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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.
a9913044 46 DRM Direct Rendering Management support is enabled.
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47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 HW Appropriate hardware is enabled.
1da177e4 52 IA-64 IA-64 architecture is enabled.
6146f0d5 53 IMA Integrity measurement architecture is enabled.
1da177e4 54 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 55 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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56 ISAPNP ISA PnP code is enabled.
57 ISDN Appropriate ISDN support is enabled.
58 JOY Appropriate joystick support is enabled.
11ef697b 59 LIBATA Libata driver is enabled
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60 LP Printer support is enabled.
61 LOOP Loopback device support is enabled.
62 M68k M68k architecture is enabled.
63 These options have more detailed description inside of
64 Documentation/m68k/kernel-options.txt.
65 MCA MCA bus support is enabled.
66 MDA MDA console support is enabled.
67 MOUSE Appropriate mouse support is enabled.
309e57df 68 MSI Message Signaled Interrupts (PCI).
c8facbb6 69 MTD MTD (Memory Technology Device) support is enabled.
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70 NET Appropriate network support is enabled.
71 NUMA NUMA support is enabled.
734efb46 72 GENERIC_TIME The generic timeofday code is enabled.
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73 NFS Appropriate NFS support is enabled.
74 OSS OSS sound support is enabled.
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75 PV_OPS A paravirtualized kernel is enabled.
76 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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77 PARISC The PA-RISC architecture is enabled.
78 PCI PCI bus support is enabled.
7f785763 79 PCIE PCI Express support is enabled.
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80 PCMCIA The PCMCIA subsystem is enabled.
81 PNP Plug & Play support is enabled.
82 PPC PowerPC architecture is enabled.
83 PPT Parallel port support is enabled.
84 PS2 Appropriate PS/2 support is enabled.
85 RAM RAM disk support is enabled.
20510f2f 86 ROOTPLUG The example Root Plug LSM is enabled.
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87 S390 S390 architecture is enabled.
88 SCSI Appropriate SCSI support is enabled.
89 A lot of drivers has their options described inside of
90 Documentation/scsi/.
20510f2f 91 SECURITY Different security models are enabled.
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92 SELINUX SELinux support is enabled.
93 SERIAL Serial support is enabled.
e523d93c 94 SH SuperH architecture is enabled.
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95 SMP The kernel is an SMP kernel.
96 SPARC Sparc architecture is enabled.
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97 SWSUSP Software suspend (hibernation) is enabled.
98 SUSPEND System suspend states are enabled.
f38f1d2a 99 FTRACE Function tracing enabled.
1da177e4 100 TS Appropriate touchscreen support is enabled.
d4f373e5 101 UMS USB Mass Storage support is enabled.
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102 USB USB support is enabled.
103 USBHID USB Human Interface Device support is enabled.
104 V4L Video For Linux support is enabled.
105 VGA The VGA console has been enabled.
106 VT Virtual terminal support is enabled.
107 WDT Watchdog support is enabled.
108 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 109 X86-32 X86-32, aka i386 architecture is enabled.
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110 X86-64 X86-64 architecture is enabled.
111 More X86-64 boot options can be found in
71cced6e 112 Documentation/x86/x86_64/boot-options.txt .
c0115606 113 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
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114
115In addition, the following text indicates that the option:
116
117 BUGS= Relates to possible processor bugs on the said processor.
118 KNL Is a kernel start-up parameter.
119 BOOT Is a boot loader parameter.
120
121Parameters denoted with BOOT are actually interpreted by the boot
122loader, and have no meaning to the kernel directly.
123Do not modify the syntax of boot loader parameters without extreme
954a8b81 124need or coordination with <Documentation/x86/boot.txt>.
1da177e4 125
5558870b 126There are also arch-specific kernel-parameters not documented here.
71cced6e 127See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 128
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129Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
130a trailing = on the name of any parameter states that that parameter will
131be entered as an environment variable, whereas its absence indicates that
132it will appear as a kernel argument readable via /proc/cmdline by programs
133running once the system is up.
134
9c4751fd 135The number of kernel parameters is not limited, but the length of the
136complete command line (parameters including spaces etc.) is limited to
137a fixed number of characters. This limit depends on the architecture
138and is between 256 and 4096 characters. It is defined in the file
139./include/asm/setup.h as COMMAND_LINE_SIZE.
140
141
6cececfc 142 acpi= [HW,ACPI,X86]
03d926f8 143 Advanced Configuration and Power Interface
af23f573 144 Format: { force | off | ht | strict | noirq | rsdt }
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145 force -- enable ACPI if default was off
146 off -- disable ACPI if default was on
147 noirq -- do not use ACPI for IRQ routing
148 ht -- run only enough ACPI to enable Hyper Threading
a9913044 149 strict -- Be less tolerant of platforms that are not
1da177e4 150 strictly ACPI specification compliant.
237889bf 151 rsdt -- prefer RSDT over (default) XSDT
1da177e4 152
53471121 153 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 154
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155 acpi_apic_instance= [ACPI, IOAPIC]
156 Format: <int>
157 2: use 2nd APIC table, if available
158 1,0: use 1st APIC table
4e381a4f 159 default: 0
a1fdcc0d 160
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161 acpi_backlight= [HW,ACPI]
162 acpi_backlight=vendor
163 acpi_backlight=video
164 If set to vendor, prefer vendor specific driver
165 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
166 of the ACPI video.ko driver.
167
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168 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
169 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 170 Format: <int>
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171 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
172 debug output. Bits in debug_layer correspond to a
173 _COMPONENT in an ACPI source file, e.g.,
174 #define _COMPONENT ACPI_PCI_COMPONENT
175 Bits in debug_level correspond to a level in
176 ACPI_DEBUG_PRINT statements, e.g.,
177 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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178 The debug_level mask defaults to "info". See
179 Documentation/acpi/debug.txt for more information about
180 debug layers and levels.
a0d84a92 181
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182 Enable processor driver info messages:
183 acpi.debug_layer=0x20000000
184 Enable PCI/PCI interrupt routing info messages:
185 acpi.debug_layer=0x400000
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186 Enable AML "Debug" output, i.e., stores to the Debug
187 object while interpreting AML:
188 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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189 Enable all messages related to ACPI hardware:
190 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
191
192 Some values produce so much output that the system is
193 unusable. The "log_buf_len" parameter may be useful
194 if you need to capture more output.
f989106c 195
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196 acpi_display_output= [HW,ACPI]
197 acpi_display_output=vendor
198 acpi_display_output=video
199 See above.
200
201 acpi_irq_balance [HW,ACPI]
202 ACPI will balance active IRQs
203 default in APIC mode
204
205 acpi_irq_nobalance [HW,ACPI]
206 ACPI will not move active IRQs (default)
207 default in PIC mode
208
209 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
210 Format: <irq>,<irq>...
211
212 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
213 use by PCI
214 Format: <irq>,<irq>...
215
216 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
217
218 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
219 Format: To spoof as Windows 98: ="Microsoft Windows"
220
221 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
222 acpi_osi="string1" # add string1 -- only one string
223 acpi_osi="!string2" # remove built-in string2
224 acpi_osi= # disable all strings
225
6cececfc 226 acpi_pm_good [X86]
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227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
230
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231 acpi.power_nocheck= [HW,ACPI]
232 Format: 1/0 enable/disable the check of power state.
233 On some bogus BIOS the _PSC object/_STA object of
234 power resource can't return the correct device power
235 state. In such case it is unneccessary to check its
236 power state again in power transition.
237 1 : disable the power state check
238
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239 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
240 Format: { level | edge | high | low }
241
242 acpi_serialize [HW,ACPI] force serialization of AML methods
243
244 acpi_skip_timer_override [HW,ACPI]
245 Recognize and ignore IRQ0/pin2 Interrupt Override.
246 For broken nForce2 BIOS resulting in XT-PIC timer.
247
248 acpi_sleep= [HW,ACPI] Sleep options
249 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
250 old_ordering, s4_nonvs }
251 See Documentation/power/video.txt for information on
252 s3_bios and s3_mode.
253 s3_beep is for debugging; it makes the PC's speaker beep
254 as soon as the kernel's real-mode entry point is called.
255 s4_nohwsig prevents ACPI hardware signature from being
256 used during resume from hibernation.
257 old_ordering causes the ACPI 1.0 ordering of the _PTS
258 control method, with respect to putting devices into
259 low power states, to be enforced (the ACPI 2.0 ordering
260 of _PTS is used by default).
261 s4_nonvs prevents the kernel from saving/restoring the
262 ACPI NVS memory during hibernation.
263
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
267
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268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
283
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284 ad1848= [HW,OSS]
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
286
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287 add_efi_memmap [EFI; X86] Include EFI memory map in
288 kernel's map of available physical RAM.
289
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290 advansys= [HW,SCSI]
291 See header of drivers/scsi/advansys.c.
292
293 advwdt= [HW,WDT] Advantech WDT
294 Format: <iostart>,<iostop>
295
296 aedsp16= [HW,OSS] Audio Excel DSP 16
297 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
298 See also header of sound/oss/aedsp16.c.
a9913044 299
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300 agp= [AGP]
301 { off | try_unsupported }
302 off: disable AGP support
303 try_unsupported: try to drive unsupported chipsets
304 (may crash computer or cause data corruption)
305
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306 aha152x= [HW,SCSI]
307 See Documentation/scsi/aha152x.txt.
308
309 aha1542= [HW,SCSI]
310 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
311
312 aic7xxx= [HW,SCSI]
313 See Documentation/scsi/aic7xxx.txt.
314
315 aic79xx= [HW,SCSI]
316 See Documentation/scsi/aic79xx.txt.
317
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318 amd_iommu= [HW,X86-84]
319 Pass parameters to the AMD IOMMU driver in the system.
320 Possible values are:
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321 isolate - enable device isolation (each device, as far
322 as possible, will get its own protection
3ce1f93c 323 domain) [default]
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324 share - put every device behind one IOMMU into the
325 same protection domain
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326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
329 is a lot of faster
330
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331 amd_iommu_size= [HW,X86-64]
332 Define the size of the aperture for the AMD IOMMU
333 driver. Possible values are:
334 '32M', '64M' (default), '128M', '256M', '512M', '1G'
335
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336 amijoy.map= [HW,JOY] Amiga joystick support
337 Map of devices attached to JOY0DAT and JOY1DAT
338 Format: <a>,<b>
339 See also Documentation/kernel/input/joystick.txt
340
341 analog.map= [HW,JOY] Analog joystick and gamepad support
342 Specifies type or capabilities of an analog joystick
343 connected to one of 16 gameports
344 Format: <type1>,<type2>,..<type16>
345
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346 apc= [HW,SPARC]
347 Power management functions (SPARCstation-4/5 + deriv.)
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348 Format: noidle
349 Disable APC CPU standby support. SPARCstation-Fox does
350 not play well with APC CPU idle - disable it if you have
351 APC and your system crashes randomly.
352
ca1eda2d 353 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 354 Change the output verbosity whilst booting
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355 Format: { quiet (default) | verbose | debug }
356 Change the amount of debugging information output
357 when initialising the APIC and IO-APIC components.
a9913044 358
1da177e4 359 apm= [APM] Advanced Power Management
71f77055 360 See header of arch/x86/kernel/apm_32.c.
1da177e4 361
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362 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
363 Format: <io>,<irq>,<nodeID>
364
365 ataflop= [HW,M68k]
366
367 atarimouse= [HW,MOUSE] Atari Mouse
368
369 atascsi= [HW,SCSI] Atari SCSI
370
371 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
372 EzKey and similar keyboards
373
374 atkbd.reset= [HW] Reset keyboard during initialization
375
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376 atkbd.set= [HW] Select keyboard code set
377 Format: <int> (2 = AT (default), 3 = PS/2)
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378
379 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
380 keyboards
381
382 atkbd.softraw= [HW] Choose between synthetic and real raw mode
383 Format: <bool> (0 = real, 1 = synthetic (default))
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384
385 atkbd.softrepeat= [HW]
386 Use software keyboard repeat
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387
388 autotest [IA64]
389
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390 baycom_epp= [HW,AX25]
391 Format: <io>,<mode>
a9913044 392
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393 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
394 Format: <io>,<mode>
395 See header of drivers/net/hamradio/baycom_par.c.
396
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397 baycom_ser_fdx= [HW,AX25]
398 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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399 Format: <io>,<irq>,<mode>[,<baud>]
400 See header of drivers/net/hamradio/baycom_ser_fdx.c.
401
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402 baycom_ser_hdx= [HW,AX25]
403 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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404 Format: <io>,<irq>,<mode>
405 See header of drivers/net/hamradio/baycom_ser_hdx.c.
406
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407 boot_delay= Milliseconds to delay each printk during boot.
408 Values larger than 10 seconds (10000) are changed to
409 no delay (0).
410 Format: integer
411
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412 bootmem_debug [KNL] Enable bootmem allocator debug messages.
413
1da177e4 414 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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415 bttv.radio= Most important insmod options are available as
416 kernel args too.
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417 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
418 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
419
420 BusLogic= [HW,SCSI]
421 See drivers/scsi/BusLogic.c, comment before function
422 BusLogic_ParseDriverOptions().
423
424 c101= [NET] Moxa C101 synchronous serial card
425
cd4f0ef7 426 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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427 Sometimes CPU hardware bugs make them report the cache
428 size incorrectly. The kernel will attempt work arounds
429 to fix known problems, but for some CPUs it is not
430 possible to determine what the correct size should be.
431 This option provides an override for these situations.
432
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433 capability.disable=
434 [SECURITY] Disable capabilities. This would normally
435 be used only if an alternative security model is to be
436 configured. Potentially dangerous and should only be
437 used if you are entirely sure of the consequences.
438
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439 ccw_timeout_log [S390]
440 See Documentation/s390/CommonIO for details.
1da177e4 441
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442 cgroup_disable= [KNL] Disable a particular controller
443 Format: {name of the controller(s) to disable}
444 {Currently supported controllers - "memory"}
445
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446 checkreqprot [SELINUX] Set initial checkreqprot flag value.
447 Format: { "0" | "1" }
448 See security/selinux/Kconfig help text.
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449 0 -- check protection applied by kernel (includes
450 any implied execute protection).
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451 1 -- check protection requested by application.
452 Default value is set via a kernel config option.
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453 Value can be changed at runtime via
454 /selinux/checkreqprot.
455
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456 cio_ignore= [S390]
457 See Documentation/s390/CommonIO for details.
458
cd4f0ef7 459 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 460 [Deprecated]
3f6dee9b 461 Forces specified clocksource (if available) to be used
734efb46 462 when calculating gettimeofday(). If specified
3f6dee9b 463 clocksource is not available, it defaults to PIT.
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464 Format: { pit | tsc | cyclone | pmtmr }
465
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466 clocksource= [GENERIC_TIME] Override the default clocksource
467 Format: <string>
468 Override the default clocksource and use the clocksource
469 with the name specified.
470 Some clocksource names to choose from, depending on
471 the platform:
472 [all] jiffies (this is the base, fallback clocksource)
473 [ACPI] acpi_pm
474 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
475 pxa_timer,timer3,32k_counter,timer0_1
476 [AVR32] avr32
cd4f0ef7 477 [X86-32] pit,hpet,tsc,vmi-timer;
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478 scx200_hrt on Geode; cyclone on IBM x440
479 [MIPS] MIPS
480 [PARISC] cr16
481 [S390] tod
482 [SH] SuperH
483 [SPARC64] tick
484 [X86-64] hpet,tsc
485
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486 clearcpuid=BITNUM [X86]
487 Disable CPUID feature X for the kernel. See
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488 arch/x86/include/asm/cpufeature.h for the valid bit
489 numbers. Note the Linux specific bits are not necessarily
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490 stable over kernel options, but the vendor specific
491 ones should be.
492 Also note that user programs calling CPUID directly
493 or using the feature without checking anything
494 will still see it. This just prevents it from
495 being used by the kernel or shown in /proc/cpuinfo.
496 Also note the kernel might malfunction if you disable
497 some critical bits.
498
6cececfc 499 code_bytes [X86] How many bytes of object code to print
a25bd949 500 in an oops report.
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501 Range: 0 - 8192
502 Default: 64
503
1da177e4 504 com20020= [HW,NET] ARCnet - COM20020 chipset
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505 Format:
506 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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507
508 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
509 Format: <io>[,<irq>]
510
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511 com90xx= [HW,NET]
512 ARCnet - COM90xx chipset (memory-mapped buffers)
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513 Format: <io>[,<irq>[,<memstart>]]
514
515 condev= [HW,S390] console device
516 conmode=
a9913044 517
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518 console= [KNL] Output console device and options.
519
520 tty<n> Use the virtual console device <n>.
521
522 ttyS<n>[,options]
f1a1c2dc 523 ttyUSB0[,options]
1da177e4 524 Use the specified serial port. The options are of
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525 the form "bbbbpnf", where "bbbb" is the baud rate,
526 "p" is parity ("n", "o", or "e"), "n" is number of
527 bits, and "f" is flow control ("r" for RTS or
528 omit it). Default is "9600n8".
529
530 See Documentation/serial-console.txt for more
531 information. See
532 Documentation/networking/netconsole.txt for an
533 alternative.
1da177e4 534
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535 uart[8250],io,<addr>[,options]
536 uart[8250],mmio,<addr>[,options]
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537 Start an early, polled-mode console on the 8250/16550
538 UART at the specified I/O port or MMIO address,
539 switching to the matching ttyS device later. The
540 options are the same as for ttyS, above.
541
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542 If the device connected to the port is not a TTY but a braille
543 device, prepend "brl," before the device type, for instance
544 console=brl,ttyS0
545 For now, only VisioBraille is supported.
546
4cb0e11b
HK
547 coredump_filter=
548 [KNL] Change the default value for
549 /proc/<pid>/coredump_filter.
550 See also Documentation/filesystems/proc.txt.
551
1da177e4 552 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
553 Format:
554 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 555
dc009d92
EB
556 crashkernel=nn[KMG]@ss[KMG]
557 [KNL] Reserve a chunk of physical memory to
558 hold a kernel to switch to with kexec on panic.
559
fb391599
BW
560 crashkernel=range1:size1[,range2:size2,...][@offset]
561 [KNL] Same as above, but depends on the memory
562 in the running system. The syntax of range is
563 start-[end] where start and end are both
564 a memory unit (amount[KMG]). See also
565 Documentation/kdump/kdump.txt for a example.
566
1da177e4
LT
567 cs89x0_dma= [HW,NET]
568 Format: <dma>
569
570 cs89x0_media= [HW,NET]
571 Format: { rj45 | aui | bnc }
a9913044 572
a9913044 573 dasd= [HW,NET]
1da177e4
LT
574 See header of drivers/s390/block/dasd_devmap.c.
575
576 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
577 (one device per port)
578 Format: <port#>,<type>
579 See also Documentation/input/joystick-parport.txt
580
581 debug [KNL] Enable kernel debugging (events log level).
582
cae2ed9a
IM
583 debug_locks_verbose=
584 [KNL] verbose self-tests
585 Format=<0|1>
586 Print debugging info while doing the locking API
587 self-tests.
588 We default to 0 (no extra messages), setting it to
589 1 will print _a lot_ more information - normally
590 only useful to kernel developers.
591
3ac7fe5a
TG
592 debug_objects [KNL] Enable object debugging
593
3e8ebb5c
KM
594 no_debug_objects
595 [KNL] Disable object debugging
596
d3af01f1
TG
597 debugpat [X86] Enable PAT debugging
598
2d27a966 599 decnet.addr= [HW,NET]
1da177e4
LT
600 Format: <area>[,<node>]
601 See also Documentation/networking/decnet.txt.
602
0cb55ad2
RD
603 default_hugepagesz=
604 [same as hugepagesz=] The size of the default
605 HugeTLB page size. This is the size represented by
606 the legacy /proc/ hugepages APIs, used for SHM, and
607 default size when mounting hugetlbfs filesystems.
608 Defaults to the default architecture's huge page size
609 if not specified.
55ff9780 610
1da177e4
LT
611 dhash_entries= [KNL]
612 Set number of hash buckets for dentry cache.
a9913044 613
1da177e4
LT
614 digi= [HW,SERIAL]
615 IO parameters + enable/disable command.
616
617 digiepca= [HW,SERIAL]
618 See drivers/char/README.epca and
31c00fc1 619 Documentation/serial/digiepca.txt.
1da177e4 620
95ffa243 621 disable_mtrr_cleanup [X86]
95ffa243
YL
622 The kernel tries to adjust MTRR layout from continuous
623 to discrete, to make X server driver able to add WB
0cb55ad2 624 entry later. This parameter disables that.
95ffa243 625
093af8d7 626 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
627 By default the kernel will trim any uncacheable
628 memory out of your available memory pool based on
629 MTRR settings. This parameter disables that behavior,
630 possibly causing your machine to run very slowly.
631
6cececfc 632 disable_timer_pin_1 [X86]
0cb55ad2
RD
633 Disable PIN 1 of APIC timer
634 Can be useful to work around chipset bugs.
635
1da177e4
LT
636 dmasound= [HW,OSS] Sound subsystem buffers
637
0cb55ad2
RD
638 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
639 this option disables the debugging code at boot.
640
641 dma_debug_entries=<number>
642 This option allows to tune the number of preallocated
643 entries for DMA-API debugging code. One entry is
644 required per DMA-API allocation. Use this if the
645 DMA-API debugging code disables itself because the
646 architectural default is too low.
647
1da177e4
LT
648 dscc4.setup= [NET]
649
650 dtc3181e= [HW,SCSI]
651
0cb55ad2
RD
652 dynamic_printk Enables pr_debug()/dev_dbg() calls if
653 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
654 These can also be switched on/off via
655 <debugfs>/dynamic_printk/modules
656
657 earlycon= [KNL] Output early console device and options.
658 uart[8250],io,<addr>[,options]
659 uart[8250],mmio,<addr>[,options]
660 Start an early, polled-mode console on the 8250/16550
661 UART at the specified I/O port or MMIO address.
662 The options are the same as for ttyS, above.
663
6cececfc 664 earlyprintk= [X86,SH,BLACKFIN]
1da177e4
LT
665 earlyprintk=vga
666 earlyprintk=serial[,ttySn[,baudrate]]
5c05917e 667 earlyprintk=dbgp
1da177e4 668
a9913044 669 Append ",keep" to not disable it when the real console
1da177e4
LT
670 takes over.
671
5c05917e 672 Only vga or serial or usb debug port at a time.
1da177e4
LT
673
674 Currently only ttyS0 and ttyS1 are supported.
675
676 Interaction with the standard serial driver is not
677 very good.
678
679 The VGA output is eventually overwritten by the real
680 console.
681
682 eata= [HW,SCSI]
683
1da177e4 684 edd= [EDD]
8c4dd606 685 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 686
1da177e4
LT
687 eisa_irq_edge= [PARISC,HW]
688 See header of drivers/parisc/eisa.c.
689
cd4f0ef7 690 elanfreq= [X86-32]
1da177e4 691 See comment before function elanfreq_setup() in
71f77055 692 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
693
694 elevator= [IOSCHED]
16ab3adf 695 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
696 See Documentation/block/as-iosched.txt and
697 Documentation/block/deadline-iosched.txt for details.
698
6cececfc 699 elfcorehdr= [IA64,PPC,SH,X86]
a9913044 700 Specifies physical address of start of kernel core
aac04b32
VG
701 image elf header. Generally kexec loader will
702 pass this option to capture kernel.
