Grab partclone

On both the server you want to image, and the server you want to restore to, boot a live usb that has netcat and partclone. I create
my own using the gentoo LiveUSB install, and copy the tools onto the usb stick.

On target node:

nc -l -p 999 | partclone.ext4 -r -o /dev/sda2

On source node:

partclone.ext4 -c -s /dev/sda2 | nc 999.

It will send the image over the network, and will do so efficiently without wasting bandwidth on sending empty disk sectors, as it's a logical partition dump.