NIC not found after installing image
 

I have two identical computers. Installed Debian on one of them. Made an image and put it on the other machine. Now it cannot find the network controller.

Does this have anything to do with the MAC address? What do I have to change?

Who says it can't?Check the output of lspci to determine whether the NIC is recognized or not.

It seems more likely to me that you are running into issues because your image has stored the hardware address of the NIC in your first computer, which obviously will be different from the address in the second one. If that is correct, then you'll need to edit your network entries in /etc/udev.d.