docker-mongodb is responsible for creating a Docker container that runs a MongoDB service. This directory also contains the data written to the MongoDB from the nodeos container courtesy of the MongoDB plugin upon startup of the nodeos instance.
Firstly, be sure that this working directory has a data directory. If not, you can create one yourself by doing mkdir data. While there are shell scripts available for your convenience, you can also manually start the MongoDB service by running the following Docker command:
docker run -d -p 27788:27788 --name eosio_mongodb -v $(pwd)/data:/data/db mongo
This creates a Docker container called eosio_mongodb which should be started first before starting the Docker container running nodeos.
If you wish to re-initialize your MongoDB service, then you will have to remove and remake the data directory, and then remove and run the MongoDB container once more. You can run everything in one line by entering the following command:
rm -rf data/ && mkdir data && docker rm -fv eosio_mongodb && docker run -d -p 27788:27788 --name eosio_mongodb -v $(pwd)/data:/data/db mongo