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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
26 loadable modules too.
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 cpu lists:
37 ----------
39 Some kernel parameters take a list of CPUs as a value, e.g. isolcpus,
40 nohz_full, irqaffinity, rcu_nocbs. The format of this list is:
42 <cpu number>,...,<cpu number>
44 or
46 <cpu number>-<cpu number>
47 (must be a positive range in ascending order)
49 or a mixture
51 <cpu number>,...,<cpu number>-<cpu number>
53 Note that for the special case of a range one can split the range into equal
54 sized groups and for each group use some amount from the beginning of that
55 group:
57 <cpu number>-cpu number>:<used size>/<group size>
59 For example one can add to the command line following parameter:
61 isolcpus=1,2,10-20,100-2000:2/25
63 where the final item represents CPUs 100,101,125,126,150,151,...
67 This document may not be entirely up to date and comprehensive. The command
68 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
69 module. Loadable modules, after being loaded into the running kernel, also
70 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
71 parameters may be changed at runtime by the command
72 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
74 The parameters listed below are only valid if certain kernel build options were
75 enabled and if respective hardware is present. The text in square brackets at
76 the beginning of each description states the restrictions within which a
77 parameter is applicable:
79 ACPI ACPI support is enabled.
80 AGP AGP (Accelerated Graphics Port) is enabled.
81 ALSA ALSA sound support is enabled.
82 APIC APIC support is enabled.
83 APM Advanced Power Management support is enabled.
84 ARM ARM architecture is enabled.
85 AVR32 AVR32 architecture is enabled.
86 AX25 Appropriate AX.25 support is enabled.
87 BLACKFIN Blackfin architecture is enabled.
88 CLK Common clock infrastructure is enabled.
89 CMA Contiguous Memory Area support is enabled.
90 DRM Direct Rendering Management support is enabled.
91 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
92 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
93 EFI EFI Partitioning (GPT) is enabled
94 EIDE EIDE/ATAPI support is enabled.
95 EVM Extended Verification Module
96 FB The frame buffer device is enabled.
97 FTRACE Function tracing enabled.
98 GCOV GCOV profiling is enabled.
99 HW Appropriate hardware is enabled.
100 IA-64 IA-64 architecture is enabled.
101 IMA Integrity measurement architecture is enabled.
102 IOSCHED More than one I/O scheduler is enabled.
103 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
104 IPV6 IPv6 support is enabled.
105 ISAPNP ISA PnP code is enabled.
106 ISDN Appropriate ISDN support is enabled.
107 JOY Appropriate joystick support is enabled.
108 KGDB Kernel debugger support is enabled.
109 KVM Kernel Virtual Machine support is enabled.
110 LIBATA Libata driver is enabled
111 LP Printer support is enabled.
112 LOOP Loopback device support is enabled.
113 M68k M68k architecture is enabled.
114 These options have more detailed description inside of
115 Documentation/m68k/kernel-options.txt.
116 MDA MDA console support is enabled.
117 MIPS MIPS architecture is enabled.
118 MOUSE Appropriate mouse support is enabled.
119 MSI Message Signaled Interrupts (PCI).
120 MTD MTD (Memory Technology Device) support is enabled.
121 NET Appropriate network support is enabled.
122 NUMA NUMA support is enabled.
123 NFS Appropriate NFS support is enabled.
124 OSS OSS sound support is enabled.
125 PV_OPS A paravirtualized kernel is enabled.
126 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
127 PARISC The PA-RISC architecture is enabled.
128 PCI PCI bus support is enabled.
129 PCIE PCI Express support is enabled.
130 PCMCIA The PCMCIA subsystem is enabled.
131 PNP Plug & Play support is enabled.
132 PPC PowerPC architecture is enabled.
133 PPT Parallel port support is enabled.
134 PS2 Appropriate PS/2 support is enabled.
135 RAM RAM disk support is enabled.
136 S390 S390 architecture is enabled.
137 SCSI Appropriate SCSI support is enabled.
138 A lot of drivers have their options described inside
139 the Documentation/scsi/ sub-directory.
140 SECURITY Different security models are enabled.
141 SELINUX SELinux support is enabled.
142 APPARMOR AppArmor support is enabled.
143 SERIAL Serial support is enabled.
144 SH SuperH architecture is enabled.
145 SMP The kernel is an SMP kernel.
146 SPARC Sparc architecture is enabled.
147 SWSUSP Software suspend (hibernation) is enabled.
148 SUSPEND System suspend states are enabled.
149 TPM TPM drivers are enabled.
150 TS Appropriate touchscreen support is enabled.
151 UMS USB Mass Storage support is enabled.
152 USB USB support is enabled.
153 USBHID USB Human Interface Device support is enabled.
154 V4L Video For Linux support is enabled.
155 VMMIO Driver for memory mapped virtio devices is enabled.
156 VGA The VGA console has been enabled.
157 VT Virtual terminal support is enabled.
158 WDT Watchdog support is enabled.
159 XT IBM PC/XT MFM hard disk support is enabled.
160 X86-32 X86-32, aka i386 architecture is enabled.
161 X86-64 X86-64 architecture is enabled.
162 More X86-64 boot options can be found in
163 Documentation/x86/x86_64/boot-options.txt .
164 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
165 X86_UV SGI UV support is enabled.
166 XEN Xen support is enabled
168 In addition, the following text indicates that the option:
170 BUGS= Relates to possible processor bugs on the said processor.
171 KNL Is a kernel start-up parameter.
172 BOOT Is a boot loader parameter.
174 Parameters denoted with BOOT are actually interpreted by the boot
175 loader, and have no meaning to the kernel directly.
176 Do not modify the syntax of boot loader parameters without extreme
177 need or coordination with <Documentation/x86/boot.txt>.
179 There are also arch-specific kernel-parameters not documented here.
180 See for example <Documentation/x86/x86_64/boot-options.txt>.
182 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
183 a trailing = on the name of any parameter states that that parameter will
184 be entered as an environment variable, whereas its absence indicates that
185 it will appear as a kernel argument readable via /proc/cmdline by programs
186 running once the system is up.
188 The number of kernel parameters is not limited, but the length of the
189 complete command line (parameters including spaces etc.) is limited to
190 a fixed number of characters. This limit depends on the architecture
191 and is between 256 and 4096 characters. It is defined in the file
192 ./include/asm/setup.h as COMMAND_LINE_SIZE.
194 Finally, the [KMG] suffix is commonly described after a number of kernel
195 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
196 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
197 bytes respectively. Such letter suffixes can also be entirely omitted.
200 acpi= [HW,ACPI,X86,ARM64]
201 Advanced Configuration and Power Interface
202 Format: { force | on | off | strict | noirq | rsdt |
203 copy_dsdt }
204 force -- enable ACPI if default was off
205 on -- enable ACPI but allow fallback to DT [arm64]
206 off -- disable ACPI if default was on
207 noirq -- do not use ACPI for IRQ routing
208 strict -- Be less tolerant of platforms that are not
209 strictly ACPI specification compliant.
210 rsdt -- prefer RSDT over (default) XSDT
211 copy_dsdt -- copy DSDT to memory
212 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
213 are available
215 See also Documentation/power/runtime_pm.txt, pci=noacpi
217 acpi_apic_instance= [ACPI, IOAPIC]
218 Format: <int>
219 2: use 2nd APIC table, if available
220 1,0: use 1st APIC table
221 default: 0
223 acpi_backlight= [HW,ACPI]
224 acpi_backlight=vendor
225 acpi_backlight=video
226 If set to vendor, prefer vendor specific driver
227 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
228 of the ACPI video.ko driver.
230 acpi_force_32bit_fadt_addr
231 force FADT to use 32 bit addresses rather than the
232 64 bit X_* addresses. Some firmware have broken 64
233 bit addresses for force ACPI ignore these and use
234 the older legacy 32 bit addresses.
236 acpica_no_return_repair [HW, ACPI]
237 Disable AML predefined validation mechanism
238 This mechanism can repair the evaluation result to make
239 the return objects more ACPI specification compliant.
240 This option is useful for developers to identify the
241 root cause of an AML interpreter issue when the issue
242 has something to do with the repair mechanism.
244 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
245 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
246 Format: <int>
247 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
248 debug output. Bits in debug_layer correspond to a
249 _COMPONENT in an ACPI source file, e.g.,
250 #define _COMPONENT ACPI_PCI_COMPONENT
251 Bits in debug_level correspond to a level in
252 ACPI_DEBUG_PRINT statements, e.g.,
253 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
254 The debug_level mask defaults to "info". See
255 Documentation/acpi/debug.txt for more information about
256 debug layers and levels.
258 Enable processor driver info messages:
259 acpi.debug_layer=0x20000000
260 Enable PCI/PCI interrupt routing info messages:
261 acpi.debug_layer=0x400000
262 Enable AML "Debug" output, i.e., stores to the Debug
263 object while interpreting AML:
264 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
265 Enable all messages related to ACPI hardware:
266 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
268 Some values produce so much output that the system is
269 unusable. The "log_buf_len" parameter may be useful
270 if you need to capture more output.
272 acpi_enforce_resources= [ACPI]
273 { strict | lax | no }
274 Check for resource conflicts between native drivers
275 and ACPI OperationRegions (SystemIO and SystemMemory
276 only). IO ports and memory declared in ACPI might be
277 used by the ACPI subsystem in arbitrary AML code and
278 can interfere with legacy drivers.
279 strict (default): access to resources claimed by ACPI
280 is denied; legacy drivers trying to access reserved
281 resources will fail to bind to device using them.
282 lax: access to resources claimed by ACPI is allowed;
283 legacy drivers trying to access reserved resources
284 will bind successfully but a warning message is logged.
285 no: ACPI OperationRegions are not marked as reserved,
286 no further checks are performed.
288 acpi_force_table_verification [HW,ACPI]
289 Enable table checksum verification during early stage.
290 By default, this is disabled due to x86 early mapping
291 size limitation.
293 acpi_irq_balance [HW,ACPI]
294 ACPI will balance active IRQs
295 default in APIC mode
297 acpi_irq_nobalance [HW,ACPI]
298 ACPI will not move active IRQs (default)
299 default in PIC mode
301 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
302 Format: <irq>,<irq>...
304 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
305 use by PCI
306 Format: <irq>,<irq>...
308 acpi_no_auto_serialize [HW,ACPI]
309 Disable auto-serialization of AML methods
310 AML control methods that contain the opcodes to create
311 named objects will be marked as "Serialized" by the
312 auto-serialization feature.
313 This feature is enabled by default.
314 This option allows to turn off the feature.
316 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
317 kernels.
319 acpi_no_static_ssdt [HW,ACPI]
320 Disable installation of static SSDTs at early boot time
321 By default, SSDTs contained in the RSDT/XSDT will be
322 installed automatically and they will appear under
323 /sys/firmware/acpi/tables.
324 This option turns off this feature.
325 Note that specifying this option does not affect
326 dynamic table installation which will install SSDT
327 tables to /sys/firmware/acpi/tables/dynamic.
329 acpi_rsdp= [ACPI,EFI,KEXEC]
330 Pass the RSDP address to the kernel, mostly used
331 on machines running EFI runtime service to boot the
332 second kernel for kdump.
334 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
335 Format: To spoof as Windows 98: ="Microsoft Windows"
337 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
338 of 2 which is mandated by ACPI 6) as the supported ACPI
339 specification revision (when using this switch, it may
340 be necessary to carry out a cold reboot _twice_ in a
341 row to make it take effect on the platform firmware).
343 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
344 acpi_osi="string1" # add string1
345 acpi_osi="!string2" # remove string2
346 acpi_osi=!* # remove all strings
347 acpi_osi=! # disable all built-in OS vendor
348 strings
349 acpi_osi=!! # enable all built-in OS vendor
350 strings
351 acpi_osi= # disable all strings
353 'acpi_osi=!' can be used in combination with single or
354 multiple 'acpi_osi="string1"' to support specific OS
355 vendor string(s). Note that such command can only
356 affect the default state of the OS vendor strings, thus
357 it cannot affect the default state of the feature group
358 strings and the current state of the OS vendor strings,
359 specifying it multiple times through kernel command line
360 is meaningless. This command is useful when one do not
361 care about the state of the feature group strings which
362 should be controlled by the OSPM.
363 Examples:
364 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
365 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
366 can make '_OSI("Windows 2000")' TRUE.
368 'acpi_osi=' cannot be used in combination with other
369 'acpi_osi=' command lines, the _OSI method will not
370 exist in the ACPI namespace. NOTE that such command can
371 only affect the _OSI support state, thus specifying it
372 multiple times through kernel command line is also
373 meaningless.
374 Examples:
375 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
376 FALSE.
378 'acpi_osi=!*' can be used in combination with single or
379 multiple 'acpi_osi="string1"' to support specific
380 string(s). Note that such command can affect the
381 current state of both the OS vendor strings and the
382 feature group strings, thus specifying it multiple times
383 through kernel command line is meaningful. But it may
384 still not able to affect the final state of a string if
385 there are quirks related to this string. This command
386 is useful when one want to control the state of the
387 feature group strings to debug BIOS issues related to
388 the OSPM features.
389 Examples:
390 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
391 '_OSI("Module Device")' FALSE.
392 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
393 '_OSI("Module Device")' TRUE.
394 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
395 equivalent to
396 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
397 and
398 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
399 they all will make '_OSI("Windows 2000")' TRUE.
401 acpi_pm_good [X86]
402 Override the pmtimer bug detection: force the kernel
403 to assume that this machine's pmtimer latches its value
404 and always returns good values.
406 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
407 Format: { level | edge | high | low }
409 acpi_skip_timer_override [HW,ACPI]
410 Recognize and ignore IRQ0/pin2 Interrupt Override.
411 For broken nForce2 BIOS resulting in XT-PIC timer.
413 acpi_sleep= [HW,ACPI] Sleep options
414 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
415 old_ordering, nonvs, sci_force_enable }
416 See Documentation/power/video.txt for information on
417 s3_bios and s3_mode.
418 s3_beep is for debugging; it makes the PC's speaker beep
419 as soon as the kernel's real-mode entry point is called.
420 s4_nohwsig prevents ACPI hardware signature from being
421 used during resume from hibernation.
422 old_ordering causes the ACPI 1.0 ordering of the _PTS
423 control method, with respect to putting devices into
424 low power states, to be enforced (the ACPI 2.0 ordering
425 of _PTS is used by default).
426 nonvs prevents the kernel from saving/restoring the
427 ACPI NVS memory during suspend/hibernation and resume.
428 sci_force_enable causes the kernel to set SCI_EN directly
429 on resume from S1/S3 (which is against the ACPI spec,
430 but some broken systems don't work without it).
432 acpi_use_timer_override [HW,ACPI]
433 Use timer override. For some broken Nvidia NF5 boards
434 that require a timer override, but don't have HPET
436 add_efi_memmap [EFI; X86] Include EFI memory map in
437 kernel's map of available physical RAM.
439 agp= [AGP]
440 { off | try_unsupported }
441 off: disable AGP support
442 try_unsupported: try to drive unsupported chipsets
443 (may crash computer or cause data corruption)
445 ALSA [HW,ALSA]
446 See Documentation/sound/alsa/alsa-parameters.txt
448 alignment= [KNL,ARM]
449 Allow the default userspace alignment fault handler
450 behaviour to be specified. Bit 0 enables warnings,
451 bit 1 enables fixups, and bit 2 sends a segfault.
453 align_va_addr= [X86-64]
454 Align virtual addresses by clearing slice [14:12] when
455 allocating a VMA at process creation time. This option
456 gives you up to 3% performance improvement on AMD F15h
457 machines (where it is enabled by default) for a
458 CPU-intensive style benchmark, and it can vary highly in
459 a microbenchmark depending on workload and compiler.
461 32: only for 32-bit processes
462 64: only for 64-bit processes
463 on: enable for both 32- and 64-bit processes
464 off: disable for both 32- and 64-bit processes
466 alloc_snapshot [FTRACE]
467 Allocate the ftrace snapshot buffer on boot up when the
468 main buffer is allocated. This is handy if debugging
469 and you need to use tracing_snapshot() on boot up, and
470 do not want to use tracing_snapshot_alloc() as it needs
471 to be done where GFP_KERNEL allocations are allowed.
473 amd_iommu= [HW,X86-64]
474 Pass parameters to the AMD IOMMU driver in the system.
475 Possible values are:
476 fullflush - enable flushing of IO/TLB entries when
477 they are unmapped. Otherwise they are
478 flushed before they will be reused, which
479 is a lot of faster
480 off - do not initialize any AMD IOMMU found in
481 the system
482 force_isolation - Force device isolation for all
483 devices. The IOMMU driver is not
484 allowed anymore to lift isolation
485 requirements as needed. This option
486 does not override iommu=pt
488 amd_iommu_dump= [HW,X86-64]
489 Enable AMD IOMMU driver option to dump the ACPI table
490 for AMD IOMMU. With this option enabled, AMD IOMMU
491 driver will print ACPI tables for AMD IOMMU during
492 IOMMU initialization.
494 amd_iommu_intr= [HW,X86-64]
495 Specifies one of the following AMD IOMMU interrupt
496 remapping modes:
497 legacy - Use legacy interrupt remapping mode.
498 vapic - Use virtual APIC mode, which allows IOMMU
499 to inject interrupts directly into guest.
500 This mode requires kvm-amd.avic=1.
501 (Default when IOMMU HW support is present.)
503 amijoy.map= [HW,JOY] Amiga joystick support
504 Map of devices attached to JOY0DAT and JOY1DAT
505 Format: <a>,<b>
506 See also Documentation/input/joystick.txt
508 analog.map= [HW,JOY] Analog joystick and gamepad support
509 Specifies type or capabilities of an analog joystick
510 connected to one of 16 gameports
511 Format: <type1>,<type2>,..<type16>
513 apc= [HW,SPARC]
514 Power management functions (SPARCstation-4/5 + deriv.)
515 Format: noidle
516 Disable APC CPU standby support. SPARCstation-Fox does
517 not play well with APC CPU idle - disable it if you have
518 APC and your system crashes randomly.
520 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
521 Change the output verbosity whilst booting
522 Format: { quiet (default) | verbose | debug }
523 Change the amount of debugging information output
524 when initialising the APIC and IO-APIC components.
526 apic_extnmi= [APIC,X86] External NMI delivery setting
527 Format: { bsp (default) | all | none }
528 bsp: External NMI is delivered only to CPU 0
529 all: External NMIs are broadcast to all CPUs as a
530 backup of CPU 0
531 none: External NMI is masked for all CPUs. This is
532 useful so that a dump capture kernel won't be
533 shot down by NMI
535 autoconf= [IPV6]
536 See Documentation/networking/ipv6.txt.
538 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
539 Limit apic dumping. The parameter defines the maximal
540 number of local apics being dumped. Also it is possible
541 to set it to "all" by meaning -- no limit here.
542 Format: { 1 (default) | 2 | ... | all }.
543 The parameter valid if only apic=debug or
544 apic=verbose is specified.
545 Example: apic=debug show_lapic=all
547 apm= [APM] Advanced Power Management
548 See header of arch/x86/kernel/apm_32.c.
550 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
551 Format: <io>,<irq>,<nodeID>
553 ataflop= [HW,M68k]
555 atarimouse= [HW,MOUSE] Atari Mouse
557 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
558 EzKey and similar keyboards
560 atkbd.reset= [HW] Reset keyboard during initialization
562 atkbd.set= [HW] Select keyboard code set
563 Format: <int> (2 = AT (default), 3 = PS/2)
565 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
566 keyboards
568 atkbd.softraw= [HW] Choose between synthetic and real raw mode
569 Format: <bool> (0 = real, 1 = synthetic (default))
571 atkbd.softrepeat= [HW]
572 Use software keyboard repeat
574 audit= [KNL] Enable the audit sub-system
575 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
576 0 - kernel audit is disabled and can not be enabled
577 until the next reboot
578 unset - kernel audit is initialized but disabled and
579 will be fully enabled by the userspace auditd.
580 1 - kernel audit is initialized and partially enabled,
581 storing at most audit_backlog_limit messages in
582 RAM until it is fully enabled by the userspace
583 auditd.
