it is possible to clone a running GnuLinux system onto another machine on the network, using netcat, dd and a simple pipe. this assumes the machine target has been booted from a rescue disk, or hdX other than the one to clone onto.
NOTE: if the disks are not identical (or possibly just not the same size), fsck and grub-install might be needed to clean up the target drive.
(based on notes found at > http://www.rajeevnet.com/hacks_hints/os_clone/os_cloning.html