4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpica_no_return_repair [HW, ACPI]
235 Disable AML predefined validation mechanism
236 This mechanism can repair the evaluation result to make
237 the return objects more ACPI specification compliant.
238 This option is useful for developers to identify the
239 root cause of an AML interpreter issue when the issue
240 has something to do with the repair mechanism.
242 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
243 Format: To spoof as Windows 98: ="Microsoft Windows"
245 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
246 acpi_osi="string1" # add string1
247 acpi_osi="!string2" # remove string2
248 acpi_osi=!* # remove all strings
249 acpi_osi=! # disable all built-in OS vendor
251 acpi_osi= # disable all strings
253 'acpi_osi=!' can be used in combination with single or
254 multiple 'acpi_osi="string1"' to support specific OS
255 vendor string(s). Note that such command can only
256 affect the default state of the OS vendor strings, thus
257 it cannot affect the default state of the feature group
258 strings and the current state of the OS vendor strings,
259 specifying it multiple times through kernel command line
260 is meaningless. This command is useful when one do not
261 care about the state of the feature group strings which
262 should be controlled by the OSPM.
264 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
265 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
266 can make '_OSI("Windows 2000")' TRUE.
268 'acpi_osi=' cannot be used in combination with other
269 'acpi_osi=' command lines, the _OSI method will not
270 exist in the ACPI namespace. NOTE that such command can
271 only affect the _OSI support state, thus specifying it
272 multiple times through kernel command line is also
275 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
278 'acpi_osi=!*' can be used in combination with single or
279 multiple 'acpi_osi="string1"' to support specific
280 string(s). Note that such command can affect the
281 current state of both the OS vendor strings and the
282 feature group strings, thus specifying it multiple times
283 through kernel command line is meaningful. But it may
284 still not able to affect the final state of a string if
285 there are quirks related to this string. This command
286 is useful when one want to control the state of the
287 feature group strings to debug BIOS issues related to
290 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
291 '_OSI("Module Device")' FALSE.
292 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
293 '_OSI("Module Device")' TRUE.
294 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
296 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
298 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
299 they all will make '_OSI("Windows 2000")' TRUE.
302 Override the pmtimer bug detection: force the kernel
303 to assume that this machine's pmtimer latches its value
304 and always returns good values.
306 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
307 Format: { level | edge | high | low }
309 acpi_serialize [HW,ACPI] force serialization of AML methods
311 acpi_skip_timer_override [HW,ACPI]
312 Recognize and ignore IRQ0/pin2 Interrupt Override.
313 For broken nForce2 BIOS resulting in XT-PIC timer.
315 acpi_sleep= [HW,ACPI] Sleep options
316 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
317 old_ordering, nonvs, sci_force_enable }
318 See Documentation/power/video.txt for information on
320 s3_beep is for debugging; it makes the PC's speaker beep
321 as soon as the kernel's real-mode entry point is called.
322 s4_nohwsig prevents ACPI hardware signature from being
323 used during resume from hibernation.
324 old_ordering causes the ACPI 1.0 ordering of the _PTS
325 control method, with respect to putting devices into
326 low power states, to be enforced (the ACPI 2.0 ordering
327 of _PTS is used by default).
328 nonvs prevents the kernel from saving/restoring the
329 ACPI NVS memory during suspend/hibernation and resume.
330 sci_force_enable causes the kernel to set SCI_EN directly
331 on resume from S1/S3 (which is against the ACPI spec,
332 but some broken systems don't work without it).
334 acpi_use_timer_override [HW,ACPI]
335 Use timer override. For some broken Nvidia NF5 boards
336 that require a timer override, but don't have HPET
338 acpi_enforce_resources= [ACPI]
339 { strict | lax | no }
340 Check for resource conflicts between native drivers
341 and ACPI OperationRegions (SystemIO and SystemMemory
342 only). IO ports and memory declared in ACPI might be
343 used by the ACPI subsystem in arbitrary AML code and
344 can interfere with legacy drivers.
345 strict (default): access to resources claimed by ACPI
346 is denied; legacy drivers trying to access reserved
347 resources will fail to bind to device using them.
348 lax: access to resources claimed by ACPI is allowed;
349 legacy drivers trying to access reserved resources
350 will bind successfully but a warning message is logged.
351 no: ACPI OperationRegions are not marked as reserved,
352 no further checks are performed.
354 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
357 add_efi_memmap [EFI; X86] Include EFI memory map in
358 kernel's map of available physical RAM.
361 { off | try_unsupported }
362 off: disable AGP support
363 try_unsupported: try to drive unsupported chipsets
364 (may crash computer or cause data corruption)
367 See Documentation/sound/alsa/alsa-parameters.txt
370 Allow the default userspace alignment fault handler
371 behaviour to be specified. Bit 0 enables warnings,
372 bit 1 enables fixups, and bit 2 sends a segfault.
374 align_va_addr= [X86-64]
375 Align virtual addresses by clearing slice [14:12] when
376 allocating a VMA at process creation time. This option
377 gives you up to 3% performance improvement on AMD F15h
378 machines (where it is enabled by default) for a
379 CPU-intensive style benchmark, and it can vary highly in
380 a microbenchmark depending on workload and compiler.
382 32: only for 32-bit processes
383 64: only for 64-bit processes
384 on: enable for both 32- and 64-bit processes
385 off: disable for both 32- and 64-bit processes
387 alloc_snapshot [FTRACE]
388 Allocate the ftrace snapshot buffer on boot up when the
389 main buffer is allocated. This is handy if debugging
390 and you need to use tracing_snapshot() on boot up, and
391 do not want to use tracing_snapshot_alloc() as it needs
392 to be done where GFP_KERNEL allocations are allowed.
394 amd_iommu= [HW,X86-64]
395 Pass parameters to the AMD IOMMU driver in the system.
397 fullflush - enable flushing of IO/TLB entries when
398 they are unmapped. Otherwise they are
399 flushed before they will be reused, which
401 off - do not initialize any AMD IOMMU found in
403 force_isolation - Force device isolation for all
404 devices. The IOMMU driver is not
405 allowed anymore to lift isolation
406 requirements as needed. This option
407 does not override iommu=pt
409 amd_iommu_dump= [HW,X86-64]
410 Enable AMD IOMMU driver option to dump the ACPI table
411 for AMD IOMMU. With this option enabled, AMD IOMMU
412 driver will print ACPI tables for AMD IOMMU during
413 IOMMU initialization.
415 amijoy.map= [HW,JOY] Amiga joystick support
416 Map of devices attached to JOY0DAT and JOY1DAT
418 See also Documentation/input/joystick.txt
420 analog.map= [HW,JOY] Analog joystick and gamepad support
421 Specifies type or capabilities of an analog joystick
422 connected to one of 16 gameports
423 Format: <type1>,<type2>,..<type16>
426 Power management functions (SPARCstation-4/5 + deriv.)
428 Disable APC CPU standby support. SPARCstation-Fox does
429 not play well with APC CPU idle - disable it if you have
430 APC and your system crashes randomly.
432 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
433 Change the output verbosity whilst booting
434 Format: { quiet (default) | verbose | debug }
435 Change the amount of debugging information output
436 when initialising the APIC and IO-APIC components.
439 See Documentation/networking/ipv6.txt.
441 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
442 Limit apic dumping. The parameter defines the maximal
443 number of local apics being dumped. Also it is possible
444 to set it to "all" by meaning -- no limit here.
445 Format: { 1 (default) | 2 | ... | all }.
446 The parameter valid if only apic=debug or
447 apic=verbose is specified.
448 Example: apic=debug show_lapic=all
450 apm= [APM] Advanced Power Management
451 See header of arch/x86/kernel/apm_32.c.
453 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
454 Format: <io>,<irq>,<nodeID>
458 atarimouse= [HW,MOUSE] Atari Mouse
460 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
461 EzKey and similar keyboards
463 atkbd.reset= [HW] Reset keyboard during initialization
465 atkbd.set= [HW] Select keyboard code set
466 Format: <int> (2 = AT (default), 3 = PS/2)
468 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
471 atkbd.softraw= [HW] Choose between synthetic and real raw mode
472 Format: <bool> (0 = real, 1 = synthetic (default))
474 atkbd.softrepeat= [HW]
475 Use software keyboard repeat
477 audit= [KNL] Enable the audit sub-system
478 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
479 0 - kernel audit is disabled and can not be enabled
480 until the next reboot
481 unset - kernel audit is initialized but disabled and
482 will be fully enabled by the userspace auditd.
483 1 - kernel audit is initialized and partially enabled,
484 storing at most audit_backlog_limit messages in
485 RAM until it is fully enabled by the userspace
489 audit_backlog_limit= [KNL] Set the audit queue size limit.
490 Format: <int> (must be >=0)
493 baycom_epp= [HW,AX25]
496 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
498 See header of drivers/net/hamradio/baycom_par.c.
500 baycom_ser_fdx= [HW,AX25]
501 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
502 Format: <io>,<irq>,<mode>[,<baud>]
503 See header of drivers/net/hamradio/baycom_ser_fdx.c.
505 baycom_ser_hdx= [HW,AX25]
506 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
507 Format: <io>,<irq>,<mode>
508 See header of drivers/net/hamradio/baycom_ser_hdx.c.
510 blkdevparts= Manual partition parsing of block device(s) for
511 embedded devices based on command line input.
512 See Documentation/block/cmdline-partition.txt
514 boot_delay= Milliseconds to delay each printk during boot.
515 Values larger than 10 seconds (10000) are changed to
519 bootmem_debug [KNL] Enable bootmem allocator debug messages.
521 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
522 bttv.radio= Most important insmod options are available as
524 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
527 bulk_remove=off [PPC] This parameter disables the use of the pSeries
528 firmware feature for flushing multiple hpte entries
531 c101= [NET] Moxa C101 synchronous serial card
533 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
534 Sometimes CPU hardware bugs make them report the cache
535 size incorrectly. The kernel will attempt work arounds
536 to fix known problems, but for some CPUs it is not
537 possible to determine what the correct size should be.
538 This option provides an override for these situations.
540 ccw_timeout_log [S390]
541 See Documentation/s390/CommonIO for details.
543 cgroup_disable= [KNL] Disable a particular controller
544 Format: {name of the controller(s) to disable}
545 The effects of cgroup_disable=foo are:
546 - foo isn't auto-mounted if you mount all cgroups in
548 - foo isn't visible as an individually mountable
550 {Currently only "memory" controller deal with this and
551 cut the overhead, others just disable the usage. So
552 only cgroup_disable=memory is actually worthy}
554 checkreqprot [SELINUX] Set initial checkreqprot flag value.
555 Format: { "0" | "1" }
556 See security/selinux/Kconfig help text.
557 0 -- check protection applied by kernel (includes
558 any implied execute protection).
559 1 -- check protection requested by application.
560 Default value is set via a kernel config option.
561 Value can be changed at runtime via
562 /selinux/checkreqprot.
565 See Documentation/s390/CommonIO for details.
568 Keep all clocks already enabled by bootloader on,
569 even if no driver has claimed them. This is useful
570 for debug and development, but should not be
571 needed on a platform with proper driver support.
572 For more information, see Documentation/clk.txt.
574 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
576 Forces specified clocksource (if available) to be used
577 when calculating gettimeofday(). If specified
578 clocksource is not available, it defaults to PIT.
579 Format: { pit | tsc | cyclone | pmtmr }
581 clocksource= Override the default clocksource
583 Override the default clocksource and use the clocksource
584 with the name specified.
585 Some clocksource names to choose from, depending on
587 [all] jiffies (this is the base, fallback clocksource)
589 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
590 pxa_timer,timer3,32k_counter,timer0_1
592 [X86-32] pit,hpet,tsc;
593 scx200_hrt on Geode; cyclone on IBM x440
601 clearcpuid=BITNUM [X86]
602 Disable CPUID feature X for the kernel. See
603 arch/x86/include/asm/cpufeature.h for the valid bit
604 numbers. Note the Linux specific bits are not necessarily
605 stable over kernel options, but the vendor specific
607 Also note that user programs calling CPUID directly
608 or using the feature without checking anything
609 will still see it. This just prevents it from
610 being used by the kernel or shown in /proc/cpuinfo.
611 Also note the kernel might malfunction if you disable
615 Sets the size of kernel global memory area for contiguous
616 memory allocations. For more information, see
617 include/linux/dma-contiguous.h
619 cmo_free_hint= [PPC] Format: { yes | no }
620 Specify whether pages are marked as being inactive
621 when they are freed. This is used in CMO environments
622 to determine OS memory pressure for page stealing by
626 coherent_pool=nn[KMG] [ARM,KNL]
627 Sets the size of memory pool for coherent, atomic dma
628 allocations, by default set to 256K.
630 code_bytes [X86] How many bytes of object code to print
635 com20020= [HW,NET] ARCnet - COM20020 chipset
637 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
639 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
643 ARCnet - COM90xx chipset (memory-mapped buffers)
644 Format: <io>[,<irq>[,<memstart>]]
646 condev= [HW,S390] console device
649 console= [KNL] Output console device and options.
651 tty<n> Use the virtual console device <n>.
655 Use the specified serial port. The options are of
656 the form "bbbbpnf", where "bbbb" is the baud rate,
657 "p" is parity ("n", "o", or "e"), "n" is number of
658 bits, and "f" is flow control ("r" for RTS or
659 omit it). Default is "9600n8".
