To convince systemd to write to this socket, go to /etc/systemd/journald.conf and set
ForwardToSyslog=yes
then issue a journald restart
systemctl restart systemd-journald
You can install syslog-ng and it should pick up the logs. Test it now by making a log entry with
logger -t WARN zool
and check /var/log/syslog.log
[..]
Configure the syslog-ng.conf’s source src { system(); }; to pick up the socket file:
source src {
unix-dgram("/run/systemd/journal/syslog");
internal();
};