Cannot set postgres user password

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http://serverfault.com – Trying to install PostgreSQL with Ruby on Rails with Nginx on CentOS 6.5 using the following guide: http://karolgalanciak.com/blog/2013/07/19/centos-6-4-server-setup-with-r... After install I went to configure the user, so issued command sudo su postgres then psql. When I do this, I get the following error: could not change directory to "/root": Permission denied psql (9.3.4) Ignoring this, I issued the command: alter user postgres with password 'postgres-user-password'; Then I went to change the auth method to md5 dy doing: sudo vi /var/lib/pgsql/9.3/dat (HowTos)