Backing up Asterisk Data
Backing up Asterisk is not a complex task. Mostly, you just need to know where the files are and then employ common tools for archiving and storing those files somewhere.
Files to consider for backup
The Directory and File structure page should direct you to where most of these files reside. Otherwise check the individual wiki pages for information on the location of their output.
Other than just using tar to archive and compress the files, you might set up a cron job in Linux to regularly perform that process and send the files off-site. In general, use whatever backup processes you use for any other Linux applications that you manage.
Restoring a Backup
When restoring a backup to a new major version of Asterisk you'll need to take the same steps as if you were upgrading Asterisk. That is because a new major version may include changes to the format or syntax of configuration, required database schema, or applications and functions could be deprecated, removed or just have different behavior.