Copy files from pod to local

[bboysoulcn]

Which project are you requesting an enhancement for?

kr8s

What do you need?

Copy files from pod to local

[jacobtomlinson]

This would be great. It looks like kubectl uses the exec API to implement this so we would need to implement #169 before we could do this.

[jacobtomlinson]

Now that Pod.exec() is available in v0.11.0 we can do things like copying individual files locally via stdout.

import kr8s

# Copy file from my-pod:/etc/os-release to /tmp/os-release
with open("/tmp/os-release", "wb") as fh:
    pod = kr8s.objects.Pod.get("my-pod")
    pod.exec(["cat", "/etc/os-release"], stdout=fh)

Copying in the other direction seems to be trickier due to #212. If we can find a workaround to this then we could implement a Pod.cp() convenience method and make more use of tar to enable copying whole directories (see #210 (comment)).

[bboysoulcn]

Thank you for your contribution

[marcio-pessoa]

I never found a solution to this problem, so I finally wrote an application to copy files without tar.
It is just a beta, but is working fine on my environment.

https://github.com/marcio-pessoa/kubectl-cp

[jacobtomlinson]

@marcio-pessoa neat! Looking over the code it looks like it requires sh, cat, tee, find and mkdir to all be present and on the path in the remote container. So you wouldn't be able to use it on a container like scratch. I'm curious which container images you see which have all of those binaries, but not tar?

[marcio-pessoa]

I'm sorry @jacobtomlinson .
I thought I could help in some way.

[jacobtomlinson]

Sure, please don't take offence to my question. I was just curious about the use case for your project?

[marcio-pessoa]

No problem.

I have some examples, but I can't use them all because of my contract.
But it is a RedHat practice. I also recently worked with container by Oracle without tar.

But Keycloak is a good example.

quay.io/keycloak/keycloak

However, your project, the kr8s library is extremely elegant and is probably the best way to solve the problem currently.

[jacobtomlinson]

Ah that's interesting. Yeah it looks like any container built from registry.access.redhat.com/ubi9-micro doesn't have tar, but it does have the other binaries you are depending on.

I wonder if we could go in a totally different direction and use an EphemeralContainer instead. We would make the image configurable but default to something very small that does contain the dependencies necessary for copying files. That way we could even support scratch based distroless images and still copy files in/out.

[marcio-pessoa]

Until the official kubectl cp does not have the definitive solution for copying files in scratch containers, the approach suggested by @jacobtomlinson using EphemeralContainer is probably the almost ultimate solution.

Let's work together to make this dream come true.