logrotate config that actually works: how to rotate app logs without dropping log lines and without making the app crash on the rename

Your app writes to /var/log/app.log. The disk fills up. You write a quick logrotate config, copy-paste from the first Stack Overflow result, set up a daily rotate. Two months later the disk is fine but you discover the app …

SSH key management for a multi-server fleet: ed25519, ssh-agent, ProxyJump, YubiKey FIDO2, and when agent forwarding is the wrong tool

You manage five servers. Each has a different SSH key in ~/.ssh/authorized_keys from the day you set it up — one’s an old id_rsa from 2018, two have your laptop’s current ed25519 key, one has an ancient ECDSA key from …