// +optional
	ExtraEnvs []EnvVar

	// ServerCertSANs sets extra Subject Alternative Names for the etcd server signing cert.
	ServerCertSANs []string
	// PeerCertSANs sets extra Subject Alternative Names for the etcd peer signing cert.
	PeerCertSANs []string
}

// ExternalEtcd describes an external etcd cluster
type ExternalEtcd struct {

	// Endpoints of etcd members. Useful for using external etcd.

//	    imageTag: "3.2.24"
//	    dataDir: "/var/lib/etcd"
//	    extraArgs:
//	      listen-client-urls: "http://10.100.0.1:2379"
//	    serverCertSANs:
//	    -  "ec2-10-100-0-1.compute-1.amazonaws.com"
//	    peerCertSANs:
//	    - "10.100.0.1"
//	  # external:
//	    # endpoints:
//	    # - "10.100.0.1:2379"
//	    # - "10.100.0.2:2379"
//	    # caFile: "/etcd/kubernetes/pki/etcd/etcd-ca.crt"

		allErrs = append(allErrs, ValidateCertSANs(e.Local.ServerCertSANs, localPath.Child("serverCertSANs"))...)
		allErrs = append(allErrs, ValidateCertSANs(e.Local.PeerCertSANs, localPath.Child("peerCertSANs"))...)
		if len(e.Local.ImageRepository) > 0 {
			allErrs = append(allErrs, ValidateImageRepository(e.Local.ImageRepository, localPath.Child("imageRepository"))...)
		}

		LocalAPIEndpoint: kubeadmapi.APIEndpoint{AdvertiseAddress: advertiseIP},
		ClusterConfiguration: kubeadmapi.ClusterConfiguration{
			Etcd: kubeadmapi.Etcd{
				Local: &kubeadmapi.LocalEtcd{
					PeerCertSANs: []string{
						proxy,
						proxyIP,
						"1.2.3.L",
						"invalid,commas,in,DNS",
					},
				},
			},
		},
		NodeRegistration: kubeadmapi.NodeRegistrationOptions{Name: hostname},
	}