CentOS 6.4 安装 epel 源后报这个错误，百度一下都是说 

  “

编辑/etc/yum.repos.d/epel.repo，把基础的恢复，镜像的地址注释掉

#baseurl
mirrorlist

改成

baseurl
#mirrorlist

 ”

这个可以称为 “扬汤止沸”。真正的解决还得借签歪果仁的方法，

"

You just needed to update ca-certificates package. Before that just disable all repos with https that are failing. That's why sollution with commenting mirrorlist or using http instead https would work also.

For example if you need to disable only epel repo:

yum --disablerepo=epel -y update  ca-certificates

This will also help wget, curl, and anything else that uses SSL certificates.

"

这是因为 ca-certificates 这个包太旧的原因，更新一下就好了。在新一些的 比如 centos-6.7 上是没有这个问题的。