The runtime base image provides the OS-level dependencies for applications at runtime.
We need a Dockerfile similar to the following:
# Define the base image FROM ubuntu:noble # Install packages that we want to make available at run time RUN apt-get update && \ apt-get install -y xz-utils ca-certificates && \ rm -rf /var/lib/apt/lists/* # Create user and group ARG cnb_uid=1000 ARG cnb_gid=1000 RUN groupadd cnb --gid ${cnb_gid} && \ useradd --uid ${cnb_uid} --gid ${cnb_gid} -m -s /bin/bash cnb # Set user and group USER ${cnb_uid}:${cnb_gid} # Set required CNB target information LABEL io.buildpacks.base.distro.name="your distro name" LABEL io.buildpacks.base.distro.version="your distro version" We start with ubuntu:noble as our base image. You can use any operating system, operating system distribution, and operating system distribution version of your choosing, as long as your application will run there.
Install any system packages that your application will need.
The USER in the image config may be different from the build-time user (though the group ID should probably be the same). You should consult the documentation for your buildpacks to determine what is supported.
Finally, we need to label the image with operating system distribution information for platforms and the lifecycle to use.
To determine which values to provide, see targets concept information.
docker build . -t cnbs/sample-base-run:noble