As etapas a seguir funcionaram para mim em um sistema debian-ubuntu.
* Create a virtualbox guest , with appropriate disk and memory calculation on the target.
* Install the debian OS. Just the OS only with ssh and network configured.
* Keep one or two terminals open on your new virtual box.
* Sync all the files from your source to new virtual guest , like shown from the original server
rsync -vaP --archive --delete --numeric-ids --one-file-system --exclude=/proc --exclude=/sys / Virtual_Guest:/
* Post changes before you reboot.
a> Change your networking information back to virtualbox settings.
b> Change your fstab entries.
c> run "update-grub" , depends on what debian flavor
d> Remove the appropriate udev rules.
Eg:- /etc/udev/rules.d/70-persistent-net.rules
e> check your /etc/hosts.
f> Check anywhere you hardcoded the original name and ip.
* Reboot the box. You should have the clone of the original server. Again make sure to check your application configurations to point to the new name and ip of the virtual box.