I would start trying unit_test capture test.
Do you have the folder /unit_test?
find for some test with capture within the name.
Then you can try to capture something using your camera. What camera are you using?
I don't have a unit test.
I'm using Samsung 5Mpixel K5ECG MIPI CSI sensor
So, find the unit_test and use ti.
I think you would need to install it. (sorry, I´m not used with Ubuntu rootfs)