I am asking if this is official Canonical image or is it prepared by 3 party person?
For the test I want to do I need specifically release 12.04.
To build up image from ISO. Following link shows there is a way to do that. Not really straight from ISO but certainly it is possible to prepare “safe” image (without worry about 3 party person hidden malware/bacdors/etc) https://groups.google.com/forum/#!topic/docker-user/HlPU1XIVw40