@Craig Ringer, I am afraid I didn't understand your solution.
The scenario I am having is a system which has only user as root. I have all the permissions and privileges of the system as the user is root. But pgsql doesn't allow initdb to be executed by root.
I think the solution you proposed gives root permissions for a non-root user.
But I believe, I am looking forward for the exact opposite of it. In other words, a possible work around for a root user to execute certain executable(s) as an unprivileged user.
