Core Concepts (13%)
Creating a Pod and Inspecting it
- Create the namespace
ckad-prep. - In the namespace
ckad-prepcreate a new Pod namedmypodwith the imagenginx:2.3.5. Expose the port 80. - Identify the issue with creating the container. Write down the root cause of issue in a file named
pod-error.txt. - Change the image of the Pod to
nginx:1.15.12. - List the Pod and ensure that the container is running.
- Log into the container and run the
lscommand. Write down the output. Log out of the container. - Retrieve the IP address of the Pod
mypod. - Run a temporary Pod using the image
busybox, shell into it and run awgetcommand against thenginxPod using port 80. - Render the logs of Pod
mypod. - Delete the Pod and the namespace.
Solution:
First, create the namespace.
$ kubectl create namespace ckad-prep
Next, create the Pod in the new namespace.
$ kubectl run mypod --image=nginx:2.3.5 --restart=Never --port=80 --namespace=ckad-prep
pod/mypod created
You will see that the image cannot be pulled as it doesn't exist with this tag.
$ kubectl get pod -n ckad-prep
NAME READY STATUS RESTARTS AGE
mypod 0/1 ImagePullBackOff 0 1m
The list of events can give you a deeper insight.
$ kubectl describe pod -n ckad-prep
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 3m3s default-scheduler Successfully assigned mypod to docker-for-desktop
Normal SuccessfulMountVolume 3m2s kubelet, docker-for-desktop MountVolume.SetUp succeeded for volume "default-token-jbcl6"
Normal Pulling 84s (x4 over 3m2s) kubelet, docker-for-desktop pulling image "nginx:2.3.5"
Warning Failed 83s (x4 over 3m1s) kubelet, docker-for-desktop Failed to pull image "nginx:2.3.5": rpc error: code = Unknown desc = Error response from daemon: manifest for nginx:2.3.5 not found
Warning Failed 83s (x4 over 3m1s) kubelet, docker-for-desktop Error: ErrImagePull
Normal BackOff 69s (x6 over 3m) kubelet, docker-for-desktop Back-off pulling image "nginx:2.3.5"
Warning Failed 69s (x6 over 3m) kubelet, docker-for-desktop Error: ImagePullBackOff
Go ahead and edit the existing Pod. Alternatively, you could also just use the kubectl set image pod mypod mypod=nginx --namespace=ckad-prep command.
$ kubectl edit pod mypod --namespace=ckad-prep
After setting an image that does exist, the Pod should render the status Running.
$ kubectl get pod -n ckad-prep
NAME READY STATUS RESTARTS AGE
mypod 1/1 Running 0 14m
You can shell into the container and run the ls command.
$ kubectl exec mypod -it --namespace=ckad-prep -- /bin/sh
/ # ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
/ # exit
Retrieve the IP address of the Pod with the -o wide command line option.
$ kubectl get pods -o wide -n ckad-prep
NAME READY STATUS RESTARTS AGE IP NODE
mypod 1/1 Running 0 12m 192.168.60.149 docker-for-desktop
Remember to use the --rm to create a temporary Pod.
$ kubectl run busybox --image=busybox --rm -it --restart=Never -n ckad-prep -- /bin/sh
If you don't see a command prompt, try pressing enter.
/ # wget -O- 192.168.60.149:80
Connecting to 192.168.60.149:80 (192.168.60.149:80)
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
- 100% |**********************************************************************| 612 0:00:00 ETA
/ # exit
The logs of the Pod should show a single line indicating our request.
$ kubectl logs mypod -n ckad-prep
192.168.60.162 - - [17/May/2019:13:35:59 +0000] "GET / HTTP/1.1" 200 612 "-" "Wget" "-"
Delete the Pod and namespace after you are done.
$ kubectl delete pod mypod --namespace=ckad-prep
pod "mypod" deleted
$ kubectl delete namespace ckad-prep
namespace "ckad-prep" deleted