Re: saving cheatcodes

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Klaus Knopper wrote:
> if you want to modify the ISO image directly,
> you can edit the isolinux.cfg content by using a binary file editor like
> "hexedit" in order to modify/overwrite the boot options without changing
> the file size or other content. isolinux.cfg has some spare bytes which
> allows space to also add new options.

Wow. Is this one of the reasons why it is called "cheatcodes" ? :))


xorriso can tell the position of the file's content in the ISO:

  xorriso -indev KNOPPIX_V8.1-2017-09-05-EN.iso \
          -find /boot/isolinux/isolinux.cfg -exec report_lba --

reports on stdout:

  Report layout: xt , Startlba ,   Blocks , Filesize , ISO image path
  File data lba:  0 ,      934 ,        3 ,     4166 , '/boot/isolinux/isolinux.cfg'

This means that the file content is at byte offset
   934 * 2048 = 1,912,832 = 0x001D3000

Up to now i saw no reason to publish the address of the directory record
of a file, where its name and size are stored. But the fact that its size
could be safely expanded to 3 * 2048 = 6144 begins to give me ideas ...


Have a nice day :)

Thomas