Thanks Rob for your reply. I can hardly say, it's a bug as I'm not an
experienced user of Linux. Good point from your msg on SGID. Thanks.
Regards,
Vidol
----- Original Message -----
From: "Robert Locke" <lists@xxxxxxxxx>
To: "For users of Fedora Core releases" <fedora-list@xxxxxxxxxx>
Sent: Thursday, August 25, 2005 9:54 AM
Subject: Re: The newgrp command
> On Thu, 2005-08-25 at 08:24 +0700, Vidol Loeung wrote:
> > Thanks Richard. When I as a user used newgrp to switch myself to a new
> > group, I of course gave the password of that group, which was assigned
by
> > the gpasswd comamnd as you mentioned. I also agree that, this command is
> > rarely used and I think, it only makes sense when a user would like
> > files/directories (s)he creates to belong to a particular group. Having
the
> > user as a member in each group is fine.
> >
> > My question was out of curiosity as I was trying to experiment the
newgrp
> > command and found that it did not seem to work the way it should as its
> > manual and documentations stated that the command is used to switch a
user
> > to a new group and requires the group password.
> >
> > Let me give a scenario here:
> > - I logged in as user 'joe'.
> > - Then, I typed this command ('joe' is not a member of group 'users'):
> > $ newgrp users
> > Password:
> > newgrp: Permission denied
> >
> > I've wondering what the group passwd command is used for and found that
the
> > newgrp command is the one that needs the group passwd. Now, when I tried
it
> > as above it did not work.
> >
> > Would someone kindly clarify a bit more on the use of the newgrp
command?
> >
> > Regards,
> > Vidol
> >
> <snip>
>
> I'll give it a try....
>
> A user may belong to more than one group, but one group is considered
> that user's primary group (the one delineated in the fourth field
> of /etc/passwd). When that user creates a file, the file needs both a
> user and group associated with the file. The user is the user but the
> group, by default, will be that user's primary group.
>
> Now since a user may belong to more than one group and that user may
> desire that a file they create belong to one of their "secondary" or
> "auxiliary" groups, there are two ways to override the default behavior.
>
> 1) A file created in a directory where the SGID bit is set will assume
> the group of the directory rather than the primary group of the user
> creating the file.... And since I need write access to the directory in
> order to create a file, there is an implication that I am a member of
> the group associated with the directory....
>
> 2) The newgrp command will spawn a "sub-shell" where the primary group
> of the user is switched from the one defined in /etc/passwd to the
> groupname specified as an argument to "newgrp". Thus files created by
> processes spawned by this subshell will assume the "new group"....
>
> Now, as to your problem of being able to specify the password when
> utilizing the newgrp command, I must admit to only trying to newgrp
> myself in to groups that I am a pre-defined member of and consequently
> the password has been moot, so I cannot be of much help there, though,
> perhaps your relatively unique testing has uncovered a "bug"....
>
> HTH,
>
> --Rob
>
>
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