4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpi_force_32bit_fadt_addr
197 force FADT to use 32 bit addresses rather than the
198 64 bit X_* addresses. Some firmware have broken 64
199 bit addresses for force ACPI ignore these and use
200 the older legacy 32 bit addresses.
202 acpica_no_return_repair [HW, ACPI]
203 Disable AML predefined validation mechanism
204 This mechanism can repair the evaluation result to make
205 the return objects more ACPI specification compliant.
206 This option is useful for developers to identify the
207 root cause of an AML interpreter issue when the issue
208 has something to do with the repair mechanism.
210 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
211 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
213 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
214 debug output. Bits in debug_layer correspond to a
215 _COMPONENT in an ACPI source file, e.g.,
216 #define _COMPONENT ACPI_PCI_COMPONENT
217 Bits in debug_level correspond to a level in
218 ACPI_DEBUG_PRINT statements, e.g.,
219 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
220 The debug_level mask defaults to "info". See
221 Documentation/acpi/debug.txt for more information about
222 debug layers and levels.
224 Enable processor driver info messages:
225 acpi.debug_layer=0x20000000
226 Enable PCI/PCI interrupt routing info messages:
227 acpi.debug_layer=0x400000
228 Enable AML "Debug" output, i.e., stores to the Debug
229 object while interpreting AML:
230 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
231 Enable all messages related to ACPI hardware:
232 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
234 Some values produce so much output that the system is
235 unusable. The "log_buf_len" parameter may be useful
236 if you need to capture more output.
238 acpi_enforce_resources= [ACPI]
239 { strict | lax | no }
240 Check for resource conflicts between native drivers
241 and ACPI OperationRegions (SystemIO and SystemMemory
242 only). IO ports and memory declared in ACPI might be
243 used by the ACPI subsystem in arbitrary AML code and
244 can interfere with legacy drivers.
245 strict (default): access to resources claimed by ACPI
246 is denied; legacy drivers trying to access reserved
247 resources will fail to bind to device using them.
248 lax: access to resources claimed by ACPI is allowed;
249 legacy drivers trying to access reserved resources
250 will bind successfully but a warning message is logged.
251 no: ACPI OperationRegions are not marked as reserved,
252 no further checks are performed.
254 acpi_force_table_verification [HW,ACPI]
255 Enable table checksum verification during early stage.
256 By default, this is disabled due to x86 early mapping
259 acpi_irq_balance [HW,ACPI]
260 ACPI will balance active IRQs
263 acpi_irq_nobalance [HW,ACPI]
264 ACPI will not move active IRQs (default)
267 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
268 Format: <irq>,<irq>...
270 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
272 Format: <irq>,<irq>...
274 acpi_no_auto_serialize [HW,ACPI]
275 Disable auto-serialization of AML methods
276 AML control methods that contain the opcodes to create
277 named objects will be marked as "Serialized" by the
278 auto-serialization feature.
279 This feature is enabled by default.
280 This option allows to turn off the feature.
282 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
285 acpi_no_static_ssdt [HW,ACPI]
286 Disable installation of static SSDTs at early boot time
287 By default, SSDTs contained in the RSDT/XSDT will be
288 installed automatically and they will appear under
289 /sys/firmware/acpi/tables.
290 This option turns off this feature.
291 Note that specifying this option does not affect
292 dynamic table installation which will install SSDT
293 tables to /sys/firmware/acpi/tables/dynamic.
295 acpi_rsdp= [ACPI,EFI,KEXEC]
296 Pass the RSDP address to the kernel, mostly used
297 on machines running EFI runtime service to boot the
298 second kernel for kdump.
300 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
301 Format: To spoof as Windows 98: ="Microsoft Windows"
303 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
304 of 2 which is mandated by ACPI 6) as the supported ACPI
305 specification revision (when using this switch, it may
306 be necessary to carry out a cold reboot _twice_ in a
307 row to make it take effect on the platform firmware).
309 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
310 acpi_osi="string1" # add string1
311 acpi_osi="!string2" # remove string2
312 acpi_osi=!* # remove all strings
313 acpi_osi=! # disable all built-in OS vendor
315 acpi_osi= # disable all strings
317 'acpi_osi=!' can be used in combination with single or
318 multiple 'acpi_osi="string1"' to support specific OS
319 vendor string(s). Note that such command can only
320 affect the default state of the OS vendor strings, thus
321 it cannot affect the default state of the feature group
322 strings and the current state of the OS vendor strings,
323 specifying it multiple times through kernel command line
324 is meaningless. This command is useful when one do not
325 care about the state of the feature group strings which
326 should be controlled by the OSPM.
328 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
329 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
330 can make '_OSI("Windows 2000")' TRUE.
332 'acpi_osi=' cannot be used in combination with other
333 'acpi_osi=' command lines, the _OSI method will not
334 exist in the ACPI namespace. NOTE that such command can
335 only affect the _OSI support state, thus specifying it
336 multiple times through kernel command line is also
339 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
342 'acpi_osi=!*' can be used in combination with single or
343 multiple 'acpi_osi="string1"' to support specific
344 string(s). Note that such command can affect the
345 current state of both the OS vendor strings and the
346 feature group strings, thus specifying it multiple times
347 through kernel command line is meaningful. But it may
348 still not able to affect the final state of a string if
349 there are quirks related to this string. This command
350 is useful when one want to control the state of the
351 feature group strings to debug BIOS issues related to
354 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
355 '_OSI("Module Device")' FALSE.
356 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
357 '_OSI("Module Device")' TRUE.
358 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
360 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
362 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
363 they all will make '_OSI("Windows 2000")' TRUE.
366 Override the pmtimer bug detection: force the kernel
367 to assume that this machine's pmtimer latches its value
368 and always returns good values.
370 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
371 Format: { level | edge | high | low }
373 acpi_skip_timer_override [HW,ACPI]
374 Recognize and ignore IRQ0/pin2 Interrupt Override.
375 For broken nForce2 BIOS resulting in XT-PIC timer.
377 acpi_sleep= [HW,ACPI] Sleep options
378 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
379 old_ordering, nonvs, sci_force_enable }
380 See Documentation/power/video.txt for information on
382 s3_beep is for debugging; it makes the PC's speaker beep
383 as soon as the kernel's real-mode entry point is called.
384 s4_nohwsig prevents ACPI hardware signature from being
385 used during resume from hibernation.
386 old_ordering causes the ACPI 1.0 ordering of the _PTS
387 control method, with respect to putting devices into
388 low power states, to be enforced (the ACPI 2.0 ordering
389 of _PTS is used by default).
390 nonvs prevents the kernel from saving/restoring the
391 ACPI NVS memory during suspend/hibernation and resume.
392 sci_force_enable causes the kernel to set SCI_EN directly
393 on resume from S1/S3 (which is against the ACPI spec,
394 but some broken systems don't work without it).
396 acpi_use_timer_override [HW,ACPI]
397 Use timer override. For some broken Nvidia NF5 boards
398 that require a timer override, but don't have HPET
400 add_efi_memmap [EFI; X86] Include EFI memory map in
401 kernel's map of available physical RAM.
404 { off | try_unsupported }
405 off: disable AGP support
406 try_unsupported: try to drive unsupported chipsets
407 (may crash computer or cause data corruption)
410 See Documentation/sound/alsa/alsa-parameters.txt
413 Allow the default userspace alignment fault handler
414 behaviour to be specified. Bit 0 enables warnings,
415 bit 1 enables fixups, and bit 2 sends a segfault.
417 align_va_addr= [X86-64]
418 Align virtual addresses by clearing slice [14:12] when
419 allocating a VMA at process creation time. This option
420 gives you up to 3% performance improvement on AMD F15h
421 machines (where it is enabled by default) for a
422 CPU-intensive style benchmark, and it can vary highly in
423 a microbenchmark depending on workload and compiler.
425 32: only for 32-bit processes
426 64: only for 64-bit processes
427 on: enable for both 32- and 64-bit processes
428 off: disable for both 32- and 64-bit processes
430 alloc_snapshot [FTRACE]
431 Allocate the ftrace snapshot buffer on boot up when the
432 main buffer is allocated. This is handy if debugging
433 and you need to use tracing_snapshot() on boot up, and
434 do not want to use tracing_snapshot_alloc() as it needs
435 to be done where GFP_KERNEL allocations are allowed.
437 amd_iommu= [HW,X86-64]
438 Pass parameters to the AMD IOMMU driver in the system.
440 fullflush - enable flushing of IO/TLB entries when
441 they are unmapped. Otherwise they are
442 flushed before they will be reused, which
444 off - do not initialize any AMD IOMMU found in
446 force_isolation - Force device isolation for all
447 devices. The IOMMU driver is not
448 allowed anymore to lift isolation
449 requirements as needed. This option
450 does not override iommu=pt
452 amd_iommu_dump= [HW,X86-64]
453 Enable AMD IOMMU driver option to dump the ACPI table
454 for AMD IOMMU. With this option enabled, AMD IOMMU
455 driver will print ACPI tables for AMD IOMMU during
456 IOMMU initialization.
458 amijoy.map= [HW,JOY] Amiga joystick support
459 Map of devices attached to JOY0DAT and JOY1DAT
461 See also Documentation/input/joystick.txt
463 analog.map= [HW,JOY] Analog joystick and gamepad support
464 Specifies type or capabilities of an analog joystick
465 connected to one of 16 gameports
466 Format: <type1>,<type2>,..<type16>
469 Power management functions (SPARCstation-4/5 + deriv.)
471 Disable APC CPU standby support. SPARCstation-Fox does
472 not play well with APC CPU idle - disable it if you have
473 APC and your system crashes randomly.
475 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
476 Change the output verbosity whilst booting
477 Format: { quiet (default) | verbose | debug }
478 Change the amount of debugging information output
479 when initialising the APIC and IO-APIC components.
481 apic_extnmi= [APIC,X86] External NMI delivery setting
482 Format: { bsp (default) | all | none }
483 bsp: External NMI is delivered only to CPU 0
484 all: External NMIs are broadcast to all CPUs as a
486 none: External NMI is masked for all CPUs. This is
487 useful so that a dump capture kernel won't be
491 See Documentation/networking/ipv6.txt.
493 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
494 Limit apic dumping. The parameter defines the maximal
495 number of local apics being dumped. Also it is possible
496 to set it to "all" by meaning -- no limit here.
497 Format: { 1 (default) | 2 | ... | all }.
498 The parameter valid if only apic=debug or
499 apic=verbose is specified.
500 Example: apic=debug show_lapic=all
502 apm= [APM] Advanced Power Management
503 See header of arch/x86/kernel/apm_32.c.
505 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
506 Format: <io>,<irq>,<nodeID>
510 atarimouse= [HW,MOUSE] Atari Mouse
512 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
513 EzKey and similar keyboards
515 atkbd.reset= [HW] Reset keyboard during initialization
517 atkbd.set= [HW] Select keyboard code set
518 Format: <int> (2 = AT (default), 3 = PS/2)
520 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
523 atkbd.softraw= [HW] Choose between synthetic and real raw mode
524 Format: <bool> (0 = real, 1 = synthetic (default))
526 atkbd.softrepeat= [HW]
527 Use software keyboard repeat
529 audit= [KNL] Enable the audit sub-system
530 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
531 0 - kernel audit is disabled and can not be enabled
532 until the next reboot
533 unset - kernel audit is initialized but disabled and
534 will be fully enabled by the userspace auditd.
535 1 - kernel audit is initialized and partially enabled,
536 storing at most audit_backlog_limit messages in
537 RAM until it is fully enabled by the userspace
541 audit_backlog_limit= [KNL] Set the audit queue size limit.
542 Format: <int> (must be >=0)
545 baycom_epp= [HW,AX25]
548 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
550 See header of drivers/net/hamradio/baycom_par.c.
552 baycom_ser_fdx= [HW,AX25]
553 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
554 Format: <io>,<irq>,<mode>[,<baud>]
555 See header of drivers/net/hamradio/baycom_ser_fdx.c.
557 baycom_ser_hdx= [HW,AX25]
558 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
559 Format: <io>,<irq>,<mode>
560 See header of drivers/net/hamradio/baycom_ser_hdx.c.
562 blkdevparts= Manual partition parsing of block device(s) for
563 embedded devices based on command line input.
564 See Documentation/block/cmdline-partition.txt
566 boot_delay= Milliseconds to delay each printk during boot.
567 Values larger than 10 seconds (10000) are changed to
571 bootmem_debug [KNL] Enable bootmem allocator debug messages.
573 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
574 bttv.radio= Most important insmod options are available as
576 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
579 bulk_remove=off [PPC] This parameter disables the use of the pSeries
580 firmware feature for flushing multiple hpte entries
583 c101= [NET] Moxa C101 synchronous serial card
585 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
586 Sometimes CPU hardware bugs make them report the cache
587 size incorrectly. The kernel will attempt work arounds
588 to fix known problems, but for some CPUs it is not
589 possible to determine what the correct size should be.
590 This option provides an override for these situations.
592 ca_keys= [KEYS] This parameter identifies a specific key(s) on
593 the system trusted keyring to be used for certificate
595 format: { id:<keyid> | builtin }
597 cca= [MIPS] Override the kernel pages' cache coherency
598 algorithm. Accepted values range from 0 to 7
599 inclusive. See arch/mips/include/asm/pgtable-bits.h
600 for platform specific values (SB1, Loongson3 and
603 ccw_timeout_log [S390]
604 See Documentation/s390/CommonIO for details.
606 cgroup_disable= [KNL] Disable a particular controller
607 Format: {name of the controller(s) to disable}
608 The effects of cgroup_disable=foo are:
609 - foo isn't auto-mounted if you mount all cgroups in
611 - foo isn't visible as an individually mountable
613 {Currently only "memory" controller deal with this and
614 cut the overhead, others just disable the usage. So
615 only cgroup_disable=memory is actually worthy}
617 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
619 nosocket -- Disable socket memory accounting.
620 nokmem -- Disable kernel memory accounting.
622 checkreqprot [SELINUX] Set initial checkreqprot flag value.
623 Format: { "0" | "1" }
624 See security/selinux/Kconfig help text.
625 0 -- check protection applied by kernel (includes
626 any implied execute protection).
627 1 -- check protection requested by application.
628 Default value is set via a kernel config option.
629 Value can be changed at runtime via
630 /selinux/checkreqprot.
633 See Documentation/s390/CommonIO for details.
636 Prevents the clock framework from automatically gating
637 clocks that have not been explicitly enabled by a Linux
638 device driver but are enabled in hardware at reset or
639 by the bootloader/firmware. Note that this does not
640 force such clocks to be always-on nor does it reserve
641 those clocks in any way. This parameter is useful for
642 debug and development, but should not be needed on a
643 platform with proper driver support. For more
644 information, see Documentation/clk.txt.
646 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
648 Forces specified clocksource (if available) to be used
649 when calculating gettimeofday(). If specified
650 clocksource is not available, it defaults to PIT.
651 Format: { pit | tsc | cyclone | pmtmr }
653 clocksource= Override the default clocksource
655 Override the default clocksource and use the clocksource
656 with the name specified.
657 Some clocksource names to choose from, depending on
659 [all] jiffies (this is the base, fallback clocksource)
661 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
662 pxa_timer,timer3,32k_counter,timer0_1
664 [X86-32] pit,hpet,tsc;
665 scx200_hrt on Geode; cyclone on IBM x440
673 clearcpuid=BITNUM [X86]
674 Disable CPUID feature X for the kernel. See
675 arch/x86/include/asm/cpufeature.h for the valid bit
676 numbers. Note the Linux specific bits are not necessarily
677 stable over kernel options, but the vendor specific
679 Also note that user programs calling CPUID directly
680 or using the feature without checking anything
681 will still see it. This just prevents it from
682 being used by the kernel or shown in /proc/cpuinfo.
683 Also note the kernel might malfunction if you disable
686 cma=nn[MG]@[start[MG][-end[MG]]]
688 Sets the size of kernel global memory area for
689 contiguous memory allocations and optionally the
690 placement constraint by the physical address range of
691 memory allocations. A value of 0 disables CMA
692 altogether. For more information, see
693 include/linux/dma-contiguous.h
695 cmo_free_hint= [PPC] Format: { yes | no }
696 Specify whether pages are marked as being inactive
697 when they are freed. This is used in CMO environments
698 to determine OS memory pressure for page stealing by
702 coherent_pool=nn[KMG] [ARM,KNL]
703 Sets the size of memory pool for coherent, atomic dma
704 allocations, by default set to 256K.
