mingetty on console on demo disk

mingetty on console on demo disk

[Barry Silverman]

I am using the latest unstable Xen, and am using the demo CD to boot the
non-0 domains. It would really be a lot easier if you could start a "getty"
on the console on the demo CD (since the unstable release now supports
bidirectional I/O).

Would that break the 1.2 release if you did that?

Barry Silverman



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Re: mingetty on console on demo disk

[Ian Pratt]

[back on list]

> The xend interface doesn't pass some of the more arcane terminal protocols
> (window resizing, interrupt characters, ...). Are these something hard to
> add? 

It's not xend that's the problem, but something in the tty driver
in xenolinux. To be honest, we can't make head nor tail of the
Linux tty code, and have no idea why resizing etc doesn't work.
We're probably just not setting some parameter some
where. However, we appear to be 'bug compatible' with using a
serial console on RH9.

Perhaps someone on xen-devel knows about tty's and could take a
look ???

> Keir mentioned on the list that he was planning to rewrite
> Xend...

That won't effect things, as xend is just an 8bit clean pipe.


Ian


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RE: mingetty on console on demo disk

[Barry Silverman]

The problem seems to be that xend doesn't support enough of the telnet
protocol to force the connection into "character mode". At least on my
system, telnet is going into "obsolete line-at-time" mode that has these
nasty interactions like locally echoing the whole command line, trapping
control characters, row wrapping, ....

When I give the telnet escape, followed by the command "mode character", it
behaves much more rationally.

I believe you can work around the problem by having a .telnetrc file with
the "mode character" command in it, but the proper fix would be to a) have
xend give the protocol sequence to force the telnet client into character
mode
or b) use some simpler home brew client that doesn't try to use telnet's
fancy local processing.

Barry Silverman

-----Original Message-----
From: Ian Pratt [mailto:Ian.Pratt@cl.cam.ac.uk]
Sent: Thursday, March 11, 2004 5:06 PM
To: Barry Silverman
Cc: Ian Pratt; xen-devel@lists.sourceforge.net
Subject: Re: [Xen-devel] mingetty on console on demo disk



[back on list]

> The xend interface doesn't pass some of the more arcane terminal protocols
> (window resizing, interrupt characters, ...). Are these something hard to
> add?

It's not xend that's the problem, but something in the tty driver
in xenolinux. To be honest, we can't make head nor tail of the
Linux tty code, and have no idea why resizing etc doesn't work.
We're probably just not setting some parameter some
where. However, we appear to be 'bug compatible' with using a
serial console on RH9.

Perhaps someone on xen-devel knows about tty's and could take a
look ???

> Keir mentioned on the list that he was planning to rewrite
> Xend...

That won't effect things, as xend is just an 8bit clean pipe.


Ian



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RE: mingetty on console on demo disk

[Kip Macy]

Maybe pulling xend into telnetd itself would work?

In my environment I run a bunch of OS simulators for testing. The test
harness manages the interface to the simulator itself so it effectively
owns the pty. Some of the developers wanted to be able to interact with
the console while the tests were running under the harness. The first
thing I tried doing was just writing some python code that would
multiplex a connection. I quickly discovered that that wasn't adequate
for having a well-behaved telnet connection. There is a lot of terminal
negotiation that goes on under the covers with telnetd. What I ended up
doing was hacking telnetd internal interfaces to be re-entrant so that
they could allow multiple connections to the same pty at once.

Perhaps you could also customize telnetd to leverage all the telnet
negoatiation code. Ideally, of course, you'd pull the negotiation code
out of telnet. However, that would be a bigger undertaking.


				-Kip


On Fri, 12 Mar 2004, Barry Silverman wrote:

> The problem seems to be that xend doesn't support enough of the telnet
> protocol to force the connection into "character mode". At least on my
> system, telnet is going into "obsolete line-at-time" mode that has these
> nasty interactions like locally echoing the whole command line, trapping
> control characters, row wrapping, ....
>
> When I give the telnet escape, followed by the command "mode character", it
> behaves much more rationally.
>
> I believe you can work around the problem by having a .telnetrc file with
> the "mode character" command in it, but the proper fix would be to a) have
> xend give the protocol sequence to force the telnet client into character
> mode
> or b) use some simpler home brew client that doesn't try to use telnet's
> fancy local processing.
>
> Barry Silverman
>
> -----Original Message-----
> From: Ian Pratt [mailto:Ian.Pratt@cl.cam.ac.uk]
> Sent: Thursday, March 11, 2004 5:06 PM
> To: Barry Silverman
> Cc: Ian Pratt; xen-devel@lists.sourceforge.net
> Subject: Re: [Xen-devel] mingetty on console on demo disk
>
>
>
> [back on list]
>
> > The xend interface doesn't pass some of the more arcane terminal protocols
> > (window resizing, interrupt characters, ...). Are these something hard to
> > add?
>
> It's not xend that's the problem, but something in the tty driver
> in xenolinux. To be honest, we can't make head nor tail of the
> Linux tty code, and have no idea why resizing etc doesn't work.
> We're probably just not setting some parameter some
> where. However, we appear to be 'bug compatible' with using a
> serial console on RH9.
>
> Perhaps someone on xen-devel knows about tty's and could take a
> look ???
>
> > Keir mentioned on the list that he was planning to rewrite
> > Xend...
>
> That won't effect things, as xend is just an 8bit clean pipe.
>
>
> Ian
>
>
>
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Re: mingetty on console on demo disk

[Keir Fraser]

> Maybe pulling xend into telnetd itself would work?
> 
> In my environment I run a bunch of OS simulators for testing. The test
> harness manages the interface to the simulator itself so it effectively
> owns the pty. Some of the developers wanted to be able to interact with
> the console while the tests were running under the harness. The first
> thing I tried doing was just writing some python code that would
> multiplex a connection. I quickly discovered that that wasn't adequate
> for having a well-behaved telnet connection. There is a lot of terminal
> negotiation that goes on under the covers with telnetd. What I ended up
> doing was hacking telnetd internal interfaces to be re-entrant so that
> they could allow multiple connections to the same pty at once.
> 
> Perhaps you could also customize telnetd to leverage all the telnet
> negoatiation code. Ideally, of course, you'd pull the negotiation code
> out of telnet. However, that would be a bigger undertaking.

Actually I think that telnet is most likely the wrong thing to be
using here. Perhaps it would be better to write a dumb terminal
program that exchanges 8-bit clean characters between local console
and a TCP socket -- then we can add in smartness for things like
probing terminal size on an as-needed basis.

 -- Keir


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