update for ubuntu nix

scripts/nix-maintain.sh

@@ -5,11 +5,13 @@ set -e
 HOST=$(hostname)
 FLAKE_PATH="${HOME}/nixConfig"
 
+nix-channel --update
+
 echo "🔁 Rebuilding system for host: $HOST"
 sudo nixos-rebuild switch --flake "$FLAKE_PATH#$HOST"
 
 echo "🧹 Collecting garbage..."
-sudo nix-collect-garbage -d
+sudo nix-collect-garbage --delete-older-than 15d
 nix store gc
 
 echo "✅ System rebuilt and cleaned."