Every time I boot into Ubuntu (not dual boot, only have one OS installed) it boots me into the GRUB rescue prompt. I fix it every time with the same commands:

set root=(hd0,msdos5) 
set prefix=(hd0,msdos5)/boot/grub 
insmod normal 

I can use the set command to see that it defaults the prefix and root to (hd0,msdos1). How can I set it to start from (hd0,msdos5) at boot?

  • Try using boot repair disk. Follow the steps in this link. Or try to reconfigure grub using sudo update-grub May 23, 2021 at 18:59
  • Update of grub only updates grub menu. You have to reinstall grub so MBR is update (or if UEFI then UEFI is updated). If UEFI really should be gpt, not msdos partitions. Boot-Repair is a gui and easy, but all you really need if you can boot is sudo grub-install. If not using boot repair from live installer, then you have to mount partitions, / (root) and nay other system partition and then install grub to those or full chroot to mount everything.
    – oldfred
    May 24, 2021 at 2:45

2 Answers 2


Use Grub customizer. It is a GUI, very easy to use.

Note that for Ubuntu 20 you don't need to add any external ppa as indicated in some sources. You can simply install it with

sudo apt-get update
sudo apt-get install grub-customizer

Otherwise, operation is very easy and you can use the linked pages as a reference.


this can be fixed with one command in your Linux terminal

sudo grub-install /dev/sda

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