Docker 数据管理-Volumes

Volumes是Docker最为推荐的数据持久化方法。

Volumes have several advantages over bind mounts:

Volumes are easier to back up or migrate than bind mounts.
You can manage volumes using Docker CLI commands or the Docker API.
Volumes work on both Linux and Windows containers.
Volumes can be more safely shared among multiple containers.
Volume drivers allow you to store volumes on remote hosts or cloud providers, to encrypt the contents of volumes, or to add other functionality.
A new volume’s contents can be pre-populated by a container.

Choose the -v or --mount flag

　　起初, the -v or --volume flag was used for 单机版-Containers and the --mount flag was used for Swarm services. However, starting with Docker 17.06, you can also use --mount with 单机版-Containers. In general, --mount 更清晰 and 更冗长. 最大的不同是 -v 语法将所有的选项组合在一起，--mount语法将他们进行了分离。

Tip: 新永不应该使用--mount语法，有经验的用户更熟悉-v or --volume语法。但是更鼓励使用--mount，因为调查发现它更容易被使用。

If you need to specify volume driver options, you must use --mount.

--mount: 由多个<key>=<value>对组成，使用逗号进行分割。The --mount syntax is more verbose than -v or --volume, but the order of the keys is not significant, and the value of the flag is easier to understand.
- The type of the mount, which can be bind, volume, or tmpfs. This topic discusses volumes, so the type is always volume.
- The source of the mount. For named volumes, this is the name of the volume. For anonymous volumes, this field is omitted. May be specified as source or src.
- The destination takes as its value the path where the file or directory is mounted in the container. May be specified as destination, dst, or target.
- The readonly option, if present, causes the bind mount to be mounted into the container as read-only.
- The volume-opt option, which can be specified more than once, takes a key-value pair consisting of the option name and its value.

Create and manage volumes

Unlike a bind mount, you can create and manage volumes outside the scope of any container.

Create a volume:

$ docker volume create my-vol

List volumes:

$ docker volume ls

local               my-vol

Inspect a volume:

$ docker volume inspect my-vol

[

    {

        "Driver": "local",

        "Labels": {},

        "Mountpoint": "/var/lib/docker/volumes/my-vol/_data",

        "Name": "my-vol",

        "Options": {},

        "Scope": "local"

    }

]

Remove a volume:

$ docker volume rm my-vol

Start a container with a volume

If you start a container with a volume that does not yet exist, Docker creates the volume for you. The following example mounts the volume myvol2 into /app/ in the container.

The -v and --mount examples below produce the same result. You can’t run them both unless you remove the devtest container and the myvol2 volume after running the first one.

$ docker run -d \

  --name devtest \

  --mount source=myvol2,target=/app \

  nginx:latest

$ docker run -d \

  --name devtest \

  -v myvol2:/app \

  nginx:latest

可以为多个Container mount同一个volume，以达到数据在多个Container之间共享的目的；
如果 mount target指向的是已有目录，原有数据会被复制到source volume 中。

参考文档： https://docs.docker.com/