netfilter: xt_connbytes: Force CT accounting to be enabled
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / kernel-parameters.txt
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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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3
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
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20Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
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26This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
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33The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
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37
38 ACPI ACPI support is enabled.
c99c108a 39 AGP AGP (Accelerated Graphics Port) is enabled.
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40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
e7ba176b 43 AVR32 AVR32 architecture is enabled.
1da177e4 44 AX25 Appropriate AX.25 support is enabled.
0ae53640 45 BLACKFIN Blackfin architecture is enabled.
a9913044 46 DRM Direct Rendering Management support is enabled.
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47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
2521f2c2 51 GCOV GCOV profiling is enabled.
1da177e4 52 HW Appropriate hardware is enabled.
1da177e4 53 IA-64 IA-64 architecture is enabled.
6146f0d5 54 IMA Integrity measurement architecture is enabled.
1da177e4 55 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
b0f83b28 57 IPV6 IPv6 support is enabled.
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58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
84c08fd6 61 KGDB Kernel debugger support is enabled.
fef07aae 62 KVM Kernel Virtual Machine support is enabled.
11ef697b 63 LIBATA Libata driver is enabled
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64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
309e57df 72 MSI Message Signaled Interrupts (PCI).
c8facbb6 73 MTD MTD (Memory Technology Device) support is enabled.
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74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
734efb46 76 GENERIC_TIME The generic timeofday code is enabled.
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77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
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79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
7f785763 83 PCIE PCI Express support is enabled.
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84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers has their options described inside of
93 Documentation/scsi/.
20510f2f 94 SECURITY Different security models are enabled.
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95 SELINUX SELinux support is enabled.
96 SERIAL Serial support is enabled.
e523d93c 97 SH SuperH architecture is enabled.
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98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
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100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
f38f1d2a 102 FTRACE Function tracing enabled.
225a9be2 103 TPM TPM drivers are enabled.
1da177e4 104 TS Appropriate touchscreen support is enabled.
d4f373e5 105 UMS USB Mass Storage support is enabled.
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106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 113 X86-32 X86-32, aka i386 architecture is enabled.
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114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
71cced6e 116 Documentation/x86/x86_64/boot-options.txt .
c0115606 117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
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118
119In addition, the following text indicates that the option:
120
121 BUGS= Relates to possible processor bugs on the said processor.
122 KNL Is a kernel start-up parameter.
123 BOOT Is a boot loader parameter.
124
125Parameters denoted with BOOT are actually interpreted by the boot
126loader, and have no meaning to the kernel directly.
127Do not modify the syntax of boot loader parameters without extreme
954a8b81 128need or coordination with <Documentation/x86/boot.txt>.
1da177e4 129
5558870b 130There are also arch-specific kernel-parameters not documented here.
71cced6e 131See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 132
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133Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
134a trailing = on the name of any parameter states that that parameter will
135be entered as an environment variable, whereas its absence indicates that
136it will appear as a kernel argument readable via /proc/cmdline by programs
137running once the system is up.
138
9c4751fd 139The number of kernel parameters is not limited, but the length of the
140complete command line (parameters including spaces etc.) is limited to
141a fixed number of characters. This limit depends on the architecture
142and is between 256 and 4096 characters. It is defined in the file
143./include/asm/setup.h as COMMAND_LINE_SIZE.
144
145
6cececfc 146 acpi= [HW,ACPI,X86]
03d926f8 147 Advanced Configuration and Power Interface
68ca4069 148 Format: { force | off | strict | noirq | rsdt }
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149 force -- enable ACPI if default was off
150 off -- disable ACPI if default was on
151 noirq -- do not use ACPI for IRQ routing
a9913044 152 strict -- Be less tolerant of platforms that are not
1da177e4 153 strictly ACPI specification compliant.
237889bf 154 rsdt -- prefer RSDT over (default) XSDT
aa2110cb 155 copy_dsdt -- copy DSDT to memory
1da177e4 156
53471121 157 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 158
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159 acpi_apic_instance= [ACPI, IOAPIC]
160 Format: <int>
161 2: use 2nd APIC table, if available
162 1,0: use 1st APIC table
4e381a4f 163 default: 0
a1fdcc0d 164
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165 acpi_backlight= [HW,ACPI]
166 acpi_backlight=vendor
167 acpi_backlight=video
168 If set to vendor, prefer vendor specific driver
169 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
170 of the ACPI video.ko driver.
171
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172 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
173 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 174 Format: <int>
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175 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
176 debug output. Bits in debug_layer correspond to a
177 _COMPONENT in an ACPI source file, e.g.,
178 #define _COMPONENT ACPI_PCI_COMPONENT
179 Bits in debug_level correspond to a level in
180 ACPI_DEBUG_PRINT statements, e.g.,
181 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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182 The debug_level mask defaults to "info". See
183 Documentation/acpi/debug.txt for more information about
184 debug layers and levels.
a0d84a92 185
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186 Enable processor driver info messages:
187 acpi.debug_layer=0x20000000
188 Enable PCI/PCI interrupt routing info messages:
189 acpi.debug_layer=0x400000
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190 Enable AML "Debug" output, i.e., stores to the Debug
191 object while interpreting AML:
192 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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193 Enable all messages related to ACPI hardware:
194 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
195
196 Some values produce so much output that the system is
197 unusable. The "log_buf_len" parameter may be useful
198 if you need to capture more output.
f989106c 199
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200 acpi_display_output= [HW,ACPI]
201 acpi_display_output=vendor
202 acpi_display_output=video
203 See above.
204
205 acpi_irq_balance [HW,ACPI]
206 ACPI will balance active IRQs
207 default in APIC mode
208
209 acpi_irq_nobalance [HW,ACPI]
210 ACPI will not move active IRQs (default)
211 default in PIC mode
212
213 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
214 Format: <irq>,<irq>...
215
216 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
217 use by PCI
218 Format: <irq>,<irq>...
219
220 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
221
222 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
223 Format: To spoof as Windows 98: ="Microsoft Windows"
224
225 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
226 acpi_osi="string1" # add string1 -- only one string
227 acpi_osi="!string2" # remove built-in string2
228 acpi_osi= # disable all strings
229
6cececfc 230 acpi_pm_good [X86]
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231 Override the pmtimer bug detection: force the kernel
232 to assume that this machine's pmtimer latches its value
233 and always returns good values.
234
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235 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge | high | low }
237
238 acpi_serialize [HW,ACPI] force serialization of AML methods
239
240 acpi_skip_timer_override [HW,ACPI]
241 Recognize and ignore IRQ0/pin2 Interrupt Override.
242 For broken nForce2 BIOS resulting in XT-PIC timer.
243
244 acpi_sleep= [HW,ACPI] Sleep options
245 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
d7f0eea9 246 old_ordering, s4_nonvs, sci_force_enable }
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247 See Documentation/power/video.txt for information on
248 s3_bios and s3_mode.
249 s3_beep is for debugging; it makes the PC's speaker beep
250 as soon as the kernel's real-mode entry point is called.
251 s4_nohwsig prevents ACPI hardware signature from being
252 used during resume from hibernation.
253 old_ordering causes the ACPI 1.0 ordering of the _PTS
254 control method, with respect to putting devices into
255 low power states, to be enforced (the ACPI 2.0 ordering
256 of _PTS is used by default).
257 s4_nonvs prevents the kernel from saving/restoring the
258 ACPI NVS memory during hibernation.
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259 sci_force_enable causes the kernel to set SCI_EN directly
260 on resume from S1/S3 (which is against the ACPI spec,
261 but some broken systems don't work without it).
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262
263 acpi_use_timer_override [HW,ACPI]
264 Use timer override. For some broken Nvidia NF5 boards
265 that require a timer override, but don't have HPET
266
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267 acpi_enforce_resources= [ACPI]
268 { strict | lax | no }
269 Check for resource conflicts between native drivers
270 and ACPI OperationRegions (SystemIO and SystemMemory
271 only). IO ports and memory declared in ACPI might be
272 used by the ACPI subsystem in arbitrary AML code and
273 can interfere with legacy drivers.
274 strict (default): access to resources claimed by ACPI
275 is denied; legacy drivers trying to access reserved
276 resources will fail to bind to device using them.
277 lax: access to resources claimed by ACPI is allowed;
278 legacy drivers trying to access reserved resources
279 will bind successfully but a warning message is logged.
280 no: ACPI OperationRegions are not marked as reserved,
281 no further checks are performed.
282
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283 ad1848= [HW,OSS]
284 Format: <io>,<irq>,<dma>,<dma2>,<type>
285
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286 add_efi_memmap [EFI; X86] Include EFI memory map in
287 kernel's map of available physical RAM.
288
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289 advansys= [HW,SCSI]
290 See header of drivers/scsi/advansys.c.
291
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292 aedsp16= [HW,OSS] Audio Excel DSP 16
293 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
294 See also header of sound/oss/aedsp16.c.
a9913044 295
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296 agp= [AGP]
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
301
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302 aha152x= [HW,SCSI]
303 See Documentation/scsi/aha152x.txt.
304
305 aha1542= [HW,SCSI]
306 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
307
308 aic7xxx= [HW,SCSI]
309 See Documentation/scsi/aic7xxx.txt.
310
311 aic79xx= [HW,SCSI]
312 See Documentation/scsi/aic79xx.txt.
313
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314 alignment= [KNL,ARM]
315 Allow the default userspace alignment fault handler
316 behaviour to be specified. Bit 0 enables warnings,
317 bit 1 enables fixups, and bit 2 sends a segfault.
318
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319 amd_iommu= [HW,X86-84]
320 Pass parameters to the AMD IOMMU driver in the system.
321 Possible values are:
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322 fullflush - enable flushing of IO/TLB entries when
323 they are unmapped. Otherwise they are
324 flushed before they will be reused, which
325 is a lot of faster
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326 off - do not initialize any AMD IOMMU found in
327 the system
afa9fdc2 328
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329 amijoy.map= [HW,JOY] Amiga joystick support
330 Map of devices attached to JOY0DAT and JOY1DAT
331 Format: <a>,<b>
332 See also Documentation/kernel/input/joystick.txt
333
334 analog.map= [HW,JOY] Analog joystick and gamepad support
335 Specifies type or capabilities of an analog joystick
336 connected to one of 16 gameports
337 Format: <type1>,<type2>,..<type16>
338
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339 apc= [HW,SPARC]
340 Power management functions (SPARCstation-4/5 + deriv.)
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341 Format: noidle
342 Disable APC CPU standby support. SPARCstation-Fox does
343 not play well with APC CPU idle - disable it if you have
344 APC and your system crashes randomly.
345
ca1eda2d 346 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 347 Change the output verbosity whilst booting
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348 Format: { quiet (default) | verbose | debug }
349 Change the amount of debugging information output
350 when initialising the APIC and IO-APIC components.
a9913044 351
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352 autoconf= [IPV6]
353 See Documentation/networking/ipv6.txt.
354
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355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
363
1da177e4 364 apm= [APM] Advanced Power Management
71f77055 365 See header of arch/x86/kernel/apm_32.c.
1da177e4 366
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367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
369
370 ataflop= [HW,M68k]
371
372 atarimouse= [HW,MOUSE] Atari Mouse
373
374 atascsi= [HW,SCSI] Atari SCSI
375
376 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
377 EzKey and similar keyboards
378
379 atkbd.reset= [HW] Reset keyboard during initialization
380
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381 atkbd.set= [HW] Select keyboard code set
382 Format: <int> (2 = AT (default), 3 = PS/2)
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383
384 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
385 keyboards
386
387 atkbd.softraw= [HW] Choose between synthetic and real raw mode
388 Format: <bool> (0 = real, 1 = synthetic (default))
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389
390 atkbd.softrepeat= [HW]
391 Use software keyboard repeat
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392
393 autotest [IA64]
394
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395 baycom_epp= [HW,AX25]
396 Format: <io>,<mode>
a9913044 397
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398 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
399 Format: <io>,<mode>
400 See header of drivers/net/hamradio/baycom_par.c.
401
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402 baycom_ser_fdx= [HW,AX25]
403 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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404 Format: <io>,<irq>,<mode>[,<baud>]
405 See header of drivers/net/hamradio/baycom_ser_fdx.c.
406
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407 baycom_ser_hdx= [HW,AX25]
408 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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409 Format: <io>,<irq>,<mode>
410 See header of drivers/net/hamradio/baycom_ser_hdx.c.
411
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412 boot_delay= Milliseconds to delay each printk during boot.
413 Values larger than 10 seconds (10000) are changed to
414 no delay (0).
415 Format: integer
416
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417 bootmem_debug [KNL] Enable bootmem allocator debug messages.
418
1da177e4 419 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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420 bttv.radio= Most important insmod options are available as
421 kernel args too.
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422 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
423 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
424
425 BusLogic= [HW,SCSI]
426 See drivers/scsi/BusLogic.c, comment before function
427 BusLogic_ParseDriverOptions().
428
429 c101= [NET] Moxa C101 synchronous serial card
430
cd4f0ef7 431 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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432 Sometimes CPU hardware bugs make them report the cache
433 size incorrectly. The kernel will attempt work arounds
434 to fix known problems, but for some CPUs it is not
435 possible to determine what the correct size should be.
436 This option provides an override for these situations.
437
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438 capability.disable=
439 [SECURITY] Disable capabilities. This would normally
440 be used only if an alternative security model is to be
441 configured. Potentially dangerous and should only be
442 used if you are entirely sure of the consequences.
