How To Create Ansible Role for Launching Kubernetes Multi-Node Cluster

Hey guys hope you all are doing good so finally, I am here with an ansible project to create a multi-node cluster of Kubernetes. Today we are going to create two roles one for setting up the master node and the other for setting up the worker node.

Let's get started with creating an Ansible role for setting up the master node.

ansible-galaxy init role_name=> To make ansible role

From the above command empty role is created inside it head over to the tasks folder and open the main.yml file using your favorite editor and put the below code in it.

   - name: installing docker
     package:
        name: docker
        state: present
   - name: adding damemon to docker
     copy:
       src: daemon.json
       dest: /etc/docker/daemon.json
   - name: enabling docker
     service:
       name: docker
       state: restarted
       enabled: yes
   - name: adding kube repo
     copy:
      src: /k8s/k
      dest: /etc/yum.repos.d/kubernetes.repo
   - name: installing master software
     package:
        name:
          - kubelet
          - kubeadm
          - kubectl
        state: present
   - name: enabling kubelet
     service:
       name: kubelet
       state: started
       enabled: yes
   - name: config image
     command:
        cmd: "kubeadm config images pull"
   - name: installing iproute
     package:
        name: iproute-tc
        state: present
   - name: config basic network
     shell: 'echo "1" > /proc/sys/net/bridge/bridge-nf-call-ip tables' 
   - name: config master
     shell: "kubeadm init --pod-network-cidr=10.244.0.0/16 --ignore-preflight-errors=NumCPU --ignore-preflight-errors=Mem"
   - name: config master to work
     shell: mkdir -p $HOME/.kube
   - name: config master to work
     shell: sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
   - name: config master to work
     shell: sudo chown $(id -u):$(id -g) $HOME/.kube/config
   - name: token creation
     shell: kubeadm token create --print-join-command
     register: token
   - debug:
       var: token.stdout
   - name: saving output
     local_action:
        copy content="{{ token.stdout }}" dest="/k8s/newtoken"
   - name: config Networking
     shell: 'kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml'

Note:- Going to provide GitHub URL for all the code files if you copy from above you may get an indentation error.

After putting the above code in the main.yml file just save and close it that's it your first role for configuring the master node is done.

Let's understand line by line what is role doing

Step1 We have to install docker in our slave system for that we are using

- name: installing docker
     package:
        name: docker
        state: present

Step2 We have to change the daemon group of docker for this we are using.

In the below code daemon.json is one file in my local system in which ansible is running that I am copying to slave with ansible same file will be provided in the git hub repo attached below

- name: adding damemon to docker
     copy:
       src: daemon.json
       dest: /etc/docker/daemon.json

(daemon is a kind of API which help request and manage images, container etc)

Step3 We have to start the service and enable it that is achieved by

- name: enabling docker
     service:
       name: docker
       state: restarted
       enabled: yes

Step4 Once all this is done now we have to configure the yum repo to download some necessary software for configuring the master node.

In the below code daemon.json is one file in my local system in which ansible is running that I am copying to slave with ansible same file will be provided in the git hub repo attached below

- name: adding kube repo
     copy:
      src: /k8s/kubernetes.repo
      dest: /etc/yum.repos.d/kubernetes.repo

Step5 After configuring the yum repo now we have to download the necessary software required for configuring the master node

- name: installing master software
     package:
        name:
          - kubelet
          - kubeadm
          - kubectl
        state: present

Step6 After downloading the software we have to enable the kubelet service.

- name: enabling kubelet
     service:
       name: kubelet
       state: started
       enabled: yes

Step7 After enabling kubelet we have to pull all docker images required for configuring the master node for that kubeadm provides one command that will fetch all docker images used for configuring the master node.

- name: config image
     command:
        cmd: "kubeadm config images pull"

Step 8 We also need software called iproute for configuring master node

- name: installing iproute
     package:
        name: iproute-tc
        state: present

Step9 Now we have to run the final command to configure master node for Kubernetes

- name: config master
     shell: "kubeadm init --pod-network-cidr=10.244.0.0/16 --ignore-preflight-errors=NumCPU --ignore-preflight-errors=Mem"

Note:- Above command has only to be run once strictly else it will cause an error this is the reason it is suggested to run this role on master node only once

Step10 Now once you have done till step9 now we have to run three commands to make the kubectl command work in master so you can check no of pods and launch pod from master itself.

