The Red Hat Network Daemon (rhnsd) periodically connects to Red Hat Network to check for updates and notifications. The daemon, which runs in the background, is typically started from the initialization scripts in /etc/init.d/rhnsd or /etc/rc.d/init.d/rhnsd.

To check for updates, rhnsd runs an external program called rhn_check located in /usr/sbin/. This is a small application that makes the network connection to RHN. The Red Hat Network Daemon does not listen on any network ports or talk to the network directly. All network activity is done via the rhn_check utility.