default:
  version: '2.4'
Red Hat Enterprise Linux Server-6:
  version: '2.2'
Red Hat Enterprise Linux Server-7:
  version: '2.4'
CentOS-6:
  version: '2.2'
CentOS-7:
  version: '2.4'
Oracle Linux Server-6:
  version: '2.2'
Oracle Linux Server-7:
  version: '2.4'