I use Debian 8.

I have a nice backup system using rsync per this backup post..
Then my hard disk self-destructed.
The problem is the above post refers only to a cleartext installation, not encrypted lvm.
So IIRC I created a NEW encrypted lvm installation on a NEW disk, copied in the old grub.cfg file, and changed IDs....using a parallel installation.

1. I changed the uuid of the /boot partition (in grub.cfg)
2. I changed the uuid of the encrypted lvm partition
3. ...similar changes to the /etc/fstab and /etc/cryptab (using losetup...I forget)
4. I merged the old .mod files into the new /grub/...
5. And I discovered I needed to change the LVM id of 2. above (how do I get this conveniently?)

At this point it actually worked...after a fashion. It bitched and moaned about some unknown disk not being present...which I could never find. It did this for 1.5 minutes. Then it came up.
Then I did another backup.

THEN I DID A SYSTEM UPDATE.

The grub update trashed everything. System is now completely and unbootably broken.

HHHAAAAAALLLPPP!!!!!
Ideally I'd love to create my own grub.cfg files. I'm learning never to trust grub updates, especially on encrypted lvm installs. Can someone recommend a great webpage for manually creating one's own grub.cfg? ...please?

Linux From Scratch uses grub but it doesn't have any grub scripts. You are expected to make your own grub.cfg and there is a section in the book on how to do it. How that would work with encrypted disks, I don't know. The example given is for a simple set-up.

I answered my own questions and solved my own problem(s) in this thread. I'll post my solution(s) soon.
The short answer(s) is that you ALSO need to delete then recreate the initramfs along with grub and everything else.
If you want my full solution sooner rather than later, just ask.
Best URLs to read:

1. theory: https://en.wikipedia.org/wiki/Initrd
2. theory: https://en.wikipedia.org/wiki/initramfs
3. theory: https://en.wikipedia.org/wiki/Linux_startup_process
4. theory/practice: https://www.gnu.org/software/grub/ma...index.html#Top
5. theory/practice: https://wiki.archlinux.org/index.php/GRUB
6. practice(BEST): https://ubuntuforums.org/showthread.php?t=2266650
   -- this almost better than all the rest put together...almost
   -- also need to bind mount /sys/ in above
7. the man page on update-initramfs (use the -d first, THEN -c)

The above technique is outstanding for doing a total system recovery from rsync backup of a complete encrypted LVM system,. This is after a total encrypted/lvm disk crash.

I suspect I will bash script the whole process...just to make life simpler for next time. reference my previous backup thread here.