661 See Documentation/serial-console.txt for more
663 Documentation/networking/netconsole.txt for an
666 uart[8250],io,<addr>[,options]
667 uart[8250],mmio,<addr>[,options]
668 Start an early, polled-mode console on the 8250/16550
669 UART at the specified I/O port or MMIO address,
670 switching to the matching ttyS device later. The
671 options are the same as for ttyS, above.
672 hvc<n> Use the hypervisor console device <n>. This is for
673 both Xen and PowerPC hypervisors.
675 If the device connected to the port is not a TTY but a braille
676 device, prepend "brl," before the device type, for instance
678 For now, only VisioBraille is supported.
680 consoleblank= [KNL] The console blank (screen saver) timeout in
681 seconds. Defaults to 10*60 = 10mins. A value of 0
682 disables the blank timer.
685 [KNL] Change the default value for
686 /proc/<pid>/coredump_filter.
687 See also Documentation/filesystems/proc.txt.
689 cpuidle.off=1 [CPU_IDLE]
690 disable the cpuidle sub-system
692 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
694 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
696 crashkernel=size[KMG][@offset[KMG]]
697 [KNL] Using kexec, Linux can switch to a 'crash kernel'
698 upon panic. This parameter reserves the physical
699 memory region [offset, offset + size] for that kernel
700 image. If '@offset' is omitted, then a suitable offset
701 is selected automatically. Check
702 Documentation/kdump/kdump.txt for further details.
704 crashkernel=range1:size1[,range2:size2,...][@offset]
705 [KNL] Same as above, but depends on the memory
706 in the running system. The syntax of range is
707 start-[end] where start and end are both
708 a memory unit (amount[KMG]). See also
709 Documentation/kdump/kdump.txt for an example.
711 crashkernel=size[KMG],high
712 [KNL, x86_64] range could be above 4G. Allow kernel
713 to allocate physical memory region from top, so could
714 be above 4G if system have more than 4G ram installed.
715 Otherwise memory region will be allocated below 4G, if
717 It will be ignored if crashkernel=X is specified.
718 crashkernel=size[KMG],low
719 [KNL, x86_64] range under 4G. When crashkernel=X,high
720 is passed, kernel could allocate physical memory region
721 above 4G, that cause second kernel crash on system
722 that require some amount of low memory, e.g. swiotlb
723 requires at least 64M+32K low memory. Kernel would
724 try to allocate 72M below 4G automatically.
725 This one let user to specify own low range under 4G
726 for second kernel instead.
727 0: to disable low allocation.
728 It will be ignored when crashkernel=X,high is not used
729 or memory reserved is below 4G.
734 cs89x0_media= [HW,NET]
735 Format: { rj45 | aui | bnc }
738 See header of drivers/s390/block/dasd_devmap.c.
740 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
741 (one device per port)
742 Format: <port#>,<type>
743 See also Documentation/input/joystick-parport.txt
745 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
746 time. See Documentation/dynamic-debug-howto.txt for
747 details. Deprecated, see dyndbg.
749 debug [KNL] Enable kernel debugging (events log level).
752 [KNL] verbose self-tests
754 Print debugging info while doing the locking API
756 We default to 0 (no extra messages), setting it to
757 1 will print _a lot_ more information - normally
758 only useful to kernel developers.
760 debug_objects [KNL] Enable object debugging
763 [KNL] Disable object debugging
765 debug_guardpage_minorder=
766 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
767 parameter allows control of the order of pages that will
768 be intentionally kept free (and hence protected) by the
769 buddy allocator. Bigger value increase the probability
770 of catching random memory corruption, but reduce the
771 amount of memory for normal system use. The maximum
772 possible value is MAX_ORDER/2. Setting this parameter
773 to 1 or 2 should be enough to identify most random
774 memory corruption problems caused by bugs in kernel or
775 driver code when a CPU writes to (or reads from) a
776 random memory location. Note that there exists a class
777 of memory corruptions problems caused by buggy H/W or
778 F/W or by drivers badly programing DMA (basically when
779 memory is written at bus level and the CPU MMU is
780 bypassed) which are not detectable by
781 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
782 tracking down these problems.
784 debugpat [X86] Enable PAT debugging
786 decnet.addr= [HW,NET]
787 Format: <area>[,<node>]
788 See also Documentation/networking/decnet.txt.
791 [same as hugepagesz=] The size of the default
792 HugeTLB page size. This is the size represented by
793 the legacy /proc/ hugepages APIs, used for SHM, and
794 default size when mounting hugetlbfs filesystems.
795 Defaults to the default architecture's huge page size
799 Set number of hash buckets for dentry cache.
802 IO parameters + enable/disable command.
804 digiepca= [HW,SERIAL]
805 See drivers/char/README.epca and
806 Documentation/serial/digiepca.txt.
809 See Documentation/networking/ipv6.txt.
811 disable_cpu_apicid= [X86,APIC,SMP]
813 The number of initial APIC ID for the
814 corresponding CPU to be disabled at boot,
815 mostly used for the kdump 2nd kernel to
816 disable BSP to wake up multiple CPUs without
817 causing system reset or hang due to sending
820 disable_ddw [PPC/PSERIES]
821 Disable Dynamic DMA Window support. Use this if
822 to workaround buggy firmware.
825 See Documentation/networking/ipv6.txt.
827 disable_mtrr_cleanup [X86]
828 The kernel tries to adjust MTRR layout from continuous
829 to discrete, to make X server driver able to add WB
830 entry later. This parameter disables that.
832 disable_mtrr_trim [X86, Intel and AMD only]
833 By default the kernel will trim any uncacheable
834 memory out of your available memory pool based on
835 MTRR settings. This parameter disables that behavior,
836 possibly causing your machine to run very slowly.
838 disable_timer_pin_1 [X86]
839 Disable PIN 1 of APIC timer
840 Can be useful to work around chipset bugs.
842 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
843 this option disables the debugging code at boot.
845 dma_debug_entries=<number>
846 This option allows to tune the number of preallocated
847 entries for DMA-API debugging code. One entry is
848 required per DMA-API allocation. Use this if the
849 DMA-API debugging code disables itself because the
850 architectural default is too low.
852 dma_debug_driver=<driver_name>
853 With this option the DMA-API debugging driver
854 filter feature can be enabled at boot time. Just
855 pass the driver to filter for as the parameter.
856 The filter can be disabled or changed to another
857 driver later using sysfs.
859 drm_kms_helper.edid_firmware=[<connector>:]<file>
860 Broken monitors, graphic adapters and KVMs may
861 send no or incorrect EDID data sets. This parameter
862 allows to specify an EDID data set in the
863 /lib/firmware directory that is used instead.
864 Generic built-in EDID data sets are used, if one of
865 edid/1024x768.bin, edid/1280x1024.bin,
866 edid/1680x1050.bin, or edid/1920x1080.bin is given
867 and no file with the same name exists. Details and
868 instructions how to build your own EDID data are
869 available in Documentation/EDID/HOWTO.txt. An EDID
870 data set will only be used for a particular connector,
871 if its name and a colon are prepended to the EDID
876 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
877 module.dyndbg[="val"]
878 Enable debug messages at boot time. See
879 Documentation/dynamic-debug-howto.txt for details.
881 earlycon= [KNL] Output early console device and options.
882 uart[8250],io,<addr>[,options]
883 uart[8250],mmio,<addr>[,options]
884 uart[8250],mmio32,<addr>[,options]
885 Start an early, polled-mode console on the 8250/16550
886 UART at the specified I/O port or MMIO address.
887 MMIO inter-register address stride is either 8-bit
888 (mmio) or 32-bit (mmio32).
889 The options are the same as for ttyS, above.
891 earlyprintk= [X86,SH,BLACKFIN,ARM]
895 earlyprintk=serial[,ttySn[,baudrate]]
896 earlyprintk=serial[,0x...[,baudrate]]
897 earlyprintk=ttySn[,baudrate]
898 earlyprintk=dbgp[debugController#]
900 earlyprintk is useful when the kernel crashes before
901 the normal console is initialized. It is not enabled by
902 default because it has some cosmetic problems.
904 Append ",keep" to not disable it when the real console
907 Only one of vga, efi, serial, or usb debug port can
910 Currently only ttyS0 and ttyS1 may be specified by
911 name. Other I/O ports may be explicitly specified
912 on some architectures (x86 and arm at least) by
913 replacing ttySn with an I/O port address, like this:
914 earlyprintk=serial,0x1008,115200
915 You can find the port for a given device in
916 /proc/tty/driver/serial:
917 2: uart:ST16650V2 port:00001008 irq:18 ...
919 Interaction with the standard serial driver is not
922 The VGA and EFI output is eventually overwritten by
925 The xen output can only be used by Xen PV guests.
927 edac_report= [HW,EDAC] Control how to report EDAC event
928 Format: {"on" | "off" | "force"}
929 on: enable EDAC to report H/W event. May be overridden
930 by other higher priority error reporting module.
931 off: disable H/W event reporting through EDAC.
932 force: enforce the use of EDAC to report H/W event.
935 ekgdboc= [X86,KGDB] Allow early kernel console debugging
938 This is designed to be used in conjunction with
939 the boot argument: earlyprintk=vga
942 Format: {"off" | "on" | "skip[mbr]"}
945 Format: { "old_map" }
946 old_map [X86-64]: switch to the old ioremap-based EFI
947 runtime services mapping. 32-bit still uses this one by
950 efi_no_storage_paranoia [EFI; X86]
951 Using this parameter you can use more than 50% of
952 your efi variable storage. Use this parameter only if
953 you are really sure that your UEFI does sane gc and
954 fulfills the spec otherwise your board may brick.
956 eisa_irq_edge= [PARISC,HW]
957 See header of drivers/parisc/eisa.c.
960 See comment before function elanfreq_setup() in
961 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
964 Format: {"cfq" | "deadline" | "noop"}
965 See Documentation/block/cfq-iosched.txt and
966 Documentation/block/deadline-iosched.txt for details.
968 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
969 Specifies physical address of start of kernel core
970 image elf header and optionally the size. Generally
971 kexec loader will pass this option to capture kernel.
972 See Documentation/kdump/kdump.txt for details.
974 enable_mtrr_cleanup [X86]
975 The kernel tries to adjust MTRR layout from continuous
976 to discrete, to make X server driver able to add WB
977 entry later. This parameter enables that.
979 enable_timer_pin_1 [X86]
980 Enable PIN 1 of APIC timer
981 Can be useful to work around chipset bugs
982 (in particular on some ATI chipsets).
983 The kernel tries to set a reasonable default.
985 enforcing [SELINUX] Set initial enforcing status.
987 See security/selinux/Kconfig help text.
988 0 -- permissive (log only, no denials).
989 1 -- enforcing (deny and log).
991 Value can be changed at runtime via /selinux/enforce.
994 Disable Error Record Serialization Table (ERST)
997 ether= [HW,NET] Ethernet cards parameters
998 This option is obsoleted by the "netdev=" option, which
999 has equivalent usage. See its documentation for details.
1003 Permit 'security.evm' to be updated regardless of
1004 current integrity status.
1008 fail_make_request=[KNL]
1009 General fault injection mechanism.
1010 Format: <interval>,<probability>,<space>,<times>
1011 See also Documentation/fault-injection/.
1014 See Documentation/blockdev/floppy.txt.
1016 force_pal_cache_flush
1017 [IA-64] Avoid check_sal_cache_flush which may hang on
1018 buggy SAL_CACHE_FLUSH implementations. Using this
1019 parameter will force ia64_sal_cache_flush to call
1020 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1023 [FTRACE] will set and start the specified tracer
1024 as early as possible in order to facilitate early
1027 ftrace_dump_on_oops[=orig_cpu]
1028 [FTRACE] will dump the trace buffers on oops.
1029 If no parameter is passed, ftrace will dump
1030 buffers of all CPUs, but if you pass orig_cpu, it will
1031 dump only the buffer of the CPU that triggered the
1034 ftrace_filter=[function-list]
1035 [FTRACE] Limit the functions traced by the function
1036 tracer at boot up. function-list is a comma separated
1037 list of functions. This list can be changed at run
1038 time by the set_ftrace_filter file in the debugfs
1041 ftrace_notrace=[function-list]
1042 [FTRACE] Do not trace the functions specified in
1043 function-list. This list can be changed at run time
1044 by the set_ftrace_notrace file in the debugfs
1047 ftrace_graph_filter=[function-list]
1048 [FTRACE] Limit the top level callers functions traced
1049 by the function graph tracer at boot up.
1050 function-list is a comma separated list of functions
1051 that can be changed at run time by the
1052 set_graph_function file in the debugfs tracing directory.
1055 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1056 support via parallel port (up to 5 devices per port)
1057 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1058 See also Documentation/input/joystick-parport.txt
1062 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1066 gcov_persist= [GCOV] When non-zero (default), profiling data for
1067 kernel modules is saved and remains accessible via
1068 debugfs, even when the module is unloaded/reloaded.
1069 When zero, profiling data is discarded and associated
1070 debugfs files are removed at module unload time.
1072 gpt [EFI] Forces disk with valid GPT signature but
1073 invalid Protective MBR to be treated as GPT. If the
1074 primary GPT is corrupted, it enables the backup/alternate
1075 GPT to be used instead.
1077 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1078 the "Enable 0" bit of the configuration register.
1081 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1082 the "Enable 0" bit of the configuration register.
1085 grcan.select= [HW] Select which physical interface to use.
1088 grcan.txsize= [HW] Sets the size of the tx buffer.
1089 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1091 grcan.rxsize= [HW] Sets the size of the rx buffer.
1092 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1095 hashdist= [KNL,NUMA] Large hashes allocated during boot
1096 are distributed across NUMA nodes. Defaults on
1097 for 64-bit NUMA, off otherwise.
1098 Format: 0 | 1 (for off | on)
1100 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1102 hd= [EIDE] (E)IDE hard drive subsystem geometry
1103 Format: <cyl>,<head>,<sect>
1106 Disable Hardware Error Source Table (HEST) support;
1107 corresponding firmware-first mode error processing
1108 logic will be disabled.
1110 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1111 size of <nn>. This works even on boxes that have no
1112 highmem otherwise. This also works to reduce highmem
1113 size on bigger boxes.
1115 highres= [KNL] Enable/disable high resolution timer mode.
1116 Valid parameters: "on", "off"
1120 See Documentation/isdn/README.HiSax.
1124 hpet= [X86-32,HPET] option to control HPET usage
1125 Format: { enable (default) | disable | force |
1127 disable: disable HPET and use PIT instead
1128 force: allow force enabled of undocumented chips (ICH4,
1130 verbose: show contents of HPET registers during setup
1132 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1133 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1135 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1136 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1137 On x86-64 and powerpc, this option can be specified
1138 multiple times interleaved with hugepages= to reserve
1139 huge pages of different sizes. Valid pages sizes on
1140 x86-64 are 2M (when the CPU supports "pse") and 1G
1141 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1142 Note that 1GB pages can only be allocated at boot time
1143 using hugepages= and not freed afterwards.
1145 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1146 terminal devices. Valid values: 0..8
1147 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1148 If specified, z/VM IUCV HVC accepts connections
1149 from listed z/VM user IDs only.
1151 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1152 hardware thread id mappings.
1153 Format: <cpu>:<hwthread>
1156 Do not unregister boot console at start. This is only
1157 useful for debugging when something happens in the window
1158 between unregistering the boot console and initializing
1161 i2c_bus= [HW] Override the default board specific I2C bus speed
1162 or register an additional I2C bus that is not
1163 registered from board initialization code.
1167 i8042.debug [HW] Toggle i8042 debug mode
1168 i8042.direct [HW] Put keyboard port into non-translated mode
1169 i8042.dumbkbd [HW] Pretend that controller can only read data from
1170 keyboard and cannot control its state
1171 (Don't attempt to blink the leds)
1172 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1173 i8042.nokbd [HW] Don't check/create keyboard port
1174 i8042.noloop [HW] Disable the AUX Loopback command while probing
1176 i8042.nomux [HW] Don't check presence of an active multiplexing
1178 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1180 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1181 i8042.reset [HW] Reset the controller during init and cleanup
1182 i8042.unlock [HW] Unlock (ignore) the keylock
1186 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1187 indicates that the driver is running on unsupported
1189 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1190 does not match list of supported models.
1192 [HW] Report power status in /proc/i8k
1193 (disabled by default)
1194 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1197 i915.invert_brightness=
1198 [DRM] Invert the sense of the variable that is used to
1199 set the brightness of the panel backlight. Normally a
1200 brightness value of 0 indicates backlight switched off,
1201 and the maximum of the brightness value sets the backlight
1202 to maximum brightness. If this parameter is set to 0
1203 (default) and the machine requires it, or this parameter
1204 is set to 1, a brightness value of 0 sets the backlight
1205 to maximum brightness, and the maximum of the brightness
1206 value switches the backlight off.
1207 -1 -- never invert brightness
1208 0 -- machine default
1209 1 -- force brightness inversion
1212 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1214 ide-core.nodma= [HW] (E)IDE subsystem
1215 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1216 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1217 .cdrom .chs .ignore_cable are additional options
1218 See Documentation/ide/ide.txt.
1220 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1221 Claim all unknown PCI IDE storage controllers.
1224 Format: idle=poll, idle=halt, idle=nomwait
1225 Poll forces a polling idle loop that can slightly
1226 improve the performance of waking up a idle CPU, but
1227 will use a lot of power and make the system run hot.
1229 idle=halt: Halt is forced to be used for CPU idle.
1230 In such case C2/C3 won't be used again.
1231 idle=nomwait: Disable mwait for CPU C-states
1233 ignore_loglevel [KNL]
1234 Ignore loglevel setting - this will print /all/
1235 kernel messages to the console. Useful for debugging.
1236 We also add it as printk module parameter, so users
1237 could change it dynamically, usually by
1238 /sys/module/printk/parameters/ignore_loglevel.
1240 ihash_entries= [KNL]
1241 Set number of hash buckets for inode cache.
1243 ima_appraise= [IMA] appraise integrity measurements
1244 Format: { "off" | "enforce" | "fix" }
1247 ima_appraise_tcb [IMA]
1248 The builtin appraise policy appraises all files
1252 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1256 The list of supported hash algorithms is defined
1257 in crypto/hash_info.h.
1260 Load a policy which meets the needs of the Trusted
1261 Computing Base. This means IMA will measure all
1262 programs exec'd, files mmap'd for exec, and all files
1263 opened for read by uid=0.
1266 Select one of defined IMA measurements template formats.
1267 Formats: { "ima" | "ima-ng" }
1272 Run specified binary instead of /sbin/init as init
1275 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1276 for working out where the kernel is dying during
1279 initrd= [BOOT] Specify the location of the initial ramdisk
1281 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1284 int_pln_enable [x86] Enable power limit notification interrupt
1286 integrity_audit=[IMA]
1287 Format: { "0" | "1" }
1288 0 -- basic integrity auditing messages. (Default)
1289 1 -- additional integrity auditing messages.
1291 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1293 Enable intel iommu driver.
1295 Disable intel iommu driver.
1296 igfx_off [Default Off]
1297 By default, gfx is mapped as normal device. If a gfx
1298 device has a dedicated DMAR unit, the DMAR unit is
1299 bypassed by not enabling DMAR with this option. In
1300 this case, gfx device will use physical address for
1303 With this option iommu will not optimize to look
1304 for io virtual address below 32-bit forcing dual
1305 address cycle on pci bus for cards supporting greater
1306 than 32-bit addressing. The default is to look
1307 for translation below 32-bit and if not available
1308 then look in the higher range.
1309 strict [Default Off]
1310 With this option on every unmap_single operation will
1311 result in a hardware IOTLB flush operation as opposed
1312 to batching them for performance.
1313 sp_off [Default Off]
1314 By default, super page will be supported if Intel IOMMU
1315 has the capability. With this option, super page will
1318 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1319 0 disables intel_idle and fall back on acpi_idle.
1320 1 to 6 specify maximum depth of C-state.
1324 Do not enable intel_pstate as the default
1325 scaling driver for the supported processors
1327 intremap= [X86-64, Intel-IOMMU]
1328 on enable Interrupt Remapping (default)
1329 off disable Interrupt Remapping
1330 nosid disable Source ID checking
1332 BIOS x2APIC opt-out request will be ignored
1334 iomem= Disable strict checking of access to MMIO memory
1335 strict regions from userspace.
1352 io7= [HW] IO7 for Marvel based alpha systems
1353 See comment before marvel_specify_io7 in
1354 arch/alpha/kernel/core_marvel.c.
1356 io_delay= [X86] I/O delay method
1358 Standard port 0x80 based delay
1360 Alternate port 0xed based delay (needed on some systems)
1362 Simple two microseconds delay
1367 See Documentation/filesystems/nfs/nfsroot.txt.
1369 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1370 See comment before ip2_setup() in
1371 drivers/char/ip2/ip2base.c.
1374 When an interrupt is not handled search all handlers
1375 for it. Intended to get systems with badly broken
1379 When an interrupt is not handled search all handlers
1380 for it. Also check all handlers each timer
1381 interrupt. Intended to get systems with badly broken
1385 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1387 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1389 <cpu number>,...,<cpu number>
1391 <cpu number>-<cpu number>
1392 (must be a positive range in ascending order)
1394 <cpu number>,...,<cpu number>-<cpu number>
1396 This option can be used to specify one or more CPUs
1397 to isolate from the general SMP balancing and scheduling
1398 algorithms. You can move a process onto or off an
1399 "isolated" CPU via the CPU affinity syscalls or cpuset.
1400 <cpu number> begins at 0 and the maximum value is
1401 "number of CPUs in system - 1".
1403 This option is the preferred way to isolate CPUs. The
1404 alternative -- manually setting the CPU mask of all
1405 tasks in the system -- can cause problems and
1406 suboptimal load balancer performance.
1410 ivrs_ioapic [HW,X86_64]
1411 Provide an override to the IOAPIC-ID<->DEVICE-ID
1412 mapping provided in the IVRS ACPI table. For
1413 example, to map IOAPIC-ID decimal 10 to
1414 PCI device 00:14.0 write the parameter as:
1415 ivrs_ioapic[10]=00:14.0
1417 ivrs_hpet [HW,X86_64]
1418 Provide an override to the HPET-ID<->DEVICE-ID
1419 mapping provided in the IVRS ACPI table. For
1420 example, to map HPET-ID decimal 0 to
1421 PCI device 00:14.0 write the parameter as:
1422 ivrs_hpet[0]=00:14.0
1424 js= [HW,JOY] Analog joystick
1425 See Documentation/input/joystick.txt.
1429 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1430 specifies the amount of memory usable by the kernel
1431 for non-movable allocations. The requested amount is
1432 spread evenly throughout all nodes in the system. The
1433 remaining memory in each node is used for Movable
1434 pages. In the event, a node is too small to have both
1435 kernelcore and Movable pages, kernelcore pages will
1436 take priority and other nodes will have a larger number
1437 of Movable pages. The Movable zone is used for the
1438 allocation of pages that may be reclaimed or moved
1439 by the page migration subsystem. This means that
1440 HugeTLB pages may not be allocated from this zone.
1441 Note that allocations like PTEs-from-HighMem still
1442 use the HighMem zone if it exists, and the Normal
1443 zone if it does not.
1445 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1446 Format: <Controller#>[,poll interval]
1447 The controller # is the number of the ehci usb debug
1448 port as it is probed via PCI. The poll interval is
1449 optional and is the number seconds in between
1450 each poll cycle to the debug port in case you need
1451 the functionality for interrupting the kernel with
1452 gdb or control-c on the dbgp connection. When
1453 not using this parameter you use sysrq-g to break into
1454 the kernel debugger.
1456 kgdboc= [KGDB,HW] kgdb over consoles.
1457 Requires a tty driver that supports console polling,
1458 or a supported polling keyboard driver (non-usb).
1459 Serial only format: <serial_device>[,baud]
1460 keyboard only format: kbd
1461 keyboard and serial format: kbd,<serial_device>[,baud]
1462 Optional Kernel mode setting:
1463 kms, kbd format: kms,kbd
1464 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1466 kgdbwait [KGDB] Stop kernel execution and enter the
1467 kernel debugger at the earliest opportunity.
1469 kmac= [MIPS] korina ethernet MAC address.
1470 Configure the RouterBoard 532 series on-chip
1471 Ethernet adapter MAC address.
1473 kmemleak= [KNL] Boot-time kmemleak enable/disable
1474 Valid arguments: on, off
1477 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1478 Valid arguments: 0, 1, 2
1479 kmemcheck=0 (disabled)
1480 kmemcheck=1 (enabled)
1481 kmemcheck=2 (one-shot mode)
1482 Default: 2 (one-shot mode)
1484 kstack=N [X86] Print N words from the kernel stack
1487 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1488 Default is 0 (don't ignore, but inject #GP)
1490 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1494 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1495 Default is 1 (enabled)
1497 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1499 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1501 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1502 (virtualized MMU) support on capable Intel chips.
1503 Default is 1 (enabled)
1505 kvm-intel.emulate_invalid_guest_state=
1506 [KVM,Intel] Enable emulation of invalid guest states
1507 Default is 0 (disabled)
1509 kvm-intel.flexpriority=
1510 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1511 Default is 1 (enabled)
1514 [KVM,Intel] Enable VMX nesting (nVMX).
1515 Default is 0 (disabled)
1517 kvm-intel.unrestricted_guest=
1518 [KVM,Intel] Disable unrestricted guest feature
1519 (virtualized real and unpaged mode) on capable
1520 Intel chips. Default is 1 (enabled)
1522 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1523 feature (tagged TLBs) on capable Intel chips.
1524 Default is 1 (enabled)
1530 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1533 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1534 value for LAPIC timer one-shot implementation. Default
1535 back to the programmable timer unit in the LAPIC.
1537 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1540 libata.dma= [LIBATA] DMA control
1541 libata.dma=0 Disable all PATA and SATA DMA
1542 libata.dma=1 PATA and SATA Disk DMA only
1543 libata.dma=2 ATAPI (CDROM) DMA only
1544 libata.dma=4 Compact Flash DMA only
1545 Combinations also work, so libata.dma=3 enables DMA
1546 for disks and CDROMs, but not CFs.
