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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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3
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
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20Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
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26This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
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33The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
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37
38 ACPI ACPI support is enabled.
c99c108a 39 AGP AGP (Accelerated Graphics Port) is enabled.
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40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
e7ba176b 43 AVR32 AVR32 architecture is enabled.
1da177e4 44 AX25 Appropriate AX.25 support is enabled.
0ae53640 45 BLACKFIN Blackfin architecture is enabled.
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46 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
47 EFI EFI Partitioning (GPT) is enabled
48 EIDE EIDE/ATAPI support is enabled.
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49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
1da177e4 51 FB The frame buffer device is enabled.
2521f2c2 52 GCOV GCOV profiling is enabled.
1da177e4 53 HW Appropriate hardware is enabled.
1da177e4 54 IA-64 IA-64 architecture is enabled.
6146f0d5 55 IMA Integrity measurement architecture is enabled.
1da177e4 56 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
b0f83b28 58 IPV6 IPv6 support is enabled.
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59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
84c08fd6 62 KGDB Kernel debugger support is enabled.
fef07aae 63 KVM Kernel Virtual Machine support is enabled.
11ef697b 64 LIBATA Libata driver is enabled
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65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
309e57df 73 MSI Message Signaled Interrupts (PCI).
c8facbb6 74 MTD MTD (Memory Technology Device) support is enabled.
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75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
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79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
7f785763 83 PCIE PCI Express support is enabled.
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84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
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92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
20510f2f 94 SECURITY Different security models are enabled.
1da177e4 95 SELINUX SELinux support is enabled.
c1c124e9 96 APPARMOR AppArmor support is enabled.
1da177e4 97 SERIAL Serial support is enabled.
e523d93c 98 SH SuperH architecture is enabled.
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99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
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101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
f38f1d2a 103 FTRACE Function tracing enabled.
225a9be2 104 TPM TPM drivers are enabled.
1da177e4 105 TS Appropriate touchscreen support is enabled.
d4f373e5 106 UMS USB Mass Storage support is enabled.
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107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 114 X86-32 X86-32, aka i386 architecture is enabled.
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115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
71cced6e 117 Documentation/x86/x86_64/boot-options.txt .
c0115606 118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
c1c5413a 119 XEN Xen support is enabled
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120
121In addition, the following text indicates that the option:
122
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
126
127Parameters denoted with BOOT are actually interpreted by the boot
128loader, and have no meaning to the kernel directly.
129Do not modify the syntax of boot loader parameters without extreme
954a8b81 130need or coordination with <Documentation/x86/boot.txt>.
1da177e4 131
5558870b 132There are also arch-specific kernel-parameters not documented here.
71cced6e 133See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 134
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135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136a trailing = on the name of any parameter states that that parameter will
137be entered as an environment variable, whereas its absence indicates that
138it will appear as a kernel argument readable via /proc/cmdline by programs
139running once the system is up.
140
9c4751fd 141The number of kernel parameters is not limited, but the length of the
142complete command line (parameters including spaces etc.) is limited to
143a fixed number of characters. This limit depends on the architecture
144and is between 256 and 4096 characters. It is defined in the file
145./include/asm/setup.h as COMMAND_LINE_SIZE.
146
147
6cececfc 148 acpi= [HW,ACPI,X86]
03d926f8 149 Advanced Configuration and Power Interface
68ca4069 150 Format: { force | off | strict | noirq | rsdt }
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151 force -- enable ACPI if default was off
152 off -- disable ACPI if default was on
153 noirq -- do not use ACPI for IRQ routing
a9913044 154 strict -- Be less tolerant of platforms that are not
1da177e4 155 strictly ACPI specification compliant.
237889bf 156 rsdt -- prefer RSDT over (default) XSDT
aa2110cb 157 copy_dsdt -- copy DSDT to memory
1da177e4 158
53471121 159 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 160
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161 acpi_apic_instance= [ACPI, IOAPIC]
162 Format: <int>
163 2: use 2nd APIC table, if available
164 1,0: use 1st APIC table
4e381a4f 165 default: 0
a1fdcc0d 166
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167 acpi_backlight= [HW,ACPI]
168 acpi_backlight=vendor
169 acpi_backlight=video
170 If set to vendor, prefer vendor specific driver
171 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
172 of the ACPI video.ko driver.
173
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174 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
175 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 176 Format: <int>
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177 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
178 debug output. Bits in debug_layer correspond to a
179 _COMPONENT in an ACPI source file, e.g.,
180 #define _COMPONENT ACPI_PCI_COMPONENT
181 Bits in debug_level correspond to a level in
182 ACPI_DEBUG_PRINT statements, e.g.,
183 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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184 The debug_level mask defaults to "info". See
185 Documentation/acpi/debug.txt for more information about
186 debug layers and levels.
a0d84a92 187
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188 Enable processor driver info messages:
189 acpi.debug_layer=0x20000000
190 Enable PCI/PCI interrupt routing info messages:
191 acpi.debug_layer=0x400000
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192 Enable AML "Debug" output, i.e., stores to the Debug
193 object while interpreting AML:
194 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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195 Enable all messages related to ACPI hardware:
196 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197
198 Some values produce so much output that the system is
199 unusable. The "log_buf_len" parameter may be useful
200 if you need to capture more output.
f989106c 201
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202 acpi_display_output= [HW,ACPI]
203 acpi_display_output=vendor
204 acpi_display_output=video
205 See above.
206
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
209 default in APIC mode
210
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
213 default in PIC mode
214
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
217
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 use by PCI
220 Format: <irq>,<irq>...
221
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
226
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
231
6cececfc 232 acpi_pm_good [X86]
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233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
236
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237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
239
240 acpi_serialize [HW,ACPI] force serialization of AML methods
241
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
245
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
d7f0eea9 248 old_ordering, s4_nonvs, sci_force_enable }
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249 See Documentation/power/video.txt for information on
250 s3_bios and s3_mode.
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
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259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
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261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
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264
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
268
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269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
284
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285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
287
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288 agp= [AGP]
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
293
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294 ALSA [HW,ALSA]
295 See Documentation/sound/alsa/alsa-parameters.txt
296
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297 alignment= [KNL,ARM]
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
301
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302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
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305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
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309 off - do not initialize any AMD IOMMU found in
310 the system
afa9fdc2 311
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312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
314 Format: <a>,<b>
315 See also Documentation/kernel/input/joystick.txt
316
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
321
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322 apc= [HW,SPARC]
323 Power management functions (SPARCstation-4/5 + deriv.)
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324 Format: noidle
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
328
ca1eda2d 329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 330 Change the output verbosity whilst booting
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331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
a9913044 334
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335 autoconf= [IPV6]
336 See Documentation/networking/ipv6.txt.
337
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338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
346
1da177e4 347 apm= [APM] Advanced Power Management
71f77055 348 See header of arch/x86/kernel/apm_32.c.
1da177e4 349
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350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
352
353 ataflop= [HW,M68k]
354
355 atarimouse= [HW,MOUSE] Atari Mouse
356
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357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
359
360 atkbd.reset= [HW] Reset keyboard during initialization
361
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362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
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364
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
366 keyboards
367
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
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370
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
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373
374 autotest [IA64]
375
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376 baycom_epp= [HW,AX25]
377 Format: <io>,<mode>
a9913044 378
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379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380 Format: <io>,<mode>
381 See header of drivers/net/hamradio/baycom_par.c.
382
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383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
387
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388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
392
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393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
395 no delay (0).
396 Format: integer
397
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398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
399
1da177e4 400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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401 bttv.radio= Most important insmod options are available as
402 kernel args too.
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403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405
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406 c101= [NET] Moxa C101 synchronous serial card
407
cd4f0ef7 408 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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409 Sometimes CPU hardware bugs make them report the cache
410 size incorrectly. The kernel will attempt work arounds
411 to fix known problems, but for some CPUs it is not
412 possible to determine what the correct size should be.
413 This option provides an override for these situations.
414
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415 capability.disable=
416 [SECURITY] Disable capabilities. This would normally
417 be used only if an alternative security model is to be
418 configured. Potentially dangerous and should only be
419 used if you are entirely sure of the consequences.
420
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421 ccw_timeout_log [S390]
422 See Documentation/s390/CommonIO for details.
1da177e4 423
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424 cgroup_disable= [KNL] Disable a particular controller
425 Format: {name of the controller(s) to disable}
426 {Currently supported controllers - "memory"}
427
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428 checkreqprot [SELINUX] Set initial checkreqprot flag value.
429 Format: { "0" | "1" }
430 See security/selinux/Kconfig help text.
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431 0 -- check protection applied by kernel (includes
432 any implied execute protection).
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433 1 -- check protection requested by application.
434 Default value is set via a kernel config option.
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435 Value can be changed at runtime via
436 /selinux/checkreqprot.
437
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438 cio_ignore= [S390]
439 See Documentation/s390/CommonIO for details.
440
cd4f0ef7 441 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 442 [Deprecated]
3f6dee9b 443 Forces specified clocksource (if available) to be used
734efb46 444 when calculating gettimeofday(). If specified
3f6dee9b 445 clocksource is not available, it defaults to PIT.
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446 Format: { pit | tsc | cyclone | pmtmr }
447
592913ec 448 clocksource= Override the default clocksource
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449 Format: <string>
450 Override the default clocksource and use the clocksource
451 with the name specified.
452 Some clocksource names to choose from, depending on
453 the platform:
454 [all] jiffies (this is the base, fallback clocksource)
455 [ACPI] acpi_pm
456 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
457 pxa_timer,timer3,32k_counter,timer0_1
458 [AVR32] avr32
9863c90f 459 [X86-32] pit,hpet,tsc;
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460 scx200_hrt on Geode; cyclone on IBM x440
461 [MIPS] MIPS
462 [PARISC] cr16
463 [S390] tod
464 [SH] SuperH
465 [SPARC64] tick
466 [X86-64] hpet,tsc
467
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468 clearcpuid=BITNUM [X86]
469 Disable CPUID feature X for the kernel. See
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470 arch/x86/include/asm/cpufeature.h for the valid bit
471 numbers. Note the Linux specific bits are not necessarily
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472 stable over kernel options, but the vendor specific
473 ones should be.
474 Also note that user programs calling CPUID directly
475 or using the feature without checking anything
476 will still see it. This just prevents it from
477 being used by the kernel or shown in /proc/cpuinfo.
478 Also note the kernel might malfunction if you disable
479 some critical bits.
480
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481 cmo_free_hint= [PPC] Format: { yes | no }
482 Specify whether pages are marked as being inactive
483 when they are freed. This is used in CMO environments
484 to determine OS memory pressure for page stealing by
485 a hypervisor.
486 Default: yes
487
6cececfc 488 code_bytes [X86] How many bytes of object code to print
a25bd949 489 in an oops report.
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490 Range: 0 - 8192
491 Default: 64
492
1da177e4 493 com20020= [HW,NET] ARCnet - COM20020 chipset
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494 Format:
495 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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496
497 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
498 Format: <io>[,<irq>]
499
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500 com90xx= [HW,NET]
501 ARCnet - COM90xx chipset (memory-mapped buffers)
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502 Format: <io>[,<irq>[,<memstart>]]
503
504 condev= [HW,S390] console device
505 conmode=
a9913044 506
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507 console= [KNL] Output console device and options.
508
509 tty<n> Use the virtual console device <n>.
510
511 ttyS<n>[,options]
f1a1c2dc 512 ttyUSB0[,options]
1da177e4 513 Use the specified serial port. The options are of
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514 the form "bbbbpnf", where "bbbb" is the baud rate,
515 "p" is parity ("n", "o", or "e"), "n" is number of
516 bits, and "f" is flow control ("r" for RTS or
517 omit it). Default is "9600n8".
518
519 See Documentation/serial-console.txt for more
520 information. See
521 Documentation/networking/netconsole.txt for an
522 alternative.
1da177e4 523
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524 uart[8250],io,<addr>[,options]
525 uart[8250],mmio,<addr>[,options]
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526 Start an early, polled-mode console on the 8250/16550
527 UART at the specified I/O port or MMIO address,
528 switching to the matching ttyS device later. The
529 options are the same as for ttyS, above.