703 See Documentation/kdump/kdump.txt for details.
1da177e4 704
0cb55ad2
RD
705 enable_mtrr_cleanup [X86]
706 The kernel tries to adjust MTRR layout from continuous
707 to discrete, to make X server driver able to add WB
708 entry later. This parameter enables that.
709
ca1eda2d 710 enable_timer_pin_1 [X86]
0cb55ad2
RD
711 Enable PIN 1 of APIC timer
712 Can be useful to work around chipset bugs
713 (in particular on some ATI chipsets).
714 The kernel tries to set a reasonable default.
715
1da177e4
LT
716 enforcing [SELINUX] Set initial enforcing status.
717 Format: {"0" | "1"}
718 See security/selinux/Kconfig help text.
719 0 -- permissive (log only, no denials).
720 1 -- enforcing (deny and log).
721 Default value is 0.
722 Value can be changed at runtime via /selinux/enforce.
723
1da177e4
LT
724 ether= [HW,NET] Ethernet cards parameters
725 This option is obsoleted by the "netdev=" option, which
726 has equivalent usage. See its documentation for details.
727
728 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
729 Format: <io>[,<irq>]
730
de1ba09b
AM
731 failslab=
732 fail_page_alloc=
733 fail_make_request=[KNL]
734 General fault injection mechanism.
735 Format: <interval>,<probability>,<space>,<times>
736 See also /Documentation/fault-injection/.
737
1da177e4
LT
738 fd_mcs= [HW,SCSI]
739 See header of drivers/scsi/fd_mcs.c.
740
741 fdomain= [HW,SCSI]
742 See header of drivers/scsi/fdomain.c.
743
744 floppy= [HW]
31c00fc1 745 See Documentation/blockdev/floppy.txt.
1da177e4 746
f13ae30e
AC
747 force_pal_cache_flush
748 [IA-64] Avoid check_sal_cache_flush which may hang on
749 buggy SAL_CACHE_FLUSH implementations. Using this
750 parameter will force ia64_sal_cache_flush to call
751 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
752
d9e54076
PZ
753 ftrace=[tracer]
754 [ftrace] will set and start the specified tracer
755 as early as possible in order to facilitate early
756 boot debugging.
757
758 ftrace_dump_on_oops
759 [ftrace] will dump the trace buffers on oops.
760
1da177e4
LT
761 gamecon.map[2|3]=
762 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
763 support via parallel port (up to 5 devices per port)
764 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
765 See also Documentation/input/joystick-parport.txt
766
767 gamma= [HW,DRM]
768
aaf23042
YL
769 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
770 Format: off | on
771 default: on
772
1da177e4
LT
773 gdth= [HW,SCSI]
774 See header of drivers/scsi/gdth.c.
775
776 gpt [EFI] Forces disk with valid GPT signature but
777 invalid Protective MBR to be treated as GPT.
778
1da177e4
LT
779 gvp11= [HW,SCSI]
780
781 hashdist= [KNL,NUMA] Large hashes allocated during boot
782 are distributed across NUMA nodes. Defaults on
429aa0fc 783 for 64bit NUMA, off otherwise.
a9913044 784 Format: 0 | 1 (for off | on)
1da177e4
LT
785
786 hcl= [IA-64] SGI's Hardware Graph compatibility layer
787
788 hd= [EIDE] (E)IDE hard drive subsystem geometry
789 Format: <cyl>,<head>,<sect>
790
1da177e4
LT
791 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
792 size of <nn>. This works even on boxes that have no
793 highmem otherwise. This also works to reduce highmem
794 size on bigger boxes.
795
54cdfdb4
TG
796 highres= [KNL] Enable/disable high resolution timer mode.
797 Valid parameters: "on", "off"
798 Default: "on"
799
1da177e4
LT
800 hisax= [HW,ISDN]
801 See Documentation/isdn/README.HiSax.
802
0cb55ad2
RD
803 hlt [BUGS=ARM,SH]
804
805 hpet= [X86-32,HPET] option to control HPET usage
806 Format: { enable (default) | disable | force |
807 verbose }
808 disable: disable HPET and use PIT instead
809 force: allow force enabled of undocumented chips (ICH4,
810 VIA, nVidia)
811 verbose: show contents of HPET registers during setup
812
b4718e62
AK
813 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
814 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
815 On x86-64 and powerpc, this option can be specified
816 multiple times interleaved with hugepages= to reserve
817 huge pages of different sizes. Valid pages sizes on
818 x86-64 are 2M (when the CPU supports "pse") and 1G
819 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
820 Note that 1GB pages can only be allocated at boot time
821 using hugepages= and not freed afterwards.
6902aa84 822
555d61d6
HB
823 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
824 terminal devices. Valid values: 0..8
431429ff
HB
825 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
826 If specified, z/VM IUCV HVC accepts connections
827 from listed z/VM user IDs only.
cef7125d 828
3a853fb9 829 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
830 or register an additional I2C bus that is not
831 registered from board initialization code.
3a853fb9
JN
832 Format:
833 <bus_id>,<clkrate>
834
36d95739 835 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 836 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
837 i8042.dumbkbd [HW] Pretend that controller can only read data from
838 keyboard and cannot control its state
1da177e4
LT
839 (Don't attempt to blink the leds)
840 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 841 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
842 i8042.noloop [HW] Disable the AUX Loopback command while probing
843 for the AUX port
1da177e4
LT
844 i8042.nomux [HW] Don't check presence of an active multiplexing
845 controller
846 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
847 controllers
848 i8042.panicblink=
849 [HW] Frequency with which keyboard LEDs should blink
850 when kernel panics (default is 0.5 sec)
851 i8042.reset [HW] Reset the controller during init and cleanup
852 i8042.unlock [HW] Unlock (ignore) the keylock
853
854 i810= [HW,DRM]
855
e70c9d5e
DT
856 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
857 indicates that the driver is running on unsupported
858 hardware.
1da177e4
LT
859 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
860 does not match list of supported models.
861 i8k.power_status
862 [HW] Report power status in /proc/i8k
863 (disabled by default)
864 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
865 capability is set.
866
867 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
868 See Documentation/mca.txt.
869
870 icn= [HW,ISDN]
871 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
872
0af80c04
DF
873 ide-core.nodma= [HW] (E)IDE subsystem
874 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
875 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
876 .chs .ignore_cable are additional options
1c10e938 877 See Documentation/ide/ide.txt.
1da177e4 878
1da177e4 879 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 880 See Documentation/ide/ide.txt.
1da177e4 881
0cb55ad2
RD
882 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
883 Claim all unknown PCI IDE storage controllers.
884
f039b754 885 idle= [X86]
ada9cfdd
RD
886 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
887 Poll forces a polling idle loop that can slightly
888 improve the performance of waking up a idle CPU, but
889 will use a lot of power and make the system run hot.
890 Not recommended.
891 idle=mwait: On systems which support MONITOR/MWAIT but
892 the kernel chose to not use it because it doesn't save
893 as much power as a normal idle loop, use the
894 MONITOR/MWAIT idle loop anyways. Performance should be
895 the same as idle=poll.
896 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 897 In such case C2/C3 won't be used again.
ada9cfdd 898 idle=nomwait: Disable mwait for CPU C-states
a9913044 899
79290822
IM
900 ignore_loglevel [KNL]
901 Ignore loglevel setting - this will print /all/
902 kernel messages to the console. Useful for debugging.
903
1da177e4
LT
904 ihash_entries= [KNL]
905 Set number of hash buckets for inode cache.
906
3323eec9
MZ
907 ima_audit= [IMA]
908 Format: { "0" | "1" }
909 0 -- integrity auditing messages. (Default)
910 1 -- enable informational integrity auditing messages.
911
912 ima_hash= [IMA]
913 Formt: { "sha1" | "md5" }
914 default: "sha1"
915
1da177e4
LT
916 in2000= [HW,SCSI]
917 See header of drivers/scsi/in2000.c.
918
919 init= [KNL]
920 Format: <full_path>
921 Run specified binary instead of /sbin/init as init
922 process.
923
924 initcall_debug [KNL] Trace initcalls as they are executed. Useful
925 for working out where the kernel is dying during
926 startup.
927
928 initrd= [BOOT] Specify the location of the initial ramdisk
929
930 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
931 Format: <irq>
932
ba395927 933 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
934 on
935 Enable intel iommu driver.
ba395927
KA
936 off
937 Disable intel iommu driver.
938 igfx_off [Default Off]
939 By default, gfx is mapped as normal device. If a gfx
940 device has a dedicated DMAR unit, the DMAR unit is
941 bypassed by not enabling DMAR with this option. In
942 this case, gfx device will use physical address for
943 DMA.
7d3b03ce
KA
944 forcedac [x86_64]
945 With this option iommu will not optimize to look
946 for io virtual address below 32 bit forcing dual
947 address cycle on pci bus for cards supporting greater
948 than 32 bit addressing. The default is to look
949 for translation below 32 bit and if not available
950 then look in the higher range.
5e0d2a6f 951 strict [Default Off]
952 With this option on every unmap_single operation will
953 result in a hardware IOTLB flush operation as opposed
954 to batching them for performance.
ba395927 955
0cb55ad2
RD
956 inttest= [IA64]
957
958 iomem= Disable strict checking of access to MMIO memory
959 strict regions from userspace.
960 relaxed
961
962 iommu= [x86]
963 off
964 force
965 noforce
966 biomerge
967 panic
968 nopanic
969 merge
970 nomerge
971 forcesac
972 soft
973
974 io7= [HW] IO7 for Marvel based alpha systems
975 See comment before marvel_specify_io7 in
976 arch/alpha/kernel/core_marvel.c.
977
6cececfc 978 io_delay= [X86] I/O delay method
6e7c4025
IM
979 0x80
980 Standard port 0x80 based delay
981 0xed
982 Alternate port 0xed based delay (needed on some systems)
b02aae9c 983 udelay
6e7c4025
IM
984 Simple two microseconds delay
985 none
986 No delay
b02aae9c 987
1da177e4 988 ip= [IP_PNP]
6ded55da 989 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
990
991 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
992 See comment before ip2_setup() in
993 drivers/char/ip2/ip2base.c.
1da177e4
LT
994
995 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
996 See header of drivers/scsi/ips.c.
997
200803df
AC
998 irqfixup [HW]
999 When an interrupt is not handled search all handlers
1000 for it. Intended to get systems with badly broken
1001 firmware running.
1002
1003 irqpoll [HW]
1004 When an interrupt is not handled search all handlers
1005 for it. Also check all handlers each timer
1006 interrupt. Intended to get systems with badly broken
1007 firmware running.
1008
1da177e4 1009 isapnp= [ISAPNP]
a9913044 1010 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1011
1012 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1013 Format:
1014 <cpu number>,...,<cpu number>
1015 or
b225d44e
LZ
1016 <cpu number>-<cpu number>
1017 (must be a positive range in ascending order)
22f2e280
DF
1018 or a mixture
1019 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1020
1da177e4
LT
1021 This option can be used to specify one or more CPUs
1022 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1023 algorithms. You can move a process onto or off an
1024 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1025 <cpu number> begins at 0 and the maximum value is
1026 "number of CPUs in system - 1".
1027
1028 This option is the preferred way to isolate CPUs. The
a9913044
RD
1029 alternative -- manually setting the CPU mask of all
1030 tasks in the system -- can cause problems and
1031 suboptimal load balancer performance.
