xenserver 7.0 based on centos 7.2

https://docs.citrix.com/content/dam/docs/en-us/xenserver/xenserver-7-0/downloads/xenserver-7-0-installation-guide.pdf states:

 The Control Domain: Also known as 'Domain0', or 'dom0', the Control Domain is a secure, privileged Linux VM (based on a CentOS 7.2 distribution) that runs the XenServer management toolstack. Besides providing XenServer management functions, the Control Domain also runs the driver stack that provides user created Virtual Machines (VMs) access to physical devices.