Linux OS

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 !