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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
53471121 141 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 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_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
174
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175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
177
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178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
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182
183 acpi_serialize [HW,ACPI] force serialization of AML methods
184
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
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188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
191 HPET
1da177e4 192
f989106c 193 acpi.debug_layer= [HW,ACPI]
1da177e4 194 Format: <int>
a9913044 195 Each bit of the <int> indicates an ACPI debug layer,
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196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
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198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
209
210 acpi.debug_level= [HW,ACPI]
1da177e4 211 Format: <int>
a9913044 212 Each bit of the <int> indicates an ACPI debug level,
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213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
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215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
227
cd4f0ef7 228 acpi_pm_good [X86-32,X86-64]
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229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
232
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233 agp= [AGP]
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
238
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239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
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241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
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243 The kernel tries to set a reasonable default.
244
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
248
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249 ad1848= [HW,OSS]
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
251
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252 advansys= [HW,SCSI]
253 See header of drivers/scsi/advansys.c.
254
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
257
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
a9913044 261
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262 aha152x= [HW,SCSI]
263 See Documentation/scsi/aha152x.txt.
264
265 aha1542= [HW,SCSI]
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267
268 aic7xxx= [HW,SCSI]
269 See Documentation/scsi/aic7xxx.txt.
270
271 aic79xx= [HW,SCSI]
272 See Documentation/scsi/aic79xx.txt.
273
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274 amd_iommu= [HW,X86-84]
275 Pass parameters to the AMD IOMMU driver in the system.
276 Possible values are:
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277 isolate - enable device isolation (each device, as far
278 as possible, will get its own protection
279 domain)
280 amd_iommu_size= [HW,X86-64]
281 Define the size of the aperture for the AMD IOMMU
282 driver. Possible values are:
283 '32M', '64M' (default), '128M', '256M', '512M', '1G'
284
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285 amijoy.map= [HW,JOY] Amiga joystick support
286 Map of devices attached to JOY0DAT and JOY1DAT
287 Format: <a>,<b>
288 See also Documentation/kernel/input/joystick.txt
289
290 analog.map= [HW,JOY] Analog joystick and gamepad support
291 Specifies type or capabilities of an analog joystick
292 connected to one of 16 gameports
293 Format: <type1>,<type2>,..<type16>
294
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295 apc= [HW,SPARC]
296 Power management functions (SPARCstation-4/5 + deriv.)
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297 Format: noidle
298 Disable APC CPU standby support. SPARCstation-Fox does
299 not play well with APC CPU idle - disable it if you have
300 APC and your system crashes randomly.
301
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302 apic= [APIC,i386] Advanced Programmable Interrupt Controller
303 Change the output verbosity whilst booting
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304 Format: { quiet (default) | verbose | debug }
305 Change the amount of debugging information output
306 when initialising the APIC and IO-APIC components.
a9913044 307
1da177e4 308 apm= [APM] Advanced Power Management
71f77055 309 See header of arch/x86/kernel/apm_32.c.
1da177e4 310
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311 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
312 Format: <io>,<irq>,<nodeID>
313
314 ataflop= [HW,M68k]
315
316 atarimouse= [HW,MOUSE] Atari Mouse
317
318 atascsi= [HW,SCSI] Atari SCSI
319
320 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
321 EzKey and similar keyboards
322
323 atkbd.reset= [HW] Reset keyboard during initialization
324
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325 atkbd.set= [HW] Select keyboard code set
326 Format: <int> (2 = AT (default), 3 = PS/2)
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327
328 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
329 keyboards
330
331 atkbd.softraw= [HW] Choose between synthetic and real raw mode
332 Format: <bool> (0 = real, 1 = synthetic (default))
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333
334 atkbd.softrepeat= [HW]
335 Use software keyboard repeat
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336
337 autotest [IA64]
338
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339 baycom_epp= [HW,AX25]
340 Format: <io>,<mode>
a9913044 341
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342 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
343 Format: <io>,<mode>
344 See header of drivers/net/hamradio/baycom_par.c.
345
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346 baycom_ser_fdx= [HW,AX25]
347 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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348 Format: <io>,<irq>,<mode>[,<baud>]
349 See header of drivers/net/hamradio/baycom_ser_fdx.c.
350
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351 baycom_ser_hdx= [HW,AX25]
352 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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353 Format: <io>,<irq>,<mode>
354 See header of drivers/net/hamradio/baycom_ser_hdx.c.
355
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356 boot_delay= Milliseconds to delay each printk during boot.
357 Values larger than 10 seconds (10000) are changed to
358 no delay (0).
359 Format: integer
360
1da177e4 361 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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362 bttv.radio= Most important insmod options are available as
363 kernel args too.
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364 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
365 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
366
367 BusLogic= [HW,SCSI]
368 See drivers/scsi/BusLogic.c, comment before function
369 BusLogic_ParseDriverOptions().
370
371 c101= [NET] Moxa C101 synchronous serial card
372
cd4f0ef7 373 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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374 Sometimes CPU hardware bugs make them report the cache
375 size incorrectly. The kernel will attempt work arounds
376 to fix known problems, but for some CPUs it is not
377 possible to determine what the correct size should be.
378 This option provides an override for these situations.
379
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380 security= [SECURITY] Choose a security module to enable at boot.
381 If this boot parameter is not specified, only the first
382 security module asking for security registration will be
383 loaded. An invalid security module name will be treated
384 as if no module has been chosen.
385
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386 capability.disable=
387 [SECURITY] Disable capabilities. This would normally
388 be used only if an alternative security model is to be
389 configured. Potentially dangerous and should only be
390 used if you are entirely sure of the consequences.
391
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392 ccw_timeout_log [S390]
393 See Documentation/s390/CommonIO for details.
1da177e4 394
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395 cgroup_disable= [KNL] Disable a particular controller
396 Format: {name of the controller(s) to disable}
397 {Currently supported controllers - "memory"}
398
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399 checkreqprot [SELINUX] Set initial checkreqprot flag value.
400 Format: { "0" | "1" }
401 See security/selinux/Kconfig help text.
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402 0 -- check protection applied by kernel (includes
403 any implied execute protection).
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404 1 -- check protection requested by application.
405 Default value is set via a kernel config option.
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406 Value can be changed at runtime via
407 /selinux/checkreqprot.
408
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409 cio_ignore= [S390]
410 See Documentation/s390/CommonIO for details.
411
cd4f0ef7 412 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 413 [Deprecated]
3f6dee9b 414 Forces specified clocksource (if available) to be used
734efb46 415 when calculating gettimeofday(). If specified
3f6dee9b 416 clocksource is not available, it defaults to PIT.
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417 Format: { pit | tsc | cyclone | pmtmr }
418
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419 clocksource= [GENERIC_TIME] Override the default clocksource
420 Format: <string>
421 Override the default clocksource and use the clocksource
422 with the name specified.
423 Some clocksource names to choose from, depending on
424 the platform:
425 [all] jiffies (this is the base, fallback clocksource)
426 [ACPI] acpi_pm
427 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
428 pxa_timer,timer3,32k_counter,timer0_1
429 [AVR32] avr32
cd4f0ef7 430 [X86-32] pit,hpet,tsc,vmi-timer;
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431 scx200_hrt on Geode; cyclone on IBM x440
432 [MIPS] MIPS
433 [PARISC] cr16
434 [S390] tod
435 [SH] SuperH
436 [SPARC64] tick
437 [X86-64] hpet,tsc
438
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439 clearcpuid=BITNUM [X86]
440 Disable CPUID feature X for the kernel. See
441 include/asm-x86/cpufeature.h for the valid bit numbers.
442 Note the Linux specific bits are not necessarily
443 stable over kernel options, but the vendor specific
444 ones should be.
445 Also note that user programs calling CPUID directly
446 or using the feature without checking anything
447 will still see it. This just prevents it from
448 being used by the kernel or shown in /proc/cpuinfo.
449 Also note the kernel might malfunction if you disable
450 some critical bits.
451
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452 code_bytes [IA32/X86_64] How many bytes of object code to print
453 in an oops report.
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454 Range: 0 - 8192
455 Default: 64
456
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457 disable_8254_timer
458 enable_8254_timer
459 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
460 over the 8254 in addition to over the IO-APIC. The
461 kernel tries to set a sensible default.
462
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463 hpet= [X86-32,HPET] option to control HPET usage
464 Format: { enable (default) | disable | force }
465 disable: disable HPET and use PIT instead
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466 force: allow force enabled of undocumented chips (ICH4,
467 VIA, nVidia)
1da177e4 468
1da177e4 469 com20020= [HW,NET] ARCnet - COM20020 chipset
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470 Format:
471 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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472
473 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
474 Format: <io>[,<irq>]
475
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476 com90xx= [HW,NET]
477 ARCnet - COM90xx chipset (memory-mapped buffers)
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478 Format: <io>[,<irq>[,<memstart>]]
479
480 condev= [HW,S390] console device
481 conmode=
a9913044 482
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483 console= [KNL] Output console device and options.
