4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
39 Some kernel parameters take a list of CPUs as a value, e.g. isolcpus,
40 nohz_full, irqaffinity, rcu_nocbs. The format of this list is:
42 <cpu number>,...,<cpu number>
46 <cpu number>-<cpu number>
47 (must be a positive range in ascending order)
51 <cpu number>,...,<cpu number>-<cpu number>
53 Note that for the special case of a range one can split the range into equal
54 sized groups and for each group use some amount from the beginning of that
57 <cpu number>-cpu number>:<used size>/<group size>
59 For example one can add to the command line following parameter:
61 isolcpus=1,2,10-20,100-2000:2/25
63 where the final item represents CPUs 100,101,125,126,150,151,...
67 This document may not be entirely up to date and comprehensive. The command
68 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
69 module. Loadable modules, after being loaded into the running kernel, also
70 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
71 parameters may be changed at runtime by the command
72 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
74 The parameters listed below are only valid if certain kernel build options were
75 enabled and if respective hardware is present. The text in square brackets at
76 the beginning of each description states the restrictions within which a
77 parameter is applicable:
79 ACPI ACPI support is enabled.
80 AGP AGP (Accelerated Graphics Port) is enabled.
81 ALSA ALSA sound support is enabled.
82 APIC APIC support is enabled.
83 APM Advanced Power Management support is enabled.
84 ARM ARM architecture is enabled.
85 AVR32 AVR32 architecture is enabled.
86 AX25 Appropriate AX.25 support is enabled.
87 BLACKFIN Blackfin architecture is enabled.
88 CLK Common clock infrastructure is enabled.
89 CMA Contiguous Memory Area support is enabled.
90 DRM Direct Rendering Management support is enabled.
91 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
92 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
93 EFI EFI Partitioning (GPT) is enabled
94 EIDE EIDE/ATAPI support is enabled.
95 EVM Extended Verification Module
96 FB The frame buffer device is enabled.
97 FTRACE Function tracing enabled.
98 GCOV GCOV profiling is enabled.
99 HW Appropriate hardware is enabled.
100 IA-64 IA-64 architecture is enabled.
101 IMA Integrity measurement architecture is enabled.
102 IOSCHED More than one I/O scheduler is enabled.
103 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
104 IPV6 IPv6 support is enabled.
105 ISAPNP ISA PnP code is enabled.
106 ISDN Appropriate ISDN support is enabled.
107 JOY Appropriate joystick support is enabled.
108 KGDB Kernel debugger support is enabled.
109 KVM Kernel Virtual Machine support is enabled.
110 LIBATA Libata driver is enabled
111 LP Printer support is enabled.
112 LOOP Loopback device support is enabled.
113 M68k M68k architecture is enabled.
114 These options have more detailed description inside of
115 Documentation/m68k/kernel-options.txt.
116 MDA MDA console support is enabled.
117 MIPS MIPS architecture is enabled.
118 MOUSE Appropriate mouse support is enabled.
119 MSI Message Signaled Interrupts (PCI).
120 MTD MTD (Memory Technology Device) support is enabled.
121 NET Appropriate network support is enabled.
122 NUMA NUMA support is enabled.
123 NFS Appropriate NFS support is enabled.
124 OSS OSS sound support is enabled.
125 PV_OPS A paravirtualized kernel is enabled.
126 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
127 PARISC The PA-RISC architecture is enabled.
128 PCI PCI bus support is enabled.
129 PCIE PCI Express support is enabled.
130 PCMCIA The PCMCIA subsystem is enabled.
131 PNP Plug & Play support is enabled.
132 PPC PowerPC architecture is enabled.
133 PPT Parallel port support is enabled.
134 PS2 Appropriate PS/2 support is enabled.
135 RAM RAM disk support is enabled.
136 S390 S390 architecture is enabled.
137 SCSI Appropriate SCSI support is enabled.
138 A lot of drivers have their options described inside
139 the Documentation/scsi/ sub-directory.
140 SECURITY Different security models are enabled.
141 SELINUX SELinux support is enabled.
142 APPARMOR AppArmor support is enabled.
143 SERIAL Serial support is enabled.
144 SH SuperH architecture is enabled.
145 SMP The kernel is an SMP kernel.
146 SPARC Sparc architecture is enabled.
147 SWSUSP Software suspend (hibernation) is enabled.
148 SUSPEND System suspend states are enabled.
149 TPM TPM drivers are enabled.
150 TS Appropriate touchscreen support is enabled.
151 UMS USB Mass Storage support is enabled.
152 USB USB support is enabled.
153 USBHID USB Human Interface Device support is enabled.
154 V4L Video For Linux support is enabled.
155 VMMIO Driver for memory mapped virtio devices is enabled.
156 VGA The VGA console has been enabled.
157 VT Virtual terminal support is enabled.
158 WDT Watchdog support is enabled.
159 XT IBM PC/XT MFM hard disk support is enabled.
160 X86-32 X86-32, aka i386 architecture is enabled.
161 X86-64 X86-64 architecture is enabled.
162 More X86-64 boot options can be found in
163 Documentation/x86/x86_64/boot-options.txt .
164 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
165 X86_UV SGI UV support is enabled.
166 XEN Xen support is enabled
168 In addition, the following text indicates that the option:
170 BUGS= Relates to possible processor bugs on the said processor.
171 KNL Is a kernel start-up parameter.
172 BOOT Is a boot loader parameter.
174 Parameters denoted with BOOT are actually interpreted by the boot
175 loader, and have no meaning to the kernel directly.
176 Do not modify the syntax of boot loader parameters without extreme
177 need or coordination with <Documentation/x86/boot.txt>.
179 There are also arch-specific kernel-parameters not documented here.
180 See for example <Documentation/x86/x86_64/boot-options.txt>.
182 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
183 a trailing = on the name of any parameter states that that parameter will
184 be entered as an environment variable, whereas its absence indicates that
185 it will appear as a kernel argument readable via /proc/cmdline by programs
186 running once the system is up.
188 The number of kernel parameters is not limited, but the length of the
189 complete command line (parameters including spaces etc.) is limited to
190 a fixed number of characters. This limit depends on the architecture
191 and is between 256 and 4096 characters. It is defined in the file
192 ./include/asm/setup.h as COMMAND_LINE_SIZE.
194 Finally, the [KMG] suffix is commonly described after a number of kernel
195 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
196 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
197 bytes respectively. Such letter suffixes can also be entirely omitted.
200 acpi= [HW,ACPI,X86,ARM64]
201 Advanced Configuration and Power Interface
202 Format: { force | on | off | strict | noirq | rsdt |
204 force -- enable ACPI if default was off
205 on -- enable ACPI but allow fallback to DT [arm64]
206 off -- disable ACPI if default was on
207 noirq -- do not use ACPI for IRQ routing
208 strict -- Be less tolerant of platforms that are not
209 strictly ACPI specification compliant.
210 rsdt -- prefer RSDT over (default) XSDT
211 copy_dsdt -- copy DSDT to memory
212 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
215 See also Documentation/power/runtime_pm.txt, pci=noacpi
217 acpi_apic_instance= [ACPI, IOAPIC]
219 2: use 2nd APIC table, if available
220 1,0: use 1st APIC table
223 acpi_backlight= [HW,ACPI]
224 acpi_backlight=vendor
226 If set to vendor, prefer vendor specific driver
227 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
228 of the ACPI video.ko driver.
230 acpi_force_32bit_fadt_addr
231 force FADT to use 32 bit addresses rather than the
232 64 bit X_* addresses. Some firmware have broken 64
233 bit addresses for force ACPI ignore these and use
234 the older legacy 32 bit addresses.
236 acpica_no_return_repair [HW, ACPI]
237 Disable AML predefined validation mechanism
238 This mechanism can repair the evaluation result to make
239 the return objects more ACPI specification compliant.
240 This option is useful for developers to identify the
241 root cause of an AML interpreter issue when the issue
242 has something to do with the repair mechanism.
244 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
245 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
247 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
248 debug output. Bits in debug_layer correspond to a
249 _COMPONENT in an ACPI source file, e.g.,
250 #define _COMPONENT ACPI_PCI_COMPONENT
251 Bits in debug_level correspond to a level in
252 ACPI_DEBUG_PRINT statements, e.g.,
253 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
254 The debug_level mask defaults to "info". See
255 Documentation/acpi/debug.txt for more information about
256 debug layers and levels.
258 Enable processor driver info messages:
259 acpi.debug_layer=0x20000000
260 Enable PCI/PCI interrupt routing info messages:
261 acpi.debug_layer=0x400000
262 Enable AML "Debug" output, i.e., stores to the Debug
263 object while interpreting AML:
264 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
265 Enable all messages related to ACPI hardware:
266 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
268 Some values produce so much output that the system is
269 unusable. The "log_buf_len" parameter may be useful
270 if you need to capture more output.
272 acpi_enforce_resources= [ACPI]
273 { strict | lax | no }
274 Check for resource conflicts between native drivers
275 and ACPI OperationRegions (SystemIO and SystemMemory
276 only). IO ports and memory declared in ACPI might be
277 used by the ACPI subsystem in arbitrary AML code and
278 can interfere with legacy drivers.
279 strict (default): access to resources claimed by ACPI
280 is denied; legacy drivers trying to access reserved
281 resources will fail to bind to device using them.
282 lax: access to resources claimed by ACPI is allowed;
283 legacy drivers trying to access reserved resources
284 will bind successfully but a warning message is logged.
285 no: ACPI OperationRegions are not marked as reserved,
286 no further checks are performed.
288 acpi_force_table_verification [HW,ACPI]
289 Enable table checksum verification during early stage.
290 By default, this is disabled due to x86 early mapping
293 acpi_irq_balance [HW,ACPI]
294 ACPI will balance active IRQs
297 acpi_irq_nobalance [HW,ACPI]
298 ACPI will not move active IRQs (default)
301 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
302 Format: <irq>,<irq>...
304 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
306 Format: <irq>,<irq>...
308 acpi_no_auto_serialize [HW,ACPI]
309 Disable auto-serialization of AML methods
310 AML control methods that contain the opcodes to create
311 named objects will be marked as "Serialized" by the
312 auto-serialization feature.
313 This feature is enabled by default.
314 This option allows to turn off the feature.
316 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
319 acpi_no_static_ssdt [HW,ACPI]
320 Disable installation of static SSDTs at early boot time
321 By default, SSDTs contained in the RSDT/XSDT will be
322 installed automatically and they will appear under
323 /sys/firmware/acpi/tables.
324 This option turns off this feature.
325 Note that specifying this option does not affect
326 dynamic table installation which will install SSDT
327 tables to /sys/firmware/acpi/tables/dynamic.
329 acpi_rsdp= [ACPI,EFI,KEXEC]
330 Pass the RSDP address to the kernel, mostly used
331 on machines running EFI runtime service to boot the
332 second kernel for kdump.
334 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
335 Format: To spoof as Windows 98: ="Microsoft Windows"
337 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
338 of 2 which is mandated by ACPI 6) as the supported ACPI
339 specification revision (when using this switch, it may
340 be necessary to carry out a cold reboot _twice_ in a
341 row to make it take effect on the platform firmware).
343 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
344 acpi_osi="string1" # add string1
345 acpi_osi="!string2" # remove string2
346 acpi_osi=!* # remove all strings
347 acpi_osi=! # disable all built-in OS vendor
349 acpi_osi=!! # enable all built-in OS vendor
351 acpi_osi= # disable all strings
353 'acpi_osi=!' can be used in combination with single or
354 multiple 'acpi_osi="string1"' to support specific OS
355 vendor string(s). Note that such command can only
356 affect the default state of the OS vendor strings, thus
357 it cannot affect the default state of the feature group
358 strings and the current state of the OS vendor strings,
359 specifying it multiple times through kernel command line
360 is meaningless. This command is useful when one do not
361 care about the state of the feature group strings which
362 should be controlled by the OSPM.
364 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
365 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
366 can make '_OSI("Windows 2000")' TRUE.
368 'acpi_osi=' cannot be used in combination with other
369 'acpi_osi=' command lines, the _OSI method will not
370 exist in the ACPI namespace. NOTE that such command can
371 only affect the _OSI support state, thus specifying it
372 multiple times through kernel command line is also
375 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
378 'acpi_osi=!*' can be used in combination with single or
379 multiple 'acpi_osi="string1"' to support specific
380 string(s). Note that such command can affect the
381 current state of both the OS vendor strings and the
382 feature group strings, thus specifying it multiple times
383 through kernel command line is meaningful. But it may
384 still not able to affect the final state of a string if
385 there are quirks related to this string. This command
386 is useful when one want to control the state of the
387 feature group strings to debug BIOS issues related to
390 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
391 '_OSI("Module Device")' FALSE.
392 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
393 '_OSI("Module Device")' TRUE.
394 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
396 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
398 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
399 they all will make '_OSI("Windows 2000")' TRUE.
402 Override the pmtimer bug detection: force the kernel
403 to assume that this machine's pmtimer latches its value
404 and always returns good values.
406 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
407 Format: { level | edge | high | low }
409 acpi_skip_timer_override [HW,ACPI]
410 Recognize and ignore IRQ0/pin2 Interrupt Override.
411 For broken nForce2 BIOS resulting in XT-PIC timer.
413 acpi_sleep= [HW,ACPI] Sleep options
414 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
415 old_ordering, nonvs, sci_force_enable }
416 See Documentation/power/video.txt for information on
418 s3_beep is for debugging; it makes the PC's speaker beep
419 as soon as the kernel's real-mode entry point is called.
420 s4_nohwsig prevents ACPI hardware signature from being
421 used during resume from hibernation.
422 old_ordering causes the ACPI 1.0 ordering of the _PTS
423 control method, with respect to putting devices into
424 low power states, to be enforced (the ACPI 2.0 ordering
425 of _PTS is used by default).
426 nonvs prevents the kernel from saving/restoring the
427 ACPI NVS memory during suspend/hibernation and resume.
428 sci_force_enable causes the kernel to set SCI_EN directly
429 on resume from S1/S3 (which is against the ACPI spec,
430 but some broken systems don't work without it).
432 acpi_use_timer_override [HW,ACPI]
433 Use timer override. For some broken Nvidia NF5 boards
434 that require a timer override, but don't have HPET
436 add_efi_memmap [EFI; X86] Include EFI memory map in
437 kernel's map of available physical RAM.
440 { off | try_unsupported }
441 off: disable AGP support
442 try_unsupported: try to drive unsupported chipsets
443 (may crash computer or cause data corruption)
446 See Documentation/sound/alsa/alsa-parameters.txt
449 Allow the default userspace alignment fault handler
450 behaviour to be specified. Bit 0 enables warnings,
451 bit 1 enables fixups, and bit 2 sends a segfault.
453 align_va_addr= [X86-64]
454 Align virtual addresses by clearing slice [14:12] when
455 allocating a VMA at process creation time. This option
456 gives you up to 3% performance improvement on AMD F15h
457 machines (where it is enabled by default) for a
458 CPU-intensive style benchmark, and it can vary highly in
459 a microbenchmark depending on workload and compiler.
461 32: only for 32-bit processes
462 64: only for 64-bit processes
463 on: enable for both 32- and 64-bit processes
464 off: disable for both 32- and 64-bit processes
466 alloc_snapshot [FTRACE]
467 Allocate the ftrace snapshot buffer on boot up when the
468 main buffer is allocated. This is handy if debugging
469 and you need to use tracing_snapshot() on boot up, and
470 do not want to use tracing_snapshot_alloc() as it needs
471 to be done where GFP_KERNEL allocations are allowed.
473 amd_iommu= [HW,X86-64]
474 Pass parameters to the AMD IOMMU driver in the system.
476 fullflush - enable flushing of IO/TLB entries when
477 they are unmapped. Otherwise they are
478 flushed before they will be reused, which
480 off - do not initialize any AMD IOMMU found in
482 force_isolation - Force device isolation for all
483 devices. The IOMMU driver is not
484 allowed anymore to lift isolation
485 requirements as needed. This option
486 does not override iommu=pt
488 amd_iommu_dump= [HW,X86-64]
489 Enable AMD IOMMU driver option to dump the ACPI table
490 for AMD IOMMU. With this option enabled, AMD IOMMU
491 driver will print ACPI tables for AMD IOMMU during
492 IOMMU initialization.
494 amd_iommu_intr= [HW,X86-64]
495 Specifies one of the following AMD IOMMU interrupt
497 legacy - Use legacy interrupt remapping mode.
498 vapic - Use virtual APIC mode, which allows IOMMU
499 to inject interrupts directly into guest.
500 This mode requires kvm-amd.avic=1.
501 (Default when IOMMU HW support is present.)
503 amijoy.map= [HW,JOY] Amiga joystick support
504 Map of devices attached to JOY0DAT and JOY1DAT
506 See also Documentation/input/joystick.txt
508 analog.map= [HW,JOY] Analog joystick and gamepad support
509 Specifies type or capabilities of an analog joystick
510 connected to one of 16 gameports
511 Format: <type1>,<type2>,..<type16>
514 Power management functions (SPARCstation-4/5 + deriv.)
516 Disable APC CPU standby support. SPARCstation-Fox does
517 not play well with APC CPU idle - disable it if you have
518 APC and your system crashes randomly.
520 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
521 Change the output verbosity whilst booting
522 Format: { quiet (default) | verbose | debug }
523 Change the amount of debugging information output
524 when initialising the APIC and IO-APIC components.
526 apic_extnmi= [APIC,X86] External NMI delivery setting
527 Format: { bsp (default) | all | none }
528 bsp: External NMI is delivered only to CPU 0
529 all: External NMIs are broadcast to all CPUs as a
531 none: External NMI is masked for all CPUs. This is
532 useful so that a dump capture kernel won't be
536 See Documentation/networking/ipv6.txt.
538 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
539 Limit apic dumping. The parameter defines the maximal
540 number of local apics being dumped. Also it is possible
541 to set it to "all" by meaning -- no limit here.
542 Format: { 1 (default) | 2 | ... | all }.
543 The parameter valid if only apic=debug or
544 apic=verbose is specified.
