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 DM Device mapper support is enabled.
60 DRM Direct Rendering Management support is enabled.
61 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
62 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
63 EFI EFI Partitioning (GPT) is enabled
64 EIDE EIDE/ATAPI support is enabled.
65 EVM Extended Verification Module
66 FB The frame buffer device is enabled.
67 FTRACE Function tracing enabled.
68 GCOV GCOV profiling is enabled.
69 HW Appropriate hardware is enabled.
70 IA-64 IA-64 architecture is enabled.
71 IMA Integrity measurement architecture is enabled.
72 IOSCHED More than one I/O scheduler is enabled.
73 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
74 IPV6 IPv6 support is enabled.
75 ISAPNP ISA PnP code is enabled.
76 ISDN Appropriate ISDN support is enabled.
77 JOY Appropriate joystick support is enabled.
78 KGDB Kernel debugger support is enabled.
79 KVM Kernel Virtual Machine support is enabled.
80 LIBATA Libata driver is enabled
81 LP Printer support is enabled.
82 LOOP Loopback device support is enabled.
83 M68k M68k architecture is enabled.
84 These options have more detailed description inside of
85 Documentation/m68k/kernel-options.txt.
86 MDA MDA console support is enabled.
87 MIPS MIPS architecture is enabled.
88 MOUSE Appropriate mouse support is enabled.
89 MSI Message Signaled Interrupts (PCI).
90 MTD MTD (Memory Technology Device) support is enabled.
91 NET Appropriate network support is enabled.
92 NUMA NUMA support is enabled.
93 NFS Appropriate NFS support is enabled.
94 OSS OSS sound support is enabled.
95 PV_OPS A paravirtualized kernel is enabled.
96 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
97 PARISC The PA-RISC architecture is enabled.
98 PCI PCI bus support is enabled.
99 PCIE PCI Express support is enabled.
100 PCMCIA The PCMCIA subsystem is enabled.
101 PNP Plug & Play support is enabled.
102 PPC PowerPC architecture is enabled.
103 PPT Parallel port support is enabled.
104 PS2 Appropriate PS/2 support is enabled.
105 RAM RAM disk support is enabled.
106 S390 S390 architecture is enabled.
107 SCSI Appropriate SCSI support is enabled.
108 A lot of drivers have their options described inside
109 the Documentation/scsi/ sub-directory.
110 SECURITY Different security models are enabled.
111 SELINUX SELinux support is enabled.
112 APPARMOR AppArmor support is enabled.
113 SERIAL Serial support is enabled.
114 SH SuperH architecture is enabled.
115 SMP The kernel is an SMP kernel.
116 SPARC Sparc architecture is enabled.
117 SWSUSP Software suspend (hibernation) is enabled.
118 SUSPEND System suspend states are enabled.
119 TPM TPM drivers are enabled.
120 TS Appropriate touchscreen support is enabled.
121 UMS USB Mass Storage support is enabled.
122 USB USB support is enabled.
123 USBHID USB Human Interface Device support is enabled.
124 V4L Video For Linux support is enabled.
125 VMMIO Driver for memory mapped virtio devices is enabled.
126 VGA The VGA console has been enabled.
127 VT Virtual terminal support is enabled.
128 WDT Watchdog support is enabled.
129 XT IBM PC/XT MFM hard disk support is enabled.
130 X86-32 X86-32, aka i386 architecture is enabled.
131 X86-64 X86-64 architecture is enabled.
132 More X86-64 boot options can be found in
133 Documentation/x86/x86_64/boot-options.txt .
134 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
135 XEN Xen support is enabled
137 In addition, the following text indicates that the option:
139 BUGS= Relates to possible processor bugs on the said processor.
140 KNL Is a kernel start-up parameter.
141 BOOT Is a boot loader parameter.
143 Parameters denoted with BOOT are actually interpreted by the boot
144 loader, and have no meaning to the kernel directly.
145 Do not modify the syntax of boot loader parameters without extreme
146 need or coordination with <Documentation/x86/boot.txt>.
148 There are also arch-specific kernel-parameters not documented here.
149 See for example <Documentation/x86/x86_64/boot-options.txt>.
151 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
152 a trailing = on the name of any parameter states that that parameter will
153 be entered as an environment variable, whereas its absence indicates that
154 it will appear as a kernel argument readable via /proc/cmdline by programs
155 running once the system is up.
157 The number of kernel parameters is not limited, but the length of the
158 complete command line (parameters including spaces etc.) is limited to
159 a fixed number of characters. This limit depends on the architecture
160 and is between 256 and 4096 characters. It is defined in the file
161 ./include/asm/setup.h as COMMAND_LINE_SIZE.
163 Finally, the [KMG] suffix is commonly described after a number of kernel
164 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
165 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
166 bytes respectively. Such letter suffixes can also be entirely omitted.
169 acpi= [HW,ACPI,X86,ARM64]
170 Advanced Configuration and Power Interface
171 Format: { force | off | strict | noirq | rsdt |
173 force -- enable ACPI if default was off
174 off -- disable ACPI if default was on
175 noirq -- do not use ACPI for IRQ routing
176 strict -- Be less tolerant of platforms that are not
177 strictly ACPI specification compliant.
178 rsdt -- prefer RSDT over (default) XSDT
179 copy_dsdt -- copy DSDT to memory
180 For ARM64, ONLY "acpi=off" or "acpi=force" are available
182 See also Documentation/power/runtime_pm.txt, pci=noacpi
184 acpi_apic_instance= [ACPI, IOAPIC]
186 2: use 2nd APIC table, if available
187 1,0: use 1st APIC table
190 acpi_backlight= [HW,ACPI]
191 acpi_backlight=vendor
193 If set to vendor, prefer vendor specific driver
194 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
195 of the ACPI video.ko driver.
197 acpica_no_return_repair [HW, ACPI]
198 Disable AML predefined validation mechanism
199 This mechanism can repair the evaluation result to make
200 the return objects more ACPI specification compliant.
201 This option is useful for developers to identify the
202 root cause of an AML interpreter issue when the issue
203 has something to do with the repair mechanism.
205 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
206 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
208 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
209 debug output. Bits in debug_layer correspond to a
210 _COMPONENT in an ACPI source file, e.g.,
211 #define _COMPONENT ACPI_PCI_COMPONENT
212 Bits in debug_level correspond to a level in
213 ACPI_DEBUG_PRINT statements, e.g.,
214 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
215 The debug_level mask defaults to "info". See
216 Documentation/acpi/debug.txt for more information about
217 debug layers and levels.
219 Enable processor driver info messages:
220 acpi.debug_layer=0x20000000
221 Enable PCI/PCI interrupt routing info messages:
222 acpi.debug_layer=0x400000
223 Enable AML "Debug" output, i.e., stores to the Debug
224 object while interpreting AML:
225 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
226 Enable all messages related to ACPI hardware:
227 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
229 Some values produce so much output that the system is
230 unusable. The "log_buf_len" parameter may be useful
231 if you need to capture more output.
233 acpi_enforce_resources= [ACPI]
234 { strict | lax | no }
235 Check for resource conflicts between native drivers
236 and ACPI OperationRegions (SystemIO and SystemMemory
237 only). IO ports and memory declared in ACPI might be
238 used by the ACPI subsystem in arbitrary AML code and
239 can interfere with legacy drivers.
240 strict (default): access to resources claimed by ACPI
241 is denied; legacy drivers trying to access reserved
242 resources will fail to bind to device using them.
243 lax: access to resources claimed by ACPI is allowed;
244 legacy drivers trying to access reserved resources
245 will bind successfully but a warning message is logged.
246 no: ACPI OperationRegions are not marked as reserved,
247 no further checks are performed.
249 acpi_force_table_verification [HW,ACPI]
250 Enable table checksum verification during early stage.
251 By default, this is disabled due to x86 early mapping
254 acpi_irq_balance [HW,ACPI]
255 ACPI will balance active IRQs
258 acpi_irq_nobalance [HW,ACPI]
259 ACPI will not move active IRQs (default)
262 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
263 Format: <irq>,<irq>...
265 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
267 Format: <irq>,<irq>...
269 acpi_no_auto_serialize [HW,ACPI]
270 Disable auto-serialization of AML methods
271 AML control methods that contain the opcodes to create
272 named objects will be marked as "Serialized" by the
273 auto-serialization feature.
274 This feature is enabled by default.
275 This option allows to turn off the feature.
277 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
280 acpi_no_static_ssdt [HW,ACPI]
281 Disable installation of static SSDTs at early boot time
282 By default, SSDTs contained in the RSDT/XSDT will be
283 installed automatically and they will appear under
284 /sys/firmware/acpi/tables.
285 This option turns off this feature.
286 Note that specifying this option does not affect
287 dynamic table installation which will install SSDT
288 tables to /sys/firmware/acpi/tables/dynamic.
290 acpi_rsdp= [ACPI,EFI,KEXEC]
291 Pass the RSDP address to the kernel, mostly used
292 on machines running EFI runtime service to boot the
293 second kernel for kdump.
295 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
296 Format: To spoof as Windows 98: ="Microsoft Windows"
298 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
299 of 2 which is mandated by ACPI 6) as the supported ACPI
300 specification revision (when using this switch, it may
301 be necessary to carry out a cold reboot _twice_ in a
302 row to make it take effect on the platform firmware).
304 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
305 acpi_osi="string1" # add string1
306 acpi_osi="!string2" # remove string2
307 acpi_osi=!* # remove all strings
308 acpi_osi=! # disable all built-in OS vendor
310 acpi_osi= # disable all strings
312 'acpi_osi=!' can be used in combination with single or
313 multiple 'acpi_osi="string1"' to support specific OS
314 vendor string(s). Note that such command can only
315 affect the default state of the OS vendor strings, thus
316 it cannot affect the default state of the feature group
317 strings and the current state of the OS vendor strings,
318 specifying it multiple times through kernel command line
319 is meaningless. This command is useful when one do not
320 care about the state of the feature group strings which
321 should be controlled by the OSPM.
323 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
324 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
325 can make '_OSI("Windows 2000")' TRUE.
327 'acpi_osi=' cannot be used in combination with other
328 'acpi_osi=' command lines, the _OSI method will not
329 exist in the ACPI namespace. NOTE that such command can
330 only affect the _OSI support state, thus specifying it
331 multiple times through kernel command line is also
334 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
337 'acpi_osi=!*' can be used in combination with single or
338 multiple 'acpi_osi="string1"' to support specific
339 string(s). Note that such command can affect the
340 current state of both the OS vendor strings and the
341 feature group strings, thus specifying it multiple times
342 through kernel command line is meaningful. But it may
343 still not able to affect the final state of a string if
344 there are quirks related to this string. This command
345 is useful when one want to control the state of the
346 feature group strings to debug BIOS issues related to
349 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
350 '_OSI("Module Device")' FALSE.
351 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
352 '_OSI("Module Device")' TRUE.
353 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
355 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
357 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
358 they all will make '_OSI("Windows 2000")' TRUE.
361 Override the pmtimer bug detection: force the kernel
362 to assume that this machine's pmtimer latches its value
363 and always returns good values.
365 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
366 Format: { level | edge | high | low }
368 acpi_skip_timer_override [HW,ACPI]
369 Recognize and ignore IRQ0/pin2 Interrupt Override.
370 For broken nForce2 BIOS resulting in XT-PIC timer.
372 acpi_sleep= [HW,ACPI] Sleep options
373 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
374 old_ordering, nonvs, sci_force_enable }
375 See Documentation/power/video.txt for information on
377 s3_beep is for debugging; it makes the PC's speaker beep
378 as soon as the kernel's real-mode entry point is called.
379 s4_nohwsig prevents ACPI hardware signature from being
380 used during resume from hibernation.
381 old_ordering causes the ACPI 1.0 ordering of the _PTS
382 control method, with respect to putting devices into
383 low power states, to be enforced (the ACPI 2.0 ordering
384 of _PTS is used by default).
385 nonvs prevents the kernel from saving/restoring the
386 ACPI NVS memory during suspend/hibernation and resume.
387 sci_force_enable causes the kernel to set SCI_EN directly
388 on resume from S1/S3 (which is against the ACPI spec,
389 but some broken systems don't work without it).
391 acpi_use_timer_override [HW,ACPI]
392 Use timer override. For some broken Nvidia NF5 boards
393 that require a timer override, but don't have HPET
395 add_efi_memmap [EFI; X86] Include EFI memory map in
396 kernel's map of available physical RAM.
399 { off | try_unsupported }
400 off: disable AGP support
401 try_unsupported: try to drive unsupported chipsets
402 (may crash computer or cause data corruption)
405 See Documentation/sound/alsa/alsa-parameters.txt
408 Allow the default userspace alignment fault handler
409 behaviour to be specified. Bit 0 enables warnings,
410 bit 1 enables fixups, and bit 2 sends a segfault.
412 align_va_addr= [X86-64]
413 Align virtual addresses by clearing slice [14:12] when
414 allocating a VMA at process creation time. This option
415 gives you up to 3% performance improvement on AMD F15h
416 machines (where it is enabled by default) for a
417 CPU-intensive style benchmark, and it can vary highly in
418 a microbenchmark depending on workload and compiler.
420 32: only for 32-bit processes
421 64: only for 64-bit processes
422 on: enable for both 32- and 64-bit processes
423 off: disable for both 32- and 64-bit processes
425 alloc_snapshot [FTRACE]
426 Allocate the ftrace snapshot buffer on boot up when the
427 main buffer is allocated. This is handy if debugging
428 and you need to use tracing_snapshot() on boot up, and
429 do not want to use tracing_snapshot_alloc() as it needs
430 to be done where GFP_KERNEL allocations are allowed.
432 amd_iommu= [HW,X86-64]
433 Pass parameters to the AMD IOMMU driver in the system.
435 fullflush - enable flushing of IO/TLB entries when
436 they are unmapped. Otherwise they are
437 flushed before they will be reused, which
439 off - do not initialize any AMD IOMMU found in
441 force_isolation - Force device isolation for all
442 devices. The IOMMU driver is not
443 allowed anymore to lift isolation
444 requirements as needed. This option
445 does not override iommu=pt
447 amd_iommu_dump= [HW,X86-64]
448 Enable AMD IOMMU driver option to dump the ACPI table
449 for AMD IOMMU. With this option enabled, AMD IOMMU
450 driver will print ACPI tables for AMD IOMMU during
451 IOMMU initialization.
453 amijoy.map= [HW,JOY] Amiga joystick support
454 Map of devices attached to JOY0DAT and JOY1DAT
456 See also Documentation/input/joystick.txt
458 analog.map= [HW,JOY] Analog joystick and gamepad support
459 Specifies type or capabilities of an analog joystick
460 connected to one of 16 gameports
461 Format: <type1>,<type2>,..<type16>
464 Power management functions (SPARCstation-4/5 + deriv.)
466 Disable APC CPU standby support. SPARCstation-Fox does
467 not play well with APC CPU idle - disable it if you have
468 APC and your system crashes randomly.
470 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
471 Change the output verbosity whilst booting
472 Format: { quiet (default) | verbose | debug }
473 Change the amount of debugging information output
474 when initialising the APIC and IO-APIC components.
477 See Documentation/networking/ipv6.txt.
479 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
480 Limit apic dumping. The parameter defines the maximal
481 number of local apics being dumped. Also it is possible
482 to set it to "all" by meaning -- no limit here.
483 Format: { 1 (default) | 2 | ... | all }.
484 The parameter valid if only apic=debug or
485 apic=verbose is specified.
486 Example: apic=debug show_lapic=all
488 apm= [APM] Advanced Power Management
489 See header of arch/x86/kernel/apm_32.c.
491 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
492 Format: <io>,<irq>,<nodeID>
496 atarimouse= [HW,MOUSE] Atari Mouse
498 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
499 EzKey and similar keyboards
501 atkbd.reset= [HW] Reset keyboard during initialization
503 atkbd.set= [HW] Select keyboard code set
504 Format: <int> (2 = AT (default), 3 = PS/2)
506 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
509 atkbd.softraw= [HW] Choose between synthetic and real raw mode
510 Format: <bool> (0 = real, 1 = synthetic (default))
512 atkbd.softrepeat= [HW]
513 Use software keyboard repeat
515 audit= [KNL] Enable the audit sub-system
516 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
517 0 - kernel audit is disabled and can not be enabled
518 until the next reboot
519 unset - kernel audit is initialized but disabled and
520 will be fully enabled by the userspace auditd.
521 1 - kernel audit is initialized and partially enabled,
522 storing at most audit_backlog_limit messages in
523 RAM until it is fully enabled by the userspace
527 audit_backlog_limit= [KNL] Set the audit queue size limit.
