• Create the Service File
• Enable and Start
• Daily Commands
• Useful Patterns
• Debugging

You wrote a script. It works. Now you want it to run forever, start on boot, and restart if it crashes. Here’s how, using systemd.

§Create the Service File

sudo nano /etc/systemd/system/myapp.service

[Unit]
Description=My Application
After=network.target
Wants=network-online.target

[Service]
Type=simple
User=appuser
Group=appuser
WorkingDirectory=/opt/myapp
ExecStart=/opt/myapp/start.sh
Restart=on-failure
RestartSec=5
StartLimitBurst=3
StartLimitIntervalSec=60

# Security hardening
NoNewPrivileges=true
ProtectSystem=strict
ProtectHome=true
ReadWritePaths=/opt/myapp/data
PrivateTmp=true

# Environment
Environment=NODE_ENV=production
EnvironmentFile=/opt/myapp/.env

# Logging
StandardOutput=journal
StandardError=journal
SyslogIdentifier=myapp

[Install]
WantedBy=multi-user.target

§Enable and Start

sudo systemctl daemon-reload
sudo systemctl enable myapp
sudo systemctl start myapp

§Daily Commands

# Check status
systemctl status myapp

# View logs
journalctl -u myapp -f           # follow
journalctl -u myapp --since today # today's logs
journalctl -u myapp -n 50        # last 50 lines

# Restart after code changes
sudo systemctl restart myapp

# Stop
sudo systemctl stop myapp

§Useful Patterns

Timer (instead of cron):

# /etc/systemd/system/backup.timer
[Unit]
Description=Daily backup

[Timer]
OnCalendar=<em>-</em>-* 02:00:00
Persistent=true

[Install]
WantedBy=timers.target

Socket activation (start on first request):

# /etc/systemd/system/myapp.socket
[Unit]
Description=My App Socket

[Socket]
ListenStream=8080

[Install]
WantedBy=sockets.target

§Debugging

# Why did it fail?
systemctl status myapp
journalctl -u myapp -e

# Check config syntax
systemd-analyze verify myapp.service

# See all failed services
systemctl --failed

# See service dependencies
systemctl list-dependencies myapp

The security hardening options (NoNewPrivileges, ProtectSystem, ProtectHome) are free security improvements that most tutorials skip. Use them.