Not able to push to registry from within the cluster

[bartgras]

My setup is as follows:

• Registry created with k3d registry create registry.localhost --port 5000

• Created registries.yaml file with content:

  mirrors:
    "localhost:5000":
      endpoint:
        - http://k3d-registry.localhost:5000
  

• Created cluster
  k3d cluster create kfc --api-port 6550 --servers 1 --port 8080:80@loadbalancer \ --registry-use k3d-registry.localhost:5000 --registry-config registries.yaml

I can push to registry and create deployment like in documentation. All works fine up to that point.
If I describe created Pod, the image is k3d-registry.localhost:5000/nginx:latest

Inside the cluster (as a part of the app I'm building) there is Kaniko Pod which is supposed to build images and (in k3d-based development environment) push images to the local registry.

The issue I'm having is that Kaniko Pod fails with following error message:

error checking push permissions -- make sure you entered the correct tag name, and that you are authenticated correctly, and try again: 
checking push permission for "k3d-registry.localhost:5000/k3s_test:latest": 
creating push check transport for k3d-registry.localhost:5000 failed: 
Get "https://k3d-registry.localhost:5000/v2/": dial tcp: lookup k3d-registry.localhost on 10.43.0.10:53: no such host; 
Get "http://k3d-registry.localhost:5000/v2/": dial tcp: lookup k3d-registry.localhost on 10.43.0.10:53: no such host

My system is Mac OS.
k3d/k3s version:

k3d version v4.4.8
k3s version v1.21.3-k3s1 (default)

(I've used this comment and this as a reference for registry and cluster setup)

[iwilltry42]

Hi @bartgras , thanks for starting this discussion!
Two things to mention here:

1. In your case, --registry-use ... is enough, as it will generate that registries.yaml internally.
2. CoreDNS doesn't know about that registry, so pods cannot resolve the name. This changed in k3d v5.0.0 (see [BUG] k3d container registry is not dns resolvable from the kubernetes cluster #522 (comment))

I guess with the change in v5.0.0 your issue should be solved 👍

[bartgras]

I can confirm that 5.0.0 fixes the issue. Thank you @iwilltry42 for pointing at the solution!