706 code_bytes [X86] How many bytes of object code to print
711 com20020= [HW,NET] ARCnet - COM20020 chipset
713 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
715 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
719 ARCnet - COM90xx chipset (memory-mapped buffers)
720 Format: <io>[,<irq>[,<memstart>]]
722 condev= [HW,S390] console device
725 console= [KNL] Output console device and options.
727 tty<n> Use the virtual console device <n>.
731 Use the specified serial port. The options are of
732 the form "bbbbpnf", where "bbbb" is the baud rate,
733 "p" is parity ("n", "o", or "e"), "n" is number of
734 bits, and "f" is flow control ("r" for RTS or
735 omit it). Default is "9600n8".
737 See Documentation/serial-console.txt for more
739 Documentation/networking/netconsole.txt for an
742 uart[8250],io,<addr>[,options]
743 uart[8250],mmio,<addr>[,options]
744 uart[8250],mmio16,<addr>[,options]
745 uart[8250],mmio32,<addr>[,options]
746 uart[8250],0x<addr>[,options]
747 Start an early, polled-mode console on the 8250/16550
748 UART at the specified I/O port or MMIO address,
749 switching to the matching ttyS device later.
750 MMIO inter-register address stride is either 8-bit
751 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
752 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
753 to be equivalent to 'mmio'. 'options' are specified in
754 the same format described for ttyS above; if unspecified,
755 the h/w is not re-initialized.
757 hvc<n> Use the hypervisor console device <n>. This is for
758 both Xen and PowerPC hypervisors.
760 If the device connected to the port is not a TTY but a braille
761 device, prepend "brl," before the device type, for instance
763 For now, only VisioBraille is supported.
765 consoleblank= [KNL] The console blank (screen saver) timeout in
766 seconds. Defaults to 10*60 = 10mins. A value of 0
767 disables the blank timer.
770 [KNL] Change the default value for
771 /proc/<pid>/coredump_filter.
772 See also Documentation/filesystems/proc.txt.
774 cpuidle.off=1 [CPU_IDLE]
775 disable the cpuidle sub-system
778 [X86] Delay for N microsec between assert and de-assert
779 of APIC INIT to start processors. This delay occurs
780 on every CPU online, such as boot, and resume from suspend.
783 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
785 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
787 crashkernel=size[KMG][@offset[KMG]]
788 [KNL] Using kexec, Linux can switch to a 'crash kernel'
789 upon panic. This parameter reserves the physical
790 memory region [offset, offset + size] for that kernel
791 image. If '@offset' is omitted, then a suitable offset
792 is selected automatically. Check
793 Documentation/kdump/kdump.txt for further details.
795 crashkernel=range1:size1[,range2:size2,...][@offset]
796 [KNL] Same as above, but depends on the memory
797 in the running system. The syntax of range is
798 start-[end] where start and end are both
799 a memory unit (amount[KMG]). See also
800 Documentation/kdump/kdump.txt for an example.
802 crashkernel=size[KMG],high
803 [KNL, x86_64] range could be above 4G. Allow kernel
804 to allocate physical memory region from top, so could
805 be above 4G if system have more than 4G ram installed.
806 Otherwise memory region will be allocated below 4G, if
808 It will be ignored if crashkernel=X is specified.
809 crashkernel=size[KMG],low
810 [KNL, x86_64] range under 4G. When crashkernel=X,high
811 is passed, kernel could allocate physical memory region
812 above 4G, that cause second kernel crash on system
813 that require some amount of low memory, e.g. swiotlb
814 requires at least 64M+32K low memory, also enough extra
815 low memory is needed to make sure DMA buffers for 32-bit
816 devices won't run out. Kernel would try to allocate at
817 at least 256M below 4G automatically.
818 This one let user to specify own low range under 4G
819 for second kernel instead.
820 0: to disable low allocation.
821 It will be ignored when crashkernel=X,high is not used
822 or memory reserved is below 4G.
827 cs89x0_media= [HW,NET]
828 Format: { rj45 | aui | bnc }
831 See header of drivers/s390/block/dasd_devmap.c.
833 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
834 (one device per port)
835 Format: <port#>,<type>
836 See also Documentation/input/joystick-parport.txt
838 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
839 time. See Documentation/dynamic-debug-howto.txt for
840 details. Deprecated, see dyndbg.
842 debug [KNL] Enable kernel debugging (events log level).
845 [KNL] verbose self-tests
847 Print debugging info while doing the locking API
849 We default to 0 (no extra messages), setting it to
850 1 will print _a lot_ more information - normally
851 only useful to kernel developers.
853 debug_objects [KNL] Enable object debugging
856 [KNL] Disable object debugging
858 debug_guardpage_minorder=
859 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
860 parameter allows control of the order of pages that will
861 be intentionally kept free (and hence protected) by the
862 buddy allocator. Bigger value increase the probability
863 of catching random memory corruption, but reduce the
864 amount of memory for normal system use. The maximum
865 possible value is MAX_ORDER/2. Setting this parameter
866 to 1 or 2 should be enough to identify most random
867 memory corruption problems caused by bugs in kernel or
868 driver code when a CPU writes to (or reads from) a
869 random memory location. Note that there exists a class
870 of memory corruptions problems caused by buggy H/W or
871 F/W or by drivers badly programing DMA (basically when
872 memory is written at bus level and the CPU MMU is
873 bypassed) which are not detectable by
874 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
875 tracking down these problems.
878 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
879 parameter enables the feature at boot time. In
880 default, it is disabled. We can avoid allocating huge
881 chunk of memory for debug pagealloc if we don't enable
882 it at boot time and the system will work mostly same
883 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
884 on: enable the feature
886 debugpat [X86] Enable PAT debugging
888 decnet.addr= [HW,NET]
889 Format: <area>[,<node>]
890 See also Documentation/networking/decnet.txt.
893 [same as hugepagesz=] The size of the default
894 HugeTLB page size. This is the size represented by
895 the legacy /proc/ hugepages APIs, used for SHM, and
896 default size when mounting hugetlbfs filesystems.
897 Defaults to the default architecture's huge page size
901 Set number of hash buckets for dentry cache.
904 See Documentation/networking/ipv6.txt.
906 disable_cpu_apicid= [X86,APIC,SMP]
908 The number of initial APIC ID for the
909 corresponding CPU to be disabled at boot,
910 mostly used for the kdump 2nd kernel to
911 disable BSP to wake up multiple CPUs without
912 causing system reset or hang due to sending
915 disable_ddw [PPC/PSERIES]
916 Disable Dynamic DMA Window support. Use this if
917 to workaround buggy firmware.
920 See Documentation/networking/ipv6.txt.
922 disable_mtrr_cleanup [X86]
923 The kernel tries to adjust MTRR layout from continuous
924 to discrete, to make X server driver able to add WB
925 entry later. This parameter disables that.
927 disable_mtrr_trim [X86, Intel and AMD only]
928 By default the kernel will trim any uncacheable
929 memory out of your available memory pool based on
930 MTRR settings. This parameter disables that behavior,
931 possibly causing your machine to run very slowly.
933 disable_timer_pin_1 [X86]
934 Disable PIN 1 of APIC timer
935 Can be useful to work around chipset bugs.
937 dis_ucode_ldr [X86] Disable the microcode loader.
939 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
940 this option disables the debugging code at boot.
942 dma_debug_entries=<number>
943 This option allows to tune the number of preallocated
944 entries for DMA-API debugging code. One entry is
945 required per DMA-API allocation. Use this if the
946 DMA-API debugging code disables itself because the
947 architectural default is too low.
949 dma_debug_driver=<driver_name>
950 With this option the DMA-API debugging driver
951 filter feature can be enabled at boot time. Just
952 pass the driver to filter for as the parameter.
953 The filter can be disabled or changed to another
954 driver later using sysfs.
956 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
957 Broken monitors, graphic adapters, KVMs and EDIDless
958 panels may send no or incorrect EDID data sets.
959 This parameter allows to specify an EDID data sets
960 in the /lib/firmware directory that are used instead.
961 Generic built-in EDID data sets are used, if one of
962 edid/1024x768.bin, edid/1280x1024.bin,
963 edid/1680x1050.bin, or edid/1920x1080.bin is given
964 and no file with the same name exists. Details and
965 instructions how to build your own EDID data are
966 available in Documentation/EDID/HOWTO.txt. An EDID
967 data set will only be used for a particular connector,
968 if its name and a colon are prepended to the EDID
969 name. Each connector may use a unique EDID data
970 set by separating the files with a comma. An EDID
971 data set with no connector name will be used for
972 any connectors not explicitly specified.
976 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
977 module.dyndbg[="val"]
978 Enable debug messages at boot time. See
979 Documentation/dynamic-debug-howto.txt for details.
981 nompx [X86] Disables Intel Memory Protection Extensions.
982 See Documentation/x86/intel_mpx.txt for more
983 information about the feature.
986 on enable eager fpu restore
987 off disable eager fpu restore
988 auto selects the default scheme, which automatically
989 enables eagerfpu restore for xsaveopt.
991 module.async_probe [KNL]
992 Enable asynchronous probe on this module.
994 early_ioremap_debug [KNL]
995 Enable debug messages in early_ioremap support. This
996 is useful for tracking down temporary early mappings
997 which are not unmapped.
999 earlycon= [KNL] Output early console device and options.
1001 When used with no options, the early console is
1002 determined by the stdout-path property in device
1006 Start an early, polled-mode console on a cadence serial
1007 port at the specified address. The cadence serial port
1008 must already be setup and configured. Options are not
1011 uart[8250],io,<addr>[,options]
1012 uart[8250],mmio,<addr>[,options]
1013 uart[8250],mmio32,<addr>[,options]
1014 uart[8250],mmio32be,<addr>[,options]
1015 uart[8250],0x<addr>[,options]
1016 Start an early, polled-mode console on the 8250/16550
1017 UART at the specified I/O port or MMIO address.
1018 MMIO inter-register address stride is either 8-bit
1019 (mmio) or 32-bit (mmio32 or mmio32be).
1020 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1021 to be equivalent to 'mmio'. 'options' are specified
1022 in the same format described for "console=ttyS<n>"; if
1023 unspecified, the h/w is not initialized.
1027 Start an early, polled-mode console on a pl011 serial
1028 port at the specified address. The pl011 serial port
1029 must already be setup and configured. Options are not
1030 yet supported. If 'mmio32' is specified, then only
1031 the driver will use only 32-bit accessors to read/write
1032 the device registers.
1035 Start an early, polled-mode console on an msm serial
1036 port at the specified address. The serial port
1037 must already be setup and configured. Options are not
1040 msm_serial_dm,<addr>
1041 Start an early, polled-mode console on an msm serial
1042 dm port at the specified address. The serial port
1043 must already be setup and configured. Options are not
1046 smh Use ARM semihosting calls for early console.
1054 Use early console provided by serial driver available
1055 on Samsung SoCs, requires selecting proper type and
1056 a correct base address of the selected UART port. The
1057 serial port must already be setup and configured.
1058 Options are not yet supported.
1062 Use early console provided by Freescale LP UART driver
1063 found on Freescale Vybrid and QorIQ LS1021A processors.
1064 A valid base address must be provided, and the serial
1065 port must already be setup and configured.
1067 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1071 earlyprintk=serial[,ttySn[,baudrate]]
1072 earlyprintk=serial[,0x...[,baudrate]]
1073 earlyprintk=ttySn[,baudrate]
1074 earlyprintk=dbgp[debugController#]
1075 earlyprintk=pciserial,bus:device.function[,baudrate]
1077 earlyprintk is useful when the kernel crashes before
1078 the normal console is initialized. It is not enabled by
1079 default because it has some cosmetic problems.
1081 Append ",keep" to not disable it when the real console
1084 Only one of vga, efi, serial, or usb debug port can
1087 Currently only ttyS0 and ttyS1 may be specified by
1088 name. Other I/O ports may be explicitly specified
1089 on some architectures (x86 and arm at least) by
1090 replacing ttySn with an I/O port address, like this:
1091 earlyprintk=serial,0x1008,115200
1092 You can find the port for a given device in
1093 /proc/tty/driver/serial:
1094 2: uart:ST16650V2 port:00001008 irq:18 ...
1096 Interaction with the standard serial driver is not
1099 The VGA and EFI output is eventually overwritten by
1102 The xen output can only be used by Xen PV guests.
1104 edac_report= [HW,EDAC] Control how to report EDAC event
1105 Format: {"on" | "off" | "force"}
1106 on: enable EDAC to report H/W event. May be overridden
1107 by other higher priority error reporting module.
1108 off: disable H/W event reporting through EDAC.
1109 force: enforce the use of EDAC to report H/W event.
1112 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1115 This is designed to be used in conjunction with
1116 the boot argument: earlyprintk=vga
1119 Format: {"off" | "on" | "skip[mbr]"}
1122 Format: { "old_map", "nochunk", "noruntime", "debug" }
1123 old_map [X86-64]: switch to the old ioremap-based EFI
1124 runtime services mapping. 32-bit still uses this one by
1126 nochunk: disable reading files in "chunks" in the EFI
1127 boot stub, as chunking can cause problems with some
1128 firmware implementations.
1129 noruntime : disable EFI runtime services support
1130 debug: enable misc debug output
1132 efi_no_storage_paranoia [EFI; X86]
1133 Using this parameter you can use more than 50% of
1134 your efi variable storage. Use this parameter only if
1135 you are really sure that your UEFI does sane gc and
1136 fulfills the spec otherwise your board may brick.
1138 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1139 Add arbitrary attribute to specific memory range by
1140 updating original EFI memory map.
1141 Region of memory which aa attribute is added to is
1143 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1144 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1145 attribute is added to range 0x100000000-0x180000000 and
1146 0x10a0000000-0x1120000000.
1148 Using this parameter you can do debugging of EFI memmap
1149 related feature. For example, you can do debugging of
1150 Address Range Mirroring feature even if your box
1153 eisa_irq_edge= [PARISC,HW]
1154 See header of drivers/parisc/eisa.c.
1157 See comment before function elanfreq_setup() in
1158 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1161 Format: {"cfq" | "deadline" | "noop"}
1162 See Documentation/block/cfq-iosched.txt and
1163 Documentation/block/deadline-iosched.txt for details.
1165 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1166 Specifies physical address of start of kernel core
1167 image elf header and optionally the size. Generally
1168 kexec loader will pass this option to capture kernel.
1169 See Documentation/kdump/kdump.txt for details.
1171 enable_mtrr_cleanup [X86]
1172 The kernel tries to adjust MTRR layout from continuous
1173 to discrete, to make X server driver able to add WB
1174 entry later. This parameter enables that.
1176 enable_timer_pin_1 [X86]
1177 Enable PIN 1 of APIC timer
1178 Can be useful to work around chipset bugs
1179 (in particular on some ATI chipsets).
1180 The kernel tries to set a reasonable default.
1182 enforcing [SELINUX] Set initial enforcing status.
1184 See security/selinux/Kconfig help text.
1185 0 -- permissive (log only, no denials).
1186 1 -- enforcing (deny and log).
1188 Value can be changed at runtime via /selinux/enforce.
1191 Disable Error Record Serialization Table (ERST)
1194 ether= [HW,NET] Ethernet cards parameters
1195 This option is obsoleted by the "netdev=" option, which
1196 has equivalent usage. See its documentation for details.
1200 Permit 'security.evm' to be updated regardless of
1201 current integrity status.
1205 fail_make_request=[KNL]
1206 General fault injection mechanism.
1207 Format: <interval>,<probability>,<space>,<times>
1208 See also Documentation/fault-injection/.
1211 See Documentation/blockdev/floppy.txt.
1213 force_pal_cache_flush
1214 [IA-64] Avoid check_sal_cache_flush which may hang on
1215 buggy SAL_CACHE_FLUSH implementations. Using this
1216 parameter will force ia64_sal_cache_flush to call
1217 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1220 Forcefully enable Physical Address Extension (PAE).
1221 Many Pentium M systems disable PAE but may have a
1222 functionally usable PAE implementation.
1223 Warning: use of this parameter will taint the kernel
1224 and may cause unknown problems.
1227 [FTRACE] will set and start the specified tracer
1228 as early as possible in order to facilitate early
1231 ftrace_dump_on_oops[=orig_cpu]
1232 [FTRACE] will dump the trace buffers on oops.
