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 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 baycom_epp= [HW,AX25]
469 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
471 See header of drivers/net/hamradio/baycom_par.c.
473 baycom_ser_fdx= [HW,AX25]
474 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
475 Format: <io>,<irq>,<mode>[,<baud>]
476 See header of drivers/net/hamradio/baycom_ser_fdx.c.
478 baycom_ser_hdx= [HW,AX25]
479 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
480 Format: <io>,<irq>,<mode>
481 See header of drivers/net/hamradio/baycom_ser_hdx.c.
483 blkdevparts= Manual partition parsing of block device(s) for
484 embedded devices based on command line input.
485 See Documentation/block/cmdline-partition.txt
487 boot_delay= Milliseconds to delay each printk during boot.
488 Values larger than 10 seconds (10000) are changed to
492 bootmem_debug [KNL] Enable bootmem allocator debug messages.
494 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
495 bttv.radio= Most important insmod options are available as
497 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
500 bulk_remove=off [PPC] This parameter disables the use of the pSeries
501 firmware feature for flushing multiple hpte entries
504 c101= [NET] Moxa C101 synchronous serial card
506 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
507 Sometimes CPU hardware bugs make them report the cache
508 size incorrectly. The kernel will attempt work arounds
509 to fix known problems, but for some CPUs it is not
510 possible to determine what the correct size should be.
511 This option provides an override for these situations.
513 ccw_timeout_log [S390]
514 See Documentation/s390/CommonIO for details.
516 cgroup_disable= [KNL] Disable a particular controller
517 Format: {name of the controller(s) to disable}
518 {Currently supported controllers - "memory"}
520 checkreqprot [SELINUX] Set initial checkreqprot flag value.
521 Format: { "0" | "1" }
522 See security/selinux/Kconfig help text.
523 0 -- check protection applied by kernel (includes
524 any implied execute protection).
525 1 -- check protection requested by application.
526 Default value is set via a kernel config option.
527 Value can be changed at runtime via
528 /selinux/checkreqprot.
531 See Documentation/s390/CommonIO for details.
534 Keep all clocks already enabled by bootloader on,
535 even if no driver has claimed them. This is useful
536 for debug and development, but should not be
537 needed on a platform with proper driver support.
538 For more information, see Documentation/clk.txt.
540 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
542 Forces specified clocksource (if available) to be used
543 when calculating gettimeofday(). If specified
544 clocksource is not available, it defaults to PIT.
545 Format: { pit | tsc | cyclone | pmtmr }
547 clocksource= Override the default clocksource
549 Override the default clocksource and use the clocksource
550 with the name specified.
551 Some clocksource names to choose from, depending on
553 [all] jiffies (this is the base, fallback clocksource)
555 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
556 pxa_timer,timer3,32k_counter,timer0_1
558 [X86-32] pit,hpet,tsc;
559 scx200_hrt on Geode; cyclone on IBM x440
567 clearcpuid=BITNUM [X86]
568 Disable CPUID feature X for the kernel. See
569 arch/x86/include/asm/cpufeature.h for the valid bit
570 numbers. Note the Linux specific bits are not necessarily
571 stable over kernel options, but the vendor specific
573 Also note that user programs calling CPUID directly
574 or using the feature without checking anything
575 will still see it. This just prevents it from
576 being used by the kernel or shown in /proc/cpuinfo.
577 Also note the kernel might malfunction if you disable
581 Sets the size of kernel global memory area for contiguous
582 memory allocations. For more information, see
583 include/linux/dma-contiguous.h
585 cmo_free_hint= [PPC] Format: { yes | no }
586 Specify whether pages are marked as being inactive
587 when they are freed. This is used in CMO environments
588 to determine OS memory pressure for page stealing by
592 coherent_pool=nn[KMG] [ARM,KNL]
593 Sets the size of memory pool for coherent, atomic dma
594 allocations, by default set to 256K.
596 code_bytes [X86] How many bytes of object code to print
601 com20020= [HW,NET] ARCnet - COM20020 chipset
603 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
605 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
609 ARCnet - COM90xx chipset (memory-mapped buffers)
610 Format: <io>[,<irq>[,<memstart>]]
612 condev= [HW,S390] console device
615 console= [KNL] Output console device and options.
617 tty<n> Use the virtual console device <n>.
621 Use the specified serial port. The options are of
622 the form "bbbbpnf", where "bbbb" is the baud rate,
623 "p" is parity ("n", "o", or "e"), "n" is number of
624 bits, and "f" is flow control ("r" for RTS or
625 omit it). Default is "9600n8".
627 See Documentation/serial-console.txt for more
629 Documentation/networking/netconsole.txt for an
632 uart[8250],io,<addr>[,options]
633 uart[8250],mmio,<addr>[,options]
634 Start an early, polled-mode console on the 8250/16550
635 UART at the specified I/O port or MMIO address,
636 switching to the matching ttyS device later. The
637 options are the same as for ttyS, above.
638 hvc<n> Use the hypervisor console device <n>. This is for
639 both Xen and PowerPC hypervisors.
641 If the device connected to the port is not a TTY but a braille
642 device, prepend "brl," before the device type, for instance
644 For now, only VisioBraille is supported.
646 consoleblank= [KNL] The console blank (screen saver) timeout in
647 seconds. Defaults to 10*60 = 10mins. A value of 0
648 disables the blank timer.
651 [KNL] Change the default value for
652 /proc/<pid>/coredump_filter.
653 See also Documentation/filesystems/proc.txt.
655 cpuidle.off=1 [CPU_IDLE]
656 disable the cpuidle sub-system
658 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
660 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
662 crashkernel=size[KMG][@offset[KMG]]
663 [KNL] Using kexec, Linux can switch to a 'crash kernel'
664 upon panic. This parameter reserves the physical
665 memory region [offset, offset + size] for that kernel
666 image. If '@offset' is omitted, then a suitable offset
667 is selected automatically. Check
668 Documentation/kdump/kdump.txt for further details.
670 crashkernel=range1:size1[,range2:size2,...][@offset]
671 [KNL] Same as above, but depends on the memory
672 in the running system. The syntax of range is
673 start-[end] where start and end are both
674 a memory unit (amount[KMG]). See also
675 Documentation/kdump/kdump.txt for an example.
677 crashkernel=size[KMG],high
678 [KNL, x86_64] range could be above 4G. Allow kernel
679 to allocate physical memory region from top, so could
680 be above 4G if system have more than 4G ram installed.
681 Otherwise memory region will be allocated below 4G, if
683 It will be ignored if crashkernel=X is specified.
684 crashkernel=size[KMG],low
685 [KNL, x86_64] range under 4G. When crashkernel=X,high
686 is passed, kernel could allocate physical memory region
687 above 4G, that cause second kernel crash on system
688 that require some amount of low memory, e.g. swiotlb
689 requires at least 64M+32K low memory. Kernel would
690 try to allocate 72M below 4G automatically.
691 This one let user to specify own low range under 4G
692 for second kernel instead.
693 0: to disable low allocation.
694 It will be ignored when crashkernel=X,high is not used
695 or memory reserved is below 4G.
700 cs89x0_media= [HW,NET]
701 Format: { rj45 | aui | bnc }
704 See header of drivers/s390/block/dasd_devmap.c.
706 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
707 (one device per port)
708 Format: <port#>,<type>
709 See also Documentation/input/joystick-parport.txt
711 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
712 time. See Documentation/dynamic-debug-howto.txt for
713 details. Deprecated, see dyndbg.
715 debug [KNL] Enable kernel debugging (events log level).
718 [KNL] verbose self-tests
720 Print debugging info while doing the locking API
722 We default to 0 (no extra messages), setting it to
723 1 will print _a lot_ more information - normally
724 only useful to kernel developers.
726 debug_objects [KNL] Enable object debugging
729 [KNL] Disable object debugging
731 debug_guardpage_minorder=
732 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
733 parameter allows control of the order of pages that will
734 be intentionally kept free (and hence protected) by the
735 buddy allocator. Bigger value increase the probability
736 of catching random memory corruption, but reduce the
737 amount of memory for normal system use. The maximum
738 possible value is MAX_ORDER/2. Setting this parameter
739 to 1 or 2 should be enough to identify most random
740 memory corruption problems caused by bugs in kernel or
741 driver code when a CPU writes to (or reads from) a
742 random memory location. Note that there exists a class
743 of memory corruptions problems caused by buggy H/W or
744 F/W or by drivers badly programing DMA (basically when
745 memory is written at bus level and the CPU MMU is
746 bypassed) which are not detectable by
747 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
748 tracking down these problems.
750 debugpat [X86] Enable PAT debugging
752 decnet.addr= [HW,NET]
753 Format: <area>[,<node>]
754 See also Documentation/networking/decnet.txt.
757 [same as hugepagesz=] The size of the default
758 HugeTLB page size. This is the size represented by
759 the legacy /proc/ hugepages APIs, used for SHM, and
760 default size when mounting hugetlbfs filesystems.
761 Defaults to the default architecture's huge page size
765 Set number of hash buckets for dentry cache.
768 IO parameters + enable/disable command.
770 digiepca= [HW,SERIAL]
771 See drivers/char/README.epca and
772 Documentation/serial/digiepca.txt.
775 See Documentation/networking/ipv6.txt.
777 disable_ddw [PPC/PSERIES]
778 Disable Dynamic DMA Window support. Use this if
779 to workaround buggy firmware.
782 See Documentation/networking/ipv6.txt.
784 disable_mtrr_cleanup [X86]
785 The kernel tries to adjust MTRR layout from continuous
786 to discrete, to make X server driver able to add WB
787 entry later. This parameter disables that.
789 disable_mtrr_trim [X86, Intel and AMD only]
790 By default the kernel will trim any uncacheable
791 memory out of your available memory pool based on
792 MTRR settings. This parameter disables that behavior,
793 possibly causing your machine to run very slowly.
795 disable_timer_pin_1 [X86]
796 Disable PIN 1 of APIC timer
797 Can be useful to work around chipset bugs.
799 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
800 this option disables the debugging code at boot.
802 dma_debug_entries=<number>
803 This option allows to tune the number of preallocated
804 entries for DMA-API debugging code. One entry is
805 required per DMA-API allocation. Use this if the
806 DMA-API debugging code disables itself because the
807 architectural default is too low.
809 dma_debug_driver=<driver_name>
810 With this option the DMA-API debugging driver
811 filter feature can be enabled at boot time. Just
812 pass the driver to filter for as the parameter.
813 The filter can be disabled or changed to another
814 driver later using sysfs.
816 drm_kms_helper.edid_firmware=[<connector>:]<file>
817 Broken monitors, graphic adapters and KVMs may
818 send no or incorrect EDID data sets. This parameter
819 allows to specify an EDID data set in the
820 /lib/firmware directory that is used instead.
821 Generic built-in EDID data sets are used, if one of
822 edid/1024x768.bin, edid/1280x1024.bin,
823 edid/1680x1050.bin, or edid/1920x1080.bin is given
824 and no file with the same name exists. Details and
825 instructions how to build your own EDID data are
826 available in Documentation/EDID/HOWTO.txt. An EDID
827 data set will only be used for a particular connector,
828 if its name and a colon are prepended to the EDID
833 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
834 module.dyndbg[="val"]
835 Enable debug messages at boot time. See
836 Documentation/dynamic-debug-howto.txt for details.
838 earlycon= [KNL] Output early console device and options.
839 uart[8250],io,<addr>[,options]
840 uart[8250],mmio,<addr>[,options]
841 uart[8250],mmio32,<addr>[,options]
842 Start an early, polled-mode console on the 8250/16550
843 UART at the specified I/O port or MMIO address.
844 MMIO inter-register address stride is either 8-bit
845 (mmio) or 32-bit (mmio32).
846 The options are the same as for ttyS, above.
848 earlyprintk= [X86,SH,BLACKFIN,ARM]
852 earlyprintk=serial[,ttySn[,baudrate]]
853 earlyprintk=serial[,0x...[,baudrate]]
854 earlyprintk=ttySn[,baudrate]
855 earlyprintk=dbgp[debugController#]
857 earlyprintk is useful when the kernel crashes before
858 the normal console is initialized. It is not enabled by
859 default because it has some cosmetic problems.
