Based on kernel version 2.6.33. Page generated on 2010-02-24 15:36 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 Hyphens (dashes) and underscores are equivalent in parameter names, so 21 log_buf_len=1M print-fatal-signals=1 22 can also be entered as 23 log-buf-len=1M print_fatal_signals=1 24 25 26 This document may not be entirely up to date and comprehensive. The command 27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable 28 module. Loadable modules, after being loaded into the running kernel, also 29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these 30 parameters may be changed at runtime by the command 31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". 32 33 The parameters listed below are only valid if certain kernel build options were 34 enabled and if respective hardware is present. The text in square brackets at 35 the beginning of each description states the restrictions within which a 36 parameter is applicable: 37 38 ACPI ACPI support is enabled. 39 AGP AGP (Accelerated Graphics Port) is enabled. 40 ALSA ALSA sound support is enabled. 41 APIC APIC support is enabled. 42 APM Advanced Power Management support is enabled. 43 AVR32 AVR32 architecture is enabled. 44 AX25 Appropriate AX.25 support is enabled. 45 BLACKFIN Blackfin architecture is enabled. 46 DRM Direct Rendering Management support is enabled. 47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled 48 EFI EFI Partitioning (GPT) is enabled 49 EIDE EIDE/ATAPI support is enabled. 50 FB The frame buffer device is enabled. 51 GCOV GCOV profiling is enabled. 52 HW Appropriate hardware is enabled. 53 IA-64 IA-64 architecture is enabled. 54 IMA Integrity measurement architecture is enabled. 55 IOSCHED More than one I/O scheduler is enabled. 56 IP_PNP IP DHCP, BOOTP, or RARP is enabled. 57 ISAPNP ISA PnP code is enabled. 58 ISDN Appropriate ISDN support is enabled. 59 JOY Appropriate joystick support is enabled. 60 KVM Kernel Virtual Machine support is enabled. 61 LIBATA Libata driver is enabled 62 LP Printer support is enabled. 63 LOOP Loopback device support is enabled. 64 M68k M68k architecture is enabled. 65 These options have more detailed description inside of 66 Documentation/m68k/kernel-options.txt. 67 MCA MCA bus support is enabled. 68 MDA MDA console support is enabled. 69 MOUSE Appropriate mouse support is enabled. 70 MSI Message Signaled Interrupts (PCI). 71 MTD MTD (Memory Technology Device) support is enabled. 72 NET Appropriate network support is enabled. 73 NUMA NUMA support is enabled. 74 GENERIC_TIME The generic timeofday code is enabled. 75 NFS Appropriate NFS support is enabled. 76 OSS OSS sound support is enabled. 77 PV_OPS A paravirtualized kernel is enabled. 78 PARIDE The ParIDE (parallel port IDE) subsystem is enabled. 79 PARISC The PA-RISC architecture is enabled. 80 PCI PCI bus support is enabled. 81 PCIE PCI Express support is enabled. 82 PCMCIA The PCMCIA subsystem is enabled. 83 PNP Plug & Play support is enabled. 84 PPC PowerPC architecture is enabled. 85 PPT Parallel port support is enabled. 86 PS2 Appropriate PS/2 support is enabled. 87 RAM RAM disk support is enabled. 88 S390 S390 architecture is enabled. 89 SCSI Appropriate SCSI support is enabled. 90 A lot of drivers has their options described inside of 91 Documentation/scsi/. 92 SECURITY Different security models are enabled. 93 SELINUX SELinux support is enabled. 94 SERIAL Serial support is enabled. 95 SH SuperH architecture is enabled. 96 SMP The kernel is an SMP kernel. 97 SPARC Sparc architecture is enabled. 98 SWSUSP Software suspend (hibernation) is enabled. 99 SUSPEND System suspend states are enabled. 100 FTRACE Function tracing enabled. 101 TS Appropriate touchscreen support is enabled. 102 UMS USB Mass Storage support is enabled. 103 USB USB support is enabled. 104 USBHID USB Human Interface Device support is enabled. 105 V4L Video For Linux support is enabled. 106 VGA The VGA console has been enabled. 107 VT Virtual terminal support is enabled. 108 WDT Watchdog support is enabled. 109 XT IBM PC/XT MFM hard disk support is enabled. 110 X86-32 X86-32, aka i386 architecture is enabled. 111 X86-64 X86-64 architecture is enabled. 112 More X86-64 boot options can be found in 113 Documentation/x86/x86_64/boot-options.txt . 114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64) 115 116 In addition, the following text indicates that the option: 117 118 BUGS= Relates to possible processor bugs on the said processor. 119 KNL Is a kernel start-up parameter. 120 BOOT Is a boot loader parameter. 121 122 Parameters denoted with BOOT are actually interpreted by the boot 123 loader, and have no meaning to the kernel directly. 124 Do not modify the syntax of boot loader parameters without extreme 125 need or coordination with <Documentation/x86/boot.txt>. 126 127 There are also arch-specific kernel-parameters not documented here. 128 See for example <Documentation/x86/x86_64/boot-options.txt>. 129 130 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 131 a trailing = on the name of any parameter states that that parameter will 132 be entered as an environment variable, whereas its absence indicates that 133 it will appear as a kernel argument readable via /proc/cmdline by programs 134 running once the system is up. 135 136 The number of kernel parameters is not limited, but the length of the 137 complete command line (parameters including spaces etc.) is limited to 138 a fixed number of characters. This limit depends on the architecture 139 and is between 256 and 4096 characters. It is defined in the file 140 ./include/asm/setup.h as COMMAND_LINE_SIZE. 141 142 143 acpi= [HW,ACPI,X86] 144 Advanced Configuration and Power Interface 145 Format: { force | off | ht | strict | noirq | rsdt } 146 force -- enable ACPI if default was off 147 off -- disable ACPI if default was on 148 noirq -- do not use ACPI for IRQ routing 149 ht -- run only enough ACPI to enable Hyper Threading 150 strict -- Be less tolerant of platforms that are not 151 strictly ACPI specification compliant. 152 rsdt -- prefer RSDT over (default) XSDT 153 154 See also Documentation/power/pm.txt, pci=noacpi 155 156 acpi_apic_instance= [ACPI, IOAPIC] 157 Format: <int> 158 2: use 2nd APIC table, if available 159 1,0: use 1st APIC table 160 default: 0 161 162 acpi_backlight= [HW,ACPI] 163 acpi_backlight=vendor 164 acpi_backlight=video 165 If set to vendor, prefer vendor specific driver 166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead 167 of the ACPI video.ko driver. 168 169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 171 Format: <int> 172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI 173 debug output. Bits in debug_layer correspond to a 174 _COMPONENT in an ACPI source file, e.g., 175 #define _COMPONENT ACPI_PCI_COMPONENT 176 Bits in debug_level correspond to a level in 177 ACPI_DEBUG_PRINT statements, e.g., 178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... 179 The debug_level mask defaults to "info". See 180 Documentation/acpi/debug.txt for more information about 181 debug layers and levels. 182 183 Enable processor driver info messages: 184 acpi.debug_layer=0x20000000 185 Enable PCI/PCI interrupt routing info messages: 186 acpi.debug_layer=0x400000 187 Enable AML "Debug" output, i.e., stores to the Debug 188 object while interpreting AML: 189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2 190 Enable all messages related to ACPI hardware: 191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 192 193 Some values produce so much output that the system is 194 unusable. The "log_buf_len" parameter may be useful 195 if you need to capture more output. 196 197 acpi_display_output= [HW,ACPI] 198 acpi_display_output=vendor 199 acpi_display_output=video 200 See above. 201 202 acpi_early_pdc_eval [HW,ACPI] Evaluate processor _PDC methods 203 early. Needed on some platforms to properly 204 initialize the EC. 205 206 acpi_irq_balance [HW,ACPI] 207 ACPI will balance active IRQs 208 default in APIC mode 209 210 acpi_irq_nobalance [HW,ACPI] 211 ACPI will not move active IRQs (default) 212 default in PIC mode 213 214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 215 Format: <irq>,<irq>... 216 217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 218 use by PCI 219 Format: <irq>,<irq>... 220 221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 222 223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 224 Format: To spoof as Windows 98: ="Microsoft Windows" 225 226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 227 acpi_osi="string1" # add string1 -- only one string 228 acpi_osi="!string2" # remove built-in string2 229 acpi_osi= # disable all strings 230 231 acpi_pm_good [X86] 232 Override the pmtimer bug detection: force the kernel 233 to assume that this machine's pmtimer latches its value 234 and always returns good values. 235 236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 237 Format: { level | edge | high | low } 238 239 acpi_serialize [HW,ACPI] force serialization of AML methods 240 241 acpi_skip_timer_override [HW,ACPI] 242 Recognize and ignore IRQ0/pin2 Interrupt Override. 243 For broken nForce2 BIOS resulting in XT-PIC timer. 244 245 acpi_sleep= [HW,ACPI] Sleep options 246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 247 old_ordering, s4_nonvs, sci_force_enable } 248 See Documentation/power/video.txt for information on 249 s3_bios and s3_mode. 250 s3_beep is for debugging; it makes the PC's speaker beep 251 as soon as the kernel's real-mode entry point is called. 252 s4_nohwsig prevents ACPI hardware signature from being 253 used during resume from hibernation. 254 old_ordering causes the ACPI 1.0 ordering of the _PTS 255 control method, with respect to putting devices into 256 low power states, to be enforced (the ACPI 2.0 ordering 257 of _PTS is used by default). 258 s4_nonvs prevents the kernel from saving/restoring the 259 ACPI NVS memory during hibernation. 260 sci_force_enable causes the kernel to set SCI_EN directly 261 on resume from S1/S3 (which is against the ACPI spec, 262 but some broken systems don't work without it). 263 264 acpi_use_timer_override [HW,ACPI] 265 Use timer override. For some broken Nvidia NF5 boards 266 that require a timer override, but don't have HPET 267 268 acpi_enforce_resources= [ACPI] 269 { strict | lax | no } 270 Check for resource conflicts between native drivers 271 and ACPI OperationRegions (SystemIO and SystemMemory 272 only). IO ports and memory declared in ACPI might be 273 used by the ACPI subsystem in arbitrary AML code and 274 can interfere with legacy drivers. 275 strict (default): access to resources claimed by ACPI 276 is denied; legacy drivers trying to access reserved 277 resources will fail to bind to device using them. 278 lax: access to resources claimed by ACPI is allowed; 279 legacy drivers trying to access reserved resources 280 will bind successfully but a warning message is logged. 281 no: ACPI OperationRegions are not marked as reserved, 282 no further checks are performed. 283 284 ad1848= [HW,OSS] 285 Format: <io>,<irq>,<dma>,<dma2>,<type> 286 287 add_efi_memmap [EFI; X86] Include EFI memory map in 288 kernel's map of available physical RAM. 289 290 advansys= [HW,SCSI] 291 See header of drivers/scsi/advansys.c. 292 293 advwdt= [HW,WDT] Advantech WDT 294 Format: <iostart>,<iostop> 295 296 aedsp16= [HW,OSS] Audio Excel DSP 16 297 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq> 298 See also header of sound/oss/aedsp16.c. 299 300 agp= [AGP] 301 { off | try_unsupported } 302 off: disable AGP support 303 try_unsupported: try to drive unsupported chipsets 304 (may crash computer or cause data corruption) 305 306 aha152x= [HW,SCSI] 307 See Documentation/scsi/aha152x.txt. 308 309 aha1542= [HW,SCSI] 310 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]] 311 312 aic7xxx= [HW,SCSI] 313 See Documentation/scsi/aic7xxx.txt. 314 315 aic79xx= [HW,SCSI] 316 See Documentation/scsi/aic79xx.txt. 317 318 alignment= [KNL,ARM] 319 Allow the default userspace alignment fault handler 320 behaviour to be specified. Bit 0 enables warnings, 321 bit 1 enables fixups, and bit 2 sends a segfault. 