docker-compose Update Module

tutorial

The docker-compose Update Module is included in Mender Client 6.0 or newer. You can find the source code in the mender-container-modules repository.

The docker-compose Update Module will be available in mender-convert 5.2.0 or newer.

To install the docker-compose Update Module in the converted image, set:

echo 'MENDER_DOCKER_COMPOSE_INSTALL="y"' >> configs/docker_compose_config

The default version is set to latest, meaning the latest released version. You can manually override the version to install by setting:

# Valid values are "latest" (default), "main" or a specific version.
echo 'MENDER_DOCKER_COMPOSE_VERSION="main"' >> configs/docker_compose_config

The docker-compose Update Module depends on Docker and Docker Compose. The package will automatically install the dependencies, so we recommend to increase the size of the image mounted during the package installation. To expand by 512MB, set:

echo 'MENDER_EXPAND_WORK_ROOTFS="512M"' >> configs/docker_compose_config

The argument to MENDER_EXPAND_WORK_ROOTFS is an integer and an optional unit (example: 10K is 10*1024). See truncate man page for more details. Note that this does not directly affect the final image size; it only expands the root filesystem extracted from the input image to ensure there is enough space to install the packages and their dependencies. The final rootfs image size is calculated separately based on actual disk usage plus IMAGE_ROOTFS_EXTRA_SPACE and IMAGE_OVERHEAD_FACTOR.

By default, Docker will store the container images in /var/lib/docker. In order for container images to persist over rootfs updates, it's necessary to configure Docker to use persistent storage. We can modify the Docker storage by configuring the data-root in /etc/docker/daemon.json.

Before creating the config, we'll create a rootfs overlay for hosted Mender:

# choose hosting region, from either 'eu' and 'us' ('us' if nothing is specified)
./scripts/bootstrap-rootfs-overlay-hosted-server.sh \
    --output-dir input/rootfs_overlay_docker_compose \
    --region us \
    --tenant-token "Paste token from https://hosted.mender.io/ui/settings/organization"

See Rootfs overlays for more information.

We can then create the config:

sudo mkdir -p input/rootfs_overlay_docker_compose/etc/docker
cat <<EOF | sudo tee input/rootfs_overlay_docker_compose/etc/docker/daemon.json
{
   "data-root": "/data/docker"
}
EOF
sudo chmod 600 input/rootfs_overlay_docker_compose/etc/docker/daemon.json
sudo chown root:root input/rootfs_overlay_docker_compose

sudo is required to modify the rootfs overlay because the bootstrap-rootfs-overlay scripts set the owner and group to root

To use the config defined in configs/docker_compose_config and the overlay in input/rootfs_overlay_docker_compose, you must include --config configs/docker_compose_config and --overlay input/rootfs_overlay_docker_compose/ as arguments when running mender-convert.

See Customization for more information.

Next steps

For information on how to create docker-compose Artifacts, see Create a docker-compose update Artifact.

We welcome contributions to improve this documentation. To submit a change, use the Edit link at the top of the page or email us at .