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1 Kernel Parameters 2 ~~~~~~~~~~~~~~~~~ 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 20This document may not be entirely up to date and comprehensive. The command 21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable 22module. Loadable modules, after being loaded into the running kernel, also 23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these 24parameters may be changed at runtime by the command 25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". 26 27The parameters listed below are only valid if certain kernel build options were 28enabled and if respective hardware is present. The text in square brackets at 29the beginning of each description states the restrictions within which a 30parameter is applicable: 31 32 ACPI ACPI support is enabled. 33 AGP AGP (Accelerated Graphics Port) is enabled. 34 ALSA ALSA sound support is enabled. 35 APIC APIC support is enabled. 36 APM Advanced Power Management support is enabled. 37 AVR32 AVR32 architecture is enabled. 38 AX25 Appropriate AX.25 support is enabled. 39 BLACKFIN Blackfin architecture is enabled. 40 DRM Direct Rendering Management support is enabled. 41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled 42 EFI EFI Partitioning (GPT) is enabled 43 EIDE EIDE/ATAPI support is enabled. 44 FB The frame buffer device is enabled. 45 HW Appropriate hardware is enabled. 46 IA-64 IA-64 architecture is enabled. 47 IOSCHED More than one I/O scheduler is enabled. 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled. 49 ISAPNP ISA PnP code is enabled. 50 ISDN Appropriate ISDN support is enabled. 51 JOY Appropriate joystick support is enabled. 52 LIBATA Libata driver is enabled 53 LP Printer support is enabled. 54 LOOP Loopback device support is enabled. 55 M68k M68k architecture is enabled. 56 These options have more detailed description inside of 57 Documentation/m68k/kernel-options.txt. 58 MCA MCA bus support is enabled. 59 MDA MDA console support is enabled. 60 MOUSE Appropriate mouse support is enabled. 61 MSI Message Signaled Interrupts (PCI). 62 MTD MTD (Memory Technology Device) support is enabled. 63 NET Appropriate network support is enabled. 64 NUMA NUMA support is enabled. 65 GENERIC_TIME The generic timeofday code is enabled. 66 NFS Appropriate NFS support is enabled. 67 OSS OSS sound support is enabled. 68 PV_OPS A paravirtualized kernel is enabled. 69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled. 70 PARISC The PA-RISC architecture is enabled. 71 PCI PCI bus support is enabled. 72 PCIE PCI Express support is enabled. 73 PCMCIA The PCMCIA subsystem is enabled. 74 PNP Plug & Play support is enabled. 75 PPC PowerPC architecture is enabled. 76 PPT Parallel port support is enabled. 77 PS2 Appropriate PS/2 support is enabled. 78 RAM RAM disk support is enabled. 79 ROOTPLUG The example Root Plug LSM is enabled. 80 S390 S390 architecture is enabled. 81 SCSI Appropriate SCSI support is enabled. 82 A lot of drivers has their options described inside of 83 Documentation/scsi/. 84 SECURITY Different security models are enabled. 85 SELINUX SELinux support is enabled. 86 SERIAL Serial support is enabled. 87 SH SuperH architecture is enabled. 88 SMP The kernel is an SMP kernel. 89 SPARC Sparc architecture is enabled. 90 SWSUSP Software suspend (hibernation) is enabled. 91 SUSPEND System suspend states are enabled. 92 TS Appropriate touchscreen support is enabled. 93 USB USB support is enabled. 94 USBHID USB Human Interface Device support is enabled. 95 V4L Video For Linux support is enabled. 96 VGA The VGA console has been enabled. 97 VT Virtual terminal support is enabled. 98 WDT Watchdog support is enabled. 99 XT IBM PC/XT MFM hard disk support is enabled. 100 X86-32 X86-32, aka i386 architecture is enabled. 101 X86-64 X86-64 architecture is enabled. 102 More X86-64 boot options can be found in 103 Documentation/x86_64/boot-options.txt . 104 105In addition, the following text indicates that the option: 106 107 BUGS= Relates to possible processor bugs on the said processor. 108 KNL Is a kernel start-up parameter. 109 BOOT Is a boot loader parameter. 110 111Parameters denoted with BOOT are actually interpreted by the boot 112loader, and have no meaning to the kernel directly. 113Do not modify the syntax of boot loader parameters without extreme 114need or coordination with <Documentation/i386/boot.txt>. 115 116There are also arch-specific kernel-parameters not documented here. 117See for example <Documentation/x86_64/boot-options.txt>. 118 119Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 120a trailing = on the name of any parameter states that that parameter will 121be entered as an environment variable, whereas its absence indicates that 122it will appear as a kernel argument readable via /proc/cmdline by programs 123running once the system is up. 124 125The number of kernel parameters is not limited, but the length of the 126complete command line (parameters including spaces etc.) is limited to 127a fixed number of characters. This limit depends on the architecture 128and is between 256 and 4096 characters. It is defined in the file 129./include/asm/setup.h as COMMAND_LINE_SIZE. 130 131 132 acpi= [HW,ACPI,X86-64,i386] 133 Advanced Configuration and Power Interface 134 Format: { force | off | ht | strict | noirq } 135 force -- enable ACPI if default was off 136 off -- disable ACPI if default was on 137 noirq -- do not use ACPI for IRQ routing 138 ht -- run only enough ACPI to enable Hyper Threading 139 strict -- Be less tolerant of platforms that are not 140 strictly ACPI specification compliant. 141 142 See also Documentation/power/pm.txt, pci=noacpi 143 144 acpi_apic_instance= [ACPI, IOAPIC] 145 Format: <int> 146 2: use 2nd APIC table, if available 147 1,0: use 1st APIC table 148 default: 0 149 150 acpi_sleep= [HW,ACPI] Sleep options 151 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering } 152 See Documentation/power/video.txt for s3_bios and s3_mode. 153 s3_beep is for debugging; it makes the PC's speaker beep 154 as soon as the kernel's real-mode entry point is called. 155 s4_nohwsig prevents ACPI hardware signature from being 156 used during resume from hibernation. 157 old_ordering causes the ACPI 1.0 ordering of the _PTS 158 control method, wrt putting devices into low power 159 states, to be enforced (the ACPI 2.0 ordering of _PTS is 160 used by default). 161 162 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 163 Format: { level | edge | high | low } 164 165 acpi_irq_balance [HW,ACPI] 166 ACPI will balance active IRQs 167 default in APIC mode 168 169 acpi_irq_nobalance [HW,ACPI] 170 ACPI will not move active IRQs (default) 171 default in PIC mode 172 173 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 174 use by PCI 175 Format: <irq>,<irq>... 176 177 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 178 Format: <irq>,<irq>... 179 180 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 181 182 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 183 Format: To spoof as Windows 98: ="Microsoft Windows" 184 185 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 186 acpi_osi="string1" # add string1 -- only one string 187 acpi_osi="!string2" # remove built-in string2 188 acpi_osi= # disable all strings 189 190 acpi_serialize [HW,ACPI] force serialization of AML methods 191 192 acpi_skip_timer_override [HW,ACPI] 193 Recognize and ignore IRQ0/pin2 Interrupt Override. 194 For broken nForce2 BIOS resulting in XT-PIC timer. 195 acpi_use_timer_override [HW,ACPI} 196 Use timer override. For some broken Nvidia NF5 boards 197 that require a timer override, but don't have 198 HPET 199 200 acpi.debug_layer= [HW,ACPI] 201 Format: <int> 202 Each bit of the <int> indicates an ACPI debug layer, 203 1: enable, 0: disable. It is useful for boot time 204 debugging. After system has booted up, it can be set 205 via /sys/module/acpi/parameters/debug_layer. 206 CONFIG_ACPI_DEBUG must be enabled for this to produce any output. 207 Available bits (add the numbers together) to enable debug output 208 for specific parts of the ACPI subsystem: 209 0x01 utilities 0x02 hardware 0x04 events 0x08 tables 210 0x10 namespace 0x20 parser 0x40 dispatcher 211 0x80 executer 0x100 resources 0x200 acpica debugger 212 0x400 os services 0x800 acpica disassembler. 213 The number can be in decimal or prefixed with 0x in hex. 214 Warning: Many of these options can produce a lot of 215 output and make your system unusable. Be very careful. 216 217 acpi.debug_level= [HW,ACPI] 218 Format: <int> 219 Each bit of the <int> indicates an ACPI debug level, 220 1: enable, 0: disable. It is useful for boot time 221 debugging. After system has booted up, it can be set 222 via /sys/module/acpi/parameters/debug_level. 223 CONFIG_ACPI_DEBUG must be enabled for this to produce any output. 224 Available bits (add the numbers together) to enable different 225 debug output levels of the ACPI subsystem: 226 0x01 error 0x02 warn 0x04 init 0x08 debug object 227 0x10 info 0x20 init names 0x40 parse 0x80 load 228 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region 229 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects 230 0x10000 resources 0x20000 user requests 0x40000 package. 231 The number can be in decimal or prefixed with 0x in hex. 232 Warning: Many of these options can produce a lot of 233 output and make your system unusable. Be very careful. 234 235 acpi_pm_good [X86-32,X86-64] 236 Override the pmtimer bug detection: force the kernel 237 to assume that this machine's pmtimer latches its value 238 and always returns good values. 