I was getting “Failed to verify krb5 credentials: Server not found in Kerberos database” errors when trying to use Kerberos authentication in Apache2. The problem was in my /etc/hosts file. I needed to change this:

10.183.97.44    charity.progclub.org charity
67.207.128.184  charity-public

To this:

10.183.97.44    charity.progclub.org charity
67.207.128.184  charity.progclub.org charity-public