## 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.

<sup>* [Source](http://stackoverflow.com/a/21889759/2945616) </sup>