# Add block device mappings to an AMI
<a name="ami-block-device-mapping"></a>

Each AMI has a block device mapping that specifies the block devices to attach to an instance when it is launched from the AMI. To add more block devices to an AMI, you must create your own AMI.

**Topics**
+ [

## Specify a block device mapping for an AMI
](#create-ami-bdm)
+ [

## View the EBS volumes in an AMI block device mapping
](#view-ami-bdm)

## Specify a block device mapping for an AMI
<a name="create-ami-bdm"></a>

There are two ways to specify volumes in addition to the root volume when you create an AMI. If you've already attached volumes to a running instance before you create an AMI from the instance, the block device mapping for the AMI includes those same volumes. For EBS volumes, the existing data is saved to a new snapshot, and it's this new snapshot that's specified in the block device mapping. For instance store volumes, the data is not preserved.

For an EBS-backed AMI, you can add EBS volumes and instance store volumes using a block device mapping. For an Amazon S3-backed AMI, you can add instance store volumes only by modifying the block device mapping entries in the image manifest file when registering the image.

**Note**  
For M3 instances, you must specify instance store volumes in the block device mapping for the instance when you launch it. When you launch an M3 instance, instance store volumes specified in the block device mapping for the AMI may be ignored if they are not specified as part of the instance block device mapping.

------
#### [ Console ]

**To add volumes to an AMI**

1. Open the Amazon EC2 console.

1. In the navigation pane, choose **Instances**.

1. Select an instance and choose **Actions**, **Image and templates**, **Create image**.

1. Enter a name and a description for the image.

1. The instance volumes appear under **Instance volumes**. To add another volume, choose **Add volume**.

1. For **Volume type**, choose the volume type. For **Device** choose the device name. For an EBS volume, you can specify additional details, such as a snapshot, volume size, volume type, IOPS, and encryption state.

1. Choose **Create image**.

------
#### [ AWS CLI ]

**To add volumes to an AMI**

Use the [create-image](https://docs.aws.amazon.com/cli/latest/reference/ec2/create-image.html) command to specify a block device mapping for an EBS-backed AMI. Use the [register-image](https://docs.aws.amazon.com/cli/latest/reference/ec2/register-image.html) command to specify a block device mapping for an Amazon S3-backed AMI.

Specify the block device mapping using the `--block-device-mappings` parameter. You can specified arguments encoded in JSON directly on the command line or by referencing a JSON file, as shown here.

```
--block-device-mappings file://mapping.json
```

To add an instance store volume, use the following mapping. Note that NVMe instance store volumes are added automatically.

```
{
    "DeviceName": "device_name",
    "VirtualName": "ephemeral0"
}
```

To add an empty 100 GiB volume, use the following mapping.

```
{
    "DeviceName": "device_name",
    "Ebs": {
      "VolumeSize": 100
    }
}
```

To add an EBS volume based on a snapshot, use the following mapping.

```
{
    "DeviceName": "device_name",
    "Ebs": {
      "SnapshotId": "snap-1234567890abcdef0"
    }
}
```

To omit a mapping for a device, use the following mapping.

```
{
    "DeviceName": "device_name",
    "NoDevice": ""
}
```

------
#### [ PowerShell ]

Use the [New-EC2Image](https://docs.aws.amazon.com/powershell/latest/reference/items/New-EC2Image.html) cmdlet to specify a block device mapping for an EBS-backed AMI. Use the [Register-EC2Image](https://docs.aws.amazon.com/powershell/latest/reference/items/Register-EC2Image.html) cmdlet to specify a block device mapping for an Amazon S3-backed AMI.

Add the `-BlockDeviceMapping` option, specifying the updates in `bdm`:

```
-BlockDeviceMapping $bdm
```

The following mapping adds a volume based on a snapshot.

```
$ebd = New-Object -TypeName Amazon.EC2.Model.EbsBlockDevice
$ebd.SnapshotId = "snap-1234567890abcdef0"
$bdm = New-Object -TypeName Amazon.EC2.Model.BlockDeviceMapping
$bdm.DeviceName = "device_name"
$bdm.Ebs = $ebd
```

The following mapping adds an empty 100 GB volume.

```
$ebd = New-Object -TypeName Amazon.EC2.Model.EbsBlockDevice
$ebd.VolumeSize = 100
$bdm = New-Object -TypeName Amazon.EC2.Model.BlockDeviceMapping
$bdm.DeviceName = "device_name"
$bdm.Ebs = $ebd
```

------

## View the EBS volumes in an AMI block device mapping
<a name="view-ami-bdm"></a>

You can easily enumerate the EBS volumes in the block device mapping for an AMI.

------
#### [ Console ]

**To view the EBS volumes for an AMI**

1. Open the Amazon EC2 console.

1. In the navigation pane, choose **AMIs**.

1. Choose **EBS images** from the **Filter** list to get a list of EBS-backed AMIs. 

1. Select the desired AMI, and look at the **Details** tab. At a minimum, the following information is available for the root volume (where the term **root device** is equivalent to **root volume**):
   + **Root Device Type** (`ebs`)
   + **Root Device Name** (for example, `/dev/sda1`)
   + **Block Devices** (for example, `/dev/sda1=snap-1234567890abcdef0:8:true`)

   If the AMI was created with additional EBS volumes using a block device mapping, the **Block Devices** field displays the mapping for those additional volumes as well. (This screen doesn't display instance store volumes.)

------
#### [ AWS CLI ]

**To view the EBS volumes for an AMI**  
Use the [describe-images](https://docs.aws.amazon.com/cli/latest/reference/ec2/describe-images.html) command.

```
aws ec2 describe-images \
    --image-ids ami-0abcdef1234567890 \
    --query Image[0].BlockDeviceMappings
```

------
#### [ PowerShell ]

**To view the EBS volumes for an AMI**  
Use the [Get-EC2Image](https://docs.aws.amazon.com/powershell/latest/reference/items/Get-EC2Image.html) cmdlet.

```
(Get-EC2Image -ImageId ami-0abcdef1234567890).BlockDeviceMappings
```

------