1548 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1549 libata.ignore_hpa=0 keep BIOS limits (default)
1550 libata.ignore_hpa=1 ignore limits, using full disk
1552 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1556 libata.force= [LIBATA] Force configurations. The format is comma
1557 separated list of "[ID:]VAL" where ID is
1558 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1559 matching port, link or device. Basically, it matches
1560 the ATA ID string printed on console by libata. If
1561 the whole ID part is omitted, the last PORT and DEVICE
1562 values are used. If ID hasn't been specified yet, the
1563 configuration applies to all ports, links and devices.
1565 If only DEVICE is omitted, the parameter applies to
1566 the port and all links and devices behind it. DEVICE
1567 number of 0 either selects the first device or the
1568 first fan-out link behind PMP device. It does not
1569 select the host link. DEVICE number of 15 selects the
1570 host link and device attached to it.
1572 The VAL specifies the configuration to force. As long
1573 as there's no ambiguity shortcut notation is allowed.
1574 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1575 The following configurations can be forced.
1577 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1578 Any ID with matching PORT is used.
1580 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1582 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1583 udma[/][16,25,33,44,66,100,133] notation is also
1586 * [no]ncq: Turn on or off NCQ.
1588 * nohrst, nosrst, norst: suppress hard, soft
1591 * rstonce: only attempt one reset during
1592 hot-unplug link recovery
1594 * dump_id: dump IDENTIFY data.
1596 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1598 * disable: Disable this device.
1600 If there are multiple matching configurations changing
1601 the same attribute, the last one is used.
1603 memblock=debug [KNL] Enable memblock debug messages.
1605 load_ramdisk= [RAM] List of ramdisks to load from floppy
1606 See Documentation/blockdev/ramdisk.txt.
1608 lockd.nlm_grace_period=P [NFS] Assign grace period.
1611 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1614 lockd.nlm_timeout=T [NFS] Assign timeout value.
1617 lockd.nlm_udpport=M [NFS] Assign UDP port.
1620 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1623 loglevel= All Kernel Messages with a loglevel smaller than the
1624 console loglevel will be printed to the console. It can
1625 also be changed with klogd or other programs. The
1626 loglevels are defined as follows:
1628 0 (KERN_EMERG) system is unusable
1629 1 (KERN_ALERT) action must be taken immediately
1630 2 (KERN_CRIT) critical conditions
1631 3 (KERN_ERR) error conditions
1632 4 (KERN_WARNING) warning conditions
1633 5 (KERN_NOTICE) normal but significant condition
1634 6 (KERN_INFO) informational
1635 7 (KERN_DEBUG) debug-level messages
1637 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1638 in bytes. n must be a power of two. The default
1639 size is set in the kernel config file.
1641 logo.nologo [FB] Disables display of the built-in Linux logo.
1642 This may be used to provide more screen space for
1643 kernel log messages and is useful when debugging
1644 kernel boot problems.
1646 lp=0 [LP] Specify parallel ports to use, e.g,
1647 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1648 lp=reset first parallel port). 'lp=0' disables the
1649 lp=auto printer driver. 'lp=reset' (which can be
1650 specified in addition to the ports) causes
1651 attached printers to be reset. Using
1652 lp=port1,port2,... specifies the parallel ports
1653 to associate lp devices with, starting with
1654 lp0. A port specification may be 'none' to skip
1655 that lp device, or a parport name such as
1656 'parport0'. Specifying 'lp=auto' instead of a
1657 port specification list means that device IDs
1658 from each port should be examined, to see if
1659 an IEEE 1284-compliant printer is attached; if
1660 so, the driver will manage that printer.
1661 See also header of drivers/char/lp.c.
1664 Sets loops_per_jiffy to given constant, thus avoiding
1665 time-consuming boot-time autodetection (up to 250 ms per
1666 CPU). 0 enables autodetection (default). To determine
1667 the correct value for your kernel, boot with normal
1668 autodetection and see what value is printed. Note that
1669 on SMP systems the preset will be applied to all CPUs,
1670 which is likely to cause problems if your CPUs need
1671 significantly divergent settings. An incorrect value
1672 will cause delays in the kernel to be wrong, leading to
1673 unpredictable I/O errors and other breakage. Although
1674 unlikely, in the extreme case this might damage your
1678 Format: <io>,<irq>,<dma>
1680 machvec= [IA-64] Force the use of a particular machine-vector
1681 (machvec) in a generic kernel.
1682 Example: machvec=hpzx1_swiotlb
1684 machtype= [Loongson] Share the same kernel image file between different
1686 Example: machtype=lemote-yeeloong-2f-7inch
1688 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1689 than or equal to this physical address is ignored.
1691 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1692 should make use of. maxcpus=n : n >= 0 limits the
1693 kernel to using 'n' processors. n=0 is a special case,
1694 it is equivalent to "nosmp", which also disables
1697 max_loop= [LOOP] The number of loop block devices that get
1698 (loop.max_loop) unconditionally pre-created at init time. The default
1699 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1700 of statically allocating a predefined number, loop
1701 devices can be requested on-demand with the
1702 /dev/loop-control interface.
1704 mce [X86-32] Machine Check Exception
1706 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1708 md= [HW] RAID subsystems devices and level
1709 See Documentation/md.txt.
1712 Format: <first>,<last>
1713 Specifies range of consoles to be captured by the MDA.
1715 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1716 Amount of memory to be used when the kernel is not able
1717 to see the whole system memory or for test.
1718 [X86] Work as limiting max address. Use together
1719 with memmap= to avoid physical address space collisions.
1720 Without memmap= PCI devices could be placed at addresses
1721 belonging to unused RAM.
1723 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1727 [KNL,SH] Allow user to override the default size for
1728 per-device physically contiguous DMA buffers.
1730 memmap=exactmap [KNL,X86] Enable setting of an exact
1731 E820 memory map, as specified by the user.
1732 Such memmap=exactmap lines can be constructed based on
1733 BIOS output or other requirements. See the memmap=nn@ss
1736 memmap=nn[KMG]@ss[KMG]
1737 [KNL] Force usage of a specific region of memory.
1738 Region of memory to be used is from ss to ss+nn.
1740 memmap=nn[KMG]#ss[KMG]
1741 [KNL,ACPI] Mark specific memory as ACPI data.
1742 Region of memory to be marked is from ss to ss+nn.
1744 memmap=nn[KMG]$ss[KMG]
1745 [KNL,ACPI] Mark specific memory as reserved.
1746 Region of memory to be reserved is from ss to ss+nn.
1747 Example: Exclude memory from 0x18690000-0x1869ffff
1748 memmap=64K$0x18690000
1750 memmap=0x10000$0x18690000
1752 memory_corruption_check=0/1 [X86]
1753 Some BIOSes seem to corrupt the first 64k of
1754 memory when doing things like suspend/resume.
1755 Setting this option will scan the memory
1756 looking for corruption. Enabling this will
1757 both detect corruption and prevent the kernel
1758 from using the memory being corrupted.
1759 However, its intended as a diagnostic tool; if
1760 repeatable BIOS-originated corruption always
1761 affects the same memory, you can use memmap=
1762 to prevent the kernel from using that memory.
1764 memory_corruption_check_size=size [X86]
1765 By default it checks for corruption in the low
1766 64k, making this memory unavailable for normal
1767 use. Use this parameter to scan for
1768 corruption in more or less memory.
1770 memory_corruption_check_period=seconds [X86]
1771 By default it checks for corruption every 60
1772 seconds. Use this parameter to check at some
1773 other rate. 0 disables periodic checking.
1775 memtest= [KNL,X86] Enable memtest
1777 default : 0 <disable>
1778 Specifies the number of memtest passes to be
1779 performed. Each pass selects another test
1780 pattern from a given set of patterns. Memtest
1781 fills the memory with this pattern, validates
1782 memory contents and reserves bad memory
1783 regions that are detected.
1785 meye.*= [HW] Set MotionEye Camera parameters
1786 See Documentation/video4linux/meye.txt.
1788 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1789 Multi-Function General Purpose Timers on AMD Geode
1792 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1793 the BIOS has incorrectly applied a workaround. TinyBIOS
1794 version 0.98 is known to be affected, 0.99 fixes the
1795 problem by letting the user disable the workaround.
1799 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1800 physical address is ignored.
1802 mini2440= [ARM,HW,KNL]
1803 Format:[0..2][b][c][t]
1805 MINI2440 configuration specification:
1806 0 - The attached screen is the 3.5" TFT
1807 1 - The attached screen is the 7" TFT
1808 2 - The VGA Shield is attached (1024x768)
1809 Leaving out the screen size parameter will not load
1810 the TFT driver, and the framebuffer will be left
1812 b - Enable backlight. The TFT backlight pin will be
1813 linked to the kernel VESA blanking code and a GPIO
1814 LED. This parameter is not necessary when using the
1816 c - Enable the s3c camera interface.
1817 t - Reserved for enabling touchscreen support. The
1818 touchscreen support is not enabled in the mainstream
1819 kernel as of 2.6.30, a preliminary port can be found
1820 in the "bleeding edge" mini2440 support kernel at
1821 http://repo.or.cz/w/linux-2.6/mini2440.git
1824 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1825 parameter allows control of the logging verbosity for
1826 the additional memory initialisation checks. A value
1827 of 0 disables mminit logging and a level of 4 will
1828 log everything. Information is printed at KERN_DEBUG
1829 so loglevel=8 may also need to be specified.
1832 [KNL] When CONFIG_MODULE_SIG is set, this means that
1833 modules without (valid) signatures will fail to load.
1834 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1835 is always true, so this option does nothing.
1838 [MOUSE] Maximum time between finger touching and
1839 leaving touchpad surface for touch to be considered
1840 a tap and be reported as a left button click (for
1841 touchpads working in absolute mode only).
1843 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1844 reporting absolute coordinates, such as tablets
1845 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1846 reporting absolute coordinates, such as tablets
1848 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1849 is similar to kernelcore except it specifies the
1850 amount of memory used for migratable allocations.
1851 If both kernelcore and movablecore is specified,
1852 then kernelcore will be at *least* the specified
1853 value but may be more. If movablecore on its own
1854 is specified, the administrator must be careful
1855 that the amount of memory usable for all allocations
1858 movable_node [KNL,X86] Boot-time switch to enable the effects
1859 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1861 MTD_Partition= [MTD]
1862 Format: <name>,<region-number>,<size>,<offset>
1864 MTD_Region= [MTD] Format:
1865 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1868 See drivers/mtd/cmdlinepart.c.
1870 multitce=off [PPC] This parameter disables the use of the pSeries
1871 firmware feature for updating multiple TCE entries
1874 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1876 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1878 boundary - index of last SLC block on Flex-OneNAND.
1879 The remaining blocks are configured as MLC blocks.
1880 lock - Configure if Flex-OneNAND boundary should be locked.
1881 Once locked, the boundary cannot be changed.
1882 1 indicates lock status, 0 indicates unlock status.
1885 ARM/S3C2412 JIVE boot control
1887 See arch/arm/mach-s3c2412/mach-jive.c
1889 mtouchusb.raw_coordinates=
1890 [HW] Make the MicroTouch USB driver use raw coordinates
1891 ('y', default) or cooked coordinates ('n')
1893 mtrr_chunk_size=nn[KMG] [X86]
1894 used for mtrr cleanup. It is largest continuous chunk
1895 that could hold holes aka. UC entries.
1897 mtrr_gran_size=nn[KMG] [X86]
1898 Used for mtrr cleanup. It is granularity of mtrr block.
1900 Large value could prevent small alignment from
1903 mtrr_spare_reg_nr=n [X86]
1905 Range: 0,7 : spare reg number
1907 Used for mtrr cleanup. It is spare mtrr entries number.
1908 Set to 2 or more if your graphical card needs more.
1910 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1912 netdev= [NET] Network devices parameters
1913 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1914 Note that mem_start is often overloaded to mean
1915 something different and driver-specific.
1916 This usage is only documented in each driver source
1920 [NETFILTER] Enable connection tracking flow accounting
1921 0 to disable accounting
1922 1 to enable accounting
1925 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1926 See Documentation/filesystems/nfs/nfsroot.txt.
1928 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1929 See Documentation/filesystems/nfs/nfsroot.txt.
1931 nfsrootdebug [NFS] enable nfsroot debugging messages.
1932 See Documentation/filesystems/nfs/nfsroot.txt.
1934 nfs.callback_tcpport=
1935 [NFS] set the TCP port on which the NFSv4 callback
1936 channel should listen.
1939 [NFS] sets the pathname to the program which is used
1940 to update the NFS client cache entries.
1942 nfs.cache_getent_timeout=
1943 [NFS] sets the timeout after which an attempt to
1944 update a cache entry is deemed to have failed.
1946 nfs.idmap_cache_timeout=
1947 [NFS] set the maximum lifetime for idmapper cache
1951 [NFS] enable 64-bit inode numbers.
1952 If zero, the NFS client will fake up a 32-bit inode
1953 number for the readdir() and stat() syscalls instead
1954 of returning the full 64-bit number.
1955 The default is to return 64-bit inode numbers.
1957 nfs.max_session_slots=
1958 [NFSv4.1] Sets the maximum number of session slots
1959 the client will attempt to negotiate with the server.
1960 This limits the number of simultaneous RPC requests
1961 that the client can send to the NFSv4.1 server.
1962 Note that there is little point in setting this
1963 value higher than the max_tcp_slot_table_limit.
1965 nfs.nfs4_disable_idmapping=
1966 [NFSv4] When set to the default of '1', this option
1967 ensures that both the RPC level authentication
1968 scheme and the NFS level operations agree to use
1969 numeric uids/gids if the mount is using the
1970 'sec=sys' security flavour. In effect it is
1971 disabling idmapping, which can make migration from
1972 legacy NFSv2/v3 systems to NFSv4 easier.
1973 Servers that do not support this mode of operation
1974 will be autodetected by the client, and it will fall
1975 back to using the idmapper.
1976 To turn off this behaviour, set the value to '0'.
1978 [NFS4] Specify an additional fixed unique ident-
1979 ification string that NFSv4 clients can insert into
1980 their nfs_client_id4 string. This is typically a
1981 UUID that is generated at system install time.
1983 nfs.send_implementation_id =
1984 [NFSv4.1] Send client implementation identification
1985 information in exchange_id requests.
1986 If zero, no implementation identification information
1988 The default is to send the implementation identification
1991 nfs.recover_lost_locks =
1992 [NFSv4] Attempt to recover locks that were lost due
1993 to a lease timeout on the server. Please note that
1994 doing this risks data corruption, since there are
1995 no guarantees that the file will remain unchanged
1996 after the locks are lost.
1997 If you want to enable the kernel legacy behaviour of
1998 attempting to recover these locks, then set this
2000 The default parameter value of '0' causes the kernel
2001 not to attempt recovery of lost locks.
2003 nfsd.nfs4_disable_idmapping=
2004 [NFSv4] When set to the default of '1', the NFSv4
2005 server will return only numeric uids and gids to
2006 clients using auth_sys, and will accept numeric uids
2007 and gids from such clients. This is intended to ease
2008 migration from NFSv2/v3.
2010 objlayoutdriver.osd_login_prog=
2011 [NFS] [OBJLAYOUT] sets the pathname to the program which
2012 is used to automatically discover and login into new
2013 osd-targets. Please see:
2014 Documentation/filesystems/pnfs.txt for more explanations
2016 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2017 when a NMI is triggered.
2018 Format: [state][,regs][,debounce][,die]
2020 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2021 Format: [panic,][nopanic,][num]
2023 0 - turn nmi_watchdog off
2024 When panic is specified, panic when an NMI watchdog
2025 timeout occurs (or 'nopanic' to override the opposite
2027 This is useful when you use a panic=... timeout and
2028 need the box quickly up again.
2030 netpoll.carrier_timeout=
2031 [NET] Specifies amount of time (in seconds) that
2032 netpoll should wait for a carrier. By default netpoll
2035 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2036 emulation library even if a 387 maths coprocessor
2040 [HW] Never suspend the console
2041 Disable suspending of consoles during suspend and
2042 hibernate operations. Once disabled, debugging
2043 messages can reach various consoles while the rest
2044 of the system is being put to sleep (ie, while
2045 debugging driver suspend/resume hooks). This may
2046 not work reliably with all consoles, but is known
2047 to work with serial and VGA consoles.
2048 To facilitate more flexible debugging, we also add
2049 console_suspend, a printk module parameter to control
2050 it. Users could use console_suspend (usually
2051 /sys/module/printk/parameters/console_suspend) to
2052 turn on/off it dynamically.
2054 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2055 caches in the slab allocator. Saves per-node memory,
2056 but will impact performance.
2060 noapic [SMP,APIC] Tells the kernel to not make use of any
2061 IOAPICs that may be present in the system.
2064 Disable kernel base offset ASLR (Address Space
2065 Layout Randomization) if built into the kernel.
2067 noautogroup Disable scheduler automatic task group creation.
2069 nobats [PPC] Do not use BATs for mapping kernel lowmem
2070 on "Classic" PPC cores.
2074 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2076 nodelayacct [KNL] Disable per-task delay accounting
2078 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2080 nodsp [SH] Disable hardware DSP at boot time.
2082 noefi [X86] Disable EFI runtime services support.
2087 On X86-32 available only on PAE configured kernels.
2088 noexec=on: enable non-executable mappings (default)
2089 noexec=off: disable non-executable mappings
2092 Disable SMAP (Supervisor Mode Access Prevention)
2093 even if it is supported by processor.
2096 Disable SMEP (Supervisor Mode Execution Prevention)
2097 even if it is supported by processor.
2100 This affects only 32-bit executables.
2101 noexec32=on: enable non-executable mappings (default)
2102 read doesn't imply executable mappings
2103 noexec32=off: disable non-executable mappings
2104 read implies executable mappings
2106 nofpu [SH] Disable hardware FPU at boot time.
2108 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2109 register save and restore. The kernel will only save
2110 legacy floating-point registers on task switch.
2112 noxsave [BUGS=X86] Disables x86 extended register state save
2113 and restore using xsave. The kernel will fallback to
2114 enabling legacy floating-point and sse state.
2117 on enable eager fpu restore
2118 off disable eager fpu restore
2119 auto selects the default scheme, which automatically
2120 enables eagerfpu restore for xsaveopt.
2122 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2123 wfi(ARM) instruction doesn't work correctly and not to
2124 use it. This is also useful when using JTAG debugger.
2126 no_file_caps Tells the kernel not to honor file capabilities. The
2127 only way then for a file to be executed with privilege
2128 is to be setuid root or executed by root.
2130 nohalt [IA-64] Tells the kernel not to use the power saving
2131 function PAL_HALT_LIGHT when idle. This increases
2132 power-consumption. On the positive side, it reduces
2133 interrupt wake-up latency, which may improve performance
2134 in certain environments such as networked servers or
2137 nohz= [KNL] Boottime enable/disable dynamic ticks
2138 Valid arguments: on, off
2141 nohz_full= [KNL,BOOT]
2142 In kernels built with CONFIG_NO_HZ_FULL=y, set
2143 the specified list of CPUs whose tick will be stopped
2144 whenever possible. The boot CPU will be forced outside
2145 the range to maintain the timekeeping.
2146 The CPUs in this range must also be included in the
2149 noiotrap [SH] Disables trapped I/O port accesses.
2151 noirqdebug [X86-32] Disables the code which attempts to detect and
2152 disable unhandled interrupt sources.
2154 no_timer_check [X86,APIC] Disables the code which tests for
2155 broken timer IRQ sources.
2157 noisapnp [ISAPNP] Disables ISA PnP code.
2159 noinitrd [RAM] Tells the kernel not to load any configured
2162 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2164 [Deprecated - use intremap=off]
2168 nojitter [IA-64] Disables jitter checking for ITC timers.
2170 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2172 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2175 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2176 steal time is computed, but won't influence scheduler
2179 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2181 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2183 noltlbs [PPC] Do not use large page/tlb entries for kernel
2184 lowmem mapping on PPC40x.
2186 nomca [IA-64] Disable machine check abort handling
2188 nomce [X86-32] Machine Check Exception
2190 nomfgpt [X86-32] Disable Multi-Function General Purpose
2191 Timer usage (for AMD Geode machines).
2193 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2194 shutdown the other cpus. Instead use the REBOOT_VECTOR
2197 nomodule Disable module load
2199 nopat [X86] Disable PAT (page attribute table extension of
2200 pagetables) support.
2202 norandmaps Don't use address space randomization. Equivalent to
2203 echo 0 > /proc/sys/kernel/randomize_va_space
2205 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2207 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2208 with UP alternatives
2210 nordrand [X86] Disable the direct use of the RDRAND
2211 instruction even if it is supported by the
2212 processor. RDRAND is still available to user
2215 noresume [SWSUSP] Disables resume and restores original swap
2218 no-scroll [VGA] Disables scrollback.
2219 This is required for the Braillex ib80-piezo Braille
2220 reader made by F.H. Papenmeier (Germany).
2224 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2226 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2227 and disable the IO APIC. legacy for "maxcpus=0".
2229 nosoftlockup [KNL] Disable the soft-lockup detector.
2231 nosync [HW,M68K] Disables sync negotiation for all devices.
2233 notsc [BUGS=X86-32] Disable Time Stamp Counter
2235 nousb [USB] Disable the USB subsystem
2237 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2241 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2243 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2244 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2245 Some features depend on CPU0. Known dependencies are:
2246 1. Resume from suspend/hibernate depends on CPU0.
2247 Suspend/hibernate will fail if CPU0 is offline and you
2248 need to online CPU0 before suspend/hibernate.
2249 2. PIC interrupts also depend on CPU0. CPU0 can't be
2250 removed if a PIC interrupt is detected.
2251 It's said poweroff/reboot may depend on CPU0 on some
2252 machines although I haven't seen such issues so far
2253 after CPU0 is offline on a few tested machines.
2254 If the dependencies are under your control, you can
2255 turn on cpu0_hotplug.
2257 nptcg= [IA-64] Override max number of concurrent global TLB
2258 purges which is reported from either PAL_VM_SUMMARY or
2261 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2262 could support. nr_cpus=n : n >= 1 limits the kernel to
2263 supporting 'n' processors. Later in runtime you can not
2264 use hotplug cpu feature to put more cpu back to online.
2265 just like you compile the kernel NR_CPUS=n
2267 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2269 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2270 Allowed values are enable and disable
2272 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2273 one of ['zone', 'node', 'default'] can be specified
2274 This can be set from sysctl after boot.
2275 See Documentation/sysctl/vm.txt for details.
2277 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2278 See Documentation/debugging-via-ohci1394.txt for more
2281 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2282 Rather than timing out after 20 ms if an EC
2283 command is not properly ACKed, override the length
2284 of the timeout. We have interrupts disabled while
2285 waiting for the ACK, so if this is set too high
2286 interrupts *may* be lost!
2288 omap_mux= [OMAP] Override bootloader pin multiplexing.
2289 Format: <mux_mode0.mode_name=value>...
2290 For example, to override I2C bus2:
2291 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2293 oprofile.timer= [HW]
2294 Use timer interrupt instead of performance counters
2296 oprofile.cpu_type= Force an oprofile cpu type
2297 This might be useful if you have an older oprofile
2298 userland or if you want common events.
2299 Format: { arch_perfmon }
2300 arch_perfmon: [X86] Force use of architectural
2301 perfmon on Intel CPUs instead of the
2302 CPU specific event set.
2303 timer: [X86] Force use of architectural NMI
2304 timer mode (see also oprofile.timer
2305 for generic hr timer mode)
2306 [s390] Force legacy basic mode sampling
2307 (report cpu_type "timer")
2309 oops=panic Always panic on oopses. Default is to just kill the
2310 process, but there is a small probability of
2311 deadlocking the machine.
2312 This will also cause panics on machine check exceptions.
2313 Useful together with panic=30 to trigger a reboot.
2316 See Documentation/sound/oss/oss-parameters.txt
2318 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2319 timeout > 0: seconds before rebooting
2320 timeout = 0: wait forever
2321 timeout < 0: reboot immediately
2324 parkbd.port= [HW] Parallel port number the keyboard adapter is
2325 connected to, default is 0.
2327 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2328 0 for XT, 1 for AT (default is AT).
2331 parport= [HW,PPT] Specify parallel ports. 0 disables.
2332 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2333 Use 'auto' to force the driver to use any
2334 IRQ/DMA settings detected (the default is to
2335 ignore detected IRQ/DMA settings because of
2336 possible conflicts). You can specify the base
2337 address, IRQ, and DMA settings; IRQ and DMA
2338 should be numbers, or 'auto' (for using detected
2339 settings on that particular port), or 'nofifo'
2340 (to avoid using a FIFO even if it is detected).
2341 Parallel ports are assigned in the order they
2342 are specified on the command line, starting
2345 parport_init_mode= [HW,PPT]
2346 Configure VIA parallel port to operate in
2347 a specific mode. This is necessary on Pegasos
2348 computer where firmware has no options for setting
2349 up parallel port mode and sets it to spp.
2350 Currently this function knows 686a and 8231 chips.
2351 Format: [spp|ps2|epp|ecp|ecpepp]
2354 Halt all CPUs after the first oops has been printed for
2355 the specified number of seconds. This is to be used if
2356 your oopses keep scrolling off the screen.
2361 See header of drivers/block/paride/pcd.c.
2362 See also Documentation/blockdev/paride.txt.
2364 pci=option[,option...] [PCI] various PCI subsystem options:
2365 earlydump [X86] dump PCI config space before the kernel
2367 off [X86] don't probe for the PCI bus
2368 bios [X86-32] force use of PCI BIOS, don't access
2369 the hardware directly. Use this if your machine
2370 has a non-standard PCI host bridge.
2371 nobios [X86-32] disallow use of PCI BIOS, only direct
2372 hardware access methods are allowed. Use this
2373 if you experience crashes upon bootup and you
2374 suspect they are caused by the BIOS.
2375 conf1 [X86] Force use of PCI Configuration
2377 conf2 [X86] Force use of PCI Configuration
2379 noaer [PCIE] If the PCIEAER kernel config parameter is
2380 enabled, this kernel boot option can be used to
2381 disable the use of PCIE advanced error reporting.
