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Create a launch configuration

This topic describes how to create a launch configuration.

After you create a launch configuration, you cannot modify it. Instead, you must create a new launch configuration.

To associate a new launch configuration with an existing Auto Scaling group, see Change the launch configuration for an Auto Scaling group. To create a new Auto Scaling group, see Create an Auto Scaling group using a launch configuration.

Create a launch configuration

Configure the instance metadata options

Amazon EC2 Auto Scaling supports configuring the Instance Metadata Service (IMDS) in launch configurations. This gives you the option of using launch configurations to configure the Amazon EC2 instances in your Auto Scaling groups to require Instance Metadata Service Version 2 (IMDSv2), which is a session-oriented method for requesting instance metadata. For details about IMDSv2's advantages, see this article on the Amazon Blog about enhancements to add defense in depth to the EC2 instance metadata service.

You can configure IMDS to support both IMDSv2 and IMDSv1 (the default), or to require the use of IMDSv2. If you are using the Amazon CLI or one of the SDKs to configure IMDS, you must use the latest version of the Amazon CLI or the SDK to require the use of IMDSv2.

You can configure your launch configuration for the following:

You can find more details on configuring the Instance Metadata Service in the following topic: Configuring the instance metadata service in the Amazon EC2 User Guide for Linux Instances.

Use the following procedure to configure IMDS options in a launch configuration. After you create your launch configuration, you can associate it with your Auto Scaling group. If you associate the launch configuration with an existing Auto Scaling group, the existing launch configuration is disassociated from the Auto Scaling group, and existing instances will require replacement to use the IMDS options that you specified in the new launch configuration. For more information, see Change the launch configuration for an Auto Scaling group.

To require the use of IMDSv2 in a launch configuration using the Amazon CLI

Use the following create-launch-configuration command with --metadata-options set to HttpTokens=required. When you specify a value for HttpTokens, you must also set HttpEndpoint to enabled. Because the secure token header is set to required for metadata retrieval requests, this opts in the instance to require using IMDSv2 when requesting instance metadata.

aws autoscaling create-launch-configuration \
  --launch-configuration-name my-lc-with-imdsv2 \
  --image-id ami-01e24be29428c15b2 \
  --instance-type t2.micro \
      ...    
  --metadata-options "HttpEndpoint=enabled,HttpTokens=required" 

To turn off access to instance metadata

Use the following create-launch-configuration command to turn off access to instance metadata. You can turn access back on later by using the modify-instance-metadata-options command.

aws autoscaling create-launch-configuration \
  --launch-configuration-name my-lc-with-imds-disabled \
  --image-id ami-01e24be29428c15b2 \
  --instance-type t2.micro \
      ...    
  --metadata-options "HttpEndpoint=disabled" 

Create a launch configuration using an EC2 instance

You also have the option to create a launch configuration using the attributes from a running EC2 instance.

There are differences between creating a launch configuration from scratch and creating a launch configuration from an existing EC2 instance. When you create a launch configuration from scratch, you specify the image ID, instance type, optional resources (such as storage devices), and optional settings (like monitoring). When you create a launch configuration from a running instance, Amazon EC2 Auto Scaling derives attributes for the launch configuration from the specified instance. Attributes are also derived from the block device mapping for the AMI from which the instance was launched, ignoring any additional block devices that were added after launch.

When you create a launch configuration using a running instance, you can override the following attributes by specifying them as part of the same request: AMI, block devices, key pair, instance profile, instance type, kernel, instance monitoring, placement tenancy, ramdisk, security groups, Spot (max) price, user data, whether the instance has a public IP address, and whether the instance is EBS-optimized.

Create a launch configuration from an EC2 instance (Amazon CLI)

Use the following create-launch-configuration command to create a launch configuration from an instance using the same attributes as the instance. Any block devices added after launch are ignored.

aws autoscaling create-launch-configuration --launch-configuration-name my-lc-from-instance --instance-id i-a8e09d9c

You can use the following describe-launch-configurations command to describe the launch configuration and verify that its attributes match those of the instance.

aws autoscaling describe-launch-configurations --launch-configuration-names my-lc-from-instance

The following is an example response.

{
    "LaunchConfigurations": [
        {
            "UserData": null,
            "EbsOptimized": false,
            "LaunchConfigurationARN": "arn",
            "InstanceMonitoring": {
                "Enabled": false
            },
            "ImageId": "ami-05355a6c",
            "CreatedTime": "2014-12-29T16:14:50.382Z",
            "BlockDeviceMappings": [],
            "KeyName": "my-key-pair",
            "SecurityGroups": [
                "sg-8422d1eb"
            ],
            "LaunchConfigurationName": "my-lc-from-instance",
            "KernelId": "null",
            "RamdiskId": null,
            "InstanceType": "t1.micro",
            "AssociatePublicIpAddress": true
        }
    ]
}

Create a launch configuration from an instance and override the block devices (Amazon CLI)

By default, Amazon EC2 Auto Scaling uses the attributes from the EC2 instance that you specify to create the launch configuration. However, the block devices come from the AMI used to launch the instance, not the instance. To add block devices to the launch configuration, override the block device mapping for the launch configuration.

Use the following create-launch-configuration command to create a launch configuration using an EC2 instance but with a custom block device mapping.

aws autoscaling create-launch-configuration --launch-configuration-name my-lc-from-instance-bdm --instance-id i-a8e09d9c \
  --block-device-mappings "[{\"DeviceName\":\"/dev/sda1\",\"Ebs\":{\"SnapshotId\":\"snap-3decf207\"}},{\"DeviceName\":\"/dev/sdf\",\"Ebs\":{\"SnapshotId\":\"snap-eed6ac86\"}}]"

Use the following describe-launch-configurations command to describe the launch configuration and verify that it uses your custom block device mapping.

aws autoscaling describe-launch-configurations --launch-configuration-names my-lc-from-instance-bdm

The following example response describes the launch configuration.

{
    "LaunchConfigurations": [
        {
            "UserData": null,
            "EbsOptimized": false,
            "LaunchConfigurationARN": "arn",
            "InstanceMonitoring": {
                "Enabled": false
            },
            "ImageId": "ami-c49c0dac",
            "CreatedTime": "2015-01-07T14:51:26.065Z",
            "BlockDeviceMappings": [
                {
                    "DeviceName": "/dev/sda1",
                    "Ebs": {
                        "SnapshotId": "snap-3decf207"
                    }
                },
                {
                    "DeviceName": "/dev/sdf",
                    "Ebs": {
                        "SnapshotId": "snap-eed6ac86"
                    }
                }
            ],
            "KeyName": "my-key-pair",
            "SecurityGroups": [
                "sg-8637d3e3"
            ],
            "LaunchConfigurationName": "my-lc-from-instance-bdm",
            "KernelId": null,
            "RamdiskId": null,
            "InstanceType": "t1.micro",
            "AssociatePublicIpAddress": true
        }
    ]
}

Create a launch configuration and override the instance type (Amazon CLI)

By default, Amazon EC2 Auto Scaling uses the attributes from the EC2 instance you specify to create the launch configuration. Depending on your requirements, you might want to override attributes from the instance and use the values that you need. For example, you can override the instance type.

Use the following create-launch-configuration command to create a launch configuration using an EC2 instance but with a different instance type (for example t2.medium) than the instance (for example t2.micro).

aws autoscaling create-launch-configuration --launch-configuration-name my-lc-from-instance-changetype \
  --instance-id i-a8e09d9c --instance-type t2.medium

Use the following describe-launch-configurations command to describe the launch configuration and verify that the instance type was overridden.

aws autoscaling describe-launch-configurations --launch-configuration-names my-lc-from-instance-changetype

The following example response describes the launch configuration.

{
    "LaunchConfigurations": [
        {
            "UserData": null,
            "EbsOptimized": false,
            "LaunchConfigurationARN": "arn",
            "InstanceMonitoring": {
                "Enabled": false
            },
            "ImageId": "ami-05355a6c",
            "CreatedTime": "2014-12-29T16:14:50.382Z",
            "BlockDeviceMappings": [],
            "KeyName": "my-key-pair",
            "SecurityGroups": [
                "sg-8422d1eb"
            ],
            "LaunchConfigurationName": "my-lc-from-instance-changetype",
            "KernelId": "null",
            "RamdiskId": null,
            "InstanceType": "t2.medium",
            "AssociatePublicIpAddress": true
        }
    ]
}