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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
d8f3de0d 150 Format: { s3_bios, s3_mode, s3_beep, old_ordering }
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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.
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154 old_ordering causes the ACPI 1.0 ordering of the _PTS
155 control method, wrt putting devices into low power
156 states, to be enforced (the ACPI 2.0 ordering of _PTS is
157 used by default).
a9913044 158
1da177e4 159 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 160 Format: { level | edge | high | low }
1da177e4 161
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162 acpi_irq_balance [HW,ACPI]
163 ACPI will balance active IRQs
164 default in APIC mode
1da177e4 165
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166 acpi_irq_nobalance [HW,ACPI]
167 ACPI will not move active IRQs (default)
168 default in PIC mode
1da177e4 169
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170 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
171 use by PCI
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172 Format: <irq>,<irq>...
173
a9913044 174 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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175 Format: <irq>,<irq>...
176
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177 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
178
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179 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
180 Format: To spoof as Windows 98: ="Microsoft Windows"
181
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182 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
183 acpi_osi="string1" # add string1 -- only one string
184 acpi_osi="!string2" # remove built-in string2
185 acpi_osi= # disable all strings
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186
187 acpi_serialize [HW,ACPI] force serialization of AML methods
188
189 acpi_skip_timer_override [HW,ACPI]
190 Recognize and ignore IRQ0/pin2 Interrupt Override.
191 For broken nForce2 BIOS resulting in XT-PIC timer.
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192 acpi_use_timer_override [HW,ACPI}
193 Use timer override. For some broken Nvidia NF5 boards
194 that require a timer override, but don't have
195 HPET
1da177e4 196
f989106c 197 acpi.debug_layer= [HW,ACPI]
1da177e4 198 Format: <int>
a9913044 199 Each bit of the <int> indicates an ACPI debug layer,
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200 1: enable, 0: disable. It is useful for boot time
201 debugging. After system has booted up, it can be set
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202 via /sys/module/acpi/parameters/debug_layer.
203 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
204 Available bits (add the numbers together) to enable debug output
205 for specific parts of the ACPI subsystem:
206 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
207 0x10 namespace 0x20 parser 0x40 dispatcher
208 0x80 executer 0x100 resources 0x200 acpica debugger
209 0x400 os services 0x800 acpica disassembler.
210 The number can be in decimal or prefixed with 0x in hex.
211 Warning: Many of these options can produce a lot of
212 output and make your system unusable. Be very careful.
213
214 acpi.debug_level= [HW,ACPI]
1da177e4 215 Format: <int>
a9913044 216 Each bit of the <int> indicates an ACPI debug level,
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217 1: enable, 0: disable. It is useful for boot time
218 debugging. After system has booted up, it can be set
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219 via /sys/module/acpi/parameters/debug_level.
220 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
221 Available bits (add the numbers together) to enable different
222 debug output levels of the ACPI subsystem:
223 0x01 error 0x02 warn 0x04 init 0x08 debug object
224 0x10 info 0x20 init names 0x40 parse 0x80 load
225 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
226 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
227 0x10000 resources 0x20000 user requests 0x40000 package.
228 The number can be in decimal or prefixed with 0x in hex.
229 Warning: Many of these options can produce a lot of
230 output and make your system unusable. Be very careful.
231
cd4f0ef7 232 acpi_pm_good [X86-32,X86-64]
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233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
236
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237 agp= [AGP]
238 { off | try_unsupported }
239 off: disable AGP support
240 try_unsupported: try to drive unsupported chipsets
241 (may crash computer or cause data corruption)
242
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243 enable_timer_pin_1 [i386,x86-64]
244 Enable PIN 1 of APIC timer
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245 Can be useful to work around chipset bugs
246 (in particular on some ATI chipsets).
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247 The kernel tries to set a reasonable default.
248
249 disable_timer_pin_1 [i386,x86-64]
250 Disable PIN 1 of APIC timer
251 Can be useful to work around chipset bugs.
252
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253 ad1848= [HW,OSS]
254 Format: <io>,<irq>,<dma>,<dma2>,<type>
255
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256 advansys= [HW,SCSI]
257 See header of drivers/scsi/advansys.c.
258
259 advwdt= [HW,WDT] Advantech WDT
260 Format: <iostart>,<iostop>
261
262 aedsp16= [HW,OSS] Audio Excel DSP 16
263 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
264 See also header of sound/oss/aedsp16.c.
a9913044 265
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266 aha152x= [HW,SCSI]
267 See Documentation/scsi/aha152x.txt.
268
269 aha1542= [HW,SCSI]
270 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
271
272 aic7xxx= [HW,SCSI]
273 See Documentation/scsi/aic7xxx.txt.
274
275 aic79xx= [HW,SCSI]
276 See Documentation/scsi/aic79xx.txt.
277
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278 amd_iommu= [HW,X86-84]
279 Pass parameters to the AMD IOMMU driver in the system.
280 Possible values are:
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281 isolate - enable device isolation (each device, as far
282 as possible, will get its own protection
283 domain)
284 amd_iommu_size= [HW,X86-64]
285 Define the size of the aperture for the AMD IOMMU
286 driver. Possible values are:
287 '32M', '64M' (default), '128M', '256M', '512M', '1G'
288
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289 amijoy.map= [HW,JOY] Amiga joystick support
290 Map of devices attached to JOY0DAT and JOY1DAT
291 Format: <a>,<b>
292 See also Documentation/kernel/input/joystick.txt
293
294 analog.map= [HW,JOY] Analog joystick and gamepad support
295 Specifies type or capabilities of an analog joystick
296 connected to one of 16 gameports
297 Format: <type1>,<type2>,..<type16>
298
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299 apc= [HW,SPARC]
300 Power management functions (SPARCstation-4/5 + deriv.)
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301 Format: noidle
302 Disable APC CPU standby support. SPARCstation-Fox does
303 not play well with APC CPU idle - disable it if you have
304 APC and your system crashes randomly.
305
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306 apic= [APIC,i386] Advanced Programmable Interrupt Controller
307 Change the output verbosity whilst booting
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308 Format: { quiet (default) | verbose | debug }
309 Change the amount of debugging information output
310 when initialising the APIC and IO-APIC components.
a9913044 311
1da177e4 312 apm= [APM] Advanced Power Management
71f77055 313 See header of arch/x86/kernel/apm_32.c.
1da177e4 314
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315 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
316 Format: <io>,<irq>,<nodeID>
317
318 ataflop= [HW,M68k]
319
320 atarimouse= [HW,MOUSE] Atari Mouse
321
322 atascsi= [HW,SCSI] Atari SCSI
323
324 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
325 EzKey and similar keyboards
326
327 atkbd.reset= [HW] Reset keyboard during initialization
328
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329 atkbd.set= [HW] Select keyboard code set
330 Format: <int> (2 = AT (default), 3 = PS/2)
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331
332 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
333 keyboards
334
335 atkbd.softraw= [HW] Choose between synthetic and real raw mode
336 Format: <bool> (0 = real, 1 = synthetic (default))
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337
338 atkbd.softrepeat= [HW]
339 Use software keyboard repeat
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340
341 autotest [IA64]
342
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343 baycom_epp= [HW,AX25]
344 Format: <io>,<mode>
a9913044 345
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346 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
347 Format: <io>,<mode>
348 See header of drivers/net/hamradio/baycom_par.c.
349
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350 baycom_ser_fdx= [HW,AX25]
351 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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352 Format: <io>,<irq>,<mode>[,<baud>]
353 See header of drivers/net/hamradio/baycom_ser_fdx.c.
354
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355 baycom_ser_hdx= [HW,AX25]
356 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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357 Format: <io>,<irq>,<mode>
358 See header of drivers/net/hamradio/baycom_ser_hdx.c.
359
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360 boot_delay= Milliseconds to delay each printk during boot.
361 Values larger than 10 seconds (10000) are changed to
362 no delay (0).
363 Format: integer
364
1da177e4 365 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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366 bttv.radio= Most important insmod options are available as
367 kernel args too.
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368 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
369 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
370
371 BusLogic= [HW,SCSI]
372 See drivers/scsi/BusLogic.c, comment before function
373 BusLogic_ParseDriverOptions().
374
375 c101= [NET] Moxa C101 synchronous serial card
376
cd4f0ef7 377 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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378 Sometimes CPU hardware bugs make them report the cache
379 size incorrectly. The kernel will attempt work arounds
380 to fix known problems, but for some CPUs it is not
381 possible to determine what the correct size should be.
382 This option provides an override for these situations.
383
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384 security= [SECURITY] Choose a security module to enable at boot.
385 If this boot parameter is not specified, only the first
386 security module asking for security registration will be
387 loaded. An invalid security module name will be treated
388 as if no module has been chosen.
389
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390 capability.disable=
391 [SECURITY] Disable capabilities. This would normally
392 be used only if an alternative security model is to be
393 configured. Potentially dangerous and should only be
394 used if you are entirely sure of the consequences.
395
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396 ccw_timeout_log [S390]
397 See Documentation/s390/CommonIO for details.
1da177e4 398
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399 cgroup_disable= [KNL] Disable a particular controller
400 Format: {name of the controller(s) to disable}
401 {Currently supported controllers - "memory"}
402
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403 checkreqprot [SELINUX] Set initial checkreqprot flag value.
404 Format: { "0" | "1" }
405 See security/selinux/Kconfig help text.
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406 0 -- check protection applied by kernel (includes
407 any implied execute protection).
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408 1 -- check protection requested by application.
409 Default value is set via a kernel config option.
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410 Value can be changed at runtime via
411 /selinux/checkreqprot.
412
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413 cio_ignore= [S390]
414 See Documentation/s390/CommonIO for details.
415
cd4f0ef7 416 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 417 [Deprecated]
3f6dee9b 418 Forces specified clocksource (if available) to be used
734efb46 419 when calculating gettimeofday(). If specified
3f6dee9b 420 clocksource is not available, it defaults to PIT.
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421 Format: { pit | tsc | cyclone | pmtmr }
422
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423 clocksource= [GENERIC_TIME] Override the default clocksource
424 Format: <string>
425 Override the default clocksource and use the clocksource
426 with the name specified.
427 Some clocksource names to choose from, depending on
428 the platform:
429 [all] jiffies (this is the base, fallback clocksource)
430 [ACPI] acpi_pm
431 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
432 pxa_timer,timer3,32k_counter,timer0_1
433 [AVR32] avr32
cd4f0ef7 434 [X86-32] pit,hpet,tsc,vmi-timer;
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435 scx200_hrt on Geode; cyclone on IBM x440
436 [MIPS] MIPS
437 [PARISC] cr16
438 [S390] tod
439 [SH] SuperH
440 [SPARC64] tick
441 [X86-64] hpet,tsc
442
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443 clearcpuid=BITNUM [X86]
444 Disable CPUID feature X for the kernel. See
445 include/asm-x86/cpufeature.h for the valid bit numbers.
446 Note the Linux specific bits are not necessarily
447 stable over kernel options, but the vendor specific
448 ones should be.
449 Also note that user programs calling CPUID directly
450 or using the feature without checking anything
451 will still see it. This just prevents it from
452 being used by the kernel or shown in /proc/cpuinfo.
453 Also note the kernel might malfunction if you disable
454 some critical bits.
455
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456 code_bytes [IA32/X86_64] How many bytes of object code to print
457 in an oops report.
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458 Range: 0 - 8192
459 Default: 64
460
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461 disable_8254_timer
462 enable_8254_timer
463 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
464 over the 8254 in addition to over the IO-APIC. The
465 kernel tries to set a sensible default.
466
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467 hpet= [X86-32,HPET] option to control HPET usage
468 Format: { enable (default) | disable | force }
469 disable: disable HPET and use PIT instead
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470 force: allow force enabled of undocumented chips (ICH4,
471 VIA, nVidia)
1da177e4 472
1da177e4 473 com20020= [HW,NET] ARCnet - COM20020 chipset
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474 Format:
475 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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476
477 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
478 Format: <io>[,<irq>]
479
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480 com90xx= [HW,NET]
481 ARCnet - COM90xx chipset (memory-mapped buffers)
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482 Format: <io>[,<irq>[,<memstart>]]
483
484 condev= [HW,S390] console device
485 conmode=
a9913044 486
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487 console= [KNL] Output console device and options.
488
489 tty<n> Use the virtual console device <n>.
490
491 ttyS<n>[,options]
f1a1c2dc 492 ttyUSB0[,options]
1da177e4 493 Use the specified serial port. The options are of
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494 the form "bbbbpnf", where "bbbb" is the baud rate,
495 "p" is parity ("n", "o", or "e"), "n" is number of
496 bits, and "f" is flow control ("r" for RTS or
497 omit it). Default is "9600n8".
498
499 See Documentation/serial-console.txt for more
500 information. See
501 Documentation/networking/netconsole.txt for an
502 alternative.
1da177e4 503
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504 uart[8250],io,<addr>[,options]
505 uart[8250],mmio,<addr>[,options]
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506 Start an early, polled-mode console on the 8250/16550
507 UART at the specified I/O port or MMIO address,
508 switching to the matching ttyS device later. The
509 options are the same as for ttyS, above.
510
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511 If the device connected to the port is not a TTY but a braille
512 device, prepend "brl," before the device type, for instance
513 console=brl,ttyS0
514 For now, only VisioBraille is supported.
515
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516 earlycon= [KNL] Output early console device and options.
517 uart[8250],io,<addr>[,options]
518 uart[8250],mmio,<addr>[,options]
519 Start an early, polled-mode console on the 8250/16550
520 UART at the specified I/O port or MMIO address.
521 The options are the same as for ttyS, above.
522
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523 no_console_suspend
524 [HW] Never suspend the console
525 Disable suspending of consoles during suspend and
526 hibernate operations. Once disabled, debugging
527 messages can reach various consoles while the rest
528 of the system is being put to sleep (ie, while
529 debugging driver suspend/resume hooks). This may
530 not work reliably with all consoles, but is known
531 to work with serial and VGA consoles.
532
1da177e4 533 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
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534 Format:
535 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 536
dc009d92
EB
537 crashkernel=nn[KMG]@ss[KMG]
538 [KNL] Reserve a chunk of physical memory to
539 hold a kernel to switch to with kexec on panic.
540
fb391599
BW
541 crashkernel=range1:size1[,range2:size2,...][@offset]
542 [KNL] Same as above, but depends on the memory
543 in the running system. The syntax of range is
544 start-[end] where start and end are both
545 a memory unit (amount[KMG]). See also
546 Documentation/kdump/kdump.txt for a example.
547
1da177e4
LT
548 cs4232= [HW,OSS]
549 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
550
551 cs89x0_dma= [HW,NET]
552 Format: <dma>
553
554 cs89x0_media= [HW,NET]
555 Format: { rj45 | aui | bnc }
a9913044 556
a9913044 557 dasd= [HW,NET]
1da177e4
LT
558 See header of drivers/s390/block/dasd_devmap.c.
559
560 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
561 (one device per port)
562 Format: <port#>,<type>
563 See also Documentation/input/joystick-parport.txt
564
565 debug [KNL] Enable kernel debugging (events log level).
566
cae2ed9a
IM
567 debug_locks_verbose=
568 [KNL] verbose self-tests
569 Format=<0|1>
570 Print debugging info while doing the locking API
571 self-tests.
572 We default to 0 (no extra messages), setting it to
573 1 will print _a lot_ more information - normally
574 only useful to kernel developers.
575
3ac7fe5a
TG
576 debug_objects [KNL] Enable object debugging
577
d3af01f1
TG
578 debugpat [X86] Enable PAT debugging
579
2d27a966 580 decnet.addr= [HW,NET]
1da177e4
LT
581 Format: <area>[,<node>]
582 See also Documentation/networking/decnet.txt.
583
ecb77fa9 584 vt.default_blu= [VT]
55ff9780
AD
585 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
586 Change the default blue palette of the console.
587 This is a 16-member array composed of values
588 ranging from 0-255.
589
ecb77fa9 590 vt.default_grn= [VT]
55ff9780
AD
591 Format: <green0>,<green1>,<green2>,...,<green15>
592 Change the default green palette of the console.
593 This is a 16-member array composed of values
594 ranging from 0-255.
595
ecb77fa9 596 vt.default_red= [VT]
55ff9780
AD
597 Format: <red0>,<red1>,<red2>,...,<red15>
598 Change the default red palette of the console.
599 This is a 16-member array composed of values
600 ranging from 0-255.
601
ecb77fa9
ST
602 vt.default_utf8=
603 [VT]
55ff9780
AD
604 Format=<0|1>
605 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
606 Default is 1, i.e. UTF-8 mode is enabled for all
607 newly opened terminals.
55ff9780 608
1da177e4
LT
609 dhash_entries= [KNL]
610 Set number of hash buckets for dentry cache.
a9913044 611
1da177e4
LT
612 digi= [HW,SERIAL]
613 IO parameters + enable/disable command.
614
615 digiepca= [HW,SERIAL]
616 See drivers/char/README.epca and
617 Documentation/digiepca.txt.
618
95ffa243
YL
619 disable_mtrr_cleanup [X86]
620 enable_mtrr_cleanup [X86]
621 The kernel tries to adjust MTRR layout from continuous
622 to discrete, to make X server driver able to add WB
623 entry later. This parameter enables/disables that.
624
625 mtrr_chunk_size=nn[KMG] [X86]
626 used for mtrr cleanup. It is largest continous chunk
627 that could hold holes aka. UC entries.
628
629 mtrr_gran_size=nn[KMG] [X86]
12031a62
YL
630 Used for mtrr cleanup. It is granularity of mtrr block.
631 Default is 1.
632 Large value could prevent small alignment from
633 using up MTRRs.
634
635 mtrr_spare_reg_nr=n [X86]
636 Format: <integer>
637 Range: 0,7 : spare reg number
638 Default : 1
639 Used for mtrr cleanup. It is spare mtrr entries number.
640 Set to 2 or more if your graphical card needs more.
95ffa243 641
093af8d7 642 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
643 By default the kernel will trim any uncacheable
644 memory out of your available memory pool based on
645 MTRR settings. This parameter disables that behavior,
646 possibly causing your machine to run very slowly.
647
1da177e4
LT
648 dmasound= [HW,OSS] Sound subsystem buffers
649
650 dscc4.setup= [NET]
651
652 dtc3181e= [HW,SCSI]
653
0ae53640 654 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
655 earlyprintk=vga
656 earlyprintk=serial[,ttySn[,baudrate]]
657
a9913044 658 Append ",keep" to not disable it when the real console
1da177e4
LT
659 takes over.
660
661 Only vga or serial at a time, not both.
662
663 Currently only ttyS0 and ttyS1 are supported.
664
665 Interaction with the standard serial driver is not
666 very good.
667
668 The VGA output is eventually overwritten by the real
669 console.
