使用buildkit和mirror.gcr.io构建的Docker在未缓存的映像上失败

问题描述

在构建引用未在mirror.gcr.io上缓存的映像的Dockerfile时，以及在使用DOCKER_BUILDKIT=1启用时；构建失败：

$ cat Dockerfile.test
FROM debian:10

$ sudo cat /etc/docker/daemon.json
{
        "registry-mirrors": ["https://mirror.gcr.io"]
}

$ DOCKER_BUILDKIT=1 docker build -f Dockerfile.test . 
[+] Building 1.0s (4/4) FINISHED                                                                                                                                                                                
 => [internal] load .dockerignore                                                                                                                                                                          0.0s
 => => transferring context: 2B                                                                                                                                                                            0.0s
 => [internal] load build deFinition from Dockerfile.test                                                                                                                                                  0.0s
 => => transferring dockerfile: 42B                                                                                                                                                                        0.0s
 => ERROR [internal] load Metadata for docker.io/library/debian:10                                                                                                                                         0.6s
 => ERROR [1/1] FROM docker.io/library/debian:10                                                                                                                                                           0.3s
 => => resolve docker.io/library/debian:10                                                                                                                                                                 0.3s
------
 > [internal] load Metadata for docker.io/library/debian:10:
------
------
 > [1/1] FROM docker.io/library/debian:10:
------
Failed to solve with frontend dockerfile.v0: Failed to build LLB: Failed to load cache key: docker.io/library/debian:10 not found

解决方法

最新（稳定）的docker没有最新的buildkit。如果在镜像上找不到映像，则Buildkit 0.7实际上会故障转移到普通的Docker Hub。

与Github上@tonistiigi的per instruction一样：使用docker 20.10（当前为beta），或将docker buildx与更新的buildkit一起使用。