apt-get install aclAllowing members of other groups the full access to a directory, resursively:
setfacl -m d:g:groupname:rwx -R path/foldernamed means default so modifying the default ACL results that all of newly created files and directories will inherit this setting.
Modify the permissions of existing files and directories only [not the default]
setfacl -m g:groupname:rwx foldername
Important notes regarding files: Files can't have default ACL because they can't have child objects. An access ACL for an individual file can override the default: if a file has a special ACL that conflicts the inherited ACL, the file ACL wins: owerwrites the inherited default one.
Clearing an ACL, e.g.:
setfacl -x u:johnny /path/folder