snap-build

name

snap-build

description

Package and publish a Linux desktop application to the Snap Store. Covers snapcraft.yaml authoring (parts, plugs, slots, confinement), build via LXD/Multipass, naming registration on Snap Store, channels strategy (edge/beta/candidate/stable), branch tracks, public/private/unlisted visibility, and CI/CD integration. Use this skill when the user asks about Snap Store, snapcraft, Snapcraft, Ubuntu Store, Linux app distribution, snap publishing, '.snap' files, snap channels, snap confinement, classic snaps, or 'publish to Snap Store'.

Snap Build & Publish for the Snap Store

The Snap Store (snapcraft.io) is Canonical's app store for Ubuntu and other Linux distributions that ship snapd. A snap is a self-contained, sandboxed package that bundles your app + all dependencies + a confinement profile.

This skill walks through:

1. Authoring snapcraft.yaml
2. Building the snap locally
3. Registering the name on snapcraft.io
4. Publishing to channels (edge → beta → candidate → stable)
5. Visibility settings (public, private, unlisted)
6. Updates and tracks

When to invoke

• During /app-gtm-release:ship-snap Gates 0-4
• When the user asks: "publish to Snap Store", "snapcraft setup", "snap channels", "Linux desktop distribution via snap", "Ubuntu app store"

Bar 1 — snapcraft.yaml authoring

Snap configuration is a single file at the project root: snap/snapcraft.yaml or ./snapcraft.yaml.

Minimum viable snapcraft.yaml (Flutter desktop example)

name: myapp
base: core24
version: '1.0.0'
summary: Short one-line description
description: |
  Multi-line description.
  Supports Markdown formatting.

grade: stable
confinement: strict

apps:
  myapp:
    command: myapp
    extensions:
      - gnome
    plugs:
      - home
      - network
      - network-bind
      - desktop
      - desktop-legacy
      - wayland
      - x11
      - opengl
      - audio-playback
      - removable-media

parts:
  myapp:
    plugin: flutter
    source: .
    flutter-target: lib/main.dart

Required fields

Field	Values	Notes
name	snap-name	Lowercase, alphanumeric + hyphens, ≤ 40 chars. Must match Snap Store registration.
base	core24 (Ubuntu 24.04) / core22 / core20	Base system. core24 recommended for new snaps.
version	string or git	semver string OR git to derive from git describe
summary	string	≤ 80 chars. Tagline shown in Snap Store search.
description	string	Multi-line Markdown. Shown on Snap Store detail page.
grade	stable / devel	devel cannot be released to stable channel.
confinement	strict / classic / devmode	See "Confinement" below.
apps	object	Defines executables exposed to the user.
parts	object	Build definition (sources, plugins, dependencies).

Confinement modes

Mode	Sandbox	Use case	Snap Store approval
strict	Full sandbox via AppArmor + seccomp + cgroups	95% of apps. Default for new snaps.	Automatic
classic	No sandbox; full system access like a regular package	Tools that NEED full access (compilers, IDEs, system utilities)	Manual review by Canonical (1-2 weeks). Strong justification required.
devmode	Sandbox is logging-only (warns instead of blocks)	Development testing only	Cannot be released to stable channel.

For most apps: use strict. Add specific plugs for capabilities you need.

Common plugs (capabilities your app requests)

Plug	What it grants
home	Read/write user's home directory
network	Outbound network
network-bind	Listen on network ports
desktop	Modern desktop integration (notifications, etc.)
desktop-legacy	Legacy desktop integration (Xorg, gtk2/3)
wayland	Wayland display protocol
x11	X11 display protocol
opengl	OpenGL access
audio-playback	Audio output via PulseAudio/PipeWire
audio-record	Audio input
camera	Webcam access
removable-media	Read/write to /media/* (USB drives)
system-files	Specific paths (must list each)
personal-files	Specific paths in $HOME (must list each)

Plugin choice (under parts)

Plugin	For
flutter	Flutter desktop apps (Linux build)
electron	Electron apps
python	Python apps
nodejs	Node.js apps
go	Go apps
rust	Rust apps
make / autotools / cmake	C/C++ apps with traditional build
nil	No build; just bundle pre-built binary via override-build script

For non-trivial setups, use nil + override-build shell script:

parts:
  myapp:
    plugin: nil
    source: .
    override-build: |
      cd $CRAFT_PART_SRC
      ./build.sh
      cp -r build/release/* $CRAFT_PART_INSTALL/
    build-packages:
      - make
      - gcc
    stage-packages:
      - libgtk-3-0
      - libssl3

Bar 2 — Local build

Prerequisites

# Ubuntu 24.04 host
sudo snap install snapcraft --classic
sudo snap install lxd
sudo lxd init --auto
sudo usermod -a -G lxd $USER
newgrp lxd

For non-Ubuntu hosts: install multipass instead of LXD. Snapcraft uses Multipass to spin up an Ubuntu VM for the build.

Build command

cd /path/to/your/project
snapcraft

Output: myapp_1.0.0_amd64.snap in the current directory.

Test the snap locally

sudo snap install --dangerous ./myapp_1.0.0_amd64.snap
# --dangerous skips signature verification (snap is unsigned at this stage)

# Run it
myapp

# Inspect interfaces (which plugs are connected)
snap connections myapp

# Connect a plug if needed
sudo snap connect myapp:network

# Uninstall
sudo snap remove myapp

Common build issues

Symptom	Cause	Fix
parts/myapp/build fails with missing dependency	Missing build-packages	Add to parts.myapp.build-packages
Snap installs but app fails to launch with "permission denied"	Missing plugs	Run app with snap run --shell myapp to debug; check syslog
App can't access user files	home plug not connected	sudo snap connect myapp:home (or use auto-connect for known plugs)
Snap is too large (> 200MB)	Dependencies bloat	Use prime field to exclude unneeded files; review stage-packages

Bar 3 — Snap Store name registration

You need an Ubuntu One account (free): https://snapcraft.io/account

Then register your snap name (claims it for 30 days; you must publish a snap within that window or it returns to the pool):

snapcraft login
snapcraft register myapp

Names are first-come-first-served. Check availability: https://snapcraft.io/store/snap-name-check

Bar 4 — Channels strategy

Snap Store uses a 4-channel risk model. Users subscribe to a channel; updates flow within that channel.

Channel	Purpose	Typical audience	Update cadence
edge	Latest builds, possibly broken	Internal team, early adopters	Multiple per day OK
beta	Feature-complete pre-release	Beta testers	Weekly
candidate	Release candidate	QA + release sign-off	A few per release
stable	Production	Public users	Per release

A user installs with snap install myapp (defaults to stable). To install from a different channel:

sudo snap install myapp --channel=beta
sudo snap refresh myapp --channel=stable  # promote later

Branch tracks (parallel release lines)

For long-lived versions:

snapcraft upload --release=2.x/stable myapp_2.5.0_amd64.snap  # 2.x track
snapcraft upload --release=3.x/stable myapp_3.0.0_amd64.snap  # 3.x track

Users on the 2.x track only get 2.x updates. Useful for maintaining LTS versions.

Bar 5 — Publishing flow

First release

snapcraft upload myapp_1.0.0_amd64.snap --release=edge

Wait for review (automated for strict confinement: minutes; manual for classic: 1-2 weeks).

After review passes, the snap is in the edge channel. Test it:

sudo snap install myapp --channel=edge

Promoting through channels

After validating in edge, promote to beta:

snapcraft promote myapp --from-channel=edge --to-channel=beta

Or release a new build directly to beta:

snapcraft upload myapp_1.0.1_amd64.snap --release=beta

Continue: beta → candidate → stable.

Visibility settings (Public, Private, Unlisted)

Snap Store supports three visibility modes:

Mode	Discoverable in search	Installable by name	Use case
Public	Yes	Yes	Default. Open distribution.
Unlisted	No	Yes (need exact name + URL)	Internal tools, soft launch, link-only sharing
Private	No	No (only specific accounts you allow)	Org-internal apps, paid pre-release

Set via Snap Store dashboard: https://snapcraft.io/{your-snap}/listing → Visibility.

For private snaps, allow specific Ubuntu One accounts under "Members" tab. They install with:

sudo snap install myapp  # works because Snap Store recognizes their account

Bar 6 — Updates (after first release)

Increment version in snapcraft.yaml:

version: '1.0.1'

Or use git describe to auto-version:

version: git

Build + upload + release:

snapcraft
snapcraft upload --release=edge myapp_1.0.1_amd64.snap

Snapd on user machines auto-refreshes (default: 4x daily, configurable).

Holding refreshes

Users can defer with sudo snap refresh --hold=24h myapp. For mandatory updates (security fixes), publishers can't force, but you can communicate via the snap's metadata or in-app notice.

CI/CD integration

GitHub Actions

- uses: snapcore/action-build@v1
  id: build
- uses: snapcore/action-publish@v1
  with:
    store_login: ${{ secrets.SNAPCRAFT_TOKEN }}
    snap: ${{ steps.build.outputs.snap }}
    release: edge

Generate the token:

snapcraft export-login --snaps myapp --channels edge,beta,candidate,stable -
# Outputs a base64 blob → save as SNAPCRAFT_TOKEN secret in GitHub

GitLab CI / Codemagic / others

Same pattern: install snapcraft → build → upload with token.

Output for /ship-snap Gate 4

Save outcomes to ./go-to-market/snap/notes/gate-4-publish.md:

# Snap Store Publish — {date}

## Registration
- Name: {value}
- Owner: {Ubuntu One account}
- Registered: {date}

## Build
- snapcraft.yaml: {path}
- Output: {filename}
- Size: {MB}
- Confinement: {strict|classic}
- Base: {core22|core24}

## Channels released
- edge: {version|-}
- beta: {version|-}
- candidate: {version|-}
- stable: {version|-}

## Visibility
{public|unlisted|private}

## Snap Store URL
{https://snapcraft.io/myapp}

Resources

• Snapcraft docs — official
• snapcraft.yaml reference — full schema
• Channels & tracks — channel concepts
• Public, private, unlisted snaps — visibility deep dive
• Snapcraft GitHub Action — CI/CD recipe
• Linux app store experience blog — Canonical's perspective