239 240 agp= [AGP] 241 { off | try_unsupported } 242 off: disable AGP support 243 try_unsupported: try to drive unsupported chipsets 244 (may crash computer or cause data corruption) 245 246 enable_timer_pin_1 [i386,x86-64] 247 Enable PIN 1 of APIC timer 248 Can be useful to work around chipset bugs 249 (in particular on some ATI chipsets). 250 The kernel tries to set a reasonable default. 251 252 disable_timer_pin_1 [i386,x86-64] 253 Disable PIN 1 of APIC timer 254 Can be useful to work around chipset bugs. 255 256 ad1848= [HW,OSS] 257 Format: <io>,<irq>,<dma>,<dma2>,<type> 258 259 advansys= [HW,SCSI] 260 See header of drivers/scsi/advansys.c. 261 262 advwdt= [HW,WDT] Advantech WDT 263 Format: <iostart>,<iostop> 264 265 aedsp16= [HW,OSS] Audio Excel DSP 16 266 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq> 267 See also header of sound/oss/aedsp16.c. 268 269 aha152x= [HW,SCSI] 270 See Documentation/scsi/aha152x.txt. 271 272 aha1542= [HW,SCSI] 273 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]] 274 275 aic7xxx= [HW,SCSI] 276 See Documentation/scsi/aic7xxx.txt. 277 278 aic79xx= [HW,SCSI] 279 See Documentation/scsi/aic79xx.txt. 280 281 amd_iommu= [HW,X86-84] 282 Pass parameters to the AMD IOMMU driver in the system. 283 Possible values are: 284 isolate - enable device isolation (each device, as far 285 as possible, will get its own protection 286 domain) 287 amd_iommu_size= [HW,X86-64] 288 Define the size of the aperture for the AMD IOMMU 289 driver. Possible values are: 290 '32M', '64M' (default), '128M', '256M', '512M', '1G' 291 292 amijoy.map= [HW,JOY] Amiga joystick support 293 Map of devices attached to JOY0DAT and JOY1DAT 294 Format: <a>,<b> 295 See also Documentation/kernel/input/joystick.txt 296 297 analog.map= [HW,JOY] Analog joystick and gamepad support 298 Specifies type or capabilities of an analog joystick 299 connected to one of 16 gameports 300 Format: <type1>,<type2>,..<type16> 301 302 apc= [HW,SPARC] 303 Power management functions (SPARCstation-4/5 + deriv.) 304 Format: noidle 305 Disable APC CPU standby support. SPARCstation-Fox does 306 not play well with APC CPU idle - disable it if you have 307 APC and your system crashes randomly. 308 309 apic= [APIC,i386] Advanced Programmable Interrupt Controller 310 Change the output verbosity whilst booting 311 Format: { quiet (default) | verbose | debug } 312 Change the amount of debugging information output 313 when initialising the APIC and IO-APIC components. 314 315 apm= [APM] Advanced Power Management 316 See header of arch/x86/kernel/apm_32.c. 317 318 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 319 Format: <io>,<irq>,<nodeID> 320 321 ataflop= [HW,M68k] 322 323 atarimouse= [HW,MOUSE] Atari Mouse 324 325 atascsi= [HW,SCSI] Atari SCSI 326 327 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 328 EzKey and similar keyboards 329 330 atkbd.reset= [HW] Reset keyboard during initialization 331 332 atkbd.set= [HW] Select keyboard code set 333 Format: <int> (2 = AT (default), 3 = PS/2) 334 335 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 336 keyboards 337 338 atkbd.softraw= [HW] Choose between synthetic and real raw mode 339 Format: <bool> (0 = real, 1 = synthetic (default)) 340 341 atkbd.softrepeat= [HW] 342 Use software keyboard repeat 343 344 autotest [IA64] 345 346 baycom_epp= [HW,AX25] 347 Format: <io>,<mode> 348 349 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 350 Format: <io>,<mode> 351 See header of drivers/net/hamradio/baycom_par.c. 352 353 baycom_ser_fdx= [HW,AX25] 354 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 355 Format: <io>,<irq>,<mode>[,<baud>] 356 See header of drivers/net/hamradio/baycom_ser_fdx.c. 357 358 baycom_ser_hdx= [HW,AX25] 359 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 360 Format: <io>,<irq>,<mode> 361 See header of drivers/net/hamradio/baycom_ser_hdx.c. 362 363 boot_delay= Milliseconds to delay each printk during boot. 364 Values larger than 10 seconds (10000) are changed to 365 no delay (0). 366 Format: integer 367 368 bootmem_debug [KNL] Enable bootmem allocator debug messages. 369 370 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 371 bttv.radio= Most important insmod options are available as 372 kernel args too. 373 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 374 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 375 376 BusLogic= [HW,SCSI] 377 See drivers/scsi/BusLogic.c, comment before function 378 BusLogic_ParseDriverOptions(). 379 380 c101= [NET] Moxa C101 synchronous serial card 381 382 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 383 Sometimes CPU hardware bugs make them report the cache 384 size incorrectly. The kernel will attempt work arounds 385 to fix known problems, but for some CPUs it is not 386 possible to determine what the correct size should be. 387 This option provides an override for these situations. 388 389 security= [SECURITY] Choose a security module to enable at boot. 390 If this boot parameter is not specified, only the first 391 security module asking for security registration will be 392 loaded. An invalid security module name will be treated 393 as if no module has been chosen. 394 395 capability.disable= 396 [SECURITY] Disable capabilities. This would normally 397 be used only if an alternative security model is to be 398 configured. Potentially dangerous and should only be 399 used if you are entirely sure of the consequences. 400 401 ccw_timeout_log [S390] 402 See Documentation/s390/CommonIO for details. 403 404 cgroup_disable= [KNL] Disable a particular controller 405 Format: {name of the controller(s) to disable} 406 {Currently supported controllers - "memory"} 407 408 checkreqprot [SELINUX] Set initial checkreqprot flag value. 409 Format: { "0" | "1" } 410 See security/selinux/Kconfig help text. 411 0 -- check protection applied by kernel (includes 412 any implied execute protection). 413 1 -- check protection requested by application. 414 Default value is set via a kernel config option. 415 Value can be changed at runtime via 416 /selinux/checkreqprot. 417 418 cio_ignore= [S390] 419 See Documentation/s390/CommonIO for details. 420 421 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 422 [Deprecated] 423 Forces specified clocksource (if available) to be used 424 when calculating gettimeofday(). If specified 425 clocksource is not available, it defaults to PIT. 426 Format: { pit | tsc | cyclone | pmtmr } 427 428 clocksource= [GENERIC_TIME] Override the default clocksource 429 Format: <string> 430 Override the default clocksource and use the clocksource 431 with the name specified. 432 Some clocksource names to choose from, depending on 433 the platform: 434 [all] jiffies (this is the base, fallback clocksource) 435 [ACPI] acpi_pm 436 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 437 pxa_timer,timer3,32k_counter,timer0_1 438 [AVR32] avr32 439 [X86-32] pit,hpet,tsc,vmi-timer; 440 scx200_hrt on Geode; cyclone on IBM x440 441 [MIPS] MIPS 442 [PARISC] cr16 443 [S390] tod 444 [SH] SuperH 445 [SPARC64] tick 446 [X86-64] hpet,tsc 447 448 clearcpuid=BITNUM [X86] 449 Disable CPUID feature X for the kernel. See 450 include/asm-x86/cpufeature.h for the valid bit numbers. 451 Note the Linux specific bits are not necessarily 452 stable over kernel options, but the vendor specific 453 ones should be. 454 Also note that user programs calling CPUID directly 455 or using the feature without checking anything 456 will still see it. This just prevents it from 457 being used by the kernel or shown in /proc/cpuinfo. 458 Also note the kernel might malfunction if you disable 459 some critical bits. 460 461 code_bytes [IA32/X86_64] How many bytes of object code to print 462 in an oops report. 463 Range: 0 - 8192 464 Default: 64 465 466 disable_8254_timer 467 enable_8254_timer 468 [IA32/X86_64] Disable/Enable interrupt 0 timer routing 469 over the 8254 in addition to over the IO-APIC. The 470 kernel tries to set a sensible default. 471 472 hpet= [X86-32,HPET] option to control HPET usage 473 Format: { enable (default) | disable | force } 474 disable: disable HPET and use PIT instead 475 force: allow force enabled of undocumented chips (ICH4, 476 VIA, nVidia) 477 478 com20020= [HW,NET] ARCnet - COM20020 chipset 479 Format: 480 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 481 482 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 483 Format: <io>[,<irq>] 484 485 com90xx= [HW,NET] 486 ARCnet - COM90xx chipset (memory-mapped buffers) 487 Format: <io>[,<irq>[,<memstart>]] 488 489 condev= [HW,S390] console device 490 conmode= 491 492 console= [KNL] Output console device and options. 493 494 tty<n> Use the virtual console device <n>. 495 496 ttyS<n>[,options] 497 ttyUSB0[,options] 498 Use the specified serial port. The options are of 499 the form "bbbbpnf", where "bbbb" is the baud rate, 500 "p" is parity ("n", "o", or "e"), "n" is number of 501 bits, and "f" is flow control ("r" for RTS or 502 omit it). Default is "9600n8". 503 504 See Documentation/serial-console.txt for more 505 information. See 506 Documentation/networking/netconsole.txt for an 507 alternative. 508 509 uart[8250],io,<addr>[,options] 510 uart[8250],mmio,<addr>[,options] 511 Start an early, polled-mode console on the 8250/16550 512 UART at the specified I/O port or MMIO address, 513 switching to the matching ttyS device later. The 514 options are the same as for ttyS, above. 515 516 If the device connected to the port is not a TTY but a braille 517 device, prepend "brl," before the device type, for instance 518 console=brl,ttyS0 519 For now, only VisioBraille is supported. 520 521 earlycon= [KNL] Output early console device and options. 