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

The problem is still your pg_hba.conf file*.

This line:

local   all             postgres                                peer

Should be:

local   all             postgres                                md5

* The location of this file isn't very consistent. The command locate pg_hba.conf should help; here's some examples: /etc/postgresql/*/main/pg_hba.conf and /var/lib/pgsql/data/pg_hba.conf.

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

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

Peer authentication

The peer authentication method works by obtaining the client'soperating system user name from the kernel and using it as the alloweddatabase user name (with optional user name mapping). This method isonly supported on local connections.

Password authentication

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

If you are at all concerned about password "sniffing" attacks then md5is preferred. Plain password should always be avoided if possible.However, md5 cannot be used with the db_user_namespace feature. If theconnection is protected by SSL encryption then password can be usedsafely (though SSL certificate authentication might be a better choiceif one is depending on using SSL).

Sample location for pg_hba.conf:
/etc/postgresql/9.1/main/pg_hba.conf

After installing Postgresql I did the below steps.

1. Open the file pg_hba.conf. For Ubuntu, use for example /etc/postgresql/13/main$ sudo nano pg_hba.conf and change this line at the bottom of the file, it should be the first line of the settings:

   local   all             postgres                                peer

   to

   local   all             postgres                                trust

   Side note: If you want to be able to connect with other users as well, you also need to change:

   local   all             all                                peer

   to

   local   all             all                                md5

   If you used nano editor, exit with double Escape, x, y, Enter to save the config file.

2. Restart the server

    $ sudo service postgresql restart

   Output: * Restarting PostgreSQL 13 database server

3. Login into psql and set your password

    $ psql -U postgres db> ALTER USER postgres with password 'your-pass';

   Output: ALTER ROLE

   Side note: If you have other users, they will need a password as well:

    db> ALTER USER my_user with password 'your-pass';

   Then enter:

    exit

4. Finally change the pg_hba.conf from

   local   all             postgres                                trust

   to

   local   all             postgres                                md5

5. Restart the server again

    $ sudo service postgresql restart

   Output: * Restarting PostgreSQL 13 database server

6. Login at psql with postgres user

   After restarting the postgresql server, the postgres user accepts the password that you chose:

    psql -U postgres

   Output:
   Password for user postgres:

   psql (13.4 (Ubuntu 13.4-1.pgdg20.04+1))

   Type "help" for help.

   And you are in psql:

   postgres=#

   Side note: Same now works for my_user if you added the user and password:

    psql -d YOUR_DB_NAME -U my_user

   Which will ask you for the new password of my_user.

Authentication methods details:

trust - anyone who can connect to the server is authorized to access the database

peer - use client's operating system user name as database user name to access it.

md5 - password-base authentication

for further reference check here

If you connect over localhost (127.0.0.1) you shouldn't experience that particular issue. I wouldn't muck much with the pg_hba.conf but instead I would adjust your connection string:

psql -U someuser -h 127.0.0.1 database

where someuser is your user you're connecting as and database is the database your user has permission to connect to.

Here is what I do on Debian to setup postgres:

http://www.postgresql.org/download/linux/debian/  (Wheezy 7.x)as root …    root@www0:~# echo "deb http://apt.postgresql.org/pub/repos/apt/ wheezy-pgdg main" >> /etc/apt/sources.list    root@www0:~# wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add -    root@www0:~# apt-get update    root@www0:~# apt-get install postgresql-9.4            root@www0:~# su - postgres     postgres@www0:~$ createuser --interactive -P someuser    Enter password for new role:    Enter it again:    Shall the new role be a superuser? (y/n) n    Shall the new role be allowed to create databases? (y/n) y    Shall the new role be allowed to create more new roles? (y/n) n    postgres@www0:~$ createdb -O someuser database    postgres@www0:~$ psql -U someuser -h 127.0.0.1 database

Enjoy!