Amazon EC2 Root Device Volume

You can launch an instance from one of two types of AMIs: an Amazon EC2 instance store-backed AMI or an Amazon EBS-backed AMI. The description of an AMI includes type of AMI it is; you'll see the root device referred to in some places as either ebs (for Amazon EBS-backed) or instance store (for Amazon EC2 instance store-backed). This is important because there are significant differences between what you can do with each type of AMI. For more information about these differences, see Storage for the Root Device.

Instance Store-backed Instances

Instances that use instance stores for the root device automatically have instance store volumes available, with one serving as the root device volume. When an instance is launched, the image that is used to boot the instance is copied to the root volume (typically sda1). Any data on the instance store volumes persists as long as the instance is running and is deleted when the instance is stopped, terminated, or fails (such as if an underlying drive fails).

After an instance store-backed instance fails or terminates, it cannot be restored. If you plan to use Amazon EC2 instance store-backed instances, we highly recommend that you distribute the data on your instance stores across multiple Availability Zones. You should also back up the data on your instance store volumes to Amazon S3 on a regular basis.

For more information, see Amazon EC2 Instance Store.

Amazon EBS-backed Instances

Instances that use Amazon EBS for the root device automatically have an Amazon EBS volume attached. When you launch an Amazon EBS-backed instance, we create an Amazon EBS volume for each EBS snapshot referenced by the AMI you use. You can optionally use other Amazon EBS volumes or instance store volumes.

An Amazon EBS-backed instance can be stopped and later restarted without affecting data stored in the attached volumes. There are various instance– and volume-related tasks you can do when an Amazon EBS-backed instance is in a stopped state. For example, you can modify the properties of the instance, you can change the size of your instance or update the kernel it is using, or you can attach your root volume to a different running instance for debugging or any other purpose.

By default, the root device volume and the other Amazon EBS volumes attached when you launch an Amazon EBS-backed instance are automatically deleted when the instance terminates. For information about how to change this behavior when you launch an instance, see Changing the Root Device Volume to Persist.

By default, any Amazon EBS volumes that you attach to a running instance are detached with their data intact when the instance terminates. You can attach a detached volume to any running instance.

If an Amazon EBS-backed instance fails, you can restore your session by following one of these methods:

We recommend using either the first or the second method for failed instances with normal volume size and the third method for failed instances with large volumes.

You can implement Amazon EBS-backed AMIs by creating a set of snapshots and registering an AMI that uses those snapshots. The AMI publisher controls the default size of the root device through the size of the snapshot. The default size can be increased up to 1TiB to accommodate the requirements of the application either at the time you register the Amazon EBS-backed AMI or while you launch the Amazon EBS-backed instance.

The following list describes the tasks for creating a snapshot of the root device of an Amazon EC2 instance store-backed instance. The snapshot is created using an Amazon EBS volume. You can use this snapshot to create a new Amazon EBS-backed AMI or to launch another instance.

Amazon EC2 instance store-backed AMIs are limited to 10GiB storage for the root device. If you require additional storage on your root device, you must first convert the Amazon EC2 instance store-backed AMI to an Amazon EBS-backed AMI and then launch an Amazon EBS-backed instance with increased root storage.

By default, the root device volume for an AMI backed by Amazon EBS is deleted when the instance terminates. To change the default behavior, set the DeleteOnTermination flag to false in the instance's block device mapping.

AWS Management Console

To change the root device volume to persist when you launch an instance

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

2. From the Amazon EC2 console dashboard, click Launch Instance.

3. On the Create a New Instance page, click Classic Wizard.

4. On the CHOOSE AN AMI page, choose the AMI to use and click Select.

5. Follow the wizard to complete the first and second INSTANCE DETAIL pages.

6. On the third INSTANCE DETAIL page, under Storage Device Configuration, click Edit.

7. Deselect Delete On Termination on the Root Volume tab, click Save, and then click Continue.

   

8. Complete the remaining wizard pages, and then click Launch Instance.

You can verify the setting by viewing details for the root device volume on the instance's details pane in the AWS Management Console. Under Block Devices, click the entry for the root device volume. By default, Delete on termination is Yes. If you change the default behavior, Delete on termination is No.

PROMPT>  ec2-run-instances ami_id  -b root_device_name=::false other parameters... -v

PROMPT>  ec2-run-instances ami-1a2b3c4d  -b /dev/sda1=::false other parameters... -v

PROMPT>  ec2-run-instances ami-1a2b3c4d  -b "xvda=::false" other parameters... -v

...
<blockDeviceMapping>
   <item>
     <deviceName>/dev/sda1</deviceName>
     <ebs>
       <deleteOnTermination>false</deleteOnTermination>
     </ebs>
   </item>
</blockDeviceMapping>
...