[Devel] Re: [PATCH 0/6] containers: Generic Process Containers (V6)

[Paul Menage]

Hi Serge,

On 1/3/07, Serge E. Hallyn <serue at us.ibm.com> wrote:
> From: Serge E. Hallyn <serue at us.ibm.com>
> Subject: [RFC] [PATCH 1/1] container: define a namespace container subsystem
>
> Here's a stab at a namespace container subsystem based on
> Paul Menage's containers patch, just to experiment with
> how semantics suit what we want.

Thanks for looking at this.

What you have here is the basic boilerplate for any generic container
subsystem. I realise that my current containers patch has some
incompatibilities with the way that nsproxy wants to work.

>
> A few things we'll want to address:
>
>         1. We'll want to be able to hook things like
>            rmdir, so that we can rm -rf /containers/vserver1
>            to kill all processes in that container and all
>            child containers.

The current model is that rmdir fails if there are any processes still
in the container; so you'd have to kill processes by looking for pids
in the "tasks" info file. This was behaviour inherited from the
cpusets code; I'd be open to making this more configurable (e.g.
specifying that rmdir should try to kill any remaining tasks).

>
>         2. We need a semantic difference between attaching
>            to a container, and being the first to join the
>            container you just created.

Right - the way to do this would probably be some kind of
"container_clone()" function that duplicates the properties of the
current container in a child, and immediately moves the current
process into that container.

>
>         3. We will want to be able to give the container
>            attach function more info, so that we can ask to
>            attach to just the network namespace, but none of
>            the others, in the container we're attaching to.

If you want to be able to attach to different namespaces separately,
then possibly they should be separate container subsystems?

Paul