Rust has rich tools for packaging and distributing applications. Snapcraft builds on top of these familiar tools such as Rustup, Cargo and
rustc to create snaps.
What problems do snaps solve for Rust applications?
Linux installation instructions for Rust applications often
curl a script
and pipe it to a shell. This can be a cause for concern for users and
the installation scripts themselves are complex, have to accommodate
multiple Linux distributions and architectures. With snapcraft it’s one
command to produce a bundle that works anywhere.
Here are some snap advantages that will benefit many Rust projects:
- Bundle all the runtime requirements, with support for multiple architectures.
- Simplify installation instructions, regardless of distribution, to
snap install myrustapp.
- Directly control the delivery of automatic application updates.
- Extremely simple creation of services.
- No complex installation shell scripts to maintain.
How long will this guide take to complete?
Typically this guide will take around 20 minutes and will result in a working Rust-based snap. Once complete, you’ll understand how to package Rust applications as snaps and deliver them to millions of Linux users. After making the snap available in the store, you’ll get access to installation metrics and tools to directly manage the delvery of updates to Linux users.
By way of an example, let’s look at how a snap is created for the Parity app.
Snaps are defined in a single yaml file placed in the root of your project. The Parity example shows the entire
snapcraft.yaml for an existing project, leveraging the existing
Cargo.toml to satisfy runtime requirements. We’ll break this down.
name: parity version: git summary: Fast, light, robust Ethereum implementation description: | Parity's goal is to be the fastest, lightest, and most secure Ethereum client. We are developing Parity using the sophisticated and cutting-edge Rust programming language. Parity is licensed under the GPLv3, and can be used for all your Ethereum needs. confinement: devmode apps: parity: command: parity parts: parity: source: . plugin: rust build-attributes: [no-system-libraries] build-packages: - libudev-dev - libssl-dev - make - pkg-config stage-packages: - libssl1.0.0 - libudev1 - libstdc++6
snapcraft.yaml starts with a small amount of human-readable metadata, which usually can be lifted from the GitHub description or project README.md. This data is used in the presentation of your app in the Snap Store. The
summary: can not exceed 79 characters. You can use a pipe in the
description: key to declare a multi-line description.
name: parity version: git summary: Fast, light, robust Ethereum implementation description: | Parity's goal is to be the fastest, lightest, and most secure Ethereum client. We are developing Parity using the sophisticated and cutting-edge Rust programming language. Parity is licensed under the GPLv3, and can be used for all your Ethereum needs.
To get started we won’t confine this application. Unconfined applications, specified with
devmode, can only be released to the hidden “edge” channel where you and other developers can install them.
Parts define how to build your app. Parts can be anything: programs, libraries, or other assets needed to create and run your application. In this case we have one: the Parity source code. In other cases these can point to local directories, remote git repositories, or tarballs.
This example will also bundle the current stable release of Rust in the snap using Rustup and you can define the exact version of Rust with the optional ` - rust-revision:
keyword, should you have specific requirements. Dependencies from your Cargo.toml
will also be bundled.
include any packages from the Ubuntu archive required for just the build step and stage-packages:` bundles packages from the Ubuntu archive that are required at runtime.
parts: parity: source: . plugin: rust build-attributes: [no-system-libraries] build-packages: - libudev-dev - libssl-dev - make - pkg-config stage-packages: - libssl1.0.0 - libudev1 - libstdc++6
Apps are the commands and services exposed to end users. If your command name matches the snap
name, users will be able execute the command directly. If they differ, then apps are prefixed with the snap
parity.command-name, for example). This is to avoid conflicting with the apps defined by other installed snaps.
If you don’t want your command prefixed you can request an alias for it on the Snapcraft forum. These are set up automatically when your snap is installed from the Snap Store.
apps: parity: command: parity
If your application is intended to run as a service you simply add the line
daemon: simple after the command keyword. This will automatically keep the service running on install, update and reboot.
Building the snap
You’ll first need to install snap support, and then install the snapcraft tool:
sudo snap install --candidate --classic snapcraft
If you have just installed snap support, start a new shell so your
PATH is updated to include
/snap/bin. You can then build this example yourself:
git clone https://github.com/snapcraft-docs/parity cd parity snapcraft
The resulting snap can be installed locally. This requires the
--dangerous flag because the snap is not signed by the Snap Store. The
--devmode flag acknowledges that you are installing an unconfined application:
sudo snap install parity_*.snap --devmode --dangerous
You can then try running Parity.
Removing the snap is simple too:
sudo snap remove parity
Share with your friends
To share your snaps you need to publish them in the Snap Store. First, create an account on the dashboard. Here you can customize how your snaps are presented, review your uploads and control publishing.
You’ll need to choose a unique “developer namespace” as part of the account creation process. This name will be visible by users and associated with your published snaps.
Make sure the
snapcraft command is authenticated using the email address attached to your store account:
Reserve a name for your snap
You can publish your own version of a snap, provided you do so under a name you have rights to.
snapcraft register myrustsnap
Be sure to update the
name: field in your
snapcraft.yaml to match this registered name, then run
Upload your snap
Use snapcraft to push the snap to the Snap Store.
snapcraft push --release=edge myrustsnap_amd64.snap
If you’re happy with the result, you can commit the snapcraft.yaml to your GitHub repo and turn on automatic builds so any further commits automatically get released to edge, without requiring you to manually build locally.