Install Drush 7 With Composer

Drupal 8 requires Drush >= 7 to work properly. If you try to use Drush 6 with Drupal 8, you'll get errors like this

PHP Fatal Error: Class 'Drupal' not found in .../core/includes/bootstrap.inc on line 178

You can install Drush using Composer. The following example assumes you are ssh'd into a Vagrant box and Composer is installed.

Install Drush with Composer

sudo composer global require drush/drush:dev-master

This will install the latest Drush 7.0-dev release (or whatever is most current).

Add a symlink

Here's the part that assumes you're in a Vagrant machine. You can adjust this to reflect your own environment or even add the path to your $PATH variable in ~/.bashrc.

sudo ln -s /home/vagrant/.composer/vendor/bin/drush /usr/bin/drush

Check your work

# This should return something like 
# Drush Version    :    7.0-dev
drush version