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Register EC2 Cloud Images with uefi-preferred AMI flag

Summary

A new feature of EC2 is to be able to register AMIs with a boot mode of uefi-preferred rather than picking one of bios or uefi. In EC2, aarch64 has always been UEFI, while x86-64 started out as BIOS only and some instance types have recently begun to support booting in UEFI mode. Previously, an AMI had to pick if it was UEFI or BIOS. With uefi-preferred it allows an AMI to launch with whatever firmware stack is available for the instance type, preferring UEFI when UEFI is an option.

This proposal is to register the Fedora EC2 images with uefi-preferred, having the effect of switching to booting in UEFI mode on x86-64 in EC2 where available.

Owner

Current status

Detailed Description

Some features of some EC2 instance types (such as secure boot) are only available in UEFI mode. There is also the standard set of advantages of UEFI over BIOS. All aarch64 instance types in EC2 have always been UEFI, while all x86-64 instance types were historically all BIOS. Recently, some x86-64 instance types have started to support UEFI mode. This was originally implemented as an option for instance launches and AMI registration. An AMI could state that it should be booted in UEFI mode. An AMI registered for UEFI would *not* boot on BIOS-only instance types. This meant that if you wanted to make available an OS that could boot on all instance types, you'd need a trio of AMIs: aarch64 UEFI, x86-64 BIOS, and x86-64 UEFI.

With the uefi-preferred boot mode, one AMI registered for x86-64 will boot on UEFI where possible, but also boot BIOS if the instance type doesn't support UEFI.

By registering Fedora AMIs with this boot mode, EC2 features that require UEFI (such as Secure Boot and NitroTPM) will be able to be used in Fedora, while still maintaining compatibility with BIOS only instance types.

Feedback

We have started registering Amazon Linux 2023 AMIs with this boot mode, albeit quite late in the development cycle of AL2023 due to the timing of when the uefi-preferred boot mode flag was added to EC2.

Benefit to Fedora

UEFI is becoming more ubiquitous amongst hardware, and operating under UEFI inside EC2 unlocks an increasing number of features such as Secure Boot and NitroTPM. The benefit for Fedora is a more uniform experience across cloud and non-cloud environments, simplifying the boot and runtime software stack.

Scope

  • Proposal owners: Modify the AMI registration call to include uefi-preferred, verifying that Fedora AMIs are assembled correctly for booting under UEFI.
  • Other developers: No changes needed by other developers
  • Release engineering: N/A
  • Policies and guidelines: N/A (not needed for this Change)
  • Trademark approval: N/A (not needed for this Change)
  • Alignment with Community Initiatives:

Upgrade/compatibility impact

How To Test

Once the AMI is registered, verify that the parameter is set, and that instances can be launched for each instance type. Normal testing should cover this.

User Experience

Users will be able to use features in EC2 that require UEFI such as Secure Boot and NitroTPM.

Dependencies

Contingency Plan

  • Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
  • Contingency deadline: N/A (not a System Wide Change)
  • Blocks release? N/A (not a System Wide Change), Yes/No


Documentation


Release Notes

EC2 images are now registered with the uefi-preferred boot mode, thus boot in UEFI mode where possible.

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