1da177e4 1032
a9913044 1033 iucv= [HW,NET]
1da177e4
LT
1034
1035 js= [HW,JOY] Analog joystick
1036 See Documentation/input/joystick.txt.
1037
0cb55ad2
RD
1038 keepinitrd [HW,ARM]
1039
6cececfc 1040 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1041 specifies the amount of memory usable by the kernel
1042 for non-movable allocations. The requested amount is
1043 spread evenly throughout all nodes in the system. The
1044 remaining memory in each node is used for Movable
1045 pages. In the event, a node is too small to have both
1046 kernelcore and Movable pages, kernelcore pages will
1047 take priority and other nodes will have a larger number
1048 of kernelcore pages. The Movable zone is used for the
1049 allocation of pages that may be reclaimed or moved
1050 by the page migration subsystem. This means that
1051 HugeTLB pages may not be allocated from this zone.
1052 Note that allocations like PTEs-from-HighMem still
1053 use the HighMem zone if it exists, and the Normal
1054 zone if it does not.
1055
6cdf6e06
JW
1056 kgdboc= [HW] kgdb over consoles.
1057 Requires a tty driver that supports console polling.
1058 (only serial suported for now)
1059 Format: <serial_device>[,baud]
1060
9bed90c6
FF
1061 kmac= [MIPS] korina ethernet MAC address.
1062 Configure the RouterBoard 532 series on-chip
1063 Ethernet adapter MAC address.
1064
6cececfc 1065 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1066 in oops dumps.
1067
1da177e4
LT
1068 l2cr= [PPC]
1069
a78bfbfc
RB
1070 l3cr= [PPC]
1071
cd4f0ef7 1072 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1073 disabled it.
1da177e4 1074
6cececfc 1075 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1076 in C2 power state.
e585bef8 1077
fcb71f6f
FC
1078 libata.dma= [LIBATA] DMA control
1079 libata.dma=0 Disable all PATA and SATA DMA
1080 libata.dma=1 PATA and SATA Disk DMA only
1081 libata.dma=2 ATAPI (CDROM) DMA only
1082 libata.dma=4 Compact Flash DMA only
1083 Combinations also work, so libata.dma=3 enables DMA
1084 for disks and CDROMs, but not CFs.
1085
78e70c23
DJ
1086 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1087 when set.
1088 Format: <int>
1089
33267325
TH
1090 libata.force= [LIBATA] Force configurations. The format is comma
1091 separated list of "[ID:]VAL" where ID is
1092 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1093 matching port, link or device. Basically, it matches
1094 the ATA ID string printed on console by libata. If
1095 the whole ID part is omitted, the last PORT and DEVICE
1096 values are used. If ID hasn't been specified yet, the
1097 configuration applies to all ports, links and devices.
1098
1099 If only DEVICE is omitted, the parameter applies to
1100 the port and all links and devices behind it. DEVICE
1101 number of 0 either selects the first device or the
1102 first fan-out link behind PMP device. It does not
1103 select the host link. DEVICE number of 15 selects the
1104 host link and device attached to it.
1105
1106 The VAL specifies the configuration to force. As long
1107 as there's no ambiguity shortcut notation is allowed.
1108 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1109 The following configurations can be forced.
1110
1111 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1112 Any ID with matching PORT is used.
1113
1114 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1115
1116 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1117 udma[/][16,25,33,44,66,100,133] notation is also
1118 allowed.
1119
1120 * [no]ncq: Turn on or off NCQ.
1121
05944bdf
TH
1122 * nohrst, nosrst, norst: suppress hard, soft
1123 and both resets.
1124
33267325
TH
1125 If there are multiple matching configurations changing
1126 the same attribute, the last one is used.
1127
7c4be253
RD
1128 lmb=debug [KNL] Enable lmb debug messages.
1129
1da177e4 1130 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1131 See Documentation/blockdev/ramdisk.txt.
1da177e4 1132
a6b25b67
RD
1133 lockd.nlm_grace_period=P [NFS] Assign grace period.
1134 Format: <integer>
1da177e4 1135
a6b25b67
RD
1136 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1137 Format: <integer>
1138
1139 lockd.nlm_timeout=T [NFS] Assign timeout value.
1140 Format: <integer>
1141
1142 lockd.nlm_udpport=M [NFS] Assign UDP port.
1143 Format: <integer>
1da177e4
LT
1144
1145 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1146 Format: <irq>
1147
1148 loglevel= All Kernel Messages with a loglevel smaller than the
1149 console loglevel will be printed to the console. It can
1150 also be changed with klogd or other programs. The
1151 loglevels are defined as follows:
1152
1153 0 (KERN_EMERG) system is unusable
1154 1 (KERN_ALERT) action must be taken immediately
1155 2 (KERN_CRIT) critical conditions
1156 3 (KERN_ERR) error conditions
1157 4 (KERN_WARNING) warning conditions
1158 5 (KERN_NOTICE) normal but significant condition
1159 6 (KERN_INFO) informational
1160 7 (KERN_DEBUG) debug-level messages
1161
1162 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1163 Format: { n | nk | nM }
1164 n must be a power of two. The default size
1165 is set in the kernel config file.
1da177e4 1166
accaa24c
RD
1167 logo.nologo [FB] Disables display of the built-in Linux logo.
1168 This may be used to provide more screen space for
1169 kernel log messages and is useful when debugging
1170 kernel boot problems.
1171
1da177e4
LT
1172 lp=0 [LP] Specify parallel ports to use, e.g,
1173 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1174 lp=reset first parallel port). 'lp=0' disables the
1175 lp=auto printer driver. 'lp=reset' (which can be
1176 specified in addition to the ports) causes
1177 attached printers to be reset. Using
1178 lp=port1,port2,... specifies the parallel ports
1179 to associate lp devices with, starting with
1180 lp0. A port specification may be 'none' to skip
1181 that lp device, or a parport name such as
1182 'parport0'. Specifying 'lp=auto' instead of a
1183 port specification list means that device IDs
1184 from each port should be examined, to see if
1185 an IEEE 1284-compliant printer is attached; if
1186 so, the driver will manage that printer.
1187 See also header of drivers/char/lp.c.
1188
1189 lpj=n [KNL]
1190 Sets loops_per_jiffy to given constant, thus avoiding
1191 time-consuming boot-time autodetection (up to 250 ms per
1192 CPU). 0 enables autodetection (default). To determine
1193 the correct value for your kernel, boot with normal
1194 autodetection and see what value is printed. Note that
1195 on SMP systems the preset will be applied to all CPUs,
1196 which is likely to cause problems if your CPUs need
1197 significantly divergent settings. An incorrect value
1198 will cause delays in the kernel to be wrong, leading to
1199 unpredictable I/O errors and other breakage. Although
1200 unlikely, in the extreme case this might damage your
1201 hardware.
1202
1203 ltpc= [NET]
1204 Format: <io>,<irq>,<dma>
1205
a9913044
RD
1206 mac5380= [HW,SCSI] Format:
1207 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1208
a9913044
RD
1209 machvec= [IA64] Force the use of a particular machine-vector
1210 (machvec) in a generic kernel.
1211 Example: machvec=hpzx1_swiotlb
1da177e4 1212
0cb55ad2
RD
1213 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1214 than or equal to this physical address is ignored.
1da177e4
LT
1215
1216 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1217 should make use of. maxcpus=n : n >= 0 limits the
1218 kernel to using 'n' processors. n=0 is a special case,
1219 it is equivalent to "nosmp", which also disables
1220 the IO APIC.
1da177e4 1221
0cb55ad2
RD
1222 max_loop= [LOOP] Maximum number of loopback devices that can
1223 be mounted
1224 Format: <1-256>
2b2c3750 1225
a9913044 1226 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1227 Should be between 1 and 2^32-1.
1228
1229 max_report_luns=
a9913044 1230 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1231 Should be between 1 and 16384.
1232
1da177e4
LT
1233 mcatest= [IA-64]
1234
cd4f0ef7 1235 mce [X86-32] Machine Check Exception
1da177e4 1236
71cced6e 1237 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1238
1da177e4
LT
1239 md= [HW] RAID subsystems devices and level
1240 See Documentation/md.txt.
a9913044 1241
1da177e4
LT
1242 mdacon= [MDA]
1243 Format: <first>,<last>
1244 Specifies range of consoles to be captured by the MDA.
a9913044 1245
1da177e4
LT
1246 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1247 Amount of memory to be used when the kernel is not able
1248 to see the whole system memory or for test.
cd4f0ef7 1249 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1250 address space collisions. Without memmap= PCI devices
1251 could be placed at addresses belonging to unused RAM.
1252
cd4f0ef7 1253 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1254 memory.
1255
6902aa84
PM
1256 memchunk=nn[KMG]
1257 [KNL,SH] Allow user to override the default size for
1258 per-device physically contiguous DMA buffers.
1259
6cececfc 1260 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1261 E820 memory map, as specified by the user.
1262 Such memmap=exactmap lines can be constructed based on
1263 BIOS output or other requirements. See the memmap=nn@ss
1264 option description.
1265
1266 memmap=nn[KMG]@ss[KMG]
1267 [KNL] Force usage of a specific region of memory
1268 Region of memory to be used, from ss to ss+nn.
1269
1270 memmap=nn[KMG]#ss[KMG]
1271 [KNL,ACPI] Mark specific memory as ACPI data.
1272 Region of memory to be used, from ss to ss+nn.
1273
1274 memmap=nn[KMG]$ss[KMG]
1275 [KNL,ACPI] Mark specific memory as reserved.
1276 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1277 Example: Exclude memory from 0x18690000-0x1869ffff
1278 memmap=64K$0x18690000
1279 or
1280 memmap=0x10000$0x18690000
1da177e4 1281
9f077871
JF
1282 memory_corruption_check=0/1 [X86]
1283 Some BIOSes seem to corrupt the first 64k of
1284 memory when doing things like suspend/resume.
1285 Setting this option will scan the memory
1286 looking for corruption. Enabling this will
1287 both detect corruption and prevent the kernel
1288 from using the memory being corrupted.
1289 However, its intended as a diagnostic tool; if
1290 repeatable BIOS-originated corruption always
1291 affects the same memory, you can use memmap=
1292 to prevent the kernel from using that memory.
1293
1294 memory_corruption_check_size=size [X86]
1295 By default it checks for corruption in the low
1296 64k, making this memory unavailable for normal
1297 use. Use this parameter to scan for
1298 corruption in more or less memory.
1299
1300 memory_corruption_check_period=seconds [X86]
1301 By default it checks for corruption every 60
1302 seconds. Use this parameter to check at some
1303 other rate. 0 disables periodic checking.
1304
caadbdce 1305 memtest= [KNL,X86] Enable memtest
c64df707 1306 Format: <integer>
c64df707 1307 default : 0 <disable>
9e5f6cf5
AH
1308 Specifies the number of memtest passes to be
1309 performed. Each pass selects another test
1310 pattern from a given set of patterns. Memtest
1311 fills the memory with this pattern, validates
1312 memory contents and reserves bad memory
1313 regions that are detected.
c64df707 1314
1da177e4
LT
1315 meye.*= [HW] Set MotionEye Camera parameters
1316 See Documentation/video4linux/meye.txt.
1317
8f36881b
AS
1318 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1319 Multi-Function General Purpose Timers on AMD Geode
1320 platforms.
1321
e6c4dc6c
WT
1322 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1323 the BIOS has incorrectly applied a workaround. TinyBIOS
1324 version 0.98 is known to be affected, 0.99 fixes the
1325 problem by letting the user disable the workaround.
1326
1da177e4
LT
1327 mga= [HW,DRM]
1328
1c207f95
RD
1329 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1330 physical address is ignored.
1331
6b74ab97
MG
1332 mminit_loglevel=
1333 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1334 parameter allows control of the logging verbosity for
1335 the additional memory initialisation checks. A value
1336 of 0 disables mminit logging and a level of 4 will
1337 log everything. Information is printed at KERN_DEBUG
1338 so loglevel=8 may also need to be specified.
1339
1da177e4
LT
1340 mousedev.tap_time=
1341 [MOUSE] Maximum time between finger touching and
1342 leaving touchpad surface for touch to be considered
1343 a tap and be reported as a left button click (for
1344 touchpads working in absolute mode only).
1345 Format: <msecs>
1346 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1347 reporting absolute coordinates, such as tablets
1348 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1349 reporting absolute coordinates, such as tablets
1350
6cececfc 1351 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1352 is similar to kernelcore except it specifies the
1353 amount of memory used for migratable allocations.
1354 If both kernelcore and movablecore is specified,
1355 then kernelcore will be at *least* the specified
1356 value but may be more. If movablecore on its own
1357 is specified, the administrator must be careful
1358 that the amount of memory usable for all allocations
1359 is not too small.
1360
1da177e4
LT
1361 mpu401= [HW,OSS]
1362 Format: <io>,<irq>
1363
1364 MTD_Partition= [MTD]
1365 Format: <name>,<region-number>,<size>,<offset>
1366
a9913044
RD
1367 MTD_Region= [MTD] Format:
1368 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1369
1370 mtdparts= [MTD]
c8facbb6 1371 See drivers/mtd/cmdlinepart.c.
1da177e4 1372
9db829f4
BD
1373 mtdset= [ARM]
1374 ARM/S3C2412 JIVE boot control
1375
1376 See arch/arm/mach-s3c2412/mach-jive.c
1377
1da177e4 1378 mtouchusb.raw_coordinates=
a9913044
RD
1379 [HW] Make the MicroTouch USB driver use raw coordinates
1380 ('y', default) or cooked coordinates ('n')
1da177e4 1381
0cb55ad2
RD
1382 mtrr_chunk_size=nn[KMG] [X86]
1383 used for mtrr cleanup. It is largest continous chunk
1384 that could hold holes aka. UC entries.
1385
1386 mtrr_gran_size=nn[KMG] [X86]
1387 Used for mtrr cleanup. It is granularity of mtrr block.
1388 Default is 1.
1389 Large value could prevent small alignment from
1390 using up MTRRs.
1391
1392 mtrr_spare_reg_nr=n [X86]
1393 Format: <integer>
1394 Range: 0,7 : spare reg number
1395 Default : 1
1396 Used for mtrr cleanup. It is spare mtrr entries number.
1397 Set to 2 or more if your graphical card needs more.
1398
1da177e4
LT
1399 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1400
1401 NCR_D700= [HW,SCSI]
1402 See header of drivers/scsi/NCR_D700.c.
1403
1404 ncr5380= [HW,SCSI]
1405
1406 ncr53c400= [HW,SCSI]
1407
1408 ncr53c400a= [HW,SCSI]
1409
1410 ncr53c406a= [HW,SCSI]
1411
1412 ncr53c8xx= [HW,SCSI]
1413
1414 netdev= [NET] Network devices parameters
1415 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1416 Note that mem_start is often overloaded to mean
1417 something different and driver-specific.
a9913044
RD
1418 This usage is only documented in each driver source
1419 file if at all.
1420
58401572
KPO
1421 nf_conntrack.acct=
1422 [NETFILTER] Enable connection tracking flow accounting
1423 0 to disable accounting
1424 1 to enable accounting
1425 Default value depends on CONFIG_NF_CT_ACCT that is
1426 going to be removed in 2.6.29.
1427
1da177e4 1428 nfsaddrs= [NFS]
6ded55da 1429 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1430
1431 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1432 See Documentation/filesystems/nfsroot.txt.
1da177e4 1433
a72b4422
TM
1434 nfs.callback_tcpport=
1435 [NFS] set the TCP port on which the NFSv4 callback
1436 channel should listen.
1437
58df095b
TM
1438 nfs.idmap_cache_timeout=
1439 [NFS] set the maximum lifetime for idmapper cache
1440 entries.
1441
f43bf0be
TM
1442 nfs.enable_ino64=
1443 [NFS] enable 64-bit inode numbers.
1444 If zero, the NFS client will fake up a 32-bit inode
1445 number for the readdir() and stat() syscalls instead
1446 of returning the full 64-bit number.
1447 The default is to return 64-bit inode numbers.
1448
e7ba176b
HS
1449 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1450 when a NMI is triggered.
1451 Format: [state][,regs][,debounce][,die]
1452
6cececfc 1453 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
5b9a0e14
CG
1454 Format: [panic,][num]
1455 Valid num: 0,1,2
1456 0 - turn nmi_watchdog off
1457 1 - use the IO-APIC timer for the NMI watchdog
1458 2 - use the local APIC for the NMI watchdog using
0cb55ad2
RD
1459 a performance counter. Note: This will use one
1460 performance counter and the local APIC's performance
1461 vector.
1462 When panic is specified, panic when an NMI watchdog
1463 timeout occurs.
1464 This is useful when you use a panic=... timeout and
1465 need the box quickly up again.
5b9a0e14
CG
1466 Instead of 1 and 2 it is possible to use the following
1467 symbolic names: lapic and ioapic
1468 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1469
cd4f0ef7 1470 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1471 emulation library even if a 387 maths coprocessor
1472 is present.
1473
0cb55ad2
RD
1474 no_console_suspend
1475 [HW] Never suspend the console
1476 Disable suspending of consoles during suspend and
1477 hibernate operations. Once disabled, debugging
1478 messages can reach various consoles while the rest
1479 of the system is being put to sleep (ie, while
1480 debugging driver suspend/resume hooks). This may
1481 not work reliably with all consoles, but is known
1482 to work with serial and VGA consoles.
1483
c1aee215
CL
1484 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1485 caches in the slab allocator. Saves per-node memory,
1486 but will impact performance.
3395ee05 1487
a9913044
RD
1488 noalign [KNL,ARM]
1489
1da177e4
LT
1490 noapic [SMP,APIC] Tells the kernel to not make use of any
1491 IOAPICs that may be present in the system.
1492
1da177e4
LT
1493 nobats [PPC] Do not use BATs for mapping kernel lowmem
1494 on "Classic" PPC cores.
1495
1496 nocache [ARM]
a9913044 1497
0cb55ad2
RD
1498 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1499
163ecdff
SN
1500 nodelayacct [KNL] Disable per-task delay accounting
1501
1da177e4
LT
1502 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1503
6902aa84
PM
1504 nodsp [SH] Disable hardware DSP at boot time.
1505
6cececfc 1506 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1507
1da177e4
LT
1508 noexec [IA-64]
1509
6cececfc 1510 noexec [X86]
f5a1b191 1511 On X86-32 available only on PAE configured kernels.
1da177e4 1512 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1513 noexec=off: disable non-executable mappings
1514
1515 noexec32 [X86-64]
1516 This affects only 32-bit executables.
1517 noexec32=on: enable non-executable mappings (default)
1518 read doesn't imply executable mappings
1519 noexec32=off: disable non-executable mappings
1520 read implies executable mappings
1da177e4 1521
6902aa84
PM
1522 nofpu [SH] Disable hardware FPU at boot time.
1523
cd4f0ef7 1524 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1525 register save and restore. The kernel will only save
1526 legacy floating-point registers on task switch.
1da177e4 1527
01a24d2b
PZ
1528 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1529 wfi(ARM) instruction doesn't work correctly and not to
1530 use it. This is also useful when using JTAG debugger.
a9913044 1531
cd4f0ef7 1532 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1533 instruction doesn't work correctly and not to
1534 use it.
1535
1f29fae2
SH
1536 no_file_caps Tells the kernel not to honor file capabilities. The
1537 only way then for a file to be executed with privilege
1538 is to be setuid root or executed by root.
1539
1da177e4
LT
1540 nohalt [IA-64] Tells the kernel not to use the power saving
1541 function PAL_HALT_LIGHT when idle. This increases
1542 power-consumption. On the positive side, it reduces
1543 interrupt wake-up latency, which may improve performance
1544 in certain environments such as networked servers or
1545 real-time systems.
1546
79bf2bb3
TG
1547 nohz= [KNL] Boottime enable/disable dynamic ticks
1548 Valid arguments: on, off
1549 Default: on
1550
eeee7853
PM
1551 noiotrap [SH] Disables trapped I/O port accesses.
1552
cd4f0ef7 1553 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1554 disable unhandled interrupt sources.
1555
6cececfc 1556 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
1557 broken timer IRQ sources.
1558
1da177e4
LT
1559 noisapnp [ISAPNP] Disables ISA PnP code.
1560
1561 noinitrd [RAM] Tells the kernel not to load any configured
1562 initial RAM disk.
1563
1564 nointroute [IA-64]
1565
0aa366f3
TL
1566 nojitter [IA64] Disables jitter checking for ITC timers.
1567
cd4f0ef7 1568 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1569
cd4f0ef7 1570 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1571
1da177e4
LT
1572 noltlbs [PPC] Do not use large page/tlb entries for kernel
1573 lowmem mapping on PPC40x.
1574
312f1f01
H
1575 nomca [IA-64] Disable machine check abort handling
1576
cd4f0ef7 1577 nomce [X86-32] Machine Check Exception
abe37e5a 1578
83d7384f
AS
1579 nomfgpt [X86-32] Disable Multi-Function General Purpose
1580 Timer usage (for AMD Geode machines).
1581
0cb55ad2
RD
1582 norandmaps Don't use address space randomization. Equivalent to
1583 echo 0 > /proc/sys/kernel/randomize_va_space
1584
cd4f0ef7 1585 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1586
cd4f0ef7 1587 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1588 with UP alternatives
1589
1da177e4
LT
1590 noresidual [PPC] Don't use residual data on PReP machines.
1591
a9913044
RD
1592 noresume [SWSUSP] Disables resume and restores original swap
1593 space.
1594
1da177e4
LT
1595 no-scroll [VGA] Disables scrollback.
1596 This is required for the Braillex ib80-piezo Braille
1597 reader made by F.H. Papenmeier (Germany).
1598
1599 nosbagart [IA-64]
1600
cd4f0ef7 1601 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1602
61ec7567
LB
1603 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1604 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1605
97842216
DJ
1606 nosoftlockup [KNL] Disable the soft-lockup detector.
1607
c077719b 1608 noswapaccount [KNL] Disable accounting of swap in memory resource
21acb9ca 1609 controller. (See Documentation/cgroups/memory.txt)
c077719b 1610
1da177e4
LT
1611 nosync [HW,M68K] Disables sync negotiation for all devices.
1612
cd4f0ef7 1613 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1614
1615 nousb [USB] Disable the USB subsystem
1616
1617 nowb [ARM]
a9913044 1618
8b5b94e4
WH
1619 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1620
a6c75b86
FY
1621 nptcg= [IA64] Override max number of concurrent global TLB
1622 purges which is reported from either PAL_VM_SUMMARY or
1623 SAL PALO.
1624
0cb55ad2
RD
1625 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1626
f0c0b2b8
KH
1627 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1628 one of ['zone', 'node', 'default'] can be specified
1629 This can be set from sysctl after boot.
1630 See Documentation/sysctl/vm.txt for details.
1631
7c4be253
RD
1632 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1633 See Documentation/debugging-via-ohci1394.txt for more
1634 info.
1635
3ef0e1f8
AS
1636 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1637 Rather than timing out after 20 ms if an EC
1638 command is not properly ACKed, override the length
1639 of the timeout. We have interrupts disabled while
1640 waiting for the ACK, so if this is set too high
1641 interrupts *may* be lost!
