> Unix solved [the problem of rainbow tables] in the nineteen seventies.

> incremental crackers [were used to] harvest thousands of passwords [and] forced Unix systems in the 1990's to adopt "shadowed" password files.

As someone who is interested in security but has not spent significant time studying it, I'd be interested to hear more about this. How did Unix solve the rainbow table issue? What is an incremental cracker and how does it relate to shadowed password files? (I'm familiar with the latter but not the former, and a Google search generates more noise than signal without more keywords to go on.)