SSH Key Authentication
Password-based SSH is weak. Generate an SSH key pair, install the public key on the server, and disable password login entirely.
UFW Firewall
Uncomplicated Firewall is a user-friendly front-end to iptables. Open only the ports you actually need.
Systemd Service Management
On modern Linux distributions every service is managed by systemd. You can ship your own applications as unit files the same way.
Cron Scheduling
Conclusion
These four fundamentals — SSH keys, firewall, systemd, and cron — are the minimum every Linux administrator should know. Layer monitoring (Prometheus, Grafana) and automated deployment on top to build the kind of professional infrastructure KEYDAL runs.