Additional K8s Resources

Kubespray inventory.ini Examples

inventory.ini Overview

The Kubespray inventory.ini file is composed of several key groups:

• kube_control_plane: list of servers where Kubernetes control plane components (apiserver, scheduler, controller) will run
• kube_node: list of Kubernetes nodes where the pods will run
• etcd: list of servers to compose the etcd server.
• etcd
  : typically includes kube_control_plane for stacked etcd topology

Please following these links for YAML examples and depending on your preferred topology:

• Kubespray inventory.ini Examples
  • Inventory File Overview
• All-In-One Node
  • Topology
  • Pros
  • Cons
  • Example Inventory File
• One Control Plane Node with Multiple Worker Nodes
  • Topology
  • Pros
  • Cons
  • Example Inventory File
• Multiple Control Plane Nodes with Multiple Worker Nodes
  • Topology
  • Pros
  • Cons
  • Example Inventory File

All-In-One Node

Topology

• node1 - is a single control plane + etcd node
• node1 - is also running the pods

Pros

• Easy to manage

Cons

• Single point of failure for K8s/etcd/pods;
• Thinner security barrier since pods are running on control plane / etcd nodes;

Example Inventory File

[kube_control_plane]
node1 ansible_host=95.54.0.12  # ip=10.3.0.1 etcd_member_name=etcd1

[etcd:children]
kube_control_plane

[kube_node]
node1 ansible_host=95.54.0.12  # ip=10.3.0.1

One Control Plane Node with Multiple Worker Nodes

Topology

• node1 - single control plane + etcd node
• node2..N - kube nodes where the pods will run

Pros

• Better security barrier since pods aren’t running on control plane / etcd nodes
• Can scale by adding either more control plane nodes or worker nodes

Cons

• Single point of failure only for K8s/etcd but not the pods

Example Inventory File

[kube_control_plane]
node1 ansible_host=95.54.0.12  # ip=10.3.0.1 etcd_member_name=etcd1

[etcd:children]
kube_control_plane

[kube_node]
node2 ansible_host=95.54.0.13  # ip=10.3.0.2
node3 ansible_host=95.54.0.14  # ip=10.3.0.3

Multiple Control Plane Nodes with Multiple Worker Nodes

Topology

• Nodes 1-3 - the control plane + etcd nodes; (This makes K8s High Available)
• Node 4-N - the kube nodes on which the Pods will run

Pros

• Highly available control plane / etcd
• Better security barrier since pods aren’t running on control plane / etcd nodes
• Can scale by adding either more control plane nodes or worker nodes

Cons

• More complex environment makes its configuration & management more difficult

Example Inventory File

[kube_control_plane]
node1 ansible_host=95.54.0.12  # ip=10.3.0.1 etcd_member_name=etcd1
node2 ansible_host=95.54.0.13  # ip=10.3.0.2 etcd_member_name=etcd2
node3 ansible_host=95.54.0.14  # ip=10.3.0.3 etcd_member_name=etcd3

[etcd:children]
kube_control_plane

[kube_node]
node4 ansible_host=95.54.0.15  # ip=10.3.0.4
node5 ansible_host=95.54.0.16  # ip=10.3.0.5
node6 ansible_host=95.54.0.17  # ip=10.3.0.6