efivar

Efivar is an open-source userspace project that provides a library and utilities for accessing and managing UEFI (Unified Extensible Firmware Interface) variables on systems that expose them to the operating system. It is primarily used on Linux systems that present UEFI variables through the kernel interfaces such as efivarfs or the efivars sysfs entries.

Functionality includes enumerating, reading, creating, modifying, and deleting UEFI variables identified by GUID namespaces and names. The project supports handling of common EFI variable attributes (for example, runtime and hardware-backed flags), binary payloads, and operations related to authenticated variables used by Secure Boot (such as signature lists and key management). Typical use cases include managing boot entries, Secure Boot keys, platform configuration data, and vendor-specific firmware settings.

Efivar is implemented as a lightweight C library with accompanying command-line tools that require elevated privileges because UEFI variables can affect firmware behavior. It is integrated into many Linux distributions’ tooling and is often used by installers, firmware utilities, and system management scripts. Users are advised to exercise caution when modifying variables, since incorrect changes can render firmware configuration inaccessible or affect system boot. The project is maintained as an open-source component and is intended to provide a stable, programmatic interface to UEFI variable storage on supported systems.