RedHat Enterprise Linux 5.2が出てから約1ヶ月たったけど、そのクローンのCent OS 5.2がリリースされました。http://lists.centos.org/pipermail/centos-announce/2008-June/014999.html
Updating from CentOS-5.0 and 5.1
If you are already running CentOS-5 ( either 5.0 or 5.1 ), all you need to do is run : "yum upgrade" on your machine, and that will bring in the new packages from 5.2 and update your machine. Note that the command required is 'upgrade' and not the usual 'update'. Refer to the yum man page for details on how those two differ in operation.
Should the CentOS-Base.repo file on your existing CentOS-5 install be modified, you might need to pay more attention to the output from the 'yum upgrade' command. If the following command produces no output, your CentOS-Base.repo file is intact :
rpm -V centos-release | grep CentOS-Base