error/moodle/cannot empty backup temp dir

My customer pointed out today that one of our courses was missing part of its content.  The general and topic 1 sections were there, but 2 - 6 were missing.  I was able to determine what was missing by looking on our content server and comparing the course in question with the master copy.

The solution is to create a backup from the master copy that includes only those topics missing.  This is a procedure we have used a few times in similar scenarios.

After I started the backup and choose the content I received this error when trying to create the backup

error/moodle/cannot empty backup temp dir

This is a new message.  I did not believe it and restarted my content server and tried again, this time with no error.

Moral of the story?

Moodle is complex software and sometimes confuses itself.  Reach for the lowest hanging fruit first, rebooting the server will often clean things up and remove server ambiquity.