This is Dockerfile/spec/patches to create Docker RPM for CentOS6.
docker build -t docker-rpm-el6 .
docker run docker-rpm-el6 tar cf - -C /rpmbuild RPMS | tar xf -
or you can also do this:
$ docker run maebashi/docker-rpm-el6 tar cf - -C /rpmbuild RPMS | tar xf -