528 Format: <int> (must be >=0)
531 baycom_epp= [HW,AX25]
534 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
536 See header of drivers/net/hamradio/baycom_par.c.
538 baycom_ser_fdx= [HW,AX25]
539 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
540 Format: <io>,<irq>,<mode>[,<baud>]
541 See header of drivers/net/hamradio/baycom_ser_fdx.c.
543 baycom_ser_hdx= [HW,AX25]
544 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
545 Format: <io>,<irq>,<mode>
546 See header of drivers/net/hamradio/baycom_ser_hdx.c.
548 blkdevparts= Manual partition parsing of block device(s) for
549 embedded devices based on command line input.
550 See Documentation/block/cmdline-partition.txt
552 boot_delay= Milliseconds to delay each printk during boot.
553 Values larger than 10 seconds (10000) are changed to
557 bootmem_debug [KNL] Enable bootmem allocator debug messages.
559 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
560 bttv.radio= Most important insmod options are available as
562 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
565 bulk_remove=off [PPC] This parameter disables the use of the pSeries
566 firmware feature for flushing multiple hpte entries
569 c101= [NET] Moxa C101 synchronous serial card
571 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
572 Sometimes CPU hardware bugs make them report the cache
573 size incorrectly. The kernel will attempt work arounds
574 to fix known problems, but for some CPUs it is not
575 possible to determine what the correct size should be.
576 This option provides an override for these situations.
578 ca_keys= [KEYS] This parameter identifies a specific key(s) on
579 the system trusted keyring to be used for certificate
581 format: { id:<keyid> | builtin }
583 cca= [MIPS] Override the kernel pages' cache coherency
584 algorithm. Accepted values range from 0 to 7
585 inclusive. See arch/mips/include/asm/pgtable-bits.h
586 for platform specific values (SB1, Loongson3 and
589 ccw_timeout_log [S390]
590 See Documentation/s390/CommonIO for details.
592 cgroup_disable= [KNL] Disable a particular controller
593 Format: {name of the controller(s) to disable}
594 The effects of cgroup_disable=foo are:
595 - foo isn't auto-mounted if you mount all cgroups in
597 - foo isn't visible as an individually mountable
599 {Currently only "memory" controller deal with this and
600 cut the overhead, others just disable the usage. So
601 only cgroup_disable=memory is actually worthy}
603 checkreqprot [SELINUX] Set initial checkreqprot flag value.
604 Format: { "0" | "1" }
605 See security/selinux/Kconfig help text.
606 0 -- check protection applied by kernel (includes
607 any implied execute protection).
608 1 -- check protection requested by application.
609 Default value is set via a kernel config option.
610 Value can be changed at runtime via
611 /selinux/checkreqprot.
614 See Documentation/s390/CommonIO for details.
617 Prevents the clock framework from automatically gating
618 clocks that have not been explicitly enabled by a Linux
619 device driver but are enabled in hardware at reset or
620 by the bootloader/firmware. Note that this does not
621 force such clocks to be always-on nor does it reserve
622 those clocks in any way. This parameter is useful for
623 debug and development, but should not be needed on a
624 platform with proper driver support. For more
625 information, see Documentation/clk.txt.
627 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
629 Forces specified clocksource (if available) to be used
630 when calculating gettimeofday(). If specified
631 clocksource is not available, it defaults to PIT.
632 Format: { pit | tsc | cyclone | pmtmr }
634 clocksource= Override the default clocksource
636 Override the default clocksource and use the clocksource
637 with the name specified.
638 Some clocksource names to choose from, depending on
640 [all] jiffies (this is the base, fallback clocksource)
642 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
643 pxa_timer,timer3,32k_counter,timer0_1
645 [X86-32] pit,hpet,tsc;
646 scx200_hrt on Geode; cyclone on IBM x440
654 clearcpuid=BITNUM [X86]
655 Disable CPUID feature X for the kernel. See
656 arch/x86/include/asm/cpufeature.h for the valid bit
657 numbers. Note the Linux specific bits are not necessarily
658 stable over kernel options, but the vendor specific
660 Also note that user programs calling CPUID directly
661 or using the feature without checking anything
662 will still see it. This just prevents it from
663 being used by the kernel or shown in /proc/cpuinfo.
664 Also note the kernel might malfunction if you disable
667 cma=nn[MG]@[start[MG][-end[MG]]]
669 Sets the size of kernel global memory area for
670 contiguous memory allocations and optionally the
671 placement constraint by the physical address range of
672 memory allocations. A value of 0 disables CMA
673 altogether. For more information, see
674 include/linux/dma-contiguous.h
676 cmo_free_hint= [PPC] Format: { yes | no }
677 Specify whether pages are marked as being inactive
678 when they are freed. This is used in CMO environments
679 to determine OS memory pressure for page stealing by
683 coherent_pool=nn[KMG] [ARM,KNL]
684 Sets the size of memory pool for coherent, atomic dma
685 allocations, by default set to 256K.
687 code_bytes [X86] How many bytes of object code to print
692 com20020= [HW,NET] ARCnet - COM20020 chipset
694 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
696 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
700 ARCnet - COM90xx chipset (memory-mapped buffers)
701 Format: <io>[,<irq>[,<memstart>]]
703 condev= [HW,S390] console device
706 console= [KNL] Output console device and options.
708 tty<n> Use the virtual console device <n>.
712 Use the specified serial port. The options are of
713 the form "bbbbpnf", where "bbbb" is the baud rate,
714 "p" is parity ("n", "o", or "e"), "n" is number of
715 bits, and "f" is flow control ("r" for RTS or
716 omit it). Default is "9600n8".
718 See Documentation/serial-console.txt for more
720 Documentation/networking/netconsole.txt for an
723 uart[8250],io,<addr>[,options]
724 uart[8250],mmio,<addr>[,options]
725 uart[8250],mmio32,<addr>[,options]
726 uart[8250],0x<addr>[,options]
727 Start an early, polled-mode console on the 8250/16550
728 UART at the specified I/O port or MMIO address,
729 switching to the matching ttyS device later.
730 MMIO inter-register address stride is either 8-bit
731 (mmio) or 32-bit (mmio32).
732 If none of [io|mmio|mmio32], <addr> is assumed to be
733 equivalent to 'mmio'. 'options' are specified in the
734 same format described for ttyS above; if unspecified,
735 the h/w is not re-initialized.
737 hvc<n> Use the hypervisor console device <n>. This is for
738 both Xen and PowerPC hypervisors.
740 If the device connected to the port is not a TTY but a braille
741 device, prepend "brl," before the device type, for instance
743 For now, only VisioBraille is supported.
745 consoleblank= [KNL] The console blank (screen saver) timeout in
746 seconds. Defaults to 10*60 = 10mins. A value of 0
747 disables the blank timer.
750 [KNL] Change the default value for
751 /proc/<pid>/coredump_filter.
752 See also Documentation/filesystems/proc.txt.
754 cpuidle.off=1 [CPU_IDLE]
755 disable the cpuidle sub-system
758 [X86] Delay for N microsec between assert and de-assert
759 of APIC INIT to start processors. This delay occurs
760 on every CPU online, such as boot, and resume from suspend.
763 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
765 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
767 crashkernel=size[KMG][@offset[KMG]]
768 [KNL] Using kexec, Linux can switch to a 'crash kernel'
769 upon panic. This parameter reserves the physical
770 memory region [offset, offset + size] for that kernel
771 image. If '@offset' is omitted, then a suitable offset
772 is selected automatically. Check
773 Documentation/kdump/kdump.txt for further details.
775 crashkernel=range1:size1[,range2:size2,...][@offset]
776 [KNL] Same as above, but depends on the memory
777 in the running system. The syntax of range is
778 start-[end] where start and end are both
779 a memory unit (amount[KMG]). See also
780 Documentation/kdump/kdump.txt for an example.
782 crashkernel=size[KMG],high
783 [KNL, x86_64] range could be above 4G. Allow kernel
784 to allocate physical memory region from top, so could
785 be above 4G if system have more than 4G ram installed.
786 Otherwise memory region will be allocated below 4G, if
788 It will be ignored if crashkernel=X is specified.
789 crashkernel=size[KMG],low
790 [KNL, x86_64] range under 4G. When crashkernel=X,high
791 is passed, kernel could allocate physical memory region
792 above 4G, that cause second kernel crash on system
793 that require some amount of low memory, e.g. swiotlb
794 requires at least 64M+32K low memory, also enough extra
795 low memory is needed to make sure DMA buffers for 32-bit
796 devices won't run out. Kernel would try to allocate at
797 at least 256M below 4G automatically.
798 This one let user to specify own low range under 4G
799 for second kernel instead.
800 0: to disable low allocation.
801 It will be ignored when crashkernel=X,high is not used
802 or memory reserved is below 4G.
807 cs89x0_media= [HW,NET]
808 Format: { rj45 | aui | bnc }
811 See header of drivers/s390/block/dasd_devmap.c.
813 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
814 (one device per port)
815 Format: <port#>,<type>
816 See also Documentation/input/joystick-parport.txt
818 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
819 time. See Documentation/dynamic-debug-howto.txt for
820 details. Deprecated, see dyndbg.
822 debug [KNL] Enable kernel debugging (events log level).
825 [KNL] verbose self-tests
827 Print debugging info while doing the locking API
829 We default to 0 (no extra messages), setting it to
830 1 will print _a lot_ more information - normally
831 only useful to kernel developers.
833 debug_objects [KNL] Enable object debugging
836 [KNL] Disable object debugging
838 debug_guardpage_minorder=
839 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
840 parameter allows control of the order of pages that will
841 be intentionally kept free (and hence protected) by the
842 buddy allocator. Bigger value increase the probability
843 of catching random memory corruption, but reduce the
844 amount of memory for normal system use. The maximum
845 possible value is MAX_ORDER/2. Setting this parameter
846 to 1 or 2 should be enough to identify most random
847 memory corruption problems caused by bugs in kernel or
848 driver code when a CPU writes to (or reads from) a
849 random memory location. Note that there exists a class
850 of memory corruptions problems caused by buggy H/W or
851 F/W or by drivers badly programing DMA (basically when
852 memory is written at bus level and the CPU MMU is
853 bypassed) which are not detectable by
854 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
855 tracking down these problems.
858 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
859 parameter enables the feature at boot time. In
860 default, it is disabled. We can avoid allocating huge
861 chunk of memory for debug pagealloc if we don't enable
862 it at boot time and the system will work mostly same
863 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
864 on: enable the feature
866 debugpat [X86] Enable PAT debugging
868 decnet.addr= [HW,NET]
869 Format: <area>[,<node>]
870 See also Documentation/networking/decnet.txt.
873 [same as hugepagesz=] The size of the default
874 HugeTLB page size. This is the size represented by
875 the legacy /proc/ hugepages APIs, used for SHM, and
876 default size when mounting hugetlbfs filesystems.
877 Defaults to the default architecture's huge page size
881 Set number of hash buckets for dentry cache.
884 See Documentation/networking/ipv6.txt.
886 disable_cpu_apicid= [X86,APIC,SMP]
888 The number of initial APIC ID for the
889 corresponding CPU to be disabled at boot,
890 mostly used for the kdump 2nd kernel to
891 disable BSP to wake up multiple CPUs without
892 causing system reset or hang due to sending
895 disable_ddw [PPC/PSERIES]
896 Disable Dynamic DMA Window support. Use this if
897 to workaround buggy firmware.
900 See Documentation/networking/ipv6.txt.
902 disable_mtrr_cleanup [X86]
903 The kernel tries to adjust MTRR layout from continuous
904 to discrete, to make X server driver able to add WB
905 entry later. This parameter disables that.
907 disable_mtrr_trim [X86, Intel and AMD only]
908 By default the kernel will trim any uncacheable
909 memory out of your available memory pool based on
910 MTRR settings. This parameter disables that behavior,
911 possibly causing your machine to run very slowly.
913 disable_timer_pin_1 [X86]
914 Disable PIN 1 of APIC timer
915 Can be useful to work around chipset bugs.
917 dis_ucode_ldr [X86] Disable the microcode loader.
919 dm= [DM] Allows early creation of a device-mapper device.
920 See Documentation/device-mapper/boot.txt.
922 dmasound= [HW,OSS] Sound subsystem buff
924 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
925 this option disables the debugging code at boot.
927 dma_debug_entries=<number>
928 This option allows to tune the number of preallocated
929 entries for DMA-API debugging code. One entry is
930 required per DMA-API allocation. Use this if the
931 DMA-API debugging code disables itself because the
932 architectural default is too low.
934 dma_debug_driver=<driver_name>
935 With this option the DMA-API debugging driver
936 filter feature can be enabled at boot time. Just
937 pass the driver to filter for as the parameter.
938 The filter can be disabled or changed to another
939 driver later using sysfs.
941 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
942 Broken monitors, graphic adapters, KVMs and EDIDless
943 panels may send no or incorrect EDID data sets.
944 This parameter allows to specify an EDID data sets
945 in the /lib/firmware directory that are used instead.
946 Generic built-in EDID data sets are used, if one of
947 edid/1024x768.bin, edid/1280x1024.bin,
948 edid/1680x1050.bin, or edid/1920x1080.bin is given
949 and no file with the same name exists. Details and
950 instructions how to build your own EDID data are
951 available in Documentation/EDID/HOWTO.txt. An EDID
952 data set will only be used for a particular connector,
953 if its name and a colon are prepended to the EDID
954 name. Each connector may use a unique EDID data
955 set by separating the files with a comma. An EDID
956 data set with no connector name will be used for
957 any connectors not explicitly specified.
961 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
962 module.dyndbg[="val"]
963 Enable debug messages at boot time. See
964 Documentation/dynamic-debug-howto.txt for details.
966 nompx [X86] Disables Intel Memory Protection Extensions.
967 See Documentation/x86/intel_mpx.txt for more
968 information about the feature.
971 on enable eager fpu restore
972 off disable eager fpu restore
973 auto selects the default scheme, which automatically
974 enables eagerfpu restore for xsaveopt.
976 module.async_probe [KNL]
977 Enable asynchronous probe on this module.
979 early_ioremap_debug [KNL]
980 Enable debug messages in early_ioremap support. This
981 is useful for tracking down temporary early mappings
982 which are not unmapped.
984 earlycon= [KNL] Output early console device and options.
986 When used with no options, the early console is
987 determined by the stdout-path property in device
991 Start an early, polled-mode console on a cadence serial
992 port at the specified address. The cadence serial port
993 must already be setup and configured. Options are not
996 uart[8250],io,<addr>[,options]
997 uart[8250],mmio,<addr>[,options]
998 uart[8250],mmio32,<addr>[,options]
999 uart[8250],mmio32be,<addr>[,options]
1000 uart[8250],0x<addr>[,options]
1001 Start an early, polled-mode console on the 8250/16550
1002 UART at the specified I/O port or MMIO address.
1003 MMIO inter-register address stride is either 8-bit
1004 (mmio) or 32-bit (mmio32 or mmio32be).
1005 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1006 to be equivalent to 'mmio'. 'options' are specified
1007 in the same format described for "console=ttyS<n>"; if
1008 unspecified, the h/w is not initialized.
1011 Start an early, polled-mode console on a pl011 serial
1012 port at the specified address. The pl011 serial port
1013 must already be setup and configured. Options are not
1017 Start an early, polled-mode console on an msm serial
1018 port at the specified address. The serial port
1019 must already be setup and configured. Options are not
1022 msm_serial_dm,<addr>
1023 Start an early, polled-mode console on an msm serial
1024 dm port at the specified address. The serial port
1025 must already be setup and configured. Options are not
1028 smh Use ARM semihosting calls for early console.
1036 Use early console provided by serial driver available
1037 on Samsung SoCs, requires selecting proper type and
1038 a correct base address of the selected UART port. The
1039 serial port must already be setup and configured.
1040 Options are not yet supported.
1044 Use early console provided by Freescale LP UART driver
1045 found on Freescale Vybrid and QorIQ LS1021A processors.
1046 A valid base address must be provided, and the serial
1047 port must already be setup and configured.
1049 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1053 earlyprintk=serial[,ttySn[,baudrate]]
1054 earlyprintk=serial[,0x...[,baudrate]]
1055 earlyprintk=ttySn[,baudrate]
1056 earlyprintk=dbgp[debugController#]
1057 earlyprintk=pciserial,bus:device.function[,baudrate]
1059 earlyprintk is useful when the kernel crashes before
1060 the normal console is initialized. It is not enabled by
1061 default because it has some cosmetic problems.
