website/v1.1/docs/user-guide/getting-into-containers.md

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docwithnav	Getting into containers: kubectl exec

Getting into containers: kubectl exec

Developers can use kubectl exec to run commands in a container. This guide demonstrates two use cases.

Using kubectl exec to check the environment variables of a container

Kubernetes exposes services through environment variables. It is convenient to check these environment variables using kubectl exec.

We first create a pod and a service,

{% highlight console %} {% raw %} $ kubectl create -f examples/guestbook/redis-master-controller.yaml $ kubectl create -f examples/guestbook/redis-master-service.yaml {% endraw %} {% endhighlight %}

wait until the pod is Running and Ready,

{% highlight console %} {% raw %} $ kubectl get pod NAME READY REASON RESTARTS AGE redis-master-ft9ex 1/1 Running 0 12s {% endraw %} {% endhighlight %}

then we can check the environment variables of the pod,

{% highlight console %} {% raw %} $ kubectl exec redis-master-ft9ex env ... REDIS_MASTER_SERVICE_PORT=6379 REDIS_MASTER_SERVICE_HOST=10.0.0.219 ... {% endraw %} {% endhighlight %}

We can use these environment variables in applications to find the service.

Using kubectl exec to check the mounted volumes

It is convenient to use kubectl exec to check if the volumes are mounted as expected. We first create a Pod with a volume mounted at /data/redis,

{% highlight console %} {% raw %} kubectl create -f docs/user-guide/walkthrough/pod-redis.yaml {% endraw %} {% endhighlight %}

wait until the pod is Running and Ready,

{% highlight console %} {% raw %} $ kubectl get pods NAME READY REASON RESTARTS AGE storage 1/1 Running 0 1m {% endraw %} {% endhighlight %}

we then use kubectl exec to verify that the volume is mounted at /data/redis,

{% highlight console %} {% raw %} $ kubectl exec storage ls /data redis {% endraw %} {% endhighlight %}

Using kubectl exec to open a bash terminal in a pod

After all, open a terminal in a pod is the most direct way to introspect the pod. Assuming the pod/storage is still running, run

{% highlight console %} {% raw %} $ kubectl exec -ti storage -- bash root@storage:/data# {% endraw %} {% endhighlight %}

This gets you a terminal.