Just a few weeks ago, we were migrating CIO East Africa from a shared host to a Virtual Private Server (VPS). After a hectic time setting mail on server, it was time to set up the Joomla sites. One of the site worked but the CIO Site worked was a difficulty getting off the ground, always giving a blank page.
Restarting the server worked for a while before one of the section gives a blank page. Checking on the Apache/PHP logs showed that several of the modules were giving Fatal Error, predominantly from modules associated with images (cant rem the specific ones, it was a while back).
It took several days to narrow down the error to a PHP module.
PHP GD is a library that deals with imaging in PHP applications and is required by several of Joomla modules but is not required by Joomla itself to function. It may be hard to pinpoint the error to this library given the above reason, but I am sure it accounts for several headaches for newly set up Joomla Sites.
Several Linux flavours have specific binaries through which you can install PHP GD, just search in your package installer.