Run levels in Linux

12 May 2020

Self-documenting… going to try out dwm tiling window manager. Seems pretty cool.

Run levels are states or modes that are defined by the services listed in the /etc/rc.d/rc<x>.d, where <x> is the number of the runlevel. More information: Fedora guides: Runlevels.

The following runlevels exist:

• 0 - Halt
• 1 - Single-user mode
• 2 - Not used (user-definable)
• 3 - Full multi-user mode
• 4 - Not used (user-definable)
• 5 - Full multiuser mode (with an X-based login screen)
• 6 - Reboot

When logging in, if you need to login via a text-only screen then it means you’re running in runlevel 3. If a graphical login screen is present, you’re running in runlevel 5.

The default runlevel can be changed by modifying the /etc/inittab file, which should contain a line similar to the following

id:5:initdefault:

Changing the number in this line to the desired runlevel. Need a reboot to take effect.

UPDATE: I just found out that the linux system I’m using right now (Fedora 32 Workstation) does not use runlevels like this anymore. It uses systemd for that purpose. Quoting the /etc/inittab file in my system:

# inittab is no longer used.
#
# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
#
# systemd uses 'targets' instead of runlevels. By default, there are two main targets:
#
# multi-user.target: analogous to runlevel 3
# graphical.target: analogous to runlevel 5
#
# To view current default target, run:
# systemctl get-default
#
# To set a default target, run:
# systemctl set-default TARGET.target