Error: cannot retrieve metalink for repository epel. please verify its path and try again

I got that error message when I tried to use YUM on CentOS 6.

Two possible issues and solutions:

1. system time is incorrect.

2. ca-cert needs to be updated.

 

For #1, install NTP and set date/time:

1. yum install ntp npdate
2. chkconfig ntpd on
3. ntpdate pool.ntp.org
4. service ntpd start

For #2, update CA-cert: yum update -y ca-certificates