861 Append ",keep" to not disable it when the real console
864 Only one of vga, efi, serial, or usb debug port can
867 Currently only ttyS0 and ttyS1 may be specified by
868 name. Other I/O ports may be explicitly specified
869 on some architectures (x86 and arm at least) by
870 replacing ttySn with an I/O port address, like this:
871 earlyprintk=serial,0x1008,115200
872 You can find the port for a given device in
873 /proc/tty/driver/serial:
874 2: uart:ST16650V2 port:00001008 irq:18 ...
876 Interaction with the standard serial driver is not
879 The VGA and EFI output is eventually overwritten by
882 The xen output can only be used by Xen PV guests.
884 ekgdboc= [X86,KGDB] Allow early kernel console debugging
887 This is designed to be used in conjunction with
888 the boot argument: earlyprintk=vga
891 Format: {"off" | "on" | "skip[mbr]"}
894 Format: { "old_map" }
895 old_map [X86-64]: switch to the old ioremap-based EFI
896 runtime services mapping. 32-bit still uses this one by
899 efi_no_storage_paranoia [EFI; X86]
900 Using this parameter you can use more than 50% of
901 your efi variable storage. Use this parameter only if
902 you are really sure that your UEFI does sane gc and
903 fulfills the spec otherwise your board may brick.
905 eisa_irq_edge= [PARISC,HW]
906 See header of drivers/parisc/eisa.c.
909 See comment before function elanfreq_setup() in
910 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
913 Format: {"cfq" | "deadline" | "noop"}
914 See Documentation/block/cfq-iosched.txt and
915 Documentation/block/deadline-iosched.txt for details.
917 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
918 Specifies physical address of start of kernel core
919 image elf header and optionally the size. Generally
920 kexec loader will pass this option to capture kernel.
921 See Documentation/kdump/kdump.txt for details.
923 enable_mtrr_cleanup [X86]
924 The kernel tries to adjust MTRR layout from continuous
925 to discrete, to make X server driver able to add WB
926 entry later. This parameter enables that.
928 enable_timer_pin_1 [X86]
929 Enable PIN 1 of APIC timer
930 Can be useful to work around chipset bugs
931 (in particular on some ATI chipsets).
932 The kernel tries to set a reasonable default.
934 enforcing [SELINUX] Set initial enforcing status.
936 See security/selinux/Kconfig help text.
937 0 -- permissive (log only, no denials).
938 1 -- enforcing (deny and log).
940 Value can be changed at runtime via /selinux/enforce.
943 Disable Error Record Serialization Table (ERST)
946 ether= [HW,NET] Ethernet cards parameters
947 This option is obsoleted by the "netdev=" option, which
948 has equivalent usage. See its documentation for details.
952 Permit 'security.evm' to be updated regardless of
953 current integrity status.
957 fail_make_request=[KNL]
958 General fault injection mechanism.
959 Format: <interval>,<probability>,<space>,<times>
960 See also Documentation/fault-injection/.
963 See Documentation/blockdev/floppy.txt.
965 force_pal_cache_flush
966 [IA-64] Avoid check_sal_cache_flush which may hang on
967 buggy SAL_CACHE_FLUSH implementations. Using this
968 parameter will force ia64_sal_cache_flush to call
969 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
972 [FTRACE] will set and start the specified tracer
973 as early as possible in order to facilitate early
976 ftrace_dump_on_oops[=orig_cpu]
977 [FTRACE] will dump the trace buffers on oops.
978 If no parameter is passed, ftrace will dump
979 buffers of all CPUs, but if you pass orig_cpu, it will
980 dump only the buffer of the CPU that triggered the
983 ftrace_filter=[function-list]
984 [FTRACE] Limit the functions traced by the function
985 tracer at boot up. function-list is a comma separated
986 list of functions. This list can be changed at run
987 time by the set_ftrace_filter file in the debugfs
990 ftrace_notrace=[function-list]
991 [FTRACE] Do not trace the functions specified in
992 function-list. This list can be changed at run time
993 by the set_ftrace_notrace file in the debugfs
996 ftrace_graph_filter=[function-list]
997 [FTRACE] Limit the top level callers functions traced
998 by the function graph tracer at boot up.
999 function-list is a comma separated list of functions
1000 that can be changed at run time by the
1001 set_graph_function file in the debugfs tracing directory.
1004 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1005 support via parallel port (up to 5 devices per port)
1006 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1007 See also Documentation/input/joystick-parport.txt
1011 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1015 gcov_persist= [GCOV] When non-zero (default), profiling data for
1016 kernel modules is saved and remains accessible via
1017 debugfs, even when the module is unloaded/reloaded.
1018 When zero, profiling data is discarded and associated
1019 debugfs files are removed at module unload time.
1021 gpt [EFI] Forces disk with valid GPT signature but
1022 invalid Protective MBR to be treated as GPT.
1024 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1025 the "Enable 0" bit of the configuration register.
1028 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1029 the "Enable 0" bit of the configuration register.
1032 grcan.select= [HW] Select which physical interface to use.
1035 grcan.txsize= [HW] Sets the size of the tx buffer.
1036 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1038 grcan.rxsize= [HW] Sets the size of the rx buffer.
1039 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1042 hashdist= [KNL,NUMA] Large hashes allocated during boot
1043 are distributed across NUMA nodes. Defaults on
1044 for 64-bit NUMA, off otherwise.
1045 Format: 0 | 1 (for off | on)
1047 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1049 hd= [EIDE] (E)IDE hard drive subsystem geometry
1050 Format: <cyl>,<head>,<sect>
1053 Disable Hardware Error Source Table (HEST) support;
1054 corresponding firmware-first mode error processing
1055 logic will be disabled.
1057 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1058 size of <nn>. This works even on boxes that have no
1059 highmem otherwise. This also works to reduce highmem
1060 size on bigger boxes.
1062 highres= [KNL] Enable/disable high resolution timer mode.
1063 Valid parameters: "on", "off"
1067 See Documentation/isdn/README.HiSax.
1071 hpet= [X86-32,HPET] option to control HPET usage
1072 Format: { enable (default) | disable | force |
1074 disable: disable HPET and use PIT instead
1075 force: allow force enabled of undocumented chips (ICH4,
1077 verbose: show contents of HPET registers during setup
1079 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1080 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1082 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1083 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1084 On x86-64 and powerpc, this option can be specified
1085 multiple times interleaved with hugepages= to reserve
1086 huge pages of different sizes. Valid pages sizes on
1087 x86-64 are 2M (when the CPU supports "pse") and 1G
1088 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1089 Note that 1GB pages can only be allocated at boot time
1090 using hugepages= and not freed afterwards.
1092 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1093 terminal devices. Valid values: 0..8
1094 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1095 If specified, z/VM IUCV HVC accepts connections
1096 from listed z/VM user IDs only.
1098 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1099 hardware thread id mappings.
1100 Format: <cpu>:<hwthread>
1103 Do not unregister boot console at start. This is only
1104 useful for debugging when something happens in the window
1105 between unregistering the boot console and initializing
1108 i2c_bus= [HW] Override the default board specific I2C bus speed
1109 or register an additional I2C bus that is not
1110 registered from board initialization code.
1114 i8042.debug [HW] Toggle i8042 debug mode
1115 i8042.direct [HW] Put keyboard port into non-translated mode
1116 i8042.dumbkbd [HW] Pretend that controller can only read data from
1117 keyboard and cannot control its state
1118 (Don't attempt to blink the leds)
1119 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1120 i8042.nokbd [HW] Don't check/create keyboard port
1121 i8042.noloop [HW] Disable the AUX Loopback command while probing
1123 i8042.nomux [HW] Don't check presence of an active multiplexing
1125 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1127 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1128 i8042.reset [HW] Reset the controller during init and cleanup
1129 i8042.unlock [HW] Unlock (ignore) the keylock
1133 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1134 indicates that the driver is running on unsupported
1136 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1137 does not match list of supported models.
1139 [HW] Report power status in /proc/i8k
1140 (disabled by default)
1141 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1144 i915.invert_brightness=
1145 [DRM] Invert the sense of the variable that is used to
1146 set the brightness of the panel backlight. Normally a
1147 brightness value of 0 indicates backlight switched off,
1148 and the maximum of the brightness value sets the backlight
1149 to maximum brightness. If this parameter is set to 0
1150 (default) and the machine requires it, or this parameter
1151 is set to 1, a brightness value of 0 sets the backlight
1152 to maximum brightness, and the maximum of the brightness
1153 value switches the backlight off.
1154 -1 -- never invert brightness
1155 0 -- machine default
1156 1 -- force brightness inversion
1159 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1161 ide-core.nodma= [HW] (E)IDE subsystem
1162 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1163 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1164 .cdrom .chs .ignore_cable are additional options
1165 See Documentation/ide/ide.txt.
1167 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1168 Claim all unknown PCI IDE storage controllers.
1171 Format: idle=poll, idle=halt, idle=nomwait
1172 Poll forces a polling idle loop that can slightly
1173 improve the performance of waking up a idle CPU, but
1174 will use a lot of power and make the system run hot.
1176 idle=halt: Halt is forced to be used for CPU idle.
1177 In such case C2/C3 won't be used again.
1178 idle=nomwait: Disable mwait for CPU C-states
1180 ignore_loglevel [KNL]
1181 Ignore loglevel setting - this will print /all/
1182 kernel messages to the console. Useful for debugging.
1183 We also add it as printk module parameter, so users
1184 could change it dynamically, usually by
1185 /sys/module/printk/parameters/ignore_loglevel.
1187 ihash_entries= [KNL]
1188 Set number of hash buckets for inode cache.
1190 ima_appraise= [IMA] appraise integrity measurements
1191 Format: { "off" | "enforce" | "fix" }
1194 ima_appraise_tcb [IMA]
1195 The builtin appraise policy appraises all files
1199 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1203 The list of supported hash algorithms is defined
1204 in crypto/hash_info.h.
1207 Load a policy which meets the needs of the Trusted
1208 Computing Base. This means IMA will measure all
1209 programs exec'd, files mmap'd for exec, and all files
1210 opened for read by uid=0.
1213 Select one of defined IMA measurements template formats.
1214 Formats: { "ima" | "ima-ng" }
1219 Run specified binary instead of /sbin/init as init
1222 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1223 for working out where the kernel is dying during
1226 initrd= [BOOT] Specify the location of the initial ramdisk
1228 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1231 int_pln_enable [x86] Enable power limit notification interrupt
1233 integrity_audit=[IMA]
1234 Format: { "0" | "1" }
1235 0 -- basic integrity auditing messages. (Default)
1236 1 -- additional integrity auditing messages.
1238 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1240 Enable intel iommu driver.
1242 Disable intel iommu driver.
1243 igfx_off [Default Off]
1244 By default, gfx is mapped as normal device. If a gfx
1245 device has a dedicated DMAR unit, the DMAR unit is
1246 bypassed by not enabling DMAR with this option. In
1247 this case, gfx device will use physical address for
1250 With this option iommu will not optimize to look
1251 for io virtual address below 32-bit forcing dual
1252 address cycle on pci bus for cards supporting greater
1253 than 32-bit addressing. The default is to look
1254 for translation below 32-bit and if not available
1255 then look in the higher range.
1256 strict [Default Off]
1257 With this option on every unmap_single operation will
1258 result in a hardware IOTLB flush operation as opposed
1259 to batching them for performance.
1260 sp_off [Default Off]
1261 By default, super page will be supported if Intel IOMMU
1262 has the capability. With this option, super page will
1265 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1266 0 disables intel_idle and fall back on acpi_idle.
1267 1 to 6 specify maximum depth of C-state.
