The following error is reported when CentOS uses yum, a third-party source.
GPGkeyretrievalfailed:[Errno14]Couldnotopen/readfile:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL
Two Solutions:
edit etc/yum.repos.d/rpmforge.repo and change gpgcheck=0
Execution rpm--import/etc/pki/rpm-gpg/RPM* or rpm--importhttp://apt.sw.be/RPM-GPG-KEY.dag.txt