Reset PostgreSQL database password

Backup this file:

cp /var/lib/pgsql/data/{pg_hba.conf,pg_hba.conf.backup}

Overwrite all content with super user mode:

echo local  all   all   trust> /var/lib/pgsql/data/pg_hba.conf

Check if there really is some content:

cat /var/lib/pgsql/data/pg_hba.conf

Restart service:

service postgresql restart

Enter database mode:

psql -U postgres

Set new password to user postgres:

ALTER USER postgres with password 'rand0m';

Exit database mode:

\q

Restore configuration file:

cp /var/lib/pgsql/data/{pg_hba.conf.backup,pg_hba.conf}

Check if there is some old content:

grep -v "^$\|#" /var/lib/pgsql/data/pg_hba.conf

Restart service:

service postgresql restart