"Grub failed to install to the following devices do you want to continue anyway? If you do your computer may not start up properly."

[cpoptic]

I suspect this issue is related to having both Windows/Ubuntu-via-WSL 2 running (maybe?):

I'm on a Windows 10 machine that has WSL 2 installed (Ubuntu 20.04). I was updating/reinstalling Docker per instructions [(https://docs.docker.com/engine/install/ubuntu/)] through the Ubuntu terminal and after the sudo apt update && sudo apt upgrade command, was prompted with the following:

The grub-pc package is being upgraded. This menu allows you to select which devices you'd like grub-install to be automatically run for, if any.

Running grub-install automatically is recommended in most situations, to prevent the installed GRUB core image from getting out of sync with GRUB modules or grub.cfg.

If you're unsure which drive is designated as boot drive by your BIOS, it is often a good idea to install GRUB to all of them.

Note: it is possible to install GRUB to partition boot records as well, and some appropriate partitions are offered here. However, this forces GRUB to use the blocklist mechanism, which makes it less reliable, and therefore is not recommended.

GRUB install devices:

[*] /dev/sda (274877 MB; ???)

[*] /dev/sdb (274877 MB; ???)

[*] /dev/sdb (274877 MB; ???)

[*] /dev/sdd (274877 MB; ???)

[*] /dev/sdd (274877 MB; ???)

I follow the suggestions and select all 5 devices, but then am blocked by this message:

Grub failed to install to the following devices do you want to continue anyway? If you do your computer may not start up properly.

That last sentence has me terrified. What to do here?

Environment

Windows build number: Microsoft Windows [Version 10.0.20206.1000]
Your Distribution version:   20.04
Whether the issue is on WSL 2 and/or WSL 1:  I'm using WSL 2:   
> Linux version 4.19.104-microsoft-standard (oe-user@oe-host) (gcc version 8.2.0 (GCC)) #1 SMP Wed Feb 19 06:37:35 UTC 2020

Steps to reproduce

WSL logs:

Expected behavior

Actual behavior

[onomatopellan]

Don't worry. Grub is a boot loader for the real Ubuntu on metal while WSL2 is a lightweight virtual machine and doesn't even need it to boot.

There are plenty of messages that you can safely ignore in WSL2. They are shown because the distro thinks they are running in a real PC.

[sibtainrawn]

i am using real ubuntu and installing localwp , then it happens. should i continue?

[cpoptic]

Okay, thanks that's what I suspected; as WSL2 is decoupled from the physical metal, but I wanted to double check before doing anything potentially irreversible. Thanks so much.

[therealkenc]

There are a few related tickets eg #4903. There is probably a way to make the upstream grub package more tolerant of environments where is ends up installed but is not applicable, like WSL, Docker, diskless boots, etc. I tend to apt remove it when it gets installed as a side-effect of other packages. I suspect everyone else does too, which is probably why it has never been made more tolerant.