Kubernetes Docker process inside pod - docker

Question

I have a Docker image with the CMD to run a Java application.
This application is being deployed to container into Kubernetes. Since, I am deploying it as a Docker image, I was expecting it as running as a Docker process. So, I just logged into the pods and was trying "docker ps".
But, I was surprised that it is running as a Java process and not as a docker process. I am able to see the process by "ps -ef"
I am confused, how does it work internally?

Answer 1

As others stated, Kubernetes uses docker internally to deploy the containers. To explain in detail consider the cluster which has 4 nodes, 1 master and 3 slaves.
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
******.mylabserver.com Ready master 13d v1.10.5
******.mylabserver.com Ready <none> 13d v1.10.5
******.mylabserver.com Ready <none> 13d v1.10.5
******.mylabserver.com Ready <none> 13d v1.10.5
I am deploying a pod with nignx docker image.
$ cat pod-nginx.yml
apiVersion: v1
kind: Pod
metadata:
name: alpine
namespace: default
spec:
containers:
- name: alpine
image: alpine
command:
- sleep
- "3600"
imagePullPolicy: IfNotPresent
restartPolicy: Always
You can get the status of the pod as below:
$ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE
alpine 1/1 Running 0 21s 10.244.3.4 ******.mylabserver.com
Kube-scheduler will schedule the pod on one of the available nodes.
Now the pod is deployed to a server, where you can login to that particular server and find the information that you are looking for.
root#******:/home/user# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS
PORTS NAMES
6486de4410ad alpine#sha256:e1871801d30885a610511c867de0d6baca7ed4e6a2573d506bbec7fd3b03873f "sleep 3600" 58 seconds ago Up 57 seconds
k8s_alpine_alpine_default_2e2b3016-79c8-11e8-aaab-
Run the docker exec command in that server to see the process running inside.
root#******:/home/user# docker exec -it 6486de4410ad /bin/sh
/ # ps -eaf
PID USER TIME COMMAND
1 root 0:00 sleep 3600
7 root 0:00 /bin/sh
11 root 0:00 ps -eaf
/ #
https://kubernetes.io/docs/home/- this can give you more info about pods and how deployments happen with pods/containers.
Hope this helps.

Answer 2

Kubernetes using the yaml file that the user provides, deploys a pod (smaller unit of Kubernetes deployment) with one or more containers in it.
You can access the containers inside the pod using the kubectl tool.
For example, in case your pod has one container you can open a shell inside it:
kubectl exec -ti <pod-name> -n <pod-namespace> bash
Through this shell, you can run ps commands and your output will be the isolated processes running inside your container.
In case you want to observe the Docker containers which Kubernetes has deployed in a node, you can connect to that node and run docker ps commands.