Some of the common problems often seen with OpenBSD "how-to" instructions found on the Internet from unofficial sources
- They are out-of-date
- They contain misleading or incomplete information
- They are written for a specific implementation rather than general use
- They are written by proud newbies who may not understand best practices.
You didn't provide a link, and I'm not going to go hunting for the how-to, but as your author has you modifying /etc/rc, I'm betting #3 and #4 apply.
/etc/rc should, under normal circumstances,
never be modified by the OpenBSD administrator. We have /etc/rc.local for manual scripts, if needed.
However, the syslog-ng package includes an
/etc/rc.d script to start and stop the daemon. If you installed the OpenBSD package for syslog-ng, you will find this script automatically installed in the /etc/rc.d directory.
Please see the rc.d(8) man page for instructions on how the scripts get run if you ever wish to start/stop manually, or if you find you need to set a variable when you execute the script.
Please see the rc.conf(8) manual for setting the pkg_scripts variable in your /etc/rc.conf.local file to automatically start and stop local daemons at startup and shutdown.