createrepo -g /enp/comps.xml .
yum -y --downloadonly --downloaddir=/enp/Packages upgrade
mkisofs -o /srv/openStackPackages-again.iso -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -R -J -v -T /enp/
原文：http://www.cnblogs.com/ruiy/p/5404818.html