Change from core22 to core24

This guide describes the process for migrating a snap that uses core22 as its base to core24.

Support for core24 is provided by the Craft Application library. Craft Application introduced changes to the lifecycle, added a new remote builder, and replaced the concept of architectures with platforms. These updates inform the migration process.

Deprecated features

The following features are deprecated in core22 and removed in core24:

  • The parameters --enable-manifest and --manifest-image-information. Generation of the build’s manifest in core24 is controlled exclusively by the SNAPCRAFT_BUILD_INFO environment variable, and the image information parameter is completely removed.

  • The snapcraftctl command in scriptlets is no longer supported and should be replaced with craftctl.

  • The architectures key has been replaced by platforms. See details below.

  • The environment variable CRAFT_ARCH_TRIPLET. Use CRAFT_ARCH_TRIPLET_BUILD_FOR instead.

  • The environment variable CRAFT_TARGET_ARCH. Use CRAFT_ARCH_BUILD_FOR instead.

Destructive builds

  • Destructive builds that generate more than one snap are no longer supported, as this feature was never intended.

  • Destructive builds that generate no snaps are no longer supported, as this feature was never intended. It used to be a no-op but now will fail with an error message.

  • Destructive builds with a project whose build-base does not match the host environment will fail with an error message. An exception is made for devel build-bases. In this case the only requirement is that the host be an Ubuntu system.

Remote build

A new remote builder has been introduced. While the previous remote builder is available for older bases, core24 snaps must use the new remote builder.

  • The remote build command now only allows a single active remote build per project for core24 snaps. As a consequence, snapcraft remote-build --recover no longer accepts a --build-id parameter. Instead, snapcraft will recover the remote build for the project in the current working directory.

  • Projects must be at the top level of a git repository.

  • Projects cannot be shallow clones (git clone --depth 1).

Platforms

A new platforms key is the way for core24 snaps to declare the systems where the snap should be built. This aligns with Charmcraft’s and Rockcraft’s platforms key.

platforms is an optional key. If it’s not defined, then Snapcraft will build a snap for the host architecture. Valid architectures are defined here.

The syntax is:

snapcraft.yaml
platforms:
  <platform 1>:
    build-on: [<arch 1>, <arch 2>]
    build-for: [<arch 1>]
  <platform 2>:
    build-on: [<arch 3>]
    build-for: [<arch 4>]
  ...

The definitions of build-on and build-for are unchanged (see core22 definitions here).

Similar to core22, only one build-for architecture is supported and it may be defined as a list or a string.

The platform name is a free-form string. Some simplifications are gained if the platform name is a supported architecture:

  • build-on and build-for may be omitted

  • build-for may be omitted if build-on is defined

When migrating an existing snap to core24, existing architectures definitions can be rewritten as platforms. For example:

snapcraft.yaml
architectures:
  - build-on: [amd64]
    build-for: [amd64]
  - build-on: [amd64, arm64]
    build-for: [arm64]

can be migrated to core24 as:

snapcraft.yaml
platforms:
  amd64:
  arm64:
    build-on: [amd64, arm64]
    build-for: [arm64]

For more information on platforms see the how-to, explanation, and reference pages.

Known issues

  • The command snapcraft try is not yet supported for core24 snaps.