530
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531 If the device connected to the port is not a TTY but a braille
532 device, prepend "brl," before the device type, for instance
533 console=brl,ttyS0
534 For now, only VisioBraille is supported.
535
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536 consoleblank= [KNL] The console blank (screen saver) timeout in
537 seconds. Defaults to 10*60 = 10mins. A value of 0
538 disables the blank timer.
539
4cb0e11b
HK
540 coredump_filter=
541 [KNL] Change the default value for
542 /proc/<pid>/coredump_filter.
543 See also Documentation/filesystems/proc.txt.
544
1da177e4 545 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
546 Format:
547 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 548
dc009d92
EB
549 crashkernel=nn[KMG]@ss[KMG]
550 [KNL] Reserve a chunk of physical memory to
551 hold a kernel to switch to with kexec on panic.
552
fb391599
BW
553 crashkernel=range1:size1[,range2:size2,...][@offset]
554 [KNL] Same as above, but depends on the memory
555 in the running system. The syntax of range is
556 start-[end] where start and end are both
557 a memory unit (amount[KMG]). See also
558 Documentation/kdump/kdump.txt for a example.
559
1da177e4
LT
560 cs89x0_dma= [HW,NET]
561 Format: <dma>
562
563 cs89x0_media= [HW,NET]
564 Format: { rj45 | aui | bnc }
a9913044 565
a9913044 566 dasd= [HW,NET]
1da177e4
LT
567 See header of drivers/s390/block/dasd_devmap.c.
568
569 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
570 (one device per port)
571 Format: <port#>,<type>
572 See also Documentation/input/joystick-parport.txt
573
a648ec05
TR
574 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
575 time. See Documentation/dynamic-debug-howto.txt for
576 details.
577
1da177e4
LT
578 debug [KNL] Enable kernel debugging (events log level).
579
cae2ed9a
IM
580 debug_locks_verbose=
581 [KNL] verbose self-tests
582 Format=<0|1>
583 Print debugging info while doing the locking API
584 self-tests.
585 We default to 0 (no extra messages), setting it to
586 1 will print _a lot_ more information - normally
587 only useful to kernel developers.
588
3ac7fe5a
TG
589 debug_objects [KNL] Enable object debugging
590
3e8ebb5c
KM
591 no_debug_objects
592 [KNL] Disable object debugging
593
d3af01f1
TG
594 debugpat [X86] Enable PAT debugging
595
2d27a966 596 decnet.addr= [HW,NET]
1da177e4
LT
597 Format: <area>[,<node>]
598 See also Documentation/networking/decnet.txt.
599
0cb55ad2
RD
600 default_hugepagesz=
601 [same as hugepagesz=] The size of the default
602 HugeTLB page size. This is the size represented by
603 the legacy /proc/ hugepages APIs, used for SHM, and
604 default size when mounting hugetlbfs filesystems.
605 Defaults to the default architecture's huge page size
606 if not specified.
55ff9780 607
1da177e4
LT
608 dhash_entries= [KNL]
609 Set number of hash buckets for dentry cache.
a9913044 610
1da177e4
LT
611 digi= [HW,SERIAL]
612 IO parameters + enable/disable command.
613
614 digiepca= [HW,SERIAL]
615 See drivers/char/README.epca and
31c00fc1 616 Documentation/serial/digiepca.txt.
1da177e4 617
b0f83b28
BH
618 disable= [IPV6]
619 See Documentation/networking/ipv6.txt.
620
621 disable_ipv6= [IPV6]
622 See Documentation/networking/ipv6.txt.
623
95ffa243 624 disable_mtrr_cleanup [X86]
95ffa243
YL
625 The kernel tries to adjust MTRR layout from continuous
626 to discrete, to make X server driver able to add WB
0cb55ad2 627 entry later. This parameter disables that.
95ffa243 628
093af8d7 629 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
630 By default the kernel will trim any uncacheable
631 memory out of your available memory pool based on
632 MTRR settings. This parameter disables that behavior,
633 possibly causing your machine to run very slowly.
634
6cececfc 635 disable_timer_pin_1 [X86]
0cb55ad2
RD
636 Disable PIN 1 of APIC timer
637 Can be useful to work around chipset bugs.
638
0cb55ad2
RD
639 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
640 this option disables the debugging code at boot.
641
642 dma_debug_entries=<number>
643 This option allows to tune the number of preallocated
644 entries for DMA-API debugging code. One entry is
645 required per DMA-API allocation. Use this if the
646 DMA-API debugging code disables itself because the
647 architectural default is too low.
648
1745de5e
JR
649 dma_debug_driver=<driver_name>
650 With this option the DMA-API debugging driver
651 filter feature can be enabled at boot time. Just
652 pass the driver to filter for as the parameter.
653 The filter can be disabled or changed to another
654 driver later using sysfs.
655
1da177e4
LT
656 dscc4.setup= [NET]
657
0cb55ad2
RD
658 dynamic_printk Enables pr_debug()/dev_dbg() calls if
659 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
660 These can also be switched on/off via
661 <debugfs>/dynamic_printk/modules
662
663 earlycon= [KNL] Output early console device and options.
664 uart[8250],io,<addr>[,options]
665 uart[8250],mmio,<addr>[,options]
1917ac76 666 uart[8250],mmio32,<addr>[,options]
0cb55ad2
RD
667 Start an early, polled-mode console on the 8250/16550
668 UART at the specified I/O port or MMIO address.
1917ac76
SG
669 MMIO inter-register address stride is either 8bit (mmio)
670 or 32bit (mmio32).
0cb55ad2
RD
671 The options are the same as for ttyS, above.
672
6cececfc 673 earlyprintk= [X86,SH,BLACKFIN]
1da177e4
LT
674 earlyprintk=vga
675 earlyprintk=serial[,ttySn[,baudrate]]
ea3acb19 676 earlyprintk=ttySn[,baudrate]
9780bc41 677 earlyprintk=dbgp[debugController#]
1da177e4 678
a9913044 679 Append ",keep" to not disable it when the real console
1da177e4
LT
680 takes over.
681
5c05917e 682 Only vga or serial or usb debug port at a time.
1da177e4
LT
683
684 Currently only ttyS0 and ttyS1 are supported.
685
686 Interaction with the standard serial driver is not
687 very good.
688
689 The VGA output is eventually overwritten by the real
690 console.
691
9731191f
JW
692 ekgdboc= [X86,KGDB] Allow early kernel console debugging
693 ekgdboc=kbd
694
695 This is desgined to be used in conjunction with
696 the boot argument: earlyprintk=vga
697
1da177e4 698 edd= [EDD]
8c4dd606 699 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 700
1da177e4
LT
701 eisa_irq_edge= [PARISC,HW]
702 See header of drivers/parisc/eisa.c.
703
cd4f0ef7 704 elanfreq= [X86-32]
1da177e4 705 See comment before function elanfreq_setup() in
71f77055 706 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
707
708 elevator= [IOSCHED]
16ab3adf 709 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
710 See Documentation/block/as-iosched.txt and
711 Documentation/block/deadline-iosched.txt for details.
712
6cececfc 713 elfcorehdr= [IA64,PPC,SH,X86]
a9913044 714 Specifies physical address of start of kernel core
aac04b32
VG
715 image elf header. Generally kexec loader will
716 pass this option to capture kernel.
717 See Documentation/kdump/kdump.txt for details.
1da177e4 718
0cb55ad2
RD
719 enable_mtrr_cleanup [X86]
720 The kernel tries to adjust MTRR layout from continuous
721 to discrete, to make X server driver able to add WB
722 entry later. This parameter enables that.
723
ca1eda2d 724 enable_timer_pin_1 [X86]
0cb55ad2
RD
725 Enable PIN 1 of APIC timer
726 Can be useful to work around chipset bugs
727 (in particular on some ATI chipsets).
728 The kernel tries to set a reasonable default.
729
1da177e4
LT
730 enforcing [SELINUX] Set initial enforcing status.
731 Format: {"0" | "1"}
732 See security/selinux/Kconfig help text.
733 0 -- permissive (log only, no denials).
734 1 -- enforcing (deny and log).
735 Default value is 0.
736 Value can be changed at runtime via /selinux/enforce.
737
a08f82d0
HY
738 erst_disable [ACPI]
739 Disable Error Record Serialization Table (ERST)
740 support.
741
1da177e4
LT
742 ether= [HW,NET] Ethernet cards parameters
743 This option is obsoleted by the "netdev=" option, which
744 has equivalent usage. See its documentation for details.
745
de1ba09b
AM
746 failslab=
747 fail_page_alloc=
748 fail_make_request=[KNL]
749 General fault injection mechanism.
750 Format: <interval>,<probability>,<space>,<times>
751 See also /Documentation/fault-injection/.
752
1da177e4 753 floppy= [HW]
31c00fc1 754 See Documentation/blockdev/floppy.txt.
1da177e4 755
f13ae30e
AC
756 force_pal_cache_flush
757 [IA-64] Avoid check_sal_cache_flush which may hang on
758 buggy SAL_CACHE_FLUSH implementations. Using this
759 parameter will force ia64_sal_cache_flush to call
760 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
761
d9e54076 762 ftrace=[tracer]
2af15d6a 763 [FTRACE] will set and start the specified tracer
d9e54076
PZ
764 as early as possible in order to facilitate early
765 boot debugging.
766
cecbca96 767 ftrace_dump_on_oops[=orig_cpu]
2af15d6a 768 [FTRACE] will dump the trace buffers on oops.
cecbca96
FW
769 If no parameter is passed, ftrace will dump
770 buffers of all CPUs, but if you pass orig_cpu, it will
771 dump only the buffer of the CPU that triggered the
772 oops.
2af15d6a
SR
773
774 ftrace_filter=[function-list]
775 [FTRACE] Limit the functions traced by the function
776 tracer at boot up. function-list is a comma separated
777 list of functions. This list can be changed at run
778 time by the set_ftrace_filter file in the debugfs
779 tracing directory.
780
781 ftrace_notrace=[function-list]
782 [FTRACE] Do not trace the functions specified in
783 function-list. This list can be changed at run time
784 by the set_ftrace_notrace file in the debugfs
785 tracing directory.
d9e54076 786
369bc18f
SA
787 ftrace_graph_filter=[function-list]
788 [FTRACE] Limit the top level callers functions traced
789 by the function graph tracer at boot up.
790 function-list is a comma separated list of functions
791 that can be changed at run time by the
792 set_graph_function file in the debugfs tracing directory.
793
1da177e4
LT
794 gamecon.map[2|3]=
795 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
796 support via parallel port (up to 5 devices per port)
797 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
798 See also Documentation/input/joystick-parport.txt
799
800 gamma= [HW,DRM]
801
aaf23042
YL
802 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
803 Format: off | on
804 default: on
805
2521f2c2
PO
806 gcov_persist= [GCOV] When non-zero (default), profiling data for
807 kernel modules is saved and remains accessible via
808 debugfs, even when the module is unloaded/reloaded.
809 When zero, profiling data is discarded and associated
810 debugfs files are removed at module unload time.
811
1da177e4
LT
812 gpt [EFI] Forces disk with valid GPT signature but
813 invalid Protective MBR to be treated as GPT.
814
1da177e4
LT
815 hashdist= [KNL,NUMA] Large hashes allocated during boot
816 are distributed across NUMA nodes. Defaults on
429aa0fc 817 for 64bit NUMA, off otherwise.
a9913044 818 Format: 0 | 1 (for off | on)
1da177e4
LT
819
820 hcl= [IA-64] SGI's Hardware Graph compatibility layer
821
822 hd= [EIDE] (E)IDE hard drive subsystem geometry
823 Format: <cyl>,<head>,<sect>
824
ea8c071c
HY
825 hest_disable [ACPI]
826 Disable Hardware Error Source Table (HEST) support;
827 corresponding firmware-first mode error processing
828 logic will be disabled.
829
1da177e4
LT
830 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
831 size of <nn>. This works even on boxes that have no
832 highmem otherwise. This also works to reduce highmem
833 size on bigger boxes.
834
54cdfdb4
TG
835 highres= [KNL] Enable/disable high resolution timer mode.