322 323 amd_iommu= [HW,X86-84] 324 Pass parameters to the AMD IOMMU driver in the system. 325 Possible values are: 326 isolate - enable device isolation (each device, as far 327 as possible, will get its own protection 328 domain) [default] 329 share - put every device behind one IOMMU into the 330 same protection domain 331 fullflush - enable flushing of IO/TLB entries when 332 they are unmapped. Otherwise they are 333 flushed before they will be reused, which 334 is a lot of faster 335 336 amijoy.map= [HW,JOY] Amiga joystick support 337 Map of devices attached to JOY0DAT and JOY1DAT 338 Format: <a>,<b> 339 See also Documentation/kernel/input/joystick.txt 340 341 analog.map= [HW,JOY] Analog joystick and gamepad support 342 Specifies type or capabilities of an analog joystick 343 connected to one of 16 gameports 344 Format: <type1>,<type2>,..<type16> 345 346 apc= [HW,SPARC] 347 Power management functions (SPARCstation-4/5 + deriv.) 348 Format: noidle 349 Disable APC CPU standby support. SPARCstation-Fox does 350 not play well with APC CPU idle - disable it if you have 351 APC and your system crashes randomly. 352 353 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller 354 Change the output verbosity whilst booting 355 Format: { quiet (default) | verbose | debug } 356 Change the amount of debugging information output 357 when initialising the APIC and IO-APIC components. 358 359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 360 Limit apic dumping. The parameter defines the maximal 361 number of local apics being dumped. Also it is possible 362 to set it to "all" by meaning -- no limit here. 363 Format: { 1 (default) | 2 | ... | all }. 364 The parameter valid if only apic=debug or 365 apic=verbose is specified. 366 Example: apic=debug show_lapic=all 367 368 apm= [APM] Advanced Power Management 369 See header of arch/x86/kernel/apm_32.c. 370 371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 372 Format: <io>,<irq>,<nodeID> 373 374 ataflop= [HW,M68k] 375 376 atarimouse= [HW,MOUSE] Atari Mouse 377 378 atascsi= [HW,SCSI] Atari SCSI 379 380 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 381 EzKey and similar keyboards 382 383 atkbd.reset= [HW] Reset keyboard during initialization 384 385 atkbd.set= [HW] Select keyboard code set 386 Format: <int> (2 = AT (default), 3 = PS/2) 387 388 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 389 keyboards 390 391 atkbd.softraw= [HW] Choose between synthetic and real raw mode 392 Format: <bool> (0 = real, 1 = synthetic (default)) 393 394 atkbd.softrepeat= [HW] 395 Use software keyboard repeat 396 397 autotest [IA64] 398 399 baycom_epp= [HW,AX25] 400 Format: <io>,<mode> 401 402 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 403 Format: <io>,<mode> 404 See header of drivers/net/hamradio/baycom_par.c. 405 406 baycom_ser_fdx= [HW,AX25] 407 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 408 Format: <io>,<irq>,<mode>[,<baud>] 409 See header of drivers/net/hamradio/baycom_ser_fdx.c. 410 411 baycom_ser_hdx= [HW,AX25] 412 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 413 Format: <io>,<irq>,<mode> 414 See header of drivers/net/hamradio/baycom_ser_hdx.c. 415 416 boot_delay= Milliseconds to delay each printk during boot. 417 Values larger than 10 seconds (10000) are changed to 418 no delay (0). 419 Format: integer 420 421 bootmem_debug [KNL] Enable bootmem allocator debug messages. 422 423 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 424 bttv.radio= Most important insmod options are available as 425 kernel args too. 426 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 427 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 428 429 BusLogic= [HW,SCSI] 430 See drivers/scsi/BusLogic.c, comment before function 431 BusLogic_ParseDriverOptions(). 432 433 c101= [NET] Moxa C101 synchronous serial card 434 435 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 436 Sometimes CPU hardware bugs make them report the cache 437 size incorrectly. The kernel will attempt work arounds 438 to fix known problems, but for some CPUs it is not 439 possible to determine what the correct size should be. 440 This option provides an override for these situations. 441 442 capability.disable= 443 [SECURITY] Disable capabilities. This would normally 444 be used only if an alternative security model is to be 445 configured. Potentially dangerous and should only be 446 used if you are entirely sure of the consequences. 447 448 ccw_timeout_log [S390] 449 See Documentation/s390/CommonIO for details. 450 451 cgroup_disable= [KNL] Disable a particular controller 452 Format: {name of the controller(s) to disable} 453 {Currently supported controllers - "memory"} 454 455 checkreqprot [SELINUX] Set initial checkreqprot flag value. 456 Format: { "0" | "1" } 457 See security/selinux/Kconfig help text. 458 0 -- check protection applied by kernel (includes 459 any implied execute protection). 460 1 -- check protection requested by application. 461 Default value is set via a kernel config option. 462 Value can be changed at runtime via 463 /selinux/checkreqprot. 464 465 cio_ignore= [S390] 466 See Documentation/s390/CommonIO for details. 467 468 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 469 [Deprecated] 470 Forces specified clocksource (if available) to be used 471 when calculating gettimeofday(). If specified 472 clocksource is not available, it defaults to PIT. 473 Format: { pit | tsc | cyclone | pmtmr } 474 475 clocksource= [GENERIC_TIME] Override the default clocksource 476 Format: <string> 477 Override the default clocksource and use the clocksource 478 with the name specified. 479 Some clocksource names to choose from, depending on 480 the platform: 481 [all] jiffies (this is the base, fallback clocksource) 482 [ACPI] acpi_pm 483 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 484 pxa_timer,timer3,32k_counter,timer0_1 485 [AVR32] avr32 486 [X86-32] pit,hpet,tsc,vmi-timer; 487 scx200_hrt on Geode; cyclone on IBM x440 488 [MIPS] MIPS 489 [PARISC] cr16 490 [S390] tod 491 [SH] SuperH 492 [SPARC64] tick 493 [X86-64] hpet,tsc 494 495 clearcpuid=BITNUM [X86] 496 Disable CPUID feature X for the kernel. See 497 arch/x86/include/asm/cpufeature.h for the valid bit 498 numbers. Note the Linux specific bits are not necessarily 499 stable over kernel options, but the vendor specific 500 ones should be. 501 Also note that user programs calling CPUID directly 502 or using the feature without checking anything 503 will still see it. This just prevents it from 504 being used by the kernel or shown in /proc/cpuinfo. 505 Also note the kernel might malfunction if you disable 506 some critical bits. 507 508 cmo_free_hint= [PPC] Format: { yes | no } 509 Specify whether pages are marked as being inactive 510 when they are freed. This is used in CMO environments 511 to determine OS memory pressure for page stealing by 512 a hypervisor. 513 Default: yes 514 515 code_bytes [X86] How many bytes of object code to print 516 in an oops report. 517 Range: 0 - 8192 518 Default: 64 519 520 com20020= [HW,NET] ARCnet - COM20020 chipset 521 Format: 522 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 523 524 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 525 Format: <io>[,<irq>] 526 527 com90xx= [HW,NET] 528 ARCnet - COM90xx chipset (memory-mapped buffers) 529 Format: <io>[,<irq>[,<memstart>]] 530 531 condev= [HW,S390] console device 532 conmode= 533 534 console= [KNL] Output console device and options. 535 536 tty<n> Use the virtual console device <n>. 537 538 ttyS<n>[,options] 539 ttyUSB0[,options] 540 Use the specified serial port. The options are of 541 the form "bbbbpnf", where "bbbb" is the baud rate, 542 "p" is parity ("n", "o", or "e"), "n" is number of 543 bits, and "f" is flow control ("r" for RTS or 544 omit it). Default is "9600n8". 545 546 See Documentation/serial-console.txt for more 547 information. See 548 Documentation/networking/netconsole.txt for an 549 alternative. 550 551 uart[8250],io,<addr>[,options] 552 uart[8250],mmio,<addr>[,options] 553 Start an early, polled-mode console on the 8250/16550 554 UART at the specified I/O port or MMIO address, 555 switching to the matching ttyS device later. The 556 options are the same as for ttyS, above. 557 558 If the device connected to the port is not a TTY but a braille 559 device, prepend "brl," before the device type, for instance 560 console=brl,ttyS0 561 For now, only VisioBraille is supported. 562 563 consoleblank= [KNL] The console blank (screen saver) timeout in 564 seconds. Defaults to 10*60 = 10mins. A value of 0 565 disables the blank timer. 566 567 coredump_filter= 568 [KNL] Change the default value for 569 /proc/<pid>/coredump_filter. 570 See also Documentation/filesystems/proc.txt. 571 572 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 573 Format: 574 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 575 576 crashkernel=nn[KMG]@ss[KMG] 577 [KNL] Reserve a chunk of physical memory to 578 hold a kernel to switch to with kexec on panic. 579 580 crashkernel=range1:size1[,range2:size2,...][@offset] 581 [KNL] Same as above, but depends on the memory 582 in the running system. The syntax of range is 583 start-[end] where start and end are both 584 a memory unit (amount[KMG]). See also 585 Documentation/kdump/kdump.txt for a example. 586 587 cs89x0_dma= [HW,NET] 588 Format: <dma> 589 590 cs89x0_media= [HW,NET] 591 Format: { rj45 | aui | bnc } 592 593 dasd= [HW,NET] 594 See header of drivers/s390/block/dasd_devmap.c. 595 596 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 597 (one device per port) 598 Format: <port#>,<type> 599 See also Documentation/input/joystick-parport.txt 600 601 debug [KNL] Enable kernel debugging (events log level). 602 603 debug_locks_verbose= 604 [KNL] verbose self-tests 605 Format=<0|1> 606 Print debugging info while doing the locking API 607 self-tests. 608 We default to 0 (no extra messages), setting it to 609 1 will print _a lot_ more information - normally 610 only useful to kernel developers. 611 612 debug_objects [KNL] Enable object debugging 613 614 no_debug_objects 615 [KNL] Disable object debugging 616 617 debugpat [X86] Enable PAT debugging 618 619 decnet.addr= [HW,NET] 620 Format: <area>[,<node>] 621 See also Documentation/networking/decnet.txt. 622 623 default_hugepagesz= 624 [same as hugepagesz=] The size of the default 625 HugeTLB page size. This is the size represented by 626 the legacy /proc/ hugepages APIs, used for SHM, and 627 default size when mounting hugetlbfs filesystems. 628 Defaults to the default architecture's huge page size 629 if not specified. 630 631 dhash_entries= [KNL] 632 Set number of hash buckets for dentry cache. 633 634 digi= [HW,SERIAL] 635 IO parameters + enable/disable command. 636 637 digiepca= [HW,SERIAL] 638 See drivers/char/README.epca and 639 Documentation/serial/digiepca.txt. 640 641 disable_mtrr_cleanup [X86] 642 The kernel tries to adjust MTRR layout from continuous 643 to discrete, to make X server driver able to add WB 644 entry later. This parameter disables that. 645 646 disable_mtrr_trim [X86, Intel and AMD only] 647 By default the kernel will trim any uncacheable 648 memory out of your available memory pool based on 649 MTRR settings. This parameter disables that behavior, 650 possibly causing your machine to run very slowly. 651 652 disable_timer_pin_1 [X86] 653 Disable PIN 1 of APIC timer 654 Can be useful to work around chipset bugs. 655 656 dmasound= [HW,OSS] Sound subsystem buffers 657 658 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 659 this option disables the debugging code at boot. 660 661 dma_debug_entries=<number> 662 This option allows to tune the number of preallocated 663 entries for DMA-API debugging code. One entry is 664 required per DMA-API allocation. Use this if the 665 DMA-API debugging code disables itself because the 666 architectural default is too low. 667 668 dma_debug_driver=<driver_name> 669 With this option the DMA-API debugging driver 670 filter feature can be enabled at boot time. Just 671 pass the driver to filter for as the parameter. 672 The filter can be disabled or changed to another 673 driver later using sysfs. 