Karthick B
07. July 2022 · Write a comment · Categories: Miscellaneous

In the growing IOT world, Embedded devices are playing a major role in people day2day life. Earlier in 1980’s to 2000 embedded product will be having a specific feature such as printing/display etc., and it will be updated only for bug fixes. Now a days in 2022 due to technology growth, a product is having multiple features/use cases and it has been upgraded for bug fixes and new features in the interest of customer/end.

So, if we look in to product upgrade history. in 1990 – 2000 OEM’s use to upgrade a device once in a year, but now the same is getting upgraded at least 10 times in a year. Number varies based on the use case and feature competition.

Now a days feature/application is developed with some dependency on 3rd party components such as Openssl, Cloud Library, Databases, Protobuf etc. These 3rd party component owners share an updated version addressing bug fixes or including new features. OEM must adapt the new versions and release an update for existing products. In this process there are certain challenges inevitable such as i) All modules in product need to be updated. ii) Retesting of all features. iii) Mitigate the impact for existing users etc.

All modules in product need to be updated

Since we cannot have multiple versions of 3rd party component in the product. if the component is getting changed, it’s the responsibility of all module/feature owners to adapt the new component along with their new feature roadmap.

This challenge can be addressed in couple of ways by making product as dockerized or snap based approach. In this way, we no need to wait for all module/feature owners to complete adapting the component to release an upgrade

Here we will look in to snap based approach and how that helps in rolling out new product feature rollout to market in less time.

Legacy Product Architecture

If you have one physical machine dedicated to only one thing this is the best option. Has full access to the hardware and best performance with no overhead.

What is SNAP?

Snap is a Linux-based software utility for packaging and deploying applications. It works with major Linux distributions such as Ubuntu, Debian, Arch Linux, Fedora, CentOS, and Manjaro. Snaps are self-contained apps that run in a sandbox and have limited access to the host system. It uses the.snap file format, which is a single compressed file system that uses the SquashFS standard. Applications and libraries, as well as declarative metadata, make up the file system.

Any Linux based product feature can be packaged as a snap, making it easy to deploy across distributions and devices with isolated environments. Snap has a flexible upgradable or down gradable support that does not affect other snaps/features, this enables secure execution and better transactional management. Snaps can also be upgraded remotely.

Easy and clean installation of full software packages. It can deploy complex systems with all support systems, such as database servers, and everything will be already configured to working perfectly

Elements in SNAP

The Snap’s key elements are as follows:

  • Snapd: Snapd used snap metadata to create a safe and secure sandbox for a program on the system. Because Snap is nothing more than SnapDaemon, all of the system’s functions, such as maintaining and administering the complete snap environment, continue in the background.
  • Snaps: Snaps are a set of Snap packages that are dependency-free and simple to install. It includes the whole module, including the application and its dependencies, in the.snap file.
  • Channels: A channel determines which release of a snap is installed and checked for updates

    $ snap install xxx –channel=latest/edge
    • Tracks : There is a default track for all snaps. The default track is called newest unless the snap developer specifies otherwise. When no track is supplied, a snap will install from the latest track by default. It’s also possible to specify the track explicitly.
    • Risk Levels : Stable, candidate, beta, and edge are the four risk levels. Installing from a risk-level that is less stable will usually result in more frequent updates.
    • Stable: suitable for the great majority of users in production scenarios.
      • Candidate: for users who need to test changes prior to a stable deployment, or who want to double-check that an issue has been handled. 
      • Beta: for users who wish to try out new features before they go live, usually outside of a production environment. 
      • Edge: for those who wish to keep a close eye on their progress.

Use the –channel option to select a different risk-level

$ snap install –channel=beta xxxx

After installation, the risk-level being tracked can be changed with:

$ snap switch –channel=stable xxxx

  • Branches: As a developer, you may have a released programme with defects that users encounter but that you are unable to duplicate. A temporary branch can be used to store a bug-fixing test build of the application you’re working on. If you’re tracking and fixing many bugs at the same time, each one can have its own branch in the Snap Store under the same snap name. Because branches are ‘hidden,’ users are unlikely to come across potentially broken bug-fix builds of your application unless they guess the name. Branches are only active for 30 days before being destroyed, and any user with the snap will be transferred to the channel’s most recent track.
  • Snap Store: It is like any other package manager, where the packages are published by creators and consumers install them.
  • Snap Craft: It’s a tool to build snaps.

