# AttachInstances
<a name="API_AttachInstances"></a>

Attaches one or more EC2 instances to the specified Auto Scaling group.

When you attach instances, Amazon EC2 Auto Scaling increases the desired capacity of the group by the number of instances being attached. If the number of instances being attached plus the desired capacity of the group exceeds the maximum size of the group, the operation fails.

If there is a Classic Load Balancer attached to your Auto Scaling group, the instances are also registered with the load balancer. If there are target groups attached to your Auto Scaling group, the instances are also registered with the target groups.

For more information, see [Detach or attach instances](https://docs.aws.amazon.com/autoscaling/ec2/userguide/ec2-auto-scaling-detach-attach-instances.html) in the *Amazon EC2 Auto Scaling User Guide*.

## Request Parameters
<a name="API_AttachInstances_RequestParameters"></a>

 For information about the parameters that are common to all actions, see [Common Parameters](CommonParameters.md).

 ** AutoScalingGroupName **   
The name of the Auto Scaling group.  
Type: String  
Length Constraints: Minimum length of 1. Maximum length of 255.  
Pattern: `[\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*`   
Required: Yes

 **InstanceIds.member.N**   
The IDs of the instances. You can specify up to 20 instances.  
Type: Array of strings  
Length Constraints: Minimum length of 1. Maximum length of 19.  
Pattern: `[\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*`   
Required: No

## Errors
<a name="API_AttachInstances_Errors"></a>

For information about the errors that are common to all actions, see [Common Error Types](CommonErrors.md).

 ** ResourceContention **   
You already have a pending update to an Amazon EC2 Auto Scaling resource (for example, an Auto Scaling group, instance, or load balancer).    
 ** message **   

HTTP Status Code: 500

 ** ServiceLinkedRoleFailure **   
The service-linked role is not yet ready for use.  
HTTP Status Code: 500

## Examples
<a name="API_AttachInstances_Examples"></a>

### Example
<a name="API_AttachInstances_Example_1"></a>

This example illustrates one usage of AttachInstances.

#### Sample Request
<a name="API_AttachInstances_Example_1_Request"></a>

```
https://autoscaling.amazonaws.com/?Action=AttachInstances
&AutoScalingGroupName=my-asg
&InstanceIds.member.1=i-1234567890abcdef0
&Version=2011-01-01
&AUTHPARAMS
```

## See Also
<a name="API_AttachInstances_SeeAlso"></a>

For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS Command Line Interface V2](https://docs.aws.amazon.com/goto/cli2/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for .NET V4](https://docs.aws.amazon.com/goto/DotNetSDKV4/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for Go v2](https://docs.aws.amazon.com/goto/SdkForGoV2/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for JavaScript V3](https://docs.aws.amazon.com/goto/SdkForJavaScriptV3/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for Kotlin](https://docs.aws.amazon.com/goto/SdkForKotlin/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for PHP V3](https://docs.aws.amazon.com/goto/SdkForPHPV3/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for Python](https://docs.aws.amazon.com/goto/boto3/autoscaling-2011-01-01/AttachInstances) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/autoscaling-2011-01-01/AttachInstances)