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 edac_report= [HW,EDAC] Control how to report EDAC event
894 Format: {"on" | "off" | "force"}
895 on: enable EDAC to report H/W event. May be overridden
896 by other higher priority error reporting module.
897 off: disable H/W event reporting through EDAC.
898 force: enforce the use of EDAC to report H/W event.
901 ekgdboc= [X86,KGDB] Allow early kernel console debugging
904 This is designed to be used in conjunction with
905 the boot argument: earlyprintk=vga
908 Format: {"off" | "on" | "skip[mbr]"}
911 Format: { "old_map" }
912 old_map [X86-64]: switch to the old ioremap-based EFI
913 runtime services mapping. 32-bit still uses this one by
916 efi_no_storage_paranoia [EFI; X86]
917 Using this parameter you can use more than 50% of
918 your efi variable storage. Use this parameter only if
919 you are really sure that your UEFI does sane gc and
920 fulfills the spec otherwise your board may brick.
922 eisa_irq_edge= [PARISC,HW]
923 See header of drivers/parisc/eisa.c.
926 See comment before function elanfreq_setup() in
927 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
930 Format: {"cfq" | "deadline" | "noop"}
931 See Documentation/block/cfq-iosched.txt and
932 Documentation/block/deadline-iosched.txt for details.
934 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
935 Specifies physical address of start of kernel core
936 image elf header and optionally the size. Generally
937 kexec loader will pass this option to capture kernel.
938 See Documentation/kdump/kdump.txt for details.
940 enable_mtrr_cleanup [X86]
941 The kernel tries to adjust MTRR layout from continuous
942 to discrete, to make X server driver able to add WB
943 entry later. This parameter enables that.
945 enable_timer_pin_1 [X86]
946 Enable PIN 1 of APIC timer
947 Can be useful to work around chipset bugs
948 (in particular on some ATI chipsets).
949 The kernel tries to set a reasonable default.
951 enforcing [SELINUX] Set initial enforcing status.
953 See security/selinux/Kconfig help text.
954 0 -- permissive (log only, no denials).
955 1 -- enforcing (deny and log).
957 Value can be changed at runtime via /selinux/enforce.
960 Disable Error Record Serialization Table (ERST)
963 ether= [HW,NET] Ethernet cards parameters
964 This option is obsoleted by the "netdev=" option, which
965 has equivalent usage. See its documentation for details.
969 Permit 'security.evm' to be updated regardless of
970 current integrity status.
974 fail_make_request=[KNL]
975 General fault injection mechanism.
976 Format: <interval>,<probability>,<space>,<times>
977 See also Documentation/fault-injection/.
980 See Documentation/blockdev/floppy.txt.
982 force_pal_cache_flush
983 [IA-64] Avoid check_sal_cache_flush which may hang on
984 buggy SAL_CACHE_FLUSH implementations. Using this
985 parameter will force ia64_sal_cache_flush to call
986 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
989 [FTRACE] will set and start the specified tracer
990 as early as possible in order to facilitate early
993 ftrace_dump_on_oops[=orig_cpu]
994 [FTRACE] will dump the trace buffers on oops.
995 If no parameter is passed, ftrace will dump
996 buffers of all CPUs, but if you pass orig_cpu, it will
997 dump only the buffer of the CPU that triggered the
1000 ftrace_filter=[function-list]
1001 [FTRACE] Limit the functions traced by the function
1002 tracer at boot up. function-list is a comma separated
1003 list of functions. This list can be changed at run
1004 time by the set_ftrace_filter file in the debugfs
1007 ftrace_notrace=[function-list]
1008 [FTRACE] Do not trace the functions specified in
1009 function-list. This list can be changed at run time
1010 by the set_ftrace_notrace file in the debugfs
1013 ftrace_graph_filter=[function-list]
1014 [FTRACE] Limit the top level callers functions traced
1015 by the function graph tracer at boot up.
1016 function-list is a comma separated list of functions
1017 that can be changed at run time by the
1018 set_graph_function file in the debugfs tracing directory.
1021 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1022 support via parallel port (up to 5 devices per port)
1023 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1024 See also Documentation/input/joystick-parport.txt
1028 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1032 gcov_persist= [GCOV] When non-zero (default), profiling data for
1033 kernel modules is saved and remains accessible via
1034 debugfs, even when the module is unloaded/reloaded.
1035 When zero, profiling data is discarded and associated
1036 debugfs files are removed at module unload time.
1038 gpt [EFI] Forces disk with valid GPT signature but
1039 invalid Protective MBR to be treated as GPT.
1041 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1042 the "Enable 0" bit of the configuration register.
1045 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1046 the "Enable 0" bit of the configuration register.
1049 grcan.select= [HW] Select which physical interface to use.
1052 grcan.txsize= [HW] Sets the size of the tx buffer.
1053 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1055 grcan.rxsize= [HW] Sets the size of the rx buffer.
1056 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1059 hashdist= [KNL,NUMA] Large hashes allocated during boot
1060 are distributed across NUMA nodes. Defaults on
1061 for 64-bit NUMA, off otherwise.
1062 Format: 0 | 1 (for off | on)
1064 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1066 hd= [EIDE] (E)IDE hard drive subsystem geometry
1067 Format: <cyl>,<head>,<sect>
1070 Disable Hardware Error Source Table (HEST) support;
1071 corresponding firmware-first mode error processing
1072 logic will be disabled.
1074 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1075 size of <nn>. This works even on boxes that have no
1076 highmem otherwise. This also works to reduce highmem
1077 size on bigger boxes.
1079 highres= [KNL] Enable/disable high resolution timer mode.
1080 Valid parameters: "on", "off"
1084 See Documentation/isdn/README.HiSax.
1088 hpet= [X86-32,HPET] option to control HPET usage
1089 Format: { enable (default) | disable | force |
1091 disable: disable HPET and use PIT instead
1092 force: allow force enabled of undocumented chips (ICH4,
1094 verbose: show contents of HPET registers during setup
1096 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1097 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1099 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1100 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1101 On x86-64 and powerpc, this option can be specified
1102 multiple times interleaved with hugepages= to reserve
1103 huge pages of different sizes. Valid pages sizes on
1104 x86-64 are 2M (when the CPU supports "pse") and 1G
1105 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1106 Note that 1GB pages can only be allocated at boot time
1107 using hugepages= and not freed afterwards.
1109 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1110 terminal devices. Valid values: 0..8
1111 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1112 If specified, z/VM IUCV HVC accepts connections
1113 from listed z/VM user IDs only.
1115 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1116 hardware thread id mappings.
1117 Format: <cpu>:<hwthread>
1120 Do not unregister boot console at start. This is only
1121 useful for debugging when something happens in the window
1122 between unregistering the boot console and initializing
1125 i2c_bus= [HW] Override the default board specific I2C bus speed
1126 or register an additional I2C bus that is not
1127 registered from board initialization code.
1131 i8042.debug [HW] Toggle i8042 debug mode
1132 i8042.direct [HW] Put keyboard port into non-translated mode
1133 i8042.dumbkbd [HW] Pretend that controller can only read data from
1134 keyboard and cannot control its state
1135 (Don't attempt to blink the leds)
1136 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1137 i8042.nokbd [HW] Don't check/create keyboard port
1138 i8042.noloop [HW] Disable the AUX Loopback command while probing
1140 i8042.nomux [HW] Don't check presence of an active multiplexing
1142 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1144 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1145 i8042.reset [HW] Reset the controller during init and cleanup
1146 i8042.unlock [HW] Unlock (ignore) the keylock
1150 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1151 indicates that the driver is running on unsupported
1153 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1154 does not match list of supported models.
1156 [HW] Report power status in /proc/i8k
1157 (disabled by default)
1158 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1161 i915.invert_brightness=
1162 [DRM] Invert the sense of the variable that is used to
1163 set the brightness of the panel backlight. Normally a
1164 brightness value of 0 indicates backlight switched off,
1165 and the maximum of the brightness value sets the backlight
1166 to maximum brightness. If this parameter is set to 0
1167 (default) and the machine requires it, or this parameter
1168 is set to 1, a brightness value of 0 sets the backlight
1169 to maximum brightness, and the maximum of the brightness
1170 value switches the backlight off.
1171 -1 -- never invert brightness
1172 0 -- machine default
1173 1 -- force brightness inversion
1176 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1178 ide-core.nodma= [HW] (E)IDE subsystem
1179 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1180 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1181 .cdrom .chs .ignore_cable are additional options
1182 See Documentation/ide/ide.txt.
1184 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1185 Claim all unknown PCI IDE storage controllers.
1188 Format: idle=poll, idle=halt, idle=nomwait
1189 Poll forces a polling idle loop that can slightly
1190 improve the performance of waking up a idle CPU, but
1191 will use a lot of power and make the system run hot.
1193 idle=halt: Halt is forced to be used for CPU idle.
1194 In such case C2/C3 won't be used again.
1195 idle=nomwait: Disable mwait for CPU C-states
1197 ignore_loglevel [KNL]
1198 Ignore loglevel setting - this will print /all/
1199 kernel messages to the console. Useful for debugging.
1200 We also add it as printk module parameter, so users
1201 could change it dynamically, usually by
1202 /sys/module/printk/parameters/ignore_loglevel.
1204 ihash_entries= [KNL]
1205 Set number of hash buckets for inode cache.
1207 ima_appraise= [IMA] appraise integrity measurements
1208 Format: { "off" | "enforce" | "fix" }
1211 ima_appraise_tcb [IMA]
1212 The builtin appraise policy appraises all files
1216 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1220 The list of supported hash algorithms is defined
1221 in crypto/hash_info.h.
1224 Load a policy which meets the needs of the Trusted
1225 Computing Base. This means IMA will measure all
1226 programs exec'd, files mmap'd for exec, and all files
1227 opened for read by uid=0.
1230 Select one of defined IMA measurements template formats.
1231 Formats: { "ima" | "ima-ng" }
1236 Run specified binary instead of /sbin/init as init
1239 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1240 for working out where the kernel is dying during
1243 initrd= [BOOT] Specify the location of the initial ramdisk
1245 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1248 int_pln_enable [x86] Enable power limit notification interrupt
1250 integrity_audit=[IMA]
1251 Format: { "0" | "1" }
1252 0 -- basic integrity auditing messages. (Default)
1253 1 -- additional integrity auditing messages.
1255 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1257 Enable intel iommu driver.
1259 Disable intel iommu driver.
1260 igfx_off [Default Off]
1261 By default, gfx is mapped as normal device. If a gfx
1262 device has a dedicated DMAR unit, the DMAR unit is
1263 bypassed by not enabling DMAR with this option. In
1264 this case, gfx device will use physical address for
1267 With this option iommu will not optimize to look
1268 for io virtual address below 32-bit forcing dual
1269 address cycle on pci bus for cards supporting greater
1270 than 32-bit addressing. The default is to look
1271 for translation below 32-bit and if not available
1272 then look in the higher range.
1273 strict [Default Off]
1274 With this option on every unmap_single operation will
1275 result in a hardware IOTLB flush operation as opposed
1276 to batching them for performance.
1277 sp_off [Default Off]
1278 By default, super page will be supported if Intel IOMMU
1279 has the capability. With this option, super page will
1282 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1283 0 disables intel_idle and fall back on acpi_idle.
1284 1 to 6 specify maximum depth of C-state.
1288 Do not enable intel_pstate as the default
1289 scaling driver for the supported processors
1291 intremap= [X86-64, Intel-IOMMU]
1292 on enable Interrupt Remapping (default)
1293 off disable Interrupt Remapping
1294 nosid disable Source ID checking
1296 BIOS x2APIC opt-out request will be ignored
1298 iomem= Disable strict checking of access to MMIO memory
1299 strict regions from userspace.
1316 io7= [HW] IO7 for Marvel based alpha systems
1317 See comment before marvel_specify_io7 in
1318 arch/alpha/kernel/core_marvel.c.
1320 io_delay= [X86] I/O delay method
1322 Standard port 0x80 based delay
1324 Alternate port 0xed based delay (needed on some systems)
1326 Simple two microseconds delay
1331 See Documentation/filesystems/nfs/nfsroot.txt.
1333 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1334 See comment before ip2_setup() in
1335 drivers/char/ip2/ip2base.c.
1338 When an interrupt is not handled search all handlers
1339 for it. Intended to get systems with badly broken
1343 When an interrupt is not handled search all handlers
1344 for it. Also check all handlers each timer
1345 interrupt. Intended to get systems with badly broken
1349 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1351 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1353 <cpu number>,...,<cpu number>
1355 <cpu number>-<cpu number>
1356 (must be a positive range in ascending order)
1358 <cpu number>,...,<cpu number>-<cpu number>
1360 This option can be used to specify one or more CPUs
1361 to isolate from the general SMP balancing and scheduling
1362 algorithms. You can move a process onto or off an
1363 "isolated" CPU via the CPU affinity syscalls or cpuset.
1364 <cpu number> begins at 0 and the maximum value is
1365 "number of CPUs in system - 1".
1367 This option is the preferred way to isolate CPUs. The
1368 alternative -- manually setting the CPU mask of all
1369 tasks in the system -- can cause problems and
1370 suboptimal load balancer performance.
1374 ivrs_ioapic [HW,X86_64]
1375 Provide an override to the IOAPIC-ID<->DEVICE-ID
1376 mapping provided in the IVRS ACPI table. For
1377 example, to map IOAPIC-ID decimal 10 to
1378 PCI device 00:14.0 write the parameter as:
1379 ivrs_ioapic[10]=00:14.0
1381 ivrs_hpet [HW,X86_64]
1382 Provide an override to the HPET-ID<->DEVICE-ID
1383 mapping provided in the IVRS ACPI table. For
1384 example, to map HPET-ID decimal 0 to
1385 PCI device 00:14.0 write the parameter as:
1386 ivrs_hpet[0]=00:14.0
1388 js= [HW,JOY] Analog joystick
1389 See Documentation/input/joystick.txt.
1393 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1394 specifies the amount of memory usable by the kernel
1395 for non-movable allocations. The requested amount is
1396 spread evenly throughout all nodes in the system. The
1397 remaining memory in each node is used for Movable
1398 pages. In the event, a node is too small to have both
1399 kernelcore and Movable pages, kernelcore pages will
1400 take priority and other nodes will have a larger number
1401 of Movable pages. The Movable zone is used for the
1402 allocation of pages that may be reclaimed or moved
1403 by the page migration subsystem. This means that
1404 HugeTLB pages may not be allocated from this zone.
1405 Note that allocations like PTEs-from-HighMem still
1406 use the HighMem zone if it exists, and the Normal
1407 zone if it does not.
1409 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1410 Format: <Controller#>[,poll interval]
1411 The controller # is the number of the ehci usb debug
1412 port as it is probed via PCI. The poll interval is
1413 optional and is the number seconds in between
1414 each poll cycle to the debug port in case you need
1415 the functionality for interrupting the kernel with
1416 gdb or control-c on the dbgp connection. When
1417 not using this parameter you use sysrq-g to break into
1418 the kernel debugger.
1420 kgdboc= [KGDB,HW] kgdb over consoles.
1421 Requires a tty driver that supports console polling,
1422 or a supported polling keyboard driver (non-usb).
1423 Serial only format: <serial_device>[,baud]
1424 keyboard only format: kbd
1425 keyboard and serial format: kbd,<serial_device>[,baud]
1426 Optional Kernel mode setting:
1427 kms, kbd format: kms,kbd
1428 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1430 kgdbwait [KGDB] Stop kernel execution and enter the
1431 kernel debugger at the earliest opportunity.
1433 kmac= [MIPS] korina ethernet MAC address.
1434 Configure the RouterBoard 532 series on-chip
1435 Ethernet adapter MAC address.
1437 kmemleak= [KNL] Boot-time kmemleak enable/disable
1438 Valid arguments: on, off
1441 kstack=N [X86] Print N words from the kernel stack
1444 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1445 Default is 0 (don't ignore, but inject #GP)
1447 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1451 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1452 Default is 1 (enabled)
1454 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1456 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1458 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1459 (virtualized MMU) support on capable Intel chips.
1460 Default is 1 (enabled)
1462 kvm-intel.emulate_invalid_guest_state=
1463 [KVM,Intel] Enable emulation of invalid guest states
1464 Default is 0 (disabled)
1466 kvm-intel.flexpriority=
1467 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1468 Default is 1 (enabled)
1471 [KVM,Intel] Enable VMX nesting (nVMX).
1472 Default is 0 (disabled)
1474 kvm-intel.unrestricted_guest=
1475 [KVM,Intel] Disable unrestricted guest feature
1476 (virtualized real and unpaged mode) on capable
1477 Intel chips. Default is 1 (enabled)
1479 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1480 feature (tagged TLBs) on capable Intel chips.
1481 Default is 1 (enabled)
1487 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1490 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1491 value for LAPIC timer one-shot implementation. Default
1492 back to the programmable timer unit in the LAPIC.
1494 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1497 libata.dma= [LIBATA] DMA control
1498 libata.dma=0 Disable all PATA and SATA DMA
1499 libata.dma=1 PATA and SATA Disk DMA only
1500 libata.dma=2 ATAPI (CDROM) DMA only
1501 libata.dma=4 Compact Flash DMA only
1502 Combinations also work, so libata.dma=3 enables DMA
1503 for disks and CDROMs, but not CFs.
1505 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1506 libata.ignore_hpa=0 keep BIOS limits (default)
1507 libata.ignore_hpa=1 ignore limits, using full disk
1509 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1513 libata.force= [LIBATA] Force configurations. The format is comma
1514 separated list of "[ID:]VAL" where ID is
1515 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1516 matching port, link or device. Basically, it matches
1517 the ATA ID string printed on console by libata. If
1518 the whole ID part is omitted, the last PORT and DEVICE
1519 values are used. If ID hasn't been specified yet, the
1520 configuration applies to all ports, links and devices.
1522 If only DEVICE is omitted, the parameter applies to
1523 the port and all links and devices behind it. DEVICE
1524 number of 0 either selects the first device or the
1525 first fan-out link behind PMP device. It does not
1526 select the host link. DEVICE number of 15 selects the
1527 host link and device attached to it.
1529 The VAL specifies the configuration to force. As long
1530 as there's no ambiguity shortcut notation is allowed.
1531 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1532 The following configurations can be forced.
1534 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1535 Any ID with matching PORT is used.
1537 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1539 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1540 udma[/][16,25,33,44,66,100,133] notation is also
1543 * [no]ncq: Turn on or off NCQ.
1545 * nohrst, nosrst, norst: suppress hard, soft
1548 * rstonce: only attempt one reset during
1549 hot-unplug link recovery
1551 * dump_id: dump IDENTIFY data.
1553 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1555 * disable: Disable this device.
1557 If there are multiple matching configurations changing
1558 the same attribute, the last one is used.
1560 memblock=debug [KNL] Enable memblock debug messages.
1562 load_ramdisk= [RAM] List of ramdisks to load from floppy
1563 See Documentation/blockdev/ramdisk.txt.
1565 lockd.nlm_grace_period=P [NFS] Assign grace period.
1568 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1571 lockd.nlm_timeout=T [NFS] Assign timeout value.
1574 lockd.nlm_udpport=M [NFS] Assign UDP port.
1577 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1580 loglevel= All Kernel Messages with a loglevel smaller than the
1581 console loglevel will be printed to the console. It can
1582 also be changed with klogd or other programs. The
1583 loglevels are defined as follows:
1585 0 (KERN_EMERG) system is unusable
1586 1 (KERN_ALERT) action must be taken immediately
1587 2 (KERN_CRIT) critical conditions
1588 3 (KERN_ERR) error conditions
1589 4 (KERN_WARNING) warning conditions
1590 5 (KERN_NOTICE) normal but significant condition
1591 6 (KERN_INFO) informational
1592 7 (KERN_DEBUG) debug-level messages
1594 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1595 in bytes. n must be a power of two. The default
1596 size is set in the kernel config file.
1598 logo.nologo [FB] Disables display of the built-in Linux logo.
1599 This may be used to provide more screen space for
1600 kernel log messages and is useful when debugging
1601 kernel boot problems.
1603 lp=0 [LP] Specify parallel ports to use, e.g,
1604 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1605 lp=reset first parallel port). 'lp=0' disables the
1606 lp=auto printer driver. 'lp=reset' (which can be
1607 specified in addition to the ports) causes
1608 attached printers to be reset. Using
1609 lp=port1,port2,... specifies the parallel ports
1610 to associate lp devices with, starting with
1611 lp0. A port specification may be 'none' to skip
1612 that lp device, or a parport name such as
1613 'parport0'. Specifying 'lp=auto' instead of a
1614 port specification list means that device IDs
1615 from each port should be examined, to see if
1616 an IEEE 1284-compliant printer is attached; if
1617 so, the driver will manage that printer.
1618 See also header of drivers/char/lp.c.
1621 Sets loops_per_jiffy to given constant, thus avoiding
1622 time-consuming boot-time autodetection (up to 250 ms per
1623 CPU). 0 enables autodetection (default). To determine
1624 the correct value for your kernel, boot with normal
1625 autodetection and see what value is printed. Note that
1626 on SMP systems the preset will be applied to all CPUs,
1627 which is likely to cause problems if your CPUs need
1628 significantly divergent settings. An incorrect value
1629 will cause delays in the kernel to be wrong, leading to
1630 unpredictable I/O errors and other breakage. Although
1631 unlikely, in the extreme case this might damage your
1635 Format: <io>,<irq>,<dma>
1637 machvec= [IA-64] Force the use of a particular machine-vector
1638 (machvec) in a generic kernel.
1639 Example: machvec=hpzx1_swiotlb
1641 machtype= [Loongson] Share the same kernel image file between different
1643 Example: machtype=lemote-yeeloong-2f-7inch
1645 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1646 than or equal to this physical address is ignored.
1648 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1649 should make use of. maxcpus=n : n >= 0 limits the
1650 kernel to using 'n' processors. n=0 is a special case,
1651 it is equivalent to "nosmp", which also disables
1654 max_loop= [LOOP] The number of loop block devices that get
1655 (loop.max_loop) unconditionally pre-created at init time. The default
1656 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1657 of statically allocating a predefined number, loop
1658 devices can be requested on-demand with the
1659 /dev/loop-control interface.
1661 mce [X86-32] Machine Check Exception
1663 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1665 md= [HW] RAID subsystems devices and level
1666 See Documentation/md.txt.
1669 Format: <first>,<last>
1670 Specifies range of consoles to be captured by the MDA.
1672 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1673 Amount of memory to be used when the kernel is not able
1674 to see the whole system memory or for test.
1675 [X86] Work as limiting max address. Use together
1676 with memmap= to avoid physical address space collisions.
1677 Without memmap= PCI devices could be placed at addresses
1678 belonging to unused RAM.
1680 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1684 [KNL,SH] Allow user to override the default size for
1685 per-device physically contiguous DMA buffers.
1687 memmap=exactmap [KNL,X86] Enable setting of an exact
1688 E820 memory map, as specified by the user.
1689 Such memmap=exactmap lines can be constructed based on
1690 BIOS output or other requirements. See the memmap=nn@ss
1693 memmap=nn[KMG]@ss[KMG]
1694 [KNL] Force usage of a specific region of memory
1695 Region of memory to be used, from ss to ss+nn.
1697 memmap=nn[KMG]#ss[KMG]
1698 [KNL,ACPI] Mark specific memory as ACPI data.
1699 Region of memory to be used, from ss to ss+nn.
1701 memmap=nn[KMG]$ss[KMG]
1702 [KNL,ACPI] Mark specific memory as reserved.
1703 Region of memory to be used, from ss to ss+nn.
1704 Example: Exclude memory from 0x18690000-0x1869ffff
1705 memmap=64K$0x18690000
1707 memmap=0x10000$0x18690000
1709 memory_corruption_check=0/1 [X86]
1710 Some BIOSes seem to corrupt the first 64k of
1711 memory when doing things like suspend/resume.
1712 Setting this option will scan the memory
1713 looking for corruption. Enabling this will
1714 both detect corruption and prevent the kernel
1715 from using the memory being corrupted.
1716 However, its intended as a diagnostic tool; if
1717 repeatable BIOS-originated corruption always
1718 affects the same memory, you can use memmap=
1719 to prevent the kernel from using that memory.
1721 memory_corruption_check_size=size [X86]
1722 By default it checks for corruption in the low
1723 64k, making this memory unavailable for normal
1724 use. Use this parameter to scan for
1725 corruption in more or less memory.
1727 memory_corruption_check_period=seconds [X86]
1728 By default it checks for corruption every 60
1729 seconds. Use this parameter to check at some
1730 other rate. 0 disables periodic checking.
1732 memtest= [KNL,X86] Enable memtest
1734 default : 0 <disable>
1735 Specifies the number of memtest passes to be
1736 performed. Each pass selects another test
1737 pattern from a given set of patterns. Memtest
1738 fills the memory with this pattern, validates
1739 memory contents and reserves bad memory
1740 regions that are detected.
1742 meye.*= [HW] Set MotionEye Camera parameters
1743 See Documentation/video4linux/meye.txt.
1745 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1746 Multi-Function General Purpose Timers on AMD Geode
1749 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1750 the BIOS has incorrectly applied a workaround. TinyBIOS
1751 version 0.98 is known to be affected, 0.99 fixes the
1752 problem by letting the user disable the workaround.
1756 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1757 physical address is ignored.
1759 mini2440= [ARM,HW,KNL]
1760 Format:[0..2][b][c][t]
1762 MINI2440 configuration specification:
1763 0 - The attached screen is the 3.5" TFT
1764 1 - The attached screen is the 7" TFT
1765 2 - The VGA Shield is attached (1024x768)
1766 Leaving out the screen size parameter will not load
1767 the TFT driver, and the framebuffer will be left
1769 b - Enable backlight. The TFT backlight pin will be
1770 linked to the kernel VESA blanking code and a GPIO
1771 LED. This parameter is not necessary when using the
1773 c - Enable the s3c camera interface.
1774 t - Reserved for enabling touchscreen support. The
1775 touchscreen support is not enabled in the mainstream
1776 kernel as of 2.6.30, a preliminary port can be found
1777 in the "bleeding edge" mini2440 support kernel at
1778 http://repo.or.cz/w/linux-2.6/mini2440.git
1781 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1782 parameter allows control of the logging verbosity for
1783 the additional memory initialisation checks. A value
1784 of 0 disables mminit logging and a level of 4 will
1785 log everything. Information is printed at KERN_DEBUG
1786 so loglevel=8 may also need to be specified.
1789 [KNL] When CONFIG_MODULE_SIG is set, this means that
1790 modules without (valid) signatures will fail to load.
1791 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1792 is always true, so this option does nothing.
1795 [MOUSE] Maximum time between finger touching and
1796 leaving touchpad surface for touch to be considered
1797 a tap and be reported as a left button click (for
1798 touchpads working in absolute mode only).
1800 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1801 reporting absolute coordinates, such as tablets
1802 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1803 reporting absolute coordinates, such as tablets
1805 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1806 is similar to kernelcore except it specifies the
1807 amount of memory used for migratable allocations.
1808 If both kernelcore and movablecore is specified,
1809 then kernelcore will be at *least* the specified
1810 value but may be more. If movablecore on its own
1811 is specified, the administrator must be careful
1812 that the amount of memory usable for all allocations
1815 movable_node [KNL,X86] Boot-time switch to enable the effects
1816 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1818 MTD_Partition= [MTD]
1819 Format: <name>,<region-number>,<size>,<offset>
1821 MTD_Region= [MTD] Format:
1822 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1825 See drivers/mtd/cmdlinepart.c.
1827 multitce=off [PPC] This parameter disables the use of the pSeries
1828 firmware feature for updating multiple TCE entries
1831 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1833 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1835 boundary - index of last SLC block on Flex-OneNAND.
1836 The remaining blocks are configured as MLC blocks.
1837 lock - Configure if Flex-OneNAND boundary should be locked.
1838 Once locked, the boundary cannot be changed.
1839 1 indicates lock status, 0 indicates unlock status.
1842 ARM/S3C2412 JIVE boot control
1844 See arch/arm/mach-s3c2412/mach-jive.c
1846 mtouchusb.raw_coordinates=
1847 [HW] Make the MicroTouch USB driver use raw coordinates
1848 ('y', default) or cooked coordinates ('n')
1850 mtrr_chunk_size=nn[KMG] [X86]
1851 used for mtrr cleanup. It is largest continuous chunk
1852 that could hold holes aka. UC entries.
1854 mtrr_gran_size=nn[KMG] [X86]
1855 Used for mtrr cleanup. It is granularity of mtrr block.
1857 Large value could prevent small alignment from
1860 mtrr_spare_reg_nr=n [X86]
1862 Range: 0,7 : spare reg number
1864 Used for mtrr cleanup. It is spare mtrr entries number.
1865 Set to 2 or more if your graphical card needs more.
1867 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1869 netdev= [NET] Network devices parameters
1870 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1871 Note that mem_start is often overloaded to mean
1872 something different and driver-specific.
1873 This usage is only documented in each driver source
1877 [NETFILTER] Enable connection tracking flow accounting
1878 0 to disable accounting
1879 1 to enable accounting
1882 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1883 See Documentation/filesystems/nfs/nfsroot.txt.
1885 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1886 See Documentation/filesystems/nfs/nfsroot.txt.
1888 nfsrootdebug [NFS] enable nfsroot debugging messages.
1889 See Documentation/filesystems/nfs/nfsroot.txt.
1891 nfs.callback_tcpport=
1892 [NFS] set the TCP port on which the NFSv4 callback
1893 channel should listen.
1896 [NFS] sets the pathname to the program which is used
1897 to update the NFS client cache entries.
1899 nfs.cache_getent_timeout=
1900 [NFS] sets the timeout after which an attempt to
1901 update a cache entry is deemed to have failed.
1903 nfs.idmap_cache_timeout=
1904 [NFS] set the maximum lifetime for idmapper cache
1908 [NFS] enable 64-bit inode numbers.
1909 If zero, the NFS client will fake up a 32-bit inode
1910 number for the readdir() and stat() syscalls instead
1911 of returning the full 64-bit number.
1912 The default is to return 64-bit inode numbers.
1914 nfs.max_session_slots=
1915 [NFSv4.1] Sets the maximum number of session slots
1916 the client will attempt to negotiate with the server.
1917 This limits the number of simultaneous RPC requests
1918 that the client can send to the NFSv4.1 server.
1919 Note that there is little point in setting this
1920 value higher than the max_tcp_slot_table_limit.
1922 nfs.nfs4_disable_idmapping=
1923 [NFSv4] When set to the default of '1', this option
1924 ensures that both the RPC level authentication
1925 scheme and the NFS level operations agree to use
1926 numeric uids/gids if the mount is using the
1927 'sec=sys' security flavour. In effect it is
1928 disabling idmapping, which can make migration from
1929 legacy NFSv2/v3 systems to NFSv4 easier.
1930 Servers that do not support this mode of operation
1931 will be autodetected by the client, and it will fall
1932 back to using the idmapper.