484
485 tty<n> Use the virtual console device <n>.
486
487 ttyS<n>[,options]
f1a1c2dc 488 ttyUSB0[,options]
1da177e4 489 Use the specified serial port. The options are of
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490 the form "bbbbpnf", where "bbbb" is the baud rate,
491 "p" is parity ("n", "o", or "e"), "n" is number of
492 bits, and "f" is flow control ("r" for RTS or
493 omit it). Default is "9600n8".
494
495 See Documentation/serial-console.txt for more
496 information. See
497 Documentation/networking/netconsole.txt for an
498 alternative.
1da177e4 499
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500 uart[8250],io,<addr>[,options]
501 uart[8250],mmio,<addr>[,options]
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502 Start an early, polled-mode console on the 8250/16550
503 UART at the specified I/O port or MMIO address,
504 switching to the matching ttyS device later. The
505 options are the same as for ttyS, above.
506
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507 If the device connected to the port is not a TTY but a braille
508 device, prepend "brl," before the device type, for instance
509 console=brl,ttyS0
510 For now, only VisioBraille is supported.
511
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512 earlycon= [KNL] Output early console device and options.
513 uart[8250],io,<addr>[,options]
514 uart[8250],mmio,<addr>[,options]
515 Start an early, polled-mode console on the 8250/16550
516 UART at the specified I/O port or MMIO address.
517 The options are the same as for ttyS, above.
518
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519 no_console_suspend
520 [HW] Never suspend the console
521 Disable suspending of consoles during suspend and
522 hibernate operations. Once disabled, debugging
523 messages can reach various consoles while the rest
524 of the system is being put to sleep (ie, while
525 debugging driver suspend/resume hooks). This may
526 not work reliably with all consoles, but is known
527 to work with serial and VGA consoles.
528
1da177e4 529 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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530 Format:
531 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 532
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EB
533 crashkernel=nn[KMG]@ss[KMG]
534 [KNL] Reserve a chunk of physical memory to
535 hold a kernel to switch to with kexec on panic.
536
fb391599
BW
537 crashkernel=range1:size1[,range2:size2,...][@offset]
538 [KNL] Same as above, but depends on the memory
539 in the running system. The syntax of range is
540 start-[end] where start and end are both
541 a memory unit (amount[KMG]). See also
542 Documentation/kdump/kdump.txt for a example.
543
1da177e4
LT
544 cs4232= [HW,OSS]
545 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
546
547 cs89x0_dma= [HW,NET]
548 Format: <dma>
549
550 cs89x0_media= [HW,NET]
551 Format: { rj45 | aui | bnc }
a9913044 552
a9913044 553 dasd= [HW,NET]
1da177e4
LT
554 See header of drivers/s390/block/dasd_devmap.c.
555
556 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
557 (one device per port)
558 Format: <port#>,<type>
559 See also Documentation/input/joystick-parport.txt
560
561 debug [KNL] Enable kernel debugging (events log level).
562
cae2ed9a
IM
563 debug_locks_verbose=
564 [KNL] verbose self-tests
565 Format=<0|1>
566 Print debugging info while doing the locking API
567 self-tests.
568 We default to 0 (no extra messages), setting it to
569 1 will print _a lot_ more information - normally
570 only useful to kernel developers.
571
3ac7fe5a
TG
572 debug_objects [KNL] Enable object debugging
573
2d27a966 574 decnet.addr= [HW,NET]
1da177e4
LT
575 Format: <area>[,<node>]
576 See also Documentation/networking/decnet.txt.
577
ecb77fa9 578 vt.default_blu= [VT]
55ff9780
AD
579 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
580 Change the default blue palette of the console.
581 This is a 16-member array composed of values
582 ranging from 0-255.
583
ecb77fa9 584 vt.default_grn= [VT]
55ff9780
AD
585 Format: <green0>,<green1>,<green2>,...,<green15>
586 Change the default green palette of the console.
587 This is a 16-member array composed of values
588 ranging from 0-255.
589
ecb77fa9 590 vt.default_red= [VT]
55ff9780
AD
591 Format: <red0>,<red1>,<red2>,...,<red15>
592 Change the default red palette of the console.
593 This is a 16-member array composed of values
594 ranging from 0-255.
595
ecb77fa9
ST
596 vt.default_utf8=
597 [VT]
55ff9780
AD
598 Format=<0|1>
599 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
600 Default is 1, i.e. UTF-8 mode is enabled for all
601 newly opened terminals.
55ff9780 602
1da177e4
LT
603 dhash_entries= [KNL]
604 Set number of hash buckets for dentry cache.
a9913044 605
1da177e4
LT
606 digi= [HW,SERIAL]
607 IO parameters + enable/disable command.
608
609 digiepca= [HW,SERIAL]
610 See drivers/char/README.epca and
611 Documentation/digiepca.txt.
612
95ffa243
YL
613 disable_mtrr_cleanup [X86]
614 enable_mtrr_cleanup [X86]
615 The kernel tries to adjust MTRR layout from continuous
616 to discrete, to make X server driver able to add WB
617 entry later. This parameter enables/disables that.
618
619 mtrr_chunk_size=nn[KMG] [X86]
620 used for mtrr cleanup. It is largest continous chunk
621 that could hold holes aka. UC entries.
622
623 mtrr_gran_size=nn[KMG] [X86]
12031a62
YL
624 Used for mtrr cleanup. It is granularity of mtrr block.
625 Default is 1.
626 Large value could prevent small alignment from
627 using up MTRRs.
628
629 mtrr_spare_reg_nr=n [X86]
630 Format: <integer>
631 Range: 0,7 : spare reg number
632 Default : 1
633 Used for mtrr cleanup. It is spare mtrr entries number.
634 Set to 2 or more if your graphical card needs more.
95ffa243 635
093af8d7 636 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
637 By default the kernel will trim any uncacheable
638 memory out of your available memory pool based on
639 MTRR settings. This parameter disables that behavior,
640 possibly causing your machine to run very slowly.
641
1da177e4
LT
642 dmasound= [HW,OSS] Sound subsystem buffers
643
644 dscc4.setup= [NET]
645
646 dtc3181e= [HW,SCSI]
647
0ae53640 648 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
649 earlyprintk=vga
650 earlyprintk=serial[,ttySn[,baudrate]]
651
a9913044 652 Append ",keep" to not disable it when the real console
1da177e4
LT
653 takes over.
654
655 Only vga or serial at a time, not both.
656
657 Currently only ttyS0 and ttyS1 are supported.
658
659 Interaction with the standard serial driver is not
660 very good.
661
662 The VGA output is eventually overwritten by the real
663 console.
664
665 eata= [HW,SCSI]
666
1da177e4 667 edd= [EDD]
8c4dd606 668 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 669
1da177e4
LT
670 eisa_irq_edge= [PARISC,HW]
671 See header of drivers/parisc/eisa.c.
672
cd4f0ef7 673 elanfreq= [X86-32]
1da177e4 674 See comment before function elanfreq_setup() in
71f77055 675 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
676
677 elevator= [IOSCHED]
16ab3adf 678 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
679 See Documentation/block/as-iosched.txt and
680 Documentation/block/deadline-iosched.txt for details.
681
cd4f0ef7 682 elfcorehdr= [X86-32, X86_64]
a9913044 683 Specifies physical address of start of kernel core
aac04b32
VG
684 image elf header. Generally kexec loader will
685 pass this option to capture kernel.
686 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
687
688 enforcing [SELINUX] Set initial enforcing status.
689 Format: {"0" | "1"}
690 See security/selinux/Kconfig help text.
691 0 -- permissive (log only, no denials).
692 1 -- enforcing (deny and log).
693 Default value is 0.
694 Value can be changed at runtime via /selinux/enforce.
695
1da177e4
LT
696 es1371= [HW,OSS]
697 Format: <spdif>,[<nomix>,[<amplifier>]]
698 See also header of sound/oss/es1371.c.
a9913044 699
1da177e4
LT
700 ether= [HW,NET] Ethernet cards parameters
701 This option is obsoleted by the "netdev=" option, which
702 has equivalent usage. See its documentation for details.
703
704 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
705 Format: <io>[,<irq>]
706
de1ba09b
AM
707 failslab=
708 fail_page_alloc=
709 fail_make_request=[KNL]
710 General fault injection mechanism.
711 Format: <interval>,<probability>,<space>,<times>
712 See also /Documentation/fault-injection/.
713
1da177e4
LT
714 fd_mcs= [HW,SCSI]
715 See header of drivers/scsi/fd_mcs.c.
716
717 fdomain= [HW,SCSI]
718 See header of drivers/scsi/fdomain.c.
719
720 floppy= [HW]
721 See Documentation/floppy.txt.
722
f13ae30e
AC
723 force_pal_cache_flush
724 [IA-64] Avoid check_sal_cache_flush which may hang on
725 buggy SAL_CACHE_FLUSH implementations. Using this
726 parameter will force ia64_sal_cache_flush to call
727 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
728
1da177e4
LT
729 gamecon.map[2|3]=
730 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
731 support via parallel port (up to 5 devices per port)
732 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
733 See also Documentation/input/joystick-parport.txt
734
735 gamma= [HW,DRM]
736
aaf23042
YL
737 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
738 Format: off | on
739 default: on
740
1da177e4
LT
741 gdth= [HW,SCSI]
742 See header of drivers/scsi/gdth.c.
743
744 gpt [EFI] Forces disk with valid GPT signature but
745 invalid Protective MBR to be treated as GPT.
