clone a linux system over the network

Hi,

I need to migrate a Linux system from a server to another one.

I cannot reinstall the OS and applications on the new server and then
migrate the data from the old server, since that would require too much
time.

In the past, to migrate a Linux system from a server to a new one with
HD of the same size, I shut down the servers, booted a Linux live CD
(Knoppix) on them and used 'dd' and 'netcat' to clone the system over
the network: that worked fine, but with two cons:

- It is pretty slow, since it will copy over even blank data.

- You cannot resize the partitions: if the new server has a bigger disk,
you cannot enlarge the original partition to use the additional space.

Do you know any better way to clone the system over the network that
will fix the above problems?

I think the commercial application Symantec Ghost can do it, but I am
looking for something free.

It would be great if such tool supported PXE boot too.

On a separate note, do you know how to boot Knoppix via PXE without
using the Knoppix Terminal Server (that requires an additional machine)?
I already have a Linux host running TFTP/DHCP/NFS servers and use it to
perform Red Hat Enterprise Linux installations via PXE.
How do I configure it to perform Knoppix boots via PXE?

Thanks a lot.