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:

• Killercoda
• KodeKloud
• 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

apiVersion:v1kind:Podmetadata:name:shell-demospec:volumes:- name:shared-dataemptyDir:{}containers:- name:nginximage:nginxvolumeMounts:- name:shared-datamountPath:/usr/share/nginx/htmlhostNetwork:truednsPolicy: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 

In your shell, list the root directory:

# Run this inside the containerls / 

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

# You can run these example commands inside the containerls / 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 containerecho'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 containerapt-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 

What's next

• Read about kubectl exec