By default, NixOS uses DHCP (specifically, dhcpcd) to automatically configure network interfaces. However, you can configure an interface manually as follows: networking.interfaces.eth0 = { ipAddress = "192.168.1.2"; prefixLength = 24; }; (The network prefix can also be specified using the option subnetMask, e.g. "255.255.255.0", but this is deprecated.) Typically you’ll also want to set a default gateway and set of name servers: networking.defaultGateway = "192.168.1.1"; networking.nameservers = [ "8.8.8.8" ]; Statically configured interfaces are set up by the systemd service interface-name-cfg.service. The default gateway and name server configuration is performed by network-setup.service. The host name is set using networking.hostName: networking.hostName = "cartman"; The default host name is nixos. Set it to the empty string ("") to allow the DHCP server to provide the host name.