Ansible for beginners: automate your server hardening checklist
Your first Ansible playbook: the server hardening checklist, written once and applied to every server the same way. Inventory, modules, handlers, check mode, and verifying the result.
SSH
Articles about SSH.
How to secure a new Linux server: a beginner's hardening checklist
The first hour on a new Ubuntu or Debian server: SSH keys, a firewall, automatic security updates, fail2ban and an audit. Step by step, with the catches explained.