Ansible playbook and roles to create a simple Kubernetes cluster with kubeadm

Configuration

1. run ./deploy.sh to configured your nodes within k8s.
2. the IP address definition could be changed at: ./roles/kubeadm/install/defaults/main.yml master_ip: "10.10.20.1" worker1_ip: "10.10.20.2" worker2_ip: "10.10.20.3" worker3_ip: "10.10.20.4"

master: netmaster worker1: k8s-worker-1 worker2: k8s-worker-2 worker3: k8s-worker-3

3. contiv version can be changed once it is updated: https://github.com/iceworld/ansible/blob/master/group_vars/all.yml: contiv_ver: 1.0.0 the contiv release page: https://github.com/contiv/install/releases

Goal

Provide an Ansible playbook that implements the steps described in Installing Kubernetes on Linux with kubeadm

Assumptions

This playbook assumes:

• You have access to 3+ Linux machines, with either CentOS 7 or Ubuntu 16.04 installed
• Full network connectivty exists between the machines, and the Ansible control machine (e.g. your computer)
• The machines have access to the Internet
• You are Ansible-knowledgable, can ssh into all the machines, and can sudo with no password prompt
• Make sure your machines are time-synchronized, and that you understand their firewall configuration and status

1. Copy, rename, and edit the file INVENTORY-EXAMPLE
2. Enter the FQDN of the machine assigned the role of Kubernetes master in the [master] group.
3. Enter the FQDNs of the machines assigned the role of Kubernetes node in the [nodes] group.
4. Edit cluster_name (this will become the basename of a file used to store the admission_token)
5. Optionally uncomment and edit master_ip_address_configured in the [master:vars] section, if your master machine has multiple interfaces, and the default interface is NOT the interface you want the nodes to use to connect to the master.

After you have done this, you should be able to succesfully execute something like this:

    ansible -m ping -i YOUR-INVENTORY-FILE cluster

And your master and node machines should respond. Don't bother proceeding until this works!

Run the playbook

When you are ready to proceed, run:

    ansible-playbook cluster.yml -i YOUR-INVENTORY-FILE

This should execute/implement all four installation steps in the aforementioned installation guide.

The guide then provides examples you can run to test your cluster.

If you want to interact with your cluster via the kubectl command on your own machine (and why wouldn't you?), take note of the last note in the "Limitations" section of the guide:

         There is not yet an easy way to generate a kubeconfig file which can be used to authenticate to the cluster remotely with kubectl on, 
         for example, your workstation. Workaround: copy the kubelet’s kubeconfig from the master: use 
           scp root@<master>:/etc/kubernetes/admin.conf . 
         and then e.g. kubectl --kubeconfig ./admin.conf get nodes from your workstation.

The playbook retrieves the admin.conf file, and stores it locally as ./remotes/cluster_name.conf to facilitate remote kubectl access.

Idempotency

• I belive I have made admission token generation idempotent. Generated tokens are stored in ./tokens/cluster_name.yml, and reused on subsequent playbook runs
• I'm not sure how to know that the init and join operations have successfully completed, I've tried to base it on files/directories that are created, but not yet certain that is correct.
• It seems like re-issuing the kubectl apply -f https://git.io/weave-kube is harmless, but again, I'm not certain...

Notes and Caveats

• This playbook is under active development, but is not extensively tested.
• I have successfully run this to completion on a 3 machine Ubuntu setup, it basically worked the first time.
• I haven't yet succeeded in getting a cluster working perfectly on Centos 7. I spent all day today (2016-09-30) trying to do so, and ran into all kinds of issues, stay tuned for updates.
• I don't yet understand much or anything about the Kubernetes pod network "Weave Net" the guide and this playbook installs. Be forewarned!

Acknowlegements

• Huge kudos to the authors of kubeadm and its getting started guide
• Joe Beda provided the code to generate tokens, and how to feed a token into kubeadm init
• @marun pointed me to the documentation about how to access the master remotely via kubectl

Contributing

Pull requests and issues are welcome.