> 1) host=xx.xx.xx.100 = localhost?
No, it is not
> 2) In postgresql.conf what is listen_addresses set to?
*
> 3) What are the settings in /etc/hosts?
Standard Ubuntu settings:
127.0.0.1 localhost
127.0.1.1 abc cde
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
Regards
Daniel