kuberneteskubeadm

Joining cluster takes forever


I have set up my master node and I am trying to join a worker node as follows:

kubeadm join 192.168.30.1:6443 --token 3czfua.os565d6l3ggpagw7 --discovery-token-ca-cert-hash sha256:3a94ce61080c71d319dbfe3ce69b555027bfe20f4dbe21a9779fd902421b1a63

However the command hangs forever in the following state:

[preflight] Running pre-flight checks
    [WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/

Since this is just a warning, why does it actually fails?

edit: I noticed the following in my /var/log/syslog

Mar 29 15:03:15 ubuntu-xenial kubelet[9626]: F0329 15:03:15.353432    9626 server.go:193] failed to load Kubelet config file /var/lib/kubelet/config.yaml, error failed to read kubelet config file "/var/lib/kubelet/config.yaml", error: open /var/lib/kubelet/config.yaml: no such file or directory
Mar 29 15:03:15 ubuntu-xenial systemd[1]: kubelet.service: Main process exited, code=exited, status=255/n/a
Mar 29 15:03:15 ubuntu-xenial systemd[1]: kubelet.service: Unit entered failed state.

Solution

  • The problem had to do with kubeadm not installing a networking CNI-compatible solution out of the box;

    Therefore, without this step the kubernetes nodes/master are unable to establish any form of communication;

    The following task addressed the issue:

    - name: kubernetes.yml --> Install Flannel
      shell: kubectl -n kube-system apply -f https://raw.githubusercontent.com/coreos/flannel/bc79dd1505b0c8681ece4de4c0d86c5cd2643275/Documentation/kube-flannel.yml
      become: yes
      environment:
        KUBECONFIG: "/etc/kubernetes/admin.conf"
      when: inventory_hostname in (groups['masters'] | last)