I need some help with grub bootloader. I have ubuntu installed and Windows 10, Grub used to load automatically but I messed some partitions and now it is not (automatically boots into windows). I have booted from flash and I can see my files are there partitions, the 457Gb is the ubuntu and the 230Gb is the windows (not sure what the third one is from image). Anyway I would like to restore grub (so I can manually choose which OS to load). I tried

fdisk -l
sudo update-grub

but got this error /usr/sbin/grub-probe: error: failed to get canonical path of/cow'.` terminal ubuntu, I really hope there is a solution for this withot me losing the data (specially the data on ubuntu)

  • i suggest to try first # sudo grub-install --recheck , # sudo grub-install /dev/sdX , if the commands complete without any error try to run # sudo update-grub , if it still not work and you receive the error message , boot to linux os from falsh usb , then mount the drives, chroot to system then mount , /dev , /proc , /sys , /pts , connect the internet copy the resolv.conf using -L option to to be able internet inside chroot system the reinstall agaien grub2 grub-pc and grub-common GOODLUCK . – user643653 Nov 2 '19 at 21:32
  • The /cow means you are trying to update the live installer not your install. Answer below using Boot-Repair is often easier, but you can mount your install partitions and install grub or do a full chroot into install and run updates & repairs. – oldfred Nov 3 '19 at 14:41

Lifted from the community wiki:

  1. Insert your Ubuntu CD, reboot your computer and set it to boot from CD in the BIOS and boot into a live session. You can also use a LiveUSB if you have created one in the past.
  2. Install and run Boot-Repair.

sudo add-apt-repository ppa:yannubuntu/boot-repair sudo apt-get update sudo apt-get install -y boot-repair && boot-repair

  1. Click "Recommended Repair".
  2. Now reboot your system. The usual GRUB boot menu should appear.

Alternatively download the boot-repair-disk.iso, make a bootable cd or usb key from this and boot it to perform the repair

boot repair disk

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