Re: writing iso file to usb stick with dd - garbled files - usb eject error?

[David Christensen <dpchrist@holgerdanske.com>]

On 8/3/25 14:54, Thomas Schmitt wrote:
> Hi,
>
> David Christensen wrote:
> > Beware that the Debian installer (d-i) can change the contents of the USB
> > flash drive when it runs (!).
>
> I am not aware that the Debian installer writes into the byte range
> of the ISO 9660 filesystem.
>
> The ISO 9660 filesystem itself is quite safe from being overwritten.
> But MS-Windows or the boot firmware might decide to add files to
> the EFI partition which is advertised by the partition table in the
> System Area of the ISO filesystem.
>
>
> > I reported the above on this list sometime in the past (few years?), but am
> > unable to locate the thread at this time.  I seem to recall the report was
> > confirmed, but the details were not where I had guessed.
>
> Possibly
>    https://lists.debian.org/debian-user/2024/04/msg00040.html
> to which i replied in
>    https://lists.debian.org/debian-user/2024/04/msg00045.html
> and pointed to
>    https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1056998
>
> Time is circular ... or rather Jeremy Bearimy.
>
>
> > I have burned my most recent d-i images to CD-R discs
>
> I heartfully support the use of optical media. :))
>
>
> Have a nice day :)
>
> Thomas


Thank you, Thomas, for finding that.  So, I AIUI the d-i does not modify 
the USB flash drive, but the motherboard firmware can (BIOS/EFI/UEFI) 
and some operating systems can.  The result is that the ISO checksum and 
the USB flash drive checksum will differ.  So, verification of the USB 
flash drive must be done immediately after burning and later checksums 
are not meaningful.


David