use systemd timer

backup.nix

@@ -12,10 +12,26 @@ let
 
   backupConfigFile = "/etc/misskey-backup/conf";
   s3Cfg = "/etc/misskey-backup/s3cfg";
-  backupScript = pkgs.writeShellApplication {
-    name = "misskey-backup";
+in {
+  users.users."${user}" = {
+    isSystemUser = true;
+    inherit group;
+  };
+  users.groups."${group}" = { };
+  services.postgresql.ensureUsers = [{ name = user; }];
 
-    runtimeInputs = with pkgs; [
+  systemd.services.misskey-backup = {
+    description = "Misskey backup";
+
+    restartIfChanged = false;
+    unitConfig.X-StopOnRemoval = false;
+    unitConfig.User = user;
+
+    serviceConfig.Type = "oneshot";
+
+    startAt = "weekly";
+
+    path = with pkgs; [
       gzip
       config.services.postgresql.package
       s3cmd
@@ -23,21 +39,18 @@ let
       age
     ];
 
-    text = ''
-      configFile="$1"
-      s3cfg="$2"
-
+    script = ''
       ageRecipient="age17ckyc69njpryytc63ynn545jswyucg28k5xg3043g3j6q38dxqwq0wzhm2"
-      bucket="$(grep 'bucket=' < "$configFile" | sed 's/bucket \?= \?')"
-      prefix="$(grep 'prefix=' < "$configFile" | sed 's/prefix \?= \?')"
+      bucket="$(grep 'bucket=' < "${backupConfigFile}" | sed 's/bucket \?= \?')"
+      prefix="$(grep 'prefix=' < "${backupConfigFile}" | sed 's/prefix \?= \?')"
 
-      s3Dir="s3://$bucket/$prefix""misskey-$(date --iso-8601)"
+      s3Dir="s3://$bucket/$prefix""misskey-$(date +'%d-%m-%YT%H.%M.%S')"
       echo "Uploading backups to '$s3Dir'"
 
       function upload () {
         name="$1"
 
-        age -r "$ageRecipient" | s3cmd put --config "$s3cfg" - "$s3Dir/$name.age"
+        age -r "$ageRecipient" | s3cmd put --config "${s3Cfg}" - "$s3Dir/$name.age"
       }
 
       echo "Uploading config"
@@ -51,20 +64,11 @@ let
 
       echo "Backup complete to '$s3Dir'"
     '';
-  };
-in {
-  users.users."${user}" = {
-    isSystemUser = true;
-    inherit group;
-  };
-  users.groups."${group}" = { };
-  services.postgresql.ensureUsers = [{ name = user; }];
 
-  services.cron = {
-    enable = true;
-    systemCronJobs = [
-      # run every monday at ass in the morning, EST"
-      "0 8 0 0 1 ${user} ${backupScript} ${backupConfigFile} ${s3Cfg}"
-    ];
+    after = [ "network-online.target" ];
+    wants = [ "network-online.target" ];
+    requires = [ "postgresql.service" ];
   };
+
+  systemd.timers.misskey-backup = { timerConfig.Persistent = true; };
 }