[Cialug] SDHC support

[Zachary Kotlarek]

On Aug 7, 2008, at 9:41 AM, Tim Champion wrote:

> I'm still trying to figure out how to boot Ubuntu from it on my  
> internal card reader on my Dell D420.  The BIOS doesn't see it, so  
> from what I've gathered so far, I have to load up a linux kernel  
> from the hard drive first, and then transfer to the SD card.  I can  
> get it to boot using the included USB card reader, but I think  
> booting from the card slot is beyond my skilz. :)

I don't know if the D420 can be manipulated into booting directly from  
your card slot, but even if you need to read the kernel from the hard  
drive, it's not a big problem.

You just need to put GRUB and the kernel on your hard drive, or some  
other device the BIOS can see. Once you can load a kernel into memory  
this problem goes away -- the BIOS will load GRUB, GRUB will use the  
BIOS disk access to load the kernel, and the kernel can read your SDHC  
media without a problem.

When booting from the kernel/GRUB on another disk, pass the kernel  
root=/dev/<sdhc media> to the kernel, just as you would if you had  
everything installed on the SDHC media. The kernel, once loaded into  
memory, can read your SDHC slot and use it for the root drive, and  
will never touch the BIOS-accessible drive containing the kernel again  
(unless you tell it to).

Just be sure that the kernel has all the necessary bits compiled in  
monolithically, as you won't be able to load modules until after the  
disk is mounted, or that your initramfs has all the necessary modules,  
depending on what kind of boot mechanism you're using.

As others have noted you can all just put /boot on your hard disk and  
everything else on the SDHC media; that's essentially the same process  
I described, but the media containing the kernel sticks around rather  
than being ignored after boot.

	Zach

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 1682 bytes
Desc: not available
Url : http://cialug.org/pipermail/cialug/attachments/20080807/63a6ce67/smime.bin