4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 DRM Direct Rendering Management support is enabled.
49 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
50 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
51 EFI EFI Partitioning (GPT) is enabled
52 EIDE EIDE/ATAPI support is enabled.
53 EVM Extended Verification Module
54 FB The frame buffer device is enabled.
55 FTRACE Function tracing enabled.
56 GCOV GCOV profiling is enabled.
57 HW Appropriate hardware is enabled.
58 IA-64 IA-64 architecture is enabled.
59 IMA Integrity measurement architecture is enabled.
60 IOSCHED More than one I/O scheduler is enabled.
61 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
62 IPV6 IPv6 support is enabled.
63 ISAPNP ISA PnP code is enabled.
64 ISDN Appropriate ISDN support is enabled.
65 JOY Appropriate joystick support is enabled.
66 KGDB Kernel debugger support is enabled.
67 KVM Kernel Virtual Machine support is enabled.
68 LIBATA Libata driver is enabled
69 LP Printer support is enabled.
70 LOOP Loopback device support is enabled.
71 M68k M68k architecture is enabled.
72 These options have more detailed description inside of
73 Documentation/m68k/kernel-options.txt.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VMMIO Driver for memory mapped virtio devices is enabled.
114 VGA The VGA console has been enabled.
115 VT Virtual terminal support is enabled.
116 WDT Watchdog support is enabled.
117 XT IBM PC/XT MFM hard disk support is enabled.
118 X86-32 X86-32, aka i386 architecture is enabled.
119 X86-64 X86-64 architecture is enabled.
120 More X86-64 boot options can be found in
121 Documentation/x86/x86_64/boot-options.txt .
122 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
123 XEN Xen support is enabled
125 In addition, the following text indicates that the option:
127 BUGS= Relates to possible processor bugs on the said processor.
128 KNL Is a kernel start-up parameter.
129 BOOT Is a boot loader parameter.
131 Parameters denoted with BOOT are actually interpreted by the boot
132 loader, and have no meaning to the kernel directly.
133 Do not modify the syntax of boot loader parameters without extreme
134 need or coordination with <Documentation/x86/boot.txt>.
136 There are also arch-specific kernel-parameters not documented here.
137 See for example <Documentation/x86/x86_64/boot-options.txt>.
139 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
140 a trailing = on the name of any parameter states that that parameter will
141 be entered as an environment variable, whereas its absence indicates that
142 it will appear as a kernel argument readable via /proc/cmdline by programs
143 running once the system is up.
145 The number of kernel parameters is not limited, but the length of the
146 complete command line (parameters including spaces etc.) is limited to
147 a fixed number of characters. This limit depends on the architecture
148 and is between 256 and 4096 characters. It is defined in the file
149 ./include/asm/setup.h as COMMAND_LINE_SIZE.
151 Finally, the [KMG] suffix is commonly described after a number of kernel
152 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
153 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
154 bytes respectively. Such letter suffixes can also be entirely omitted.
158 Advanced Configuration and Power Interface
159 Format: { force | off | strict | noirq | rsdt }
160 force -- enable ACPI if default was off
161 off -- disable ACPI if default was on
162 noirq -- do not use ACPI for IRQ routing
163 strict -- Be less tolerant of platforms that are not
164 strictly ACPI specification compliant.
165 rsdt -- prefer RSDT over (default) XSDT
166 copy_dsdt -- copy DSDT to memory
168 See also Documentation/power/runtime_pm.txt, pci=noacpi
170 acpi_rsdp= [ACPI,EFI,KEXEC]
171 Pass the RSDP address to the kernel, mostly used
172 on machines running EFI runtime service to boot the
173 second kernel for kdump.
175 acpi_apic_instance= [ACPI, IOAPIC]
177 2: use 2nd APIC table, if available
178 1,0: use 1st APIC table
181 acpi_backlight= [HW,ACPI]
182 acpi_backlight=vendor
184 If set to vendor, prefer vendor specific driver
185 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
186 of the ACPI video.ko driver.
188 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
189 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
191 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
192 debug output. Bits in debug_layer correspond to a
193 _COMPONENT in an ACPI source file, e.g.,
194 #define _COMPONENT ACPI_PCI_COMPONENT
195 Bits in debug_level correspond to a level in
196 ACPI_DEBUG_PRINT statements, e.g.,
197 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
198 The debug_level mask defaults to "info". See
199 Documentation/acpi/debug.txt for more information about
200 debug layers and levels.
202 Enable processor driver info messages:
203 acpi.debug_layer=0x20000000
204 Enable PCI/PCI interrupt routing info messages:
205 acpi.debug_layer=0x400000
206 Enable AML "Debug" output, i.e., stores to the Debug
207 object while interpreting AML:
208 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
209 Enable all messages related to ACPI hardware:
210 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212 Some values produce so much output that the system is
213 unusable. The "log_buf_len" parameter may be useful
214 if you need to capture more output.
216 acpi_irq_balance [HW,ACPI]
217 ACPI will balance active IRQs
220 acpi_irq_nobalance [HW,ACPI]
221 ACPI will not move active IRQs (default)
224 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
225 Format: <irq>,<irq>...
227 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 Format: <irq>,<irq>...
231 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
234 Format: To spoof as Windows 98: ="Microsoft Windows"
236 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
237 acpi_osi="string1" # add string1 -- only one string
238 acpi_osi="!string2" # remove built-in string2
239 acpi_osi= # disable all strings
242 Override the pmtimer bug detection: force the kernel
243 to assume that this machine's pmtimer latches its value
244 and always returns good values.
246 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
247 Format: { level | edge | high | low }
249 acpi_serialize [HW,ACPI] force serialization of AML methods
251 acpi_skip_timer_override [HW,ACPI]
252 Recognize and ignore IRQ0/pin2 Interrupt Override.
253 For broken nForce2 BIOS resulting in XT-PIC timer.
255 acpi_sleep= [HW,ACPI] Sleep options
256 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
257 old_ordering, nonvs, sci_force_enable }
258 See Documentation/power/video.txt for information on
260 s3_beep is for debugging; it makes the PC's speaker beep
261 as soon as the kernel's real-mode entry point is called.
262 s4_nohwsig prevents ACPI hardware signature from being
263 used during resume from hibernation.
264 old_ordering causes the ACPI 1.0 ordering of the _PTS
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
267 of _PTS is used by default).
268 nonvs prevents the kernel from saving/restoring the
269 ACPI NVS memory during suspend/hibernation and resume.
270 sci_force_enable causes the kernel to set SCI_EN directly
271 on resume from S1/S3 (which is against the ACPI spec,
272 but some broken systems don't work without it).
274 acpi_use_timer_override [HW,ACPI]
275 Use timer override. For some broken Nvidia NF5 boards
276 that require a timer override, but don't have HPET
278 acpi_enforce_resources= [ACPI]
279 { strict | lax | no }
280 Check for resource conflicts between native drivers
281 and ACPI OperationRegions (SystemIO and SystemMemory
282 only). IO ports and memory declared in ACPI might be
283 used by the ACPI subsystem in arbitrary AML code and
284 can interfere with legacy drivers.
285 strict (default): access to resources claimed by ACPI
286 is denied; legacy drivers trying to access reserved
287 resources will fail to bind to device using them.
288 lax: access to resources claimed by ACPI is allowed;
289 legacy drivers trying to access reserved resources
290 will bind successfully but a warning message is logged.
291 no: ACPI OperationRegions are not marked as reserved,
292 no further checks are performed.
294 add_efi_memmap [EFI; X86] Include EFI memory map in
295 kernel's map of available physical RAM.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/sound/alsa/alsa-parameters.txt
307 Allow the default userspace alignment fault handler
308 behaviour to be specified. Bit 0 enables warnings,
309 bit 1 enables fixups, and bit 2 sends a segfault.
311 align_va_addr= [X86-64]
312 Align virtual addresses by clearing slice [14:12] when
313 allocating a VMA at process creation time. This option
314 gives you up to 3% performance improvement on AMD F15h
315 machines (where it is enabled by default) for a
316 CPU-intensive style benchmark, and it can vary highly in
317 a microbenchmark depending on workload and compiler.
319 32: only for 32-bit processes
320 64: only for 64-bit processes
321 on: enable for both 32- and 64-bit processes
322 off: disable for both 32- and 64-bit processes
324 alloc_snapshot [FTRACE]
325 Allocate the ftrace snapshot buffer on boot up when the
326 main buffer is allocated. This is handy if debugging
327 and you need to use tracing_snapshot() on boot up, and
328 do not want to use tracing_snapshot_alloc() as it needs
329 to be done where GFP_KERNEL allocations are allowed.
331 amd_iommu= [HW,X86-64]
332 Pass parameters to the AMD IOMMU driver in the system.
334 fullflush - enable flushing of IO/TLB entries when
335 they are unmapped. Otherwise they are
336 flushed before they will be reused, which
338 off - do not initialize any AMD IOMMU found in
340 force_isolation - Force device isolation for all
341 devices. The IOMMU driver is not
342 allowed anymore to lift isolation
343 requirements as needed. This option
344 does not override iommu=pt
346 amd_iommu_dump= [HW,X86-64]
347 Enable AMD IOMMU driver option to dump the ACPI table
348 for AMD IOMMU. With this option enabled, AMD IOMMU
349 driver will print ACPI tables for AMD IOMMU during
350 IOMMU initialization.
352 amijoy.map= [HW,JOY] Amiga joystick support
353 Map of devices attached to JOY0DAT and JOY1DAT
355 See also Documentation/input/joystick.txt
357 analog.map= [HW,JOY] Analog joystick and gamepad support
358 Specifies type or capabilities of an analog joystick
359 connected to one of 16 gameports
360 Format: <type1>,<type2>,..<type16>
363 Power management functions (SPARCstation-4/5 + deriv.)
365 Disable APC CPU standby support. SPARCstation-Fox does
366 not play well with APC CPU idle - disable it if you have
367 APC and your system crashes randomly.
369 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
370 Change the output verbosity whilst booting
371 Format: { quiet (default) | verbose | debug }
372 Change the amount of debugging information output
373 when initialising the APIC and IO-APIC components.
376 See Documentation/networking/ipv6.txt.
378 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
379 Limit apic dumping. The parameter defines the maximal
380 number of local apics being dumped. Also it is possible
381 to set it to "all" by meaning -- no limit here.
382 Format: { 1 (default) | 2 | ... | all }.
383 The parameter valid if only apic=debug or
384 apic=verbose is specified.
385 Example: apic=debug show_lapic=all
387 apm= [APM] Advanced Power Management
388 See header of arch/x86/kernel/apm_32.c.
390 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
391 Format: <io>,<irq>,<nodeID>
395 atarimouse= [HW,MOUSE] Atari Mouse
397 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
398 EzKey and similar keyboards
400 atkbd.reset= [HW] Reset keyboard during initialization
402 atkbd.set= [HW] Select keyboard code set
403 Format: <int> (2 = AT (default), 3 = PS/2)
405 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
408 atkbd.softraw= [HW] Choose between synthetic and real raw mode
409 Format: <bool> (0 = real, 1 = synthetic (default))
411 atkbd.softrepeat= [HW]
412 Use software keyboard repeat
414 baycom_epp= [HW,AX25]
417 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
419 See header of drivers/net/hamradio/baycom_par.c.
421 baycom_ser_fdx= [HW,AX25]
422 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
423 Format: <io>,<irq>,<mode>[,<baud>]
424 See header of drivers/net/hamradio/baycom_ser_fdx.c.
426 baycom_ser_hdx= [HW,AX25]
427 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
428 Format: <io>,<irq>,<mode>
429 See header of drivers/net/hamradio/baycom_ser_hdx.c.
431 boot_delay= Milliseconds to delay each printk during boot.
432 Values larger than 10 seconds (10000) are changed to
436 bootmem_debug [KNL] Enable bootmem allocator debug messages.
438 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
439 bttv.radio= Most important insmod options are available as
441 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
444 bulk_remove=off [PPC] This parameter disables the use of the pSeries
445 firmware feature for flushing multiple hpte entries
448 c101= [NET] Moxa C101 synchronous serial card
450 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
451 Sometimes CPU hardware bugs make them report the cache
452 size incorrectly. The kernel will attempt work arounds
453 to fix known problems, but for some CPUs it is not
454 possible to determine what the correct size should be.
455 This option provides an override for these situations.
457 ccw_timeout_log [S390]
458 See Documentation/s390/CommonIO for details.
460 cgroup_disable= [KNL] Disable a particular controller
461 Format: {name of the controller(s) to disable}
462 {Currently supported controllers - "memory"}
464 checkreqprot [SELINUX] Set initial checkreqprot flag value.
465 Format: { "0" | "1" }
466 See security/selinux/Kconfig help text.
467 0 -- check protection applied by kernel (includes
468 any implied execute protection).
469 1 -- check protection requested by application.
470 Default value is set via a kernel config option.
471 Value can be changed at runtime via
472 /selinux/checkreqprot.
475 See Documentation/s390/CommonIO for details.
478 Keep all clocks already enabled by bootloader on,
479 even if no driver has claimed them. This is useful
480 for debug and development, but should not be
481 needed on a platform with proper driver support.
482 For more information, see Documentation/clk.txt.
484 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
486 Forces specified clocksource (if available) to be used
487 when calculating gettimeofday(). If specified
488 clocksource is not available, it defaults to PIT.
489 Format: { pit | tsc | cyclone | pmtmr }
491 clocksource= Override the default clocksource
493 Override the default clocksource and use the clocksource
494 with the name specified.
495 Some clocksource names to choose from, depending on
497 [all] jiffies (this is the base, fallback clocksource)
499 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
500 pxa_timer,timer3,32k_counter,timer0_1
502 [X86-32] pit,hpet,tsc;
503 scx200_hrt on Geode; cyclone on IBM x440
511 clearcpuid=BITNUM [X86]
512 Disable CPUID feature X for the kernel. See
513 arch/x86/include/asm/cpufeature.h for the valid bit
514 numbers. Note the Linux specific bits are not necessarily
515 stable over kernel options, but the vendor specific
517 Also note that user programs calling CPUID directly
518 or using the feature without checking anything
519 will still see it. This just prevents it from
520 being used by the kernel or shown in /proc/cpuinfo.
521 Also note the kernel might malfunction if you disable
525 Sets the size of kernel global memory area for contiguous
526 memory allocations. For more information, see
527 include/linux/dma-contiguous.h
529 cmo_free_hint= [PPC] Format: { yes | no }
530 Specify whether pages are marked as being inactive
531 when they are freed. This is used in CMO environments
532 to determine OS memory pressure for page stealing by
536 coherent_pool=nn[KMG] [ARM,KNL]
537 Sets the size of memory pool for coherent, atomic dma
538 allocations, by default set to 256K.
540 code_bytes [X86] How many bytes of object code to print
545 com20020= [HW,NET] ARCnet - COM20020 chipset
547 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
549 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
553 ARCnet - COM90xx chipset (memory-mapped buffers)
554 Format: <io>[,<irq>[,<memstart>]]
556 condev= [HW,S390] console device
559 console= [KNL] Output console device and options.
561 tty<n> Use the virtual console device <n>.
565 Use the specified serial port. The options are of
566 the form "bbbbpnf", where "bbbb" is the baud rate,
567 "p" is parity ("n", "o", or "e"), "n" is number of
568 bits, and "f" is flow control ("r" for RTS or
569 omit it). Default is "9600n8".
571 See Documentation/serial-console.txt for more
573 Documentation/networking/netconsole.txt for an
576 uart[8250],io,<addr>[,options]
577 uart[8250],mmio,<addr>[,options]
578 Start an early, polled-mode console on the 8250/16550
579 UART at the specified I/O port or MMIO address,
580 switching to the matching ttyS device later. The
581 options are the same as for ttyS, above.
582 hvc<n> Use the hypervisor console device <n>. This is for
583 both Xen and PowerPC hypervisors.
585 If the device connected to the port is not a TTY but a braille
586 device, prepend "brl," before the device type, for instance
588 For now, only VisioBraille is supported.
590 consoleblank= [KNL] The console blank (screen saver) timeout in
591 seconds. Defaults to 10*60 = 10mins. A value of 0
592 disables the blank timer.
595 [KNL] Change the default value for
596 /proc/<pid>/coredump_filter.
597 See also Documentation/filesystems/proc.txt.
599 cpuidle.off=1 [CPU_IDLE]
600 disable the cpuidle sub-system
602 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
604 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
606 crashkernel=size[KMG][@offset[KMG]]
607 [KNL] Using kexec, Linux can switch to a 'crash kernel'
608 upon panic. This parameter reserves the physical
609 memory region [offset, offset + size] for that kernel
610 image. If '@offset' is omitted, then a suitable offset
611 is selected automatically. Check
612 Documentation/kdump/kdump.txt for further details.
614 crashkernel=range1:size1[,range2:size2,...][@offset]
615 [KNL] Same as above, but depends on the memory
616 in the running system. The syntax of range is
617 start-[end] where start and end are both
618 a memory unit (amount[KMG]). See also
619 Documentation/kdump/kdump.txt for an example.
621 crashkernel=size[KMG],high
622 [KNL, x86_64] range could be above 4G. Allow kernel
623 to allocate physical memory region from top, so could
624 be above 4G if system have more than 4G ram installed.
625 Otherwise memory region will be allocated below 4G, if
627 It will be ignored if crashkernel=X is specified.
628 crashkernel=size[KMG],low
629 [KNL, x86_64] range under 4G. When crashkernel=X,high
630 is passed, kernel could allocate physical memory region
631 above 4G, that cause second kernel crash on system
632 that require some amount of low memory, e.g. swiotlb
633 requires at least 64M+32K low memory. Kernel would
634 try to allocate 72M below 4G automatically.
635 This one let user to specify own low range under 4G
636 for second kernel instead.
637 0: to disable low allocation.
638 It will be ignored when crashkernel=X,high is not used
639 or memory reserved is below 4G.
644 cs89x0_media= [HW,NET]
645 Format: { rj45 | aui | bnc }
648 See header of drivers/s390/block/dasd_devmap.c.
650 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
651 (one device per port)
652 Format: <port#>,<type>
653 See also Documentation/input/joystick-parport.txt
655 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
656 time. See Documentation/dynamic-debug-howto.txt for
657 details. Deprecated, see dyndbg.
659 debug [KNL] Enable kernel debugging (events log level).
662 [KNL] verbose self-tests
664 Print debugging info while doing the locking API
666 We default to 0 (no extra messages), setting it to
667 1 will print _a lot_ more information - normally
668 only useful to kernel developers.
670 debug_objects [KNL] Enable object debugging
673 [KNL] Disable object debugging
675 debug_guardpage_minorder=
676 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
677 parameter allows control of the order of pages that will
678 be intentionally kept free (and hence protected) by the
679 buddy allocator. Bigger value increase the probability
680 of catching random memory corruption, but reduce the
681 amount of memory for normal system use. The maximum
682 possible value is MAX_ORDER/2. Setting this parameter
683 to 1 or 2 should be enough to identify most random
684 memory corruption problems caused by bugs in kernel or
685 driver code when a CPU writes to (or reads from) a
686 random memory location. Note that there exists a class
687 of memory corruptions problems caused by buggy H/W or
688 F/W or by drivers badly programing DMA (basically when
689 memory is written at bus level and the CPU MMU is
690 bypassed) which are not detectable by
691 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
692 tracking down these problems.
694 debugpat [X86] Enable PAT debugging
696 decnet.addr= [HW,NET]
697 Format: <area>[,<node>]
698 See also Documentation/networking/decnet.txt.
701 [same as hugepagesz=] The size of the default
702 HugeTLB page size. This is the size represented by
703 the legacy /proc/ hugepages APIs, used for SHM, and
704 default size when mounting hugetlbfs filesystems.
705 Defaults to the default architecture's huge page size
709 Set number of hash buckets for dentry cache.
712 IO parameters + enable/disable command.
714 digiepca= [HW,SERIAL]
715 See drivers/char/README.epca and
716 Documentation/serial/digiepca.txt.
719 See Documentation/networking/ipv6.txt.
721 disable_ddw [PPC/PSERIES]
722 Disable Dynamic DMA Window support. Use this if
723 to workaround buggy firmware.
726 See Documentation/networking/ipv6.txt.
728 disable_mtrr_cleanup [X86]
729 The kernel tries to adjust MTRR layout from continuous
730 to discrete, to make X server driver able to add WB
731 entry later. This parameter disables that.
733 disable_mtrr_trim [X86, Intel and AMD only]
734 By default the kernel will trim any uncacheable
735 memory out of your available memory pool based on
736 MTRR settings. This parameter disables that behavior,
737 possibly causing your machine to run very slowly.
739 disable_timer_pin_1 [X86]
740 Disable PIN 1 of APIC timer
741 Can be useful to work around chipset bugs.
743 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
744 this option disables the debugging code at boot.
746 dma_debug_entries=<number>
747 This option allows to tune the number of preallocated
748 entries for DMA-API debugging code. One entry is
749 required per DMA-API allocation. Use this if the
750 DMA-API debugging code disables itself because the
751 architectural default is too low.
753 dma_debug_driver=<driver_name>
754 With this option the DMA-API debugging driver
755 filter feature can be enabled at boot time. Just
756 pass the driver to filter for as the parameter.
757 The filter can be disabled or changed to another
758 driver later using sysfs.
760 drm_kms_helper.edid_firmware=[<connector>:]<file>
761 Broken monitors, graphic adapters and KVMs may
762 send no or incorrect EDID data sets. This parameter
763 allows to specify an EDID data set in the
764 /lib/firmware directory that is used instead.
765 Generic built-in EDID data sets are used, if one of
766 edid/1024x768.bin, edid/1280x1024.bin,
767 edid/1680x1050.bin, or edid/1920x1080.bin is given
768 and no file with the same name exists. Details and
769 instructions how to build your own EDID data are
770 available in Documentation/EDID/HOWTO.txt. An EDID
771 data set will only be used for a particular connector,
772 if its name and a colon are prepended to the EDID
777 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
778 module.dyndbg[="val"]
779 Enable debug messages at boot time. See
780 Documentation/dynamic-debug-howto.txt for details.
782 earlycon= [KNL] Output early console device and options.
783 uart[8250],io,<addr>[,options]
784 uart[8250],mmio,<addr>[,options]
785 uart[8250],mmio32,<addr>[,options]
786 Start an early, polled-mode console on the 8250/16550
787 UART at the specified I/O port or MMIO address.
788 MMIO inter-register address stride is either 8-bit
789 (mmio) or 32-bit (mmio32).
790 The options are the same as for ttyS, above.
792 earlyprintk= [X86,SH,BLACKFIN]
795 earlyprintk=serial[,ttySn[,baudrate]]
796 earlyprintk=ttySn[,baudrate]
797 earlyprintk=dbgp[debugController#]
799 Append ",keep" to not disable it when the real console
802 Only vga or serial or usb debug port at a time.
804 Currently only ttyS0 and ttyS1 are supported.
806 Interaction with the standard serial driver is not
809 The VGA output is eventually overwritten by the real
812 The xen output can only be used by Xen PV guests.
814 ekgdboc= [X86,KGDB] Allow early kernel console debugging
817 This is designed to be used in conjunction with
818 the boot argument: earlyprintk=vga
821 Format: {"off" | "on" | "skip[mbr]"}
823 efi_no_storage_paranoia [EFI; X86]
824 Using this parameter you can use more than 50% of
825 your efi variable storage. Use this parameter only if
826 you are really sure that your UEFI does sane gc and
827 fulfills the spec otherwise your board may brick.
829 eisa_irq_edge= [PARISC,HW]
830 See header of drivers/parisc/eisa.c.
833 See comment before function elanfreq_setup() in
834 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
837 Format: {"cfq" | "deadline" | "noop"}
838 See Documentation/block/cfq-iosched.txt and
839 Documentation/block/deadline-iosched.txt for details.
841 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
842 Specifies physical address of start of kernel core
843 image elf header and optionally the size. Generally
844 kexec loader will pass this option to capture kernel.
845 See Documentation/kdump/kdump.txt for details.
847 enable_mtrr_cleanup [X86]
848 The kernel tries to adjust MTRR layout from continuous
849 to discrete, to make X server driver able to add WB
850 entry later. This parameter enables that.
852 enable_timer_pin_1 [X86]
853 Enable PIN 1 of APIC timer
854 Can be useful to work around chipset bugs
855 (in particular on some ATI chipsets).
856 The kernel tries to set a reasonable default.
858 enforcing [SELINUX] Set initial enforcing status.
860 See security/selinux/Kconfig help text.
861 0 -- permissive (log only, no denials).
862 1 -- enforcing (deny and log).
864 Value can be changed at runtime via /selinux/enforce.
867 Disable Error Record Serialization Table (ERST)
870 ether= [HW,NET] Ethernet cards parameters
871 This option is obsoleted by the "netdev=" option, which
872 has equivalent usage. See its documentation for details.
876 Permit 'security.evm' to be updated regardless of
877 current integrity status.
