There are 2 backup systems.

1) The recommended one is the DirectAdmin backup system. It will create a tar.gz file for each DirectAdmin account storing all information specific to that User (databases, email accounts, email data, domains, website, subdomains, etc, etc..) This is the recommended method because it has a simple 1 click restore. It's handy for user backups and to move accounts between servers. This backup system has 3 different levels of interface, all which create a file with the same contents:

  Admin Level -> Admin Backup/Transfer
  Reseller Level -> Manage User Backups
  User Level -> Site Backup

2) The other backup system is:

  Admin Level -> System Backup

this is an interface to the “sysbk” backup script (which didn't write sysbk) The System Backup will backup all data including config files for services (like the /etc/exim.conf, directadmin.conf etc…) which are not part of the DA backup. This tool can also be customized to add/remove paths that you would like. However, this tool does not have a 1 click restore option. Each tar.gz that it creates must be restored manually with the tar command.