Description
Our documentation on in-built roles seems to imply that the backup role is sufficient to allow backups using mongodump:
Provides minimal privileges needed for backing up data. This role provides sufficient privileges to use the MongoDB Management Service (MMS) backup agent, or to use mongodump to back up an entire mongod instance.
However, if you actually try to use mongodump with a user that only has backup, then it may error out on the system.profile collection, if this exists.
This caveat is mentioned on the mongodump documentation page (http://docs.mongodb.org/manual/reference/program/mongodump/), however, I believe it should also be made clear on the in-built roles page as well.