How to fix error “Unable to get IAM security credentials from ec2 instance metadata service”

In this blog, we will discuss the error "Unable to get IAM security credentials from EC2 instance metadata service" that developers often encounter when working with AWS. We will explain the reasons behind this issue and provide a step-by-step guide on how to fix it. This blog post is intended for beginner to intermediate developers who are familiar with AWS services, particularly with EC2 and IAM.

Introduction to EC2 Instance Metadata Service

The EC2 instance metadata service is a feature provided by AWS that allows you to query metadata about an EC2 instance from within the instance itself. This can be valuable for various use-cases, such as configuring applications running on the instance, gathering information for logging purposes, and more.

One of the metadata elements available is the IAM security credentials associated with the instance profile or role. These credentials are temporary and automatically rotated by AWS. Accessing these credentials allows applications running on the instance to authenticate and authorize actions using AWS services without having to manage long-term access keys.

Understanding the Error

The error "Unable to get IAM security credentials from EC2 instance metadata service" typically occurs when an application or service running on an EC2 instance is unable to fetch the IAM security credentials from the instance metadata service. There are several reasons why this might happen, such as:

1. The instance is not configured with an IAM role.
2. The instance metadata service is not accessible.
3. The application or service is misconfigured or encountering issues.

In the following sections, we will go through each of these scenarios and provide solutions to fix the error.

Ensuring the EC2 Instance is Configured with an IAM Role

To access IAM security credentials from the instance metadata service, your EC2 instance must be associated with an IAM role. To verify or configure an IAM role for your instance, follow these steps:

1. Log in to the AWS Management Console.
2. Navigate to the EC2 Dashboard.
3. In the "Instances" section, select your instance.
4. In the "Description" tab, look for the "IAM role" field. If an IAM role is associated with the instance, it will be listed here. If not, follow the next steps to associate an IAM role.
5. In the top-right corner of the "Description" tab, click "Actions" and select "Modify IAM role."
6. In the "Modify IAM role" dialog, select the desired IAM role from the dropdown menu. If you don't have an appropriate IAM role, you can create one in the IAM Console.
7. Click "Save" to apply the IAM role to the instance.

Now that your instance is associated with an IAM role, the metadata service should provide the necessary IAM security credentials. However, if the error persists, proceed to the next section.

Verifying Access to the Instance Metadata Service

To ensure the instance metadata service is accessible, you can test querying the metadata from within the instance. Follow these steps to verify access to the instance metadata service:

1. SSH into your EC2 instance using your preferred SSH client.
2. Run the following command to fetch the IAM security credentials:

curl http://169.254.169.254/latest/meta-data/iam/security-credentials/

If the command returns the name of the IAM role associated with the instance, the metadata service is accessible, and you can proceed to the next section. If not, check the following:

• Ensure your instance is running Amazon Linux, Amazon Linux 2, or the AWS-provided Ubuntu images, as these distributions have the necessary tools and configurations to access the instance metadata service out of the box. If you are using a custom or non-AWS-provided image, you might need to configure the instance metadata service manually.
• Verify that your instance is running in a VPC and that the instance metadata service is enabled in the VPC settings. You can check this by navigating to the VPC Dashboard in the AWS Management Console, selecting your VPC, and verifying the "Metadata service options" setting.

Checking Application or Service Configuration

If you have confirmed that your instance has an IAM role and the instance metadata service is accessible, the error may be due to a misconfiguration or issue with the application or service running on the instance. Some possible solutions include:

1. Ensure your application or service is using the correct SDK or library for accessing AWS services and fetching IAM credentials. For example, if you are using the AWS SDK for Python (Boto3), make sure you have the latest version installed and are using the recommended method for retrieving credentials.
2. Verify that your application or service is not hardcoding AWS access keys or using environment variables for credentials. Instead, use the instance metadata service to fetch temporary credentials.
3. Check for any network configurations, such as security groups or network ACLs, that might be blocking access to the instance metadata service.

FAQ

Q: What is the instance metadata service?

A: The instance metadata service is a feature provided by AWS that allows you to query metadata about an EC2 instance from within the instance itself. This can be valuable for various use-cases, such as configuring applications running on the instance, gathering information for logging purposes, and more.

Q: How do I access the instance metadata service?

A: You can access the instance metadata service by making HTTP requests to the following URL: http://169.254.169.254/latest/meta-data/. The available metadata elements are organized in a hierarchical structure, and you can append specific paths to the URL to query specific metadata elements.

Q: How do I create an IAM role for my EC2 instance?

A: You can create an IAM role for your EC2 instance by following these steps:

1. Log in to the AWS Management Console.
2. Navigate to the IAM Dashboard.
3. In the left navigation menu, click "Roles" and then click "Create role."
4. In the "Select type of trusted entity" section, choose "AWS service" and then select "EC2."
5. Click "Next: Permissions" and attach the necessary policies to the role.
6. Click "Next: Tags" and add any desired tags.
7. Click "Next: Review," give your role a name and description, and click "Create role."

Q: Can I access IAM security credentials from an EC2 instance without an associated IAM role?

A: No, you cannot access IAM security credentials from the instance metadata service without an associated IAM role. To access IAM security credentials, you must configure your EC2 instance with an appropriate IAM role.

By following the steps outlined in this blog post, you should now be able to resolve the "Unable to get IAM security credentials from EC2 instance metadata service" error and successfully access IAM security credentials from your EC2 instance. If you still encounter issues, consider reviewing the official AWS documentation or reaching out to the AWS support for further assistance.