The parameter file is the main location for defining parameter values for the PostgreSQL server. All the parameters can be set in the parameter file, which is known as postgresql.conf.
There are also two other parameter files: pg_hba.conf and pg_ident.conf. Both of these relate to connections and security, so we'll cover them in the appropriate chapters that follow.
Some of the parameters take effect only when the server is first started. A typical example might be shared_buffers, which defines the size of the shared memory cache.
Many of the parameters can be changed while the server is still running. After changing the required parameters, we issue a reload operation to the server, forcing PostgreSQL to reread the postgresql.conf file (and all other configuration files):
pg_ctl reload
As noted earlier, Debian and Ubuntu have different multiversion architecture, so you should issue the...