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 edac_report= [HW,EDAC] Control how to report EDAC event
885 Format: {"on" | "off" | "force"}
886 on: enable EDAC to report H/W event. May be overridden
887 by other higher priority error reporting module.
888 off: disable H/W event reporting through EDAC.
889 force: enforce the use of EDAC to report H/W event.
892 ekgdboc= [X86,KGDB] Allow early kernel console debugging
895 This is designed to be used in conjunction with
896 the boot argument: earlyprintk=vga
899 Format: {"off" | "on" | "skip[mbr]"}
901 efi_no_storage_paranoia [EFI; X86]
902 Using this parameter you can use more than 50% of
903 your efi variable storage. Use this parameter only if
904 you are really sure that your UEFI does sane gc and
905 fulfills the spec otherwise your board may brick.
907 eisa_irq_edge= [PARISC,HW]
908 See header of drivers/parisc/eisa.c.
911 See comment before function elanfreq_setup() in
912 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
915 Format: {"cfq" | "deadline" | "noop"}
916 See Documentation/block/cfq-iosched.txt and
917 Documentation/block/deadline-iosched.txt for details.
919 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
920 Specifies physical address of start of kernel core
921 image elf header and optionally the size. Generally
922 kexec loader will pass this option to capture kernel.
923 See Documentation/kdump/kdump.txt for details.
925 enable_mtrr_cleanup [X86]
926 The kernel tries to adjust MTRR layout from continuous
927 to discrete, to make X server driver able to add WB
928 entry later. This parameter enables that.
930 enable_timer_pin_1 [X86]
931 Enable PIN 1 of APIC timer
932 Can be useful to work around chipset bugs
933 (in particular on some ATI chipsets).
934 The kernel tries to set a reasonable default.
936 enforcing [SELINUX] Set initial enforcing status.
938 See security/selinux/Kconfig help text.
939 0 -- permissive (log only, no denials).
940 1 -- enforcing (deny and log).
942 Value can be changed at runtime via /selinux/enforce.
945 Disable Error Record Serialization Table (ERST)
948 ether= [HW,NET] Ethernet cards parameters
949 This option is obsoleted by the "netdev=" option, which
950 has equivalent usage. See its documentation for details.
954 Permit 'security.evm' to be updated regardless of
955 current integrity status.
959 fail_make_request=[KNL]
960 General fault injection mechanism.
961 Format: <interval>,<probability>,<space>,<times>
962 See also Documentation/fault-injection/.
965 See Documentation/blockdev/floppy.txt.
967 force_pal_cache_flush
968 [IA-64] Avoid check_sal_cache_flush which may hang on
969 buggy SAL_CACHE_FLUSH implementations. Using this
970 parameter will force ia64_sal_cache_flush to call
971 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
974 [FTRACE] will set and start the specified tracer
975 as early as possible in order to facilitate early
978 ftrace_dump_on_oops[=orig_cpu]
979 [FTRACE] will dump the trace buffers on oops.
980 If no parameter is passed, ftrace will dump
981 buffers of all CPUs, but if you pass orig_cpu, it will
982 dump only the buffer of the CPU that triggered the
985 ftrace_filter=[function-list]
986 [FTRACE] Limit the functions traced by the function
987 tracer at boot up. function-list is a comma separated
988 list of functions. This list can be changed at run
989 time by the set_ftrace_filter file in the debugfs
992 ftrace_notrace=[function-list]
993 [FTRACE] Do not trace the functions specified in
994 function-list. This list can be changed at run time
995 by the set_ftrace_notrace file in the debugfs
998 ftrace_graph_filter=[function-list]
999 [FTRACE] Limit the top level callers functions traced
1000 by the function graph tracer at boot up.
1001 function-list is a comma separated list of functions
1002 that can be changed at run time by the
1003 set_graph_function file in the debugfs tracing directory.
1006 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1007 support via parallel port (up to 5 devices per port)
1008 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1009 See also Documentation/input/joystick-parport.txt
1013 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1017 gcov_persist= [GCOV] When non-zero (default), profiling data for
1018 kernel modules is saved and remains accessible via
1019 debugfs, even when the module is unloaded/reloaded.
1020 When zero, profiling data is discarded and associated
1021 debugfs files are removed at module unload time.
1023 gpt [EFI] Forces disk with valid GPT signature but
1024 invalid Protective MBR to be treated as GPT.
1026 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1027 the "Enable 0" bit of the configuration register.
1030 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1031 the "Enable 0" bit of the configuration register.
1034 grcan.select= [HW] Select which physical interface to use.
1037 grcan.txsize= [HW] Sets the size of the tx buffer.
1038 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1040 grcan.rxsize= [HW] Sets the size of the rx buffer.
1041 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1044 hashdist= [KNL,NUMA] Large hashes allocated during boot
1045 are distributed across NUMA nodes. Defaults on
1046 for 64-bit NUMA, off otherwise.
1047 Format: 0 | 1 (for off | on)
1049 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1051 hd= [EIDE] (E)IDE hard drive subsystem geometry
1052 Format: <cyl>,<head>,<sect>
1055 Disable Hardware Error Source Table (HEST) support;
1056 corresponding firmware-first mode error processing
1057 logic will be disabled.
1059 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1060 size of <nn>. This works even on boxes that have no
1061 highmem otherwise. This also works to reduce highmem
1062 size on bigger boxes.
1064 highres= [KNL] Enable/disable high resolution timer mode.
1065 Valid parameters: "on", "off"
1069 See Documentation/isdn/README.HiSax.
1073 hpet= [X86-32,HPET] option to control HPET usage
1074 Format: { enable (default) | disable | force |
1076 disable: disable HPET and use PIT instead
1077 force: allow force enabled of undocumented chips (ICH4,
1079 verbose: show contents of HPET registers during setup
1081 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1082 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1084 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1085 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1086 On x86-64 and powerpc, this option can be specified
1087 multiple times interleaved with hugepages= to reserve
1088 huge pages of different sizes. Valid pages sizes on
1089 x86-64 are 2M (when the CPU supports "pse") and 1G
1090 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1091 Note that 1GB pages can only be allocated at boot time
1092 using hugepages= and not freed afterwards.
1094 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1095 terminal devices. Valid values: 0..8
1096 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1097 If specified, z/VM IUCV HVC accepts connections
1098 from listed z/VM user IDs only.
1100 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1101 hardware thread id mappings.
1102 Format: <cpu>:<hwthread>
1105 Do not unregister boot console at start. This is only
1106 useful for debugging when something happens in the window
1107 between unregistering the boot console and initializing
1110 i2c_bus= [HW] Override the default board specific I2C bus speed
1111 or register an additional I2C bus that is not
1112 registered from board initialization code.
1116 i8042.debug [HW] Toggle i8042 debug mode
1117 i8042.direct [HW] Put keyboard port into non-translated mode
1118 i8042.dumbkbd [HW] Pretend that controller can only read data from
1119 keyboard and cannot control its state
1120 (Don't attempt to blink the leds)
1121 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1122 i8042.nokbd [HW] Don't check/create keyboard port
1123 i8042.noloop [HW] Disable the AUX Loopback command while probing
1125 i8042.nomux [HW] Don't check presence of an active multiplexing
1127 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1129 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1130 i8042.reset [HW] Reset the controller during init and cleanup
1131 i8042.unlock [HW] Unlock (ignore) the keylock
1135 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1136 indicates that the driver is running on unsupported
1138 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1139 does not match list of supported models.
1141 [HW] Report power status in /proc/i8k
1142 (disabled by default)
1143 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1146 i915.invert_brightness=
1147 [DRM] Invert the sense of the variable that is used to
1148 set the brightness of the panel backlight. Normally a
1149 brightness value of 0 indicates backlight switched off,
1150 and the maximum of the brightness value sets the backlight
1151 to maximum brightness. If this parameter is set to 0
1152 (default) and the machine requires it, or this parameter
1153 is set to 1, a brightness value of 0 sets the backlight
1154 to maximum brightness, and the maximum of the brightness
1155 value switches the backlight off.
1156 -1 -- never invert brightness
1157 0 -- machine default
1158 1 -- force brightness inversion
1161 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1163 ide-core.nodma= [HW] (E)IDE subsystem
1164 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1165 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1166 .cdrom .chs .ignore_cable are additional options
1167 See Documentation/ide/ide.txt.
1169 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1170 Claim all unknown PCI IDE storage controllers.
1173 Format: idle=poll, idle=halt, idle=nomwait
1174 Poll forces a polling idle loop that can slightly
1175 improve the performance of waking up a idle CPU, but
1176 will use a lot of power and make the system run hot.
1178 idle=halt: Halt is forced to be used for CPU idle.
1179 In such case C2/C3 won't be used again.
1180 idle=nomwait: Disable mwait for CPU C-states
1182 ignore_loglevel [KNL]
1183 Ignore loglevel setting - this will print /all/
1184 kernel messages to the console. Useful for debugging.
1185 We also add it as printk module parameter, so users
1186 could change it dynamically, usually by
1187 /sys/module/printk/parameters/ignore_loglevel.
1189 ihash_entries= [KNL]
1190 Set number of hash buckets for inode cache.
1192 ima_appraise= [IMA] appraise integrity measurements
1193 Format: { "off" | "enforce" | "fix" }
1196 ima_appraise_tcb [IMA]
1197 The builtin appraise policy appraises all files
1201 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1205 The list of supported hash algorithms is defined
1206 in crypto/hash_info.h.
1209 Load a policy which meets the needs of the Trusted
1210 Computing Base. This means IMA will measure all
1211 programs exec'd, files mmap'd for exec, and all files
1212 opened for read by uid=0.
1215 Select one of defined IMA measurements template formats.
1216 Formats: { "ima" | "ima-ng" }
1221 Run specified binary instead of /sbin/init as init
1224 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1225 for working out where the kernel is dying during
1228 initrd= [BOOT] Specify the location of the initial ramdisk
1230 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1233 int_pln_enable [x86] Enable power limit notification interrupt
1235 integrity_audit=[IMA]
1236 Format: { "0" | "1" }
1237 0 -- basic integrity auditing messages. (Default)
1238 1 -- additional integrity auditing messages.
1240 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1242 Enable intel iommu driver.
1244 Disable intel iommu driver.
1245 igfx_off [Default Off]
1246 By default, gfx is mapped as normal device. If a gfx
1247 device has a dedicated DMAR unit, the DMAR unit is
1248 bypassed by not enabling DMAR with this option. In
1249 this case, gfx device will use physical address for
1252 With this option iommu will not optimize to look
1253 for io virtual address below 32-bit forcing dual
1254 address cycle on pci bus for cards supporting greater
1255 than 32-bit addressing. The default is to look
1256 for translation below 32-bit and if not available
1257 then look in the higher range.
1258 strict [Default Off]
1259 With this option on every unmap_single operation will
1260 result in a hardware IOTLB flush operation as opposed
1261 to batching them for performance.
1262 sp_off [Default Off]
1263 By default, super page will be supported if Intel IOMMU
1264 has the capability. With this option, super page will
1267 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1268 0 disables intel_idle and fall back on acpi_idle.
1269 1 to 6 specify maximum depth of C-state.
1273 Do not enable intel_pstate as the default
1274 scaling driver for the supported processors
1276 intremap= [X86-64, Intel-IOMMU]
1277 on enable Interrupt Remapping (default)
1278 off disable Interrupt Remapping
1279 nosid disable Source ID checking
1281 BIOS x2APIC opt-out request will be ignored
1283 iomem= Disable strict checking of access to MMIO memory
1284 strict regions from userspace.
1301 io7= [HW] IO7 for Marvel based alpha systems
1302 See comment before marvel_specify_io7 in
1303 arch/alpha/kernel/core_marvel.c.
1305 io_delay= [X86] I/O delay method
1307 Standard port 0x80 based delay
1309 Alternate port 0xed based delay (needed on some systems)
1311 Simple two microseconds delay
1316 See Documentation/filesystems/nfs/nfsroot.txt.
1318 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1319 See comment before ip2_setup() in
1320 drivers/char/ip2/ip2base.c.
1323 When an interrupt is not handled search all handlers
1324 for it. Intended to get systems with badly broken
1328 When an interrupt is not handled search all handlers
1329 for it. Also check all handlers each timer
1330 interrupt. Intended to get systems with badly broken
1334 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1336 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1338 <cpu number>,...,<cpu number>
1340 <cpu number>-<cpu number>
1341 (must be a positive range in ascending order)
1343 <cpu number>,...,<cpu number>-<cpu number>
1345 This option can be used to specify one or more CPUs
1346 to isolate from the general SMP balancing and scheduling
1347 algorithms. You can move a process onto or off an
1348 "isolated" CPU via the CPU affinity syscalls or cpuset.
1349 <cpu number> begins at 0 and the maximum value is
1350 "number of CPUs in system - 1".
1352 This option is the preferred way to isolate CPUs. The
1353 alternative -- manually setting the CPU mask of all
1354 tasks in the system -- can cause problems and
1355 suboptimal load balancer performance.
1359 ivrs_ioapic [HW,X86_64]
1360 Provide an override to the IOAPIC-ID<->DEVICE-ID
1361 mapping provided in the IVRS ACPI table. For
1362 example, to map IOAPIC-ID decimal 10 to
1363 PCI device 00:14.0 write the parameter as:
1364 ivrs_ioapic[10]=00:14.0
1366 ivrs_hpet [HW,X86_64]
1367 Provide an override to the HPET-ID<->DEVICE-ID
1368 mapping provided in the IVRS ACPI table. For
1369 example, to map HPET-ID decimal 0 to
1370 PCI device 00:14.0 write the parameter as:
1371 ivrs_hpet[0]=00:14.0
1373 js= [HW,JOY] Analog joystick
1374 See Documentation/input/joystick.txt.
1378 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1379 specifies the amount of memory usable by the kernel
1380 for non-movable allocations. The requested amount is
1381 spread evenly throughout all nodes in the system. The
1382 remaining memory in each node is used for Movable
1383 pages. In the event, a node is too small to have both
1384 kernelcore and Movable pages, kernelcore pages will
1385 take priority and other nodes will have a larger number
1386 of Movable pages. The Movable zone is used for the
1387 allocation of pages that may be reclaimed or moved
1388 by the page migration subsystem. This means that
1389 HugeTLB pages may not be allocated from this zone.
1390 Note that allocations like PTEs-from-HighMem still
1391 use the HighMem zone if it exists, and the Normal
1392 zone if it does not.
1394 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1395 Format: <Controller#>[,poll interval]
1396 The controller # is the number of the ehci usb debug
1397 port as it is probed via PCI. The poll interval is
1398 optional and is the number seconds in between
1399 each poll cycle to the debug port in case you need
1400 the functionality for interrupting the kernel with
1401 gdb or control-c on the dbgp connection. When
1402 not using this parameter you use sysrq-g to break into
1403 the kernel debugger.
1405 kgdboc= [KGDB,HW] kgdb over consoles.
1406 Requires a tty driver that supports console polling,
1407 or a supported polling keyboard driver (non-usb).
1408 Serial only format: <serial_device>[,baud]
1409 keyboard only format: kbd
1410 keyboard and serial format: kbd,<serial_device>[,baud]
1411 Optional Kernel mode setting:
1412 kms, kbd format: kms,kbd
1413 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1415 kgdbwait [KGDB] Stop kernel execution and enter the
1416 kernel debugger at the earliest opportunity.
1418 kmac= [MIPS] korina ethernet MAC address.
1419 Configure the RouterBoard 532 series on-chip
1420 Ethernet adapter MAC address.
1422 kmemleak= [KNL] Boot-time kmemleak enable/disable
1423 Valid arguments: on, off
1426 kstack=N [X86] Print N words from the kernel stack
1429 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1430 Default is 0 (don't ignore, but inject #GP)
1432 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1436 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1437 Default is 1 (enabled)
1439 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1441 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1443 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1444 (virtualized MMU) support on capable Intel chips.
1445 Default is 1 (enabled)
1447 kvm-intel.emulate_invalid_guest_state=
1448 [KVM,Intel] Enable emulation of invalid guest states
1449 Default is 0 (disabled)
1451 kvm-intel.flexpriority=
1452 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1453 Default is 1 (enabled)
1456 [KVM,Intel] Enable VMX nesting (nVMX).
1457 Default is 0 (disabled)
1459 kvm-intel.unrestricted_guest=
1460 [KVM,Intel] Disable unrestricted guest feature
1461 (virtualized real and unpaged mode) on capable
1462 Intel chips. Default is 1 (enabled)
1464 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1465 feature (tagged TLBs) on capable Intel chips.
1466 Default is 1 (enabled)
1472 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1475 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1476 value for LAPIC timer one-shot implementation. Default
1477 back to the programmable timer unit in the LAPIC.
1479 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1482 libata.dma= [LIBATA] DMA control
1483 libata.dma=0 Disable all PATA and SATA DMA
1484 libata.dma=1 PATA and SATA Disk DMA only
1485 libata.dma=2 ATAPI (CDROM) DMA only
1486 libata.dma=4 Compact Flash DMA only
1487 Combinations also work, so libata.dma=3 enables DMA
1488 for disks and CDROMs, but not CFs.
1490 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1491 libata.ignore_hpa=0 keep BIOS limits (default)
1492 libata.ignore_hpa=1 ignore limits, using full disk
1494 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1498 libata.force= [LIBATA] Force configurations. The format is comma
1499 separated list of "[ID:]VAL" where ID is
1500 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1501 matching port, link or device. Basically, it matches
1502 the ATA ID string printed on console by libata. If
1503 the whole ID part is omitted, the last PORT and DEVICE
1504 values are used. If ID hasn't been specified yet, the
1505 configuration applies to all ports, links and devices.
1507 If only DEVICE is omitted, the parameter applies to
1508 the port and all links and devices behind it. DEVICE
1509 number of 0 either selects the first device or the
1510 first fan-out link behind PMP device. It does not
1511 select the host link. DEVICE number of 15 selects the
1512 host link and device attached to it.
1514 The VAL specifies the configuration to force. As long
1515 as there's no ambiguity shortcut notation is allowed.
1516 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1517 The following configurations can be forced.
1519 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1520 Any ID with matching PORT is used.
1522 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1524 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1525 udma[/][16,25,33,44,66,100,133] notation is also
1528 * [no]ncq: Turn on or off NCQ.
1530 * nohrst, nosrst, norst: suppress hard, soft
1533 * rstonce: only attempt one reset during
1534 hot-unplug link recovery
1536 * dump_id: dump IDENTIFY data.
1538 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1540 If there are multiple matching configurations changing
1541 the same attribute, the last one is used.
1543 memblock=debug [KNL] Enable memblock debug messages.
1545 load_ramdisk= [RAM] List of ramdisks to load from floppy
1546 See Documentation/blockdev/ramdisk.txt.
1548 lockd.nlm_grace_period=P [NFS] Assign grace period.
1551 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1554 lockd.nlm_timeout=T [NFS] Assign timeout value.
1557 lockd.nlm_udpport=M [NFS] Assign UDP port.
1560 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1563 loglevel= All Kernel Messages with a loglevel smaller than the
1564 console loglevel will be printed to the console. It can
1565 also be changed with klogd or other programs. The
1566 loglevels are defined as follows:
1568 0 (KERN_EMERG) system is unusable
1569 1 (KERN_ALERT) action must be taken immediately
1570 2 (KERN_CRIT) critical conditions
1571 3 (KERN_ERR) error conditions
1572 4 (KERN_WARNING) warning conditions
1573 5 (KERN_NOTICE) normal but significant condition
1574 6 (KERN_INFO) informational
1575 7 (KERN_DEBUG) debug-level messages
1577 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1578 in bytes. n must be a power of two. The default
1579 size is set in the kernel config file.
1581 logo.nologo [FB] Disables display of the built-in Linux logo.
1582 This may be used to provide more screen space for
1583 kernel log messages and is useful when debugging
1584 kernel boot problems.
1586 lp=0 [LP] Specify parallel ports to use, e.g,
1587 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1588 lp=reset first parallel port). 'lp=0' disables the
1589 lp=auto printer driver. 'lp=reset' (which can be
1590 specified in addition to the ports) causes
1591 attached printers to be reset. Using
1592 lp=port1,port2,... specifies the parallel ports
1593 to associate lp devices with, starting with
1594 lp0. A port specification may be 'none' to skip
1595 that lp device, or a parport name such as
1596 'parport0'. Specifying 'lp=auto' instead of a
1597 port specification list means that device IDs
1598 from each port should be examined, to see if
1599 an IEEE 1284-compliant printer is attached; if
1600 so, the driver will manage that printer.
1601 See also header of drivers/char/lp.c.
1604 Sets loops_per_jiffy to given constant, thus avoiding
1605 time-consuming boot-time autodetection (up to 250 ms per
1606 CPU). 0 enables autodetection (default). To determine
1607 the correct value for your kernel, boot with normal
1608 autodetection and see what value is printed. Note that
1609 on SMP systems the preset will be applied to all CPUs,
1610 which is likely to cause problems if your CPUs need
1611 significantly divergent settings. An incorrect value
1612 will cause delays in the kernel to be wrong, leading to
1613 unpredictable I/O errors and other breakage. Although
1614 unlikely, in the extreme case this might damage your
1618 Format: <io>,<irq>,<dma>
1620 machvec= [IA-64] Force the use of a particular machine-vector
1621 (machvec) in a generic kernel.
1622 Example: machvec=hpzx1_swiotlb
1624 machtype= [Loongson] Share the same kernel image file between different
1626 Example: machtype=lemote-yeeloong-2f-7inch
1628 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1629 than or equal to this physical address is ignored.
1631 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1632 should make use of. maxcpus=n : n >= 0 limits the
1633 kernel to using 'n' processors. n=0 is a special case,
1634 it is equivalent to "nosmp", which also disables
1637 max_loop= [LOOP] The number of loop block devices that get
1638 (loop.max_loop) unconditionally pre-created at init time. The default
1639 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1640 of statically allocating a predefined number, loop
1641 devices can be requested on-demand with the
1642 /dev/loop-control interface.
1644 mce [X86-32] Machine Check Exception
1646 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1648 md= [HW] RAID subsystems devices and level
1649 See Documentation/md.txt.
1652 Format: <first>,<last>
1653 Specifies range of consoles to be captured by the MDA.
1655 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1656 Amount of memory to be used when the kernel is not able
1657 to see the whole system memory or for test.
1658 [X86] Work as limiting max address. Use together
1659 with memmap= to avoid physical address space collisions.
1660 Without memmap= PCI devices could be placed at addresses
1661 belonging to unused RAM.
1663 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1667 [KNL,SH] Allow user to override the default size for
1668 per-device physically contiguous DMA buffers.
1670 memmap=exactmap [KNL,X86] Enable setting of an exact
1671 E820 memory map, as specified by the user.
1672 Such memmap=exactmap lines can be constructed based on
1673 BIOS output or other requirements. See the memmap=nn@ss
1676 memmap=nn[KMG]@ss[KMG]
1677 [KNL] Force usage of a specific region of memory
1678 Region of memory to be used, from ss to ss+nn.
1680 memmap=nn[KMG]#ss[KMG]
1681 [KNL,ACPI] Mark specific memory as ACPI data.
1682 Region of memory to be used, from ss to ss+nn.
1684 memmap=nn[KMG]$ss[KMG]
1685 [KNL,ACPI] Mark specific memory as reserved.
1686 Region of memory to be used, from ss to ss+nn.
1687 Example: Exclude memory from 0x18690000-0x1869ffff
1688 memmap=64K$0x18690000
1690 memmap=0x10000$0x18690000
1692 memory_corruption_check=0/1 [X86]
1693 Some BIOSes seem to corrupt the first 64k of
1694 memory when doing things like suspend/resume.
1695 Setting this option will scan the memory
1696 looking for corruption. Enabling this will
1697 both detect corruption and prevent the kernel
1698 from using the memory being corrupted.
1699 However, its intended as a diagnostic tool; if
1700 repeatable BIOS-originated corruption always
1701 affects the same memory, you can use memmap=
1702 to prevent the kernel from using that memory.
1704 memory_corruption_check_size=size [X86]
1705 By default it checks for corruption in the low
1706 64k, making this memory unavailable for normal
1707 use. Use this parameter to scan for
1708 corruption in more or less memory.
1710 memory_corruption_check_period=seconds [X86]
1711 By default it checks for corruption every 60
1712 seconds. Use this parameter to check at some
1713 other rate. 0 disables periodic checking.
1715 memtest= [KNL,X86] Enable memtest
1717 default : 0 <disable>
1718 Specifies the number of memtest passes to be
1719 performed. Each pass selects another test
1720 pattern from a given set of patterns. Memtest
1721 fills the memory with this pattern, validates
1722 memory contents and reserves bad memory
1723 regions that are detected.
1725 meye.*= [HW] Set MotionEye Camera parameters
1726 See Documentation/video4linux/meye.txt.
1728 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1729 Multi-Function General Purpose Timers on AMD Geode
1732 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1733 the BIOS has incorrectly applied a workaround. TinyBIOS
1734 version 0.98 is known to be affected, 0.99 fixes the
1735 problem by letting the user disable the workaround.
1739 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1740 physical address is ignored.
1742 mini2440= [ARM,HW,KNL]
1743 Format:[0..2][b][c][t]
1745 MINI2440 configuration specification:
1746 0 - The attached screen is the 3.5" TFT
1747 1 - The attached screen is the 7" TFT
1748 2 - The VGA Shield is attached (1024x768)
1749 Leaving out the screen size parameter will not load
1750 the TFT driver, and the framebuffer will be left
1752 b - Enable backlight. The TFT backlight pin will be
1753 linked to the kernel VESA blanking code and a GPIO
1754 LED. This parameter is not necessary when using the
1756 c - Enable the s3c camera interface.
1757 t - Reserved for enabling touchscreen support. The
1758 touchscreen support is not enabled in the mainstream
1759 kernel as of 2.6.30, a preliminary port can be found
1760 in the "bleeding edge" mini2440 support kernel at
1761 http://repo.or.cz/w/linux-2.6/mini2440.git
1764 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1765 parameter allows control of the logging verbosity for
1766 the additional memory initialisation checks. A value
1767 of 0 disables mminit logging and a level of 4 will
1768 log everything. Information is printed at KERN_DEBUG
1769 so loglevel=8 may also need to be specified.
1772 [KNL] When CONFIG_MODULE_SIG is set, this means that
1773 modules without (valid) signatures will fail to load.
1774 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1775 is always true, so this option does nothing.
1778 [MOUSE] Maximum time between finger touching and
1779 leaving touchpad surface for touch to be considered
1780 a tap and be reported as a left button click (for
1781 touchpads working in absolute mode only).
1783 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1784 reporting absolute coordinates, such as tablets
1785 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1786 reporting absolute coordinates, such as tablets
1788 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1789 is similar to kernelcore except it specifies the
1790 amount of memory used for migratable allocations.
1791 If both kernelcore and movablecore is specified,
1792 then kernelcore will be at *least* the specified
1793 value but may be more. If movablecore on its own
1794 is specified, the administrator must be careful
1795 that the amount of memory usable for all allocations
1798 movable_node [KNL,X86] Boot-time switch to enable the effects
1799 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1801 MTD_Partition= [MTD]
1802 Format: <name>,<region-number>,<size>,<offset>
1804 MTD_Region= [MTD] Format:
1805 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1808 See drivers/mtd/cmdlinepart.c.
1810 multitce=off [PPC] This parameter disables the use of the pSeries
1811 firmware feature for updating multiple TCE entries
1814 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1816 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1818 boundary - index of last SLC block on Flex-OneNAND.
1819 The remaining blocks are configured as MLC blocks.
1820 lock - Configure if Flex-OneNAND boundary should be locked.
1821 Once locked, the boundary cannot be changed.
1822 1 indicates lock status, 0 indicates unlock status.
1825 ARM/S3C2412 JIVE boot control
1827 See arch/arm/mach-s3c2412/mach-jive.c
1829 mtouchusb.raw_coordinates=
1830 [HW] Make the MicroTouch USB driver use raw coordinates
1831 ('y', default) or cooked coordinates ('n')
1833 mtrr_chunk_size=nn[KMG] [X86]
1834 used for mtrr cleanup. It is largest continuous chunk
1835 that could hold holes aka. UC entries.
1837 mtrr_gran_size=nn[KMG] [X86]
1838 Used for mtrr cleanup. It is granularity of mtrr block.
1840 Large value could prevent small alignment from
1843 mtrr_spare_reg_nr=n [X86]
1845 Range: 0,7 : spare reg number
1847 Used for mtrr cleanup. It is spare mtrr entries number.
1848 Set to 2 or more if your graphical card needs more.
1850 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1852 netdev= [NET] Network devices parameters
1853 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1854 Note that mem_start is often overloaded to mean
1855 something different and driver-specific.
1856 This usage is only documented in each driver source
1860 [NETFILTER] Enable connection tracking flow accounting
1861 0 to disable accounting
1862 1 to enable accounting
1865 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1866 See Documentation/filesystems/nfs/nfsroot.txt.
1868 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1869 See Documentation/filesystems/nfs/nfsroot.txt.
1871 nfsrootdebug [NFS] enable nfsroot debugging messages.
1872 See Documentation/filesystems/nfs/nfsroot.txt.
1874 nfs.callback_tcpport=
1875 [NFS] set the TCP port on which the NFSv4 callback
1876 channel should listen.
1879 [NFS] sets the pathname to the program which is used
1880 to update the NFS client cache entries.
1882 nfs.cache_getent_timeout=
1883 [NFS] sets the timeout after which an attempt to
1884 update a cache entry is deemed to have failed.
1886 nfs.idmap_cache_timeout=
1887 [NFS] set the maximum lifetime for idmapper cache
1891 [NFS] enable 64-bit inode numbers.
1892 If zero, the NFS client will fake up a 32-bit inode
1893 number for the readdir() and stat() syscalls instead
1894 of returning the full 64-bit number.
1895 The default is to return 64-bit inode numbers.
1897 nfs.max_session_slots=
1898 [NFSv4.1] Sets the maximum number of session slots
1899 the client will attempt to negotiate with the server.
1900 This limits the number of simultaneous RPC requests
1901 that the client can send to the NFSv4.1 server.
1902 Note that there is little point in setting this
1903 value higher than the max_tcp_slot_table_limit.
1905 nfs.nfs4_disable_idmapping=
1906 [NFSv4] When set to the default of '1', this option
1907 ensures that both the RPC level authentication
1908 scheme and the NFS level operations agree to use
1909 numeric uids/gids if the mount is using the
1910 'sec=sys' security flavour. In effect it is
1911 disabling idmapping, which can make migration from
1912 legacy NFSv2/v3 systems to NFSv4 easier.
1913 Servers that do not support this mode of operation
1914 will be autodetected by the client, and it will fall
1915 back to using the idmapper.
1916 To turn off this behaviour, set the value to '0'.
1918 [NFS4] Specify an additional fixed unique ident-
1919 ification string that NFSv4 clients can insert into
1920 their nfs_client_id4 string. This is typically a
1921 UUID that is generated at system install time.
1923 nfs.send_implementation_id =
1924 [NFSv4.1] Send client implementation identification
1925 information in exchange_id requests.
1926 If zero, no implementation identification information
1928 The default is to send the implementation identification
1931 nfs.recover_lost_locks =
1932 [NFSv4] Attempt to recover locks that were lost due
1933 to a lease timeout on the server. Please note that
1934 doing this risks data corruption, since there are
1935 no guarantees that the file will remain unchanged
1936 after the locks are lost.
1937 If you want to enable the kernel legacy behaviour of
1938 attempting to recover these locks, then set this
1940 The default parameter value of '0' causes the kernel
1941 not to attempt recovery of lost locks.
1943 nfsd.nfs4_disable_idmapping=
1944 [NFSv4] When set to the default of '1', the NFSv4
1945 server will return only numeric uids and gids to
1946 clients using auth_sys, and will accept numeric uids
1947 and gids from such clients. This is intended to ease
1948 migration from NFSv2/v3.
1950 objlayoutdriver.osd_login_prog=
1951 [NFS] [OBJLAYOUT] sets the pathname to the program which
1952 is used to automatically discover and login into new
1953 osd-targets. Please see:
1954 Documentation/filesystems/pnfs.txt for more explanations
1956 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1957 when a NMI is triggered.
1958 Format: [state][,regs][,debounce][,die]
1960 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1961 Format: [panic,][nopanic,][num]
1963 0 - turn nmi_watchdog off
1964 When panic is specified, panic when an NMI watchdog
1965 timeout occurs (or 'nopanic' to override the opposite
1967 This is useful when you use a panic=... timeout and
1968 need the box quickly up again.
1970 netpoll.carrier_timeout=
1971 [NET] Specifies amount of time (in seconds) that
1972 netpoll should wait for a carrier. By default netpoll
1975 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1976 emulation library even if a 387 maths coprocessor
1980 [HW] Never suspend the console
1981 Disable suspending of consoles during suspend and
1982 hibernate operations. Once disabled, debugging
1983 messages can reach various consoles while the rest
1984 of the system is being put to sleep (ie, while
1985 debugging driver suspend/resume hooks). This may
1986 not work reliably with all consoles, but is known
1987 to work with serial and VGA consoles.
1988 To facilitate more flexible debugging, we also add
1989 console_suspend, a printk module parameter to control
1990 it. Users could use console_suspend (usually
1991 /sys/module/printk/parameters/console_suspend) to
1992 turn on/off it dynamically.
1994 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1995 caches in the slab allocator. Saves per-node memory,
1996 but will impact performance.
2000 noapic [SMP,APIC] Tells the kernel to not make use of any
2001 IOAPICs that may be present in the system.
2003 noautogroup Disable scheduler automatic task group creation.
2005 nobats [PPC] Do not use BATs for mapping kernel lowmem
2006 on "Classic" PPC cores.
2010 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2012 nodelayacct [KNL] Disable per-task delay accounting
2014 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2016 nodsp [SH] Disable hardware DSP at boot time.
2018 noefi [X86] Disable EFI runtime services support.
2023 On X86-32 available only on PAE configured kernels.
2024 noexec=on: enable non-executable mappings (default)
2025 noexec=off: disable non-executable mappings
2028 Disable SMAP (Supervisor Mode Access Prevention)
2029 even if it is supported by processor.
2032 Disable SMEP (Supervisor Mode Execution Prevention)
2033 even if it is supported by processor.
2036 This affects only 32-bit executables.
2037 noexec32=on: enable non-executable mappings (default)
2038 read doesn't imply executable mappings
2039 noexec32=off: disable non-executable mappings
2040 read implies executable mappings
2042 nofpu [SH] Disable hardware FPU at boot time.
2044 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2045 register save and restore. The kernel will only save
2046 legacy floating-point registers on task switch.
2048 noxsave [BUGS=X86] Disables x86 extended register state save
2049 and restore using xsave. The kernel will fallback to
2050 enabling legacy floating-point and sse state.
2053 on enable eager fpu restore
2054 off disable eager fpu restore
2055 auto selects the default scheme, which automatically
2056 enables eagerfpu restore for xsaveopt.
2058 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2059 wfi(ARM) instruction doesn't work correctly and not to
2060 use it. This is also useful when using JTAG debugger.
2062 no_file_caps Tells the kernel not to honor file capabilities. The
2063 only way then for a file to be executed with privilege
2064 is to be setuid root or executed by root.
2066 nohalt [IA-64] Tells the kernel not to use the power saving
2067 function PAL_HALT_LIGHT when idle. This increases
2068 power-consumption. On the positive side, it reduces
2069 interrupt wake-up latency, which may improve performance
2070 in certain environments such as networked servers or
2073 nohz= [KNL] Boottime enable/disable dynamic ticks
2074 Valid arguments: on, off
2077 nohz_full= [KNL,BOOT]
2078 In kernels built with CONFIG_NO_HZ_FULL=y, set
2079 the specified list of CPUs whose tick will be stopped
2080 whenever possible. The boot CPU will be forced outside
2081 the range to maintain the timekeeping.
2082 The CPUs in this range must also be included in the
2085 noiotrap [SH] Disables trapped I/O port accesses.
2087 noirqdebug [X86-32] Disables the code which attempts to detect and
2088 disable unhandled interrupt sources.
2090 no_timer_check [X86,APIC] Disables the code which tests for
2091 broken timer IRQ sources.
2093 noisapnp [ISAPNP] Disables ISA PnP code.
2095 noinitrd [RAM] Tells the kernel not to load any configured
2098 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2100 [Deprecated - use intremap=off]
2104 nojitter [IA-64] Disables jitter checking for ITC timers.
2106 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2108 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2111 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2112 steal time is computed, but won't influence scheduler
2115 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2117 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2119 noltlbs [PPC] Do not use large page/tlb entries for kernel
2120 lowmem mapping on PPC40x.
2122 nomca [IA-64] Disable machine check abort handling
2124 nomce [X86-32] Machine Check Exception
2126 nomfgpt [X86-32] Disable Multi-Function General Purpose
2127 Timer usage (for AMD Geode machines).
2129 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2130 shutdown the other cpus. Instead use the REBOOT_VECTOR
2133 nomodule Disable module load
2135 nopat [X86] Disable PAT (page attribute table extension of
2136 pagetables) support.
2138 norandmaps Don't use address space randomization. Equivalent to
2139 echo 0 > /proc/sys/kernel/randomize_va_space
2141 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2143 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2144 with UP alternatives
2146 nordrand [X86] Disable the direct use of the RDRAND
2147 instruction even if it is supported by the
2148 processor. RDRAND is still available to user
2151 noresume [SWSUSP] Disables resume and restores original swap
2154 no-scroll [VGA] Disables scrollback.
2155 This is required for the Braillex ib80-piezo Braille
2156 reader made by F.H. Papenmeier (Germany).
2160 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2162 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2163 and disable the IO APIC. legacy for "maxcpus=0".
2165 nosoftlockup [KNL] Disable the soft-lockup detector.
2167 nosync [HW,M68K] Disables sync negotiation for all devices.
2169 notsc [BUGS=X86-32] Disable Time Stamp Counter
2171 nousb [USB] Disable the USB subsystem
2173 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2177 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2179 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2180 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2181 Some features depend on CPU0. Known dependencies are:
2182 1. Resume from suspend/hibernate depends on CPU0.
2183 Suspend/hibernate will fail if CPU0 is offline and you
2184 need to online CPU0 before suspend/hibernate.
2185 2. PIC interrupts also depend on CPU0. CPU0 can't be
2186 removed if a PIC interrupt is detected.
2187 It's said poweroff/reboot may depend on CPU0 on some
2188 machines although I haven't seen such issues so far
2189 after CPU0 is offline on a few tested machines.
2190 If the dependencies are under your control, you can
2191 turn on cpu0_hotplug.
2193 nptcg= [IA-64] Override max number of concurrent global TLB
2194 purges which is reported from either PAL_VM_SUMMARY or
2197 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2198 could support. nr_cpus=n : n >= 1 limits the kernel to
2199 supporting 'n' processors. Later in runtime you can not
2200 use hotplug cpu feature to put more cpu back to online.
2201 just like you compile the kernel NR_CPUS=n
2203 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2205 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2206 Allowed values are enable and disable
2208 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2209 one of ['zone', 'node', 'default'] can be specified
2210 This can be set from sysctl after boot.
2211 See Documentation/sysctl/vm.txt for details.
2213 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2214 See Documentation/debugging-via-ohci1394.txt for more
2217 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2218 Rather than timing out after 20 ms if an EC
2219 command is not properly ACKed, override the length
2220 of the timeout. We have interrupts disabled while
2221 waiting for the ACK, so if this is set too high
2222 interrupts *may* be lost!
2224 omap_mux= [OMAP] Override bootloader pin multiplexing.
2225 Format: <mux_mode0.mode_name=value>...
2226 For example, to override I2C bus2:
2227 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2229 oprofile.timer= [HW]
2230 Use timer interrupt instead of performance counters
2232 oprofile.cpu_type= Force an oprofile cpu type
2233 This might be useful if you have an older oprofile
2234 userland or if you want common events.
2235 Format: { arch_perfmon }
2236 arch_perfmon: [X86] Force use of architectural
2237 perfmon on Intel CPUs instead of the
2238 CPU specific event set.
2239 timer: [X86] Force use of architectural NMI
2240 timer mode (see also oprofile.timer
2241 for generic hr timer mode)
2242 [s390] Force legacy basic mode sampling
2243 (report cpu_type "timer")
2245 oops=panic Always panic on oopses. Default is to just kill the
2246 process, but there is a small probability of
2247 deadlocking the machine.
2248 This will also cause panics on machine check exceptions.
2249 Useful together with panic=30 to trigger a reboot.
2252 See Documentation/sound/oss/oss-parameters.txt
2254 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2255 timeout > 0: seconds before rebooting
2256 timeout = 0: wait forever
2257 timeout < 0: reboot immediately
2260 parkbd.port= [HW] Parallel port number the keyboard adapter is
2261 connected to, default is 0.
2263 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2264 0 for XT, 1 for AT (default is AT).
2267 parport= [HW,PPT] Specify parallel ports. 0 disables.
