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 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
567 hvc<n> Use the hypervisor console device <n>. This is for
568 both Xen and PowerPC hypervisors.
570 If the device connected to the port is not a TTY but a braille
571 device, prepend "brl," before the device type, for instance
573 For now, only VisioBraille is supported.
575 consoleblank= [KNL] The console blank (screen saver) timeout in
576 seconds. Defaults to 10*60 = 10mins. A value of 0
577 disables the blank timer.
580 [KNL] Change the default value for
581 /proc/<pid>/coredump_filter.
582 See also Documentation/filesystems/proc.txt.
584 cpuidle.off=1 [CPU_IDLE]
585 disable the cpuidle sub-system
587 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
589 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
591 crashkernel=size[KMG][@offset[KMG]]
592 [KNL] Using kexec, Linux can switch to a 'crash kernel'
593 upon panic. This parameter reserves the physical
594 memory region [offset, offset + size] for that kernel
595 image. If '@offset' is omitted, then a suitable offset
596 is selected automatically. Check
597 Documentation/kdump/kdump.txt for further details.
599 crashkernel=range1:size1[,range2:size2,...][@offset]
600 [KNL] Same as above, but depends on the memory
601 in the running system. The syntax of range is
602 start-[end] where start and end are both
603 a memory unit (amount[KMG]). See also
604 Documentation/kdump/kdump.txt for an example.
606 crashkernel=size[KMG],high
607 [KNL, x86_64] range could be above 4G. Allow kernel
608 to allocate physical memory region from top, so could
609 be above 4G if system have more than 4G ram installed.
610 Otherwise memory region will be allocated below 4G, if
612 It will be ignored if crashkernel=X is specified.
613 crashkernel=size[KMG],low
614 [KNL, x86_64] range under 4G. When crashkernel=X,high
615 is passed, kernel could allocate physical memory region
616 above 4G, that cause second kernel crash on system
617 that require some amount of low memory, e.g. swiotlb
618 requires at least 64M+32K low memory. Kernel would
619 try to allocate 72M below 4G automatically.
620 This one let user to specify own low range under 4G
621 for second kernel instead.
622 0: to disable low allocation.
623 It will be ignored when crashkernel=X,high is not used
624 or memory reserved is below 4G.
629 cs89x0_media= [HW,NET]
630 Format: { rj45 | aui | bnc }
633 See header of drivers/s390/block/dasd_devmap.c.
635 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
636 (one device per port)
637 Format: <port#>,<type>
638 See also Documentation/input/joystick-parport.txt
640 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
641 time. See Documentation/dynamic-debug-howto.txt for
642 details. Deprecated, see dyndbg.
644 debug [KNL] Enable kernel debugging (events log level).
647 [KNL] verbose self-tests
649 Print debugging info while doing the locking API
651 We default to 0 (no extra messages), setting it to
652 1 will print _a lot_ more information - normally
653 only useful to kernel developers.
655 debug_objects [KNL] Enable object debugging
658 [KNL] Disable object debugging
660 debug_guardpage_minorder=
661 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
662 parameter allows control of the order of pages that will
663 be intentionally kept free (and hence protected) by the
664 buddy allocator. Bigger value increase the probability
665 of catching random memory corruption, but reduce the
666 amount of memory for normal system use. The maximum
667 possible value is MAX_ORDER/2. Setting this parameter
668 to 1 or 2 should be enough to identify most random
669 memory corruption problems caused by bugs in kernel or
670 driver code when a CPU writes to (or reads from) a
671 random memory location. Note that there exists a class
672 of memory corruptions problems caused by buggy H/W or
673 F/W or by drivers badly programing DMA (basically when
674 memory is written at bus level and the CPU MMU is
675 bypassed) which are not detectable by
676 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
677 tracking down these problems.
679 debugpat [X86] Enable PAT debugging
681 decnet.addr= [HW,NET]
682 Format: <area>[,<node>]
683 See also Documentation/networking/decnet.txt.
686 [same as hugepagesz=] The size of the default
687 HugeTLB page size. This is the size represented by
688 the legacy /proc/ hugepages APIs, used for SHM, and
689 default size when mounting hugetlbfs filesystems.
690 Defaults to the default architecture's huge page size
694 Set number of hash buckets for dentry cache.
697 IO parameters + enable/disable command.
699 digiepca= [HW,SERIAL]
700 See drivers/char/README.epca and
701 Documentation/serial/digiepca.txt.
704 See Documentation/networking/ipv6.txt.
706 disable_ddw [PPC/PSERIES]
707 Disable Dynamic DMA Window support. Use this if
708 to workaround buggy firmware.
711 See Documentation/networking/ipv6.txt.
713 disable_mtrr_cleanup [X86]
714 The kernel tries to adjust MTRR layout from continuous
715 to discrete, to make X server driver able to add WB
716 entry later. This parameter disables that.
718 disable_mtrr_trim [X86, Intel and AMD only]
719 By default the kernel will trim any uncacheable
720 memory out of your available memory pool based on
721 MTRR settings. This parameter disables that behavior,
722 possibly causing your machine to run very slowly.
724 disable_timer_pin_1 [X86]
725 Disable PIN 1 of APIC timer
726 Can be useful to work around chipset bugs.
728 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
729 this option disables the debugging code at boot.
731 dma_debug_entries=<number>
732 This option allows to tune the number of preallocated
733 entries for DMA-API debugging code. One entry is
734 required per DMA-API allocation. Use this if the
735 DMA-API debugging code disables itself because the
736 architectural default is too low.
738 dma_debug_driver=<driver_name>
739 With this option the DMA-API debugging driver
740 filter feature can be enabled at boot time. Just
741 pass the driver to filter for as the parameter.
742 The filter can be disabled or changed to another
743 driver later using sysfs.
745 drm_kms_helper.edid_firmware=[<connector>:]<file>
746 Broken monitors, graphic adapters and KVMs may
747 send no or incorrect EDID data sets. This parameter
748 allows to specify an EDID data set in the
749 /lib/firmware directory that is used instead.
750 Generic built-in EDID data sets are used, if one of
751 edid/1024x768.bin, edid/1280x1024.bin,
752 edid/1680x1050.bin, or edid/1920x1080.bin is given
753 and no file with the same name exists. Details and
754 instructions how to build your own EDID data are
755 available in Documentation/EDID/HOWTO.txt. An EDID
756 data set will only be used for a particular connector,
757 if its name and a colon are prepended to the EDID
762 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
763 module.dyndbg[="val"]
764 Enable debug messages at boot time. See
765 Documentation/dynamic-debug-howto.txt for details.
767 earlycon= [KNL] Output early console device and options.
768 uart[8250],io,<addr>[,options]
769 uart[8250],mmio,<addr>[,options]
770 uart[8250],mmio32,<addr>[,options]
771 Start an early, polled-mode console on the 8250/16550
772 UART at the specified I/O port or MMIO address.
773 MMIO inter-register address stride is either 8-bit
774 (mmio) or 32-bit (mmio32).
775 The options are the same as for ttyS, above.
777 earlyprintk= [X86,SH,BLACKFIN]
780 earlyprintk=serial[,ttySn[,baudrate]]
781 earlyprintk=ttySn[,baudrate]
782 earlyprintk=dbgp[debugController#]
784 Append ",keep" to not disable it when the real console
787 Only vga or serial or usb debug port at a time.
789 Currently only ttyS0 and ttyS1 are supported.
791 Interaction with the standard serial driver is not
794 The VGA output is eventually overwritten by the real
797 The xen output can only be used by Xen PV guests.
799 ekgdboc= [X86,KGDB] Allow early kernel console debugging
802 This is designed to be used in conjunction with
803 the boot argument: earlyprintk=vga
806 Format: {"off" | "on" | "skip[mbr]"}
808 efi_no_storage_paranoia [EFI; X86]
809 Using this parameter you can use more than 50% of
810 your efi variable storage. Use this parameter only if
811 you are really sure that your UEFI does sane gc and
812 fulfills the spec otherwise your board may brick.
814 eisa_irq_edge= [PARISC,HW]
815 See header of drivers/parisc/eisa.c.
818 See comment before function elanfreq_setup() in
819 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
822 Format: {"cfq" | "deadline" | "noop"}
823 See Documentation/block/cfq-iosched.txt and
824 Documentation/block/deadline-iosched.txt for details.
826 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
827 Specifies physical address of start of kernel core
828 image elf header and optionally the size. Generally
829 kexec loader will pass this option to capture kernel.
830 See Documentation/kdump/kdump.txt for details.
832 enable_mtrr_cleanup [X86]
833 The kernel tries to adjust MTRR layout from continuous
834 to discrete, to make X server driver able to add WB
835 entry later. This parameter enables that.
837 enable_timer_pin_1 [X86]
838 Enable PIN 1 of APIC timer
839 Can be useful to work around chipset bugs
840 (in particular on some ATI chipsets).
841 The kernel tries to set a reasonable default.
843 enforcing [SELINUX] Set initial enforcing status.
845 See security/selinux/Kconfig help text.
846 0 -- permissive (log only, no denials).
847 1 -- enforcing (deny and log).
849 Value can be changed at runtime via /selinux/enforce.
852 Disable Error Record Serialization Table (ERST)
855 ether= [HW,NET] Ethernet cards parameters
856 This option is obsoleted by the "netdev=" option, which
857 has equivalent usage. See its documentation for details.
861 Permit 'security.evm' to be updated regardless of
862 current integrity status.
866 fail_make_request=[KNL]
867 General fault injection mechanism.
868 Format: <interval>,<probability>,<space>,<times>
869 See also Documentation/fault-injection/.
872 See Documentation/blockdev/floppy.txt.
874 force_pal_cache_flush
875 [IA-64] Avoid check_sal_cache_flush which may hang on
876 buggy SAL_CACHE_FLUSH implementations. Using this
877 parameter will force ia64_sal_cache_flush to call
878 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
881 [FTRACE] will set and start the specified tracer
882 as early as possible in order to facilitate early
885 ftrace_dump_on_oops[=orig_cpu]
886 [FTRACE] will dump the trace buffers on oops.
887 If no parameter is passed, ftrace will dump
888 buffers of all CPUs, but if you pass orig_cpu, it will
889 dump only the buffer of the CPU that triggered the
892 ftrace_filter=[function-list]
893 [FTRACE] Limit the functions traced by the function
894 tracer at boot up. function-list is a comma separated
895 list of functions. This list can be changed at run
896 time by the set_ftrace_filter file in the debugfs
899 ftrace_notrace=[function-list]
900 [FTRACE] Do not trace the functions specified in
901 function-list. This list can be changed at run time
902 by the set_ftrace_notrace file in the debugfs
905 ftrace_graph_filter=[function-list]
906 [FTRACE] Limit the top level callers functions traced
907 by the function graph tracer at boot up.