1233 If no parameter is passed, ftrace will dump
1234 buffers of all CPUs, but if you pass orig_cpu, it will
1235 dump only the buffer of the CPU that triggered the
1238 ftrace_filter=[function-list]
1239 [FTRACE] Limit the functions traced by the function
1240 tracer at boot up. function-list is a comma separated
1241 list of functions. This list can be changed at run
1242 time by the set_ftrace_filter file in the debugfs
1245 ftrace_notrace=[function-list]
1246 [FTRACE] Do not trace the functions specified in
1247 function-list. This list can be changed at run time
1248 by the set_ftrace_notrace file in the debugfs
1251 ftrace_graph_filter=[function-list]
1252 [FTRACE] Limit the top level callers functions traced
1253 by the function graph tracer at boot up.
1254 function-list is a comma separated list of functions
1255 that can be changed at run time by the
1256 set_graph_function file in the debugfs tracing directory.
1258 ftrace_graph_notrace=[function-list]
1259 [FTRACE] Do not trace from the functions specified in
1260 function-list. This list is a comma separated list of
1261 functions that can be changed at run time by the
1262 set_graph_notrace file in the debugfs tracing directory.
1265 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1266 support via parallel port (up to 5 devices per port)
1267 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1268 See also Documentation/input/joystick-parport.txt
1272 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1276 gcov_persist= [GCOV] When non-zero (default), profiling data for
1277 kernel modules is saved and remains accessible via
1278 debugfs, even when the module is unloaded/reloaded.
1279 When zero, profiling data is discarded and associated
1280 debugfs files are removed at module unload time.
1282 gpt [EFI] Forces disk with valid GPT signature but
1283 invalid Protective MBR to be treated as GPT. If the
1284 primary GPT is corrupted, it enables the backup/alternate
1285 GPT to be used instead.
1287 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1288 the "Enable 0" bit of the configuration register.
1291 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1292 the "Enable 0" bit of the configuration register.
1295 grcan.select= [HW] Select which physical interface to use.
1298 grcan.txsize= [HW] Sets the size of the tx buffer.
1299 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1301 grcan.rxsize= [HW] Sets the size of the rx buffer.
1302 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1305 hardlockup_all_cpu_backtrace=
1306 [KNL] Should the hard-lockup detector generate
1307 backtraces on all cpus.
1310 hashdist= [KNL,NUMA] Large hashes allocated during boot
1311 are distributed across NUMA nodes. Defaults on
1312 for 64-bit NUMA, off otherwise.
1313 Format: 0 | 1 (for off | on)
1315 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1317 hd= [EIDE] (E)IDE hard drive subsystem geometry
1318 Format: <cyl>,<head>,<sect>
1321 Disable Hardware Error Source Table (HEST) support;
1322 corresponding firmware-first mode error processing
1323 logic will be disabled.
1325 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1326 size of <nn>. This works even on boxes that have no
1327 highmem otherwise. This also works to reduce highmem
1328 size on bigger boxes.
1330 highres= [KNL] Enable/disable high resolution timer mode.
1331 Valid parameters: "on", "off"
1335 See Documentation/isdn/README.HiSax.
1339 hpet= [X86-32,HPET] option to control HPET usage
1340 Format: { enable (default) | disable | force |
1342 disable: disable HPET and use PIT instead
1343 force: allow force enabled of undocumented chips (ICH4,
1345 verbose: show contents of HPET registers during setup
1347 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1348 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1350 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1351 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1352 On x86-64 and powerpc, this option can be specified
1353 multiple times interleaved with hugepages= to reserve
1354 huge pages of different sizes. Valid pages sizes on
1355 x86-64 are 2M (when the CPU supports "pse") and 1G
1356 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1358 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1359 terminal devices. Valid values: 0..8
1360 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1361 If specified, z/VM IUCV HVC accepts connections
1362 from listed z/VM user IDs only.
1364 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1365 hardware thread id mappings.
1366 Format: <cpu>:<hwthread>
1369 Do not unregister boot console at start. This is only
1370 useful for debugging when something happens in the window
1371 between unregistering the boot console and initializing
1374 i2c_bus= [HW] Override the default board specific I2C bus speed
1375 or register an additional I2C bus that is not
1376 registered from board initialization code.
1380 i8042.debug [HW] Toggle i8042 debug mode
1381 i8042.unmask_kbd_data
1382 [HW] Enable printing of interrupt data from the KBD port
1383 (disabled by default, and as a pre-condition
1384 requires that i8042.debug=1 be enabled)
1385 i8042.direct [HW] Put keyboard port into non-translated mode
1386 i8042.dumbkbd [HW] Pretend that controller can only read data from
1387 keyboard and cannot control its state
1388 (Don't attempt to blink the leds)
1389 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1390 i8042.nokbd [HW] Don't check/create keyboard port
1391 i8042.noloop [HW] Disable the AUX Loopback command while probing
1393 i8042.nomux [HW] Don't check presence of an active multiplexing
1395 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1397 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1398 i8042.reset [HW] Reset the controller during init and cleanup
1399 i8042.unlock [HW] Unlock (ignore) the keylock
1400 i8042.kbdreset [HW] Reset device connected to KBD port
1404 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1405 indicates that the driver is running on unsupported
1407 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1408 does not match list of supported models.
1410 [HW] Report power status in /proc/i8k
1411 (disabled by default)
1412 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1415 i915.invert_brightness=
1416 [DRM] Invert the sense of the variable that is used to
1417 set the brightness of the panel backlight. Normally a
1418 brightness value of 0 indicates backlight switched off,
1419 and the maximum of the brightness value sets the backlight
1420 to maximum brightness. If this parameter is set to 0
1421 (default) and the machine requires it, or this parameter
1422 is set to 1, a brightness value of 0 sets the backlight
1423 to maximum brightness, and the maximum of the brightness
1424 value switches the backlight off.
1425 -1 -- never invert brightness
1426 0 -- machine default
1427 1 -- force brightness inversion
1430 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1432 ide-core.nodma= [HW] (E)IDE subsystem
1433 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1434 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1435 .cdrom .chs .ignore_cable are additional options
1436 See Documentation/ide/ide.txt.
1438 ide-generic.probe-mask= [HW] (E)IDE subsystem
1440 Probe mask for legacy ISA IDE ports. Depending on
1441 platform up to 6 ports are supported, enabled by
1442 setting corresponding bits in the mask to 1. The
1443 default value is 0x0, which has a special meaning.
1444 On systems that have PCI, it triggers scanning the
1445 PCI bus for the first and the second port, which
1446 are then probed. On systems without PCI the value
1447 of 0x0 enables probing the two first ports as if it
1450 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1451 Claim all unknown PCI IDE storage controllers.
1454 Format: idle=poll, idle=halt, idle=nomwait
1455 Poll forces a polling idle loop that can slightly
1456 improve the performance of waking up a idle CPU, but
1457 will use a lot of power and make the system run hot.
1459 idle=halt: Halt is forced to be used for CPU idle.
1460 In such case C2/C3 won't be used again.
1461 idle=nomwait: Disable mwait for CPU C-states
1463 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1464 Format: { strict | legacy | 2008 | relaxed }
1467 Choose which programs will be accepted for execution
1468 based on the IEEE 754 NaN encoding(s) supported by
1469 the FPU and the NaN encoding requested with the value
1470 of an ELF file header flag individually set by each
1471 binary. Hardware implementations are permitted to
1472 support either or both of the legacy and the 2008 NaN
1475 Available settings are as follows:
1476 strict accept binaries that request a NaN encoding
1477 supported by the FPU
1478 legacy only accept legacy-NaN binaries, if supported
1480 2008 only accept 2008-NaN binaries, if supported
1482 relaxed accept any binaries regardless of whether
1483 supported by the FPU
1485 The FPU emulator is always able to support both NaN
1486 encodings, so if no FPU hardware is present or it has
1487 been disabled with 'nofpu', then the settings of
1488 'legacy' and '2008' strap the emulator accordingly,
1489 'relaxed' straps the emulator for both legacy-NaN and
1490 2008-NaN, whereas 'strict' enables legacy-NaN only on
1491 legacy processors and both NaN encodings on MIPS32 or
1494 The setting for ABS.fmt/NEG.fmt instruction execution
1495 mode generally follows that for the NaN encoding,
1496 except where unsupported by hardware.
1498 ignore_loglevel [KNL]
1499 Ignore loglevel setting - this will print /all/
1500 kernel messages to the console. Useful for debugging.
1501 We also add it as printk module parameter, so users
1502 could change it dynamically, usually by
1503 /sys/module/printk/parameters/ignore_loglevel.
1506 Ignore RLIMIT_DATA setting for data mappings,
1507 print warning at first misuse. Can be changed via
1508 /sys/module/kernel/parameters/ignore_rlimit_data.
1510 ihash_entries= [KNL]
1511 Set number of hash buckets for inode cache.
1513 ima_appraise= [IMA] appraise integrity measurements
1514 Format: { "off" | "enforce" | "fix" | "log" }
1517 ima_appraise_tcb [IMA]
1518 The builtin appraise policy appraises all files
1522 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1526 The list of supported hash algorithms is defined
1527 in crypto/hash_info.h.
1530 The builtin measurement policy to load during IMA
1531 setup. Specyfing "tcb" as the value, measures all
1532 programs exec'd, files mmap'd for exec, and all files
1533 opened with the read mode bit set by either the
1534 effective uid (euid=0) or uid=0.
1537 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1538 Load a policy which meets the needs of the Trusted
1539 Computing Base. This means IMA will measure all
1540 programs exec'd, files mmap'd for exec, and all files
1541 opened for read by uid=0.
1544 Select one of defined IMA measurements template formats.
1545 Formats: { "ima" | "ima-ng" | "ima-sig" }
1549 [IMA] Define a custom template format.
1550 Format: { "field1|...|fieldN" }
1552 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1553 Format: <min_file_size>
1554 Set the minimal file size for using asynchronous hash.
1555 If left unspecified, ahash usage is disabled.
1557 ahash performance varies for different data sizes on
1558 different crypto accelerators. This option can be used
1559 to achieve the best performance for a particular HW.
1561 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1563 Set hashing buffer size. Default: 4k.
1565 ahash performance varies for different chunk sizes on
1566 different crypto accelerators. This option can be used
1567 to achieve best performance for particular HW.
1571 Run specified binary instead of /sbin/init as init
1574 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1575 for working out where the kernel is dying during
1578 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1579 initcall functions. Useful for debugging built-in
1580 modules and initcalls.
1582 initrd= [BOOT] Specify the location of the initial ramdisk
1584 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1587 int_pln_enable [x86] Enable power limit notification interrupt
1589 integrity_audit=[IMA]
1590 Format: { "0" | "1" }
1591 0 -- basic integrity auditing messages. (Default)
1592 1 -- additional integrity auditing messages.
1594 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1596 Enable intel iommu driver.
1598 Disable intel iommu driver.
1599 igfx_off [Default Off]
1600 By default, gfx is mapped as normal device. If a gfx
1601 device has a dedicated DMAR unit, the DMAR unit is
1602 bypassed by not enabling DMAR with this option. In
1603 this case, gfx device will use physical address for
1606 With this option iommu will not optimize to look
1607 for io virtual address below 32-bit forcing dual
1608 address cycle on pci bus for cards supporting greater
1609 than 32-bit addressing. The default is to look
1610 for translation below 32-bit and if not available
1611 then look in the higher range.
1612 strict [Default Off]
1613 With this option on every unmap_single operation will
1614 result in a hardware IOTLB flush operation as opposed
1615 to batching them for performance.
1616 sp_off [Default Off]
1617 By default, super page will be supported if Intel IOMMU
1618 has the capability. With this option, super page will
1620 ecs_off [Default Off]
1621 By default, extended context tables will be supported if
1622 the hardware advertises that it has support both for the
1623 extended tables themselves, and also PASID support. With
1624 this option set, extended tables will not be used even
1625 on hardware which claims to support them.
1627 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1628 0 disables intel_idle and fall back on acpi_idle.
1629 1 to 6 specify maximum depth of C-state.
1633 Do not enable intel_pstate as the default
1634 scaling driver for the supported processors
1636 Enable intel_pstate on systems that prohibit it by default
1637 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1638 instead of acpi-cpufreq may disable platform features, such
1639 as thermal controls and power capping, that rely on ACPI
1640 P-States information being indicated to OSPM and therefore
1641 should be used with caution. This option does not work with
1642 processors that aren't supported by the intel_pstate driver
1643 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1645 Do not enable hardware P state control (HWP)
1648 Only load intel_pstate on systems which support
1649 hardware P state control (HWP) if available.
1651 intremap= [X86-64, Intel-IOMMU]
1652 on enable Interrupt Remapping (default)
1653 off disable Interrupt Remapping
1654 nosid disable Source ID checking
1656 BIOS x2APIC opt-out request will be ignored
1657 nopost disable Interrupt Posting
1659 iomem= Disable strict checking of access to MMIO memory
1660 strict regions from userspace.
1675 nobypass [PPC/POWERNV]
1676 Disable IOMMU bypass, using IOMMU for PCI devices.
1679 io7= [HW] IO7 for Marvel based alpha systems
1680 See comment before marvel_specify_io7 in
1681 arch/alpha/kernel/core_marvel.c.
1683 io_delay= [X86] I/O delay method
1685 Standard port 0x80 based delay
1687 Alternate port 0xed based delay (needed on some systems)
1689 Simple two microseconds delay
1694 See Documentation/filesystems/nfs/nfsroot.txt.
1697 When an interrupt is not handled search all handlers
1698 for it. Intended to get systems with badly broken
1702 When an interrupt is not handled search all handlers
1703 for it. Also check all handlers each timer
1704 interrupt. Intended to get systems with badly broken
1708 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1710 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1712 <cpu number>,...,<cpu number>
1714 <cpu number>-<cpu number>
1715 (must be a positive range in ascending order)
1717 <cpu number>,...,<cpu number>-<cpu number>
1719 This option can be used to specify one or more CPUs
1720 to isolate from the general SMP balancing and scheduling
1721 algorithms. You can move a process onto or off an
1722 "isolated" CPU via the CPU affinity syscalls or cpuset.
1723 <cpu number> begins at 0 and the maximum value is
1724 "number of CPUs in system - 1".
1726 This option is the preferred way to isolate CPUs. The
1727 alternative -- manually setting the CPU mask of all
1728 tasks in the system -- can cause problems and
1729 suboptimal load balancer performance.
1733 ivrs_ioapic [HW,X86_64]
1734 Provide an override to the IOAPIC-ID<->DEVICE-ID
1735 mapping provided in the IVRS ACPI table. For
1736 example, to map IOAPIC-ID decimal 10 to
1737 PCI device 00:14.0 write the parameter as:
1738 ivrs_ioapic[10]=00:14.0
1740 ivrs_hpet [HW,X86_64]
1741 Provide an override to the HPET-ID<->DEVICE-ID
1742 mapping provided in the IVRS ACPI table. For
1743 example, to map HPET-ID decimal 0 to
1744 PCI device 00:14.0 write the parameter as:
1745 ivrs_hpet[0]=00:14.0
1747 js= [HW,JOY] Analog joystick
1748 See Documentation/input/joystick.txt.
1751 Enable/disable kernel and module base offset ASLR
1752 (Address Space Layout Randomization) if built into
1753 the kernel. When CONFIG_HIBERNATION is selected,
1754 kASLR is disabled by default. When kASLR is enabled,
1755 hibernation will be disabled.
1759 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1760 specifies the amount of memory usable by the kernel
1761 for non-movable allocations. The requested amount is
1762 spread evenly throughout all nodes in the system. The
1763 remaining memory in each node is used for Movable
1764 pages. In the event, a node is too small to have both
1765 kernelcore and Movable pages, kernelcore pages will
1766 take priority and other nodes will have a larger number
1767 of Movable pages. The Movable zone is used for the
1768 allocation of pages that may be reclaimed or moved
1769 by the page migration subsystem. This means that
1770 HugeTLB pages may not be allocated from this zone.
1771 Note that allocations like PTEs-from-HighMem still
1772 use the HighMem zone if it exists, and the Normal
1773 zone if it does not.
1775 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1776 Format: <Controller#>[,poll interval]
1777 The controller # is the number of the ehci usb debug
1778 port as it is probed via PCI. The poll interval is
1779 optional and is the number seconds in between
1780 each poll cycle to the debug port in case you need
1781 the functionality for interrupting the kernel with
1782 gdb or control-c on the dbgp connection. When
1783 not using this parameter you use sysrq-g to break into
1784 the kernel debugger.