1642
1da177e4
LT
1643 opl3= [HW,OSS]
1644 Format: <io>
1645
1da177e4
LT
1646 oprofile.timer= [HW]
1647 Use timer interrupt instead of performance counters
1648
1da177e4
LT
1649 osst= [HW,SCSI] SCSI Tape Driver
1650 Format: <buffer_size>,<write_threshold>
1651 See also Documentation/scsi/st.txt.
1652
1653 panic= [KNL] Kernel behaviour on panic
1654 Format: <timeout>
1655
1656 parkbd.port= [HW] Parallel port number the keyboard adapter is
1657 connected to, default is 0.
1658 Format: <parport#>
1659 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1660 0 for XT, 1 for AT (default is AT).
a9913044
RD
1661 Format: <mode>
1662
1663 parport= [HW,PPT] Specify parallel ports. 0 disables.
1664 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1665 Use 'auto' to force the driver to use any
1666 IRQ/DMA settings detected (the default is to
1667 ignore detected IRQ/DMA settings because of
1668 possible conflicts). You can specify the base
1669 address, IRQ, and DMA settings; IRQ and DMA
1670 should be numbers, or 'auto' (for using detected
1671 settings on that particular port), or 'nofifo'
1672 (to avoid using a FIFO even if it is detected).
1673 Parallel ports are assigned in the order they
1674 are specified on the command line, starting
1675 with parport0.
1676
1677 parport_init_mode= [HW,PPT]
1678 Configure VIA parallel port to operate in
1679 a specific mode. This is necessary on Pegasos
1680 computer where firmware has no options for setting
1681 up parallel port mode and sets it to spp.
1682 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1683 Format: [spp|ps2|epp|ecp|ecpepp]
1684
a9913044
RD
1685 pas2= [HW,OSS] Format:
1686 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1687
1da177e4
LT
1688 pas16= [HW,SCSI]
1689 See header of drivers/scsi/pas16.c.
1690
dd287796
AM
1691 pause_on_oops=
1692 Halt all CPUs after the first oops has been printed for
1693 the specified number of seconds. This is to be used if
1694 your oopses keep scrolling off the screen.
1695
1da177e4
LT
1696 pcbit= [HW,ISDN]
1697
1698 pcd. [PARIDE]
1699 See header of drivers/block/paride/pcd.c.
31c00fc1 1700 See also Documentation/blockdev/paride.txt.
1da177e4 1701
a9913044 1702 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
1703 earlydump [X86] dump PCI config space before the kernel
1704 changes anything
c0115606 1705 off [X86] don't probe for the PCI bus
cd4f0ef7 1706 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1707 the hardware directly. Use this if your machine
1708 has a non-standard PCI host bridge.
cd4f0ef7 1709 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1710 hardware access methods are allowed. Use this
1711 if you experience crashes upon bootup and you
1712 suspect they are caused by the BIOS.
c0115606 1713 conf1 [X86] Force use of PCI Configuration
a9913044 1714 Mechanism 1.
c0115606 1715 conf2 [X86] Force use of PCI Configuration
a9913044 1716 Mechanism 2.
7f785763
RD
1717 noaer [PCIE] If the PCIEAER kernel config parameter is
1718 enabled, this kernel boot option can be used to
1719 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1720 nodomains [PCI] Disable support for multiple PCI
1721 root domains (aka PCI segments, in ACPI-speak).
6cececfc 1722 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 1723 Configuration
309e57df
MW
1724 nomsi [MSI] If the PCI_MSI kernel config parameter is
1725 enabled, this kernel boot option can be used to
1726 disable the use of MSI interrupts system-wide.
a9322f64
SA
1727 noioapicquirk [APIC] Disable all boot interrupt quirks.
1728 Safety option to keep boot IRQs enabled. This
1729 should never be necessary.
9197979b
SA
1730 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1731 primary IO-APIC for bridges that cannot disable
1732 boot IRQs. This fixes a source of spurious IRQs
1733 when the system masks IRQs.
41b9eb26
SA
1734 noioapicreroute [APIC] Disable workaround that uses the
1735 boot IRQ equivalent of an IRQ that connects to
1736 a chipset where boot IRQs cannot be disabled.
1737 The opposite of ioapicreroute.
cd4f0ef7 1738 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1739 routing table. These calls are known to be buggy
1740 on several machines and they hang the machine
1741 when used, but on other computers it's the only
1742 way to get the interrupt routing table. Try
1743 this option if the kernel is unable to allocate
1744 IRQs or discover secondary PCI buses on your
1745 motherboard.
c0115606 1746 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1747 Use with caution as certain devices share
1748 address decoders between ROMs and other
1749 resources.
c0115606 1750 norom [X86] Do not assign address space to
bb71ad88
GH
1751 expansion ROMs that do not already have
1752 BIOS assigned address ranges.
c0115606 1753 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1754 assigned automatically to PCI devices. You can
1755 make the kernel exclude IRQs of your ISA cards
1756 this way.
c0115606 1757 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1758 of the PIRQ table (normally generated
1759 by the BIOS) if it is outside the
1760 F0000h-100000h range.
c0115606 1761 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1762 useful if the kernel is unable to find your
1763 secondary buses and you want to tell it
1764 explicitly which ones they are.
c0115606 1765 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1766 numbers ourselves, overriding
1767 whatever the firmware may have done.
c0115606 1768 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1769 in the BIOS $PIR table. This is needed on
1770 some systems with broken BIOSes, notably
1771 some HP Pavilion N5400 and Omnibook XE3
1772 notebooks. This will have no effect if ACPI
1773 IRQ routing is enabled.
c0115606 1774 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1775 or for PCI scanning.
c0115606 1776 use_crs [X86] Use _CRS for PCI resource
62f420f8 1777 allocation.
a9913044
RD
1778 routeirq Do IRQ routing for all PCI devices.
1779 This is normally done in pci_enable_device(),
1780 so this option is a temporary workaround
1781 for broken drivers that don't call it.
13a6ddb0
YL
1782 skip_isa_align [X86] do not align io start addr, so can
1783 handle more pci cards
a9913044
RD
1784 firmware [ARM] Do not re-enumerate the bus but instead
1785 just use the configuration from the
1786 bootloader. This is currently used on
1787 IXP2000 systems where the bus has to be
1788 configured a certain way for adjunct CPUs.
0637a70a
AK
1789 noearly [X86] Don't do any early type 1 scanning.
1790 This might help on some broken boards which
1791 machine check when some devices' config space
1792 is read. But various workarounds are disabled
1793 and some IOMMU drivers will not work.
6b4b78fe
MD
1794 bfsort Sort PCI devices into breadth-first order.
1795 This sorting is done to get a device
1796 order compatible with older (<= 2.4) kernels.
1797 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1798 cbiosize=nn[KMG] The fixed amount of bus space which is
1799 reserved for the CardBus bridge's IO window.
1800 The default value is 256 bytes.
1801 cbmemsize=nn[KMG] The fixed amount of bus space which is
1802 reserved for the CardBus bridge's memory
1803 window. The default value is 64 megabytes.
32a9a682
YS
1804 resource_alignment=
1805 Format:
1806 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1807 Specifies alignment and device to reassign
1808 aligned memory resources.
1809 If <order of align> is not specified,
1810 PAGE_SIZE is used as alignment.
1811 PCI-PCI bridge can be specified, if resource
1812 windows need to be expanded.
6b4b78fe 1813
e5665a45
CE
1814 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1815 Management.
1816 off Disable ASPM.
1817 force Enable ASPM even on devices that claim not to support it.
1818 WARNING: Forcing ASPM on may cause system lockups.
1819
1da177e4
LT
1820 pcmv= [HW,PCMCIA] BadgePAD 4
1821
1822 pd. [PARIDE]
31c00fc1 1823 See Documentation/blockdev/paride.txt.
1da177e4
LT
1824
1825 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1826 boot time.
1827 Format: { 0 | 1 }
1828 See arch/parisc/kernel/pdc_chassis.c
1829
1830 pf. [PARIDE]
31c00fc1 1831 See Documentation/blockdev/paride.txt.
1da177e4
LT
1832
1833 pg. [PARIDE]
31c00fc1 1834 See Documentation/blockdev/paride.txt.
1da177e4
LT
1835
1836 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 1837 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
1838
1839 plip= [PPT,NET] Parallel port network link
1840 Format: { parport<nr> | timid | 0 }
1841 See also Documentation/parport.txt.
1842
de32a243
TG
1843 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1844 Override pmtimer IOPort with a hex value.
1845 e.g. pmtmr=0x508
1846
97ef062b
BH
1847 pnp.debug [PNP]
1848 Enable PNP debug messages. This depends on the
1849 CONFIG_PNP_DEBUG_MESSAGES option.
1850
1da177e4
LT
1851 pnpacpi= [ACPI]
1852 { off }
1853
1854 pnpbios= [ISAPNP]
1855 { on | off | curr | res | no-curr | no-res }
1856
1857 pnp_reserve_irq=
1858 [ISAPNP] Exclude IRQs for the autoconfiguration
1859
1860 pnp_reserve_dma=
1861 [ISAPNP] Exclude DMAs for the autoconfiguration
1862
1863 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1864 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1865
1866 pnp_reserve_mem=
a9913044
RD
1867 [ISAPNP] Exclude memory regions for the
1868 autoconfiguration.
1da177e4
LT
1869 Ranges are in pairs (memory base and size).
1870
4af94f39
RD
1871 ports= [IP_VS_FTP] IPVS ftp helper module
1872 Default is 21.
1873 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1874 may be specified.
1875 Format: <port>,<port>....
1876
45807a1d
IM
1877 print-fatal-signals=
1878 [KNL] debug: print fatal signals
1879 print-fatal-signals=1: print segfault info to
1880 the kernel console.
1881 default: off.
1882
e84845c4
RD
1883 printk.time= Show timing data prefixed to each printk message line
1884 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1885
0cb55ad2
RD
1886 processor.max_cstate= [HW,ACPI]
1887 Limit processor to maximum C-state
1888 max_cstate=9 overrides any DMI blacklist limit.
1889
1890 processor.nocst [HW,ACPI]
1891 Ignore the _CST method to determine C-states,
1892 instead using the legacy FADT method
1893
1da177e4 1894 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1895 Format: [schedule,]<number>
1896 Param: "schedule" - profile schedule points.
1897 Param: <number> - step/bucket size as a power of 2 for
1898 statistical time based profiling.
b3da2a73
MG
1899 Param: "sleep" - profile D-state sleeping (millisecs).
1900 Requires CONFIG_SCHEDSTATS
c0fe2e69 1901 Param: "kvm" - profile VM exits.
1da177e4 1902
1da177e4
LT
1903 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1904 before loading.
31c00fc1 1905 See Documentation/blockdev/ramdisk.txt.
1da177e4 1906
a9913044
RD
1907 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1908 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1909 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1910 per second.
a9913044
RD
1911 psmouse.resetafter= [HW,MOUSE]
1912 Try to reset the device after so many bad packets
1da177e4
LT
1913 (0 = never).
1914 psmouse.resolution=
1915 [HW,MOUSE] Set desired mouse resolution, in dpi.
1916 psmouse.smartscroll=
a9913044 1917 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1918 0 = disabled, 1 = enabled (default).
1919
1920 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1921 Format:
1922 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1923
1924 pt. [PARIDE]
31c00fc1 1925 See Documentation/blockdev/paride.txt.
1da177e4 1926
dc8c8587
KS
1927 pty.legacy_count=
1928 [KNL] Number of legacy pty's. Overwrites compiled-in
1929 default number.
