sudo ubuntu-device-flash core rolling --oem beagleblack --enable-ssh --channel edge -o outputarm.img
Determining oem configuration
Starting download of beagleblack
280.74 KB / 280.74 KB [============================================================================================================================================================================================================================] 100.00 % 332.40 KB/s 
Done
Fetching information from server...
Downloading and setting up...
Installing beagleblack
Starting download of beagleblack
280.74 KB / 280.74 KB [============================================================================================================================================================================================================================] 100.00 % 363.40 KB/s 
Done
New image complete
Summary:
 Output: outputarm.img
 Architecture: armhf
 Channel: edge
 Version: 18