Snap-preseed plugin¶

The Snap-preseed plugin creates the seed directory for a classic image with the snap prepare-image --classic command. This downloads snaps and their assertions from the Snap Store and prepares them to be installed during the initial boot.

Keys¶

This plugin provides the following unique keys.

snap-preseed-model-assert¶

Type: string

The path to the model assertion file that defines the target device. If this key is set, the model assertion’s classic key must be set to true.

The Ubuntu Core documentation details model assertions and their fields in model.

snap-preseed-snaps¶

Type: list of strings

The snaps to seed into the image. Valid entries are:

a snap name
a snap name and channel in the format <snap-name> @ <channel> (spaces around @ are optional)
a path to a local snap within the project directory

If the model assertion has a grade of signed or secured, only snaps declared in the model assertion can be specified, and they can’t be referenced by a local path. This is commonly used to include optional snaps from the model assertion.

snap-preseed-channel¶

Type: string

The default store channel to fetch snaps from, overriding any channels in the model assertion, if one is provided. If a model assertion is provided and has a grade, it must be set to dangerous.

This is overridden by snaps listed with a channel in snap-preseed-snaps.

snap-preseed-validation¶

Type: string

Default: enforce

Controls whether validation set constraints are enforced. Valid values are ignore and enforce.

snap-preseed-assertions¶

Type: list of strings

Additional assertion files to include in the image.

The Ubuntu Core documentation lists the available assertion types in Assertions.

snap-preseed-revisions¶

Type: string

Path to a manifest file specifying snap revisions to use.

Each line in a manifest file identifies a snap by name and revision number, like so:

core24 1587
snapd 26865

snap-preseed-write-revisions¶

Type: string or boolean

Default: False

If set to true, the plugin writes the resolved snap revisions to the seed.manifest file. If set to a file path, the revisions are written there instead.

Output¶

The seeded snaps are placed in var/lib/snapd/seed. Use the organize key to place var in the root file system.

Example¶

The following snippet seeds the core24 snap from the latest/stable channel and the hello-world snap from the latest/edge channel into a classic image.

parts:
  seed-snaps:
    plugin: snap-preseed
    snap-preseed-snaps:
      - core24
      - hello-world @ latest/edge
    organize:
      "var/*": (overlay)/var/