system update script

vm/desktop.nix

@@ -58,6 +58,7 @@ in
       tmux
       firefox
       atom
+      (pkgs.callPackage ./update.nix {})
     ];
   };
 }

vm/update.nix

+{pkgs, ...}:
+pkgs.writeShellScriptBin "liucs-update" ''
+  # run as root
+  [[ $(id -un) == root ]] || {
+      exec sudo -H $0 "$@"
+  }
+  nix-channel --update liucs --option tarball-ttl 0
+  nixos-rebuild switch
+''