Imaging a live system disk, what a stupid idea, right? It actually is.. but hey, I was just looking for an alternative solution for an off-site backup of my servers: DD reading my disk bit by bit, while spitting out data through the pipeline to gzip which spits out data to OpenSSL through another pipeline, and OpenSSL finally pipes all the final data to netcat.
That's a handful of words right there! It's relatively simple, actually. This is the command I ran on my server:
sudo dd if=/dev/vda conv=sync,noerror status=progress | openssl aes-192-cbc -salt -e | gzip -9 -c | nc -l 10.11.12.1 56002
Netcat starts a TCP listener on the IP address 10.11.12.1 and port number 56002, and waits for an incoming connection. You will be prompted to enter a password to put on your data after you run this long command, your data gets protected with AES-192 encryption which is more than sufficient. Make sure you remember this password, because it is the ONLY key to your data!
I used my local computer which runs Linux to stream the disk image to. The local machine connects to the remote server and the transfer will start as soon when a TCP connection has been initialised with the server. You can even follow the throughput like on the screenshot above! Pretty cool, huh?
The command to run on your client machine is:
nc 10.11.12.1 56002 | gunzip -c | openssl aes-192-cbc -salt -d > disk.img
It took me around 15-20 minutes to copy a live 20GB VM over to my local computer. This server has 1 core and 512MB RAM so I'd say that the results are pretty acceptable.
And the good thing is that the Linux disk was actually bootable! Since the output is a raw disk image, I had to convert it over to a VMware .vmdk file and that file worked. I'm pretty amazed!
Awesome, now let's hope that there's an equivalent alternative for Windows available 😜