1786 kgdboc= [KGDB,HW] kgdb over consoles.
1787 Requires a tty driver that supports console polling,
1788 or a supported polling keyboard driver (non-usb).
1789 Serial only format: <serial_device>[,baud]
1790 keyboard only format: kbd
1791 keyboard and serial format: kbd,<serial_device>[,baud]
1792 Optional Kernel mode setting:
1793 kms, kbd format: kms,kbd
1794 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1796 kgdbwait [KGDB] Stop kernel execution and enter the
1797 kernel debugger at the earliest opportunity.
1799 kmac= [MIPS] korina ethernet MAC address.
1800 Configure the RouterBoard 532 series on-chip
1801 Ethernet adapter MAC address.
1803 kmemleak= [KNL] Boot-time kmemleak enable/disable
1804 Valid arguments: on, off
1806 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1809 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1810 Valid arguments: 0, 1, 2
1811 kmemcheck=0 (disabled)
1812 kmemcheck=1 (enabled)
1813 kmemcheck=2 (one-shot mode)
1814 Default: 2 (one-shot mode)
1816 kstack=N [X86] Print N words from the kernel stack
1819 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1820 Default is 0 (don't ignore, but inject #GP)
1822 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1826 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1827 Default is 1 (enabled)
1829 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1831 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1833 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1834 (virtualized MMU) support on capable Intel chips.
1835 Default is 1 (enabled)
1837 kvm-intel.emulate_invalid_guest_state=
1838 [KVM,Intel] Enable emulation of invalid guest states
1839 Default is 0 (disabled)
1841 kvm-intel.flexpriority=
1842 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1843 Default is 1 (enabled)
1846 [KVM,Intel] Enable VMX nesting (nVMX).
1847 Default is 0 (disabled)
1849 kvm-intel.unrestricted_guest=
1850 [KVM,Intel] Disable unrestricted guest feature
1851 (virtualized real and unpaged mode) on capable
1852 Intel chips. Default is 1 (enabled)
1854 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1855 feature (tagged TLBs) on capable Intel chips.
1856 Default is 1 (enabled)
1862 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1865 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1866 value for LAPIC timer one-shot implementation. Default
1867 back to the programmable timer unit in the LAPIC.
1869 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1872 libata.dma= [LIBATA] DMA control
1873 libata.dma=0 Disable all PATA and SATA DMA
1874 libata.dma=1 PATA and SATA Disk DMA only
1875 libata.dma=2 ATAPI (CDROM) DMA only
1876 libata.dma=4 Compact Flash DMA only
1877 Combinations also work, so libata.dma=3 enables DMA
1878 for disks and CDROMs, but not CFs.
1880 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1881 libata.ignore_hpa=0 keep BIOS limits (default)
1882 libata.ignore_hpa=1 ignore limits, using full disk
1884 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1888 libata.force= [LIBATA] Force configurations. The format is comma
1889 separated list of "[ID:]VAL" where ID is
1890 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1891 matching port, link or device. Basically, it matches
1892 the ATA ID string printed on console by libata. If
1893 the whole ID part is omitted, the last PORT and DEVICE
1894 values are used. If ID hasn't been specified yet, the
1895 configuration applies to all ports, links and devices.
1897 If only DEVICE is omitted, the parameter applies to
1898 the port and all links and devices behind it. DEVICE
1899 number of 0 either selects the first device or the
1900 first fan-out link behind PMP device. It does not
1901 select the host link. DEVICE number of 15 selects the
1902 host link and device attached to it.
1904 The VAL specifies the configuration to force. As long
1905 as there's no ambiguity shortcut notation is allowed.
1906 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1907 The following configurations can be forced.
1909 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1910 Any ID with matching PORT is used.
1912 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1914 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1915 udma[/][16,25,33,44,66,100,133] notation is also
1918 * [no]ncq: Turn on or off NCQ.
1920 * [no]ncqtrim: Turn off queued DSM TRIM.
1922 * nohrst, nosrst, norst: suppress hard, soft
1925 * rstonce: only attempt one reset during
1926 hot-unplug link recovery
1928 * dump_id: dump IDENTIFY data.
1930 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1932 * disable: Disable this device.
1934 If there are multiple matching configurations changing
1935 the same attribute, the last one is used.
1937 memblock=debug [KNL] Enable memblock debug messages.
1939 load_ramdisk= [RAM] List of ramdisks to load from floppy
1940 See Documentation/blockdev/ramdisk.txt.
1942 lockd.nlm_grace_period=P [NFS] Assign grace period.
1945 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1948 lockd.nlm_timeout=T [NFS] Assign timeout value.
1951 lockd.nlm_udpport=M [NFS] Assign UDP port.
1954 locktorture.nreaders_stress= [KNL]
1955 Set the number of locking read-acquisition kthreads.
1956 Defaults to being automatically set based on the
1957 number of online CPUs.
1959 locktorture.nwriters_stress= [KNL]
1960 Set the number of locking write-acquisition kthreads.
1962 locktorture.onoff_holdoff= [KNL]
1963 Set time (s) after boot for CPU-hotplug testing.
1965 locktorture.onoff_interval= [KNL]
1966 Set time (s) between CPU-hotplug operations, or
1967 zero to disable CPU-hotplug testing.
1969 locktorture.shuffle_interval= [KNL]
1970 Set task-shuffle interval (jiffies). Shuffling
1971 tasks allows some CPUs to go into dyntick-idle
1972 mode during the locktorture test.
1974 locktorture.shutdown_secs= [KNL]
1975 Set time (s) after boot system shutdown. This
1976 is useful for hands-off automated testing.
1978 locktorture.stat_interval= [KNL]
1979 Time (s) between statistics printk()s.
1981 locktorture.stutter= [KNL]
1982 Time (s) to stutter testing, for example,
1983 specifying five seconds causes the test to run for
1984 five seconds, wait for five seconds, and so on.
1985 This tests the locking primitive's ability to
1986 transition abruptly to and from idle.
1988 locktorture.torture_runnable= [BOOT]
1989 Start locktorture running at boot time.
1991 locktorture.torture_type= [KNL]
1992 Specify the locking implementation to test.
1994 locktorture.verbose= [KNL]
1995 Enable additional printk() statements.
1997 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2000 loglevel= All Kernel Messages with a loglevel smaller than the
2001 console loglevel will be printed to the console. It can
2002 also be changed with klogd or other programs. The
2003 loglevels are defined as follows:
2005 0 (KERN_EMERG) system is unusable
2006 1 (KERN_ALERT) action must be taken immediately
2007 2 (KERN_CRIT) critical conditions
2008 3 (KERN_ERR) error conditions
2009 4 (KERN_WARNING) warning conditions
2010 5 (KERN_NOTICE) normal but significant condition
2011 6 (KERN_INFO) informational
2012 7 (KERN_DEBUG) debug-level messages
2014 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2015 in bytes. n must be a power of two and greater
2016 than the minimal size. The minimal size is defined
2017 by LOG_BUF_SHIFT kernel config parameter. There is
2018 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2019 that allows to increase the default size depending on
2020 the number of CPUs. See init/Kconfig for more details.
2022 logo.nologo [FB] Disables display of the built-in Linux logo.
2023 This may be used to provide more screen space for
2024 kernel log messages and is useful when debugging
2025 kernel boot problems.
2027 lp=0 [LP] Specify parallel ports to use, e.g,
2028 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2029 lp=reset first parallel port). 'lp=0' disables the
2030 lp=auto printer driver. 'lp=reset' (which can be
2031 specified in addition to the ports) causes
2032 attached printers to be reset. Using
2033 lp=port1,port2,... specifies the parallel ports
2034 to associate lp devices with, starting with
2035 lp0. A port specification may be 'none' to skip
2036 that lp device, or a parport name such as
2037 'parport0'. Specifying 'lp=auto' instead of a
2038 port specification list means that device IDs
2039 from each port should be examined, to see if
2040 an IEEE 1284-compliant printer is attached; if
2041 so, the driver will manage that printer.
2042 See also header of drivers/char/lp.c.
2045 Sets loops_per_jiffy to given constant, thus avoiding
2046 time-consuming boot-time autodetection (up to 250 ms per
2047 CPU). 0 enables autodetection (default). To determine
2048 the correct value for your kernel, boot with normal
2049 autodetection and see what value is printed. Note that
2050 on SMP systems the preset will be applied to all CPUs,
2051 which is likely to cause problems if your CPUs need
2052 significantly divergent settings. An incorrect value
2053 will cause delays in the kernel to be wrong, leading to
2054 unpredictable I/O errors and other breakage. Although
2055 unlikely, in the extreme case this might damage your
2059 Format: <io>,<irq>,<dma>
2061 machvec= [IA-64] Force the use of a particular machine-vector
2062 (machvec) in a generic kernel.
2063 Example: machvec=hpzx1_swiotlb
2065 machtype= [Loongson] Share the same kernel image file between different
2067 Example: machtype=lemote-yeeloong-2f-7inch
2069 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2070 than or equal to this physical address is ignored.
2072 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2073 should make use of. maxcpus=n : n >= 0 limits the
2074 kernel to using 'n' processors. n=0 is a special case,
2075 it is equivalent to "nosmp", which also disables
2078 max_loop= [LOOP] The number of loop block devices that get
2079 (loop.max_loop) unconditionally pre-created at init time. The default
2080 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2081 of statically allocating a predefined number, loop
2082 devices can be requested on-demand with the
2083 /dev/loop-control interface.
2085 mce [X86-32] Machine Check Exception
2087 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2089 md= [HW] RAID subsystems devices and level
2090 See Documentation/md.txt.
2093 Format: <first>,<last>
2094 Specifies range of consoles to be captured by the MDA.
2096 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2097 Amount of memory to be used when the kernel is not able
2098 to see the whole system memory or for test.
2099 [X86] Work as limiting max address. Use together
2100 with memmap= to avoid physical address space collisions.
2101 Without memmap= PCI devices could be placed at addresses
2102 belonging to unused RAM.
2104 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2108 [KNL,SH] Allow user to override the default size for
2109 per-device physically contiguous DMA buffers.
2111 memmap=exactmap [KNL,X86] Enable setting of an exact
2112 E820 memory map, as specified by the user.
2113 Such memmap=exactmap lines can be constructed based on
2114 BIOS output or other requirements. See the memmap=nn@ss
2117 memmap=nn[KMG]@ss[KMG]
2118 [KNL] Force usage of a specific region of memory.
2119 Region of memory to be used is from ss to ss+nn.
2121 memmap=nn[KMG]#ss[KMG]
2122 [KNL,ACPI] Mark specific memory as ACPI data.
2123 Region of memory to be marked is from ss to ss+nn.
2125 memmap=nn[KMG]$ss[KMG]
2126 [KNL,ACPI] Mark specific memory as reserved.
2127 Region of memory to be reserved is from ss to ss+nn.
2128 Example: Exclude memory from 0x18690000-0x1869ffff
2129 memmap=64K$0x18690000
2131 memmap=0x10000$0x18690000
2133 memmap=nn[KMG]!ss[KMG]
2134 [KNL,X86] Mark specific memory as protected.
2135 Region of memory to be used, from ss to ss+nn.
2136 The memory region may be marked as e820 type 12 (0xc)
2137 and is NVDIMM or ADR memory.
2139 memory_corruption_check=0/1 [X86]
2140 Some BIOSes seem to corrupt the first 64k of
2141 memory when doing things like suspend/resume.
2142 Setting this option will scan the memory
2143 looking for corruption. Enabling this will
2144 both detect corruption and prevent the kernel
2145 from using the memory being corrupted.
2146 However, its intended as a diagnostic tool; if
2147 repeatable BIOS-originated corruption always
2148 affects the same memory, you can use memmap=
2149 to prevent the kernel from using that memory.
2151 memory_corruption_check_size=size [X86]
2152 By default it checks for corruption in the low
2153 64k, making this memory unavailable for normal
2154 use. Use this parameter to scan for
2155 corruption in more or less memory.
2157 memory_corruption_check_period=seconds [X86]
2158 By default it checks for corruption every 60
2159 seconds. Use this parameter to check at some
2160 other rate. 0 disables periodic checking.
2162 memtest= [KNL,X86,ARM] Enable memtest
2164 default : 0 <disable>
2165 Specifies the number of memtest passes to be
2166 performed. Each pass selects another test
2167 pattern from a given set of patterns. Memtest
2168 fills the memory with this pattern, validates
2169 memory contents and reserves bad memory
2170 regions that are detected.
2172 meye.*= [HW] Set MotionEye Camera parameters
2173 See Documentation/video4linux/meye.txt.
2175 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2176 Multi-Function General Purpose Timers on AMD Geode
2179 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2180 the BIOS has incorrectly applied a workaround. TinyBIOS
2181 version 0.98 is known to be affected, 0.99 fixes the
2182 problem by letting the user disable the workaround.
2186 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2187 physical address is ignored.
2189 mini2440= [ARM,HW,KNL]
2190 Format:[0..2][b][c][t]
2192 MINI2440 configuration specification:
2193 0 - The attached screen is the 3.5" TFT
2194 1 - The attached screen is the 7" TFT
2195 2 - The VGA Shield is attached (1024x768)
2196 Leaving out the screen size parameter will not load
2197 the TFT driver, and the framebuffer will be left
2199 b - Enable backlight. The TFT backlight pin will be
2200 linked to the kernel VESA blanking code and a GPIO
2201 LED. This parameter is not necessary when using the
2203 c - Enable the s3c camera interface.
2204 t - Reserved for enabling touchscreen support. The
2205 touchscreen support is not enabled in the mainstream
2206 kernel as of 2.6.30, a preliminary port can be found
2207 in the "bleeding edge" mini2440 support kernel at
2208 http://repo.or.cz/w/linux-2.6/mini2440.git
2211 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2212 parameter allows control of the logging verbosity for
2213 the additional memory initialisation checks. A value
2214 of 0 disables mminit logging and a level of 4 will
2215 log everything. Information is printed at KERN_DEBUG
2216 so loglevel=8 may also need to be specified.
2219 [KNL] When CONFIG_MODULE_SIG is set, this means that
2220 modules without (valid) signatures will fail to load.
2221 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2222 is always true, so this option does nothing.
2225 [MOUSE] Maximum time between finger touching and
2226 leaving touchpad surface for touch to be considered
2227 a tap and be reported as a left button click (for
2228 touchpads working in absolute mode only).
2230 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2231 reporting absolute coordinates, such as tablets
2232 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2233 reporting absolute coordinates, such as tablets
2235 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2236 is similar to kernelcore except it specifies the
2237 amount of memory used for migratable allocations.
2238 If both kernelcore and movablecore is specified,
2239 then kernelcore will be at *least* the specified
2240 value but may be more. If movablecore on its own
2241 is specified, the administrator must be careful
2242 that the amount of memory usable for all allocations
2245 movable_node [KNL,X86] Boot-time switch to enable the effects
2246 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2248 MTD_Partition= [MTD]
2249 Format: <name>,<region-number>,<size>,<offset>
2251 MTD_Region= [MTD] Format:
2252 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2255 See drivers/mtd/cmdlinepart.c.
2257 multitce=off [PPC] This parameter disables the use of the pSeries
2258 firmware feature for updating multiple TCE entries
2261 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2263 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2265 boundary - index of last SLC block on Flex-OneNAND.
2266 The remaining blocks are configured as MLC blocks.
2267 lock - Configure if Flex-OneNAND boundary should be locked.
2268 Once locked, the boundary cannot be changed.
2269 1 indicates lock status, 0 indicates unlock status.
2272 ARM/S3C2412 JIVE boot control
2274 See arch/arm/mach-s3c2412/mach-jive.c
2276 mtouchusb.raw_coordinates=
2277 [HW] Make the MicroTouch USB driver use raw coordinates
2278 ('y', default) or cooked coordinates ('n')
2280 mtrr_chunk_size=nn[KMG] [X86]
2281 used for mtrr cleanup. It is largest continuous chunk
2282 that could hold holes aka. UC entries.
2284 mtrr_gran_size=nn[KMG] [X86]
2285 Used for mtrr cleanup. It is granularity of mtrr block.
2287 Large value could prevent small alignment from
2290 mtrr_spare_reg_nr=n [X86]
2292 Range: 0,7 : spare reg number
2294 Used for mtrr cleanup. It is spare mtrr entries number.
2295 Set to 2 or more if your graphical card needs more.
2297 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2299 netdev= [NET] Network devices parameters
2300 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2301 Note that mem_start is often overloaded to mean
2302 something different and driver-specific.