1063 Append ",keep" to not disable it when the real console
1066 Only one of vga, efi, serial, or usb debug port can
1069 Currently only ttyS0 and ttyS1 may be specified by
1070 name. Other I/O ports may be explicitly specified
1071 on some architectures (x86 and arm at least) by
1072 replacing ttySn with an I/O port address, like this:
1073 earlyprintk=serial,0x1008,115200
1074 You can find the port for a given device in
1075 /proc/tty/driver/serial:
1076 2: uart:ST16650V2 port:00001008 irq:18 ...
1078 Interaction with the standard serial driver is not
1081 The VGA and EFI output is eventually overwritten by
1084 The xen output can only be used by Xen PV guests.
1086 edac_report= [HW,EDAC] Control how to report EDAC event
1087 Format: {"on" | "off" | "force"}
1088 on: enable EDAC to report H/W event. May be overridden
1089 by other higher priority error reporting module.
1090 off: disable H/W event reporting through EDAC.
1091 force: enforce the use of EDAC to report H/W event.
1094 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1097 This is designed to be used in conjunction with
1098 the boot argument: earlyprintk=vga
1101 Format: {"off" | "on" | "skip[mbr]"}
1104 Format: { "old_map", "nochunk", "noruntime", "debug" }
1105 old_map [X86-64]: switch to the old ioremap-based EFI
1106 runtime services mapping. 32-bit still uses this one by
1108 nochunk: disable reading files in "chunks" in the EFI
1109 boot stub, as chunking can cause problems with some
1110 firmware implementations.
1111 noruntime : disable EFI runtime services support
1112 debug: enable misc debug output
1114 efi_no_storage_paranoia [EFI; X86]
1115 Using this parameter you can use more than 50% of
1116 your efi variable storage. Use this parameter only if
1117 you are really sure that your UEFI does sane gc and
1118 fulfills the spec otherwise your board may brick.
1120 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1121 Add arbitrary attribute to specific memory range by
1122 updating original EFI memory map.
1123 Region of memory which aa attribute is added to is
1125 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1126 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1127 attribute is added to range 0x100000000-0x180000000 and
1128 0x10a0000000-0x1120000000.
1130 Using this parameter you can do debugging of EFI memmap
1131 related feature. For example, you can do debugging of
1132 Address Range Mirroring feature even if your box
1135 eisa_irq_edge= [PARISC,HW]
1136 See header of drivers/parisc/eisa.c.
1139 See comment before function elanfreq_setup() in
1140 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1143 Format: {"cfq" | "deadline" | "noop"}
1144 See Documentation/block/cfq-iosched.txt and
1145 Documentation/block/deadline-iosched.txt for details.
1147 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1148 Specifies physical address of start of kernel core
1149 image elf header and optionally the size. Generally
1150 kexec loader will pass this option to capture kernel.
1151 See Documentation/kdump/kdump.txt for details.
1153 enable_mtrr_cleanup [X86]
1154 The kernel tries to adjust MTRR layout from continuous
1155 to discrete, to make X server driver able to add WB
1156 entry later. This parameter enables that.
1158 enable_timer_pin_1 [X86]
1159 Enable PIN 1 of APIC timer
1160 Can be useful to work around chipset bugs
1161 (in particular on some ATI chipsets).
1162 The kernel tries to set a reasonable default.
1164 enforcing [SELINUX] Set initial enforcing status.
1166 See security/selinux/Kconfig help text.
1167 0 -- permissive (log only, no denials).
1168 1 -- enforcing (deny and log).
1170 Value can be changed at runtime via /selinux/enforce.
1173 Disable Error Record Serialization Table (ERST)
1176 ether= [HW,NET] Ethernet cards parameters
1177 This option is obsoleted by the "netdev=" option, which
1178 has equivalent usage. See its documentation for details.
1182 Permit 'security.evm' to be updated regardless of
1183 current integrity status.
1187 fail_make_request=[KNL]
1188 General fault injection mechanism.
1189 Format: <interval>,<probability>,<space>,<times>
1190 See also Documentation/fault-injection/.
1193 See Documentation/blockdev/floppy.txt.
1195 force_pal_cache_flush
1196 [IA-64] Avoid check_sal_cache_flush which may hang on
1197 buggy SAL_CACHE_FLUSH implementations. Using this
1198 parameter will force ia64_sal_cache_flush to call
1199 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1202 Forcefully enable Physical Address Extension (PAE).
1203 Many Pentium M systems disable PAE but may have a
1204 functionally usable PAE implementation.
1205 Warning: use of this parameter will taint the kernel
1206 and may cause unknown problems.
1209 [FTRACE] will set and start the specified tracer
1210 as early as possible in order to facilitate early
1213 ftrace_dump_on_oops[=orig_cpu]
1214 [FTRACE] will dump the trace buffers on oops.
1215 If no parameter is passed, ftrace will dump
1216 buffers of all CPUs, but if you pass orig_cpu, it will
1217 dump only the buffer of the CPU that triggered the
1220 ftrace_filter=[function-list]
1221 [FTRACE] Limit the functions traced by the function
1222 tracer at boot up. function-list is a comma separated
1223 list of functions. This list can be changed at run
1224 time by the set_ftrace_filter file in the debugfs
1227 ftrace_notrace=[function-list]
1228 [FTRACE] Do not trace the functions specified in
1229 function-list. This list can be changed at run time
1230 by the set_ftrace_notrace file in the debugfs
1233 ftrace_graph_filter=[function-list]
1234 [FTRACE] Limit the top level callers functions traced
1235 by the function graph tracer at boot up.
1236 function-list is a comma separated list of functions
1237 that can be changed at run time by the
1238 set_graph_function file in the debugfs tracing directory.
1240 ftrace_graph_notrace=[function-list]
1241 [FTRACE] Do not trace from the functions specified in
1242 function-list. This list is a comma separated list of
1243 functions that can be changed at run time by the
1244 set_graph_notrace file in the debugfs tracing directory.
1247 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1248 support via parallel port (up to 5 devices per port)
1249 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1250 See also Documentation/input/joystick-parport.txt
1254 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1258 gcov_persist= [GCOV] When non-zero (default), profiling data for
1259 kernel modules is saved and remains accessible via
1260 debugfs, even when the module is unloaded/reloaded.
1261 When zero, profiling data is discarded and associated
1262 debugfs files are removed at module unload time.
1264 gpt [EFI] Forces disk with valid GPT signature but
1265 invalid Protective MBR to be treated as GPT. If the
1266 primary GPT is corrupted, it enables the backup/alternate
1267 GPT to be used instead.
1269 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1270 the "Enable 0" bit of the configuration register.
1273 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1274 the "Enable 0" bit of the configuration register.
1277 grcan.select= [HW] Select which physical interface to use.
1280 grcan.txsize= [HW] Sets the size of the tx buffer.
1281 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1283 grcan.rxsize= [HW] Sets the size of the rx buffer.
1284 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1287 hardlockup_all_cpu_backtrace=
1288 [KNL] Should the hard-lockup detector generate
1289 backtraces on all cpus.
1292 hashdist= [KNL,NUMA] Large hashes allocated during boot
1293 are distributed across NUMA nodes. Defaults on
1294 for 64-bit NUMA, off otherwise.
1295 Format: 0 | 1 (for off | on)
1297 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1299 hd= [EIDE] (E)IDE hard drive subsystem geometry
1300 Format: <cyl>,<head>,<sect>
1303 Disable Hardware Error Source Table (HEST) support;
1304 corresponding firmware-first mode error processing
1305 logic will be disabled.
1307 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1308 size of <nn>. This works even on boxes that have no
1309 highmem otherwise. This also works to reduce highmem
1310 size on bigger boxes.
1312 highres= [KNL] Enable/disable high resolution timer mode.
1313 Valid parameters: "on", "off"
1317 See Documentation/isdn/README.HiSax.
1321 hpet= [X86-32,HPET] option to control HPET usage
1322 Format: { enable (default) | disable | force |
1324 disable: disable HPET and use PIT instead
1325 force: allow force enabled of undocumented chips (ICH4,
1327 verbose: show contents of HPET registers during setup
1329 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1330 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1332 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1333 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1334 On x86-64 and powerpc, this option can be specified
1335 multiple times interleaved with hugepages= to reserve
1336 huge pages of different sizes. Valid pages sizes on
1337 x86-64 are 2M (when the CPU supports "pse") and 1G
1338 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1340 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1341 terminal devices. Valid values: 0..8
1342 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1343 If specified, z/VM IUCV HVC accepts connections
1344 from listed z/VM user IDs only.
1346 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1347 hardware thread id mappings.
1348 Format: <cpu>:<hwthread>
1351 Do not unregister boot console at start. This is only
1352 useful for debugging when something happens in the window
1353 between unregistering the boot console and initializing
1356 i2c_bus= [HW] Override the default board specific I2C bus speed
1357 or register an additional I2C bus that is not
1358 registered from board initialization code.
1362 i8042.debug [HW] Toggle i8042 debug mode
1363 i8042.unmask_kbd_data
1364 [HW] Enable printing of interrupt data from the KBD port
1365 (disabled by default, and as a pre-condition
1366 requires that i8042.debug=1 be enabled)
1367 i8042.direct [HW] Put keyboard port into non-translated mode
1368 i8042.dumbkbd [HW] Pretend that controller can only read data from
1369 keyboard and cannot control its state
1370 (Don't attempt to blink the leds)
1371 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1372 i8042.nokbd [HW] Don't check/create keyboard port
1373 i8042.noloop [HW] Disable the AUX Loopback command while probing
1375 i8042.nomux [HW] Don't check presence of an active multiplexing
1377 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1379 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1380 i8042.reset [HW] Reset the controller during init and cleanup
1381 i8042.unlock [HW] Unlock (ignore) the keylock
1382 i8042.kbdreset [HW] Reset device connected to KBD port
1386 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1387 indicates that the driver is running on unsupported
1389 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1390 does not match list of supported models.
1392 [HW] Report power status in /proc/i8k
1393 (disabled by default)
1394 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1397 i915.invert_brightness=
1398 [DRM] Invert the sense of the variable that is used to
1399 set the brightness of the panel backlight. Normally a
1400 brightness value of 0 indicates backlight switched off,
1401 and the maximum of the brightness value sets the backlight
1402 to maximum brightness. If this parameter is set to 0
1403 (default) and the machine requires it, or this parameter
1404 is set to 1, a brightness value of 0 sets the backlight
1405 to maximum brightness, and the maximum of the brightness
1406 value switches the backlight off.
1407 -1 -- never invert brightness
1408 0 -- machine default
1409 1 -- force brightness inversion
1412 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1414 ide-core.nodma= [HW] (E)IDE subsystem
1415 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1416 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1417 .cdrom .chs .ignore_cable are additional options
1418 See Documentation/ide/ide.txt.
1420 ide-generic.probe-mask= [HW] (E)IDE subsystem
1422 Probe mask for legacy ISA IDE ports. Depending on
1423 platform up to 6 ports are supported, enabled by
1424 setting corresponding bits in the mask to 1. The
1425 default value is 0x0, which has a special meaning.
1426 On systems that have PCI, it triggers scanning the
1427 PCI bus for the first and the second port, which
1428 are then probed. On systems without PCI the value
1429 of 0x0 enables probing the two first ports as if it
1432 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1433 Claim all unknown PCI IDE storage controllers.
1436 Format: idle=poll, idle=halt, idle=nomwait
1437 Poll forces a polling idle loop that can slightly
1438 improve the performance of waking up a idle CPU, but
1439 will use a lot of power and make the system run hot.
1441 idle=halt: Halt is forced to be used for CPU idle.
1442 In such case C2/C3 won't be used again.
1443 idle=nomwait: Disable mwait for CPU C-states
1445 ignore_loglevel [KNL]
1446 Ignore loglevel setting - this will print /all/
1447 kernel messages to the console. Useful for debugging.
1448 We also add it as printk module parameter, so users
1449 could change it dynamically, usually by
1450 /sys/module/printk/parameters/ignore_loglevel.
1452 ihash_entries= [KNL]
1453 Set number of hash buckets for inode cache.
1455 ima_appraise= [IMA] appraise integrity measurements
1456 Format: { "off" | "enforce" | "fix" | "log" }
1459 ima_appraise_tcb [IMA]
1460 The builtin appraise policy appraises all files
1464 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1468 The list of supported hash algorithms is defined
1469 in crypto/hash_info.h.
1472 The builtin measurement policy to load during IMA
1473 setup. Specyfing "tcb" as the value, measures all
1474 programs exec'd, files mmap'd for exec, and all files
1475 opened with the read mode bit set by either the
1476 effective uid (euid=0) or uid=0.
1479 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1480 Load a policy which meets the needs of the Trusted
1481 Computing Base. This means IMA will measure all
1482 programs exec'd, files mmap'd for exec, and all files
1483 opened for read by uid=0.
1486 Select one of defined IMA measurements template formats.
1487 Formats: { "ima" | "ima-ng" | "ima-sig" }
1491 [IMA] Define a custom template format.
1492 Format: { "field1|...|fieldN" }
1494 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1495 Format: <min_file_size>
1496 Set the minimal file size for using asynchronous hash.
1497 If left unspecified, ahash usage is disabled.
1499 ahash performance varies for different data sizes on
1500 different crypto accelerators. This option can be used
1501 to achieve the best performance for a particular HW.
1503 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1505 Set hashing buffer size. Default: 4k.
1507 ahash performance varies for different chunk sizes on
1508 different crypto accelerators. This option can be used
1509 to achieve best performance for particular HW.
1513 Run specified binary instead of /sbin/init as init
1516 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1517 for working out where the kernel is dying during
1520 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1521 initcall functions. Useful for debugging built-in
1522 modules and initcalls.
1524 initrd= [BOOT] Specify the location of the initial ramdisk
1526 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1529 int_pln_enable [x86] Enable power limit notification interrupt
1531 integrity_audit=[IMA]
1532 Format: { "0" | "1" }
1533 0 -- basic integrity auditing messages. (Default)
1534 1 -- additional integrity auditing messages.
1536 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1538 Enable intel iommu driver.
1540 Disable intel iommu driver.
1541 igfx_off [Default Off]
1542 By default, gfx is mapped as normal device. If a gfx
1543 device has a dedicated DMAR unit, the DMAR unit is
1544 bypassed by not enabling DMAR with this option. In
1545 this case, gfx device will use physical address for
1548 With this option iommu will not optimize to look
1549 for io virtual address below 32-bit forcing dual
1550 address cycle on pci bus for cards supporting greater
1551 than 32-bit addressing. The default is to look
1552 for translation below 32-bit and if not available
1553 then look in the higher range.
1554 strict [Default Off]
1555 With this option on every unmap_single operation will
1556 result in a hardware IOTLB flush operation as opposed
1557 to batching them for performance.
1558 sp_off [Default Off]
1559 By default, super page will be supported if Intel IOMMU
1560 has the capability. With this option, super page will
1562 ecs_off [Default Off]
1563 By default, extended context tables will be supported if
1564 the hardware advertises that it has support both for the
1565 extended tables themselves, and also PASID support. With
1566 this option set, extended tables will not be used even
1567 on hardware which claims to support them.
1569 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1570 0 disables intel_idle and fall back on acpi_idle.
1571 1 to 6 specify maximum depth of C-state.
1575 Do not enable intel_pstate as the default
1576 scaling driver for the supported processors
1578 Enable intel_pstate on systems that prohibit it by default
1579 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1580 instead of acpi-cpufreq may disable platform features, such
1581 as thermal controls and power capping, that rely on ACPI
1582 P-States information being indicated to OSPM and therefore
1583 should be used with caution. This option does not work with
1584 processors that aren't supported by the intel_pstate driver
1585 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1587 Do not enable hardware P state control (HWP)
1590 Only load intel_pstate on systems which support
1591 hardware P state control (HWP) if available.
1593 intremap= [X86-64, Intel-IOMMU]
1594 on enable Interrupt Remapping (default)
1595 off disable Interrupt Remapping
1596 nosid disable Source ID checking
1598 BIOS x2APIC opt-out request will be ignored
1599 nopost disable Interrupt Posting
1601 iomem= Disable strict checking of access to MMIO memory
1602 strict regions from userspace.
1617 nobypass [PPC/POWERNV]
1618 Disable IOMMU bypass, using IOMMU for PCI devices.
1621 io7= [HW] IO7 for Marvel based alpha systems
1622 See comment before marvel_specify_io7 in
1623 arch/alpha/kernel/core_marvel.c.
