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I have a theoretical question about multi-booting in UEFI mode. I have Manjaro 20.2.1 installed alongside Ubuntu 20.04. Because Manjaro was installed later. Grub menu is configured by Manjaro. I want to give the control back to Ubuntu. I understand UEFI partition.

I tried to look in the internet. I found some commands:

  1. update-grub
  2. grub-install

I know partially about them only. The first one to update /etc/default/grub into actual grub. The second one to install a grub (for managing boot)

I also found some files and folder:

  1. /boot/EFI (UEFI partition)
  2. /boot/grub (corresponding os partition)
  3. /etc/default/grub (cfg file to change grub option)

What I want to know?

  1. What are the contribution of the commands and files/folders. What they actually do?

  2. How to change the OS that would controls grub? (in my case from manjaro to ubuntu)

Thanks in advance ! :)

Sayan Dey
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  • Any question should always include the version of Ubuntu you are using. Please edit the question or add a flag. What version is it? – David Jan 26 '21 at 13:24
  • This article pretty much answers all your questions. https://itsfoss.com/update-grub/ If you type sudo update-grub in a terminal on your Ubuntu installation it should take over grub. – PonJar Jan 26 '21 at 15:16
  • A grub reinstall will reset boot order until other system does a reinstall or major update. If UEFI Ubuntu based you only have one Ubuntu entry in UEFI. But other systems use grub or name of distribution in UEFI. See this: sudo efibootmgr -v And you can change boot order with efibootmgr. See. man efibootmgr and http://askubuntu.com/questions/485261/change-boot-order-using-efibootmgr Grub install uses efibootmgr to set boot order. – oldfred Jan 26 '21 at 15:51
  • Duplicate of this? https://askubuntu.com/questions/1311041/change-grub-controller-in-two-linux-dual-boot – oldfred Jan 26 '21 at 15:53
  • @oldfred that helped got ubuntu as grub constroller, but now I can't boot into manjaro. It is showing in the boot menu, but stuck at the splash screen like this Don't know whether the grub install was the reason. :( – Sayan Dey Jan 26 '21 at 16:00
  • Not a duplicate. The questions although share common stuff, aim at different goals. – Sayan Dey Jan 26 '21 at 16:02
  • Does sudo update-grub add manjaro? If LVM or other type install, you need to mount it first. If not copy a manjoro boot stanza into 40_custom. sudo nano -B /etc/grub.d/40_custom & see menu at bottom for commands. Then do: sudo update-grub – oldfred Jan 26 '21 at 16:05
  • Umm... manjaro appears in efrbootmgr, it is there in the boot menu but the moment I enter press to boot to manjaro, I am stuck at the screen. I think it is a manjaro specific issue. – Sayan Dey Jan 26 '21 at 16:08

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