Mastering Systemd Services and Timers: A Complete Guide

Introduction to Systemd

Systemd is the modern init system for Linux, providing powerful service management capabilities and dependency handling.

Creating Systemd Services

Basic Service Unit

[Unit]
Description=My Custom Service
After=network.target

[Service]
ExecStart=/usr/bin/myscript.sh
Restart=always
User=serviceuser
Group=servicegroup

[Install]
WantedBy=multi-user.target

Advanced Features

  1. Environment variables:
Environment="DB_HOST=localhost"
Environment="DB_PORT=5432"
  1. Resource limits:
LimitNOFILE=65535
LimitNPROC=4096

Systemd Timers

Creating Timers

[Unit]
Description=Run backup daily

[Timer]
OnCalendar=daily
Persistent=true
Unit=backup.service

[Install]
WantedBy=timers.target

Advanced Timer Options

  1. Randomized delay:
RandomizedDelaySec=1h
  1. Accuracy control:
AccuracySec=1min

Troubleshooting and Debugging

  1. Check service status:
systemctl status myservice
  1. View logs:
journalctl -u myservice
  1. Dependency analysis:
systemd-analyze critical-chain myservice

Performance Optimization

  1. Parallel startup:
DefaultDependencies=no
  1. Service isolation:
ProtectSystem=full
PrivateTmp=true

Conclusion

Systemd provides robust service management capabilities that are essential for modern Linux system administration.