Aegir: Site backup error "Could not back up sites directory for drupal"

If you encounter,

when trying to back up a site using Aegir, then this is because there are some permission issues with some of the files in the sites directory.

In my case, these files were in the private/temp/ directory. Listing all offending files can be done by the following command:

If anything other than the usual .htaccess file is found, then that is probably a likely culprit. Checking file permissions should confirm this.

Deleting these files got the backup operation back up and running.

Hope this helps!