Re: Update on GuixSD containers

[Ludovic Courtès]

"Thompson, David" <address@hidden> skribis:

> On Sat, Jun 13, 2015 at 9:06 AM, Ludovic Courtès <address@hidden> wrote:
>> "Thompson, David" <address@hidden> skribis:
>>
>>> On Fri, Jun 12, 2015 at 11:12 AM, Ludovic Courtès <address@hidden> wrote:
>>>> "Thompson, David" <address@hidden> skribis:
>>>>
>>>>> Yeah, our daemon would do the same thing.  We could maybe even have a
>>>>> little Guile library that allows one to evaluate arbitrary scheme code
>>>>> from within the container. :)
>>>>
>>>> Actually, something quite easily feasible would be this:
>>>>
>>>>   (eval-in-container #~(system* #$evil-program
>>>>                                 #$(local-file "important-data.txt"))
>>>>                      #:networking? #f)
>>>>
>>>> ... where the container’s store would be populated with just
>>>> EVIL-PROGRAM and the local file.
>>>>
>>>> Food for thought...
>>>
>>> Ooooh yeah!  That would be cool.  Though I think we should still spawn
>>> a dmd process as PID 1 to deal with reaping zombie processes.  We
>>> could generate a single service that runs the gexp script.  How does
>>> that sound?
>>
>> Wouldn’t it be enough to have the Guile process that evaluates the
>> expression be PID 1 in the container, as is the case in guix-daemon
>> containers?
>
> Sure, it would work, but my concern is that a long-running process on
> a user's machine could create and orphan tons of child processes and
> nothing would be able to clean them up until the PID namespace is
> garbage collected.

My understanding was that killing a container’s PID 1 (from the outside)
effectively killed all the processes of that PID name space.  Isn’t it
the case?

(The daemon works around that by running processes under a separate UID
and doing kill(-1, SIGKILL) under that UID.)

Ludo’.