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kubernetes for beginners

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Dominique Dumont

A small introduction to get started on Kubernetes as a user. This explains the main concepts like pod, deployment and services and gives some hints to help you use kubectl command. These slides were presented in Grenoble Docker meetup in November 2017.

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Kubernetes for beginners Dominique Dumont Debian Project Nov 2017 Dominique Dumont k8s for beginners
Why Kubernetes ? docker is nice, but containers tend to multiply needs to manage / orchestrate them need to handle network setup between all these images (micro services beget mega network) handle ”smooth” updates Solutions: docker swarm, Kubernetes (other ?) Dominique Dumont k8s for beginners
New concepts and terminology New concepts compared to docker: pod: a group of containers that provide a functionality node: a worker machine (or VM). old term: minion deployment: controls lifecycle of a group of pods (rolling upgrades) service: deployment frontend. Configure load-balancer and external access Dominique Dumont k8s for beginners
Pod in more details A pod is a group of containers: share the same IP address. Must set different listening ports on each container declare external ports that are mapped to container ports can mount shared volumes can be configured with ConfigMaps and Secrets through environment variables or files Pod Container Dominique Dumont k8s for beginners
Deployment A deployment with its ReplicaSet is a group of pods (of the same kind): ReplicaSet ensures failover manage liveness and readiness probes manage rolling upgrades Deployment Pod Container Replica controler Pod Container Pod Container Dominique Dumont k8s for beginners
Services A Service is the external front end of a Deployment: manage load balancing between the pod instances of a Deployment map port between external port (e.g. 80) and container ports (e.g. 8080) Deployment Service Pod Container Replica controler Balancer Load Pod Container Pod Container Dominique Dumont k8s for beginners
Pod example Inside a deployment: spec: containers: - name: my-contained-server image: my-contained-image:latest imagePullPolicy: Always livenessProbe: httpGet: { path: /ping, scheme: HTTPS } initialDelaySeconds: 15 periodSeconds: 10 timeoutSeconds: 3 readinessProbe: # similar volumeMounts: - name: shared-stuff mountPath: "/var/lib/shared" - name: side-car image: side-car:latest Dominique Dumont k8s for beginners
Deployment example apiVersion: extensions/v1beta1 kind: Deployment metadata: name: super-duper-server spec: replicas: 1 strategy: type: RollingUpdate rollingUpdate: { maxUnavailable: 0, maxSurge: 2 } template: metadata: name: super-mega-server labels: # used by Service my-server: mega-server spec: containers: [ pod specification ] Dominique Dumont k8s for beginners
Service example apiVersion: v1 kind: Service metadata: labels: name: my-super-service name: super-service spec: ports: - {port: 443, targetPort: 8090} type: LoadBalancer # load balancer target selector: my-server: mega-server Dominique Dumont k8s for beginners
Config namespace: isolated sandboxes within a cluster. Great for tests context: associate cluster and namespace Commands: $ kubectl config get-contexts CURRENT NAME CLUSTER AUTHINFO NAMESPACE minikube minikube minikube * dev-us-west-2 k-uw2.xxx.com us-west-2-user dod-dev-us-w2 k-uw2.xxx.com us-west-2-user dod-playground $ kubectl config use-context dod-dev-us-w2 $ kubectl config set-context ... Dominique Dumont k8s for beginners
Config namespace: isolated sandboxes within a cluster. Great for tests context: associate cluster and namespace Commands: $ kubectl config get-contexts CURRENT NAME CLUSTER AUTHINFO NAMESPACE minikube minikube minikube * dev-us-west-2 k-uw2.xxx.com us-west-2-user dod-dev-us-w2 k-uw2.xxx.com us-west-2-user dod-playground $ kubectl config use-context dod-dev-us-w2 $ kubectl config set-context ... Dominique Dumont k8s for beginners
Sending config Create Deployment or services: $ kubectl apply -f .../file.yaml Update a deployment: $ kubectl replace -f .../file.yaml Dominique Dumont k8s for beginners
Kubernetes console If enabled by admin, cluster can be controled with a web interface $ kubectl proxy Starting to serve on 127.0.0.1:8001 Dominique Dumont k8s for beginners
Connecting to a container In enabled by sys admin, you can connect to a container in the cluster: $ kubectl exec --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs -c omg date Thu Oct 26 18:01:58 UTC 2017 $ kubectl exec --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs -c omg -ti sh / # Dominique Dumont k8s for beginners
Getting logs Getting log may be the only way to get debug information. To get log from a container: $ kubectl logs --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs omg --since 10s $ kubectl logs --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs omg -f Logs from many pods Problems can occur in any deployed pod. You need to setup a log aggregator (kibana...) Dominique Dumont k8s for beginners
Auto-completion Typings all these options and arguments is tedious and error prone. Add this in your ~/.bashrc KFILE=/tmp/kube-completion if [ -f /usr/local/bin/kubectl ]; then /usr/local/bin/kubectl completion bash > $KFILE . $KFILE rm $KFILE fi Dominique Dumont k8s for beginners
Other tools You can have your prompt display the current environment: For a command prompt that shows your context, add this in your ~/.bashrc NORMAL="[033[00m]" YELLOW="[e[1;33m]" __kube_prompt() { # Get current context CONTEXT=$(perl -nE ’print if s/current-context: //;’ ~/.kube/config) if [[ -n "$CONTEXT" ]] then echo "$YELLOW(k8s: ${CONTEXT})$NORMALn" fi } PS1=$(__kube_prompt)’${USER}@${HOSTNAME}:${PWD/$HOME/~}$ ’ Dominique Dumont k8s for beginners
Other tools You can have your prompt display the current environment: For a command prompt that shows your context, add this in your ~/.bashrc NORMAL="[033[00m]" YELLOW="[e[1;33m]" __kube_prompt() { # Get current context CONTEXT=$(perl -nE ’print if s/current-context: //;’ ~/.kube/config) if [[ -n "$CONTEXT" ]] then echo "$YELLOW(k8s: ${CONTEXT})$NORMALn" fi } PS1=$(__kube_prompt)’${USER}@${HOSTNAME}:${PWD/$HOME/~}$ ’ Dominique Dumont k8s for beginners
MiniKube MiniKube lets you play with kubernetes your laptop. Can use kubernetes console to control your minikube Note: docker commands deal with a docker daemon running in minikube, not with your ”regular” docker daemon Dominique Dumont k8s for beginners

