As part of automatic installs of Fedora Core, our customization stepinstalls of the current Red Hat updates from a local mirror. We use yum for this, because it both handles dependencies and uses compactmetadata files instead of having to read all of the update and base OSRPMs themselves. (We have 100 megabit networks, but it still adds upand slows down installs.)

We do this by feeding yum a custom configuration file; basically wetake the standard /etc/yum.conf file and add

If a piece of information doesn't have to be correct for the systemto work, sooner or later it won't be.

(Yanked out of my spam by ASN summary , where aversion of it got a mention in passing.)

It's easy to see this aphorism in action. For example, if yourhost/domain name to IP address mapping information is wrong you noticeright away. But nothing common breaks if the information to map froman IP address to a hostname is missing,