kuid

Kuid is a term used in computing that may refer to different concepts depending on the context. It is not a single, universally defined identifier, and its meaning is context-dependent.

The most common usage is in the Linux kernel, where kuid_t represents a kernel-level user identifier. In systems employing user namespaces, user IDs in a given namespace can be remapped, so the kernel uses kuid_t to hold internal IDs that may differ from the traditional user-space UID. The API provides helpers such as make_kuid and from_kuid, and kuid_t is typically paired with kgid_t for groups. Initializers like KUIDT_INIT are used to create constant kuid values. This design helps isolate and map identities across namespaces while keeping kernel code type-safe.

Outside of Linux kernel sources, the acronym kuid may appear in other projects with meanings that vary by context. If you encounter kuid in documentation or code, consult the specific project’s documentation to determine its intended meaning.