674 675 dscc4.setup= [NET] 676 677 dtc3181e= [HW,SCSI] 678 679 dynamic_printk Enables pr_debug()/dev_dbg() calls if 680 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. 681 These can also be switched on/off via 682 <debugfs>/dynamic_printk/modules 683 684 earlycon= [KNL] Output early console device and options. 685 uart[8250],io,<addr>[,options] 686 uart[8250],mmio,<addr>[,options] 687 Start an early, polled-mode console on the 8250/16550 688 UART at the specified I/O port or MMIO address. 689 The options are the same as for ttyS, above. 690 691 earlyprintk= [X86,SH,BLACKFIN] 692 earlyprintk=vga 693 earlyprintk=serial[,ttySn[,baudrate]] 694 earlyprintk=ttySn[,baudrate] 695 earlyprintk=dbgp[debugController#] 696 697 Append ",keep" to not disable it when the real console 698 takes over. 699 700 Only vga or serial or usb debug port at a time. 701 702 Currently only ttyS0 and ttyS1 are supported. 703 704 Interaction with the standard serial driver is not 705 very good. 706 707 The VGA output is eventually overwritten by the real 708 console. 709 710 eata= [HW,SCSI] 711 712 edd= [EDD] 713 Format: {"off" | "on" | "skip[mbr]"} 714 715 eisa_irq_edge= [PARISC,HW] 716 See header of drivers/parisc/eisa.c. 717 718 elanfreq= [X86-32] 719 See comment before function elanfreq_setup() in 720 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 721 722 elevator= [IOSCHED] 723 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 724 See Documentation/block/as-iosched.txt and 725 Documentation/block/deadline-iosched.txt for details. 726 727 elfcorehdr= [IA64,PPC,SH,X86] 728 Specifies physical address of start of kernel core 729 image elf header. Generally kexec loader will 730 pass this option to capture kernel. 731 See Documentation/kdump/kdump.txt for details. 732 733 enable_mtrr_cleanup [X86] 734 The kernel tries to adjust MTRR layout from continuous 735 to discrete, to make X server driver able to add WB 736 entry later. This parameter enables that. 737 738 enable_timer_pin_1 [X86] 739 Enable PIN 1 of APIC timer 740 Can be useful to work around chipset bugs 741 (in particular on some ATI chipsets). 742 The kernel tries to set a reasonable default. 743 744 enforcing [SELINUX] Set initial enforcing status. 745 Format: {"0" | "1"} 746 See security/selinux/Kconfig help text. 747 0 -- permissive (log only, no denials). 748 1 -- enforcing (deny and log). 749 Default value is 0. 750 Value can be changed at runtime via /selinux/enforce. 751 752 ether= [HW,NET] Ethernet cards parameters 753 This option is obsoleted by the "netdev=" option, which 754 has equivalent usage. See its documentation for details. 755 756 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog. 757 Format: <io>[,<irq>] 758 759 failslab= 760 fail_page_alloc= 761 fail_make_request=[KNL] 762 General fault injection mechanism. 763 Format: <interval>,<probability>,<space>,<times> 764 See also /Documentation/fault-injection/. 765 766 fd_mcs= [HW,SCSI] 767 See header of drivers/scsi/fd_mcs.c. 768 769 fdomain= [HW,SCSI] 770 See header of drivers/scsi/fdomain.c. 771 772 floppy= [HW] 773 See Documentation/blockdev/floppy.txt. 774 775 force_pal_cache_flush 776 [IA-64] Avoid check_sal_cache_flush which may hang on 777 buggy SAL_CACHE_FLUSH implementations. Using this 778 parameter will force ia64_sal_cache_flush to call 779 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 780 781 ftrace=[tracer] 782 [FTRACE] will set and start the specified tracer 783 as early as possible in order to facilitate early 784 boot debugging. 785 786 ftrace_dump_on_oops 787 [FTRACE] will dump the trace buffers on oops. 788 789 ftrace_filter=[function-list] 790 [FTRACE] Limit the functions traced by the function 791 tracer at boot up. function-list is a comma separated 792 list of functions. This list can be changed at run 793 time by the set_ftrace_filter file in the debugfs 794 tracing directory. 795 796 ftrace_notrace=[function-list] 797 [FTRACE] Do not trace the functions specified in 798 function-list. This list can be changed at run time 799 by the set_ftrace_notrace file in the debugfs 800 tracing directory. 801 802 ftrace_graph_filter=[function-list] 803 [FTRACE] Limit the top level callers functions traced 804 by the function graph tracer at boot up. 805 function-list is a comma separated list of functions 806 that can be changed at run time by the 807 set_graph_function file in the debugfs tracing directory. 808 809 gamecon.map[2|3]= 810 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 811 support via parallel port (up to 5 devices per port) 812 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 813 See also Documentation/input/joystick-parport.txt 814 815 gamma= [HW,DRM] 816 817 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 818 Format: off | on 819 default: on 820 821 gcov_persist= [GCOV] When non-zero (default), profiling data for 822 kernel modules is saved and remains accessible via 823 debugfs, even when the module is unloaded/reloaded. 824 When zero, profiling data is discarded and associated 825 debugfs files are removed at module unload time. 826 827 gdth= [HW,SCSI] 828 See header of drivers/scsi/gdth.c. 829 830 gpt [EFI] Forces disk with valid GPT signature but 831 invalid Protective MBR to be treated as GPT. 832 833 gvp11= [HW,SCSI] 834 835 hashdist= [KNL,NUMA] Large hashes allocated during boot 836 are distributed across NUMA nodes. Defaults on 837 for 64bit NUMA, off otherwise. 838 Format: 0 | 1 (for off | on) 839 840 hcl= [IA-64] SGI's Hardware Graph compatibility layer 841 842 hd= [EIDE] (E)IDE hard drive subsystem geometry 843 Format: <cyl>,<head>,<sect> 844 845 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 846 size of <nn>. This works even on boxes that have no 847 highmem otherwise. This also works to reduce highmem 848 size on bigger boxes. 849 850 highres= [KNL] Enable/disable high resolution timer mode. 851 Valid parameters: "on", "off" 852 Default: "on" 853 854 hisax= [HW,ISDN] 855 See Documentation/isdn/README.HiSax. 856 857 hlt [BUGS=ARM,SH] 858 859 hpet= [X86-32,HPET] option to control HPET usage 860 Format: { enable (default) | disable | force | 861 verbose } 862 disable: disable HPET and use PIT instead 863 force: allow force enabled of undocumented chips (ICH4, 864 VIA, nVidia) 865 verbose: show contents of HPET registers during setup 866 867 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 868 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 869 On x86-64 and powerpc, this option can be specified 870 multiple times interleaved with hugepages= to reserve 871 huge pages of different sizes. Valid pages sizes on 872 x86-64 are 2M (when the CPU supports "pse") and 1G 873 (when the CPU supports the "pdpe1gb" cpuinfo flag) 874 Note that 1GB pages can only be allocated at boot time 875 using hugepages= and not freed afterwards. 876 877 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 878 terminal devices. Valid values: 0..8 879 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 880 If specified, z/VM IUCV HVC accepts connections 881 from listed z/VM user IDs only. 882 883 i2c_bus= [HW] Override the default board specific I2C bus speed 884 or register an additional I2C bus that is not 885 registered from board initialization code. 886 Format: 887 <bus_id>,<clkrate> 888 889 i8042.debug [HW] Toggle i8042 debug mode 890 i8042.direct [HW] Put keyboard port into non-translated mode 891 i8042.dumbkbd [HW] Pretend that controller can only read data from 892 keyboard and cannot control its state 893 (Don't attempt to blink the leds) 894 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 895 i8042.nokbd [HW] Don't check/create keyboard port 896 i8042.noloop [HW] Disable the AUX Loopback command while probing 897 for the AUX port 898 i8042.nomux [HW] Don't check presence of an active multiplexing 899 controller 900 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 901 controllers 902 i8042.panicblink= 903 [HW] Frequency with which keyboard LEDs should blink 904 when kernel panics (default is 0.5 sec) 905 i8042.reset [HW] Reset the controller during init and cleanup 906 i8042.unlock [HW] Unlock (ignore) the keylock 907 908 i810= [HW,DRM] 909 910 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 911 indicates that the driver is running on unsupported 912 hardware. 913 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 914 does not match list of supported models. 915 i8k.power_status 916 [HW] Report power status in /proc/i8k 917 (disabled by default) 918 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 919 capability is set. 920 921 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter 922 See Documentation/mca.txt. 923 924 icn= [HW,ISDN] 925 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 926 927 ide-core.nodma= [HW] (E)IDE subsystem 928 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 929 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 930 .cdrom .chs .ignore_cable are additional options 931 See Documentation/ide/ide.txt. 932 933 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 934 Claim all unknown PCI IDE storage controllers. 935 936 idle= [X86] 937 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait 938 Poll forces a polling idle loop that can slightly 939 improve the performance of waking up a idle CPU, but 940 will use a lot of power and make the system run hot. 941 Not recommended. 942 idle=mwait: On systems which support MONITOR/MWAIT but 943 the kernel chose to not use it because it doesn't save 944 as much power as a normal idle loop, use the 945 MONITOR/MWAIT idle loop anyways. Performance should be 946 the same as idle=poll. 947 idle=halt: Halt is forced to be used for CPU idle. 948 In such case C2/C3 won't be used again. 949 idle=nomwait: Disable mwait for CPU C-states 950 951 ignore_loglevel [KNL] 952 Ignore loglevel setting - this will print /all/ 953 kernel messages to the console. Useful for debugging. 954 955 ihash_entries= [KNL] 956 Set number of hash buckets for inode cache. 957 958 ima_audit= [IMA] 959 Format: { "0" | "1" } 960 0 -- integrity auditing messages. (Default) 961 1 -- enable informational integrity auditing messages. 962 963 ima_hash= [IMA] 964 Format: { "sha1" | "md5" } 965 default: "sha1" 966 967 ima_tcb [IMA] 968 Load a policy which meets the needs of the Trusted 969 Computing Base. This means IMA will measure all 970 programs exec'd, files mmap'd for exec, and all files 971 opened for read by uid=0. 972 973 in2000= [HW,SCSI] 974 See header of drivers/scsi/in2000.c. 975 976 init= [KNL] 977 Format: <full_path> 978 Run specified binary instead of /sbin/init as init 979 process. 980 981 initcall_debug [KNL] Trace initcalls as they are executed. Useful 982 for working out where the kernel is dying during 983 startup. 984 985 initrd= [BOOT] Specify the location of the initial ramdisk 986 987 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 988 Format: <irq> 989 990 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 991 on 992 Enable intel iommu driver. 993 off 994 Disable intel iommu driver. 995 igfx_off [Default Off] 996 By default, gfx is mapped as normal device. If a gfx 997 device has a dedicated DMAR unit, the DMAR unit is 998 bypassed by not enabling DMAR with this option. In 999 this case, gfx device will use physical address for 1000 DMA. 1001 forcedac [x86_64] 1002 With this option iommu will not optimize to look 1003 for io virtual address below 32 bit forcing dual 1004 address cycle on pci bus for cards supporting greater 1005 than 32 bit addressing. The default is to look 1006 for translation below 32 bit and if not available 1007 then look in the higher range. 1008 strict [Default Off] 1009 With this option on every unmap_single operation will 1010 result in a hardware IOTLB flush operation as opposed 1011 to batching them for performance. 1012 1013 inttest= [IA64] 1014 1015 iomem= Disable strict checking of access to MMIO memory 1016 strict regions from userspace. 1017 relaxed 1018 1019 iommu= [x86] 1020 off 1021 force 1022 noforce 1023 biomerge 1024 panic 1025 nopanic 1026 merge 1027 nomerge 1028 forcesac 1029 soft 1030 pt [x86, IA64] 1031 1032 io7= [HW] IO7 for Marvel based alpha systems 1033 See comment before marvel_specify_io7 in 1034 arch/alpha/kernel/core_marvel.c. 1035 1036 io_delay= [X86] I/O delay method 1037 0x80 1038 Standard port 0x80 based delay 1039 0xed 1040 Alternate port 0xed based delay (needed on some systems) 1041 udelay 1042 Simple two microseconds delay 1043 none 1044 No delay 1045 1046 ip= [IP_PNP] 1047 See Documentation/filesystems/nfs/nfsroot.txt. 1048 1049 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 1050 See comment before ip2_setup() in 1051 drivers/char/ip2/ip2base.c. 1052 1053 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller 1054 See header of drivers/scsi/ips.c. 1055 1056 irqfixup [HW] 1057 When an interrupt is not handled search all handlers 1058 for it. Intended to get systems with badly broken 1059 firmware running. 1060 1061 irqpoll [HW] 1062 When an interrupt is not handled search all handlers 1063 for it. Also check all handlers each timer 1064 interrupt. Intended to get systems with badly broken 1065 firmware running. 1066 1067 isapnp= [ISAPNP] 1068 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1069 1070 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 1071 Format: 1072 <cpu number>,...,<cpu number> 1073 or 1074 <cpu number>-<cpu number> 1075 (must be a positive range in ascending order) 1076 or a mixture 1077 <cpu number>,...,<cpu number>-<cpu number> 1078 1079 This option can be used to specify one or more CPUs 1080 to isolate from the general SMP balancing and scheduling 1081 algorithms. You can move a process onto or off an 1082 "isolated" CPU via the CPU affinity syscalls or cpuset. 1083 <cpu number> begins at 0 and the maximum value is 1084 "number of CPUs in system - 1". 1085 1086 This option is the preferred way to isolate CPUs. The 1087 alternative -- manually setting the CPU mask of all 1088 tasks in the system -- can cause problems and 1089 suboptimal load balancer performance. 1090 1091 iucv= [HW,NET] 1092 1093 js= [HW,JOY] Analog joystick 1094 See Documentation/input/joystick.txt. 1095 1096 keepinitrd [HW,ARM] 1097 1098 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1099 specifies the amount of memory usable by the kernel 1100 for non-movable allocations. The requested amount is 1101 spread evenly throughout all nodes in the system. The 1102 remaining memory in each node is used for Movable 1103 pages. In the event, a node is too small to have both 1104 kernelcore and Movable pages, kernelcore pages will 1105 take priority and other nodes will have a larger number 1106 of kernelcore pages. The Movable zone is used for the 1107 allocation of pages that may be reclaimed or moved 1108 by the page migration subsystem. This means that 1109 HugeTLB pages may not be allocated from this zone. 1110 Note that allocations like PTEs-from-HighMem still 1111 use the HighMem zone if it exists, and the Normal 1112 zone if it does not. 1113 1114 kgdboc= [HW] kgdb over consoles. 1115 Requires a tty driver that supports console polling. 1116 (only serial supported for now) 1117 Format: <serial_device>[,baud] 1118 1119 kmac= [MIPS] korina ethernet MAC address. 1120 Configure the RouterBoard 532 series on-chip 1121 Ethernet adapter MAC address. 1122 1123 kmemleak= [KNL] Boot-time kmemleak enable/disable 1124 Valid arguments: on, off 1125 Default: on 1126 1127 kstack=N [X86] Print N words from the kernel stack 1128 in oops dumps. 1129 1130 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 1131 Default is 0 (don't ignore, but inject #GP) 1132 1133 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging. 1134 Default is 1 (enabled) 1135 1136 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 1137 Default is 0 (off) 1138 1139 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 1140 for all guests. 1141 Default is 1 (enabled) if in 64bit or 32bit-PAE mode 1142 1143 kvm-intel.bypass_guest_pf= 1144 [KVM,Intel] Disables bypassing of guest page faults 1145 on Intel chips. Default is 1 (enabled) 1146 1147 kvm-intel.ept= [KVM,Intel] Disable extended page tables 1148 (virtualized MMU) support on capable Intel chips. 1149 Default is 1 (enabled) 1150 1151 kvm-intel.emulate_invalid_guest_state= 1152 [KVM,Intel] Enable emulation of invalid guest states 1153 Default is 0 (disabled) 1154 1155 kvm-intel.flexpriority= 1156 [KVM,Intel] Disable FlexPriority feature (TPR shadow). 1157 Default is 1 (enabled) 1158 1159 kvm-intel.unrestricted_guest= 1160 [KVM,Intel] Disable unrestricted guest feature 1161 (virtualized real and unpaged mode) on capable 1162 Intel chips. Default is 1 (enabled) 1163 1164 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 1165 feature (tagged TLBs) on capable Intel chips. 1166 Default is 1 (enabled) 1167 1168 l2cr= [PPC] 1169 1170 l3cr= [PPC] 1171 1172 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1173 disabled it. 1174 1175 lapic_timer_c2_ok [X86,APIC] trust the local apic timer 1176 in C2 power state. 1177 1178 libata.dma= [LIBATA] DMA control 1179 libata.dma=0 Disable all PATA and SATA DMA 1180 libata.dma=1 PATA and SATA Disk DMA only 1181 libata.dma=2 ATAPI (CDROM) DMA only 1182 libata.dma=4 Compact Flash DMA only 1183 Combinations also work, so libata.dma=3 enables DMA 1184 for disks and CDROMs, but not CFs. 1185 1186 libata.ignore_hpa= [LIBATA] Ignore HPA limit 1187 libata.ignore_hpa=0 keep BIOS limits (default) 1188 libata.ignore_hpa=1 ignore limits, using full disk 1189 1190 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1191 when set. 1192 Format: <int> 1193 1194 libata.force= [LIBATA] Force configurations. The format is comma 1195 separated list of "[ID:]VAL" where ID is 1196 PORT[:DEVICE]. PORT and DEVICE are decimal numbers 1197 matching port, link or device. Basically, it matches 1198 the ATA ID string printed on console by libata. If 1199 the whole ID part is omitted, the last PORT and DEVICE 1200 values are used. If ID hasn't been specified yet, the 1201 configuration applies to all ports, links and devices. 1202 1203 If only DEVICE is omitted, the parameter applies to 1204 the port and all links and devices behind it. DEVICE 1205 number of 0 either selects the first device or the 1206 first fan-out link behind PMP device. It does not 1207 select the host link. DEVICE number of 15 selects the 1208 host link and device attached to it. 1209 1210 The VAL specifies the configuration to force. As long 1211 as there's no ambiguity shortcut notation is allowed. 1212 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1213 The following configurations can be forced. 1214 1215 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1216 Any ID with matching PORT is used. 1217 1218 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1219 1220 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1221 udma[/][16,25,33,44,66,100,133] notation is also 1222 allowed. 1223 1224 * [no]ncq: Turn on or off NCQ. 1225 1226 * nohrst, nosrst, norst: suppress hard, soft 1227 and both resets. 1228 1229 If there are multiple matching configurations changing 1230 the same attribute, the last one is used. 1231 1232 lmb=debug [KNL] Enable lmb debug messages. 1233 1234 load_ramdisk= [RAM] List of ramdisks to load from floppy 1235 See Documentation/blockdev/ramdisk.txt. 1236 1237 lockd.nlm_grace_period=P [NFS] Assign grace period. 1238 Format: <integer> 1239 1240 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1241 Format: <integer> 1242 1243 lockd.nlm_timeout=T [NFS] Assign timeout value. 1244 Format: <integer> 1245 1246 lockd.nlm_udpport=M [NFS] Assign UDP port. 1247 Format: <integer> 1248 1249 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1250 Format: <irq> 1251 1252 loglevel= All Kernel Messages with a loglevel smaller than the 1253 console loglevel will be printed to the console. It can 1254 also be changed with klogd or other programs. The 1255 loglevels are defined as follows: 1256 1257 0 (KERN_EMERG) system is unusable 1258 1 (KERN_ALERT) action must be taken immediately 1259 2 (KERN_CRIT) critical conditions 1260 3 (KERN_ERR) error conditions 1261 4 (KERN_WARNING) warning conditions 1262 5 (KERN_NOTICE) normal but significant condition 1263 6 (KERN_INFO) informational 1264 7 (KERN_DEBUG) debug-level messages 1265 1266 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1267 Format: { n | nk | nM } 1268 n must be a power of two. The default size 1269 is set in the kernel config file. 1270 1271 logo.nologo [FB] Disables display of the built-in Linux logo. 1272 This may be used to provide more screen space for 1273 kernel log messages and is useful when debugging 1274 kernel boot problems. 1275 1276 lp=0 [LP] Specify parallel ports to use, e.g, 1277 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1278 lp=reset first parallel port). 'lp=0' disables the 1279 lp=auto printer driver. 'lp=reset' (which can be 1280 specified in addition to the ports) causes 1281 attached printers to be reset. Using 1282 lp=port1,port2,... specifies the parallel ports 1283 to associate lp devices with, starting with 1284 lp0. A port specification may be 'none' to skip 1285 that lp device, or a parport name such as 1286 'parport0'. Specifying 'lp=auto' instead of a 1287 port specification list means that device IDs 1288 from each port should be examined, to see if 1289 an IEEE 1284-compliant printer is attached; if 1290 so, the driver will manage that printer. 1291 See also header of drivers/char/lp.c. 1292 1293 lpj=n [KNL] 1294 Sets loops_per_jiffy to given constant, thus avoiding 1295 time-consuming boot-time autodetection (up to 250 ms per 1296 CPU). 0 enables autodetection (default). To determine 1297 the correct value for your kernel, boot with normal 1298 autodetection and see what value is printed. Note that 1299 on SMP systems the preset will be applied to all CPUs, 1300 which is likely to cause problems if your CPUs need 1301 significantly divergent settings. An incorrect value 1302 will cause delays in the kernel to be wrong, leading to 1303 unpredictable I/O errors and other breakage. Although 1304 unlikely, in the extreme case this might damage your 1305 hardware. 1306 1307 ltpc= [NET] 1308 Format: <io>,<irq>,<dma> 1309 1310 mac5380= [HW,SCSI] Format: 1311 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1312 1313 machvec= [IA64] Force the use of a particular machine-vector 1314 (machvec) in a generic kernel. 1315 Example: machvec=hpzx1_swiotlb 1316 1317 machtype= [Loongson] Share the same kernel image file between different 1318 yeeloong laptop. 1319 Example: machtype=lemote-yeeloong-2f-7inch 1320 1321 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 1322 than or equal to this physical address is ignored. 1323 1324 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1325 should make use of. maxcpus=n : n >= 0 limits the 1326 kernel to using 'n' processors. n=0 is a special case, 1327 it is equivalent to "nosmp", which also disables 1328 the IO APIC. 1329 1330 max_loop= [LOOP] Maximum number of loopback devices that can 1331 be mounted 1332 Format: <1-256> 1333 1334 max_luns= [SCSI] Maximum number of LUNs to probe. 1335 Should be between 1 and 2^32-1. 1336 1337 max_report_luns= 1338 [SCSI] Maximum number of LUNs received. 1339 Should be between 1 and 16384. 1340 1341 mcatest= [IA-64] 1342 1343 mce [X86-32] Machine Check Exception 1344 1345 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 1346 1347 md= [HW] RAID subsystems devices and level 1348 See Documentation/md.txt. 1349 1350 mdacon= [MDA] 1351 Format: <first>,<last> 1352 Specifies range of consoles to be captured by the MDA. 1353 1354 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1355 Amount of memory to be used when the kernel is not able 1356 to see the whole system memory or for test. 1357 [X86-32] Use together with memmap= to avoid physical 1358 address space collisions. Without memmap= PCI devices 1359 could be placed at addresses belonging to unused RAM. 1360 1361 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1362 memory. 1363 1364 memchunk=nn[KMG] 1365 [KNL,SH] Allow user to override the default size for 1366 per-device physically contiguous DMA buffers. 1367 1368 memmap=exactmap [KNL,X86] Enable setting of an exact 1369 E820 memory map, as specified by the user. 1370 Such memmap=exactmap lines can be constructed based on 1371 BIOS output or other requirements. See the memmap=nn@ss 1372 option description. 1373 1374 memmap=nn[KMG]@ss[KMG] 1375 [KNL] Force usage of a specific region of memory 1376 Region of memory to be used, from ss to ss+nn. 1377 1378 memmap=nn[KMG]#ss[KMG] 1379 [KNL,ACPI] Mark specific memory as ACPI data. 1380 Region of memory to be used, from ss to ss+nn. 1381 1382 memmap=nn[KMG]$ss[KMG] 1383 [KNL,ACPI] Mark specific memory as reserved. 1384 Region of memory to be used, from ss to ss+nn. 1385 Example: Exclude memory from 0x18690000-0x1869ffff 1386 memmap=64K$0x18690000 1387 or 1388 memmap=0x10000$0x18690000 1389 1390 memory_corruption_check=0/1 [X86] 1391 Some BIOSes seem to corrupt the first 64k of 1392 memory when doing things like suspend/resume. 1393 Setting this option will scan the memory 1394 looking for corruption. Enabling this will 1395 both detect corruption and prevent the kernel 1396 from using the memory being corrupted. 1397 However, its intended as a diagnostic tool; if 1398 repeatable BIOS-originated corruption always 1399 affects the same memory, you can use memmap= 1400 to prevent the kernel from using that memory. 1401 1402 memory_corruption_check_size=size [X86] 1403 By default it checks for corruption in the low 1404 64k, making this memory unavailable for normal 1405 use. Use this parameter to scan for 1406 corruption in more or less memory. 1407 1408 memory_corruption_check_period=seconds [X86] 1409 By default it checks for corruption every 60 1410 seconds. Use this parameter to check at some 1411 other rate. 0 disables periodic checking. 1412 1413 memtest= [KNL,X86] Enable memtest 1414 Format: <integer> 1415 default : 0 <disable> 1416 Specifies the number of memtest passes to be 1417 performed. Each pass selects another test 1418 pattern from a given set of patterns. Memtest 1419 fills the memory with this pattern, validates 1420 memory contents and reserves bad memory 1421 regions that are detected. 1422 1423 meye.*= [HW] Set MotionEye Camera parameters 1424 See Documentation/video4linux/meye.txt. 1425 1426 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1427 Multi-Function General Purpose Timers on AMD Geode 1428 platforms. 1429 1430 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1431 the BIOS has incorrectly applied a workaround. TinyBIOS 1432 version 0.98 is known to be affected, 0.99 fixes the 1433 problem by letting the user disable the workaround. 1434 1435 mga= [HW,DRM] 1436 1437 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 1438 physical address is ignored. 1439 1440 mini2440= [ARM,HW,KNL] 1441 Format:[0..2][b][c][t] 1442 Default: "0tb" 1443 MINI2440 configuration specification: 1444 0 - The attached screen is the 3.5" TFT 1445 1 - The attached screen is the 7" TFT 1446 2 - The VGA Shield is attached (1024x768) 1447 Leaving out the screen size parameter will not load 1448 the TFT driver, and the framebuffer will be left 1449 unconfigured. 1450 b - Enable backlight. The TFT backlight pin will be 1451 linked to the kernel VESA blanking code and a GPIO 1452 LED. This parameter is not necessary when using the 1453 VGA shield. 1454 c - Enable the s3c camera interface. 1455 t - Reserved for enabling touchscreen support. The 1456 touchscreen support is not enabled in the mainstream 1457 kernel as of 2.6.30, a preliminary port can be found 1458 in the "bleeding edge" mini2440 support kernel at 1459 http://repo.or.cz/w/linux-2.6/mini2440.git 1460 1461 mminit_loglevel= 1462 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1463 parameter allows control of the logging verbosity for 1464 the additional memory initialisation checks. A value 1465 of 0 disables mminit logging and a level of 4 will 1466 log everything. Information is printed at KERN_DEBUG 1467 so loglevel=8 may also need to be specified. 1468 1469 mousedev.tap_time= 1470 [MOUSE] Maximum time between finger touching and 1471 leaving touchpad surface for touch to be considered 1472 a tap and be reported as a left button click (for 1473 touchpads working in absolute mode only). 1474 Format: <msecs> 1475 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1476 reporting absolute coordinates, such as tablets 1477 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1478 reporting absolute coordinates, such as tablets 1479 1480 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1481 is similar to kernelcore except it specifies the 1482 amount of memory used for migratable allocations. 1483 If both kernelcore and movablecore is specified, 1484 then kernelcore will be at *least* the specified 1485 value but may be more. If movablecore on its own 1486 is specified, the administrator must be careful 1487 that the amount of memory usable for all allocations 1488 is not too small. 1489 1490 mpu401= [HW,OSS] 1491 Format: <io>,<irq> 1492 1493 MTD_Partition= [MTD] 1494 Format: <name>,<region-number>,<size>,<offset> 1495 1496 MTD_Region= [MTD] Format: 1497 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1498 1499 mtdparts= [MTD] 1500 See drivers/mtd/cmdlinepart.c. 1501 1502 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 1503 1504 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 1505 1506 boundary - index of last SLC block on Flex-OneNAND. 1507 The remaining blocks are configured as MLC blocks. 1508 lock - Configure if Flex-OneNAND boundary should be locked. 1509 Once locked, the boundary cannot be changed. 1510 1 indicates lock status, 0 indicates unlock status. 1511 1512 mtdset= [ARM] 1513 ARM/S3C2412 JIVE boot control 1514 1515 See arch/arm/mach-s3c2412/mach-jive.c 1516 1517 mtouchusb.raw_coordinates= 1518 [HW] Make the MicroTouch USB driver use raw coordinates 1519 ('y', default) or cooked coordinates ('n') 1520 1521 mtrr_chunk_size=nn[KMG] [X86] 1522 used for mtrr cleanup. It is largest continuous chunk 1523 that could hold holes aka. UC entries. 1524 1525 mtrr_gran_size=nn[KMG] [X86] 1526 Used for mtrr cleanup. It is granularity of mtrr block. 1527 Default is 1. 1528 Large value could prevent small alignment from 1529 using up MTRRs. 1530 1531 mtrr_spare_reg_nr=n [X86] 1532 Format: <integer> 1533 Range: 0,7 : spare reg number 1534 Default : 1 1535 Used for mtrr cleanup. It is spare mtrr entries number. 1536 Set to 2 or more if your graphical card needs more. 1537 1538 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1539 1540 NCR_D700= [HW,SCSI] 1541 See header of drivers/scsi/NCR_D700.c. 1542 1543 ncr5380= [HW,SCSI] 1544 1545 ncr53c400= [HW,SCSI] 1546 1547 ncr53c400a= [HW,SCSI] 1548 1549 ncr53c406a= [HW,SCSI] 1550 1551 ncr53c8xx= [HW,SCSI] 1552 1553 netdev= [NET] Network devices parameters 1554 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1555 Note that mem_start is often overloaded to mean 1556 something different and driver-specific. 1557 This usage is only documented in each driver source 1558 file if at all. 1559 1560 nf_conntrack.acct= 1561 [NETFILTER] Enable connection tracking flow accounting 1562 0 to disable accounting 1563 1 to enable accounting 1564 Default value depends on CONFIG_NF_CT_ACCT that is 1565 going to be removed in 2.6.29. 1566 1567 nfsaddrs= [NFS] 1568 See Documentation/filesystems/nfs/nfsroot.txt. 1569 1570 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1571 See Documentation/filesystems/nfs/nfsroot.txt. 1572 1573 nfs.callback_tcpport= 1574 [NFS] set the TCP port on which the NFSv4 callback 1575 channel should listen. 1576 1577 nfs.cache_getent= 1578 [NFS] sets the pathname to the program which is used 1579 to update the NFS client cache entries. 1580 1581 nfs.cache_getent_timeout= 1582 [NFS] sets the timeout after which an attempt to 1583 update a cache entry is deemed to have failed. 1584 1585 nfs.idmap_cache_timeout= 1586 [NFS] set the maximum lifetime for idmapper cache 1587 entries. 1588 1589 nfs.enable_ino64= 1590 [NFS] enable 64-bit inode numbers. 1591 If zero, the NFS client will fake up a 32-bit inode 1592 number for the readdir() and stat() syscalls instead 1593 of returning the full 64-bit number. 1594 The default is to return 64-bit inode numbers. 1595 1596 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take 1597 when a NMI is triggered. 1598 Format: [state][,regs][,debounce][,die] 1599 1600 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 1601 Format: [panic,][num] 1602 Valid num: 0,1,2 1603 0 - turn nmi_watchdog off 1604 1 - use the IO-APIC timer for the NMI watchdog 1605 2 - use the local APIC for the NMI watchdog using 1606 a performance counter. Note: This will use one 1607 performance counter and the local APIC's performance 1608 vector. 1609 When panic is specified, panic when an NMI watchdog 1610 timeout occurs. 1611 This is useful when you use a panic=... timeout and 1612 need the box quickly up again. 1613 Instead of 1 and 2 it is possible to use the following 1614 symbolic names: lapic and ioapic 1615 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic 1616 1617 netpoll.carrier_timeout= 1618 [NET] Specifies amount of time (in seconds) that 1619 netpoll should wait for a carrier. By default netpoll 1620 waits 4 seconds. 1621 1622 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1623 emulation library even if a 387 maths coprocessor 1624 is present. 1625 1626 no_console_suspend 1627 [HW] Never suspend the console 1628 Disable suspending of consoles during suspend and 1629 hibernate operations. Once disabled, debugging 1630 messages can reach various consoles while the rest 1631 of the system is being put to sleep (ie, while 1632 debugging driver suspend/resume hooks). This may 1633 not work reliably with all consoles, but is known 1634 to work with serial and VGA consoles. 1635 1636 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1637 caches in the slab allocator. Saves per-node memory, 1638 but will impact performance. 1639 1640 noalign [KNL,ARM] 1641 1642 noapic [SMP,APIC] Tells the kernel to not make use of any 1643 IOAPICs that may be present in the system. 1644 1645 nobats [PPC] Do not use BATs for mapping kernel lowmem 1646 on "Classic" PPC cores. 1647 1648 nocache [ARM] 1649 1650 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1651 1652 nodelayacct [KNL] Disable per-task delay accounting 1653 1654 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1655 1656 nodsp [SH] Disable hardware DSP at boot time. 1657 1658 noefi [X86] Disable EFI runtime services support. 1659 1660 noexec [IA-64] 1661 1662 noexec [X86] 1663 On X86-32 available only on PAE configured kernels. 1664 noexec=on: enable non-executable mappings (default) 1665 noexec=off: disable non-executable mappings 1666 1667 noexec32 [X86-64] 1668 This affects only 32-bit executables. 1669 noexec32=on: enable non-executable mappings (default) 1670 read doesn't imply executable mappings 1671 noexec32=off: disable non-executable mappings 1672 read implies executable mappings 1673 1674 nofpu [SH] Disable hardware FPU at boot time. 1675 1676 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1677 register save and restore. The kernel will only save 1678 legacy floating-point registers on task switch. 1679 1680 noxsave [BUGS=X86] Disables x86 extended register state save 1681 and restore using xsave. The kernel will fallback to 1682 enabling legacy floating-point and sse state. 1683 1684 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 1685 wfi(ARM) instruction doesn't work correctly and not to 1686 use it. This is also useful when using JTAG debugger. 1687 1688 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1689 instruction doesn't work correctly and not to 1690 use it. 1691 1692 no_file_caps Tells the kernel not to honor file capabilities. The 1693 only way then for a file to be executed with privilege 1694 is to be setuid root or executed by root. 1695 1696 nohalt [IA-64] Tells the kernel not to use the power saving 1697 function PAL_HALT_LIGHT when idle. This increases 1698 power-consumption. On the positive side, it reduces 1699 interrupt wake-up latency, which may improve performance 1700 in certain environments such as networked servers or 1701 real-time systems. 1702 1703 nohz= [KNL] Boottime enable/disable dynamic ticks 1704 Valid arguments: on, off 1705 Default: on 1706 1707 noiotrap [SH] Disables trapped I/O port accesses. 1708 1709 noirqdebug [X86-32] Disables the code which attempts to detect and 1710 disable unhandled interrupt sources. 1711 1712 no_timer_check [X86,APIC] Disables the code which tests for 1713 broken timer IRQ sources. 1714 1715 noisapnp [ISAPNP] Disables ISA PnP code. 1716 1717 noinitrd [RAM] Tells the kernel not to load any configured 1718 initial RAM disk. 1719 1720 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 1721 remapping. 1722 1723 nointroute [IA-64] 1724 1725 nojitter [IA64] Disables jitter checking for ITC timers. 1726 1727 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1728 1729 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1730 1731 noltlbs [PPC] Do not use large page/tlb entries for kernel 1732 lowmem mapping on PPC40x. 1733 1734 nomca [IA-64] Disable machine check abort handling 1735 1736 nomce [X86-32] Machine Check Exception 1737 1738 nomfgpt [X86-32] Disable Multi-Function General Purpose 1739 Timer usage (for AMD Geode machines). 1740 1741 norandmaps Don't use address space randomization. Equivalent to 1742 echo 0 > /proc/sys/kernel/randomize_va_space 1743 1744 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1745 1746 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1747 with UP alternatives 1748 1749 noresidual [PPC] Don't use residual data on PReP machines. 1750 1751 noresume [SWSUSP] Disables resume and restores original swap 1752 space. 1753 1754 no-scroll [VGA] Disables scrollback. 1755 This is required for the Braillex ib80-piezo Braille 1756 reader made by F.H. Papenmeier (Germany). 1757 1758 nosbagart [IA-64] 1759 1760 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1761 1762 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1763 and disable the IO APIC. legacy for "maxcpus=0". 1764 1765 nosoftlockup [KNL] Disable the soft-lockup detector. 1766 1767 noswapaccount [KNL] Disable accounting of swap in memory resource 1768 controller. (See Documentation/cgroups/memory.txt) 1769 1770 nosync [HW,M68K] Disables sync negotiation for all devices. 1771 1772 notsc [BUGS=X86-32] Disable Time Stamp Counter 1773 1774 nousb [USB] Disable the USB subsystem 1775 1776 nowb [ARM] 1777 1778 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 1779 1780 nptcg= [IA64] Override max number of concurrent global TLB 1781 purges which is reported from either PAL_VM_SUMMARY or 1782 SAL PALO. 1783 1784 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1785 1786 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1787 one of ['zone', 'node', 'default'] can be specified 1788 This can be set from sysctl after boot. 1789 See Documentation/sysctl/vm.txt for details. 1790 1791 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 1792 See Documentation/debugging-via-ohci1394.txt for more 1793 info. 1794 1795 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1796 Rather than timing out after 20 ms if an EC 1797 command is not properly ACKed, override the length 1798 of the timeout. We have interrupts disabled while 1799 waiting for the ACK, so if this is set too high 1800 interrupts *may* be lost! 1801 1802 omap_mux= [OMAP] Override bootloader pin multiplexing. 1803 Format: <mux_mode0.mode_name=value>... 1804 For example, to override I2C bus2: 1805 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 1806 1807 opl3= [HW,OSS] 1808 Format: <io> 1809 1810 oprofile.timer= [HW] 1811 Use timer interrupt instead of performance counters 1812 1813 oprofile.cpu_type= Force an oprofile cpu type 1814 This might be useful if you have an older oprofile 1815 userland or if you want common events. 1816 Format: { arch_perfmon } 1817 arch_perfmon: [X86] Force use of architectural 1818 perfmon on Intel CPUs instead of the 1819 CPU specific event set. 1820 1821 osst= [HW,SCSI] SCSI Tape Driver 1822 Format: <buffer_size>,<write_threshold> 1823 See also Documentation/scsi/st.txt. 1824 1825 panic= [KNL] Kernel behaviour on panic 1826 Format: <timeout> 1827 1828 parkbd.port= [HW] Parallel port number the keyboard adapter is 1829 connected to, default is 0. 1830 Format: <parport#> 1831 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1832 0 for XT, 1 for AT (default is AT). 1833 Format: <mode> 1834 1835 parport= [HW,PPT] Specify parallel ports. 0 disables. 1836 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1837 Use 'auto' to force the driver to use any 1838 IRQ/DMA settings detected (the default is to 1839 ignore detected IRQ/DMA settings because of 1840 possible conflicts). You can specify the base 1841 address, IRQ, and DMA settings; IRQ and DMA 1842 should be numbers, or 'auto' (for using detected 1843 settings on that particular port), or 'nofifo' 1844 (to avoid using a FIFO even if it is detected). 1845 Parallel ports are assigned in the order they 1846 are specified on the command line, starting 1847 with parport0. 1848 1849 parport_init_mode= [HW,PPT] 1850 Configure VIA parallel port to operate in 1851 a specific mode. This is necessary on Pegasos 1852 computer where firmware has no options for setting 1853 up parallel port mode and sets it to spp. 1854 Currently this function knows 686a and 8231 chips. 1855 Format: [spp|ps2|epp|ecp|ecpepp] 1856 1857 pas2= [HW,OSS] Format: 1858 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16> 1859 1860 pas16= [HW,SCSI] 1861 See header of drivers/scsi/pas16.c. 1862 1863 pause_on_oops= 1864 Halt all CPUs after the first oops has been printed for 1865 the specified number of seconds. This is to be used if 1866 your oopses keep scrolling off the screen. 1867 1868 pcbit= [HW,ISDN] 1869 1870 pcd. [PARIDE] 1871 See header of drivers/block/paride/pcd.c. 1872 See also Documentation/blockdev/paride.txt. 1873 1874 pci=option[,option...] [PCI] various PCI subsystem options: 1875 earlydump [X86] dump PCI config space before the kernel 1876 changes anything 1877 off [X86] don't probe for the PCI bus 1878 bios [X86-32] force use of PCI BIOS, don't access 1879 the hardware directly. Use this if your machine 1880 has a non-standard PCI host bridge. 1881 nobios [X86-32] disallow use of PCI BIOS, only direct 1882 hardware access methods are allowed. Use this 1883 if you experience crashes upon bootup and you 1884 suspect they are caused by the BIOS. 1885 conf1 [X86] Force use of PCI Configuration 1886 Mechanism 1. 1887 conf2 [X86] Force use of PCI Configuration 1888 Mechanism 2. 1889 noaer [PCIE] If the PCIEAER kernel config parameter is 1890 enabled, this kernel boot option can be used to 1891 disable the use of PCIE advanced error reporting. 1892 nodomains [PCI] Disable support for multiple PCI 1893 root domains (aka PCI segments, in ACPI-speak). 1894 nommconf [X86] Disable use of MMCONFIG for PCI 1895 Configuration 1896 check_enable_amd_mmconf [X86] check for and enable 1897 properly configured MMIO access to PCI 1898 config space on AMD family 10h CPU 1899 nomsi [MSI] If the PCI_MSI kernel config parameter is 1900 enabled, this kernel boot option can be used to 1901 disable the use of MSI interrupts system-wide. 1902 noioapicquirk [APIC] Disable all boot interrupt quirks. 1903 Safety option to keep boot IRQs enabled. This 1904 should never be necessary. 1905 ioapicreroute [APIC] Enable rerouting of boot IRQs to the 1906 primary IO-APIC for bridges that cannot disable 1907 boot IRQs. This fixes a source of spurious IRQs 1908 when the system masks IRQs. 1909 noioapicreroute [APIC] Disable workaround that uses the 1910 boot IRQ equivalent of an IRQ that connects to 1911 a chipset where boot IRQs cannot be disabled. 1912 The opposite of ioapicreroute. 1913 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1914 routing table. These calls are known to be buggy 1915 on several machines and they hang the machine 1916 when used, but on other computers it's the only 1917 way to get the interrupt routing table. Try 1918 this option if the kernel is unable to allocate 1919 IRQs or discover secondary PCI buses on your 1920 motherboard. 1921 rom [X86] Assign address space to expansion ROMs. 1922 Use with caution as certain devices share 1923 address decoders between ROMs and other 1924 resources. 1925 norom [X86] Do not assign address space to 1926 expansion ROMs that do not already have 1927 BIOS assigned address ranges. 1928 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 1929 assigned automatically to PCI devices. You can 1930 make the kernel exclude IRQs of your ISA cards 1931 this way. 1932 pirqaddr=0xAAAAA [X86] Specify the physical address 1933 of the PIRQ table (normally generated 1934 by the BIOS) if it is outside the 1935 F0000h-100000h range. 1936 lastbus=N [X86] Scan all buses thru bus #N. Can be 1937 useful if the kernel is unable to find your 1938 secondary buses and you want to tell it 1939 explicitly which ones they are. 1940 assign-busses [X86] Always assign all PCI bus 1941 numbers ourselves, overriding 1942 whatever the firmware may have done. 1943 usepirqmask [X86] Honor the possible IRQ mask stored 1944 in the BIOS $PIR table. This is needed on 1945 some systems with broken BIOSes, notably 1946 some HP Pavilion N5400 and Omnibook XE3 1947 notebooks. This will have no effect if ACPI 1948 IRQ routing is enabled. 1949 noacpi [X86] Do not use ACPI for IRQ routing 1950 or for PCI scanning. 1951 use_crs [X86] Use _CRS for PCI resource 1952 allocation. 1953 routeirq Do IRQ routing for all PCI devices. 1954 This is normally done in pci_enable_device(), 1955 so this option is a temporary workaround 1956 for broken drivers that don't call it. 1957 skip_isa_align [X86] do not align io start addr, so can 1958 handle more pci cards 1959 firmware [ARM] Do not re-enumerate the bus but instead 1960 just use the configuration from the 1961 bootloader. This is currently used on 1962 IXP2000 systems where the bus has to be 1963 configured a certain way for adjunct CPUs. 1964 noearly [X86] Don't do any early type 1 scanning. 1965 This might help on some broken boards which 1966 machine check when some devices' config space 1967 is read. But various workarounds are disabled 1968 and some IOMMU drivers will not work. 1969 bfsort Sort PCI devices into breadth-first order. 1970 This sorting is done to get a device 1971 order compatible with older (<= 2.4) kernels. 1972 nobfsort Don't sort PCI devices into breadth-first order. 1973 cbiosize=nn[KMG] The fixed amount of bus space which is 1974 reserved for the CardBus bridge's IO window. 1975 The default value is 256 bytes. 1976 cbmemsize=nn[KMG] The fixed amount of bus space which is 1977 reserved for the CardBus bridge's memory 1978 window. The default value is 64 megabytes. 1979 resource_alignment= 1980 Format: 1981 [<order of align>[AT]][<domain>:]<bus>:<slot>.<func>[; ..[DOT]] 1982 Specifies alignment and device to reassign 1983 aligned memory resources. 1984 If <order of align> is not specified, 1985 PAGE_SIZE is used as alignment. 1986 PCI-PCI bridge can be specified, if resource 1987 windows need to be expanded. 1988 ecrc= Enable/disable PCIe ECRC (transaction layer 1989 end-to-end CRC checking). 1990 bios: Use BIOS/firmware settings. This is the 1991 the default. 1992 off: Turn ECRC off 1993 on: Turn ECRC on. 1994 1995 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 1996 Management. 1997 off Disable ASPM. 1998 force Enable ASPM even on devices that claim not to support it. 1999 WARNING: Forcing ASPM on may cause system lockups. 2000 2001 pcmv= [HW,PCMCIA] BadgePAD 4 2002 2003 pd. [PARIDE] 2004 See Documentation/blockdev/paride.txt. 2005 2006 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 2007 boot time. 2008 Format: { 0 | 1 } 2009 See arch/parisc/kernel/pdc_chassis.c 2010 2011 percpu_alloc= Select which percpu first chunk allocator to use. 2012 Currently supported values are "embed" and "page". 2013 Archs may support subset or none of the selections. 2014 See comments in mm/percpu.c for details on each 2015 allocator. This parameter is primarily for debugging 2016 and performance comparison. 