The GD Graphics Library is a useful bit of code that lets PHP manipulate digital image files. If you have a WordPress site that has a lot of graphical manipulation, odds are that your site uses the GD Library. That means if you’re running a WordPress site off Ubuntu, not having the GD Library for PHP can cause quite a few problems.
Fortunately, it’s quite easy to install. On a system that has PHP 5 installed, simply go to a command prompt and type this command:
sudo apt-get install php5-gd
Enter your password to authenticate, and apt-get will download and install the GD Library for you. After the installation is complete, any PHP scripts that rely upon the GD Library should now function properly.
-JM