2382 nodomains [PCI] Disable support for multiple PCI
2383 root domains (aka PCI segments, in ACPI-speak).
2384 nommconf [X86] Disable use of MMCONFIG for PCI
2386 check_enable_amd_mmconf [X86] check for and enable
2387 properly configured MMIO access to PCI
2388 config space on AMD family 10h CPU
2389 nomsi [MSI] If the PCI_MSI kernel config parameter is
2390 enabled, this kernel boot option can be used to
2391 disable the use of MSI interrupts system-wide.
2392 noioapicquirk [APIC] Disable all boot interrupt quirks.
2393 Safety option to keep boot IRQs enabled. This
2394 should never be necessary.
2395 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2396 primary IO-APIC for bridges that cannot disable
2397 boot IRQs. This fixes a source of spurious IRQs
2398 when the system masks IRQs.
2399 noioapicreroute [APIC] Disable workaround that uses the
2400 boot IRQ equivalent of an IRQ that connects to
2401 a chipset where boot IRQs cannot be disabled.
2402 The opposite of ioapicreroute.
2403 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2404 routing table. These calls are known to be buggy
2405 on several machines and they hang the machine
2406 when used, but on other computers it's the only
2407 way to get the interrupt routing table. Try
2408 this option if the kernel is unable to allocate
2409 IRQs or discover secondary PCI buses on your
2411 rom [X86] Assign address space to expansion ROMs.
2412 Use with caution as certain devices share
2413 address decoders between ROMs and other
2415 norom [X86] Do not assign address space to
2416 expansion ROMs that do not already have
2417 BIOS assigned address ranges.
2418 nobar [X86] Do not assign address space to the
2419 BARs that weren't assigned by the BIOS.
2420 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2421 assigned automatically to PCI devices. You can
2422 make the kernel exclude IRQs of your ISA cards
2424 pirqaddr=0xAAAAA [X86] Specify the physical address
2425 of the PIRQ table (normally generated
2426 by the BIOS) if it is outside the
2427 F0000h-100000h range.
2428 lastbus=N [X86] Scan all buses thru bus #N. Can be
2429 useful if the kernel is unable to find your
2430 secondary buses and you want to tell it
2431 explicitly which ones they are.
2432 assign-busses [X86] Always assign all PCI bus
2433 numbers ourselves, overriding
2434 whatever the firmware may have done.
2435 usepirqmask [X86] Honor the possible IRQ mask stored
2436 in the BIOS $PIR table. This is needed on
2437 some systems with broken BIOSes, notably
2438 some HP Pavilion N5400 and Omnibook XE3
2439 notebooks. This will have no effect if ACPI
2440 IRQ routing is enabled.
2441 noacpi [X86] Do not use ACPI for IRQ routing
2442 or for PCI scanning.
2443 use_crs [X86] Use PCI host bridge window information
2444 from ACPI. On BIOSes from 2008 or later, this
2445 is enabled by default. If you need to use this,
2446 please report a bug.
2447 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2448 If you need to use this, please report a bug.
2449 routeirq Do IRQ routing for all PCI devices.
2450 This is normally done in pci_enable_device(),
2451 so this option is a temporary workaround
2452 for broken drivers that don't call it.
2453 skip_isa_align [X86] do not align io start addr, so can
2454 handle more pci cards
2455 firmware [ARM] Do not re-enumerate the bus but instead
2456 just use the configuration from the
2457 bootloader. This is currently used on
2458 IXP2000 systems where the bus has to be
2459 configured a certain way for adjunct CPUs.
2460 noearly [X86] Don't do any early type 1 scanning.
2461 This might help on some broken boards which
2462 machine check when some devices' config space
2463 is read. But various workarounds are disabled
2464 and some IOMMU drivers will not work.
2465 bfsort Sort PCI devices into breadth-first order.
2466 This sorting is done to get a device
2467 order compatible with older (<= 2.4) kernels.
2468 nobfsort Don't sort PCI devices into breadth-first order.
2469 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2470 tuning and use the BIOS-configured MPS defaults.
2471 pcie_bus_safe Set every device's MPS to the largest value
2472 supported by all devices below the root complex.
2473 pcie_bus_perf Set device MPS to the largest allowable MPS
2474 based on its parent bus. Also set MRRS (Max
2475 Read Request Size) to the largest supported
2476 value (no larger than the MPS that the device
2477 or bus can support) for best performance.
2478 pcie_bus_peer2peer Set every device's MPS to 128B, which
2479 every device is guaranteed to support. This
2480 configuration allows peer-to-peer DMA between
2481 any pair of devices, possibly at the cost of
2482 reduced performance. This also guarantees
2483 that hot-added devices will work.
2484 cbiosize=nn[KMG] The fixed amount of bus space which is
2485 reserved for the CardBus bridge's IO window.
2486 The default value is 256 bytes.
2487 cbmemsize=nn[KMG] The fixed amount of bus space which is
2488 reserved for the CardBus bridge's memory
2489 window. The default value is 64 megabytes.
2492 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2493 Specifies alignment and device to reassign
2494 aligned memory resources.
2495 If <order of align> is not specified,
2496 PAGE_SIZE is used as alignment.
2497 PCI-PCI bridge can be specified, if resource
2498 windows need to be expanded.
2499 ecrc= Enable/disable PCIe ECRC (transaction layer
2500 end-to-end CRC checking).
2501 bios: Use BIOS/firmware settings. This is the
2505 hpiosize=nn[KMG] The fixed amount of bus space which is
2506 reserved for hotplug bridge's IO window.
2507 Default size is 256 bytes.
2508 hpmemsize=nn[KMG] The fixed amount of bus space which is
2509 reserved for hotplug bridge's memory window.
2510 Default size is 2 megabytes.
2511 realloc= Enable/disable reallocating PCI bridge resources
2512 if allocations done by BIOS are too small to
2513 accommodate resources required by all child
2515 off: Turn realloc off
2517 realloc same as realloc=on
2518 noari do not use PCIe ARI.
2519 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2520 only look for one device below a PCIe downstream
2523 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2526 force Enable ASPM even on devices that claim not to support it.
2527 WARNING: Forcing ASPM on may cause system lockups.
2529 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2530 nomsi Do not use MSI for PCI Express Native Hotplug (this
2531 makes all PCIe ports use INTx for hotplug services).
2533 pcie_ports= [PCIE] PCIe ports handling:
2534 auto Ask the BIOS whether or not to use native PCIe services
2535 associated with PCIe ports (PME, hot-plug, AER). Use
2536 them only if that is allowed by the BIOS.
2537 native Use native PCIe services associated with PCIe ports
2539 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2542 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2543 nomsi Do not use MSI for native PCIe PME signaling (this makes
2544 all PCIe root ports use INTx for all services).
2546 pcmv= [HW,PCMCIA] BadgePAD 4
2549 See Documentation/blockdev/paride.txt.
2551 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2554 See arch/parisc/kernel/pdc_chassis.c
2556 percpu_alloc= Select which percpu first chunk allocator to use.
2557 Currently supported values are "embed" and "page".
2558 Archs may support subset or none of the selections.
2559 See comments in mm/percpu.c for details on each
2560 allocator. This parameter is primarily for debugging
2561 and performance comparison.
2564 See Documentation/blockdev/paride.txt.
2567 See Documentation/blockdev/paride.txt.
2569 pirq= [SMP,APIC] Manual mp-table setup
2570 See Documentation/x86/i386/IO-APIC.txt.
2572 plip= [PPT,NET] Parallel port network link
2573 Format: { parport<nr> | timid | 0 }
2574 See also Documentation/parport.txt.
2576 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2577 Override pmtimer IOPort with a hex value.
2581 Enable PNP debug messages (depends on the
2582 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2583 via /sys/module/pnp/parameters/debug. We always show
2584 current resource usage; turning this on also shows
2585 possible settings and some assignment information.
2591 { on | off | curr | res | no-curr | no-res }
2594 [ISAPNP] Exclude IRQs for the autoconfiguration
2597 [ISAPNP] Exclude DMAs for the autoconfiguration
2599 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2600 Ranges are in pairs (I/O port base and size).
2603 [ISAPNP] Exclude memory regions for the
2605 Ranges are in pairs (memory base and size).
2607 ports= [IP_VS_FTP] IPVS ftp helper module
2609 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2611 Format: <port>,<port>....
2613 print-fatal-signals=
2614 [KNL] debug: print fatal signals
2616 If enabled, warn about various signal handling
2617 related application anomalies: too many signals,
2618 too many POSIX.1 timers, fatal signals causing a
2621 If you hit the warning due to signal overflow,
2622 you might want to try "ulimit -i unlimited".
2626 printk.always_kmsg_dump=
2627 Trigger kmsg_dump for cases other than kernel oops or
2629 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2632 printk.time= Show timing data prefixed to each printk message line
2633 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2635 processor.max_cstate= [HW,ACPI]
2636 Limit processor to maximum C-state
2637 max_cstate=9 overrides any DMI blacklist limit.
2639 processor.nocst [HW,ACPI]
2640 Ignore the _CST method to determine C-states,
2641 instead using the legacy FADT method
2643 profile= [KNL] Enable kernel profiling via /proc/profile
2644 Format: [schedule,]<number>
2645 Param: "schedule" - profile schedule points.
2646 Param: <number> - step/bucket size as a power of 2 for
2647 statistical time based profiling.
2648 Param: "sleep" - profile D-state sleeping (millisecs).
2649 Requires CONFIG_SCHEDSTATS
2650 Param: "kvm" - profile VM exits.
2652 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2654 See Documentation/blockdev/ramdisk.txt.
2656 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2657 probe for; one of (bare|imps|exps|lifebook|any).
2658 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2660 psmouse.resetafter= [HW,MOUSE]
2661 Try to reset the device after so many bad packets
2664 [HW,MOUSE] Set desired mouse resolution, in dpi.
2665 psmouse.smartscroll=
2666 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2667 0 = disabled, 1 = enabled (default).
2669 pstore.backend= Specify the name of the pstore backend to use
2672 See Documentation/blockdev/paride.txt.
2675 [KNL] Number of legacy pty's. Overwrites compiled-in
2678 quiet [KNL] Disable most log messages
2683 See Documentation/md.txt.
2685 ramdisk_blocksize= [RAM]
2686 See Documentation/blockdev/ramdisk.txt.
2688 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2689 See Documentation/blockdev/ramdisk.txt.
2692 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2693 the specified list of CPUs to be no-callback CPUs.
2694 Invocation of these CPUs' RCU callbacks will
2695 be offloaded to "rcuox/N" kthreads created for
2696 that purpose, where "x" is "b" for RCU-bh, "p"
2697 for RCU-preempt, and "s" for RCU-sched, and "N"
2698 is the CPU number. This reduces OS jitter on the
2699 offloaded CPUs, which can be useful for HPC and
2700 real-time workloads. It can also improve energy
2701 efficiency for asymmetric multiprocessors.
2704 Rather than requiring that offloaded CPUs
2705 (specified by rcu_nocbs= above) explicitly
2706 awaken the corresponding "rcuoN" kthreads,
2707 make these kthreads poll for callbacks.
2708 This improves the real-time response for the
2709 offloaded CPUs by relieving them of the need to
2710 wake up the corresponding kthread, but degrades
2711 energy efficiency by requiring that the kthreads
2712 periodically wake up to do the polling.
2714 rcutree.blimit= [KNL]
2715 Set maximum number of finished RCU callbacks to
2716 process in one batch.
2718 rcutree.rcu_fanout_leaf= [KNL]
2719 Increase the number of CPUs assigned to each
2720 leaf rcu_node structure. Useful for very large
2723 rcutree.jiffies_till_first_fqs= [KNL]
2724 Set delay from grace-period initialization to
2725 first attempt to force quiescent states.
2726 Units are jiffies, minimum value is zero,
2727 and maximum value is HZ.
2729 rcutree.jiffies_till_next_fqs= [KNL]
2730 Set delay between subsequent attempts to force
2731 quiescent states. Units are jiffies, minimum
2732 value is one, and maximum value is HZ.
2734 rcutree.qhimark= [KNL]
2735 Set threshold of queued RCU callbacks beyond which
2736 batch limiting is disabled.
2738 rcutree.qlowmark= [KNL]
2739 Set threshold of queued RCU callbacks below which
2740 batch limiting is re-enabled.
2742 rcutree.rcu_idle_gp_delay= [KNL]
2743 Set wakeup interval for idle CPUs that have
2744 RCU callbacks (RCU_FAST_NO_HZ=y).
2746 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2747 Set wakeup interval for idle CPUs that have
2748 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2749 Lazy RCU callbacks are those which RCU can
2750 prove do nothing more than free memory.
2752 rcutorture.fqs_duration= [KNL]
2753 Set duration of force_quiescent_state bursts.
2755 rcutorture.fqs_holdoff= [KNL]
2756 Set holdoff time within force_quiescent_state bursts.
2758 rcutorture.fqs_stutter= [KNL]
2759 Set wait time between force_quiescent_state bursts.
2761 rcutorture.gp_exp= [KNL]
2762 Use expedited update-side primitives.
2764 rcutorture.gp_normal= [KNL]
2765 Use normal (non-expedited) update-side primitives.
2766 If both gp_exp and gp_normal are set, do both.
2767 If neither gp_exp nor gp_normal are set, still
2770 rcutorture.n_barrier_cbs= [KNL]
2771 Set callbacks/threads for rcu_barrier() testing.
2773 rcutorture.nfakewriters= [KNL]
2774 Set number of concurrent RCU writers. These just
2775 stress RCU, they don't participate in the actual
2776 test, hence the "fake".
