CentOS 4 Offers Strong RHEL Alternative - page 4
One of the most critical aspects of any distribution and in particular an Enterprise distribution is the update mechanism. When I first installed CentOS 4 from the ISO's, the update tool was called Red Hat Network Update (just as it is in RHEL 4). It looked and behaved just like the "real" Red Hat version--without the Red Hat logo (see Figure 2). After I updated it though with Up2date, one of the updates was for the update mechanism and Red Hat Network Update became CentOS Network Update. From a practical point of view, it doesn't really matter that much as the bottom line is that the update network, works and works well. The first update (as you can expect with an "everything" install) is quite large and as best as I was able to determine was a complete and accurate update of everything that Red Hat themselves have updated packages for.
In terms of timing on security as well as Errata updates for CentOS as compared to RHEL4, I found over the past month of use that the two line up quite well. Security updates happened the same day in almost every case, usually within a few hours.
In a good number of examples in fact, CentOS 4 will use the same RPMs as
RHEL4 with the same name (another example is a recent MySQL update: mysql-4.1.10a-1.RHEL4.1.i386.rpm).
Certainly not all CentOS 4 fixes use the same exact nomenclature as
RHEL4 (in some cases "centos4" is appended somewhere in the name) and not
all of them are immediate. One recent example is for an up2date bug, which the CentOS update mirrors didn't have until five days later.