Container images are fundamental building blocks for deploying applications in Azure. They encapsulate your application code, runtime, libraries, and dependencies into a portable, consistent package that can run anywhere containers are supported.
**Azure Container Registry (ACR)** is Microsoft's m…Container images are fundamental building blocks for deploying applications in Azure. They encapsulate your application code, runtime, libraries, and dependencies into a portable, consistent package that can run anywhere containers are supported.
**Azure Container Registry (ACR)** is Microsoft's managed Docker registry service for storing and managing container images. Key features include geo-replication, automated image builds, and integration with Azure DevOps pipelines.
**Creating Container Images:**
1. **Dockerfile Creation**: Define your image using a Dockerfile that specifies the base image, copies application files, installs dependencies, and sets entry points.
2. **Building Images**: Use Docker CLI commands like 'docker build -t myimage:v1 .' to create images locally, or leverage ACR Tasks for cloud-based builds.
3. **ACR Tasks**: Enable automated builds triggered by source code commits, base image updates, or scheduled timers. This supports continuous integration workflows.
**Managing Container Images:**
1. **Pushing to Registry**: Use 'docker push' or 'az acr build' to upload images to ACR after authenticating with 'az acr login'.
2. **Image Tagging**: Apply meaningful tags (version numbers, environment names) to organize and identify images. Consider semantic versioning for production deployments.
3. **Security Scanning**: ACR integrates with Microsoft Defender to scan images for vulnerabilities and compliance issues.
4. **Retention Policies**: Configure automatic purging of old or untagged images to manage storage costs and maintain registry hygiene.
5. **Replication**: Enable geo-replication to distribute images across multiple Azure regions for faster pulls and redundancy.
**Best Practices:**
- Use multi-stage builds to minimize image size
- Implement image signing for authenticity verification
- Store secrets using Azure Key Vault rather than embedding in images
- Regularly update base images for security patches
- Use specific tags rather than 'latest' for production deployments
These capabilities enable reliable, secure container workflows for Azure solutions.
Create and Manage Container Images for Solutions - AZ-204 Exam Guide
Why is This Important?
Container images are fundamental to modern cloud-native development. For the AZ-204 exam, understanding how to create and manage container images is essential because Azure heavily relies on containerization for deploying scalable, portable applications. This knowledge directly impacts your ability to work with Azure Container Registry (ACR), Azure Container Instances (ACI), and Azure Kubernetes Service (AKS).
What Are Container Images?
A container image is a lightweight, standalone, executable package that includes everything needed to run an application: code, runtime, system tools, libraries, and settings. Container images are built from Dockerfiles and stored in container registries like Azure Container Registry.
Key Components: - Dockerfile: A text file containing instructions to build an image - Base Image: The foundation layer (e.g., alpine, ubuntu, .NET runtime) - Layers: Each instruction creates a new layer, making images efficient and cacheable - Tags: Version identifiers for images (e.g., myapp:v1.0, myapp:latest)
How It Works
1. Creating Container Images: - Write a Dockerfile with instructions (FROM, COPY, RUN, EXPOSE, CMD) - Build the image using docker build -t imagename:tag . - Use multi-stage builds to reduce image size
2. Azure Container Registry (ACR): - ACR is a managed Docker registry service - SKUs: Basic, Standard, Premium - Features: geo-replication, content trust, private endpoints - Authentication: Azure AD, admin account, service principals
3. Key ACR Commands: - az acr create - Create a registry - az acr build - Build images in ACR (no local Docker needed) - az acr login - Authenticate to registry - docker push - Push images to ACR - az acr task - Automate image builds
4. ACR Tasks: - Quick tasks for on-demand builds - Triggered tasks based on source code commits or base image updates - Multi-step tasks defined in YAML
Best Practices: - Use specific tags instead of 'latest' for production - Implement multi-stage builds to minimize image size - Scan images for vulnerabilities - Use managed identities for authentication - Enable content trust for image signing
Exam Tips: Answering Questions on Create and Manage Container Images
Focus Areas: - Know the difference between ACR SKUs (Basic lacks geo-replication, Premium has all features) - Understand authentication methods: service principals for CI/CD, managed identities for Azure services - Remember az acr build builds in the cloud - useful when Docker is not installed locally - ACR Tasks trigger on base image updates - important for security patching scenarios
Common Question Patterns: - Scenarios asking which SKU to choose based on requirements - Questions about automating builds when source code changes - Authentication scenarios between Azure services and ACR - Dockerfile instruction ordering for optimal caching
Key Facts to Remember: - Premium SKU is required for geo-replication and private endpoints - Admin account should be disabled for production workloads - az acr task create with --commit-trigger-enabled enables CI builds - Multi-stage builds use multiple FROM statements - EXPOSE instruction documents ports but does not publish them
Watch Out For: - Questions mixing up ACR authentication methods - Scenarios requiring you to identify the correct Dockerfile instruction order - Distinguishing between docker build (local) and az acr build (cloud) - Understanding when to use webhooks versus ACR Tasks