As reported in http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=609905 deleting a usershare does not disconnect active clients. This means connected users can still use the share and the filesystem cannot be unmounted (because some files are still open). New connections fail (as expected). It might make sense to disconnect users where a usershare is deleted. To reproduce the problem: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=609905#68 Ivo