SNAP Updates

The snap list command displays all available revisions for all installed snaps. By specifying a snap name in the snap list —all command, only results for that snap will be returned.

$ snap list –all xxxxx

Snaps are automatically updated. To check for updates manually, run the following command:

            $ snap refresh xxxx

With the snap reverse command, a snap can be reverted to a previous revision.

            $ snap revert xxxx 

SNAP Configuration

The following files control the behavior of a snap:

            snap.yaml

            hooks

            icon.{svg,png}

            *.desktop

.yaml :  Every snap package contains a meta/snap.yaml file that holds the basic metadata for the snap.

snap.yaml lives inside every snap package, read by snapd. snapcraft.yaml contains instructions to create a snap package, read by the snapcraft command used to build snaps

Hooks: A hook is an executable file that runs within a snap’s confined environment when a certain action occurs. Hooks provide a mechanism for snapd to alert snaps that something has happened, or to ask the snap to provide its opinion about an operation that is in progress.

Common examples of actions requiring hooks include:

Notifying a snap that something has happened

Example: If a snap has been upgraded, the snap may need to trigger a scripted migration process to port an old data format to the new one.

Notifying a snap that a specific operation is in progress

Example: A snap may need to know when a specific interface connects or disconnects.

SNAP Overview

Create your own SNAP

Make your working directory first, then enter there.

            $ mkdir snap-workspace

$ cd snap-workspace

A tool for creating snaps is called SnapCraft. Running $  snapcraft init  will produce a template in the snap/snapcraft.yaml file.

The directory structure looks like this,

mysnaps/

└── snap-workspace

    └── snap

        └── snapcraft.yaml

The snapcraft.yaml file looks like if you were to open it.

name: snap-demo

base: core18

version: ‘0.1’

summary: Single-line elevator pitch for your amazing snap

description: This is my-snap’s description.

grade: devel # must be ‘stable’ to release into candidate/stable channels

confinement: devmode # use ‘strict’ once you have the right plugs and slots

Where,

Name: The name of the snap.

Base: A foundation snap that gives users a run-time environment and a small selection of libraries used by most apps. Core18, which is equivalent to Ubuntu 18.04 LTS, is the default setting for the template.

Version: The current version of the snap

Summary: A short, one-line summary or tag-line for your snap.

Description: A longer description of the snap.

Grade: The publisher may use this to express their level of satisfaction with the construction quality. The store will stop ‘devel’ grade builds from being published to the ‘stable’ channel.

Confinement: There are three levels of confinement for snaps: strict, classic, and devmode. The level of confinement a snap has from your system determines how isolated it is.

strict snaps run in complete isolation. Devmode snaps run as strict but with open access to the system, while classic snaps have open access to system resources.

SNAP Compilation:

To build hello world app, add the following ‘parts’ to our snapcraft.yaml file (replace anything else that might be there):

parts:

  gnu-hello:

    source: http://ftp.gnu.org/gnu/hello/hello-2.10.tar.gz

    plugin: autotools

Added a ‘part’ called gnu-hello (its name is arbitrary). The  ‘source’ represent,  a tarball located on the GNU project’s FTP server. As ‘plugin’ we’ve chosen auto tools which uses the traditional. /configure && make && make install build steps.

To build our snap,

            $ snapcraft

Snapcraft will produce a lot of output while the build is underway, but a successful build will result in:

[…]

Staging gnu-hello

+ snapcraftctl stage

Priming gnu-hello

+ snapcraftctl prime

Snapping |                                                                                                                                                 

Snapped hello_2.10_amd64.snap

To Install the SNAP,

$ sudo snap install –devmode hello_2.10_amd64.snap

Output:

            hello 2.10 installed

To execute,

            $ hello

Output:

Hello World

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