You cannot migrate from CentOS 5 to a newer major release. Even the theoretically supported migration from Centos 6 to 7 comes with so many limitations that in practical terms I found it to be useless.
You will need to install a new server with CentOS 7, reinstall your applications and migrate your data.
If you have chef recipes that created your CentOS 5 server, you can probably modify them (or if you are lucky, use them out of the box) and use them to set up a CentOS 7 server. Be sure to test this carefully before applying it in production.
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