I have made a back up of 2.0 and also taken a snapshot of the server. Thank you for the explanation, because now I can see that vufind-2.1 local/config/vufind doesn’t have anything in it other than a readme.
I did follow your instructions for local customizations and also understand about the SOLR. As per your recommendations I also made explicit paths because I’m running on Windows.
I’m not nearly so terrified now. Maybe only just a little bit.
The recommended procedure is in fact to drop 2.1 on top of vufind and overwrite all the files. If you have followed all the recommendations for customizing things, none of the files you have changed (configurations, custom theme, local module) will be overwritten by this process, because all of your customizations should be in new files that you have created rather than through edits to existing files. (The one exception to this is Solr configuration files, which have to be edited in-place).
Obviously, if you haven’t followed the recommendations and have made in-place edits, you’ll need to reapply those after the upgrade. If that’s the case, tell me more about what you’ve done and I can make some suggestions on how to do things in a more upgrade-friendly way in the future.
And, of course, it probably goes without saying, but I strongly recommend making a backup before doing the upgrade, just to be on the safe side! Then if you accidentally overwrite a local change that you’ve simply forgotten about, you can easily get it back later.
Please let me know if you still have questions.