Different Linux distros have their preferred place of where stuff goes and of course the default location on windows is completely different from that too. So there isn't really one default location where you can find PostgreSQL data cluster. Of course user's can pick their
locations as well. So what is a casual DBA supposed to do?
The pg_settings table
PostgreSQL has a convenient system
table view called pg_settings that stores a lot of information. It stores the location of the data cluster, the pg_hbafile and other conf files.
In additon to that you can interogate it to find out information you will find in the postgresql.conf file. Why sift thru that postgresql.conf file (assuming you can already query your postgresql server) when you can find the answers you are looking
for with an SQL query?