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_cpu_apicid= [X86,APIC,SMP]
779 The number of initial APIC ID for the
780 corresponding CPU to be disabled at boot,
781 mostly used for the kdump 2nd kernel to
782 disable BSP to wake up multiple CPUs without
783 causing system reset or hang due to sending
786 disable_ddw [PPC/PSERIES]
787 Disable Dynamic DMA Window support. Use this if
788 to workaround buggy firmware.
791 See Documentation/networking/ipv6.txt.
793 disable_mtrr_cleanup [X86]
794 The kernel tries to adjust MTRR layout from continuous
795 to discrete, to make X server driver able to add WB
796 entry later. This parameter disables that.
798 disable_mtrr_trim [X86, Intel and AMD only]
799 By default the kernel will trim any uncacheable
800 memory out of your available memory pool based on
801 MTRR settings. This parameter disables that behavior,
802 possibly causing your machine to run very slowly.
804 disable_timer_pin_1 [X86]
805 Disable PIN 1 of APIC timer
806 Can be useful to work around chipset bugs.
808 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
809 this option disables the debugging code at boot.
811 dma_debug_entries=<number>
812 This option allows to tune the number of preallocated
813 entries for DMA-API debugging code. One entry is
814 required per DMA-API allocation. Use this if the
815 DMA-API debugging code disables itself because the
816 architectural default is too low.
818 dma_debug_driver=<driver_name>
819 With this option the DMA-API debugging driver
820 filter feature can be enabled at boot time. Just
821 pass the driver to filter for as the parameter.
822 The filter can be disabled or changed to another
823 driver later using sysfs.
825 drm_kms_helper.edid_firmware=[<connector>:]<file>
826 Broken monitors, graphic adapters and KVMs may
827 send no or incorrect EDID data sets. This parameter
828 allows to specify an EDID data set in the
829 /lib/firmware directory that is used instead.
830 Generic built-in EDID data sets are used, if one of
831 edid/1024x768.bin, edid/1280x1024.bin,
832 edid/1680x1050.bin, or edid/1920x1080.bin is given
833 and no file with the same name exists. Details and
834 instructions how to build your own EDID data are
835 available in Documentation/EDID/HOWTO.txt. An EDID
836 data set will only be used for a particular connector,
837 if its name and a colon are prepended to the EDID
842 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
843 module.dyndbg[="val"]
844 Enable debug messages at boot time. See
845 Documentation/dynamic-debug-howto.txt for details.
847 earlycon= [KNL] Output early console device and options.
848 uart[8250],io,<addr>[,options]
849 uart[8250],mmio,<addr>[,options]
850 uart[8250],mmio32,<addr>[,options]
851 Start an early, polled-mode console on the 8250/16550
852 UART at the specified I/O port or MMIO address.
853 MMIO inter-register address stride is either 8-bit
854 (mmio) or 32-bit (mmio32).
855 The options are the same as for ttyS, above.
857 earlyprintk= [X86,SH,BLACKFIN,ARM]
861 earlyprintk=serial[,ttySn[,baudrate]]
862 earlyprintk=serial[,0x...[,baudrate]]
863 earlyprintk=ttySn[,baudrate]
864 earlyprintk=dbgp[debugController#]
866 earlyprintk is useful when the kernel crashes before
867 the normal console is initialized. It is not enabled by
868 default because it has some cosmetic problems.
870 Append ",keep" to not disable it when the real console
873 Only one of vga, efi, serial, or usb debug port can
876 Currently only ttyS0 and ttyS1 may be specified by
877 name. Other I/O ports may be explicitly specified
878 on some architectures (x86 and arm at least) by
879 replacing ttySn with an I/O port address, like this:
880 earlyprintk=serial,0x1008,115200
881 You can find the port for a given device in
882 /proc/tty/driver/serial:
883 2: uart:ST16650V2 port:00001008 irq:18 ...
885 Interaction with the standard serial driver is not
888 The VGA and EFI output is eventually overwritten by
891 The xen output can only be used by Xen PV guests.
893 ekgdboc= [X86,KGDB] Allow early kernel console debugging
896 This is designed to be used in conjunction with
897 the boot argument: earlyprintk=vga
900 Format: {"off" | "on" | "skip[mbr]"}
902 efi_no_storage_paranoia [EFI; X86]
903 Using this parameter you can use more than 50% of
904 your efi variable storage. Use this parameter only if
905 you are really sure that your UEFI does sane gc and
906 fulfills the spec otherwise your board may brick.
908 eisa_irq_edge= [PARISC,HW]
909 See header of drivers/parisc/eisa.c.
912 See comment before function elanfreq_setup() in
913 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
916 Format: {"cfq" | "deadline" | "noop"}
917 See Documentation/block/cfq-iosched.txt and
918 Documentation/block/deadline-iosched.txt for details.
920 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
921 Specifies physical address of start of kernel core
922 image elf header and optionally the size. Generally
923 kexec loader will pass this option to capture kernel.
924 See Documentation/kdump/kdump.txt for details.
926 enable_mtrr_cleanup [X86]
927 The kernel tries to adjust MTRR layout from continuous
928 to discrete, to make X server driver able to add WB
929 entry later. This parameter enables that.
931 enable_timer_pin_1 [X86]
932 Enable PIN 1 of APIC timer
933 Can be useful to work around chipset bugs
934 (in particular on some ATI chipsets).
935 The kernel tries to set a reasonable default.
937 enforcing [SELINUX] Set initial enforcing status.
939 See security/selinux/Kconfig help text.
940 0 -- permissive (log only, no denials).
941 1 -- enforcing (deny and log).
943 Value can be changed at runtime via /selinux/enforce.
946 Disable Error Record Serialization Table (ERST)
949 ether= [HW,NET] Ethernet cards parameters
950 This option is obsoleted by the "netdev=" option, which
951 has equivalent usage. See its documentation for details.
955 Permit 'security.evm' to be updated regardless of
956 current integrity status.
960 fail_make_request=[KNL]
961 General fault injection mechanism.
962 Format: <interval>,<probability>,<space>,<times>
963 See also Documentation/fault-injection/.
966 See Documentation/blockdev/floppy.txt.
968 force_pal_cache_flush
969 [IA-64] Avoid check_sal_cache_flush which may hang on
970 buggy SAL_CACHE_FLUSH implementations. Using this
971 parameter will force ia64_sal_cache_flush to call
972 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
975 [FTRACE] will set and start the specified tracer
976 as early as possible in order to facilitate early
979 ftrace_dump_on_oops[=orig_cpu]
980 [FTRACE] will dump the trace buffers on oops.
981 If no parameter is passed, ftrace will dump
982 buffers of all CPUs, but if you pass orig_cpu, it will
983 dump only the buffer of the CPU that triggered the
986 ftrace_filter=[function-list]
987 [FTRACE] Limit the functions traced by the function
988 tracer at boot up. function-list is a comma separated
989 list of functions. This list can be changed at run
990 time by the set_ftrace_filter file in the debugfs
993 ftrace_notrace=[function-list]
994 [FTRACE] Do not trace the functions specified in
995 function-list. This list can be changed at run time
996 by the set_ftrace_notrace file in the debugfs
999 ftrace_graph_filter=[function-list]
1000 [FTRACE] Limit the top level callers functions traced
1001 by the function graph tracer at boot up.
1002 function-list is a comma separated list of functions
1003 that can be changed at run time by the
1004 set_graph_function file in the debugfs tracing directory.
1007 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1008 support via parallel port (up to 5 devices per port)
1009 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1010 See also Documentation/input/joystick-parport.txt
1014 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1018 gcov_persist= [GCOV] When non-zero (default), profiling data for
1019 kernel modules is saved and remains accessible via
1020 debugfs, even when the module is unloaded/reloaded.
1021 When zero, profiling data is discarded and associated
1022 debugfs files are removed at module unload time.
1024 gpt [EFI] Forces disk with valid GPT signature but
1025 invalid Protective MBR to be treated as GPT.
1027 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1028 the "Enable 0" bit of the configuration register.
1031 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1032 the "Enable 0" bit of the configuration register.
1035 grcan.select= [HW] Select which physical interface to use.
1038 grcan.txsize= [HW] Sets the size of the tx buffer.
1039 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1041 grcan.rxsize= [HW] Sets the size of the rx buffer.
1042 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1045 hashdist= [KNL,NUMA] Large hashes allocated during boot
1046 are distributed across NUMA nodes. Defaults on
1047 for 64-bit NUMA, off otherwise.
1048 Format: 0 | 1 (for off | on)
1050 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1052 hd= [EIDE] (E)IDE hard drive subsystem geometry
1053 Format: <cyl>,<head>,<sect>
1056 Disable Hardware Error Source Table (HEST) support;
1057 corresponding firmware-first mode error processing
1058 logic will be disabled.
1060 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1061 size of <nn>. This works even on boxes that have no
1062 highmem otherwise. This also works to reduce highmem
1063 size on bigger boxes.
1065 highres= [KNL] Enable/disable high resolution timer mode.
1066 Valid parameters: "on", "off"
1070 See Documentation/isdn/README.HiSax.
1074 hpet= [X86-32,HPET] option to control HPET usage
1075 Format: { enable (default) | disable | force |
1077 disable: disable HPET and use PIT instead
1078 force: allow force enabled of undocumented chips (ICH4,
1080 verbose: show contents of HPET registers during setup
1082 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1083 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1085 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1086 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1087 On x86-64 and powerpc, this option can be specified
1088 multiple times interleaved with hugepages= to reserve
1089 huge pages of different sizes. Valid pages sizes on
1090 x86-64 are 2M (when the CPU supports "pse") and 1G
1091 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1092 Note that 1GB pages can only be allocated at boot time
1093 using hugepages= and not freed afterwards.
1095 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1096 terminal devices. Valid values: 0..8
1097 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1098 If specified, z/VM IUCV HVC accepts connections
1099 from listed z/VM user IDs only.
1101 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1102 hardware thread id mappings.
1103 Format: <cpu>:<hwthread>
1106 Do not unregister boot console at start. This is only
1107 useful for debugging when something happens in the window
1108 between unregistering the boot console and initializing
1111 i2c_bus= [HW] Override the default board specific I2C bus speed
1112 or register an additional I2C bus that is not
1113 registered from board initialization code.
1117 i8042.debug [HW] Toggle i8042 debug mode
1118 i8042.direct [HW] Put keyboard port into non-translated mode
1119 i8042.dumbkbd [HW] Pretend that controller can only read data from
1120 keyboard and cannot control its state
1121 (Don't attempt to blink the leds)
1122 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1123 i8042.nokbd [HW] Don't check/create keyboard port
1124 i8042.noloop [HW] Disable the AUX Loopback command while probing
1126 i8042.nomux [HW] Don't check presence of an active multiplexing
1128 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1130 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1131 i8042.reset [HW] Reset the controller during init and cleanup
1132 i8042.unlock [HW] Unlock (ignore) the keylock
1136 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1137 indicates that the driver is running on unsupported
1139 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1140 does not match list of supported models.
