Lỗi php .gd drupal 7 trên ubuntu 14.04

Drupal requires you to enable the PHP extensions in the following list .gd

In my case (php 5.6, Ubuntu 14.04) the following command worked for me:
sudo apt-get install php5.6-gd

Nếu bạn run sudo apt-get install php-gd sẽ không được 

Sau khi cài xong restart apache2 

sudo service apache2 restart