746
1da177e4
LT
747 gvp11= [HW,SCSI]
748
749 hashdist= [KNL,NUMA] Large hashes allocated during boot
750 are distributed across NUMA nodes. Defaults on
751 for IA-64, off otherwise.
a9913044 752 Format: 0 | 1 (for off | on)
1da177e4
LT
753
754 hcl= [IA-64] SGI's Hardware Graph compatibility layer
755
756 hd= [EIDE] (E)IDE hard drive subsystem geometry
757 Format: <cyl>,<head>,<sect>
758
759 hd?= [HW] (E)IDE subsystem
1c10e938 760 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
761
762 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
763 size of <nn>. This works even on boxes that have no
764 highmem otherwise. This also works to reduce highmem
765 size on bigger boxes.
766
54cdfdb4
TG
767 highres= [KNL] Enable/disable high resolution timer mode.
768 Valid parameters: "on", "off"
769 Default: "on"
770
1da177e4
LT
771 hisax= [HW,ISDN]
772 See Documentation/isdn/README.HiSax.
773
cd4f0ef7 774 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 775 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 776
1da177e4 777 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
778 i8042.dumbkbd [HW] Pretend that controller can only read data from
779 keyboard and cannot control its state
1da177e4
LT
780 (Don't attempt to blink the leds)
781 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 782 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
783 i8042.noloop [HW] Disable the AUX Loopback command while probing
784 for the AUX port
1da177e4
LT
785 i8042.nomux [HW] Don't check presence of an active multiplexing
786 controller
787 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
788 controllers
789 i8042.panicblink=
790 [HW] Frequency with which keyboard LEDs should blink
791 when kernel panics (default is 0.5 sec)
792 i8042.reset [HW] Reset the controller during init and cleanup
793 i8042.unlock [HW] Unlock (ignore) the keylock
794
795 i810= [HW,DRM]
796
e70c9d5e
DT
797 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
798 indicates that the driver is running on unsupported
799 hardware.
1da177e4
LT
800 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
801 does not match list of supported models.
802 i8k.power_status
803 [HW] Report power status in /proc/i8k
804 (disabled by default)
805 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
806 capability is set.
807
808 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
809 See Documentation/mca.txt.
810
811 icn= [HW,ISDN]
812 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
813
814 ide= [HW] (E)IDE subsystem
a594eeb1 815 Format: ide=nodma or ide=doubler
1c10e938 816 See Documentation/ide/ide.txt.
1da177e4 817
1da177e4 818 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 819 See Documentation/ide/ide.txt.
1da177e4 820
f039b754
AK
821 idle= [X86]
822 Format: idle=poll or idle=mwait
823 Poll forces a polling idle loop that can slightly improves the performance
824 of waking up a idle CPU, but will use a lot of power and make the system
825 run hot. Not recommended.
826 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
827 to not use it because it doesn't save as much power as a normal idle
828 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
829 as idle=poll.
a9913044 830
594765a7
DC
831 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
832 Claim all unknown PCI IDE storage controllers.
833
79290822
IM
834 ignore_loglevel [KNL]
835 Ignore loglevel setting - this will print /all/
836 kernel messages to the console. Useful for debugging.
837
1da177e4
LT
838 ihash_entries= [KNL]
839 Set number of hash buckets for inode cache.
840
841 in2000= [HW,SCSI]
842 See header of drivers/scsi/in2000.c.
843
844 init= [KNL]
845 Format: <full_path>
846 Run specified binary instead of /sbin/init as init
847 process.
848
849 initcall_debug [KNL] Trace initcalls as they are executed. Useful
850 for working out where the kernel is dying during
851 startup.
852
853 initrd= [BOOT] Specify the location of the initial ramdisk
854
855 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
856 Format: <irq>
857
858 inttest= [IA64]
859
b552da87
PM
860 iommu= [x86]
861 off
862 force
863 noforce
864 biomerge
865 panic
866 nopanic
867 merge
868 nomerge
869 forcesac
870 soft
871
872
ba395927
KA
873 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
874 off
875 Disable intel iommu driver.
876 igfx_off [Default Off]
877 By default, gfx is mapped as normal device. If a gfx
878 device has a dedicated DMAR unit, the DMAR unit is
879 bypassed by not enabling DMAR with this option. In
880 this case, gfx device will use physical address for
881 DMA.
7d3b03ce
KA
882 forcedac [x86_64]
883 With this option iommu will not optimize to look
884 for io virtual address below 32 bit forcing dual
885 address cycle on pci bus for cards supporting greater
886 than 32 bit addressing. The default is to look
887 for translation below 32 bit and if not available
888 then look in the higher range.
5e0d2a6f 889 strict [Default Off]
890 With this option on every unmap_single operation will
891 result in a hardware IOTLB flush operation as opposed
892 to batching them for performance.
ba395927 893
b02aae9c 894 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
895 0x80
896 Standard port 0x80 based delay
897 0xed
898 Alternate port 0xed based delay (needed on some systems)
b02aae9c 899 udelay
6e7c4025
IM
900 Simple two microseconds delay
901 none
902 No delay
b02aae9c 903
1da177e4
LT
904 io7= [HW] IO7 for Marvel based alpha systems
905 See comment before marvel_specify_io7 in
906 arch/alpha/kernel/core_marvel.c.
907
908 ip= [IP_PNP]
6ded55da 909 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
910
911 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
912 See comment before ip2_setup() in
913 drivers/char/ip2/ip2base.c.
1da177e4
LT
914
915 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
916 See header of drivers/scsi/ips.c.
917
72c4a13a
SH
918 ports= [IP_VS_FTP] IPVS ftp helper module
919 Default is 21.
920 Up to 8 (IP_VS_APP_MAX_PORTS) ports
921 may be specified.
922 Format: <port>,<port>....
923
200803df
AC
924 irqfixup [HW]
925 When an interrupt is not handled search all handlers
926 for it. Intended to get systems with badly broken
927 firmware running.
928
929 irqpoll [HW]
930 When an interrupt is not handled search all handlers
931 for it. Also check all handlers each timer
932 interrupt. Intended to get systems with badly broken
933 firmware running.
934
1da177e4 935 isapnp= [ISAPNP]
a9913044 936 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
937
938 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
939 Format:
940 <cpu number>,...,<cpu number>
941 or
942 <cpu number>-<cpu number> (must be a positive range in ascending order)
943 or a mixture
944 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
945 This option can be used to specify one or more CPUs
946 to isolate from the general SMP balancing and scheduling
947 algorithms. The only way to move a process onto or off
948 an "isolated" CPU is via the CPU affinity syscalls.
949 <cpu number> begins at 0 and the maximum value is
950 "number of CPUs in system - 1".
951
952 This option is the preferred way to isolate CPUs. The
a9913044
RD
953 alternative -- manually setting the CPU mask of all
954 tasks in the system -- can cause problems and
955 suboptimal load balancer performance.
1da177e4 956
a9913044 957 iucv= [HW,NET]
1da177e4
LT
958
959 js= [HW,JOY] Analog joystick
960 See Documentation/input/joystick.txt.
961
cd4f0ef7 962 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
963 specifies the amount of memory usable by the kernel
964 for non-movable allocations. The requested amount is
965 spread evenly throughout all nodes in the system. The
966 remaining memory in each node is used for Movable
967 pages. In the event, a node is too small to have both
968 kernelcore and Movable pages, kernelcore pages will
969 take priority and other nodes will have a larger number
970 of kernelcore pages. The Movable zone is used for the
971 allocation of pages that may be reclaimed or moved
972 by the page migration subsystem. This means that
973 HugeTLB pages may not be allocated from this zone.
974 Note that allocations like PTEs-from-HighMem still
975 use the HighMem zone if it exists, and the Normal
976 zone if it does not.
977
cd4f0ef7 978 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
979 is similar to kernelcore except it specifies the
980 amount of memory used for migratable allocations.
981 If both kernelcore and movablecore is specified,
982 then kernelcore will be at *least* the specified
983 value but may be more. If movablecore on its own
984 is specified, the administrator must be careful
985 that the amount of memory usable for all allocations
986 is not too small.
987
1da177e4
LT
988 keepinitrd [HW,ARM]
989
cd4f0ef7 990 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
991 in oops dumps.
992
6cdf6e06
JW
993 kgdboc= [HW] kgdb over consoles.
