I wanted to share this problem and solution: I had developed a report in PDI locally (Windows laptop) that reports against an Oracle database. I published it to my server (Ubuntu linux) and created a datasource (named 'Falcon' just as on my laptop) to use with the report.

The report would not run from the server and gave me the Unknown Host error.

After banging my head for a while, I realized the problem: on my laptop, the Falcon connection in PDI pointed to the Oracle server as just 'Falcon' whereas the connection on the Pentaho server pointed to 'Falcon.mycompany.com'

Once I changed my laptop's connection to include 'mycompany.com' and republished the report, it worked fine.

Lesson learned, I only hope I remember it next time. I hope this helps someone.

- Russell