I’ve recently published a few snaps of various Node.js projects. So I was encouraged to write a tutorial on building snaps out of Node.js projects. This tutorial will detail how to get setup with necessary tools, go over the snapcraft.yaml format, explain how to build a snap of a Node.js project, and detail how to publish that snap to the Ubuntu snap store.
To get started snapping Node.js modules you’ll need to have
installed. snapd will include the
snap command that will allow you to search
and install snaps from the store. snapd is available on
many different Linux distributions,
but if you are using Ubuntu 16.04 or greater you can just run:
sudo apt install snapd
snapcraft is a tool for creating and building snap packages. Installing snapcraft on Ubuntu is as simple as:
sudo apt install snapcraft
If you are also developing the Node module to be packaged, you’ll want to have
npm installed. Covering that is outside the scope of this tutorial.
You can find more info on the Node.js website.
Defining how a snap is built is a simple YAML file called snapcraft.yaml. The yaml file contains all the necessary pieces to build a snap.
name: hello-node-snap version: "1.0.0" summary: A simple hello world command description: A command that simply prints hello world. confinement: strict apps: hello-node-snap: command: bin/hello-node-snap plugs: [network] parts: hello-node-snap: plugin: nodejs node-packages: - hello-node-snap
You can find this snapcraft.yaml and the rest of the hello-node-snap example on GitHub. This file is fairly small and easily understood, so I’ll break the file down into chunks to expand upon each section.
name: hello-node-snap version: "1.0.0" summary: A simple hello world command description: A command that simply prints hello world.
The first part of the snap is all the human friendly portions. The name, version, summary, and description are used in the snap store to help users find your app. The summary should be a very short description of your app, and is limited to only 78 characters. The description should be more verbose so that users can make an informed choice when installing your snap.
The next section is the confinement of your app. This may be either
devmode. Strict means that it will run under full confinement and will not be
able to access parts of the host system that are outside of its boundaries. When
in devmode a snap will have full access to the underlying system. It is not
recommend to distribute an app with devmode confinement, but devmode can be
very useful for developing your snap.
apps: hello-node-snap: command: bin/hello-node-snap plugs: [network]
The apps section is a list of commands or daemons that this snap exposes. This
snap exposes one command
hello-node-snap. This is how users will be able
to run your app. Underneath the
hello-node-snap app is the command, which
is the path to the command to run. This is relative to the root of the snap.
After the command is the plugs section. The plugs section is a list of interfaces
that allow a command to access shared resources on the host machine. They could
be loosely thought of as permissions. A list of common and reserved interfaces
can be found in the snapcraft documentation.
In this example we are requesting access to the
network is for accessing
the network as a client. On the other hand, you may need
network-bind if you
want to set up a server. Another common interface is the
home interface, which
grants you access to a users home directory.
Note: Network access is not actually needed for this tutorial, but it is there to show how to use the interfaces.
parts: hello-node-snap: plugin: nodejs node-packages: - hello-node-snap
The final part of our snapcraft.yaml file is the parts section. Parts define how
your app is built and from what sources. You can mix and match parts as needed,
but for a Node.js snap you may only need one part. The
nodejs plugin. This plugin will tell snapcraft to download a version
of Node.js and any modules you specify for inclusion in your snap (listed under
node-packages). For this tutorial we only need one node module, the
hello-node-snap module (created
specifically for this tutorial).
If you require a specific version of Node.js for your snap, you can do so by
node-engine to your part.
node-engine is a string of the version you
build-packages: - python - build-essential
And any other necessary packages (these are the names of Ubuntu packages in apt).
For more information about the different available parts, check out the snapcraft plugin documentation.
Building the Snap
Now that we have a snapcraft.yaml setup, we can use
snapcraft to package
our new snap. From within the same directory as the snapcraft.yaml, run:
Snapcraft will run through different steps preparing your snap package. When
it completes you’ll be greeted with a shiny new snap, and in the case of
this tutorial the snap will be called
To test your snap locally before you upload it to the store (and I cannot stress enough the importance of testing your snaps locally), you can run:
sudo snap install hello-node-snap_1.0.0_amd64.snap
If you already have the package installed you may need to remove the old snap by running:
sudo snap remove hello-node-snap
Now that the snap is installed you can run our hello world command:
Now that you have a working step it is time to publish it to the store. But before publishing your snap, it is recommended to run:
This command builds the snap in a clean LXC container. Doing so can help you catch any issues with missing build-packages and the like.
Publishing the Snap
In order to publish a snap to the Ubuntu store you need to log in to both snapcraft and snap with your snapcraft.io account.
snapcraft login snap login [email protected]
In order to publish your snap you need to register a snap name, you can do this on register snap or via the command line:
snapcraft register hello-node-snap
When the upload finishes, you can then visit snapcraft.io to finalize any details before publishing your snap to the store. An important thing to add is a support url, in case users run into any issues using your snap. You need to set your snap channels by clicking on the latest release (since this is the first upload it will be #1). Then click the “Edit” button next to “Channels”. For an explanation of the different channels, check out this guide to publishing snaps.
After you square away the details of your snap, click the “Publish your application” button to publish it to the store. Now you can find your snap and install it with snapd:
sudo snap find hello sudo snap install hello-node-snap
After a short while your new snap will show up on uApp Explorer. And you have successfully published a snap!
- hello-node-snap source on GitHub
- The Snappy Playpen is a great collection of snaps that can help you get squared away with your snap.
- The Snapcraft Docs has a wealth of information on all things snap.
- Ask Ubuntu already has questions and answers about snaps.
- Other Node.js Snap examples: