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Chapter 5

  1. To create a service run
$ kubectl create -f kubapp-svc.yaml
  1. To list the services run:
$ kubectl get svc
  1. To remotely execute command in running container run:
$ kubectl exec <name_of_the_pod> -- curl -s http://address
  1. To configure session affinity on the service run:
$ kubectl create -f kubapp-svc-affinity.yaml
$ kubectl exec <name_of_the_pod> -- curl -s http://address

Note: you will hit the same pod

  1. Accessing the bash shell in a container inside a pod
$ kubectl exec -it <pods name> bash

Example:

  $ kubectl exec -it kubapp-ds72z bash
  root@kubapp-ds72z:/# curl http://kubapp
  You've hit kubapp-ds72z
  root@kubapp-ds72z:/# curl http://kubapp.default
  You've hit kubapp-ds72z
  root@kubapp-ds72z:/# cat /etc/resolv.conf
  search default.svc.cluster.local svc.cluster.local cluster.local
  nameserver 10.0.0.10
  options ndots:5
  1. Create endpoints and service separately:
$ kubectl create -f kubapp-endpoints.yaml
$ kubectl create -f kubapp-manual-svc-endpoint.yaml

Check service' functionality via:

$ kubectl exec <name of the pod> -- curl http://ip_of_the_service

  1. An example of the ExternalName service can be found here

  2. An example of exposing service externally by setting an external IP address on it can be found here

  3. An example of a NodePort service can be found here

  4. An example of a LoadBalancer service can be found here

If you wanna test it with Minikube, run

$ minikube service <name of the service>
  1. For the Ingress testing, activate Ingress addon in minikube first:
$ minikube addons enable ingress

then create the Ingress service (example is here)

$ kubectl create -f ingress.yaml

check that Ingress service was created successfully

$ kubectl get ing
NAME             HOSTS                ADDRESS          PORTS     AGE
kubapp-ingress   kubapp.example.com   192.168.99.100   80        18h

check Ingress functionality:

$ curl 192.168.99.100

Readiness Probes

Edit RC settings:

$ kubectl edit rc kubapp

and add something like:

spec:
  containers:
  - name: kubapp
    image: evalle/kubapp
    readinessProbe:
      exec:
        command:
        - ls
        - /var/ready

then delete your previos pods and check pods again:

$ kubectl delete po --all
$ kubectl get po
NAME           READY     STATUS    RESTARTS   AGE
kubapp-7hfz8   0/1       Running   0          9m
kubapp-fvhv7   0/1       Running   0          9m
kubapp-lvlxr   0/1       Running   0          9m

To make one of the pods ready run

$ kubectl exec kubapp-7hfz8 -- touch /var/ready

Check pod's status again

$ kubectl get po 
NAME           READY     STATUS    RESTARTS   AGE
kubapp-7hfz8   1/1       Running   0          12m
kubapp-fvhv7   0/1       Running   0          12m
kubapp-lvlxr   0/1       Running   0          12m

Running a pod without writing a YAML manifest

$ kubectl run dnsutils --image=tutum/dnsutils --generator=run-pod/v1 \
  --command -- sleep infinity
pod "dnsutils" created