The thing nobody does until they wish they had.
WHAT TO RECORD
Operating system and version Installed software and versions Non-default configuration decisions and why File locations for applications, configuration and logs Cron jobs and what they do Database names and which application uses each DNS records and where they are hosted Third-party services and integrations
Backup arrangements: what, where, how often
Credentials location, not the credentials themselves
WHERE TO KEEP IT
Not on the server. A document in shared storage, or a repository.
WHY
Rebuilding after a disaster from memory takes far longer and misses things. If you are unavailable, someone else must be able to operate the server. Six months later you will not remember why a setting is unusual.
KEEPING IT CURRENT
Update it when you change something. A document describing a configuration from two years ago is worse than none, because it misleads.
A PRACTICAL START
Half a page listing what runs, where things are, and how backups work. Expand it as you go.