1933 To turn off this behaviour, set the value to '0'.
1935 [NFS4] Specify an additional fixed unique ident-
1936 ification string that NFSv4 clients can insert into
1937 their nfs_client_id4 string. This is typically a
1938 UUID that is generated at system install time.
1940 nfs.send_implementation_id =
1941 [NFSv4.1] Send client implementation identification
1942 information in exchange_id requests.
1943 If zero, no implementation identification information
1945 The default is to send the implementation identification
1948 nfs.recover_lost_locks =
1949 [NFSv4] Attempt to recover locks that were lost due
1950 to a lease timeout on the server. Please note that
1951 doing this risks data corruption, since there are
1952 no guarantees that the file will remain unchanged
1953 after the locks are lost.
1954 If you want to enable the kernel legacy behaviour of
1955 attempting to recover these locks, then set this
1957 The default parameter value of '0' causes the kernel
1958 not to attempt recovery of lost locks.
1960 nfsd.nfs4_disable_idmapping=
1961 [NFSv4] When set to the default of '1', the NFSv4
1962 server will return only numeric uids and gids to
1963 clients using auth_sys, and will accept numeric uids
1964 and gids from such clients. This is intended to ease
1965 migration from NFSv2/v3.
1967 objlayoutdriver.osd_login_prog=
1968 [NFS] [OBJLAYOUT] sets the pathname to the program which
1969 is used to automatically discover and login into new
1970 osd-targets. Please see:
1971 Documentation/filesystems/pnfs.txt for more explanations
1973 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1974 when a NMI is triggered.
1975 Format: [state][,regs][,debounce][,die]
1977 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1978 Format: [panic,][nopanic,][num]
1980 0 - turn nmi_watchdog off
1981 When panic is specified, panic when an NMI watchdog
1982 timeout occurs (or 'nopanic' to override the opposite
1984 This is useful when you use a panic=... timeout and
1985 need the box quickly up again.
1987 netpoll.carrier_timeout=
1988 [NET] Specifies amount of time (in seconds) that
1989 netpoll should wait for a carrier. By default netpoll
1992 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1993 emulation library even if a 387 maths coprocessor
1997 [HW] Never suspend the console
1998 Disable suspending of consoles during suspend and
1999 hibernate operations. Once disabled, debugging
2000 messages can reach various consoles while the rest
2001 of the system is being put to sleep (ie, while
2002 debugging driver suspend/resume hooks). This may
2003 not work reliably with all consoles, but is known
2004 to work with serial and VGA consoles.
2005 To facilitate more flexible debugging, we also add
2006 console_suspend, a printk module parameter to control
2007 it. Users could use console_suspend (usually
2008 /sys/module/printk/parameters/console_suspend) to
2009 turn on/off it dynamically.
2011 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2012 caches in the slab allocator. Saves per-node memory,
2013 but will impact performance.
2017 noapic [SMP,APIC] Tells the kernel to not make use of any
2018 IOAPICs that may be present in the system.
2021 Disable kernel base offset ASLR (Address Space
2022 Layout Randomization) if built into the kernel.
2024 noautogroup Disable scheduler automatic task group creation.
2026 nobats [PPC] Do not use BATs for mapping kernel lowmem
2027 on "Classic" PPC cores.
2031 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2033 nodelayacct [KNL] Disable per-task delay accounting
2035 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2037 nodsp [SH] Disable hardware DSP at boot time.
2039 noefi [X86] Disable EFI runtime services support.
2044 On X86-32 available only on PAE configured kernels.
2045 noexec=on: enable non-executable mappings (default)
2046 noexec=off: disable non-executable mappings
2049 Disable SMAP (Supervisor Mode Access Prevention)
2050 even if it is supported by processor.
2053 Disable SMEP (Supervisor Mode Execution Prevention)
2054 even if it is supported by processor.
2057 This affects only 32-bit executables.
2058 noexec32=on: enable non-executable mappings (default)
2059 read doesn't imply executable mappings
2060 noexec32=off: disable non-executable mappings
2061 read implies executable mappings
2063 nofpu [SH] Disable hardware FPU at boot time.
2065 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2066 register save and restore. The kernel will only save
2067 legacy floating-point registers on task switch.
2069 noxsave [BUGS=X86] Disables x86 extended register state save
2070 and restore using xsave. The kernel will fallback to
2071 enabling legacy floating-point and sse state.
2074 on enable eager fpu restore
2075 off disable eager fpu restore
2076 auto selects the default scheme, which automatically
2077 enables eagerfpu restore for xsaveopt.
2079 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2080 wfi(ARM) instruction doesn't work correctly and not to
2081 use it. This is also useful when using JTAG debugger.
2083 no_file_caps Tells the kernel not to honor file capabilities. The
2084 only way then for a file to be executed with privilege
2085 is to be setuid root or executed by root.
2087 nohalt [IA-64] Tells the kernel not to use the power saving
2088 function PAL_HALT_LIGHT when idle. This increases
2089 power-consumption. On the positive side, it reduces
2090 interrupt wake-up latency, which may improve performance
2091 in certain environments such as networked servers or
2094 nohz= [KNL] Boottime enable/disable dynamic ticks
2095 Valid arguments: on, off
2098 nohz_full= [KNL,BOOT]
2099 In kernels built with CONFIG_NO_HZ_FULL=y, set
2100 the specified list of CPUs whose tick will be stopped
2101 whenever possible. The boot CPU will be forced outside
2102 the range to maintain the timekeeping.
2103 The CPUs in this range must also be included in the
2106 noiotrap [SH] Disables trapped I/O port accesses.
2108 noirqdebug [X86-32] Disables the code which attempts to detect and
2109 disable unhandled interrupt sources.
2111 no_timer_check [X86,APIC] Disables the code which tests for
2112 broken timer IRQ sources.
2114 noisapnp [ISAPNP] Disables ISA PnP code.
2116 noinitrd [RAM] Tells the kernel not to load any configured
2119 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2121 [Deprecated - use intremap=off]
2125 nojitter [IA-64] Disables jitter checking for ITC timers.
2127 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2129 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2132 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2133 steal time is computed, but won't influence scheduler
2136 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2138 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2140 noltlbs [PPC] Do not use large page/tlb entries for kernel
2141 lowmem mapping on PPC40x.
2143 nomca [IA-64] Disable machine check abort handling
2145 nomce [X86-32] Machine Check Exception
2147 nomfgpt [X86-32] Disable Multi-Function General Purpose
2148 Timer usage (for AMD Geode machines).
2150 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2151 shutdown the other cpus. Instead use the REBOOT_VECTOR
2154 nomodule Disable module load
2156 nopat [X86] Disable PAT (page attribute table extension of
2157 pagetables) support.
2159 norandmaps Don't use address space randomization. Equivalent to
2160 echo 0 > /proc/sys/kernel/randomize_va_space
2162 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2164 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2165 with UP alternatives
2167 nordrand [X86] Disable the direct use of the RDRAND
2168 instruction even if it is supported by the
2169 processor. RDRAND is still available to user
2172 noresume [SWSUSP] Disables resume and restores original swap
2175 no-scroll [VGA] Disables scrollback.
2176 This is required for the Braillex ib80-piezo Braille
2177 reader made by F.H. Papenmeier (Germany).
2181 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2183 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2184 and disable the IO APIC. legacy for "maxcpus=0".
2186 nosoftlockup [KNL] Disable the soft-lockup detector.
2188 nosync [HW,M68K] Disables sync negotiation for all devices.
2190 notsc [BUGS=X86-32] Disable Time Stamp Counter
2192 nousb [USB] Disable the USB subsystem
2194 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2198 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2200 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2201 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2202 Some features depend on CPU0. Known dependencies are:
2203 1. Resume from suspend/hibernate depends on CPU0.
2204 Suspend/hibernate will fail if CPU0 is offline and you
2205 need to online CPU0 before suspend/hibernate.
2206 2. PIC interrupts also depend on CPU0. CPU0 can't be
2207 removed if a PIC interrupt is detected.
2208 It's said poweroff/reboot may depend on CPU0 on some
2209 machines although I haven't seen such issues so far
2210 after CPU0 is offline on a few tested machines.
2211 If the dependencies are under your control, you can
2212 turn on cpu0_hotplug.
2214 nptcg= [IA-64] Override max number of concurrent global TLB
2215 purges which is reported from either PAL_VM_SUMMARY or
2218 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2219 could support. nr_cpus=n : n >= 1 limits the kernel to
2220 supporting 'n' processors. Later in runtime you can not
2221 use hotplug cpu feature to put more cpu back to online.
2222 just like you compile the kernel NR_CPUS=n
2224 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2226 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2227 Allowed values are enable and disable
2229 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2230 one of ['zone', 'node', 'default'] can be specified
2231 This can be set from sysctl after boot.
2232 See Documentation/sysctl/vm.txt for details.
2234 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2235 See Documentation/debugging-via-ohci1394.txt for more
2238 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2239 Rather than timing out after 20 ms if an EC
2240 command is not properly ACKed, override the length
2241 of the timeout. We have interrupts disabled while
2242 waiting for the ACK, so if this is set too high
2243 interrupts *may* be lost!
2245 omap_mux= [OMAP] Override bootloader pin multiplexing.
2246 Format: <mux_mode0.mode_name=value>...
2247 For example, to override I2C bus2:
2248 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2250 oprofile.timer= [HW]
2251 Use timer interrupt instead of performance counters
2253 oprofile.cpu_type= Force an oprofile cpu type
2254 This might be useful if you have an older oprofile
2255 userland or if you want common events.
2256 Format: { arch_perfmon }
2257 arch_perfmon: [X86] Force use of architectural
2258 perfmon on Intel CPUs instead of the
2259 CPU specific event set.
2260 timer: [X86] Force use of architectural NMI
2261 timer mode (see also oprofile.timer
2262 for generic hr timer mode)
2263 [s390] Force legacy basic mode sampling
2264 (report cpu_type "timer")
2266 oops=panic Always panic on oopses. Default is to just kill the
2267 process, but there is a small probability of
2268 deadlocking the machine.
2269 This will also cause panics on machine check exceptions.
2270 Useful together with panic=30 to trigger a reboot.
2273 See Documentation/sound/oss/oss-parameters.txt
2275 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2276 timeout > 0: seconds before rebooting
2277 timeout = 0: wait forever
2278 timeout < 0: reboot immediately
2281 parkbd.port= [HW] Parallel port number the keyboard adapter is
2282 connected to, default is 0.
