[lxc-users] lxc-console produces no output

[Robert Pendell]

On Thu, May 8, 2014 at 10:56 PM, Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> Quoting Robert Pendell (shinji at elite-systems.org):
>> OS: Ubuntu 14.04 LTS x86_64
>> Kernel: Host-Supplied 3.14.1
>> Provider: Linode
>> Host Virtualization: Xen Paravirtualized
>> LXC Version: 1.0.3-0ubuntu3
>> Guest: CentOS 6 i386
>>
>> I know I've seen this issue crop up before however I don't know how it
>> has been fixed and the solution may vary.
>>
>> I'm using a standard Centos template created using the download type.
>> It is running in unprivileged mode and for some reason lxc-console
>> isn't producing any output when I attempt to connect to it.
>>
>> Here is what I get:
>> shinji at icarus:~$ sudo lxc-console -n gateone
>>
>> Connected to tty 1
>> Type <Ctrl+a q> to exit the console, <Ctrl+a Ctrl+a> to enter Ctrl+a itself
>
> Before you run lxc-console, find the host pid of the mingetty on
> pts/1, and strace -f -p that one.
>

Heh... I tried and it keeps telling me the process id doesn't exist
then I noticed that the pid is changing so I went into the guest and
looked at the messages log and it is being spammed with this...

May  8 23:54:17 localhost init: tty (/dev/tty1) main process (2335)
terminated with status 1
May  8 23:54:17 localhost init: tty (/dev/tty1) main process ended, respawning
May  8 23:54:17 localhost /sbin/mingetty[2348]: tty1: vhangup() failed

*a few minutes later*
Found the fix.  This might have to go into the prep script for CentOS
as it seems to happen for others as well.  It seems the folks working
on the Oracle image figured this out.

https://github.com/lxc/lxc/blob/master/templates/lxc-oracle.in
Line 368 comments about how vhangup fails with userns.  It probably is
related to unprivileged containers only although I have not checked
with privileged so don't quote me on that last bit.  All I know is it
fixed the issue for me.  Others may gain usefulness in this.

Basically I edited the /etc/init/tty.conf script and added --nohangup
to the mingetty exec command in the script.

It became this: exec /sbin/mingetty $TTY --nohangup

This will propagate to /dev/console as well due to the way that it is
being created during boot (it calls the tty init using TTY=console as
a parameter).