How to connect to k8s cluster of docker desktop on another machine? - kubernetes

Question

I have a macbook (192.168.1.101) and a macmini(192.168.1.104) over same wifi.
I launched a k8s cluster through docker-desktop on macmini and would like to access it through kubectl on macbook.
Here is how my ~/.kube/config on macmini looks like:
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: ******
server: https://kubernetes.docker.internal:6443
name: docker-desktop
contexts:
- context:
cluster: docker-desktop
user: docker-desktop
name: docker-desktop
- context:
cluster: docker-desktop
user: docker-desktop
name: docker-for-desktop
current-context: docker-desktop
kind: Config
preferences: {}
users:
- name: docker-desktop
user:
client-certificate-data: ******
client-key-data: ******
How can I write ~/.kube/config on macbook? Currently I followed official doc and got following errors.
$ kubectl config view
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: DATA+OMITTED
server: http://192.168.1.104:6443
name: macmini-cluster
contexts:
- context:
cluster: macmini-cluster
user: macmini-user
name: macmini-context
current-context: macmini-context
kind: Config
preferences: {}
users:
- name: macmini-user
user:
client-certificate-data: REDACTED
client-key-data: REDACTED
$ kubectl get pods
The connection to the server 192.168.1.104 was refused - did you specify the right host or port?
Update:
I added port 6443 to server of cluster and tried to telnet macmini's port 6443, but got:
$ telnet 192.168.1.104 6443
Trying 192.168.1.104...
telnet: connect to address 192.168.1.104: Connection refused
telnet: Unable to connect to remote host
When I checked on macmini:
$ netstat -na|grep 6443
tcp4 0 0 127.0.0.1.6443 *.* LISTEN
There seems to be an unresolved related issue.

Answer 1

It seems your kubernetes api server did not bind to a local network accessible ipv4 address, instead it is bound to host's loopback adapter at 127.0.0.1
$ netstat -na|grep 6443
tcp4 0 0 127.0.0.1.6443 *.* LISTEN
Which means it can only be accessed by the machine running the process.
You need to proxy this port to your local ipv4 network. You can do this as below with command prompt running in kubernetes host computer as administrator:
netsh interface portproxy add v4tov4 listenaddress=192.168.1.104 listenport=6443 connectaddress=127.0.0.1 connectport=6443

Answer 2

In the macbook, the port number has to be specified as below. That's the port number of the K8S APIServer. (1)
server: http://192.168.1.104:6443

Answer 3

You can just copy your .kube/config file from the mac-mini desktop to macbook, you dont have to write the config file again if you want to use the same context.

Answer 4

There's an internal hostname docker-desktop pointing to kubernetes api-server, however, this hostname can be accessed by any of the inside containers without the --link option, which we can give a hack below to make a port-forwarding trick
docker run -d -p 0.0.0.0:6444:6443 bobrik/socat TCP-LISTEN:6443,fork TCP:docker-desktop:6443
I once thought to leverage kubernetes service, but no time to keep digging, hope anyone else has any ideas on this trick.
In addition to that, don't forget to make a little change on your ~/.kube/config below to avoid the x509 certificate verification
clusters:
- cluster:
server: https://<your docker host>:6444
insecure-skip-tls-verify: true
name: docker-desktop