Snapcraft Extensions

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

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

:information_source: For more details on the snap building process, see Creating a snap

Using Extensions

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

$ snapcraft extensions
Extension name    Supported bases
----------------  -----------------
gnome-3-28        core18
...

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
...

Supported Extensions

Extension name Description
gnome-3-28 This extension eases creation of snaps that integrate with GNOME and GTK 3.28
1 Like

@galgalesh thanks so much for this - this is great work which I’ll add to the top-level outline. We’ve currently got someone porting a number of the original Gnome packages to use the new Gnome extension, and they’re also (hopefully) making their own set of notes about the process which we’ll be able to incorporate here.

1 Like