Difference between revisions of "Kernel parameters"

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There are three ways to pass options to the kernel and thus control its behaviour:
 
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Revision as of 19:53, 4 December 2012

There are three ways to pass options to the kernel and thus control its behaviour:

  1. When building the kernel.
  2. When starting the kernel (usually, when invoked from a boot loader).
  3. At runtime (through the files in /proc and /sys).

This page now explains in more detail the second method and shows a list of most used kernel parameters in Arch Linux.

Configuration

Kernel parameters can be set either temporarily by editing the boot menu when it shows up, or by modifying the boot loader's configuration file.

Here we are adding the parameters quiet and splash to Syslinux, GRUB, GRUB Legacy and LILO.

Syslinux

  • Press Template:Keypress when the menu shows up and add them at the end of the string:
> .linux ../vmlinuz-linux root=/dev/sda3 ro initrd=../initramfs-linux.img quiet splash
Press Template:Keypress to boot with these parameters.
  • To make the change persistent after reboot, edit /boot/syslinux/syslinux.cfg and add them to the APPEND line:
APPEND root=/dev/sda3 ro quiet splash

For more information on configuring Syslinux, see the Syslinux article.

GRUB

linux   /boot/vmlinuz-linux root=UUID=978e3e81-8048-4ae1-8a06-aa727458e8ff ro  quiet splash
Press Template:Keypress to boot with these parameters.
  • To make the change persistent after reboot, while you could manually edit /boot/grub/grub.cfg with the exact line from above, for beginners it's recommended to:
Edit /etc/default/grub and append your kernel options to the GRUB_CMDLINE_LINUX_DEFAULT line:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
And then automatically re-generate the grub.cfg file with:
# grub-mkconfig -o /boot/grub/grub.cfg

For more information on configuring GRUB, see the GRUB article.

GRUB Legacy

kernel /boot/vmlinuz-linux root=/dev/sda3 ro quiet splash
Press Template:Keypress to boot with these parameters.
  • To make the change persistent after reboot, edit /boot/grub/menu.lst and add them to the kernel line, exactly like above.

For more information on configuring GRUB Legacy, see the GRUB Legacy article.

LILO

  • Add them to /etc/lilo.conf:
image=/boot/vmlinuz-linux
        ...
        quiet splash

For more information on configuring LILO, see the LILO article.

Parameters list

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: The list needs more parameters. (Discuss in Talk:Kernel parameters#)
Note: Not all of the listed options are always available. Most are associated with subsystems and work only if the kernel is configured with those subsystems built in. They also depend on the presence of the hardware they are associated with.
SysVinit systemd Description
3 systemd.unit=multi-user Boot to a specified runlevel (3, in this case). Works with 1-6.
1 systemd.unit=rescue Boot to Single-user mode (root).
nomodeset nomodeset Disable Kernel Mode Setting.
loglevel=3 loglevel=3 Removes "misaligned reg" and "unknown connector type" messages during boot with the Nouveau driver. See this topic.
-- init=/usr/lib/systemd/systemd Boot using systemd instead of SysVinit.
init=/bin/sh rw init=/bin/sh rw Boot to Shell.

All of these parameters are case-sensitive.

For a complete list of all known options, please see the kernel documentation.

See Also