Merge branch 'stable-3.17' of git://git.infradead.org/users/pcmoore/selinux
[deliverable/linux.git] / Documentation / kernel-parameters.txt
1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
3
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.
9
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.
15
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.:
18
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
21
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
26 loadable modules too.
27
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
32
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
35
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}".
42
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:
47
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
135
136 In addition, the following text indicates that the option:
137
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.
141
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>.
146
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
149
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.
155
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.
161
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.
166
167
168 acpi= [HW,ACPI,X86]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
178
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
180
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
185
186 acpi_apic_instance= [ACPI, IOAPIC]
187 Format: <int>
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
190 default: 0
191
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
194 acpi_backlight=video
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
198
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
201 Format: <int>
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
212
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
222
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
226
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
230 size limitation.
231
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
234 default in APIC mode
235
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
238 default in PIC mode
239
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
242
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
244 use by PCI
245 Format: <irq>,<irq>...
246
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
254
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
264
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
272
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
275
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
281 strings
282 acpi_osi= # disable all strings
283
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
294 Examples:
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
298
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
304 meaningless.
305 Examples:
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
307 FALSE.
308
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
319 the OSPM features.
320 Examples:
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
326 equivalent to
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
328 and
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
331
332 acpi_pm_good [X86]
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
336
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
339
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
343
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
348 s3_bios and s3_mode.
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
362
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
366
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
382
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
384 kernels.
385
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
388
389 agp= [AGP]
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
394
395 ALSA [HW,ALSA]
396 See Documentation/sound/alsa/alsa-parameters.txt
397
398 alignment= [KNL,ARM]
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
402
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
410
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
415
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
422
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
425 Possible values are:
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
429 is a lot of faster
430 off - do not initialize any AMD IOMMU found in
431 the system
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
437
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
443
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
446 Format: <a>,<b>
447 See also Documentation/input/joystick.txt
448
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
453
454 apc= [HW,SPARC]
455 Power management functions (SPARCstation-4/5 + deriv.)
456 Format: noidle
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
460
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
466
467 autoconf= [IPV6]
468 See Documentation/networking/ipv6.txt.
469
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
478
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
481
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
484
485 ataflop= [HW,M68k]
486
487 atarimouse= [HW,MOUSE] Atari Mouse
488
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
491
492 atkbd.reset= [HW] Reset keyboard during initialization
493
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
496
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
498 keyboards
499
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
502
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
505
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
515 auditd.
516 Default: unset
517
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
520 Default: 64
521
522 baycom_epp= [HW,AX25]
523 Format: <io>,<mode>
524
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
526 Format: <io>,<mode>
527 See header of drivers/net/hamradio/baycom_par.c.
528
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
533
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
538
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
542
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
545 no delay (0).
546 Format: integer
547
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
549
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
552 kernel args too.
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
554 bttv.tuner=
555
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
558 at a time.
559
560 c101= [NET] Moxa C101 synchronous serial card
561
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
568
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
571 trust validation.
572 format: { id:<keyid> | builtin }
573
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
578 others).
579
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
582
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
587 a single hierarchy
588 - foo isn't visible as an individually mountable
589 subsystem
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
593
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
603
604 cio_ignore= [S390]
605 See Documentation/s390/CommonIO for details.
606 clk_ignore_unused
607 [CLK]
608 Keep all clocks already enabled by bootloader on,
609 even if no driver has claimed them. This is useful
610 for debug and development, but should not be
611 needed on a platform with proper driver support.
612 For more information, see Documentation/clk.txt.
613
614 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
615 [Deprecated]
616 Forces specified clocksource (if available) to be used
617 when calculating gettimeofday(). If specified
618 clocksource is not available, it defaults to PIT.
619 Format: { pit | tsc | cyclone | pmtmr }
620
621 clocksource= Override the default clocksource
622 Format: <string>
623 Override the default clocksource and use the clocksource
624 with the name specified.
625 Some clocksource names to choose from, depending on
626 the platform:
627 [all] jiffies (this is the base, fallback clocksource)
628 [ACPI] acpi_pm
629 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
630 pxa_timer,timer3,32k_counter,timer0_1
631 [AVR32] avr32
632 [X86-32] pit,hpet,tsc;
633 scx200_hrt on Geode; cyclone on IBM x440
634 [MIPS] MIPS
635 [PARISC] cr16
636 [S390] tod
637 [SH] SuperH
638 [SPARC64] tick
639 [X86-64] hpet,tsc
640
641 clearcpuid=BITNUM [X86]
642 Disable CPUID feature X for the kernel. See
643 arch/x86/include/asm/cpufeature.h for the valid bit
644 numbers. Note the Linux specific bits are not necessarily
645 stable over kernel options, but the vendor specific
646 ones should be.
647 Also note that user programs calling CPUID directly
648 or using the feature without checking anything
649 will still see it. This just prevents it from
650 being used by the kernel or shown in /proc/cpuinfo.
651 Also note the kernel might malfunction if you disable
652 some critical bits.
653
654 cma=nn[MG]@[start[MG][-end[MG]]]
655 [ARM,X86,KNL]
656 Sets the size of kernel global memory area for
657 contiguous memory allocations and optionally the
658 placement constraint by the physical address range of
659 memory allocations. For more information, see
660 include/linux/dma-contiguous.h
661
662 cmo_free_hint= [PPC] Format: { yes | no }
663 Specify whether pages are marked as being inactive
664 when they are freed. This is used in CMO environments
665 to determine OS memory pressure for page stealing by
666 a hypervisor.
667 Default: yes
668
669 coherent_pool=nn[KMG] [ARM,KNL]
670 Sets the size of memory pool for coherent, atomic dma
671 allocations, by default set to 256K.
672
673 code_bytes [X86] How many bytes of object code to print
674 in an oops report.
675 Range: 0 - 8192
676 Default: 64
677
678 com20020= [HW,NET] ARCnet - COM20020 chipset
679 Format:
680 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
681
682 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
683 Format: <io>[,<irq>]
684
685 com90xx= [HW,NET]
686 ARCnet - COM90xx chipset (memory-mapped buffers)
687 Format: <io>[,<irq>[,<memstart>]]
688
689 condev= [HW,S390] console device
690 conmode=
691
692 console= [KNL] Output console device and options.
693
694 tty<n> Use the virtual console device <n>.
695
696 ttyS<n>[,options]
697 ttyUSB0[,options]
698 Use the specified serial port. The options are of
699 the form "bbbbpnf", where "bbbb" is the baud rate,
700 "p" is parity ("n", "o", or "e"), "n" is number of
701 bits, and "f" is flow control ("r" for RTS or
702 omit it). Default is "9600n8".
703
704 See Documentation/serial-console.txt for more
705 information. See
706 Documentation/networking/netconsole.txt for an
707 alternative.
708
709 uart[8250],io,<addr>[,options]
710 uart[8250],mmio,<addr>[,options]
711 Start an early, polled-mode console on the 8250/16550
712 UART at the specified I/O port or MMIO address,
713 switching to the matching ttyS device later. The
714 options are the same as for ttyS, above.
715 hvc<n> Use the hypervisor console device <n>. This is for
716 both Xen and PowerPC hypervisors.
717
718 If the device connected to the port is not a TTY but a braille
719 device, prepend "brl," before the device type, for instance
720 console=brl,ttyS0
721 For now, only VisioBraille is supported.
722
723 consoleblank= [KNL] The console blank (screen saver) timeout in
724 seconds. Defaults to 10*60 = 10mins. A value of 0
725 disables the blank timer.
726
727 coredump_filter=
728 [KNL] Change the default value for
729 /proc/<pid>/coredump_filter.
730 See also Documentation/filesystems/proc.txt.
731
732 cpuidle.off=1 [CPU_IDLE]
733 disable the cpuidle sub-system
734
735 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
736 Format:
737 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
738
739 crashkernel=size[KMG][@offset[KMG]]
740 [KNL] Using kexec, Linux can switch to a 'crash kernel'
741 upon panic. This parameter reserves the physical
742 memory region [offset, offset + size] for that kernel
743 image. If '@offset' is omitted, then a suitable offset
744 is selected automatically. Check
745 Documentation/kdump/kdump.txt for further details.
746
747 crashkernel=range1:size1[,range2:size2,...][@offset]
748 [KNL] Same as above, but depends on the memory
749 in the running system. The syntax of range is
750 start-[end] where start and end are both
751 a memory unit (amount[KMG]). See also
752 Documentation/kdump/kdump.txt for an example.
753
754 crashkernel=size[KMG],high
755 [KNL, x86_64] range could be above 4G. Allow kernel
756 to allocate physical memory region from top, so could
757 be above 4G if system have more than 4G ram installed.
758 Otherwise memory region will be allocated below 4G, if
759 available.
760 It will be ignored if crashkernel=X is specified.
761 crashkernel=size[KMG],low
762 [KNL, x86_64] range under 4G. When crashkernel=X,high
763 is passed, kernel could allocate physical memory region
764 above 4G, that cause second kernel crash on system
765 that require some amount of low memory, e.g. swiotlb
766 requires at least 64M+32K low memory. Kernel would
767 try to allocate 72M below 4G automatically.
768 This one let user to specify own low range under 4G
769 for second kernel instead.
770 0: to disable low allocation.
771 It will be ignored when crashkernel=X,high is not used
772 or memory reserved is below 4G.
773
774 cs89x0_dma= [HW,NET]
775 Format: <dma>
776
777 cs89x0_media= [HW,NET]
778 Format: { rj45 | aui | bnc }
779
780 dasd= [HW,NET]
781 See header of drivers/s390/block/dasd_devmap.c.
782
783 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
784 (one device per port)
785 Format: <port#>,<type>
786 See also Documentation/input/joystick-parport.txt
787
788 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
789 time. See Documentation/dynamic-debug-howto.txt for
790 details. Deprecated, see dyndbg.
791
792 debug [KNL] Enable kernel debugging (events log level).
793
794 debug_locks_verbose=
795 [KNL] verbose self-tests
796 Format=<0|1>
797 Print debugging info while doing the locking API
798 self-tests.
799 We default to 0 (no extra messages), setting it to
800 1 will print _a lot_ more information - normally
801 only useful to kernel developers.
802
803 debug_objects [KNL] Enable object debugging
804
805 no_debug_objects
806 [KNL] Disable object debugging
807
808 debug_guardpage_minorder=
809 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
810 parameter allows control of the order of pages that will
811 be intentionally kept free (and hence protected) by the
812 buddy allocator. Bigger value increase the probability
813 of catching random memory corruption, but reduce the
814 amount of memory for normal system use. The maximum
815 possible value is MAX_ORDER/2. Setting this parameter
816 to 1 or 2 should be enough to identify most random
817 memory corruption problems caused by bugs in kernel or
818 driver code when a CPU writes to (or reads from) a
819 random memory location. Note that there exists a class
820 of memory corruptions problems caused by buggy H/W or
821 F/W or by drivers badly programing DMA (basically when
822 memory is written at bus level and the CPU MMU is
823 bypassed) which are not detectable by
824 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
825 tracking down these problems.
826
827 debugpat [X86] Enable PAT debugging
828
829 decnet.addr= [HW,NET]
830 Format: <area>[,<node>]
831 See also Documentation/networking/decnet.txt.
832
833 default_hugepagesz=
834 [same as hugepagesz=] The size of the default
835 HugeTLB page size. This is the size represented by
836 the legacy /proc/ hugepages APIs, used for SHM, and
837 default size when mounting hugetlbfs filesystems.
838 Defaults to the default architecture's huge page size
839 if not specified.
840
841 dhash_entries= [KNL]
842 Set number of hash buckets for dentry cache.
843
844 disable= [IPV6]
845 See Documentation/networking/ipv6.txt.
846
847 disable_cpu_apicid= [X86,APIC,SMP]
848 Format: <int>
849 The number of initial APIC ID for the
850 corresponding CPU to be disabled at boot,
851 mostly used for the kdump 2nd kernel to
852 disable BSP to wake up multiple CPUs without
853 causing system reset or hang due to sending
854 INIT from AP to BSP.
855
856 disable_ddw [PPC/PSERIES]
857 Disable Dynamic DMA Window support. Use this if
858 to workaround buggy firmware.
859
860 disable_ipv6= [IPV6]
861 See Documentation/networking/ipv6.txt.
862
863 disable_mtrr_cleanup [X86]
864 The kernel tries to adjust MTRR layout from continuous
865 to discrete, to make X server driver able to add WB
866 entry later. This parameter disables that.
867
868 disable_mtrr_trim [X86, Intel and AMD only]
869 By default the kernel will trim any uncacheable
870 memory out of your available memory pool based on
871 MTRR settings. This parameter disables that behavior,
872 possibly causing your machine to run very slowly.
873
874 disable_timer_pin_1 [X86]
875 Disable PIN 1 of APIC timer
876 Can be useful to work around chipset bugs.
877
878 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
879 this option disables the debugging code at boot.
880
881 dma_debug_entries=<number>
882 This option allows to tune the number of preallocated
883 entries for DMA-API debugging code. One entry is
884 required per DMA-API allocation. Use this if the
885 DMA-API debugging code disables itself because the
886 architectural default is too low.
887
888 dma_debug_driver=<driver_name>
889 With this option the DMA-API debugging driver
890 filter feature can be enabled at boot time. Just
891 pass the driver to filter for as the parameter.
892 The filter can be disabled or changed to another
893 driver later using sysfs.
894
895 drm_kms_helper.edid_firmware=[<connector>:]<file>
896 Broken monitors, graphic adapters and KVMs may
897 send no or incorrect EDID data sets. This parameter
898 allows to specify an EDID data set in the
899 /lib/firmware directory that is used instead.
900 Generic built-in EDID data sets are used, if one of
901 edid/1024x768.bin, edid/1280x1024.bin,
902 edid/1680x1050.bin, or edid/1920x1080.bin is given
903 and no file with the same name exists. Details and
904 instructions how to build your own EDID data are
905 available in Documentation/EDID/HOWTO.txt. An EDID
906 data set will only be used for a particular connector,
907 if its name and a colon are prepended to the EDID
908 name.
909
910 dscc4.setup= [NET]
911
912 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
913 module.dyndbg[="val"]
914 Enable debug messages at boot time. See
915 Documentation/dynamic-debug-howto.txt for details.
916
917 early_ioremap_debug [KNL]
918 Enable debug messages in early_ioremap support. This
919 is useful for tracking down temporary early mappings
920 which are not unmapped.
921
922 earlycon= [KNL] Output early console device and options.
923
924 uart[8250],io,<addr>[,options]
925 uart[8250],mmio,<addr>[,options]
926 uart[8250],mmio32,<addr>[,options]
927 Start an early, polled-mode console on the 8250/16550
928 UART at the specified I/O port or MMIO address.
929 MMIO inter-register address stride is either 8-bit
930 (mmio) or 32-bit (mmio32).
