This backs up every volume attached to an instance that has a tag “backup:true” and ignores all others. The EBS Volumes attached to the instance must also have a “name:xxx” tag where xxx = some decent identifier about what it is… such as “TESTSERVER_OS”. It also will delete any snapshots that are >2 days old (Except after Monday (at Tuesday ~1am), since Friday is only 2 'working' days away)).
