enkron/local-kubernetes-lab

networking

The network infrastructure will be used by kvm vms with libvirt (virsh)

ref: https://www.enkron.org/pub/entries/2.html

prerequisites

first check kvm (kernel-based virtual machine for Linux on x86) is enabled in system

kvm-ok

sudo apt update
sudo apt install -y libvirt-daemon-system virtinst

check qemu emulator is installed

qemu-system-x86_64 --version

cloud image

Cloud images use cloud-init method for instance initialisation (eg. ubuntu cloud images archive https://cloud-images.ubuntu.com)

curl -fLO# http://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img

user-data file contains instructions for bootstrapping kubernetes toolchains along with dependencies like containerd or cni plugins.

NOTE: all package versions are currently hardcoded into the file, so need to pay attention to maintenance
NOTE: change $SSH_PUBKEY variable to actual public key

kubernetes toolchains

kubeadm: bootstrap a cluster. Should be installed on all the hosts,
kubelet: component that runs on all of machines in a cluster and does
things like starting pods and containers,
kubectl: command line utility to talk to a cluster.

NOTE: kubelet won't work with a swap file

cluster initialization

After installing each component to the control plane host cluster could initialized with the following command:

sudo kubeadm init

To start using the cluster run the following commands:

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

deploy a pod network to the cluster

https://kubernetes.io/docs/concepts/cluster-administration/addons/

kubectl apply -f <POD_NETWORK>.yaml

for example:

kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml

This command deploys weave net that connects docker containers across multiple hosts and enables their automatic discovery

join nodes to the cluster

kubeadm token create --print-join-command

use an output from the command above to join a worker node to the cluster

virsh tool commmands

virsh is a cli for virsh guest domains

list vms

virsh list --all

get vms addresses

virsh net-dhcp-leases --network default

shutdown vm gracefully

virsh shutdown <VM_TAG>

start a vm

virsh start --domain <VM_TAG>