psql: FATAL: Peer authentication failed for user “postgres” (or any user)

The connection failed because by default psql connects over UNIX sockets using peer authentication, that requires the current UNIX user to have the same user name as psql. So you will have to create the UNIX user postgres and then login as postgres or use sudo -u postgres psql database-name for accessing the database (and psql should not ask for a password).

If you cannot or do not want to create the UNIX user, like if you just want to connect to your database for ad hoc queries, forcing a socket connection using psql --host=localhost --dbname=database-name --username=postgres (as pointed out by @meyerson answer) will solve your immediate problem.

But if you intend to force password authentication over Unix sockets instead of the peer method, try changing the following pg_hba.conf* line:

from

# TYPE DATABASE USER ADDRESS METHOD
local  all      all          peer

to

# TYPE DATABASE USER ADDRESS METHOD
local  all      all          md5

• peer means it will trust the identity (authenticity) of UNIX user. So not asking for a password.

• md5 means it will always ask for a password, and validate it after hashing with MD5.

• trust means it will never ask for a password, and always trust any connection.

You can, of course, also create more specific rules for a specific database or user, with some users having peer and others requiring passwords.

After changing pg_hba.conf you'll need to restart PostgreSQL if it's running. E.g. sudo service postgresql restart

Steps to change/create default postgres user's password:

1. trust connection by adding in pg_hba.conf file

• local all postgres trust

2. Restart postgresql service

• sudo service postgresql restart

3. psql -U postgres

4. At the postgres=# prompt, change the user name postgres password:

• ALTER USER postgres with password ‘new-password’;

5. Revert the changes in pg_hba.conf file from trust to md5 and restart postgresql.

pg_hba.conf file location

The file pg_hba.conf will most likely be at /etc/postgresql/9.x/main/pg_hba.conf To check location of pg_hba.conf connect to postgres db using psql then type SHOW hba_file; command.

After change pg_hba.conf file, you can execute SELECT pg_reload_conf(); or pg_ctl reload with superuser instead of restart postgresql service.

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