~snappy-dev/snapcraft/core

Committer: Snappy Tarmac
Author(s): Michael Terry, Michael Vogt
Date: 2015-08-04 21:01:35 UTC
mfrom: (105.3.11 docs-1)
Revision ID: snappy_tarmac-20150804210135-w8e1to44t689ju6k

Add intro and tutorial docs.

The intro file explains Snappy and the general Snapcraft concepts a bit. It covers the same material as flow.md, so I dropped that file.

The tutorial file goes through crafting a webcam demo snap [1].

I want to add an installing/testing/uploading-to-store section too, but I want to get some experience using the webcam bit and dealing with apparmor for it (seeing if I can get kvm to use my laptop webcam or if I need to have a real USB webcam with a beaglebone). But that addition can happen in a separate branch.

This is taking over from lp:~mvo/snapcraft/docs-1 since mvo is on vacation.

[1] Very similar to https://developer.ubuntu.com/en/snappy/guides/appliance-builder-guide-webcam/ by snappy-dev approved by elopio

files added:
README.md

docs/intro.md

docs/tutorial.md

files removed:
docs/flow.md

files renamed:
README.md => HACKING.md

files modified:
examples/webcam-webui-snap/snapcraft.yaml

examples/webcam-webui-snap/webcam-webui

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docs/intro.md

# Intro

Snapcraft allows easy crafting of packages for Snappy Ubuntu. It makes it

easy to incorporate components from different sources like GitHub, Launchpad,

or npm.

# Snappy

Snappy Ubuntu Core is a new rendition of Ubuntu with transactional updates — a

minimal server image with the same libraries as today’s Ubuntu, but

applications are provided through a simpler mechanism.

Snappy apps and Ubuntu Core itself can be upgraded atomically and rolled back

if needed. Apps are also strictly confined and sandboxed to safeguard your

data and system.

# Key concepts

A .snap package for the Ubuntu Core system contains all its

dependencies. This has a couple of advantages over traditional deb or

rpm based dependency handling, the most important being that a

developer can always be assured that there are no regressions triggered by

changes to the system underneath their app.

Snapcraft makes bundling these dependencies easy by allowing you to

specify them as “parts” in the snapcraft.yaml file.

## Parts

A central aspect of a snapcraft recipe is a “part”. A part is a piece

of software or data that the snap package requires to work or to

build other parts. Each part is managed by a snapcraft plugin and parts

are usually independent of each other.

## Plugins

Snapcraft plugins are written in Python and have a yaml

description. A lot of default plugins are included, for example for

projects written in Go, Java, Python or C. It is also possible

to simply download binary content as part of the snapcraft recipe.

## Lifecycle

Each part goes through the following steps:

### Pull

The first is that each part is pulled. This step will download

content, e.g. checkout a git repository or download a binary component

like the Java SDK. Snapcraft will create a parts/ directory with

sub-directories like parts/part-name/src for each part that contains

the downloaded content.

#### Build

The next step is that each part is built in its parts/part-name/build

directory and installs itself into parts/part-name/install.

### Stage

After the build of each part the parts are combined into a single

directory tree that is called the “staging area”. It can be found

under the ./stage directory.

This ./stage directory is useful for building outside code that isn’t in the

snapcraft.yaml recipe against the snap contents. For example, you might build a

local project against the libraries in ./stage by running

`snapcraft shell make`. Though in general, you are encouraged to add even local

projects to snapcraft.yaml with a local `source:` path.

### Snap

The snap step moves the data into a ./snap directory. It contains only

the content that will be put into the final snap package, unlike the staging

area which may include some development files not destined for your package.

The Snappy metadata information about your project will also now be placed in

./snap/meta.

This ./snap directory is useful for inspecting what is going into your snap

and to make any final post-processing on snapcraft’s output.

### Assemble

The final step builds a snap package out of the snap directory. This .snap file

can be uploaded to the Ubuntu Store and published directly to Snappy users.

# Next

After introducing the key concept of snapcraft it is probably a good

time to look at the tutorial in docs/tutorial.md to see how it works

for an example project.

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