881 fail_make_request=[KNL]
882 General fault injection mechanism.
883 Format: <interval>,<probability>,<space>,<times>
884 See also Documentation/fault-injection/.
887 See Documentation/blockdev/floppy.txt.
889 force_pal_cache_flush
890 [IA-64] Avoid check_sal_cache_flush which may hang on
891 buggy SAL_CACHE_FLUSH implementations. Using this
892 parameter will force ia64_sal_cache_flush to call
893 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
896 [FTRACE] will set and start the specified tracer
897 as early as possible in order to facilitate early
900 ftrace_dump_on_oops[=orig_cpu]
901 [FTRACE] will dump the trace buffers on oops.
902 If no parameter is passed, ftrace will dump
903 buffers of all CPUs, but if you pass orig_cpu, it will
904 dump only the buffer of the CPU that triggered the
907 ftrace_filter=[function-list]
908 [FTRACE] Limit the functions traced by the function
909 tracer at boot up. function-list is a comma separated
910 list of functions. This list can be changed at run
911 time by the set_ftrace_filter file in the debugfs
914 ftrace_notrace=[function-list]
915 [FTRACE] Do not trace the functions specified in
916 function-list. This list can be changed at run time
917 by the set_ftrace_notrace file in the debugfs
920 ftrace_graph_filter=[function-list]
921 [FTRACE] Limit the top level callers functions traced
922 by the function graph tracer at boot up.
923 function-list is a comma separated list of functions
924 that can be changed at run time by the
925 set_graph_function file in the debugfs tracing directory.
928 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
929 support via parallel port (up to 5 devices per port)
930 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
931 See also Documentation/input/joystick-parport.txt
935 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
939 gcov_persist= [GCOV] When non-zero (default), profiling data for
940 kernel modules is saved and remains accessible via
941 debugfs, even when the module is unloaded/reloaded.
942 When zero, profiling data is discarded and associated
943 debugfs files are removed at module unload time.
945 gpt [EFI] Forces disk with valid GPT signature but
946 invalid Protective MBR to be treated as GPT.
948 grcan.enable0= [HW] Configuration of physical interface 0. Determines
949 the "Enable 0" bit of the configuration register.
952 grcan.enable1= [HW] Configuration of physical interface 1. Determines
953 the "Enable 0" bit of the configuration register.
956 grcan.select= [HW] Select which physical interface to use.
959 grcan.txsize= [HW] Sets the size of the tx buffer.
960 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
962 grcan.rxsize= [HW] Sets the size of the rx buffer.
963 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
966 hashdist= [KNL,NUMA] Large hashes allocated during boot
967 are distributed across NUMA nodes. Defaults on
968 for 64-bit NUMA, off otherwise.
969 Format: 0 | 1 (for off | on)
971 hcl= [IA-64] SGI's Hardware Graph compatibility layer
973 hd= [EIDE] (E)IDE hard drive subsystem geometry
974 Format: <cyl>,<head>,<sect>
977 Disable Hardware Error Source Table (HEST) support;
978 corresponding firmware-first mode error processing
979 logic will be disabled.
981 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
982 size of <nn>. This works even on boxes that have no
983 highmem otherwise. This also works to reduce highmem
984 size on bigger boxes.
986 highres= [KNL] Enable/disable high resolution timer mode.
987 Valid parameters: "on", "off"
991 See Documentation/isdn/README.HiSax.
995 hpet= [X86-32,HPET] option to control HPET usage
996 Format: { enable (default) | disable | force |
998 disable: disable HPET and use PIT instead
999 force: allow force enabled of undocumented chips (ICH4,
1001 verbose: show contents of HPET registers during setup
1003 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1004 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1005 On x86-64 and powerpc, this option can be specified
1006 multiple times interleaved with hugepages= to reserve
1007 huge pages of different sizes. Valid pages sizes on
1008 x86-64 are 2M (when the CPU supports "pse") and 1G
1009 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1010 Note that 1GB pages can only be allocated at boot time
1011 using hugepages= and not freed afterwards.
1013 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1014 terminal devices. Valid values: 0..8
1015 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1016 If specified, z/VM IUCV HVC accepts connections
1017 from listed z/VM user IDs only.
1019 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1020 hardware thread id mappings.
1021 Format: <cpu>:<hwthread>
1024 Do not unregister boot console at start. This is only
1025 useful for debugging when something happens in the window
1026 between unregistering the boot console and initializing
1029 i2c_bus= [HW] Override the default board specific I2C bus speed
1030 or register an additional I2C bus that is not
1031 registered from board initialization code.
1035 i8042.debug [HW] Toggle i8042 debug mode
1036 i8042.direct [HW] Put keyboard port into non-translated mode
1037 i8042.dumbkbd [HW] Pretend that controller can only read data from
1038 keyboard and cannot control its state
1039 (Don't attempt to blink the leds)
1040 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1041 i8042.nokbd [HW] Don't check/create keyboard port
1042 i8042.noloop [HW] Disable the AUX Loopback command while probing
1044 i8042.nomux [HW] Don't check presence of an active multiplexing
1046 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1048 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1049 i8042.reset [HW] Reset the controller during init and cleanup
1050 i8042.unlock [HW] Unlock (ignore) the keylock
1054 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1055 indicates that the driver is running on unsupported
1057 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1058 does not match list of supported models.
1060 [HW] Report power status in /proc/i8k
1061 (disabled by default)
1062 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1065 i915.invert_brightness=
1066 [DRM] Invert the sense of the variable that is used to
1067 set the brightness of the panel backlight. Normally a
1068 brightness value of 0 indicates backlight switched off,
1069 and the maximum of the brightness value sets the backlight
1070 to maximum brightness. If this parameter is set to 0
1071 (default) and the machine requires it, or this parameter
1072 is set to 1, a brightness value of 0 sets the backlight
1073 to maximum brightness, and the maximum of the brightness
1074 value switches the backlight off.
1075 -1 -- never invert brightness
1076 0 -- machine default
1077 1 -- force brightness inversion
1080 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1082 ide-core.nodma= [HW] (E)IDE subsystem
1083 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1084 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1085 .cdrom .chs .ignore_cable are additional options
1086 See Documentation/ide/ide.txt.
1088 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1089 Claim all unknown PCI IDE storage controllers.
1092 Format: idle=poll, idle=halt, idle=nomwait
1093 Poll forces a polling idle loop that can slightly
1094 improve the performance of waking up a idle CPU, but
1095 will use a lot of power and make the system run hot.
1097 idle=halt: Halt is forced to be used for CPU idle.
1098 In such case C2/C3 won't be used again.
1099 idle=nomwait: Disable mwait for CPU C-states
1101 ignore_loglevel [KNL]
1102 Ignore loglevel setting - this will print /all/
1103 kernel messages to the console. Useful for debugging.
1104 We also add it as printk module parameter, so users
1105 could change it dynamically, usually by
1106 /sys/module/printk/parameters/ignore_loglevel.
1108 ihash_entries= [KNL]
1109 Set number of hash buckets for inode cache.
1111 ima_appraise= [IMA] appraise integrity measurements
1112 Format: { "off" | "enforce" | "fix" }
1115 ima_appraise_tcb [IMA]
1116 The builtin appraise policy appraises all files
1120 Format: { "0" | "1" }
1121 0 -- integrity auditing messages. (Default)
1122 1 -- enable informational integrity auditing messages.
1125 Format: { "sha1" | "md5" }
1129 Load a policy which meets the needs of the Trusted
1130 Computing Base. This means IMA will measure all
1131 programs exec'd, files mmap'd for exec, and all files
1132 opened for read by uid=0.
1136 Run specified binary instead of /sbin/init as init
1139 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1140 for working out where the kernel is dying during
1143 initrd= [BOOT] Specify the location of the initial ramdisk
1145 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1148 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1150 Enable intel iommu driver.
1152 Disable intel iommu driver.
1153 igfx_off [Default Off]
1154 By default, gfx is mapped as normal device. If a gfx
1155 device has a dedicated DMAR unit, the DMAR unit is
1156 bypassed by not enabling DMAR with this option. In
1157 this case, gfx device will use physical address for
1160 With this option iommu will not optimize to look
1161 for io virtual address below 32-bit forcing dual
1162 address cycle on pci bus for cards supporting greater
1163 than 32-bit addressing. The default is to look
1164 for translation below 32-bit and if not available
1165 then look in the higher range.
1166 strict [Default Off]
1167 With this option on every unmap_single operation will
1168 result in a hardware IOTLB flush operation as opposed
1169 to batching them for performance.
1170 sp_off [Default Off]
1171 By default, super page will be supported if Intel IOMMU
1172 has the capability. With this option, super page will
1175 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1176 0 disables intel_idle and fall back on acpi_idle.
1177 1 to 6 specify maximum depth of C-state.
1181 Do not enable intel_pstate as the default
1182 scaling driver for the supported processors
1184 intremap= [X86-64, Intel-IOMMU]
1185 on enable Interrupt Remapping (default)
1186 off disable Interrupt Remapping
1187 nosid disable Source ID checking
1189 BIOS x2APIC opt-out request will be ignored
1191 iomem= Disable strict checking of access to MMIO memory
1192 strict regions from userspace.
1209 io7= [HW] IO7 for Marvel based alpha systems
1210 See comment before marvel_specify_io7 in
1211 arch/alpha/kernel/core_marvel.c.
1213 io_delay= [X86] I/O delay method
1215 Standard port 0x80 based delay
1217 Alternate port 0xed based delay (needed on some systems)
1219 Simple two microseconds delay
1224 See Documentation/filesystems/nfs/nfsroot.txt.
1226 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1227 See comment before ip2_setup() in
1228 drivers/char/ip2/ip2base.c.
1231 When an interrupt is not handled search all handlers
1232 for it. Intended to get systems with badly broken
1236 When an interrupt is not handled search all handlers
1237 for it. Also check all handlers each timer
1238 interrupt. Intended to get systems with badly broken
1242 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1244 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1246 <cpu number>,...,<cpu number>
1248 <cpu number>-<cpu number>
1249 (must be a positive range in ascending order)
1251 <cpu number>,...,<cpu number>-<cpu number>
1253 This option can be used to specify one or more CPUs
1254 to isolate from the general SMP balancing and scheduling
1255 algorithms. You can move a process onto or off an
1256 "isolated" CPU via the CPU affinity syscalls or cpuset.
1257 <cpu number> begins at 0 and the maximum value is
1258 "number of CPUs in system - 1".
1260 This option is the preferred way to isolate CPUs. The
1261 alternative -- manually setting the CPU mask of all
1262 tasks in the system -- can cause problems and
1263 suboptimal load balancer performance.
1267 js= [HW,JOY] Analog joystick
1268 See Documentation/input/joystick.txt.
1272 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1273 specifies the amount of memory usable by the kernel
1274 for non-movable allocations. The requested amount is
1275 spread evenly throughout all nodes in the system. The
1276 remaining memory in each node is used for Movable
1277 pages. In the event, a node is too small to have both
1278 kernelcore and Movable pages, kernelcore pages will
1279 take priority and other nodes will have a larger number
1280 of kernelcore pages. The Movable zone is used for the
1281 allocation of pages that may be reclaimed or moved
1282 by the page migration subsystem. This means that
1283 HugeTLB pages may not be allocated from this zone.
1284 Note that allocations like PTEs-from-HighMem still
1285 use the HighMem zone if it exists, and the Normal
1286 zone if it does not.
1288 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1289 Format: <Controller#>[,poll interval]
1290 The controller # is the number of the ehci usb debug
1291 port as it is probed via PCI. The poll interval is
1292 optional and is the number seconds in between
1293 each poll cycle to the debug port in case you need
1294 the functionality for interrupting the kernel with
1295 gdb or control-c on the dbgp connection. When
1296 not using this parameter you use sysrq-g to break into
1297 the kernel debugger.
1299 kgdboc= [KGDB,HW] kgdb over consoles.
1300 Requires a tty driver that supports console polling,
1301 or a supported polling keyboard driver (non-usb).
1302 Serial only format: <serial_device>[,baud]
1303 keyboard only format: kbd
1304 keyboard and serial format: kbd,<serial_device>[,baud]
1305 Optional Kernel mode setting:
1306 kms, kbd format: kms,kbd
1307 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1309 kgdbwait [KGDB] Stop kernel execution and enter the
1310 kernel debugger at the earliest opportunity.
1312 kmac= [MIPS] korina ethernet MAC address.
1313 Configure the RouterBoard 532 series on-chip
1314 Ethernet adapter MAC address.
1316 kmemleak= [KNL] Boot-time kmemleak enable/disable
1317 Valid arguments: on, off
1320 kstack=N [X86] Print N words from the kernel stack
1323 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1324 Default is 0 (don't ignore, but inject #GP)
1326 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1330 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1331 Default is 1 (enabled)
1333 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1335 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1337 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1338 (virtualized MMU) support on capable Intel chips.
