George -
I just finished doing the same thing for my shiny-new Hackrf.
Here is what worked for me on the same Ubuntu and GNURadio:
sudo apt-get install hackrf-tools
Add a one-line file to enable USB access to hackrf.
sudo gedit
Start a new file and enter this one line:
ATTR{idVendor}=="1d50", ATTR{idProduct}=="6089",
SYMLINK+="hackrf-one-%k", MODE="660", GROUP="plugdev"
Right-click on the file tab, click Save As, click on Computer,
then go to this directory:
/etc/udev/rules.d Enter this file name:
52-hackrf.rules then click Save.
Exit gedit
Reboot
With Hackrf One plugged in to USB, test it:
hackrf_info
A few lines of data should display.
Doug