584 Default: unset
586 audit_backlog_limit= [KNL] Set the audit queue size limit.
587 Format: <int> (must be >=0)
588 Default: 64
590 bau= [X86_UV] Enable the BAU on SGI UV. The default
591 behavior is to disable the BAU (i.e. bau=0).
592 Format: { "0" | "1" }
593 0 - Disable the BAU.
594 1 - Enable the BAU.
595 unset - Disable the BAU.
597 baycom_epp= [HW,AX25]
598 Format: <io>,<mode>
600 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
601 Format: <io>,<mode>
602 See header of drivers/net/hamradio/baycom_par.c.
604 baycom_ser_fdx= [HW,AX25]
605 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
606 Format: <io>,<irq>,<mode>[,<baud>]
607 See header of drivers/net/hamradio/baycom_ser_fdx.c.
609 baycom_ser_hdx= [HW,AX25]
610 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
611 Format: <io>,<irq>,<mode>
612 See header of drivers/net/hamradio/baycom_ser_hdx.c.
614 blkdevparts= Manual partition parsing of block device(s) for
615 embedded devices based on command line input.
616 See Documentation/block/cmdline-partition.txt
618 boot_delay= Milliseconds to delay each printk during boot.
619 Values larger than 10 seconds (10000) are changed to
620 no delay (0).
621 Format: integer
623 bootmem_debug [KNL] Enable bootmem allocator debug messages.
625 bert_disable [ACPI]
626 Disable BERT OS support on buggy BIOSes.
628 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
629 bttv.radio= Most important insmod options are available as
630 kernel args too.
631 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
632 bttv.tuner=
634 bulk_remove=off [PPC] This parameter disables the use of the pSeries
635 firmware feature for flushing multiple hpte entries
636 at a time.
638 c101= [NET] Moxa C101 synchronous serial card
640 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
641 Sometimes CPU hardware bugs make them report the cache
642 size incorrectly. The kernel will attempt work arounds
643 to fix known problems, but for some CPUs it is not
644 possible to determine what the correct size should be.
645 This option provides an override for these situations.
647 ca_keys= [KEYS] This parameter identifies a specific key(s) on
648 the system trusted keyring to be used for certificate
649 trust validation.
650 format: { id:<keyid> | builtin }
652 cca= [MIPS] Override the kernel pages' cache coherency
653 algorithm. Accepted values range from 0 to 7
654 inclusive. See arch/mips/include/asm/pgtable-bits.h
655 for platform specific values (SB1, Loongson3 and
656 others).
658 ccw_timeout_log [S390]
659 See Documentation/s390/CommonIO for details.
661 cgroup_disable= [KNL] Disable a particular controller
662 Format: {name of the controller(s) to disable}
663 The effects of cgroup_disable=foo are:
664 - foo isn't auto-mounted if you mount all cgroups in
665 a single hierarchy
666 - foo isn't visible as an individually mountable
667 subsystem
668 {Currently only "memory" controller deal with this and
669 cut the overhead, others just disable the usage. So
670 only cgroup_disable=memory is actually worthy}
672 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
673 Format: { controller[,controller...] | "all" }
674 Like cgroup_disable, but only applies to cgroup v1;
675 the blacklisted controllers remain available in cgroup2.
677 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
678 Format: <string>
679 nosocket -- Disable socket memory accounting.
680 nokmem -- Disable kernel memory accounting.
682 checkreqprot [SELINUX] Set initial checkreqprot flag value.
683 Format: { "0" | "1" }
684 See security/selinux/Kconfig help text.
685 0 -- check protection applied by kernel (includes
686 any implied execute protection).
687 1 -- check protection requested by application.
688 Default value is set via a kernel config option.
689 Value can be changed at runtime via
690 /selinux/checkreqprot.
692 cio_ignore= [S390]
693 See Documentation/s390/CommonIO for details.
694 clk_ignore_unused
695 [CLK]
696 Prevents the clock framework from automatically gating
697 clocks that have not been explicitly enabled by a Linux
698 device driver but are enabled in hardware at reset or
699 by the bootloader/firmware. Note that this does not
700 force such clocks to be always-on nor does it reserve
701 those clocks in any way. This parameter is useful for
702 debug and development, but should not be needed on a
703 platform with proper driver support. For more
704 information, see Documentation/clk.txt.
706 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
707 [Deprecated]
708 Forces specified clocksource (if available) to be used
709 when calculating gettimeofday(). If specified
710 clocksource is not available, it defaults to PIT.
711 Format: { pit | tsc | cyclone | pmtmr }
713 clocksource= Override the default clocksource
714 Format: <string>
715 Override the default clocksource and use the clocksource
716 with the name specified.
717 Some clocksource names to choose from, depending on
718 the platform:
719 [all] jiffies (this is the base, fallback clocksource)
720 [ACPI] acpi_pm
721 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
722 pxa_timer,timer3,32k_counter,timer0_1
723 [AVR32] avr32
724 [X86-32] pit,hpet,tsc;
725 scx200_hrt on Geode; cyclone on IBM x440
726 [MIPS] MIPS
727 [PARISC] cr16
728 [S390] tod
729 [SH] SuperH
730 [SPARC64] tick
731 [X86-64] hpet,tsc
733 clocksource.arm_arch_timer.evtstrm=
734 [ARM,ARM64]
735 Format: <bool>
736 Enable/disable the eventstream feature of the ARM
737 architected timer so that code using WFE-based polling
738 loops can be debugged more effectively on production
739 systems.
741 clocksource.arm_arch_timer.fsl-a008585=
742 [ARM64]
743 Format: <bool>
744 Enable/disable the workaround of Freescale/NXP
745 erratum A-008585. This can be useful for KVM
746 guests, if the guest device tree doesn't show the
747 erratum. If unspecified, the workaround is
748 enabled based on the device tree.
750 clearcpuid=BITNUM [X86]
751 Disable CPUID feature X for the kernel. See
752 arch/x86/include/asm/cpufeatures.h for the valid bit
753 numbers. Note the Linux specific bits are not necessarily
754 stable over kernel options, but the vendor specific
755 ones should be.
756 Also note that user programs calling CPUID directly
757 or using the feature without checking anything
758 will still see it. This just prevents it from
759 being used by the kernel or shown in /proc/cpuinfo.
760 Also note the kernel might malfunction if you disable
761 some critical bits.
763 cma=nn[MG]@[start[MG][-end[MG]]]
764 [ARM,X86,KNL]
765 Sets the size of kernel global memory area for
766 contiguous memory allocations and optionally the
767 placement constraint by the physical address range of
768 memory allocations. A value of 0 disables CMA
769 altogether. For more information, see
770 include/linux/dma-contiguous.h
772 cmo_free_hint= [PPC] Format: { yes | no }
773 Specify whether pages are marked as being inactive
774 when they are freed. This is used in CMO environments
775 to determine OS memory pressure for page stealing by
776 a hypervisor.
777 Default: yes
779 coherent_pool=nn[KMG] [ARM,KNL]
780 Sets the size of memory pool for coherent, atomic dma
781 allocations, by default set to 256K.
783 code_bytes [X86] How many bytes of object code to print
784 in an oops report.
785 Range: 0 - 8192
786 Default: 64
788 com20020= [HW,NET] ARCnet - COM20020 chipset
789 Format:
790 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
792 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
793 Format: <io>[,<irq>]
795 com90xx= [HW,NET]
796 ARCnet - COM90xx chipset (memory-mapped buffers)
797 Format: <io>[,<irq>[,<memstart>]]
799 condev= [HW,S390] console device
800 conmode=
802 console= [KNL] Output console device and options.
804 tty<n> Use the virtual console device <n>.
806 ttyS<n>[,options]
807 ttyUSB0[,options]
808 Use the specified serial port. The options are of
809 the form "bbbbpnf", where "bbbb" is the baud rate,
810 "p" is parity ("n", "o", or "e"), "n" is number of
811 bits, and "f" is flow control ("r" for RTS or
812 omit it). Default is "9600n8".
814 See Documentation/serial-console.txt for more
815 information. See
816 Documentation/networking/netconsole.txt for an
817 alternative.
819 uart[8250],io,<addr>[,options]
820 uart[8250],mmio,<addr>[,options]
821 uart[8250],mmio16,<addr>[,options]
822 uart[8250],mmio32,<addr>[,options]
823 uart[8250],0x<addr>[,options]
824 Start an early, polled-mode console on the 8250/16550
825 UART at the specified I/O port or MMIO address,
826 switching to the matching ttyS device later.
827 MMIO inter-register address stride is either 8-bit
828 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
829 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
830 to be equivalent to 'mmio'. 'options' are specified in
831 the same format described for ttyS above; if unspecified,
832 the h/w is not re-initialized.
834 hvc<n> Use the hypervisor console device <n>. This is for
835 both Xen and PowerPC hypervisors.
837 If the device connected to the port is not a TTY but a braille
838 device, prepend "brl," before the device type, for instance
839 console=brl,ttyS0
840 For now, only VisioBraille is supported.
842 consoleblank= [KNL] The console blank (screen saver) timeout in
843 seconds. Defaults to 10*60 = 10mins. A value of 0
844 disables the blank timer.
846 coredump_filter=
847 [KNL] Change the default value for
848 /proc/<pid>/coredump_filter.
849 See also Documentation/filesystems/proc.txt.
851 cpuidle.off=1 [CPU_IDLE]
852 disable the cpuidle sub-system
854 cpu_init_udelay=N
855 [X86] Delay for N microsec between assert and de-assert
856 of APIC INIT to start processors. This delay occurs
857 on every CPU online, such as boot, and resume from suspend.
858 Default: 10000
860 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
861 Format:
862 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
864 crashkernel=size[KMG][@offset[KMG]]
865 [KNL] Using kexec, Linux can switch to a 'crash kernel'
866 upon panic. This parameter reserves the physical
867 memory region [offset, offset + size] for that kernel
868 image. If '@offset' is omitted, then a suitable offset
869 is selected automatically. Check
870 Documentation/kdump/kdump.txt for further details.
872 crashkernel=range1:size1[,range2:size2,...][@offset]
873 [KNL] Same as above, but depends on the memory
874 in the running system. The syntax of range is
875 start-[end] where start and end are both
876 a memory unit (amount[KMG]). See also
877 Documentation/kdump/kdump.txt for an example.
879 crashkernel=size[KMG],high
880 [KNL, x86_64] range could be above 4G. Allow kernel
881 to allocate physical memory region from top, so could
882 be above 4G if system have more than 4G ram installed.
883 Otherwise memory region will be allocated below 4G, if
884 available.
885 It will be ignored if crashkernel=X is specified.
886 crashkernel=size[KMG],low
887 [KNL, x86_64] range under 4G. When crashkernel=X,high
888 is passed, kernel could allocate physical memory region
889 above 4G, that cause second kernel crash on system
890 that require some amount of low memory, e.g. swiotlb
891 requires at least 64M+32K low memory, also enough extra
892 low memory is needed to make sure DMA buffers for 32-bit
893 devices won't run out. Kernel would try to allocate at
894 at least 256M below 4G automatically.
895 This one let user to specify own low range under 4G
896 for second kernel instead.
897 0: to disable low allocation.
898 It will be ignored when crashkernel=X,high is not used
899 or memory reserved is below 4G.
901 cryptomgr.notests
902 [KNL] Disable crypto self-tests
904 cs89x0_dma= [HW,NET]
905 Format: <dma>
907 cs89x0_media= [HW,NET]
908 Format: { rj45 | aui | bnc }
910 dasd= [HW,NET]
911 See header of drivers/s390/block/dasd_devmap.c.
913 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
914 (one device per port)
915 Format: <port#>,<type>
916 See also Documentation/input/joystick-parport.txt
918 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
919 time. See Documentation/dynamic-debug-howto.txt for
920 details. Deprecated, see dyndbg.
922 debug [KNL] Enable kernel debugging (events log level).
924 debug_locks_verbose=
925 [KNL] verbose self-tests
926 Format=<0|1>
927 Print debugging info while doing the locking API
928 self-tests.
929 We default to 0 (no extra messages), setting it to
930 1 will print _a lot_ more information - normally
931 only useful to kernel developers.
933 debug_objects [KNL] Enable object debugging
935 no_debug_objects
936 [KNL] Disable object debugging
938 debug_guardpage_minorder=
939 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
940 parameter allows control of the order of pages that will
941 be intentionally kept free (and hence protected) by the
942 buddy allocator. Bigger value increase the probability
943 of catching random memory corruption, but reduce the
944 amount of memory for normal system use. The maximum
945 possible value is MAX_ORDER/2. Setting this parameter
946 to 1 or 2 should be enough to identify most random
947 memory corruption problems caused by bugs in kernel or
948 driver code when a CPU writes to (or reads from) a
949 random memory location. Note that there exists a class
950 of memory corruptions problems caused by buggy H/W or
951 F/W or by drivers badly programing DMA (basically when
952 memory is written at bus level and the CPU MMU is
953 bypassed) which are not detectable by
954 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
955 tracking down these problems.
957 debug_pagealloc=
958 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
959 parameter enables the feature at boot time. In
960 default, it is disabled. We can avoid allocating huge
961 chunk of memory for debug pagealloc if we don't enable
962 it at boot time and the system will work mostly same
963 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
964 on: enable the feature
966 debugpat [X86] Enable PAT debugging
968 decnet.addr= [HW,NET]
969 Format: <area>[,<node>]
970 See also Documentation/networking/decnet.txt.
972 default_hugepagesz=
973 [same as hugepagesz=] The size of the default
974 HugeTLB page size. This is the size represented by
975 the legacy /proc/ hugepages APIs, used for SHM, and
976 default size when mounting hugetlbfs filesystems.
977 Defaults to the default architecture's huge page size
978 if not specified.
980 dhash_entries= [KNL]
981 Set number of hash buckets for dentry cache.
983 disable_1tb_segments [PPC]
984 Disables the use of 1TB hash page table segments. This
985 causes the kernel to fall back to 256MB segments which
986 can be useful when debugging issues that require an SLB
987 miss to occur.
989 disable= [IPV6]
990 See Documentation/networking/ipv6.txt.
992 disable_radix [PPC]
993 Disable RADIX MMU mode on POWER9
995 disable_cpu_apicid= [X86,APIC,SMP]
996 Format: <int>
997 The number of initial APIC ID for the
998 corresponding CPU to be disabled at boot,
999 mostly used for the kdump 2nd kernel to
1000 disable BSP to wake up multiple CPUs without
1001 causing system reset or hang due to sending
1002 INIT from AP to BSP.
1004 disable_ddw [PPC/PSERIES]
1005 Disable Dynamic DMA Window support. Use this if
1006 to workaround buggy firmware.
1008 disable_ipv6= [IPV6]
1009 See Documentation/networking/ipv6.txt.
1011 disable_mtrr_cleanup [X86]
1012 The kernel tries to adjust MTRR layout from continuous
1013 to discrete, to make X server driver able to add WB
1014 entry later. This parameter disables that.
1016 disable_mtrr_trim [X86, Intel and AMD only]
1017 By default the kernel will trim any uncacheable
1018 memory out of your available memory pool based on
1019 MTRR settings. This parameter disables that behavior,
1020 possibly causing your machine to run very slowly.
1022 disable_timer_pin_1 [X86]
1023 Disable PIN 1 of APIC timer
1024 Can be useful to work around chipset bugs.
1026 dis_ucode_ldr [X86] Disable the microcode loader.
1028 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1029 this option disables the debugging code at boot.
1031 dma_debug_entries=<number>
1032 This option allows to tune the number of preallocated
1033 entries for DMA-API debugging code. One entry is
1034 required per DMA-API allocation. Use this if the
1035 DMA-API debugging code disables itself because the
1036 architectural default is too low.
1038 dma_debug_driver=<driver_name>
1039 With this option the DMA-API debugging driver
1040 filter feature can be enabled at boot time. Just
1041 pass the driver to filter for as the parameter.
1042 The filter can be disabled or changed to another
1043 driver later using sysfs.
1045 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1046 Broken monitors, graphic adapters, KVMs and EDIDless
1047 panels may send no or incorrect EDID data sets.
1048 This parameter allows to specify an EDID data sets
1049 in the /lib/firmware directory that are used instead.
1050 Generic built-in EDID data sets are used, if one of
1051 edid/1024x768.bin, edid/1280x1024.bin,
1052 edid/1680x1050.bin, or edid/1920x1080.bin is given
1053 and no file with the same name exists. Details and
1054 instructions how to build your own EDID data are
1055 available in Documentation/EDID/HOWTO.txt. An EDID
1056 data set will only be used for a particular connector,
1057 if its name and a colon are prepended to the EDID
1058 name. Each connector may use a unique EDID data
1059 set by separating the files with a comma. An EDID
1060 data set with no connector name will be used for
1061 any connectors not explicitly specified.
1063 dscc4.setup= [NET]
1065 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1066 module.dyndbg[="val"]
1067 Enable debug messages at boot time. See
1068 Documentation/dynamic-debug-howto.txt for details.
1070 nompx [X86] Disables Intel Memory Protection Extensions.
1071 See Documentation/x86/intel_mpx.txt for more
1072 information about the feature.
1074 nopku [X86] Disable Memory Protection Keys CPU feature found
1075 in some Intel CPUs.
1077 eagerfpu= [X86]
1078 on enable eager fpu restore
1079 off disable eager fpu restore
1080 auto selects the default scheme, which automatically
1081 enables eagerfpu restore for xsaveopt.
1083 module.async_probe [KNL]
1084 Enable asynchronous probe on this module.
1086 early_ioremap_debug [KNL]
1087 Enable debug messages in early_ioremap support. This
1088 is useful for tracking down temporary early mappings
1089 which are not unmapped.
1091 earlycon= [KNL] Output early console device and options.
1093 When used with no options, the early console is
1094 determined by the stdout-path property in device
1095 tree's chosen node.
1097 cdns,<addr>[,options]
1098 Start an early, polled-mode console on a Cadence
1099 (xuartps) serial port at the specified address. Only
1100 supported option is baud rate. If baud rate is not
1101 specified, the serial port must already be setup and
1102 configured.
1104 uart[8250],io,<addr>[,options]
1105 uart[8250],mmio,<addr>[,options]
1106 uart[8250],mmio32,<addr>[,options]
1107 uart[8250],mmio32be,<addr>[,options]
1108 uart[8250],0x<addr>[,options]
1109 Start an early, polled-mode console on the 8250/16550
1110 UART at the specified I/O port or MMIO address.
1111 MMIO inter-register address stride is either 8-bit
1112 (mmio) or 32-bit (mmio32 or mmio32be).
1113 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1114 to be equivalent to 'mmio'. 'options' are specified
1115 in the same format described for "console=ttyS<n>"; if
1116 unspecified, the h/w is not initialized.
1118 pl011,<addr>
1119 pl011,mmio32,<addr>
1120 Start an early, polled-mode console on a pl011 serial
1121 port at the specified address. The pl011 serial port
1122 must already be setup and configured. Options are not
1123 yet supported. If 'mmio32' is specified, then only
1124 the driver will use only 32-bit accessors to read/write
1125 the device registers.
1127 meson,<addr>
1128 Start an early, polled-mode console on a meson serial
1129 port at the specified address. The serial port must
1130 already be setup and configured. Options are not yet
1131 supported.
1133 msm_serial,<addr>
1134 Start an early, polled-mode console on an msm serial
1135 port at the specified address. The serial port
1136 must already be setup and configured. Options are not
1137 yet supported.
1139 msm_serial_dm,<addr>
1140 Start an early, polled-mode console on an msm serial
1141 dm port at the specified address. The serial port
1142 must already be setup and configured. Options are not
1143 yet supported.
1145 smh Use ARM semihosting calls for early console.
1147 s3c2410,<addr>
1148 s3c2412,<addr>
1149 s3c2440,<addr>
1150 s3c6400,<addr>
1151 s5pv210,<addr>
1152 exynos4210,<addr>
1153 Use early console provided by serial driver available
1154 on Samsung SoCs, requires selecting proper type and
1155 a correct base address of the selected UART port. The
1156 serial port must already be setup and configured.
