I am using Ansible to automate the setup of a Kubernetes cluster. The master node setup works fine, but I’m having issues when trying to join worker nodes to the cluster. This is the only part where SSH fails. I can connect manually, and I have installed all dependencies using my playbook, but joining the cluster fails every time.

The relevant task in my role is as follows:

- name: Join cluster
  ansible.builtin.shell: "{{ join_command }}  >> node_joined.log"
  args:
    chdir: /home/ubuntu
    creates: node_joined.log
  vars:
    ansible_command_timeout: 3000
  when: join_command is defined
 

join_command comes from this task:

- name: Set join command
  ansible.builtin.set_fact:
    join_command: "kubeadm join --token {{ join_token }} {{ master_node_ip }}:6443 --discovery-token-ca-cert-hash sha256:{{ ca_cert_hash.stdout }}"
  run_once: true

I keep encountering the following error message during the execution of the task:

TASK [kubernetes-worker-setup : Join cluster] **********************************
task path: /home/runner/work/kubernetes/kubernetes/roles/kubernetes-worker-setup/tasks/main.yml:39
Read vars_file 'vars.yml'

fatal: [k8s-master-3]: UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: OpenSSH_8.9p1 Ubuntu-3ubuntu0.10, OpenSSL 3.0.2 15 Mar 2022
    debug1: Reading configuration data /etc/ssh/ssh_config
    debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
    debug1: /etc/ssh/ssh_config line 21: Applying options for *
    debug2: resolve_canonicalize: hostname 195.201.11.184 is address
    debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/home/runner/.ssh/known_hosts'
    debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/home/runner/.ssh/known_hosts2'
    debug1: auto-mux: Trying existing master
    debug2: fd 3 setting O_NONBLOCK
    debug2: mux_client_hello_exchange: master version 4
    debug3: mux_client_forwards: request forwardings: 0 local, 0 remote
    debug3: mux_client_request_session: entering
    debug3: mux_client_request_alive: entering
    debug3: mux_client_request_alive: done pid = 1846
    debug3: mux_client_request_session: session request sent
    debug1: mux_client_request_session: master session id: 2
    debug3: mux_client_read_packet: read header failed: Broken pipe
    debug2: Control master terminated unexpectedly
    Shared connection to 195.201.11.184 closed.",
    "unreachable": true
}