guix system: Invoking 'guix system init' twice keeps timestamps zeroed.

Fixes a bug whereby running 'guix system init config.scm /mnt' twice
would, on the second run, change timestamps in /mnt/gnu/store from the
Epoch to now.  This is because the 'register-path' call would bypass the
'reset-timestamps' phase altogether in that case, as a consequence of
commit bb3b6ccb05550fbfbeb459c68819a752327d6e1e.

Reported by Christopher Baines.

* guix/scripts/system.scm (install): When TARGET/var/guix exists, delete
it.  As a side-effect, this ensures that later on, the 'register-path'
call invokes 'reset-timestamps' on all the copied store items.

1 files changed, 7 insertions, 0 deletions

diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index d2be0cf8fb..9ba9428a08 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -235,6 +235,13 @@ When INSTALL-BOOTLOADER? is true, install bootloader using BOOTCFG."
 the ownership of '~a' may be incorrect!~%")
                target))
 
+  ;; If a previous installation was attempted, make sure we start anew; in
+  ;; particular, we don't want to keep a store database that might not
+  ;; correspond to what we're actually putting in the store.
+  (let ((state (string-append target "/var/guix")))
+    (when (file-exists? state)
+      (delete-file-recursively state)))
+
   (chmod target #o755)
   (let ((os-dir   (derivation->output-path os-drv))
         (format   (lift format %store-monad))