2778 rcutorture.nreaders= [KNL]
2779 Set number of RCU readers.
2781 rcutorture.object_debug= [KNL]
2782 Enable debug-object double-call_rcu() testing.
2784 rcutorture.onoff_holdoff= [KNL]
2785 Set time (s) after boot for CPU-hotplug testing.
2787 rcutorture.onoff_interval= [KNL]
2788 Set time (s) between CPU-hotplug operations, or
2789 zero to disable CPU-hotplug testing.
2791 rcutorture.rcutorture_runnable= [BOOT]
2792 Start rcutorture running at boot time.
2794 rcutorture.shuffle_interval= [KNL]
2795 Set task-shuffle interval (s). Shuffling tasks
2796 allows some CPUs to go into dyntick-idle mode
2797 during the rcutorture test.
2799 rcutorture.shutdown_secs= [KNL]
2800 Set time (s) after boot system shutdown. This
2801 is useful for hands-off automated testing.
2803 rcutorture.stall_cpu= [KNL]
2804 Duration of CPU stall (s) to test RCU CPU stall
2805 warnings, zero to disable.
2807 rcutorture.stall_cpu_holdoff= [KNL]
2808 Time to wait (s) after boot before inducing stall.
2810 rcutorture.stat_interval= [KNL]
2811 Time (s) between statistics printk()s.
2813 rcutorture.stutter= [KNL]
2814 Time (s) to stutter testing, for example, specifying
2815 five seconds causes the test to run for five seconds,
2816 wait for five seconds, and so on. This tests RCU's
2817 ability to transition abruptly to and from idle.
2819 rcutorture.test_boost= [KNL]
2820 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2821 "Maybe" means test if the RCU implementation
2822 under test support RCU priority boosting.
2824 rcutorture.test_boost_duration= [KNL]
2825 Duration (s) of each individual boost test.
2827 rcutorture.test_boost_interval= [KNL]
2828 Interval (s) between each boost test.
2830 rcutorture.test_no_idle_hz= [KNL]
2831 Test RCU's dyntick-idle handling. See also the
2832 rcutorture.shuffle_interval parameter.
2834 rcutorture.torture_type= [KNL]
2835 Specify the RCU implementation to test.
2837 rcutorture.verbose= [KNL]
2838 Enable additional printk() statements.
2840 rcupdate.rcu_expedited= [KNL]
2841 Use expedited grace-period primitives, for
2842 example, synchronize_rcu_expedited() instead
2843 of synchronize_rcu(). This reduces latency,
2844 but can increase CPU utilization, degrade
2845 real-time latency, and degrade energy efficiency.
2847 rcupdate.rcu_cpu_stall_suppress= [KNL]
2848 Suppress RCU CPU stall warning messages.
2850 rcupdate.rcu_cpu_stall_timeout= [KNL]
2851 Set timeout for RCU CPU stall warning messages.
2855 Run specified binary instead of /init from the ramdisk,
2856 used for early userspace startup. See initrd.
2859 Format (x86 or x86_64):
2860 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2862 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2864 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2865 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2866 reboot_force is either force or not specified,
2867 reboot_cpu is s[mp]#### with #### being the processor
2868 to be used for rebooting.
2871 [KNL, SMP] Set scheduler's default relax_domain_level.
2872 See Documentation/cgroups/cpusets.txt.
2874 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2876 reservetop= [X86-32]
2878 Reserves a hole at the top of the kernel virtual
2883 Set the amount of memory to reserve for BIOS at
2884 the bottom of the address space.
2886 reset_devices [KNL] Force drivers to reset the underlying device
2887 during initialization.
2890 Specify the partition device for software suspend
2892 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2894 resume_offset= [SWSUSP]
2895 Specify the offset from the beginning of the partition
2896 given by "resume=" at which the swap header is located,
2897 in <PAGE_SIZE> units (needed only for swap files).
2898 See Documentation/power/swsusp-and-swap-files.txt
2900 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2901 read the resume files
2903 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2904 Useful for devices that are detected asynchronously
2905 (e.g. USB and MMC devices).
2907 hibernate= [HIBERNATION]
2908 noresume Don't check if there's a hibernation image
2909 present during boot.
2910 nocompress Don't compress/decompress hibernation images.
2912 retain_initrd [RAM] Keep initrd memory after extraction
2914 rhash_entries= [KNL,NET]
2915 Set number of hash buckets for route cache
2917 riscom8= [HW,SERIAL]
2918 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2920 ro [KNL] Mount root device read-only on boot
2922 root= [KNL] Root filesystem
2923 See name_to_dev_t comment in init/do_mounts.c.
2925 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2926 mount the root filesystem
2928 rootflags= [KNL] Set root filesystem mount option string
2930 rootfstype= [KNL] Set root filesystem type
2932 rootwait [KNL] Wait (indefinitely) for root device to show up.
2933 Useful for devices that are detected asynchronously
2934 (e.g. USB and MMC devices).
2936 rproc_mem=nn[KMG][@address]
2937 [KNL,ARM,CMA] Remoteproc physical memory block.
2938 Memory area to be used by remote processor image,
2941 rw [KNL] Mount root device read-write on boot
2943 S [KNL] Run init in single mode
2946 See drivers/net/irda/sa1100_ir.c.
2948 sbni= [NET] Granch SBNI12 leased line adapter
2950 sched_debug [KNL] Enables verbose scheduler debug messages.
2952 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2953 xtime_lock contention on larger systems, and/or RCU lock
2954 contention on all systems with CONFIG_MAXSMP set.
2955 Format: { "0" | "1" }
2956 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2958 Note: increases power consumption, thus should only be
2959 enabled if running jitter sensitive (HPC/RT) workloads.
2961 security= [SECURITY] Choose a security module to enable at boot.
2962 If this boot parameter is not specified, only the first
2963 security module asking for security registration will be
2964 loaded. An invalid security module name will be treated
2965 as if no module has been chosen.
2967 selinux= [SELINUX] Disable or enable SELinux at boot time.
2968 Format: { "0" | "1" }
2969 See security/selinux/Kconfig help text.
2972 Default value is set via kernel config option.
2973 If enabled at boot time, /selinux/disable can be used
2974 later to disable prior to initial policy load.
2976 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2977 Format: { "0" | "1" }
2978 See security/apparmor/Kconfig help text
2981 Default value is set via kernel config option.
2983 serialnumber [BUGS=X86-32]
2986 Maximal number of shapers.
2988 show_msr= [x86] show boot-time MSR settings
2989 Format: { <integer> }
2990 Show boot-time (BIOS-initialized) MSR settings.
2991 The parameter means the number of CPUs to show,
2992 for example 1 means boot CPU only.
2999 slab_max_order= [MM, SLAB]
3000 Determines the maximum allowed order for slabs.
3001 A high setting may cause OOMs due to memory
3002 fragmentation. Defaults to 1 for systems with
3003 more than 32MB of RAM, 0 otherwise.
3005 slub_debug[=options[,slabs]] [MM, SLUB]
3006 Enabling slub_debug allows one to determine the
3007 culprit if slab objects become corrupted. Enabling
3008 slub_debug can create guard zones around objects and
3009 may poison objects when not in use. Also tracks the
3010 last alloc / free. For more information see
3011 Documentation/vm/slub.txt.
3013 slub_max_order= [MM, SLUB]
3014 Determines the maximum allowed order for slabs.
3015 A high setting may cause OOMs due to memory
3016 fragmentation. For more information see
3017 Documentation/vm/slub.txt.
3019 slub_min_objects= [MM, SLUB]
3020 The minimum number of objects per slab. SLUB will
3021 increase the slab order up to slub_max_order to
3022 generate a sufficiently large slab able to contain
3023 the number of objects indicated. The higher the number
3024 of objects the smaller the overhead of tracking slabs
3025 and the less frequently locks need to be acquired.
3026 For more information see Documentation/vm/slub.txt.
3028 slub_min_order= [MM, SLUB]
3029 Determines the minimum page order for slabs. Must be
3030 lower than slub_max_order.
3031 For more information see Documentation/vm/slub.txt.
3033 slub_nomerge [MM, SLUB]
3034 Disable merging of slabs with similar size. May be
3035 necessary if there is some reason to distinguish
3036 allocs to different slabs. Debug options disable
3037 merging on their own.
3038 For more information see Documentation/vm/slub.txt.
3041 Format: <io1>[,<io2>[,...,<io8>]]
3043 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3044 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3045 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3046 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3047 smsc-ircc2.ircc_irq= [HW] IRQ line
3048 smsc-ircc2.ircc_dma= [HW] DMA channel
3049 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3050 0: Toshiba Satellite 1800 (GP data pin select)
3051 1: Fast pin select (default)
3055 [KNL] Should the soft-lockup detector generate panics.
3058 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3059 See Documentation/laptops/sonypi.txt
3061 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3062 See Documentation/serial/specialix.txt.
3064 spia_io_base= [HW,MTD]
3070 Enabled the stack tracer on boot up.
3072 stacktrace_filter=[function-list]
3073 [FTRACE] Limit the functions that the stack tracer
3074 will trace at boot up. function-list is a comma separated
3075 list of functions. This list can be changed at run
3076 time by the stack_trace_filter file in the debugfs
3077 tracing directory. Note, this enables stack tracing
3078 and the stacktrace above is not needed.
3082 Set the STI (builtin display/keyboard on the HP-PARISC
3083 machines) console (graphic card) which should be used
3084 as the initial boot-console.
3085 See also comment in drivers/video/console/sticore.c.
3088 See comment in drivers/video/console/sticore.c.
3091 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3093 sunrpc.min_resvport=
3094 sunrpc.max_resvport=
3096 SunRPC servers often require that client requests
3097 originate from a privileged port (i.e. a port in the
3098 range 0 < portnr < 1024).
3099 An administrator who wishes to reserve some of these
3100 ports for other uses may adjust the range that the
3101 kernel's sunrpc client considers to be privileged
3102 using these two parameters to set the minimum and
3103 maximum port values.
3107 Control how the NFS server code allocates CPUs to
3108 service thread pools. Depending on how many NICs
3109 you have and where their interrupts are bound, this
3110 option will affect which CPUs will do NFS serving.
3111 Note: this parameter cannot be changed while the
3112 NFS server is running.
3114 auto the server chooses an appropriate mode
3115 automatically using heuristics
3116 global a single global pool contains all CPUs
3117 percpu one pool for each CPU
3118 pernode one pool for each NUMA node (equivalent
3119 to global on non-NUMA machines)
3121 sunrpc.tcp_slot_table_entries=
3122 sunrpc.udp_slot_table_entries=
3124 Sets the upper limit on the number of simultaneous
3125 RPC calls that can be sent from the client to a
3126 server. Increasing these values may allow you to
3127 improve throughput, but will also increase the
3128 amount of memory reserved for use by the client.
3131 [KNL] Enable accounting of swap in memory resource
3132 controller if no parameter or 1 is given or disable
3133 it if 0 is given (See Documentation/cgroups/memory.txt)
3135 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3136 Format: { <int> | force }
3137 <int> -- Number of I/O TLB slabs
3138 force -- force using of bounce buffers even if they
3139 wouldn't be automatically used by the kernel
3143 sysfs.deprecated=0|1 [KNL]
3144 Enable/disable old style sysfs layout for old udev
3145 on older distributions. When this option is enabled
3146 very new udev will not work anymore. When this option
3147 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3148 in older udev will not work anymore.
3149 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3150 the kernel configuration.
3152 sysrq_always_enabled
3154 Ignore sysrq setting - this boot parameter will
3155 neutralize any effect of /proc/sys/kernel/sysrq.
3156 Useful for debugging.
3160 test_suspend= [SUSPEND]
3161 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3162 standby suspend) as the system sleep state to briefly
3163 enter during system startup. The system is woken from
3164 this state using a wakeup-capable RTC alarm.
3166 thash_entries= [KNL,NET]
3167 Set number of hash buckets for TCP connection
3169 thermal.act= [HW,ACPI]
3170 -1: disable all active trip points in all thermal zones
3171 <degrees C>: override all lowest active trip points
3173 thermal.crt= [HW,ACPI]
3174 -1: disable all critical trip points in all thermal zones
3175 <degrees C>: override all critical trip points
3177 thermal.nocrt= [HW,ACPI]
3178 Set to disable actions on ACPI thermal zone
3179 critical and hot trip points.
3181 thermal.off= [HW,ACPI]
3182 1: disable ACPI thermal control
3184 thermal.psv= [HW,ACPI]
3185 -1: disable all passive trip points
3186 <degrees C>: override all passive trip points to this
3189 thermal.tzp= [HW,ACPI]
3190 Specify global default ACPI thermal zone polling rate
3191 <deci-seconds>: poll all this frequency
3192 0: no polling (default)
3195 Force threading of all interrupt handlers except those
3196 marked explicitly IRQF_NO_THREAD.
