Based on kernel version 2.6.25. Page generated on 2008-04-18 21:22 EST.
1 Kernel Parameters 2 ~~~~~~~~~~~~~~~~~ 3 4 The 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 7 case insensitive manner), and with descriptions where known. 8 9 Module parameters for loadable modules are specified only as the 10 parameter name with optional '=' and value as appropriate, such as: 11 12 modprobe usbcore blinkenlights=1 13 14 Module parameters for modules that are built into the kernel image 15 are 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 20 This document may not be entirely up to date and comprehensive. The command 21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable 22 module. Loadable modules, after being loaded into the running kernel, also 23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these 24 parameters may be changed at runtime by the command 25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". 26 27 The parameters listed below are only valid if certain kernel build options were 28 enabled and if respective hardware is present. The text in square brackets at 29 the beginning of each description states the restrictions within which a 30 parameter 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 is enabled. 91 TS Appropriate touchscreen support is enabled. 92 USB USB support is enabled. 93 USBHID USB Human Interface Device support is enabled. 94 V4L Video For Linux support is enabled. 95 VGA The VGA console has been enabled. 96 VT Virtual terminal support is enabled. 97 WDT Watchdog support is enabled. 98 XT IBM PC/XT MFM hard disk support is enabled. 99 X86-32 X86-32, aka i386 architecture is enabled. 100 X86-64 X86-64 architecture is enabled. 101 More X86-64 boot options can be found in 102 Documentation/x86_64/boot-options.txt . 103 104 In addition, the following text indicates that the option: 105 106 BUGS= Relates to possible processor bugs on the said processor. 107 KNL Is a kernel start-up parameter. 108 BOOT Is a boot loader parameter. 109 110 Parameters denoted with BOOT are actually interpreted by the boot 111 loader, and have no meaning to the kernel directly. 112 Do not modify the syntax of boot loader parameters without extreme 113 need or coordination with <Documentation/i386/boot.txt>. 114 115 There are also arch-specific kernel-parameters not documented here. 116 See for example <Documentation/x86_64/boot-options.txt>. 117 118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 119 a trailing = on the name of any parameter states that that parameter will 120 be entered as an environment variable, whereas its absence indicates that 121 it will appear as a kernel argument readable via /proc/cmdline by programs 122 running once the system is up. 123 124 The number of kernel parameters is not limited, but the length of the 125 complete command line (parameters including spaces etc.) is limited to 126 a fixed number of characters. This limit depends on the architecture 127 and is between 256 and 4096 characters. It is defined in the file 128 ./include/asm/setup.h as COMMAND_LINE_SIZE. 129 130 131 acpi= [HW,ACPI,X86-64,i386] 132 Advanced Configuration and Power Interface 133 Format: { force | off | ht | strict | noirq } 134 force -- enable ACPI if default was off 135 off -- disable ACPI if default was on 136 noirq -- do not use ACPI for IRQ routing 137 ht -- run only enough ACPI to enable Hyper Threading 138 strict -- Be less tolerant of platforms that are not 139 strictly ACPI specification compliant. 140 141 See also Documentation/power/pm.txt, pci=noacpi 142 143 acpi_apic_instance= [ACPI, IOAPIC] 144 Format: <int> 145 2: use 2nd APIC table, if available 146 1,0: use 1st APIC table 147 default: 0 148 149 acpi_sleep= [HW,ACPI] Sleep options 150 Format: { s3_bios, s3_mode, s3_beep } 151 See Documentation/power/video.txt for s3_bios and s3_mode. 152 s3_beep is for debugging; it makes the PC's speaker beep 153 as soon as the kernel's real-mode entry point is called. 154 155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 156 Format: { level | edge | high | low } 157 158 acpi_irq_balance [HW,ACPI] 159 ACPI will balance active IRQs 160 default in APIC mode 161 162 acpi_irq_nobalance [HW,ACPI] 163 ACPI will not move active IRQs (default) 164 default in PIC mode 165 166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 167 use by PCI 168 Format: <irq>,<irq>... 169 170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 171 Format: <irq>,<irq>... 172 173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 174 175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 176 Format: To spoof as Windows 98: ="Microsoft Windows" 177 178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 179 acpi_osi="string1" # add string1 -- only one string 180 acpi_osi="!string2" # remove built-in string2 181 acpi_osi= # disable all strings 182 183 acpi_serialize [HW,ACPI] force serialization of AML methods 184 185 acpi_skip_timer_override [HW,ACPI] 186 Recognize and ignore IRQ0/pin2 Interrupt Override. 187 For broken nForce2 BIOS resulting in XT-PIC timer. 188 acpi_use_timer_override [HW,ACPI} 189 Use timer override. For some broken Nvidia NF5 boards 190 that require a timer override, but don't have 191 HPET 192 193 acpi.debug_layer= [HW,ACPI] 194 Format: <int> 195 Each bit of the <int> indicates an ACPI debug layer, 196 1: enable, 0: disable. It is useful for boot time 197 debugging. After system has booted up, it can be set 198 via /sys/module/acpi/parameters/debug_layer. 199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output. 200 Available bits (add the numbers together) to enable debug output 201 for specific parts of the ACPI subsystem: 202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables 203 0x10 namespace 0x20 parser 0x40 dispatcher 204 0x80 executer 0x100 resources 0x200 acpica debugger 205 0x400 os services 0x800 acpica disassembler. 