Change to the Ubuntu 26.04 LTS base

This guide describes the process for migrating a charm from a lower base to Ubuntu 26.04 LTS.

Migrate from the charm plugin

The Charm plugin isn’t available for the Ubuntu 26.04 LTS base. If your charm uses it, switch to one of the replacement plugins:

• Migrate from the Charm plugin to the uv plugin

• Migrate from the Charm plugin to the Python plugin

• Migrate from the Charm plugin to the Poetry plugin

Update the base

Charms built with Ubuntu 22.04 LTS or lower might use the bases key in their project file. This key is not supported by the Ubuntu 26.04 LTS base and must be replaced with the base and platforms keys. The base key declares which Ubuntu release the charm uses, while the platforms key declares the CPU architectures of the build and production machines.

For a charm with a bases key as follows:

charmcraft.yaml

bases:
  - build-on:
      - name: ubuntu
        channel: "22.04"
    run-on:
      - name: ubuntu
        channel: "22.04"

Replace the bases key with:

charmcraft.yaml

base: ubuntu@26.04
platforms:
  amd64:
  arm64:
  riscv64:
  s390x:

Platforms has all the details about the platforms key, including the syntax for specifying multiple bases and architectures.

Update part names

If you update a charm to use the Ubuntu 26.04 LTS base, then you must also verify its part names. Part names on 26.04 and later bases can’t contain any forward slashes (/). We recommend replacing them with a hyphen (-):

charmcraft.yaml

 base: ubuntu@26.04

 # ...

 parts:
-  my/part:
+  my-part: