Introduction

This section allows setting non-volatile UEFI variables commonly described as NVRAM variables. Refer to man nvram for details. The macOS operating system extensively uses NVRAM variables for OS — Bootloader — Firmware intercommunication. Hence, the supply of several NVRAM variables is required for the proper functioning of macOS.

Each NVRAM variable consists of its name, value, attributes (refer to UEFI specification), and its GUID, representing which ‘section’ the NVRAM variable belongs to. The macOS operating system makes use of several GUIDs, including but not limited to:

4D1EDE05-38C7-4A6A-9CC6-4BCCA8B38C14 (APPLE_VENDOR_VARIABLE_GUID)
7C436110-AB2A-4BBB-A880-FE41995C9F82 (APPLE_BOOT_VARIABLE_GUID)
5EDDA193-A070-416A-85EB-2A1181F45B18 (Apple Hardware Configuration Storage for MacPro7,1)
8BE4DF61-93CA-11D2-AA0D-00E098032B8C (EFI_GLOBAL_VARIABLE_GUID)
4D1FDA02-38C7-4A6A-9CC6-4BCCA8B30102 (OC_VENDOR_VARIABLE_GUID)

Note: Some of the variables may be added by the PlatformNVRAM or Generic subsections of the PlatformInfo section. Please ensure that variables set in this section do not conflict with items in those subsections as the implementation behaviour is undefined otherwise.

The OC_FIRMWARE_RUNTIME protocol implementation, currently offered as a part of the OpenRuntime driver, is often required for macOS to function properly. While this brings many benefits, there are some limitations that should be considered for certain use cases.

Not all tools may be aware of protected namespaces. When RequestBootVarRouting is used, Boot-prefixed variable access is restricted and protected in a separate namespace. To access the original variables, tools must be aware of the OC_FIRMWARE_RUNTIME logic.