# to let the options be overridable by user (such as 'ro').
$oo=";$oo;";
$oo=~tr/,/;/;
-$oo=~s/;(ro|rw);/;--$1/g;
+$oo=~s/;(ro|rw);/;--$1;/g;
+$oo=~s/;(?:no)?auto;/;/g; # ignore
$oo=""
."mntent.mnt_fsname=$image,mntent.mnt_type=captive-$fsname," # Double-dashes forbidden.
."dir_cache_entries=0,"