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If you need to use RMI follow directions at end of the framework\appserver\templates\wasce2\README file. Note that I only tried without SSL using this tip
You will get an issue on Windows due to Geronimo, Security Manager and RMI. A workaround is suggested in the README file. If interested see https://issues.apache.org/jira/browse/GERONIMO-4037.
Multi-instances
The appserver "-setup" deployment option is able to deploy OFBiz multi-instances in Geronimo. Actually there are, at least, 2 cases for multi-instances.
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