670
671 eata= [HW,SCSI]
672
1da177e4 673 edd= [EDD]
8c4dd606 674 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 675
1da177e4
LT
676 eisa_irq_edge= [PARISC,HW]
677 See header of drivers/parisc/eisa.c.
678
cd4f0ef7 679 elanfreq= [X86-32]
1da177e4 680 See comment before function elanfreq_setup() in
71f77055 681 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
682
683 elevator= [IOSCHED]
16ab3adf 684 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
685 See Documentation/block/as-iosched.txt and
686 Documentation/block/deadline-iosched.txt for details.
687
cd4f0ef7 688 elfcorehdr= [X86-32, X86_64]
a9913044 689 Specifies physical address of start of kernel core
aac04b32
VG
690 image elf header. Generally kexec loader will
691 pass this option to capture kernel.
692 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
693
694 enforcing [SELINUX] Set initial enforcing status.
695 Format: {"0" | "1"}
696 See security/selinux/Kconfig help text.
697 0 -- permissive (log only, no denials).
698 1 -- enforcing (deny and log).
699 Default value is 0.
700 Value can be changed at runtime via /selinux/enforce.
701
1da177e4
LT
702 es1371= [HW,OSS]
703 Format: <spdif>,[<nomix>,[<amplifier>]]
704 See also header of sound/oss/es1371.c.
a9913044 705
1da177e4
LT
706 ether= [HW,NET] Ethernet cards parameters
707 This option is obsoleted by the "netdev=" option, which
708 has equivalent usage. See its documentation for details.
709
710 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
711 Format: <io>[,<irq>]
712
de1ba09b
AM
713 failslab=
714 fail_page_alloc=
715 fail_make_request=[KNL]
716 General fault injection mechanism.
717 Format: <interval>,<probability>,<space>,<times>
718 See also /Documentation/fault-injection/.
719
1da177e4
LT
720 fd_mcs= [HW,SCSI]
721 See header of drivers/scsi/fd_mcs.c.
722
723 fdomain= [HW,SCSI]
724 See header of drivers/scsi/fdomain.c.
725
726 floppy= [HW]
727 See Documentation/floppy.txt.
728
f13ae30e
AC
729 force_pal_cache_flush
730 [IA-64] Avoid check_sal_cache_flush which may hang on
731 buggy SAL_CACHE_FLUSH implementations. Using this
732 parameter will force ia64_sal_cache_flush to call
733 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
734
1da177e4
LT
735 gamecon.map[2|3]=
736 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
737 support via parallel port (up to 5 devices per port)
738 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
739 See also Documentation/input/joystick-parport.txt
740
741 gamma= [HW,DRM]
742
aaf23042
YL
743 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
744 Format: off | on
745 default: on
746
1da177e4
LT
747 gdth= [HW,SCSI]
748 See header of drivers/scsi/gdth.c.
749
750 gpt [EFI] Forces disk with valid GPT signature but
751 invalid Protective MBR to be treated as GPT.
752
1da177e4
LT
753 gvp11= [HW,SCSI]
754
755 hashdist= [KNL,NUMA] Large hashes allocated during boot
756 are distributed across NUMA nodes. Defaults on
757 for IA-64, off otherwise.
a9913044 758 Format: 0 | 1 (for off | on)
1da177e4
LT
759
760 hcl= [IA-64] SGI's Hardware Graph compatibility layer
761
762 hd= [EIDE] (E)IDE hard drive subsystem geometry
763 Format: <cyl>,<head>,<sect>
764
1da177e4
LT
765 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
766 size of <nn>. This works even on boxes that have no
767 highmem otherwise. This also works to reduce highmem
768 size on bigger boxes.
769
54cdfdb4
TG
770 highres= [KNL] Enable/disable high resolution timer mode.
771 Valid parameters: "on", "off"
772 Default: "on"
773
1da177e4
LT
774 hisax= [HW,ISDN]
775 See Documentation/isdn/README.HiSax.
776
cd4f0ef7 777 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 778 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 779
1da177e4 780 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
781 i8042.dumbkbd [HW] Pretend that controller can only read data from
782 keyboard and cannot control its state
1da177e4
LT
783 (Don't attempt to blink the leds)
784 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 785 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
786 i8042.noloop [HW] Disable the AUX Loopback command while probing
787 for the AUX port
1da177e4
LT
788 i8042.nomux [HW] Don't check presence of an active multiplexing
789 controller
790 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
791 controllers
792 i8042.panicblink=
793 [HW] Frequency with which keyboard LEDs should blink
794 when kernel panics (default is 0.5 sec)
795 i8042.reset [HW] Reset the controller during init and cleanup
796 i8042.unlock [HW] Unlock (ignore) the keylock
797
798 i810= [HW,DRM]
799
e70c9d5e
DT
800 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
801 indicates that the driver is running on unsupported
802 hardware.
1da177e4
LT
803 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
804 does not match list of supported models.
805 i8k.power_status
806 [HW] Report power status in /proc/i8k
807 (disabled by default)
808 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
809 capability is set.
810
811 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
812 See Documentation/mca.txt.
813
814 icn= [HW,ISDN]
815 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
816
817 ide= [HW] (E)IDE subsystem
a594eeb1 818 Format: ide=nodma or ide=doubler
1c10e938 819 See Documentation/ide/ide.txt.
1da177e4 820
1da177e4 821 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 822 See Documentation/ide/ide.txt.
1da177e4 823
f039b754 824 idle= [X86]
da5e09a1 825 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
f039b754
AK
826 Poll forces a polling idle loop that can slightly improves the performance
827 of waking up a idle CPU, but will use a lot of power and make the system
828 run hot. Not recommended.
829 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
830 to not use it because it doesn't save as much power as a normal idle
831 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
832 as idle=poll.
c1e3b377
ZY
833 idle=halt. Halt is forced to be used for CPU idle.
834 In such case C2/C3 won't be used again.
da5e09a1 835 idle=nomwait. Disable mwait for CPU C-states
a9913044 836
594765a7
DC
837 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
838 Claim all unknown PCI IDE storage controllers.
839
79290822
IM
840 ignore_loglevel [KNL]
841 Ignore loglevel setting - this will print /all/
842 kernel messages to the console. Useful for debugging.
843
1da177e4
LT
844 ihash_entries= [KNL]
845 Set number of hash buckets for inode cache.
846
847 in2000= [HW,SCSI]
848 See header of drivers/scsi/in2000.c.
849
850 init= [KNL]
851 Format: <full_path>
852 Run specified binary instead of /sbin/init as init
853 process.
854
855 initcall_debug [KNL] Trace initcalls as they are executed. Useful
856 for working out where the kernel is dying during
857 startup.
858
859 initrd= [BOOT] Specify the location of the initial ramdisk
860
861 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
862 Format: <irq>
863
864 inttest= [IA64]
865
b552da87
PM
866 iommu= [x86]
867 off
868 force
869 noforce
870 biomerge
871 panic
872 nopanic
873 merge
874 nomerge
875 forcesac
876 soft
877
878
ba395927
KA
879 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
880 off
881 Disable intel iommu driver.
882 igfx_off [Default Off]
883 By default, gfx is mapped as normal device. If a gfx
884 device has a dedicated DMAR unit, the DMAR unit is
885 bypassed by not enabling DMAR with this option. In
886 this case, gfx device will use physical address for
887 DMA.
7d3b03ce
KA
888 forcedac [x86_64]
889 With this option iommu will not optimize to look
890 for io virtual address below 32 bit forcing dual
891 address cycle on pci bus for cards supporting greater
892 than 32 bit addressing. The default is to look
893 for translation below 32 bit and if not available
894 then look in the higher range.
5e0d2a6f 895 strict [Default Off]
896 With this option on every unmap_single operation will
897 result in a hardware IOTLB flush operation as opposed
898 to batching them for performance.
ba395927 899
b02aae9c 900 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
901 0x80
902 Standard port 0x80 based delay
903 0xed
904 Alternate port 0xed based delay (needed on some systems)
b02aae9c 905 udelay
6e7c4025
IM
906 Simple two microseconds delay
907 none
908 No delay
b02aae9c 909
1da177e4
LT
910 io7= [HW] IO7 for Marvel based alpha systems
911 See comment before marvel_specify_io7 in
912 arch/alpha/kernel/core_marvel.c.
913
914 ip= [IP_PNP]
6ded55da 915 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
916
917 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
918 See comment before ip2_setup() in
919 drivers/char/ip2/ip2base.c.
1da177e4
LT
920
921 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
922 See header of drivers/scsi/ips.c.
923
72c4a13a
SH
924 ports= [IP_VS_FTP] IPVS ftp helper module
925 Default is 21.
926 Up to 8 (IP_VS_APP_MAX_PORTS) ports
927 may be specified.
928 Format: <port>,<port>....
929
200803df
AC
930 irqfixup [HW]
931 When an interrupt is not handled search all handlers
932 for it. Intended to get systems with badly broken
933 firmware running.
934
935 irqpoll [HW]
936 When an interrupt is not handled search all handlers
937 for it. Also check all handlers each timer
938 interrupt. Intended to get systems with badly broken
939 firmware running.
940
1da177e4 941 isapnp= [ISAPNP]
a9913044 942 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
943
944 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
945 Format:
946 <cpu number>,...,<cpu number>
947 or
948 <cpu number>-<cpu number> (must be a positive range in ascending order)
949 or a mixture
950 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
951 This option can be used to specify one or more CPUs
952 to isolate from the general SMP balancing and scheduling
953 algorithms. The only way to move a process onto or off
954 an "isolated" CPU is via the CPU affinity syscalls.