2268 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2269 Use 'auto' to force the driver to use any
2270 IRQ/DMA settings detected (the default is to
2271 ignore detected IRQ/DMA settings because of
2272 possible conflicts). You can specify the base
2273 address, IRQ, and DMA settings; IRQ and DMA
2274 should be numbers, or 'auto' (for using detected
2275 settings on that particular port), or 'nofifo'
2276 (to avoid using a FIFO even if it is detected).
2277 Parallel ports are assigned in the order they
2278 are specified on the command line, starting
2281 parport_init_mode= [HW,PPT]
2282 Configure VIA parallel port to operate in
2283 a specific mode. This is necessary on Pegasos
2284 computer where firmware has no options for setting
2285 up parallel port mode and sets it to spp.
2286 Currently this function knows 686a and 8231 chips.
2287 Format: [spp|ps2|epp|ecp|ecpepp]
2290 Halt all CPUs after the first oops has been printed for
2291 the specified number of seconds. This is to be used if
2292 your oopses keep scrolling off the screen.
2297 See header of drivers/block/paride/pcd.c.
2298 See also Documentation/blockdev/paride.txt.
2300 pci=option[,option...] [PCI] various PCI subsystem options:
2301 earlydump [X86] dump PCI config space before the kernel
2303 off [X86] don't probe for the PCI bus
2304 bios [X86-32] force use of PCI BIOS, don't access
2305 the hardware directly. Use this if your machine
2306 has a non-standard PCI host bridge.
2307 nobios [X86-32] disallow use of PCI BIOS, only direct
2308 hardware access methods are allowed. Use this
2309 if you experience crashes upon bootup and you
2310 suspect they are caused by the BIOS.
2311 conf1 [X86] Force use of PCI Configuration
2313 conf2 [X86] Force use of PCI Configuration
2315 noaer [PCIE] If the PCIEAER kernel config parameter is
2316 enabled, this kernel boot option can be used to
2317 disable the use of PCIE advanced error reporting.
2318 nodomains [PCI] Disable support for multiple PCI
2319 root domains (aka PCI segments, in ACPI-speak).
2320 nommconf [X86] Disable use of MMCONFIG for PCI
2322 check_enable_amd_mmconf [X86] check for and enable
2323 properly configured MMIO access to PCI
2324 config space on AMD family 10h CPU
2325 nomsi [MSI] If the PCI_MSI kernel config parameter is
2326 enabled, this kernel boot option can be used to
2327 disable the use of MSI interrupts system-wide.
2328 noioapicquirk [APIC] Disable all boot interrupt quirks.
2329 Safety option to keep boot IRQs enabled. This
2330 should never be necessary.
2331 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2332 primary IO-APIC for bridges that cannot disable
2333 boot IRQs. This fixes a source of spurious IRQs
2334 when the system masks IRQs.
2335 noioapicreroute [APIC] Disable workaround that uses the
2336 boot IRQ equivalent of an IRQ that connects to
2337 a chipset where boot IRQs cannot be disabled.
2338 The opposite of ioapicreroute.
2339 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2340 routing table. These calls are known to be buggy
2341 on several machines and they hang the machine
2342 when used, but on other computers it's the only
2343 way to get the interrupt routing table. Try
2344 this option if the kernel is unable to allocate
2345 IRQs or discover secondary PCI buses on your
2347 rom [X86] Assign address space to expansion ROMs.
2348 Use with caution as certain devices share
2349 address decoders between ROMs and other
2351 norom [X86] Do not assign address space to
2352 expansion ROMs that do not already have
2353 BIOS assigned address ranges.
2354 nobar [X86] Do not assign address space to the
2355 BARs that weren't assigned by the BIOS.
2356 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2357 assigned automatically to PCI devices. You can
2358 make the kernel exclude IRQs of your ISA cards
2360 pirqaddr=0xAAAAA [X86] Specify the physical address
2361 of the PIRQ table (normally generated
2362 by the BIOS) if it is outside the
2363 F0000h-100000h range.
2364 lastbus=N [X86] Scan all buses thru bus #N. Can be
2365 useful if the kernel is unable to find your
2366 secondary buses and you want to tell it
2367 explicitly which ones they are.
2368 assign-busses [X86] Always assign all PCI bus
2369 numbers ourselves, overriding
2370 whatever the firmware may have done.
2371 usepirqmask [X86] Honor the possible IRQ mask stored
2372 in the BIOS $PIR table. This is needed on
2373 some systems with broken BIOSes, notably
2374 some HP Pavilion N5400 and Omnibook XE3
2375 notebooks. This will have no effect if ACPI
2376 IRQ routing is enabled.
2377 noacpi [X86] Do not use ACPI for IRQ routing
2378 or for PCI scanning.
2379 use_crs [X86] Use PCI host bridge window information
2380 from ACPI. On BIOSes from 2008 or later, this
2381 is enabled by default. If you need to use this,
2382 please report a bug.
2383 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2384 If you need to use this, please report a bug.
2385 routeirq Do IRQ routing for all PCI devices.
2386 This is normally done in pci_enable_device(),
2387 so this option is a temporary workaround
2388 for broken drivers that don't call it.
2389 skip_isa_align [X86] do not align io start addr, so can
2390 handle more pci cards
2391 firmware [ARM] Do not re-enumerate the bus but instead
2392 just use the configuration from the
2393 bootloader. This is currently used on
2394 IXP2000 systems where the bus has to be
2395 configured a certain way for adjunct CPUs.
2396 noearly [X86] Don't do any early type 1 scanning.
2397 This might help on some broken boards which
2398 machine check when some devices' config space
2399 is read. But various workarounds are disabled
2400 and some IOMMU drivers will not work.
2401 bfsort Sort PCI devices into breadth-first order.
2402 This sorting is done to get a device
2403 order compatible with older (<= 2.4) kernels.
2404 nobfsort Don't sort PCI devices into breadth-first order.
2405 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2406 tuning and use the BIOS-configured MPS defaults.
2407 pcie_bus_safe Set every device's MPS to the largest value
2408 supported by all devices below the root complex.
2409 pcie_bus_perf Set device MPS to the largest allowable MPS
2410 based on its parent bus. Also set MRRS (Max
2411 Read Request Size) to the largest supported
2412 value (no larger than the MPS that the device
2413 or bus can support) for best performance.
2414 pcie_bus_peer2peer Set every device's MPS to 128B, which
2415 every device is guaranteed to support. This
2416 configuration allows peer-to-peer DMA between
2417 any pair of devices, possibly at the cost of
2418 reduced performance. This also guarantees
2419 that hot-added devices will work.
2420 cbiosize=nn[KMG] The fixed amount of bus space which is
2421 reserved for the CardBus bridge's IO window.
2422 The default value is 256 bytes.
2423 cbmemsize=nn[KMG] The fixed amount of bus space which is
2424 reserved for the CardBus bridge's memory
2425 window. The default value is 64 megabytes.
2428 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2429 Specifies alignment and device to reassign
2430 aligned memory resources.
2431 If <order of align> is not specified,
2432 PAGE_SIZE is used as alignment.
2433 PCI-PCI bridge can be specified, if resource
2434 windows need to be expanded.
2435 ecrc= Enable/disable PCIe ECRC (transaction layer
2436 end-to-end CRC checking).
2437 bios: Use BIOS/firmware settings. This is the
2441 hpiosize=nn[KMG] The fixed amount of bus space which is
2442 reserved for hotplug bridge's IO window.
2443 Default size is 256 bytes.
2444 hpmemsize=nn[KMG] The fixed amount of bus space which is
2445 reserved for hotplug bridge's memory window.
2446 Default size is 2 megabytes.
2447 realloc= Enable/disable reallocating PCI bridge resources
2448 if allocations done by BIOS are too small to
2449 accommodate resources required by all child
2451 off: Turn realloc off
2453 realloc same as realloc=on
2454 noari do not use PCIe ARI.
2455 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2456 only look for one device below a PCIe downstream
2459 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2462 force Enable ASPM even on devices that claim not to support it.
2463 WARNING: Forcing ASPM on may cause system lockups.
2465 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2466 nomsi Do not use MSI for PCI Express Native Hotplug (this
2467 makes all PCIe ports use INTx for hotplug services).
2469 pcie_ports= [PCIE] PCIe ports handling:
2470 auto Ask the BIOS whether or not to use native PCIe services
2471 associated with PCIe ports (PME, hot-plug, AER). Use
2472 them only if that is allowed by the BIOS.
2473 native Use native PCIe services associated with PCIe ports
2475 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2478 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2479 nomsi Do not use MSI for native PCIe PME signaling (this makes
2480 all PCIe root ports use INTx for all services).
2482 pcmv= [HW,PCMCIA] BadgePAD 4
2485 See Documentation/blockdev/paride.txt.
2487 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2490 See arch/parisc/kernel/pdc_chassis.c
2492 percpu_alloc= Select which percpu first chunk allocator to use.
2493 Currently supported values are "embed" and "page".
2494 Archs may support subset or none of the selections.
2495 See comments in mm/percpu.c for details on each
2496 allocator. This parameter is primarily for debugging
2497 and performance comparison.
2500 See Documentation/blockdev/paride.txt.
2503 See Documentation/blockdev/paride.txt.
2505 pirq= [SMP,APIC] Manual mp-table setup
2506 See Documentation/x86/i386/IO-APIC.txt.
2508 plip= [PPT,NET] Parallel port network link
2509 Format: { parport<nr> | timid | 0 }
2510 See also Documentation/parport.txt.
2512 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2513 Override pmtimer IOPort with a hex value.
2517 Enable PNP debug messages (depends on the
2518 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2519 via /sys/module/pnp/parameters/debug. We always show
2520 current resource usage; turning this on also shows
2521 possible settings and some assignment information.
2527 { on | off | curr | res | no-curr | no-res }
2530 [ISAPNP] Exclude IRQs for the autoconfiguration
2533 [ISAPNP] Exclude DMAs for the autoconfiguration
2535 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2536 Ranges are in pairs (I/O port base and size).
2539 [ISAPNP] Exclude memory regions for the
2541 Ranges are in pairs (memory base and size).
2543 ports= [IP_VS_FTP] IPVS ftp helper module
2545 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2547 Format: <port>,<port>....
2549 print-fatal-signals=
2550 [KNL] debug: print fatal signals
2552 If enabled, warn about various signal handling
2553 related application anomalies: too many signals,
2554 too many POSIX.1 timers, fatal signals causing a
2557 If you hit the warning due to signal overflow,
2558 you might want to try "ulimit -i unlimited".
