diff --git a/shell/mount.sh b/shell/mount.sh
index fe5b273..cb7bb5a 100644
--- a/shell/mount.sh
+++ b/shell/mount.sh
@@ -1,12 +1,14 @@
 mo() {
-	local directory="${1}"
-	local file
-	if [ -n "${directory}" ]; then
-		directory="$(realpath "${directory}")"
-		file="${directory}/filesystem.squashfs"
+	local root="${1}"
+	local directory file
+	if [ -n "${root}" ]; then
+		root="$(realpath "${root}")"
+		file="${root}/filesystem.squashfs"
 		if mkdir "overlay"; then
 			cd "overlay"
-			mkdir {lower,upper,work,mount}
+			for directory in "lower" "upper" "work" "mount"; do
+				mkdir "${directory}"
+			done
 			if mount "${file}" "lower"; then
 				mount \
 					-o lowerdir="lower",upperdir="upper",workdir="work" \
@@ -16,7 +18,8 @@ mo() {
 			cd ..
 		fi
 	else
-		echo "KO: directory?"
+		log_fatal "No root"
+		return 1
 	fi
 }
 
@@ -68,11 +71,14 @@ um() {
 
 ms() {
 	local directory="${1}"
+	local file
 	local level="${2}"
 	if [ -n "${directory}" ]; then
 		if mkdir "${directory}"; then
 			[ -n "${level}" ] || level="18"
-			cp overlay/mount/{vmlinuz,initrd.img} "${directory}"
+			for file in "vmlinuz" "initrd.img"; do
+				cp "overlay/mount/${file}" "${directory}"
+			done
 			mksquashfs \
 				"overlay/mount" "${directory}/filesystem.squashfs" \
 				-noappend \