CentOS 4 offers both yum and up2date to do updates of the operating system. You can use either or both of these to manage your updates.
Prior to using yum, you must import the RPM-GPG-KEY for CentOS-4 like this
rpm --import /usr/share/doc/centos-release-4/RPM-GPG-KEY
The following files are changed from the upstream RPMS. All changes are trademark and look/feel related unless otherwise noted under the specific RPM.
anaconda
anaconda-help
anaconda-product
anaconda-runtime
apr and apr-devel
centos-release
desktop-backgrounds-basic
desktop-backgrounds-extra
devhelp and devhelp-devel
dhcp-devel
firefox
firstboot
fontconfig and fontconfig-devel
glade2
gnome-desktop
gnome-desktop-devel
gnome-session
httpd
httpd-devel
httpd-manual
httpd-suexec
indexhtml
initscripts
libtool and libtool-devel
mod_perl
mod_perl-devel
mod_ssl
redhat-artwork
redhat-logos
redhat-release and rpmdb-redhat
rhgb
rhn-applet
seamonkey
seamonkey-chat
seamonkey-devel
seamonkey-dom-inspector
seamonkey-js-debugger
seamonkey-mail
seamonkey-nspr
seamonkey-nspr-devel
seamonkey-nss
seamonkey-nss-devel
squirrelmail
thunderbird
up2date
up2date-gnome
createrepo
centos-yumconf
sqlite
sqlite-devel
python-elementtree
python-sqlite
python-urlgrabber
yum
For more Information, see the CentOS-4 Documentation at CentOS.org, or the /NOTES directory on CD-1 of this distribution. The documentation is provided {and copyrighted} by Red Hat®,Inc. The CentOS Project redistributes these original works (in their unmodified form) as a reference for CentOS-4. CentOS-4 is built from publicly available, open source SRPMs.
Major changes this upgrade cycle include providing a DomU Xen kernel. See the U5 notes in the /NOTES directory for more details.