994 Requires a tty driver that supports console polling.
995 (only serial suported for now)
996 Format: <serial_device>[,baud]
997
1da177e4
LT
998 l2cr= [PPC]
999
a78bfbfc
RB
1000 l3cr= [PPC]
1001
cd4f0ef7 1002 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1003 disabled it.
1da177e4 1004
cd4f0ef7 1005 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
1006 C2 power state.
1007
fcb71f6f
FC
1008 libata.dma= [LIBATA] DMA control
1009 libata.dma=0 Disable all PATA and SATA DMA
1010 libata.dma=1 PATA and SATA Disk DMA only
1011 libata.dma=2 ATAPI (CDROM) DMA only
1012 libata.dma=4 Compact Flash DMA only
1013 Combinations also work, so libata.dma=3 enables DMA
1014 for disks and CDROMs, but not CFs.
1015
78e70c23
DJ
1016 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1017 when set.
1018 Format: <int>
1019
33267325
TH
1020 libata.force= [LIBATA] Force configurations. The format is comma
1021 separated list of "[ID:]VAL" where ID is
1022 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1023 matching port, link or device. Basically, it matches
1024 the ATA ID string printed on console by libata. If
1025 the whole ID part is omitted, the last PORT and DEVICE
1026 values are used. If ID hasn't been specified yet, the
1027 configuration applies to all ports, links and devices.
1028
1029 If only DEVICE is omitted, the parameter applies to
1030 the port and all links and devices behind it. DEVICE
1031 number of 0 either selects the first device or the
1032 first fan-out link behind PMP device. It does not
1033 select the host link. DEVICE number of 15 selects the
1034 host link and device attached to it.
1035
1036 The VAL specifies the configuration to force. As long
1037 as there's no ambiguity shortcut notation is allowed.
1038 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1039 The following configurations can be forced.
1040
1041 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1042 Any ID with matching PORT is used.
1043
1044 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1045
1046 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1047 udma[/][16,25,33,44,66,100,133] notation is also
1048 allowed.
1049
1050 * [no]ncq: Turn on or off NCQ.
1051
1052 If there are multiple matching configurations changing
1053 the same attribute, the last one is used.
1054
1da177e4
LT
1055 load_ramdisk= [RAM] List of ramdisks to load from floppy
1056 See Documentation/ramdisk.txt.
1057
a6b25b67
RD
1058 lockd.nlm_grace_period=P [NFS] Assign grace period.
1059 Format: <integer>
1da177e4 1060
a6b25b67
RD
1061 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1062 Format: <integer>
1063
1064 lockd.nlm_timeout=T [NFS] Assign timeout value.
1065 Format: <integer>
1066
1067 lockd.nlm_udpport=M [NFS] Assign UDP port.
1068 Format: <integer>
1da177e4
LT
1069
1070 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1071 Format: <irq>
1072
1073 loglevel= All Kernel Messages with a loglevel smaller than the
1074 console loglevel will be printed to the console. It can
1075 also be changed with klogd or other programs. The
1076 loglevels are defined as follows:
1077
1078 0 (KERN_EMERG) system is unusable
1079 1 (KERN_ALERT) action must be taken immediately
1080 2 (KERN_CRIT) critical conditions
1081 3 (KERN_ERR) error conditions
1082 4 (KERN_WARNING) warning conditions
1083 5 (KERN_NOTICE) normal but significant condition
1084 6 (KERN_INFO) informational
1085 7 (KERN_DEBUG) debug-level messages
1086
1087 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1088 Format: { n | nk | nM }
1089 n must be a power of two. The default size
1090 is set in the kernel config file.
1da177e4 1091
accaa24c
RD
1092 logo.nologo [FB] Disables display of the built-in Linux logo.
1093 This may be used to provide more screen space for
1094 kernel log messages and is useful when debugging
1095 kernel boot problems.
1096
1da177e4
LT
1097 lp=0 [LP] Specify parallel ports to use, e.g,
1098 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1099 lp=reset first parallel port). 'lp=0' disables the
1100 lp=auto printer driver. 'lp=reset' (which can be
1101 specified in addition to the ports) causes
1102 attached printers to be reset. Using
1103 lp=port1,port2,... specifies the parallel ports
1104 to associate lp devices with, starting with
1105 lp0. A port specification may be 'none' to skip
1106 that lp device, or a parport name such as
1107 'parport0'. Specifying 'lp=auto' instead of a
1108 port specification list means that device IDs
1109 from each port should be examined, to see if
1110 an IEEE 1284-compliant printer is attached; if
1111 so, the driver will manage that printer.
1112 See also header of drivers/char/lp.c.
1113
1114 lpj=n [KNL]
1115 Sets loops_per_jiffy to given constant, thus avoiding
1116 time-consuming boot-time autodetection (up to 250 ms per
1117 CPU). 0 enables autodetection (default). To determine
1118 the correct value for your kernel, boot with normal
1119 autodetection and see what value is printed. Note that
1120 on SMP systems the preset will be applied to all CPUs,
1121 which is likely to cause problems if your CPUs need
1122 significantly divergent settings. An incorrect value
1123 will cause delays in the kernel to be wrong, leading to
1124 unpredictable I/O errors and other breakage. Although
1125 unlikely, in the extreme case this might damage your
1126 hardware.
1127
1128 ltpc= [NET]
1129 Format: <io>,<irq>,<dma>
1130
a9913044
RD
1131 mac5380= [HW,SCSI] Format:
1132 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1133
a9913044
RD
1134 machvec= [IA64] Force the use of a particular machine-vector
1135 (machvec) in a generic kernel.
1136 Example: machvec=hpzx1_swiotlb
1da177e4 1137
a9913044 1138 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1139 be mounted
1140 Format: <1-256>
1141
1142 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1143 should make use of. maxcpus=n : n >= 0 limits the
1144 kernel to using 'n' processors. n=0 is a special case,
1145 it is equivalent to "nosmp", which also disables
1146 the IO APIC.
1da177e4 1147
2b2c3750
BP
1148 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1149 equal to this physical address is ignored.
1150
a9913044 1151 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1152 Should be between 1 and 2^32-1.
1153
1154 max_report_luns=
a9913044 1155 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1156 Should be between 1 and 16384.
1157
1da177e4
LT
1158 mcatest= [IA-64]
1159
cd4f0ef7 1160 mce [X86-32] Machine Check Exception
1da177e4 1161
909dd324
AK
1162 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1163
1da177e4
LT
1164 md= [HW] RAID subsystems devices and level
1165 See Documentation/md.txt.
a9913044 1166
1da177e4
LT
1167 mdacon= [MDA]
1168 Format: <first>,<last>
1169 Specifies range of consoles to be captured by the MDA.
a9913044 1170
1da177e4
LT
1171 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1172 Amount of memory to be used when the kernel is not able
1173 to see the whole system memory or for test.
cd4f0ef7 1174 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1175 address space collisions. Without memmap= PCI devices
1176 could be placed at addresses belonging to unused RAM.
1177
cd4f0ef7 1178 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1179 memory.
1180
cd4f0ef7 1181 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1182 E820 memory map, as specified by the user.
1183 Such memmap=exactmap lines can be constructed based on
1184 BIOS output or other requirements. See the memmap=nn@ss
1185 option description.
1186
1187 memmap=nn[KMG]@ss[KMG]
1188 [KNL] Force usage of a specific region of memory
1189 Region of memory to be used, from ss to ss+nn.
1190
1191 memmap=nn[KMG]#ss[KMG]
1192 [KNL,ACPI] Mark specific memory as ACPI data.
1193 Region of memory to be used, from ss to ss+nn.
1194
1195 memmap=nn[KMG]$ss[KMG]
1196 [KNL,ACPI] Mark specific memory as reserved.
1197 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1198 Example: Exclude memory from 0x18690000-0x1869ffff
1199 memmap=64K$0x18690000
1200 or
1201 memmap=0x10000$0x18690000
1da177e4 1202
c64df707
YL
1203 memtest= [KNL,X86_64] Enable memtest
1204 Format: <integer>
1205 range: 0,4 : pattern number
1206 default : 0 <disable>
1207
1da177e4
LT
1208 meye.*= [HW] Set MotionEye Camera parameters
1209 See Documentation/video4linux/meye.txt.
1210
8f36881b
AS
1211 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1212 Multi-Function General Purpose Timers on AMD Geode
1213 platforms.
1214
e6c4dc6c
WT
1215 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1216 the BIOS has incorrectly applied a workaround. TinyBIOS
1217 version 0.98 is known to be affected, 0.99 fixes the
1218 problem by letting the user disable the workaround.
1219
1da177e4
LT
1220 mga= [HW,DRM]
1221
1222 mousedev.tap_time=
1223 [MOUSE] Maximum time between finger touching and
1224 leaving touchpad surface for touch to be considered
1225 a tap and be reported as a left button click (for
1226 touchpads working in absolute mode only).
1227 Format: <msecs>
1228 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1229 reporting absolute coordinates, such as tablets
1230 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1231 reporting absolute coordinates, such as tablets
1232
1233 mpu401= [HW,OSS]
1234 Format: <io>,<irq>
1235
1236 MTD_Partition= [MTD]
1237 Format: <name>,<region-number>,<size>,<offset>
1238
a9913044
RD
1239 MTD_Region= [MTD] Format:
1240 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1241
1242 mtdparts= [MTD]
c8facbb6 1243 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1244
1245 mtouchusb.raw_coordinates=
a9913044
RD
1246 [HW] Make the MicroTouch USB driver use raw coordinates
1247 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1248
1249 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1250
1251 NCR_D700= [HW,SCSI]
1252 See header of drivers/scsi/NCR_D700.c.
1253
1254 ncr5380= [HW,SCSI]
1255
1256 ncr53c400= [HW,SCSI]
1257
1258 ncr53c400a= [HW,SCSI]
1259
1260 ncr53c406a= [HW,SCSI]
1261
1262 ncr53c8xx= [HW,SCSI]
1263
1264 netdev= [NET] Network devices parameters
1265 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1266 Note that mem_start is often overloaded to mean
1267 something different and driver-specific.
a9913044
RD
1268 This usage is only documented in each driver source
1269 file if at all.
1270
1da177e4 1271 nfsaddrs= [NFS]
6ded55da 1272 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1273
1274 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1275 See Documentation/filesystems/nfsroot.txt.
1da177e4 1276
a72b4422
TM
1277 nfs.callback_tcpport=
1278 [NFS] set the TCP port on which the NFSv4 callback
1279 channel should listen.
1280
58df095b
TM
1281 nfs.idmap_cache_timeout=
1282 [NFS] set the maximum lifetime for idmapper cache
1283 entries.
1284
f43bf0be
TM
1285 nfs.enable_ino64=
1286 [NFS] enable 64-bit inode numbers.
1287 If zero, the NFS client will fake up a 32-bit inode
1288 number for the readdir() and stat() syscalls instead
1289 of returning the full 64-bit number.
1290 The default is to return 64-bit inode numbers.
1291
e7ba176b
HS
1292 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1293 when a NMI is triggered.
1294 Format: [state][,regs][,debounce][,die]
1295
cd4f0ef7 1296 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1297
cd4f0ef7 1298 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1299 emulation library even if a 387 maths coprocessor
1300 is present.
1301
c1aee215
CL
1302 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1303 caches in the slab allocator. Saves per-node memory,
1304 but will impact performance.
3395ee05 1305
a9913044
RD
1306 noalign [KNL,ARM]
1307
1da177e4
LT
1308 noapic [SMP,APIC] Tells the kernel to not make use of any
1309 IOAPICs that may be present in the system.
1310
1da177e4
LT
1311 nobats [PPC] Do not use BATs for mapping kernel lowmem
1312 on "Classic" PPC cores.
1313
1314 nocache [ARM]
a9913044 1315
163ecdff
SN
1316 nodelayacct [KNL] Disable per-task delay accounting
1317
1da177e4
LT
1318 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1319
8b2cb7a8
HY
1320 noefi [X86-32,X86-64] Disable EFI runtime services support.
1321
1da177e4
LT
1322 noexec [IA-64]
1323
cd4f0ef7 1324 noexec [X86-32,X86-64]
f5a1b191 1325 On X86-32 available only on PAE configured kernels.
1da177e4 1326 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1327 noexec=off: disable non-executable mappings
1328
1329 noexec32 [X86-64]
1330 This affects only 32-bit executables.
1331 noexec32=on: enable non-executable mappings (default)
1332 read doesn't imply executable mappings
1333 noexec32=off: disable non-executable mappings
1334 read implies executable mappings
1da177e4 1335
cd4f0ef7 1336 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1337 register save and restore. The kernel will only save
1338 legacy floating-point registers on task switch.
1da177e4 1339
191679fd
AK
1340 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1341
1da177e4 1342 nohlt [BUGS=ARM]
a9913044 1343
cd4f0ef7 1344 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1345 instruction doesn't work correctly and not to
1346 use it.
1347
1348 nohalt [IA-64] Tells the kernel not to use the power saving
1349 function PAL_HALT_LIGHT when idle. This increases
1350 power-consumption. On the positive side, it reduces
1351 interrupt wake-up latency, which may improve performance
1352 in certain environments such as networked servers or
1353 real-time systems.
1354
79bf2bb3
TG
1355 nohz= [KNL] Boottime enable/disable dynamic ticks
1356 Valid arguments: on, off
1357 Default: on
1358
cd4f0ef7 1359 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1360
cd4f0ef7 1361 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1362 disable unhandled interrupt sources.
1363
cd4f0ef7 1364 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1365 broken timer IRQ sources.
1366
1da177e4
LT
1367 noisapnp [ISAPNP] Disables ISA PnP code.
1368
1369 noinitrd [RAM] Tells the kernel not to load any configured
1370 initial RAM disk.
1371
1372 nointroute [IA-64]
1373
0aa366f3
TL
1374 nojitter [IA64] Disables jitter checking for ITC timers.
1375
cd4f0ef7 1376 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1377
cd4f0ef7 1378 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1379
1da177e4
LT
1380 noltlbs [PPC] Do not use large page/tlb entries for kernel
1381 lowmem mapping on PPC40x.
1382
312f1f01
H
1383 nomca [IA-64] Disable machine check abort handling
1384
cd4f0ef7 1385 nomce [X86-32] Machine Check Exception
abe37e5a 1386
83d7384f
AS
1387 nomfgpt [X86-32] Disable Multi-Function General Purpose
1388 Timer usage (for AMD Geode machines).
1389
cd4f0ef7 1390 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1391
cd4f0ef7 1392 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1393 with UP alternatives
1394
1da177e4
LT
1395 noresidual [PPC] Don't use residual data on PReP machines.
1396
a9913044
RD
1397 noresume [SWSUSP] Disables resume and restores original swap
1398 space.
1399
1da177e4
LT
1400 no-scroll [VGA] Disables scrollback.
1401 This is required for the Braillex ib80-piezo Braille
1402 reader made by F.H. Papenmeier (Germany).
1403
1404 nosbagart [IA-64]
1405
cd4f0ef7 1406 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1407
61ec7567
LB
1408 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1409 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1410
97842216
DJ
1411 nosoftlockup [KNL] Disable the soft-lockup detector.
1412
1da177e4
LT
1413 nosync [HW,M68K] Disables sync negotiation for all devices.
1414
cd4f0ef7 1415 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1416
1417 nousb [USB] Disable the USB subsystem
1418
1419 nowb [ARM]
a9913044 1420
a6c75b86
FY
1421 nptcg= [IA64] Override max number of concurrent global TLB
1422 purges which is reported from either PAL_VM_SUMMARY or
1423 SAL PALO.
1424
f0c0b2b8
KH
1425 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1426 one of ['zone', 'node', 'default'] can be specified
1427 This can be set from sysctl after boot.
1428 See Documentation/sysctl/vm.txt for details.
1429
a61c2d78
DJ
1430 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1431
3ef0e1f8
AS
1432 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1433 Rather than timing out after 20 ms if an EC
1434 command is not properly ACKed, override the length
1435 of the timeout. We have interrupts disabled while
1436 waiting for the ACK, so if this is set too high
1437 interrupts *may* be lost!
1438
1da177e4
LT
1439 opl3= [HW,OSS]
1440 Format: <io>
1441
1da177e4
LT
1442 oprofile.timer= [HW]
1443 Use timer interrupt instead of performance counters
1444
1da177e4
LT
1445 osst= [HW,SCSI] SCSI Tape Driver
1446 Format: <buffer_size>,<write_threshold>
1447 See also Documentation/scsi/st.txt.
1448
1449 panic= [KNL] Kernel behaviour on panic
1450 Format: <timeout>
1451
1452 parkbd.port= [HW] Parallel port number the keyboard adapter is
1453 connected to, default is 0.
1454 Format: <parport#>
1455 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1456 0 for XT, 1 for AT (default is AT).
a9913044
RD
1457 Format: <mode>
1458
1459 parport= [HW,PPT] Specify parallel ports. 0 disables.
1460 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1461 Use 'auto' to force the driver to use any
1462 IRQ/DMA settings detected (the default is to
1463 ignore detected IRQ/DMA settings because of
1464 possible conflicts). You can specify the base
1465 address, IRQ, and DMA settings; IRQ and DMA
1466 should be numbers, or 'auto' (for using detected
1467 settings on that particular port), or 'nofifo'
1468 (to avoid using a FIFO even if it is detected).
1469 Parallel ports are assigned in the order they
1470 are specified on the command line, starting
1471 with parport0.
1472
1473 parport_init_mode= [HW,PPT]
1474 Configure VIA parallel port to operate in
1475 a specific mode. This is necessary on Pegasos
1476 computer where firmware has no options for setting
1477 up parallel port mode and sets it to spp.
