In OKD 4.1, Red Hat introduced the concept of channels for recommending the appropriate release versions for cluster upgrades. 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 4.8 upgrade channels recommend upgrades to 4.8 and upgrades within 4.8. They also recommend upgrades within 4.7 and from 4.7 to 4.8, to allow clusters on 4.7 to eventually upgrade to 4.8. They do not recommend upgrades to 4.9 or later releases. 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
openshift-install binary file for a specific version of OKD always installs that version.
OKD 4 offers the following upgrade channel:
Releases are added to the
stable-4 channel after passing all tests.
You can use the
stable-4 channel to upgrade from a previous minor version of OKD.
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. It will not suggest updating to a version of OKD that contains known vulnerabilities. For example, 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 presence of an update recommendation in the
stable-4 channel is a declaration that the update is fully supported while it is in the channel. While releases will never be removed from the channel, update recommendations that exhibit serious issues will be removed from the channel. Updates initiated after the update recommendation has been removed might not be supported.
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.