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Just before someone publicly lynches me for asking this - I searched online for many fixes and neither of them worked. I tried chrooting, using commands, even using the boot repair tool - all to no avail. I wanted to update grub when this error popped up.

In terms of my system, I am running a live Ubuntu system with persistence thanks to Rufus on a 240GB SSD - non-external, it's plugged into a drive dock and then I boot from it in the boot menu. The default system on my PC is Windows 11 Pro (wish it was Linux - but my family cannot use anything else :/). The reason it's live is so that I can boot from Windows desktops as well - if I had a proper install on a drive only Linux computers detected the disk.

I encountered the error both when updating grub and running Grub Customizer - I am building my own Ubuntu derivative system and I wanted to customize it.

I really have no idea about what to do now. My computer has GRUB installed and it plops up normally whenever I boot from the Ubuntu 22.04 LTS SSD.

I hope that the kind people on this forum will give me advice. Any is appreciated!

Renegade
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1 Answers1

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My advice would be to not try to change the GRUB loader of an existing Live system.

The early boot process in a "Live system" is more complex. You have found that your system doesn't support updating its own grub loader. Perhaps it is a bug, but I would not have expected it to work properly.

("cow" usually stands for "copy-on-write". Probably part of the persistent live system, e.g. see df -h displays /cow as one of the devices what does this mean?)

Personally, I would want to double-check this part:

if I had a proper install on a drive only Linux computers detected the disk.

Note this is not directly caused by the Linux install that is already on the computer. Hypothetically, the BIOS/UEFI boot menus would behave the same even if you destroyed the computer's Linux install :-).

Assuming UEFI boot, you want your GRUB to be installed in "removable" mode. This means it is installed to EFI/boot/bootx64.efi inside your EFI System Partition. This file is created using the --removable option of grub-install.

I don't know if Ubuntu is supposed to automatically detect when you try to install to a removable drive. If you have to manually install GRUB using the removable option, I don't know whether software updates will automatically reinstall GRUB and forget the --removable option.

Standard warning: be careful to avoid overwriting other partitions / operating systems / boot loaders when installing. Make sure any data you would get in trouble for losing, has been backed up somewhere else. Be extra careful if installing using MBR (not UEFI) boot.

sourcejedi
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  • But I want to run GRUB customizer... I only needed some advice. – Renegade Nov 05 '23 at 18:18
  • Maybe other people will be more familiar with your type of setup. It would be fair to say I'm not familiar and I'm extrapolating beyond my direct experience. For the combination of live system + persistent + update-grub + /cow error message, all I have to share is a bad feeling. Whereas, for a "proper install" with grub-efi in removable mode, I have a computer that once booted that way. – sourcejedi Nov 05 '23 at 20:08
  • I am certain there are some customizations that aren't possible, unless you turn it into something that's not a live system anymore. And the only sensible way to do that is to start again. I can understand that's not what you want to hear. – sourcejedi Nov 05 '23 at 20:16
  • Thy mean reinstall Ubuntu live system? – Renegade Nov 06 '23 at 07:26
  • I reinstalled the ubuntu live system - same error when I try to update grub. – Renegade Nov 06 '23 at 08:52
  • Is there nothing else that I can do? I need to customize my GRUB. Maybe I should log in as the live session user? – Renegade Nov 06 '23 at 08:53
  • I mean that update-grub isn't working on a "live system", it should be able to work on a "proper install". – sourcejedi Nov 06 '23 at 10:55