1625 io_delay= [X86] I/O delay method
1627 Standard port 0x80 based delay
1629 Alternate port 0xed based delay (needed on some systems)
1631 Simple two microseconds delay
1636 See Documentation/filesystems/nfs/nfsroot.txt.
1639 When an interrupt is not handled search all handlers
1640 for it. Intended to get systems with badly broken
1644 When an interrupt is not handled search all handlers
1645 for it. Also check all handlers each timer
1646 interrupt. Intended to get systems with badly broken
1650 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1652 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1654 <cpu number>,...,<cpu number>
1656 <cpu number>-<cpu number>
1657 (must be a positive range in ascending order)
1659 <cpu number>,...,<cpu number>-<cpu number>
1661 This option can be used to specify one or more CPUs
1662 to isolate from the general SMP balancing and scheduling
1663 algorithms. You can move a process onto or off an
1664 "isolated" CPU via the CPU affinity syscalls or cpuset.
1665 <cpu number> begins at 0 and the maximum value is
1666 "number of CPUs in system - 1".
1668 This option is the preferred way to isolate CPUs. The
1669 alternative -- manually setting the CPU mask of all
1670 tasks in the system -- can cause problems and
1671 suboptimal load balancer performance.
1675 ivrs_ioapic [HW,X86_64]
1676 Provide an override to the IOAPIC-ID<->DEVICE-ID
1677 mapping provided in the IVRS ACPI table. For
1678 example, to map IOAPIC-ID decimal 10 to
1679 PCI device 00:14.0 write the parameter as:
1680 ivrs_ioapic[10]=00:14.0
1682 ivrs_hpet [HW,X86_64]
1683 Provide an override to the HPET-ID<->DEVICE-ID
1684 mapping provided in the IVRS ACPI table. For
1685 example, to map HPET-ID decimal 0 to
1686 PCI device 00:14.0 write the parameter as:
1687 ivrs_hpet[0]=00:14.0
1689 js= [HW,JOY] Analog joystick
1690 See Documentation/input/joystick.txt.
1693 Enable/disable kernel and module base offset ASLR
1694 (Address Space Layout Randomization) if built into
1695 the kernel. When CONFIG_HIBERNATION is selected,
1696 kASLR is disabled by default. When kASLR is enabled,
1697 hibernation will be disabled.
1701 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1702 specifies the amount of memory usable by the kernel
1703 for non-movable allocations. The requested amount is
1704 spread evenly throughout all nodes in the system. The
1705 remaining memory in each node is used for Movable
1706 pages. In the event, a node is too small to have both
1707 kernelcore and Movable pages, kernelcore pages will
1708 take priority and other nodes will have a larger number
1709 of Movable pages. The Movable zone is used for the
1710 allocation of pages that may be reclaimed or moved
1711 by the page migration subsystem. This means that
1712 HugeTLB pages may not be allocated from this zone.
1713 Note that allocations like PTEs-from-HighMem still
1714 use the HighMem zone if it exists, and the Normal
1715 zone if it does not.
1717 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1718 Format: <Controller#>[,poll interval]
1719 The controller # is the number of the ehci usb debug
1720 port as it is probed via PCI. The poll interval is
1721 optional and is the number seconds in between
1722 each poll cycle to the debug port in case you need
1723 the functionality for interrupting the kernel with
1724 gdb or control-c on the dbgp connection. When
1725 not using this parameter you use sysrq-g to break into
1726 the kernel debugger.
1728 kgdboc= [KGDB,HW] kgdb over consoles.
1729 Requires a tty driver that supports console polling,
1730 or a supported polling keyboard driver (non-usb).
1731 Serial only format: <serial_device>[,baud]
1732 keyboard only format: kbd
1733 keyboard and serial format: kbd,<serial_device>[,baud]
1734 Optional Kernel mode setting:
1735 kms, kbd format: kms,kbd
1736 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1738 kgdbwait [KGDB] Stop kernel execution and enter the
1739 kernel debugger at the earliest opportunity.
1741 kmac= [MIPS] korina ethernet MAC address.
1742 Configure the RouterBoard 532 series on-chip
1743 Ethernet adapter MAC address.
1745 kmemleak= [KNL] Boot-time kmemleak enable/disable
1746 Valid arguments: on, off
1748 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1751 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1752 Valid arguments: 0, 1, 2
1753 kmemcheck=0 (disabled)
1754 kmemcheck=1 (enabled)
1755 kmemcheck=2 (one-shot mode)
1756 Default: 2 (one-shot mode)
1758 kstack=N [X86] Print N words from the kernel stack
1761 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1762 Default is 0 (don't ignore, but inject #GP)
1764 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1768 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1769 Default is 1 (enabled)
1771 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1773 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1775 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1776 (virtualized MMU) support on capable Intel chips.
1777 Default is 1 (enabled)
1779 kvm-intel.emulate_invalid_guest_state=
1780 [KVM,Intel] Enable emulation of invalid guest states
1781 Default is 0 (disabled)
1783 kvm-intel.flexpriority=
1784 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1785 Default is 1 (enabled)
1788 [KVM,Intel] Enable VMX nesting (nVMX).
1789 Default is 0 (disabled)
1791 kvm-intel.unrestricted_guest=
1792 [KVM,Intel] Disable unrestricted guest feature
1793 (virtualized real and unpaged mode) on capable
1794 Intel chips. Default is 1 (enabled)
1796 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1797 feature (tagged TLBs) on capable Intel chips.
1798 Default is 1 (enabled)
1804 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1807 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1808 value for LAPIC timer one-shot implementation. Default
1809 back to the programmable timer unit in the LAPIC.
1811 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1814 libata.dma= [LIBATA] DMA control
1815 libata.dma=0 Disable all PATA and SATA DMA
1816 libata.dma=1 PATA and SATA Disk DMA only
1817 libata.dma=2 ATAPI (CDROM) DMA only
1818 libata.dma=4 Compact Flash DMA only
1819 Combinations also work, so libata.dma=3 enables DMA
1820 for disks and CDROMs, but not CFs.
1822 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1823 libata.ignore_hpa=0 keep BIOS limits (default)
1824 libata.ignore_hpa=1 ignore limits, using full disk
1826 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1830 libata.force= [LIBATA] Force configurations. The format is comma
1831 separated list of "[ID:]VAL" where ID is
1832 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1833 matching port, link or device. Basically, it matches
1834 the ATA ID string printed on console by libata. If
1835 the whole ID part is omitted, the last PORT and DEVICE
1836 values are used. If ID hasn't been specified yet, the
1837 configuration applies to all ports, links and devices.
1839 If only DEVICE is omitted, the parameter applies to
1840 the port and all links and devices behind it. DEVICE
1841 number of 0 either selects the first device or the
1842 first fan-out link behind PMP device. It does not
1843 select the host link. DEVICE number of 15 selects the
1844 host link and device attached to it.
1846 The VAL specifies the configuration to force. As long
1847 as there's no ambiguity shortcut notation is allowed.
1848 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1849 The following configurations can be forced.
1851 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1852 Any ID with matching PORT is used.
1854 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1856 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1857 udma[/][16,25,33,44,66,100,133] notation is also
1860 * [no]ncq: Turn on or off NCQ.
1862 * [no]ncqtrim: Turn off queued DSM TRIM.
1864 * nohrst, nosrst, norst: suppress hard, soft
1867 * rstonce: only attempt one reset during
1868 hot-unplug link recovery
1870 * dump_id: dump IDENTIFY data.
1872 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1874 * disable: Disable this device.
1876 If there are multiple matching configurations changing
1877 the same attribute, the last one is used.
1879 memblock=debug [KNL] Enable memblock debug messages.
1881 load_ramdisk= [RAM] List of ramdisks to load from floppy
1882 See Documentation/blockdev/ramdisk.txt.
1884 lockd.nlm_grace_period=P [NFS] Assign grace period.
1887 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1890 lockd.nlm_timeout=T [NFS] Assign timeout value.
1893 lockd.nlm_udpport=M [NFS] Assign UDP port.
1896 locktorture.nreaders_stress= [KNL]
1897 Set the number of locking read-acquisition kthreads.
1898 Defaults to being automatically set based on the
1899 number of online CPUs.
1901 locktorture.nwriters_stress= [KNL]
1902 Set the number of locking write-acquisition kthreads.
1904 locktorture.onoff_holdoff= [KNL]
1905 Set time (s) after boot for CPU-hotplug testing.
1907 locktorture.onoff_interval= [KNL]
1908 Set time (s) between CPU-hotplug operations, or
1909 zero to disable CPU-hotplug testing.
1911 locktorture.shuffle_interval= [KNL]
1912 Set task-shuffle interval (jiffies). Shuffling
1913 tasks allows some CPUs to go into dyntick-idle
1914 mode during the locktorture test.
1916 locktorture.shutdown_secs= [KNL]
1917 Set time (s) after boot system shutdown. This
1918 is useful for hands-off automated testing.
1920 locktorture.stat_interval= [KNL]
1921 Time (s) between statistics printk()s.
1923 locktorture.stutter= [KNL]
1924 Time (s) to stutter testing, for example,
1925 specifying five seconds causes the test to run for
1926 five seconds, wait for five seconds, and so on.
1927 This tests the locking primitive's ability to
1928 transition abruptly to and from idle.
1930 locktorture.torture_runnable= [BOOT]
1931 Start locktorture running at boot time.
1933 locktorture.torture_type= [KNL]
1934 Specify the locking implementation to test.
1936 locktorture.verbose= [KNL]
1937 Enable additional printk() statements.
1939 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1942 loglevel= All Kernel Messages with a loglevel smaller than the
1943 console loglevel will be printed to the console. It can
1944 also be changed with klogd or other programs. The
1945 loglevels are defined as follows:
1947 0 (KERN_EMERG) system is unusable
1948 1 (KERN_ALERT) action must be taken immediately
1949 2 (KERN_CRIT) critical conditions
1950 3 (KERN_ERR) error conditions
1951 4 (KERN_WARNING) warning conditions
1952 5 (KERN_NOTICE) normal but significant condition
1953 6 (KERN_INFO) informational
1954 7 (KERN_DEBUG) debug-level messages
1956 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1957 in bytes. n must be a power of two and greater
1958 than the minimal size. The minimal size is defined
1959 by LOG_BUF_SHIFT kernel config parameter. There is
1960 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1961 that allows to increase the default size depending on
1962 the number of CPUs. See init/Kconfig for more details.
1964 logo.nologo [FB] Disables display of the built-in Linux logo.
1965 This may be used to provide more screen space for
1966 kernel log messages and is useful when debugging
1967 kernel boot problems.
1969 lp=0 [LP] Specify parallel ports to use, e.g,
1970 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1971 lp=reset first parallel port). 'lp=0' disables the
1972 lp=auto printer driver. 'lp=reset' (which can be
1973 specified in addition to the ports) causes
1974 attached printers to be reset. Using
1975 lp=port1,port2,... specifies the parallel ports
1976 to associate lp devices with, starting with
1977 lp0. A port specification may be 'none' to skip
1978 that lp device, or a parport name such as
1979 'parport0'. Specifying 'lp=auto' instead of a
1980 port specification list means that device IDs
1981 from each port should be examined, to see if
1982 an IEEE 1284-compliant printer is attached; if
1983 so, the driver will manage that printer.
1984 See also header of drivers/char/lp.c.
1987 Sets loops_per_jiffy to given constant, thus avoiding
1988 time-consuming boot-time autodetection (up to 250 ms per
1989 CPU). 0 enables autodetection (default). To determine
1990 the correct value for your kernel, boot with normal
1991 autodetection and see what value is printed. Note that
1992 on SMP systems the preset will be applied to all CPUs,
1993 which is likely to cause problems if your CPUs need
1994 significantly divergent settings. An incorrect value
1995 will cause delays in the kernel to be wrong, leading to
1996 unpredictable I/O errors and other breakage. Although
1997 unlikely, in the extreme case this might damage your
2001 Format: <io>,<irq>,<dma>
2003 machvec= [IA-64] Force the use of a particular machine-vector
2004 (machvec) in a generic kernel.
2005 Example: machvec=hpzx1_swiotlb
2007 machtype= [Loongson] Share the same kernel image file between different
2009 Example: machtype=lemote-yeeloong-2f-7inch
2011 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2012 than or equal to this physical address is ignored.
2014 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2015 should make use of. maxcpus=n : n >= 0 limits the
2016 kernel to using 'n' processors. n=0 is a special case,
2017 it is equivalent to "nosmp", which also disables
2020 max_loop= [LOOP] The number of loop block devices that get
2021 (loop.max_loop) unconditionally pre-created at init time. The default
2022 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2023 of statically allocating a predefined number, loop
2024 devices can be requested on-demand with the
2025 /dev/loop-control interface.
2027 mce [X86-32] Machine Check Exception
2029 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2031 md= [HW] RAID subsystems devices and level
2032 See Documentation/md.txt.
2035 Format: <first>,<last>
2036 Specifies range of consoles to be captured by the MDA.
2038 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2039 Amount of memory to be used when the kernel is not able
2040 to see the whole system memory or for test.
2041 [X86] Work as limiting max address. Use together
2042 with memmap= to avoid physical address space collisions.
2043 Without memmap= PCI devices could be placed at addresses
2044 belonging to unused RAM.
2046 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2050 [KNL,SH] Allow user to override the default size for
2051 per-device physically contiguous DMA buffers.
2053 memmap=exactmap [KNL,X86] Enable setting of an exact
2054 E820 memory map, as specified by the user.
2055 Such memmap=exactmap lines can be constructed based on
2056 BIOS output or other requirements. See the memmap=nn@ss
2059 memmap=nn[KMG]@ss[KMG]
2060 [KNL] Force usage of a specific region of memory.
2061 Region of memory to be used is from ss to ss+nn.
2063 memmap=nn[KMG]#ss[KMG]
2064 [KNL,ACPI] Mark specific memory as ACPI data.
2065 Region of memory to be marked is from ss to ss+nn.
2067 memmap=nn[KMG]$ss[KMG]
2068 [KNL,ACPI] Mark specific memory as reserved.
2069 Region of memory to be reserved is from ss to ss+nn.
2070 Example: Exclude memory from 0x18690000-0x1869ffff
2071 memmap=64K$0x18690000
2073 memmap=0x10000$0x18690000
2075 memmap=nn[KMG]!ss[KMG]
2076 [KNL,X86] Mark specific memory as protected.
2077 Region of memory to be used, from ss to ss+nn.
2078 The memory region may be marked as e820 type 12 (0xc)
2079 and is NVDIMM or ADR memory.
2081 memory_corruption_check=0/1 [X86]
2082 Some BIOSes seem to corrupt the first 64k of
2083 memory when doing things like suspend/resume.
2084 Setting this option will scan the memory
2085 looking for corruption. Enabling this will
2086 both detect corruption and prevent the kernel
2087 from using the memory being corrupted.
2088 However, its intended as a diagnostic tool; if
2089 repeatable BIOS-originated corruption always
2090 affects the same memory, you can use memmap=
2091 to prevent the kernel from using that memory.
2093 memory_corruption_check_size=size [X86]
2094 By default it checks for corruption in the low
2095 64k, making this memory unavailable for normal
2096 use. Use this parameter to scan for
2097 corruption in more or less memory.
2099 memory_corruption_check_period=seconds [X86]
2100 By default it checks for corruption every 60
2101 seconds. Use this parameter to check at some
2102 other rate. 0 disables periodic checking.
2104 memtest= [KNL,X86,ARM] Enable memtest
2106 default : 0 <disable>
2107 Specifies the number of memtest passes to be
2108 performed. Each pass selects another test
2109 pattern from a given set of patterns. Memtest
2110 fills the memory with this pattern, validates
2111 memory contents and reserves bad memory
2112 regions that are detected.
2114 meye.*= [HW] Set MotionEye Camera parameters
2115 See Documentation/video4linux/meye.txt.
2117 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2118 Multi-Function General Purpose Timers on AMD Geode
2121 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2122 the BIOS has incorrectly applied a workaround. TinyBIOS
2123 version 0.98 is known to be affected, 0.99 fixes the
2124 problem by letting the user disable the workaround.
2128 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2129 physical address is ignored.
2131 mini2440= [ARM,HW,KNL]
2132 Format:[0..2][b][c][t]
2134 MINI2440 configuration specification:
2135 0 - The attached screen is the 3.5" TFT
2136 1 - The attached screen is the 7" TFT
2137 2 - The VGA Shield is attached (1024x768)
2138 Leaving out the screen size parameter will not load
2139 the TFT driver, and the framebuffer will be left
2141 b - Enable backlight. The TFT backlight pin will be
2142 linked to the kernel VESA blanking code and a GPIO
2143 LED. This parameter is not necessary when using the
2145 c - Enable the s3c camera interface.
