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.
568 If the device connected to the port is not a TTY but a braille
569 device, prepend "brl," before the device type, for instance
571 For now, only VisioBraille is supported.
573 consoleblank= [KNL] The console blank (screen saver) timeout in
574 seconds. Defaults to 10*60 = 10mins. A value of 0
575 disables the blank timer.
578 [KNL] Change the default value for
579 /proc/<pid>/coredump_filter.
580 See also Documentation/filesystems/proc.txt.
582 cpuidle.off=1 [CPU_IDLE]
583 disable the cpuidle sub-system
585 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
587 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
589 crashkernel=size[KMG][@offset[KMG]]
590 [KNL] Using kexec, Linux can switch to a 'crash kernel'
591 upon panic. This parameter reserves the physical
592 memory region [offset, offset + size] for that kernel
593 image. If '@offset' is omitted, then a suitable offset
594 is selected automatically. Check
595 Documentation/kdump/kdump.txt for further details.
597 crashkernel=range1:size1[,range2:size2,...][@offset]
598 [KNL] Same as above, but depends on the memory
599 in the running system. The syntax of range is
600 start-[end] where start and end are both
601 a memory unit (amount[KMG]). See also
602 Documentation/kdump/kdump.txt for an example.
607 cs89x0_media= [HW,NET]
608 Format: { rj45 | aui | bnc }
611 See header of drivers/s390/block/dasd_devmap.c.
613 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
614 (one device per port)
615 Format: <port#>,<type>
616 See also Documentation/input/joystick-parport.txt
618 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
619 time. See Documentation/dynamic-debug-howto.txt for
620 details. Deprecated, see dyndbg.
622 debug [KNL] Enable kernel debugging (events log level).
625 [KNL] verbose self-tests
627 Print debugging info while doing the locking API
629 We default to 0 (no extra messages), setting it to
630 1 will print _a lot_ more information - normally
631 only useful to kernel developers.
633 debug_objects [KNL] Enable object debugging
636 [KNL] Disable object debugging
638 debug_guardpage_minorder=
639 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
640 parameter allows control of the order of pages that will
641 be intentionally kept free (and hence protected) by the
642 buddy allocator. Bigger value increase the probability
643 of catching random memory corruption, but reduce the
644 amount of memory for normal system use. The maximum
645 possible value is MAX_ORDER/2. Setting this parameter
646 to 1 or 2 should be enough to identify most random
647 memory corruption problems caused by bugs in kernel or
648 driver code when a CPU writes to (or reads from) a
649 random memory location. Note that there exists a class
650 of memory corruptions problems caused by buggy H/W or
651 F/W or by drivers badly programing DMA (basically when
652 memory is written at bus level and the CPU MMU is
653 bypassed) which are not detectable by
654 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
655 tracking down these problems.
657 debugpat [X86] Enable PAT debugging
659 decnet.addr= [HW,NET]
660 Format: <area>[,<node>]
661 See also Documentation/networking/decnet.txt.
664 [same as hugepagesz=] The size of the default
665 HugeTLB page size. This is the size represented by
666 the legacy /proc/ hugepages APIs, used for SHM, and
667 default size when mounting hugetlbfs filesystems.
668 Defaults to the default architecture's huge page size
672 Set number of hash buckets for dentry cache.
675 IO parameters + enable/disable command.
677 digiepca= [HW,SERIAL]
678 See drivers/char/README.epca and
679 Documentation/serial/digiepca.txt.
682 See Documentation/networking/ipv6.txt.
684 disable_ddw [PPC/PSERIES]
685 Disable Dynamic DMA Window support. Use this if
686 to workaround buggy firmware.
689 See Documentation/networking/ipv6.txt.
691 disable_mtrr_cleanup [X86]
692 The kernel tries to adjust MTRR layout from continuous
693 to discrete, to make X server driver able to add WB
694 entry later. This parameter disables that.
696 disable_mtrr_trim [X86, Intel and AMD only]
697 By default the kernel will trim any uncacheable
698 memory out of your available memory pool based on
699 MTRR settings. This parameter disables that behavior,
700 possibly causing your machine to run very slowly.
702 disable_timer_pin_1 [X86]
703 Disable PIN 1 of APIC timer
704 Can be useful to work around chipset bugs.
706 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
707 this option disables the debugging code at boot.
709 dma_debug_entries=<number>
710 This option allows to tune the number of preallocated
711 entries for DMA-API debugging code. One entry is
712 required per DMA-API allocation. Use this if the
713 DMA-API debugging code disables itself because the
714 architectural default is too low.
716 dma_debug_driver=<driver_name>
717 With this option the DMA-API debugging driver
718 filter feature can be enabled at boot time. Just
719 pass the driver to filter for as the parameter.
720 The filter can be disabled or changed to another
721 driver later using sysfs.
723 drm_kms_helper.edid_firmware=[<connector>:]<file>
724 Broken monitors, graphic adapters and KVMs may
725 send no or incorrect EDID data sets. This parameter
726 allows to specify an EDID data set in the
727 /lib/firmware directory that is used instead.
728 Generic built-in EDID data sets are used, if one of
729 edid/1024x768.bin, edid/1280x1024.bin,
730 edid/1680x1050.bin, or edid/1920x1080.bin is given
731 and no file with the same name exists. Details and
732 instructions how to build your own EDID data are
733 available in Documentation/EDID/HOWTO.txt. An EDID
734 data set will only be used for a particular connector,
735 if its name and a colon are prepended to the EDID
740 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
741 module.dyndbg[="val"]
742 Enable debug messages at boot time. See
743 Documentation/dynamic-debug-howto.txt for details.
745 earlycon= [KNL] Output early console device and options.
746 uart[8250],io,<addr>[,options]
747 uart[8250],mmio,<addr>[,options]
748 uart[8250],mmio32,<addr>[,options]
749 Start an early, polled-mode console on the 8250/16550
750 UART at the specified I/O port or MMIO address.
751 MMIO inter-register address stride is either 8-bit
752 (mmio) or 32-bit (mmio32).
753 The options are the same as for ttyS, above.
755 earlyprintk= [X86,SH,BLACKFIN]
758 earlyprintk=serial[,ttySn[,baudrate]]
759 earlyprintk=ttySn[,baudrate]
760 earlyprintk=dbgp[debugController#]
762 Append ",keep" to not disable it when the real console
765 Only vga or serial or usb debug port at a time.
767 Currently only ttyS0 and ttyS1 are supported.
769 Interaction with the standard serial driver is not
772 The VGA output is eventually overwritten by the real
775 The xen output can only be used by Xen PV guests.
777 ekgdboc= [X86,KGDB] Allow early kernel console debugging
780 This is designed to be used in conjunction with
781 the boot argument: earlyprintk=vga
784 Format: {"off" | "on" | "skip[mbr]"}
786 eisa_irq_edge= [PARISC,HW]
787 See header of drivers/parisc/eisa.c.
790 See comment before function elanfreq_setup() in
791 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
794 Format: {"cfq" | "deadline" | "noop"}
795 See Documentation/block/cfq-iosched.txt and
796 Documentation/block/deadline-iosched.txt for details.
798 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
799 Specifies physical address of start of kernel core
800 image elf header and optionally the size. Generally
801 kexec loader will pass this option to capture kernel.
802 See Documentation/kdump/kdump.txt for details.
804 enable_mtrr_cleanup [X86]
805 The kernel tries to adjust MTRR layout from continuous
806 to discrete, to make X server driver able to add WB
807 entry later. This parameter enables that.
809 enable_timer_pin_1 [X86]
810 Enable PIN 1 of APIC timer
811 Can be useful to work around chipset bugs
812 (in particular on some ATI chipsets).
813 The kernel tries to set a reasonable default.
815 enforcing [SELINUX] Set initial enforcing status.
817 See security/selinux/Kconfig help text.
818 0 -- permissive (log only, no denials).
819 1 -- enforcing (deny and log).
821 Value can be changed at runtime via /selinux/enforce.
824 Disable Error Record Serialization Table (ERST)
827 ether= [HW,NET] Ethernet cards parameters
828 This option is obsoleted by the "netdev=" option, which
829 has equivalent usage. See its documentation for details.
833 Permit 'security.evm' to be updated regardless of
834 current integrity status.
838 fail_make_request=[KNL]
839 General fault injection mechanism.
840 Format: <interval>,<probability>,<space>,<times>
841 See also Documentation/fault-injection/.
844 See Documentation/blockdev/floppy.txt.
846 force_pal_cache_flush
847 [IA-64] Avoid check_sal_cache_flush which may hang on
848 buggy SAL_CACHE_FLUSH implementations. Using this
849 parameter will force ia64_sal_cache_flush to call
850 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
853 [FTRACE] will set and start the specified tracer
854 as early as possible in order to facilitate early
857 ftrace_dump_on_oops[=orig_cpu]
858 [FTRACE] will dump the trace buffers on oops.
859 If no parameter is passed, ftrace will dump
860 buffers of all CPUs, but if you pass orig_cpu, it will
861 dump only the buffer of the CPU that triggered the
864 ftrace_filter=[function-list]
865 [FTRACE] Limit the functions traced by the function
866 tracer at boot up. function-list is a comma separated
867 list of functions. This list can be changed at run
868 time by the set_ftrace_filter file in the debugfs
871 ftrace_notrace=[function-list]
872 [FTRACE] Do not trace the functions specified in
873 function-list. This list can be changed at run time
874 by the set_ftrace_notrace file in the debugfs
877 ftrace_graph_filter=[function-list]
878 [FTRACE] Limit the top level callers functions traced
879 by the function graph tracer at boot up.
880 function-list is a comma separated list of functions
881 that can be changed at run time by the
882 set_graph_function file in the debugfs tracing directory.
885 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
886 support via parallel port (up to 5 devices per port)
887 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
888 See also Documentation/input/joystick-parport.txt
892 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
896 gcov_persist= [GCOV] When non-zero (default), profiling data for
897 kernel modules is saved and remains accessible via
898 debugfs, even when the module is unloaded/reloaded.
899 When zero, profiling data is discarded and associated
900 debugfs files are removed at module unload time.
902 gpt [EFI] Forces disk with valid GPT signature but
903 invalid Protective MBR to be treated as GPT.
905 grcan.enable0= [HW] Configuration of physical interface 0. Determines
906 the "Enable 0" bit of the configuration register.
909 grcan.enable1= [HW] Configuration of physical interface 1. Determines
910 the "Enable 0" bit of the configuration register.
913 grcan.select= [HW] Select which physical interface to use.
916 grcan.txsize= [HW] Sets the size of the tx buffer.
917 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
919 grcan.rxsize= [HW] Sets the size of the rx buffer.
920 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
923 hashdist= [KNL,NUMA] Large hashes allocated during boot
924 are distributed across NUMA nodes. Defaults on
925 for 64-bit NUMA, off otherwise.
926 Format: 0 | 1 (for off | on)
928 hcl= [IA-64] SGI's Hardware Graph compatibility layer
930 hd= [EIDE] (E)IDE hard drive subsystem geometry
931 Format: <cyl>,<head>,<sect>
934 Disable Hardware Error Source Table (HEST) support;
935 corresponding firmware-first mode error processing
936 logic will be disabled.
938 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
939 size of <nn>. This works even on boxes that have no
940 highmem otherwise. This also works to reduce highmem
941 size on bigger boxes.
943 highres= [KNL] Enable/disable high resolution timer mode.
944 Valid parameters: "on", "off"
948 See Documentation/isdn/README.HiSax.
952 hpet= [X86-32,HPET] option to control HPET usage
953 Format: { enable (default) | disable | force |
955 disable: disable HPET and use PIT instead
956 force: allow force enabled of undocumented chips (ICH4,
958 verbose: show contents of HPET registers during setup
960 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
961 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
962 On x86-64 and powerpc, this option can be specified
963 multiple times interleaved with hugepages= to reserve
964 huge pages of different sizes. Valid pages sizes on
965 x86-64 are 2M (when the CPU supports "pse") and 1G
966 (when the CPU supports the "pdpe1gb" cpuinfo flag)
967 Note that 1GB pages can only be allocated at boot time
968 using hugepages= and not freed afterwards.
970 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
971 terminal devices. Valid values: 0..8
972 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
973 If specified, z/VM IUCV HVC accepts connections
974 from listed z/VM user IDs only.
977 Do not unregister boot console at start. This is only
978 useful for debugging when something happens in the window
979 between unregistering the boot console and initializing
982 i2c_bus= [HW] Override the default board specific I2C bus speed
983 or register an additional I2C bus that is not
984 registered from board initialization code.
988 i8042.debug [HW] Toggle i8042 debug mode
989 i8042.direct [HW] Put keyboard port into non-translated mode
990 i8042.dumbkbd [HW] Pretend that controller can only read data from
991 keyboard and cannot control its state
992 (Don't attempt to blink the leds)
993 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
994 i8042.nokbd [HW] Don't check/create keyboard port
995 i8042.noloop [HW] Disable the AUX Loopback command while probing
997 i8042.nomux [HW] Don't check presence of an active multiplexing
999 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1001 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1002 i8042.reset [HW] Reset the controller during init and cleanup
1003 i8042.unlock [HW] Unlock (ignore) the keylock
1007 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1008 indicates that the driver is running on unsupported
1010 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1011 does not match list of supported models.
1013 [HW] Report power status in /proc/i8k
1014 (disabled by default)
1015 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1018 i915.invert_brightness=
1019 [DRM] Invert the sense of the variable that is used to
1020 set the brightness of the panel backlight. Normally a
1021 brightness value of 0 indicates backlight switched off,
1022 and the maximum of the brightness value sets the backlight
1023 to maximum brightness. If this parameter is set to 0
1024 (default) and the machine requires it, or this parameter
1025 is set to 1, a brightness value of 0 sets the backlight
1026 to maximum brightness, and the maximum of the brightness
1027 value switches the backlight off.
1028 -1 -- never invert brightness
1029 0 -- machine default
1030 1 -- force brightness inversion
1033 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1035 ide-core.nodma= [HW] (E)IDE subsystem
1036 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1037 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1038 .cdrom .chs .ignore_cable are additional options
1039 See Documentation/ide/ide.txt.
1041 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1042 Claim all unknown PCI IDE storage controllers.
1045 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1046 Poll forces a polling idle loop that can slightly
1047 improve the performance of waking up a idle CPU, but
1048 will use a lot of power and make the system run hot.
1050 idle=mwait: On systems which support MONITOR/MWAIT but
1051 the kernel chose to not use it because it doesn't save
1052 as much power as a normal idle loop, use the
1053 MONITOR/MWAIT idle loop anyways. Performance should be
1054 the same as idle=poll.
1055 idle=halt: Halt is forced to be used for CPU idle.
1056 In such case C2/C3 won't be used again.
1057 idle=nomwait: Disable mwait for CPU C-states
1059 ignore_loglevel [KNL]
1060 Ignore loglevel setting - this will print /all/
1061 kernel messages to the console. Useful for debugging.
1062 We also add it as printk module parameter, so users
1063 could change it dynamically, usually by
1064 /sys/module/printk/parameters/ignore_loglevel.
1066 ihash_entries= [KNL]
1067 Set number of hash buckets for inode cache.
1069 ima_appraise= [IMA] appraise integrity measurements
1070 Format: { "off" | "enforce" | "fix" }
1073 ima_appraise_tcb [IMA]
1074 The builtin appraise policy appraises all files
1078 Format: { "0" | "1" }
1079 0 -- integrity auditing messages. (Default)
1080 1 -- enable informational integrity auditing messages.
1083 Format: { "sha1" | "md5" }
1087 Load a policy which meets the needs of the Trusted
1088 Computing Base. This means IMA will measure all
1089 programs exec'd, files mmap'd for exec, and all files
1090 opened for read by uid=0.
