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From: edler@cmcl2.NYU.EDU (Jan Edler)
Newsgroups: comp.unix.wizards
Subject: umask and multiple groups
Message-ID: <21241@cmcl2.NYU.EDU>
Date: Thu, 5-Nov-87 11:32:06 EST
Article-I.D.: cmcl2.21241
Posted: Thu Nov  5 11:32:06 1987
Date-Received: Sun, 8-Nov-87 03:34:36 EST
Reply-To: edler@cmcl2.UUCP (Jan Edler)
Organization: New York University, Ultracomputer project
Lines: 28

In 4.[23]bsd, when you create a file, the gid of the file is taken from
the gid of the directory you create it in (even if you aren't a member
of that group).  It seems to me that the single umask(2) mechanism is
crippled in this environment.  If I work in several different groups,
and I don't want my files in each group created with the same group
permissions, I have to change the umask every time I switch back and
forth between working on different groups; a situation akin to that
which motivated the establishment of multiple groups in the first place
(elimination of the newgrp command).

The only alternatives I can think of are:
	- Allow a separate umask in the kernel for each group a user
	  is a member of.  An extra umask would also be needed for
	  groups that the user is not a member of.
	- Add a file mode mask to each directory, to apply for all
	  files created there.
With either of these alternatives, the existing umask could remain as
well, so that the mode of a newly created file would be influenced by
two masks; this would help make either change upward compatible, since
users happy with the old semantics could just ignore the new masks
(leave them 0).

Any thoughts on this?  Other ideas?  Does everyone think things are
fine the way they are?  Were multiple groups a bad idea?

Jan Edler
edler@nyu.nyu.edu
...!cmcl2!edler