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kubernetes for beginners

  • 1. Kubernetes for beginners Dominique Dumont Debian Project Nov 2017 Dominique Dumont k8s for beginners
  • 2. Why Kubernetes ? docker is nice, but containers tend to multiply needs to manage / orchestrate them need to handle network setup between all these images (micro services beget mega network) handle ”smooth” updates Solutions: docker swarm, Kubernetes (other ?) Dominique Dumont k8s for beginners
  • 3. New concepts and terminology New concepts compared to docker: pod: a group of containers that provide a functionality node: a worker machine (or VM). old term: minion deployment: controls lifecycle of a group of pods (rolling upgrades) service: deployment frontend. Configure load-balancer and external access Dominique Dumont k8s for beginners
  • 4. Pod in more details A pod is a group of containers: share the same IP address. Must set different listening ports on each container declare external ports that are mapped to container ports can mount shared volumes can be configured with ConfigMaps and Secrets through environment variables or files Pod Container Dominique Dumont k8s for beginners
  • 5. Deployment A deployment with its ReplicaSet is a group of pods (of the same kind): ReplicaSet ensures failover manage liveness and readiness probes manage rolling upgrades Deployment Pod Container Replica controler Pod Container Pod Container Dominique Dumont k8s for beginners
  • 6. Services A Service is the external front end of a Deployment: manage load balancing between the pod instances of a Deployment map port between external port (e.g. 80) and container ports (e.g. 8080) Deployment Service Pod Container Replica controler Balancer Load Pod Container Pod Container Dominique Dumont k8s for beginners
  • 7. Pod example Inside a deployment: spec: containers: - name: my-contained-server image: my-contained-image:latest imagePullPolicy: Always livenessProbe: httpGet: { path: /ping, scheme: HTTPS } initialDelaySeconds: 15 periodSeconds: 10 timeoutSeconds: 3 readinessProbe: # similar volumeMounts: - name: shared-stuff mountPath: "/var/lib/shared" - name: side-car image: side-car:latest Dominique Dumont k8s for beginners
  • 8. Deployment example apiVersion: extensions/v1beta1 kind: Deployment metadata: name: super-duper-server spec: replicas: 1 strategy: type: RollingUpdate rollingUpdate: { maxUnavailable: 0, maxSurge: 2 } template: metadata: name: super-mega-server labels: # used by Service my-server: mega-server spec: containers: [ pod specification ] Dominique Dumont k8s for beginners
  • 9. Service example apiVersion: v1 kind: Service metadata: labels: name: my-super-service name: super-service spec: ports: - {port: 443, targetPort: 8090} type: LoadBalancer # load balancer target selector: my-server: mega-server Dominique Dumont k8s for beginners
  • 10. Config namespace: isolated sandboxes within a cluster. Great for tests context: associate cluster and namespace Commands: $ kubectl config get-contexts CURRENT NAME CLUSTER AUTHINFO NAMESPACE minikube minikube minikube * dev-us-west-2 k-uw2.xxx.com us-west-2-user dod-dev-us-w2 k-uw2.xxx.com us-west-2-user dod-playground $ kubectl config use-context dod-dev-us-w2 $ kubectl config set-context ... Dominique Dumont k8s for beginners
