# Launch instances into Capacity Reservations in a group
You can launch instances into your existing Capacity Reservations by specifying a Capacity Reservation Resource Group ARN. Instances that target a group match with any Capacity Reservation in the group that has matching attributes (instance type, platform, Availability Zone, and tenancy) and available capacity.
When you launch instances using the [launch instance wizard](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-launch-instance-wizard.html) or the RunInstances API, you can specify only one purchasing option (one reservation type) per launch. To launch into multiple reservation types in the group at once, use [Amazon EC2 Fleet](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-fleet.html) or [Auto Scaling groups](https://docs.aws.amazon.com/autoscaling/ec2/userguide/).
For step-by-step walkthroughs on how to launch instances into multiple Capacity Reservation types using a Capacity Reservation Resource Group, see the following tutorials: via [EC2 Fleet](ec2-fleet-launch-instances-multiple-cr-types-walkthrough.md) and via [Amazon EC2 Auto Scaling](https://docs.aws.amazon.com/autoscaling/ec2/userguide/use-distribution-segments.html).
## On-Demand Capacity Reservations
To launch instances into On-Demand Capacity Reservations in a group, specify the group ARN using the `CapacityReservationTarget` parameter with the `CapacityReservationResourceGroupArn` field.
Amazon EC2 launches instances into any matching On-Demand Capacity Reservation in the group. If no matching capacity is available, the instances launch using On-Demand capacity.
If you don't want instances to launch as On-Demand when no matching capacity is available, set `CapacityReservationPreference` to `capacity-reservations-only`. With this setting, instances fail to launch if no matching On-Demand Capacity Reservation in the group has available capacity.
------
#### [ Console ]
**To launch instances into On-Demand Capacity Reservations in a group**
1. Follow the procedure to launch an instance, but don't launch the instance until you've completed the following steps.
1. Expand **Advanced details**.
1. For **Purchasing option**, leave as **None** (default).
1. For **Capacity Reservation**, choose **Specify Capacity Reservation Resource Group** (default) or **Only launch in a Capacity Reservation Resource Group** (to prevent On-Demand fallback), then select the group.
1. Choose **Launch instance**.
------
#### [ AWS CLI ]
**To launch instances into On-Demand Capacity Reservations in a group**
Use the [run-instances](https://docs.aws.amazon.com/cli/latest/reference/ec2/run-instances.html) command with the `--capacity-reservation-specification` parameter.
The following example launches instances into a group. If the group does not have an ODCR with matching attributes and available capacity, the instances launch as On-Demand instances.
```
aws ec2 run-instances \
--instance-type {{c5.xlarge}} \
--image-id {{ami-0abcdef1234567890}} \
--count {{3}} \
--capacity-reservation-specification \
CapacityReservationTarget={CapacityReservationResourceGroupArn={{arn:aws:resource-groups:sa-east-1:123456789012:group/MyCRGroup}}}
```
The following example launches instances into a group. If the group does not have an ODCR with matching attributes and available capacity, the instances fail to launch.
```
aws ec2 run-instances \
--instance-type {{c5.xlarge}} \
--image-id {{ami-0abcdef1234567890}} \
--count {{3}} \
--capacity-reservation-specification \
CapacityReservationPreference=capacity-reservations-only,CapacityReservationTarget={CapacityReservationResourceGroupArn={{arn:aws:resource-groups:sa-east-1:123456789012:group/MyCRGroup}}}
```
------
### Targeting a specific placement group
Optionally, if your group contains On-Demand Capacity Reservations in a placement group, you can also specify the placement group ID along with the Capacity Reservation Resource Group ARN to place all launched instances into that placement group.
**Note**
Capacity Blocks do not support placement groups. You can't specify a placement group when your request targets Capacity Blocks in a Capacity Reservation Resource Group.
## Interruptible Capacity Reservations
To launch instances into interruptible Capacity Reservations in a group, specify the group ARN and select the interruptible purchasing option. Amazon EC2 places instances into any active interruptible Capacity Reservation in the group with matching attributes and available capacity. If no matching capacity is available, the instances fail to launch.
------
#### [ Console ]
**To launch instances into interruptible Capacity Reservations in a group**
1. Follow the procedure to launch an instance, but don't launch the instance until you've completed the following steps.
1. Expand **Advanced details**.
1. For **Purchasing option**, choose **Interruptible Capacity Reservations**.
1. For **Capacity Reservation**, choose **Specify Capacity Reservation Resource Group** and select the group.
1. Choose **Launch instance**.
------
#### [ AWS CLI ]
**To launch instances into interruptible Capacity Reservations in a group**
Use the [run-instances](https://docs.aws.amazon.com/cli/latest/reference/ec2/run-instances.html) command with the `--instance-market-options` and `--capacity-reservation-specification` parameters.
```
aws ec2 run-instances \
--instance-type {{c5.xlarge}} \
--image-id {{ami-0abcdef1234567890}} \
--count {{3}} \
--instance-market-options MarketType=interruptible-capacity-reservation \
--capacity-reservation-specification \
CapacityReservationTarget={CapacityReservationResourceGroupArn={{arn:aws:resource-groups:sa-east-1:123456789012:group/MyCRGroup}}}
```
------
## Capacity Blocks
To launch instances into Capacity Blocks in a group, specify the group ARN and select the Capacity Blocks purchasing option. Amazon EC2 places instances into any active Capacity Block in the group with matching attributes and available capacity. If no matching capacity is available, the instances fail to launch.
**Note**
You can't specify a placement group when launching into Capacity Blocks in a Capacity Reservation Resource Group.
------
#### [ Console ]
**To launch instances into Capacity Blocks in a group**
1. Follow the procedure to launch an instance, but don't launch the instance until you've completed the following steps.
1. Expand **Advanced details**.
1. For **Purchasing option**, choose **Capacity Blocks**.
1. For **Capacity Reservation**, choose **Specify Capacity Reservation Resource Group** and select the group.
1. Choose **Launch instance**.
------
#### [ AWS CLI ]
**To launch instances into Capacity Blocks in a group**
Use the [run-instances](https://docs.aws.amazon.com/cli/latest/reference/ec2/run-instances.html) command with the `--instance-market-options` and `--capacity-reservation-specification` parameters.
```
aws ec2 run-instances \
--instance-type {{p5.48xlarge}} \
--image-id {{ami-0abcdef1234567890}} \
--count {{1}} \
--instance-market-options MarketType=capacity-block \
--capacity-reservation-specification \
CapacityReservationTarget={CapacityReservationResourceGroupArn={{arn:aws:resource-groups:sa-east-1:123456789012:group/MyCRGroup}}}
```
------