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1 Kernel Parameters 2 ~~~~~~~~~~~~~~~~~ 3 4The following is a consolidated list of the kernel parameters as implemented 5(mostly) by the __setup() macro and sorted into English Dictionary order 6(defined as ignoring all punctuation and sorting digits before letters in a 7case insensitive manner), and with descriptions where known. 8 9Module parameters for loadable modules are specified only as the 10parameter name with optional '=' and value as appropriate, such as: 11 12 modprobe usbcore blinkenlights=1 13 14Module parameters for modules that are built into the kernel image 15are specified on the kernel command line with the module name plus 16'.' plus parameter name, with '=' and value if appropriate, such as: 17 18 usbcore.blinkenlights=1 19 20Hyphens (dashes) and underscores are equivalent in parameter names, so 21 log_buf_len=1M print-fatal-signals=1 22can also be entered as 23 log-buf-len=1M print_fatal_signals=1 24 25 26This document may not be entirely up to date and comprehensive. The command 27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable 28module. Loadable modules, after being loaded into the running kernel, also 29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these 30parameters may be changed at runtime by the command 31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". 32 33The parameters listed below are only valid if certain kernel build options were 34enabled and if respective hardware is present. The text in square brackets at 35the beginning of each description states the restrictions within which a 36parameter is applicable: 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 116In 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 122Parameters denoted with BOOT are actually interpreted by the boot 123loader, and have no meaning to the kernel directly. 124Do not modify the syntax of boot loader parameters without extreme 125need or coordination with <Documentation/x86/boot.txt>. 126 127There are also arch-specific kernel-parameters not documented here. 128See for example <Documentation/x86/x86_64/boot-options.txt>. 129 130Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 131a trailing = on the name of any parameter states that that parameter will 132be entered as an environment variable, whereas its absence indicates that 133it will appear as a kernel argument readable via /proc/cmdline by programs 134running once the system is up. 135 136The number of kernel parameters is not limited, but the length of the 137complete command line (parameters including spaces etc.) is limited to 138a fixed number of characters. This limit depends on the architecture 139and 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_irq_balance [HW,ACPI] 203 ACPI will balance active IRQs 204 default in APIC mode 205 206 acpi_irq_nobalance [HW,ACPI] 207 ACPI will not move active IRQs (default) 208 default in PIC mode 209 210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 211 Format: <irq>,<irq>... 212 213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 214 use by PCI 215 Format: <irq>,<irq>... 216 217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 218 219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 220 Format: To spoof as Windows 98: ="Microsoft Windows" 221 222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 223 acpi_osi="string1" # add string1 -- only one string 224 acpi_osi="!string2" # remove built-in string2 225 acpi_osi= # disable all strings 226 227 acpi_pm_good [X86] 228 Override the pmtimer bug detection: force the kernel 229 to assume that this machine's pmtimer latches its value 230 and always returns good values. 231 232 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 233 Format: { level | edge | high | low } 234 235 acpi_serialize [HW,ACPI] force serialization of AML methods 236 237 acpi_skip_timer_override [HW,ACPI] 238 Recognize and ignore IRQ0/pin2 Interrupt Override. 239 For broken nForce2 BIOS resulting in XT-PIC timer. 240 241 acpi_sleep= [HW,ACPI] Sleep options 242 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 243 old_ordering, s4_nonvs } 244 See Documentation/power/video.txt for information on 245 s3_bios and s3_mode. 246 s3_beep is for debugging; it makes the PC's speaker beep 247 as soon as the kernel's real-mode entry point is called. 248 s4_nohwsig prevents ACPI hardware signature from being 249 used during resume from hibernation. 250 old_ordering causes the ACPI 1.0 ordering of the _PTS 251 control method, with respect to putting devices into 252 low power states, to be enforced (the ACPI 2.0 ordering 253 of _PTS is used by default). 254 s4_nonvs prevents the kernel from saving/restoring the 255 ACPI NVS memory during hibernation. 256 257 acpi_use_timer_override [HW,ACPI] 258 Use timer override. For some broken Nvidia NF5 boards 259 that require a timer override, but don't have HPET 260 261 acpi_enforce_resources= [ACPI] 262 { strict | lax | no } 263 Check for resource conflicts between native drivers 264 and ACPI OperationRegions (SystemIO and SystemMemory 265 only). IO ports and memory declared in ACPI might be 266 used by the ACPI subsystem in arbitrary AML code and 267 can interfere with legacy drivers. 268 strict (default): access to resources claimed by ACPI 269 is denied; legacy drivers trying to access reserved 270 resources will fail to bind to device using them. 271 lax: access to resources claimed by ACPI is allowed; 272 legacy drivers trying to access reserved resources 273 will bind successfully but a warning message is logged. 274 no: ACPI OperationRegions are not marked as reserved, 275 no further checks are performed. 276 277 ad1848= [HW,OSS] 278 Format: <io>,<irq>,<dma>,<dma2>,<type> 279 280 add_efi_memmap [EFI; X86] Include EFI memory map in 281 kernel's map of available physical RAM. 282 283 advansys= [HW,SCSI] 284 See header of drivers/scsi/advansys.c. 285 286 advwdt= [HW,WDT] Advantech WDT 287 Format: <iostart>,<iostop> 288 289 aedsp16= [HW,OSS] Audio Excel DSP 16 290 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq> 291 See also header of sound/oss/aedsp16.c. 292 293 agp= [AGP] 294 { off | try_unsupported } 295 off: disable AGP support 296 try_unsupported: try to drive unsupported chipsets 297 (may crash computer or cause data corruption) 298 299 aha152x= [HW,SCSI] 300 See Documentation/scsi/aha152x.txt. 301 302 aha1542= [HW,SCSI] 303 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]] 304 305 aic7xxx= [HW,SCSI] 306 See Documentation/scsi/aic7xxx.txt. 307 308 aic79xx= [HW,SCSI] 309 See Documentation/scsi/aic79xx.txt. 310 311 amd_iommu= [HW,X86-84] 312 Pass parameters to the AMD IOMMU driver in the system. 313 Possible values are: 314 isolate - enable device isolation (each device, as far 315 as possible, will get its own protection 316 domain) [default] 317 share - put every device behind one IOMMU into the 318 same protection domain 319 fullflush - enable flushing of IO/TLB entries when 320 they are unmapped. Otherwise they are 321 flushed before they will be reused, which 322 is a lot of faster 323 324 amijoy.map= [HW,JOY] Amiga joystick support 325 Map of devices attached to JOY0DAT and JOY1DAT 326 Format: <a>,<b> 327 See also Documentation/kernel/input/joystick.txt 328 329 analog.map= [HW,JOY] Analog joystick and gamepad support 330 Specifies type or capabilities of an analog joystick 331 connected to one of 16 gameports 332 Format: <type1>,<type2>,..<type16> 333 334 apc= [HW,SPARC] 335 Power management functions (SPARCstation-4/5 + deriv.) 336 Format: noidle 337 Disable APC CPU standby support. SPARCstation-Fox does 338 not play well with APC CPU idle - disable it if you have 339 APC and your system crashes randomly. 340 341 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller 342 Change the output verbosity whilst booting 343 Format: { quiet (default) | verbose | debug } 344 Change the amount of debugging information output 345 when initialising the APIC and IO-APIC components. 346 347 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 348 Limit apic dumping. The parameter defines the maximal 349 number of local apics being dumped. Also it is possible 350 to set it to "all" by meaning -- no limit here. 351 Format: { 1 (default) | 2 | ... | all }. 352 The parameter valid if only apic=debug or 353 apic=verbose is specified. 354 Example: apic=debug show_lapic=all 355 356 apm= [APM] Advanced Power Management 357 See header of arch/x86/kernel/apm_32.c. 358 359 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 360 Format: <io>,<irq>,<nodeID> 361 362 ataflop= [HW,M68k] 363 364 atarimouse= [HW,MOUSE] Atari Mouse 365 366 atascsi= [HW,SCSI] Atari SCSI 367 368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 369 EzKey and similar keyboards 370 371 atkbd.reset= [HW] Reset keyboard during initialization 372 373 atkbd.set= [HW] Select keyboard code set 374 Format: <int> (2 = AT (default), 3 = PS/2) 375 376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 377 keyboards 378 379 atkbd.softraw= [HW] Choose between synthetic and real raw mode 380 Format: <bool> (0 = real, 1 = synthetic (default)) 381 382 atkbd.softrepeat= [HW] 383 Use software keyboard repeat 384 385 autotest [IA64] 386 387 baycom_epp= [HW,AX25] 388 Format: <io>,<mode> 389 390 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 391 Format: <io>,<mode> 392 See header of drivers/net/hamradio/baycom_par.c. 393 394 baycom_ser_fdx= [HW,AX25] 395 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 396 Format: <io>,<irq>,<mode>[,<baud>] 397 See header of drivers/net/hamradio/baycom_ser_fdx.c. 398 399 baycom_ser_hdx= [HW,AX25] 400 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 401 Format: <io>,<irq>,<mode> 402 See header of drivers/net/hamradio/baycom_ser_hdx.c. 403 404 boot_delay= Milliseconds to delay each printk during boot. 405 Values larger than 10 seconds (10000) are changed to 406 no delay (0). 407 Format: integer 408 409 bootmem_debug [KNL] Enable bootmem allocator debug messages. 410 411 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 412 bttv.radio= Most important insmod options are available as 413 kernel args too. 414 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 415 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 416 417 BusLogic= [HW,SCSI] 418 See drivers/scsi/BusLogic.c, comment before function 419 BusLogic_ParseDriverOptions(). 420 421 c101= [NET] Moxa C101 synchronous serial card 422 423 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 424 Sometimes CPU hardware bugs make them report the cache 425 size incorrectly. The kernel will attempt work arounds 426 to fix known problems, but for some CPUs it is not 427 possible to determine what the correct size should be. 428 This option provides an override for these situations. 429 430 capability.disable= 431 [SECURITY] Disable capabilities. This would normally 432 be used only if an alternative security model is to be 433 configured. Potentially dangerous and should only be 434 used if you are entirely sure of the consequences. 435 436 ccw_timeout_log [S390] 437 See Documentation/s390/CommonIO for details. 438 439 cgroup_disable= [KNL] Disable a particular controller 440 Format: {name of the controller(s) to disable} 441 {Currently supported controllers - "memory"} 442 443 checkreqprot [SELINUX] Set initial checkreqprot flag value. 444 Format: { "0" | "1" } 445 See security/selinux/Kconfig help text. 446 0 -- check protection applied by kernel (includes 447 any implied execute protection). 