206 The number can be in decimal or prefixed with 0x in hex. 207 Warning: Many of these options can produce a lot of 208 output and make your system unusable. Be very careful. 209 210 acpi.debug_level= [HW,ACPI] 211 Format: <int> 212 Each bit of the <int> indicates an ACPI debug level, 213 1: enable, 0: disable. It is useful for boot time 214 debugging. After system has booted up, it can be set 215 via /sys/module/acpi/parameters/debug_level. 216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output. 217 Available bits (add the numbers together) to enable different 218 debug output levels of the ACPI subsystem: 219 0x01 error 0x02 warn 0x04 init 0x08 debug object 220 0x10 info 0x20 init names 0x40 parse 0x80 load 221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region 222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects 223 0x10000 resources 0x20000 user requests 0x40000 package. 224 The number can be in decimal or prefixed with 0x in hex. 225 Warning: Many of these options can produce a lot of 226 output and make your system unusable. Be very careful. 227 228 acpi_pm_good [X86-32,X86-64] 229 Override the pmtimer bug detection: force the kernel 230 to assume that this machine's pmtimer latches its value 231 and always returns good values. 232 233 agp= [AGP] 234 { off | try_unsupported } 235 off: disable AGP support 236 try_unsupported: try to drive unsupported chipsets 237 (may crash computer or cause data corruption) 238 239 enable_timer_pin_1 [i386,x86-64] 240 Enable PIN 1 of APIC timer 241 Can be useful to work around chipset bugs 242 (in particular on some ATI chipsets). 243 The kernel tries to set a reasonable default. 244 245 disable_timer_pin_1 [i386,x86-64] 246 Disable PIN 1 of APIC timer 247 Can be useful to work around chipset bugs. 248 249 ad1848= [HW,OSS] 250 Format: <io>,<irq>,<dma>,<dma2>,<type> 251 252 advansys= [HW,SCSI] 253 See header of drivers/scsi/advansys.c. 254 255 advwdt= [HW,WDT] Advantech WDT 256 Format: <iostart>,<iostop> 257 258 aedsp16= [HW,OSS] Audio Excel DSP 16 259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq> 260 See also header of sound/oss/aedsp16.c. 261 262 aha152x= [HW,SCSI] 263 See Documentation/scsi/aha152x.txt. 264 265 aha1542= [HW,SCSI] 266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]] 267 268 aic7xxx= [HW,SCSI] 269 See Documentation/scsi/aic7xxx.txt. 270 271 aic79xx= [HW,SCSI] 272 See Documentation/scsi/aic79xx.txt. 273 274 amijoy.map= [HW,JOY] Amiga joystick support 275 Map of devices attached to JOY0DAT and JOY1DAT 276 Format: <a>,<b> 277 See also Documentation/kernel/input/joystick.txt 278 279 analog.map= [HW,JOY] Analog joystick and gamepad support 280 Specifies type or capabilities of an analog joystick 281 connected to one of 16 gameports 282 Format: <type1>,<type2>,..<type16> 283 284 apc= [HW,SPARC] 285 Power management functions (SPARCstation-4/5 + deriv.) 286 Format: noidle 287 Disable APC CPU standby support. SPARCstation-Fox does 288 not play well with APC CPU idle - disable it if you have 289 APC and your system crashes randomly. 290 291 apic= [APIC,i386] Advanced Programmable Interrupt Controller 292 Change the output verbosity whilst booting 293 Format: { quiet (default) | verbose | debug } 294 Change the amount of debugging information output 295 when initialising the APIC and IO-APIC components. 296 297 apm= [APM] Advanced Power Management 298 See header of arch/i386/kernel/apm.c. 299 300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 301 Format: <io>,<irq>,<nodeID> 302 303 ataflop= [HW,M68k] 304 305 atarimouse= [HW,MOUSE] Atari Mouse 306 307 atascsi= [HW,SCSI] Atari SCSI 308 309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 310 EzKey and similar keyboards 311 312 atkbd.reset= [HW] Reset keyboard during initialization 313 314 atkbd.set= [HW] Select keyboard code set 315 Format: <int> (2 = AT (default), 3 = PS/2) 316 317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 318 keyboards 319 320 atkbd.softraw= [HW] Choose between synthetic and real raw mode 321 Format: <bool> (0 = real, 1 = synthetic (default)) 322 323 atkbd.softrepeat= [HW] 324 Use software keyboard repeat 325 326 autotest [IA64] 327 328 baycom_epp= [HW,AX25] 329 Format: <io>,<mode> 330 331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 332 Format: <io>,<mode> 333 See header of drivers/net/hamradio/baycom_par.c. 334 335 baycom_ser_fdx= [HW,AX25] 336 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 337 Format: <io>,<irq>,<mode>[,<baud>] 338 See header of drivers/net/hamradio/baycom_ser_fdx.c. 339 340 baycom_ser_hdx= [HW,AX25] 341 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 342 Format: <io>,<irq>,<mode> 343 See header of drivers/net/hamradio/baycom_ser_hdx.c. 344 345 boot_delay= Milliseconds to delay each printk during boot. 346 Values larger than 10 seconds (10000) are changed to 347 no delay (0). 348 Format: integer 349 350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 351 bttv.radio= Most important insmod options are available as 352 kernel args too. 353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 355 356 BusLogic= [HW,SCSI] 357 See drivers/scsi/BusLogic.c, comment before function 358 BusLogic_ParseDriverOptions(). 359 360 c101= [NET] Moxa C101 synchronous serial card 361 362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 363 Sometimes CPU hardware bugs make them report the cache 364 size incorrectly. The kernel will attempt work arounds 365 to fix known problems, but for some CPUs it is not 366 possible to determine what the correct size should be. 367 This option provides an override for these situations. 