linux-container: Support container network sharing.

* gnu/system/linux-container.scm (container-essential-services): If network is
to be shared with the host, remove network configuration files from etc
service.
(containerized-operating-system): If network is to be shared with the host,
remove nscd service and map host's /var/run/nscd if it exists.
(container-script): If network is to be shared with the host, do not create
network namespace.
* 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? argument.
* doc/guix.texi (Invoking guix system): Document the "-N, --network" option.

Co-authored-by: Christopher Baines <mail@cbaines.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 843e909fb2..27e0f72ccb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -24587,6 +24587,11 @@ When this option is omitted, @command{guix system} computes an estimate
 of the image size as a function of the size of the system declared in
 @var{file}.
 
+@item --network
+@itemx -N
+For the @code{container} action, allow containers to access the host network,
+that is, do not create a network namespace.
+
 @item --root=@var{file}
 @itemx -r @var{file}
 Make @var{file} a symlink to the result, and register it as a garbage