Kubernetes examples

Prerequisites

• Kubernetes
• Minikube

Nomenclatura

• pod -> "Point Od Delivery". E' l'unica atomica di elaborazione di kubernetes. Può contenere uno o più container e risorse (tipo volumi)
• service -> Permettono di far/poter dialogare i pod con l'esterno o con altri nodi

Tipi di service

A Service in Kubernetes is an abstraction which defines a logical set of Pods and a policy by which to access them

• ClusterIp -> Exposes the Service on an internal IP in the cluster. This type makes the Service only reachable from within the cluster
• NodePort -> Exposes the Service on the same port of each selected Node in the cluster using NAT. Makes a Service accessible from outside the cluster using :. Superset of ClusterIP.
• LoadBalancer -> Creates an external load balancer in the current cloud (if supported) and assigns a fixed, external IP to the Service
• ExternalName -> Maps the Service to the contents of the externalName field (e.g. foo.bar.example.com), by returning a CNAME record with its value

Comandi

• minikube start -> it allows to start minikube
• kubectl cluster-info -> Cluster's info
• kubectl get nodes -> Get all the nodes of the cluster
• kubectl get pods -> Get all the pods of the cluster
• kubectl describe pods -> Get details of the pods
• kubectl proxy -> ?
• kubectl exec <podName> -- env -> Execute "env" command on the selected pod
• kubectl exec -it <podName> -- bash -> Esegue il comando bash sul pod indicato
• kubectl wait --for=condition=ready pod -l app=inventory -> aspettare la readiness del pod inventory
• kubectl create configmap sys-app-name --from-literal name=my-system -> creare un configMap. Una mappa chiave/valore in chiaro
• kubectl create secret generic sys-app-credentials --from-literal username=bob --from-literal password=bobpwd -> Mappa chiave/valore cifrata (con cosa?)
• kubectl replace --force -f kubernetes.yaml -> DOVREBBE rimpiazzare
• kubectl get --watch pods -> Boh
• kubectl get deployment mysql -o yaml -> Allows to get the yaml of the selected kind