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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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20This document may not be entirely up to date and comprehensive. The command
21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22module. Loadable modules, after being loaded into the running kernel, also
23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24parameters may be changed at runtime by the command
25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
26
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27The parameters listed below are only valid if certain kernel build options were
28enabled and if respective hardware is present. The text in square brackets at
29the beginning of each description states the restrictions within which a
30parameter is applicable:
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31
32 ACPI ACPI support is enabled.
c99c108a 33 AGP AGP (Accelerated Graphics Port) is enabled.
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34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
e7ba176b 37 AVR32 AVR32 architecture is enabled.
1da177e4 38 AX25 Appropriate AX.25 support is enabled.
0ae53640 39 BLACKFIN Blackfin architecture is enabled.
a9913044 40 DRM Direct Rendering Management support is enabled.
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41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
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46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
11ef697b 52 LIBATA Libata driver is enabled
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53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
309e57df 61 MSI Message Signaled Interrupts (PCI).
c8facbb6 62 MTD MTD (Memory Technology Device) support is enabled.
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63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
734efb46 65 GENERIC_TIME The generic timeofday code is enabled.
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66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
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68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
7f785763 72 PCIE PCI Express support is enabled.
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73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
20510f2f 79 ROOTPLUG The example Root Plug LSM is enabled.
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80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
20510f2f 84 SECURITY Different security models are enabled.
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85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
e523d93c 87 SH SuperH architecture is enabled.
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88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
a9913044 90 SWSUSP Software suspend is enabled.
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91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 99 X86-32 X86-32, aka i386 architecture is enabled.
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100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
103
104In addition, the following text indicates that the option:
105
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
109
110Parameters denoted with BOOT are actually interpreted by the boot
111loader, and have no meaning to the kernel directly.
112Do not modify the syntax of boot loader parameters without extreme
113need or coordination with <Documentation/i386/boot.txt>.
114
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115There are also arch-specific kernel-parameters not documented here.
116See for example <Documentation/x86_64/boot-options.txt>.
117
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118Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119a trailing = on the name of any parameter states that that parameter will
120be entered as an environment variable, whereas its absence indicates that
121it will appear as a kernel argument readable via /proc/cmdline by programs
122running once the system is up.
123
9c4751fd 124The number of kernel parameters is not limited, but the length of the
125complete command line (parameters including spaces etc.) is limited to
126a fixed number of characters. This limit depends on the architecture
127and is between 256 and 4096 characters. It is defined in the file
128./include/asm/setup.h as COMMAND_LINE_SIZE.
129
130
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131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
a9913044 133 Format: { force | off | ht | strict | noirq }
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134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
a9913044 138 strict -- Be less tolerant of platforms that are not
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139 strictly ACPI specification compliant.
140
141 See also Documentation/pm.txt, pci=noacpi
142
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143 acpi_apic_instance= [ACPI, IOAPIC]
144 Format: <int>
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
4e381a4f 147 default: 0
a1fdcc0d 148
1da177e4 149 acpi_sleep= [HW,ACPI] Sleep options
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150 Format: { s3_bios, s3_mode, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
a9913044 154
1da177e4 155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 156 Format: { level | edge | high | low }
1da177e4 157
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158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
160 default in APIC mode
1da177e4 161
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162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
164 default in PIC mode
1da177e4 165
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166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
167 use by PCI
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168 Format: <irq>,<irq>...
169
a9913044 170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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171 Format: <irq>,<irq>...
172
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173 acpi_new_pts_ordering [HW,ACPI]
174 Enforce the ACPI 2.0 ordering of the _PTS control
175 method wrt putting devices into low power states
176 default: pre ACPI 2.0 ordering of _PTS
177
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178 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
179
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180 acpi_no_initrd_override [KNL,ACPI]
181 Disable loading custom ACPI tables from the initramfs
182
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183 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
184 Format: To spoof as Windows 98: ="Microsoft Windows"
185
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186 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
187 acpi_osi="string1" # add string1 -- only one string
188 acpi_osi="!string2" # remove built-in string2
189 acpi_osi= # disable all strings
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190
191 acpi_serialize [HW,ACPI] force serialization of AML methods
192
193 acpi_skip_timer_override [HW,ACPI]
194 Recognize and ignore IRQ0/pin2 Interrupt Override.
195 For broken nForce2 BIOS resulting in XT-PIC timer.
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196 acpi_use_timer_override [HW,ACPI}
197 Use timer override. For some broken Nvidia NF5 boards
198 that require a timer override, but don't have
199 HPET
1da177e4 200
f989106c 201 acpi.debug_layer= [HW,ACPI]
1da177e4 202 Format: <int>
a9913044 203 Each bit of the <int> indicates an ACPI debug layer,
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204 1: enable, 0: disable. It is useful for boot time
205 debugging. After system has booted up, it can be set
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206 via /sys/module/acpi/parameters/debug_layer.
207 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
208 Available bits (add the numbers together) to enable debug output
209 for specific parts of the ACPI subsystem:
210 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
211 0x10 namespace 0x20 parser 0x40 dispatcher
212 0x80 executer 0x100 resources 0x200 acpica debugger
213 0x400 os services 0x800 acpica disassembler.
214 The number can be in decimal or prefixed with 0x in hex.
215 Warning: Many of these options can produce a lot of
216 output and make your system unusable. Be very careful.
217
218 acpi.debug_level= [HW,ACPI]
1da177e4 219 Format: <int>
a9913044 220 Each bit of the <int> indicates an ACPI debug level,
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221 1: enable, 0: disable. It is useful for boot time
222 debugging. After system has booted up, it can be set
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223 via /sys/module/acpi/parameters/debug_level.
224 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
225 Available bits (add the numbers together) to enable different
226 debug output levels of the ACPI subsystem:
227 0x01 error 0x02 warn 0x04 init 0x08 debug object
228 0x10 info 0x20 init names 0x40 parse 0x80 load
229 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
230 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
231 0x10000 resources 0x20000 user requests 0x40000 package.
232 The number can be in decimal or prefixed with 0x in hex.
233 Warning: Many of these options can produce a lot of
234 output and make your system unusable. Be very careful.
235
cd4f0ef7 236 acpi_pm_good [X86-32,X86-64]
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237 Override the pmtimer bug detection: force the kernel
238 to assume that this machine's pmtimer latches its value
239 and always returns good values.
240
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241 agp= [AGP]
242 { off | try_unsupported }
243 off: disable AGP support
244 try_unsupported: try to drive unsupported chipsets
245 (may crash computer or cause data corruption)
246
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247 enable_timer_pin_1 [i386,x86-64]
248 Enable PIN 1 of APIC timer
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249 Can be useful to work around chipset bugs
250 (in particular on some ATI chipsets).
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251 The kernel tries to set a reasonable default.
252
253 disable_timer_pin_1 [i386,x86-64]
254 Disable PIN 1 of APIC timer
255 Can be useful to work around chipset bugs.
256
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257 ad1848= [HW,OSS]
258 Format: <io>,<irq>,<dma>,<dma2>,<type>
259
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260 advansys= [HW,SCSI]
261 See header of drivers/scsi/advansys.c.
262
263 advwdt= [HW,WDT] Advantech WDT
264 Format: <iostart>,<iostop>
265
266 aedsp16= [HW,OSS] Audio Excel DSP 16
267 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
268 See also header of sound/oss/aedsp16.c.
a9913044 269
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270 aha152x= [HW,SCSI]
271 See Documentation/scsi/aha152x.txt.
272
273 aha1542= [HW,SCSI]
274 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
275
276 aic7xxx= [HW,SCSI]
277 See Documentation/scsi/aic7xxx.txt.
278
279 aic79xx= [HW,SCSI]
280 See Documentation/scsi/aic79xx.txt.
281
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282 amijoy.map= [HW,JOY] Amiga joystick support
283 Map of devices attached to JOY0DAT and JOY1DAT
284 Format: <a>,<b>
285 See also Documentation/kernel/input/joystick.txt
286
287 analog.map= [HW,JOY] Analog joystick and gamepad support
288 Specifies type or capabilities of an analog joystick
289 connected to one of 16 gameports
290 Format: <type1>,<type2>,..<type16>
291
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292 apc= [HW,SPARC]
293 Power management functions (SPARCstation-4/5 + deriv.)
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294 Format: noidle
295 Disable APC CPU standby support. SPARCstation-Fox does
296 not play well with APC CPU idle - disable it if you have
297 APC and your system crashes randomly.
298
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299 apic= [APIC,i386] Advanced Programmable Interrupt Controller
300 Change the output verbosity whilst booting
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301 Format: { quiet (default) | verbose | debug }
302 Change the amount of debugging information output
303 when initialising the APIC and IO-APIC components.
a9913044 304
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305 apm= [APM] Advanced Power Management
306 See header of arch/i386/kernel/apm.c.
307
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308 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
309 Format: <io>,<irq>,<nodeID>
310
311 ataflop= [HW,M68k]
312
313 atarimouse= [HW,MOUSE] Atari Mouse
314
315 atascsi= [HW,SCSI] Atari SCSI
316
317 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
318 EzKey and similar keyboards
319
320 atkbd.reset= [HW] Reset keyboard during initialization
321
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322 atkbd.set= [HW] Select keyboard code set
323 Format: <int> (2 = AT (default), 3 = PS/2)
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324
325 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
326 keyboards
327
328 atkbd.softraw= [HW] Choose between synthetic and real raw mode
329 Format: <bool> (0 = real, 1 = synthetic (default))
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330
331 atkbd.softrepeat= [HW]
332 Use software keyboard repeat
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333
334 autotest [IA64]
335
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336 baycom_epp= [HW,AX25]
337 Format: <io>,<mode>
a9913044 338
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339 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
340 Format: <io>,<mode>
341 See header of drivers/net/hamradio/baycom_par.c.
342
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343 baycom_ser_fdx= [HW,AX25]
344 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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345 Format: <io>,<irq>,<mode>[,<baud>]
346 See header of drivers/net/hamradio/baycom_ser_fdx.c.
347
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348 baycom_ser_hdx= [HW,AX25]
349 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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350 Format: <io>,<irq>,<mode>
351 See header of drivers/net/hamradio/baycom_ser_hdx.c.
352
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353 boot_delay= Milliseconds to delay each printk during boot.
