Get a Shell to a Running Container

This page shows how to use kubectl exec to get a shell to a running container. Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

Katacoda
Play with Kubernetes

Getting a shell to a container

In this exercise, you create a Pod that has one container. The container runs the nginx image. Here is the configuration file for the Pod: application/shell-demo.yaml [Copy application/shell-demo.yaml to clipboard]

apiVersion: v1 kind: Pod metadata: name: shell-demo spec: volumes:

• name: shared-data emptyDir: {} containers:
• name: nginx image: nginx volumeMounts:
  • name: shared-data mountPath: /usr/share/nginx/html hostNetwork: true dnsPolicy: Default

Create the Pod:

kubectl apply -f https://k8s.io/examples/application/shell-demo.yaml

Verify that the container is running:

kubectl get pod shell-demo

Get a shell to the running container:

kubectl exec --stdin --tty shell-demo -- /bin/bash

Note: The double dash (--) separates the arguments you want to pass to the command from the kubectl arguments.

In your shell, list the root directory:

Run this inside the container

ls /

In your shell, experiment with other commands. Here are some examples:

You can run these example commands inside the container

ls / cat /proc/mounts cat /proc/1/maps apt-get update apt-get install -y tcpdump tcpdump apt-get install -y lsof lsof apt-get install -y procps ps aux ps aux | grep nginx

Writing the root page for nginx

Look again at the configuration file for your Pod. The Pod has an emptyDir volume, and the container mounts the volume at /usr/share/nginx/html.

In your shell, create an index.html file in the /usr/share/nginx/html directory:

Run this inside the container

echo 'Hello shell demo' > /usr/share/nginx/html/index.html

In your shell, send a GET request to the nginx server:

Run this in the shell inside your container

apt-get update apt-get install curl curl http://localhost/

The output shows the text that you wrote to the index.html file:

Hello shell demo

When you are finished with your shell, enter exit.

exit # To quit the shell in the container

Running individual commands in a container

In an ordinary command window, not your shell, list the environment variables in the running container:

kubectl exec shell-demo env

Experiment with running other commands. Here are some examples:

kubectl exec shell-demo -- ps aux kubectl exec shell-demo -- ls / kubectl exec shell-demo -- cat /proc/1/mounts

Opening a shell when a Pod has more than one container

If a Pod has more than one container, use --container or -c to specify a container in the kubectl exec command. For example, suppose you have a Pod named my-pod, and the Pod has two containers named main-app and helper-app. The following command would open a shell to the main-app container.

kubectl exec -i -t my-pod --container main-app -- /bin/bash

Note: The short options -i and -t are the same as the long options --stdin and --tty