1142 [HW] Report power status in /proc/i8k
1143 (disabled by default)
1144 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1147 i915.invert_brightness=
1148 [DRM] Invert the sense of the variable that is used to
1149 set the brightness of the panel backlight. Normally a
1150 brightness value of 0 indicates backlight switched off,
1151 and the maximum of the brightness value sets the backlight
1152 to maximum brightness. If this parameter is set to 0
1153 (default) and the machine requires it, or this parameter
1154 is set to 1, a brightness value of 0 sets the backlight
1155 to maximum brightness, and the maximum of the brightness
1156 value switches the backlight off.
1157 -1 -- never invert brightness
1158 0 -- machine default
1159 1 -- force brightness inversion
1162 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1164 ide-core.nodma= [HW] (E)IDE subsystem
1165 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1166 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1167 .cdrom .chs .ignore_cable are additional options
1168 See Documentation/ide/ide.txt.
1170 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1171 Claim all unknown PCI IDE storage controllers.
1174 Format: idle=poll, idle=halt, idle=nomwait
1175 Poll forces a polling idle loop that can slightly
1176 improve the performance of waking up a idle CPU, but
1177 will use a lot of power and make the system run hot.
1179 idle=halt: Halt is forced to be used for CPU idle.
1180 In such case C2/C3 won't be used again.
1181 idle=nomwait: Disable mwait for CPU C-states
1183 ignore_loglevel [KNL]
1184 Ignore loglevel setting - this will print /all/
1185 kernel messages to the console. Useful for debugging.
1186 We also add it as printk module parameter, so users
1187 could change it dynamically, usually by
1188 /sys/module/printk/parameters/ignore_loglevel.
1190 ihash_entries= [KNL]
1191 Set number of hash buckets for inode cache.
1193 ima_appraise= [IMA] appraise integrity measurements
1194 Format: { "off" | "enforce" | "fix" }
1197 ima_appraise_tcb [IMA]
1198 The builtin appraise policy appraises all files
1202 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1206 The list of supported hash algorithms is defined
1207 in crypto/hash_info.h.
1210 Load a policy which meets the needs of the Trusted
1211 Computing Base. This means IMA will measure all
1212 programs exec'd, files mmap'd for exec, and all files
1213 opened for read by uid=0.
1216 Select one of defined IMA measurements template formats.
1217 Formats: { "ima" | "ima-ng" }
1222 Run specified binary instead of /sbin/init as init
1225 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1226 for working out where the kernel is dying during
1229 initrd= [BOOT] Specify the location of the initial ramdisk
1231 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1234 int_pln_enable [x86] Enable power limit notification interrupt
1236 integrity_audit=[IMA]
1237 Format: { "0" | "1" }
1238 0 -- basic integrity auditing messages. (Default)
1239 1 -- additional integrity auditing messages.
1241 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1243 Enable intel iommu driver.
1245 Disable intel iommu driver.
1246 igfx_off [Default Off]
1247 By default, gfx is mapped as normal device. If a gfx
1248 device has a dedicated DMAR unit, the DMAR unit is
1249 bypassed by not enabling DMAR with this option. In
1250 this case, gfx device will use physical address for
1253 With this option iommu will not optimize to look
1254 for io virtual address below 32-bit forcing dual
1255 address cycle on pci bus for cards supporting greater
1256 than 32-bit addressing. The default is to look
1257 for translation below 32-bit and if not available
1258 then look in the higher range.
1259 strict [Default Off]
1260 With this option on every unmap_single operation will
1261 result in a hardware IOTLB flush operation as opposed
1262 to batching them for performance.
1263 sp_off [Default Off]
1264 By default, super page will be supported if Intel IOMMU
1265 has the capability. With this option, super page will
1268 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1269 0 disables intel_idle and fall back on acpi_idle.
1270 1 to 6 specify maximum depth of C-state.
1274 Do not enable intel_pstate as the default
1275 scaling driver for the supported processors
1277 intremap= [X86-64, Intel-IOMMU]
1278 on enable Interrupt Remapping (default)
1279 off disable Interrupt Remapping
1280 nosid disable Source ID checking
1282 BIOS x2APIC opt-out request will be ignored
1284 iomem= Disable strict checking of access to MMIO memory
1285 strict regions from userspace.
1302 io7= [HW] IO7 for Marvel based alpha systems
1303 See comment before marvel_specify_io7 in
1304 arch/alpha/kernel/core_marvel.c.
1306 io_delay= [X86] I/O delay method
1308 Standard port 0x80 based delay
1310 Alternate port 0xed based delay (needed on some systems)
1312 Simple two microseconds delay
1317 See Documentation/filesystems/nfs/nfsroot.txt.
1319 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1320 See comment before ip2_setup() in
1321 drivers/char/ip2/ip2base.c.
1324 When an interrupt is not handled search all handlers
1325 for it. Intended to get systems with badly broken
1329 When an interrupt is not handled search all handlers
1330 for it. Also check all handlers each timer
1331 interrupt. Intended to get systems with badly broken
1335 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1337 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1339 <cpu number>,...,<cpu number>
1341 <cpu number>-<cpu number>
1342 (must be a positive range in ascending order)
1344 <cpu number>,...,<cpu number>-<cpu number>
1346 This option can be used to specify one or more CPUs
1347 to isolate from the general SMP balancing and scheduling
1348 algorithms. You can move a process onto or off an
1349 "isolated" CPU via the CPU affinity syscalls or cpuset.
1350 <cpu number> begins at 0 and the maximum value is
1351 "number of CPUs in system - 1".
1353 This option is the preferred way to isolate CPUs. The
1354 alternative -- manually setting the CPU mask of all
1355 tasks in the system -- can cause problems and
1356 suboptimal load balancer performance.
1360 ivrs_ioapic [HW,X86_64]
1361 Provide an override to the IOAPIC-ID<->DEVICE-ID
1362 mapping provided in the IVRS ACPI table. For
1363 example, to map IOAPIC-ID decimal 10 to
1364 PCI device 00:14.0 write the parameter as:
1365 ivrs_ioapic[10]=00:14.0
1367 ivrs_hpet [HW,X86_64]
1368 Provide an override to the HPET-ID<->DEVICE-ID
1369 mapping provided in the IVRS ACPI table. For
1370 example, to map HPET-ID decimal 0 to
1371 PCI device 00:14.0 write the parameter as:
1372 ivrs_hpet[0]=00:14.0
1374 js= [HW,JOY] Analog joystick
1375 See Documentation/input/joystick.txt.
1379 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1380 specifies the amount of memory usable by the kernel
1381 for non-movable allocations. The requested amount is
1382 spread evenly throughout all nodes in the system. The
1383 remaining memory in each node is used for Movable
1384 pages. In the event, a node is too small to have both
1385 kernelcore and Movable pages, kernelcore pages will
1386 take priority and other nodes will have a larger number
1387 of Movable pages. The Movable zone is used for the
1388 allocation of pages that may be reclaimed or moved
1389 by the page migration subsystem. This means that
1390 HugeTLB pages may not be allocated from this zone.
1391 Note that allocations like PTEs-from-HighMem still
1392 use the HighMem zone if it exists, and the Normal
1393 zone if it does not.
1395 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1396 Format: <Controller#>[,poll interval]
1397 The controller # is the number of the ehci usb debug
1398 port as it is probed via PCI. The poll interval is
1399 optional and is the number seconds in between
1400 each poll cycle to the debug port in case you need
1401 the functionality for interrupting the kernel with
1402 gdb or control-c on the dbgp connection. When
1403 not using this parameter you use sysrq-g to break into
1404 the kernel debugger.
1406 kgdboc= [KGDB,HW] kgdb over consoles.
1407 Requires a tty driver that supports console polling,
1408 or a supported polling keyboard driver (non-usb).
1409 Serial only format: <serial_device>[,baud]
1410 keyboard only format: kbd
1411 keyboard and serial format: kbd,<serial_device>[,baud]
1412 Optional Kernel mode setting:
1413 kms, kbd format: kms,kbd
1414 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1416 kgdbwait [KGDB] Stop kernel execution and enter the
1417 kernel debugger at the earliest opportunity.
1419 kmac= [MIPS] korina ethernet MAC address.
1420 Configure the RouterBoard 532 series on-chip
1421 Ethernet adapter MAC address.
1423 kmemleak= [KNL] Boot-time kmemleak enable/disable
1424 Valid arguments: on, off
1427 kstack=N [X86] Print N words from the kernel stack
1430 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1431 Default is 0 (don't ignore, but inject #GP)
1433 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1437 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1438 Default is 1 (enabled)
1440 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1442 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1444 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1445 (virtualized MMU) support on capable Intel chips.
1446 Default is 1 (enabled)
1448 kvm-intel.emulate_invalid_guest_state=
1449 [KVM,Intel] Enable emulation of invalid guest states
1450 Default is 0 (disabled)
1452 kvm-intel.flexpriority=
1453 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1454 Default is 1 (enabled)
1457 [KVM,Intel] Enable VMX nesting (nVMX).
1458 Default is 0 (disabled)
1460 kvm-intel.unrestricted_guest=
1461 [KVM,Intel] Disable unrestricted guest feature
1462 (virtualized real and unpaged mode) on capable
1463 Intel chips. Default is 1 (enabled)
1465 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1466 feature (tagged TLBs) on capable Intel chips.
1467 Default is 1 (enabled)
1473 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1476 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1477 value for LAPIC timer one-shot implementation. Default
1478 back to the programmable timer unit in the LAPIC.
1480 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1483 libata.dma= [LIBATA] DMA control
1484 libata.dma=0 Disable all PATA and SATA DMA
1485 libata.dma=1 PATA and SATA Disk DMA only
1486 libata.dma=2 ATAPI (CDROM) DMA only
1487 libata.dma=4 Compact Flash DMA only
1488 Combinations also work, so libata.dma=3 enables DMA
1489 for disks and CDROMs, but not CFs.
1491 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1492 libata.ignore_hpa=0 keep BIOS limits (default)
1493 libata.ignore_hpa=1 ignore limits, using full disk
1495 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1499 libata.force= [LIBATA] Force configurations. The format is comma
1500 separated list of "[ID:]VAL" where ID is
1501 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1502 matching port, link or device. Basically, it matches
1503 the ATA ID string printed on console by libata. If
1504 the whole ID part is omitted, the last PORT and DEVICE
1505 values are used. If ID hasn't been specified yet, the
1506 configuration applies to all ports, links and devices.
1508 If only DEVICE is omitted, the parameter applies to
1509 the port and all links and devices behind it. DEVICE
1510 number of 0 either selects the first device or the
1511 first fan-out link behind PMP device. It does not
1512 select the host link. DEVICE number of 15 selects the
1513 host link and device attached to it.
1515 The VAL specifies the configuration to force. As long
1516 as there's no ambiguity shortcut notation is allowed.
1517 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1518 The following configurations can be forced.
1520 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1521 Any ID with matching PORT is used.
1523 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1525 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1526 udma[/][16,25,33,44,66,100,133] notation is also
1529 * [no]ncq: Turn on or off NCQ.
1531 * nohrst, nosrst, norst: suppress hard, soft
1534 * rstonce: only attempt one reset during
1535 hot-unplug link recovery
1537 * dump_id: dump IDENTIFY data.
1539 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1541 * disable: Disable this device.
1543 If there are multiple matching configurations changing
1544 the same attribute, the last one is used.
1546 memblock=debug [KNL] Enable memblock debug messages.
1548 load_ramdisk= [RAM] List of ramdisks to load from floppy
1549 See Documentation/blockdev/ramdisk.txt.
1551 lockd.nlm_grace_period=P [NFS] Assign grace period.
1554 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1557 lockd.nlm_timeout=T [NFS] Assign timeout value.
1560 lockd.nlm_udpport=M [NFS] Assign UDP port.
1563 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1566 loglevel= All Kernel Messages with a loglevel smaller than the
1567 console loglevel will be printed to the console. It can
1568 also be changed with klogd or other programs. The
1569 loglevels are defined as follows:
1571 0 (KERN_EMERG) system is unusable
1572 1 (KERN_ALERT) action must be taken immediately
1573 2 (KERN_CRIT) critical conditions
1574 3 (KERN_ERR) error conditions
1575 4 (KERN_WARNING) warning conditions
1576 5 (KERN_NOTICE) normal but significant condition
1577 6 (KERN_INFO) informational
1578 7 (KERN_DEBUG) debug-level messages
1580 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1581 in bytes. n must be a power of two. The default
1582 size is set in the kernel config file.
1584 logo.nologo [FB] Disables display of the built-in Linux logo.
1585 This may be used to provide more screen space for
1586 kernel log messages and is useful when debugging
1587 kernel boot problems.
1589 lp=0 [LP] Specify parallel ports to use, e.g,
1590 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1591 lp=reset first parallel port). 'lp=0' disables the
1592 lp=auto printer driver. 'lp=reset' (which can be
1593 specified in addition to the ports) causes
1594 attached printers to be reset. Using
1595 lp=port1,port2,... specifies the parallel ports
1596 to associate lp devices with, starting with
1597 lp0. A port specification may be 'none' to skip
1598 that lp device, or a parport name such as
1599 'parport0'. Specifying 'lp=auto' instead of a
1600 port specification list means that device IDs
1601 from each port should be examined, to see if
1602 an IEEE 1284-compliant printer is attached; if
1603 so, the driver will manage that printer.
1604 See also header of drivers/char/lp.c.
1607 Sets loops_per_jiffy to given constant, thus avoiding
1608 time-consuming boot-time autodetection (up to 250 ms per
1609 CPU). 0 enables autodetection (default). To determine
1610 the correct value for your kernel, boot with normal
1611 autodetection and see what value is printed. Note that
1612 on SMP systems the preset will be applied to all CPUs,
1613 which is likely to cause problems if your CPUs need
1614 significantly divergent settings. An incorrect value
1615 will cause delays in the kernel to be wrong, leading to
1616 unpredictable I/O errors and other breakage. Although
1617 unlikely, in the extreme case this might damage your
1621 Format: <io>,<irq>,<dma>
1623 machvec= [IA-64] Force the use of a particular machine-vector
1624 (machvec) in a generic kernel.
1625 Example: machvec=hpzx1_swiotlb
1627 machtype= [Loongson] Share the same kernel image file between different
1629 Example: machtype=lemote-yeeloong-2f-7inch
1631 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1632 than or equal to this physical address is ignored.
1634 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1635 should make use of. maxcpus=n : n >= 0 limits the
1636 kernel to using 'n' processors. n=0 is a special case,
1637 it is equivalent to "nosmp", which also disables
1640 max_loop= [LOOP] The number of loop block devices that get
1641 (loop.max_loop) unconditionally pre-created at init time. The default
1642 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1643 of statically allocating a predefined number, loop
1644 devices can be requested on-demand with the
1645 /dev/loop-control interface.
1647 mce [X86-32] Machine Check Exception
1649 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1651 md= [HW] RAID subsystems devices and level
1652 See Documentation/md.txt.
1655 Format: <first>,<last>
1656 Specifies range of consoles to be captured by the MDA.
1658 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1659 Amount of memory to be used when the kernel is not able
1660 to see the whole system memory or for test.
1661 [X86] Work as limiting max address. Use together
1662 with memmap= to avoid physical address space collisions.
1663 Without memmap= PCI devices could be placed at addresses
1664 belonging to unused RAM.
1666 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1670 [KNL,SH] Allow user to override the default size for
1671 per-device physically contiguous DMA buffers.
1673 memmap=exactmap [KNL,X86] Enable setting of an exact
1674 E820 memory map, as specified by the user.
1675 Such memmap=exactmap lines can be constructed based on
1676 BIOS output or other requirements. See the memmap=nn@ss
1679 memmap=nn[KMG]@ss[KMG]
1680 [KNL] Force usage of a specific region of memory
1681 Region of memory to be used, from ss to ss+nn.
1683 memmap=nn[KMG]#ss[KMG]
1684 [KNL,ACPI] Mark specific memory as ACPI data.
1685 Region of memory to be used, from ss to ss+nn.
1687 memmap=nn[KMG]$ss[KMG]
1688 [KNL,ACPI] Mark specific memory as reserved.
1689 Region of memory to be used, from ss to ss+nn.
1690 Example: Exclude memory from 0x18690000-0x1869ffff
1691 memmap=64K$0x18690000
1693 memmap=0x10000$0x18690000
1695 memory_corruption_check=0/1 [X86]
1696 Some BIOSes seem to corrupt the first 64k of
1697 memory when doing things like suspend/resume.
1698 Setting this option will scan the memory
1699 looking for corruption. Enabling this will
1700 both detect corruption and prevent the kernel
1701 from using the memory being corrupted.
1702 However, its intended as a diagnostic tool; if
1703 repeatable BIOS-originated corruption always
1704 affects the same memory, you can use memmap=
1705 to prevent the kernel from using that memory.
1707 memory_corruption_check_size=size [X86]
1708 By default it checks for corruption in the low
1709 64k, making this memory unavailable for normal
1710 use. Use this parameter to scan for
1711 corruption in more or less memory.
1713 memory_corruption_check_period=seconds [X86]
1714 By default it checks for corruption every 60
1715 seconds. Use this parameter to check at some
1716 other rate. 0 disables periodic checking.
1718 memtest= [KNL,X86] Enable memtest
1720 default : 0 <disable>
1721 Specifies the number of memtest passes to be
1722 performed. Each pass selects another test
1723 pattern from a given set of patterns. Memtest
1724 fills the memory with this pattern, validates
1725 memory contents and reserves bad memory
1726 regions that are detected.
1728 meye.*= [HW] Set MotionEye Camera parameters
1729 See Documentation/video4linux/meye.txt.
1731 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1732 Multi-Function General Purpose Timers on AMD Geode
1735 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1736 the BIOS has incorrectly applied a workaround. TinyBIOS
1737 version 0.98 is known to be affected, 0.99 fixes the
1738 problem by letting the user disable the workaround.
1742 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1743 physical address is ignored.
1745 mini2440= [ARM,HW,KNL]
1746 Format:[0..2][b][c][t]
1748 MINI2440 configuration specification:
1749 0 - The attached screen is the 3.5" TFT
1750 1 - The attached screen is the 7" TFT
1751 2 - The VGA Shield is attached (1024x768)
1752 Leaving out the screen size parameter will not load
1753 the TFT driver, and the framebuffer will be left
1755 b - Enable backlight. The TFT backlight pin will be
1756 linked to the kernel VESA blanking code and a GPIO
1757 LED. This parameter is not necessary when using the
1759 c - Enable the s3c camera interface.
1760 t - Reserved for enabling touchscreen support. The
1761 touchscreen support is not enabled in the mainstream
1762 kernel as of 2.6.30, a preliminary port can be found
1763 in the "bleeding edge" mini2440 support kernel at
1764 http://repo.or.cz/w/linux-2.6/mini2440.git
1767 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1768 parameter allows control of the logging verbosity for
1769 the additional memory initialisation checks. A value
1770 of 0 disables mminit logging and a level of 4 will
1771 log everything. Information is printed at KERN_DEBUG
1772 so loglevel=8 may also need to be specified.
1775 [KNL] When CONFIG_MODULE_SIG is set, this means that
1776 modules without (valid) signatures will fail to load.
1777 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1778 is always true, so this option does nothing.
1781 [MOUSE] Maximum time between finger touching and
1782 leaving touchpad surface for touch to be considered
1783 a tap and be reported as a left button click (for
1784 touchpads working in absolute mode only).
1786 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1787 reporting absolute coordinates, such as tablets
1788 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1789 reporting absolute coordinates, such as tablets
1791 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1792 is similar to kernelcore except it specifies the
1793 amount of memory used for migratable allocations.
1794 If both kernelcore and movablecore is specified,
1795 then kernelcore will be at *least* the specified
1796 value but may be more. If movablecore on its own
1797 is specified, the administrator must be careful
1798 that the amount of memory usable for all allocations
1801 movable_node [KNL,X86] Boot-time switch to enable the effects
1802 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1804 MTD_Partition= [MTD]
1805 Format: <name>,<region-number>,<size>,<offset>
1807 MTD_Region= [MTD] Format:
1808 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1811 See drivers/mtd/cmdlinepart.c.
1813 multitce=off [PPC] This parameter disables the use of the pSeries
1814 firmware feature for updating multiple TCE entries
1817 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1819 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1821 boundary - index of last SLC block on Flex-OneNAND.
1822 The remaining blocks are configured as MLC blocks.
1823 lock - Configure if Flex-OneNAND boundary should be locked.
1824 Once locked, the boundary cannot be changed.
1825 1 indicates lock status, 0 indicates unlock status.
1828 ARM/S3C2412 JIVE boot control
1830 See arch/arm/mach-s3c2412/mach-jive.c
1832 mtouchusb.raw_coordinates=
1833 [HW] Make the MicroTouch USB driver use raw coordinates
1834 ('y', default) or cooked coordinates ('n')
1836 mtrr_chunk_size=nn[KMG] [X86]
1837 used for mtrr cleanup. It is largest continuous chunk
1838 that could hold holes aka. UC entries.
1840 mtrr_gran_size=nn[KMG] [X86]
1841 Used for mtrr cleanup. It is granularity of mtrr block.
1843 Large value could prevent small alignment from
1846 mtrr_spare_reg_nr=n [X86]
1848 Range: 0,7 : spare reg number
1850 Used for mtrr cleanup. It is spare mtrr entries number.
1851 Set to 2 or more if your graphical card needs more.
1853 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1855 netdev= [NET] Network devices parameters
1856 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1857 Note that mem_start is often overloaded to mean
1858 something different and driver-specific.
1859 This usage is only documented in each driver source
1863 [NETFILTER] Enable connection tracking flow accounting
1864 0 to disable accounting
1865 1 to enable accounting
1868 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1869 See Documentation/filesystems/nfs/nfsroot.txt.
1871 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1872 See Documentation/filesystems/nfs/nfsroot.txt.
1874 nfsrootdebug [NFS] enable nfsroot debugging messages.
1875 See Documentation/filesystems/nfs/nfsroot.txt.
1877 nfs.callback_tcpport=
1878 [NFS] set the TCP port on which the NFSv4 callback
1879 channel should listen.
1882 [NFS] sets the pathname to the program which is used
1883 to update the NFS client cache entries.
1885 nfs.cache_getent_timeout=
1886 [NFS] sets the timeout after which an attempt to
1887 update a cache entry is deemed to have failed.
1889 nfs.idmap_cache_timeout=
1890 [NFS] set the maximum lifetime for idmapper cache
1894 [NFS] enable 64-bit inode numbers.
1895 If zero, the NFS client will fake up a 32-bit inode
1896 number for the readdir() and stat() syscalls instead
1897 of returning the full 64-bit number.
1898 The default is to return 64-bit inode numbers.
1900 nfs.max_session_slots=
1901 [NFSv4.1] Sets the maximum number of session slots
1902 the client will attempt to negotiate with the server.
1903 This limits the number of simultaneous RPC requests
1904 that the client can send to the NFSv4.1 server.
1905 Note that there is little point in setting this
1906 value higher than the max_tcp_slot_table_limit.
1908 nfs.nfs4_disable_idmapping=
1909 [NFSv4] When set to the default of '1', this option
1910 ensures that both the RPC level authentication
1911 scheme and the NFS level operations agree to use
1912 numeric uids/gids if the mount is using the
1913 'sec=sys' security flavour. In effect it is
1914 disabling idmapping, which can make migration from
1915 legacy NFSv2/v3 systems to NFSv4 easier.
1916 Servers that do not support this mode of operation
1917 will be autodetected by the client, and it will fall
1918 back to using the idmapper.
1919 To turn off this behaviour, set the value to '0'.
1921 [NFS4] Specify an additional fixed unique ident-
1922 ification string that NFSv4 clients can insert into
1923 their nfs_client_id4 string. This is typically a
1924 UUID that is generated at system install time.
1926 nfs.send_implementation_id =
1927 [NFSv4.1] Send client implementation identification
1928 information in exchange_id requests.
1929 If zero, no implementation identification information
1931 The default is to send the implementation identification
1934 nfs.recover_lost_locks =
1935 [NFSv4] Attempt to recover locks that were lost due
1936 to a lease timeout on the server. Please note that
1937 doing this risks data corruption, since there are
1938 no guarantees that the file will remain unchanged
1939 after the locks are lost.
1940 If you want to enable the kernel legacy behaviour of
1941 attempting to recover these locks, then set this
1943 The default parameter value of '0' causes the kernel
1944 not to attempt recovery of lost locks.
1946 nfsd.nfs4_disable_idmapping=
1947 [NFSv4] When set to the default of '1', the NFSv4
1948 server will return only numeric uids and gids to
1949 clients using auth_sys, and will accept numeric uids
1950 and gids from such clients. This is intended to ease
1951 migration from NFSv2/v3.
1953 objlayoutdriver.osd_login_prog=
1954 [NFS] [OBJLAYOUT] sets the pathname to the program which
1955 is used to automatically discover and login into new
1956 osd-targets. Please see:
1957 Documentation/filesystems/pnfs.txt for more explanations
1959 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1960 when a NMI is triggered.
1961 Format: [state][,regs][,debounce][,die]
1963 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1964 Format: [panic,][nopanic,][num]
1966 0 - turn nmi_watchdog off
1967 When panic is specified, panic when an NMI watchdog
1968 timeout occurs (or 'nopanic' to override the opposite
1970 This is useful when you use a panic=... timeout and
1971 need the box quickly up again.
1973 netpoll.carrier_timeout=
1974 [NET] Specifies amount of time (in seconds) that
1975 netpoll should wait for a carrier. By default netpoll
1978 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1979 emulation library even if a 387 maths coprocessor
1983 [HW] Never suspend the console
1984 Disable suspending of consoles during suspend and
1985 hibernate operations. Once disabled, debugging
1986 messages can reach various consoles while the rest
1987 of the system is being put to sleep (ie, while
1988 debugging driver suspend/resume hooks). This may
1989 not work reliably with all consoles, but is known
1990 to work with serial and VGA consoles.
1991 To facilitate more flexible debugging, we also add
1992 console_suspend, a printk module parameter to control
1993 it. Users could use console_suspend (usually
1994 /sys/module/printk/parameters/console_suspend) to
1995 turn on/off it dynamically.
1997 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1998 caches in the slab allocator. Saves per-node memory,
1999 but will impact performance.
2003 noapic [SMP,APIC] Tells the kernel to not make use of any
2004 IOAPICs that may be present in the system.
2006 noautogroup Disable scheduler automatic task group creation.
2008 nobats [PPC] Do not use BATs for mapping kernel lowmem
2009 on "Classic" PPC cores.
2013 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2015 nodelayacct [KNL] Disable per-task delay accounting
2017 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2019 nodsp [SH] Disable hardware DSP at boot time.
2021 noefi [X86] Disable EFI runtime services support.
2026 On X86-32 available only on PAE configured kernels.
2027 noexec=on: enable non-executable mappings (default)
2028 noexec=off: disable non-executable mappings
2031 Disable SMAP (Supervisor Mode Access Prevention)
2032 even if it is supported by processor.
2035 Disable SMEP (Supervisor Mode Execution Prevention)
2036 even if it is supported by processor.
2039 This affects only 32-bit executables.
2040 noexec32=on: enable non-executable mappings (default)
2041 read doesn't imply executable mappings
2042 noexec32=off: disable non-executable mappings
2043 read implies executable mappings
2045 nofpu [SH] Disable hardware FPU at boot time.
2047 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2048 register save and restore. The kernel will only save
2049 legacy floating-point registers on task switch.
2051 noxsave [BUGS=X86] Disables x86 extended register state save
2052 and restore using xsave. The kernel will fallback to
2053 enabling legacy floating-point and sse state.
2056 on enable eager fpu restore
2057 off disable eager fpu restore
2058 auto selects the default scheme, which automatically
2059 enables eagerfpu restore for xsaveopt.
2061 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2062 wfi(ARM) instruction doesn't work correctly and not to
2063 use it. This is also useful when using JTAG debugger.
2065 no_file_caps Tells the kernel not to honor file capabilities. The
2066 only way then for a file to be executed with privilege
2067 is to be setuid root or executed by root.
2069 nohalt [IA-64] Tells the kernel not to use the power saving
2070 function PAL_HALT_LIGHT when idle. This increases
2071 power-consumption. On the positive side, it reduces
2072 interrupt wake-up latency, which may improve performance
2073 in certain environments such as networked servers or
2076 nohz= [KNL] Boottime enable/disable dynamic ticks
2077 Valid arguments: on, off
2080 nohz_full= [KNL,BOOT]
2081 In kernels built with CONFIG_NO_HZ_FULL=y, set
2082 the specified list of CPUs whose tick will be stopped
2083 whenever possible. The boot CPU will be forced outside
2084 the range to maintain the timekeeping.
2085 The CPUs in this range must also be included in the
2088 noiotrap [SH] Disables trapped I/O port accesses.
2090 noirqdebug [X86-32] Disables the code which attempts to detect and
2091 disable unhandled interrupt sources.
2093 no_timer_check [X86,APIC] Disables the code which tests for
2094 broken timer IRQ sources.
2096 noisapnp [ISAPNP] Disables ISA PnP code.
2098 noinitrd [RAM] Tells the kernel not to load any configured
2101 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2103 [Deprecated - use intremap=off]
2107 nojitter [IA-64] Disables jitter checking for ITC timers.
2109 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2111 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2114 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2115 steal time is computed, but won't influence scheduler
2118 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2120 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2122 noltlbs [PPC] Do not use large page/tlb entries for kernel
2123 lowmem mapping on PPC40x.
2125 nomca [IA-64] Disable machine check abort handling
2127 nomce [X86-32] Machine Check Exception
2129 nomfgpt [X86-32] Disable Multi-Function General Purpose
2130 Timer usage (for AMD Geode machines).
2132 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2133 shutdown the other cpus. Instead use the REBOOT_VECTOR
2136 nomodule Disable module load
2138 nopat [X86] Disable PAT (page attribute table extension of
2139 pagetables) support.
2141 norandmaps Don't use address space randomization. Equivalent to
2142 echo 0 > /proc/sys/kernel/randomize_va_space
2144 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2146 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2147 with UP alternatives
2149 nordrand [X86] Disable the direct use of the RDRAND
2150 instruction even if it is supported by the
2151 processor. RDRAND is still available to user
2154 noresume [SWSUSP] Disables resume and restores original swap
2157 no-scroll [VGA] Disables scrollback.
2158 This is required for the Braillex ib80-piezo Braille
2159 reader made by F.H. Papenmeier (Germany).
2163 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2165 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2166 and disable the IO APIC. legacy for "maxcpus=0".
2168 nosoftlockup [KNL] Disable the soft-lockup detector.
2170 nosync [HW,M68K] Disables sync negotiation for all devices.
2172 notsc [BUGS=X86-32] Disable Time Stamp Counter
2174 nousb [USB] Disable the USB subsystem
2176 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2180 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2182 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2183 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2184 Some features depend on CPU0. Known dependencies are:
2185 1. Resume from suspend/hibernate depends on CPU0.
2186 Suspend/hibernate will fail if CPU0 is offline and you
2187 need to online CPU0 before suspend/hibernate.
2188 2. PIC interrupts also depend on CPU0. CPU0 can't be
2189 removed if a PIC interrupt is detected.
2190 It's said poweroff/reboot may depend on CPU0 on some
2191 machines although I haven't seen such issues so far
2192 after CPU0 is offline on a few tested machines.
2193 If the dependencies are under your control, you can
2194 turn on cpu0_hotplug.
2196 nptcg= [IA-64] Override max number of concurrent global TLB
2197 purges which is reported from either PAL_VM_SUMMARY or
2200 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2201 could support. nr_cpus=n : n >= 1 limits the kernel to
2202 supporting 'n' processors. Later in runtime you can not
2203 use hotplug cpu feature to put more cpu back to online.