2146 t - Reserved for enabling touchscreen support. The
2147 touchscreen support is not enabled in the mainstream
2148 kernel as of 2.6.30, a preliminary port can be found
2149 in the "bleeding edge" mini2440 support kernel at
2150 http://repo.or.cz/w/linux-2.6/mini2440.git
2153 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2154 parameter allows control of the logging verbosity for
2155 the additional memory initialisation checks. A value
2156 of 0 disables mminit logging and a level of 4 will
2157 log everything. Information is printed at KERN_DEBUG
2158 so loglevel=8 may also need to be specified.
2161 [KNL] When CONFIG_MODULE_SIG is set, this means that
2162 modules without (valid) signatures will fail to load.
2163 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2164 is always true, so this option does nothing.
2167 [MOUSE] Maximum time between finger touching and
2168 leaving touchpad surface for touch to be considered
2169 a tap and be reported as a left button click (for
2170 touchpads working in absolute mode only).
2172 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2173 reporting absolute coordinates, such as tablets
2174 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2175 reporting absolute coordinates, such as tablets
2177 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2178 is similar to kernelcore except it specifies the
2179 amount of memory used for migratable allocations.
2180 If both kernelcore and movablecore is specified,
2181 then kernelcore will be at *least* the specified
2182 value but may be more. If movablecore on its own
2183 is specified, the administrator must be careful
2184 that the amount of memory usable for all allocations
2187 movable_node [KNL,X86] Boot-time switch to enable the effects
2188 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2190 MTD_Partition= [MTD]
2191 Format: <name>,<region-number>,<size>,<offset>
2193 MTD_Region= [MTD] Format:
2194 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2197 See drivers/mtd/cmdlinepart.c.
2199 multitce=off [PPC] This parameter disables the use of the pSeries
2200 firmware feature for updating multiple TCE entries
2203 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2205 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2207 boundary - index of last SLC block on Flex-OneNAND.
2208 The remaining blocks are configured as MLC blocks.
2209 lock - Configure if Flex-OneNAND boundary should be locked.
2210 Once locked, the boundary cannot be changed.
2211 1 indicates lock status, 0 indicates unlock status.
2214 ARM/S3C2412 JIVE boot control
2216 See arch/arm/mach-s3c2412/mach-jive.c
2218 mtouchusb.raw_coordinates=
2219 [HW] Make the MicroTouch USB driver use raw coordinates
2220 ('y', default) or cooked coordinates ('n')
2222 mtrr_chunk_size=nn[KMG] [X86]
2223 used for mtrr cleanup. It is largest continuous chunk
2224 that could hold holes aka. UC entries.
2226 mtrr_gran_size=nn[KMG] [X86]
2227 Used for mtrr cleanup. It is granularity of mtrr block.
2229 Large value could prevent small alignment from
2232 mtrr_spare_reg_nr=n [X86]
2234 Range: 0,7 : spare reg number
2236 Used for mtrr cleanup. It is spare mtrr entries number.
2237 Set to 2 or more if your graphical card needs more.
2239 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2241 netdev= [NET] Network devices parameters
2242 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2243 Note that mem_start is often overloaded to mean
2244 something different and driver-specific.
2245 This usage is only documented in each driver source
2249 [NETFILTER] Enable connection tracking flow accounting
2250 0 to disable accounting
2251 1 to enable accounting
2254 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2255 See Documentation/filesystems/nfs/nfsroot.txt.
2257 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2258 See Documentation/filesystems/nfs/nfsroot.txt.
2260 nfsrootdebug [NFS] enable nfsroot debugging messages.
2261 See Documentation/filesystems/nfs/nfsroot.txt.
2263 nfs.callback_tcpport=
2264 [NFS] set the TCP port on which the NFSv4 callback
2265 channel should listen.
2268 [NFS] sets the pathname to the program which is used
2269 to update the NFS client cache entries.
2271 nfs.cache_getent_timeout=
2272 [NFS] sets the timeout after which an attempt to
2273 update a cache entry is deemed to have failed.
2275 nfs.idmap_cache_timeout=
2276 [NFS] set the maximum lifetime for idmapper cache
2280 [NFS] enable 64-bit inode numbers.
2281 If zero, the NFS client will fake up a 32-bit inode
2282 number for the readdir() and stat() syscalls instead
2283 of returning the full 64-bit number.
2284 The default is to return 64-bit inode numbers.
2286 nfs.max_session_slots=
2287 [NFSv4.1] Sets the maximum number of session slots
2288 the client will attempt to negotiate with the server.
2289 This limits the number of simultaneous RPC requests
2290 that the client can send to the NFSv4.1 server.
2291 Note that there is little point in setting this
2292 value higher than the max_tcp_slot_table_limit.
2294 nfs.nfs4_disable_idmapping=
2295 [NFSv4] When set to the default of '1', this option
2296 ensures that both the RPC level authentication
2297 scheme and the NFS level operations agree to use
2298 numeric uids/gids if the mount is using the
2299 'sec=sys' security flavour. In effect it is
2300 disabling idmapping, which can make migration from
2301 legacy NFSv2/v3 systems to NFSv4 easier.
2302 Servers that do not support this mode of operation
2303 will be autodetected by the client, and it will fall
2304 back to using the idmapper.
2305 To turn off this behaviour, set the value to '0'.
2307 [NFS4] Specify an additional fixed unique ident-
2308 ification string that NFSv4 clients can insert into
2309 their nfs_client_id4 string. This is typically a
2310 UUID that is generated at system install time.
2312 nfs.send_implementation_id =
2313 [NFSv4.1] Send client implementation identification
2314 information in exchange_id requests.
2315 If zero, no implementation identification information
2317 The default is to send the implementation identification
2320 nfs.recover_lost_locks =
2321 [NFSv4] Attempt to recover locks that were lost due
2322 to a lease timeout on the server. Please note that
2323 doing this risks data corruption, since there are
2324 no guarantees that the file will remain unchanged
2325 after the locks are lost.
2326 If you want to enable the kernel legacy behaviour of
2327 attempting to recover these locks, then set this
2329 The default parameter value of '0' causes the kernel
2330 not to attempt recovery of lost locks.
2332 nfs4.layoutstats_timer =
2333 [NFSv4.2] Change the rate at which the kernel sends
2334 layoutstats to the pNFS metadata server.
2336 Setting this to value to 0 causes the kernel to use
2337 whatever value is the default set by the layout
2338 driver. A non-zero value sets the minimum interval
2339 in seconds between layoutstats transmissions.
2341 nfsd.nfs4_disable_idmapping=
2342 [NFSv4] When set to the default of '1', the NFSv4
2343 server will return only numeric uids and gids to
2344 clients using auth_sys, and will accept numeric uids
2345 and gids from such clients. This is intended to ease
2346 migration from NFSv2/v3.
2348 objlayoutdriver.osd_login_prog=
2349 [NFS] [OBJLAYOUT] sets the pathname to the program which
2350 is used to automatically discover and login into new
2351 osd-targets. Please see:
2352 Documentation/filesystems/pnfs.txt for more explanations
2354 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2355 when a NMI is triggered.
2356 Format: [state][,regs][,debounce][,die]
2358 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2359 Format: [panic,][nopanic,][num]
2361 0 - turn hardlockup detector in nmi_watchdog off
2362 1 - turn hardlockup detector in nmi_watchdog on
2363 When panic is specified, panic when an NMI watchdog
2364 timeout occurs (or 'nopanic' to override the opposite
2365 default). To disable both hard and soft lockup detectors,
2366 please see 'nowatchdog'.
2367 This is useful when you use a panic=... timeout and
2368 need the box quickly up again.
2370 netpoll.carrier_timeout=
2371 [NET] Specifies amount of time (in seconds) that
2372 netpoll should wait for a carrier. By default netpoll
2375 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2376 emulation library even if a 387 maths coprocessor
2380 [HW] Never suspend the console
2381 Disable suspending of consoles during suspend and
2382 hibernate operations. Once disabled, debugging
2383 messages can reach various consoles while the rest
2384 of the system is being put to sleep (ie, while
2385 debugging driver suspend/resume hooks). This may
2386 not work reliably with all consoles, but is known
2387 to work with serial and VGA consoles.
2388 To facilitate more flexible debugging, we also add
2389 console_suspend, a printk module parameter to control
2390 it. Users could use console_suspend (usually
2391 /sys/module/printk/parameters/console_suspend) to
2392 turn on/off it dynamically.
2394 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2395 caches in the slab allocator. Saves per-node memory,
2396 but will impact performance.
2400 noapic [SMP,APIC] Tells the kernel to not make use of any
2401 IOAPICs that may be present in the system.
2403 noautogroup Disable scheduler automatic task group creation.
2405 nobats [PPC] Do not use BATs for mapping kernel lowmem
2406 on "Classic" PPC cores.
2410 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2412 nodelayacct [KNL] Disable per-task delay accounting
2414 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2416 nodsp [SH] Disable hardware DSP at boot time.
2418 noefi Disable EFI runtime services support.
2423 On X86-32 available only on PAE configured kernels.
2424 noexec=on: enable non-executable mappings (default)
2425 noexec=off: disable non-executable mappings
2428 Disable SMAP (Supervisor Mode Access Prevention)
2429 even if it is supported by processor.
2432 Disable SMEP (Supervisor Mode Execution Prevention)
2433 even if it is supported by processor.
2436 This affects only 32-bit executables.
2437 noexec32=on: enable non-executable mappings (default)
2438 read doesn't imply executable mappings
2439 noexec32=off: disable non-executable mappings
2440 read implies executable mappings
2442 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2444 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2445 register save and restore. The kernel will only save
2446 legacy floating-point registers on task switch.
2448 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2450 noxsave [BUGS=X86] Disables x86 extended register state save
2451 and restore using xsave. The kernel will fallback to
2452 enabling legacy floating-point and sse state.
2454 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2455 register states. The kernel will fall back to use
2456 xsave to save the states. By using this parameter,
2457 performance of saving the states is degraded because
2458 xsave doesn't support modified optimization while
2459 xsaveopt supports it on xsaveopt enabled systems.
2461 noxsaves [X86] Disables xsaves and xrstors used in saving and
2462 restoring x86 extended register state in compacted
2463 form of xsave area. The kernel will fall back to use
2464 xsaveopt and xrstor to save and restore the states
2465 in standard form of xsave area. By using this
2466 parameter, xsave area per process might occupy more
2467 memory on xsaves enabled systems.
2469 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2470 wfi(ARM) instruction doesn't work correctly and not to
2471 use it. This is also useful when using JTAG debugger.
2473 no_file_caps Tells the kernel not to honor file capabilities. The
2474 only way then for a file to be executed with privilege
2475 is to be setuid root or executed by root.
2477 nohalt [IA-64] Tells the kernel not to use the power saving
2478 function PAL_HALT_LIGHT when idle. This increases
2479 power-consumption. On the positive side, it reduces
2480 interrupt wake-up latency, which may improve performance
2481 in certain environments such as networked servers or
2484 nohibernate [HIBERNATION] Disable hibernation and resume.
2486 nohz= [KNL] Boottime enable/disable dynamic ticks
2487 Valid arguments: on, off
2490 nohz_full= [KNL,BOOT]
2491 In kernels built with CONFIG_NO_HZ_FULL=y, set
2492 the specified list of CPUs whose tick will be stopped
2493 whenever possible. The boot CPU will be forced outside
2494 the range to maintain the timekeeping.
2495 The CPUs in this range must also be included in the
2498 noiotrap [SH] Disables trapped I/O port accesses.
2500 noirqdebug [X86-32] Disables the code which attempts to detect and
2501 disable unhandled interrupt sources.
2503 no_timer_check [X86,APIC] Disables the code which tests for
2504 broken timer IRQ sources.
2506 noisapnp [ISAPNP] Disables ISA PnP code.
2508 noinitrd [RAM] Tells the kernel not to load any configured
2511 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2513 [Deprecated - use intremap=off]
2517 nojitter [IA-64] Disables jitter checking for ITC timers.
2519 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2521 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2524 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2525 steal time is computed, but won't influence scheduler
2528 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2530 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2532 noltlbs [PPC] Do not use large page/tlb entries for kernel
2533 lowmem mapping on PPC40x.
2535 nomca [IA-64] Disable machine check abort handling
2537 nomce [X86-32] Disable Machine Check Exception
2539 nomfgpt [X86-32] Disable Multi-Function General Purpose
2540 Timer usage (for AMD Geode machines).
2542 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2543 shutdown the other cpus. Instead use the REBOOT_VECTOR
2546 nomodule Disable module load
2548 nopat [X86] Disable PAT (page attribute table extension of
2549 pagetables) support.
2551 norandmaps Don't use address space randomization. Equivalent to
2552 echo 0 > /proc/sys/kernel/randomize_va_space
2554 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2556 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2557 with UP alternatives
2559 nordrand [X86] Disable kernel use of the RDRAND and
2560 RDSEED instructions even if they are supported
2561 by the processor. RDRAND and RDSEED are still
2562 available to user space applications.
2564 noresume [SWSUSP] Disables resume and restores original swap
2567 no-scroll [VGA] Disables scrollback.
2568 This is required for the Braillex ib80-piezo Braille
2569 reader made by F.H. Papenmeier (Germany).
2573 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2575 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2576 and disable the IO APIC. legacy for "maxcpus=0".
2578 nosoftlockup [KNL] Disable the soft-lockup detector.
2580 nosync [HW,M68K] Disables sync negotiation for all devices.
2582 notsc [BUGS=X86-32] Disable Time Stamp Counter
2584 nousb [USB] Disable the USB subsystem
2586 nowatchdog [KNL] Disable both lockup detectors, i.e.
2587 soft-lockup and NMI watchdog (hard-lockup).
2591 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2593 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2594 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2595 Some features depend on CPU0. Known dependencies are:
2596 1. Resume from suspend/hibernate depends on CPU0.
2597 Suspend/hibernate will fail if CPU0 is offline and you
2598 need to online CPU0 before suspend/hibernate.
2599 2. PIC interrupts also depend on CPU0. CPU0 can't be
2600 removed if a PIC interrupt is detected.
2601 It's said poweroff/reboot may depend on CPU0 on some
2602 machines although I haven't seen such issues so far
2603 after CPU0 is offline on a few tested machines.
2604 If the dependencies are under your control, you can
2605 turn on cpu0_hotplug.
2607 nptcg= [IA-64] Override max number of concurrent global TLB
2608 purges which is reported from either PAL_VM_SUMMARY or
2611 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2612 could support. nr_cpus=n : n >= 1 limits the kernel to
2613 supporting 'n' processors. Later in runtime you can not
2614 use hotplug cpu feature to put more cpu back to online.
2615 just like you compile the kernel NR_CPUS=n
2617 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2619 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2620 Allowed values are enable and disable
2622 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2623 one of ['zone', 'node', 'default'] can be specified
2624 This can be set from sysctl after boot.
2625 See Documentation/sysctl/vm.txt for details.
2627 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2628 See Documentation/debugging-via-ohci1394.txt for more
2631 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2632 Rather than timing out after 20 ms if an EC
2633 command is not properly ACKed, override the length
2634 of the timeout. We have interrupts disabled while
2635 waiting for the ACK, so if this is set too high
2636 interrupts *may* be lost!
2638 omap_mux= [OMAP] Override bootloader pin multiplexing.
2639 Format: <mux_mode0.mode_name=value>...
2640 For example, to override I2C bus2:
2641 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2643 oprofile.timer= [HW]
2644 Use timer interrupt instead of performance counters
2646 oprofile.cpu_type= Force an oprofile cpu type
2647 This might be useful if you have an older oprofile
2648 userland or if you want common events.
2649 Format: { arch_perfmon }
2650 arch_perfmon: [X86] Force use of architectural
2651 perfmon on Intel CPUs instead of the
2652 CPU specific event set.
2653 timer: [X86] Force use of architectural NMI
2654 timer mode (see also oprofile.timer
2655 for generic hr timer mode)
2656 [s390] Force legacy basic mode sampling
2657 (report cpu_type "timer")
2659 oops=panic Always panic on oopses. Default is to just kill the
2660 process, but there is a small probability of
2661 deadlocking the machine.
2662 This will also cause panics on machine check exceptions.
2663 Useful together with panic=30 to trigger a reboot.
2666 See Documentation/sound/oss/oss-parameters.txt
2668 page_owner= [KNL] Boot-time page_owner enabling option.
2669 Storage of the information about who allocated
2670 each page is disabled in default. With this switch,
2672 on: enable the feature
2674 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2675 timeout > 0: seconds before rebooting
2676 timeout = 0: wait forever
2677 timeout < 0: reboot immediately
2680 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2683 crash_kexec_post_notifiers
2684 Run kdump after running panic-notifiers and dumping
2685 kmsg. This only for the users who doubt kdump always
2686 succeeds in any situation.
