My few cents on the subject. Assuming that kubectl is working then the closest command that would be equivalent to the docker command that you mentioned in your question, would be something like this.

$ kubectl run ubuntu --image=ubuntu --restart=Never --command sleep infinity

Above command will create a single Pod in default namespace and, it will execute sleep command with infinity argument -this way you will have a process that runs in foreground keeping container alive.

Afterwords, you can interact with Pod by running kubectl exec command.

$ kubectl exec ubuntu -it -- bash

This technique is very useful for creating a Pod resource and ad-hoc debugging.

Containers are meant to run to completion. You need to provide your container with a task that will never finish. Something like this should work:

apiVersion: v1
kind: Pod
metadata:
  name: ubuntu
spec:
  containers:
  - name: ubuntu
    image: ubuntu:latest
    # Just spin & wait forever
    command: [ "/bin/bash", "-c", "--" ]
    args: [ "while true; do sleep 30; done;" ]

You could use this CMD in your Dockerfile:

CMD exec /bin/bash -c "trap : TERM INT; sleep infinity & wait"

This will keep your container alive until it is told to stop. Using trap and wait will make your container react immediately to a stop request. Without trap/wait stopping will take a few seconds.

For busybox based images (used in alpine based images) sleep does not know about the infinity argument. This workaround gives you the same immediate response to a docker stop like in the above example:

CMD exec /bin/sh -c "trap : TERM INT; (while true; do sleep 1000; done) & wait"

1. In your Dockerfile use this command:

   CMD ["sh", "-c", "tail -f /dev/null"]

2. Build your docker image.

3. Push it to your cluster or similar, just to make sure the image it's available.

4. kubectl run debug-container -it --image=<your-image>

In order to keep a POD running the POD should to be performing certain task, otherwise Kubernetes will find it unnecessary, therefore it exits. There are many ways to keep a POD running.

I have faced similar problems when I needed a POD just to run continuously without doing anything. The following are the two ways those worked for me:

1. Firing up a sleep command while running the container.
2. Running an infinite loop inside the container.

Although the first option is easier than the second one and may suffice the requirement, it is not the best option. As, there is a limit as far as the number of seconds you are going to assign in the sleep command. But a container with infinite loop running inside it never exits.

However, I will describe both the ways(Considering you are running busybox container):

1. Sleep Command

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  labels:
    app: busybox
spec:
  containers:
  - name: busybox
    image: busybox
    ports:
    - containerPort: 80
    command: ["/bin/sh", "-ec", "sleep 1000"]
  nodeSelector:
    beta.kubernetes.io/os: linux

2. Infinite Loop

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  labels:
    app: busybox
spec:
  containers:
  - name: busybox
    image: busybox
    ports:
    - containerPort: 80
    command: ["/bin/sh", "-ec", "while :; do echo '.'; sleep 5 ; done"]
  nodeSelector:
    beta.kubernetes.io/os: linux

Run the following command to run the pod:

kubectl apply -f <pod-yaml-file-name>.yaml

Hope it helps!

I was able to get this to work with the command sleep infinity in Kubernetes, which will keep the container open. See this answer for alternatives when that doesn't work.

The simplest command as it can be for k8s pod manifest to run container forever:

apiVersion: v1
kind: Pod
metadata:
  name: ubuntu
spec:
  containers:
  - name: ubuntu
    image: ubuntu:latest
    # Just sleep forever
    command: [ "sleep" ]
    args: [ "infinity" ]

Use this command inside you Dockerfile to keep the container running in your K8s cluster:

• CMD tail -f /dev/null

In my case, a pod with an initContainer failed to initialize. Running docker ps -a and then docker logs exited-container-id-here gave me a log message which kubectl logs podname didn't display. Mystery solved :-)

There are many different ways for accomplishing this, but one of the most elegant one is:

kubectl run -i --tty --image ubuntu:latest ubuntu-test --restart=Never --rm /bin/sh