clusterCreate: add --no-hostip flag to disable the automatic injection of the host.k3d.internal entry into /etc/hosts and CoreDNS

cmd/cluster/clusterCreate.go

@@ -134,6 +134,7 @@ func NewCmdClusterCreate() *cobra.Command {
 	cmd.Flags().BoolVar(&updateCurrentContext, "switch-context", true, "Directly switch the default kubeconfig's current-context to the new cluster's context (requires --update-default-kubeconfig)")
 	cmd.Flags().BoolVar(&createClusterOpts.DisableLoadBalancer, "no-lb", false, "Disable the creation of a LoadBalancer in front of the server nodes")
 	cmd.Flags().BoolVar(&noRollback, "no-rollback", false, "Disable the automatic rollback actions, if anything goes wrong")
+	cmd.Flags().BoolVar(&createClusterOpts.PrepDisableHostIPInjection, "no-hostip", false, "Disable the automatic injection of the Host IP as 'host.k3d.internal' into the containers and CoreDNS")
 
 	/* Image Importing */
 	cmd.Flags().BoolVar(&createClusterOpts.DisableImageVolume, "no-image-volume", false, "Disable the creation of a volume for importing images")

pkg/cluster/cluster.go

@@ -358,24 +358,26 @@ func ClusterCreate(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clus
 	 * Networking Magic
 	 */
 
-	// add extra host
-	hostIP, err := GetHostIP(clusterPrepCtx, runtime, cluster)
-	if err != nil {
-		log.Errorln("Failed to get HostIP")
-		return err
-	}
-	hostsEntry := fmt.Sprintf("%s %s", hostIP, k3d.DefaultK3dInternalHostRecord)
-	log.Debugf("Adding extra host entry '%s'...", hostsEntry)
-	for _, node := range cluster.Nodes {
-		if err := runtime.ExecInNode(clusterPrepCtx, node, []string{"sh", "-c", fmt.Sprintf("echo '%s' >> /etc/hosts", hostsEntry)}); err != nil {
-			log.Warnf("Failed to add extra entry '%s' to /etc/hosts in node '%s'", hostsEntry, node.Name)
+	// add /etc/hosts and CoreDNS entry for host.k3d.internal, referring to the host system
+	if !cluster.CreateClusterOpts.PrepDisableHostIPInjection {
+		hostIP, err := GetHostIP(clusterPrepCtx, runtime, cluster)
+		if err != nil {
+			log.Errorln("Failed to get HostIP")
+			return err
+		}
+		hostsEntry := fmt.Sprintf("%s %s", hostIP, k3d.DefaultK3dInternalHostRecord)
+		log.Debugf("Adding extra host entry '%s'...", hostsEntry)
+		for _, node := range cluster.Nodes {
+			if err := runtime.ExecInNode(clusterPrepCtx, node, []string{"sh", "-c", fmt.Sprintf("echo '%s' >> /etc/hosts", hostsEntry)}); err != nil {
+				log.Warnf("Failed to add extra entry '%s' to /etc/hosts in node '%s'", hostsEntry, node.Name)
+			}
 		}
-	}
 
-	patchCmd := `test=$(kubectl get cm coredns -n kube-system --template='{{.data.NodeHosts}}' | sed -n -E -e '/[0-9\.]{4,12}\s+host\.k3d\.internal$/!p' -e '$a` + hostsEntry + `' | tr '\n' '^' | xargs -0 printf '{"data": {"NodeHosts":"%s"}}'| sed -E 's%\^%\\n%g') && kubectl patch cm coredns -n kube-system -p="$test"`
-	err = runtime.ExecInNode(clusterPrepCtx, cluster.Nodes[0], []string{"sh", "-c", patchCmd})
-	if err != nil {
-		log.Warnf("Failed to patch CoreDNS ConfigMap to include entry '%s': %+v", hostsEntry, err)
+		patchCmd := `test=$(kubectl get cm coredns -n kube-system --template='{{.data.NodeHosts}}' | sed -n -E -e '/[0-9\.]{4,12}\s+host\.k3d\.internal$/!p' -e '$a` + hostsEntry + `' | tr '\n' '^' | xargs -0 printf '{"data": {"NodeHosts":"%s"}}'| sed -E 's%\^%\\n%g') && kubectl patch cm coredns -n kube-system -p="$test"`
+		err = runtime.ExecInNode(clusterPrepCtx, cluster.Nodes[0], []string{"sh", "-c", patchCmd})
+		if err != nil {
+			log.Warnf("Failed to patch CoreDNS ConfigMap to include entry '%s': %+v", hostsEntry, err)
+		}
 	}
 
 	return nil

pkg/types/types.go

@@ -133,12 +133,13 @@ var DoNotCopyServerFlags = []string{
 
 // ClusterCreateOpts describe a set of options one can set when creating a cluster
 type ClusterCreateOpts struct {
-	DisableImageVolume  bool
-	WaitForServer       bool
-	Timeout             time.Duration
-	DisableLoadBalancer bool
-	K3sServerArgs       []string
-	K3sAgentArgs        []string
+	PrepDisableHostIPInjection bool
+	DisableImageVolume         bool
+	WaitForServer              bool
+	Timeout                    time.Duration
+	DisableLoadBalancer        bool
+	K3sServerArgs              []string
+	K3sAgentArgs               []string
 }
 
 // ClusterStartOpts describe a set of options one can set when (re-)starting a cluster