2562 printk.always_kmsg_dump=
2563 Trigger kmsg_dump for cases other than kernel oops or
2565 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2568 printk.time= Show timing data prefixed to each printk message line
2569 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2571 processor.max_cstate= [HW,ACPI]
2572 Limit processor to maximum C-state
2573 max_cstate=9 overrides any DMI blacklist limit.
2575 processor.nocst [HW,ACPI]
2576 Ignore the _CST method to determine C-states,
2577 instead using the legacy FADT method
2579 profile= [KNL] Enable kernel profiling via /proc/profile
2580 Format: [schedule,]<number>
2581 Param: "schedule" - profile schedule points.
2582 Param: <number> - step/bucket size as a power of 2 for
2583 statistical time based profiling.
2584 Param: "sleep" - profile D-state sleeping (millisecs).
2585 Requires CONFIG_SCHEDSTATS
2586 Param: "kvm" - profile VM exits.
2588 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2590 See Documentation/blockdev/ramdisk.txt.
2592 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2593 probe for; one of (bare|imps|exps|lifebook|any).
2594 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2596 psmouse.resetafter= [HW,MOUSE]
2597 Try to reset the device after so many bad packets
2600 [HW,MOUSE] Set desired mouse resolution, in dpi.
2601 psmouse.smartscroll=
2602 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2603 0 = disabled, 1 = enabled (default).
2605 pstore.backend= Specify the name of the pstore backend to use
2608 See Documentation/blockdev/paride.txt.
2611 [KNL] Number of legacy pty's. Overwrites compiled-in
2614 quiet [KNL] Disable most log messages
2619 See Documentation/md.txt.
2621 ramdisk_blocksize= [RAM]
2622 See Documentation/blockdev/ramdisk.txt.
2624 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2625 See Documentation/blockdev/ramdisk.txt.
2628 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2629 the specified list of CPUs to be no-callback CPUs.
2630 Invocation of these CPUs' RCU callbacks will
2631 be offloaded to "rcuox/N" kthreads created for
2632 that purpose, where "x" is "b" for RCU-bh, "p"
2633 for RCU-preempt, and "s" for RCU-sched, and "N"
2634 is the CPU number. This reduces OS jitter on the
2635 offloaded CPUs, which can be useful for HPC and
2637 real-time workloads. It can also improve energy
2638 efficiency for asymmetric multiprocessors.
2641 Rather than requiring that offloaded CPUs
2642 (specified by rcu_nocbs= above) explicitly
2643 awaken the corresponding "rcuoN" kthreads,
2644 make these kthreads poll for callbacks.
2645 This improves the real-time response for the
2646 offloaded CPUs by relieving them of the need to
2647 wake up the corresponding kthread, but degrades
2648 energy efficiency by requiring that the kthreads
2649 periodically wake up to do the polling.
2651 rcutree.blimit= [KNL]
2652 Set maximum number of finished RCU callbacks to process
2655 rcutree.rcu_fanout_leaf= [KNL]
2656 Increase the number of CPUs assigned to each
2657 leaf rcu_node structure. Useful for very large
2660 rcutree.jiffies_till_first_fqs= [KNL]
2661 Set delay from grace-period initialization to
2662 first attempt to force quiescent states.
2663 Units are jiffies, minimum value is zero,
2664 and maximum value is HZ.
2666 rcutree.jiffies_till_next_fqs= [KNL]
2667 Set delay between subsequent attempts to force
2668 quiescent states. Units are jiffies, minimum
2669 value is one, and maximum value is HZ.
2671 rcutree.qhimark= [KNL]
2672 Set threshold of queued
2673 RCU callbacks over which batch limiting is disabled.
2675 rcutree.qlowmark= [KNL]
2676 Set threshold of queued RCU callbacks below which
2677 batch limiting is re-enabled.
2679 rcutree.rcu_idle_gp_delay= [KNL]
2680 Set wakeup interval for idle CPUs that have
2681 RCU callbacks (RCU_FAST_NO_HZ=y).
2683 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2684 Set wakeup interval for idle CPUs that have
2685 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2686 Lazy RCU callbacks are those which RCU can
2687 prove do nothing more than free memory.
2689 rcutorture.fqs_duration= [KNL]
2690 Set duration of force_quiescent_state bursts.
2692 rcutorture.fqs_holdoff= [KNL]
2693 Set holdoff time within force_quiescent_state bursts.
2695 rcutorture.fqs_stutter= [KNL]
2696 Set wait time between force_quiescent_state bursts.
2698 rcutorture.gp_exp= [KNL]
2699 Use expedited update-side primitives.
2701 rcutorture.gp_normal= [KNL]
2702 Use normal (non-expedited) update-side primitives.
2703 If both gp_exp and gp_normal are set, do both.
2704 If neither gp_exp nor gp_normal are set, still
2707 rcutorture.n_barrier_cbs= [KNL]
2708 Set callbacks/threads for rcu_barrier() testing.
2710 rcutorture.nfakewriters= [KNL]
2711 Set number of concurrent RCU writers. These just
2712 stress RCU, they don't participate in the actual
2713 test, hence the "fake".
2715 rcutorture.nreaders= [KNL]
2716 Set number of RCU readers.
2718 rcutorture.object_debug= [KNL]
2719 Enable debug-object double-call_rcu() testing.
2721 rcutorture.onoff_holdoff= [KNL]
2722 Set time (s) after boot for CPU-hotplug testing.
2724 rcutorture.onoff_interval= [KNL]
2725 Set time (s) between CPU-hotplug operations, or
2726 zero to disable CPU-hotplug testing.
2728 rcutorture.rcutorture_runnable= [BOOT]
2729 Start rcutorture running at boot time.
2731 rcutorture.shuffle_interval= [KNL]
2732 Set task-shuffle interval (s). Shuffling tasks
2733 allows some CPUs to go into dyntick-idle mode
2734 during the rcutorture test.
2736 rcutorture.shutdown_secs= [KNL]
2737 Set time (s) after boot system shutdown. This
2738 is useful for hands-off automated testing.
2740 rcutorture.stall_cpu= [KNL]
2741 Duration of CPU stall (s) to test RCU CPU stall
2742 warnings, zero to disable.
2744 rcutorture.stall_cpu_holdoff= [KNL]
2745 Time to wait (s) after boot before inducing stall.
2747 rcutorture.stat_interval= [KNL]
2748 Time (s) between statistics printk()s.
2750 rcutorture.stutter= [KNL]
2751 Time (s) to stutter testing, for example, specifying
2752 five seconds causes the test to run for five seconds,
2753 wait for five seconds, and so on. This tests RCU's
2754 ability to transition abruptly to and from idle.
2756 rcutorture.test_boost= [KNL]
2757 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2758 "Maybe" means test if the RCU implementation
2759 under test support RCU priority boosting.
2761 rcutorture.test_boost_duration= [KNL]
2762 Duration (s) of each individual boost test.
2764 rcutorture.test_boost_interval= [KNL]
2765 Interval (s) between each boost test.
2767 rcutorture.test_no_idle_hz= [KNL]
2768 Test RCU's dyntick-idle handling. See also the
2769 rcutorture.shuffle_interval parameter.
2771 rcutorture.torture_type= [KNL]
2772 Specify the RCU implementation to test.
2774 rcutorture.verbose= [KNL]
2775 Enable additional printk() statements.
2777 rcupdate.rcu_expedited= [KNL]
2778 Use expedited grace-period primitives, for
2779 example, synchronize_rcu_expedited() instead
2780 of synchronize_rcu(). This reduces latency,
2781 but can increase CPU utilization, degrade
2782 real-time latency, and degrade energy efficiency.
2784 rcupdate.rcu_cpu_stall_suppress= [KNL]
2785 Suppress RCU CPU stall warning messages.
2787 rcupdate.rcu_cpu_stall_timeout= [KNL]
2788 Set timeout for RCU CPU stall warning messages.
2792 Run specified binary instead of /init from the ramdisk,
2793 used for early userspace startup. See initrd.
2796 Format (x86 or x86_64):
2797 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2799 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2801 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2802 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2803 reboot_force is either force or not specified,
2804 reboot_cpu is s[mp]#### with #### being the processor
2805 to be used for rebooting.
2808 [KNL, SMP] Set scheduler's default relax_domain_level.
2809 See Documentation/cgroups/cpusets.txt.
2811 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2813 reservetop= [X86-32]
2815 Reserves a hole at the top of the kernel virtual
2820 Set the amount of memory to reserve for BIOS at
2821 the bottom of the address space.
2823 reset_devices [KNL] Force drivers to reset the underlying device
2824 during initialization.
2827 Specify the partition device for software suspend
2829 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2831 resume_offset= [SWSUSP]
2832 Specify the offset from the beginning of the partition
2833 given by "resume=" at which the swap header is located,
2834 in <PAGE_SIZE> units (needed only for swap files).
2835 See Documentation/power/swsusp-and-swap-files.txt
2837 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2838 read the resume files
2840 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2841 Useful for devices that are detected asynchronously
2842 (e.g. USB and MMC devices).
2844 hibernate= [HIBERNATION]
2845 noresume Don't check if there's a hibernation image
2846 present during boot.
2847 nocompress Don't compress/decompress hibernation images.
2849 retain_initrd [RAM] Keep initrd memory after extraction
2851 rhash_entries= [KNL,NET]
2852 Set number of hash buckets for route cache
2854 riscom8= [HW,SERIAL]
2855 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2857 ro [KNL] Mount root device read-only on boot
2859 root= [KNL] Root filesystem
2860 See name_to_dev_t comment in init/do_mounts.c.
2862 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2863 mount the root filesystem
2865 rootflags= [KNL] Set root filesystem mount option string
2867 rootfstype= [KNL] Set root filesystem type
2869 rootwait [KNL] Wait (indefinitely) for root device to show up.
2870 Useful for devices that are detected asynchronously
2871 (e.g. USB and MMC devices).
2873 rproc_mem=nn[KMG][@address]
2874 [KNL,ARM,CMA] Remoteproc physical memory block.
2875 Memory area to be used by remote processor image,
2878 rw [KNL] Mount root device read-write on boot
2880 S [KNL] Run init in single mode
2883 See drivers/net/irda/sa1100_ir.c.
2885 sbni= [NET] Granch SBNI12 leased line adapter
2887 sched_debug [KNL] Enables verbose scheduler debug messages.