955 <cpu number> begins at 0 and the maximum value is
956 "number of CPUs in system - 1".
957
958 This option is the preferred way to isolate CPUs. The
a9913044
RD
959 alternative -- manually setting the CPU mask of all
960 tasks in the system -- can cause problems and
961 suboptimal load balancer performance.
1da177e4 962
a9913044 963 iucv= [HW,NET]
1da177e4
LT
964
965 js= [HW,JOY] Analog joystick
966 See Documentation/input/joystick.txt.
967
cd4f0ef7 968 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
969 specifies the amount of memory usable by the kernel
970 for non-movable allocations. The requested amount is
971 spread evenly throughout all nodes in the system. The
972 remaining memory in each node is used for Movable
973 pages. In the event, a node is too small to have both
974 kernelcore and Movable pages, kernelcore pages will
975 take priority and other nodes will have a larger number
976 of kernelcore pages. The Movable zone is used for the
977 allocation of pages that may be reclaimed or moved
978 by the page migration subsystem. This means that
979 HugeTLB pages may not be allocated from this zone.
980 Note that allocations like PTEs-from-HighMem still
981 use the HighMem zone if it exists, and the Normal
982 zone if it does not.
983
cd4f0ef7 984 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
985 is similar to kernelcore except it specifies the
986 amount of memory used for migratable allocations.
987 If both kernelcore and movablecore is specified,
988 then kernelcore will be at *least* the specified
989 value but may be more. If movablecore on its own
990 is specified, the administrator must be careful
991 that the amount of memory usable for all allocations
992 is not too small.
993
1da177e4
LT
994 keepinitrd [HW,ARM]
995
cd4f0ef7 996 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
997 in oops dumps.
998
6cdf6e06
JW
999 kgdboc= [HW] kgdb over consoles.
1000 Requires a tty driver that supports console polling.
1001 (only serial suported for now)
1002 Format: <serial_device>[,baud]
1003
1da177e4
LT
1004 l2cr= [PPC]
1005
a78bfbfc
RB
1006 l3cr= [PPC]
1007
cd4f0ef7 1008 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1009 disabled it.
1da177e4 1010
cd4f0ef7 1011 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
1012 C2 power state.
1013
fcb71f6f
FC
1014 libata.dma= [LIBATA] DMA control
1015 libata.dma=0 Disable all PATA and SATA DMA
1016 libata.dma=1 PATA and SATA Disk DMA only
1017 libata.dma=2 ATAPI (CDROM) DMA only
1018 libata.dma=4 Compact Flash DMA only
1019 Combinations also work, so libata.dma=3 enables DMA
1020 for disks and CDROMs, but not CFs.
1021
78e70c23
DJ
1022 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1023 when set.
1024 Format: <int>
1025
33267325
TH
1026 libata.force= [LIBATA] Force configurations. The format is comma
1027 separated list of "[ID:]VAL" where ID is
1028 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1029 matching port, link or device. Basically, it matches
1030 the ATA ID string printed on console by libata. If
1031 the whole ID part is omitted, the last PORT and DEVICE
1032 values are used. If ID hasn't been specified yet, the
1033 configuration applies to all ports, links and devices.
1034
1035 If only DEVICE is omitted, the parameter applies to
1036 the port and all links and devices behind it. DEVICE
1037 number of 0 either selects the first device or the
1038 first fan-out link behind PMP device. It does not
1039 select the host link. DEVICE number of 15 selects the
1040 host link and device attached to it.
1041
1042 The VAL specifies the configuration to force. As long
1043 as there's no ambiguity shortcut notation is allowed.
1044 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1045 The following configurations can be forced.
1046
1047 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1048 Any ID with matching PORT is used.
1049
1050 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1051
1052 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1053 udma[/][16,25,33,44,66,100,133] notation is also
1054 allowed.
1055
1056 * [no]ncq: Turn on or off NCQ.
1057
1058 If there are multiple matching configurations changing
1059 the same attribute, the last one is used.
1060
1da177e4
LT
1061 load_ramdisk= [RAM] List of ramdisks to load from floppy
1062 See Documentation/ramdisk.txt.
1063
a6b25b67
RD
1064 lockd.nlm_grace_period=P [NFS] Assign grace period.
1065 Format: <integer>
1da177e4 1066
a6b25b67
RD
1067 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1068 Format: <integer>
1069
1070 lockd.nlm_timeout=T [NFS] Assign timeout value.
1071 Format: <integer>
1072
1073 lockd.nlm_udpport=M [NFS] Assign UDP port.
1074 Format: <integer>
1da177e4
LT
1075
1076 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1077 Format: <irq>
1078
1079 loglevel= All Kernel Messages with a loglevel smaller than the
1080 console loglevel will be printed to the console. It can
1081 also be changed with klogd or other programs. The
1082 loglevels are defined as follows:
1083
1084 0 (KERN_EMERG) system is unusable
1085 1 (KERN_ALERT) action must be taken immediately
1086 2 (KERN_CRIT) critical conditions
1087 3 (KERN_ERR) error conditions
1088 4 (KERN_WARNING) warning conditions
1089 5 (KERN_NOTICE) normal but significant condition
1090 6 (KERN_INFO) informational
1091 7 (KERN_DEBUG) debug-level messages
1092
1093 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1094 Format: { n | nk | nM }
1095 n must be a power of two. The default size
1096 is set in the kernel config file.
1da177e4 1097
accaa24c
RD
1098 logo.nologo [FB] Disables display of the built-in Linux logo.
1099 This may be used to provide more screen space for
1100 kernel log messages and is useful when debugging
1101 kernel boot problems.
1102
1da177e4
LT
1103 lp=0 [LP] Specify parallel ports to use, e.g,
1104 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1105 lp=reset first parallel port). 'lp=0' disables the
1106 lp=auto printer driver. 'lp=reset' (which can be
1107 specified in addition to the ports) causes
1108 attached printers to be reset. Using
1109 lp=port1,port2,... specifies the parallel ports
1110 to associate lp devices with, starting with
1111 lp0. A port specification may be 'none' to skip
1112 that lp device, or a parport name such as
1113 'parport0'. Specifying 'lp=auto' instead of a
1114 port specification list means that device IDs
1115 from each port should be examined, to see if
1116 an IEEE 1284-compliant printer is attached; if
1117 so, the driver will manage that printer.
1118 See also header of drivers/char/lp.c.
1119
1120 lpj=n [KNL]
1121 Sets loops_per_jiffy to given constant, thus avoiding
1122 time-consuming boot-time autodetection (up to 250 ms per
1123 CPU). 0 enables autodetection (default). To determine
1124 the correct value for your kernel, boot with normal
1125 autodetection and see what value is printed. Note that
1126 on SMP systems the preset will be applied to all CPUs,
1127 which is likely to cause problems if your CPUs need
1128 significantly divergent settings. An incorrect value
1129 will cause delays in the kernel to be wrong, leading to
1130 unpredictable I/O errors and other breakage. Although
1131 unlikely, in the extreme case this might damage your
1132 hardware.
1133
1134 ltpc= [NET]
1135 Format: <io>,<irq>,<dma>
1136
a9913044
RD
1137 mac5380= [HW,SCSI] Format:
1138 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1139
a9913044
RD
1140 machvec= [IA64] Force the use of a particular machine-vector
1141 (machvec) in a generic kernel.
1142 Example: machvec=hpzx1_swiotlb
1da177e4 1143
a9913044 1144 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1145 be mounted
1146 Format: <1-256>
1147
1148 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1149 should make use of. maxcpus=n : n >= 0 limits the
1150 kernel to using 'n' processors. n=0 is a special case,
1151 it is equivalent to "nosmp", which also disables
1152 the IO APIC.
1da177e4 1153
2b2c3750
BP
1154 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1155 equal to this physical address is ignored.
1156
a9913044 1157 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1158 Should be between 1 and 2^32-1.
1159
1160 max_report_luns=
a9913044 1161 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1162 Should be between 1 and 16384.
1163
1da177e4
LT
1164 mcatest= [IA-64]
1165
cd4f0ef7 1166 mce [X86-32] Machine Check Exception
1da177e4 1167
909dd324
AK
1168 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1169
1da177e4
LT
1170 md= [HW] RAID subsystems devices and level
1171 See Documentation/md.txt.
a9913044 1172
1da177e4
LT
1173 mdacon= [MDA]
1174 Format: <first>,<last>
1175 Specifies range of consoles to be captured by the MDA.
a9913044 1176
1da177e4
LT
1177 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1178 Amount of memory to be used when the kernel is not able
1179 to see the whole system memory or for test.
cd4f0ef7 1180 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1181 address space collisions. Without memmap= PCI devices
1182 could be placed at addresses belonging to unused RAM.
1183
cd4f0ef7 1184 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1185 memory.
1186
cd4f0ef7 1187 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1188 E820 memory map, as specified by the user.
1189 Such memmap=exactmap lines can be constructed based on
1190 BIOS output or other requirements. See the memmap=nn@ss
1191 option description.
1192
1193 memmap=nn[KMG]@ss[KMG]
1194 [KNL] Force usage of a specific region of memory
1195 Region of memory to be used, from ss to ss+nn.
1196
1197 memmap=nn[KMG]#ss[KMG]
1198 [KNL,ACPI] Mark specific memory as ACPI data.
1199 Region of memory to be used, from ss to ss+nn.
1200
1201 memmap=nn[KMG]$ss[KMG]
1202 [KNL,ACPI] Mark specific memory as reserved.
1203 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1204 Example: Exclude memory from 0x18690000-0x1869ffff
1205 memmap=64K$0x18690000
1206 or
1207 memmap=0x10000$0x18690000
1da177e4 1208
caadbdce 1209 memtest= [KNL,X86] Enable memtest
c64df707
YL
1210 Format: <integer>
1211 range: 0,4 : pattern number
1212 default : 0 <disable>
1213
1da177e4
LT
1214 meye.*= [HW] Set MotionEye Camera parameters
1215 See Documentation/video4linux/meye.txt.
1216
8f36881b
AS
1217 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1218 Multi-Function General Purpose Timers on AMD Geode
1219 platforms.
1220
e6c4dc6c
WT
1221 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1222 the BIOS has incorrectly applied a workaround. TinyBIOS
1223 version 0.98 is known to be affected, 0.99 fixes the
1224 problem by letting the user disable the workaround.
1225
1da177e4
LT
1226 mga= [HW,DRM]
1227
1228 mousedev.tap_time=
1229 [MOUSE] Maximum time between finger touching and
1230 leaving touchpad surface for touch to be considered
1231 a tap and be reported as a left button click (for
1232 touchpads working in absolute mode only).
1233 Format: <msecs>
1234 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1235 reporting absolute coordinates, such as tablets
1236 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1237 reporting absolute coordinates, such as tablets
1238
1239 mpu401= [HW,OSS]
1240 Format: <io>,<irq>
1241
1242 MTD_Partition= [MTD]
1243 Format: <name>,<region-number>,<size>,<offset>
1244
a9913044
RD
1245 MTD_Region= [MTD] Format:
1246 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1247
1248 mtdparts= [MTD]
c8facbb6 1249 See drivers/mtd/cmdlinepart.c.
1da177e4 1250
9db829f4
BD
1251 mtdset= [ARM]
1252 ARM/S3C2412 JIVE boot control
1253
1254 See arch/arm/mach-s3c2412/mach-jive.c
1255
1da177e4 1256 mtouchusb.raw_coordinates=
a9913044
RD
1257 [HW] Make the MicroTouch USB driver use raw coordinates
1258 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1259
1260 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1261
1262 NCR_D700= [HW,SCSI]
1263 See header of drivers/scsi/NCR_D700.c.
1264
1265 ncr5380= [HW,SCSI]
1266
1267 ncr53c400= [HW,SCSI]
1268
1269 ncr53c400a= [HW,SCSI]
1270
1271 ncr53c406a= [HW,SCSI]
1272
1273 ncr53c8xx= [HW,SCSI]
1274
1275 netdev= [NET] Network devices parameters
1276 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1277 Note that mem_start is often overloaded to mean
1278 something different and driver-specific.
a9913044
RD
1279 This usage is only documented in each driver source
1280 file if at all.
1281
58401572
KPO
1282 nf_conntrack.acct=
1283 [NETFILTER] Enable connection tracking flow accounting
1284 0 to disable accounting
1285 1 to enable accounting
1286 Default value depends on CONFIG_NF_CT_ACCT that is
1287 going to be removed in 2.6.29.
1288
1da177e4 1289 nfsaddrs= [NFS]
6ded55da 1290 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1291
1292 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1293 See Documentation/filesystems/nfsroot.txt.
1da177e4 1294
a72b4422
TM
1295 nfs.callback_tcpport=
1296 [NFS] set the TCP port on which the NFSv4 callback
1297 channel should listen.
1298
58df095b
TM
1299 nfs.idmap_cache_timeout=
1300 [NFS] set the maximum lifetime for idmapper cache
1301 entries.
1302
f43bf0be
TM
1303 nfs.enable_ino64=
1304 [NFS] enable 64-bit inode numbers.
1305 If zero, the NFS client will fake up a 32-bit inode
1306 number for the readdir() and stat() syscalls instead
1307 of returning the full 64-bit number.
1308 The default is to return 64-bit inode numbers.
1309
e7ba176b
HS
1310 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1311 when a NMI is triggered.
1312 Format: [state][,regs][,debounce][,die]
1313
cd4f0ef7 1314 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1315
cd4f0ef7 1316 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1317 emulation library even if a 387 maths coprocessor
1318 is present.
1319
c1aee215
CL
1320 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1321 caches in the slab allocator. Saves per-node memory,
1322 but will impact performance.
3395ee05 1323
a9913044
RD
1324 noalign [KNL,ARM]
1325
1da177e4
LT
1326 noapic [SMP,APIC] Tells the kernel to not make use of any
1327 IOAPICs that may be present in the system.
1328
1da177e4
LT
1329 nobats [PPC] Do not use BATs for mapping kernel lowmem
1330 on "Classic" PPC cores.
1331
1332 nocache [ARM]
a9913044 1333
163ecdff
SN
1334 nodelayacct [KNL] Disable per-task delay accounting
1335
1da177e4
LT
1336 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1337
8b2cb7a8
HY
1338 noefi [X86-32,X86-64] Disable EFI runtime services support.
1339
1da177e4
LT
1340 noexec [IA-64]
1341
cd4f0ef7 1342 noexec [X86-32,X86-64]
f5a1b191 1343 On X86-32 available only on PAE configured kernels.
1da177e4 1344 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1345 noexec=off: disable non-executable mappings
1346
1347 noexec32 [X86-64]
1348 This affects only 32-bit executables.
1349 noexec32=on: enable non-executable mappings (default)
1350 read doesn't imply executable mappings
1351 noexec32=off: disable non-executable mappings
1352 read implies executable mappings
1da177e4 1353
cd4f0ef7 1354 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1355 register save and restore. The kernel will only save
1356 legacy floating-point registers on task switch.
1da177e4 1357
191679fd
AK
1358 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1359
1da177e4 1360 nohlt [BUGS=ARM]
a9913044 1361
cd4f0ef7 1362 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1363 instruction doesn't work correctly and not to
1364 use it.
1365
1366 nohalt [IA-64] Tells the kernel not to use the power saving
1367 function PAL_HALT_LIGHT when idle. This increases
1368 power-consumption. On the positive side, it reduces
1369 interrupt wake-up latency, which may improve performance
1370 in certain environments such as networked servers or
1371 real-time systems.
1372
79bf2bb3
TG
1373 nohz= [KNL] Boottime enable/disable dynamic ticks
1374 Valid arguments: on, off
1375 Default: on
1376
cd4f0ef7 1377 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1378
cd4f0ef7 1379 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1380 disable unhandled interrupt sources.
1381
cd4f0ef7 1382 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1383 broken timer IRQ sources.
1384
1da177e4
LT
1385 noisapnp [ISAPNP] Disables ISA PnP code.
1386
1387 noinitrd [RAM] Tells the kernel not to load any configured
1388 initial RAM disk.
1389
1390 nointroute [IA-64]
1391
0aa366f3
TL
1392 nojitter [IA64] Disables jitter checking for ITC timers.
1393
cd4f0ef7 1394 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1395
cd4f0ef7 1396 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1397
1da177e4
LT
1398 noltlbs [PPC] Do not use large page/tlb entries for kernel
1399 lowmem mapping on PPC40x.
1400
312f1f01
H
1401 nomca [IA-64] Disable machine check abort handling
1402
cd4f0ef7 1403 nomce [X86-32] Machine Check Exception
abe37e5a 1404
83d7384f
AS
1405 nomfgpt [X86-32] Disable Multi-Function General Purpose
1406 Timer usage (for AMD Geode machines).
1407
cd4f0ef7 1408 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1409
cd4f0ef7 1410 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1411 with UP alternatives
1412
1da177e4
LT
1413 noresidual [PPC] Don't use residual data on PReP machines.
1414
a9913044
RD
1415 noresume [SWSUSP] Disables resume and restores original swap
1416 space.
1417
1da177e4
LT
1418 no-scroll [VGA] Disables scrollback.
1419 This is required for the Braillex ib80-piezo Braille
1420 reader made by F.H. Papenmeier (Germany).
1421
1422 nosbagart [IA-64]
1423
cd4f0ef7 1424 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1425
61ec7567
LB
1426 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1427 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1428
97842216
DJ
1429 nosoftlockup [KNL] Disable the soft-lockup detector.
1430
1da177e4
LT
1431 nosync [HW,M68K] Disables sync negotiation for all devices.
1432
cd4f0ef7 1433 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1434
1435 nousb [USB] Disable the USB subsystem
1436
1437 nowb [ARM]
a9913044 1438
a6c75b86
FY
1439 nptcg= [IA64] Override max number of concurrent global TLB
1440 purges which is reported from either PAL_VM_SUMMARY or
1441 SAL PALO.
1442
f0c0b2b8
KH
1443 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1444 one of ['zone', 'node', 'default'] can be specified
1445 This can be set from sysctl after boot.
1446 See Documentation/sysctl/vm.txt for details.
1447
a61c2d78
DJ
1448 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1449
3ef0e1f8
AS
1450 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1451 Rather than timing out after 20 ms if an EC
1452 command is not properly ACKed, override the length
1453 of the timeout. We have interrupts disabled while
1454 waiting for the ACK, so if this is set too high
1455 interrupts *may* be lost!
1456
1da177e4
LT
1457 opl3= [HW,OSS]
1458 Format: <io>
1459
1da177e4
LT
1460 oprofile.timer= [HW]
1461 Use timer interrupt instead of performance counters
1462
1da177e4
LT
1463 osst= [HW,SCSI] SCSI Tape Driver
1464 Format: <buffer_size>,<write_threshold>
1465 See also Documentation/scsi/st.txt.
1466
1467 panic= [KNL] Kernel behaviour on panic
1468 Format: <timeout>
1469
1470 parkbd.port= [HW] Parallel port number the keyboard adapter is
1471 connected to, default is 0.
1472 Format: <parport#>
1473 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1474 0 for XT, 1 for AT (default is AT).
a9913044
RD
1475 Format: <mode>
1476
1477 parport= [HW,PPT] Specify parallel ports. 0 disables.
1478 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1479 Use 'auto' to force the driver to use any
1480 IRQ/DMA settings detected (the default is to
1481 ignore detected IRQ/DMA settings because of
1482 possible conflicts). You can specify the base
1483 address, IRQ, and DMA settings; IRQ and DMA
1484 should be numbers, or 'auto' (for using detected
1485 settings on that particular port), or 'nofifo'
1486 (to avoid using a FIFO even if it is detected).
1487 Parallel ports are assigned in the order they
1488 are specified on the command line, starting
1489 with parport0.
1490
1491 parport_init_mode= [HW,PPT]
1492 Configure VIA parallel port to operate in
1493 a specific mode. This is necessary on Pegasos
1494 computer where firmware has no options for setting
1495 up parallel port mode and sets it to spp.
1496 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1497 Format: [spp|ps2|epp|ecp|ecpepp]
1498
a9913044
RD
1499 pas2= [HW,OSS] Format:
1500 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1501
1da177e4
LT
1502 pas16= [HW,SCSI]
1503 See header of drivers/scsi/pas16.c.
1504
dd287796
AM
1505 pause_on_oops=
1506 Halt all CPUs after the first oops has been printed for
1507 the specified number of seconds. This is to be used if
1508 your oopses keep scrolling off the screen.
1509
1da177e4
LT
1510 pcbit= [HW,ISDN]
1511
1512 pcd. [PARIDE]
1513 See header of drivers/block/paride/pcd.c.
1514 See also Documentation/paride.txt.
1515
a9913044 1516 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1517 off [X86-32] don't probe for the PCI bus
1518 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1519 the hardware directly. Use this if your machine
1520 has a non-standard PCI host bridge.
cd4f0ef7 1521 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1522 hardware access methods are allowed. Use this
1523 if you experience crashes upon bootup and you
1524 suspect they are caused by the BIOS.
cd4f0ef7 1525 conf1 [X86-32] Force use of PCI Configuration
a9913044 1526 Mechanism 1.
cd4f0ef7 1527 conf2 [X86-32] Force use of PCI Configuration
a9913044 1528 Mechanism 2.
7f785763
RD
1529 noaer [PCIE] If the PCIEAER kernel config parameter is
1530 enabled, this kernel boot option can be used to
1531 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1532 nodomains [PCI] Disable support for multiple PCI
1533 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1534 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1535 Configuration
309e57df
MW
1536 nomsi [MSI] If the PCI_MSI kernel config parameter is
1537 enabled, this kernel boot option can be used to
1538 disable the use of MSI interrupts system-wide.
cd4f0ef7 1539 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1540 routing table. These calls are known to be buggy
1541 on several machines and they hang the machine
1542 when used, but on other computers it's the only
1543 way to get the interrupt routing table. Try
1544 this option if the kernel is unable to allocate
1545 IRQs or discover secondary PCI buses on your
1546 motherboard.
cd4f0ef7 1547 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1548 Use with caution as certain devices share
1549 address decoders between ROMs and other
1550 resources.
bb71ad88
GH
1551 norom [X86-32,X86_64] Do not assign address space to
1552 expansion ROMs that do not already have
1553 BIOS assigned address ranges.
cd4f0ef7 1554 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1555 assigned automatically to PCI devices. You can
1556 make the kernel exclude IRQs of your ISA cards
1557 this way.
cd4f0ef7 1558 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1559 of the PIRQ table (normally generated
1560 by the BIOS) if it is outside the
1561 F0000h-100000h range.
cd4f0ef7 1562 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1563 useful if the kernel is unable to find your
1564 secondary buses and you want to tell it
1565 explicitly which ones they are.
cd4f0ef7 1566 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1567 numbers ourselves, overriding
1568 whatever the firmware may have done.
cd4f0ef7 1569 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1570 in the BIOS $PIR table. This is needed on
1571 some systems with broken BIOSes, notably
1572 some HP Pavilion N5400 and Omnibook XE3
1573 notebooks. This will have no effect if ACPI
1574 IRQ routing is enabled.
cd4f0ef7 1575 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1576 or for PCI scanning.
62f420f8
GH
1577 use_crs [X86-32] Use _CRS for PCI resource
1578 allocation.
a9913044
RD
1579 routeirq Do IRQ routing for all PCI devices.
1580 This is normally done in pci_enable_device(),
1581 so this option is a temporary workaround
1582 for broken drivers that don't call it.
13a6ddb0
YL
1583 skip_isa_align [X86] do not align io start addr, so can
1584 handle more pci cards
a9913044
RD
1585 firmware [ARM] Do not re-enumerate the bus but instead
1586 just use the configuration from the
1587 bootloader. This is currently used on
1588 IXP2000 systems where the bus has to be
1589 configured a certain way for adjunct CPUs.
0637a70a
AK
1590 noearly [X86] Don't do any early type 1 scanning.
1591 This might help on some broken boards which
1592 machine check when some devices' config space
1593 is read. But various workarounds are disabled
1594 and some IOMMU drivers will not work.
6b4b78fe
MD
1595 bfsort Sort PCI devices into breadth-first order.
1596 This sorting is done to get a device
1597 order compatible with older (<= 2.4) kernels.
1598 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1599 cbiosize=nn[KMG] The fixed amount of bus space which is
1600 reserved for the CardBus bridge's IO window.
1601 The default value is 256 bytes.
1602 cbmemsize=nn[KMG] The fixed amount of bus space which is
1603 reserved for the CardBus bridge's memory
1604 window. The default value is 64 megabytes.
6b4b78fe 1605
1da177e4
LT
1606 pcmv= [HW,PCMCIA] BadgePAD 4
1607
1608 pd. [PARIDE]
1609 See Documentation/paride.txt.
1610
1611 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1612 boot time.
1613 Format: { 0 | 1 }
1614 See arch/parisc/kernel/pdc_chassis.c
1615
1616 pf. [PARIDE]
1617 See Documentation/paride.txt.
1618
1619 pg. [PARIDE]
1620 See Documentation/paride.txt.
1621
1622 pirq= [SMP,APIC] Manual mp-table setup
1623 See Documentation/i386/IO-APIC.txt.
1624
1625 plip= [PPT,NET] Parallel port network link
1626 Format: { parport<nr> | timid | 0 }
1627 See also Documentation/parport.txt.
1628
de32a243
TG
1629 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1630 Override pmtimer IOPort with a hex value.
1631 e.g. pmtmr=0x508
1632
1da177e4
LT
1633 pnpacpi= [ACPI]
1634 { off }
1635
1636 pnpbios= [ISAPNP]
1637 { on | off | curr | res | no-curr | no-res }
1638
1639 pnp_reserve_irq=
1640 [ISAPNP] Exclude IRQs for the autoconfiguration
1641
1642 pnp_reserve_dma=
1643 [ISAPNP] Exclude DMAs for the autoconfiguration
1644
1645 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1646 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1647
1648 pnp_reserve_mem=
a9913044
RD
1649 [ISAPNP] Exclude memory regions for the
1650 autoconfiguration.
1da177e4
LT
1651 Ranges are in pairs (memory base and size).
1652
45807a1d
IM
1653 print-fatal-signals=
1654 [KNL] debug: print fatal signals
1655 print-fatal-signals=1: print segfault info to
1656 the kernel console.
1657 default: off.
1658
e84845c4
RD
1659 printk.time= Show timing data prefixed to each printk message line
1660 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1661
1da177e4 1662 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1663 Format: [schedule,]<number>
1664 Param: "schedule" - profile schedule points.
1665 Param: <number> - step/bucket size as a power of 2 for
1666 statistical time based profiling.
b3da2a73
MG
1667 Param: "sleep" - profile D-state sleeping (millisecs).
1668 Requires CONFIG_SCHEDSTATS
c0fe2e69 1669 Param: "kvm" - profile VM exits.
1da177e4 1670
a9913044 1671 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1672 Limit processor to maximum C-state
1673 max_cstate=9 overrides any DMI blacklist limit.
1674
41c0d868
LB
1675 processor.nocst [HW,ACPI]
1676 Ignore the _CST method to determine C-states,
1677 instead using the legacy FADT method
1678
1da177e4
LT
1679 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1680 before loading.
1681 See Documentation/ramdisk.txt.
1682
a9913044
RD
1683 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1684 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1685 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1686 per second.
a9913044
RD
1687 psmouse.resetafter= [HW,MOUSE]
1688 Try to reset the device after so many bad packets
1da177e4
LT
1689 (0 = never).
1690 psmouse.resolution=
1691 [HW,MOUSE] Set desired mouse resolution, in dpi.
1692 psmouse.smartscroll=
a9913044 1693 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1694 0 = disabled, 1 = enabled (default).
1695
1696 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1697 Format:
1698 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1699
1700 pt. [PARIDE]
1701 See Documentation/paride.txt.
1702
dc8c8587
KS
1703 pty.legacy_count=
1704 [KNL] Number of legacy pty's. Overwrites compiled-in
1705 default number.
1706
7d2c502f 1707 quiet [KNL] Disable most log messages
a9913044 1708
1da177e4
LT
1709 r128= [HW,DRM]
1710
1711 raid= [HW,RAID]
1712 See Documentation/md.txt.
1713
a9913044 1714 ramdisk_blocksize= [RAM]
1da177e4 1715 See Documentation/ramdisk.txt.
a9913044 1716
1da177e4 1717 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1718 See Documentation/ramdisk.txt.
1719
24aaef8d
RD
1720 rcupdate.blimit= [KNL,BOOT]
1721 Set maximum number of finished RCU callbacks to process
1722 in one batch.
21a1ea9e 1723
24aaef8d
RD
1724 rcupdate.qhimark= [KNL,BOOT]
1725 Set threshold of queued
21a1ea9e
DS
1726 RCU callbacks over which batch limiting is disabled.
1727
24aaef8d
RD
1728 rcupdate.qlowmark= [KNL,BOOT]
1729 Set threshold of queued RCU callbacks below which
1730 batch limiting is re-enabled.
21a1ea9e 1731
ffdfc409
OJ
1732 rdinit= [KNL]
1733 Format: <full_path>
1734 Run specified binary instead of /init from the ramdisk,
1735 used for early userspace startup. See initrd.
1736
cd4f0ef7 1737 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1738 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1739 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 1740
46b6d94e
PJ
1741 relax_domain_level=
1742 [KNL, SMP] Set scheduler's default relax_domain_level.
1743 See Documentation/cpusets.txt.
1744
1da177e4
LT
1745 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1746
cd4f0ef7 1747 reservetop= [X86-32]
461a9aff
ZA
1748 Format: nn[KMG]
1749 Reserves a hole at the top of the kernel virtual
1750 address space.
1751
7e96287d
VG
1752 reset_devices [KNL] Force drivers to reset the underlying device
1753 during initialization.
1754
a9913044
RD
1755 resume= [SWSUSP]
1756 Specify the partition device for software suspend
1da177e4 1757
ecbd0da1
RW
1758 resume_offset= [SWSUSP]
1759 Specify the offset from the beginning of the partition
1760 given by "resume=" at which the swap header is located,
1761 in <PAGE_SIZE> units (needed only for swap files).
1762 See Documentation/power/swsusp-and-swap-files.txt
1763
0a7b35cb
MN
1764 retain_initrd [RAM] Keep initrd memory after extraction
1765
1da177e4
LT
1766 rhash_entries= [KNL,NET]
1767 Set number of hash buckets for route cache
1768
1769 riscom8= [HW,SERIAL]
1770 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1771
1772 ro [KNL] Mount root device read-only on boot
1773
1774 root= [KNL] Root filesystem
1775
1776 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1777 mount the root filesystem
1778
1779 rootflags= [KNL] Set root filesystem mount option string
1780
1781 rootfstype= [KNL] Set root filesystem type
1782
cc1ed754
PO
1783 rootwait [KNL] Wait (indefinitely) for root device to show up.
1784 Useful for devices that are detected asynchronously
1785 (e.g. USB and MMC devices).
1786
20510f2f
JM
1787 root_plug.vendor_id=
1788 [ROOTPLUG] Override the default vendor ID
1789
1790 root_plug.product_id=
1791 [ROOTPLUG] Override the default product ID
1792
1793 root_plug.debug=
1794 [ROOTPLUG] Enable debugging output
1795
1da177e4
LT
1796 rw [KNL] Mount root device read-write on boot
1797
1798 S [KNL] Run init in single mode
1799
1800 sa1100ir [NET]
1801 See drivers/net/irda/sa1100_ir.c.
1802
1da177e4 1803 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1804
1da177e4
LT
1805 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1806 Format: <io>[,<timeout>[,<isapnp>]]
1807
1808 scsi_debug_*= [SCSI]
1809 See drivers/scsi/scsi_debug.c.
1810
1811 scsi_default_dev_flags=
1812 [SCSI] SCSI default device flags
1813 Format: <integer>
1814
1815 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1816 Format: <vendor>:<model>:<flags>
1817 (flags are integer value)
1818
6af6632a
RD
1819 scsi_logging_level= [SCSI] a bit mask of logging levels
1820 See drivers/scsi/scsi_logging.h for bits. Also
1821 settable via sysctl at dev.scsi.logging_level
1822 (/proc/sys/dev/scsi/logging_level).
1823 There is also a nice 'scsi_logging_level' script in the
1824 S390-tools package, available for download at
1825 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1826
3e082a91
MW
1827 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1828 discovered. async scans them in kernel threads,
1829 allowing boot to proceed. none ignores them, expecting
1830 user space to do the scan.
1831
1da177e4
LT
1832 selinux [SELINUX] Disable or enable SELinux at boot time.
1833 Format: { "0" | "1" }
1834 See security/selinux/Kconfig help text.
1835 0 -- disable.
1836 1 -- enable.
1837 Default value is set via kernel config option.
1838 If enabled at boot time, /selinux/disable can be used
1839 later to disable prior to initial policy load.
1840
4e5ab4cb
JM
1841 selinux_compat_net =
1842 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1843 Format: { "0" | "1" }
1844 0 -- use new secmark-based packet controls
1845 1 -- use legacy packet controls
1846 Default value is 0 (preferred).
1847 Value can be changed at runtime via
1848 /selinux/compat_net.
4e5ab4cb 1849
cd4f0ef7 1850 serialnumber [BUGS=X86-32]
1da177e4 1851
1da177e4
LT
1852 shapers= [NET]
1853 Maximal number of shapers.
a9913044 1854
1da177e4
LT
1855 sim710= [SCSI,HW]
1856 See header of drivers/scsi/sim710.c.
1857
1858 simeth= [IA-64]
1859 simscsi=
a9913044 1860
1da177e4
LT
1861 slram= [HW,MTD]
1862
f0630fff
CL
1863 slub_debug[=options[,slabs]] [MM, SLUB]
1864 Enabling slub_debug allows one to determine the
1865 culprit if slab objects become corrupted. Enabling
1866 slub_debug can create guard zones around objects and
1867 may poison objects when not in use. Also tracks the
1868 last alloc / free. For more information see
1869 Documentation/vm/slub.txt.
c1aee215
CL
1870
1871 slub_max_order= [MM, SLUB]
f0630fff
CL
1872 Determines the maximum allowed order for slabs.
1873 A high setting may cause OOMs due to memory
1874 fragmentation. For more information see
1875 Documentation/vm/slub.txt.
c1aee215
CL
1876
1877 slub_min_objects= [MM, SLUB]
f0630fff
CL
1878 The minimum number of objects per slab. SLUB will
1879 increase the slab order up to slub_max_order to
1880 generate a sufficiently large slab able to contain
1881 the number of objects indicated. The higher the number
1882 of objects the smaller the overhead of tracking slabs
1883 and the less frequently locks need to be acquired.
c1aee215
CL
1884 For more information see Documentation/vm/slub.txt.
1885
1886 slub_min_order= [MM, SLUB]
1887 Determines the mininum page order for slabs. Must be
f0630fff 1888 lower than slub_max_order.
c1aee215
CL
1889 For more information see Documentation/vm/slub.txt.
1890
1891 slub_nomerge [MM, SLUB]
f0630fff 1892 Disable merging of slabs with similar size. May be
c1aee215 1893 necessary if there is some reason to distinguish
f0630fff
CL
1894 allocs to different slabs. Debug options disable
1895 merging on their own.
c1aee215
CL
1896 For more information see Documentation/vm/slub.txt.
1897
1da177e4
LT
1898 smart2= [HW]
1899 Format: <io1>[,<io2>[,...,<io8>]]
1900
cd4f0ef7 1901 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1902 attempt to substitute SMP alternatives once at boot.
