On 05/25/2012 04:17 AM, Matthijs Kooijman wrote: > Hi Stéphane, > >> - stop: Is run after the container died >> [...] >> Potential other hooks include pre-start and post-stop > What would be the difference between stop and post-stop, if stop also > runs _after_ the container died? > > Gr. > > Matthijs
It'd be run after the umount has been done. But that got me to go and read the OpenVZ definition of these and made me catch a "small" detail I had missed. The start and stop hooks in OpenVZ are actually run in the container's namespaces. Basically the timeline would be: - HOOK: pre-start (host namespace) - LXC: mount rootfs and fstab entries - HOOK: mount (host namespace) - LXC: spawn init - HOOK: start (container namespace) - USER: do whatever they want in the container - LXC: stops the container - HOOK: stop (container namespace) - LXC: kill the container - HOOK: umount (host namespace) - LXC: umount rootfs and fstab entries - HOOK: post-stop (host namespace) Based on OpenVZ documentation, if we aim at implementing something similar, then: - "start" would be run inside the container (but script lives outside of it) and called right before init is spawned. - "stop" would be run inside the container (but script lives outside of it) and called right after init dies. I must admit never having used these two and I'm a bit unsure whether they are really that useful and whether we can even implement them with the current state of things. Something else I didn't mention in my original post is the behavior on exit failure for the hooks. OpenVZ typically treats any non-zero return code as a failure and tries to kill the container but without calling any additional hook. For example, a failure in the "start" hook will cause the container to be shutdown and unmounted but without calling the stop, umount or post-stop hooks. (I'm mostly looking at http://download.openvz.org/doc/OpenVZ-Users-Guide.pdf in the "OpenVZ Action Scripts" section) -- Stéphane Graber Ubuntu developer http://www.ubuntu.com
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