Editing Repair GRUB Installation (section)

== Fixing It ==
The process summarized below is from this web page:

 https://phoenixnap.com/kb/grub-rescue

That page describes the process for restoring a GRUB configuration from the GRUB command line if you don't have a live ISO image available; it does require a significant level of knowledge about the system being restored ... which may not be available.

Also on that page is the rather simple process using his boot-repair tool (free) to rescue a ubuntu system.  There is a lot of context on that page, but the gist is here.  Once you get the live image booted, open a terminal and issue these commands:

 sudo add-apt-repository ppa:yannubuntu/boot-repair
 sudo apt update
 sudo apt install boot-repair -y
 sudo boot-repair

The application will show a status dialog with a bunch of activities, then give you a big dialog with an option to implement the recommended changes ... if you have anything other than a single-disk simple configuration, click on the 'Advanced Options' link to look at what it wants to do.  Make sure the location of your deployment is correct; it assumes the first disk with a reasonably valid configuration is what you want (not always the case).  Make any changes and then hit the 'Apply' button.  Cross your fingers ... and you will hopefully get the success dialog.  Then you reboot back into your normal configuration.