It’s rather trivial task to make some changes into already burned installation or live CD. It may be performed to add some files to this CD or edit files on it. In any case it’s impossible to loop mount .iso file and then save it as iso9660 filesystem is read-only.
So, just mount your CD or iso image to some directory by commands:
sudo mkdir /mnt/image
sudo mount /dev/cdrom /mnt/image
sudo mount /path/to/your.iso /mnt/image -o loop
then copy it’s contents to some directory:
cp -r /mnt/image /tmp/newiso
sudo mkisofs -o /tmp/new.iso -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -J -R -V “new iso name” .
After mkisofs is finished new ISO file will be created at /tmp directory.
It works in any Linux distributions like Ubuntu, Debian or Fedora