CentOS is a free, community-driven Linux operating system project. Its current distribution, CentOS Stream, runs on servers, cloud instances, containers, virtual machines and workstations. The project builds an enterprise-class platform that sits directly upstream of Red Hat Enterprise Linux (RHEL). What appears in CentOS Stream is the work being prepared for the next RHEL minor release. It runs on 64-bit Intel and AMD processors, 64-bit ARM, IBM Power and IBM Z, and costs nothing to download and use.
From CentOS Linux to CentOS Stream
For many years the CentOS name meant CentOS Linux, a rebuild of RHEL released after each RHEL version. That edition is no longer maintained. Its old releases remain in the CentOS Vault without updates, so choosing CentOS today means choosing CentOS Stream.
The change reversed the position of CentOS in the Enterprise Linux family. Fedora Linux is where new software and ideas are developed first. CentOS Stream branches from Fedora and turns that material into a stable enterprise base. RHEL is then built from CentOS Stream. The RHEL engineering team maintains CentOS Stream and carries only updates intended for RHEL. It delivers them as they are built rather than in large point releases.
Release cycle and support length
CentOS Stream gets a new major release roughly every three years. Each major release is maintained for about five years. Its end of life is tied to the end of the matching RHEL major version’s full support phase. In practice the project keeps two major releases available at the same time. This gives administrators a window to move servers from the older branch to the newer one.
Within a major release there are no numbered minor versions to upgrade between. Packages arrive as continuous updates through the normal package manager. The project positions it as a production system, a development environment for software that must run on RHEL, and a preview of the next RHEL minor release.
Repositories and package management
CentOS Stream installs and updates software as RPM packages managed with DNF. Packages are split into repositories with different purposes:
- BaseOS holds the core operating system and is maintained for the full life of the major release.
- AppStream carries user-space applications, programming language runtimes and databases. Some of these components follow shorter lifecycles linked to RHEL Application Streams.
- CRB contains development packages and is disabled by default.
When more than one version of a component is offered, the newest major release of CentOS Stream ships the alternatives as ordinary separate RPM packages. It uses these instead of the older modularity system. The software selection covers typical server work: Apache HTTP Server and nginx for web serving; PostgreSQL, MariaDB, MySQL and Valkey for databases; and Python, Ruby, Node.js, PHP, Go, Rust, OpenJDK, GCC and LLVM for development.
Desktop and graphics stack
CentOS Stream includes the GNOME desktop. In the newest major release Wayland is the only display server, with Xwayland running older X11 applications. The standalone Xorg server has been removed. Several large desktop applications such as LibreOffice, GIMP and Inkscape are no longer part of the base distribution either. Following the direction of RHEL, they are meant to be installed as Flatpak packages from Flathub or requested for the EPEL repository.
Hardware architectures and CPU baselines
Every CentOS Stream release is built for four architectures: x86_64, aarch64 (ARM64), ppc64le (IBM Power) and s390x (IBM Z). Each build targets a minimum processor capability level. On x86_64 the newest major release requires the x86-64-v3 level, which lets the compiler use newer instructions but excludes older processors. A RISC-V image is also produced by the community as an alternative build.
Installation media and images
The CentOS project distributes CentOS Stream in several forms so it can be deployed the same way across different environments:
- DVD ISO images for installing on physical or virtual machines on all four architectures, served through a network of mirrors with SHA-256 checksums for verification.
- Cloud images for generic cloud platforms, plus official images on Amazon Web Services.
- Container images on Quay and Docker Hub for building container-based applications.
- Vagrant boxes for x86_64, used to create disposable development machines.
The Alternative Images group adds Live ISOs that boot a complete system without installing it. These come with a single desktop such as GNOME or KDE, a MAX image containing every available desktop, or a MIN text-only image. The same group publishes CentOS Stream images for Windows Subsystem for Linux on x86_64 and ARM64. It refreshes all of these images at least every three months.
Special Interest Groups
Much of what makes CentOS useful beyond the base system comes from Special Interest Groups (SIGs). Each SIG builds and maintains its own packages or variants on top of CentOS Stream. These packages or variants are usually enabled on an existing system by installing a small release package that adds the SIG’s repository. Examples include:
- Cloud, which packages the RDO OpenStack distribution, the OKD Kubernetes distribution and Stream CoreOS builds.
- Storage, which provides packaging for Ceph, Gluster, NFS Ganesha and Samba.
- Virtualization, which delivers a complete virtualization stack from deployment to updates.
- Kmods, which supplies extra kernel modules for the stock Enterprise Linux kernel and Fedora-based kernels.
- Automotive, which produces AutoSD, a preview of Red Hat’s in-vehicle operating system.
Hyperscale variant
The Hyperscale SIG adapts CentOS Stream for very large server fleets. Its repositories carry faster-moving backports of base packages including systemd, a newer kernel that tracks the ARK kernel project with Btrfs and live kernel patching support, and an optional experimental repository. The SIG also publishes its own Live ISOs, cloud images and container images.
Contributing changes to RHEL
Because CentOS Stream is developed in the open, users can propose changes that end up in RHEL. Package sources live in GitLab under the CentOS Stream namespace. A contributor first files an issue against the package in Red Hat’s issue tracker, then forks the package repository. They make the change, reference the issue in each commit and open a merge request. The RHEL maintainer for that package reviews it and may ask for changes. The maintainer merges it once the issue is approved for a release.
After a merged change is built, the package passes through gating with RHEL continuous integration tests. It is then added to the build environment and to the next CentOS Stream compose. The same path carries the change into the following RHEL minor release. CentOS Stream thus both shows and lets users influence what RHEL will contain.
