Create a Capacity Reservation Launch instances into an existing Capacity Reservation Modify a Capacity Reservation Modify an instance's Capacity Reservation settings View a Capacity Reservation Cancel a Capacity Reservation

Work with Capacity Reservations

To start using Capacity Reservations, you create the capacity reservation in the required Availability Zone. Then, you can launch instances into the reserved capacity, view its capacity utilization in real time, and increase or decrease its capacity as needed.

By default, Capacity Reservations automatically match new instances and running instances that have matching attributes (instance type, platform, and Availability Zone). This means that any instance with matching attributes automatically runs in the Capacity Reservation. However, you can also target a Capacity Reservation for specific workloads. This enables you to explicitly control which instances are allowed to run in that reserved capacity.

You can specify how the reservation ends. You can choose to cancel the Capacity Reservation or end it automatically at a specified time. If you specify an end time, the Capacity Reservation is canceled within an hour of the specified time. For example, if you specify 5/31/2019, 13:30:55, the Capacity Reservation is guaranteed to end between 13:30:55 and 14:30:55 on 5/31/2019. After a reservation ends, you can no longer target instances to the Capacity Reservation. Instances running in the reserved capacity continue to run uninterrupted. If instances targeting a Capacity Reservation are stopped, you cannot restart them until you remove their Capacity Reservation targeting preference or configure them to target a different Capacity Reservation.

Create a Capacity Reservation

If your request to create a Capacity Reservation succeeds, the capacity is available immediately. The capacity remains reserved for your use as long as the Capacity Reservation is active, and you can launch instances into it at any time. If the Capacity Reservation is open, new instances and existing instances that have matching attributes automatically run in the capacity of the Capacity Reservation. If the Capacity Reservation is targeted, instances must specifically target it to run in the reserved capacity.

Your request to create a Capacity Reservation could fail if one of the following is true:

Amazon EC2 does not have sufficient capacity to fulfill the request. Either try again at a later time, try a different Availability Zone, or try a smaller request. If your application is flexible across instance types and sizes, try different instance attributes.
The requested quantity exceeds your On-Demand Instance limit for the selected instance family. Increase your On-Demand Instance limit for the instance family and try again. For more information, see On-Demand Instance quotas.

To create a Capacity Reservation using the console

Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
Choose Capacity Reservations, and then choose Create Capacity Reservation.
On the Create a Capacity Reservation page, configure the following settings in the Instance details section. The instance type, platform, and Availability Zone of the instances that you launch must match the instance type, platform, and Availability Zone that you specify here or the Capacity Reservation is not applied. For example, if an open Capacity Reservation doesn't match, an instance launch that targets that Capacity Reservation explicitly will fail.
1. Instance Type—The type of instance to launch into the reserved capacity.
2. Launch EBS-optimized instances—Specify whether to reserve the capacity for EBS-optimized instances. This option is selected by default for some instance types. For more information, see Amazon EBS–optimized instances.
3. Platform—The operating system for your instances. For more information, see Supported platforms. For more information about the supported Windows platforms, see Supported platforms in the Amazon EC2 User Guide for Windows Instances.
4. Availability Zone—The Availability Zone in which to reserve the capacity.
5. Tenancy—Specify whether to run on shared hardware (default) or a dedicated instance.
6. (Optional) Placement group ARN —The ARN of the cluster placement group in which to create the Capacity Reservation.
  
  For more information, see Capacity Reservations in cluster placement groups.
7. Quantity—The number of instances for which to reserve capacity. If you specify a quantity that exceeds your remaining On-Demand Instance limit for the selected instance type, the request is denied.
Configure the following settings in the Reservation details section:
1. Reservation Ends—Choose one of the following options:
  - Manually—Reserve the capacity until you explicitly cancel it.
  - Specific time—Cancel the capacity reservation automatically at the specified date and time.
2. Instance eligibility—Choose one of the following options:
  - open—(Default) The Capacity Reservation matches any instance that has matching attributes (instance type, platform, and Availability Zone). If you launch an instance with matching attributes, it is placed into the reserved capacity automatically.
  - targeted—The Capacity Reservation only accepts instances that have matching attributes (instance type, platform, and Availability Zone), and that explicitly target the reservation.
Choose Request reservation.

To create a Capacity Reservation using the AWS CLI

Use the create-capacity-reservation command. For more information, see Supported platforms. For more information about the supported Windows platforms, see Supported platforms in the Amazon EC2 User Guide for Windows Instances.

For example, the following command creates a Capacity Reservation that reserves capacity for three m5.2xlarge instances running Red Hat Enterprise Linux AMIs in the us-east-1a Availability Zone.


aws ec2 create-capacity-reservation --instance-type m5.2xlarge --instance-platform Red Hat Enterprise Linux --availability-zone us-east-1a --instance-count 3

Launch instances into an existing Capacity Reservation

When you launch an instance, you can specify whether to launch the instance into any open Capacity Reservation, into a specific Capacity Reservation, or into a group of Capacity Reservations. You can only launch an instance into a Capacity Reservation that has matching attributes (instance type, platform, and Availability Zone) and sufficient capacity. Alternatively, you can configure the instance to avoid running in a Capacity Reservation, even if you have an open Capacity Reservation that has matching attributes and available capacity.

