show logs with journald for update-system

sw/default.nix

@@ -77,7 +77,16 @@ in
           inputs.agenix.packages.${stdenv.hostPlatform.system}.default
           # Custom update script
           (writeShellScriptBin "update-system" ''
-            systemctl start update-system
+            #!/usr/bin/env bash
+            set -euo pipefail
+
+            UNIT="update-system.service"
+
+            # start the service
+            systemctl start "$UNIT"
+
+            # follow logs until it exits
+            journalctl -u "$UNIT" -f -n 20
           '')
         ];
     }