guix system: init: Overwrite the items in the target store.

Fixes <http://bugs.gnu.org/20722>.
Reported by Eric Bavier <ericbavier@openmailbox.org>.

* guix/scripts/system.scm (copy-item): Check whether DEST exists and remove it
  if it does.

1 files changed, 7 insertions, 0 deletions

diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index f7c9d83e9a..aa9b3f838a 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -76,6 +76,13 @@
     (let ((dest  (string-append target item))
           (state (string-append target "/var/guix")))
       (format log-port "copying '~a'...~%" item)
+
+      ;; Remove DEST if it exists to make sure that (1) we do not fail badly
+      ;; while trying to overwrite it (see <http://bugs.gnu.org/20722>), and
+      ;; (2) we end up with the right contents.
+      (when (file-exists? dest)
+        (delete-file-recursively dest))
+
       (copy-recursively item dest
                         #:log (%make-void-port "w"))