Kernel Parameter


Kernel parameters can be used to change some kernel settings at boot time. You can change the parameter temporary (only for a single boot) or permanently.

Temporary Change

These changes are valid only once. If you restart your system, they no longer hold.

  1. Reboot
  2. Open the grub menu at boot
    1. Use „arrow key up“ or „arrow key down“ to stop the countdown
    2. If the grub menu does not appear, press „shift“ several times during booting
  3. Select the desired kernel entry
  4. Press „e
  5. Edit the line, which starts with linux. The last words on this line are the kernel parameters.
  6. Press „F10“ to boot

For example:

menuentry 'Ubuntu, with Linux 3.5.0-54-generic (Writable)' --class ubuntu --class gnu-linux --class gnu --class os {
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	search --no-floppy --fs-uuid --set=root 28adfe9d-c122-479a-ab81-de57d16516dc
	linux	/vmlinuz-3.5.0-54-generic root=/dev/mapper/faramir-root ro  quiet splash
	initrd	/initrd.img-3.5.0-54-generic
	linux	/vmlinuz-3.5.0-54-generic root=/dev/mapper/faramir-root ro  quiet splash

The three kernel parameters in this example are ro quiet splash.

Change Kernel Parameters permanently

  1. sudo nano /etc/default/grub
  2. Add your parameters to the line:
    • GRUB_CMDLINE_LINUX_DEFAULT=„quiet splash“ (this line may contain different kernel parameters)
  3. It should look like this:
    • GRUB_CMDLINE_LINUX_DEFAULT=„quiet splash yourParameter=1
  4. sudo update-grub
  5. reboot the pc

Check Kernel Parameters

To display the current kernel parameter run:

cat /proc/cmdline