Update Streams

Individual Update Streams

Fedora CoreOS (FCOS) has several individual update streams that are available to end users. They are:

  • stable

    • The stable stream is the most reliable stream offered with changes only reaching that stream after spending a period of time in the testing stream.

  • testing

    • The testing stream represents what is coming in the next stable release. Content in this stream is updated regularly and offers our community an opportunity to catch breaking changes before they hit the stable stream.

  • next

    • The next stream represents the future. It will often be used to experiment with new features and also test out rebases of our platform on top of the next major version of Fedora. The content in the next stream will also eventually filter down into testing and on to stable.

When following a stream, a system is updated automatically when a new release is rolled out on that stream. While all streams of FCOS are automatically tested, it is strongly encouraged for users to devote a percentage of their FCOS deployment to running the testing and next streams. This ensures possible breaking changes can be caught early enough that stable deployments experience fewer regressions.

Switching to a Different Stream

In order to switch between the different streams of Fedora CoreOS (FCOS) a user can leverage the rpm-ostree rebase command.

It may be a good idea to backup data under /var before switching streams.

Software updates generally follow the next → testing → stable flow, meaning next has the newest software and stable has the oldest software. Upstream software components are generally tested for upgrading, not downgrading, which means that upstream software typically can handle a data/configuration migration forward (upgrade), but not backwards (downgrade). For this reason it is typically safer to rebase from stable → testing or testing → next, but less safe to go the other direction.

Switching between streams may introduce regressions or bugs due to skipping update barriers. If you experience a regression please attempt a rollback.

 
# Stop the service that performs automatic updates
sudo systemctl stop zincati.service

# Perform the rebase to a different stream
# Available streams: "stable", "testing", and "next"
STREAM="testing"
sudo rpm-ostree rebase --bypass-driver "fedora/x86_64/coreos/${STREAM}"

Fedora CoreOS system upgrades are usually controlled by Zincati. Passing --bypass-driver tells RPM-OSTree to bypass Zincati for this operation.

After inspecting the package difference the user can reboot. After boot the system will be loaded into the latest release on the new stream and will follow that stream for future updates.