[syslinux] 2 disks boot

H. Peter Anvin hpa at zytor.com
Thu Dec 18 03:50:50 PST 2003


ZIGLIO Frediano wrote:
> 
> You are right, ':' it's better that '@'..
> Before start coding it's however better to plan changes. Thinking at
> future perhaps most easy and simple syntax should be
> 
> "n-m:file.ext"
> or 
> "n:file.ext"
> 
> So we have a range of disks... for future possible extensions. Also it
> would be glad if images get numbered as perl do, ie if we have
> "initrd=2-4:initrd.img" will have:
> 
> initrd.img (disk #2)
> initrd.imf (disk #3)
> initrd.imh (disk #4)
> 

No, I don't think that's a particularly good idea.  I think stick to the 
filename given.

> The problem is perhaps image sizes (difficult to compute from first
> disk)... I didn't watch so deeply ldlinux code... However the first
> change I want to write is support "n:initrd_name.ext" syntax where n is a digit

It would be hard to retrofit a change into syslinux such that the image 
size is not known a priori.  This is (part of) the reason for the need 
for "tsize" support in pxelinux.

It would certainly not be impossible, but it would require significant 
changes in the handling of initrd especially.

> - do not support multi-disk and kernel not on the first disk
> - support for different disks size/format options reloading first sector
> (optional??) This should be sufficient even for 2.6 kernel...

Support for different clustersizes across the disks would require 
changing the current cluster-oriented syslinux into a sector-oriented 
one.  This in itself is not a bad thing; the fact that we currently 
can't handle 32K clusters is kind of lame, plus it would be a good step 
towards supporting FAT32.

In syslinux this would entail making SI instead of a cluster number a 
pointer to a structure containing, at least, disk number/cluster 
number/sector index in cluster.  It already is a pointer in pxelinux and 
isolinux, so this is not a radical change.

The biggest constraint (other than development time) is that I'm 
extremely leery of letting syslinux grow too much; after all, it still 
needs to be able to fit on a boot floppy.

	-hpa




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