This document will guide you through the installation of Drush (Versions 6 and newer) using Composer on your shared Linux hosting account. Topics include requesting SSH access to your account, using an SSH Client, general Bash usage, Composer installation and Drush installation.

That indicates that Drupal needed more memory than PHP was allowed to give it.

Where is my php.ini file in Drupal to see my memory limit? - Every system is different. To see your php configuration, create a new php file in your sites root directory and name it "myinfo.php". Inside this newly created blank php file, simply type <?php phpinfo(); ?> then browse to that file in your web browser by going to http://yoursite.com/myinfo.php

Now you can see where the original php.ini file is as well as other information about your config such as memory_limit.