Docker build --no-cache 实际上会下载并刷新基础镜像吗？

docker build --no-cache 刷新吗updated是否远程基础镜像？文档似乎没有具体说明。

The --no-cache选项将重建图像而不使用本地缓存图层。但是，那FROM如果构建主机上存在已提取的基础映像，该行将重用该基础映像（来自行本身可能不会被缓存，但它提取的图像会被缓存）。如果你想再次拉取基础镜像，你可以使用--pull构建命令的选项。例如。

$ docker build --no-cache --pull -t new-image-name:latest .

要查看构建命令采用的所有选项，您可以运行

$ docker build --help

或查看文档https://docs.docker.com/engine/reference/commandline/build/

以下是您如何自行测试此行为的示例：

$ # very simple Dockerfile
$ cat df.test
FROM busybox:latest
RUN echo hello >test.txt

$ # pull an older version of busybox
$ docker pull busybox:1.29.2
1.29.2: Pulling from library/busybox
8c5a7da1afbc: Pull complete
Digest: sha256:cb63aa0641a885f54de20f61d152187419e8f6b159ed11a251a09d115fdff9bd
Status: Downloaded newer image for busybox:1.29.2

$ # retag that locally as latest
$ docker tag busybox:1.29.2 busybox:latest

$ # run the build, note the image id at the end of each build step
$ DOCKER_BUILDKIT=0 docker build --no-cache -f df.test .
Sending build context to Docker daemon  23.04kB
Step 1/2 : FROM busybox:latest
 ---> e1ddd7948a1c
Step 2/2 : RUN echo hello >test.txt
 ---> Running in dba83fef49f9
Removing intermediate container dba83fef49f9
 ---> 1f824ff05612
Successfully built 1f824ff05612

$ # rerun the build, note step 1 keeps the same id and never pulled a new latest
$ DOCKER_BUILDKIT=0 docker build --no-cache -f df.test .
Sending build context to Docker daemon  23.04kB
Step 1/2 : FROM busybox:latest
 ---> e1ddd7948a1c
Step 2/2 : RUN echo hello >test.txt
 ---> Running in 73df884b0f48
Removing intermediate container 73df884b0f48
 ---> e5870de6c24f
Successfully built e5870de6c24f

$ # run with --pull and see docker update the latest image, new container id from step 1
$ DOCKER_BUILDKIT=0 docker build --no-cache --pull -f df.test .
Sending build context to Docker daemon  23.04kB
Step 1/2 : FROM busybox:latest
latest: Pulling from library/busybox
Digest: sha256:2a03a6059f21e150ae84b0973863609494aad70f0a80eaeb64bddd8d92465812
Status: Downloaded newer image for busybox:latest
 ---> 59788edf1f3e
Step 2/2 : RUN echo hello >test.txt
 ---> Running in 7204116ecbf4
Removing intermediate container 7204116ecbf4
 ---> 2c6d8c48661b
Successfully built 2c6d8c48661b

$ # one last run now that busybox:latest is updated shows the pull has nothing to do
$ DOCKER_BUILDKIT=0 docker build --no-cache --pull -f df.test .
Sending build context to Docker daemon  23.04kB
Step 1/2 : FROM busybox:latest
latest: Pulling from library/busybox
Digest: sha256:2a03a6059f21e150ae84b0973863609494aad70f0a80eaeb64bddd8d92465812
Status: Image is up to date for busybox:latest
 ---> 59788edf1f3e
Step 2/2 : RUN echo hello >test.txt
 ---> Running in f37e19024e99
Removing intermediate container f37e19024e99
 ---> 044a5d4011c4
Successfully built 044a5d4011c4