  • 11. Config namespace: isolated sandboxes within a cluster. Great for tests context: associate cluster and namespace Commands: $ kubectl config get-contexts CURRENT NAME CLUSTER AUTHINFO NAMESPACE minikube minikube minikube * dev-us-west-2 k-uw2.xxx.com us-west-2-user dod-dev-us-w2 k-uw2.xxx.com us-west-2-user dod-playground $ kubectl config use-context dod-dev-us-w2 $ kubectl config set-context ... Dominique Dumont k8s for beginners
  • 12. Sending config Create Deployment or services: $ kubectl apply -f .../file.yaml Update a deployment: $ kubectl replace -f .../file.yaml Dominique Dumont k8s for beginners
  • 13. Kubernetes console If enabled by admin, cluster can be controled with a web interface $ kubectl proxy Starting to serve on 127.0.0.1:8001 Dominique Dumont k8s for beginners
  • 14. Connecting to a container In enabled by sys admin, you can connect to a container in the cluster: $ kubectl exec --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs -c omg date Thu Oct 26 18:01:58 UTC 2017 $ kubectl exec --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs -c omg -ti sh / # Dominique Dumont k8s for beginners
  • 15. Getting logs Getting log may be the only way to get debug information. To get log from a container: $ kubectl logs --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs omg --since 10s $ kubectl logs --namespace francois-sandbox fco-mode1-n9r-812209105-9wfcs omg -f Logs from many pods Problems can occur in any deployed pod. You need to setup a log aggregator (kibana...) Dominique Dumont k8s for beginners
  • 16. Auto-completion Typings all these options and arguments is tedious and error prone. Add this in your ~/.bashrc KFILE=/tmp/kube-completion if [ -f /usr/local/bin/kubectl ]; then /usr/local/bin/kubectl completion bash > $KFILE . $KFILE rm $KFILE fi Dominique Dumont k8s for beginners
  • 17. Other tools You can have your prompt display the current environment: For a command prompt that shows your context, add this in your ~/.bashrc NORMAL="[033[00m]" YELLOW="[e[1;33m]" __kube_prompt() { # Get current context CONTEXT=$(perl -nE ’print if s/current-context: //;’ ~/.kube/config) if [[ -n "$CONTEXT" ]] then echo "$YELLOW(k8s: ${CONTEXT})$NORMALn" fi } PS1=$(__kube_prompt)’${USER}@${HOSTNAME}:${PWD/$HOME/~}$ ’ Dominique Dumont k8s for beginners
  • 18. Other tools You can have your prompt display the current environment: For a command prompt that shows your context, add this in your ~/.bashrc NORMAL="[033[00m]" YELLOW="[e[1;33m]" __kube_prompt() { # Get current context CONTEXT=$(perl -nE ’print if s/current-context: //;’ ~/.kube/config) if [[ -n "$CONTEXT" ]] then echo "$YELLOW(k8s: ${CONTEXT})$NORMALn" fi } PS1=$(__kube_prompt)’${USER}@${HOSTNAME}:${PWD/$HOME/~}$ ’ Dominique Dumont k8s for beginners
  • 19. MiniKube MiniKube lets you play with kubernetes your laptop. Can use kubernetes console to control your minikube Note: docker commands deal with a docker daemon running in minikube, not with your ”regular” docker daemon Dominique Dumont k8s for beginners