How to start LaunchPad service of SQL Server on Ubuntu? I'm running SQL Server 2017 on Ubuntu 16.04. 

When trying to run an external Python script, I got the following error:

Msg 39011, Level 16, State 1, Line 0
SQL Server was unable to communicate with the LaunchPad service. Please verify the configuration of the service. 


I searched and found out that the solution on Windows is to start the service of LaunchPad with Windows' service manager. 

But I need the equivalent of Ubuntu. I don't even know what the LaunchPad service is called.
Linux Support Roadmap for SQL Server Machine Learning Services:

"Machine learning using R or Python in-database is not currently supported in SQL Server on Linux. Look for announcements in a later release.

However, on Linux you can perform native scoring using the T-SQL PREDICT function. Native scoring lets you score from a pretrained model very fast, without calling or even requiring an R runtime. This means you can use SQL Server on Linux to generate predictions very fast, to serve client applications."

The stand-alone Machine Learning Server is already supported on Linux.