Automatic Login on Linux

This document explains how to configure automatic login on Linux so the system signs in automatically after startup or reboot, without requiring user interaction.

Automatic login support on Linux depends on the display manager and the desktop environment in use. The most common configurations are covered below.

Supported systems

This guide applies to Linux systems using:

• GNOME with GDM (Ubuntu, Debian, Fedora)
• LightDM (older Ubuntu versions, some desktop environments)

The configuration may differ on other display managers.

Security notice

Enabling automatic login significantly reduces the physical security of the device.

When automatic login is enabled:

• The system signs in automatically at boot
• No password is required at the login screen
• Anyone with physical access can use the computer

This configuration should be used only on personal devices located in trusted and private environments.

Linux-specific considerations

• Automatic login is handled by the display manager
• Disk encryption (LUKS) will still require a password at boot
• Automatic login happens after disk decryption
• Only one user can be configured for automatic login

Required information

Before configuring automatic login, the following information is required:

• The Linux username
• Administrator (sudo) privileges
• The display manager in use (GDM or LightDM)

Determine the Linux username

The username is the name of the home directory and can be verified by running: whoami

The returned value is the username that must be used for automatic login.

Method 1: Automatic login with GNOME (GDM)

This is the most common setup on modern Linux distributions.

Graphical configuration

• Open Settings
• Go to Users
• Unlock the settings using administrator privileges
• Enable Automatic Login for the desired user

Once enabled, the system will log in automatically at startup.

Manual configuration (GDM)

If the graphical option is not available, automatic login can be configured manually.

Edit the following file: /etc/gdm3/custom.conf

Modify or add the following lines: [daemon] AutomaticLoginEnable=true AutomaticLogin=username

Replace username with the correct Linux username.

Save the file and restart the system.

Method 2: Automatic login with LightDM

On systems using LightDM, automatic login is configured via its main configuration file.

Edit: /etc/lightdm/lightdm.conf

Add or modify the following lines: [Seat:*] autologin-user=username autologin-user-timeout=0

Replace username with the correct Linux username.

Restart the system to apply the changes.

Restart and verify

Restart the computer.

If the configuration is correct:

• Linux will log in automatically
• The desktop will be available immediately after boot
• No password prompt will appear

Notes about disk encryption

• Automatic login does NOT bypass full-disk encryption
• If LUKS encryption is enabled, a password is still required at boot
• Automatic login occurs only after the disk is unlocked

This behavior is expected and recommended for security.

Security considerations

• Automatic login does not bypass BIOS or firmware passwords
• Disk encryption remains the primary security layer
• Anyone with physical access can use the logged-in account
• This configuration prioritizes convenience over physical security

Troubleshooting

If automatic login does not work:

• Verify the correct username is configured
• Ensure the correct display manager is used
• Check configuration file syntax
• Restart the system after changes
• Review system logs for display manager errors

Use cases

Automatic login on Linux is commonly used for:

• Remote desktop access
• Headless or unattended systems
• Home servers
• Raspberry Pi setups
• Systems that must recover automatically after reboot