1903
d0d4f69b
BH
1904 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1905 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1906 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1907 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1908 smsc-ircc2.ircc_irq= [HW] IRQ line
1909 smsc-ircc2.ircc_dma= [HW] DMA channel
1910 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1911 0: Toshiba Satellite 1800 (GP data pin select)
1912 1: Fast pin select (default)
1913 2: ATC IRMode
1914
1da177e4
LT
1915 snd-ad1816a= [HW,ALSA]
1916
1917 snd-ad1848= [HW,ALSA]
1918
1919 snd-ali5451= [HW,ALSA]
1920
1921 snd-als100= [HW,ALSA]
1922
1923 snd-als4000= [HW,ALSA]
1924
1925 snd-azt2320= [HW,ALSA]
1926
1927 snd-cmi8330= [HW,ALSA]
1928
1929 snd-cmipci= [HW,ALSA]
1930
1931 snd-cs4231= [HW,ALSA]
1932
1933 snd-cs4232= [HW,ALSA]
1934
1935 snd-cs4236= [HW,ALSA]
1936
1937 snd-cs4281= [HW,ALSA]
1938
1939 snd-cs46xx= [HW,ALSA]
1940
1941 snd-dt019x= [HW,ALSA]
1942
1943 snd-dummy= [HW,ALSA]
1944
1945 snd-emu10k1= [HW,ALSA]
1946
1947 snd-ens1370= [HW,ALSA]
1948
1949 snd-ens1371= [HW,ALSA]
1950
1951 snd-es968= [HW,ALSA]
1952
1953 snd-es1688= [HW,ALSA]
1954
1955 snd-es18xx= [HW,ALSA]
1956
1957 snd-es1938= [HW,ALSA]
1958
1959 snd-es1968= [HW,ALSA]
1960
1961 snd-fm801= [HW,ALSA]
1962
1963 snd-gusclassic= [HW,ALSA]
1964
1965 snd-gusextreme= [HW,ALSA]
1966
1967 snd-gusmax= [HW,ALSA]
1968
1969 snd-hdsp= [HW,ALSA]
1970
1971 snd-ice1712= [HW,ALSA]
1972
1973 snd-intel8x0= [HW,ALSA]
1974
1975 snd-interwave= [HW,ALSA]
1976
1977 snd-interwave-stb=
1978 [HW,ALSA]
1979
1980 snd-korg1212= [HW,ALSA]
1981
1982 snd-maestro3= [HW,ALSA]
1983
1984 snd-mpu401= [HW,ALSA]
1985
1986 snd-mtpav= [HW,ALSA]
1987
1988 snd-nm256= [HW,ALSA]
1989
1990 snd-opl3sa2= [HW,ALSA]
1991
1992 snd-opti92x-ad1848=
1993 [HW,ALSA]
1994
1995 snd-opti92x-cs4231=
1996 [HW,ALSA]
1997
1998 snd-opti93x= [HW,ALSA]
1999
2000 snd-pmac= [HW,ALSA]
2001
2002 snd-rme32= [HW,ALSA]
2003
2004 snd-rme96= [HW,ALSA]
2005
2006 snd-rme9652= [HW,ALSA]
2007
2008 snd-sb8= [HW,ALSA]
2009
2010 snd-sb16= [HW,ALSA]
2011
2012 snd-sbawe= [HW,ALSA]
2013
2014 snd-serial= [HW,ALSA]
2015
2016 snd-sgalaxy= [HW,ALSA]
2017
2018 snd-sonicvibes= [HW,ALSA]
2019
2020 snd-sun-amd7930=
2021 [HW,ALSA]
2022
2023 snd-sun-cs4231= [HW,ALSA]
2024
2025 snd-trident= [HW,ALSA]
2026
2027 snd-usb-audio= [HW,ALSA,USB]
2028
2029 snd-via82xx= [HW,ALSA]
2030
2031 snd-virmidi= [HW,ALSA]
2032
2033 snd-wavefront= [HW,ALSA]
2034
2035 snd-ymfpci= [HW,ALSA]
a9913044 2036
9c44bc03
IM
2037 softlockup_panic=
2038 [KNL] Should the soft-lockup detector generate panics.
2039
1da177e4
LT
2040 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2041 See Documentation/sonypi.txt
2042
2043 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2044 See Documentation/specialix.txt.
2045
2046 spia_io_base= [HW,MTD]
2047 spia_fio_base=
2048 spia_pedr=
2049 spia_peddr=
2050
2051 sscape= [HW,OSS]
2052 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2053
1da177e4
LT
2054 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2055 See Documentation/scsi/st.txt.
2056
1da177e4
LT
2057 sti= [PARISC,HW]
2058 Format: <num>
2059 Set the STI (builtin display/keyboard on the HP-PARISC
2060 machines) console (graphic card) which should be used
2061 as the initial boot-console.
2062 See also comment in drivers/video/console/sticore.c.
2063
2064 sti_font= [HW]
2065 See comment in drivers/video/console/sticore.c.
2066
2067 stifb= [HW]
2068 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2069
42a7fc4a
GB
2070 sunrpc.pool_mode=
2071 [NFS]
2072 Control how the NFS server code allocates CPUs to
2073 service thread pools. Depending on how many NICs
2074 you have and where their interrupts are bound, this
2075 option will affect which CPUs will do NFS serving.
2076 Note: this parameter cannot be changed while the
2077 NFS server is running.
2078
2079 auto the server chooses an appropriate mode
2080 automatically using heuristics
2081 global a single global pool contains all CPUs
2082 percpu one pool for each CPU
2083 pernode one pool for each NUMA node (equivalent
2084 to global on non-NUMA machines)
2085
1da177e4 2086 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2087
1da177e4
LT
2088 switches= [HW,M68k]
2089
2090 sym53c416= [HW,SCSI]
2091 See header of drivers/scsi/sym53c416.c.
2092
5d6f647f
IM
2093 sysrq_always_enabled
2094 [KNL]
2095 Ignore sysrq setting - this boot parameter will
2096 neutralize any effect of /proc/sys/kernel/sysrq.
2097 Useful for debugging.
2098
1da177e4
LT
2099 t128= [HW,SCSI]
2100 See header of drivers/scsi/t128.c.
2101
2102 tdfx= [HW,DRM]
2103
2104 thash_entries= [KNL,NET]
2105 Set number of hash buckets for TCP connection
2106
f8707ec9
LB
2107 thermal.act= [HW,ACPI]
2108 -1: disable all active trip points in all thermal zones
2109 <degrees C>: override all lowest active trip points
2110
c52a7419
LB
2111 thermal.crt= [HW,ACPI]
2112 -1: disable all critical trip points in all thermal zones
2113 <degrees C>: lower all critical trip points
2114
f5487145
LB
2115 thermal.nocrt= [HW,ACPI]
2116 Set to disable actions on ACPI thermal zone
2117 critical and hot trip points.
2118
72b33ef8
LB
2119 thermal.off= [HW,ACPI]
2120 1: disable ACPI thermal control
2121
a70cdc52
LB
2122 thermal.psv= [HW,ACPI]
2123 -1: disable all passive trip points
2124 <degrees C>: override all passive trip points to this value
2125
730ff34d
LB
2126 thermal.tzp= [HW,ACPI]
2127 Specify global default ACPI thermal zone polling rate
2128 <deci-seconds>: poll all this frequency
2129 0: no polling (default)
2130
1da177e4
LT
2131 tipar.timeout= [HW,PPT]
2132 Set communications timeout in tenths of a second
2133 (default 15).
2134
2135 tipar.delay= [HW,PPT]
2136 Set inter-bit delay in microseconds (default 10).
2137
1da177e4
LT
2138 tmscsim= [HW,SCSI]
2139 See comment before function dc390_setup() in
2140 drivers/scsi/tmscsim.c.
2141
2142 tp720= [HW,PS2]
2143
2144 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2145 Format:
2146 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2147
a9913044
RD
2148 turbografx.map[2|3]= [HW,JOY]
2149 TurboGraFX parallel port interface
2150 Format:
2151 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2152 See also Documentation/input/joystick-parport.txt
2153
2154 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2155 See header of drivers/scsi/u14-34f.c.
2156
2157 uart401= [HW,OSS]
2158 Format: <io>,<irq>
2159
2160 uart6850= [HW,OSS]
2161 Format: <io>,<irq>
2162
5f8364b7
AS
2163 uhci-hcd.ignore_oc=
2164 [USB] Ignore overcurrent events (default N).
2165 Some badly-designed motherboards generate lots of
2166 bogus events, for ports that aren't wired to
2167 anything. Set this parameter to avoid log spamming.
2168 Note that genuine overcurrent events won't be
2169 reported either.
2170
e3a61b0a
SA
2171 unknown_nmi_panic
2172 [X86-32,X86-64]
2173 Set unknown_nmi_panic=1 early on boot.
2174
b5e795f8
AS
2175 usbcore.autosuspend=
2176 [USB] The autosuspend time delay (in seconds) used
2177 for newly-detected USB devices (default 2). This
2178 is the time required before an idle device will be
2179 autosuspended. Devices for which the delay is set
eaafbc3a 2180 to a negative value won't be autosuspended at all.
b5e795f8 2181
1da177e4
LT
2182 usbhid.mousepoll=
2183 [USBHID] The interval which mice are to be polled at.
a9913044 2184
200001eb
PJ
2185 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2186 kernel's map of available physical RAM.
2187
cd4f0ef7 2188 vdso= [X86-32,SH,x86-64]
1dbf527c 2189 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2190 vdso=1: enable VDSO (default)
2191 vdso=0: disable VDSO mapping
2192
af65d648
RM
2193 vdso32= [X86-32,X86-64]
2194 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2195 vdso32=1: enable 32-bit VDSO (default)
2196 vdso32=0: disable 32-bit VDSO mapping
2197
d080d397
YI
2198 vector= [IA-64,SMP]
2199 vector=percpu: enable percpu vector domain
2200
1da177e4
LT
2201 video= [FB] Frame buffer configuration
2202 See Documentation/fb/modedb.txt.
2203
cd4f0ef7 2204 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2205 See Documentation/i386/boot.txt and
2206 Documentation/svga.txt.
1da177e4
LT
2207 Use vga=ask for menu.
2208 This is actually a boot loader parameter; the value is
2209 passed to the kernel using a special protocol.
2210
a9913044 2211 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2212 size of <nn>. This can be used to increase the
2213 minimum size (128MB on x86). It can also be used to
2214 decrease the size and leave more room for directly
2215 mapped kernel RAM.
2216
585c3047
PO
2217 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2218 Format: <command>
1da177e4 2219
585c3047
PO
2220 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2221 Format: <command>
2222
2223 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2224 Format: <command>
a9913044 2225
1da177e4
LT
2226 waveartist= [HW,OSS]
2227 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2228
1da177e4
LT
2229 wd33c93= [HW,SCSI]
2230 See header of drivers/scsi/wd33c93.c.
2231
2232 wd7000= [HW,SCSI]
2233 See header of drivers/scsi/wd7000.c.
2234
2235 wdt= [WDT] Watchdog
8dfe9c21 2236 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2237
2238 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2239 xd_geo= See header of drivers/block/xd.c.
2240
2241 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2242 Format:
2243 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2244
a62eaf15
AK
2245 norandmaps Don't use address space randomization
2246 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2247
a9913044 2248______________________________________________________________________
1da177e4
LT
2249
2250TODO:
2251
2252 Add documentation for ALSA options.
2253 Add more DRM drivers.