psql: FATAL:  Ident authentication failed for user "username" Error and Solution
Q. I've installed Postgresql under Red Hat Enterprise Linux 5.x server. I've created username / password and database. But when I try to connect it via PHP or psql using following syntax:

 {{{
psql -d  myDb -U username  -W}}}
It gives me an error that read as follows:

 {{{
psql: FATAL:  Ident authentication failed for user "username"}}}
How do I fix this error?

 A. To fix this error open PostgreSQL client authentication configuration file /var/lib/pgsql/data/pg_hba.conf :

{{{
# vi  /var/lib/pgsql/data/pg_hba.conf}}}
 This file controls:

 1. Which hosts are allowed to connect
 1. How clients are authenticated
 1. Which PostgreSQL user names they can use
 1. Which databases they can access
By default Postgresql uses IDENT-based authentication. All you have to do is allow username and password based authentication for your network or webserver. IDENT will never allow you to login via -U and -W options. Append following to allow login via localhost only:

{{{
local	all	all	trust
host	all	127.0.0.1/32	trust}}}
Save and close the file. Restart Postgresql  server:

{{{
# service postgresql restart}}}
 Now, you should able to login using following command:

{{{
$ psql -d  myDb -U username  -W}}}