836 Valid parameters: "on", "off"
837 Default: "on"
838
1da177e4
LT
839 hisax= [HW,ISDN]
840 See Documentation/isdn/README.HiSax.
841
0cb55ad2
RD
842 hlt [BUGS=ARM,SH]
843
844 hpet= [X86-32,HPET] option to control HPET usage
845 Format: { enable (default) | disable | force |
846 verbose }
847 disable: disable HPET and use PIT instead
848 force: allow force enabled of undocumented chips (ICH4,
849 VIA, nVidia)
850 verbose: show contents of HPET registers during setup
851
b4718e62
AK
852 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
853 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
854 On x86-64 and powerpc, this option can be specified
855 multiple times interleaved with hugepages= to reserve
856 huge pages of different sizes. Valid pages sizes on
857 x86-64 are 2M (when the CPU supports "pse") and 1G
858 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
859 Note that 1GB pages can only be allocated at boot time
860 using hugepages= and not freed afterwards.
6902aa84 861
555d61d6
HB
862 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
863 terminal devices. Valid values: 0..8
431429ff
HB
864 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
865 If specified, z/VM IUCV HVC accepts connections
866 from listed z/VM user IDs only.
cef7125d 867
3a853fb9 868 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
869 or register an additional I2C bus that is not
870 registered from board initialization code.
3a853fb9
JN
871 Format:
872 <bus_id>,<clkrate>
873
36d95739 874 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 875 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
876 i8042.dumbkbd [HW] Pretend that controller can only read data from
877 keyboard and cannot control its state
1da177e4
LT
878 (Don't attempt to blink the leds)
879 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 880 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
881 i8042.noloop [HW] Disable the AUX Loopback command while probing
882 for the AUX port
1da177e4
LT
883 i8042.nomux [HW] Don't check presence of an active multiplexing
884 controller
885 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
886 controllers
1da177e4
LT
887 i8042.reset [HW] Reset the controller during init and cleanup
888 i8042.unlock [HW] Unlock (ignore) the keylock
889
890 i810= [HW,DRM]
891
e70c9d5e
DT
892 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
893 indicates that the driver is running on unsupported
894 hardware.
1da177e4
LT
895 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
896 does not match list of supported models.
897 i8k.power_status
898 [HW] Report power status in /proc/i8k
899 (disabled by default)
900 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
901 capability is set.
902
1da177e4
LT
903 icn= [HW,ISDN]
904 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
905
0af80c04
DF
906 ide-core.nodma= [HW] (E)IDE subsystem
907 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
075affcb
BZ
908 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
909 .cdrom .chs .ignore_cable are additional options
1c10e938 910 See Documentation/ide/ide.txt.
1da177e4 911
0cb55ad2
RD
912 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
913 Claim all unknown PCI IDE storage controllers.
914
f039b754 915 idle= [X86]
ada9cfdd
RD
916 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
917 Poll forces a polling idle loop that can slightly
918 improve the performance of waking up a idle CPU, but
919 will use a lot of power and make the system run hot.
920 Not recommended.
921 idle=mwait: On systems which support MONITOR/MWAIT but
922 the kernel chose to not use it because it doesn't save
923 as much power as a normal idle loop, use the
924 MONITOR/MWAIT idle loop anyways. Performance should be
925 the same as idle=poll.
926 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 927 In such case C2/C3 won't be used again.
ada9cfdd 928 idle=nomwait: Disable mwait for CPU C-states
a9913044 929
79290822
IM
930 ignore_loglevel [KNL]
931 Ignore loglevel setting - this will print /all/
932 kernel messages to the console. Useful for debugging.
933
1da177e4
LT
934 ihash_entries= [KNL]
935 Set number of hash buckets for inode cache.
936
3323eec9
MZ
937 ima_audit= [IMA]
938 Format: { "0" | "1" }
939 0 -- integrity auditing messages. (Default)
940 1 -- enable informational integrity auditing messages.
941
942 ima_hash= [IMA]
a9ed83a5 943 Format: { "sha1" | "md5" }
3323eec9
MZ
944 default: "sha1"
945
5789ba3b
EP
946 ima_tcb [IMA]
947 Load a policy which meets the needs of the Trusted
948 Computing Base. This means IMA will measure all
949 programs exec'd, files mmap'd for exec, and all files
950 opened for read by uid=0.
951
1da177e4
LT
952 init= [KNL]
953 Format: <full_path>
954 Run specified binary instead of /sbin/init as init
955 process.
956
957 initcall_debug [KNL] Trace initcalls as they are executed. Useful
958 for working out where the kernel is dying during
959 startup.
960
961 initrd= [BOOT] Specify the location of the initial ramdisk
962
963 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
964 Format: <irq>
965
ba395927 966 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
967 on
968 Enable intel iommu driver.
ba395927
KA
969 off
970 Disable intel iommu driver.
971 igfx_off [Default Off]
972 By default, gfx is mapped as normal device. If a gfx
973 device has a dedicated DMAR unit, the DMAR unit is
974 bypassed by not enabling DMAR with this option. In
975 this case, gfx device will use physical address for
976 DMA.
7d3b03ce
KA
977 forcedac [x86_64]
978 With this option iommu will not optimize to look
979 for io virtual address below 32 bit forcing dual
980 address cycle on pci bus for cards supporting greater
981 than 32 bit addressing. The default is to look
982 for translation below 32 bit and if not available
983 then look in the higher range.
5e0d2a6f 984 strict [Default Off]
985 With this option on every unmap_single operation will
986 result in a hardware IOTLB flush operation as opposed
987 to batching them for performance.
ba395927 988
d1423d56
CW
989 intremap= [X86-64, Intel-IOMMU]
990 Format: { on (default) | off | nosid }
991 on enable Interrupt Remapping (default)
992 off disable Interrupt Remapping
993 nosid disable Source ID checking
994
0cb55ad2
RD
995 inttest= [IA64]
996
997 iomem= Disable strict checking of access to MMIO memory
998 strict regions from userspace.
999 relaxed
1000
1001 iommu= [x86]
1002 off
1003 force
1004 noforce
1005 biomerge
1006 panic
1007 nopanic
1008 merge
1009 nomerge
1010 forcesac
1011 soft
4ed0d3e6 1012 pt [x86, IA64]
0cb55ad2
RD
1013
1014 io7= [HW] IO7 for Marvel based alpha systems
1015 See comment before marvel_specify_io7 in
1016 arch/alpha/kernel/core_marvel.c.
1017
6cececfc 1018 io_delay= [X86] I/O delay method
6e7c4025
IM
1019 0x80
1020 Standard port 0x80 based delay
1021 0xed
1022 Alternate port 0xed based delay (needed on some systems)
b02aae9c 1023 udelay
6e7c4025
IM
1024 Simple two microseconds delay
1025 none
1026 No delay
b02aae9c 1027
1da177e4 1028 ip= [IP_PNP]
dc7a0816 1029 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1030
1031 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
1032 See comment before ip2_setup() in
1033 drivers/char/ip2/ip2base.c.
1da177e4 1034
200803df
AC
1035 irqfixup [HW]
1036 When an interrupt is not handled search all handlers
1037 for it. Intended to get systems with badly broken
1038 firmware running.
1039
1040 irqpoll [HW]
1041 When an interrupt is not handled search all handlers
1042 for it. Also check all handlers each timer
1043 interrupt. Intended to get systems with badly broken
1044 firmware running.
1045
1da177e4 1046 isapnp= [ISAPNP]
a9913044 1047 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1048
1049 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1050 Format:
1051 <cpu number>,...,<cpu number>
1052 or
b225d44e
LZ
1053 <cpu number>-<cpu number>
1054 (must be a positive range in ascending order)
22f2e280
DF
1055 or a mixture
1056 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1057
1da177e4
LT
1058 This option can be used to specify one or more CPUs
1059 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1060 algorithms. You can move a process onto or off an
1061 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1062 <cpu number> begins at 0 and the maximum value is
1063 "number of CPUs in system - 1".
1064
1065 This option is the preferred way to isolate CPUs. The
a9913044
RD
1066 alternative -- manually setting the CPU mask of all
1067 tasks in the system -- can cause problems and
1068 suboptimal load balancer performance.
1da177e4 1069
a9913044 1070 iucv= [HW,NET]
1da177e4
LT
1071
1072 js= [HW,JOY] Analog joystick
1073 See Documentation/input/joystick.txt.
1074
0cb55ad2
RD
1075 keepinitrd [HW,ARM]
1076
6cececfc 1077 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1078 specifies the amount of memory usable by the kernel
1079 for non-movable allocations. The requested amount is
1080 spread evenly throughout all nodes in the system. The
1081 remaining memory in each node is used for Movable
1082 pages. In the event, a node is too small to have both
1083 kernelcore and Movable pages, kernelcore pages will
1084 take priority and other nodes will have a larger number
1085 of kernelcore pages. The Movable zone is used for the
1086 allocation of pages that may be reclaimed or moved
1087 by the page migration subsystem. This means that
1088 HugeTLB pages may not be allocated from this zone.
1089 Note that allocations like PTEs-from-HighMem still
1090 use the HighMem zone if it exists, and the Normal
1091 zone if it does not.
1092
4fe1da4e
JW
1093 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1094 Format: <Controller#>[,poll interval]
1095 The controller # is the number of the ehci usb debug
1096 port as it is probed via PCI. The poll interval is
1097 optional and is the number seconds in between
1098 each poll cycle to the debug port in case you need
1099 the functionality for interrupting the kernel with
1100 gdb or control-c on the dbgp connection. When
1101 not using this parameter you use sysrq-g to break into
1102 the kernel debugger.
1103
84c08fd6 1104 kgdboc= [KGDB,HW] kgdb over consoles.
ada64e4c
JW
1105 Requires a tty driver that supports console polling,
1106 or a supported polling keyboard driver (non-usb).
65b5ac14
JW
1107 Serial only format: <serial_device>[,baud]
1108 keyboard only format: kbd
1109 keyboard and serial format: kbd,<serial_device>[,baud]
1110 Optional Kernel mode setting:
1111 kms, kbd format: kms,kbd
1112 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
6cdf6e06 1113
84c08fd6
JW
1114 kgdbwait [KGDB] Stop kernel execution and enter the
1115 kernel debugger at the earliest opportunity.
1116
9bed90c6
FF
1117 kmac= [MIPS] korina ethernet MAC address.
1118 Configure the RouterBoard 532 series on-chip
1119 Ethernet adapter MAC address.
1120
04f70336
CM
1121 kmemleak= [KNL] Boot-time kmemleak enable/disable
1122 Valid arguments: on, off
1123 Default: on
1124
6cececfc 1125 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1126 in oops dumps.
1127
fef07aae
AP
1128 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1129 Default is 0 (don't ignore, but inject #GP)
1130
1131 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1132 Default is 1 (enabled)
1133
a182d873
XG
1134 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1135 KVM MMU at runtime.
fef07aae
AP
1136 Default is 0 (off)
1137
fef07aae 1138 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
8475f94a 1139 Default is 1 (enabled)
fef07aae
AP
1140
1141 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1142 for all guests.
1143 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1144
1145 kvm-intel.bypass_guest_pf=
1146 [KVM,Intel] Disables bypassing of guest page faults
1147 on Intel chips. Default is 1 (enabled)
1148
1149 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1150 (virtualized MMU) support on capable Intel chips.
1151 Default is 1 (enabled)
1152
1153 kvm-intel.emulate_invalid_guest_state=
1154 [KVM,Intel] Enable emulation of invalid guest states
1155 Default is 0 (disabled)
1156
1157 kvm-intel.flexpriority=
1158 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1159 Default is 1 (enabled)
1160
1161 kvm-intel.unrestricted_guest=
1162 [KVM,Intel] Disable unrestricted guest feature
1163 (virtualized real and unpaged mode) on capable
1164 Intel chips. Default is 1 (enabled)
1165
1166 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1167 feature (tagged TLBs) on capable Intel chips.
1168 Default is 1 (enabled)
1169
1da177e4
LT
1170 l2cr= [PPC]
1171
a78bfbfc
RB
1172 l3cr= [PPC]
1173
cd4f0ef7 1174 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1175 disabled it.
