# BlockDeviceMapping
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Describes a block device mapping.

## Contents
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 ** DeviceName **   
The device name assigned to the volume (for example, `/dev/sdh` or `xvdh`). For more information, see [Device naming on Linux instances](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/device_naming.html) in the *Amazon EC2 User Guide*.  
To define a block device mapping, set the device name and exactly one of the following properties: `Ebs`, `NoDevice`, or `VirtualName`.
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

 ** Ebs **   
Information to attach an EBS volume to an instance at launch.  
Type: [Ebs](API_Ebs.md) object  
Required: No

 ** NoDevice **   
Setting this value to `true` prevents a volume that is included in the block device mapping of the AMI from being mapped to the specified device name at launch.  
If `NoDevice` is `true` for the root device, instances might fail the EC2 health check. In that case, Amazon EC2 Auto Scaling launches replacement instances.  
Type: Boolean  
Required: No

 ** VirtualName **   
The name of the instance store volume (virtual device) to attach to an instance at launch. The name must be in the form ephemeral*X* where *X* is a number starting from zero (0), for example, `ephemeral0`.  
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: No

## See Also
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For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/autoscaling-2011-01-01/BlockDeviceMapping) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/autoscaling-2011-01-01/BlockDeviceMapping) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/autoscaling-2011-01-01/BlockDeviceMapping)