To remaster an ISO do the following:
*Also all commands are performed as root
Copy the ISO to the tmp directory:
mount -o loop Linux.iso /tmp/cdrom
cp -a /tmp/cdrom /tmp/iso
cd into /tmp/iso and copy .*sqfs or *.squashfs to /tmp
Make Changes now Then...
mksquashfs /tmp/squashfs-root *.SQFS
So far the Only way I have managed to remaster the ISO is either if the ISO has a makeiso.script or by using ISOMaster to open the original ISO remove the old sqfs and then insert new one and remaster ISO.