Comment 2 for bug 1304953

To fix this:

$ usermod -a -G winbindd_priv www-data
$ chgrp winbindd_priv /var/lib/samba/winbindd_privileged
$ ln -s /var/lib/samba/winbindd_privileged/pipe /var/run/samba/winbindd_privileged/pipe

The Apache module expects the winbindd pipe socket to be found in /var/run/samba/winbindd_privileged/. The new location of the file however seems to be /var/lib/samba/winbindd_privileged/.