1da177e4 1176
6cececfc 1177 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1178 in C2 power state.
e585bef8 1179
fcb71f6f
FC
1180 libata.dma= [LIBATA] DMA control
1181 libata.dma=0 Disable all PATA and SATA DMA
1182 libata.dma=1 PATA and SATA Disk DMA only
1183 libata.dma=2 ATAPI (CDROM) DMA only
1184 libata.dma=4 Compact Flash DMA only
1185 Combinations also work, so libata.dma=3 enables DMA
1186 for disks and CDROMs, but not CFs.
20308871
MP
1187
1188 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1189 libata.ignore_hpa=0 keep BIOS limits (default)
1190 libata.ignore_hpa=1 ignore limits, using full disk
fcb71f6f 1191
78e70c23
DJ
1192 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1193 when set.
1194 Format: <int>
1195
33267325
TH
1196 libata.force= [LIBATA] Force configurations. The format is comma
1197 separated list of "[ID:]VAL" where ID is
4c44f309 1198 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
33267325
TH
1199 matching port, link or device. Basically, it matches
1200 the ATA ID string printed on console by libata. If
1201 the whole ID part is omitted, the last PORT and DEVICE
1202 values are used. If ID hasn't been specified yet, the
1203 configuration applies to all ports, links and devices.
1204
1205 If only DEVICE is omitted, the parameter applies to
1206 the port and all links and devices behind it. DEVICE
1207 number of 0 either selects the first device or the
1208 first fan-out link behind PMP device. It does not
1209 select the host link. DEVICE number of 15 selects the
1210 host link and device attached to it.
1211
1212 The VAL specifies the configuration to force. As long
1213 as there's no ambiguity shortcut notation is allowed.
1214 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1215 The following configurations can be forced.
1216
1217 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1218 Any ID with matching PORT is used.
1219
1220 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1221
1222 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1223 udma[/][16,25,33,44,66,100,133] notation is also
1224 allowed.
1225
1226 * [no]ncq: Turn on or off NCQ.
1227
05944bdf
TH
1228 * nohrst, nosrst, norst: suppress hard, soft
1229 and both resets.
1230
43c9c591
TH
1231 * dump_id: dump IDENTIFY data.
1232
33267325
TH
1233 If there are multiple matching configurations changing
1234 the same attribute, the last one is used.
1235
95f72d1e 1236 memblock=debug [KNL] Enable memblock debug messages.
7c4be253 1237
1da177e4 1238 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1239 See Documentation/blockdev/ramdisk.txt.
1da177e4 1240
a6b25b67
RD
1241 lockd.nlm_grace_period=P [NFS] Assign grace period.
1242 Format: <integer>
1da177e4 1243
a6b25b67
RD
1244 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1245 Format: <integer>
1246
1247 lockd.nlm_timeout=T [NFS] Assign timeout value.
1248 Format: <integer>
1249
1250 lockd.nlm_udpport=M [NFS] Assign UDP port.
1251 Format: <integer>
1da177e4
LT
1252
1253 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1254 Format: <irq>
1255
1256 loglevel= All Kernel Messages with a loglevel smaller than the
1257 console loglevel will be printed to the console. It can
1258 also be changed with klogd or other programs. The
1259 loglevels are defined as follows:
1260
1261 0 (KERN_EMERG) system is unusable
1262 1 (KERN_ALERT) action must be taken immediately
1263 2 (KERN_CRIT) critical conditions
1264 3 (KERN_ERR) error conditions
1265 4 (KERN_WARNING) warning conditions
1266 5 (KERN_NOTICE) normal but significant condition
1267 6 (KERN_INFO) informational
1268 7 (KERN_DEBUG) debug-level messages
1269
1270 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1271 Format: { n | nk | nM }
1272 n must be a power of two. The default size
1273 is set in the kernel config file.
1da177e4 1274
accaa24c
RD
1275 logo.nologo [FB] Disables display of the built-in Linux logo.
1276 This may be used to provide more screen space for
1277 kernel log messages and is useful when debugging
1278 kernel boot problems.
1279
1da177e4
LT
1280 lp=0 [LP] Specify parallel ports to use, e.g,
1281 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1282 lp=reset first parallel port). 'lp=0' disables the
1283 lp=auto printer driver. 'lp=reset' (which can be
1284 specified in addition to the ports) causes
1285 attached printers to be reset. Using
1286 lp=port1,port2,... specifies the parallel ports
1287 to associate lp devices with, starting with
1288 lp0. A port specification may be 'none' to skip
1289 that lp device, or a parport name such as
1290 'parport0'. Specifying 'lp=auto' instead of a
1291 port specification list means that device IDs
1292 from each port should be examined, to see if
1293 an IEEE 1284-compliant printer is attached; if
1294 so, the driver will manage that printer.
1295 See also header of drivers/char/lp.c.
1296
1297 lpj=n [KNL]
1298 Sets loops_per_jiffy to given constant, thus avoiding
1299 time-consuming boot-time autodetection (up to 250 ms per
1300 CPU). 0 enables autodetection (default). To determine
1301 the correct value for your kernel, boot with normal
1302 autodetection and see what value is printed. Note that
1303 on SMP systems the preset will be applied to all CPUs,
1304 which is likely to cause problems if your CPUs need
1305 significantly divergent settings. An incorrect value
1306 will cause delays in the kernel to be wrong, leading to
1307 unpredictable I/O errors and other breakage. Although
1308 unlikely, in the extreme case this might damage your
1309 hardware.
1310
1311 ltpc= [NET]
1312 Format: <io>,<irq>,<dma>
1313
a9913044
RD
1314 machvec= [IA64] Force the use of a particular machine-vector
1315 (machvec) in a generic kernel.
1316 Example: machvec=hpzx1_swiotlb
1da177e4 1317
3209e70e
WZ
1318 machtype= [Loongson] Share the same kernel image file between different
1319 yeeloong laptop.
1320 Example: machtype=lemote-yeeloong-2f-7inch
1321
0cb55ad2
RD
1322 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1323 than or equal to this physical address is ignored.
1da177e4
LT
1324
1325 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1326 should make use of. maxcpus=n : n >= 0 limits the
1327 kernel to using 'n' processors. n=0 is a special case,
1328 it is equivalent to "nosmp", which also disables
1329 the IO APIC.
1da177e4 1330
0cb55ad2
RD
1331 max_loop= [LOOP] Maximum number of loopback devices that can
1332 be mounted
1333 Format: <1-256>
2b2c3750 1334
1da177e4
LT
1335 mcatest= [IA-64]
1336
cd4f0ef7 1337 mce [X86-32] Machine Check Exception
1da177e4 1338
71cced6e 1339 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1340
1da177e4
LT
1341 md= [HW] RAID subsystems devices and level
1342 See Documentation/md.txt.
a9913044 1343
1da177e4
LT
1344 mdacon= [MDA]
1345 Format: <first>,<last>
1346 Specifies range of consoles to be captured by the MDA.
a9913044 1347
1da177e4
LT
1348 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1349 Amount of memory to be used when the kernel is not able
1350 to see the whole system memory or for test.
cd4f0ef7 1351 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1352 address space collisions. Without memmap= PCI devices
1353 could be placed at addresses belonging to unused RAM.
1354
cd4f0ef7 1355 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1356 memory.
1357
6902aa84
PM
1358 memchunk=nn[KMG]
1359 [KNL,SH] Allow user to override the default size for
1360 per-device physically contiguous DMA buffers.
1361
6cececfc 1362 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1363 E820 memory map, as specified by the user.
1364 Such memmap=exactmap lines can be constructed based on
1365 BIOS output or other requirements. See the memmap=nn@ss
1366 option description.
1367
1368 memmap=nn[KMG]@ss[KMG]
1369 [KNL] Force usage of a specific region of memory
1370 Region of memory to be used, from ss to ss+nn.
1371
1372 memmap=nn[KMG]#ss[KMG]
1373 [KNL,ACPI] Mark specific memory as ACPI data.
1374 Region of memory to be used, from ss to ss+nn.
1375
1376 memmap=nn[KMG]$ss[KMG]
1377 [KNL,ACPI] Mark specific memory as reserved.
1378 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1379 Example: Exclude memory from 0x18690000-0x1869ffff
1380 memmap=64K$0x18690000
1381 or
1382 memmap=0x10000$0x18690000
1da177e4 1383
9f077871
JF
1384 memory_corruption_check=0/1 [X86]
1385 Some BIOSes seem to corrupt the first 64k of
1386 memory when doing things like suspend/resume.
1387 Setting this option will scan the memory
1388 looking for corruption. Enabling this will
1389 both detect corruption and prevent the kernel
1390 from using the memory being corrupted.
1391 However, its intended as a diagnostic tool; if
1392 repeatable BIOS-originated corruption always
1393 affects the same memory, you can use memmap=
1394 to prevent the kernel from using that memory.
1395
1396 memory_corruption_check_size=size [X86]
1397 By default it checks for corruption in the low
1398 64k, making this memory unavailable for normal
1399 use. Use this parameter to scan for
1400 corruption in more or less memory.
1401
1402 memory_corruption_check_period=seconds [X86]
1403 By default it checks for corruption every 60
1404 seconds. Use this parameter to check at some
1405 other rate. 0 disables periodic checking.
1406
caadbdce 1407 memtest= [KNL,X86] Enable memtest
c64df707 1408 Format: <integer>
c64df707 1409 default : 0 <disable>
9e5f6cf5
AH
1410 Specifies the number of memtest passes to be
1411 performed. Each pass selects another test
1412 pattern from a given set of patterns. Memtest
1413 fills the memory with this pattern, validates
1414 memory contents and reserves bad memory
1415 regions that are detected.
c64df707 1416
1da177e4
LT
1417 meye.*= [HW] Set MotionEye Camera parameters
1418 See Documentation/video4linux/meye.txt.
1419
8f36881b
AS
1420 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1421 Multi-Function General Purpose Timers on AMD Geode
1422 platforms.
1423
e6c4dc6c
WT
1424 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1425 the BIOS has incorrectly applied a workaround. TinyBIOS
1426 version 0.98 is known to be affected, 0.99 fixes the
1427 problem by letting the user disable the workaround.
1428
1da177e4
LT
1429 mga= [HW,DRM]
1430
1c207f95
RD
1431 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1432 physical address is ignored.
1433
39f45d7b
MP
1434 mini2440= [ARM,HW,KNL]
1435 Format:[0..2][b][c][t]
1436 Default: "0tb"
1437 MINI2440 configuration specification:
1438 0 - The attached screen is the 3.5" TFT
1439 1 - The attached screen is the 7" TFT
1440 2 - The VGA Shield is attached (1024x768)
1441 Leaving out the screen size parameter will not load
1442 the TFT driver, and the framebuffer will be left
1443 unconfigured.
1444 b - Enable backlight. The TFT backlight pin will be
1445 linked to the kernel VESA blanking code and a GPIO
1446 LED. This parameter is not necessary when using the
1447 VGA shield.
1448 c - Enable the s3c camera interface.
1449 t - Reserved for enabling touchscreen support. The
1450 touchscreen support is not enabled in the mainstream
1451 kernel as of 2.6.30, a preliminary port can be found
1452 in the "bleeding edge" mini2440 support kernel at
1453 http://repo.or.cz/w/linux-2.6/mini2440.git
1454
6b74ab97
MG
1455 mminit_loglevel=
1456 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1457 parameter allows control of the logging verbosity for
1458 the additional memory initialisation checks. A value
1459 of 0 disables mminit logging and a level of 4 will
1460 log everything. Information is printed at KERN_DEBUG
1461 so loglevel=8 may also need to be specified.
1462
1da177e4
LT
1463 mousedev.tap_time=
1464 [MOUSE] Maximum time between finger touching and
1465 leaving touchpad surface for touch to be considered
1466 a tap and be reported as a left button click (for
1467 touchpads working in absolute mode only).
1468 Format: <msecs>
1469 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1470 reporting absolute coordinates, such as tablets
1471 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1472 reporting absolute coordinates, such as tablets
1473
6cececfc 1474 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1475 is similar to kernelcore except it specifies the
1476 amount of memory used for migratable allocations.