2017 2018 pf. [PARIDE] 2019 See Documentation/blockdev/paride.txt. 2020 2021 pg. [PARIDE] 2022 See Documentation/blockdev/paride.txt. 2023 2024 pirq= [SMP,APIC] Manual mp-table setup 2025 See Documentation/x86/i386/IO-APIC.txt. 2026 2027 plip= [PPT,NET] Parallel port network link 2028 Format: { parport<nr> | timid | 0 } 2029 See also Documentation/parport.txt. 2030 2031 pmtmr= [X86] Manual setup of pmtmr I/O Port. 2032 Override pmtimer IOPort with a hex value. 2033 e.g. pmtmr=0x508 2034 2035 pnp.debug [PNP] 2036 Enable PNP debug messages. This depends on the 2037 CONFIG_PNP_DEBUG_MESSAGES option. 2038 2039 pnpacpi= [ACPI] 2040 { off } 2041 2042 pnpbios= [ISAPNP] 2043 { on | off | curr | res | no-curr | no-res } 2044 2045 pnp_reserve_irq= 2046 [ISAPNP] Exclude IRQs for the autoconfiguration 2047 2048 pnp_reserve_dma= 2049 [ISAPNP] Exclude DMAs for the autoconfiguration 2050 2051 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 2052 Ranges are in pairs (I/O port base and size). 2053 2054 pnp_reserve_mem= 2055 [ISAPNP] Exclude memory regions for the 2056 autoconfiguration. 2057 Ranges are in pairs (memory base and size). 2058 2059 ports= [IP_VS_FTP] IPVS ftp helper module 2060 Default is 21. 2061 Up to 8 (IP_VS_APP_MAX_PORTS) ports 2062 may be specified. 2063 Format: <port>,<port>.... 2064 2065 print-fatal-signals= 2066 [KNL] debug: print fatal signals 2067 2068 If enabled, warn about various signal handling 2069 related application anomalies: too many signals, 2070 too many POSIX.1 timers, fatal signals causing a 2071 coredump - etc. 2072 2073 If you hit the warning due to signal overflow, 2074 you might want to try "ulimit -i unlimited". 2075 2076 default: off. 2077 2078 printk.time= Show timing data prefixed to each printk message line 2079 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 2080 2081 processor.max_cstate= [HW,ACPI] 2082 Limit processor to maximum C-state 2083 max_cstate=9 overrides any DMI blacklist limit. 2084 2085 processor.nocst [HW,ACPI] 2086 Ignore the _CST method to determine C-states, 2087 instead using the legacy FADT method 2088 2089 profile= [KNL] Enable kernel profiling via /proc/profile 2090 Format: [schedule,]<number> 2091 Param: "schedule" - profile schedule points. 2092 Param: <number> - step/bucket size as a power of 2 for 2093 statistical time based profiling. 2094 Param: "sleep" - profile D-state sleeping (millisecs). 2095 Requires CONFIG_SCHEDSTATS 2096 Param: "kvm" - profile VM exits. 2097 2098 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 2099 before loading. 2100 See Documentation/blockdev/ramdisk.txt. 2101 2102 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 2103 probe for; one of (bare|imps|exps|lifebook|any). 2104 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 2105 per second. 2106 psmouse.resetafter= [HW,MOUSE] 2107 Try to reset the device after so many bad packets 2108 (0 = never). 2109 psmouse.resolution= 2110 [HW,MOUSE] Set desired mouse resolution, in dpi. 2111 psmouse.smartscroll= 2112 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 2113 0 = disabled, 1 = enabled (default). 2114 2115 pss= [HW,OSS] Personal Sound System (ECHO ESC614) 2116 Format: 2117 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq> 2118 2119 pt. [PARIDE] 2120 See Documentation/blockdev/paride.txt. 2121 2122 pty.legacy_count= 2123 [KNL] Number of legacy pty's. Overwrites compiled-in 2124 default number. 2125 2126 quiet [KNL] Disable most log messages 2127 2128 r128= [HW,DRM] 2129 2130 raid= [HW,RAID] 2131 See Documentation/md.txt. 2132 2133 ramdisk_blocksize= [RAM] 2134 See Documentation/blockdev/ramdisk.txt. 2135 2136 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 2137 See Documentation/blockdev/ramdisk.txt. 2138 2139 rcupdate.blimit= [KNL,BOOT] 2140 Set maximum number of finished RCU callbacks to process 2141 in one batch. 2142 2143 rcupdate.qhimark= [KNL,BOOT] 2144 Set threshold of queued 2145 RCU callbacks over which batch limiting is disabled. 2146 2147 rcupdate.qlowmark= [KNL,BOOT] 2148 Set threshold of queued RCU callbacks below which 2149 batch limiting is re-enabled. 2150 2151 rdinit= [KNL] 2152 Format: <full_path> 2153 Run specified binary instead of /init from the ramdisk, 2154 used for early userspace startup. See initrd. 2155 2156 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 2157 Format: <reboot_mode>[,<reboot_mode2>[,...]] 2158 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 2159 2160 relax_domain_level= 2161 [KNL, SMP] Set scheduler's default relax_domain_level. 2162 See Documentation/cgroups/cpusets.txt. 2163 2164 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 2165 2166 reservetop= [X86-32] 2167 Format: nn[KMG] 2168 Reserves a hole at the top of the kernel virtual 2169 address space. 2170 2171 reset_devices [KNL] Force drivers to reset the underlying device 2172 during initialization. 2173 2174 resume= [SWSUSP] 2175 Specify the partition device for software suspend 2176 2177 resume_offset= [SWSUSP] 2178 Specify the offset from the beginning of the partition 2179 given by "resume=" at which the swap header is located, 2180 in <PAGE_SIZE> units (needed only for swap files). 2181 See Documentation/power/swsusp-and-swap-files.txt 2182 2183 retain_initrd [RAM] Keep initrd memory after extraction 2184 2185 rhash_entries= [KNL,NET] 2186 Set number of hash buckets for route cache 2187 2188 riscom8= [HW,SERIAL] 2189 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 2190 2191 ro [KNL] Mount root device read-only on boot 2192 2193 root= [KNL] Root filesystem 2194 2195 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 2196 mount the root filesystem 2197 2198 rootflags= [KNL] Set root filesystem mount option string 2199 2200 rootfstype= [KNL] Set root filesystem type 2201 2202 rootwait [KNL] Wait (indefinitely) for root device to show up. 2203 Useful for devices that are detected asynchronously 2204 (e.g. USB and MMC devices). 2205 2206 rw [KNL] Mount root device read-write on boot 2207 2208 S [KNL] Run init in single mode 2209 2210 sa1100ir [NET] 2211 See drivers/net/irda/sa1100_ir.c. 2212 2213 sbni= [NET] Granch SBNI12 leased line adapter 2214 2215 sched_debug [KNL] Enables verbose scheduler debug messages. 2216 2217 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver 2218 Format: <io>[,<timeout>[,<isapnp>]] 2219 2220 scsi_debug_*= [SCSI] 2221 See drivers/scsi/scsi_debug.c. 2222 2223 scsi_default_dev_flags= 2224 [SCSI] SCSI default device flags 2225 Format: <integer> 2226 2227 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model 2228 Format: <vendor>:<model>:<flags> 2229 (flags are integer value) 2230 2231 scsi_logging_level= [SCSI] a bit mask of logging levels 2232 See drivers/scsi/scsi_logging.h for bits. Also 2233 settable via sysctl at dev.scsi.logging_level 2234 (/proc/sys/dev/scsi/logging_level). 2235 There is also a nice 'scsi_logging_level' script in the 2236 S390-tools package, available for download at 2237 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html 2238 2239 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are 2240 discovered. async scans them in kernel threads, 2241 allowing boot to proceed. none ignores them, expecting 2242 user space to do the scan. 2243 2244 security= [SECURITY] Choose a security module to enable at boot. 2245 If this boot parameter is not specified, only the first 2246 security module asking for security registration will be 2247 loaded. An invalid security module name will be treated 2248 as if no module has been chosen. 2249 2250 selinux= [SELINUX] Disable or enable SELinux at boot time. 2251 Format: { "0" | "1" } 2252 See security/selinux/Kconfig help text. 2253 0 -- disable. 2254 1 -- enable. 2255 Default value is set via kernel config option. 2256 If enabled at boot time, /selinux/disable can be used 2257 later to disable prior to initial policy load. 2258 2259 serialnumber [BUGS=X86-32] 2260 2261 shapers= [NET] 2262 Maximal number of shapers. 2263 2264 show_msr= [x86] show boot-time MSR settings 2265 Format: { <integer> } 2266 Show boot-time (BIOS-initialized) MSR settings. 2267 The parameter means the number of CPUs to show, 2268 for example 1 means boot CPU only. 2269 2270 sim710= [SCSI,HW] 2271 See header of drivers/scsi/sim710.c. 2272 2273 simeth= [IA-64] 2274 simscsi= 2275 2276 slram= [HW,MTD] 2277 2278 slub_debug[=options[,slabs]] [MM, SLUB] 2279 Enabling slub_debug allows one to determine the 2280 culprit if slab objects become corrupted. Enabling 2281 slub_debug can create guard zones around objects and 2282 may poison objects when not in use. Also tracks the 2283 last alloc / free. For more information see 2284 Documentation/vm/slub.txt. 2285 2286 slub_max_order= [MM, SLUB] 2287 Determines the maximum allowed order for slabs. 2288 A high setting may cause OOMs due to memory 2289 fragmentation. For more information see 2290 Documentation/vm/slub.txt. 2291 2292 slub_min_objects= [MM, SLUB] 2293 The minimum number of objects per slab. SLUB will 2294 increase the slab order up to slub_max_order to 2295 generate a sufficiently large slab able to contain 2296 the number of objects indicated. The higher the number 2297 of objects the smaller the overhead of tracking slabs 2298 and the less frequently locks need to be acquired. 2299 For more information see Documentation/vm/slub.txt. 2300 2301 slub_min_order= [MM, SLUB] 2302 Determines the mininum page order for slabs. Must be 2303 lower than slub_max_order. 2304 For more information see Documentation/vm/slub.txt. 2305 2306 slub_nomerge [MM, SLUB] 2307 Disable merging of slabs with similar size. May be 2308 necessary if there is some reason to distinguish 2309 allocs to different slabs. Debug options disable 2310 merging on their own. 2311 For more information see Documentation/vm/slub.txt. 2312 2313 smart2= [HW] 2314 Format: <io1>[,<io2>[,...,<io8>]] 2315 2316 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 2317 attempt to substitute SMP alternatives once at boot. 2318 2319 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 2320 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 2321 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 2322 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 2323 smsc-ircc2.ircc_irq= [HW] IRQ line 2324 smsc-ircc2.ircc_dma= [HW] DMA channel 2325 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 2326 0: Toshiba Satellite 1800 (GP data pin select) 2327 1: Fast pin select (default) 2328 2: ATC IRMode 2329 2330 snd-ad1816a= [HW,ALSA] 2331 2332 snd-ad1848= [HW,ALSA] 2333 2334 snd-ali5451= [HW,ALSA] 2335 2336 snd-als100= [HW,ALSA] 2337 2338 snd-als4000= [HW,ALSA] 2339 2340 snd-azt2320= [HW,ALSA] 2341 2342 snd-cmi8330= [HW,ALSA] 2343 2344 snd-cmipci= [HW,ALSA] 2345 2346 snd-cs4231= [HW,ALSA] 2347 2348 snd-cs4232= [HW,ALSA] 2349 2350 snd-cs4236= [HW,ALSA] 2351 2352 snd-cs4281= [HW,ALSA] 2353 2354 snd-cs46xx= [HW,ALSA] 2355 2356 snd-dt019x= [HW,ALSA] 2357 2358 snd-dummy= [HW,ALSA] 2359 2360 snd-emu10k1= [HW,ALSA] 2361 2362 snd-ens1370= [HW,ALSA] 2363 2364 snd-ens1371= [HW,ALSA] 2365 2366 snd-es968= [HW,ALSA] 2367 2368 snd-es1688= [HW,ALSA] 2369 2370 snd-es18xx= [HW,ALSA] 2371 2372 snd-es1938= [HW,ALSA] 2373 2374 snd-es1968= [HW,ALSA] 2375 2376 snd-fm801= [HW,ALSA] 2377 2378 snd-gusclassic= [HW,ALSA] 2379 2380 snd-gusextreme= [HW,ALSA] 2381 2382 snd-gusmax= [HW,ALSA] 2383 2384 snd-hdsp= [HW,ALSA] 2385 2386 snd-ice1712= [HW,ALSA] 2387 2388 snd-intel8x0= [HW,ALSA] 2389 2390 snd-interwave= [HW,ALSA] 2391 2392 snd-interwave-stb= 2393 [HW,ALSA] 2394 2395 snd-korg1212= [HW,ALSA] 2396 2397 snd-maestro3= [HW,ALSA] 2398 2399 snd-mpu401= [HW,ALSA] 2400 2401 snd-mtpav= [HW,ALSA] 2402 2403 snd-nm256= [HW,ALSA] 2404 2405 snd-opl3sa2= [HW,ALSA] 2406 2407 snd-opti92x-ad1848= 2408 [HW,ALSA] 2409 2410 snd-opti92x-cs4231= 2411 [HW,ALSA] 2412 2413 snd-opti93x= [HW,ALSA] 2414 2415 snd-pmac= [HW,ALSA] 2416 2417 snd-rme32= [HW,ALSA] 2418 2419 snd-rme96= [HW,ALSA] 2420 2421 snd-rme9652= [HW,ALSA] 2422 2423 snd-sb8= [HW,ALSA] 2424 2425 snd-sb16= [HW,ALSA] 2426 2427 snd-sbawe= [HW,ALSA] 2428 2429 snd-serial= [HW,ALSA] 2430 2431 snd-sgalaxy= [HW,ALSA] 2432 2433 snd-sonicvibes= [HW,ALSA] 2434 2435 snd-sun-amd7930= 2436 [HW,ALSA] 2437 2438 snd-sun-cs4231= [HW,ALSA] 2439 2440 snd-trident= [HW,ALSA] 2441 2442 snd-usb-audio= [HW,ALSA,USB] 2443 2444 snd-via82xx= [HW,ALSA] 2445 2446 snd-virmidi= [HW,ALSA] 2447 2448 snd-wavefront= [HW,ALSA] 2449 2450 snd-ymfpci= [HW,ALSA] 2451 2452 softlockup_panic= 2453 [KNL] Should the soft-lockup detector generate panics. 