2303 This usage is only documented in each driver source
2307 [NETFILTER] Enable connection tracking flow accounting
2308 0 to disable accounting
2309 1 to enable accounting
2312 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2313 See Documentation/filesystems/nfs/nfsroot.txt.
2315 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2316 See Documentation/filesystems/nfs/nfsroot.txt.
2318 nfsrootdebug [NFS] enable nfsroot debugging messages.
2319 See Documentation/filesystems/nfs/nfsroot.txt.
2321 nfs.callback_tcpport=
2322 [NFS] set the TCP port on which the NFSv4 callback
2323 channel should listen.
2326 [NFS] sets the pathname to the program which is used
2327 to update the NFS client cache entries.
2329 nfs.cache_getent_timeout=
2330 [NFS] sets the timeout after which an attempt to
2331 update a cache entry is deemed to have failed.
2333 nfs.idmap_cache_timeout=
2334 [NFS] set the maximum lifetime for idmapper cache
2338 [NFS] enable 64-bit inode numbers.
2339 If zero, the NFS client will fake up a 32-bit inode
2340 number for the readdir() and stat() syscalls instead
2341 of returning the full 64-bit number.
2342 The default is to return 64-bit inode numbers.
2344 nfs.max_session_slots=
2345 [NFSv4.1] Sets the maximum number of session slots
2346 the client will attempt to negotiate with the server.
2347 This limits the number of simultaneous RPC requests
2348 that the client can send to the NFSv4.1 server.
2349 Note that there is little point in setting this
2350 value higher than the max_tcp_slot_table_limit.
2352 nfs.nfs4_disable_idmapping=
2353 [NFSv4] When set to the default of '1', this option
2354 ensures that both the RPC level authentication
2355 scheme and the NFS level operations agree to use
2356 numeric uids/gids if the mount is using the
2357 'sec=sys' security flavour. In effect it is
2358 disabling idmapping, which can make migration from
2359 legacy NFSv2/v3 systems to NFSv4 easier.
2360 Servers that do not support this mode of operation
2361 will be autodetected by the client, and it will fall
2362 back to using the idmapper.
2363 To turn off this behaviour, set the value to '0'.
2365 [NFS4] Specify an additional fixed unique ident-
2366 ification string that NFSv4 clients can insert into
2367 their nfs_client_id4 string. This is typically a
2368 UUID that is generated at system install time.
2370 nfs.send_implementation_id =
2371 [NFSv4.1] Send client implementation identification
2372 information in exchange_id requests.
2373 If zero, no implementation identification information
2375 The default is to send the implementation identification
2378 nfs.recover_lost_locks =
2379 [NFSv4] Attempt to recover locks that were lost due
2380 to a lease timeout on the server. Please note that
2381 doing this risks data corruption, since there are
2382 no guarantees that the file will remain unchanged
2383 after the locks are lost.
2384 If you want to enable the kernel legacy behaviour of
2385 attempting to recover these locks, then set this
2387 The default parameter value of '0' causes the kernel
2388 not to attempt recovery of lost locks.
2390 nfs4.layoutstats_timer =
2391 [NFSv4.2] Change the rate at which the kernel sends
2392 layoutstats to the pNFS metadata server.
2394 Setting this to value to 0 causes the kernel to use
2395 whatever value is the default set by the layout
2396 driver. A non-zero value sets the minimum interval
2397 in seconds between layoutstats transmissions.
2399 nfsd.nfs4_disable_idmapping=
2400 [NFSv4] When set to the default of '1', the NFSv4
2401 server will return only numeric uids and gids to
2402 clients using auth_sys, and will accept numeric uids
2403 and gids from such clients. This is intended to ease
2404 migration from NFSv2/v3.
2406 objlayoutdriver.osd_login_prog=
2407 [NFS] [OBJLAYOUT] sets the pathname to the program which
2408 is used to automatically discover and login into new
2409 osd-targets. Please see:
2410 Documentation/filesystems/pnfs.txt for more explanations
2412 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2413 when a NMI is triggered.
2414 Format: [state][,regs][,debounce][,die]
2416 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2417 Format: [panic,][nopanic,][num]
2419 0 - turn hardlockup detector in nmi_watchdog off
2420 1 - turn hardlockup detector in nmi_watchdog on
2421 When panic is specified, panic when an NMI watchdog
2422 timeout occurs (or 'nopanic' to override the opposite
2423 default). To disable both hard and soft lockup detectors,
2424 please see 'nowatchdog'.
2425 This is useful when you use a panic=... timeout and
2426 need the box quickly up again.
2428 netpoll.carrier_timeout=
2429 [NET] Specifies amount of time (in seconds) that
2430 netpoll should wait for a carrier. By default netpoll
2433 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2434 emulation library even if a 387 maths coprocessor
2438 [HW] Never suspend the console
2439 Disable suspending of consoles during suspend and
2440 hibernate operations. Once disabled, debugging
2441 messages can reach various consoles while the rest
2442 of the system is being put to sleep (ie, while
2443 debugging driver suspend/resume hooks). This may
2444 not work reliably with all consoles, but is known
2445 to work with serial and VGA consoles.
2446 To facilitate more flexible debugging, we also add
2447 console_suspend, a printk module parameter to control
2448 it. Users could use console_suspend (usually
2449 /sys/module/printk/parameters/console_suspend) to
2450 turn on/off it dynamically.
2452 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2453 caches in the slab allocator. Saves per-node memory,
2454 but will impact performance.
2458 noapic [SMP,APIC] Tells the kernel to not make use of any
2459 IOAPICs that may be present in the system.
2461 noautogroup Disable scheduler automatic task group creation.
2463 nobats [PPC] Do not use BATs for mapping kernel lowmem
2464 on "Classic" PPC cores.
2468 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2470 nodelayacct [KNL] Disable per-task delay accounting
2472 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2474 nodsp [SH] Disable hardware DSP at boot time.
2476 noefi Disable EFI runtime services support.
2481 On X86-32 available only on PAE configured kernels.
2482 noexec=on: enable non-executable mappings (default)
2483 noexec=off: disable non-executable mappings
2486 Disable SMAP (Supervisor Mode Access Prevention)
2487 even if it is supported by processor.
2490 Disable SMEP (Supervisor Mode Execution Prevention)
2491 even if it is supported by processor.
2494 This affects only 32-bit executables.
2495 noexec32=on: enable non-executable mappings (default)
2496 read doesn't imply executable mappings
2497 noexec32=off: disable non-executable mappings
2498 read implies executable mappings
2500 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2502 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2503 register save and restore. The kernel will only save
2504 legacy floating-point registers on task switch.
2506 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2508 noxsave [BUGS=X86] Disables x86 extended register state save
2509 and restore using xsave. The kernel will fallback to
2510 enabling legacy floating-point and sse state.
2512 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2513 register states. The kernel will fall back to use
2514 xsave to save the states. By using this parameter,
2515 performance of saving the states is degraded because
2516 xsave doesn't support modified optimization while
2517 xsaveopt supports it on xsaveopt enabled systems.
2519 noxsaves [X86] Disables xsaves and xrstors used in saving and
2520 restoring x86 extended register state in compacted
2521 form of xsave area. The kernel will fall back to use
2522 xsaveopt and xrstor to save and restore the states
2523 in standard form of xsave area. By using this
2524 parameter, xsave area per process might occupy more
2525 memory on xsaves enabled systems.
2527 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2528 wfi(ARM) instruction doesn't work correctly and not to
2529 use it. This is also useful when using JTAG debugger.
2531 no_file_caps Tells the kernel not to honor file capabilities. The
2532 only way then for a file to be executed with privilege
2533 is to be setuid root or executed by root.
2535 nohalt [IA-64] Tells the kernel not to use the power saving
2536 function PAL_HALT_LIGHT when idle. This increases
2537 power-consumption. On the positive side, it reduces
2538 interrupt wake-up latency, which may improve performance
2539 in certain environments such as networked servers or
2542 nohibernate [HIBERNATION] Disable hibernation and resume.
2544 nohz= [KNL] Boottime enable/disable dynamic ticks
2545 Valid arguments: on, off
2548 nohz_full= [KNL,BOOT]
2549 In kernels built with CONFIG_NO_HZ_FULL=y, set
2550 the specified list of CPUs whose tick will be stopped
2551 whenever possible. The boot CPU will be forced outside
2552 the range to maintain the timekeeping.
2553 The CPUs in this range must also be included in the
2556 noiotrap [SH] Disables trapped I/O port accesses.
2558 noirqdebug [X86-32] Disables the code which attempts to detect and
2559 disable unhandled interrupt sources.
2561 no_timer_check [X86,APIC] Disables the code which tests for
2562 broken timer IRQ sources.
2564 noisapnp [ISAPNP] Disables ISA PnP code.
2566 noinitrd [RAM] Tells the kernel not to load any configured
2569 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2571 [Deprecated - use intremap=off]
2575 nojitter [IA-64] Disables jitter checking for ITC timers.
2577 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2579 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2582 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2583 steal time is computed, but won't influence scheduler
2586 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2588 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2590 noltlbs [PPC] Do not use large page/tlb entries for kernel
2591 lowmem mapping on PPC40x.
2593 nomca [IA-64] Disable machine check abort handling
2595 nomce [X86-32] Disable Machine Check Exception
2597 nomfgpt [X86-32] Disable Multi-Function General Purpose
2598 Timer usage (for AMD Geode machines).
2600 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2601 shutdown the other cpus. Instead use the REBOOT_VECTOR
2604 nomodule Disable module load
2606 nopat [X86] Disable PAT (page attribute table extension of
2607 pagetables) support.
2609 norandmaps Don't use address space randomization. Equivalent to
2610 echo 0 > /proc/sys/kernel/randomize_va_space
2612 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2614 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2615 with UP alternatives
2617 nordrand [X86] Disable kernel use of the RDRAND and
2618 RDSEED instructions even if they are supported
2619 by the processor. RDRAND and RDSEED are still
2620 available to user space applications.
2622 noresume [SWSUSP] Disables resume and restores original swap
2625 no-scroll [VGA] Disables scrollback.
2626 This is required for the Braillex ib80-piezo Braille
2627 reader made by F.H. Papenmeier (Germany).
2631 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2633 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2634 and disable the IO APIC. legacy for "maxcpus=0".
2636 nosoftlockup [KNL] Disable the soft-lockup detector.
2638 nosync [HW,M68K] Disables sync negotiation for all devices.
2640 notsc [BUGS=X86-32] Disable Time Stamp Counter
2642 nowatchdog [KNL] Disable both lockup detectors, i.e.
2643 soft-lockup and NMI watchdog (hard-lockup).
2647 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2649 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2650 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2651 Some features depend on CPU0. Known dependencies are:
2652 1. Resume from suspend/hibernate depends on CPU0.
2653 Suspend/hibernate will fail if CPU0 is offline and you
2654 need to online CPU0 before suspend/hibernate.
2655 2. PIC interrupts also depend on CPU0. CPU0 can't be
2656 removed if a PIC interrupt is detected.
2657 It's said poweroff/reboot may depend on CPU0 on some
2658 machines although I haven't seen such issues so far
2659 after CPU0 is offline on a few tested machines.
2660 If the dependencies are under your control, you can
2661 turn on cpu0_hotplug.
2663 nptcg= [IA-64] Override max number of concurrent global TLB
2664 purges which is reported from either PAL_VM_SUMMARY or
2667 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2668 could support. nr_cpus=n : n >= 1 limits the kernel to
2669 supporting 'n' processors. Later in runtime you can not
2670 use hotplug cpu feature to put more cpu back to online.
2671 just like you compile the kernel NR_CPUS=n
2673 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2675 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2676 Allowed values are enable and disable
2678 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2679 one of ['zone', 'node', 'default'] can be specified
2680 This can be set from sysctl after boot.
2681 See Documentation/sysctl/vm.txt for details.
2683 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2684 See Documentation/debugging-via-ohci1394.txt for more
2687 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2688 Rather than timing out after 20 ms if an EC
2689 command is not properly ACKed, override the length
2690 of the timeout. We have interrupts disabled while
2691 waiting for the ACK, so if this is set too high
2692 interrupts *may* be lost!
2694 omap_mux= [OMAP] Override bootloader pin multiplexing.
2695 Format: <mux_mode0.mode_name=value>...
2696 For example, to override I2C bus2:
2697 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2699 oprofile.timer= [HW]
2700 Use timer interrupt instead of performance counters
2702 oprofile.cpu_type= Force an oprofile cpu type
2703 This might be useful if you have an older oprofile
2704 userland or if you want common events.
2705 Format: { arch_perfmon }
2706 arch_perfmon: [X86] Force use of architectural
2707 perfmon on Intel CPUs instead of the
2708 CPU specific event set.
2709 timer: [X86] Force use of architectural NMI
2710 timer mode (see also oprofile.timer
2711 for generic hr timer mode)
2712 [s390] Force legacy basic mode sampling
2713 (report cpu_type "timer")
2715 oops=panic Always panic on oopses. Default is to just kill the
2716 process, but there is a small probability of
2717 deadlocking the machine.
2718 This will also cause panics on machine check exceptions.
2719 Useful together with panic=30 to trigger a reboot.
2722 See Documentation/sound/oss/oss-parameters.txt
2724 page_owner= [KNL] Boot-time page_owner enabling option.
2725 Storage of the information about who allocated
2726 each page is disabled in default. With this switch,
2728 on: enable the feature
2730 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2731 timeout > 0: seconds before rebooting
2732 timeout = 0: wait forever
2733 timeout < 0: reboot immediately
2736 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2739 crash_kexec_post_notifiers
2740 Run kdump after running panic-notifiers and dumping
2741 kmsg. This only for the users who doubt kdump always
2742 succeeds in any situation.
2743 Note that this also increases risks of kdump failure,
2744 because some panic notifiers can make the crashed
2745 kernel more unstable.
2747 parkbd.port= [HW] Parallel port number the keyboard adapter is
2748 connected to, default is 0.
2750 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2751 0 for XT, 1 for AT (default is AT).
2754 parport= [HW,PPT] Specify parallel ports. 0 disables.
2755 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2756 Use 'auto' to force the driver to use any
2757 IRQ/DMA settings detected (the default is to
2758 ignore detected IRQ/DMA settings because of
2759 possible conflicts). You can specify the base
2760 address, IRQ, and DMA settings; IRQ and DMA
2761 should be numbers, or 'auto' (for using detected
2762 settings on that particular port), or 'nofifo'
2763 (to avoid using a FIFO even if it is detected).
2764 Parallel ports are assigned in the order they
2765 are specified on the command line, starting
2768 parport_init_mode= [HW,PPT]
2769 Configure VIA parallel port to operate in
2770 a specific mode. This is necessary on Pegasos
2771 computer where firmware has no options for setting
2772 up parallel port mode and sets it to spp.
2773 Currently this function knows 686a and 8231 chips.
2774 Format: [spp|ps2|epp|ecp|ecpepp]
2777 Halt all CPUs after the first oops has been printed for
2778 the specified number of seconds. This is to be used if
2779 your oopses keep scrolling off the screen.
2784 See header of drivers/block/paride/pcd.c.
2785 See also Documentation/blockdev/paride.txt.
2787 pci=option[,option...] [PCI] various PCI subsystem options:
2788 earlydump [X86] dump PCI config space before the kernel
2790 off [X86] don't probe for the PCI bus
2791 bios [X86-32] force use of PCI BIOS, don't access
2792 the hardware directly. Use this if your machine
2793 has a non-standard PCI host bridge.
2794 nobios [X86-32] disallow use of PCI BIOS, only direct
2795 hardware access methods are allowed. Use this
2796 if you experience crashes upon bootup and you
2797 suspect they are caused by the BIOS.
2798 conf1 [X86] Force use of PCI Configuration Access
2799 Mechanism 1 (config address in IO port 0xCF8,
2800 data in IO port 0xCFC, both 32-bit).
2801 conf2 [X86] Force use of PCI Configuration Access
2802 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2803 the function, IO port 0xCFA, also 8-bit, sets
2804 bus number. The config space is then accessed
2805 through ports 0xC000-0xCFFF).
2806 See http://wiki.osdev.org/PCI for more info
2807 on the configuration access mechanisms.
