So I was banging my head on the common issue of:

ERROR: Installation can not proceeed. Please fix your /etc/hosts file to contain: localhost.localdomain localhost

I had followed all the set up recommendations

hostname --fqdn ... was fine
/etc/hosts .. was fine the localhost entry was correct, the format was fqdn shortname
/etc/resolv.conf .. was good with my split dns first
dig mx .. fine
dig any ... fine
host `hostname` ... fine

I was pulling out my hair wondering what the heck it was.

So I looked at the code and saw that what the script checks for is getent hosts.

So I ran the command and saw some weird entries...

So that put me on the right track... The issue was that I was running nscd, and it had cached old values of my hosts file.

I flushed nscd with nscd -i hosts, and it works like a charm.

I figured that might save someone a few headaches down the road