Create an Auto Scaling group using parameters from an
existing instance

Important

This topic only applies to creating an Auto Scaling group using a launch configuration. We
provide information about launch configurations for customers who have not yet migrated
from launch configurations to launch templates.

If this is your first time creating an Auto Scaling group, we recommend you use the console to
create a launch template from an existing EC2 instance. Then use the launch template to
create a new Auto Scaling group. For this procedure, see Create an Auto Scaling group using the Amazon EC2 launch
wizard.

The following procedure shows how to create an Auto Scaling group by specifying an existing
instance to use as a base for launching other instances. Multiple parameters are required to
create an EC2 instance, such as the Amazon Machine Image (AMI) ID, instance type, key pair,
and security group. All of this information is also used by Amazon EC2 Auto Scaling to launch instances on
your behalf when there is a need to scale. This information is stored in either a launch
template or a launch configuration.

When you use an existing instance, Amazon EC2 Auto Scaling creates an Auto Scaling group that launches instances
based on a launch configuration that’s created at the same time. The new launch
configuration has the same name as the Auto Scaling group, and it includes certain configuration
details from the identified instance.

The following configuration details are copied from the identified instance into the
launch configuration:

• AMI ID

• Instance type

• Key pair

• Security groups

• IP address type (public or private)

• IAM instance profile, if applicable

• Monitoring (true or false)

• EBS optimized (true or false)

• Tenancy setting, if launching into a VPC (shared or dedicated)

• Kernel ID and RAM disk ID, if applicable

• User data, if specified

• Spot (maximum) price

The following configuration details are not copied from your identified instance:

• Storage: The block devices (EBS volumes and instance store volumes) are not copied
  from the identified instance. Instead, the block device mapping created as part of
  creating the AMI determines which devices are used.

• Number of network interfaces: The network interfaces are not copied from your
  identified instance. Instead, Amazon EC2 Auto Scaling uses its default settings to create one
  network interface, which is the primary network interface (eth0).

• Instance metadata options: The metadata accessible, metadata version, and token
  response hop limit settings are not copied from the identified instance. Instead,
  Amazon EC2 Auto Scaling uses its default settings. For more information, see Configure the instance metadata
  options.

• Load balancers: If the identified instance is registered with one or more load
  balancers, the information about the load balancer is not copied to the load
  balancer or target group attribute of the new Auto Scaling group.

• Tags: If the identified instance has tags, the tags are not copied to the
  Tags attribute of the new Auto Scaling group.

The new Auto Scaling group launches instances into the same Availability Zone, VPC, and subnet in
which the identified instance is located.

If the identified instance is in a placement group, the new Auto Scaling group launches instances
into the same placement group as the identified instance. Because the launch configuration
settings do not allow a placement group to be specified, the placement group is copied to
the PlacementGroup attribute of the new Auto Scaling group.

Prerequisites

The EC2 instance must meet the following criteria:

• The instance is in the subnet and Availability Zone in which you want to
  create the Auto Scaling group.

• The instance is not a member of another Auto Scaling group.

• The instance is in the running state.

• The AMI that was used to launch the instance must still exist.

Create an Auto Scaling group from an EC2
instance (console)

To create an Auto Scaling group from an EC2 instance

1. Open the Amazon EC2 console at
   https://console.aws.amazon.com/ec2/.

2. On the navigation pane, under Instances, choose
   Instances, and then select an instance.

3. Choose Actions, Instance settings,
   Attach to Auto Scaling Group.

4. On the Attach to Auto Scaling group page, for
   Auto Scaling Group, enter a name for the group, and
   then choose Attach.

   After the instance is attached, it is considered part of the Auto Scaling group. The
   new Auto Scaling group is created using a new launch configuration with the same name
   that you specified for the Auto Scaling group. The Auto Scaling group has a desired capacity and
   maximum size of 1.

5. (Optional) To edit the settings for the Auto Scaling group, on the navigation pane,
   under Auto Scaling, choose Auto Scaling
   Groups. Select the check box next to the new Auto Scaling group, choose
   the Edit button that is above the list of groups, change
   the settings as needed, and then choose Update.

Create an Auto Scaling group from an EC2
instance (AWS CLI)

In this exercise, we demonstrate how to use the AWS CLI to create an Auto Scaling group from an
EC2 instance.

This procedure does not add the instance to the Auto Scaling group. For the instance to be
attached, you must run the attach-instances command after the Auto Scaling group has been created.

Before you begin, find the ID of the EC2 instance using the Amazon EC2 console or the
describe-instances
command.

To use your current instance as a template

• Use the following create-auto-scaling-group command to create an Auto Scaling group,
  my-asg-from-instance, from the EC2 instance
  i-0e69cc3f05f825f4f.

  aws autoscaling create-auto-scaling-group --auto-scaling-group-name my-asg-from-instance \
    --instance-id i-0e69cc3f05f825f4f --min-size 1 --max-size 2 --desired-capacity 2

To verify that your Auto Scaling group has launched instances

• Use the following describe-auto-scaling-groups command to verify that the Auto Scaling group
  was created successfully.

  aws autoscaling describe-auto-scaling-groups --auto-scaling-group-name my-asg-from-instance

  The following example response shows that the desired capacity of the group is
  2, the group has 2 running instances, and the launch configuration is named
  my-asg-from-instance.

  {
    "AutoScalingGroups":[
      
  {
        "AutoScalingGroupName":"my-asg-from-instance",
        "AutoScalingGroupARN":"arn",
        "LaunchConfigurationName":"my-asg-from-instance",
        "MinSize":1,
        "MaxSize":2,
        "DesiredCapacity":2,
        "DefaultCooldown":300,
        "AvailabilityZones":[
          "us-west-2a"
        ],
        "LoadBalancerNames":[ ],
        "TargetGroupARNs":[ ],
        "HealthCheckType":"EC2",
        "HealthCheckGracePeriod":0,
        "Instances":[
          
  {
            "InstanceId":"i-06905f55584de02da",
            "InstanceType":"t2.micro",
            "AvailabilityZone":"us-west-2a",
            "LifecycleState":"InService",
            "HealthStatus":"Healthy",
            "LaunchConfigurationName":"my-asg-from-instance",
            "ProtectedFromScaleIn":false
          },
          
  {
            "InstanceId":"i-087b42219468eacde",
            "InstanceType":"t2.micro",
            "AvailabilityZone":"us-west-2a",
            "LifecycleState":"InService",
            "HealthStatus":"Healthy",
            "LaunchConfigurationName":"my-asg-from-instance",
            "ProtectedFromScaleIn":false
          }
        ],
        "CreatedTime":"2020-10-28T02:39:22.152Z",
        "SuspendedProcesses":[ ],
        "VPCZoneIdentifier":"subnet-6bea5f06",
        "EnabledMetrics":[ ],
        "Tags":[ ],
        "TerminationPolicies":[
          "Default"
        ],
        "NewInstancesProtectedFromScaleIn":false,
        "ServiceLinkedRoleARN":"arn"
      }
    ]
  }

To view the launch configuration

• Use the following describe-launch-configurations command to view the details of the
  launch configuration.

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

  The following is example output:

  {
    "LaunchConfigurations":[
      
  {
        "LaunchConfigurationName":"my-asg-from-instance",
        "LaunchConfigurationARN":"arn",
        "ImageId":"ami-0528a5175983e7f28",
        "KeyName":"my-key-pair-uswest2",
        "SecurityGroups":[
          "sg-05eaec502fcdadc2e"
        ],
        "ClassicLinkVPCSecurityGroups":[ ],
        "UserData":"",
        "InstanceType":"t2.micro",
        "KernelId":"",
        "RamdiskId":"",
        "BlockDeviceMappings":[ ],
        "InstanceMonitoring":
  {
          "Enabled":true
        },
        "CreatedTime":"2020-10-28T02:39:22.321Z",
        "EbsOptimized":false,
        "AssociatePublicIpAddress":true
      }
    ]
  }             

To terminate the instance

• If you no longer need the instance, you can terminate it. The following terminate-instances command terminates the instance
  i-0e69cc3f05f825f4f.

  aws ec2 terminate-instances --instance-ids i-0e69cc3f05f825f4f

  After you terminate an Amazon EC2 instance, you can’t restart the instance. After
  termination, its data is gone and the volume can’t be attached to any instance.
  To learn more about terminating instances, see Terminate an instance in the Amazon EC2 User Guide for Linux Instances.