Determine the boot mode of an instance

The boot mode of an instance is displayed in the Boot mode field in the Amazon EC2 console, and by the currentInstanceBootMode parameter in the AWS CLI.

When an instance is launched, the value for its boot mode parameter is determined by the value of the boot mode parameter of the AMI used to launch it, as follows:

• An AMI with a boot mode parameter of uefi creates an instance with a currentInstanceBootMode parameter of uefi.

• An AMI with a boot mode parameter of legacy-bios creates an instance with a currentInstanceBootMode parameter of legacy-bios.

• An AMI with a boot mode parameter of uefi-preferred creates an instance with a currentInstanceBootMode parameter of uefi if the instance type supports UEFI; otherwise, it creates an instance with a currentInstanceBootMode parameter of legacy-bios.

• An AMI with no boot mode parameter value creates an instance with a currentInstanceBootMode parameter value that is dependent on whether the AMI architecture is ARM or x86 and the supported boot mode of the instance type. The default boot mode is uefi on Graviton instance types, and legacy-bios on Intel and AMD instance types.

To determine the boot mode of an instance (console)

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

2. In the navigation pane, choose Instances, and then select your instance.

3. On the Details tab, inspect the Boot mode field.

To determine the boot mode of an instance (AWS CLI)

Use the describe-instances command to determine the boot mode of an instance. You can also determine the boot mode of the AMI that was used to the create the instance.

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

In the output, the following parameters describe the boot mode:

• BootMode – The boot mode of the AMI that was used to create the instance.

• CurrentInstanceBootMode – The boot mode that is used to boot the instance at launch or start.

Expected output

{
    "Reservations": [
        {
            "Groups": [],
            "Instances": [
                {
                    "AmiLaunchIndex": 0,
                    "ImageId": "ami-0e2063e7f6dc3bee8",
                    "InstanceId": "i-1234567890abcdef0",
                    "InstanceType": "m5.2xlarge",
                    ... 
                    },
                   "BootMode": "uefi",
                   "CurrentInstanceBootMode": "uefi"
                }
            ],
            "OwnerId": "1234567890",
            "ReservationId": "r-1234567890abcdef0"
        }
    ]
}