3.4 Kernel Boot Parameters

The following table lists commonly used kernel boot parameters.

Option

Description

0, 1, 2, 3, 4, 5, or 6, or systemd.unit=runlevelN.target

Specifies the nearest systemd-equivalent system-state target to an Oracle Linux 6 run level. N can take an integer value between 0 and 6.

For a description of system-state targets, see Section 3.7, “About System-State Targets”.

1, s, S, single, or systemd.unit=rescue.target

Specifies the rescue shell. The system boots to single-user mode prompts for the root password.

3 or systemd.unit=multi-user.target

Specifies the systemd target for multi-user, non-graphical login.

5 or systemd.unit=graphical.target

Specifies the systemd target for multi-user, graphical login.

-b, emergency, or systemd.unit=emergency.target

Specifies emergency mode. The system boots to single-user mode and prompts for the root password. Fewer services are started than when in rescue mode.

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.

SYSFONT=font

Specifies 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
BOOT_IMAGE=/vmlinuz-3.10.0-123.el7.x86_64 root=UUID=52c1cab6-969f-4872-958d-47f8518267de
ro rootflags=subvol=root vconsole.font=latarcyrheb-sun16 crashkernel=auto vconsole.keymap=uk
rhgb quiet LANG=en_GB.UTF-8

For more information, see the kernel-command-line(7) manual page.