1339 Default is 1 (enabled)
1341 kvm-intel.emulate_invalid_guest_state=
1342 [KVM,Intel] Enable emulation of invalid guest states
1343 Default is 0 (disabled)
1345 kvm-intel.flexpriority=
1346 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1347 Default is 1 (enabled)
1350 [KVM,Intel] Enable VMX nesting (nVMX).
1351 Default is 0 (disabled)
1353 kvm-intel.unrestricted_guest=
1354 [KVM,Intel] Disable unrestricted guest feature
1355 (virtualized real and unpaged mode) on capable
1356 Intel chips. Default is 1 (enabled)
1358 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1359 feature (tagged TLBs) on capable Intel chips.
1360 Default is 1 (enabled)
1366 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1369 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1370 value for LAPIC timer one-shot implementation. Default
1371 back to the programmable timer unit in the LAPIC.
1373 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1376 libata.dma= [LIBATA] DMA control
1377 libata.dma=0 Disable all PATA and SATA DMA
1378 libata.dma=1 PATA and SATA Disk DMA only
1379 libata.dma=2 ATAPI (CDROM) DMA only
1380 libata.dma=4 Compact Flash DMA only
1381 Combinations also work, so libata.dma=3 enables DMA
1382 for disks and CDROMs, but not CFs.
1384 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1385 libata.ignore_hpa=0 keep BIOS limits (default)
1386 libata.ignore_hpa=1 ignore limits, using full disk
1388 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1392 libata.force= [LIBATA] Force configurations. The format is comma
1393 separated list of "[ID:]VAL" where ID is
1394 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1395 matching port, link or device. Basically, it matches
1396 the ATA ID string printed on console by libata. If
1397 the whole ID part is omitted, the last PORT and DEVICE
1398 values are used. If ID hasn't been specified yet, the
1399 configuration applies to all ports, links and devices.
1401 If only DEVICE is omitted, the parameter applies to
1402 the port and all links and devices behind it. DEVICE
1403 number of 0 either selects the first device or the
1404 first fan-out link behind PMP device. It does not
1405 select the host link. DEVICE number of 15 selects the
1406 host link and device attached to it.
1408 The VAL specifies the configuration to force. As long
1409 as there's no ambiguity shortcut notation is allowed.
1410 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1411 The following configurations can be forced.
1413 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1414 Any ID with matching PORT is used.
1416 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1418 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1419 udma[/][16,25,33,44,66,100,133] notation is also
1422 * [no]ncq: Turn on or off NCQ.
1424 * nohrst, nosrst, norst: suppress hard, soft
1427 * rstonce: only attempt one reset during
1428 hot-unplug link recovery
1430 * dump_id: dump IDENTIFY data.
1432 If there are multiple matching configurations changing
1433 the same attribute, the last one is used.
1435 memblock=debug [KNL] Enable memblock debug messages.
1437 load_ramdisk= [RAM] List of ramdisks to load from floppy
1438 See Documentation/blockdev/ramdisk.txt.
1440 lockd.nlm_grace_period=P [NFS] Assign grace period.
1443 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1446 lockd.nlm_timeout=T [NFS] Assign timeout value.
1449 lockd.nlm_udpport=M [NFS] Assign UDP port.
1452 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1455 loglevel= All Kernel Messages with a loglevel smaller than the
1456 console loglevel will be printed to the console. It can
1457 also be changed with klogd or other programs. The
1458 loglevels are defined as follows:
1460 0 (KERN_EMERG) system is unusable
1461 1 (KERN_ALERT) action must be taken immediately
1462 2 (KERN_CRIT) critical conditions
1463 3 (KERN_ERR) error conditions
1464 4 (KERN_WARNING) warning conditions
1465 5 (KERN_NOTICE) normal but significant condition
1466 6 (KERN_INFO) informational
1467 7 (KERN_DEBUG) debug-level messages
1469 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1470 in bytes. n must be a power of two. The default
1471 size is set in the kernel config file.
1473 logo.nologo [FB] Disables display of the built-in Linux logo.
1474 This may be used to provide more screen space for
1475 kernel log messages and is useful when debugging
1476 kernel boot problems.
1478 lp=0 [LP] Specify parallel ports to use, e.g,
1479 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1480 lp=reset first parallel port). 'lp=0' disables the
1481 lp=auto printer driver. 'lp=reset' (which can be
1482 specified in addition to the ports) causes
1483 attached printers to be reset. Using
1484 lp=port1,port2,... specifies the parallel ports
1485 to associate lp devices with, starting with
1486 lp0. A port specification may be 'none' to skip
1487 that lp device, or a parport name such as
1488 'parport0'. Specifying 'lp=auto' instead of a
1489 port specification list means that device IDs
1490 from each port should be examined, to see if
1491 an IEEE 1284-compliant printer is attached; if
1492 so, the driver will manage that printer.
1493 See also header of drivers/char/lp.c.
1496 Sets loops_per_jiffy to given constant, thus avoiding
1497 time-consuming boot-time autodetection (up to 250 ms per
1498 CPU). 0 enables autodetection (default). To determine
1499 the correct value for your kernel, boot with normal
1500 autodetection and see what value is printed. Note that
1501 on SMP systems the preset will be applied to all CPUs,
1502 which is likely to cause problems if your CPUs need
1503 significantly divergent settings. An incorrect value
1504 will cause delays in the kernel to be wrong, leading to
1505 unpredictable I/O errors and other breakage. Although
1506 unlikely, in the extreme case this might damage your
1510 Format: <io>,<irq>,<dma>
1512 machvec= [IA-64] Force the use of a particular machine-vector
1513 (machvec) in a generic kernel.
1514 Example: machvec=hpzx1_swiotlb
1516 machtype= [Loongson] Share the same kernel image file between different
1518 Example: machtype=lemote-yeeloong-2f-7inch
1520 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1521 than or equal to this physical address is ignored.
1523 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1524 should make use of. maxcpus=n : n >= 0 limits the
1525 kernel to using 'n' processors. n=0 is a special case,
1526 it is equivalent to "nosmp", which also disables
1529 max_loop= [LOOP] The number of loop block devices that get
1530 (loop.max_loop) unconditionally pre-created at init time. The default
1531 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1532 of statically allocating a predefined number, loop
1533 devices can be requested on-demand with the
1534 /dev/loop-control interface.
1536 mce [X86-32] Machine Check Exception
1538 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1540 md= [HW] RAID subsystems devices and level
1541 See Documentation/md.txt.
1544 Format: <first>,<last>
1545 Specifies range of consoles to be captured by the MDA.
1547 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1548 Amount of memory to be used when the kernel is not able
1549 to see the whole system memory or for test.
1550 [X86] Work as limiting max address. Use together
1551 with memmap= to avoid physical address space collisions.
1552 Without memmap= PCI devices could be placed at addresses
1553 belonging to unused RAM.
1555 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1559 [KNL,SH] Allow user to override the default size for
1560 per-device physically contiguous DMA buffers.
1562 memmap=exactmap [KNL,X86] Enable setting of an exact
1563 E820 memory map, as specified by the user.
1564 Such memmap=exactmap lines can be constructed based on
1565 BIOS output or other requirements. See the memmap=nn@ss
1568 memmap=nn[KMG]@ss[KMG]
1569 [KNL] Force usage of a specific region of memory
1570 Region of memory to be used, from ss to ss+nn.
1572 memmap=nn[KMG]#ss[KMG]
1573 [KNL,ACPI] Mark specific memory as ACPI data.
1574 Region of memory to be used, from ss to ss+nn.
1576 memmap=nn[KMG]$ss[KMG]
1577 [KNL,ACPI] Mark specific memory as reserved.
1578 Region of memory to be used, from ss to ss+nn.
1579 Example: Exclude memory from 0x18690000-0x1869ffff
1580 memmap=64K$0x18690000
1582 memmap=0x10000$0x18690000
1584 memory_corruption_check=0/1 [X86]
1585 Some BIOSes seem to corrupt the first 64k of
1586 memory when doing things like suspend/resume.
1587 Setting this option will scan the memory
1588 looking for corruption. Enabling this will
1589 both detect corruption and prevent the kernel
1590 from using the memory being corrupted.
1591 However, its intended as a diagnostic tool; if
1592 repeatable BIOS-originated corruption always
1593 affects the same memory, you can use memmap=
1594 to prevent the kernel from using that memory.
1596 memory_corruption_check_size=size [X86]
1597 By default it checks for corruption in the low
1598 64k, making this memory unavailable for normal
1599 use. Use this parameter to scan for
1600 corruption in more or less memory.
1602 memory_corruption_check_period=seconds [X86]
1603 By default it checks for corruption every 60
1604 seconds. Use this parameter to check at some
1605 other rate. 0 disables periodic checking.
1607 memtest= [KNL,X86] Enable memtest
1609 default : 0 <disable>
1610 Specifies the number of memtest passes to be
1611 performed. Each pass selects another test
1612 pattern from a given set of patterns. Memtest
1613 fills the memory with this pattern, validates
1614 memory contents and reserves bad memory
1615 regions that are detected.
1617 meye.*= [HW] Set MotionEye Camera parameters
1618 See Documentation/video4linux/meye.txt.
1620 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1621 Multi-Function General Purpose Timers on AMD Geode
1624 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1625 the BIOS has incorrectly applied a workaround. TinyBIOS
1626 version 0.98 is known to be affected, 0.99 fixes the
1627 problem by letting the user disable the workaround.
1631 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1632 physical address is ignored.
1634 mini2440= [ARM,HW,KNL]
1635 Format:[0..2][b][c][t]
1637 MINI2440 configuration specification:
1638 0 - The attached screen is the 3.5" TFT
1639 1 - The attached screen is the 7" TFT
1640 2 - The VGA Shield is attached (1024x768)
1641 Leaving out the screen size parameter will not load
1642 the TFT driver, and the framebuffer will be left
1644 b - Enable backlight. The TFT backlight pin will be
1645 linked to the kernel VESA blanking code and a GPIO
1646 LED. This parameter is not necessary when using the
1648 c - Enable the s3c camera interface.
1649 t - Reserved for enabling touchscreen support. The
1650 touchscreen support is not enabled in the mainstream
1651 kernel as of 2.6.30, a preliminary port can be found
1652 in the "bleeding edge" mini2440 support kernel at
1653 http://repo.or.cz/w/linux-2.6/mini2440.git
1656 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1657 parameter allows control of the logging verbosity for
1658 the additional memory initialisation checks. A value
1659 of 0 disables mminit logging and a level of 4 will
1660 log everything. Information is printed at KERN_DEBUG
1661 so loglevel=8 may also need to be specified.
1664 [KNL] When CONFIG_MODULE_SIG is set, this means that
1665 modules without (valid) signatures will fail to load.
1666 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1667 is always true, so this option does nothing.
1670 [MOUSE] Maximum time between finger touching and
1671 leaving touchpad surface for touch to be considered
1672 a tap and be reported as a left button click (for
1673 touchpads working in absolute mode only).
1675 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1676 reporting absolute coordinates, such as tablets
1677 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1678 reporting absolute coordinates, such as tablets
1680 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1681 is similar to kernelcore except it specifies the
1682 amount of memory used for migratable allocations.
1683 If both kernelcore and movablecore is specified,
1684 then kernelcore will be at *least* the specified
1685 value but may be more. If movablecore on its own
1686 is specified, the administrator must be careful
1687 that the amount of memory usable for all allocations
1690 MTD_Partition= [MTD]
1691 Format: <name>,<region-number>,<size>,<offset>
1693 MTD_Region= [MTD] Format:
1694 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1697 See drivers/mtd/cmdlinepart.c.
1699 multitce=off [PPC] This parameter disables the use of the pSeries
1700 firmware feature for updating multiple TCE entries
1703 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1705 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1707 boundary - index of last SLC block on Flex-OneNAND.
1708 The remaining blocks are configured as MLC blocks.
1709 lock - Configure if Flex-OneNAND boundary should be locked.
1710 Once locked, the boundary cannot be changed.
1711 1 indicates lock status, 0 indicates unlock status.
1714 ARM/S3C2412 JIVE boot control
1716 See arch/arm/mach-s3c2412/mach-jive.c
1718 mtouchusb.raw_coordinates=
1719 [HW] Make the MicroTouch USB driver use raw coordinates
1720 ('y', default) or cooked coordinates ('n')
1722 mtrr_chunk_size=nn[KMG] [X86]
1723 used for mtrr cleanup. It is largest continuous chunk
1724 that could hold holes aka. UC entries.
