how to crack Linux password

 Crack Linux password:                                        

Using  unshadow and john commands

Install John the Ripper Password Cracking Tool

John the ripper is not installed by default. If you are using Debian / Ubuntu Linux, enter:

rahul@rahul-desktop:~$ sudo apt-get install john
Note: RHEL, CentOS, Fedora, Redhat Linux user can grab john the ripper here. Once downloaded use rpm command:

rahul@rahul-desktop:~# rpm -ivh john*

How do I use John the ripper to  crack passwords?

First use the unshadow command to combines the /etc/passwdand /etc/shadowfiles so John can use them. You might need this since if you only used your shadow file,  On a normal system you’ll need to run unshadow as root to be able to read the shadow file. So login as root or use sudo / su command under

In Debian / Ubuntu Linux 

$ sudo /usr/sbin/unshadow /etc/passwd /etc/shadow > /tmp/crackpasswd.db

In RHEL / CentOS / Fedora

# /usr/bin/unshadow /etc/passwd /etc/shadow > /tmp/crackpasswd.db

WARNING! Do at your own risk
To use John, you just need to supply it a password file created using unshadow command along with desired options.

To Crack Passwd
rahul@rahul-desktop:~$sudo john /tmp/crackpasswd.db
Output:

Created directory: /root/.john
Loaded 5 password hashes with 5 different salts (generic crypt(3) [?/32])
redhat            (rahul)
654321            (test)

This procedure will take its own time. To see the cracked passwords, enter:


rahul@rahul-desktop:~$john -show /tmp/crackpasswd.db

test:654321:1002:1002:test,,,:/home/test:/bin/bash
rahul:redhat:1003:1003::/home/rahul:/bin/bash
2 passwords cracked, 4 left

Above output clearly indicates - user test has 654321 and rahul has redhat password.

Enjoy................