In OKD 4.1, Red Hat introduced the concept of channels for
recommending the appropriate release versions for cluster upgrade. By controlling
the pace of upgrades, these upgrade channels allow you to choose an upgrade
strategy. Upgrade channels are tied to a minor version of
OKD. For instance, OKD 4
upgrade channels will never include an upgrade to a 4.7 release. This strategy ensures that
administrators explicitly decide to upgrade to the next minor version of
OKD. Upgrade channels control only release selection and do not impact the version of the cluster that you install; the
binary file for a specific version of OKD always installs that version.
OKD 4 offers the following upgrade channels:
candidate-4 channel contains candidate builds for a z-stream
Release candidates contain all the features of the product but are not supported. Use release candidate versions to test feature acceptance and assist in qualifying the next version
A release candidate is any build that is available in the candidate channel, including ones that do not contain a pre-release version such as
-rc in their names.
After a version is available in the candidate channel, it goes through more quality checks. If
it meets the quality standard, it is promoted to the
Because of this strategy, if a specific release is available in both the
candidate-4 channel and in the
stable-4 channels, it is a Red Hat supported version.
candidate-4 channel can include release versions from which there are no recommended updates in any channel.
You can use the
candidate-4 channel to upgrade from a previous minor version of
Release candidates differ from the nightly builds. Nightly
builds are available for early access to features, but updating to or from nightly
builds is neither recommended nor supported. Nightly builds are not available in
any upgrade channel. You can reference the OKD
for more build information.
fast-4 channel is updated with new 4
versions as soon as Red Hat declares the given version as a general availability
release. As such, these releases are fully supported, are production quality, and have
performed well while available as a release candidate in the
channel from where they were promoted. Some time after a release appears in the
fast-4 channel, it is added to the
stable-4 channel. Releases
never appear in the
stable-4 channel before they appear in the
You can use the
fast-4 channel to upgrade from a previous minor version of
fast-4 channel contains releases as soon
as their errata are published, releases are added to the
after a delay. During this delay, data is collected from Red Hat SRE teams, Red Hat support services,
and pre-production and production environments that participate in connected customer program about the stability of the release.
You can use the
stable-4 channel to upgrade from a previous minor version of
Upgrade version paths
OKD maintains an upgrade recommendation service that understands the
version of OKD 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
The service recommends only upgrades that have been tested and have no serious issues.
If your cluster is on 4.1 and OKD suggests
4.4, then it is safe for you to update from 4.1 to 4.4. Do not rely on consecutive patch numbers. In this example, 4.2 is not, and never was, available in the channel. The update service will not suggest updating to a version of OKD that contains known vulnerabilities.
Update stability depends on your channel. The presence of an update recommendation in
candidate-4 channel does not imply that the update is supported.
It means that no serious issues have been found with the update yet, but there might
not be significant traffic through the update to suggest stability. The presence of
an update recommendation in the
channels is a declaration that the update is fully supported while it is in the
channel. While releases will never be removed from a channel, update recommendations
that exhibit serious issues will be removed from all channels. Updates initiated
after the update recommendation has been removed might not be supported.
Red Hat will eventually provide supported update paths from any supported release in the
stable-4 channels to the latest release in 4.z,
although there can be delays while safe paths away from troubled releases are
constructed and verified.
Fast and stable channel use and strategies
stable-4 channels present a choice between receiving
general availability releases as soon as they are available or allowing Red Hat to
control the rollout of those updates. If issues are detected during rollout or at a
later time, upgrades to that version might be blocked in both the
stable-4 channels, and a new version might be introduced that becomes the new
preferred upgrade target.
Customers can improve this process by configuring pre-production systems on the
fast-4 channel, configuring production systems on the
and participating in Red Hat’s connected customer program. Red
Hat uses this program to observe the impact of updates on your specific hardware and software
configurations. Future releases might improve or alter the pace at which updates move
fast-4 to the
Restricted network clusters
If you manage the container images for your OKD clusters yourself, you must consult the Red Hat errata that is associated with product releases and note any comments that impact upgrades.
During upgrade, the user interface might warn you about switching between these versions,
so you must ensure that you selected an appropriate version before you bypass those warnings.
Switching between channels
Your cluster is still supported if you change from the
stable-4 channel to
fast-4 channel. Although you can switch to the
candidate-4 channel at any time, some releases in that channel might be unsupported release candidates.
You can switch from the
candidate-4 channel to the
if your current release is a general availability release. You can always
switch from the
fast-4 channel to the
stable-4 channel, although if the current release was recently promoted to
fast-4 there can
be a delay of up to a day for the release to be promoted to
stable-4. If you change to a channel that does not include your
current release, an alert displays and no updates can be recommended, but you can
safely change back to your original channel at any point.