prune backups older than 3 days

nixos/hosts/varda/default.nix

@@ -1,5 +1,5 @@
 { pkgs, ... }: {
-  imports = [ ];
+  imports = [ ./resources/prune-backup.nix ];
 
   networking.hostId = "cdab8473";
   networking.hostName = "varda"; # Define your hostname.
@@ -22,6 +22,7 @@
 
   swapDevices = [ ];
 
+
   # System settings and services.
   mySystem = {
     purpose = "Production";

nixos/hosts/varda/resources/prune-backup.nix

@@ -0,0 +1,24 @@
+{ pkgs, ... }:
+
+let
+  cleanupScript = pkgs.writeScript "cleanup-backups.sh" (builtins.readFile ./prune-backups.sh);
+in
+{
+  systemd.timers.cleanup-backups = {
+    wantedBy = [ "timers.target" ];
+    timerConfig = {
+      OnCalendar = "daily";
+      Persistent = true;
+    };
+  };
+
+  systemd.services.cleanup-backups = {
+    script = "${cleanupScript}";
+    serviceConfig = {
+      Type = "oneshot";
+      User = "forgejo";
+      StandardOutput = "journal+console";
+      StandardError = "journal+console";
+    };
+  };
+}

nixos/hosts/varda/resources/prune-backups.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+# Set the backup directory
+BACKUP_DIR="/var/lib/forgejo/dump"
+
+# Keep the 3 most recent backups
+KEEP_NUM=3
+
+echo "Starting backup cleanup process..."
+echo "Keeping the $KEEP_NUM most recent backups in $BACKUP_DIR"
+
+# Find all backup files, sort by modification time (newest first),
+# skip the first 3, and delete the rest
+find "$BACKUP_DIR" -type f -name "forgejo-dump-*" -print0 |
+  sort -z -t_ -k2 -r |
+  tail -z -n +$((KEEP_NUM + 1)) |
+  while IFS= read -r -d '' file; do
+    echo "Deleting: $file"
+    rm -f "$file"
+  done
+
+echo "Cleanup complete. Deleted all but the $KEEP_NUM most recent backups."