Snapcraft Extensions

Snapcraft extensions enable snap developers to easily incorporate a set of common requirements into a snap.

These requirements can include build and staging packages, plugs and interfaces, file layouts and environments, and whatever other snapcraft.yaml elements may be required to build a functioning system.

A snap developer creating a GTK 3 application snap, for example, can use the gnome-3-28 extension to expose the GTK 3 libraries to a snap at build and runtime without the snap developer needing specific deep knowledge about GTK 3.

Extensions help:

• avoid repetitive tasks in the snap building process
• obviate the need for in-depth knowledge of the target software stack
• create a standard template for common application requirements
• reduce the testing and security burden, as they’re tested and updated independently

For a full list of supported extensions, see Supported extensions.

Using Extensions

To use an extension, the app metadata section of the snap’s snapcraft.yaml needs include the extensions definition. The following snippet, for example, shows how the Firefox snap uses the gnome-3-34 extension to add Gnome desktop support:

apps:
  firefox:
    command: firefox
    command-chain: [tmpdir]
    desktop: distribution/firefox.desktop
    extensions: [gnome-3-34]
[...]

All extensions are included with Snapcraft and can be listed with the following command:

$ snapcraft extensions
Extension name    Supported bases
----------------  -----------------
gnome-3-28        core18
gnome-3-38        core20
kde-neon          core18, core20
[...]

See Supported Extensions for the full list of extensions.

Further information about any specific extension can be obtained by typing snapcraft extension followed by the extension name:

$ snapcraft extension gnome-3-28
This extension eases creation of snaps that integrate with GNOME 3.28
...

Extensions modify the snapcraft.yaml definition before a build. You can use the expand-extensions command from your project’s root directory to see how the snapcraft.yaml file will look with the extensions applied.

$ snapcraft expand-extensions
name: foliate
...
layout:
  /usr/lib/$SNAPCRAFT_ARCH_TRIPLET/webkit2gtk-4.0:
    bind: $SNAP/gnome-platform/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/webkit2gtk-4.0
  /usr/share/xml/iso-codes:
    bind: $SNAP/gnome-platform/usr/share/xml/iso-codes
apps:
  foliate:
    command: usr/bin/com.github.johnfactotum.Foliate
    plugs:
    - gsettings
    - home
    - desktop
    - desktop-legacy
    - wayland
    - x11
    slots:
    - dbus-daemon
    common-id: com.github.johnfactotum.Foliate.desktop
    desktop: usr/share/applications/com.github.johnfactotum.Foliate.desktop
    command-chain:
    - snap/command-chain/desktop-launch
...

Last updated 4 months ago.