preload a docker image on the k3s node agents

[juliens]

This PR adds preloading existing container images ( docker save format ) from /var/lib/rancher/k3s/agent/images

Fixes #92

[dduportal]

Confirmed that this version is working for my use case in #92

[ibuildthecloud]

Does this work with compressed archives too? Just curious.

[ibuildthecloud]

You need to add a new struct field, cfg.Containerd.Images which is the path to the images and then setup the real path in pkg/agent/config/config.go run(...)

[ibuildthecloud]

This is going to cause memory issues because you are reading the whole thing into memory (could be gigabytes). Can you just open the file and pass that to import?

[dduportal]

Does this work with compressed archives too? Just curious.

Have not tried yet.

Also, I have a strange issue: when using this image only for worker nodes, coredns never starts.
On the (debug) server node, I see the manifest to be written, but then nothing happens.

Trying to work from latest v0.2.0-rc2 to provide a reproducible use case.

[ibuildthecloud]

@dduportal Sorry v0.2.0-rc2 is not working. I deleted the tag because it completely fails to start. So master is basically broken. I'm trying to fix now. Also need better CI :/

[ibuildthecloud]

Master is fixed and v0.2.0-rc3 is released which is stable again.

[juliens]

Does this work with compressed archives too? Just curious.

I think that the containerd.import doesn't handle compressed archives, so it needs to be a specific developpement.

[ibuildthecloud]

@juliens That's fine. We can add support for compression later. I left just one more small comment, if you can address that I'll merge and do a build with this in it.

[ibuildthecloud]

@juliens This should be in v0.2.0-rc4 now if you could please validate the build that would be great!

[ldez]

We (the Traefik team: @juliens, @dduportal and me) will validate if the k3s-inator 😄 works well tomorrow morning (it's 2am for us).

[mmatur]

It works perfectly. Thanks ;) 👏

[dduportal]

Confirmed here also: works like a charm (v0.2.0-rc4 with image preloading).
Thanks @ibuildthecloud for this tool, adn thanks @juliens for the contribution

[crdil]

I have added images which I exported with docker save to /var/lib/rancher/k3s/agent/images and then restarted k3s. In my k8s deployment I've added the image name to -image: <name> , but k3s still tries to fetch the image from docker.io.

I get the following error.

"rpc error: code = Unknown desc = failed to resolve image \"docker.io/library...

This should work right?

[demikl]

I have added images which I exported with docker save to /var/lib/rancher/k3s/agent/images and then restarted k3s. In my k8s deployment I've added the image name to -image: <name> , but k3s still tries to fetch the image from docker.io.

I get the following error.

"rpc error: code = Unknown desc = failed to resolve image \"docker.io/library...

This should work right?

Hi, I just used this feature today. It looks like an image tagged as myimage in docker would result, in the containerd embedded in k3s, as :

docker.io/library/myimage

This can be observed through this command:

$ sudo k3s crictl images
IMAGE                                      TAG                 IMAGE ID            SIZE
docker.io/library/myimage                  latest              652014e0a66b3       82MB