Instance launch behavior with Amazon EC2 boot modes
When a computer boots, the first software that it runs is responsible for initializing theplatform and providing an interface for the operating system to perform platform-specificoperations.
In Amazon EC2, two variants of the boot mode software are supported: Unified Extensible Firmware Interface (UEFI) and Legacy BIOS.
Possible boot mode parameters on an AMI
An AMI can have one of the following boot mode parameter values:uefi,legacy-bios, oruefi-preferred. The AMI boot modeparameter is optional. For AMIs with no boot mode parameter, the instances launched fromthese AMIs use the default boot mode value of the instance type.
Purpose of the AMI boot mode parameter
The AMI boot mode parameter signals to Amazon EC2 which boot mode to use when launching aninstance. When the boot mode parameter is set touefi, EC2 attempts tolaunch the instance on UEFI. If the operating system is not configured to support UEFI,the instance launch will be unsuccessful.
UEFI Preferred boot mode parameter
You can create AMIs that support both UEFI and Legacy BIOS by using theuefi-preferred boot mode parameter. When the boot mode parameter is set touefi-preferred, and if the instance type supports UEFI, the instance is launched on UEFI. If the instance type does not support UEFI, the instance is launched on Legacy BIOS.
Some features, like UEFI Secure Boot, are only available on instances that boot on UEFI.When you use theuefi-preferred AMI boot mode parameter with aninstance type that does not support UEFI, the instance will launch as Legacy BIOSand the UEFI-dependent feature will be disabled. If you rely on the availability ofa UEFI-dependent feature, set your AMI boot mode parameter touefi.
Default boot modes for instance types
Graviton instance types: UEFI
Intel and AMD instance types: Legacy BIOS
Zone support
UEFI boot is not supported in Wavelength Zones.