368 369 capability.disable= 370 [SECURITY] Disable capabilities. This would normally 371 be used only if an alternative security model is to be 372 configured. Potentially dangerous and should only be 373 used if you are entirely sure of the consequences. 374 375 ccw_timeout_log [S390] 376 See Documentation/s390/CommonIO for details. 377 378 cgroup_disable= [KNL] Disable a particular controller 379 Format: {name of the controller(s) to disable} 380 {Currently supported controllers - "memory"} 381 382 checkreqprot [SELINUX] Set initial checkreqprot flag value. 383 Format: { "0" | "1" } 384 See security/selinux/Kconfig help text. 385 0 -- check protection applied by kernel (includes 386 any implied execute protection). 387 1 -- check protection requested by application. 388 Default value is set via a kernel config option. 389 Value can be changed at runtime via 390 /selinux/checkreqprot. 391 392 cio_ignore= [S390] 393 See Documentation/s390/CommonIO for details. 394 395 cio_msg= [S390] 396 See Documentation/s390/CommonIO for details. 397 398 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 399 [Deprecated] 400 Forces specified clocksource (if available) to be used 401 when calculating gettimeofday(). If specified 402 clocksource is not available, it defaults to PIT. 403 Format: { pit | tsc | cyclone | pmtmr } 404 405 clocksource= [GENERIC_TIME] Override the default clocksource 406 Format: <string> 407 Override the default clocksource and use the clocksource 408 with the name specified. 409 Some clocksource names to choose from, depending on 410 the platform: 411 [all] jiffies (this is the base, fallback clocksource) 412 [ACPI] acpi_pm 413 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 414 pxa_timer,timer3,32k_counter,timer0_1 415 [AVR32] avr32 416 [X86-32] pit,hpet,tsc,vmi-timer; 417 scx200_hrt on Geode; cyclone on IBM x440 418 [MIPS] MIPS 419 [PARISC] cr16 420 [S390] tod 421 [SH] SuperH 422 [SPARC64] tick 423 [X86-64] hpet,tsc 424 425 clearcpuid=BITNUM [X86] 426 Disable CPUID feature X for the kernel. See 427 include/asm-x86/cpufeature.h for the valid bit numbers. 428 Note the Linux specific bits are not necessarily 429 stable over kernel options, but the vendor specific 430 ones should be. 431 Also note that user programs calling CPUID directly 432 or using the feature without checking anything 433 will still see it. This just prevents it from 434 being used by the kernel or shown in /proc/cpuinfo. 435 Also note the kernel might malfunction if you disable 436 some critical bits. 437 438 code_bytes [IA32/X86_64] How many bytes of object code to print 439 in an oops report. 440 Range: 0 - 8192 441 Default: 64 442 443 disable_8254_timer 444 enable_8254_timer 445 [IA32/X86_64] Disable/Enable interrupt 0 timer routing 446 over the 8254 in addition to over the IO-APIC. The 447 kernel tries to set a sensible default. 448 449 hpet= [X86-32,HPET] option to control HPET usage 450 Format: { enable (default) | disable | force } 451 disable: disable HPET and use PIT instead 452 force: allow force enabled of undocumented chips (ICH4, 453 VIA, nVidia) 454 455 com20020= [HW,NET] ARCnet - COM20020 chipset 456 Format: 457 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 458 459 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 460 Format: <io>[,<irq>] 461 462 com90xx= [HW,NET] 463 ARCnet - COM90xx chipset (memory-mapped buffers) 464 Format: <io>[,<irq>[,<memstart>]] 465 466 condev= [HW,S390] console device 467 conmode= 468 469 console= [KNL] Output console device and options. 470 471 tty<n> Use the virtual console device <n>. 472 473 ttyS<n>[,options] 474 ttyUSB0[,options] 475 Use the specified serial port. The options are of 476 the form "bbbbpnf", where "bbbb" is the baud rate, 477 "p" is parity ("n", "o", or "e"), "n" is number of 478 bits, and "f" is flow control ("r" for RTS or 479 omit it). Default is "9600n8". 480 481 See Documentation/serial-console.txt for more 482 information. See 483 Documentation/networking/netconsole.txt for an 484 alternative. 485 486 uart[8250],io,<addr>[,options] 487 uart[8250],mmio,<addr>[,options] 488 Start an early, polled-mode console on the 8250/16550 489 UART at the specified I/O port or MMIO address, 490 switching to the matching ttyS device later. The 491 options are the same as for ttyS, above. 492 493 earlycon= [KNL] Output early console device and options. 494 uart[8250],io,<addr>[,options] 495 uart[8250],mmio,<addr>[,options] 496 Start an early, polled-mode console on the 8250/16550 497 UART at the specified I/O port or MMIO address. 498 The options are the same as for ttyS, above. 499 500 no_console_suspend 501 [HW] Never suspend the console 502 Disable suspending of consoles during suspend and 503 hibernate operations. Once disabled, debugging 504 messages can reach various consoles while the rest 505 of the system is being put to sleep (ie, while 506 debugging driver suspend/resume hooks). This may 507 not work reliably with all consoles, but is known 508 to work with serial and VGA consoles. 509 510 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 511 Format: 512 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 513 514 crashkernel=nn[KMG]@ss[KMG] 515 [KNL] Reserve a chunk of physical memory to 516 hold a kernel to switch to with kexec on panic. 517 518 crashkernel=range1:size1[,range2:size2,...][@offset] 519 [KNL] Same as above, but depends on the memory 520 in the running system. The syntax of range is 521 start-[end] where start and end are both 522 a memory unit (amount[KMG]). See also 523 Documentation/kdump/kdump.txt for a example. 524 525 cs4232= [HW,OSS] 526 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq> 527 528 cs89x0_dma= [HW,NET] 529 Format: <dma> 530 531 cs89x0_media= [HW,NET] 532 Format: { rj45 | aui | bnc } 533 534 dasd= [HW,NET] 535 See header of drivers/s390/block/dasd_devmap.c. 536 537 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 538 (one device per port) 539 Format: <port#>,<type> 540 See also Documentation/input/joystick-parport.txt 541 542 debug [KNL] Enable kernel debugging (events log level). 543 544 debug_locks_verbose= 545 [KNL] verbose self-tests 546 Format=<0|1> 547 Print debugging info while doing the locking API 548 self-tests. 549 We default to 0 (no extra messages), setting it to 550 1 will print _a lot_ more information - normally 551 only useful to kernel developers. 552 553 decnet.addr= [HW,NET] 554 Format: <area>[,<node>] 555 See also Documentation/networking/decnet.txt. 556 557 vt.default_blu= [VT] 558 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 559 Change the default blue palette of the console. 560 This is a 16-member array composed of values 561 ranging from 0-255. 562 563 vt.default_grn= [VT] 564 Format: <green0>,<green1>,<green2>,...,<green15> 565 Change the default green palette of the console. 566 This is a 16-member array composed of values 567 ranging from 0-255. 568 569 vt.default_red= [VT] 570 Format: <red0>,<red1>,<red2>,...,<red15> 571 Change the default red palette of the console. 572 This is a 16-member array composed of values 573 ranging from 0-255. 574 575 vt.default_utf8= 576 [VT] 577 Format=<0|1> 578 Set system-wide default UTF-8 mode for all tty's. 579 Default is 1, i.e. UTF-8 mode is enabled for all 580 newly opened terminals. 581 582 dhash_entries= [KNL] 583 Set number of hash buckets for dentry cache. 584 585 digi= [HW,SERIAL] 586 IO parameters + enable/disable command. 587 588 digiepca= [HW,SERIAL] 589 See drivers/char/README.epca and 590 Documentation/digiepca.txt. 591 592 disable_mtrr_trim [X86, Intel and AMD only] 593 By default the kernel will trim any uncacheable 594 memory out of your available memory pool based on 595 MTRR settings. This parameter disables that behavior, 596 possibly causing your machine to run very slowly. 597 598 dmasound= [HW,OSS] Sound subsystem buffers 599 600 dscc4.setup= [NET] 601 602 dtc3181e= [HW,SCSI] 603 604 earlyprintk= [X86-32,X86-64,SH,BLACKFIN] 605 earlyprintk=vga 606 earlyprintk=serial[,ttySn[,baudrate]] 607 608 Append ",keep" to not disable it when the real console 609 takes over. 610 611 Only vga or serial at a time, not both. 612 613 Currently only ttyS0 and ttyS1 are supported. 614 615 Interaction with the standard serial driver is not 616 very good. 617 618 The VGA output is eventually overwritten by the real 619 console. 620 621 eata= [HW,SCSI] 622 623 edd= [EDD] 624 Format: {"of[f]" | "sk[ipmbr]"} 625 See comment in arch/i386/boot/edd.S 626 627 eisa_irq_edge= [PARISC,HW] 628 See header of drivers/parisc/eisa.c. 629 630 elanfreq= [X86-32] 631 See comment before function elanfreq_setup() in 632 arch/i386/kernel/cpu/cpufreq/elanfreq.c. 633 634 elevator= [IOSCHED] 635 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 636 See Documentation/block/as-iosched.txt and 637 Documentation/block/deadline-iosched.txt for details. 638 639 elfcorehdr= [X86-32, X86_64] 640 Specifies physical address of start of kernel core 641 image elf header. Generally kexec loader will 642 pass this option to capture kernel. 643 See Documentation/kdump/kdump.txt for details. 644 645 enforcing [SELINUX] Set initial enforcing status. 646 Format: {"0" | "1"} 647 See security/selinux/Kconfig help text. 648 0 -- permissive (log only, no denials). 649 1 -- enforcing (deny and log). 650 Default value is 0. 651 Value can be changed at runtime via /selinux/enforce. 652 653 es1371= [HW,OSS] 654 Format: <spdif>,[<nomix>,[<amplifier>]] 655 See also header of sound/oss/es1371.c. 656 657 ether= [HW,NET] Ethernet cards parameters 658 This option is obsoleted by the "netdev=" option, which 659 has equivalent usage. See its documentation for details. 660 661 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog. 662 Format: <io>[,<irq>] 663 664 failslab= 665 fail_page_alloc= 666 fail_make_request=[KNL] 667 General fault injection mechanism. 668 Format: <interval>,<probability>,<space>,<times> 669 See also /Documentation/fault-injection/. 670 671 fd_mcs= [HW,SCSI] 672 See header of drivers/scsi/fd_mcs.c. 673 674 fdomain= [HW,SCSI] 675 See header of drivers/scsi/fdomain.c. 676 677 floppy= [HW] 678 See Documentation/floppy.txt. 679 680 gamecon.map[2|3]= 681 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 682 support via parallel port (up to 5 devices per port) 683 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 684 See also Documentation/input/joystick-parport.txt 685 686 gamma= [HW,DRM] 687 688 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 689 Format: off | on 690 default: on 691 692 gdth= [HW,SCSI] 693 See header of drivers/scsi/gdth.c. 694 695 gpt [EFI] Forces disk with valid GPT signature but 696 invalid Protective MBR to be treated as GPT. 697 698 gvp11= [HW,SCSI] 699 700 hashdist= [KNL,NUMA] Large hashes allocated during boot 701 are distributed across NUMA nodes. Defaults on 702 for IA-64, off otherwise. 703 Format: 0 | 1 (for off | on) 704 705 hcl= [IA-64] SGI's Hardware Graph compatibility layer 706 707 hd= [EIDE] (E)IDE hard drive subsystem geometry 708 Format: <cyl>,<head>,<sect> 709 710 hd?= [HW] (E)IDE subsystem 711 hd?lun= See Documentation/ide/ide.txt. 712 713 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 714 size of <nn>. This works even on boxes that have no 715 highmem otherwise. This also works to reduce highmem 716 size on bigger boxes. 717 718 highres= [KNL] Enable/disable high resolution timer mode. 719 Valid parameters: "on", "off" 720 Default: "on" 721 722 hisax= [HW,ISDN] 723 See Documentation/isdn/README.HiSax. 724 725 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages. 726 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages. 727 728 i8042.direct [HW] Put keyboard port into non-translated mode 729 i8042.dumbkbd [HW] Pretend that controller can only read data from 730 keyboard and cannot control its state 731 (Don't attempt to blink the leds) 732 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 733 i8042.nokbd [HW] Don't check/create keyboard port 734 i8042.noloop [HW] Disable the AUX Loopback command while probing 735 for the AUX port 736 i8042.nomux [HW] Don't check presence of an active multiplexing 737 controller 738 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 739 controllers 740 i8042.panicblink= 741 [HW] Frequency with which keyboard LEDs should blink 742 when kernel panics (default is 0.5 sec) 743 i8042.reset [HW] Reset the controller during init and cleanup 744 i8042.unlock [HW] Unlock (ignore) the keylock 745 746 i810= [HW,DRM] 747 748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 749 indicates that the driver is running on unsupported 750 hardware. 751 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 752 does not match list of supported models. 753 i8k.power_status 754 [HW] Report power status in /proc/i8k 755 (disabled by default) 756 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 757 capability is set. 758 759 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter 760 See Documentation/mca.txt. 761 762 icn= [HW,ISDN] 763 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 764 765 ide= [HW] (E)IDE subsystem 766 Format: ide=nodma or ide=doubler or ide=reverse 767 See Documentation/ide/ide.txt. 768 769 ide?= [HW] (E)IDE subsystem 770 Format: ide?=noprobe or chipset specific parameters. 771 See Documentation/ide/ide.txt. 772 773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed 774 See Documentation/ide/ide.txt. 775 776 idle= [X86] 777 Format: idle=poll or idle=mwait 778 Poll forces a polling idle loop that can slightly improves the performance 779 of waking up a idle CPU, but will use a lot of power and make the system 780 run hot. Not recommended. 781 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose 782 to not use it because it doesn't save as much power as a normal idle 783 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same 784 as idle=poll. 785 786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 787 Claim all unknown PCI IDE storage controllers. 788 789 ignore_loglevel [KNL] 790 Ignore loglevel setting - this will print /all/ 791 kernel messages to the console. Useful for debugging. 792 793 ihash_entries= [KNL] 794 Set number of hash buckets for inode cache. 795 796 in2000= [HW,SCSI] 797 See header of drivers/scsi/in2000.c. 798 799 init= [KNL] 800 Format: <full_path> 801 Run specified binary instead of /sbin/init as init 802 process. 803 804 initcall_debug [KNL] Trace initcalls as they are executed. Useful 805 for working out where the kernel is dying during 806 startup. 807 808 initrd= [BOOT] Specify the location of the initial ramdisk 809 810 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 811 Format: <irq> 812 813 inttest= [IA64] 814 815 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 816 off 817 Disable intel iommu driver. 818 igfx_off [Default Off] 819 By default, gfx is mapped as normal device. If a gfx 820 device has a dedicated DMAR unit, the DMAR unit is 821 bypassed by not enabling DMAR with this option. In 822 this case, gfx device will use physical address for 823 DMA. 824 forcedac [x86_64] 825 With this option iommu will not optimize to look 826 for io virtual address below 32 bit forcing dual 827 address cycle on pci bus for cards supporting greater 828 than 32 bit addressing. The default is to look 829 for translation below 32 bit and if not available 830 then look in the higher range. 831 832 io_delay= [X86-32,X86-64] I/O delay method 833 0x80 834 Standard port 0x80 based delay 835 0xed 836 Alternate port 0xed based delay (needed on some systems) 837 udelay 838 Simple two microseconds delay 839 none 840 No delay 841 842 io7= [HW] IO7 for Marvel based alpha systems 843 See comment before marvel_specify_io7 in 844 arch/alpha/kernel/core_marvel.c. 845 846 ip= [IP_PNP] 847 See Documentation/filesystems/nfsroot.txt. 848 849 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 850 See comment before ip2_setup() in 851 drivers/char/ip2/ip2base.c. 852 853 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller 854 See header of drivers/scsi/ips.c. 855 856 ports= [IP_VS_FTP] IPVS ftp helper module 857 Default is 21. 858 Up to 8 (IP_VS_APP_MAX_PORTS) ports 859 may be specified. 860 Format: <port>,<port>.... 861 862 irqfixup [HW] 863 When an interrupt is not handled search all handlers 864 for it. Intended to get systems with badly broken 865 firmware running. 866 867 irqpoll [HW] 868 When an interrupt is not handled search all handlers 869 for it. Also check all handlers each timer 870 interrupt. Intended to get systems with badly broken 871 firmware running. 872 873 isapnp= [ISAPNP] 874 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 875 876 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 877 Format: 878 <cpu number>,...,<cpu number> 879 or 880 <cpu number>-<cpu number> (must be a positive range in ascending order) 881 or a mixture 882 <cpu number>,...,<cpu number>-<cpu number> 883 This option can be used to specify one or more CPUs 884 to isolate from the general SMP balancing and scheduling 885 algorithms. The only way to move a process onto or off 886 an "isolated" CPU is via the CPU affinity syscalls. 887 <cpu number> begins at 0 and the maximum value is 888 "number of CPUs in system - 1". 889 890 This option is the preferred way to isolate CPUs. The 891 alternative -- manually setting the CPU mask of all 892 tasks in the system -- can cause problems and 893 suboptimal load balancer performance. 894 895 iucv= [HW,NET] 896 897 js= [HW,JOY] Analog joystick 898 See Documentation/input/joystick.txt. 899 900 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 901 specifies the amount of memory usable by the kernel 902 for non-movable allocations. The requested amount is 903 spread evenly throughout all nodes in the system. The 904 remaining memory in each node is used for Movable 905 pages. In the event, a node is too small to have both 906 kernelcore and Movable pages, kernelcore pages will 907 take priority and other nodes will have a larger number 908 of kernelcore pages. The Movable zone is used for the 909 allocation of pages that may be reclaimed or moved 910 by the page migration subsystem. This means that 911 HugeTLB pages may not be allocated from this zone. 912 Note that allocations like PTEs-from-HighMem still 913 use the HighMem zone if it exists, and the Normal 914 zone if it does not. 915 916 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 917 is similar to kernelcore except it specifies the 918 amount of memory used for migratable allocations. 919 If both kernelcore and movablecore is specified, 920 then kernelcore will be at *least* the specified 921 value but may be more. If movablecore on its own 922 is specified, the administrator must be careful 923 that the amount of memory usable for all allocations 924 is not too small. 925 926 keepinitrd [HW,ARM] 927 928 kstack=N [X86-32,X86-64] Print N words from the kernel stack 929 in oops dumps. 930 931 l2cr= [PPC] 932 933 lapic [X86-32,APIC] Enable the local APIC even if BIOS 934 disabled it. 935 936 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in 937 C2 power state. 938 939 libata.dma= [LIBATA] DMA control 940 libata.dma=0 Disable all PATA and SATA DMA 941 libata.dma=1 PATA and SATA Disk DMA only 942 libata.dma=2 ATAPI (CDROM) DMA only 943 libata.dma=4 Compact Flash DMA only 944 Combinations also work, so libata.dma=3 enables DMA 945 for disks and CDROMs, but not CFs. 946 947 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 948 when set. 949 Format: <int> 950 951 libata.force= [LIBATA] Force configurations. The format is comma 952 separated list of "[ID:]VAL" where ID is 953 PORT[:DEVICE]. PORT and DEVICE are decimal numbers 954 matching port, link or device. Basically, it matches 955 the ATA ID string printed on console by libata. If 956 the whole ID part is omitted, the last PORT and DEVICE 957 values are used. If ID hasn't been specified yet, the 958 configuration applies to all ports, links and devices. 959 960 If only DEVICE is omitted, the parameter applies to 961 the port and all links and devices behind it. DEVICE 962 number of 0 either selects the first device or the 963 first fan-out link behind PMP device. It does not 964 select the host link. DEVICE number of 15 selects the 965 host link and device attached to it. 966 967 The VAL specifies the configuration to force. As long 968 as there's no ambiguity shortcut notation is allowed. 969 For example, both 1.5 and 1.5G would work for 1.5Gbps. 970 The following configurations can be forced. 971 972 * Cable type: 40c, 80c, short40c, unk, ign or sata. 973 Any ID with matching PORT is used. 974 975 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 976 977 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 978 udma[/][16,25,33,44,66,100,133] notation is also 979 allowed. 980 981 * [no]ncq: Turn on or off NCQ. 982 983 If there are multiple matching configurations changing 984 the same attribute, the last one is used. 985 986 load_ramdisk= [RAM] List of ramdisks to load from floppy 987 See Documentation/ramdisk.txt. 988 989 lockd.nlm_grace_period=P [NFS] Assign grace period. 990 Format: <integer> 991 992 lockd.nlm_tcpport=N [NFS] Assign TCP port. 993 Format: <integer> 994 995 lockd.nlm_timeout=T [NFS] Assign timeout value. 996 Format: <integer> 997 998 lockd.nlm_udpport=M [NFS] Assign UDP port. 999 Format: <integer> 1000 1001 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1002 Format: <irq> 1003 1004 loglevel= All Kernel Messages with a loglevel smaller than the 1005 console loglevel will be printed to the console. It can 1006 also be changed with klogd or other programs. The 1007 loglevels are defined as follows: 1008 1009 0 (KERN_EMERG) system is unusable 1010 1 (KERN_ALERT) action must be taken immediately 1011 2 (KERN_CRIT) critical conditions 1012 3 (KERN_ERR) error conditions 1013 4 (KERN_WARNING) warning conditions 1014 5 (KERN_NOTICE) normal but significant condition 1015 6 (KERN_INFO) informational 1016 7 (KERN_DEBUG) debug-level messages 1017 1018 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1019 Format: { n | nk | nM } 1020 n must be a power of two. The default size 1021 is set in the kernel config file. 1022 1023 logo.nologo [FB] Disables display of the built-in Linux logo. 1024 This may be used to provide more screen space for 1025 kernel log messages and is useful when debugging 1026 kernel boot problems. 1027 1028 lp=0 [LP] Specify parallel ports to use, e.g, 1029 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1030 lp=reset first parallel port). 'lp=0' disables the 1031 lp=auto printer driver. 'lp=reset' (which can be 1032 specified in addition to the ports) causes 1033 attached printers to be reset. Using 1034 lp=port1,port2,... specifies the parallel ports 1035 to associate lp devices with, starting with 1036 lp0. A port specification may be 'none' to skip 1037 that lp device, or a parport name such as 1038 'parport0'. Specifying 'lp=auto' instead of a 1039 port specification list means that device IDs 1040 from each port should be examined, to see if 1041 an IEEE 1284-compliant printer is attached; if 1042 so, the driver will manage that printer. 