931 The options are the same as for ttyS, above.
932
933 pl011,<addr>
934 Start an early, polled-mode console on a pl011 serial
935 port at the specified address. The pl011 serial port
936 must already be setup and configured. Options are not
937 yet supported.
938
939 smh Use ARM semihosting calls for early console.
940
941 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
942 earlyprintk=vga
943 earlyprintk=efi
944 earlyprintk=xen
945 earlyprintk=serial[,ttySn[,baudrate]]
946 earlyprintk=serial[,0x...[,baudrate]]
947 earlyprintk=ttySn[,baudrate]
948 earlyprintk=dbgp[debugController#]
949
950 earlyprintk is useful when the kernel crashes before
951 the normal console is initialized. It is not enabled by
952 default because it has some cosmetic problems.
953
954 Append ",keep" to not disable it when the real console
955 takes over.
956
957 Only one of vga, efi, serial, or usb debug port can
958 be used at a time.
959
960 Currently only ttyS0 and ttyS1 may be specified by
961 name. Other I/O ports may be explicitly specified
962 on some architectures (x86 and arm at least) by
963 replacing ttySn with an I/O port address, like this:
964 earlyprintk=serial,0x1008,115200
965 You can find the port for a given device in
966 /proc/tty/driver/serial:
967 2: uart:ST16650V2 port:00001008 irq:18 ...
968
969 Interaction with the standard serial driver is not
970 very good.
971
972 The VGA and EFI output is eventually overwritten by
973 the real console.
974
975 The xen output can only be used by Xen PV guests.
976
977 edac_report= [HW,EDAC] Control how to report EDAC event
978 Format: {"on" | "off" | "force"}
979 on: enable EDAC to report H/W event. May be overridden
980 by other higher priority error reporting module.
981 off: disable H/W event reporting through EDAC.
982 force: enforce the use of EDAC to report H/W event.
983 default: on.
984
985 ekgdboc= [X86,KGDB] Allow early kernel console debugging
986 ekgdboc=kbd
987
988 This is designed to be used in conjunction with
989 the boot argument: earlyprintk=vga
990
991 edd= [EDD]
992 Format: {"off" | "on" | "skip[mbr]"}
993
994 efi= [EFI]
995 Format: { "old_map" }
996 old_map [X86-64]: switch to the old ioremap-based EFI
997 runtime services mapping. 32-bit still uses this one by
998 default.
999
1000 efi_no_storage_paranoia [EFI; X86]
1001 Using this parameter you can use more than 50% of
1002 your efi variable storage. Use this parameter only if
1003 you are really sure that your UEFI does sane gc and
1004 fulfills the spec otherwise your board may brick.
1005
1006 eisa_irq_edge= [PARISC,HW]
1007 See header of drivers/parisc/eisa.c.
1008
1009 elanfreq= [X86-32]
1010 See comment before function elanfreq_setup() in
1011 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1012
1013 elevator= [IOSCHED]
1014 Format: {"cfq" | "deadline" | "noop"}
1015 See Documentation/block/cfq-iosched.txt and
1016 Documentation/block/deadline-iosched.txt for details.
1017
1018 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1019 Specifies physical address of start of kernel core
1020 image elf header and optionally the size. Generally
1021 kexec loader will pass this option to capture kernel.
1022 See Documentation/kdump/kdump.txt for details.
1023
1024 enable_mtrr_cleanup [X86]
1025 The kernel tries to adjust MTRR layout from continuous
1026 to discrete, to make X server driver able to add WB
1027 entry later. This parameter enables that.
1028
1029 enable_timer_pin_1 [X86]
1030 Enable PIN 1 of APIC timer
1031 Can be useful to work around chipset bugs
1032 (in particular on some ATI chipsets).
1033 The kernel tries to set a reasonable default.
1034
1035 enforcing [SELINUX] Set initial enforcing status.
1036 Format: {"0" | "1"}
1037 See security/selinux/Kconfig help text.
1038 0 -- permissive (log only, no denials).
1039 1 -- enforcing (deny and log).
1040 Default value is 0.
1041 Value can be changed at runtime via /selinux/enforce.
1042
1043 erst_disable [ACPI]
1044 Disable Error Record Serialization Table (ERST)
1045 support.
1046
1047 ether= [HW,NET] Ethernet cards parameters
1048 This option is obsoleted by the "netdev=" option, which
1049 has equivalent usage. See its documentation for details.
1050
1051 evm= [EVM]
1052 Format: { "fix" }
1053 Permit 'security.evm' to be updated regardless of
1054 current integrity status.
1055
1056 failslab=
1057 fail_page_alloc=
1058 fail_make_request=[KNL]
1059 General fault injection mechanism.
1060 Format: <interval>,<probability>,<space>,<times>
1061 See also Documentation/fault-injection/.
1062
1063 floppy= [HW]
1064 See Documentation/blockdev/floppy.txt.
1065
1066 force_pal_cache_flush
1067 [IA-64] Avoid check_sal_cache_flush which may hang on
1068 buggy SAL_CACHE_FLUSH implementations. Using this
1069 parameter will force ia64_sal_cache_flush to call
1070 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1071
1072 forcepae [X86-32]
1073 Forcefully enable Physical Address Extension (PAE).
1074 Many Pentium M systems disable PAE but may have a
1075 functionally usable PAE implementation.
1076 Warning: use of this parameter will taint the kernel
1077 and may cause unknown problems.
1078
1079 ftrace=[tracer]
1080 [FTRACE] will set and start the specified tracer
1081 as early as possible in order to facilitate early
1082 boot debugging.
1083
1084 ftrace_dump_on_oops[=orig_cpu]
1085 [FTRACE] will dump the trace buffers on oops.
1086 If no parameter is passed, ftrace will dump
1087 buffers of all CPUs, but if you pass orig_cpu, it will
1088 dump only the buffer of the CPU that triggered the
1089 oops.
1090
1091 ftrace_filter=[function-list]
1092 [FTRACE] Limit the functions traced by the function
1093 tracer at boot up. function-list is a comma separated
1094 list of functions. This list can be changed at run
1095 time by the set_ftrace_filter file in the debugfs
1096 tracing directory.
1097
1098 ftrace_notrace=[function-list]
1099 [FTRACE] Do not trace the functions specified in
1100 function-list. This list can be changed at run time
1101 by the set_ftrace_notrace file in the debugfs
1102 tracing directory.
1103
1104 ftrace_graph_filter=[function-list]
1105 [FTRACE] Limit the top level callers functions traced
1106 by the function graph tracer at boot up.
1107 function-list is a comma separated list of functions
1108 that can be changed at run time by the
1109 set_graph_function file in the debugfs tracing directory.
1110
1111 ftrace_graph_notrace=[function-list]
1112 [FTRACE] Do not trace from the functions specified in
1113 function-list. This list is a comma separated list of
1114 functions that can be changed at run time by the
1115 set_graph_notrace file in the debugfs tracing directory.
1116
1117 gamecon.map[2|3]=
1118 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1119 support via parallel port (up to 5 devices per port)
1120 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1121 See also Documentation/input/joystick-parport.txt
1122
1123 gamma= [HW,DRM]
1124
1125 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1126 Format: off | on
1127 default: on
1128
1129 gcov_persist= [GCOV] When non-zero (default), profiling data for
1130 kernel modules is saved and remains accessible via
1131 debugfs, even when the module is unloaded/reloaded.
1132 When zero, profiling data is discarded and associated
1133 debugfs files are removed at module unload time.
1134
1135 gpt [EFI] Forces disk with valid GPT signature but
1136 invalid Protective MBR to be treated as GPT. If the
1137 primary GPT is corrupted, it enables the backup/alternate
1138 GPT to be used instead.
1139
1140 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1141 the "Enable 0" bit of the configuration register.
1142 Format: 0 | 1
1143 Default: 0
1144 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1145 the "Enable 0" bit of the configuration register.
1146 Format: 0 | 1
1147 Default: 0
1148 grcan.select= [HW] Select which physical interface to use.
1149 Format: 0 | 1
1150 Default: 0
1151 grcan.txsize= [HW] Sets the size of the tx buffer.
1152 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1153 Default: 1024
1154 grcan.rxsize= [HW] Sets the size of the rx buffer.
1155 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1156 Default: 1024
1157
1158 hashdist= [KNL,NUMA] Large hashes allocated during boot
1159 are distributed across NUMA nodes. Defaults on
1160 for 64-bit NUMA, off otherwise.
1161 Format: 0 | 1 (for off | on)
1162
1163 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1164
1165 hd= [EIDE] (E)IDE hard drive subsystem geometry
1166 Format: <cyl>,<head>,<sect>
1167
1168 hest_disable [ACPI]
1169 Disable Hardware Error Source Table (HEST) support;
1170 corresponding firmware-first mode error processing
1171 logic will be disabled.
1172
1173 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1174 size of <nn>. This works even on boxes that have no
1175 highmem otherwise. This also works to reduce highmem
1176 size on bigger boxes.
1177
1178 highres= [KNL] Enable/disable high resolution timer mode.
1179 Valid parameters: "on", "off"
1180 Default: "on"
1181
1182 hisax= [HW,ISDN]
1183 See Documentation/isdn/README.HiSax.
1184
1185 hlt [BUGS=ARM,SH]
1186
1187 hpet= [X86-32,HPET] option to control HPET usage
1188 Format: { enable (default) | disable | force |
1189 verbose }
1190 disable: disable HPET and use PIT instead
1191 force: allow force enabled of undocumented chips (ICH4,
1192 VIA, nVidia)
1193 verbose: show contents of HPET registers during setup
1194
1195 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1196 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1197
1198 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1199 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1200 On x86-64 and powerpc, this option can be specified
1201 multiple times interleaved with hugepages= to reserve
1202 huge pages of different sizes. Valid pages sizes on
1203 x86-64 are 2M (when the CPU supports "pse") and 1G
1204 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1205 Note that 1GB pages can only be allocated at boot time
1206 using hugepages= and not freed afterwards.
1207
1208 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1209 terminal devices. Valid values: 0..8
1210 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1211 If specified, z/VM IUCV HVC accepts connections
1212 from listed z/VM user IDs only.
1213
1214 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1215 hardware thread id mappings.
1216 Format: <cpu>:<hwthread>
1217
1218 keep_bootcon [KNL]
1219 Do not unregister boot console at start. This is only
1220 useful for debugging when something happens in the window
1221 between unregistering the boot console and initializing
1222 the real console.
1223
1224 i2c_bus= [HW] Override the default board specific I2C bus speed
1225 or register an additional I2C bus that is not
1226 registered from board initialization code.
1227 Format:
1228 <bus_id>,<clkrate>
1229
1230 i8042.debug [HW] Toggle i8042 debug mode
1231 i8042.direct [HW] Put keyboard port into non-translated mode
1232 i8042.dumbkbd [HW] Pretend that controller can only read data from
1233 keyboard and cannot control its state
1234 (Don't attempt to blink the leds)
1235 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1236 i8042.nokbd [HW] Don't check/create keyboard port
1237 i8042.noloop [HW] Disable the AUX Loopback command while probing
1238 for the AUX port
1239 i8042.nomux [HW] Don't check presence of an active multiplexing
1240 controller
1241 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1242 controllers
1243 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1244 i8042.reset [HW] Reset the controller during init and cleanup
1245 i8042.unlock [HW] Unlock (ignore) the keylock
1246
1247 i810= [HW,DRM]
1248
1249 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1250 indicates that the driver is running on unsupported
1251 hardware.
1252 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1253 does not match list of supported models.
1254 i8k.power_status
1255 [HW] Report power status in /proc/i8k
1256 (disabled by default)
1257 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1258 capability is set.
1259
1260 i915.invert_brightness=
1261 [DRM] Invert the sense of the variable that is used to
1262 set the brightness of the panel backlight. Normally a
1263 brightness value of 0 indicates backlight switched off,
1264 and the maximum of the brightness value sets the backlight
1265 to maximum brightness. If this parameter is set to 0
1266 (default) and the machine requires it, or this parameter
1267 is set to 1, a brightness value of 0 sets the backlight
1268 to maximum brightness, and the maximum of the brightness
1269 value switches the backlight off.
1270 -1 -- never invert brightness
1271 0 -- machine default
1272 1 -- force brightness inversion
1273
1274 icn= [HW,ISDN]
1275 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1276
1277 ide-core.nodma= [HW] (E)IDE subsystem
1278 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1279 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1280 .cdrom .chs .ignore_cable are additional options
1281 See Documentation/ide/ide.txt.
1282
1283 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1284 Claim all unknown PCI IDE storage controllers.
1285
1286 idle= [X86]
1287 Format: idle=poll, idle=halt, idle=nomwait
1288 Poll forces a polling idle loop that can slightly
1289 improve the performance of waking up a idle CPU, but
1290 will use a lot of power and make the system run hot.
1291 Not recommended.
1292 idle=halt: Halt is forced to be used for CPU idle.
1293 In such case C2/C3 won't be used again.
1294 idle=nomwait: Disable mwait for CPU C-states
1295
1296 ignore_loglevel [KNL]
1297 Ignore loglevel setting - this will print /all/
1298 kernel messages to the console. Useful for debugging.
1299 We also add it as printk module parameter, so users
1300 could change it dynamically, usually by
1301 /sys/module/printk/parameters/ignore_loglevel.
1302
1303 ihash_entries= [KNL]
1304 Set number of hash buckets for inode cache.
1305
1306 ima_appraise= [IMA] appraise integrity measurements
1307 Format: { "off" | "enforce" | "fix" }
1308 default: "enforce"
1309
1310 ima_appraise_tcb [IMA]
1311 The builtin appraise policy appraises all files
1312 owned by uid=0.
1313
1314 ima_hash= [IMA]
1315 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1316 | sha512 | ... }
1317 default: "sha1"
1318
1319 The list of supported hash algorithms is defined
1320 in crypto/hash_info.h.
1321
1322 ima_tcb [IMA]
1323 Load a policy which meets the needs of the Trusted
1324 Computing Base. This means IMA will measure all
1325 programs exec'd, files mmap'd for exec, and all files
1326 opened for read by uid=0.
1327
1328 ima_template= [IMA]
1329 Select one of defined IMA measurements template formats.
1330 Formats: { "ima" | "ima-ng" }
1331 Default: "ima-ng"
1332
1333 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1334 Format: <min_file_size>
1335 Set the minimal file size for using asynchronous hash.
1336 If left unspecified, ahash usage is disabled.
1337
1338 ahash performance varies for different data sizes on
1339 different crypto accelerators. This option can be used
1340 to achieve the best performance for a particular HW.
