Can Docker COPY commands be chained

Question

Is is possible to chain the COPY commands together like what can be done with the RUN command?

Example of chaining run command:

RUN echo "root:user_2017" | chpasswd && \
    groupadd -g 1000 user && \
    useradd -u 1000 -m -s /bin/bash user && \
    passwd -d user

Would something like what is shown below prevent the introduction of multiple intermediate images if I had to perform many copies from the host to the image? I know what is shown below won't work because each line needs to be a separate command when the && is used to tie multiple lines together.

COPY ./folder1A/* /home/user/folder1B/ && \
     ./folder2A/* /home/user/folder2B/ && \
     ./folder3A/* /home/user/folder3B/ && \
     ./folder4A/* /home/user/folder4B/ && \

Answer 1

Since COPY commands cannot be chained, it's typically best to structure your context (directories you are copying from) in a way that is friendly to copy into the image.

So instead of:

COPY ./folder1A/* /home/user/folder1B/ && \
     ./folder2A/* /home/user/folder2B/ && \
     ./folder3A/* /home/user/folder3B/ && \
     ./folder4A/* /home/user/folder4B/ && \

Place those folders into a common directory and run:

COPY user/ /home/user/

If you are copying files, you can copy multiple into a single target:

COPY file1.zip file2.txt file3.cfg /target/app/

If you try to do this with a directory, you'll find that docker flattens it by one level, hence the suggestion to reorganize your directories into a common parent folder.