1、系统自带
base
extras
updates
2、epel
yum install epel-release
https://fedoraproject.org/wiki/EPEL
3、el（用于升级内核）
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org rpm -Uvh http://www.elrepo.org/elrepo-release-6-6.el6.elrepo.noarch.rpm
http://elrepo.org/tiki/tiki-index.php
4、sclo（用于安装Red Hat software collection）
yum install centos-release-scl-rh centos-release-scl
https://wiki.centos.org/AdditionalResources/Repositories/SCL