Well, here are the relevant parts of the service file:
get_config() {
[ -f "${PGDATA%/}/postgresql.conf" ] || return 1
eval echo $(sed -e 's:#.*::' "${PGDATA%/}/postgresql.conf" \
| awk '$1 == "'$1'" { print ($2 == "=" ? $3 : $2) }')
}
depend() {
use net
provide postgresql
if [ "$(get_config log_destination)" = "syslog" ]; then
use logger
fi
}
If PostgreSQL has been configured, this reads its config file, looks to see if it's configured to use 'syslog' as its log destination, and -if so- adds a dependency on the 'logger' "meta-service". [0]
What would this look like with a systemd service file generator?
[0] What's a "meta-service"? 'provide postgresql' makes the service started by this service file provide the 'postgresql' "meta-service". This is useful for PostgreSQL because you can install multiple versions of the software simultaneously... so the service files are named like postgresql-17, and postgresql-18. The 'logger' "meta-service" is useful because who cares which syslog software you have installed... you only care that it speaks syslog.
What would this look like with a systemd service file generator?
[0] What's a "meta-service"? 'provide postgresql' makes the service started by this service file provide the 'postgresql' "meta-service". This is useful for PostgreSQL because you can install multiple versions of the software simultaneously... so the service files are named like postgresql-17, and postgresql-18. The 'logger' "meta-service" is useful because who cares which syslog software you have installed... you only care that it speaks syslog.