Re: Changing the data directory path before the initial configuration of PostgreSQL 10.7.1

The easiest way is moving /var/lib/pgsql/data under /xyz directory
(when the db is not running) and create a symlink in the original
location:

chown postgres: /xyz
su - postgres
mv /var/lib/pgsql/data /xyz/10-data
ln -s /xyz/10-data /var/lib/pgsql/data

Then you can use setup script as usual.

Another alternative is creating a copy of the unit file under
/etc/systemd/system, changing $PGDATA inside that file and run the
setup script. This should be documented on the top of the unit file.