1726 mtrr_gran_size=nn[KMG] [X86]
1727 Used for mtrr cleanup. It is granularity of mtrr block.
1729 Large value could prevent small alignment from
1732 mtrr_spare_reg_nr=n [X86]
1734 Range: 0,7 : spare reg number
1736 Used for mtrr cleanup. It is spare mtrr entries number.
1737 Set to 2 or more if your graphical card needs more.
1739 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1741 netdev= [NET] Network devices parameters
1742 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1743 Note that mem_start is often overloaded to mean
1744 something different and driver-specific.
1745 This usage is only documented in each driver source
1749 [NETFILTER] Enable connection tracking flow accounting
1750 0 to disable accounting
1751 1 to enable accounting
1754 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1755 See Documentation/filesystems/nfs/nfsroot.txt.
1757 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1758 See Documentation/filesystems/nfs/nfsroot.txt.
1760 nfsrootdebug [NFS] enable nfsroot debugging messages.
1761 See Documentation/filesystems/nfs/nfsroot.txt.
1763 nfs.callback_tcpport=
1764 [NFS] set the TCP port on which the NFSv4 callback
1765 channel should listen.
1768 [NFS] sets the pathname to the program which is used
1769 to update the NFS client cache entries.
1771 nfs.cache_getent_timeout=
1772 [NFS] sets the timeout after which an attempt to
1773 update a cache entry is deemed to have failed.
1775 nfs.idmap_cache_timeout=
1776 [NFS] set the maximum lifetime for idmapper cache
1780 [NFS] enable 64-bit inode numbers.
1781 If zero, the NFS client will fake up a 32-bit inode
1782 number for the readdir() and stat() syscalls instead
1783 of returning the full 64-bit number.
1784 The default is to return 64-bit inode numbers.
1786 nfs.max_session_slots=
1787 [NFSv4.1] Sets the maximum number of session slots
1788 the client will attempt to negotiate with the server.
1789 This limits the number of simultaneous RPC requests
1790 that the client can send to the NFSv4.1 server.
1791 Note that there is little point in setting this
1792 value higher than the max_tcp_slot_table_limit.
1794 nfs.nfs4_disable_idmapping=
1795 [NFSv4] When set to the default of '1', this option
1796 ensures that both the RPC level authentication
1797 scheme and the NFS level operations agree to use
1798 numeric uids/gids if the mount is using the
1799 'sec=sys' security flavour. In effect it is
1800 disabling idmapping, which can make migration from
1801 legacy NFSv2/v3 systems to NFSv4 easier.
1802 Servers that do not support this mode of operation
1803 will be autodetected by the client, and it will fall
1804 back to using the idmapper.
1805 To turn off this behaviour, set the value to '0'.
1807 [NFS4] Specify an additional fixed unique ident-
1808 ification string that NFSv4 clients can insert into
1809 their nfs_client_id4 string. This is typically a
1810 UUID that is generated at system install time.
1812 nfs.send_implementation_id =
1813 [NFSv4.1] Send client implementation identification
1814 information in exchange_id requests.
1815 If zero, no implementation identification information
1817 The default is to send the implementation identification
1820 nfsd.nfs4_disable_idmapping=
1821 [NFSv4] When set to the default of '1', the NFSv4
1822 server will return only numeric uids and gids to
1823 clients using auth_sys, and will accept numeric uids
1824 and gids from such clients. This is intended to ease
1825 migration from NFSv2/v3.
1827 objlayoutdriver.osd_login_prog=
1828 [NFS] [OBJLAYOUT] sets the pathname to the program which
1829 is used to automatically discover and login into new
1830 osd-targets. Please see:
1831 Documentation/filesystems/pnfs.txt for more explanations
1833 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1834 when a NMI is triggered.
1835 Format: [state][,regs][,debounce][,die]
1837 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1838 Format: [panic,][nopanic,][num]
1840 0 - turn nmi_watchdog off
1841 When panic is specified, panic when an NMI watchdog
1842 timeout occurs (or 'nopanic' to override the opposite
1844 This is useful when you use a panic=... timeout and
1845 need the box quickly up again.
1847 netpoll.carrier_timeout=
1848 [NET] Specifies amount of time (in seconds) that
1849 netpoll should wait for a carrier. By default netpoll
1852 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1853 emulation library even if a 387 maths coprocessor
1857 [HW] Never suspend the console
1858 Disable suspending of consoles during suspend and
1859 hibernate operations. Once disabled, debugging
1860 messages can reach various consoles while the rest
1861 of the system is being put to sleep (ie, while
1862 debugging driver suspend/resume hooks). This may
1863 not work reliably with all consoles, but is known
1864 to work with serial and VGA consoles.
1865 To facilitate more flexible debugging, we also add
1866 console_suspend, a printk module parameter to control
1867 it. Users could use console_suspend (usually
1868 /sys/module/printk/parameters/console_suspend) to
1869 turn on/off it dynamically.
1871 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1872 caches in the slab allocator. Saves per-node memory,
1873 but will impact performance.
1877 noapic [SMP,APIC] Tells the kernel to not make use of any
1878 IOAPICs that may be present in the system.
1880 noautogroup Disable scheduler automatic task group creation.
1882 nobats [PPC] Do not use BATs for mapping kernel lowmem
1883 on "Classic" PPC cores.
1887 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1889 nodelayacct [KNL] Disable per-task delay accounting
1891 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1893 nodsp [SH] Disable hardware DSP at boot time.
1895 noefi [X86] Disable EFI runtime services support.
1900 On X86-32 available only on PAE configured kernels.
1901 noexec=on: enable non-executable mappings (default)
1902 noexec=off: disable non-executable mappings
1905 Disable SMAP (Supervisor Mode Access Prevention)
1906 even if it is supported by processor.
1909 Disable SMEP (Supervisor Mode Execution Prevention)
1910 even if it is supported by processor.
1913 This affects only 32-bit executables.
1914 noexec32=on: enable non-executable mappings (default)
1915 read doesn't imply executable mappings
1916 noexec32=off: disable non-executable mappings
1917 read implies executable mappings
1919 nofpu [SH] Disable hardware FPU at boot time.
1921 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1922 register save and restore. The kernel will only save
1923 legacy floating-point registers on task switch.
1925 noxsave [BUGS=X86] Disables x86 extended register state save
1926 and restore using xsave. The kernel will fallback to
1927 enabling legacy floating-point and sse state.
1930 on enable eager fpu restore
1931 off disable eager fpu restore
1932 auto selects the default scheme, which automatically
1933 enables eagerfpu restore for xsaveopt.
1935 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1936 wfi(ARM) instruction doesn't work correctly and not to
1937 use it. This is also useful when using JTAG debugger.
1939 no_file_caps Tells the kernel not to honor file capabilities. The
1940 only way then for a file to be executed with privilege
1941 is to be setuid root or executed by root.
1943 nohalt [IA-64] Tells the kernel not to use the power saving
1944 function PAL_HALT_LIGHT when idle. This increases
1945 power-consumption. On the positive side, it reduces
1946 interrupt wake-up latency, which may improve performance
1947 in certain environments such as networked servers or
1950 nohz= [KNL] Boottime enable/disable dynamic ticks
1951 Valid arguments: on, off
1954 nohz_full= [KNL,BOOT]
1955 In kernels built with CONFIG_NO_HZ_FULL=y, set
1956 the specified list of CPUs whose tick will be stopped
1957 whenever possible. The boot CPU will be forced outside
1958 the range to maintain the timekeeping.
1959 The CPUs in this range must also be included in the
1962 noiotrap [SH] Disables trapped I/O port accesses.
1964 noirqdebug [X86-32] Disables the code which attempts to detect and
1965 disable unhandled interrupt sources.
1967 no_timer_check [X86,APIC] Disables the code which tests for
1968 broken timer IRQ sources.
1970 noisapnp [ISAPNP] Disables ISA PnP code.
1972 noinitrd [RAM] Tells the kernel not to load any configured
1975 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1977 [Deprecated - use intremap=off]
1981 nojitter [IA-64] Disables jitter checking for ITC timers.
1983 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1985 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1988 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1989 steal time is computed, but won't influence scheduler
1992 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1994 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1996 noltlbs [PPC] Do not use large page/tlb entries for kernel
1997 lowmem mapping on PPC40x.
1999 nomca [IA-64] Disable machine check abort handling
2001 nomce [X86-32] Machine Check Exception
2003 nomfgpt [X86-32] Disable Multi-Function General Purpose
2004 Timer usage (for AMD Geode machines).
2006 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2007 shutdown the other cpus. Instead use the REBOOT_VECTOR
2010 nomodule Disable module load
2012 nopat [X86] Disable PAT (page attribute table extension of
2013 pagetables) support.
2015 norandmaps Don't use address space randomization. Equivalent to
2016 echo 0 > /proc/sys/kernel/randomize_va_space
2018 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2020 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2021 with UP alternatives
2023 noresidual [PPC] Don't use residual data on PReP machines.
2025 nordrand [X86] Disable the direct use of the RDRAND
2026 instruction even if it is supported by the
2027 processor. RDRAND is still available to user
2030 noresume [SWSUSP] Disables resume and restores original swap
2033 no-scroll [VGA] Disables scrollback.
2034 This is required for the Braillex ib80-piezo Braille
2035 reader made by F.H. Papenmeier (Germany).
2039 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2041 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2042 and disable the IO APIC. legacy for "maxcpus=0".
2044 nosoftlockup [KNL] Disable the soft-lockup detector.
2046 nosync [HW,M68K] Disables sync negotiation for all devices.
2048 notsc [BUGS=X86-32] Disable Time Stamp Counter
2050 nousb [USB] Disable the USB subsystem
2052 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2056 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2058 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2059 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2060 Some features depend on CPU0. Known dependencies are:
2061 1. Resume from suspend/hibernate depends on CPU0.
2062 Suspend/hibernate will fail if CPU0 is offline and you
2063 need to online CPU0 before suspend/hibernate.
2064 2. PIC interrupts also depend on CPU0. CPU0 can't be
2065 removed if a PIC interrupt is detected.
2066 It's said poweroff/reboot may depend on CPU0 on some
2067 machines although I haven't seen such issues so far
2068 after CPU0 is offline on a few tested machines.
2069 If the dependencies are under your control, you can
2070 turn on cpu0_hotplug.
2072 nptcg= [IA-64] Override max number of concurrent global TLB
2073 purges which is reported from either PAL_VM_SUMMARY or
2076 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2077 could support. nr_cpus=n : n >= 1 limits the kernel to
2078 supporting 'n' processors. Later in runtime you can not
2079 use hotplug cpu feature to put more cpu back to online.
2080 just like you compile the kernel NR_CPUS=n
2082 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2084 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2085 Allowed values are enable and disable
2087 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2088 one of ['zone', 'node', 'default'] can be specified
2089 This can be set from sysctl after boot.
2090 See Documentation/sysctl/vm.txt for details.
2092 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2093 See Documentation/debugging-via-ohci1394.txt for more
2096 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2097 Rather than timing out after 20 ms if an EC
2098 command is not properly ACKed, override the length
2099 of the timeout. We have interrupts disabled while
2100 waiting for the ACK, so if this is set too high
2101 interrupts *may* be lost!
2103 omap_mux= [OMAP] Override bootloader pin multiplexing.
2104 Format: <mux_mode0.mode_name=value>...
2105 For example, to override I2C bus2:
2106 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2108 oprofile.timer= [HW]
2109 Use timer interrupt instead of performance counters
2111 oprofile.cpu_type= Force an oprofile cpu type
2112 This might be useful if you have an older oprofile
2113 userland or if you want common events.
2114 Format: { arch_perfmon }
2115 arch_perfmon: [X86] Force use of architectural
2116 perfmon on Intel CPUs instead of the
2117 CPU specific event set.
2118 timer: [X86] Force use of architectural NMI
2119 timer mode (see also oprofile.timer
2120 for generic hr timer mode)
2121 [s390] Force legacy basic mode sampling
2122 (report cpu_type "timer")
2124 oops=panic Always panic on oopses. Default is to just kill the
2125 process, but there is a small probability of
2126 deadlocking the machine.
2127 This will also cause panics on machine check exceptions.
2128 Useful together with panic=30 to trigger a reboot.
2131 See Documentation/sound/oss/oss-parameters.txt
2133 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2134 timeout > 0: seconds before rebooting
2135 timeout = 0: wait forever
2136 timeout < 0: reboot immediately
2139 parkbd.port= [HW] Parallel port number the keyboard adapter is
2140 connected to, default is 0.
2142 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2143 0 for XT, 1 for AT (default is AT).
2146 parport= [HW,PPT] Specify parallel ports. 0 disables.
2147 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2148 Use 'auto' to force the driver to use any
2149 IRQ/DMA settings detected (the default is to
2150 ignore detected IRQ/DMA settings because of
2151 possible conflicts). You can specify the base
2152 address, IRQ, and DMA settings; IRQ and DMA
2153 should be numbers, or 'auto' (for using detected
2154 settings on that particular port), or 'nofifo'
2155 (to avoid using a FIFO even if it is detected).