1341
1342 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1343 Format: <bufsize>
1344 Set hashing buffer size. Default: 4k.
1345
1346 ahash performance varies for different chunk sizes on
1347 different crypto accelerators. This option can be used
1348 to achieve best performance for particular HW.
1349
1350 init= [KNL]
1351 Format: <full_path>
1352 Run specified binary instead of /sbin/init as init
1353 process.
1354
1355 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1356 for working out where the kernel is dying during
1357 startup.
1358
1359 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1360 initcall functions. Useful for debugging built-in
1361 modules and initcalls.
1362
1363 initrd= [BOOT] Specify the location of the initial ramdisk
1364
1365 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1366 Format: <irq>
1367
1368 int_pln_enable [x86] Enable power limit notification interrupt
1369
1370 integrity_audit=[IMA]
1371 Format: { "0" | "1" }
1372 0 -- basic integrity auditing messages. (Default)
1373 1 -- additional integrity auditing messages.
1374
1375 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1376 on
1377 Enable intel iommu driver.
1378 off
1379 Disable intel iommu driver.
1380 igfx_off [Default Off]
1381 By default, gfx is mapped as normal device. If a gfx
1382 device has a dedicated DMAR unit, the DMAR unit is
1383 bypassed by not enabling DMAR with this option. In
1384 this case, gfx device will use physical address for
1385 DMA.
1386 forcedac [x86_64]
1387 With this option iommu will not optimize to look
1388 for io virtual address below 32-bit forcing dual
1389 address cycle on pci bus for cards supporting greater
1390 than 32-bit addressing. The default is to look
1391 for translation below 32-bit and if not available
1392 then look in the higher range.
1393 strict [Default Off]
1394 With this option on every unmap_single operation will
1395 result in a hardware IOTLB flush operation as opposed
1396 to batching them for performance.
1397 sp_off [Default Off]
1398 By default, super page will be supported if Intel IOMMU
1399 has the capability. With this option, super page will
1400 not be supported.
1401
1402 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1403 0 disables intel_idle and fall back on acpi_idle.
1404 1 to 6 specify maximum depth of C-state.
1405
1406 intel_pstate= [X86]
1407 disable
1408 Do not enable intel_pstate as the default
1409 scaling driver for the supported processors
1410
1411 intremap= [X86-64, Intel-IOMMU]
1412 on enable Interrupt Remapping (default)
1413 off disable Interrupt Remapping
1414 nosid disable Source ID checking
1415 no_x2apic_optout
1416 BIOS x2APIC opt-out request will be ignored
1417
1418 iomem= Disable strict checking of access to MMIO memory
1419 strict regions from userspace.
1420 relaxed
1421
1422 iommu= [x86]
1423 off
1424 force
1425 noforce
1426 biomerge
1427 panic
1428 nopanic
1429 merge
1430 nomerge
1431 forcesac
1432 soft
1433 pt [x86, IA-64]
1434
1435
1436 io7= [HW] IO7 for Marvel based alpha systems
1437 See comment before marvel_specify_io7 in
1438 arch/alpha/kernel/core_marvel.c.
1439
1440 io_delay= [X86] I/O delay method
1441 0x80
1442 Standard port 0x80 based delay
1443 0xed
1444 Alternate port 0xed based delay (needed on some systems)
1445 udelay
1446 Simple two microseconds delay
1447 none
1448 No delay
1449
1450 ip= [IP_PNP]
1451 See Documentation/filesystems/nfs/nfsroot.txt.
1452
1453 irqfixup [HW]
1454 When an interrupt is not handled search all handlers
1455 for it. Intended to get systems with badly broken
1456 firmware running.
1457
1458 irqpoll [HW]
1459 When an interrupt is not handled search all handlers
1460 for it. Also check all handlers each timer
1461 interrupt. Intended to get systems with badly broken
1462 firmware running.
1463
1464 isapnp= [ISAPNP]
1465 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1466
1467 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1468 Format:
1469 <cpu number>,...,<cpu number>
1470 or
1471 <cpu number>-<cpu number>
1472 (must be a positive range in ascending order)
1473 or a mixture
1474 <cpu number>,...,<cpu number>-<cpu number>
1475
1476 This option can be used to specify one or more CPUs
1477 to isolate from the general SMP balancing and scheduling
1478 algorithms. You can move a process onto or off an
1479 "isolated" CPU via the CPU affinity syscalls or cpuset.
1480 <cpu number> begins at 0 and the maximum value is
1481 "number of CPUs in system - 1".
1482
1483 This option is the preferred way to isolate CPUs. The
1484 alternative -- manually setting the CPU mask of all
1485 tasks in the system -- can cause problems and
1486 suboptimal load balancer performance.
1487
1488 iucv= [HW,NET]
1489
1490 ivrs_ioapic [HW,X86_64]
1491 Provide an override to the IOAPIC-ID<->DEVICE-ID
1492 mapping provided in the IVRS ACPI table. For
1493 example, to map IOAPIC-ID decimal 10 to
1494 PCI device 00:14.0 write the parameter as:
1495 ivrs_ioapic[10]=00:14.0
1496
1497 ivrs_hpet [HW,X86_64]
1498 Provide an override to the HPET-ID<->DEVICE-ID
1499 mapping provided in the IVRS ACPI table. For
1500 example, to map HPET-ID decimal 0 to
1501 PCI device 00:14.0 write the parameter as:
1502 ivrs_hpet[0]=00:14.0
1503
1504 js= [HW,JOY] Analog joystick
1505 See Documentation/input/joystick.txt.
1506
1507 kaslr/nokaslr [X86]
1508 Enable/disable kernel and module base offset ASLR
1509 (Address Space Layout Randomization) if built into
1510 the kernel. When CONFIG_HIBERNATION is selected,
1511 kASLR is disabled by default. When kASLR is enabled,
1512 hibernation will be disabled.
1513
1514 keepinitrd [HW,ARM]
1515
1516 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1517 specifies the amount of memory usable by the kernel
1518 for non-movable allocations. The requested amount is
1519 spread evenly throughout all nodes in the system. The
1520 remaining memory in each node is used for Movable
1521 pages. In the event, a node is too small to have both
1522 kernelcore and Movable pages, kernelcore pages will
1523 take priority and other nodes will have a larger number
1524 of Movable pages. The Movable zone is used for the
1525 allocation of pages that may be reclaimed or moved
1526 by the page migration subsystem. This means that
1527 HugeTLB pages may not be allocated from this zone.
1528 Note that allocations like PTEs-from-HighMem still
1529 use the HighMem zone if it exists, and the Normal
1530 zone if it does not.
1531
1532 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1533 Format: <Controller#>[,poll interval]
1534 The controller # is the number of the ehci usb debug
1535 port as it is probed via PCI. The poll interval is
1536 optional and is the number seconds in between
1537 each poll cycle to the debug port in case you need
1538 the functionality for interrupting the kernel with
1539 gdb or control-c on the dbgp connection. When
1540 not using this parameter you use sysrq-g to break into
1541 the kernel debugger.
1542
1543 kgdboc= [KGDB,HW] kgdb over consoles.
1544 Requires a tty driver that supports console polling,
1545 or a supported polling keyboard driver (non-usb).
1546 Serial only format: <serial_device>[,baud]
1547 keyboard only format: kbd
1548 keyboard and serial format: kbd,<serial_device>[,baud]
1549 Optional Kernel mode setting:
1550 kms, kbd format: kms,kbd
1551 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1552
1553 kgdbwait [KGDB] Stop kernel execution and enter the
1554 kernel debugger at the earliest opportunity.
1555
1556 kmac= [MIPS] korina ethernet MAC address.
1557 Configure the RouterBoard 532 series on-chip
1558 Ethernet adapter MAC address.
1559
1560 kmemleak= [KNL] Boot-time kmemleak enable/disable
1561 Valid arguments: on, off
1562 Default: on
1563
1564 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1565 Valid arguments: 0, 1, 2
1566 kmemcheck=0 (disabled)
1567 kmemcheck=1 (enabled)
1568 kmemcheck=2 (one-shot mode)
1569 Default: 2 (one-shot mode)
1570
1571 kstack=N [X86] Print N words from the kernel stack
1572 in oops dumps.
1573
1574 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1575 Default is 0 (don't ignore, but inject #GP)
1576
1577 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1578 KVM MMU at runtime.
1579 Default is 0 (off)
1580
1581 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1582 Default is 1 (enabled)
1583
1584 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1585 for all guests.
1586 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1587
1588 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1589 (virtualized MMU) support on capable Intel chips.
1590 Default is 1 (enabled)
1591
1592 kvm-intel.emulate_invalid_guest_state=
1593 [KVM,Intel] Enable emulation of invalid guest states
1594 Default is 0 (disabled)
1595
1596 kvm-intel.flexpriority=
1597 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1598 Default is 1 (enabled)
1599
1600 kvm-intel.nested=
1601 [KVM,Intel] Enable VMX nesting (nVMX).
1602 Default is 0 (disabled)
1603
1604 kvm-intel.unrestricted_guest=
1605 [KVM,Intel] Disable unrestricted guest feature
1606 (virtualized real and unpaged mode) on capable
1607 Intel chips. Default is 1 (enabled)
1608
1609 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1610 feature (tagged TLBs) on capable Intel chips.
1611 Default is 1 (enabled)
1612
1613 l2cr= [PPC]
1614
1615 l3cr= [PPC]
1616
1617 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1618 disabled it.
1619
1620 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1621 value for LAPIC timer one-shot implementation. Default
1622 back to the programmable timer unit in the LAPIC.
1623
1624 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1625 in C2 power state.
1626
1627 libata.dma= [LIBATA] DMA control
1628 libata.dma=0 Disable all PATA and SATA DMA
1629 libata.dma=1 PATA and SATA Disk DMA only
1630 libata.dma=2 ATAPI (CDROM) DMA only
1631 libata.dma=4 Compact Flash DMA only
1632 Combinations also work, so libata.dma=3 enables DMA
1633 for disks and CDROMs, but not CFs.
1634
1635 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1636 libata.ignore_hpa=0 keep BIOS limits (default)
1637 libata.ignore_hpa=1 ignore limits, using full disk
1638
1639 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1640 when set.
1641 Format: <int>
1642
1643 libata.force= [LIBATA] Force configurations. The format is comma
1644 separated list of "[ID:]VAL" where ID is
1645 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1646 matching port, link or device. Basically, it matches
1647 the ATA ID string printed on console by libata. If
1648 the whole ID part is omitted, the last PORT and DEVICE
1649 values are used. If ID hasn't been specified yet, the
1650 configuration applies to all ports, links and devices.
1651
1652 If only DEVICE is omitted, the parameter applies to
1653 the port and all links and devices behind it. DEVICE
1654 number of 0 either selects the first device or the
1655 first fan-out link behind PMP device. It does not
1656 select the host link. DEVICE number of 15 selects the
1657 host link and device attached to it.
1658
1659 The VAL specifies the configuration to force. As long
1660 as there's no ambiguity shortcut notation is allowed.
1661 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1662 The following configurations can be forced.
1663
1664 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1665 Any ID with matching PORT is used.
1666
1667 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1668
1669 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1670 udma[/][16,25,33,44,66,100,133] notation is also
1671 allowed.
1672
1673 * [no]ncq: Turn on or off NCQ.
1674
1675 * nohrst, nosrst, norst: suppress hard, soft
1676 and both resets.
1677
1678 * rstonce: only attempt one reset during
1679 hot-unplug link recovery
1680
1681 * dump_id: dump IDENTIFY data.
1682
1683 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1684
1685 * disable: Disable this device.
1686
1687 If there are multiple matching configurations changing
1688 the same attribute, the last one is used.
1689
1690 memblock=debug [KNL] Enable memblock debug messages.
1691
1692 load_ramdisk= [RAM] List of ramdisks to load from floppy
1693 See Documentation/blockdev/ramdisk.txt.
1694
1695 lockd.nlm_grace_period=P [NFS] Assign grace period.
1696 Format: <integer>
1697
1698 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1699 Format: <integer>
1700
1701 lockd.nlm_timeout=T [NFS] Assign timeout value.
1702 Format: <integer>
1703
1704 lockd.nlm_udpport=M [NFS] Assign UDP port.
1705 Format: <integer>
1706
1707 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1708 Format: <irq>
1709
1710 loglevel= All Kernel Messages with a loglevel smaller than the
1711 console loglevel will be printed to the console. It can
1712 also be changed with klogd or other programs. The
1713 loglevels are defined as follows:
1714
1715 0 (KERN_EMERG) system is unusable
1716 1 (KERN_ALERT) action must be taken immediately
1717 2 (KERN_CRIT) critical conditions
1718 3 (KERN_ERR) error conditions
1719 4 (KERN_WARNING) warning conditions
1720 5 (KERN_NOTICE) normal but significant condition
1721 6 (KERN_INFO) informational
1722 7 (KERN_DEBUG) debug-level messages
1723
1724 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1725 in bytes. n must be a power of two and greater
1726 than the minimal size. The minimal size is defined
1727 by LOG_BUF_SHIFT kernel config parameter. There is
1728 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1729 that allows to increase the default size depending on
1730 the number of CPUs. See init/Kconfig for more details.
1731
1732 logo.nologo [FB] Disables display of the built-in Linux logo.
1733 This may be used to provide more screen space for
1734 kernel log messages and is useful when debugging
1735 kernel boot problems.
1736
1737 lp=0 [LP] Specify parallel ports to use, e.g,
1738 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1739 lp=reset first parallel port). 'lp=0' disables the
1740 lp=auto printer driver. 'lp=reset' (which can be
1741 specified in addition to the ports) causes
1742 attached printers to be reset. Using
1743 lp=port1,port2,... specifies the parallel ports
1744 to associate lp devices with, starting with
1745 lp0. A port specification may be 'none' to skip
1746 that lp device, or a parport name such as
1747 'parport0'. Specifying 'lp=auto' instead of a
1748 port specification list means that device IDs
1749 from each port should be examined, to see if
1750 an IEEE 1284-compliant printer is attached; if
1751 so, the driver will manage that printer.
1752 See also header of drivers/char/lp.c.
1753
1754 lpj=n [KNL]
1755 Sets loops_per_jiffy to given constant, thus avoiding
1756 time-consuming boot-time autodetection (up to 250 ms per
1757 CPU). 0 enables autodetection (default). To determine
1758 the correct value for your kernel, boot with normal
1759 autodetection and see what value is printed. Note that
1760 on SMP systems the preset will be applied to all CPUs,
1761 which is likely to cause problems if your CPUs need
1762 significantly divergent settings. An incorrect value
1763 will cause delays in the kernel to be wrong, leading to
1764 unpredictable I/O errors and other breakage. Although
1765 unlikely, in the extreme case this might damage your
1766 hardware.