354 Values larger than 10 seconds (10000) are changed to
355 no delay (0).
356 Format: integer
357
1da177e4 358 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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359 bttv.radio= Most important insmod options are available as
360 kernel args too.
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361 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
362 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
363
364 BusLogic= [HW,SCSI]
365 See drivers/scsi/BusLogic.c, comment before function
366 BusLogic_ParseDriverOptions().
367
368 c101= [NET] Moxa C101 synchronous serial card
369
cd4f0ef7 370 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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371 Sometimes CPU hardware bugs make them report the cache
372 size incorrectly. The kernel will attempt work arounds
373 to fix known problems, but for some CPUs it is not
374 possible to determine what the correct size should be.
375 This option provides an override for these situations.
376
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377 capability.disable=
378 [SECURITY] Disable capabilities. This would normally
379 be used only if an alternative security model is to be
380 configured. Potentially dangerous and should only be
381 used if you are entirely sure of the consequences.
382
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383 ccw_timeout_log [S390]
384 See Documentation/s390/CommonIO for details.
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385
386 checkreqprot [SELINUX] Set initial checkreqprot flag value.
387 Format: { "0" | "1" }
388 See security/selinux/Kconfig help text.
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389 0 -- check protection applied by kernel (includes
390 any implied execute protection).
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391 1 -- check protection requested by application.
392 Default value is set via a kernel config option.
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393 Value can be changed at runtime via
394 /selinux/checkreqprot.
395
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396 cio_ignore= [S390]
397 See Documentation/s390/CommonIO for details.
398
399 cio_msg= [S390]
400 See Documentation/s390/CommonIO for details.
401
cd4f0ef7 402 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 403 [Deprecated]
3f6dee9b 404 Forces specified clocksource (if available) to be used
734efb46 405 when calculating gettimeofday(). If specified
3f6dee9b 406 clocksource is not available, it defaults to PIT.
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407 Format: { pit | tsc | cyclone | pmtmr }
408
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409 clocksource= [GENERIC_TIME] Override the default clocksource
410 Format: <string>
411 Override the default clocksource and use the clocksource
412 with the name specified.
413 Some clocksource names to choose from, depending on
414 the platform:
415 [all] jiffies (this is the base, fallback clocksource)
416 [ACPI] acpi_pm
417 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
418 pxa_timer,timer3,32k_counter,timer0_1
419 [AVR32] avr32
cd4f0ef7 420 [X86-32] pit,hpet,tsc,vmi-timer;
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421 scx200_hrt on Geode; cyclone on IBM x440
422 [MIPS] MIPS
423 [PARISC] cr16
424 [S390] tod
425 [SH] SuperH
426 [SPARC64] tick
427 [X86-64] hpet,tsc
428
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429 clearcpuid=BITNUM [X86]
430 Disable CPUID feature X for the kernel. See
431 include/asm-x86/cpufeature.h for the valid bit numbers.
432 Note the Linux specific bits are not necessarily
433 stable over kernel options, but the vendor specific
434 ones should be.
435 Also note that user programs calling CPUID directly
436 or using the feature without checking anything
437 will still see it. This just prevents it from
438 being used by the kernel or shown in /proc/cpuinfo.
439 Also note the kernel might malfunction if you disable
440 some critical bits.
441
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442 code_bytes [IA32/X86_64] How many bytes of object code to print
443 in an oops report.
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444 Range: 0 - 8192
445 Default: 64
446
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447 disable_8254_timer
448 enable_8254_timer
449 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
450 over the 8254 in addition to over the IO-APIC. The
451 kernel tries to set a sensible default.
452
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453 hpet= [X86-32,HPET] option to control HPET usage
454 Format: { enable (default) | disable | force }
455 disable: disable HPET and use PIT instead
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456 force: allow force enabled of undocumented chips (ICH4,
457 VIA, nVidia)
1da177e4 458
1da177e4 459 com20020= [HW,NET] ARCnet - COM20020 chipset
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460 Format:
461 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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LT
462
463 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
464 Format: <io>[,<irq>]
465
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466 com90xx= [HW,NET]
467 ARCnet - COM90xx chipset (memory-mapped buffers)
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LT
468 Format: <io>[,<irq>[,<memstart>]]
469
470 condev= [HW,S390] console device
471 conmode=
a9913044 472
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LT
473 console= [KNL] Output console device and options.
474
475 tty<n> Use the virtual console device <n>.
476
477 ttyS<n>[,options]
f1a1c2dc 478 ttyUSB0[,options]
1da177e4 479 Use the specified serial port. The options are of
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480 the form "bbbbpnf", where "bbbb" is the baud rate,
481 "p" is parity ("n", "o", or "e"), "n" is number of
482 bits, and "f" is flow control ("r" for RTS or
483 omit it). Default is "9600n8".
484
485 See Documentation/serial-console.txt for more
486 information. See
487 Documentation/networking/netconsole.txt for an
488 alternative.
1da177e4 489
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490 uart[8250],io,<addr>[,options]
491 uart[8250],mmio,<addr>[,options]
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LT
492 Start an early, polled-mode console on the 8250/16550
493 UART at the specified I/O port or MMIO address,
494 switching to the matching ttyS device later. The
495 options are the same as for ttyS, above.
496
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497 earlycon= [KNL] Output early console device and options.
498 uart[8250],io,<addr>[,options]
499 uart[8250],mmio,<addr>[,options]
500 Start an early, polled-mode console on the 8250/16550
501 UART at the specified I/O port or MMIO address.
502 The options are the same as for ttyS, above.
503
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504 no_console_suspend
505 [HW] Never suspend the console
506 Disable suspending of consoles during suspend and
507 hibernate operations. Once disabled, debugging
508 messages can reach various consoles while the rest
509 of the system is being put to sleep (ie, while
510 debugging driver suspend/resume hooks). This may
511 not work reliably with all consoles, but is known
512 to work with serial and VGA consoles.
513
1da177e4 514 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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515 Format:
516 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 517
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518 crashkernel=nn[KMG]@ss[KMG]
519 [KNL] Reserve a chunk of physical memory to
520 hold a kernel to switch to with kexec on panic.
521
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522 crashkernel=range1:size1[,range2:size2,...][@offset]
523 [KNL] Same as above, but depends on the memory
524 in the running system. The syntax of range is
525 start-[end] where start and end are both
526 a memory unit (amount[KMG]). See also
527 Documentation/kdump/kdump.txt for a example.
528
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LT
529 cs4232= [HW,OSS]
530 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
531
532 cs89x0_dma= [HW,NET]
533 Format: <dma>
534
535 cs89x0_media= [HW,NET]
536 Format: { rj45 | aui | bnc }
a9913044 537
a9913044 538 dasd= [HW,NET]
1da177e4
LT
539 See header of drivers/s390/block/dasd_devmap.c.
540
541 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
542 (one device per port)
543 Format: <port#>,<type>
544 See also Documentation/input/joystick-parport.txt
545
546 debug [KNL] Enable kernel debugging (events log level).
547
cae2ed9a
IM
548 debug_locks_verbose=
549 [KNL] verbose self-tests
550 Format=<0|1>
551 Print debugging info while doing the locking API
552 self-tests.
553 We default to 0 (no extra messages), setting it to
554 1 will print _a lot_ more information - normally
555 only useful to kernel developers.
556
2d27a966 557 decnet.addr= [HW,NET]
1da177e4
LT
558 Format: <area>[,<node>]
559 See also Documentation/networking/decnet.txt.
560
ecb77fa9 561 vt.default_blu= [VT]
55ff9780
AD
562 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
563 Change the default blue palette of the console.
564 This is a 16-member array composed of values
565 ranging from 0-255.
566
ecb77fa9 567 vt.default_grn= [VT]
55ff9780
AD
568 Format: <green0>,<green1>,<green2>,...,<green15>
569 Change the default green palette of the console.
570 This is a 16-member array composed of values
571 ranging from 0-255.
