Best way to backup and restore multiboot?

[Tripredacus]

I have redone my notebook to have a dual boot with Windows 10 and Linux, and now before I attempt to update Win10, I want to make sure I can restore the multiboot ability should Windows Update decide to rewrite things. Windows 10 is an LTSB edition, so it should never get a feature update. Currently the system boots to the Linux boot menu, from there I can choose the OS and I'd rather like to keep it that way. The disk type is MBR. There are 3 partitions: 1: Boot, 2: OS (first two windows) and 3: Linux. It is an SSD if that matters.

What are some ways I can easily back up and restore the boot information/menu should Windows decide to take back control of that? Preferrably something that can be run in a WinPE.

[jaclaz]

There is no such thing as "Linux boot menu".

The boot menu is what the bootmanager loads, very likely you have GRUB2 as bootmanager/bootloader.

And of course you are not dual booting Linux and Windows 10, you decide if you want to remain generically vague (i.e. Linux and Windows) or if you want to detail which Linux distro AND version it is besides Windows 10 LTSB.

More generically, if you actually have GRUB2 as bootmanager, you should be actually preoccupied of the Linux updates/upgrades, as most times they do run an "update-grub" command that actually rebuilds (or rather attempts to rebuild) the GRUB2 configuration file (which is usually grub.cfg).

If you prefer,  the grub.cfg menu (which is very likely what you see when you boot) in GRUB2 is not "static" and is generated (at install time and re-generated with the grub-update command) starting from a set of "base" files.

Depending on the EXACT way the GRUB2 has been installed and on the contents of these files, and on the EXACT distro/versions of the Linux distro you are using, this (stupid) auto-magic regeneration may work or it may not.

Most of the times it just works, of course, but when it doesn't you'd better have a plan B.

Having a backup of the "current" grub.cfg is of course obligatory, but you will need to get familiar with the (complex) mechanism of grub.cfg (stupid) auto-generation and also IMHO get familiar with a few needed GRUB2 commands, as if for whatever reasons the grub.cfg is not found or it has been automagically updated and the update didn't work you will find yourself incapable of booting and stuck at a grub-rescue> prompt.

Here is an exceptionally good tutorial:

https://www.dedoimedo.com/computers/grub-2.html

You want to make sure that either there is a directory corresponding to your Window install or that the provisions for it are inside the 40_custom one, but you should learn also how to boot both the Windows and the Linux from a plain grub-rescue> prompt via a sequence of commands, and - adviced - have handy a copy of the SuperGrubDisk:

https://www.supergrubdisk.org/

https://www.supergrubdisk.org/super-grub2-disk/

just in case.

jaclaz