Postgres Problems with Phusion Deployment (Rails)
Read the Ubuntu documentation on their PostgreSQL packages, which you'll find in /usr/share/doc . Alternately, there's a nice wiki page on it here: https://help.ubuntu.com/community/PostgreSQL (first hit for "ubuntu postgresql").

You have a pg_hba.conf file that's set to try to use ident authentication for host (TCP/IP) connections, but you don't have an identd running or you're trying to connect as a different PostgreSQL user to your unix username.

You need to set a paassword for the user and change the authentication method to md5. See the client authentication chapter of the documentation.

(A truly definitive answer would be easier to make if you'd given the command you ran to get that error).