I have a server on OVH with Cpanel which has 2 x 2TB partitions and its lsblk command output looks like this. http://prntscr.com/nz4xd2 A few days back I ran some upgrades and after rebooting my server didn't boot properly and halted during the boot process and displayed a prompt like this:


I did some research and I was able to boot the server by running following commands at the grub prompt:

set prefix=(hd0,gpt2)/boot/grub2
set root=(hd0,gpt2)
linux (hd0,gpt2)/boot/vmlinuz-4...…… root=/dev/md2 ro

Then I searched for a permanent solution for this which took me to some URLs like this https://www.linux.com/LEARN/HOW-RESCUE-NON-BOOTING-GRUB-2-LINUX which suggest to reinstall grub using commands:

# update-grub
# grub2-install /dev/sda

I am on Centos which doesn't have the command update-grub but I was able to run other commands:

[root@server2 ~]# grub2-install /dev/sdb
Installing for i386-pc platform.
Installation finished. No error reported.

after this when rebooting I got the same grub prompt again. I am not sure what is wrong here. Can anyone please suggest something?


CentOS is a little different from what you saw in the repair instructions. See https://wiki.centos.org/HowTos/Grub2 which is specifically for CentOS 7.

Also see https://superuser.com/questions/781300/searching-for-grub-configuration-file-in-centos-7#781352.

The grub configuration is done with grub2-mkconfig, based on the files in /etc/default/grub and /etc/grub.d

Note that when booting from a RAID-1 (which you are doing), you need to install grub on both /dev/sda and /dev/sdb. That should have already been done by the install, and you obviously have it since you got to the grub prompt in the first place.

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