How to install Drush in CentOS Linux for Drupal Development?
This command has been successfully tested on Debian, Ubuntu, CentOS and should work for most *NIX systems.
sudo wget --quiet -O - http://ftp.drupal.org/files/projects/drush-7.x-4.5.tar.gz | sudo tar -zxf - -C /usr/local/share
sudo ln -s /usr/local/share/drush/drush /usr/local/bin/drush
sudo mkdir /usr/local/share/
sudo mkdir /usr/local/bin/