908 function-list is a comma separated list of functions
909 that can be changed at run time by the
910 set_graph_function file in the debugfs tracing directory.
913 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
914 support via parallel port (up to 5 devices per port)
915 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
916 See also Documentation/input/joystick-parport.txt
920 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
924 gcov_persist= [GCOV] When non-zero (default), profiling data for
925 kernel modules is saved and remains accessible via
926 debugfs, even when the module is unloaded/reloaded.
927 When zero, profiling data is discarded and associated
928 debugfs files are removed at module unload time.
930 gpt [EFI] Forces disk with valid GPT signature but
931 invalid Protective MBR to be treated as GPT.
933 grcan.enable0= [HW] Configuration of physical interface 0. Determines
934 the "Enable 0" bit of the configuration register.
937 grcan.enable1= [HW] Configuration of physical interface 1. Determines
938 the "Enable 0" bit of the configuration register.
941 grcan.select= [HW] Select which physical interface to use.
944 grcan.txsize= [HW] Sets the size of the tx buffer.
945 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
947 grcan.rxsize= [HW] Sets the size of the rx buffer.
948 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
951 hashdist= [KNL,NUMA] Large hashes allocated during boot
952 are distributed across NUMA nodes. Defaults on
953 for 64-bit NUMA, off otherwise.
954 Format: 0 | 1 (for off | on)
956 hcl= [IA-64] SGI's Hardware Graph compatibility layer
958 hd= [EIDE] (E)IDE hard drive subsystem geometry
959 Format: <cyl>,<head>,<sect>
962 Disable Hardware Error Source Table (HEST) support;
963 corresponding firmware-first mode error processing
964 logic will be disabled.
966 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
967 size of <nn>. This works even on boxes that have no
968 highmem otherwise. This also works to reduce highmem
969 size on bigger boxes.
971 highres= [KNL] Enable/disable high resolution timer mode.
972 Valid parameters: "on", "off"
976 See Documentation/isdn/README.HiSax.
980 hpet= [X86-32,HPET] option to control HPET usage
981 Format: { enable (default) | disable | force |
983 disable: disable HPET and use PIT instead
984 force: allow force enabled of undocumented chips (ICH4,
986 verbose: show contents of HPET registers during setup
988 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
989 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
990 On x86-64 and powerpc, this option can be specified
991 multiple times interleaved with hugepages= to reserve
992 huge pages of different sizes. Valid pages sizes on
993 x86-64 are 2M (when the CPU supports "pse") and 1G
994 (when the CPU supports the "pdpe1gb" cpuinfo flag)
995 Note that 1GB pages can only be allocated at boot time
996 using hugepages= and not freed afterwards.
998 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
999 terminal devices. Valid values: 0..8
1000 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1001 If specified, z/VM IUCV HVC accepts connections
1002 from listed z/VM user IDs only.
1004 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1005 hardware thread id mappings.
1006 Format: <cpu>:<hwthread>
1009 Do not unregister boot console at start. This is only
1010 useful for debugging when something happens in the window
1011 between unregistering the boot console and initializing
1014 i2c_bus= [HW] Override the default board specific I2C bus speed
1015 or register an additional I2C bus that is not
1016 registered from board initialization code.
1020 i8042.debug [HW] Toggle i8042 debug mode
1021 i8042.direct [HW] Put keyboard port into non-translated mode
1022 i8042.dumbkbd [HW] Pretend that controller can only read data from
1023 keyboard and cannot control its state
1024 (Don't attempt to blink the leds)
1025 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1026 i8042.nokbd [HW] Don't check/create keyboard port
1027 i8042.noloop [HW] Disable the AUX Loopback command while probing
1029 i8042.nomux [HW] Don't check presence of an active multiplexing
1031 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1033 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1034 i8042.reset [HW] Reset the controller during init and cleanup
1035 i8042.unlock [HW] Unlock (ignore) the keylock
1039 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1040 indicates that the driver is running on unsupported
1042 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1043 does not match list of supported models.
1045 [HW] Report power status in /proc/i8k
1046 (disabled by default)
1047 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1050 i915.invert_brightness=
1051 [DRM] Invert the sense of the variable that is used to
1052 set the brightness of the panel backlight. Normally a
1053 brightness value of 0 indicates backlight switched off,
1054 and the maximum of the brightness value sets the backlight
1055 to maximum brightness. If this parameter is set to 0
1056 (default) and the machine requires it, or this parameter
1057 is set to 1, a brightness value of 0 sets the backlight
1058 to maximum brightness, and the maximum of the brightness
1059 value switches the backlight off.
1060 -1 -- never invert brightness
1061 0 -- machine default
1062 1 -- force brightness inversion
1065 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1067 ide-core.nodma= [HW] (E)IDE subsystem
1068 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1069 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1070 .cdrom .chs .ignore_cable are additional options
1071 See Documentation/ide/ide.txt.
1073 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1074 Claim all unknown PCI IDE storage controllers.
1077 Format: idle=poll, idle=halt, idle=nomwait
1078 Poll forces a polling idle loop that can slightly
1079 improve the performance of waking up a idle CPU, but
1080 will use a lot of power and make the system run hot.
1082 idle=halt: Halt is forced to be used for CPU idle.
1083 In such case C2/C3 won't be used again.
1084 idle=nomwait: Disable mwait for CPU C-states
1086 ignore_loglevel [KNL]
1087 Ignore loglevel setting - this will print /all/
1088 kernel messages to the console. Useful for debugging.
1089 We also add it as printk module parameter, so users
1090 could change it dynamically, usually by
1091 /sys/module/printk/parameters/ignore_loglevel.
1093 ihash_entries= [KNL]
1094 Set number of hash buckets for inode cache.
1096 ima_appraise= [IMA] appraise integrity measurements
1097 Format: { "off" | "enforce" | "fix" }
1100 ima_appraise_tcb [IMA]
1101 The builtin appraise policy appraises all files
1105 Format: { "0" | "1" }
1106 0 -- integrity auditing messages. (Default)
1107 1 -- enable informational integrity auditing messages.
1110 Format: { "sha1" | "md5" }
1114 Load a policy which meets the needs of the Trusted
1115 Computing Base. This means IMA will measure all
1116 programs exec'd, files mmap'd for exec, and all files
1117 opened for read by uid=0.
1121 Run specified binary instead of /sbin/init as init
1124 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1125 for working out where the kernel is dying during
1128 initrd= [BOOT] Specify the location of the initial ramdisk
1130 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1133 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1135 Enable intel iommu driver.
1137 Disable intel iommu driver.
1138 igfx_off [Default Off]
1139 By default, gfx is mapped as normal device. If a gfx
1140 device has a dedicated DMAR unit, the DMAR unit is
1141 bypassed by not enabling DMAR with this option. In
1142 this case, gfx device will use physical address for
1145 With this option iommu will not optimize to look
1146 for io virtual address below 32-bit forcing dual
1147 address cycle on pci bus for cards supporting greater
1148 than 32-bit addressing. The default is to look
1149 for translation below 32-bit and if not available
1150 then look in the higher range.
1151 strict [Default Off]
1152 With this option on every unmap_single operation will
1153 result in a hardware IOTLB flush operation as opposed
1154 to batching them for performance.
1155 sp_off [Default Off]
1156 By default, super page will be supported if Intel IOMMU
1157 has the capability. With this option, super page will
1160 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1161 0 disables intel_idle and fall back on acpi_idle.
1162 1 to 6 specify maximum depth of C-state.
1166 Do not enable intel_pstate as the default
1167 scaling driver for the supported processors
1169 intremap= [X86-64, Intel-IOMMU]
1170 on enable Interrupt Remapping (default)
1171 off disable Interrupt Remapping
1172 nosid disable Source ID checking
1174 BIOS x2APIC opt-out request will be ignored
1176 iomem= Disable strict checking of access to MMIO memory
1177 strict regions from userspace.
1194 io7= [HW] IO7 for Marvel based alpha systems
1195 See comment before marvel_specify_io7 in
1196 arch/alpha/kernel/core_marvel.c.
1198 io_delay= [X86] I/O delay method
1200 Standard port 0x80 based delay
1202 Alternate port 0xed based delay (needed on some systems)
1204 Simple two microseconds delay
1209 See Documentation/filesystems/nfs/nfsroot.txt.
1211 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1212 See comment before ip2_setup() in
1213 drivers/char/ip2/ip2base.c.
1216 When an interrupt is not handled search all handlers
1217 for it. Intended to get systems with badly broken
1221 When an interrupt is not handled search all handlers
1222 for it. Also check all handlers each timer
1223 interrupt. Intended to get systems with badly broken
1227 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1229 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1231 <cpu number>,...,<cpu number>
1233 <cpu number>-<cpu number>
1234 (must be a positive range in ascending order)
1236 <cpu number>,...,<cpu number>-<cpu number>
1238 This option can be used to specify one or more CPUs
1239 to isolate from the general SMP balancing and scheduling
1240 algorithms. You can move a process onto or off an
1241 "isolated" CPU via the CPU affinity syscalls or cpuset.
1242 <cpu number> begins at 0 and the maximum value is
1243 "number of CPUs in system - 1".
1245 This option is the preferred way to isolate CPUs. The
1246 alternative -- manually setting the CPU mask of all
1247 tasks in the system -- can cause problems and
1248 suboptimal load balancer performance.
1252 js= [HW,JOY] Analog joystick
1253 See Documentation/input/joystick.txt.
1257 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1258 specifies the amount of memory usable by the kernel
1259 for non-movable allocations. The requested amount is
1260 spread evenly throughout all nodes in the system. The
1261 remaining memory in each node is used for Movable
1262 pages. In the event, a node is too small to have both
1263 kernelcore and Movable pages, kernelcore pages will
1264 take priority and other nodes will have a larger number
1265 of kernelcore pages. The Movable zone is used for the
1266 allocation of pages that may be reclaimed or moved
1267 by the page migration subsystem. This means that
1268 HugeTLB pages may not be allocated from this zone.
1269 Note that allocations like PTEs-from-HighMem still
1270 use the HighMem zone if it exists, and the Normal
1271 zone if it does not.
1273 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1274 Format: <Controller#>[,poll interval]
1275 The controller # is the number of the ehci usb debug
1276 port as it is probed via PCI. The poll interval is
1277 optional and is the number seconds in between
1278 each poll cycle to the debug port in case you need
1279 the functionality for interrupting the kernel with
1280 gdb or control-c on the dbgp connection. When
1281 not using this parameter you use sysrq-g to break into
1282 the kernel debugger.
