I'm trying to save my newish installation of Debian 10 Xfce on an old 64-bit AMD Toshiba Satellite L505 laptop. The recently damaged boot routine drops to 'grub rescue >'. So far, the suggested remedies I can find for working from 'grub rescue >' have not worked out; however, I'm given to understand that alternative strategies might be more appropriate. To wit, I have both a live USB stick and a persistent installation of Debain 10 Xfce on a USB stick that (except for a great deal of data and installed software) is virtually identical to the damaged installation. I made this for occassional use on another laptop of similar vintage. It was created and runs fine on the computer with the boot problem.
From the desktop of the persistent USB, I can easily see and manipulate my HDD files. I can also see and contrast side-by-side the nearly identical files of the working system with the damaged system. (Not that it yet helps much.)
My take from what I've read is that, theoretically, it ought to be pretty simple to get in there and 'chroot' into the broken installation and update or reinstall grub. The problem is that I don't have the experience to understand exactly what I'm doing or properly interpret the generic instructions I've found, so I keep falling down rabbit holes.
From the sort of error messages I've been getting, it seems that in using 'chroot' I'm having trouble understanding how to exactly acertain where I am. The prompt leads me to suspect I'm still actually working in the system on the USB stick. Beyond that, I apparently don't know how I should properly mount the partition (or partitions) I'm trying to be root in.
How lvm and mbr and efi partitions do or do not interact with all this confuses me too. The installation is lvm on a single partition, I believe. Any suggestions? Tom