448 1 -- check protection requested by application. 449 Default value is set via a kernel config option. 450 Value can be changed at runtime via 451 /selinux/checkreqprot. 452 453 cio_ignore= [S390] 454 See Documentation/s390/CommonIO for details. 455 456 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 457 [Deprecated] 458 Forces specified clocksource (if available) to be used 459 when calculating gettimeofday(). If specified 460 clocksource is not available, it defaults to PIT. 461 Format: { pit | tsc | cyclone | pmtmr } 462 463 clocksource= [GENERIC_TIME] Override the default clocksource 464 Format: <string> 465 Override the default clocksource and use the clocksource 466 with the name specified. 467 Some clocksource names to choose from, depending on 468 the platform: 469 [all] jiffies (this is the base, fallback clocksource) 470 [ACPI] acpi_pm 471 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 472 pxa_timer,timer3,32k_counter,timer0_1 473 [AVR32] avr32 474 [X86-32] pit,hpet,tsc,vmi-timer; 475 scx200_hrt on Geode; cyclone on IBM x440 476 [MIPS] MIPS 477 [PARISC] cr16 478 [S390] tod 479 [SH] SuperH 480 [SPARC64] tick 481 [X86-64] hpet,tsc 482 483 clearcpuid=BITNUM [X86] 484 Disable CPUID feature X for the kernel. See 485 arch/x86/include/asm/cpufeature.h for the valid bit 486 numbers. Note the Linux specific bits are not necessarily 487 stable over kernel options, but the vendor specific 488 ones should be. 489 Also note that user programs calling CPUID directly 490 or using the feature without checking anything 491 will still see it. This just prevents it from 492 being used by the kernel or shown in /proc/cpuinfo. 493 Also note the kernel might malfunction if you disable 494 some critical bits. 495 496 cmo_free_hint= [PPC] Format: { yes | no } 497 Specify whether pages are marked as being inactive 498 when they are freed. This is used in CMO environments 499 to determine OS memory pressure for page stealing by 500 a hypervisor. 501 Default: yes 502 503 code_bytes [X86] How many bytes of object code to print 504 in an oops report. 505 Range: 0 - 8192 506 Default: 64 507 508 com20020= [HW,NET] ARCnet - COM20020 chipset 509 Format: 510 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 511 512 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 513 Format: <io>[,<irq>] 514 515 com90xx= [HW,NET] 516 ARCnet - COM90xx chipset (memory-mapped buffers) 517 Format: <io>[,<irq>[,<memstart>]] 518 519 condev= [HW,S390] console device 520 conmode= 521 522 console= [KNL] Output console device and options. 523 524 tty<n> Use the virtual console device <n>. 525 526 ttyS<n>[,options] 527 ttyUSB0[,options] 528 Use the specified serial port. The options are of 529 the form "bbbbpnf", where "bbbb" is the baud rate, 530 "p" is parity ("n", "o", or "e"), "n" is number of 531 bits, and "f" is flow control ("r" for RTS or 532 omit it). Default is "9600n8". 533 534 See Documentation/serial-console.txt for more 535 information. See 536 Documentation/networking/netconsole.txt for an 537 alternative. 538 539 uart[8250],io,<addr>[,options] 540 uart[8250],mmio,<addr>[,options] 541 Start an early, polled-mode console on the 8250/16550 542 UART at the specified I/O port or MMIO address, 543 switching to the matching ttyS device later. The 544 options are the same as for ttyS, above. 545 546 If the device connected to the port is not a TTY but a braille 547 device, prepend "brl," before the device type, for instance 548 console=brl,ttyS0 549 For now, only VisioBraille is supported. 550 551 consoleblank= [KNL] The console blank (screen saver) timeout in 552 seconds. Defaults to 10*60 = 10mins. A value of 0 553 disables the blank timer. 554 555 coredump_filter= 556 [KNL] Change the default value for 557 /proc/<pid>/coredump_filter. 558 See also Documentation/filesystems/proc.txt. 559 560 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 561 Format: 562 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 563 564 crashkernel=nn[KMG]@ss[KMG] 565 [KNL] Reserve a chunk of physical memory to 566 hold a kernel to switch to with kexec on panic. 567 568 crashkernel=range1:size1[,range2:size2,...][@offset] 569 [KNL] Same as above, but depends on the memory 570 in the running system. The syntax of range is 571 start-[end] where start and end are both 572 a memory unit (amount[KMG]). See also 573 Documentation/kdump/kdump.txt for a example. 574 575 cs89x0_dma= [HW,NET] 576 Format: <dma> 577 578 cs89x0_media= [HW,NET] 579 Format: { rj45 | aui | bnc } 580 581 dasd= [HW,NET] 582 See header of drivers/s390/block/dasd_devmap.c. 583 584 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 585 (one device per port) 586 Format: <port#>,<type> 587 See also Documentation/input/joystick-parport.txt 588 589 debug [KNL] Enable kernel debugging (events log level). 590 591 debug_locks_verbose= 592 [KNL] verbose self-tests 593 Format=<0|1> 594 Print debugging info while doing the locking API 595 self-tests. 596 We default to 0 (no extra messages), setting it to 597 1 will print _a lot_ more information - normally 598 only useful to kernel developers. 599 600 debug_objects [KNL] Enable object debugging 601 602 no_debug_objects 603 [KNL] Disable object debugging 604 605 debugpat [X86] Enable PAT debugging 606 607 decnet.addr= [HW,NET] 608 Format: <area>[,<node>] 609 See also Documentation/networking/decnet.txt. 610 611 default_hugepagesz= 612 [same as hugepagesz=] The size of the default 613 HugeTLB page size. This is the size represented by 614 the legacy /proc/ hugepages APIs, used for SHM, and 615 default size when mounting hugetlbfs filesystems. 616 Defaults to the default architecture's huge page size 617 if not specified. 618 619 dhash_entries= [KNL] 620 Set number of hash buckets for dentry cache. 621 622 digi= [HW,SERIAL] 623 IO parameters + enable/disable command. 624 625 digiepca= [HW,SERIAL] 626 See drivers/char/README.epca and 627 Documentation/serial/digiepca.txt. 628 629 disable_mtrr_cleanup [X86] 630 The kernel tries to adjust MTRR layout from continuous 631 to discrete, to make X server driver able to add WB 632 entry later. This parameter disables that. 633 634 disable_mtrr_trim [X86, Intel and AMD only] 635 By default the kernel will trim any uncacheable 636 memory out of your available memory pool based on 637 MTRR settings. This parameter disables that behavior, 638 possibly causing your machine to run very slowly. 639 640 disable_timer_pin_1 [X86] 641 Disable PIN 1 of APIC timer 642 Can be useful to work around chipset bugs. 643 644 dmasound= [HW,OSS] Sound subsystem buffers 645 646 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 647 this option disables the debugging code at boot. 648 649 dma_debug_entries=<number> 650 This option allows to tune the number of preallocated 651 entries for DMA-API debugging code. One entry is 652 required per DMA-API allocation. Use this if the 653 DMA-API debugging code disables itself because the 654 architectural default is too low. 655 656 dma_debug_driver=<driver_name> 657 With this option the DMA-API debugging driver 658 filter feature can be enabled at boot time. Just 659 pass the driver to filter for as the parameter. 660 The filter can be disabled or changed to another 661 driver later using sysfs. 662 663 dscc4.setup= [NET] 664 665 dtc3181e= [HW,SCSI] 666 667 dynamic_printk Enables pr_debug()/dev_dbg() calls if 668 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. 669 These can also be switched on/off via 670 <debugfs>/dynamic_printk/modules 671 672 earlycon= [KNL] Output early console device and options. 673 uart[8250],io,<addr>[,options] 674 uart[8250],mmio,<addr>[,options] 675 Start an early, polled-mode console on the 8250/16550 676 UART at the specified I/O port or MMIO address. 677 The options are the same as for ttyS, above. 678 679 earlyprintk= [X86,SH,BLACKFIN] 680 earlyprintk=vga 681 earlyprintk=serial[,ttySn[,baudrate]] 682 earlyprintk=ttySn[,baudrate] 683 earlyprintk=dbgp[debugController#] 684 685 Append ",keep" to not disable it when the real console 686 takes over. 687 688 Only vga or serial or usb debug port at a time. 689 690 Currently only ttyS0 and ttyS1 are supported. 691 692 Interaction with the standard serial driver is not 693 very good. 694 695 The VGA output is eventually overwritten by the real 696 console. 697 698 eata= [HW,SCSI] 699 700 edd= [EDD] 701 Format: {"off" | "on" | "skip[mbr]"} 702 703 eisa_irq_edge= [PARISC,HW] 704 See header of drivers/parisc/eisa.c. 705 706 elanfreq= [X86-32] 707 See comment before function elanfreq_setup() in 708 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 709 710 elevator= [IOSCHED] 711 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 712 See Documentation/block/as-iosched.txt and 713 Documentation/block/deadline-iosched.txt for details. 714 715 elfcorehdr= [IA64,PPC,SH,X86] 716 Specifies physical address of start of kernel core 717 image elf header. Generally kexec loader will 718 pass this option to capture kernel. 719 See Documentation/kdump/kdump.txt for details. 720 721 enable_mtrr_cleanup [X86] 722 The kernel tries to adjust MTRR layout from continuous 723 to discrete, to make X server driver able to add WB 724 entry later. This parameter enables that. 725 726 enable_timer_pin_1 [X86] 727 Enable PIN 1 of APIC timer 728 Can be useful to work around chipset bugs 729 (in particular on some ATI chipsets). 730 The kernel tries to set a reasonable default. 731 732 enforcing [SELINUX] Set initial enforcing status. 733 Format: {"0" | "1"} 734 See security/selinux/Kconfig help text. 735 0 -- permissive (log only, no denials). 736 1 -- enforcing (deny and log). 737 Default value is 0. 738 Value can be changed at runtime via /selinux/enforce. 739 740 ether= [HW,NET] Ethernet cards parameters 741 This option is obsoleted by the "netdev=" option, which 742 has equivalent usage. See its documentation for details. 743 744 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog. 745 Format: <io>[,<irq>] 746 747 failslab= 748 fail_page_alloc= 749 fail_make_request=[KNL] 750 General fault injection mechanism. 751 Format: <interval>,<probability>,<space>,<times> 752 See also /Documentation/fault-injection/. 753 754 fd_mcs= [HW,SCSI] 755 See header of drivers/scsi/fd_mcs.c. 756 757 fdomain= [HW,SCSI] 758 See header of drivers/scsi/fdomain.c. 759 760 floppy= [HW] 761 See Documentation/blockdev/floppy.txt. 762 763 force_pal_cache_flush 764 [IA-64] Avoid check_sal_cache_flush which may hang on 765 buggy SAL_CACHE_FLUSH implementations. Using this 766 parameter will force ia64_sal_cache_flush to call 767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 768 769 ftrace=[tracer] 770 [FTRACE] will set and start the specified tracer 771 as early as possible in order to facilitate early 772 boot debugging. 773 774 ftrace_dump_on_oops 775 [FTRACE] will dump the trace buffers on oops. 776 777 ftrace_filter=[function-list] 778 [FTRACE] Limit the functions traced by the function 779 tracer at boot up. function-list is a comma separated 780 list of functions. This list can be changed at run 781 time by the set_ftrace_filter file in the debugfs 782 tracing directory. 783 784 ftrace_notrace=[function-list] 785 [FTRACE] Do not trace the functions specified in 786 function-list. This list can be changed at run time 787 by the set_ftrace_notrace file in the debugfs 788 tracing directory. 789 790 ftrace_graph_filter=[function-list] 791 [FTRACE] Limit the top level callers functions traced 792 by the function graph tracer at boot up. 793 function-list is a comma separated list of functions 794 that can be changed at run time by the 795 set_graph_function file in the debugfs tracing directory. 796 797 gamecon.map[2|3]= 798 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 799 support via parallel port (up to 5 devices per port) 800 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 801 See also Documentation/input/joystick-parport.txt 802 803 gamma= [HW,DRM] 804 805 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 806 Format: off | on 807 default: on 808 809 gcov_persist= [GCOV] When non-zero (default), profiling data for 810 kernel modules is saved and remains accessible via 811 debugfs, even when the module is unloaded/reloaded. 812 When zero, profiling data is discarded and associated 813 debugfs files are removed at module unload time. 814 815 gdth= [HW,SCSI] 816 See header of drivers/scsi/gdth.c. 817 818 gpt [EFI] Forces disk with valid GPT signature but 819 invalid Protective MBR to be treated as GPT. 820 821 gvp11= [HW,SCSI] 822 823 hashdist= [KNL,NUMA] Large hashes allocated during boot 824 are distributed across NUMA nodes. Defaults on 825 for 64bit NUMA, off otherwise. 826 Format: 0 | 1 (for off | on) 827 828 hcl= [IA-64] SGI's Hardware Graph compatibility layer 829 830 hd= [EIDE] (E)IDE hard drive subsystem geometry 831 Format: <cyl>,<head>,<sect> 832 833 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 834 size of <nn>. This works even on boxes that have no 835 highmem otherwise. This also works to reduce highmem 836 size on bigger boxes. 837 838 highres= [KNL] Enable/disable high resolution timer mode. 839 Valid parameters: "on", "off" 840 Default: "on" 841 842 hisax= [HW,ISDN] 843 See Documentation/isdn/README.HiSax. 844 845 hlt [BUGS=ARM,SH] 846 847 hpet= [X86-32,HPET] option to control HPET usage 848 Format: { enable (default) | disable | force | 849 verbose } 850 disable: disable HPET and use PIT instead 851 force: allow force enabled of undocumented chips (ICH4, 852 VIA, nVidia) 853 verbose: show contents of HPET registers during setup 854 855 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 856 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 857 On x86-64 and powerpc, this option can be specified 858 multiple times interleaved with hugepages= to reserve 859 huge pages of different sizes. Valid pages sizes on 860 x86-64 are 2M (when the CPU supports "pse") and 1G 861 (when the CPU supports the "pdpe1gb" cpuinfo flag) 862 Note that 1GB pages can only be allocated at boot time 863 using hugepages= and not freed afterwards. 864 865 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 866 terminal devices. Valid values: 0..8 867 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 868 If specified, z/VM IUCV HVC accepts connections 869 from listed z/VM user IDs only. 870 871 i2c_bus= [HW] Override the default board specific I2C bus speed 872 or register an additional I2C bus that is not 873 registered from board initialization code. 874 Format: 875 <bus_id>,<clkrate> 876 877 i8042.debug [HW] Toggle i8042 debug mode 878 i8042.direct [HW] Put keyboard port into non-translated mode 879 i8042.dumbkbd [HW] Pretend that controller can only read data from 880 keyboard and cannot control its state 881 (Don't attempt to blink the leds) 882 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 883 i8042.nokbd [HW] Don't check/create keyboard port 884 i8042.noloop [HW] Disable the AUX Loopback command while probing 885 for the AUX port 886 i8042.nomux [HW] Don't check presence of an active multiplexing 887 controller 888 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 889 controllers 890 i8042.panicblink= 891 [HW] Frequency with which keyboard LEDs should blink 892 when kernel panics (default is 0.5 sec) 893 i8042.reset [HW] Reset the controller during init and cleanup 894 i8042.unlock [HW] Unlock (ignore) the keylock 895 896 i810= [HW,DRM] 897 898 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 899 indicates that the driver is running on unsupported 900 hardware. 901 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 902 does not match list of supported models. 903 i8k.power_status 904 [HW] Report power status in /proc/i8k 905 (disabled by default) 906 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 907 capability is set. 908 909 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter 910 See Documentation/mca.txt. 911 912 icn= [HW,ISDN] 913 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 914 915 ide-core.nodma= [HW] (E)IDE subsystem 916 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 917 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 918 .cdrom .chs .ignore_cable are additional options 919 See Documentation/ide/ide.txt. 920 921 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 922 Claim all unknown PCI IDE storage controllers. 923 924 idle= [X86] 925 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait 926 Poll forces a polling idle loop that can slightly 927 improve the performance of waking up a idle CPU, but 928 will use a lot of power and make the system run hot. 929 Not recommended. 930 idle=mwait: On systems which support MONITOR/MWAIT but 931 the kernel chose to not use it because it doesn't save 932 as much power as a normal idle loop, use the 933 MONITOR/MWAIT idle loop anyways. Performance should be 934 the same as idle=poll. 935 idle=halt: Halt is forced to be used for CPU idle. 936 In such case C2/C3 won't be used again. 937 idle=nomwait: Disable mwait for CPU C-states 938 939 ignore_loglevel [KNL] 940 Ignore loglevel setting - this will print /all/ 941 kernel messages to the console. Useful for debugging. 942 943 ihash_entries= [KNL] 944 Set number of hash buckets for inode cache. 945 946 ima_audit= [IMA] 947 Format: { "0" | "1" } 948 0 -- integrity auditing messages. (Default) 949 1 -- enable informational integrity auditing messages. 950 951 ima_hash= [IMA] 952 Format: { "sha1" | "md5" } 953 default: "sha1" 954 955 ima_tcb [IMA] 956 Load a policy which meets the needs of the Trusted 957 Computing Base. This means IMA will measure all 958 programs exec'd, files mmap'd for exec, and all files 959 opened for read by uid=0. 960 961 in2000= [HW,SCSI] 962 See header of drivers/scsi/in2000.c. 963 964 init= [KNL] 965 Format: <full_path> 966 Run specified binary instead of /sbin/init as init 967 process. 968 969 initcall_debug [KNL] Trace initcalls as they are executed. Useful 970 for working out where the kernel is dying during 971 startup. 972 973 initrd= [BOOT] Specify the location of the initial ramdisk 974 975 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 976 Format: <irq> 977 978 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 979 on 980 Enable intel iommu driver. 981 off 982 Disable intel iommu driver. 983 igfx_off [Default Off] 984 By default, gfx is mapped as normal device. If a gfx 985 device has a dedicated DMAR unit, the DMAR unit is 986 bypassed by not enabling DMAR with this option. In 987 this case, gfx device will use physical address for 988 DMA. 989 forcedac [x86_64] 990 With this option iommu will not optimize to look 991 for io virtual address below 32 bit forcing dual 992 address cycle on pci bus for cards supporting greater 993 than 32 bit addressing. The default is to look 994 for translation below 32 bit and if not available 995 then look in the higher range. 996 strict [Default Off] 997 With this option on every unmap_single operation will 998 result in a hardware IOTLB flush operation as opposed 999 to batching them for performance. 1000 1001 inttest= [IA64] 1002 1003 iomem= Disable strict checking of access to MMIO memory 1004 strict regions from userspace. 1005 relaxed 1006 1007 iommu= [x86] 1008 off 1009 force 1010 noforce 1011 biomerge 1012 panic 1013 nopanic 1014 merge 1015 nomerge 1016 forcesac 1017 soft 1018 pt [x86, IA64] 1019 1020 io7= [HW] IO7 for Marvel based alpha systems 1021 See comment before marvel_specify_io7 in 1022 arch/alpha/kernel/core_marvel.c. 1023 1024 io_delay= [X86] I/O delay method 1025 0x80 1026 Standard port 0x80 based delay 1027 0xed 1028 Alternate port 0xed based delay (needed on some systems) 1029 udelay 1030 Simple two microseconds delay 1031 none 1032 No delay 1033 1034 ip= [IP_PNP] 1035 See Documentation/filesystems/nfs/nfsroot.txt. 1036 1037 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 1038 See comment before ip2_setup() in 1039 drivers/char/ip2/ip2base.c. 1040 1041 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller 1042 See header of drivers/scsi/ips.c. 1043 1044 irqfixup [HW] 1045 When an interrupt is not handled search all handlers 1046 for it. Intended to get systems with badly broken 1047 firmware running. 1048 1049 irqpoll [HW] 1050 When an interrupt is not handled search all handlers 1051 for it. Also check all handlers each timer 1052 interrupt. Intended to get systems with badly broken 1053 firmware running. 1054 1055 isapnp= [ISAPNP] 1056 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1057 1058 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 1059 Format: 1060 <cpu number>,...,<cpu number> 1061 or 1062 <cpu number>-<cpu number> 1063 (must be a positive range in ascending order) 1064 or a mixture 1065 <cpu number>,...,<cpu number>-<cpu number> 1066 1067 This option can be used to specify one or more CPUs 1068 to isolate from the general SMP balancing and scheduling 1069 algorithms. You can move a process onto or off an 1070 "isolated" CPU via the CPU affinity syscalls or cpuset. 1071 <cpu number> begins at 0 and the maximum value is 1072 "number of CPUs in system - 1". 1073 1074 This option is the preferred way to isolate CPUs. The 1075 alternative -- manually setting the CPU mask of all 1076 tasks in the system -- can cause problems and 1077 suboptimal load balancer performance. 1078 1079 iucv= [HW,NET] 1080 1081 js= [HW,JOY] Analog joystick 1082 See Documentation/input/joystick.txt. 1083 1084 keepinitrd [HW,ARM] 1085 1086 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1087 specifies the amount of memory usable by the kernel 1088 for non-movable allocations. The requested amount is 1089 spread evenly throughout all nodes in the system. The 1090 remaining memory in each node is used for Movable 1091 pages. In the event, a node is too small to have both 1092 kernelcore and Movable pages, kernelcore pages will 1093 take priority and other nodes will have a larger number 1094 of kernelcore pages. The Movable zone is used for the 1095 allocation of pages that may be reclaimed or moved 1096 by the page migration subsystem. This means that 1097 HugeTLB pages may not be allocated from this zone. 1098 Note that allocations like PTEs-from-HighMem still 1099 use the HighMem zone if it exists, and the Normal 1100 zone if it does not. 1101 1102 kgdboc= [HW] kgdb over consoles. 1103 Requires a tty driver that supports console polling. 1104 (only serial supported for now) 1105 Format: <serial_device>[,baud] 1106 1107 kmac= [MIPS] korina ethernet MAC address. 1108 Configure the RouterBoard 532 series on-chip 1109 Ethernet adapter MAC address. 1110 1111 kmemleak= [KNL] Boot-time kmemleak enable/disable 1112 Valid arguments: on, off 1113 Default: on 1114 1115 kstack=N [X86] Print N words from the kernel stack 1116 in oops dumps. 1117 1118 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 1119 Default is 0 (don't ignore, but inject #GP) 1120 1121 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging. 1122 Default is 1 (enabled) 1123 1124 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 1125 Default is 0 (off) 1126 1127 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 1128 for all guests. 1129 Default is 1 (enabled) if in 64bit or 32bit-PAE mode 1130 1131 kvm-intel.bypass_guest_pf= 1132 [KVM,Intel] Disables bypassing of guest page faults 1133 on Intel chips. Default is 1 (enabled) 1134 1135 kvm-intel.ept= [KVM,Intel] Disable extended page tables 1136 (virtualized MMU) support on capable Intel chips. 1137 Default is 1 (enabled) 1138 1139 kvm-intel.emulate_invalid_guest_state= 1140 [KVM,Intel] Enable emulation of invalid guest states 1141 Default is 0 (disabled) 1142 1143 kvm-intel.flexpriority= 1144 [KVM,Intel] Disable FlexPriority feature (TPR shadow). 1145 Default is 1 (enabled) 1146 1147 kvm-intel.unrestricted_guest= 1148 [KVM,Intel] Disable unrestricted guest feature 1149 (virtualized real and unpaged mode) on capable 1150 Intel chips. Default is 1 (enabled) 1151 1152 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 1153 feature (tagged TLBs) on capable Intel chips. 1154 Default is 1 (enabled) 1155 1156 l2cr= [PPC] 1157 1158 l3cr= [PPC] 1159 1160 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1161 disabled it. 1162 1163 lapic_timer_c2_ok [X86,APIC] trust the local apic timer 1164 in C2 power state. 1165 1166 libata.dma= [LIBATA] DMA control 1167 libata.dma=0 Disable all PATA and SATA DMA 1168 libata.dma=1 PATA and SATA Disk DMA only 1169 libata.dma=2 ATAPI (CDROM) DMA only 1170 libata.dma=4 Compact Flash DMA only 1171 Combinations also work, so libata.dma=3 enables DMA 1172 for disks and CDROMs, but not CFs. 1173 1174 libata.ignore_hpa= [LIBATA] Ignore HPA limit 1175 libata.ignore_hpa=0 keep BIOS limits (default) 1176 libata.ignore_hpa=1 ignore limits, using full disk 1177 1178 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1179 when set. 1180 Format: <int> 1181 1182 libata.force= [LIBATA] Force configurations. The format is comma 1183 separated list of "[ID:]VAL" where ID is 1184 PORT[:DEVICE]. PORT and DEVICE are decimal numbers 1185 matching port, link or device. Basically, it matches 1186 the ATA ID string printed on console by libata. If 1187 the whole ID part is omitted, the last PORT and DEVICE 1188 values are used. If ID hasn't been specified yet, the 1189 configuration applies to all ports, links and devices. 1190 1191 If only DEVICE is omitted, the parameter applies to 1192 the port and all links and devices behind it. DEVICE 1193 number of 0 either selects the first device or the 1194 first fan-out link behind PMP device. It does not 1195 select the host link. DEVICE number of 15 selects the 1196 host link and device attached to it. 1197 1198 The VAL specifies the configuration to force. As long 1199 as there's no ambiguity shortcut notation is allowed. 1200 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1201 The following configurations can be forced. 1202 1203 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1204 Any ID with matching PORT is used. 1205 1206 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1207 1208 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1209 udma[/][16,25,33,44,66,100,133] notation is also 1210 allowed. 1211 1212 * [no]ncq: Turn on or off NCQ. 1213 1214 * nohrst, nosrst, norst: suppress hard, soft 1215 and both resets. 1216 1217 If there are multiple matching configurations changing 1218 the same attribute, the last one is used. 1219 1220 lmb=debug [KNL] Enable lmb debug messages. 1221 1222 load_ramdisk= [RAM] List of ramdisks to load from floppy 1223 See Documentation/blockdev/ramdisk.txt. 1224 1225 lockd.nlm_grace_period=P [NFS] Assign grace period. 1226 Format: <integer> 1227 1228 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1229 Format: <integer> 1230 1231 lockd.nlm_timeout=T [NFS] Assign timeout value. 1232 Format: <integer> 1233 1234 lockd.nlm_udpport=M [NFS] Assign UDP port. 1235 Format: <integer> 1236 1237 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1238 Format: <irq> 1239 1240 loglevel= All Kernel Messages with a loglevel smaller than the 1241 console loglevel will be printed to the console. It can 1242 also be changed with klogd or other programs. The 1243 loglevels are defined as follows: 1244 1245 0 (KERN_EMERG) system is unusable 1246 1 (KERN_ALERT) action must be taken immediately 1247 2 (KERN_CRIT) critical conditions 1248 3 (KERN_ERR) error conditions 1249 4 (KERN_WARNING) warning conditions 1250 5 (KERN_NOTICE) normal but significant condition 1251 6 (KERN_INFO) informational 1252 7 (KERN_DEBUG) debug-level messages 1253 1254 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1255 Format: { n | nk | nM } 1256 n must be a power of two. The default size 1257 is set in the kernel config file. 1258 1259 logo.nologo [FB] Disables display of the built-in Linux logo. 1260 This may be used to provide more screen space for 1261 kernel log messages and is useful when debugging 1262 kernel boot problems. 1263 1264 lp=0 [LP] Specify parallel ports to use, e.g, 1265 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1266 lp=reset first parallel port). 'lp=0' disables the 1267 lp=auto printer driver. 'lp=reset' (which can be 1268 specified in addition to the ports) causes 1269 attached printers to be reset. Using 1270 lp=port1,port2,... specifies the parallel ports 1271 to associate lp devices with, starting with 1272 lp0. A port specification may be 'none' to skip 1273 that lp device, or a parport name such as 1274 'parport0'. Specifying 'lp=auto' instead of a 1275 port specification list means that device IDs 1276 from each port should be examined, to see if 1277 an IEEE 1284-compliant printer is attached; if 1278 so, the driver will manage that printer. 1279 See also header of drivers/char/lp.c. 1280 1281 lpj=n [KNL] 1282 Sets loops_per_jiffy to given constant, thus avoiding 1283 time-consuming boot-time autodetection (up to 250 ms per 1284 CPU). 0 enables autodetection (default). To determine 1285 the correct value for your kernel, boot with normal 1286 autodetection and see what value is printed. Note that 1287 on SMP systems the preset will be applied to all CPUs, 1288 which is likely to cause problems if your CPUs need 1289 significantly divergent settings. An incorrect value 1290 will cause delays in the kernel to be wrong, leading to 1291 unpredictable I/O errors and other breakage. Although 1292 unlikely, in the extreme case this might damage your 1293 hardware. 1294 1295 ltpc= [NET] 1296 Format: <io>,<irq>,<dma> 1297 1298 mac5380= [HW,SCSI] Format: 1299 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1300 1301 machvec= [IA64] Force the use of a particular machine-vector 1302 (machvec) in a generic kernel. 1303 Example: machvec=hpzx1_swiotlb 1304 1305 machtype= [Loongson] Share the same kernel image file between different 1306 yeeloong laptop. 1307 Example: machtype=lemote-yeeloong-2f-7inch 1308 1309 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 1310 than or equal to this physical address is ignored. 1311 1312 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1313 should make use of. maxcpus=n : n >= 0 limits the 1314 kernel to using 'n' processors. n=0 is a special case, 1315 it is equivalent to "nosmp", which also disables 1316 the IO APIC. 1317 1318 max_loop= [LOOP] Maximum number of loopback devices that can 1319 be mounted 1320 Format: <1-256> 1321 1322 max_luns= [SCSI] Maximum number of LUNs to probe. 1323 Should be between 1 and 2^32-1. 1324 1325 max_report_luns= 1326 [SCSI] Maximum number of LUNs received. 1327 Should be between 1 and 16384. 1328 1329 mcatest= [IA-64] 1330 1331 mce [X86-32] Machine Check Exception 1332 1333 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 1334 1335 md= [HW] RAID subsystems devices and level 1336 See Documentation/md.txt. 1337 1338 mdacon= [MDA] 1339 Format: <first>,<last> 1340 Specifies range of consoles to be captured by the MDA. 1341 1342 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1343 Amount of memory to be used when the kernel is not able 1344 to see the whole system memory or for test. 1345 [X86-32] Use together with memmap= to avoid physical 1346 address space collisions. Without memmap= PCI devices 1347 could be placed at addresses belonging to unused RAM. 1348 1349 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1350 memory. 1351 1352 memchunk=nn[KMG] 1353 [KNL,SH] Allow user to override the default size for 1354 per-device physically contiguous DMA buffers. 1355 1356 memmap=exactmap [KNL,X86] Enable setting of an exact 1357 E820 memory map, as specified by the user. 1358 Such memmap=exactmap lines can be constructed based on 1359 BIOS output or other requirements. See the memmap=nn@ss 1360 option description. 1361 1362 memmap=nn[KMG]@ss[KMG] 1363 [KNL] Force usage of a specific region of memory 1364 Region of memory to be used, from ss to ss+nn. 1365 1366 memmap=nn[KMG]#ss[KMG] 1367 [KNL,ACPI] Mark specific memory as ACPI data. 1368 Region of memory to be used, from ss to ss+nn. 1369 1370 memmap=nn[KMG]$ss[KMG] 1371 [KNL,ACPI] Mark specific memory as reserved. 1372 Region of memory to be used, from ss to ss+nn. 1373 Example: Exclude memory from 0x18690000-0x1869ffff 1374 memmap=64K$0x18690000 1375 or 1376 memmap=0x10000$0x18690000 1377 1378 memory_corruption_check=0/1 [X86] 1379 Some BIOSes seem to corrupt the first 64k of 1380 memory when doing things like suspend/resume. 1381 Setting this option will scan the memory 1382 looking for corruption. Enabling this will 1383 both detect corruption and prevent the kernel 1384 from using the memory being corrupted. 1385 However, its intended as a diagnostic tool; if 1386 repeatable BIOS-originated corruption always 1387 affects the same memory, you can use memmap= 1388 to prevent the kernel from using that memory. 1389 1390 memory_corruption_check_size=size [X86] 1391 By default it checks for corruption in the low 1392 64k, making this memory unavailable for normal 1393 use. Use this parameter to scan for 1394 corruption in more or less memory. 1395 1396 memory_corruption_check_period=seconds [X86] 1397 By default it checks for corruption every 60 1398 seconds. Use this parameter to check at some 1399 other rate. 0 disables periodic checking. 1400 1401 memtest= [KNL,X86] Enable memtest 1402 Format: <integer> 1403 default : 0 <disable> 1404 Specifies the number of memtest passes to be 1405 performed. Each pass selects another test 1406 pattern from a given set of patterns. Memtest 1407 fills the memory with this pattern, validates 1408 memory contents and reserves bad memory 1409 regions that are detected. 1410 1411 meye.*= [HW] Set MotionEye Camera parameters 1412 See Documentation/video4linux/meye.txt. 1413 1414 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1415 Multi-Function General Purpose Timers on AMD Geode 1416 platforms. 1417 1418 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1419 the BIOS has incorrectly applied a workaround. TinyBIOS 1420 version 0.98 is known to be affected, 0.99 fixes the 1421 problem by letting the user disable the workaround. 1422 1423 mga= [HW,DRM] 1424 1425 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 1426 physical address is ignored. 1427 1428 mini2440= [ARM,HW,KNL] 1429 Format:[0..2][b][c][t] 1430 Default: "0tb" 1431 MINI2440 configuration specification: 1432 0 - The attached screen is the 3.5" TFT 1433 1 - The attached screen is the 7" TFT 1434 2 - The VGA Shield is attached (1024x768) 1435 Leaving out the screen size parameter will not load 1436 the TFT driver, and the framebuffer will be left 1437 unconfigured. 1438 b - Enable backlight. The TFT backlight pin will be 1439 linked to the kernel VESA blanking code and a GPIO 1440 LED. This parameter is not necessary when using the 1441 VGA shield. 1442 c - Enable the s3c camera interface. 1443 t - Reserved for enabling touchscreen support. The 1444 touchscreen support is not enabled in the mainstream 1445 kernel as of 2.6.30, a preliminary port can be found 1446 in the "bleeding edge" mini2440 support kernel at 1447 http://repo.or.cz/w/linux-2.6/mini2440.git 1448 1449 mminit_loglevel= 1450 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1451 parameter allows control of the logging verbosity for 1452 the additional memory initialisation checks. A value 1453 of 0 disables mminit logging and a level of 4 will 1454 log everything. Information is printed at KERN_DEBUG 1455 so loglevel=8 may also need to be specified. 1456 1457 mousedev.tap_time= 1458 [MOUSE] Maximum time between finger touching and 1459 leaving touchpad surface for touch to be considered 1460 a tap and be reported as a left button click (for 1461 touchpads working in absolute mode only). 1462 Format: <msecs> 1463 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1464 reporting absolute coordinates, such as tablets 1465 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1466 reporting absolute coordinates, such as tablets 1467 1468 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1469 is similar to kernelcore except it specifies the 1470 amount of memory used for migratable allocations. 1471 If both kernelcore and movablecore is specified, 1472 then kernelcore will be at *least* the specified 1473 value but may be more. If movablecore on its own 1474 is specified, the administrator must be careful 1475 that the amount of memory usable for all allocations 1476 is not too small. 1477 1478 mpu401= [HW,OSS] 1479 Format: <io>,<irq> 1480 1481 MTD_Partition= [MTD] 1482 Format: <name>,<region-number>,<size>,<offset> 1483 1484 MTD_Region= [MTD] Format: 1485 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1486 1487 mtdparts= [MTD] 1488 See drivers/mtd/cmdlinepart.c. 1489 1490 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 1491 1492 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 1493 1494 boundary - index of last SLC block on Flex-OneNAND. 1495 The remaining blocks are configured as MLC blocks. 1496 lock - Configure if Flex-OneNAND boundary should be locked. 1497 Once locked, the boundary cannot be changed. 1498 1 indicates lock status, 0 indicates unlock status. 1499 1500 mtdset= [ARM] 1501 ARM/S3C2412 JIVE boot control 1502 1503 See arch/arm/mach-s3c2412/mach-jive.c 1504 1505 mtouchusb.raw_coordinates= 1506 [HW] Make the MicroTouch USB driver use raw coordinates 1507 ('y', default) or cooked coordinates ('n') 1508 1509 mtrr_chunk_size=nn[KMG] [X86] 1510 used for mtrr cleanup. It is largest continuous chunk 1511 that could hold holes aka. UC entries. 1512 1513 mtrr_gran_size=nn[KMG] [X86] 1514 Used for mtrr cleanup. It is granularity of mtrr block. 1515 Default is 1. 1516 Large value could prevent small alignment from 1517 using up MTRRs. 1518 1519 mtrr_spare_reg_nr=n [X86] 1520 Format: <integer> 1521 Range: 0,7 : spare reg number 1522 Default : 1 1523 Used for mtrr cleanup. It is spare mtrr entries number. 1524 Set to 2 or more if your graphical card needs more. 1525 1526 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1527 1528 NCR_D700= [HW,SCSI] 1529 See header of drivers/scsi/NCR_D700.c. 1530 1531 ncr5380= [HW,SCSI] 1532 1533 ncr53c400= [HW,SCSI] 1534 1535 ncr53c400a= [HW,SCSI] 1536 1537 ncr53c406a= [HW,SCSI] 1538 1539 ncr53c8xx= [HW,SCSI] 1540 1541 netdev= [NET] Network devices parameters 1542 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1543 Note that mem_start is often overloaded to mean 1544 something different and driver-specific. 1545 This usage is only documented in each driver source 1546 file if at all. 1547 1548 nf_conntrack.acct= 1549 [NETFILTER] Enable connection tracking flow accounting 1550 0 to disable accounting 1551 1 to enable accounting 1552 Default value depends on CONFIG_NF_CT_ACCT that is 1553 going to be removed in 2.6.29. 1554 1555 nfsaddrs= [NFS] 1556 See Documentation/filesystems/nfs/nfsroot.txt. 1557 1558 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1559 See Documentation/filesystems/nfs/nfsroot.txt. 1560 1561 nfs.callback_tcpport= 1562 [NFS] set the TCP port on which the NFSv4 callback 1563 channel should listen. 1564 1565 nfs.cache_getent= 1566 [NFS] sets the pathname to the program which is used 1567 to update the NFS client cache entries. 1568 1569 nfs.cache_getent_timeout= 1570 [NFS] sets the timeout after which an attempt to 1571 update a cache entry is deemed to have failed. 1572 1573 nfs.idmap_cache_timeout= 1574 [NFS] set the maximum lifetime for idmapper cache 1575 entries. 1576 1577 nfs.enable_ino64= 1578 [NFS] enable 64-bit inode numbers. 1579 If zero, the NFS client will fake up a 32-bit inode 1580 number for the readdir() and stat() syscalls instead 1581 of returning the full 64-bit number. 1582 The default is to return 64-bit inode numbers. 1583 1584 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take 1585 when a NMI is triggered. 1586 Format: [state][,regs][,debounce][,die] 1587 1588 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 1589 Format: [panic,][num] 1590 Valid num: 0,1,2 1591 0 - turn nmi_watchdog off 1592 1 - use the IO-APIC timer for the NMI watchdog 1593 2 - use the local APIC for the NMI watchdog using 1594 a performance counter. Note: This will use one 1595 performance counter and the local APIC's performance 1596 vector. 1597 When panic is specified, panic when an NMI watchdog 1598 timeout occurs. 1599 This is useful when you use a panic=... timeout and 1600 need the box quickly up again. 1601 Instead of 1 and 2 it is possible to use the following 1602 symbolic names: lapic and ioapic 1603 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic 1604 1605 netpoll.carrier_timeout= 1606 [NET] Specifies amount of time (in seconds) that 1607 netpoll should wait for a carrier. By default netpoll 1608 waits 4 seconds. 1609 1610 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1611 emulation library even if a 387 maths coprocessor 1612 is present. 1613 1614 no_console_suspend 1615 [HW] Never suspend the console 1616 Disable suspending of consoles during suspend and 1617 hibernate operations. Once disabled, debugging 1618 messages can reach various consoles while the rest 1619 of the system is being put to sleep (ie, while 1620 debugging driver suspend/resume hooks). This may 1621 not work reliably with all consoles, but is known 1622 to work with serial and VGA consoles. 1623 1624 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1625 caches in the slab allocator. Saves per-node memory, 1626 but will impact performance. 1627 1628 noalign [KNL,ARM] 1629 1630 noapic [SMP,APIC] Tells the kernel to not make use of any 1631 IOAPICs that may be present in the system. 1632 1633 nobats [PPC] Do not use BATs for mapping kernel lowmem 1634 on "Classic" PPC cores. 1635 1636 nocache [ARM] 1637 1638 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1639 1640 nodelayacct [KNL] Disable per-task delay accounting 1641 1642 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1643 1644 nodsp [SH] Disable hardware DSP at boot time. 1645 1646 noefi [X86] Disable EFI runtime services support. 1647 1648 noexec [IA-64] 1649 1650 noexec [X86] 1651 On X86-32 available only on PAE configured kernels. 1652 noexec=on: enable non-executable mappings (default) 1653 noexec=off: disable non-executable mappings 1654 1655 noexec32 [X86-64] 1656 This affects only 32-bit executables. 1657 noexec32=on: enable non-executable mappings (default) 1658 read doesn't imply executable mappings 1659 noexec32=off: disable non-executable mappings 1660 read implies executable mappings 1661 1662 nofpu [SH] Disable hardware FPU at boot time. 1663 1664 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1665 register save and restore. The kernel will only save 1666 legacy floating-point registers on task switch. 1667 1668 noxsave [BUGS=X86] Disables x86 extended register state save 1669 and restore using xsave. The kernel will fallback to 1670 enabling legacy floating-point and sse state. 1671 1672 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 1673 wfi(ARM) instruction doesn't work correctly and not to 1674 use it. This is also useful when using JTAG debugger. 1675 1676 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1677 instruction doesn't work correctly and not to 1678 use it. 1679 1680 no_file_caps Tells the kernel not to honor file capabilities. The 1681 only way then for a file to be executed with privilege 1682 is to be setuid root or executed by root. 1683 1684 nohalt [IA-64] Tells the kernel not to use the power saving 1685 function PAL_HALT_LIGHT when idle. This increases 1686 power-consumption. On the positive side, it reduces 1687 interrupt wake-up latency, which may improve performance 1688 in certain environments such as networked servers or 1689 real-time systems. 1690 1691 nohz= [KNL] Boottime enable/disable dynamic ticks 1692 Valid arguments: on, off 1693 Default: on 1694 1695 noiotrap [SH] Disables trapped I/O port accesses. 1696 1697 noirqdebug [X86-32] Disables the code which attempts to detect and 1698 disable unhandled interrupt sources. 1699 1700 no_timer_check [X86,APIC] Disables the code which tests for 1701 broken timer IRQ sources. 1702 1703 noisapnp [ISAPNP] Disables ISA PnP code. 1704 1705 noinitrd [RAM] Tells the kernel not to load any configured 1706 initial RAM disk. 1707 1708 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 1709 remapping. 1710 1711 nointroute [IA-64] 1712 1713 nojitter [IA64] Disables jitter checking for ITC timers. 1714 1715 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1716 1717 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1718 1719 noltlbs [PPC] Do not use large page/tlb entries for kernel 1720 lowmem mapping on PPC40x. 1721 1722 nomca [IA-64] Disable machine check abort handling 1723 1724 nomce [X86-32] Machine Check Exception 1725 1726 nomfgpt [X86-32] Disable Multi-Function General Purpose 1727 Timer usage (for AMD Geode machines). 1728 1729 norandmaps Don't use address space randomization. Equivalent to 1730 echo 0 > /proc/sys/kernel/randomize_va_space 1731 1732 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1733 1734 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1735 with UP alternatives 1736 1737 noresidual [PPC] Don't use residual data on PReP machines. 1738 1739 noresume [SWSUSP] Disables resume and restores original swap 1740 space. 1741 1742 no-scroll [VGA] Disables scrollback. 1743 This is required for the Braillex ib80-piezo Braille 1744 reader made by F.H. Papenmeier (Germany). 1745 1746 nosbagart [IA-64] 1747 1748 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1749 1750 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1751 and disable the IO APIC. legacy for "maxcpus=0". 1752 1753 nosoftlockup [KNL] Disable the soft-lockup detector. 1754 1755 noswapaccount [KNL] Disable accounting of swap in memory resource 1756 controller. (See Documentation/cgroups/memory.txt) 1757 1758 nosync [HW,M68K] Disables sync negotiation for all devices. 1759 1760 notsc [BUGS=X86-32] Disable Time Stamp Counter 1761 1762 nousb [USB] Disable the USB subsystem 1763 1764 nowb [ARM] 1765 1766 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 1767 1768 nptcg= [IA64] Override max number of concurrent global TLB 1769 purges which is reported from either PAL_VM_SUMMARY or 1770 SAL PALO. 1771 1772 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1773 1774 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1775 one of ['zone', 'node', 'default'] can be specified 1776 This can be set from sysctl after boot. 1777 See Documentation/sysctl/vm.txt for details. 1778 1779 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 1780 See Documentation/debugging-via-ohci1394.txt for more 1781 info. 1782 1783 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1784 Rather than timing out after 20 ms if an EC 1785 command is not properly ACKed, override the length 1786 of the timeout. We have interrupts disabled while 1787 waiting for the ACK, so if this is set too high 1788 interrupts *may* be lost! 1789 1790 omap_mux= [OMAP] Override bootloader pin multiplexing. 1791 Format: <mux_mode0.mode_name=value>... 1792 For example, to override I2C bus2: 1793 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 1794 1795 opl3= [HW,OSS] 1796 Format: <io> 1797 1798 oprofile.timer= [HW] 1799 Use timer interrupt instead of performance counters 1800 1801 oprofile.cpu_type= Force an oprofile cpu type 1802 This might be useful if you have an older oprofile 1803 userland or if you want common events. 1804 Format: { arch_perfmon } 1805 arch_perfmon: [X86] Force use of architectural 1806 perfmon on Intel CPUs instead of the 1807 CPU specific event set. 1808 1809 osst= [HW,SCSI] SCSI Tape Driver 1810 Format: <buffer_size>,<write_threshold> 1811 See also Documentation/scsi/st.txt. 1812 1813 panic= [KNL] Kernel behaviour on panic 1814 Format: <timeout> 1815 1816 parkbd.port= [HW] Parallel port number the keyboard adapter is 1817 connected to, default is 0. 1818 Format: <parport#> 1819 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1820 0 for XT, 1 for AT (default is AT). 1821 Format: <mode> 1822 1823 parport= [HW,PPT] Specify parallel ports. 0 disables. 1824 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1825 Use 'auto' to force the driver to use any 1826 IRQ/DMA settings detected (the default is to 1827 ignore detected IRQ/DMA settings because of 1828 possible conflicts). You can specify the base 1829 address, IRQ, and DMA settings; IRQ and DMA 1830 should be numbers, or 'auto' (for using detected 1831 settings on that particular port), or 'nofifo' 1832 (to avoid using a FIFO even if it is detected). 1833 Parallel ports are assigned in the order they 1834 are specified on the command line, starting 1835 with parport0. 1836 1837 parport_init_mode= [HW,PPT] 1838 Configure VIA parallel port to operate in 1839 a specific mode. This is necessary on Pegasos 1840 computer where firmware has no options for setting 1841 up parallel port mode and sets it to spp. 1842 Currently this function knows 686a and 8231 chips. 1843 Format: [spp|ps2|epp|ecp|ecpepp] 1844 1845 pas2= [HW,OSS] Format: 1846 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16> 1847 1848 pas16= [HW,SCSI] 1849 See header of drivers/scsi/pas16.c. 1850 1851 pause_on_oops= 1852 Halt all CPUs after the first oops has been printed for 1853 the specified number of seconds. This is to be used if 1854 your oopses keep scrolling off the screen. 1855 1856 pcbit= [HW,ISDN] 1857 1858 pcd. [PARIDE] 1859 See header of drivers/block/paride/pcd.c. 1860 See also Documentation/blockdev/paride.txt. 1861 1862 pci=option[,option...] [PCI] various PCI subsystem options: 1863 earlydump [X86] dump PCI config space before the kernel 1864 changes anything 1865 off [X86] don't probe for the PCI bus 1866 bios [X86-32] force use of PCI BIOS, don't access 1867 the hardware directly. Use this if your machine 1868 has a non-standard PCI host bridge. 1869 nobios [X86-32] disallow use of PCI BIOS, only direct 1870 hardware access methods are allowed. Use this 1871 if you experience crashes upon bootup and you 1872 suspect they are caused by the BIOS. 1873 conf1 [X86] Force use of PCI Configuration 1874 Mechanism 1. 1875 conf2 [X86] Force use of PCI Configuration 1876 Mechanism 2. 1877 noaer [PCIE] If the PCIEAER kernel config parameter is 1878 enabled, this kernel boot option can be used to 1879 disable the use of PCIE advanced error reporting. 1880 nodomains [PCI] Disable support for multiple PCI 1881 root domains (aka PCI segments, in ACPI-speak). 1882 nommconf [X86] Disable use of MMCONFIG for PCI 1883 Configuration 1884 check_enable_amd_mmconf [X86] check for and enable 1885 properly configured MMIO access to PCI 1886 config space on AMD family 10h CPU 1887 nomsi [MSI] If the PCI_MSI kernel config parameter is 1888 enabled, this kernel boot option can be used to 1889 disable the use of MSI interrupts system-wide. 1890 noioapicquirk [APIC] Disable all boot interrupt quirks. 1891 Safety option to keep boot IRQs enabled. This 1892 should never be necessary. 1893 ioapicreroute [APIC] Enable rerouting of boot IRQs to the 1894 primary IO-APIC for bridges that cannot disable 1895 boot IRQs. This fixes a source of spurious IRQs 1896 when the system masks IRQs. 1897 noioapicreroute [APIC] Disable workaround that uses the 1898 boot IRQ equivalent of an IRQ that connects to 1899 a chipset where boot IRQs cannot be disabled. 1900 The opposite of ioapicreroute. 1901 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1902 routing table. These calls are known to be buggy 1903 on several machines and they hang the machine 1904 when used, but on other computers it's the only 1905 way to get the interrupt routing table. Try 1906 this option if the kernel is unable to allocate 1907 IRQs or discover secondary PCI buses on your 1908 motherboard. 1909 rom [X86] Assign address space to expansion ROMs. 1910 Use with caution as certain devices share 1911 address decoders between ROMs and other 1912 resources. 1913 norom [X86] Do not assign address space to 1914 expansion ROMs that do not already have 1915 BIOS assigned address ranges. 1916 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 1917 assigned automatically to PCI devices. You can 1918 make the kernel exclude IRQs of your ISA cards 1919 this way. 1920 pirqaddr=0xAAAAA [X86] Specify the physical address 1921 of the PIRQ table (normally generated 1922 by the BIOS) if it is outside the 1923 F0000h-100000h range. 1924 lastbus=N [X86] Scan all buses thru bus #N. Can be 1925 useful if the kernel is unable to find your 1926 secondary buses and you want to tell it 1927 explicitly which ones they are. 1928 assign-busses [X86] Always assign all PCI bus 1929 numbers ourselves, overriding 1930 whatever the firmware may have done. 1931 usepirqmask [X86] Honor the possible IRQ mask stored 1932 in the BIOS $PIR table. This is needed on 1933 some systems with broken BIOSes, notably 1934 some HP Pavilion N5400 and Omnibook XE3 1935 notebooks. This will have no effect if ACPI 1936 IRQ routing is enabled. 1937 noacpi [X86] Do not use ACPI for IRQ routing 1938 or for PCI scanning. 1939 use_crs [X86] Use _CRS for PCI resource 1940 allocation. 1941 routeirq Do IRQ routing for all PCI devices. 1942 This is normally done in pci_enable_device(), 1943 so this option is a temporary workaround 1944 for broken drivers that don't call it. 1945 skip_isa_align [X86] do not align io start addr, so can 1946 handle more pci cards 1947 firmware [ARM] Do not re-enumerate the bus but instead 1948 just use the configuration from the 1949 bootloader. This is currently used on 1950 IXP2000 systems where the bus has to be 1951 configured a certain way for adjunct CPUs. 1952 noearly [X86] Don't do any early type 1 scanning. 1953 This might help on some broken boards which 1954 machine check when some devices' config space 1955 is read. But various workarounds are disabled 1956 and some IOMMU drivers will not work. 1957 bfsort Sort PCI devices into breadth-first order. 1958 This sorting is done to get a device 1959 order compatible with older (<= 2.4) kernels. 1960 nobfsort Don't sort PCI devices into breadth-first order. 1961 cbiosize=nn[KMG] The fixed amount of bus space which is 1962 reserved for the CardBus bridge's IO window. 1963 The default value is 256 bytes. 1964 cbmemsize=nn[KMG] The fixed amount of bus space which is 1965 reserved for the CardBus bridge's memory 1966 window. The default value is 64 megabytes. 1967 resource_alignment= 1968 Format: 1969 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] 1970 Specifies alignment and device to reassign 1971 aligned memory resources. 1972 If <order of align> is not specified, 1973 PAGE_SIZE is used as alignment. 1974 PCI-PCI bridge can be specified, if resource 1975 windows need to be expanded. 1976 ecrc= Enable/disable PCIe ECRC (transaction layer 1977 end-to-end CRC checking). 1978 bios: Use BIOS/firmware settings. This is the 1979 the default. 1980 off: Turn ECRC off 1981 on: Turn ECRC on. 1982 1983 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 1984 Management. 1985 off Disable ASPM. 1986 force Enable ASPM even on devices that claim not to support it. 1987 WARNING: Forcing ASPM on may cause system lockups. 1988 1989 pcmv= [HW,PCMCIA] BadgePAD 4 1990 1991 pd. [PARIDE] 1992 See Documentation/blockdev/paride.txt. 1993 1994 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 1995 boot time. 1996 Format: { 0 | 1 } 1997 See arch/parisc/kernel/pdc_chassis.c 1998 1999 percpu_alloc= Select which percpu first chunk allocator to use. 2000 Currently supported values are "embed" and "page". 2001 Archs may support subset or none of the selections. 2002 See comments in mm/percpu.c for details on each 2003 allocator. This parameter is primarily for debugging 2004 and performance comparison. 2005 2006 pf. [PARIDE] 2007 See Documentation/blockdev/paride.txt. 2008 2009 pg. [PARIDE] 2010 See Documentation/blockdev/paride.txt. 2011 2012 pirq= [SMP,APIC] Manual mp-table setup 2013 See Documentation/x86/i386/IO-APIC.txt. 2014 2015 plip= [PPT,NET] Parallel port network link 2016 Format: { parport<nr> | timid | 0 } 2017 See also Documentation/parport.txt. 2018 2019 pmtmr= [X86] Manual setup of pmtmr I/O Port. 2020 Override pmtimer IOPort with a hex value. 2021 e.g. pmtmr=0x508 2022 2023 pnp.debug [PNP] 2024 Enable PNP debug messages. This depends on the 2025 CONFIG_PNP_DEBUG_MESSAGES option. 2026 2027 pnpacpi= [ACPI] 2028 { off } 2029 2030 pnpbios= [ISAPNP] 2031 { on | off | curr | res | no-curr | no-res } 2032 2033 pnp_reserve_irq= 2034 [ISAPNP] Exclude IRQs for the autoconfiguration 2035 2036 pnp_reserve_dma= 2037 [ISAPNP] Exclude DMAs for the autoconfiguration 2038 2039 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 2040 Ranges are in pairs (I/O port base and size). 2041 2042 pnp_reserve_mem= 2043 [ISAPNP] Exclude memory regions for the 2044 autoconfiguration. 2045 Ranges are in pairs (memory base and size). 2046 2047 ports= [IP_VS_FTP] IPVS ftp helper module 2048 Default is 21. 2049 Up to 8 (IP_VS_APP_MAX_PORTS) ports 2050 may be specified. 2051 Format: <port>,<port>.... 