UEFI HTTP Boot

For a detailed description on UEFI HTTP Boot, see the "HTTP Boot" section of the UEFI Specification.

HTTP Boot: Getting Started

Please refer to the white paper EDK II HTTP Boot Getting Started Guide for a step by step guide of the HTTP Boot enabling and server configuration in corporate environment.

Additional information is available on the openSUSE Wiki: UEFI HTTPBoot with OVMF.

Besides the standard DHCP parameters like the station IP, gateway and DNS server address, the EDK II HTTP Boot driver will use the extensions below, assigned by the DHCP server in a corporate environment.

Tag Name	Tag # (DHCPv4)	Tag # (DHCPv6)	Length	Data Field
Boot File	'file' field in DHCP header, or option 67	59	Varies	Boot File URI String (eg. "http://Webserver/Boot/Boot.efi" or "http://Webserver/Boot/Boot.iso")
Class Identifier	60	16	10	"HTTPClient"

URI Configuration in Home Environment

Unlike the corporate network, the DHCP server in a typical home network environment is only available for host IP configuration assignment. This means the boot file URI must be entered by the user instead of the DHCP HTTPBoot extensions.

EDK II HTTP Boot driver provides a configuration page for the boot file URI setup.

1. In the main page of Boot Manager Menu, enter [Device Manager] -> [Network Device List] -> Select a NIC device -> [HTTP Boot Configuration], set the HTTP boot parameters such as the boot option title, IP start version and the URI address as below.
   
2. Save the configuration and back to the main page, enter [Boot Manager] menu as below, select the new created boot option to start the HTTP Boot.
   
3. To delete the boot option, enter [Boot Maintenance Manager] -> [Boot Options] -> [Delete Boot Option].

RAM Disk Boot from HTTP

Besides the UEFI formatted executable image, the downloaded boot file could also be an archive file (hard disk image) or an ISO image. The file should contain an UEFI-compliant file system and will be mounted as a RAM disk by HTTP Boot driver, to be proceeded in the subsequent boot process.

In EDKII HTTP Boot driver, the image type is identified by the media type, or the filename extensions if "Content-Type" header is not present in the HTTP response message.

Media Type	Filename Extensions	Image Type
application/vnd.efi.iso	*.iso	Virtual CD Image
application/vnd.efi.img	*.img	Virtual Disk Image
application/efi	Others (typically *.efi)	UEFI Executable Image

RAM Disk Image Size

According to section 5.2.25.2 "System Physical Address (SPA) Range Structure" in ACPI 6.2 specification, UEFI firmware will try to allocate memory from Reserved memory range to store the downloaded boot image. So the maximum RAM disk image size depends on how much continuous reserved memory block the platform could provide.

System physical address ranges described as address type Virtual CD or Virtual Disk shall be described as EFI Reserved Memory Type in UEFI GetMemoryMap API (AddressRangeReserved in E820 Table).

Feature Enabling

UEFI HTTP boot is supported in UDK2017 release. In previous UDK release, you may need to modify your code to enable the HTTP boot. Beside the HttpDxe/HttpBootDxe driver, the RamDiskDxe driver and the UefiBootManagerLib (commit b1bb6f5, commit fb5848c and commit 3a986a3) are also required.

[LibraryClasses]
  UefiBootManagerLib|MdeModulePkg/Library/UefiBootManagerLib/UefiBootManagerLib.inf
[Components]
  MdeModulePkg/Universal/Disk/RamDiskDxe/RamDiskDxe.inf

Usually the UEFI HTTP Boot is forbidden due to security consideration (only HTTPS is allowed by default), please modify below PCD setting to TRUE in your platform to enable it.

  gEfiNetworkPkgTokenSpaceGuid.PcdAllowHttpConnections