Write lock error when copying Solr container

Copying a folder/container in /var/solr/data causes a write.lock error. I have no clue how to edit the container manually.

I renamed the core in core.properties, renamed the folder with the same name, and deleted write.lock in the index/data directory (then tried deleting everything in the index/data directory).
http://stackoverflow.com/questions/16943134/how-do-i-get-solr-back-up-when-indexes-are-locked-and-unlockonstartuptrue-does
http://lucene.472066.n3.nabble.com/removing-write-lock-file-in-solr-after-indexing-td3699356.html
https://cwiki.apache.org/confluence/display/solr/IndexConfig+in+SolrConfig

Well I am going to watch some videos:

Solr and Lucene First Steps
https://www.youtube.com/watch?v=rq3stslcvIw

Apache Solr Tutorial for Beginners -1 | Apache Lucene Tutorial -1 | Solr Search Tutorial | Edureka 

https://www.youtube.com/watch?v=7WIbU3ZlTe4

 Also see:

https://github.com/wikier/marmotta-search