EL 8: BaseOS and AppStream

EL 8 redesigned the distribution’s repository layout: one “system” repository, BaseOS, plus one “application” repository, AppStream. The goal of the split is to keep the core system on its ten-year stability promise while letting application components update faster — even several major versions in parallel. Module streams were born inside AppStream, and retired in EL 10.

What changed

• BaseOS: kernel, systemd, glibc, base tools — the operating system proper. Its lifecycle matches the release (10 years), with security and bug fixes only.
• AppStream: language runtimes, databases, web servers, and other application components, offered in two forms:
  • plain RPM packages (most software);
  • module streams: several major versions of one piece of software in parallel (such as postgresql:10 / postgresql:13), selected with dnf module enable.

User-visible changes: dnf repolist shows two main repositories; images and Kickstart files must enable both; and “before installing, think whether you need to enable a module” became daily life in the EL 8/9 era.

EL 7 vs EL 8

Item	EL 7	EL 8
Repository layout	single main repository	BaseOS + AppStream
Multiple app versions	via SCL (separate install)	AppStream module streams (built in)
Version-selection command	none	dnf module list/enable
Core-system update promise	mixed	BaseOS on its own long cycle

What it means for you

• Images / Kickstart / offline mirrors: mirroring only BaseOS leads to “the OS installed fine but nginx will not”; offline repositories must sync both.
• Multi-version needs: module streams on EL 8/9; after modularity retires on EL 10, versioned packages and third-party repositories take over (see EL 10: Module streams retired).
• Lifecycle awareness: some AppStream components have lifecycles shorter than the release itself (certain runtimes are supported only up to some minor release); check the component lifecycle, not just the release’s.

Tip

Debugging “it is in the repository but will not install”: first dnf repolist to confirm both BaseOS and AppStream are present; then dnf module list <name> to see whether a module stream has locked you to another version.

Checking and using

Inspect repositories and modules

dnf repolist
dnf module list
dnf module list postgresql

Enable a module stream and install (EL 8/9)

sudo dnf module enable postgresql:13
sudo dnf install postgresql-server

Further reading

• Repositories — repository configuration and offline mirrors in practice
• EL 10: Module streams retired — how the modularity story ends
• EL 8: A new toolchain — the toolchain refresh in the same release
• EL version timeline — lifecycles of every release