update nixos config backup

backup-nixos-configs.sh

@@ -1,2 +1,11 @@
 #!/usr/bin/env bash
+
+DEVICE=$1
+
+if [ -z $DEVICE ] ; then
+	echo "missing 1st argument (DEVICE), ie. the name of the device where the backup is being done"
+	exit 1
+fi
+
 cp /etc/nixos/* ./nixos/
+mv ./nixos/configuration.nix ./nixos/$DEVICE-configuration.nix