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I've decided recently to install Ubuntu on an external SSD. I want to use it as a "work OS" that I could plug anywhere.

After some research, I found that with usb 3.0 throughput, there are no problems running an OS from an external drive.

I have also found this recent guide to install a portable ubuntu on an external drive.

I've managed to install ubuntu 20.04 (rather than 19.10 in his tutorial) which works quite well but is bound to the computer where I installed it.

So in order to manage this issue, while being on a "Try ubuntu" thumb drive session, they describe how to mount the external device with the fresh ubuntu install, to change the mount points in /mnt/etc/fstab and to chroot in it for installing grub on the efs partition. (If you wanna check, part E of his guide)

The problem is that I have followed each steps carefully 3 times, but when I boot on this device with another computer that only has a W10 on it, my screen freezes with this error: error: file ./boot' not found. I have checked on my SSD and the /boot/* directory does exist.

The message on my screen when I boot on the external SSD

I have tried different arguments with grub-install but nothing seems to change.

Do you have any ideas as to why another computer couldn't find the grub installation on my SSD?

Speedphoenix
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Asarim
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  • Does the first computer that has Windows 10 only, you used to create the Ubuntu USB boot properly? Or does it boot to grub if the USB is unplugged? – user68186 Aug 02 '20 at 22:22
  • @user68186 ok I should have said that. The PC I used to install Ubuntu on my external SSD was a PC that already had a dual-boot w10 - ubuntu 20.04. I used a bootable key for the installation. The ubuntu 20.04 from external SSD boot normaly when I use it on this PC. But I got the error when I try with another PC than the one I used to install it. – Asarim Aug 02 '20 at 22:53
  • It sounds like you may have copied the EFI files of the wrong installed version of Ubuntu in the USB. I can't be sure. – user68186 Aug 03 '20 at 02:41
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    Try to start over. Use this answer as model. Except you have an external drive and an internal drive. – user68186 Aug 03 '20 at 02:48
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    The tutorial you followed does not have a BIOS boot partition. If you want it to boot in either BIOS or UEFI mode, see any of the methods here: https://askubuntu.com/questions/1217832/how-to-create-a-full-install-of-ubuntu-20-04-to-usb-device-step-by-step – C.S.Cameron Aug 03 '20 at 05:26
  • @user68186 I deleted my old ubuntu partitions (so now I just have a pc with W10 installed) then I start your tutorial. I could boot ubuntu/W10 with grub on this computer, but if I try to plug my ssd with ubuntu fresh install on my desktop pc, I can't choose it anymore as a boot option. – Asarim Aug 05 '20 at 09:50
  • This is a different problem. Please search the site for similar questions. If you don't find an answer, please ask a new question. – user68186 Aug 05 '20 at 12:47
  • Update: It finaly works on any device, I don't really know why. It's most likely because I updated Ubuntu and grub to the last version. Thanks again @user68186. NB : I had another problem with grub which doesn't want to launch ubuntu. It was due to a bios setting which allow to boot only on a windows system EFI that I had to change. – Asarim Oct 10 '20 at 15:53

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