Create
Server → Backups → Create backup. Give it a name you will recognise later (before-1.21-update). Optionally list files to ignore, one per line (logs, cache). The backup runs in the background; a big server takes a minute or two. Do this before every risky change: version updates, big plugin installs, world edits.
Lock
The padlock icon protects a backup from automatic rotation and from accidental deletion. Lock the "last known good" backup after a successful update.
Restore
The server must be stopped. Click Restore on a backup. Choose whether to delete all files first:
- Yes: the server folder is emptied, then the backup is unpacked. The result is exactly the state at backup time. Use this to roll back a bad update.
- No: the backup is unpacked over the current files. Files that exist in the backup are replaced, newer files that are not in the backup stay. Use this to get a world back without losing plugins you added since.
Restoring takes about as long as creating. Start the server afterwards.