Symptoms

Thumbnails do not render. The following appears in the atlassian-confluence.log:

"This Confluence installation can not generate thumbnails: no image support in Java runtime" while generating thumbnails

Cause

On some Java installations (i.e. Unix without X11), you need to pass an additional parameter to Java when you are starting up to tell it how to use its image-manipulation libraries - to run in a headless mode, thus appending -Djava.awt.headless=true option. Getting thumbnail support working in this configuration depends on your application server. You can learn more about Headless Mode here.

Resolution

On Linux:

1. Edit Confluence install\bin\setenv.sh and add the '-Djava.awt.headless=true' parameter. For example JAVA_OPTS="-Xms128m -Xmx256m $JAVA_OPTS -Djava.awt.headless=true "
2. If you are using Fedora Linux, you will also need to install the xorg-x11-deprecated-libs package. (See: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=130239)

On Windows:

1. Edit the file Confluence install\bin\setenv.bat
2. Modify the line set JAVA_OPTS line by appending -Djava.awt.headless=true, for example set JAVA_OPTS=%JAVA_OPTS% -Xms128m -Xmx256m -Djava.awt.headless=true

As a Windows Service:

1. Open a command prompt in the Confluence install\bin directory
2. Execute tomcat5 //US//Confluence ++JvmOptions="-Djava.awt.headless=true"