In OpenShift Container Platform 4.1, Red Hat introduced the concept of upgrade channels for
recommending the appropriate upgrade versions to your cluster. Upgrade channels
separate upgrade strategies and also are used to control the cadence of updates.
Channels are tied to a minor version of OpenShift Container Platform. For instance,
OpenShift Container Platform 4.2 channels will never include an upgrade to a
4.3 release. This ensures administrators make an explicit decision to upgrade to
the next minor version of OpenShift Container Platform. Channels only control updates and
have no impact on the version of the cluster you install; the
openshift-install binary for a given patch level of OpenShift Container Platform always
installs that patch level.
OpenShift Container Platform 4.2, which includes the upgrade from the previous 4.1
release, has three upgrade channels to choose from:
The upgrade channels contain two types of updates:
General Availability Software (or GA) - These versions of OpenShift Container Platform are
fully supported and are considered production quality. You may upgrade to the general
availability release from either of the fast and stable channels.
Release Candidate Software (or RC) - These versions of OpenShift Container Platform are
representative of the eventual general availability release and are available only
in the candidate-4.2 channel. The release candidate will contain all
the features of the product. You are allowed to upgrade from a release candidate to
another release candidate and to upgrade from a previous minor version of
OpenShift Container Platform to the current release candidate. Release candidate builds are not
supported by Red Hat and you will not be able to upgrade from a release candidate to
the general availability release of OpenShift Container Platform. Candidates should be used to
test feature acceptance and assist in qualifying the next version of
OpenShift Container Platform in your infrastructure.
Release candidates differ from the nightly builds found on try.openshift.com. You
cannot upgrade nightly builds to nightly builds. Nightly builds are available for
early access to features but are not upgradable or supported.
For GA versions, the fast and stable channels present a choice between receiving
updates as soon as they are available or allowing Red Hat to control the rollout of
The fast channel is updated with new 4.2 patch versions as soon as Red
Hat declares they are generally available. Use this channel if you wish to receive
updates as soon as they are available or for your pre-production environments when
participating in the connected customer program. This channel will contain all
z-stream (4.2.z) updates but will not suggest upgrades to the next
minor release (4.3.z) when the next minor release is available.
The stable channel will contain updates on a time delay as they are gradually
rolled out to customers based on data from our SRE teams, support services, and
pre-production and production environments that participate in our connected
customer program, rather than being immediately available as they are in the fast
channel. For patch and CVE fixes this can range from several hours to a day and
allows an extra period of assessment in how the software performs. If issues are
detected during rollout, upgrades to that version may be blocked in both the fast
and stable channels, and a new version may be introduced that will be the new
preferred upgrade target.
Customers can improve this process by configuring pre-production systems on the
fast channel, production systems on the stable channel, and participating in Red
Hat’s connected customer program - this allows Red Hat to observe the impact of
updates on your specific hardware and software configurations. Future releases may
improve or alter the pace at which updates move from the fast to the stable channels.
If issues are discovered with an upgrade between patch levels, Red Hat may withdraw
that suggested upgrade for affected versions. A newer patch would become available
in the appropriate channels and be suggested for upgrade.
Upgrade version paths
OpenShift Container Platform maintains an upgrade recommendation service that understands the
version of OpenShift Container Platform you have installed as well as the path to take within
the channel you choose to get you to the next release. You can imagine seeing the
following in the fast-4.2 channel:
The service only recommends upgrades that have been tested and have no known issues.
If you are on 4.2.1 and OpenShift Container Platform is allowing you to select
4.2.4, then it is safe for you to go from .4.2.1 to .4.2.4. Likewise,
the absence of 4.2.2 may be due to a CVE that was fixed in 4.2.3 and Red Hat no
longer suggests upgrading to a known vulnerable version. If an issue is found that
results in a new version being retracted from the recommendations, Red Hat will
release a new version that is capable of upgrading from all necessary versions,
including the retracted version.
Customers which have chosen to not be connected to Red Hat and are curating their
own OpenShift Container Platform container image content manually should consult the Red Hat
errata associated with product releases and note any comments impacting upgrades.
During upgrade the user interface may caution about switching between these versions
and it is up to the customer to ensure they have correctly selected the appropriate
version before bypassing those cautions.
Switching between channels
It is supported for customers to switch between the fast and stable channel at any
time. Channels only offer suggested upgrades, and will never suggest a dangerous
upgrade. If you switch to the candidate channel after installing from a GA version,
you will see a warning the current version is not recognized, and you can safely
switch back to a GA channel.