Bug#857597: debian-cd: "isolinux.bin missing or corrupt" when booting USB flash drive in old PC

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

Hi,

Steve McIntyre wrote:
> Do you have suggested text we can use?

Modulo english language, URL of the binary file, and clarity of mind.

$$...$$ means that properties of the download offer have to be inserted.
The answer is intended to be put after
  "How do I write a CD/DVD/BD image to a USB flash drive?"
I hope to have used the same terms as in that answer.

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Q: What if booting a USB flash drive says "isolinux.bin missing or corrupt" ?

A:
Old PCs might encounter this bug within the isohybrid MBR code at the very
start of the Debian image. It affects BIOS firmware from about 2005
or older which announces to only support C/H/S addressing of blocks on
the flash drive.
Because the bug is exotic and the affected MBR code has proven to work
with most PCs since many years, the fix is not yet included in the Debian
and Debian Live images.

If your PC shows the message "isolinux.bin missing or corrupt" then
you may try whether the fixed MBR code brings better results.

* Download it from
  $$ URL of copy of binary file with 432 bytes from
     http://www.ludd.ltu.se/~ams/tmp/isohdpfx.bin.170324 
     or of a isohdpfx.bin assembled from newest SYSLINUX git $$

* Optionally check the sha512sum of the download:
   $$ f0883df50945754801111dd7d1c31ac03c68f26a346d31c172b077964450594eec447992327d1bee3cbf3fff652e1787f61c49123481b46f82471bac457c2d38
      or the SHA512 of the SYSLINUX git based binary $$

* Put it onto the first 432 bytes of the USB flash drive like in the previous
  answer "How do I write a CD/DVD/BD image to a USB flash drive?":

    cp <$$filename.from.URL$$> <device>

  or

    dd if=<$$filename.from.URL$$> of=<device> bs=1 count=432 conv=notrunc; sync

  The "cp" example is only suitable for <device> being a device file.
  If you want to put the fixed MBR into a Debian image data file then
  you must use the "dd" command with "conv=notrunc" or else you will
  lose the complete image data. In this case <device> shall be the name
  of the Debian image file.

----------------------------------------------------------------------------

The file  http://www.ludd.ltu.se/~ams/tmp/isohdpfx.bin.170324  is still
available and shows the same SHA512 as the file which i downloaded march 26,
when David Christensen confirmed that it works for him.
I leave it to Debian policy whether we can use that binary or need to
assemble a new one from SYSLINUX source. If the SHAs differ, we would have
to ask David to test again.

Both proposed copy commands have been tested with a USB stick.
dd was tested with a data file, too.
I prescribe a size restriction by "count=" just in case the download
yields more than 432 bytes. If so, then dd will not spoil the ISO and
one can later try again with a better download.


Have a nice day :)

Thomas