Issue
From Mar 31, 2017 onwards, CentOS 5 is EOL.
When updating OnApp software packages using yum, you may now see errors like:
[Errno 14] HTTP Error 404: Not Found
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: updates. Please verify its path and try again
Resolution
Edit the config file /etc/yum.repos.d/CentOS-Base.repo and under each section add the following line:
baseurl=http://vault.centos.org/5.11/os/$basearch/