In vSphere 6.0 the vCenter Server Appliance (vCSA) has been changed a lot. Joining an Active Directory Domain is now included in the infrastructure node configuration which is part of the Platform Services Controller. Please note standard AD requirements like time synchronisation and naming. You can't join an AD if you've set an IP address as name during the VCSA guided installer.
- Open vSphere Web Client (https://[vcenter]/vsphere-client)
- Login as Single Sign-On Administrator (Password set during installation)
- Navigate to Administration > Deployment > System Configuration
- Open Nodes and select the infrastructure node that is associated with Single Sign-On
- Navigate to Manage > Advanced > Active Directory
- Click Join...
- Enter AD domain information
- Press OK
- Reboot the Appliance
When the appliance comes back up it is now part of the Active Directory Domain. The next step is to configure the AD as identity source to login to the vCenter with AD credentials.