John the Ripper, Password Cracker tool

John the Ripper is free and Open Source software,its the most famous and one of the best password cracker in the real time world.
its most widely used tool to crack the passwords in the unix  environment.Its distributed primarily in source code form.

If you would rather use a commercial product tailored for your specific operating systemJohn the Ripper is a program that decyrpts Unix passwords using DES (Data Encryption Standard). 

Step 1: Download JTR.

Step 2: Extract JTR. using the command

##--tar -xzf john-1.6.tar.gz

The filename must include the .txt extension. This is the regular crack that file with .txt extension will be used as a dictionary 

user name to use the john the ripper

##--User:gyuJo098KkLy9

Save the file as crackme.txt (just an example) and go to the prompt and type 'john crackme.txt'if you know the streanth of the password  the you can use Single crack mode. This is only recommended for weak passwords as it includes only a few rules and a small wordlist

##--john -single crackme.txt

Wordfile: Uses a wordlist (basically a dictionary attack). What this does is tries every word in the list until it finds a match or you reach the end of the list. This is quicker than the default (bruteforce) attack, but I don't recommend this because it doesn't always find a match. More notes on wordlists below.

##--john -wordfile:password.lst crackme.txt

Restore: Ok, let's say that you need to stop the crack in the middle. Press crtl+break.A file will be created in the JTR directory named 'restore' (no quotes doofus, and yes, no file extention). You can start the crack back up from that restore point

##--john -restore:restore

Session: Use this if you know that you will have to stop JTR in the middle of a crack. It allows you to create a new file that holds the data of your session. You can then restore your session later.

##--john -session:[save to filename] crackme.txt

Shows how fast JTR will work on your computer

##- john -test