443
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444 ccw_timeout_log [S390]
445 See Documentation/s390/CommonIO for details.
1da177e4 446
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447 cgroup_disable= [KNL] Disable a particular controller
448 Format: {name of the controller(s) to disable}
449 {Currently supported controllers - "memory"}
450
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451 checkreqprot [SELINUX] Set initial checkreqprot flag value.
452 Format: { "0" | "1" }
453 See security/selinux/Kconfig help text.
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454 0 -- check protection applied by kernel (includes
455 any implied execute protection).
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456 1 -- check protection requested by application.
457 Default value is set via a kernel config option.
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458 Value can be changed at runtime via
459 /selinux/checkreqprot.
460
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461 cio_ignore= [S390]
462 See Documentation/s390/CommonIO for details.
463
cd4f0ef7 464 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 465 [Deprecated]
3f6dee9b 466 Forces specified clocksource (if available) to be used
734efb46 467 when calculating gettimeofday(). If specified
3f6dee9b 468 clocksource is not available, it defaults to PIT.
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469 Format: { pit | tsc | cyclone | pmtmr }
470
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471 clocksource= [GENERIC_TIME] Override the default clocksource
472 Format: <string>
473 Override the default clocksource and use the clocksource
474 with the name specified.
475 Some clocksource names to choose from, depending on
476 the platform:
477 [all] jiffies (this is the base, fallback clocksource)
478 [ACPI] acpi_pm
479 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
480 pxa_timer,timer3,32k_counter,timer0_1
481 [AVR32] avr32
cd4f0ef7 482 [X86-32] pit,hpet,tsc,vmi-timer;
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483 scx200_hrt on Geode; cyclone on IBM x440
484 [MIPS] MIPS
485 [PARISC] cr16
486 [S390] tod
487 [SH] SuperH
488 [SPARC64] tick
489 [X86-64] hpet,tsc
490
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491 clearcpuid=BITNUM [X86]
492 Disable CPUID feature X for the kernel. See
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493 arch/x86/include/asm/cpufeature.h for the valid bit
494 numbers. Note the Linux specific bits are not necessarily
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495 stable over kernel options, but the vendor specific
496 ones should be.
497 Also note that user programs calling CPUID directly
498 or using the feature without checking anything
499 will still see it. This just prevents it from
500 being used by the kernel or shown in /proc/cpuinfo.
501 Also note the kernel might malfunction if you disable
502 some critical bits.
503
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504 cmo_free_hint= [PPC] Format: { yes | no }
505 Specify whether pages are marked as being inactive
506 when they are freed. This is used in CMO environments
507 to determine OS memory pressure for page stealing by
508 a hypervisor.
509 Default: yes
510
6cececfc 511 code_bytes [X86] How many bytes of object code to print
a25bd949 512 in an oops report.
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513 Range: 0 - 8192
514 Default: 64
515
1da177e4 516 com20020= [HW,NET] ARCnet - COM20020 chipset
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517 Format:
518 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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519
520 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
521 Format: <io>[,<irq>]
522
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523 com90xx= [HW,NET]
524 ARCnet - COM90xx chipset (memory-mapped buffers)
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525 Format: <io>[,<irq>[,<memstart>]]
526
527 condev= [HW,S390] console device
528 conmode=
a9913044 529
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530 console= [KNL] Output console device and options.
531
532 tty<n> Use the virtual console device <n>.
533
534 ttyS<n>[,options]
f1a1c2dc 535 ttyUSB0[,options]
1da177e4 536 Use the specified serial port. The options are of
f1a1c2dc
RD
537 the form "bbbbpnf", where "bbbb" is the baud rate,
538 "p" is parity ("n", "o", or "e"), "n" is number of
539 bits, and "f" is flow control ("r" for RTS or
540 omit it). Default is "9600n8".
541
542 See Documentation/serial-console.txt for more
543 information. See
544 Documentation/networking/netconsole.txt for an
545 alternative.
1da177e4 546
18a8bd94
YL
547 uart[8250],io,<addr>[,options]
548 uart[8250],mmio,<addr>[,options]
1da177e4
LT
549 Start an early, polled-mode console on the 8250/16550
550 UART at the specified I/O port or MMIO address,
551 switching to the matching ttyS device later. The
552 options are the same as for ttyS, above.
553
f7511d5f
ST
554 If the device connected to the port is not a TTY but a braille
555 device, prepend "brl," before the device type, for instance
556 console=brl,ttyS0
557 For now, only VisioBraille is supported.
558
f324edc8
DM
559 consoleblank= [KNL] The console blank (screen saver) timeout in
560 seconds. Defaults to 10*60 = 10mins. A value of 0
561 disables the blank timer.
562
4cb0e11b
HK
563 coredump_filter=
564 [KNL] Change the default value for
565 /proc/<pid>/coredump_filter.
566 See also Documentation/filesystems/proc.txt.
567
1da177e4 568 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
569 Format:
570 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 571
dc009d92
EB
572 crashkernel=nn[KMG]@ss[KMG]
573 [KNL] Reserve a chunk of physical memory to
574 hold a kernel to switch to with kexec on panic.
575
fb391599
BW
576 crashkernel=range1:size1[,range2:size2,...][@offset]
577 [KNL] Same as above, but depends on the memory
578 in the running system. The syntax of range is
579 start-[end] where start and end are both
580 a memory unit (amount[KMG]). See also
581 Documentation/kdump/kdump.txt for a example.
582
1da177e4
LT
583 cs89x0_dma= [HW,NET]
584 Format: <dma>
585
586 cs89x0_media= [HW,NET]
587 Format: { rj45 | aui | bnc }
a9913044 588
a9913044 589 dasd= [HW,NET]
1da177e4
LT
590 See header of drivers/s390/block/dasd_devmap.c.
591
592 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
593 (one device per port)
594 Format: <port#>,<type>
595 See also Documentation/input/joystick-parport.txt
596
597 debug [KNL] Enable kernel debugging (events log level).
598
cae2ed9a
IM
599 debug_locks_verbose=
600 [KNL] verbose self-tests
601 Format=<0|1>
602 Print debugging info while doing the locking API
603 self-tests.
604 We default to 0 (no extra messages), setting it to
605 1 will print _a lot_ more information - normally
606 only useful to kernel developers.
607
3ac7fe5a
TG
608 debug_objects [KNL] Enable object debugging
609
3e8ebb5c
KM
610 no_debug_objects
611 [KNL] Disable object debugging
612
d3af01f1
TG
613 debugpat [X86] Enable PAT debugging
614
2d27a966 615 decnet.addr= [HW,NET]
1da177e4
LT
616 Format: <area>[,<node>]
617 See also Documentation/networking/decnet.txt.
618
0cb55ad2
RD
619 default_hugepagesz=
620 [same as hugepagesz=] The size of the default
621 HugeTLB page size. This is the size represented by
622 the legacy /proc/ hugepages APIs, used for SHM, and
623 default size when mounting hugetlbfs filesystems.
624 Defaults to the default architecture's huge page size
625 if not specified.
55ff9780 626
1da177e4
LT
627 dhash_entries= [KNL]
628 Set number of hash buckets for dentry cache.
a9913044 629
1da177e4
LT
630 digi= [HW,SERIAL]
631 IO parameters + enable/disable command.
632
633 digiepca= [HW,SERIAL]
634 See drivers/char/README.epca and
31c00fc1 635 Documentation/serial/digiepca.txt.
1da177e4 636
b0f83b28
BH
637 disable= [IPV6]
638 See Documentation/networking/ipv6.txt.
639
640 disable_ipv6= [IPV6]
641 See Documentation/networking/ipv6.txt.
642
95ffa243 643 disable_mtrr_cleanup [X86]
95ffa243
YL
644 The kernel tries to adjust MTRR layout from continuous
645 to discrete, to make X server driver able to add WB
0cb55ad2 646 entry later. This parameter disables that.
95ffa243 647
093af8d7 648 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
649 By default the kernel will trim any uncacheable
650 memory out of your available memory pool based on
651 MTRR settings. This parameter disables that behavior,
652 possibly causing your machine to run very slowly.
653
6cececfc 654 disable_timer_pin_1 [X86]
0cb55ad2
RD
655 Disable PIN 1 of APIC timer
656 Can be useful to work around chipset bugs.
657
1da177e4
LT
658 dmasound= [HW,OSS] Sound subsystem buffers
659
0cb55ad2
RD
660 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
661 this option disables the debugging code at boot.
662
663 dma_debug_entries=<number>
664 This option allows to tune the number of preallocated
665 entries for DMA-API debugging code. One entry is
666 required per DMA-API allocation. Use this if the
667 DMA-API debugging code disables itself because the
668 architectural default is too low.
669
1745de5e
JR
670 dma_debug_driver=<driver_name>
671 With this option the DMA-API debugging driver
672 filter feature can be enabled at boot time. Just
673 pass the driver to filter for as the parameter.
674 The filter can be disabled or changed to another
675 driver later using sysfs.
676
1da177e4
LT
677 dscc4.setup= [NET]
678
679 dtc3181e= [HW,SCSI]
680
0cb55ad2
RD
681 dynamic_printk Enables pr_debug()/dev_dbg() calls if
682 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
683 These can also be switched on/off via
684 <debugfs>/dynamic_printk/modules
685
686 earlycon= [KNL] Output early console device and options.
687 uart[8250],io,<addr>[,options]
688 uart[8250],mmio,<addr>[,options]
689 Start an early, polled-mode console on the 8250/16550
690 UART at the specified I/O port or MMIO address.
691 The options are the same as for ttyS, above.
692
6cececfc 693 earlyprintk= [X86,SH,BLACKFIN]
1da177e4
LT
694 earlyprintk=vga
695 earlyprintk=serial[,ttySn[,baudrate]]
ea3acb19 696 earlyprintk=ttySn[,baudrate]
9780bc41 697 earlyprintk=dbgp[debugController#]
1da177e4 698
a9913044 699 Append ",keep" to not disable it when the real console
1da177e4
LT
700 takes over.
701
5c05917e 702 Only vga or serial or usb debug port at a time.
1da177e4
LT
703
704 Currently only ttyS0 and ttyS1 are supported.
705
706 Interaction with the standard serial driver is not
707 very good.
708
709 The VGA output is eventually overwritten by the real
710 console.
711
9731191f
JW
712 ekgdboc= [X86,KGDB] Allow early kernel console debugging
713 ekgdboc=kbd
714
715 This is desgined to be used in conjunction with
716 the boot argument: earlyprintk=vga
717
1da177e4
LT
718 eata= [HW,SCSI]
719
1da177e4 720 edd= [EDD]
8c4dd606 721 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 722
1da177e4
LT
723 eisa_irq_edge= [PARISC,HW]
724 See header of drivers/parisc/eisa.c.
725
cd4f0ef7 726 elanfreq= [X86-32]
1da177e4 727 See comment before function elanfreq_setup() in
71f77055 728 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
729
730 elevator= [IOSCHED]
16ab3adf 731 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
732 See Documentation/block/as-iosched.txt and
733 Documentation/block/deadline-iosched.txt for details.
734
6cececfc 735 elfcorehdr= [IA64,PPC,SH,X86]
a9913044 736 Specifies physical address of start of kernel core
aac04b32
VG
737 image elf header. Generally kexec loader will
738 pass this option to capture kernel.
739 See Documentation/kdump/kdump.txt for details.
1da177e4 740
0cb55ad2
RD
741 enable_mtrr_cleanup [X86]
742 The kernel tries to adjust MTRR layout from continuous
743 to discrete, to make X server driver able to add WB
744 entry later. This parameter enables that.
745
ca1eda2d 746 enable_timer_pin_1 [X86]
0cb55ad2
RD
747 Enable PIN 1 of APIC timer
748 Can be useful to work around chipset bugs
749 (in particular on some ATI chipsets).
750 The kernel tries to set a reasonable default.
751
1da177e4
LT
752 enforcing [SELINUX] Set initial enforcing status.
753 Format: {"0" | "1"}
754 See security/selinux/Kconfig help text.
755 0 -- permissive (log only, no denials).
756 1 -- enforcing (deny and log).
757 Default value is 0.
758 Value can be changed at runtime via /selinux/enforce.
759
a08f82d0
HY
760 erst_disable [ACPI]
761 Disable Error Record Serialization Table (ERST)
762 support.
763
1da177e4
LT
764 ether= [HW,NET] Ethernet cards parameters
765 This option is obsoleted by the "netdev=" option, which
766 has equivalent usage. See its documentation for details.
767
de1ba09b
AM
768 failslab=
769 fail_page_alloc=
770 fail_make_request=[KNL]
771 General fault injection mechanism.
772 Format: <interval>,<probability>,<space>,<times>
773 See also /Documentation/fault-injection/.
774
1da177e4
LT
775 fd_mcs= [HW,SCSI]
776 See header of drivers/scsi/fd_mcs.c.
777
778 fdomain= [HW,SCSI]
779 See header of drivers/scsi/fdomain.c.
780
781 floppy= [HW]
31c00fc1 782 See Documentation/blockdev/floppy.txt.
1da177e4 783
f13ae30e
AC
784 force_pal_cache_flush
785 [IA-64] Avoid check_sal_cache_flush which may hang on
786 buggy SAL_CACHE_FLUSH implementations. Using this
787 parameter will force ia64_sal_cache_flush to call
788 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
789
d9e54076 790 ftrace=[tracer]
2af15d6a 791 [FTRACE] will set and start the specified tracer
d9e54076
PZ
792 as early as possible in order to facilitate early
793 boot debugging.
794
cecbca96 795 ftrace_dump_on_oops[=orig_cpu]
2af15d6a 796 [FTRACE] will dump the trace buffers on oops.
cecbca96
FW
797 If no parameter is passed, ftrace will dump
798 buffers of all CPUs, but if you pass orig_cpu, it will
799 dump only the buffer of the CPU that triggered the
800 oops.
2af15d6a
SR
801
802 ftrace_filter=[function-list]
803 [FTRACE] Limit the functions traced by the function
804 tracer at boot up. function-list is a comma separated
805 list of functions. This list can be changed at run
806 time by the set_ftrace_filter file in the debugfs
807 tracing directory.
808
809 ftrace_notrace=[function-list]
810 [FTRACE] Do not trace the functions specified in
811 function-list. This list can be changed at run time
812 by the set_ftrace_notrace file in the debugfs
813 tracing directory.
d9e54076 814
369bc18f
SA
815 ftrace_graph_filter=[function-list]
816 [FTRACE] Limit the top level callers functions traced
817 by the function graph tracer at boot up.
818 function-list is a comma separated list of functions
819 that can be changed at run time by the
820 set_graph_function file in the debugfs tracing directory.
821
1da177e4
LT
822 gamecon.map[2|3]=
823 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
824 support via parallel port (up to 5 devices per port)
825 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
826 See also Documentation/input/joystick-parport.txt
827
828 gamma= [HW,DRM]
829
aaf23042
YL
830 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
831 Format: off | on
832 default: on
833
2521f2c2
PO
834 gcov_persist= [GCOV] When non-zero (default), profiling data for
835 kernel modules is saved and remains accessible via
836 debugfs, even when the module is unloaded/reloaded.
837 When zero, profiling data is discarded and associated
838 debugfs files are removed at module unload time.
839
1da177e4
LT
840 gdth= [HW,SCSI]
841 See header of drivers/scsi/gdth.c.
842
843 gpt [EFI] Forces disk with valid GPT signature but
844 invalid Protective MBR to be treated as GPT.
845
1da177e4
LT
846 gvp11= [HW,SCSI]
847
848 hashdist= [KNL,NUMA] Large hashes allocated during boot
849 are distributed across NUMA nodes. Defaults on
429aa0fc 850 for 64bit NUMA, off otherwise.
a9913044 851 Format: 0 | 1 (for off | on)
1da177e4
LT
852
853 hcl= [IA-64] SGI's Hardware Graph compatibility layer
854
855 hd= [EIDE] (E)IDE hard drive subsystem geometry
856 Format: <cyl>,<head>,<sect>
857
ea8c071c
HY
858 hest_disable [ACPI]
859 Disable Hardware Error Source Table (HEST) support;
860 corresponding firmware-first mode error processing
861 logic will be disabled.
862
1da177e4
LT
863 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
864 size of <nn>. This works even on boxes that have no
865 highmem otherwise. This also works to reduce highmem
866 size on bigger boxes.
867
54cdfdb4
TG
868 highres= [KNL] Enable/disable high resolution timer mode.
869 Valid parameters: "on", "off"
870 Default: "on"
871
1da177e4
LT
872 hisax= [HW,ISDN]
873 See Documentation/isdn/README.HiSax.
874
0cb55ad2
RD
875 hlt [BUGS=ARM,SH]
876
877 hpet= [X86-32,HPET] option to control HPET usage
878 Format: { enable (default) | disable | force |
879 verbose }
880 disable: disable HPET and use PIT instead
881 force: allow force enabled of undocumented chips (ICH4,
882 VIA, nVidia)
883 verbose: show contents of HPET registers during setup
884
b4718e62
AK
885 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
886 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
887 On x86-64 and powerpc, this option can be specified
888 multiple times interleaved with hugepages= to reserve
889 huge pages of different sizes. Valid pages sizes on
890 x86-64 are 2M (when the CPU supports "pse") and 1G
891 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
892 Note that 1GB pages can only be allocated at boot time
893 using hugepages= and not freed afterwards.
6902aa84 894
555d61d6
HB
895 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
896 terminal devices. Valid values: 0..8
431429ff
HB
897 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
898 If specified, z/VM IUCV HVC accepts connections
899 from listed z/VM user IDs only.
cef7125d 900
3a853fb9 901 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
902 or register an additional I2C bus that is not
903 registered from board initialization code.
3a853fb9
JN
904 Format:
905 <bus_id>,<clkrate>
906
36d95739 907 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 908 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
909 i8042.dumbkbd [HW] Pretend that controller can only read data from
910 keyboard and cannot control its state
1da177e4
LT
911 (Don't attempt to blink the leds)
912 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 913 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
914 i8042.noloop [HW] Disable the AUX Loopback command while probing
915 for the AUX port
1da177e4
LT
916 i8042.nomux [HW] Don't check presence of an active multiplexing
917 controller
918 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
919 controllers
920 i8042.panicblink=
921 [HW] Frequency with which keyboard LEDs should blink
922 when kernel panics (default is 0.5 sec)
923 i8042.reset [HW] Reset the controller during init and cleanup
924 i8042.unlock [HW] Unlock (ignore) the keylock
925
926 i810= [HW,DRM]
927
e70c9d5e
DT
928 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
929 indicates that the driver is running on unsupported
930 hardware.
1da177e4
LT
931 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
932 does not match list of supported models.
933 i8k.power_status
934 [HW] Report power status in /proc/i8k
935 (disabled by default)
936 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
937 capability is set.
938
939 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
940 See Documentation/mca.txt.
941
942 icn= [HW,ISDN]
943 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
944
0af80c04
DF
945 ide-core.nodma= [HW] (E)IDE subsystem
946 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
075affcb
BZ
947 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
948 .cdrom .chs .ignore_cable are additional options
1c10e938 949 See Documentation/ide/ide.txt.
1da177e4 950
0cb55ad2
RD
951 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
952 Claim all unknown PCI IDE storage controllers.
953
f039b754 954 idle= [X86]
ada9cfdd
RD
955 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
956 Poll forces a polling idle loop that can slightly
957 improve the performance of waking up a idle CPU, but
958 will use a lot of power and make the system run hot.
959 Not recommended.
960 idle=mwait: On systems which support MONITOR/MWAIT but
961 the kernel chose to not use it because it doesn't save
962 as much power as a normal idle loop, use the
963 MONITOR/MWAIT idle loop anyways. Performance should be
964 the same as idle=poll.
965 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 966 In such case C2/C3 won't be used again.
ada9cfdd 967 idle=nomwait: Disable mwait for CPU C-states
a9913044 968
79290822
IM
969 ignore_loglevel [KNL]
970 Ignore loglevel setting - this will print /all/
971 kernel messages to the console. Useful for debugging.
972
1da177e4
LT
973 ihash_entries= [KNL]
974 Set number of hash buckets for inode cache.
975
3323eec9
MZ
976 ima_audit= [IMA]
977 Format: { "0" | "1" }
978 0 -- integrity auditing messages. (Default)
979 1 -- enable informational integrity auditing messages.
980
981 ima_hash= [IMA]
a9ed83a5 982 Format: { "sha1" | "md5" }
3323eec9
MZ
983 default: "sha1"
984
5789ba3b
EP
985 ima_tcb [IMA]
986 Load a policy which meets the needs of the Trusted
987 Computing Base. This means IMA will measure all
988 programs exec'd, files mmap'd for exec, and all files
989 opened for read by uid=0.
990
1da177e4
LT
991 in2000= [HW,SCSI]
992 See header of drivers/scsi/in2000.c.
993
994 init= [KNL]
995 Format: <full_path>
996 Run specified binary instead of /sbin/init as init
997 process.
998
999 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1000 for working out where the kernel is dying during
1001 startup.
1002
1003 initrd= [BOOT] Specify the location of the initial ramdisk
1004
1005 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1006 Format: <irq>
1007
ba395927 1008 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
1009 on
1010 Enable intel iommu driver.
ba395927
KA
1011 off
1012 Disable intel iommu driver.
1013 igfx_off [Default Off]
1014 By default, gfx is mapped as normal device. If a gfx
1015 device has a dedicated DMAR unit, the DMAR unit is
1016 bypassed by not enabling DMAR with this option. In
1017 this case, gfx device will use physical address for
1018 DMA.
7d3b03ce
KA
1019 forcedac [x86_64]
1020 With this option iommu will not optimize to look
1021 for io virtual address below 32 bit forcing dual
1022 address cycle on pci bus for cards supporting greater
1023 than 32 bit addressing. The default is to look
1024 for translation below 32 bit and if not available
1025 then look in the higher range.
5e0d2a6f 1026 strict [Default Off]
1027 With this option on every unmap_single operation will
1028 result in a hardware IOTLB flush operation as opposed
1029 to batching them for performance.
ba395927 1030
0cb55ad2
RD
1031 inttest= [IA64]
1032
1033 iomem= Disable strict checking of access to MMIO memory
1034 strict regions from userspace.
1035 relaxed
1036
1037 iommu= [x86]
1038 off
1039 force
1040 noforce
1041 biomerge
1042 panic
1043 nopanic
1044 merge
1045 nomerge
1046 forcesac
1047 soft
4ed0d3e6 1048 pt [x86, IA64]
0cb55ad2
RD
1049
1050 io7= [HW] IO7 for Marvel based alpha systems
1051 See comment before marvel_specify_io7 in
1052 arch/alpha/kernel/core_marvel.c.
1053
6cececfc 1054 io_delay= [X86] I/O delay method
6e7c4025
IM
1055 0x80
1056 Standard port 0x80 based delay
1057 0xed
1058 Alternate port 0xed based delay (needed on some systems)
b02aae9c 1059 udelay
6e7c4025
IM
1060 Simple two microseconds delay
1061 none
1062 No delay
b02aae9c 1063
1da177e4 1064 ip= [IP_PNP]
dc7a0816 1065 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1066
1067 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
1068 See comment before ip2_setup() in
1069 drivers/char/ip2/ip2base.c.
1da177e4
LT
1070
1071 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1072 See header of drivers/scsi/ips.c.
1073
200803df
AC
1074 irqfixup [HW]
1075 When an interrupt is not handled search all handlers
1076 for it. Intended to get systems with badly broken
1077 firmware running.
1078
1079 irqpoll [HW]
1080 When an interrupt is not handled search all handlers
1081 for it. Also check all handlers each timer
1082 interrupt. Intended to get systems with badly broken
1083 firmware running.
1084
1da177e4 1085 isapnp= [ISAPNP]
a9913044 1086 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1087
1088 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1089 Format:
1090 <cpu number>,...,<cpu number>
1091 or
b225d44e
LZ
1092 <cpu number>-<cpu number>
1093 (must be a positive range in ascending order)
22f2e280
DF
1094 or a mixture
1095 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1096
1da177e4
LT
1097 This option can be used to specify one or more CPUs
1098 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1099 algorithms. You can move a process onto or off an
1100 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1101 <cpu number> begins at 0 and the maximum value is
1102 "number of CPUs in system - 1".
1103
1104 This option is the preferred way to isolate CPUs. The
a9913044
RD
1105 alternative -- manually setting the CPU mask of all
1106 tasks in the system -- can cause problems and
1107 suboptimal load balancer performance.
1da177e4 1108
a9913044 1109 iucv= [HW,NET]
1da177e4
LT
1110
1111 js= [HW,JOY] Analog joystick
1112 See Documentation/input/joystick.txt.
1113
0cb55ad2
RD
1114 keepinitrd [HW,ARM]
1115
6cececfc 1116 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1117 specifies the amount of memory usable by the kernel
1118 for non-movable allocations. The requested amount is
1119 spread evenly throughout all nodes in the system. The
1120 remaining memory in each node is used for Movable
1121 pages. In the event, a node is too small to have both
1122 kernelcore and Movable pages, kernelcore pages will
1123 take priority and other nodes will have a larger number
1124 of kernelcore pages. The Movable zone is used for the
1125 allocation of pages that may be reclaimed or moved
1126 by the page migration subsystem. This means that
1127 HugeTLB pages may not be allocated from this zone.
1128 Note that allocations like PTEs-from-HighMem still
1129 use the HighMem zone if it exists, and the Normal
1130 zone if it does not.
1131
4fe1da4e
JW
1132 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1133 Format: <Controller#>[,poll interval]
1134 The controller # is the number of the ehci usb debug
1135 port as it is probed via PCI. The poll interval is
1136 optional and is the number seconds in between
1137 each poll cycle to the debug port in case you need
1138 the functionality for interrupting the kernel with
1139 gdb or control-c on the dbgp connection. When
1140 not using this parameter you use sysrq-g to break into
1141 the kernel debugger.
1142
84c08fd6 1143 kgdboc= [KGDB,HW] kgdb over consoles.
ada64e4c
JW
1144 Requires a tty driver that supports console polling,
1145 or a supported polling keyboard driver (non-usb).
1146 Serial only format: <serial_device>[,baud]
1147 keyboard only format: kbd
1148 keyboard and serial format: kbd,<serial_device>[,baud]
6cdf6e06 1149
84c08fd6
JW
1150 kgdbwait [KGDB] Stop kernel execution and enter the
1151 kernel debugger at the earliest opportunity.
