Establecer contraseña para el usuario de Postgres Ubuntu
sudo -u postgres psql
ALTER USER <myuser> WITH PASSWORD 'mypassword';
Classy Answer
sudo -u postgres psql
ALTER USER <myuser> WITH PASSWORD 'mypassword';ALTER USER user_name WITH PASSWORD 'new_password';ALTER USER user_name WITH PASSWORD 'new_password';
sudo -u postgres psql
\password postgres