Index: head/usr.sbin/bsdinstall/scripts/umount
===================================================================
--- head/usr.sbin/bsdinstall/scripts/umount	(revision 363100)
+++ head/usr.sbin/bsdinstall/scripts/umount	(revision 363101)
@@ -1,42 +1,44 @@
 #!/bin/sh
 #-
 # Copyright (c) 2011 Nathan Whitehorn
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 # 1. Redistributions of source code must retain the above copyright
 #    notice, this list of conditions and the following disclaimer.
 # 2. Redistributions in binary form must reproduce the above copyright
 #    notice, this list of conditions and the following disclaimer in the
 #    documentation and/or other materials provided with the distribution.
 #
 # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 # ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 # SUCH DAMAGE.
 #
 # $FreeBSD$
 
 TMP_FSTAB=${TMPDIR:-"/tmp"}/bsdinstall-tmp-fstab
 
 cat $PATH_FSTAB | awk -v BSDINSTALL_CHROOT=$BSDINSTALL_CHROOT '{
 	if ($2 ~ "^/.*") {
 		fsname = $2;
 		if (fsname == "/")
 			fsname = ""
 		printf("%s\t%s%s\t%s\t%s\t%s\t%s\n", $1, BSDINSTALL_CHROOT,
 		    fsname, $3, $4, $5, $6);
 	}
 }' > $TMP_FSTAB
 
 umount $BSDINSTALL_CHROOT/dev 2>/dev/null
-umount -F $TMP_FSTAB -a 2>/dev/null
+if [ -n "$TMP_FSTAB" ]; then
+	umount -F $TMP_FSTAB -a 2>/dev/null
+fi