Creating Task Definitions - AWS ECS Tutorial

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Task definitions are a fundamental concept in Amazon Elastic Container Service (ECS) that define the containers, resources, and configurations required to run a task. A task represents a group of related containers that work together to form an application. By creating task definitions, you can easily deploy and manage containerized applications in ECS. This tutorial will guide you through the process of creating task definitions in ECS.

Creating Task Definitions

To create a task definition in Amazon ECS, follow these steps:

  1. Define the Container Image: Specify the Docker image for each container in the task. You can use images from a container registry like Amazon Elastic Container Registry (ECR) or a public registry.
  2. Configure Resources: Define the CPU and memory requirements for each container. This ensures that containers have sufficient resources to run efficiently.
  3. Set Container Options: Configure container-level settings such as environment variables, logging options, networking, and security settings.
  4. Define Task-level Options: Specify task-level settings such as task execution role, task placement constraints, and volumes.
  5. Create the Task Definition: Use the AWS Management Console, AWS CLI, or AWS SDKs to create the task definition, providing the container configurations and options.

Example: Creating a Task Definition

Here's an example of creating a task definition using AWS CLI commands:

aws ecs register-task-definition
--family my-task-definition
--network-mode awsvpc
--container-definitions '[
"name": "my-container",
"image": "my-registry/my-container-image",
"portMappings": [
"containerPort": 80,
"protocol": "tcp"
"memory": 512,
"cpu": 256
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Common Mistakes

  • Not specifying accurate resource requirements, leading to underprovisioning or overprovisioning of CPU and memory.
  • Overlooking container dependencies or inter-container communication requirements, resulting in application failures.
  • Not properly defining port mappings for container-to-container or container-to-host communication.
  • Forgetting to configure environment variables or not providing the necessary configuration values for the containers.
  • Ignoring container logging configuration, which is crucial for troubleshooting and monitoring.

Frequently Asked Questions

  1. Can I update a task definition after it has been created?

    Yes, you can update a task definition to modify container configurations, resource requirements, and other settings. However, you cannot modify the revision of an active task definition.

  2. Can I use environment variables in task definitions?

    Yes, you can define environment variables at the container level in the task definition to pass configuration values to your containers.

  3. Can I mount volumes in task definitions?

    Yes, you can define volumes in the task definition and mount them in your containers. Volumes enable persistent storage and data sharing between containers.

  4. Can I specify resource limits for containers?

    Yes, you can set CPU and memory limits for containers in the task definition to ensure efficient resource allocation.

  5. Can I use task definition templates or version control for task definitions?

    Yes, you can leverage Infrastructure as Code (IaC) tools like AWS CloudFormation or AWS CDK to define and manage task definitions in a version-controlled manner.


Creating task definitions is an essential step in deploying containerized applications in Amazon Elastic Container Service (ECS). By following the step-by-step guide, avoiding common mistakes, and understanding the FAQs, you can effectively create task definitions that define the containers, resources, and configurations required for your applications to run successfully in ECS.