Node.js has the
package.json format and npm or yarn to assist in packaging and distributing applications to other developers. But these are not user-oriented tools. Nor do they offer a solution for notifying users of available updates.
Snaps address these gaps while building upon the work you’ve already done to teach Node how to package your app.
Ready to get started? By the end of this guide, you’ll understand how to make a snap of your Node.js app that can be published in the Snap Store, showcasing it to millions of Linux users.
For a brief overview of the snap creation process, including how to install snapcraft and how it’s used, see Snapcraft overview. For a more comprehensive breakdown of the steps involved, take a look at Creating a snap.
Snaps are defined in a single YAML file placed in the root folder of your project. The following example shows the entire snapcraft.yaml file for an existing project, Wethr. Don’t worry, we’ll break this down.
name: test-wethr version: git summary: Command line weather tool. description: | Get current weather:- $ wethr Get current weather in metric units $ wethr --metric Get current weather in imperial units $ wethr --imperial base: core18 confinement: devmode parts: test-wethr: plugin: nodejs source: . apps: test-wethr: command: wethr
snapcraft.yaml file 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.
name: test-wethr version: git summary: Command line weather tool. description: | Get current weather:- $ wethr Get current weather in metric units $ wethr --metric Get current weather in imperial units $ wethr --imperial
name must be unique in the Snap Store. Valid snap names consist of lower-case alphanumeric characters and hyphens. They cannot be all numbers. They also cannot start or end with a hyphen.
git for the version, the current git tag or commit will be used as the version string. Versions carry no semantic meaning in snaps.
summary can not exceed 79 characters. You can use a chevron ‘>’ in the
description key to declare a multi-line description.
The base keyword defines a special kind of snap that provides a run-time environment with a minimal set of libraries that are common to most applications. They’re transparent to users, but they need to be considered, and specified, when building a snap.
The next section describes the level of confinement applied to your app.
Snaps are containerised to ensure more predictable application behaviour and greater security. Unlike other container systems, the shape of this confinement can be changed through a set of interfaces. These are declarations that tell the system to give permission for a specific task, such as accessing a webcam or binding to a network port.
It’s best to start a snap with the confinement in warning mode, rather than strictly applied. This is indicated through the
devmode keyword. When a snap is in devmode, runtime confinement violations will be allowed but reported. These can be reviewed by running
Because devmode is only intended for development, snaps must be set to strict confinement before they can be published as “stable” in the Snap Store. Once an app is working well in devmode, you can review confinement violations, add appropriate interfaces, and switch to strict confinement.
Parts define what sources are needed to assemble your app. Parts can be anything: programs, libraries, or other needed assets. We’ll deal with libraries and other assets later, so for now we just have one part: the wethr source code.
parts: test-wethr: plugin: nodejs source: .
nodejs plugin builds upon the work you’ve already done to describe your app’s dependencies in your package.json. It will automatically include these in your snap.
It will also include Node 6. This can be changed with the
For more details on Node-specific metadata, see The nodejs plugin.
Apps are the commands you want to expose to users and any background services your application provides. Each key under
apps is the command name that should be made available on users’ systems.
command specifies the path to the binary to be run. This is resolved relative to the root of your snap contents and automatically searches in the
bin sub-directories of your snap.
apps: test-wethr: command: wethr
If your command name matches the snap
name, users will be able run the command directly. If the names differ, then apps are prefixed with the snap
wethr.command-name, for example). This is to avoid conflicting with apps defined by other installed snaps.
You can request an alias on the Snapcraft forum if your command name and snap name do not match but you don’t want your command prefixed. These aliases are set up automatically when your snap is installed from the Snap Store.
You can download the example repository with the following command:
$ git clone https://github.com/snapcraft-docs/wethr
After you’ve created the snapcraft.yaml, you can build the snap by simply executing the snapcraft command in the project directory:
$ snapcraft Using 'snapcraft.yaml': Project assets will be searched for from the 'snap' directory. Launching a VM. [...] Snapped test-wethr_v1.4.0+git2.95879f4-dirty_amd64.snap
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 test-wethr_*.snap --devmode --dangerous
You can then try it out:
$ test-wethr London, GB: 17.04C 🌧
Removing the snap is simple too:
$ sudo snap remove test-wethr
You can also clean up the build environment, although this will slow down the next initial build:
$ snapcraft clean
By default, when you make a change to snapcraft.yaml, snapcraft only builds the parts that have changed. Cleaning a build, however, forces your snap to be rebuilt in a clean environment and will take longer.
To share your snaps you need to publish them in the Snap Store. First, create an account on the dashboard. Here you can customise 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 Snap Store account:
$ snapcraft login
You can publish your own version of a snap, provided you do so under a name you have rights to. You can register a name on dashboard.snapcraft.io, or by running the following command:
$ snapcraft register mynodesnap
Be sure to update the
name: in your
snapcraft.yaml to match this registered name, then run
Use snapcraft to push the snap to the Snap Store.
$ snapcraft push --release=edge mynodesnap_*.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.
Congratulations! You’ve just built and published your first Go snap. For a more in-depth overview of the snap building process, see Creating a snap.