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@thinkpad root]#  su postgres
root@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@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