On Wed, 29 Sep 1999, Art Lemasters wrote: > has had its group permission changed to from x to s without my doing > so, a couple of times. For example, in the /home directory, one user
This is fine. Depending on the user this may be helpful or even necessary. Is it a real human or a program that owns that directory? > I did not manually chmod the permissions that way. What > might have caused this, and what are the implications, anyone? Setting +s group on a directory means that new files created in that directory will be group-owned by the owner of the directory instead of the current group of the user. It does not grant g+s to those files themselves, and of course the actual owner of the file can change the group owner to anything he wants. It is merely a convenience - for example, you have two users collaborating on something. They both belong to group 'project' and agree to store their stuff in a particular directory owned by group 'project'. Normally both users belong to group 'users' - that won't work for this though, because then everybody on the system could tinker with their stuff. So they set g+s on the 'project' directory. Now, all the files they create in there are group-owned by project, so they can both modify them, but other users can't. Of course, there are a variety of uses for this setgid ability of directories - that's just an example.