2052 2053 print-fatal-signals= 2054 [KNL] debug: print fatal signals 2055 2056 If enabled, warn about various signal handling 2057 related application anomalies: too many signals, 2058 too many POSIX.1 timers, fatal signals causing a 2059 coredump - etc. 2060 2061 If you hit the warning due to signal overflow, 2062 you might want to try "ulimit -i unlimited". 2063 2064 default: off. 2065 2066 printk.time= Show timing data prefixed to each printk message line 2067 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 2068 2069 processor.max_cstate= [HW,ACPI] 2070 Limit processor to maximum C-state 2071 max_cstate=9 overrides any DMI blacklist limit. 2072 2073 processor.nocst [HW,ACPI] 2074 Ignore the _CST method to determine C-states, 2075 instead using the legacy FADT method 2076 2077 profile= [KNL] Enable kernel profiling via /proc/profile 2078 Format: [schedule,]<number> 2079 Param: "schedule" - profile schedule points. 2080 Param: <number> - step/bucket size as a power of 2 for 2081 statistical time based profiling. 2082 Param: "sleep" - profile D-state sleeping (millisecs). 2083 Requires CONFIG_SCHEDSTATS 2084 Param: "kvm" - profile VM exits. 2085 2086 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 2087 before loading. 2088 See Documentation/blockdev/ramdisk.txt. 2089 2090 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 2091 probe for; one of (bare|imps|exps|lifebook|any). 2092 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 2093 per second. 2094 psmouse.resetafter= [HW,MOUSE] 2095 Try to reset the device after so many bad packets 2096 (0 = never). 2097 psmouse.resolution= 2098 [HW,MOUSE] Set desired mouse resolution, in dpi. 2099 psmouse.smartscroll= 2100 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 2101 0 = disabled, 1 = enabled (default). 2102 2103 pss= [HW,OSS] Personal Sound System (ECHO ESC614) 2104 Format: 2105 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq> 2106 2107 pt. [PARIDE] 2108 See Documentation/blockdev/paride.txt. 2109 2110 pty.legacy_count= 2111 [KNL] Number of legacy pty's. Overwrites compiled-in 2112 default number. 2113 2114 quiet [KNL] Disable most log messages 2115 2116 r128= [HW,DRM] 2117 2118 raid= [HW,RAID] 2119 See Documentation/md.txt. 2120 2121 ramdisk_blocksize= [RAM] 2122 See Documentation/blockdev/ramdisk.txt. 2123 2124 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 2125 See Documentation/blockdev/ramdisk.txt. 2126 2127 rcupdate.blimit= [KNL,BOOT] 2128 Set maximum number of finished RCU callbacks to process 2129 in one batch. 2130 2131 rcupdate.qhimark= [KNL,BOOT] 2132 Set threshold of queued 2133 RCU callbacks over which batch limiting is disabled. 2134 2135 rcupdate.qlowmark= [KNL,BOOT] 2136 Set threshold of queued RCU callbacks below which 2137 batch limiting is re-enabled. 2138 2139 rdinit= [KNL] 2140 Format: <full_path> 2141 Run specified binary instead of /init from the ramdisk, 2142 used for early userspace startup. See initrd. 2143 2144 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 2145 Format: <reboot_mode>[,<reboot_mode2>[,...]] 2146 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 2147 2148 relax_domain_level= 2149 [KNL, SMP] Set scheduler's default relax_domain_level. 2150 See Documentation/cgroups/cpusets.txt. 2151 2152 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 2153 2154 reservetop= [X86-32] 2155 Format: nn[KMG] 2156 Reserves a hole at the top of the kernel virtual 2157 address space. 2158 2159 reset_devices [KNL] Force drivers to reset the underlying device 2160 during initialization. 2161 2162 resume= [SWSUSP] 2163 Specify the partition device for software suspend 2164 2165 resume_offset= [SWSUSP] 2166 Specify the offset from the beginning of the partition 2167 given by "resume=" at which the swap header is located, 2168 in <PAGE_SIZE> units (needed only for swap files). 2169 See Documentation/power/swsusp-and-swap-files.txt 2170 2171 retain_initrd [RAM] Keep initrd memory after extraction 2172 2173 rhash_entries= [KNL,NET] 2174 Set number of hash buckets for route cache 2175 2176 riscom8= [HW,SERIAL] 2177 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 2178 2179 ro [KNL] Mount root device read-only on boot 2180 2181 root= [KNL] Root filesystem 2182 2183 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 2184 mount the root filesystem 2185 2186 rootflags= [KNL] Set root filesystem mount option string 2187 2188 rootfstype= [KNL] Set root filesystem type 2189 2190 rootwait [KNL] Wait (indefinitely) for root device to show up. 2191 Useful for devices that are detected asynchronously 2192 (e.g. USB and MMC devices). 2193 2194 rw [KNL] Mount root device read-write on boot 2195 2196 S [KNL] Run init in single mode 2197 2198 sa1100ir [NET] 2199 See drivers/net/irda/sa1100_ir.c. 2200 2201 sbni= [NET] Granch SBNI12 leased line adapter 2202 2203 sched_debug [KNL] Enables verbose scheduler debug messages. 2204 2205 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver 2206 Format: <io>[,<timeout>[,<isapnp>]] 2207 2208 scsi_debug_*= [SCSI] 2209 See drivers/scsi/scsi_debug.c. 2210 2211 scsi_default_dev_flags= 2212 [SCSI] SCSI default device flags 2213 Format: <integer> 2214 2215 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model 2216 Format: <vendor>:<model>:<flags> 2217 (flags are integer value) 2218 2219 scsi_logging_level= [SCSI] a bit mask of logging levels 2220 See drivers/scsi/scsi_logging.h for bits. Also 2221 settable via sysctl at dev.scsi.logging_level 2222 (/proc/sys/dev/scsi/logging_level). 2223 There is also a nice 'scsi_logging_level' script in the 2224 S390-tools package, available for download at 2225 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html 2226 2227 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are 2228 discovered. async scans them in kernel threads, 2229 allowing boot to proceed. none ignores them, expecting 2230 user space to do the scan. 2231 2232 security= [SECURITY] Choose a security module to enable at boot. 2233 If this boot parameter is not specified, only the first 2234 security module asking for security registration will be 2235 loaded. An invalid security module name will be treated 2236 as if no module has been chosen. 2237 2238 selinux= [SELINUX] Disable or enable SELinux at boot time. 2239 Format: { "0" | "1" } 2240 See security/selinux/Kconfig help text. 2241 0 -- disable. 2242 1 -- enable. 2243 Default value is set via kernel config option. 2244 If enabled at boot time, /selinux/disable can be used 2245 later to disable prior to initial policy load. 2246 2247 serialnumber [BUGS=X86-32] 2248 2249 shapers= [NET] 2250 Maximal number of shapers. 2251 2252 show_msr= [x86] show boot-time MSR settings 2253 Format: { <integer> } 2254 Show boot-time (BIOS-initialized) MSR settings. 2255 The parameter means the number of CPUs to show, 2256 for example 1 means boot CPU only. 2257 2258 sim710= [SCSI,HW] 2259 See header of drivers/scsi/sim710.c. 2260 2261 simeth= [IA-64] 2262 simscsi= 2263 2264 slram= [HW,MTD] 2265 2266 slub_debug[=options[,slabs]] [MM, SLUB] 2267 Enabling slub_debug allows one to determine the 2268 culprit if slab objects become corrupted. Enabling 2269 slub_debug can create guard zones around objects and 2270 may poison objects when not in use. Also tracks the 2271 last alloc / free. For more information see 2272 Documentation/vm/slub.txt. 2273 2274 slub_max_order= [MM, SLUB] 2275 Determines the maximum allowed order for slabs. 2276 A high setting may cause OOMs due to memory 2277 fragmentation. For more information see 2278 Documentation/vm/slub.txt. 2279 2280 slub_min_objects= [MM, SLUB] 2281 The minimum number of objects per slab. SLUB will 2282 increase the slab order up to slub_max_order to 2283 generate a sufficiently large slab able to contain 2284 the number of objects indicated. The higher the number 2285 of objects the smaller the overhead of tracking slabs 2286 and the less frequently locks need to be acquired. 2287 For more information see Documentation/vm/slub.txt. 2288 2289 slub_min_order= [MM, SLUB] 2290 Determines the mininum page order for slabs. Must be 2291 lower than slub_max_order. 2292 For more information see Documentation/vm/slub.txt. 2293 2294 slub_nomerge [MM, SLUB] 2295 Disable merging of slabs with similar size. May be 2296 necessary if there is some reason to distinguish 2297 allocs to different slabs. Debug options disable 2298 merging on their own. 2299 For more information see Documentation/vm/slub.txt. 2300 2301 smart2= [HW] 2302 Format: <io1>[,<io2>[,...,<io8>]] 2303 2304 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 2305 attempt to substitute SMP alternatives once at boot. 2306 2307 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 2308 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 2309 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 2310 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 2311 smsc-ircc2.ircc_irq= [HW] IRQ line 2312 smsc-ircc2.ircc_dma= [HW] DMA channel 2313 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 2314 0: Toshiba Satellite 1800 (GP data pin select) 2315 1: Fast pin select (default) 2316 2: ATC IRMode 2317 2318 snd-ad1816a= [HW,ALSA] 2319 2320 snd-ad1848= [HW,ALSA] 2321 2322 snd-ali5451= [HW,ALSA] 2323 2324 snd-als100= [HW,ALSA] 2325 2326 snd-als4000= [HW,ALSA] 2327 2328 snd-azt2320= [HW,ALSA] 2329 2330 snd-cmi8330= [HW,ALSA] 2331 2332 snd-cmipci= [HW,ALSA] 2333 2334 snd-cs4231= [HW,ALSA] 2335 2336 snd-cs4232= [HW,ALSA] 2337 2338 snd-cs4236= [HW,ALSA] 2339 2340 snd-cs4281= [HW,ALSA] 2341 2342 snd-cs46xx= [HW,ALSA] 2343 2344 snd-dt019x= [HW,ALSA] 2345 2346 snd-dummy= [HW,ALSA] 2347 2348 snd-emu10k1= [HW,ALSA] 2349 2350 snd-ens1370= [HW,ALSA] 2351 2352 snd-ens1371= [HW,ALSA] 2353 2354 snd-es968= [HW,ALSA] 2355 2356 snd-es1688= [HW,ALSA] 2357 2358 snd-es18xx= [HW,ALSA] 2359 2360 snd-es1938= [HW,ALSA] 2361 2362 snd-es1968= [HW,ALSA] 2363 2364 snd-fm801= [HW,ALSA] 2365 2366 snd-gusclassic= [HW,ALSA] 2367 2368 snd-gusextreme= [HW,ALSA] 2369 2370 snd-gusmax= [HW,ALSA] 2371 2372 snd-hdsp= [HW,ALSA] 2373 2374 snd-ice1712= [HW,ALSA] 2375 2376 snd-intel8x0= [HW,ALSA] 2377 2378 snd-interwave= [HW,ALSA] 2379 2380 snd-interwave-stb= 2381 [HW,ALSA] 2382 2383 snd-korg1212= [HW,ALSA] 2384 2385 snd-maestro3= [HW,ALSA] 2386 2387 snd-mpu401= [HW,ALSA] 2388 2389 snd-mtpav= [HW,ALSA] 2390 2391 snd-nm256= [HW,ALSA] 2392 2393 snd-opl3sa2= [HW,ALSA] 2394 2395 snd-opti92x-ad1848= 2396 [HW,ALSA] 2397 2398 snd-opti92x-cs4231= 2399 [HW,ALSA] 2400 2401 snd-opti93x= [HW,ALSA] 2402 2403 snd-pmac= [HW,ALSA] 2404 2405 snd-rme32= [HW,ALSA] 2406 2407 snd-rme96= [HW,ALSA] 2408 2409 snd-rme9652= [HW,ALSA] 2410 2411 snd-sb8= [HW,ALSA] 2412 2413 snd-sb16= [HW,ALSA] 2414 2415 snd-sbawe= [HW,ALSA] 2416 2417 snd-serial= [HW,ALSA] 2418 2419 snd-sgalaxy= [HW,ALSA] 2420 2421 snd-sonicvibes= [HW,ALSA] 2422 2423 snd-sun-amd7930= 2424 [HW,ALSA] 2425 2426 snd-sun-cs4231= [HW,ALSA] 2427 2428 snd-trident= [HW,ALSA] 2429 2430 snd-usb-audio= [HW,ALSA,USB] 2431 2432 snd-via82xx= [HW,ALSA] 2433 2434 snd-virmidi= [HW,ALSA] 2435 2436 snd-wavefront= [HW,ALSA] 2437 2438 snd-ymfpci= [HW,ALSA] 2439 2440 softlockup_panic= 2441 [KNL] Should the soft-lockup detector generate panics. 2442 2443 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2444 See Documentation/sonypi.txt 2445 2446 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2447 See Documentation/serial/specialix.txt. 2448 2449 spia_io_base= [HW,MTD] 2450 spia_fio_base= 2451 spia_pedr= 2452 spia_peddr= 2453 2454 sscape= [HW,OSS] 2455 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq> 2456 2457 st= [HW,SCSI] SCSI tape parameters (buffers, etc.) 2458 See Documentation/scsi/st.txt. 2459 2460 stacktrace [FTRACE] 2461 Enabled the stack tracer on boot up. 2462 2463 sti= [PARISC,HW] 2464 Format: <num> 2465 Set the STI (builtin display/keyboard on the HP-PARISC 2466 machines) console (graphic card) which should be used 2467 as the initial boot-console. 