1478 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1479 Format: [spp|ps2|epp|ecp|ecpepp]
1480
a9913044
RD
1481 pas2= [HW,OSS] Format:
1482 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1483
1da177e4
LT
1484 pas16= [HW,SCSI]
1485 See header of drivers/scsi/pas16.c.
1486
dd287796
AM
1487 pause_on_oops=
1488 Halt all CPUs after the first oops has been printed for
1489 the specified number of seconds. This is to be used if
1490 your oopses keep scrolling off the screen.
1491
1da177e4
LT
1492 pcbit= [HW,ISDN]
1493
1494 pcd. [PARIDE]
1495 See header of drivers/block/paride/pcd.c.
1496 See also Documentation/paride.txt.
1497
a9913044 1498 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1499 off [X86-32] don't probe for the PCI bus
1500 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1501 the hardware directly. Use this if your machine
1502 has a non-standard PCI host bridge.
cd4f0ef7 1503 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1504 hardware access methods are allowed. Use this
1505 if you experience crashes upon bootup and you
1506 suspect they are caused by the BIOS.
cd4f0ef7 1507 conf1 [X86-32] Force use of PCI Configuration
a9913044 1508 Mechanism 1.
cd4f0ef7 1509 conf2 [X86-32] Force use of PCI Configuration
a9913044 1510 Mechanism 2.
7f785763
RD
1511 noaer [PCIE] If the PCIEAER kernel config parameter is
1512 enabled, this kernel boot option can be used to
1513 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1514 nodomains [PCI] Disable support for multiple PCI
1515 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1516 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1517 Configuration
309e57df
MW
1518 nomsi [MSI] If the PCI_MSI kernel config parameter is
1519 enabled, this kernel boot option can be used to
1520 disable the use of MSI interrupts system-wide.
cd4f0ef7 1521 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1522 routing table. These calls are known to be buggy
1523 on several machines and they hang the machine
1524 when used, but on other computers it's the only
1525 way to get the interrupt routing table. Try
1526 this option if the kernel is unable to allocate
1527 IRQs or discover secondary PCI buses on your
1528 motherboard.
cd4f0ef7 1529 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1530 Use with caution as certain devices share
1531 address decoders between ROMs and other
1532 resources.
cd4f0ef7 1533 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1534 assigned automatically to PCI devices. You can
1535 make the kernel exclude IRQs of your ISA cards
1536 this way.
cd4f0ef7 1537 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1538 of the PIRQ table (normally generated
1539 by the BIOS) if it is outside the
1540 F0000h-100000h range.
cd4f0ef7 1541 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1542 useful if the kernel is unable to find your
1543 secondary buses and you want to tell it
1544 explicitly which ones they are.
cd4f0ef7 1545 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1546 numbers ourselves, overriding
1547 whatever the firmware may have done.
cd4f0ef7 1548 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1549 in the BIOS $PIR table. This is needed on
1550 some systems with broken BIOSes, notably
1551 some HP Pavilion N5400 and Omnibook XE3
1552 notebooks. This will have no effect if ACPI
1553 IRQ routing is enabled.
cd4f0ef7 1554 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1555 or for PCI scanning.
62f420f8
GH
1556 use_crs [X86-32] Use _CRS for PCI resource
1557 allocation.
a9913044
RD
1558 routeirq Do IRQ routing for all PCI devices.
1559 This is normally done in pci_enable_device(),
1560 so this option is a temporary workaround
1561 for broken drivers that don't call it.
13a6ddb0
YL
1562 skip_isa_align [X86] do not align io start addr, so can
1563 handle more pci cards
a9913044
RD
1564 firmware [ARM] Do not re-enumerate the bus but instead
1565 just use the configuration from the
1566 bootloader. This is currently used on
1567 IXP2000 systems where the bus has to be
1568 configured a certain way for adjunct CPUs.
0637a70a
AK
1569 noearly [X86] Don't do any early type 1 scanning.
1570 This might help on some broken boards which
1571 machine check when some devices' config space
1572 is read. But various workarounds are disabled
1573 and some IOMMU drivers will not work.
6b4b78fe
MD
1574 bfsort Sort PCI devices into breadth-first order.
1575 This sorting is done to get a device
1576 order compatible with older (<= 2.4) kernels.
1577 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1578 cbiosize=nn[KMG] The fixed amount of bus space which is
1579 reserved for the CardBus bridge's IO window.
1580 The default value is 256 bytes.
1581 cbmemsize=nn[KMG] The fixed amount of bus space which is
1582 reserved for the CardBus bridge's memory
1583 window. The default value is 64 megabytes.
6b4b78fe 1584
1da177e4
LT
1585 pcmv= [HW,PCMCIA] BadgePAD 4
1586
1587 pd. [PARIDE]
1588 See Documentation/paride.txt.
1589
1590 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1591 boot time.
1592 Format: { 0 | 1 }
1593 See arch/parisc/kernel/pdc_chassis.c
1594
1595 pf. [PARIDE]
1596 See Documentation/paride.txt.
1597
1598 pg. [PARIDE]
1599 See Documentation/paride.txt.
1600
1601 pirq= [SMP,APIC] Manual mp-table setup
1602 See Documentation/i386/IO-APIC.txt.
1603
1604 plip= [PPT,NET] Parallel port network link
1605 Format: { parport<nr> | timid | 0 }
1606 See also Documentation/parport.txt.
1607
1608 pnpacpi= [ACPI]
1609 { off }
1610
1611 pnpbios= [ISAPNP]
1612 { on | off | curr | res | no-curr | no-res }
1613
1614 pnp_reserve_irq=
1615 [ISAPNP] Exclude IRQs for the autoconfiguration
1616
1617 pnp_reserve_dma=
1618 [ISAPNP] Exclude DMAs for the autoconfiguration
1619
1620 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1621 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1622
1623 pnp_reserve_mem=
a9913044
RD
1624 [ISAPNP] Exclude memory regions for the
1625 autoconfiguration.
1da177e4
LT
1626 Ranges are in pairs (memory base and size).
1627
45807a1d
IM
1628 print-fatal-signals=
1629 [KNL] debug: print fatal signals
1630 print-fatal-signals=1: print segfault info to
1631 the kernel console.
1632 default: off.
1633
e84845c4
RD
1634 printk.time= Show timing data prefixed to each printk message line
1635 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1636
1da177e4 1637 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1638 Format: [schedule,]<number>
1639 Param: "schedule" - profile schedule points.
1640 Param: <number> - step/bucket size as a power of 2 for
1641 statistical time based profiling.
b3da2a73
MG
1642 Param: "sleep" - profile D-state sleeping (millisecs).
1643 Requires CONFIG_SCHEDSTATS
c0fe2e69 1644 Param: "kvm" - profile VM exits.
1da177e4 1645
a9913044 1646 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1647 Limit processor to maximum C-state
1648 max_cstate=9 overrides any DMI blacklist limit.
1649
41c0d868
LB
1650 processor.nocst [HW,ACPI]
1651 Ignore the _CST method to determine C-states,
1652 instead using the legacy FADT method
1653
1da177e4
LT
1654 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1655 before loading.
1656 See Documentation/ramdisk.txt.
1657
a9913044
RD
1658 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1659 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1660 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1661 per second.
a9913044
RD
1662 psmouse.resetafter= [HW,MOUSE]
1663 Try to reset the device after so many bad packets
1da177e4
LT
1664 (0 = never).
1665 psmouse.resolution=
1666 [HW,MOUSE] Set desired mouse resolution, in dpi.
1667 psmouse.smartscroll=
a9913044 1668 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1669 0 = disabled, 1 = enabled (default).
1670
1671 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1672 Format:
1673 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1674
1675 pt. [PARIDE]
1676 See Documentation/paride.txt.
1677
dc8c8587
KS
1678 pty.legacy_count=
1679 [KNL] Number of legacy pty's. Overwrites compiled-in
1680 default number.
1681
7d2c502f 1682 quiet [KNL] Disable most log messages
a9913044 1683
1da177e4
LT
1684 r128= [HW,DRM]
1685
1686 raid= [HW,RAID]
1687 See Documentation/md.txt.
1688
a9913044 1689 ramdisk_blocksize= [RAM]
1da177e4 1690 See Documentation/ramdisk.txt.
a9913044 1691
1da177e4 1692 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1693 See Documentation/ramdisk.txt.
1694
24aaef8d
RD
1695 rcupdate.blimit= [KNL,BOOT]
1696 Set maximum number of finished RCU callbacks to process
1697 in one batch.
21a1ea9e 1698
24aaef8d
RD
1699 rcupdate.qhimark= [KNL,BOOT]
1700 Set threshold of queued
21a1ea9e
DS
1701 RCU callbacks over which batch limiting is disabled.
1702
24aaef8d
RD
1703 rcupdate.qlowmark= [KNL,BOOT]
1704 Set threshold of queued RCU callbacks below which
1705 batch limiting is re-enabled.
21a1ea9e 1706
ffdfc409
OJ
1707 rdinit= [KNL]
1708 Format: <full_path>
1709 Run specified binary instead of /init from the ramdisk,
1710 used for early userspace startup. See initrd.
1711
cd4f0ef7 1712 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1713 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1714 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 1715
46b6d94e
PJ
1716 relax_domain_level=
1717 [KNL, SMP] Set scheduler's default relax_domain_level.
1718 See Documentation/cpusets.txt.
1719
1da177e4
LT
1720 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1721
cd4f0ef7 1722 reservetop= [X86-32]
461a9aff
ZA
1723 Format: nn[KMG]
1724 Reserves a hole at the top of the kernel virtual
1725 address space.
1726
7e96287d
VG
1727 reset_devices [KNL] Force drivers to reset the underlying device
1728 during initialization.
1729
a9913044
RD
1730 resume= [SWSUSP]
1731 Specify the partition device for software suspend
1da177e4 1732
ecbd0da1
RW
1733 resume_offset= [SWSUSP]
1734 Specify the offset from the beginning of the partition
1735 given by "resume=" at which the swap header is located,
1736 in <PAGE_SIZE> units (needed only for swap files).
1737 See Documentation/power/swsusp-and-swap-files.txt
1738
0a7b35cb
MN
1739 retain_initrd [RAM] Keep initrd memory after extraction
1740
1da177e4
LT
1741 rhash_entries= [KNL,NET]
1742 Set number of hash buckets for route cache
1743
1744 riscom8= [HW,SERIAL]
1745 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1746
1747 ro [KNL] Mount root device read-only on boot
1748
1749 root= [KNL] Root filesystem
1750
1751 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1752 mount the root filesystem
1753
1754 rootflags= [KNL] Set root filesystem mount option string
1755
1756 rootfstype= [KNL] Set root filesystem type
1757
cc1ed754
PO
1758 rootwait [KNL] Wait (indefinitely) for root device to show up.
1759 Useful for devices that are detected asynchronously
1760 (e.g. USB and MMC devices).
1761
20510f2f
JM
1762 root_plug.vendor_id=
1763 [ROOTPLUG] Override the default vendor ID
1764
1765 root_plug.product_id=
1766 [ROOTPLUG] Override the default product ID
1767
1768 root_plug.debug=
1769 [ROOTPLUG] Enable debugging output
1770
1da177e4
LT
1771 rw [KNL] Mount root device read-write on boot
1772
1773 S [KNL] Run init in single mode
1774
1775 sa1100ir [NET]
1776 See drivers/net/irda/sa1100_ir.c.
1777
1da177e4 1778 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1779
1da177e4
LT
1780 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1781 Format: <io>[,<timeout>[,<isapnp>]]
1782
1783 scsi_debug_*= [SCSI]
1784 See drivers/scsi/scsi_debug.c.
1785
1786 scsi_default_dev_flags=
1787 [SCSI] SCSI default device flags
1788 Format: <integer>
1789
1790 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1791 Format: <vendor>:<model>:<flags>
1792 (flags are integer value)
1793
6af6632a
RD
1794 scsi_logging_level= [SCSI] a bit mask of logging levels
1795 See drivers/scsi/scsi_logging.h for bits. Also
1796 settable via sysctl at dev.scsi.logging_level
1797 (/proc/sys/dev/scsi/logging_level).
1798 There is also a nice 'scsi_logging_level' script in the
1799 S390-tools package, available for download at
1800 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1801
3e082a91
MW
1802 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1803 discovered. async scans them in kernel threads,
1804 allowing boot to proceed. none ignores them, expecting
1805 user space to do the scan.
1806
1da177e4
LT
1807 selinux [SELINUX] Disable or enable SELinux at boot time.
1808 Format: { "0" | "1" }
1809 See security/selinux/Kconfig help text.
1810 0 -- disable.
1811 1 -- enable.
1812 Default value is set via kernel config option.
1813 If enabled at boot time, /selinux/disable can be used
1814 later to disable prior to initial policy load.
1815
4e5ab4cb
JM
1816 selinux_compat_net =
1817 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1818 Format: { "0" | "1" }
1819 0 -- use new secmark-based packet controls
1820 1 -- use legacy packet controls
1821 Default value is 0 (preferred).
1822 Value can be changed at runtime via
1823 /selinux/compat_net.
4e5ab4cb 1824
cd4f0ef7 1825 serialnumber [BUGS=X86-32]
1da177e4 1826
1da177e4
LT
1827 shapers= [NET]
1828 Maximal number of shapers.
a9913044 1829
1da177e4
LT
1830 sim710= [SCSI,HW]
1831 See header of drivers/scsi/sim710.c.
1832
1833 simeth= [IA-64]
1834 simscsi=
a9913044 1835
1da177e4
LT
1836 slram= [HW,MTD]
1837
f0630fff
CL
1838 slub_debug[=options[,slabs]] [MM, SLUB]
1839 Enabling slub_debug allows one to determine the
1840 culprit if slab objects become corrupted. Enabling
1841 slub_debug can create guard zones around objects and
1842 may poison objects when not in use. Also tracks the
1843 last alloc / free. For more information see
1844 Documentation/vm/slub.txt.
c1aee215
CL
1845
1846 slub_max_order= [MM, SLUB]
f0630fff
CL
1847 Determines the maximum allowed order for slabs.
1848 A high setting may cause OOMs due to memory
1849 fragmentation. For more information see
1850 Documentation/vm/slub.txt.
c1aee215
CL
1851
1852 slub_min_objects= [MM, SLUB]
f0630fff
CL
1853 The minimum number of objects per slab. SLUB will
1854 increase the slab order up to slub_max_order to
1855 generate a sufficiently large slab able to contain
1856 the number of objects indicated. The higher the number
1857 of objects the smaller the overhead of tracking slabs
1858 and the less frequently locks need to be acquired.
c1aee215
CL
1859 For more information see Documentation/vm/slub.txt.
1860
1861 slub_min_order= [MM, SLUB]
1862 Determines the mininum page order for slabs. Must be
f0630fff 1863 lower than slub_max_order.
c1aee215
CL
1864 For more information see Documentation/vm/slub.txt.
1865
1866 slub_nomerge [MM, SLUB]
f0630fff 1867 Disable merging of slabs with similar size. May be
c1aee215 1868 necessary if there is some reason to distinguish
f0630fff
CL
1869 allocs to different slabs. Debug options disable
1870 merging on their own.
c1aee215
CL
1871 For more information see Documentation/vm/slub.txt.
1872
1da177e4
LT
1873 smart2= [HW]
1874 Format: <io1>[,<io2>[,...,<io8>]]
1875
cd4f0ef7 1876 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1877 attempt to substitute SMP alternatives once at boot.
1878
d0d4f69b
BH
1879 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1880 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1881 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1882 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1883 smsc-ircc2.ircc_irq= [HW] IRQ line
1884 smsc-ircc2.ircc_dma= [HW] DMA channel
1885 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1886 0: Toshiba Satellite 1800 (GP data pin select)
1887 1: Fast pin select (default)
1888 2: ATC IRMode
1889
1da177e4
LT
1890 snd-ad1816a= [HW,ALSA]
1891
1892 snd-ad1848= [HW,ALSA]
1893
1894 snd-ali5451= [HW,ALSA]
1895
1896 snd-als100= [HW,ALSA]
1897
1898 snd-als4000= [HW,ALSA]
1899
1900 snd-azt2320= [HW,ALSA]
1901
1902 snd-cmi8330= [HW,ALSA]
1903
1904 snd-cmipci= [HW,ALSA]
1905
1906 snd-cs4231= [HW,ALSA]
1907
1908 snd-cs4232= [HW,ALSA]
1909
1910 snd-cs4236= [HW,ALSA]
1911
1912 snd-cs4281= [HW,ALSA]
1913
1914 snd-cs46xx= [HW,ALSA]
1915
1916 snd-dt019x= [HW,ALSA]
1917
1918 snd-dummy= [HW,ALSA]
1919
1920 snd-emu10k1= [HW,ALSA]
1921
1922 snd-ens1370= [HW,ALSA]
1923
1924 snd-ens1371= [HW,ALSA]
1925
1926 snd-es968= [HW,ALSA]
1927
1928 snd-es1688= [HW,ALSA]
1929
1930 snd-es18xx= [HW,ALSA]
1931
1932 snd-es1938= [HW,ALSA]
1933
1934 snd-es1968= [HW,ALSA]
1935
1936 snd-fm801= [HW,ALSA]
1937
1938 snd-gusclassic= [HW,ALSA]
1939
1940 snd-gusextreme= [HW,ALSA]
1941
1942 snd-gusmax= [HW,ALSA]
1943
1944 snd-hdsp= [HW,ALSA]
1945
1946 snd-ice1712= [HW,ALSA]
1947
1948 snd-intel8x0= [HW,ALSA]
1949
1950 snd-interwave= [HW,ALSA]
1951
1952 snd-interwave-stb=
1953 [HW,ALSA]
1954
1955 snd-korg1212= [HW,ALSA]
1956
1957 snd-maestro3= [HW,ALSA]
1958
1959 snd-mpu401= [HW,ALSA]
1960
1961 snd-mtpav= [HW,ALSA]
1962
1963 snd-nm256= [HW,ALSA]
1964
1965 snd-opl3sa2= [HW,ALSA]
1966
1967 snd-opti92x-ad1848=
1968 [HW,ALSA]
1969
1970 snd-opti92x-cs4231=
1971 [HW,ALSA]
1972
1973 snd-opti93x= [HW,ALSA]
1974
1975 snd-pmac= [HW,ALSA]
1976
1977 snd-rme32= [HW,ALSA]
1978
1979 snd-rme96= [HW,ALSA]
1980
1981 snd-rme9652= [HW,ALSA]
1982
1983 snd-sb8= [HW,ALSA]
1984
1985 snd-sb16= [HW,ALSA]
1986
1987 snd-sbawe= [HW,ALSA]
1988
1989 snd-serial= [HW,ALSA]
1990
1991 snd-sgalaxy= [HW,ALSA]
1992
1993 snd-sonicvibes= [HW,ALSA]
1994
1995 snd-sun-amd7930=
1996 [HW,ALSA]
1997
1998 snd-sun-cs4231= [HW,ALSA]
1999
2000 snd-trident= [HW,ALSA]
2001
2002 snd-usb-audio= [HW,ALSA,USB]
2003
2004 snd-via82xx= [HW,ALSA]
2005
2006 snd-virmidi= [HW,ALSA]
2007
2008 snd-wavefront= [HW,ALSA]
2009
2010 snd-ymfpci= [HW,ALSA]
a9913044 2011
1da177e4
LT
2012 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2013 See Documentation/sonypi.txt
2014
2015 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2016 See Documentation/specialix.txt.
