Docker named volumes vs DOC (data-only-containers)

问题:

Up to recent version of Docker (v1.10), we were thought that we can use DOC: data-only containers. So I would create such DOC (based on e.g. busybox) and use --volumes-from to link it to my container. You can still read about this in Docker documentation.

With new version of docker, it is said that instead of DOC we should use named volumes. Here is an example of docker-compose.yml:

version: '2'    
services:
  elasticsearch:
    image: elasticsearch:2.2.0
    command: elasticsearch -Des.network.host=0.0.0.0
    ports:
      - "9201:9200"
    volumes:
      - "es-data:/usr/share/elasticsearch/data"

volumes:    
  es-data:

Here we created and use named volume es-data.

There is still not much documentation on this new feature. I am asking:

• Can we replace DOC with named containers? How long volume is persisted? What if I remove the container that is using it?
• How can we e.g. backup now? Previously, I could docker run --rm --volumes-from es-data ... and then tar it.

回答1:

Can we replace DOC with named containers?

In many cases, yes, named containers will be a better option.

How long volume is persisted? What if I remove the container that is using it?

If you remove the container, the volume will still be there. The only way to remove the volume is to use docker-compose down -v or docker volume rm <volume name>.

How can we e.g. backup now? Previously, I could docker run --rm --volumes-from es-data ... and then tar it.

Instead of --volumes-from, you can use --volume=<volume name>.

Note that volumes created by docker-compose are always prefixed with the project name, so if you use it with a docker command the full name is actually <project_name>_es-data.