cgsecurity.org

"dd bs=4M if=path/to/linux.iso of=/dev/sdx" is the command that I have now accidentally used on two hard drives. Images that I have used were about 250mb both. Running testdisk on hard drives show partitions even from way back 2013. How would I go on from here? Is there a way to safe any data from them?

Use 'p' to list the files of the selected partition.
You have to switch from D(eleted) to *(bootable), P(rimary) or L(ogical) all partitions you want to keep/recover.