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Chapter 28. Building Custom System Images with Composer

Composer is a tool for creating custom system images. The following sections describe how to install it and how to use it.

28.1. Introduction to Composer

Composer is a tool that enables users to create customized system images of Red Hat Enterprise Linux. On Red Hat Enterprise Linux 7.6, Composer is available in the Extras channel as a Technology Preview in the lorax-composer package.


Composer is available as a Technology Preview. See the Technology Preview Features Support Scope for more details.
Customers deploying Composer are encouraged to provide feedback to Red Hat.

Composer Output Formats

Composer can create these output formats:
DescriptionCLI namefile extension
Ext4 File System Image
Raw Partitioned Disk Image
Live Bootable ISO
TAR Archive

Composer User Interfaces

The Composer back end runs as a system service lorax-composer. Users can interact with this service through two front ends:
  • GUI available as a Cockpit plugin. This is the preferred method.
  • CLI available as the composer-cli tool for running commands.

Composer Blueprints

In Composer, a blueprint defines a customized system image by listing packages that will be part of the system. Blueprints can be edited and they are versioned.
When a system image is created from a blueprint, the image is associated with the blueprint in Composer Cockpit interface.