545 Example: apic=debug show_lapic=all
547 apm= [APM] Advanced Power Management
548 See header of arch/x86/kernel/apm_32.c.
550 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
551 Format: <io>,<irq>,<nodeID>
555 atarimouse= [HW,MOUSE] Atari Mouse
557 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
558 EzKey and similar keyboards
560 atkbd.reset= [HW] Reset keyboard during initialization
562 atkbd.set= [HW] Select keyboard code set
563 Format: <int> (2 = AT (default), 3 = PS/2)
565 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
568 atkbd.softraw= [HW] Choose between synthetic and real raw mode
569 Format: <bool> (0 = real, 1 = synthetic (default))
571 atkbd.softrepeat= [HW]
572 Use software keyboard repeat
574 audit= [KNL] Enable the audit sub-system
575 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
576 0 - kernel audit is disabled and can not be enabled
577 until the next reboot
578 unset - kernel audit is initialized but disabled and
579 will be fully enabled by the userspace auditd.
580 1 - kernel audit is initialized and partially enabled,
581 storing at most audit_backlog_limit messages in
582 RAM until it is fully enabled by the userspace
586 audit_backlog_limit= [KNL] Set the audit queue size limit.
587 Format: <int> (must be >=0)
590 bau= [X86_UV] Enable the BAU on SGI UV. The default
591 behavior is to disable the BAU (i.e. bau=0).
592 Format: { "0" | "1" }
595 unset - Disable the BAU.
597 baycom_epp= [HW,AX25]
600 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
602 See header of drivers/net/hamradio/baycom_par.c.
604 baycom_ser_fdx= [HW,AX25]
605 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
606 Format: <io>,<irq>,<mode>[,<baud>]
607 See header of drivers/net/hamradio/baycom_ser_fdx.c.
609 baycom_ser_hdx= [HW,AX25]
610 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
611 Format: <io>,<irq>,<mode>
612 See header of drivers/net/hamradio/baycom_ser_hdx.c.
614 blkdevparts= Manual partition parsing of block device(s) for
615 embedded devices based on command line input.
616 See Documentation/block/cmdline-partition.txt
618 boot_delay= Milliseconds to delay each printk during boot.
619 Values larger than 10 seconds (10000) are changed to
623 bootmem_debug [KNL] Enable bootmem allocator debug messages.
626 Disable BERT OS support on buggy BIOSes.
628 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
629 bttv.radio= Most important insmod options are available as
631 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
634 bulk_remove=off [PPC] This parameter disables the use of the pSeries
635 firmware feature for flushing multiple hpte entries
638 c101= [NET] Moxa C101 synchronous serial card
640 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
641 Sometimes CPU hardware bugs make them report the cache
642 size incorrectly. The kernel will attempt work arounds
643 to fix known problems, but for some CPUs it is not
644 possible to determine what the correct size should be.
645 This option provides an override for these situations.
647 ca_keys= [KEYS] This parameter identifies a specific key(s) on
648 the system trusted keyring to be used for certificate
650 format: { id:<keyid> | builtin }
652 cca= [MIPS] Override the kernel pages' cache coherency
653 algorithm. Accepted values range from 0 to 7
654 inclusive. See arch/mips/include/asm/pgtable-bits.h
655 for platform specific values (SB1, Loongson3 and
658 ccw_timeout_log [S390]
659 See Documentation/s390/CommonIO for details.
661 cgroup_disable= [KNL] Disable a particular controller
662 Format: {name of the controller(s) to disable}
663 The effects of cgroup_disable=foo are:
664 - foo isn't auto-mounted if you mount all cgroups in
666 - foo isn't visible as an individually mountable
668 {Currently only "memory" controller deal with this and
669 cut the overhead, others just disable the usage. So
670 only cgroup_disable=memory is actually worthy}
672 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
673 Format: { controller[,controller...] | "all" }
674 Like cgroup_disable, but only applies to cgroup v1;
675 the blacklisted controllers remain available in cgroup2.
677 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
679 nosocket -- Disable socket memory accounting.
680 nokmem -- Disable kernel memory accounting.
682 checkreqprot [SELINUX] Set initial checkreqprot flag value.
683 Format: { "0" | "1" }
684 See security/selinux/Kconfig help text.
685 0 -- check protection applied by kernel (includes
686 any implied execute protection).
687 1 -- check protection requested by application.
688 Default value is set via a kernel config option.
689 Value can be changed at runtime via
690 /selinux/checkreqprot.
693 See Documentation/s390/CommonIO for details.
696 Prevents the clock framework from automatically gating
697 clocks that have not been explicitly enabled by a Linux
698 device driver but are enabled in hardware at reset or
699 by the bootloader/firmware. Note that this does not
700 force such clocks to be always-on nor does it reserve
701 those clocks in any way. This parameter is useful for
702 debug and development, but should not be needed on a
703 platform with proper driver support. For more
704 information, see Documentation/clk.txt.
706 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
708 Forces specified clocksource (if available) to be used
709 when calculating gettimeofday(). If specified
710 clocksource is not available, it defaults to PIT.
711 Format: { pit | tsc | cyclone | pmtmr }
713 clocksource= Override the default clocksource
715 Override the default clocksource and use the clocksource
716 with the name specified.
717 Some clocksource names to choose from, depending on
719 [all] jiffies (this is the base, fallback clocksource)
721 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
722 pxa_timer,timer3,32k_counter,timer0_1
724 [X86-32] pit,hpet,tsc;
725 scx200_hrt on Geode; cyclone on IBM x440
733 clocksource.arm_arch_timer.evtstrm=
736 Enable/disable the eventstream feature of the ARM
737 architected timer so that code using WFE-based polling
738 loops can be debugged more effectively on production
741 clocksource.arm_arch_timer.fsl-a008585=
744 Enable/disable the workaround of Freescale/NXP
745 erratum A-008585. This can be useful for KVM
746 guests, if the guest device tree doesn't show the
747 erratum. If unspecified, the workaround is
748 enabled based on the device tree.
750 clearcpuid=BITNUM [X86]
751 Disable CPUID feature X for the kernel. See
752 arch/x86/include/asm/cpufeatures.h for the valid bit
753 numbers. Note the Linux specific bits are not necessarily
754 stable over kernel options, but the vendor specific
756 Also note that user programs calling CPUID directly
757 or using the feature without checking anything
758 will still see it. This just prevents it from
759 being used by the kernel or shown in /proc/cpuinfo.
760 Also note the kernel might malfunction if you disable
763 cma=nn[MG]@[start[MG][-end[MG]]]
765 Sets the size of kernel global memory area for
766 contiguous memory allocations and optionally the
767 placement constraint by the physical address range of
768 memory allocations. A value of 0 disables CMA
769 altogether. For more information, see
770 include/linux/dma-contiguous.h
772 cmo_free_hint= [PPC] Format: { yes | no }
773 Specify whether pages are marked as being inactive
774 when they are freed. This is used in CMO environments
775 to determine OS memory pressure for page stealing by
779 coherent_pool=nn[KMG] [ARM,KNL]
780 Sets the size of memory pool for coherent, atomic dma
781 allocations, by default set to 256K.
783 code_bytes [X86] How many bytes of object code to print
788 com20020= [HW,NET] ARCnet - COM20020 chipset
790 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
792 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
796 ARCnet - COM90xx chipset (memory-mapped buffers)
797 Format: <io>[,<irq>[,<memstart>]]
799 condev= [HW,S390] console device
802 console= [KNL] Output console device and options.
804 tty<n> Use the virtual console device <n>.
808 Use the specified serial port. The options are of
809 the form "bbbbpnf", where "bbbb" is the baud rate,
810 "p" is parity ("n", "o", or "e"), "n" is number of
811 bits, and "f" is flow control ("r" for RTS or
812 omit it). Default is "9600n8".
814 See Documentation/serial-console.txt for more
816 Documentation/networking/netconsole.txt for an
819 uart[8250],io,<addr>[,options]
820 uart[8250],mmio,<addr>[,options]
821 uart[8250],mmio16,<addr>[,options]
822 uart[8250],mmio32,<addr>[,options]
823 uart[8250],0x<addr>[,options]
824 Start an early, polled-mode console on the 8250/16550
825 UART at the specified I/O port or MMIO address,
826 switching to the matching ttyS device later.
827 MMIO inter-register address stride is either 8-bit
828 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
829 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
830 to be equivalent to 'mmio'. 'options' are specified in
831 the same format described for ttyS above; if unspecified,
832 the h/w is not re-initialized.
834 hvc<n> Use the hypervisor console device <n>. This is for
835 both Xen and PowerPC hypervisors.
837 If the device connected to the port is not a TTY but a braille
838 device, prepend "brl," before the device type, for instance
840 For now, only VisioBraille is supported.
842 consoleblank= [KNL] The console blank (screen saver) timeout in
843 seconds. Defaults to 10*60 = 10mins. A value of 0
844 disables the blank timer.
847 [KNL] Change the default value for
848 /proc/<pid>/coredump_filter.
849 See also Documentation/filesystems/proc.txt.
851 cpuidle.off=1 [CPU_IDLE]
852 disable the cpuidle sub-system
855 [X86] Delay for N microsec between assert and de-assert
856 of APIC INIT to start processors. This delay occurs
857 on every CPU online, such as boot, and resume from suspend.
860 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
862 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
864 crashkernel=size[KMG][@offset[KMG]]
865 [KNL] Using kexec, Linux can switch to a 'crash kernel'
866 upon panic. This parameter reserves the physical
867 memory region [offset, offset + size] for that kernel
868 image. If '@offset' is omitted, then a suitable offset
869 is selected automatically. Check
870 Documentation/kdump/kdump.txt for further details.
872 crashkernel=range1:size1[,range2:size2,...][@offset]
873 [KNL] Same as above, but depends on the memory
874 in the running system. The syntax of range is
875 start-[end] where start and end are both
876 a memory unit (amount[KMG]). See also
877 Documentation/kdump/kdump.txt for an example.
879 crashkernel=size[KMG],high
880 [KNL, x86_64] range could be above 4G. Allow kernel
881 to allocate physical memory region from top, so could
882 be above 4G if system have more than 4G ram installed.
883 Otherwise memory region will be allocated below 4G, if
885 It will be ignored if crashkernel=X is specified.
886 crashkernel=size[KMG],low
887 [KNL, x86_64] range under 4G. When crashkernel=X,high
888 is passed, kernel could allocate physical memory region
889 above 4G, that cause second kernel crash on system
890 that require some amount of low memory, e.g. swiotlb
891 requires at least 64M+32K low memory, also enough extra
892 low memory is needed to make sure DMA buffers for 32-bit
893 devices won't run out. Kernel would try to allocate at
894 at least 256M below 4G automatically.
895 This one let user to specify own low range under 4G
896 for second kernel instead.
897 0: to disable low allocation.
898 It will be ignored when crashkernel=X,high is not used
899 or memory reserved is below 4G.
902 [KNL] Disable crypto self-tests
907 cs89x0_media= [HW,NET]
908 Format: { rj45 | aui | bnc }
911 See header of drivers/s390/block/dasd_devmap.c.
913 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
914 (one device per port)
915 Format: <port#>,<type>
916 See also Documentation/input/joystick-parport.txt
918 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
919 time. See Documentation/dynamic-debug-howto.txt for
920 details. Deprecated, see dyndbg.
922 debug [KNL] Enable kernel debugging (events log level).
925 [KNL] verbose self-tests
927 Print debugging info while doing the locking API
929 We default to 0 (no extra messages), setting it to
930 1 will print _a lot_ more information - normally
931 only useful to kernel developers.
933 debug_objects [KNL] Enable object debugging
936 [KNL] Disable object debugging
938 debug_guardpage_minorder=
939 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
940 parameter allows control of the order of pages that will
941 be intentionally kept free (and hence protected) by the
942 buddy allocator. Bigger value increase the probability
943 of catching random memory corruption, but reduce the
944 amount of memory for normal system use. The maximum
945 possible value is MAX_ORDER/2. Setting this parameter
946 to 1 or 2 should be enough to identify most random
947 memory corruption problems caused by bugs in kernel or
948 driver code when a CPU writes to (or reads from) a
949 random memory location. Note that there exists a class
950 of memory corruptions problems caused by buggy H/W or
951 F/W or by drivers badly programing DMA (basically when
952 memory is written at bus level and the CPU MMU is
953 bypassed) which are not detectable by
954 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
955 tracking down these problems.
958 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
959 parameter enables the feature at boot time. In
960 default, it is disabled. We can avoid allocating huge
961 chunk of memory for debug pagealloc if we don't enable
962 it at boot time and the system will work mostly same
963 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
964 on: enable the feature
966 debugpat [X86] Enable PAT debugging
968 decnet.addr= [HW,NET]
969 Format: <area>[,<node>]
970 See also Documentation/networking/decnet.txt.
973 [same as hugepagesz=] The size of the default
974 HugeTLB page size. This is the size represented by
975 the legacy /proc/ hugepages APIs, used for SHM, and
976 default size when mounting hugetlbfs filesystems.
977 Defaults to the default architecture's huge page size
981 Set number of hash buckets for dentry cache.
983 disable_1tb_segments [PPC]
984 Disables the use of 1TB hash page table segments. This
985 causes the kernel to fall back to 256MB segments which
986 can be useful when debugging issues that require an SLB
990 See Documentation/networking/ipv6.txt.
993 Disable RADIX MMU mode on POWER9
995 disable_cpu_apicid= [X86,APIC,SMP]
997 The number of initial APIC ID for the
998 corresponding CPU to be disabled at boot,
999 mostly used for the kdump 2nd kernel to
1000 disable BSP to wake up multiple CPUs without
1001 causing system reset or hang due to sending
1002 INIT from AP to BSP.
1004 disable_ddw [PPC/PSERIES]
1005 Disable Dynamic DMA Window support. Use this if
1006 to workaround buggy firmware.
1008 disable_ipv6= [IPV6]
1009 See Documentation/networking/ipv6.txt.
1011 disable_mtrr_cleanup [X86]
1012 The kernel tries to adjust MTRR layout from continuous
1013 to discrete, to make X server driver able to add WB
1014 entry later. This parameter disables that.
1016 disable_mtrr_trim [X86, Intel and AMD only]
1017 By default the kernel will trim any uncacheable
1018 memory out of your available memory pool based on
1019 MTRR settings. This parameter disables that behavior,
1020 possibly causing your machine to run very slowly.
1022 disable_timer_pin_1 [X86]
1023 Disable PIN 1 of APIC timer
1024 Can be useful to work around chipset bugs.
1026 dis_ucode_ldr [X86] Disable the microcode loader.
1028 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1029 this option disables the debugging code at boot.
1031 dma_debug_entries=<number>
1032 This option allows to tune the number of preallocated
1033 entries for DMA-API debugging code. One entry is
1034 required per DMA-API allocation. Use this if the
1035 DMA-API debugging code disables itself because the
1036 architectural default is too low.
1038 dma_debug_driver=<driver_name>
1039 With this option the DMA-API debugging driver
1040 filter feature can be enabled at boot time. Just
1041 pass the driver to filter for as the parameter.
1042 The filter can be disabled or changed to another
1043 driver later using sysfs.
1045 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1046 Broken monitors, graphic adapters, KVMs and EDIDless
1047 panels may send no or incorrect EDID data sets.
1048 This parameter allows to specify an EDID data sets
1049 in the /lib/firmware directory that are used instead.
1050 Generic built-in EDID data sets are used, if one of
1051 edid/1024x768.bin, edid/1280x1024.bin,
1052 edid/1680x1050.bin, or edid/1920x1080.bin is given
1053 and no file with the same name exists. Details and
1054 instructions how to build your own EDID data are
1055 available in Documentation/EDID/HOWTO.txt. An EDID
1056 data set will only be used for a particular connector,
1057 if its name and a colon are prepended to the EDID
1058 name. Each connector may use a unique EDID data
1059 set by separating the files with a comma. An EDID
1060 data set with no connector name will be used for
1061 any connectors not explicitly specified.
1065 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1066 module.dyndbg[="val"]
1067 Enable debug messages at boot time. See
1068 Documentation/dynamic-debug-howto.txt for details.
1070 nompx [X86] Disables Intel Memory Protection Extensions.
1071 See Documentation/x86/intel_mpx.txt for more
1072 information about the feature.
1074 nopku [X86] Disable Memory Protection Keys CPU feature found
1078 on enable eager fpu restore
1079 off disable eager fpu restore
1080 auto selects the default scheme, which automatically
1081 enables eagerfpu restore for xsaveopt.
1083 module.async_probe [KNL]
1084 Enable asynchronous probe on this module.
1086 early_ioremap_debug [KNL]
1087 Enable debug messages in early_ioremap support. This
1088 is useful for tracking down temporary early mappings
1089 which are not unmapped.
1091 earlycon= [KNL] Output early console device and options.
1093 When used with no options, the early console is
1094 determined by the stdout-path property in device
1097 cdns,<addr>[,options]
1098 Start an early, polled-mode console on a Cadence
1099 (xuartps) serial port at the specified address. Only
1100 supported option is baud rate. If baud rate is not
1101 specified, the serial port must already be setup and
1104 uart[8250],io,<addr>[,options]
1105 uart[8250],mmio,<addr>[,options]
1106 uart[8250],mmio32,<addr>[,options]
1107 uart[8250],mmio32be,<addr>[,options]
1108 uart[8250],0x<addr>[,options]
1109 Start an early, polled-mode console on the 8250/16550
1110 UART at the specified I/O port or MMIO address.
1111 MMIO inter-register address stride is either 8-bit
1112 (mmio) or 32-bit (mmio32 or mmio32be).
1113 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1114 to be equivalent to 'mmio'. 'options' are specified
1115 in the same format described for "console=ttyS<n>"; if
1116 unspecified, the h/w is not initialized.
1120 Start an early, polled-mode console on a pl011 serial
1121 port at the specified address. The pl011 serial port
1122 must already be setup and configured. Options are not
1123 yet supported. If 'mmio32' is specified, then only
1124 the driver will use only 32-bit accessors to read/write
1125 the device registers.
1128 Start an early, polled-mode console on a meson serial
1129 port at the specified address. The serial port must
1130 already be setup and configured. Options are not yet
1134 Start an early, polled-mode console on an msm serial
1135 port at the specified address. The serial port
1136 must already be setup and configured. Options are not
1139 msm_serial_dm,<addr>
1140 Start an early, polled-mode console on an msm serial
1141 dm port at the specified address. The serial port
1142 must already be setup and configured. Options are not
1145 smh Use ARM semihosting calls for early console.
