Problems with initdb

Hi all,

I'm endeavouring to build postgresql from source (something with which I
have no experience). I can configure, make and make install and all runs
fine but when I try to run initdb it fails with a message about shared
memory buffers and maximum connections. The docs refer to changing these in
the .config file but if I create a config file and place it in the data
folder then initdb refuses to run on that folder.

Is there another way to change the maximum connections and shared buffer
size - prior to any dbs being initialised? Can this be set somewhere when
doing the make or make install?

Any help for a newbie trying hard to understand would be appreciated.

cheers

Kim