1284 kgdboc= [KGDB,HW] kgdb over consoles.
1285 Requires a tty driver that supports console polling,
1286 or a supported polling keyboard driver (non-usb).
1287 Serial only format: <serial_device>[,baud]
1288 keyboard only format: kbd
1289 keyboard and serial format: kbd,<serial_device>[,baud]
1290 Optional Kernel mode setting:
1291 kms, kbd format: kms,kbd
1292 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1294 kgdbwait [KGDB] Stop kernel execution and enter the
1295 kernel debugger at the earliest opportunity.
1297 kmac= [MIPS] korina ethernet MAC address.
1298 Configure the RouterBoard 532 series on-chip
1299 Ethernet adapter MAC address.
1301 kmemleak= [KNL] Boot-time kmemleak enable/disable
1302 Valid arguments: on, off
1305 kstack=N [X86] Print N words from the kernel stack
1308 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1309 Default is 0 (don't ignore, but inject #GP)
1311 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1315 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1316 Default is 1 (enabled)
1318 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1320 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1322 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1323 (virtualized MMU) support on capable Intel chips.
1324 Default is 1 (enabled)
1326 kvm-intel.emulate_invalid_guest_state=
1327 [KVM,Intel] Enable emulation of invalid guest states
1328 Default is 0 (disabled)
1330 kvm-intel.flexpriority=
1331 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1332 Default is 1 (enabled)
1335 [KVM,Intel] Enable VMX nesting (nVMX).
1336 Default is 0 (disabled)
1338 kvm-intel.unrestricted_guest=
1339 [KVM,Intel] Disable unrestricted guest feature
1340 (virtualized real and unpaged mode) on capable
1341 Intel chips. Default is 1 (enabled)
1343 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1344 feature (tagged TLBs) on capable Intel chips.
1345 Default is 1 (enabled)
1351 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1354 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1355 value for LAPIC timer one-shot implementation. Default
1356 back to the programmable timer unit in the LAPIC.
1358 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1361 libata.dma= [LIBATA] DMA control
1362 libata.dma=0 Disable all PATA and SATA DMA
1363 libata.dma=1 PATA and SATA Disk DMA only
1364 libata.dma=2 ATAPI (CDROM) DMA only
1365 libata.dma=4 Compact Flash DMA only
1366 Combinations also work, so libata.dma=3 enables DMA
1367 for disks and CDROMs, but not CFs.
1369 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1370 libata.ignore_hpa=0 keep BIOS limits (default)
1371 libata.ignore_hpa=1 ignore limits, using full disk
1373 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1377 libata.force= [LIBATA] Force configurations. The format is comma
1378 separated list of "[ID:]VAL" where ID is
1379 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1380 matching port, link or device. Basically, it matches
1381 the ATA ID string printed on console by libata. If
1382 the whole ID part is omitted, the last PORT and DEVICE
1383 values are used. If ID hasn't been specified yet, the
1384 configuration applies to all ports, links and devices.
1386 If only DEVICE is omitted, the parameter applies to
1387 the port and all links and devices behind it. DEVICE
1388 number of 0 either selects the first device or the
1389 first fan-out link behind PMP device. It does not
1390 select the host link. DEVICE number of 15 selects the
1391 host link and device attached to it.
1393 The VAL specifies the configuration to force. As long
1394 as there's no ambiguity shortcut notation is allowed.
1395 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1396 The following configurations can be forced.
1398 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1399 Any ID with matching PORT is used.
1401 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1403 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1404 udma[/][16,25,33,44,66,100,133] notation is also
1407 * [no]ncq: Turn on or off NCQ.
1409 * nohrst, nosrst, norst: suppress hard, soft
1412 * rstonce: only attempt one reset during
1413 hot-unplug link recovery
1415 * dump_id: dump IDENTIFY data.
1417 If there are multiple matching configurations changing
1418 the same attribute, the last one is used.
1420 memblock=debug [KNL] Enable memblock debug messages.
1422 load_ramdisk= [RAM] List of ramdisks to load from floppy
1423 See Documentation/blockdev/ramdisk.txt.
1425 lockd.nlm_grace_period=P [NFS] Assign grace period.
1428 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1431 lockd.nlm_timeout=T [NFS] Assign timeout value.
1434 lockd.nlm_udpport=M [NFS] Assign UDP port.
1437 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1440 loglevel= All Kernel Messages with a loglevel smaller than the
1441 console loglevel will be printed to the console. It can
1442 also be changed with klogd or other programs. The
1443 loglevels are defined as follows:
1445 0 (KERN_EMERG) system is unusable
1446 1 (KERN_ALERT) action must be taken immediately
1447 2 (KERN_CRIT) critical conditions
1448 3 (KERN_ERR) error conditions
1449 4 (KERN_WARNING) warning conditions
1450 5 (KERN_NOTICE) normal but significant condition
1451 6 (KERN_INFO) informational
1452 7 (KERN_DEBUG) debug-level messages
1454 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1455 in bytes. n must be a power of two. The default
1456 size is set in the kernel config file.
1458 logo.nologo [FB] Disables display of the built-in Linux logo.
1459 This may be used to provide more screen space for
1460 kernel log messages and is useful when debugging
1461 kernel boot problems.
1463 lp=0 [LP] Specify parallel ports to use, e.g,
1464 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1465 lp=reset first parallel port). 'lp=0' disables the
1466 lp=auto printer driver. 'lp=reset' (which can be
1467 specified in addition to the ports) causes
1468 attached printers to be reset. Using
1469 lp=port1,port2,... specifies the parallel ports
1470 to associate lp devices with, starting with
1471 lp0. A port specification may be 'none' to skip
1472 that lp device, or a parport name such as
1473 'parport0'. Specifying 'lp=auto' instead of a
1474 port specification list means that device IDs
1475 from each port should be examined, to see if
1476 an IEEE 1284-compliant printer is attached; if
1477 so, the driver will manage that printer.
1478 See also header of drivers/char/lp.c.
1481 Sets loops_per_jiffy to given constant, thus avoiding
1482 time-consuming boot-time autodetection (up to 250 ms per
1483 CPU). 0 enables autodetection (default). To determine
1484 the correct value for your kernel, boot with normal
1485 autodetection and see what value is printed. Note that
1486 on SMP systems the preset will be applied to all CPUs,
1487 which is likely to cause problems if your CPUs need
1488 significantly divergent settings. An incorrect value
1489 will cause delays in the kernel to be wrong, leading to
1490 unpredictable I/O errors and other breakage. Although
1491 unlikely, in the extreme case this might damage your
1495 Format: <io>,<irq>,<dma>
1497 machvec= [IA-64] Force the use of a particular machine-vector
1498 (machvec) in a generic kernel.
1499 Example: machvec=hpzx1_swiotlb
1501 machtype= [Loongson] Share the same kernel image file between different
1503 Example: machtype=lemote-yeeloong-2f-7inch
1505 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1506 than or equal to this physical address is ignored.
1508 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1509 should make use of. maxcpus=n : n >= 0 limits the
1510 kernel to using 'n' processors. n=0 is a special case,
1511 it is equivalent to "nosmp", which also disables
1514 max_loop= [LOOP] The number of loop block devices that get
1515 (loop.max_loop) unconditionally pre-created at init time. The default
1516 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1517 of statically allocating a predefined number, loop
1518 devices can be requested on-demand with the
1519 /dev/loop-control interface.
1521 mce [X86-32] Machine Check Exception
1523 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1525 md= [HW] RAID subsystems devices and level
1526 See Documentation/md.txt.
1529 Format: <first>,<last>
1530 Specifies range of consoles to be captured by the MDA.
1532 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1533 Amount of memory to be used when the kernel is not able
1534 to see the whole system memory or for test.
1535 [X86] Work as limiting max address. Use together
1536 with memmap= to avoid physical address space collisions.
1537 Without memmap= PCI devices could be placed at addresses
1538 belonging to unused RAM.
1540 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1544 [KNL,SH] Allow user to override the default size for
1545 per-device physically contiguous DMA buffers.
1547 memmap=exactmap [KNL,X86] Enable setting of an exact
1548 E820 memory map, as specified by the user.
1549 Such memmap=exactmap lines can be constructed based on
1550 BIOS output or other requirements. See the memmap=nn@ss
1553 memmap=nn[KMG]@ss[KMG]
1554 [KNL] Force usage of a specific region of memory
1555 Region of memory to be used, from ss to ss+nn.
1557 memmap=nn[KMG]#ss[KMG]
1558 [KNL,ACPI] Mark specific memory as ACPI data.
1559 Region of memory to be used, from ss to ss+nn.
1561 memmap=nn[KMG]$ss[KMG]
1562 [KNL,ACPI] Mark specific memory as reserved.
1563 Region of memory to be used, from ss to ss+nn.
1564 Example: Exclude memory from 0x18690000-0x1869ffff
1565 memmap=64K$0x18690000
1567 memmap=0x10000$0x18690000
1569 memory_corruption_check=0/1 [X86]
1570 Some BIOSes seem to corrupt the first 64k of
1571 memory when doing things like suspend/resume.
1572 Setting this option will scan the memory
1573 looking for corruption. Enabling this will
1574 both detect corruption and prevent the kernel
1575 from using the memory being corrupted.
1576 However, its intended as a diagnostic tool; if
1577 repeatable BIOS-originated corruption always
1578 affects the same memory, you can use memmap=
1579 to prevent the kernel from using that memory.
1581 memory_corruption_check_size=size [X86]
1582 By default it checks for corruption in the low
1583 64k, making this memory unavailable for normal
1584 use. Use this parameter to scan for
1585 corruption in more or less memory.
1587 memory_corruption_check_period=seconds [X86]
1588 By default it checks for corruption every 60
1589 seconds. Use this parameter to check at some
1590 other rate. 0 disables periodic checking.
1592 memtest= [KNL,X86] Enable memtest
1594 default : 0 <disable>
1595 Specifies the number of memtest passes to be
1596 performed. Each pass selects another test
1597 pattern from a given set of patterns. Memtest
1598 fills the memory with this pattern, validates
1599 memory contents and reserves bad memory
1600 regions that are detected.
1602 meye.*= [HW] Set MotionEye Camera parameters
1603 See Documentation/video4linux/meye.txt.
1605 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1606 Multi-Function General Purpose Timers on AMD Geode
1609 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1610 the BIOS has incorrectly applied a workaround. TinyBIOS
1611 version 0.98 is known to be affected, 0.99 fixes the
1612 problem by letting the user disable the workaround.
1616 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1617 physical address is ignored.
