On 1/20/2013 7:40 PM, John Hupp wrote:
On 1/20/2013 2:27 PM, Ioannis Vranos wrote:
On Sun, Jan 20, 2013 at 8:56 PM, John Hupp<[email protected]> wrote:
This opens up yet more questions. /etc/passwd only contains the original
GID's for user1 and user2. It does not reflect that both have now been also
added to the "users" group. So it seems that more than one user/group
configuration system is being supported.
I have been reading today the manpages for adduser, addgroup, and
adduser.conf. Interestingly, it does not document where it stores the
configuration information -- perhaps because adduser and addgroup are only
front-ends for useradd and groupadd. There is no mention of /etc/passwd,
for instance.
But apart from that, Lubuntu's GUI tool for Users and Groups is users-admin
(which I used for my customizations), and I have not yet found any handy
documentation for that. There may be something somewhere at
library.gnome.org, but I have not found it yet. But poking around a bit in
the interface, I see that it does not even show that user1 is a member of
the user1 group, and likewise with user2. So again, that indicates to me
that more than one user/group configuration system in effect.
Users can belong to many groups, one of them is the "primary group".
You can change a user's primary group, from the Users and Groups
program. Select the user, and go to Advanced Settings->Advanced->Main
group.
OK, thanks to all who have responded so far.
From the several responses here and additional reading, I'm glad to
come to the understanding that there is only one set of user/group
configuration information (/etc/passwd, /etc/group and /etc/shadow),
though it can be managed by different available tools. (This in
contrast to network configuration, which really does support two
different configuration systems.)
For a case where it is desirable for a couple users to work with the
same set of files, I'm now thinking that my fundamental approach was
not quite right and that I do not need to involve or maybe should not
involve the "users" system group.
What I'm now thinking should be the setup:
1) Assign /home/user1 as the co-home directory for user2.
2) Assign user2 to the user1 group as user2's *primary* group.
3) Leave the ownership of /home/user1 as Owner: user1 and Group:
user1. With the /home/user1 permissions such that owner and group can
edit, user1 and user2 should then be able to freely create, access and
edit everything in /home/user1.
4) Delete /home/user2.
I expect then that this would solve my original problem in which new
sub-folders did not inherit ownership by the "users" group. And maybe
better respects Linux design principles.
Is that a good and workable proposed setup? Is there any obvious
consideration I am missing?
Thanks Wes, Ioannis and Phill for the very helpful responses to the
above post.
I know a fair amount more on this topic now than when I first posted,
and though the first post (by Wes) about SetUID, and SetGID went
directly over my head, subsequent posts make it clear that this should
probably be part of the solution here. In fact, I had already realized
that my proposed setup would result in a mixture of user ownership in
the user1 directory -- perhaps not a problem, but setuid and setgid
would clean that up.
In the manpage for adduser.conf, there is this somewhat vague caution
involving setgid, but no one here has echoed any concerns about it for
my situation (unless it plays into Wes's point about dot files):
SETGID_HOME
If this is set to yes, then home directories for
users with
their own group ( USERGROUPS=yes ) will have the setgid
bit set.
This was the default setting for adduser versions
<< 3.13.
Unfortunately it has some bad side effects, so we no
longer do
this per default. If you want it nevertheless you
can still
activate it here.
The point about having only one set of dot files for more than one user
is also well taken, but at the moment I am not envisioning that as a
real issue for this scenario.
It's also instructive that Ioannis does not see membership of normal
users in the system group "users" as any sort of transgression against
the intent or design of the default system group layout. Perhaps this
is the very sort of thing the "users" group is intended for.
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