Also there is a node-wide kubelet flag `--rkt-stage1-image1` to set the default isolation environments, which can be overridden by the per pod annotation `rkt.a

Also there is a node-wide kubelet flag `--rkt-stage1-image1` to set the default isolation environments, which can be overridden by the per pod annotation `rkt.alpha.kubernetes.io/stage1-name-override`