1157 Options are not yet supported.
1159 lpuart,<addr>
1160 lpuart32,<addr>
1161 Use early console provided by Freescale LP UART driver
1162 found on Freescale Vybrid and QorIQ LS1021A processors.
1163 A valid base address must be provided, and the serial
1164 port must already be setup and configured.
1166 armada3700_uart,<addr>
1167 Start an early, polled-mode console on the
1168 Armada 3700 serial port at the specified
1169 address. The serial port must already be setup
1170 and configured. Options are not yet supported.
1172 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1173 earlyprintk=vga
1174 earlyprintk=efi
1175 earlyprintk=xen
1176 earlyprintk=serial[,ttySn[,baudrate]]
1177 earlyprintk=serial[,0x...[,baudrate]]
1178 earlyprintk=ttySn[,baudrate]
1179 earlyprintk=dbgp[debugController#]
1180 earlyprintk=pciserial,bus:device.function[,baudrate]
1182 earlyprintk is useful when the kernel crashes before
1183 the normal console is initialized. It is not enabled by
1184 default because it has some cosmetic problems.
1186 Append ",keep" to not disable it when the real console
1187 takes over.
1189 Only one of vga, efi, serial, or usb debug port can
1190 be used at a time.
1192 Currently only ttyS0 and ttyS1 may be specified by
1193 name. Other I/O ports may be explicitly specified
1194 on some architectures (x86 and arm at least) by
1195 replacing ttySn with an I/O port address, like this:
1196 earlyprintk=serial,0x1008,115200
1197 You can find the port for a given device in
1198 /proc/tty/driver/serial:
1199 2: uart:ST16650V2 port:00001008 irq:18 ...
1201 Interaction with the standard serial driver is not
1202 very good.
1204 The VGA and EFI output is eventually overwritten by
1205 the real console.
1207 The xen output can only be used by Xen PV guests.
1209 edac_report= [HW,EDAC] Control how to report EDAC event
1210 Format: {"on" | "off" | "force"}
1211 on: enable EDAC to report H/W event. May be overridden
1212 by other higher priority error reporting module.
1213 off: disable H/W event reporting through EDAC.
1214 force: enforce the use of EDAC to report H/W event.
1215 default: on.
1217 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1218 ekgdboc=kbd
1220 This is designed to be used in conjunction with
1221 the boot argument: earlyprintk=vga
1223 edd= [EDD]
1224 Format: {"off" | "on" | "skip[mbr]"}
1226 efi= [EFI]
1227 Format: { "old_map", "nochunk", "noruntime", "debug" }
1228 old_map [X86-64]: switch to the old ioremap-based EFI
1229 runtime services mapping. 32-bit still uses this one by
1230 default.
1231 nochunk: disable reading files in "chunks" in the EFI
1232 boot stub, as chunking can cause problems with some
1233 firmware implementations.
1234 noruntime : disable EFI runtime services support
1235 debug: enable misc debug output
1237 efi_no_storage_paranoia [EFI; X86]
1238 Using this parameter you can use more than 50% of
1239 your efi variable storage. Use this parameter only if
1240 you are really sure that your UEFI does sane gc and
1241 fulfills the spec otherwise your board may brick.
1243 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1244 Add arbitrary attribute to specific memory range by
1245 updating original EFI memory map.
1246 Region of memory which aa attribute is added to is
1247 from ss to ss+nn.
1248 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1249 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1250 attribute is added to range 0x100000000-0x180000000 and
1251 0x10a0000000-0x1120000000.
1253 Using this parameter you can do debugging of EFI memmap
1254 related feature. For example, you can do debugging of
1255 Address Range Mirroring feature even if your box
1256 doesn't support it.
1258 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1259 that is to be dynamically loaded by Linux. If there are
1260 multiple variables with the same name but with different
1261 vendor GUIDs, all of them will be loaded. See
1262 Documentation/acpi/ssdt-overlays.txt for details.
1265 eisa_irq_edge= [PARISC,HW]
1266 See header of drivers/parisc/eisa.c.
1268 elanfreq= [X86-32]
1269 See comment before function elanfreq_setup() in
1270 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1272 elevator= [IOSCHED]
1273 Format: {"cfq" | "deadline" | "noop"}
1274 See Documentation/block/cfq-iosched.txt and
1275 Documentation/block/deadline-iosched.txt for details.
1277 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1278 Specifies physical address of start of kernel core
1279 image elf header and optionally the size. Generally
1280 kexec loader will pass this option to capture kernel.
1281 See Documentation/kdump/kdump.txt for details.
1283 enable_mtrr_cleanup [X86]
1284 The kernel tries to adjust MTRR layout from continuous
1285 to discrete, to make X server driver able to add WB
1286 entry later. This parameter enables that.
1288 enable_timer_pin_1 [X86]
1289 Enable PIN 1 of APIC timer
1290 Can be useful to work around chipset bugs
1291 (in particular on some ATI chipsets).
1292 The kernel tries to set a reasonable default.
1294 enforcing [SELINUX] Set initial enforcing status.
1295 Format: {"0" | "1"}
1296 See security/selinux/Kconfig help text.
1297 0 -- permissive (log only, no denials).
1298 1 -- enforcing (deny and log).
1299 Default value is 0.
1300 Value can be changed at runtime via /selinux/enforce.
1302 erst_disable [ACPI]
1303 Disable Error Record Serialization Table (ERST)
1304 support.
1306 ether= [HW,NET] Ethernet cards parameters
1307 This option is obsoleted by the "netdev=" option, which
1308 has equivalent usage. See its documentation for details.
1310 evm= [EVM]
1311 Format: { "fix" }
1312 Permit 'security.evm' to be updated regardless of
1313 current integrity status.
1315 failslab=
1316 fail_page_alloc=
1317 fail_make_request=[KNL]
1318 General fault injection mechanism.
1319 Format: <interval>,<probability>,<space>,<times>
1320 See also Documentation/fault-injection/.
1322 floppy= [HW]
1323 See Documentation/blockdev/floppy.txt.
1325 force_pal_cache_flush
1326 [IA-64] Avoid check_sal_cache_flush which may hang on
1327 buggy SAL_CACHE_FLUSH implementations. Using this
1328 parameter will force ia64_sal_cache_flush to call
1329 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1331 forcepae [X86-32]
1332 Forcefully enable Physical Address Extension (PAE).
1333 Many Pentium M systems disable PAE but may have a
1334 functionally usable PAE implementation.
1335 Warning: use of this parameter will taint the kernel
1336 and may cause unknown problems.
1338 ftrace=[tracer]
1339 [FTRACE] will set and start the specified tracer
1340 as early as possible in order to facilitate early
1341 boot debugging.
1343 ftrace_dump_on_oops[=orig_cpu]
1344 [FTRACE] will dump the trace buffers on oops.
1345 If no parameter is passed, ftrace will dump
1346 buffers of all CPUs, but if you pass orig_cpu, it will
1347 dump only the buffer of the CPU that triggered the
1348 oops.
1350 ftrace_filter=[function-list]
1351 [FTRACE] Limit the functions traced by the function
1352 tracer at boot up. function-list is a comma separated
1353 list of functions. This list can be changed at run
1354 time by the set_ftrace_filter file in the debugfs
1355 tracing directory.
1357 ftrace_notrace=[function-list]
1358 [FTRACE] Do not trace the functions specified in
1359 function-list. This list can be changed at run time
1360 by the set_ftrace_notrace file in the debugfs
1361 tracing directory.
1363 ftrace_graph_filter=[function-list]
1364 [FTRACE] Limit the top level callers functions traced
1365 by the function graph tracer at boot up.
1366 function-list is a comma separated list of functions
1367 that can be changed at run time by the
1368 set_graph_function file in the debugfs tracing directory.
1370 ftrace_graph_notrace=[function-list]
1371 [FTRACE] Do not trace from the functions specified in
1372 function-list. This list is a comma separated list of
1373 functions that can be changed at run time by the
1374 set_graph_notrace file in the debugfs tracing directory.
1376 gamecon.map[2|3]=
1377 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1378 support via parallel port (up to 5 devices per port)
1379 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1380 See also Documentation/input/joystick-parport.txt
1382 gamma= [HW,DRM]
1384 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1385 Format: off | on
1386 default: on
1388 gcov_persist= [GCOV] When non-zero (default), profiling data for
1389 kernel modules is saved and remains accessible via
1390 debugfs, even when the module is unloaded/reloaded.
1391 When zero, profiling data is discarded and associated
1392 debugfs files are removed at module unload time.
1394 gpt [EFI] Forces disk with valid GPT signature but
1395 invalid Protective MBR to be treated as GPT. If the
1396 primary GPT is corrupted, it enables the backup/alternate
1397 GPT to be used instead.
1399 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1400 the "Enable 0" bit of the configuration register.
1401 Format: 0 | 1
1402 Default: 0
1403 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1404 the "Enable 0" bit of the configuration register.
1405 Format: 0 | 1
1406 Default: 0
1407 grcan.select= [HW] Select which physical interface to use.
1408 Format: 0 | 1
1409 Default: 0
1410 grcan.txsize= [HW] Sets the size of the tx buffer.
1411 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1412 Default: 1024
1413 grcan.rxsize= [HW] Sets the size of the rx buffer.
1414 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1415 Default: 1024
1417 gpio-mockup.gpio_mockup_ranges
1418 [HW] Sets the ranges of gpiochip of for this device.
1419 Format: <start1>,<end1>,<start2>,<end2>...
1421 hardlockup_all_cpu_backtrace=
1422 [KNL] Should the hard-lockup detector generate
1423 backtraces on all cpus.
1424 Format: <integer>
1426 hashdist= [KNL,NUMA] Large hashes allocated during boot
1427 are distributed across NUMA nodes. Defaults on
1428 for 64-bit NUMA, off otherwise.
1429 Format: 0 | 1 (for off | on)
1431 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1433 hd= [EIDE] (E)IDE hard drive subsystem geometry
1434 Format: <cyl>,<head>,<sect>
1436 hest_disable [ACPI]
1437 Disable Hardware Error Source Table (HEST) support;
1438 corresponding firmware-first mode error processing
1439 logic will be disabled.
1441 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1442 size of <nn>. This works even on boxes that have no
1443 highmem otherwise. This also works to reduce highmem
1444 size on bigger boxes.
1446 highres= [KNL] Enable/disable high resolution timer mode.
1447 Valid parameters: "on", "off"
1448 Default: "on"
1450 hisax= [HW,ISDN]
1451 See Documentation/isdn/README.HiSax.
1453 hlt [BUGS=ARM,SH]
1455 hpet= [X86-32,HPET] option to control HPET usage
1456 Format: { enable (default) | disable | force |
1457 verbose }
1458 disable: disable HPET and use PIT instead
1459 force: allow force enabled of undocumented chips (ICH4,
1460 VIA, nVidia)
1461 verbose: show contents of HPET registers during setup
1463 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1464 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1466 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1467 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1468 On x86-64 and powerpc, this option can be specified
1469 multiple times interleaved with hugepages= to reserve
1470 huge pages of different sizes. Valid pages sizes on
1471 x86-64 are 2M (when the CPU supports "pse") and 1G
1472 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1474 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1475 terminal devices. Valid values: 0..8
1476 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1477 If specified, z/VM IUCV HVC accepts connections
1478 from listed z/VM user IDs only.
1480 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1481 hardware thread id mappings.
1482 Format: <cpu>:<hwthread>
1484 keep_bootcon [KNL]
1485 Do not unregister boot console at start. This is only
1486 useful for debugging when something happens in the window
1487 between unregistering the boot console and initializing
1488 the real console.
1490 i2c_bus= [HW] Override the default board specific I2C bus speed
1491 or register an additional I2C bus that is not
1492 registered from board initialization code.
1493 Format:
1494 <bus_id>,<clkrate>
1496 i8042.debug [HW] Toggle i8042 debug mode
1497 i8042.unmask_kbd_data
1498 [HW] Enable printing of interrupt data from the KBD port
1499 (disabled by default, and as a pre-condition
1500 requires that i8042.debug=1 be enabled)
1501 i8042.direct [HW] Put keyboard port into non-translated mode
1502 i8042.dumbkbd [HW] Pretend that controller can only read data from
1503 keyboard and cannot control its state
1504 (Don't attempt to blink the leds)
1505 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1506 i8042.nokbd [HW] Don't check/create keyboard port
1507 i8042.noloop [HW] Disable the AUX Loopback command while probing
1508 for the AUX port
1509 i8042.nomux [HW] Don't check presence of an active multiplexing
1510 controller
1511 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1512 controllers
1513 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1514 i8042.reset [HW] Reset the controller during init, cleanup and
1515 suspend-to-ram transitions, only during s2r
1516 transitions, or never reset
1517 Format: { 1 | Y | y | 0 | N | n }
1518 1, Y, y: always reset controller
1519 0, N, n: don't ever reset controller
1520 Default: only on s2r transitions on x86; most other
1521 architectures force reset to be always executed
1522 i8042.unlock [HW] Unlock (ignore) the keylock
1523 i8042.kbdreset [HW] Reset device connected to KBD port
1525 i810= [HW,DRM]
1527 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1528 indicates that the driver is running on unsupported
1529 hardware.
1530 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1531 does not match list of supported models.
1532 i8k.power_status
1533 [HW] Report power status in /proc/i8k
1534 (disabled by default)
1535 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1536 capability is set.
1538 i915.invert_brightness=
1539 [DRM] Invert the sense of the variable that is used to
1540 set the brightness of the panel backlight. Normally a
1541 brightness value of 0 indicates backlight switched off,
1542 and the maximum of the brightness value sets the backlight
1543 to maximum brightness. If this parameter is set to 0
1544 (default) and the machine requires it, or this parameter
1545 is set to 1, a brightness value of 0 sets the backlight
1546 to maximum brightness, and the maximum of the brightness
1547 value switches the backlight off.
1548 -1 -- never invert brightness
1549 0 -- machine default
1550 1 -- force brightness inversion
1552 icn= [HW,ISDN]
1553 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1555 ide-core.nodma= [HW] (E)IDE subsystem
1556 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1557 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1558 .cdrom .chs .ignore_cable are additional options
1559 See Documentation/ide/ide.txt.
1561 ide-generic.probe-mask= [HW] (E)IDE subsystem
1562 Format: <int>
1563 Probe mask for legacy ISA IDE ports. Depending on
1564 platform up to 6 ports are supported, enabled by
1565 setting corresponding bits in the mask to 1. The
1566 default value is 0x0, which has a special meaning.
1567 On systems that have PCI, it triggers scanning the
1568 PCI bus for the first and the second port, which
1569 are then probed. On systems without PCI the value
1570 of 0x0 enables probing the two first ports as if it
1571 was 0x3.
1573 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1574 Claim all unknown PCI IDE storage controllers.
1576 idle= [X86]
1577 Format: idle=poll, idle=halt, idle=nomwait
1578 Poll forces a polling idle loop that can slightly
1579 improve the performance of waking up a idle CPU, but
1580 will use a lot of power and make the system run hot.
1581 Not recommended.
1582 idle=halt: Halt is forced to be used for CPU idle.
1583 In such case C2/C3 won't be used again.
1584 idle=nomwait: Disable mwait for CPU C-states
1586 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1587 Format: { strict | legacy | 2008 | relaxed }
1588 Default: strict
1590 Choose which programs will be accepted for execution
1591 based on the IEEE 754 NaN encoding(s) supported by
1592 the FPU and the NaN encoding requested with the value
1593 of an ELF file header flag individually set by each
1594 binary. Hardware implementations are permitted to
1595 support either or both of the legacy and the 2008 NaN
1596 encoding mode.
1598 Available settings are as follows:
1599 strict accept binaries that request a NaN encoding
1600 supported by the FPU
1601 legacy only accept legacy-NaN binaries, if supported
1602 by the FPU
1603 2008 only accept 2008-NaN binaries, if supported
1604 by the FPU
1605 relaxed accept any binaries regardless of whether
1606 supported by the FPU
1608 The FPU emulator is always able to support both NaN
1609 encodings, so if no FPU hardware is present or it has
1610 been disabled with 'nofpu', then the settings of
1611 'legacy' and '2008' strap the emulator accordingly,
1612 'relaxed' straps the emulator for both legacy-NaN and
1613 2008-NaN, whereas 'strict' enables legacy-NaN only on
1614 legacy processors and both NaN encodings on MIPS32 or
1615 MIPS64 CPUs.
1617 The setting for ABS.fmt/NEG.fmt instruction execution
1618 mode generally follows that for the NaN encoding,
1619 except where unsupported by hardware.
1621 ignore_loglevel [KNL]
1622 Ignore loglevel setting - this will print /all/
1623 kernel messages to the console. Useful for debugging.
1624 We also add it as printk module parameter, so users
1625 could change it dynamically, usually by
1626 /sys/module/printk/parameters/ignore_loglevel.
1628 ignore_rlimit_data
1629 Ignore RLIMIT_DATA setting for data mappings,
1630 print warning at first misuse. Can be changed via
1631 /sys/module/kernel/parameters/ignore_rlimit_data.
1633 ihash_entries= [KNL]
1634 Set number of hash buckets for inode cache.
1636 ima_appraise= [IMA] appraise integrity measurements
1637 Format: { "off" | "enforce" | "fix" | "log" }
1638 default: "enforce"
1640 ima_appraise_tcb [IMA]
1641 The builtin appraise policy appraises all files
1642 owned by uid=0.
1644 ima_hash= [IMA]
1645 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1646 | sha512 | ... }
1647 default: "sha1"
1649 The list of supported hash algorithms is defined
1650 in crypto/hash_info.h.
1652 ima_policy= [IMA]
1653 The builtin measurement policy to load during IMA
1654 setup. Specyfing "tcb" as the value, measures all
1655 programs exec'd, files mmap'd for exec, and all files
1656 opened with the read mode bit set by either the
1657 effective uid (euid=0) or uid=0.
1658 Format: "tcb"
1660 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1661 Load a policy which meets the needs of the Trusted
1662 Computing Base. This means IMA will measure all
1663 programs exec'd, files mmap'd for exec, and all files
1664 opened for read by uid=0.
1666 ima_template= [IMA]
1667 Select one of defined IMA measurements template formats.
1668 Formats: { "ima" | "ima-ng" | "ima-sig" }
1669 Default: "ima-ng"
1671 ima_template_fmt=
1672 [IMA] Define a custom template format.
1673 Format: { "field1|...|fieldN" }
1675 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1676 Format: <min_file_size>
1677 Set the minimal file size for using asynchronous hash.
1678 If left unspecified, ahash usage is disabled.
1680 ahash performance varies for different data sizes on
1681 different crypto accelerators. This option can be used
1682 to achieve the best performance for a particular HW.
1684 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1685 Format: <bufsize>
1686 Set hashing buffer size. Default: 4k.
1688 ahash performance varies for different chunk sizes on
1689 different crypto accelerators. This option can be used
1690 to achieve best performance for particular HW.
1692 init= [KNL]
1693 Format: <full_path>
1694 Run specified binary instead of /sbin/init as init
1695 process.
1697 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1698 for working out where the kernel is dying during
1699 startup.
1701 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1702 initcall functions. Useful for debugging built-in
1703 modules and initcalls.
1705 initrd= [BOOT] Specify the location of the initial ramdisk
1707 init_pkru= [x86] Specify the default memory protection keys rights
1708 register contents for all processes. 0x55555554 by
1709 default (disallow access to all but pkey 0). Can
1710 override in debugfs after boot.
1712 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1713 Format: <irq>
1715 int_pln_enable [x86] Enable power limit notification interrupt
1717 integrity_audit=[IMA]
1718 Format: { "0" | "1" }
1719 0 -- basic integrity auditing messages. (Default)
1720 1 -- additional integrity auditing messages.
1722 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1723 on
1724 Enable intel iommu driver.
1725 off
1726 Disable intel iommu driver.
1727 igfx_off [Default Off]
1728 By default, gfx is mapped as normal device. If a gfx
1729 device has a dedicated DMAR unit, the DMAR unit is
1730 bypassed by not enabling DMAR with this option. In
1731 this case, gfx device will use physical address for
1732 DMA.
1733 forcedac [x86_64]
1734 With this option iommu will not optimize to look
1735 for io virtual address below 32-bit forcing dual
1736 address cycle on pci bus for cards supporting greater
1737 than 32-bit addressing. The default is to look
1738 for translation below 32-bit and if not available
1739 then look in the higher range.
