the matching ttyS device later. The
720 options are the same as for ttyS, above.
721 hvc<n> Use the hypervisor console device <n>. This is for
722 both Xen and PowerPC hypervisors.
724 If the device connected to the port is not a TTY but a braille
725 device, prepend "brl," before the device type, for instance
727 For now, only VisioBraille is supported.
729 consoleblank= [KNL] The console blank (screen saver) timeout in
730 seconds. Defaults to 10*60 = 10mins. A value of 0
731 disables the blank timer.
734 [KNL] Change the default value for
735 /proc/<pid>/coredump_filter.
736 See also Documentation/filesystems/proc.txt.
738 cpuidle.off=1 [CPU_IDLE]
739 disable the cpuidle sub-system
741 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
743 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
745 crashkernel=size[KMG][@offset[KMG]]
746 [KNL] Using kexec, Linux can switch to a 'crash kernel'
747 upon panic. This parameter reserves the physical
748 memory region [offset, offset + size] for that kernel
749 image. If '@offset' is omitted, then a suitable offset
750 is selected automatically. Check
751 Documentation/kdump/kdump.txt for further details.
753 crashkernel=range1:size1[,range2:size2,...][@offset]
754 [KNL] Same as above, but depends on the memory
755 in the running system. The syntax of range is
756 start-[end] where start and end are both
757 a memory unit (amount[KMG]). See also
758 Documentation/kdump/kdump.txt for an example.
760 crashkernel=size[KMG],high
761 [KNL, x86_64] range could be above 4G. Allow kernel
762 to allocate physical memory region from top, so could
763 be above 4G if system have more than 4G ram installed.
764 Otherwise memory region will be allocated below 4G, if
766 It will be ignored if crashkernel=X is specified.
767 crashkernel=size[KMG],low
768 [KNL, x86_64] range under 4G. When crashkernel=X,high
769 is passed, kernel could allocate physical memory region
770 above 4G, that cause second kernel crash on system
771 that require some amount of low memory, e.g. swiotlb
772 requires at least 64M+32K low memory. Kernel would
773 try to allocate 72M below 4G automatically.
774 This one let user to specify own low range under 4G
775 for second kernel instead.
776 0: to disable low allocation.
777 It will be ignored when crashkernel=X,high is not used
778 or memory reserved is below 4G.
783 cs89x0_media= [HW,NET]
784 Format: { rj45 | aui | bnc }
787 See header of drivers/s390/block/dasd_devmap.c.
789 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
790 (one device per port)
791 Format: <port#>,<type>
792 See also Documentation/input/joystick-parport.txt
794 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
795 time. See Documentation/dynamic-debug-howto.txt for
796 details. Deprecated, see dyndbg.
798 debug [KNL] Enable kernel debugging (events log level).
801 [KNL] verbose self-tests
803 Print debugging info while doing the locking API
805 We default to 0 (no extra messages), setting it to
806 1 will print _a lot_ more information - normally
807 only useful to kernel developers.
809 debug_objects [KNL] Enable object debugging
812 [KNL] Disable object debugging
814 debug_guardpage_minorder=
815 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
816 parameter allows control of the order of pages that will
817 be intentionally kept free (and hence protected) by the
818 buddy allocator. Bigger value increase the probability
819 of catching random memory corruption, but reduce the
820 amount of memory for normal system use. The maximum
821 possible value is MAX_ORDER/2. Setting this parameter
822 to 1 or 2 should be enough to identify most random
823 memory corruption problems caused by bugs in kernel or
824 driver code when a CPU writes to (or reads from) a
825 random memory location. Note that there exists a class
826 of memory corruptions problems caused by buggy H/W or
827 F/W or by drivers badly programing DMA (basically when
828 memory is written at bus level and the CPU MMU is
829 bypassed) which are not detectable by
830 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
831 tracking down these problems.
834 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
835 parameter enables the feature at boot time. In
836 default, it is disabled. We can avoid allocating huge
837 chunk of memory for debug pagealloc if we don't enable
838 it at boot time and the system will work mostly same
839 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
840 on: enable the feature
842 debugpat [X86] Enable PAT debugging
844 decnet.addr= [HW,NET]
845 Format: <area>[,<node>]
846 See also Documentation/networking/decnet.txt.
849 [same as hugepagesz=] The size of the default
850 HugeTLB page size. This is the size represented by
851 the legacy /proc/ hugepages APIs, used for SHM, and
852 default size when mounting hugetlbfs filesystems.
853 Defaults to the default architecture's huge page size
857 Set number of hash buckets for dentry cache.
860 See Documentation/networking/ipv6.txt.
862 disable_cpu_apicid= [X86,APIC,SMP]
864 The number of initial APIC ID for the
865 corresponding CPU to be disabled at boot,
866 mostly used for the kdump 2nd kernel to
867 disable BSP to wake up multiple CPUs without
868 causing system reset or hang due to sending
871 disable_ddw [PPC/PSERIES]
872 Disable Dynamic DMA Window support. Use this if
873 to workaround buggy firmware.
876 See Documentation/networking/ipv6.txt.
878 disable_mtrr_cleanup [X86]
879 The kernel tries to adjust MTRR layout from continuous
880 to discrete, to make X server driver able to add WB
881 entry later. This parameter disables that.
883 disable_mtrr_trim [X86, Intel and AMD only]
884 By default the kernel will trim any uncacheable
885 memory out of your available memory pool based on
886 MTRR settings. This parameter disables that behavior,
887 possibly causing your machine to run very slowly.
889 disable_timer_pin_1 [X86]
890 Disable PIN 1 of APIC timer
891 Can be useful to work around chipset bugs.
893 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
894 this option disables the debugging code at boot.
896 dma_debug_entries=<number>
897 This option allows to tune the number of preallocated
898 entries for DMA-API debugging code. One entry is
899 required per DMA-API allocation. Use this if the
900 DMA-API debugging code disables itself because the
901 architectural default is too low.
903 dma_debug_driver=<driver_name>
904 With this option the DMA-API debugging driver
905 filter feature can be enabled at boot time. Just
906 pass the driver to filter for as the parameter.
907 The filter can be disabled or changed to another
908 driver later using sysfs.
910 drm_kms_helper.edid_firmware=[<connector>:]<file>
911 Broken monitors, graphic adapters and KVMs may
912 send no or incorrect EDID data sets. This parameter
913 allows to specify an EDID data set in the
914 /lib/firmware directory that is used instead.
915 Generic built-in EDID data sets are used, if one of
916 edid/1024x768.bin, edid/1280x1024.bin,
917 edid/1680x1050.bin, or edid/1920x1080.bin is given
918 and no file with the same name exists. Details and
919 instructions how to build your own EDID data are
920 available in Documentation/EDID/HOWTO.txt. An EDID
921 data set will only be used for a particular connector,
922 if its name and a colon are prepended to the EDID
927 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
928 module.dyndbg[="val"]
929 Enable debug messages at boot time. See
930 Documentation/dynamic-debug-howto.txt for details.
933 on enable eager fpu restore
934 off disable eager fpu restore
935 auto selects the default scheme, which automatically
936 enables eagerfpu restore for xsaveopt.
938 early_ioremap_debug [KNL]
939 Enable debug messages in early_ioremap support. This
940 is useful for tracking down temporary early mappings
941 which are not unmapped.
943 earlycon= [KNL] Output early console device and options.
946 Start an early, polled-mode console on a cadence serial
947 port at the specified address. The cadence serial port
948 must already be setup and configured. Options are not
951 uart[8250],io,<addr>[,options]
952 uart[8250],mmio,<addr>[,options]
953 uart[8250],mmio32,<addr>[,options]
954 Start an early, polled-mode console on the 8250/16550
955 UART at the specified I/O port or MMIO address.
956 MMIO inter-register address stride is either 8-bit
957 (mmio) or 32-bit (mmio32).
958 The options are the same as for ttyS, above.
961 Start an early, polled-mode console on a pl011 serial
962 port at the specified address. The pl011 serial port
963 must already be setup and configured. Options are not
967 Start an early, polled-mode console on an msm serial
968 port at the specified address. The serial port
969 must already be setup and configured. Options are not
973 Start an early, polled-mode console on an msm serial
974 dm port at the specified address. The serial port
975 must already be setup and configured. Options are not
978 smh Use ARM semihosting calls for early console.
986 Use early console provided by serial driver available
987 on Samsung SoCs, requires selecting proper type and
988 a correct base address of the selected UART port. The
989 serial port must already be setup and configured.
990 Options are not yet supported.
992 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
996 earlyprintk=serial[,ttySn[,baudrate]]
997 earlyprintk=serial[,0x...[,baudrate]]
998 earlyprintk=ttySn[,baudrate]
999 earlyprintk=dbgp[debugController#]
1001 earlyprintk is useful when the kernel crashes before
1002 the normal console is initialized. It is not enabled by
1003 default because it has some cosmetic problems.
1005 Append ",keep" to not disable it when the real console
1008 Only one of vga, efi, serial, or usb debug port can
1011 Currently only ttyS0 and ttyS1 may be specified by
1012 name. Other I/O ports may be explicitly specified
1013 on some architectures (x86 and arm at least) by
1014 replacing ttySn with an I/O port address, like this:
1015 earlyprintk=serial,0x1008,115200
1016 You can find the port for a given device in
1017 /proc/tty/driver/serial:
1018 2: uart:ST16650V2 port:00001008 irq:18 ...
1020 Interaction with the standard serial driver is not
1023 The VGA and EFI output is eventually overwritten by
1026 The xen output can only be used by Xen PV guests.
1028 edac_report= [HW,EDAC] Control how to report EDAC event
1029 Format: {"on" | "off" | "force"}
1030 on: enable EDAC to report H/W event. May be overridden
1031 by other higher priority error reporting module.
1032 off: disable H/W event reporting through EDAC.
1033 force: enforce the use of EDAC to report H/W event.
1036 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1039 This is designed to be used in conjunction with
1040 the boot argument: earlyprintk=vga
1043 Format: {"off" | "on" | "skip[mbr]"}
1046 Format: { "old_map", "nochunk", "noruntime", "debug" }
1047 old_map [X86-64]: switch to the old ioremap-based EFI
1048 runtime services mapping. 32-bit still uses this one by
1050 nochunk: disable reading files in "chunks" in the EFI
1051 boot stub, as chunking can cause problems with some
1052 firmware implementations.
1053 noruntime : disable EFI runtime services support
1054 debug: enable misc debug output
1056 efi_no_storage_paranoia [EFI; X86]
1057 Using this parameter you can use more than 50% of
1058 your efi variable storage. Use this parameter only if
1059 you are really sure that your UEFI does sane gc and
1060 fulfills the spec otherwise your board may brick.
1062 eisa_irq_edge= [PARISC,HW]
1063 See header of drivers/parisc/eisa.c.
1066 See comment before function elanfreq_setup() in
1067 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1070 Format: {"cfq" | "deadline" | "noop"}
1071 See Documentation/block/cfq-iosched.txt and
1072 Documentation/block/deadline-iosched.txt for details.
1074 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1075 Specifies physical address of start of kernel core
1076 image elf header and optionally the size. Generally
1077 kexec loader will pass this option to capture kernel.
1078 See Documentation/kdump/kdump.txt for details.
1080 enable_mtrr_cleanup [X86]
1081 The kernel tries to adjust MTRR layout from continuous
1082 to discrete, to make X server driver able to add WB
1083 entry later. This parameter enables that.
1085 enable_timer_pin_1 [X86]
1086 Enable PIN 1 of APIC timer
1087 Can be useful to work around chipset bugs
1088 (in particular on some ATI chipsets).
1089 The kernel tries to set a reasonable default.
1091 enforcing [SELINUX] Set initial enforcing status.
1093 See security/selinux/Kconfig help text.
1094 0 -- permissive (log only, no denials).
1095 1 -- enforcing (deny and log).
1097 Value can be changed at runtime via /selinux/enforce.
1100 Disable Error Record Serialization Table (ERST)
1103 ether= [HW,NET] Ethernet cards parameters
1104 This option is obsoleted by the "netdev=" option, which
1105 has equivalent usage. See its documentation for details.
1109 Permit 'security.evm' to be updated regardless of
1110 current integrity status.
1114 fail_make_request=[KNL]
1115 General fault injection mechanism.
1116 Format: <interval>,<probability>,<space>,<times>
1117 See also Documentation/fault-injection/.
1120 See Documentation/blockdev/floppy.txt.
1122 force_pal_cache_flush
1123 [IA-64] Avoid check_sal_cache_flush which may hang on
1124 buggy SAL_CACHE_FLUSH implementations. Using this
1125 parameter will force ia64_sal_cache_flush to call
1126 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1129 Forcefully enable Physical Address Extension (PAE).
1130 Many Pentium M systems disable PAE but may have a
1131 functionally usable PAE implementation.
1132 Warning: use of this parameter will taint the kernel
1133 and may cause unknown problems.
1136 [FTRACE] will set and start the specified tracer
1137 as early as possible in order to facilitate early
1140 ftrace_dump_on_oops[=orig_cpu]
1141 [FTRACE] will dump the trace buffers on oops.
