# What is Rust?

Rust is a systems programming language sponsored by Mozilla Research. It is designed to be a "safe, concurrent, practical language", supporting functional and imperative-procedural paradigms. Rust is syntactically similar to C++, but is designed for better memory safety while maintaining performance.

> [wikipedia.org/wiki/Rust_(programming_language)](https://en.wikipedia.org/wiki/Rust_%28programming_language%29)

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# How to use this image

## Start a Rust instance running your app

The most straightforward way to use this image is to use a Rust container as both the build and runtime environment. In your `Dockerfile`, writing something along the lines of the following will compile and run your project:

```dockerfile
FROM %%IMAGE%%:1.31

WORKDIR /usr/src/myapp
COPY . .

RUN cargo install --path .

CMD ["myapp"]
```

Then, build and run the Docker image:

```console
$ docker build -t my-rust-app .
$ docker run -it --rm --name my-running-app my-rust-app
```

This creates an image that has all of the rust tooling for the image, which is 1.8gb. If you just want the compiled application:

```dockerfile
FROM rust:1.40 as builder
WORKDIR /usr/src/myapp
COPY . .
RUN cargo install --path .

FROM debian:buster-slim
RUN apt-get update && apt-get install -y extra-runtime-dependencies
COPY --from=builder /usr/local/cargo/bin/myapp /usr/local/bin/myapp
CMD ["myapp"]
```

Note: Some shared libraries may need to be installed as shown in the installation of the `extra-runtime-dependencies` line above.

This method will create an image that is less than 200mb. If you switch to using the Alpine-based rust image, you might be able to save another 60mb.

See https://docs.docker.com/develop/develop-images/multistage-build/ for more information.

## Compile your app inside the Docker container

There may be occasions where it is not appropriate to run your app inside a container. To compile, but not run your app inside the Docker instance, you can write something like:

```console
$ docker run --rm --user "$(id -u)":"$(id -g)" -v "$PWD":/usr/src/myapp -w /usr/src/myapp %%IMAGE%%:1.23.0 cargo build --release
```

This will add your current directory, as a volume, to the container, set the working directory to the volume, and run the command `cargo build --release`. This tells Cargo, Rust's build system, to compile the crate in `myapp` and output the executable to `target/release/myapp`.
