From 73f61f06872aa12d796f9f5359ae1f53907e5638 Mon Sep 17 00:00:00 2001
From: Franco Fichtner <franco@opnsense.org>
Date: Sat, 24 Sep 2016 06:59:39 +0200
Subject: [PATCH] util: keep the probing file, it prevents spurious writes

---
 src/etc/inc/util.inc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/etc/inc/util.inc b/src/etc/inc/util.inc
index 059ab1062..02d9c438f 100644
--- a/src/etc/inc/util.inc
+++ b/src/etc/inc/util.inc
@@ -1566,12 +1566,15 @@ function is_install_media()
      * Despite unionfs underneath, / is still not writeable,
      * making the following the perfect test for install media.
      */
-
     $file = '/.probe.for.install.media';
+
+    if (file_exists($file)) {
+        return false;
+    }
+
     $fd = @fopen($file, 'w');
     if ($fd) {
         fclose($fd);
-        unlink($file);
         return false;
     }