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Chapter 1. RHEL image builder description
To deploy a system, create a system image. To create RHEL system images, use the RHEL image builder tool. You can use RHEL image builder to create customized system images of RHEL, including system images prepared for deployment on cloud platforms. RHEL image builder automatically handles the setup details for each output type and is therefore easier to use and faster to work with than manual methods of image creation. You can access the RHEL image builder functionalities by using the command-line interface in the composer-cli tool, or the graphical user interface in the RHEL web console.
From RHEL 8.3 onward, the osbuild-composer back end replaces lorax-composer. The new service provides REST APIs for image building.
1.1. RHEL image builder terminology
RHEL image builder uses the following concepts:
- Blueprint
A blueprint is a description of a customized system image. It lists the packages and customizations that will be part of the system. You can edit blueprints with customizations and save them as a particular version. When you create a system image from a blueprint, the image is associated with the blueprint in the RHEL image builder interface.
Create blueprints in the TOML format.
- Compose
- Composes are individual builds of a system image, based on a specific version of a particular blueprint. Compose as a term refers to the system image, the logs from its creation, inputs, metadata, and the process itself.
- Customizations
- Customizations are specifications for the image that are not packages. This includes users, groups, and SSH keys.
1.2. RHEL image builder output formats
RHEL image builder can create images in multiple output formats shown in the following table.
Table 1.1. RHEL image builder output formats
| Description | CLI name | File extension |
|---|---|---|
| QEMU Image |
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| Disk Archive |
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| Amazon Web Services |
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| Microsoft Azure |
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| Google Cloud Platform |
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| VMware vSphere |
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| VMware vSphere |
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| Openstack |
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| RHEL for Edge Commit |
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| RHEL for Edge Container |
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| RHEL for Edge Installer |
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| RHEL for Edge Raw Image |
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| RHEL for Edge Simplified Installer |
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| RHEL for Edge AMI |
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| RHEL for Edge VMDK |
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| RHEL Installer |
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| Oracle Cloud Infrastructure |
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To check the supported types, run the command:
# composer-cli compose types
1.3. RHEL image builder system requirements
The host that runs RHEL image builder must meet the following requirements:
Table 1.2. RHEL image builder system requirements
| Parameter | Minimal Required Value |
|---|---|
| System type | A dedicated host or virtual machine. Note that RHEL image builder is not supported in containers, including Red Hat Universal Base Images (UBI). |
| Processor | 2 cores |
| Memory | 4 GiB |
| Disk space | 20 GiB of free space in the ` /var/cache/` filesystem |
| Access privileges | root |
| Network | Internet connectivity to the Red Hat Content Delivery Network (CDN). |
If you do not have internet connectivity, use RHEL image builder in isolated networks. For that, you must override the default repositories to point to your local repositories to not connect to Red Hat Content Delivery Network (CDN). Ensure that you have your content mirrored internally or use Red Hat Satellite.
Additional resources