postgres database objects are represented as files, or directories on the filesystem level (inside $PGDATA/base/).
I can see that i.e. for database, table.
What is the presentation of a postgres role/user on the fs level?
This can be useful in order to see when a user was created or modified which is what I want to do atm.
for this I neither can see any function with such kind of information.
Database objects are not represented as files in PostgreSQL.
True, each table has one or more data files, but a table is more than these files: it is defined by entries in metadata tables like pg_class, pg_attribute, pg_attrdef, pg_type (to name only a few).
A PostgreSQL role doesn't have data files, since it doesn't contain any data. It only consists of an entry in pg_authid. Now PostgreSQL doesn't store the time when a table row was created, so there is no way to find out when a role was created.
Your best bet is to use an event trigger that writes an entry into a logging table whenever a role is created.
