Trying to migrate slug from memory stick to external HDD

[John Winters <john@sinodun.org.uk>]

I've got a slug which currently runs Debian Lenny quite happily from a
memory stick.  The stick is partitioned as follows:

/dev/sda1	Swap space
/dev/sda2	/

and that's it.

I want to move the system to using an external HDD - one which I've used
before with the same slug.

I attached the drive and partitioned it in much the same way (although
with a larger / partition).  /dev/sdb1 is swap and /dev/sdb2 is the
intended /.  I did a mkswap on /dev/sdb1 and a mke2fs -j /dev/sdb2.  I
also created a third partition using up the rest of the space on the HDD
which I flagged as being for LVM.

I then mounted /dev/sdb2 as /mnt/target and did:

# cd /
# cp -ax . /mnt/target
# cp /dev/MAKEDEV /mnt/target/dev
# cd /mnt/target/dev
# ./MAKEDEV generic

I then shut down the slug, removed the memory stick and connected the
HDD in its place.

The trouble is the slug then won't boot.  It goes through its fancy
light display and then settles down with just "Ethernet" light pretty
solidly on (it flickers occasionally).

I know I'm going to kick myself when someone points out what I've
forgotten to do, but...

TIA,
John