- name: config master to work
     shell: mkdir -p $HOME/.kube
   - name: config master to work
     shell: sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
   - name: config master to work
     shell: sudo chown $(id -u):$(id -g) $HOME/.kube/config

Step11 Once you have done all the above steps you are done you can now go in master and can run the kubectl command to perform the operation but if you want to connect the node to the master node then we have to use one token provided by the master. For this, we are creating a token and saving that token in one file in our local system of ansible.

- name: token creation
     shell: kubeadm token create --print-join-command
     register: token
   - debug:
       var: token.stdout
   - name: saving output
     local_action:
        copy content="{{ token.stdout }}" dest="/k8s/newtoken"
  

Step12 Now we have to configure the flannel network that help to make the connection between the master and worker node

- name: config Networking
     shell: 'kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml'

That's it we are done with the configuration of the master node.

Now you can use your role to configure the Kubernetes master node.

To use the role we have to create a playbook and inside it, we have to pass the role we want to use as shown below

- hosts: master
 roles:
 — k8s_master

Here I am using aws ec2 instance to ssh in the instances I have used below inventory.

Ansible inventory to configure aws instance

Note while launching an instance in AWS or any other cloud allow all traffic in a security firewall.

Once the master is configured now we are ready to configure the node while creating the node we have to give the token that we have saved in our file name token while configuring the master node.

Configuring master node and worker node are have similar steps but I preferred to create a sep role for both of them.

First, let's create one more role for configuring the worker node and inside it go to the tasks folder and open main.yml, and put the below code.

- name: installing docker
  package:
     name: docker
     state: present
 — name: adding damemon
   copy:
     src: daemon.json
     dest: /etc/docker/daemon.json
 — name: enabling docker
   service:
      name: docker
      state: restarted
      enabled: yes
 — name: adding kube repo
   copy:
     src: /k8s/kubernetes.repo
     dest: /etc/yum.repos.d/kubernetes.repo
 — name: installing kubelet
   package:
     name:
       — kubelet
       — kubeadm
       — kubect
     state: present
 — name: enabling kubeadm
   service:
     name: kubelet
     state: started
     enabled: yes
 — name: installing iproute-tc
   package:
     name: iproute-tc
     state: present
 — name: config basic requirment
   shell: ‘echo -e “net.bridge.bridge-nf-call-ip6tables = 1 \r\n net.bridge.bridge-nf-call-iptables=1” >> /etc/sysctl.d/k8s.conf’
 — name: running token
   shell: “{{token}}”

As you can see above code is similar to the code we have used for configuring the master node only a few new commands we have added.

The below command is used to configure basic networking requirements in the worker node.

— name: config basic requirment
  shell: ‘echo -e “net.bridge.bridge-nf-call-ip6tables = 1 \r\n net.bridge.bridge-nf-call-iptables=1” >> /etc/sysctl.d/k8s.conf’

Below command is the final command in which we have to run the command/token provided by the master node here we are taking token from users while they run the playbook.

— name: running token
  shell: “{{token}}”

That’s it we are done with the configuration of the worker node.

Now you can use your role to configure the Kubernetes worker node.

To use the role we have to create a playbook and inside it, we have to pass the role we want to use as shown below in the below playbook we are creating taking as input from the user and saving it in a variable called token.

- hosts: worker
  vars_prompt:
   - name: token
     prompt: enter token
     private: no
  roles:
   - k8s_workernode

Once you have made all the roles now you can run them using playbook as I have shown and enjoy the power of automation.

If want to download the above role directly can use the below commands.

ansible-galaxy install guptaadi123.k8s_master
ansible-galaxy install guptaadi123.k8s_workernode

Once we have created a role we can push them to ansible-galaxy workspace who to push their will cover in the next article.

For playbooks and supporting daemon file and Kube repo file follow below GitHub link

Git repo:-https://github.com/guptaadi123/k8s_multinode-cluster.git

Git repo for configuring k8s master role:-https://github.com/guptaadi123/K8s_master.git

Git repo for configuring k8s worker role:-https://github.com/guptaadi123/k8s_workernode.git

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