1142 If no parameter is passed, ftrace will dump
1143 buffers of all CPUs, but if you pass orig_cpu, it will
1144 dump only the buffer of the CPU that triggered the
1147 ftrace_filter=[function-list]
1148 [FTRACE] Limit the functions traced by the function
1149 tracer at boot up. function-list is a comma separated
1150 list of functions. This list can be changed at run
1151 time by the set_ftrace_filter file in the debugfs
1154 ftrace_notrace=[function-list]
1155 [FTRACE] Do not trace the functions specified in
1156 function-list. This list can be changed at run time
1157 by the set_ftrace_notrace file in the debugfs
1160 ftrace_graph_filter=[function-list]
1161 [FTRACE] Limit the top level callers functions traced
1162 by the function graph tracer at boot up.
1163 function-list is a comma separated list of functions
1164 that can be changed at run time by the
1165 set_graph_function file in the debugfs tracing directory.
1167 ftrace_graph_notrace=[function-list]
1168 [FTRACE] Do not trace from the functions specified in
1169 function-list. This list is a comma separated list of
1170 functions that can be changed at run time by the
1171 set_graph_notrace file in the debugfs tracing directory.
1174 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1175 support via parallel port (up to 5 devices per port)
1176 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1177 See also Documentation/input/joystick-parport.txt
1181 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1185 gcov_persist= [GCOV] When non-zero (default), profiling data for
1186 kernel modules is saved and remains accessible via
1187 debugfs, even when the module is unloaded/reloaded.
1188 When zero, profiling data is discarded and associated
1189 debugfs files are removed at module unload time.
1191 gpt [EFI] Forces disk with valid GPT signature but
1192 invalid Protective MBR to be treated as GPT. If the
1193 primary GPT is corrupted, it enables the backup/alternate
1194 GPT to be used instead.
1196 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1197 the "Enable 0" bit of the configuration register.
1200 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1201 the "Enable 0" bit of the configuration register.
1204 grcan.select= [HW] Select which physical interface to use.
1207 grcan.txsize= [HW] Sets the size of the tx buffer.
1208 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1210 grcan.rxsize= [HW] Sets the size of the rx buffer.
1211 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1214 hashdist= [KNL,NUMA] Large hashes allocated during boot
1215 are distributed across NUMA nodes. Defaults on
1216 for 64-bit NUMA, off otherwise.
1217 Format: 0 | 1 (for off | on)
1219 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1221 hd= [EIDE] (E)IDE hard drive subsystem geometry
1222 Format: <cyl>,<head>,<sect>
1225 Disable Hardware Error Source Table (HEST) support;
1226 corresponding firmware-first mode error processing
1227 logic will be disabled.
1229 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1230 size of <nn>. This works even on boxes that have no
1231 highmem otherwise. This also works to reduce highmem
1232 size on bigger boxes.
1234 highres= [KNL] Enable/disable high resolution timer mode.
1235 Valid parameters: "on", "off"
1239 See Documentation/isdn/README.HiSax.
1243 hpet= [X86-32,HPET] option to control HPET usage
1244 Format: { enable (default) | disable | force |
1246 disable: disable HPET and use PIT instead
1247 force: allow force enabled of undocumented chips (ICH4,
1249 verbose: show contents of HPET registers during setup
1251 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1252 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1254 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1255 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1256 On x86-64 and powerpc, this option can be specified
1257 multiple times interleaved with hugepages= to reserve
1258 huge pages of different sizes. Valid pages sizes on
1259 x86-64 are 2M (when the CPU supports "pse") and 1G
1260 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1262 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1263 terminal devices. Valid values: 0..8
1264 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1265 If specified, z/VM IUCV HVC accepts connections
1266 from listed z/VM user IDs only.
1268 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1269 hardware thread id mappings.
1270 Format: <cpu>:<hwthread>
1273 Do not unregister boot console at start. This is only
1274 useful for debugging when something happens in the window
1275 between unregistering the boot console and initializing
1278 i2c_bus= [HW] Override the default board specific I2C bus speed
1279 or register an additional I2C bus that is not
1280 registered from board initialization code.
1284 i8042.debug [HW] Toggle i8042 debug mode
1285 i8042.direct [HW] Put keyboard port into non-translated mode
1286 i8042.dumbkbd [HW] Pretend that controller can only read data from
1287 keyboard and cannot control its state
1288 (Don't attempt to blink the leds)
1289 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1290 i8042.nokbd [HW] Don't check/create keyboard port
1291 i8042.noloop [HW] Disable the AUX Loopback command while probing
1293 i8042.nomux [HW] Don't check presence of an active multiplexing
1295 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1297 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1298 i8042.reset [HW] Reset the controller during init and cleanup
1299 i8042.unlock [HW] Unlock (ignore) the keylock
1300 i8042.kbdreset [HW] Reset device connected to KBD port
1304 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1305 indicates that the driver is running on unsupported
1307 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1308 does not match list of supported models.
1310 [HW] Report power status in /proc/i8k
1311 (disabled by default)
1312 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1315 i915.invert_brightness=
1316 [DRM] Invert the sense of the variable that is used to
1317 set the brightness of the panel backlight. Normally a
1318 brightness value of 0 indicates backlight switched off,
1319 and the maximum of the brightness value sets the backlight
1320 to maximum brightness. If this parameter is set to 0
1321 (default) and the machine requires it, or this parameter
1322 is set to 1, a brightness value of 0 sets the backlight
1323 to maximum brightness, and the maximum of the brightness
1324 value switches the backlight off.
1325 -1 -- never invert brightness
1326 0 -- machine default
1327 1 -- force brightness inversion
1330 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1332 ide-core.nodma= [HW] (E)IDE subsystem
1333 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1334 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1335 .cdrom .chs .ignore_cable are additional options
1336 See Documentation/ide/ide.txt.
1338 ide-generic.probe-mask= [HW] (E)IDE subsystem
1340 Probe mask for legacy ISA IDE ports. Depending on
1341 platform up to 6 ports are supported, enabled by
1342 setting corresponding bits in the mask to 1. The
1343 default value is 0x0, which has a special meaning.
1344 On systems that have PCI, it triggers scanning the
1345 PCI bus for the first and the second port, which
1346 are then probed. On systems without PCI the value
1347 of 0x0 enables probing the two first ports as if it
1350 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1351 Claim all unknown PCI IDE storage controllers.
1354 Format: idle=poll, idle=halt, idle=nomwait
1355 Poll forces a polling idle loop that can slightly
1356 improve the performance of waking up a idle CPU, but
1357 will use a lot of power and make the system run hot.
1359 idle=halt: Halt is forced to be used for CPU idle.
1360 In such case C2/C3 won't be used again.
1361 idle=nomwait: Disable mwait for CPU C-states
1363 ignore_loglevel [KNL]
1364 Ignore loglevel setting - this will print /all/
1365 kernel messages to the console. Useful for debugging.
1366 We also add it as printk module parameter, so users
1367 could change it dynamically, usually by
1368 /sys/module/printk/parameters/ignore_loglevel.
1370 ihash_entries= [KNL]
1371 Set number of hash buckets for inode cache.
1373 ima_appraise= [IMA] appraise integrity measurements
1374 Format: { "off" | "enforce" | "fix" | "log" }
1377 ima_appraise_tcb [IMA]
1378 The builtin appraise policy appraises all files
1382 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1386 The list of supported hash algorithms is defined
1387 in crypto/hash_info.h.
1390 Load a policy which meets the needs of the Trusted
1391 Computing Base. This means IMA will measure all
1392 programs exec'd, files mmap'd for exec, and all files
1393 opened for read by uid=0.
1396 Select one of defined IMA measurements template formats.
1397 Formats: { "ima" | "ima-ng" }
1401 [IMA] Define a custom template format.
1402 Format: { "field1|...|fieldN" }
1404 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1405 Format: <min_file_size>
1406 Set the minimal file size for using asynchronous hash.
1407 If left unspecified, ahash usage is disabled.
1409 ahash performance varies for different data sizes on
1410 different crypto accelerators. This option can be used
1411 to achieve the best performance for a particular HW.
1413 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1415 Set hashing buffer size. Default: 4k.
1417 ahash performance varies for different chunk sizes on
1418 different crypto accelerators. This option can be used
1419 to achieve best performance for particular HW.
1423 Run specified binary instead of /sbin/init as init
1426 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1427 for working out where the kernel is dying during
1430 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1431 initcall functions. Useful for debugging built-in
1432 modules and initcalls.
1434 initrd= [BOOT] Specify the location of the initial ramdisk
1436 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1439 int_pln_enable [x86] Enable power limit notification interrupt
1441 integrity_audit=[IMA]
1442 Format: { "0" | "1" }
1443 0 -- basic integrity auditing messages. (Default)
1444 1 -- additional integrity auditing messages.
1446 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1448 Enable intel iommu driver.
1450 Disable intel iommu driver.
1451 igfx_off [Default Off]
1452 By default, gfx is mapped as normal device. If a gfx
1453 device has a dedicated DMAR unit, the DMAR unit is
1454 bypassed by not enabling DMAR with this option. In
1455 this case, gfx device will use physical address for
1458 With this option iommu will not optimize to look
1459 for io virtual address below 32-bit forcing dual
1460 address cycle on pci bus for cards supporting greater
1461 than 32-bit addressing. The default is to look
1462 for translation below 32-bit and if not available
1463 then look in the higher range.
1464 strict [Default Off]
1465 With this option on every unmap_single operation will
1466 result in a hardware IOTLB flush operation as opposed
1467 to batching them for performance.
1468 sp_off [Default Off]
1469 By default, super page will be supported if Intel IOMMU
1470 has the capability. With this option, super page will
1473 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1474 0 disables intel_idle and fall back on acpi_idle.
1475 1 to 6 specify maximum depth of C-state.
1479 Do not enable intel_pstate as the default
1480 scaling driver for the supported processors
1482 Enable intel_pstate on systems that prohibit it by default
1483 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1484 instead of acpi-cpufreq may disable platform features, such
1485 as thermal controls and power capping, that rely on ACPI
1486 P-States information being indicated to OSPM and therefore
1487 should be used with caution. This option does not work with
1488 processors that aren't supported by the intel_pstate driver
1489 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1491 Do not enable hardware P state control (HWP)
1494 Only load intel_pstate on systems which support
1495 hardware P state control (HWP) if available.
1497 intremap= [X86-64, Intel-IOMMU]
1498 on enable Interrupt Remapping (default)
1499 off disable Interrupt Remapping
1500 nosid disable Source ID checking
1502 BIOS x2APIC opt-out request will be ignored
1504 iomem= Disable strict checking of access to MMIO memory
1505 strict regions from userspace.
1520 nobypass [PPC/POWERNV]
1521 Disable IOMMU bypass, using IOMMU for PCI devices.
1524 io7= [HW] IO7 for Marvel based alpha systems
1525 See comment before marvel_specify_io7 in
1526 arch/alpha/kernel/core_marvel.c.
1528 io_delay= [X86] I/O delay method
1530 Standard port 0x80 based delay
1532 Alternate port 0xed based delay (needed on some systems)
1534 Simple two microseconds delay
1539 See Documentation/filesystems/nfs/nfsroot.txt.
1542 When an interrupt is not handled search all handlers
1543 for it. Intended to get systems with badly broken
1547 When an interrupt is not handled search all handlers
1548 for it. Also check all handlers each timer
1549 interrupt. Intended to get systems with badly broken
1553 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1555 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1557 <cpu number>,...,<cpu number>
1559 <cpu number>-<cpu number>
1560 (must be a positive range in ascending order)
1562 <cpu number>,...,<cpu number>-<cpu number>
1564 This option can be used to specify one or more CPUs
1565 to isolate from the general SMP balancing and scheduling
1566 algorithms. You can move a process onto or off an
1567 "isolated" CPU via the CPU affinity syscalls or cpuset.
1568 <cpu number> begins at 0 and the maximum value is
1569 "number of CPUs in system - 1".
1571 This option is the preferred way to isolate CPUs. The
1572 alternative -- manually setting the CPU mask of all
1573 tasks in the system -- can cause problems and
1574 suboptimal load balancer performance.
1578 ivrs_ioapic [HW,X86_64]
1579 Provide an override to the IOAPIC-ID<->DEVICE-ID
1580 mapping provided in the IVRS ACPI table. For
1581 example, to map IOAPIC-ID decimal 10 to
1582 PCI device 00:14.0 write the parameter as:
1583 ivrs_ioapic[10]=00:14.0
1585 ivrs_hpet [HW,X86_64]
1586 Provide an override to the HPET-ID<->DEVICE-ID
1587 mapping provided in the IVRS ACPI table. For
1588 example, to map HPET-ID decimal 0 to
1589 PCI device 00:14.0 write the parameter as:
1590 ivrs_hpet[0]=00:14.0
1592 js= [HW,JOY] Analog joystick
1593 See Documentation/input/joystick.txt.
1596 Enable/disable kernel and module base offset ASLR
1597 (Address Space Layout Randomization) if built into
1598 the kernel. When CONFIG_HIBERNATION is selected,
1599 kASLR is disabled by default. When kASLR is enabled,
1600 hibernation will be disabled.
1604 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1605 specifies the amount of memory usable by the kernel
1606 for non-movable allocations. The requested amount is
1607 spread evenly throughout all nodes in the system. The
1608 remaining memory in each node is used for Movable
1609 pages. In the event, a node is too small to have both
1610 kernelcore and Movable pages, kernelcore pages will
1611 take priority and other nodes will have a larger number
1612 of Movable pages. The Movable zone is used for the
1613 allocation of pages that may be reclaimed or moved
1614 by the page migration subsystem. This means that
1615 HugeTLB pages may not be allocated from this zone.
1616 Note that allocations like PTEs-from-HighMem still
1617 use the HighMem zone if it exists, and the Normal
1618 zone if it does not.
1620 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1621 Format: <Controller#>[,poll interval]
1622 The controller # is the number of the ehci usb debug
1623 port as it is probed via PCI. The poll interval is
1624 optional and is the number seconds in between
1625 each poll cycle to the debug port in case you need
1626 the functionality for interrupting the kernel with
1627 gdb or control-c on the dbgp connection. When
1628 not using this parameter you use sysrq-g to break into
1629 the kernel debugger.
1631 kgdboc= [KGDB,HW] kgdb over consoles.
1632 Requires a tty driver that supports console polling,
1633 or a supported polling keyboard driver (non-usb).
1634 Serial only format: <serial_device>[,baud]
1635 keyboard only format: kbd
1636 keyboard and serial format: kbd,<serial_device>[,baud]
1637 Optional Kernel mode setting:
1638 kms, kbd format: kms,kbd
1639 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1641 kgdbwait [KGDB] Stop kernel execution and enter the
1642 kernel debugger at the earliest opportunity.
1644 kmac= [MIPS] korina ethernet MAC address.
1645 Configure the RouterBoard 532 series on-chip
1646 Ethernet adapter MAC address.
1648 kmemleak= [KNL] Boot-time kmemleak enable/disable
1649 Valid arguments: on, off
1651 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1654 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1655 Valid arguments: 0, 1, 2
1656 kmemcheck=0 (disabled)
1657 kmemcheck=1 (enabled)
1658 kmemcheck=2 (one-shot mode)
1659 Default: 2 (one-shot mode)
1661 kstack=N [X86] Print N words from the kernel stack
1664 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1665 Default is 0 (don't ignore, but inject #GP)
1667 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1671 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1672 Default is 1 (enabled)
1674 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1676 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1678 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1679 (virtualized MMU) support on capable Intel chips.
1680 Default is 1 (enabled)
1682 kvm-intel.emulate_invalid_guest_state=
1683 [KVM,Intel] Enable emulation of invalid guest states
1684 Default is 0 (disabled)
1686 kvm-intel.flexpriority=
1687 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1688 Default is 1 (enabled)
1691 [KVM,Intel] Enable VMX nesting (nVMX).
1692 Default is 0 (disabled)
1694 kvm-intel.unrestricted_guest=
1695 [KVM,Intel] Disable unrestricted guest feature
1696 (virtualized real and unpaged mode) on capable
1697 Intel chips. Default is 1 (enabled)
1699 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1700 feature (tagged TLBs) on capable Intel chips.
1701 Default is 1 (enabled)
1707 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1710 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1711 value for LAPIC timer one-shot implementation. Default
1712 back to the programmable timer unit in the LAPIC.
1714 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1717 libata.dma= [LIBATA] DMA control
1718 libata.dma=0 Disable all PATA and SATA DMA
1719 libata.dma=1 PATA and SATA Disk DMA only
1720 libata.dma=2 ATAPI (CDROM) DMA only
1721 libata.dma=4 Compact Flash DMA only
1722 Combinations also work, so libata.dma=3 enables DMA
1723 for disks and CDROMs, but not CFs.
1725 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1726 libata.ignore_hpa=0 keep BIOS limits (default)
1727 libata.ignore_hpa=1 ignore limits, using full disk
1729 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1733 libata.force= [LIBATA] Force configurations. The format is comma
1734 separated list of "[ID:]VAL" where ID is
1735 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1736 matching port, link or device. Basically, it matches
1737 the ATA ID string printed on console by libata. If
1738 the whole ID part is omitted, the last PORT and DEVICE
1739 values are used. If ID hasn't been specified yet, the
1740 configuration applies to all ports, links and devices.
1742 If only DEVICE is omitted, the parameter applies to
1743 the port and all links and devices behind it. DEVICE
1744 number of 0 either selects the first device or the
1745 first fan-out link behind PMP device. It does not
1746 select the host link. DEVICE number of 15 selects the
1747 host link and device attached to it.
1749 The VAL specifies the configuration to force. As long
1750 as there's no ambiguity shortcut notation is allowed.
1751 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1752 The following configurations can be forced.
1754 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1755 Any ID with matching PORT is used.
1757 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1759 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1760 udma[/][16,25,33,44,66,100,133] notation is also
1763 * [no]ncq: Turn on or off NCQ.
1765 * nohrst, nosrst, norst: suppress hard, soft
1768 * rstonce: only attempt one reset during
1769 hot-unplug link recovery
1771 * dump_id: dump IDENTIFY data.
1773 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1775 * disable: Disable this device.
1777 If there are multiple matching configurations changing
1778 the same attribute, the last one is used.
1780 memblock=debug [KNL] Enable memblock debug messages.
1782 load_ramdisk= [RAM] List of ramdisks to load from floppy
1783 See Documentation/blockdev/ramdisk.txt.
1785 lockd.nlm_grace_period=P [NFS] Assign grace period.
1788 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1791 lockd.nlm_timeout=T [NFS] Assign timeout value.
1794 lockd.nlm_udpport=M [NFS] Assign UDP port.
1797 locktorture.nreaders_stress= [KNL]
1798 Set the number of locking read-acquisition kthreads.
1799 Defaults to being automatically set based on the
1800 number of online CPUs.
1802 locktorture.nwriters_stress= [KNL]
1803 Set the number of locking write-acquisition kthreads.
1805 locktorture.onoff_holdoff= [KNL]
1806 Set time (s) after boot for CPU-hotplug testing.
1808 locktorture.onoff_interval= [KNL]
1809 Set time (s) between CPU-hotplug operations, or
1810 zero to disable CPU-hotplug testing.
1812 locktorture.shuffle_interval= [KNL]
1813 Set task-shuffle interval (jiffies). Shuffling
1814 tasks allows some CPUs to go into dyntick-idle
1815 mode during the locktorture test.
1817 locktorture.shutdown_secs= [KNL]
1818 Set time (s) after boot system shutdown. This
1819 is useful for hands-off automated testing.
1821 locktorture.stat_interval= [KNL]
1822 Time (s) between statistics printk()s.
1824 locktorture.stutter= [KNL]
1825 Time (s) to stutter testing, for example,
1826 specifying five seconds causes the test to run for
1827 five seconds, wait for five seconds, and so on.
1828 This tests the locking primitive's ability to
1829 transition abruptly to and from idle.
1831 locktorture.torture_runnable= [BOOT]
1832 Start locktorture running at boot time.
1834 locktorture.torture_type= [KNL]
1835 Specify the locking implementation to test.
1837 locktorture.verbose= [KNL]
1838 Enable additional printk() statements.
1840 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1843 loglevel= All Kernel Messages with a loglevel smaller than the
1844 console loglevel will be printed to the console. It can
1845 also be changed with klogd or other programs. The
1846 loglevels are defined as follows:
1848 0 (KERN_EMERG) system is unusable
1849 1 (KERN_ALERT) action must be taken immediately
1850 2 (KERN_CRIT) critical conditions
1851 3 (KERN_ERR) error conditions
1852 4 (KERN_WARNING) warning conditions
1853 5 (KERN_NOTICE) normal but significant condition
1854 6 (KERN_INFO) informational
1855 7 (KERN_DEBUG) debug-level messages
1857 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1858 in bytes. n must be a power of two and greater
1859 than the minimal size. The minimal size is defined
1860 by LOG_BUF_SHIFT kernel config parameter. There is
1861 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1862 that allows to increase the default size depending on
1863 the number of CPUs. See init/Kconfig for more details.
1865 logo.nologo [FB] Disables display of the built-in Linux logo.
1866 This may be used to provide more screen space for
1867 kernel log messages and is useful when debugging
1868 kernel boot problems.
1870 lp=0 [LP] Specify parallel ports to use, e.g,
1871 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1872 lp=reset first parallel port). 'lp=0' disables the
1873 lp=auto printer driver. 'lp=reset' (which can be
1874 specified in addition to the ports) causes
1875 attached printers to be reset. Using
1876 lp=port1,port2,... specifies the parallel ports
1877 to associate lp devices with, starting with
1878 lp0. A port specification may be 'none' to skip
1879 that lp device, or a parport name such as
1880 'parport0'. Specifying 'lp=auto' instead of a
1881 port specification list means that device IDs
1882 from each port should be examined, to see if
1883 an IEEE 1284-compliant printer is attached; if
1884 so, the driver will manage that printer.
1885 See also header of drivers/char/lp.c.
1888 Sets loops_per_jiffy to given constant, thus avoiding
1889 time-consuming boot-time autodetection (up to 250 ms per
1890 CPU). 0 enables autodetection (default). To determine
1891 the correct value for your kernel, boot with normal
1892 autodetection and see what value is printed. Note that
1893 on SMP systems the preset will be applied to all CPUs,
1894 which is likely to cause problems if your CPUs need
1895 significantly divergent settings. An incorrect value
1896 will cause delays in the kernel to be wrong, leading to
1897 unpredictable I/O errors and other breakage. Although
1898 unlikely, in the extreme case this might damage your
1902 Format: <io>,<irq>,<dma>
1904 machvec= [IA-64] Force the use of a particular machine-vector
1905 (machvec) in a generic kernel.
1906 Example: machvec=hpzx1_swiotlb
1908 machtype= [Loongson] Share the same kernel image file between different
1910 Example: machtype=lemote-yeeloong-2f-7inch
1912 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1913 than or equal to this physical address is ignored.
1915 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1916 should make use of. maxcpus=n : n >= 0 limits the
1917 kernel to using 'n' processors. n=0 is a special case,
1918 it is equivalent to "nosmp", which also disables
1921 max_loop= [LOOP] The number of loop block devices that get
1922 (loop.max_loop) unconditionally pre-created at init time. The default
1923 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1924 of statically allocating a predefined number, loop
1925 devices can be requested on-demand with the
1926 /dev/loop-control interface.
1928 mce [X86-32] Machine Check Exception
1930 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1932 md= [HW] RAID subsystems devices and level
1933 See Documentation/md.txt.
1936 Format: <first>,<last>
1937 Specifies range of consoles to be captured by the MDA.
1939 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1940 Amount of memory to be used when the kernel is not able
1941 to see the whole system memory or for test.
1942 [X86] Work as limiting max address. Use together
1943 with memmap= to avoid physical address space collisions.
1944 Without memmap= PCI devices could be placed at addresses
1945 belonging to unused RAM.
1947 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1951 [KNL,SH] Allow user to override the default size for
1952 per-device physically contiguous DMA buffers.
1954 memmap=exactmap [KNL,X86] Enable setting of an exact
1955 E820 memory map, as specified by the user.
1956 Such memmap=exactmap lines can be constructed based on
1957 BIOS output or other requirements. See the memmap=nn@ss
1960 memmap=nn[KMG]@ss[KMG]
1961 [KNL] Force usage of a specific region of memory.
1962 Region of memory to be used is from ss to ss+nn.
1964 memmap=nn[KMG]#ss[KMG]
1965 [KNL,ACPI] Mark specific memory as ACPI data.
1966 Region of memory to be marked is from ss to ss+nn.
1968 memmap=nn[KMG]$ss[KMG]
1969 [KNL,ACPI] Mark specific memory as reserved.
1970 Region of memory to be reserved is from ss to ss+nn.
1971 Example: Exclude memory from 0x18690000-0x1869ffff
1972 memmap=64K$0x18690000
1974 memmap=0x10000$0x18690000
1976 memmap=nn[KMG]!ss[KMG]
1977 [KNL,X86] Mark specific memory as protected.
1978 Region of memory to be used, from ss to ss+nn.
1979 The memory region may be marked as e820 type 12 (0xc)
1980 and is NVDIMM or ADR memory.
1982 memory_corruption_check=0/1 [X86]
1983 Some BIOSes seem to corrupt the first 64k of
1984 memory when doing things like suspend/resume.
1985 Setting this option will scan the memory
1986 looking for corruption. Enabling this will
1987 both detect corruption and prevent the kernel
1988 from using the memory being corrupted.
1989 However, its intended as a diagnostic tool; if
1990 repeatable BIOS-originated corruption always
1991 affects the same memory, you can use memmap=
1992 to prevent the kernel from using that memory.
1994 memory_corruption_check_size=size [X86]
1995 By default it checks for corruption in the low
1996 64k, making this memory unavailable for normal
1997 use. Use this parameter to scan for
1998 corruption in more or less memory.
2000 memory_corruption_check_period=seconds [X86]
2001 By default it checks for corruption every 60
2002 seconds. Use this parameter to check at some
2003 other rate. 0 disables periodic checking.
2005 memtest= [KNL,X86] Enable memtest
2007 default : 0 <disable>
2008 Specifies the number of memtest passes to be
2009 performed. Each pass selects another test
2010 pattern from a given set of patterns. Memtest
2011 fills the memory with this pattern, validates
2012 memory contents and reserves bad memory
2013 regions that are detected.
2015 meye.*= [HW] Set MotionEye Camera parameters
2016 See Documentation/video4linux/meye.txt.
2018 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2019 Multi-Function General Purpose Timers on AMD Geode
2022 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2023 the BIOS has incorrectly applied a workaround. TinyBIOS
2024 version 0.98 is known to be affected, 0.99 fixes the
2025 problem by letting the user disable the workaround.
2029 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2030 physical address is ignored.
2032 mini2440= [ARM,HW,KNL]
2033 Format:[0..2][b][c][t]
2035 MINI2440 configuration specification:
2036 0 - The attached screen is the 3.5" TFT
2037 1 - The attached screen is the 7" TFT
2038 2 - The VGA Shield is attached (1024x768)
2039 Leaving out the screen size parameter will not load
2040 the TFT driver, and the framebuffer will be left
2042 b - Enable backlight. The TFT backlight pin will be
2043 linked to the kernel VESA blanking code and a GPIO
2044 LED. This parameter is not necessary when using the
2046 c - Enable the s3c camera interface.
2047 t - Reserved for enabling touchscreen support. The
2048 touchscreen support is not enabled in the mainstream
2049 kernel as of 2.6.30, a preliminary port can be found
2050 in the "bleeding edge" mini2440 support kernel at
2051 http://repo.or.cz/w/linux-2.6/mini2440.git
2054 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2055 parameter allows control of the logging verbosity for
2056 the additional memory initialisation checks. A value
2057 of 0 disables mminit logging and a level of 4 will
2058 log everything. Information is printed at KERN_DEBUG
2059 so loglevel=8 may also need to be specified.
2062 [KNL] When CONFIG_MODULE_SIG is set, this means that
2063 modules without (valid) signatures will fail to load.
2064 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2065 is always true, so this option does nothing.
2068 [MOUSE] Maximum time between finger touching and
2069 leaving touchpad surface for touch to be considered
2070 a tap and be reported as a left button click (for
2071 touchpads working in absolute mode only).
2073 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2074 reporting absolute coordinates, such as tablets
2075 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2076 reporting absolute coordinates, such as tablets
2078 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2079 is similar to kernelcore except it specifies the
2080 amount of memory used for migratable allocations.
2081 If both kernelcore and movablecore is specified,
2082 then kernelcore will be at *least* the specified
2083 value but may be more. If movablecore on its own
2084 is specified, the administrator must be careful
2085 that the amount of memory usable for all allocations
2088 movable_node [KNL,X86] Boot-time switch to enable the effects
2089 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2091 MTD_Partition= [MTD]
2092 Format: <name>,<region-number>,<size>,<offset>
2094 MTD_Region= [MTD] Format:
2095 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2098 See drivers/mtd/cmdlinepart.c.
2100 multitce=off [PPC] This parameter disables the use of the pSeries
2101 firmware feature for updating multiple TCE entries
2104 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2106 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2108 boundary - index of last SLC block on Flex-OneNAND.
2109 The remaining blocks are configured as MLC blocks.
2110 lock - Configure if Flex-OneNAND boundary should be locked.
2111 Once locked, the boundary cannot be changed.
2112 1 indicates lock status, 0 indicates unlock status.
2115 ARM/S3C2412 JIVE boot control
2117 See arch/arm/mach-s3c2412/mach-jive.c
2119 mtouchusb.raw_coordinates=
2120 [HW] Make the MicroTouch USB driver use raw coordinates
2121 ('y', default) or cooked coordinates ('n')
2123 mtrr_chunk_size=nn[KMG] [X86]
2124 used for mtrr cleanup. It is largest continuous chunk
2125 that could hold holes aka. UC entries.
2127 mtrr_gran_size=nn[KMG] [X86]
2128 Used for mtrr cleanup. It is granularity of mtrr block.
2130 Large value could prevent small alignment from
2133 mtrr_spare_reg_nr=n [X86]
2135 Range: 0,7 : spare reg number
2137 Used for mtrr cleanup. It is spare mtrr entries number.
2138 Set to 2 or more if your graphical card needs more.
2140 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2142 netdev= [NET] Network devices parameters
2143 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2144 Note that mem_start is often overloaded to mean
2145 something different and driver-specific.
2146 This usage is only documented in each driver source
2150 [NETFILTER] Enable connection tracking flow accounting
2151 0 to disable accounting
2152 1 to enable accounting
2155 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2156 See Documentation/filesystems/nfs/nfsroot.txt.
2158 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2159 See Documentation/filesystems/nfs/nfsroot.txt.
2161 nfsrootdebug [NFS] enable nfsroot debugging messages.
2162 See Documentation/filesystems/nfs/nfsroot.txt.
2164 nfs.callback_tcpport=
2165 [NFS] set the TCP port on which the NFSv4 callback
2166 channel should listen.
2169 [NFS] sets the pathname to the program which is used
2170 to update the NFS client cache entries.
2172 nfs.cache_getent_timeout=
2173 [NFS] sets the timeout after which an attempt to
2174 update a cache entry is deemed to have failed.
2176 nfs.idmap_cache_timeout=
2177 [NFS] set the maximum lifetime for idmapper cache
2181 [NFS] enable 64-bit inode numbers.
2182 If zero, the NFS client will fake up a 32-bit inode
2183 number for the readdir() and stat() syscalls instead
2184 of returning the full 64-bit number.
2185 The default is to return 64-bit inode numbers.
2187 nfs.max_session_slots=
2188 [NFSv4.1] Sets the maximum number of session slots
2189 the client will attempt to negotiate with the server.
2190 This limits the number of simultaneous RPC requests
2191 that the client can send to the NFSv4.1 server.
2192 Note that there is little point in setting this
2193 value higher than the max_tcp_slot_table_limit.
2195 nfs.nfs4_disable_idmapping=
2196 [NFSv4] When set to the default of '1', this option
2197 ensures that both the RPC level authentication
2198 scheme and the NFS level operations agree to use
2199 numeric uids/gids if the mount is using the
2200 'sec=sys' security flavour. In effect it is
2201 disabling idmapping, which can make migration from
2202 legacy NFSv2/v3 systems to NFSv4 easier.
2203 Servers that do not support this mode of operation
2204 will be autodetected by the client, and it will fall
2205 back to using the idmapper.
2206 To turn off this behaviour, set the value to '0'.
2208 [NFS4] Specify an additional fixed unique ident-
2209 ification string that NFSv4 clients can insert into
2210 their nfs_client_id4 string. This is typically a
2211 UUID that is generated at system install time.
2213 nfs.send_implementation_id =
2214 [NFSv4.1] Send client implementation identification
2215 information in exchange_id requests.
2216 If zero, no implementation identification information
2218 The default is to send the implementation identification
2221 nfs.recover_lost_locks =
2222 [NFSv4] Attempt to recover locks that were lost due
2223 to a lease timeout on the server. Please note that
2224 doing this risks data corruption, since there are
2225 no guarantees that the file will remain unchanged
2226 after the locks are lost.
2227 If you want to enable the kernel legacy behaviour of
2228 attempting to recover these locks, then set this
2230 The default parameter value of '0' causes the kernel
2231 not to attempt recovery of lost locks.
2233 nfsd.nfs4_disable_idmapping=
2234 [NFSv4] When set to the default of '1', the NFSv4
2235 server will return only numeric uids and gids to
2236 clients using auth_sys, and will accept numeric uids
2237 and gids from such clients. This is intended to ease
2238 migration from NFSv2/v3.
2240 objlayoutdriver.osd_login_prog=
2241 [NFS] [OBJLAYOUT] sets the pathname to the program which
2242 is used to automatically discover and login into new
2243 osd-targets. Please see:
2244 Documentation/filesystems/pnfs.txt for more explanations
2246 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2247 when a NMI is triggered.
2248 Format: [state][,regs][,debounce][,die]
2250 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2251 Format: [panic,][nopanic,][num]
2253 0 - turn nmi_watchdog off
2254 When panic is specified, panic when an NMI watchdog
2255 timeout occurs (or 'nopanic' to override the opposite
2257 This is useful when you use a panic=... timeout and
2258 need the box quickly up again.
2260 netpoll.carrier_timeout=
2261 [NET] Specifies amount of time (in seconds) that
2262 netpoll should wait for a carrier. By default netpoll
2265 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2266 emulation library even if a 387 maths coprocessor
2270 [HW] Never suspend the console
2271 Disable suspending of consoles during suspend and
2272 hibernate operations. Once disabled, debugging
2273 messages can reach various consoles while the rest
2274 of the system is being put to sleep (ie, while
2275 debugging driver suspend/resume hooks). This may
2276 not work reliably with all consoles, but is known
2277 to work with serial and VGA consoles.
2278 To facilitate more flexible debugging, we also add
2279 console_suspend, a printk module parameter to control
2280 it. Users could use console_suspend (usually
2281 /sys/module/printk/parameters/console_suspend) to
2282 turn on/off it dynamically.
2284 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2285 caches in the slab allocator. Saves per-node memory,
2286 but will impact performance.
2290 noapic [SMP,APIC] Tells the kernel to not make use of any
2291 IOAPICs that may be present in the system.
2293 noautogroup Disable scheduler automatic task group creation.
2295 nobats [PPC] Do not use BATs for mapping kernel lowmem
2296 on "Classic" PPC cores.
2300 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2302 nodelayacct [KNL] Disable per-task delay accounting
2304 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2306 nodsp [SH] Disable hardware DSP at boot time.
2308 noefi Disable EFI runtime services support.
2313 On X86-32 available only on PAE configured kernels.
2314 noexec=on: enable non-executable mappings (default)
2315 noexec=off: disable non-executable mappings
2318 Disable SMAP (Supervisor Mode Access Prevention)
2319 even if it is supported by processor.
2322 Disable SMEP (Supervisor Mode Execution Prevention)
2323 even if it is supported by processor.
2326 This affects only 32-bit executables.
2327 noexec32=on: enable non-executable mappings (default)
2328 read doesn't imply executable mappings
2329 noexec32=off: disable non-executable mappings
2330 read implies executable mappings
2332 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2334 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2335 register save and restore. The kernel will only save
2336 legacy floating-point registers on task switch.
2338 noxsave [BUGS=X86] Disables x86 extended register state save
2339 and restore using xsave. The kernel will fallback to
2340 enabling legacy floating-point and sse state.
2342 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2343 register states. The kernel will fall back to use
2344 xsave to save the states. By using this parameter,
2345 performance of saving the states is degraded because
2346 xsave doesn't support modified optimization while
2347 xsaveopt supports it on xsaveopt enabled systems.
2349 noxsaves [X86] Disables xsaves and xrstors used in saving and
2350 restoring x86 extended register state in compacted
2351 form of xsave area. The kernel will fall back to use
2352 xsaveopt and xrstor to save and restore the states
2353 in standard form of xsave area. By using this
2354 parameter, xsave area per process might occupy more
2355 memory on xsaves enabled systems.
2357 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2358 wfi(ARM) instruction doesn't work correctly and not to
2359 use it. This is also useful when using JTAG debugger.
2361 no_file_caps Tells the kernel not to honor file capabilities. The
2362 only way then for a file to be executed with privilege
2363 is to be setuid root or executed by root.
2365 nohalt [IA-64] Tells the kernel not to use the power saving
2366 function PAL_HALT_LIGHT when idle. This increases
2367 power-consumption. On the positive side, it reduces
2368 interrupt wake-up latency, which may improve performance
2369 in certain environments such as networked servers or
2372 nohibernate [HIBERNATION] Disable hibernation and resume.
2374 nohz= [KNL] Boottime enable/disable dynamic ticks
2375 Valid arguments: on, off
2378 nohz_full= [KNL,BOOT]
2379 In kernels built with CONFIG_NO_HZ_FULL=y, set
2380 the specified list of CPUs whose tick will be stopped
2381 whenever possible. The boot CPU will be forced outside
2382 the range to maintain the timekeeping.
2383 The CPUs in this range must also be included in the
2386 noiotrap [SH] Disables trapped I/O port accesses.
2388 noirqdebug [X86-32] Disables the code which attempts to detect and
2389 disable unhandled interrupt sources.
2391 no_timer_check [X86,APIC] Disables the code which tests for
2392 broken timer IRQ sources.
2394 noisapnp [ISAPNP] Disables ISA PnP code.
2396 noinitrd [RAM] Tells the kernel not to load any configured
2399 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2401 [Deprecated - use intremap=off]
2405 nojitter [IA-64] Disables jitter checking for ITC timers.
2407 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2409 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2412 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2413 steal time is computed, but won't influence scheduler
2416 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2418 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2420 noltlbs [PPC] Do not use large page/tlb entries for kernel
2421 lowmem mapping on PPC40x.
2423 nomca [IA-64] Disable machine check abort handling
2425 nomce [X86-32] Machine Check Exception
2427 nomfgpt [X86-32] Disable Multi-Function General Purpose
2428 Timer usage (for AMD Geode machines).
2430 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2431 shutdown the other cpus. Instead use the REBOOT_VECTOR
2434 nomodule Disable module load
2436 nopat [X86] Disable PAT (page attribute table extension of
2437 pagetables) support.
2439 norandmaps Don't use address space randomization. Equivalent to
2440 echo 0 > /proc/sys/kernel/randomize_va_space
2442 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2444 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2445 with UP alternatives
2447 nordrand [X86] Disable kernel use of the RDRAND and
2448 RDSEED instructions even if they are supported
2449 by the processor. RDRAND and RDSEED are still
2450 available to user space applications.
2452 noresume [SWSUSP] Disables resume and restores original swap
2455 no-scroll [VGA] Disables scrollback.
2456 This is required for the Braillex ib80-piezo Braille
2457 reader made by F.H. Papenmeier (Germany).
2461 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2463 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2464 and disable the IO APIC. legacy for "maxcpus=0".
2466 nosoftlockup [KNL] Disable the soft-lockup detector.
2468 nosync [HW,M68K] Disables sync negotiation for all devices.
2470 notsc [BUGS=X86-32] Disable Time Stamp Counter
2472 nousb [USB] Disable the USB subsystem
2474 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2478 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2480 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2481 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2482 Some features depend on CPU0. Known dependencies are:
2483 1. Resume from suspend/hibernate depends on CPU0.
2484 Suspend/hibernate will fail if CPU0 is offline and you
2485 need to online CPU0 before suspend/hibernate.
2486 2. PIC interrupts also depend on CPU0. CPU0 can't be
2487 removed if a PIC interrupt is detected.
2488 It's said poweroff/reboot may depend on CPU0 on some
2489 machines although I haven't seen such issues so far
2490 after CPU0 is offline on a few tested machines.
2491 If the dependencies are under your control, you can
2492 turn on cpu0_hotplug.
2494 nptcg= [IA-64] Override max number of concurrent global TLB
2495 purges which is reported from either PAL_VM_SUMMARY or
2498 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2499 could support. nr_cpus=n : n >= 1 limits the kernel to
2500 supporting 'n' processors. Later in runtime you can not
2501 use hotplug cpu feature to put more cpu back to online.
2502 just like you compile the kernel NR_CPUS=n
2504 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2506 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2507 Allowed values are enable and disable
2509 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2510 one of ['zone', 'node', 'default'] can be specified
2511 This can be set from sysctl after boot.
2512 See Documentation/sysctl/vm.txt for details.
2514 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2515 See Documentation/debugging-via-ohci1394.txt for more
2518 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2519 Rather than timing out after 20 ms if an EC
2520 command is not properly ACKed, override the length
2521 of the timeout. We have interrupts disabled while
2522 waiting for the ACK, so if this is set too high
2523 interrupts *may* be lost!
2525 omap_mux= [OMAP] Override bootloader pin multiplexing.
2526 Format: <mux_mode0.mode_name=value>...
2527 For example, to override I2C bus2:
2528 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2530 oprofile.timer= [HW]
2531 Use timer interrupt instead of performance counters
2533 oprofile.cpu_type= Force an oprofile cpu type
2534 This might be useful if you have an older oprofile
2535 userland or if you want common events.
2536 Format: { arch_perfmon }
2537 arch_perfmon: [X86] Force use of architectural
2538 perfmon on Intel CPUs instead of the
2539 CPU specific event set.
2540 timer: [X86] Force use of architectural NMI
2541 timer mode (see also oprofile.timer
2542 for generic hr timer mode)
2543 [s390] Force legacy basic mode sampling
2544 (report cpu_type "timer")
2546 oops=panic Always panic on oopses. Default is to just kill the
2547 process, but there is a small probability of
2548 deadlocking the machine.
2549 This will also cause panics on machine check exceptions.
2550 Useful together with panic=30 to trigger a reboot.
2553 See Documentation/sound/oss/oss-parameters.txt
2555 page_owner= [KNL] Boot-time page_owner enabling option.
2556 Storage of the information about who allocated
2557 each page is disabled in default. With this switch,
2559 on: enable the feature
2561 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2562 timeout > 0: seconds before rebooting
2563 timeout = 0: wait forever
2564 timeout < 0: reboot immediately
2567 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2570 crash_kexec_post_notifiers
2571 Run kdump after running panic-notifiers and dumping
2572 kmsg. This only for the users who doubt kdump always
2573 succeeds in any situation.
2574 Note that this also increases risks of kdump failure,
2575 because some panic notifiers can make the crashed
2576 kernel more unstable.
2578 parkbd.port= [HW] Parallel port number the keyboard adapter is
2579 connected to, default is 0.
2581 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2582 0 for XT, 1 for AT (default is AT).
2585 parport= [HW,PPT] Specify parallel ports. 0 disables.
2586 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2587 Use 'auto' to force the driver to use any
2588 IRQ/DMA settings detected (the default is to
2589 ignore detected IRQ/DMA settings because of
2590 possible conflicts). You can specify the base
2591 address, IRQ, and DMA settings; IRQ and DMA
2592 should be numbers, or 'auto' (for using detected
2593 settings on that particular port), or 'nofifo'
2594 (to avoid using a FIFO even if it is detected).
2595 Parallel ports are assigned in the order they
2596 are specified on the command line, starting
2599 parport_init_mode= [HW,PPT]
2600 Configure VIA parallel port to operate in
2601 a specific mode. This is necessary on Pegasos
2602 computer where firmware has no options for setting
2603 up parallel port mode and sets it to spp.
2604 Currently this function knows 686a and 8231 chips.
2605 Format: [spp|ps2|epp|ecp|ecpepp]
2608 Halt all CPUs after the first oops has been printed for
2609 the specified number of seconds. This is to be used if
2610 your oopses keep scrolling off the screen.
2615 See header of drivers/block/paride/pcd.c.
2616 See also Documentation/blockdev/paride.txt.
2618 pci=option[,option...] [PCI] various PCI subsystem options:
2619 earlydump [X86] dump PCI config space before the kernel
2621 off [X86] don't probe for the PCI bus
2622 bios [X86-32] force use of PCI BIOS, don't access
2623 the hardware directly. Use this if your machine
2624 has a non-standard PCI host bridge.
2625 nobios [X86-32] disallow use of PCI BIOS, only direct
2626 hardware access methods are allowed. Use this
2627 if you experience crashes upon bootup and you
2628 suspect they are caused by the BIOS.
2629 conf1 [X86] Force use of PCI Configuration
2631 conf2 [X86] Force use of PCI Configuration
2633 noaer [PCIE] If the PCIEAER kernel config parameter is
2634 enabled, this kernel boot option can be used to
2635 disable the use of PCIE advanced error reporting.
2636 nodomains [PCI] Disable support for multiple PCI
2637 root domains (aka PCI segments, in ACPI-speak).
2638 nommconf [X86] Disable use of MMCONFIG for PCI
2640 check_enable_amd_mmconf [X86] check for and enable
2641 properly configured MMIO access to PCI
2642 config space on AMD family 10h CPU
2643 nomsi [MSI] If the PCI_MSI kernel config parameter is
2644 enabled, this kernel boot option can be used to
2645 disable the use of MSI interrupts system-wide.
2646 noioapicquirk [APIC] Disable all boot interrupt quirks.
2647 Safety option to keep boot IRQs enabled. This
2648 should never be necessary.
2649 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2650 primary IO-APIC for bridges that cannot disable
2651 boot IRQs. This fixes a source of spurious IRQs
2652 when the system masks IRQs.
2653 noioapicreroute [APIC] Disable workaround that uses the
2654 boot IRQ equivalent of an IRQ that connects to
2655 a chipset where boot IRQs cannot be disabled.
2656 The opposite of ioapicreroute.
2657 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2658 routing table. These calls are known to be buggy
2659 on several machines and they hang the machine
2660 when used, but on other computers it's the only
2661 way to get the interrupt routing table. Try
2662 this option if the kernel is unable to allocate
2663 IRQs or discover secondary PCI buses on your
2665 rom [X86] Assign address space to expansion ROMs.
2666 Use with caution as certain devices share
2667 address decoders between ROMs and other
2669 norom [X86] Do not assign address space to
2670 expansion ROMs that do not already have
2671 BIOS assigned address ranges.
2672 nobar [X86] Do not assign address space to the
2673 BARs that weren't assigned by the BIOS.
2674 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2675 assigned automatically to PCI devices. You can
2676 make the kernel exclude IRQs of your ISA cards
2678 pirqaddr=0xAAAAA [X86] Specify the physical address
2679 of the PIRQ table (normally generated
2680 by the BIOS) if it is outside the
2681 F0000h-100000h range.
2682 lastbus=N [X86] Scan all buses thru bus #N. Can be
2683 useful if the kernel is unable to find your
2684 secondary buses and you want to tell it
2685 explicitly which ones they are.
2686 assign-busses [X86] Always assign all PCI bus
2687 numbers ourselves, overriding
2688 whatever the firmware may have done.
2689 usepirqmask [X86] Honor the possible IRQ mask stored
2690 in the BIOS $PIR table. This is needed on
2691 some systems with broken BIOSes, notably
2692 some HP Pavilion N5400 and Omnibook XE3
2693 notebooks. This will have no effect if ACPI
2694 IRQ routing is enabled.
2695 noacpi [X86] Do not use ACPI for IRQ routing
2696 or for PCI scanning.
2697 use_crs [X86] Use PCI host bridge window information
2698 from ACPI. On BIOSes from 2008 or later, this
2699 is enabled by default. If you need to use this,
2700 please report a bug.
2701 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2702 If you need to use this, please report a bug.
2703 routeirq Do IRQ routing for all PCI devices.
2704 This is normally done in pci_enable_device(),
2705 so this option is a temporary workaround
2706 for broken drivers that don't call it.
2707 skip_isa_align [X86] do not align io start addr, so can
2708 handle more pci cards
2709 firmware [ARM] Do not re-enumerate the bus but instead
2710 just use the configuration from the
2711 bootloader. This is currently used on
2712 IXP2000 systems where the bus has to be
2713 configured a certain way for adjunct CPUs.
2714 noearly [X86] Don't do any early type 1 scanning.
2715 This might help on some broken boards which
2716 machine check when some devices' config space
2717 is read. But various workarounds are disabled
2718 and some IOMMU drivers will not work.
2719 bfsort Sort PCI devices into breadth-first order.
2720 This sorting is done to get a device
2721 order compatible with older (<= 2.4) kernels.
2722 nobfsort Don't sort PCI devices into breadth-first order.
2723 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2724 tuning and use the BIOS-configured MPS defaults.
2725 pcie_bus_safe Set every device's MPS to the largest value
2726 supported by all devices below the root complex.
2727 pcie_bus_perf Set device MPS to the largest allowable MPS
2728 based on its parent bus. Also set MRRS (Max
2729 Read Request Size) to the largest supported
2730 value (no larger than the MPS that the device
2731 or bus can support) for best performance.
2732 pcie_bus_peer2peer Set every device's MPS to 128B, which
2733 every device is guaranteed to support. This
2734 configuration allows peer-to-peer DMA between
2735 any pair of devices, possibly at the cost of
2736 reduced performance. This also guarantees
2737 that hot-added devices will work.
2738 cbiosize=nn[KMG] The fixed amount of bus space which is
2739 reserved for the CardBus bridge's IO window.
2740 The default value is 256 bytes.
2741 cbmemsize=nn[KMG] The fixed amount of bus space which is
2742 reserved for the CardBus bridge's memory
2743 window. The default value is 64 megabytes.
2746 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2747 Specifies alignment and device to reassign
2748 aligned memory resources.
2749 If <order of align> is not specified,
2750 PAGE_SIZE is used as alignment.
2751 PCI-PCI bridge can be specified, if resource
2752 windows need to be expanded.
2753 ecrc= Enable/disable PCIe ECRC (transaction layer
2754 end-to-end CRC checking).
2755 bios: Use BIOS/firmware settings. This is the
2759 hpiosize=nn[KMG] The fixed amount of bus space which is
2760 reserved for hotplug bridge's IO window.
2761 Default size is 256 bytes.
2762 hpmemsize=nn[KMG] The fixed amount of bus space which is
2763 reserved for hotplug bridge's memory window.
2764 Default size is 2 megabytes.
2765 realloc= Enable/disable reallocating PCI bridge resources
2766 if allocations done by BIOS are too small to
2767 accommodate resources required by all child
2769 off: Turn realloc off
2771 realloc same as realloc=on
2772 noari do not use PCIe ARI.
2773 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2774 only look for one device below a PCIe downstream
2777 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2780 force Enable ASPM even on devices that claim not to support it.
2781 WARNING: Forcing ASPM on may cause system lockups.
2783 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2784 nomsi Do not use MSI for PCI Express Native Hotplug (this
2785 makes all PCIe ports use INTx for hotplug services).
2787 pcie_ports= [PCIE] PCIe ports handling:
2788 auto Ask the BIOS whether or not to use native PCIe services
2789 associated with PCIe ports (PME, hot-plug, AER). Use
2790 them only if that is allowed by the BIOS.
2791 native Use native PCIe services associated with PCIe ports
2793 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2796 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2797 nomsi Do not use MSI for native PCIe PME signaling (this makes
2798 all PCIe root ports use INTx for all services).
2800 pcmv= [HW,PCMCIA] BadgePAD 4
2804 Keep all power-domains already enabled by bootloader on,
2805 even if no driver has claimed them. This is useful
2806 for debug and development, but should not be
2807 needed on a platform with proper driver support.
2810 See Documentation/blockdev/paride.txt.
2812 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2815 See arch/parisc/kernel/pdc_chassis.c
2817 percpu_alloc= Select which percpu first chunk allocator to use.
2818 Currently supported values are "embed" and "page".
2819 Archs may support subset or none of the selections.
2820 See comments in mm/percpu.c for details on each
2821 allocator. This parameter is primarily for debugging
2822 and performance comparison.
2825 See Documentation/blockdev/paride.txt.
2828 See Documentation/blockdev/paride.txt.
2830 pirq= [SMP,APIC] Manual mp-table setup
2831 See Documentation/x86/i386/IO-APIC.txt.
2833 plip= [PPT,NET] Parallel port network link
2834 Format: { parport<nr> | timid | 0 }
2835 See also Documentation/parport.txt.
2837 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2838 Override pmtimer IOPort with a hex value.
2842 Enable PNP debug messages (depends on the
2843 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2844 via /sys/module/pnp/parameters/debug. We always show
2845 current resource usage; turning this on also shows
2846 possible settings and some assignment information.
2852 { on | off | curr | res | no-curr | no-res }
2855 [ISAPNP] Exclude IRQs for the autoconfiguration
2858 [ISAPNP] Exclude DMAs for the autoconfiguration
2860 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2861 Ranges are in pairs (I/O port base and size).
2864 [ISAPNP] Exclude memory regions for the
2866 Ranges are in pairs (memory base and size).
2868 ports= [IP_VS_FTP] IPVS ftp helper module
2870 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2872 Format: <port>,<port>....
2874 print-fatal-signals=
2875 [KNL] debug: print fatal signals
2877 If enabled, warn about various signal handling
2878 related application anomalies: too many signals,
2879 too many POSIX.1 timers, fatal signals causing a
2882 If you hit the warning due to signal overflow,
2883 you might want to try "ulimit -i unlimited".
2887 printk.always_kmsg_dump=
2888 Trigger kmsg_dump for cases other than kernel oops or
2890 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2893 printk.time= Show timing data prefixed to each printk message line
2894 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2896 processor.max_cstate= [HW,ACPI]
2897 Limit processor to maximum C-state
2898 max_cstate=9 overrides any DMI blacklist limit.
2900 processor.nocst [HW,ACPI]
2901 Ignore the _CST method to determine C-states,
2902 instead using the legacy FADT method
2904 profile= [KNL] Enable kernel profiling via /proc/profile
2905 Format: [schedule,]<number>
2906 Param: "schedule" - profile schedule points.
2907 Param: <number> - step/bucket size as a power of 2 for
2908 statistical time based profiling.
2909 Param: "sleep" - profile D-state sleeping (millisecs).
2910 Requires CONFIG_SCHEDSTATS
2911 Param: "kvm" - profile VM exits.
2913 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2915 See Documentation/blockdev/ramdisk.txt.
2917 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2918 probe for; one of (bare|imps|exps|lifebook|any).
2919 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2921 psmouse.resetafter= [HW,MOUSE]
2922 Try to reset the device after so many bad packets
2925 [HW,MOUSE] Set desired mouse resolution, in dpi.
2926 psmouse.smartscroll=
2927 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2928 0 = disabled, 1 = enabled (default).
2930 pstore.backend= Specify the name of the pstore backend to use
2933 See Documentation/blockdev/paride.txt.
2936 [KNL] Number of legacy pty's. Overwrites compiled-in
2939 quiet [KNL] Disable most log messages
2944 See Documentation/md.txt.
2946 ramdisk_blocksize= [RAM]
2947 See Documentation/blockdev/ramdisk.txt.
2949 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2950 See Documentation/blockdev/ramdisk.txt.
2953 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2954 the specified list of CPUs to be no-callback CPUs.
2955 Invocation of these CPUs' RCU callbacks will
2956 be offloaded to "rcuox/N" kthreads created for
2957 that purpose, where "x" is "b" for RCU-bh, "p"
2958 for RCU-preempt, and "s" for RCU-sched, and "N"
2959 is the CPU number. This reduces OS jitter on the
2960 offloaded CPUs, which can be useful for HPC and
2961 real-time workloads. It can also improve energy
2962 efficiency for asymmetric multiprocessors.
2965 Rather than requiring that offloaded CPUs
2966 (specified by rcu_nocbs= above) explicitly
2967 awaken the corresponding "rcuoN" kthreads,
2968 make these kthreads poll for callbacks.
2969 This improves the real-time response for the
2970 offloaded CPUs by relieving them of the need to
2971 wake up the corresponding kthread, but degrades
2972 energy efficiency by requiring that the kthreads
2973 periodically wake up to do the polling.
2975 rcutree.blimit= [KNL]
2976 Set maximum number of finished RCU callbacks to
2977 process in one batch.
2979 rcutree.gp_init_delay= [KNL]
2980 Set the number of jiffies to delay each step of
2981 RCU grace-period initialization. This only has
2982 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
2985 rcutree.rcu_fanout_leaf= [KNL]
2986 Increase the number of CPUs assigned to each
2987 leaf rcu_node structure. Useful for very large
2990 rcutree.jiffies_till_sched_qs= [KNL]
2991 Set required age in jiffies for a
2992 given grace period before RCU starts
2993 soliciting quiescent-state help from
2994 rcu_note_context_switch().
2996 rcutree.jiffies_till_first_fqs= [KNL]
2997 Set delay from grace-period initialization to
2998 first attempt to force quiescent states.
2999 Units are jiffies, minimum value is zero,
3000 and maximum value is HZ.
3002 rcutree.jiffies_till_next_fqs= [KNL]
3003 Set delay between subsequent attempts to force
3004 quiescent states. Units are jiffies, minimum
3005 value is one, and maximum value is HZ.
3007 rcutree.kthread_prio= [KNL,BOOT]
3008 Set the SCHED_FIFO priority of the RCU per-CPU
3009 kthreads (rcuc/N). This value is also used for
3010 the priority of the RCU boost threads (rcub/N)
3011 and for the RCU grace-period kthreads (rcu_bh,
3012 rcu_preempt, and rcu_sched). If RCU_BOOST is
3013 set, valid values are 1-99 and the default is 1
3014 (the least-favored priority). Otherwise, when
3015 RCU_BOOST is not set, valid values are 0-99 and
3016 the default is zero (non-realtime operation).
3018 rcutree.rcu_nocb_leader_stride= [KNL]
3019 Set the number of NOCB kthread groups, which
3020 defaults to the square root of the number of
3021 CPUs. Larger numbers reduces the wakeup overhead
3022 on the per-CPU grace-period kthreads, but increases
3023 that same overhead on each group's leader.
3025 rcutree.qhimark= [KNL]
3026 Set threshold of queued RCU callbacks beyond which
3027 batch limiting is disabled.
3029 rcutree.qlowmark= [KNL]
3030 Set threshold of queued RCU callbacks below which
3031 batch limiting is re-enabled.
3033 rcutree.rcu_idle_gp_delay= [KNL]
3034 Set wakeup interval for idle CPUs that have
3035 RCU callbacks (RCU_FAST_NO_HZ=y).
3037 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3038 Set wakeup interval for idle CPUs that have
3039 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3040 Lazy RCU callbacks are those which RCU can
3041 prove do nothing more than free memory.
3043 rcutorture.cbflood_inter_holdoff= [KNL]
3044 Set holdoff time (jiffies) between successive
3045 callback-flood tests.
3047 rcutorture.cbflood_intra_holdoff= [KNL]
3048 Set holdoff time (jiffies) between successive
3049 bursts of callbacks within a given callback-flood
3052 rcutorture.cbflood_n_burst= [KNL]
3053 Set the number of bursts making up a given
3054 callback-flood test. Set this to zero to
3055 disable callback-flood testing.
3057 rcutorture.cbflood_n_per_burst= [KNL]
3058 Set the number of callbacks to be registered
3059 in a given burst of a callback-flood test.
3061 rcutorture.fqs_duration= [KNL]
3062 Set duration of force_quiescent_state bursts.
3064 rcutorture.fqs_holdoff= [KNL]
3065 Set holdoff time within force_quiescent_state bursts.
3067 rcutorture.fqs_stutter= [KNL]
3068 Set wait time between force_quiescent_state bursts.
3070 rcutorture.gp_exp= [KNL]
3071 Use expedited update-side primitives.
3073 rcutorture.gp_normal= [KNL]
3074 Use normal (non-expedited) update-side primitives.
3075 If both gp_exp and gp_normal are set, do both.
3076 If neither gp_exp nor gp_normal are set, still
3079 rcutorture.n_barrier_cbs= [KNL]
3080 Set callbacks/threads for rcu_barrier() testing.
3082 rcutorture.nfakewriters= [KNL]
3083 Set number of concurrent RCU writers. These just
3084 stress RCU, they don't participate in the actual
3085 test, hence the "fake".
3087 rcutorture.nreaders= [KNL]
3088 Set number of RCU readers.
3090 rcutorture.object_debug= [KNL]
3091 Enable debug-object double-call_rcu() testing.
3093 rcutorture.onoff_holdoff= [KNL]
3094 Set time (s) after boot for CPU-hotplug testing.
3096 rcutorture.onoff_interval= [KNL]
3097 Set time (s) between CPU-hotplug operations, or
3098 zero to disable CPU-hotplug testing.
3100 rcutorture.torture_runnable= [BOOT]
3101 Start rcutorture running at boot time.
3103 rcutorture.shuffle_interval= [KNL]
3104 Set task-shuffle interval (s). Shuffling tasks
3105 allows some CPUs to go into dyntick-idle mode
3106 during the rcutorture test.
3108 rcutorture.shutdown_secs= [KNL]
3109 Set time (s) after boot system shutdown. This
3110 is useful for hands-off automated testing.
3112 rcutorture.stall_cpu= [KNL]
3113 Duration of CPU stall (s) to test RCU CPU stall
3114 warnings, zero to disable.
3116 rcutorture.stall_cpu_holdoff= [KNL]
3117 Time to wait (s) after boot before inducing stall.
3119 rcutorture.stat_interval= [KNL]
3120 Time (s) between statistics printk()s.
3122 rcutorture.stutter= [KNL]
3123 Time (s) to stutter testing, for example, specifying
3124 five seconds causes the test to run for five seconds,
3125 wait for five seconds, and so on. This tests RCU's
3126 ability to transition abruptly to and from idle.
3128 rcutorture.test_boost= [KNL]
3129 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3130 "Maybe" means test if the RCU implementation
3131 under test support RCU priority boosting.
3133 rcutorture.test_boost_duration= [KNL]
3134 Duration (s) of each individual boost test.
3136 rcutorture.test_boost_interval= [KNL]
3137 Interval (s) between each boost test.
3139 rcutorture.test_no_idle_hz= [KNL]
3140 Test RCU's dyntick-idle handling. See also the
3141 rcutorture.shuffle_interval parameter.
3143 rcutorture.torture_type= [KNL]
3144 Specify the RCU implementation to test.
3146 rcutorture.verbose= [KNL]
3147 Enable additional printk() statements.
3149 rcupdate.rcu_expedited= [KNL]
3150 Use expedited grace-period primitives, for
3151 example, synchronize_rcu_expedited() instead
3152 of synchronize_rcu(). This reduces latency,
3153 but can increase CPU utilization, degrade
3154 real-time latency, and degrade energy efficiency.
3156 rcupdate.rcu_cpu_stall_suppress= [KNL]
3157 Suppress RCU CPU stall warning messages.
3159 rcupdate.rcu_cpu_stall_timeout= [KNL]
3160 Set timeout for RCU CPU stall warning messages.
3162 rcupdate.rcu_task_stall_timeout= [KNL]
3163 Set timeout in jiffies for RCU task stall warning
3164 messages. Disable with a value less than or equal
3167 rcupdate.rcu_self_test= [KNL]
3168 Run the RCU early boot self tests
3170 rcupdate.rcu_self_test_bh= [KNL]
3171 Run the RCU bh early boot self tests
3173 rcupdate.rcu_self_test_sched= [KNL]
3174 Run the RCU sched early boot self tests
3178 Run specified binary instead of /init from the ramdisk,
3179 used for early userspace startup. See initrd.
3182 Format (x86 or x86_64):
3183 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3185 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3187 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3188 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3189 reboot_force is either force or not specified,
3190 reboot_cpu is s[mp]#### with #### being the processor
3191 to be used for rebooting.