1619 mini2440= [ARM,HW,KNL]
1620 Format:[0..2][b][c][t]
1622 MINI2440 configuration specification:
1623 0 - The attached screen is the 3.5" TFT
1624 1 - The attached screen is the 7" TFT
1625 2 - The VGA Shield is attached (1024x768)
1626 Leaving out the screen size parameter will not load
1627 the TFT driver, and the framebuffer will be left
1629 b - Enable backlight. The TFT backlight pin will be
1630 linked to the kernel VESA blanking code and a GPIO
1631 LED. This parameter is not necessary when using the
1633 c - Enable the s3c camera interface.
1634 t - Reserved for enabling touchscreen support. The
1635 touchscreen support is not enabled in the mainstream
1636 kernel as of 2.6.30, a preliminary port can be found
1637 in the "bleeding edge" mini2440 support kernel at
1638 http://repo.or.cz/w/linux-2.6/mini2440.git
1641 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1642 parameter allows control of the logging verbosity for
1643 the additional memory initialisation checks. A value
1644 of 0 disables mminit logging and a level of 4 will
1645 log everything. Information is printed at KERN_DEBUG
1646 so loglevel=8 may also need to be specified.
1649 [KNL] When CONFIG_MODULE_SIG is set, this means that
1650 modules without (valid) signatures will fail to load.
1651 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1652 is always true, so this option does nothing.
1655 [MOUSE] Maximum time between finger touching and
1656 leaving touchpad surface for touch to be considered
1657 a tap and be reported as a left button click (for
1658 touchpads working in absolute mode only).
1660 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1661 reporting absolute coordinates, such as tablets
1662 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1663 reporting absolute coordinates, such as tablets
1665 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1666 is similar to kernelcore except it specifies the
1667 amount of memory used for migratable allocations.
1668 If both kernelcore and movablecore is specified,
1669 then kernelcore will be at *least* the specified
1670 value but may be more. If movablecore on its own
1671 is specified, the administrator must be careful
1672 that the amount of memory usable for all allocations
1675 MTD_Partition= [MTD]
1676 Format: <name>,<region-number>,<size>,<offset>
1678 MTD_Region= [MTD] Format:
1679 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1682 See drivers/mtd/cmdlinepart.c.
1684 multitce=off [PPC] This parameter disables the use of the pSeries
1685 firmware feature for updating multiple TCE entries
1688 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1690 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1692 boundary - index of last SLC block on Flex-OneNAND.
1693 The remaining blocks are configured as MLC blocks.
1694 lock - Configure if Flex-OneNAND boundary should be locked.
1695 Once locked, the boundary cannot be changed.
1696 1 indicates lock status, 0 indicates unlock status.
1699 ARM/S3C2412 JIVE boot control
1701 See arch/arm/mach-s3c2412/mach-jive.c
1703 mtouchusb.raw_coordinates=
1704 [HW] Make the MicroTouch USB driver use raw coordinates
1705 ('y', default) or cooked coordinates ('n')
1707 mtrr_chunk_size=nn[KMG] [X86]
1708 used for mtrr cleanup. It is largest continuous chunk
1709 that could hold holes aka. UC entries.
1711 mtrr_gran_size=nn[KMG] [X86]
1712 Used for mtrr cleanup. It is granularity of mtrr block.
1714 Large value could prevent small alignment from
1717 mtrr_spare_reg_nr=n [X86]
1719 Range: 0,7 : spare reg number
1721 Used for mtrr cleanup. It is spare mtrr entries number.
1722 Set to 2 or more if your graphical card needs more.
1724 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1726 netdev= [NET] Network devices parameters
1727 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1728 Note that mem_start is often overloaded to mean
1729 something different and driver-specific.
1730 This usage is only documented in each driver source
1734 [NETFILTER] Enable connection tracking flow accounting
1735 0 to disable accounting
1736 1 to enable accounting
1739 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1740 See Documentation/filesystems/nfs/nfsroot.txt.
1742 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1743 See Documentation/filesystems/nfs/nfsroot.txt.
1745 nfsrootdebug [NFS] enable nfsroot debugging messages.
1746 See Documentation/filesystems/nfs/nfsroot.txt.
1748 nfs.callback_tcpport=
1749 [NFS] set the TCP port on which the NFSv4 callback
1750 channel should listen.
1753 [NFS] sets the pathname to the program which is used
1754 to update the NFS client cache entries.
1756 nfs.cache_getent_timeout=
1757 [NFS] sets the timeout after which an attempt to
1758 update a cache entry is deemed to have failed.
1760 nfs.idmap_cache_timeout=
1761 [NFS] set the maximum lifetime for idmapper cache
1765 [NFS] enable 64-bit inode numbers.
1766 If zero, the NFS client will fake up a 32-bit inode
1767 number for the readdir() and stat() syscalls instead
1768 of returning the full 64-bit number.
1769 The default is to return 64-bit inode numbers.
1771 nfs.max_session_slots=
1772 [NFSv4.1] Sets the maximum number of session slots
1773 the client will attempt to negotiate with the server.
1774 This limits the number of simultaneous RPC requests
1775 that the client can send to the NFSv4.1 server.
1776 Note that there is little point in setting this
1777 value higher than the max_tcp_slot_table_limit.
1779 nfs.nfs4_disable_idmapping=
1780 [NFSv4] When set to the default of '1', this option
1781 ensures that both the RPC level authentication
1782 scheme and the NFS level operations agree to use
1783 numeric uids/gids if the mount is using the
1784 'sec=sys' security flavour. In effect it is
1785 disabling idmapping, which can make migration from
1786 legacy NFSv2/v3 systems to NFSv4 easier.
1787 Servers that do not support this mode of operation
1788 will be autodetected by the client, and it will fall
1789 back to using the idmapper.
1790 To turn off this behaviour, set the value to '0'.
1792 [NFS4] Specify an additional fixed unique ident-
1793 ification string that NFSv4 clients can insert into
1794 their nfs_client_id4 string. This is typically a
1795 UUID that is generated at system install time.
1797 nfs.send_implementation_id =
1798 [NFSv4.1] Send client implementation identification
1799 information in exchange_id requests.
1800 If zero, no implementation identification information
1802 The default is to send the implementation identification
1805 nfsd.nfs4_disable_idmapping=
1806 [NFSv4] When set to the default of '1', the NFSv4
1807 server will return only numeric uids and gids to
1808 clients using auth_sys, and will accept numeric uids
1809 and gids from such clients. This is intended to ease
1810 migration from NFSv2/v3.
1812 objlayoutdriver.osd_login_prog=
1813 [NFS] [OBJLAYOUT] sets the pathname to the program which
1814 is used to automatically discover and login into new
1815 osd-targets. Please see:
1816 Documentation/filesystems/pnfs.txt for more explanations
1818 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1819 when a NMI is triggered.
1820 Format: [state][,regs][,debounce][,die]
1822 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1823 Format: [panic,][nopanic,][num]
1825 0 - turn nmi_watchdog off
1826 When panic is specified, panic when an NMI watchdog
1827 timeout occurs (or 'nopanic' to override the opposite
1829 This is useful when you use a panic=... timeout and
1830 need the box quickly up again.
1832 netpoll.carrier_timeout=
1833 [NET] Specifies amount of time (in seconds) that
1834 netpoll should wait for a carrier. By default netpoll
1837 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1838 emulation library even if a 387 maths coprocessor
1842 [HW] Never suspend the console
1843 Disable suspending of consoles during suspend and
1844 hibernate operations. Once disabled, debugging
1845 messages can reach various consoles while the rest
1846 of the system is being put to sleep (ie, while
1847 debugging driver suspend/resume hooks). This may
1848 not work reliably with all consoles, but is known
1849 to work with serial and VGA consoles.
1850 To facilitate more flexible debugging, we also add
1851 console_suspend, a printk module parameter to control
1852 it. Users could use console_suspend (usually
1853 /sys/module/printk/parameters/console_suspend) to
1854 turn on/off it dynamically.
1856 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1857 caches in the slab allocator. Saves per-node memory,
1858 but will impact performance.
1862 noapic [SMP,APIC] Tells the kernel to not make use of any
1863 IOAPICs that may be present in the system.
1865 noautogroup Disable scheduler automatic task group creation.
1867 nobats [PPC] Do not use BATs for mapping kernel lowmem
1868 on "Classic" PPC cores.
1872 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1874 nodelayacct [KNL] Disable per-task delay accounting
1876 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1878 nodsp [SH] Disable hardware DSP at boot time.
1880 noefi [X86] Disable EFI runtime services support.
1885 On X86-32 available only on PAE configured kernels.
1886 noexec=on: enable non-executable mappings (default)
1887 noexec=off: disable non-executable mappings
1890 Disable SMAP (Supervisor Mode Access Prevention)
1891 even if it is supported by processor.
1894 Disable SMEP (Supervisor Mode Execution Prevention)
1895 even if it is supported by processor.
1898 This affects only 32-bit executables.
1899 noexec32=on: enable non-executable mappings (default)
1900 read doesn't imply executable mappings
1901 noexec32=off: disable non-executable mappings
1902 read implies executable mappings
1904 nofpu [SH] Disable hardware FPU at boot time.
1906 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1907 register save and restore. The kernel will only save
1908 legacy floating-point registers on task switch.
1910 noxsave [BUGS=X86] Disables x86 extended register state save
1911 and restore using xsave. The kernel will fallback to
1912 enabling legacy floating-point and sse state.
1915 on enable eager fpu restore
1916 off disable eager fpu restore
1917 auto selects the default scheme, which automatically
1918 enables eagerfpu restore for xsaveopt.
1920 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1921 wfi(ARM) instruction doesn't work correctly and not to
1922 use it. This is also useful when using JTAG debugger.
1924 no_file_caps Tells the kernel not to honor file capabilities. The
1925 only way then for a file to be executed with privilege
1926 is to be setuid root or executed by root.
1928 nohalt [IA-64] Tells the kernel not to use the power saving
1929 function PAL_HALT_LIGHT when idle. This increases
1930 power-consumption. On the positive side, it reduces
1931 interrupt wake-up latency, which may improve performance
1932 in certain environments such as networked servers or
1935 nohz= [KNL] Boottime enable/disable dynamic ticks
1936 Valid arguments: on, off
1939 noiotrap [SH] Disables trapped I/O port accesses.
1941 noirqdebug [X86-32] Disables the code which attempts to detect and
1942 disable unhandled interrupt sources.
1944 no_timer_check [X86,APIC] Disables the code which tests for
1945 broken timer IRQ sources.
1947 noisapnp [ISAPNP] Disables ISA PnP code.