1153 Use early console provided by serial driver available
1154 on Samsung SoCs, requires selecting proper type and
1155 a correct base address of the selected UART port. The
1156 serial port must already be setup and configured.
1157 Options are not yet supported.
1161 Use early console provided by Freescale LP UART driver
1162 found on Freescale Vybrid and QorIQ LS1021A processors.
1163 A valid base address must be provided, and the serial
1164 port must already be setup and configured.
1166 armada3700_uart,<addr>
1167 Start an early, polled-mode console on the
1168 Armada 3700 serial port at the specified
1169 address. The serial port must already be setup
1170 and configured. Options are not yet supported.
1172 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1176 earlyprintk=serial[,ttySn[,baudrate]]
1177 earlyprintk=serial[,0x...[,baudrate]]
1178 earlyprintk=ttySn[,baudrate]
1179 earlyprintk=dbgp[debugController#]
1180 earlyprintk=pciserial,bus:device.function[,baudrate]
1182 earlyprintk is useful when the kernel crashes before
1183 the normal console is initialized. It is not enabled by
1184 default because it has some cosmetic problems.
1186 Append ",keep" to not disable it when the real console
1189 Only one of vga, efi, serial, or usb debug port can
1192 Currently only ttyS0 and ttyS1 may be specified by
1193 name. Other I/O ports may be explicitly specified
1194 on some architectures (x86 and arm at least) by
1195 replacing ttySn with an I/O port address, like this:
1196 earlyprintk=serial,0x1008,115200
1197 You can find the port for a given device in
1198 /proc/tty/driver/serial:
1199 2: uart:ST16650V2 port:00001008 irq:18 ...
1201 Interaction with the standard serial driver is not
1204 The VGA and EFI output is eventually overwritten by
1207 The xen output can only be used by Xen PV guests.
1209 edac_report= [HW,EDAC] Control how to report EDAC event
1210 Format: {"on" | "off" | "force"}
1211 on: enable EDAC to report H/W event. May be overridden
1212 by other higher priority error reporting module.
1213 off: disable H/W event reporting through EDAC.
1214 force: enforce the use of EDAC to report H/W event.
1217 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1220 This is designed to be used in conjunction with
1221 the boot argument: earlyprintk=vga
1224 Format: {"off" | "on" | "skip[mbr]"}
1227 Format: { "old_map", "nochunk", "noruntime", "debug" }
1228 old_map [X86-64]: switch to the old ioremap-based EFI
1229 runtime services mapping. 32-bit still uses this one by
1231 nochunk: disable reading files in "chunks" in the EFI
1232 boot stub, as chunking can cause problems with some
1233 firmware implementations.
1234 noruntime : disable EFI runtime services support
1235 debug: enable misc debug output
1237 efi_no_storage_paranoia [EFI; X86]
1238 Using this parameter you can use more than 50% of
1239 your efi variable storage. Use this parameter only if
1240 you are really sure that your UEFI does sane gc and
1241 fulfills the spec otherwise your board may brick.
1243 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1244 Add arbitrary attribute to specific memory range by
1245 updating original EFI memory map.
1246 Region of memory which aa attribute is added to is
1248 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1249 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1250 attribute is added to range 0x100000000-0x180000000 and
1251 0x10a0000000-0x1120000000.
1253 Using this parameter you can do debugging of EFI memmap
1254 related feature. For example, you can do debugging of
1255 Address Range Mirroring feature even if your box
1258 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1259 that is to be dynamically loaded by Linux. If there are
1260 multiple variables with the same name but with different
1261 vendor GUIDs, all of them will be loaded. See
1262 Documentation/acpi/ssdt-overlays.txt for details.
1265 eisa_irq_edge= [PARISC,HW]
1266 See header of drivers/parisc/eisa.c.
1269 See comment before function elanfreq_setup() in
1270 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1273 Format: {"cfq" | "deadline" | "noop"}
1274 See Documentation/block/cfq-iosched.txt and
1275 Documentation/block/deadline-iosched.txt for details.
1277 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1278 Specifies physical address of start of kernel core
1279 image elf header and optionally the size. Generally
1280 kexec loader will pass this option to capture kernel.
1281 See Documentation/kdump/kdump.txt for details.
1283 enable_mtrr_cleanup [X86]
1284 The kernel tries to adjust MTRR layout from continuous
1285 to discrete, to make X server driver able to add WB
1286 entry later. This parameter enables that.
1288 enable_timer_pin_1 [X86]
1289 Enable PIN 1 of APIC timer
1290 Can be useful to work around chipset bugs
1291 (in particular on some ATI chipsets).
1292 The kernel tries to set a reasonable default.
1294 enforcing [SELINUX] Set initial enforcing status.
1296 See security/selinux/Kconfig help text.
1297 0 -- permissive (log only, no denials).
1298 1 -- enforcing (deny and log).
1300 Value can be changed at runtime via /selinux/enforce.
1303 Disable Error Record Serialization Table (ERST)
1306 ether= [HW,NET] Ethernet cards parameters
1307 This option is obsoleted by the "netdev=" option, which
1308 has equivalent usage. See its documentation for details.
1312 Permit 'security.evm' to be updated regardless of
1313 current integrity status.
1317 fail_make_request=[KNL]
1318 General fault injection mechanism.
1319 Format: <interval>,<probability>,<space>,<times>
1320 See also Documentation/fault-injection/.
1323 See Documentation/blockdev/floppy.txt.
1325 force_pal_cache_flush
1326 [IA-64] Avoid check_sal_cache_flush which may hang on
1327 buggy SAL_CACHE_FLUSH implementations. Using this
1328 parameter will force ia64_sal_cache_flush to call
1329 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1332 Forcefully enable Physical Address Extension (PAE).
1333 Many Pentium M systems disable PAE but may have a
1334 functionally usable PAE implementation.
1335 Warning: use of this parameter will taint the kernel
1336 and may cause unknown problems.
1339 [FTRACE] will set and start the specified tracer
1340 as early as possible in order to facilitate early
1343 ftrace_dump_on_oops[=orig_cpu]
1344 [FTRACE] will dump the trace buffers on oops.
1345 If no parameter is passed, ftrace will dump
1346 buffers of all CPUs, but if you pass orig_cpu, it will
1347 dump only the buffer of the CPU that triggered the
1350 ftrace_filter=[function-list]
1351 [FTRACE] Limit the functions traced by the function
1352 tracer at boot up. function-list is a comma separated
1353 list of functions. This list can be changed at run
1354 time by the set_ftrace_filter file in the debugfs
1357 ftrace_notrace=[function-list]
1358 [FTRACE] Do not trace the functions specified in
1359 function-list. This list can be changed at run time
1360 by the set_ftrace_notrace file in the debugfs
1363 ftrace_graph_filter=[function-list]
1364 [FTRACE] Limit the top level callers functions traced
1365 by the function graph tracer at boot up.
1366 function-list is a comma separated list of functions
1367 that can be changed at run time by the
1368 set_graph_function file in the debugfs tracing directory.
1370 ftrace_graph_notrace=[function-list]
1371 [FTRACE] Do not trace from the functions specified in
1372 function-list. This list is a comma separated list of
1373 functions that can be changed at run time by the
1374 set_graph_notrace file in the debugfs tracing directory.
1377 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1378 support via parallel port (up to 5 devices per port)
1379 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1380 See also Documentation/input/joystick-parport.txt
1384 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1388 gcov_persist= [GCOV] When non-zero (default), profiling data for
1389 kernel modules is saved and remains accessible via
1390 debugfs, even when the module is unloaded/reloaded.
1391 When zero, profiling data is discarded and associated
1392 debugfs files are removed at module unload time.
1394 gpt [EFI] Forces disk with valid GPT signature but
1395 invalid Protective MBR to be treated as GPT. If the
1396 primary GPT is corrupted, it enables the backup/alternate
1397 GPT to be used instead.
1399 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1400 the "Enable 0" bit of the configuration register.
1403 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1404 the "Enable 0" bit of the configuration register.
1407 grcan.select= [HW] Select which physical interface to use.
1410 grcan.txsize= [HW] Sets the size of the tx buffer.
1411 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1413 grcan.rxsize= [HW] Sets the size of the rx buffer.
1414 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1417 gpio-mockup.gpio_mockup_ranges
1418 [HW] Sets the ranges of gpiochip of for this device.
1419 Format: <start1>,<end1>,<start2>,<end2>...
1421 hardlockup_all_cpu_backtrace=
1422 [KNL] Should the hard-lockup detector generate
1423 backtraces on all cpus.
1426 hashdist= [KNL,NUMA] Large hashes allocated during boot
1427 are distributed across NUMA nodes. Defaults on
1428 for 64-bit NUMA, off otherwise.
1429 Format: 0 | 1 (for off | on)
1431 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1433 hd= [EIDE] (E)IDE hard drive subsystem geometry
1434 Format: <cyl>,<head>,<sect>
1437 Disable Hardware Error Source Table (HEST) support;
1438 corresponding firmware-first mode error processing
1439 logic will be disabled.
1441 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1442 size of <nn>. This works even on boxes that have no
1443 highmem otherwise. This also works to reduce highmem
1444 size on bigger boxes.
1446 highres= [KNL] Enable/disable high resolution timer mode.
1447 Valid parameters: "on", "off"
1451 See Documentation/isdn/README.HiSax.
1455 hpet= [X86-32,HPET] option to control HPET usage
1456 Format: { enable (default) | disable | force |
1458 disable: disable HPET and use PIT instead
1459 force: allow force enabled of undocumented chips (ICH4,
1461 verbose: show contents of HPET registers during setup
1463 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1464 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1466 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1467 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1468 On x86-64 and powerpc, this option can be specified
1469 multiple times interleaved with hugepages= to reserve
1470 huge pages of different sizes. Valid pages sizes on
1471 x86-64 are 2M (when the CPU supports "pse") and 1G
1472 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1474 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1475 terminal devices. Valid values: 0..8
1476 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1477 If specified, z/VM IUCV HVC accepts connections
1478 from listed z/VM user IDs only.
1480 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1481 hardware thread id mappings.
1482 Format: <cpu>:<hwthread>
1485 Do not unregister boot console at start. This is only
1486 useful for debugging when something happens in the window
1487 between unregistering the boot console and initializing
1490 i2c_bus= [HW] Override the default board specific I2C bus speed
1491 or register an additional I2C bus that is not
1492 registered from board initialization code.
1496 i8042.debug [HW] Toggle i8042 debug mode
1497 i8042.unmask_kbd_data
1498 [HW] Enable printing of interrupt data from the KBD port
1499 (disabled by default, and as a pre-condition
1500 requires that i8042.debug=1 be enabled)
1501 i8042.direct [HW] Put keyboard port into non-translated mode
1502 i8042.dumbkbd [HW] Pretend that controller can only read data from
1503 keyboard and cannot control its state
1504 (Don't attempt to blink the leds)
1505 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1506 i8042.nokbd [HW] Don't check/create keyboard port
1507 i8042.noloop [HW] Disable the AUX Loopback command while probing
1509 i8042.nomux [HW] Don't check presence of an active multiplexing
1511 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1513 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1514 i8042.reset [HW] Reset the controller during init and cleanup
1515 i8042.unlock [HW] Unlock (ignore) the keylock
1516 i8042.kbdreset [HW] Reset device connected to KBD port
1520 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1521 indicates that the driver is running on unsupported
1523 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1524 does not match list of supported models.
1526 [HW] Report power status in /proc/i8k
1527 (disabled by default)
1528 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1531 i915.invert_brightness=
1532 [DRM] Invert the sense of the variable that is used to
1533 set the brightness of the panel backlight. Normally a
1534 brightness value of 0 indicates backlight switched off,
1535 and the maximum of the brightness value sets the backlight
1536 to maximum brightness. If this parameter is set to 0
1537 (default) and the machine requires it, or this parameter
1538 is set to 1, a brightness value of 0 sets the backlight
1539 to maximum brightness, and the maximum of the brightness
1540 value switches the backlight off.
1541 -1 -- never invert brightness
1542 0 -- machine default
1543 1 -- force brightness inversion
1546 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1548 ide-core.nodma= [HW] (E)IDE subsystem
1549 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1550 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1551 .cdrom .chs .ignore_cable are additional options
1552 See Documentation/ide/ide.txt.
1554 ide-generic.probe-mask= [HW] (E)IDE subsystem
1556 Probe mask for legacy ISA IDE ports. Depending on
1557 platform up to 6 ports are supported, enabled by
1558 setting corresponding bits in the mask to 1. The
1559 default value is 0x0, which has a special meaning.
1560 On systems that have PCI, it triggers scanning the
1561 PCI bus for the first and the second port, which
1562 are then probed. On systems without PCI the value
1563 of 0x0 enables probing the two first ports as if it
1566 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1567 Claim all unknown PCI IDE storage controllers.
1570 Format: idle=poll, idle=halt, idle=nomwait
1571 Poll forces a polling idle loop that can slightly
1572 improve the performance of waking up a idle CPU, but
1573 will use a lot of power and make the system run hot.
1575 idle=halt: Halt is forced to be used for CPU idle.
1576 In such case C2/C3 won't be used again.
1577 idle=nomwait: Disable mwait for CPU C-states
1579 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1580 Format: { strict | legacy | 2008 | relaxed }
1583 Choose which programs will be accepted for execution
1584 based on the IEEE 754 NaN encoding(s) supported by
1585 the FPU and the NaN encoding requested with the value
1586 of an ELF file header flag individually set by each
1587 binary. Hardware implementations are permitted to
1588 support either or both of the legacy and the 2008 NaN
1591 Available settings are as follows:
1592 strict accept binaries that request a NaN encoding
1593 supported by the FPU
1594 legacy only accept legacy-NaN binaries, if supported
1596 2008 only accept 2008-NaN binaries, if supported
1598 relaxed accept any binaries regardless of whether
1599 supported by the FPU
1601 The FPU emulator is always able to support both NaN
1602 encodings, so if no FPU hardware is present or it has
1603 been disabled with 'nofpu', then the settings of
1604 'legacy' and '2008' strap the emulator accordingly,
1605 'relaxed' straps the emulator for both legacy-NaN and
1606 2008-NaN, whereas 'strict' enables legacy-NaN only on
1607 legacy processors and both NaN encodings on MIPS32 or
1610 The setting for ABS.fmt/NEG.fmt instruction execution
1611 mode generally follows that for the NaN encoding,
1612 except where unsupported by hardware.
1614 ignore_loglevel [KNL]
1615 Ignore loglevel setting - this will print /all/
1616 kernel messages to the console. Useful for debugging.
1617 We also add it as printk module parameter, so users
1618 could change it dynamically, usually by
1619 /sys/module/printk/parameters/ignore_loglevel.
1622 Ignore RLIMIT_DATA setting for data mappings,
1623 print warning at first misuse. Can be changed via
1624 /sys/module/kernel/parameters/ignore_rlimit_data.
1626 ihash_entries= [KNL]
1627 Set number of hash buckets for inode cache.
1629 ima_appraise= [IMA] appraise integrity measurements
1630 Format: { "off" | "enforce" | "fix" | "log" }
1633 ima_appraise_tcb [IMA]
1634 The builtin appraise policy appraises all files
1638 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1642 The list of supported hash algorithms is defined
1643 in crypto/hash_info.h.
1646 The builtin measurement policy to load during IMA
1647 setup. Specyfing "tcb" as the value, measures all
1648 programs exec'd, files mmap'd for exec, and all files
1649 opened with the read mode bit set by either the
1650 effective uid (euid=0) or uid=0.
1653 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1654 Load a policy which meets the needs of the Trusted
1655 Computing Base. This means IMA will measure all
1656 programs exec'd, files mmap'd for exec, and all files
1657 opened for read by uid=0.
1660 Select one of defined IMA measurements template formats.
1661 Formats: { "ima" | "ima-ng" | "ima-sig" }
1665 [IMA] Define a custom template format.
1666 Format: { "field1|...|fieldN" }
1668 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1669 Format: <min_file_size>
1670 Set the minimal file size for using asynchronous hash.
1671 If left unspecified, ahash usage is disabled.
1673 ahash performance varies for different data sizes on
1674 different crypto accelerators. This option can be used
1675 to achieve the best performance for a particular HW.
1677 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1679 Set hashing buffer size. Default: 4k.
1681 ahash performance varies for different chunk sizes on
1682 different crypto accelerators. This option can be used
1683 to achieve best performance for particular HW.
1687 Run specified binary instead of /sbin/init as init
1690 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1691 for working out where the kernel is dying during
1694 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1695 initcall functions. Useful for debugging built-in
1696 modules and initcalls.
1698 initrd= [BOOT] Specify the location of the initial ramdisk
1700 init_pkru= [x86] Specify the default memory protection keys rights
1701 register contents for all processes. 0x55555554 by
1702 default (disallow access to all but pkey 0). Can
1703 override in debugfs after boot.
1705 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1708 int_pln_enable [x86] Enable power limit notification interrupt
1710 integrity_audit=[IMA]
1711 Format: { "0" | "1" }
1712 0 -- basic integrity auditing messages. (Default)
1713 1 -- additional integrity auditing messages.
1715 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1717 Enable intel iommu driver.
1719 Disable intel iommu driver.
1720 igfx_off [Default Off]
1721 By default, gfx is mapped as normal device. If a gfx
1722 device has a dedicated DMAR unit, the DMAR unit is
1723 bypassed by not enabling DMAR with this option. In
1724 this case, gfx device will use physical address for
1727 With this option iommu will not optimize to look
1728 for io virtual address below 32-bit forcing dual
1729 address cycle on pci bus for cards supporting greater
1730 than 32-bit addressing. The default is to look
1731 for translation below 32-bit and if not available
1732 then look in the higher range.
1733 strict [Default Off]
1734 With this option on every unmap_single operation will
1735 result in a hardware IOTLB flush operation as opposed
1736 to batching them for performance.
1737 sp_off [Default Off]
1738 By default, super page will be supported if Intel IOMMU
1739 has the capability. With this option, super page will
1741 ecs_off [Default Off]
1742 By default, extended context tables will be supported if
1743 the hardware advertises that it has support both for the
1744 extended tables themselves, and also PASID support. With
1745 this option set, extended tables will not be used even
1746 on hardware which claims to support them.
1748 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1749 0 disables intel_idle and fall back on acpi_idle.
1750 1 to 9 specify maximum depth of C-state.
1754 Do not enable intel_pstate as the default
1755 scaling driver for the supported processors
1757 Enable intel_pstate on systems that prohibit it by default
1758 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1759 instead of acpi-cpufreq may disable platform features, such
1760 as thermal controls and power capping, that rely on ACPI
1761 P-States information being indicated to OSPM and therefore
1762 should be used with caution. This option does not work with
1763 processors that aren't supported by the intel_pstate driver
1764 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1766 Do not enable hardware P state control (HWP)
1769 Only load intel_pstate on systems which support
1770 hardware P state control (HWP) if available.
1772 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1773 Description Table, specifies preferred power management
1774 profile as "Enterprise Server" or "Performance Server",
1775 then this feature is turned on by default.
1777 intremap= [X86-64, Intel-IOMMU]
1778 on enable Interrupt Remapping (default)
1779 off disable Interrupt Remapping
1780 nosid disable Source ID checking
1782 BIOS x2APIC opt-out request will be ignored
1783 nopost disable Interrupt Posting
1785 iomem= Disable strict checking of access to MMIO memory
1786 strict regions from userspace.
1801 nobypass [PPC/POWERNV]
1802 Disable IOMMU bypass, using IOMMU for PCI devices.
1805 io7= [HW] IO7 for Marvel based alpha systems
1806 See comment before marvel_specify_io7 in
1807 arch/alpha/kernel/core_marvel.c.
1809 io_delay= [X86] I/O delay method
1811 Standard port 0x80 based delay
1813 Alternate port 0xed based delay (needed on some systems)
1815 Simple two microseconds delay
1820 See Documentation/filesystems/nfs/nfsroot.txt.
1822 irqaffinity= [SMP] Set the default irq affinity mask
1823 The argument is a cpu list, as described above.
1826 When an interrupt is not handled search all handlers
1827 for it. Intended to get systems with badly broken
1831 When an interrupt is not handled search all handlers
1832 for it. Also check all handlers each timer
1833 interrupt. Intended to get systems with badly broken
1837 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1839 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1840 The argument is a cpu list, as described above.
1842 This option can be used to specify one or more CPUs
1843 to isolate from the general SMP balancing and scheduling
1844 algorithms. You can move a process onto or off an
1845 "isolated" CPU via the CPU affinity syscalls or cpuset.
1846 <cpu number> begins at 0 and the maximum value is
1847 "number of CPUs in system - 1".
1849 This option is the preferred way to isolate CPUs. The
1850 alternative -- manually setting the CPU mask of all
1851 tasks in the system -- can cause problems and
1852 suboptimal load balancer performance.
1856 ivrs_ioapic [HW,X86_64]
1857 Provide an override to the IOAPIC-ID<->DEVICE-ID
1858 mapping provided in the IVRS ACPI table. For
1859 example, to map IOAPIC-ID decimal 10 to
1860 PCI device 00:14.0 write the parameter as:
1861 ivrs_ioapic[10]=00:14.0
1863 ivrs_hpet [HW,X86_64]
1864 Provide an override to the HPET-ID<->DEVICE-ID
1865 mapping provided in the IVRS ACPI table. For
1866 example, to map HPET-ID decimal 0 to
1867 PCI device 00:14.0 write the parameter as:
1868 ivrs_hpet[0]=00:14.0
1870 ivrs_acpihid [HW,X86_64]
1871 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1872 mapping provided in the IVRS ACPI table. For
1873 example, to map UART-HID:UID AMD0020:0 to
1874 PCI device 00:14.5 write the parameter as:
1875 ivrs_acpihid[00:14.5]=AMD0020:0
1877 js= [HW,JOY] Analog joystick
1878 See Documentation/input/joystick.txt.
1881 When CONFIG_RANDOMIZE_BASE is set, this disables
1882 kernel and module base offset ASLR (Address Space
1883 Layout Randomization).
1887 kernelcore= [KNL,X86,IA-64,PPC]
1888 Format: nn[KMGTPE] | "mirror"
1890 specifies the amount of memory usable by the kernel
1891 for non-movable allocations. The requested amount is
1892 spread evenly throughout all nodes in the system. The
1893 remaining memory in each node is used for Movable
1894 pages. In the event, a node is too small to have both
1895 kernelcore and Movable pages, kernelcore pages will
1896 take priority and other nodes will have a larger number
1897 of Movable pages. The Movable zone is used for the
1898 allocation of pages that may be reclaimed or moved
1899 by the page migration subsystem. This means that
1900 HugeTLB pages may not be allocated from this zone.
1901 Note that allocations like PTEs-from-HighMem still
1902 use the HighMem zone if it exists, and the Normal
1903 zone if it does not.
1905 Instead of specifying the amount of memory (nn[KMGTPE]),
1906 you can specify "mirror" option. In case "mirror"
1907 option is specified, mirrored (reliable) memory is used
1908 for non-movable allocations and remaining memory is used
1909 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1910 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1913 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1914 Format: <Controller#>[,poll interval]
1915 The controller # is the number of the ehci usb debug
1916 port as it is probed via PCI. The poll interval is
1917 optional and is the number seconds in between
1918 each poll cycle to the debug port in case you need
1919 the functionality for interrupting the kernel with
1920 gdb or control-c on the dbgp connection. When
1921 not using this parameter you use sysrq-g to break into
1922 the kernel debugger.
1924 kgdboc= [KGDB,HW] kgdb over consoles.
1925 Requires a tty driver that supports console polling,
1926 or a supported polling keyboard driver (non-usb).
1927 Serial only format: <serial_device>[,baud]
1928 keyboard only format: kbd
1929 keyboard and serial format: kbd,<serial_device>[,baud]
1930 Optional Kernel mode setting:
1931 kms, kbd format: kms,kbd
1932 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1934 kgdbwait [KGDB] Stop kernel execution and enter the
1935 kernel debugger at the earliest opportunity.
1937 kmac= [MIPS] korina ethernet MAC address.
1938 Configure the RouterBoard 532 series on-chip
1939 Ethernet adapter MAC address.
1941 kmemleak= [KNL] Boot-time kmemleak enable/disable
1942 Valid arguments: on, off
1944 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1947 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1948 Valid arguments: 0, 1, 2
1949 kmemcheck=0 (disabled)
1950 kmemcheck=1 (enabled)
1951 kmemcheck=2 (one-shot mode)
1952 Default: 2 (one-shot mode)
1954 kstack=N [X86] Print N words from the kernel stack
1957 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1958 Default is 0 (don't ignore, but inject #GP)
1960 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1964 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1965 Default is 1 (enabled)
1967 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1969 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1971 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1972 (virtualized MMU) support on capable Intel chips.
1973 Default is 1 (enabled)
1975 kvm-intel.emulate_invalid_guest_state=
1976 [KVM,Intel] Enable emulation of invalid guest states
1977 Default is 0 (disabled)
1979 kvm-intel.flexpriority=
1980 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1981 Default is 1 (enabled)
1984 [KVM,Intel] Enable VMX nesting (nVMX).
1985 Default is 0 (disabled)
1987 kvm-intel.unrestricted_guest=
1988 [KVM,Intel] Disable unrestricted guest feature
1989 (virtualized real and unpaged mode) on capable
1990 Intel chips. Default is 1 (enabled)
1992 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1993 feature (tagged TLBs) on capable Intel chips.
1994 Default is 1 (enabled)
2000 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2003 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2004 value for LAPIC timer one-shot implementation. Default
2005 back to the programmable timer unit in the LAPIC.
2007 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2010 libata.dma= [LIBATA] DMA control
2011 libata.dma=0 Disable all PATA and SATA DMA
2012 libata.dma=1 PATA and SATA Disk DMA only
2013 libata.dma=2 ATAPI (CDROM) DMA only
2014 libata.dma=4 Compact Flash DMA only
2015 Combinations also work, so libata.dma=3 enables DMA
2016 for disks and CDROMs, but not CFs.
2018 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2019 libata.ignore_hpa=0 keep BIOS limits (default)
2020 libata.ignore_hpa=1 ignore limits, using full disk
2022 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2026 libata.force= [LIBATA] Force configurations. The format is comma
2027 separated list of "[ID:]VAL" where ID is
2028 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2029 matching port, link or device. Basically, it matches
2030 the ATA ID string printed on console by libata. If
2031 the whole ID part is omitted, the last PORT and DEVICE
2032 values are used. If ID hasn't been specified yet, the
2033 configuration applies to all ports, links and devices.
2035 If only DEVICE is omitted, the parameter applies to
2036 the port and all links and devices behind it. DEVICE
2037 number of 0 either selects the first device or the
2038 first fan-out link behind PMP device. It does not
2039 select the host link. DEVICE number of 15 selects the
2040 host link and device attached to it.
2042 The VAL specifies the configuration to force. As long
2043 as there's no ambiguity shortcut notation is allowed.
2044 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2045 The following configurations can be forced.
2047 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2048 Any ID with matching PORT is used.
2050 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2052 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2053 udma[/][16,25,33,44,66,100,133] notation is also
2056 * [no]ncq: Turn on or off NCQ.
2058 * [no]ncqtrim: Turn off queued DSM TRIM.
2060 * nohrst, nosrst, norst: suppress hard, soft
2063 * rstonce: only attempt one reset during
2064 hot-unplug link recovery
2066 * dump_id: dump IDENTIFY data.
2068 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2070 * disable: Disable this device.
2072 If there are multiple matching configurations changing
2073 the same attribute, the last one is used.
2075 memblock=debug [KNL] Enable memblock debug messages.
2077 load_ramdisk= [RAM] List of ramdisks to load from floppy
2078 See Documentation/blockdev/ramdisk.txt.
2080 lockd.nlm_grace_period=P [NFS] Assign grace period.
2083 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2086 lockd.nlm_timeout=T [NFS] Assign timeout value.
2089 lockd.nlm_udpport=M [NFS] Assign UDP port.
2092 locktorture.nreaders_stress= [KNL]
2093 Set the number of locking read-acquisition kthreads.
2094 Defaults to being automatically set based on the
2095 number of online CPUs.
2097 locktorture.nwriters_stress= [KNL]
2098 Set the number of locking write-acquisition kthreads.
2100 locktorture.onoff_holdoff= [KNL]
2101 Set time (s) after boot for CPU-hotplug testing.
2103 locktorture.onoff_interval= [KNL]
2104 Set time (s) between CPU-hotplug operations, or
2105 zero to disable CPU-hotplug testing.
2107 locktorture.shuffle_interval= [KNL]
2108 Set task-shuffle interval (jiffies). Shuffling
2109 tasks allows some CPUs to go into dyntick-idle
2110 mode during the locktorture test.
2112 locktorture.shutdown_secs= [KNL]
2113 Set time (s) after boot system shutdown. This
2114 is useful for hands-off automated testing.
2116 locktorture.stat_interval= [KNL]
2117 Time (s) between statistics printk()s.
2119 locktorture.stutter= [KNL]
2120 Time (s) to stutter testing, for example,
2121 specifying five seconds causes the test to run for
2122 five seconds, wait for five seconds, and so on.
2123 This tests the locking primitive's ability to
2124 transition abruptly to and from idle.
2126 locktorture.torture_runnable= [BOOT]
2127 Start locktorture running at boot time.
2129 locktorture.torture_type= [KNL]
2130 Specify the locking implementation to test.
2132 locktorture.verbose= [KNL]
2133 Enable additional printk() statements.
2135 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2138 loglevel= All Kernel Messages with a loglevel smaller than the
2139 console loglevel will be printed to the console. It can
2140 also be changed with klogd or other programs. The
2141 loglevels are defined as follows:
2143 0 (KERN_EMERG) system is unusable
2144 1 (KERN_ALERT) action must be taken immediately
2145 2 (KERN_CRIT) critical conditions
2146 3 (KERN_ERR) error conditions
2147 4 (KERN_WARNING) warning conditions
2148 5 (KERN_NOTICE) normal but significant condition
2149 6 (KERN_INFO) informational
2150 7 (KERN_DEBUG) debug-level messages
2152 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2153 in bytes. n must be a power of two and greater
2154 than the minimal size. The minimal size is defined
2155 by LOG_BUF_SHIFT kernel config parameter. There is
2156 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2157 that allows to increase the default size depending on
2158 the number of CPUs. See init/Kconfig for more details.
2160 logo.nologo [FB] Disables display of the built-in Linux logo.
2161 This may be used to provide more screen space for
2162 kernel log messages and is useful when debugging
2163 kernel boot problems.
2165 lp=0 [LP] Specify parallel ports to use, e.g,
2166 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2167 lp=reset first parallel port). 'lp=0' disables the
2168 lp=auto printer driver. 'lp=reset' (which can be
2169 specified in addition to the ports) causes
2170 attached printers to be reset. Using
2171 lp=port1,port2,... specifies the parallel ports
2172 to associate lp devices with, starting with
2173 lp0. A port specification may be 'none' to skip
2174 that lp device, or a parport name such as
2175 'parport0'. Specifying 'lp=auto' instead of a
2176 port specification list means that device IDs
2177 from each port should be examined, to see if
2178 an IEEE 1284-compliant printer is attached; if
2179 so, the driver will manage that printer.
2180 See also header of drivers/char/lp.c.
2183 Sets loops_per_jiffy to given constant, thus avoiding
2184 time-consuming boot-time autodetection (up to 250 ms per
2185 CPU). 0 enables autodetection (default). To determine
2186 the correct value for your kernel, boot with normal
2187 autodetection and see what value is printed. Note that
2188 on SMP systems the preset will be applied to all CPUs,
2189 which is likely to cause problems if your CPUs need
2190 significantly divergent settings. An incorrect value
2191 will cause delays in the kernel to be wrong, leading to
2192 unpredictable I/O errors and other breakage. Although
2193 unlikely, in the extreme case this might damage your
2197 Format: <io>,<irq>,<dma>
2199 machvec= [IA-64] Force the use of a particular machine-vector
2200 (machvec) in a generic kernel.
2201 Example: machvec=hpzx1_swiotlb
2203 machtype= [Loongson] Share the same kernel image file between different
2205 Example: machtype=lemote-yeeloong-2f-7inch
2207 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2208 than or equal to this physical address is ignored.
2210 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2211 will bring up during bootup. maxcpus=n : n >= 0 limits
2212 the kernel to bring up 'n' processors. Surely after
2213 bootup you can bring up the other plugged cpu by executing
2214 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2215 only takes effect during system bootup.
2216 While n=0 is a special case, it is equivalent to "nosmp",
2217 which also disables the IO APIC.
2219 max_loop= [LOOP] The number of loop block devices that get
2220 (loop.max_loop) unconditionally pre-created at init time. The default
2221 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2222 of statically allocating a predefined number, loop
2223 devices can be requested on-demand with the
2224 /dev/loop-control interface.
2226 mce [X86-32] Machine Check Exception
2228 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2230 md= [HW] RAID subsystems devices and level
2231 See Documentation/md.txt.
2234 Format: <first>,<last>
2235 Specifies range of consoles to be captured by the MDA.
2237 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2238 Amount of memory to be used when the kernel is not able
2239 to see the whole system memory or for test.
2240 [X86] Work as limiting max address. Use together
2241 with memmap= to avoid physical address space collisions.
2242 Without memmap= PCI devices could be placed at addresses
2243 belonging to unused RAM.
2245 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2249 [KNL,SH] Allow user to override the default size for
2250 per-device physically contiguous DMA buffers.
2252 memhp_default_state=online/offline
2253 [KNL] Set the initial state for the memory hotplug
2254 onlining policy. If not specified, the default value is
2255 set according to the
2256 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2258 See Documentation/memory-hotplug.txt.
2260 memmap=exactmap [KNL,X86] Enable setting of an exact
2261 E820 memory map, as specified by the user.
2262 Such memmap=exactmap lines can be constructed based on
2263 BIOS output or other requirements. See the memmap=nn@ss
2266 memmap=nn[KMG]@ss[KMG]
2267 [KNL] Force usage of a specific region of memory.
2268 Region of memory to be used is from ss to ss+nn.
2270 memmap=nn[KMG]#ss[KMG]
2271 [KNL,ACPI] Mark specific memory as ACPI data.
2272 Region of memory to be marked is from ss to ss+nn.
2274 memmap=nn[KMG]$ss[KMG]
2275 [KNL,ACPI] Mark specific memory as reserved.
2276 Region of memory to be reserved is from ss to ss+nn.
2277 Example: Exclude memory from 0x18690000-0x1869ffff
2278 memmap=64K$0x18690000
2280 memmap=0x10000$0x18690000
2282 memmap=nn[KMG]!ss[KMG]
2283 [KNL,X86] Mark specific memory as protected.
2284 Region of memory to be used, from ss to ss+nn.
2285 The memory region may be marked as e820 type 12 (0xc)
2286 and is NVDIMM or ADR memory.
2288 memory_corruption_check=0/1 [X86]
2289 Some BIOSes seem to corrupt the first 64k of
2290 memory when doing things like suspend/resume.
2291 Setting this option will scan the memory
2292 looking for corruption. Enabling this will
2293 both detect corruption and prevent the kernel
2294 from using the memory being corrupted.
2295 However, its intended as a diagnostic tool; if
2296 repeatable BIOS-originated corruption always
2297 affects the same memory, you can use memmap=
2298 to prevent the kernel from using that memory.
2300 memory_corruption_check_size=size [X86]
2301 By default it checks for corruption in the low
2302 64k, making this memory unavailable for normal
2303 use. Use this parameter to scan for
2304 corruption in more or less memory.
2306 memory_corruption_check_period=seconds [X86]
2307 By default it checks for corruption every 60
2308 seconds. Use this parameter to check at some
2309 other rate. 0 disables periodic checking.
2311 memtest= [KNL,X86,ARM] Enable memtest
2313 default : 0 <disable>
2314 Specifies the number of memtest passes to be
2315 performed. Each pass selects another test
2316 pattern from a given set of patterns. Memtest
2317 fills the memory with this pattern, validates
2318 memory contents and reserves bad memory
2319 regions that are detected.
2321 meye.*= [HW] Set MotionEye Camera parameters
2322 See Documentation/video4linux/meye.txt.
2324 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2325 Multi-Function General Purpose Timers on AMD Geode
2328 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2329 the BIOS has incorrectly applied a workaround. TinyBIOS
2330 version 0.98 is known to be affected, 0.99 fixes the
2331 problem by letting the user disable the workaround.