2889 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2890 xtime_lock contention on larger systems, and/or RCU lock
2891 contention on all systems with CONFIG_MAXSMP set.
2892 Format: { "0" | "1" }
2893 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2895 Note: increases power consumption, thus should only be
2896 enabled if running jitter sensitive (HPC/RT) workloads.
2898 security= [SECURITY] Choose a security module to enable at boot.
2899 If this boot parameter is not specified, only the first
2900 security module asking for security registration will be
2901 loaded. An invalid security module name will be treated
2902 as if no module has been chosen.
2904 selinux= [SELINUX] Disable or enable SELinux at boot time.
2905 Format: { "0" | "1" }
2906 See security/selinux/Kconfig help text.
2909 Default value is set via kernel config option.
2910 If enabled at boot time, /selinux/disable can be used
2911 later to disable prior to initial policy load.
2913 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2914 Format: { "0" | "1" }
2915 See security/apparmor/Kconfig help text
2918 Default value is set via kernel config option.
2920 serialnumber [BUGS=X86-32]
2923 Maximal number of shapers.
2925 show_msr= [x86] show boot-time MSR settings
2926 Format: { <integer> }
2927 Show boot-time (BIOS-initialized) MSR settings.
2928 The parameter means the number of CPUs to show,
2929 for example 1 means boot CPU only.
2936 slab_max_order= [MM, SLAB]
2937 Determines the maximum allowed order for slabs.
2938 A high setting may cause OOMs due to memory
2939 fragmentation. Defaults to 1 for systems with
2940 more than 32MB of RAM, 0 otherwise.
2942 slub_debug[=options[,slabs]] [MM, SLUB]
2943 Enabling slub_debug allows one to determine the
2944 culprit if slab objects become corrupted. Enabling
2945 slub_debug can create guard zones around objects and
2946 may poison objects when not in use. Also tracks the
2947 last alloc / free. For more information see
2948 Documentation/vm/slub.txt.
2950 slub_max_order= [MM, SLUB]
2951 Determines the maximum allowed order for slabs.
2952 A high setting may cause OOMs due to memory
2953 fragmentation. For more information see
2954 Documentation/vm/slub.txt.
2956 slub_min_objects= [MM, SLUB]
2957 The minimum number of objects per slab. SLUB will
2958 increase the slab order up to slub_max_order to
2959 generate a sufficiently large slab able to contain
2960 the number of objects indicated. The higher the number
2961 of objects the smaller the overhead of tracking slabs
2962 and the less frequently locks need to be acquired.
2963 For more information see Documentation/vm/slub.txt.
2965 slub_min_order= [MM, SLUB]
2966 Determines the minimum page order for slabs. Must be
2967 lower than slub_max_order.
2968 For more information see Documentation/vm/slub.txt.
2970 slub_nomerge [MM, SLUB]
2971 Disable merging of slabs with similar size. May be
2972 necessary if there is some reason to distinguish
2973 allocs to different slabs. Debug options disable
2974 merging on their own.
2975 For more information see Documentation/vm/slub.txt.
2978 Format: <io1>[,<io2>[,...,<io8>]]
2980 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2981 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2982 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2983 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2984 smsc-ircc2.ircc_irq= [HW] IRQ line
2985 smsc-ircc2.ircc_dma= [HW] DMA channel
2986 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2987 0: Toshiba Satellite 1800 (GP data pin select)
2988 1: Fast pin select (default)
2992 [KNL] Should the soft-lockup detector generate panics.
2995 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2996 See Documentation/laptops/sonypi.txt
2998 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2999 See Documentation/serial/specialix.txt.
3001 spia_io_base= [HW,MTD]
3007 Enabled the stack tracer on boot up.
3009 stacktrace_filter=[function-list]
3010 [FTRACE] Limit the functions that the stack tracer
3011 will trace at boot up. function-list is a comma separated
3012 list of functions. This list can be changed at run
3013 time by the stack_trace_filter file in the debugfs
3014 tracing directory. Note, this enables stack tracing
3015 and the stacktrace above is not needed.
3019 Set the STI (builtin display/keyboard on the HP-PARISC
3020 machines) console (graphic card) which should be used
3021 as the initial boot-console.
3022 See also comment in drivers/video/console/sticore.c.
3025 See comment in drivers/video/console/sticore.c.
3028 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3030 sunrpc.min_resvport=
3031 sunrpc.max_resvport=
3033 SunRPC servers often require that client requests
3034 originate from a privileged port (i.e. a port in the
3035 range 0 < portnr < 1024).
3036 An administrator who wishes to reserve some of these
3037 ports for other uses may adjust the range that the
3038 kernel's sunrpc client considers to be privileged
3039 using these two parameters to set the minimum and
3040 maximum port values.
3044 Control how the NFS server code allocates CPUs to
3045 service thread pools. Depending on how many NICs
3046 you have and where their interrupts are bound, this
3047 option will affect which CPUs will do NFS serving.
3048 Note: this parameter cannot be changed while the
3049 NFS server is running.
3051 auto the server chooses an appropriate mode
3052 automatically using heuristics
3053 global a single global pool contains all CPUs
3054 percpu one pool for each CPU
3055 pernode one pool for each NUMA node (equivalent
3056 to global on non-NUMA machines)
3058 sunrpc.tcp_slot_table_entries=
3059 sunrpc.udp_slot_table_entries=
3061 Sets the upper limit on the number of simultaneous
3062 RPC calls that can be sent from the client to a
3063 server. Increasing these values may allow you to
3064 improve throughput, but will also increase the
3065 amount of memory reserved for use by the client.
3068 [KNL] Enable accounting of swap in memory resource
3069 controller if no parameter or 1 is given or disable
3070 it if 0 is given (See Documentation/cgroups/memory.txt)
3072 swiotlb= [IA-64] Number of I/O TLB slabs
3076 sysfs.deprecated=0|1 [KNL]
3077 Enable/disable old style sysfs layout for old udev
3078 on older distributions. When this option is enabled
3079 very new udev will not work anymore. When this option
3080 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3081 in older udev will not work anymore.
3082 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3083 the kernel configuration.
3085 sysrq_always_enabled
3087 Ignore sysrq setting - this boot parameter will
3088 neutralize any effect of /proc/sys/kernel/sysrq.
3089 Useful for debugging.
3093 test_suspend= [SUSPEND]
3094 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3095 standby suspend) as the system sleep state to briefly
3096 enter during system startup. The system is woken from
3097 this state using a wakeup-capable RTC alarm.
3099 thash_entries= [KNL,NET]
3100 Set number of hash buckets for TCP connection
3102 thermal.act= [HW,ACPI]
3103 -1: disable all active trip points in all thermal zones
3104 <degrees C>: override all lowest active trip points
3106 thermal.crt= [HW,ACPI]
3107 -1: disable all critical trip points in all thermal zones
3108 <degrees C>: override all critical trip points
3110 thermal.nocrt= [HW,ACPI]
3111 Set to disable actions on ACPI thermal zone
3112 critical and hot trip points.
3114 thermal.off= [HW,ACPI]
3115 1: disable ACPI thermal control
3117 thermal.psv= [HW,ACPI]
3118 -1: disable all passive trip points
3119 <degrees C>: override all passive trip points to this
3122 thermal.tzp= [HW,ACPI]
3123 Specify global default ACPI thermal zone polling rate
3124 <deci-seconds>: poll all this frequency
3125 0: no polling (default)
3128 Force threading of all interrupt handlers except those
3129 marked explicitly IRQF_NO_THREAD.
3132 Enable the Transcendent memory driver if built-in.
3134 tmem.cleancache=0|1 [KNL, XEN]
3135 Default is on (1). Disable the usage of the cleancache
3136 API to send anonymous pages to the hypervisor.
3138 tmem.frontswap=0|1 [KNL, XEN]
3139 Default is on (1). Disable the usage of the frontswap
3140 API to send swap pages to the hypervisor. If disabled
3141 the selfballooning and selfshrinking are force disabled.
3143 tmem.selfballooning=0|1 [KNL, XEN]
3144 Default is on (1). Disable the driving of swap pages
3147 tmem.selfshrinking=0|1 [KNL, XEN]
3148 Default is on (1). Partial swapoff that immediately
3149 transfers pages from Xen hypervisor back to the
3150 kernel based on different criteria.
3154 Specify if the kernel should make use of the cpu
3155 topology information if the hardware supports this.
3156 The scheduler will make use of this information and
3157 e.g. base its process migration decisions on it.
3162 tpm_suspend_pcr=[HW,TPM]
3163 Format: integer pcr id
3164 Specify that at suspend time, the tpm driver
3165 should extend the specified pcr with zeros,
3166 as a workaround for some chips which fail to
3167 flush the last written pcr on TPM_SaveState.
3168 This will guarantee that all the other pcrs
3171 trace_buf_size=nn[KMG]
3172 [FTRACE] will set tracing buffer size.
3174 trace_event=[event-list]
3175 [FTRACE] Set and start specified trace events in order
3176 to facilitate early boot debugging.
3177 See also Documentation/trace/events.txt
3179 trace_options=[option-list]
3180 [FTRACE] Enable or disable tracer options at boot.
3181 The option-list is a comma delimited list of options
3182 that can be enabled or disabled just as if you were
3183 to echo the option name into
3185 /sys/kernel/debug/tracing/trace_options
3187 For example, to enable stacktrace option (to dump the
3188 stack trace of each event), add to the command line:
3190 trace_options=stacktrace
3192 See also Documentation/trace/ftrace.txt "trace options"
3196 [FTRACE] enable this option to disable tracing when a
3197 warning is hit. This turns off "tracing_on". Tracing can
3198 be enabled again by echoing '1' into the "tracing_on"
3199 file located in /sys/kernel/debug/tracing/
3201 This option is useful, as it disables the trace before
3202 the WARNING dump is called, which prevents the trace to
3203 be filled with content caused by the warning output.
3205 This option can also be set at run time via the sysctl
3206 option: kernel/traceoff_on_warning
3208 transparent_hugepage=
3210 Format: [always|madvise|never]
3211 Can be used to control the default behavior of the system
3212 with respect to transparent hugepages.
3213 See Documentation/vm/transhuge.txt for more details.
3215 tsc= Disable clocksource stability checks for TSC.
3217 [x86] reliable: mark tsc clocksource as reliable, this
3218 disables clocksource verification at runtime, as well
3219 as the stability checks done at bootup. Used to enable
3220 high-resolution timer mode on older hardware, and in
3221 virtualized environment.
