Andrew Bartlett abartlet at
Wed Jan 30 13:40:18 GMT 2002

Scott Gifford wrote:
> David Lee <t.d.lee at> writes:
> [...]
> > > As someone pointed out, pseudo terminals come pretty much in
> > > 2 flavors: BSD & System V.
> >
> > I suspect we may be using loose terminology.  I think the phrase "pseudo
> > terminal" was intended to represent a model of doing things, not
> > necessarily as an real implementation detail.
> I believe that I'm the one that started talking about pseudo
> terminals, and I actually did intend it as an implementation detail.
> They are widely available, mostly portable, easily understood, and
> well-tested.
> You can pretty much copy a couple dozen lines out of Stevens' Advanced
> Programming in the UNIX Environment and have a quite portable
> implementation in an hour or so.

We already have most of this, becouse the 'unix password sync' occurs
over a tty.

> Why would it be a problem to ask admins to create additional
> pseudo-ttys or else not use this feature?  On systems with heavy
> interactive user, I have seen upwards of 1000 pseudo-ttys with no ill
> effects.  There's no significant performance penalty for creating many
> of them, either
> In the traditional UNIX world, each user telnetted into a system and
> was allocated a tty; you had to allocate a tty for each user.  Now,
> users come in via other methods, including filesharing with samba, but
> I don't see a reason why it would be a big deal to still allocate them
> ttys.

A default linux kernel comes with only 256 ttys.  (Can be configured to
whatever number is desired)

Andrew Bartlett                                 abartlet at
Manager, Authentication Subsystems, Samba Team  abartlet at
Student Network Administrator, Hawker College   abartlet at

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