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How to Check Which Display Manager is Running Using the Command Line

Display managers play a crucial role in Linux systems, as they provide the graphical interface to log into your desktop environment. Popular display managers include GDM (GNOME Display Manager), SDDM (Simple Desktop Display Manager), LightDM, and others. Knowing which display manager is active on your system can be useful for troubleshooting, optimizing performance, or configuring your system.

Here’s a simple guide to check which display manager is running on your Linux system using the command line.

Steps to Check the Active Display Manager

Method 1: Using the ps Command

The ps command displays information about active processes on your system. Use it to locate the running display manager:

This command filters the process list to show only those related to common display managers.

Example Output:

1234 ? 00:00:05 gdm

In this case, gdm is the running display manager.

Method 2: Checking the Display Manager Service

On systems that use systemd, you can check the status of the display manager service to identify the active one:

systemctl status display-manager

Example Output:

● gdm.service - GNOME Display Manager

Loaded: loaded (/usr/lib/systemd/system/gdm.service; enabled; vendor preset: enabled)

Active: active (running) since Wed 2025-01-03 10:15:00 UTC; 1h 12min ago

Here, the output confirms that GDM (GNOME Display Manager) is active.

Method 3: Inspecting the /etc/X11/default-display-manager File

Most Linux distributions maintain a configuration file that specifies the default display manager. You can check this file to find the name of the display manager:

cat /etc/X11/default-display-manager

Example Output:

/usr/sbin/gdm3

This indicates that GDM is the default display manager.

Method 4: Checking the Session Details

Sometimes, the currently active session provides clues about the running display manager. You can inspect the session details:

loginctl show-session $(loginctl | grep $(whoami) | awk '{print $1}') -p Display

This command reveals the active display session, which indirectly relates to the display manager.

When Is It Really Required to Know the Display Manager on a Production Server?

For production servers, knowing the display manager is rarely critical unless the server is configured to provide a graphical interface. For instance:

Remote Access & Debugging: If you’re troubleshooting graphical access through VNC or RDP, knowing the active display manager can help ensure compatibility.
Customizations & Optimizations: In specific cases where a lightweight graphical environment is required, understanding the current display manager can help optimize performance.

In most production environments, servers are configured without a graphical interface, making this information unnecessary.