Postgres User and Password

I was not able to get an RPM build for Calder Edesktop 2.3 & 2.4..
So, I downloaded source for Postgres v 7.0.3 and rolled my own..
I compiled the source to 3 linux boxes and Installed to 3 OS/2 boxes.

My problem is with my Linux Posgres installations.
I compiled as root and installed as root user. As root I can
root(at)thinkpad root]# su postgres
root(at)thinkpad root]# pg_ctl start ........... Or use postmaster

and successfully start the server.. As I have set all Path and Data
enviormental variables.
But, if I try this as a user
Bob(at)thinkpad Bob]# su postgres ............. My results is
password: ............ Then no
matter whats entered, even NULL

........... I get
su: incorrect password

I had no password for User postgres but I finally gave it one but no
help..
I made root and Bob both members of Group database.. no help.
Once server is started Bob is a postgres user and can start and use
psql...

Very inconvenient to log in as root then su postgres then back to User
login to
development tools..
How can I fix this problem..

Thank You
Bob T