Using AppStream

The following sections provide an overview of the concepts related to the AppStream repository in CentOS 8.

Distribution of content in CentOS describes how content in CentOS 8 is split into BaseOS and AppStream.
Application Streams describes the concept of Application Streams.
Packaging methods in CentOS describes the types of content provided by AppStream.
Package management using YUM in CentOS describes how the YUM package manager provided in CentOS 8 combines the traditional and modular features.

Distribution of content in CentOS 8

RHEL 8 content is distributed through the two main repositories: BaseOS and AppStream.

BaseOS: 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 CentOS.
AppStream: Content in the AppStream repository includes additional user space applications, runtime languages, and databases in support of the varied workloads and use cases. Content in AppStream is available in one of two formats - the familiar RPM format and an extension to the RPM format called modules.

Both BaseOS and AppStream content sets are required for a basic installation. For installation instructions, see the Performing a standard installation Performing an advanced installation documents.

Application Streams

CentOS 8 introduces the concept of Application Streams - versions of user space components. Multiple versions of these components are now delivered and updated more frequently than the core operating system packages. This provides greater flexibility to customize CentOS without impacting the underlying stability of the platform or specific deployments.

Components made available as Application Streams can be packaged as modules or RPM packages and are delivered through the AppStream repository in CentOS 8. Each AppStream component has a given life cycle.

Not all modules are Application Streams. Dependencies of other modules are not considered AppStream components.

Packaging methods in CentOS 8

The AppStream repository contains content packaged in two ways:

Individual RPM packages: Traditional RPM packages available for immediate installation.
Modules: 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.

Package management using YUM in CentOS 8

The YUM package management tool is now based on the DNF technology and it adds support for the new modular features.

Usage of YUM has not been changed when handling individual RPM packages. For handling the modular content, the yum module command has been added.

See Installing CentOS Content for additional details.

Where required, the modular functionality automatically selects the appropriate combination of modules and streams to enable installation of logical sets of packages for convenient usage.