1094 Run specified binary instead of /sbin/init as init
1097 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1098 for working out where the kernel is dying during
1101 initrd= [BOOT] Specify the location of the initial ramdisk
1103 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1106 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1108 Enable intel iommu driver.
1110 Disable intel iommu driver.
1111 igfx_off [Default Off]
1112 By default, gfx is mapped as normal device. If a gfx
1113 device has a dedicated DMAR unit, the DMAR unit is
1114 bypassed by not enabling DMAR with this option. In
1115 this case, gfx device will use physical address for
1118 With this option iommu will not optimize to look
1119 for io virtual address below 32-bit forcing dual
1120 address cycle on pci bus for cards supporting greater
1121 than 32-bit addressing. The default is to look
1122 for translation below 32-bit and if not available
1123 then look in the higher range.
1124 strict [Default Off]
1125 With this option on every unmap_single operation will
1126 result in a hardware IOTLB flush operation as opposed
1127 to batching them for performance.
1128 sp_off [Default Off]
1129 By default, super page will be supported if Intel IOMMU
1130 has the capability. With this option, super page will
1133 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1134 0 disables intel_idle and fall back on acpi_idle.
1135 1 to 6 specify maximum depth of C-state.
1137 intremap= [X86-64, Intel-IOMMU]
1138 on enable Interrupt Remapping (default)
1139 off disable Interrupt Remapping
1140 nosid disable Source ID checking
1142 BIOS x2APIC opt-out request will be ignored
1144 iomem= Disable strict checking of access to MMIO memory
1145 strict regions from userspace.
1162 io7= [HW] IO7 for Marvel based alpha systems
1163 See comment before marvel_specify_io7 in
1164 arch/alpha/kernel/core_marvel.c.
1166 io_delay= [X86] I/O delay method
1168 Standard port 0x80 based delay
1170 Alternate port 0xed based delay (needed on some systems)
1172 Simple two microseconds delay
1177 See Documentation/filesystems/nfs/nfsroot.txt.
1179 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1180 See comment before ip2_setup() in
1181 drivers/char/ip2/ip2base.c.
1184 When an interrupt is not handled search all handlers
1185 for it. Intended to get systems with badly broken
1189 When an interrupt is not handled search all handlers
1190 for it. Also check all handlers each timer
1191 interrupt. Intended to get systems with badly broken
1195 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1197 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1199 <cpu number>,...,<cpu number>
1201 <cpu number>-<cpu number>
1202 (must be a positive range in ascending order)
1204 <cpu number>,...,<cpu number>-<cpu number>
1206 This option can be used to specify one or more CPUs
1207 to isolate from the general SMP balancing and scheduling
1208 algorithms. You can move a process onto or off an
1209 "isolated" CPU via the CPU affinity syscalls or cpuset.
1210 <cpu number> begins at 0 and the maximum value is
1211 "number of CPUs in system - 1".
1213 This option is the preferred way to isolate CPUs. The
1214 alternative -- manually setting the CPU mask of all
1215 tasks in the system -- can cause problems and
1216 suboptimal load balancer performance.
1220 js= [HW,JOY] Analog joystick
1221 See Documentation/input/joystick.txt.
1225 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1226 specifies the amount of memory usable by the kernel
1227 for non-movable allocations. The requested amount is
1228 spread evenly throughout all nodes in the system. The
1229 remaining memory in each node is used for Movable
1230 pages. In the event, a node is too small to have both
1231 kernelcore and Movable pages, kernelcore pages will
1232 take priority and other nodes will have a larger number
1233 of kernelcore pages. The Movable zone is used for the
1234 allocation of pages that may be reclaimed or moved
1235 by the page migration subsystem. This means that
1236 HugeTLB pages may not be allocated from this zone.
1237 Note that allocations like PTEs-from-HighMem still
1238 use the HighMem zone if it exists, and the Normal
1239 zone if it does not.
1241 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1242 Format: <Controller#>[,poll interval]
1243 The controller # is the number of the ehci usb debug
1244 port as it is probed via PCI. The poll interval is
1245 optional and is the number seconds in between
1246 each poll cycle to the debug port in case you need
1247 the functionality for interrupting the kernel with
1248 gdb or control-c on the dbgp connection. When
1249 not using this parameter you use sysrq-g to break into
1250 the kernel debugger.
1252 kgdboc= [KGDB,HW] kgdb over consoles.
1253 Requires a tty driver that supports console polling,
1254 or a supported polling keyboard driver (non-usb).
1255 Serial only format: <serial_device>[,baud]
1256 keyboard only format: kbd
1257 keyboard and serial format: kbd,<serial_device>[,baud]
1258 Optional Kernel mode setting:
1259 kms, kbd format: kms,kbd
1260 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1262 kgdbwait [KGDB] Stop kernel execution and enter the
1263 kernel debugger at the earliest opportunity.
1265 kmac= [MIPS] korina ethernet MAC address.
1266 Configure the RouterBoard 532 series on-chip
1267 Ethernet adapter MAC address.
1269 kmemleak= [KNL] Boot-time kmemleak enable/disable
1270 Valid arguments: on, off
1273 kstack=N [X86] Print N words from the kernel stack
1276 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1277 Default is 0 (don't ignore, but inject #GP)
1279 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1283 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1284 Default is 1 (enabled)
1286 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1288 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1290 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1291 (virtualized MMU) support on capable Intel chips.
1292 Default is 1 (enabled)
1294 kvm-intel.emulate_invalid_guest_state=
1295 [KVM,Intel] Enable emulation of invalid guest states
1296 Default is 0 (disabled)
1298 kvm-intel.flexpriority=
1299 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1300 Default is 1 (enabled)
1303 [KVM,Intel] Enable VMX nesting (nVMX).
1304 Default is 0 (disabled)
1306 kvm-intel.unrestricted_guest=
1307 [KVM,Intel] Disable unrestricted guest feature
1308 (virtualized real and unpaged mode) on capable
1309 Intel chips. Default is 1 (enabled)
1311 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1312 feature (tagged TLBs) on capable Intel chips.
1313 Default is 1 (enabled)
1319 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1322 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1323 value for LAPIC timer one-shot implementation. Default
1324 back to the programmable timer unit in the LAPIC.
1326 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1329 libata.dma= [LIBATA] DMA control
1330 libata.dma=0 Disable all PATA and SATA DMA
1331 libata.dma=1 PATA and SATA Disk DMA only
1332 libata.dma=2 ATAPI (CDROM) DMA only
1333 libata.dma=4 Compact Flash DMA only
1334 Combinations also work, so libata.dma=3 enables DMA
1335 for disks and CDROMs, but not CFs.
1337 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1338 libata.ignore_hpa=0 keep BIOS limits (default)
1339 libata.ignore_hpa=1 ignore limits, using full disk
1341 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1345 libata.force= [LIBATA] Force configurations. The format is comma
1346 separated list of "[ID:]VAL" where ID is
1347 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1348 matching port, link or device. Basically, it matches
1349 the ATA ID string printed on console by libata. If
1350 the whole ID part is omitted, the last PORT and DEVICE
1351 values are used. If ID hasn't been specified yet, the
1352 configuration applies to all ports, links and devices.
1354 If only DEVICE is omitted, the parameter applies to
1355 the port and all links and devices behind it. DEVICE
1356 number of 0 either selects the first device or the
1357 first fan-out link behind PMP device. It does not
1358 select the host link. DEVICE number of 15 selects the
1359 host link and device attached to it.
1361 The VAL specifies the configuration to force. As long
1362 as there's no ambiguity shortcut notation is allowed.
1363 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1364 The following configurations can be forced.
1366 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1367 Any ID with matching PORT is used.
1369 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1371 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1372 udma[/][16,25,33,44,66,100,133] notation is also
1375 * [no]ncq: Turn on or off NCQ.
1377 * nohrst, nosrst, norst: suppress hard, soft
1380 * rstonce: only attempt one reset during
1381 hot-unplug link recovery
1383 * dump_id: dump IDENTIFY data.
1385 If there are multiple matching configurations changing
1386 the same attribute, the last one is used.
1388 memblock=debug [KNL] Enable memblock debug messages.
1390 load_ramdisk= [RAM] List of ramdisks to load from floppy
1391 See Documentation/blockdev/ramdisk.txt.
1393 lockd.nlm_grace_period=P [NFS] Assign grace period.
1396 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1399 lockd.nlm_timeout=T [NFS] Assign timeout value.
1402 lockd.nlm_udpport=M [NFS] Assign UDP port.
1405 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1408 loglevel= All Kernel Messages with a loglevel smaller than the
1409 console loglevel will be printed to the console. It can
1410 also be changed with klogd or other programs. The
1411 loglevels are defined as follows:
1413 0 (KERN_EMERG) system is unusable
1414 1 (KERN_ALERT) action must be taken immediately
1415 2 (KERN_CRIT) critical conditions
1416 3 (KERN_ERR) error conditions
1417 4 (KERN_WARNING) warning conditions
1418 5 (KERN_NOTICE) normal but significant condition
1419 6 (KERN_INFO) informational
1420 7 (KERN_DEBUG) debug-level messages
1422 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1423 in bytes. n must be a power of two. The default
1424 size is set in the kernel config file.
1426 logo.nologo [FB] Disables display of the built-in Linux logo.
1427 This may be used to provide more screen space for
1428 kernel log messages and is useful when debugging
1429 kernel boot problems.
1431 lp=0 [LP] Specify parallel ports to use, e.g,
1432 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1433 lp=reset first parallel port). 'lp=0' disables the
1434 lp=auto printer driver. 'lp=reset' (which can be
1435 specified in addition to the ports) causes
1436 attached printers to be reset. Using
1437 lp=port1,port2,... specifies the parallel ports
1438 to associate lp devices with, starting with
1439 lp0. A port specification may be 'none' to skip
1440 that lp device, or a parport name such as
1441 'parport0'. Specifying 'lp=auto' instead of a
1442 port specification list means that device IDs
1443 from each port should be examined, to see if
1444 an IEEE 1284-compliant printer is attached; if
1445 so, the driver will manage that printer.
1446 See also header of drivers/char/lp.c.
1449 Sets loops_per_jiffy to given constant, thus avoiding
1450 time-consuming boot-time autodetection (up to 250 ms per
1451 CPU). 0 enables autodetection (default). To determine
1452 the correct value for your kernel, boot with normal
1453 autodetection and see what value is printed. Note that
1454 on SMP systems the preset will be applied to all CPUs,
1455 which is likely to cause problems if your CPUs need
1456 significantly divergent settings. An incorrect value
1457 will cause delays in the kernel to be wrong, leading to
1458 unpredictable I/O errors and other breakage. Although
1459 unlikely, in the extreme case this might damage your
1463 Format: <io>,<irq>,<dma>
1465 machvec= [IA-64] Force the use of a particular machine-vector
1466 (machvec) in a generic kernel.
1467 Example: machvec=hpzx1_swiotlb
1469 machtype= [Loongson] Share the same kernel image file between different
1471 Example: machtype=lemote-yeeloong-2f-7inch
1473 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1474 than or equal to this physical address is ignored.
1476 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1477 should make use of. maxcpus=n : n >= 0 limits the
1478 kernel to using 'n' processors. n=0 is a special case,
1479 it is equivalent to "nosmp", which also disables
1482 max_loop= [LOOP] The number of loop block devices that get
1483 (loop.max_loop) unconditionally pre-created at init time. The default
1484 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1485 of statically allocating a predefined number, loop
1486 devices can be requested on-demand with the
1487 /dev/loop-control interface.
1489 mce [X86-32] Machine Check Exception
1491 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1493 md= [HW] RAID subsystems devices and level
1494 See Documentation/md.txt.
1497 Format: <first>,<last>
1498 Specifies range of consoles to be captured by the MDA.
1500 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1501 Amount of memory to be used when the kernel is not able
1502 to see the whole system memory or for test.
1503 [X86] Work as limiting max address. Use together
1504 with memmap= to avoid physical address space collisions.
1505 Without memmap= PCI devices could be placed at addresses
1506 belonging to unused RAM.
1508 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1512 [KNL,SH] Allow user to override the default size for
1513 per-device physically contiguous DMA buffers.
1515 memmap=exactmap [KNL,X86] Enable setting of an exact
1516 E820 memory map, as specified by the user.
1517 Such memmap=exactmap lines can be constructed based on
1518 BIOS output or other requirements. See the memmap=nn@ss
1521 memmap=nn[KMG]@ss[KMG]
1522 [KNL] Force usage of a specific region of memory
1523 Region of memory to be used, from ss to ss+nn.
1525 memmap=nn[KMG]#ss[KMG]
1526 [KNL,ACPI] Mark specific memory as ACPI data.
1527 Region of memory to be used, from ss to ss+nn.
1529 memmap=nn[KMG]$ss[KMG]
1530 [KNL,ACPI] Mark specific memory as reserved.
1531 Region of memory to be used, from ss to ss+nn.
1532 Example: Exclude memory from 0x18690000-0x1869ffff
1533 memmap=64K$0x18690000
1535 memmap=0x10000$0x18690000
1537 memory_corruption_check=0/1 [X86]
1538 Some BIOSes seem to corrupt the first 64k of
1539 memory when doing things like suspend/resume.
1540 Setting this option will scan the memory
1541 looking for corruption. Enabling this will
1542 both detect corruption and prevent the kernel
1543 from using the memory being corrupted.
1544 However, its intended as a diagnostic tool; if
1545 repeatable BIOS-originated corruption always
1546 affects the same memory, you can use memmap=
1547 to prevent the kernel from using that memory.
1549 memory_corruption_check_size=size [X86]
1550 By default it checks for corruption in the low
1551 64k, making this memory unavailable for normal
1552 use. Use this parameter to scan for
1553 corruption in more or less memory.
1555 memory_corruption_check_period=seconds [X86]
1556 By default it checks for corruption every 60
1557 seconds. Use this parameter to check at some
1558 other rate. 0 disables periodic checking.
1560 memtest= [KNL,X86] Enable memtest
1562 default : 0 <disable>
1563 Specifies the number of memtest passes to be
1564 performed. Each pass selects another test
1565 pattern from a given set of patterns. Memtest
1566 fills the memory with this pattern, validates
1567 memory contents and reserves bad memory
1568 regions that are detected.
1570 meye.*= [HW] Set MotionEye Camera parameters
1571 See Documentation/video4linux/meye.txt.
1573 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1574 Multi-Function General Purpose Timers on AMD Geode
1577 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1578 the BIOS has incorrectly applied a workaround. TinyBIOS
1579 version 0.98 is known to be affected, 0.99 fixes the
1580 problem by letting the user disable the workaround.
1584 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1585 physical address is ignored.
1587 mini2440= [ARM,HW,KNL]
1588 Format:[0..2][b][c][t]
1590 MINI2440 configuration specification:
1591 0 - The attached screen is the 3.5" TFT
1592 1 - The attached screen is the 7" TFT
1593 2 - The VGA Shield is attached (1024x768)
1594 Leaving out the screen size parameter will not load
1595 the TFT driver, and the framebuffer will be left
1597 b - Enable backlight. The TFT backlight pin will be
1598 linked to the kernel VESA blanking code and a GPIO
1599 LED. This parameter is not necessary when using the
1601 c - Enable the s3c camera interface.
1602 t - Reserved for enabling touchscreen support. The
1603 touchscreen support is not enabled in the mainstream
1604 kernel as of 2.6.30, a preliminary port can be found
1605 in the "bleeding edge" mini2440 support kernel at
1606 http://repo.or.cz/w/linux-2.6/mini2440.git
1609 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1610 parameter allows control of the logging verbosity for
1611 the additional memory initialisation checks. A value
1612 of 0 disables mminit logging and a level of 4 will
1613 log everything. Information is printed at KERN_DEBUG
1614 so loglevel=8 may also need to be specified.
