參考教程：https://docs.docker.com/engine/reference/builder/

環境

1. virtual box 6.1
2. centos 7.8
3. docker 19.03

資料卷

VOLUME ["/data"]

The VOLUME instruction creates a mount point with the specified name and marks it as holding externally mounted volumes from native host or other containers. The value can be a JSON array, VOLUME ["/var/log/"]

VOLUME 指令建立具有指定名稱的掛載點，並將其標記為儲存來自本地主機或其他容器的外部安裝的資料卷。該值可以是 JSON 陣列，VOLUME ["/var/log/"]

The docker run command initializes the newly created volume with any data that exists at the specified location within the base image. For example, consider the following Dockerfile snippet:

docker run 命令使用基礎映象內指定位置上存在的任何資料初始化新建立的卷。例如，考慮以下 Dockerfile 片段：

FROM ubuntu
RUN mkdir /myvol
RUN echo "hello world" > /myvol/greeting
VOLUME /myvol

This Dockerfile results in an image that causes docker run to create a new mount point at /myvol and copy the greeting file into the newly created volume.

這個 Dockerfile 生成一個映象，該映象使 docker run 在/myvol 目錄建立一個新的掛載點，並將 greeting 檔案複製到新建立的卷中。

關於指定卷的注意事項

Keep the following things in mind about volumes in the Dockerfile.
關於 Dockerfile 中的卷，請記住以下幾點。

• Volumes on Windows-based containers: When using Windows-based containers, the destination of a volume inside the container must be one of:

• 基於 Windows 的容器上的卷：使用基於 Windows 的容器時，容器內卷的目的地必須是以下之一：

  • a non-existing or empty directory
  • a drive other than C:
  • 不存在或空目錄
  • 除C：以外的驅動器

• Changing the volume from within the Dockerfile: If any build steps change the data within the volume after it has been declared, those changes will be discarded.

• 從 Dockerfile 內更改卷：如果在聲明瞭卷後有任何構建步驟更改了卷中的資料，則這些更改將被丟棄。

• JSON formatting: The list is parsed as a JSON array. You must enclose words with double quotes (") rather than single quotes (').

• JSON 格式：該列表被解析為 JSON 陣列。您必須用雙引號（"）而不是單引號（'）括起單詞。

• The host directory is declared at container run-time: The host directory (the mountpoint) is, by its nature, host-dependent. This is to preserve image portability, since a given host directory can’t be guaranteed to be available on all hosts. For this reason, you can’t mount a host directory from within the Dockerfile. The VOLUME instruction does not support specifying a host-dir parameter. You must specify the mountpoint when you create or run the container.

• 主機目錄是在容器執行時宣告的：主機目錄（掛載點）從本質上說是依賴於主機的。這是為了保留映象的可移植性，因為不能保證給定的主機目錄在所有主機上都可用。因此，您無法從 Dockerfile 中掛載主機目錄。VOLUME 指令不支援指定 host-dir 引數。建立或執行容器時，必須指定掛載點。

總結

介紹了 Dockerfile 中 VOLUME 指令的用法和注意事項。