On Thu, Mar 05, 2026 at 08:23:53PM +0100, Thomas Schmitt wrote: [...]
> ISO images which are bootable by EFI from USB stick contain a partition > table which points to some data range inside the image file. > In case of Debian netinst ISO this range is the content of data file > /boot/grub/efi.img . So the EFI partition is even inside the ISO 9660 > filesystem: [...] > In modern Ubuntu ISOs the EFI partition is outside the ISO 9660 > filesystem, but nevertheless inside the image file. [...] > The offending mainboard firmwares and operating systems feel entitled > to add files to the FAT filesystem in the EFI partition. This changes > the content of /boot/grub/efi.img in the Debian ISO and thus the > checksum of the data range of the original image on the USB stick. > In the Ubuntu image the change does not hit the ISO 9660 filesystem > but still the byte range for which its download checksum was computed. Ouch. Is there any more systematic account for that? A way to find out (post mortem, perhaps?) Or a list of bad firmwares? I'm asking, because we had a couple of Linux install fests, and the install sticks were some times (not often, but more than once) not bootable after the install. We always assumed fat-finger (aka pilot error), for example, partitioning the "wrong" target media (the install stick itself). But perhaps there are other viable hypotheses... Cheers -- t
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