[lxc-devel] Shutting down containers properly

[Stéphane Graber]

On 05/25/2012 11:24 AM, Christian Seiler wrote:
> Hi,
> 
>> Have you looked at the lxc-shutdown script we have in Ubuntu and the
>> integration we have with upstart?
> 
> No, not yet, but I'll look at it later.
> 
>> lxc-shutdown sends two different signals:
>>  reboot => SIGINT
>>  shutdown => SIGPWR
>>
>> These are caught by upstart and will trigger a clean reboot or 
>> shutdown
>> of the container. It's what happens on shutdown of the host in 12.04 
>> LTS.
> 
> On a Debian container I had lying around here it had no effect 
> whatsoever, because there's nothing in the /etc/inittab catching it.
> 
> Is it document behaviour that upstart shuts down on SIGPWR? (upstart 
> has no /etc/inittab where this may be configured, right?) Because if it 
> is that easy to cause upstart deterministically to shut down, then that 
> is definitely something we should use.

Upstart sends an event when it gets SIGPWR, in 12.04, I introduced a new
job in upstart that triggers on it and triggers the shutdown:

stgraber at castiana:~$ cat /etc/init/shutdown.conf
# Trigger an immediate shutdown when upstart receives SIGPWR
# this is useful for some UPS monitoring tools and for clean
# shutdown of containers

description "Trigger an immediate shutdown on SIGPWR"
start on power-status-changed

task
exec shutdown -h now "SIGPWR received"

> 
> Still, I think my initial rationale still holds that lxc-stop should 
> shut down by default, because I certainly didn't expect lxc-stop to kill 
> everything with SIGKILL when I tried it for the first time. So basically 
> all I'm saying is that Ubuntu's lxc-shutdown logic should be implemented 
> in lxc-stop and that it should be a bit more generic with the 
> possibility that the user can configure different methods in the config 
> file.

I remember Serge and I discussed that at some point and ended up making
it a separate tool. I can't remember the exact rational for this so I'll
let Serge answer :)

> 
> Regards,
> Christian


-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com

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