1949 noinitrd [RAM] Tells the kernel not to load any configured
1952 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1954 [Deprecated - use intremap=off]
1958 nojitter [IA-64] Disables jitter checking for ITC timers.
1960 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1962 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1965 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1966 steal time is computed, but won't influence scheduler
1969 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1971 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1973 noltlbs [PPC] Do not use large page/tlb entries for kernel
1974 lowmem mapping on PPC40x.
1976 nomca [IA-64] Disable machine check abort handling
1978 nomce [X86-32] Machine Check Exception
1980 nomfgpt [X86-32] Disable Multi-Function General Purpose
1981 Timer usage (for AMD Geode machines).
1983 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1984 shutdown the other cpus. Instead use the REBOOT_VECTOR
1987 nomodule Disable module load
1989 nopat [X86] Disable PAT (page attribute table extension of
1990 pagetables) support.
1992 norandmaps Don't use address space randomization. Equivalent to
1993 echo 0 > /proc/sys/kernel/randomize_va_space
1995 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1997 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1998 with UP alternatives
2000 noresidual [PPC] Don't use residual data on PReP machines.
2002 nordrand [X86] Disable the direct use of the RDRAND
2003 instruction even if it is supported by the
2004 processor. RDRAND is still available to user
2007 noresume [SWSUSP] Disables resume and restores original swap
2010 no-scroll [VGA] Disables scrollback.
2011 This is required for the Braillex ib80-piezo Braille
2012 reader made by F.H. Papenmeier (Germany).
2016 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2018 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2019 and disable the IO APIC. legacy for "maxcpus=0".
2021 nosoftlockup [KNL] Disable the soft-lockup detector.
2023 nosync [HW,M68K] Disables sync negotiation for all devices.
2025 notsc [BUGS=X86-32] Disable Time Stamp Counter
2027 nousb [USB] Disable the USB subsystem
2029 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2033 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2035 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2036 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2037 Some features depend on CPU0. Known dependencies are:
2038 1. Resume from suspend/hibernate depends on CPU0.
2039 Suspend/hibernate will fail if CPU0 is offline and you
2040 need to online CPU0 before suspend/hibernate.
2041 2. PIC interrupts also depend on CPU0. CPU0 can't be
2042 removed if a PIC interrupt is detected.
2043 It's said poweroff/reboot may depend on CPU0 on some
2044 machines although I haven't seen such issues so far
2045 after CPU0 is offline on a few tested machines.
2046 If the dependencies are under your control, you can
2047 turn on cpu0_hotplug.
2049 nptcg= [IA-64] Override max number of concurrent global TLB
2050 purges which is reported from either PAL_VM_SUMMARY or
2053 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2054 could support. nr_cpus=n : n >= 1 limits the kernel to
2055 supporting 'n' processors. Later in runtime you can not
2056 use hotplug cpu feature to put more cpu back to online.
2057 just like you compile the kernel NR_CPUS=n
2059 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2061 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2062 Allowed values are enable and disable
2064 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2065 one of ['zone', 'node', 'default'] can be specified
2066 This can be set from sysctl after boot.
2067 See Documentation/sysctl/vm.txt for details.
2069 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2070 See Documentation/debugging-via-ohci1394.txt for more
2073 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2074 Rather than timing out after 20 ms if an EC
2075 command is not properly ACKed, override the length
2076 of the timeout. We have interrupts disabled while
2077 waiting for the ACK, so if this is set too high
2078 interrupts *may* be lost!
2080 omap_mux= [OMAP] Override bootloader pin multiplexing.
2081 Format: <mux_mode0.mode_name=value>...
2082 For example, to override I2C bus2:
2083 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2085 oprofile.timer= [HW]
2086 Use timer interrupt instead of performance counters
2088 oprofile.cpu_type= Force an oprofile cpu type
2089 This might be useful if you have an older oprofile
2090 userland or if you want common events.
2091 Format: { arch_perfmon }
2092 arch_perfmon: [X86] Force use of architectural
2093 perfmon on Intel CPUs instead of the
2094 CPU specific event set.
2095 timer: [X86] Force use of architectural NMI
2096 timer mode (see also oprofile.timer
2097 for generic hr timer mode)
2098 [s390] Force legacy basic mode sampling
2099 (report cpu_type "timer")
2101 oops=panic Always panic on oopses. Default is to just kill the
2102 process, but there is a small probability of
2103 deadlocking the machine.
2104 This will also cause panics on machine check exceptions.
2105 Useful together with panic=30 to trigger a reboot.
2108 See Documentation/sound/oss/oss-parameters.txt
2110 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2111 timeout > 0: seconds before rebooting
2112 timeout = 0: wait forever
2113 timeout < 0: reboot immediately
2116 parkbd.port= [HW] Parallel port number the keyboard adapter is
2117 connected to, default is 0.
2119 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2120 0 for XT, 1 for AT (default is AT).
2123 parport= [HW,PPT] Specify parallel ports. 0 disables.
2124 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2125 Use 'auto' to force the driver to use any
2126 IRQ/DMA settings detected (the default is to
2127 ignore detected IRQ/DMA settings because of
2128 possible conflicts). You can specify the base
2129 address, IRQ, and DMA settings; IRQ and DMA
2130 should be numbers, or 'auto' (for using detected
2131 settings on that particular port), or 'nofifo'
2132 (to avoid using a FIFO even if it is detected).
2133 Parallel ports are assigned in the order they
2134 are specified on the command line, starting
2137 parport_init_mode= [HW,PPT]
2138 Configure VIA parallel port to operate in
2139 a specific mode. This is necessary on Pegasos
2140 computer where firmware has no options for setting
2141 up parallel port mode and sets it to spp.
2142 Currently this function knows 686a and 8231 chips.
2143 Format: [spp|ps2|epp|ecp|ecpepp]
2146 Halt all CPUs after the first oops has been printed for
2147 the specified number of seconds. This is to be used if
2148 your oopses keep scrolling off the screen.
2153 See header of drivers/block/paride/pcd.c.
2154 See also Documentation/blockdev/paride.txt.
2156 pci=option[,option...] [PCI] various PCI subsystem options:
2157 earlydump [X86] dump PCI config space before the kernel
2159 off [X86] don't probe for the PCI bus
2160 bios [X86-32] force use of PCI BIOS, don't access
2161 the hardware directly. Use this if your machine
2162 has a non-standard PCI host bridge.
2163 nobios [X86-32] disallow use of PCI BIOS, only direct
2164 hardware access methods are allowed. Use this
2165 if you experience crashes upon bootup and you
2166 suspect they are caused by the BIOS.
2167 conf1 [X86] Force use of PCI Configuration
2169 conf2 [X86] Force use of PCI Configuration
2171 noaer [PCIE] If the PCIEAER kernel config parameter is
2172 enabled, this kernel boot option can be used to
2173 disable the use of PCIE advanced error reporting.
2174 nodomains [PCI] Disable support for multiple PCI
2175 root domains (aka PCI segments, in ACPI-speak).
2176 nommconf [X86] Disable use of MMCONFIG for PCI
2178 check_enable_amd_mmconf [X86] check for and enable
2179 properly configured MMIO access to PCI
2180 config space on AMD family 10h CPU
2181 nomsi [MSI] If the PCI_MSI kernel config parameter is
2182 enabled, this kernel boot option can be used to
2183 disable the use of MSI interrupts system-wide.
2184 noioapicquirk [APIC] Disable all boot interrupt quirks.
2185 Safety option to keep boot IRQs enabled. This
2186 should never be necessary.
2187 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2188 primary IO-APIC for bridges that cannot disable
2189 boot IRQs. This fixes a source of spurious IRQs
2190 when the system masks IRQs.
2191 noioapicreroute [APIC] Disable workaround that uses the
2192 boot IRQ equivalent of an IRQ that connects to
2193 a chipset where boot IRQs cannot be disabled.
2194 The opposite of ioapicreroute.
2195 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2196 routing table. These calls are known to be buggy
2197 on several machines and they hang the machine
2198 when used, but on other computers it's the only
2199 way to get the interrupt routing table. Try
2200 this option if the kernel is unable to allocate
2201 IRQs or discover secondary PCI buses on your
2203 rom [X86] Assign address space to expansion ROMs.
2204 Use with caution as certain devices share
2205 address decoders between ROMs and other
2207 norom [X86] Do not assign address space to
2208 expansion ROMs that do not already have
2209 BIOS assigned address ranges.
2210 nobar [X86] Do not assign address space to the
2211 BARs that weren't assigned by the BIOS.
2212 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2213 assigned automatically to PCI devices. You can
2214 make the kernel exclude IRQs of your ISA cards
2216 pirqaddr=0xAAAAA [X86] Specify the physical address
2217 of the PIRQ table (normally generated
2218 by the BIOS) if it is outside the
2219 F0000h-100000h range.
2220 lastbus=N [X86] Scan all buses thru bus #N. Can be
2221 useful if the kernel is unable to find your
2222 secondary buses and you want to tell it
2223 explicitly which ones they are.
2224 assign-busses [X86] Always assign all PCI bus
2225 numbers ourselves, overriding
2226 whatever the firmware may have done.
2227 usepirqmask [X86] Honor the possible IRQ mask stored
2228 in the BIOS $PIR table. This is needed on
2229 some systems with broken BIOSes, notably
2230 some HP Pavilion N5400 and Omnibook XE3
2231 notebooks. This will have no effect if ACPI
2232 IRQ routing is enabled.
2233 noacpi [X86] Do not use ACPI for IRQ routing
2234 or for PCI scanning.
2235 use_crs [X86] Use PCI host bridge window information
2236 from ACPI. On BIOSes from 2008 or later, this
2237 is enabled by default. If you need to use this,
2238 please report a bug.
2239 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2240 If you need to use this, please report a bug.
2241 routeirq Do IRQ routing for all PCI devices.
2242 This is normally done in pci_enable_device(),
2243 so this option is a temporary workaround
2244 for broken drivers that don't call it.
2245 skip_isa_align [X86] do not align io start addr, so can
2246 handle more pci cards
2247 firmware [ARM] Do not re-enumerate the bus but instead
2248 just use the configuration from the
2249 bootloader. This is currently used on
2250 IXP2000 systems where the bus has to be
2251 configured a certain way for adjunct CPUs.
2252 noearly [X86] Don't do any early type 1 scanning.
2253 This might help on some broken boards which
2254 machine check when some devices' config space
2255 is read. But various workarounds are disabled
2256 and some IOMMU drivers will not work.
2257 bfsort Sort PCI devices into breadth-first order.
2258 This sorting is done to get a device
2259 order compatible with older (<= 2.4) kernels.
