When you first install XenServer, a user account is added to XenServer automatically. This account is the local super user (LSU) , or root, which is authenticated locally by the XenServer computer. You can create additional users by adding Active Directory accounts from the Users tab in XenCenter. (Note that the term "user" here refers to anybody with a XenServer account, that is, anyone administering XenServers, regardless of level of their role.) If you want to have multiple user accounts on a server or a pool, you must use Active Directory user accounts for authentication. This lets XenServer users log in to the servers in a pool using their Windows domain credentials.
All editions of XenServer can add user accounts from Active Directory. However, only XenServer Enterprise and Platinum editions let you assign these Active Directory accounts different levels of permissions depending on the user's role, using the Role Based Access Control (RBAC) feature. If you do not use Active Directory in your environment, you are limited to the LSU account.
The permissions assigned to users when you first add their accounts varies according to your version of XenServer:
Even though XenServers are Linux-based, XenServer lets you use Active Directory accounts for XenServer user accounts. To do so, it passes Active Directory credentials to the Active Directory domain controller.
When added to XenServer, Active Directory users and groups become XenServer subjects, generally referred to as simply users in XenCenter. When a subject is registered with XenServer, users/groups are authenticated with Active Directory on login and do not need to qualify their user name with a domain name.
The external authentication process works as follows:
When you join a domain, you enable Active Directory authentication for the pool. However, when a pool is joined to a domain, only users in that domain (or a domain with which it has trust relationships) can connect to the pool.