Chapter 3. Distribution of content in RHEL 9

3.1. Installation

Red Hat Enterprise Linux 9 is installed using ISO images. Two types of ISO image are available for the AMD64, Intel 64-bit, 64-bit ARM, IBM Power Systems, and IBM Z architectures:

  • Installation ISO: A full installation image that contains the BaseOS and AppStream repositories and allows you to complete the installation without additional repositories. On the Red Hat Customer Portal Downloads page, the Installation ISO is referred to as Binary DVD.

    Note

    The Installation ISO image is in multiple GB size, and as a result, it might not fit on optical media formats. A USB key or USB hard drive is recommended when using the Installation ISO image to create bootable installation media. You can also use the Image Builder tool to create customized RHEL images. For more information about Image Builder, see the Composing a customized RHEL system image document.

  • Boot ISO: A minimal boot ISO image that is used to boot into the installation program. This option requires access to the BaseOS and AppStream repositories to install software packages. The repositories are part of the Installation ISO image. You can also register to Red Hat CDN or Satellite during the installation to use the latest BaseOS and AppStream content from Red Hat CDN or Satellite.

See the Performing a standard RHEL installation document for instructions on downloading ISO images, creating installation media, and completing a RHEL installation. For automated Kickstart installations and other advanced topics, see the Performing an advanced RHEL installation document.

3.2. Repositories

Red Hat Enterprise Linux 9 is distributed through two main repositories:

  • BaseOS
  • AppStream

Both repositories are required for a basic RHEL installation, and are available with all RHEL subscriptions.

Content in the BaseOS repository is intended to provide the core set of the underlying OS functionality that provides the foundation for all installations. This content is available in the RPM format and is subject to support terms similar to those in previous releases of RHEL.

Content in the AppStream repository includes additional user-space applications, runtime languages, and databases in support of the varied workloads and use cases.

In addition, the CodeReady Linux Builder repository is available with all RHEL subscriptions. It provides additional packages for use by developers. Packages included in the CodeReady Linux Builder repository are unsupported.

3.3. Application Streams

Multiple versions of user-space components are delivered as Application Streams and updated more frequently than the core operating system packages. This provides greater flexibility to customize RHEL without impacting the underlying stability of the platform or specific deployments.

Application Streams are available in the familiar RPM format, as an extension to the RPM format called modules, as Software Collections, or as Flatpaks.

Each Application Stream component has a given life cycle, either the same as RHEL 9 or shorter.

RHEL 9 improves the Application Streams experience by providing initial Application Stream versions that can be installed as RPM packages using the traditional yum install command.

Some additional Application Stream versions will be distributed as modules with a shorter life cycle in future minor RHEL 9 releases.

Modules are collections of packages representing a logical unit: an application, a language stack, a database, or a set of tools. These packages are built, tested, and released together. Detailed module commands are described in the Managing software with YUM document.

Content that needs rapid updating, such as alternate compilers and container tools, is available in rolling streams that will not provide alternative versions in parallel. Rolling streams may be packaged as RPMs or modules.

Note

Application Streams versions and formats distributed in RHEL 9.0 Beta might differ from versions and formats provided at the time of general availability of RHEL 9.0.

3.4. Package management with YUM/DNF

Throughout this document, YUM and DNF can be used interchangeably.

In Red Hat Enterprise Linux 9, software installation is ensured by DNF. Red Hat continues to support the usage of the yum term for consistency with previous major versions of RHEL. If you type dnf instead of yum, the command works as expected because both are aliases for compatibility.

Although RHEL 8 and RHEL 9 are based on DNF, they are compatible with YUM used in RHEL 7.

For more information, see Managing software with YUM.