Re: Miniroot

On Tue, Jan 03, 2006 at 22:10:20 +0100, Christer O. Andersson wrote:

> On Tue, Jan 03, 2006 at 06:35:58PM +0300, Valeriy E. Ushakov wrote:
> 
> > Right, you can still used embedded miniroot.  There's a kernel option
> > MEMORY_DISK_IS_ROOT that tells kernel to ignore the root fs option and
> > to always use the embedded miniroot.
> 
> > What are the MEMORY_DISK_* kernel options that you use?
> 
> options         MEMORY_DISK_HOOKS
> options         MEMORY_DISK_IS_ROOT     # force root on memory disk
> options         MEMORY_DISK_SERVER=0    # no userspace memory disk support
> #options        MEMORY_DISK_IMAGE
> #options        MEMORY_DISK_DYNAMIC     # fs image don't exist in data section.
> options         MEMORY_DISK_ROOT_SIZE=2048      # size of memory disk, in blocks
> 
> I think I had MEMORY_DISK_DYNAMIC active and MEMORY_DISK_ROOT_SIZE=2048
> commented while trying a detached miniroot.
> 
> So, next time I'll try commenting MEMORY_DISK_IS_ROOT.

From a cursory look at md_root.c and hpcsh machdep.c and autoconf.c I
think that enabling MEMORY_DISK_DYNAMIC and disabling
MEMORY_DISK_IS_ROOT should result in a kernel that would boot from the
detached miniroot if one is supplied and only then, but I haven't
tried it.

The idea is that hpcboot copies the miniroot image, and tells the
kernel it has one.  The kernel then should pick it up with
md_root_setconf in machdep.c.


> But this is the same as RAMDISK use, at least -current, except that
> it uses MEMORY_DISK_ROOT_SIZE=8192. Doesn't that indicate that the
> miniroot is embedded? I also seem to recall that somebody on the
> list mentioned booting an install kernel without a detached miniroot.

Doh!  I always looked at this from the hpcboot side, so I didn't
looked into md_root.c that thoroughly.  Shame on me.

Oh, and autoconf.h doesn't even bother to include opt_md.h (to pick up
MEMORY_DISK_IS_ROOT)!  This needs some fixing...

SY, Uwe
-- 
[email protected]                         |       Zu Grunde kommen
http://snark.ptc.spbu.ru/~uwe/          |       Ist zu Grunde gehen