2687 Note that this also increases risks of kdump failure,
2688 because some panic notifiers can make the crashed
2689 kernel more unstable.
2691 parkbd.port= [HW] Parallel port number the keyboard adapter is
2692 connected to, default is 0.
2694 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2695 0 for XT, 1 for AT (default is AT).
2698 parport= [HW,PPT] Specify parallel ports. 0 disables.
2699 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2700 Use 'auto' to force the driver to use any
2701 IRQ/DMA settings detected (the default is to
2702 ignore detected IRQ/DMA settings because of
2703 possible conflicts). You can specify the base
2704 address, IRQ, and DMA settings; IRQ and DMA
2705 should be numbers, or 'auto' (for using detected
2706 settings on that particular port), or 'nofifo'
2707 (to avoid using a FIFO even if it is detected).
2708 Parallel ports are assigned in the order they
2709 are specified on the command line, starting
2712 parport_init_mode= [HW,PPT]
2713 Configure VIA parallel port to operate in
2714 a specific mode. This is necessary on Pegasos
2715 computer where firmware has no options for setting
2716 up parallel port mode and sets it to spp.
2717 Currently this function knows 686a and 8231 chips.
2718 Format: [spp|ps2|epp|ecp|ecpepp]
2721 Halt all CPUs after the first oops has been printed for
2722 the specified number of seconds. This is to be used if
2723 your oopses keep scrolling off the screen.
2728 See header of drivers/block/paride/pcd.c.
2729 See also Documentation/blockdev/paride.txt.
2731 pci=option[,option...] [PCI] various PCI subsystem options:
2732 earlydump [X86] dump PCI config space before the kernel
2734 off [X86] don't probe for the PCI bus
2735 bios [X86-32] force use of PCI BIOS, don't access
2736 the hardware directly. Use this if your machine
2737 has a non-standard PCI host bridge.
2738 nobios [X86-32] disallow use of PCI BIOS, only direct
2739 hardware access methods are allowed. Use this
2740 if you experience crashes upon bootup and you
2741 suspect they are caused by the BIOS.
2742 conf1 [X86] Force use of PCI Configuration
2744 conf2 [X86] Force use of PCI Configuration
2746 noaer [PCIE] If the PCIEAER kernel config parameter is
2747 enabled, this kernel boot option can be used to
2748 disable the use of PCIE advanced error reporting.
2749 nodomains [PCI] Disable support for multiple PCI
2750 root domains (aka PCI segments, in ACPI-speak).
2751 nommconf [X86] Disable use of MMCONFIG for PCI
2753 check_enable_amd_mmconf [X86] check for and enable
2754 properly configured MMIO access to PCI
2755 config space on AMD family 10h CPU
2756 nomsi [MSI] If the PCI_MSI kernel config parameter is
2757 enabled, this kernel boot option can be used to
2758 disable the use of MSI interrupts system-wide.
2759 noioapicquirk [APIC] Disable all boot interrupt quirks.
2760 Safety option to keep boot IRQs enabled. This
2761 should never be necessary.
2762 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2763 primary IO-APIC for bridges that cannot disable
2764 boot IRQs. This fixes a source of spurious IRQs
2765 when the system masks IRQs.
2766 noioapicreroute [APIC] Disable workaround that uses the
2767 boot IRQ equivalent of an IRQ that connects to
2768 a chipset where boot IRQs cannot be disabled.
2769 The opposite of ioapicreroute.
2770 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2771 routing table. These calls are known to be buggy
2772 on several machines and they hang the machine
2773 when used, but on other computers it's the only
2774 way to get the interrupt routing table. Try
2775 this option if the kernel is unable to allocate
2776 IRQs or discover secondary PCI buses on your
2778 rom [X86] Assign address space to expansion ROMs.
2779 Use with caution as certain devices share
2780 address decoders between ROMs and other
2782 norom [X86] Do not assign address space to
2783 expansion ROMs that do not already have
2784 BIOS assigned address ranges.
2785 nobar [X86] Do not assign address space to the
2786 BARs that weren't assigned by the BIOS.
2787 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2788 assigned automatically to PCI devices. You can
2789 make the kernel exclude IRQs of your ISA cards
2791 pirqaddr=0xAAAAA [X86] Specify the physical address
2792 of the PIRQ table (normally generated
2793 by the BIOS) if it is outside the
2794 F0000h-100000h range.
2795 lastbus=N [X86] Scan all buses thru bus #N. Can be
2796 useful if the kernel is unable to find your
2797 secondary buses and you want to tell it
2798 explicitly which ones they are.
2799 assign-busses [X86] Always assign all PCI bus
2800 numbers ourselves, overriding
2801 whatever the firmware may have done.
2802 usepirqmask [X86] Honor the possible IRQ mask stored
2803 in the BIOS $PIR table. This is needed on
2804 some systems with broken BIOSes, notably
2805 some HP Pavilion N5400 and Omnibook XE3
2806 notebooks. This will have no effect if ACPI
2807 IRQ routing is enabled.
2808 noacpi [X86] Do not use ACPI for IRQ routing
2809 or for PCI scanning.
2810 use_crs [X86] Use PCI host bridge window information
2811 from ACPI. On BIOSes from 2008 or later, this
2812 is enabled by default. If you need to use this,
2813 please report a bug.
2814 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2815 If you need to use this, please report a bug.
2816 routeirq Do IRQ routing for all PCI devices.
2817 This is normally done in pci_enable_device(),
2818 so this option is a temporary workaround
2819 for broken drivers that don't call it.
2820 skip_isa_align [X86] do not align io start addr, so can
2821 handle more pci cards
2822 firmware [ARM] Do not re-enumerate the bus but instead
2823 just use the configuration from the
2824 bootloader. This is currently used on
2825 IXP2000 systems where the bus has to be
2826 configured a certain way for adjunct CPUs.
2827 noearly [X86] Don't do any early type 1 scanning.
2828 This might help on some broken boards which
2829 machine check when some devices' config space
2830 is read. But various workarounds are disabled
2831 and some IOMMU drivers will not work.
2832 bfsort Sort PCI devices into breadth-first order.
2833 This sorting is done to get a device
2834 order compatible with older (<= 2.4) kernels.
2835 nobfsort Don't sort PCI devices into breadth-first order.
2836 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2837 tuning and use the BIOS-configured MPS defaults.
2838 pcie_bus_safe Set every device's MPS to the largest value
2839 supported by all devices below the root complex.
2840 pcie_bus_perf Set device MPS to the largest allowable MPS
2841 based on its parent bus. Also set MRRS (Max
2842 Read Request Size) to the largest supported
2843 value (no larger than the MPS that the device
2844 or bus can support) for best performance.
2845 pcie_bus_peer2peer Set every device's MPS to 128B, which
2846 every device is guaranteed to support. This
2847 configuration allows peer-to-peer DMA between
2848 any pair of devices, possibly at the cost of
2849 reduced performance. This also guarantees
2850 that hot-added devices will work.
2851 cbiosize=nn[KMG] The fixed amount of bus space which is
2852 reserved for the CardBus bridge's IO window.
2853 The default value is 256 bytes.
2854 cbmemsize=nn[KMG] The fixed amount of bus space which is
2855 reserved for the CardBus bridge's memory
2856 window. The default value is 64 megabytes.
2859 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2860 Specifies alignment and device to reassign
2861 aligned memory resources.
2862 If <order of align> is not specified,
2863 PAGE_SIZE is used as alignment.
2864 PCI-PCI bridge can be specified, if resource
2865 windows need to be expanded.
2866 ecrc= Enable/disable PCIe ECRC (transaction layer
2867 end-to-end CRC checking).
2868 bios: Use BIOS/firmware settings. This is the
2872 hpiosize=nn[KMG] The fixed amount of bus space which is
2873 reserved for hotplug bridge's IO window.
2874 Default size is 256 bytes.
2875 hpmemsize=nn[KMG] The fixed amount of bus space which is
2876 reserved for hotplug bridge's memory window.
2877 Default size is 2 megabytes.
2878 realloc= Enable/disable reallocating PCI bridge resources
2879 if allocations done by BIOS are too small to
2880 accommodate resources required by all child
2882 off: Turn realloc off
2884 realloc same as realloc=on
2885 noari do not use PCIe ARI.
2886 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2887 only look for one device below a PCIe downstream
2890 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2893 force Enable ASPM even on devices that claim not to support it.
2894 WARNING: Forcing ASPM on may cause system lockups.
2896 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2897 nomsi Do not use MSI for PCI Express Native Hotplug (this
2898 makes all PCIe ports use INTx for hotplug services).
2900 pcie_ports= [PCIE] PCIe ports handling:
2901 auto Ask the BIOS whether or not to use native PCIe services
2902 associated with PCIe ports (PME, hot-plug, AER). Use
2903 them only if that is allowed by the BIOS.
2904 native Use native PCIe services associated with PCIe ports
2906 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2909 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2910 nomsi Do not use MSI for native PCIe PME signaling (this makes
2911 all PCIe root ports use INTx for all services).
2913 pcmv= [HW,PCMCIA] BadgePAD 4
2917 Keep all power-domains already enabled by bootloader on,
2918 even if no driver has claimed them. This is useful
2919 for debug and development, but should not be
2920 needed on a platform with proper driver support.
2923 See Documentation/blockdev/paride.txt.
2925 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2928 See arch/parisc/kernel/pdc_chassis.c
2930 percpu_alloc= Select which percpu first chunk allocator to use.
2931 Currently supported values are "embed" and "page".
2932 Archs may support subset or none of the selections.
2933 See comments in mm/percpu.c for details on each
2934 allocator. This parameter is primarily for debugging
2935 and performance comparison.
2938 See Documentation/blockdev/paride.txt.
2941 See Documentation/blockdev/paride.txt.
2943 pirq= [SMP,APIC] Manual mp-table setup
2944 See Documentation/x86/i386/IO-APIC.txt.
2946 plip= [PPT,NET] Parallel port network link
2947 Format: { parport<nr> | timid | 0 }
2948 See also Documentation/parport.txt.
2950 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2951 Override pmtimer IOPort with a hex value.
2955 Enable PNP debug messages (depends on the
2956 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2957 via /sys/module/pnp/parameters/debug. We always show
2958 current resource usage; turning this on also shows
2959 possible settings and some assignment information.
2965 { on | off | curr | res | no-curr | no-res }
2968 [ISAPNP] Exclude IRQs for the autoconfiguration
2971 [ISAPNP] Exclude DMAs for the autoconfiguration
2973 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2974 Ranges are in pairs (I/O port base and size).
2977 [ISAPNP] Exclude memory regions for the
2979 Ranges are in pairs (memory base and size).
2981 ports= [IP_VS_FTP] IPVS ftp helper module
2983 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2985 Format: <port>,<port>....
2987 print-fatal-signals=
2988 [KNL] debug: print fatal signals
2990 If enabled, warn about various signal handling
2991 related application anomalies: too many signals,
2992 too many POSIX.1 timers, fatal signals causing a
2995 If you hit the warning due to signal overflow,
2996 you might want to try "ulimit -i unlimited".
3000 printk.always_kmsg_dump=
3001 Trigger kmsg_dump for cases other than kernel oops or
3003 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3006 printk.time= Show timing data prefixed to each printk message line
3007 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3009 processor.max_cstate= [HW,ACPI]
3010 Limit processor to maximum C-state
3011 max_cstate=9 overrides any DMI blacklist limit.
3013 processor.nocst [HW,ACPI]
3014 Ignore the _CST method to determine C-states,
3015 instead using the legacy FADT method
3017 profile= [KNL] Enable kernel profiling via /proc/profile
3018 Format: [schedule,]<number>
3019 Param: "schedule" - profile schedule points.
3020 Param: <number> - step/bucket size as a power of 2 for
3021 statistical time based profiling.
3022 Param: "sleep" - profile D-state sleeping (millisecs).
3023 Requires CONFIG_SCHEDSTATS
3024 Param: "kvm" - profile VM exits.
3026 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3028 See Documentation/blockdev/ramdisk.txt.
3030 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3031 probe for; one of (bare|imps|exps|lifebook|any).
3032 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3034 psmouse.resetafter= [HW,MOUSE]
3035 Try to reset the device after so many bad packets
3038 [HW,MOUSE] Set desired mouse resolution, in dpi.
3039 psmouse.smartscroll=
3040 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3041 0 = disabled, 1 = enabled (default).
3043 pstore.backend= Specify the name of the pstore backend to use
3046 See Documentation/blockdev/paride.txt.
3049 [KNL] Number of legacy pty's. Overwrites compiled-in
3052 quiet [KNL] Disable most log messages
3057 See Documentation/md.txt.
3059 ramdisk_blocksize= [RAM]
3060 See Documentation/blockdev/ramdisk.txt.
3062 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3063 See Documentation/blockdev/ramdisk.txt.
3066 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3067 the specified list of CPUs to be no-callback CPUs.
3068 Invocation of these CPUs' RCU callbacks will
3069 be offloaded to "rcuox/N" kthreads created for
3070 that purpose, where "x" is "b" for RCU-bh, "p"
3071 for RCU-preempt, and "s" for RCU-sched, and "N"
3072 is the CPU number. This reduces OS jitter on the
3073 offloaded CPUs, which can be useful for HPC and
3074 real-time workloads. It can also improve energy
3075 efficiency for asymmetric multiprocessors.
3078 Rather than requiring that offloaded CPUs
3079 (specified by rcu_nocbs= above) explicitly
3080 awaken the corresponding "rcuoN" kthreads,
3081 make these kthreads poll for callbacks.
3082 This improves the real-time response for the
3083 offloaded CPUs by relieving them of the need to
3084 wake up the corresponding kthread, but degrades
3085 energy efficiency by requiring that the kthreads
3086 periodically wake up to do the polling.
3088 rcutree.blimit= [KNL]
3089 Set maximum number of finished RCU callbacks to
3090 process in one batch.
3092 rcutree.dump_tree= [KNL]
3093 Dump the structure of the rcu_node combining tree
3094 out at early boot. This is used for diagnostic
3095 purposes, to verify correct tree setup.
3097 rcutree.gp_cleanup_delay= [KNL]
3098 Set the number of jiffies to delay each step of
3099 RCU grace-period cleanup. This only has effect
3100 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3102 rcutree.gp_init_delay= [KNL]
3103 Set the number of jiffies to delay each step of
3104 RCU grace-period initialization. This only has
3105 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3108 rcutree.gp_preinit_delay= [KNL]
3109 Set the number of jiffies to delay each step of
3110 RCU grace-period pre-initialization, that is,
3111 the propagation of recent CPU-hotplug changes up
3112 the rcu_node combining tree. This only has effect
3113 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3115 rcutree.rcu_fanout_exact= [KNL]
3116 Disable autobalancing of the rcu_node combining
3117 tree. This is used by rcutorture, and might
3118 possibly be useful for architectures having high
3119 cache-to-cache transfer latencies.
3121 rcutree.rcu_fanout_leaf= [KNL]
3122 Change the number of CPUs assigned to each
3123 leaf rcu_node structure. Useful for very
3124 large systems, which will choose the value 64,
3125 and for NUMA systems with large remote-access
3126 latencies, which will choose a value aligned
3127 with the appropriate hardware boundaries.
3129 rcutree.jiffies_till_sched_qs= [KNL]
3130 Set required age in jiffies for a
3131 given grace period before RCU starts
3132 soliciting quiescent-state help from
3133 rcu_note_context_switch().
3135 rcutree.jiffies_till_first_fqs= [KNL]
3136 Set delay from grace-period initialization to
3137 first attempt to force quiescent states.
3138 Units are jiffies, minimum value is zero,
3139 and maximum value is HZ.
3141 rcutree.jiffies_till_next_fqs= [KNL]
3142 Set delay between subsequent attempts to force
3143 quiescent states. Units are jiffies, minimum
3144 value is one, and maximum value is HZ.
3146 rcutree.kthread_prio= [KNL,BOOT]
3147 Set the SCHED_FIFO priority of the RCU per-CPU
3148 kthreads (rcuc/N). This value is also used for
3149 the priority of the RCU boost threads (rcub/N)
3150 and for the RCU grace-period kthreads (rcu_bh,
3151 rcu_preempt, and rcu_sched). If RCU_BOOST is
3152 set, valid values are 1-99 and the default is 1
3153 (the least-favored priority). Otherwise, when
3154 RCU_BOOST is not set, valid values are 0-99 and
3155 the default is zero (non-realtime operation).