Launching an instance into a Capacity Reservation reduces its available capacity by the number of instances launched. For example, if you launch three instances, the available capacity of the Capacity Reservation is reduced by three.

To launch instances into an existing Capacity Reservation using the console

Follow the procedure to launch an instance, but don't launch the instance until you've completed the following steps to specify the settings for the placement group and Capacity Reservation.
Expand Advanced details and do the following:
1. For Placement group, select the cluster placement group in which to launch the instance.
2. For Capacity Reservation, choose one of the following options depending on the configuration of the Capacity Reservation:
  - None – Prevents the instances from launching into a Capacity Reservation. The instances run in On-Demand capacity.
  - Open – Launches the instances into any Capacity Reservation that has matching attributes and sufficient capacity for the number of instances you selected. If there is no matching Capacity Reservation with sufficient capacity, the instance uses On-Demand capacity.
  - Target by ID – Launches the instances into the selected Capacity Reservation. If the selected Capacity Reservation does not have sufficient capacity for the number of instances you selected, the instance launch fails.
  - Target by group – Launches the instances into any Capacity Reservation with matching attributes and available capacity in the selected Capacity Reservation group. If the selected group does not have a Capacity Reservation with matching attributes and available capacity, the instances launch into On-Demand capacity.
In the Summary panel, review your instance configuration, and then choose Launch instance. For more information, see Launch an instance using the new launch instance wizard.

To launch an instance into an existing Capacity Reservation using the AWS CLI

Use the run-instances command and specify the --capacity-reservation-specification parameter.

The following example launches a t2.micro instance into any open Capacity Reservation that has matching attributes and available capacity:


aws ec2 run-instances --image-id ami-abc12345 --count 1 --instance-type t2.micro --key-name MyKeyPair --subnet-id subnet-1234567890abcdef1 --capacity-reservation-specification CapacityReservationPreference=open

The following example launches a t2.micro instance into a targeted Capacity Reservation:


aws ec2 run-instances --image-id ami-abc12345 --count 1 --instance-type t2.micro --key-name MyKeyPair --subnet-id subnet-1234567890abcdef1 --capacity-reservation-specification CapacityReservationTarget={CapacityReservationId=cr-a1234567}

The following example launches a t2.micro instance into a Capacity Reservation group:


aws ec2 run-instances --image-id ami-abc12345 --count 1 --instance-type t2.micro --key-name MyKeyPair --subnet-id subnet-1234567890abcdef1 --capacity-reservation-specification CapacityReservationTarget={CapacityReservationResourceGroupArn=arn:aws:resource-groups:us-west-1:123456789012:group/my-cr-group}

Modify a Capacity Reservation

You can change the attributes of an active Capacity Reservation after you have created it. You cannot modify a Capacity Reservation after it has expired or after you have explicitly canceled it.

When modifying a Capacity Reservation, you can only increase or decrease the quantity and change the way in which it is released. You cannot change the instance type, EBS optimization, platform, Availability Zone, or instance eligibility of a Capacity Reservation. If you need to modify any of these attributes, we recommend that you cancel the reservation, and then create a new one with the required attributes.

If you specify a new quantity that exceeds your remaining On-Demand Instance limit for the selected instance type, the update fails.

To modify a Capacity Reservation using the console

Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
Choose Capacity Reservations, select the Capacity Reservation to modify, and then choose Edit.
Modify the Quantity or Reservation ends options as needed, and choose Save changes.

To modify a Capacity Reservation using the AWS CLI

Use the modify-capacity-reservation command:

For example, the following command modifies a Capacity Reservation to reserve capacity for eight instances.


aws ec2 modify-capacity-reservation --capacity-reservation-id cr-1234567890abcdef0 --instance-count 8

Modify an instance's Capacity Reservation settings

You can modify the following Capacity Reservation settings for a stopped instance at any time:

Start in any Capacity Reservation that has matching attributes (instance type, platform, and Availability Zone) and available capacity.
Start the instance in a specific Capacity Reservation.
Start in any Capacity Reservation that has matching attributes and available capacity in a Capacity Reservation group
Prevent the instance from starting in a Capacity Reservation.

To modify an instance's Capacity Reservation settings using the console

Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
Choose Instances and select the instance to modify. Stop the instance if it is not already stopped.
Choose Actions, Modify Capacity Reservation Settings.
For Capacity Reservation, choose one of the following options:
- Open — Launches the instances into any Capacity Reservation that has matching attributes and sufficient capacity for the number of instances you selected. If there is no matching Capacity Reservation with sufficient capacity, the instance uses On-Demand capacity.
- None — Prevents the instances from launching into a Capacity Reservation. The instances run in On-Demand capacity.
- Specify Capacity Reservation — Launches the instances into the selected Capacity Reservation. If the selected Capacity Reservation does not have sufficient capacity for the number of instances you selected, the instance launch fails.
- Specify Capacity Reservation group — Launches the instances into any Capacity Reservation with matching attributes and available capacity in the selected Capacity Reservation group. If the selected group does not have a Capacity Reservation with matching attributes and available capacity, the instances launch into On-Demand capacity.

