step-4-ansible-inventory.md

STEP 4 - Ansible Inventory

Ansible will use an inventory file to determine the hosts Kubernetes should be installed on.

Inventory File

• Use the following commands on the Ansible host and in the “kubespray” directory
• Replace the IP addresses in the declare command with the addresses of your Kubernetes hosts (master/control-plane and worker nodes)
• Running these commands will create a hosts.yaml file within the kubespray/inventory/akash directory
• NOTE - ensure that you are still within the Python virtual environment when running these commands. Your cursor should have a “(venv)” prefix. If needed - re-enter the virtual environment by issuing:
  • source venv/bin/activate

cd ~/kubespray

cp -rfp inventory/sample inventory/akash

#REPLACE IP ADDRESSES BELOW WITH YOUR KUBERNETES CLUSTER IP ADDRESSES
declare -a IPS=(10.0.10.136 10.0.10.239 10.0.10.253 10.0.10.9)

CONFIG_FILE=inventory/akash/hosts.yaml python3 contrib/inventory_builder/inventory.py ${IPS[@]}

Expected Result (Example)

(venv) root@ip-10-0-10-145:/home/ubuntu/kubespray# CONFIG_FILE=inventory/akash/hosts.yaml python3 contrib/inventory_builder/inventory.py ${IPS[@]}

DEBUG: Adding group all
DEBUG: Adding group kube_control_plane
DEBUG: Adding group kube_node
DEBUG: Adding group etcd
DEBUG: Adding group k8s_cluster
DEBUG: Adding group calico_rr
DEBUG: adding host node1 to group all
DEBUG: adding host node2 to group all
DEBUG: adding host node3 to group all
DEBUG: adding host node4 to group all
DEBUG: adding host node1 to group etcd
DEBUG: adding host node2 to group etcd
DEBUG: adding host node3 to group etcd
DEBUG: adding host node1 to group kube_control_plane
DEBUG: adding host node2 to group kube_control_plane
DEBUG: adding host node3 to group kube_control_plane

DEBUG: adding host node1 to group kube_node
DEBUG: adding host node2 to group kube_node
DEBUG: adding host node3 to group kube_node
DEBUG: adding host node4 to group kube_node

Verification of Generated File

• Open the hosts.yaml file in VI (Visual Editor) or nano
• Update the kube_control_plane category if needed with full list of hosts that should be master nodes
• Ensure you have either 1 or 3 Kubernetes control plane nodes under kube_control_plane. If 2 are listed, change that to 1 or 3, depending on whether you want Kubernetes be Highly Available.
• Ensure you have only control plane nodes listed under etcd. If you would like to review additional best practices for etcd, please review this guide.
• For additional details regarding hosts.yaml best practices and example configurations, review this guide.

vi ~/kubespray/inventory/akash/hosts.yaml

Example hosts.yaml File

• Additional hosts.yaml examples, based on different Kubernetes cluster topologies, may be found here

all:
  hosts:
    node1:
      ansible_host: 10.0.10.136
      ip: 10.0.10.136
      access_ip: 10.0.10.136
    node2:
      ansible_host: 10.0.10.239
      ip: 10.0.10.239
      access_ip: 10.0.10.239
    node3:
      ansible_host: 10.0.10.253
      ip: 10.0.10.253
      access_ip: 10.0.10.253
    node4:
      ansible_host: 10.0.10.9
      ip: 10.0.10.9
      access_ip: 10.0.10.9
  children:
    kube_control_plane:
      hosts:
        node1:
        node2:
        node3:
    kube_node:
      hosts:
        node1:
        node2:
        node3:
        node4:
    etcd:
      hosts:
        node1:
        node2:
        node3:
    k8s_cluster:
      children:
        kube_control_plane:
        kube_node:
    calico_rr:
      hosts: {}

Manual Edits/Insertions of the hosts.yaml Inventory File

• Open the hosts.yaml file in VI (Visual Editor) or nano

vi ~/kubespray/inventory/akash/hosts.yaml

• Within the YAML file’s “all” stanza and prior to the “hosts” sub-stanza level - insert the following vars stanza

vars:
  ansible_user: root

• The hosts.yaml file should look like this once finished

all:
  vars:
    ansible_user: root
  hosts:
    node1:
      ansible_host: 10.0.10.136
      ip: 10.0.10.136
      access_ip: 10.0.10.136
    node2:
      ansible_host: 10.0.10.239
      ip: 10.0.10.239
      access_ip: 10.0.10.239
    node3:
      ansible_host: 10.0.10.253
      ip: 10.0.10.253
      access_ip: 10.0.10.253
    node4:
      ansible_host: 10.0.10.9
      ip: 10.0.10.9
      access_ip: 10.0.10.9
  children:
    kube_control_plane:
      hosts:
        node1:
        node2:
        node3:
    kube_node:
      hosts:
        node1:
        node2:
        node3:
        node4:
    etcd:
      hosts:
        node1:
        node2:
        node3:
    k8s_cluster:
      children:
        kube_control_plane:
        kube_node:
    calico_rr:
      hosts: {}

Additional Kubespray Documentation

Use these resources for a more through understanding of Kubespray and for troubleshooting purposes

• Adding/replacing a node
• Upgrading Kubernetes in Kubespray