[lxc-devel] How does the console work in most recent release?

[Rob Landley]

On 01/05/2011 05:19 AM, Daniel Lezcano wrote:
> On 01/04/2011 09:36 AM, Rob Landley wrote:
>> I'm attempting to write a simple HOWTO for setting up a container with
>> LXC. Unfortunately, console handling is really really brittle and the
>> only way I've gotten it to work is kind of unpleasant to document.
>>
>> Using lxc 0.7.3 (both in debian sid and built from source myself), I
>> can lxc-create a container, and when I run lxc-start it launches init
>> in the container. But the console is screwy.
>>
>> If my init program is just a command shell, the first key I type will
>> crash lxc-start with an I/O error. (Wrapping said shell with a script
>> to redirect stdin/stdout/stderr to various /dev character devices
>> doesn't seem to improve matters.)
>>
>> Using the busybox template and the busybox-i686 binary off of
>> busybox.net, it runs init and connects to the various tty devices, and
>> this somehow prevents lxc-start from crashing. But if I "press enter
>> to active this console" like it says, the resulting shell prompt is
>> completely unusable. If I'm running from an actual TTY device, then
>> some of the keys I type go to the container and some don't. If my
>> console is connected to a PTY when I run lxc-start (such as if I ssh
>> in and run lxc-start from the ssh session), _none_ of the characters I
>> type go to the shell prompt.
>>
>> To get a usable shell prompt in the container, what I have to do is
>> lxc-start in one window, ssh into the server to get a fresh terminal,
>> and then run lxc-console in that second terminal. That's the only
>> magic sequence I've found so far that works.
>>
>> The attached html file is a long drawn-out reproduction sequence for
>> this.
>>
>> I tried downloading lxc-git to see if this is already fixed, but
>> running "autoconf" doesn't seem to want to produce a ./configure file
>> for me. ("configure.ac:8: error: possibly undefined macro:
>> AM_CONFIG_HEADER") I'm really not an autoconf expert (the whole thing
>> is just a horrible idea at the design level), so have no idea what I'm
>> doing wrong there.
>
> Hi Rob,
>
> there is a small bug when installing the template in the inittab, it
> should be:
>
> ::sysinit:/etc/init.d/rcS
> tty1::respawn:/bin/getty -L tty1 115200 vt100
> console::askfirst:/bin/sh
>
> Otherwise, I think the busybox version you are using is bogus. I had the
> same problem than you but I installed busybox-1.18.1, compiled as
> static, ran the template script, modified the inittab and it works like
> a charm.

The modified inittab fixed it for me.

Huh, and now that I know what it's doing, using this as /sbin/init:

   #!/bin/sh

   exec /bin/sh < /dev/console > /dev/console 2>/dev/console

Seems to be working fine with lxc-start.  (Dunno why it wasn't before...)

Thanks,

Rob