Automatic Minecraft backups

by Stef Pletinck

Say you run a Minecraft server (like EndTech) and you want it to backup automatically and manually. This is needed because people make mistakes or your players like to experiment, which might crash the game.

A minecraft world is simply a folder called world, which you could just copy to another location. Once it’s there, you can expose it to the internet, copy it over to an offsite location (using e.g. rclone) or just copy it to another disk.

There are, of course, a few issues with simple cp:

1. The server can’t have pending writes before the backup start
2. The server can’t write to disk while the backup is running
3. Ideally, the server can’t shut down during backup
4. The backup process can’t corrupt the backup or the currently running world

A simple cp will just not do for this. It might work fine most of the time, but invariably that one time it does go wrong, is the time you really really needed a backup.

RCON

What we really need is a way to tell the Minecraft server to save everything it’s got in the queue and then stop writing until we tell it to start writing again. If we had access to the console, that would be easy. Just a simple save-all flush and save-off, copy the files and do save-on. But we are writing a script, accessing the console is a pain.

Enter RCON. RCON is a protocol you can use to remotely send commands to a Minecraft server. This could even go over the internet if you really wanted to! We don’t want that though, because RCON has OP level access.

First we have to enable RCON on our server. For that, we need to set the enable-rcon=true option in server.properties and choose a password in rcon.password=passw0rd. Restart the server.

Connecting to RCON is slightly complicated, but luckily Tiiffi has made mcrcon. After installing it, we can easily send any command we like over to our minecraft server.

The final result

The final script looks like this and is called daily using a cron job: