Install a custom package slice¶

When a sliced package isn’t available in the Chisel releases, you will need to create it yourself. Once it’s created, you can install it in your rock.

In this guide, we show how to install the vim-tiny slice built in Slice a package from the Chisel documentation. As you’re working through it, replace any mention of vim-tiny with your slice.

Chisel will only recognize slices belonging to a Chisel release, so you need to copy your slice definitions file – vim-tiny.yaml – into the chisel-releases/slices/ folder in your clone of the chisel-releases repository. Note that if a slice definitions file with the same name already exists, it most likely means that the package you’re slicing has already been sliced before, and in this case, you only need to merge your changes into that existing file.

After this, you should be able to find your custom slice bins in the local Chisel release:

chisel find --release=./chisel-releases/ vim-tiny_bins

If you wanted to test it with Chisel alone, you could now simply run

# Testing with Chisel directly:
mkdir -p my-custom-vim-tiny-fs
chisel cut --release ./chisel-releases --root my-custom-vim-tiny-fs vim-tiny_bins

You should end up with a my-custom-vim-tiny-fs/ directory containing a few directories, amongst which there would be usr/bin/vim-tiny.

To install the custom package slice into a rock, you need to use Rockcraft.

Start by initialising a new Rockcraft project:

rockcraft init

After this command, you should find a new rockcraft.yaml file in your current path.

Adjust the project file according to the following content. Feel free to adjust the metadata, but pay special attention to the parts section:

rockcraft.yaml¶

name: custom-<package>-rock
base: bare
build-base: "ubuntu@26.04"
version: "0.0.1"
summary: A chiseled rock with a custom vim-tiny slice
description: |
  A rock containing only the binaries (and corresponding dependencies) from the vim-tiny package.
  Built from a custom Chisel release.
license: GPL-3.0
platforms:
  amd64:
parts:
  build-context:
    plugin: nil
    source: chisel-releases/
    source-type: local
    override-build: chisel cut --release ./ --root ${CRAFT_PART_INSTALL} vim-tiny_bins

The build-context part allows you to send the local chisel-releases folder into the builder. The override-build key enables you to install your custom slice.

This level of customization is only needed when you want to install from a custom Chisel release. If the desired slice definitions are already upstream, then you can simply use the stage-packages key, as demonstrated in Chisel a rock.

Build your rock with:

rockcraft pack

Test that the vim-tiny binaries have been correctly installed with the following:

sudo rockcraft.skopeo --insecure-policy copy oci-archive:custom-vim-tiny-rock_0.0.1_amd64.rock docker-daemon:chisel-vim-tiny:latest

The output will be:

Getting image source signatures
Copying blob 253d707d7e97 done
Copying blob 7044a53e1935 done
Copying config c114b59704 done
Writing manifest to image destination
Storing signatures

And after:

docker run --rm chisel-vim-tiny exec vim-tiny

And that’s it! You’ve now built your own rock from a custom slice and a custom Chisel release.