On 2/14/2022 10:19 AM, Bijan Soleymani wrote:
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 thebehavior of the Debian installer (i.e., it boots an image (with a Linux kernel) into RAM to use temporarily for the installation.
AFAIK a ramdisk image is not only loaded when using the Debian installer, it is also loaded when booting a full installation on a disk. For example, the initrd.img-5.10.0-11-amd64 file that is created when installing a kernel and installed under /boot on bullseye systems contains the compressed contents of a filesystem that is loaded into RAM upon initial boot, and AFAIK that filesystem does not contain a kernel but it does contain kernel modules that are binary-compatible with the running kernel to support the proper initialization of various hardware. The main job of that initrd environment is to find and mount the installed root filesystem that is usually on an SSD these days.
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!
IMHO it's not noise if you are trying to clarify or correct something.
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).
Also, grub has its own shell, and sometimes if something is not configured right, grub may drop into its shell where a knowledgeable user can type in commands such as the ls command to list files on the disks attached to the system and the configfile command which can be used to load the grub configuration if for some reason grub was unable to find the grub.cfg file that tells grub how to boot the system. This is a useful feature for those who know how to use it, and it has saved me from having to reinstall on more that one occasion.
Chuck