john software package provides active password cracking tool, you can install in your Ubuntu 12.04 LTS (Precise Pangolin) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install john
john is installed in your system.
Make ensure the john package were installed using the commands given below,
$ sudo dpkg-query -l | grep john *
You will get with john package name, version, architecture and description in a table
| Distro | Ubuntu 12 04 lts precise pangolin |
| Section | Administration Utilities |
| Package | john |
| Version | 1.7.8-1 |
| Description | active password cracking tool |
| Sub Section | Admin |