Here are five popular ways to capture desktop screencast for Linux
1) Istanbul: Istanbul is one of the more widely used desktop recording software out there. You can download Istanbul from here. Debian and Fedora users should be able to install it from the repo. Istanbul has a very simple interface (or lack of). When you first start up Istanbul, you will see a small red button on your desktop panel.
Right click on the button and it will give you options and ways to record you desktop by window you choose or desktop area you select by mouse.
You can stop recording you session by left clicking on the record button, and it will prompt you save the screencast: