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    SubjectRe: [Devel] Re: [PATCH] allow a task to join a pid namespace
    On 06/05/2012 12:00 PM, Glauber Costa wrote:
    > On 06/05/2012 01:37 PM, Glauber Costa wrote:
    >> On 06/05/2012 01:36 PM, Daniel Lezcano wrote:
    >>> On 06/04/2012 03:33 PM, Glauber Costa wrote:
    >>>> Currently, it is possible for a process to join existing
    >>>> net, uts and ipc namespaces. This patch allows a process to join an
    >>>> existing pid namespace as well.
    >>>>
    >>>> For that to remain sane, some restrictions are made in the calling
    >>>> process:
    >>>>
    >>>> * It needs to be in the parent namespace of the namespace it wants to
    >>>> jump to
    >>>> * It needs to sit in its own session and group as a leader.
    >>>>
    >>>> The rationale for that, is that people want to trigger actions in a
    >>>> Container
    >>>> from the outside. For instance, mainstream linux recently gained the
    >>>> ability
    >>>> to safely reboot a container. It would be desirable, however, that
    >>>> this
    >>>> action is triggered from an admin in the outside world, very much
    >>>> like a
    >>>> power switch in a physical box.
    >>>>
    >>>> This would also allow us to connect a console to the container,
    >>>> provide a
    >>>> repair mode for setups without networking (or with a broken one), etc.
    >>>
    >>> Hi Glauber,
    >>>
    >>> I am in favor of this patch but I think the pidns support won't be
    >>> complete and some corner-cases are not handled.
    >>>
    >>> May be you can look at Eric's patchset [1] where, IMO, everything is
    >>> taken into account. Some of the patches may be already upstream.
    >>>
    >>> Thanks
    >>> -- Daniel
    >>
    >> I don't remember seeing such patchset in the mailing lists, but that
    >> might be my fault, due to traffic...
    >>
    >> I'll take a look. If it does what I need, I can just drop this.
    >>
    >
    > Ok. In a quick look, it does not seem to go all the way. This is just
    > by reading, but your reboot patch, for instance, is unlikely to work
    > with that, since if it doesn't alter pid->level, things like task
    > ns_of_pid won't work.
    >
    > Running the test scripts I wrote for my testing of that patch also
    > doesn't seem to produce the expected result:
    >
    > after doing setns, the pid won't show up in that namespace.

    Yes, AFAIR, pid won't show up, you have to do fork-exec.




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