On Tue, 17 Dec 2024, Thomas Schmitt wrote:

dd if=debian-12.8.0-and64-DVD-1.iso of=/dev/sdj1 bs=4M && sync

The "1" in "/dev/sdj1" is surplus.

I rebuilt the USB stick using just /dev/sdj .

On Tue, 17 Dec 2024, Max Nikulin wrote:

Am I right that you have internal SSD (SATA? NVME?) and a USB stick?

I have 1) Internal Kingston SSD to be formatted to run Debian.
2) The original Microsoft SSD that came with the machine, and which didn't impede the previous Debian 12 install.
3) Two spinning disks forming a RAID1 for my data.

Have you tried to plug the stick into another USB port (e.g. USB2 instead of USB3 or vice versa)? Try full power cycle, not just reboot.

All the 10 USB ports on my T5820 are specified as USB 3.1 Gen 1. I always do a full powercycle.

To figure out what happens in your case you may try the following commands:

grub> echo $prefix
(hd2,gpt1)/boot/grub ### Note: Filesystem FAT 102400KiB
grub> echo $root
hd2,gpt1
grub> echo $cmdpath
(hd2,gpt1)/EFI/debian
grub> echo $fw_path
### no output ###

(hd2,gpt3) and (hd2,gpt4) have filesystem ntfs, so hd2 is the Microsoft SSD.

On Mon, 16 Dec 2024, David Christensen wrote:

Please use Debian Stable or Debian Old Stable ISO.

I'm now using 12.8.

Disconnect all drives except the drive onto which you want to install Debian.

I pulled out the Microsoft SSD, powered off, waited 10s, powered on and I got to
the Debian 12.8 Graphical Install menu ! But the installation failed with a "debootstrap error". To avoid this I not only had to disconnect other drives, but also abandon partitions which contained non-UEFI operating systems.

Finally, I installed Debian 12.8 taking care to specify the special file type EFI for the small bootable partition. When the installation was complete I removed the USB stick, rebooted and was greeted by the Debian 12.8 login window.
Success!

My thanks to everyone who made the useful suggestions which helped me solve the multiple problems.

Roger

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