如何通过 Docker Hub API 确定标签的 Docker 镜像 ID？

Question

给定一个标签 `latest`，我们想在 Docker Hub 上找出另一个具有相同镜像 ID 的标签。

这里是如何使用 Docker Hub API v2 找出 repo 的所有标签：

TOKEN=$(curl -s -H "Content-Type: application/json" -X POST -d '{"username": "'${UNAME}'", "password": "'${UPASS}'"}' https://hub.docker.com/v2/users/login/ | jq -r .token)
curl -s -H "Authorization: JWT ${TOKEN}" https://hub.docker.com/v2/repositories/fluent/fluentd/tags/?page_size=100 | jq

（见gist.github.com/kizbitz）

不幸的是，它不包含图像 ID，但该键始终为 `null` 值：

$ curl -s -H "Authorization: JWT ${TOKEN}" https://hub.docker.com/v2/repositories/fluent/fluentd/tags/?page_size=100 | jq
{
  "count": 36,
  "next": null,
  "previous": null,
  "results": [
...
    {
      "name": "v0.14.11",
      "full_size": 11964464,
      "id": 7084687,
      "repository": 219785,
      "creator": 2923,
      "last_updater": 2923,
      "last_updated": "2016-12-27T07:16:41.294807Z",
      "image_id": null,
      "v2": true,
      "platforms": [
        5
      ]
    },
...

很遗憾，图片 ID 与上述 JSON 中的 `id` 不同。

$ docker images | grep fluent
docker.io/fluent/fluentd                  v0.14.11            1441d57beff9        3 weeks ago         38.25 MB

理论上，应该可以通过此 Docker Registry 调用访问 Docker Manifests 和映像 ID，但它也无济于事：

$ curl -s -H "Authorization: JWT ${TOKEN}" "https://registry.hub.docker.com/v2/fluent/fluentd/manifests/latest"
{"errors":[{"code":"UNAUTHORIZED","message":"authentication required","detail":[{"Type":"repository","Name":"fluent/fluentd","Action":"pull"}]}]}

（见stackoverflow.com）

这里是 Docker GitHub 存储库中的一个类似问题，但我仍然无法找出解决方案：https://github.com/docker/distribution/issues/1490。

P.S.：这是我尝试推送测试映像的 Docker 版本：

$ docker version
Client:
 Version:         1.12.6
 API version:     1.24
 Package version: docker-common-1.12.6-5.git037a2f5.fc25.x86_64
 Go version:      go1.7.4
 Git commit:      037a2f5/1.12.6
 Built:           Wed Jan 18 12:11:29 2017
 OS/Arch:         linux/amd64

Answer 1

Docker Registry API v2 使用镜像摘要而不是镜像 ID 来区分镜像身份。

可以通过以下 API 调用从 HTTP 响应头的Docker-Content-Digest 获取图像摘要：

$ REPOSITORY=fluent/fluentd

$ TOKEN=$(curl -s "https://auth.docker.io/token?service=registry.docker.io&scope=repository:$REPOSITORY:pull" | jq -r .token)

$ curl -s -D - -H "Authorization: Bearer $TOKEN" -H "Accept: application/vnd.docker.distribution.manifest.v2+json" https://index.docker.io/v2/$REPOSITORY/manifests/latest
HTTP/1.1 200 OK
Content-Length: 1982
Content-Type: application/vnd.docker.distribution.manifest.v2+json
Docker-Content-Digest: sha256:eaea1edffc34cff3b5e31ee738ea56e46326f90731b4139a19948814a4f0a4db
Docker-Distribution-Api-Version: registry/2.0
Etag: "sha256:eaea1edffc34cff3b5e31ee738ea56e46326f90731b4139a19948814a4f0a4db"
Date: Tue, 24 Jan 2017 13:34:53 GMT
Strict-Transport-Security: max-age=31536000
...

所有标签都可以通过以下API调用获取：

$ curl -s -H "Authorization: Bearer $TOKEN" https://index.docker.io/v2/$REPOSITORY/tags/list
{"name":"fluent/fluentd","tags":["edge-onbuild","edge","jemalloc","latest-onbuild","latest","onbuild","stable-onbuild","stable","ubuntu-base","v0.12-latest-onbuild","v0.12-latest","v0.12-onbuild","v0.12.16","v0.12.18","v0.12.19","v0.12.20","v0.12.21","v0.12.23","v0.12.24","v0.12.26-2","v0.12.26-onbuild","v0.12.26","v0.12.27-onbuild","v0.12.27","v0.12.28-onbuild","v0.12.28","v0.12.29-onbuild","v0.12.29","v0.12.30-onbuild","v0.12.30","v0.12.31-onbuild","v0.12.31","v0.12","v0.14-latest-onbuild","v0.14-latest","v0.14-onbuild","v0.14.1","v0.14.10-onbuild","v0.14.10","v0.14.11-onbuild","v0.14.11","v0.14.2","v0.14.6","v0.14.8","v0.14"]}

基于上述，要找到与特定标签相同的摘要，它将是如下脚本。

#!/bin/bash

REPOSITORY=$1
TARGET_TAG=$2

# get authorization token
TOKEN=$(curl -s "https://auth.docker.io/token?service=registry.docker.io&scope=repository:$REPOSITORY:pull" | jq -r .token)

# find all tags
ALL_TAGS=$(curl -s -H "Authorization: Bearer $TOKEN" https://index.docker.io/v2/$REPOSITORY/tags/list | jq -r .tags[])

# get image digest for target
TARGET_DIGEST=$(curl -s -D - -H "Authorization: Bearer $TOKEN" -H "Accept: application/vnd.docker.distribution.manifest.v2+json" https://index.docker.io/v2/$REPOSITORY/manifests/$TARGET_TAG | grep Docker-Content-Digest | cut -d ' ' -f 2)

# for each tags
for tag in ${ALL_TAGS[@]}; do
  # get image digest
  digest=$(curl -s -D - -H "Authorization: Bearer $TOKEN" -H "Accept: application/vnd.docker.distribution.manifest.v2+json" https://index.docker.io/v2/$REPOSITORY/manifests/$tag | grep Docker-Content-Digest | cut -d ' ' -f 2)

  # check digest
  if [[ $TARGET_DIGEST = $digest ]]; then
    echo "$tag $digest"
  fi
done

结果如下：

$ ./find_same_digest.sh fluent/fluentd latest
latest sha256:eaea1edffc34cff3b5e31ee738ea56e46326f90731b4139a19948814a4f0a4db
stable sha256:eaea1edffc34cff3b5e31ee738ea56e46326f90731b4139a19948814a4f0a4db
v0.12.31 sha256:eaea1edffc34cff3b5e31ee738ea56e46326f90731b4139a19948814a4f0a4db
v0.12 sha256:eaea1edffc34cff3b5e31ee738ea56e46326f90731b4139a19948814a4f0a4db

如果要查看本地图片的摘要，可以通过docker images --digests获取：

$ docker images --digests | grep fluentd
fluent/fluentd                  latest              sha256:eaea1edffc34cff3b5e31ee738ea56e46326f90731b4139a19948814a4f0a4db   1788ee7dcfcc        14 hours ago        35.41 MB

Answer 2

上面的答案很棒！此外，如果您想在私有 repo 上使用它，您需要使用您的注册表用户凭据添加基本身份验证，以及附加范围参数 'account='

（见http://www.cakesolutions.net/teamblogs/docker-registry-api-calls-as-an-authenticated-user）