2204 just like you compile the kernel NR_CPUS=n
2206 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2208 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2209 Allowed values are enable and disable
2211 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2212 one of ['zone', 'node', 'default'] can be specified
2213 This can be set from sysctl after boot.
2214 See Documentation/sysctl/vm.txt for details.
2216 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2217 See Documentation/debugging-via-ohci1394.txt for more
2220 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2221 Rather than timing out after 20 ms if an EC
2222 command is not properly ACKed, override the length
2223 of the timeout. We have interrupts disabled while
2224 waiting for the ACK, so if this is set too high
2225 interrupts *may* be lost!
2227 omap_mux= [OMAP] Override bootloader pin multiplexing.
2228 Format: <mux_mode0.mode_name=value>...
2229 For example, to override I2C bus2:
2230 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2232 oprofile.timer= [HW]
2233 Use timer interrupt instead of performance counters
2235 oprofile.cpu_type= Force an oprofile cpu type
2236 This might be useful if you have an older oprofile
2237 userland or if you want common events.
2238 Format: { arch_perfmon }
2239 arch_perfmon: [X86] Force use of architectural
2240 perfmon on Intel CPUs instead of the
2241 CPU specific event set.
2242 timer: [X86] Force use of architectural NMI
2243 timer mode (see also oprofile.timer
2244 for generic hr timer mode)
2245 [s390] Force legacy basic mode sampling
2246 (report cpu_type "timer")
2248 oops=panic Always panic on oopses. Default is to just kill the
2249 process, but there is a small probability of
2250 deadlocking the machine.
2251 This will also cause panics on machine check exceptions.
2252 Useful together with panic=30 to trigger a reboot.
2255 See Documentation/sound/oss/oss-parameters.txt
2257 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2258 timeout > 0: seconds before rebooting
2259 timeout = 0: wait forever
2260 timeout < 0: reboot immediately
2263 parkbd.port= [HW] Parallel port number the keyboard adapter is
2264 connected to, default is 0.
2266 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2267 0 for XT, 1 for AT (default is AT).
2270 parport= [HW,PPT] Specify parallel ports. 0 disables.
2271 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2272 Use 'auto' to force the driver to use any
2273 IRQ/DMA settings detected (the default is to
2274 ignore detected IRQ/DMA settings because of
2275 possible conflicts). You can specify the base
2276 address, IRQ, and DMA settings; IRQ and DMA
2277 should be numbers, or 'auto' (for using detected
2278 settings on that particular port), or 'nofifo'
2279 (to avoid using a FIFO even if it is detected).
2280 Parallel ports are assigned in the order they
2281 are specified on the command line, starting
2284 parport_init_mode= [HW,PPT]
2285 Configure VIA parallel port to operate in
2286 a specific mode. This is necessary on Pegasos
2287 computer where firmware has no options for setting
2288 up parallel port mode and sets it to spp.
2289 Currently this function knows 686a and 8231 chips.
2290 Format: [spp|ps2|epp|ecp|ecpepp]
2293 Halt all CPUs after the first oops has been printed for
2294 the specified number of seconds. This is to be used if
2295 your oopses keep scrolling off the screen.
2300 See header of drivers/block/paride/pcd.c.
2301 See also Documentation/blockdev/paride.txt.
2303 pci=option[,option...] [PCI] various PCI subsystem options:
2304 earlydump [X86] dump PCI config space before the kernel
2306 off [X86] don't probe for the PCI bus
2307 bios [X86-32] force use of PCI BIOS, don't access
2308 the hardware directly. Use this if your machine
2309 has a non-standard PCI host bridge.
2310 nobios [X86-32] disallow use of PCI BIOS, only direct
2311 hardware access methods are allowed. Use this
2312 if you experience crashes upon bootup and you
2313 suspect they are caused by the BIOS.
2314 conf1 [X86] Force use of PCI Configuration
2316 conf2 [X86] Force use of PCI Configuration
2318 noaer [PCIE] If the PCIEAER kernel config parameter is
2319 enabled, this kernel boot option can be used to
2320 disable the use of PCIE advanced error reporting.
2321 nodomains [PCI] Disable support for multiple PCI
2322 root domains (aka PCI segments, in ACPI-speak).
2323 nommconf [X86] Disable use of MMCONFIG for PCI
2325 check_enable_amd_mmconf [X86] check for and enable
2326 properly configured MMIO access to PCI
2327 config space on AMD family 10h CPU
2328 nomsi [MSI] If the PCI_MSI kernel config parameter is
2329 enabled, this kernel boot option can be used to
2330 disable the use of MSI interrupts system-wide.
2331 noioapicquirk [APIC] Disable all boot interrupt quirks.
2332 Safety option to keep boot IRQs enabled. This
2333 should never be necessary.
2334 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2335 primary IO-APIC for bridges that cannot disable
2336 boot IRQs. This fixes a source of spurious IRQs
2337 when the system masks IRQs.
2338 noioapicreroute [APIC] Disable workaround that uses the
2339 boot IRQ equivalent of an IRQ that connects to
2340 a chipset where boot IRQs cannot be disabled.
2341 The opposite of ioapicreroute.
2342 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2343 routing table. These calls are known to be buggy
2344 on several machines and they hang the machine
2345 when used, but on other computers it's the only
2346 way to get the interrupt routing table. Try
2347 this option if the kernel is unable to allocate
2348 IRQs or discover secondary PCI buses on your
2350 rom [X86] Assign address space to expansion ROMs.
2351 Use with caution as certain devices share
2352 address decoders between ROMs and other
2354 norom [X86] Do not assign address space to
2355 expansion ROMs that do not already have
2356 BIOS assigned address ranges.
2357 nobar [X86] Do not assign address space to the
2358 BARs that weren't assigned by the BIOS.
2359 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2360 assigned automatically to PCI devices. You can
2361 make the kernel exclude IRQs of your ISA cards
2363 pirqaddr=0xAAAAA [X86] Specify the physical address
2364 of the PIRQ table (normally generated
2365 by the BIOS) if it is outside the
2366 F0000h-100000h range.
2367 lastbus=N [X86] Scan all buses thru bus #N. Can be
2368 useful if the kernel is unable to find your
2369 secondary buses and you want to tell it
2370 explicitly which ones they are.
2371 assign-busses [X86] Always assign all PCI bus
2372 numbers ourselves, overriding
2373 whatever the firmware may have done.
2374 usepirqmask [X86] Honor the possible IRQ mask stored
2375 in the BIOS $PIR table. This is needed on
2376 some systems with broken BIOSes, notably
2377 some HP Pavilion N5400 and Omnibook XE3
2378 notebooks. This will have no effect if ACPI
2379 IRQ routing is enabled.
2380 noacpi [X86] Do not use ACPI for IRQ routing
2381 or for PCI scanning.
2382 use_crs [X86] Use PCI host bridge window information
2383 from ACPI. On BIOSes from 2008 or later, this
2384 is enabled by default. If you need to use this,
2385 please report a bug.
2386 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2387 If you need to use this, please report a bug.
2388 routeirq Do IRQ routing for all PCI devices.
2389 This is normally done in pci_enable_device(),
2390 so this option is a temporary workaround
2391 for broken drivers that don't call it.
2392 skip_isa_align [X86] do not align io start addr, so can
2393 handle more pci cards
2394 firmware [ARM] Do not re-enumerate the bus but instead
2395 just use the configuration from the
2396 bootloader. This is currently used on
2397 IXP2000 systems where the bus has to be
2398 configured a certain way for adjunct CPUs.
2399 noearly [X86] Don't do any early type 1 scanning.
2400 This might help on some broken boards which
2401 machine check when some devices' config space
2402 is read. But various workarounds are disabled
2403 and some IOMMU drivers will not work.
2404 bfsort Sort PCI devices into breadth-first order.
2405 This sorting is done to get a device
2406 order compatible with older (<= 2.4) kernels.
2407 nobfsort Don't sort PCI devices into breadth-first order.
2408 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2409 tuning and use the BIOS-configured MPS defaults.
2410 pcie_bus_safe Set every device's MPS to the largest value
2411 supported by all devices below the root complex.
2412 pcie_bus_perf Set device MPS to the largest allowable MPS
2413 based on its parent bus. Also set MRRS (Max
2414 Read Request Size) to the largest supported
2415 value (no larger than the MPS that the device
2416 or bus can support) for best performance.
2417 pcie_bus_peer2peer Set every device's MPS to 128B, which
2418 every device is guaranteed to support. This
2419 configuration allows peer-to-peer DMA between
2420 any pair of devices, possibly at the cost of
2421 reduced performance. This also guarantees
2422 that hot-added devices will work.
2423 cbiosize=nn[KMG] The fixed amount of bus space which is
2424 reserved for the CardBus bridge's IO window.
2425 The default value is 256 bytes.
2426 cbmemsize=nn[KMG] The fixed amount of bus space which is
2427 reserved for the CardBus bridge's memory
2428 window. The default value is 64 megabytes.
2431 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2432 Specifies alignment and device to reassign
2433 aligned memory resources.
2434 If <order of align> is not specified,
2435 PAGE_SIZE is used as alignment.
2436 PCI-PCI bridge can be specified, if resource
2437 windows need to be expanded.
2438 ecrc= Enable/disable PCIe ECRC (transaction layer
2439 end-to-end CRC checking).
2440 bios: Use BIOS/firmware settings. This is the
2444 hpiosize=nn[KMG] The fixed amount of bus space which is
2445 reserved for hotplug bridge's IO window.
2446 Default size is 256 bytes.
2447 hpmemsize=nn[KMG] The fixed amount of bus space which is
2448 reserved for hotplug bridge's memory window.
2449 Default size is 2 megabytes.
2450 realloc= Enable/disable reallocating PCI bridge resources
2451 if allocations done by BIOS are too small to
2452 accommodate resources required by all child
2454 off: Turn realloc off
2456 realloc same as realloc=on
2457 noari do not use PCIe ARI.
2458 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2459 only look for one device below a PCIe downstream
2462 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2465 force Enable ASPM even on devices that claim not to support it.
2466 WARNING: Forcing ASPM on may cause system lockups.
2468 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2469 nomsi Do not use MSI for PCI Express Native Hotplug (this
2470 makes all PCIe ports use INTx for hotplug services).
2472 pcie_ports= [PCIE] PCIe ports handling:
2473 auto Ask the BIOS whether or not to use native PCIe services
2474 associated with PCIe ports (PME, hot-plug, AER). Use
2475 them only if that is allowed by the BIOS.
2476 native Use native PCIe services associated with PCIe ports
2478 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2481 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2482 nomsi Do not use MSI for native PCIe PME signaling (this makes
2483 all PCIe root ports use INTx for all services).
2485 pcmv= [HW,PCMCIA] BadgePAD 4
2488 See Documentation/blockdev/paride.txt.
2490 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2493 See arch/parisc/kernel/pdc_chassis.c
2495 percpu_alloc= Select which percpu first chunk allocator to use.
2496 Currently supported values are "embed" and "page".
2497 Archs may support subset or none of the selections.
2498 See comments in mm/percpu.c for details on each
2499 allocator. This parameter is primarily for debugging
2500 and performance comparison.
