At present time, 2013-04-30, the Red Hat Enterprise Linux operating system (64 bit version of 5.4, 5.5, 5.6, 5.8, 6.1, 6.2 and 6.3) is the only one officially supported by VMware for vCloud Director (vCD) 5.1.2. Please see the vCD 5.1.2 release notes found here regarding the Red Hat Enterprise Linux 6.3 support since the the …