Scott Gifford sgifford at
Wed Jan 30 12:28:05 GMT 2002

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

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.


> > As for allocating a pseudo terminal per smb client; again, I'm going
> > to stick to the flavors of Unix that I know, and pick on Solaris.  Out
> > of the box, Solaris builds 48 pseudo terminals.  Because sometimes 
> > users use an X-Windows program (such as exceed) to fire of say "xterm" 
> > via "rlogin" or "telnet", etc. (thus "soaking up" 2 pseudo terminals 
> > for one user login), this ends up supporting about 30 users.  Of
> > course, you can bump this up (to 1024) by editing /etc/systems and
> > doing a reconfiguration reboot ("boot -r" in Sun lingo).  As someone
> > mentioned here, they have 800+ smb clients on their system.  You
> > could easily run out of psuedo terminals if you allocated one per smb 
> > client.  If you had enough smb clients, you could allocate all of
> > your pseudo terminals for your smb clients and then not have any
> > left for people to login with.
> Ah!  here we get to a misunderstanding.  I wasn't anticipating or
> suggesting using real pseudo-ttys (that phrase sounds weird!).  Rather
> using some means analogous to pttys, which might be OS-variable.

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


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