The wiki gives instructions on modifying the ISO[1] and the last step is to recreate the actual ISO file. I've got my Arch installers on USB sticks, but is it absolutely necessary to do this? Couldn't I just copy the root-image.fs.sfs to the appropriate directory on my USB (/path/to/USB/device/arch/x86_64/root-image.fs.sfs) instead, and regenerate the checksums? [1]https://wiki.archlinux.org/index.php/Remastering_the_Install_ISO