Difference between revisions of "Kernel parameters"

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Some aspects of the Linux kernels behaviour are controllable via so called kernel parameters. These are parameters similar to the ones that you would provide for a command like ls or cp in a shell, only that they are appended to the kernel/image line in your bootmanagers config file (for lilo this would typically be {{path|/etc/lilo.conf}}, for grub it would be {{path|/boot/grub/menu.lst}}).
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Some aspects of the Linux kernels behaviour are controllable via so called kernel parameters. These are parameters similar to the ones that you would provide for a command like {{cmduser|ls}} or {{cmduser|cp}} in a shell, only that they are appended to the kernel/image line in your bootmanagers config file (for lilo this would typically be {{path|/etc/lilo.conf}}, for grub it would be {{path|/boot/grub/menu.lst}}).
  
 
An example line from grub could look like this:
 
An example line from grub could look like this:
Line 12: Line 12:
 
! parameter !! description
 
! parameter !! description
 
|-
 
|-
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| acpi=off || disables ACPI (keeps it from overriding APM)
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| {{bootparm|acpi|off}} || disables ACPI (keeps it from overriding APM)
 
|-
 
|-
−
| acpi_sleep=s3_bios || makes the system call the video BIOS to reenable video on resume from suspend-to-ram (use this if you experience a blank display after resume while your system seems elsewise awake)
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| {{bootparm|acpi_sleep|s3_bios}} || makes the system call the video BIOS to reenable video on resume from suspend-to-ram (use this if you experience a blank display after resume while your system seems elsewise awake)
 
|-
 
|-
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| idebus=66 || set IDE bus speed to 66 MHz (66 is maximum supported)
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| {{bootparm|hda|noprobe}} || Sometimes needed for DMA support for system hard disk on recent models (see [[Problems_with_SATA_and_Linux##No_DMA_on_system_hard_disk|Problems with SATA and Linux]])
 
|-
 
|-
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| nolapic || tells the kernel not to use the local APIC (use if you have problems with ACPI)
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| {{bootparm|hdc|noprobe}}<br />{{bootparm|libata.atapi_enabled|1}} || Sometimes needed for DMA support for the optical drive on recent models (see [[Problems_with_SATA_and_Linux#No_DMA_on_DVD_drive|Problems with SATA and Linux]])
 
|-
 
|-
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| noresume || boots without resuming after a suspend-to-disk
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| {{bootparm|idebus|66}} || set IDE bus speed to 66 MHz (66 is maximum supported)
 
|-
 
|-
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| resume=/dev/hdaX || tells the kernel where to find the suspend-to-disk image to resume from
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| {{bootparm|nolapic|}} || tells the kernel not to use the local APIC (use if you have problems with ACPI)
 
|-
 
|-
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| root=/dev/hdaX || tells the kernel where to find the root filesystem
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| {{bootparm|lapic|}} || tells the kernel to use the local APIC, even when it is disabled by the BIOS (older models like a T42 or R51 don't have this option in the BIOS and don't enable the local APIC)
 
|-
 
|-
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| speedstep_coppermine=??? || supposed to tell the kernel that you have a speedstep capable coppermine processor, but could possibly not work anymore with newer kernels
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| {{bootparm|noresume|}}<br />{{bootparm|noresume2|}} || boots without resuming after a suspend-to-disk (for [[swsusp]] and [[Software Suspend 2|suspend2]], respectively)
 
|-
 
|-
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| vga=835 || for 1400x1050 framebuffer resolution
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| {{bootparm|resume|/dev/hdaX}}<br />{{bootparm|resume2|/dev/hdaX}} || tells the kernel where to find the suspend-to-disk image to resume from (for [[swsusp]] and [[Software Suspend 2|suspend2]], respectively)
 
|-
 
|-
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| video=radeonfb:vesa:1400x1050-32@60  || for using accelerated radeonfb framebuffer
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| {{bootparm|root|/dev/hdaX}} || tells the kernel where to find the root filesystem
 +
|-
 +
| {{bootparm|speedstep_coppermine|???}} || supposed to tell the kernel that you have a speedstep capable coppermine processor, but could possibly not work anymore with newer kernels
 +
|-
 +
| {{bootparm|forcepae|}} || tells the kernel that the CPU supports [[PAE|Physical Address Extension (PAE)]], even if it is not the list of supported CPU flags (see [[Intel Pentium M (Dothan)|Pentium M Dothan]])
 
|-
 
|-
 
|}
 
|}
  
 +
==Framebuffer related parameters for ThinkPads==
 +
The following table gives an overview of the kernel parameters typically needed on ThinkPads.
 +
{| border="1" cellspacing="0" cellpadding="2"
 +
|+ useful framebuffer related kernel parameters
 +
! parameter !! description
 +
|-
 +
| {{bootparm|vga|835}} || for 1400x1050 framebuffer resolution
 +
|-
 +
|{{bootparm|vga|0x33c}} || same as above
 +
|-
 +
| {{bootparm|video|vesa:ywrap,mtrr}} || enables mtrr and ....
 +
|-
 +
| {{bootparm|video|radeonfb:vesa:1400x1050-32@60}}  || for using accelerated radeonfb framebuffer
 +
|-
 +
|}
  
 
[[Category:Glossary]]
 
[[Category:Glossary]]

Latest revision as of 17:09, 12 March 2017

Some aspects of the Linux kernels behaviour are controllable via so called kernel parameters. These are parameters similar to the ones that you would provide for a command like $ ls or $ cp in a shell, only that they are appended to the kernel/image line in your bootmanagers config file (for lilo this would typically be /etc/lilo.conf, for grub it would be /boot/grub/menu.lst).

An example line from grub could look like this: 

kernel /lfskernel-2.6.9 root=/dev/hda6 rw idebus=66 vga=791 splash=silent acpi_sleep=s3_bios

For a complete overview of all available parameters see /lib/modules/`uname -r`/source/Documentation/kernel-parameters.txt.

Typical parameters used on ThinkPads

The following table gives an overview of the kernel parameters typically needed on ThinkPads.

useful kernel parameters
parameter description
acpi=off disables ACPI (keeps it from overriding APM)
acpi_sleep=s3_bios makes the system call the video BIOS to reenable video on resume from suspend-to-ram (use this if you experience a blank display after resume while your system seems elsewise awake)
hda=noprobe Sometimes needed for DMA support for system hard disk on recent models (see Problems with SATA and Linux)
hdc=noprobe
libata.atapi_enabled=1		 Sometimes needed for DMA support for the optical drive on recent models (see Problems with SATA and Linux)
idebus=66 set IDE bus speed to 66 MHz (66 is maximum supported)
nolapic tells the kernel not to use the local APIC (use if you have problems with ACPI)
lapic tells the kernel to use the local APIC, even when it is disabled by the BIOS (older models like a T42 or R51 don't have this option in the BIOS and don't enable the local APIC)
noresume
noresume2		 boots without resuming after a suspend-to-disk (for swsusp and suspend2, respectively)
resume=/dev/hdaX
resume2=/dev/hdaX		 tells the kernel where to find the suspend-to-disk image to resume from (for swsusp and suspend2, respectively)
root=/dev/hdaX tells the kernel where to find the root filesystem
speedstep_coppermine=??? supposed to tell the kernel that you have a speedstep capable coppermine processor, but could possibly not work anymore with newer kernels
forcepae tells the kernel that the CPU supports Physical Address Extension (PAE), even if it is not the list of supported CPU flags (see Pentium M Dothan)

Framebuffer related parameters for ThinkPads

The following table gives an overview of the kernel parameters typically needed on ThinkPads.

useful framebuffer related kernel parameters
parameter description
vga=835 for 1400x1050 framebuffer resolution
vga=0x33c same as above
video=vesa:ywrap,mtrr enables mtrr and ....
video=radeonfb:vesa:1400x1050-32@60 for using accelerated radeonfb framebuffer
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