Tool for desktop recording in available on Ubuntu 16.04 is gtk-recordmydesktop, install:

sudo apt-get install gtk-recordmydesktop

It produces file in .ogv format. Conversion to mp4 can by done with command:

ffmpeg -i "out.ogv" -codec:v libx264 -quality good -cpu-used 0 -profile:v baseline -level 30 -y -maxrate 2000k -bufsize 2000k -threads 4 -codec:a copy -b:a 128k "output.mp4"