I want to reinstall GRUB 2 and I found these instructions: How to Repair, Restore, or Reinstall Grub 2 with a Ubuntu Live CD or USB. In my case, the boot loader is installed in the EFI partition. If I use the commands provided in this guide, will GRUB be reinstalled to the EFI partition automatically, or will it be installed into the root partition where Ubuntu is installed ? Obviously, I do not want this to happen.
Reinstall the GRUB boot loader to your Ubuntu installation in EFI mode this way ...
Boot from the Ubuntu installation medium and select 'Try Ubuntu without installing'.
(Boot your install medium in EFI mode, select the Ubuntu entry with UEFI in front.)
Once you are on the Live desktop, open a terminal and execute these commands :
sudo mount /dev/sdXY /mnt sudo mount /dev/sdXX /mnt/boot/efi for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done sudo chroot /mnt grub-install /dev/sdX update-grub
sdX = disk |
sdXX = efi partition |
sdXY = system partition
To identify the partitions use GParted, the tool is included in the installation medium.
After having run the commands GRUB will be installed in the separate EFI partition.
this is the only way that worked for me: (System: sdb8, boot: sdb6, efi: sdb2)
sudo mount /dev/sdb8 /mnt sudo mount /dev/sdb6 /mnt/boot sudo mount /dev/sdb2 /mnt/boot/efi sudo mount --bind /dev /mnt/dev && sudo mount --bind /dev/pts /mnt/dev/pts && sudo mount --bind /proc /mnt/proc && sudo mount --bind /sys /mnt/sys sudo chroot /mnt grub-install --target=x86_64-efi /dev/sdb grub-install --recheck /dev/sdb exit && sudo umount /mnt/sys && sudo umount /mnt/proc && sudo umount /mnt/dev/pts && sudo umount /mnt/dev && sudo umount /mnt
Thanks to @cl-netbox for the instructions!
After I upgraded (Linux Mint 18.2 Sonya to 18.3 Sylvia) my system wouldn't boot so I followed the instructions above but still no success. I noticed however that my machine has /boot in a separate partition (possibly because I am using LVM) so my slightly modified process was:
sudo mount /dev/sdXXX /mnt sudo mount /dev/sdXY /mnt/boot sudo mount /dev/sdXX /mnt/boot/efi for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done sudo chroot /mnt grub-install /dev/sdX update-grub
Note : sdX = disk | sdXX = efi partition | sdXY = boot partition | sdXXX = system partition
This is how I did it on a standard x86_amd64 EFI desktop, without chrooting, assuming you have a partition containing Ubuntu on your hard drive and possibly an EFI partition where GRUB should be installed.
# boot on a live Ubuntu, I used 18.04 but more recent should work # if you have currently no EFI partition (maybe it was deleted, # or you are migrating to a new drive): # sudo gparted # - create a FAT 32 partition of around 100 MB on the disk of your choice # (in general the one that host the Ubuntu partition). If you plan to # move or resize some paritions, anticipate that (for instance by # creating the EFI partition at the end of the free space). # - set the flag esp on this partition (the flag boot will also be selected) # now assuming that the Ubuntu partition is `/dev/sda2` and the (possibly new) EFI partition is `/dev/sda1` sudo apt install grub-efi sudo mkdir /media/root && sudo mount /dev/sda2 /media/root sudo mkdir /media/efi && sudo mount /dev/sda1 /media/efi sudo grub-install --target=x86_64-efi /dev/sda --efi-directory=/media/efi --boot-directory=/media/root/boot
This should give:
Installing for x86_64-efi platform.
Installation finished. No error reported.
Then reboot and you should be done. You may have to tell your BIOS which drive to use, or which EFI partition to use, or which EFI binary to use.
If you created a new EFI partition, you may have to add it to
/etc/fstab to have
update-grub working correctly.
For more information : https://wiki.archlinux.org/index.php/Multiboot_USB_drive#Hybrid_UEFI_GPT_+_BIOS_GPT/MBR_boot
Also, if booting from live cd to recover it might happen that you are missing grub-efi-amd64-bin package and then line
"grub-install --target=x86_64-efi /dev/sdb"
fails with error message: "grub-install: error: /usr/lib/grub/x86_64-efi/modinfo.sh doesn't exist. Please specify --target or --directory."
In this case run this outside of chroot
sudo apt get grub-efi-amd64-bin
and then add /usr/lib/grub/x86_64-efi to chroot mounts.
BTW "/dev/sdb" param is obsolete and is being ignored.
If you happen to lose your EFI partition, it's easy to get it back. You can use a partitioning tool such as
parted to create a new partition sdXY (e.g. sda1) with type "EFI partition (1)" and format it with:
sudo mkfs.msdos /dev/sdXY
then mount it with:
sudo mount /dev/sdXY /boot/efi
and you can reinstall GRUB by running:
sudo grub-install --efi-directory=/boot/efi
as mentioned in other solutions.
in addition to ci-netbox answer.
If your pendrive OS version does not match the one that is installed on the disk, grub-install may have difficulties to identify the right grub installation:
$ sudo chroot /mnt # grub-install /dev/sdX grub-install: error: /usr/lib/grub/i386-pc/modinfo.sh doesn't exist. Please specify --target or --directory.
Try to identify manually the installation to use
# ls /usr/lib/grub/ grub-mkconfig_lib x86_64-efi x86_64-efi-signed
Then restart grub-install :
# grub-install --target=x86_64-efi /dev/sdX Installing for x86_64-efi platform. Installation finished. No error reported.
I can't comment (not enough reputation), but @Chilu Pereira's answer is the way to go in an EFi or multiboot situation. It is similar to the approach in the gentoo-guide.
They use a slightly different approach :
Instead of a
mount --bind they use
mount --rbind followed by
mount --make-rslave for sys and dev and proc gets simply mounted again.
In gentoo I used to create mounts from a live-system like this:
mount -t proc /proc /mnt/proc mount --rbind /sys /mnt/sys mount --make-rslave /mnt/sys mount --rbind /dev /mnt/dev mount --make-rslave /mnt/dev chmod 1777 /mnt/dev/shm
(Anybody knows what is exactly the difference between
--rbind / --make-rslave btw ?)
But today I got two errors in chroot from grub2, I never experienced before :
connect: No such file or directory Please make sure that the zfs-fuse daemon is running
grub-install: warning: Cannot read EFI Boot* variables. grub-install: warning: read_file: could not read from file: Input/output error.
The zfs-fuse error seems not to matter but for Efivars I had to add one more mount :
mount --bind /sys/firmware/efi/efivars /mnt/sys/firmware/efi/efivars
I guess /sys/firmware/efi/efivars does not exist in chroot or maybe it's read only - but anyway it worked
During the last months there have been some updates to the libraries involved.
The steps below were useful for me. They took ideas from old answers as well as from other forums.
Make sure that you booted using EFI
sudo mount /dev/nvme0n1p5 /mnt sudo mount /dev/nvme0n1p1 /mnt/boot/efi for i in /dev /dev/pts /proc /sys /sys/firmware/efi/efivars /run; do sudo mount -B $i /mnt$i; done sudo chroot /mnt grub-install --target=x86_64-efi /dev/nvme0n1 grub-install --recheck /dev/nvme0n1 # as a second attempt, you could also try (assuming _debian_ is your distro) # grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=debian # grub-mkconfig -o /boot/grub/grub.cfg update-grub2 exit && sudo umount /mnt/sys && sudo umount /mnt/proc && sudo umount /mnt/dev/pts && sudo umount /mnt/dev && sudo umount /mnt
Make sure that
efibootmgr lists your Linux as an entry
What caused the loss of the Grub2 menu in the first place?
Universal answer 112 (cl-netbox Sep 2016, Dec 2020) should always work to reinstall grub. The maze of steps required will not answer this festering question which most everyone asks.
Assume a working Ubuntu install on a gpt SSD followed one year later by a new install of a newer Ubuntu version on a gpt spinning disk. Boot after the new install has lost the grub2 menu of the SSD and boots instead to the spinning disk.
Curiosity can sometimes lead to learning more about how grub2 works. Learning from the example proceeds as follows. Assume hereafter the spinning disk boots ubuntu.
Sudo mount the EFI partition of the SSD on /mnt Open a terminal on /mnt cd to /mnt/EFI/ubuntu and open grub.cfg in a text editor like xed
The contents of grub.cfg looks like this:
search.fs_uuid 0caa0215-f19c-4cbf-8b27-1ffd0984bef8 root hd1,gpt12 set prefix=($root)'/boot/grub' configfile $prefix/grub.cfg**strong text**
Observe that file name grub.cfg is also used by grub2 in folder /boot/grub in a ubuntu ext4 partition. The two files have completely different contents.
The uuid=0caa0215-f19c-4cbf-8b27-1ffd0984bef8 is the key to discovering what happened. In another terminal examine the output of command blkid to see if the spinning disk has the above uuid.
What caused the loss of the Grub2 menu in the first place? If the uuid belongs to the spinning disk instead of the ssd, then the new ubuntu install re-wrote the info in the EFI partition. The EFI ubuntu file grub.cfg then causes EFI firmware to access the spinning disk instead of the ssd (slower than ssd, wrong grub menu).
A Shortcut? The details of answer 112 depend on a few wizard skills not owned yet by novices. Is a shortcut possible, like editing the UUID in the display above to the correct UUID? Grub2 uses the EFI vfat partition to boot ubuntu, the target partition for the boot given by the 3 boldface items below. Editing the 3 items can restore the ssd boot in the example. But direct editing can produce a non-booting system, which explains why answer 112 is a tool to be learned, independent of shortcuts that sometimes work. If you wear a Wizard's Hat, then the shortcut idea is another tool.
search.fs_uuid 0caa0215-f19c-4cbf-8b27-1ffd0984bef8 root hd1,gpt12