# 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:1.39 as builder
WORKDIR /usr/src/myapp
COPY . .
RUN cargo install --path .

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

Note: Some shared libraries may need to be installed as shown in the installation of the libssl 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`.