Boot modes - Amazon Elastic Compute Cloud
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Boot modes

When a computer boots, the first software that it runs is responsible for initializing the platform and providing an interface for the operating system to perform platform-specific operations.

Default boot modes

In EC2, two variants of the boot mode software are supported: Unified Extensible Firmware Interface (UEFI) and Legacy BIOS. By default, Graviton instance types run on UEFI, and Intel and AMD instance types run on Legacy BIOS.

Running Intel and AMD instances types on UEFI

Most Intel and AMD instance types can run on both UEFI and Legacy BIOS. To use UEFI, you must select an AMI with the boot mode parameter set to uefi, and the operating system contained in the AMI must be configured to support UEFI.

Purpose of the AMI boot mode parameter

The AMI boot mode parameter signals to EC2 which boot mode to use when launching an instance. When the boot mode parameter is set to uefi, EC2 attempts to launch the instance on UEFI. If the operating system is not configured to support UEFI, the instance launch might be unsuccessful.

Warning

Setting the boot mode parameter does not automatically configure the operating system for the specified boot mode. The configuration is specific to the operating system. For the configuration instructions, see the manual for your operating system.

Possible boot mode parameters on an AMI

The AMI boot mode parameter is optional. An AMI can have one of the following boot mode parameter values: uefi or legacy-bios. Some AMIs do not have a boot mode parameter. For AMIs with no boot mode parameter, the instances launched from these AMIs use the default value of the instance type—uefi on Graviton, and legacy-bios on all Intel and AMD instance types.