Steps

To move an existing XWiki instance to a different server and upgrade it, do the two operations one after the other rather than together:

1. Install on the new server the same XWiki version as the one running on the old server.
2. Move the database and the permanent data (the /data directory) to the new server.
3. Start the instance on the new server.
4. Check that the content and the features work as they did on the old server.
5. Upgrade the instance on the new server.

The wiki then runs the new version on the new server, and any problem you met along the way belongs to one of the two operations rather than to both at once.

FAQ

Why should the server migration be separated from the XWiki upgrade process?

Separating the server migration from the upgrade makes it easier to identify and fix problems, instead of mixing infrastructure issues with data migration issues.