2260 nobfsort Don't sort PCI devices into breadth-first order.
2261 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2262 tuning and use the BIOS-configured MPS defaults.
2263 pcie_bus_safe Set every device's MPS to the largest value
2264 supported by all devices below the root complex.
2265 pcie_bus_perf Set device MPS to the largest allowable MPS
2266 based on its parent bus. Also set MRRS (Max
2267 Read Request Size) to the largest supported
2268 value (no larger than the MPS that the device
2269 or bus can support) for best performance.
2270 pcie_bus_peer2peer Set every device's MPS to 128B, which
2271 every device is guaranteed to support. This
2272 configuration allows peer-to-peer DMA between
2273 any pair of devices, possibly at the cost of
2274 reduced performance. This also guarantees
2275 that hot-added devices will work.
2276 cbiosize=nn[KMG] The fixed amount of bus space which is
2277 reserved for the CardBus bridge's IO window.
2278 The default value is 256 bytes.
2279 cbmemsize=nn[KMG] The fixed amount of bus space which is
2280 reserved for the CardBus bridge's memory
2281 window. The default value is 64 megabytes.
2284 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2285 Specifies alignment and device to reassign
2286 aligned memory resources.
2287 If <order of align> is not specified,
2288 PAGE_SIZE is used as alignment.
2289 PCI-PCI bridge can be specified, if resource
2290 windows need to be expanded.
2291 ecrc= Enable/disable PCIe ECRC (transaction layer
2292 end-to-end CRC checking).
2293 bios: Use BIOS/firmware settings. This is the
2297 hpiosize=nn[KMG] The fixed amount of bus space which is
2298 reserved for hotplug bridge's IO window.
2299 Default size is 256 bytes.
2300 hpmemsize=nn[KMG] The fixed amount of bus space which is
2301 reserved for hotplug bridge's memory window.
2302 Default size is 2 megabytes.
2303 realloc= Enable/disable reallocating PCI bridge resources
2304 if allocations done by BIOS are too small to
2305 accommodate resources required by all child
2307 off: Turn realloc off
2309 realloc same as realloc=on
2310 noari do not use PCIe ARI.
2311 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2312 only look for one device below a PCIe downstream
2315 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2318 force Enable ASPM even on devices that claim not to support it.
2319 WARNING: Forcing ASPM on may cause system lockups.
2321 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2322 nomsi Do not use MSI for PCI Express Native Hotplug (this
2323 makes all PCIe ports use INTx for hotplug services).
2325 pcie_ports= [PCIE] PCIe ports handling:
2326 auto Ask the BIOS whether or not to use native PCIe services
2327 associated with PCIe ports (PME, hot-plug, AER). Use
2328 them only if that is allowed by the BIOS.
2329 native Use native PCIe services associated with PCIe ports
2331 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2334 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2335 nomsi Do not use MSI for native PCIe PME signaling (this makes
2336 all PCIe root ports use INTx for all services).
2338 pcmv= [HW,PCMCIA] BadgePAD 4
2341 See Documentation/blockdev/paride.txt.
2343 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2346 See arch/parisc/kernel/pdc_chassis.c
2348 percpu_alloc= Select which percpu first chunk allocator to use.
2349 Currently supported values are "embed" and "page".
2350 Archs may support subset or none of the selections.
2351 See comments in mm/percpu.c for details on each
2352 allocator. This parameter is primarily for debugging
2353 and performance comparison.
2356 See Documentation/blockdev/paride.txt.
2359 See Documentation/blockdev/paride.txt.
2361 pirq= [SMP,APIC] Manual mp-table setup
2362 See Documentation/x86/i386/IO-APIC.txt.
2364 plip= [PPT,NET] Parallel port network link
2365 Format: { parport<nr> | timid | 0 }
2366 See also Documentation/parport.txt.
2368 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2369 Override pmtimer IOPort with a hex value.
2373 Enable PNP debug messages (depends on the
2374 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2375 via /sys/module/pnp/parameters/debug. We always show
2376 current resource usage; turning this on also shows
2377 possible settings and some assignment information.
2383 { on | off | curr | res | no-curr | no-res }
2386 [ISAPNP] Exclude IRQs for the autoconfiguration
2389 [ISAPNP] Exclude DMAs for the autoconfiguration
2391 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2392 Ranges are in pairs (I/O port base and size).
2395 [ISAPNP] Exclude memory regions for the
2397 Ranges are in pairs (memory base and size).
2399 ports= [IP_VS_FTP] IPVS ftp helper module
2401 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2403 Format: <port>,<port>....
2405 print-fatal-signals=
2406 [KNL] debug: print fatal signals
2408 If enabled, warn about various signal handling
2409 related application anomalies: too many signals,
2410 too many POSIX.1 timers, fatal signals causing a
2413 If you hit the warning due to signal overflow,
2414 you might want to try "ulimit -i unlimited".
2418 printk.always_kmsg_dump=
2419 Trigger kmsg_dump for cases other than kernel oops or
2421 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2424 printk.time= Show timing data prefixed to each printk message line
2425 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2427 processor.max_cstate= [HW,ACPI]
2428 Limit processor to maximum C-state
2429 max_cstate=9 overrides any DMI blacklist limit.
2431 processor.nocst [HW,ACPI]
2432 Ignore the _CST method to determine C-states,
2433 instead using the legacy FADT method
2435 profile= [KNL] Enable kernel profiling via /proc/profile
2436 Format: [schedule,]<number>
2437 Param: "schedule" - profile schedule points.
2438 Param: <number> - step/bucket size as a power of 2 for
2439 statistical time based profiling.
2440 Param: "sleep" - profile D-state sleeping (millisecs).
2441 Requires CONFIG_SCHEDSTATS
2442 Param: "kvm" - profile VM exits.
2444 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2446 See Documentation/blockdev/ramdisk.txt.
2448 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2449 probe for; one of (bare|imps|exps|lifebook|any).
2450 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2452 psmouse.resetafter= [HW,MOUSE]
2453 Try to reset the device after so many bad packets
2456 [HW,MOUSE] Set desired mouse resolution, in dpi.
2457 psmouse.smartscroll=
2458 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2459 0 = disabled, 1 = enabled (default).
2461 pstore.backend= Specify the name of the pstore backend to use
2464 See Documentation/blockdev/paride.txt.
2467 [KNL] Number of legacy pty's. Overwrites compiled-in
2470 quiet [KNL] Disable most log messages
2475 See Documentation/md.txt.
2477 ramdisk_blocksize= [RAM]
2478 See Documentation/blockdev/ramdisk.txt.
2480 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2481 See Documentation/blockdev/ramdisk.txt.
2483 rcu_nocbs= [KNL,BOOT]
2484 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2485 the specified list of CPUs to be no-callback CPUs.
2486 Invocation of these CPUs' RCU callbacks will
2487 be offloaded to "rcuoN" kthreads created for
2488 that purpose. This reduces OS jitter on the
2489 offloaded CPUs, which can be useful for HPC and
2490 real-time workloads. It can also improve energy
2491 efficiency for asymmetric multiprocessors.
2493 rcu_nocb_poll [KNL,BOOT]
2494 Rather than requiring that offloaded CPUs
2495 (specified by rcu_nocbs= above) explicitly
2496 awaken the corresponding "rcuoN" kthreads,
2497 make these kthreads poll for callbacks.
2498 This improves the real-time response for the
2499 offloaded CPUs by relieving them of the need to
2500 wake up the corresponding kthread, but degrades
2501 energy efficiency by requiring that the kthreads
2502 periodically wake up to do the polling.
2504 rcutree.blimit= [KNL,BOOT]
2505 Set maximum number of finished RCU callbacks to process
2508 rcutree.fanout_leaf= [KNL,BOOT]
2509 Increase the number of CPUs assigned to each
2510 leaf rcu_node structure. Useful for very large
2513 rcutree.qhimark= [KNL,BOOT]
2514 Set threshold of queued
2515 RCU callbacks over which batch limiting is disabled.
2517 rcutree.qlowmark= [KNL,BOOT]
2518 Set threshold of queued RCU callbacks below which
2519 batch limiting is re-enabled.
2521 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2522 Suppress RCU CPU stall warning messages.
2524 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2525 Set timeout for RCU CPU stall warning messages.
2527 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2528 Set delay from grace-period initialization to
2529 first attempt to force quiescent states.
2530 Units are jiffies, minimum value is zero,
2531 and maximum value is HZ.
2533 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2534 Set delay between subsequent attempts to force
2535 quiescent states. Units are jiffies, minimum
2536 value is one, and maximum value is HZ.
2538 rcutorture.fqs_duration= [KNL,BOOT]
2539 Set duration of force_quiescent_state bursts.
2541 rcutorture.fqs_holdoff= [KNL,BOOT]
2542 Set holdoff time within force_quiescent_state bursts.
2544 rcutorture.fqs_stutter= [KNL,BOOT]
2545 Set wait time between force_quiescent_state bursts.
2547 rcutorture.irqreader= [KNL,BOOT]
2548 Test RCU readers from irq handlers.
2550 rcutorture.n_barrier_cbs= [KNL,BOOT]
2551 Set callbacks/threads for rcu_barrier() testing.
2553 rcutorture.nfakewriters= [KNL,BOOT]
2554 Set number of concurrent RCU writers. These just
2555 stress RCU, they don't participate in the actual
2556 test, hence the "fake".
2558 rcutorture.nreaders= [KNL,BOOT]
2559 Set number of RCU readers.
2561 rcutorture.onoff_holdoff= [KNL,BOOT]
2562 Set time (s) after boot for CPU-hotplug testing.
2564 rcutorture.onoff_interval= [KNL,BOOT]
2565 Set time (s) between CPU-hotplug operations, or
2566 zero to disable CPU-hotplug testing.
2568 rcutorture.shuffle_interval= [KNL,BOOT]
2569 Set task-shuffle interval (s). Shuffling tasks
2570 allows some CPUs to go into dyntick-idle mode
2571 during the rcutorture test.
2573 rcutorture.shutdown_secs= [KNL,BOOT]
2574 Set time (s) after boot system shutdown. This
2575 is useful for hands-off automated testing.
2577 rcutorture.stall_cpu= [KNL,BOOT]
2578 Duration of CPU stall (s) to test RCU CPU stall
2579 warnings, zero to disable.
2581 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2582 Time to wait (s) after boot before inducing stall.
2584 rcutorture.stat_interval= [KNL,BOOT]
2585 Time (s) between statistics printk()s.
2587 rcutorture.stutter= [KNL,BOOT]
2588 Time (s) to stutter testing, for example, specifying
2589 five seconds causes the test to run for five seconds,
2590 wait for five seconds, and so on. This tests RCU's
2591 ability to transition abruptly to and from idle.
