Although it is quite safe to restart ```libvirtd``` when there are only ```qemu``` machines, in case if there are ```libvirt_lxc``` containers, a restart may result in putting the whole system into an odd state: the containers go on running but the new ```libvirtd``` daemons do not see them.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at http://nixos.org/nixos and in the manual in doc/manual.