Many rustup commands deal with toolchains, a single installation of the Rust compiler. rustup supports multiple types of toolchains. The most basic track the official release channels: stable, beta and nightly; but rustup can also install toolchains from the official archives, for alternate host platforms, and from local builds.

Toolchain specification

Standard release channel toolchain names have the following form:


<channel>       = stable|beta|nightly|<major.minor>|<major.minor.patch>
<date>          = YYYY-MM-DD
<host>          = <target-triple>

'channel' is a named release channel, a major and minor version number such as 1.42, or a fully specified version number, such as 1.42.0. Channel names can be optionally appended with an archive date, as in nightly-2014-12-18, in which case the toolchain is downloaded from the archive for that date.

Finally, the host may be specified as a target triple. This is most useful for installing a 32-bit compiler on a 64-bit platform, or for installing the MSVC-based toolchain on Windows. For example:

$ rustup toolchain install stable-x86_64-pc-windows-msvc

For convenience, elements of the target triple that are omitted will be inferred, so the above could be written:

$ rustup toolchain install stable-msvc

Toolchain names that don't name a channel instead can be used to name custom toolchains.

Custom toolchains

For convenience of developers working on Rust itself, rustup can manage local builds of the Rust toolchain. To teach rustup about your build, run:

$ rustup toolchain link my-toolchain path/to/my/toolchain/sysroot

For example, on Ubuntu you might clone rust-lang/rust into ~/rust, build it, and then run:

$ rustup toolchain link my-toolchain ~/rust/build/x86_64-unknown-linux-gnu/stage2/
$ rustup default my-toolchain

Now you can name my-toolchain as any other rustup toolchain. Create a rustup toolchain for each of your rust-lang/rust workspaces and test them easily with rustup run my-toolchain rustc.

Because the rust-lang/rust tree does not include Cargo, when cargo is invoked for a custom toolchain and it is not available, rustup will attempt to use cargo from one of the release channels, preferring 'nightly', then 'beta' or 'stable'.