kubectl unable to connect to server: x509: certificate signed by unknown authority

Question

i\'m getting an error when running kubectl one one machine (windows)

the k8s cluster is running on CentOs 7 kubernetes cluster 1.7 master, worker

Here\'s my

Answer 1

Run:

gcloud container clusters get-credentials standard-cluster-1 --zone us-central1-a --project devops1-218400

here devops1-218400 is my project name. Replace it with your project name.

Answer 2

This is an old question but in case that also helps someone else here is another possible reason.

Let's assume that you have deployed Kubernetes with user x. If the .kube dir is under the /home/x user and you connect to the node with root or y user it will give you this error.

You need to switch to the user profile so kubernetes can load the configuration from the .kube dir.

Update: When copying the ~/.kube/config file content on a local pc from a master node make sure to replace the hostname of the loadbalancer with a valid IP. In my case the problem was related to the dns lookup.

Hope this helps.

Answer 3

One more solution in case it helps anyone:

My scenario:

• using Windows 10
• Kubernetes installed via Docker Desktop ui 2.1.0.1
• the installer created config file at ~/.kube/config
• the value in ~/.kube/config for server is https://kubernetes.docker.internal:6443
• using proxy

Issue: kubectl commands to this endpoint were going through the proxy, I figured it out after running kubectl --insecure-skip-tls-verify cluster-info dump which displayed the proxy html error page.

Fix: just making sure that this URL doesn't go through the proxy, in my case in bash I used export no_proxy=$no_proxy,*.docker.internal

Answer 4

So kubectl doesn't trust the cluster, because for whatever reason the configuration has been messed up (mine included). To fix this, you can use openssl to extract the certificate from the cluster

openssl.exe s_client -showcerts -connect IP:PORT

IP:PORT should be what in your config is written after server:

Copy paste stuff starting from -----BEGIN CERTIFICATE----- to -----END CERTIFICATE----- (these lines included) into a new text file, say... myCert.crt If there are multiple entries, copy all of them.

Now go to .kube\config and instead of

certificate-authority-data: <wrongEncodedPublicKey>`

put

certificate-authority: myCert.crt

(it assumes you put myCert.crt in the same folder as the config file) If you made the cert correctly it will trust the cluster (tried renaming the file and it no longer trusted afterwards). I wish I knew what encoding certificate-authority-data uses, but after a few hours of googling I resorted to this solution, and looking back I think it's more elegant anyway.

Answer 5

I just want to share, sorry I wasn't able to provide this earlier as I just realized this is causing

so on the master node we're running a kubectl proxy

kubectl proxy --address 0.0.0.0 --accept-hosts '.*'

I stopped this and voila the error was gone.

I'm now able to do

    kubectl get nodes
NAME                    STATUS    AGE       VERSION
centos-k8s2             Ready     3d        v1.7.5
localhost.localdomain   Ready     3d        v1.7.5

I hope this helps those who stumbled upon this scenario

Answer 6

For those of you that were late to the thread like I was and none of these answers worked for you I may have the solution:

When I copied over my .kube/config file to my windows 10 machine (with kubectl installed) I didn't change the IP address from 127.0.0.1:6443 to the master's IP address which was 192.168.x.x. (running windows 10 machine connecting to raspberry pi cluster on the same network). Make sure that you do this and it may fix your problem like it did mine.