[Question on ow to do the equivalent of Samba "force group" for netatalk]
Isn't this built in to Linux as "sticky groups"? It seems to work for me.
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Sticky groups: if a directory has the setgid bit on, then all files and folders
created in it will be given the group of the directory (provided the creator is in
that group).
So to create a share foo that can be shared by the XY group:
chgroup -R XY foo
chmod -R g+s foo
make the default umask 002. Give each login a private group as their default group,
thus even with an 002 umask they will not share their private files, but any files
they create below foo will be shared with group XY.
