Ubuntu server, postgresql, python, "Peer auth failed"

Question

Hi I'm getting the following and the other solutions I've seen for this don't seem to be working... Within the ubuntu server terminal (a virtualbox vm): Error FATAL: Peer authentication failed for user "a4apps"

My Ubuntu server os user name is the same. I have restarted my postgres. I have tried changing my pg_hba.conf file by: changing the IPv4 host method from md5 to "trust" and by adding a line under it "host all all myubuntuserverip/32 trust"

I am trying to access it via a python script. I am using psycopg

con = psycopg2.connect(database='fieldtest2', user='a4apps')

I created the user: sudo -u postgres create user a4apps superuser no, create databases yes, create other users no. Created database: sudo -u postgres createdb fieldtest2 -O a4apps

I was following this tutorial: here

I'm running out of ideas. Any guidance would be appreciated. Thanks Mike

Answer 1

This specific error message:

Peer authentication failed for user "a4apps"

means that the peer authentication method was selected per pg_hba.conf and that the connection attempt was not made by the OS user a4apps, contrary to what this auth method requires.

The default Ubuntu pg_hba.conf has these lines:

# Database administrative login by Unix domain socket
local   all             postgres                                peer

# TYPE  DATABASE        USER            ADDRESS                 METHOD

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

To allow local passwordless connections for any user except postgres, you may replace peer by trust in the last line.

The IPv4-related changes you tried in pg_hba.conf had no effect on your script because it doesn't connect through TCP/IP. If the connection string mentioned a hostname, it would then use TCP/IP and trigger the corresponding rules in pg_hba.conf.