Resolve Pod Deployment Issue.md

Problem Statement

A junior DevOps team member encountered difficulties deploying a stack on the Kubernetes cluster. The pod fails to start, presenting errors. Let's troubleshoot and rectify the issue promptly.

• There is a pod named webserver, and the container within it is named httpd-container, which utilizes the httpd:latest image.
• Additionally, there's a sidecar container named sidecar-container using the ubuntu:latest image.

Identify and address the issue to ensure the pod is running and the application is accessible.

Solution

First, we need to check if the pod is running.

kubectl get pods
NAME        READY   STATUS             RESTARTS   AGE
webserver   1/2     ImagePullBackOff   0          89s

Here, we can see that the pod is not fully operational. The status is ImagePullBackOff, indicating that there is an issue with pulling the container image. There are two possible reasons for this:

1. The image name is incorrect.
2. The image is not available in the specified repository.

To diagnose the issue further, we need to look at the detailed status of the webserver pod.

~$ kubectl describe pod webserver 
Name:             webserver
Namespace:        default
Priority:         0
Service Account:  default
Node:             kodekloud-control-plane/172.17.0.2
Start Time:       Thu, 18 Jul 2024 05:51:26 +0000
Labels:           app=web-app
Annotations:      <none>
Status:           Pending
IP:               10.244.0.5
IPs:
  IP:  10.244.0.5
Containers:
  httpd-container:
    Container ID:   
    Image:          httpd:latests
    Image ID:       
    Port:           <none>
    Host Port:      <none>
    State:          Waiting
      Reason:       ImagePullBackOff
    Ready:          False
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/log/httpd from shared-logs (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-x8t5d (ro)
  sidecar-container:
    Container ID:  containerd://a3c7c130a43f560e2f09ff72366aa42e9d07aa9818ae636be44dbf5105517161
    Image:         ubuntu:latest
    Image ID:      docker.io/library/ubuntu@sha256:2e863c44b718727c860746568e1d54afd13b2fa71b160f5cd9058fc436217b30
    Port:          <none>
    Host Port:     <none>
    Command:
      sh
      -c
      while true; do cat /var/log/httpd/access.log /var/log/httpd/error.log; sleep 30; done
    State:          Running
      Started:      Thu, 18 Jul 2024 05:51:31 +0000
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/log/httpd from shared-logs (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-x8t5d (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             False 
  ContainersReady   False 
  PodScheduled      True 
Volumes:
  shared-logs:
    Type:       EmptyDir (a temporary directory that shares a pod's lifetime)
    Medium:     
    SizeLimit:  <unset>
  kube-api-access-x8t5d:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type     Reason     Age                 From               Message
  ----     ------     ----                ----               -------
  Normal   Scheduled  104s                default-scheduler  Successfully assigned default/webserver to kodekloud-control-plane
  Normal   Pulling    103s                kubelet            Pulling image "ubuntu:latest"
  Normal   Pulled     100s                kubelet            Successfully pulled image "ubuntu:latest" in 3.536798142s (3.536807827s including waiting)
  Normal   Created    99s                 kubelet            Created container sidecar-container
  Normal   Started    99s                 kubelet            Started container sidecar-container
  Normal   Pulling    56s (x3 over 103s)  kubelet            Pulling image "httpd:latests"
  Warning  Failed     56s (x3 over 103s)  kubelet            Failed to pull image "httpd:latests": rpc error: code = NotFound desc = failed to pull and unpack image "docker.io/library/httpd:latests": failed to resolve reference "docker.io/library/httpd:latests": docker.io/library/httpd:latests: not found
  Warning  Failed     56s (x3 over 103s)  kubelet            Error: ErrImagePull
  Normal   BackOff    18s (x6 over 99s)   kubelet            Back-off pulling image "httpd:latests"
  Warning  Failed     18s (x6 over 99s)   kubelet            Error: ImagePullBackOff

From the logs, we can see that the image name httpd:latests is incorrect; it should be httpd:latest. This is causing the ImagePullBackOff error because Kubernetes is unable to find the image httpd:latests.

To fix this, we need to edit the pod and correct the image name.

~$ kubectl edit pod webserver
pod/webserver edited

After editing the pod and correcting the image name, we should verify if the pod is now running.

~$ kubectl get pod
NAME        READY   STATUS    RESTARTS      AGE
webserver   2/2     Running   1 (28s ago)   11m

As seen above, the pod is now running correctly with both containers in a READY state. This indicates that the issue was successfully resolved, and the application should be accessible as intended.