2335 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2336 physical address is ignored.
2338 mini2440= [ARM,HW,KNL]
2339 Format:[0..2][b][c][t]
2341 MINI2440 configuration specification:
2342 0 - The attached screen is the 3.5" TFT
2343 1 - The attached screen is the 7" TFT
2344 2 - The VGA Shield is attached (1024x768)
2345 Leaving out the screen size parameter will not load
2346 the TFT driver, and the framebuffer will be left
2348 b - Enable backlight. The TFT backlight pin will be
2349 linked to the kernel VESA blanking code and a GPIO
2350 LED. This parameter is not necessary when using the
2352 c - Enable the s3c camera interface.
2353 t - Reserved for enabling touchscreen support. The
2354 touchscreen support is not enabled in the mainstream
2355 kernel as of 2.6.30, a preliminary port can be found
2356 in the "bleeding edge" mini2440 support kernel at
2357 http://repo.or.cz/w/linux-2.6/mini2440.git
2360 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2361 parameter allows control of the logging verbosity for
2362 the additional memory initialisation checks. A value
2363 of 0 disables mminit logging and a level of 4 will
2364 log everything. Information is printed at KERN_DEBUG
2365 so loglevel=8 may also need to be specified.
2368 [KNL] When CONFIG_MODULE_SIG is set, this means that
2369 modules without (valid) signatures will fail to load.
2370 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2371 is always true, so this option does nothing.
2373 module_blacklist= [KNL] Do not load a comma-separated list of
2374 modules. Useful for debugging problem modules.
2377 [MOUSE] Maximum time between finger touching and
2378 leaving touchpad surface for touch to be considered
2379 a tap and be reported as a left button click (for
2380 touchpads working in absolute mode only).
2382 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2383 reporting absolute coordinates, such as tablets
2384 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2385 reporting absolute coordinates, such as tablets
2387 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2388 is similar to kernelcore except it specifies the
2389 amount of memory used for migratable allocations.
2390 If both kernelcore and movablecore is specified,
2391 then kernelcore will be at *least* the specified
2392 value but may be more. If movablecore on its own
2393 is specified, the administrator must be careful
2394 that the amount of memory usable for all allocations
2397 movable_node [KNL,X86] Boot-time switch to enable the effects
2398 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2400 MTD_Partition= [MTD]
2401 Format: <name>,<region-number>,<size>,<offset>
2403 MTD_Region= [MTD] Format:
2404 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2407 See drivers/mtd/cmdlinepart.c.
2409 multitce=off [PPC] This parameter disables the use of the pSeries
2410 firmware feature for updating multiple TCE entries
2413 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2415 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2417 boundary - index of last SLC block on Flex-OneNAND.
2418 The remaining blocks are configured as MLC blocks.
2419 lock - Configure if Flex-OneNAND boundary should be locked.
2420 Once locked, the boundary cannot be changed.
2421 1 indicates lock status, 0 indicates unlock status.
2424 ARM/S3C2412 JIVE boot control
2426 See arch/arm/mach-s3c2412/mach-jive.c
2428 mtouchusb.raw_coordinates=
2429 [HW] Make the MicroTouch USB driver use raw coordinates
2430 ('y', default) or cooked coordinates ('n')
2432 mtrr_chunk_size=nn[KMG] [X86]
2433 used for mtrr cleanup. It is largest continuous chunk
2434 that could hold holes aka. UC entries.
2436 mtrr_gran_size=nn[KMG] [X86]
2437 Used for mtrr cleanup. It is granularity of mtrr block.
2439 Large value could prevent small alignment from
2442 mtrr_spare_reg_nr=n [X86]
2444 Range: 0,7 : spare reg number
2446 Used for mtrr cleanup. It is spare mtrr entries number.
2447 Set to 2 or more if your graphical card needs more.
2449 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2451 netdev= [NET] Network devices parameters
2452 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2453 Note that mem_start is often overloaded to mean
2454 something different and driver-specific.
2455 This usage is only documented in each driver source
2459 [NETFILTER] Enable connection tracking flow accounting
2460 0 to disable accounting
2461 1 to enable accounting
2464 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2465 See Documentation/filesystems/nfs/nfsroot.txt.
2467 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2468 See Documentation/filesystems/nfs/nfsroot.txt.
2470 nfsrootdebug [NFS] enable nfsroot debugging messages.
2471 See Documentation/filesystems/nfs/nfsroot.txt.
2473 nfs.callback_nr_threads=
2474 [NFSv4] set the total number of threads that the
2475 NFS client will assign to service NFSv4 callback
2478 nfs.callback_tcpport=
2479 [NFS] set the TCP port on which the NFSv4 callback
2480 channel should listen.
2483 [NFS] sets the pathname to the program which is used
2484 to update the NFS client cache entries.
2486 nfs.cache_getent_timeout=
2487 [NFS] sets the timeout after which an attempt to
2488 update a cache entry is deemed to have failed.
2490 nfs.idmap_cache_timeout=
2491 [NFS] set the maximum lifetime for idmapper cache
2495 [NFS] enable 64-bit inode numbers.
2496 If zero, the NFS client will fake up a 32-bit inode
2497 number for the readdir() and stat() syscalls instead
2498 of returning the full 64-bit number.
2499 The default is to return 64-bit inode numbers.
2501 nfs.max_session_cb_slots=
2502 [NFSv4.1] Sets the maximum number of session
2503 slots the client will assign to the callback
2504 channel. This determines the maximum number of
2505 callbacks the client will process in parallel for
2506 a particular server.
2508 nfs.max_session_slots=
2509 [NFSv4.1] Sets the maximum number of session slots
2510 the client will attempt to negotiate with the server.
2511 This limits the number of simultaneous RPC requests
2512 that the client can send to the NFSv4.1 server.
2513 Note that there is little point in setting this
2514 value higher than the max_tcp_slot_table_limit.
2516 nfs.nfs4_disable_idmapping=
2517 [NFSv4] When set to the default of '1', this option
2518 ensures that both the RPC level authentication
2519 scheme and the NFS level operations agree to use
2520 numeric uids/gids if the mount is using the
2521 'sec=sys' security flavour. In effect it is
2522 disabling idmapping, which can make migration from
2523 legacy NFSv2/v3 systems to NFSv4 easier.
2524 Servers that do not support this mode of operation
2525 will be autodetected by the client, and it will fall
2526 back to using the idmapper.
2527 To turn off this behaviour, set the value to '0'.
2529 [NFS4] Specify an additional fixed unique ident-
2530 ification string that NFSv4 clients can insert into
2531 their nfs_client_id4 string. This is typically a
2532 UUID that is generated at system install time.
2534 nfs.send_implementation_id =
2535 [NFSv4.1] Send client implementation identification
2536 information in exchange_id requests.
2537 If zero, no implementation identification information
2539 The default is to send the implementation identification
2542 nfs.recover_lost_locks =
2543 [NFSv4] Attempt to recover locks that were lost due
2544 to a lease timeout on the server. Please note that
2545 doing this risks data corruption, since there are
2546 no guarantees that the file will remain unchanged
2547 after the locks are lost.
2548 If you want to enable the kernel legacy behaviour of
2549 attempting to recover these locks, then set this
2551 The default parameter value of '0' causes the kernel
2552 not to attempt recovery of lost locks.
2554 nfs4.layoutstats_timer =
2555 [NFSv4.2] Change the rate at which the kernel sends
2556 layoutstats to the pNFS metadata server.
2558 Setting this to value to 0 causes the kernel to use
2559 whatever value is the default set by the layout
2560 driver. A non-zero value sets the minimum interval
2561 in seconds between layoutstats transmissions.
2563 nfsd.nfs4_disable_idmapping=
2564 [NFSv4] When set to the default of '1', the NFSv4
2565 server will return only numeric uids and gids to
2566 clients using auth_sys, and will accept numeric uids
2567 and gids from such clients. This is intended to ease
2568 migration from NFSv2/v3.
2570 objlayoutdriver.osd_login_prog=
2571 [NFS] [OBJLAYOUT] sets the pathname to the program which
2572 is used to automatically discover and login into new
2573 osd-targets. Please see:
2574 Documentation/filesystems/pnfs.txt for more explanations
2576 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2577 when a NMI is triggered.
2578 Format: [state][,regs][,debounce][,die]
2580 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2581 Format: [panic,][nopanic,][num]
2583 0 - turn hardlockup detector in nmi_watchdog off
2584 1 - turn hardlockup detector in nmi_watchdog on
2585 When panic is specified, panic when an NMI watchdog
2586 timeout occurs (or 'nopanic' to override the opposite
2587 default). To disable both hard and soft lockup detectors,
2588 please see 'nowatchdog'.
2589 This is useful when you use a panic=... timeout and
2590 need the box quickly up again.
2592 netpoll.carrier_timeout=
2593 [NET] Specifies amount of time (in seconds) that
2594 netpoll should wait for a carrier. By default netpoll
2597 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2598 emulation library even if a 387 maths coprocessor
2602 [HW] Never suspend the console
2603 Disable suspending of consoles during suspend and
2604 hibernate operations. Once disabled, debugging
2605 messages can reach various consoles while the rest
2606 of the system is being put to sleep (ie, while
2607 debugging driver suspend/resume hooks). This may
2608 not work reliably with all consoles, but is known
2609 to work with serial and VGA consoles.
2610 To facilitate more flexible debugging, we also add
2611 console_suspend, a printk module parameter to control
2612 it. Users could use console_suspend (usually
2613 /sys/module/printk/parameters/console_suspend) to
2614 turn on/off it dynamically.
2616 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2617 caches in the slab allocator. Saves per-node memory,
2618 but will impact performance.
2622 noapic [SMP,APIC] Tells the kernel to not make use of any
2623 IOAPICs that may be present in the system.
2625 noautogroup Disable scheduler automatic task group creation.
2627 nobats [PPC] Do not use BATs for mapping kernel lowmem
2628 on "Classic" PPC cores.
2632 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2634 nodelayacct [KNL] Disable per-task delay accounting
2636 nodsp [SH] Disable hardware DSP at boot time.
2638 noefi Disable EFI runtime services support.
2643 On X86-32 available only on PAE configured kernels.
2644 noexec=on: enable non-executable mappings (default)
2645 noexec=off: disable non-executable mappings
2648 Disable SMAP (Supervisor Mode Access Prevention)
2649 even if it is supported by processor.
2652 Disable SMEP (Supervisor Mode Execution Prevention)
2653 even if it is supported by processor.
2656 This affects only 32-bit executables.
2657 noexec32=on: enable non-executable mappings (default)
2658 read doesn't imply executable mappings
2659 noexec32=off: disable non-executable mappings
2660 read implies executable mappings
2662 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2664 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2665 register save and restore. The kernel will only save
2666 legacy floating-point registers on task switch.
2668 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2670 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2671 Equivalent to smt=1.
2673 noxsave [BUGS=X86] Disables x86 extended register state save
2674 and restore using xsave. The kernel will fallback to
2675 enabling legacy floating-point and sse state.
2677 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2678 register states. The kernel will fall back to use
2679 xsave to save the states. By using this parameter,
2680 performance of saving the states is degraded because
2681 xsave doesn't support modified optimization while
2682 xsaveopt supports it on xsaveopt enabled systems.
2684 noxsaves [X86] Disables xsaves and xrstors used in saving and
2685 restoring x86 extended register state in compacted
2686 form of xsave area. The kernel will fall back to use
2687 xsaveopt and xrstor to save and restore the states
2688 in standard form of xsave area. By using this
2689 parameter, xsave area per process might occupy more
2690 memory on xsaves enabled systems.
2692 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2693 wfi(ARM) instruction doesn't work correctly and not to
2694 use it. This is also useful when using JTAG debugger.
2696 no_file_caps Tells the kernel not to honor file capabilities. The
2697 only way then for a file to be executed with privilege
2698 is to be setuid root or executed by root.
2700 nohalt [IA-64] Tells the kernel not to use the power saving
2701 function PAL_HALT_LIGHT when idle. This increases
2702 power-consumption. On the positive side, it reduces
2703 interrupt wake-up latency, which may improve performance
2704 in certain environments such as networked servers or
2707 nohibernate [HIBERNATION] Disable hibernation and resume.
2709 nohz= [KNL] Boottime enable/disable dynamic ticks
2710 Valid arguments: on, off
2713 nohz_full= [KNL,BOOT]
2714 The argument is a cpu list, as described above.
2715 In kernels built with CONFIG_NO_HZ_FULL=y, set
2716 the specified list of CPUs whose tick will be stopped
2717 whenever possible. The boot CPU will be forced outside
2718 the range to maintain the timekeeping.
2719 The CPUs in this range must also be included in the
2722 noiotrap [SH] Disables trapped I/O port accesses.
2724 noirqdebug [X86-32] Disables the code which attempts to detect and
2725 disable unhandled interrupt sources.
2727 no_timer_check [X86,APIC] Disables the code which tests for
2728 broken timer IRQ sources.
2730 noisapnp [ISAPNP] Disables ISA PnP code.
2732 noinitrd [RAM] Tells the kernel not to load any configured
2735 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2737 [Deprecated - use intremap=off]
2741 noinvpcid [X86] Disable the INVPCID cpu feature.
2743 nojitter [IA-64] Disables jitter checking for ITC timers.
2745 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2747 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2750 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2751 steal time is computed, but won't influence scheduler
2754 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2756 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2758 noltlbs [PPC] Do not use large page/tlb entries for kernel
2759 lowmem mapping on PPC40x and PPC8xx
2761 nomca [IA-64] Disable machine check abort handling
2763 nomce [X86-32] Disable Machine Check Exception
2765 nomfgpt [X86-32] Disable Multi-Function General Purpose
2766 Timer usage (for AMD Geode machines).
2768 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2769 shutdown the other cpus. Instead use the REBOOT_VECTOR
2772 nomodule Disable module load
2774 nopat [X86] Disable PAT (page attribute table extension of
2775 pagetables) support.
2777 norandmaps Don't use address space randomization. Equivalent to
2778 echo 0 > /proc/sys/kernel/randomize_va_space
2780 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2782 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2783 with UP alternatives
2785 nordrand [X86] Disable kernel use of the RDRAND and
2786 RDSEED instructions even if they are supported
2787 by the processor. RDRAND and RDSEED are still
2788 available to user space applications.
2790 noresume [SWSUSP] Disables resume and restores original swap
2793 no-scroll [VGA] Disables scrollback.
2794 This is required for the Braillex ib80-piezo Braille
2795 reader made by F.H. Papenmeier (Germany).
2799 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2801 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2802 and disable the IO APIC. legacy for "maxcpus=0".
2804 nosoftlockup [KNL] Disable the soft-lockup detector.
2806 nosync [HW,M68K] Disables sync negotiation for all devices.
2808 notsc [BUGS=X86-32] Disable Time Stamp Counter
2810 nowatchdog [KNL] Disable both lockup detectors, i.e.
2811 soft-lockup and NMI watchdog (hard-lockup).
2815 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2817 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2818 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2819 Some features depend on CPU0. Known dependencies are:
2820 1. Resume from suspend/hibernate depends on CPU0.
2821 Suspend/hibernate will fail if CPU0 is offline and you
2822 need to online CPU0 before suspend/hibernate.
2823 2. PIC interrupts also depend on CPU0. CPU0 can't be
2824 removed if a PIC interrupt is detected.
2825 It's said poweroff/reboot may depend on CPU0 on some
2826 machines although I haven't seen such issues so far
2827 after CPU0 is offline on a few tested machines.
2828 If the dependencies are under your control, you can
2829 turn on cpu0_hotplug.
2831 nptcg= [IA-64] Override max number of concurrent global TLB
2832 purges which is reported from either PAL_VM_SUMMARY or
2835 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2836 could support. nr_cpus=n : n >= 1 limits the kernel to
2837 support 'n' processors. It could be larger than the
2838 number of already plugged CPU during bootup, later in
2839 runtime you can physically add extra cpu until it reaches
2840 n. So during boot up some boot time memory for per-cpu
2841 variables need be pre-allocated for later physical cpu
2844 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2846 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2847 Allowed values are enable and disable
2849 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2850 one of ['zone', 'node', 'default'] can be specified
2851 This can be set from sysctl after boot.
2852 See Documentation/sysctl/vm.txt for details.
2854 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2855 See Documentation/debugging-via-ohci1394.txt for more
2858 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2859 Rather than timing out after 20 ms if an EC
2860 command is not properly ACKed, override the length
2861 of the timeout. We have interrupts disabled while
2862 waiting for the ACK, so if this is set too high
2863 interrupts *may* be lost!
2865 omap_mux= [OMAP] Override bootloader pin multiplexing.
2866 Format: <mux_mode0.mode_name=value>...
2867 For example, to override I2C bus2:
2868 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2870 oprofile.timer= [HW]
2871 Use timer interrupt instead of performance counters
2873 oprofile.cpu_type= Force an oprofile cpu type
2874 This might be useful if you have an older oprofile
2875 userland or if you want common events.
2876 Format: { arch_perfmon }
2877 arch_perfmon: [X86] Force use of architectural
2878 perfmon on Intel CPUs instead of the
2879 CPU specific event set.
2880 timer: [X86] Force use of architectural NMI
2881 timer mode (see also oprofile.timer
2882 for generic hr timer mode)
2884 oops=panic Always panic on oopses. Default is to just kill the
2885 process, but there is a small probability of
2886 deadlocking the machine.
2887 This will also cause panics on machine check exceptions.
2888 Useful together with panic=30 to trigger a reboot.
2891 See Documentation/sound/oss/oss-parameters.txt
2893 page_owner= [KNL] Boot-time page_owner enabling option.
2894 Storage of the information about who allocated
2895 each page is disabled in default. With this switch,
2897 on: enable the feature
2899 page_poison= [KNL] Boot-time parameter changing the state of
2900 poisoning on the buddy allocator.
2901 off: turn off poisoning
2902 on: turn on poisoning
2904 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2905 timeout > 0: seconds before rebooting
2906 timeout = 0: wait forever
2907 timeout < 0: reboot immediately
2910 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2913 crash_kexec_post_notifiers
2914 Run kdump after running panic-notifiers and dumping
2915 kmsg. This only for the users who doubt kdump always
2916 succeeds in any situation.
