Getting error: Peer authentication failed for user “postgres”, when trying to get pgsql working with rails

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The problem is still your pg_hba.conf file*.

This line:

local   all             postgres                                peer

Should be:

local   all             postgres                                md5

After altering this file, don’t forget to restart your PostgreSQL server. If you’re on Linux, that would be sudo service postgresql restart.

Locating hba.conf

Note that the location of this file isn’t very consistent.

You can use locate pg_hba.conf or ask PostgreSQL SHOW hba_file; to discover the file location.

Usual locations are /etc/postgresql/[version]/main/pg_hba.conf and /var/lib/pgsql/data/pg_hba.conf.

These are brief descriptions of the peer vs md5 options according to the official PostgreSQL docs on authentication methods.

Peer authentication

The peer authentication method works by obtaining the client’s
operating system user name from the kernel and using it as the allowed
database user name (with optional user name mapping). This method is
only supported on local connections.

Password authentication

The password-based authentication methods are md5 and password. These
methods operate similarly except for the way that the password is sent
across the connection, namely MD5-hashed and clear-text respectively.

If you are at all concerned about password “sniffing” attacks then md5
is preferred. Plain password should always be avoided if possible.
However, md5 cannot be used with the db_user_namespace feature. If the
connection is protected by SSL encryption then password can be used
safely (though SSL certificate authentication might be a better choice
if one is depending on using SSL).

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