diff --git a/bash/mount.sh b/bash/mount.sh
index 5fe26a7..9fda047 100644
--- a/bash/mount.sh
+++ b/bash/mount.sh
@@ -4,36 +4,36 @@ local file
 if [ "${directory}" ] ; then
     directory="$(realpath "${directory}")"
     file="${directory}/filesystem.squashfs"
-    if mkdir 'overlay' ; then
-        cd 'overlay'
+    if mkdir "overlay" ; then
+        cd "overlay"
         mkdir {lower,upper,work,mount}
-        if mount "${file}" 'lower' ; then
-            mount -t 'overlay' 'overlay' 'mount' \
--o lowerdir='lower',upperdir='upper',workdir='work'
+        if mount "${file}" "lower" ; then
+            mount -t "overlay" "overlay" "mount" \
+-o lowerdir="lower",upperdir="upper",workdir="work"
         fi
         cd ..
     fi
 else
-    echo 'KO: directory?'
+    echo "KO: directory?"
 fi
 }
 
 uo() {
-cd 'overlay'
-if umount 'mount' ; then
-    rmdir 'mount'
-    rm --recursive 'upper' 'work'
-    if umount 'lower' ; then
-        rmdir 'lower'
+cd "overlay"
+if umount "mount" ; then
+    rmdir "mount"
+    rm --recursive "upper" "work"
+    if umount "lower" ; then
+        rmdir "lower"
     fi
 fi
 cd ..
-rmdir 'overlay'
+rmdir "overlay"
 }
 
 
 mr() {
-for f in 'dev' 'dev/pts' 'proc' 'sys' ; do
+for f in "dev" "dev/pts" "proc" "sys" ; do
     mount --bind "/${f}" "overlay/mount/${f}"
 done
 }
@@ -50,18 +50,18 @@ chroot \
 "
 
 ur() {
-for f in 'sys' 'proc' 'dev/pts' 'dev' ; do
+for f in "sys" "proc" "dev/pts" "dev" ; do
     umount --lazy "overlay/mount/${f}"
 done
 }
 
 
 mm() {
-mount --make-rslave --rbind '/deb' 'overlay/mount/deb'
+mount --make-rslave --rbind "/deb" "overlay/mount/deb"
 }
 
 um() {
-umount --recursive 'overlay/mount/deb'
+umount --recursive "overlay/mount/deb"
 }
 
 
@@ -70,12 +70,12 @@ local directory="${1}"
 local level="${2}"
 if [ "${directory}" ] ; then
     if mkdir "${directory}" ; then
-        [ "${level}" ] || level='18'
+        [ "${level}" ] || level="18"
         cp overlay/mount/{vmlinuz,initrd.img} "${directory}"
         mksquashfs \
-'overlay/mount' "${directory}/filesystem.squashfs" \
+"overlay/mount" "${directory}/filesystem.squashfs" \
 -noappend \
--comp 'zstd' -Xcompression-level "${level}"
+-comp "zstd" -Xcompression-level "${level}"
         chown --recursive 1000:1000 "${directory}"
     fi
 fi