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3.3. Evacuating and decommissioning blue nodes
For larger deployments, it is possible to have other labels that help determine how evacuation can be coordinated. The most conservative approach for avoiding downtime is to evacuate one node host at a time.
If services are composed of pods using zone anti-affinity, you can evacuate an entire zone at one time. You must ensure that the storage volumes used are available in the new zone. Follow the directions in your cloud provider’s documentation.
A node host evacuation is triggered whenever the node service is stopped. Node labeling is very important and can cause issues if nodes are mislabeled or commands are run on nodes with generalized labels. Exercise caution if master hosts are also labeled with color=blue.
When you are ready to continue with the upgrade process, follow these steps.
Evacuate and delete all blue nodes with the following commands:
$ oc adm manage-node --selector=color=blue --evacuate $ oc delete node --selector=color=blue
After the blue node hosts no longer contain pods and have been removed from OpenShift Container Platform, they are safe to power off. As a safety precaution, confirm that there are no issues with the upgrade before you power off the hosts.
Unregister each old host:
# subscription-manager clean
- Back up any useful scripts or required files that are stored on the hosts.
- After you are comfortable that the upgrade succeeded, remove these hosts.
