drush software package provides command line shell and Unix scripting interface for Drupal, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install drush
drush is installed in your system.
Make ensure the drush package were installed using the commands given below,
$ sudo dpkg-query -l | grep drush *
You will get with drush package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | PHP |
| Package | drush |
| Version | 5.10.0-2 |
| Description | command line shell and Unix scripting interface for Drupal |
| Sub Section | PHP |