add initdb command

lib.nix

@@ -102,6 +102,17 @@ in
           )
         );
       };
+      script = pkgs.writeShellApplication {
+        name = "run-postgres";
+        text = ''
+                  if [! -d "${data_dir}"]; then
+                    echo "Database directory does not exist. Initializing"
+                    initdb -D ${data_dir}
+                  fi
+          ${package}/bin/postgres -D ${data_dir} --config-file ${configFile}
+
+        '';
+      };
     in
     # configFileCheck = pkgs.runCommand {} ''
     #     ${package}/bin/postgres -D${configFile} -C config_file
@@ -109,7 +120,7 @@ in
     #   '';
     {
       processes."${name}" = {
-        command = "${package}/bin/postgres -D ${data_dir} --config-file ${configFile}";
+        command = "${script}/bin/run-postgres";
       };
     };
 }