On first startup:
$ sudo docker run -it -p 8182:8182 --name janusgraph-container -v /home/misunderstandings/Desktop/max/shared_understandings/exports:/opt/janusgraph/exports --name janusgraph-container janusgraph/janusgraph
And then in another window:
$ sudo docker exec -u 0:0 janusgraph-container chown -R janusgraph /opt/janusgraph/exports