522 uart[8250],io,<addr>[,options] 523 uart[8250],mmio,<addr>[,options] 524 Start an early, polled-mode console on the 8250/16550 525 UART at the specified I/O port or MMIO address. 526 The options are the same as for ttyS, above. 527 528 no_console_suspend 529 [HW] Never suspend the console 530 Disable suspending of consoles during suspend and 531 hibernate operations. Once disabled, debugging 532 messages can reach various consoles while the rest 533 of the system is being put to sleep (ie, while 534 debugging driver suspend/resume hooks). This may 535 not work reliably with all consoles, but is known 536 to work with serial and VGA consoles. 537 538 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 539 Format: 540 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 541 542 crashkernel=nn[KMG]@ss[KMG] 543 [KNL] Reserve a chunk of physical memory to 544 hold a kernel to switch to with kexec on panic. 545 546 crashkernel=range1:size1[,range2:size2,...][@offset] 547 [KNL] Same as above, but depends on the memory 548 in the running system. The syntax of range is 549 start-[end] where start and end are both 550 a memory unit (amount[KMG]). See also 551 Documentation/kdump/kdump.txt for a example. 552 553 cs4232= [HW,OSS] 554 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq> 555 556 cs89x0_dma= [HW,NET] 557 Format: <dma> 558 559 cs89x0_media= [HW,NET] 560 Format: { rj45 | aui | bnc } 561 562 dasd= [HW,NET] 563 See header of drivers/s390/block/dasd_devmap.c. 564 565 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 566 (one device per port) 567 Format: <port#>,<type> 568 See also Documentation/input/joystick-parport.txt 569 570 debug [KNL] Enable kernel debugging (events log level). 571 572 debug_locks_verbose= 573 [KNL] verbose self-tests 574 Format=<0|1> 575 Print debugging info while doing the locking API 576 self-tests. 577 We default to 0 (no extra messages), setting it to 578 1 will print _a lot_ more information - normally 579 only useful to kernel developers. 580 581 debug_objects [KNL] Enable object debugging 582 583 debugpat [X86] Enable PAT debugging 584 585 decnet.addr= [HW,NET] 586 Format: <area>[,<node>] 587 See also Documentation/networking/decnet.txt. 588 589 vt.default_blu= [VT] 590 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 591 Change the default blue palette of the console. 592 This is a 16-member array composed of values 593 ranging from 0-255. 594 595 vt.default_grn= [VT] 596 Format: <green0>,<green1>,<green2>,...,<green15> 597 Change the default green palette of the console. 598 This is a 16-member array composed of values 599 ranging from 0-255. 600 601 vt.default_red= [VT] 602 Format: <red0>,<red1>,<red2>,...,<red15> 603 Change the default red palette of the console. 604 This is a 16-member array composed of values 605 ranging from 0-255. 606 607 vt.default_utf8= 608 [VT] 609 Format=<0|1> 610 Set system-wide default UTF-8 mode for all tty's. 611 Default is 1, i.e. UTF-8 mode is enabled for all 612 newly opened terminals. 613 614 dhash_entries= [KNL] 615 Set number of hash buckets for dentry cache. 616 617 digi= [HW,SERIAL] 618 IO parameters + enable/disable command. 619 620 digiepca= [HW,SERIAL] 621 See drivers/char/README.epca and 622 Documentation/digiepca.txt. 623 624 disable_mtrr_cleanup [X86] 625 enable_mtrr_cleanup [X86] 626 The kernel tries to adjust MTRR layout from continuous 627 to discrete, to make X server driver able to add WB 628 entry later. This parameter enables/disables that. 629 630 mtrr_chunk_size=nn[KMG] [X86] 631 used for mtrr cleanup. It is largest continous chunk 632 that could hold holes aka. UC entries. 633 634 mtrr_gran_size=nn[KMG] [X86] 635 Used for mtrr cleanup. It is granularity of mtrr block. 636 Default is 1. 637 Large value could prevent small alignment from 638 using up MTRRs. 639 640 mtrr_spare_reg_nr=n [X86] 641 Format: <integer> 642 Range: 0,7 : spare reg number 643 Default : 1 644 Used for mtrr cleanup. It is spare mtrr entries number. 645 Set to 2 or more if your graphical card needs more. 646 647 disable_mtrr_trim [X86, Intel and AMD only] 648 By default the kernel will trim any uncacheable 649 memory out of your available memory pool based on 650 MTRR settings. This parameter disables that behavior, 651 possibly causing your machine to run very slowly. 652 653 dmasound= [HW,OSS] Sound subsystem buffers 654 655 dscc4.setup= [NET] 656 657 dtc3181e= [HW,SCSI] 658 659 earlyprintk= [X86-32,X86-64,SH,BLACKFIN] 660 earlyprintk=vga 661 earlyprintk=serial[,ttySn[,baudrate]] 662 663 Append ",keep" to not disable it when the real console 664 takes over. 665 666 Only vga or serial at a time, not both. 667 668 Currently only ttyS0 and ttyS1 are supported. 669 670 Interaction with the standard serial driver is not 671 very good. 672 673 The VGA output is eventually overwritten by the real 674 console. 675 676 eata= [HW,SCSI] 677 678 edd= [EDD] 679 Format: {"off" | "on" | "skip[mbr]"} 680 681 eisa_irq_edge= [PARISC,HW] 682 See header of drivers/parisc/eisa.c. 683 684 elanfreq= [X86-32] 685 See comment before function elanfreq_setup() in 686 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 687 688 elevator= [IOSCHED] 689 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 690 See Documentation/block/as-iosched.txt and 691 Documentation/block/deadline-iosched.txt for details. 692 693 elfcorehdr= [X86-32, X86_64] 694 Specifies physical address of start of kernel core 695 image elf header. Generally kexec loader will 696 pass this option to capture kernel. 697 See Documentation/kdump/kdump.txt for details. 698 699 enforcing [SELINUX] Set initial enforcing status. 700 Format: {"0" | "1"} 701 See security/selinux/Kconfig help text. 702 0 -- permissive (log only, no denials). 703 1 -- enforcing (deny and log). 704 Default value is 0. 705 Value can be changed at runtime via /selinux/enforce. 706 707 es1371= [HW,OSS] 708 Format: <spdif>,[<nomix>,[<amplifier>]] 709 See also header of sound/oss/es1371.c. 710 711 ether= [HW,NET] Ethernet cards parameters 712 This option is obsoleted by the "netdev=" option, which 713 has equivalent usage. See its documentation for details. 714 715 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog. 716 Format: <io>[,<irq>] 717 718 failslab= 719 fail_page_alloc= 720 fail_make_request=[KNL] 721 General fault injection mechanism. 722 Format: <interval>,<probability>,<space>,<times> 723 See also /Documentation/fault-injection/. 724 725 fd_mcs= [HW,SCSI] 726 See header of drivers/scsi/fd_mcs.c. 727 728 fdomain= [HW,SCSI] 729 See header of drivers/scsi/fdomain.c. 730 731 floppy= [HW] 732 See Documentation/floppy.txt. 733 734 force_pal_cache_flush 735 [IA-64] Avoid check_sal_cache_flush which may hang on 736 buggy SAL_CACHE_FLUSH implementations. Using this 737 parameter will force ia64_sal_cache_flush to call 738 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 739 740 gamecon.map[2|3]= 741 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 742 support via parallel port (up to 5 devices per port) 743 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 744 See also Documentation/input/joystick-parport.txt 745 746 gamma= [HW,DRM] 747 748 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 749 Format: off | on 750 default: on 751 752 gdth= [HW,SCSI] 753 See header of drivers/scsi/gdth.c. 754 755 gpt [EFI] Forces disk with valid GPT signature but 756 invalid Protective MBR to be treated as GPT. 757 758 gvp11= [HW,SCSI] 759 760 hashdist= [KNL,NUMA] Large hashes allocated during boot 761 are distributed across NUMA nodes. Defaults on 762 for IA-64, off otherwise. 763 Format: 0 | 1 (for off | on) 764 765 hcl= [IA-64] SGI's Hardware Graph compatibility layer 766 767 hd= [EIDE] (E)IDE hard drive subsystem geometry 768 Format: <cyl>,<head>,<sect> 769 770 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 771 size of <nn>. This works even on boxes that have no 772 highmem otherwise. This also works to reduce highmem 773 size on bigger boxes. 774 775 highres= [KNL] Enable/disable high resolution timer mode. 776 Valid parameters: "on", "off" 777 Default: "on" 778 779 hisax= [HW,ISDN] 780 See Documentation/isdn/README.HiSax. 781 782 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 783 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 784 On x86-64 and powerpc, this option can be specified 785 multiple times interleaved with hugepages= to reserve 786 huge pages of different sizes. Valid pages sizes on 787 x86-64 are 2M (when the CPU supports "pse") and 1G 788 (when the CPU supports the "pdpe1gb" cpuinfo flag) 789 Note that 1GB pages can only be allocated at boot time 790 using hugepages= and not freed afterwards. 791 default_hugepagesz= 792 [same as hugepagesz=] The size of the default 793 HugeTLB page size. This is the size represented by 794 the legacy /proc/ hugepages APIs, used for SHM, and 795 default size when mounting hugetlbfs filesystems. 796 Defaults to the default architecture's huge page size 797 if not specified. 798 799 i8042.direct [HW] Put keyboard port into non-translated mode 800 i8042.dumbkbd [HW] Pretend that controller can only read data from 801 keyboard and cannot control its state 802 (Don't attempt to blink the leds) 803 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 804 i8042.nokbd [HW] Don't check/create keyboard port 805 i8042.noloop [HW] Disable the AUX Loopback command while probing 806 for the AUX port 807 i8042.nomux [HW] Don't check presence of an active multiplexing 808 controller 809 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 810 controllers 811 i8042.panicblink= 812 [HW] Frequency with which keyboard LEDs should blink 813 when kernel panics (default is 0.5 sec) 814 i8042.reset [HW] Reset the controller during init and cleanup 815 i8042.unlock [HW] Unlock (ignore) the keylock 816 817 i810= [HW,DRM] 818 819 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 820 indicates that the driver is running on unsupported 821 hardware. 822 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 823 does not match list of supported models. 824 i8k.power_status 825 [HW] Report power status in /proc/i8k 826 (disabled by default) 827 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 828 capability is set. 829 830 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter 831 See Documentation/mca.txt. 832 833 icn= [HW,ISDN] 834 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 835 836 ide= [HW] (E)IDE subsystem 837 Format: ide=nodma or ide=doubler 838 See Documentation/ide/ide.txt. 839 840 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed 841 See Documentation/ide/ide.txt. 842 843 idle= [X86] 844 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait 845 Poll forces a polling idle loop that can slightly improves the performance 846 of waking up a idle CPU, but will use a lot of power and make the system 847 run hot. Not recommended. 848 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose 849 to not use it because it doesn't save as much power as a normal idle 850 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same 851 as idle=poll. 852 idle=halt. Halt is forced to be used for CPU idle. 853 In such case C2/C3 won't be used again. 854 idle=nomwait. Disable mwait for CPU C-states 855 856 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 857 Claim all unknown PCI IDE storage controllers. 858 859 ignore_loglevel [KNL] 860 Ignore loglevel setting - this will print /all/ 861 kernel messages to the console. Useful for debugging. 862 863 ihash_entries= [KNL] 864 Set number of hash buckets for inode cache. 865 866 in2000= [HW,SCSI] 867 See header of drivers/scsi/in2000.c. 868 869 init= [KNL] 870 Format: <full_path> 871 Run specified binary instead of /sbin/init as init 872 process. 873 874 initcall_debug [KNL] Trace initcalls as they are executed. Useful 875 for working out where the kernel is dying during 876 startup. 877 878 initrd= [BOOT] Specify the location of the initial ramdisk 879 880 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 881 Format: <irq> 882 883 inttest= [IA64] 884 885 iommu= [x86] 886 off 887 force 888 noforce 889 biomerge 890 panic 891 nopanic 892 merge 893 nomerge 894 forcesac 895 soft 896 897 898 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 899 off 900 Disable intel iommu driver. 901 igfx_off [Default Off] 902 By default, gfx is mapped as normal device. If a gfx 903 device has a dedicated DMAR unit, the DMAR unit is 904 bypassed by not enabling DMAR with this option. In 905 this case, gfx device will use physical address for 906 DMA. 907 forcedac [x86_64] 908 With this option iommu will not optimize to look 909 for io virtual address below 32 bit forcing dual 910 address cycle on pci bus for cards supporting greater 911 than 32 bit addressing. The default is to look 912 for translation below 32 bit and if not available 913 then look in the higher range. 914 strict [Default Off] 915 With this option on every unmap_single operation will 916 result in a hardware IOTLB flush operation as opposed 917 to batching them for performance. 918 919 io_delay= [X86-32,X86-64] I/O delay method 920 0x80 921 Standard port 0x80 based delay 922 0xed 923 Alternate port 0xed based delay (needed on some systems) 924 udelay 925 Simple two microseconds delay 926 none 927 No delay 928 929 io7= [HW] IO7 for Marvel based alpha systems 930 See comment before marvel_specify_io7 in 931 arch/alpha/kernel/core_marvel.c. 932 933 ip= [IP_PNP] 934 See Documentation/filesystems/nfsroot.txt. 935 936 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 937 See comment before ip2_setup() in 938 drivers/char/ip2/ip2base.c. 939 940 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller 941 See header of drivers/scsi/ips.c. 942 943 ports= [IP_VS_FTP] IPVS ftp helper module 944 Default is 21. 945 Up to 8 (IP_VS_APP_MAX_PORTS) ports 946 may be specified. 947 Format: <port>,<port>.... 948 949 irqfixup [HW] 950 When an interrupt is not handled search all handlers 951 for it. Intended to get systems with badly broken 952 firmware running. 953 954 irqpoll [HW] 955 When an interrupt is not handled search all handlers 956 for it. Also check all handlers each timer 957 interrupt. Intended to get systems with badly broken 958 firmware running. 959 960 isapnp= [ISAPNP] 961 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 962 963 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 964 Format: 965 <cpu number>,...,<cpu number> 966 or 967 <cpu number>-<cpu number> (must be a positive range in ascending order) 968 or a mixture 969 <cpu number>,...,<cpu number>-<cpu number> 970 This option can be used to specify one or more CPUs 971 to isolate from the general SMP balancing and scheduling 972 algorithms. The only way to move a process onto or off 973 an "isolated" CPU is via the CPU affinity syscalls. 974 <cpu number> begins at 0 and the maximum value is 975 "number of CPUs in system - 1". 976 977 This option is the preferred way to isolate CPUs. The 978 alternative -- manually setting the CPU mask of all 979 tasks in the system -- can cause problems and 980 suboptimal load balancer performance. 981 982 iucv= [HW,NET] 983 984 js= [HW,JOY] Analog joystick 985 See Documentation/input/joystick.txt. 986 987 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 988 specifies the amount of memory usable by the kernel 989 for non-movable allocations. The requested amount is 990 spread evenly throughout all nodes in the system. The 991 remaining memory in each node is used for Movable 992 pages. In the event, a node is too small to have both 993 kernelcore and Movable pages, kernelcore pages will 994 take priority and other nodes will have a larger number 995 of kernelcore pages. The Movable zone is used for the 996 allocation of pages that may be reclaimed or moved 997 by the page migration subsystem. This means that 998 HugeTLB pages may not be allocated from this zone. 999 Note that allocations like PTEs-from-HighMem still 1000 use the HighMem zone if it exists, and the Normal 1001 zone if it does not. 1002 1003 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 1004 is similar to kernelcore except it specifies the 1005 amount of memory used for migratable allocations. 1006 If both kernelcore and movablecore is specified, 1007 then kernelcore will be at *least* the specified 1008 value but may be more. If movablecore on its own 1009 is specified, the administrator must be careful 1010 that the amount of memory usable for all allocations 1011 is not too small. 1012 1013 keepinitrd [HW,ARM] 1014 1015 kstack=N [X86-32,X86-64] Print N words from the kernel stack 1016 in oops dumps. 1017 1018 kgdboc= [HW] kgdb over consoles. 1019 Requires a tty driver that supports console polling. 1020 (only serial suported for now) 1021 Format: <serial_device>[,baud] 1022 1023 l2cr= [PPC] 1024 1025 l3cr= [PPC] 1026 1027 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1028 disabled it. 1029 1030 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in 1031 C2 power state. 1032 1033 libata.dma= [LIBATA] DMA control 1034 libata.dma=0 Disable all PATA and SATA DMA 1035 libata.dma=1 PATA and SATA Disk DMA only 1036 libata.dma=2 ATAPI (CDROM) DMA only 1037 libata.dma=4 Compact Flash DMA only 1038 Combinations also work, so libata.dma=3 enables DMA 1039 for disks and CDROMs, but not CFs. 1040 1041 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1042 when set. 1043 Format: <int> 1044 1045 libata.force= [LIBATA] Force configurations. The format is comma 1046 separated list of "[ID:]VAL" where ID is 1047 PORT[:DEVICE]. PORT and DEVICE are decimal numbers 1048 matching port, link or device. Basically, it matches 1049 the ATA ID string printed on console by libata. If 1050 the whole ID part is omitted, the last PORT and DEVICE 1051 values are used. If ID hasn't been specified yet, the 1052 configuration applies to all ports, links and devices. 1053 1054 If only DEVICE is omitted, the parameter applies to 1055 the port and all links and devices behind it. DEVICE 1056 number of 0 either selects the first device or the 1057 first fan-out link behind PMP device. It does not 1058 select the host link. DEVICE number of 15 selects the 1059 host link and device attached to it. 1060 1061 The VAL specifies the configuration to force. As long 1062 as there's no ambiguity shortcut notation is allowed. 1063 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1064 The following configurations can be forced. 1065 1066 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1067 Any ID with matching PORT is used. 1068 1069 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1070 1071 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1072 udma[/][16,25,33,44,66,100,133] notation is also 1073 allowed. 1074 1075 * [no]ncq: Turn on or off NCQ. 1076 1077 If there are multiple matching configurations changing 1078 the same attribute, the last one is used. 1079 1080 load_ramdisk= [RAM] List of ramdisks to load from floppy 1081 See Documentation/ramdisk.txt. 1082 1083 lockd.nlm_grace_period=P [NFS] Assign grace period. 1084 Format: <integer> 1085 1086 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1087 Format: <integer> 1088 1089 lockd.nlm_timeout=T [NFS] Assign timeout value. 1090 Format: <integer> 1091 1092 lockd.nlm_udpport=M [NFS] Assign UDP port. 1093 Format: <integer> 1094 1095 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1096 Format: <irq> 1097 1098 loglevel= All Kernel Messages with a loglevel smaller than the 1099 console loglevel will be printed to the console. It can 1100 also be changed with klogd or other programs. The 1101 loglevels are defined as follows: 1102 1103 0 (KERN_EMERG) system is unusable 1104 1 (KERN_ALERT) action must be taken immediately 1105 2 (KERN_CRIT) critical conditions 1106 3 (KERN_ERR) error conditions 1107 4 (KERN_WARNING) warning conditions 1108 5 (KERN_NOTICE) normal but significant condition 1109 6 (KERN_INFO) informational 1110 7 (KERN_DEBUG) debug-level messages 1111 1112 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1113 Format: { n | nk | nM } 1114 n must be a power of two. The default size 1115 is set in the kernel config file. 1116 1117 logo.nologo [FB] Disables display of the built-in Linux logo. 1118 This may be used to provide more screen space for 1119 kernel log messages and is useful when debugging 1120 kernel boot problems. 1121 1122 lp=0 [LP] Specify parallel ports to use, e.g, 1123 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1124 lp=reset first parallel port). 'lp=0' disables the 1125 lp=auto printer driver. 'lp=reset' (which can be 1126 specified in addition to the ports) causes 1127 attached printers to be reset. Using 1128 lp=port1,port2,... specifies the parallel ports 1129 to associate lp devices with, starting with 1130 lp0. A port specification may be 'none' to skip 1131 that lp device, or a parport name such as 1132 'parport0'. Specifying 'lp=auto' instead of a 1133 port specification list means that device IDs 1134 from each port should be examined, to see if 1135 an IEEE 1284-compliant printer is attached; if 1136 so, the driver will manage that printer. 1137 See also header of drivers/char/lp.c. 1138 1139 lpj=n [KNL] 1140 Sets loops_per_jiffy to given constant, thus avoiding 1141 time-consuming boot-time autodetection (up to 250 ms per 1142 CPU). 0 enables autodetection (default). To determine 1143 the correct value for your kernel, boot with normal 1144 autodetection and see what value is printed. Note that 1145 on SMP systems the preset will be applied to all CPUs, 1146 which is likely to cause problems if your CPUs need 1147 significantly divergent settings. An incorrect value 1148 will cause delays in the kernel to be wrong, leading to 1149 unpredictable I/O errors and other breakage. Although 1150 unlikely, in the extreme case this might damage your 1151 hardware. 1152 1153 ltpc= [NET] 1154 Format: <io>,<irq>,<dma> 1155 1156 mac5380= [HW,SCSI] Format: 1157 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1158 1159 machvec= [IA64] Force the use of a particular machine-vector 1160 (machvec) in a generic kernel. 1161 Example: machvec=hpzx1_swiotlb 1162 1163 max_loop= [LOOP] Maximum number of loopback devices that can 1164 be mounted 1165 Format: <1-256> 1166 1167 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1168 should make use of. maxcpus=n : n >= 0 limits the 1169 kernel to using 'n' processors. n=0 is a special case, 1170 it is equivalent to "nosmp", which also disables 1171 the IO APIC. 1172 1173 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or 1174 equal to this physical address is ignored. 1175 1176 max_luns= [SCSI] Maximum number of LUNs to probe. 1177 Should be between 1 and 2^32-1. 1178 1179 max_report_luns= 1180 [SCSI] Maximum number of LUNs received. 1181 Should be between 1 and 16384. 1182 1183 mcatest= [IA-64] 1184 1185 mce [X86-32] Machine Check Exception 1186 1187 mce=option [X86-64] See Documentation/x86_64/boot-options.txt 1188 1189 md= [HW] RAID subsystems devices and level 1190 See Documentation/md.txt. 1191 1192 mdacon= [MDA] 1193 Format: <first>,<last> 1194 Specifies range of consoles to be captured by the MDA. 1195 1196 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1197 Amount of memory to be used when the kernel is not able 1198 to see the whole system memory or for test. 1199 [X86-32] Use together with memmap= to avoid physical 1200 address space collisions. Without memmap= PCI devices 1201 could be placed at addresses belonging to unused RAM. 1202 1203 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1204 memory. 1205 1206 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact 1207 E820 memory map, as specified by the user. 1208 Such memmap=exactmap lines can be constructed based on 1209 BIOS output or other requirements. See the memmap=nn@ss 1210 option description. 1211 1212 memmap=nn[KMG]@ss[KMG] 1213 [KNL] Force usage of a specific region of memory 1214 Region of memory to be used, from ss to ss+nn. 1215 1216 memmap=nn[KMG]#ss[KMG] 1217 [KNL,ACPI] Mark specific memory as ACPI data. 1218 Region of memory to be used, from ss to ss+nn. 1219 1220 memmap=nn[KMG]$ss[KMG] 1221 [KNL,ACPI] Mark specific memory as reserved. 1222 Region of memory to be used, from ss to ss+nn. 1223 Example: Exclude memory from 0x18690000-0x1869ffff 1224 memmap=64K$0x18690000 1225 or 1226 memmap=0x10000$0x18690000 1227 1228 memtest= [KNL,X86] Enable memtest 1229 Format: <integer> 1230 range: 0,4 : pattern number 1231 default : 0 <disable> 1232 1233 meye.*= [HW] Set MotionEye Camera parameters 1234 See Documentation/video4linux/meye.txt. 1235 1236 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1237 Multi-Function General Purpose Timers on AMD Geode 1238 platforms. 1239 1240 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1241 the BIOS has incorrectly applied a workaround. TinyBIOS 1242 version 0.98 is known to be affected, 0.99 fixes the 1243 problem by letting the user disable the workaround. 1244 1245 mga= [HW,DRM] 1246 1247 mminit_loglevel= 1248 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1249 parameter allows control of the logging verbosity for 1250 the additional memory initialisation checks. A value 1251 of 0 disables mminit logging and a level of 4 will 1252 log everything. Information is printed at KERN_DEBUG 1253 so loglevel=8 may also need to be specified. 1254 1255 mousedev.tap_time= 1256 [MOUSE] Maximum time between finger touching and 1257 leaving touchpad surface for touch to be considered 1258 a tap and be reported as a left button click (for 1259 touchpads working in absolute mode only). 1260 Format: <msecs> 1261 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1262 reporting absolute coordinates, such as tablets 1263 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1264 reporting absolute coordinates, such as tablets 1265 1266 mpu401= [HW,OSS] 1267 Format: <io>,<irq> 1268 1269 MTD_Partition= [MTD] 1270 Format: <name>,<region-number>,<size>,<offset> 1271 1272 MTD_Region= [MTD] Format: 1273 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1274 1275 mtdparts= [MTD] 1276 See drivers/mtd/cmdlinepart.c. 1277 1278 mtdset= [ARM] 1279 ARM/S3C2412 JIVE boot control 1280 1281 See arch/arm/mach-s3c2412/mach-jive.c 1282 1283 mtouchusb.raw_coordinates= 1284 [HW] Make the MicroTouch USB driver use raw coordinates 1285 ('y', default) or cooked coordinates ('n') 1286 1287 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1288 1289 NCR_D700= [HW,SCSI] 1290 See header of drivers/scsi/NCR_D700.c. 1291 1292 ncr5380= [HW,SCSI] 1293 1294 ncr53c400= [HW,SCSI] 1295 1296 ncr53c400a= [HW,SCSI] 1297 1298 ncr53c406a= [HW,SCSI] 1299 1300 ncr53c8xx= [HW,SCSI] 1301 1302 netdev= [NET] Network devices parameters 1303 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1304 Note that mem_start is often overloaded to mean 1305 something different and driver-specific. 1306 This usage is only documented in each driver source 1307 file if at all. 1308 1309 nf_conntrack.acct= 1310 [NETFILTER] Enable connection tracking flow accounting 1311 0 to disable accounting 1312 1 to enable accounting 1313 Default value depends on CONFIG_NF_CT_ACCT that is 1314 going to be removed in 2.6.29. 1315 1316 nfsaddrs= [NFS] 1317 See Documentation/filesystems/nfsroot.txt. 1318 1319 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1320 See Documentation/filesystems/nfsroot.txt. 1321 1322 nfs.callback_tcpport= 1323 [NFS] set the TCP port on which the NFSv4 callback 1324 channel should listen. 1325 1326 nfs.idmap_cache_timeout= 1327 [NFS] set the maximum lifetime for idmapper cache 1328 entries. 1329 1330 nfs.enable_ino64= 1331 [NFS] enable 64-bit inode numbers. 1332 If zero, the NFS client will fake up a 32-bit inode 1333 number for the readdir() and stat() syscalls instead 1334 of returning the full 64-bit number. 1335 The default is to return 64-bit inode numbers. 1336 1337 nmi_debug= [KNL,AVR32] Specify one or more actions to take 1338 when a NMI is triggered. 1339 Format: [state][,regs][,debounce][,die] 1340 1341 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels 1342 1343 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1344 emulation library even if a 387 maths coprocessor 1345 is present. 1346 1347 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1348 caches in the slab allocator. Saves per-node memory, 1349 but will impact performance. 1350 1351 noalign [KNL,ARM] 1352 1353 noapic [SMP,APIC] Tells the kernel to not make use of any 1354 IOAPICs that may be present in the system. 1355 1356 nobats [PPC] Do not use BATs for mapping kernel lowmem 1357 on "Classic" PPC cores. 1358 1359 nocache [ARM] 1360 1361 nodelayacct [KNL] Disable per-task delay accounting 1362 1363 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1364 1365 noefi [X86-32,X86-64] Disable EFI runtime services support. 1366 1367 noexec [IA-64] 1368 1369 noexec [X86-32,X86-64] 1370 On X86-32 available only on PAE configured kernels. 1371 noexec=on: enable non-executable mappings (default) 1372 noexec=off: disable non-executable mappings 1373 1374 noexec32 [X86-64] 1375 This affects only 32-bit executables. 1376 noexec32=on: enable non-executable mappings (default) 1377 read doesn't imply executable mappings 1378 noexec32=off: disable non-executable mappings 1379 read implies executable mappings 1380 1381 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1382 register save and restore. The kernel will only save 1383 legacy floating-point registers on task switch. 1384 1385 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1386 1387 nohlt [BUGS=ARM] 1388 1389 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1390 instruction doesn't work correctly and not to 1391 use it. 1392 1393 nohalt [IA-64] Tells the kernel not to use the power saving 1394 function PAL_HALT_LIGHT when idle. This increases 1395 power-consumption. On the positive side, it reduces 1396 interrupt wake-up latency, which may improve performance 1397 in certain environments such as networked servers or 1398 real-time systems. 1399 1400 nohz= [KNL] Boottime enable/disable dynamic ticks 1401 Valid arguments: on, off 1402 Default: on 1403 1404 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing 1405 1406 noirqdebug [X86-32] Disables the code which attempts to detect and 1407 disable unhandled interrupt sources. 1408 1409 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for 1410 broken timer IRQ sources. 1411 1412 noisapnp [ISAPNP] Disables ISA PnP code. 1413 1414 noinitrd [RAM] Tells the kernel not to load any configured 1415 initial RAM disk. 1416 1417 nointroute [IA-64] 1418 1419 nojitter [IA64] Disables jitter checking for ITC timers. 1420 1421 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1422 1423 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1424 1425 noltlbs [PPC] Do not use large page/tlb entries for kernel 1426 lowmem mapping on PPC40x. 1427 1428 nomca [IA-64] Disable machine check abort handling 1429 1430 nomce [X86-32] Machine Check Exception 1431 1432 nomfgpt [X86-32] Disable Multi-Function General Purpose 1433 Timer usage (for AMD Geode machines). 1434 1435 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1436 1437 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1438 with UP alternatives 1439 1440 noresidual [PPC] Don't use residual data on PReP machines. 1441 1442 noresume [SWSUSP] Disables resume and restores original swap 1443 space. 1444 1445 no-scroll [VGA] Disables scrollback. 1446 This is required for the Braillex ib80-piezo Braille 1447 reader made by F.H. Papenmeier (Germany). 1448 1449 nosbagart [IA-64] 1450 1451 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1452 1453 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1454 and disable the IO APIC. legacy for "maxcpus=0". 1455 1456 nosoftlockup [KNL] Disable the soft-lockup detector. 1457 1458 nosync [HW,M68K] Disables sync negotiation for all devices. 1459 1460 notsc [BUGS=X86-32] Disable Time Stamp Counter 1461 1462 nousb [USB] Disable the USB subsystem 1463 1464 nowb [ARM] 1465 1466 nptcg= [IA64] Override max number of concurrent global TLB 1467 purges which is reported from either PAL_VM_SUMMARY or 1468 SAL PALO. 1469 1470 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1471 one of ['zone', 'node', 'default'] can be specified 1472 This can be set from sysctl after boot. 1473 See Documentation/sysctl/vm.txt for details. 1474 1475 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1476 1477 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1478 Rather than timing out after 20 ms if an EC 1479 command is not properly ACKed, override the length 1480 of the timeout. We have interrupts disabled while 1481 waiting for the ACK, so if this is set too high 1482 interrupts *may* be lost! 1483 1484 opl3= [HW,OSS] 1485 Format: <io> 1486 1487 oprofile.timer= [HW] 1488 Use timer interrupt instead of performance counters 1489 1490 osst= [HW,SCSI] SCSI Tape Driver 1491 Format: <buffer_size>,<write_threshold> 1492 See also Documentation/scsi/st.txt. 1493 1494 panic= [KNL] Kernel behaviour on panic 1495 Format: <timeout> 1496 1497 parkbd.port= [HW] Parallel port number the keyboard adapter is 1498 connected to, default is 0. 1499 Format: <parport#> 1500 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1501 0 for XT, 1 for AT (default is AT). 1502 Format: <mode> 1503 1504 parport= [HW,PPT] Specify parallel ports. 0 disables. 1505 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1506 Use 'auto' to force the driver to use any 1507 IRQ/DMA settings detected (the default is to 1508 ignore detected IRQ/DMA settings because of 1509 possible conflicts). You can specify the base 1510 address, IRQ, and DMA settings; IRQ and DMA 1511 should be numbers, or 'auto' (for using detected 1512 settings on that particular port), or 'nofifo' 1513 (to avoid using a FIFO even if it is detected). 1514 Parallel ports are assigned in the order they 1515 are specified on the command line, starting 1516 with parport0. 1517 1518 parport_init_mode= [HW,PPT] 1519 Configure VIA parallel port to operate in 1520 a specific mode. This is necessary on Pegasos 1521 computer where firmware has no options for setting 1522 up parallel port mode and sets it to spp. 1523 Currently this function knows 686a and 8231 chips. 1524 Format: [spp|ps2|epp|ecp|ecpepp] 1525 1526 pas2= [HW,OSS] Format: 1527 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16> 1528 1529 pas16= [HW,SCSI] 1530 See header of drivers/scsi/pas16.c. 1531 1532 pause_on_oops= 1533 Halt all CPUs after the first oops has been printed for 1534 the specified number of seconds. This is to be used if 1535 your oopses keep scrolling off the screen. 1536 1537 pcbit= [HW,ISDN] 1538 1539 pcd. [PARIDE] 1540 See header of drivers/block/paride/pcd.c. 1541 See also Documentation/paride.txt. 1542 1543 pci=option[,option...] [PCI] various PCI subsystem options: 1544 off [X86-32] don't probe for the PCI bus 1545 bios [X86-32] force use of PCI BIOS, don't access 1546 the hardware directly. Use this if your machine 1547 has a non-standard PCI host bridge. 1548 nobios [X86-32] disallow use of PCI BIOS, only direct 1549 hardware access methods are allowed. Use this 1550 if you experience crashes upon bootup and you 1551 suspect they are caused by the BIOS. 1552 conf1 [X86-32] Force use of PCI Configuration 1553 Mechanism 1. 1554 conf2 [X86-32] Force use of PCI Configuration 1555 Mechanism 2. 1556 noaer [PCIE] If the PCIEAER kernel config parameter is 1557 enabled, this kernel boot option can be used to 1558 disable the use of PCIE advanced error reporting. 1559 nodomains [PCI] Disable support for multiple PCI 1560 root domains (aka PCI segments, in ACPI-speak). 1561 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI 1562 Configuration 1563 nomsi [MSI] If the PCI_MSI kernel config parameter is 1564 enabled, this kernel boot option can be used to 1565 disable the use of MSI interrupts system-wide. 1566 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1567 routing table. These calls are known to be buggy 1568 on several machines and they hang the machine 1569 when used, but on other computers it's the only 1570 way to get the interrupt routing table. Try 1571 this option if the kernel is unable to allocate 1572 IRQs or discover secondary PCI buses on your 1573 motherboard. 1574 rom [X86-32] Assign address space to expansion ROMs. 1575 Use with caution as certain devices share 1576 address decoders between ROMs and other 1577 resources. 1578 norom [X86-32,X86_64] Do not assign address space to 1579 expansion ROMs that do not already have 1580 BIOS assigned address ranges. 1581 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be 1582 assigned automatically to PCI devices. You can 1583 make the kernel exclude IRQs of your ISA cards 1584 this way. 1585 pirqaddr=0xAAAAA [X86-32] Specify the physical address 1586 of the PIRQ table (normally generated 1587 by the BIOS) if it is outside the 1588 F0000h-100000h range. 1589 lastbus=N [X86-32] Scan all buses thru bus #N. Can be 1590 useful if the kernel is unable to find your 1591 secondary buses and you want to tell it 1592 explicitly which ones they are. 1593 assign-busses [X86-32] Always assign all PCI bus 1594 numbers ourselves, overriding 1595 whatever the firmware may have done. 1596 usepirqmask [X86-32] Honor the possible IRQ mask stored 1597 in the BIOS $PIR table. This is needed on 1598 some systems with broken BIOSes, notably 1599 some HP Pavilion N5400 and Omnibook XE3 1600 notebooks. This will have no effect if ACPI 1601 IRQ routing is enabled. 1602 noacpi [X86-32] Do not use ACPI for IRQ routing 1603 or for PCI scanning. 1604 use_crs [X86-32] Use _CRS for PCI resource 1605 allocation. 1606 routeirq Do IRQ routing for all PCI devices. 1607 This is normally done in pci_enable_device(), 1608 so this option is a temporary workaround 1609 for broken drivers that don't call it. 1610 skip_isa_align [X86] do not align io start addr, so can 1611 handle more pci cards 1612 firmware [ARM] Do not re-enumerate the bus but instead 1613 just use the configuration from the 1614 bootloader. This is currently used on 1615 IXP2000 systems where the bus has to be 1616 configured a certain way for adjunct CPUs. 1617 noearly [X86] Don't do any early type 1 scanning. 1618 This might help on some broken boards which 1619 machine check when some devices' config space 1620 is read. But various workarounds are disabled 1621 and some IOMMU drivers will not work. 1622 bfsort Sort PCI devices into breadth-first order. 1623 This sorting is done to get a device 1624 order compatible with older (<= 2.4) kernels. 1625 nobfsort Don't sort PCI devices into breadth-first order. 1626 cbiosize=nn[KMG] The fixed amount of bus space which is 1627 reserved for the CardBus bridge's IO window. 1628 The default value is 256 bytes. 1629 cbmemsize=nn[KMG] The fixed amount of bus space which is 1630 reserved for the CardBus bridge's memory 1631 window. The default value is 64 megabytes. 1632 1633 pcmv= [HW,PCMCIA] BadgePAD 4 1634 1635 pd. [PARIDE] 1636 See Documentation/paride.txt. 1637 1638 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 1639 boot time. 1640 Format: { 0 | 1 } 1641 See arch/parisc/kernel/pdc_chassis.c 1642 1643 pf. [PARIDE] 1644 See Documentation/paride.txt. 1645 1646 pg. [PARIDE] 1647 See Documentation/paride.txt. 1648 1649 pirq= [SMP,APIC] Manual mp-table setup 1650 See Documentation/i386/IO-APIC.txt. 1651 1652 plip= [PPT,NET] Parallel port network link 1653 Format: { parport<nr> | timid | 0 } 1654 See also Documentation/parport.txt. 1655 1656 pmtmr= [X86] Manual setup of pmtmr I/O Port. 1657 Override pmtimer IOPort with a hex value. 1658 e.g. pmtmr=0x508 1659 1660 pnpacpi= [ACPI] 1661 { off } 1662 1663 pnpbios= [ISAPNP] 1664 { on | off | curr | res | no-curr | no-res } 1665 1666 pnp_reserve_irq= 1667 [ISAPNP] Exclude IRQs for the autoconfiguration 1668 1669 pnp_reserve_dma= 1670 [ISAPNP] Exclude DMAs for the autoconfiguration 1671 1672 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 1673 Ranges are in pairs (I/O port base and size). 1674 1675 pnp_reserve_mem= 1676 [ISAPNP] Exclude memory regions for the 1677 autoconfiguration. 1678 Ranges are in pairs (memory base and size). 1679 1680 print-fatal-signals= 1681 [KNL] debug: print fatal signals 1682 print-fatal-signals=1: print segfault info to 1683 the kernel console. 1684 default: off. 1685 1686 printk.time= Show timing data prefixed to each printk message line 1687 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 1688 1689 profile= [KNL] Enable kernel profiling via /proc/profile 1690 Format: [schedule,]<number> 1691 Param: "schedule" - profile schedule points. 1692 Param: <number> - step/bucket size as a power of 2 for 1693 statistical time based profiling. 1694 Param: "sleep" - profile D-state sleeping (millisecs). 1695 Requires CONFIG_SCHEDSTATS 1696 Param: "kvm" - profile VM exits. 1697 1698 processor.max_cstate= [HW,ACPI] 1699 Limit processor to maximum C-state 1700 max_cstate=9 overrides any DMI blacklist limit. 1701 1702 processor.nocst [HW,ACPI] 1703 Ignore the _CST method to determine C-states, 1704 instead using the legacy FADT method 1705 1706 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 1707 before loading. 1708 See Documentation/ramdisk.txt. 1709 1710 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 1711 probe for; one of (bare|imps|exps|lifebook|any). 1712 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 1713 per second. 1714 psmouse.resetafter= [HW,MOUSE] 1715 Try to reset the device after so many bad packets 1716 (0 = never). 1717 psmouse.resolution= 1718 [HW,MOUSE] Set desired mouse resolution, in dpi. 1719 psmouse.smartscroll= 1720 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 1721 0 = disabled, 1 = enabled (default). 1722 1723 pss= [HW,OSS] Personal Sound System (ECHO ESC614) 1724 Format: 1725 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq> 1726 1727 pt. [PARIDE] 1728 See Documentation/paride.txt. 1729 1730 pty.legacy_count= 1731 [KNL] Number of legacy pty's. Overwrites compiled-in 1732 default number. 1733 1734 quiet [KNL] Disable most log messages 1735 1736 r128= [HW,DRM] 1737 1738 raid= [HW,RAID] 1739 See Documentation/md.txt. 1740 1741 ramdisk_blocksize= [RAM] 1742 See Documentation/ramdisk.txt. 1743 1744 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 1745 See Documentation/ramdisk.txt. 1746 1747 rcupdate.blimit= [KNL,BOOT] 1748 Set maximum number of finished RCU callbacks to process 1749 in one batch. 1750 1751 rcupdate.qhimark= [KNL,BOOT] 1752 Set threshold of queued 1753 RCU callbacks over which batch limiting is disabled. 1754 1755 rcupdate.qlowmark= [KNL,BOOT] 1756 Set threshold of queued RCU callbacks below which 1757 batch limiting is re-enabled. 1758 1759 rdinit= [KNL] 1760 Format: <full_path> 1761 Run specified binary instead of /init from the ramdisk, 1762 used for early userspace startup. See initrd. 1763 1764 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 1765 Format: <reboot_mode>[,<reboot_mode2>[,...]] 1766 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 1767 1768 relax_domain_level= 1769 [KNL, SMP] Set scheduler's default relax_domain_level. 1770 See Documentation/cpusets.txt. 1771 1772 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 1773 1774 reservetop= [X86-32] 1775 Format: nn[KMG] 1776 Reserves a hole at the top of the kernel virtual 1777 address space. 1778 1779 reset_devices [KNL] Force drivers to reset the underlying device 1780 during initialization. 1781 1782 resume= [SWSUSP] 1783 Specify the partition device for software suspend 1784 1785 resume_offset= [SWSUSP] 1786 Specify the offset from the beginning of the partition 1787 given by "resume=" at which the swap header is located, 1788 in <PAGE_SIZE> units (needed only for swap files). 1789 See Documentation/power/swsusp-and-swap-files.txt 1790 1791 retain_initrd [RAM] Keep initrd memory after extraction 1792 1793 rhash_entries= [KNL,NET] 1794 Set number of hash buckets for route cache 1795 1796 riscom8= [HW,SERIAL] 1797 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 1798 1799 ro [KNL] Mount root device read-only on boot 1800 1801 root= [KNL] Root filesystem 1802 1803 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 1804 mount the root filesystem 1805 1806 rootflags= [KNL] Set root filesystem mount option string 1807 1808 rootfstype= [KNL] Set root filesystem type 1809 1810 rootwait [KNL] Wait (indefinitely) for root device to show up. 1811 Useful for devices that are detected asynchronously 1812 (e.g. USB and MMC devices). 1813 1814 root_plug.vendor_id= 1815 [ROOTPLUG] Override the default vendor ID 1816 1817 root_plug.product_id= 1818 [ROOTPLUG] Override the default product ID 1819 1820 root_plug.debug= 1821 [ROOTPLUG] Enable debugging output 1822 1823 rw [KNL] Mount root device read-write on boot 1824 1825 S [KNL] Run init in single mode 1826 1827 sa1100ir [NET] 1828 See drivers/net/irda/sa1100_ir.c. 1829 1830 sbni= [NET] Granch SBNI12 leased line adapter 1831 1832 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver 1833 Format: <io>[,<timeout>[,<isapnp>]] 1834 1835 scsi_debug_*= [SCSI] 1836 See drivers/scsi/scsi_debug.c. 1837 1838 scsi_default_dev_flags= 1839 [SCSI] SCSI default device flags 1840 Format: <integer> 1841 1842 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model 1843 Format: <vendor>:<model>:<flags> 1844 (flags are integer value) 1845 1846 scsi_logging_level= [SCSI] a bit mask of logging levels 1847 See drivers/scsi/scsi_logging.h for bits. Also 1848 settable via sysctl at dev.scsi.logging_level 1849 (/proc/sys/dev/scsi/logging_level). 1850 There is also a nice 'scsi_logging_level' script in the 1851 S390-tools package, available for download at 1852 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html 1853 1854 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are 1855 discovered. async scans them in kernel threads, 1856 allowing boot to proceed. none ignores them, expecting 1857 user space to do the scan. 1858 1859 selinux [SELINUX] Disable or enable SELinux at boot time. 1860 Format: { "0" | "1" } 1861 See security/selinux/Kconfig help text. 1862 0 -- disable. 1863 1 -- enable. 1864 Default value is set via kernel config option. 1865 If enabled at boot time, /selinux/disable can be used 1866 later to disable prior to initial policy load. 1867 1868 selinux_compat_net = 1869 [SELINUX] Set initial selinux_compat_net flag value. 1870 Format: { "0" | "1" } 1871 0 -- use new secmark-based packet controls 1872 1 -- use legacy packet controls 1873 Default value is 0 (preferred). 1874 Value can be changed at runtime via 1875 /selinux/compat_net. 1876 1877 serialnumber [BUGS=X86-32] 1878 1879 shapers= [NET] 1880 Maximal number of shapers. 1881 1882 sim710= [SCSI,HW] 1883 See header of drivers/scsi/sim710.c. 1884 1885 simeth= [IA-64] 1886 simscsi= 1887 1888 slram= [HW,MTD] 1889 1890 slub_debug[=options[,slabs]] [MM, SLUB] 1891 Enabling slub_debug allows one to determine the 1892 culprit if slab objects become corrupted. Enabling 1893 slub_debug can create guard zones around objects and 1894 may poison objects when not in use. Also tracks the 1895 last alloc / free. For more information see 1896 Documentation/vm/slub.txt. 1897 1898 slub_max_order= [MM, SLUB] 1899 Determines the maximum allowed order for slabs. 1900 A high setting may cause OOMs due to memory 1901 fragmentation. For more information see 1902 Documentation/vm/slub.txt. 1903 1904 slub_min_objects= [MM, SLUB] 1905 The minimum number of objects per slab. SLUB will 1906 increase the slab order up to slub_max_order to 1907 generate a sufficiently large slab able to contain 1908 the number of objects indicated. The higher the number 1909 of objects the smaller the overhead of tracking slabs 1910 and the less frequently locks need to be acquired. 1911 For more information see Documentation/vm/slub.txt. 1912 1913 slub_min_order= [MM, SLUB] 1914 Determines the mininum page order for slabs. Must be 1915 lower than slub_max_order. 