Got this from DistroWatch. Seems to be an easy way to at least get into the system:
Corrupted boot loader
One of my least favourite situations to try to recover from is rescuing a system where the boot loader is no longer working. Usually this can be fixed by booting a live disc, creating a chroot environment and re-installing the boot loader. However, there are several steps involved in this kind of rescue and sometimes our priority is to just get our main operating system back on-line quickly. For these situations there is Super Grub2 Disk. Super Grub2 Disk is a live CD which can be used to boot operating systems, even when the GRUB boot loader has been corrupted or overwritten. Super Grub2 Disk is not a full operating system, it just gives us the tools to boot our existing, on-disk operating system so we can start making repairs. This may be easier or faster than trying to repair the operating system from a separate, live disc environment.
I wonder if there is an easy way to make a Super Grub2 disk on a usb stick? I was looking this up and it is unclear whether or not a program like unetbootin or etcher would work. Anyone tried this?
Yes, I believe I have it on a Yumi multiboot usb flash drive. I also have another mbr repair program, on the same flash drive.
I have used them to recover from a non booting notebook.
Bill
Thanks for sharing, Harry!