2593 rcutorture.test_boost= [KNL,BOOT]
2594 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2595 "Maybe" means test if the RCU implementation
2596 under test support RCU priority boosting.
2598 rcutorture.test_boost_duration= [KNL,BOOT]
2599 Duration (s) of each individual boost test.
2601 rcutorture.test_boost_interval= [KNL,BOOT]
2602 Interval (s) between each boost test.
2604 rcutorture.test_no_idle_hz= [KNL,BOOT]
2605 Test RCU's dyntick-idle handling. See also the
2606 rcutorture.shuffle_interval parameter.
2608 rcutorture.torture_type= [KNL,BOOT]
2609 Specify the RCU implementation to test.
2611 rcutorture.verbose= [KNL,BOOT]
2612 Enable additional printk() statements.
2616 Run specified binary instead of /init from the ramdisk,
2617 used for early userspace startup. See initrd.
2619 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2620 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2621 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2624 [KNL, SMP] Set scheduler's default relax_domain_level.
2625 See Documentation/cgroups/cpusets.txt.
2627 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2629 reservetop= [X86-32]
2631 Reserves a hole at the top of the kernel virtual
2636 Set the amount of memory to reserve for BIOS at
2637 the bottom of the address space.
2639 reset_devices [KNL] Force drivers to reset the underlying device
2640 during initialization.
2643 Specify the partition device for software suspend
2645 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2647 resume_offset= [SWSUSP]
2648 Specify the offset from the beginning of the partition
2649 given by "resume=" at which the swap header is located,
2650 in <PAGE_SIZE> units (needed only for swap files).
2651 See Documentation/power/swsusp-and-swap-files.txt
2653 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2654 read the resume files
2656 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2657 Useful for devices that are detected asynchronously
2658 (e.g. USB and MMC devices).
2660 hibernate= [HIBERNATION]
2661 noresume Don't check if there's a hibernation image
2662 present during boot.
2663 nocompress Don't compress/decompress hibernation images.
2665 retain_initrd [RAM] Keep initrd memory after extraction
2667 rhash_entries= [KNL,NET]
2668 Set number of hash buckets for route cache
2670 riscom8= [HW,SERIAL]
2671 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2673 ro [KNL] Mount root device read-only on boot
2675 root= [KNL] Root filesystem
2676 See name_to_dev_t comment in init/do_mounts.c.
2678 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2679 mount the root filesystem
2681 rootflags= [KNL] Set root filesystem mount option string
2683 rootfstype= [KNL] Set root filesystem type
2685 rootwait [KNL] Wait (indefinitely) for root device to show up.
2686 Useful for devices that are detected asynchronously
2687 (e.g. USB and MMC devices).
2689 rw [KNL] Mount root device read-write on boot
2691 S [KNL] Run init in single mode
2694 See drivers/net/irda/sa1100_ir.c.
2696 sbni= [NET] Granch SBNI12 leased line adapter
2698 sched_debug [KNL] Enables verbose scheduler debug messages.
2700 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2701 xtime_lock contention on larger systems, and/or RCU lock
2702 contention on all systems with CONFIG_MAXSMP set.
2703 Format: { "0" | "1" }
2704 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2706 Note: increases power consumption, thus should only be
2707 enabled if running jitter sensitive (HPC/RT) workloads.
2709 security= [SECURITY] Choose a security module to enable at boot.
2710 If this boot parameter is not specified, only the first
2711 security module asking for security registration will be
2712 loaded. An invalid security module name will be treated
2713 as if no module has been chosen.
2715 selinux= [SELINUX] Disable or enable SELinux at boot time.
2716 Format: { "0" | "1" }
2717 See security/selinux/Kconfig help text.
2720 Default value is set via kernel config option.
2721 If enabled at boot time, /selinux/disable can be used
2722 later to disable prior to initial policy load.
2724 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2725 Format: { "0" | "1" }
2726 See security/apparmor/Kconfig help text
2729 Default value is set via kernel config option.
2731 serialnumber [BUGS=X86-32]
2734 Maximal number of shapers.
2736 show_msr= [x86] show boot-time MSR settings
2737 Format: { <integer> }
2738 Show boot-time (BIOS-initialized) MSR settings.
2739 The parameter means the number of CPUs to show,
2740 for example 1 means boot CPU only.
2747 slab_max_order= [MM, SLAB]
2748 Determines the maximum allowed order for slabs.
2749 A high setting may cause OOMs due to memory
2750 fragmentation. Defaults to 1 for systems with
2751 more than 32MB of RAM, 0 otherwise.
2753 slub_debug[=options[,slabs]] [MM, SLUB]
2754 Enabling slub_debug allows one to determine the
2755 culprit if slab objects become corrupted. Enabling
2756 slub_debug can create guard zones around objects and
2757 may poison objects when not in use. Also tracks the
2758 last alloc / free. For more information see
2759 Documentation/vm/slub.txt.
2761 slub_max_order= [MM, SLUB]
2762 Determines the maximum allowed order for slabs.
2763 A high setting may cause OOMs due to memory
2764 fragmentation. For more information see
2765 Documentation/vm/slub.txt.
2767 slub_min_objects= [MM, SLUB]
2768 The minimum number of objects per slab. SLUB will
2769 increase the slab order up to slub_max_order to
2770 generate a sufficiently large slab able to contain
2771 the number of objects indicated. The higher the number
2772 of objects the smaller the overhead of tracking slabs
2773 and the less frequently locks need to be acquired.
2774 For more information see Documentation/vm/slub.txt.
2776 slub_min_order= [MM, SLUB]
2777 Determines the minimum page order for slabs. Must be
2778 lower than slub_max_order.
2779 For more information see Documentation/vm/slub.txt.
2781 slub_nomerge [MM, SLUB]
2782 Disable merging of slabs with similar size. May be
2783 necessary if there is some reason to distinguish
2784 allocs to different slabs. Debug options disable
2785 merging on their own.
2786 For more information see Documentation/vm/slub.txt.
2789 Format: <io1>[,<io2>[,...,<io8>]]
2791 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2792 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2793 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2794 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2795 smsc-ircc2.ircc_irq= [HW] IRQ line
2796 smsc-ircc2.ircc_dma= [HW] DMA channel
2797 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2798 0: Toshiba Satellite 1800 (GP data pin select)
2799 1: Fast pin select (default)
2803 [KNL] Should the soft-lockup detector generate panics.
2806 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2807 See Documentation/laptops/sonypi.txt
2809 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2810 See Documentation/serial/specialix.txt.
2812 spia_io_base= [HW,MTD]
2818 Enabled the stack tracer on boot up.
2820 stacktrace_filter=[function-list]
2821 [FTRACE] Limit the functions that the stack tracer
2822 will trace at boot up. function-list is a comma separated
2823 list of functions. This list can be changed at run
2824 time by the stack_trace_filter file in the debugfs
2825 tracing directory. Note, this enables stack tracing
2826 and the stacktrace above is not needed.
2830 Set the STI (builtin display/keyboard on the HP-PARISC
2831 machines) console (graphic card) which should be used
2832 as the initial boot-console.
2833 See also comment in drivers/video/console/sticore.c.
2836 See comment in drivers/video/console/sticore.c.
2839 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2841 sunrpc.min_resvport=
2842 sunrpc.max_resvport=
2844 SunRPC servers often require that client requests
2845 originate from a privileged port (i.e. a port in the
2846 range 0 < portnr < 1024).
2847 An administrator who wishes to reserve some of these
2848 ports for other uses may adjust the range that the
2849 kernel's sunrpc client considers to be privileged
2850 using these two parameters to set the minimum and
2851 maximum port values.
2855 Control how the NFS server code allocates CPUs to
2856 service thread pools. Depending on how many NICs
2857 you have and where their interrupts are bound, this
2858 option will affect which CPUs will do NFS serving.
2859 Note: this parameter cannot be changed while the
2860 NFS server is running.
2862 auto the server chooses an appropriate mode
2863 automatically using heuristics
2864 global a single global pool contains all CPUs
2865 percpu one pool for each CPU
2866 pernode one pool for each NUMA node (equivalent
2867 to global on non-NUMA machines)
2869 sunrpc.tcp_slot_table_entries=
2870 sunrpc.udp_slot_table_entries=
2872 Sets the upper limit on the number of simultaneous
2873 RPC calls that can be sent from the client to a
2874 server. Increasing these values may allow you to
2875 improve throughput, but will also increase the
2876 amount of memory reserved for use by the client.
2879 [KNL] Enable accounting of swap in memory resource
2880 controller if no parameter or 1 is given or disable
2881 it if 0 is given (See Documentation/cgroups/memory.txt)
2883 swiotlb= [IA-64] Number of I/O TLB slabs
2887 sysfs.deprecated=0|1 [KNL]
2888 Enable/disable old style sysfs layout for old udev
2889 on older distributions. When this option is enabled
2890 very new udev will not work anymore. When this option
2891 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2892 in older udev will not work anymore.
2893 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2894 the kernel configuration.
2896 sysrq_always_enabled
2898 Ignore sysrq setting - this boot parameter will
2899 neutralize any effect of /proc/sys/kernel/sysrq.
2900 Useful for debugging.
2904 test_suspend= [SUSPEND]
2905 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2906 standby suspend) as the system sleep state to briefly
2907 enter during system startup. The system is woken from
2908 this state using a wakeup-capable RTC alarm.
2910 thash_entries= [KNL,NET]
2911 Set number of hash buckets for TCP connection
2913 thermal.act= [HW,ACPI]
2914 -1: disable all active trip points in all thermal zones
2915 <degrees C>: override all lowest active trip points
2917 thermal.crt= [HW,ACPI]
2918 -1: disable all critical trip points in all thermal zones
2919 <degrees C>: override all critical trip points
2921 thermal.nocrt= [HW,ACPI]
2922 Set to disable actions on ACPI thermal zone
2923 critical and hot trip points.
2925 thermal.off= [HW,ACPI]
2926 1: disable ACPI thermal control
2928 thermal.psv= [HW,ACPI]
2929 -1: disable all passive trip points
2930 <degrees C>: override all passive trip points to this
2933 thermal.tzp= [HW,ACPI]
2934 Specify global default ACPI thermal zone polling rate
2935 <deci-seconds>: poll all this frequency
2936 0: no polling (default)
2939 Force threading of all interrupt handlers except those
2940 marked explicitly IRQF_NO_THREAD.
2944 Specify if the kernel should make use of the cpu
2945 topology information if the hardware supports this.
2946 The scheduler will make use of this information and
2947 e.g. base its process migration decisions on it.
2952 tpm_suspend_pcr=[HW,TPM]
2953 Format: integer pcr id
2954 Specify that at suspend time, the tpm driver
2955 should extend the specified pcr with zeros,
2956 as a workaround for some chips which fail to
2957 flush the last written pcr on TPM_SaveState.
2958 This will guarantee that all the other pcrs
2961 trace_buf_size=nn[KMG]
2962 [FTRACE] will set tracing buffer size.
2964 trace_event=[event-list]
2965 [FTRACE] Set and start specified trace events in order
2966 to facilitate early boot debugging.
2967 See also Documentation/trace/events.txt
2969 trace_options=[option-list]
2970 [FTRACE] Enable or disable tracer options at boot.
2971 The option-list is a comma delimited list of options
2972 that can be enabled or disabled just as if you were
2973 to echo the option name into
2975 /sys/kernel/debug/tracing/trace_options
2977 For example, to enable stacktrace option (to dump the
2978 stack trace of each event), add to the command line:
2980 trace_options=stacktrace
2982 See also Documentation/trace/ftrace.txt "trace options"
2985 transparent_hugepage=
2987 Format: [always|madvise|never]
2988 Can be used to control the default behavior of the system
2989 with respect to transparent hugepages.
2990 See Documentation/vm/transhuge.txt for more details.
2992 tsc= Disable clocksource stability checks for TSC.
2994 [x86] reliable: mark tsc clocksource as reliable, this
2995 disables clocksource verification at runtime, as well
2996 as the stability checks done at bootup. Used to enable
2997 high-resolution timer mode on older hardware, and in
2998 virtualized environment.
2999 [x86] noirqtime: Do not use TSC to do irq accounting.
3000 Used to run time disable IRQ_TIME_ACCOUNTING on any
3001 platforms where RDTSC is slow and this accounting
3004 turbografx.map[2|3]= [HW,JOY]
3005 TurboGraFX parallel port interface
3007 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3008 See also Documentation/input/joystick-parport.txt
3010 udbg-immortal [PPC] When debugging early kernel crashes that
3011 happen after console_init() and before a proper
3012 console driver takes over, this boot options might
3013 help "seeing" what's going on.
3015 uhash_entries= [KNL,NET]
3016 Set number of hash buckets for UDP/UDP-Lite connections
3019 [USB] Ignore overcurrent events (default N).
3020 Some badly-designed motherboards generate lots of
3021 bogus events, for ports that aren't wired to
3022 anything. Set this parameter to avoid log spamming.
3023 Note that genuine overcurrent events won't be
3027 [X86] Cause panic on unknown NMI.
3029 usbcore.authorized_default=
3030 [USB] Default USB device authorization:
3031 (default -1 = authorized except for wireless USB,
3032 0 = not authorized, 1 = authorized)
3034 usbcore.autosuspend=
3035 [USB] The autosuspend time delay (in seconds) used
3036 for newly-detected USB devices (default 2). This
3037 is the time required before an idle device will be
3038 autosuspended. Devices for which the delay is set
3039 to a negative value won't be autosuspended at all.
3041 usbcore.usbfs_snoop=
3042 [USB] Set to log all usbfs traffic (default 0 = off).
3044 usbcore.blinkenlights=
3045 [USB] Set to cycle leds on hubs (default 0 = off).
3047 usbcore.old_scheme_first=
3048 [USB] Start with the old device initialization
3049 scheme (default 0 = off).
3051 usbcore.usbfs_memory_mb=
3052 [USB] Memory limit (in MB) for buffers allocated by
3053 usbfs (default = 16, 0 = max = 2047).
3055 usbcore.use_both_schemes=
3056 [USB] Try the other device initialization scheme
3057 if the first one fails (default 1 = enabled).
3059 usbcore.initial_descriptor_timeout=
3060 [USB] Specifies timeout for the initial 64-byte
3061 USB_REQ_GET_DESCRIPTOR request in milliseconds
3062 (default 5000 = 5.0 seconds).
3065 [USBHID] The interval which mice are to be polled at.
3067 usb-storage.delay_use=
3068 [UMS] The delay in seconds before a new device is
3069 scanned for Logical Units (default 5).
3072 [UMS] A list of quirks entries to supplement or
3073 override the built-in unusual_devs list. List
3074 entries are separated by commas. Each entry has
3075 the form VID:PID:Flags where VID and PID are Vendor
3076 and Product ID values (4-digit hex numbers) and
3077 Flags is a set of characters, each corresponding
3078 to a common usb-storage quirk flag as follows:
3079 a = SANE_SENSE (collect more than 18 bytes
3081 b = BAD_SENSE (don't collect more than 18
3082 bytes of sense data);
3083 c = FIX_CAPACITY (decrease the reported
3084 device capacity by one sector);
3085 d = NO_READ_DISC_INFO (don't use
3086 READ_DISC_INFO command);
3087 e = NO_READ_CAPACITY_16 (don't use
3088 READ_CAPACITY_16 command);
3089 h = CAPACITY_HEURISTICS (decrease the
3090 reported device capacity by one
3091 sector if the number is odd);
3092 i = IGNORE_DEVICE (don't bind to this
3094 l = NOT_LOCKABLE (don't try to lock and
3095 unlock ejectable media);
3096 m = MAX_SECTORS_64 (don't transfer more
3097 than 64 sectors = 32 KB at a time);
3098 n = INITIAL_READ10 (force a retry of the
3099 initial READ(10) command);
3100 o = CAPACITY_OK (accept the capacity
3101 reported by the device);
3102 p = WRITE_CACHE (the device cache is ON
3104 r = IGNORE_RESIDUE (the device reports
3105 bogus residue values);
3106 s = SINGLE_LUN (the device has only one
3108 w = NO_WP_DETECT (don't test whether the
3109 medium is write-protected).
3110 Example: quirks=0419:aaf5:rl,0421:0433:rc
3112 user_debug= [KNL,ARM]
3114 See arch/arm/Kconfig.debug help text.
3115 1 - undefined instruction events
3117 4 - invalid data aborts
3120 Example: user_debug=31
3123 [X86] Flags controlling user PTE allocations.
3125 nohigh = do not allocate PTE pages in
3126 HIGHMEM regardless of setting
3130 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3131 vdso=1: enable VDSO (default)
3132 vdso=0: disable VDSO mapping
3135 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3136 vdso32=1: enable 32-bit VDSO (default)
3137 vdso32=0: disable 32-bit VDSO mapping
3140 vector=percpu: enable percpu vector domain
3142 video= [FB] Frame buffer configuration
3143 See Documentation/fb/modedb.txt.
3146 [VMMIO] Memory mapped virtio (platform) device.
3148 <size>@<baseaddr>:<irq>[:<id>]
3150 <size> := size (can use standard suffixes
3152 <baseaddr> := physical base address
3153 <irq> := interrupt number (as passed to
3155 <id> := (optional) platform device id
3157 virtio_mmio.device=1K@0x100b0000:48:7
3159 Can be used multiple times for multiple devices.
3161 vga= [BOOT,X86-32] Select a particular video mode
3162 See Documentation/x86/boot.txt and
3163 Documentation/svga.txt.
3164 Use vga=ask for menu.
3165 This is actually a boot loader parameter; the value is
3166 passed to the kernel using a special protocol.
3168 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3169 size of <nn>. This can be used to increase the
3170 minimum size (128MB on x86). It can also be used to
3171 decrease the size and leave more room for directly
3174 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3177 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3180 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3184 Controls the behavior of vsyscalls (i.e. calls to
3185 fixed addresses of 0xffffffffff600x00 from legacy
3186 code). Most statically-linked binaries and older
3187 versions of glibc use these calls. Because these
3188 functions are at fixed addresses, they make nice
3189 targets for exploits that can control RIP.
3191 emulate [default] Vsyscalls turn into traps and are
3192 emulated reasonably safely.
3194 native Vsyscalls are native syscall instructions.
3195 This is a little bit faster than trapping
3196 and makes a few dynamic recompilers work
3197 better than they would in emulation mode.
3198 It also makes exploits much easier to write.
3200 none Vsyscalls don't work at all. This makes
3201 them quite hard to use for exploits but
3202 might break your system.
3204 vt.cur_default= [VT] Default cursor shape.
3205 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3206 the parameters of the <Esc>[?A;B;Cc escape sequence;
3207 see VGA-softcursor.txt. Default: 2 = underline.
3209 vt.default_blu= [VT]
3210 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3211 Change the default blue palette of the console.
3212 This is a 16-member array composed of values
3215 vt.default_grn= [VT]
3216 Format: <green0>,<green1>,<green2>,...,<green15>
3217 Change the default green palette of the console.
3218 This is a 16-member array composed of values
3221 vt.default_red= [VT]
3222 Format: <red0>,<red1>,<red2>,...,<red15>
3223 Change the default red palette of the console.
3224 This is a 16-member array composed of values
3230 Set system-wide default UTF-8 mode for all tty's.
3231 Default is 1, i.e. UTF-8 mode is enabled for all
3232 newly opened terminals.
3234 vt.global_cursor_default=
3237 Set system-wide default for whether a cursor
3238 is shown on new VTs. Default is -1,
3239 i.e. cursors will be created by default unless
3240 overridden by individual drivers. 0 will hide
3241 cursors, 1 will display them.
3243 watchdog timers [HW,WDT] For information on watchdog timers,
3244 see Documentation/watchdog/watchdog-parameters.txt
3245 or other driver-specific files in the
3246 Documentation/watchdog/ directory.
3248 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3249 default x2apic cluster mode on platforms
3252 x86_mrst_timer= [X86-32,APBT]
3253 Choose timer option for x86 Moorestown MID platform.
3254 Two valid options are apbt timer only and lapic timer
3255 plus one apbt timer for broadcast timer.
3256 x86_mrst_timer=apbt_only | lapic_and_apbt
3258 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3259 xd_geo= See header of drivers/block/xd.c.
3261 xen_emul_unplug= [HW,X86,XEN]
3262 Unplug Xen emulated devices
3263 Format: [unplug0,][unplug1]
3264 ide-disks -- unplug primary master IDE devices
3265 aux-ide-disks -- unplug non-primary-master IDE devices
3266 nics -- unplug network devices
3267 all -- unplug all emulated devices (NICs and IDE disks)
3268 unnecessary -- unplugging emulated devices is
3269 unnecessary even if the host did not respond to
3271 never -- do not unplug even if version check succeeds
3273 xirc2ps_cs= [NET,PCMCIA]
3275 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3277 ______________________________________________________________________
3281 Add more DRM drivers.
projects / deliverable / linux.git / blob