build is ready, how to repartition?

Gerard Beekmans gerard at linuxfromscratch.org
Tue Jan 14 15:19:11 PST 2003


On January 14, 2003 04:32 am, Blender wrote:
> I managed to get a working kernel the first time. I added some lines to my
> grub config (got confused by initrd.img, but learned it was necessary only
> on SCSI systems so skipped it) and now my LFS system is up and running.

Just want to counter this misconception. initrd's are INITial RamDisks. They 
can be used for many reasons. One of the functions is to create a virtual 
disk in memory (that's the ramdisk part) and put a bunch of files there. 
Those files can be modules. One of the modules can be a SCSI driver but 
that's not the primary reason. An initrd can be used to load a module into 
your kernel before you mount the actual filesystems. But it could just as 
well contain an IDE module. Or a videocard driver, or network.

A different use of initrd that I use on my bootable cdroms. Cdrom boots and 
loads an initrd image. This image contains a very small Linux system, just a 
few files and a few scripts. It'll boot these scripts and detect where the 
cdrom is located physically. It could be /dev/hdb or /dev/hdd or something, 
so you couldn't add "root=/dev/hdx" and boot the CD directly because it won't 
work on every computer. Or if you have computers with a mixed IDE/SCSI 
environment. Can't hard-code the cdrom device location at all then. Instead a 
ramdisk is used as a virtual disk and booted from that, it then finds the 
cdrom device, mounts it and chroots into it. Then after chroot init on the 
cdrom is started and the boot process continues.

Anyways comes down to: a common application of initrd's is to provide a 
virtual disk, copy some files to it, boot from it and perform hardware 
detection, maybe load some modules, in order to continue booting. Could be 
SCSI. Could be a CDROM. IDE too.

-- 
Gerard Beekmans
www.linuxfromscratch.org

-*- If Linux doesn't have the solution, you have the wrong problem -*-
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