COPY和ADD的`--chown`选项不允许变量。有解决方法吗？

Question

在Dockerfile中，将目录复制为非root用户（例如$ UID 1000）的常用方法如下：

COPY --chown=1000:1000 /path/to/host/dir/ /path/to/container/dir

但是，我想改用变量。例如

ARG USER_ID=1000
ARG GROUP_ID=1000
COPY --chown=${USER_ID}:${GROUP_ID} /path/to/host/dir/ /path/to/container/dir

但这是不可能的。有解决方法吗？

请注意，我知道一个可能的解决方法是将目录复制为root，然后在目录上运行chown（变量与可以很好地配合使用RUN）。但是，仅在单独的命令中使用chown时，图像的大小会增加。

Answer 1

You can create a user before running the --chown;

mkdir -p test && cd test
mkdir -p path/to/host/dir/
touch path/to/host/dir/myfile

Create your Dockerfile:

FROM busybox

ARG USER_ID=1000
ARG GROUP_ID=1000

RUN addgroup -g ${GROUP_ID} mygroup \
 && adduser -D myuser -u ${USER_ID} -g myuser -G mygroup -s /bin/sh -h /

COPY --chown=myuser:mygroup /path/to/host/dir/ /path/to/container/dir

Build the image

docker build -t example .

Or build it with a custom UID/GID:

docker build -t example --build-arg USER_ID=1234 --build-arg GROUP_ID=2345 .

And verify that the file was chown'ed

docker run --rm example ls -la /path/to/container/dir

total 8
drwxr-xr-x    2 myuser   mygroup       4096 Dec 22 16:08 .
drwxr-xr-x    3 root     root          4096 Dec 22 16:08 ..
-rw-r--r--    1 myuser   mygroup          0 Dec 22 15:51 myfile

Verify that it has the correct uid/gid:

docker run --rm example ls -lan /path/to/container/dir

total 8
drwxr-xr-x    2 1234     2345          4096 Dec 22 16:08 .
drwxr-xr-x    3 0        0             4096 Dec 22 16:08 ..
-rw-r--r--    1 1234     2345             0 Dec 22 15:51 myfile

Note: there is an open feature-request for adding this functionality: issue #35018 "Allow COPY command's --chown to be dynamically populated via ENV or ARG"