1477 If both kernelcore and movablecore is specified,
1478 then kernelcore will be at *least* the specified
1479 value but may be more. If movablecore on its own
1480 is specified, the administrator must be careful
1481 that the amount of memory usable for all allocations
1482 is not too small.
1483
1da177e4
LT
1484 MTD_Partition= [MTD]
1485 Format: <name>,<region-number>,<size>,<offset>
1486
a9913044
RD
1487 MTD_Region= [MTD] Format:
1488 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1489
1490 mtdparts= [MTD]
c8facbb6 1491 See drivers/mtd/cmdlinepart.c.
1da177e4 1492
5988af23
RH
1493 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1494
1495 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1496
1497 boundary - index of last SLC block on Flex-OneNAND.
1498 The remaining blocks are configured as MLC blocks.
1499 lock - Configure if Flex-OneNAND boundary should be locked.
1500 Once locked, the boundary cannot be changed.
1501 1 indicates lock status, 0 indicates unlock status.
1502
9db829f4
BD
1503 mtdset= [ARM]
1504 ARM/S3C2412 JIVE boot control
1505
1506 See arch/arm/mach-s3c2412/mach-jive.c
1507
1da177e4 1508 mtouchusb.raw_coordinates=
a9913044
RD
1509 [HW] Make the MicroTouch USB driver use raw coordinates
1510 ('y', default) or cooked coordinates ('n')
1da177e4 1511
0cb55ad2 1512 mtrr_chunk_size=nn[KMG] [X86]
19f59460 1513 used for mtrr cleanup. It is largest continuous chunk
0cb55ad2
RD
1514 that could hold holes aka. UC entries.
1515
1516 mtrr_gran_size=nn[KMG] [X86]
1517 Used for mtrr cleanup. It is granularity of mtrr block.
1518 Default is 1.
1519 Large value could prevent small alignment from
1520 using up MTRRs.
1521
1522 mtrr_spare_reg_nr=n [X86]
1523 Format: <integer>
1524 Range: 0,7 : spare reg number
1525 Default : 1
1526 Used for mtrr cleanup. It is spare mtrr entries number.
1527 Set to 2 or more if your graphical card needs more.
1528
1da177e4
LT
1529 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1530
1da177e4
LT
1531 netdev= [NET] Network devices parameters
1532 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1533 Note that mem_start is often overloaded to mean
1534 something different and driver-specific.
a9913044
RD
1535 This usage is only documented in each driver source
1536 file if at all.
1537
58401572
KPO
1538 nf_conntrack.acct=
1539 [NETFILTER] Enable connection tracking flow accounting
1540 0 to disable accounting
1541 1 to enable accounting
d70a011d 1542 Default value is 0.
58401572 1543
1da177e4 1544 nfsaddrs= [NFS]
dc7a0816 1545 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1546
1547 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
dc7a0816 1548 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 1549
a72b4422
TM
1550 nfs.callback_tcpport=
1551 [NFS] set the TCP port on which the NFSv4 callback
1552 channel should listen.
1553
e571cbf1
TM
1554 nfs.cache_getent=
1555 [NFS] sets the pathname to the program which is used
1556 to update the NFS client cache entries.
1557
1558 nfs.cache_getent_timeout=
1559 [NFS] sets the timeout after which an attempt to
1560 update a cache entry is deemed to have failed.
1561
58df095b
TM
1562 nfs.idmap_cache_timeout=
1563 [NFS] set the maximum lifetime for idmapper cache
1564 entries.
1565
f43bf0be
TM
1566 nfs.enable_ino64=
1567 [NFS] enable 64-bit inode numbers.
1568 If zero, the NFS client will fake up a 32-bit inode
1569 number for the readdir() and stat() syscalls instead
1570 of returning the full 64-bit number.
1571 The default is to return 64-bit inode numbers.
1572
1e1030dc 1573 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
e7ba176b
HS
1574 when a NMI is triggered.
1575 Format: [state][,regs][,debounce][,die]
1576
6cececfc 1577 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
5b9a0e14
CG
1578 Format: [panic,][num]
1579 Valid num: 0,1,2
1580 0 - turn nmi_watchdog off
1581 1 - use the IO-APIC timer for the NMI watchdog
1582 2 - use the local APIC for the NMI watchdog using
0cb55ad2
RD
1583 a performance counter. Note: This will use one
1584 performance counter and the local APIC's performance
1585 vector.
1586 When panic is specified, panic when an NMI watchdog
1587 timeout occurs.
1588 This is useful when you use a panic=... timeout and
1589 need the box quickly up again.
5b9a0e14
CG
1590 Instead of 1 and 2 it is possible to use the following
1591 symbolic names: lapic and ioapic
1592 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1593
bff38771
AV
1594 netpoll.carrier_timeout=
1595 [NET] Specifies amount of time (in seconds) that
1596 netpoll should wait for a carrier. By default netpoll
1597 waits 4 seconds.
1598
cd4f0ef7 1599 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1600 emulation library even if a 387 maths coprocessor
1601 is present.
1602
0cb55ad2
RD
1603 no_console_suspend
1604 [HW] Never suspend the console
1605 Disable suspending of consoles during suspend and
1606 hibernate operations. Once disabled, debugging
1607 messages can reach various consoles while the rest
1608 of the system is being put to sleep (ie, while
1609 debugging driver suspend/resume hooks). This may
1610 not work reliably with all consoles, but is known
1611 to work with serial and VGA consoles.
1612
c1aee215
CL
1613 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1614 caches in the slab allocator. Saves per-node memory,
1615 but will impact performance.
3395ee05 1616
a9913044
RD
1617 noalign [KNL,ARM]
1618
1da177e4
LT
1619 noapic [SMP,APIC] Tells the kernel to not make use of any
1620 IOAPICs that may be present in the system.
1621
1da177e4
LT
1622 nobats [PPC] Do not use BATs for mapping kernel lowmem
1623 on "Classic" PPC cores.
1624
1625 nocache [ARM]
a9913044 1626
0cb55ad2
RD
1627 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1628
163ecdff
SN
1629 nodelayacct [KNL] Disable per-task delay accounting
1630
1da177e4
LT
1631 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1632
6902aa84
PM
1633 nodsp [SH] Disable hardware DSP at boot time.
1634
6cececfc 1635 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1636
1da177e4
LT
1637 noexec [IA-64]
1638
6cececfc 1639 noexec [X86]
f5a1b191 1640 On X86-32 available only on PAE configured kernels.
1da177e4 1641 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1642 noexec=off: disable non-executable mappings
1643
1644 noexec32 [X86-64]
1645 This affects only 32-bit executables.
1646 noexec32=on: enable non-executable mappings (default)
1647 read doesn't imply executable mappings
1648 noexec32=off: disable non-executable mappings
1649 read implies executable mappings
1da177e4 1650
6902aa84
PM
1651 nofpu [SH] Disable hardware FPU at boot time.
1652
cd4f0ef7 1653 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1654 register save and restore. The kernel will only save
1655 legacy floating-point registers on task switch.
1da177e4 1656
0c752a93
SS
1657 noxsave [BUGS=X86] Disables x86 extended register state save
1658 and restore using xsave. The kernel will fallback to
1659 enabling legacy floating-point and sse state.
1660
01a24d2b
PZ
1661 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1662 wfi(ARM) instruction doesn't work correctly and not to
1663 use it. This is also useful when using JTAG debugger.
a9913044 1664
cd4f0ef7 1665 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1666 instruction doesn't work correctly and not to
1667 use it.
1668
1f29fae2
SH
1669 no_file_caps Tells the kernel not to honor file capabilities. The
1670 only way then for a file to be executed with privilege
1671 is to be setuid root or executed by root.
1672
1da177e4
LT
1673 nohalt [IA-64] Tells the kernel not to use the power saving
1674 function PAL_HALT_LIGHT when idle. This increases
1675 power-consumption. On the positive side, it reduces
1676 interrupt wake-up latency, which may improve performance
1677 in certain environments such as networked servers or
1678 real-time systems.
1679
79bf2bb3
TG
1680 nohz= [KNL] Boottime enable/disable dynamic ticks
1681 Valid arguments: on, off
1682 Default: on
1683
eeee7853
PM
1684 noiotrap [SH] Disables trapped I/O port accesses.
1685
cd4f0ef7 1686 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1687 disable unhandled interrupt sources.
1688
6cececfc 1689 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
1690 broken timer IRQ sources.
1691
1da177e4
LT
1692 noisapnp [ISAPNP] Disables ISA PnP code.
1693
1694 noinitrd [RAM] Tells the kernel not to load any configured
1695 initial RAM disk.
1696
03ea8155
WH
1697 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1698 remapping.
d1423d56 1699 [Deprecated - use intremap=off]
03ea8155 1700
1da177e4
LT
1701 nointroute [IA-64]
1702
0aa366f3
TL
1703 nojitter [IA64] Disables jitter checking for ITC timers.
1704
9cf4c4fc
JK
1705 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1706
cd4f0ef7 1707 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1708
cd4f0ef7 1709 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1710
1da177e4
LT
1711 noltlbs [PPC] Do not use large page/tlb entries for kernel
1712 lowmem mapping on PPC40x.
1713
312f1f01
H
1714 nomca [IA-64] Disable machine check abort handling
1715
cd4f0ef7 1716 nomce [X86-32] Machine Check Exception
abe37e5a 1717
83d7384f
AS
1718 nomfgpt [X86-32] Disable Multi-Function General Purpose
1719 Timer usage (for AMD Geode machines).
1720
016ddd9b
JK
1721 nopat [X86] Disable PAT (page attribute table extension of
1722 pagetables) support.
1723
0cb55ad2
RD
1724 norandmaps Don't use address space randomization. Equivalent to
1725 echo 0 > /proc/sys/kernel/randomize_va_space
1726
bbff2168 1727 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
959b4fdf 1728
cd4f0ef7 1729 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1730 with UP alternatives
1731
1da177e4
LT
1732 noresidual [PPC] Don't use residual data on PReP machines.
1733
a9913044
RD
1734 noresume [SWSUSP] Disables resume and restores original swap
1735 space.
1736
1da177e4
LT
1737 no-scroll [VGA] Disables scrollback.
1738 This is required for the Braillex ib80-piezo Braille
1739 reader made by F.H. Papenmeier (Germany).
1740
1741 nosbagart [IA-64]
1742
cd4f0ef7 1743 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1744
61ec7567
LB
1745 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1746 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1747
97842216
DJ
1748 nosoftlockup [KNL] Disable the soft-lockup detector.
1749
c077719b 1750 noswapaccount [KNL] Disable accounting of swap in memory resource
21acb9ca 1751 controller. (See Documentation/cgroups/memory.txt)
c077719b 1752
1da177e4
LT
1753 nosync [HW,M68K] Disables sync negotiation for all devices.
1754
cd4f0ef7 1755 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1756
1757 nousb [USB] Disable the USB subsystem
1758
58687acb
DZ
1759 nowatchdog [KNL] Disable the lockup detector.
1760
1da177e4 1761 nowb [ARM]
a9913044 1762
2b2fd87a
WH
1763 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1764
a6c75b86
FY
1765 nptcg= [IA64] Override max number of concurrent global TLB
1766 purges which is reported from either PAL_VM_SUMMARY or
1767 SAL PALO.
1768
2b633e3f
YL
1769 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1770 could support. nr_cpus=n : n >= 1 limits the kernel to
1771 supporting 'n' processors. Later in runtime you can not
1772 use hotplug cpu feature to put more cpu back to online.
1773 just like you compile the kernel NR_CPUS=n
1774
0cb55ad2
RD
1775 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1776
f0c0b2b8
KH
1777 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1778 one of ['zone', 'node', 'default'] can be specified
1779 This can be set from sysctl after boot.
1780 See Documentation/sysctl/vm.txt for details.
1781
7c4be253
RD
1782 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1783 See Documentation/debugging-via-ohci1394.txt for more
1784 info.
1785
3ef0e1f8
AS
1786 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1787 Rather than timing out after 20 ms if an EC
1788 command is not properly ACKed, override the length
1789 of the timeout. We have interrupts disabled while
1790 waiting for the ACK, so if this is set too high
1791 interrupts *may* be lost!
