[Adduser-devel] Bug#453086: Bug#453086: adduser --system --group should ensure uid==gid

Ian Jackson ian at davenant.greenend.org.uk
Tue Nov 27 20:44:53 UTC 2007

Stephen Gran writes ("Re: [Adduser-devel] Bug#453086: adduser --system --group should ensure uid==gid"):
> What's the benefit?  The reason they don't match is that there are some
> groups in the 'system gid' range assigned that don't have matching users
> - specifically, the groups crontab and users.  These use 100 and 101 on
> most systems, so system users that come after can either have their uid's
> renumbered up to match, or we can take the course adduser currently does
> and just not worry about something that's not an issue in practice.

It doesn't cause any trouble for the computers.  But uid==gid is much
easier for humans - it makes life less error-prone because you only
have to remember one id which applies everywhere.  It's already the
case for non-system users.

> I guess I do see the aesthetic appeal, but I'm not sure I want to rule
> out use of some parts of the already fairly small system range, just
> because either the uid or the gid is already taken.

I thought about the problem of exhaustion, but I think in practice
this change wouldn't cause that to be more likely.

On any particular system, either allocation of users or groups will
dominate.  And these uids and gids are each allocated sequentially.
So the set of used uids will be a subset of the set of used gids, or
vice versa.


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