Backup all cores in a standalone Solr server

A very, very simple script which will backup all cores in a standalone Solr server. It accepts exactly one argument, which is the root URL of the solr server it should connect to (i.e. the portion before "/solr" in the URL).

docker run --rm --network solr_network ghcr.io/berkeleylibrary/docker-solr-backup:v1.0.0 http://solr:8983

Includes a simple test script which runs against a Docker compose stack with a fresh, empty Solr server.