1271 Do not enable intel_pstate as the default
1272 scaling driver for the supported processors
1274 intremap= [X86-64, Intel-IOMMU]
1275 on enable Interrupt Remapping (default)
1276 off disable Interrupt Remapping
1277 nosid disable Source ID checking
1279 BIOS x2APIC opt-out request will be ignored
1281 iomem= Disable strict checking of access to MMIO memory
1282 strict regions from userspace.
1299 io7= [HW] IO7 for Marvel based alpha systems
1300 See comment before marvel_specify_io7 in
1301 arch/alpha/kernel/core_marvel.c.
1303 io_delay= [X86] I/O delay method
1305 Standard port 0x80 based delay
1307 Alternate port 0xed based delay (needed on some systems)
1309 Simple two microseconds delay
1314 See Documentation/filesystems/nfs/nfsroot.txt.
1316 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1317 See comment before ip2_setup() in
1318 drivers/char/ip2/ip2base.c.
1321 When an interrupt is not handled search all handlers
1322 for it. Intended to get systems with badly broken
1326 When an interrupt is not handled search all handlers
1327 for it. Also check all handlers each timer
1328 interrupt. Intended to get systems with badly broken
1332 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1334 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1336 <cpu number>,...,<cpu number>
1338 <cpu number>-<cpu number>
1339 (must be a positive range in ascending order)
1341 <cpu number>,...,<cpu number>-<cpu number>
1343 This option can be used to specify one or more CPUs
1344 to isolate from the general SMP balancing and scheduling
1345 algorithms. You can move a process onto or off an
1346 "isolated" CPU via the CPU affinity syscalls or cpuset.
1347 <cpu number> begins at 0 and the maximum value is
1348 "number of CPUs in system - 1".
1350 This option is the preferred way to isolate CPUs. The
1351 alternative -- manually setting the CPU mask of all
1352 tasks in the system -- can cause problems and
1353 suboptimal load balancer performance.
1357 ivrs_ioapic [HW,X86_64]
1358 Provide an override to the IOAPIC-ID<->DEVICE-ID
1359 mapping provided in the IVRS ACPI table. For
1360 example, to map IOAPIC-ID decimal 10 to
1361 PCI device 00:14.0 write the parameter as:
1362 ivrs_ioapic[10]=00:14.0
1364 ivrs_hpet [HW,X86_64]
1365 Provide an override to the HPET-ID<->DEVICE-ID
1366 mapping provided in the IVRS ACPI table. For
1367 example, to map HPET-ID decimal 0 to
1368 PCI device 00:14.0 write the parameter as:
1369 ivrs_hpet[0]=00:14.0
1371 js= [HW,JOY] Analog joystick
1372 See Documentation/input/joystick.txt.
1376 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1377 specifies the amount of memory usable by the kernel
1378 for non-movable allocations. The requested amount is
1379 spread evenly throughout all nodes in the system. The
1380 remaining memory in each node is used for Movable
1381 pages. In the event, a node is too small to have both
1382 kernelcore and Movable pages, kernelcore pages will
1383 take priority and other nodes will have a larger number
1384 of Movable pages. The Movable zone is used for the
1385 allocation of pages that may be reclaimed or moved
1386 by the page migration subsystem. This means that
1387 HugeTLB pages may not be allocated from this zone.
1388 Note that allocations like PTEs-from-HighMem still
1389 use the HighMem zone if it exists, and the Normal
1390 zone if it does not.
1392 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1393 Format: <Controller#>[,poll interval]
1394 The controller # is the number of the ehci usb debug
1395 port as it is probed via PCI. The poll interval is
1396 optional and is the number seconds in between
1397 each poll cycle to the debug port in case you need
1398 the functionality for interrupting the kernel with
1399 gdb or control-c on the dbgp connection. When
1400 not using this parameter you use sysrq-g to break into
1401 the kernel debugger.
1403 kgdboc= [KGDB,HW] kgdb over consoles.
1404 Requires a tty driver that supports console polling,
1405 or a supported polling keyboard driver (non-usb).
1406 Serial only format: <serial_device>[,baud]
1407 keyboard only format: kbd
1408 keyboard and serial format: kbd,<serial_device>[,baud]
1409 Optional Kernel mode setting:
1410 kms, kbd format: kms,kbd
1411 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1413 kgdbwait [KGDB] Stop kernel execution and enter the
1414 kernel debugger at the earliest opportunity.
1416 kmac= [MIPS] korina ethernet MAC address.
1417 Configure the RouterBoard 532 series on-chip
1418 Ethernet adapter MAC address.
1420 kmemleak= [KNL] Boot-time kmemleak enable/disable
1421 Valid arguments: on, off
1424 kstack=N [X86] Print N words from the kernel stack
1427 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1428 Default is 0 (don't ignore, but inject #GP)
1430 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1434 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1435 Default is 1 (enabled)
1437 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1439 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1441 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1442 (virtualized MMU) support on capable Intel chips.
1443 Default is 1 (enabled)
1445 kvm-intel.emulate_invalid_guest_state=
1446 [KVM,Intel] Enable emulation of invalid guest states
1447 Default is 0 (disabled)
1449 kvm-intel.flexpriority=
1450 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1451 Default is 1 (enabled)
1454 [KVM,Intel] Enable VMX nesting (nVMX).
1455 Default is 0 (disabled)
1457 kvm-intel.unrestricted_guest=
1458 [KVM,Intel] Disable unrestricted guest feature
1459 (virtualized real and unpaged mode) on capable
1460 Intel chips. Default is 1 (enabled)
1462 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1463 feature (tagged TLBs) on capable Intel chips.
1464 Default is 1 (enabled)
1470 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1473 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1474 value for LAPIC timer one-shot implementation. Default
1475 back to the programmable timer unit in the LAPIC.
1477 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1480 libata.dma= [LIBATA] DMA control
1481 libata.dma=0 Disable all PATA and SATA DMA
1482 libata.dma=1 PATA and SATA Disk DMA only
1483 libata.dma=2 ATAPI (CDROM) DMA only
1484 libata.dma=4 Compact Flash DMA only
1485 Combinations also work, so libata.dma=3 enables DMA
1486 for disks and CDROMs, but not CFs.
1488 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1489 libata.ignore_hpa=0 keep BIOS limits (default)
1490 libata.ignore_hpa=1 ignore limits, using full disk
1492 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1496 libata.force= [LIBATA] Force configurations. The format is comma
1497 separated list of "[ID:]VAL" where ID is
1498 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1499 matching port, link or device. Basically, it matches
1500 the ATA ID string printed on console by libata. If
1501 the whole ID part is omitted, the last PORT and DEVICE
1502 values are used. If ID hasn't been specified yet, the
1503 configuration applies to all ports, links and devices.
1505 If only DEVICE is omitted, the parameter applies to
1506 the port and all links and devices behind it. DEVICE
1507 number of 0 either selects the first device or the
1508 first fan-out link behind PMP device. It does not
1509 select the host link. DEVICE number of 15 selects the
1510 host link and device attached to it.
1512 The VAL specifies the configuration to force. As long
1513 as there's no ambiguity shortcut notation is allowed.
1514 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1515 The following configurations can be forced.
1517 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1518 Any ID with matching PORT is used.
1520 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1522 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1523 udma[/][16,25,33,44,66,100,133] notation is also
1526 * [no]ncq: Turn on or off NCQ.
1528 * nohrst, nosrst, norst: suppress hard, soft
1531 * rstonce: only attempt one reset during
1532 hot-unplug link recovery
1534 * dump_id: dump IDENTIFY data.
1536 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1538 If there are multiple matching configurations changing
1539 the same attribute, the last one is used.
1541 memblock=debug [KNL] Enable memblock debug messages.
1543 load_ramdisk= [RAM] List of ramdisks to load from floppy
1544 See Documentation/blockdev/ramdisk.txt.
1546 lockd.nlm_grace_period=P [NFS] Assign grace period.
1549 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1552 lockd.nlm_timeout=T [NFS] Assign timeout value.
1555 lockd.nlm_udpport=M [NFS] Assign UDP port.
1558 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1561 loglevel= All Kernel Messages with a loglevel smaller than the
1562 console loglevel will be printed to the console. It can
1563 also be changed with klogd or other programs. The
1564 loglevels are defined as follows:
1566 0 (KERN_EMERG) system is unusable
1567 1 (KERN_ALERT) action must be taken immediately
1568 2 (KERN_CRIT) critical conditions
1569 3 (KERN_ERR) error conditions
1570 4 (KERN_WARNING) warning conditions
1571 5 (KERN_NOTICE) normal but significant condition
1572 6 (KERN_INFO) informational
1573 7 (KERN_DEBUG) debug-level messages
1575 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1576 in bytes. n must be a power of two. The default
1577 size is set in the kernel config file.
1579 logo.nologo [FB] Disables display of the built-in Linux logo.
1580 This may be used to provide more screen space for
1581 kernel log messages and is useful when debugging
1582 kernel boot problems.
1584 lp=0 [LP] Specify parallel ports to use, e.g,
1585 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1586 lp=reset first parallel port). 'lp=0' disables the
1587 lp=auto printer driver. 'lp=reset' (which can be
1588 specified in addition to the ports) causes
1589 attached printers to be reset. Using
1590 lp=port1,port2,... specifies the parallel ports
1591 to associate lp devices with, starting with
1592 lp0. A port specification may be 'none' to skip
1593 that lp device, or a parport name such as
1594 'parport0'. Specifying 'lp=auto' instead of a
1595 port specification list means that device IDs
1596 from each port should be examined, to see if
1597 an IEEE 1284-compliant printer is attached; if
1598 so, the driver will manage that printer.
1599 See also header of drivers/char/lp.c.
1602 Sets loops_per_jiffy to given constant, thus avoiding
1603 time-consuming boot-time autodetection (up to 250 ms per
1604 CPU). 0 enables autodetection (default). To determine
1605 the correct value for your kernel, boot with normal
1606 autodetection and see what value is printed. Note that
1607 on SMP systems the preset will be applied to all CPUs,
1608 which is likely to cause problems if your CPUs need
1609 significantly divergent settings. An incorrect value
1610 will cause delays in the kernel to be wrong, leading to
1611 unpredictable I/O errors and other breakage. Although
1612 unlikely, in the extreme case this might damage your
1616 Format: <io>,<irq>,<dma>
1618 machvec= [IA-64] Force the use of a particular machine-vector
1619 (machvec) in a generic kernel.
1620 Example: machvec=hpzx1_swiotlb
1622 machtype= [Loongson] Share the same kernel image file between different
1624 Example: machtype=lemote-yeeloong-2f-7inch
1626 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1627 than or equal to this physical address is ignored.
1629 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1630 should make use of. maxcpus=n : n >= 0 limits the
1631 kernel to using 'n' processors. n=0 is a special case,
1632 it is equivalent to "nosmp", which also disables
1635 max_loop= [LOOP] The number of loop block devices that get
1636 (loop.max_loop) unconditionally pre-created at init time. The default
1637 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1638 of statically allocating a predefined number, loop
1639 devices can be requested on-demand with the
1640 /dev/loop-control interface.
1642 mce [X86-32] Machine Check Exception
1644 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1646 md= [HW] RAID subsystems devices and level
1647 See Documentation/md.txt.
1650 Format: <first>,<last>
1651 Specifies range of consoles to be captured by the MDA.
1653 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1654 Amount of memory to be used when the kernel is not able
1655 to see the whole system memory or for test.
1656 [X86] Work as limiting max address. Use together
1657 with memmap= to avoid physical address space collisions.
1658 Without memmap= PCI devices could be placed at addresses
1659 belonging to unused RAM.
1661 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1665 [KNL,SH] Allow user to override the default size for
1666 per-device physically contiguous DMA buffers.
1668 memmap=exactmap [KNL,X86] Enable setting of an exact
1669 E820 memory map, as specified by the user.
1670 Such memmap=exactmap lines can be constructed based on
1671 BIOS output or other requirements. See the memmap=nn@ss
1674 memmap=nn[KMG]@ss[KMG]
1675 [KNL] Force usage of a specific region of memory
1676 Region of memory to be used, from ss to ss+nn.
1678 memmap=nn[KMG]#ss[KMG]
1679 [KNL,ACPI] Mark specific memory as ACPI data.
1680 Region of memory to be used, from ss to ss+nn.
1682 memmap=nn[KMG]$ss[KMG]
1683 [KNL,ACPI] Mark specific memory as reserved.
1684 Region of memory to be used, from ss to ss+nn.
1685 Example: Exclude memory from 0x18690000-0x1869ffff
1686 memmap=64K$0x18690000
1688 memmap=0x10000$0x18690000
1690 memory_corruption_check=0/1 [X86]
1691 Some BIOSes seem to corrupt the first 64k of
1692 memory when doing things like suspend/resume.
1693 Setting this option will scan the memory
1694 looking for corruption. Enabling this will
1695 both detect corruption and prevent the kernel
1696 from using the memory being corrupted.
1697 However, its intended as a diagnostic tool; if
1698 repeatable BIOS-originated corruption always
1699 affects the same memory, you can use memmap=
1700 to prevent the kernel from using that memory.
1702 memory_corruption_check_size=size [X86]
1703 By default it checks for corruption in the low
1704 64k, making this memory unavailable for normal
1705 use. Use this parameter to scan for
1706 corruption in more or less memory.
1708 memory_corruption_check_period=seconds [X86]
1709 By default it checks for corruption every 60
1710 seconds. Use this parameter to check at some
1711 other rate. 0 disables periodic checking.
1713 memtest= [KNL,X86] Enable memtest
1715 default : 0 <disable>
1716 Specifies the number of memtest passes to be
1717 performed. Each pass selects another test
1718 pattern from a given set of patterns. Memtest
1719 fills the memory with this pattern, validates
1720 memory contents and reserves bad memory
1721 regions that are detected.
1723 meye.*= [HW] Set MotionEye Camera parameters
1724 See Documentation/video4linux/meye.txt.
1726 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1727 Multi-Function General Purpose Timers on AMD Geode
1730 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1731 the BIOS has incorrectly applied a workaround. TinyBIOS
1732 version 0.98 is known to be affected, 0.99 fixes the
1733 problem by letting the user disable the workaround.
1737 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1738 physical address is ignored.
1740 mini2440= [ARM,HW,KNL]
1741 Format:[0..2][b][c][t]
1743 MINI2440 configuration specification:
1744 0 - The attached screen is the 3.5" TFT
1745 1 - The attached screen is the 7" TFT
1746 2 - The VGA Shield is attached (1024x768)
1747 Leaving out the screen size parameter will not load
1748 the TFT driver, and the framebuffer will be left
1750 b - Enable backlight. The TFT backlight pin will be
1751 linked to the kernel VESA blanking code and a GPIO
1752 LED. This parameter is not necessary when using the
1754 c - Enable the s3c camera interface.
1755 t - Reserved for enabling touchscreen support. The
1756 touchscreen support is not enabled in the mainstream
1757 kernel as of 2.6.30, a preliminary port can be found
1758 in the "bleeding edge" mini2440 support kernel at
1759 http://repo.or.cz/w/linux-2.6/mini2440.git
1762 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1763 parameter allows control of the logging verbosity for
1764 the additional memory initialisation checks. A value
1765 of 0 disables mminit logging and a level of 4 will
1766 log everything. Information is printed at KERN_DEBUG
1767 so loglevel=8 may also need to be specified.
1770 [KNL] When CONFIG_MODULE_SIG is set, this means that
1771 modules without (valid) signatures will fail to load.
1772 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1773 is always true, so this option does nothing.
1776 [MOUSE] Maximum time between finger touching and
1777 leaving touchpad surface for touch to be considered
1778 a tap and be reported as a left button click (for
1779 touchpads working in absolute mode only).
1781 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1782 reporting absolute coordinates, such as tablets
1783 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1784 reporting absolute coordinates, such as tablets
1786 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1787 is similar to kernelcore except it specifies the
1788 amount of memory used for migratable allocations.
1789 If both kernelcore and movablecore is specified,
1790 then kernelcore will be at *least* the specified
1791 value but may be more. If movablecore on its own
1792 is specified, the administrator must be careful
1793 that the amount of memory usable for all allocations
1796 movable_node [KNL,X86] Boot-time switch to enable the effects
1797 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1799 MTD_Partition= [MTD]
1800 Format: <name>,<region-number>,<size>,<offset>
1802 MTD_Region= [MTD] Format:
1803 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1806 See drivers/mtd/cmdlinepart.c.
1808 multitce=off [PPC] This parameter disables the use of the pSeries
1809 firmware feature for updating multiple TCE entries
1812 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1814 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1816 boundary - index of last SLC block on Flex-OneNAND.
1817 The remaining blocks are configured as MLC blocks.
1818 lock - Configure if Flex-OneNAND boundary should be locked.
1819 Once locked, the boundary cannot be changed.
1820 1 indicates lock status, 0 indicates unlock status.
1823 ARM/S3C2412 JIVE boot control
1825 See arch/arm/mach-s3c2412/mach-jive.c
1827 mtouchusb.raw_coordinates=
1828 [HW] Make the MicroTouch USB driver use raw coordinates
1829 ('y', default) or cooked coordinates ('n')
1831 mtrr_chunk_size=nn[KMG] [X86]
1832 used for mtrr cleanup. It is largest continuous chunk
1833 that could hold holes aka. UC entries.
1835 mtrr_gran_size=nn[KMG] [X86]
1836 Used for mtrr cleanup. It is granularity of mtrr block.
1838 Large value could prevent small alignment from
1841 mtrr_spare_reg_nr=n [X86]
1843 Range: 0,7 : spare reg number
1845 Used for mtrr cleanup. It is spare mtrr entries number.
1846 Set to 2 or more if your graphical card needs more.
1848 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1850 netdev= [NET] Network devices parameters
1851 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1852 Note that mem_start is often overloaded to mean
1853 something different and driver-specific.
1854 This usage is only documented in each driver source
1858 [NETFILTER] Enable connection tracking flow accounting
1859 0 to disable accounting
1860 1 to enable accounting
1863 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1864 See Documentation/filesystems/nfs/nfsroot.txt.
1866 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1867 See Documentation/filesystems/nfs/nfsroot.txt.
1869 nfsrootdebug [NFS] enable nfsroot debugging messages.
1870 See Documentation/filesystems/nfs/nfsroot.txt.
1872 nfs.callback_tcpport=
1873 [NFS] set the TCP port on which the NFSv4 callback
1874 channel should listen.
1877 [NFS] sets the pathname to the program which is used
1878 to update the NFS client cache entries.
1880 nfs.cache_getent_timeout=
1881 [NFS] sets the timeout after which an attempt to
1882 update a cache entry is deemed to have failed.
1884 nfs.idmap_cache_timeout=
1885 [NFS] set the maximum lifetime for idmapper cache
1889 [NFS] enable 64-bit inode numbers.
1890 If zero, the NFS client will fake up a 32-bit inode
1891 number for the readdir() and stat() syscalls instead
1892 of returning the full 64-bit number.
1893 The default is to return 64-bit inode numbers.
1895 nfs.max_session_slots=
1896 [NFSv4.1] Sets the maximum number of session slots
1897 the client will attempt to negotiate with the server.
1898 This limits the number of simultaneous RPC requests
1899 that the client can send to the NFSv4.1 server.
1900 Note that there is little point in setting this
1901 value higher than the max_tcp_slot_table_limit.
1903 nfs.nfs4_disable_idmapping=
1904 [NFSv4] When set to the default of '1', this option
1905 ensures that both the RPC level authentication
1906 scheme and the NFS level operations agree to use
1907 numeric uids/gids if the mount is using the
1908 'sec=sys' security flavour. In effect it is
1909 disabling idmapping, which can make migration from
1910 legacy NFSv2/v3 systems to NFSv4 easier.
1911 Servers that do not support this mode of operation
1912 will be autodetected by the client, and it will fall
1913 back to using the idmapper.
1914 To turn off this behaviour, set the value to '0'.
1916 [NFS4] Specify an additional fixed unique ident-
1917 ification string that NFSv4 clients can insert into
1918 their nfs_client_id4 string. This is typically a
1919 UUID that is generated at system install time.
1921 nfs.send_implementation_id =
1922 [NFSv4.1] Send client implementation identification
1923 information in exchange_id requests.
1924 If zero, no implementation identification information
1926 The default is to send the implementation identification
1929 nfs.recover_lost_locks =
1930 [NFSv4] Attempt to recover locks that were lost due
1931 to a lease timeout on the server. Please note that
1932 doing this risks data corruption, since there are
1933 no guarantees that the file will remain unchanged
1934 after the locks are lost.
1935 If you want to enable the kernel legacy behaviour of
1936 attempting to recover these locks, then set this
1938 The default parameter value of '0' causes the kernel
1939 not to attempt recovery of lost locks.
1941 nfsd.nfs4_disable_idmapping=
1942 [NFSv4] When set to the default of '1', the NFSv4
1943 server will return only numeric uids and gids to
1944 clients using auth_sys, and will accept numeric uids
1945 and gids from such clients. This is intended to ease
1946 migration from NFSv2/v3.
1948 objlayoutdriver.osd_login_prog=
1949 [NFS] [OBJLAYOUT] sets the pathname to the program which
1950 is used to automatically discover and login into new
1951 osd-targets. Please see:
1952 Documentation/filesystems/pnfs.txt for more explanations
1954 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1955 when a NMI is triggered.
1956 Format: [state][,regs][,debounce][,die]
1958 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1959 Format: [panic,][nopanic,][num]
1961 0 - turn nmi_watchdog off
1962 When panic is specified, panic when an NMI watchdog
1963 timeout occurs (or 'nopanic' to override the opposite
1965 This is useful when you use a panic=... timeout and
1966 need the box quickly up again.
1968 netpoll.carrier_timeout=
1969 [NET] Specifies amount of time (in seconds) that
1970 netpoll should wait for a carrier. By default netpoll
1973 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1974 emulation library even if a 387 maths coprocessor
1978 [HW] Never suspend the console
1979 Disable suspending of consoles during suspend and
1980 hibernate operations. Once disabled, debugging
1981 messages can reach various consoles while the rest
1982 of the system is being put to sleep (ie, while
1983 debugging driver suspend/resume hooks). This may
1984 not work reliably with all consoles, but is known
1985 to work with serial and VGA consoles.
1986 To facilitate more flexible debugging, we also add
1987 console_suspend, a printk module parameter to control
1988 it. Users could use console_suspend (usually
1989 /sys/module/printk/parameters/console_suspend) to
1990 turn on/off it dynamically.
1992 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1993 caches in the slab allocator. Saves per-node memory,
1994 but will impact performance.
1998 noapic [SMP,APIC] Tells the kernel to not make use of any
1999 IOAPICs that may be present in the system.
2001 noautogroup Disable scheduler automatic task group creation.
2003 nobats [PPC] Do not use BATs for mapping kernel lowmem
2004 on "Classic" PPC cores.
2008 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2010 nodelayacct [KNL] Disable per-task delay accounting
2012 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2014 nodsp [SH] Disable hardware DSP at boot time.
2016 noefi [X86] Disable EFI runtime services support.
2021 On X86-32 available only on PAE configured kernels.
2022 noexec=on: enable non-executable mappings (default)
2023 noexec=off: disable non-executable mappings
2026 Disable SMAP (Supervisor Mode Access Prevention)
2027 even if it is supported by processor.
2030 Disable SMEP (Supervisor Mode Execution Prevention)
2031 even if it is supported by processor.
2034 This affects only 32-bit executables.
2035 noexec32=on: enable non-executable mappings (default)
2036 read doesn't imply executable mappings
2037 noexec32=off: disable non-executable mappings
2038 read implies executable mappings
2040 nofpu [SH] Disable hardware FPU at boot time.
2042 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2043 register save and restore. The kernel will only save
2044 legacy floating-point registers on task switch.
2046 noxsave [BUGS=X86] Disables x86 extended register state save
2047 and restore using xsave. The kernel will fallback to
2048 enabling legacy floating-point and sse state.
