rust-musl-builder: Docker container for easily building static Rust binaries

Do you want to compile a completely static Rust binary with no external dependencies? If so, try:

alias rust-musl-builder='docker run --rm -it -v "$(pwd)":/home/rust/src ekidd/rust-musl-builder'
rust-musl-builder cargo build --release

This command assumes that $(pwd) is readable and writable by uid 1000, gid 1000. It will output binaries in target/x86_64-unknown-linux-musl/release. At the moment, it doesn't attempt to cache libraries between builds, so this is best reserved for making final release builds.

Deploying your Rust application

With a bit of luck, you should be able to just copy your application binary from target/x86_64-unknown-linux-musl/release, and install it directly on any reasonably modern x86_64 Linux machine. In particular, you should be able to copy your Rust application into an Alpine Linux container.

How it works

rust-musl-builder uses musl-libc, musl-gcc, and the new rustup target support. It includes static versions of several libraries:

• The standard musl-libc libraries.
• OpenSSL, which is needed by many Rust applications.

Adding more C libraries

If you're using Docker crates which require specific C libraries to be installed, you can create a Dockerfile based on this one, and use musl-gcc to compile the libraries you need. For example:

FROM ekidd/rust-musl-builder

RUN VERS=1.2.8 && \
    cd /home/rust/libs && \
    curl -LO http://zlib.net/zlib-$VERS.tar.gz && \
    tar xzf zlib-$VERS.tar.gz && cd zlib-$VERS && \
    CC=musl-gcc ./configure --static --prefix=/usr/local/musl && \
    make && sudo make install && \
    cd .. && rm -rf zlib-$VERS.tar.gz zlib-$VERS

This usually involves a bit of experimentation for each new library, but it seems to work well for most simple, standalone libraries.

If you need an especially common library, please feel free to submit a pull request adding it to the main Dockerfile! We'd like to support popular Rust crates out of the box.

Making static releases with Travis CI and GitHub

These instructions are inspired by rust-cross.

First, read the Travis CI: GitHub Releases Uploading page, and run travis setup releases as instructed. Then add the following lines to your existing .travis.yml file, replacing myapp with the name of your package:

language: rust
sudo: required
os:
- linux
- osx
rust:
- stable
services:
- docker
before_deploy: "./build-release myapp ${TRAVIS_TAG}-${TRAVIS_OS_NAME}"
deploy:
  provider: releases
  api_key:
    secure: "..."
  file_glob: true
  file: "myapp-${TRAVIS_TAG}-${TRAVIS_OS_NAME}.*"
  skip_cleanup: true
  on:
    rust: stable
    tags: true

Next, copy build-release into your project and run chmod +x build-release.

When you push a new tag to your project, build-release will automatically build new Linux binaries using rust-musl-builder, and new Mac binaries with Cargo, and it will upload both to the GitHub releases page for your repository.

For a working example, see faradayio/conductor.

Development notes

After modifying the image, run ./test-image to make sure that everything works.

MAINTAINERS ONLY: After making changes, they must be pushed to the stable branch to build the official stable and latest images on Docker Hub. Tagged versions of Rust (such as 1.11) must be given their own branches and manually configured on Docker Hub.

git push origin master:stable
git push origin master:rust-$(rustc --version | awk '{ print $2 }')

License

Either the Apache 2.0 license, or the MIT license.