1767
1768 ltpc= [NET]
1769 Format: <io>,<irq>,<dma>
1770
1771 machvec= [IA-64] Force the use of a particular machine-vector
1772 (machvec) in a generic kernel.
1773 Example: machvec=hpzx1_swiotlb
1774
1775 machtype= [Loongson] Share the same kernel image file between different
1776 yeeloong laptop.
1777 Example: machtype=lemote-yeeloong-2f-7inch
1778
1779 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1780 than or equal to this physical address is ignored.
1781
1782 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1783 should make use of. maxcpus=n : n >= 0 limits the
1784 kernel to using 'n' processors. n=0 is a special case,
1785 it is equivalent to "nosmp", which also disables
1786 the IO APIC.
1787
1788 max_loop= [LOOP] The number of loop block devices that get
1789 (loop.max_loop) unconditionally pre-created at init time. The default
1790 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1791 of statically allocating a predefined number, loop
1792 devices can be requested on-demand with the
1793 /dev/loop-control interface.
1794
1795 mce [X86-32] Machine Check Exception
1796
1797 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1798
1799 md= [HW] RAID subsystems devices and level
1800 See Documentation/md.txt.
1801
1802 mdacon= [MDA]
1803 Format: <first>,<last>
1804 Specifies range of consoles to be captured by the MDA.
1805
1806 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1807 Amount of memory to be used when the kernel is not able
1808 to see the whole system memory or for test.
1809 [X86] Work as limiting max address. Use together
1810 with memmap= to avoid physical address space collisions.
1811 Without memmap= PCI devices could be placed at addresses
1812 belonging to unused RAM.
1813
1814 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1815 memory.
1816
1817 memchunk=nn[KMG]
1818 [KNL,SH] Allow user to override the default size for
1819 per-device physically contiguous DMA buffers.
1820
1821 memmap=exactmap [KNL,X86] Enable setting of an exact
1822 E820 memory map, as specified by the user.
1823 Such memmap=exactmap lines can be constructed based on
1824 BIOS output or other requirements. See the memmap=nn@ss
1825 option description.
1826
1827 memmap=nn[KMG]@ss[KMG]
1828 [KNL] Force usage of a specific region of memory.
1829 Region of memory to be used is from ss to ss+nn.
1830
1831 memmap=nn[KMG]#ss[KMG]
1832 [KNL,ACPI] Mark specific memory as ACPI data.
1833 Region of memory to be marked is from ss to ss+nn.
1834
1835 memmap=nn[KMG]$ss[KMG]
1836 [KNL,ACPI] Mark specific memory as reserved.
1837 Region of memory to be reserved is from ss to ss+nn.
1838 Example: Exclude memory from 0x18690000-0x1869ffff
1839 memmap=64K$0x18690000
1840 or
1841 memmap=0x10000$0x18690000
1842
1843 memory_corruption_check=0/1 [X86]
1844 Some BIOSes seem to corrupt the first 64k of
1845 memory when doing things like suspend/resume.
1846 Setting this option will scan the memory
1847 looking for corruption. Enabling this will
1848 both detect corruption and prevent the kernel
1849 from using the memory being corrupted.
1850 However, its intended as a diagnostic tool; if
1851 repeatable BIOS-originated corruption always
1852 affects the same memory, you can use memmap=
1853 to prevent the kernel from using that memory.
1854
1855 memory_corruption_check_size=size [X86]
1856 By default it checks for corruption in the low
1857 64k, making this memory unavailable for normal
1858 use. Use this parameter to scan for
1859 corruption in more or less memory.
1860
1861 memory_corruption_check_period=seconds [X86]
1862 By default it checks for corruption every 60
1863 seconds. Use this parameter to check at some
1864 other rate. 0 disables periodic checking.
1865
1866 memtest= [KNL,X86] Enable memtest
1867 Format: <integer>
1868 default : 0 <disable>
1869 Specifies the number of memtest passes to be
1870 performed. Each pass selects another test
1871 pattern from a given set of patterns. Memtest
1872 fills the memory with this pattern, validates
1873 memory contents and reserves bad memory
1874 regions that are detected.
1875
1876 meye.*= [HW] Set MotionEye Camera parameters
1877 See Documentation/video4linux/meye.txt.
1878
1879 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1880 Multi-Function General Purpose Timers on AMD Geode
1881 platforms.
1882
1883 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1884 the BIOS has incorrectly applied a workaround. TinyBIOS
1885 version 0.98 is known to be affected, 0.99 fixes the
1886 problem by letting the user disable the workaround.
1887
1888 mga= [HW,DRM]
1889
1890 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1891 physical address is ignored.
1892
1893 mini2440= [ARM,HW,KNL]
1894 Format:[0..2][b][c][t]
1895 Default: "0tb"
1896 MINI2440 configuration specification:
1897 0 - The attached screen is the 3.5" TFT
1898 1 - The attached screen is the 7" TFT
1899 2 - The VGA Shield is attached (1024x768)
1900 Leaving out the screen size parameter will not load
1901 the TFT driver, and the framebuffer will be left
1902 unconfigured.
1903 b - Enable backlight. The TFT backlight pin will be
1904 linked to the kernel VESA blanking code and a GPIO
1905 LED. This parameter is not necessary when using the
1906 VGA shield.
1907 c - Enable the s3c camera interface.
1908 t - Reserved for enabling touchscreen support. The
1909 touchscreen support is not enabled in the mainstream
1910 kernel as of 2.6.30, a preliminary port can be found
1911 in the "bleeding edge" mini2440 support kernel at
1912 http://repo.or.cz/w/linux-2.6/mini2440.git
1913
1914 mminit_loglevel=
1915 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1916 parameter allows control of the logging verbosity for
1917 the additional memory initialisation checks. A value
1918 of 0 disables mminit logging and a level of 4 will
1919 log everything. Information is printed at KERN_DEBUG
1920 so loglevel=8 may also need to be specified.
1921
1922 module.sig_enforce
1923 [KNL] When CONFIG_MODULE_SIG is set, this means that
1924 modules without (valid) signatures will fail to load.
1925 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1926 is always true, so this option does nothing.
1927
1928 mousedev.tap_time=
1929 [MOUSE] Maximum time between finger touching and
1930 leaving touchpad surface for touch to be considered
1931 a tap and be reported as a left button click (for
1932 touchpads working in absolute mode only).
1933 Format: <msecs>
1934 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1935 reporting absolute coordinates, such as tablets
1936 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1937 reporting absolute coordinates, such as tablets
1938
1939 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1940 is similar to kernelcore except it specifies the
1941 amount of memory used for migratable allocations.
1942 If both kernelcore and movablecore is specified,
1943 then kernelcore will be at *least* the specified
1944 value but may be more. If movablecore on its own
1945 is specified, the administrator must be careful
1946 that the amount of memory usable for all allocations
1947 is not too small.
1948
1949 movable_node [KNL,X86] Boot-time switch to enable the effects
1950 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1951
1952 MTD_Partition= [MTD]
1953 Format: <name>,<region-number>,<size>,<offset>
1954
1955 MTD_Region= [MTD] Format:
1956 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1957
1958 mtdparts= [MTD]
1959 See drivers/mtd/cmdlinepart.c.
1960
1961 multitce=off [PPC] This parameter disables the use of the pSeries
1962 firmware feature for updating multiple TCE entries
1963 at a time.
1964
1965 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1966
1967 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1968
1969 boundary - index of last SLC block on Flex-OneNAND.
1970 The remaining blocks are configured as MLC blocks.
1971 lock - Configure if Flex-OneNAND boundary should be locked.
1972 Once locked, the boundary cannot be changed.
1973 1 indicates lock status, 0 indicates unlock status.
1974
1975 mtdset= [ARM]
1976 ARM/S3C2412 JIVE boot control
1977
1978 See arch/arm/mach-s3c2412/mach-jive.c
1979
1980 mtouchusb.raw_coordinates=
1981 [HW] Make the MicroTouch USB driver use raw coordinates
1982 ('y', default) or cooked coordinates ('n')
1983
1984 mtrr_chunk_size=nn[KMG] [X86]
1985 used for mtrr cleanup. It is largest continuous chunk
1986 that could hold holes aka. UC entries.
1987
1988 mtrr_gran_size=nn[KMG] [X86]
1989 Used for mtrr cleanup. It is granularity of mtrr block.
1990 Default is 1.
1991 Large value could prevent small alignment from
1992 using up MTRRs.
1993
1994 mtrr_spare_reg_nr=n [X86]
1995 Format: <integer>
1996 Range: 0,7 : spare reg number
1997 Default : 1
1998 Used for mtrr cleanup. It is spare mtrr entries number.
1999 Set to 2 or more if your graphical card needs more.
2000
2001 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2002
2003 netdev= [NET] Network devices parameters
2004 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2005 Note that mem_start is often overloaded to mean
2006 something different and driver-specific.
2007 This usage is only documented in each driver source
2008 file if at all.
2009
2010 nf_conntrack.acct=
2011 [NETFILTER] Enable connection tracking flow accounting
2012 0 to disable accounting
2013 1 to enable accounting
2014 Default value is 0.
2015
2016 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2017 See Documentation/filesystems/nfs/nfsroot.txt.
2018
2019 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2020 See Documentation/filesystems/nfs/nfsroot.txt.
2021
2022 nfsrootdebug [NFS] enable nfsroot debugging messages.
2023 See Documentation/filesystems/nfs/nfsroot.txt.
2024
2025 nfs.callback_tcpport=
2026 [NFS] set the TCP port on which the NFSv4 callback
2027 channel should listen.
2028
2029 nfs.cache_getent=
2030 [NFS] sets the pathname to the program which is used
2031 to update the NFS client cache entries.
2032
2033 nfs.cache_getent_timeout=
2034 [NFS] sets the timeout after which an attempt to
2035 update a cache entry is deemed to have failed.
2036
2037 nfs.idmap_cache_timeout=
2038 [NFS] set the maximum lifetime for idmapper cache
2039 entries.
2040
2041 nfs.enable_ino64=
2042 [NFS] enable 64-bit inode numbers.
2043 If zero, the NFS client will fake up a 32-bit inode
2044 number for the readdir() and stat() syscalls instead
2045 of returning the full 64-bit number.
2046 The default is to return 64-bit inode numbers.
2047
2048 nfs.max_session_slots=
2049 [NFSv4.1] Sets the maximum number of session slots
2050 the client will attempt to negotiate with the server.
2051 This limits the number of simultaneous RPC requests
2052 that the client can send to the NFSv4.1 server.
2053 Note that there is little point in setting this
2054 value higher than the max_tcp_slot_table_limit.
2055
2056 nfs.nfs4_disable_idmapping=
2057 [NFSv4] When set to the default of '1', this option
2058 ensures that both the RPC level authentication
2059 scheme and the NFS level operations agree to use
2060 numeric uids/gids if the mount is using the
2061 'sec=sys' security flavour. In effect it is
2062 disabling idmapping, which can make migration from
2063 legacy NFSv2/v3 systems to NFSv4 easier.
2064 Servers that do not support this mode of operation
2065 will be autodetected by the client, and it will fall
2066 back to using the idmapper.
2067 To turn off this behaviour, set the value to '0'.
2068 nfs.nfs4_unique_id=
2069 [NFS4] Specify an additional fixed unique ident-
2070 ification string that NFSv4 clients can insert into
2071 their nfs_client_id4 string. This is typically a
2072 UUID that is generated at system install time.
2073
2074 nfs.send_implementation_id =
2075 [NFSv4.1] Send client implementation identification
2076 information in exchange_id requests.
2077 If zero, no implementation identification information
2078 will be sent.
2079 The default is to send the implementation identification
2080 information.
2081
2082 nfs.recover_lost_locks =
2083 [NFSv4] Attempt to recover locks that were lost due
2084 to a lease timeout on the server. Please note that
2085 doing this risks data corruption, since there are
2086 no guarantees that the file will remain unchanged
2087 after the locks are lost.
2088 If you want to enable the kernel legacy behaviour of
2089 attempting to recover these locks, then set this
2090 parameter to '1'.
2091 The default parameter value of '0' causes the kernel
2092 not to attempt recovery of lost locks.
2093
2094 nfsd.nfs4_disable_idmapping=
2095 [NFSv4] When set to the default of '1', the NFSv4
2096 server will return only numeric uids and gids to
2097 clients using auth_sys, and will accept numeric uids
2098 and gids from such clients. This is intended to ease
2099 migration from NFSv2/v3.
2100
2101 objlayoutdriver.osd_login_prog=
2102 [NFS] [OBJLAYOUT] sets the pathname to the program which
2103 is used to automatically discover and login into new
2104 osd-targets. Please see:
2105 Documentation/filesystems/pnfs.txt for more explanations
2106
2107 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2108 when a NMI is triggered.
2109 Format: [state][,regs][,debounce][,die]
2110
2111 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2112 Format: [panic,][nopanic,][num]
2113 Valid num: 0
2114 0 - turn nmi_watchdog off
2115 When panic is specified, panic when an NMI watchdog
2116 timeout occurs (or 'nopanic' to override the opposite
2117 default).
2118 This is useful when you use a panic=... timeout and
2119 need the box quickly up again.
2120
2121 netpoll.carrier_timeout=
2122 [NET] Specifies amount of time (in seconds) that
2123 netpoll should wait for a carrier. By default netpoll
2124 waits 4 seconds.
2125
2126 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2127 emulation library even if a 387 maths coprocessor
2128 is present.
2129
2130 no_console_suspend
2131 [HW] Never suspend the console
2132 Disable suspending of consoles during suspend and
2133 hibernate operations. Once disabled, debugging
2134 messages can reach various consoles while the rest
2135 of the system is being put to sleep (ie, while
2136 debugging driver suspend/resume hooks). This may
2137 not work reliably with all consoles, but is known
2138 to work with serial and VGA consoles.
2139 To facilitate more flexible debugging, we also add
2140 console_suspend, a printk module parameter to control
2141 it. Users could use console_suspend (usually
2142 /sys/module/printk/parameters/console_suspend) to
2143 turn on/off it dynamically.
2144
2145 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2146 caches in the slab allocator. Saves per-node memory,
2147 but will impact performance.
2148
2149 noalign [KNL,ARM]
2150
2151 noapic [SMP,APIC] Tells the kernel to not make use of any
2152 IOAPICs that may be present in the system.
2153
2154 noautogroup Disable scheduler automatic task group creation.
2155
2156 nobats [PPC] Do not use BATs for mapping kernel lowmem
2157 on "Classic" PPC cores.
2158
2159 nocache [ARM]
2160
2161 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2162
2163 nodelayacct [KNL] Disable per-task delay accounting
2164
2165 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2166
2167 nodsp [SH] Disable hardware DSP at boot time.
2168
2169 noefi [X86] Disable EFI runtime services support.
2170
2171 noexec [IA-64]
2172
2173 noexec [X86]
2174 On X86-32 available only on PAE configured kernels.
2175 noexec=on: enable non-executable mappings (default)
2176 noexec=off: disable non-executable mappings
2177
2178 nosmap [X86]
2179 Disable SMAP (Supervisor Mode Access Prevention)
2180 even if it is supported by processor.
2181
2182 nosmep [X86]
2183 Disable SMEP (Supervisor Mode Execution Prevention)
2184 even if it is supported by processor.
2185
2186 noexec32 [X86-64]
2187 This affects only 32-bit executables.
2188 noexec32=on: enable non-executable mappings (default)
2189 read doesn't imply executable mappings
2190 noexec32=off: disable non-executable mappings
2191 read implies executable mappings
2192
2193 nofpu [SH] Disable hardware FPU at boot time.
2194
2195 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2196 register save and restore. The kernel will only save
2197 legacy floating-point registers on task switch.
2198
2199 noxsave [BUGS=X86] Disables x86 extended register state save
2200 and restore using xsave. The kernel will fallback to
2201 enabling legacy floating-point and sse state.
2202
2203 eagerfpu= [X86]
2204 on enable eager fpu restore
2205 off disable eager fpu restore
2206 auto selects the default scheme, which automatically
2207 enables eagerfpu restore for xsaveopt.
2208
2209 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2210 wfi(ARM) instruction doesn't work correctly and not to
2211 use it. This is also useful when using JTAG debugger.
2212
2213 no_file_caps Tells the kernel not to honor file capabilities. The
2214 only way then for a file to be executed with privilege
2215 is to be setuid root or executed by root.
2216
2217 nohalt [IA-64] Tells the kernel not to use the power saving
2218 function PAL_HALT_LIGHT when idle. This increases
2219 power-consumption. On the positive side, it reduces
2220 interrupt wake-up latency, which may improve performance
2221 in certain environments such as networked servers or
2222 real-time systems.
2223
2224 nohibernate [HIBERNATION] Disable hibernation and resume.
2225
2226 nohz= [KNL] Boottime enable/disable dynamic ticks
2227 Valid arguments: on, off
2228 Default: on
2229
2230 nohz_full= [KNL,BOOT]
2231 In kernels built with CONFIG_NO_HZ_FULL=y, set
2232 the specified list of CPUs whose tick will be stopped
2233 whenever possible. The boot CPU will be forced outside
2234 the range to maintain the timekeeping.
2235 The CPUs in this range must also be included in the
2236 rcu_nocbs= set.
2237
2238 noiotrap [SH] Disables trapped I/O port accesses.
2239
2240 noirqdebug [X86-32] Disables the code which attempts to detect and
2241 disable unhandled interrupt sources.
2242
2243 no_timer_check [X86,APIC] Disables the code which tests for
2244 broken timer IRQ sources.
2245
2246 noisapnp [ISAPNP] Disables ISA PnP code.
2247
2248 noinitrd [RAM] Tells the kernel not to load any configured
2249 initial RAM disk.
2250
2251 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2252 remapping.
2253 [Deprecated - use intremap=off]
2254
2255 nointroute [IA-64]
2256
2257 nojitter [IA-64] Disables jitter checking for ITC timers.
2258
2259 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2260
2261 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2262 fault handling.
2263
2264 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2265 steal time is computed, but won't influence scheduler
2266 behaviour
2267
2268 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2269
2270 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2271
2272 noltlbs [PPC] Do not use large page/tlb entries for kernel
2273 lowmem mapping on PPC40x.
2274
2275 nomca [IA-64] Disable machine check abort handling
2276
2277 nomce [X86-32] Machine Check Exception
2278
2279 nomfgpt [X86-32] Disable Multi-Function General Purpose
2280 Timer usage (for AMD Geode machines).
2281
2282 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2283 shutdown the other cpus. Instead use the REBOOT_VECTOR
2284 irq.
2285
2286 nomodule Disable module load
2287
2288 nopat [X86] Disable PAT (page attribute table extension of
2289 pagetables) support.
2290
2291 norandmaps Don't use address space randomization. Equivalent to
2292 echo 0 > /proc/sys/kernel/randomize_va_space
2293
2294 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2295
2296 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2297 with UP alternatives
2298
2299 nordrand [X86] Disable kernel use of the RDRAND and
2300 RDSEED instructions even if they are supported
2301 by the processor. RDRAND and RDSEED are still
2302 available to user space applications.
2303
2304 noresume [SWSUSP] Disables resume and restores original swap
2305 space.
2306
2307 no-scroll [VGA] Disables scrollback.
2308 This is required for the Braillex ib80-piezo Braille
2309 reader made by F.H. Papenmeier (Germany).
2310
2311 nosbagart [IA-64]
2312
2313 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2314
2315 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2316 and disable the IO APIC. legacy for "maxcpus=0".
2317
2318 nosoftlockup [KNL] Disable the soft-lockup detector.
2319
2320 nosync [HW,M68K] Disables sync negotiation for all devices.
2321
2322 notsc [BUGS=X86-32] Disable Time Stamp Counter
2323
2324 nousb [USB] Disable the USB subsystem
2325
2326 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2327
2328 nowb [ARM]
2329
2330 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2331
2332 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2333 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2334 Some features depend on CPU0. Known dependencies are:
2335 1. Resume from suspend/hibernate depends on CPU0.
2336 Suspend/hibernate will fail if CPU0 is offline and you
2337 need to online CPU0 before suspend/hibernate.
2338 2. PIC interrupts also depend on CPU0. CPU0 can't be
2339 removed if a PIC interrupt is detected.
2340 It's said poweroff/reboot may depend on CPU0 on some
2341 machines although I haven't seen such issues so far
2342 after CPU0 is offline on a few tested machines.
2343 If the dependencies are under your control, you can
2344 turn on cpu0_hotplug.
2345
2346 nptcg= [IA-64] Override max number of concurrent global TLB
2347 purges which is reported from either PAL_VM_SUMMARY or
2348 SAL PALO.
2349
2350 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2351 could support. nr_cpus=n : n >= 1 limits the kernel to
2352 supporting 'n' processors. Later in runtime you can not
2353 use hotplug cpu feature to put more cpu back to online.
2354 just like you compile the kernel NR_CPUS=n
2355
2356 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2357
2358 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2359 Allowed values are enable and disable
2360
2361 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2362 one of ['zone', 'node', 'default'] can be specified
2363 This can be set from sysctl after boot.
2364 See Documentation/sysctl/vm.txt for details.
2365
2366 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2367 See Documentation/debugging-via-ohci1394.txt for more
2368 info.
2369
2370 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2371 Rather than timing out after 20 ms if an EC
2372 command is not properly ACKed, override the length
2373 of the timeout. We have interrupts disabled while
2374 waiting for the ACK, so if this is set too high
2375 interrupts *may* be lost!
2376
2377 omap_mux= [OMAP] Override bootloader pin multiplexing.
2378 Format: <mux_mode0.mode_name=value>...
2379 For example, to override I2C bus2:
2380 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2381
2382 oprofile.timer= [HW]
2383 Use timer interrupt instead of performance counters
2384
2385 oprofile.cpu_type= Force an oprofile cpu type
2386 This might be useful if you have an older oprofile
2387 userland or if you want common events.
2388 Format: { arch_perfmon }
2389 arch_perfmon: [X86] Force use of architectural
2390 perfmon on Intel CPUs instead of the
2391 CPU specific event set.
2392 timer: [X86] Force use of architectural NMI
2393 timer mode (see also oprofile.timer
2394 for generic hr timer mode)
2395 [s390] Force legacy basic mode sampling
2396 (report cpu_type "timer")
2397
2398 oops=panic Always panic on oopses. Default is to just kill the
2399 process, but there is a small probability of
2400 deadlocking the machine.
2401 This will also cause panics on machine check exceptions.
2402 Useful together with panic=30 to trigger a reboot.
2403
2404 OSS [HW,OSS]
2405 See Documentation/sound/oss/oss-parameters.txt
2406
2407 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2408 timeout > 0: seconds before rebooting
2409 timeout = 0: wait forever
2410 timeout < 0: reboot immediately
2411 Format: <timeout>
2412
2413 crash_kexec_post_notifiers
2414 Run kdump after running panic-notifiers and dumping
2415 kmsg. This only for the users who doubt kdump always
2416 succeeds in any situation.
2417 Note that this also increases risks of kdump failure,
2418 because some panic notifiers can make the crashed
2419 kernel more unstable.
2420
2421 parkbd.port= [HW] Parallel port number the keyboard adapter is
2422 connected to, default is 0.
2423 Format: <parport#>
2424 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2425 0 for XT, 1 for AT (default is AT).
2426 Format: <mode>
2427
2428 parport= [HW,PPT] Specify parallel ports. 0 disables.
2429 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2430 Use 'auto' to force the driver to use any
2431 IRQ/DMA settings detected (the default is to
2432 ignore detected IRQ/DMA settings because of
2433 possible conflicts). You can specify the base
2434 address, IRQ, and DMA settings; IRQ and DMA
2435 should be numbers, or 'auto' (for using detected
2436 settings on that particular port), or 'nofifo'
2437 (to avoid using a FIFO even if it is detected).
2438 Parallel ports are assigned in the order they
2439 are specified on the command line, starting
2440 with parport0.
2441
2442 parport_init_mode= [HW,PPT]
2443 Configure VIA parallel port to operate in
2444 a specific mode. This is necessary on Pegasos
2445 computer where firmware has no options for setting
2446 up parallel port mode and sets it to spp.
2447 Currently this function knows 686a and 8231 chips.
2448 Format: [spp|ps2|epp|ecp|ecpepp]
2449
2450 pause_on_oops=
2451 Halt all CPUs after the first oops has been printed for
2452 the specified number of seconds. This is to be used if
2453 your oopses keep scrolling off the screen.
2454
2455 pcbit= [HW,ISDN]
2456
2457 pcd. [PARIDE]
2458 See header of drivers/block/paride/pcd.c.
2459 See also Documentation/blockdev/paride.txt.
2460
2461 pci=option[,option...] [PCI] various PCI subsystem options:
2462 earlydump [X86] dump PCI config space before the kernel
2463 changes anything
2464 off [X86] don't probe for the PCI bus
2465 bios [X86-32] force use of PCI BIOS, don't access
2466 the hardware directly. Use this if your machine
2467 has a non-standard PCI host bridge.
2468 nobios [X86-32] disallow use of PCI BIOS, only direct
2469 hardware access methods are allowed. Use this
2470 if you experience crashes upon bootup and you
2471 suspect they are caused by the BIOS.
2472 conf1 [X86] Force use of PCI Configuration
2473 Mechanism 1.
2474 conf2 [X86] Force use of PCI Configuration
2475 Mechanism 2.
2476 noaer [PCIE] If the PCIEAER kernel config parameter is
2477 enabled, this kernel boot option can be used to
2478 disable the use of PCIE advanced error reporting.
2479 nodomains [PCI] Disable support for multiple PCI
2480 root domains (aka PCI segments, in ACPI-speak).
2481 nommconf [X86] Disable use of MMCONFIG for PCI
2482 Configuration
2483 check_enable_amd_mmconf [X86] check for and enable
2484 properly configured MMIO access to PCI
2485 config space on AMD family 10h CPU
2486 nomsi [MSI] If the PCI_MSI kernel config parameter is
2487 enabled, this kernel boot option can be used to
2488 disable the use of MSI interrupts system-wide.
2489 noioapicquirk [APIC] Disable all boot interrupt quirks.
2490 Safety option to keep boot IRQs enabled. This
2491 should never be necessary.
2492 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2493 primary IO-APIC for bridges that cannot disable
2494 boot IRQs. This fixes a source of spurious IRQs
2495 when the system masks IRQs.
2496 noioapicreroute [APIC] Disable workaround that uses the
2497 boot IRQ equivalent of an IRQ that connects to
2498 a chipset where boot IRQs cannot be disabled.
2499 The opposite of ioapicreroute.
2500 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2501 routing table. These calls are known to be buggy
2502 on several machines and they hang the machine
2503 when used, but on other computers it's the only
2504 way to get the interrupt routing table. Try
2505 this option if the kernel is unable to allocate
2506 IRQs or discover secondary PCI buses on your
2507 motherboard.
2508 rom [X86] Assign address space to expansion ROMs.
2509 Use with caution as certain devices share
2510 address decoders between ROMs and other
2511 resources.
2512 norom [X86] Do not assign address space to
2513 expansion ROMs that do not already have
2514 BIOS assigned address ranges.
2515 nobar [X86] Do not assign address space to the
2516 BARs that weren't assigned by the BIOS.
2517 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2518 assigned automatically to PCI devices. You can
2519 make the kernel exclude IRQs of your ISA cards
2520 this way.
2521 pirqaddr=0xAAAAA [X86] Specify the physical address
2522 of the PIRQ table (normally generated
2523 by the BIOS) if it is outside the
2524 F0000h-100000h range.
2525 lastbus=N [X86] Scan all buses thru bus #N. Can be
2526 useful if the kernel is unable to find your
2527 secondary buses and you want to tell it
2528 explicitly which ones they are.
2529 assign-busses [X86] Always assign all PCI bus
2530 numbers ourselves, overriding
2531 whatever the firmware may have done.
2532 usepirqmask [X86] Honor the possible IRQ mask stored
2533 in the BIOS $PIR table. This is needed on
2534 some systems with broken BIOSes, notably
2535 some HP Pavilion N5400 and Omnibook XE3
2536 notebooks. This will have no effect if ACPI
2537 IRQ routing is enabled.
2538 noacpi [X86] Do not use ACPI for IRQ routing
2539 or for PCI scanning.
2540 use_crs [X86] Use PCI host bridge window information
2541 from ACPI. On BIOSes from 2008 or later, this
2542 is enabled by default. If you need to use this,
2543 please report a bug.
2544 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2545 If you need to use this, please report a bug.
2546 routeirq Do IRQ routing for all PCI devices.
2547 This is normally done in pci_enable_device(),
2548 so this option is a temporary workaround
2549 for broken drivers that don't call it.
2550 skip_isa_align [X86] do not align io start addr, so can
2551 handle more pci cards
2552 firmware [ARM] Do not re-enumerate the bus but instead
2553 just use the configuration from the
2554 bootloader. This is currently used on
2555 IXP2000 systems where the bus has to be
2556 configured a certain way for adjunct CPUs.
2557 noearly [X86] Don't do any early type 1 scanning.
