I recently installed Debian "Stretch" amd64 on an external HDD.

What I have done:

1. Created a 64GB ext4 partition for mount point /   .
2. Created a swap area. 
3. The rest is unallocated.
4. Chose to install as non UEFI.
5. Installed GRUB on external hard drive.
6. Finish & restart.

Key info:

1. External HDD is 1TB and not GPT.
2. I used Debian 9 amd64 installer.
3. My bios is set to legacy boot.
4. Booting to my external hard drive gives me "Operating system not found"

How can I solve this? Or

1 Answer 1


The Errormessage is from the BIOS/UEFI not from GRUB? Did you install grub to /dev/sdX (eg sda) or /dev/sdXY (eg sda1)?

  • Remove any disk except the one you want to boot from. Still the same error?
  • Boot from any linux live CD and reinstall grub to the disk using grub-install /dev/sdX
  • try again booting
  • tell us what's happening
  • Yes, but I just installed it with no problem. I choose Yes on installing GRUB on my main HDD but it prompted me what drive I should install it anyway. I booted my external hdd and GRUB shows up and Debian is booting fine Sep 30, 2017 at 15:06
  • 1
    so does that mean your problem is solved? You are allowed to answer your question yourself...
    – JPT
    Sep 30, 2017 at 17:46

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