How Do You Get yum Commands to Work?

Problem scenario
You run run commands, but they fail. The error you see is "Trying other mirror [Errno 14] curl #7…"

What should you do?

Solution

1. If the output refers to a DNS name, see if the DNS name is for a load balancer (e.g., an ELB), a router, or a server. See if it is pingable. If it is not, find a Linux server in your network that has yum commands working. See if you can ping the DNS name from that Linux server.
2. If another server on your network has yum commands working, compare /etc/yum.conf files of both. Compare /etc/yum.repos.d/*.repo files too.
3. See if a firewall, network ACL, AWS Security Group, or Azure Network Security Group is preventing communication with the internet. In other words see if you can ping 8.8.8.8.
4. See also How Do You Troubleshoot Yum Commands Not Working with the Error “Could Not Resolve Host: mirror.centos.org Unknown Error?