Docker: add a volume

Question

I am running three docker instances of multichain nodes for testing purposes. Now in the Readme it says that I have to add a volume:

Add a volume

:/root/.multichain

Link to GitHub

So my question is very simple: How do I add this volume? is :/root/.multichain a path of the host system or is it some relative path inside the docker container?

Thanks a lot

Answer 1

It leaves how do you map your volume up to you (namely giving you 2 persistent options). This Readme only defines what location in container should be persisted.

Method 1 (named volume)

version: '2'
services:
    masternode:
        build: ./master
        volumes:
           - namedvolume:/root/.multichain
        # further definitions

    slavenode:
        build: ./node
        volumes:
           - namedvolume:/root/.multichain
        # further definitions

    explorernode:
        build: ./explorer
        volumes:
           - namedvolume:/root/.multichain
        # further definitions

    # further services definitions

Method 2 (direct mapping into host):

version: '2'
services:
    masternode:
        build: ./master
        volumes:
           - /some/path/in/host:/root/.multichain
        # further definitions

    slavenode:
        build: ./node
        volumes:
           - /some/path/in/host:/root/.multichain
        # further definitions

    explorernode:
        build: ./explorer
        volumes:
           - /some/path/in/host:/root/.multichain
        # further definitions

    # further services definitions

Note that this volume should be shared across all the services so that all the services (nodes in this case) will have the same files and will be able to maintain the same state.

Official docs ref and further reading