drush software package provides command line shell and Unix scripting interface for Drupal, you can install in your Debian 7 (Wheezy) 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 | Debian 7 wheezy |
| Section | PHP |
| Package | drush |
| Version | 5.4-1 |
| Description | command line shell and Unix scripting interface for Drupal |
| Sub Section | PHP |