QGIS PostGIS Authentication Failure with "trust" option I'm trying to setup a PostGIS db using PostgreSQL 9.1 on Ubuntu 12.04. I've set up the database, created a user account "jay" with no password, added spatial functionality following section 2.5 here, and set my  pg_hba.conf for local to:

# "local" is for Unix domain socket connections only
local   all             all                                     trust


I can can connect to the database using the pgAdminIII, requiring no password to connect, but connection fails when I try to connect via PostGIS or with QuantumGIS. Here's a screencap of the connection window in QuantumGIS:


Looking into the problem a bit, I came across this post which led me to try connecting via the terminal using psql -U jay -h localhost gis. psql prompted me for a password, I hit enter because I had not set a password, and it returned psql: fe_sendauth: no password supplied. I tried again, this time supplying my Ubuntu user password, which returned 


psql: FATAL:  password authentication failed for user "jay"
FATAL:  password authentication failed for user "jay"



I then tried setting a password for jay using ALTER USER, and entering this password in the prompt, and this failed as well. Clearly, I am unable to connect. However, I'm having trouble figuring out what troubleshooting steps to take next.

Any ideas?
Just don't leave the Database field empty in the connection dialog.

When left empty, it will attempt to connect to a database named after your OS login name, which probably doesn't exist in your case.

The Host field should be left empty to use a Unix domain socket connection, as hinted by the snippet of your pg_hba.conf shown in the question.

When you put localhost in this field, it attempts a TCP connection which is not what's called local in the pg_hba.conf terminology, so that the entry local all all trust will not match with such a connection.