RFC-0081: fastboot boot

RFC-0081: fastboot boot
  • General

Replace Zedboot based netbooting flows with fastboot boot

Gerrit change
Date submitted (year-month-day)2021-03-09
Date reviewed (year-month-day)2021-03-25


This document proposes deprecating RAM loading via Zedboot's netsvc. Instead, it proposes replacing the netsvc based RAM loading flows with flows based on fastboot boot.


Without netsvc RAM loading we can avoid the duplication of this functionality between Zedboot and bootloaders. This RFC is inline with RFC Deprecate Zedboot-based paving for provisioning devices, converging around the use of fastboot instead of Zedboot, allowing for the eventual deprecation and removal of Zedboot.


Netsvc RAM loading is commonly used for bringup workflows using Zedboot. However bootloaders supporting fastboot boot already provide this functionality, e.g. RAM loading a build deployed to a device via the network, and also provide RAM loading via USB. Zedboot was initially developed as a simple networking alternative to using bootloaders because UEFI bootloaders vary in quality and in some fastboot would not be reliable enough. This is less of a problem for targets currently supported by Fuchsia with good enough support or support in the works (e.g. https://fxbug.dev/42137791). Platforms where fastboot is not available have the backup option of flashing Fuchsia to a USB device and booting from it.


Fastboot is a mature mechansim and in use in Android devices. Bootloaders that support Fuchsia MUST follow the fastboot protocol.


Backwards Compatibility

Once fx scripts are updated and Zedboot is removed, there will be no backward compatibility with netsvc.

Security and Privacy considerations

fastboot boot will be supported in unlocked "dev" bootloaders. fastboot boot support for locked bootloaders and unlocked "prod" bootloaders is under consideration but not defined in this RFC.


Documentation for developer workflows will need to be updated to reflect the new fasboot boot based flows.

Drawbacks, alternatives, and unknowns

A drawback is that this creates a commitment to support fastboot in other Fuchsia bootloaders besides those that already support it. This means, as new boards are brought up in Fuchsia, fastboot support is required during early bringup. This includes support for fastboot boot on Gigaboot bootloaders used on Intel NUCs (https://fxbug.dev/42137791) and on coreboot based systems like Pixelbooks.

Prior art and references

Fastboot is a mature mechansim and in use in Android devices.