3194 [KNL, SMP] Set scheduler's default relax_domain_level.
3195 See Documentation/cgroups/cpusets.txt.
3197 relative_sleep_states=
3198 [SUSPEND] Use sleep state labeling where the deepest
3199 state available other than hibernation is always "mem".
3200 Format: { "0" | "1" }
3201 0 -- Traditional sleep state labels.
3202 1 -- Relative sleep state labels.
3204 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3206 reservetop= [X86-32]
3208 Reserves a hole at the top of the kernel virtual
3213 Set the amount of memory to reserve for BIOS at
3214 the bottom of the address space.
3216 reset_devices [KNL] Force drivers to reset the underlying device
3217 during initialization.
3220 Specify the partition device for software suspend
3222 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3224 resume_offset= [SWSUSP]
3225 Specify the offset from the beginning of the partition
3226 given by "resume=" at which the swap header is located,
3227 in <PAGE_SIZE> units (needed only for swap files).
3228 See Documentation/power/swsusp-and-swap-files.txt
3230 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3231 read the resume files
3233 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3234 Useful for devices that are detected asynchronously
3235 (e.g. USB and MMC devices).
3237 hibernate= [HIBERNATION]
3238 noresume Don't check if there's a hibernation image
3239 present during boot.
3240 nocompress Don't compress/decompress hibernation images.
3241 no Disable hibernation and resume.
3243 retain_initrd [RAM] Keep initrd memory after extraction
3245 rfkill.default_state=
3246 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3247 etc. communication is blocked by default.
3250 rfkill.master_switch_mode=
3251 0 The "airplane mode" button does nothing.
3252 1 The "airplane mode" button toggles between everything
3253 blocked and the previous configuration.
3254 2 The "airplane mode" button toggles between everything
3255 blocked and everything unblocked.
3257 rhash_entries= [KNL,NET]
3258 Set number of hash buckets for route cache
3260 ro [KNL] Mount root device read-only on boot
3262 root= [KNL] Root filesystem
3263 See name_to_dev_t comment in init/do_mounts.c.
3265 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3266 mount the root filesystem
3268 rootflags= [KNL] Set root filesystem mount option string
3270 rootfstype= [KNL] Set root filesystem type
3272 rootwait [KNL] Wait (indefinitely) for root device to show up.
3273 Useful for devices that are detected asynchronously
3274 (e.g. USB and MMC devices).
3276 rproc_mem=nn[KMG][@address]
3277 [KNL,ARM,CMA] Remoteproc physical memory block.
3278 Memory area to be used by remote processor image,
3281 rw [KNL] Mount root device read-write on boot
3283 S [KNL] Run init in single mode
3285 s390_iommu= [HW,S390]
3286 Set s390 IOTLB flushing mode
3288 With strict flushing every unmap operation will result in
3289 an IOTLB flush. Default is lazy flushing before reuse,
3293 See drivers/net/irda/sa1100_ir.c.
3295 sbni= [NET] Granch SBNI12 leased line adapter
3297 sched_debug [KNL] Enables verbose scheduler debug messages.
3299 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3300 xtime_lock contention on larger systems, and/or RCU lock
3301 contention on all systems with CONFIG_MAXSMP set.
3302 Format: { "0" | "1" }
3303 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3305 Note: increases power consumption, thus should only be
3306 enabled if running jitter sensitive (HPC/RT) workloads.
3308 security= [SECURITY] Choose a security module to enable at boot.
3309 If this boot parameter is not specified, only the first
3310 security module asking for security registration will be
3311 loaded. An invalid security module name will be treated
3312 as if no module has been chosen.
3314 selinux= [SELINUX] Disable or enable SELinux at boot time.
3315 Format: { "0" | "1" }
3316 See security/selinux/Kconfig help text.
3319 Default value is set via kernel config option.
3320 If enabled at boot time, /selinux/disable can be used
3321 later to disable prior to initial policy load.
3323 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3324 Format: { "0" | "1" }
3325 See security/apparmor/Kconfig help text
3328 Default value is set via kernel config option.
3330 serialnumber [BUGS=X86-32]
3333 Maximal number of shapers.
3335 show_msr= [x86] show boot-time MSR settings
3336 Format: { <integer> }
3337 Show boot-time (BIOS-initialized) MSR settings.
3338 The parameter means the number of CPUs to show,
3339 for example 1 means boot CPU only.
3347 Disable merging of slabs with similar size. May be
3348 necessary if there is some reason to distinguish
3349 allocs to different slabs. Debug options disable
3350 merging on their own.
3351 For more information see Documentation/vm/slub.txt.
3353 slab_max_order= [MM, SLAB]
3354 Determines the maximum allowed order for slabs.
3355 A high setting may cause OOMs due to memory
3356 fragmentation. Defaults to 1 for systems with
3357 more than 32MB of RAM, 0 otherwise.
3359 slub_debug[=options[,slabs]] [MM, SLUB]
3360 Enabling slub_debug allows one to determine the
3361 culprit if slab objects become corrupted. Enabling
3362 slub_debug can create guard zones around objects and
3363 may poison objects when not in use. Also tracks the
3364 last alloc / free. For more information see
3365 Documentation/vm/slub.txt.
3367 slub_max_order= [MM, SLUB]
3368 Determines the maximum allowed order for slabs.
3369 A high setting may cause OOMs due to memory
3370 fragmentation. For more information see
3371 Documentation/vm/slub.txt.
3373 slub_min_objects= [MM, SLUB]
3374 The minimum number of objects per slab. SLUB will
3375 increase the slab order up to slub_max_order to
3376 generate a sufficiently large slab able to contain
3377 the number of objects indicated. The higher the number
3378 of objects the smaller the overhead of tracking slabs
3379 and the less frequently locks need to be acquired.
3380 For more information see Documentation/vm/slub.txt.
3382 slub_min_order= [MM, SLUB]
3383 Determines the minimum page order for slabs. Must be
3384 lower than slub_max_order.
3385 For more information see Documentation/vm/slub.txt.
3387 slub_nomerge [MM, SLUB]
3388 Same with slab_nomerge. This is supported for legacy.
3389 See slab_nomerge for more information.
3392 Format: <io1>[,<io2>[,...,<io8>]]
3394 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3395 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3396 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3397 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3398 smsc-ircc2.ircc_irq= [HW] IRQ line
3399 smsc-ircc2.ircc_dma= [HW] DMA channel
3400 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3401 0: Toshiba Satellite 1800 (GP data pin select)
3402 1: Fast pin select (default)
3406 [KNL] Should the soft-lockup detector generate panics.
3409 softlockup_all_cpu_backtrace=
3410 [KNL] Should the soft-lockup detector generate
3411 backtraces on all cpus.
3414 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3415 See Documentation/laptops/sonypi.txt
3417 spia_io_base= [HW,MTD]
3423 Enabled the stack tracer on boot up.
3425 stacktrace_filter=[function-list]
3426 [FTRACE] Limit the functions that the stack tracer
3427 will trace at boot up. function-list is a comma separated
3428 list of functions. This list can be changed at run
3429 time by the stack_trace_filter file in the debugfs
3430 tracing directory. Note, this enables stack tracing
3431 and the stacktrace above is not needed.
3435 Set the STI (builtin display/keyboard on the HP-PARISC
3436 machines) console (graphic card) which should be used
3437 as the initial boot-console.
3438 See also comment in drivers/video/console/sticore.c.
3441 See comment in drivers/video/console/sticore.c.
3444 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3446 sunrpc.min_resvport=
3447 sunrpc.max_resvport=
3449 SunRPC servers often require that client requests
3450 originate from a privileged port (i.e. a port in the
3451 range 0 < portnr < 1024).
3452 An administrator who wishes to reserve some of these
3453 ports for other uses may adjust the range that the
3454 kernel's sunrpc client considers to be privileged
3455 using these two parameters to set the minimum and
3456 maximum port values.
3460 Control how the NFS server code allocates CPUs to
3461 service thread pools. Depending on how many NICs
3462 you have and where their interrupts are bound, this
3463 option will affect which CPUs will do NFS serving.
3464 Note: this parameter cannot be changed while the
3465 NFS server is running.
3467 auto the server chooses an appropriate mode
3468 automatically using heuristics
3469 global a single global pool contains all CPUs
3470 percpu one pool for each CPU
3471 pernode one pool for each NUMA node (equivalent
3472 to global on non-NUMA machines)
3474 sunrpc.tcp_slot_table_entries=
3475 sunrpc.udp_slot_table_entries=
3477 Sets the upper limit on the number of simultaneous
3478 RPC calls that can be sent from the client to a
3479 server. Increasing these values may allow you to
3480 improve throughput, but will also increase the
3481 amount of memory reserved for use by the client.
3483 suspend.pm_test_delay=
3485 Sets the number of seconds to remain in a suspend test
3486 mode before resuming the system (see
3487 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3488 is set. Default value is 5.
3491 [KNL] Enable accounting of swap in memory resource
3492 controller if no parameter or 1 is given or disable
3493 it if 0 is given (See Documentation/cgroups/memory.txt)
3495 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3496 Format: { <int> | force }
3497 <int> -- Number of I/O TLB slabs
3498 force -- force using of bounce buffers even if they
3499 wouldn't be automatically used by the kernel
3503 sysfs.deprecated=0|1 [KNL]
3504 Enable/disable old style sysfs layout for old udev
3505 on older distributions. When this option is enabled
3506 very new udev will not work anymore. When this option
3507 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3508 in older udev will not work anymore.
3509 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3510 the kernel configuration.
3512 sysrq_always_enabled
3514 Ignore sysrq setting - this boot parameter will
3515 neutralize any effect of /proc/sys/kernel/sysrq.
3516 Useful for debugging.
3518 tcpmhash_entries= [KNL,NET]
3519 Set the number of tcp_metrics_hash slots.
3520 Default value is 8192 or 16384 depending on total
3521 ram pages. This is used to specify the TCP metrics
3522 cache size. See Documentation/networking/ip-sysctl.txt
3523 "tcp_no_metrics_save" section for more details.
3527 test_suspend= [SUSPEND][,N]
3528 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3529 standby suspend) or "freeze" (for suspend type freeze)
3530 as the system sleep state during system startup with
3531 the optional capability to repeat N number of times.
3532 The system is woken from this state using a
3533 wakeup-capable RTC alarm.
3535 thash_entries= [KNL,NET]
3536 Set number of hash buckets for TCP connection
3538 thermal.act= [HW,ACPI]
3539 -1: disable all active trip points in all thermal zones
3540 <degrees C>: override all lowest active trip points
3542 thermal.crt= [HW,ACPI]
3543 -1: disable all critical trip points in all thermal zones
3544 <degrees C>: override all critical trip points
3546 thermal.nocrt= [HW,ACPI]
3547 Set to disable actions on ACPI thermal zone
3548 critical and hot trip points.
3550 thermal.off= [HW,ACPI]
3551 1: disable ACPI thermal control
3553 thermal.psv= [HW,ACPI]
3554 -1: disable all passive trip points
3555 <degrees C>: override all passive trip points to this
3558 thermal.tzp= [HW,ACPI]
3559 Specify global default ACPI thermal zone polling rate
3560 <deci-seconds>: poll all this frequency
3561 0: no polling (default)
3564 Force threading of all interrupt handlers except those
3565 marked explicitly IRQF_NO_THREAD.
3568 Enable the Transcendent memory driver if built-in.
3570 tmem.cleancache=0|1 [KNL, XEN]
3571 Default is on (1). Disable the usage of the cleancache
3572 API to send anonymous pages to the hypervisor.
3574 tmem.frontswap=0|1 [KNL, XEN]
3575 Default is on (1). Disable the usage of the frontswap
3576 API to send swap pages to the hypervisor. If disabled
3577 the selfballooning and selfshrinking are force disabled.
3579 tmem.selfballooning=0|1 [KNL, XEN]
3580 Default is on (1). Disable the driving of swap pages
3583 tmem.selfshrinking=0|1 [KNL, XEN]
3584 Default is on (1). Partial swapoff that immediately
3585 transfers pages from Xen hypervisor back to the
3586 kernel based on different criteria.
3590 Specify if the kernel should make use of the cpu
3591 topology information if the hardware supports this.
3592 The scheduler will make use of this information and
3593 e.g. base its process migration decisions on it.
3596 topology_updates= [KNL, PPC, NUMA]
3598 Specify if the kernel should ignore (off)
3599 topology updates sent by the hypervisor to this
3604 tpm_suspend_pcr=[HW,TPM]
3605 Format: integer pcr id
3606 Specify that at suspend time, the tpm driver
3607 should extend the specified pcr with zeros,
3608 as a workaround for some chips which fail to
3609 flush the last written pcr on TPM_SaveState.
3610 This will guarantee that all the other pcrs
3613 trace_buf_size=nn[KMG]
3614 [FTRACE] will set tracing buffer size on each cpu.
3616 trace_event=[event-list]
3617 [FTRACE] Set and start specified trace events in order
3618 to facilitate early boot debugging.
3619 See also Documentation/trace/events.txt
3621 trace_options=[option-list]
3622 [FTRACE] Enable or disable tracer options at boot.