2156 Parallel ports are assigned in the order they
2157 are specified on the command line, starting
2160 parport_init_mode= [HW,PPT]
2161 Configure VIA parallel port to operate in
2162 a specific mode. This is necessary on Pegasos
2163 computer where firmware has no options for setting
2164 up parallel port mode and sets it to spp.
2165 Currently this function knows 686a and 8231 chips.
2166 Format: [spp|ps2|epp|ecp|ecpepp]
2169 Halt all CPUs after the first oops has been printed for
2170 the specified number of seconds. This is to be used if
2171 your oopses keep scrolling off the screen.
2176 See header of drivers/block/paride/pcd.c.
2177 See also Documentation/blockdev/paride.txt.
2179 pci=option[,option...] [PCI] various PCI subsystem options:
2180 earlydump [X86] dump PCI config space before the kernel
2182 off [X86] don't probe for the PCI bus
2183 bios [X86-32] force use of PCI BIOS, don't access
2184 the hardware directly. Use this if your machine
2185 has a non-standard PCI host bridge.
2186 nobios [X86-32] disallow use of PCI BIOS, only direct
2187 hardware access methods are allowed. Use this
2188 if you experience crashes upon bootup and you
2189 suspect they are caused by the BIOS.
2190 conf1 [X86] Force use of PCI Configuration
2192 conf2 [X86] Force use of PCI Configuration
2194 noaer [PCIE] If the PCIEAER kernel config parameter is
2195 enabled, this kernel boot option can be used to
2196 disable the use of PCIE advanced error reporting.
2197 nodomains [PCI] Disable support for multiple PCI
2198 root domains (aka PCI segments, in ACPI-speak).
2199 nommconf [X86] Disable use of MMCONFIG for PCI
2201 check_enable_amd_mmconf [X86] check for and enable
2202 properly configured MMIO access to PCI
2203 config space on AMD family 10h CPU
2204 nomsi [MSI] If the PCI_MSI kernel config parameter is
2205 enabled, this kernel boot option can be used to
2206 disable the use of MSI interrupts system-wide.
2207 noioapicquirk [APIC] Disable all boot interrupt quirks.
2208 Safety option to keep boot IRQs enabled. This
2209 should never be necessary.
2210 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2211 primary IO-APIC for bridges that cannot disable
2212 boot IRQs. This fixes a source of spurious IRQs
2213 when the system masks IRQs.
2214 noioapicreroute [APIC] Disable workaround that uses the
2215 boot IRQ equivalent of an IRQ that connects to
2216 a chipset where boot IRQs cannot be disabled.
2217 The opposite of ioapicreroute.
2218 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2219 routing table. These calls are known to be buggy
2220 on several machines and they hang the machine
2221 when used, but on other computers it's the only
2222 way to get the interrupt routing table. Try
2223 this option if the kernel is unable to allocate
2224 IRQs or discover secondary PCI buses on your
2226 rom [X86] Assign address space to expansion ROMs.
2227 Use with caution as certain devices share
2228 address decoders between ROMs and other
2230 norom [X86] Do not assign address space to
2231 expansion ROMs that do not already have
2232 BIOS assigned address ranges.
2233 nobar [X86] Do not assign address space to the
2234 BARs that weren't assigned by the BIOS.
2235 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2236 assigned automatically to PCI devices. You can
2237 make the kernel exclude IRQs of your ISA cards
2239 pirqaddr=0xAAAAA [X86] Specify the physical address
2240 of the PIRQ table (normally generated
2241 by the BIOS) if it is outside the
2242 F0000h-100000h range.
2243 lastbus=N [X86] Scan all buses thru bus #N. Can be
2244 useful if the kernel is unable to find your
2245 secondary buses and you want to tell it
2246 explicitly which ones they are.
2247 assign-busses [X86] Always assign all PCI bus
2248 numbers ourselves, overriding
2249 whatever the firmware may have done.
2250 usepirqmask [X86] Honor the possible IRQ mask stored
2251 in the BIOS $PIR table. This is needed on
2252 some systems with broken BIOSes, notably
2253 some HP Pavilion N5400 and Omnibook XE3
2254 notebooks. This will have no effect if ACPI
2255 IRQ routing is enabled.
2256 noacpi [X86] Do not use ACPI for IRQ routing
2257 or for PCI scanning.
2258 use_crs [X86] Use PCI host bridge window information
2259 from ACPI. On BIOSes from 2008 or later, this
2260 is enabled by default. If you need to use this,
2261 please report a bug.
2262 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2263 If you need to use this, please report a bug.
2264 routeirq Do IRQ routing for all PCI devices.
2265 This is normally done in pci_enable_device(),
2266 so this option is a temporary workaround
2267 for broken drivers that don't call it.
2268 skip_isa_align [X86] do not align io start addr, so can
2269 handle more pci cards
2270 firmware [ARM] Do not re-enumerate the bus but instead
2271 just use the configuration from the
2272 bootloader. This is currently used on
2273 IXP2000 systems where the bus has to be
2274 configured a certain way for adjunct CPUs.
2275 noearly [X86] Don't do any early type 1 scanning.
2276 This might help on some broken boards which
2277 machine check when some devices' config space
2278 is read. But various workarounds are disabled
2279 and some IOMMU drivers will not work.
2280 bfsort Sort PCI devices into breadth-first order.
2281 This sorting is done to get a device
2282 order compatible with older (<= 2.4) kernels.
2283 nobfsort Don't sort PCI devices into breadth-first order.
2284 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2285 tuning and use the BIOS-configured MPS defaults.
2286 pcie_bus_safe Set every device's MPS to the largest value
2287 supported by all devices below the root complex.
2288 pcie_bus_perf Set device MPS to the largest allowable MPS
2289 based on its parent bus. Also set MRRS (Max
2290 Read Request Size) to the largest supported
2291 value (no larger than the MPS that the device
2292 or bus can support) for best performance.
2293 pcie_bus_peer2peer Set every device's MPS to 128B, which
2294 every device is guaranteed to support. This
2295 configuration allows peer-to-peer DMA between
2296 any pair of devices, possibly at the cost of
2297 reduced performance. This also guarantees
2298 that hot-added devices will work.
2299 cbiosize=nn[KMG] The fixed amount of bus space which is
2300 reserved for the CardBus bridge's IO window.
2301 The default value is 256 bytes.
2302 cbmemsize=nn[KMG] The fixed amount of bus space which is
2303 reserved for the CardBus bridge's memory
2304 window. The default value is 64 megabytes.
2307 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2308 Specifies alignment and device to reassign
2309 aligned memory resources.
2310 If <order of align> is not specified,
2311 PAGE_SIZE is used as alignment.
2312 PCI-PCI bridge can be specified, if resource
2313 windows need to be expanded.
2314 ecrc= Enable/disable PCIe ECRC (transaction layer
2315 end-to-end CRC checking).
2316 bios: Use BIOS/firmware settings. This is the
2320 hpiosize=nn[KMG] The fixed amount of bus space which is
2321 reserved for hotplug bridge's IO window.
2322 Default size is 256 bytes.
2323 hpmemsize=nn[KMG] The fixed amount of bus space which is
2324 reserved for hotplug bridge's memory window.
2325 Default size is 2 megabytes.
2326 realloc= Enable/disable reallocating PCI bridge resources
2327 if allocations done by BIOS are too small to
2328 accommodate resources required by all child
2330 off: Turn realloc off
2332 realloc same as realloc=on
2333 noari do not use PCIe ARI.
2334 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2335 only look for one device below a PCIe downstream
2338 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2341 force Enable ASPM even on devices that claim not to support it.
2342 WARNING: Forcing ASPM on may cause system lockups.
2344 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2345 nomsi Do not use MSI for PCI Express Native Hotplug (this
2346 makes all PCIe ports use INTx for hotplug services).
2348 pcie_ports= [PCIE] PCIe ports handling:
2349 auto Ask the BIOS whether or not to use native PCIe services
2350 associated with PCIe ports (PME, hot-plug, AER). Use
2351 them only if that is allowed by the BIOS.
2352 native Use native PCIe services associated with PCIe ports
2354 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2357 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2358 nomsi Do not use MSI for native PCIe PME signaling (this makes
2359 all PCIe root ports use INTx for all services).
2361 pcmv= [HW,PCMCIA] BadgePAD 4
2364 See Documentation/blockdev/paride.txt.
2366 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2369 See arch/parisc/kernel/pdc_chassis.c
2371 percpu_alloc= Select which percpu first chunk allocator to use.
2372 Currently supported values are "embed" and "page".
2373 Archs may support subset or none of the selections.
2374 See comments in mm/percpu.c for details on each
2375 allocator. This parameter is primarily for debugging
2376 and performance comparison.
2379 See Documentation/blockdev/paride.txt.
2382 See Documentation/blockdev/paride.txt.
2384 pirq= [SMP,APIC] Manual mp-table setup
2385 See Documentation/x86/i386/IO-APIC.txt.
2387 plip= [PPT,NET] Parallel port network link
2388 Format: { parport<nr> | timid | 0 }
2389 See also Documentation/parport.txt.
2391 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2392 Override pmtimer IOPort with a hex value.
2396 Enable PNP debug messages (depends on the
2397 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2398 via /sys/module/pnp/parameters/debug. We always show
2399 current resource usage; turning this on also shows
2400 possible settings and some assignment information.
2406 { on | off | curr | res | no-curr | no-res }
2409 [ISAPNP] Exclude IRQs for the autoconfiguration
2412 [ISAPNP] Exclude DMAs for the autoconfiguration
2414 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2415 Ranges are in pairs (I/O port base and size).
2418 [ISAPNP] Exclude memory regions for the
2420 Ranges are in pairs (memory base and size).
2422 ports= [IP_VS_FTP] IPVS ftp helper module
2424 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2426 Format: <port>,<port>....
2428 print-fatal-signals=
2429 [KNL] debug: print fatal signals
2431 If enabled, warn about various signal handling
2432 related application anomalies: too many signals,
2433 too many POSIX.1 timers, fatal signals causing a
2436 If you hit the warning due to signal overflow,
2437 you might want to try "ulimit -i unlimited".
2441 printk.always_kmsg_dump=
2442 Trigger kmsg_dump for cases other than kernel oops or
2444 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2447 printk.time= Show timing data prefixed to each printk message line
2448 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2450 processor.max_cstate= [HW,ACPI]
2451 Limit processor to maximum C-state
2452 max_cstate=9 overrides any DMI blacklist limit.
2454 processor.nocst [HW,ACPI]
2455 Ignore the _CST method to determine C-states,
2456 instead using the legacy FADT method
2458 profile= [KNL] Enable kernel profiling via /proc/profile
2459 Format: [schedule,]<number>
2460 Param: "schedule" - profile schedule points.
2461 Param: <number> - step/bucket size as a power of 2 for
2462 statistical time based profiling.
2463 Param: "sleep" - profile D-state sleeping (millisecs).
2464 Requires CONFIG_SCHEDSTATS
2465 Param: "kvm" - profile VM exits.
2467 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2469 See Documentation/blockdev/ramdisk.txt.
2471 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2472 probe for; one of (bare|imps|exps|lifebook|any).
2473 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2475 psmouse.resetafter= [HW,MOUSE]
2476 Try to reset the device after so many bad packets
2479 [HW,MOUSE] Set desired mouse resolution, in dpi.
2480 psmouse.smartscroll=
2481 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2482 0 = disabled, 1 = enabled (default).
2484 pstore.backend= Specify the name of the pstore backend to use
2487 See Documentation/blockdev/paride.txt.
2490 [KNL] Number of legacy pty's. Overwrites compiled-in
2493 quiet [KNL] Disable most log messages
2498 See Documentation/md.txt.
2500 ramdisk_blocksize= [RAM]
2501 See Documentation/blockdev/ramdisk.txt.
2503 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2504 See Documentation/blockdev/ramdisk.txt.
2506 rcu_nocbs= [KNL,BOOT]
2507 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2508 the specified list of CPUs to be no-callback CPUs.
2509 Invocation of these CPUs' RCU callbacks will
2510 be offloaded to "rcuox/N" kthreads created for
2511 that purpose, where "x" is "b" for RCU-bh, "p"
2512 for RCU-preempt, and "s" for RCU-sched, and "N"
2513 is the CPU number. This reduces OS jitter on the
2514 offloaded CPUs, which can be useful for HPC and
2516 real-time workloads. It can also improve energy
2517 efficiency for asymmetric multiprocessors.
2519 rcu_nocb_poll [KNL,BOOT]
2520 Rather than requiring that offloaded CPUs
2521 (specified by rcu_nocbs= above) explicitly
2522 awaken the corresponding "rcuoN" kthreads,
2523 make these kthreads poll for callbacks.
