#  yum  -y  install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

# yum clean all

# yum repolist 

参考

EPEL
https://fedoraproject.org/wiki/EPEL

Extra Packages for Enterprise Linux (EPEL)
https://docs.fedoraproject.org/en-US/epel/