Add support for --chown flag to COPY command

[priyawadhwa]

See #1 for details

[pmcq]

Hi I'm interested in getting this issue resolved for multi-stage builds we are working on, but don't have experience contributing to a go repo. I'd like to help out if possible though (at least for some of the --chown syntax)

[priyawadhwa]

Hey @pmcq , thanks for your interest. I've outlined a few steps you might want to take to add this feature

1. In copy.go, in Execute, you'll first want to get uid/gid from c.cmd.Chown, which is a string. We do something similar for the USER command here, so you might be able to move some of that logic into a separate function which both COPY and USER could call.
2. In the copy command we call util.CopyDir and util.CopyFile. You'll need to change the signatures of these functions here and here to take in the uid/gid, and apply it to every file that's copied over in those functions.
3. You can run our unit tests by running make test (you'll have to update some of them since I think we use CopyFile and CopyDir in a few different places).

Let me know if you have any more questions.

[pmcq]

I made changes in a fork here: https://github.com/GoogleContainerTools/kaniko/compare/master...pmcq:copy-chown?expand=1 and built an image and used it to run dockerfiles with COPY --chown flag succesfully. All existing unit tests pass, however I don't see any existing tests on util.CopyDir/CopyFile or CopySymlink that need modification.

I was thinking of creating new tests that just copy file/dir/symlink but since the user running the testcases isn't going to be a root user, it wouldn't be allowed to chown the file to someone else, so the testcase wouldn't add anything specific checks for this change. Should I open a PR or is there a different type of testing you would like?

[priyawadhwa]

@pmcq thanks for opening a PR!

[swistaczek]

Hey, this is still an active issue. PR #250 is closed and abandoned.

[ataillefer]

Hi, any news on this?

It's really problematic when using multi-stage to not be able to use COPY and change the owner of the copied directory.

Of course, a workaround is to call an extra RUN chown -R uid:gid mydir after the COPY instruction, but it adds a layer of the size of the copied directory, so directly impacts the final image size...

Thanks

[fredr]

@ataillefer beware, that walkaround has some unexpected problems of its own, see #845

[wstrange]

Any updates on this issue?

[diclophis]

I just ran into this bug as well...