The process of getting from source code to an image suitable for loading
into a target device with Apertis is a clearly defined multi-step
process. The initial step is to build the source and package the
resulting artefacts into
.deb packages. For the vast majority of
packages this is already done and provided by Apertis in the package
repositories. This page will not
cover this step of the process an will assume all required packages have
been successfully built and are available in the package repositories.
There are two further steps to generating an image:
- Building an Operating System package (OSpack)
- Combining the OSpack with a Hardware package (HWpack) to create an image
Both the process of building OSpacks and images from them is carried out using Debos. It is strongly recommended to utilise the appropriate Docker image builder container to perform these steps, though the Apertis SDK image running in a VM can be used with reduced reliability.
The OSpack is a root file system containing all the generic software for
a particular image type and hardware architecture (e.g. the arm
architecture). Apertis provides stock Debos recipes in the form of
.yaml files in the
gitlab repository, with a name of the form
one providing a different balance of packages for different tasks.
It is best to build these packages images from the appropriate image-builder docker container. This is documented in the apertis-image-recipes README.md.
Building an image with a HWpack
Unlike the OSpack, that is generic, the HWpack contains the bits needed to boot on a specific target. The HWpack configuration typically extracts an OSpack, creates an image containing the required partition layout for the specific hardware, writes the extracted OSpack into it, adds extra components necessary for the target and may perform some tweaks to the image (tweaking configuration files etc). Finally the image is compressed to minimise storage space.
Image creation is the point where a set of standard packages are combined to
build a solution for a specific use case. This goal is accomplish thanks to
Debos, a flexible tool to configure the
build of Debian-based operating systems. Debos uses tools like
already present in the environment and relies on virtualisation to securely do
privileged operations without requiring root access.
Ospacks and how they should be processed to generate images are defined through YAML files.
This is an example configuration for an ARMv7 image,
And this is the
ospack-armhf.yaml configuration for the ARMv7 ospack:
Additionally at this stage customizations can be applied by using overlays.
This process allows the default content of packages to be combined with
custom modifications to provide the desired solution. A common case is to apply
overlays to change some default system settings found in
/etc such as default
hostname or default package configuration.
As an example of this mechanism, the following section is used to customize the
Thanks to this action, the contents of the
directory will be applied to the image, which in this case consist of
This file will be added to the rootfs, which in this instance will change the default behaviour of dpkg to suit the needs of the image
Collections of images are built every night and published on the deployable image hosting website, such that developers can always download the latest image to deploy it to a target device and start using it immediately.