When you set up a server instance, always set up automatic snapshots that backup your existing config. Then you won't spend a few hours pouring through documents and trying to find the right search terms for what went wrong when all you did was a simple point release upgrade of Ubuntu.
If you have the backup snapshot, all you have to do it spin up a new instance and add it into the load balancer, or repoint your dns to the new instance. Then your site has little to no downtime due to possible fat finger mistakes where you deployed while a server was being updated.
Take it from someone who learned the hard way - set up your backups and server snapshots now - before you need them.