3157 rcutree.rcu_nocb_leader_stride= [KNL]
3158 Set the number of NOCB kthread groups, which
3159 defaults to the square root of the number of
3160 CPUs. Larger numbers reduces the wakeup overhead
3161 on the per-CPU grace-period kthreads, but increases
3162 that same overhead on each group's leader.
3164 rcutree.qhimark= [KNL]
3165 Set threshold of queued RCU callbacks beyond which
3166 batch limiting is disabled.
3168 rcutree.qlowmark= [KNL]
3169 Set threshold of queued RCU callbacks below which
3170 batch limiting is re-enabled.
3172 rcutree.rcu_idle_gp_delay= [KNL]
3173 Set wakeup interval for idle CPUs that have
3174 RCU callbacks (RCU_FAST_NO_HZ=y).
3176 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3177 Set wakeup interval for idle CPUs that have
3178 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3179 Lazy RCU callbacks are those which RCU can
3180 prove do nothing more than free memory.
3182 rcutorture.cbflood_inter_holdoff= [KNL]
3183 Set holdoff time (jiffies) between successive
3184 callback-flood tests.
3186 rcutorture.cbflood_intra_holdoff= [KNL]
3187 Set holdoff time (jiffies) between successive
3188 bursts of callbacks within a given callback-flood
3191 rcutorture.cbflood_n_burst= [KNL]
3192 Set the number of bursts making up a given
3193 callback-flood test. Set this to zero to
3194 disable callback-flood testing.
3196 rcutorture.cbflood_n_per_burst= [KNL]
3197 Set the number of callbacks to be registered
3198 in a given burst of a callback-flood test.
3200 rcutorture.fqs_duration= [KNL]
3201 Set duration of force_quiescent_state bursts
3204 rcutorture.fqs_holdoff= [KNL]
3205 Set holdoff time within force_quiescent_state bursts
3208 rcutorture.fqs_stutter= [KNL]
3209 Set wait time between force_quiescent_state bursts
3212 rcutorture.gp_cond= [KNL]
3213 Use conditional/asynchronous update-side
3214 primitives, if available.
3216 rcutorture.gp_exp= [KNL]
3217 Use expedited update-side primitives, if available.
3219 rcutorture.gp_normal= [KNL]
3220 Use normal (non-expedited) asynchronous
3221 update-side primitives, if available.
3223 rcutorture.gp_sync= [KNL]
3224 Use normal (non-expedited) synchronous
3225 update-side primitives, if available. If all
3226 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3227 rcutorture.gp_normal=, and rcutorture.gp_sync=
3228 are zero, rcutorture acts as if is interpreted
3229 they are all non-zero.
3231 rcutorture.n_barrier_cbs= [KNL]
3232 Set callbacks/threads for rcu_barrier() testing.
3234 rcutorture.nfakewriters= [KNL]
3235 Set number of concurrent RCU writers. These just
3236 stress RCU, they don't participate in the actual
3237 test, hence the "fake".
3239 rcutorture.nreaders= [KNL]
3240 Set number of RCU readers. The value -1 selects
3241 N-1, where N is the number of CPUs. A value
3242 "n" less than -1 selects N-n-2, where N is again
3243 the number of CPUs. For example, -2 selects N
3244 (the number of CPUs), -3 selects N+1, and so on.
3246 rcutorture.object_debug= [KNL]
3247 Enable debug-object double-call_rcu() testing.
3249 rcutorture.onoff_holdoff= [KNL]
3250 Set time (s) after boot for CPU-hotplug testing.
3252 rcutorture.onoff_interval= [KNL]
3253 Set time (s) between CPU-hotplug operations, or
3254 zero to disable CPU-hotplug testing.
3256 rcutorture.shuffle_interval= [KNL]
3257 Set task-shuffle interval (s). Shuffling tasks
3258 allows some CPUs to go into dyntick-idle mode
3259 during the rcutorture test.
3261 rcutorture.shutdown_secs= [KNL]
3262 Set time (s) after boot system shutdown. This
3263 is useful for hands-off automated testing.
3265 rcutorture.stall_cpu= [KNL]
3266 Duration of CPU stall (s) to test RCU CPU stall
3267 warnings, zero to disable.
3269 rcutorture.stall_cpu_holdoff= [KNL]
3270 Time to wait (s) after boot before inducing stall.
3272 rcutorture.stat_interval= [KNL]
3273 Time (s) between statistics printk()s.
3275 rcutorture.stutter= [KNL]
3276 Time (s) to stutter testing, for example, specifying
3277 five seconds causes the test to run for five seconds,
3278 wait for five seconds, and so on. This tests RCU's
3279 ability to transition abruptly to and from idle.
3281 rcutorture.test_boost= [KNL]
3282 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3283 "Maybe" means test if the RCU implementation
3284 under test support RCU priority boosting.
3286 rcutorture.test_boost_duration= [KNL]
3287 Duration (s) of each individual boost test.
3289 rcutorture.test_boost_interval= [KNL]
3290 Interval (s) between each boost test.
3292 rcutorture.test_no_idle_hz= [KNL]
3293 Test RCU's dyntick-idle handling. See also the
3294 rcutorture.shuffle_interval parameter.
3296 rcutorture.torture_runnable= [BOOT]
3297 Start rcutorture running at boot time.
3299 rcutorture.torture_type= [KNL]
3300 Specify the RCU implementation to test.
3302 rcutorture.verbose= [KNL]
3303 Enable additional printk() statements.
3305 rcupdate.rcu_expedited= [KNL]
3306 Use expedited grace-period primitives, for
3307 example, synchronize_rcu_expedited() instead
3308 of synchronize_rcu(). This reduces latency,
3309 but can increase CPU utilization, degrade
3310 real-time latency, and degrade energy efficiency.
3312 rcupdate.rcu_cpu_stall_suppress= [KNL]
3313 Suppress RCU CPU stall warning messages.
3315 rcupdate.rcu_cpu_stall_timeout= [KNL]
3316 Set timeout for RCU CPU stall warning messages.
3318 rcupdate.rcu_task_stall_timeout= [KNL]
3319 Set timeout in jiffies for RCU task stall warning
3320 messages. Disable with a value less than or equal
3323 rcupdate.rcu_self_test= [KNL]
3324 Run the RCU early boot self tests
3326 rcupdate.rcu_self_test_bh= [KNL]
3327 Run the RCU bh early boot self tests
3329 rcupdate.rcu_self_test_sched= [KNL]
3330 Run the RCU sched early boot self tests
3334 Run specified binary instead of /init from the ramdisk,
3335 used for early userspace startup. See initrd.
3338 Format (x86 or x86_64):
3339 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3341 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3343 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3344 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3345 reboot_force is either force or not specified,
3346 reboot_cpu is s[mp]#### with #### being the processor
3347 to be used for rebooting.
3350 [KNL, SMP] Set scheduler's default relax_domain_level.
3351 See Documentation/cgroups/cpusets.txt.
3353 relative_sleep_states=
3354 [SUSPEND] Use sleep state labeling where the deepest
3355 state available other than hibernation is always "mem".
3356 Format: { "0" | "1" }
3357 0 -- Traditional sleep state labels.
3358 1 -- Relative sleep state labels.
3360 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3362 reservetop= [X86-32]
3364 Reserves a hole at the top of the kernel virtual
3369 Set the amount of memory to reserve for BIOS at
3370 the bottom of the address space.
3372 reset_devices [KNL] Force drivers to reset the underlying device
3373 during initialization.
3376 Specify the partition device for software suspend
3378 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3380 resume_offset= [SWSUSP]
3381 Specify the offset from the beginning of the partition
3382 given by "resume=" at which the swap header is located,
3383 in <PAGE_SIZE> units (needed only for swap files).
3384 See Documentation/power/swsusp-and-swap-files.txt
3386 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3387 read the resume files
3389 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3390 Useful for devices that are detected asynchronously
3391 (e.g. USB and MMC devices).
3393 hibernate= [HIBERNATION]
3394 noresume Don't check if there's a hibernation image
3395 present during boot.
3396 nocompress Don't compress/decompress hibernation images.
3397 no Disable hibernation and resume.
3399 retain_initrd [RAM] Keep initrd memory after extraction
3401 rfkill.default_state=
3402 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3403 etc. communication is blocked by default.
3406 rfkill.master_switch_mode=
3407 0 The "airplane mode" button does nothing.
3408 1 The "airplane mode" button toggles between everything
3409 blocked and the previous configuration.
3410 2 The "airplane mode" button toggles between everything
3411 blocked and everything unblocked.
3413 rhash_entries= [KNL,NET]
3414 Set number of hash buckets for route cache
3416 ro [KNL] Mount root device read-only on boot
3419 on Mark read-only kernel memory as read-only (default).
3420 off Leave read-only kernel memory writable for debugging.
3422 root= [KNL] Root filesystem
3423 See name_to_dev_t comment in init/do_mounts.c.
3425 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3426 mount the root filesystem
3428 rootflags= [KNL] Set root filesystem mount option string
3430 rootfstype= [KNL] Set root filesystem type
3432 rootwait [KNL] Wait (indefinitely) for root device to show up.
3433 Useful for devices that are detected asynchronously
3434 (e.g. USB and MMC devices).
3436 rproc_mem=nn[KMG][@address]
3437 [KNL,ARM,CMA] Remoteproc physical memory block.
3438 Memory area to be used by remote processor image,
3441 rw [KNL] Mount root device read-write on boot
3443 S [KNL] Run init in single mode
3445 s390_iommu= [HW,S390]
3446 Set s390 IOTLB flushing mode
3448 With strict flushing every unmap operation will result in
3449 an IOTLB flush. Default is lazy flushing before reuse,
3453 See drivers/net/irda/sa1100_ir.c.
3455 sbni= [NET] Granch SBNI12 leased line adapter
3457 sched_debug [KNL] Enables verbose scheduler debug messages.
3459 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3460 xtime_lock contention on larger systems, and/or RCU lock
3461 contention on all systems with CONFIG_MAXSMP set.
3462 Format: { "0" | "1" }
3463 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3465 Note: increases power consumption, thus should only be
3466 enabled if running jitter sensitive (HPC/RT) workloads.
3468 security= [SECURITY] Choose a security module to enable at boot.
3469 If this boot parameter is not specified, only the first
3470 security module asking for security registration will be
3471 loaded. An invalid security module name will be treated
3472 as if no module has been chosen.
3474 selinux= [SELINUX] Disable or enable SELinux at boot time.
3475 Format: { "0" | "1" }
3476 See security/selinux/Kconfig help text.
3479 Default value is set via kernel config option.
3480 If enabled at boot time, /selinux/disable can be used
3481 later to disable prior to initial policy load.
3483 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3484 Format: { "0" | "1" }
3485 See security/apparmor/Kconfig help text
3488 Default value is set via kernel config option.
3490 serialnumber [BUGS=X86-32]
3493 Maximal number of shapers.
3495 show_msr= [x86] show boot-time MSR settings
3496 Format: { <integer> }
3497 Show boot-time (BIOS-initialized) MSR settings.
3498 The parameter means the number of CPUs to show,
3499 for example 1 means boot CPU only.
3507 Disable merging of slabs with similar size. May be
3508 necessary if there is some reason to distinguish
3509 allocs to different slabs. Debug options disable
3510 merging on their own.
3511 For more information see Documentation/vm/slub.txt.
3513 slab_max_order= [MM, SLAB]
3514 Determines the maximum allowed order for slabs.
3515 A high setting may cause OOMs due to memory
3516 fragmentation. Defaults to 1 for systems with
3517 more than 32MB of RAM, 0 otherwise.
3519 slub_debug[=options[,slabs]] [MM, SLUB]
3520 Enabling slub_debug allows one to determine the
3521 culprit if slab objects become corrupted. Enabling
3522 slub_debug can create guard zones around objects and
3523 may poison objects when not in use. Also tracks the
3524 last alloc / free. For more information see
3525 Documentation/vm/slub.txt.
3527 slub_max_order= [MM, SLUB]
3528 Determines the maximum allowed order for slabs.
3529 A high setting may cause OOMs due to memory
3530 fragmentation. For more information see
3531 Documentation/vm/slub.txt.
3533 slub_min_objects= [MM, SLUB]
3534 The minimum number of objects per slab. SLUB will
3535 increase the slab order up to slub_max_order to
3536 generate a sufficiently large slab able to contain
3537 the number of objects indicated. The higher the number
3538 of objects the smaller the overhead of tracking slabs
3539 and the less frequently locks need to be acquired.
3540 For more information see Documentation/vm/slub.txt.
3542 slub_min_order= [MM, SLUB]
3543 Determines the minimum page order for slabs. Must be
3544 lower than slub_max_order.
3545 For more information see Documentation/vm/slub.txt.
3547 slub_nomerge [MM, SLUB]
3548 Same with slab_nomerge. This is supported for legacy.
3549 See slab_nomerge for more information.
3552 Format: <io1>[,<io2>[,...,<io8>]]
3554 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3555 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3556 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3557 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3558 smsc-ircc2.ircc_irq= [HW] IRQ line
3559 smsc-ircc2.ircc_dma= [HW] DMA channel
3560 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3561 0: Toshiba Satellite 1800 (GP data pin select)
3562 1: Fast pin select (default)
3566 [KNL] Should the soft-lockup detector generate panics.
3569 softlockup_all_cpu_backtrace=
3570 [KNL] Should the soft-lockup detector generate
3571 backtraces on all cpus.
3574 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3575 See Documentation/laptops/sonypi.txt
3577 spia_io_base= [HW,MTD]
3583 Enabled the stack tracer on boot up.
3585 stacktrace_filter=[function-list]
3586 [FTRACE] Limit the functions that the stack tracer
3587 will trace at boot up. function-list is a comma separated
3588 list of functions. This list can be changed at run
3589 time by the stack_trace_filter file in the debugfs
3590 tracing directory. Note, this enables stack tracing
3591 and the stacktrace above is not needed.
3595 Set the STI (builtin display/keyboard on the HP-PARISC
3596 machines) console (graphic card) which should be used
3597 as the initial boot-console.
3598 See also comment in drivers/video/console/sticore.c.
3601 See comment in drivers/video/console/sticore.c.
3604 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3606 sunrpc.min_resvport=
3607 sunrpc.max_resvport=
3609 SunRPC servers often require that client requests
3610 originate from a privileged port (i.e. a port in the
3611 range 0 < portnr < 1024).
3612 An administrator who wishes to reserve some of these
3613 ports for other uses may adjust the range that the
3614 kernel's sunrpc client considers to be privileged
3615 using these two parameters to set the minimum and
3616 maximum port values.
3620 Control how the NFS server code allocates CPUs to
3621 service thread pools. Depending on how many NICs
3622 you have and where their interrupts are bound, this
3623 option will affect which CPUs will do NFS serving.
3624 Note: this parameter cannot be changed while the
3625 NFS server is running.
3627 auto the server chooses an appropriate mode
3628 automatically using heuristics
3629 global a single global pool contains all CPUs
3630 percpu one pool for each CPU
3631 pernode one pool for each NUMA node (equivalent
3632 to global on non-NUMA machines)
3634 sunrpc.tcp_slot_table_entries=
3635 sunrpc.udp_slot_table_entries=
3637 Sets the upper limit on the number of simultaneous
3638 RPC calls that can be sent from the client to a
3639 server. Increasing these values may allow you to
3640 improve throughput, but will also increase the
3641 amount of memory reserved for use by the client.
3643 suspend.pm_test_delay=
3645 Sets the number of seconds to remain in a suspend test
3646 mode before resuming the system (see
3647 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3648 is set. Default value is 5.
3651 [KNL] Enable accounting of swap in memory resource
3652 controller if no parameter or 1 is given or disable
3653 it if 0 is given (See Documentation/cgroups/memory.txt)
3655 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3656 Format: { <int> | force }
3657 <int> -- Number of I/O TLB slabs
3658 force -- force using of bounce buffers even if they
3659 wouldn't be automatically used by the kernel
3663 sysfs.deprecated=0|1 [KNL]
3664 Enable/disable old style sysfs layout for old udev
3665 on older distributions. When this option is enabled
3666 very new udev will not work anymore. When this option
3667 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3668 in older udev will not work anymore.
3669 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3670 the kernel configuration.
3672 sysrq_always_enabled
3674 Ignore sysrq setting - this boot parameter will
3675 neutralize any effect of /proc/sys/kernel/sysrq.
3676 Useful for debugging.
3678 tcpmhash_entries= [KNL,NET]
3679 Set the number of tcp_metrics_hash slots.
3680 Default value is 8192 or 16384 depending on total
3681 ram pages. This is used to specify the TCP metrics
3682 cache size. See Documentation/networking/ip-sysctl.txt
3683 "tcp_no_metrics_save" section for more details.
