Comment 14 for bug 1768069

I don't know how cubic modifies the iso, but you're probably going about this the hard way. What curtinator produces is a tar.gz with the files exactly as they will be uncompressed on the installed filesystem. So you can simply uncompress that tar.gz, put the files you need in place, and then recompress it. Just make sure to do this as root and use the -numeric-owner option to tar.