2017
2018 spia_io_base= [HW,MTD]
2019 spia_fio_base=
2020 spia_pedr=
2021 spia_peddr=
2022
2023 sscape= [HW,OSS]
2024 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2025
1da177e4
LT
2026 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2027 See Documentation/scsi/st.txt.
2028
1da177e4
LT
2029 sti= [PARISC,HW]
2030 Format: <num>
2031 Set the STI (builtin display/keyboard on the HP-PARISC
2032 machines) console (graphic card) which should be used
2033 as the initial boot-console.
2034 See also comment in drivers/video/console/sticore.c.
2035
2036 sti_font= [HW]
2037 See comment in drivers/video/console/sticore.c.
2038
2039 stifb= [HW]
2040 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2041
42a7fc4a
GB
2042 sunrpc.pool_mode=
2043 [NFS]
2044 Control how the NFS server code allocates CPUs to
2045 service thread pools. Depending on how many NICs
2046 you have and where their interrupts are bound, this
2047 option will affect which CPUs will do NFS serving.
2048 Note: this parameter cannot be changed while the
2049 NFS server is running.
2050
2051 auto the server chooses an appropriate mode
2052 automatically using heuristics
2053 global a single global pool contains all CPUs
2054 percpu one pool for each CPU
2055 pernode one pool for each NUMA node (equivalent
2056 to global on non-NUMA machines)
2057
1da177e4 2058 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2059
1da177e4
LT
2060 switches= [HW,M68k]
2061
2062 sym53c416= [HW,SCSI]
2063 See header of drivers/scsi/sym53c416.c.
2064
5d6f647f
IM
2065 sysrq_always_enabled
2066 [KNL]
2067 Ignore sysrq setting - this boot parameter will
2068 neutralize any effect of /proc/sys/kernel/sysrq.
2069 Useful for debugging.
2070
1da177e4
LT
2071 t128= [HW,SCSI]
2072 See header of drivers/scsi/t128.c.
2073
2074 tdfx= [HW,DRM]
2075
2076 thash_entries= [KNL,NET]
2077 Set number of hash buckets for TCP connection
2078
f8707ec9
LB
2079 thermal.act= [HW,ACPI]
2080 -1: disable all active trip points in all thermal zones
2081 <degrees C>: override all lowest active trip points
2082
c52a7419
LB
2083 thermal.crt= [HW,ACPI]
2084 -1: disable all critical trip points in all thermal zones
2085 <degrees C>: lower all critical trip points
2086
f5487145
LB
2087 thermal.nocrt= [HW,ACPI]
2088 Set to disable actions on ACPI thermal zone
2089 critical and hot trip points.
2090
72b33ef8
LB
2091 thermal.off= [HW,ACPI]
2092 1: disable ACPI thermal control
2093
a70cdc52
LB
2094 thermal.psv= [HW,ACPI]
2095 -1: disable all passive trip points
2096 <degrees C>: override all passive trip points to this value
2097
730ff34d
LB
2098 thermal.tzp= [HW,ACPI]
2099 Specify global default ACPI thermal zone polling rate
2100 <deci-seconds>: poll all this frequency
2101 0: no polling (default)
2102
1da177e4
LT
2103 tipar.timeout= [HW,PPT]
2104 Set communications timeout in tenths of a second
2105 (default 15).
2106
2107 tipar.delay= [HW,PPT]
2108 Set inter-bit delay in microseconds (default 10).
2109
1da177e4
LT
2110 tmscsim= [HW,SCSI]
2111 See comment before function dc390_setup() in
2112 drivers/scsi/tmscsim.c.
2113
2114 tp720= [HW,PS2]
2115
2116 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2117 Format:
2118 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2119
a9913044
RD
2120 turbografx.map[2|3]= [HW,JOY]
2121 TurboGraFX parallel port interface
2122 Format:
2123 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2124 See also Documentation/input/joystick-parport.txt
2125
2126 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2127 See header of drivers/scsi/u14-34f.c.
2128
2129 uart401= [HW,OSS]
2130 Format: <io>,<irq>
2131
2132 uart6850= [HW,OSS]
2133 Format: <io>,<irq>
2134
5f8364b7
AS
2135 uhci-hcd.ignore_oc=
2136 [USB] Ignore overcurrent events (default N).
2137 Some badly-designed motherboards generate lots of
2138 bogus events, for ports that aren't wired to
2139 anything. Set this parameter to avoid log spamming.
2140 Note that genuine overcurrent events won't be
2141 reported either.
2142
b5e795f8
AS
2143 usbcore.autosuspend=
2144 [USB] The autosuspend time delay (in seconds) used
2145 for newly-detected USB devices (default 2). This
2146 is the time required before an idle device will be
2147 autosuspended. Devices for which the delay is set
eaafbc3a 2148 to a negative value won't be autosuspended at all.
b5e795f8 2149
1da177e4
LT
2150 usbhid.mousepoll=
2151 [USBHID] The interval which mice are to be polled at.
a9913044 2152
200001eb
PJ
2153 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2154 kernel's map of available physical RAM.
2155
cd4f0ef7 2156 vdso= [X86-32,SH,x86-64]
1dbf527c 2157 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2158 vdso=1: enable VDSO (default)
2159 vdso=0: disable VDSO mapping
2160
af65d648
RM
2161 vdso32= [X86-32,X86-64]
2162 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2163 vdso32=1: enable 32-bit VDSO (default)
2164 vdso32=0: disable 32-bit VDSO mapping
2165
d080d397
YI
2166 vector= [IA-64,SMP]
2167 vector=percpu: enable percpu vector domain
2168
1da177e4
LT
2169 video= [FB] Frame buffer configuration
2170 See Documentation/fb/modedb.txt.
2171
cd4f0ef7 2172 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2173 See Documentation/i386/boot.txt and
2174 Documentation/svga.txt.
1da177e4
LT
2175 Use vga=ask for menu.
2176 This is actually a boot loader parameter; the value is
2177 passed to the kernel using a special protocol.
2178
a9913044 2179 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2180 size of <nn>. This can be used to increase the
2181 minimum size (128MB on x86). It can also be used to
2182 decrease the size and leave more room for directly
2183 mapped kernel RAM.
2184
585c3047
PO
2185 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2186 Format: <command>
1da177e4 2187
585c3047
PO
2188 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2189 Format: <command>
2190
2191 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2192 Format: <command>
a9913044 2193
1da177e4
LT
2194 waveartist= [HW,OSS]
2195 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2196
1da177e4
LT
2197 wd33c93= [HW,SCSI]
2198 See header of drivers/scsi/wd33c93.c.
2199
2200 wd7000= [HW,SCSI]
2201 See header of drivers/scsi/wd7000.c.
2202
2203 wdt= [WDT] Watchdog
8dfe9c21 2204 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2205
2206 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2207 xd_geo= See header of drivers/block/xd.c.
2208
2209 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2210 Format:
2211 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2212
a62eaf15
AK
2213 norandmaps Don't use address space randomization
2214 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2215
a9913044 2216______________________________________________________________________
1da177e4
LT
2217
2218TODO:
2219
2220 Add documentation for ALSA options.
2221 Add more DRM drivers.