Add purge guard, to avoid accidents

modules/k8s.nix

@@ -117,6 +117,13 @@ let
             }
 
             [ -z "$namespace" ] && echo "namespace must be set" && exit 1
+
+            if [ "$apply" = delete ]; then
+                echo "WARNING: Really delete $(basename $TOP)? YES/no:"
+                read ans
+                [ "$ans" != YES ] && exit 0
+            fi
+
             export_vars
             EOF
         '';