How to move only "blocks" and "chainstate" folders on an external USB hard-drive while running Bitcoin Client on connected laptop with Ubuntu?
The easiest way to do this according to the Bitcoin Core Wiki is to append the datadir option after running bitcoind to launch the client according to the following syntax: 


bitcoind -datadir=/media/myusername/backup/.bitcoin 


example provided thusly:


bitcoind -datadir=/media/alexanderjsingleton/SEAGATE/.bitcoin


Also, don't forget to mount the external USB hard-drive by using the ls -l /dev/disk/by-uuid/ option by command line or by GUI-method.