Arduino Command Line Interface - How to change boardsmanager.additional.urls I am building a Travis CI job to test my Arduino Library and it needs to install external board definitions.

Is there a way that I can set the boardsmanager.additional.urls from the command prompt like it would have been done in the Preferences window?

Or should I create preferences.txt file? (If so where does that live in a Linux environment)
Found the solution:

arduino --pref "boardsmanager.additional.urls=http://arduino.esp8266.com/stable/package_esp8266com_index.json"