1152
9bed90c6
FF
1153 kmac= [MIPS] korina ethernet MAC address.
1154 Configure the RouterBoard 532 series on-chip
1155 Ethernet adapter MAC address.
1156
04f70336
CM
1157 kmemleak= [KNL] Boot-time kmemleak enable/disable
1158 Valid arguments: on, off
1159 Default: on
1160
6cececfc 1161 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1162 in oops dumps.
1163
fef07aae
AP
1164 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1165 Default is 0 (don't ignore, but inject #GP)
1166
1167 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1168 Default is 1 (enabled)
1169
1170 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1171 Default is 0 (off)
1172
1173 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1174 for all guests.
1175 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1176
1177 kvm-intel.bypass_guest_pf=
1178 [KVM,Intel] Disables bypassing of guest page faults
1179 on Intel chips. Default is 1 (enabled)
1180
1181 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1182 (virtualized MMU) support on capable Intel chips.
1183 Default is 1 (enabled)
1184
1185 kvm-intel.emulate_invalid_guest_state=
1186 [KVM,Intel] Enable emulation of invalid guest states
1187 Default is 0 (disabled)
1188
1189 kvm-intel.flexpriority=
1190 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1191 Default is 1 (enabled)
1192
1193 kvm-intel.unrestricted_guest=
1194 [KVM,Intel] Disable unrestricted guest feature
1195 (virtualized real and unpaged mode) on capable
1196 Intel chips. Default is 1 (enabled)
1197
1198 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1199 feature (tagged TLBs) on capable Intel chips.
1200 Default is 1 (enabled)
1201
1da177e4
LT
1202 l2cr= [PPC]
1203
a78bfbfc
RB
1204 l3cr= [PPC]
1205
cd4f0ef7 1206 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1207 disabled it.
1da177e4 1208
6cececfc 1209 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1210 in C2 power state.
e585bef8 1211
fcb71f6f
FC
1212 libata.dma= [LIBATA] DMA control
1213 libata.dma=0 Disable all PATA and SATA DMA
1214 libata.dma=1 PATA and SATA Disk DMA only
1215 libata.dma=2 ATAPI (CDROM) DMA only
1216 libata.dma=4 Compact Flash DMA only
1217 Combinations also work, so libata.dma=3 enables DMA
1218 for disks and CDROMs, but not CFs.
20308871
MP
1219
1220 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1221 libata.ignore_hpa=0 keep BIOS limits (default)
1222 libata.ignore_hpa=1 ignore limits, using full disk
fcb71f6f 1223
78e70c23
DJ
1224 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1225 when set.
1226 Format: <int>
1227
33267325
TH
1228 libata.force= [LIBATA] Force configurations. The format is comma
1229 separated list of "[ID:]VAL" where ID is
4c44f309 1230 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
33267325
TH
1231 matching port, link or device. Basically, it matches
1232 the ATA ID string printed on console by libata. If
1233 the whole ID part is omitted, the last PORT and DEVICE
1234 values are used. If ID hasn't been specified yet, the
1235 configuration applies to all ports, links and devices.
1236
1237 If only DEVICE is omitted, the parameter applies to
1238 the port and all links and devices behind it. DEVICE
1239 number of 0 either selects the first device or the
1240 first fan-out link behind PMP device. It does not
1241 select the host link. DEVICE number of 15 selects the
1242 host link and device attached to it.
1243
1244 The VAL specifies the configuration to force. As long
1245 as there's no ambiguity shortcut notation is allowed.
1246 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1247 The following configurations can be forced.
1248
1249 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1250 Any ID with matching PORT is used.
1251
1252 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1253
1254 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1255 udma[/][16,25,33,44,66,100,133] notation is also
1256 allowed.
1257
1258 * [no]ncq: Turn on or off NCQ.
1259
05944bdf
TH
1260 * nohrst, nosrst, norst: suppress hard, soft
1261 and both resets.
1262
43c9c591
TH
1263 * dump_id: dump IDENTIFY data.
1264
33267325
TH
1265 If there are multiple matching configurations changing
1266 the same attribute, the last one is used.
1267
7c4be253
RD
1268 lmb=debug [KNL] Enable lmb debug messages.
1269
1da177e4 1270 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1271 See Documentation/blockdev/ramdisk.txt.
1da177e4 1272
a6b25b67
RD
1273 lockd.nlm_grace_period=P [NFS] Assign grace period.
1274 Format: <integer>
1da177e4 1275
a6b25b67
RD
1276 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1277 Format: <integer>
1278
1279 lockd.nlm_timeout=T [NFS] Assign timeout value.
1280 Format: <integer>
1281
1282 lockd.nlm_udpport=M [NFS] Assign UDP port.
1283 Format: <integer>
1da177e4
LT
1284
1285 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1286 Format: <irq>
1287
1288 loglevel= All Kernel Messages with a loglevel smaller than the
1289 console loglevel will be printed to the console. It can
1290 also be changed with klogd or other programs. The
1291 loglevels are defined as follows:
1292
1293 0 (KERN_EMERG) system is unusable
1294 1 (KERN_ALERT) action must be taken immediately
1295 2 (KERN_CRIT) critical conditions
1296 3 (KERN_ERR) error conditions
1297 4 (KERN_WARNING) warning conditions
1298 5 (KERN_NOTICE) normal but significant condition
1299 6 (KERN_INFO) informational
1300 7 (KERN_DEBUG) debug-level messages
1301
1302 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1303 Format: { n | nk | nM }
1304 n must be a power of two. The default size
1305 is set in the kernel config file.
1da177e4 1306
accaa24c
RD
1307 logo.nologo [FB] Disables display of the built-in Linux logo.
1308 This may be used to provide more screen space for
1309 kernel log messages and is useful when debugging
1310 kernel boot problems.
1311
1da177e4
LT
1312 lp=0 [LP] Specify parallel ports to use, e.g,
1313 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1314 lp=reset first parallel port). 'lp=0' disables the
1315 lp=auto printer driver. 'lp=reset' (which can be
1316 specified in addition to the ports) causes
1317 attached printers to be reset. Using
1318 lp=port1,port2,... specifies the parallel ports
1319 to associate lp devices with, starting with
1320 lp0. A port specification may be 'none' to skip
1321 that lp device, or a parport name such as
1322 'parport0'. Specifying 'lp=auto' instead of a
1323 port specification list means that device IDs
1324 from each port should be examined, to see if
1325 an IEEE 1284-compliant printer is attached; if
1326 so, the driver will manage that printer.
1327 See also header of drivers/char/lp.c.
1328
1329 lpj=n [KNL]
1330 Sets loops_per_jiffy to given constant, thus avoiding
1331 time-consuming boot-time autodetection (up to 250 ms per
1332 CPU). 0 enables autodetection (default). To determine
1333 the correct value for your kernel, boot with normal
1334 autodetection and see what value is printed. Note that
1335 on SMP systems the preset will be applied to all CPUs,
1336 which is likely to cause problems if your CPUs need
1337 significantly divergent settings. An incorrect value
1338 will cause delays in the kernel to be wrong, leading to
1339 unpredictable I/O errors and other breakage. Although
1340 unlikely, in the extreme case this might damage your
1341 hardware.
1342
1343 ltpc= [NET]
1344 Format: <io>,<irq>,<dma>
1345
a9913044
RD
1346 mac5380= [HW,SCSI] Format:
1347 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1348
a9913044
RD
1349 machvec= [IA64] Force the use of a particular machine-vector
1350 (machvec) in a generic kernel.
1351 Example: machvec=hpzx1_swiotlb
1da177e4 1352
3209e70e
WZ
1353 machtype= [Loongson] Share the same kernel image file between different
1354 yeeloong laptop.
1355 Example: machtype=lemote-yeeloong-2f-7inch
1356
0cb55ad2
RD
1357 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1358 than or equal to this physical address is ignored.
1da177e4
LT
1359
1360 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1361 should make use of. maxcpus=n : n >= 0 limits the
1362 kernel to using 'n' processors. n=0 is a special case,
1363 it is equivalent to "nosmp", which also disables
1364 the IO APIC.
1da177e4 1365
0cb55ad2
RD
1366 max_loop= [LOOP] Maximum number of loopback devices that can
1367 be mounted
1368 Format: <1-256>
2b2c3750 1369
a9913044 1370 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1371 Should be between 1 and 2^32-1.
1372
1373 max_report_luns=
a9913044 1374 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1375 Should be between 1 and 16384.
1376
1da177e4
LT
1377 mcatest= [IA-64]
1378
cd4f0ef7 1379 mce [X86-32] Machine Check Exception
1da177e4 1380
71cced6e 1381 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1382
1da177e4
LT
1383 md= [HW] RAID subsystems devices and level
1384 See Documentation/md.txt.
a9913044 1385
1da177e4
LT
1386 mdacon= [MDA]
1387 Format: <first>,<last>
1388 Specifies range of consoles to be captured by the MDA.
a9913044 1389
1da177e4
LT
1390 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1391 Amount of memory to be used when the kernel is not able
1392 to see the whole system memory or for test.
cd4f0ef7 1393 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1394 address space collisions. Without memmap= PCI devices
1395 could be placed at addresses belonging to unused RAM.
1396
cd4f0ef7 1397 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1398 memory.
1399
6902aa84
PM
1400 memchunk=nn[KMG]
1401 [KNL,SH] Allow user to override the default size for
1402 per-device physically contiguous DMA buffers.
1403
6cececfc 1404 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1405 E820 memory map, as specified by the user.
1406 Such memmap=exactmap lines can be constructed based on
1407 BIOS output or other requirements. See the memmap=nn@ss
1408 option description.
1409
1410 memmap=nn[KMG]@ss[KMG]
1411 [KNL] Force usage of a specific region of memory
1412 Region of memory to be used, from ss to ss+nn.
1413
1414 memmap=nn[KMG]#ss[KMG]
1415 [KNL,ACPI] Mark specific memory as ACPI data.
1416 Region of memory to be used, from ss to ss+nn.
1417
1418 memmap=nn[KMG]$ss[KMG]
1419 [KNL,ACPI] Mark specific memory as reserved.
1420 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1421 Example: Exclude memory from 0x18690000-0x1869ffff
1422 memmap=64K$0x18690000
1423 or
1424 memmap=0x10000$0x18690000
1da177e4 1425
9f077871
JF
1426 memory_corruption_check=0/1 [X86]
1427 Some BIOSes seem to corrupt the first 64k of
1428 memory when doing things like suspend/resume.
1429 Setting this option will scan the memory
1430 looking for corruption. Enabling this will
1431 both detect corruption and prevent the kernel
1432 from using the memory being corrupted.
1433 However, its intended as a diagnostic tool; if
1434 repeatable BIOS-originated corruption always
1435 affects the same memory, you can use memmap=
1436 to prevent the kernel from using that memory.
1437
1438 memory_corruption_check_size=size [X86]
1439 By default it checks for corruption in the low
1440 64k, making this memory unavailable for normal
1441 use. Use this parameter to scan for
1442 corruption in more or less memory.
1443
1444 memory_corruption_check_period=seconds [X86]
1445 By default it checks for corruption every 60
1446 seconds. Use this parameter to check at some
1447 other rate. 0 disables periodic checking.
1448
caadbdce 1449 memtest= [KNL,X86] Enable memtest
c64df707 1450 Format: <integer>
c64df707 1451 default : 0 <disable>
9e5f6cf5
AH
1452 Specifies the number of memtest passes to be
1453 performed. Each pass selects another test
1454 pattern from a given set of patterns. Memtest
1455 fills the memory with this pattern, validates
1456 memory contents and reserves bad memory
1457 regions that are detected.
c64df707 1458
1da177e4
LT
1459 meye.*= [HW] Set MotionEye Camera parameters
1460 See Documentation/video4linux/meye.txt.
1461
8f36881b
AS
1462 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1463 Multi-Function General Purpose Timers on AMD Geode
1464 platforms.
1465
e6c4dc6c
WT
1466 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1467 the BIOS has incorrectly applied a workaround. TinyBIOS
1468 version 0.98 is known to be affected, 0.99 fixes the
1469 problem by letting the user disable the workaround.
1470
1da177e4
LT
1471 mga= [HW,DRM]
1472
1c207f95
RD
1473 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1474 physical address is ignored.
1475
39f45d7b
MP
1476 mini2440= [ARM,HW,KNL]
1477 Format:[0..2][b][c][t]
1478 Default: "0tb"
1479 MINI2440 configuration specification:
1480 0 - The attached screen is the 3.5" TFT
1481 1 - The attached screen is the 7" TFT
1482 2 - The VGA Shield is attached (1024x768)
1483 Leaving out the screen size parameter will not load
1484 the TFT driver, and the framebuffer will be left
1485 unconfigured.
1486 b - Enable backlight. The TFT backlight pin will be
1487 linked to the kernel VESA blanking code and a GPIO
1488 LED. This parameter is not necessary when using the
1489 VGA shield.
1490 c - Enable the s3c camera interface.
1491 t - Reserved for enabling touchscreen support. The
1492 touchscreen support is not enabled in the mainstream
1493 kernel as of 2.6.30, a preliminary port can be found
1494 in the "bleeding edge" mini2440 support kernel at
1495 http://repo.or.cz/w/linux-2.6/mini2440.git
1496
6b74ab97
MG
1497 mminit_loglevel=
1498 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1499 parameter allows control of the logging verbosity for
1500 the additional memory initialisation checks. A value
1501 of 0 disables mminit logging and a level of 4 will
1502 log everything. Information is printed at KERN_DEBUG
1503 so loglevel=8 may also need to be specified.
