website/content/en/docs/tasks/debug-application-cluster/get-shell-running-container.md

reviewers	title	content_type
caesarxuchao mikedanese	Get a Shell to a Running Container	task

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

{{% heading "prerequisites" %}}

{{< include "task-tutorial-prereqs.md" >}}

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:

{{< codenew file="application/shell-demo.yaml" >}}

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. {{< /note >}}

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 {{< /note >}}

{{% heading "whatsnext" %}}

• Read about kubectl exec