2284 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2285 0 for XT, 1 for AT (default is AT).
2288 parport= [HW,PPT] Specify parallel ports. 0 disables.
2289 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2290 Use 'auto' to force the driver to use any
2291 IRQ/DMA settings detected (the default is to
2292 ignore detected IRQ/DMA settings because of
2293 possible conflicts). You can specify the base
2294 address, IRQ, and DMA settings; IRQ and DMA
2295 should be numbers, or 'auto' (for using detected
2296 settings on that particular port), or 'nofifo'
2297 (to avoid using a FIFO even if it is detected).
2298 Parallel ports are assigned in the order they
2299 are specified on the command line, starting
2302 parport_init_mode= [HW,PPT]
2303 Configure VIA parallel port to operate in
2304 a specific mode. This is necessary on Pegasos
2305 computer where firmware has no options for setting
2306 up parallel port mode and sets it to spp.
2307 Currently this function knows 686a and 8231 chips.
2308 Format: [spp|ps2|epp|ecp|ecpepp]
2311 Halt all CPUs after the first oops has been printed for
2312 the specified number of seconds. This is to be used if
2313 your oopses keep scrolling off the screen.
2318 See header of drivers/block/paride/pcd.c.
2319 See also Documentation/blockdev/paride.txt.
2321 pci=option[,option...] [PCI] various PCI subsystem options:
2322 earlydump [X86] dump PCI config space before the kernel
2324 off [X86] don't probe for the PCI bus
2325 bios [X86-32] force use of PCI BIOS, don't access
2326 the hardware directly. Use this if your machine
2327 has a non-standard PCI host bridge.
2328 nobios [X86-32] disallow use of PCI BIOS, only direct
2329 hardware access methods are allowed. Use this
2330 if you experience crashes upon bootup and you
2331 suspect they are caused by the BIOS.
2332 conf1 [X86] Force use of PCI Configuration
2334 conf2 [X86] Force use of PCI Configuration
2336 noaer [PCIE] If the PCIEAER kernel config parameter is
2337 enabled, this kernel boot option can be used to
2338 disable the use of PCIE advanced error reporting.
2339 nodomains [PCI] Disable support for multiple PCI
2340 root domains (aka PCI segments, in ACPI-speak).
2341 nommconf [X86] Disable use of MMCONFIG for PCI
2343 check_enable_amd_mmconf [X86] check for and enable
2344 properly configured MMIO access to PCI
2345 config space on AMD family 10h CPU
2346 nomsi [MSI] If the PCI_MSI kernel config parameter is
2347 enabled, this kernel boot option can be used to
2348 disable the use of MSI interrupts system-wide.
2349 noioapicquirk [APIC] Disable all boot interrupt quirks.
2350 Safety option to keep boot IRQs enabled. This
2351 should never be necessary.
2352 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2353 primary IO-APIC for bridges that cannot disable
2354 boot IRQs. This fixes a source of spurious IRQs
2355 when the system masks IRQs.
2356 noioapicreroute [APIC] Disable workaround that uses the
2357 boot IRQ equivalent of an IRQ that connects to
2358 a chipset where boot IRQs cannot be disabled.
2359 The opposite of ioapicreroute.
2360 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2361 routing table. These calls are known to be buggy
2362 on several machines and they hang the machine
2363 when used, but on other computers it's the only
2364 way to get the interrupt routing table. Try
2365 this option if the kernel is unable to allocate
2366 IRQs or discover secondary PCI buses on your
2368 rom [X86] Assign address space to expansion ROMs.
2369 Use with caution as certain devices share
2370 address decoders between ROMs and other
2372 norom [X86] Do not assign address space to
2373 expansion ROMs that do not already have
2374 BIOS assigned address ranges.
2375 nobar [X86] Do not assign address space to the
2376 BARs that weren't assigned by the BIOS.
2377 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2378 assigned automatically to PCI devices. You can
2379 make the kernel exclude IRQs of your ISA cards
2381 pirqaddr=0xAAAAA [X86] Specify the physical address
2382 of the PIRQ table (normally generated
2383 by the BIOS) if it is outside the
2384 F0000h-100000h range.
2385 lastbus=N [X86] Scan all buses thru bus #N. Can be
2386 useful if the kernel is unable to find your
2387 secondary buses and you want to tell it
2388 explicitly which ones they are.
2389 assign-busses [X86] Always assign all PCI bus
2390 numbers ourselves, overriding
2391 whatever the firmware may have done.
2392 usepirqmask [X86] Honor the possible IRQ mask stored
2393 in the BIOS $PIR table. This is needed on
2394 some systems with broken BIOSes, notably
2395 some HP Pavilion N5400 and Omnibook XE3
2396 notebooks. This will have no effect if ACPI
2397 IRQ routing is enabled.
2398 noacpi [X86] Do not use ACPI for IRQ routing
2399 or for PCI scanning.
2400 use_crs [X86] Use PCI host bridge window information
2401 from ACPI. On BIOSes from 2008 or later, this
2402 is enabled by default. If you need to use this,
2403 please report a bug.
2404 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2405 If you need to use this, please report a bug.
2406 routeirq Do IRQ routing for all PCI devices.
2407 This is normally done in pci_enable_device(),
2408 so this option is a temporary workaround
2409 for broken drivers that don't call it.
2410 skip_isa_align [X86] do not align io start addr, so can
2411 handle more pci cards
2412 firmware [ARM] Do not re-enumerate the bus but instead
2413 just use the configuration from the
2414 bootloader. This is currently used on
2415 IXP2000 systems where the bus has to be
2416 configured a certain way for adjunct CPUs.
2417 noearly [X86] Don't do any early type 1 scanning.
2418 This might help on some broken boards which
2419 machine check when some devices' config space
2420 is read. But various workarounds are disabled
2421 and some IOMMU drivers will not work.
2422 bfsort Sort PCI devices into breadth-first order.
2423 This sorting is done to get a device
2424 order compatible with older (<= 2.4) kernels.
2425 nobfsort Don't sort PCI devices into breadth-first order.
2426 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2427 tuning and use the BIOS-configured MPS defaults.
2428 pcie_bus_safe Set every device's MPS to the largest value
2429 supported by all devices below the root complex.
2430 pcie_bus_perf Set device MPS to the largest allowable MPS
2431 based on its parent bus. Also set MRRS (Max
2432 Read Request Size) to the largest supported
2433 value (no larger than the MPS that the device
2434 or bus can support) for best performance.
2435 pcie_bus_peer2peer Set every device's MPS to 128B, which
2436 every device is guaranteed to support. This
2437 configuration allows peer-to-peer DMA between
2438 any pair of devices, possibly at the cost of
2439 reduced performance. This also guarantees
2440 that hot-added devices will work.
2441 cbiosize=nn[KMG] The fixed amount of bus space which is
2442 reserved for the CardBus bridge's IO window.
2443 The default value is 256 bytes.
2444 cbmemsize=nn[KMG] The fixed amount of bus space which is
2445 reserved for the CardBus bridge's memory
2446 window. The default value is 64 megabytes.
2449 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2450 Specifies alignment and device to reassign
2451 aligned memory resources.
2452 If <order of align> is not specified,
2453 PAGE_SIZE is used as alignment.
2454 PCI-PCI bridge can be specified, if resource
2455 windows need to be expanded.
2456 ecrc= Enable/disable PCIe ECRC (transaction layer
2457 end-to-end CRC checking).
2458 bios: Use BIOS/firmware settings. This is the
2462 hpiosize=nn[KMG] The fixed amount of bus space which is
2463 reserved for hotplug bridge's IO window.
2464 Default size is 256 bytes.
2465 hpmemsize=nn[KMG] The fixed amount of bus space which is
2466 reserved for hotplug bridge's memory window.
2467 Default size is 2 megabytes.
2468 realloc= Enable/disable reallocating PCI bridge resources
2469 if allocations done by BIOS are too small to
2470 accommodate resources required by all child
2472 off: Turn realloc off
2474 realloc same as realloc=on
2475 noari do not use PCIe ARI.
2476 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2477 only look for one device below a PCIe downstream
2480 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2483 force Enable ASPM even on devices that claim not to support it.
2484 WARNING: Forcing ASPM on may cause system lockups.
2486 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2487 nomsi Do not use MSI for PCI Express Native Hotplug (this
2488 makes all PCIe ports use INTx for hotplug services).
2490 pcie_ports= [PCIE] PCIe ports handling:
2491 auto Ask the BIOS whether or not to use native PCIe services
2492 associated with PCIe ports (PME, hot-plug, AER). Use
2493 them only if that is allowed by the BIOS.
2494 native Use native PCIe services associated with PCIe ports
2496 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2499 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2500 nomsi Do not use MSI for native PCIe PME signaling (this makes
2501 all PCIe root ports use INTx for all services).
2503 pcmv= [HW,PCMCIA] BadgePAD 4
2506 See Documentation/blockdev/paride.txt.
2508 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2511 See arch/parisc/kernel/pdc_chassis.c
2513 percpu_alloc= Select which percpu first chunk allocator to use.
2514 Currently supported values are "embed" and "page".
2515 Archs may support subset or none of the selections.
2516 See comments in mm/percpu.c for details on each
2517 allocator. This parameter is primarily for debugging
2518 and performance comparison.
2521 See Documentation/blockdev/paride.txt.
2524 See Documentation/blockdev/paride.txt.
2526 pirq= [SMP,APIC] Manual mp-table setup
2527 See Documentation/x86/i386/IO-APIC.txt.
2529 plip= [PPT,NET] Parallel port network link
2530 Format: { parport<nr> | timid | 0 }
2531 See also Documentation/parport.txt.
2533 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2534 Override pmtimer IOPort with a hex value.
2538 Enable PNP debug messages (depends on the
2539 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2540 via /sys/module/pnp/parameters/debug. We always show
2541 current resource usage; turning this on also shows
2542 possible settings and some assignment information.
2548 { on | off | curr | res | no-curr | no-res }
2551 [ISAPNP] Exclude IRQs for the autoconfiguration
2554 [ISAPNP] Exclude DMAs for the autoconfiguration
2556 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2557 Ranges are in pairs (I/O port base and size).
2560 [ISAPNP] Exclude memory regions for the
2562 Ranges are in pairs (memory base and size).
2564 ports= [IP_VS_FTP] IPVS ftp helper module
2566 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2568 Format: <port>,<port>....
