Permission to postgres to another user's folder

Hello,

Can anyone please throw some light on the behavior of postgres when it comes
to permission issues... I'm using enterprisedb 8.3 on opensuse linux 10.3
and 11 (2 machines).
This is what i have understood so far:

Lets say user user1 is a non-root user. I login to the machine as root and
install enterprisedb. During installation i'm asked for an existing
non-root user to act as the 'owner' of the installation. I provide 'user1'.
So user1 becomes the 'owner' of the installation and has the privilege of
starting and stopping the service. Also the file .pgpass (postgres password
file) gets automatically created in user1's home folder and it contains a
line for localhost, specifying the password of user postgres. If this
file exists in any user's home, then that user will be allowed to connect to
postgres server without a password.

Now during installation, the user 'postgres' will be created if it doesnt
already exist. And these 2 users (user1, postgres) will have write
permissions to each other's home directories.

Please tell me if my understanding so far is correct and if you can
enlighten me further.

My requirement is to let postgres have write access to another user's home
directory (say 'tomcat' which could be a system user) and vice versa ie
tomcat should have write access to postgres' home and also password-less
access to psql. And similarly other OS users might need the same
permissions.

Another doubt: How and when does the .pgpass file gets created and its
contents get added? I saw that explicitly creating a file for an OS user
and adding an entry for localhost enables the user to connect to psql w/o a
password. And similarly if remote connection is enabled in a remote server,
an entry should exist for the remote server in the local .pgpass file. I
want to know how much of this happens automatically and when.

Thanks a ton,
Shruthi