[libvirt] lxc: setsid() usage

[Richard Weinberger]

Am 23.06.2015 um 14:18 schrieb Richard Weinberger:
> Am 22.06.2015 um 16:51 schrieb Daniel P. Berrange:
>> On Mon, Jun 22, 2015 at 04:40:37PM +0200, Richard Weinberger wrote:
>>> Hi!
>>>
>>> Why is libvirt-lxc issuing a setsid() in lxcContainerSetupFDs()?
>>> To me it seems like a hack to have a controlling TTY if PID 1 is /bin/bash.
>>
>> I honestly can't remember the reason. It might have been to ensure we have
>> separation from the libvirt_lxc session.
> 
> Hm, can be.
> 
>>> If one runs a sysv init style distro (like Debian) in libvirt-lxc the setsid() has
>>> a major downside, when getty spawns a login shell on /dev/tty1 it cannot become
>>> the controlling tty. Hence, if one presses ctrl-c in such a session, the container will
>>> reboot.
>>
>> Is that problem due to the fact we call setsid(), or due to use calling
>> ioctl(TIOCSCTTY) ?
> 
> If I remove the TIOCSCTTY nothing changes.
> Without setsid() libvirt is unable to start the container at all.
> So, I fear you're right that it has something do to with the libvirt session.

Found a way to deal with that. Patch is on the way.
The setsid() really only seems to be there to have a controlling TTY if PID 1 is bash.

Thanks,
//richard