572
ecb77fa9 573 vt.default_red= [VT]
55ff9780
AD
574 Format: <red0>,<red1>,<red2>,...,<red15>
575 Change the default red palette of the console.
576 This is a 16-member array composed of values
577 ranging from 0-255.
578
ecb77fa9
ST
579 vt.default_utf8=
580 [VT]
55ff9780
AD
581 Format=<0|1>
582 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
583 Default is 1, i.e. UTF-8 mode is enabled for all
584 newly opened terminals.
55ff9780 585
1da177e4
LT
586 dhash_entries= [KNL]
587 Set number of hash buckets for dentry cache.
a9913044 588
1da177e4
LT
589 digi= [HW,SERIAL]
590 IO parameters + enable/disable command.
591
592 digiepca= [HW,SERIAL]
593 See drivers/char/README.epca and
594 Documentation/digiepca.txt.
595
093af8d7 596 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
597 By default the kernel will trim any uncacheable
598 memory out of your available memory pool based on
599 MTRR settings. This parameter disables that behavior,
600 possibly causing your machine to run very slowly.
601
1da177e4
LT
602 dmasound= [HW,OSS] Sound subsystem buffers
603
604 dscc4.setup= [NET]
605
606 dtc3181e= [HW,SCSI]
607
0ae53640 608 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
609 earlyprintk=vga
610 earlyprintk=serial[,ttySn[,baudrate]]
611
a9913044 612 Append ",keep" to not disable it when the real console
1da177e4
LT
613 takes over.
614
615 Only vga or serial at a time, not both.
616
617 Currently only ttyS0 and ttyS1 are supported.
618
619 Interaction with the standard serial driver is not
620 very good.
621
622 The VGA output is eventually overwritten by the real
623 console.
624
625 eata= [HW,SCSI]
626
1da177e4
LT
627 edd= [EDD]
628 Format: {"of[f]" | "sk[ipmbr]"}
629 See comment in arch/i386/boot/edd.S
630
1da177e4
LT
631 eisa_irq_edge= [PARISC,HW]
632 See header of drivers/parisc/eisa.c.
633
cd4f0ef7 634 elanfreq= [X86-32]
1da177e4
LT
635 See comment before function elanfreq_setup() in
636 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
637
638 elevator= [IOSCHED]
16ab3adf 639 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
640 See Documentation/block/as-iosched.txt and
641 Documentation/block/deadline-iosched.txt for details.
642
cd4f0ef7 643 elfcorehdr= [X86-32, X86_64]
a9913044 644 Specifies physical address of start of kernel core
aac04b32
VG
645 image elf header. Generally kexec loader will
646 pass this option to capture kernel.
647 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
648
649 enforcing [SELINUX] Set initial enforcing status.
650 Format: {"0" | "1"}
651 See security/selinux/Kconfig help text.
652 0 -- permissive (log only, no denials).
653 1 -- enforcing (deny and log).
654 Default value is 0.
655 Value can be changed at runtime via /selinux/enforce.
656
1da177e4
LT
657 es1371= [HW,OSS]
658 Format: <spdif>,[<nomix>,[<amplifier>]]
659 See also header of sound/oss/es1371.c.
a9913044 660
1da177e4
LT
661 ether= [HW,NET] Ethernet cards parameters
662 This option is obsoleted by the "netdev=" option, which
663 has equivalent usage. See its documentation for details.
664
665 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
666 Format: <io>[,<irq>]
667
de1ba09b
AM
668 failslab=
669 fail_page_alloc=
670 fail_make_request=[KNL]
671 General fault injection mechanism.
672 Format: <interval>,<probability>,<space>,<times>
673 See also /Documentation/fault-injection/.
674
1da177e4
LT
675 fd_mcs= [HW,SCSI]
676 See header of drivers/scsi/fd_mcs.c.
677
678 fdomain= [HW,SCSI]
679 See header of drivers/scsi/fdomain.c.
680
681 floppy= [HW]
682 See Documentation/floppy.txt.
683
1da177e4
LT
684 gamecon.map[2|3]=
685 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
686 support via parallel port (up to 5 devices per port)
687 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
688 See also Documentation/input/joystick-parport.txt
689
690 gamma= [HW,DRM]
691
aaf23042
YL
692 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
693 Format: off | on
694 default: on
695
1da177e4
LT
696 gdth= [HW,SCSI]
697 See header of drivers/scsi/gdth.c.
698
699 gpt [EFI] Forces disk with valid GPT signature but
700 invalid Protective MBR to be treated as GPT.
701
1da177e4
LT
702 gvp11= [HW,SCSI]
703
704 hashdist= [KNL,NUMA] Large hashes allocated during boot
705 are distributed across NUMA nodes. Defaults on
706 for IA-64, off otherwise.
a9913044 707 Format: 0 | 1 (for off | on)
1da177e4
LT
708
709 hcl= [IA-64] SGI's Hardware Graph compatibility layer
710
711 hd= [EIDE] (E)IDE hard drive subsystem geometry
712 Format: <cyl>,<head>,<sect>
713
714 hd?= [HW] (E)IDE subsystem
715 hd?lun= See Documentation/ide.txt.
716
717 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
718 size of <nn>. This works even on boxes that have no
719 highmem otherwise. This also works to reduce highmem
720 size on bigger boxes.
721
54cdfdb4
TG
722 highres= [KNL] Enable/disable high resolution timer mode.
723 Valid parameters: "on", "off"
724 Default: "on"
725
1da177e4
LT
726 hisax= [HW,ISDN]
727 See Documentation/isdn/README.HiSax.
728
cd4f0ef7 729 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 730 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 731
1da177e4 732 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
733 i8042.dumbkbd [HW] Pretend that controller can only read data from
734 keyboard and cannot control its state
1da177e4
LT
735 (Don't attempt to blink the leds)
736 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 737 i8042.nokbd [HW] Don't check/create keyboard port
1da177e4
LT
738 i8042.nomux [HW] Don't check presence of an active multiplexing
739 controller
740 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
741 controllers
742 i8042.panicblink=
743 [HW] Frequency with which keyboard LEDs should blink
744 when kernel panics (default is 0.5 sec)
745 i8042.reset [HW] Reset the controller during init and cleanup
746 i8042.unlock [HW] Unlock (ignore) the keylock
747
748 i810= [HW,DRM]
749
e70c9d5e
DT
750 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
751 indicates that the driver is running on unsupported
752 hardware.
1da177e4
LT
753 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
754 does not match list of supported models.
755 i8k.power_status
756 [HW] Report power status in /proc/i8k
757 (disabled by default)
758 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
759 capability is set.
760
761 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
762 See Documentation/mca.txt.
763
764 icn= [HW,ISDN]
765 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
766
767 ide= [HW] (E)IDE subsystem
768 Format: ide=nodma or ide=doubler or ide=reverse
769 See Documentation/ide.txt.
770
771 ide?= [HW] (E)IDE subsystem
772 Format: ide?=noprobe or chipset specific parameters.
773 See Documentation/ide.txt.
a9913044 774
1da177e4
LT
775 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
776 See Documentation/ide.txt.
777
f039b754
AK
778 idle= [X86]
779 Format: idle=poll or idle=mwait
780 Poll forces a polling idle loop that can slightly improves the performance
781 of waking up a idle CPU, but will use a lot of power and make the system
782 run hot. Not recommended.
783 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
784 to not use it because it doesn't save as much power as a normal idle
785 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
786 as idle=poll.
a9913044 787
594765a7
DC
788 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
789 Claim all unknown PCI IDE storage controllers.
790
79290822
IM
791 ignore_loglevel [KNL]
792 Ignore loglevel setting - this will print /all/
793 kernel messages to the console. Useful for debugging.
794
1da177e4
LT
795 ihash_entries= [KNL]
796 Set number of hash buckets for inode cache.
797
798 in2000= [HW,SCSI]
799 See header of drivers/scsi/in2000.c.
800
801 init= [KNL]
802 Format: <full_path>
803 Run specified binary instead of /sbin/init as init
804 process.
805
806 initcall_debug [KNL] Trace initcalls as they are executed. Useful
807 for working out where the kernel is dying during
808 startup.
809
810 initrd= [BOOT] Specify the location of the initial ramdisk
811
812 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
813 Format: <irq>
814
815 inttest= [IA64]
816
ba395927
KA
817 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
818 off
819 Disable intel iommu driver.
820 igfx_off [Default Off]
821 By default, gfx is mapped as normal device. If a gfx
822 device has a dedicated DMAR unit, the DMAR unit is
823 bypassed by not enabling DMAR with this option. In
824 this case, gfx device will use physical address for
825 DMA.
7d3b03ce
KA
826 forcedac [x86_64]
827 With this option iommu will not optimize to look
828 for io virtual address below 32 bit forcing dual
829 address cycle on pci bus for cards supporting greater
830 than 32 bit addressing. The default is to look
831 for translation below 32 bit and if not available
832 then look in the higher range.
ba395927 833
b02aae9c 834 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
835 0x80
836 Standard port 0x80 based delay
837 0xed
838 Alternate port 0xed based delay (needed on some systems)
b02aae9c 839 udelay
6e7c4025
IM
840 Simple two microseconds delay
841 none
842 No delay
b02aae9c 843
1da177e4
LT
844 io7= [HW] IO7 for Marvel based alpha systems
845 See comment before marvel_specify_io7 in
846 arch/alpha/kernel/core_marvel.c.
847
848 ip= [IP_PNP]
849 See Documentation/nfsroot.txt.
850
851 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
852 See comment before ip2_setup() in
853 drivers/char/ip2/ip2base.c.
1da177e4
LT
854
855 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
856 See header of drivers/scsi/ips.c.
857
72c4a13a
SH
858 ports= [IP_VS_FTP] IPVS ftp helper module
859 Default is 21.
860 Up to 8 (IP_VS_APP_MAX_PORTS) ports
861 may be specified.
862 Format: <port>,<port>....
863
200803df
AC
864 irqfixup [HW]
865 When an interrupt is not handled search all handlers
866 for it. Intended to get systems with badly broken
867 firmware running.
868
869 irqpoll [HW]
870 When an interrupt is not handled search all handlers
871 for it. Also check all handlers each timer
872 interrupt. Intended to get systems with badly broken
873 firmware running.
874
1da177e4 875 isapnp= [ISAPNP]
a9913044 876 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
877
878 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
879 Format:
880 <cpu number>,...,<cpu number>
881 or
882 <cpu number>-<cpu number> (must be a positive range in ascending order)
883 or a mixture
884 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
885 This option can be used to specify one or more CPUs
886 to isolate from the general SMP balancing and scheduling
887 algorithms. The only way to move a process onto or off
888 an "isolated" CPU is via the CPU affinity syscalls.
889 <cpu number> begins at 0 and the maximum value is
890 "number of CPUs in system - 1".
891
892 This option is the preferred way to isolate CPUs. The
a9913044
RD
893 alternative -- manually setting the CPU mask of all
894 tasks in the system -- can cause problems and
895 suboptimal load balancer performance.
1da177e4 896
a9913044 897 iucv= [HW,NET]
1da177e4
LT
898
899 js= [HW,JOY] Analog joystick
900 See Documentation/input/joystick.txt.
901
cd4f0ef7 902 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
903 specifies the amount of memory usable by the kernel
904 for non-movable allocations. The requested amount is
905 spread evenly throughout all nodes in the system. The
906 remaining memory in each node is used for Movable
907 pages. In the event, a node is too small to have both
908 kernelcore and Movable pages, kernelcore pages will
909 take priority and other nodes will have a larger number
910 of kernelcore pages. The Movable zone is used for the
911 allocation of pages that may be reclaimed or moved
912 by the page migration subsystem. This means that
913 HugeTLB pages may not be allocated from this zone.
914 Note that allocations like PTEs-from-HighMem still
915 use the HighMem zone if it exists, and the Normal
916 zone if it does not.
917
cd4f0ef7 918 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
919 is similar to kernelcore except it specifies the
920 amount of memory used for migratable allocations.
921 If both kernelcore and movablecore is specified,
922 then kernelcore will be at *least* the specified
923 value but may be more. If movablecore on its own
924 is specified, the administrator must be careful
925 that the amount of memory usable for all allocations
926 is not too small.
927
1da177e4
LT
928 keepinitrd [HW,ARM]
929
cd4f0ef7 930 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
931 in oops dumps.
932
933 l2cr= [PPC]
934
cd4f0ef7 935 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 936 disabled it.
1da177e4 937
cd4f0ef7 938 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
939 C2 power state.
940
fcb71f6f
FC
941 libata.dma= [LIBATA] DMA control
942 libata.dma=0 Disable all PATA and SATA DMA
943 libata.dma=1 PATA and SATA Disk DMA only
944 libata.dma=2 ATAPI (CDROM) DMA only
945 libata.dma=4 Compact Flash DMA only
946 Combinations also work, so libata.dma=3 enables DMA
947 for disks and CDROMs, but not CFs.
948
78e70c23
DJ
949 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
950 when set.
951 Format: <int>
952
1da177e4
LT
953 load_ramdisk= [RAM] List of ramdisks to load from floppy
954 See Documentation/ramdisk.txt.
955
a6b25b67
RD
956 lockd.nlm_grace_period=P [NFS] Assign grace period.
957 Format: <integer>
1da177e4 958
a6b25b67
RD
959 lockd.nlm_tcpport=N [NFS] Assign TCP port.
960 Format: <integer>
961
962 lockd.nlm_timeout=T [NFS] Assign timeout value.
963 Format: <integer>
964
965 lockd.nlm_udpport=M [NFS] Assign UDP port.
966 Format: <integer>
1da177e4
LT
967
968 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
969 Format: <irq>
970
971 loglevel= All Kernel Messages with a loglevel smaller than the
972 console loglevel will be printed to the console. It can
973 also be changed with klogd or other programs. The
974 loglevels are defined as follows:
975
976 0 (KERN_EMERG) system is unusable
977 1 (KERN_ALERT) action must be taken immediately
978 2 (KERN_CRIT) critical conditions
979 3 (KERN_ERR) error conditions
980 4 (KERN_WARNING) warning conditions
981 5 (KERN_NOTICE) normal but significant condition
982 6 (KERN_INFO) informational
983 7 (KERN_DEBUG) debug-level messages
984
985 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
986 Format: { n | nk | nM }
987 n must be a power of two. The default size
988 is set in the kernel config file.
1da177e4 989
accaa24c
RD
990 logo.nologo [FB] Disables display of the built-in Linux logo.
991 This may be used to provide more screen space for
992 kernel log messages and is useful when debugging
993 kernel boot problems.
994
1da177e4
LT
995 lp=0 [LP] Specify parallel ports to use, e.g,
996 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
997 lp=reset first parallel port). 'lp=0' disables the
998 lp=auto printer driver. 'lp=reset' (which can be
999 specified in addition to the ports) causes
1000 attached printers to be reset. Using
1001 lp=port1,port2,... specifies the parallel ports
1002 to associate lp devices with, starting with
1003 lp0. A port specification may be 'none' to skip
1004 that lp device, or a parport name such as
1005 'parport0'. Specifying 'lp=auto' instead of a
1006 port specification list means that device IDs
1007 from each port should be examined, to see if
1008 an IEEE 1284-compliant printer is attached; if
1009 so, the driver will manage that printer.
1010 See also header of drivers/char/lp.c.
1011
1012 lpj=n [KNL]
1013 Sets loops_per_jiffy to given constant, thus avoiding
1014 time-consuming boot-time autodetection (up to 250 ms per
1015 CPU). 0 enables autodetection (default). To determine
1016 the correct value for your kernel, boot with normal
1017 autodetection and see what value is printed. Note that
1018 on SMP systems the preset will be applied to all CPUs,
1019 which is likely to cause problems if your CPUs need
1020 significantly divergent settings. An incorrect value
1021 will cause delays in the kernel to be wrong, leading to
1022 unpredictable I/O errors and other breakage. Although
1023 unlikely, in the extreme case this might damage your
1024 hardware.
1025
1026 ltpc= [NET]
1027 Format: <io>,<irq>,<dma>
1028
a9913044
RD
1029 mac5380= [HW,SCSI] Format:
1030 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1031
a9913044
RD
1032 mac53c9x= [HW,SCSI] Format:
1033 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1034
a9913044
RD
1035 machvec= [IA64] Force the use of a particular machine-vector
1036 (machvec) in a generic kernel.
1037 Example: machvec=hpzx1_swiotlb
1da177e4 1038
a9913044 1039 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1040 be mounted
1041 Format: <1-256>
1042
1043 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1044 should make use of. maxcpus=n : n >= 0 limits the
1045 kernel to using 'n' processors. n=0 is a special case,
1046 it is equivalent to "nosmp", which also disables
1047 the IO APIC.
1da177e4 1048
2b2c3750
BP
1049 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1050 equal to this physical address is ignored.
1051
a9913044 1052 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1053 Should be between 1 and 2^32-1.
1054
1055 max_report_luns=
a9913044 1056 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1057 Should be between 1 and 16384.
1058
cd4f0ef7 1059 mca-pentium [BUGS=X86-32]
1da177e4
LT
1060
1061 mcatest= [IA-64]
1062
cd4f0ef7 1063 mce [X86-32] Machine Check Exception
1da177e4 1064
909dd324
AK
1065 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1066
1da177e4
LT
1067 md= [HW] RAID subsystems devices and level
1068 See Documentation/md.txt.
a9913044 1069
1da177e4
LT
1070 mdacon= [MDA]
1071 Format: <first>,<last>
1072 Specifies range of consoles to be captured by the MDA.
a9913044 1073
1da177e4
LT
1074 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1075 Amount of memory to be used when the kernel is not able
1076 to see the whole system memory or for test.
cd4f0ef7 1077 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1078 address space collisions. Without memmap= PCI devices
1079 could be placed at addresses belonging to unused RAM.
1080
cd4f0ef7 1081 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1082 memory.
1083
cd4f0ef7 1084 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1085 E820 memory map, as specified by the user.
1086 Such memmap=exactmap lines can be constructed based on
1087 BIOS output or other requirements. See the memmap=nn@ss
1088 option description.
1089
1090 memmap=nn[KMG]@ss[KMG]
1091 [KNL] Force usage of a specific region of memory
1092 Region of memory to be used, from ss to ss+nn.
1093
1094 memmap=nn[KMG]#ss[KMG]
1095 [KNL,ACPI] Mark specific memory as ACPI data.
1096 Region of memory to be used, from ss to ss+nn.
1097
1098 memmap=nn[KMG]$ss[KMG]
1099 [KNL,ACPI] Mark specific memory as reserved.
1100 Region of memory to be used, from ss to ss+nn.
1101
1102 meye.*= [HW] Set MotionEye Camera parameters
1103 See Documentation/video4linux/meye.txt.
1104
8f36881b
AS
1105 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1106 Multi-Function General Purpose Timers on AMD Geode
1107 platforms.
1108
e6c4dc6c
WT
1109 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1110 the BIOS has incorrectly applied a workaround. TinyBIOS
1111 version 0.98 is known to be affected, 0.99 fixes the
1112 problem by letting the user disable the workaround.
1113
1da177e4
LT
1114 mga= [HW,DRM]
1115
1116 mousedev.tap_time=
1117 [MOUSE] Maximum time between finger touching and
1118 leaving touchpad surface for touch to be considered
1119 a tap and be reported as a left button click (for
1120 touchpads working in absolute mode only).
1121 Format: <msecs>
1122 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1123 reporting absolute coordinates, such as tablets
1124 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1125 reporting absolute coordinates, such as tablets
1126
1127 mpu401= [HW,OSS]
1128 Format: <io>,<irq>
1129
1130 MTD_Partition= [MTD]
1131 Format: <name>,<region-number>,<size>,<offset>
1132
a9913044
RD
1133 MTD_Region= [MTD] Format:
1134 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1135
1136 mtdparts= [MTD]
c8facbb6 1137 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1138
1139 mtouchusb.raw_coordinates=
a9913044
RD
1140 [HW] Make the MicroTouch USB driver use raw coordinates
1141 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1142
1143 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1144
1145 NCR_D700= [HW,SCSI]
1146 See header of drivers/scsi/NCR_D700.c.
1147
1148 ncr5380= [HW,SCSI]
1149
1150 ncr53c400= [HW,SCSI]
1151
1152 ncr53c400a= [HW,SCSI]
1153
1154 ncr53c406a= [HW,SCSI]
1155
1156 ncr53c8xx= [HW,SCSI]
1157
1158 netdev= [NET] Network devices parameters
1159 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1160 Note that mem_start is often overloaded to mean
1161 something different and driver-specific.
a9913044
RD
1162 This usage is only documented in each driver source
1163 file if at all.
1164
1da177e4
LT
1165 nfsaddrs= [NFS]
1166 See Documentation/nfsroot.txt.
1167
1168 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1169 See Documentation/nfsroot.txt.
1170
a72b4422
TM
1171 nfs.callback_tcpport=
1172 [NFS] set the TCP port on which the NFSv4 callback
1173 channel should listen.
1174
58df095b
TM
1175 nfs.idmap_cache_timeout=
1176 [NFS] set the maximum lifetime for idmapper cache
1177 entries.
1178
f43bf0be
TM
1179 nfs.enable_ino64=
1180 [NFS] enable 64-bit inode numbers.
1181 If zero, the NFS client will fake up a 32-bit inode
1182 number for the readdir() and stat() syscalls instead
1183 of returning the full 64-bit number.
1184 The default is to return 64-bit inode numbers.
1185
e7ba176b
HS
1186 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1187 when a NMI is triggered.
1188 Format: [state][,regs][,debounce][,die]
1189
cd4f0ef7 1190 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1191
cd4f0ef7 1192 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1193 emulation library even if a 387 maths coprocessor
1194 is present.
1195
c1aee215
CL
1196 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1197 caches in the slab allocator. Saves per-node memory,
1198 but will impact performance.
3395ee05 1199
a9913044
RD
1200 noalign [KNL,ARM]
1201
1da177e4
LT
1202 noapic [SMP,APIC] Tells the kernel to not make use of any
1203 IOAPICs that may be present in the system.
1204
1da177e4
LT
1205 nobats [PPC] Do not use BATs for mapping kernel lowmem
1206 on "Classic" PPC cores.
1207
1208 nocache [ARM]
a9913044 1209
163ecdff
SN
1210 nodelayacct [KNL] Disable per-task delay accounting
1211
1da177e4
LT
1212 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1213
8b2cb7a8
HY
1214 noefi [X86-32,X86-64] Disable EFI runtime services support.
1215
1da177e4
LT
1216 noexec [IA-64]
1217
cd4f0ef7 1218 noexec [X86-32,X86-64]
1da177e4
LT
1219 noexec=on: enable non-executable mappings (default)
1220 noexec=off: disable nn-executable mappings
1221
cd4f0ef7 1222 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1223 register save and restore. The kernel will only save
1224 legacy floating-point registers on task switch.
1da177e4 1225
191679fd
AK
1226 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1227
1da177e4 1228 nohlt [BUGS=ARM]
a9913044 1229
cd4f0ef7 1230 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1231 instruction doesn't work correctly and not to
1232 use it.
1233
1234 nohalt [IA-64] Tells the kernel not to use the power saving
1235 function PAL_HALT_LIGHT when idle. This increases
1236 power-consumption. On the positive side, it reduces
1237 interrupt wake-up latency, which may improve performance
1238 in certain environments such as networked servers or
1239 real-time systems.
1240
79bf2bb3
TG
1241 nohz= [KNL] Boottime enable/disable dynamic ticks
1242 Valid arguments: on, off
1243 Default: on
1244
cd4f0ef7 1245 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1246
cd4f0ef7 1247 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1248 disable unhandled interrupt sources.
1249
cd4f0ef7 1250 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1251 broken timer IRQ sources.
1252
1da177e4
LT
1253 noisapnp [ISAPNP] Disables ISA PnP code.
1254
1255 noinitrd [RAM] Tells the kernel not to load any configured
1256 initial RAM disk.
1257
1258 nointroute [IA-64]
1259
0aa366f3
TL
1260 nojitter [IA64] Disables jitter checking for ITC timers.
1261
cd4f0ef7 1262 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1263
cd4f0ef7 1264 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1265
1da177e4
LT
1266 noltlbs [PPC] Do not use large page/tlb entries for kernel
1267 lowmem mapping on PPC40x.
1268
312f1f01
H
1269 nomca [IA-64] Disable machine check abort handling
1270
cd4f0ef7 1271 nomce [X86-32] Machine Check Exception
abe37e5a 1272
83d7384f
AS
1273 nomfgpt [X86-32] Disable Multi-Function General Purpose
1274 Timer usage (for AMD Geode machines).
1275
cd4f0ef7 1276 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1277
cd4f0ef7 1278 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1279 with UP alternatives
1280
1da177e4
LT
1281 noresidual [PPC] Don't use residual data on PReP machines.
1282
a9913044
RD
1283 noresume [SWSUSP] Disables resume and restores original swap
1284 space.
1285
1da177e4
LT
1286 no-scroll [VGA] Disables scrollback.
1287 This is required for the Braillex ib80-piezo Braille
1288 reader made by F.H. Papenmeier (Germany).
1289
1290 nosbagart [IA-64]
1291
cd4f0ef7 1292 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1293
61ec7567
LB
1294 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1295 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1296
97842216
DJ
1297 nosoftlockup [KNL] Disable the soft-lockup detector.
1298
1da177e4
LT
1299 nosync [HW,M68K] Disables sync negotiation for all devices.
1300
cd4f0ef7 1301 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1302
1303 nousb [USB] Disable the USB subsystem
1304
1305 nowb [ARM]
a9913044 1306
f0c0b2b8
KH
1307 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1308 one of ['zone', 'node', 'default'] can be specified
1309 This can be set from sysctl after boot.
1310 See Documentation/sysctl/vm.txt for details.
1311
a61c2d78
DJ
1312 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1313
1da177e4
LT
1314 opl3= [HW,OSS]
1315 Format: <io>
1316
1da177e4
LT
1317 oprofile.timer= [HW]
1318 Use timer interrupt instead of performance counters
1319
1da177e4
LT
1320 osst= [HW,SCSI] SCSI Tape Driver
1321 Format: <buffer_size>,<write_threshold>
1322 See also Documentation/scsi/st.txt.
1323
1324 panic= [KNL] Kernel behaviour on panic
1325 Format: <timeout>
1326
1327 parkbd.port= [HW] Parallel port number the keyboard adapter is
1328 connected to, default is 0.
1329 Format: <parport#>
1330 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1331 0 for XT, 1 for AT (default is AT).
a9913044
RD
1332 Format: <mode>
1333
1334 parport= [HW,PPT] Specify parallel ports. 0 disables.
1335 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1336 Use 'auto' to force the driver to use any
1337 IRQ/DMA settings detected (the default is to
1338 ignore detected IRQ/DMA settings because of
1339 possible conflicts). You can specify the base
1340 address, IRQ, and DMA settings; IRQ and DMA
1341 should be numbers, or 'auto' (for using detected
1342 settings on that particular port), or 'nofifo'
1343 (to avoid using a FIFO even if it is detected).
