CentOS6 is horrible outdated and needs out-of-tree drivers while any moden linux distribution has everything needed in the upstream kernel, the initrd of CentOS6 is also a possible problem, years ago Fedora wasn't even able to boot from a converted ext4 rootfs and after a dist-upgrade as Fedora swicthed to dracut it was no problem, you need to prepare the migratoon and the probem is that virtually nonody is still running CentOS6
theeasiest way would be setup a new verital machine and rsync the data, moved a complete company that way form Apple to Linux