Guides

Keeping a certificate renewed

Check the expiry date once a week, make sure the renewal job runs on a timer, and test the renewal with a dry run after every server change.

DNS records that matter

Keep the TTL short while you are moving a service, write down the old value before you change it, and wait for caches to expire before you retire the old address.

When a service stops answering

Work from the outside in: can you resolve the name, can you reach the port, does the handshake complete, does the application answer. The first step that fails tells you where to look.