linux-container: Make the guest UID and GID a parameter.

* gnu/build/linux-container.scm (initialize-user-namespace): Add
 #:guest-uid and #:guest-gid parameters and honor them.
(run-container): Likewise.
(call-with-container): Likewise.
* tests/containers.scm ("call-with-container, user namespace, guest UID/GID"):
New test.

1 files changed, 11 insertions, 0 deletions

diff --git a/tests/containers.scm b/tests/containers.scm
index 5323e5037dc..37408f380d3 100644
--- a/tests/containers.scm
+++ b/tests/containers.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015 David Thompson <davet@gnu.org>
+;;; Copyright © 2016, 2017, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -52,6 +53,16 @@
      #:namespaces '(user))))
 
 (skip-if-unsupported)
+(test-assert "call-with-container, user namespace, guest UID/GID"
+  (zero?
+   (call-with-container '()
+     (lambda ()
+       (assert-exit (and (= 42 (getuid)) (= 77 (getgid)))))
+     #:guest-uid 42
+     #:guest-gid 77
+     #:namespaces '(user))))
+
+(skip-if-unsupported)
 (test-assert "call-with-container, uts namespace"
   (zero?
    (call-with-container '()