Systemd Services & Unit Files

Also Known As

TL;DR

Explanation

A systemd service unit file (.service) defines: ExecStart (command to run), Restart policy (on-failure, always), User/Group (run as specific user), Environment (environment variables), After/Requires (dependency ordering), and WantedBy (when to start). Key commands: systemctl start/stop/restart/status servicename, systemctl enable (start on boot), journalctl -u servicename (logs). PHP applications use systemd for PHP-FPM, queue workers (Horizon, custom workers), scheduled tasks (alternatives to cron), and WebSocket servers.

Common Misconception

Why It Matters

Common Mistakes

• Not setting Restart=on-failure — crashed services stay down until manually restarted.
• Running services as root — always specify User= and Group= for security.
• Not setting WantedBy=multi-user.target — the service doesn't start on boot after systemctl enable.
• Not reloading systemd after editing unit files: systemctl daemon-reload.

Code Examples

# No systemd — manual process management:
# Start worker: php artisan queue:work &
# Worker crashes: nobody notices until queue backs up
# Server restarts: worker never comes back
# Multiple workers: manual tracking of PIDs
# Logs: mixed into syslog or lost

# /etc/systemd/system/queue-worker.service:
[Unit]
Description=Laravel Queue Worker
After=network.target

[Service]
User=www-data
Group=www-data
WorkingDirectory=/var/www/app
ExecStart=/usr/bin/php artisan queue:work --sleep=3 --tries=3
Restart=on-failure
RestartSec=5
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target

# Enable and start:
# systemctl daemon-reload
# systemctl enable --now queue-worker
# journalctl -u queue-worker -f

References

• ↗ https://www.freedesktop.org/software/systemd/man/systemd.service.html

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