fix

pkg/client/cluster.go

@@ -1051,26 +1051,33 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 			// -> inject hostAliases and network members into CoreDNS configmap
 			if len(servers) > 0 {
 				postStartErrgrp.Go(func() error {
-					net, err := runtime.GetNetwork(postStartErrgrpCtx, &cluster.Network)
-					if err != nil {
-						return fmt.Errorf("failed to get cluster network %s to inject host records into CoreDNS: %w", cluster.Network.Name, err)
+					type record struct {
+						IP       string
+						Hostname string
 					}
-					hosts := make([]string, 0, len(net.Members)+1)
+
+					records := make([]record, 0)
 
 					// hosts: hostAliases (including host.k3d.internal)
 					for _, hostAlias := range clusterStartOpts.HostAliases {
-						hosts = append(hosts, fmt.Sprintf("%s %s\n", hostAlias.IP, strings.Join(hostAlias.Hostnames, " ")))
+						for _, hostname := range hostAlias.Hostnames {
+							records = append(records, record{IP: hostAlias.IP, Hostname: hostname})
+						}
 					}
 
 					// more hosts: network members ("neighbor" containers)
+					net, err := runtime.GetNetwork(postStartErrgrpCtx, &cluster.Network)
+					if err != nil {
+						return fmt.Errorf("failed to get cluster network %s to inject host records into CoreDNS: %w", cluster.Network.Name, err)
+					}
 					for _, member := range net.Members {
-						hosts = append(hosts, fmt.Sprintf("%s %s\n", member.IP.String(), member.Name))
+						records = append(records, record{IP: member.IP.String(), Hostname: member.Name})
 					}
 
 					// inject CoreDNS configmap
 					l.Log().Infof("Injecting records for hostAliases (incl. host.k3d.internal) and for %d network members into CoreDNS configmap...", len(net.Members))
 					var custom_dns bytes.Buffer
-					err = customDNSTemplate.Execute(&custom_dns, hosts)
+					err = customDNSTemplate.Execute(&custom_dns, records)
 					if err != nil {
 						return fmt.Errorf("failed to render template: %w", err)
 					}

pkg/client/templates/coredns-custom.yaml.tmpl

@@ -5,9 +5,11 @@ metadata:
   namespace: kube-system
 data:
   hosts.override: |
-    hosts {
-        {{- range . }}
-        {{ . }}
-        {{- end }}
-        fallthrough
-    }
+    file /etc/coredns/custom/additional-dns.db
+
+  # a SOA record is required
+  additional-dns.db: |
+    @ 3600 IN SOA a.root-servers.net. nstld.verisign-grs.com. 2024061200 1800 900 604800 86400
+    {{- range . }}
+    {{ .Hostname }} IN A {{ .IP }}
+    {{- end }}