[CentOS] upgrade reference docs

[Jonathan Billings]

On Mon, Oct 10, 2016 at 02:20:03PM -0500, Chuck Campbell wrote:
> Is there a Centos 6.x to Centos 7.x guide somewhere? What has changed, that
> I need to learn about as an admin, before I jump in and flounder?

This applies to CentOS too:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Migration_Planning_Guide/index.html

Just ignore the "How to upgrade" section since it talks about the
tools to upgrade from RHEL6 to RHEL7, which I don't believe is
supported in CentOS.  The other sections are what you want to read. 

-- 
Jonathan Billings <billings at negate.org>