Set the boot mode of an Amazon EC2 AMI - Amazon Elastic Compute Cloud

Set the boot mode of an Amazon EC2 AMI

When you create an AMI using the register-image command, you can set the boot mode of the AMI to either uefi, legacy-bios, or uefi-preferred.

When the AMI boot mode is set to uefi-preferred, the instance boots as follows:

  • For instance types that support both UEFI and Legacy BIOS (for example, m5.large), the instance boots using UEFI.

  • For instance types that support only Legacy BIOS (for example, m4.large), the instance boots using Legacy BIOS.

Note

If you set the AMI boot mode to uefi-preferred, the operating system must support the ability to boot both UEFI and Legacy BIOS.

Currently, you can't use the register-image command to create an AMI that supports both NitroTPM and UEFI Preferred.

Warning

Some features, like UEFI Secure Boot, are only available on instances that boot on UEFI. When you use the uefi-preferred AMI boot mode parameter with an instance type that does not support UEFI, the instance will launch as Legacy BIOS and the UEFI-dependent feature will be disabled. If you rely on the availability of a UEFI-dependent feature, set your AMI boot mode parameter to uefi.

To convert an existing Legacy BIOS-based instance to UEFI, or an existing UEFI-based instance to Legacy BIOS, you need to perform a number of steps: First, modify the instance's volume and operating system to support the selected boot mode. Then, create a snapshot of the volume. Finally, use register-image to create the AMI using the snapshot.

You can't set the boot mode of an AMI using the create-image command. With create-image, the AMI inherits the boot mode of the EC2 instance used for creating the AMI. For example, if you create an AMI from an EC2 instance running on Legacy BIOS, the AMI boot mode will be configured as legacy-bios. If you create an AMI from an EC2 instance that was launched using an AMI with a boot mode set to uefi-preferred, the AMI that is created will also have its boot mode set to uefi-preferred.

Warning

Setting the AMI boot mode parameter does not automatically configure the operating system for the specified boot mode. Before proceeding with these steps, you must first make suitable modifications to the instance's volume and operating system to support booting using the selected boot mode; otherwise, the resulting AMI will not be usable. For example, if you are converting a Legacy BIOS-based Windows instance to UEFI, you can use the MBR2GPT tool from Microsoft to convert the system disk from MBR to GPT. The modifications that are required are operating system-specific. For more information, see the manual for your operating system.

To set the boot mode of an AMI (AWS CLI)

  1. Make suitable modifications to the instance's volume and operating system to support booting via the selected boot mode. The modifications that are required are operating system-specific. For more information, see the manual for your operating system.

    Note

    If you don't perform this step, the AMI will not be usable.

  2. To find the volume ID of the instance, use the describe-instances command. You'll create a snapshot of this volume in the next step.

    aws ec2 describe-instances --region us-east-1 --instance-ids i-1234567890abcdef0

    Expected output

    ...
            "BlockDeviceMappings": [
                        {
                            "DeviceName": "/dev/sda1",
                            "Ebs": {
                                "AttachTime": "",
                                "DeleteOnTermination": true,
                                "Status": "attached",
                                "VolumeId": "vol-1234567890abcdef0"
                            }
                        }
                        ...

  3. To create a snapshot of the volume, use the create-snapshot command. Use the volume ID from the previous step.

    aws ec2 create-snapshot --region us-east-1 --volume-id vol-1234567890abcdef0 --description "add text"

    Expected output

    {
 "Description": "add text",
 "Encrypted": false,
 "OwnerId": "123",
 "Progress": "",
 "SnapshotId": "snap-01234567890abcdef",
 "StartTime": "",
 "State": "pending",
 "VolumeId": "vol-1234567890abcdef0",
 "VolumeSize": 30,
 "Tags": []
}

  4. Note the snapshot ID in the output from the previous step.

  5. Wait until the snapshot creation is completed before going to the next step. To query the state of the snapshot, use the describe-snapshots command.

    aws ec2 describe-snapshots --region us-east-1 --snapshot-ids snap-01234567890abcdef

    Example output

    {
    "Snapshots": [
        {
            "Description": "This is my snapshot",
            "Encrypted": false,
            "VolumeId": "vol-049df61146c4d7901",
            "State": "completed",
            "VolumeSize": 8,
            "StartTime": "2019-02-28T21:28:32.000Z",
            "Progress": "100%",
            "OwnerId": "012345678910",
            "SnapshotId": "snap-01234567890abcdef",
...

  6. To create a new AMI, use the register-image command. Use the snapshot ID that you noted in the earlier step.

    • To set the boot mode to UEFI, add the --boot-mode parameter to the command and specify uefi as the value.

      aws ec2 register-image \
   --region us-east-1 \
   --description "add description" \
   --name "add name" \
   --block-device-mappings "DeviceName=/dev/sda1,Ebs={SnapshotId=snap-01234567890abcdef,DeleteOnTermination=true}" \
   --architecture x86_64 \
   --root-device-name /dev/sda1 \
   --virtualization-type hvm \
   --ena-support \
   --boot-mode uefi

    • To set the boot mode to uefi-preferred, add the --boot-mode parameter to the command and specify uefi-preferred as the value.

      aws ec2 register-image \
   --region us-east-1 \
   --description "add description" \
   --name "add name" \
   --block-device-mappings "DeviceName=/dev/sda1,Ebs={SnapshotId=snap-01234567890abcdef,DeleteOnTermination=true}" \
   --architecture x86_64 \
   --root-device-name /dev/sda1 \
   --virtualization-type hvm \
   --ena-support \
   --boot-mode uefi-preferred

    Expected output

    {
"ImageId": "ami-new_ami_123"
}

  7. To verify that the newly-created AMI has the boot mode that you specified in the previous step, use the describe-images command.

    aws ec2 describe-images --region us-east-1 --image-id ami-new_ami_123

    Expected output

    {
  "Images": [
   {
   "Architecture": "x86_64",
   "CreationDate": "2021-01-06T14:31:04.000Z",
   "ImageId": "ami-new_ami_123",
   "ImageLocation": "",
   ...
   "BootMode": "uefi"
   }
   ]
}

  8. Launch a new instance using the newly-created AMI.

    If the AMI boot mode is uefi or legacy-bios, instances created from this AMI will have the same boot mode as the AMI. If the AMI boot mode is uefi-preferred, the instance will boot using UEFI if the instance type supports UEFI; otherwise, the instance will boot using Legacy BIOS.

  9. To verify that the new instance has the expected boot mode, use the describe-instances command.