Change from core20 to core22¶

core22 support in Snapcraft introduces new underlying layers and concepts that require some changes when migrating from core20 to core22. Support for core20 and other bases is unaffected.

Parts¶

Snapcraft has moved to a more general syntactical mechanism that can be used consistently across the *craft ecosystem. Most of the following changes are a reflection of that alignment.

While snapcraftctl is still supported, craftctl is now preferred.

Override pull¶

override-pull: |
  snapcraftctl pull

translates to:

override-pull: |
  craftctl default

Override build¶

override-pull: |
  snapcraftctl build

translates to:

override-pull: |
  craftctl default

Override stage¶

override-pull: |
  snapcraftctl stage

translates to:

override-pull: |
  craftctl default

Override prime¶

override-pull: |
  snapcraftctl prime

translates to:

override-pull: |
  craftctl default

Set a version¶

override-<step>: |
  snapcraftctl set-version 1.0.0

translates to:

override-<step>: |
  craftctl set version=1.0.0

Set a grade¶

override-<step>: |
  snapcraftctl set-grade stable

translates to:

override-<step>: |
  craftctl set grade=stable

Grammar¶

The try keyword is no longer available. Instead, use the architecture-specific entry. Consider the following example:

stage-packages:
  - try:
    - criu

This is equivalent to using the architecture-specific entry as follows:

stage-packages:
  - on amd64:
    - criu

Architectures¶

The keywords for achitectures are now build-on and build-for.

architectures:
  - build-on: [amd64]
    run-on: [arm64]

translates to:

architectures:
  - build-on: [amd64]
    build-for: [arm64]

Environment variables¶

The following core20 environment variables are still supported, but should be migrated to core22 as follows:

core20	core22
`SNAPCRAFT_PART_SRC_WORK`	`CRAFT_PART_SRC_WORK`
`SNAPCRAFT_PART_SRC`	`CRAFT_PART_SRC`
`SNAPCRAFT_PROJECT_DIR`	`CRAFT_PROJECT_DIR`
`SNAPCRAFT_PART_BUILD`	`CRAFT_PART_BUILD`
`SNAPCRAFT_PROJECT_NAME`	`CRAFT_PROJECT_NAME`
`SNAPCRAFT_PART_BUILD_WORK`	`CRAFT_PART_BUILD_WORK`
`SNAPCRAFT_ARCH_TRIPLET`	`CRAFT_ARCH_TRIPLET`
`SNAPCRAFT_PARALLEL_BUILD_COUNT`	`CRAFT_PARALLEL_BUILD_COUNT`
`SNAPCRAFT_PRIME`	`CRAFT_PRIME`
`SNAPCRAFT_TARGET_ARCH`	`CRAFT_TARGET_ARCH`
`SNAPCRAFT_STAGE`	`CRAFT_STAGE`
`SNAPCRAFT_PART_NAME`	`CRAFT_PART_NAME`
`SNAPCRAFT_PART_INSTALL`	`CRAFT_PART_INSTALL`

Get the grade¶

While SNAPCRAFT_PROJECT_GRADE is still supported, craftctl get grade is now preferred.

Get the version¶

While SNAPCRAFT_PROJECT_VERSION is still supported, craftctl get version is now preferred.

Unbound variable verification¶

Snapcraft will now report errors for unbound variables in user scriptlets and variables set by the user in build-environment. This can happen if LD_LIBRARY_PATH is extended and no previous value is set. In this case, the :+ parameter expansion syntax can be used, as shown in the following example. Alternatively, a new value can be assigned since the variable has not been previously set.

snapcraft.yaml¶

part:
  user-part:
    ...
    build-environment:
      - LD_LIBRARY_PATH: $CRAFT_STAGE/usr/lib/$CRAFT_ARCH_TRIPLET${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}

Filesets¶

The filesets keyword is no longer supported in snapcraft project files. Instead, files and directories to include or exclude should be defined with the stage and prime keywords for a part.

Application environments¶

Snapcraft previously set up a snap.yaml file similar to the following:

snap.yaml¶

apps:
  <user-defined-app>:
    command-chain: [snap/snapcraft-runner.sh]
    command: <user-defined-command>

This was not overridable, and to get rid of it, users had to define the following in their project file:

snapcraft.yaml¶

apps:
  <user-defined-app>:
    adapter: none
    command: <user-defined-command>

Snapcraft has moved to defining an environment for each application entry instead of setting up a command-chain, with a simple way to overwride or disable.

Default behavior¶

snapcraft.yaml has no entries in the root environment. snap.yaml includes:

snap.yaml¶

environment:
  LD_LIBRARY_PATH: <snapcraft-value>
  PATH: <snapcraft-value>

Override an entry¶

A user can override the default behavior by defining it themselves. If PATH is defined as:

snapcraft.yaml¶

environment:
  PATH: <user-value>

then snap.yaml will include:

snap.yaml¶

environment:
  LD_LIBRARY_PATH: <snapcraft-value>
  PATH: <user-value>

Nullify an entry¶

A user can nullify an entry by using a YAML null entry. If PATH is defined as:

snapcraft.yaml¶

PATH: null

then snap.yaml will include:

snap.yaml¶

environment:
  LD_LIBRARY_PATH: <snapcraft-value>

Plugins¶

By default, most plugins don’t install the base dependency to allow more control when building.

Go plugin¶

The Go plugin is no longer installed by default. To add the Go snap from the latest/stable channel, include the following in your project file:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: go
    build-snaps: [go/latest/stable]

To install from the deb, include:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: go
    build-packages: [golang-go]

To build Go from source, include:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: go
    after: [go-deps]
  go-deps:
    source: ...
    plugin: ...

Rust plugin¶

The rustc and cargo plugins are no longer installed by default. To install the deb, include the following in your project file:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: rust
    build-packages: [cargo, rustc]

NPM plugin¶

The Node and NPM plugins are no longer installed by default. To add the Node snap, include the following in your project file:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: npm
    build-snaps: [node/16/stable]

To include the Node binary in the build (and provide NPM), include:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: npm
    npm-include-node: true

Meson plugin¶

The Meson plugin is no longer installed by default. To add the Meson deb, include the following in your project file:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: meson
    build-packages: [meson, ninja-build]

To build Meson from an alternate source, include:

snapcraft.yaml¶

parts:
  user-part:
    source: .
    plugin: meson
    after: [meson-deps]
  meson-deps:
    plugin: nil
    override-build: |
      pip install meson

Python plugin¶

The following environment variable names should be migrated as follows:

core20	core22
`SNAPCRAFT_PYTHON_INTERPRETER`	`PARTS_PYTHON_INTERPRETER`
`SNAPCRAFT_PYTHON_VENV_ARGS`	`PARTS_PYTHON_VENV_ARGS`

Destructive mode¶

sudo is no longer run on behalf of the user. It was a leftover from the pre-containerization era and, because Snapcraft already runs as root in the managed environment, is considered redundant with build instance usage.

Additionally, to avoid any interaction during lifecycle processing that could be blocking, the CLI library in today’s UI doesn’t support user input. If required, use sudo in the call to Snapcraft itself.