如何通过Docker Hub API确定标签的Docker镜像ID？

Docker Registry API v2使用图像摘要而不是图像ID来区分图像标识.

Docker-Content-Digest通过进行以下API调用,可以从HTTP响应头获取图像摘要:

$ 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
...

可以使用以下API调用获取所有标记:

$ 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"]}

基于以上所述,为了找到与特定标签相同的摘要,它将是如下的脚本.

#!/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

如果要查看本地图像的摘要,可以通过以下方式获取docker images --digests:

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