# Overview¶

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Abstract

This document provides a conceptual overview about the steps of creating an image with KIWI. It also explains the terminology regarding the concept and process when building system images with KIWI 9.16.27.

## Conceptual Overview¶

A system image (usually called “image”), is a complete installation of a Linux system within a file. The image represents an operation system and, optionally, contains the “final” configuration.

KIWI creates images in a two step process:

1. The first step, the prepare operation, generates a so-called unpacked image tree (directory) using the information provided in the image description.
2. The second step, the create operation, creates the packed image or image in the specified format based on the unpacked image and the information provided in the configuration file.

The image creation process with KIWI is automated and does not require any user interaction. The information required for the image creation process is provided by the image description.

## Terminology¶

Appliance
An appliance is a ready to use image of an operating system including a preconfigured application for a specific use case. The appliance is provided as an image file and needs to be deployed to, or activated in the target system or service.
Image
The result of a KIWI build process.
Image Description
Specification to define an appliance. The image description is a collection of human readable files in a directory. At least one XML file config.xml or .kiwi is required. In addition there may be as well other files like scripts or configuration data. These can be used to customize certain parts either of the KIWI build process or of the initial start-up behavior of the image.
Overlay Files
A directory structure with files and subdirectories stored as part of the Image Description. This directory structure is packaged as a file root.tar.gz or stored below a directory named root. The content of the directory structure is copied over the existing file system (overlayed) of the appliance root. This includes permissions and attributes as a supplement.
KIWI
An OS appliance builder.
Virtualization Technology
Software simulated computer hardware. A virtual machine acts like a real computer, but is separated from the physical hardware. Within this documentation the Qemu virtualization system is used.

## System Requirements¶

To use and run KIWI, you need:

• A recent Linux distribution, see Supported Distributions for details. Alternatively a Linux distribution which supports the docker container system as it would be required when running KIWI in a container, see: Building in a Self-Contained Environment
• Enough free disk space to build and store the image. We recommend a minimum of 10GB.
• Python version 2.7, 3.4 or higher; as KIWI supports both Python versions, the information in this guide applies also to both packages, be it python3-kiwi or python2-kiwi.
• Git (package git-core) to clone a repository.
• Virtualization technology to start the image. We recommend QEMU