2 Tool for Building Images and Managing Containers #

Docker is a system for creating and managing containers. Its core is the Docker Open Source Engine—a lightweight virtualization solution to run containers simultaneously on a single host. Docker containers can be built using Dockerfiles (see Dockerfile). For a general introduction to Docker Open Source Engine, refer to Chapter 3, Docker Open Source Engine Overview.

Podman stands for Pod Manager tool. It is a daemonless container engine for developing, managing, and running Open Container Initiative (OCI) containers on a Linux system, and it offers a drop-in alternative for Docker. Podman is the default container runtime in openSUSE Kubic—a certified Kubernetes distribution built on top of openSUSE. For a general introduction to Podman, refer to Chapter 10, Podman Overview.

Buildah facilitates building OCI container images. It is a complimentary tool to Podman, and podman build uses Buildah to perform container image builds. Buildah makes it possible to build images from scratch, from existing images, and using Dockerfiles. OCI images built using the Buildah command-line tool and the underlying OCI-based technologies (for example, containers/image and containers/storage ) are portable and can therefore run in a Docker Open Source Engine environment.

For information on installing and using Buildah, refer to Chapter 11, Buildah Overview.

The Open Build Service (OBS) provides free infrastructure for building and storing RPM packages including various container formats. The OBS Container Registry provides a detailed listing of all container images built by the OBS, complete with commands for pulling the images into your local Docker environment. The OBS openSUSE container image templates can be modified to specific needs, which offers the easiest way to create your own container branch. Container images can be built with native Docker tools from an existing image using a Dockerfile. Alternatively, images can be built from scratch using the KIWI image-building solution.

Instructions on how to build images on OBS can be found at https://openbuildservice.org/2018/05/09/container-building-and-distribution/ .

KIWI Next Generation is a multi-purpose tool for building images. In addition to container images, regular installation ISO images, and images for virtual machines, KIWI can build images that boot via PXE or Vagrant boxes. The main building block in KIWI is an image XML description, a directory that includes the config.xml or .kiwi file along with scripts or configuration data. The process of creating images with KIWI is fully automated and does not require any user interaction. Any information required for the image creation process is provided by the primary configuration file config.xml . The image can be customized using the config.sh and images.sh scripts.

Note

It is important to distinguish between KIWI NG (currently version 9.20.9) and its unmaintained legacy versions (7.x.x or older), now called KIWI Legacy .

For specific information on how to install KIWI and use it to build images, see the KIWI documentation . A collection of example image descriptions can be found on the KIWI GitHub repository .

KIWI's man pages provide information on using the tool. To access man pages, install the kiwi-man-pages package.