2570 print-fatal-signals=
2571 [KNL] debug: print fatal signals
2573 If enabled, warn about various signal handling
2574 related application anomalies: too many signals,
2575 too many POSIX.1 timers, fatal signals causing a
2578 If you hit the warning due to signal overflow,
2579 you might want to try "ulimit -i unlimited".
2583 printk.always_kmsg_dump=
2584 Trigger kmsg_dump for cases other than kernel oops or
2586 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2589 printk.time= Show timing data prefixed to each printk message line
2590 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2592 processor.max_cstate= [HW,ACPI]
2593 Limit processor to maximum C-state
2594 max_cstate=9 overrides any DMI blacklist limit.
2596 processor.nocst [HW,ACPI]
2597 Ignore the _CST method to determine C-states,
2598 instead using the legacy FADT method
2600 profile= [KNL] Enable kernel profiling via /proc/profile
2601 Format: [schedule,]<number>
2602 Param: "schedule" - profile schedule points.
2603 Param: <number> - step/bucket size as a power of 2 for
2604 statistical time based profiling.
2605 Param: "sleep" - profile D-state sleeping (millisecs).
2606 Requires CONFIG_SCHEDSTATS
2607 Param: "kvm" - profile VM exits.
2609 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2611 See Documentation/blockdev/ramdisk.txt.
2613 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2614 probe for; one of (bare|imps|exps|lifebook|any).
2615 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2617 psmouse.resetafter= [HW,MOUSE]
2618 Try to reset the device after so many bad packets
2621 [HW,MOUSE] Set desired mouse resolution, in dpi.
2622 psmouse.smartscroll=
2623 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2624 0 = disabled, 1 = enabled (default).
2626 pstore.backend= Specify the name of the pstore backend to use
2629 See Documentation/blockdev/paride.txt.
2632 [KNL] Number of legacy pty's. Overwrites compiled-in
2635 quiet [KNL] Disable most log messages
2640 See Documentation/md.txt.
2642 ramdisk_blocksize= [RAM]
2643 See Documentation/blockdev/ramdisk.txt.
2645 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2646 See Documentation/blockdev/ramdisk.txt.
2649 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2650 the specified list of CPUs to be no-callback CPUs.
2651 Invocation of these CPUs' RCU callbacks will
2652 be offloaded to "rcuox/N" kthreads created for
2653 that purpose, where "x" is "b" for RCU-bh, "p"
2654 for RCU-preempt, and "s" for RCU-sched, and "N"
2655 is the CPU number. This reduces OS jitter on the
2656 offloaded CPUs, which can be useful for HPC and
2657 real-time workloads. It can also improve energy
2658 efficiency for asymmetric multiprocessors.
2661 Rather than requiring that offloaded CPUs
2662 (specified by rcu_nocbs= above) explicitly
2663 awaken the corresponding "rcuoN" kthreads,
2664 make these kthreads poll for callbacks.
2665 This improves the real-time response for the
2666 offloaded CPUs by relieving them of the need to
2667 wake up the corresponding kthread, but degrades
2668 energy efficiency by requiring that the kthreads
2669 periodically wake up to do the polling.
2671 rcutree.blimit= [KNL]
2672 Set maximum number of finished RCU callbacks to
2673 process in one batch.
2675 rcutree.rcu_fanout_leaf= [KNL]
2676 Increase the number of CPUs assigned to each
2677 leaf rcu_node structure. Useful for very large
2680 rcutree.jiffies_till_first_fqs= [KNL]
2681 Set delay from grace-period initialization to
2682 first attempt to force quiescent states.
2683 Units are jiffies, minimum value is zero,
2684 and maximum value is HZ.
2686 rcutree.jiffies_till_next_fqs= [KNL]
2687 Set delay between subsequent attempts to force
2688 quiescent states. Units are jiffies, minimum
2689 value is one, and maximum value is HZ.
2691 rcutree.qhimark= [KNL]
2692 Set threshold of queued RCU callbacks beyond which
2693 batch limiting is disabled.
2695 rcutree.qlowmark= [KNL]
2696 Set threshold of queued RCU callbacks below which
2697 batch limiting is re-enabled.
2699 rcutree.rcu_idle_gp_delay= [KNL]
2700 Set wakeup interval for idle CPUs that have
2701 RCU callbacks (RCU_FAST_NO_HZ=y).
2703 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2704 Set wakeup interval for idle CPUs that have
2705 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2706 Lazy RCU callbacks are those which RCU can
2707 prove do nothing more than free memory.
2709 rcutorture.fqs_duration= [KNL]
2710 Set duration of force_quiescent_state bursts.
2712 rcutorture.fqs_holdoff= [KNL]
2713 Set holdoff time within force_quiescent_state bursts.
2715 rcutorture.fqs_stutter= [KNL]
2716 Set wait time between force_quiescent_state bursts.
2718 rcutorture.gp_exp= [KNL]
2719 Use expedited update-side primitives.
2721 rcutorture.gp_normal= [KNL]
2722 Use normal (non-expedited) update-side primitives.
2723 If both gp_exp and gp_normal are set, do both.
2724 If neither gp_exp nor gp_normal are set, still
2727 rcutorture.n_barrier_cbs= [KNL]
2728 Set callbacks/threads for rcu_barrier() testing.
2730 rcutorture.nfakewriters= [KNL]
2731 Set number of concurrent RCU writers. These just
2732 stress RCU, they don't participate in the actual
2733 test, hence the "fake".
2735 rcutorture.nreaders= [KNL]
2736 Set number of RCU readers.
2738 rcutorture.object_debug= [KNL]
2739 Enable debug-object double-call_rcu() testing.
2741 rcutorture.onoff_holdoff= [KNL]
2742 Set time (s) after boot for CPU-hotplug testing.
2744 rcutorture.onoff_interval= [KNL]
2745 Set time (s) between CPU-hotplug operations, or
2746 zero to disable CPU-hotplug testing.
2748 rcutorture.rcutorture_runnable= [BOOT]
2749 Start rcutorture running at boot time.
2751 rcutorture.shuffle_interval= [KNL]
2752 Set task-shuffle interval (s). Shuffling tasks
2753 allows some CPUs to go into dyntick-idle mode
2754 during the rcutorture test.
2756 rcutorture.shutdown_secs= [KNL]
2757 Set time (s) after boot system shutdown. This
2758 is useful for hands-off automated testing.
2760 rcutorture.stall_cpu= [KNL]
2761 Duration of CPU stall (s) to test RCU CPU stall
2762 warnings, zero to disable.
2764 rcutorture.stall_cpu_holdoff= [KNL]
2765 Time to wait (s) after boot before inducing stall.
2767 rcutorture.stat_interval= [KNL]
2768 Time (s) between statistics printk()s.
2770 rcutorture.stutter= [KNL]
2771 Time (s) to stutter testing, for example, specifying
2772 five seconds causes the test to run for five seconds,
2773 wait for five seconds, and so on. This tests RCU's
2774 ability to transition abruptly to and from idle.
2776 rcutorture.test_boost= [KNL]
2777 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2778 "Maybe" means test if the RCU implementation
2779 under test support RCU priority boosting.
2781 rcutorture.test_boost_duration= [KNL]
2782 Duration (s) of each individual boost test.
2784 rcutorture.test_boost_interval= [KNL]
2785 Interval (s) between each boost test.
2787 rcutorture.test_no_idle_hz= [KNL]
2788 Test RCU's dyntick-idle handling. See also the
2789 rcutorture.shuffle_interval parameter.
2791 rcutorture.torture_type= [KNL]
2792 Specify the RCU implementation to test.
2794 rcutorture.verbose= [KNL]
2795 Enable additional printk() statements.
2797 rcupdate.rcu_expedited= [KNL]
2798 Use expedited grace-period primitives, for
2799 example, synchronize_rcu_expedited() instead
2800 of synchronize_rcu(). This reduces latency,
2801 but can increase CPU utilization, degrade
2802 real-time latency, and degrade energy efficiency.
2804 rcupdate.rcu_cpu_stall_suppress= [KNL]
2805 Suppress RCU CPU stall warning messages.
2807 rcupdate.rcu_cpu_stall_timeout= [KNL]
2808 Set timeout for RCU CPU stall warning messages.
2812 Run specified binary instead of /init from the ramdisk,
2813 used for early userspace startup. See initrd.
2816 Format (x86 or x86_64):
2817 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2819 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2821 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2822 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2823 reboot_force is either force or not specified,
2824 reboot_cpu is s[mp]#### with #### being the processor
2825 to be used for rebooting.
2828 [KNL, SMP] Set scheduler's default relax_domain_level.
2829 See Documentation/cgroups/cpusets.txt.
2831 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2833 reservetop= [X86-32]
2835 Reserves a hole at the top of the kernel virtual
2840 Set the amount of memory to reserve for BIOS at
2841 the bottom of the address space.
2843 reset_devices [KNL] Force drivers to reset the underlying device
2844 during initialization.
2847 Specify the partition device for software suspend
2849 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2851 resume_offset= [SWSUSP]
2852 Specify the offset from the beginning of the partition
2853 given by "resume=" at which the swap header is located,
2854 in <PAGE_SIZE> units (needed only for swap files).
2855 See Documentation/power/swsusp-and-swap-files.txt
2857 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2858 read the resume files
2860 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2861 Useful for devices that are detected asynchronously
2862 (e.g. USB and MMC devices).
2864 hibernate= [HIBERNATION]
2865 noresume Don't check if there's a hibernation image
2866 present during boot.
2867 nocompress Don't compress/decompress hibernation images.
2869 retain_initrd [RAM] Keep initrd memory after extraction
2871 rhash_entries= [KNL,NET]
2872 Set number of hash buckets for route cache
2874 riscom8= [HW,SERIAL]
2875 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2877 ro [KNL] Mount root device read-only on boot
2879 root= [KNL] Root filesystem
2880 See name_to_dev_t comment in init/do_mounts.c.
2882 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2883 mount the root filesystem
2885 rootflags= [KNL] Set root filesystem mount option string
2887 rootfstype= [KNL] Set root filesystem type
2889 rootwait [KNL] Wait (indefinitely) for root device to show up.
2890 Useful for devices that are detected asynchronously
2891 (e.g. USB and MMC devices).
2893 rproc_mem=nn[KMG][@address]
2894 [KNL,ARM,CMA] Remoteproc physical memory block.
2895 Memory area to be used by remote processor image,
2898 rw [KNL] Mount root device read-write on boot
2900 S [KNL] Run init in single mode
2903 See drivers/net/irda/sa1100_ir.c.
2905 sbni= [NET] Granch SBNI12 leased line adapter
2907 sched_debug [KNL] Enables verbose scheduler debug messages.
