The PostgreSQL system user id must have write permission on any directory used as a target for any backup.

Regardless of the backup file format selected, each database will be backed up into a single file having the form: <name>.<extension> where <extension> will be one of 'post', 'tar', or 'sql'.

Commands specified to run before and after backup are triggered before and after each database and NOT just once before and once after the entire set.