I deleted my collection in solr and now the LucidWorks UI doesn't work anymore. What is wrong and how can I fix it?
The way the current dashboard works is that it assumes that you are using the LucidWorks REST API for such functions: http://docs.lucidworks.com/display/lweug/Collections. So you either need to delete the collection via the UI or via the REST API that the UI utilizes for such things. If you deleted the collection via Solr, the UI has a problem. It still thinks the collection should be there and that makes it not start up at all. Granted, not starting up is something that needs to be fixed in the future.
So you don't want to use the Solr API for configuration type of changes like this. You can view the LucidWorks API in full to see the functionality that you can get out of it. The way you can eliminate the problem is that you can delete the information about the collection in the collections.yml file and any datasources that belonged to that collection in datasources.yml.
These .yml files are located in $ROOT_DIR/data/lwe-core/...
Go and find all the information about the your collection and delete it down to where it names all users that have access for that collection in collections.yml. Save a backup and follow the indentation. Make sure that you delete any datasources that were part of that collection. Make sure you clear your browser's cache and maybe restart your browser. It should come up then.