installer: Run the installation inside a container.

When the store overlay is mounted, other processes such as kmscon, udev
and guix-daemon may open files from the store, preventing the
underlying install support from being umounted. See:
https://lists.gnu.org/archive/html/guix-devel/2018-12/msg00161.html.

To avoid this situation, mount the store overlay inside a container,
and run the installation from within that container.

* gnu/build/shepherd.scm (fork+exec-command/container): New procedure.
* gnu/services/base.scm (guix-shepherd-service): Support an optional PID
argument passed to the "start" method. If that argument is passed, ensure that
guix-daemon enters the given PID MNT namespace by using
fork+exec-command/container procedure.
* gnu/installer/final.scm (umount-cow-store): Remove it,
(install-system): run the installation from within a container.
* gnu/installer/newt/final.scm (run-install-shell): Remove the display hack.

1 files changed, 16 insertions, 2 deletions

diff --git a/gnu/build/shepherd.scm b/gnu/build/shepherd.scm
index fd93e7f3f4..65141bd60f 100644
--- a/gnu/build/shepherd.scm
+++ b/gnu/build/shepherd.scm
@@ -20,10 +20,12 @@
   #:use-module (gnu system file-systems)
   #:use-module (gnu build linux-container)
   #:use-module (guix build utils)
+  #:use-module (guix utils)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:use-module (ice-9 match)
-  #:export (make-forkexec-constructor/container))
+  #:export (make-forkexec-constructor/container
+            fork+exec-command/container))
 
 ;;; Commentary:
 ;;;
@@ -93,7 +95,8 @@
 ;; XXX: Lazy-bind the Shepherd to avoid a compile-time dependency.
 (module-autoload! (current-module)
                   '(shepherd service)
-                  '(read-pid-file exec-command %precious-signals))
+                  '(fork+exec-command read-pid-file exec-command
+                    %precious-signals))
 (module-autoload! (current-module)
                   '(shepherd system) '(unblock-signals))
 
@@ -188,6 +191,17 @@ namespace, in addition to essential bind-mounts such /proc."
               (read-pid-file pid-file #:max-delay pid-file-timeout))
           pid))))
 
+(define* (fork+exec-command/container command
+                                      #:key pid
+                                      #:allow-other-keys
+                                      #:rest args)
+  "This is a variant of 'fork+exec-command' procedure, that joins the
+namespaces of process PID beforehand."
+  (container-excursion* pid
+    (lambda ()
+      (apply fork+exec-command command
+             (strip-keyword-arguments '(#:pid) args)))))
+
 ;; Local Variables:
 ;; eval: (put 'container-excursion* 'scheme-indent-function 1)
 ;; End: