[Devel] Re: Shutting down a container?

Daniel Lezcano daniel.lezcano at free.fr
Fri Nov 13 09:58:01 PST 2009

Michael Tokarev wrote:
> What's the supposed way to stop a container?
> Let's assume I've a container that's running a complete
> system inside, together with its own init and the like.
> It should clean some stuff when "shutting down", it's
> not wise to kill it right away.  So I run something like
> a shutdown in the container.  And it goes up to `halt'
> and just sits here, with only one process left - it's
> the init process with virtual PID=1, which is reading
> from it's /dev/initctl.
> I tried to change /etc/init.d/halt to kill a process with
> pid=1, but that does not work - apparently the signal is
> ignored (even with kill -9) -- ie, init continues as if
> there was no signal.
> _But_, when I attempt to run strace on the ("virtual")
> init process, it gets killed with `kill -9' immediately.
> It also can be killed (also with -9) from the host system
> regardless of strace.
> Should there be some different init perhaps, that will
> exit given some command or signal, instead of sysvinit?
> Or is there other way to shutdown a container?
> P.S.  Using debian lenny with kernel and lxc
> utils from yesterdays git.
Unfortunately, it's not supported by the kernel yet.

Random thought : may be it could be interesting to have the kernel to 
send a signal to the init's parent when:

 * LINUX_REBOOT_CMD_POWER_OFF : the parent process kills the pid 1

 * LINUX_REBOOT_CMD_RESTART : the parent process kills the pid 1 and 
relaunch the container

 * LINUX_REBOOT_CMD_HALT: the parent process freeze the container

may be later:
 * LINUX_REBOOT_CMD_SW_SUSPEND : the parent process checkpoint the container

Well it's just an idea.
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