Those are the slides that were used to give an introduction to Kubernetes at the Nardoz Berlin Meetup on the 2018-06-28.

1. Introduction to Kubernetes
2018-06-28 - Nardoz Berlin
Raffaele Di Fazio - @x0rg

2. Agenda
● What is Kubernetes?
● Architecture
● Main concepts with hands on examples

3. Pre-check: who doesn’t know what a container is?
● “Containers are an abstraction at the app layer that packages code and
dependencies together.”
● They don’t really exist…
○ CGroups
○ Namespaces
● Docker: nice UX on top of running isolated self contained applications
● Immutable artifacts

4. Kubernetes
● Open Source container orchestration system
● Inspired by Borg, Omega, Mesos
● Started at Google, donated to CNCF

5. The history so far

6. The OSS history so far

7. Kubernetes (April 2018)

8. Kubernetes (June 2018)

9. Kubernetes Architecture

10. Kubernetes architecture
API Server
Controller
manager
Scheduler
etcd
Worker Node (VM)
Worker Node (VM)
Kubelet
Kubelet
nginx
nginx
nginx
kube-proxy
kube-proxy

11. Kubernetes: running an application
API Server

12. Kubernetes: running an application
API Server
Deployment
yaml

13. Kubernetes: running an application
API Server
Deployment
yaml
Scheduler

14. Kubernetes: running an application
API Server
Kubelet
Deployment
yaml
Scheduler

15. Kubernetes: running an application
API Server
Kubelet
Deployment
yaml
Scheduler
Controller
manager

16. Kubernetes: running an application
https://jvns.ca/blog/2017/07/27/how-does-the-kubernetes-scheduler-work/

17. Main Concepts

18. Pod
● The “scheduling unit” of Kubernetes
● Doesn’t get restarted when terminates (can be one shot)
● Pods are collection of one or more containers

19. Pod in one picture
Instance (node 1)
Pod 1 Pod 2
Container 1
Container 2
Container 3
Container 4
Instance (node 2)
Pod 3 Pod 4
Container 5
Container 6
Container 7
Container 8

20. Pod
● Containers in the same pod are guaranteed to be on the same host
● Containers in the same pod can talk via localhost
● Every pod gets a dedicated virtual IP address in the “pod network”
● Analogy: your application instance in AWS

21. Pod
apiVersion: v1
kind: Pod
metadata:
name: pod-example
spec:
containers:
- name: ubuntu
image: ubuntu:trusty
command: ["echo"]
args: ["Hello World"]

22. Kubernetes patterns: reconciler
● Controllers in Kubernetes are built by implementing the reconciler pattern
○ GetCurrentState()
○ GetDesiredState()
○ Apply()
● Controller manager: enforces deployment replicas

23. Deployment
● Defines a single application in Kubernetes handled by the system
● Analogy: Autoscaling Group in AWS
○ You set the desired state, Kubernetes enforces it

24. Deployment
apiVersion: apps/v1beta1
kind: Deployment
metadata:
# Unique key of the Deploymentinstance
name: deployment-example
spec:
# 3 Pods should exist at all times.
replicas: 3
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
# Run this image
image: nginx:1.10

25. Demo

26. Kubernetes’ overlay networking
● Every pod gets its own IP from a dedicated overlay network
○ Solves the problem of port mapping
○ No NAT needed
● Implemented via software solution (flannel, calico, weave, …)
● Iptables everywhere!

27. Service
● Defines how to to reach your app
● Internal Service: cluster valid IP + DNS
● Can use service as Service Discovery (DNS based)
● Label based selection of targets

28. Service
kind: Service
apiVersion: v1
metadata:
name: service-example
spec:
ports:
- name: http
port: 80
targetPort: 80
selector:
app: nginx
type: LoadBalancer

29. Demo

30. ConfigMap & Secrets
● Object containing a K/V storage for configuration purposes
● Can be “mounted”:
○ File
○ Environment variable
● Keep your configuration for the app generic and customize via ConfigMap
● Secret: like a ConfigMap with hidden fields :-)

31. DaemonSet
● Run one instance of the pod for each node of the cluster
● Useful mostly for cluster ops
● Ideal for “system agents”

32. Daemonset
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
name: daemonset-example
spec:
template:
metadata:
labels:
app: daemonset-example
spec:
containers:
- name: daemonset-example
image: ubuntu:trusty
command:
- /bin/sh
args:
- -c
- >-
while [ true ]; do
echo "DaemonSet running on $(hostname)" ; sleep 10 ;
done

33. Demo

34. A lot more to cover
● StatefulSets
● ServiceAccounts
● Namespaces
● Quotas
● ….
● Check out: https://kubernetes.io

35. If you want to know more
https://www.youtube.com/watch?v=WwBdNXt6wO4

36. If you want to know more
https://www.youtube.com/watch?v=9YYeE-bMWv8&list=PLvmPtYZtoXOENHJiAQc6HmV2jmuexKfrJ

37. If you want to know more
https://www.youtube.com/watch?v=w34txLmpEuM

38. Thank you!
Raffaele Di Fazio - @x0rg