Re: grub: eval vars for linux command / write config agnostic to other disks

[Pascal Hambourg]

Le 29/03/2020 à 07:46, address@hidden a écrit :
>     One more question. Initrd is what actually reads and executes grub 
> and friends?

I don't know what you mean by "friends" but no, the initrd does not read 
and execute GRUB.

Boot sequence is :
- platform firmware (BIOS, UEFI) loads and run GRUB
- GRUB loads kernel image (vmlinuz) and initramfs (initrd) into memory
- GRUB boots kernel
- kernel mounts initramfs as initial root filesystem and runs /init
- /init mounts the actual root filesystem (and /usr if needed) and runs 
/sbin/init

The initramfs is also in charge of making the root device appear in some 
situations such as LVM, software RAID or block level encryption. The 
kernel cannot do it by itself because it requires userspace tools and 
configuration.

Note that the initramfs may be embedded into the kernel image instead of 
being a separate file.

>     In the system I am running, antiX, initrd is much bigger than 
> vmlinuz.

This is a common situation. General purpose distributions provide a 
kernel image which includes only essential drivers and build a generic 
initramfs which contains all drivers (modules) for storage devices and 
filesystems, which makes it quite big. This way only modules required 
for the current hardware are loaded into memory. The initramfs generator 
tool may have a configuration option which allows to build a compact 
initramfs which contains only required modules for the hardware.

> On the other hand, Knoppix 7.2 has a larger kernel and a 
> smaller minirt.gz file. I am guessing Knoppix adds another boot level to 
> getting the final linux system up and running?

I don't know about Knoppix. Maybe the kernel image contains more drivers.