1792
15ac7afe
TL
1793 omap_mux= [OMAP] Override bootloader pin multiplexing.
1794 Format: <mux_mode0.mode_name=value>...
1795 For example, to override I2C bus2:
1796 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1797
1da177e4
LT
1798 oprofile.timer= [HW]
1799 Use timer interrupt instead of performance counters
1800
7e4e0bd5
RR
1801 oprofile.cpu_type= Force an oprofile cpu type
1802 This might be useful if you have an older oprofile
1803 userland or if you want common events.
8d7ff4f2
RR
1804 Format: { arch_perfmon }
1805 arch_perfmon: [X86] Force use of architectural
7e4e0bd5
RR
1806 perfmon on Intel CPUs instead of the
1807 CPU specific event set.
1dcdb5a9 1808
bcfde334
RD
1809 OSS [HW,OSS]
1810 See Documentation/sound/oss/oss-parameters.txt
1811
1da177e4
LT
1812 panic= [KNL] Kernel behaviour on panic
1813 Format: <timeout>
1814
1815 parkbd.port= [HW] Parallel port number the keyboard adapter is
1816 connected to, default is 0.
1817 Format: <parport#>
1818 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1819 0 for XT, 1 for AT (default is AT).
a9913044
RD
1820 Format: <mode>
1821
1822 parport= [HW,PPT] Specify parallel ports. 0 disables.
1823 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1824 Use 'auto' to force the driver to use any
1825 IRQ/DMA settings detected (the default is to
1826 ignore detected IRQ/DMA settings because of
1827 possible conflicts). You can specify the base
1828 address, IRQ, and DMA settings; IRQ and DMA
1829 should be numbers, or 'auto' (for using detected
1830 settings on that particular port), or 'nofifo'
1831 (to avoid using a FIFO even if it is detected).
1832 Parallel ports are assigned in the order they
1833 are specified on the command line, starting
1834 with parport0.
1835
1836 parport_init_mode= [HW,PPT]
1837 Configure VIA parallel port to operate in
1838 a specific mode. This is necessary on Pegasos
1839 computer where firmware has no options for setting
1840 up parallel port mode and sets it to spp.
1841 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1842 Format: [spp|ps2|epp|ecp|ecpepp]
1843
dd287796
AM
1844 pause_on_oops=
1845 Halt all CPUs after the first oops has been printed for
1846 the specified number of seconds. This is to be used if
1847 your oopses keep scrolling off the screen.
1848
1da177e4
LT
1849 pcbit= [HW,ISDN]
1850
1851 pcd. [PARIDE]
1852 See header of drivers/block/paride/pcd.c.
31c00fc1 1853 See also Documentation/blockdev/paride.txt.
1da177e4 1854
a9913044 1855 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
1856 earlydump [X86] dump PCI config space before the kernel
1857 changes anything
c0115606 1858 off [X86] don't probe for the PCI bus
cd4f0ef7 1859 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1860 the hardware directly. Use this if your machine
1861 has a non-standard PCI host bridge.
cd4f0ef7 1862 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1863 hardware access methods are allowed. Use this
1864 if you experience crashes upon bootup and you
1865 suspect they are caused by the BIOS.
c0115606 1866 conf1 [X86] Force use of PCI Configuration
a9913044 1867 Mechanism 1.
c0115606 1868 conf2 [X86] Force use of PCI Configuration
a9913044 1869 Mechanism 2.
7f785763
RD
1870 noaer [PCIE] If the PCIEAER kernel config parameter is
1871 enabled, this kernel boot option can be used to
1872 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1873 nodomains [PCI] Disable support for multiple PCI
1874 root domains (aka PCI segments, in ACPI-speak).
6cececfc 1875 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 1876 Configuration
12983077
AH
1877 check_enable_amd_mmconf [X86] check for and enable
1878 properly configured MMIO access to PCI
1879 config space on AMD family 10h CPU
309e57df
MW
1880 nomsi [MSI] If the PCI_MSI kernel config parameter is
1881 enabled, this kernel boot option can be used to
1882 disable the use of MSI interrupts system-wide.
a9322f64
SA
1883 noioapicquirk [APIC] Disable all boot interrupt quirks.
1884 Safety option to keep boot IRQs enabled. This
1885 should never be necessary.
9197979b
SA
1886 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1887 primary IO-APIC for bridges that cannot disable
1888 boot IRQs. This fixes a source of spurious IRQs
1889 when the system masks IRQs.
41b9eb26
SA
1890 noioapicreroute [APIC] Disable workaround that uses the
1891 boot IRQ equivalent of an IRQ that connects to
1892 a chipset where boot IRQs cannot be disabled.
1893 The opposite of ioapicreroute.
cd4f0ef7 1894 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1895 routing table. These calls are known to be buggy
1896 on several machines and they hang the machine
1897 when used, but on other computers it's the only
1898 way to get the interrupt routing table. Try
1899 this option if the kernel is unable to allocate
1900 IRQs or discover secondary PCI buses on your
1901 motherboard.
c0115606 1902 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1903 Use with caution as certain devices share
1904 address decoders between ROMs and other
1905 resources.
c0115606 1906 norom [X86] Do not assign address space to
bb71ad88
GH
1907 expansion ROMs that do not already have
1908 BIOS assigned address ranges.
7bd1c365
MH
1909 nobar [X86] Do not assign address space to the
1910 BARs that weren't assigned by the BIOS.
c0115606 1911 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1912 assigned automatically to PCI devices. You can
1913 make the kernel exclude IRQs of your ISA cards
1914 this way.
c0115606 1915 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1916 of the PIRQ table (normally generated
1917 by the BIOS) if it is outside the
1918 F0000h-100000h range.
c0115606 1919 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1920 useful if the kernel is unable to find your
1921 secondary buses and you want to tell it
1922 explicitly which ones they are.
c0115606 1923 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1924 numbers ourselves, overriding
1925 whatever the firmware may have done.
c0115606 1926 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1927 in the BIOS $PIR table. This is needed on
1928 some systems with broken BIOSes, notably
1929 some HP Pavilion N5400 and Omnibook XE3
1930 notebooks. This will have no effect if ACPI
1931 IRQ routing is enabled.
c0115606 1932 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1933 or for PCI scanning.
7bc5e3f2
BH
1934 use_crs [X86] Use PCI host bridge window information
1935 from ACPI. On BIOSes from 2008 or later, this
1936 is enabled by default. If you need to use this,
1937 please report a bug.
1938 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1939 If you need to use this, please report a bug.
a9913044
RD
1940 routeirq Do IRQ routing for all PCI devices.
1941 This is normally done in pci_enable_device(),
1942 so this option is a temporary workaround
1943 for broken drivers that don't call it.
13a6ddb0
YL
1944 skip_isa_align [X86] do not align io start addr, so can
1945 handle more pci cards
a9913044
RD
1946 firmware [ARM] Do not re-enumerate the bus but instead
1947 just use the configuration from the
1948 bootloader. This is currently used on
1949 IXP2000 systems where the bus has to be
1950 configured a certain way for adjunct CPUs.
0637a70a
AK
1951 noearly [X86] Don't do any early type 1 scanning.
1952 This might help on some broken boards which
1953 machine check when some devices' config space
1954 is read. But various workarounds are disabled
1955 and some IOMMU drivers will not work.
6b4b78fe
MD
1956 bfsort Sort PCI devices into breadth-first order.
1957 This sorting is done to get a device
1958 order compatible with older (<= 2.4) kernels.
1959 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1960 cbiosize=nn[KMG] The fixed amount of bus space which is
1961 reserved for the CardBus bridge's IO window.
1962 The default value is 256 bytes.
1963 cbmemsize=nn[KMG] The fixed amount of bus space which is
1964 reserved for the CardBus bridge's memory
1965 window. The default value is 64 megabytes.
32a9a682
YS
1966 resource_alignment=
1967 Format:
1968 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1969 Specifies alignment and device to reassign
1970 aligned memory resources.
1971 If <order of align> is not specified,
1972 PAGE_SIZE is used as alignment.
1973 PCI-PCI bridge can be specified, if resource
1974 windows need to be expanded.
43c16408
AP
1975 ecrc= Enable/disable PCIe ECRC (transaction layer
1976 end-to-end CRC checking).
1977 bios: Use BIOS/firmware settings. This is the
1978 the default.
1979 off: Turn ECRC off
1980 on: Turn ECRC on.
6b4b78fe 1981
e5665a45
CE
1982 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1983 Management.
1984 off Disable ASPM.
1985 force Enable ASPM even on devices that claim not to support it.
1986 WARNING: Forcing ASPM on may cause system lockups.
1987
79dd9182 1988 pcie_ports= [PCIE] PCIe ports handling:
28eb5f27
RW
1989 auto Ask the BIOS whether or not to use native PCIe services
1990 associated with PCIe ports (PME, hot-plug, AER). Use
1991 them only if that is allowed by the BIOS.
1992 native Use native PCIe services associated with PCIe ports
1993 unconditionally.
79dd9182
RW
1994 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1995 ports driver.
1996
c7f48656 1997 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
c39fae14 1998 nomsi Do not use MSI for native PCIe PME signaling (this makes
28eb5f27 1999 all PCIe root ports use INTx for all services).
c7f48656 2000
1da177e4
LT
2001 pcmv= [HW,PCMCIA] BadgePAD 4
2002
2003 pd. [PARIDE]
31c00fc1 2004 See Documentation/blockdev/paride.txt.
1da177e4
LT
2005
2006 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2007 boot time.
2008 Format: { 0 | 1 }
2009 See arch/parisc/kernel/pdc_chassis.c
2010
f58dc01b 2011 percpu_alloc= Select which percpu first chunk allocator to use.
e933a73f
TH
2012 Currently supported values are "embed" and "page".
2013 Archs may support subset or none of the selections.
2014 See comments in mm/percpu.c for details on each
2015 allocator. This parameter is primarily for debugging
2016 and performance comparison.
fa8a7094 2017
1da177e4 2018 pf. [PARIDE]
31c00fc1 2019 See Documentation/blockdev/paride.txt.
1da177e4
LT
2020
2021 pg. [PARIDE]
31c00fc1 2022 See Documentation/blockdev/paride.txt.
1da177e4
LT
2023
2024 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 2025 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
2026
2027 plip= [PPT,NET] Parallel port network link
2028 Format: { parport<nr> | timid | 0 }
2029 See also Documentation/parport.txt.
2030
de32a243
TG
2031 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2032 Override pmtimer IOPort with a hex value.
2033 e.g. pmtmr=0x508
2034
97ef062b
BH
2035 pnp.debug [PNP]
2036 Enable PNP debug messages. This depends on the
2037 CONFIG_PNP_DEBUG_MESSAGES option.
2038
1da177e4
LT
2039 pnpacpi= [ACPI]
2040 { off }
2041
2042 pnpbios= [ISAPNP]
2043 { on | off | curr | res | no-curr | no-res }
2044
2045 pnp_reserve_irq=
2046 [ISAPNP] Exclude IRQs for the autoconfiguration
2047
2048 pnp_reserve_dma=
2049 [ISAPNP] Exclude DMAs for the autoconfiguration
2050
2051 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 2052 Ranges are in pairs (I/O port base and size).
1da177e4
LT
2053
2054 pnp_reserve_mem=
a9913044
RD
2055 [ISAPNP] Exclude memory regions for the
2056 autoconfiguration.
1da177e4
LT
2057 Ranges are in pairs (memory base and size).
2058
4af94f39
RD
2059 ports= [IP_VS_FTP] IPVS ftp helper module
2060 Default is 21.
2061 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2062 may be specified.
2063 Format: <port>,<port>....
2064
45807a1d
IM
2065 print-fatal-signals=
2066 [KNL] debug: print fatal signals
f84d49b2
NO
2067
2068 If enabled, warn about various signal handling
2069 related application anomalies: too many signals,
2070 too many POSIX.1 timers, fatal signals causing a
2071 coredump - etc.
2072
2073 If you hit the warning due to signal overflow,
2074 you might want to try "ulimit -i unlimited".
2075
45807a1d
IM
2076 default: off.
