Bug#1056998: cdrom: Installation media changes after booting it

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

Hi,

Ram Reddy wrote:
> [...] usb drive [...] debian-12.2.0-amd64-netinst.iso [...]
> [...] Integrity Test section [...]
> ./boot/grub/efi.img failed the MD5 checksum verification. Your installation
> media or this file may have been corrupted.
> [...]
> It was always byte 2303211, line 21165 which changed.

I'd say that corruption of ISO image or USB is quite unlikely.

It rather looks like some change was made to the FAT filesystem in the
EFI partition by the parts of the installer which ran in your experiments.
(I expect EFI firmware not to manipulate that filesystem ...)
The EFI partition of this particular ISO begins at byte 2291712. The
alteration thus happened 11499 bytes inside that partition and its
filesystem. In the original ISO i see a sequence of 0-bytes there.

It would be interesting to check whether any errors get reported if the
ISO is presented on a read-only CD or DVD instead of a writable USB stick.
(To be absolutely read-only it would have to be CD-R, unformatted CD-RW,
DVD+R, DVD-R, or unformatted DVD-RW. The others can be overwritten without
burn program.)

Explanation why the file in the read-only ISO filesystem is reported as
being altered:
The partition shares its block range with the ISO file /boot/grub/efi.img
which is mentioned in the ISO file /md5sum.txt . So the integrity check
detects the difference between recorded MD5 and the MD5 of the altered
FAT filesystem image file /boot/grub/efi.img.


Have a nice day :)

Thomas