2808 noaer [PCIE] If the PCIEAER kernel config parameter is
2809 enabled, this kernel boot option can be used to
2810 disable the use of PCIE advanced error reporting.
2811 nodomains [PCI] Disable support for multiple PCI
2812 root domains (aka PCI segments, in ACPI-speak).
2813 nommconf [X86] Disable use of MMCONFIG for PCI
2815 check_enable_amd_mmconf [X86] check for and enable
2816 properly configured MMIO access to PCI
2817 config space on AMD family 10h CPU
2818 nomsi [MSI] If the PCI_MSI kernel config parameter is
2819 enabled, this kernel boot option can be used to
2820 disable the use of MSI interrupts system-wide.
2821 noioapicquirk [APIC] Disable all boot interrupt quirks.
2822 Safety option to keep boot IRQs enabled. This
2823 should never be necessary.
2824 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2825 primary IO-APIC for bridges that cannot disable
2826 boot IRQs. This fixes a source of spurious IRQs
2827 when the system masks IRQs.
2828 noioapicreroute [APIC] Disable workaround that uses the
2829 boot IRQ equivalent of an IRQ that connects to
2830 a chipset where boot IRQs cannot be disabled.
2831 The opposite of ioapicreroute.
2832 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2833 routing table. These calls are known to be buggy
2834 on several machines and they hang the machine
2835 when used, but on other computers it's the only
2836 way to get the interrupt routing table. Try
2837 this option if the kernel is unable to allocate
2838 IRQs or discover secondary PCI buses on your
2840 rom [X86] Assign address space to expansion ROMs.
2841 Use with caution as certain devices share
2842 address decoders between ROMs and other
2844 norom [X86] Do not assign address space to
2845 expansion ROMs that do not already have
2846 BIOS assigned address ranges.
2847 nobar [X86] Do not assign address space to the
2848 BARs that weren't assigned by the BIOS.
2849 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2850 assigned automatically to PCI devices. You can
2851 make the kernel exclude IRQs of your ISA cards
2853 pirqaddr=0xAAAAA [X86] Specify the physical address
2854 of the PIRQ table (normally generated
2855 by the BIOS) if it is outside the
2856 F0000h-100000h range.
2857 lastbus=N [X86] Scan all buses thru bus #N. Can be
2858 useful if the kernel is unable to find your
2859 secondary buses and you want to tell it
2860 explicitly which ones they are.
2861 assign-busses [X86] Always assign all PCI bus
2862 numbers ourselves, overriding
2863 whatever the firmware may have done.
2864 usepirqmask [X86] Honor the possible IRQ mask stored
2865 in the BIOS $PIR table. This is needed on
2866 some systems with broken BIOSes, notably
2867 some HP Pavilion N5400 and Omnibook XE3
2868 notebooks. This will have no effect if ACPI
2869 IRQ routing is enabled.
2870 noacpi [X86] Do not use ACPI for IRQ routing
2871 or for PCI scanning.
2872 use_crs [X86] Use PCI host bridge window information
2873 from ACPI. On BIOSes from 2008 or later, this
2874 is enabled by default. If you need to use this,
2875 please report a bug.
2876 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2877 If you need to use this, please report a bug.
2878 routeirq Do IRQ routing for all PCI devices.
2879 This is normally done in pci_enable_device(),
2880 so this option is a temporary workaround
2881 for broken drivers that don't call it.
2882 skip_isa_align [X86] do not align io start addr, so can
2883 handle more pci cards
2884 firmware [ARM] Do not re-enumerate the bus but instead
2885 just use the configuration from the
2886 bootloader. This is currently used on
2887 IXP2000 systems where the bus has to be
2888 configured a certain way for adjunct CPUs.
2889 noearly [X86] Don't do any early type 1 scanning.
2890 This might help on some broken boards which
2891 machine check when some devices' config space
2892 is read. But various workarounds are disabled
2893 and some IOMMU drivers will not work.
2894 bfsort Sort PCI devices into breadth-first order.
2895 This sorting is done to get a device
2896 order compatible with older (<= 2.4) kernels.
2897 nobfsort Don't sort PCI devices into breadth-first order.
2898 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2899 tuning and use the BIOS-configured MPS defaults.
2900 pcie_bus_safe Set every device's MPS to the largest value
2901 supported by all devices below the root complex.
2902 pcie_bus_perf Set device MPS to the largest allowable MPS
2903 based on its parent bus. Also set MRRS (Max
2904 Read Request Size) to the largest supported
2905 value (no larger than the MPS that the device
2906 or bus can support) for best performance.
2907 pcie_bus_peer2peer Set every device's MPS to 128B, which
2908 every device is guaranteed to support. This
2909 configuration allows peer-to-peer DMA between
2910 any pair of devices, possibly at the cost of
2911 reduced performance. This also guarantees
2912 that hot-added devices will work.
2913 cbiosize=nn[KMG] The fixed amount of bus space which is
2914 reserved for the CardBus bridge's IO window.
2915 The default value is 256 bytes.
2916 cbmemsize=nn[KMG] The fixed amount of bus space which is
2917 reserved for the CardBus bridge's memory
2918 window. The default value is 64 megabytes.
2921 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2922 Specifies alignment and device to reassign
2923 aligned memory resources.
2924 If <order of align> is not specified,
2925 PAGE_SIZE is used as alignment.
2926 PCI-PCI bridge can be specified, if resource
2927 windows need to be expanded.
2928 ecrc= Enable/disable PCIe ECRC (transaction layer
2929 end-to-end CRC checking).
2930 bios: Use BIOS/firmware settings. This is the
2934 hpiosize=nn[KMG] The fixed amount of bus space which is
2935 reserved for hotplug bridge's IO window.
2936 Default size is 256 bytes.
2937 hpmemsize=nn[KMG] The fixed amount of bus space which is
2938 reserved for hotplug bridge's memory window.
2939 Default size is 2 megabytes.
2940 realloc= Enable/disable reallocating PCI bridge resources
2941 if allocations done by BIOS are too small to
2942 accommodate resources required by all child
2944 off: Turn realloc off
2946 realloc same as realloc=on
2947 noari do not use PCIe ARI.
2948 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2949 only look for one device below a PCIe downstream
2952 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2955 force Enable ASPM even on devices that claim not to support it.
2956 WARNING: Forcing ASPM on may cause system lockups.
2958 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2959 nomsi Do not use MSI for PCI Express Native Hotplug (this
2960 makes all PCIe ports use INTx for hotplug services).
2962 pcie_ports= [PCIE] PCIe ports handling:
2963 auto Ask the BIOS whether or not to use native PCIe services
2964 associated with PCIe ports (PME, hot-plug, AER). Use
2965 them only if that is allowed by the BIOS.
2966 native Use native PCIe services associated with PCIe ports
2968 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2971 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2972 nomsi Do not use MSI for native PCIe PME signaling (this makes
2973 all PCIe root ports use INTx for all services).
2975 pcmv= [HW,PCMCIA] BadgePAD 4
2979 Keep all power-domains already enabled by bootloader on,
2980 even if no driver has claimed them. This is useful
2981 for debug and development, but should not be
2982 needed on a platform with proper driver support.
2985 See Documentation/blockdev/paride.txt.
2987 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2990 See arch/parisc/kernel/pdc_chassis.c
2992 percpu_alloc= Select which percpu first chunk allocator to use.
2993 Currently supported values are "embed" and "page".
2994 Archs may support subset or none of the selections.
2995 See comments in mm/percpu.c for details on each
2996 allocator. This parameter is primarily for debugging
2997 and performance comparison.
3000 See Documentation/blockdev/paride.txt.
3003 See Documentation/blockdev/paride.txt.
3005 pirq= [SMP,APIC] Manual mp-table setup
3006 See Documentation/x86/i386/IO-APIC.txt.
3008 plip= [PPT,NET] Parallel port network link
3009 Format: { parport<nr> | timid | 0 }
3010 See also Documentation/parport.txt.
3012 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3013 Override pmtimer IOPort with a hex value.
3017 Enable PNP debug messages (depends on the
3018 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3019 via /sys/module/pnp/parameters/debug. We always show
3020 current resource usage; turning this on also shows
3021 possible settings and some assignment information.
3027 { on | off | curr | res | no-curr | no-res }
3030 [ISAPNP] Exclude IRQs for the autoconfiguration
3033 [ISAPNP] Exclude DMAs for the autoconfiguration
3035 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3036 Ranges are in pairs (I/O port base and size).
3039 [ISAPNP] Exclude memory regions for the
3041 Ranges are in pairs (memory base and size).
3043 ports= [IP_VS_FTP] IPVS ftp helper module
3045 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3047 Format: <port>,<port>....
3049 ppc_strict_facility_enable
3050 [PPC] This option catches any kernel floating point,
3051 Altivec, VSX and SPE outside of regions specifically
3052 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3053 There is some performance impact when enabling this.
3055 print-fatal-signals=
3056 [KNL] debug: print fatal signals
3058 If enabled, warn about various signal handling
3059 related application anomalies: too many signals,
3060 too many POSIX.1 timers, fatal signals causing a
3063 If you hit the warning due to signal overflow,
3064 you might want to try "ulimit -i unlimited".
3068 printk.always_kmsg_dump=
3069 Trigger kmsg_dump for cases other than kernel oops or
3071 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3074 printk.time= Show timing data prefixed to each printk message line
3075 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3077 processor.max_cstate= [HW,ACPI]
3078 Limit processor to maximum C-state
3079 max_cstate=9 overrides any DMI blacklist limit.
3081 processor.nocst [HW,ACPI]
3082 Ignore the _CST method to determine C-states,
3083 instead using the legacy FADT method
3085 profile= [KNL] Enable kernel profiling via /proc/profile
3086 Format: [schedule,]<number>
3087 Param: "schedule" - profile schedule points.
3088 Param: <number> - step/bucket size as a power of 2 for
3089 statistical time based profiling.
3090 Param: "sleep" - profile D-state sleeping (millisecs).
3091 Requires CONFIG_SCHEDSTATS
3092 Param: "kvm" - profile VM exits.
3094 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3096 See Documentation/blockdev/ramdisk.txt.
3098 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3099 probe for; one of (bare|imps|exps|lifebook|any).
3100 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3102 psmouse.resetafter= [HW,MOUSE]
3103 Try to reset the device after so many bad packets
3106 [HW,MOUSE] Set desired mouse resolution, in dpi.
3107 psmouse.smartscroll=
3108 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3109 0 = disabled, 1 = enabled (default).
3111 pstore.backend= Specify the name of the pstore backend to use
3114 See Documentation/blockdev/paride.txt.
3117 [KNL] Number of legacy pty's. Overwrites compiled-in
3120 quiet [KNL] Disable most log messages
3125 See Documentation/md.txt.
3127 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3128 See Documentation/blockdev/ramdisk.txt.
3131 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3132 the specified list of CPUs to be no-callback CPUs.
3133 Invocation of these CPUs' RCU callbacks will
3134 be offloaded to "rcuox/N" kthreads created for
3135 that purpose, where "x" is "b" for RCU-bh, "p"
3136 for RCU-preempt, and "s" for RCU-sched, and "N"
3137 is the CPU number. This reduces OS jitter on the
3138 offloaded CPUs, which can be useful for HPC and
3139 real-time workloads. It can also improve energy
3140 efficiency for asymmetric multiprocessors.
3143 Rather than requiring that offloaded CPUs
3144 (specified by rcu_nocbs= above) explicitly
3145 awaken the corresponding "rcuoN" kthreads,
3146 make these kthreads poll for callbacks.
3147 This improves the real-time response for the
3148 offloaded CPUs by relieving them of the need to
3149 wake up the corresponding kthread, but degrades
3150 energy efficiency by requiring that the kthreads
3151 periodically wake up to do the polling.
3153 rcutree.blimit= [KNL]
3154 Set maximum number of finished RCU callbacks to
3155 process in one batch.
3157 rcutree.dump_tree= [KNL]
3158 Dump the structure of the rcu_node combining tree
3159 out at early boot. This is used for diagnostic
3160 purposes, to verify correct tree setup.
3162 rcutree.gp_cleanup_delay= [KNL]
3163 Set the number of jiffies to delay each step of
3164 RCU grace-period cleanup. This only has effect
3165 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3167 rcutree.gp_init_delay= [KNL]
3168 Set the number of jiffies to delay each step of
3169 RCU grace-period initialization. This only has
3170 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3173 rcutree.gp_preinit_delay= [KNL]
3174 Set the number of jiffies to delay each step of
3175 RCU grace-period pre-initialization, that is,
3176 the propagation of recent CPU-hotplug changes up
3177 the rcu_node combining tree. This only has effect
3178 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3180 rcutree.rcu_fanout_exact= [KNL]
3181 Disable autobalancing of the rcu_node combining
3182 tree. This is used by rcutorture, and might
3183 possibly be useful for architectures having high
3184 cache-to-cache transfer latencies.
3186 rcutree.rcu_fanout_leaf= [KNL]
3187 Change the number of CPUs assigned to each
3188 leaf rcu_node structure. Useful for very
3189 large systems, which will choose the value 64,
3190 and for NUMA systems with large remote-access
3191 latencies, which will choose a value aligned
3192 with the appropriate hardware boundaries.
3194 rcutree.jiffies_till_sched_qs= [KNL]
3195 Set required age in jiffies for a
3196 given grace period before RCU starts
3197 soliciting quiescent-state help from
3198 rcu_note_context_switch().
3200 rcutree.jiffies_till_first_fqs= [KNL]
3201 Set delay from grace-period initialization to
3202 first attempt to force quiescent states.
3203 Units are jiffies, minimum value is zero,
3204 and maximum value is HZ.
3206 rcutree.jiffies_till_next_fqs= [KNL]
3207 Set delay between subsequent attempts to force
3208 quiescent states. Units are jiffies, minimum
3209 value is one, and maximum value is HZ.
3211 rcutree.kthread_prio= [KNL,BOOT]
3212 Set the SCHED_FIFO priority of the RCU per-CPU
3213 kthreads (rcuc/N). This value is also used for
3214 the priority of the RCU boost threads (rcub/N)
3215 and for the RCU grace-period kthreads (rcu_bh,
3216 rcu_preempt, and rcu_sched). If RCU_BOOST is
3217 set, valid values are 1-99 and the default is 1
3218 (the least-favored priority). Otherwise, when
3219 RCU_BOOST is not set, valid values are 0-99 and
3220 the default is zero (non-realtime operation).
3222 rcutree.rcu_nocb_leader_stride= [KNL]
3223 Set the number of NOCB kthread groups, which
3224 defaults to the square root of the number of
3225 CPUs. Larger numbers reduces the wakeup overhead
3226 on the per-CPU grace-period kthreads, but increases
3227 that same overhead on each group's leader.
3229 rcutree.qhimark= [KNL]
3230 Set threshold of queued RCU callbacks beyond which
3231 batch limiting is disabled.
3233 rcutree.qlowmark= [KNL]
3234 Set threshold of queued RCU callbacks below which
3235 batch limiting is re-enabled.
3237 rcutree.rcu_idle_gp_delay= [KNL]
3238 Set wakeup interval for idle CPUs that have
3239 RCU callbacks (RCU_FAST_NO_HZ=y).
3241 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3242 Set wakeup interval for idle CPUs that have
3243 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3244 Lazy RCU callbacks are those which RCU can
3245 prove do nothing more than free memory.
3247 rcutorture.cbflood_inter_holdoff= [KNL]
3248 Set holdoff time (jiffies) between successive
3249 callback-flood tests.
3251 rcutorture.cbflood_intra_holdoff= [KNL]
3252 Set holdoff time (jiffies) between successive
3253 bursts of callbacks within a given callback-flood
3256 rcutorture.cbflood_n_burst= [KNL]
3257 Set the number of bursts making up a given
3258 callback-flood test. Set this to zero to
3259 disable callback-flood testing.
3261 rcutorture.cbflood_n_per_burst= [KNL]
3262 Set the number of callbacks to be registered
3263 in a given burst of a callback-flood test.
3265 rcutorture.fqs_duration= [KNL]
3266 Set duration of force_quiescent_state bursts
3269 rcutorture.fqs_holdoff= [KNL]
3270 Set holdoff time within force_quiescent_state bursts
3273 rcutorture.fqs_stutter= [KNL]
3274 Set wait time between force_quiescent_state bursts
3277 rcutorture.gp_cond= [KNL]
3278 Use conditional/asynchronous update-side
3279 primitives, if available.