1344 Parallel ports are assigned in the order they
1345 are specified on the command line, starting
1346 with parport0.
1347
1348 parport_init_mode= [HW,PPT]
1349 Configure VIA parallel port to operate in
1350 a specific mode. This is necessary on Pegasos
1351 computer where firmware has no options for setting
1352 up parallel port mode and sets it to spp.
1353 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1354 Format: [spp|ps2|epp|ecp|ecpepp]
1355
a9913044
RD
1356 pas2= [HW,OSS] Format:
1357 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1358
1da177e4
LT
1359 pas16= [HW,SCSI]
1360 See header of drivers/scsi/pas16.c.
1361
dd287796
AM
1362 pause_on_oops=
1363 Halt all CPUs after the first oops has been printed for
1364 the specified number of seconds. This is to be used if
1365 your oopses keep scrolling off the screen.
1366
1da177e4
LT
1367 pcbit= [HW,ISDN]
1368
1369 pcd. [PARIDE]
1370 See header of drivers/block/paride/pcd.c.
1371 See also Documentation/paride.txt.
1372
a9913044 1373 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1374 off [X86-32] don't probe for the PCI bus
1375 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1376 the hardware directly. Use this if your machine
1377 has a non-standard PCI host bridge.
cd4f0ef7 1378 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1379 hardware access methods are allowed. Use this
1380 if you experience crashes upon bootup and you
1381 suspect they are caused by the BIOS.
cd4f0ef7 1382 conf1 [X86-32] Force use of PCI Configuration
a9913044 1383 Mechanism 1.
cd4f0ef7 1384 conf2 [X86-32] Force use of PCI Configuration
a9913044 1385 Mechanism 2.
7f785763
RD
1386 noaer [PCIE] If the PCIEAER kernel config parameter is
1387 enabled, this kernel boot option can be used to
1388 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1389 nodomains [PCI] Disable support for multiple PCI
1390 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1391 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1392 Configuration
309e57df
MW
1393 nomsi [MSI] If the PCI_MSI kernel config parameter is
1394 enabled, this kernel boot option can be used to
1395 disable the use of MSI interrupts system-wide.
cd4f0ef7 1396 nosort [X86-32] Don't sort PCI devices according to
a9913044
RD
1397 order given by the PCI BIOS. This sorting is
1398 done to get a device order compatible with
1399 older kernels.
cd4f0ef7 1400 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1401 routing table. These calls are known to be buggy
1402 on several machines and they hang the machine
1403 when used, but on other computers it's the only
1404 way to get the interrupt routing table. Try
1405 this option if the kernel is unable to allocate
1406 IRQs or discover secondary PCI buses on your
1407 motherboard.
cd4f0ef7 1408 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1409 Use with caution as certain devices share
1410 address decoders between ROMs and other
1411 resources.
cd4f0ef7 1412 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1413 assigned automatically to PCI devices. You can
1414 make the kernel exclude IRQs of your ISA cards
1415 this way.
cd4f0ef7 1416 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1417 of the PIRQ table (normally generated
1418 by the BIOS) if it is outside the
1419 F0000h-100000h range.
cd4f0ef7 1420 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1421 useful if the kernel is unable to find your
1422 secondary buses and you want to tell it
1423 explicitly which ones they are.
cd4f0ef7 1424 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1425 numbers ourselves, overriding
1426 whatever the firmware may have done.
cd4f0ef7 1427 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1428 in the BIOS $PIR table. This is needed on
1429 some systems with broken BIOSes, notably
1430 some HP Pavilion N5400 and Omnibook XE3
1431 notebooks. This will have no effect if ACPI
1432 IRQ routing is enabled.
cd4f0ef7 1433 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1434 or for PCI scanning.
62f420f8
GH
1435 use_crs [X86-32] Use _CRS for PCI resource
1436 allocation.
a9913044
RD
1437 routeirq Do IRQ routing for all PCI devices.
1438 This is normally done in pci_enable_device(),
1439 so this option is a temporary workaround
1440 for broken drivers that don't call it.
1441 firmware [ARM] Do not re-enumerate the bus but instead
1442 just use the configuration from the
1443 bootloader. This is currently used on
1444 IXP2000 systems where the bus has to be
1445 configured a certain way for adjunct CPUs.
0637a70a
AK
1446 noearly [X86] Don't do any early type 1 scanning.
1447 This might help on some broken boards which
1448 machine check when some devices' config space
1449 is read. But various workarounds are disabled
1450 and some IOMMU drivers will not work.
6b4b78fe
MD
1451 bfsort Sort PCI devices into breadth-first order.
1452 This sorting is done to get a device
1453 order compatible with older (<= 2.4) kernels.
1454 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1455 cbiosize=nn[KMG] The fixed amount of bus space which is
1456 reserved for the CardBus bridge's IO window.
1457 The default value is 256 bytes.
1458 cbmemsize=nn[KMG] The fixed amount of bus space which is
1459 reserved for the CardBus bridge's memory
1460 window. The default value is 64 megabytes.
6b4b78fe 1461
1da177e4
LT
1462 pcmv= [HW,PCMCIA] BadgePAD 4
1463
1464 pd. [PARIDE]
1465 See Documentation/paride.txt.
1466
1467 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1468 boot time.
1469 Format: { 0 | 1 }
1470 See arch/parisc/kernel/pdc_chassis.c
1471
1472 pf. [PARIDE]
1473 See Documentation/paride.txt.
1474
1475 pg. [PARIDE]
1476 See Documentation/paride.txt.
1477
1478 pirq= [SMP,APIC] Manual mp-table setup
1479 See Documentation/i386/IO-APIC.txt.
1480
1481 plip= [PPT,NET] Parallel port network link
1482 Format: { parport<nr> | timid | 0 }
1483 See also Documentation/parport.txt.
1484
1485 pnpacpi= [ACPI]
1486 { off }
1487
1488 pnpbios= [ISAPNP]
1489 { on | off | curr | res | no-curr | no-res }
1490
1491 pnp_reserve_irq=
1492 [ISAPNP] Exclude IRQs for the autoconfiguration
1493
1494 pnp_reserve_dma=
1495 [ISAPNP] Exclude DMAs for the autoconfiguration
1496
1497 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1498 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1499
1500 pnp_reserve_mem=
a9913044
RD
1501 [ISAPNP] Exclude memory regions for the
1502 autoconfiguration.
1da177e4
LT
1503 Ranges are in pairs (memory base and size).
1504
45807a1d
IM
1505 print-fatal-signals=
1506 [KNL] debug: print fatal signals
1507 print-fatal-signals=1: print segfault info to
1508 the kernel console.
1509 default: off.
1510
e84845c4
RD
1511 printk.time= Show timing data prefixed to each printk message line
1512 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1513
1da177e4 1514 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1515 Format: [schedule,]<number>
1516 Param: "schedule" - profile schedule points.
1517 Param: <number> - step/bucket size as a power of 2 for
1518 statistical time based profiling.
b3da2a73
MG
1519 Param: "sleep" - profile D-state sleeping (millisecs).
1520 Requires CONFIG_SCHEDSTATS
c0fe2e69 1521 Param: "kvm" - profile VM exits.
1da177e4 1522
a9913044 1523 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1524 Limit processor to maximum C-state
1525 max_cstate=9 overrides any DMI blacklist limit.
1526
41c0d868
LB
1527 processor.nocst [HW,ACPI]
1528 Ignore the _CST method to determine C-states,
1529 instead using the legacy FADT method
1530
1da177e4
LT
1531 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1532 before loading.
1533 See Documentation/ramdisk.txt.
1534
a9913044
RD
1535 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1536 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1537 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1538 per second.
a9913044
RD
1539 psmouse.resetafter= [HW,MOUSE]
1540 Try to reset the device after so many bad packets
1da177e4
LT
1541 (0 = never).
1542 psmouse.resolution=
1543 [HW,MOUSE] Set desired mouse resolution, in dpi.
1544 psmouse.smartscroll=
a9913044 1545 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1546 0 = disabled, 1 = enabled (default).
1547
1548 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1549 Format:
1550 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1551
1552 pt. [PARIDE]
1553 See Documentation/paride.txt.
1554
dc8c8587
KS
1555 pty.legacy_count=
1556 [KNL] Number of legacy pty's. Overwrites compiled-in
1557 default number.
1558
7d2c502f 1559 quiet [KNL] Disable most log messages
a9913044 1560
1da177e4
LT
1561 r128= [HW,DRM]
1562
1563 raid= [HW,RAID]
1564 See Documentation/md.txt.
1565
a9913044 1566 ramdisk_blocksize= [RAM]
1da177e4 1567 See Documentation/ramdisk.txt.
a9913044 1568
1da177e4 1569 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1570 See Documentation/ramdisk.txt.
1571
24aaef8d
RD
1572 rcupdate.blimit= [KNL,BOOT]
1573 Set maximum number of finished RCU callbacks to process
1574 in one batch.
21a1ea9e 1575
24aaef8d
RD
1576 rcupdate.qhimark= [KNL,BOOT]
1577 Set threshold of queued
21a1ea9e
DS
1578 RCU callbacks over which batch limiting is disabled.
1579
24aaef8d
RD
1580 rcupdate.qlowmark= [KNL,BOOT]
1581 Set threshold of queued RCU callbacks below which
1582 batch limiting is re-enabled.
21a1ea9e 1583
ffdfc409
OJ
1584 rdinit= [KNL]
1585 Format: <full_path>
1586 Run specified binary instead of /init from the ramdisk,
1587 used for early userspace startup. See initrd.
1588
cd4f0ef7 1589 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1590 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1591 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1592
1593 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1594
cd4f0ef7 1595 reservetop= [X86-32]
461a9aff
ZA
1596 Format: nn[KMG]
1597 Reserves a hole at the top of the kernel virtual
1598 address space.
1599
7e96287d
VG
1600 reset_devices [KNL] Force drivers to reset the underlying device
1601 during initialization.
1602
a9913044
RD
1603 resume= [SWSUSP]
1604 Specify the partition device for software suspend
1da177e4 1605
ecbd0da1
RW
1606 resume_offset= [SWSUSP]
1607 Specify the offset from the beginning of the partition
1608 given by "resume=" at which the swap header is located,
1609 in <PAGE_SIZE> units (needed only for swap files).
1610 See Documentation/power/swsusp-and-swap-files.txt
1611
0a7b35cb
MN
1612 retain_initrd [RAM] Keep initrd memory after extraction
1613
1da177e4
LT
1614 rhash_entries= [KNL,NET]
1615 Set number of hash buckets for route cache
1616
1617 riscom8= [HW,SERIAL]
1618 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1619
1620 ro [KNL] Mount root device read-only on boot
1621
1622 root= [KNL] Root filesystem
1623
1624 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1625 mount the root filesystem
1626
1627 rootflags= [KNL] Set root filesystem mount option string
1628
1629 rootfstype= [KNL] Set root filesystem type
1630
cc1ed754
PO
1631 rootwait [KNL] Wait (indefinitely) for root device to show up.
1632 Useful for devices that are detected asynchronously
1633 (e.g. USB and MMC devices).
1634
20510f2f
JM
1635 root_plug.vendor_id=
1636 [ROOTPLUG] Override the default vendor ID
1637
1638 root_plug.product_id=
1639 [ROOTPLUG] Override the default product ID
1640
1641 root_plug.debug=
1642 [ROOTPLUG] Enable debugging output
1643
1da177e4
LT
1644 rw [KNL] Mount root device read-write on boot
1645
1646 S [KNL] Run init in single mode
1647
1648 sa1100ir [NET]
1649 See drivers/net/irda/sa1100_ir.c.
1650
1da177e4 1651 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1652
1da177e4
LT
1653 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1654 Format: <io>[,<timeout>[,<isapnp>]]
1655
1656 scsi_debug_*= [SCSI]
1657 See drivers/scsi/scsi_debug.c.
1658
1659 scsi_default_dev_flags=
1660 [SCSI] SCSI default device flags
1661 Format: <integer>
1662
1663 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1664 Format: <vendor>:<model>:<flags>
1665 (flags are integer value)
1666
6af6632a
RD
1667 scsi_logging_level= [SCSI] a bit mask of logging levels
1668 See drivers/scsi/scsi_logging.h for bits. Also
1669 settable via sysctl at dev.scsi.logging_level
1670 (/proc/sys/dev/scsi/logging_level).
1671 There is also a nice 'scsi_logging_level' script in the
1672 S390-tools package, available for download at
1673 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1674
3e082a91
MW
1675 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1676 discovered. async scans them in kernel threads,
1677 allowing boot to proceed. none ignores them, expecting
1678 user space to do the scan.
1679
1da177e4
LT
1680 selinux [SELINUX] Disable or enable SELinux at boot time.
1681 Format: { "0" | "1" }
1682 See security/selinux/Kconfig help text.
1683 0 -- disable.
1684 1 -- enable.
1685 Default value is set via kernel config option.
1686 If enabled at boot time, /selinux/disable can be used
1687 later to disable prior to initial policy load.
1688
4e5ab4cb
JM
1689 selinux_compat_net =
1690 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1691 Format: { "0" | "1" }
1692 0 -- use new secmark-based packet controls
1693 1 -- use legacy packet controls
1694 Default value is 0 (preferred).
1695 Value can be changed at runtime via
1696 /selinux/compat_net.
4e5ab4cb 1697
cd4f0ef7 1698 serialnumber [BUGS=X86-32]
1da177e4 1699
1da177e4
LT
1700 shapers= [NET]
1701 Maximal number of shapers.
a9913044 1702
1da177e4
LT
1703 sim710= [SCSI,HW]
1704 See header of drivers/scsi/sim710.c.
1705
1706 simeth= [IA-64]
1707 simscsi=
a9913044 1708
1da177e4
LT
1709 slram= [HW,MTD]
1710
f0630fff
CL
1711 slub_debug[=options[,slabs]] [MM, SLUB]
1712 Enabling slub_debug allows one to determine the
1713 culprit if slab objects become corrupted. Enabling
1714 slub_debug can create guard zones around objects and
1715 may poison objects when not in use. Also tracks the
1716 last alloc / free. For more information see
1717 Documentation/vm/slub.txt.
c1aee215
CL
1718
1719 slub_max_order= [MM, SLUB]
f0630fff
CL
1720 Determines the maximum allowed order for slabs.
1721 A high setting may cause OOMs due to memory
1722 fragmentation. For more information see
1723 Documentation/vm/slub.txt.
c1aee215
CL
1724
1725 slub_min_objects= [MM, SLUB]
f0630fff
CL
1726 The minimum number of objects per slab. SLUB will
1727 increase the slab order up to slub_max_order to
1728 generate a sufficiently large slab able to contain
1729 the number of objects indicated. The higher the number
1730 of objects the smaller the overhead of tracking slabs
1731 and the less frequently locks need to be acquired.
c1aee215
CL
1732 For more information see Documentation/vm/slub.txt.
1733
1734 slub_min_order= [MM, SLUB]
1735 Determines the mininum page order for slabs. Must be
f0630fff 1736 lower than slub_max_order.
c1aee215
CL
1737 For more information see Documentation/vm/slub.txt.
1738
1739 slub_nomerge [MM, SLUB]
f0630fff 1740 Disable merging of slabs with similar size. May be
c1aee215 1741 necessary if there is some reason to distinguish
f0630fff
CL
1742 allocs to different slabs. Debug options disable
1743 merging on their own.
c1aee215
CL
1744 For more information see Documentation/vm/slub.txt.
1745
1da177e4
LT
1746 smart2= [HW]
1747 Format: <io1>[,<io2>[,...,<io8>]]
1748
cd4f0ef7 1749 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1750 attempt to substitute SMP alternatives once at boot.
1751
d0d4f69b
BH
1752 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1753 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1754 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1755 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1756 smsc-ircc2.ircc_irq= [HW] IRQ line
1757 smsc-ircc2.ircc_dma= [HW] DMA channel
1758 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1759 0: Toshiba Satellite 1800 (GP data pin select)
1760 1: Fast pin select (default)
1761 2: ATC IRMode
1762
1da177e4
LT
1763 snd-ad1816a= [HW,ALSA]
1764
1765 snd-ad1848= [HW,ALSA]
1766
1767 snd-ali5451= [HW,ALSA]
1768
1769 snd-als100= [HW,ALSA]
1770
1771 snd-als4000= [HW,ALSA]
1772
1773 snd-azt2320= [HW,ALSA]
1774
1775 snd-cmi8330= [HW,ALSA]
1776
1777 snd-cmipci= [HW,ALSA]
1778
1779 snd-cs4231= [HW,ALSA]
1780
1781 snd-cs4232= [HW,ALSA]
1782
1783 snd-cs4236= [HW,ALSA]
1784
1785 snd-cs4281= [HW,ALSA]
1786
1787 snd-cs46xx= [HW,ALSA]
1788
1789 snd-dt019x= [HW,ALSA]
1790
1791 snd-dummy= [HW,ALSA]
1792
1793 snd-emu10k1= [HW,ALSA]
1794
1795 snd-ens1370= [HW,ALSA]
1796
1797 snd-ens1371= [HW,ALSA]
1798
1799 snd-es968= [HW,ALSA]
1800
1801 snd-es1688= [HW,ALSA]
1802
1803 snd-es18xx= [HW,ALSA]
1804
1805 snd-es1938= [HW,ALSA]
1806
1807 snd-es1968= [HW,ALSA]
1808
1809 snd-fm801= [HW,ALSA]
1810
1811 snd-gusclassic= [HW,ALSA]
1812
1813 snd-gusextreme= [HW,ALSA]
1814
1815 snd-gusmax= [HW,ALSA]
1816
1817 snd-hdsp= [HW,ALSA]
1818
1819 snd-ice1712= [HW,ALSA]
1820
1821 snd-intel8x0= [HW,ALSA]
1822
1823 snd-interwave= [HW,ALSA]
1824
1825 snd-interwave-stb=
1826 [HW,ALSA]
1827
1828 snd-korg1212= [HW,ALSA]
1829
1830 snd-maestro3= [HW,ALSA]
1831
1832 snd-mpu401= [HW,ALSA]
1833
1834 snd-mtpav= [HW,ALSA]
1835
1836 snd-nm256= [HW,ALSA]
1837
1838 snd-opl3sa2= [HW,ALSA]
1839
1840 snd-opti92x-ad1848=
1841 [HW,ALSA]
1842
1843 snd-opti92x-cs4231=
1844 [HW,ALSA]
1845
1846 snd-opti93x= [HW,ALSA]
1847
1848 snd-pmac= [HW,ALSA]
1849
1850 snd-rme32= [HW,ALSA]
1851
1852 snd-rme96= [HW,ALSA]
1853
1854 snd-rme9652= [HW,ALSA]
1855
1856 snd-sb8= [HW,ALSA]
1857
1858 snd-sb16= [HW,ALSA]
1859
1860 snd-sbawe= [HW,ALSA]
1861
1862 snd-serial= [HW,ALSA]
1863
1864 snd-sgalaxy= [HW,ALSA]
1865
1866 snd-sonicvibes= [HW,ALSA]
1867
1868 snd-sun-amd7930=
1869 [HW,ALSA]
1870
1871 snd-sun-cs4231= [HW,ALSA]
1872
1873 snd-trident= [HW,ALSA]
1874
1875 snd-usb-audio= [HW,ALSA,USB]
1876
1877 snd-via82xx= [HW,ALSA]
1878
1879 snd-virmidi= [HW,ALSA]
1880
1881 snd-wavefront= [HW,ALSA]
1882
1883 snd-ymfpci= [HW,ALSA]
a9913044 1884
1da177e4
LT
1885 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1886 See Documentation/sonypi.txt
1887
1888 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1889 See Documentation/specialix.txt.
