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A Red Hat training course is available for RHEL 8

Chapter 2. Installing Image Builder

Before using Image Builder, you must install Image Builder in a virtual machine.

2.1. Installing Image Builder in a virtual machine

To install Image Builder on a dedicated virtual machine, follow these steps:


  • Connect to the virtual machine.
  • The virtual machine for Image Builder must be installed, subscribed to Red Hat Subscription Manager (RHSM) or Red Hat Satellite, and running.


  1. Install the Image Builder and other necessary packages on the virtual machine:

    • osbuild-composer - supported from RHEL 8.3 onward
    • composer-cli
    • cockpit-composer
    • bash-completion
    # yum install osbuild-composer composer-cli cockpit-composer bash-completion

    The web console is installed as a dependency of the cockpit-composer package.

  2. Enable Image Builder to start after each reboot:

    # systemctl enable --now osbuild-composer.socket
    # systemctl enable --now cockpit.socket

    The osbuild-composer and cockpit services start automatically on first access.

  3. Load the shell configuration script so that the autocomplete feature for the composer-cli command starts working immediately without reboot:

    $ source /etc/bash_completion.d/composer-cli

The osbuild-composer package is the new backend engine that will be the preferred default and focus of all new functionality beginning with Red Hat Enterprise Linux 8.3 and later. The previous backend lorax-composer package is considered deprecated, will only receive select fixes for the remainder of the Red Hat Enterprise Linux 8 life cycle and will be omitted from future major releases. It is recommended to uninstall lorax-composer in favor of osbuild-composer.


You can use a system journal to track Image Builder service activities. Additionally, you can find the log messages in the file.

  • To find the journal output for traceback, run the following commands:

    $ journalctl | grep osbuild
  • To show both remote or local workers:

    $ journalctl -u osbuild-worker*
  • To show the running services:

    $ journalctl -u osbuild-composer.service

2.2. Reverting to lorax-composer Image Builder backend

The osbuild-composer backend, though much more extensible, does not currently achieve feature parity with the previous lorax-composer backend.

To revert to the previous backend, follow the steps:


  • You have installed the osbuild-composer package


  1. Remove the osbuild-composer backend.

    # yum remove osbuild-composer
  2. In the /etc/yum.conf file, add an exclude entry for osbuild-composer package.

    # cat /etc/yum.conf
  3. Install the lorax-composer package.

    # yum install lorax-composer
  4. Enable and start the lorax-composer service to start after each reboot.

    # systemctl enable --now lorax-composer.socket
    # systemctl start lorax-composer

Additional resources