Harden your public webserver (Part 3: shutdown SSH)
One of the main points of attack is the SSH interface. Script kiddies love an open SSH port.
Harden your public webserver (Part 2: crowdsec)
Quickly after the server is on the Internet, it is open for script kiddies to eat. One of the first annoyances are bruteforce attacks.
Harden your public webserver (Part 1: unattended-upgrades)
Everyone who at some point comes across the idea of renting their own root server knows the queasy feeling that the server has been released for attack.
Show Graylog alerts in icinga2
Graylog is a log monitoring tool. Icinga is a tool for machine monitoring. While both tools overlap in many ways, they cannot replace each other.