1740 strict [Default Off]
1741 With this option on every unmap_single operation will
1742 result in a hardware IOTLB flush operation as opposed
1743 to batching them for performance.
1744 sp_off [Default Off]
1745 By default, super page will be supported if Intel IOMMU
1746 has the capability. With this option, super page will
1747 not be supported.
1748 ecs_off [Default Off]
1749 By default, extended context tables will be supported if
1750 the hardware advertises that it has support both for the
1751 extended tables themselves, and also PASID support. With
1752 this option set, extended tables will not be used even
1753 on hardware which claims to support them.
1755 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1756 0 disables intel_idle and fall back on acpi_idle.
1757 1 to 9 specify maximum depth of C-state.
1759 intel_pstate= [X86]
1760 disable
1761 Do not enable intel_pstate as the default
1762 scaling driver for the supported processors
1763 force
1764 Enable intel_pstate on systems that prohibit it by default
1765 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1766 instead of acpi-cpufreq may disable platform features, such
1767 as thermal controls and power capping, that rely on ACPI
1768 P-States information being indicated to OSPM and therefore
1769 should be used with caution. This option does not work with
1770 processors that aren't supported by the intel_pstate driver
1771 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1772 no_hwp
1773 Do not enable hardware P state control (HWP)
1774 if available.
1775 hwp_only
1776 Only load intel_pstate on systems which support
1777 hardware P state control (HWP) if available.
1778 support_acpi_ppc
1779 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1780 Description Table, specifies preferred power management
1781 profile as "Enterprise Server" or "Performance Server",
1782 then this feature is turned on by default.
1784 intremap= [X86-64, Intel-IOMMU]
1785 on enable Interrupt Remapping (default)
1786 off disable Interrupt Remapping
1787 nosid disable Source ID checking
1788 no_x2apic_optout
1789 BIOS x2APIC opt-out request will be ignored
1790 nopost disable Interrupt Posting
1792 iomem= Disable strict checking of access to MMIO memory
1793 strict regions from userspace.
1794 relaxed
1796 iommu= [x86]
1797 off
1798 force
1799 noforce
1800 biomerge
1801 panic
1802 nopanic
1803 merge
1804 nomerge
1805 forcesac
1806 soft
1807 pt [x86, IA-64]
1808 nobypass [PPC/POWERNV]
1809 Disable IOMMU bypass, using IOMMU for PCI devices.
1812 io7= [HW] IO7 for Marvel based alpha systems
1813 See comment before marvel_specify_io7 in
1814 arch/alpha/kernel/core_marvel.c.
1816 io_delay= [X86] I/O delay method
1817 0x80
1818 Standard port 0x80 based delay
1819 0xed
1820 Alternate port 0xed based delay (needed on some systems)
1821 udelay
1822 Simple two microseconds delay
1823 none
1824 No delay
1826 ip= [IP_PNP]
1827 See Documentation/filesystems/nfs/nfsroot.txt.
1829 irqaffinity= [SMP] Set the default irq affinity mask
1830 The argument is a cpu list, as described above.
1832 irqfixup [HW]
1833 When an interrupt is not handled search all handlers
1834 for it. Intended to get systems with badly broken
1835 firmware running.
1837 irqpoll [HW]
1838 When an interrupt is not handled search all handlers
1839 for it. Also check all handlers each timer
1840 interrupt. Intended to get systems with badly broken
1841 firmware running.
1843 isapnp= [ISAPNP]
1844 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1846 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1847 The argument is a cpu list, as described above.
1849 This option can be used to specify one or more CPUs
1850 to isolate from the general SMP balancing and scheduling
1851 algorithms. You can move a process onto or off an
1852 "isolated" CPU via the CPU affinity syscalls or cpuset.
1853 <cpu number> begins at 0 and the maximum value is
1854 "number of CPUs in system - 1".
1856 This option is the preferred way to isolate CPUs. The
1857 alternative -- manually setting the CPU mask of all
1858 tasks in the system -- can cause problems and
1859 suboptimal load balancer performance.
1861 iucv= [HW,NET]
1863 ivrs_ioapic [HW,X86_64]
1864 Provide an override to the IOAPIC-ID<->DEVICE-ID
1865 mapping provided in the IVRS ACPI table. For
1866 example, to map IOAPIC-ID decimal 10 to
1867 PCI device 00:14.0 write the parameter as:
1868 ivrs_ioapic[10]=00:14.0
1870 ivrs_hpet [HW,X86_64]
1871 Provide an override to the HPET-ID<->DEVICE-ID
1872 mapping provided in the IVRS ACPI table. For
1873 example, to map HPET-ID decimal 0 to
1874 PCI device 00:14.0 write the parameter as:
1875 ivrs_hpet[0]=00:14.0
1877 ivrs_acpihid [HW,X86_64]
1878 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1879 mapping provided in the IVRS ACPI table. For
1880 example, to map UART-HID:UID AMD0020:0 to
1881 PCI device 00:14.5 write the parameter as:
1882 ivrs_acpihid[00:14.5]=AMD0020:0
1884 js= [HW,JOY] Analog joystick
1885 See Documentation/input/joystick.txt.
1887 nokaslr [KNL]
1888 When CONFIG_RANDOMIZE_BASE is set, this disables
1889 kernel and module base offset ASLR (Address Space
1890 Layout Randomization).
1892 keepinitrd [HW,ARM]
1894 kernelcore= [KNL,X86,IA-64,PPC]
1895 Format: nn[KMGTPE] | "mirror"
1896 This parameter
1897 specifies the amount of memory usable by the kernel
1898 for non-movable allocations. The requested amount is
1899 spread evenly throughout all nodes in the system. The
1900 remaining memory in each node is used for Movable
1901 pages. In the event, a node is too small to have both
1902 kernelcore and Movable pages, kernelcore pages will
1903 take priority and other nodes will have a larger number
1904 of Movable pages. The Movable zone is used for the
1905 allocation of pages that may be reclaimed or moved
1906 by the page migration subsystem. This means that
1907 HugeTLB pages may not be allocated from this zone.
1908 Note that allocations like PTEs-from-HighMem still
1909 use the HighMem zone if it exists, and the Normal
1910 zone if it does not.
1912 Instead of specifying the amount of memory (nn[KMGTPE]),
1913 you can specify "mirror" option. In case "mirror"
1914 option is specified, mirrored (reliable) memory is used
1915 for non-movable allocations and remaining memory is used
1916 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1917 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1918 time.
1920 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1921 Format: <Controller#>[,poll interval]
1922 The controller # is the number of the ehci usb debug
1923 port as it is probed via PCI. The poll interval is
1924 optional and is the number seconds in between
1925 each poll cycle to the debug port in case you need
1926 the functionality for interrupting the kernel with
1927 gdb or control-c on the dbgp connection. When
1928 not using this parameter you use sysrq-g to break into
1929 the kernel debugger.
1931 kgdboc= [KGDB,HW] kgdb over consoles.
1932 Requires a tty driver that supports console polling,
1933 or a supported polling keyboard driver (non-usb).
1934 Serial only format: <serial_device>[,baud]
1935 keyboard only format: kbd
1936 keyboard and serial format: kbd,<serial_device>[,baud]
1937 Optional Kernel mode setting:
1938 kms, kbd format: kms,kbd
1939 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1941 kgdbwait [KGDB] Stop kernel execution and enter the
1942 kernel debugger at the earliest opportunity.
1944 kmac= [MIPS] korina ethernet MAC address.
1945 Configure the RouterBoard 532 series on-chip
1946 Ethernet adapter MAC address.
1948 kmemleak= [KNL] Boot-time kmemleak enable/disable
1949 Valid arguments: on, off
1950 Default: on
1951 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1952 the default is off.
1954 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1955 Valid arguments: 0, 1, 2
1956 kmemcheck=0 (disabled)
1957 kmemcheck=1 (enabled)
1958 kmemcheck=2 (one-shot mode)
1959 Default: 2 (one-shot mode)
1961 kstack=N [X86] Print N words from the kernel stack
1962 in oops dumps.
1964 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1965 Default is 0 (don't ignore, but inject #GP)
1967 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1968 KVM MMU at runtime.
1969 Default is 0 (off)
1971 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1972 Default is 1 (enabled)
1974 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1975 for all guests.
1976 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1978 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1979 (virtualized MMU) support on capable Intel chips.
1980 Default is 1 (enabled)
1982 kvm-intel.emulate_invalid_guest_state=
1983 [KVM,Intel] Enable emulation of invalid guest states
1984 Default is 0 (disabled)
1986 kvm-intel.flexpriority=
1987 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1988 Default is 1 (enabled)
1990 kvm-intel.nested=
1991 [KVM,Intel] Enable VMX nesting (nVMX).
1992 Default is 0 (disabled)
1994 kvm-intel.unrestricted_guest=
1995 [KVM,Intel] Disable unrestricted guest feature
1996 (virtualized real and unpaged mode) on capable
1997 Intel chips. Default is 1 (enabled)
1999 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2000 feature (tagged TLBs) on capable Intel chips.
2001 Default is 1 (enabled)
2003 l2cr= [PPC]
2005 l3cr= [PPC]
2007 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2008 disabled it.
2010 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2011 value for LAPIC timer one-shot implementation. Default
2012 back to the programmable timer unit in the LAPIC.
2014 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2015 in C2 power state.
2017 libata.dma= [LIBATA] DMA control
2018 libata.dma=0 Disable all PATA and SATA DMA
2019 libata.dma=1 PATA and SATA Disk DMA only
2020 libata.dma=2 ATAPI (CDROM) DMA only
2021 libata.dma=4 Compact Flash DMA only
2022 Combinations also work, so libata.dma=3 enables DMA
2023 for disks and CDROMs, but not CFs.
2025 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2026 libata.ignore_hpa=0 keep BIOS limits (default)
2027 libata.ignore_hpa=1 ignore limits, using full disk
2029 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2030 when set.
2031 Format: <int>
2033 libata.force= [LIBATA] Force configurations. The format is comma
2034 separated list of "[ID:]VAL" where ID is
2035 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2036 matching port, link or device. Basically, it matches
2037 the ATA ID string printed on console by libata. If
2038 the whole ID part is omitted, the last PORT and DEVICE
2039 values are used. If ID hasn't been specified yet, the
2040 configuration applies to all ports, links and devices.
2042 If only DEVICE is omitted, the parameter applies to
2043 the port and all links and devices behind it. DEVICE
2044 number of 0 either selects the first device or the
2045 first fan-out link behind PMP device. It does not
2046 select the host link. DEVICE number of 15 selects the
2047 host link and device attached to it.
2049 The VAL specifies the configuration to force. As long
2050 as there's no ambiguity shortcut notation is allowed.
2051 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2052 The following configurations can be forced.
2054 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2055 Any ID with matching PORT is used.
2057 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2059 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2060 udma[/][16,25,33,44,66,100,133] notation is also
2061 allowed.
2063 * [no]ncq: Turn on or off NCQ.
2065 * [no]ncqtrim: Turn off queued DSM TRIM.
2067 * nohrst, nosrst, norst: suppress hard, soft
2068 and both resets.
2070 * rstonce: only attempt one reset during
2071 hot-unplug link recovery
2073 * dump_id: dump IDENTIFY data.
2075 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2077 * disable: Disable this device.
2079 If there are multiple matching configurations changing
2080 the same attribute, the last one is used.
2082 memblock=debug [KNL] Enable memblock debug messages.
2084 load_ramdisk= [RAM] List of ramdisks to load from floppy
2085 See Documentation/blockdev/ramdisk.txt.
2087 lockd.nlm_grace_period=P [NFS] Assign grace period.
2088 Format: <integer>
2090 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2091 Format: <integer>
2093 lockd.nlm_timeout=T [NFS] Assign timeout value.
2094 Format: <integer>
2096 lockd.nlm_udpport=M [NFS] Assign UDP port.
2097 Format: <integer>
2099 locktorture.nreaders_stress= [KNL]
2100 Set the number of locking read-acquisition kthreads.
2101 Defaults to being automatically set based on the
2102 number of online CPUs.
2104 locktorture.nwriters_stress= [KNL]
2105 Set the number of locking write-acquisition kthreads.
2107 locktorture.onoff_holdoff= [KNL]
2108 Set time (s) after boot for CPU-hotplug testing.
2110 locktorture.onoff_interval= [KNL]
2111 Set time (s) between CPU-hotplug operations, or
2112 zero to disable CPU-hotplug testing.
2114 locktorture.shuffle_interval= [KNL]
2115 Set task-shuffle interval (jiffies). Shuffling
2116 tasks allows some CPUs to go into dyntick-idle
2117 mode during the locktorture test.
2119 locktorture.shutdown_secs= [KNL]
2120 Set time (s) after boot system shutdown. This
2121 is useful for hands-off automated testing.
2123 locktorture.stat_interval= [KNL]
2124 Time (s) between statistics printk()s.
2126 locktorture.stutter= [KNL]
2127 Time (s) to stutter testing, for example,
2128 specifying five seconds causes the test to run for
2129 five seconds, wait for five seconds, and so on.
2130 This tests the locking primitive's ability to
2131 transition abruptly to and from idle.
2133 locktorture.torture_runnable= [BOOT]
2134 Start locktorture running at boot time.
2136 locktorture.torture_type= [KNL]
2137 Specify the locking implementation to test.
2139 locktorture.verbose= [KNL]
2140 Enable additional printk() statements.
2142 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2143 Format: <irq>
2145 loglevel= All Kernel Messages with a loglevel smaller than the
2146 console loglevel will be printed to the console. It can
2147 also be changed with klogd or other programs. The
2148 loglevels are defined as follows:
2150 0 (KERN_EMERG) system is unusable
2151 1 (KERN_ALERT) action must be taken immediately
2152 2 (KERN_CRIT) critical conditions
2153 3 (KERN_ERR) error conditions
2154 4 (KERN_WARNING) warning conditions
2155 5 (KERN_NOTICE) normal but significant condition
2156 6 (KERN_INFO) informational
2157 7 (KERN_DEBUG) debug-level messages
2159 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2160 in bytes. n must be a power of two and greater
2161 than the minimal size. The minimal size is defined
2162 by LOG_BUF_SHIFT kernel config parameter. There is
2163 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2164 that allows to increase the default size depending on
2165 the number of CPUs. See init/Kconfig for more details.
2167 logo.nologo [FB] Disables display of the built-in Linux logo.
2168 This may be used to provide more screen space for
2169 kernel log messages and is useful when debugging
2170 kernel boot problems.
2172 lp=0 [LP] Specify parallel ports to use, e.g,
2173 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2174 lp=reset first parallel port). 'lp=0' disables the
2175 lp=auto printer driver. 'lp=reset' (which can be
2176 specified in addition to the ports) causes
2177 attached printers to be reset. Using
2178 lp=port1,port2,... specifies the parallel ports
2179 to associate lp devices with, starting with
2180 lp0. A port specification may be 'none' to skip
2181 that lp device, or a parport name such as
2182 'parport0'. Specifying 'lp=auto' instead of a
2183 port specification list means that device IDs
2184 from each port should be examined, to see if
2185 an IEEE 1284-compliant printer is attached; if
2186 so, the driver will manage that printer.
2187 See also header of drivers/char/lp.c.
2189 lpj=n [KNL]
2190 Sets loops_per_jiffy to given constant, thus avoiding
2191 time-consuming boot-time autodetection (up to 250 ms per
2192 CPU). 0 enables autodetection (default). To determine
2193 the correct value for your kernel, boot with normal
2194 autodetection and see what value is printed. Note that
2195 on SMP systems the preset will be applied to all CPUs,
2196 which is likely to cause problems if your CPUs need
2197 significantly divergent settings. An incorrect value
2198 will cause delays in the kernel to be wrong, leading to
2199 unpredictable I/O errors and other breakage. Although
2200 unlikely, in the extreme case this might damage your
2201 hardware.
2203 ltpc= [NET]
2204 Format: <io>,<irq>,<dma>
2206 machvec= [IA-64] Force the use of a particular machine-vector
2207 (machvec) in a generic kernel.
2208 Example: machvec=hpzx1_swiotlb
2210 machtype= [Loongson] Share the same kernel image file between different
2211 yeeloong laptop.
2212 Example: machtype=lemote-yeeloong-2f-7inch
2214 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2215 than or equal to this physical address is ignored.
2217 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2218 will bring up during bootup. maxcpus=n : n >= 0 limits
2219 the kernel to bring up 'n' processors. Surely after
2220 bootup you can bring up the other plugged cpu by executing
2221 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2222 only takes effect during system bootup.
2223 While n=0 is a special case, it is equivalent to "nosmp",
2224 which also disables the IO APIC.
2226 max_loop= [LOOP] The number of loop block devices that get
2227 (loop.max_loop) unconditionally pre-created at init time. The default
2228 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2229 of statically allocating a predefined number, loop
2230 devices can be requested on-demand with the
2231 /dev/loop-control interface.
2233 mce [X86-32] Machine Check Exception
2235 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2237 md= [HW] RAID subsystems devices and level
2238 See Documentation/md.txt.
2240 mdacon= [MDA]
2241 Format: <first>,<last>
2242 Specifies range of consoles to be captured by the MDA.
2244 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2245 Amount of memory to be used when the kernel is not able
2246 to see the whole system memory or for test.
2247 [X86] Work as limiting max address. Use together
2248 with memmap= to avoid physical address space collisions.
2249 Without memmap= PCI devices could be placed at addresses
2250 belonging to unused RAM.
2252 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2253 memory.
2255 memchunk=nn[KMG]
2256 [KNL,SH] Allow user to override the default size for
2257 per-device physically contiguous DMA buffers.
2259 memhp_default_state=online/offline
2260 [KNL] Set the initial state for the memory hotplug
2261 onlining policy. If not specified, the default value is
2262 set according to the
2263 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2264 option.
2265 See Documentation/memory-hotplug.txt.
2267 memmap=exactmap [KNL,X86] Enable setting of an exact
2268 E820 memory map, as specified by the user.
2269 Such memmap=exactmap lines can be constructed based on
2270 BIOS output or other requirements. See the memmap=nn@ss
2271 option description.
2273 memmap=nn[KMG]@ss[KMG]
2274 [KNL] Force usage of a specific region of memory.
2275 Region of memory to be used is from ss to ss+nn.
2277 memmap=nn[KMG]#ss[KMG]
2278 [KNL,ACPI] Mark specific memory as ACPI data.
2279 Region of memory to be marked is from ss to ss+nn.
2281 memmap=nn[KMG]$ss[KMG]
2282 [KNL,ACPI] Mark specific memory as reserved.
2283 Region of memory to be reserved is from ss to ss+nn.
2284 Example: Exclude memory from 0x18690000-0x1869ffff
2285 memmap=64K$0x18690000
2286 or
2287 memmap=0x10000$0x18690000
2289 memmap=nn[KMG]!ss[KMG]
2290 [KNL,X86] Mark specific memory as protected.
2291 Region of memory to be used, from ss to ss+nn.
2292 The memory region may be marked as e820 type 12 (0xc)
2293 and is NVDIMM or ADR memory.
2295 memory_corruption_check=0/1 [X86]
2296 Some BIOSes seem to corrupt the first 64k of
2297 memory when doing things like suspend/resume.
2298 Setting this option will scan the memory
2299 looking for corruption. Enabling this will
2300 both detect corruption and prevent the kernel
2301 from using the memory being corrupted.
2302 However, its intended as a diagnostic tool; if
2303 repeatable BIOS-originated corruption always
2304 affects the same memory, you can use memmap=
2305 to prevent the kernel from using that memory.
2307 memory_corruption_check_size=size [X86]
2308 By default it checks for corruption in the low
2309 64k, making this memory unavailable for normal
2310 use. Use this parameter to scan for
2311 corruption in more or less memory.
2313 memory_corruption_check_period=seconds [X86]
2314 By default it checks for corruption every 60
2315 seconds. Use this parameter to check at some
2316 other rate. 0 disables periodic checking.