2524 This improves the real-time response for the
2525 offloaded CPUs by relieving them of the need to
2526 wake up the corresponding kthread, but degrades
2527 energy efficiency by requiring that the kthreads
2528 periodically wake up to do the polling.
2530 rcutree.blimit= [KNL,BOOT]
2531 Set maximum number of finished RCU callbacks to process
2534 rcutree.fanout_leaf= [KNL,BOOT]
2535 Increase the number of CPUs assigned to each
2536 leaf rcu_node structure. Useful for very large
2539 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2540 Set delay from grace-period initialization to
2541 first attempt to force quiescent states.
2542 Units are jiffies, minimum value is zero,
2543 and maximum value is HZ.
2545 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2546 Set delay between subsequent attempts to force
2547 quiescent states. Units are jiffies, minimum
2548 value is one, and maximum value is HZ.
2550 rcutree.qhimark= [KNL,BOOT]
2551 Set threshold of queued
2552 RCU callbacks over which batch limiting is disabled.
2554 rcutree.qlowmark= [KNL,BOOT]
2555 Set threshold of queued RCU callbacks below which
2556 batch limiting is re-enabled.
2558 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2559 Suppress RCU CPU stall warning messages.
2561 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2562 Set timeout for RCU CPU stall warning messages.
2564 rcutree.rcu_idle_gp_delay= [KNL,BOOT]
2565 Set wakeup interval for idle CPUs that have
2566 RCU callbacks (RCU_FAST_NO_HZ=y).
2568 rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
2569 Set wakeup interval for idle CPUs that have
2570 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2571 Lazy RCU callbacks are those which RCU can
2572 prove do nothing more than free memory.
2574 rcutorture.fqs_duration= [KNL,BOOT]
2575 Set duration of force_quiescent_state bursts.
2577 rcutorture.fqs_holdoff= [KNL,BOOT]
2578 Set holdoff time within force_quiescent_state bursts.
2580 rcutorture.fqs_stutter= [KNL,BOOT]
2581 Set wait time between force_quiescent_state bursts.
2583 rcutorture.irqreader= [KNL,BOOT]
2584 Test RCU readers from irq handlers.
2586 rcutorture.n_barrier_cbs= [KNL,BOOT]
2587 Set callbacks/threads for rcu_barrier() testing.
2589 rcutorture.nfakewriters= [KNL,BOOT]
2590 Set number of concurrent RCU writers. These just
2591 stress RCU, they don't participate in the actual
2592 test, hence the "fake".
2594 rcutorture.nreaders= [KNL,BOOT]
2595 Set number of RCU readers.
2597 rcutorture.onoff_holdoff= [KNL,BOOT]
2598 Set time (s) after boot for CPU-hotplug testing.
2600 rcutorture.onoff_interval= [KNL,BOOT]
2601 Set time (s) between CPU-hotplug operations, or
2602 zero to disable CPU-hotplug testing.
2604 rcutorture.shuffle_interval= [KNL,BOOT]
2605 Set task-shuffle interval (s). Shuffling tasks
2606 allows some CPUs to go into dyntick-idle mode
2607 during the rcutorture test.
2609 rcutorture.shutdown_secs= [KNL,BOOT]
2610 Set time (s) after boot system shutdown. This
2611 is useful for hands-off automated testing.
2613 rcutorture.stall_cpu= [KNL,BOOT]
2614 Duration of CPU stall (s) to test RCU CPU stall
2615 warnings, zero to disable.
2617 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2618 Time to wait (s) after boot before inducing stall.
2620 rcutorture.stat_interval= [KNL,BOOT]
2621 Time (s) between statistics printk()s.
2623 rcutorture.stutter= [KNL,BOOT]
2624 Time (s) to stutter testing, for example, specifying
2625 five seconds causes the test to run for five seconds,
2626 wait for five seconds, and so on. This tests RCU's
2627 ability to transition abruptly to and from idle.
2629 rcutorture.test_boost= [KNL,BOOT]
2630 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2631 "Maybe" means test if the RCU implementation
2632 under test support RCU priority boosting.
2634 rcutorture.test_boost_duration= [KNL,BOOT]
2635 Duration (s) of each individual boost test.
2637 rcutorture.test_boost_interval= [KNL,BOOT]
2638 Interval (s) between each boost test.
2640 rcutorture.test_no_idle_hz= [KNL,BOOT]
2641 Test RCU's dyntick-idle handling. See also the
2642 rcutorture.shuffle_interval parameter.
2644 rcutorture.torture_type= [KNL,BOOT]
2645 Specify the RCU implementation to test.
2647 rcutorture.verbose= [KNL,BOOT]
2648 Enable additional printk() statements.
2652 Run specified binary instead of /init from the ramdisk,
2653 used for early userspace startup. See initrd.
2655 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2656 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2657 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2660 [KNL, SMP] Set scheduler's default relax_domain_level.
2661 See Documentation/cgroups/cpusets.txt.
2663 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2665 reservetop= [X86-32]
2667 Reserves a hole at the top of the kernel virtual
2672 Set the amount of memory to reserve for BIOS at
2673 the bottom of the address space.
2675 reset_devices [KNL] Force drivers to reset the underlying device
2676 during initialization.
2679 Specify the partition device for software suspend
2681 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2683 resume_offset= [SWSUSP]
2684 Specify the offset from the beginning of the partition
2685 given by "resume=" at which the swap header is located,
2686 in <PAGE_SIZE> units (needed only for swap files).
2687 See Documentation/power/swsusp-and-swap-files.txt
2689 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2690 read the resume files
2692 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2693 Useful for devices that are detected asynchronously
2694 (e.g. USB and MMC devices).
2696 hibernate= [HIBERNATION]
2697 noresume Don't check if there's a hibernation image
2698 present during boot.
2699 nocompress Don't compress/decompress hibernation images.
2701 retain_initrd [RAM] Keep initrd memory after extraction
2703 rhash_entries= [KNL,NET]
2704 Set number of hash buckets for route cache
2706 riscom8= [HW,SERIAL]
2707 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2709 ro [KNL] Mount root device read-only on boot
2711 root= [KNL] Root filesystem
2712 See name_to_dev_t comment in init/do_mounts.c.
2714 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2715 mount the root filesystem
2717 rootflags= [KNL] Set root filesystem mount option string
2719 rootfstype= [KNL] Set root filesystem type
2721 rootwait [KNL] Wait (indefinitely) for root device to show up.
2722 Useful for devices that are detected asynchronously
2723 (e.g. USB and MMC devices).
2725 rw [KNL] Mount root device read-write on boot
2727 S [KNL] Run init in single mode
2730 See drivers/net/irda/sa1100_ir.c.
2732 sbni= [NET] Granch SBNI12 leased line adapter
2734 sched_debug [KNL] Enables verbose scheduler debug messages.
2736 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2737 xtime_lock contention on larger systems, and/or RCU lock
2738 contention on all systems with CONFIG_MAXSMP set.
2739 Format: { "0" | "1" }
2740 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2742 Note: increases power consumption, thus should only be
2743 enabled if running jitter sensitive (HPC/RT) workloads.
2745 security= [SECURITY] Choose a security module to enable at boot.
2746 If this boot parameter is not specified, only the first
2747 security module asking for security registration will be
2748 loaded. An invalid security module name will be treated
2749 as if no module has been chosen.
2751 selinux= [SELINUX] Disable or enable SELinux at boot time.
2752 Format: { "0" | "1" }
2753 See security/selinux/Kconfig help text.
2756 Default value is set via kernel config option.
2757 If enabled at boot time, /selinux/disable can be used
2758 later to disable prior to initial policy load.
2760 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2761 Format: { "0" | "1" }
2762 See security/apparmor/Kconfig help text
2765 Default value is set via kernel config option.
2767 serialnumber [BUGS=X86-32]
2770 Maximal number of shapers.
2772 show_msr= [x86] show boot-time MSR settings
2773 Format: { <integer> }
2774 Show boot-time (BIOS-initialized) MSR settings.
2775 The parameter means the number of CPUs to show,
2776 for example 1 means boot CPU only.
2783 slab_max_order= [MM, SLAB]
2784 Determines the maximum allowed order for slabs.
2785 A high setting may cause OOMs due to memory
2786 fragmentation. Defaults to 1 for systems with
2787 more than 32MB of RAM, 0 otherwise.
2789 slub_debug[=options[,slabs]] [MM, SLUB]
2790 Enabling slub_debug allows one to determine the
2791 culprit if slab objects become corrupted. Enabling
2792 slub_debug can create guard zones around objects and
2793 may poison objects when not in use. Also tracks the
2794 last alloc / free. For more information see
2795 Documentation/vm/slub.txt.
2797 slub_max_order= [MM, SLUB]
2798 Determines the maximum allowed order for slabs.
2799 A high setting may cause OOMs due to memory
2800 fragmentation. For more information see
2801 Documentation/vm/slub.txt.
2803 slub_min_objects= [MM, SLUB]
2804 The minimum number of objects per slab. SLUB will
2805 increase the slab order up to slub_max_order to
2806 generate a sufficiently large slab able to contain
2807 the number of objects indicated. The higher the number
2808 of objects the smaller the overhead of tracking slabs
2809 and the less frequently locks need to be acquired.
2810 For more information see Documentation/vm/slub.txt.
2812 slub_min_order= [MM, SLUB]
2813 Determines the minimum page order for slabs. Must be
2814 lower than slub_max_order.
2815 For more information see Documentation/vm/slub.txt.
2817 slub_nomerge [MM, SLUB]
2818 Disable merging of slabs with similar size. May be
2819 necessary if there is some reason to distinguish
2820 allocs to different slabs. Debug options disable
2821 merging on their own.
2822 For more information see Documentation/vm/slub.txt.
2825 Format: <io1>[,<io2>[,...,<io8>]]
2827 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2828 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2829 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2830 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2831 smsc-ircc2.ircc_irq= [HW] IRQ line
2832 smsc-ircc2.ircc_dma= [HW] DMA channel
2833 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2834 0: Toshiba Satellite 1800 (GP data pin select)
2835 1: Fast pin select (default)
2839 [KNL] Should the soft-lockup detector generate panics.
2842 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2843 See Documentation/laptops/sonypi.txt
2845 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2846 See Documentation/serial/specialix.txt.
2848 spia_io_base= [HW,MTD]
2854 Enabled the stack tracer on boot up.
2856 stacktrace_filter=[function-list]
2857 [FTRACE] Limit the functions that the stack tracer
2858 will trace at boot up. function-list is a comma separated
2859 list of functions. This list can be changed at run
2860 time by the stack_trace_filter file in the debugfs
2861 tracing directory. Note, this enables stack tracing
2862 and the stacktrace above is not needed.
2866 Set the STI (builtin display/keyboard on the HP-PARISC
2867 machines) console (graphic card) which should be used
2868 as the initial boot-console.
2869 See also comment in drivers/video/console/sticore.c.
2872 See comment in drivers/video/console/sticore.c.
2875 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2877 sunrpc.min_resvport=
2878 sunrpc.max_resvport=
2880 SunRPC servers often require that client requests
2881 originate from a privileged port (i.e. a port in the
2882 range 0 < portnr < 1024).
2883 An administrator who wishes to reserve some of these
2884 ports for other uses may adjust the range that the
2885 kernel's sunrpc client considers to be privileged
2886 using these two parameters to set the minimum and
2887 maximum port values.
2891 Control how the NFS server code allocates CPUs to
2892 service thread pools. Depending on how many NICs
2893 you have and where their interrupts are bound, this
2894 option will affect which CPUs will do NFS serving.
2895 Note: this parameter cannot be changed while the
2896 NFS server is running.
2898 auto the server chooses an appropriate mode
2899 automatically using heuristics
2900 global a single global pool contains all CPUs
2901 percpu one pool for each CPU
2902 pernode one pool for each NUMA node (equivalent
2903 to global on non-NUMA machines)
2905 sunrpc.tcp_slot_table_entries=
2906 sunrpc.udp_slot_table_entries=
2908 Sets the upper limit on the number of simultaneous
2909 RPC calls that can be sent from the client to a
2910 server. Increasing these values may allow you to
2911 improve throughput, but will also increase the
2912 amount of memory reserved for use by the client.
2915 [KNL] Enable accounting of swap in memory resource
2916 controller if no parameter or 1 is given or disable
2917 it if 0 is given (See Documentation/cgroups/memory.txt)
2919 swiotlb= [IA-64] Number of I/O TLB slabs
2923 sysfs.deprecated=0|1 [KNL]
2924 Enable/disable old style sysfs layout for old udev
2925 on older distributions. When this option is enabled
2926 very new udev will not work anymore. When this option
2927 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2928 in older udev will not work anymore.
2929 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2930 the kernel configuration.
2932 sysrq_always_enabled
2934 Ignore sysrq setting - this boot parameter will
2935 neutralize any effect of /proc/sys/kernel/sysrq.
2936 Useful for debugging.
2940 test_suspend= [SUSPEND]
2941 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2942 standby suspend) as the system sleep state to briefly
2943 enter during system startup. The system is woken from
2944 this state using a wakeup-capable RTC alarm.
2946 thash_entries= [KNL,NET]
2947 Set number of hash buckets for TCP connection
2949 thermal.act= [HW,ACPI]
2950 -1: disable all active trip points in all thermal zones
2951 <degrees C>: override all lowest active trip points
2953 thermal.crt= [HW,ACPI]
2954 -1: disable all critical trip points in all thermal zones
2955 <degrees C>: override all critical trip points
2957 thermal.nocrt= [HW,ACPI]
2958 Set to disable actions on ACPI thermal zone
2959 critical and hot trip points.
2961 thermal.off= [HW,ACPI]
2962 1: disable ACPI thermal control
2964 thermal.psv= [HW,ACPI]
2965 -1: disable all passive trip points
2966 <degrees C>: override all passive trip points to this
2969 thermal.tzp= [HW,ACPI]
2970 Specify global default ACPI thermal zone polling rate
2971 <deci-seconds>: poll all this frequency
2972 0: no polling (default)
2975 Force threading of all interrupt handlers except those
2976 marked explicitly IRQF_NO_THREAD.
2980 Specify if the kernel should make use of the cpu
2981 topology information if the hardware supports this.
2982 The scheduler will make use of this information and
2983 e.g. base its process migration decisions on it.
2988 tpm_suspend_pcr=[HW,TPM]
2989 Format: integer pcr id
2990 Specify that at suspend time, the tpm driver
2991 should extend the specified pcr with zeros,
2992 as a workaround for some chips which fail to
2993 flush the last written pcr on TPM_SaveState.
2994 This will guarantee that all the other pcrs
2997 trace_buf_size=nn[KMG]
2998 [FTRACE] will set tracing buffer size.
3000 trace_event=[event-list]
3001 [FTRACE] Set and start specified trace events in order
3002 to facilitate early boot debugging.
3003 See also Documentation/trace/events.txt
3005 trace_options=[option-list]
3006 [FTRACE] Enable or disable tracer options at boot.
3007 The option-list is a comma delimited list of options
3008 that can be enabled or disabled just as if you were
3009 to echo the option name into
3011 /sys/kernel/debug/tracing/trace_options
3013 For example, to enable stacktrace option (to dump the
3014 stack trace of each event), add to the command line:
3016 trace_options=stacktrace
3018 See also Documentation/trace/ftrace.txt "trace options"
3021 transparent_hugepage=
3023 Format: [always|madvise|never]
3024 Can be used to control the default behavior of the system
3025 with respect to transparent hugepages.
3026 See Documentation/vm/transhuge.txt for more details.
3028 tsc= Disable clocksource stability checks for TSC.
3030 [x86] reliable: mark tsc clocksource as reliable, this
3031 disables clocksource verification at runtime, as well
3032 as the stability checks done at bootup. Used to enable
3033 high-resolution timer mode on older hardware, and in
3034 virtualized environment.
3035 [x86] noirqtime: Do not use TSC to do irq accounting.
3036 Used to run time disable IRQ_TIME_ACCOUNTING on any
3037 platforms where RDTSC is slow and this accounting
3040 turbografx.map[2|3]= [HW,JOY]
3041 TurboGraFX parallel port interface
3043 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3044 See also Documentation/input/joystick-parport.txt
3046 udbg-immortal [PPC] When debugging early kernel crashes that
3047 happen after console_init() and before a proper
3048 console driver takes over, this boot options might
3049 help "seeing" what's going on.
3051 uhash_entries= [KNL,NET]
3052 Set number of hash buckets for UDP/UDP-Lite connections
3055 [USB] Ignore overcurrent events (default N).
3056 Some badly-designed motherboards generate lots of
3057 bogus events, for ports that aren't wired to
3058 anything. Set this parameter to avoid log spamming.
3059 Note that genuine overcurrent events won't be
3063 [X86] Cause panic on unknown NMI.
3065 usbcore.authorized_default=
3066 [USB] Default USB device authorization:
3067 (default -1 = authorized except for wireless USB,
3068 0 = not authorized, 1 = authorized)
3070 usbcore.autosuspend=
3071 [USB] The autosuspend time delay (in seconds) used
3072 for newly-detected USB devices (default 2). This
3073 is the time required before an idle device will be
3074 autosuspended. Devices for which the delay is set
3075 to a negative value won't be autosuspended at all.
3077 usbcore.usbfs_snoop=
3078 [USB] Set to log all usbfs traffic (default 0 = off).
3080 usbcore.blinkenlights=
3081 [USB] Set to cycle leds on hubs (default 0 = off).
3083 usbcore.old_scheme_first=
3084 [USB] Start with the old device initialization
3085 scheme (default 0 = off).
3087 usbcore.usbfs_memory_mb=
3088 [USB] Memory limit (in MB) for buffers allocated by
3089 usbfs (default = 16, 0 = max = 2047).
3091 usbcore.use_both_schemes=
3092 [USB] Try the other device initialization scheme
3093 if the first one fails (default 1 = enabled).
3095 usbcore.initial_descriptor_timeout=
3096 [USB] Specifies timeout for the initial 64-byte
3097 USB_REQ_GET_DESCRIPTOR request in milliseconds
3098 (default 5000 = 5.0 seconds).
3101 [USBHID] The interval which mice are to be polled at.
3103 usb-storage.delay_use=
3104 [UMS] The delay in seconds before a new device is
3105 scanned for Logical Units (default 5).
3108 [UMS] A list of quirks entries to supplement or
3109 override the built-in unusual_devs list. List
3110 entries are separated by commas. Each entry has
3111 the form VID:PID:Flags where VID and PID are Vendor
3112 and Product ID values (4-digit hex numbers) and
3113 Flags is a set of characters, each corresponding
3114 to a common usb-storage quirk flag as follows:
3115 a = SANE_SENSE (collect more than 18 bytes
3117 b = BAD_SENSE (don't collect more than 18
3118 bytes of sense data);
3119 c = FIX_CAPACITY (decrease the reported
3120 device capacity by one sector);
3121 d = NO_READ_DISC_INFO (don't use
3122 READ_DISC_INFO command);
3123 e = NO_READ_CAPACITY_16 (don't use
3124 READ_CAPACITY_16 command);
3125 h = CAPACITY_HEURISTICS (decrease the
3126 reported device capacity by one
3127 sector if the number is odd);
3128 i = IGNORE_DEVICE (don't bind to this
3130 l = NOT_LOCKABLE (don't try to lock and
3131 unlock ejectable media);
3132 m = MAX_SECTORS_64 (don't transfer more
3133 than 64 sectors = 32 KB at a time);
3134 n = INITIAL_READ10 (force a retry of the
3135 initial READ(10) command);
3136 o = CAPACITY_OK (accept the capacity
3137 reported by the device);
3138 p = WRITE_CACHE (the device cache is ON
3140 r = IGNORE_RESIDUE (the device reports
3141 bogus residue values);
3142 s = SINGLE_LUN (the device has only one
3144 w = NO_WP_DETECT (don't test whether the
3145 medium is write-protected).
3146 Example: quirks=0419:aaf5:rl,0421:0433:rc
3148 user_debug= [KNL,ARM]
3150 See arch/arm/Kconfig.debug help text.
3151 1 - undefined instruction events
3153 4 - invalid data aborts
3156 Example: user_debug=31
3159 [X86] Flags controlling user PTE allocations.
3161 nohigh = do not allocate PTE pages in
3162 HIGHMEM regardless of setting
3166 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3167 vdso=1: enable VDSO (default)
3168 vdso=0: disable VDSO mapping
3171 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3172 vdso32=1: enable 32-bit VDSO (default)
3173 vdso32=0: disable 32-bit VDSO mapping
3176 vector=percpu: enable percpu vector domain
3178 video= [FB] Frame buffer configuration
3179 See Documentation/fb/modedb.txt.
3182 [VMMIO] Memory mapped virtio (platform) device.
3184 <size>@<baseaddr>:<irq>[:<id>]
3186 <size> := size (can use standard suffixes
3188 <baseaddr> := physical base address
3189 <irq> := interrupt number (as passed to
3191 <id> := (optional) platform device id
3193 virtio_mmio.device=1K@0x100b0000:48:7
3195 Can be used multiple times for multiple devices.
3197 vga= [BOOT,X86-32] Select a particular video mode
3198 See Documentation/x86/boot.txt and
3199 Documentation/svga.txt.
3200 Use vga=ask for menu.
3201 This is actually a boot loader parameter; the value is
3202 passed to the kernel using a special protocol.
3204 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3205 size of <nn>. This can be used to increase the
3206 minimum size (128MB on x86). It can also be used to
3207 decrease the size and leave more room for directly
3210 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3213 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3216 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3220 Controls the behavior of vsyscalls (i.e. calls to
3221 fixed addresses of 0xffffffffff600x00 from legacy
3222 code). Most statically-linked binaries and older
3223 versions of glibc use these calls. Because these
3224 functions are at fixed addresses, they make nice
3225 targets for exploits that can control RIP.
3227 emulate [default] Vsyscalls turn into traps and are
3228 emulated reasonably safely.
3230 native Vsyscalls are native syscall instructions.
3231 This is a little bit faster than trapping
3232 and makes a few dynamic recompilers work
3233 better than they would in emulation mode.
3234 It also makes exploits much easier to write.
3236 none Vsyscalls don't work at all. This makes
3237 them quite hard to use for exploits but
3238 might break your system.
3240 vt.cur_default= [VT] Default cursor shape.
3241 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3242 the parameters of the <Esc>[?A;B;Cc escape sequence;
3243 see VGA-softcursor.txt. Default: 2 = underline.
3245 vt.default_blu= [VT]
3246 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3247 Change the default blue palette of the console.
3248 This is a 16-member array composed of values
3251 vt.default_grn= [VT]
3252 Format: <green0>,<green1>,<green2>,...,<green15>
3253 Change the default green palette of the console.
3254 This is a 16-member array composed of values
3257 vt.default_red= [VT]
3258 Format: <red0>,<red1>,<red2>,...,<red15>
3259 Change the default red palette of the console.
3260 This is a 16-member array composed of values
3266 Set system-wide default UTF-8 mode for all tty's.
3267 Default is 1, i.e. UTF-8 mode is enabled for all
3268 newly opened terminals.
3270 vt.global_cursor_default=
3273 Set system-wide default for whether a cursor
3274 is shown on new VTs. Default is -1,
3275 i.e. cursors will be created by default unless
3276 overridden by individual drivers. 0 will hide
3277 cursors, 1 will display them.
3279 watchdog timers [HW,WDT] For information on watchdog timers,
3280 see Documentation/watchdog/watchdog-parameters.txt
3281 or other driver-specific files in the
3282 Documentation/watchdog/ directory.
3284 workqueue.disable_numa
3285 By default, all work items queued to unbound
3286 workqueues are affine to the NUMA nodes they're
3287 issued on, which results in better behavior in
3288 general. If NUMA affinity needs to be disabled for
3289 whatever reason, this option can be used. Note
3290 that this also can be controlled per-workqueue for
3291 workqueues visible under /sys/bus/workqueue/.
3293 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3294 default x2apic cluster mode on platforms
3297 x86_mrst_timer= [X86-32,APBT]
3298 Choose timer option for x86 Moorestown MID platform.
3299 Two valid options are apbt timer only and lapic timer
3300 plus one apbt timer for broadcast timer.
3301 x86_mrst_timer=apbt_only | lapic_and_apbt
3303 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3304 xd_geo= See header of drivers/block/xd.c.
3306 xen_emul_unplug= [HW,X86,XEN]
3307 Unplug Xen emulated devices
3308 Format: [unplug0,][unplug1]
3309 ide-disks -- unplug primary master IDE devices
3310 aux-ide-disks -- unplug non-primary-master IDE devices
3311 nics -- unplug network devices
3312 all -- unplug all emulated devices (NICs and IDE disks)
3313 unnecessary -- unplugging emulated devices is
3314 unnecessary even if the host did not respond to
3316 never -- do not unplug even if version check succeeds
3318 xirc2ps_cs= [NET,PCMCIA]
3320 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3322 ______________________________________________________________________
3326 Add more DRM drivers.
projects / GitHub / mt8127 / android_kernel_alcatel_ttab.git / blob