3281 rcutorture.gp_exp= [KNL]
3282 Use expedited update-side primitives, if available.
3284 rcutorture.gp_normal= [KNL]
3285 Use normal (non-expedited) asynchronous
3286 update-side primitives, if available.
3288 rcutorture.gp_sync= [KNL]
3289 Use normal (non-expedited) synchronous
3290 update-side primitives, if available. If all
3291 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3292 rcutorture.gp_normal=, and rcutorture.gp_sync=
3293 are zero, rcutorture acts as if is interpreted
3294 they are all non-zero.
3296 rcutorture.n_barrier_cbs= [KNL]
3297 Set callbacks/threads for rcu_barrier() testing.
3299 rcutorture.nfakewriters= [KNL]
3300 Set number of concurrent RCU writers. These just
3301 stress RCU, they don't participate in the actual
3302 test, hence the "fake".
3304 rcutorture.nreaders= [KNL]
3305 Set number of RCU readers. The value -1 selects
3306 N-1, where N is the number of CPUs. A value
3307 "n" less than -1 selects N-n-2, where N is again
3308 the number of CPUs. For example, -2 selects N
3309 (the number of CPUs), -3 selects N+1, and so on.
3311 rcutorture.object_debug= [KNL]
3312 Enable debug-object double-call_rcu() testing.
3314 rcutorture.onoff_holdoff= [KNL]
3315 Set time (s) after boot for CPU-hotplug testing.
3317 rcutorture.onoff_interval= [KNL]
3318 Set time (s) between CPU-hotplug operations, or
3319 zero to disable CPU-hotplug testing.
3321 rcutorture.shuffle_interval= [KNL]
3322 Set task-shuffle interval (s). Shuffling tasks
3323 allows some CPUs to go into dyntick-idle mode
3324 during the rcutorture test.
3326 rcutorture.shutdown_secs= [KNL]
3327 Set time (s) after boot system shutdown. This
3328 is useful for hands-off automated testing.
3330 rcutorture.stall_cpu= [KNL]
3331 Duration of CPU stall (s) to test RCU CPU stall
3332 warnings, zero to disable.
3334 rcutorture.stall_cpu_holdoff= [KNL]
3335 Time to wait (s) after boot before inducing stall.
3337 rcutorture.stat_interval= [KNL]
3338 Time (s) between statistics printk()s.
3340 rcutorture.stutter= [KNL]
3341 Time (s) to stutter testing, for example, specifying
3342 five seconds causes the test to run for five seconds,
3343 wait for five seconds, and so on. This tests RCU's
3344 ability to transition abruptly to and from idle.
3346 rcutorture.test_boost= [KNL]
3347 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3348 "Maybe" means test if the RCU implementation
3349 under test support RCU priority boosting.
3351 rcutorture.test_boost_duration= [KNL]
3352 Duration (s) of each individual boost test.
3354 rcutorture.test_boost_interval= [KNL]
3355 Interval (s) between each boost test.
3357 rcutorture.test_no_idle_hz= [KNL]
3358 Test RCU's dyntick-idle handling. See also the
3359 rcutorture.shuffle_interval parameter.
3361 rcutorture.torture_runnable= [BOOT]
3362 Start rcutorture running at boot time.
3364 rcutorture.torture_type= [KNL]
3365 Specify the RCU implementation to test.
3367 rcutorture.verbose= [KNL]
3368 Enable additional printk() statements.
3370 rcupdate.rcu_cpu_stall_suppress= [KNL]
3371 Suppress RCU CPU stall warning messages.
3373 rcupdate.rcu_cpu_stall_timeout= [KNL]
3374 Set timeout for RCU CPU stall warning messages.
3376 rcupdate.rcu_expedited= [KNL]
3377 Use expedited grace-period primitives, for
3378 example, synchronize_rcu_expedited() instead
3379 of synchronize_rcu(). This reduces latency,
3380 but can increase CPU utilization, degrade
3381 real-time latency, and degrade energy efficiency.
3382 No effect on CONFIG_TINY_RCU kernels.
3384 rcupdate.rcu_normal= [KNL]
3385 Use only normal grace-period primitives,
3386 for example, synchronize_rcu() instead of
3387 synchronize_rcu_expedited(). This improves
3388 real-time latency, CPU utilization, and
3389 energy efficiency, but can expose users to
3390 increased grace-period latency. This parameter
3391 overrides rcupdate.rcu_expedited. No effect on
3392 CONFIG_TINY_RCU kernels.
3394 rcupdate.rcu_normal_after_boot= [KNL]
3395 Once boot has completed (that is, after
3396 rcu_end_inkernel_boot() has been invoked), use
3397 only normal grace-period primitives. No effect
3398 on CONFIG_TINY_RCU kernels.
3400 rcupdate.rcu_task_stall_timeout= [KNL]
3401 Set timeout in jiffies for RCU task stall warning
3402 messages. Disable with a value less than or equal
3405 rcupdate.rcu_self_test= [KNL]
3406 Run the RCU early boot self tests
3408 rcupdate.rcu_self_test_bh= [KNL]
3409 Run the RCU bh early boot self tests
3411 rcupdate.rcu_self_test_sched= [KNL]
3412 Run the RCU sched early boot self tests
3416 Run specified binary instead of /init from the ramdisk,
3417 used for early userspace startup. See initrd.
3420 Format (x86 or x86_64):
3421 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3423 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3425 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3426 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3427 reboot_force is either force or not specified,
3428 reboot_cpu is s[mp]#### with #### being the processor
3429 to be used for rebooting.
3432 [KNL, SMP] Set scheduler's default relax_domain_level.
3433 See Documentation/cgroups/cpusets.txt.
3435 relative_sleep_states=
3436 [SUSPEND] Use sleep state labeling where the deepest
3437 state available other than hibernation is always "mem".
3438 Format: { "0" | "1" }
3439 0 -- Traditional sleep state labels.
3440 1 -- Relative sleep state labels.
3442 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3444 reservetop= [X86-32]
3446 Reserves a hole at the top of the kernel virtual
3451 Set the amount of memory to reserve for BIOS at
3452 the bottom of the address space.
3454 reset_devices [KNL] Force drivers to reset the underlying device
3455 during initialization.
3458 Specify the partition device for software suspend
3460 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3462 resume_offset= [SWSUSP]
3463 Specify the offset from the beginning of the partition
3464 given by "resume=" at which the swap header is located,
3465 in <PAGE_SIZE> units (needed only for swap files).
3466 See Documentation/power/swsusp-and-swap-files.txt
3468 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3469 read the resume files
3471 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3472 Useful for devices that are detected asynchronously
3473 (e.g. USB and MMC devices).
3475 hibernate= [HIBERNATION]
3476 noresume Don't check if there's a hibernation image
3477 present during boot.
3478 nocompress Don't compress/decompress hibernation images.
3479 no Disable hibernation and resume.
3481 retain_initrd [RAM] Keep initrd memory after extraction
3483 rfkill.default_state=
3484 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3485 etc. communication is blocked by default.
3488 rfkill.master_switch_mode=
3489 0 The "airplane mode" button does nothing.
3490 1 The "airplane mode" button toggles between everything
3491 blocked and the previous configuration.
3492 2 The "airplane mode" button toggles between everything
3493 blocked and everything unblocked.
3495 rhash_entries= [KNL,NET]
3496 Set number of hash buckets for route cache
3498 ro [KNL] Mount root device read-only on boot
3500 root= [KNL] Root filesystem
3501 See name_to_dev_t comment in init/do_mounts.c.
3503 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3504 mount the root filesystem
3506 rootflags= [KNL] Set root filesystem mount option string
3508 rootfstype= [KNL] Set root filesystem type
3510 rootwait [KNL] Wait (indefinitely) for root device to show up.
3511 Useful for devices that are detected asynchronously
3512 (e.g. USB and MMC devices).
3514 rproc_mem=nn[KMG][@address]
3515 [KNL,ARM,CMA] Remoteproc physical memory block.
3516 Memory area to be used by remote processor image,
3519 rw [KNL] Mount root device read-write on boot
3521 S [KNL] Run init in single mode
3523 s390_iommu= [HW,S390]
3524 Set s390 IOTLB flushing mode
3526 With strict flushing every unmap operation will result in
3527 an IOTLB flush. Default is lazy flushing before reuse,
3531 See drivers/net/irda/sa1100_ir.c.
3533 sbni= [NET] Granch SBNI12 leased line adapter
3535 sched_debug [KNL] Enables verbose scheduler debug messages.
3537 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3538 xtime_lock contention on larger systems, and/or RCU lock
3539 contention on all systems with CONFIG_MAXSMP set.
3540 Format: { "0" | "1" }
3541 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3543 Note: increases power consumption, thus should only be
3544 enabled if running jitter sensitive (HPC/RT) workloads.
3546 security= [SECURITY] Choose a security module to enable at boot.
3547 If this boot parameter is not specified, only the first
3548 security module asking for security registration will be
3549 loaded. An invalid security module name will be treated
3550 as if no module has been chosen.
3552 selinux= [SELINUX] Disable or enable SELinux at boot time.
3553 Format: { "0" | "1" }
3554 See security/selinux/Kconfig help text.
3557 Default value is set via kernel config option.
3558 If enabled at boot time, /selinux/disable can be used
3559 later to disable prior to initial policy load.
3561 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3562 Format: { "0" | "1" }
3563 See security/apparmor/Kconfig help text
3566 Default value is set via kernel config option.
3568 serialnumber [BUGS=X86-32]
3571 Maximal number of shapers.
3573 show_msr= [x86] show boot-time MSR settings
3574 Format: { <integer> }
3575 Show boot-time (BIOS-initialized) MSR settings.
3576 The parameter means the number of CPUs to show,
3577 for example 1 means boot CPU only.
3585 Disable merging of slabs with similar size. May be
3586 necessary if there is some reason to distinguish
3587 allocs to different slabs. Debug options disable
3588 merging on their own.
3589 For more information see Documentation/vm/slub.txt.
3591 slab_max_order= [MM, SLAB]
3592 Determines the maximum allowed order for slabs.
3593 A high setting may cause OOMs due to memory
3594 fragmentation. Defaults to 1 for systems with
3595 more than 32MB of RAM, 0 otherwise.
3597 slub_debug[=options[,slabs]] [MM, SLUB]
3598 Enabling slub_debug allows one to determine the
3599 culprit if slab objects become corrupted. Enabling
3600 slub_debug can create guard zones around objects and
3601 may poison objects when not in use. Also tracks the
3602 last alloc / free. For more information see
3603 Documentation/vm/slub.txt.
3605 slub_max_order= [MM, SLUB]
3606 Determines the maximum allowed order for slabs.
3607 A high setting may cause OOMs due to memory
3608 fragmentation. For more information see
3609 Documentation/vm/slub.txt.
3611 slub_min_objects= [MM, SLUB]
3612 The minimum number of objects per slab. SLUB will
3613 increase the slab order up to slub_max_order to
3614 generate a sufficiently large slab able to contain
3615 the number of objects indicated. The higher the number
3616 of objects the smaller the overhead of tracking slabs
3617 and the less frequently locks need to be acquired.
3618 For more information see Documentation/vm/slub.txt.
3620 slub_min_order= [MM, SLUB]
3621 Determines the minimum page order for slabs. Must be
3622 lower than slub_max_order.
3623 For more information see Documentation/vm/slub.txt.
3625 slub_nomerge [MM, SLUB]
3626 Same with slab_nomerge. This is supported for legacy.
3627 See slab_nomerge for more information.
3630 Format: <io1>[,<io2>[,...,<io8>]]
3632 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3633 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3634 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3635 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3636 smsc-ircc2.ircc_irq= [HW] IRQ line
3637 smsc-ircc2.ircc_dma= [HW] DMA channel
3638 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3639 0: Toshiba Satellite 1800 (GP data pin select)
3640 1: Fast pin select (default)
3644 [KNL] Should the soft-lockup detector generate panics.
3647 softlockup_all_cpu_backtrace=
3648 [KNL] Should the soft-lockup detector generate
3649 backtraces on all cpus.
3652 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3653 See Documentation/laptops/sonypi.txt
3655 spia_io_base= [HW,MTD]
3661 Enabled the stack tracer on boot up.
3663 stacktrace_filter=[function-list]
3664 [FTRACE] Limit the functions that the stack tracer
3665 will trace at boot up. function-list is a comma separated
3666 list of functions. This list can be changed at run
3667 time by the stack_trace_filter file in the debugfs
3668 tracing directory. Note, this enables stack tracing
3669 and the stacktrace above is not needed.
3673 Set the STI (builtin display/keyboard on the HP-PARISC
3674 machines) console (graphic card) which should be used
3675 as the initial boot-console.
3676 See also comment in drivers/video/console/sticore.c.
3679 See comment in drivers/video/console/sticore.c.
3682 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3684 sunrpc.min_resvport=
3685 sunrpc.max_resvport=
3687 SunRPC servers often require that client requests
3688 originate from a privileged port (i.e. a port in the
3689 range 0 < portnr < 1024).
3690 An administrator who wishes to reserve some of these
3691 ports for other uses may adjust the range that the
3692 kernel's sunrpc client considers to be privileged
3693 using these two parameters to set the minimum and
3694 maximum port values.
3698 Control how the NFS server code allocates CPUs to
3699 service thread pools. Depending on how many NICs
3700 you have and where their interrupts are bound, this
3701 option will affect which CPUs will do NFS serving.
3702 Note: this parameter cannot be changed while the
3703 NFS server is running.
3705 auto the server chooses an appropriate mode
3706 automatically using heuristics
3707 global a single global pool contains all CPUs
3708 percpu one pool for each CPU
3709 pernode one pool for each NUMA node (equivalent
3710 to global on non-NUMA machines)
3712 sunrpc.tcp_slot_table_entries=
3713 sunrpc.udp_slot_table_entries=
3715 Sets the upper limit on the number of simultaneous
3716 RPC calls that can be sent from the client to a
3717 server. Increasing these values may allow you to
3718 improve throughput, but will also increase the
3719 amount of memory reserved for use by the client.
3721 suspend.pm_test_delay=
3723 Sets the number of seconds to remain in a suspend test
3724 mode before resuming the system (see
3725 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3726 is set. Default value is 5.
3729 [KNL] Enable accounting of swap in memory resource
3730 controller if no parameter or 1 is given or disable
3731 it if 0 is given (See Documentation/cgroups/memory.txt)
3733 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3734 Format: { <int> | force }
3735 <int> -- Number of I/O TLB slabs
3736 force -- force using of bounce buffers even if they
3737 wouldn't be automatically used by the kernel
3741 sysfs.deprecated=0|1 [KNL]
3742 Enable/disable old style sysfs layout for old udev
3743 on older distributions. When this option is enabled
3744 very new udev will not work anymore. When this option
3745 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3746 in older udev will not work anymore.
3747 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3748 the kernel configuration.
3750 sysrq_always_enabled
3752 Ignore sysrq setting - this boot parameter will
3753 neutralize any effect of /proc/sys/kernel/sysrq.
3754 Useful for debugging.
3756 tcpmhash_entries= [KNL,NET]
3757 Set the number of tcp_metrics_hash slots.
3758 Default value is 8192 or 16384 depending on total
3759 ram pages. This is used to specify the TCP metrics
3760 cache size. See Documentation/networking/ip-sysctl.txt
3761 "tcp_no_metrics_save" section for more details.
3765 test_suspend= [SUSPEND][,N]
3766 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3767 standby suspend) or "freeze" (for suspend type freeze)
3768 as the system sleep state during system startup with
3769 the optional capability to repeat N number of times.
3770 The system is woken from this state using a
3771 wakeup-capable RTC alarm.
3773 thash_entries= [KNL,NET]
3774 Set number of hash buckets for TCP connection
3776 thermal.act= [HW,ACPI]
3777 -1: disable all active trip points in all thermal zones
3778 <degrees C>: override all lowest active trip points
3780 thermal.crt= [HW,ACPI]
3781 -1: disable all critical trip points in all thermal zones
3782 <degrees C>: override all critical trip points
3784 thermal.nocrt= [HW,ACPI]
3785 Set to disable actions on ACPI thermal zone
3786 critical and hot trip points.
