begind namespace deprecation

lib/service/service.go

@@ -2250,7 +2250,11 @@ func (process *TeleportProcess) initSSH() error {
 		}
 		// TODO: are we missing rm.Close()
 
-		// make sure the namespace exists
+		// make sure the default namespace is used
+		if ns := cfg.SSH.Namespace; ns != "" && ns != apidefaults.Namespace {
+			return trace.BadParameter("cannot start with custom namespace %q, custom namespaces are deprecated. "+
+				"use builtin namespace %q, or omit the 'namespace' config option.", ns, apidefaults.Namespace)
+		}
 		namespace := types.ProcessNamespace(cfg.SSH.Namespace)
 		_, err = authClient.GetNamespace(namespace)
 		if err != nil {

lib/services/local/presence.go

@@ -242,7 +242,11 @@ func (s *PresenceService) GetNodes(ctx context.Context, namespace string) ([]typ
 // specified duration with second resolution if it's >= 1 second.
 func (s *PresenceService) UpsertNode(ctx context.Context, server types.Server) (*types.KeepAlive, error) {
 	if server.GetNamespace() == "" {
-		return nil, trace.BadParameter("missing node namespace")
+		server.SetNamespace(apidefaults.Namespace)
+	}
+
+	if n := server.GetNamespace(); n != apidefaults.Namespace {
+		return nil, trace.BadParameter("cannot place node in namespace %q, custom namespaces are deprecated", n)
 	}
 
 	value, err := services.MarshalServer(server)