Base snaps

A base snap is a special kind of snap that provides a run-time environment with a minimal set of libraries that are common to most applications. They’re transparent to users, but they need to be considered, and specified, when building a snap.

Bases are defined by adding the base: keyword to a snap’s snapcraft.yaml followed by the base name.

There are currently two supported bases:

For example, to specify core 18, use the following:

base: core18

To specify core 16, use the following

base: core

The base snap mounts itself as the root filesystem within your snap such that when your application runs, the base’s library paths are searched directly after the paths for your specific snap.

When building your snap with no specified base, Snapcraft will operate in legacy mode. This is essentially a prior (2.43-era) version of Snapcraft, and will lose the functionalities and bug fixes introduced in the new version.

Building a base snap

While it is possible to build your own base snap, its publisher needs to take responsibility for its maintenance and updates. In particular:

  • bases need to be built from stable packages
  • ABI compatibility cannot broken (ie. never replace symbols or libraries, and be strict)
  • security updates must be pro-active

Base snaps can be either bootable or non-bootable. The former needs to include systemd while the latter can be leaner.

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