2917 Note that this also increases risks of kdump failure,
2918 because some panic notifiers can make the crashed
2919 kernel more unstable.
2921 parkbd.port= [HW] Parallel port number the keyboard adapter is
2922 connected to, default is 0.
2924 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2925 0 for XT, 1 for AT (default is AT).
2928 parport= [HW,PPT] Specify parallel ports. 0 disables.
2929 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2930 Use 'auto' to force the driver to use any
2931 IRQ/DMA settings detected (the default is to
2932 ignore detected IRQ/DMA settings because of
2933 possible conflicts). You can specify the base
2934 address, IRQ, and DMA settings; IRQ and DMA
2935 should be numbers, or 'auto' (for using detected
2936 settings on that particular port), or 'nofifo'
2937 (to avoid using a FIFO even if it is detected).
2938 Parallel ports are assigned in the order they
2939 are specified on the command line, starting
2942 parport_init_mode= [HW,PPT]
2943 Configure VIA parallel port to operate in
2944 a specific mode. This is necessary on Pegasos
2945 computer where firmware has no options for setting
2946 up parallel port mode and sets it to spp.
2947 Currently this function knows 686a and 8231 chips.
2948 Format: [spp|ps2|epp|ecp|ecpepp]
2951 Halt all CPUs after the first oops has been printed for
2952 the specified number of seconds. This is to be used if
2953 your oopses keep scrolling off the screen.
2958 See header of drivers/block/paride/pcd.c.
2959 See also Documentation/blockdev/paride.txt.
2961 pci=option[,option...] [PCI] various PCI subsystem options:
2962 earlydump [X86] dump PCI config space before the kernel
2964 off [X86] don't probe for the PCI bus
2965 bios [X86-32] force use of PCI BIOS, don't access
2966 the hardware directly. Use this if your machine
2967 has a non-standard PCI host bridge.
2968 nobios [X86-32] disallow use of PCI BIOS, only direct
2969 hardware access methods are allowed. Use this
2970 if you experience crashes upon bootup and you
2971 suspect they are caused by the BIOS.
2972 conf1 [X86] Force use of PCI Configuration Access
2973 Mechanism 1 (config address in IO port 0xCF8,
2974 data in IO port 0xCFC, both 32-bit).
2975 conf2 [X86] Force use of PCI Configuration Access
2976 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2977 the function, IO port 0xCFA, also 8-bit, sets
2978 bus number. The config space is then accessed
2979 through ports 0xC000-0xCFFF).
2980 See http://wiki.osdev.org/PCI for more info
2981 on the configuration access mechanisms.
2982 noaer [PCIE] If the PCIEAER kernel config parameter is
2983 enabled, this kernel boot option can be used to
2984 disable the use of PCIE advanced error reporting.
2985 nodomains [PCI] Disable support for multiple PCI
2986 root domains (aka PCI segments, in ACPI-speak).
2987 nommconf [X86] Disable use of MMCONFIG for PCI
2989 check_enable_amd_mmconf [X86] check for and enable
2990 properly configured MMIO access to PCI
2991 config space on AMD family 10h CPU
2992 nomsi [MSI] If the PCI_MSI kernel config parameter is
2993 enabled, this kernel boot option can be used to
2994 disable the use of MSI interrupts system-wide.
2995 noioapicquirk [APIC] Disable all boot interrupt quirks.
2996 Safety option to keep boot IRQs enabled. This
2997 should never be necessary.
2998 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2999 primary IO-APIC for bridges that cannot disable
3000 boot IRQs. This fixes a source of spurious IRQs
3001 when the system masks IRQs.
3002 noioapicreroute [APIC] Disable workaround that uses the
3003 boot IRQ equivalent of an IRQ that connects to
3004 a chipset where boot IRQs cannot be disabled.
3005 The opposite of ioapicreroute.
3006 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
3007 routing table. These calls are known to be buggy
3008 on several machines and they hang the machine
3009 when used, but on other computers it's the only
3010 way to get the interrupt routing table. Try
3011 this option if the kernel is unable to allocate
3012 IRQs or discover secondary PCI buses on your
3014 rom [X86] Assign address space to expansion ROMs.
3015 Use with caution as certain devices share
3016 address decoders between ROMs and other
3018 norom [X86] Do not assign address space to
3019 expansion ROMs that do not already have
3020 BIOS assigned address ranges.
3021 nobar [X86] Do not assign address space to the
3022 BARs that weren't assigned by the BIOS.
3023 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
3024 assigned automatically to PCI devices. You can
3025 make the kernel exclude IRQs of your ISA cards
3027 pirqaddr=0xAAAAA [X86] Specify the physical address
3028 of the PIRQ table (normally generated
3029 by the BIOS) if it is outside the
3030 F0000h-100000h range.
3031 lastbus=N [X86] Scan all buses thru bus #N. Can be
3032 useful if the kernel is unable to find your
3033 secondary buses and you want to tell it
3034 explicitly which ones they are.
3035 assign-busses [X86] Always assign all PCI bus
3036 numbers ourselves, overriding
3037 whatever the firmware may have done.
3038 usepirqmask [X86] Honor the possible IRQ mask stored
3039 in the BIOS $PIR table. This is needed on
3040 some systems with broken BIOSes, notably
3041 some HP Pavilion N5400 and Omnibook XE3
3042 notebooks. This will have no effect if ACPI
3043 IRQ routing is enabled.
3044 noacpi [X86] Do not use ACPI for IRQ routing
3045 or for PCI scanning.
3046 use_crs [X86] Use PCI host bridge window information
3047 from ACPI. On BIOSes from 2008 or later, this
3048 is enabled by default. If you need to use this,
3049 please report a bug.
3050 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3051 If you need to use this, please report a bug.
3052 routeirq Do IRQ routing for all PCI devices.
3053 This is normally done in pci_enable_device(),
3054 so this option is a temporary workaround
3055 for broken drivers that don't call it.
3056 skip_isa_align [X86] do not align io start addr, so can
3057 handle more pci cards
3058 noearly [X86] Don't do any early type 1 scanning.
3059 This might help on some broken boards which
3060 machine check when some devices' config space
3061 is read. But various workarounds are disabled
3062 and some IOMMU drivers will not work.
3063 bfsort Sort PCI devices into breadth-first order.
3064 This sorting is done to get a device
3065 order compatible with older (<= 2.4) kernels.
3066 nobfsort Don't sort PCI devices into breadth-first order.
3067 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3068 tuning and use the BIOS-configured MPS defaults.
3069 pcie_bus_safe Set every device's MPS to the largest value
3070 supported by all devices below the root complex.
3071 pcie_bus_perf Set device MPS to the largest allowable MPS
3072 based on its parent bus. Also set MRRS (Max
3073 Read Request Size) to the largest supported
3074 value (no larger than the MPS that the device
3075 or bus can support) for best performance.
3076 pcie_bus_peer2peer Set every device's MPS to 128B, which
3077 every device is guaranteed to support. This
3078 configuration allows peer-to-peer DMA between
3079 any pair of devices, possibly at the cost of
3080 reduced performance. This also guarantees
3081 that hot-added devices will work.
3082 cbiosize=nn[KMG] The fixed amount of bus space which is
3083 reserved for the CardBus bridge's IO window.
3084 The default value is 256 bytes.
3085 cbmemsize=nn[KMG] The fixed amount of bus space which is
3086 reserved for the CardBus bridge's memory
3087 window. The default value is 64 megabytes.
3090 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3091 [<order of align>@]pci:<vendor>:<device>\
3092 [:<subvendor>:<subdevice>][; ...]
3093 Specifies alignment and device to reassign
3094 aligned memory resources.
3095 If <order of align> is not specified,
3096 PAGE_SIZE is used as alignment.
3097 PCI-PCI bridge can be specified, if resource
3098 windows need to be expanded.
3099 To specify the alignment for several
3100 instances of a device, the PCI vendor,
3101 device, subvendor, and subdevice may be
3102 specified, e.g., 4096@pci:8086:9c22:103c:198f
3103 ecrc= Enable/disable PCIe ECRC (transaction layer
3104 end-to-end CRC checking).
3105 bios: Use BIOS/firmware settings. This is the
3109 hpiosize=nn[KMG] The fixed amount of bus space which is
3110 reserved for hotplug bridge's IO window.
3111 Default size is 256 bytes.
3112 hpmemsize=nn[KMG] The fixed amount of bus space which is
3113 reserved for hotplug bridge's memory window.
3114 Default size is 2 megabytes.
3115 hpbussize=nn The minimum amount of additional bus numbers
3116 reserved for buses below a hotplug bridge.
3118 realloc= Enable/disable reallocating PCI bridge resources
3119 if allocations done by BIOS are too small to
3120 accommodate resources required by all child
3122 off: Turn realloc off
3124 realloc same as realloc=on
3125 noari do not use PCIe ARI.
3126 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3127 only look for one device below a PCIe downstream
3130 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3133 force Enable ASPM even on devices that claim not to support it.
3134 WARNING: Forcing ASPM on may cause system lockups.
3136 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3137 nomsi Do not use MSI for PCI Express Native Hotplug (this
3138 makes all PCIe ports use INTx for hotplug services).
3140 pcie_ports= [PCIE] PCIe ports handling:
3141 auto Ask the BIOS whether or not to use native PCIe services
3142 associated with PCIe ports (PME, hot-plug, AER). Use
3143 them only if that is allowed by the BIOS.
3144 native Use native PCIe services associated with PCIe ports
3146 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3149 pcie_port_pm= [PCIE] PCIe port power management handling:
3150 off Disable power management of all PCIe ports
3151 force Forcibly enable power management of all PCIe ports
3153 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3154 nomsi Do not use MSI for native PCIe PME signaling (this makes
3155 all PCIe root ports use INTx for all services).
3157 pcmv= [HW,PCMCIA] BadgePAD 4
3161 Keep all power-domains already enabled by bootloader on,
3162 even if no driver has claimed them. This is useful
3163 for debug and development, but should not be
3164 needed on a platform with proper driver support.
3167 See Documentation/blockdev/paride.txt.
3169 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3172 See arch/parisc/kernel/pdc_chassis.c
3174 percpu_alloc= Select which percpu first chunk allocator to use.
3175 Currently supported values are "embed" and "page".
3176 Archs may support subset or none of the selections.
3177 See comments in mm/percpu.c for details on each
3178 allocator. This parameter is primarily for debugging
3179 and performance comparison.
3182 See Documentation/blockdev/paride.txt.
3185 See Documentation/blockdev/paride.txt.
3187 pirq= [SMP,APIC] Manual mp-table setup
3188 See Documentation/x86/i386/IO-APIC.txt.
3190 plip= [PPT,NET] Parallel port network link
3191 Format: { parport<nr> | timid | 0 }
3192 See also Documentation/parport.txt.
3194 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3195 Override pmtimer IOPort with a hex value.
3199 Enable PNP debug messages (depends on the
3200 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3201 via /sys/module/pnp/parameters/debug. We always show
3202 current resource usage; turning this on also shows
3203 possible settings and some assignment information.
3209 { on | off | curr | res | no-curr | no-res }
3212 [ISAPNP] Exclude IRQs for the autoconfiguration
3215 [ISAPNP] Exclude DMAs for the autoconfiguration
3217 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3218 Ranges are in pairs (I/O port base and size).
3221 [ISAPNP] Exclude memory regions for the
3223 Ranges are in pairs (memory base and size).
3225 ports= [IP_VS_FTP] IPVS ftp helper module
3227 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3229 Format: <port>,<port>....
3231 ppc_strict_facility_enable
3232 [PPC] This option catches any kernel floating point,
3233 Altivec, VSX and SPE outside of regions specifically
3234 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3235 There is some performance impact when enabling this.
3237 print-fatal-signals=
3238 [KNL] debug: print fatal signals
3240 If enabled, warn about various signal handling
3241 related application anomalies: too many signals,
3242 too many POSIX.1 timers, fatal signals causing a
3245 If you hit the warning due to signal overflow,
3246 you might want to try "ulimit -i unlimited".
3250 printk.always_kmsg_dump=
3251 Trigger kmsg_dump for cases other than kernel oops or
3253 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3256 printk.devkmsg={on,off,ratelimit}
3257 Control writing to /dev/kmsg.
3258 on - unlimited logging to /dev/kmsg from userspace
3259 off - logging to /dev/kmsg disabled
3260 ratelimit - ratelimit the logging
3263 printk.time= Show timing data prefixed to each printk message line
3264 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3266 processor.max_cstate= [HW,ACPI]
3267 Limit processor to maximum C-state
3268 max_cstate=9 overrides any DMI blacklist limit.
3270 processor.nocst [HW,ACPI]
3271 Ignore the _CST method to determine C-states,
3272 instead using the legacy FADT method
3274 profile= [KNL] Enable kernel profiling via /proc/profile
3275 Format: [schedule,]<number>
3276 Param: "schedule" - profile schedule points.
3277 Param: <number> - step/bucket size as a power of 2 for
3278 statistical time based profiling.
3279 Param: "sleep" - profile D-state sleeping (millisecs).
3280 Requires CONFIG_SCHEDSTATS
3281 Param: "kvm" - profile VM exits.
3283 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3285 See Documentation/blockdev/ramdisk.txt.
3287 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3288 probe for; one of (bare|imps|exps|lifebook|any).
3289 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3291 psmouse.resetafter= [HW,MOUSE]
3292 Try to reset the device after so many bad packets
3295 [HW,MOUSE] Set desired mouse resolution, in dpi.
3296 psmouse.smartscroll=
3297 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3298 0 = disabled, 1 = enabled (default).
3300 pstore.backend= Specify the name of the pstore backend to use
3303 See Documentation/blockdev/paride.txt.
3306 [KNL] Number of legacy pty's. Overwrites compiled-in
3309 quiet [KNL] Disable most log messages
3314 See Documentation/md.txt.
3316 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3317 See Documentation/blockdev/ramdisk.txt.
3320 The argument is a cpu list, as described above.
3322 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3323 the specified list of CPUs to be no-callback CPUs.
3324 Invocation of these CPUs' RCU callbacks will
3325 be offloaded to "rcuox/N" kthreads created for
3326 that purpose, where "x" is "b" for RCU-bh, "p"
3327 for RCU-preempt, and "s" for RCU-sched, and "N"
3328 is the CPU number. This reduces OS jitter on the
3329 offloaded CPUs, which can be useful for HPC and
3330 real-time workloads. It can also improve energy
3331 efficiency for asymmetric multiprocessors.
3334 Rather than requiring that offloaded CPUs
3335 (specified by rcu_nocbs= above) explicitly
3336 awaken the corresponding "rcuoN" kthreads,
3337 make these kthreads poll for callbacks.
3338 This improves the real-time response for the
3339 offloaded CPUs by relieving them of the need to
3340 wake up the corresponding kthread, but degrades
3341 energy efficiency by requiring that the kthreads
3342 periodically wake up to do the polling.
3344 rcutree.blimit= [KNL]
3345 Set maximum number of finished RCU callbacks to
3346 process in one batch.
3348 rcutree.dump_tree= [KNL]
3349 Dump the structure of the rcu_node combining tree
3350 out at early boot. This is used for diagnostic
3351 purposes, to verify correct tree setup.
3353 rcutree.gp_cleanup_delay= [KNL]
3354 Set the number of jiffies to delay each step of
3355 RCU grace-period cleanup. This only has effect
3356 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3358 rcutree.gp_init_delay= [KNL]
3359 Set the number of jiffies to delay each step of
3360 RCU grace-period initialization. This only has
3361 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3364 rcutree.gp_preinit_delay= [KNL]
3365 Set the number of jiffies to delay each step of
3366 RCU grace-period pre-initialization, that is,
3367 the propagation of recent CPU-hotplug changes up
3368 the rcu_node combining tree. This only has effect
3369 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3371 rcutree.rcu_fanout_exact= [KNL]
3372 Disable autobalancing of the rcu_node combining
3373 tree. This is used by rcutorture, and might
3374 possibly be useful for architectures having high
3375 cache-to-cache transfer latencies.
3377 rcutree.rcu_fanout_leaf= [KNL]
3378 Change the number of CPUs assigned to each
3379 leaf rcu_node structure. Useful for very
3380 large systems, which will choose the value 64,
3381 and for NUMA systems with large remote-access
3382 latencies, which will choose a value aligned
3383 with the appropriate hardware boundaries.
3385 rcutree.jiffies_till_sched_qs= [KNL]
3386 Set required age in jiffies for a
3387 given grace period before RCU starts
3388 soliciting quiescent-state help from
3389 rcu_note_context_switch().
3391 rcutree.jiffies_till_first_fqs= [KNL]
3392 Set delay from grace-period initialization to
3393 first attempt to force quiescent states.
3394 Units are jiffies, minimum value is zero,
3395 and maximum value is HZ.
3397 rcutree.jiffies_till_next_fqs= [KNL]
3398 Set delay between subsequent attempts to force
3399 quiescent states. Units are jiffies, minimum
3400 value is one, and maximum value is HZ.
3402 rcutree.kthread_prio= [KNL,BOOT]
3403 Set the SCHED_FIFO priority of the RCU per-CPU
3404 kthreads (rcuc/N). This value is also used for
3405 the priority of the RCU boost threads (rcub/N)
3406 and for the RCU grace-period kthreads (rcu_bh,
3407 rcu_preempt, and rcu_sched). If RCU_BOOST is
3408 set, valid values are 1-99 and the default is 1
3409 (the least-favored priority). Otherwise, when
3410 RCU_BOOST is not set, valid values are 0-99 and
3411 the default is zero (non-realtime operation).
3413 rcutree.rcu_nocb_leader_stride= [KNL]
3414 Set the number of NOCB kthread groups, which
3415 defaults to the square root of the number of
3416 CPUs. Larger numbers reduces the wakeup overhead
3417 on the per-CPU grace-period kthreads, but increases
3418 that same overhead on each group's leader.
3420 rcutree.qhimark= [KNL]
3421 Set threshold of queued RCU callbacks beyond which
3422 batch limiting is disabled.
3424 rcutree.qlowmark= [KNL]
3425 Set threshold of queued RCU callbacks below which
3426 batch limiting is re-enabled.
3428 rcutree.rcu_idle_gp_delay= [KNL]
3429 Set wakeup interval for idle CPUs that have
3430 RCU callbacks (RCU_FAST_NO_HZ=y).
3432 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3433 Set wakeup interval for idle CPUs that have
3434 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3435 Lazy RCU callbacks are those which RCU can
3436 prove do nothing more than free memory.
3438 rcuperf.gp_exp= [KNL]
3439 Measure performance of expedited synchronous
3440 grace-period primitives.
3442 rcuperf.holdoff= [KNL]
3443 Set test-start holdoff period. The purpose of
3444 this parameter is to delay the start of the
3445 test until boot completes in order to avoid
3448 rcuperf.nreaders= [KNL]
3449 Set number of RCU readers. The value -1 selects
3450 N, where N is the number of CPUs. A value
3451 "n" less than -1 selects N-n+1, where N is again
3452 the number of CPUs. For example, -2 selects N
3453 (the number of CPUs), -3 selects N+1, and so on.
3454 A value of "n" less than or equal to -N selects
3457 rcuperf.nwriters= [KNL]
3458 Set number of RCU writers. The values operate
3459 the same as for rcuperf.nreaders.
3460 N, where N is the number of CPUs
3462 rcuperf.perf_runnable= [BOOT]
3463 Start rcuperf running at boot time.
3465 rcuperf.shutdown= [KNL]
3466 Shut the system down after performance tests
3467 complete. This is useful for hands-off automated
3470 rcuperf.perf_type= [KNL]
3471 Specify the RCU implementation to test.
3473 rcuperf.verbose= [KNL]
3474 Enable additional printk() statements.
3476 rcutorture.cbflood_inter_holdoff= [KNL]
3477 Set holdoff time (jiffies) between successive
3478 callback-flood tests.
3480 rcutorture.cbflood_intra_holdoff= [KNL]
3481 Set holdoff time (jiffies) between successive
3482 bursts of callbacks within a given callback-flood
3485 rcutorture.cbflood_n_burst= [KNL]
3486 Set the number of bursts making up a given
3487 callback-flood test. Set this to zero to
3488 disable callback-flood testing.
3490 rcutorture.cbflood_n_per_burst= [KNL]
3491 Set the number of callbacks to be registered
3492 in a given burst of a callback-flood test.
3494 rcutorture.fqs_duration= [KNL]
3495 Set duration of force_quiescent_state bursts
3498 rcutorture.fqs_holdoff= [KNL]
3499 Set holdoff time within force_quiescent_state bursts
3502 rcutorture.fqs_stutter= [KNL]
3503 Set wait time between force_quiescent_state bursts
3506 rcutorture.gp_cond= [KNL]
3507 Use conditional/asynchronous update-side
3508 primitives, if available.
3510 rcutorture.gp_exp= [KNL]
3511 Use expedited update-side primitives, if available.
3513 rcutorture.gp_normal= [KNL]
3514 Use normal (non-expedited) asynchronous
3515 update-side primitives, if available.
3517 rcutorture.gp_sync= [KNL]
3518 Use normal (non-expedited) synchronous
3519 update-side primitives, if available. If all
3520 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3521 rcutorture.gp_normal=, and rcutorture.gp_sync=
3522 are zero, rcutorture acts as if is interpreted
3523 they are all non-zero.
3525 rcutorture.n_barrier_cbs= [KNL]
3526 Set callbacks/threads for rcu_barrier() testing.
3528 rcutorture.nfakewriters= [KNL]
3529 Set number of concurrent RCU writers. These just
3530 stress RCU, they don't participate in the actual
3531 test, hence the "fake".
3533 rcutorture.nreaders= [KNL]
3534 Set number of RCU readers. The value -1 selects
3535 N-1, where N is the number of CPUs. A value
3536 "n" less than -1 selects N-n-2, where N is again
3537 the number of CPUs. For example, -2 selects N
3538 (the number of CPUs), -3 selects N+1, and so on.
3540 rcutorture.object_debug= [KNL]
3541 Enable debug-object double-call_rcu() testing.
3543 rcutorture.onoff_holdoff= [KNL]
3544 Set time (s) after boot for CPU-hotplug testing.
3546 rcutorture.onoff_interval= [KNL]
3547 Set time (s) between CPU-hotplug operations, or
3548 zero to disable CPU-hotplug testing.
3550 rcutorture.shuffle_interval= [KNL]
3551 Set task-shuffle interval (s). Shuffling tasks
3552 allows some CPUs to go into dyntick-idle mode
3553 during the rcutorture test.
3555 rcutorture.shutdown_secs= [KNL]
3556 Set time (s) after boot system shutdown. This
3557 is useful for hands-off automated testing.
3559 rcutorture.stall_cpu= [KNL]
3560 Duration of CPU stall (s) to test RCU CPU stall
3561 warnings, zero to disable.
3563 rcutorture.stall_cpu_holdoff= [KNL]
3564 Time to wait (s) after boot before inducing stall.
3566 rcutorture.stat_interval= [KNL]
3567 Time (s) between statistics printk()s.
3569 rcutorture.stutter= [KNL]
3570 Time (s) to stutter testing, for example, specifying
3571 five seconds causes the test to run for five seconds,
3572 wait for five seconds, and so on. This tests RCU's
3573 ability to transition abruptly to and from idle.
3575 rcutorture.test_boost= [KNL]
3576 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3577 "Maybe" means test if the RCU implementation
3578 under test support RCU priority boosting.
3580 rcutorture.test_boost_duration= [KNL]
3581 Duration (s) of each individual boost test.
3583 rcutorture.test_boost_interval= [KNL]
3584 Interval (s) between each boost test.
3586 rcutorture.test_no_idle_hz= [KNL]
3587 Test RCU's dyntick-idle handling. See also the
3588 rcutorture.shuffle_interval parameter.
3590 rcutorture.torture_runnable= [BOOT]
3591 Start rcutorture running at boot time.
3593 rcutorture.torture_type= [KNL]
3594 Specify the RCU implementation to test.
3596 rcutorture.verbose= [KNL]
3597 Enable additional printk() statements.
3599 rcupdate.rcu_cpu_stall_suppress= [KNL]
3600 Suppress RCU CPU stall warning messages.
3602 rcupdate.rcu_cpu_stall_timeout= [KNL]
3603 Set timeout for RCU CPU stall warning messages.
3605 rcupdate.rcu_expedited= [KNL]
3606 Use expedited grace-period primitives, for
3607 example, synchronize_rcu_expedited() instead
3608 of synchronize_rcu(). This reduces latency,
3609 but can increase CPU utilization, degrade
3610 real-time latency, and degrade energy efficiency.
3611 No effect on CONFIG_TINY_RCU kernels.
3613 rcupdate.rcu_normal= [KNL]
3614 Use only normal grace-period primitives,
3615 for example, synchronize_rcu() instead of
3616 synchronize_rcu_expedited(). This improves
3617 real-time latency, CPU utilization, and
3618 energy efficiency, but can expose users to
3619 increased grace-period latency. This parameter
3620 overrides rcupdate.rcu_expedited. No effect on
3621 CONFIG_TINY_RCU kernels.
3623 rcupdate.rcu_normal_after_boot= [KNL]
3624 Once boot has completed (that is, after
3625 rcu_end_inkernel_boot() has been invoked), use
3626 only normal grace-period primitives. No effect
3627 on CONFIG_TINY_RCU kernels.
3629 rcupdate.rcu_task_stall_timeout= [KNL]
3630 Set timeout in jiffies for RCU task stall warning
3631 messages. Disable with a value less than or equal
3634 rcupdate.rcu_self_test= [KNL]
3635 Run the RCU early boot self tests
3637 rcupdate.rcu_self_test_bh= [KNL]
3638 Run the RCU bh early boot self tests
3640 rcupdate.rcu_self_test_sched= [KNL]
3641 Run the RCU sched early boot self tests
3645 Run specified binary instead of /init from the ramdisk,
3646 used for early userspace startup. See initrd.
3649 Format (x86 or x86_64):
3650 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3652 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3654 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3655 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3656 reboot_force is either force or not specified,
3657 reboot_cpu is s[mp]#### with #### being the processor
3658 to be used for rebooting.
3661 [KNL, SMP] Set scheduler's default relax_domain_level.
3662 See Documentation/cgroup-v1/cpusets.txt.
3664 relative_sleep_states=
3665 [SUSPEND] Use sleep state labeling where the deepest
3666 state available other than hibernation is always "mem".
3667 Format: { "0" | "1" }
3668 0 -- Traditional sleep state labels.
3669 1 -- Relative sleep state labels.
3671 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3673 reservetop= [X86-32]
3675 Reserves a hole at the top of the kernel virtual
3680 Set the amount of memory to reserve for BIOS at
3681 the bottom of the address space.
3683 reset_devices [KNL] Force drivers to reset the underlying device
3684 during initialization.
3687 Specify the partition device for software suspend
3689 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3691 resume_offset= [SWSUSP]
3692 Specify the offset from the beginning of the partition
3693 given by "resume=" at which the swap header is located,
3694 in <PAGE_SIZE> units (needed only for swap files).
3695 See Documentation/power/swsusp-and-swap-files.txt
3697 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3698 read the resume files
3700 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3701 Useful for devices that are detected asynchronously
3702 (e.g. USB and MMC devices).
3704 hibernate= [HIBERNATION]
3705 noresume Don't check if there's a hibernation image
3706 present during boot.
3707 nocompress Don't compress/decompress hibernation images.
3708 no Disable hibernation and resume.
3709 protect_image Turn on image protection during restoration
3710 (that will set all pages holding image data
3711 during restoration read-only).
3713 retain_initrd [RAM] Keep initrd memory after extraction
3715 rfkill.default_state=
3716 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3717 etc. communication is blocked by default.
3720 rfkill.master_switch_mode=
3721 0 The "airplane mode" button does nothing.
3722 1 The "airplane mode" button toggles between everything
3723 blocked and the previous configuration.
3724 2 The "airplane mode" button toggles between everything
3725 blocked and everything unblocked.
3727 rhash_entries= [KNL,NET]
3728 Set number of hash buckets for route cache
3730 ro [KNL] Mount root device read-only on boot
3733 on Mark read-only kernel memory as read-only (default).
3734 off Leave read-only kernel memory writable for debugging.
3737 Enable the uart passthrough on the designated usb port
3738 on Rockchip SoCs. When active, the signals of the
3739 debug-uart get routed to the D+ and D- pins of the usb
3740 port and the regular usb controller gets disabled.
3742 root= [KNL] Root filesystem
3743 See name_to_dev_t comment in init/do_mounts.c.
3745 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3746 mount the root filesystem
3748 rootflags= [KNL] Set root filesystem mount option string
3750 rootfstype= [KNL] Set root filesystem type
3752 rootwait [KNL] Wait (indefinitely) for root device to show up.
3753 Useful for devices that are detected asynchronously
3754 (e.g. USB and MMC devices).
3756 rproc_mem=nn[KMG][@address]
3757 [KNL,ARM,CMA] Remoteproc physical memory block.
3758 Memory area to be used by remote processor image,
3761 rw [KNL] Mount root device read-write on boot
3763 S [KNL] Run init in single mode
3765 s390_iommu= [HW,S390]
3766 Set s390 IOTLB flushing mode
3768 With strict flushing every unmap operation will result in
3769 an IOTLB flush. Default is lazy flushing before reuse,
3773 See drivers/net/irda/sa1100_ir.c.
3775 sbni= [NET] Granch SBNI12 leased line adapter
3777 sched_debug [KNL] Enables verbose scheduler debug messages.
3779 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3780 Allowed values are enable and disable. This feature
3781 incurs a small amount of overhead in the scheduler
3782 but is useful for debugging and performance tuning.
3784 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3785 xtime_lock contention on larger systems, and/or RCU lock
3786 contention on all systems with CONFIG_MAXSMP set.
3787 Format: { "0" | "1" }
3788 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3790 Note: increases power consumption, thus should only be
3791 enabled if running jitter sensitive (HPC/RT) workloads.
3793 security= [SECURITY] Choose a security module to enable at boot.
3794 If this boot parameter is not specified, only the first
3795 security module asking for security registration will be
3796 loaded. An invalid security module name will be treated
3797 as if no module has been chosen.
3799 selinux= [SELINUX] Disable or enable SELinux at boot time.
3800 Format: { "0" | "1" }
3801 See security/selinux/Kconfig help text.
3804 Default value is set via kernel config option.
3805 If enabled at boot time, /selinux/disable can be used
3806 later to disable prior to initial policy load.
3808 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3809 Format: { "0" | "1" }
3810 See security/apparmor/Kconfig help text
3813 Default value is set via kernel config option.
3815 serialnumber [BUGS=X86-32]
3818 Maximal number of shapers.
3820 show_msr= [x86] show boot-time MSR settings
3821 Format: { <integer> }
3822 Show boot-time (BIOS-initialized) MSR settings.
3823 The parameter means the number of CPUs to show,
3824 for example 1 means boot CPU only.
3832 Disable merging of slabs with similar size. May be
3833 necessary if there is some reason to distinguish
3834 allocs to different slabs. Debug options disable
3835 merging on their own.
3836 For more information see Documentation/vm/slub.txt.
3838 slab_max_order= [MM, SLAB]
3839 Determines the maximum allowed order for slabs.
3840 A high setting may cause OOMs due to memory
3841 fragmentation. Defaults to 1 for systems with
3842 more than 32MB of RAM, 0 otherwise.
3844 slub_debug[=options[,slabs]] [MM, SLUB]
3845 Enabling slub_debug allows one to determine the
3846 culprit if slab objects become corrupted. Enabling
3847 slub_debug can create guard zones around objects and
3848 may poison objects when not in use. Also tracks the
3849 last alloc / free. For more information see
3850 Documentation/vm/slub.txt.
3852 slub_max_order= [MM, SLUB]
3853 Determines the maximum allowed order for slabs.
3854 A high setting may cause OOMs due to memory
3855 fragmentation. For more information see
3856 Documentation/vm/slub.txt.
3858 slub_min_objects= [MM, SLUB]
3859 The minimum number of objects per slab. SLUB will
3860 increase the slab order up to slub_max_order to
3861 generate a sufficiently large slab able to contain
3862 the number of objects indicated. The higher the number
3863 of objects the smaller the overhead of tracking slabs
3864 and the less frequently locks need to be acquired.
3865 For more information see Documentation/vm/slub.txt.
3867 slub_min_order= [MM, SLUB]
3868 Determines the minimum page order for slabs. Must be
3869 lower than slub_max_order.
3870 For more information see Documentation/vm/slub.txt.
3872 slub_nomerge [MM, SLUB]
3873 Same with slab_nomerge. This is supported for legacy.
3874 See slab_nomerge for more information.
3877 Format: <io1>[,<io2>[,...,<io8>]]
3879 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3880 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3881 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3882 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3883 smsc-ircc2.ircc_irq= [HW] IRQ line
3884 smsc-ircc2.ircc_dma= [HW] DMA channel
3885 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3886 0: Toshiba Satellite 1800 (GP data pin select)
3887 1: Fast pin select (default)
3890 smt [KNL,S390] Set the maximum number of threads (logical
3891 CPUs) to use per physical CPU on systems capable of
3892 symmetric multithreading (SMT). Will be capped to the
3893 actual hardware limit.
3895 Default: -1 (no limit)
3898 [KNL] Should the soft-lockup detector generate panics.
3901 softlockup_all_cpu_backtrace=
3902 [KNL] Should the soft-lockup detector generate
3903 backtraces on all cpus.
3906 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3907 See Documentation/laptops/sonypi.txt
3909 spia_io_base= [HW,MTD]
3915 Enabled the stack tracer on boot up.
3917 stacktrace_filter=[function-list]
3918 [FTRACE] Limit the functions that the stack tracer
3919 will trace at boot up. function-list is a comma separated
3920 list of functions. This list can be changed at run
3921 time by the stack_trace_filter file in the debugfs
3922 tracing directory. Note, this enables stack tracing
3923 and the stacktrace above is not needed.
3927 Set the STI (builtin display/keyboard on the HP-PARISC
3928 machines) console (graphic card) which should be used
3929 as the initial boot-console.
3930 See also comment in drivers/video/console/sticore.c.
3933 See comment in drivers/video/console/sticore.c.
3936 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3938 sunrpc.min_resvport=
3939 sunrpc.max_resvport=
3941 SunRPC servers often require that client requests
3942 originate from a privileged port (i.e. a port in the
3943 range 0 < portnr < 1024).
3944 An administrator who wishes to reserve some of these
3945 ports for other uses may adjust the range that the
3946 kernel's sunrpc client considers to be privileged
3947 using these two parameters to set the minimum and
3948 maximum port values.
3950 sunrpc.svc_rpc_per_connection_limit=
3952 Limit the number of requests that the server will
3953 process in parallel from a single connection.
3954 The default value is 0 (no limit).
3958 Control how the NFS server code allocates CPUs to
3959 service thread pools. Depending on how many NICs
3960 you have and where their interrupts are bound, this
3961 option will affect which CPUs will do NFS serving.
3962 Note: this parameter cannot be changed while the
3963 NFS server is running.
3965 auto the server chooses an appropriate mode
3966 automatically using heuristics
3967 global a single global pool contains all CPUs
3968 percpu one pool for each CPU
3969 pernode one pool for each NUMA node (equivalent
3970 to global on non-NUMA machines)
3972 sunrpc.tcp_slot_table_entries=
3973 sunrpc.udp_slot_table_entries=
3975 Sets the upper limit on the number of simultaneous
3976 RPC calls that can be sent from the client to a
3977 server. Increasing these values may allow you to
3978 improve throughput, but will also increase the
3979 amount of memory reserved for use by the client.
3981 suspend.pm_test_delay=
3983 Sets the number of seconds to remain in a suspend test
3984 mode before resuming the system (see
3985 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3986 is set. Default value is 5.
3989 [KNL] Enable accounting of swap in memory resource
3990 controller if no parameter or 1 is given or disable
3991 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
3993 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3994 Format: { <int> | force }
3995 <int> -- Number of I/O TLB slabs
3996 force -- force using of bounce buffers even if they
3997 wouldn't be automatically used by the kernel
4001 sysfs.deprecated=0|1 [KNL]
4002 Enable/disable old style sysfs layout for old udev
4003 on older distributions. When this option is enabled
4004 very new udev will not work anymore. When this option
4005 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4006 in older udev will not work anymore.