3687 test_suspend= [SUSPEND][,N]
3688 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3689 standby suspend) or "freeze" (for suspend type freeze)
3690 as the system sleep state during system startup with
3691 the optional capability to repeat N number of times.
3692 The system is woken from this state using a
3693 wakeup-capable RTC alarm.
3695 thash_entries= [KNL,NET]
3696 Set number of hash buckets for TCP connection
3698 thermal.act= [HW,ACPI]
3699 -1: disable all active trip points in all thermal zones
3700 <degrees C>: override all lowest active trip points
3702 thermal.crt= [HW,ACPI]
3703 -1: disable all critical trip points in all thermal zones
3704 <degrees C>: override all critical trip points
3706 thermal.nocrt= [HW,ACPI]
3707 Set to disable actions on ACPI thermal zone
3708 critical and hot trip points.
3710 thermal.off= [HW,ACPI]
3711 1: disable ACPI thermal control
3713 thermal.psv= [HW,ACPI]
3714 -1: disable all passive trip points
3715 <degrees C>: override all passive trip points to this
3718 thermal.tzp= [HW,ACPI]
3719 Specify global default ACPI thermal zone polling rate
3720 <deci-seconds>: poll all this frequency
3721 0: no polling (default)
3724 Force threading of all interrupt handlers except those
3725 marked explicitly IRQF_NO_THREAD.
3728 Enable the Transcendent memory driver if built-in.
3730 tmem.cleancache=0|1 [KNL, XEN]
3731 Default is on (1). Disable the usage of the cleancache
3732 API to send anonymous pages to the hypervisor.
3734 tmem.frontswap=0|1 [KNL, XEN]
3735 Default is on (1). Disable the usage of the frontswap
3736 API to send swap pages to the hypervisor. If disabled
3737 the selfballooning and selfshrinking are force disabled.
3739 tmem.selfballooning=0|1 [KNL, XEN]
3740 Default is on (1). Disable the driving of swap pages
3743 tmem.selfshrinking=0|1 [KNL, XEN]
3744 Default is on (1). Partial swapoff that immediately
3745 transfers pages from Xen hypervisor back to the
3746 kernel based on different criteria.
3750 Specify if the kernel should make use of the cpu
3751 topology information if the hardware supports this.
3752 The scheduler will make use of this information and
3753 e.g. base its process migration decisions on it.
3756 topology_updates= [KNL, PPC, NUMA]
3758 Specify if the kernel should ignore (off)
3759 topology updates sent by the hypervisor to this
3764 tpm_suspend_pcr=[HW,TPM]
3765 Format: integer pcr id
3766 Specify that at suspend time, the tpm driver
3767 should extend the specified pcr with zeros,
3768 as a workaround for some chips which fail to
3769 flush the last written pcr on TPM_SaveState.
3770 This will guarantee that all the other pcrs
3773 trace_buf_size=nn[KMG]
3774 [FTRACE] will set tracing buffer size on each cpu.
3776 trace_event=[event-list]
3777 [FTRACE] Set and start specified trace events in order
3778 to facilitate early boot debugging.
3779 See also Documentation/trace/events.txt
3781 trace_options=[option-list]
3782 [FTRACE] Enable or disable tracer options at boot.
3783 The option-list is a comma delimited list of options
3784 that can be enabled or disabled just as if you were
3785 to echo the option name into
3787 /sys/kernel/debug/tracing/trace_options
3789 For example, to enable stacktrace option (to dump the
3790 stack trace of each event), add to the command line:
3792 trace_options=stacktrace
3794 See also Documentation/trace/ftrace.txt "trace options"
3798 Have the tracepoints sent to printk as well as the
3799 tracing ring buffer. This is useful for early boot up
3800 where the system hangs or reboots and does not give the
3801 option for reading the tracing buffer or performing a
3802 ftrace_dump_on_oops.
3804 To turn off having tracepoints sent to printk,
3805 echo 0 > /proc/sys/kernel/tracepoint_printk
3806 Note, echoing 1 into this file without the
3807 tracepoint_printk kernel cmdline option has no effect.
3811 Having tracepoints sent to printk() and activating high
3812 frequency tracepoints such as irq or sched, can cause
3813 the system to live lock.
3816 [FTRACE] enable this option to disable tracing when a
3817 warning is hit. This turns off "tracing_on". Tracing can
3818 be enabled again by echoing '1' into the "tracing_on"
3819 file located in /sys/kernel/debug/tracing/
3821 This option is useful, as it disables the trace before
3822 the WARNING dump is called, which prevents the trace to
3823 be filled with content caused by the warning output.
3825 This option can also be set at run time via the sysctl
3826 option: kernel/traceoff_on_warning
3828 transparent_hugepage=
3830 Format: [always|madvise|never]
3831 Can be used to control the default behavior of the system
3832 with respect to transparent hugepages.
3833 See Documentation/vm/transhuge.txt for more details.
3835 tsc= Disable clocksource stability checks for TSC.
3837 [x86] reliable: mark tsc clocksource as reliable, this
3838 disables clocksource verification at runtime, as well
3839 as the stability checks done at bootup. Used to enable
3840 high-resolution timer mode on older hardware, and in
3841 virtualized environment.
3842 [x86] noirqtime: Do not use TSC to do irq accounting.
3843 Used to run time disable IRQ_TIME_ACCOUNTING on any
3844 platforms where RDTSC is slow and this accounting
3847 turbografx.map[2|3]= [HW,JOY]
3848 TurboGraFX parallel port interface
3850 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3851 See also Documentation/input/joystick-parport.txt
3853 udbg-immortal [PPC] When debugging early kernel crashes that
3854 happen after console_init() and before a proper
3855 console driver takes over, this boot options might
3856 help "seeing" what's going on.
3858 uhash_entries= [KNL,NET]
3859 Set number of hash buckets for UDP/UDP-Lite connections
3862 [USB] Ignore overcurrent events (default N).
3863 Some badly-designed motherboards generate lots of
3864 bogus events, for ports that aren't wired to
3865 anything. Set this parameter to avoid log spamming.
3866 Note that genuine overcurrent events won't be
3870 [X86] Cause panic on unknown NMI.
3872 usbcore.authorized_default=
3873 [USB] Default USB device authorization:
3874 (default -1 = authorized except for wireless USB,
3875 0 = not authorized, 1 = authorized)
3877 usbcore.autosuspend=
3878 [USB] The autosuspend time delay (in seconds) used
3879 for newly-detected USB devices (default 2). This
3880 is the time required before an idle device will be
3881 autosuspended. Devices for which the delay is set
3882 to a negative value won't be autosuspended at all.
3884 usbcore.usbfs_snoop=
3885 [USB] Set to log all usbfs traffic (default 0 = off).
3887 usbcore.blinkenlights=
3888 [USB] Set to cycle leds on hubs (default 0 = off).
3890 usbcore.old_scheme_first=
3891 [USB] Start with the old device initialization
3892 scheme (default 0 = off).
3894 usbcore.usbfs_memory_mb=
3895 [USB] Memory limit (in MB) for buffers allocated by
3896 usbfs (default = 16, 0 = max = 2047).
3898 usbcore.use_both_schemes=
3899 [USB] Try the other device initialization scheme
3900 if the first one fails (default 1 = enabled).
3902 usbcore.initial_descriptor_timeout=
3903 [USB] Specifies timeout for the initial 64-byte
3904 USB_REQ_GET_DESCRIPTOR request in milliseconds
3905 (default 5000 = 5.0 seconds).
3908 [USBHID] The interval which mice are to be polled at.
3910 usb-storage.delay_use=
3911 [UMS] The delay in seconds before a new device is
3912 scanned for Logical Units (default 1).
3915 [UMS] A list of quirks entries to supplement or
3916 override the built-in unusual_devs list. List
3917 entries are separated by commas. Each entry has
3918 the form VID:PID:Flags where VID and PID are Vendor
3919 and Product ID values (4-digit hex numbers) and
3920 Flags is a set of characters, each corresponding
3921 to a common usb-storage quirk flag as follows:
3922 a = SANE_SENSE (collect more than 18 bytes
3924 b = BAD_SENSE (don't collect more than 18
3925 bytes of sense data);
3926 c = FIX_CAPACITY (decrease the reported
3927 device capacity by one sector);
3928 d = NO_READ_DISC_INFO (don't use
3929 READ_DISC_INFO command);
3930 e = NO_READ_CAPACITY_16 (don't use
3931 READ_CAPACITY_16 command);
3932 f = NO_REPORT_OPCODES (don't use report opcodes
3934 g = MAX_SECTORS_240 (don't transfer more than
3935 240 sectors at a time, uas only);
3936 h = CAPACITY_HEURISTICS (decrease the
3937 reported device capacity by one
3938 sector if the number is odd);
3939 i = IGNORE_DEVICE (don't bind to this
3941 j = NO_REPORT_LUNS (don't use report luns
3943 l = NOT_LOCKABLE (don't try to lock and
3944 unlock ejectable media);
3945 m = MAX_SECTORS_64 (don't transfer more
3946 than 64 sectors = 32 KB at a time);
3947 n = INITIAL_READ10 (force a retry of the
3948 initial READ(10) command);
3949 o = CAPACITY_OK (accept the capacity
3950 reported by the device);
3951 p = WRITE_CACHE (the device cache is ON
3953 r = IGNORE_RESIDUE (the device reports
3954 bogus residue values);
3955 s = SINGLE_LUN (the device has only one
3957 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3958 commands, uas only);
3959 u = IGNORE_UAS (don't bind to the uas driver);
3960 w = NO_WP_DETECT (don't test whether the
3961 medium is write-protected).
3962 Example: quirks=0419:aaf5:rl,0421:0433:rc
3964 user_debug= [KNL,ARM]
3966 See arch/arm/Kconfig.debug help text.
3967 1 - undefined instruction events
3969 4 - invalid data aborts
3972 Example: user_debug=31
3975 [X86] Flags controlling user PTE allocations.
3977 nohigh = do not allocate PTE pages in
3978 HIGHMEM regardless of setting
3982 On X86_32, this is an alias for vdso32=. Otherwise:
3984 vdso=1: enable VDSO (the default)
3985 vdso=0: disable VDSO mapping
3987 vdso32= [X86] Control the 32-bit vDSO
3988 vdso32=1: enable 32-bit VDSO
3989 vdso32=0 or vdso32=2: disable 32-bit VDSO
3991 See the help text for CONFIG_COMPAT_VDSO for more
3992 details. If CONFIG_COMPAT_VDSO is set, the default is
3993 vdso32=0; otherwise, the default is vdso32=1.
3995 For compatibility with older kernels, vdso32=2 is an
3998 Try vdso32=0 if you encounter an error that says:
3999 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4002 vector=percpu: enable percpu vector domain
4004 video= [FB] Frame buffer configuration
4005 See Documentation/fb/modedb.txt.
4007 video.brightness_switch_enabled= [0,1]
4008 If set to 1, on receiving an ACPI notify event
4009 generated by hotkey, video driver will adjust brightness
4010 level and then send out the event to user space through
4011 the allocated input device; If set to 0, video driver
4012 will only send out the event without touching backlight
4017 [VMMIO] Memory mapped virtio (platform) device.
4019 <size>@<baseaddr>:<irq>[:<id>]
4021 <size> := size (can use standard suffixes
4023 <baseaddr> := physical base address
4024 <irq> := interrupt number (as passed to
4026 <id> := (optional) platform device id
4028 virtio_mmio.device=1K@0x100b0000:48:7
4030 Can be used multiple times for multiple devices.
4032 vga= [BOOT,X86-32] Select a particular video mode
4033 See Documentation/x86/boot.txt and
4034 Documentation/svga.txt.
4035 Use vga=ask for menu.
4036 This is actually a boot loader parameter; the value is
4037 passed to the kernel using a special protocol.
4039 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4040 size of <nn>. This can be used to increase the
4041 minimum size (128MB on x86). It can also be used to
4042 decrease the size and leave more room for directly
4045 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4048 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4051 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4055 Controls the behavior of vsyscalls (i.e. calls to
4056 fixed addresses of 0xffffffffff600x00 from legacy
4057 code). Most statically-linked binaries and older
4058 versions of glibc use these calls. Because these
4059 functions are at fixed addresses, they make nice
4060 targets for exploits that can control RIP.
4062 emulate [default] Vsyscalls turn into traps and are
4063 emulated reasonably safely.
4065 native Vsyscalls are native syscall instructions.
4066 This is a little bit faster than trapping
4067 and makes a few dynamic recompilers work
4068 better than they would in emulation mode.
4069 It also makes exploits much easier to write.
4071 none Vsyscalls don't work at all. This makes
4072 them quite hard to use for exploits but
4073 might break your system.
4075 vt.color= [VT] Default text color.
4076 Format: 0xYX, X = foreground, Y = background.
4077 Default: 0x07 = light gray on black.
4079 vt.cur_default= [VT] Default cursor shape.
4080 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4081 the parameters of the <Esc>[?A;B;Cc escape sequence;
4082 see VGA-softcursor.txt. Default: 2 = underline.
4084 vt.default_blu= [VT]
4085 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4086 Change the default blue palette of the console.
4087 This is a 16-member array composed of values
4090 vt.default_grn= [VT]
4091 Format: <green0>,<green1>,<green2>,...,<green15>
4092 Change the default green palette of the console.
4093 This is a 16-member array composed of values
4096 vt.default_red= [VT]
4097 Format: <red0>,<red1>,<red2>,...,<red15>
4098 Change the default red palette of the console.
4099 This is a 16-member array composed of values
4105 Set system-wide default UTF-8 mode for all tty's.
4106 Default is 1, i.e. UTF-8 mode is enabled for all
4107 newly opened terminals.
4109 vt.global_cursor_default=
4112 Set system-wide default for whether a cursor
4113 is shown on new VTs. Default is -1,
4114 i.e. cursors will be created by default unless
4115 overridden by individual drivers. 0 will hide
4116 cursors, 1 will display them.
4118 vt.italic= [VT] Default color for italic text; 0-15.
4121 vt.underline= [VT] Default color for underlined text; 0-15.
4124 watchdog timers [HW,WDT] For information on watchdog timers,
4125 see Documentation/watchdog/watchdog-parameters.txt
4126 or other driver-specific files in the
4127 Documentation/watchdog/ directory.
4129 workqueue.disable_numa
4130 By default, all work items queued to unbound
4131 workqueues are affine to the NUMA nodes they're
4132 issued on, which results in better behavior in
4133 general. If NUMA affinity needs to be disabled for
4134 whatever reason, this option can be used. Note
4135 that this also can be controlled per-workqueue for
4136 workqueues visible under /sys/bus/workqueue/.
4138 workqueue.power_efficient
4139 Per-cpu workqueues are generally preferred because
4140 they show better performance thanks to cache
4141 locality; unfortunately, per-cpu workqueues tend to
4142 be more power hungry than unbound workqueues.
4144 Enabling this makes the per-cpu workqueues which
4145 were observed to contribute significantly to power
4146 consumption unbound, leading to measurably lower
4147 power usage at the cost of small performance
4150 The default value of this parameter is determined by
4151 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4153 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4154 default x2apic cluster mode on platforms
4157 x86_intel_mid_timer= [X86-32,APBT]
4158 Choose timer option for x86 Intel MID platform.
4159 Two valid options are apbt timer only and lapic timer
4160 plus one apbt timer for broadcast timer.
4161 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4163 xen_512gb_limit [KNL,X86-64,XEN]
4164 Restricts the kernel running paravirtualized under Xen
4165 to use only up to 512 GB of RAM. The reason to do so is
4166 crash analysis tools and Xen tools for doing domain
4167 save/restore/migration must be enabled to handle larger
4170 xen_emul_unplug= [HW,X86,XEN]
4171 Unplug Xen emulated devices
4172 Format: [unplug0,][unplug1]
4173 ide-disks -- unplug primary master IDE devices
4174 aux-ide-disks -- unplug non-primary-master IDE devices
4175 nics -- unplug network devices
4176 all -- unplug all emulated devices (NICs and IDE disks)
4177 unnecessary -- unplugging emulated devices is
4178 unnecessary even if the host did not respond to
4180 never -- do not unplug even if version check succeeds
4182 xen_nopvspin [X86,XEN]
4183 Disables the ticketlock slowpath using Xen PV
4187 Disables the PV optimizations forcing the HVM guest to
4188 run as generic HVM guest with no PV drivers.
4190 xirc2ps_cs= [NET,PCMCIA]
4192 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4194 ______________________________________________________________________
4198 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob