Master Linux Runlevel: View and Change System Run Levels

runlevel: Display System Run Level

Function Description

Using the runlevel command can output both the previous and the current run level. The command reads the system UTMP file; if no file is specified, it defaults to /var/run/utmp to locate the most recent run level records.

Command Syntax

runlevel [UTMP_file]

Examples

Example 1

Show the previous and current run level:

# runlevel
N 3
// N indicates there is no previous run level

Example 2

After switching the Linux system run level to 5, display the run levels:

# init 5

# runlevel
3 5
// Current run level is 5, previous run level was 3

Knowledge Expansion

The Linux operating system goes through several distinct stages during boot and shutdown; these stages are called runlevels. Similarly, shutting down the system also passes through specific runlevels.

Runlevels can be thought of as system states, analogous to Windows modes such as Normal, Safe Mode, and Command Prompt only. Entering each runlevel starts or stops a set of services, which are placed as init scripts in directories like /etc/rc.d/rc?.d/ or /etc/rc?.d/, where ? represents the runlevel number.

Most Linux distributions define eight runlevels:

0  Halt
1  Single-user mode
2  Multi-user, no NFS
3  Full multi-user mode
4  Unused
5  Graphical interface
6  Reboot
S  Single user mode (pre‑boot preparation)

Desktop Linux systems typically default to runlevel 5 (graphical interface), while server versions default to runlevel 3 (text console). Runlevels 1 and 2 are rarely used except for debugging, and runlevels s/S are reserved for preparing single‑user mode.

The advantage of Linux runlevels over Windows startup modes is that you can switch runlevels on the fly using the init command. When shutting down or restarting, the system invokes runlevel 0 or 6 to terminate all running processes gracefully.