systemd: unit is masked

systemd: unit is masked

systemd produces "unit is masked" when a unit file is symlinked to /dev/null, preventing it from starting or being enabled.

When systemd Produces This Error

systemd reports "Failed to start {service}: Unit {service} is masked" when attempting to start or enable a masked unit. Masking is an explicit administrator action that prevents a unit from running under any circumstances.

What Causes "unit is masked" in systemd

A unit is masked when an administrator runs systemctl mask {service}, which creates a symlink from the unit file to /dev/null. Package scripts or system hardening tools may also mask units during installation.

How to Fix "unit is masked" in systemd

1. Confirm the unit is masked:

   systemctl status myapp.service

   The output shows Loaded: masked (/dev/null; bad).

2. Unmask the unit:

   sudo systemctl unmask myapp.service

3. Start and enable the service:

   sudo systemctl enable --now myapp.service

How to Verify the Fix

systemctl status should show Loaded: loaded (not masked) and Active: active (running).