How to automate Let's Encrypt certificate renewal in Kubernetes with cert-manager on a bare-metal cluster? - kubernetes

Question

I would like to access my Kubernetes bare-metal cluster with an exposed Nginx Ingress Controller for TLS termination. To be able to automate certificate renewal, I would like to use the Kubernetes addon cert-manager, which is kube-lego's successor.
What I have done so far:
Set up a Kubernetes (v1.9.3) cluster on bare-metal (1 master, 1 minion, both running Ubuntu 16.04.4 LTS) with kubeadm and flannel as pod network following this guide.
Installed nginx-ingress (chart version 0.9.5) with Kubernetes package manager helm
helm install --name nginx-ingress --namespace kube-system stable/nginx-ingress --set controller.hostNetwork=true,rbac.create=true,controller.service.type=ClusterIP
Installed cert-manager (chart version 0.2.2) with helm
helm install --name cert-manager --namespace kube-system stable/cert-manager --set rbac.create=true
The Ingress Controller is exposed successfully and works as expected when I test with an Ingress resource. For proper Let's Encrypt certificate management and automatic renewal with cert-manager I do first of all need an Issuer resource. I created it from this acme-staging-issuer.yaml:
apiVersion: certmanager.k8s.io/v1alpha1
kind: Issuer
metadata:
name: letsencrypt-staging
namespace: default
spec:
acme:
server: https://acme-staging.api.letsencrypt.org/directory
email: email#example.com
privateKeySecretRef:
name: letsencrypt-staging
http01: {}
kubectl create -f acme-staging-issuer.yaml runs successfully but kubectl describe issuer/letsencrypt-staging gives me:
Status:
Acme:
Uri:
Conditions:
Last Transition Time: 2018-03-05T21:29:41Z
Message: Failed to verify ACME account: Get https://acme-staging.api.letsencrypt.org/directory: tls: oversized record received with length 20291
Reason: ErrRegisterACMEAccount
Status: False
Type: Ready
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning ErrVerifyACMEAccount 1s (x11 over 7s) cert-manager-controller Failed to verify ACME account: Get https://acme-staging.api.letsencrypt.org/directory: tls: oversized record received with length 20291
Warning ErrInitIssuer 1s (x11 over 7s) cert-manager-controller Error initializing issuer: Get https://acme-staging.api.letsencrypt.org/directory: tls: oversized record received with length 20291
Without a ready Issuer, I can not proceed to generate cert-manager Certificates or utilse the ingress-shim (for automatic renewal).
What am I missing in my setup? Is it sufficient to expose the ingress controller using hostNetwork=true or is there a better way to expose the its ports 80 and 443 on a bare-metal cluster? How can I resolve tls: oversized record received error when creating a cert-manager Issuer resource?

Answer 1

The tls: oversized record received error was caused by a misconfigured /etc/resolv.conf of the Kubernetes minion. It could be resolved by editing it like this:
$ sudo vi /etc/resolvconf/resolv.conf.d/base
Add nameserver list:
nameserver 8.8.8.8
nameserver 8.8.4.4
Update resolvconf:
$ sudo resolvconf -u