runlevel Command Linux: Complete Guide to Display Current and Previous System States

The runlevel command is a fundamental system administration tool in Linux that displays the current and previous system runlevels. Understanding runlevels is crucial for system administrators and Linux users who need to manage system states, troubleshoot boot issues, or configure services properly.

What are Runlevels in Linux?

Runlevels are predefined system states that determine which services and processes are running on a Linux system. Each runlevel corresponds to a specific operational mode, from system shutdown to full multi-user mode with networking capabilities.

Standard Linux Runlevels

• Runlevel 0: System halt/shutdown
• Runlevel 1: Single-user mode (rescue mode)
• Runlevel 2: Multi-user mode without networking
• Runlevel 3: Multi-user mode with networking (text mode)
• Runlevel 4: User-defined (typically unused)
• Runlevel 5: Multi-user mode with networking and GUI
• Runlevel 6: System reboot

Basic Syntax of runlevel Command

The runlevel command has a simple syntax:

runlevel [utmp-file]

Where utmp-file is an optional parameter specifying the utmp file to read from (defaults to /var/run/utmp).

How to Use the runlevel Command

Display Current and Previous Runlevel

Simply type runlevel in the terminal:

$ runlevel
N 5

This output shows:

• N: No previous runlevel (system booted directly to current level)
• 5: Current runlevel is 5 (multi-user with GUI)

Example Outputs and Their Meanings

Fresh Boot Scenario

$ runlevel
N 3

Interpretation: System booted directly to runlevel 3 (multi-user text mode) with no previous runlevel.

After Runlevel Change

$ sudo init 5
$ runlevel
3 5

Interpretation: Previous runlevel was 3, current runlevel is 5 (switched from text mode to GUI mode).

Specifying Alternative utmp Files

You can specify a different utmp file to read runlevel information:

$ runlevel /var/log/wtmp
N 5

Practical Examples and Use Cases

System Maintenance Scenario

When performing system maintenance, you might need to switch to single-user mode and back:

# Check current runlevel
$ runlevel
N 5

# Switch to single-user mode
$ sudo init 1

# After maintenance, check runlevel
$ runlevel
5 1

# Return to multi-user GUI mode
$ sudo init 5

# Verify the change
$ runlevel
1 5

Server Environment Example

On a typical server without GUI:

$ runlevel
N 3

This indicates the server is running in multi-user mode with networking but without a graphical interface, which is optimal for server environments.

Understanding runlevel Output Format

The runlevel command always returns two values separated by a space:

Alternative Commands and Modern Equivalents

Using who Command

The who command with the -r option provides similar information:

$ who -r
         run-level 5  2025-08-26 13:45

systemctl for systemd Systems

On modern Linux distributions using systemd, you can use:

# Check current target (equivalent to runlevel)
$ systemctl get-default
graphical.target

# List all available targets
$ systemctl list-units --type=target

systemd Target to Runlevel Mapping

Changing Runlevels

While the runlevel command only displays information, you can change runlevels using these methods:

Using init Command

# Switch to runlevel 3
$ sudo init 3

# Switch to runlevel 5
$ sudo init 5

Using telinit Command

# Switch to single-user mode
$ sudo telinit 1

# Switch to multi-user mode
$ sudo telinit 3

Using systemctl (systemd)

# Switch to text mode
$ sudo systemctl isolate multi-user.target

# Switch to GUI mode
$ sudo systemctl isolate graphical.target

Troubleshooting Common Issues

runlevel Command Not Found

If the runlevel command is not available, install the sysvinit-utils package:

# Ubuntu/Debian
$ sudo apt-get install sysvinit-utils

# CentOS/RHEL
$ sudo yum install sysvinit-tools

No Output from runlevel Command

If runlevel returns no output, check if the utmp file exists:

$ ls -la /var/run/utmp
$ ls -la /run/utmp

Understanding ‘unknown’ Output

Sometimes you might see:

$ runlevel
unknown

This typically occurs when:

• The system uses systemd exclusively
• The utmp file is corrupted or missing
• The system hasn’t properly initialized runlevel information

Script Integration and Automation

Bash Script Example

#!/bin/bash

# Get current runlevel
current_runlevel=$(runlevel | cut -d' ' -f2)

echo "Current runlevel: $current_runlevel"

case $current_runlevel in
    1) echo "System is in single-user mode" ;;
    3) echo "System is in multi-user text mode" ;;
    5) echo "System is in multi-user GUI mode" ;;
    *) echo "Unknown or special runlevel" ;;
esac

Checking Previous Runlevel

#!/bin/bash

runlevel_output=$(runlevel)
previous=$(echo $runlevel_output | cut -d' ' -f1)
current=$(echo $runlevel_output | cut -d' ' -f2)

if [ "$previous" = "N" ]; then
    echo "System booted directly to runlevel $current"
else
    echo "System changed from runlevel $previous to $current"
fi

Security Considerations

When working with runlevels and the runlevel command:

• Access Control: The command doesn’t require special privileges to read runlevel information
• Log Monitoring: Monitor runlevel changes in system logs for security auditing
• Service Management: Understand which services start at different runlevels to maintain security

Best Practices

Regular Monitoring

• Include runlevel checks in system monitoring scripts
• Document expected runlevels for different server roles
• Monitor unexpected runlevel changes

System Administration

• Always verify the current runlevel before making system changes
• Use appropriate runlevels for maintenance tasks
• Understand the implications of each runlevel change

Conclusion

The runlevel command is an essential tool for Linux system administrators, providing crucial information about system states. While modern Linux distributions increasingly use systemd targets instead of traditional runlevels, understanding the runlevel concept remains valuable for system management, troubleshooting, and maintaining compatibility with older systems.

Whether you’re managing servers, troubleshooting boot issues, or automating system tasks, the ability to quickly check current and previous runlevels using the runlevel command will enhance your Linux administration skills and help ensure smooth system operations.