Good news for CentOS users! CentOS 5.6 is here. This is the sixth update released for CentOS 5, making the latest release version 5.6. The latest release supports both 
i386 and x86_64 architectures, it contains a number of bug fixes, new functionality, and updates. The new release has been released to CentOS mirrors worldwide, it is is available in two DVD images, one for i386 and other for x86_64. In addition to traditional DVD images, CentOS 5.6 is also available as a Live CD and ‘netinstall’ images. Users can grab their favorite image from one of the mirrors or directly from CentOS website.
CentOS 5.6 is based on the upstream Red Hat Enterprise Linux 5.6 source packages. CentOS integrates the source packages from both client and server editions of RHEL 5.6 into one distribution, so the users get the benefits of both worlds. Users who are keen on laying their hands on Enterprice class Linux for free, CentOS could be one of the best options.
Upgrade to CentOS 5.6 :
If you have Centos 5.5 already installed, before to do anything first back up anything you care about. Then you can upgrade by using the commands bellow :
yum clean all
yum update glibc*
yum update yum* rpm* python*
yum clean all
yum update
reboot
Check your new version with :
lsb_release -a
Important : If you have ISPConfig installed on Centos using The Perfect Server installations, you’ll probably have Karanbir Singh’s famous Centos Testing Repository as active – kbs-CentOS-Testing
The repository kbs-CentOS-Testing lzo/lzop package is attempting to replace Dag Wieers’ also famous RPMFORGE Repository package for lzo/lzop thus causing the dependencies.
Thus, disabling kbs-CentOS-Testing when you update via yum would be the answer..
yum update --exclude="postfix" --disablerepo=kbs-CentOS-Testing
Is done !
