There's two "types" of backups (available under WHM->Backup Configuration->Files), "Backup User Accounts" and "Backup System Files".
User Accounts
Backing up only user accounts will only allow restoration of the user accounts via either the WHM->Backup Restoration , WHM->Transfer or Restore a cPanel account or via cPanel itself.
I can confirm the backups contain the entire /home/username/ directory, MySQL databases, PostgreSQL database and DNS configuration. You can confirm this yourself by downloading the individual backups from /backup/ and examining them "by hand" or deleting a test cPanel account and restoring it. By default it does not backup access logs or bandwidth data, but those are
selectable in the backup configuration screen.
System backup Files
These backups cover the main cPanel/WHM related server configuration (as detailed on
System Backups | cPanel & WHM Documentation ), but NOT any "OS specific configurations" (so /etc/ passwd is backed up as WHM writes to it, but not (for example) /etc/ csh.login or /etc/ rc* .
Full System Restore
If you need to do a full system restore, you will need to reinstall the OS, reinstall WHM/cPanel and then copy over your backups from Backblaze to the server (say into /backup/ ). You will need to
manually restore the server level configuration files (just a case of copying them across) and then you can do the WHM->Backup Restoration and select all accounts
