server certificate verification failed while installing Kubernetes on Ubuntu 16.04 - ssl

Question

I'm setting up a Kubernetes cluster and as part of that, I ran the following command (mentioned on official docs: https://kubernetes.io/docs/tasks/tools/install-kubectl/) :
sudo apt-get update && sudo apt-get install -y apt-transport-https
However, it fails with the following error:
Err:3 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 Packages
server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
Now, I fetch the certificate with this command :
ex +'/BEGIN CERTIFICATE/,/END CERTIFICATE/p' <(echo | openssl s_client -showcerts -connect packages.cloud.google.com:443) -scq > kubecertificate.crt
I get the following response :
verify error:num=20:unable to get local issuer certificate
DONE
But since I see content inside my kubecertificate.crt file , I go ahead and copy the certificate in /usr/local/share/ca-certificates/ directory.
Then I run:
update-ca-certificates
After updating my ca certificates bundle, I re run the first command mentioned.
It again fails with the server certificate verification failed error.
Please help me understand where am I going wrong? Is it because I'm unable to get the local issuer certificate? Please help.

Answer 1

Are you using i386 image or is there some firewall involved? If it is 64bit version of Xenial then it must be some kind of system issue.
Take a look at this case. Especially I would check the current system time date -R and apt-get install NTP as advised by #davidthings as I remember having similar problem. There is also a lot of different solutions which could help, listed in the linked case - check which one is applicable for your and update if you succeeded.
After that you can try with this, to download kubectl, kubelet and kubeadm (or edit it accordingly if you want just one)
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg |
apt-key add -
cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb http://apt.kubernetes.io/ kubernetes-xenial main
EOF
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl