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/