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Bug#1024346: cdrom: debian-11.5.0-amd64-netinst.iso boots to Grub CLI on Dell Optiplex 5090

Hi Rob,

I see Andy has been helping you!

On Sat, Nov 19, 2022 at 03:38:33PM +0000, r@tekhax.io wrote:
>Thanks, after messing with it for quite awhile, I finally got it to work with the standard ISO.
>I booted with the Arch live image and did:
>wipefs -a /dev/nvme0n1
>dd if=/dev/zero of=/dev/nvme0n1 bs=512 count=100000
>then I used efibootmgr to delete all existing entries.
>Once I did that, the netinst booted into the installer
>immediately. Not sure if it was the actual existence of valid
>partitions on the drive, or just the existence of EFI entries in the

If your system has (had) existing EFI boot entries, then the firmware
would normally attempt to boot those. AIUI you selected the USB stick
and that failed to boot?

The partitioning on Debian images is slightly complex, to make them
work as a so-called "isohybrid". (This means that you can use the same
image both when written to optical media and when written to a USB
stick.) But the partitions should still show up. For example, looking
at the netinst image file here:

$ fdisk -l debian-11.5.0-amd64-netinst.iso
Disk debian-11.5.0-amd64-netinst.iso: 382 MiB, 400556032 bytes, 782336 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x5004a58b

Device                           Boot Start    End Sectors  Size Id Type
debian-11.5.0-amd64-netinst.iso1 *        0 782335  782336  382M  0 Empty
debian-11.5.0-amd64-netinst.iso2       4064   9247    5184  2.5M ef EFI (FAT-12/16/32)

The first partition covers the whole of the image; the second one is
*just* the EFI boot setup that you've seen already. If you're only
seeing the second partition then it appears there is some other
problem here.

Checking your original report here, you said you wrote to the USB
stick using dd if=<debian.iso> of=/dev/sdb. Did you run "sync" or
similar to make 100% sure that the image was all flushed to the USB
stick before removing it / booting it? Unless you tell it otherwise,
Linux will cache writes to USB drives and it can appear that writes
have completed well before the data is actually written to the
drive. This is a common cause of confusion for people in this
situation, I'm afraid.

Andy already mentioned a different way to force writing data, using
the "oflag=sync" option to dd. Using that with "bs=4M" should also
give good performance when writing out an image to a USB stick.

Could you possibly retry this and check if it works for you please?

Steve McIntyre, Cambridge, UK.                                steve@einval.com
< liw> everything I know about UK hotels I learned from "Fawlty Towers"

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