Dockerfile Copy Optional

[rsalazari]

In my pipeline I am using service docker. I am trying to Copy a file if it exists, but the engine version , Copy needs at least one file to exist otherwise it fails. I have tried with global expressions, resource/*.txt, resource/*.tx[t] resource/*.?xt. it doesn't work but in docker desktop it works normal to date. but in my pipeline the same instruction returns this error no error is returned: no source files were specified

[Theodora Boudale · Accepted solution]

Hi @rsalazari and welcome to the community.

If the resource/ directory contains only text files (when it's not empty) and you want to copy all of them, you can try the following command instead

COPY resource/ /path-to-destination-dir/

I have tested this in Pipelines and the command doesn't fail if the resource/ directory is empty.

If the resource/ directory may contain files other than .txt ones that you don't want to copy, I would suggest copying the txt files first in a separate directory before you build the Docker image, so you can then use a COPY command similar to what I have shared.

You mentioned that locally you haven't had any issues. Could you perhaps let me know the output of docker version on this machine, and the OS + version of the machine?

Kind regards,
Theodora

[rsalazari]

Thank you very much for the answer in that in my resources folder there are more than one sensitive file and I do not want to copy all of them, only one specific one, of course, as long as the file exists. This is because the idea is to make a dockerfile Generic - my projects contain the same instructions with the differential that some do not have that file and also not copy

[Theodora Boudale]

Hi @rsalazari,

Thank you for your reply and the additional details about your use case. Does my suggestion work for you or are you still having any issues?

Kind regards,
Theodora

[rsalazari]

It works, but since I have files that should not be copied for security reasons, copying them is not feasible yet. I would think it would be great if the COPY instruction would not fail even if it does not find a resource, it would just throw a waring.

[Theodora Boudale]

Hi,

I understand what you are saying; this is the only workaround I can think of at the moment, which would work if the files you want to copy are saved in a separate folder from the ones you don't want to copy.

With Docker Desktop this indeed does not fail. However, I tried installing the latest version of Docker Engine on a Linux machine, and the copy fails as well (with resource/*.txt and resource/*) if there are no files in the directory. It doesn't look like the issue is specific to Pipelines and the version of Docker in Pipelines; it looks like this is something that works with Docker Desktop but not with Docker Engine.

Kind regards,
Theodora