[SOLVED] Docker - COPY file from different working directory to another is not working

Docker - COPY file from different working directory to another is not working

I'm using:

Docker 18.09.1
Ubuntu 16.04

I want to copy a file from a specific folder from my docker image to another folder in my docker image using the Dockerfile.

My docker commands are:

sudo docker build -t mytest .
sudo docker run mytest

My Dockerfile is:

FROM ubuntu:16.04

RUN mkdir -p out/
COPY . out/            <---- this works
COPY /usr/bin/yes /opt <---- this doesn't work!!

CMD out/helloworld

I have a C++ application called helloworld on my out/ working folder. However, I want to copy a file called "yes" which is under /user/bin/ to my /opt folder.

I've tried the COPY command and also the CMD command but without success.

I tried to check if the file was there by running the command on my Ubuntu VM:

docker run mytest ls -l /opt
total 0

My COPY try:

COPY /usr/bin/yes /opt

My CMD try:

CMD ["cp /usr/bin/yes /opt"]

Error:

COPY failed: stat /var/lib/docker/tmp/docker-builder737799611/usr/bin/yes: no such file or directory

Both doesn't work. How can I copy a file to another folder (inside the same docker image)?

Solution

This is stated here that you cannot use absolute path to copy file from your host to your container. It is not supported: https://github.com/moby/moby/issues/4592. So you have to prepare all your files in your current directory first.