I've just recovered a broken image that crashed upon startup. There was some problem with a SerialPort that stayed open and tried to write/read into a physical port that didn't exist no more, or something of the sort.

So here's the magic line:

$ bin/myVm shared/MyImage.image eval "SmalltalkImage backupTo: 'recover'"

This makes a copy of the image into a new image called "recover.image", but as the documentation states:

--
Bernat Romagosa.