3199 Enable the Transcendent memory driver if built-in.
3201 tmem.cleancache=0|1 [KNL, XEN]
3202 Default is on (1). Disable the usage of the cleancache
3203 API to send anonymous pages to the hypervisor.
3205 tmem.frontswap=0|1 [KNL, XEN]
3206 Default is on (1). Disable the usage of the frontswap
3207 API to send swap pages to the hypervisor. If disabled
3208 the selfballooning and selfshrinking are force disabled.
3210 tmem.selfballooning=0|1 [KNL, XEN]
3211 Default is on (1). Disable the driving of swap pages
3214 tmem.selfshrinking=0|1 [KNL, XEN]
3215 Default is on (1). Partial swapoff that immediately
3216 transfers pages from Xen hypervisor back to the
3217 kernel based on different criteria.
3221 Specify if the kernel should make use of the cpu
3222 topology information if the hardware supports this.
3223 The scheduler will make use of this information and
3224 e.g. base its process migration decisions on it.
3229 tpm_suspend_pcr=[HW,TPM]
3230 Format: integer pcr id
3231 Specify that at suspend time, the tpm driver
3232 should extend the specified pcr with zeros,
3233 as a workaround for some chips which fail to
3234 flush the last written pcr on TPM_SaveState.
3235 This will guarantee that all the other pcrs
3238 trace_buf_size=nn[KMG]
3239 [FTRACE] will set tracing buffer size.
3241 trace_event=[event-list]
3242 [FTRACE] Set and start specified trace events in order
3243 to facilitate early boot debugging.
3244 See also Documentation/trace/events.txt
3246 trace_options=[option-list]
3247 [FTRACE] Enable or disable tracer options at boot.
3248 The option-list is a comma delimited list of options
3249 that can be enabled or disabled just as if you were
3250 to echo the option name into
3252 /sys/kernel/debug/tracing/trace_options
3254 For example, to enable stacktrace option (to dump the
3255 stack trace of each event), add to the command line:
3257 trace_options=stacktrace
3259 See also Documentation/trace/ftrace.txt "trace options"
3263 [FTRACE] enable this option to disable tracing when a
3264 warning is hit. This turns off "tracing_on". Tracing can
3265 be enabled again by echoing '1' into the "tracing_on"
3266 file located in /sys/kernel/debug/tracing/
3268 This option is useful, as it disables the trace before
3269 the WARNING dump is called, which prevents the trace to
3270 be filled with content caused by the warning output.
3272 This option can also be set at run time via the sysctl
3273 option: kernel/traceoff_on_warning
3275 transparent_hugepage=
3277 Format: [always|madvise|never]
3278 Can be used to control the default behavior of the system
3279 with respect to transparent hugepages.
3280 See Documentation/vm/transhuge.txt for more details.
3282 tsc= Disable clocksource stability checks for TSC.
3284 [x86] reliable: mark tsc clocksource as reliable, this
3285 disables clocksource verification at runtime, as well
3286 as the stability checks done at bootup. Used to enable
3287 high-resolution timer mode on older hardware, and in
3288 virtualized environment.
3289 [x86] noirqtime: Do not use TSC to do irq accounting.
3290 Used to run time disable IRQ_TIME_ACCOUNTING on any
3291 platforms where RDTSC is slow and this accounting
3294 turbografx.map[2|3]= [HW,JOY]
3295 TurboGraFX parallel port interface
3297 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3298 See also Documentation/input/joystick-parport.txt
3300 udbg-immortal [PPC] When debugging early kernel crashes that
3301 happen after console_init() and before a proper
3302 console driver takes over, this boot options might
3303 help "seeing" what's going on.
3305 uhash_entries= [KNL,NET]
3306 Set number of hash buckets for UDP/UDP-Lite connections
3309 [USB] Ignore overcurrent events (default N).
3310 Some badly-designed motherboards generate lots of
3311 bogus events, for ports that aren't wired to
3312 anything. Set this parameter to avoid log spamming.
3313 Note that genuine overcurrent events won't be
3317 [X86] Cause panic on unknown NMI.
3319 usbcore.authorized_default=
3320 [USB] Default USB device authorization:
3321 (default -1 = authorized except for wireless USB,
3322 0 = not authorized, 1 = authorized)
3324 usbcore.autosuspend=
3325 [USB] The autosuspend time delay (in seconds) used
3326 for newly-detected USB devices (default 2). This
3327 is the time required before an idle device will be
3328 autosuspended. Devices for which the delay is set
3329 to a negative value won't be autosuspended at all.
3331 usbcore.usbfs_snoop=
3332 [USB] Set to log all usbfs traffic (default 0 = off).
3334 usbcore.blinkenlights=
3335 [USB] Set to cycle leds on hubs (default 0 = off).
3337 usbcore.old_scheme_first=
3338 [USB] Start with the old device initialization
3339 scheme (default 0 = off).
3341 usbcore.usbfs_memory_mb=
3342 [USB] Memory limit (in MB) for buffers allocated by
3343 usbfs (default = 16, 0 = max = 2047).
3345 usbcore.use_both_schemes=
3346 [USB] Try the other device initialization scheme
3347 if the first one fails (default 1 = enabled).
3349 usbcore.initial_descriptor_timeout=
3350 [USB] Specifies timeout for the initial 64-byte
3351 USB_REQ_GET_DESCRIPTOR request in milliseconds
3352 (default 5000 = 5.0 seconds).
3355 [USBHID] The interval which mice are to be polled at.
3357 usb-storage.delay_use=
3358 [UMS] The delay in seconds before a new device is
3359 scanned for Logical Units (default 5).
3362 [UMS] A list of quirks entries to supplement or
3363 override the built-in unusual_devs list. List
3364 entries are separated by commas. Each entry has
3365 the form VID:PID:Flags where VID and PID are Vendor
3366 and Product ID values (4-digit hex numbers) and
3367 Flags is a set of characters, each corresponding
3368 to a common usb-storage quirk flag as follows:
3369 a = SANE_SENSE (collect more than 18 bytes
3371 b = BAD_SENSE (don't collect more than 18
3372 bytes of sense data);
3373 c = FIX_CAPACITY (decrease the reported
3374 device capacity by one sector);
3375 d = NO_READ_DISC_INFO (don't use
3376 READ_DISC_INFO command);
3377 e = NO_READ_CAPACITY_16 (don't use
3378 READ_CAPACITY_16 command);
3379 h = CAPACITY_HEURISTICS (decrease the
3380 reported device capacity by one
3381 sector if the number is odd);
3382 i = IGNORE_DEVICE (don't bind to this
3384 l = NOT_LOCKABLE (don't try to lock and
3385 unlock ejectable media);
3386 m = MAX_SECTORS_64 (don't transfer more
3387 than 64 sectors = 32 KB at a time);
3388 n = INITIAL_READ10 (force a retry of the
3389 initial READ(10) command);
3390 o = CAPACITY_OK (accept the capacity
3391 reported by the device);
3392 p = WRITE_CACHE (the device cache is ON
3394 r = IGNORE_RESIDUE (the device reports
3395 bogus residue values);
3396 s = SINGLE_LUN (the device has only one
3398 w = NO_WP_DETECT (don't test whether the
3399 medium is write-protected).
3400 Example: quirks=0419:aaf5:rl,0421:0433:rc
3402 user_debug= [KNL,ARM]
3404 See arch/arm/Kconfig.debug help text.
3405 1 - undefined instruction events
3407 4 - invalid data aborts
3410 Example: user_debug=31
3413 [X86] Flags controlling user PTE allocations.
3415 nohigh = do not allocate PTE pages in
3416 HIGHMEM regardless of setting
3420 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3421 vdso=1: enable VDSO (default)
3422 vdso=0: disable VDSO mapping
3425 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3426 vdso32=1: enable 32-bit VDSO (default)
3427 vdso32=0: disable 32-bit VDSO mapping
3430 vector=percpu: enable percpu vector domain
3432 video= [FB] Frame buffer configuration
3433 See Documentation/fb/modedb.txt.
3435 video.brightness_switch_enabled= [0,1]
3436 If set to 1, on receiving an ACPI notify event
3437 generated by hotkey, video driver will adjust brightness
3438 level and then send out the event to user space through
3439 the allocated input device; If set to 0, video driver
3440 will only send out the event without touching backlight
3445 [VMMIO] Memory mapped virtio (platform) device.
3447 <size>@<baseaddr>:<irq>[:<id>]
3449 <size> := size (can use standard suffixes
3451 <baseaddr> := physical base address
3452 <irq> := interrupt number (as passed to
3454 <id> := (optional) platform device id
3456 virtio_mmio.device=1K@0x100b0000:48:7
3458 Can be used multiple times for multiple devices.
3460 vga= [BOOT,X86-32] Select a particular video mode
3461 See Documentation/x86/boot.txt and
3462 Documentation/svga.txt.
3463 Use vga=ask for menu.
3464 This is actually a boot loader parameter; the value is
3465 passed to the kernel using a special protocol.
3467 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3468 size of <nn>. This can be used to increase the
3469 minimum size (128MB on x86). It can also be used to
3470 decrease the size and leave more room for directly
3473 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3476 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3479 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3483 Controls the behavior of vsyscalls (i.e. calls to
3484 fixed addresses of 0xffffffffff600x00 from legacy
3485 code). Most statically-linked binaries and older
3486 versions of glibc use these calls. Because these
3487 functions are at fixed addresses, they make nice
3488 targets for exploits that can control RIP.
3490 emulate [default] Vsyscalls turn into traps and are
3491 emulated reasonably safely.
3493 native Vsyscalls are native syscall instructions.
3494 This is a little bit faster than trapping
3495 and makes a few dynamic recompilers work
3496 better than they would in emulation mode.
3497 It also makes exploits much easier to write.
3499 none Vsyscalls don't work at all. This makes
3500 them quite hard to use for exploits but
3501 might break your system.
3503 vt.color= [VT] Default text color.
3504 Format: 0xYX, X = foreground, Y = background.
3505 Default: 0x07 = light gray on black.
3507 vt.cur_default= [VT] Default cursor shape.
3508 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3509 the parameters of the <Esc>[?A;B;Cc escape sequence;
3510 see VGA-softcursor.txt. Default: 2 = underline.
3512 vt.default_blu= [VT]
3513 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3514 Change the default blue palette of the console.
3515 This is a 16-member array composed of values
3518 vt.default_grn= [VT]
3519 Format: <green0>,<green1>,<green2>,...,<green15>
3520 Change the default green palette of the console.
3521 This is a 16-member array composed of values
3524 vt.default_red= [VT]
3525 Format: <red0>,<red1>,<red2>,...,<red15>
3526 Change the default red palette of the console.
3527 This is a 16-member array composed of values
3533 Set system-wide default UTF-8 mode for all tty's.
3534 Default is 1, i.e. UTF-8 mode is enabled for all
3535 newly opened terminals.
3537 vt.global_cursor_default=
3540 Set system-wide default for whether a cursor
3541 is shown on new VTs. Default is -1,
3542 i.e. cursors will be created by default unless
3543 overridden by individual drivers. 0 will hide
3544 cursors, 1 will display them.
3546 vt.italic= [VT] Default color for italic text; 0-15.
3549 vt.underline= [VT] Default color for underlined text; 0-15.
3552 watchdog timers [HW,WDT] For information on watchdog timers,
3553 see Documentation/watchdog/watchdog-parameters.txt
3554 or other driver-specific files in the
3555 Documentation/watchdog/ directory.
3557 workqueue.disable_numa
3558 By default, all work items queued to unbound
3559 workqueues are affine to the NUMA nodes they're
3560 issued on, which results in better behavior in
3561 general. If NUMA affinity needs to be disabled for
3562 whatever reason, this option can be used. Note
3563 that this also can be controlled per-workqueue for
3564 workqueues visible under /sys/bus/workqueue/.
3566 workqueue.power_efficient
3567 Per-cpu workqueues are generally preferred because
3568 they show better performance thanks to cache
3569 locality; unfortunately, per-cpu workqueues tend to
3570 be more power hungry than unbound workqueues.
3572 Enabling this makes the per-cpu workqueues which
3573 were observed to contribute significantly to power
3574 consumption unbound, leading to measurably lower
3575 power usage at the cost of small performance
3578 The default value of this parameter is determined by
3579 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3581 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3582 default x2apic cluster mode on platforms
3585 x86_intel_mid_timer= [X86-32,APBT]
3586 Choose timer option for x86 Intel MID platform.
3587 Two valid options are apbt timer only and lapic timer
3588 plus one apbt timer for broadcast timer.
3589 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3591 xen_emul_unplug= [HW,X86,XEN]
3592 Unplug Xen emulated devices
3593 Format: [unplug0,][unplug1]
3594 ide-disks -- unplug primary master IDE devices
3595 aux-ide-disks -- unplug non-primary-master IDE devices
3596 nics -- unplug network devices
3597 all -- unplug all emulated devices (NICs and IDE disks)
3598 unnecessary -- unplugging emulated devices is
3599 unnecessary even if the host did not respond to
3601 never -- do not unplug even if version check succeeds
3603 xen_nopvspin [X86,XEN]
3604 Disables the ticketlock slowpath using Xen PV
3607 xirc2ps_cs= [NET,PCMCIA]
3609 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3611 ______________________________________________________________________
3615 Add more DRM drivers.