2909 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2910 xtime_lock contention on larger systems, and/or RCU lock
2911 contention on all systems with CONFIG_MAXSMP set.
2912 Format: { "0" | "1" }
2913 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2915 Note: increases power consumption, thus should only be
2916 enabled if running jitter sensitive (HPC/RT) workloads.
2918 security= [SECURITY] Choose a security module to enable at boot.
2919 If this boot parameter is not specified, only the first
2920 security module asking for security registration will be
2921 loaded. An invalid security module name will be treated
2922 as if no module has been chosen.
2924 selinux= [SELINUX] Disable or enable SELinux at boot time.
2925 Format: { "0" | "1" }
2926 See security/selinux/Kconfig help text.
2929 Default value is set via kernel config option.
2930 If enabled at boot time, /selinux/disable can be used
2931 later to disable prior to initial policy load.
2933 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2934 Format: { "0" | "1" }
2935 See security/apparmor/Kconfig help text
2938 Default value is set via kernel config option.
2940 serialnumber [BUGS=X86-32]
2943 Maximal number of shapers.
2945 show_msr= [x86] show boot-time MSR settings
2946 Format: { <integer> }
2947 Show boot-time (BIOS-initialized) MSR settings.
2948 The parameter means the number of CPUs to show,
2949 for example 1 means boot CPU only.
2956 slab_max_order= [MM, SLAB]
2957 Determines the maximum allowed order for slabs.
2958 A high setting may cause OOMs due to memory
2959 fragmentation. Defaults to 1 for systems with
2960 more than 32MB of RAM, 0 otherwise.
2962 slub_debug[=options[,slabs]] [MM, SLUB]
2963 Enabling slub_debug allows one to determine the
2964 culprit if slab objects become corrupted. Enabling
2965 slub_debug can create guard zones around objects and
2966 may poison objects when not in use. Also tracks the
2967 last alloc / free. For more information see
2968 Documentation/vm/slub.txt.
2970 slub_max_order= [MM, SLUB]
2971 Determines the maximum allowed order for slabs.
2972 A high setting may cause OOMs due to memory
2973 fragmentation. For more information see
2974 Documentation/vm/slub.txt.
2976 slub_min_objects= [MM, SLUB]
2977 The minimum number of objects per slab. SLUB will
2978 increase the slab order up to slub_max_order to
2979 generate a sufficiently large slab able to contain
2980 the number of objects indicated. The higher the number
2981 of objects the smaller the overhead of tracking slabs
2982 and the less frequently locks need to be acquired.
2983 For more information see Documentation/vm/slub.txt.
2985 slub_min_order= [MM, SLUB]
2986 Determines the minimum page order for slabs. Must be
2987 lower than slub_max_order.
2988 For more information see Documentation/vm/slub.txt.
2990 slub_nomerge [MM, SLUB]
2991 Disable merging of slabs with similar size. May be
2992 necessary if there is some reason to distinguish
2993 allocs to different slabs. Debug options disable
2994 merging on their own.
2995 For more information see Documentation/vm/slub.txt.
2998 Format: <io1>[,<io2>[,...,<io8>]]
3000 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3001 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3002 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3003 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3004 smsc-ircc2.ircc_irq= [HW] IRQ line
3005 smsc-ircc2.ircc_dma= [HW] DMA channel
3006 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3007 0: Toshiba Satellite 1800 (GP data pin select)
3008 1: Fast pin select (default)
3012 [KNL] Should the soft-lockup detector generate panics.
3015 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3016 See Documentation/laptops/sonypi.txt
3018 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3019 See Documentation/serial/specialix.txt.
3021 spia_io_base= [HW,MTD]
3027 Enabled the stack tracer on boot up.
3029 stacktrace_filter=[function-list]
3030 [FTRACE] Limit the functions that the stack tracer
3031 will trace at boot up. function-list is a comma separated
3032 list of functions. This list can be changed at run
3033 time by the stack_trace_filter file in the debugfs
3034 tracing directory. Note, this enables stack tracing
3035 and the stacktrace above is not needed.
3039 Set the STI (builtin display/keyboard on the HP-PARISC
3040 machines) console (graphic card) which should be used
3041 as the initial boot-console.
3042 See also comment in drivers/video/console/sticore.c.
3045 See comment in drivers/video/console/sticore.c.
3048 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3050 sunrpc.min_resvport=
3051 sunrpc.max_resvport=
3053 SunRPC servers often require that client requests
3054 originate from a privileged port (i.e. a port in the
3055 range 0 < portnr < 1024).
3056 An administrator who wishes to reserve some of these
3057 ports for other uses may adjust the range that the
3058 kernel's sunrpc client considers to be privileged
3059 using these two parameters to set the minimum and
3060 maximum port values.
3064 Control how the NFS server code allocates CPUs to
3065 service thread pools. Depending on how many NICs
3066 you have and where their interrupts are bound, this
3067 option will affect which CPUs will do NFS serving.
3068 Note: this parameter cannot be changed while the
3069 NFS server is running.
3071 auto the server chooses an appropriate mode
3072 automatically using heuristics
3073 global a single global pool contains all CPUs
3074 percpu one pool for each CPU
3075 pernode one pool for each NUMA node (equivalent
3076 to global on non-NUMA machines)
3078 sunrpc.tcp_slot_table_entries=
3079 sunrpc.udp_slot_table_entries=
3081 Sets the upper limit on the number of simultaneous
3082 RPC calls that can be sent from the client to a
3083 server. Increasing these values may allow you to
3084 improve throughput, but will also increase the
3085 amount of memory reserved for use by the client.
3088 [KNL] Enable accounting of swap in memory resource
3089 controller if no parameter or 1 is given or disable
3090 it if 0 is given (See Documentation/cgroups/memory.txt)
3092 swiotlb= [IA-64] Number of I/O TLB slabs
3096 sysfs.deprecated=0|1 [KNL]
3097 Enable/disable old style sysfs layout for old udev
3098 on older distributions. When this option is enabled
3099 very new udev will not work anymore. When this option
3100 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3101 in older udev will not work anymore.
3102 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3103 the kernel configuration.
3105 sysrq_always_enabled
3107 Ignore sysrq setting - this boot parameter will
3108 neutralize any effect of /proc/sys/kernel/sysrq.
3109 Useful for debugging.
3113 test_suspend= [SUSPEND]
3114 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3115 standby suspend) as the system sleep state to briefly
3116 enter during system startup. The system is woken from
3117 this state using a wakeup-capable RTC alarm.
3119 thash_entries= [KNL,NET]
3120 Set number of hash buckets for TCP connection
3122 thermal.act= [HW,ACPI]
3123 -1: disable all active trip points in all thermal zones
3124 <degrees C>: override all lowest active trip points
3126 thermal.crt= [HW,ACPI]
3127 -1: disable all critical trip points in all thermal zones
3128 <degrees C>: override all critical trip points
3130 thermal.nocrt= [HW,ACPI]
3131 Set to disable actions on ACPI thermal zone
3132 critical and hot trip points.
3134 thermal.off= [HW,ACPI]
3135 1: disable ACPI thermal control
3137 thermal.psv= [HW,ACPI]
3138 -1: disable all passive trip points
3139 <degrees C>: override all passive trip points to this
3142 thermal.tzp= [HW,ACPI]
3143 Specify global default ACPI thermal zone polling rate
3144 <deci-seconds>: poll all this frequency
3145 0: no polling (default)
3148 Force threading of all interrupt handlers except those
3149 marked explicitly IRQF_NO_THREAD.
3152 Enable the Transcendent memory driver if built-in.
3154 tmem.cleancache=0|1 [KNL, XEN]
3155 Default is on (1). Disable the usage of the cleancache
3156 API to send anonymous pages to the hypervisor.
3158 tmem.frontswap=0|1 [KNL, XEN]
3159 Default is on (1). Disable the usage of the frontswap
3160 API to send swap pages to the hypervisor. If disabled
3161 the selfballooning and selfshrinking are force disabled.
3163 tmem.selfballooning=0|1 [KNL, XEN]
3164 Default is on (1). Disable the driving of swap pages
3167 tmem.selfshrinking=0|1 [KNL, XEN]
3168 Default is on (1). Partial swapoff that immediately
3169 transfers pages from Xen hypervisor back to the
3170 kernel based on different criteria.
3174 Specify if the kernel should make use of the cpu
3175 topology information if the hardware supports this.
3176 The scheduler will make use of this information and
3177 e.g. base its process migration decisions on it.
3182 tpm_suspend_pcr=[HW,TPM]
3183 Format: integer pcr id
3184 Specify that at suspend time, the tpm driver
3185 should extend the specified pcr with zeros,
3186 as a workaround for some chips which fail to
3187 flush the last written pcr on TPM_SaveState.
3188 This will guarantee that all the other pcrs
3191 trace_buf_size=nn[KMG]
3192 [FTRACE] will set tracing buffer size.
3194 trace_event=[event-list]
3195 [FTRACE] Set and start specified trace events in order
3196 to facilitate early boot debugging.
3197 See also Documentation/trace/events.txt
3199 trace_options=[option-list]
3200 [FTRACE] Enable or disable tracer options at boot.
3201 The option-list is a comma delimited list of options
3202 that can be enabled or disabled just as if you were
3203 to echo the option name into
3205 /sys/kernel/debug/tracing/trace_options
3207 For example, to enable stacktrace option (to dump the
3208 stack trace of each event), add to the command line:
3210 trace_options=stacktrace
3212 See also Documentation/trace/ftrace.txt "trace options"
3216 [FTRACE] enable this option to disable tracing when a
3217 warning is hit. This turns off "tracing_on". Tracing can
3218 be enabled again by echoing '1' into the "tracing_on"
3219 file located in /sys/kernel/debug/tracing/
3221 This option is useful, as it disables the trace before
3222 the WARNING dump is called, which prevents the trace to
3223 be filled with content caused by the warning output.
3225 This option can also be set at run time via the sysctl
3226 option: kernel/traceoff_on_warning
3228 transparent_hugepage=
3230 Format: [always|madvise|never]
3231 Can be used to control the default behavior of the system
3232 with respect to transparent hugepages.
3233 See Documentation/vm/transhuge.txt for more details.
3235 tsc= Disable clocksource stability checks for TSC.
3237 [x86] reliable: mark tsc clocksource as reliable, this
3238 disables clocksource verification at runtime, as well
3239 as the stability checks done at bootup. Used to enable
3240 high-resolution timer mode on older hardware, and in
3241 virtualized environment.
3242 [x86] noirqtime: Do not use TSC to do irq accounting.
3243 Used to run time disable IRQ_TIME_ACCOUNTING on any
3244 platforms where RDTSC is slow and this accounting
3247 turbografx.map[2|3]= [HW,JOY]
3248 TurboGraFX parallel port interface
3250 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3251 See also Documentation/input/joystick-parport.txt
3253 udbg-immortal [PPC] When debugging early kernel crashes that
3254 happen after console_init() and before a proper
3255 console driver takes over, this boot options might
3256 help "seeing" what's going on.
3258 uhash_entries= [KNL,NET]
3259 Set number of hash buckets for UDP/UDP-Lite connections
3262 [USB] Ignore overcurrent events (default N).
3263 Some badly-designed motherboards generate lots of
3264 bogus events, for ports that aren't wired to
3265 anything. Set this parameter to avoid log spamming.
3266 Note that genuine overcurrent events won't be
3270 [X86] Cause panic on unknown NMI.
3272 usbcore.authorized_default=
3273 [USB] Default USB device authorization:
3274 (default -1 = authorized except for wireless USB,
3275 0 = not authorized, 1 = authorized)
3277 usbcore.autosuspend=
3278 [USB] The autosuspend time delay (in seconds) used
3279 for newly-detected USB devices (default 2). This
3280 is the time required before an idle device will be
3281 autosuspended. Devices for which the delay is set
3282 to a negative value won't be autosuspended at all.
3284 usbcore.usbfs_snoop=
3285 [USB] Set to log all usbfs traffic (default 0 = off).
3287 usbcore.blinkenlights=
3288 [USB] Set to cycle leds on hubs (default 0 = off).
3290 usbcore.old_scheme_first=
3291 [USB] Start with the old device initialization
3292 scheme (default 0 = off).
3294 usbcore.usbfs_memory_mb=
3295 [USB] Memory limit (in MB) for buffers allocated by
3296 usbfs (default = 16, 0 = max = 2047).
3298 usbcore.use_both_schemes=
3299 [USB] Try the other device initialization scheme
3300 if the first one fails (default 1 = enabled).
3302 usbcore.initial_descriptor_timeout=
3303 [USB] Specifies timeout for the initial 64-byte
3304 USB_REQ_GET_DESCRIPTOR request in milliseconds
3305 (default 5000 = 5.0 seconds).
3308 [USBHID] The interval which mice are to be polled at.
3310 usb-storage.delay_use=
3311 [UMS] The delay in seconds before a new device is
3312 scanned for Logical Units (default 5).
3315 [UMS] A list of quirks entries to supplement or
3316 override the built-in unusual_devs list. List
3317 entries are separated by commas. Each entry has
3318 the form VID:PID:Flags where VID and PID are Vendor
3319 and Product ID values (4-digit hex numbers) and
3320 Flags is a set of characters, each corresponding
3321 to a common usb-storage quirk flag as follows:
3322 a = SANE_SENSE (collect more than 18 bytes
3324 b = BAD_SENSE (don't collect more than 18
3325 bytes of sense data);
3326 c = FIX_CAPACITY (decrease the reported
3327 device capacity by one sector);
3328 d = NO_READ_DISC_INFO (don't use
3329 READ_DISC_INFO command);
3330 e = NO_READ_CAPACITY_16 (don't use
3331 READ_CAPACITY_16 command);
3332 h = CAPACITY_HEURISTICS (decrease the
3333 reported device capacity by one
3334 sector if the number is odd);
3335 i = IGNORE_DEVICE (don't bind to this
3337 l = NOT_LOCKABLE (don't try to lock and
3338 unlock ejectable media);
3339 m = MAX_SECTORS_64 (don't transfer more
3340 than 64 sectors = 32 KB at a time);
3341 n = INITIAL_READ10 (force a retry of the
3342 initial READ(10) command);
3343 o = CAPACITY_OK (accept the capacity
3344 reported by the device);
3345 p = WRITE_CACHE (the device cache is ON
3347 r = IGNORE_RESIDUE (the device reports
3348 bogus residue values);
3349 s = SINGLE_LUN (the device has only one
3351 w = NO_WP_DETECT (don't test whether the
3352 medium is write-protected).
3353 Example: quirks=0419:aaf5:rl,0421:0433:rc
3355 user_debug= [KNL,ARM]
3357 See arch/arm/Kconfig.debug help text.
3358 1 - undefined instruction events
3360 4 - invalid data aborts
3363 Example: user_debug=31
3366 [X86] Flags controlling user PTE allocations.
3368 nohigh = do not allocate PTE pages in
3369 HIGHMEM regardless of setting
3373 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3374 vdso=1: enable VDSO (default)
3375 vdso=0: disable VDSO mapping
3378 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3379 vdso32=1: enable 32-bit VDSO (default)
3380 vdso32=0: disable 32-bit VDSO mapping
3383 vector=percpu: enable percpu vector domain
3385 video= [FB] Frame buffer configuration
3386 See Documentation/fb/modedb.txt.
3388 video.brightness_switch_enabled= [0,1]
3389 If set to 1, on receiving an ACPI notify event
3390 generated by hotkey, video driver will adjust brightness
3391 level and then send out the event to user space through
3392 the allocated input device; If set to 0, video driver
3393 will only send out the event without touching backlight
3398 [VMMIO] Memory mapped virtio (platform) device.
3400 <size>@<baseaddr>:<irq>[:<id>]
3402 <size> := size (can use standard suffixes
3404 <baseaddr> := physical base address
3405 <irq> := interrupt number (as passed to
3407 <id> := (optional) platform device id
3409 virtio_mmio.device=1K@0x100b0000:48:7
3411 Can be used multiple times for multiple devices.
3413 vga= [BOOT,X86-32] Select a particular video mode
3414 See Documentation/x86/boot.txt and
3415 Documentation/svga.txt.
3416 Use vga=ask for menu.
3417 This is actually a boot loader parameter; the value is
3418 passed to the kernel using a special protocol.
3420 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3421 size of <nn>. This can be used to increase the
3422 minimum size (128MB on x86). It can also be used to
3423 decrease the size and leave more room for directly
3426 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3429 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3432 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3436 Controls the behavior of vsyscalls (i.e. calls to
3437 fixed addresses of 0xffffffffff600x00 from legacy
3438 code). Most statically-linked binaries and older
3439 versions of glibc use these calls. Because these
3440 functions are at fixed addresses, they make nice
3441 targets for exploits that can control RIP.
3443 emulate [default] Vsyscalls turn into traps and are
3444 emulated reasonably safely.
3446 native Vsyscalls are native syscall instructions.
3447 This is a little bit faster than trapping
3448 and makes a few dynamic recompilers work
3449 better than they would in emulation mode.
3450 It also makes exploits much easier to write.
3452 none Vsyscalls don't work at all. This makes
3453 them quite hard to use for exploits but
3454 might break your system.
3456 vt.color= [VT] Default text color.
3457 Format: 0xYX, X = foreground, Y = background.
3458 Default: 0x07 = light gray on black.
3460 vt.cur_default= [VT] Default cursor shape.
3461 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3462 the parameters of the <Esc>[?A;B;Cc escape sequence;
3463 see VGA-softcursor.txt. Default: 2 = underline.
3465 vt.default_blu= [VT]
3466 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3467 Change the default blue palette of the console.
3468 This is a 16-member array composed of values
3471 vt.default_grn= [VT]
3472 Format: <green0>,<green1>,<green2>,...,<green15>
3473 Change the default green palette of the console.
3474 This is a 16-member array composed of values
3477 vt.default_red= [VT]
3478 Format: <red0>,<red1>,<red2>,...,<red15>
3479 Change the default red palette of the console.
3480 This is a 16-member array composed of values
3486 Set system-wide default UTF-8 mode for all tty's.
3487 Default is 1, i.e. UTF-8 mode is enabled for all
3488 newly opened terminals.
3490 vt.global_cursor_default=
3493 Set system-wide default for whether a cursor
3494 is shown on new VTs. Default is -1,
3495 i.e. cursors will be created by default unless
3496 overridden by individual drivers. 0 will hide
3497 cursors, 1 will display them.
3499 vt.italic= [VT] Default color for italic text; 0-15.
3502 vt.underline= [VT] Default color for underlined text; 0-15.
3505 watchdog timers [HW,WDT] For information on watchdog timers,
3506 see Documentation/watchdog/watchdog-parameters.txt
3507 or other driver-specific files in the
3508 Documentation/watchdog/ directory.
3510 workqueue.disable_numa
3511 By default, all work items queued to unbound
3512 workqueues are affine to the NUMA nodes they're
3513 issued on, which results in better behavior in
3514 general. If NUMA affinity needs to be disabled for
3515 whatever reason, this option can be used. Note
3516 that this also can be controlled per-workqueue for
3517 workqueues visible under /sys/bus/workqueue/.
3519 workqueue.power_efficient
3520 Per-cpu workqueues are generally preferred because
3521 they show better performance thanks to cache
3522 locality; unfortunately, per-cpu workqueues tend to
3523 be more power hungry than unbound workqueues.
3525 Enabling this makes the per-cpu workqueues which
3526 were observed to contribute significantly to power
3527 consumption unbound, leading to measurably lower
3528 power usage at the cost of small performance
3531 The default value of this parameter is determined by
3532 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3534 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3535 default x2apic cluster mode on platforms
3538 x86_intel_mid_timer= [X86-32,APBT]
3539 Choose timer option for x86 Intel MID platform.
3540 Two valid options are apbt timer only and lapic timer
3541 plus one apbt timer for broadcast timer.
3542 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3544 xen_emul_unplug= [HW,X86,XEN]
3545 Unplug Xen emulated devices
3546 Format: [unplug0,][unplug1]
3547 ide-disks -- unplug primary master IDE devices
3548 aux-ide-disks -- unplug non-primary-master IDE devices
3549 nics -- unplug network devices
3550 all -- unplug all emulated devices (NICs and IDE disks)
3551 unnecessary -- unplugging emulated devices is
3552 unnecessary even if the host did not respond to
3554 never -- do not unplug even if version check succeeds
3556 xen_nopvspin [X86,XEN]
3557 Disables the ticketlock slowpath using Xen PV
3560 xirc2ps_cs= [NET,PCMCIA]
3562 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3564 ______________________________________________________________________
3568 Add more DRM drivers.
projects / ~andy / linux / blob