2318 memtest= [KNL,X86,ARM] Enable memtest
2319 Format: <integer>
2320 default : 0 <disable>
2321 Specifies the number of memtest passes to be
2322 performed. Each pass selects another test
2323 pattern from a given set of patterns. Memtest
2324 fills the memory with this pattern, validates
2325 memory contents and reserves bad memory
2326 regions that are detected.
2328 meye.*= [HW] Set MotionEye Camera parameters
2329 See Documentation/video4linux/meye.txt.
2331 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2332 Multi-Function General Purpose Timers on AMD Geode
2333 platforms.
2335 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2336 the BIOS has incorrectly applied a workaround. TinyBIOS
2337 version 0.98 is known to be affected, 0.99 fixes the
2338 problem by letting the user disable the workaround.
2340 mga= [HW,DRM]
2342 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2343 physical address is ignored.
2345 mini2440= [ARM,HW,KNL]
2346 Format:[0..2][b][c][t]
2347 Default: "0tb"
2348 MINI2440 configuration specification:
2349 0 - The attached screen is the 3.5" TFT
2350 1 - The attached screen is the 7" TFT
2351 2 - The VGA Shield is attached (1024x768)
2352 Leaving out the screen size parameter will not load
2353 the TFT driver, and the framebuffer will be left
2354 unconfigured.
2355 b - Enable backlight. The TFT backlight pin will be
2356 linked to the kernel VESA blanking code and a GPIO
2357 LED. This parameter is not necessary when using the
2358 VGA shield.
2359 c - Enable the s3c camera interface.
2360 t - Reserved for enabling touchscreen support. The
2361 touchscreen support is not enabled in the mainstream
2362 kernel as of 2.6.30, a preliminary port can be found
2363 in the "bleeding edge" mini2440 support kernel at
2364 http://repo.or.cz/w/linux-2.6/mini2440.git
2366 mminit_loglevel=
2367 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2368 parameter allows control of the logging verbosity for
2369 the additional memory initialisation checks. A value
2370 of 0 disables mminit logging and a level of 4 will
2371 log everything. Information is printed at KERN_DEBUG
2372 so loglevel=8 may also need to be specified.
2374 module.sig_enforce
2375 [KNL] When CONFIG_MODULE_SIG is set, this means that
2376 modules without (valid) signatures will fail to load.
2377 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2378 is always true, so this option does nothing.
2380 module_blacklist= [KNL] Do not load a comma-separated list of
2381 modules. Useful for debugging problem modules.
2383 mousedev.tap_time=
2384 [MOUSE] Maximum time between finger touching and
2385 leaving touchpad surface for touch to be considered
2386 a tap and be reported as a left button click (for
2387 touchpads working in absolute mode only).
2388 Format: <msecs>
2389 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2390 reporting absolute coordinates, such as tablets
2391 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2392 reporting absolute coordinates, such as tablets
2394 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2395 is similar to kernelcore except it specifies the
2396 amount of memory used for migratable allocations.
2397 If both kernelcore and movablecore is specified,
2398 then kernelcore will be at *least* the specified
2399 value but may be more. If movablecore on its own
2400 is specified, the administrator must be careful
2401 that the amount of memory usable for all allocations
2402 is not too small.
2404 movable_node [KNL,X86] Boot-time switch to enable the effects
2405 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2407 MTD_Partition= [MTD]
2408 Format: <name>,<region-number>,<size>,<offset>
2410 MTD_Region= [MTD] Format:
2411 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2413 mtdparts= [MTD]
2414 See drivers/mtd/cmdlinepart.c.
2416 multitce=off [PPC] This parameter disables the use of the pSeries
2417 firmware feature for updating multiple TCE entries
2418 at a time.
2420 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2422 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2424 boundary - index of last SLC block on Flex-OneNAND.
2425 The remaining blocks are configured as MLC blocks.
2426 lock - Configure if Flex-OneNAND boundary should be locked.
2427 Once locked, the boundary cannot be changed.
2428 1 indicates lock status, 0 indicates unlock status.
2430 mtdset= [ARM]
2431 ARM/S3C2412 JIVE boot control
2433 See arch/arm/mach-s3c2412/mach-jive.c
2435 mtouchusb.raw_coordinates=
2436 [HW] Make the MicroTouch USB driver use raw coordinates
2437 ('y', default) or cooked coordinates ('n')
2439 mtrr_chunk_size=nn[KMG] [X86]
2440 used for mtrr cleanup. It is largest continuous chunk
2441 that could hold holes aka. UC entries.
2443 mtrr_gran_size=nn[KMG] [X86]
2444 Used for mtrr cleanup. It is granularity of mtrr block.
2445 Default is 1.
2446 Large value could prevent small alignment from
2447 using up MTRRs.
2449 mtrr_spare_reg_nr=n [X86]
2450 Format: <integer>
2451 Range: 0,7 : spare reg number
2452 Default : 1
2453 Used for mtrr cleanup. It is spare mtrr entries number.
2454 Set to 2 or more if your graphical card needs more.
2456 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2458 netdev= [NET] Network devices parameters
2459 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2460 Note that mem_start is often overloaded to mean
2461 something different and driver-specific.
2462 This usage is only documented in each driver source
2463 file if at all.
2465 nf_conntrack.acct=
2466 [NETFILTER] Enable connection tracking flow accounting
2467 0 to disable accounting
2468 1 to enable accounting
2469 Default value is 0.
2471 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2472 See Documentation/filesystems/nfs/nfsroot.txt.
2474 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2475 See Documentation/filesystems/nfs/nfsroot.txt.
2477 nfsrootdebug [NFS] enable nfsroot debugging messages.
2478 See Documentation/filesystems/nfs/nfsroot.txt.
2480 nfs.callback_nr_threads=
2481 [NFSv4] set the total number of threads that the
2482 NFS client will assign to service NFSv4 callback
2483 requests.
2485 nfs.callback_tcpport=
2486 [NFS] set the TCP port on which the NFSv4 callback
2487 channel should listen.
2489 nfs.cache_getent=
2490 [NFS] sets the pathname to the program which is used
2491 to update the NFS client cache entries.
2493 nfs.cache_getent_timeout=
2494 [NFS] sets the timeout after which an attempt to
2495 update a cache entry is deemed to have failed.
2497 nfs.idmap_cache_timeout=
2498 [NFS] set the maximum lifetime for idmapper cache
2499 entries.
2501 nfs.enable_ino64=
2502 [NFS] enable 64-bit inode numbers.
2503 If zero, the NFS client will fake up a 32-bit inode
2504 number for the readdir() and stat() syscalls instead
2505 of returning the full 64-bit number.
2506 The default is to return 64-bit inode numbers.
2508 nfs.max_session_cb_slots=
2509 [NFSv4.1] Sets the maximum number of session
2510 slots the client will assign to the callback
2511 channel. This determines the maximum number of
2512 callbacks the client will process in parallel for
2513 a particular server.
2515 nfs.max_session_slots=
2516 [NFSv4.1] Sets the maximum number of session slots
2517 the client will attempt to negotiate with the server.
2518 This limits the number of simultaneous RPC requests
2519 that the client can send to the NFSv4.1 server.
2520 Note that there is little point in setting this
2521 value higher than the max_tcp_slot_table_limit.
2523 nfs.nfs4_disable_idmapping=
2524 [NFSv4] When set to the default of '1', this option
2525 ensures that both the RPC level authentication
2526 scheme and the NFS level operations agree to use
2527 numeric uids/gids if the mount is using the
2528 'sec=sys' security flavour. In effect it is
2529 disabling idmapping, which can make migration from
2530 legacy NFSv2/v3 systems to NFSv4 easier.
2531 Servers that do not support this mode of operation
2532 will be autodetected by the client, and it will fall
2533 back to using the idmapper.
2534 To turn off this behaviour, set the value to '0'.
2535 nfs.nfs4_unique_id=
2536 [NFS4] Specify an additional fixed unique ident-
2537 ification string that NFSv4 clients can insert into
2538 their nfs_client_id4 string. This is typically a
2539 UUID that is generated at system install time.
2541 nfs.send_implementation_id =
2542 [NFSv4.1] Send client implementation identification
2543 information in exchange_id requests.
2544 If zero, no implementation identification information
2545 will be sent.
2546 The default is to send the implementation identification
2547 information.
2549 nfs.recover_lost_locks =
2550 [NFSv4] Attempt to recover locks that were lost due
2551 to a lease timeout on the server. Please note that
2552 doing this risks data corruption, since there are
2553 no guarantees that the file will remain unchanged
2554 after the locks are lost.
2555 If you want to enable the kernel legacy behaviour of
2556 attempting to recover these locks, then set this
2557 parameter to '1'.
2558 The default parameter value of '0' causes the kernel
2559 not to attempt recovery of lost locks.
2561 nfs4.layoutstats_timer =
2562 [NFSv4.2] Change the rate at which the kernel sends
2563 layoutstats to the pNFS metadata server.
2565 Setting this to value to 0 causes the kernel to use
2566 whatever value is the default set by the layout
2567 driver. A non-zero value sets the minimum interval
2568 in seconds between layoutstats transmissions.
2570 nfsd.nfs4_disable_idmapping=
2571 [NFSv4] When set to the default of '1', the NFSv4
2572 server will return only numeric uids and gids to
2573 clients using auth_sys, and will accept numeric uids
2574 and gids from such clients. This is intended to ease
2575 migration from NFSv2/v3.
2577 objlayoutdriver.osd_login_prog=
2578 [NFS] [OBJLAYOUT] sets the pathname to the program which
2579 is used to automatically discover and login into new
2580 osd-targets. Please see:
2581 Documentation/filesystems/pnfs.txt for more explanations
2583 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2584 when a NMI is triggered.
2585 Format: [state][,regs][,debounce][,die]
2587 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2588 Format: [panic,][nopanic,][num]
2589 Valid num: 0 or 1
2590 0 - turn hardlockup detector in nmi_watchdog off
2591 1 - turn hardlockup detector in nmi_watchdog on
2592 When panic is specified, panic when an NMI watchdog
2593 timeout occurs (or 'nopanic' to override the opposite
2594 default). To disable both hard and soft lockup detectors,
2595 please see 'nowatchdog'.
2596 This is useful when you use a panic=... timeout and
2597 need the box quickly up again.
2599 netpoll.carrier_timeout=
2600 [NET] Specifies amount of time (in seconds) that
2601 netpoll should wait for a carrier. By default netpoll
2602 waits 4 seconds.
2604 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2605 emulation library even if a 387 maths coprocessor
2606 is present.
2608 no_console_suspend
2609 [HW] Never suspend the console
2610 Disable suspending of consoles during suspend and
2611 hibernate operations. Once disabled, debugging
2612 messages can reach various consoles while the rest
2613 of the system is being put to sleep (ie, while
2614 debugging driver suspend/resume hooks). This may
2615 not work reliably with all consoles, but is known
2616 to work with serial and VGA consoles.
2617 To facilitate more flexible debugging, we also add
2618 console_suspend, a printk module parameter to control
2619 it. Users could use console_suspend (usually
2620 /sys/module/printk/parameters/console_suspend) to
2621 turn on/off it dynamically.
2623 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2624 caches in the slab allocator. Saves per-node memory,
2625 but will impact performance.
2627 noalign [KNL,ARM]
2629 noapic [SMP,APIC] Tells the kernel to not make use of any
2630 IOAPICs that may be present in the system.
2632 noautogroup Disable scheduler automatic task group creation.
2634 nobats [PPC] Do not use BATs for mapping kernel lowmem
2635 on "Classic" PPC cores.
2637 nocache [ARM]
2639 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2641 nodelayacct [KNL] Disable per-task delay accounting
2643 nodsp [SH] Disable hardware DSP at boot time.
2645 noefi Disable EFI runtime services support.
2647 noexec [IA-64]
2649 noexec [X86]
2650 On X86-32 available only on PAE configured kernels.
2651 noexec=on: enable non-executable mappings (default)
2652 noexec=off: disable non-executable mappings
2654 nosmap [X86]
2655 Disable SMAP (Supervisor Mode Access Prevention)
2656 even if it is supported by processor.
2658 nosmep [X86]
2659 Disable SMEP (Supervisor Mode Execution Prevention)
2660 even if it is supported by processor.
2662 noexec32 [X86-64]
2663 This affects only 32-bit executables.
2664 noexec32=on: enable non-executable mappings (default)
2665 read doesn't imply executable mappings
2666 noexec32=off: disable non-executable mappings
2667 read implies executable mappings
2669 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2671 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2672 register save and restore. The kernel will only save
2673 legacy floating-point registers on task switch.
2675 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2677 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2678 Equivalent to smt=1.
2680 noxsave [BUGS=X86] Disables x86 extended register state save
2681 and restore using xsave. The kernel will fallback to
2682 enabling legacy floating-point and sse state.
2684 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2685 register states. The kernel will fall back to use
2686 xsave to save the states. By using this parameter,
2687 performance of saving the states is degraded because
2688 xsave doesn't support modified optimization while
2689 xsaveopt supports it on xsaveopt enabled systems.
2691 noxsaves [X86] Disables xsaves and xrstors used in saving and
2692 restoring x86 extended register state in compacted
2693 form of xsave area. The kernel will fall back to use
2694 xsaveopt and xrstor to save and restore the states
2695 in standard form of xsave area. By using this
2696 parameter, xsave area per process might occupy more
2697 memory on xsaves enabled systems.
2699 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2700 wfi(ARM) instruction doesn't work correctly and not to
2701 use it. This is also useful when using JTAG debugger.
2703 no_file_caps Tells the kernel not to honor file capabilities. The
2704 only way then for a file to be executed with privilege
2705 is to be setuid root or executed by root.
2707 nohalt [IA-64] Tells the kernel not to use the power saving
2708 function PAL_HALT_LIGHT when idle. This increases
2709 power-consumption. On the positive side, it reduces
2710 interrupt wake-up latency, which may improve performance
2711 in certain environments such as networked servers or
2712 real-time systems.
2714 nohibernate [HIBERNATION] Disable hibernation and resume.
2716 nohz= [KNL] Boottime enable/disable dynamic ticks
2717 Valid arguments: on, off
2718 Default: on
2720 nohz_full= [KNL,BOOT]
2721 The argument is a cpu list, as described above.
2722 In kernels built with CONFIG_NO_HZ_FULL=y, set
2723 the specified list of CPUs whose tick will be stopped
2724 whenever possible. The boot CPU will be forced outside
2725 the range to maintain the timekeeping.
2726 The CPUs in this range must also be included in the
2727 rcu_nocbs= set.
2729 noiotrap [SH] Disables trapped I/O port accesses.
2731 noirqdebug [X86-32] Disables the code which attempts to detect and
2732 disable unhandled interrupt sources.
2734 no_timer_check [X86,APIC] Disables the code which tests for
2735 broken timer IRQ sources.
2737 noisapnp [ISAPNP] Disables ISA PnP code.
2739 noinitrd [RAM] Tells the kernel not to load any configured
2740 initial RAM disk.
2742 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2743 remapping.
2744 [Deprecated - use intremap=off]
2746 nointroute [IA-64]
2748 noinvpcid [X86] Disable the INVPCID cpu feature.
2750 nojitter [IA-64] Disables jitter checking for ITC timers.
2752 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2754 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2755 fault handling.
2757 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2758 steal time is computed, but won't influence scheduler
2759 behaviour
2761 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2763 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2765 noltlbs [PPC] Do not use large page/tlb entries for kernel
2766 lowmem mapping on PPC40x and PPC8xx
2768 nomca [IA-64] Disable machine check abort handling
2770 nomce [X86-32] Disable Machine Check Exception
2772 nomfgpt [X86-32] Disable Multi-Function General Purpose
2773 Timer usage (for AMD Geode machines).
2775 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2776 shutdown the other cpus. Instead use the REBOOT_VECTOR
2777 irq.
2779 nomodule Disable module load
2781 nopat [X86] Disable PAT (page attribute table extension of
2782 pagetables) support.
2784 norandmaps Don't use address space randomization. Equivalent to
2785 echo 0 > /proc/sys/kernel/randomize_va_space
2787 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2789 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2790 with UP alternatives
2792 nordrand [X86] Disable kernel use of the RDRAND and
2793 RDSEED instructions even if they are supported
2794 by the processor. RDRAND and RDSEED are still
2795 available to user space applications.
2797 noresume [SWSUSP] Disables resume and restores original swap
2798 space.
2800 no-scroll [VGA] Disables scrollback.
2801 This is required for the Braillex ib80-piezo Braille
2802 reader made by F.H. Papenmeier (Germany).
2804 nosbagart [IA-64]
2806 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2808 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2809 and disable the IO APIC. legacy for "maxcpus=0".
2811 nosoftlockup [KNL] Disable the soft-lockup detector.
2813 nosync [HW,M68K] Disables sync negotiation for all devices.
2815 notsc [BUGS=X86-32] Disable Time Stamp Counter
2817 nowatchdog [KNL] Disable both lockup detectors, i.e.
2818 soft-lockup and NMI watchdog (hard-lockup).
2820 nowb [ARM]
2822 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2824 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2825 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2826 Some features depend on CPU0. Known dependencies are:
2827 1. Resume from suspend/hibernate depends on CPU0.
2828 Suspend/hibernate will fail if CPU0 is offline and you
2829 need to online CPU0 before suspend/hibernate.
2830 2. PIC interrupts also depend on CPU0. CPU0 can't be
2831 removed if a PIC interrupt is detected.
2832 It's said poweroff/reboot may depend on CPU0 on some
2833 machines although I haven't seen such issues so far
2834 after CPU0 is offline on a few tested machines.
2835 If the dependencies are under your control, you can
2836 turn on cpu0_hotplug.
2838 nptcg= [IA-64] Override max number of concurrent global TLB
2839 purges which is reported from either PAL_VM_SUMMARY or
2840 SAL PALO.
2842 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2843 could support. nr_cpus=n : n >= 1 limits the kernel to
2844 support 'n' processors. It could be larger than the
2845 number of already plugged CPU during bootup, later in
2846 runtime you can physically add extra cpu until it reaches
2847 n. So during boot up some boot time memory for per-cpu
2848 variables need be pre-allocated for later physical cpu
2849 hot plugging.
2851 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2853 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2854 Allowed values are enable and disable
2856 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2857 one of ['zone', 'node', 'default'] can be specified
2858 This can be set from sysctl after boot.
2859 See Documentation/sysctl/vm.txt for details.
2861 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2862 See Documentation/debugging-via-ohci1394.txt for more
2863 info.
2865 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2866 Rather than timing out after 20 ms if an EC
2867 command is not properly ACKed, override the length
2868 of the timeout. We have interrupts disabled while
2869 waiting for the ACK, so if this is set too high
2870 interrupts *may* be lost!
2872 omap_mux= [OMAP] Override bootloader pin multiplexing.
2873 Format: <mux_mode0.mode_name=value>...
2874 For example, to override I2C bus2:
2875 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2877 oprofile.timer= [HW]
2878 Use timer interrupt instead of performance counters
2880 oprofile.cpu_type= Force an oprofile cpu type
2881 This might be useful if you have an older oprofile
2882 userland or if you want common events.
2883 Format: { arch_perfmon }
2884 arch_perfmon: [X86] Force use of architectural
2885 perfmon on Intel CPUs instead of the
2886 CPU specific event set.
2887 timer: [X86] Force use of architectural NMI
2888 timer mode (see also oprofile.timer
2889 for generic hr timer mode)
2891 oops=panic Always panic on oopses. Default is to just kill the
2892 process, but there is a small probability of
2893 deadlocking the machine.
2894 This will also cause panics on machine check exceptions.
2895 Useful together with panic=30 to trigger a reboot.
2897 OSS [HW,OSS]
2898 See Documentation/sound/oss/oss-parameters.txt
2900 page_owner= [KNL] Boot-time page_owner enabling option.
2901 Storage of the information about who allocated
2902 each page is disabled in default. With this switch,
2903 we can turn it on.
2904 on: enable the feature
2906 page_poison= [KNL] Boot-time parameter changing the state of
2907 poisoning on the buddy allocator.
2908 off: turn off poisoning
2909 on: turn on poisoning
2911 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2912 timeout > 0: seconds before rebooting
2913 timeout = 0: wait forever
2914 timeout < 0: reboot immediately
2915 Format: <timeout>
2917 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2918 on a WARN().
2920 crash_kexec_post_notifiers
2921 Run kdump after running panic-notifiers and dumping
2922 kmsg. This only for the users who doubt kdump always
2923 succeeds in any situation.
2924 Note that this also increases risks of kdump failure,
2925 because some panic notifiers can make the crashed
2926 kernel more unstable.
2928 parkbd.port= [HW] Parallel port number the keyboard adapter is
2929 connected to, default is 0.
2930 Format: <parport#>
2931 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2932 0 for XT, 1 for AT (default is AT).
2933 Format: <mode>
2935 parport= [HW,PPT] Specify parallel ports. 0 disables.
2936 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2937 Use 'auto' to force the driver to use any
2938 IRQ/DMA settings detected (the default is to
2939 ignore detected IRQ/DMA settings because of
2940 possible conflicts). You can specify the base
2941 address, IRQ, and DMA settings; IRQ and DMA
2942 should be numbers, or 'auto' (for using detected
2943 settings on that particular port), or 'nofifo'
2944 (to avoid using a FIFO even if it is detected).
2945 Parallel ports are assigned in the order they
2946 are specified on the command line, starting
2947 with parport0.
2949 parport_init_mode= [HW,PPT]
2950 Configure VIA parallel port to operate in
2951 a specific mode. This is necessary on Pegasos
2952 computer where firmware has no options for setting
2953 up parallel port mode and sets it to spp.
2954 Currently this function knows 686a and 8231 chips.
2955 Format: [spp|ps2|epp|ecp|ecpepp]
2957 pause_on_oops=
2958 Halt all CPUs after the first oops has been printed for
2959 the specified number of seconds. This is to be used if
2960 your oopses keep scrolling off the screen.
2962 pcbit= [HW,ISDN]
2964 pcd. [PARIDE]
2965 See header of drivers/block/paride/pcd.c.
2966 See also Documentation/blockdev/paride.txt.
2968 pci=option[,option...] [PCI] various PCI subsystem options:
2969 earlydump [X86] dump PCI config space before the kernel
2970 changes anything
2971 off [X86] don't probe for the PCI bus
2972 bios [X86-32] force use of PCI BIOS, don't access
2973 the hardware directly. Use this if your machine
2974 has a non-standard PCI host bridge.
2975 nobios [X86-32] disallow use of PCI BIOS, only direct
2976 hardware access methods are allowed. Use this
2977 if you experience crashes upon bootup and you
2978 suspect they are caused by the BIOS.
2979 conf1 [X86] Force use of PCI Configuration Access
2980 Mechanism 1 (config address in IO port 0xCF8,
2981 data in IO port 0xCFC, both 32-bit).
2982 conf2 [X86] Force use of PCI Configuration Access
2983 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2984 the function, IO port 0xCFA, also 8-bit, sets
2985 bus number. The config space is then accessed
2986 through ports 0xC000-0xCFFF).
2987 See http://wiki.osdev.org/PCI for more info
2988 on the configuration access mechanisms.
2989 noaer [PCIE] If the PCIEAER kernel config parameter is
2990 enabled, this kernel boot option can be used to
2991 disable the use of PCIE advanced error reporting.
2992 nodomains [PCI] Disable support for multiple PCI
2993 root domains (aka PCI segments, in ACPI-speak).
2994 nommconf [X86] Disable use of MMCONFIG for PCI
2995 Configuration
2996 check_enable_amd_mmconf [X86] check for and enable
2997 properly configured MMIO access to PCI
2998 config space on AMD family 10h CPU
2999 nomsi [MSI] If the PCI_MSI kernel config parameter is
3000 enabled, this kernel boot option can be used to
3001 disable the use of MSI interrupts system-wide.
3002 noioapicquirk [APIC] Disable all boot interrupt quirks.
3003 Safety option to keep boot IRQs enabled. This
3004 should never be necessary.
3005 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3006 primary IO-APIC for bridges that cannot disable
3007 boot IRQs. This fixes a source of spurious IRQs
3008 when the system masks IRQs.
3009 noioapicreroute [APIC] Disable workaround that uses the
3010 boot IRQ equivalent of an IRQ that connects to
3011 a chipset where boot IRQs cannot be disabled.
3012 The opposite of ioapicreroute.
3013 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
3014 routing table. These calls are known to be buggy
3015 on several machines and they hang the machine
3016 when used, but on other computers it's the only
3017 way to get the interrupt routing table. Try
3018 this option if the kernel is unable to allocate
3019 IRQs or discover secondary PCI buses on your
3020 motherboard.
3021 rom [X86] Assign address space to expansion ROMs.
3022 Use with caution as certain devices share
3023 address decoders between ROMs and other
3024 resources.
3025 norom [X86] Do not assign address space to
3026 expansion ROMs that do not already have
3027 BIOS assigned address ranges.
3028 nobar [X86] Do not assign address space to the
3029 BARs that weren't assigned by the BIOS.
3030 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
3031 assigned automatically to PCI devices. You can
3032 make the kernel exclude IRQs of your ISA cards
3033 this way.
3034 pirqaddr=0xAAAAA [X86] Specify the physical address
3035 of the PIRQ table (normally generated
3036 by the BIOS) if it is outside the
3037 F0000h-100000h range.
3038 lastbus=N [X86] Scan all buses thru bus #N. Can be
3039 useful if the kernel is unable to find your
3040 secondary buses and you want to tell it
3041 explicitly which ones they are.
3042 assign-busses [X86] Always assign all PCI bus
3043 numbers ourselves, overriding
3044 whatever the firmware may have done.
3045 usepirqmask [X86] Honor the possible IRQ mask stored
3046 in the BIOS $PIR table. This is needed on
3047 some systems with broken BIOSes, notably
3048 some HP Pavilion N5400 and Omnibook XE3
3049 notebooks. This will have no effect if ACPI
3050 IRQ routing is enabled.
3051 noacpi [X86] Do not use ACPI for IRQ routing
3052 or for PCI scanning.
3053 use_crs [X86] Use PCI host bridge window information
3054 from ACPI. On BIOSes from 2008 or later, this
3055 is enabled by default. If you need to use this,
3056 please report a bug.
3057 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3058 If you need to use this, please report a bug.
3059 routeirq Do IRQ routing for all PCI devices.
3060 This is normally done in pci_enable_device(),
3061 so this option is a temporary workaround
3062 for broken drivers that don't call it.
3063 skip_isa_align [X86] do not align io start addr, so can
3064 handle more pci cards
3065 noearly [X86] Don't do any early type 1 scanning.
3066 This might help on some broken boards which
3067 machine check when some devices' config space
3068 is read. But various workarounds are disabled
3069 and some IOMMU drivers will not work.
3070 bfsort Sort PCI devices into breadth-first order.
3071 This sorting is done to get a device
3072 order compatible with older (<= 2.4) kernels.
3073 nobfsort Don't sort PCI devices into breadth-first order.
3074 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3075 tuning and use the BIOS-configured MPS defaults.
3076 pcie_bus_safe Set every device's MPS to the largest value
3077 supported by all devices below the root complex.
3078 pcie_bus_perf Set device MPS to the largest allowable MPS
3079 based on its parent bus. Also set MRRS (Max
3080 Read Request Size) to the largest supported
3081 value (no larger than the MPS that the device
3082 or bus can support) for best performance.
3083 pcie_bus_peer2peer Set every device's MPS to 128B, which
3084 every device is guaranteed to support. This
3085 configuration allows peer-to-peer DMA between
3086 any pair of devices, possibly at the cost of
3087 reduced performance. This also guarantees
3088 that hot-added devices will work.
3089 cbiosize=nn[KMG] The fixed amount of bus space which is
3090 reserved for the CardBus bridge's IO window.
3091 The default value is 256 bytes.
3092 cbmemsize=nn[KMG] The fixed amount of bus space which is
3093 reserved for the CardBus bridge's memory
3094 window. The default value is 64 megabytes.
3095 resource_alignment=
3096 Format:
3097 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3098 [<order of align>@]pci:<vendor>:<device>\
3099 [:<subvendor>:<subdevice>][; ...]
3100 Specifies alignment and device to reassign
3101 aligned memory resources.
3102 If <order of align> is not specified,
3103 PAGE_SIZE is used as alignment.
3104 PCI-PCI bridge can be specified, if resource
3105 windows need to be expanded.
3106 To specify the alignment for several
3107 instances of a device, the PCI vendor,
3108 device, subvendor, and subdevice may be
3109 specified, e.g., 4096@pci:8086:9c22:103c:198f
3110 ecrc= Enable/disable PCIe ECRC (transaction layer
3111 end-to-end CRC checking).
3112 bios: Use BIOS/firmware settings. This is the
3113 the default.
3114 off: Turn ECRC off
3115 on: Turn ECRC on.
3116 hpiosize=nn[KMG] The fixed amount of bus space which is
3117 reserved for hotplug bridge's IO window.
3118 Default size is 256 bytes.
3119 hpmemsize=nn[KMG] The fixed amount of bus space which is
3120 reserved for hotplug bridge's memory window.
3121 Default size is 2 megabytes.
3122 hpbussize=nn The minimum amount of additional bus numbers
3123 reserved for buses below a hotplug bridge.
3124 Default is 1.
3125 realloc= Enable/disable reallocating PCI bridge resources
3126 if allocations done by BIOS are too small to
3127 accommodate resources required by all child
3128 devices.
3129 off: Turn realloc off
3130 on: Turn realloc on
3131 realloc same as realloc=on
3132 noari do not use PCIe ARI.
3133 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3134 only look for one device below a PCIe downstream
3135 port.
3137 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3138 Management.
3139 off Disable ASPM.
3140 force Enable ASPM even on devices that claim not to support it.
3141 WARNING: Forcing ASPM on may cause system lockups.
3143 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3144 nomsi Do not use MSI for PCI Express Native Hotplug (this
3145 makes all PCIe ports use INTx for hotplug services).
3147 pcie_ports= [PCIE] PCIe ports handling:
3148 auto Ask the BIOS whether or not to use native PCIe services
3149 associated with PCIe ports (PME, hot-plug, AER). Use
3150 them only if that is allowed by the BIOS.
3151 native Use native PCIe services associated with PCIe ports
3152 unconditionally.
3153 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3154 ports driver.
3156 pcie_port_pm= [PCIE] PCIe port power management handling:
3157 off Disable power management of all PCIe ports
3158 force Forcibly enable power management of all PCIe ports
3160 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3161 nomsi Do not use MSI for native PCIe PME signaling (this makes
3162 all PCIe root ports use INTx for all services).
3164 pcmv= [HW,PCMCIA] BadgePAD 4
3166 pd_ignore_unused
3167 [PM]
3168 Keep all power-domains already enabled by bootloader on,
3169 even if no driver has claimed them. This is useful
3170 for debug and development, but should not be
3171 needed on a platform with proper driver support.
3173 pd. [PARIDE]
3174 See Documentation/blockdev/paride.txt.
3176 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3177 boot time.
3178 Format: { 0 | 1 }
3179 See arch/parisc/kernel/pdc_chassis.c
3181 percpu_alloc= Select which percpu first chunk allocator to use.
3182 Currently supported values are "embed" and "page".
3183 Archs may support subset or none of the selections.
3184 See comments in mm/percpu.c for details on each
3185 allocator. This parameter is primarily for debugging
3186 and performance comparison.
3188 pf. [PARIDE]
3189 See Documentation/blockdev/paride.txt.
3191 pg. [PARIDE]
3192 See Documentation/blockdev/paride.txt.
3194 pirq= [SMP,APIC] Manual mp-table setup
3195 See Documentation/x86/i386/IO-APIC.txt.
3197 plip= [PPT,NET] Parallel port network link
3198 Format: { parport<nr> | timid | 0 }
3199 See also Documentation/parport.txt.
3201 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3202 Override pmtimer IOPort with a hex value.
3203 e.g. pmtmr=0x508
3205 pnp.debug=1 [PNP]
3206 Enable PNP debug messages (depends on the
3207 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3208 via /sys/module/pnp/parameters/debug. We always show
3209 current resource usage; turning this on also shows
3210 possible settings and some assignment information.
3212 pnpacpi= [ACPI]
3213 { off }
3215 pnpbios= [ISAPNP]
3216 { on | off | curr | res | no-curr | no-res }
3218 pnp_reserve_irq=
3219 [ISAPNP] Exclude IRQs for the autoconfiguration
3221 pnp_reserve_dma=
3222 [ISAPNP] Exclude DMAs for the autoconfiguration
3224 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3225 Ranges are in pairs (I/O port base and size).
3227 pnp_reserve_mem=
3228 [ISAPNP] Exclude memory regions for the
3229 autoconfiguration.
3230 Ranges are in pairs (memory base and size).
3232 ports= [IP_VS_FTP] IPVS ftp helper module
3233 Default is 21.
3234 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3235 may be specified.
3236 Format: <port>,<port>....
3238 ppc_strict_facility_enable
3239 [PPC] This option catches any kernel floating point,
3240 Altivec, VSX and SPE outside of regions specifically
3241 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3242 There is some performance impact when enabling this.
3244 print-fatal-signals=
3245 [KNL] debug: print fatal signals
3247 If enabled, warn about various signal handling
3248 related application anomalies: too many signals,
3249 too many POSIX.1 timers, fatal signals causing a
3250 coredump - etc.
3252 If you hit the warning due to signal overflow,
3253 you might want to try "ulimit -i unlimited".
3255 default: off.
3257 printk.always_kmsg_dump=
3258 Trigger kmsg_dump for cases other than kernel oops or
3259 panics
3260 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3261 default: disabled
3263 printk.devkmsg={on,off,ratelimit}
3264 Control writing to /dev/kmsg.
3265 on - unlimited logging to /dev/kmsg from userspace
3266 off - logging to /dev/kmsg disabled
3267 ratelimit - ratelimit the logging
3268 Default: ratelimit
3270 printk.time= Show timing data prefixed to each printk message line
3271 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3273 processor.max_cstate= [HW,ACPI]
3274 Limit processor to maximum C-state
3275 max_cstate=9 overrides any DMI blacklist limit.
3277 processor.nocst [HW,ACPI]
3278 Ignore the _CST method to determine C-states,
3279 instead using the legacy FADT method
3281 profile= [KNL] Enable kernel profiling via /proc/profile
3282 Format: [schedule,]<number>
3283 Param: "schedule" - profile schedule points.
3284 Param: <number> - step/bucket size as a power of 2 for
3285 statistical time based profiling.
3286 Param: "sleep" - profile D-state sleeping (millisecs).
3287 Requires CONFIG_SCHEDSTATS
3288 Param: "kvm" - profile VM exits.
3290 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3291 before loading.
3292 See Documentation/blockdev/ramdisk.txt.
3294 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3295 probe for; one of (bare|imps|exps|lifebook|any).
3296 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3297 per second.
3298 psmouse.resetafter= [HW,MOUSE]
3299 Try to reset the device after so many bad packets
3300 (0 = never).
3301 psmouse.resolution=
3302 [HW,MOUSE] Set desired mouse resolution, in dpi.
3303 psmouse.smartscroll=
3304 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3305 0 = disabled, 1 = enabled (default).
3307 pstore.backend= Specify the name of the pstore backend to use
3309 pt. [PARIDE]
3310 See Documentation/blockdev/paride.txt.
3312 pty.legacy_count=
3313 [KNL] Number of legacy pty's. Overwrites compiled-in
3314 default number.
3316 quiet [KNL] Disable most log messages
3318 r128= [HW,DRM]
3320 raid= [HW,RAID]
3321 See Documentation/md.txt.
3323 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3324 See Documentation/blockdev/ramdisk.txt.
3326 rcu_nocbs= [KNL]
3327 The argument is a cpu list, as described above.
3329 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3330 the specified list of CPUs to be no-callback CPUs.
3331 Invocation of these CPUs' RCU callbacks will
3332 be offloaded to "rcuox/N" kthreads created for
3333 that purpose, where "x" is "b" for RCU-bh, "p"
3334 for RCU-preempt, and "s" for RCU-sched, and "N"
3335 is the CPU number. This reduces OS jitter on the
3336 offloaded CPUs, which can be useful for HPC and
3337 real-time workloads. It can also improve energy
3338 efficiency for asymmetric multiprocessors.
3340 rcu_nocb_poll [KNL]
3341 Rather than requiring that offloaded CPUs
3342 (specified by rcu_nocbs= above) explicitly
3343 awaken the corresponding "rcuoN" kthreads,
3344 make these kthreads poll for callbacks.
3345 This improves the real-time response for the
3346 offloaded CPUs by relieving them of the need to
3347 wake up the corresponding kthread, but degrades
3348 energy efficiency by requiring that the kthreads
3349 periodically wake up to do the polling.
3351 rcutree.blimit= [KNL]
3352 Set maximum number of finished RCU callbacks to
3353 process in one batch.
3355 rcutree.dump_tree= [KNL]
3356 Dump the structure of the rcu_node combining tree
3357 out at early boot. This is used for diagnostic
3358 purposes, to verify correct tree setup.
3360 rcutree.gp_cleanup_delay= [KNL]
3361 Set the number of jiffies to delay each step of
3362 RCU grace-period cleanup. This only has effect
3363 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3365 rcutree.gp_init_delay= [KNL]
3366 Set the number of jiffies to delay each step of
3367 RCU grace-period initialization. This only has
3368 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3369 is set.
3371 rcutree.gp_preinit_delay= [KNL]
3372 Set the number of jiffies to delay each step of
3373 RCU grace-period pre-initialization, that is,
3374 the propagation of recent CPU-hotplug changes up
3375 the rcu_node combining tree. This only has effect
3376 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3378 rcutree.rcu_fanout_exact= [KNL]
3379 Disable autobalancing of the rcu_node combining
3380 tree. This is used by rcutorture, and might
3381 possibly be useful for architectures having high
3382 cache-to-cache transfer latencies.
3384 rcutree.rcu_fanout_leaf= [KNL]
3385 Change the number of CPUs assigned to each
3386 leaf rcu_node structure. Useful for very
3387 large systems, which will choose the value 64,
3388 and for NUMA systems with large remote-access
3389 latencies, which will choose a value aligned
3390 with the appropriate hardware boundaries.
3392 rcutree.jiffies_till_sched_qs= [KNL]
3393 Set required age in jiffies for a
3394 given grace period before RCU starts
3395 soliciting quiescent-state help from
3396 rcu_note_context_switch().
3398 rcutree.jiffies_till_first_fqs= [KNL]
3399 Set delay from grace-period initialization to
3400 first attempt to force quiescent states.
3401 Units are jiffies, minimum value is zero,
3402 and maximum value is HZ.
3404 rcutree.jiffies_till_next_fqs= [KNL]
3405 Set delay between subsequent attempts to force
3406 quiescent states. Units are jiffies, minimum
3407 value is one, and maximum value is HZ.
3409 rcutree.kthread_prio= [KNL,BOOT]
3410 Set the SCHED_FIFO priority of the RCU per-CPU
3411 kthreads (rcuc/N). This value is also used for
3412 the priority of the RCU boost threads (rcub/N)
3413 and for the RCU grace-period kthreads (rcu_bh,
3414 rcu_preempt, and rcu_sched). If RCU_BOOST is
3415 set, valid values are 1-99 and the default is 1
3416 (the least-favored priority). Otherwise, when
3417 RCU_BOOST is not set, valid values are 0-99 and
3418 the default is zero (non-realtime operation).
3420 rcutree.rcu_nocb_leader_stride= [KNL]
3421 Set the number of NOCB kthread groups, which
3422 defaults to the square root of the number of
3423 CPUs. Larger numbers reduces the wakeup overhead
3424 on the per-CPU grace-period kthreads, but increases
3425 that same overhead on each group's leader.
3427 rcutree.qhimark= [KNL]
3428 Set threshold of queued RCU callbacks beyond which
3429 batch limiting is disabled.
3431 rcutree.qlowmark= [KNL]
3432 Set threshold of queued RCU callbacks below which
3433 batch limiting is re-enabled.