1930
7d2c502f 1931 quiet [KNL] Disable most log messages
a9913044 1932
1da177e4
LT
1933 r128= [HW,DRM]
1934
1935 raid= [HW,RAID]
1936 See Documentation/md.txt.
1937
a9913044 1938 ramdisk_blocksize= [RAM]
31c00fc1 1939 See Documentation/blockdev/ramdisk.txt.
a9913044 1940
1da177e4 1941 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 1942 See Documentation/blockdev/ramdisk.txt.
1da177e4 1943
24aaef8d
RD
1944 rcupdate.blimit= [KNL,BOOT]
1945 Set maximum number of finished RCU callbacks to process
1946 in one batch.
21a1ea9e 1947
24aaef8d
RD
1948 rcupdate.qhimark= [KNL,BOOT]
1949 Set threshold of queued
21a1ea9e
DS
1950 RCU callbacks over which batch limiting is disabled.
1951
24aaef8d
RD
1952 rcupdate.qlowmark= [KNL,BOOT]
1953 Set threshold of queued RCU callbacks below which
1954 batch limiting is re-enabled.
21a1ea9e 1955
ffdfc409
OJ
1956 rdinit= [KNL]
1957 Format: <full_path>
1958 Run specified binary instead of /init from the ramdisk,
1959 used for early userspace startup. See initrd.
1960
cd4f0ef7 1961 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1962 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 1963 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 1964
46b6d94e
PJ
1965 relax_domain_level=
1966 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 1967 See Documentation/cgroups/cpusets.txt.
46b6d94e 1968
1da177e4
LT
1969 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1970
cd4f0ef7 1971 reservetop= [X86-32]
461a9aff
ZA
1972 Format: nn[KMG]
1973 Reserves a hole at the top of the kernel virtual
1974 address space.
1975
7e96287d
VG
1976 reset_devices [KNL] Force drivers to reset the underlying device
1977 during initialization.
1978
a9913044
RD
1979 resume= [SWSUSP]
1980 Specify the partition device for software suspend
1da177e4 1981
ecbd0da1
RW
1982 resume_offset= [SWSUSP]
1983 Specify the offset from the beginning of the partition
1984 given by "resume=" at which the swap header is located,
1985 in <PAGE_SIZE> units (needed only for swap files).
1986 See Documentation/power/swsusp-and-swap-files.txt
1987
0a7b35cb
MN
1988 retain_initrd [RAM] Keep initrd memory after extraction
1989
1da177e4
LT
1990 rhash_entries= [KNL,NET]
1991 Set number of hash buckets for route cache
1992
1993 riscom8= [HW,SERIAL]
1994 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1995
1996 ro [KNL] Mount root device read-only on boot
1997
1998 root= [KNL] Root filesystem
1999
2000 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2001 mount the root filesystem
2002
2003 rootflags= [KNL] Set root filesystem mount option string
2004
2005 rootfstype= [KNL] Set root filesystem type
2006
cc1ed754
PO
2007 rootwait [KNL] Wait (indefinitely) for root device to show up.
2008 Useful for devices that are detected asynchronously
2009 (e.g. USB and MMC devices).
2010
20510f2f
JM
2011 root_plug.vendor_id=
2012 [ROOTPLUG] Override the default vendor ID
2013
2014 root_plug.product_id=
2015 [ROOTPLUG] Override the default product ID
2016
2017 root_plug.debug=
2018 [ROOTPLUG] Enable debugging output
2019
1da177e4
LT
2020 rw [KNL] Mount root device read-write on boot
2021
2022 S [KNL] Run init in single mode
2023
2024 sa1100ir [NET]
2025 See drivers/net/irda/sa1100_ir.c.
2026
1da177e4 2027 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2028
1da177e4
LT
2029 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2030 Format: <io>[,<timeout>[,<isapnp>]]
2031
2032 scsi_debug_*= [SCSI]
2033 See drivers/scsi/scsi_debug.c.
2034
2035 scsi_default_dev_flags=
2036 [SCSI] SCSI default device flags
2037 Format: <integer>
2038
2039 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2040 Format: <vendor>:<model>:<flags>
2041 (flags are integer value)
2042
6af6632a
RD
2043 scsi_logging_level= [SCSI] a bit mask of logging levels
2044 See drivers/scsi/scsi_logging.h for bits. Also
2045 settable via sysctl at dev.scsi.logging_level
2046 (/proc/sys/dev/scsi/logging_level).
2047 There is also a nice 'scsi_logging_level' script in the
2048 S390-tools package, available for download at
2049 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 2050
3e082a91
MW
2051 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2052 discovered. async scans them in kernel threads,
2053 allowing boot to proceed. none ignores them, expecting
2054 user space to do the scan.
2055
0cb55ad2
RD
2056 security= [SECURITY] Choose a security module to enable at boot.
2057 If this boot parameter is not specified, only the first
2058 security module asking for security registration will be
2059 loaded. An invalid security module name will be treated
2060 as if no module has been chosen.
2061
2062 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2063 Format: { "0" | "1" }
2064 See security/selinux/Kconfig help text.
2065 0 -- disable.
2066 1 -- enable.
2067 Default value is set via kernel config option.
2068 If enabled at boot time, /selinux/disable can be used
2069 later to disable prior to initial policy load.
2070
cd4f0ef7 2071 serialnumber [BUGS=X86-32]
1da177e4 2072
1da177e4
LT
2073 shapers= [NET]
2074 Maximal number of shapers.
a9913044 2075
b05f78f5
YL
2076 show_msr= [x86] show boot-time MSR settings
2077 Format: { <integer> }
2078 Show boot-time (BIOS-initialized) MSR settings.
2079 The parameter means the number of CPUs to show,
2080 for example 1 means boot CPU only.
2081
1da177e4
LT
2082 sim710= [SCSI,HW]
2083 See header of drivers/scsi/sim710.c.
2084
2085 simeth= [IA-64]
2086 simscsi=
a9913044 2087
1da177e4
LT
2088 slram= [HW,MTD]
2089
f0630fff
CL
2090 slub_debug[=options[,slabs]] [MM, SLUB]
2091 Enabling slub_debug allows one to determine the
2092 culprit if slab objects become corrupted. Enabling
2093 slub_debug can create guard zones around objects and
2094 may poison objects when not in use. Also tracks the
2095 last alloc / free. For more information see
2096 Documentation/vm/slub.txt.
c1aee215
CL
2097
2098 slub_max_order= [MM, SLUB]
f0630fff
CL
2099 Determines the maximum allowed order for slabs.
2100 A high setting may cause OOMs due to memory
2101 fragmentation. For more information see
2102 Documentation/vm/slub.txt.
c1aee215
CL
2103
2104 slub_min_objects= [MM, SLUB]
f0630fff
CL
2105 The minimum number of objects per slab. SLUB will
2106 increase the slab order up to slub_max_order to
2107 generate a sufficiently large slab able to contain
2108 the number of objects indicated. The higher the number
2109 of objects the smaller the overhead of tracking slabs
2110 and the less frequently locks need to be acquired.
c1aee215
CL
2111 For more information see Documentation/vm/slub.txt.
2112
2113 slub_min_order= [MM, SLUB]
2114 Determines the mininum page order for slabs. Must be
f0630fff 2115 lower than slub_max_order.
c1aee215
CL
2116 For more information see Documentation/vm/slub.txt.
2117
2118 slub_nomerge [MM, SLUB]
f0630fff 2119 Disable merging of slabs with similar size. May be
c1aee215 2120 necessary if there is some reason to distinguish
f0630fff
CL
2121 allocs to different slabs. Debug options disable
2122 merging on their own.
c1aee215
CL
2123 For more information see Documentation/vm/slub.txt.
2124
1da177e4
LT
2125 smart2= [HW]
2126 Format: <io1>[,<io2>[,...,<io8>]]
2127
cd4f0ef7 2128 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2129 attempt to substitute SMP alternatives once at boot.
2130
d0d4f69b
BH
2131 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2132 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2133 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2134 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2135 smsc-ircc2.ircc_irq= [HW] IRQ line
2136 smsc-ircc2.ircc_dma= [HW] DMA channel
2137 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2138 0: Toshiba Satellite 1800 (GP data pin select)
2139 1: Fast pin select (default)
2140 2: ATC IRMode
2141
1da177e4
LT
2142 snd-ad1816a= [HW,ALSA]
2143
2144 snd-ad1848= [HW,ALSA]
2145
2146 snd-ali5451= [HW,ALSA]
2147
2148 snd-als100= [HW,ALSA]
2149
2150 snd-als4000= [HW,ALSA]
2151
2152 snd-azt2320= [HW,ALSA]
2153
2154 snd-cmi8330= [HW,ALSA]
2155
2156 snd-cmipci= [HW,ALSA]
2157
2158 snd-cs4231= [HW,ALSA]
2159
2160 snd-cs4232= [HW,ALSA]
2161
2162 snd-cs4236= [HW,ALSA]
2163
2164 snd-cs4281= [HW,ALSA]
2165
2166 snd-cs46xx= [HW,ALSA]
2167
2168 snd-dt019x= [HW,ALSA]
2169
2170 snd-dummy= [HW,ALSA]
2171
2172 snd-emu10k1= [HW,ALSA]
2173
2174 snd-ens1370= [HW,ALSA]
2175
2176 snd-ens1371= [HW,ALSA]
2177
2178 snd-es968= [HW,ALSA]
2179
2180 snd-es1688= [HW,ALSA]
2181
2182 snd-es18xx= [HW,ALSA]
2183
2184 snd-es1938= [HW,ALSA]
2185
2186 snd-es1968= [HW,ALSA]
2187
2188 snd-fm801= [HW,ALSA]
2189
2190 snd-gusclassic= [HW,ALSA]
2191
2192 snd-gusextreme= [HW,ALSA]
2193
2194 snd-gusmax= [HW,ALSA]
2195
2196 snd-hdsp= [HW,ALSA]
2197
2198 snd-ice1712= [HW,ALSA]
2199
2200 snd-intel8x0= [HW,ALSA]
2201
2202 snd-interwave= [HW,ALSA]
2203
2204 snd-interwave-stb=
2205 [HW,ALSA]
2206
2207 snd-korg1212= [HW,ALSA]
2208
2209 snd-maestro3= [HW,ALSA]
2210
2211 snd-mpu401= [HW,ALSA]
2212
2213 snd-mtpav= [HW,ALSA]
2214
2215 snd-nm256= [HW,ALSA]
2216
2217 snd-opl3sa2= [HW,ALSA]
2218
2219 snd-opti92x-ad1848=
2220 [HW,ALSA]
2221
2222 snd-opti92x-cs4231=
2223 [HW,ALSA]
2224
2225 snd-opti93x= [HW,ALSA]
2226
2227 snd-pmac= [HW,ALSA]
2228
2229 snd-rme32= [HW,ALSA]
2230
2231 snd-rme96= [HW,ALSA]
2232
2233 snd-rme9652= [HW,ALSA]
2234
2235 snd-sb8= [HW,ALSA]
2236
2237 snd-sb16= [HW,ALSA]
2238
2239 snd-sbawe= [HW,ALSA]
2240
2241 snd-serial= [HW,ALSA]
2242
2243 snd-sgalaxy= [HW,ALSA]
2244
2245 snd-sonicvibes= [HW,ALSA]
2246
2247 snd-sun-amd7930=
2248 [HW,ALSA]
2249
2250 snd-sun-cs4231= [HW,ALSA]
2251
2252 snd-trident= [HW,ALSA]
2253
2254 snd-usb-audio= [HW,ALSA,USB]
2255
2256 snd-via82xx= [HW,ALSA]
2257
2258 snd-virmidi= [HW,ALSA]
2259
2260 snd-wavefront= [HW,ALSA]
2261
2262 snd-ymfpci= [HW,ALSA]
a9913044 2263
9c44bc03
IM
2264 softlockup_panic=
2265 [KNL] Should the soft-lockup detector generate panics.
