rust-musl-builder/README.md
2017-10-24 09:04:32 -04:00

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# `rust-musl-builder`: Docker container for easily building static Rust binaries
[![Docker Image](https://img.shields.io/docker/pulls/ekidd/rust-musl-builder.svg?maxAge=2592000)](https://hub.docker.com/r/ekidd/rust-musl-builder/)
Do you want to compile a completely static Rust binary with no external
dependencies? If so, try:
```sh
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 make static release binaries using TravisCI and GitHub, or you can copy your Rust application into an [Alpine Linux container][]. See below for details!
## 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.
- `libpq`, which is needed for applications that use `diesel` with PostgreSQL.
- `libz`, which is needed by `libpq`.
This library also sets up the environment variables needed to compile popular Rust crates using these libraries.
## Making OpenSSL work
If your application uses OpenSSL, you will also need to take a few extra steps to make sure that it can find OpenSSL's list of trusted certificates, which is stored in different locations on different Linux distributions. You can do this using [`openssl-probe`](https://crates.io/crates/openssl-probe) as follows:
```rust
extern crate openssl_probe;
fn main() {
openssl_probe::init_ssl_cert_env_vars();
//... your code
}
```
## Making static releases with Travis CI and GitHub
These instructions are inspired by [rust-cross][].
First, read the [Travis CI: GitHub Releases Uploading][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:
```yaml
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`](./examples/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/cage][cage].
[rust-cross]: https://github.com/japaric/rust-cross
[uploading]: https://docs.travis-ci.com/user/deployment/releases
[cage]: https://github.com/faradayio/cage
## Making tiny Docker images with Alpine Linux and Rust binaries
Docker now supports [multistage builds][multistage], which make it easy to
build your Rust application with `rust-musl-builder` and deploy it using
[Alpine Linux][]. For a working example, see
[`Dockerfile.multistage-example`](./Dockerfile.multistage-example).
[multistage]: https://docs.docker.com/engine/userguide/eng-image/multistage-build/
[Alpine Linux]: https://alpinelinux.org/
## 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:
```Dockerfile
FROM ekidd/rust-musl-builder
# EXAMPLE ONLY! libz is already included.
RUN VERS=1.2.11 && \
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.
## Development notes
After modifying the image, run `./test-image` to make sure that everything
works.
## Other ways to build portable Rust binaries
- [messense/rust-musl-cross](https://github.com/messense/rust-musl-cross) shows how to build binaries for many different architectures.
- [japaric/rust-cross](https://github.com/japaric/rust-cross) has extensive instructions on how to cross-compile Rust applications.
## License
Either the [Apache 2.0 license](./LICENSE-APACHE.txt), or the
[MIT license](./LICENSE-MIT.txt).
[Alpine Linux container]: https://hub.docker.com/_/alpine/
[musl-libc]: http://www.musl-libc.org/
[musl-gcc]: http://www.musl-libc.org/how.html
[rustup]: https://www.rustup.rs/