init nextcloud backup

nextcloud.nix

@@ -8,6 +8,27 @@ in
   environment.systemPackages = [
     nextcloud
   ];
+  systemd.timers."nextcloud-backup" = {
+    wantedBy = [ "timers.target" ];
+      timerConfig = {
+        # OnBootSec = "5m";
+        # OnUnitActiveSec = "5m";
+        OnCalendar="*-*-* 2:00:00";
+        Unit = "nextcloud-backup.service";
+      };
+  };
+
+  systemd.services."nextcloud-backup" = {
+    script = ''
+      set -eu
+      ${pkgs.postgresql}/bin/pg_dump "nextcloud" -f /tmp/dump.sql
+    '';
+    serviceConfig = {
+      Type = "oneshot";
+      User = "postgres";
+    };
+  };
+  
   services = {
     nginx.virtualHosts = {
       ${domain} = {