volume_from指令-docker撰写 [英] volumes_from instruction - docker compose

问题描述

使用以下 docker-compose.yml 文件：

test:
  build: ../../
  dockerfile: docker/dev/Dockerfile
  volumes_from:
    - cachev

cachev:
  build: ../../
  dockerfile: docker/dev/Dockerfile
  volumes:
    - /build
  entrypoint: "true"

---

cachev 服务启动卷容器，该容器在Docker主机的 / var / lib / docker / 文件夹中创建匿名卷，并创建挂载点 / cache 在卷容器中（ xx_cachev ）。

---

cachev service in above file launches volume container that creates anonymous volume in /var/lib/docker/ folder in docker host and creates mount point /cache within volume container(xx_cachev).

是否<$ test 服务下的c $ c> volumes_from 指令在<$中创建 / build 挂载点c $ c> xx_test 容器？指向 xx_cachev 容器的 / build 挂载点？

Does volumes_from instruction under test service create /build mount point in xx_test container? that points to /build mount point of xx_cachev container?

推荐答案

来自 volumes_from 文档：

从另一个服务或容器安装所有卷...

Mount all of the volumes from another service or container...

因此简短的答案是是：

volumes_from 挂载 / build 由 cachev 在 test 服务内的服务。

volumes_from mounts /build volume defined by cachev service inside test service.

长答案：

要回答您的问题，我们运行 test 服务：

To answer your question let's run the test service:

docker compose up测试

在回答问题之前，请确保描述清楚：

Before answering your question, let's make sure the description is clear:

以上文件中的

cachev服务启动了卷容器...

cachev service in above file launches volume container...

只是由于 entrypoint： true 而立即退出的常规容器。

It's just regular container which exits immediately because of entrypoint: "true".

docker ps -a 应该显示：

ac68a33abe59缓存 true 16小时前退出（0）4分钟前cache_1

但是在退出之前它会创建 volumes：中指定的卷。因此，如果其他服务使用其卷（例如进行缓存），我们可以将其称为卷容器。

But before it exits it creates volumes specified in volumes:. So we can call it volume container if its volumes are used by other service, for caching for instance.

会在docker host中的/ var / lib / docker /文件夹中创建匿名卷

that creates anonymous volume in /var/lib/docker/ folder in docker host

同意。 -/ build 是匿名卷。可以通过查看所有容器安装来验证：

Agree. - /build is anonymous volume. Can be verified by viewing all container mounts:

docker inspect [cachev_container_id] --format’{{json .Mounts}}’| jq

应显示以下内容：

  {
    "Type": "volume",
    "Name": "1ec7ff7c72bfb5a3259ed54be5b156ea694be6c8d932bcb3fa6e657cbcaea378",
    "Source": "/var/lib/docker/volumes/1ec7ff7c72bfb5a3259ed54be5b156ea694be6c8d932bcb3fa6e657cbcaea378/_data",
        "Destination": "/build",
        "Driver": "local",
        "Mode": "",
        "RW": true,
        "Propagation": ""
      }

jq 是在bash中处理json的强大工具。

jq is great utility for working with jsons in bash. Install it for the above command to work.

并在卷容器（xx_cachev）中创建安装点/ cache。

and creates mount point /cache within volume container(xx_cachev).

在您提供的 cachev：服务规范中看不到任何挂载的迹象。

Don't see any evidence of mounts in cachev: service spec you provided.

如果将映射-/ tmp / cache：/ cache 添加到其卷部分并再次运行 docker compose up test 并检查退出的容器，您应该看到：

If you add mapping - /tmp/cache:/cache to its volumes section and run docker compose up test again and inspect the exited container you should see:

  {
    "Type": "bind",
    "Source": "/tmp/cache",
    "Destination": "/cache",
    "Mode": "rw",
    "RW": true,
    "Propagation": "rprivate"
  }

请注意， docker检查[cachev_service_id] --format'{{json .Mounts}}'| jq 将显示所有容器装载，包括使用 VOLUME 在 docker / dev / Dockerfile 中指定的装载。

Please, note that docker inspect [cachev_service_id] --format '{{json .Mounts}}' | jq will show all container mounts including those specified in docker/dev/Dockerfile using VOLUME instruction.

要回答您的问题，我们需要检查 test 服务容器：

To answer to your question we need to inspect test service container:

docker inspect [test_container_id] --format'{{json .Mounts}}''| jq ：

将显示 docker / dev / Dockerfile 中指定的所有卷借助 volumes_from 指令， cachev 的所有卷。

would show all the volumes specified in docker/dev/Dockerfile if any and all the volumes of cachev thanks to volumes_from instruction.

您可以看到 test 和 cache 容器都具有：

You can see that both test and cache containers have:

  {
    "Type": "volume",
    "Name": "1ec7ff7c72bfb5a3259ed54be5b156ea694be6c8d932bcb3fa6e657cbcaea378",
    "Source": "/var/lib/docker/volumes/1ec7ff7c72bfb5a3259ed54be5b156ea694be6c8d932bcb3fa6e657cbcaea378/_data",
    "Destination": "/build",
    "Driver": "local",
    "Mode": "",
    "RW": true,
    "Propagation": ""
  }

在他们的坐骑中，该体积在随后的 docker组合测试

in their mounts and this volume survives subsequent runs of docker compose up test

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