2503 See Documentation/blockdev/paride.txt.
2506 See Documentation/blockdev/paride.txt.
2508 pirq= [SMP,APIC] Manual mp-table setup
2509 See Documentation/x86/i386/IO-APIC.txt.
2511 plip= [PPT,NET] Parallel port network link
2512 Format: { parport<nr> | timid | 0 }
2513 See also Documentation/parport.txt.
2515 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2516 Override pmtimer IOPort with a hex value.
2520 Enable PNP debug messages (depends on the
2521 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2522 via /sys/module/pnp/parameters/debug. We always show
2523 current resource usage; turning this on also shows
2524 possible settings and some assignment information.
2530 { on | off | curr | res | no-curr | no-res }
2533 [ISAPNP] Exclude IRQs for the autoconfiguration
2536 [ISAPNP] Exclude DMAs for the autoconfiguration
2538 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2539 Ranges are in pairs (I/O port base and size).
2542 [ISAPNP] Exclude memory regions for the
2544 Ranges are in pairs (memory base and size).
2546 ports= [IP_VS_FTP] IPVS ftp helper module
2548 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2550 Format: <port>,<port>....
2552 print-fatal-signals=
2553 [KNL] debug: print fatal signals
2555 If enabled, warn about various signal handling
2556 related application anomalies: too many signals,
2557 too many POSIX.1 timers, fatal signals causing a
2560 If you hit the warning due to signal overflow,
2561 you might want to try "ulimit -i unlimited".
2565 printk.always_kmsg_dump=
2566 Trigger kmsg_dump for cases other than kernel oops or
2568 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2571 printk.time= Show timing data prefixed to each printk message line
2572 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2574 processor.max_cstate= [HW,ACPI]
2575 Limit processor to maximum C-state
2576 max_cstate=9 overrides any DMI blacklist limit.
2578 processor.nocst [HW,ACPI]
2579 Ignore the _CST method to determine C-states,
2580 instead using the legacy FADT method
2582 profile= [KNL] Enable kernel profiling via /proc/profile
2583 Format: [schedule,]<number>
2584 Param: "schedule" - profile schedule points.
2585 Param: <number> - step/bucket size as a power of 2 for
2586 statistical time based profiling.
2587 Param: "sleep" - profile D-state sleeping (millisecs).
2588 Requires CONFIG_SCHEDSTATS
2589 Param: "kvm" - profile VM exits.
2591 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2593 See Documentation/blockdev/ramdisk.txt.
2595 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2596 probe for; one of (bare|imps|exps|lifebook|any).
2597 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2599 psmouse.resetafter= [HW,MOUSE]
2600 Try to reset the device after so many bad packets
2603 [HW,MOUSE] Set desired mouse resolution, in dpi.
2604 psmouse.smartscroll=
2605 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2606 0 = disabled, 1 = enabled (default).
2608 pstore.backend= Specify the name of the pstore backend to use
2611 See Documentation/blockdev/paride.txt.
2614 [KNL] Number of legacy pty's. Overwrites compiled-in
2617 quiet [KNL] Disable most log messages
2622 See Documentation/md.txt.
2624 ramdisk_blocksize= [RAM]
2625 See Documentation/blockdev/ramdisk.txt.
2627 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2628 See Documentation/blockdev/ramdisk.txt.
2631 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2632 the specified list of CPUs to be no-callback CPUs.
2633 Invocation of these CPUs' RCU callbacks will
2634 be offloaded to "rcuox/N" kthreads created for
2635 that purpose, where "x" is "b" for RCU-bh, "p"
2636 for RCU-preempt, and "s" for RCU-sched, and "N"
2637 is the CPU number. This reduces OS jitter on the
2638 offloaded CPUs, which can be useful for HPC and
2639 real-time workloads. It can also improve energy
2640 efficiency for asymmetric multiprocessors.
2643 Rather than requiring that offloaded CPUs
2644 (specified by rcu_nocbs= above) explicitly
2645 awaken the corresponding "rcuoN" kthreads,
2646 make these kthreads poll for callbacks.
2647 This improves the real-time response for the
2648 offloaded CPUs by relieving them of the need to
2649 wake up the corresponding kthread, but degrades
2650 energy efficiency by requiring that the kthreads
2651 periodically wake up to do the polling.
2653 rcutree.blimit= [KNL]
2654 Set maximum number of finished RCU callbacks to
2655 process in one batch.
2657 rcutree.rcu_fanout_leaf= [KNL]
2658 Increase the number of CPUs assigned to each
2659 leaf rcu_node structure. Useful for very large
2662 rcutree.jiffies_till_first_fqs= [KNL]
2663 Set delay from grace-period initialization to
2664 first attempt to force quiescent states.
2665 Units are jiffies, minimum value is zero,
2666 and maximum value is HZ.
2668 rcutree.jiffies_till_next_fqs= [KNL]
2669 Set delay between subsequent attempts to force
2670 quiescent states. Units are jiffies, minimum
2671 value is one, and maximum value is HZ.
2673 rcutree.qhimark= [KNL]
2674 Set threshold of queued RCU callbacks beyond which
2675 batch limiting is disabled.
2677 rcutree.qlowmark= [KNL]
2678 Set threshold of queued RCU callbacks below which
2679 batch limiting is re-enabled.
2681 rcutree.rcu_idle_gp_delay= [KNL]
2682 Set wakeup interval for idle CPUs that have
2683 RCU callbacks (RCU_FAST_NO_HZ=y).
2685 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2686 Set wakeup interval for idle CPUs that have
2687 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2688 Lazy RCU callbacks are those which RCU can
2689 prove do nothing more than free memory.
2691 rcutorture.fqs_duration= [KNL]
2692 Set duration of force_quiescent_state bursts.
2694 rcutorture.fqs_holdoff= [KNL]
2695 Set holdoff time within force_quiescent_state bursts.
2697 rcutorture.fqs_stutter= [KNL]
2698 Set wait time between force_quiescent_state bursts.
2700 rcutorture.gp_exp= [KNL]
2701 Use expedited update-side primitives.
2703 rcutorture.gp_normal= [KNL]
2704 Use normal (non-expedited) update-side primitives.
2705 If both gp_exp and gp_normal are set, do both.
2706 If neither gp_exp nor gp_normal are set, still
2709 rcutorture.n_barrier_cbs= [KNL]
2710 Set callbacks/threads for rcu_barrier() testing.
2712 rcutorture.nfakewriters= [KNL]
2713 Set number of concurrent RCU writers. These just
2714 stress RCU, they don't participate in the actual
2715 test, hence the "fake".
2717 rcutorture.nreaders= [KNL]
2718 Set number of RCU readers.
2720 rcutorture.object_debug= [KNL]
2721 Enable debug-object double-call_rcu() testing.
2723 rcutorture.onoff_holdoff= [KNL]
2724 Set time (s) after boot for CPU-hotplug testing.
2726 rcutorture.onoff_interval= [KNL]
2727 Set time (s) between CPU-hotplug operations, or
2728 zero to disable CPU-hotplug testing.
2730 rcutorture.rcutorture_runnable= [BOOT]
2731 Start rcutorture running at boot time.
2733 rcutorture.shuffle_interval= [KNL]
2734 Set task-shuffle interval (s). Shuffling tasks
2735 allows some CPUs to go into dyntick-idle mode
2736 during the rcutorture test.
2738 rcutorture.shutdown_secs= [KNL]
2739 Set time (s) after boot system shutdown. This
2740 is useful for hands-off automated testing.
2742 rcutorture.stall_cpu= [KNL]
2743 Duration of CPU stall (s) to test RCU CPU stall
2744 warnings, zero to disable.
2746 rcutorture.stall_cpu_holdoff= [KNL]
2747 Time to wait (s) after boot before inducing stall.
2749 rcutorture.stat_interval= [KNL]
2750 Time (s) between statistics printk()s.
2752 rcutorture.stutter= [KNL]
2753 Time (s) to stutter testing, for example, specifying
2754 five seconds causes the test to run for five seconds,
2755 wait for five seconds, and so on. This tests RCU's
2756 ability to transition abruptly to and from idle.
2758 rcutorture.test_boost= [KNL]
2759 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2760 "Maybe" means test if the RCU implementation
2761 under test support RCU priority boosting.
2763 rcutorture.test_boost_duration= [KNL]
2764 Duration (s) of each individual boost test.
2766 rcutorture.test_boost_interval= [KNL]
2767 Interval (s) between each boost test.
2769 rcutorture.test_no_idle_hz= [KNL]
2770 Test RCU's dyntick-idle handling. See also the
2771 rcutorture.shuffle_interval parameter.
2773 rcutorture.torture_type= [KNL]
2774 Specify the RCU implementation to test.
2776 rcutorture.verbose= [KNL]
2777 Enable additional printk() statements.
2779 rcupdate.rcu_expedited= [KNL]
2780 Use expedited grace-period primitives, for
2781 example, synchronize_rcu_expedited() instead
2782 of synchronize_rcu(). This reduces latency,
2783 but can increase CPU utilization, degrade
2784 real-time latency, and degrade energy efficiency.
2786 rcupdate.rcu_cpu_stall_suppress= [KNL]
2787 Suppress RCU CPU stall warning messages.
2789 rcupdate.rcu_cpu_stall_timeout= [KNL]
2790 Set timeout for RCU CPU stall warning messages.
2794 Run specified binary instead of /init from the ramdisk,
2795 used for early userspace startup. See initrd.
2798 Format (x86 or x86_64):
2799 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2801 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2803 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2804 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2805 reboot_force is either force or not specified,
2806 reboot_cpu is s[mp]#### with #### being the processor
2807 to be used for rebooting.
2810 [KNL, SMP] Set scheduler's default relax_domain_level.
2811 See Documentation/cgroups/cpusets.txt.
2813 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2815 reservetop= [X86-32]
2817 Reserves a hole at the top of the kernel virtual
2822 Set the amount of memory to reserve for BIOS at
2823 the bottom of the address space.
2825 reset_devices [KNL] Force drivers to reset the underlying device
2826 during initialization.
2829 Specify the partition device for software suspend
2831 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2833 resume_offset= [SWSUSP]
2834 Specify the offset from the beginning of the partition
2835 given by "resume=" at which the swap header is located,
2836 in <PAGE_SIZE> units (needed only for swap files).
2837 See Documentation/power/swsusp-and-swap-files.txt
2839 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2840 read the resume files
2842 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2843 Useful for devices that are detected asynchronously
2844 (e.g. USB and MMC devices).
2846 hibernate= [HIBERNATION]
2847 noresume Don't check if there's a hibernation image
2848 present during boot.
2849 nocompress Don't compress/decompress hibernation images.
