I have no G drivers installed in Ubuntu, though my Ubuntu Graphics works well
You do of course have a graphics driver installed -
If you mean - you do not have the proprietary graphics driver - then go
System - Administration - Hardware drivers and if Ubuntu recognises that they are available for your card, another window will open.
Before you click 0n Activate - note if the driver has been tested by Ubuntu - otherwise if you activate you may have problems.
Some graphic card manufacturers for certain chips have made available drivers for Linux based systems.
2. Until you posted I did not know F.lux for Linux - in fact I had never heard of it.I have now had a look at it. In fact I have installed it.
It worked on a terminal window with the usual sudo apt-get etc as per this link herehttp://stereopsis.com/flux/linux.html
I do not like it, the forums are full of reports from people having problems and in all honesty, unless the user had a particular optical related reason for needing such a utility - I consider it a gimmick.
I have un-installed it, using synaptics package manager and then Computer janitor.