To modify an instance's Capacity Reservation settings using the AWS CLI

Use the modify-instance-capacity-reservation-attributes command.

For example, the following command changes an instance's Capacity Reservation setting to open or none.


aws ec2 modify-instance-capacity-reservation-attributes --instance-id i-1234567890abcdef0 --capacity-reservation-specification CapacityReservationPreference=none|open

For example, the following command modifies an instance to target a specific Capacity Reservation.


aws ec2 modify-instance-capacity-reservation-attributes --instance-id i-1234567890abcdef0 --capacity-reservation-specification CapacityReservationTarget={CapacityReservationId=cr-1234567890abcdef0}

For example, the following command modifies an instance to target a specific Capacity Reservation group.


aws ec2 modify-instance-capacity-reservation-attributes --instance-id i-1234567890abcdef0 --capacity-reservation-specification CapacityReservationTarget={CapacityReservationResourceGroupArn=arn:aws:resource-groups:us-west-1:123456789012:group/my-cr-group}

View a Capacity Reservation

Capacity Reservations have the following possible states:

active—The capacity is available for use.
expired—The Capacity Reservation expired automatically at the date and time specified in your reservation request. The reserved capacity is no longer available for your use.
cancelled—The Capacity Reservation was canceled. The reserved capacity is no longer available for your use.
pending—The Capacity Reservation request was successful but the capacity provisioning is still pending.
failed—The Capacity Reservation request has failed. A request can fail due to request parameters that are not valid, capacity constraints, or instance limit constraints. You can view a failed request for 60 minutes.

Note

Due to the eventual consistency model followed by the Amazon EC2 APIs, after you create a Capacity Reservation, it can take up to 5 minutes for the console and the describe-capacity-reservations response to indicate that the Capacity Reservation is in the active state. During this time, the console and the describe-capacity-reservations response might indicate that the Capacity Reservation is in the pending state. However, the Capacity Reservation might already be available for use and you can attempt to launch instances into it.

To view your Capacity Reservations using the console

Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
Choose Capacity Reservations and select a Capacity Reservation to view.
Choose View launched instances for this reservation.

To view your Capacity Reservations using the AWS CLI

Use the describe-capacity-reservations command:

For example, the following command describes all Capacity Reservations.


aws ec2 describe-capacity-reservations

Example output.


{
    "CapacityReservations": [
        {
            "CapacityReservationId": "cr-1234abcd56EXAMPLE ",
            "EndDateType": "unlimited",
            "AvailabilityZone": "eu-west-1a",
            "InstanceMatchCriteria": "open",
            "Tags": [],
            "EphemeralStorage": false,
            "CreateDate": "2019-08-16T09:03:18.000Z",
            "AvailableInstanceCount": 1,
            "InstancePlatform": "Linux/UNIX",
            "TotalInstanceCount": 1,
            "State": "active",
            "Tenancy": "default",
            "EbsOptimized": true,
            "InstanceType": "a1.medium",
            "PlacementGroupArn": "arn:aws:ec2:us-east-1:123456789012:placement-group/MyPG"
        },
        {
            "CapacityReservationId": "cr-abcdEXAMPLE9876ef ",
            "EndDateType": "unlimited",
            "AvailabilityZone": "eu-west-1a",
            "InstanceMatchCriteria": "open",
            "Tags": [],
            "EphemeralStorage": false,
            "CreateDate": "2019-08-07T11:34:19.000Z",
            "AvailableInstanceCount": 3,
            "InstancePlatform": "Linux/UNIX",
            "TotalInstanceCount": 3,
            "State": "cancelled",
            "Tenancy": "default",
            "EbsOptimized": true,
            "InstanceType": "m5.large"
        }
    ]
}

Cancel a Capacity Reservation

You can cancel a Capacity Reservation at any time if you no longer need the reserved capacity. When you cancel a Capacity Reservation, the capacity is released immediately, and it is no longer reserved for your use.

You can cancel empty Capacity Reservations and Capacity Reservations that have running instances. If you cancel a Capacity Reservation that has running instances, the instances continue to run normally outside of the capacity reservation at standard On-Demand Instance rates or at a discounted rate if you have a matching Savings Plan or Regional Reserved Instance.

After you cancel a Capacity Reservation, instances that target it can no longer launch. Modify these instances so that they either target a different Capacity Reservation, launch into any open Capacity Reservation with matching attributes and sufficient capacity, or avoid launching into a Capacity Reservation. For more information, see Modify an instance's Capacity Reservation settings.

To cancel a Capacity Reservation using the console

Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
Choose Capacity Reservations and select the Capacity Reservation to cancel.
Choose Cancel reservation, Cancel reservation.

To cancel a Capacity Reservation using the AWS CLI

Use the cancel-capacity-reservation command:

For example, the following command cancels a Capacity Reservation with an ID of cr-1234567890abcdef0.


aws ec2 cancel-capacity-reservation --capacity-reservation-id cr-1234567890abcdef0

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Document Conventions

Capacity Reservation pricing and billing

Work with Capacity Reservation groups