Concepts

How rustup works

rustup is a toolchain multiplexer. It installs and manages many Rust toolchains and presents them all through a single set of tools installed to ~/.cargo/bin. The rustc and cargo executables installed in ~/.cargo/bin are proxies that delegate to the real toolchain. rustup then provides mechanisms to easily change the active toolchain by reconfiguring the behavior of the proxies.

So when rustup is first installed, running rustc will run the proxy in $HOME/.cargo/bin/rustc, which in turn will run the stable compiler. If you later change the default toolchain to nightly with rustup default nightly, then that same proxy will run the nightly compiler instead.

This is similar to Ruby’s rbenv, Python’s pyenv, or Node’s nvm.

Terminology

  • channel — Rust is released to three different “channels”: stable, beta, and nightly. See the Channels chapter for more details.

  • toolchain — A “toolchain” is a complete installation of the Rust compiler (rustc) and related tools (like cargo). A toolchain specification includes the release channel or version, and the host platform that the toolchain runs on.

  • target — rustc is capable of generating code for many platforms. The “target” specifies the platform that the code will be generated for. By default, cargo and rustc use the host toolchain’s platform as the target. To build for a different target, usually the target’s standard library needs to be installed first via the rustup target command. See the Cross-compilation chapter for more details.

  • component — Each release of Rust includes several “components”, some of which are required (like rustc) and some that are optional (like clippy). See the Components chapter for more detail.

  • profile — In order to make it easier to work with components, a “profile” defines a grouping of components. See the Profiles chapter for more details.

  • proxy — A wrapper for a common Rust component (like rustc), built to forward CLI invocations to the active Rust toolchain. See the Proxies chapter for more details.