Recovering from deleted /boot/efi (dual boot)

• date2021-03-22
• modified2025-08-04
• lang

  en

• tags

  system administration

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the "/boot/efi" partition used to boot is not exclusive to Linux: it is shared with Windows, and thus you can (and should) provide it to utility tools that fix boot. It is usually on /dev/sda2. You can ls -l /boot/efi from a functioning linux to check its content.

The command to "install" grub requires to provide the disk, not a specific partition (e.g. /dev/sda, not /dev/sda2)

The following lines are a crude hint, the full operation might require some other mounting.

First, create a live USB/CD system, and boot on it.

Then we mount the dead system to be able to work with it:

1 for i in /dev /dev/pts /proc /sys /sys/firmware/efi/efivars /run; do sudo mount -B /mnt$i; done

And we chroot to act as if we were on the dead system:

1 chroot /mnt

Then we mount the EFI partition:

1 mount /dev/sda2 /boot/efi

And finally we execute the "grub-install" command: The bootloader-id argument will be the name appearing in the EFI boot list if you go to the boot menu. Type the following command very carefully, a lot of people online seem to have errors simply due to typos:

1 sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=debian --recheck --debug /dev/sda

You may eventually do (once you left chroot with exit like any shell instance):

1 update-grub