create a docker data container to share data with mongodb containers

• docker create -v /data/db --name dbstore mongo bin/true

create a standard container that uses the previously created data container (--volumes-from)

• docker run -d -p 30001:27017 --name mgodb --volumes-from dbstore mongo mongod

or if we want to run as a replica set first create a network so that all instances can talk to each other:

• docker create network my-mongo-cluster

then create containers executing mongod with replSet parameter each with their own data container

• docker run -d -p 30001:27017 --volumes-from dbstore1 --net my-mongo-cluster --name mongo1 mongo mongod --replSet my-mongo-set
• docker run -d -p 30002:27017 --volumes-from dbstore2 --net my-mongo-cluster --name mongo2 mongo mongod --replSet my-mongo-set
• docker run -d -p 30003:27017 --volumes-from dbstore3 --net my-mongo-cluster --name mongo3 mongo mongod --replSet my-mongo-set

you conserve space by basing the data container and the app container on the same image

to backup data from the data container volume use mongodump as nomral - no special docker commands required

• mongodump --host localhost --port 30001 --db test --out documents/mongodata