OK - it appears that /etc/passwd.lock and /etc/shadow.lock existed, for some reason, and was the cause of the problem. I removed those file and was able to complete installed.
Closing. ** Changed in: libvirt (Ubuntu) Status: New => Fix Released -- package libvirt-bin 0.7.5-5ubuntu3 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1 https://bugs.launchpad.net/bugs/512732 You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to libvirt in ubuntu. -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs