Using Crack is very easy. Crack is a self-compiling program. One of Cracks strong points are it’s large number of rule sets which are used to create permutated words. Everytime you run Crack it builds a custom wordlist that incorporates username and information in comments field from password file. This is helpfull because it is very common for people to have their full name in GECOS field and use their password as a combination of those.
It is important to note that Crack doesn’t crack shadow password by default a little of work is needed to set it up.
The screen shot doesn’t show an actualy crack:
You can use the “Reporter” program that comes with Crack to see the result and debug/error messages:
Crack in 1 line of perl: http://cypherspace.org/adam/rsa/crack.html