1916 For more information see Documentation/vm/slub.txt. 1917 1918 slub_nomerge [MM, SLUB] 1919 Disable merging of slabs with similar size. May be 1920 necessary if there is some reason to distinguish 1921 allocs to different slabs. Debug options disable 1922 merging on their own. 1923 For more information see Documentation/vm/slub.txt. 1924 1925 smart2= [HW] 1926 Format: <io1>[,<io2>[,...,<io8>]] 1927 1928 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 1929 attempt to substitute SMP alternatives once at boot. 1930 1931 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 1932 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 1933 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 1934 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 1935 smsc-ircc2.ircc_irq= [HW] IRQ line 1936 smsc-ircc2.ircc_dma= [HW] DMA channel 1937 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 1938 0: Toshiba Satellite 1800 (GP data pin select) 1939 1: Fast pin select (default) 1940 2: ATC IRMode 1941 1942 snd-ad1816a= [HW,ALSA] 1943 1944 snd-ad1848= [HW,ALSA] 1945 1946 snd-ali5451= [HW,ALSA] 1947 1948 snd-als100= [HW,ALSA] 1949 1950 snd-als4000= [HW,ALSA] 1951 1952 snd-azt2320= [HW,ALSA] 1953 1954 snd-cmi8330= [HW,ALSA] 1955 1956 snd-cmipci= [HW,ALSA] 1957 1958 snd-cs4231= [HW,ALSA] 1959 1960 snd-cs4232= [HW,ALSA] 1961 1962 snd-cs4236= [HW,ALSA] 1963 1964 snd-cs4281= [HW,ALSA] 1965 1966 snd-cs46xx= [HW,ALSA] 1967 1968 snd-dt019x= [HW,ALSA] 1969 1970 snd-dummy= [HW,ALSA] 1971 1972 snd-emu10k1= [HW,ALSA] 1973 1974 snd-ens1370= [HW,ALSA] 1975 1976 snd-ens1371= [HW,ALSA] 1977 1978 snd-es968= [HW,ALSA] 1979 1980 snd-es1688= [HW,ALSA] 1981 1982 snd-es18xx= [HW,ALSA] 1983 1984 snd-es1938= [HW,ALSA] 1985 1986 snd-es1968= [HW,ALSA] 1987 1988 snd-fm801= [HW,ALSA] 1989 1990 snd-gusclassic= [HW,ALSA] 1991 1992 snd-gusextreme= [HW,ALSA] 1993 1994 snd-gusmax= [HW,ALSA] 1995 1996 snd-hdsp= [HW,ALSA] 1997 1998 snd-ice1712= [HW,ALSA] 1999 2000 snd-intel8x0= [HW,ALSA] 2001 2002 snd-interwave= [HW,ALSA] 2003 2004 snd-interwave-stb= 2005 [HW,ALSA] 2006 2007 snd-korg1212= [HW,ALSA] 2008 2009 snd-maestro3= [HW,ALSA] 2010 2011 snd-mpu401= [HW,ALSA] 2012 2013 snd-mtpav= [HW,ALSA] 2014 2015 snd-nm256= [HW,ALSA] 2016 2017 snd-opl3sa2= [HW,ALSA] 2018 2019 snd-opti92x-ad1848= 2020 [HW,ALSA] 2021 2022 snd-opti92x-cs4231= 2023 [HW,ALSA] 2024 2025 snd-opti93x= [HW,ALSA] 2026 2027 snd-pmac= [HW,ALSA] 2028 2029 snd-rme32= [HW,ALSA] 2030 2031 snd-rme96= [HW,ALSA] 2032 2033 snd-rme9652= [HW,ALSA] 2034 2035 snd-sb8= [HW,ALSA] 2036 2037 snd-sb16= [HW,ALSA] 2038 2039 snd-sbawe= [HW,ALSA] 2040 2041 snd-serial= [HW,ALSA] 2042 2043 snd-sgalaxy= [HW,ALSA] 2044 2045 snd-sonicvibes= [HW,ALSA] 2046 2047 snd-sun-amd7930= 2048 [HW,ALSA] 2049 2050 snd-sun-cs4231= [HW,ALSA] 2051 2052 snd-trident= [HW,ALSA] 2053 2054 snd-usb-audio= [HW,ALSA,USB] 2055 2056 snd-via82xx= [HW,ALSA] 2057 2058 snd-virmidi= [HW,ALSA] 2059 2060 snd-wavefront= [HW,ALSA] 2061 2062 snd-ymfpci= [HW,ALSA] 2063 2064 softlockup_panic= 2065 [KNL] Should the soft-lockup detector generate panics. 2066 2067 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2068 See Documentation/sonypi.txt 2069 2070 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2071 See Documentation/specialix.txt. 2072 2073 spia_io_base= [HW,MTD] 2074 spia_fio_base= 2075 spia_pedr= 2076 spia_peddr= 2077 2078 sscape= [HW,OSS] 2079 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq> 2080 2081 st= [HW,SCSI] SCSI tape parameters (buffers, etc.) 2082 See Documentation/scsi/st.txt. 2083 2084 sti= [PARISC,HW] 2085 Format: <num> 2086 Set the STI (builtin display/keyboard on the HP-PARISC 2087 machines) console (graphic card) which should be used 2088 as the initial boot-console. 2089 See also comment in drivers/video/console/sticore.c. 2090 2091 sti_font= [HW] 2092 See comment in drivers/video/console/sticore.c. 2093 2094 stifb= [HW] 2095 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2096 2097 sunrpc.pool_mode= 2098 [NFS] 2099 Control how the NFS server code allocates CPUs to 2100 service thread pools. Depending on how many NICs 2101 you have and where their interrupts are bound, this 2102 option will affect which CPUs will do NFS serving. 2103 Note: this parameter cannot be changed while the 2104 NFS server is running. 2105 2106 auto the server chooses an appropriate mode 2107 automatically using heuristics 2108 global a single global pool contains all CPUs 2109 percpu one pool for each CPU 2110 pernode one pool for each NUMA node (equivalent 2111 to global on non-NUMA machines) 2112 2113 swiotlb= [IA-64] Number of I/O TLB slabs 2114 2115 switches= [HW,M68k] 2116 2117 sym53c416= [HW,SCSI] 2118 See header of drivers/scsi/sym53c416.c. 2119 2120 sysrq_always_enabled 2121 [KNL] 2122 Ignore sysrq setting - this boot parameter will 2123 neutralize any effect of /proc/sys/kernel/sysrq. 2124 Useful for debugging. 2125 2126 t128= [HW,SCSI] 2127 See header of drivers/scsi/t128.c. 2128 2129 tdfx= [HW,DRM] 2130 2131 test_suspend= [SUSPEND] 2132 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2133 standby suspend) as the system sleep state to briefly 2134 enter during system startup. The system is woken from 2135 this state using a wakeup-capable RTC alarm. 2136 2137 thash_entries= [KNL,NET] 2138 Set number of hash buckets for TCP connection 2139 2140 thermal.act= [HW,ACPI] 2141 -1: disable all active trip points in all thermal zones 2142 <degrees C>: override all lowest active trip points 2143 2144 thermal.crt= [HW,ACPI] 2145 -1: disable all critical trip points in all thermal zones 2146 <degrees C>: lower all critical trip points 2147 2148 thermal.nocrt= [HW,ACPI] 2149 Set to disable actions on ACPI thermal zone 2150 critical and hot trip points. 2151 2152 thermal.off= [HW,ACPI] 2153 1: disable ACPI thermal control 2154 2155 thermal.psv= [HW,ACPI] 2156 -1: disable all passive trip points 2157 <degrees C>: override all passive trip points to this value 2158 2159 thermal.tzp= [HW,ACPI] 2160 Specify global default ACPI thermal zone polling rate 2161 <deci-seconds>: poll all this frequency 2162 0: no polling (default) 2163 2164 tmscsim= [HW,SCSI] 2165 See comment before function dc390_setup() in 2166 drivers/scsi/tmscsim.c. 2167 2168 tp720= [HW,PS2] 2169 2170 trix= [HW,OSS] MediaTrix AudioTrix Pro 2171 Format: 2172 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq> 2173 2174 turbografx.map[2|3]= [HW,JOY] 2175 TurboGraFX parallel port interface 2176 Format: 2177 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2178 See also Documentation/input/joystick-parport.txt 2179 2180 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter 2181 See header of drivers/scsi/u14-34f.c. 2182 2183 uart401= [HW,OSS] 2184 Format: <io>,<irq> 2185 2186 uart6850= [HW,OSS] 2187 Format: <io>,<irq> 2188 2189 uhci-hcd.ignore_oc= 2190 [USB] Ignore overcurrent events (default N). 2191 Some badly-designed motherboards generate lots of 2192 bogus events, for ports that aren't wired to 2193 anything. Set this parameter to avoid log spamming. 2194 Note that genuine overcurrent events won't be 2195 reported either. 2196 2197 unknown_nmi_panic 2198 [X86-32,X86-64] 2199 Set unknown_nmi_panic=1 early on boot. 2200 2201 usbcore.autosuspend= 2202 [USB] The autosuspend time delay (in seconds) used 2203 for newly-detected USB devices (default 2). This 2204 is the time required before an idle device will be 2205 autosuspended. Devices for which the delay is set 2206 to a negative value won't be autosuspended at all. 2207 2208 usbhid.mousepoll= 2209 [USBHID] The interval which mice are to be polled at. 2210 2211 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in 2212 kernel's map of available physical RAM. 2213 2214 vdso= [X86-32,SH,x86-64] 2215 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2216 vdso=1: enable VDSO (default) 2217 vdso=0: disable VDSO mapping 2218 2219 vdso32= [X86-32,X86-64] 2220 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2221 vdso32=1: enable 32-bit VDSO (default) 2222 vdso32=0: disable 32-bit VDSO mapping 2223 2224 vector= [IA-64,SMP] 2225 vector=percpu: enable percpu vector domain 2226 2227 video= [FB] Frame buffer configuration 2228 See Documentation/fb/modedb.txt. 2229 2230 vga= [BOOT,X86-32] Select a particular video mode 2231 See Documentation/i386/boot.txt and 2232 Documentation/svga.txt. 2233 Use vga=ask for menu. 2234 This is actually a boot loader parameter; the value is 2235 passed to the kernel using a special protocol. 2236 2237 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2238 size of <nn>. This can be used to increase the 2239 minimum size (128MB on x86). It can also be used to 2240 decrease the size and leave more room for directly 2241 mapped kernel RAM. 2242 2243 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2244 Format: <command> 2245 2246 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2247 Format: <command> 2248 2249 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2250 Format: <command> 2251 2252 waveartist= [HW,OSS] 2253 Format: <io>,<irq>,<dma>,<dma2> 2254 2255 wd33c93= [HW,SCSI] 2256 See header of drivers/scsi/wd33c93.c. 2257 2258 wd7000= [HW,SCSI] 2259 See header of drivers/scsi/wd7000.c. 2260 2261 wdt= [WDT] Watchdog 2262 See Documentation/watchdog/wdt.txt. 2263 2264 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2265 xd_geo= See header of drivers/block/xd.c. 2266 2267 xirc2ps_cs= [NET,PCMCIA] 2268 Format: 2269 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2270 2271 norandmaps Don't use address space randomization 2272 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space 2273 2274______________________________________________________________________ 2275 2276TODO: 2277 2278 Add documentation for ALSA options. 2279 Add more DRM drivers.