Re: LSB specification for adding users and groups

[Rob Browning <rlb@cs.utexas.edu>]

Daniel Quinlan <quinlan@transmeta.com> writes:

> Okay, could I get someone to summarize the functional differences
> between the Debian adduser script and the "standard" useradd program
> (originally from the shadow utils and AT&T/SVR4)?
> 
> My current plan is to base the LSB user/group specification on the
> useradd tools, mostly because it seems to be present on all Linux
> distributions, but also because it is used by lots of Unix applications
> and would make porting installation scripts to Linux easier.
> 
> (I'd like LSB applications that install users and groups (using the LSB
> user/group specification) to avoid making things difficult for Debian.)

While we're at it, could we consider adding options to usermod to
support adding and removing a user to/from a set of groups?  Right now
you can only use -G to specify a complete set of *replacement* groups
for the user, but that opens a nasty window between when you call
getgrent() repeatedly to find out which groups a user is currently in
and when you call usermod to add the user to that set of groups
plus/minus the new/deleted groups.  During that window, some other
process could call usermod -G and clobber the update in progress.

I sent mail to Guy offering to help add this to the shadow-utils if it
turns out to be useful, but I haven't heard back yet.

In general, are simultaneous calls to usermod guaranteed to be atomic?
If not, then I think they should be (protected by a lockfile or other
similar mechanism).

-- 
Rob Browning <rlb@cs.utexas.edu> PGP=E80E0D04F521A094 532B97F5D64E3930