Disable multiple login[FC or *NIX]?

[James Wilkinson]

Deepak Shrestha wrote:
> Is there a way to limit the particular user login only once in FC (or
> *nix)??or disabling the double logins. Currently a user can log in
> from different terminals using same account at same time and do
> various things. I have tried also Putty and able to login using same
> login name from windows machines. This is good for troubleshooting
> purposes like when situation goes wrong, user can log in from
> different terminal and fix it, but this also brings the anomali of two
> persons being present at the different place at the same time.
> 
> I guess this is not an concern for desktop users but exposing as
> server might need considering this. At present my question is more on
> a curiosity than of practical use.

The short answer is that this is normal, expected, and only *very*
rarely a problem. For almost all situations it's equivalent to having
multiple terminal sessions open under the same username, which is
something the vast majority of developers and a lot of power users do,
so it gets tested a *lot*.

And the reason it gets used a lot is quite simply that it's useful.
People want to multitask, and having different terminals open means they
can (for example) be composing an e-mail on one terminal while they
refer to the output of a different program on another.

As for the "anomaly" of one username being used from different places --
it's not considered an anomaly. The computer *can't tell* which sessions
are on screens that are physically close together (and GNU screen means
that "physical location" can change).  And you might still want to use
VNC (or equivalent) to sit at one desk, connect to another desktop, and
start a connection there [1] -- which location is the user supposed to
be at?

I have once -- quite some time ago, on another list -- had it
"explained" that it took too much computer power. Even then, the
consensus of opinion was that computer power was cheap, and if you need
to limit the number of users, there are better ways of doing it.

James.

[1] Remember that PuTTY and OpenSSH can be used for tunnelling
connections, and you can send print jobs over PuTTY to a remote session.

This is also useful to check that PuTTY / OpenSSH are actually working
from the remote desktop.
-- 
E-mail:     james@ | Five miles as the hippopotamus bounces...
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