2851 retain_initrd [RAM] Keep initrd memory after extraction
2853 rhash_entries= [KNL,NET]
2854 Set number of hash buckets for route cache
2856 riscom8= [HW,SERIAL]
2857 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2859 ro [KNL] Mount root device read-only on boot
2861 root= [KNL] Root filesystem
2862 See name_to_dev_t comment in init/do_mounts.c.
2864 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2865 mount the root filesystem
2867 rootflags= [KNL] Set root filesystem mount option string
2869 rootfstype= [KNL] Set root filesystem type
2871 rootwait [KNL] Wait (indefinitely) for root device to show up.
2872 Useful for devices that are detected asynchronously
2873 (e.g. USB and MMC devices).
2875 rproc_mem=nn[KMG][@address]
2876 [KNL,ARM,CMA] Remoteproc physical memory block.
2877 Memory area to be used by remote processor image,
2880 rw [KNL] Mount root device read-write on boot
2882 S [KNL] Run init in single mode
2885 See drivers/net/irda/sa1100_ir.c.
2887 sbni= [NET] Granch SBNI12 leased line adapter
2889 sched_debug [KNL] Enables verbose scheduler debug messages.
2891 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2892 xtime_lock contention on larger systems, and/or RCU lock
2893 contention on all systems with CONFIG_MAXSMP set.
2894 Format: { "0" | "1" }
2895 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2897 Note: increases power consumption, thus should only be
2898 enabled if running jitter sensitive (HPC/RT) workloads.
2900 security= [SECURITY] Choose a security module to enable at boot.
2901 If this boot parameter is not specified, only the first
2902 security module asking for security registration will be
2903 loaded. An invalid security module name will be treated
2904 as if no module has been chosen.
2906 selinux= [SELINUX] Disable or enable SELinux at boot time.
2907 Format: { "0" | "1" }
2908 See security/selinux/Kconfig help text.
2911 Default value is set via kernel config option.
2912 If enabled at boot time, /selinux/disable can be used
2913 later to disable prior to initial policy load.
2915 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2916 Format: { "0" | "1" }
2917 See security/apparmor/Kconfig help text
2920 Default value is set via kernel config option.
2922 serialnumber [BUGS=X86-32]
2925 Maximal number of shapers.
2927 show_msr= [x86] show boot-time MSR settings
2928 Format: { <integer> }
2929 Show boot-time (BIOS-initialized) MSR settings.
2930 The parameter means the number of CPUs to show,
2931 for example 1 means boot CPU only.
2938 slab_max_order= [MM, SLAB]
2939 Determines the maximum allowed order for slabs.
2940 A high setting may cause OOMs due to memory
2941 fragmentation. Defaults to 1 for systems with
2942 more than 32MB of RAM, 0 otherwise.
2944 slub_debug[=options[,slabs]] [MM, SLUB]
2945 Enabling slub_debug allows one to determine the
2946 culprit if slab objects become corrupted. Enabling
2947 slub_debug can create guard zones around objects and
2948 may poison objects when not in use. Also tracks the
2949 last alloc / free. For more information see
2950 Documentation/vm/slub.txt.
2952 slub_max_order= [MM, SLUB]
2953 Determines the maximum allowed order for slabs.
2954 A high setting may cause OOMs due to memory
2955 fragmentation. For more information see
2956 Documentation/vm/slub.txt.
2958 slub_min_objects= [MM, SLUB]
2959 The minimum number of objects per slab. SLUB will
2960 increase the slab order up to slub_max_order to
2961 generate a sufficiently large slab able to contain
2962 the number of objects indicated. The higher the number
2963 of objects the smaller the overhead of tracking slabs
2964 and the less frequently locks need to be acquired.
2965 For more information see Documentation/vm/slub.txt.
2967 slub_min_order= [MM, SLUB]
2968 Determines the minimum page order for slabs. Must be
2969 lower than slub_max_order.
2970 For more information see Documentation/vm/slub.txt.
2972 slub_nomerge [MM, SLUB]
2973 Disable merging of slabs with similar size. May be
2974 necessary if there is some reason to distinguish
2975 allocs to different slabs. Debug options disable
2976 merging on their own.
2977 For more information see Documentation/vm/slub.txt.
2980 Format: <io1>[,<io2>[,...,<io8>]]
2982 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2983 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2984 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2985 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2986 smsc-ircc2.ircc_irq= [HW] IRQ line
2987 smsc-ircc2.ircc_dma= [HW] DMA channel
2988 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2989 0: Toshiba Satellite 1800 (GP data pin select)
2990 1: Fast pin select (default)
2994 [KNL] Should the soft-lockup detector generate panics.
2997 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2998 See Documentation/laptops/sonypi.txt
3000 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3001 See Documentation/serial/specialix.txt.
3003 spia_io_base= [HW,MTD]
3009 Enabled the stack tracer on boot up.
3011 stacktrace_filter=[function-list]
3012 [FTRACE] Limit the functions that the stack tracer
3013 will trace at boot up. function-list is a comma separated
3014 list of functions. This list can be changed at run
3015 time by the stack_trace_filter file in the debugfs
3016 tracing directory. Note, this enables stack tracing
3017 and the stacktrace above is not needed.
3021 Set the STI (builtin display/keyboard on the HP-PARISC
3022 machines) console (graphic card) which should be used
3023 as the initial boot-console.
3024 See also comment in drivers/video/console/sticore.c.
3027 See comment in drivers/video/console/sticore.c.
3030 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3032 sunrpc.min_resvport=
3033 sunrpc.max_resvport=
3035 SunRPC servers often require that client requests
3036 originate from a privileged port (i.e. a port in the
3037 range 0 < portnr < 1024).
3038 An administrator who wishes to reserve some of these
3039 ports for other uses may adjust the range that the
3040 kernel's sunrpc client considers to be privileged
3041 using these two parameters to set the minimum and
3042 maximum port values.
3046 Control how the NFS server code allocates CPUs to
3047 service thread pools. Depending on how many NICs
3048 you have and where their interrupts are bound, this
3049 option will affect which CPUs will do NFS serving.
3050 Note: this parameter cannot be changed while the
3051 NFS server is running.
3053 auto the server chooses an appropriate mode
3054 automatically using heuristics
3055 global a single global pool contains all CPUs
3056 percpu one pool for each CPU
3057 pernode one pool for each NUMA node (equivalent
3058 to global on non-NUMA machines)
3060 sunrpc.tcp_slot_table_entries=
3061 sunrpc.udp_slot_table_entries=
3063 Sets the upper limit on the number of simultaneous
3064 RPC calls that can be sent from the client to a
3065 server. Increasing these values may allow you to
3066 improve throughput, but will also increase the
3067 amount of memory reserved for use by the client.
3070 [KNL] Enable accounting of swap in memory resource
3071 controller if no parameter or 1 is given or disable
3072 it if 0 is given (See Documentation/cgroups/memory.txt)
3074 swiotlb= [IA-64] Number of I/O TLB slabs
3078 sysfs.deprecated=0|1 [KNL]
3079 Enable/disable old style sysfs layout for old udev
3080 on older distributions. When this option is enabled
3081 very new udev will not work anymore. When this option
3082 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3083 in older udev will not work anymore.
3084 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3085 the kernel configuration.
3087 sysrq_always_enabled
3089 Ignore sysrq setting - this boot parameter will
3090 neutralize any effect of /proc/sys/kernel/sysrq.
3091 Useful for debugging.
3095 test_suspend= [SUSPEND]
3096 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3097 standby suspend) as the system sleep state to briefly
3098 enter during system startup. The system is woken from
3099 this state using a wakeup-capable RTC alarm.
3101 thash_entries= [KNL,NET]
3102 Set number of hash buckets for TCP connection
3104 thermal.act= [HW,ACPI]
3105 -1: disable all active trip points in all thermal zones
3106 <degrees C>: override all lowest active trip points
3108 thermal.crt= [HW,ACPI]
3109 -1: disable all critical trip points in all thermal zones
3110 <degrees C>: override all critical trip points
3112 thermal.nocrt= [HW,ACPI]
3113 Set to disable actions on ACPI thermal zone
3114 critical and hot trip points.
3116 thermal.off= [HW,ACPI]
3117 1: disable ACPI thermal control
3119 thermal.psv= [HW,ACPI]
3120 -1: disable all passive trip points
3121 <degrees C>: override all passive trip points to this
3124 thermal.tzp= [HW,ACPI]
3125 Specify global default ACPI thermal zone polling rate
3126 <deci-seconds>: poll all this frequency
3127 0: no polling (default)
3130 Force threading of all interrupt handlers except those
3131 marked explicitly IRQF_NO_THREAD.
3134 Enable the Transcendent memory driver if built-in.
3136 tmem.cleancache=0|1 [KNL, XEN]
3137 Default is on (1). Disable the usage of the cleancache
3138 API to send anonymous pages to the hypervisor.
3140 tmem.frontswap=0|1 [KNL, XEN]
3141 Default is on (1). Disable the usage of the frontswap
3142 API to send swap pages to the hypervisor. If disabled
3143 the selfballooning and selfshrinking are force disabled.
3145 tmem.selfballooning=0|1 [KNL, XEN]
3146 Default is on (1). Disable the driving of swap pages
3149 tmem.selfshrinking=0|1 [KNL, XEN]
3150 Default is on (1). Partial swapoff that immediately
3151 transfers pages from Xen hypervisor back to the
3152 kernel based on different criteria.
3156 Specify if the kernel should make use of the cpu
3157 topology information if the hardware supports this.
3158 The scheduler will make use of this information and
3159 e.g. base its process migration decisions on it.
3164 tpm_suspend_pcr=[HW,TPM]
3165 Format: integer pcr id
3166 Specify that at suspend time, the tpm driver
3167 should extend the specified pcr with zeros,
3168 as a workaround for some chips which fail to
3169 flush the last written pcr on TPM_SaveState.
3170 This will guarantee that all the other pcrs
3173 trace_buf_size=nn[KMG]
3174 [FTRACE] will set tracing buffer size.
3176 trace_event=[event-list]
3177 [FTRACE] Set and start specified trace events in order
3178 to facilitate early boot debugging.
3179 See also Documentation/trace/events.txt
3181 trace_options=[option-list]
3182 [FTRACE] Enable or disable tracer options at boot.
3183 The option-list is a comma delimited list of options
3184 that can be enabled or disabled just as if you were
3185 to echo the option name into
3187 /sys/kernel/debug/tracing/trace_options
3189 For example, to enable stacktrace option (to dump the
3190 stack trace of each event), add to the command line:
3192 trace_options=stacktrace
3194 See also Documentation/trace/ftrace.txt "trace options"
3198 [FTRACE] enable this option to disable tracing when a
3199 warning is hit. This turns off "tracing_on". Tracing can
3200 be enabled again by echoing '1' into the "tracing_on"
3201 file located in /sys/kernel/debug/tracing/
3203 This option is useful, as it disables the trace before
3204 the WARNING dump is called, which prevents the trace to
3205 be filled with content caused by the warning output.
