diff -r a8c8d86b8501 -r 4452ae59ce5f management_scripts/pre_init.sh
--- a/management_scripts/pre_init.sh	Tue Nov 04 14:23:14 2014 +0100
+++ b/management_scripts/pre_init.sh	Thu Nov 27 12:07:37 2014 +0100
@@ -50,6 +50,18 @@
 rmdir /tmp/usbmount/*
 umount /media/usb*
 
+# sometimes the umount fails with device bussy -> unknown why
+# so try until it works
+counter=0
+while ( [ -n "$(mount | grep "$DEVICE" | head -n 1 | awk '{print $3}')" ] && [ $counter -lt 10 ] )
+do
+	sleep 1
+	umount "$(mount | grep "$DEVICE" | head -n 1 | awk '{print $3}')"
+	counter=$((counter + 1))
+done
+
+
+
 # search for already encrypted volumes
 device=$(encryptionprovider.py -g)