[K12OSN] Permissions for students and teachers

[Les Mikesell]

Almquist Burke wrote:
> 
> It's been my experience that the only real limitations with UNIX 
> permissions is when you want to have one group to have read-write 
> access, one group to have read only access, and everyone else not to 
> have any access at all. This is the only thing you really can't do in 
> UNIX. The good news is that this scenario isn't terribly very common if 
> you really think about it.

If this applies to everything in a directory, make the directory and 
files group rw and other r (+x for the directory) owned by the group 
with write access, and make a directory above that group rx for the 
group with read access, no access for other.  Include all the members of 
the group with write access in the one with read access.  Only the 
combined group members can get through the upper directory, and the ones 
that aren't in the rw group will be constrained by 'other' permissions 
on the lower directory/files.

-- 
   Les Mikesell
     lesmikesell at gmail.com