2468 See also comment in drivers/video/console/sticore.c. 2469 2470 sti_font= [HW] 2471 See comment in drivers/video/console/sticore.c. 2472 2473 stifb= [HW] 2474 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2475 2476 sunrpc.min_resvport= 2477 sunrpc.max_resvport= 2478 [NFS,SUNRPC] 2479 SunRPC servers often require that client requests 2480 originate from a privileged port (i.e. a port in the 2481 range 0 < portnr < 1024). 2482 An administrator who wishes to reserve some of these 2483 ports for other uses may adjust the range that the 2484 kernel's sunrpc client considers to be privileged 2485 using these two parameters to set the minimum and 2486 maximum port values. 2487 2488 sunrpc.pool_mode= 2489 [NFS] 2490 Control how the NFS server code allocates CPUs to 2491 service thread pools. Depending on how many NICs 2492 you have and where their interrupts are bound, this 2493 option will affect which CPUs will do NFS serving. 2494 Note: this parameter cannot be changed while the 2495 NFS server is running. 2496 2497 auto the server chooses an appropriate mode 2498 automatically using heuristics 2499 global a single global pool contains all CPUs 2500 percpu one pool for each CPU 2501 pernode one pool for each NUMA node (equivalent 2502 to global on non-NUMA machines) 2503 2504 sunrpc.tcp_slot_table_entries= 2505 sunrpc.udp_slot_table_entries= 2506 [NFS,SUNRPC] 2507 Sets the upper limit on the number of simultaneous 2508 RPC calls that can be sent from the client to a 2509 server. Increasing these values may allow you to 2510 improve throughput, but will also increase the 2511 amount of memory reserved for use by the client. 2512 2513 swiotlb= [IA-64] Number of I/O TLB slabs 2514 2515 switches= [HW,M68k] 2516 2517 sym53c416= [HW,SCSI] 2518 See header of drivers/scsi/sym53c416.c. 2519 2520 sysrq_always_enabled 2521 [KNL] 2522 Ignore sysrq setting - this boot parameter will 2523 neutralize any effect of /proc/sys/kernel/sysrq. 2524 Useful for debugging. 2525 2526 t128= [HW,SCSI] 2527 See header of drivers/scsi/t128.c. 2528 2529 tdfx= [HW,DRM] 2530 2531 test_suspend= [SUSPEND] 2532 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2533 standby suspend) as the system sleep state to briefly 2534 enter during system startup. The system is woken from 2535 this state using a wakeup-capable RTC alarm. 2536 2537 thash_entries= [KNL,NET] 2538 Set number of hash buckets for TCP connection 2539 2540 thermal.act= [HW,ACPI] 2541 -1: disable all active trip points in all thermal zones 2542 <degrees C>: override all lowest active trip points 2543 2544 thermal.crt= [HW,ACPI] 2545 -1: disable all critical trip points in all thermal zones 2546 <degrees C>: override all critical trip points 2547 2548 thermal.nocrt= [HW,ACPI] 2549 Set to disable actions on ACPI thermal zone 2550 critical and hot trip points. 2551 2552 thermal.off= [HW,ACPI] 2553 1: disable ACPI thermal control 2554 2555 thermal.psv= [HW,ACPI] 2556 -1: disable all passive trip points 2557 <degrees C>: override all passive trip points to this 2558 value 2559 2560 thermal.tzp= [HW,ACPI] 2561 Specify global default ACPI thermal zone polling rate 2562 <deci-seconds>: poll all this frequency 2563 0: no polling (default) 2564 2565 tmscsim= [HW,SCSI] 2566 See comment before function dc390_setup() in 2567 drivers/scsi/tmscsim.c. 2568 2569 topology= [S390] 2570 Format: {off | on} 2571 Specify if the kernel should make use of the cpu 2572 topology informations if the hardware supports these. 2573 The scheduler will make use of these informations and 2574 e.g. base its process migration decisions on it. 2575 Default is off. 2576 2577 tp720= [HW,PS2] 2578 2579 trace_buf_size=nn[KMG] 2580 [FTRACE] will set tracing buffer size. 2581 2582 trace_event=[event-list] 2583 [FTRACE] Set and start specified trace events in order 2584 to facilitate early boot debugging. 2585 See also Documentation/trace/events.txt 2586 2587 trix= [HW,OSS] MediaTrix AudioTrix Pro 2588 Format: 2589 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq> 2590 2591 tsc= Disable clocksource-must-verify flag for TSC. 2592 Format: <string> 2593 [x86] reliable: mark tsc clocksource as reliable, this 2594 disables clocksource verification at runtime. 2595 Used to enable high-resolution timer mode on older 2596 hardware, and in virtualized environment. 2597 2598 turbografx.map[2|3]= [HW,JOY] 2599 TurboGraFX parallel port interface 2600 Format: 2601 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2602 See also Documentation/input/joystick-parport.txt 2603 2604 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter 2605 See header of drivers/scsi/u14-34f.c. 2606 2607 uart401= [HW,OSS] 2608 Format: <io>,<irq> 2609 2610 uart6850= [HW,OSS] 2611 Format: <io>,<irq> 2612 2613 uhash_entries= [KNL,NET] 2614 Set number of hash buckets for UDP/UDP-Lite connections 2615 2616 uhci-hcd.ignore_oc= 2617 [USB] Ignore overcurrent events (default N). 2618 Some badly-designed motherboards generate lots of 2619 bogus events, for ports that aren't wired to 2620 anything. Set this parameter to avoid log spamming. 2621 Note that genuine overcurrent events won't be 2622 reported either. 2623 2624 unknown_nmi_panic 2625 [X86] 2626 Set unknown_nmi_panic=1 early on boot. 2627 2628 usbcore.autosuspend= 2629 [USB] The autosuspend time delay (in seconds) used 2630 for newly-detected USB devices (default 2). This 2631 is the time required before an idle device will be 2632 autosuspended. Devices for which the delay is set 2633 to a negative value won't be autosuspended at all. 2634 2635 usbcore.usbfs_snoop= 2636 [USB] Set to log all usbfs traffic (default 0 = off). 2637 2638 usbcore.blinkenlights= 2639 [USB] Set to cycle leds on hubs (default 0 = off). 2640 2641 usbcore.old_scheme_first= 2642 [USB] Start with the old device initialization 2643 scheme (default 0 = off). 2644 2645 usbcore.use_both_schemes= 2646 [USB] Try the other device initialization scheme 2647 if the first one fails (default 1 = enabled). 2648 2649 usbcore.initial_descriptor_timeout= 2650 [USB] Specifies timeout for the initial 64-byte 2651 USB_REQ_GET_DESCRIPTOR request in milliseconds 2652 (default 5000 = 5.0 seconds). 2653 2654 usbhid.mousepoll= 2655 [USBHID] The interval which mice are to be polled at. 2656 2657 usb-storage.delay_use= 2658 [UMS] The delay in seconds before a new device is 2659 scanned for Logical Units (default 5). 2660 2661 usb-storage.quirks= 2662 [UMS] A list of quirks entries to supplement or 2663 override the built-in unusual_devs list. List 2664 entries are separated by commas. Each entry has 2665 the form VID:PID:Flags where VID and PID are Vendor 2666 and Product ID values (4-digit hex numbers) and 2667 Flags is a set of characters, each corresponding 2668 to a common usb-storage quirk flag as follows: 2669 a = SANE_SENSE (collect more than 18 bytes 2670 of sense data); 2671 b = BAD_SENSE (don't collect more than 18 2672 bytes of sense data); 2673 c = FIX_CAPACITY (decrease the reported 2674 device capacity by one sector); 2675 h = CAPACITY_HEURISTICS (decrease the 2676 reported device capacity by one 2677 sector if the number is odd); 2678 i = IGNORE_DEVICE (don't bind to this 2679 device); 2680 l = NOT_LOCKABLE (don't try to lock and 2681 unlock ejectable media); 2682 m = MAX_SECTORS_64 (don't transfer more 2683 than 64 sectors = 32 KB at a time); 2684 o = CAPACITY_OK (accept the capacity 2685 reported by the device); 2686 r = IGNORE_RESIDUE (the device reports 2687 bogus residue values); 2688 s = SINGLE_LUN (the device has only one 2689 Logical Unit); 2690 w = NO_WP_DETECT (don't test whether the 2691 medium is write-protected). 2692 Example: quirks=0419:aaf5:rl,0421:0433:rc 2693 2694 vdso= [X86,SH] 2695 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2696 vdso=1: enable VDSO (default) 2697 vdso=0: disable VDSO mapping 2698 2699 vdso32= [X86] 2700 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2701 vdso32=1: enable 32-bit VDSO (default) 2702 vdso32=0: disable 32-bit VDSO mapping 2703 2704 vector= [IA-64,SMP] 2705 vector=percpu: enable percpu vector domain 2706 2707 video= [FB] Frame buffer configuration 2708 See Documentation/fb/modedb.txt. 2709 2710 vga= [BOOT,X86-32] Select a particular video mode 2711 See Documentation/x86/boot.txt and 2712 Documentation/svga.txt. 2713 Use vga=ask for menu. 2714 This is actually a boot loader parameter; the value is 2715 passed to the kernel using a special protocol. 2716 2717 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2718 size of <nn>. This can be used to increase the 2719 minimum size (128MB on x86). It can also be used to 2720 decrease the size and leave more room for directly 2721 mapped kernel RAM. 2722 2723 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2724 Format: <command> 2725 2726 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2727 Format: <command> 2728 2729 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2730 Format: <command> 2731 2732 vt.cur_default= [VT] Default cursor shape. 2733 Format: 0xCCBBAA, where AA, BB, and CC are the same as 2734 the parameters of the <Esc>[?A;B;Cc escape sequence; 2735 see VGA-softcursor.txt. Default: 2 = underline. 2736 2737 vt.default_blu= [VT] 2738 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 2739 Change the default blue palette of the console. 2740 This is a 16-member array composed of values 2741 ranging from 0-255. 2742 2743 vt.default_grn= [VT] 2744 Format: <green0>,<green1>,<green2>,...,<green15> 2745 Change the default green palette of the console. 2746 This is a 16-member array composed of values 2747 ranging from 0-255. 2748 2749 vt.default_red= [VT] 2750 Format: <red0>,<red1>,<red2>,...,<red15> 2751 Change the default red palette of the console. 2752 This is a 16-member array composed of values 2753 ranging from 0-255. 2754 2755 vt.default_utf8= 2756 [VT] 2757 Format=<0|1> 2758 Set system-wide default UTF-8 mode for all tty's. 2759 Default is 1, i.e. UTF-8 mode is enabled for all 2760 newly opened terminals. 2761 2762 vt.global_cursor_default= 2763 [VT] 2764 Format=<-1|0|1> 2765 Set system-wide default for whether a cursor 2766 is shown on new VTs. Default is -1, 2767 i.e. cursors will be created by default unless 2768 overridden by individual drivers. 0 will hide 2769 cursors, 1 will display them. 2770 2771 waveartist= [HW,OSS] 2772 Format: <io>,<irq>,<dma>,<dma2> 2773 2774 wd33c93= [HW,SCSI] 2775 See header of drivers/scsi/wd33c93.c. 2776 2777 wd7000= [HW,SCSI] 2778 See header of drivers/scsi/wd7000.c. 2779 2780 wdt= [WDT] Watchdog 2781 See Documentation/watchdog/wdt.txt. 2782 2783 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 2784 default x2apic cluster mode on platforms 2785 supporting x2apic. 2786 2787 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2788 xd_geo= See header of drivers/block/xd.c. 2789 2790 xirc2ps_cs= [NET,PCMCIA] 2791 Format: 2792 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2793 2794______________________________________________________________________ 2795 2796TODO: 2797 2798 Add documentation for ALSA options. 2799 Add more DRM drivers.