2051 on enable eager fpu restore
2052 off disable eager fpu restore
2053 auto selects the default scheme, which automatically
2054 enables eagerfpu restore for xsaveopt.
2056 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2057 wfi(ARM) instruction doesn't work correctly and not to
2058 use it. This is also useful when using JTAG debugger.
2060 no_file_caps Tells the kernel not to honor file capabilities. The
2061 only way then for a file to be executed with privilege
2062 is to be setuid root or executed by root.
2064 nohalt [IA-64] Tells the kernel not to use the power saving
2065 function PAL_HALT_LIGHT when idle. This increases
2066 power-consumption. On the positive side, it reduces
2067 interrupt wake-up latency, which may improve performance
2068 in certain environments such as networked servers or
2071 nohz= [KNL] Boottime enable/disable dynamic ticks
2072 Valid arguments: on, off
2075 nohz_full= [KNL,BOOT]
2076 In kernels built with CONFIG_NO_HZ_FULL=y, set
2077 the specified list of CPUs whose tick will be stopped
2078 whenever possible. The boot CPU will be forced outside
2079 the range to maintain the timekeeping.
2080 The CPUs in this range must also be included in the
2083 noiotrap [SH] Disables trapped I/O port accesses.
2085 noirqdebug [X86-32] Disables the code which attempts to detect and
2086 disable unhandled interrupt sources.
2088 no_timer_check [X86,APIC] Disables the code which tests for
2089 broken timer IRQ sources.
2091 noisapnp [ISAPNP] Disables ISA PnP code.
2093 noinitrd [RAM] Tells the kernel not to load any configured
2096 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2098 [Deprecated - use intremap=off]
2102 nojitter [IA-64] Disables jitter checking for ITC timers.
2104 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2106 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2109 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2110 steal time is computed, but won't influence scheduler
2113 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2115 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2117 noltlbs [PPC] Do not use large page/tlb entries for kernel
2118 lowmem mapping on PPC40x.
2120 nomca [IA-64] Disable machine check abort handling
2122 nomce [X86-32] Machine Check Exception
2124 nomfgpt [X86-32] Disable Multi-Function General Purpose
2125 Timer usage (for AMD Geode machines).
2127 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2128 shutdown the other cpus. Instead use the REBOOT_VECTOR
2131 nomodule Disable module load
2133 nopat [X86] Disable PAT (page attribute table extension of
2134 pagetables) support.
2136 norandmaps Don't use address space randomization. Equivalent to
2137 echo 0 > /proc/sys/kernel/randomize_va_space
2139 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2141 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2142 with UP alternatives
2144 nordrand [X86] Disable the direct use of the RDRAND
2145 instruction even if it is supported by the
2146 processor. RDRAND is still available to user
2149 noresume [SWSUSP] Disables resume and restores original swap
2152 no-scroll [VGA] Disables scrollback.
2153 This is required for the Braillex ib80-piezo Braille
2154 reader made by F.H. Papenmeier (Germany).
2158 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2160 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2161 and disable the IO APIC. legacy for "maxcpus=0".
2163 nosoftlockup [KNL] Disable the soft-lockup detector.
2165 nosync [HW,M68K] Disables sync negotiation for all devices.
2167 notsc [BUGS=X86-32] Disable Time Stamp Counter
2169 nousb [USB] Disable the USB subsystem
2171 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2175 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2177 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2178 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2179 Some features depend on CPU0. Known dependencies are:
2180 1. Resume from suspend/hibernate depends on CPU0.
2181 Suspend/hibernate will fail if CPU0 is offline and you
2182 need to online CPU0 before suspend/hibernate.
2183 2. PIC interrupts also depend on CPU0. CPU0 can't be
2184 removed if a PIC interrupt is detected.
2185 It's said poweroff/reboot may depend on CPU0 on some
2186 machines although I haven't seen such issues so far
2187 after CPU0 is offline on a few tested machines.
2188 If the dependencies are under your control, you can
2189 turn on cpu0_hotplug.
2191 nptcg= [IA-64] Override max number of concurrent global TLB
2192 purges which is reported from either PAL_VM_SUMMARY or
2195 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2196 could support. nr_cpus=n : n >= 1 limits the kernel to
2197 supporting 'n' processors. Later in runtime you can not
2198 use hotplug cpu feature to put more cpu back to online.
2199 just like you compile the kernel NR_CPUS=n
2201 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2203 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2204 Allowed values are enable and disable
2206 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2207 one of ['zone', 'node', 'default'] can be specified
2208 This can be set from sysctl after boot.
2209 See Documentation/sysctl/vm.txt for details.
2211 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2212 See Documentation/debugging-via-ohci1394.txt for more
2215 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2216 Rather than timing out after 20 ms if an EC
2217 command is not properly ACKed, override the length
2218 of the timeout. We have interrupts disabled while
2219 waiting for the ACK, so if this is set too high
2220 interrupts *may* be lost!
2222 omap_mux= [OMAP] Override bootloader pin multiplexing.
2223 Format: <mux_mode0.mode_name=value>...
2224 For example, to override I2C bus2:
2225 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2227 oprofile.timer= [HW]
2228 Use timer interrupt instead of performance counters
2230 oprofile.cpu_type= Force an oprofile cpu type
2231 This might be useful if you have an older oprofile
2232 userland or if you want common events.
2233 Format: { arch_perfmon }
2234 arch_perfmon: [X86] Force use of architectural
2235 perfmon on Intel CPUs instead of the
2236 CPU specific event set.
2237 timer: [X86] Force use of architectural NMI
2238 timer mode (see also oprofile.timer
2239 for generic hr timer mode)
2240 [s390] Force legacy basic mode sampling
2241 (report cpu_type "timer")
2243 oops=panic Always panic on oopses. Default is to just kill the
2244 process, but there is a small probability of
2245 deadlocking the machine.
2246 This will also cause panics on machine check exceptions.
2247 Useful together with panic=30 to trigger a reboot.
2250 See Documentation/sound/oss/oss-parameters.txt
2252 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2253 timeout > 0: seconds before rebooting
2254 timeout = 0: wait forever
2255 timeout < 0: reboot immediately
2258 parkbd.port= [HW] Parallel port number the keyboard adapter is
2259 connected to, default is 0.
2261 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2262 0 for XT, 1 for AT (default is AT).
2265 parport= [HW,PPT] Specify parallel ports. 0 disables.
2266 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2267 Use 'auto' to force the driver to use any
2268 IRQ/DMA settings detected (the default is to
2269 ignore detected IRQ/DMA settings because of
2270 possible conflicts). You can specify the base
2271 address, IRQ, and DMA settings; IRQ and DMA
2272 should be numbers, or 'auto' (for using detected
2273 settings on that particular port), or 'nofifo'
2274 (to avoid using a FIFO even if it is detected).
2275 Parallel ports are assigned in the order they
2276 are specified on the command line, starting
2279 parport_init_mode= [HW,PPT]
2280 Configure VIA parallel port to operate in
2281 a specific mode. This is necessary on Pegasos
2282 computer where firmware has no options for setting
2283 up parallel port mode and sets it to spp.
2284 Currently this function knows 686a and 8231 chips.
2285 Format: [spp|ps2|epp|ecp|ecpepp]
2288 Halt all CPUs after the first oops has been printed for
2289 the specified number of seconds. This is to be used if
2290 your oopses keep scrolling off the screen.
2295 See header of drivers/block/paride/pcd.c.
2296 See also Documentation/blockdev/paride.txt.
2298 pci=option[,option...] [PCI] various PCI subsystem options:
2299 earlydump [X86] dump PCI config space before the kernel
2301 off [X86] don't probe for the PCI bus
2302 bios [X86-32] force use of PCI BIOS, don't access
2303 the hardware directly. Use this if your machine
2304 has a non-standard PCI host bridge.
2305 nobios [X86-32] disallow use of PCI BIOS, only direct
2306 hardware access methods are allowed. Use this
2307 if you experience crashes upon bootup and you
2308 suspect they are caused by the BIOS.
2309 conf1 [X86] Force use of PCI Configuration
2311 conf2 [X86] Force use of PCI Configuration
2313 noaer [PCIE] If the PCIEAER kernel config parameter is
2314 enabled, this kernel boot option can be used to
2315 disable the use of PCIE advanced error reporting.
2316 nodomains [PCI] Disable support for multiple PCI
2317 root domains (aka PCI segments, in ACPI-speak).
2318 nommconf [X86] Disable use of MMCONFIG for PCI
2320 check_enable_amd_mmconf [X86] check for and enable
2321 properly configured MMIO access to PCI
2322 config space on AMD family 10h CPU
2323 nomsi [MSI] If the PCI_MSI kernel config parameter is
2324 enabled, this kernel boot option can be used to
2325 disable the use of MSI interrupts system-wide.
2326 noioapicquirk [APIC] Disable all boot interrupt quirks.
2327 Safety option to keep boot IRQs enabled. This
2328 should never be necessary.
2329 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2330 primary IO-APIC for bridges that cannot disable
2331 boot IRQs. This fixes a source of spurious IRQs
2332 when the system masks IRQs.
2333 noioapicreroute [APIC] Disable workaround that uses the
2334 boot IRQ equivalent of an IRQ that connects to
2335 a chipset where boot IRQs cannot be disabled.
2336 The opposite of ioapicreroute.
2337 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2338 routing table. These calls are known to be buggy
2339 on several machines and they hang the machine
2340 when used, but on other computers it's the only
2341 way to get the interrupt routing table. Try
2342 this option if the kernel is unable to allocate
2343 IRQs or discover secondary PCI buses on your
2345 rom [X86] Assign address space to expansion ROMs.
2346 Use with caution as certain devices share
2347 address decoders between ROMs and other
2349 norom [X86] Do not assign address space to
2350 expansion ROMs that do not already have
2351 BIOS assigned address ranges.
2352 nobar [X86] Do not assign address space to the
2353 BARs that weren't assigned by the BIOS.
2354 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2355 assigned automatically to PCI devices. You can
2356 make the kernel exclude IRQs of your ISA cards
2358 pirqaddr=0xAAAAA [X86] Specify the physical address
2359 of the PIRQ table (normally generated
2360 by the BIOS) if it is outside the
2361 F0000h-100000h range.
2362 lastbus=N [X86] Scan all buses thru bus #N. Can be
2363 useful if the kernel is unable to find your
2364 secondary buses and you want to tell it
2365 explicitly which ones they are.
2366 assign-busses [X86] Always assign all PCI bus
2367 numbers ourselves, overriding
2368 whatever the firmware may have done.
2369 usepirqmask [X86] Honor the possible IRQ mask stored
2370 in the BIOS $PIR table. This is needed on
2371 some systems with broken BIOSes, notably
2372 some HP Pavilion N5400 and Omnibook XE3
2373 notebooks. This will have no effect if ACPI
2374 IRQ routing is enabled.
2375 noacpi [X86] Do not use ACPI for IRQ routing
2376 or for PCI scanning.
2377 use_crs [X86] Use PCI host bridge window information
2378 from ACPI. On BIOSes from 2008 or later, this
2379 is enabled by default. If you need to use this,
2380 please report a bug.
2381 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2382 If you need to use this, please report a bug.
2383 routeirq Do IRQ routing for all PCI devices.
2384 This is normally done in pci_enable_device(),
2385 so this option is a temporary workaround
2386 for broken drivers that don't call it.
2387 skip_isa_align [X86] do not align io start addr, so can
2388 handle more pci cards
2389 firmware [ARM] Do not re-enumerate the bus but instead
2390 just use the configuration from the
2391 bootloader. This is currently used on
2392 IXP2000 systems where the bus has to be
2393 configured a certain way for adjunct CPUs.
2394 noearly [X86] Don't do any early type 1 scanning.
2395 This might help on some broken boards which
2396 machine check when some devices' config space
2397 is read. But various workarounds are disabled
2398 and some IOMMU drivers will not work.
2399 bfsort Sort PCI devices into breadth-first order.
2400 This sorting is done to get a device
2401 order compatible with older (<= 2.4) kernels.
2402 nobfsort Don't sort PCI devices into breadth-first order.
2403 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2404 tuning and use the BIOS-configured MPS defaults.
2405 pcie_bus_safe Set every device's MPS to the largest value
2406 supported by all devices below the root complex.
2407 pcie_bus_perf Set device MPS to the largest allowable MPS
2408 based on its parent bus. Also set MRRS (Max
2409 Read Request Size) to the largest supported
2410 value (no larger than the MPS that the device
2411 or bus can support) for best performance.
2412 pcie_bus_peer2peer Set every device's MPS to 128B, which
2413 every device is guaranteed to support. This
2414 configuration allows peer-to-peer DMA between
2415 any pair of devices, possibly at the cost of
2416 reduced performance. This also guarantees
2417 that hot-added devices will work.
2418 cbiosize=nn[KMG] The fixed amount of bus space which is
2419 reserved for the CardBus bridge's IO window.
2420 The default value is 256 bytes.
2421 cbmemsize=nn[KMG] The fixed amount of bus space which is
2422 reserved for the CardBus bridge's memory
2423 window. The default value is 64 megabytes.
2426 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2427 Specifies alignment and device to reassign
2428 aligned memory resources.
2429 If <order of align> is not specified,
2430 PAGE_SIZE is used as alignment.
2431 PCI-PCI bridge can be specified, if resource
2432 windows need to be expanded.
2433 ecrc= Enable/disable PCIe ECRC (transaction layer
2434 end-to-end CRC checking).
2435 bios: Use BIOS/firmware settings. This is the
2439 hpiosize=nn[KMG] The fixed amount of bus space which is
2440 reserved for hotplug bridge's IO window.
2441 Default size is 256 bytes.
2442 hpmemsize=nn[KMG] The fixed amount of bus space which is
2443 reserved for hotplug bridge's memory window.
2444 Default size is 2 megabytes.
2445 realloc= Enable/disable reallocating PCI bridge resources
2446 if allocations done by BIOS are too small to
2447 accommodate resources required by all child
2449 off: Turn realloc off
2451 realloc same as realloc=on
2452 noari do not use PCIe ARI.
2453 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2454 only look for one device below a PCIe downstream
2457 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2460 force Enable ASPM even on devices that claim not to support it.
2461 WARNING: Forcing ASPM on may cause system lockups.
2463 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2464 nomsi Do not use MSI for PCI Express Native Hotplug (this
2465 makes all PCIe ports use INTx for hotplug services).
2467 pcie_ports= [PCIE] PCIe ports handling:
2468 auto Ask the BIOS whether or not to use native PCIe services
2469 associated with PCIe ports (PME, hot-plug, AER). Use
2470 them only if that is allowed by the BIOS.
2471 native Use native PCIe services associated with PCIe ports
2473 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2476 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2477 nomsi Do not use MSI for native PCIe PME signaling (this makes
2478 all PCIe root ports use INTx for all services).
2480 pcmv= [HW,PCMCIA] BadgePAD 4
2483 See Documentation/blockdev/paride.txt.
2485 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2488 See arch/parisc/kernel/pdc_chassis.c
2490 percpu_alloc= Select which percpu first chunk allocator to use.
2491 Currently supported values are "embed" and "page".
2492 Archs may support subset or none of the selections.
2493 See comments in mm/percpu.c for details on each
2494 allocator. This parameter is primarily for debugging
2495 and performance comparison.
2498 See Documentation/blockdev/paride.txt.
2501 See Documentation/blockdev/paride.txt.
2503 pirq= [SMP,APIC] Manual mp-table setup
2504 See Documentation/x86/i386/IO-APIC.txt.
2506 plip= [PPT,NET] Parallel port network link
2507 Format: { parport<nr> | timid | 0 }
2508 See also Documentation/parport.txt.
2510 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2511 Override pmtimer IOPort with a hex value.
2515 Enable PNP debug messages (depends on the
2516 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2517 via /sys/module/pnp/parameters/debug. We always show
2518 current resource usage; turning this on also shows
2519 possible settings and some assignment information.
2525 { on | off | curr | res | no-curr | no-res }
2528 [ISAPNP] Exclude IRQs for the autoconfiguration
2531 [ISAPNP] Exclude DMAs for the autoconfiguration
2533 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2534 Ranges are in pairs (I/O port base and size).
2537 [ISAPNP] Exclude memory regions for the
2539 Ranges are in pairs (memory base and size).
2541 ports= [IP_VS_FTP] IPVS ftp helper module
2543 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2545 Format: <port>,<port>....
2547 print-fatal-signals=
2548 [KNL] debug: print fatal signals
2550 If enabled, warn about various signal handling
2551 related application anomalies: too many signals,
2552 too many POSIX.1 timers, fatal signals causing a
2555 If you hit the warning due to signal overflow,
2556 you might want to try "ulimit -i unlimited".
2560 printk.always_kmsg_dump=
2561 Trigger kmsg_dump for cases other than kernel oops or
2563 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2566 printk.time= Show timing data prefixed to each printk message line
2567 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2569 processor.max_cstate= [HW,ACPI]
2570 Limit processor to maximum C-state
2571 max_cstate=9 overrides any DMI blacklist limit.
2573 processor.nocst [HW,ACPI]
2574 Ignore the _CST method to determine C-states,
2575 instead using the legacy FADT method
2577 profile= [KNL] Enable kernel profiling via /proc/profile
2578 Format: [schedule,]<number>
2579 Param: "schedule" - profile schedule points.
2580 Param: <number> - step/bucket size as a power of 2 for
2581 statistical time based profiling.
2582 Param: "sleep" - profile D-state sleeping (millisecs).
2583 Requires CONFIG_SCHEDSTATS
2584 Param: "kvm" - profile VM exits.
2586 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2588 See Documentation/blockdev/ramdisk.txt.
2590 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2591 probe for; one of (bare|imps|exps|lifebook|any).
2592 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2594 psmouse.resetafter= [HW,MOUSE]
2595 Try to reset the device after so many bad packets
2598 [HW,MOUSE] Set desired mouse resolution, in dpi.
2599 psmouse.smartscroll=
2600 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2601 0 = disabled, 1 = enabled (default).
2603 pstore.backend= Specify the name of the pstore backend to use
2606 See Documentation/blockdev/paride.txt.
2609 [KNL] Number of legacy pty's. Overwrites compiled-in
2612 quiet [KNL] Disable most log messages
2617 See Documentation/md.txt.
2619 ramdisk_blocksize= [RAM]
2620 See Documentation/blockdev/ramdisk.txt.
2622 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2623 See Documentation/blockdev/ramdisk.txt.
2626 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2627 the specified list of CPUs to be no-callback CPUs.
2628 Invocation of these CPUs' RCU callbacks will
2629 be offloaded to "rcuox/N" kthreads created for
2630 that purpose, where "x" is "b" for RCU-bh, "p"
2631 for RCU-preempt, and "s" for RCU-sched, and "N"
2632 is the CPU number. This reduces OS jitter on the
2633 offloaded CPUs, which can be useful for HPC and
2635 real-time workloads. It can also improve energy
2636 efficiency for asymmetric multiprocessors.
2639 Rather than requiring that offloaded CPUs
2640 (specified by rcu_nocbs= above) explicitly
2641 awaken the corresponding "rcuoN" kthreads,
2642 make these kthreads poll for callbacks.
2643 This improves the real-time response for the
2644 offloaded CPUs by relieving them of the need to
2645 wake up the corresponding kthread, but degrades
2646 energy efficiency by requiring that the kthreads
2647 periodically wake up to do the polling.
2649 rcutree.blimit= [KNL]
2650 Set maximum number of finished RCU callbacks to process
2653 rcutree.rcu_fanout_leaf= [KNL]
2654 Increase the number of CPUs assigned to each
2655 leaf rcu_node structure. Useful for very large
2658 rcutree.jiffies_till_first_fqs= [KNL]
2659 Set delay from grace-period initialization to
2660 first attempt to force quiescent states.
2661 Units are jiffies, minimum value is zero,
2662 and maximum value is HZ.
2664 rcutree.jiffies_till_next_fqs= [KNL]
2665 Set delay between subsequent attempts to force
2666 quiescent states. Units are jiffies, minimum
2667 value is one, and maximum value is HZ.
2669 rcutree.qhimark= [KNL]
2670 Set threshold of queued
2671 RCU callbacks over which batch limiting is disabled.
2673 rcutree.qlowmark= [KNL]
2674 Set threshold of queued RCU callbacks below which
2675 batch limiting is re-enabled.
2677 rcutree.rcu_idle_gp_delay= [KNL]
2678 Set wakeup interval for idle CPUs that have
2679 RCU callbacks (RCU_FAST_NO_HZ=y).
2681 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2682 Set wakeup interval for idle CPUs that have
2683 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2684 Lazy RCU callbacks are those which RCU can
2685 prove do nothing more than free memory.
2687 rcutorture.fqs_duration= [KNL]
2688 Set duration of force_quiescent_state bursts.
2690 rcutorture.fqs_holdoff= [KNL]
2691 Set holdoff time within force_quiescent_state bursts.
2693 rcutorture.fqs_stutter= [KNL]
2694 Set wait time between force_quiescent_state bursts.
2696 rcutorture.gp_exp= [KNL]
2697 Use expedited update-side primitives.
2699 rcutorture.gp_normal= [KNL]
2700 Use normal (non-expedited) update-side primitives.
2701 If both gp_exp and gp_normal are set, do both.
2702 If neither gp_exp nor gp_normal are set, still
2705 rcutorture.n_barrier_cbs= [KNL]
2706 Set callbacks/threads for rcu_barrier() testing.
2708 rcutorture.nfakewriters= [KNL]
2709 Set number of concurrent RCU writers. These just
2710 stress RCU, they don't participate in the actual
2711 test, hence the "fake".
2713 rcutorture.nreaders= [KNL]
2714 Set number of RCU readers.
2716 rcutorture.object_debug= [KNL]
2717 Enable debug-object double-call_rcu() testing.
2719 rcutorture.onoff_holdoff= [KNL]
2720 Set time (s) after boot for CPU-hotplug testing.
2722 rcutorture.onoff_interval= [KNL]
2723 Set time (s) between CPU-hotplug operations, or
2724 zero to disable CPU-hotplug testing.
2726 rcutorture.rcutorture_runnable= [BOOT]
2727 Start rcutorture running at boot time.
2729 rcutorture.shuffle_interval= [KNL]
2730 Set task-shuffle interval (s). Shuffling tasks
2731 allows some CPUs to go into dyntick-idle mode
2732 during the rcutorture test.
2734 rcutorture.shutdown_secs= [KNL]
2735 Set time (s) after boot system shutdown. This
2736 is useful for hands-off automated testing.
2738 rcutorture.stall_cpu= [KNL]
2739 Duration of CPU stall (s) to test RCU CPU stall
2740 warnings, zero to disable.
2742 rcutorture.stall_cpu_holdoff= [KNL]
2743 Time to wait (s) after boot before inducing stall.
2745 rcutorture.stat_interval= [KNL]
2746 Time (s) between statistics printk()s.
2748 rcutorture.stutter= [KNL]
2749 Time (s) to stutter testing, for example, specifying
2750 five seconds causes the test to run for five seconds,
2751 wait for five seconds, and so on. This tests RCU's
2752 ability to transition abruptly to and from idle.
2754 rcutorture.test_boost= [KNL]
2755 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2756 "Maybe" means test if the RCU implementation
2757 under test support RCU priority boosting.
2759 rcutorture.test_boost_duration= [KNL]
2760 Duration (s) of each individual boost test.
2762 rcutorture.test_boost_interval= [KNL]
2763 Interval (s) between each boost test.
2765 rcutorture.test_no_idle_hz= [KNL]
2766 Test RCU's dyntick-idle handling. See also the
2767 rcutorture.shuffle_interval parameter.