3788 thermal.off= [HW,ACPI]
3789 1: disable ACPI thermal control
3791 thermal.psv= [HW,ACPI]
3792 -1: disable all passive trip points
3793 <degrees C>: override all passive trip points to this
3796 thermal.tzp= [HW,ACPI]
3797 Specify global default ACPI thermal zone polling rate
3798 <deci-seconds>: poll all this frequency
3799 0: no polling (default)
3802 Force threading of all interrupt handlers except those
3803 marked explicitly IRQF_NO_THREAD.
3806 Enable the Transcendent memory driver if built-in.
3808 tmem.cleancache=0|1 [KNL, XEN]
3809 Default is on (1). Disable the usage of the cleancache
3810 API to send anonymous pages to the hypervisor.
3812 tmem.frontswap=0|1 [KNL, XEN]
3813 Default is on (1). Disable the usage of the frontswap
3814 API to send swap pages to the hypervisor. If disabled
3815 the selfballooning and selfshrinking are force disabled.
3817 tmem.selfballooning=0|1 [KNL, XEN]
3818 Default is on (1). Disable the driving of swap pages
3821 tmem.selfshrinking=0|1 [KNL, XEN]
3822 Default is on (1). Partial swapoff that immediately
3823 transfers pages from Xen hypervisor back to the
3824 kernel based on different criteria.
3828 Specify if the kernel should make use of the cpu
3829 topology information if the hardware supports this.
3830 The scheduler will make use of this information and
3831 e.g. base its process migration decisions on it.
3834 topology_updates= [KNL, PPC, NUMA]
3836 Specify if the kernel should ignore (off)
3837 topology updates sent by the hypervisor to this
3842 tpm_suspend_pcr=[HW,TPM]
3843 Format: integer pcr id
3844 Specify that at suspend time, the tpm driver
3845 should extend the specified pcr with zeros,
3846 as a workaround for some chips which fail to
3847 flush the last written pcr on TPM_SaveState.
3848 This will guarantee that all the other pcrs
3851 trace_buf_size=nn[KMG]
3852 [FTRACE] will set tracing buffer size on each cpu.
3854 trace_event=[event-list]
3855 [FTRACE] Set and start specified trace events in order
3856 to facilitate early boot debugging.
3857 See also Documentation/trace/events.txt
3859 trace_options=[option-list]
3860 [FTRACE] Enable or disable tracer options at boot.
3861 The option-list is a comma delimited list of options
3862 that can be enabled or disabled just as if you were
3863 to echo the option name into
3865 /sys/kernel/debug/tracing/trace_options
3867 For example, to enable stacktrace option (to dump the
3868 stack trace of each event), add to the command line:
3870 trace_options=stacktrace
3872 See also Documentation/trace/ftrace.txt "trace options"
3876 Have the tracepoints sent to printk as well as the
3877 tracing ring buffer. This is useful for early boot up
3878 where the system hangs or reboots and does not give the
3879 option for reading the tracing buffer or performing a
3880 ftrace_dump_on_oops.
3882 To turn off having tracepoints sent to printk,
3883 echo 0 > /proc/sys/kernel/tracepoint_printk
3884 Note, echoing 1 into this file without the
3885 tracepoint_printk kernel cmdline option has no effect.
3889 Having tracepoints sent to printk() and activating high
3890 frequency tracepoints such as irq or sched, can cause
3891 the system to live lock.
3894 [FTRACE] enable this option to disable tracing when a
3895 warning is hit. This turns off "tracing_on". Tracing can
3896 be enabled again by echoing '1' into the "tracing_on"
3897 file located in /sys/kernel/debug/tracing/
3899 This option is useful, as it disables the trace before
3900 the WARNING dump is called, which prevents the trace to
3901 be filled with content caused by the warning output.
3903 This option can also be set at run time via the sysctl
3904 option: kernel/traceoff_on_warning
3906 transparent_hugepage=
3908 Format: [always|madvise|never]
3909 Can be used to control the default behavior of the system
3910 with respect to transparent hugepages.
3911 See Documentation/vm/transhuge.txt for more details.
3913 tsc= Disable clocksource stability checks for TSC.
3915 [x86] reliable: mark tsc clocksource as reliable, this
3916 disables clocksource verification at runtime, as well
3917 as the stability checks done at bootup. Used to enable
3918 high-resolution timer mode on older hardware, and in
3919 virtualized environment.
3920 [x86] noirqtime: Do not use TSC to do irq accounting.
3921 Used to run time disable IRQ_TIME_ACCOUNTING on any
3922 platforms where RDTSC is slow and this accounting
3925 turbografx.map[2|3]= [HW,JOY]
3926 TurboGraFX parallel port interface
3928 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3929 See also Documentation/input/joystick-parport.txt
3931 udbg-immortal [PPC] When debugging early kernel crashes that
3932 happen after console_init() and before a proper
3933 console driver takes over, this boot options might
3934 help "seeing" what's going on.
3936 uhash_entries= [KNL,NET]
3937 Set number of hash buckets for UDP/UDP-Lite connections
3940 [USB] Ignore overcurrent events (default N).
3941 Some badly-designed motherboards generate lots of
3942 bogus events, for ports that aren't wired to
3943 anything. Set this parameter to avoid log spamming.
3944 Note that genuine overcurrent events won't be
3948 [X86] Cause panic on unknown NMI.
3950 usbcore.authorized_default=
3951 [USB] Default USB device authorization:
3952 (default -1 = authorized except for wireless USB,
3953 0 = not authorized, 1 = authorized)
3955 usbcore.autosuspend=
3956 [USB] The autosuspend time delay (in seconds) used
3957 for newly-detected USB devices (default 2). This
3958 is the time required before an idle device will be
3959 autosuspended. Devices for which the delay is set
3960 to a negative value won't be autosuspended at all.
3962 usbcore.usbfs_snoop=
3963 [USB] Set to log all usbfs traffic (default 0 = off).
3965 usbcore.usbfs_snoop_max=
3966 [USB] Maximum number of bytes to snoop in each URB
3969 usbcore.blinkenlights=
3970 [USB] Set to cycle leds on hubs (default 0 = off).
3972 usbcore.old_scheme_first=
3973 [USB] Start with the old device initialization
3974 scheme (default 0 = off).
3976 usbcore.usbfs_memory_mb=
3977 [USB] Memory limit (in MB) for buffers allocated by
3978 usbfs (default = 16, 0 = max = 2047).
3980 usbcore.use_both_schemes=
3981 [USB] Try the other device initialization scheme
3982 if the first one fails (default 1 = enabled).
3984 usbcore.initial_descriptor_timeout=
3985 [USB] Specifies timeout for the initial 64-byte
3986 USB_REQ_GET_DESCRIPTOR request in milliseconds
3987 (default 5000 = 5.0 seconds).
3989 usbcore.nousb [USB] Disable the USB subsystem
3992 [USBHID] The interval which mice are to be polled at.
3994 usb-storage.delay_use=
3995 [UMS] The delay in seconds before a new device is
3996 scanned for Logical Units (default 1).
3999 [UMS] A list of quirks entries to supplement or
4000 override the built-in unusual_devs list. List
4001 entries are separated by commas. Each entry has
4002 the form VID:PID:Flags where VID and PID are Vendor
4003 and Product ID values (4-digit hex numbers) and
4004 Flags is a set of characters, each corresponding
4005 to a common usb-storage quirk flag as follows:
4006 a = SANE_SENSE (collect more than 18 bytes
4008 b = BAD_SENSE (don't collect more than 18
4009 bytes of sense data);
4010 c = FIX_CAPACITY (decrease the reported
4011 device capacity by one sector);
4012 d = NO_READ_DISC_INFO (don't use
4013 READ_DISC_INFO command);
4014 e = NO_READ_CAPACITY_16 (don't use
4015 READ_CAPACITY_16 command);
4016 f = NO_REPORT_OPCODES (don't use report opcodes
4018 g = MAX_SECTORS_240 (don't transfer more than
4019 240 sectors at a time, uas only);
4020 h = CAPACITY_HEURISTICS (decrease the
4021 reported device capacity by one
4022 sector if the number is odd);
4023 i = IGNORE_DEVICE (don't bind to this
4025 l = NOT_LOCKABLE (don't try to lock and
4026 unlock ejectable media);
4027 m = MAX_SECTORS_64 (don't transfer more
4028 than 64 sectors = 32 KB at a time);
4029 n = INITIAL_READ10 (force a retry of the
4030 initial READ(10) command);
4031 o = CAPACITY_OK (accept the capacity
4032 reported by the device);
4033 p = WRITE_CACHE (the device cache is ON
4035 r = IGNORE_RESIDUE (the device reports
4036 bogus residue values);
4037 s = SINGLE_LUN (the device has only one
4039 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4040 commands, uas only);
4041 u = IGNORE_UAS (don't bind to the uas driver);
4042 w = NO_WP_DETECT (don't test whether the
4043 medium is write-protected).
4044 Example: quirks=0419:aaf5:rl,0421:0433:rc
4046 user_debug= [KNL,ARM]
4048 See arch/arm/Kconfig.debug help text.
4049 1 - undefined instruction events
4051 4 - invalid data aborts
4054 Example: user_debug=31
4057 [X86] Flags controlling user PTE allocations.
4059 nohigh = do not allocate PTE pages in
4060 HIGHMEM regardless of setting
4064 On X86_32, this is an alias for vdso32=. Otherwise:
4066 vdso=1: enable VDSO (the default)
4067 vdso=0: disable VDSO mapping
4069 vdso32= [X86] Control the 32-bit vDSO
4070 vdso32=1: enable 32-bit VDSO
4071 vdso32=0 or vdso32=2: disable 32-bit VDSO
4073 See the help text for CONFIG_COMPAT_VDSO for more
4074 details. If CONFIG_COMPAT_VDSO is set, the default is
4075 vdso32=0; otherwise, the default is vdso32=1.
4077 For compatibility with older kernels, vdso32=2 is an
4080 Try vdso32=0 if you encounter an error that says:
4081 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4084 vector=percpu: enable percpu vector domain
4086 video= [FB] Frame buffer configuration
4087 See Documentation/fb/modedb.txt.
4089 video.brightness_switch_enabled= [0,1]
4090 If set to 1, on receiving an ACPI notify event
4091 generated by hotkey, video driver will adjust brightness
4092 level and then send out the event to user space through
4093 the allocated input device; If set to 0, video driver
4094 will only send out the event without touching backlight
4099 [VMMIO] Memory mapped virtio (platform) device.
4101 <size>@<baseaddr>:<irq>[:<id>]
4103 <size> := size (can use standard suffixes
4105 <baseaddr> := physical base address
4106 <irq> := interrupt number (as passed to
4108 <id> := (optional) platform device id
4110 virtio_mmio.device=1K@0x100b0000:48:7
4112 Can be used multiple times for multiple devices.
4114 vga= [BOOT,X86-32] Select a particular video mode
4115 See Documentation/x86/boot.txt and
4116 Documentation/svga.txt.
4117 Use vga=ask for menu.
4118 This is actually a boot loader parameter; the value is
4119 passed to the kernel using a special protocol.
4121 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4122 size of <nn>. This can be used to increase the
4123 minimum size (128MB on x86). It can also be used to
4124 decrease the size and leave more room for directly
4127 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4130 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4133 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4137 Controls the behavior of vsyscalls (i.e. calls to
4138 fixed addresses of 0xffffffffff600x00 from legacy
4139 code). Most statically-linked binaries and older
4140 versions of glibc use these calls. Because these
4141 functions are at fixed addresses, they make nice
4142 targets for exploits that can control RIP.
4144 emulate [default] Vsyscalls turn into traps and are
4145 emulated reasonably safely.
4147 native Vsyscalls are native syscall instructions.
4148 This is a little bit faster than trapping
4149 and makes a few dynamic recompilers work
4150 better than they would in emulation mode.
4151 It also makes exploits much easier to write.
4153 none Vsyscalls don't work at all. This makes
4154 them quite hard to use for exploits but
4155 might break your system.
4157 vt.color= [VT] Default text color.
4158 Format: 0xYX, X = foreground, Y = background.
4159 Default: 0x07 = light gray on black.
4161 vt.cur_default= [VT] Default cursor shape.
4162 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4163 the parameters of the <Esc>[?A;B;Cc escape sequence;
4164 see VGA-softcursor.txt. Default: 2 = underline.
4166 vt.default_blu= [VT]
4167 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4168 Change the default blue palette of the console.
4169 This is a 16-member array composed of values
4172 vt.default_grn= [VT]
4173 Format: <green0>,<green1>,<green2>,...,<green15>
4174 Change the default green palette of the console.
4175 This is a 16-member array composed of values
4178 vt.default_red= [VT]
4179 Format: <red0>,<red1>,<red2>,...,<red15>
4180 Change the default red palette of the console.
4181 This is a 16-member array composed of values
4187 Set system-wide default UTF-8 mode for all tty's.
4188 Default is 1, i.e. UTF-8 mode is enabled for all
4189 newly opened terminals.
4191 vt.global_cursor_default=
4194 Set system-wide default for whether a cursor
4195 is shown on new VTs. Default is -1,
4196 i.e. cursors will be created by default unless
4197 overridden by individual drivers. 0 will hide
4198 cursors, 1 will display them.
4200 vt.italic= [VT] Default color for italic text; 0-15.
4203 vt.underline= [VT] Default color for underlined text; 0-15.
4206 watchdog timers [HW,WDT] For information on watchdog timers,
4207 see Documentation/watchdog/watchdog-parameters.txt
4208 or other driver-specific files in the
4209 Documentation/watchdog/ directory.
4211 workqueue.watchdog_thresh=
4212 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4213 warn stall conditions and dump internal state to
4214 help debugging. 0 disables workqueue stall
4215 detection; otherwise, it's the stall threshold
4216 duration in seconds. The default value is 30 and
4217 it can be updated at runtime by writing to the
4218 corresponding sysfs file.
4220 workqueue.disable_numa
4221 By default, all work items queued to unbound
4222 workqueues are affine to the NUMA nodes they're
4223 issued on, which results in better behavior in
4224 general. If NUMA affinity needs to be disabled for
4225 whatever reason, this option can be used. Note
4226 that this also can be controlled per-workqueue for
4227 workqueues visible under /sys/bus/workqueue/.
4229 workqueue.power_efficient
4230 Per-cpu workqueues are generally preferred because
4231 they show better performance thanks to cache
4232 locality; unfortunately, per-cpu workqueues tend to
4233 be more power hungry than unbound workqueues.
4235 Enabling this makes the per-cpu workqueues which
4236 were observed to contribute significantly to power
4237 consumption unbound, leading to measurably lower
4238 power usage at the cost of small performance
4241 The default value of this parameter is determined by
4242 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4244 workqueue.debug_force_rr_cpu
4245 Workqueue used to implicitly guarantee that work
4246 items queued without explicit CPU specified are put
4247 on the local CPU. This guarantee is no longer true
4248 and while local CPU is still preferred work items
4249 may be put on foreign CPUs. This debug option
4250 forces round-robin CPU selection to flush out
4251 usages which depend on the now broken guarantee.
4252 When enabled, memory and cache locality will be
4255 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4256 default x2apic cluster mode on platforms
4259 x86_intel_mid_timer= [X86-32,APBT]
4260 Choose timer option for x86 Intel MID platform.
4261 Two valid options are apbt timer only and lapic timer
4262 plus one apbt timer for broadcast timer.
4263 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4265 xen_512gb_limit [KNL,X86-64,XEN]
4266 Restricts the kernel running paravirtualized under Xen
4267 to use only up to 512 GB of RAM. The reason to do so is
4268 crash analysis tools and Xen tools for doing domain
4269 save/restore/migration must be enabled to handle larger
4272 xen_emul_unplug= [HW,X86,XEN]
4273 Unplug Xen emulated devices
4274 Format: [unplug0,][unplug1]
4275 ide-disks -- unplug primary master IDE devices
4276 aux-ide-disks -- unplug non-primary-master IDE devices
4277 nics -- unplug network devices
4278 all -- unplug all emulated devices (NICs and IDE disks)
4279 unnecessary -- unplugging emulated devices is
4280 unnecessary even if the host did not respond to
4282 never -- do not unplug even if version check succeeds
4284 xen_nopvspin [X86,XEN]
4285 Disables the ticketlock slowpath using Xen PV
4289 Disables the PV optimizations forcing the HVM guest to
4290 run as generic HVM guest with no PV drivers.
4292 xirc2ps_cs= [NET,PCMCIA]
4294 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4296 ______________________________________________________________________
4300 Add more DRM drivers.
git.samba.org / sfrench / cifs-2.6.git / blob