3207 This option can also be set at run time via the sysctl
3208 option: kernel/traceoff_on_warning
3210 transparent_hugepage=
3212 Format: [always|madvise|never]
3213 Can be used to control the default behavior of the system
3214 with respect to transparent hugepages.
3215 See Documentation/vm/transhuge.txt for more details.
3217 tsc= Disable clocksource stability checks for TSC.
3219 [x86] reliable: mark tsc clocksource as reliable, this
3220 disables clocksource verification at runtime, as well
3221 as the stability checks done at bootup. Used to enable
3222 high-resolution timer mode on older hardware, and in
3223 virtualized environment.
3224 [x86] noirqtime: Do not use TSC to do irq accounting.
3225 Used to run time disable IRQ_TIME_ACCOUNTING on any
3226 platforms where RDTSC is slow and this accounting
3229 turbografx.map[2|3]= [HW,JOY]
3230 TurboGraFX parallel port interface
3232 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3233 See also Documentation/input/joystick-parport.txt
3235 udbg-immortal [PPC] When debugging early kernel crashes that
3236 happen after console_init() and before a proper
3237 console driver takes over, this boot options might
3238 help "seeing" what's going on.
3240 uhash_entries= [KNL,NET]
3241 Set number of hash buckets for UDP/UDP-Lite connections
3244 [USB] Ignore overcurrent events (default N).
3245 Some badly-designed motherboards generate lots of
3246 bogus events, for ports that aren't wired to
3247 anything. Set this parameter to avoid log spamming.
3248 Note that genuine overcurrent events won't be
3252 [X86] Cause panic on unknown NMI.
3254 usbcore.authorized_default=
3255 [USB] Default USB device authorization:
3256 (default -1 = authorized except for wireless USB,
3257 0 = not authorized, 1 = authorized)
3259 usbcore.autosuspend=
3260 [USB] The autosuspend time delay (in seconds) used
3261 for newly-detected USB devices (default 2). This
3262 is the time required before an idle device will be
3263 autosuspended. Devices for which the delay is set
3264 to a negative value won't be autosuspended at all.
3266 usbcore.usbfs_snoop=
3267 [USB] Set to log all usbfs traffic (default 0 = off).
3269 usbcore.blinkenlights=
3270 [USB] Set to cycle leds on hubs (default 0 = off).
3272 usbcore.old_scheme_first=
3273 [USB] Start with the old device initialization
3274 scheme (default 0 = off).
3276 usbcore.usbfs_memory_mb=
3277 [USB] Memory limit (in MB) for buffers allocated by
3278 usbfs (default = 16, 0 = max = 2047).
3280 usbcore.use_both_schemes=
3281 [USB] Try the other device initialization scheme
3282 if the first one fails (default 1 = enabled).
3284 usbcore.initial_descriptor_timeout=
3285 [USB] Specifies timeout for the initial 64-byte
3286 USB_REQ_GET_DESCRIPTOR request in milliseconds
3287 (default 5000 = 5.0 seconds).
3290 [USBHID] The interval which mice are to be polled at.
3292 usb-storage.delay_use=
3293 [UMS] The delay in seconds before a new device is
3294 scanned for Logical Units (default 5).
3297 [UMS] A list of quirks entries to supplement or
3298 override the built-in unusual_devs list. List
3299 entries are separated by commas. Each entry has
3300 the form VID:PID:Flags where VID and PID are Vendor
3301 and Product ID values (4-digit hex numbers) and
3302 Flags is a set of characters, each corresponding
3303 to a common usb-storage quirk flag as follows:
3304 a = SANE_SENSE (collect more than 18 bytes
3306 b = BAD_SENSE (don't collect more than 18
3307 bytes of sense data);
3308 c = FIX_CAPACITY (decrease the reported
3309 device capacity by one sector);
3310 d = NO_READ_DISC_INFO (don't use
3311 READ_DISC_INFO command);
3312 e = NO_READ_CAPACITY_16 (don't use
3313 READ_CAPACITY_16 command);
3314 h = CAPACITY_HEURISTICS (decrease the
3315 reported device capacity by one
3316 sector if the number is odd);
3317 i = IGNORE_DEVICE (don't bind to this
3319 l = NOT_LOCKABLE (don't try to lock and
3320 unlock ejectable media);
3321 m = MAX_SECTORS_64 (don't transfer more
3322 than 64 sectors = 32 KB at a time);
3323 n = INITIAL_READ10 (force a retry of the
3324 initial READ(10) command);
3325 o = CAPACITY_OK (accept the capacity
3326 reported by the device);
3327 p = WRITE_CACHE (the device cache is ON
3329 r = IGNORE_RESIDUE (the device reports
3330 bogus residue values);
3331 s = SINGLE_LUN (the device has only one
3333 w = NO_WP_DETECT (don't test whether the
3334 medium is write-protected).
3335 Example: quirks=0419:aaf5:rl,0421:0433:rc
3337 user_debug= [KNL,ARM]
3339 See arch/arm/Kconfig.debug help text.
3340 1 - undefined instruction events
3342 4 - invalid data aborts
3345 Example: user_debug=31
3348 [X86] Flags controlling user PTE allocations.
3350 nohigh = do not allocate PTE pages in
3351 HIGHMEM regardless of setting
3355 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3356 vdso=1: enable VDSO (default)
3357 vdso=0: disable VDSO mapping
3360 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3361 vdso32=1: enable 32-bit VDSO (default)
3362 vdso32=0: disable 32-bit VDSO mapping
3365 vector=percpu: enable percpu vector domain
3367 video= [FB] Frame buffer configuration
3368 See Documentation/fb/modedb.txt.
3370 video.brightness_switch_enabled= [0,1]
3371 If set to 1, on receiving an ACPI notify event
3372 generated by hotkey, video driver will adjust brightness
3373 level and then send out the event to user space through
3374 the allocated input device; If set to 0, video driver
3375 will only send out the event without touching backlight
3380 [VMMIO] Memory mapped virtio (platform) device.
3382 <size>@<baseaddr>:<irq>[:<id>]
3384 <size> := size (can use standard suffixes
3386 <baseaddr> := physical base address
3387 <irq> := interrupt number (as passed to
3389 <id> := (optional) platform device id
3391 virtio_mmio.device=1K@0x100b0000:48:7
3393 Can be used multiple times for multiple devices.
3395 vga= [BOOT,X86-32] Select a particular video mode
3396 See Documentation/x86/boot.txt and
3397 Documentation/svga.txt.
3398 Use vga=ask for menu.
3399 This is actually a boot loader parameter; the value is
3400 passed to the kernel using a special protocol.
3402 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3403 size of <nn>. This can be used to increase the
3404 minimum size (128MB on x86). It can also be used to
3405 decrease the size and leave more room for directly
3408 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3411 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3414 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3418 Controls the behavior of vsyscalls (i.e. calls to
3419 fixed addresses of 0xffffffffff600x00 from legacy
3420 code). Most statically-linked binaries and older
3421 versions of glibc use these calls. Because these
3422 functions are at fixed addresses, they make nice
3423 targets for exploits that can control RIP.
3425 emulate [default] Vsyscalls turn into traps and are
3426 emulated reasonably safely.
3428 native Vsyscalls are native syscall instructions.
3429 This is a little bit faster than trapping
3430 and makes a few dynamic recompilers work
3431 better than they would in emulation mode.
3432 It also makes exploits much easier to write.
3434 none Vsyscalls don't work at all. This makes
3435 them quite hard to use for exploits but
3436 might break your system.
3438 vt.color= [VT] Default text color.
3439 Format: 0xYX, X = foreground, Y = background.
3440 Default: 0x07 = light gray on black.
3442 vt.cur_default= [VT] Default cursor shape.
3443 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3444 the parameters of the <Esc>[?A;B;Cc escape sequence;
3445 see VGA-softcursor.txt. Default: 2 = underline.
3447 vt.default_blu= [VT]
3448 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3449 Change the default blue palette of the console.
3450 This is a 16-member array composed of values
3453 vt.default_grn= [VT]
3454 Format: <green0>,<green1>,<green2>,...,<green15>
3455 Change the default green palette of the console.
3456 This is a 16-member array composed of values
3459 vt.default_red= [VT]
3460 Format: <red0>,<red1>,<red2>,...,<red15>
3461 Change the default red palette of the console.
3462 This is a 16-member array composed of values
3468 Set system-wide default UTF-8 mode for all tty's.
3469 Default is 1, i.e. UTF-8 mode is enabled for all
3470 newly opened terminals.
3472 vt.global_cursor_default=
3475 Set system-wide default for whether a cursor
3476 is shown on new VTs. Default is -1,
3477 i.e. cursors will be created by default unless
3478 overridden by individual drivers. 0 will hide
3479 cursors, 1 will display them.
3481 vt.italic= [VT] Default color for italic text; 0-15.
3484 vt.underline= [VT] Default color for underlined text; 0-15.
3487 watchdog timers [HW,WDT] For information on watchdog timers,
3488 see Documentation/watchdog/watchdog-parameters.txt
3489 or other driver-specific files in the
3490 Documentation/watchdog/ directory.
3492 workqueue.disable_numa
3493 By default, all work items queued to unbound
3494 workqueues are affine to the NUMA nodes they're
3495 issued on, which results in better behavior in
3496 general. If NUMA affinity needs to be disabled for
3497 whatever reason, this option can be used. Note
3498 that this also can be controlled per-workqueue for
3499 workqueues visible under /sys/bus/workqueue/.
3501 workqueue.power_efficient
3502 Per-cpu workqueues are generally preferred because
3503 they show better performance thanks to cache
3504 locality; unfortunately, per-cpu workqueues tend to
3505 be more power hungry than unbound workqueues.
3507 Enabling this makes the per-cpu workqueues which
3508 were observed to contribute significantly to power
3509 consumption unbound, leading to measurably lower
3510 power usage at the cost of small performance
3513 The default value of this parameter is determined by
3514 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3516 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3517 default x2apic cluster mode on platforms
3520 x86_intel_mid_timer= [X86-32,APBT]
3521 Choose timer option for x86 Intel MID platform.
3522 Two valid options are apbt timer only and lapic timer
3523 plus one apbt timer for broadcast timer.
3524 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3526 xen_emul_unplug= [HW,X86,XEN]
3527 Unplug Xen emulated devices
3528 Format: [unplug0,][unplug1]
3529 ide-disks -- unplug primary master IDE devices
3530 aux-ide-disks -- unplug non-primary-master IDE devices
3531 nics -- unplug network devices
3532 all -- unplug all emulated devices (NICs and IDE disks)
3533 unnecessary -- unplugging emulated devices is
3534 unnecessary even if the host did not respond to
3536 never -- do not unplug even if version check succeeds
3538 xen_nopvspin [X86,XEN]
3539 Disables the ticketlock slowpath using Xen PV
3542 xirc2ps_cs= [NET,PCMCIA]
3544 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3546 ______________________________________________________________________
3550 Add more DRM drivers.