Note this question IS NOT about how to change Tomcat port or jetty port or Mac or Windows native installation of GeoServer. Each configuration for different platform is different. I tried many different ways to change port to 8585 from default 8080 but it ignores my changes and still gets launched on 8080. I tried changing startup.sh and added -Djetty.port=8585 in the exec part and tried jetty-http.xml but nothing works.
I am not surprised this is not documented anywhere on their manual.
Best Answer
All you do is edit the line in
start.ini
that says:to:
start GeoServer up
./bin/start.sh
or.\bin\start.bat
and away you go.