Ubuntu copy & restore disk image over wan

I think rsync is able to do this. But you surely need to activate the boot loader from the  cd

Nb: take care of the dynamic folders like /dev or /proc for exampke

How could I do this with rsync and how to activate the boot loader from cd?. Please post commands!.

That's an hard task.

Another way could be to use the pxe boot

Check https://wiki.koeln.ccc.de/index.php/Ubuntu_PXE_Install

Thanks. Can't I do this with dd

Instead of dd with netcat I'm using dd with ssh
The command I used to copy disk image over wan is below:
On a Running VM:
apt-get install pv
dd if=/dev/sda bs=64k conv=noerror,sync | pv | gzip -c -9 | ssh root@remote_server dd of=sdX.img.gz

On a New VM with no os I booted from ubuntu live cd I used the following commands:
sudo vim /etc/apt/sources.list file -------un commented the deb's
sudo apt-get update
sudo apt-get install pv

I used the following cmd to restore the image from the remote system, but it's not the right way to use as it's blurring up and down. I need the right syntax here:
ssh root@remote-ip dd if=sda.img.gz | gunzip -c -9 | pv | dd if=/dev/sda bs=64k conv=noerror,sync
but some how restored it

When I tried to install the grub, the device is not mounting. After I restarted, the system stalled at the grub load. How could I make it boot?. FYI, I'm trying to install on a new machine.

There was no mentioning of the fact that this was about VMs.

Why didn't you simply copy over the virtual disk image (.vdi) or export/import the machine from the VBox interface?

With a VM it's easy :)

No. I should do this on cloud servers. But before that I should ensure that what I'm going to do works fine with no harm to the system and I'll check this on vm's

I'll try this.