Just follow these steps
service odoo-server stop
#Remove config file(s) rm -f /etc/odoo-server.conf rm -f /etc/odoo.conf
#Remove application code rm -R /opt/odoo
#Remove startup process update-rc.d -f odoo-server remove rm -f /etc/init.d/odoo-server
#Remove logs rm -R /var/log/odoo
#Remove databases sudo service postgresql stop
apt-get remove postgresql -y
apt-get --purge remove postgresql* -y
rm -r -f /etc/postgresql/
rm -r -f /etc/postgresql-common/
rm -r -f /var/lib/postgresql/
#Delete users and groups userdel -r postgres groupdel postgres
To Remove postgre find the file pg_hba.conf - it may be located, for example in /etc/postgresql-9.1/pg_hba.conf.
cd /etc/postgresql-9.1/
Back it up cp pg_hba.conf pg_hba.conf-backup
place the following line (as either the first uncommented line, or as the only one):
local all all trust
restart your PostgreSQL server (e.g., on Linux:)
sudo /etc/init.d/postgresql restart
you can now connect as any user. Connect as the superuser postgres (note, the superuser name may be different in your installation. In some systems it is called pgsql, for example.)
psql -U postgres
#Reset password ALTER USER my_user_name with password 'my_secure_password';
Restore the old pg_hba.conf as it is very dangerous to keep around
cp pg_hba.conf-backup pg_hba.conf
restart the server, in order to run with the safe pg_hba.conf
sudo /etc/init.d/postgresql restart