Getting Started With Snappy

This is part of a series describing how I got Transmission compiled and running for Snappy Ubuntu Core.

What is Snappy Ubuntu Core?

Snappy Ubuntu Core¹ is the Ubuntu version for clouds and devices, featuring transactional updates on a minimal server image.

One of the first noticeable differences from the regular Ubuntu version is that there is no apt-* commands and you cannot install traditional .deb packages; you manage your applications through the snappy utility that lets you install and update snap packages.

Snap packages are the base for Ubuntu Core to provide stronger security guarantees (applications run confined using AppArmor), and it should be relatively easy to build (or port) your app and make it available in the Snappy store.

Running Ubuntu Core in Virtual Box

Let’s get our first contact with a running Ubuntu Core!

One quick way to get Ubuntu Core running for a first time and make the first experiments is to download an OVA container and plug it in using VirtualBox (or other capable hypervisor).

You can download 15.04 from here. Then, you need to import the image into VirtualBox. Finally, in order to use the OVA images you need to prepare a Cloud-Config ISO.

At this point you should be able to start your Ubuntu Core setup and try the Snappy tour!

Since we would like to access installed snaps and push our own, it is a good idea to enable network access to our Ubuntu Core machine. I just enabled the Bridged Adapter as lxcbr0 in Network settings (you could also set up port forwarding). That will allow you to get WebDM in your browser at <machine-ip>:4200, as well as your other installed packages’ exposed UIs or ssh from your terminal.

Installing tools and examples

To build our snaps we’ll need to install some tools in our host:

$ sudo add-apt-repository ppa:snappy-dev/tools
$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get install snappy-tools bzr

After this you should have the snappy utilities in your system. Try for example:

$ snappy --help

You can also branch the Snappy examples from Launchpad to get a first sight of how a snap package looks like:

$ bzr branch lp:~snappy-dev/snappy-hub/snappy-examples

More on package format later, when we build our snap from scratch.

Completing the cycle

To get a taste of the full experience, let’s build one of the examples and push it to our running instance.

$ cd snappy-examples/hello-world
$ snappy build
Generated 'hello-world_1.0.18_all.snap' snap
$ snappy-remote --url=ssh://10.0.3.202 install hello-world_1.0.18_all.snap
=======================================================

Installing hello-world_1.0.18_all.snap from local environment
Installing /tmp/hello-world_1.0.18_all.snap
2015/10/31 16:55:25.742623 verify.go:85: Signature check failed, but installing anyway as requested
Name          Date       Version      Developer 
ubuntu-core   2015-09-17 5            ubuntu    
hello-world   2015-10-31 IESTYKQfgHgH sideload  
webdm         2015-06-14 0.9          ubuntu  
generic-amd64 2015-06-05 1.1.1        ubuntu  

=======================================================

(use your VirtualBox machine IP address instead of 10.0.3.202, of course).

The signature check is expected to fail because we are manually installing the package and not getting it from the store. Also note that the package is marked as sideload.

If you now check, in your Ubuntu Core instance, you should have hello-world binaries available:

(amd64)ubuntu@ubuntu-snappy:~$ hello-world.
hello-world.echo     hello-world.env      hello-world.evil     hello-world.sh       hello-world.showdev  hello-world.usehw    

Coming next

And that’s it, we have our initial development environment setup. Next steps will be:

• Build Transmission from source
• Manually snap packaging Transmission
• Build Transmission for ARM
• Build multi-architecture snap package
• Build Transmission using snapcraft

1. https://developer.ubuntu.com/en/snappy/ ↩