3435 rcutree.rcu_idle_gp_delay= [KNL]
3436 Set wakeup interval for idle CPUs that have
3437 RCU callbacks (RCU_FAST_NO_HZ=y).
3439 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3440 Set wakeup interval for idle CPUs that have
3441 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3442 Lazy RCU callbacks are those which RCU can
3443 prove do nothing more than free memory.
3445 rcuperf.gp_exp= [KNL]
3446 Measure performance of expedited synchronous
3447 grace-period primitives.
3449 rcuperf.holdoff= [KNL]
3450 Set test-start holdoff period. The purpose of
3451 this parameter is to delay the start of the
3452 test until boot completes in order to avoid
3453 interference.
3455 rcuperf.nreaders= [KNL]
3456 Set number of RCU readers. The value -1 selects
3457 N, where N is the number of CPUs. A value
3458 "n" less than -1 selects N-n+1, where N is again
3459 the number of CPUs. For example, -2 selects N
3460 (the number of CPUs), -3 selects N+1, and so on.
3461 A value of "n" less than or equal to -N selects
3462 a single reader.
3464 rcuperf.nwriters= [KNL]
3465 Set number of RCU writers. The values operate
3466 the same as for rcuperf.nreaders.
3467 N, where N is the number of CPUs
3469 rcuperf.perf_runnable= [BOOT]
3470 Start rcuperf running at boot time.
3472 rcuperf.shutdown= [KNL]
3473 Shut the system down after performance tests
3474 complete. This is useful for hands-off automated
3475 testing.
3477 rcuperf.perf_type= [KNL]
3478 Specify the RCU implementation to test.
3480 rcuperf.verbose= [KNL]
3481 Enable additional printk() statements.
3483 rcutorture.cbflood_inter_holdoff= [KNL]
3484 Set holdoff time (jiffies) between successive
3485 callback-flood tests.
3487 rcutorture.cbflood_intra_holdoff= [KNL]
3488 Set holdoff time (jiffies) between successive
3489 bursts of callbacks within a given callback-flood
3490 test.
3492 rcutorture.cbflood_n_burst= [KNL]
3493 Set the number of bursts making up a given
3494 callback-flood test. Set this to zero to
3495 disable callback-flood testing.
3497 rcutorture.cbflood_n_per_burst= [KNL]
3498 Set the number of callbacks to be registered
3499 in a given burst of a callback-flood test.
3501 rcutorture.fqs_duration= [KNL]
3502 Set duration of force_quiescent_state bursts
3503 in microseconds.
3505 rcutorture.fqs_holdoff= [KNL]
3506 Set holdoff time within force_quiescent_state bursts
3507 in microseconds.
3509 rcutorture.fqs_stutter= [KNL]
3510 Set wait time between force_quiescent_state bursts
3511 in seconds.
3513 rcutorture.gp_cond= [KNL]
3514 Use conditional/asynchronous update-side
3515 primitives, if available.
3517 rcutorture.gp_exp= [KNL]
3518 Use expedited update-side primitives, if available.
3520 rcutorture.gp_normal= [KNL]
3521 Use normal (non-expedited) asynchronous
3522 update-side primitives, if available.
3524 rcutorture.gp_sync= [KNL]
3525 Use normal (non-expedited) synchronous
3526 update-side primitives, if available. If all
3527 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3528 rcutorture.gp_normal=, and rcutorture.gp_sync=
3529 are zero, rcutorture acts as if is interpreted
3530 they are all non-zero.
3532 rcutorture.n_barrier_cbs= [KNL]
3533 Set callbacks/threads for rcu_barrier() testing.
3535 rcutorture.nfakewriters= [KNL]
3536 Set number of concurrent RCU writers. These just
3537 stress RCU, they don't participate in the actual
3538 test, hence the "fake".
3540 rcutorture.nreaders= [KNL]
3541 Set number of RCU readers. The value -1 selects
3542 N-1, where N is the number of CPUs. A value
3543 "n" less than -1 selects N-n-2, where N is again
3544 the number of CPUs. For example, -2 selects N
3545 (the number of CPUs), -3 selects N+1, and so on.
3547 rcutorture.object_debug= [KNL]
3548 Enable debug-object double-call_rcu() testing.
3550 rcutorture.onoff_holdoff= [KNL]
3551 Set time (s) after boot for CPU-hotplug testing.
3553 rcutorture.onoff_interval= [KNL]
3554 Set time (s) between CPU-hotplug operations, or
3555 zero to disable CPU-hotplug testing.
3557 rcutorture.shuffle_interval= [KNL]
3558 Set task-shuffle interval (s). Shuffling tasks
3559 allows some CPUs to go into dyntick-idle mode
3560 during the rcutorture test.
3562 rcutorture.shutdown_secs= [KNL]
3563 Set time (s) after boot system shutdown. This
3564 is useful for hands-off automated testing.
3566 rcutorture.stall_cpu= [KNL]
3567 Duration of CPU stall (s) to test RCU CPU stall
3568 warnings, zero to disable.
3570 rcutorture.stall_cpu_holdoff= [KNL]
3571 Time to wait (s) after boot before inducing stall.
3573 rcutorture.stat_interval= [KNL]
3574 Time (s) between statistics printk()s.
3576 rcutorture.stutter= [KNL]
3577 Time (s) to stutter testing, for example, specifying
3578 five seconds causes the test to run for five seconds,
3579 wait for five seconds, and so on. This tests RCU's
3580 ability to transition abruptly to and from idle.
3582 rcutorture.test_boost= [KNL]
3583 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3584 "Maybe" means test if the RCU implementation
3585 under test support RCU priority boosting.
3587 rcutorture.test_boost_duration= [KNL]
3588 Duration (s) of each individual boost test.
3590 rcutorture.test_boost_interval= [KNL]
3591 Interval (s) between each boost test.
3593 rcutorture.test_no_idle_hz= [KNL]
3594 Test RCU's dyntick-idle handling. See also the
3595 rcutorture.shuffle_interval parameter.
3597 rcutorture.torture_runnable= [BOOT]
3598 Start rcutorture running at boot time.
3600 rcutorture.torture_type= [KNL]
3601 Specify the RCU implementation to test.
3603 rcutorture.verbose= [KNL]
3604 Enable additional printk() statements.
3606 rcupdate.rcu_cpu_stall_suppress= [KNL]
3607 Suppress RCU CPU stall warning messages.
3609 rcupdate.rcu_cpu_stall_timeout= [KNL]
3610 Set timeout for RCU CPU stall warning messages.
3612 rcupdate.rcu_expedited= [KNL]
3613 Use expedited grace-period primitives, for
3614 example, synchronize_rcu_expedited() instead
3615 of synchronize_rcu(). This reduces latency,
3616 but can increase CPU utilization, degrade
3617 real-time latency, and degrade energy efficiency.
3618 No effect on CONFIG_TINY_RCU kernels.
3620 rcupdate.rcu_normal= [KNL]
3621 Use only normal grace-period primitives,
3622 for example, synchronize_rcu() instead of
3623 synchronize_rcu_expedited(). This improves
3624 real-time latency, CPU utilization, and
3625 energy efficiency, but can expose users to
3626 increased grace-period latency. This parameter
3627 overrides rcupdate.rcu_expedited. No effect on
3628 CONFIG_TINY_RCU kernels.
3630 rcupdate.rcu_normal_after_boot= [KNL]
3631 Once boot has completed (that is, after
3632 rcu_end_inkernel_boot() has been invoked), use
3633 only normal grace-period primitives. No effect
3634 on CONFIG_TINY_RCU kernels.
3636 rcupdate.rcu_task_stall_timeout= [KNL]
3637 Set timeout in jiffies for RCU task stall warning
3638 messages. Disable with a value less than or equal
3639 to zero.
3641 rcupdate.rcu_self_test= [KNL]
3642 Run the RCU early boot self tests
3644 rcupdate.rcu_self_test_bh= [KNL]
3645 Run the RCU bh early boot self tests
3647 rcupdate.rcu_self_test_sched= [KNL]
3648 Run the RCU sched early boot self tests
3650 rdinit= [KNL]
3651 Format: <full_path>
3652 Run specified binary instead of /init from the ramdisk,
3653 used for early userspace startup. See initrd.
3655 reboot= [KNL]
3656 Format (x86 or x86_64):
3657 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3658 [[,]s[mp]#### \
3659 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3660 [[,]f[orce]
3661 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3662 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3663 reboot_force is either force or not specified,
3664 reboot_cpu is s[mp]#### with #### being the processor
3665 to be used for rebooting.
3667 relax_domain_level=
3668 [KNL, SMP] Set scheduler's default relax_domain_level.
3669 See Documentation/cgroup-v1/cpusets.txt.
3671 relative_sleep_states=
3672 [SUSPEND] Use sleep state labeling where the deepest
3673 state available other than hibernation is always "mem".
3674 Format: { "0" | "1" }
3675 0 -- Traditional sleep state labels.
3676 1 -- Relative sleep state labels.
3678 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3680 reservetop= [X86-32]
3681 Format: nn[KMG]
3682 Reserves a hole at the top of the kernel virtual
3683 address space.
3685 reservelow= [X86]
3686 Format: nn[K]
3687 Set the amount of memory to reserve for BIOS at
3688 the bottom of the address space.
3690 reset_devices [KNL] Force drivers to reset the underlying device
3691 during initialization.
3693 resume= [SWSUSP]
3694 Specify the partition device for software suspend
3695 Format:
3696 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3698 resume_offset= [SWSUSP]
3699 Specify the offset from the beginning of the partition
3700 given by "resume=" at which the swap header is located,
3701 in <PAGE_SIZE> units (needed only for swap files).
3702 See Documentation/power/swsusp-and-swap-files.txt
3704 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3705 read the resume files
3707 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3708 Useful for devices that are detected asynchronously
3709 (e.g. USB and MMC devices).
3711 hibernate= [HIBERNATION]
3712 noresume Don't check if there's a hibernation image
3713 present during boot.
3714 nocompress Don't compress/decompress hibernation images.
3715 no Disable hibernation and resume.
3716 protect_image Turn on image protection during restoration
3717 (that will set all pages holding image data
3718 during restoration read-only).
3720 retain_initrd [RAM] Keep initrd memory after extraction
3722 rfkill.default_state=
3723 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3724 etc. communication is blocked by default.
3725 1 Unblocked.
3727 rfkill.master_switch_mode=
3728 0 The "airplane mode" button does nothing.
3729 1 The "airplane mode" button toggles between everything
3730 blocked and the previous configuration.
3731 2 The "airplane mode" button toggles between everything
3732 blocked and everything unblocked.
3734 rhash_entries= [KNL,NET]
3735 Set number of hash buckets for route cache
3737 ro [KNL] Mount root device read-only on boot
3739 rodata= [KNL]
3740 on Mark read-only kernel memory as read-only (default).
3741 off Leave read-only kernel memory writable for debugging.
3743 rockchip.usb_uart
3744 Enable the uart passthrough on the designated usb port
3745 on Rockchip SoCs. When active, the signals of the
3746 debug-uart get routed to the D+ and D- pins of the usb
3747 port and the regular usb controller gets disabled.
3749 root= [KNL] Root filesystem
3750 See name_to_dev_t comment in init/do_mounts.c.
3752 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3753 mount the root filesystem
3755 rootflags= [KNL] Set root filesystem mount option string
3757 rootfstype= [KNL] Set root filesystem type
3759 rootwait [KNL] Wait (indefinitely) for root device to show up.
3760 Useful for devices that are detected asynchronously
3761 (e.g. USB and MMC devices).
3763 rproc_mem=nn[KMG][@address]
3764 [KNL,ARM,CMA] Remoteproc physical memory block.
3765 Memory area to be used by remote processor image,
3766 managed by CMA.
3768 rw [KNL] Mount root device read-write on boot
3770 S [KNL] Run init in single mode
3772 s390_iommu= [HW,S390]
3773 Set s390 IOTLB flushing mode
3774 strict
3775 With strict flushing every unmap operation will result in
3776 an IOTLB flush. Default is lazy flushing before reuse,
3777 which is faster.
3779 sa1100ir [NET]
3780 See drivers/net/irda/sa1100_ir.c.
3782 sbni= [NET] Granch SBNI12 leased line adapter
3784 sched_debug [KNL] Enables verbose scheduler debug messages.
3786 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3787 Allowed values are enable and disable. This feature
3788 incurs a small amount of overhead in the scheduler
3789 but is useful for debugging and performance tuning.
3791 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3792 xtime_lock contention on larger systems, and/or RCU lock
3793 contention on all systems with CONFIG_MAXSMP set.
3794 Format: { "0" | "1" }
3795 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3796 1 -- enable.
3797 Note: increases power consumption, thus should only be
3798 enabled if running jitter sensitive (HPC/RT) workloads.
3800 security= [SECURITY] Choose a security module to enable at boot.
3801 If this boot parameter is not specified, only the first
3802 security module asking for security registration will be
3803 loaded. An invalid security module name will be treated
3804 as if no module has been chosen.
3806 selinux= [SELINUX] Disable or enable SELinux at boot time.
3807 Format: { "0" | "1" }
3808 See security/selinux/Kconfig help text.
3809 0 -- disable.
3810 1 -- enable.
3811 Default value is set via kernel config option.
3812 If enabled at boot time, /selinux/disable can be used
3813 later to disable prior to initial policy load.
3815 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3816 Format: { "0" | "1" }
3817 See security/apparmor/Kconfig help text
3818 0 -- disable.
3819 1 -- enable.
3820 Default value is set via kernel config option.
3822 serialnumber [BUGS=X86-32]
3824 shapers= [NET]
3825 Maximal number of shapers.
3827 show_msr= [x86] show boot-time MSR settings
3828 Format: { <integer> }
3829 Show boot-time (BIOS-initialized) MSR settings.
3830 The parameter means the number of CPUs to show,
3831 for example 1 means boot CPU only.
3833 simeth= [IA-64]
3834 simscsi=
3836 slram= [HW,MTD]
3838 slab_nomerge [MM]
3839 Disable merging of slabs with similar size. May be
3840 necessary if there is some reason to distinguish
3841 allocs to different slabs. Debug options disable
3842 merging on their own.
3843 For more information see Documentation/vm/slub.txt.
3845 slab_max_order= [MM, SLAB]
3846 Determines the maximum allowed order for slabs.
3847 A high setting may cause OOMs due to memory
3848 fragmentation. Defaults to 1 for systems with
3849 more than 32MB of RAM, 0 otherwise.
3851 slub_debug[=options[,slabs]] [MM, SLUB]
3852 Enabling slub_debug allows one to determine the
3853 culprit if slab objects become corrupted. Enabling
3854 slub_debug can create guard zones around objects and
3855 may poison objects when not in use. Also tracks the
3856 last alloc / free. For more information see
3857 Documentation/vm/slub.txt.
3859 slub_max_order= [MM, SLUB]
3860 Determines the maximum allowed order for slabs.
3861 A high setting may cause OOMs due to memory
3862 fragmentation. For more information see
3863 Documentation/vm/slub.txt.
3865 slub_min_objects= [MM, SLUB]
3866 The minimum number of objects per slab. SLUB will
3867 increase the slab order up to slub_max_order to
3868 generate a sufficiently large slab able to contain
3869 the number of objects indicated. The higher the number
3870 of objects the smaller the overhead of tracking slabs
3871 and the less frequently locks need to be acquired.
3872 For more information see Documentation/vm/slub.txt.
3874 slub_min_order= [MM, SLUB]
3875 Determines the minimum page order for slabs. Must be
3876 lower than slub_max_order.
3877 For more information see Documentation/vm/slub.txt.
3879 slub_nomerge [MM, SLUB]
3880 Same with slab_nomerge. This is supported for legacy.
3881 See slab_nomerge for more information.
3883 smart2= [HW]
3884 Format: <io1>[,<io2>[,...,<io8>]]
3886 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3887 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3888 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3889 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3890 smsc-ircc2.ircc_irq= [HW] IRQ line
3891 smsc-ircc2.ircc_dma= [HW] DMA channel
3892 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3893 0: Toshiba Satellite 1800 (GP data pin select)
3894 1: Fast pin select (default)
3895 2: ATC IRMode
3897 smt [KNL,S390] Set the maximum number of threads (logical
3898 CPUs) to use per physical CPU on systems capable of
3899 symmetric multithreading (SMT). Will be capped to the
3900 actual hardware limit.
3901 Format: <integer>
3902 Default: -1 (no limit)
3904 softlockup_panic=
3905 [KNL] Should the soft-lockup detector generate panics.
3906 Format: <integer>
3908 softlockup_all_cpu_backtrace=
3909 [KNL] Should the soft-lockup detector generate
3910 backtraces on all cpus.
3911 Format: <integer>
3913 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3914 See Documentation/laptops/sonypi.txt
3916 spia_io_base= [HW,MTD]
3917 spia_fio_base=
3918 spia_pedr=
3919 spia_peddr=
3921 stacktrace [FTRACE]
3922 Enabled the stack tracer on boot up.
3924 stacktrace_filter=[function-list]
3925 [FTRACE] Limit the functions that the stack tracer
3926 will trace at boot up. function-list is a comma separated
3927 list of functions. This list can be changed at run
3928 time by the stack_trace_filter file in the debugfs
3929 tracing directory. Note, this enables stack tracing
3930 and the stacktrace above is not needed.
3932 sti= [PARISC,HW]
3933 Format: <num>
3934 Set the STI (builtin display/keyboard on the HP-PARISC
3935 machines) console (graphic card) which should be used
3936 as the initial boot-console.
3937 See also comment in drivers/video/console/sticore.c.
3939 sti_font= [HW]
3940 See comment in drivers/video/console/sticore.c.
3942 stifb= [HW]
3943 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3945 sunrpc.min_resvport=
3946 sunrpc.max_resvport=
3947 [NFS,SUNRPC]
3948 SunRPC servers often require that client requests
3949 originate from a privileged port (i.e. a port in the
3950 range 0 < portnr < 1024).
3951 An administrator who wishes to reserve some of these
3952 ports for other uses may adjust the range that the
3953 kernel's sunrpc client considers to be privileged
3954 using these two parameters to set the minimum and
3955 maximum port values.
3957 sunrpc.svc_rpc_per_connection_limit=
3958 [NFS,SUNRPC]
3959 Limit the number of requests that the server will
3960 process in parallel from a single connection.
3961 The default value is 0 (no limit).
3963 sunrpc.pool_mode=
3964 [NFS]
3965 Control how the NFS server code allocates CPUs to
3966 service thread pools. Depending on how many NICs
3967 you have and where their interrupts are bound, this
3968 option will affect which CPUs will do NFS serving.
3969 Note: this parameter cannot be changed while the
3970 NFS server is running.
3972 auto the server chooses an appropriate mode
3973 automatically using heuristics
3974 global a single global pool contains all CPUs
3975 percpu one pool for each CPU
3976 pernode one pool for each NUMA node (equivalent
3977 to global on non-NUMA machines)
3979 sunrpc.tcp_slot_table_entries=
3980 sunrpc.udp_slot_table_entries=
3981 [NFS,SUNRPC]
3982 Sets the upper limit on the number of simultaneous
3983 RPC calls that can be sent from the client to a
3984 server. Increasing these values may allow you to
3985 improve throughput, but will also increase the
3986 amount of memory reserved for use by the client.
3988 suspend.pm_test_delay=
3989 [SUSPEND]
3990 Sets the number of seconds to remain in a suspend test
3991 mode before resuming the system (see
3992 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3993 is set. Default value is 5.
3995 swapaccount=[0|1]
3996 [KNL] Enable accounting of swap in memory resource
3997 controller if no parameter or 1 is given or disable
3998 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
4000 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
4001 Format: { <int> | force }
4002 <int> -- Number of I/O TLB slabs
4003 force -- force using of bounce buffers even if they
4004 wouldn't be automatically used by the kernel
4006 switches= [HW,M68k]
4008 sysfs.deprecated=0|1 [KNL]
4009 Enable/disable old style sysfs layout for old udev
4010 on older distributions. When this option is enabled
4011 very new udev will not work anymore. When this option
4012 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4013 in older udev will not work anymore.