1890
1891 spia_io_base= [HW,MTD]
1892 spia_fio_base=
1893 spia_pedr=
1894 spia_peddr=
1895
1896 sscape= [HW,OSS]
1897 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1898
1da177e4
LT
1899 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1900 See Documentation/scsi/st.txt.
1901
1da177e4
LT
1902 sti= [PARISC,HW]
1903 Format: <num>
1904 Set the STI (builtin display/keyboard on the HP-PARISC
1905 machines) console (graphic card) which should be used
1906 as the initial boot-console.
1907 See also comment in drivers/video/console/sticore.c.
1908
1909 sti_font= [HW]
1910 See comment in drivers/video/console/sticore.c.
1911
1912 stifb= [HW]
1913 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1914
42a7fc4a
GB
1915 sunrpc.pool_mode=
1916 [NFS]
1917 Control how the NFS server code allocates CPUs to
1918 service thread pools. Depending on how many NICs
1919 you have and where their interrupts are bound, this
1920 option will affect which CPUs will do NFS serving.
1921 Note: this parameter cannot be changed while the
1922 NFS server is running.
1923
1924 auto the server chooses an appropriate mode
1925 automatically using heuristics
1926 global a single global pool contains all CPUs
1927 percpu one pool for each CPU
1928 pernode one pool for each NUMA node (equivalent
1929 to global on non-NUMA machines)
1930
1da177e4 1931 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1932
1da177e4
LT
1933 switches= [HW,M68k]
1934
1935 sym53c416= [HW,SCSI]
1936 See header of drivers/scsi/sym53c416.c.
1937
5d6f647f
IM
1938 sysrq_always_enabled
1939 [KNL]
1940 Ignore sysrq setting - this boot parameter will
1941 neutralize any effect of /proc/sys/kernel/sysrq.
1942 Useful for debugging.
1943
1da177e4
LT
1944 t128= [HW,SCSI]
1945 See header of drivers/scsi/t128.c.
1946
1947 tdfx= [HW,DRM]
1948
1949 thash_entries= [KNL,NET]
1950 Set number of hash buckets for TCP connection
1951
f8707ec9
LB
1952 thermal.act= [HW,ACPI]
1953 -1: disable all active trip points in all thermal zones
1954 <degrees C>: override all lowest active trip points
1955
c52a7419
LB
1956 thermal.crt= [HW,ACPI]
1957 -1: disable all critical trip points in all thermal zones
1958 <degrees C>: lower all critical trip points
1959
f5487145
LB
1960 thermal.nocrt= [HW,ACPI]
1961 Set to disable actions on ACPI thermal zone
1962 critical and hot trip points.
1963
72b33ef8
LB
1964 thermal.off= [HW,ACPI]
1965 1: disable ACPI thermal control
1966
a70cdc52
LB
1967 thermal.psv= [HW,ACPI]
1968 -1: disable all passive trip points
1969 <degrees C>: override all passive trip points to this value
1970
730ff34d
LB
1971 thermal.tzp= [HW,ACPI]
1972 Specify global default ACPI thermal zone polling rate
1973 <deci-seconds>: poll all this frequency
1974 0: no polling (default)
1975
1da177e4 1976 time Show timing data prefixed to each printk message line
e84845c4 1977 [deprecated, see 'printk.time']
1da177e4
LT
1978
1979 tipar.timeout= [HW,PPT]
1980 Set communications timeout in tenths of a second
1981 (default 15).
1982
1983 tipar.delay= [HW,PPT]
1984 Set inter-bit delay in microseconds (default 10).
1985
1da177e4
LT
1986 tmscsim= [HW,SCSI]
1987 See comment before function dc390_setup() in
1988 drivers/scsi/tmscsim.c.
1989
1990 tp720= [HW,PS2]
1991
1992 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
1993 Format:
1994 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1995
a9913044
RD
1996 turbografx.map[2|3]= [HW,JOY]
1997 TurboGraFX parallel port interface
1998 Format:
1999 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2000 See also Documentation/input/joystick-parport.txt
2001
2002 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2003 See header of drivers/scsi/u14-34f.c.
2004
2005 uart401= [HW,OSS]
2006 Format: <io>,<irq>
2007
2008 uart6850= [HW,OSS]
2009 Format: <io>,<irq>
2010
5f8364b7
AS
2011 uhci-hcd.ignore_oc=
2012 [USB] Ignore overcurrent events (default N).
2013 Some badly-designed motherboards generate lots of
2014 bogus events, for ports that aren't wired to
2015 anything. Set this parameter to avoid log spamming.
2016 Note that genuine overcurrent events won't be
2017 reported either.
2018
b5e795f8
AS
2019 usbcore.autosuspend=
2020 [USB] The autosuspend time delay (in seconds) used
2021 for newly-detected USB devices (default 2). This
2022 is the time required before an idle device will be
2023 autosuspended. Devices for which the delay is set
eaafbc3a 2024 to a negative value won't be autosuspended at all.
b5e795f8 2025
1da177e4
LT
2026 usbhid.mousepoll=
2027 [USBHID] The interval which mice are to be polled at.
a9913044 2028
cd4f0ef7 2029 vdso= [X86-32,SH,x86-64]
1dbf527c 2030 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2031 vdso=1: enable VDSO (default)
2032 vdso=0: disable VDSO mapping
2033
af65d648
RM
2034 vdso32= [X86-32,X86-64]
2035 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2036 vdso32=1: enable 32-bit VDSO (default)
2037 vdso32=0: disable 32-bit VDSO mapping
2038
d080d397
YI
2039 vector= [IA-64,SMP]
2040 vector=percpu: enable percpu vector domain
2041
1da177e4
LT
2042 video= [FB] Frame buffer configuration
2043 See Documentation/fb/modedb.txt.
2044
cd4f0ef7 2045 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2046 See Documentation/i386/boot.txt and
2047 Documentation/svga.txt.
1da177e4
LT
2048 Use vga=ask for menu.
2049 This is actually a boot loader parameter; the value is
2050 passed to the kernel using a special protocol.
2051
a9913044 2052 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2053 size of <nn>. This can be used to increase the
2054 minimum size (128MB on x86). It can also be used to
2055 decrease the size and leave more room for directly
2056 mapped kernel RAM.
2057
585c3047
PO
2058 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2059 Format: <command>
1da177e4 2060
585c3047
PO
2061 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2062 Format: <command>
2063
2064 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2065 Format: <command>
a9913044 2066
1da177e4
LT
2067 waveartist= [HW,OSS]
2068 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2069
1da177e4
LT
2070 wd33c93= [HW,SCSI]
2071 See header of drivers/scsi/wd33c93.c.
2072
2073 wd7000= [HW,SCSI]
2074 See header of drivers/scsi/wd7000.c.
2075
2076 wdt= [WDT] Watchdog
8dfe9c21 2077 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2078
2079 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2080 xd_geo= See header of drivers/block/xd.c.
2081
2082 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2083 Format:
2084 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2085
a62eaf15
AK
2086 norandmaps Don't use address space randomization
2087 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2088
a9913044 2089______________________________________________________________________
1da177e4
LT
2090
2091TODO:
2092
2093 Add documentation for ALSA options.
2094 Add more DRM drivers.