Since he&#x27;s sysadmin in a university computer-science department (and going by the first paragraph of this post), I think group-type sharing is the specific use-case that the post author might be hypothetically tempted to solve using ACLs. Unix groups work for this but require the sysadmin to be involved every time you want a group created, users added&#x2F;removed from the group, etc. It&#x27;d be nice in some cases if a regular user, say the PI of a project or the instructor of a course, could manage their own sharing permissions, without having to open support tickets every time they need a group created or modified.<p>Conceivably you could hack up a custom solution for this, where certain groups are tagged as &quot;owned&quot; by a user, and the user can run a setuid binary to add&#x2F;remove members. Or do it via an authenticated web interface or something. Would require some careful design&#x2F;testing to avoid being a security risk. There are more esoteric possible uses of ACLs this wouldn&#x27;t solve, like giving certain users append-only permission to some files. But a way for users to manage their own groups would probably handle 90% of the likely uses of ACLs in this setting.