NFSv4 Access Control Lists
Access Control Lists (ACLs) are a way of modifying file permissions in a way that is far more granular and flexible than standard Unix file permissions. Unfortunately, ACLs are also more complex and can lead to very confusing situations if you're not careful. Consequently, we don't recommend using ACLs unless you find yourself in a situation that cannot work with the standard permission model. (When in doubt, you can always email email@example.com for help with our systems.)
Unfortunately, we haven't had time yet to fully document NFSv4 ACLs on our systems, especially since the standard permissions work in a vast majority of cases. The ACLs are accessed via the nfs4_getfacl and nfs4_setfacl programs; interested parties are encouraged to read their man pages.