On 2/14/2022 10:19 AM, Bijan Soleymani wrote:
On 2022-02-14 10:02, rhkra...@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.
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