2769 rcutorture.torture_type= [KNL]
2770 Specify the RCU implementation to test.
2772 rcutorture.verbose= [KNL]
2773 Enable additional printk() statements.
2775 rcupdate.rcu_expedited= [KNL]
2776 Use expedited grace-period primitives, for
2777 example, synchronize_rcu_expedited() instead
2778 of synchronize_rcu(). This reduces latency,
2779 but can increase CPU utilization, degrade
2780 real-time latency, and degrade energy efficiency.
2782 rcupdate.rcu_cpu_stall_suppress= [KNL]
2783 Suppress RCU CPU stall warning messages.
2785 rcupdate.rcu_cpu_stall_timeout= [KNL]
2786 Set timeout for RCU CPU stall warning messages.
2790 Run specified binary instead of /init from the ramdisk,
2791 used for early userspace startup. See initrd.
2794 Format (x86 or x86_64):
2795 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2797 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2799 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2800 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2801 reboot_force is either force or not specified,
2802 reboot_cpu is s[mp]#### with #### being the processor
2803 to be used for rebooting.
2806 [KNL, SMP] Set scheduler's default relax_domain_level.
2807 See Documentation/cgroups/cpusets.txt.
2809 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2811 reservetop= [X86-32]
2813 Reserves a hole at the top of the kernel virtual
2818 Set the amount of memory to reserve for BIOS at
2819 the bottom of the address space.
2821 reset_devices [KNL] Force drivers to reset the underlying device
2822 during initialization.
2825 Specify the partition device for software suspend
2827 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2829 resume_offset= [SWSUSP]
2830 Specify the offset from the beginning of the partition
2831 given by "resume=" at which the swap header is located,
2832 in <PAGE_SIZE> units (needed only for swap files).
2833 See Documentation/power/swsusp-and-swap-files.txt
2835 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2836 read the resume files
2838 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2839 Useful for devices that are detected asynchronously
2840 (e.g. USB and MMC devices).
2842 hibernate= [HIBERNATION]
2843 noresume Don't check if there's a hibernation image
2844 present during boot.
2845 nocompress Don't compress/decompress hibernation images.
2847 retain_initrd [RAM] Keep initrd memory after extraction
2849 rhash_entries= [KNL,NET]
2850 Set number of hash buckets for route cache
2852 riscom8= [HW,SERIAL]
2853 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2855 ro [KNL] Mount root device read-only on boot
2857 root= [KNL] Root filesystem
2858 See name_to_dev_t comment in init/do_mounts.c.
2860 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2861 mount the root filesystem
2863 rootflags= [KNL] Set root filesystem mount option string
2865 rootfstype= [KNL] Set root filesystem type
2867 rootwait [KNL] Wait (indefinitely) for root device to show up.
2868 Useful for devices that are detected asynchronously
2869 (e.g. USB and MMC devices).
2871 rproc_mem=nn[KMG][@address]
2872 [KNL,ARM,CMA] Remoteproc physical memory block.
2873 Memory area to be used by remote processor image,
2876 rw [KNL] Mount root device read-write on boot
2878 S [KNL] Run init in single mode
2881 See drivers/net/irda/sa1100_ir.c.
2883 sbni= [NET] Granch SBNI12 leased line adapter
2885 sched_debug [KNL] Enables verbose scheduler debug messages.
2887 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2888 xtime_lock contention on larger systems, and/or RCU lock
2889 contention on all systems with CONFIG_MAXSMP set.
2890 Format: { "0" | "1" }
2891 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2893 Note: increases power consumption, thus should only be
2894 enabled if running jitter sensitive (HPC/RT) workloads.
2896 security= [SECURITY] Choose a security module to enable at boot.
2897 If this boot parameter is not specified, only the first
2898 security module asking for security registration will be
2899 loaded. An invalid security module name will be treated
2900 as if no module has been chosen.
2902 selinux= [SELINUX] Disable or enable SELinux at boot time.
2903 Format: { "0" | "1" }
2904 See security/selinux/Kconfig help text.
2907 Default value is set via kernel config option.
2908 If enabled at boot time, /selinux/disable can be used
2909 later to disable prior to initial policy load.
2911 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2912 Format: { "0" | "1" }
2913 See security/apparmor/Kconfig help text
2916 Default value is set via kernel config option.
2918 serialnumber [BUGS=X86-32]
2921 Maximal number of shapers.
2923 show_msr= [x86] show boot-time MSR settings
2924 Format: { <integer> }
2925 Show boot-time (BIOS-initialized) MSR settings.
2926 The parameter means the number of CPUs to show,
2927 for example 1 means boot CPU only.
2934 slab_max_order= [MM, SLAB]
2935 Determines the maximum allowed order for slabs.
2936 A high setting may cause OOMs due to memory
2937 fragmentation. Defaults to 1 for systems with
2938 more than 32MB of RAM, 0 otherwise.
2940 slub_debug[=options[,slabs]] [MM, SLUB]
2941 Enabling slub_debug allows one to determine the
2942 culprit if slab objects become corrupted. Enabling
2943 slub_debug can create guard zones around objects and
2944 may poison objects when not in use. Also tracks the
2945 last alloc / free. For more information see
2946 Documentation/vm/slub.txt.
2948 slub_max_order= [MM, SLUB]
2949 Determines the maximum allowed order for slabs.
2950 A high setting may cause OOMs due to memory
2951 fragmentation. For more information see
2952 Documentation/vm/slub.txt.
2954 slub_min_objects= [MM, SLUB]
2955 The minimum number of objects per slab. SLUB will
2956 increase the slab order up to slub_max_order to
2957 generate a sufficiently large slab able to contain
2958 the number of objects indicated. The higher the number
2959 of objects the smaller the overhead of tracking slabs
2960 and the less frequently locks need to be acquired.
2961 For more information see Documentation/vm/slub.txt.
2963 slub_min_order= [MM, SLUB]
2964 Determines the minimum page order for slabs. Must be
2965 lower than slub_max_order.
2966 For more information see Documentation/vm/slub.txt.
2968 slub_nomerge [MM, SLUB]
2969 Disable merging of slabs with similar size. May be
2970 necessary if there is some reason to distinguish
2971 allocs to different slabs. Debug options disable
2972 merging on their own.
2973 For more information see Documentation/vm/slub.txt.
2976 Format: <io1>[,<io2>[,...,<io8>]]
2978 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2979 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2980 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2981 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2982 smsc-ircc2.ircc_irq= [HW] IRQ line
2983 smsc-ircc2.ircc_dma= [HW] DMA channel
2984 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2985 0: Toshiba Satellite 1800 (GP data pin select)
2986 1: Fast pin select (default)
2990 [KNL] Should the soft-lockup detector generate panics.
2993 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2994 See Documentation/laptops/sonypi.txt
2996 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2997 See Documentation/serial/specialix.txt.
2999 spia_io_base= [HW,MTD]
3005 Enabled the stack tracer on boot up.
3007 stacktrace_filter=[function-list]
3008 [FTRACE] Limit the functions that the stack tracer
3009 will trace at boot up. function-list is a comma separated
3010 list of functions. This list can be changed at run
3011 time by the stack_trace_filter file in the debugfs
3012 tracing directory. Note, this enables stack tracing
3013 and the stacktrace above is not needed.
3017 Set the STI (builtin display/keyboard on the HP-PARISC
3018 machines) console (graphic card) which should be used
3019 as the initial boot-console.
3020 See also comment in drivers/video/console/sticore.c.
3023 See comment in drivers/video/console/sticore.c.
3026 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3028 sunrpc.min_resvport=
3029 sunrpc.max_resvport=
3031 SunRPC servers often require that client requests
3032 originate from a privileged port (i.e. a port in the
3033 range 0 < portnr < 1024).
3034 An administrator who wishes to reserve some of these
3035 ports for other uses may adjust the range that the
3036 kernel's sunrpc client considers to be privileged
3037 using these two parameters to set the minimum and
3038 maximum port values.
3042 Control how the NFS server code allocates CPUs to
3043 service thread pools. Depending on how many NICs
3044 you have and where their interrupts are bound, this
3045 option will affect which CPUs will do NFS serving.
3046 Note: this parameter cannot be changed while the
3047 NFS server is running.
3049 auto the server chooses an appropriate mode
3050 automatically using heuristics
3051 global a single global pool contains all CPUs
3052 percpu one pool for each CPU
3053 pernode one pool for each NUMA node (equivalent
3054 to global on non-NUMA machines)
3056 sunrpc.tcp_slot_table_entries=
3057 sunrpc.udp_slot_table_entries=
3059 Sets the upper limit on the number of simultaneous
3060 RPC calls that can be sent from the client to a
3061 server. Increasing these values may allow you to
3062 improve throughput, but will also increase the
3063 amount of memory reserved for use by the client.
3066 [KNL] Enable accounting of swap in memory resource
3067 controller if no parameter or 1 is given or disable
3068 it if 0 is given (See Documentation/cgroups/memory.txt)
3070 swiotlb= [IA-64] Number of I/O TLB slabs
3074 sysfs.deprecated=0|1 [KNL]
3075 Enable/disable old style sysfs layout for old udev
3076 on older distributions. When this option is enabled
3077 very new udev will not work anymore. When this option
3078 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3079 in older udev will not work anymore.
3080 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3081 the kernel configuration.
3083 sysrq_always_enabled
3085 Ignore sysrq setting - this boot parameter will
3086 neutralize any effect of /proc/sys/kernel/sysrq.
3087 Useful for debugging.
3091 test_suspend= [SUSPEND]
3092 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3093 standby suspend) as the system sleep state to briefly
3094 enter during system startup. The system is woken from
3095 this state using a wakeup-capable RTC alarm.
3097 thash_entries= [KNL,NET]
3098 Set number of hash buckets for TCP connection
3100 thermal.act= [HW,ACPI]
3101 -1: disable all active trip points in all thermal zones
3102 <degrees C>: override all lowest active trip points
3104 thermal.crt= [HW,ACPI]
3105 -1: disable all critical trip points in all thermal zones
3106 <degrees C>: override all critical trip points
3108 thermal.nocrt= [HW,ACPI]
3109 Set to disable actions on ACPI thermal zone
3110 critical and hot trip points.
3112 thermal.off= [HW,ACPI]
3113 1: disable ACPI thermal control
3115 thermal.psv= [HW,ACPI]
3116 -1: disable all passive trip points
3117 <degrees C>: override all passive trip points to this
3120 thermal.tzp= [HW,ACPI]
3121 Specify global default ACPI thermal zone polling rate
3122 <deci-seconds>: poll all this frequency
3123 0: no polling (default)
3126 Force threading of all interrupt handlers except those
3127 marked explicitly IRQF_NO_THREAD.
3130 Enable the Transcendent memory driver if built-in.
3132 tmem.cleancache=0|1 [KNL, XEN]
3133 Default is on (1). Disable the usage of the cleancache
3134 API to send anonymous pages to the hypervisor.
3136 tmem.frontswap=0|1 [KNL, XEN]
3137 Default is on (1). Disable the usage of the frontswap
3138 API to send swap pages to the hypervisor. If disabled
3139 the selfballooning and selfshrinking are force disabled.
3141 tmem.selfballooning=0|1 [KNL, XEN]
3142 Default is on (1). Disable the driving of swap pages
3145 tmem.selfshrinking=0|1 [KNL, XEN]
3146 Default is on (1). Partial swapoff that immediately
3147 transfers pages from Xen hypervisor back to the
3148 kernel based on different criteria.
3152 Specify if the kernel should make use of the cpu
3153 topology information if the hardware supports this.
3154 The scheduler will make use of this information and
3155 e.g. base its process migration decisions on it.
3160 tpm_suspend_pcr=[HW,TPM]
3161 Format: integer pcr id
3162 Specify that at suspend time, the tpm driver
3163 should extend the specified pcr with zeros,
3164 as a workaround for some chips which fail to
3165 flush the last written pcr on TPM_SaveState.
3166 This will guarantee that all the other pcrs
3169 trace_buf_size=nn[KMG]
3170 [FTRACE] will set tracing buffer size.
