Appliance boots into GRUB Rescue screen

Summary

Guide to how to recover from a boot issue

Resolution

1. We need to boot from ISO to attempt to recover the root file system: Which Image Media Does My Unitrends Appliance Use? – Kaseya
   1. Download this ISO & burn it to a USB drive

   2.  Boot from the USB into rescue mode (Select “Troubleshooting” option from the menu)
      
      

2. After the installer loads, Select option 1 to Continue
   
   
3. To access chroot environment:

   chroot /mnt/sysimage

4. Identify the boot partition:

   lsblk

   In this case, it is sda and sdb:
    
   
   

5. Install grub:

   grub2-install /dev/sda
   grub2-install /dev/sdb

6. Regenerate GRUB configuration

   grub2-mkconfig -o /boot/grub2/grub.cfg

7. Run 'exit' two times to exit from the chroot and rescue shell.
   
   
8. From there, remove the rescue disk and reboot the appliance and it should boot normally.
   
   
9. SSH into the appliance and do a file system check and a disk health check.

Causes

An unclean shutdown might have caused issues with the kernel or system configuration files, leading to a boot failure. 

Third Party Article

How to fix Grub Rescue in CentOS and RHEL 7 (linuxsysadmins.com)