4007 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4008 the kernel configuration.
4010 sysrq_always_enabled
4012 Ignore sysrq setting - this boot parameter will
4013 neutralize any effect of /proc/sys/kernel/sysrq.
4014 Useful for debugging.
4016 tcpmhash_entries= [KNL,NET]
4017 Set the number of tcp_metrics_hash slots.
4018 Default value is 8192 or 16384 depending on total
4019 ram pages. This is used to specify the TCP metrics
4020 cache size. See Documentation/networking/ip-sysctl.txt
4021 "tcp_no_metrics_save" section for more details.
4025 test_suspend= [SUSPEND][,N]
4026 Specify "mem" (for Suspend-to-RAM) or "standby" (for
4027 standby suspend) or "freeze" (for suspend type freeze)
4028 as the system sleep state during system startup with
4029 the optional capability to repeat N number of times.
4030 The system is woken from this state using a
4031 wakeup-capable RTC alarm.
4033 thash_entries= [KNL,NET]
4034 Set number of hash buckets for TCP connection
4036 thermal.act= [HW,ACPI]
4037 -1: disable all active trip points in all thermal zones
4038 <degrees C>: override all lowest active trip points
4040 thermal.crt= [HW,ACPI]
4041 -1: disable all critical trip points in all thermal zones
4042 <degrees C>: override all critical trip points
4044 thermal.nocrt= [HW,ACPI]
4045 Set to disable actions on ACPI thermal zone
4046 critical and hot trip points.
4048 thermal.off= [HW,ACPI]
4049 1: disable ACPI thermal control
4051 thermal.psv= [HW,ACPI]
4052 -1: disable all passive trip points
4053 <degrees C>: override all passive trip points to this
4056 thermal.tzp= [HW,ACPI]
4057 Specify global default ACPI thermal zone polling rate
4058 <deci-seconds>: poll all this frequency
4059 0: no polling (default)
4062 Force threading of all interrupt handlers except those
4063 marked explicitly IRQF_NO_THREAD.
4066 Enable the Transcendent memory driver if built-in.
4068 tmem.cleancache=0|1 [KNL, XEN]
4069 Default is on (1). Disable the usage of the cleancache
4070 API to send anonymous pages to the hypervisor.
4072 tmem.frontswap=0|1 [KNL, XEN]
4073 Default is on (1). Disable the usage of the frontswap
4074 API to send swap pages to the hypervisor. If disabled
4075 the selfballooning and selfshrinking are force disabled.
4077 tmem.selfballooning=0|1 [KNL, XEN]
4078 Default is on (1). Disable the driving of swap pages
4081 tmem.selfshrinking=0|1 [KNL, XEN]
4082 Default is on (1). Partial swapoff that immediately
4083 transfers pages from Xen hypervisor back to the
4084 kernel based on different criteria.
4088 Specify if the kernel should make use of the cpu
4089 topology information if the hardware supports this.
4090 The scheduler will make use of this information and
4091 e.g. base its process migration decisions on it.
4094 topology_updates= [KNL, PPC, NUMA]
4096 Specify if the kernel should ignore (off)
4097 topology updates sent by the hypervisor to this
4102 tpm_suspend_pcr=[HW,TPM]
4103 Format: integer pcr id
4104 Specify that at suspend time, the tpm driver
4105 should extend the specified pcr with zeros,
4106 as a workaround for some chips which fail to
4107 flush the last written pcr on TPM_SaveState.
4108 This will guarantee that all the other pcrs
4111 trace_buf_size=nn[KMG]
4112 [FTRACE] will set tracing buffer size on each cpu.
4114 trace_event=[event-list]
4115 [FTRACE] Set and start specified trace events in order
4116 to facilitate early boot debugging. The event-list is a
4117 comma separated list of trace events to enable. See
4118 also Documentation/trace/events.txt
4120 trace_options=[option-list]
4121 [FTRACE] Enable or disable tracer options at boot.
4122 The option-list is a comma delimited list of options
4123 that can be enabled or disabled just as if you were
4124 to echo the option name into
4126 /sys/kernel/debug/tracing/trace_options
4128 For example, to enable stacktrace option (to dump the
4129 stack trace of each event), add to the command line:
4131 trace_options=stacktrace
4133 See also Documentation/trace/ftrace.txt "trace options"
4137 Have the tracepoints sent to printk as well as the
4138 tracing ring buffer. This is useful for early boot up
4139 where the system hangs or reboots and does not give the
4140 option for reading the tracing buffer or performing a
4141 ftrace_dump_on_oops.
4143 To turn off having tracepoints sent to printk,
4144 echo 0 > /proc/sys/kernel/tracepoint_printk
4145 Note, echoing 1 into this file without the
4146 tracepoint_printk kernel cmdline option has no effect.
4150 Having tracepoints sent to printk() and activating high
4151 frequency tracepoints such as irq or sched, can cause
4152 the system to live lock.
4155 [FTRACE] enable this option to disable tracing when a
4156 warning is hit. This turns off "tracing_on". Tracing can
4157 be enabled again by echoing '1' into the "tracing_on"
4158 file located in /sys/kernel/debug/tracing/
4160 This option is useful, as it disables the trace before
4161 the WARNING dump is called, which prevents the trace to
4162 be filled with content caused by the warning output.
4164 This option can also be set at run time via the sysctl
4165 option: kernel/traceoff_on_warning
4167 transparent_hugepage=
4169 Format: [always|madvise|never]
4170 Can be used to control the default behavior of the system
4171 with respect to transparent hugepages.
4172 See Documentation/vm/transhuge.txt for more details.
4174 tsc= Disable clocksource stability checks for TSC.
4176 [x86] reliable: mark tsc clocksource as reliable, this
4177 disables clocksource verification at runtime, as well
4178 as the stability checks done at bootup. Used to enable
4179 high-resolution timer mode on older hardware, and in
4180 virtualized environment.
4181 [x86] noirqtime: Do not use TSC to do irq accounting.
4182 Used to run time disable IRQ_TIME_ACCOUNTING on any
4183 platforms where RDTSC is slow and this accounting
4186 turbografx.map[2|3]= [HW,JOY]
4187 TurboGraFX parallel port interface
4189 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4190 See also Documentation/input/joystick-parport.txt
4192 udbg-immortal [PPC] When debugging early kernel crashes that
4193 happen after console_init() and before a proper
4194 console driver takes over, this boot options might
4195 help "seeing" what's going on.
4197 uhash_entries= [KNL,NET]
4198 Set number of hash buckets for UDP/UDP-Lite connections
4201 [USB] Ignore overcurrent events (default N).
4202 Some badly-designed motherboards generate lots of
4203 bogus events, for ports that aren't wired to
4204 anything. Set this parameter to avoid log spamming.
4205 Note that genuine overcurrent events won't be
4209 [X86] Cause panic on unknown NMI.
4211 usbcore.authorized_default=
4212 [USB] Default USB device authorization:
4213 (default -1 = authorized except for wireless USB,
4214 0 = not authorized, 1 = authorized)
4216 usbcore.autosuspend=
4217 [USB] The autosuspend time delay (in seconds) used
4218 for newly-detected USB devices (default 2). This
4219 is the time required before an idle device will be
4220 autosuspended. Devices for which the delay is set
4221 to a negative value won't be autosuspended at all.
4223 usbcore.usbfs_snoop=
4224 [USB] Set to log all usbfs traffic (default 0 = off).
4226 usbcore.usbfs_snoop_max=
4227 [USB] Maximum number of bytes to snoop in each URB
4230 usbcore.blinkenlights=
4231 [USB] Set to cycle leds on hubs (default 0 = off).
4233 usbcore.old_scheme_first=
4234 [USB] Start with the old device initialization
4235 scheme (default 0 = off).
4237 usbcore.usbfs_memory_mb=
4238 [USB] Memory limit (in MB) for buffers allocated by
4239 usbfs (default = 16, 0 = max = 2047).
4241 usbcore.use_both_schemes=
4242 [USB] Try the other device initialization scheme
4243 if the first one fails (default 1 = enabled).
4245 usbcore.initial_descriptor_timeout=
4246 [USB] Specifies timeout for the initial 64-byte
4247 USB_REQ_GET_DESCRIPTOR request in milliseconds
4248 (default 5000 = 5.0 seconds).
4250 usbcore.nousb [USB] Disable the USB subsystem
4253 [USBHID] The interval which mice are to be polled at.
4255 usb-storage.delay_use=
4256 [UMS] The delay in seconds before a new device is
4257 scanned for Logical Units (default 1).
4260 [UMS] A list of quirks entries to supplement or
4261 override the built-in unusual_devs list. List
4262 entries are separated by commas. Each entry has
4263 the form VID:PID:Flags where VID and PID are Vendor
4264 and Product ID values (4-digit hex numbers) and
4265 Flags is a set of characters, each corresponding
4266 to a common usb-storage quirk flag as follows:
4267 a = SANE_SENSE (collect more than 18 bytes
4269 b = BAD_SENSE (don't collect more than 18
4270 bytes of sense data);
4271 c = FIX_CAPACITY (decrease the reported
4272 device capacity by one sector);
4273 d = NO_READ_DISC_INFO (don't use
4274 READ_DISC_INFO command);
4275 e = NO_READ_CAPACITY_16 (don't use
4276 READ_CAPACITY_16 command);
4277 f = NO_REPORT_OPCODES (don't use report opcodes
4279 g = MAX_SECTORS_240 (don't transfer more than
4280 240 sectors at a time, uas only);
4281 h = CAPACITY_HEURISTICS (decrease the
4282 reported device capacity by one
4283 sector if the number is odd);
4284 i = IGNORE_DEVICE (don't bind to this
4286 j = NO_REPORT_LUNS (don't use report luns
4288 l = NOT_LOCKABLE (don't try to lock and
4289 unlock ejectable media);
4290 m = MAX_SECTORS_64 (don't transfer more
4291 than 64 sectors = 32 KB at a time);
4292 n = INITIAL_READ10 (force a retry of the
4293 initial READ(10) command);
4294 o = CAPACITY_OK (accept the capacity
4295 reported by the device);
4296 p = WRITE_CACHE (the device cache is ON
4298 r = IGNORE_RESIDUE (the device reports
4299 bogus residue values);
4300 s = SINGLE_LUN (the device has only one
4302 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4303 commands, uas only);
4304 u = IGNORE_UAS (don't bind to the uas driver);
4305 w = NO_WP_DETECT (don't test whether the
4306 medium is write-protected).
4307 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4308 even if the device claims no cache)
4309 Example: quirks=0419:aaf5:rl,0421:0433:rc
4311 user_debug= [KNL,ARM]
4313 See arch/arm/Kconfig.debug help text.
4314 1 - undefined instruction events
4316 4 - invalid data aborts
4319 Example: user_debug=31
4322 [X86] Flags controlling user PTE allocations.
4324 nohigh = do not allocate PTE pages in
4325 HIGHMEM regardless of setting
4329 On X86_32, this is an alias for vdso32=. Otherwise:
4331 vdso=1: enable VDSO (the default)
4332 vdso=0: disable VDSO mapping
4334 vdso32= [X86] Control the 32-bit vDSO
4335 vdso32=1: enable 32-bit VDSO
4336 vdso32=0 or vdso32=2: disable 32-bit VDSO
4338 See the help text for CONFIG_COMPAT_VDSO for more
4339 details. If CONFIG_COMPAT_VDSO is set, the default is
4340 vdso32=0; otherwise, the default is vdso32=1.
4342 For compatibility with older kernels, vdso32=2 is an
4345 Try vdso32=0 if you encounter an error that says:
4346 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4349 vector=percpu: enable percpu vector domain
4351 video= [FB] Frame buffer configuration
4352 See Documentation/fb/modedb.txt.
4354 video.brightness_switch_enabled= [0,1]
4355 If set to 1, on receiving an ACPI notify event
4356 generated by hotkey, video driver will adjust brightness
4357 level and then send out the event to user space through
4358 the allocated input device; If set to 0, video driver
4359 will only send out the event without touching backlight
4364 [VMMIO] Memory mapped virtio (platform) device.
4366 <size>@<baseaddr>:<irq>[:<id>]
4368 <size> := size (can use standard suffixes
4370 <baseaddr> := physical base address
4371 <irq> := interrupt number (as passed to
4373 <id> := (optional) platform device id
4375 virtio_mmio.device=1K@0x100b0000:48:7
4377 Can be used multiple times for multiple devices.
4379 vga= [BOOT,X86-32] Select a particular video mode
4380 See Documentation/x86/boot.txt and
4381 Documentation/svga.txt.
4382 Use vga=ask for menu.
4383 This is actually a boot loader parameter; the value is
4384 passed to the kernel using a special protocol.
4386 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4387 size of <nn>. This can be used to increase the
4388 minimum size (128MB on x86). It can also be used to
4389 decrease the size and leave more room for directly
4392 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4395 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4398 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4402 Controls the behavior of vsyscalls (i.e. calls to
4403 fixed addresses of 0xffffffffff600x00 from legacy
4404 code). Most statically-linked binaries and older
4405 versions of glibc use these calls. Because these
4406 functions are at fixed addresses, they make nice
4407 targets for exploits that can control RIP.
4409 emulate [default] Vsyscalls turn into traps and are
4410 emulated reasonably safely.
4412 native Vsyscalls are native syscall instructions.
4413 This is a little bit faster than trapping
4414 and makes a few dynamic recompilers work
4415 better than they would in emulation mode.
4416 It also makes exploits much easier to write.
4418 none Vsyscalls don't work at all. This makes
4419 them quite hard to use for exploits but
4420 might break your system.
4422 vt.color= [VT] Default text color.
4423 Format: 0xYX, X = foreground, Y = background.
4424 Default: 0x07 = light gray on black.
4426 vt.cur_default= [VT] Default cursor shape.
4427 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4428 the parameters of the <Esc>[?A;B;Cc escape sequence;
4429 see VGA-softcursor.txt. Default: 2 = underline.
4431 vt.default_blu= [VT]
4432 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4433 Change the default blue palette of the console.
4434 This is a 16-member array composed of values
4437 vt.default_grn= [VT]
4438 Format: <green0>,<green1>,<green2>,...,<green15>
4439 Change the default green palette of the console.
4440 This is a 16-member array composed of values
4443 vt.default_red= [VT]
4444 Format: <red0>,<red1>,<red2>,...,<red15>
4445 Change the default red palette of the console.
4446 This is a 16-member array composed of values
4452 Set system-wide default UTF-8 mode for all tty's.
4453 Default is 1, i.e. UTF-8 mode is enabled for all
4454 newly opened terminals.
4456 vt.global_cursor_default=
4459 Set system-wide default for whether a cursor
4460 is shown on new VTs. Default is -1,
4461 i.e. cursors will be created by default unless
4462 overridden by individual drivers. 0 will hide
4463 cursors, 1 will display them.
4465 vt.italic= [VT] Default color for italic text; 0-15.
4468 vt.underline= [VT] Default color for underlined text; 0-15.
4471 watchdog timers [HW,WDT] For information on watchdog timers,
4472 see Documentation/watchdog/watchdog-parameters.txt
4473 or other driver-specific files in the
4474 Documentation/watchdog/ directory.
4476 workqueue.watchdog_thresh=
4477 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4478 warn stall conditions and dump internal state to
4479 help debugging. 0 disables workqueue stall
4480 detection; otherwise, it's the stall threshold
4481 duration in seconds. The default value is 30 and
4482 it can be updated at runtime by writing to the
4483 corresponding sysfs file.
4485 workqueue.disable_numa
4486 By default, all work items queued to unbound
4487 workqueues are affine to the NUMA nodes they're
4488 issued on, which results in better behavior in
4489 general. If NUMA affinity needs to be disabled for
4490 whatever reason, this option can be used. Note
4491 that this also can be controlled per-workqueue for
4492 workqueues visible under /sys/bus/workqueue/.
4494 workqueue.power_efficient
4495 Per-cpu workqueues are generally preferred because
4496 they show better performance thanks to cache
4497 locality; unfortunately, per-cpu workqueues tend to
4498 be more power hungry than unbound workqueues.
4500 Enabling this makes the per-cpu workqueues which
4501 were observed to contribute significantly to power
4502 consumption unbound, leading to measurably lower
4503 power usage at the cost of small performance
4506 The default value of this parameter is determined by
4507 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4509 workqueue.debug_force_rr_cpu
4510 Workqueue used to implicitly guarantee that work
4511 items queued without explicit CPU specified are put
4512 on the local CPU. This guarantee is no longer true
4513 and while local CPU is still preferred work items
4514 may be put on foreign CPUs. This debug option
4515 forces round-robin CPU selection to flush out
4516 usages which depend on the now broken guarantee.
4517 When enabled, memory and cache locality will be
4520 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4521 default x2apic cluster mode on platforms
4524 x86_intel_mid_timer= [X86-32,APBT]
4525 Choose timer option for x86 Intel MID platform.
4526 Two valid options are apbt timer only and lapic timer
4527 plus one apbt timer for broadcast timer.
4528 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4530 xen_512gb_limit [KNL,X86-64,XEN]
4531 Restricts the kernel running paravirtualized under Xen
4532 to use only up to 512 GB of RAM. The reason to do so is
4533 crash analysis tools and Xen tools for doing domain
4534 save/restore/migration must be enabled to handle larger
4537 xen_emul_unplug= [HW,X86,XEN]
4538 Unplug Xen emulated devices
4539 Format: [unplug0,][unplug1]
4540 ide-disks -- unplug primary master IDE devices
4541 aux-ide-disks -- unplug non-primary-master IDE devices
4542 nics -- unplug network devices
4543 all -- unplug all emulated devices (NICs and IDE disks)
4544 unnecessary -- unplugging emulated devices is
4545 unnecessary even if the host did not respond to
4547 never -- do not unplug even if version check succeeds
4549 xen_nopvspin [X86,XEN]
4550 Disables the ticketlock slowpath using Xen PV
4554 Disables the PV optimizations forcing the HVM guest to
4555 run as generic HVM guest with no PV drivers.
4557 xirc2ps_cs= [NET,PCMCIA]
4559 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4561 ______________________________________________________________________
4565 Add more DRM drivers.
projects / platform / kernel / linux-rpi.git / blob