The problem here appears to be that /tmp is a tmpfs filesystem and the script is trying to nfs-export a directory on this filesystem. tmpfs filesystems do not have a UUID so nfs doesn't know how to identify them. In order to export a tmpfs filesystem to need to provide a identifying number using "fsid=NN". See "man exports". Adding the export option "fsid=23" should suffice (any number > 0 should do).