2077
e84845c4
RD
2078 printk.time= Show timing data prefixed to each printk message line
2079 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2080
0cb55ad2
RD
2081 processor.max_cstate= [HW,ACPI]
2082 Limit processor to maximum C-state
2083 max_cstate=9 overrides any DMI blacklist limit.
2084
2085 processor.nocst [HW,ACPI]
2086 Ignore the _CST method to determine C-states,
2087 instead using the legacy FADT method
2088
1da177e4 2089 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
2090 Format: [schedule,]<number>
2091 Param: "schedule" - profile schedule points.
2092 Param: <number> - step/bucket size as a power of 2 for
2093 statistical time based profiling.
b3da2a73
MG
2094 Param: "sleep" - profile D-state sleeping (millisecs).
2095 Requires CONFIG_SCHEDSTATS
c0fe2e69 2096 Param: "kvm" - profile VM exits.
1da177e4 2097
1da177e4
LT
2098 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2099 before loading.
31c00fc1 2100 See Documentation/blockdev/ramdisk.txt.
1da177e4 2101
a9913044
RD
2102 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2103 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
2104 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2105 per second.
a9913044
RD
2106 psmouse.resetafter= [HW,MOUSE]
2107 Try to reset the device after so many bad packets
1da177e4
LT
2108 (0 = never).
2109 psmouse.resolution=
2110 [HW,MOUSE] Set desired mouse resolution, in dpi.
2111 psmouse.smartscroll=
a9913044 2112 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
2113 0 = disabled, 1 = enabled (default).
2114
1da177e4 2115 pt. [PARIDE]
31c00fc1 2116 See Documentation/blockdev/paride.txt.
1da177e4 2117
dc8c8587
KS
2118 pty.legacy_count=
2119 [KNL] Number of legacy pty's. Overwrites compiled-in
2120 default number.
2121
7d2c502f 2122 quiet [KNL] Disable most log messages
a9913044 2123
1da177e4
LT
2124 r128= [HW,DRM]
2125
2126 raid= [HW,RAID]
2127 See Documentation/md.txt.
2128
a9913044 2129 ramdisk_blocksize= [RAM]
31c00fc1 2130 See Documentation/blockdev/ramdisk.txt.
a9913044 2131
1da177e4 2132 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 2133 See Documentation/blockdev/ramdisk.txt.
1da177e4 2134
24aaef8d
RD
2135 rcupdate.blimit= [KNL,BOOT]
2136 Set maximum number of finished RCU callbacks to process
2137 in one batch.
21a1ea9e 2138
24aaef8d
RD
2139 rcupdate.qhimark= [KNL,BOOT]
2140 Set threshold of queued
21a1ea9e
DS
2141 RCU callbacks over which batch limiting is disabled.
2142
24aaef8d
RD
2143 rcupdate.qlowmark= [KNL,BOOT]
2144 Set threshold of queued RCU callbacks below which
2145 batch limiting is re-enabled.
21a1ea9e 2146
ffdfc409
OJ
2147 rdinit= [KNL]
2148 Format: <full_path>
2149 Run specified binary instead of /init from the ramdisk,
2150 used for early userspace startup. See initrd.
2151
cd4f0ef7 2152 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 2153 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 2154 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 2155
46b6d94e
PJ
2156 relax_domain_level=
2157 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 2158 See Documentation/cgroups/cpusets.txt.
46b6d94e 2159
1da177e4
LT
2160 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2161
cd4f0ef7 2162 reservetop= [X86-32]
461a9aff
ZA
2163 Format: nn[KMG]
2164 Reserves a hole at the top of the kernel virtual
2165 address space.
2166
9ea77bdb
PA
2167 reservelow= [X86]
2168 Format: nn[K]
2169 Set the amount of memory to reserve for BIOS at
2170 the bottom of the address space.
2171
7e96287d
VG
2172 reset_devices [KNL] Force drivers to reset the underlying device
2173 during initialization.
2174
a9913044
RD
2175 resume= [SWSUSP]
2176 Specify the partition device for software suspend
1da177e4 2177
ecbd0da1
RW
2178 resume_offset= [SWSUSP]
2179 Specify the offset from the beginning of the partition
2180 given by "resume=" at which the swap header is located,
2181 in <PAGE_SIZE> units (needed only for swap files).
2182 See Documentation/power/swsusp-and-swap-files.txt
2183
f996fc96
BS
2184 hibernate= [HIBERNATION]
2185 noresume Don't check if there's a hibernation image
2186 present during boot.
2187 nocompress Don't compress/decompress hibernation images.
2188
0a7b35cb
MN
2189 retain_initrd [RAM] Keep initrd memory after extraction
2190
1da177e4
LT
2191 rhash_entries= [KNL,NET]
2192 Set number of hash buckets for route cache
2193
2194 riscom8= [HW,SERIAL]
2195 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2196
2197 ro [KNL] Mount root device read-only on boot
2198
2199 root= [KNL] Root filesystem
2200
2201 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2202 mount the root filesystem
2203
2204 rootflags= [KNL] Set root filesystem mount option string
2205
2206 rootfstype= [KNL] Set root filesystem type
2207
cc1ed754
PO
2208 rootwait [KNL] Wait (indefinitely) for root device to show up.
2209 Useful for devices that are detected asynchronously
2210 (e.g. USB and MMC devices).
2211
1da177e4
LT
2212 rw [KNL] Mount root device read-write on boot
2213
2214 S [KNL] Run init in single mode
2215
2216 sa1100ir [NET]
2217 See drivers/net/irda/sa1100_ir.c.
2218
1da177e4 2219 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2220
f6630114
MT
2221 sched_debug [KNL] Enables verbose scheduler debug messages.
2222
0cb55ad2
RD
2223 security= [SECURITY] Choose a security module to enable at boot.
2224 If this boot parameter is not specified, only the first
2225 security module asking for security registration will be
2226 loaded. An invalid security module name will be treated
2227 as if no module has been chosen.
2228
2229 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2230 Format: { "0" | "1" }
2231 See security/selinux/Kconfig help text.
2232 0 -- disable.
2233 1 -- enable.
2234 Default value is set via kernel config option.
2235 If enabled at boot time, /selinux/disable can be used
2236 later to disable prior to initial policy load.
2237
c1c124e9
JJ
2238 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2239 Format: { "0" | "1" }
2240 See security/apparmor/Kconfig help text
2241 0 -- disable.
2242 1 -- enable.
2243 Default value is set via kernel config option.
2244
cd4f0ef7 2245 serialnumber [BUGS=X86-32]
1da177e4 2246
1da177e4
LT
2247 shapers= [NET]
2248 Maximal number of shapers.
a9913044 2249
b05f78f5
YL
2250 show_msr= [x86] show boot-time MSR settings
2251 Format: { <integer> }
2252 Show boot-time (BIOS-initialized) MSR settings.
2253 The parameter means the number of CPUs to show,
2254 for example 1 means boot CPU only.
2255
1da177e4
LT
2256 simeth= [IA-64]
2257 simscsi=
a9913044 2258
1da177e4
LT
2259 slram= [HW,MTD]
2260
f0630fff
CL
2261 slub_debug[=options[,slabs]] [MM, SLUB]
2262 Enabling slub_debug allows one to determine the
2263 culprit if slab objects become corrupted. Enabling
2264 slub_debug can create guard zones around objects and
2265 may poison objects when not in use. Also tracks the
2266 last alloc / free. For more information see
2267 Documentation/vm/slub.txt.
c1aee215
CL
2268
2269 slub_max_order= [MM, SLUB]
f0630fff
CL
2270 Determines the maximum allowed order for slabs.
2271 A high setting may cause OOMs due to memory
2272 fragmentation. For more information see
2273 Documentation/vm/slub.txt.
c1aee215
CL
2274
2275 slub_min_objects= [MM, SLUB]
f0630fff
CL
2276 The minimum number of objects per slab. SLUB will
2277 increase the slab order up to slub_max_order to
2278 generate a sufficiently large slab able to contain
2279 the number of objects indicated. The higher the number
2280 of objects the smaller the overhead of tracking slabs
2281 and the less frequently locks need to be acquired.
c1aee215
CL
2282 For more information see Documentation/vm/slub.txt.
2283
2284 slub_min_order= [MM, SLUB]
2285 Determines the mininum page order for slabs. Must be
f0630fff 2286 lower than slub_max_order.
c1aee215
CL
2287 For more information see Documentation/vm/slub.txt.
2288
2289 slub_nomerge [MM, SLUB]
f0630fff 2290 Disable merging of slabs with similar size. May be
c1aee215 2291 necessary if there is some reason to distinguish
f0630fff
CL
2292 allocs to different slabs. Debug options disable
2293 merging on their own.
c1aee215
CL
2294 For more information see Documentation/vm/slub.txt.
2295
1da177e4
LT
2296 smart2= [HW]
2297 Format: <io1>[,<io2>[,...,<io8>]]
2298
cd4f0ef7 2299 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2300 attempt to substitute SMP alternatives once at boot.
2301
d0d4f69b
BH
2302 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2303 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2304 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2305 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2306 smsc-ircc2.ircc_irq= [HW] IRQ line
2307 smsc-ircc2.ircc_dma= [HW] DMA channel
2308 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2309 0: Toshiba Satellite 1800 (GP data pin select)
2310 1: Fast pin select (default)
2311 2: ATC IRMode
2312
9c44bc03
IM
2313 softlockup_panic=
2314 [KNL] Should the soft-lockup detector generate panics.
2315
1da177e4
LT
2316 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2317 See Documentation/sonypi.txt
2318
2319 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2320 See Documentation/serial/specialix.txt.
1da177e4
LT
2321
2322 spia_io_base= [HW,MTD]
2323 spia_fio_base=
2324 spia_pedr=
2325 spia_peddr=
2326
f38f1d2a
SR
2327 stacktrace [FTRACE]
2328 Enabled the stack tracer on boot up.
2329
1da177e4
LT
2330 sti= [PARISC,HW]
2331 Format: <num>
2332 Set the STI (builtin display/keyboard on the HP-PARISC
2333 machines) console (graphic card) which should be used
2334 as the initial boot-console.
2335 See also comment in drivers/video/console/sticore.c.
2336
2337 sti_font= [HW]
2338 See comment in drivers/video/console/sticore.c.
2339
2340 stifb= [HW]
2341 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2342
cbf11071
TM
2343 sunrpc.min_resvport=
2344 sunrpc.max_resvport=
2345 [NFS,SUNRPC]
2346 SunRPC servers often require that client requests
2347 originate from a privileged port (i.e. a port in the
2348 range 0 < portnr < 1024).
2349 An administrator who wishes to reserve some of these
2350 ports for other uses may adjust the range that the
2351 kernel's sunrpc client considers to be privileged
2352 using these two parameters to set the minimum and
2353 maximum port values.
2354
42a7fc4a
GB
2355 sunrpc.pool_mode=
2356 [NFS]
2357 Control how the NFS server code allocates CPUs to
2358 service thread pools. Depending on how many NICs
2359 you have and where their interrupts are bound, this
2360 option will affect which CPUs will do NFS serving.
2361 Note: this parameter cannot be changed while the
2362 NFS server is running.
2363
2364 auto the server chooses an appropriate mode
2365 automatically using heuristics
2366 global a single global pool contains all CPUs
2367 percpu one pool for each CPU
2368 pernode one pool for each NUMA node (equivalent
2369 to global on non-NUMA machines)
2370
cbf11071
TM
2371 sunrpc.tcp_slot_table_entries=
2372 sunrpc.udp_slot_table_entries=
2373 [NFS,SUNRPC]
2374 Sets the upper limit on the number of simultaneous
2375 RPC calls that can be sent from the client to a
2376 server. Increasing these values may allow you to
2377 improve throughput, but will also increase the
2378 amount of memory reserved for use by the client.
2379
1da177e4 2380 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2381
1da177e4
LT
2382 switches= [HW,M68k]
2383
e52eec13
AK
2384 sysfs.deprecated=0|1 [KNL]
2385 Enable/disable old style sysfs layout for old udev
2386 on older distributions. When this option is enabled
2387 very new udev will not work anymore. When this option
2388 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2389 in older udev will not work anymore.
