Open Broadcaster Software is the boss of screencasting; feature-packed, no ads, cross-platform and totally free! Specialized computer video recording software like the commercial FRAPS used to be the only feasible way to screencast games. Meanwhile most other screen-recording apps decorated your screen with ads and often couldn’t record games (DirectX or OpenGL).
OBS solves all our screen casting woes with commercial strength features wrapped up in a super-simple interface that’s available across Windows, Mac and Linux. No need to learn a different software for each, and it costs nothing at all (feel free to donate and support the devs though)!
More info from the source: https://obsproject.com/
Development is bustling over at the open-source project page too. Here’s a link…
GitHub repo: https://github.com/jp9000/obs-studio
And here’s a quick script to install it on Ubuntu, from a PPA: