--- a/sbin/ftjail	Wed Sep 11 12:59:16 2024 +0200
+++ b/sbin/ftjail	Wed Sep 11 13:43:09 2024 +0200
@@ -873,7 +873,8 @@
     local _directory _new_origin _etcupdate_tarball
     local _opt_keep _opt_old_origin
 
-    local _res _jailname _dir_mounts _dir_fn_fstab _dir_basename _dir_fn_tldir
+    local _res _jailname _dir_mounts _dir_fn_fstab _dir_fn_fstab2
+    local _dir_basename _dir_fn_tldir
     local _root_dataset _root_mountpoint _root_type _root_options
     local _clone_extra_props _canmount_prop
     local _line _opt
@@ -991,20 +992,19 @@
 
     _u_tmpdir="$(env TMPDIR=/var/tmp mktemp -d -t ftjail_${_dir_basename})"
     [ -z "${_u_tmpdir}" ] && { echo "ERROR: cannot create unique temp dir" 1>&2; return 1; }
+    # The fstab that is corrently mounted at relevant locations (normalized)
     _dir_fn_fstab="${_u_tmpdir}/fstab"
-    #
-    # XXX FIXME: handle spaces in device and mountpoint names: replace
-    #            with a literal `\040'. Note that ${_dir_mounts} is
-    #            normalized already: it uses TAB characters as field
-    #            separator exclusively.
-    #
+    # The very same fstab -- but with spaces replaced by \040
+    _dir_fn_fstab2="${_u_tmpdir}/fstab2"
     printf '%s' "${_dir_mounts}" >"${_dir_fn_fstab}"
+    # Replace all spaces with a sequence that is understood by mount
+    LC_ALL=C /usr/bin/sed -e 's/ /\\040/g' <"${_dir_fn_fstab}" >"${_dir_fn_fstab2}"
     _dir_fn_tldir="${_u_tmpdir}/tldirs"
     LC_ALL=C /usr/bin/find "${_directory}" -depth 1 -type d 2>/dev/null | LC_ALL=C /usr/bin/sort >>"${_dir_fn_tldir}"
 
     # Unmount in reverse order: unmount can do it for us
     echo "Unmounting all datasets mounted at \`${_directory}'"
-    /sbin/umount -a -F "${_dir_fn_fstab}" -v
+    /sbin/umount -a -F "${_dir_fn_fstab2}" -v
 
     #
     # XXX TBD: Hooks to create some new top-level dirs (/srv /proc et
@@ -1077,7 +1077,7 @@
     # Mount again
     echo "Mounting all datasets rooted at \`${_directory}'"
     [ ! -d "${_directory}" ] && mkdir "${_directory}"
-    /sbin/mount -a -F "${_dir_fn_fstab}" -v
+    /sbin/mount -a -F "${_dir_fn_fstab2}" -v
 
     # Update and/or merge configs
     if [ -n "${_etcupdate_tarball}" ]; then