2266
1da177e4
LT
2267 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2268 See Documentation/sonypi.txt
2269
2270 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2271 See Documentation/serial/specialix.txt.
1da177e4
LT
2272
2273 spia_io_base= [HW,MTD]
2274 spia_fio_base=
2275 spia_pedr=
2276 spia_peddr=
2277
2278 sscape= [HW,OSS]
2279 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2280
1da177e4
LT
2281 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2282 See Documentation/scsi/st.txt.
2283
f38f1d2a
SR
2284 stacktrace [FTRACE]
2285 Enabled the stack tracer on boot up.
2286
1da177e4
LT
2287 sti= [PARISC,HW]
2288 Format: <num>
2289 Set the STI (builtin display/keyboard on the HP-PARISC
2290 machines) console (graphic card) which should be used
2291 as the initial boot-console.
2292 See also comment in drivers/video/console/sticore.c.
2293
2294 sti_font= [HW]
2295 See comment in drivers/video/console/sticore.c.
2296
2297 stifb= [HW]
2298 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2299
42a7fc4a
GB
2300 sunrpc.pool_mode=
2301 [NFS]
2302 Control how the NFS server code allocates CPUs to
2303 service thread pools. Depending on how many NICs
2304 you have and where their interrupts are bound, this
2305 option will affect which CPUs will do NFS serving.
2306 Note: this parameter cannot be changed while the
2307 NFS server is running.
2308
2309 auto the server chooses an appropriate mode
2310 automatically using heuristics
2311 global a single global pool contains all CPUs
2312 percpu one pool for each CPU
2313 pernode one pool for each NUMA node (equivalent
2314 to global on non-NUMA machines)
2315
1da177e4 2316 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2317
1da177e4
LT
2318 switches= [HW,M68k]
2319
2320 sym53c416= [HW,SCSI]
2321 See header of drivers/scsi/sym53c416.c.
2322
5d6f647f
IM
2323 sysrq_always_enabled
2324 [KNL]
2325 Ignore sysrq setting - this boot parameter will
2326 neutralize any effect of /proc/sys/kernel/sysrq.
2327 Useful for debugging.
2328
1da177e4
LT
2329 t128= [HW,SCSI]
2330 See header of drivers/scsi/t128.c.
2331
2332 tdfx= [HW,DRM]
2333
77437fd4
DB
2334 test_suspend= [SUSPEND]
2335 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2336 standby suspend) as the system sleep state to briefly
2337 enter during system startup. The system is woken from
2338 this state using a wakeup-capable RTC alarm.
2339
1da177e4
LT
2340 thash_entries= [KNL,NET]
2341 Set number of hash buckets for TCP connection
2342
f8707ec9
LB
2343 thermal.act= [HW,ACPI]
2344 -1: disable all active trip points in all thermal zones
2345 <degrees C>: override all lowest active trip points
2346
c52a7419
LB
2347 thermal.crt= [HW,ACPI]
2348 -1: disable all critical trip points in all thermal zones
22a94d79 2349 <degrees C>: override all critical trip points
c52a7419 2350
f5487145
LB
2351 thermal.nocrt= [HW,ACPI]
2352 Set to disable actions on ACPI thermal zone
2353 critical and hot trip points.
2354
72b33ef8
LB
2355 thermal.off= [HW,ACPI]
2356 1: disable ACPI thermal control
2357
a70cdc52
LB
2358 thermal.psv= [HW,ACPI]
2359 -1: disable all passive trip points
ada9cfdd
RD
2360 <degrees C>: override all passive trip points to this
2361 value
a70cdc52 2362
730ff34d
LB
2363 thermal.tzp= [HW,ACPI]
2364 Specify global default ACPI thermal zone polling rate
2365 <deci-seconds>: poll all this frequency
2366 0: no polling (default)
2367
1da177e4
LT
2368 tmscsim= [HW,SCSI]
2369 See comment before function dc390_setup() in
2370 drivers/scsi/tmscsim.c.
2371
2b1a61f0
HC
2372 topology= [S390]
2373 Format: {off | on}
2374 Specify if the kernel should make use of the cpu
2375 topology informations if the hardware supports these.
2376 The scheduler will make use of these informations and
2377 e.g. base its process migration decisions on it.
2378 Default is off.
2379
1da177e4
LT
2380 tp720= [HW,PS2]
2381
631595fb
KM
2382 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2383
1da177e4 2384 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2385 Format:
2386 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2387
395628ef
AK
2388 tsc= Disable clocksource-must-verify flag for TSC.
2389 Format: <string>
2390 [x86] reliable: mark tsc clocksource as reliable, this
2391 disables clocksource verification at runtime.
2392 Used to enable high-resolution timer mode on older
2393 hardware, and in virtualized environment.
2394
a9913044
RD
2395 turbografx.map[2|3]= [HW,JOY]
2396 TurboGraFX parallel port interface
2397 Format:
2398 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2399 See also Documentation/input/joystick-parport.txt
2400
2401 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2402 See header of drivers/scsi/u14-34f.c.
2403
2404 uart401= [HW,OSS]
2405 Format: <io>,<irq>
2406
2407 uart6850= [HW,OSS]
2408 Format: <io>,<irq>
2409
5f8364b7
AS
2410 uhci-hcd.ignore_oc=
2411 [USB] Ignore overcurrent events (default N).
2412 Some badly-designed motherboards generate lots of
2413 bogus events, for ports that aren't wired to
2414 anything. Set this parameter to avoid log spamming.
2415 Note that genuine overcurrent events won't be
2416 reported either.
2417
e3a61b0a 2418 unknown_nmi_panic
6cececfc 2419 [X86]
e3a61b0a
SA
2420 Set unknown_nmi_panic=1 early on boot.
2421
b5e795f8
AS
2422 usbcore.autosuspend=
2423 [USB] The autosuspend time delay (in seconds) used
2424 for newly-detected USB devices (default 2). This
2425 is the time required before an idle device will be
2426 autosuspended. Devices for which the delay is set
eaafbc3a 2427 to a negative value won't be autosuspended at all.
b5e795f8 2428
fd7c519d
JK
2429 usbcore.usbfs_snoop=
2430 [USB] Set to log all usbfs traffic (default 0 = off).
2431
2432 usbcore.blinkenlights=
2433 [USB] Set to cycle leds on hubs (default 0 = off).
2434
2435 usbcore.old_scheme_first=
2436 [USB] Start with the old device initialization
2437 scheme (default 0 = off).
2438
2439 usbcore.use_both_schemes=
2440 [USB] Try the other device initialization scheme
2441 if the first one fails (default 1 = enabled).
2442
2443 usbcore.initial_descriptor_timeout=
2444 [USB] Specifies timeout for the initial 64-byte
2445 USB_REQ_GET_DESCRIPTOR request in milliseconds
2446 (default 5000 = 5.0 seconds).
2447
1da177e4
LT
2448 usbhid.mousepoll=
2449 [USBHID] The interval which mice are to be polled at.
a9913044 2450
d4f373e5
AS
2451 usb-storage.delay_use=
2452 [UMS] The delay in seconds before a new device is
2453 scanned for Logical Units (default 5).
2454
2455 usb-storage.quirks=
2456 [UMS] A list of quirks entries to supplement or
2457 override the built-in unusual_devs list. List
2458 entries are separated by commas. Each entry has
2459 the form VID:PID:Flags where VID and PID are Vendor
2460 and Product ID values (4-digit hex numbers) and
2461 Flags is a set of characters, each corresponding
2462 to a common usb-storage quirk flag as follows:
c838ea46
AS
2463 a = SANE_SENSE (collect more than 18 bytes
2464 of sense data);
d4f373e5
AS
2465 c = FIX_CAPACITY (decrease the reported
2466 device capacity by one sector);
c838ea46
AS
2467 h = CAPACITY_HEURISTICS (decrease the
2468 reported device capacity by one
2469 sector if the number is odd);
d4f373e5
AS
2470 i = IGNORE_DEVICE (don't bind to this
2471 device);
2472 l = NOT_LOCKABLE (don't try to lock and
2473 unlock ejectable media);
2474 m = MAX_SECTORS_64 (don't transfer more
2475 than 64 sectors = 32 KB at a time);
c838ea46
AS
2476 o = CAPACITY_OK (accept the capacity
2477 reported by the device);
d4f373e5
AS
2478 r = IGNORE_RESIDUE (the device reports
2479 bogus residue values);
2480 s = SINGLE_LUN (the device has only one
2481 Logical Unit);
2482 w = NO_WP_DETECT (don't test whether the
2483 medium is write-protected).
2484 Example: quirks=0419:aaf5:rl,0421:0433:rc
2485
6cececfc 2486 vdso= [X86,SH]
1dbf527c 2487 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2488 vdso=1: enable VDSO (default)
2489 vdso=0: disable VDSO mapping
2490
6cececfc 2491 vdso32= [X86]
af65d648
RM
2492 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2493 vdso32=1: enable 32-bit VDSO (default)
2494 vdso32=0: disable 32-bit VDSO mapping
2495
d080d397
YI
2496 vector= [IA-64,SMP]
2497 vector=percpu: enable percpu vector domain
2498
1da177e4
LT
2499 video= [FB] Frame buffer configuration
2500 See Documentation/fb/modedb.txt.
2501
cd4f0ef7 2502 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 2503 See Documentation/x86/boot.txt and
a9913044 2504 Documentation/svga.txt.
1da177e4
LT
2505 Use vga=ask for menu.
2506 This is actually a boot loader parameter; the value is
2507 passed to the kernel using a special protocol.
2508
a9913044 2509 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2510 size of <nn>. This can be used to increase the
2511 minimum size (128MB on x86). It can also be used to
2512 decrease the size and leave more room for directly
2513 mapped kernel RAM.
2514
585c3047
PO
2515 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2516 Format: <command>
1da177e4 2517
585c3047
PO
2518 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2519 Format: <command>
2520
2521 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2522 Format: <command>
a9913044 2523
0cb55ad2
RD
2524 vt.default_blu= [VT]
2525 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2526 Change the default blue palette of the console.
2527 This is a 16-member array composed of values
2528 ranging from 0-255.
2529
2530 vt.default_grn= [VT]
2531 Format: <green0>,<green1>,<green2>,...,<green15>
2532 Change the default green palette of the console.
2533 This is a 16-member array composed of values
2534 ranging from 0-255.
2535
2536 vt.default_red= [VT]
2537 Format: <red0>,<red1>,<red2>,...,<red15>
2538 Change the default red palette of the console.
2539 This is a 16-member array composed of values
2540 ranging from 0-255.
2541
2542 vt.default_utf8=
2543 [VT]
2544 Format=<0|1>
2545 Set system-wide default UTF-8 mode for all tty's.
2546 Default is 1, i.e. UTF-8 mode is enabled for all
2547 newly opened terminals.
2548
1da177e4
LT
2549 waveartist= [HW,OSS]
2550 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2551
1da177e4
LT
2552 wd33c93= [HW,SCSI]
2553 See header of drivers/scsi/wd33c93.c.
2554
2555 wd7000= [HW,SCSI]
2556 See header of drivers/scsi/wd7000.c.
2557
2558 wdt= [WDT] Watchdog
8dfe9c21 2559 See Documentation/watchdog/wdt.txt.
1da177e4 2560
0cb55ad2
RD
2561 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2562 default x2apic cluster mode on platforms
2563 supporting x2apic.
2564
1da177e4
LT
2565 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2566 xd_geo= See header of drivers/block/xd.c.
2567
2568 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2569 Format:
2570 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2571
a9913044 2572______________________________________________________________________
1da177e4
LT
2573
2574TODO:
2575
2576 Add documentation for ALSA options.
2577 Add more DRM drivers.