[plug] initrd confusion!

[Tony Breeds]

On Fri, Apr 16, 2004 at 11:28:12AM +0800, Denis Brown wrote:
> Dear PLUG list members,
> 
> I have a situation where I need to have a modularised kernel, specifically 
> with the RAID device as a module.   The reason for this, is to allow the 
> low level drive monitoring software to work.   I have been reading up on 
> initrd but find that I am confused, as follows...
> 
> 0. There are no IDE or ATA devices in this box, only SCSI in hardware RAID.
> 1. The RAID driver will be compiled into the kernel as a module.   So the 
> kernel will not be able to see any file systems until the module is loaded.
> 2. The module will be inaccessible to the kernel because, well, it cannot 
> be loaded!
> 3. Initrd would seem to offer help.   Initrd basically, if I understand it 
> correctly, will load a kernel into ramdisk, load the required RAID driver 
> module and then switch over to the "real" file system.
> 
> BUT... if initrd can see the file system in order to load the RAID driver 
> module, how is initrd's "kernel" different from the normal kernel?   I will 
> be compiling the kernel with both initrd+ramdisk and modularised RAID 
> driver support.   It seems to me that the kernel will somehow be 
> schizophrenic - sees the RAID via a module but at boot time can see the 
> RAID anyway.   Huh???

The short answer is: mkinitrd copies the modules themselves (for the
supplied kernel), along with a shell (/bin/ash.static) and
insmod.static).  It then creates a linuxrc file which loads the modules.
mounts root and passes control over to init.

-- 
Yours Tony

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