3222 [x86] noirqtime: Do not use TSC to do irq accounting.
3223 Used to run time disable IRQ_TIME_ACCOUNTING on any
3224 platforms where RDTSC is slow and this accounting
3227 turbografx.map[2|3]= [HW,JOY]
3228 TurboGraFX parallel port interface
3230 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3231 See also Documentation/input/joystick-parport.txt
3233 udbg-immortal [PPC] When debugging early kernel crashes that
3234 happen after console_init() and before a proper
3235 console driver takes over, this boot options might
3236 help "seeing" what's going on.
3238 uhash_entries= [KNL,NET]
3239 Set number of hash buckets for UDP/UDP-Lite connections
3242 [USB] Ignore overcurrent events (default N).
3243 Some badly-designed motherboards generate lots of
3244 bogus events, for ports that aren't wired to
3245 anything. Set this parameter to avoid log spamming.
3246 Note that genuine overcurrent events won't be
3250 [X86] Cause panic on unknown NMI.
3252 usbcore.authorized_default=
3253 [USB] Default USB device authorization:
3254 (default -1 = authorized except for wireless USB,
3255 0 = not authorized, 1 = authorized)
3257 usbcore.autosuspend=
3258 [USB] The autosuspend time delay (in seconds) used
3259 for newly-detected USB devices (default 2). This
3260 is the time required before an idle device will be
3261 autosuspended. Devices for which the delay is set
3262 to a negative value won't be autosuspended at all.
3264 usbcore.usbfs_snoop=
3265 [USB] Set to log all usbfs traffic (default 0 = off).
3267 usbcore.blinkenlights=
3268 [USB] Set to cycle leds on hubs (default 0 = off).
3270 usbcore.old_scheme_first=
3271 [USB] Start with the old device initialization
3272 scheme (default 0 = off).
3274 usbcore.usbfs_memory_mb=
3275 [USB] Memory limit (in MB) for buffers allocated by
3276 usbfs (default = 16, 0 = max = 2047).
3278 usbcore.use_both_schemes=
3279 [USB] Try the other device initialization scheme
3280 if the first one fails (default 1 = enabled).
3282 usbcore.initial_descriptor_timeout=
3283 [USB] Specifies timeout for the initial 64-byte
3284 USB_REQ_GET_DESCRIPTOR request in milliseconds
3285 (default 5000 = 5.0 seconds).
3288 [USBHID] The interval which mice are to be polled at.
3290 usb-storage.delay_use=
3291 [UMS] The delay in seconds before a new device is
3292 scanned for Logical Units (default 5).
3295 [UMS] A list of quirks entries to supplement or
3296 override the built-in unusual_devs list. List
3297 entries are separated by commas. Each entry has
3298 the form VID:PID:Flags where VID and PID are Vendor
3299 and Product ID values (4-digit hex numbers) and
3300 Flags is a set of characters, each corresponding
3301 to a common usb-storage quirk flag as follows:
3302 a = SANE_SENSE (collect more than 18 bytes
3304 b = BAD_SENSE (don't collect more than 18
3305 bytes of sense data);
3306 c = FIX_CAPACITY (decrease the reported
3307 device capacity by one sector);
3308 d = NO_READ_DISC_INFO (don't use
3309 READ_DISC_INFO command);
3310 e = NO_READ_CAPACITY_16 (don't use
3311 READ_CAPACITY_16 command);
3312 h = CAPACITY_HEURISTICS (decrease the
3313 reported device capacity by one
3314 sector if the number is odd);
3315 i = IGNORE_DEVICE (don't bind to this
3317 l = NOT_LOCKABLE (don't try to lock and
3318 unlock ejectable media);
3319 m = MAX_SECTORS_64 (don't transfer more
3320 than 64 sectors = 32 KB at a time);
3321 n = INITIAL_READ10 (force a retry of the
3322 initial READ(10) command);
3323 o = CAPACITY_OK (accept the capacity
3324 reported by the device);
3325 p = WRITE_CACHE (the device cache is ON
3327 r = IGNORE_RESIDUE (the device reports
3328 bogus residue values);
3329 s = SINGLE_LUN (the device has only one
3331 w = NO_WP_DETECT (don't test whether the
3332 medium is write-protected).
3333 Example: quirks=0419:aaf5:rl,0421:0433:rc
3335 user_debug= [KNL,ARM]
3337 See arch/arm/Kconfig.debug help text.
3338 1 - undefined instruction events
3340 4 - invalid data aborts
3343 Example: user_debug=31
3346 [X86] Flags controlling user PTE allocations.
3348 nohigh = do not allocate PTE pages in
3349 HIGHMEM regardless of setting
3353 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3354 vdso=1: enable VDSO (default)
3355 vdso=0: disable VDSO mapping
3358 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3359 vdso32=1: enable 32-bit VDSO (default)
3360 vdso32=0: disable 32-bit VDSO mapping
3363 vector=percpu: enable percpu vector domain
3365 video= [FB] Frame buffer configuration
3366 See Documentation/fb/modedb.txt.
3368 video.brightness_switch_enabled= [0,1]
3369 If set to 1, on receiving an ACPI notify event
3370 generated by hotkey, video driver will adjust brightness
3371 level and then send out the event to user space through
3372 the allocated input device; If set to 0, video driver
3373 will only send out the event without touching backlight
3378 [VMMIO] Memory mapped virtio (platform) device.
3380 <size>@<baseaddr>:<irq>[:<id>]
3382 <size> := size (can use standard suffixes
3384 <baseaddr> := physical base address
3385 <irq> := interrupt number (as passed to
3387 <id> := (optional) platform device id
3389 virtio_mmio.device=1K@0x100b0000:48:7
3391 Can be used multiple times for multiple devices.
3393 vga= [BOOT,X86-32] Select a particular video mode
3394 See Documentation/x86/boot.txt and
3395 Documentation/svga.txt.
3396 Use vga=ask for menu.
3397 This is actually a boot loader parameter; the value is
3398 passed to the kernel using a special protocol.
3400 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3401 size of <nn>. This can be used to increase the
3402 minimum size (128MB on x86). It can also be used to
3403 decrease the size and leave more room for directly
3406 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3409 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3412 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3416 Controls the behavior of vsyscalls (i.e. calls to
3417 fixed addresses of 0xffffffffff600x00 from legacy
3418 code). Most statically-linked binaries and older
3419 versions of glibc use these calls. Because these
3420 functions are at fixed addresses, they make nice
3421 targets for exploits that can control RIP.
3423 emulate [default] Vsyscalls turn into traps and are
3424 emulated reasonably safely.
3426 native Vsyscalls are native syscall instructions.
3427 This is a little bit faster than trapping
3428 and makes a few dynamic recompilers work
3429 better than they would in emulation mode.
3430 It also makes exploits much easier to write.
3432 none Vsyscalls don't work at all. This makes
3433 them quite hard to use for exploits but
3434 might break your system.
3436 vt.color= [VT] Default text color.
3437 Format: 0xYX, X = foreground, Y = background.
3438 Default: 0x07 = light gray on black.
3440 vt.cur_default= [VT] Default cursor shape.
3441 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3442 the parameters of the <Esc>[?A;B;Cc escape sequence;
3443 see VGA-softcursor.txt. Default: 2 = underline.
3445 vt.default_blu= [VT]
3446 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3447 Change the default blue palette of the console.
3448 This is a 16-member array composed of values
3451 vt.default_grn= [VT]
3452 Format: <green0>,<green1>,<green2>,...,<green15>
3453 Change the default green palette of the console.
3454 This is a 16-member array composed of values
3457 vt.default_red= [VT]
3458 Format: <red0>,<red1>,<red2>,...,<red15>
3459 Change the default red palette of the console.
3460 This is a 16-member array composed of values
3466 Set system-wide default UTF-8 mode for all tty's.
3467 Default is 1, i.e. UTF-8 mode is enabled for all
3468 newly opened terminals.
3470 vt.global_cursor_default=
3473 Set system-wide default for whether a cursor
3474 is shown on new VTs. Default is -1,
3475 i.e. cursors will be created by default unless
3476 overridden by individual drivers. 0 will hide
3477 cursors, 1 will display them.
3479 vt.italic= [VT] Default color for italic text; 0-15.
3482 vt.underline= [VT] Default color for underlined text; 0-15.
3485 watchdog timers [HW,WDT] For information on watchdog timers,
3486 see Documentation/watchdog/watchdog-parameters.txt
3487 or other driver-specific files in the
3488 Documentation/watchdog/ directory.
3490 workqueue.disable_numa
3491 By default, all work items queued to unbound
3492 workqueues are affine to the NUMA nodes they're
3493 issued on, which results in better behavior in
3494 general. If NUMA affinity needs to be disabled for
3495 whatever reason, this option can be used. Note
3496 that this also can be controlled per-workqueue for
3497 workqueues visible under /sys/bus/workqueue/.
3499 workqueue.power_efficient
3500 Per-cpu workqueues are generally preferred because
3501 they show better performance thanks to cache
3502 locality; unfortunately, per-cpu workqueues tend to
3503 be more power hungry than unbound workqueues.
3505 Enabling this makes the per-cpu workqueues which
3506 were observed to contribute significantly to power
3507 consumption unbound, leading to measurably lower
3508 power usage at the cost of small performance
3511 The default value of this parameter is determined by
3512 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3514 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3515 default x2apic cluster mode on platforms
3518 x86_intel_mid_timer= [X86-32,APBT]
3519 Choose timer option for x86 Intel MID platform.
3520 Two valid options are apbt timer only and lapic timer
3521 plus one apbt timer for broadcast timer.
3522 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3524 xen_emul_unplug= [HW,X86,XEN]
3525 Unplug Xen emulated devices
3526 Format: [unplug0,][unplug1]
3527 ide-disks -- unplug primary master IDE devices
3528 aux-ide-disks -- unplug non-primary-master IDE devices
3529 nics -- unplug network devices
3530 all -- unplug all emulated devices (NICs and IDE disks)
3531 unnecessary -- unplugging emulated devices is
3532 unnecessary even if the host did not respond to
3534 never -- do not unplug even if version check succeeds
3536 xen_nopvspin [X86,XEN]
3537 Disables the ticketlock slowpath using Xen PV
3540 xirc2ps_cs= [NET,PCMCIA]
3542 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3544 ______________________________________________________________________
3548 Add more DRM drivers.