On 2022-02-14 10:02, rhkramer@gmail.com wrote:
I think I did mis-remember this, and the behavior I described is more like the behavior of the Debian installer (i.e., it boots an image (with a Linux kernel) into RAM to use temporarily for the installation. I just wanted to try to correct this for posterity. If anyone can confirm this (both my mistake about grub and my (new) recollection about the Debian installer, those would be good things.:-) Sorry for the noise!
Not sure about the Debian installer (except that it does boot and run Linux, but not sure it ever switches to another kernel midway), but the Grub bootloader is kind of a mini-OS, in that it can read files from filesystems (rather than some other bootloaders that read from specific sectors/blocks of a disk).
Which is to say if you boot to grub and you are in the grub menu and see there is no entry for the particular kernel (or OS) you want, you can edit the boot parameters for any menu entry you see and boot the missing kernel (or OS) from then and there. (with other bootloaders you'd have to boot to the OS or boot from a live CD to modify the boot loader parameters).
Bijan