Host enters grub mode after a power loss and restart

Cause

An unexpected power loss caused the /boot/grub2/grub.cfg file to be lost. The system cannot boot and enters grub> mode.

Solution

1. Resolve the issue from the grub page by following these steps:

2. In grub mode, run ls to list partitions. Use ls (hd0,gpt1)/grub2 or ls (hd0,gpt2)/grub2 to find the partition containing the grub2 directory (the boot partition). The correct partition returns device.map i386-pc/ locale/ fonts/ grubenv.

   grub> ls (hd0,gpt1)/grub2

3. Set the system partition:

   grub> set root=(hd0,gpt1)

4. Mount the root device (set the boot partition as the startup partition; determine the system location based on a working host):

   grub> linuxefi /vmlinuz-3.10.0-957.27.6.da38eal.el7.x86_64 root=/dev/sde3  //`/dev/sde3` is the original `/` partition mount point; confirm this from another working physical node

5. Specify the initialization image:

   grub> initrdefi /initramfs-3.10.0-957.27.6.da38eal.el7.x86_64.img

6. Boot the system:

   grub> boot

7. After the system boots, repair the EFI partition with the following steps:

   # Generate the grub.cfg file
   [root@localhost ~]# grub2-mkconfig -o /root/grub.cfg
   # Unmount the `efi` partition to remount with updated permissions
   [root@localhost ~]# umount /boot/efi
   # Remount the `efi` partition with read-write permissions
   [root@localhost ~]# mount /dev/sde1 /boot/efi
   # Replace the damaged grub.cfg with the newly generated one
   [root@localhost ~]# mv /root/grub.cfg /boot/efi/EFI/helix/grub.cfg