How to make psql to default to localhost?

Question

I have the following scenario:

saji@geeklap:~$ psql -U postgres
psql: FATAL:  Ident authentication failed for user "postgres"

saji@geeklap:~$ psql -h localhost -U postgres
Password for user postgres: 
psql (8.4.14)
SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)
Type "help" for help.

postgres=# 

I'm trying to log into the postgresql server installed in my system as user postgres. I'm able to login only if I specify -h localhost. Whereas psql documentation says that:

If you omit the host name, psql will connect via a Unix-domain socket to a server on the local host, or via TCP/IP to localhost on machines that don't have Unix-domain sockets.

Ref: http://www.postgresql.org/docs/current/static/app-psql.html#R2-APP-PSQL-CON

Why am I unable to login without specifying the host, is there some configuration file that needs any change for things to occur as told in the psql documentation?

Answer 1

In fact, it works as documented.

When the host name is omitted, psql connects to the Unix-domain socket whose path is compiled in. That part works in your case, otherwise it would output a different error message than what the question shows.

The error message in the question:

psql: FATAL:  Ident authentication failed for user "postgres"

relates to the fact that only the Unix user postgres has the permission to connect as the database user postgres when using a Unix-domain socket. This is configured in the pg_hba.conf file.

what you should typically do in Ubuntu when you're logged in as a normal user, but you're the administrator of the system:

$ sudo -u postgres psql

Answer 2

If you don't like the default of connecting via a unix socket, you can set the environment variable PGHOST. I have

export PGHOST="db"

in my ~/.bashrc, to connect to the server with that name. A few more handy environment variables are documented at http://www.postgresql.org/docs/9.5/static/libpq-envars.html