2558 This might help on some broken boards which
2559 machine check when some devices' config space
2560 is read. But various workarounds are disabled
2561 and some IOMMU drivers will not work.
2562 bfsort Sort PCI devices into breadth-first order.
2563 This sorting is done to get a device
2564 order compatible with older (<= 2.4) kernels.
2565 nobfsort Don't sort PCI devices into breadth-first order.
2566 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2567 tuning and use the BIOS-configured MPS defaults.
2568 pcie_bus_safe Set every device's MPS to the largest value
2569 supported by all devices below the root complex.
2570 pcie_bus_perf Set device MPS to the largest allowable MPS
2571 based on its parent bus. Also set MRRS (Max
2572 Read Request Size) to the largest supported
2573 value (no larger than the MPS that the device
2574 or bus can support) for best performance.
2575 pcie_bus_peer2peer Set every device's MPS to 128B, which
2576 every device is guaranteed to support. This
2577 configuration allows peer-to-peer DMA between
2578 any pair of devices, possibly at the cost of
2579 reduced performance. This also guarantees
2580 that hot-added devices will work.
2581 cbiosize=nn[KMG] The fixed amount of bus space which is
2582 reserved for the CardBus bridge's IO window.
2583 The default value is 256 bytes.
2584 cbmemsize=nn[KMG] The fixed amount of bus space which is
2585 reserved for the CardBus bridge's memory
2586 window. The default value is 64 megabytes.
2587 resource_alignment=
2588 Format:
2589 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2590 Specifies alignment and device to reassign
2591 aligned memory resources.
2592 If <order of align> is not specified,
2593 PAGE_SIZE is used as alignment.
2594 PCI-PCI bridge can be specified, if resource
2595 windows need to be expanded.
2596 ecrc= Enable/disable PCIe ECRC (transaction layer
2597 end-to-end CRC checking).
2598 bios: Use BIOS/firmware settings. This is the
2599 the default.
2600 off: Turn ECRC off
2601 on: Turn ECRC on.
2602 hpiosize=nn[KMG] The fixed amount of bus space which is
2603 reserved for hotplug bridge's IO window.
2604 Default size is 256 bytes.
2605 hpmemsize=nn[KMG] The fixed amount of bus space which is
2606 reserved for hotplug bridge's memory window.
2607 Default size is 2 megabytes.
2608 realloc= Enable/disable reallocating PCI bridge resources
2609 if allocations done by BIOS are too small to
2610 accommodate resources required by all child
2611 devices.
2612 off: Turn realloc off
2613 on: Turn realloc on
2614 realloc same as realloc=on
2615 noari do not use PCIe ARI.
2616 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2617 only look for one device below a PCIe downstream
2618 port.
2619
2620 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2621 Management.
2622 off Disable ASPM.
2623 force Enable ASPM even on devices that claim not to support it.
2624 WARNING: Forcing ASPM on may cause system lockups.
2625
2626 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2627 nomsi Do not use MSI for PCI Express Native Hotplug (this
2628 makes all PCIe ports use INTx for hotplug services).
2629
2630 pcie_ports= [PCIE] PCIe ports handling:
2631 auto Ask the BIOS whether or not to use native PCIe services
2632 associated with PCIe ports (PME, hot-plug, AER). Use
2633 them only if that is allowed by the BIOS.
2634 native Use native PCIe services associated with PCIe ports
2635 unconditionally.
2636 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2637 ports driver.
2638
2639 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2640 nomsi Do not use MSI for native PCIe PME signaling (this makes
2641 all PCIe root ports use INTx for all services).
2642
2643 pcmv= [HW,PCMCIA] BadgePAD 4
2644
2645 pd_ignore_unused
2646 [PM]
2647 Keep all power-domains already enabled by bootloader on,
2648 even if no driver has claimed them. This is useful
2649 for debug and development, but should not be
2650 needed on a platform with proper driver support.
2651
2652 pd. [PARIDE]
2653 See Documentation/blockdev/paride.txt.
2654
2655 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2656 boot time.
2657 Format: { 0 | 1 }
2658 See arch/parisc/kernel/pdc_chassis.c
2659
2660 percpu_alloc= Select which percpu first chunk allocator to use.
2661 Currently supported values are "embed" and "page".
2662 Archs may support subset or none of the selections.
2663 See comments in mm/percpu.c for details on each
2664 allocator. This parameter is primarily for debugging
2665 and performance comparison.
2666
2667 pf. [PARIDE]
2668 See Documentation/blockdev/paride.txt.
2669
2670 pg. [PARIDE]
2671 See Documentation/blockdev/paride.txt.
2672
2673 pirq= [SMP,APIC] Manual mp-table setup
2674 See Documentation/x86/i386/IO-APIC.txt.
2675
2676 plip= [PPT,NET] Parallel port network link
2677 Format: { parport<nr> | timid | 0 }
2678 See also Documentation/parport.txt.
2679
2680 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2681 Override pmtimer IOPort with a hex value.
2682 e.g. pmtmr=0x508
2683
2684 pnp.debug=1 [PNP]
2685 Enable PNP debug messages (depends on the
2686 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2687 via /sys/module/pnp/parameters/debug. We always show
2688 current resource usage; turning this on also shows
2689 possible settings and some assignment information.
2690
2691 pnpacpi= [ACPI]
2692 { off }
2693
2694 pnpbios= [ISAPNP]
2695 { on | off | curr | res | no-curr | no-res }
2696
2697 pnp_reserve_irq=
2698 [ISAPNP] Exclude IRQs for the autoconfiguration
2699
2700 pnp_reserve_dma=
2701 [ISAPNP] Exclude DMAs for the autoconfiguration
2702
2703 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2704 Ranges are in pairs (I/O port base and size).
2705
2706 pnp_reserve_mem=
2707 [ISAPNP] Exclude memory regions for the
2708 autoconfiguration.
2709 Ranges are in pairs (memory base and size).
2710
2711 ports= [IP_VS_FTP] IPVS ftp helper module
2712 Default is 21.
2713 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2714 may be specified.
2715 Format: <port>,<port>....
2716
2717 print-fatal-signals=
2718 [KNL] debug: print fatal signals
2719
2720 If enabled, warn about various signal handling
2721 related application anomalies: too many signals,
2722 too many POSIX.1 timers, fatal signals causing a
2723 coredump - etc.
2724
2725 If you hit the warning due to signal overflow,
2726 you might want to try "ulimit -i unlimited".
2727
2728 default: off.
2729
2730 printk.always_kmsg_dump=
2731 Trigger kmsg_dump for cases other than kernel oops or
2732 panics
2733 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2734 default: disabled
2735
2736 printk.time= Show timing data prefixed to each printk message line
2737 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2738
2739 processor.max_cstate= [HW,ACPI]
2740 Limit processor to maximum C-state
2741 max_cstate=9 overrides any DMI blacklist limit.
2742
2743 processor.nocst [HW,ACPI]
2744 Ignore the _CST method to determine C-states,
2745 instead using the legacy FADT method
2746
2747 profile= [KNL] Enable kernel profiling via /proc/profile
2748 Format: [schedule,]<number>
2749 Param: "schedule" - profile schedule points.
2750 Param: <number> - step/bucket size as a power of 2 for
2751 statistical time based profiling.
2752 Param: "sleep" - profile D-state sleeping (millisecs).
2753 Requires CONFIG_SCHEDSTATS
2754 Param: "kvm" - profile VM exits.
2755
2756 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2757 before loading.
2758 See Documentation/blockdev/ramdisk.txt.
2759
2760 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2761 probe for; one of (bare|imps|exps|lifebook|any).
2762 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2763 per second.
2764 psmouse.resetafter= [HW,MOUSE]
2765 Try to reset the device after so many bad packets
2766 (0 = never).
2767 psmouse.resolution=
2768 [HW,MOUSE] Set desired mouse resolution, in dpi.
2769 psmouse.smartscroll=
2770 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2771 0 = disabled, 1 = enabled (default).
2772
2773 pstore.backend= Specify the name of the pstore backend to use
2774
2775 pt. [PARIDE]
2776 See Documentation/blockdev/paride.txt.
2777
2778 pty.legacy_count=
2779 [KNL] Number of legacy pty's. Overwrites compiled-in
2780 default number.
2781
2782 quiet [KNL] Disable most log messages
2783
2784 r128= [HW,DRM]
2785
2786 raid= [HW,RAID]
2787 See Documentation/md.txt.
2788
2789 ramdisk_blocksize= [RAM]
2790 See Documentation/blockdev/ramdisk.txt.
2791
2792 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2793 See Documentation/blockdev/ramdisk.txt.
2794
2795 rcu_nocbs= [KNL]
2796 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2797 the specified list of CPUs to be no-callback CPUs.
2798 Invocation of these CPUs' RCU callbacks will
2799 be offloaded to "rcuox/N" kthreads created for
2800 that purpose, where "x" is "b" for RCU-bh, "p"
2801 for RCU-preempt, and "s" for RCU-sched, and "N"
2802 is the CPU number. This reduces OS jitter on the
2803 offloaded CPUs, which can be useful for HPC and
2804 real-time workloads. It can also improve energy
2805 efficiency for asymmetric multiprocessors.
2806
2807 rcu_nocb_poll [KNL]
2808 Rather than requiring that offloaded CPUs
2809 (specified by rcu_nocbs= above) explicitly
2810 awaken the corresponding "rcuoN" kthreads,
2811 make these kthreads poll for callbacks.
2812 This improves the real-time response for the
2813 offloaded CPUs by relieving them of the need to
2814 wake up the corresponding kthread, but degrades
2815 energy efficiency by requiring that the kthreads
2816 periodically wake up to do the polling.
2817
2818 rcutree.blimit= [KNL]
2819 Set maximum number of finished RCU callbacks to
2820 process in one batch.
2821
2822 rcutree.rcu_fanout_leaf= [KNL]
2823 Increase the number of CPUs assigned to each
2824 leaf rcu_node structure. Useful for very large
2825 systems.
2826
2827 rcutree.jiffies_till_sched_qs= [KNL]
2828 Set required age in jiffies for a
2829 given grace period before RCU starts
2830 soliciting quiescent-state help from
2831 rcu_note_context_switch().
2832
2833 rcutree.jiffies_till_first_fqs= [KNL]
2834 Set delay from grace-period initialization to
2835 first attempt to force quiescent states.
2836 Units are jiffies, minimum value is zero,
2837 and maximum value is HZ.
2838
2839 rcutree.jiffies_till_next_fqs= [KNL]
2840 Set delay between subsequent attempts to force
2841 quiescent states. Units are jiffies, minimum
2842 value is one, and maximum value is HZ.
2843
2844 rcutree.rcu_nocb_leader_stride= [KNL]
2845 Set the number of NOCB kthread groups, which
2846 defaults to the square root of the number of
2847 CPUs. Larger numbers reduces the wakeup overhead
2848 on the per-CPU grace-period kthreads, but increases
2849 that same overhead on each group's leader.
2850
2851 rcutree.qhimark= [KNL]
2852 Set threshold of queued RCU callbacks beyond which
2853 batch limiting is disabled.
2854
2855 rcutree.qlowmark= [KNL]
2856 Set threshold of queued RCU callbacks below which
2857 batch limiting is re-enabled.
2858
2859 rcutree.rcu_idle_gp_delay= [KNL]
2860 Set wakeup interval for idle CPUs that have
2861 RCU callbacks (RCU_FAST_NO_HZ=y).
2862
2863 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2864 Set wakeup interval for idle CPUs that have
2865 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2866 Lazy RCU callbacks are those which RCU can
2867 prove do nothing more than free memory.
2868
2869 rcutorture.fqs_duration= [KNL]
2870 Set duration of force_quiescent_state bursts.
2871
2872 rcutorture.fqs_holdoff= [KNL]
2873 Set holdoff time within force_quiescent_state bursts.
2874
2875 rcutorture.fqs_stutter= [KNL]
2876 Set wait time between force_quiescent_state bursts.
2877
2878 rcutorture.gp_exp= [KNL]
2879 Use expedited update-side primitives.
2880
2881 rcutorture.gp_normal= [KNL]
2882 Use normal (non-expedited) update-side primitives.
2883 If both gp_exp and gp_normal are set, do both.
2884 If neither gp_exp nor gp_normal are set, still
2885 do both.
2886
2887 rcutorture.n_barrier_cbs= [KNL]
2888 Set callbacks/threads for rcu_barrier() testing.
2889
2890 rcutorture.nfakewriters= [KNL]
2891 Set number of concurrent RCU writers. These just
2892 stress RCU, they don't participate in the actual
2893 test, hence the "fake".
2894
2895 rcutorture.nreaders= [KNL]
2896 Set number of RCU readers.
2897
2898 rcutorture.object_debug= [KNL]
2899 Enable debug-object double-call_rcu() testing.
2900
2901 rcutorture.onoff_holdoff= [KNL]
2902 Set time (s) after boot for CPU-hotplug testing.
2903
2904 rcutorture.onoff_interval= [KNL]
2905 Set time (s) between CPU-hotplug operations, or
2906 zero to disable CPU-hotplug testing.
2907
2908 rcutorture.rcutorture_runnable= [BOOT]
2909 Start rcutorture running at boot time.
2910
2911 rcutorture.shuffle_interval= [KNL]
2912 Set task-shuffle interval (s). Shuffling tasks
2913 allows some CPUs to go into dyntick-idle mode
2914 during the rcutorture test.
2915
2916 rcutorture.shutdown_secs= [KNL]
2917 Set time (s) after boot system shutdown. This
2918 is useful for hands-off automated testing.
2919
2920 rcutorture.stall_cpu= [KNL]
2921 Duration of CPU stall (s) to test RCU CPU stall
2922 warnings, zero to disable.
2923
2924 rcutorture.stall_cpu_holdoff= [KNL]
2925 Time to wait (s) after boot before inducing stall.
2926
2927 rcutorture.stat_interval= [KNL]
2928 Time (s) between statistics printk()s.
2929
2930 rcutorture.stutter= [KNL]
2931 Time (s) to stutter testing, for example, specifying
2932 five seconds causes the test to run for five seconds,
2933 wait for five seconds, and so on. This tests RCU's
2934 ability to transition abruptly to and from idle.
2935
2936 rcutorture.test_boost= [KNL]
2937 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2938 "Maybe" means test if the RCU implementation
2939 under test support RCU priority boosting.
2940
2941 rcutorture.test_boost_duration= [KNL]
2942 Duration (s) of each individual boost test.
2943
2944 rcutorture.test_boost_interval= [KNL]
2945 Interval (s) between each boost test.
2946
2947 rcutorture.test_no_idle_hz= [KNL]
2948 Test RCU's dyntick-idle handling. See also the
2949 rcutorture.shuffle_interval parameter.
2950
2951 rcutorture.torture_type= [KNL]
2952 Specify the RCU implementation to test.
2953
2954 rcutorture.verbose= [KNL]
2955 Enable additional printk() statements.
2956
2957 rcupdate.rcu_expedited= [KNL]
2958 Use expedited grace-period primitives, for
2959 example, synchronize_rcu_expedited() instead
2960 of synchronize_rcu(). This reduces latency,
2961 but can increase CPU utilization, degrade
2962 real-time latency, and degrade energy efficiency.
2963
2964 rcupdate.rcu_cpu_stall_suppress= [KNL]
2965 Suppress RCU CPU stall warning messages.
2966
2967 rcupdate.rcu_cpu_stall_timeout= [KNL]
2968 Set timeout for RCU CPU stall warning messages.
2969
2970 rdinit= [KNL]
2971 Format: <full_path>
2972 Run specified binary instead of /init from the ramdisk,
2973 used for early userspace startup. See initrd.
2974
2975 reboot= [KNL]
2976 Format (x86 or x86_64):
2977 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2978 [[,]s[mp]#### \
2979 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2980 [[,]f[orce]
2981 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2982 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2983 reboot_force is either force or not specified,
2984 reboot_cpu is s[mp]#### with #### being the processor
2985 to be used for rebooting.
2986
2987 relax_domain_level=
2988 [KNL, SMP] Set scheduler's default relax_domain_level.
2989 See Documentation/cgroups/cpusets.txt.
2990
2991 relative_sleep_states=
2992 [SUSPEND] Use sleep state labeling where the deepest
2993 state available other than hibernation is always "mem".
2994 Format: { "0" | "1" }
2995 0 -- Traditional sleep state labels.
2996 1 -- Relative sleep state labels.
2997
2998 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2999
3000 reservetop= [X86-32]
3001 Format: nn[KMG]
3002 Reserves a hole at the top of the kernel virtual
3003 address space.
3004
3005 reservelow= [X86]
3006 Format: nn[K]
3007 Set the amount of memory to reserve for BIOS at
3008 the bottom of the address space.
3009
3010 reset_devices [KNL] Force drivers to reset the underlying device
3011 during initialization.
3012
3013 resume= [SWSUSP]
3014 Specify the partition device for software suspend
3015 Format:
3016 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3017
3018 resume_offset= [SWSUSP]
3019 Specify the offset from the beginning of the partition
3020 given by "resume=" at which the swap header is located,
3021 in <PAGE_SIZE> units (needed only for swap files).
3022 See Documentation/power/swsusp-and-swap-files.txt
3023
3024 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3025 read the resume files
3026
3027 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3028 Useful for devices that are detected asynchronously
3029 (e.g. USB and MMC devices).
3030
3031 hibernate= [HIBERNATION]
3032 noresume Don't check if there's a hibernation image
3033 present during boot.
3034 nocompress Don't compress/decompress hibernation images.
3035 no Disable hibernation and resume.
3036
3037 retain_initrd [RAM] Keep initrd memory after extraction
3038
3039 rhash_entries= [KNL,NET]
3040 Set number of hash buckets for route cache
3041
3042 ro [KNL] Mount root device read-only on boot
3043
3044 root= [KNL] Root filesystem
3045 See name_to_dev_t comment in init/do_mounts.c.
3046
3047 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3048 mount the root filesystem
3049
3050 rootflags= [KNL] Set root filesystem mount option string
3051
3052 rootfstype= [KNL] Set root filesystem type
3053
3054 rootwait [KNL] Wait (indefinitely) for root device to show up.
3055 Useful for devices that are detected asynchronously
3056 (e.g. USB and MMC devices).
3057
3058 rproc_mem=nn[KMG][@address]
3059 [KNL,ARM,CMA] Remoteproc physical memory block.
3060 Memory area to be used by remote processor image,
3061 managed by CMA.
3062
3063 rw [KNL] Mount root device read-write on boot
3064
3065 S [KNL] Run init in single mode
3066
3067 s390_iommu= [HW,S390]
3068 Set s390 IOTLB flushing mode
3069 strict
3070 With strict flushing every unmap operation will result in
3071 an IOTLB flush. Default is lazy flushing before reuse,
3072 which is faster.
3073
3074 sa1100ir [NET]
3075 See drivers/net/irda/sa1100_ir.c.
3076
3077 sbni= [NET] Granch SBNI12 leased line adapter
3078
3079 sched_debug [KNL] Enables verbose scheduler debug messages.
3080
3081 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3082 xtime_lock contention on larger systems, and/or RCU lock
3083 contention on all systems with CONFIG_MAXSMP set.
3084 Format: { "0" | "1" }
3085 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3086 1 -- enable.
3087 Note: increases power consumption, thus should only be
3088 enabled if running jitter sensitive (HPC/RT) workloads.
3089
3090 security= [SECURITY] Choose a security module to enable at boot.
3091 If this boot parameter is not specified, only the first
3092 security module asking for security registration will be
3093 loaded. An invalid security module name will be treated
3094 as if no module has been chosen.
3095
3096 selinux= [SELINUX] Disable or enable SELinux at boot time.
3097 Format: { "0" | "1" }
3098 See security/selinux/Kconfig help text.
3099 0 -- disable.
3100 1 -- enable.
3101 Default value is set via kernel config option.
3102 If enabled at boot time, /selinux/disable can be used
3103 later to disable prior to initial policy load.
3104
3105 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3106 Format: { "0" | "1" }
3107 See security/apparmor/Kconfig help text
3108 0 -- disable.
3109 1 -- enable.
3110 Default value is set via kernel config option.
3111
3112 serialnumber [BUGS=X86-32]
3113
3114 shapers= [NET]
3115 Maximal number of shapers.
3116
3117 show_msr= [x86] show boot-time MSR settings
3118 Format: { <integer> }
3119 Show boot-time (BIOS-initialized) MSR settings.
3120 The parameter means the number of CPUs to show,
3121 for example 1 means boot CPU only.
3122
3123 simeth= [IA-64]
3124 simscsi=
3125
3126 slram= [HW,MTD]
3127
3128 slab_max_order= [MM, SLAB]
3129 Determines the maximum allowed order for slabs.
3130 A high setting may cause OOMs due to memory
3131 fragmentation. Defaults to 1 for systems with
3132 more than 32MB of RAM, 0 otherwise.
3133
3134 slub_debug[=options[,slabs]] [MM, SLUB]
3135 Enabling slub_debug allows one to determine the
3136 culprit if slab objects become corrupted. Enabling
3137 slub_debug can create guard zones around objects and
3138 may poison objects when not in use. Also tracks the
3139 last alloc / free. For more information see
3140 Documentation/vm/slub.txt.
3141
3142 slub_max_order= [MM, SLUB]
3143 Determines the maximum allowed order for slabs.
3144 A high setting may cause OOMs due to memory
3145 fragmentation. For more information see
3146 Documentation/vm/slub.txt.
3147
3148 slub_min_objects= [MM, SLUB]
3149 The minimum number of objects per slab. SLUB will
3150 increase the slab order up to slub_max_order to
3151 generate a sufficiently large slab able to contain
3152 the number of objects indicated. The higher the number
3153 of objects the smaller the overhead of tracking slabs
3154 and the less frequently locks need to be acquired.
3155 For more information see Documentation/vm/slub.txt.
3156
3157 slub_min_order= [MM, SLUB]
3158 Determines the minimum page order for slabs. Must be
3159 lower than slub_max_order.
3160 For more information see Documentation/vm/slub.txt.
3161
3162 slub_nomerge [MM, SLUB]
3163 Disable merging of slabs with similar size. May be
3164 necessary if there is some reason to distinguish
3165 allocs to different slabs. Debug options disable
3166 merging on their own.
3167 For more information see Documentation/vm/slub.txt.
3168
3169 smart2= [HW]
3170 Format: <io1>[,<io2>[,...,<io8>]]
3171
3172 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3173 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3174 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3175 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3176 smsc-ircc2.ircc_irq= [HW] IRQ line
3177 smsc-ircc2.ircc_dma= [HW] DMA channel
3178 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3179 0: Toshiba Satellite 1800 (GP data pin select)
3180 1: Fast pin select (default)
3181 2: ATC IRMode
3182
3183 softlockup_panic=
3184 [KNL] Should the soft-lockup detector generate panics.
3185 Format: <integer>
3186
3187 softlockup_all_cpu_backtrace=
3188 [KNL] Should the soft-lockup detector generate
3189 backtraces on all cpus.
3190 Format: <integer>
3191
3192 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3193 See Documentation/laptops/sonypi.txt
3194
3195 spia_io_base= [HW,MTD]
3196 spia_fio_base=
3197 spia_pedr=
3198 spia_peddr=
3199
3200 stacktrace [FTRACE]
3201 Enabled the stack tracer on boot up.
3202
3203 stacktrace_filter=[function-list]
3204 [FTRACE] Limit the functions that the stack tracer
3205 will trace at boot up. function-list is a comma separated
3206 list of functions. This list can be changed at run
3207 time by the stack_trace_filter file in the debugfs
3208 tracing directory. Note, this enables stack tracing
3209 and the stacktrace above is not needed.
3210
3211 sti= [PARISC,HW]
3212 Format: <num>
3213 Set the STI (builtin display/keyboard on the HP-PARISC
3214 machines) console (graphic card) which should be used
3215 as the initial boot-console.
3216 See also comment in drivers/video/console/sticore.c.
3217
3218 sti_font= [HW]
3219 See comment in drivers/video/console/sticore.c.
3220
3221 stifb= [HW]
3222 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3223
3224 sunrpc.min_resvport=
3225 sunrpc.max_resvport=
3226 [NFS,SUNRPC]
3227 SunRPC servers often require that client requests
3228 originate from a privileged port (i.e. a port in the
3229 range 0 < portnr < 1024).
3230 An administrator who wishes to reserve some of these
3231 ports for other uses may adjust the range that the
3232 kernel's sunrpc client considers to be privileged
3233 using these two parameters to set the minimum and
3234 maximum port values.
3235
3236 sunrpc.pool_mode=
3237 [NFS]
3238 Control how the NFS server code allocates CPUs to
3239 service thread pools. Depending on how many NICs
3240 you have and where their interrupts are bound, this
3241 option will affect which CPUs will do NFS serving.
3242 Note: this parameter cannot be changed while the
3243 NFS server is running.
3244
3245 auto the server chooses an appropriate mode
3246 automatically using heuristics
3247 global a single global pool contains all CPUs
3248 percpu one pool for each CPU
3249 pernode one pool for each NUMA node (equivalent
3250 to global on non-NUMA machines)
3251
3252 sunrpc.tcp_slot_table_entries=
3253 sunrpc.udp_slot_table_entries=
3254 [NFS,SUNRPC]
3255 Sets the upper limit on the number of simultaneous
3256 RPC calls that can be sent from the client to a
3257 server. Increasing these values may allow you to
3258 improve throughput, but will also increase the
3259 amount of memory reserved for use by the client.
3260
3261 swapaccount=[0|1]
3262 [KNL] Enable accounting of swap in memory resource
3263 controller if no parameter or 1 is given or disable
3264 it if 0 is given (See Documentation/cgroups/memory.txt)
3265
3266 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3267 Format: { <int> | force }
3268 <int> -- Number of I/O TLB slabs
3269 force -- force using of bounce buffers even if they
3270 wouldn't be automatically used by the kernel
3271
3272 switches= [HW,M68k]
3273
3274 sysfs.deprecated=0|1 [KNL]
3275 Enable/disable old style sysfs layout for old udev
3276 on older distributions. When this option is enabled
3277 very new udev will not work anymore. When this option
3278 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3279 in older udev will not work anymore.
3280 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3281 the kernel configuration.
3282
3283 sysrq_always_enabled
3284 [KNL]
3285 Ignore sysrq setting - this boot parameter will
3286 neutralize any effect of /proc/sys/kernel/sysrq.
3287 Useful for debugging.
3288
3289 tdfx= [HW,DRM]
3290
3291 test_suspend= [SUSPEND]
3292 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3293 standby suspend) as the system sleep state to briefly
3294 enter during system startup. The system is woken from
3295 this state using a wakeup-capable RTC alarm.
3296
3297 thash_entries= [KNL,NET]
3298 Set number of hash buckets for TCP connection
3299
3300 thermal.act= [HW,ACPI]
3301 -1: disable all active trip points in all thermal zones
3302 <degrees C>: override all lowest active trip points
3303
3304 thermal.crt= [HW,ACPI]
3305 -1: disable all critical trip points in all thermal zones
3306 <degrees C>: override all critical trip points
3307
3308 thermal.nocrt= [HW,ACPI]
3309 Set to disable actions on ACPI thermal zone
3310 critical and hot trip points.
3311
3312 thermal.off= [HW,ACPI]
3313 1: disable ACPI thermal control
3314
3315 thermal.psv= [HW,ACPI]
3316 -1: disable all passive trip points
3317 <degrees C>: override all passive trip points to this
3318 value
3319
3320 thermal.tzp= [HW,ACPI]
3321 Specify global default ACPI thermal zone polling rate
3322 <deci-seconds>: poll all this frequency
3323 0: no polling (default)
3324
3325 threadirqs [KNL]
3326 Force threading of all interrupt handlers except those
3327 marked explicitly IRQF_NO_THREAD.
3328
3329 tmem [KNL,XEN]
3330 Enable the Transcendent memory driver if built-in.
3331
3332 tmem.cleancache=0|1 [KNL, XEN]
3333 Default is on (1). Disable the usage of the cleancache
3334 API to send anonymous pages to the hypervisor.
3335
3336 tmem.frontswap=0|1 [KNL, XEN]
3337 Default is on (1). Disable the usage of the frontswap
3338 API to send swap pages to the hypervisor. If disabled
3339 the selfballooning and selfshrinking are force disabled.
3340
3341 tmem.selfballooning=0|1 [KNL, XEN]
3342 Default is on (1). Disable the driving of swap pages
3343 to the hypervisor.
3344
3345 tmem.selfshrinking=0|1 [KNL, XEN]
3346 Default is on (1). Partial swapoff that immediately
3347 transfers pages from Xen hypervisor back to the
3348 kernel based on different criteria.
3349
3350 topology= [S390]
3351 Format: {off | on}
3352 Specify if the kernel should make use of the cpu
3353 topology information if the hardware supports this.
3354 The scheduler will make use of this information and
3355 e.g. base its process migration decisions on it.
3356 Default is on.
3357
3358 tp720= [HW,PS2]
3359
3360 tpm_suspend_pcr=[HW,TPM]
3361 Format: integer pcr id
3362 Specify that at suspend time, the tpm driver
3363 should extend the specified pcr with zeros,
3364 as a workaround for some chips which fail to
3365 flush the last written pcr on TPM_SaveState.
3366 This will guarantee that all the other pcrs
3367 are saved.
3368
3369 trace_buf_size=nn[KMG]
3370 [FTRACE] will set tracing buffer size.
3371
3372 trace_event=[event-list]
3373 [FTRACE] Set and start specified trace events in order
3374 to facilitate early boot debugging.
3375 See also Documentation/trace/events.txt
3376
3377 trace_options=[option-list]
3378 [FTRACE] Enable or disable tracer options at boot.
3379 The option-list is a comma delimited list of options
3380 that can be enabled or disabled just as if you were
3381 to echo the option name into
3382
3383 /sys/kernel/debug/tracing/trace_options
3384
3385 For example, to enable stacktrace option (to dump the
3386 stack trace of each event), add to the command line:
3387
3388 trace_options=stacktrace
3389
3390 See also Documentation/trace/ftrace.txt "trace options"
3391 section.
3392
3393 traceoff_on_warning
3394 [FTRACE] enable this option to disable tracing when a
3395 warning is hit. This turns off "tracing_on". Tracing can
3396 be enabled again by echoing '1' into the "tracing_on"
3397 file located in /sys/kernel/debug/tracing/
3398
3399 This option is useful, as it disables the trace before
3400 the WARNING dump is called, which prevents the trace to
3401 be filled with content caused by the warning output.
3402
3403 This option can also be set at run time via the sysctl
3404 option: kernel/traceoff_on_warning
3405
3406 transparent_hugepage=
3407 [KNL]
3408 Format: [always|madvise|never]
3409 Can be used to control the default behavior of the system
3410 with respect to transparent hugepages.
3411 See Documentation/vm/transhuge.txt for more details.
3412
3413 tsc= Disable clocksource stability checks for TSC.
3414 Format: <string>
3415 [x86] reliable: mark tsc clocksource as reliable, this
3416 disables clocksource verification at runtime, as well
3417 as the stability checks done at bootup. Used to enable
3418 high-resolution timer mode on older hardware, and in
3419 virtualized environment.
3420 [x86] noirqtime: Do not use TSC to do irq accounting.
3421 Used to run time disable IRQ_TIME_ACCOUNTING on any
3422 platforms where RDTSC is slow and this accounting
3423 can add overhead.
3424
3425 turbografx.map[2|3]= [HW,JOY]
3426 TurboGraFX parallel port interface
3427 Format:
3428 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3429 See also Documentation/input/joystick-parport.txt
3430
3431 udbg-immortal [PPC] When debugging early kernel crashes that
3432 happen after console_init() and before a proper
3433 console driver takes over, this boot options might
3434 help "seeing" what's going on.
3435
3436 uhash_entries= [KNL,NET]
3437 Set number of hash buckets for UDP/UDP-Lite connections
3438
3439 uhci-hcd.ignore_oc=
3440 [USB] Ignore overcurrent events (default N).
3441 Some badly-designed motherboards generate lots of
3442 bogus events, for ports that aren't wired to
3443 anything. Set this parameter to avoid log spamming.
3444 Note that genuine overcurrent events won't be
3445 reported either.
3446
3447 unknown_nmi_panic
3448 [X86] Cause panic on unknown NMI.
3449
3450 usbcore.authorized_default=
3451 [USB] Default USB device authorization:
3452 (default -1 = authorized except for wireless USB,
3453 0 = not authorized, 1 = authorized)
3454
3455 usbcore.autosuspend=
3456 [USB] The autosuspend time delay (in seconds) used
3457 for newly-detected USB devices (default 2). This
3458 is the time required before an idle device will be
3459 autosuspended. Devices for which the delay is set
3460 to a negative value won't be autosuspended at all.
3461
3462 usbcore.usbfs_snoop=
3463 [USB] Set to log all usbfs traffic (default 0 = off).
3464
3465 usbcore.blinkenlights=
3466 [USB] Set to cycle leds on hubs (default 0 = off).
3467
3468 usbcore.old_scheme_first=
3469 [USB] Start with the old device initialization
3470 scheme (default 0 = off).
3471
3472 usbcore.usbfs_memory_mb=
3473 [USB] Memory limit (in MB) for buffers allocated by
3474 usbfs (default = 16, 0 = max = 2047).
3475
3476 usbcore.use_both_schemes=
3477 [USB] Try the other device initialization scheme
3478 if the first one fails (default 1 = enabled).
3479
3480 usbcore.initial_descriptor_timeout=
3481 [USB] Specifies timeout for the initial 64-byte
3482 USB_REQ_GET_DESCRIPTOR request in milliseconds
3483 (default 5000 = 5.0 seconds).
3484
3485 usbhid.mousepoll=
3486 [USBHID] The interval which mice are to be polled at.
3487
3488 usb-storage.delay_use=
3489 [UMS] The delay in seconds before a new device is
3490 scanned for Logical Units (default 5).
3491
3492 usb-storage.quirks=
3493 [UMS] A list of quirks entries to supplement or
3494 override the built-in unusual_devs list. List
3495 entries are separated by commas. Each entry has
3496 the form VID:PID:Flags where VID and PID are Vendor
3497 and Product ID values (4-digit hex numbers) and
3498 Flags is a set of characters, each corresponding
3499 to a common usb-storage quirk flag as follows:
3500 a = SANE_SENSE (collect more than 18 bytes
3501 of sense data);
3502 b = BAD_SENSE (don't collect more than 18
3503 bytes of sense data);
3504 c = FIX_CAPACITY (decrease the reported
3505 device capacity by one sector);
3506 d = NO_READ_DISC_INFO (don't use
3507 READ_DISC_INFO command);
3508 e = NO_READ_CAPACITY_16 (don't use
3509 READ_CAPACITY_16 command);
3510 h = CAPACITY_HEURISTICS (decrease the
3511 reported device capacity by one
3512 sector if the number is odd);
3513 i = IGNORE_DEVICE (don't bind to this
3514 device);
3515 l = NOT_LOCKABLE (don't try to lock and
3516 unlock ejectable media);
3517 m = MAX_SECTORS_64 (don't transfer more
3518 than 64 sectors = 32 KB at a time);
3519 n = INITIAL_READ10 (force a retry of the
3520 initial READ(10) command);
3521 o = CAPACITY_OK (accept the capacity
3522 reported by the device);
3523 p = WRITE_CACHE (the device cache is ON
3524 by default);
3525 r = IGNORE_RESIDUE (the device reports
3526 bogus residue values);
3527 s = SINGLE_LUN (the device has only one
3528 Logical Unit);
3529 w = NO_WP_DETECT (don't test whether the
3530 medium is write-protected).
3531 Example: quirks=0419:aaf5:rl,0421:0433:rc
3532
3533 user_debug= [KNL,ARM]
3534 Format: <int>
3535 See arch/arm/Kconfig.debug help text.
3536 1 - undefined instruction events
3537 2 - system calls
3538 4 - invalid data aborts
3539 8 - SIGSEGV faults
3540 16 - SIGBUS faults
3541 Example: user_debug=31
3542
3543 userpte=
3544 [X86] Flags controlling user PTE allocations.
3545
3546 nohigh = do not allocate PTE pages in
3547 HIGHMEM regardless of setting
3548 of CONFIG_HIGHPTE.
3549
3550 vdso= [X86,SH]
3551 On X86_32, this is an alias for vdso32=. Otherwise:
3552
3553 vdso=1: enable VDSO (the default)
3554 vdso=0: disable VDSO mapping
3555
3556 vdso32= [X86] Control the 32-bit vDSO
3557 vdso32=1: enable 32-bit VDSO
3558 vdso32=0 or vdso32=2: disable 32-bit VDSO
3559
3560 See the help text for CONFIG_COMPAT_VDSO for more
3561 details. If CONFIG_COMPAT_VDSO is set, the default is
3562 vdso32=0; otherwise, the default is vdso32=1.
3563
3564 For compatibility with older kernels, vdso32=2 is an
3565 alias for vdso32=0.
3566
3567 Try vdso32=0 if you encounter an error that says:
3568 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3569
3570 vector= [IA-64,SMP]
3571 vector=percpu: enable percpu vector domain
3572
3573 video= [FB] Frame buffer configuration
3574 See Documentation/fb/modedb.txt.
3575
3576 video.brightness_switch_enabled= [0,1]
3577 If set to 1, on receiving an ACPI notify event
3578 generated by hotkey, video driver will adjust brightness
3579 level and then send out the event to user space through
3580 the allocated input device; If set to 0, video driver
3581 will only send out the event without touching backlight
3582 brightness level.
3583 default: 1
3584
3585 virtio_mmio.device=
3586 [VMMIO] Memory mapped virtio (platform) device.
3587
3588 <size>@<baseaddr>:<irq>[:<id>]
3589 where:
3590 <size> := size (can use standard suffixes
3591 like K, M and G)
3592 <baseaddr> := physical base address
3593 <irq> := interrupt number (as passed to
3594 request_irq())
3595 <id> := (optional) platform device id
3596 example:
3597 virtio_mmio.device=1K@0x100b0000:48:7
3598
3599 Can be used multiple times for multiple devices.
3600
3601 vga= [BOOT,X86-32] Select a particular video mode
3602 See Documentation/x86/boot.txt and
3603 Documentation/svga.txt.
3604 Use vga=ask for menu.
3605 This is actually a boot loader parameter; the value is
3606 passed to the kernel using a special protocol.
3607
3608 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3609 size of <nn>. This can be used to increase the
3610 minimum size (128MB on x86). It can also be used to
3611 decrease the size and leave more room for directly
3612 mapped kernel RAM.
3613
3614 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3615 Format: <command>
3616
3617 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3618 Format: <command>
3619
3620 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3621 Format: <command>
3622
3623 vsyscall= [X86-64]
3624 Controls the behavior of vsyscalls (i.e. calls to
3625 fixed addresses of 0xffffffffff600x00 from legacy
3626 code). Most statically-linked binaries and older
3627 versions of glibc use these calls. Because these
3628 functions are at fixed addresses, they make nice
3629 targets for exploits that can control RIP.
3630
3631 emulate [default] Vsyscalls turn into traps and are
3632 emulated reasonably safely.
3633
3634 native Vsyscalls are native syscall instructions.
3635 This is a little bit faster than trapping
3636 and makes a few dynamic recompilers work
3637 better than they would in emulation mode.
3638 It also makes exploits much easier to write.
3639
3640 none Vsyscalls don't work at all. This makes
3641 them quite hard to use for exploits but
3642 might break your system.
3643
3644 vt.color= [VT] Default text color.
3645 Format: 0xYX, X = foreground, Y = background.
3646 Default: 0x07 = light gray on black.
3647
3648 vt.cur_default= [VT] Default cursor shape.
3649 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3650 the parameters of the <Esc>[?A;B;Cc escape sequence;
3651 see VGA-softcursor.txt. Default: 2 = underline.
3652
3653 vt.default_blu= [VT]
3654 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3655 Change the default blue palette of the console.
3656 This is a 16-member array composed of values
3657 ranging from 0-255.
3658
3659 vt.default_grn= [VT]
3660 Format: <green0>,<green1>,<green2>,...,<green15>
3661 Change the default green palette of the console.
3662 This is a 16-member array composed of values
3663 ranging from 0-255.
3664
3665 vt.default_red= [VT]
3666 Format: <red0>,<red1>,<red2>,...,<red15>
3667 Change the default red palette of the console.
3668 This is a 16-member array composed of values
3669 ranging from 0-255.
3670
3671 vt.default_utf8=
3672 [VT]
3673 Format=<0|1>
3674 Set system-wide default UTF-8 mode for all tty's.
3675 Default is 1, i.e. UTF-8 mode is enabled for all
3676 newly opened terminals.
3677
3678 vt.global_cursor_default=
3679 [VT]
3680 Format=<-1|0|1>
3681 Set system-wide default for whether a cursor
3682 is shown on new VTs. Default is -1,
3683 i.e. cursors will be created by default unless
3684 overridden by individual drivers. 0 will hide
3685 cursors, 1 will display them.
3686
3687 vt.italic= [VT] Default color for italic text; 0-15.
3688 Default: 2 = green.
3689
3690 vt.underline= [VT] Default color for underlined text; 0-15.
3691 Default: 3 = cyan.
3692
3693 watchdog timers [HW,WDT] For information on watchdog timers,
3694 see Documentation/watchdog/watchdog-parameters.txt
3695 or other driver-specific files in the
3696 Documentation/watchdog/ directory.
3697
3698 workqueue.disable_numa
3699 By default, all work items queued to unbound
3700 workqueues are affine to the NUMA nodes they're
3701 issued on, which results in better behavior in
3702 general. If NUMA affinity needs to be disabled for
3703 whatever reason, this option can be used. Note
3704 that this also can be controlled per-workqueue for
3705 workqueues visible under /sys/bus/workqueue/.
3706
3707 workqueue.power_efficient
3708 Per-cpu workqueues are generally preferred because
3709 they show better performance thanks to cache
3710 locality; unfortunately, per-cpu workqueues tend to
3711 be more power hungry than unbound workqueues.
3712
3713 Enabling this makes the per-cpu workqueues which
3714 were observed to contribute significantly to power
3715 consumption unbound, leading to measurably lower
3716 power usage at the cost of small performance
3717 overhead.
3718
3719 The default value of this parameter is determined by
3720 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3721
3722 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3723 default x2apic cluster mode on platforms
3724 supporting x2apic.
3725
3726 x86_intel_mid_timer= [X86-32,APBT]
3727 Choose timer option for x86 Intel MID platform.
3728 Two valid options are apbt timer only and lapic timer
3729 plus one apbt timer for broadcast timer.
3730 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3731
3732 xen_emul_unplug= [HW,X86,XEN]
3733 Unplug Xen emulated devices
3734 Format: [unplug0,][unplug1]
3735 ide-disks -- unplug primary master IDE devices
3736 aux-ide-disks -- unplug non-primary-master IDE devices
3737 nics -- unplug network devices
3738 all -- unplug all emulated devices (NICs and IDE disks)
3739 unnecessary -- unplugging emulated devices is
3740 unnecessary even if the host did not respond to
3741 the unplug protocol
3742 never -- do not unplug even if version check succeeds
3743
3744 xen_nopvspin [X86,XEN]
3745 Disables the ticketlock slowpath using Xen PV
3746 optimizations.
3747
3748 xen_nopv [X86]
3749 Disables the PV optimizations forcing the HVM guest to
3750 run as generic HVM guest with no PV drivers.
3751
3752 xirc2ps_cs= [NET,PCMCIA]
3753 Format:
3754 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3755
3756 ______________________________________________________________________
3757
3758 TODO:
3759
3760 Add more DRM drivers.
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