ACL - File Access Control Lists (facl)

There are two dimensions to applying ACLs. One is how you apply them to existing files and folders, the other is applying them to future files and folders. This is the access and default ACLs, respectively.

# First, let's remove any existing ACLs in case we have messed them up already

 sudo setfacl --recursive --remove-all --remove-default Directory

# Now let's apply a group ACL to everything in the tree such that group members
# have full permissions.

sudo setfacl -m "g:someGroup:rwx,d:g:someGroup:rw" some_file
                 ^               ^
                 |               \----- The 'd' applies to future files by changing the default   
                  \---- The 'g' applies group acls to existing files