[bug#28128] [PATCH] scripts: system: Add support for container network sharing.

[ludo@gnu.org (Ludovic Courtès)]

Hi!

Sorry for the delay!

Christopher Baines <mail@cbaines.net> skribis:

> This is a port of the functionality in the Guix environment command to the
> guix system container command.
>
> This requires additional changes to the operating-system definitions used, in
> particular, networking related services may need removing if the host network
> is shared.
>
> * guix/scripts/system.scm (system-derivation-for-action): Add
>   #:container-shared-network? argument.
>   (perform-action): Add #:container-shared-network? argument.
>   (show-help): Add "-N, --network" help information.
>   (%options): Add network option.
>   (process-action): Call perform-action with #:container-shared-network?.
> * gnu/system/linux-container.scm (%network-configuration-files): New variable.
>   (container-script): Add support for returning a container script that shares
>   the host network.
> * gnu/system.scm (essential-services): Add #:container-shared-network?
>   argument.
>   (operating-system-services): Add #:container-shared-network? argument.
>   (operating-system-etc-service): Add #:container-shared-network? argument,
>   and support for ommiting some configuration if the network is shared.
>   (operating-system-activation-script): Add #:container-shared-network?
>   argument, and pass this through to the operating-system-services procedure.
>   (operating-system-boot-script): Add #:container-shared-network? argument,
>   and pass this through to the operating-system-services procedure.
>   (operating-system-derivation): Add the #:container-shared-network? argument,
>   and pass this through to the operating-system-services procedure.
>   (operating-system-profile): Add the #:container-shared-network? argument,
>   and pass this through to the operating-system-services procedure.

My gut reaction was “hey this is cool!”, and then “wait, it doesn’t feel
right to pass that argument around everywhere!”.   :-)

We already have that with #:container?, and I think that’s a bit of a
problem.  The ‘linux-bare-metal’ service addresses it somewhat in a more
elegant way, I think.

What about this:

  1. Remove from ‘operating-system-etc-service’ all the
     shared-network-related files;

  2. Add a ‘shared-network-service’ that simply adds those file to /etc;

  3. Add a ‘containerized-operating-system’ that removes it.

There’s the problem, though, that /etc/hosts can only be added from
‘essential-services’.

Now, this:

+(define %network-configuration-files
+  '("/etc/resolv.conf"
+    "/etc/nsswitch.conf"
+    "/etc/services"
+    "/etc/hosts"))

… is exactly what (gnu system file-systems) defines.

Also, we should map the host’s /var/run/nscd/socket (if it exists) in
the guest, and remove nscd from the guest.

Thoughts?

Ludo’.