3172 trace_event=[event-list]
3173 [FTRACE] Set and start specified trace events in order
3174 to facilitate early boot debugging.
3175 See also Documentation/trace/events.txt
3177 trace_options=[option-list]
3178 [FTRACE] Enable or disable tracer options at boot.
3179 The option-list is a comma delimited list of options
3180 that can be enabled or disabled just as if you were
3181 to echo the option name into
3183 /sys/kernel/debug/tracing/trace_options
3185 For example, to enable stacktrace option (to dump the
3186 stack trace of each event), add to the command line:
3188 trace_options=stacktrace
3190 See also Documentation/trace/ftrace.txt "trace options"
3194 [FTRACE] enable this option to disable tracing when a
3195 warning is hit. This turns off "tracing_on". Tracing can
3196 be enabled again by echoing '1' into the "tracing_on"
3197 file located in /sys/kernel/debug/tracing/
3199 This option is useful, as it disables the trace before
3200 the WARNING dump is called, which prevents the trace to
3201 be filled with content caused by the warning output.
3203 This option can also be set at run time via the sysctl
3204 option: kernel/traceoff_on_warning
3206 transparent_hugepage=
3208 Format: [always|madvise|never]
3209 Can be used to control the default behavior of the system
3210 with respect to transparent hugepages.
3211 See Documentation/vm/transhuge.txt for more details.
3213 tsc= Disable clocksource stability checks for TSC.
3215 [x86] reliable: mark tsc clocksource as reliable, this
3216 disables clocksource verification at runtime, as well
3217 as the stability checks done at bootup. Used to enable
3218 high-resolution timer mode on older hardware, and in
3219 virtualized environment.
3220 [x86] noirqtime: Do not use TSC to do irq accounting.
3221 Used to run time disable IRQ_TIME_ACCOUNTING on any
3222 platforms where RDTSC is slow and this accounting
3225 turbografx.map[2|3]= [HW,JOY]
3226 TurboGraFX parallel port interface
3228 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3229 See also Documentation/input/joystick-parport.txt
3231 udbg-immortal [PPC] When debugging early kernel crashes that
3232 happen after console_init() and before a proper
3233 console driver takes over, this boot options might
3234 help "seeing" what's going on.
3236 uhash_entries= [KNL,NET]
3237 Set number of hash buckets for UDP/UDP-Lite connections
3240 [USB] Ignore overcurrent events (default N).
3241 Some badly-designed motherboards generate lots of
3242 bogus events, for ports that aren't wired to
3243 anything. Set this parameter to avoid log spamming.
3244 Note that genuine overcurrent events won't be
3248 [X86] Cause panic on unknown NMI.
3250 usbcore.authorized_default=
3251 [USB] Default USB device authorization:
3252 (default -1 = authorized except for wireless USB,
3253 0 = not authorized, 1 = authorized)
3255 usbcore.autosuspend=
3256 [USB] The autosuspend time delay (in seconds) used
3257 for newly-detected USB devices (default 2). This
3258 is the time required before an idle device will be
3259 autosuspended. Devices for which the delay is set
3260 to a negative value won't be autosuspended at all.
3262 usbcore.usbfs_snoop=
3263 [USB] Set to log all usbfs traffic (default 0 = off).
3265 usbcore.blinkenlights=
3266 [USB] Set to cycle leds on hubs (default 0 = off).
3268 usbcore.old_scheme_first=
3269 [USB] Start with the old device initialization
3270 scheme (default 0 = off).
3272 usbcore.usbfs_memory_mb=
3273 [USB] Memory limit (in MB) for buffers allocated by
3274 usbfs (default = 16, 0 = max = 2047).
3276 usbcore.use_both_schemes=
3277 [USB] Try the other device initialization scheme
3278 if the first one fails (default 1 = enabled).
3280 usbcore.initial_descriptor_timeout=
3281 [USB] Specifies timeout for the initial 64-byte
3282 USB_REQ_GET_DESCRIPTOR request in milliseconds
3283 (default 5000 = 5.0 seconds).
3286 [USBHID] The interval which mice are to be polled at.
3288 usb-storage.delay_use=
3289 [UMS] The delay in seconds before a new device is
3290 scanned for Logical Units (default 5).
3293 [UMS] A list of quirks entries to supplement or
3294 override the built-in unusual_devs list. List
3295 entries are separated by commas. Each entry has
3296 the form VID:PID:Flags where VID and PID are Vendor
3297 and Product ID values (4-digit hex numbers) and
3298 Flags is a set of characters, each corresponding
3299 to a common usb-storage quirk flag as follows:
3300 a = SANE_SENSE (collect more than 18 bytes
3302 b = BAD_SENSE (don't collect more than 18
3303 bytes of sense data);
3304 c = FIX_CAPACITY (decrease the reported
3305 device capacity by one sector);
3306 d = NO_READ_DISC_INFO (don't use
3307 READ_DISC_INFO command);
3308 e = NO_READ_CAPACITY_16 (don't use
3309 READ_CAPACITY_16 command);
3310 h = CAPACITY_HEURISTICS (decrease the
3311 reported device capacity by one
3312 sector if the number is odd);
3313 i = IGNORE_DEVICE (don't bind to this
3315 l = NOT_LOCKABLE (don't try to lock and
3316 unlock ejectable media);
3317 m = MAX_SECTORS_64 (don't transfer more
3318 than 64 sectors = 32 KB at a time);
3319 n = INITIAL_READ10 (force a retry of the
3320 initial READ(10) command);
3321 o = CAPACITY_OK (accept the capacity
3322 reported by the device);
3323 p = WRITE_CACHE (the device cache is ON
3325 r = IGNORE_RESIDUE (the device reports
3326 bogus residue values);
3327 s = SINGLE_LUN (the device has only one
3329 w = NO_WP_DETECT (don't test whether the
3330 medium is write-protected).
3331 Example: quirks=0419:aaf5:rl,0421:0433:rc
3333 user_debug= [KNL,ARM]
3335 See arch/arm/Kconfig.debug help text.
3336 1 - undefined instruction events
3338 4 - invalid data aborts
3341 Example: user_debug=31
3344 [X86] Flags controlling user PTE allocations.
3346 nohigh = do not allocate PTE pages in
3347 HIGHMEM regardless of setting
3351 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3352 vdso=1: enable VDSO (default)
3353 vdso=0: disable VDSO mapping
3356 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3357 vdso32=1: enable 32-bit VDSO (default)
3358 vdso32=0: disable 32-bit VDSO mapping
3361 vector=percpu: enable percpu vector domain
3363 video= [FB] Frame buffer configuration
3364 See Documentation/fb/modedb.txt.
3366 video.brightness_switch_enabled= [0,1]
3367 If set to 1, on receiving an ACPI notify event
3368 generated by hotkey, video driver will adjust brightness
3369 level and then send out the event to user space through
3370 the allocated input device; If set to 0, video driver
3371 will only send out the event without touching backlight
3376 [VMMIO] Memory mapped virtio (platform) device.
3378 <size>@<baseaddr>:<irq>[:<id>]
3380 <size> := size (can use standard suffixes
3382 <baseaddr> := physical base address
3383 <irq> := interrupt number (as passed to
3385 <id> := (optional) platform device id
3387 virtio_mmio.device=1K@0x100b0000:48:7
3389 Can be used multiple times for multiple devices.
3391 vga= [BOOT,X86-32] Select a particular video mode
3392 See Documentation/x86/boot.txt and
3393 Documentation/svga.txt.
3394 Use vga=ask for menu.
3395 This is actually a boot loader parameter; the value is
3396 passed to the kernel using a special protocol.
3398 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3399 size of <nn>. This can be used to increase the
3400 minimum size (128MB on x86). It can also be used to
3401 decrease the size and leave more room for directly
3404 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3407 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3410 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3414 Controls the behavior of vsyscalls (i.e. calls to
3415 fixed addresses of 0xffffffffff600x00 from legacy
3416 code). Most statically-linked binaries and older
3417 versions of glibc use these calls. Because these
3418 functions are at fixed addresses, they make nice
3419 targets for exploits that can control RIP.
3421 emulate [default] Vsyscalls turn into traps and are
3422 emulated reasonably safely.
3424 native Vsyscalls are native syscall instructions.
3425 This is a little bit faster than trapping
3426 and makes a few dynamic recompilers work
3427 better than they would in emulation mode.
3428 It also makes exploits much easier to write.
3430 none Vsyscalls don't work at all. This makes
3431 them quite hard to use for exploits but
3432 might break your system.
3434 vt.color= [VT] Default text color.
3435 Format: 0xYX, X = foreground, Y = background.
3436 Default: 0x07 = light gray on black.
3438 vt.cur_default= [VT] Default cursor shape.
3439 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3440 the parameters of the <Esc>[?A;B;Cc escape sequence;
3441 see VGA-softcursor.txt. Default: 2 = underline.
3443 vt.default_blu= [VT]
3444 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3445 Change the default blue palette of the console.
3446 This is a 16-member array composed of values
3449 vt.default_grn= [VT]
3450 Format: <green0>,<green1>,<green2>,...,<green15>
3451 Change the default green palette of the console.
3452 This is a 16-member array composed of values
3455 vt.default_red= [VT]
3456 Format: <red0>,<red1>,<red2>,...,<red15>
3457 Change the default red palette of the console.
3458 This is a 16-member array composed of values
3464 Set system-wide default UTF-8 mode for all tty's.
3465 Default is 1, i.e. UTF-8 mode is enabled for all
3466 newly opened terminals.
3468 vt.global_cursor_default=
3471 Set system-wide default for whether a cursor
3472 is shown on new VTs. Default is -1,
3473 i.e. cursors will be created by default unless
3474 overridden by individual drivers. 0 will hide
3475 cursors, 1 will display them.
3477 vt.italic= [VT] Default color for italic text; 0-15.
3480 vt.underline= [VT] Default color for underlined text; 0-15.
3483 watchdog timers [HW,WDT] For information on watchdog timers,
3484 see Documentation/watchdog/watchdog-parameters.txt
3485 or other driver-specific files in the
3486 Documentation/watchdog/ directory.
3488 workqueue.disable_numa
3489 By default, all work items queued to unbound
3490 workqueues are affine to the NUMA nodes they're
3491 issued on, which results in better behavior in
3492 general. If NUMA affinity needs to be disabled for
3493 whatever reason, this option can be used. Note
3494 that this also can be controlled per-workqueue for
3495 workqueues visible under /sys/bus/workqueue/.
3497 workqueue.power_efficient
3498 Per-cpu workqueues are generally preferred because
3499 they show better performance thanks to cache
3500 locality; unfortunately, per-cpu workqueues tend to
3501 be more power hungry than unbound workqueues.
3503 Enabling this makes the per-cpu workqueues which
3504 were observed to contribute significantly to power
3505 consumption unbound, leading to measurably lower
3506 power usage at the cost of small performance
3509 The default value of this parameter is determined by
3510 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3512 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3513 default x2apic cluster mode on platforms
3516 x86_intel_mid_timer= [X86-32,APBT]
3517 Choose timer option for x86 Intel MID platform.
3518 Two valid options are apbt timer only and lapic timer
3519 plus one apbt timer for broadcast timer.
3520 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3522 xen_emul_unplug= [HW,X86,XEN]
3523 Unplug Xen emulated devices
3524 Format: [unplug0,][unplug1]
3525 ide-disks -- unplug primary master IDE devices
3526 aux-ide-disks -- unplug non-primary-master IDE devices
3527 nics -- unplug network devices
3528 all -- unplug all emulated devices (NICs and IDE disks)
3529 unnecessary -- unplugging emulated devices is
3530 unnecessary even if the host did not respond to
3532 never -- do not unplug even if version check succeeds
3534 xen_nopvspin [X86,XEN]
3535 Disables the ticketlock slowpath using Xen PV
3538 xirc2ps_cs= [NET,PCMCIA]
3540 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3542 ______________________________________________________________________
3546 Add more DRM drivers.