3.2.1.1 Kernel Boot Parameters

The following table lists commonly-used kernel boot parameters.

Option

Description

1|2|3|4|5

Specifies the run level, overriding the value set in /etc/inittab.

KEYBOARDTYPE=kbtype

Specifies the keyboard type, which is written to /etc/sysconfig/keyboard in the initramfs.

KEYTABLE=kbtype

Specifies the keyboard layout, which is written to /etc/sysconfig/keyboard in the initramfs.

LANG=language_territory.codeset

Specifies the system language and code set, which is written to /etc/sysconfig/i18n in the initramfs.

max_loop=N

Specifies the number of loop devices (/dev/loop*) that are available for accessing files as block devices. The default and maximum values of N are 8 and 255.

nouptrack

Disables Ksplice Uptrack updates from being applied to the kernel.

quiet

Reduces debugging output.

rd_LUKS_UUID=UUID

Activates an encrypted Linux Unified Key Setup (LUKS) partition with the specified UUID.

rd_LVM_VG=vg/lv_vol

Specifies an LVM volume group and volume to be activated.

rd_NO_LUKS

Disables detection of an encrypted LUKS partition.

rhgb

Specifies that the Red Hat graphical boot display should be used to indicate the progress of booting.

rn_NO_DM

Disables Device-Mapper (DM) RAID detection.

rn_NO_MD

Disables Multiple Device (MD) RAID detection.

ro root=/dev/mapper/vg-lv_root

Specifies that the root file system is to be mounted read only, and specifies the root file system by the device path of its LVM volume (where vg is the name of the volume group).

rw root=UUID=UUID

Specifies that the root (/) file system is to be mounted read-writable at boot time, and specifies the root partition by its UUID.

selinux=0

Disables SELinux.

singleBoots the computer in single-user mode, without prompting for the root password.
SYSFONT=fontSpecifies the console font, which is written to /etc/sysconfig/i18n in the initramfs.

The kernel boot parameters that were last used to boot a system are recorded in /proc/cmdline, for example:

# cat /proc/cmdline
ro root=/dev/mapper/VolGroup-lv_root rd_NO_LUKS KEYBOARDTYPE=pc KEYTABLE=us
LANG=en_US.UTF-8 rd_NO_MD rd_LVM_LV=VolGroup/lv_swap SYSFONT=latarcyrheb-sun16
rd_LVM_LV=VolGroup/lv_root rd_NO_DM rhgb quiet selinux=0