This avoids the following warning: Apr 19 10:53:48 xen systemd[1]: [/nix/store/...-unit-ddclient.service/ddclient.service:19] Unknown lvalue 'type' in section 'Service' As `Type=simple` is the default in systemd, the assignment to the service type can be simply dropped.
*** 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.