Problems connecting to PostgreSQL

[Chris Warrick]

On 8 November 2015 at 00:40, Cecil Westerhof <Cecil at decebal.nl> wrote:
> I followed http://zetcode.com/db/postgresqlpythontutorial/.
>
> I used:
>     sudo -u postgres createuser stressTest
> this create the role, but also gave:
>     could not change directory to "/root": Permission denied
> and I did not get the questions.

This is not an error, just a warning — and it comes from sudo,
postgres doesn’t care. To silence it, you need to work from a
different directory than /root.  The commands actually worked just
fine.

> Then I used:
>     sudo -u postgres createdb stressTest -O stressTest
> This gave also:
>     could not change directory to "/root": Permission denied
>
> The database is created, but when I execute:
>     conn = psycopg2.connect(database = postgres_database, user = 'stressTest')
> I get:
>     psycopg2.OperationalError: FATAL:  Peer authentication failed for user "stressTest"
>
> What do I need to do to get things working?

You need to configure your PostgreSQL database to use md5
authentication, and set a password for your user.

    # cd /
    # sudo -u postgres psql
    postgres=# ALTER ROLE stressTest WITH PASSWORD 'swordfish';
    postgres=# \q
    # vim /var/lib/postgres/data/pg_hba.conf

Change host settings to look like this:
    # IPv4 local connections:
    host    all             all             127.0.0.1/32            md5
    # IPv6 local connections:
    host    all             all             ::1/128                 md5

Then you can connect using:

    conn = psycopg2.connect(database='stressTest', user='stressTest',
password='swordfish', host='localhost')

Documentation:
http://www.postgresql.org/docs/current/static/auth-pg-hba-conf.html
http://www.postgresql.org/docs/current/static/auth-methods.html
http://www.postgresql.org/docs/current/static/sql-alterrole.html

(basically, the default peer authentication checks your Unix user name
to see if it matches 'stressTest', and fails)

-- 
Chris Warrick <https://chriswarrick.com/>
PGP: 5EAAEA16