The message you get means that you gave a boot option mentioning
isolinux.bin as the boot image, but that the path to
isolinux.bin is not
in the list of files which shall show up in the emerging ISO image.
-boot_image is the
xorriso command which controls many boot related
properties. If you did not use it then I guess you used the
emulation, where this was probably option -b (alias
expects the path inside the ISO, not in the filesystem from where your
So make sure to give with -b the path of isolinux.bin in the ISO.
In many ISOs, you will find it in
/boot/isolinux or in
So if you just pack up a mounted ISO again, you will possibly have success
(The lack of trailing slash makes these paths compatible with
expects a relative path in the working directory of the source filesystem.
mkisofs -b would work only if your
pwd is the ISO's root.)
I could give clearer advise if you tell me the URL of the ISO which you
try to use as input and the
xorrisofs options which you used.