1617 [KNL] When CONFIG_MODULE_SIG is set, this means that
1618 modules without (valid) signatures will fail to load.
1619 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1620 is always true, so this option does nothing.
1623 [MOUSE] Maximum time between finger touching and
1624 leaving touchpad surface for touch to be considered
1625 a tap and be reported as a left button click (for
1626 touchpads working in absolute mode only).
1628 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1629 reporting absolute coordinates, such as tablets
1630 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1631 reporting absolute coordinates, such as tablets
1633 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1634 is similar to kernelcore except it specifies the
1635 amount of memory used for migratable allocations.
1636 If both kernelcore and movablecore is specified,
1637 then kernelcore will be at *least* the specified
1638 value but may be more. If movablecore on its own
1639 is specified, the administrator must be careful
1640 that the amount of memory usable for all allocations
1643 MTD_Partition= [MTD]
1644 Format: <name>,<region-number>,<size>,<offset>
1646 MTD_Region= [MTD] Format:
1647 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1650 See drivers/mtd/cmdlinepart.c.
1652 multitce=off [PPC] This parameter disables the use of the pSeries
1653 firmware feature for updating multiple TCE entries
1656 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1658 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1660 boundary - index of last SLC block on Flex-OneNAND.
1661 The remaining blocks are configured as MLC blocks.
1662 lock - Configure if Flex-OneNAND boundary should be locked.
1663 Once locked, the boundary cannot be changed.
1664 1 indicates lock status, 0 indicates unlock status.
1667 ARM/S3C2412 JIVE boot control
1669 See arch/arm/mach-s3c2412/mach-jive.c
1671 mtouchusb.raw_coordinates=
1672 [HW] Make the MicroTouch USB driver use raw coordinates
1673 ('y', default) or cooked coordinates ('n')
1675 mtrr_chunk_size=nn[KMG] [X86]
1676 used for mtrr cleanup. It is largest continuous chunk
1677 that could hold holes aka. UC entries.
1679 mtrr_gran_size=nn[KMG] [X86]
1680 Used for mtrr cleanup. It is granularity of mtrr block.
1682 Large value could prevent small alignment from
1685 mtrr_spare_reg_nr=n [X86]
1687 Range: 0,7 : spare reg number
1689 Used for mtrr cleanup. It is spare mtrr entries number.
1690 Set to 2 or more if your graphical card needs more.
1692 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1694 netdev= [NET] Network devices parameters
1695 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1696 Note that mem_start is often overloaded to mean
1697 something different and driver-specific.
1698 This usage is only documented in each driver source
1702 [NETFILTER] Enable connection tracking flow accounting
1703 0 to disable accounting
1704 1 to enable accounting
1707 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1708 See Documentation/filesystems/nfs/nfsroot.txt.
1710 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1711 See Documentation/filesystems/nfs/nfsroot.txt.
1713 nfsrootdebug [NFS] enable nfsroot debugging messages.
1714 See Documentation/filesystems/nfs/nfsroot.txt.
1716 nfs.callback_tcpport=
1717 [NFS] set the TCP port on which the NFSv4 callback
1718 channel should listen.
1721 [NFS] sets the pathname to the program which is used
1722 to update the NFS client cache entries.
1724 nfs.cache_getent_timeout=
1725 [NFS] sets the timeout after which an attempt to
1726 update a cache entry is deemed to have failed.
1728 nfs.idmap_cache_timeout=
1729 [NFS] set the maximum lifetime for idmapper cache
1733 [NFS] enable 64-bit inode numbers.
1734 If zero, the NFS client will fake up a 32-bit inode
1735 number for the readdir() and stat() syscalls instead
1736 of returning the full 64-bit number.
1737 The default is to return 64-bit inode numbers.
1739 nfs.max_session_slots=
1740 [NFSv4.1] Sets the maximum number of session slots
1741 the client will attempt to negotiate with the server.
1742 This limits the number of simultaneous RPC requests
1743 that the client can send to the NFSv4.1 server.
1744 Note that there is little point in setting this
1745 value higher than the max_tcp_slot_table_limit.
1747 nfs.nfs4_disable_idmapping=
1748 [NFSv4] When set to the default of '1', this option
1749 ensures that both the RPC level authentication
1750 scheme and the NFS level operations agree to use
1751 numeric uids/gids if the mount is using the
1752 'sec=sys' security flavour. In effect it is
1753 disabling idmapping, which can make migration from
1754 legacy NFSv2/v3 systems to NFSv4 easier.
1755 Servers that do not support this mode of operation
1756 will be autodetected by the client, and it will fall
1757 back to using the idmapper.
1758 To turn off this behaviour, set the value to '0'.
1760 [NFS4] Specify an additional fixed unique ident-
1761 ification string that NFSv4 clients can insert into
1762 their nfs_client_id4 string. This is typically a
1763 UUID that is generated at system install time.
1765 nfs.send_implementation_id =
1766 [NFSv4.1] Send client implementation identification
1767 information in exchange_id requests.
1768 If zero, no implementation identification information
1770 The default is to send the implementation identification
1773 nfsd.nfs4_disable_idmapping=
1774 [NFSv4] When set to the default of '1', the NFSv4
1775 server will return only numeric uids and gids to
1776 clients using auth_sys, and will accept numeric uids
1777 and gids from such clients. This is intended to ease
1778 migration from NFSv2/v3.
1780 objlayoutdriver.osd_login_prog=
1781 [NFS] [OBJLAYOUT] sets the pathname to the program which
1782 is used to automatically discover and login into new
1783 osd-targets. Please see:
1784 Documentation/filesystems/pnfs.txt for more explanations
1786 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1787 when a NMI is triggered.
1788 Format: [state][,regs][,debounce][,die]
1790 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1791 Format: [panic,][nopanic,][num]
1793 0 - turn nmi_watchdog off
1794 When panic is specified, panic when an NMI watchdog
1795 timeout occurs (or 'nopanic' to override the opposite
1797 This is useful when you use a panic=... timeout and
1798 need the box quickly up again.
1800 netpoll.carrier_timeout=
1801 [NET] Specifies amount of time (in seconds) that
1802 netpoll should wait for a carrier. By default netpoll
1805 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1806 emulation library even if a 387 maths coprocessor
1810 [HW] Never suspend the console
1811 Disable suspending of consoles during suspend and
1812 hibernate operations. Once disabled, debugging
1813 messages can reach various consoles while the rest
1814 of the system is being put to sleep (ie, while
1815 debugging driver suspend/resume hooks). This may
1816 not work reliably with all consoles, but is known
1817 to work with serial and VGA consoles.
1818 To facilitate more flexible debugging, we also add
1819 console_suspend, a printk module parameter to control
1820 it. Users could use console_suspend (usually
1821 /sys/module/printk/parameters/console_suspend) to
1822 turn on/off it dynamically.
1824 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1825 caches in the slab allocator. Saves per-node memory,
1826 but will impact performance.
1830 noapic [SMP,APIC] Tells the kernel to not make use of any
1831 IOAPICs that may be present in the system.
1833 noautogroup Disable scheduler automatic task group creation.
1835 nobats [PPC] Do not use BATs for mapping kernel lowmem
1836 on "Classic" PPC cores.
1840 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1842 nodelayacct [KNL] Disable per-task delay accounting
1844 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1846 nodsp [SH] Disable hardware DSP at boot time.
1848 noefi [X86] Disable EFI runtime services support.
1853 On X86-32 available only on PAE configured kernels.
1854 noexec=on: enable non-executable mappings (default)
1855 noexec=off: disable non-executable mappings
1858 Disable SMAP (Supervisor Mode Access Prevention)
1859 even if it is supported by processor.
1862 Disable SMEP (Supervisor Mode Execution Prevention)
1863 even if it is supported by processor.
1866 This affects only 32-bit executables.
1867 noexec32=on: enable non-executable mappings (default)
1868 read doesn't imply executable mappings
1869 noexec32=off: disable non-executable mappings
1870 read implies executable mappings
1872 nofpu [SH] Disable hardware FPU at boot time.
1874 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1875 register save and restore. The kernel will only save
1876 legacy floating-point registers on task switch.
1878 noxsave [BUGS=X86] Disables x86 extended register state save
1879 and restore using xsave. The kernel will fallback to
1880 enabling legacy floating-point and sse state.
1883 on enable eager fpu restore
1884 off disable eager fpu restore
1885 auto selects the default scheme, which automatically
1886 enables eagerfpu restore for xsaveopt.
1888 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1889 wfi(ARM) instruction doesn't work correctly and not to
1890 use it. This is also useful when using JTAG debugger.
1892 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1893 instruction doesn't work correctly and not to
1896 no_file_caps Tells the kernel not to honor file capabilities. The
1897 only way then for a file to be executed with privilege
1898 is to be setuid root or executed by root.
1900 nohalt [IA-64] Tells the kernel not to use the power saving
1901 function PAL_HALT_LIGHT when idle. This increases
1902 power-consumption. On the positive side, it reduces
1903 interrupt wake-up latency, which may improve performance
1904 in certain environments such as networked servers or
1907 nohz= [KNL] Boottime enable/disable dynamic ticks
1908 Valid arguments: on, off
1911 noiotrap [SH] Disables trapped I/O port accesses.
1913 noirqdebug [X86-32] Disables the code which attempts to detect and
1914 disable unhandled interrupt sources.
1916 no_timer_check [X86,APIC] Disables the code which tests for
1917 broken timer IRQ sources.
1919 noisapnp [ISAPNP] Disables ISA PnP code.
1921 noinitrd [RAM] Tells the kernel not to load any configured
1924 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1926 [Deprecated - use intremap=off]
1930 nojitter [IA-64] Disables jitter checking for ITC timers.
1932 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1934 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1937 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1938 steal time is computed, but won't influence scheduler
1941 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1943 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1945 noltlbs [PPC] Do not use large page/tlb entries for kernel
1946 lowmem mapping on PPC40x.
1948 nomca [IA-64] Disable machine check abort handling
1950 nomce [X86-32] Machine Check Exception
1952 nomfgpt [X86-32] Disable Multi-Function General Purpose
1953 Timer usage (for AMD Geode machines).
1955 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1956 shutdown the other cpus. Instead use the REBOOT_VECTOR
1959 nomodule Disable module load
1961 nopat [X86] Disable PAT (page attribute table extension of
1962 pagetables) support.
1964 norandmaps Don't use address space randomization. Equivalent to
1965 echo 0 > /proc/sys/kernel/randomize_va_space
1967 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1969 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1970 with UP alternatives
1972 noresidual [PPC] Don't use residual data on PReP machines.
1974 nordrand [X86] Disable the direct use of the RDRAND
1975 instruction even if it is supported by the
1976 processor. RDRAND is still available to user
1979 noresume [SWSUSP] Disables resume and restores original swap
1982 no-scroll [VGA] Disables scrollback.
1983 This is required for the Braillex ib80-piezo Braille
1984 reader made by F.H. Papenmeier (Germany).
1988 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1990 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1991 and disable the IO APIC. legacy for "maxcpus=0".
1993 nosoftlockup [KNL] Disable the soft-lockup detector.
1995 nosync [HW,M68K] Disables sync negotiation for all devices.
1997 notsc [BUGS=X86-32] Disable Time Stamp Counter
1999 nousb [USB] Disable the USB subsystem
2001 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2005 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2007 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2008 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2009 Some features depend on CPU0. Known dependencies are:
2010 1. Resume from suspend/hibernate depends on CPU0.
2011 Suspend/hibernate will fail if CPU0 is offline and you
2012 need to online CPU0 before suspend/hibernate.
2013 2. PIC interrupts also depend on CPU0. CPU0 can't be
2014 removed if a PIC interrupt is detected.
2015 It's said poweroff/reboot may depend on CPU0 on some
2016 machines although I haven't seen such issues so far
2017 after CPU0 is offline on a few tested machines.
2018 If the dependencies are under your control, you can
2019 turn on cpu0_hotplug.
2021 nptcg= [IA-64] Override max number of concurrent global TLB
2022 purges which is reported from either PAL_VM_SUMMARY or
2025 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2026 could support. nr_cpus=n : n >= 1 limits the kernel to
2027 supporting 'n' processors. Later in runtime you can not
2028 use hotplug cpu feature to put more cpu back to online.
2029 just like you compile the kernel NR_CPUS=n
2031 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2033 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2034 Allowed values are enable and disable
2036 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2037 one of ['zone', 'node', 'default'] can be specified
2038 This can be set from sysctl after boot.
2039 See Documentation/sysctl/vm.txt for details.
2041 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2042 See Documentation/debugging-via-ohci1394.txt for more
2045 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2046 Rather than timing out after 20 ms if an EC
2047 command is not properly ACKed, override the length
2048 of the timeout. We have interrupts disabled while
2049 waiting for the ACK, so if this is set too high
2050 interrupts *may* be lost!
2052 omap_mux= [OMAP] Override bootloader pin multiplexing.
2053 Format: <mux_mode0.mode_name=value>...
2054 For example, to override I2C bus2:
2055 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2057 oprofile.timer= [HW]
2058 Use timer interrupt instead of performance counters
2060 oprofile.cpu_type= Force an oprofile cpu type
2061 This might be useful if you have an older oprofile
2062 userland or if you want common events.
2063 Format: { arch_perfmon }
2064 arch_perfmon: [X86] Force use of architectural
2065 perfmon on Intel CPUs instead of the
2066 CPU specific event set.
2067 timer: [X86] Force use of architectural NMI
2068 timer mode (see also oprofile.timer
2069 for generic hr timer mode)
2070 [s390] Force legacy basic mode sampling
2071 (report cpu_type "timer")
2073 oops=panic Always panic on oopses. Default is to just kill the
2074 process, but there is a small probability of
2075 deadlocking the machine.
2076 This will also cause panics on machine check exceptions.
2077 Useful together with panic=30 to trigger a reboot.
2080 See Documentation/sound/oss/oss-parameters.txt
2082 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2083 timeout > 0: seconds before rebooting
2084 timeout = 0: wait forever
2085 timeout < 0: reboot immediately
2088 parkbd.port= [HW] Parallel port number the keyboard adapter is
2089 connected to, default is 0.
2091 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2092 0 for XT, 1 for AT (default is AT).
2095 parport= [HW,PPT] Specify parallel ports. 0 disables.
2096 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2097 Use 'auto' to force the driver to use any
2098 IRQ/DMA settings detected (the default is to
2099 ignore detected IRQ/DMA settings because of
2100 possible conflicts). You can specify the base
2101 address, IRQ, and DMA settings; IRQ and DMA
2102 should be numbers, or 'auto' (for using detected
2103 settings on that particular port), or 'nofifo'
2104 (to avoid using a FIFO even if it is detected).
2105 Parallel ports are assigned in the order they
2106 are specified on the command line, starting
2109 parport_init_mode= [HW,PPT]
2110 Configure VIA parallel port to operate in
2111 a specific mode. This is necessary on Pegasos
2112 computer where firmware has no options for setting
2113 up parallel port mode and sets it to spp.
2114 Currently this function knows 686a and 8231 chips.
2115 Format: [spp|ps2|epp|ecp|ecpepp]
2118 Halt all CPUs after the first oops has been printed for
2119 the specified number of seconds. This is to be used if
2120 your oopses keep scrolling off the screen.
2125 See header of drivers/block/paride/pcd.c.
2126 See also Documentation/blockdev/paride.txt.
2128 pci=option[,option...] [PCI] various PCI subsystem options:
2129 earlydump [X86] dump PCI config space before the kernel
2131 off [X86] don't probe for the PCI bus
2132 bios [X86-32] force use of PCI BIOS, don't access
2133 the hardware directly. Use this if your machine
2134 has a non-standard PCI host bridge.
2135 nobios [X86-32] disallow use of PCI BIOS, only direct
2136 hardware access methods are allowed. Use this
2137 if you experience crashes upon bootup and you
2138 suspect they are caused by the BIOS.
2139 conf1 [X86] Force use of PCI Configuration
2141 conf2 [X86] Force use of PCI Configuration
2143 noaer [PCIE] If the PCIEAER kernel config parameter is
2144 enabled, this kernel boot option can be used to
2145 disable the use of PCIE advanced error reporting.
2146 nodomains [PCI] Disable support for multiple PCI
2147 root domains (aka PCI segments, in ACPI-speak).
2148 nommconf [X86] Disable use of MMCONFIG for PCI
2150 check_enable_amd_mmconf [X86] check for and enable
2151 properly configured MMIO access to PCI
2152 config space on AMD family 10h CPU
2153 nomsi [MSI] If the PCI_MSI kernel config parameter is
2154 enabled, this kernel boot option can be used to
2155 disable the use of MSI interrupts system-wide.
2156 noioapicquirk [APIC] Disable all boot interrupt quirks.
2157 Safety option to keep boot IRQs enabled. This
2158 should never be necessary.
2159 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2160 primary IO-APIC for bridges that cannot disable
2161 boot IRQs. This fixes a source of spurious IRQs
2162 when the system masks IRQs.
2163 noioapicreroute [APIC] Disable workaround that uses the
2164 boot IRQ equivalent of an IRQ that connects to
2165 a chipset where boot IRQs cannot be disabled.
2166 The opposite of ioapicreroute.
2167 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2168 routing table. These calls are known to be buggy
2169 on several machines and they hang the machine
2170 when used, but on other computers it's the only
2171 way to get the interrupt routing table. Try
2172 this option if the kernel is unable to allocate
2173 IRQs or discover secondary PCI buses on your
2175 rom [X86] Assign address space to expansion ROMs.
2176 Use with caution as certain devices share
2177 address decoders between ROMs and other
2179 norom [X86] Do not assign address space to
2180 expansion ROMs that do not already have
2181 BIOS assigned address ranges.
2182 nobar [X86] Do not assign address space to the
2183 BARs that weren't assigned by the BIOS.
2184 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2185 assigned automatically to PCI devices. You can
2186 make the kernel exclude IRQs of your ISA cards
2188 pirqaddr=0xAAAAA [X86] Specify the physical address
2189 of the PIRQ table (normally generated
2190 by the BIOS) if it is outside the
2191 F0000h-100000h range.
2192 lastbus=N [X86] Scan all buses thru bus #N. Can be
2193 useful if the kernel is unable to find your
2194 secondary buses and you want to tell it
2195 explicitly which ones they are.
2196 assign-busses [X86] Always assign all PCI bus
2197 numbers ourselves, overriding
2198 whatever the firmware may have done.
2199 usepirqmask [X86] Honor the possible IRQ mask stored
2200 in the BIOS $PIR table. This is needed on
2201 some systems with broken BIOSes, notably
2202 some HP Pavilion N5400 and Omnibook XE3
2203 notebooks. This will have no effect if ACPI
2204 IRQ routing is enabled.
2205 noacpi [X86] Do not use ACPI for IRQ routing
2206 or for PCI scanning.
2207 use_crs [X86] Use PCI host bridge window information
2208 from ACPI. On BIOSes from 2008 or later, this
2209 is enabled by default. If you need to use this,
2210 please report a bug.
2211 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2212 If you need to use this, please report a bug.
2213 routeirq Do IRQ routing for all PCI devices.
2214 This is normally done in pci_enable_device(),
2215 so this option is a temporary workaround
2216 for broken drivers that don't call it.
2217 skip_isa_align [X86] do not align io start addr, so can
2218 handle more pci cards
2219 firmware [ARM] Do not re-enumerate the bus but instead
2220 just use the configuration from the
2221 bootloader. This is currently used on
2222 IXP2000 systems where the bus has to be
2223 configured a certain way for adjunct CPUs.
2224 noearly [X86] Don't do any early type 1 scanning.
2225 This might help on some broken boards which
2226 machine check when some devices' config space
2227 is read. But various workarounds are disabled
2228 and some IOMMU drivers will not work.
2229 bfsort Sort PCI devices into breadth-first order.
2230 This sorting is done to get a device
2231 order compatible with older (<= 2.4) kernels.
2232 nobfsort Don't sort PCI devices into breadth-first order.
2233 cbiosize=nn[KMG] The fixed amount of bus space which is
2234 reserved for the CardBus bridge's IO window.
2235 The default value is 256 bytes.
2236 cbmemsize=nn[KMG] The fixed amount of bus space which is
2237 reserved for the CardBus bridge's memory
2238 window. The default value is 64 megabytes.
2241 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2242 Specifies alignment and device to reassign
2243 aligned memory resources.
2244 If <order of align> is not specified,
2245 PAGE_SIZE is used as alignment.
2246 PCI-PCI bridge can be specified, if resource
2247 windows need to be expanded.
2248 ecrc= Enable/disable PCIe ECRC (transaction layer
2249 end-to-end CRC checking).
2250 bios: Use BIOS/firmware settings. This is the
2254 realloc= Enable/disable reallocating PCI bridge resources
2255 if allocations done by BIOS are too small to
2256 accommodate resources required by all child
2258 off: Turn realloc off
2260 realloc same as realloc=on
2261 noari do not use PCIe ARI.
2262 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2263 only look for one device below a PCIe downstream
2266 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2269 force Enable ASPM even on devices that claim not to support it.
2270 WARNING: Forcing ASPM on may cause system lockups.
2272 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2273 nomsi Do not use MSI for PCI Express Native Hotplug (this
2274 makes all PCIe ports use INTx for hotplug services).
2276 pcie_ports= [PCIE] PCIe ports handling:
2277 auto Ask the BIOS whether or not to use native PCIe services
2278 associated with PCIe ports (PME, hot-plug, AER). Use
2279 them only if that is allowed by the BIOS.
2280 native Use native PCIe services associated with PCIe ports
2282 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2285 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2286 nomsi Do not use MSI for native PCIe PME signaling (this makes
2287 all PCIe root ports use INTx for all services).
2289 pcmv= [HW,PCMCIA] BadgePAD 4
2292 See Documentation/blockdev/paride.txt.
2294 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2297 See arch/parisc/kernel/pdc_chassis.c
2299 percpu_alloc= Select which percpu first chunk allocator to use.
2300 Currently supported values are "embed" and "page".
2301 Archs may support subset or none of the selections.
2302 See comments in mm/percpu.c for details on each
2303 allocator. This parameter is primarily for debugging
2304 and performance comparison.
2307 See Documentation/blockdev/paride.txt.
2310 See Documentation/blockdev/paride.txt.
2312 pirq= [SMP,APIC] Manual mp-table setup
2313 See Documentation/x86/i386/IO-APIC.txt.
2315 plip= [PPT,NET] Parallel port network link
2316 Format: { parport<nr> | timid | 0 }
2317 See also Documentation/parport.txt.
2319 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2320 Override pmtimer IOPort with a hex value.
2324 Enable PNP debug messages (depends on the
2325 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2326 via /sys/module/pnp/parameters/debug. We always show
2327 current resource usage; turning this on also shows
2328 possible settings and some assignment information.
2334 { on | off | curr | res | no-curr | no-res }
2337 [ISAPNP] Exclude IRQs for the autoconfiguration
2340 [ISAPNP] Exclude DMAs for the autoconfiguration
2342 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2343 Ranges are in pairs (I/O port base and size).
2346 [ISAPNP] Exclude memory regions for the
2348 Ranges are in pairs (memory base and size).
2350 ports= [IP_VS_FTP] IPVS ftp helper module
2352 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2354 Format: <port>,<port>....
2356 print-fatal-signals=
2357 [KNL] debug: print fatal signals
2359 If enabled, warn about various signal handling
2360 related application anomalies: too many signals,
2361 too many POSIX.1 timers, fatal signals causing a
2364 If you hit the warning due to signal overflow,
2365 you might want to try "ulimit -i unlimited".
2369 printk.always_kmsg_dump=
2370 Trigger kmsg_dump for cases other than kernel oops or
2372 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2375 printk.time= Show timing data prefixed to each printk message line
2376 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2378 processor.max_cstate= [HW,ACPI]
2379 Limit processor to maximum C-state
2380 max_cstate=9 overrides any DMI blacklist limit.
2382 processor.nocst [HW,ACPI]
2383 Ignore the _CST method to determine C-states,
2384 instead using the legacy FADT method
2386 profile= [KNL] Enable kernel profiling via /proc/profile
2387 Format: [schedule,]<number>
2388 Param: "schedule" - profile schedule points.
2389 Param: <number> - step/bucket size as a power of 2 for
2390 statistical time based profiling.
2391 Param: "sleep" - profile D-state sleeping (millisecs).
2392 Requires CONFIG_SCHEDSTATS
2393 Param: "kvm" - profile VM exits.
2395 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2397 See Documentation/blockdev/ramdisk.txt.
2399 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2400 probe for; one of (bare|imps|exps|lifebook|any).
2401 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2403 psmouse.resetafter= [HW,MOUSE]
2404 Try to reset the device after so many bad packets
2407 [HW,MOUSE] Set desired mouse resolution, in dpi.
2408 psmouse.smartscroll=
2409 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2410 0 = disabled, 1 = enabled (default).
2412 pstore.backend= Specify the name of the pstore backend to use
2415 See Documentation/blockdev/paride.txt.
2418 [KNL] Number of legacy pty's. Overwrites compiled-in
2421 quiet [KNL] Disable most log messages
2426 See Documentation/md.txt.
2428 ramdisk_blocksize= [RAM]
2429 See Documentation/blockdev/ramdisk.txt.
2431 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2432 See Documentation/blockdev/ramdisk.txt.
2434 rcu_nocbs= [KNL,BOOT]
2435 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2436 the specified list of CPUs to be no-callback CPUs.
2437 Invocation of these CPUs' RCU callbacks will
2438 be offloaded to "rcuoN" kthreads created for
2439 that purpose. This reduces OS jitter on the
2440 offloaded CPUs, which can be useful for HPC and
2441 real-time workloads. It can also improve energy
2442 efficiency for asymmetric multiprocessors.
2444 rcu_nocb_poll [KNL,BOOT]
2445 Rather than requiring that offloaded CPUs
2446 (specified by rcu_nocbs= above) explicitly
2447 awaken the corresponding "rcuoN" kthreads,
2448 make these kthreads poll for callbacks.
2449 This improves the real-time response for the
2450 offloaded CPUs by relieving them of the need to
2451 wake up the corresponding kthread, but degrades
2452 energy efficiency by requiring that the kthreads
2453 periodically wake up to do the polling.
2455 rcutree.blimit= [KNL,BOOT]
2456 Set maximum number of finished RCU callbacks to process
2459 rcutree.fanout_leaf= [KNL,BOOT]
2460 Increase the number of CPUs assigned to each
2461 leaf rcu_node structure. Useful for very large
2464 rcutree.qhimark= [KNL,BOOT]
2465 Set threshold of queued
2466 RCU callbacks over which batch limiting is disabled.
2468 rcutree.qlowmark= [KNL,BOOT]
2469 Set threshold of queued RCU callbacks below which
2470 batch limiting is re-enabled.
2472 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2473 Suppress RCU CPU stall warning messages.
2475 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2476 Set timeout for RCU CPU stall warning messages.
2478 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2479 Set delay from grace-period initialization to
2480 first attempt to force quiescent states.
2481 Units are jiffies, minimum value is zero,
2482 and maximum value is HZ.
2484 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2485 Set delay between subsequent attempts to force
2486 quiescent states. Units are jiffies, minimum
2487 value is one, and maximum value is HZ.
2489 rcutorture.fqs_duration= [KNL,BOOT]
2490 Set duration of force_quiescent_state bursts.
2492 rcutorture.fqs_holdoff= [KNL,BOOT]
2493 Set holdoff time within force_quiescent_state bursts.
2495 rcutorture.fqs_stutter= [KNL,BOOT]
2496 Set wait time between force_quiescent_state bursts.
2498 rcutorture.irqreader= [KNL,BOOT]
2499 Test RCU readers from irq handlers.
2501 rcutorture.n_barrier_cbs= [KNL,BOOT]
2502 Set callbacks/threads for rcu_barrier() testing.
2504 rcutorture.nfakewriters= [KNL,BOOT]
2505 Set number of concurrent RCU writers. These just
2506 stress RCU, they don't participate in the actual
2507 test, hence the "fake".
2509 rcutorture.nreaders= [KNL,BOOT]
2510 Set number of RCU readers.
2512 rcutorture.onoff_holdoff= [KNL,BOOT]
2513 Set time (s) after boot for CPU-hotplug testing.
2515 rcutorture.onoff_interval= [KNL,BOOT]
2516 Set time (s) between CPU-hotplug operations, or
2517 zero to disable CPU-hotplug testing.
2519 rcutorture.shuffle_interval= [KNL,BOOT]
2520 Set task-shuffle interval (s). Shuffling tasks
2521 allows some CPUs to go into dyntick-idle mode
2522 during the rcutorture test.
2524 rcutorture.shutdown_secs= [KNL,BOOT]
2525 Set time (s) after boot system shutdown. This
2526 is useful for hands-off automated testing.
2528 rcutorture.stall_cpu= [KNL,BOOT]
2529 Duration of CPU stall (s) to test RCU CPU stall
2530 warnings, zero to disable.
2532 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2533 Time to wait (s) after boot before inducing stall.
2535 rcutorture.stat_interval= [KNL,BOOT]
2536 Time (s) between statistics printk()s.
2538 rcutorture.stutter= [KNL,BOOT]
2539 Time (s) to stutter testing, for example, specifying
2540 five seconds causes the test to run for five seconds,
2541 wait for five seconds, and so on. This tests RCU's
2542 ability to transition abruptly to and from idle.
2544 rcutorture.test_boost= [KNL,BOOT]
2545 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2546 "Maybe" means test if the RCU implementation
2547 under test support RCU priority boosting.
2549 rcutorture.test_boost_duration= [KNL,BOOT]
2550 Duration (s) of each individual boost test.
2552 rcutorture.test_boost_interval= [KNL,BOOT]
2553 Interval (s) between each boost test.
2555 rcutorture.test_no_idle_hz= [KNL,BOOT]
2556 Test RCU's dyntick-idle handling. See also the
2557 rcutorture.shuffle_interval parameter.
2559 rcutorture.torture_type= [KNL,BOOT]
2560 Specify the RCU implementation to test.
2562 rcutorture.verbose= [KNL,BOOT]
2563 Enable additional printk() statements.
2567 Run specified binary instead of /init from the ramdisk,
2568 used for early userspace startup. See initrd.
2570 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2571 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2572 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2575 [KNL, SMP] Set scheduler's default relax_domain_level.
2576 See Documentation/cgroups/cpusets.txt.
2578 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2580 reservetop= [X86-32]
2582 Reserves a hole at the top of the kernel virtual
2587 Set the amount of memory to reserve for BIOS at
2588 the bottom of the address space.
2590 reset_devices [KNL] Force drivers to reset the underlying device
2591 during initialization.
2594 Specify the partition device for software suspend
2596 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2598 resume_offset= [SWSUSP]
git.openpandora.org / pandora-kernel.git / blob