List of components used in this project:

Component	Description	Cf.
CentOS 7	Operating System	https://centos.org
Docker	Container Run-time	https://docker.com
Kubernetes	Container Orchestration	https://kubernetes.io
Helm	Kubernetes package manager	https://helm.sh

Kubernetes Example

File	Description
var/aliases/k8s.sh	Shell functions for Kubernetes

Use the following shell functions:

• k8s-vm-image() - Kickstart a CentOS VM image with Kubernetes prerequisites from var/centos/7/kickstart.cfg
• k8s-upload-specs() - Upload Kubernetes specs from var/specs

The shell script ↴ source_me.sh adds the tool-chain in this repository to your shell environment:

source source_me.sh

This example uses a virtual machine setup with vm-tools:

# Kickstart a CentOS VM image and apply a basic configuration
k8s-vm-image
# list the VM image directory
ls -1 $VM_IMAGE_PATH/$K8S_VM_IMAGE

Deployment

If you already have a way to configure hosting resources, use kubeadm to bring up a cluster with a single command per machine.

https://kubernetes.io/docs/setup/pick-right-solution/#custom-solutions

kubeadm gets a minimum viable cluster up and running, cares only about bootstrapping, not about provisioning machines.

• Supports life-cycle mangement (update, downgrade, monitoring)
• Expected to be used by configuration management systems

https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm

Master

# start a VM instance for the admin node
vm shadow $K8S_VM_IMAGE $K8S_ADMIN_NODE
# adjust the VM instance configuration
vm config $K8S_ADMIN_NODE --vcpu 2 --memory 2
# restart the VM instance with the new configuration
vm redefine $K8S_ADMIN_NODE
# initialize Kubernetes
vm exec $K8S_ADMIN_NODE --root -- \
        kubeadm init --pod-network-cidr=192.168.0.0/16
# make the devops user Kubernetes admin
vm exec $K8S_ADMIN_NODE -- '
        mkdir -p $HOME/.kube
        sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
        sudo chown $(id -u):$(id -g) $HOME/.kube/config
'

This example uses the kube-router [kuber] as pod network.

# setup the pod network
vm exec $K8S_ADMIN_NODE -- \
        kubectl apply -f https://raw.githubusercontent.com/cloudnativelabs/kube-router/master/daemonset/kubeadm-kuberouter.yaml

Nodes

Add more VM instances to create a Kubernetes cluster

# list of VM instances to use
NODES=lxcc0[2-3],lxb00[1-4]
# start all cluster nodes
vn shadow $K8S_VM_IMAGE

Connect nodes with the cluster

# get the join command
vm exec $K8S_ADMIN_NODE --root -- \
        kubeadm token create --print-join-command | tr -s ' '
# execute the join command on all nodes
vn exec -r "kubeadm join 10.1.1.9:6443 --token...."

Install the Kubernetes Dashboard [webui] on the master node:

vm exec $K8S_ADMIN_NODE "
        kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/master/aio/deploy/recommended/kubernetes-dashboard.yaml
        sudo kubectl proxy --address=\$(hostname -i) -p 8001 --accept-hosts='^*$'
"

Usage

Copy object specs from var/specs to the master node, and login

k8s-upload-specs && vm exec $K8S_ADMIN_NODE

Basic command line:

kubectl get nodes               # list cluster nodes
kubectl get events              # list cluster events
kubectl get services            # list service running on the cluster
kubectl get pods                # list pods in the cluster
kubectl get pods --namespace=kube-system
kubectl get pods --all-namespaces
kubectl describe pod <name>     # show details for a given pod

References

[webui] Web-based Kubernetes user interface
https://kubernetes.io/docs/tasks/access-application-cluster/web-ui-dashboard/

[kuber] Kube-router for Kubernetes networking
https://github.com/cloudnativelabs/kube-router

[deploy] Kubernetes Deployments
https://kubernetes.io/docs/concepts/workloads/controllers/deployment