1043 See also header of drivers/char/lp.c. 1044 1045 lpj=n [KNL] 1046 Sets loops_per_jiffy to given constant, thus avoiding 1047 time-consuming boot-time autodetection (up to 250 ms per 1048 CPU). 0 enables autodetection (default). To determine 1049 the correct value for your kernel, boot with normal 1050 autodetection and see what value is printed. Note that 1051 on SMP systems the preset will be applied to all CPUs, 1052 which is likely to cause problems if your CPUs need 1053 significantly divergent settings. An incorrect value 1054 will cause delays in the kernel to be wrong, leading to 1055 unpredictable I/O errors and other breakage. Although 1056 unlikely, in the extreme case this might damage your 1057 hardware. 1058 1059 ltpc= [NET] 1060 Format: <io>,<irq>,<dma> 1061 1062 mac5380= [HW,SCSI] Format: 1063 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1064 1065 mac53c9x= [HW,SCSI] Format: 1066 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1067 1068 machvec= [IA64] Force the use of a particular machine-vector 1069 (machvec) in a generic kernel. 1070 Example: machvec=hpzx1_swiotlb 1071 1072 max_loop= [LOOP] Maximum number of loopback devices that can 1073 be mounted 1074 Format: <1-256> 1075 1076 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1077 should make use of. maxcpus=n : n >= 0 limits the 1078 kernel to using 'n' processors. n=0 is a special case, 1079 it is equivalent to "nosmp", which also disables 1080 the IO APIC. 1081 1082 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or 1083 equal to this physical address is ignored. 1084 1085 max_luns= [SCSI] Maximum number of LUNs to probe. 1086 Should be between 1 and 2^32-1. 1087 1088 max_report_luns= 1089 [SCSI] Maximum number of LUNs received. 1090 Should be between 1 and 16384. 1091 1092 mcatest= [IA-64] 1093 1094 mce [X86-32] Machine Check Exception 1095 1096 mce=option [X86-64] See Documentation/x86_64/boot-options.txt 1097 1098 md= [HW] RAID subsystems devices and level 1099 See Documentation/md.txt. 1100 1101 mdacon= [MDA] 1102 Format: <first>,<last> 1103 Specifies range of consoles to be captured by the MDA. 1104 1105 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1106 Amount of memory to be used when the kernel is not able 1107 to see the whole system memory or for test. 1108 [X86-32] Use together with memmap= to avoid physical 1109 address space collisions. Without memmap= PCI devices 1110 could be placed at addresses belonging to unused RAM. 1111 1112 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1113 memory. 1114 1115 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact 1116 E820 memory map, as specified by the user. 1117 Such memmap=exactmap lines can be constructed based on 1118 BIOS output or other requirements. See the memmap=nn@ss 1119 option description. 1120 1121 memmap=nn[KMG]@ss[KMG] 1122 [KNL] Force usage of a specific region of memory 1123 Region of memory to be used, from ss to ss+nn. 1124 1125 memmap=nn[KMG]#ss[KMG] 1126 [KNL,ACPI] Mark specific memory as ACPI data. 1127 Region of memory to be used, from ss to ss+nn. 1128 1129 memmap=nn[KMG]$ss[KMG] 1130 [KNL,ACPI] Mark specific memory as reserved. 1131 Region of memory to be used, from ss to ss+nn. 1132 Example: Exclude memory from 0x18690000-0x1869ffff 1133 memmap=64K$0x18690000 1134 or 1135 memmap=0x10000$0x18690000 1136 1137 meye.*= [HW] Set MotionEye Camera parameters 1138 See Documentation/video4linux/meye.txt. 1139 1140 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1141 Multi-Function General Purpose Timers on AMD Geode 1142 platforms. 1143 1144 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1145 the BIOS has incorrectly applied a workaround. TinyBIOS 1146 version 0.98 is known to be affected, 0.99 fixes the 1147 problem by letting the user disable the workaround. 1148 1149 mga= [HW,DRM] 1150 1151 mousedev.tap_time= 1152 [MOUSE] Maximum time between finger touching and 1153 leaving touchpad surface for touch to be considered 1154 a tap and be reported as a left button click (for 1155 touchpads working in absolute mode only). 1156 Format: <msecs> 1157 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1158 reporting absolute coordinates, such as tablets 1159 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1160 reporting absolute coordinates, such as tablets 1161 1162 mpu401= [HW,OSS] 1163 Format: <io>,<irq> 1164 1165 MTD_Partition= [MTD] 1166 Format: <name>,<region-number>,<size>,<offset> 1167 1168 MTD_Region= [MTD] Format: 1169 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1170 1171 mtdparts= [MTD] 1172 See drivers/mtd/cmdlinepart.c. 1173 1174 mtouchusb.raw_coordinates= 1175 [HW] Make the MicroTouch USB driver use raw coordinates 1176 ('y', default) or cooked coordinates ('n') 1177 1178 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1179 1180 NCR_D700= [HW,SCSI] 1181 See header of drivers/scsi/NCR_D700.c. 1182 1183 ncr5380= [HW,SCSI] 1184 1185 ncr53c400= [HW,SCSI] 1186 1187 ncr53c400a= [HW,SCSI] 1188 1189 ncr53c406a= [HW,SCSI] 1190 1191 ncr53c8xx= [HW,SCSI] 1192 1193 netdev= [NET] Network devices parameters 1194 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1195 Note that mem_start is often overloaded to mean 1196 something different and driver-specific. 1197 This usage is only documented in each driver source 1198 file if at all. 1199 1200 nfsaddrs= [NFS] 1201 See Documentation/filesystems/nfsroot.txt. 1202 1203 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1204 See Documentation/filesystems/nfsroot.txt. 1205 1206 nfs.callback_tcpport= 1207 [NFS] set the TCP port on which the NFSv4 callback 1208 channel should listen. 1209 1210 nfs.idmap_cache_timeout= 1211 [NFS] set the maximum lifetime for idmapper cache 1212 entries. 1213 1214 nfs.enable_ino64= 1215 [NFS] enable 64-bit inode numbers. 1216 If zero, the NFS client will fake up a 32-bit inode 1217 number for the readdir() and stat() syscalls instead 1218 of returning the full 64-bit number. 1219 The default is to return 64-bit inode numbers. 1220 1221 nmi_debug= [KNL,AVR32] Specify one or more actions to take 1222 when a NMI is triggered. 1223 Format: [state][,regs][,debounce][,die] 1224 1225 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels 1226 1227 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1228 emulation library even if a 387 maths coprocessor 1229 is present. 1230 1231 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1232 caches in the slab allocator. Saves per-node memory, 1233 but will impact performance. 1234 1235 noalign [KNL,ARM] 1236 1237 noapic [SMP,APIC] Tells the kernel to not make use of any 1238 IOAPICs that may be present in the system. 1239 1240 nobats [PPC] Do not use BATs for mapping kernel lowmem 1241 on "Classic" PPC cores. 1242 1243 nocache [ARM] 1244 1245 nodelayacct [KNL] Disable per-task delay accounting 1246 1247 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1248 1249 noefi [X86-32,X86-64] Disable EFI runtime services support. 1250 1251 noexec [IA-64] 1252 1253 noexec [X86-32,X86-64] 1254 noexec=on: enable non-executable mappings (default) 1255 noexec=off: disable nn-executable mappings 1256 1257 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1258 register save and restore. The kernel will only save 1259 legacy floating-point registers on task switch. 1260 1261 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1262 1263 nohlt [BUGS=ARM] 1264 1265 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1266 instruction doesn't work correctly and not to 1267 use it. 1268 1269 nohalt [IA-64] Tells the kernel not to use the power saving 1270 function PAL_HALT_LIGHT when idle. This increases 1271 power-consumption. On the positive side, it reduces 1272 interrupt wake-up latency, which may improve performance 1273 in certain environments such as networked servers or 1274 real-time systems. 1275 1276 nohz= [KNL] Boottime enable/disable dynamic ticks 1277 Valid arguments: on, off 1278 Default: on 1279 1280 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing 1281 1282 noirqdebug [X86-32] Disables the code which attempts to detect and 1283 disable unhandled interrupt sources. 1284 1285 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for 1286 broken timer IRQ sources. 1287 1288 noisapnp [ISAPNP] Disables ISA PnP code. 1289 1290 noinitrd [RAM] Tells the kernel not to load any configured 1291 initial RAM disk. 1292 1293 nointroute [IA-64] 1294 1295 nojitter [IA64] Disables jitter checking for ITC timers. 1296 1297 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1298 1299 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1300 1301 noltlbs [PPC] Do not use large page/tlb entries for kernel 1302 lowmem mapping on PPC40x. 1303 1304 nomca [IA-64] Disable machine check abort handling 1305 1306 nomce [X86-32] Machine Check Exception 1307 1308 nomfgpt [X86-32] Disable Multi-Function General Purpose 1309 Timer usage (for AMD Geode machines). 1310 1311 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1312 1313 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1314 with UP alternatives 1315 1316 noresidual [PPC] Don't use residual data on PReP machines. 1317 1318 noresume [SWSUSP] Disables resume and restores original swap 1319 space. 1320 1321 no-scroll [VGA] Disables scrollback. 1322 This is required for the Braillex ib80-piezo Braille 1323 reader made by F.H. Papenmeier (Germany). 1324 1325 nosbagart [IA-64] 1326 1327 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1328 1329 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1330 and disable the IO APIC. legacy for "maxcpus=0". 1331 1332 nosoftlockup [KNL] Disable the soft-lockup detector. 1333 1334 nosync [HW,M68K] Disables sync negotiation for all devices. 1335 1336 notsc [BUGS=X86-32] Disable Time Stamp Counter 1337 1338 nousb [USB] Disable the USB subsystem 1339 1340 nowb [ARM] 1341 1342 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1343 one of ['zone', 'node', 'default'] can be specified 1344 This can be set from sysctl after boot. 1345 See Documentation/sysctl/vm.txt for details. 1346 1347 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1348 1349 opl3= [HW,OSS] 1350 Format: <io> 1351 1352 oprofile.timer= [HW] 1353 Use timer interrupt instead of performance counters 1354 1355 osst= [HW,SCSI] SCSI Tape Driver 1356 Format: <buffer_size>,<write_threshold> 1357 See also Documentation/scsi/st.txt. 1358 1359 panic= [KNL] Kernel behaviour on panic 1360 Format: <timeout> 1361 1362 parkbd.port= [HW] Parallel port number the keyboard adapter is 1363 connected to, default is 0. 1364 Format: <parport#> 1365 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1366 0 for XT, 1 for AT (default is AT). 1367 Format: <mode> 1368 1369 parport= [HW,PPT] Specify parallel ports. 0 disables. 1370 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1371 Use 'auto' to force the driver to use any 1372 IRQ/DMA settings detected (the default is to 1373 ignore detected IRQ/DMA settings because of 1374 possible conflicts). You can specify the base 1375 address, IRQ, and DMA settings; IRQ and DMA 1376 should be numbers, or 'auto' (for using detected 1377 settings on that particular port), or 'nofifo' 1378 (to avoid using a FIFO even if it is detected). 1379 Parallel ports are assigned in the order they 1380 are specified on the command line, starting 1381 with parport0. 1382 1383 parport_init_mode= [HW,PPT] 1384 Configure VIA parallel port to operate in 1385 a specific mode. This is necessary on Pegasos 1386 computer where firmware has no options for setting 1387 up parallel port mode and sets it to spp.