The RunContainerError indicates that the container couldn’t initiate. When you see this error, it means the application inside hasn’t started because the container itself encountered a failure before it could begin loading the application.

$ kubectl get pods

NAME READY STATUS RESTARTS AGE

techops-app 0/1 RunContainerError 0 6m12s

If your pod status shows RunContainerError, it’s often due to:

Missing or incorrect volume mounts (e.g., ConfigMap or Secret).
Attempting to write to a read-only volume.
Invalid commands or missing executables.
Permissions or security context issues.

How to Fix RunContainerError

1. Check Pod Events for Detailed Errors

Start by describing the Pod to check for specific error events.

Look for any error messages in the "Message" field, such as permission denied, file not found, or invalid command.

In the below example, the error permission denied indicates a file permission issue with /app/start.sh.

$ kubectl describe pod techops-app

Events:

Type Reason Age From Message

---- ------ ---- ---- -------

Normal Scheduled 6m default-scheduler Successfully assigned default/techops-app to node-1

Normal Pulling 6m kubelet Pulling image "techops-image:latest"

Normal Pulled 6m kubelet Successfully pulled image "techops-image:latest"

Warning Failed 6m kubelet Error: failed to start container "techops-container": Error response from daemon: oci runtime error: container_linux.go:345: starting container process caused "exec: \"/app/start.sh\": permission denied"

Warning BackOff 5m (x3 over 6m) kubelet Back-off restarting failed container

2. Inspect Container Logs

If the container started briefly before failing, check logs for any application-specific error messages.

If you see errors like Permission denied or Command not found, it points to issues with permissions or command configurations in the container.

$ kubectl logs techops-app -c techops-container

/bin/sh: 1: /app/start.sh: Permission denied

3. Verify Volume Mounts

Check that any referenced ConfigMaps, Secrets, or PersistentVolumes are correctly defined and available.

If you receive Error from server (NotFound), the ConfigMap or Secret is missing, causing RunContainerError.

$ kubectl get configmap techops-config

Error from server (NotFound): configmaps "techops-config" not found

$ kubectl get secret techops-secret

Error from server (NotFound): secrets "techops-secret" not found

4. Check Commands and Entrypoints

Verify the command and args fields in your Pod’s specification. If these commands or paths are incorrect, the container won’t start.

Ensure the command path (/app/start.sh in this example) exists within the container and has the correct permissions.

containers:

- name: techops-container

image: techops-image:v1.2.3

command: ["/app/start.sh"]

args: ["--env", "production", "--debug", "false"]

5. Inspect Security Contexts

Check if the security context is properly configured in pod.yaml, as incorrect user/group settings can lead to permissions errors.

Verify that runAsUser and runAsGroup match the requirements of your container image.

securityContext:

runAsUser: 1000

runAsGroup: 3000

6. Validate Image Permissions

Some images require specific permissions to start. If needed, adjust the Pod’s serviceAccount or security settings to meet these requirements.

7. Check File and Directory Permissions

If the error message includes “permission denied,” ensure that the relevant files and directories have the correct permissions.

The file should have executable permissions (e.g., -rwxr-xr-x).

kubectl exec -it techops-app -- ls -l /app/start.sh

-rwxr-xr-- 1 appuser appgroup 4096 Nov 5 07:00 /app/start.sh

In crux, proper file permissions, valid volume mounts, accurate command paths, and appropriate user contexts help to prevent RunContainerError.

I hope this was helpful in your learning journey.

You may even like:

How To Fix OOMKilled

Kubernetes ImagePullBackOff Explained

Understanding Kubernetes CreateContainerConfigError

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