OVH CentOS 7 server grub rescue prompt

On an OVH Cpanel server running CentOS 7, the server won’t boot. When accessing the server console using IPMI, I found the following error.

I booted the server into rescue mode, checked the disk partitions with the command parted -l

Disk /dev/nvme0n1: 450GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system     Name     Flags
 1      1049kB  537MB   536MB   fat32           primary  boot, esp
 2      537MB   1073MB  536MB   ext4            primary  raid
 3      1073MB  53.5GB  52.4GB  ext4            primary  raid
 4      53.5GB  450GB   396GB   ext4            primary  raid
 5      450GB   450GB   536MB   linux-swap(v1)  primary


Disk /dev/nvme1n1: 450GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system     Name     Flags
 1      1049kB  537MB   536MB   fat32           primary  boot, esp
 2      537MB   1073MB  536MB   ext4            primary  raid
 3      1073MB  53.5GB  52.4GB  ext4            primary  raid
 4      53.5GB  450GB   396GB   ext4            primary  raid
 5      450GB   450GB   536MB   linux-swap(v1)  primary

The server had 2 NVMe disks configured as RAID 1 mirrors. The first partition with fat32 filesystem is used for boot.

To fix the problem, I chrooted to the server file system with the following command (this may be changed based on your server’s partition scheme).

mount /dev/md3 /mnt
mount /dev/md2 /mnt/boot/
mount /dev/md4 /mnt/home
mount --bind /dev /mnt/dev
mount --bind /sys /mnt/sys
mount --bind /proc /mnt/proc
mount --bind /dev/pts /mnt/dev/pts/
chroot /mnt

Reinstalled the kernel with

yum reinstall kernel

Then reinstalled grub loader. This server used UEFI, so used following commands

mkdir /nvme0n1p1
mkdir /nvme1n1p1
mount /dev/nvme0n1p1 /nvme0n1p1
mount /dev/nvme1n1p1 /nvme1n1p1
grub2-install --target=x86_64-efi --efi-directory=/nvme0n1p1 --bootloader-id=GRUB
grub2-install --target=x86_64-efi --efi-directory=/nvme1n1p1 --bootloader-id=GRUB

grub boot loaded is installed on both disks, so server will be able to boot when either one of the disk is selected as boot device.

Back to grub