Upgrading an xserve from Tiger to Leopard

[John Summerfield]

I'm new here. My recent background is Linux mostly (RHL, Fedora, 
RHEL-clone and Debian), but I have an xserve in my care.

The Boss is tired of the Tiger in the Tank and he wants  a Leopard in 
there instead.

We have one xserve, so popping a disk into another for surgery isn't an 
option. Cloning to an external drive is possible, but cloning to an 
internal drive is probably faster.

The broad plan is to clone the existing system volume to a new disk, 
then upgrade to Leopard using the new disk.

The existing system drive is 120 Gbytes, the new is 300.

The xserve has four disk bays, all occupied but replacing one disk 
temporarily doesn't pain us too much.

We've purchased a 300 Gbyte disk, removed an existing disk from the 
hotplug carrier, installed the new disk and plugged it in. OS X demanded 
to know what to do with it, so I said "Initialise with one partition." 
It seems its lack of Apple firmware doesn't seem to matter.

I've discovered booting the xserve in target mode isn't particularly 
helpful, I only see one disk. Sure, that's what the docs say, but the 
docs aren't always right.

On Linux, I would boot a CD (knoppix is my favourite) and use dd to 
clone the disk (it does work, with some caveats, when the target disk is 
equal in size (best) or larger).

Carefully, of course.

A good alternative on Linux is to boot in single-user mode; the 
filesystems are ro so one has to try hard to change things.

First question: is booting OS X to single-user mode a sensible way to 
clone the disk?

Carbon Copy Cloner is all well and good, but AFAIK it has a GUI 
interface, I've not explored running it using a CLI. Does it run from 
the commandline with no GUI, or should I use (for example) dd.

Once I have the system cloned (so I can revert quickly and easily), how 
should I go about the upgrade?

Does anyone have any handy hints?

I've seen reports of problems with openLdap; is that likely to be a problem?

What should I read?

-- 
John Summerfield