Brain transplant

David Wagner

In the lab we have a camera system composed of four cameras. The system is controlled by two identical PCs, two cameras connected to each. After a long break of operation, when we wanted to use the system again, the hard drive in one PC decided to quit science and went dead. We replaced the poor fellow with a new drive and I wanted to transfer the system as it is from the healty computer to the new drive of the braindead system . Following the brain transplant procedure in its most realistic, bloody purity.

My idea is to run on healthy:

dd if=/dev/hda | ssh user@braindead sudo dd of=/dev/sda

To this end I boot up braindead (with the new drive in) from a Debian Live CD. While setting up the network (IP address, DNS, etc.), it turns out that the network card needs some non-free firmware which are not on the Installer/Live CD. This is a bit annoying but not the end of the world. After some googling I learn that I need fimrware-linux-nonfree, so I download and put it on a USB stick and install (dpkg -i) it on braindead. Now it has network connection and an SSH server running.

To prepare for the transplant I put healthy in single user mode and mount the file system read-only (as root):

$ init 1
$ mount / -o remount,ro

Now everything is ready for the procedure. I run dd through SSH as described above. It takes some time, but the transfer works fine.

On braindead, still running the Live CD, I mount the new disk and

  • change the host name in /etc/hostname
  • generate new host keys (ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key)

I reboot braindead and voilá, it works! Well almost… I experience some problem with the networking. I quickly figure it out that the network card enumeration (eth0 eth1 swap thingy) is screwed, but it is easy to fix by editing /etc/udev/rules.d/70-persistent-net.rules and removing the lines that refer (by MAC address) to the network card which is in the other machine.