1504
1da177e4
LT
1505 mousedev.tap_time=
1506 [MOUSE] Maximum time between finger touching and
1507 leaving touchpad surface for touch to be considered
1508 a tap and be reported as a left button click (for
1509 touchpads working in absolute mode only).
1510 Format: <msecs>
1511 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1512 reporting absolute coordinates, such as tablets
1513 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1514 reporting absolute coordinates, such as tablets
1515
6cececfc 1516 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1517 is similar to kernelcore except it specifies the
1518 amount of memory used for migratable allocations.
1519 If both kernelcore and movablecore is specified,
1520 then kernelcore will be at *least* the specified
1521 value but may be more. If movablecore on its own
1522 is specified, the administrator must be careful
1523 that the amount of memory usable for all allocations
1524 is not too small.
1525
1da177e4
LT
1526 mpu401= [HW,OSS]
1527 Format: <io>,<irq>
1528
1529 MTD_Partition= [MTD]
1530 Format: <name>,<region-number>,<size>,<offset>
1531
a9913044
RD
1532 MTD_Region= [MTD] Format:
1533 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1534
1535 mtdparts= [MTD]
c8facbb6 1536 See drivers/mtd/cmdlinepart.c.
1da177e4 1537
5988af23
RH
1538 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1539
1540 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1541
1542 boundary - index of last SLC block on Flex-OneNAND.
1543 The remaining blocks are configured as MLC blocks.
1544 lock - Configure if Flex-OneNAND boundary should be locked.
1545 Once locked, the boundary cannot be changed.
1546 1 indicates lock status, 0 indicates unlock status.
1547
9db829f4
BD
1548 mtdset= [ARM]
1549 ARM/S3C2412 JIVE boot control
1550
1551 See arch/arm/mach-s3c2412/mach-jive.c
1552
1da177e4 1553 mtouchusb.raw_coordinates=
a9913044
RD
1554 [HW] Make the MicroTouch USB driver use raw coordinates
1555 ('y', default) or cooked coordinates ('n')
1da177e4 1556
0cb55ad2 1557 mtrr_chunk_size=nn[KMG] [X86]
19f59460 1558 used for mtrr cleanup. It is largest continuous chunk
0cb55ad2
RD
1559 that could hold holes aka. UC entries.
1560
1561 mtrr_gran_size=nn[KMG] [X86]
1562 Used for mtrr cleanup. It is granularity of mtrr block.
1563 Default is 1.
1564 Large value could prevent small alignment from
1565 using up MTRRs.
1566
1567 mtrr_spare_reg_nr=n [X86]
1568 Format: <integer>
1569 Range: 0,7 : spare reg number
1570 Default : 1
1571 Used for mtrr cleanup. It is spare mtrr entries number.
1572 Set to 2 or more if your graphical card needs more.
1573
1da177e4
LT
1574 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1575
1576 NCR_D700= [HW,SCSI]
1577 See header of drivers/scsi/NCR_D700.c.
1578
1579 ncr5380= [HW,SCSI]
1580
1581 ncr53c400= [HW,SCSI]
1582
1583 ncr53c400a= [HW,SCSI]
1584
1585 ncr53c406a= [HW,SCSI]
1586
1587 ncr53c8xx= [HW,SCSI]
1588
1589 netdev= [NET] Network devices parameters
1590 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1591 Note that mem_start is often overloaded to mean
1592 something different and driver-specific.
a9913044
RD
1593 This usage is only documented in each driver source
1594 file if at all.
1595
58401572
KPO
1596 nf_conntrack.acct=
1597 [NETFILTER] Enable connection tracking flow accounting
1598 0 to disable accounting
1599 1 to enable accounting
1600 Default value depends on CONFIG_NF_CT_ACCT that is
1601 going to be removed in 2.6.29.
1602
1da177e4 1603 nfsaddrs= [NFS]
dc7a0816 1604 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1605
1606 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
dc7a0816 1607 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 1608
a72b4422
TM
1609 nfs.callback_tcpport=
1610 [NFS] set the TCP port on which the NFSv4 callback
1611 channel should listen.
1612
e571cbf1
TM
1613 nfs.cache_getent=
1614 [NFS] sets the pathname to the program which is used
1615 to update the NFS client cache entries.
1616
1617 nfs.cache_getent_timeout=
1618 [NFS] sets the timeout after which an attempt to
1619 update a cache entry is deemed to have failed.
1620
58df095b
TM
1621 nfs.idmap_cache_timeout=
1622 [NFS] set the maximum lifetime for idmapper cache
1623 entries.
1624
f43bf0be
TM
1625 nfs.enable_ino64=
1626 [NFS] enable 64-bit inode numbers.
1627 If zero, the NFS client will fake up a 32-bit inode
1628 number for the readdir() and stat() syscalls instead
1629 of returning the full 64-bit number.
1630 The default is to return 64-bit inode numbers.
1631
1e1030dc 1632 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
e7ba176b
HS
1633 when a NMI is triggered.
1634 Format: [state][,regs][,debounce][,die]
1635
6cececfc 1636 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
5b9a0e14
CG
1637 Format: [panic,][num]
1638 Valid num: 0,1,2
1639 0 - turn nmi_watchdog off
1640 1 - use the IO-APIC timer for the NMI watchdog
1641 2 - use the local APIC for the NMI watchdog using
0cb55ad2
RD
1642 a performance counter. Note: This will use one
1643 performance counter and the local APIC's performance
1644 vector.
1645 When panic is specified, panic when an NMI watchdog
1646 timeout occurs.
1647 This is useful when you use a panic=... timeout and
1648 need the box quickly up again.
5b9a0e14
CG
1649 Instead of 1 and 2 it is possible to use the following
1650 symbolic names: lapic and ioapic
1651 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1652
bff38771
AV
1653 netpoll.carrier_timeout=
1654 [NET] Specifies amount of time (in seconds) that
1655 netpoll should wait for a carrier. By default netpoll
1656 waits 4 seconds.
1657
cd4f0ef7 1658 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1659 emulation library even if a 387 maths coprocessor
1660 is present.
1661
0cb55ad2
RD
1662 no_console_suspend
1663 [HW] Never suspend the console
1664 Disable suspending of consoles during suspend and
1665 hibernate operations. Once disabled, debugging
1666 messages can reach various consoles while the rest
1667 of the system is being put to sleep (ie, while
1668 debugging driver suspend/resume hooks). This may
1669 not work reliably with all consoles, but is known
1670 to work with serial and VGA consoles.
1671
c1aee215
CL
1672 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1673 caches in the slab allocator. Saves per-node memory,
1674 but will impact performance.
3395ee05 1675
a9913044
RD
1676 noalign [KNL,ARM]
1677
1da177e4
LT
1678 noapic [SMP,APIC] Tells the kernel to not make use of any
1679 IOAPICs that may be present in the system.
1680
1da177e4
LT
1681 nobats [PPC] Do not use BATs for mapping kernel lowmem
1682 on "Classic" PPC cores.
1683
1684 nocache [ARM]
a9913044 1685
0cb55ad2
RD
1686 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1687
163ecdff
SN
1688 nodelayacct [KNL] Disable per-task delay accounting
1689
1da177e4
LT
1690 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1691
6902aa84
PM
1692 nodsp [SH] Disable hardware DSP at boot time.
1693
6cececfc 1694 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1695
1da177e4
LT
1696 noexec [IA-64]
1697
6cececfc 1698 noexec [X86]
f5a1b191 1699 On X86-32 available only on PAE configured kernels.
1da177e4 1700 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1701 noexec=off: disable non-executable mappings
1702
1703 noexec32 [X86-64]
1704 This affects only 32-bit executables.
1705 noexec32=on: enable non-executable mappings (default)
1706 read doesn't imply executable mappings
1707 noexec32=off: disable non-executable mappings
1708 read implies executable mappings
1da177e4 1709
6902aa84
PM
1710 nofpu [SH] Disable hardware FPU at boot time.
1711
cd4f0ef7 1712 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1713 register save and restore. The kernel will only save
1714 legacy floating-point registers on task switch.
1da177e4 1715
0c752a93
SS
1716 noxsave [BUGS=X86] Disables x86 extended register state save
1717 and restore using xsave. The kernel will fallback to
1718 enabling legacy floating-point and sse state.
1719
01a24d2b
PZ
1720 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1721 wfi(ARM) instruction doesn't work correctly and not to
1722 use it. This is also useful when using JTAG debugger.
a9913044 1723
cd4f0ef7 1724 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1725 instruction doesn't work correctly and not to
1726 use it.
1727
1f29fae2
SH
1728 no_file_caps Tells the kernel not to honor file capabilities. The
1729 only way then for a file to be executed with privilege
1730 is to be setuid root or executed by root.
1731
1da177e4
LT
1732 nohalt [IA-64] Tells the kernel not to use the power saving
1733 function PAL_HALT_LIGHT when idle. This increases
1734 power-consumption. On the positive side, it reduces
1735 interrupt wake-up latency, which may improve performance
1736 in certain environments such as networked servers or
1737 real-time systems.
1738
79bf2bb3
TG
1739 nohz= [KNL] Boottime enable/disable dynamic ticks
1740 Valid arguments: on, off
1741 Default: on
1742
eeee7853
PM
1743 noiotrap [SH] Disables trapped I/O port accesses.
1744
cd4f0ef7 1745 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1746 disable unhandled interrupt sources.
1747
6cececfc 1748 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
1749 broken timer IRQ sources.
1750
1da177e4
LT
1751 noisapnp [ISAPNP] Disables ISA PnP code.
1752
1753 noinitrd [RAM] Tells the kernel not to load any configured
1754 initial RAM disk.
1755
03ea8155
WH
1756 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1757 remapping.
1758
1da177e4
LT
1759 nointroute [IA-64]
1760
0aa366f3
TL
1761 nojitter [IA64] Disables jitter checking for ITC timers.
1762
cd4f0ef7 1763 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1764
cd4f0ef7 1765 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1766
1da177e4
LT
1767 noltlbs [PPC] Do not use large page/tlb entries for kernel
1768 lowmem mapping on PPC40x.
1769
312f1f01
H
1770 nomca [IA-64] Disable machine check abort handling
1771
cd4f0ef7 1772 nomce [X86-32] Machine Check Exception
abe37e5a 1773
83d7384f
AS
1774 nomfgpt [X86-32] Disable Multi-Function General Purpose
1775 Timer usage (for AMD Geode machines).
1776
016ddd9b
JK
1777 nopat [X86] Disable PAT (page attribute table extension of
1778 pagetables) support.
1779
0cb55ad2
RD
1780 norandmaps Don't use address space randomization. Equivalent to
1781 echo 0 > /proc/sys/kernel/randomize_va_space
1782
cd4f0ef7 1783 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1784
cd4f0ef7 1785 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1786 with UP alternatives
1787
1da177e4
LT
1788 noresidual [PPC] Don't use residual data on PReP machines.
1789
a9913044
RD
1790 noresume [SWSUSP] Disables resume and restores original swap
1791 space.
1792
1da177e4
LT
1793 no-scroll [VGA] Disables scrollback.
1794 This is required for the Braillex ib80-piezo Braille
1795 reader made by F.H. Papenmeier (Germany).
1796
1797 nosbagart [IA-64]
1798
cd4f0ef7 1799 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1800
61ec7567
LB
1801 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1802 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1803
97842216
DJ
1804 nosoftlockup [KNL] Disable the soft-lockup detector.
1805
c077719b 1806 noswapaccount [KNL] Disable accounting of swap in memory resource
21acb9ca 1807 controller. (See Documentation/cgroups/memory.txt)
c077719b 1808
1da177e4
LT
1809 nosync [HW,M68K] Disables sync negotiation for all devices.
1810
cd4f0ef7 1811 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1812
1813 nousb [USB] Disable the USB subsystem
1814
1815 nowb [ARM]
a9913044 1816
2b2fd87a
WH
1817 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1818
a6c75b86
FY
1819 nptcg= [IA64] Override max number of concurrent global TLB
1820 purges which is reported from either PAL_VM_SUMMARY or
1821 SAL PALO.
1822
2b633e3f
YL
1823 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1824 could support. nr_cpus=n : n >= 1 limits the kernel to
1825 supporting 'n' processors. Later in runtime you can not
1826 use hotplug cpu feature to put more cpu back to online.
1827 just like you compile the kernel NR_CPUS=n
1828
0cb55ad2
RD
1829 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1830
f0c0b2b8
KH
1831 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1832 one of ['zone', 'node', 'default'] can be specified
1833 This can be set from sysctl after boot.
1834 See Documentation/sysctl/vm.txt for details.
1835
7c4be253
RD
1836 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1837 See Documentation/debugging-via-ohci1394.txt for more
1838 info.
1839
3ef0e1f8
AS
1840 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1841 Rather than timing out after 20 ms if an EC
1842 command is not properly ACKed, override the length
1843 of the timeout. We have interrupts disabled while
1844 waiting for the ACK, so if this is set too high
1845 interrupts *may* be lost!
1846
15ac7afe
TL
1847 omap_mux= [OMAP] Override bootloader pin multiplexing.
1848 Format: <mux_mode0.mode_name=value>...
1849 For example, to override I2C bus2:
1850 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1851
1da177e4
LT
1852 opl3= [HW,OSS]
1853 Format: <io>
1854
1da177e4
LT
1855 oprofile.timer= [HW]
1856 Use timer interrupt instead of performance counters
1857
7e4e0bd5
RR
1858 oprofile.cpu_type= Force an oprofile cpu type
1859 This might be useful if you have an older oprofile
1860 userland or if you want common events.
8d7ff4f2
RR
1861 Format: { arch_perfmon }
1862 arch_perfmon: [X86] Force use of architectural
7e4e0bd5
RR
1863 perfmon on Intel CPUs instead of the
1864 CPU specific event set.
1dcdb5a9 1865
1da177e4
LT
1866 osst= [HW,SCSI] SCSI Tape Driver
1867 Format: <buffer_size>,<write_threshold>
1868 See also Documentation/scsi/st.txt.
1869
1870 panic= [KNL] Kernel behaviour on panic
1871 Format: <timeout>
1872
1873 parkbd.port= [HW] Parallel port number the keyboard adapter is
1874 connected to, default is 0.
1875 Format: <parport#>
1876 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1877 0 for XT, 1 for AT (default is AT).
a9913044
RD
1878 Format: <mode>
1879
1880 parport= [HW,PPT] Specify parallel ports. 0 disables.
1881 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1882 Use 'auto' to force the driver to use any
1883 IRQ/DMA settings detected (the default is to
1884 ignore detected IRQ/DMA settings because of
1885 possible conflicts). You can specify the base
1886 address, IRQ, and DMA settings; IRQ and DMA
1887 should be numbers, or 'auto' (for using detected
1888 settings on that particular port), or 'nofifo'
1889 (to avoid using a FIFO even if it is detected).
1890 Parallel ports are assigned in the order they
1891 are specified on the command line, starting
1892 with parport0.
1893
1894 parport_init_mode= [HW,PPT]
1895 Configure VIA parallel port to operate in
1896 a specific mode. This is necessary on Pegasos
1897 computer where firmware has no options for setting
1898 up parallel port mode and sets it to spp.
1899 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1900 Format: [spp|ps2|epp|ecp|ecpepp]
1901
a9913044
RD
1902 pas2= [HW,OSS] Format:
1903 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1904
1da177e4
LT
1905 pas16= [HW,SCSI]
1906 See header of drivers/scsi/pas16.c.
1907
dd287796
AM
1908 pause_on_oops=
1909 Halt all CPUs after the first oops has been printed for
1910 the specified number of seconds. This is to be used if
1911 your oopses keep scrolling off the screen.
1912
1da177e4
LT
1913 pcbit= [HW,ISDN]
1914
1915 pcd. [PARIDE]
1916 See header of drivers/block/paride/pcd.c.
31c00fc1 1917 See also Documentation/blockdev/paride.txt.
1da177e4 1918
a9913044 1919 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
1920 earlydump [X86] dump PCI config space before the kernel
1921 changes anything
c0115606 1922 off [X86] don't probe for the PCI bus
cd4f0ef7 1923 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1924 the hardware directly. Use this if your machine
1925 has a non-standard PCI host bridge.
cd4f0ef7 1926 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1927 hardware access methods are allowed. Use this
1928 if you experience crashes upon bootup and you
1929 suspect they are caused by the BIOS.
c0115606 1930 conf1 [X86] Force use of PCI Configuration
a9913044 1931 Mechanism 1.
c0115606 1932 conf2 [X86] Force use of PCI Configuration
a9913044 1933 Mechanism 2.
7f785763
RD
1934 noaer [PCIE] If the PCIEAER kernel config parameter is
1935 enabled, this kernel boot option can be used to
1936 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1937 nodomains [PCI] Disable support for multiple PCI
1938 root domains (aka PCI segments, in ACPI-speak).
6cececfc 1939 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 1940 Configuration
12983077
AH
1941 check_enable_amd_mmconf [X86] check for and enable
1942 properly configured MMIO access to PCI
1943 config space on AMD family 10h CPU
309e57df
MW
1944 nomsi [MSI] If the PCI_MSI kernel config parameter is
1945 enabled, this kernel boot option can be used to
1946 disable the use of MSI interrupts system-wide.
a9322f64
SA
1947 noioapicquirk [APIC] Disable all boot interrupt quirks.
1948 Safety option to keep boot IRQs enabled. This
1949 should never be necessary.
9197979b
SA
1950 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1951 primary IO-APIC for bridges that cannot disable
1952 boot IRQs. This fixes a source of spurious IRQs
1953 when the system masks IRQs.
41b9eb26
SA
1954 noioapicreroute [APIC] Disable workaround that uses the
1955 boot IRQ equivalent of an IRQ that connects to
1956 a chipset where boot IRQs cannot be disabled.
1957 The opposite of ioapicreroute.
cd4f0ef7 1958 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1959 routing table. These calls are known to be buggy
1960 on several machines and they hang the machine
1961 when used, but on other computers it's the only
1962 way to get the interrupt routing table. Try
1963 this option if the kernel is unable to allocate
1964 IRQs or discover secondary PCI buses on your
1965 motherboard.
c0115606 1966 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1967 Use with caution as certain devices share
1968 address decoders between ROMs and other
1969 resources.
c0115606 1970 norom [X86] Do not assign address space to
bb71ad88
GH
1971 expansion ROMs that do not already have
1972 BIOS assigned address ranges.
c0115606 1973 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1974 assigned automatically to PCI devices. You can
1975 make the kernel exclude IRQs of your ISA cards
1976 this way.
c0115606 1977 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1978 of the PIRQ table (normally generated
1979 by the BIOS) if it is outside the
1980 F0000h-100000h range.
c0115606 1981 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1982 useful if the kernel is unable to find your
1983 secondary buses and you want to tell it
1984 explicitly which ones they are.
c0115606 1985 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1986 numbers ourselves, overriding
1987 whatever the firmware may have done.
c0115606 1988 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1989 in the BIOS $PIR table. This is needed on
1990 some systems with broken BIOSes, notably
1991 some HP Pavilion N5400 and Omnibook XE3
1992 notebooks. This will have no effect if ACPI
1993 IRQ routing is enabled.
c0115606 1994 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1995 or for PCI scanning.
7bc5e3f2
BH
1996 use_crs [X86] Use PCI host bridge window information
1997 from ACPI. On BIOSes from 2008 or later, this
1998 is enabled by default. If you need to use this,
1999 please report a bug.
2000 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2001 If you need to use this, please report a bug.
a9913044
RD
2002 routeirq Do IRQ routing for all PCI devices.
2003 This is normally done in pci_enable_device(),
2004 so this option is a temporary workaround
2005 for broken drivers that don't call it.
13a6ddb0
YL
2006 skip_isa_align [X86] do not align io start addr, so can
2007 handle more pci cards
a9913044
RD
2008 firmware [ARM] Do not re-enumerate the bus but instead
2009 just use the configuration from the
2010 bootloader. This is currently used on
2011 IXP2000 systems where the bus has to be
2012 configured a certain way for adjunct CPUs.
0637a70a
AK
2013 noearly [X86] Don't do any early type 1 scanning.
2014 This might help on some broken boards which
2015 machine check when some devices' config space
2016 is read. But various workarounds are disabled
2017 and some IOMMU drivers will not work.
6b4b78fe
MD
2018 bfsort Sort PCI devices into breadth-first order.
2019 This sorting is done to get a device
2020 order compatible with older (<= 2.4) kernels.
2021 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
2022 cbiosize=nn[KMG] The fixed amount of bus space which is
2023 reserved for the CardBus bridge's IO window.
2024 The default value is 256 bytes.
2025 cbmemsize=nn[KMG] The fixed amount of bus space which is
2026 reserved for the CardBus bridge's memory
2027 window. The default value is 64 megabytes.
32a9a682
YS
2028 resource_alignment=
2029 Format:
2030 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2031 Specifies alignment and device to reassign
2032 aligned memory resources.
2033 If <order of align> is not specified,
2034 PAGE_SIZE is used as alignment.
2035 PCI-PCI bridge can be specified, if resource
2036 windows need to be expanded.
43c16408
AP
2037 ecrc= Enable/disable PCIe ECRC (transaction layer
2038 end-to-end CRC checking).
2039 bios: Use BIOS/firmware settings. This is the
2040 the default.
2041 off: Turn ECRC off
2042 on: Turn ECRC on.
6b4b78fe 2043
e5665a45
CE
2044 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2045 Management.
2046 off Disable ASPM.
2047 force Enable ASPM even on devices that claim not to support it.
2048 WARNING: Forcing ASPM on may cause system lockups.
2049
c7f48656
RW
2050 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2051 off Do not use native PCIe PME signaling.
2052 force Use native PCIe PME signaling even if the BIOS refuses
2053 to allow the kernel to control the relevant PCIe config
2054 registers.
c39fae14
RW
2055 nomsi Do not use MSI for native PCIe PME signaling (this makes
2056 all PCIe root ports use INTx for everything).
c7f48656 2057
1da177e4
LT
2058 pcmv= [HW,PCMCIA] BadgePAD 4
2059
2060 pd. [PARIDE]
31c00fc1 2061 See Documentation/blockdev/paride.txt.
1da177e4
LT
2062
2063 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2064 boot time.
2065 Format: { 0 | 1 }
2066 See arch/parisc/kernel/pdc_chassis.c
2067
f58dc01b 2068 percpu_alloc= Select which percpu first chunk allocator to use.
e933a73f
TH
2069 Currently supported values are "embed" and "page".
2070 Archs may support subset or none of the selections.
2071 See comments in mm/percpu.c for details on each
2072 allocator. This parameter is primarily for debugging
2073 and performance comparison.
fa8a7094 2074
1da177e4 2075 pf. [PARIDE]
31c00fc1 2076 See Documentation/blockdev/paride.txt.
1da177e4
LT
2077
2078 pg. [PARIDE]
31c00fc1 2079 See Documentation/blockdev/paride.txt.
1da177e4
LT
2080
2081 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 2082 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
2083
2084 plip= [PPT,NET] Parallel port network link
2085 Format: { parport<nr> | timid | 0 }
2086 See also Documentation/parport.txt.
2087
de32a243
TG
2088 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2089 Override pmtimer IOPort with a hex value.
2090 e.g. pmtmr=0x508
2091
97ef062b
BH
2092 pnp.debug [PNP]
2093 Enable PNP debug messages. This depends on the
2094 CONFIG_PNP_DEBUG_MESSAGES option.
2095
1da177e4
LT
2096 pnpacpi= [ACPI]
2097 { off }
2098
2099 pnpbios= [ISAPNP]
2100 { on | off | curr | res | no-curr | no-res }
2101
2102 pnp_reserve_irq=
2103 [ISAPNP] Exclude IRQs for the autoconfiguration
2104
2105 pnp_reserve_dma=
2106 [ISAPNP] Exclude DMAs for the autoconfiguration
2107
2108 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 2109 Ranges are in pairs (I/O port base and size).
1da177e4
LT
2110
2111 pnp_reserve_mem=
a9913044
RD
2112 [ISAPNP] Exclude memory regions for the
2113 autoconfiguration.
1da177e4
LT
2114 Ranges are in pairs (memory base and size).
2115
4af94f39
RD
2116 ports= [IP_VS_FTP] IPVS ftp helper module
2117 Default is 21.
2118 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2119 may be specified.
2120 Format: <port>,<port>....
2121
45807a1d
IM
2122 print-fatal-signals=
2123 [KNL] debug: print fatal signals
f84d49b2
NO
2124
2125 If enabled, warn about various signal handling
2126 related application anomalies: too many signals,
2127 too many POSIX.1 timers, fatal signals causing a
2128 coredump - etc.
2129
2130 If you hit the warning due to signal overflow,
2131 you might want to try "ulimit -i unlimited".
2132
45807a1d
IM
2133 default: off.
2134
e84845c4
RD
2135 printk.time= Show timing data prefixed to each printk message line
2136 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2137
0cb55ad2
RD
2138 processor.max_cstate= [HW,ACPI]
2139 Limit processor to maximum C-state
2140 max_cstate=9 overrides any DMI blacklist limit.
2141
2142 processor.nocst [HW,ACPI]
2143 Ignore the _CST method to determine C-states,
2144 instead using the legacy FADT method
2145
1da177e4 2146 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
2147 Format: [schedule,]<number>
2148 Param: "schedule" - profile schedule points.
2149 Param: <number> - step/bucket size as a power of 2 for
2150 statistical time based profiling.
b3da2a73
MG
2151 Param: "sleep" - profile D-state sleeping (millisecs).
2152 Requires CONFIG_SCHEDSTATS
c0fe2e69 2153 Param: "kvm" - profile VM exits.
1da177e4 2154
1da177e4
LT
2155 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2156 before loading.
31c00fc1 2157 See Documentation/blockdev/ramdisk.txt.
1da177e4 2158
a9913044
RD
2159 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2160 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
2161 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2162 per second.
a9913044
RD
2163 psmouse.resetafter= [HW,MOUSE]
2164 Try to reset the device after so many bad packets
1da177e4
LT
2165 (0 = never).
2166 psmouse.resolution=
2167 [HW,MOUSE] Set desired mouse resolution, in dpi.
2168 psmouse.smartscroll=
a9913044 2169 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
2170 0 = disabled, 1 = enabled (default).
2171
2172 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
2173 Format:
2174 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
2175
2176 pt. [PARIDE]
31c00fc1 2177 See Documentation/blockdev/paride.txt.
1da177e4 2178
dc8c8587
KS
2179 pty.legacy_count=
2180 [KNL] Number of legacy pty's. Overwrites compiled-in
2181 default number.
2182
7d2c502f 2183 quiet [KNL] Disable most log messages
a9913044 2184
1da177e4
LT
2185 r128= [HW,DRM]
2186
2187 raid= [HW,RAID]
2188 See Documentation/md.txt.
2189
a9913044 2190 ramdisk_blocksize= [RAM]
31c00fc1 2191 See Documentation/blockdev/ramdisk.txt.
a9913044 2192
1da177e4 2193 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 2194 See Documentation/blockdev/ramdisk.txt.
1da177e4 2195
24aaef8d
RD
2196 rcupdate.blimit= [KNL,BOOT]
2197 Set maximum number of finished RCU callbacks to process
2198 in one batch.
21a1ea9e 2199
24aaef8d
RD
2200 rcupdate.qhimark= [KNL,BOOT]
2201 Set threshold of queued
21a1ea9e
DS
2202 RCU callbacks over which batch limiting is disabled.
2203
24aaef8d
RD
2204 rcupdate.qlowmark= [KNL,BOOT]
2205 Set threshold of queued RCU callbacks below which
2206 batch limiting is re-enabled.
21a1ea9e 2207
ffdfc409
OJ
2208 rdinit= [KNL]
2209 Format: <full_path>
2210 Run specified binary instead of /init from the ramdisk,
2211 used for early userspace startup. See initrd.
2212
cd4f0ef7 2213 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 2214 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 2215 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 2216
46b6d94e
PJ
2217 relax_domain_level=
2218 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 2219 See Documentation/cgroups/cpusets.txt.
46b6d94e 2220
1da177e4
LT
2221 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2222
cd4f0ef7 2223 reservetop= [X86-32]
461a9aff
ZA
2224 Format: nn[KMG]
2225 Reserves a hole at the top of the kernel virtual
2226 address space.
2227
7e96287d
VG
2228 reset_devices [KNL] Force drivers to reset the underlying device
2229 during initialization.
2230
a9913044
RD
2231 resume= [SWSUSP]
2232 Specify the partition device for software suspend
1da177e4 2233
ecbd0da1
RW
2234 resume_offset= [SWSUSP]
2235 Specify the offset from the beginning of the partition
2236 given by "resume=" at which the swap header is located,
2237 in <PAGE_SIZE> units (needed only for swap files).
2238 See Documentation/power/swsusp-and-swap-files.txt
2239
0a7b35cb
MN
2240 retain_initrd [RAM] Keep initrd memory after extraction
2241
1da177e4
LT
2242 rhash_entries= [KNL,NET]
2243 Set number of hash buckets for route cache
2244
2245 riscom8= [HW,SERIAL]
2246 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2247
2248 ro [KNL] Mount root device read-only on boot
2249
2250 root= [KNL] Root filesystem
2251
2252 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2253 mount the root filesystem
2254
2255 rootflags= [KNL] Set root filesystem mount option string
2256
2257 rootfstype= [KNL] Set root filesystem type
2258
cc1ed754
PO
2259 rootwait [KNL] Wait (indefinitely) for root device to show up.
2260 Useful for devices that are detected asynchronously
2261 (e.g. USB and MMC devices).
2262
1da177e4
LT
2263 rw [KNL] Mount root device read-write on boot
2264
2265 S [KNL] Run init in single mode
2266
2267 sa1100ir [NET]
2268 See drivers/net/irda/sa1100_ir.c.
2269
1da177e4 2270 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2271
f6630114
MT
2272 sched_debug [KNL] Enables verbose scheduler debug messages.
2273
1da177e4
LT
2274 scsi_debug_*= [SCSI]
2275 See drivers/scsi/scsi_debug.c.
2276
2277 scsi_default_dev_flags=
2278 [SCSI] SCSI default device flags
2279 Format: <integer>
2280
2281 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2282 Format: <vendor>:<model>:<flags>
2283 (flags are integer value)
2284
6af6632a
RD
2285 scsi_logging_level= [SCSI] a bit mask of logging levels
2286 See drivers/scsi/scsi_logging.h for bits. Also
2287 settable via sysctl at dev.scsi.logging_level
2288 (/proc/sys/dev/scsi/logging_level).
2289 There is also a nice 'scsi_logging_level' script in the
2290 S390-tools package, available for download at
2291 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 2292
3e082a91
MW
2293 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2294 discovered. async scans them in kernel threads,
2295 allowing boot to proceed. none ignores them, expecting
2296 user space to do the scan.
2297
0cb55ad2
RD
2298 security= [SECURITY] Choose a security module to enable at boot.
2299 If this boot parameter is not specified, only the first
2300 security module asking for security registration will be
2301 loaded. An invalid security module name will be treated
2302 as if no module has been chosen.
2303
2304 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2305 Format: { "0" | "1" }
2306 See security/selinux/Kconfig help text.
2307 0 -- disable.
2308 1 -- enable.
2309 Default value is set via kernel config option.
2310 If enabled at boot time, /selinux/disable can be used
2311 later to disable prior to initial policy load.
2312
cd4f0ef7 2313 serialnumber [BUGS=X86-32]
1da177e4 2314
1da177e4
LT
2315 shapers= [NET]
2316 Maximal number of shapers.
a9913044 2317
b05f78f5
YL
2318 show_msr= [x86] show boot-time MSR settings
2319 Format: { <integer> }
2320 Show boot-time (BIOS-initialized) MSR settings.
2321 The parameter means the number of CPUs to show,
2322 for example 1 means boot CPU only.
2323
1da177e4
LT
2324 sim710= [SCSI,HW]
2325 See header of drivers/scsi/sim710.c.
2326
2327 simeth= [IA-64]
2328 simscsi=
a9913044 2329
1da177e4
LT
2330 slram= [HW,MTD]
2331
f0630fff
CL
2332 slub_debug[=options[,slabs]] [MM, SLUB]
2333 Enabling slub_debug allows one to determine the
2334 culprit if slab objects become corrupted. Enabling
2335 slub_debug can create guard zones around objects and
2336 may poison objects when not in use. Also tracks the
2337 last alloc / free. For more information see
2338 Documentation/vm/slub.txt.
c1aee215
CL
2339
2340 slub_max_order= [MM, SLUB]
f0630fff
CL
2341 Determines the maximum allowed order for slabs.
2342 A high setting may cause OOMs due to memory
2343 fragmentation. For more information see
2344 Documentation/vm/slub.txt.
c1aee215
CL
2345
2346 slub_min_objects= [MM, SLUB]
f0630fff
CL
2347 The minimum number of objects per slab. SLUB will
2348 increase the slab order up to slub_max_order to
2349 generate a sufficiently large slab able to contain
2350 the number of objects indicated. The higher the number
2351 of objects the smaller the overhead of tracking slabs
2352 and the less frequently locks need to be acquired.
c1aee215
CL
2353 For more information see Documentation/vm/slub.txt.
2354
2355 slub_min_order= [MM, SLUB]
2356 Determines the mininum page order for slabs. Must be
f0630fff 2357 lower than slub_max_order.
c1aee215
CL
2358 For more information see Documentation/vm/slub.txt.
2359
2360 slub_nomerge [MM, SLUB]
f0630fff 2361 Disable merging of slabs with similar size. May be
c1aee215 2362 necessary if there is some reason to distinguish
f0630fff
CL
2363 allocs to different slabs. Debug options disable
2364 merging on their own.
c1aee215
CL
2365 For more information see Documentation/vm/slub.txt.
2366
1da177e4
LT
2367 smart2= [HW]
2368 Format: <io1>[,<io2>[,...,<io8>]]
2369
cd4f0ef7 2370 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2371 attempt to substitute SMP alternatives once at boot.
2372
d0d4f69b
BH
2373 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2374 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2375 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2376 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2377 smsc-ircc2.ircc_irq= [HW] IRQ line
2378 smsc-ircc2.ircc_dma= [HW] DMA channel
2379 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2380 0: Toshiba Satellite 1800 (GP data pin select)
2381 1: Fast pin select (default)
2382 2: ATC IRMode
2383
1da177e4
LT
2384 snd-ad1816a= [HW,ALSA]
2385
2386 snd-ad1848= [HW,ALSA]
2387
2388 snd-ali5451= [HW,ALSA]
2389
2390 snd-als100= [HW,ALSA]
2391
2392 snd-als4000= [HW,ALSA]
2393
2394 snd-azt2320= [HW,ALSA]
2395
2396 snd-cmi8330= [HW,ALSA]
2397
2398 snd-cmipci= [HW,ALSA]
2399
2400 snd-cs4231= [HW,ALSA]
2401
2402 snd-cs4232= [HW,ALSA]
2403
2404 snd-cs4236= [HW,ALSA]
2405
2406 snd-cs4281= [HW,ALSA]
2407
2408 snd-cs46xx= [HW,ALSA]
2409
2410 snd-dt019x= [HW,ALSA]
2411
2412 snd-dummy= [HW,ALSA]
2413
2414 snd-emu10k1= [HW,ALSA]
2415
2416 snd-ens1370= [HW,ALSA]
2417
2418 snd-ens1371= [HW,ALSA]
2419
2420 snd-es968= [HW,ALSA]
2421
2422 snd-es1688= [HW,ALSA]
2423
2424 snd-es18xx= [HW,ALSA]
2425
2426 snd-es1938= [HW,ALSA]
2427
2428 snd-es1968= [HW,ALSA]
2429
2430 snd-fm801= [HW,ALSA]
2431
2432 snd-gusclassic= [HW,ALSA]
2433
2434 snd-gusextreme= [HW,ALSA]
2435
2436 snd-gusmax= [HW,ALSA]
2437
2438 snd-hdsp= [HW,ALSA]
2439
2440 snd-ice1712= [HW,ALSA]
2441
2442 snd-intel8x0= [HW,ALSA]
2443
2444 snd-interwave= [HW,ALSA]
2445
2446 snd-interwave-stb=
2447 [HW,ALSA]
2448
2449 snd-korg1212= [HW,ALSA]
2450
2451 snd-maestro3= [HW,ALSA]
2452
2453 snd-mpu401= [HW,ALSA]
2454
2455 snd-mtpav= [HW,ALSA]
2456
2457 snd-nm256= [HW,ALSA]
2458
2459 snd-opl3sa2= [HW,ALSA]
2460
2461 snd-opti92x-ad1848=
2462 [HW,ALSA]
2463
2464 snd-opti92x-cs4231=
2465 [HW,ALSA]
2466
2467 snd-opti93x= [HW,ALSA]
2468
2469 snd-pmac= [HW,ALSA]
2470
2471 snd-rme32= [HW,ALSA]
2472
2473 snd-rme96= [HW,ALSA]
2474
2475 snd-rme9652= [HW,ALSA]
2476
2477 snd-sb8= [HW,ALSA]
2478
2479 snd-sb16= [HW,ALSA]
2480
2481 snd-sbawe= [HW,ALSA]
2482
2483 snd-serial= [HW,ALSA]
2484
2485 snd-sgalaxy= [HW,ALSA]
2486
2487 snd-sonicvibes= [HW,ALSA]
2488
2489 snd-sun-amd7930=
2490 [HW,ALSA]
2491
2492 snd-sun-cs4231= [HW,ALSA]
2493
2494 snd-trident= [HW,ALSA]
2495
2496 snd-usb-audio= [HW,ALSA,USB]
2497
2498 snd-via82xx= [HW,ALSA]
2499
2500 snd-virmidi= [HW,ALSA]
2501
2502 snd-wavefront= [HW,ALSA]
2503
2504 snd-ymfpci= [HW,ALSA]
a9913044 2505
9c44bc03
IM
2506 softlockup_panic=
2507 [KNL] Should the soft-lockup detector generate panics.
2508
1da177e4
LT
2509 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2510 See Documentation/sonypi.txt
2511
2512 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2513 See Documentation/serial/specialix.txt.
1da177e4
LT
2514
2515 spia_io_base= [HW,MTD]
2516 spia_fio_base=
2517 spia_pedr=
2518 spia_peddr=
2519
2520 sscape= [HW,OSS]
2521 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2522
1da177e4
LT
2523 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2524 See Documentation/scsi/st.txt.
2525
f38f1d2a
SR
2526 stacktrace [FTRACE]
2527 Enabled the stack tracer on boot up.
2528
1da177e4
LT
2529 sti= [PARISC,HW]
2530 Format: <num>
2531 Set the STI (builtin display/keyboard on the HP-PARISC
2532 machines) console (graphic card) which should be used
2533 as the initial boot-console.
2534 See also comment in drivers/video/console/sticore.c.
2535
2536 sti_font= [HW]
2537 See comment in drivers/video/console/sticore.c.
2538
2539 stifb= [HW]
2540 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2541
cbf11071
TM
2542 sunrpc.min_resvport=
2543 sunrpc.max_resvport=
2544 [NFS,SUNRPC]
2545 SunRPC servers often require that client requests
2546 originate from a privileged port (i.e. a port in the
2547 range 0 < portnr < 1024).
2548 An administrator who wishes to reserve some of these
2549 ports for other uses may adjust the range that the
2550 kernel's sunrpc client considers to be privileged
2551 using these two parameters to set the minimum and
2552 maximum port values.
2553
42a7fc4a
GB
2554 sunrpc.pool_mode=
2555 [NFS]
2556 Control how the NFS server code allocates CPUs to
2557 service thread pools. Depending on how many NICs
2558 you have and where their interrupts are bound, this
2559 option will affect which CPUs will do NFS serving.
2560 Note: this parameter cannot be changed while the
2561 NFS server is running.
2562
2563 auto the server chooses an appropriate mode
2564 automatically using heuristics
2565 global a single global pool contains all CPUs
2566 percpu one pool for each CPU
2567 pernode one pool for each NUMA node (equivalent
2568 to global on non-NUMA machines)
2569
cbf11071
TM
2570 sunrpc.tcp_slot_table_entries=
2571 sunrpc.udp_slot_table_entries=
2572 [NFS,SUNRPC]
2573 Sets the upper limit on the number of simultaneous
2574 RPC calls that can be sent from the client to a
2575 server. Increasing these values may allow you to
2576 improve throughput, but will also increase the
2577 amount of memory reserved for use by the client.
2578
1da177e4 2579 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2580
1da177e4
LT
2581 switches= [HW,M68k]
2582
2583 sym53c416= [HW,SCSI]
2584 See header of drivers/scsi/sym53c416.c.
2585
5d6f647f
IM
2586 sysrq_always_enabled
2587 [KNL]
2588 Ignore sysrq setting - this boot parameter will
2589 neutralize any effect of /proc/sys/kernel/sysrq.
2590 Useful for debugging.
2591
1da177e4
LT
2592 t128= [HW,SCSI]
2593 See header of drivers/scsi/t128.c.
2594
2595 tdfx= [HW,DRM]
2596
77437fd4
DB
2597 test_suspend= [SUSPEND]
2598 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2599 standby suspend) as the system sleep state to briefly
2600 enter during system startup. The system is woken from
2601 this state using a wakeup-capable RTC alarm.
2602
1da177e4
LT
2603 thash_entries= [KNL,NET]
2604 Set number of hash buckets for TCP connection
2605
f8707ec9
LB
2606 thermal.act= [HW,ACPI]
2607 -1: disable all active trip points in all thermal zones
2608 <degrees C>: override all lowest active trip points
2609
c52a7419
LB
2610 thermal.crt= [HW,ACPI]
2611 -1: disable all critical trip points in all thermal zones
22a94d79 2612 <degrees C>: override all critical trip points
c52a7419 2613
f5487145
LB
2614 thermal.nocrt= [HW,ACPI]
2615 Set to disable actions on ACPI thermal zone
2616 critical and hot trip points.
2617
72b33ef8
LB
2618 thermal.off= [HW,ACPI]
2619 1: disable ACPI thermal control
2620
a70cdc52
LB
2621 thermal.psv= [HW,ACPI]
2622 -1: disable all passive trip points
ada9cfdd
RD
2623 <degrees C>: override all passive trip points to this
2624 value
a70cdc52 2625
730ff34d
LB
2626 thermal.tzp= [HW,ACPI]
2627 Specify global default ACPI thermal zone polling rate
2628 <deci-seconds>: poll all this frequency
2629 0: no polling (default)
2630
1da177e4
LT
2631 tmscsim= [HW,SCSI]
2632 See comment before function dc390_setup() in
2633 drivers/scsi/tmscsim.c.
2634
2b1a61f0
HC
2635 topology= [S390]
2636 Format: {off | on}
2637 Specify if the kernel should make use of the cpu
2638 topology informations if the hardware supports these.
2639 The scheduler will make use of these informations and
2640 e.g. base its process migration decisions on it.
2641 Default is off.
2642
1da177e4
LT
2643 tp720= [HW,PS2]
2644
225a9be2
RA
2645 tpm_suspend_pcr=[HW,TPM]
2646 Format: integer pcr id
2647 Specify that at suspend time, the tpm driver
2648 should extend the specified pcr with zeros,
2649 as a workaround for some chips which fail to
2650 flush the last written pcr on TPM_SaveState.
2651 This will guarantee that all the other pcrs
2652 are saved.
2653
9d612bef
LZ
2654 trace_buf_size=nn[KMG]
2655 [FTRACE] will set tracing buffer size.
631595fb 2656
020e5f85
LZ
2657 trace_event=[event-list]
2658 [FTRACE] Set and start specified trace events in order
2659 to facilitate early boot debugging.
2660 See also Documentation/trace/events.txt
2661
1da177e4 2662 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2663 Format:
2664 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2665
395628ef
AK
2666 tsc= Disable clocksource-must-verify flag for TSC.
2667 Format: <string>
2668 [x86] reliable: mark tsc clocksource as reliable, this
2669 disables clocksource verification at runtime.
2670 Used to enable high-resolution timer mode on older
2671 hardware, and in virtualized environment.
2672
a9913044
RD
2673 turbografx.map[2|3]= [HW,JOY]
2674 TurboGraFX parallel port interface
2675 Format:
2676 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2677 See also Documentation/input/joystick-parport.txt
2678
2679 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2680 See header of drivers/scsi/u14-34f.c.
2681
2682 uart401= [HW,OSS]
2683 Format: <io>,<irq>
2684
2685 uart6850= [HW,OSS]
2686 Format: <io>,<irq>
2687
f86dcc5a
ED
2688 uhash_entries= [KNL,NET]
2689 Set number of hash buckets for UDP/UDP-Lite connections
2690
5f8364b7
AS
2691 uhci-hcd.ignore_oc=
2692 [USB] Ignore overcurrent events (default N).
2693 Some badly-designed motherboards generate lots of
2694 bogus events, for ports that aren't wired to
2695 anything. Set this parameter to avoid log spamming.
2696 Note that genuine overcurrent events won't be
2697 reported either.
2698
e3a61b0a 2699 unknown_nmi_panic
6cececfc 2700 [X86]
e3a61b0a
SA
2701 Set unknown_nmi_panic=1 early on boot.
2702
b5e795f8
AS
2703 usbcore.autosuspend=
2704 [USB] The autosuspend time delay (in seconds) used
2705 for newly-detected USB devices (default 2). This
2706 is the time required before an idle device will be
2707 autosuspended. Devices for which the delay is set
eaafbc3a 2708 to a negative value won't be autosuspended at all.
b5e795f8 2709
fd7c519d
JK
2710 usbcore.usbfs_snoop=
2711 [USB] Set to log all usbfs traffic (default 0 = off).
2712
2713 usbcore.blinkenlights=
2714 [USB] Set to cycle leds on hubs (default 0 = off).
2715
2716 usbcore.old_scheme_first=
2717 [USB] Start with the old device initialization
2718 scheme (default 0 = off).
2719
2720 usbcore.use_both_schemes=
2721 [USB] Try the other device initialization scheme
2722 if the first one fails (default 1 = enabled).
2723
2724 usbcore.initial_descriptor_timeout=
2725 [USB] Specifies timeout for the initial 64-byte
2726 USB_REQ_GET_DESCRIPTOR request in milliseconds
2727 (default 5000 = 5.0 seconds).
2728
1da177e4
LT
2729 usbhid.mousepoll=
2730 [USBHID] The interval which mice are to be polled at.
a9913044 2731
d4f373e5
AS
2732 usb-storage.delay_use=
2733 [UMS] The delay in seconds before a new device is
2734 scanned for Logical Units (default 5).
2735
2736 usb-storage.quirks=
2737 [UMS] A list of quirks entries to supplement or
2738 override the built-in unusual_devs list. List
2739 entries are separated by commas. Each entry has
2740 the form VID:PID:Flags where VID and PID are Vendor
2741 and Product ID values (4-digit hex numbers) and
2742 Flags is a set of characters, each corresponding
2743 to a common usb-storage quirk flag as follows:
c838ea46
AS
2744 a = SANE_SENSE (collect more than 18 bytes
2745 of sense data);
a0bb1081
AS
2746 b = BAD_SENSE (don't collect more than 18
2747 bytes of sense data);
d4f373e5
AS
2748 c = FIX_CAPACITY (decrease the reported
2749 device capacity by one sector);
c838ea46
AS
2750 h = CAPACITY_HEURISTICS (decrease the
2751 reported device capacity by one
2752 sector if the number is odd);
d4f373e5
AS
2753 i = IGNORE_DEVICE (don't bind to this
2754 device);
2755 l = NOT_LOCKABLE (don't try to lock and
2756 unlock ejectable media);
2757 m = MAX_SECTORS_64 (don't transfer more
2758 than 64 sectors = 32 KB at a time);
c838ea46
AS
2759 o = CAPACITY_OK (accept the capacity
2760 reported by the device);
d4f373e5
AS
2761 r = IGNORE_RESIDUE (the device reports
2762 bogus residue values);
2763 s = SINGLE_LUN (the device has only one
2764 Logical Unit);
2765 w = NO_WP_DETECT (don't test whether the
2766 medium is write-protected).
2767 Example: quirks=0419:aaf5:rl,0421:0433:rc
2768
14315592
IC
2769 userpte=
2770 [X86] Flags controlling user PTE allocations.
2771
2772 nohigh = do not allocate PTE pages in
2773 HIGHMEM regardless of setting
2774 of CONFIG_HIGHPTE.
2775
6cececfc 2776 vdso= [X86,SH]
1dbf527c 2777 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2778 vdso=1: enable VDSO (default)
2779 vdso=0: disable VDSO mapping
2780
6cececfc 2781 vdso32= [X86]
af65d648
RM
2782 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2783 vdso32=1: enable 32-bit VDSO (default)
2784 vdso32=0: disable 32-bit VDSO mapping
2785
d080d397
YI
2786 vector= [IA-64,SMP]
2787 vector=percpu: enable percpu vector domain
2788
1da177e4
LT
2789 video= [FB] Frame buffer configuration
2790 See Documentation/fb/modedb.txt.
2791
cd4f0ef7 2792 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 2793 See Documentation/x86/boot.txt and
a9913044 2794 Documentation/svga.txt.
1da177e4
LT
2795 Use vga=ask for menu.
2796 This is actually a boot loader parameter; the value is
2797 passed to the kernel using a special protocol.
2798
a9913044 2799 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2800 size of <nn>. This can be used to increase the
2801 minimum size (128MB on x86). It can also be used to
2802 decrease the size and leave more room for directly
2803 mapped kernel RAM.
2804
585c3047
PO
2805 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2806 Format: <command>
1da177e4 2807
585c3047
PO
2808 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2809 Format: <command>
2810
2811 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2812 Format: <command>
a9913044 2813
9ea9a886
CL
2814 vt.cur_default= [VT] Default cursor shape.
2815 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2816 the parameters of the <Esc>[?A;B;Cc escape sequence;
2817 see VGA-softcursor.txt. Default: 2 = underline.
2818
0cb55ad2
RD
2819 vt.default_blu= [VT]
2820 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2821 Change the default blue palette of the console.
2822 This is a 16-member array composed of values
2823 ranging from 0-255.
2824
2825 vt.default_grn= [VT]
2826 Format: <green0>,<green1>,<green2>,...,<green15>
2827 Change the default green palette of the console.
2828 This is a 16-member array composed of values
2829 ranging from 0-255.
2830
2831 vt.default_red= [VT]
2832 Format: <red0>,<red1>,<red2>,...,<red15>
2833 Change the default red palette of the console.
2834 This is a 16-member array composed of values
2835 ranging from 0-255.
2836
2837 vt.default_utf8=
2838 [VT]
2839 Format=<0|1>
2840 Set system-wide default UTF-8 mode for all tty's.
2841 Default is 1, i.e. UTF-8 mode is enabled for all
2842 newly opened terminals.
2843
f6c06b68
MG
2844 vt.global_cursor_default=
2845 [VT]
2846 Format=<-1|0|1>
2847 Set system-wide default for whether a cursor
2848 is shown on new VTs. Default is -1,
2849 i.e. cursors will be created by default unless
2850 overridden by individual drivers. 0 will hide
2851 cursors, 1 will display them.
2852
1da177e4
LT
2853 waveartist= [HW,OSS]
2854 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2855
1da177e4
LT
2856 wd33c93= [HW,SCSI]
2857 See header of drivers/scsi/wd33c93.c.
2858
2859 wd7000= [HW,SCSI]
2860 See header of drivers/scsi/wd7000.c.
2861
4724ba57
RD
2862 watchdog timers [HW,WDT] For information on watchdog timers,
2863 see Documentation/watchdog/watchdog-parameters.txt
2864 or other driver-specific files in the
2865 Documentation/watchdog/ directory.
1da177e4 2866
0cb55ad2
RD
2867 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2868 default x2apic cluster mode on platforms
2869 supporting x2apic.
2870
bb24c471
JP
2871 x86_mrst_timer= [X86-32,APBT]
2872 Choose timer option for x86 Moorestown MID platform.
2873 Two valid options are apbt timer only and lapic timer
2874 plus one apbt timer for broadcast timer.
2875 x86_mrst_timer=apbt_only | lapic_and_apbt
2876
1da177e4
LT
2877 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2878 xd_geo= See header of drivers/block/xd.c.
2879
2880 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2881 Format:
2882 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2883
a9913044 2884______________________________________________________________________
1da177e4
LT
2885
2886TODO:
2887
2888 Add documentation for ALSA options.
2889 Add more DRM drivers.