3623 The option-list is a comma delimited list of options
3624 that can be enabled or disabled just as if you were
3625 to echo the option name into
3627 /sys/kernel/debug/tracing/trace_options
3629 For example, to enable stacktrace option (to dump the
3630 stack trace of each event), add to the command line:
3632 trace_options=stacktrace
3634 See also Documentation/trace/ftrace.txt "trace options"
3638 Have the tracepoints sent to printk as well as the
3639 tracing ring buffer. This is useful for early boot up
3640 where the system hangs or reboots and does not give the
3641 option for reading the tracing buffer or performing a
3642 ftrace_dump_on_oops.
3644 To turn off having tracepoints sent to printk,
3645 echo 0 > /proc/sys/kernel/tracepoint_printk
3646 Note, echoing 1 into this file without the
3647 tracepoint_printk kernel cmdline option has no effect.
3651 Having tracepoints sent to printk() and activating high
3652 frequency tracepoints such as irq or sched, can cause
3653 the system to live lock.
3656 [FTRACE] enable this option to disable tracing when a
3657 warning is hit. This turns off "tracing_on". Tracing can
3658 be enabled again by echoing '1' into the "tracing_on"
3659 file located in /sys/kernel/debug/tracing/
3661 This option is useful, as it disables the trace before
3662 the WARNING dump is called, which prevents the trace to
3663 be filled with content caused by the warning output.
3665 This option can also be set at run time via the sysctl
3666 option: kernel/traceoff_on_warning
3668 transparent_hugepage=
3670 Format: [always|madvise|never]
3671 Can be used to control the default behavior of the system
3672 with respect to transparent hugepages.
3673 See Documentation/vm/transhuge.txt for more details.
3675 tsc= Disable clocksource stability checks for TSC.
3677 [x86] reliable: mark tsc clocksource as reliable, this
3678 disables clocksource verification at runtime, as well
3679 as the stability checks done at bootup. Used to enable
3680 high-resolution timer mode on older hardware, and in
3681 virtualized environment.
3682 [x86] noirqtime: Do not use TSC to do irq accounting.
3683 Used to run time disable IRQ_TIME_ACCOUNTING on any
3684 platforms where RDTSC is slow and this accounting
3687 turbografx.map[2|3]= [HW,JOY]
3688 TurboGraFX parallel port interface
3690 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3691 See also Documentation/input/joystick-parport.txt
3693 udbg-immortal [PPC] When debugging early kernel crashes that
3694 happen after console_init() and before a proper
3695 console driver takes over, this boot options might
3696 help "seeing" what's going on.
3698 uhash_entries= [KNL,NET]
3699 Set number of hash buckets for UDP/UDP-Lite connections
3702 [USB] Ignore overcurrent events (default N).
3703 Some badly-designed motherboards generate lots of
3704 bogus events, for ports that aren't wired to
3705 anything. Set this parameter to avoid log spamming.
3706 Note that genuine overcurrent events won't be
3710 [X86] Cause panic on unknown NMI.
3712 usbcore.authorized_default=
3713 [USB] Default USB device authorization:
3714 (default -1 = authorized except for wireless USB,
3715 0 = not authorized, 1 = authorized)
3717 usbcore.autosuspend=
3718 [USB] The autosuspend time delay (in seconds) used
3719 for newly-detected USB devices (default 2). This
3720 is the time required before an idle device will be
3721 autosuspended. Devices for which the delay is set
3722 to a negative value won't be autosuspended at all.
3724 usbcore.usbfs_snoop=
3725 [USB] Set to log all usbfs traffic (default 0 = off).
3727 usbcore.blinkenlights=
3728 [USB] Set to cycle leds on hubs (default 0 = off).
3730 usbcore.old_scheme_first=
3731 [USB] Start with the old device initialization
3732 scheme (default 0 = off).
3734 usbcore.usbfs_memory_mb=
3735 [USB] Memory limit (in MB) for buffers allocated by
3736 usbfs (default = 16, 0 = max = 2047).
3738 usbcore.use_both_schemes=
3739 [USB] Try the other device initialization scheme
3740 if the first one fails (default 1 = enabled).
3742 usbcore.initial_descriptor_timeout=
3743 [USB] Specifies timeout for the initial 64-byte
3744 USB_REQ_GET_DESCRIPTOR request in milliseconds
3745 (default 5000 = 5.0 seconds).
3748 [USBHID] The interval which mice are to be polled at.
3750 usb-storage.delay_use=
3751 [UMS] The delay in seconds before a new device is
3752 scanned for Logical Units (default 1).
3755 [UMS] A list of quirks entries to supplement or
3756 override the built-in unusual_devs list. List
3757 entries are separated by commas. Each entry has
3758 the form VID:PID:Flags where VID and PID are Vendor
3759 and Product ID values (4-digit hex numbers) and
3760 Flags is a set of characters, each corresponding
3761 to a common usb-storage quirk flag as follows:
3762 a = SANE_SENSE (collect more than 18 bytes
3764 b = BAD_SENSE (don't collect more than 18
3765 bytes of sense data);
3766 c = FIX_CAPACITY (decrease the reported
3767 device capacity by one sector);
3768 d = NO_READ_DISC_INFO (don't use
3769 READ_DISC_INFO command);
3770 e = NO_READ_CAPACITY_16 (don't use
3771 READ_CAPACITY_16 command);
3772 f = NO_REPORT_OPCODES (don't use report opcodes
3774 h = CAPACITY_HEURISTICS (decrease the
3775 reported device capacity by one
3776 sector if the number is odd);
3777 i = IGNORE_DEVICE (don't bind to this
3779 l = NOT_LOCKABLE (don't try to lock and
3780 unlock ejectable media);
3781 m = MAX_SECTORS_64 (don't transfer more
3782 than 64 sectors = 32 KB at a time);
3783 n = INITIAL_READ10 (force a retry of the
3784 initial READ(10) command);
3785 o = CAPACITY_OK (accept the capacity
3786 reported by the device);
3787 p = WRITE_CACHE (the device cache is ON
3789 r = IGNORE_RESIDUE (the device reports
3790 bogus residue values);
3791 s = SINGLE_LUN (the device has only one
3793 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3794 commands, uas only);
3795 u = IGNORE_UAS (don't bind to the uas driver);
3796 w = NO_WP_DETECT (don't test whether the
3797 medium is write-protected).
3798 Example: quirks=0419:aaf5:rl,0421:0433:rc
3800 user_debug= [KNL,ARM]
3802 See arch/arm/Kconfig.debug help text.
3803 1 - undefined instruction events
3805 4 - invalid data aborts
3808 Example: user_debug=31
3811 [X86] Flags controlling user PTE allocations.
3813 nohigh = do not allocate PTE pages in
3814 HIGHMEM regardless of setting
3818 On X86_32, this is an alias for vdso32=. Otherwise:
3820 vdso=1: enable VDSO (the default)
3821 vdso=0: disable VDSO mapping
3823 vdso32= [X86] Control the 32-bit vDSO
3824 vdso32=1: enable 32-bit VDSO
3825 vdso32=0 or vdso32=2: disable 32-bit VDSO
3827 See the help text for CONFIG_COMPAT_VDSO for more
3828 details. If CONFIG_COMPAT_VDSO is set, the default is
3829 vdso32=0; otherwise, the default is vdso32=1.
3831 For compatibility with older kernels, vdso32=2 is an
3834 Try vdso32=0 if you encounter an error that says:
3835 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3838 vector=percpu: enable percpu vector domain
3840 video= [FB] Frame buffer configuration
3841 See Documentation/fb/modedb.txt.
3843 video.brightness_switch_enabled= [0,1]
3844 If set to 1, on receiving an ACPI notify event
3845 generated by hotkey, video driver will adjust brightness
3846 level and then send out the event to user space through
3847 the allocated input device; If set to 0, video driver
3848 will only send out the event without touching backlight
3853 [VMMIO] Memory mapped virtio (platform) device.
3855 <size>@<baseaddr>:<irq>[:<id>]
3857 <size> := size (can use standard suffixes
3859 <baseaddr> := physical base address
3860 <irq> := interrupt number (as passed to
3862 <id> := (optional) platform device id
3864 virtio_mmio.device=1K@0x100b0000:48:7
3866 Can be used multiple times for multiple devices.
3868 vga= [BOOT,X86-32] Select a particular video mode
3869 See Documentation/x86/boot.txt and
3870 Documentation/svga.txt.
3871 Use vga=ask for menu.
3872 This is actually a boot loader parameter; the value is
3873 passed to the kernel using a special protocol.
3875 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3876 size of <nn>. This can be used to increase the
3877 minimum size (128MB on x86). It can also be used to
3878 decrease the size and leave more room for directly
3881 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3884 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3887 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3891 Controls the behavior of vsyscalls (i.e. calls to
3892 fixed addresses of 0xffffffffff600x00 from legacy
3893 code). Most statically-linked binaries and older
3894 versions of glibc use these calls. Because these
3895 functions are at fixed addresses, they make nice
3896 targets for exploits that can control RIP.
3898 emulate [default] Vsyscalls turn into traps and are
3899 emulated reasonably safely.
3901 native Vsyscalls are native syscall instructions.
3902 This is a little bit faster than trapping
3903 and makes a few dynamic recompilers work
3904 better than they would in emulation mode.
3905 It also makes exploits much easier to write.
3907 none Vsyscalls don't work at all. This makes
3908 them quite hard to use for exploits but
3909 might break your system.
3911 vt.color= [VT] Default text color.
3912 Format: 0xYX, X = foreground, Y = background.
3913 Default: 0x07 = light gray on black.
3915 vt.cur_default= [VT] Default cursor shape.
3916 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3917 the parameters of the <Esc>[?A;B;Cc escape sequence;
3918 see VGA-softcursor.txt. Default: 2 = underline.
3920 vt.default_blu= [VT]
3921 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3922 Change the default blue palette of the console.
3923 This is a 16-member array composed of values
3926 vt.default_grn= [VT]
3927 Format: <green0>,<green1>,<green2>,...,<green15>
3928 Change the default green palette of the console.
3929 This is a 16-member array composed of values
3932 vt.default_red= [VT]
3933 Format: <red0>,<red1>,<red2>,...,<red15>
3934 Change the default red palette of the console.
3935 This is a 16-member array composed of values
3941 Set system-wide default UTF-8 mode for all tty's.
3942 Default is 1, i.e. UTF-8 mode is enabled for all
3943 newly opened terminals.
3945 vt.global_cursor_default=
3948 Set system-wide default for whether a cursor
3949 is shown on new VTs. Default is -1,
3950 i.e. cursors will be created by default unless
3951 overridden by individual drivers. 0 will hide
3952 cursors, 1 will display them.
3954 vt.italic= [VT] Default color for italic text; 0-15.
3957 vt.underline= [VT] Default color for underlined text; 0-15.
3960 watchdog timers [HW,WDT] For information on watchdog timers,
3961 see Documentation/watchdog/watchdog-parameters.txt
3962 or other driver-specific files in the
3963 Documentation/watchdog/ directory.
3965 workqueue.disable_numa
3966 By default, all work items queued to unbound
3967 workqueues are affine to the NUMA nodes they're
3968 issued on, which results in better behavior in
3969 general. If NUMA affinity needs to be disabled for
3970 whatever reason, this option can be used. Note
3971 that this also can be controlled per-workqueue for
3972 workqueues visible under /sys/bus/workqueue/.
3974 workqueue.power_efficient
3975 Per-cpu workqueues are generally preferred because
3976 they show better performance thanks to cache
3977 locality; unfortunately, per-cpu workqueues tend to
3978 be more power hungry than unbound workqueues.
3980 Enabling this makes the per-cpu workqueues which
3981 were observed to contribute significantly to power
3982 consumption unbound, leading to measurably lower
3983 power usage at the cost of small performance
3986 The default value of this parameter is determined by
3987 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3989 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3990 default x2apic cluster mode on platforms
3993 x86_intel_mid_timer= [X86-32,APBT]
3994 Choose timer option for x86 Intel MID platform.
3995 Two valid options are apbt timer only and lapic timer
3996 plus one apbt timer for broadcast timer.
3997 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3999 xen_emul_unplug= [HW,X86,XEN]
4000 Unplug Xen emulated devices
4001 Format: [unplug0,][unplug1]
4002 ide-disks -- unplug primary master IDE devices
4003 aux-ide-disks -- unplug non-primary-master IDE devices
4004 nics -- unplug network devices
4005 all -- unplug all emulated devices (NICs and IDE disks)
4006 unnecessary -- unplugging emulated devices is
4007 unnecessary even if the host did not respond to
4009 never -- do not unplug even if version check succeeds
4011 xen_nopvspin [X86,XEN]
4012 Disables the ticketlock slowpath using Xen PV
4016 Disables the PV optimizations forcing the HVM guest to
4017 run as generic HVM guest with no PV drivers.
4019 xirc2ps_cs= [NET,PCMCIA]
4021 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4023 ______________________________________________________________________
4027 Add more DRM drivers.
projects / karo-tx-linux.git / blob