Container images are the backbone of every Kubernetes workload — they define what your Pods run and how they behave. A single typo in an image name or a misconfigured pull policy can break deployments, trigger ImagePullBackOff errors, or cause unexpected downtimes. Understanding how Kubernetes manages, updates, and authenticates images is critical for smooth and secure operations.

In this comprehensive guide, you’ll learn how to properly name, retrieve, and update container images, avoid common image-related errors, and securely pull from private registries — all while ensuring zero downtime during deployments.

Keep reading to master image management in Kubernetes ecosystem — from naming conventions to secure registry access and automated updates.

Managing Image Names in Kubernetes Pods

In Kubernetes, each container runs from an image, and the name of this image is critical for the system to pull and run it correctly. An incorrectly specified name can lead to common errors such as invalid image name or Kubernetes reporting that it couldn’t parse image name.

These errors often occur when the image name violates the expected name format or name convention, such as using uppercase letters or unsupported characters.

To avoid these issues, ensure that your image names follow Kubernetes naming rules: use lowercase letters, numbers, and allowed separators like - or _. For example:

containers:
  - name: backend-app
    image: myregistry.com/project/backend-app:1.0.0

If you need to change the image name in a running Pod, you typically update the Deployment or StatefulSet:

kubectl set image deployment/my-deployment my-container=new-image:tag

This command replaces the old image with the new one across all replicas while following Kubernetes best practices.

By adhering to proper name conventions and verifying the name format, you can prevent most image-related errors in your Pods and maintain smooth deployments.

How to Get Image Name in Kubernetes

In Kubernetes, it is often necessary to get the image name from a Pod or Deployment to verify which version of an application is running. You can retrieve this information easily using kubectl.

To get image name from a Pod, use:

kubectl get pod <pod-name> -o jsonpath="{.spec.containers[*].image}"

To get image name from a Deployment, use:

kubectl get deployment <deployment-name> -o jsonpath="{.spec.template.spec.containers[*].image}"

This helps confirm which image version is being used in a rolling update or when debugging mismatched container versions.

Sometimes, you might want to see the image details from inside a container itself. Kubernetes doesn’t automatically store this as an environment variable, but you can expose it using the Downward API.
Example with Downward API to expose the image name as an environment variable:

env:
  - name: CONTAINER_IMAGE
    valueFrom:
      fieldRef:
        fieldPath: spec.containers[0].image

After applying this to your Pod or Deployment, the container can directly access CONTAINER_IMAGE to know which image it is running.

Automatically Update Container Image in Kubernetes Without Downtime

In Kubernetes, updating a container image is a routine task, but it must be done carefully to avoid downtime. Kubernetes Deployments make this easier by rolling out new Pods while keeping existing ones running until the new ones are ready. This ensures no user faces errors or 404 pages during the update.

When you use an image like my-app:latest, Kubernetes applies the default imagePullPolicy: Always, which means it will always check the registry for new versions of that image. But even with latest, Kubernetes does not automatically restart Pods unless you trigger it manually or via automation.

So “automatically update image” means—you must combine latest + Always + a restart or GitOps tool like Argo CD / Flux.

To update the image tag without downtime, you can run:

kubectl set image deployment/my-deploy my-container=my-app:v2

This updates only the image tag, creates a new ReplicaSet, starts new Pods with my-app:v2, waits for them to become healthy, and then removes old Pods—ensuring zero downtime.

If you want to change the image registry or repository path, you can use:

kubectl set image deployment/my-deploy my-container=ghcr.io/myteam/my-app:v2

This command updates the full container image path, including registry and repository.

Changing containerPort is different—it does not trigger a rollout by itself. You must update the YAML and reapply it:

containers:
- name: my-container
  image: my-app:v2
  ports:
    - containerPort: 8080

Then apply using:

kubectl apply -f deployment.yaml

To update to the same image tag (latest) again and force Pods to restart:

kubectl rollout restart deployment/my-deploy

Kubernetes Image Pull: Authentication, Registry Access & Security

In Kubernetes, every container image used in a Pod must be pulled from a container registry such as Docker Hub, Google Container Registry (GCR), Amazon ECR, or a private registry. If an image is public, Kubernetes pulls it without any additional configuration.

When the image is private, Kubernetes needs valid credentials. That’s where Image Pull Secrets are used. These objects securely store registry credentials (username, password, tokens, etc.) and allow Kubernetes to authenticate with private repositories. Without proper credentials, Pods may fail to start and show errors like ImagePullBackOff or ErrImagePull.

To understand how Kubernetes stores registry credentials and attaches them to Pods or ServiceAccounts, we’ve created a deep-dive guide on Image Pull Secrets.

When Kubernetes pulls images, it communicates with registries over HTTPS. This relies on TLS certificates to verify the registry’s identity. If a certificate is self-signed, expired, mismatched, or untrusted, Kubernetes fails the pull process with errors like:

• x509: certificate signed by unknown authority
• ErrImagePull or ImagePullBackOff

These issues commonly appear with internal, corporate, or self-hosted registries. To resolve them, Kubernetes nodes (or the container runtime like Docker/containerd) must trust the Certificate Authority (CA) that issued the registry’s certificate. This may involve adding the CA to the node’s trust store or, in non-production environments, configuring insecure registries.

Kubernetes supports pulling images not just from public registries but also from private platforms like GitLab Container Registry, AWS ECR, Azure ACR, GCR, or on-premises/local registries. These platforms require authentication, but each uses different methods—Docker credentials, cloud tokens, service accounts, IAM roles, or access keys.

These registries may also enforce additional rules like token expiration, organization-based access, or regional endpoints. If credentials or permissions are not configured correctly, Kubernetes may reach the registry but still fail to pull the image.

Summary

Kubernetes relies on container images to run applications, and accurate image naming is essential to avoid errors like invalid image name or couldn’t parse image name. Following proper naming conventions and updating image references via Deployments ensures smooth rollouts.

Retrieving image details is equally important during debugging or audits. You can extract image names from Pods or Deployments using kubectl, or expose image information inside containers using the Downward API when needed.

Updating images without downtime is handled using Deployments, which perform rolling updates. Kubernetes won’t auto-update running Pods even if the image tag is latest—you must trigger it manually or use automation tools like Argo CD or Flux. You can update tags, repositories, or registries using kubectl set image, while port changes require YAML updates and apply.

For image pulling, Kubernetes communicates with registries like Docker Hub, GitLab, AWS ECR, Azure ACR, GCR, or local registries. Public images can be pulled directly, but private registries require ImagePullSecrets to authenticate. Misconfigured credentials trigger errors like ImagePullBackOff.

Secure image pulls also depend on valid TLS certificates. Self-signed or untrusted certificates in corporate or on-premise registries can cause x509: certificate signed by unknown authority errors. These issues are resolved by trusting the correct CA or configuring insecure registries in non-production.