@@ -14,10 +14,12 @@ import (

 // ExecIn uses an existing pid and joins the pid's namespaces with the new command.

 func (ns *linuxNs) ExecIn(container *libcontainer.Container, nspid int, args []string) (int, error) {

-	ns.logger.Println("unshare namespaces")

-	for _, ns := range container.Namespaces {

-		if err := system.Unshare(ns.Value); err != nil {

-			return -1, err

+	for _, nsv := range container.Namespaces {

+		// skip the PID namespace on unshare because it it not supported

+		if nsv.Key != "NEWPID" {

+			if err := system.Unshare(nsv.Value); err != nil {

+				return -1, err

+			}

 		}

 	}

 	fds, err := ns.getNsFds(nspid, container)