Earlier, we described the steps to create a data volume in a Docker image using the VOLUME instruction in the Dockerfile. However, Docker does not provide any mechanism to mount the host directory or file during the build time in order to ensure the Docker images to be portable. The only provision Docker provides is to mount the host directory or file to a container's data volume during the container's launch. Docker exposes the host directory or file mounting facility through the -v option of the docker run subcommand. The -v option has five different formats, enumerated as follows:
- -v <container mount path>
- -v <host path>:<container mount path>
- -v <host path>:<container mount path>:<read write mode>
- -v <volume name>:<container ...