Kernel parameters

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

• Press Template:Keypress when the menu shows up and add them on the linux line:

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

• Press Template:Keypress when the menu shows up and add them on the kernel line:

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

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.

All of these parameters are case-sensitive.

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

See Also

• sysctl
• List of kernel parameters with further explanation and grouped by similar options