4014 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4015 the kernel configuration.
4017 sysrq_always_enabled
4018 [KNL]
4019 Ignore sysrq setting - this boot parameter will
4020 neutralize any effect of /proc/sys/kernel/sysrq.
4021 Useful for debugging.
4023 tcpmhash_entries= [KNL,NET]
4024 Set the number of tcp_metrics_hash slots.
4025 Default value is 8192 or 16384 depending on total
4026 ram pages. This is used to specify the TCP metrics
4027 cache size. See Documentation/networking/ip-sysctl.txt
4028 "tcp_no_metrics_save" section for more details.
4030 tdfx= [HW,DRM]
4032 test_suspend= [SUSPEND][,N]
4033 Specify "mem" (for Suspend-to-RAM) or "standby" (for
4034 standby suspend) or "freeze" (for suspend type freeze)
4035 as the system sleep state during system startup with
4036 the optional capability to repeat N number of times.
4037 The system is woken from this state using a
4038 wakeup-capable RTC alarm.
4040 thash_entries= [KNL,NET]
4041 Set number of hash buckets for TCP connection
4043 thermal.act= [HW,ACPI]
4044 -1: disable all active trip points in all thermal zones
4045 <degrees C>: override all lowest active trip points
4047 thermal.crt= [HW,ACPI]
4048 -1: disable all critical trip points in all thermal zones
4049 <degrees C>: override all critical trip points
4051 thermal.nocrt= [HW,ACPI]
4052 Set to disable actions on ACPI thermal zone
4053 critical and hot trip points.
4055 thermal.off= [HW,ACPI]
4056 1: disable ACPI thermal control
4058 thermal.psv= [HW,ACPI]
4059 -1: disable all passive trip points
4060 <degrees C>: override all passive trip points to this
4061 value
4063 thermal.tzp= [HW,ACPI]
4064 Specify global default ACPI thermal zone polling rate
4065 <deci-seconds>: poll all this frequency
4066 0: no polling (default)
4068 threadirqs [KNL]
4069 Force threading of all interrupt handlers except those
4070 marked explicitly IRQF_NO_THREAD.
4072 tmem [KNL,XEN]
4073 Enable the Transcendent memory driver if built-in.
4075 tmem.cleancache=0|1 [KNL, XEN]
4076 Default is on (1). Disable the usage of the cleancache
4077 API to send anonymous pages to the hypervisor.
4079 tmem.frontswap=0|1 [KNL, XEN]
4080 Default is on (1). Disable the usage of the frontswap
4081 API to send swap pages to the hypervisor. If disabled
4082 the selfballooning and selfshrinking are force disabled.
4084 tmem.selfballooning=0|1 [KNL, XEN]
4085 Default is on (1). Disable the driving of swap pages
4086 to the hypervisor.
4088 tmem.selfshrinking=0|1 [KNL, XEN]
4089 Default is on (1). Partial swapoff that immediately
4090 transfers pages from Xen hypervisor back to the
4091 kernel based on different criteria.
4093 topology= [S390]
4094 Format: {off | on}
4095 Specify if the kernel should make use of the cpu
4096 topology information if the hardware supports this.
4097 The scheduler will make use of this information and
4098 e.g. base its process migration decisions on it.
4099 Default is on.
4101 topology_updates= [KNL, PPC, NUMA]
4102 Format: {off}
4103 Specify if the kernel should ignore (off)
4104 topology updates sent by the hypervisor to this
4105 LPAR.
4107 tp720= [HW,PS2]
4109 tpm_suspend_pcr=[HW,TPM]
4110 Format: integer pcr id
4111 Specify that at suspend time, the tpm driver
4112 should extend the specified pcr with zeros,
4113 as a workaround for some chips which fail to
4114 flush the last written pcr on TPM_SaveState.
4115 This will guarantee that all the other pcrs
4116 are saved.
4118 trace_buf_size=nn[KMG]
4119 [FTRACE] will set tracing buffer size on each cpu.
4121 trace_event=[event-list]
4122 [FTRACE] Set and start specified trace events in order
4123 to facilitate early boot debugging. The event-list is a
4124 comma separated list of trace events to enable. See
4125 also Documentation/trace/events.txt
4127 trace_options=[option-list]
4128 [FTRACE] Enable or disable tracer options at boot.
4129 The option-list is a comma delimited list of options
4130 that can be enabled or disabled just as if you were
4131 to echo the option name into
4133 /sys/kernel/debug/tracing/trace_options
4135 For example, to enable stacktrace option (to dump the
4136 stack trace of each event), add to the command line:
4138 trace_options=stacktrace
4140 See also Documentation/trace/ftrace.txt "trace options"
4141 section.
4143 tp_printk[FTRACE]
4144 Have the tracepoints sent to printk as well as the
4145 tracing ring buffer. This is useful for early boot up
4146 where the system hangs or reboots and does not give the
4147 option for reading the tracing buffer or performing a
4148 ftrace_dump_on_oops.
4150 To turn off having tracepoints sent to printk,
4151 echo 0 > /proc/sys/kernel/tracepoint_printk
4152 Note, echoing 1 into this file without the
4153 tracepoint_printk kernel cmdline option has no effect.
4155 ** CAUTION **
4157 Having tracepoints sent to printk() and activating high
4158 frequency tracepoints such as irq or sched, can cause
4159 the system to live lock.
4161 traceoff_on_warning
4162 [FTRACE] enable this option to disable tracing when a
4163 warning is hit. This turns off "tracing_on". Tracing can
4164 be enabled again by echoing '1' into the "tracing_on"
4165 file located in /sys/kernel/debug/tracing/
4167 This option is useful, as it disables the trace before
4168 the WARNING dump is called, which prevents the trace to
4169 be filled with content caused by the warning output.
4171 This option can also be set at run time via the sysctl
4172 option: kernel/traceoff_on_warning
4174 transparent_hugepage=
4175 [KNL]
4176 Format: [always|madvise|never]
4177 Can be used to control the default behavior of the system
4178 with respect to transparent hugepages.
4179 See Documentation/vm/transhuge.txt for more details.
4181 tsc= Disable clocksource stability checks for TSC.
4182 Format: <string>
4183 [x86] reliable: mark tsc clocksource as reliable, this
4184 disables clocksource verification at runtime, as well
4185 as the stability checks done at bootup. Used to enable
4186 high-resolution timer mode on older hardware, and in
4187 virtualized environment.
4188 [x86] noirqtime: Do not use TSC to do irq accounting.
4189 Used to run time disable IRQ_TIME_ACCOUNTING on any
4190 platforms where RDTSC is slow and this accounting
4191 can add overhead.
4193 turbografx.map[2|3]= [HW,JOY]
4194 TurboGraFX parallel port interface
4195 Format:
4196 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4197 See also Documentation/input/joystick-parport.txt
4199 udbg-immortal [PPC] When debugging early kernel crashes that
4200 happen after console_init() and before a proper
4201 console driver takes over, this boot options might
4202 help "seeing" what's going on.
4204 uhash_entries= [KNL,NET]
4205 Set number of hash buckets for UDP/UDP-Lite connections
4207 uhci-hcd.ignore_oc=
4208 [USB] Ignore overcurrent events (default N).
4209 Some badly-designed motherboards generate lots of
4210 bogus events, for ports that aren't wired to
4211 anything. Set this parameter to avoid log spamming.
4212 Note that genuine overcurrent events won't be
4213 reported either.
4215 unknown_nmi_panic
4216 [X86] Cause panic on unknown NMI.
4218 usbcore.authorized_default=
4219 [USB] Default USB device authorization:
4220 (default -1 = authorized except for wireless USB,
4221 0 = not authorized, 1 = authorized)
4223 usbcore.autosuspend=
4224 [USB] The autosuspend time delay (in seconds) used
4225 for newly-detected USB devices (default 2). This
4226 is the time required before an idle device will be
4227 autosuspended. Devices for which the delay is set
4228 to a negative value won't be autosuspended at all.
4230 usbcore.usbfs_snoop=
4231 [USB] Set to log all usbfs traffic (default 0 = off).
4233 usbcore.usbfs_snoop_max=
4234 [USB] Maximum number of bytes to snoop in each URB
4235 (default = 65536).
4237 usbcore.blinkenlights=
4238 [USB] Set to cycle leds on hubs (default 0 = off).
4240 usbcore.old_scheme_first=
4241 [USB] Start with the old device initialization
4242 scheme (default 0 = off).
4244 usbcore.usbfs_memory_mb=
4245 [USB] Memory limit (in MB) for buffers allocated by
4246 usbfs (default = 16, 0 = max = 2047).
4248 usbcore.use_both_schemes=
4249 [USB] Try the other device initialization scheme
4250 if the first one fails (default 1 = enabled).
4252 usbcore.initial_descriptor_timeout=
4253 [USB] Specifies timeout for the initial 64-byte
4254 USB_REQ_GET_DESCRIPTOR request in milliseconds
4255 (default 5000 = 5.0 seconds).
4257 usbcore.nousb [USB] Disable the USB subsystem
4259 usbhid.mousepoll=
4260 [USBHID] The interval which mice are to be polled at.
4262 usb-storage.delay_use=
4263 [UMS] The delay in seconds before a new device is
4264 scanned for Logical Units (default 1).
4266 usb-storage.quirks=
4267 [UMS] A list of quirks entries to supplement or
4268 override the built-in unusual_devs list. List
4269 entries are separated by commas. Each entry has
4270 the form VID:PID:Flags where VID and PID are Vendor
4271 and Product ID values (4-digit hex numbers) and
4272 Flags is a set of characters, each corresponding
4273 to a common usb-storage quirk flag as follows:
4274 a = SANE_SENSE (collect more than 18 bytes
4275 of sense data);
4276 b = BAD_SENSE (don't collect more than 18
4277 bytes of sense data);
4278 c = FIX_CAPACITY (decrease the reported
4279 device capacity by one sector);
4280 d = NO_READ_DISC_INFO (don't use
4281 READ_DISC_INFO command);
4282 e = NO_READ_CAPACITY_16 (don't use
4283 READ_CAPACITY_16 command);
4284 f = NO_REPORT_OPCODES (don't use report opcodes
4285 command, uas only);
4286 g = MAX_SECTORS_240 (don't transfer more than
4287 240 sectors at a time, uas only);
4288 h = CAPACITY_HEURISTICS (decrease the
4289 reported device capacity by one
4290 sector if the number is odd);
4291 i = IGNORE_DEVICE (don't bind to this
4292 device);
4293 j = NO_REPORT_LUNS (don't use report luns
4294 command, uas only);
4295 l = NOT_LOCKABLE (don't try to lock and
4296 unlock ejectable media);
4297 m = MAX_SECTORS_64 (don't transfer more
4298 than 64 sectors = 32 KB at a time);
4299 n = INITIAL_READ10 (force a retry of the
4300 initial READ(10) command);
4301 o = CAPACITY_OK (accept the capacity
4302 reported by the device);
4303 p = WRITE_CACHE (the device cache is ON
4304 by default);
4305 r = IGNORE_RESIDUE (the device reports
4306 bogus residue values);
4307 s = SINGLE_LUN (the device has only one
4308 Logical Unit);
4309 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4310 commands, uas only);
4311 u = IGNORE_UAS (don't bind to the uas driver);
4312 w = NO_WP_DETECT (don't test whether the
4313 medium is write-protected).
4314 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4315 even if the device claims no cache)
4316 Example: quirks=0419:aaf5:rl,0421:0433:rc
4318 user_debug= [KNL,ARM]
4319 Format: <int>
4320 See arch/arm/Kconfig.debug help text.
4321 1 - undefined instruction events
4322 2 - system calls
4323 4 - invalid data aborts
4324 8 - SIGSEGV faults
4325 16 - SIGBUS faults
4326 Example: user_debug=31
4328 userpte=
4329 [X86] Flags controlling user PTE allocations.
4331 nohigh = do not allocate PTE pages in
4332 HIGHMEM regardless of setting
4333 of CONFIG_HIGHPTE.
4335 vdso= [X86,SH]
4336 On X86_32, this is an alias for vdso32=. Otherwise:
4338 vdso=1: enable VDSO (the default)
4339 vdso=0: disable VDSO mapping
4341 vdso32= [X86] Control the 32-bit vDSO
4342 vdso32=1: enable 32-bit VDSO
4343 vdso32=0 or vdso32=2: disable 32-bit VDSO
4345 See the help text for CONFIG_COMPAT_VDSO for more
4346 details. If CONFIG_COMPAT_VDSO is set, the default is
4347 vdso32=0; otherwise, the default is vdso32=1.
4349 For compatibility with older kernels, vdso32=2 is an
4350 alias for vdso32=0.
4352 Try vdso32=0 if you encounter an error that says:
4353 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4355 vector= [IA-64,SMP]
4356 vector=percpu: enable percpu vector domain
4358 video= [FB] Frame buffer configuration
4359 See Documentation/fb/modedb.txt.
4361 video.brightness_switch_enabled= [0,1]
4362 If set to 1, on receiving an ACPI notify event
4363 generated by hotkey, video driver will adjust brightness
4364 level and then send out the event to user space through
4365 the allocated input device; If set to 0, video driver
4366 will only send out the event without touching backlight
4367 brightness level.
4368 default: 1
4370 virtio_mmio.device=
4371 [VMMIO] Memory mapped virtio (platform) device.
4373 <size>@<baseaddr>:<irq>[:<id>]
4374 where:
4375 <size> := size (can use standard suffixes
4376 like K, M and G)
4377 <baseaddr> := physical base address
4378 <irq> := interrupt number (as passed to
4379 request_irq())
4380 <id> := (optional) platform device id
4381 example:
4382 virtio_mmio.device=1K@0x100b0000:48:7
4384 Can be used multiple times for multiple devices.
4386 vga= [BOOT,X86-32] Select a particular video mode
4387 See Documentation/x86/boot.txt and
4388 Documentation/svga.txt.
4389 Use vga=ask for menu.
4390 This is actually a boot loader parameter; the value is
4391 passed to the kernel using a special protocol.
4393 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4394 size of <nn>. This can be used to increase the
4395 minimum size (128MB on x86). It can also be used to
4396 decrease the size and leave more room for directly
4397 mapped kernel RAM.
4399 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4400 Format: <command>
4402 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4403 Format: <command>
4405 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4406 Format: <command>
4408 vsyscall= [X86-64]
4409 Controls the behavior of vsyscalls (i.e. calls to
4410 fixed addresses of 0xffffffffff600x00 from legacy
4411 code). Most statically-linked binaries and older
4412 versions of glibc use these calls. Because these
4413 functions are at fixed addresses, they make nice
4414 targets for exploits that can control RIP.
4416 emulate [default] Vsyscalls turn into traps and are
4417 emulated reasonably safely.
4419 native Vsyscalls are native syscall instructions.
4420 This is a little bit faster than trapping
4421 and makes a few dynamic recompilers work
4422 better than they would in emulation mode.
4423 It also makes exploits much easier to write.
4425 none Vsyscalls don't work at all. This makes
4426 them quite hard to use for exploits but
4427 might break your system.
4429 vt.color= [VT] Default text color.
4430 Format: 0xYX, X = foreground, Y = background.
4431 Default: 0x07 = light gray on black.
4433 vt.cur_default= [VT] Default cursor shape.
4434 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4435 the parameters of the <Esc>[?A;B;Cc escape sequence;
4436 see VGA-softcursor.txt. Default: 2 = underline.
4438 vt.default_blu= [VT]
4439 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4440 Change the default blue palette of the console.
4441 This is a 16-member array composed of values
4442 ranging from 0-255.
4444 vt.default_grn= [VT]
4445 Format: <green0>,<green1>,<green2>,...,<green15>
4446 Change the default green palette of the console.
4447 This is a 16-member array composed of values
4448 ranging from 0-255.
4450 vt.default_red= [VT]
4451 Format: <red0>,<red1>,<red2>,...,<red15>
4452 Change the default red palette of the console.
4453 This is a 16-member array composed of values
4454 ranging from 0-255.
4456 vt.default_utf8=
4457 [VT]
4458 Format=<0|1>
4459 Set system-wide default UTF-8 mode for all tty's.
4460 Default is 1, i.e. UTF-8 mode is enabled for all
4461 newly opened terminals.
4463 vt.global_cursor_default=
4464 [VT]
4465 Format=<-1|0|1>
4466 Set system-wide default for whether a cursor
4467 is shown on new VTs. Default is -1,
4468 i.e. cursors will be created by default unless
4469 overridden by individual drivers. 0 will hide
4470 cursors, 1 will display them.
4472 vt.italic= [VT] Default color for italic text; 0-15.
4473 Default: 2 = green.
4475 vt.underline= [VT] Default color for underlined text; 0-15.
4476 Default: 3 = cyan.
4478 watchdog timers [HW,WDT] For information on watchdog timers,
4479 see Documentation/watchdog/watchdog-parameters.txt
4480 or other driver-specific files in the
4481 Documentation/watchdog/ directory.
4483 workqueue.watchdog_thresh=
4484 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4485 warn stall conditions and dump internal state to
4486 help debugging. 0 disables workqueue stall
4487 detection; otherwise, it's the stall threshold
4488 duration in seconds. The default value is 30 and
4489 it can be updated at runtime by writing to the
4490 corresponding sysfs file.
4492 workqueue.disable_numa
4493 By default, all work items queued to unbound
4494 workqueues are affine to the NUMA nodes they're
4495 issued on, which results in better behavior in
4496 general. If NUMA affinity needs to be disabled for
4497 whatever reason, this option can be used. Note
4498 that this also can be controlled per-workqueue for
4499 workqueues visible under /sys/bus/workqueue/.
4501 workqueue.power_efficient
4502 Per-cpu workqueues are generally preferred because
4503 they show better performance thanks to cache
4504 locality; unfortunately, per-cpu workqueues tend to
4505 be more power hungry than unbound workqueues.
4507 Enabling this makes the per-cpu workqueues which
4508 were observed to contribute significantly to power
4509 consumption unbound, leading to measurably lower
4510 power usage at the cost of small performance
4511 overhead.
4513 The default value of this parameter is determined by
4514 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4516 workqueue.debug_force_rr_cpu
4517 Workqueue used to implicitly guarantee that work
4518 items queued without explicit CPU specified are put
4519 on the local CPU. This guarantee is no longer true
4520 and while local CPU is still preferred work items
4521 may be put on foreign CPUs. This debug option
4522 forces round-robin CPU selection to flush out
4523 usages which depend on the now broken guarantee.
4524 When enabled, memory and cache locality will be
4525 impacted.
4527 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4528 default x2apic cluster mode on platforms
4529 supporting x2apic.
4531 x86_intel_mid_timer= [X86-32,APBT]
4532 Choose timer option for x86 Intel MID platform.
4533 Two valid options are apbt timer only and lapic timer
4534 plus one apbt timer for broadcast timer.
4535 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4537 xen_512gb_limit [KNL,X86-64,XEN]
4538 Restricts the kernel running paravirtualized under Xen
4539 to use only up to 512 GB of RAM. The reason to do so is
4540 crash analysis tools and Xen tools for doing domain
4541 save/restore/migration must be enabled to handle larger
4542 domains.
4544 xen_emul_unplug= [HW,X86,XEN]
4545 Unplug Xen emulated devices
4546 Format: [unplug0,][unplug1]
4547 ide-disks -- unplug primary master IDE devices
4548 aux-ide-disks -- unplug non-primary-master IDE devices
4549 nics -- unplug network devices
4550 all -- unplug all emulated devices (NICs and IDE disks)
4551 unnecessary -- unplugging emulated devices is
4552 unnecessary even if the host did not respond to
4553 the unplug protocol
4554 never -- do not unplug even if version check succeeds
4556 xen_nopvspin [X86,XEN]
4557 Disables the ticketlock slowpath using Xen PV
4558 optimizations.
4560 xen_nopv [X86]
4561 Disables the PV optimizations forcing the HVM guest to
4562 run as generic HVM guest with no PV drivers.
4564 xirc2ps_cs= [NET,PCMCIA]
4565 Format:
4566 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4568 ______________________________________________________________________
4570 TODO:
4572 Add more DRM drivers.