152 lines
3.2 KiB
Markdown
152 lines
3.2 KiB
Markdown
---
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reviewers:
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- caesarxuchao
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- mikedanese
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title: Get a Shell to a Running Container
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content_template: templates/task
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---
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{{% capture overview %}}
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This page shows how to use `kubectl exec` to get a shell to a
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running Container.
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{{% /capture %}}
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{{% capture prerequisites %}}
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{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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{{% /capture %}}
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{{% capture steps %}}
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## Getting a shell to a Container
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In this exercise, you create a Pod that has one Container. The Container
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runs the nginx image. Here is the configuration file for the Pod:
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{{< codenew file="application/shell-demo.yaml" >}}
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Create the Pod:
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```shell
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kubectl create -f https://k8s.io/examples/application/shell-demo.yaml
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```
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Verify that the Container is running:
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```shell
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kubectl get pod shell-demo
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```
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Get a shell to the running Container:
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```shell
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kubectl exec -it shell-demo -- /bin/bash
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```
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{{< note >}}
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The double dash symbol "--" is used to separate the arguments you want to pass to the command from the kubectl arguments.
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{{< /note >}}
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In your shell, list the root directory:
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```shell
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root@shell-demo:/# ls /
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```
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In your shell, experiment with other commands. Here are
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some examples:
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```shell
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root@shell-demo:/# ls /
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root@shell-demo:/# cat /proc/mounts
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root@shell-demo:/# cat /proc/1/maps
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root@shell-demo:/# apt-get update
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root@shell-demo:/# apt-get install -y tcpdump
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root@shell-demo:/# tcpdump
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root@shell-demo:/# apt-get install -y lsof
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root@shell-demo:/# lsof
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root@shell-demo:/# apt-get install -y procps
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root@shell-demo:/# ps aux
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root@shell-demo:/# ps aux | grep nginx
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```
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## Writing the root page for nginx
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Look again at the configuration file for your Pod. The Pod
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has an `emptyDir` volume, and the Container mounts the volume
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at `/usr/share/nginx/html`.
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In your shell, create an `index.html` file in the `/usr/share/nginx/html`
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directory:
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```shell
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root@shell-demo:/# echo Hello shell demo > /usr/share/nginx/html/index.html
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```
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In your shell, send a GET request to the nginx server:
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```shell
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root@shell-demo:/# apt-get update
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root@shell-demo:/# apt-get install curl
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root@shell-demo:/# curl localhost
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```
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The output shows the text that you wrote to the `index.html` file:
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```shell
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Hello shell demo
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```
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When you are finished with your shell, enter `exit`.
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## Running individual commands in a Container
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In an ordinary command window, not your shell, list the environment
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variables in the running Container:
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```shell
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kubectl exec shell-demo env
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```
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Experiment running other commands. Here are some examples:
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```shell
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kubectl exec shell-demo ps aux
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kubectl exec shell-demo ls /
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kubectl exec shell-demo cat /proc/1/mounts
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```
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{{% /capture %}}
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{{% capture discussion %}}
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## Opening a shell when a Pod has more than one Container
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If a Pod has more than one Container, use `--container` or `-c` to
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specify a Container in the `kubectl exec` command. For example,
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suppose you have a Pod named my-pod, and the Pod has two containers
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named main-app and helper-app. The following command would open a
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shell to the main-app Container.
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```shell
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kubectl exec -it my-pod --container main-app -- /bin/bash
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```
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{{% /capture %}}
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{{% capture whatsnext %}}
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* [kubectl exec](/docs/reference/generated/kubectl/kubectl-commands/#exec)
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{{% /capture %}}
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