2454 2455 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2456 See Documentation/sonypi.txt 2457 2458 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2459 See Documentation/serial/specialix.txt. 2460 2461 spia_io_base= [HW,MTD] 2462 spia_fio_base= 2463 spia_pedr= 2464 spia_peddr= 2465 2466 sscape= [HW,OSS] 2467 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq> 2468 2469 st= [HW,SCSI] SCSI tape parameters (buffers, etc.) 2470 See Documentation/scsi/st.txt. 2471 2472 stacktrace [FTRACE] 2473 Enabled the stack tracer on boot up. 2474 2475 sti= [PARISC,HW] 2476 Format: <num> 2477 Set the STI (builtin display/keyboard on the HP-PARISC 2478 machines) console (graphic card) which should be used 2479 as the initial boot-console. 2480 See also comment in drivers/video/console/sticore.c. 2481 2482 sti_font= [HW] 2483 See comment in drivers/video/console/sticore.c. 2484 2485 stifb= [HW] 2486 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2487 2488 sunrpc.min_resvport= 2489 sunrpc.max_resvport= 2490 [NFS,SUNRPC] 2491 SunRPC servers often require that client requests 2492 originate from a privileged port (i.e. a port in the 2493 range 0 < portnr < 1024). 2494 An administrator who wishes to reserve some of these 2495 ports for other uses may adjust the range that the 2496 kernel's sunrpc client considers to be privileged 2497 using these two parameters to set the minimum and 2498 maximum port values. 2499 2500 sunrpc.pool_mode= 2501 [NFS] 2502 Control how the NFS server code allocates CPUs to 2503 service thread pools. Depending on how many NICs 2504 you have and where their interrupts are bound, this 2505 option will affect which CPUs will do NFS serving. 2506 Note: this parameter cannot be changed while the 2507 NFS server is running. 2508 2509 auto the server chooses an appropriate mode 2510 automatically using heuristics 2511 global a single global pool contains all CPUs 2512 percpu one pool for each CPU 2513 pernode one pool for each NUMA node (equivalent 2514 to global on non-NUMA machines) 2515 2516 sunrpc.tcp_slot_table_entries= 2517 sunrpc.udp_slot_table_entries= 2518 [NFS,SUNRPC] 2519 Sets the upper limit on the number of simultaneous 2520 RPC calls that can be sent from the client to a 2521 server. Increasing these values may allow you to 2522 improve throughput, but will also increase the 2523 amount of memory reserved for use by the client. 2524 2525 swiotlb= [IA-64] Number of I/O TLB slabs 2526 2527 switches= [HW,M68k] 2528 2529 sym53c416= [HW,SCSI] 2530 See header of drivers/scsi/sym53c416.c. 2531 2532 sysrq_always_enabled 2533 [KNL] 2534 Ignore sysrq setting - this boot parameter will 2535 neutralize any effect of /proc/sys/kernel/sysrq. 2536 Useful for debugging. 2537 2538 t128= [HW,SCSI] 2539 See header of drivers/scsi/t128.c. 2540 2541 tdfx= [HW,DRM] 2542 2543 test_suspend= [SUSPEND] 2544 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2545 standby suspend) as the system sleep state to briefly 2546 enter during system startup. The system is woken from 2547 this state using a wakeup-capable RTC alarm. 2548 2549 thash_entries= [KNL,NET] 2550 Set number of hash buckets for TCP connection 2551 2552 thermal.act= [HW,ACPI] 2553 -1: disable all active trip points in all thermal zones 2554 <degrees C>: override all lowest active trip points 2555 2556 thermal.crt= [HW,ACPI] 2557 -1: disable all critical trip points in all thermal zones 2558 <degrees C>: override all critical trip points 2559 2560 thermal.nocrt= [HW,ACPI] 2561 Set to disable actions on ACPI thermal zone 2562 critical and hot trip points. 2563 2564 thermal.off= [HW,ACPI] 2565 1: disable ACPI thermal control 2566 2567 thermal.psv= [HW,ACPI] 2568 -1: disable all passive trip points 2569 <degrees C>: override all passive trip points to this 2570 value 2571 2572 thermal.tzp= [HW,ACPI] 2573 Specify global default ACPI thermal zone polling rate 2574 <deci-seconds>: poll all this frequency 2575 0: no polling (default) 2576 2577 tmscsim= [HW,SCSI] 2578 See comment before function dc390_setup() in 2579 drivers/scsi/tmscsim.c. 2580 2581 topology= [S390] 2582 Format: {off | on} 2583 Specify if the kernel should make use of the cpu 2584 topology informations if the hardware supports these. 2585 The scheduler will make use of these informations and 2586 e.g. base its process migration decisions on it. 2587 Default is off. 2588 2589 tp720= [HW,PS2] 2590 2591 trace_buf_size=nn[KMG] 2592 [FTRACE] will set tracing buffer size. 2593 2594 trace_event=[event-list] 2595 [FTRACE] Set and start specified trace events in order 2596 to facilitate early boot debugging. 2597 See also Documentation/trace/events.txt 2598 2599 trix= [HW,OSS] MediaTrix AudioTrix Pro 2600 Format: 2601 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq> 2602 2603 tsc= Disable clocksource-must-verify flag for TSC. 2604 Format: <string> 2605 [x86] reliable: mark tsc clocksource as reliable, this 2606 disables clocksource verification at runtime. 2607 Used to enable high-resolution timer mode on older 2608 hardware, and in virtualized environment. 2609 2610 turbografx.map[2|3]= [HW,JOY] 2611 TurboGraFX parallel port interface 2612 Format: 2613 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2614 See also Documentation/input/joystick-parport.txt 2615 2616 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter 2617 See header of drivers/scsi/u14-34f.c. 2618 2619 uart401= [HW,OSS] 2620 Format: <io>,<irq> 2621 2622 uart6850= [HW,OSS] 2623 Format: <io>,<irq> 2624 2625 uhash_entries= [KNL,NET] 2626 Set number of hash buckets for UDP/UDP-Lite connections 2627 2628 uhci-hcd.ignore_oc= 2629 [USB] Ignore overcurrent events (default N). 2630 Some badly-designed motherboards generate lots of 2631 bogus events, for ports that aren't wired to 2632 anything. Set this parameter to avoid log spamming. 2633 Note that genuine overcurrent events won't be 2634 reported either. 2635 2636 unknown_nmi_panic 2637 [X86] 2638 Set unknown_nmi_panic=1 early on boot. 2639 2640 usbcore.autosuspend= 2641 [USB] The autosuspend time delay (in seconds) used 2642 for newly-detected USB devices (default 2). This 2643 is the time required before an idle device will be 2644 autosuspended. Devices for which the delay is set 2645 to a negative value won't be autosuspended at all. 2646 2647 usbcore.usbfs_snoop= 2648 [USB] Set to log all usbfs traffic (default 0 = off). 2649 2650 usbcore.blinkenlights= 2651 [USB] Set to cycle leds on hubs (default 0 = off). 2652 2653 usbcore.old_scheme_first= 2654 [USB] Start with the old device initialization 2655 scheme (default 0 = off). 2656 2657 usbcore.use_both_schemes= 2658 [USB] Try the other device initialization scheme 2659 if the first one fails (default 1 = enabled). 2660 2661 usbcore.initial_descriptor_timeout= 2662 [USB] Specifies timeout for the initial 64-byte 2663 USB_REQ_GET_DESCRIPTOR request in milliseconds 2664 (default 5000 = 5.0 seconds). 2665 2666 usbhid.mousepoll= 2667 [USBHID] The interval which mice are to be polled at. 2668 2669 usb-storage.delay_use= 2670 [UMS] The delay in seconds before a new device is 2671 scanned for Logical Units (default 5). 2672 2673 usb-storage.quirks= 2674 [UMS] A list of quirks entries to supplement or 2675 override the built-in unusual_devs list. List 2676 entries are separated by commas. Each entry has 2677 the form VID:PID:Flags where VID and PID are Vendor 2678 and Product ID values (4-digit hex numbers) and 2679 Flags is a set of characters, each corresponding 2680 to a common usb-storage quirk flag as follows: 2681 a = SANE_SENSE (collect more than 18 bytes 2682 of sense data); 2683 b = BAD_SENSE (don't collect more than 18 2684 bytes of sense data); 2685 c = FIX_CAPACITY (decrease the reported 2686 device capacity by one sector); 2687 h = CAPACITY_HEURISTICS (decrease the 2688 reported device capacity by one 2689 sector if the number is odd); 2690 i = IGNORE_DEVICE (don't bind to this 2691 device); 2692 l = NOT_LOCKABLE (don't try to lock and 2693 unlock ejectable media); 2694 m = MAX_SECTORS_64 (don't transfer more 2695 than 64 sectors = 32 KB at a time); 2696 o = CAPACITY_OK (accept the capacity 2697 reported by the device); 2698 r = IGNORE_RESIDUE (the device reports 2699 bogus residue values); 2700 s = SINGLE_LUN (the device has only one 2701 Logical Unit); 2702 w = NO_WP_DETECT (don't test whether the 2703 medium is write-protected). 2704 Example: quirks=0419:aaf5:rl,0421:0433:rc 2705 2706 vdso= [X86,SH] 2707 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2708 vdso=1: enable VDSO (default) 2709 vdso=0: disable VDSO mapping 2710 2711 vdso32= [X86] 2712 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2713 vdso32=1: enable 32-bit VDSO (default) 2714 vdso32=0: disable 32-bit VDSO mapping 2715 2716 vector= [IA-64,SMP] 2717 vector=percpu: enable percpu vector domain 2718 2719 video= [FB] Frame buffer configuration 2720 See Documentation/fb/modedb.txt. 2721 2722 vga= [BOOT,X86-32] Select a particular video mode 2723 See Documentation/x86/boot.txt and 2724 Documentation/svga.txt. 2725 Use vga=ask for menu. 2726 This is actually a boot loader parameter; the value is 2727 passed to the kernel using a special protocol. 2728 2729 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2730 size of <nn>. This can be used to increase the 2731 minimum size (128MB on x86). It can also be used to 2732 decrease the size and leave more room for directly 2733 mapped kernel RAM. 2734 2735 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2736 Format: <command> 2737 2738 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2739 Format: <command> 2740 2741 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2742 Format: <command> 2743 2744 vt.cur_default= [VT] Default cursor shape. 2745 Format: 0xCCBBAA, where AA, BB, and CC are the same as 2746 the parameters of the <Esc>[?A;B;Cc escape sequence; 2747 see VGA-softcursor.txt. Default: 2 = underline. 2748 2749 vt.default_blu= [VT] 2750 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 2751 Change the default blue palette of the console. 2752 This is a 16-member array composed of values 2753 ranging from 0-255. 2754 2755 vt.default_grn= [VT] 2756 Format: <green0>,<green1>,<green2>,...,<green15> 2757 Change the default green palette of the console. 2758 This is a 16-member array composed of values 2759 ranging from 0-255. 2760 2761 vt.default_red= [VT] 2762 Format: <red0>,<red1>,<red2>,...,<red15> 2763 Change the default red palette of the console. 2764 This is a 16-member array composed of values 2765 ranging from 0-255. 2766 2767 vt.default_utf8= 2768 [VT] 2769 Format=<0|1> 2770 Set system-wide default UTF-8 mode for all tty's. 2771 Default is 1, i.e. UTF-8 mode is enabled for all 2772 newly opened terminals. 2773 2774 vt.global_cursor_default= 2775 [VT] 2776 Format=<-1|0|1> 2777 Set system-wide default for whether a cursor 2778 is shown on new VTs. Default is -1, 2779 i.e. cursors will be created by default unless 2780 overridden by individual drivers. 0 will hide 2781 cursors, 1 will display them. 2782 2783 waveartist= [HW,OSS] 2784 Format: <io>,<irq>,<dma>,<dma2> 2785 2786 wd33c93= [HW,SCSI] 2787 See header of drivers/scsi/wd33c93.c. 2788 2789 wd7000= [HW,SCSI] 2790 See header of drivers/scsi/wd7000.c. 2791 2792 wdt= [WDT] Watchdog 2793 See Documentation/watchdog/wdt.txt. 2794 2795 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 2796 default x2apic cluster mode on platforms 2797 supporting x2apic. 2798 2799 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2800 xd_geo= See header of drivers/block/xd.c. 2801 2802 xirc2ps_cs= [NET,PCMCIA] 2803 Format: 2804 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2805 2806 ______________________________________________________________________ 2807 2808 TODO: 2809 2810 Add documentation for ALSA options. 2811 Add more DRM drivers.