Docker Volume

What is a Volume?

If you try to run vi to edit a file in a Nginx Docker container, you will find that vi is not found. The reason is that only the necessary things will be included in the container. vi is not one of them.

To edit files in a container conveniently, we use volume to "share" files between container and the real machine. A volume is like a "shared directory".

Commands

• docker volume create: create a volume
• docker volume ls: check all volumes
• docker volume rm: remove a volume
• docker volume inspect: check details of a certain volume
• docker volume prune: clear unused local volumes
• docker volume --help

Create a Volume

You must add a volume to a container when calling docker run. If a container has already been created, you cannot add volumes to it. When you add a volume to a container, if the volume does not exist, it will be created automatically, which means you do not need to run docker volume create by yourself.

To add a volume to a container:

docker run -d --name nginx -p 80:80 -v [unique_volume_name]:[directory_in_container] nginx

To check volumes:

docker volume ls

To see details of a volume, including the path on physical machine:

docker volume inspect [volume_name]

By default, the volume is located at /var/lib/docker/volumes/[volume_name]/_data.

Now the directory in the physical machine and the one in the container are connected (doubly linked).