2390 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2391 the kernel configuration.
2392
5d6f647f
IM
2393 sysrq_always_enabled
2394 [KNL]
2395 Ignore sysrq setting - this boot parameter will
2396 neutralize any effect of /proc/sys/kernel/sysrq.
2397 Useful for debugging.
2398
1da177e4
LT
2399 tdfx= [HW,DRM]
2400
77437fd4
DB
2401 test_suspend= [SUSPEND]
2402 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2403 standby suspend) as the system sleep state to briefly
2404 enter during system startup. The system is woken from
2405 this state using a wakeup-capable RTC alarm.
2406
1da177e4
LT
2407 thash_entries= [KNL,NET]
2408 Set number of hash buckets for TCP connection
2409
f8707ec9
LB
2410 thermal.act= [HW,ACPI]
2411 -1: disable all active trip points in all thermal zones
2412 <degrees C>: override all lowest active trip points
2413
c52a7419
LB
2414 thermal.crt= [HW,ACPI]
2415 -1: disable all critical trip points in all thermal zones
22a94d79 2416 <degrees C>: override all critical trip points
c52a7419 2417
f5487145
LB
2418 thermal.nocrt= [HW,ACPI]
2419 Set to disable actions on ACPI thermal zone
2420 critical and hot trip points.
2421
72b33ef8
LB
2422 thermal.off= [HW,ACPI]
2423 1: disable ACPI thermal control
2424
a70cdc52
LB
2425 thermal.psv= [HW,ACPI]
2426 -1: disable all passive trip points
ada9cfdd
RD
2427 <degrees C>: override all passive trip points to this
2428 value
a70cdc52 2429
730ff34d
LB
2430 thermal.tzp= [HW,ACPI]
2431 Specify global default ACPI thermal zone polling rate
2432 <deci-seconds>: poll all this frequency
2433 0: no polling (default)
2434
2b1a61f0
HC
2435 topology= [S390]
2436 Format: {off | on}
2437 Specify if the kernel should make use of the cpu
2438 topology informations if the hardware supports these.
2439 The scheduler will make use of these informations and
2440 e.g. base its process migration decisions on it.
2441 Default is off.
2442
1da177e4
LT
2443 tp720= [HW,PS2]
2444
225a9be2
RA
2445 tpm_suspend_pcr=[HW,TPM]
2446 Format: integer pcr id
2447 Specify that at suspend time, the tpm driver
2448 should extend the specified pcr with zeros,
2449 as a workaround for some chips which fail to
2450 flush the last written pcr on TPM_SaveState.
2451 This will guarantee that all the other pcrs
2452 are saved.
2453
9d612bef
LZ
2454 trace_buf_size=nn[KMG]
2455 [FTRACE] will set tracing buffer size.
631595fb 2456
020e5f85
LZ
2457 trace_event=[event-list]
2458 [FTRACE] Set and start specified trace events in order
2459 to facilitate early boot debugging.
2460 See also Documentation/trace/events.txt
2461
395628ef
AK
2462 tsc= Disable clocksource-must-verify flag for TSC.
2463 Format: <string>
2464 [x86] reliable: mark tsc clocksource as reliable, this
2465 disables clocksource verification at runtime.
2466 Used to enable high-resolution timer mode on older
2467 hardware, and in virtualized environment.
e82b8e4e
VP
2468 [x86] noirqtime: Do not use TSC to do irq accounting.
2469 Used to run time disable IRQ_TIME_ACCOUNTING on any
2470 platforms where RDTSC is slow and this accounting
2471 can add overhead.
395628ef 2472
a9913044
RD
2473 turbografx.map[2|3]= [HW,JOY]
2474 TurboGraFX parallel port interface
2475 Format:
2476 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2477 See also Documentation/input/joystick-parport.txt
2478
f86dcc5a
ED
2479 uhash_entries= [KNL,NET]
2480 Set number of hash buckets for UDP/UDP-Lite connections
2481
5f8364b7
AS
2482 uhci-hcd.ignore_oc=
2483 [USB] Ignore overcurrent events (default N).
2484 Some badly-designed motherboards generate lots of
2485 bogus events, for ports that aren't wired to
2486 anything. Set this parameter to avoid log spamming.
2487 Note that genuine overcurrent events won't be
2488 reported either.
2489
e3a61b0a 2490 unknown_nmi_panic
6cececfc 2491 [X86]
e3a61b0a
SA
2492 Set unknown_nmi_panic=1 early on boot.
2493
b5e795f8
AS
2494 usbcore.autosuspend=
2495 [USB] The autosuspend time delay (in seconds) used
2496 for newly-detected USB devices (default 2). This
2497 is the time required before an idle device will be
2498 autosuspended. Devices for which the delay is set
eaafbc3a 2499 to a negative value won't be autosuspended at all.
b5e795f8 2500
fd7c519d
JK
2501 usbcore.usbfs_snoop=
2502 [USB] Set to log all usbfs traffic (default 0 = off).
2503
2504 usbcore.blinkenlights=
2505 [USB] Set to cycle leds on hubs (default 0 = off).
2506
2507 usbcore.old_scheme_first=
2508 [USB] Start with the old device initialization
2509 scheme (default 0 = off).
2510
2511 usbcore.use_both_schemes=
2512 [USB] Try the other device initialization scheme
2513 if the first one fails (default 1 = enabled).
2514
2515 usbcore.initial_descriptor_timeout=
2516 [USB] Specifies timeout for the initial 64-byte
2517 USB_REQ_GET_DESCRIPTOR request in milliseconds
2518 (default 5000 = 5.0 seconds).
2519
1da177e4
LT
2520 usbhid.mousepoll=
2521 [USBHID] The interval which mice are to be polled at.
a9913044 2522
d4f373e5
AS
2523 usb-storage.delay_use=
2524 [UMS] The delay in seconds before a new device is
2525 scanned for Logical Units (default 5).
2526
2527 usb-storage.quirks=
2528 [UMS] A list of quirks entries to supplement or
2529 override the built-in unusual_devs list. List
2530 entries are separated by commas. Each entry has
2531 the form VID:PID:Flags where VID and PID are Vendor
2532 and Product ID values (4-digit hex numbers) and
2533 Flags is a set of characters, each corresponding
2534 to a common usb-storage quirk flag as follows:
c838ea46
AS
2535 a = SANE_SENSE (collect more than 18 bytes
2536 of sense data);
a0bb1081
AS
2537 b = BAD_SENSE (don't collect more than 18
2538 bytes of sense data);
d4f373e5
AS
2539 c = FIX_CAPACITY (decrease the reported
2540 device capacity by one sector);
c838ea46
AS
2541 h = CAPACITY_HEURISTICS (decrease the
2542 reported device capacity by one
2543 sector if the number is odd);
d4f373e5
AS
2544 i = IGNORE_DEVICE (don't bind to this
2545 device);
2546 l = NOT_LOCKABLE (don't try to lock and
2547 unlock ejectable media);
2548 m = MAX_SECTORS_64 (don't transfer more
2549 than 64 sectors = 32 KB at a time);
c838ea46
AS
2550 o = CAPACITY_OK (accept the capacity
2551 reported by the device);
d4f373e5
AS
2552 r = IGNORE_RESIDUE (the device reports
2553 bogus residue values);
2554 s = SINGLE_LUN (the device has only one
2555 Logical Unit);
2556 w = NO_WP_DETECT (don't test whether the
2557 medium is write-protected).
2558 Example: quirks=0419:aaf5:rl,0421:0433:rc
2559
14315592
IC
2560 userpte=
2561 [X86] Flags controlling user PTE allocations.
2562
2563 nohigh = do not allocate PTE pages in
2564 HIGHMEM regardless of setting
2565 of CONFIG_HIGHPTE.
2566
6cececfc 2567 vdso= [X86,SH]
1dbf527c 2568 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2569 vdso=1: enable VDSO (default)
2570 vdso=0: disable VDSO mapping
2571
6cececfc 2572 vdso32= [X86]
af65d648
RM
2573 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2574 vdso32=1: enable 32-bit VDSO (default)
2575 vdso32=0: disable 32-bit VDSO mapping
2576
d080d397
YI
2577 vector= [IA-64,SMP]
2578 vector=percpu: enable percpu vector domain
2579
1da177e4
LT
2580 video= [FB] Frame buffer configuration
2581 See Documentation/fb/modedb.txt.
2582
cd4f0ef7 2583 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 2584 See Documentation/x86/boot.txt and
a9913044 2585 Documentation/svga.txt.
1da177e4
LT
2586 Use vga=ask for menu.
2587 This is actually a boot loader parameter; the value is
2588 passed to the kernel using a special protocol.
2589
a9913044 2590 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2591 size of <nn>. This can be used to increase the
2592 minimum size (128MB on x86). It can also be used to
2593 decrease the size and leave more room for directly
2594 mapped kernel RAM.
2595
585c3047
PO
2596 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2597 Format: <command>
1da177e4 2598
585c3047
PO
2599 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2600 Format: <command>
2601
2602 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2603 Format: <command>
a9913044 2604
9ea9a886
CL
2605 vt.cur_default= [VT] Default cursor shape.
2606 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2607 the parameters of the <Esc>[?A;B;Cc escape sequence;
2608 see VGA-softcursor.txt. Default: 2 = underline.
2609
0cb55ad2
RD
2610 vt.default_blu= [VT]
2611 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2612 Change the default blue palette of the console.
2613 This is a 16-member array composed of values
2614 ranging from 0-255.
2615
2616 vt.default_grn= [VT]
2617 Format: <green0>,<green1>,<green2>,...,<green15>
2618 Change the default green palette of the console.
2619 This is a 16-member array composed of values
2620 ranging from 0-255.
2621
2622 vt.default_red= [VT]
2623 Format: <red0>,<red1>,<red2>,...,<red15>
2624 Change the default red palette of the console.
2625 This is a 16-member array composed of values
2626 ranging from 0-255.
2627
2628 vt.default_utf8=
2629 [VT]
2630 Format=<0|1>
2631 Set system-wide default UTF-8 mode for all tty's.
2632 Default is 1, i.e. UTF-8 mode is enabled for all
2633 newly opened terminals.
2634
f6c06b68
MG
2635 vt.global_cursor_default=
2636 [VT]
2637 Format=<-1|0|1>
2638 Set system-wide default for whether a cursor
2639 is shown on new VTs. Default is -1,
2640 i.e. cursors will be created by default unless
2641 overridden by individual drivers. 0 will hide
2642 cursors, 1 will display them.
2643
4724ba57
RD
2644 watchdog timers [HW,WDT] For information on watchdog timers,
2645 see Documentation/watchdog/watchdog-parameters.txt
2646 or other driver-specific files in the
2647 Documentation/watchdog/ directory.
1da177e4 2648
0cb55ad2
RD
2649 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2650 default x2apic cluster mode on platforms
2651 supporting x2apic.
2652
bb24c471
JP
2653 x86_mrst_timer= [X86-32,APBT]
2654 Choose timer option for x86 Moorestown MID platform.
2655 Two valid options are apbt timer only and lapic timer
2656 plus one apbt timer for broadcast timer.
2657 x86_mrst_timer=apbt_only | lapic_and_apbt
2658
1da177e4
LT
2659 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2660 xd_geo= See header of drivers/block/xd.c.
2661
c1c5413a
SS
2662 xen_emul_unplug= [HW,X86,XEN]
2663 Unplug Xen emulated devices
2664 Format: [unplug0,][unplug1]
2665 ide-disks -- unplug primary master IDE devices
2666 aux-ide-disks -- unplug non-primary-master IDE devices
2667 nics -- unplug network devices
2668 all -- unplug all emulated devices (NICs and IDE disks)
1dc7ce99
IC
2669 unnecessary -- unplugging emulated devices is
2670 unnecessary even if the host did not respond to
2671 the unplug protocol
c93a4dfb 2672 never -- do not unplug even if version check succeeds
c1c5413a 2673
1da177e4 2674 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2675 Format:
2676 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2677
a9913044 2678______________________________________________________________________
1da177e4
LT
2679
2680TODO:
2681
1da177e4 2682 Add more DRM drivers.