I have ubuntu linux 16.04 x64 installed on my pc. Is there a way to transfer this system to a USB flash drive, saving all settings and programs, and then fully launch it?
UNetbootin – Install this program from the standard repository and it will create a bootable USB stick. Then you can write there all the files that you think are necessary.
Or the second option is to create an ISO image of your system and write it to a flash drive.