[Gllug] Multiple logins with NIS/YP

[Richard Cottrill]

I'm pretty sure that only one program can have a file open for writing at a
time. I think you'll get some error about 'couldn't write to file' from any
decent program. NFS should enforce this sort of thing across an entire
network too.

Now if a file is opened, written to, and closed; of course it can then be
overwritten. I think a lot of common programs use their own lock files for
managing multiple instances; Navigator and pine certainly do.

Richard

> -----Original Message-----
> From: gllug-admin at linux.co.uk [mailto:gllug-admin at linux.co.uk]On Behalf
> Of Dylan Brewis
> Sent: Wednesday, February 13, 2002 5:29 PM
> To: gllug at linux.co.uk
> Subject: Re: [Gllug] Multiple logins with NIS/YP
>
>
> On Wednesday 13 February 2002 00:59, you wrote:
> > I think more to the point is why restrict people to one login at a time?
>
> Because someone may, for example, leave their mail client open on
> one client
> then try checking mail on another - or can two programs suddenly
> write to the
> same files without problems all of a sudden...?
>
>
> > And if you do restrict people how do you handle a zombie session if/when
> > one occurs?
> >
> > At this late hour I can't think of how to make a secure means
> of managing
> > lock files without making some little daemon running as a special
> > (non-login) user to write/remove lock files for the machine
> (even one for
> > the whole network if you're not using file sharing for some
> silly reason).
> > I think it's past my bed time; there must be a simpler answer.
> Maybe a SUID
> > script and careful file permissions would suffice (although I
> don't really
> > like SUID scripts on principle).
> >
> > <pedant>
> > I also think that David's got his nomenclature mixed up and
> while it's true
> > that slaves don't know what other slaves are doing most
> machines wouldn't
> > be slaves (in any sane set-up). Slaves replicate the NIS files; whereas
> > most machines would be better described as clients. All the
> doco that uses
> > slaves and YP/NIS together uses it exclusively for something
> that could be
> > roughly termed a proxy.
> > </pedant>
> >
> > Ooooh it is late; I'm getting all picky about pointless crap.
> >
> > Richard
> >
> > > -----Original Message-----
> > > From: gllug-admin at linux.co.uk
[mailto:gllug-admin at linux.co.uk]On Behalf
> > Of Dylan Brewis
> > Sent: Tuesday, February 12, 2002 11:54 PM
> > To: gllug at linux.co.uk
> > Subject: Re: [Gllug] Multiple logins with NIS/YP
> >
> > On Tuesday 12 February 2002 23:32, you wrote:
> > > On Tuesday, 12 Feb 2002, Dylan Brewis wrote:
> > > >After much faffing, and accelerated hair loss, I've finally got NIS
> > > >functioning BUT...
> > > >It allows the same user to log on to more than one client at the same
> > > > time. Not a desirable situation!
> > >
> > > Bear in mind that YP really only passes information from the YP master
> > > to the slaves, not vice versa or between the slaves - hence, one slave
> > > has no way of knowing what's happened on another.
> > >
> > > If you mount home directories via NFS you could do something evil with
> > > user's login scripts and a lockfile in their home directory, but I
> > > would not advise that.
> >
> > er... why not, and how would I do it anyway?
> >
> >
> > --
> > Gllug mailing list  -  Gllug at linux.co.uk
> > http://list.ftech.net/mailman/listinfo/gllug

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