[Lxc-users] container shutdown

[Daniel Lezcano]

On 03/19/2012 03:50 AM, Serge Hallyn wrote:
> Quoting Daniel Lezcano (daniel.lezcano at free.fr):
>> On 03/19/2012 12:00 AM, Serge Hallyn wrote:
>>> Hi,
>>>
>>> Thanks to Jäkel's and Fajar's great ideas, we can now cleanly shut down
>>> a container by sending it SIGPWR.  I'm attaching two ways to do that.
>>> In-line is a patch which modifies lxc-stop to take optional -s and -t
>>> args - -s for shutdown (meaning send SIGPWR), and -t for a timeout,
>>> after sending SIGPWR, to hard-kill the container.
>> That may make more sense to implement a lxc-reboot | lxc-shutdow
> Is there another signal that would make sense for lxc-reboot?

Yes, SIGINT will make the init process to restart the services. I said 
lxc-reboot but that could be lxc-shutdown -r.

>> script on top of on lxc-kill.
>>
>> IMHO, I don't think adding a timeout is a good idea because the
>> shutdown process may take more than the timeout to stop the services
>> and the container could be killed while the services are doing some
>> cleanup or flush or whatever. If this option is present, people will
>> tend to use it instead of investigating if a service is stuck, or
>> working, or flushing.
>> I would recommend to let the shutdown script to handle the timeout
>> by themselves.
> By 'let the shutdown script to handle the timeout by themselves", you
> mean let the scripts calling lxc-shutdown handle the timeout?

I meant the initrd scripts within the container to be fixed to properly 
shutdown (for example add timeout or optimize the stopping services). 
The init process will send SIGTERM to all the processes and then SIGKILL 
after awhile. I don't think that should be handled from outside. Some 
services are bogus because they don't care when they are stopped in the 
shutdown process because they expect to be killed. For example, the sshd 
service was automatically respawned after being killed by init at the 
shutdown time but that was only spotted with containers.

>
> leave lxc-shutdown to be as simple as 'lxc-kill -n $1 SIGPWR" ?

Yes, lxc-shutdown could be in this case very trivial (may be adding a 
couple of things like waiting for the container to stop before exiting 
in order to have a synchronous command).