Chapter 7. Placing nodes in maintenance mode with Node Maintenance Operator
You can use the Node Maintenance Operator to place nodes in maintenance mode by using the oc adm
utility or NodeMaintenance
custom resources (CRs).
7.1. About the Node Maintenance Operator
The Node Maintenance Operator watches for new or deleted NodeMaintenance
CRs. When a new NodeMaintenance
CR is detected, no new workloads are scheduled and the node is cordoned off from the rest of the cluster. All pods that can be evicted are evicted from the node. When a NodeMaintenance
CR is deleted, the node that is referenced in the CR is made available for new workloads.
Using a NodeMaintenance
CR for node maintenance tasks achieves the same results as the oc adm cordon
and oc adm drain
commands using standard Red Hat OpenShift CR processing.
7.2. Installing the Node Maintenance Operator
You can install the Node Maintenance Operator using the web console or the OpenShift CLI (oc
).
If OpenShift Virtualization version 4.10 or less is installed in your cluster, it includes an outdated version of the Node Maintenance Operator.
7.2.1. Installing the Node Maintenance Operator by using the web console
You can use the Red Hat OpenShift web console to install the Node Maintenance Operator.
Prerequisites
-
Log in as a user with
cluster-admin
privileges.
Procedure
-
In the Red Hat OpenShift web console, navigate to Operators
OperatorHub. - Select the Node Maintenance Operator, then click Install.
-
Keep the default selection of Installation mode and namespace to ensure that the Operator will be installed to the
openshift-workload-availability
namespace. - Click Install.
Verification
To confirm that the installation is successful:
-
Navigate to the Operators
Installed Operators page. -
Check that the Operator is installed in the
openshift-workload-availability
namespace and that its status isSucceeded
.
If the Operator is not installed successfully:
-
Navigate to the Operators
Installed Operators page and inspect the Status column for any errors or failures. -
Navigate to the Operators
Installed Operators Node Maintenance Operator Details page, and inspect the Conditions
section for errors before pod creation. -
Navigate to the Workloads
Pods page, search for the Node Maintenance Operator
pod in the installed namespace, and check the logs in theLogs
tab.
7.2.2. Installing the Node Maintenance Operator by using the CLI
You can use the OpenShift CLI (oc
) to install the Node Maintenance Operator.
You can install the Node Maintenance Operator in your own namespace or in the openshift-workload-availability
namespace.
Prerequisites
-
Install the OpenShift CLI (
oc
). -
Log in as a user with
cluster-admin
privileges.
Procedure
Create a
Namespace
CR for the Node Maintenance Operator:Define the
Namespace
CR and save the YAML file, for example,workload-availability-namespace.yaml
:apiVersion: v1 kind: Namespace metadata: name: openshift-workload-availability
To create the
Namespace
CR, run the following command:$ oc create -f workload-availability-namespace.yaml
Create an
OperatorGroup
CR:Define the
OperatorGroup
CR and save the YAML file, for example,workload-availability-operator-group.yaml
:apiVersion: operators.coreos.com/v1 kind: OperatorGroup metadata: name: workload-availability-operator-group namespace: openshift-workload-availability
To create the
OperatorGroup
CR, run the following command:$ oc create -f workload-availability-operator-group.yaml
Create a
Subscription
CR:Define the
Subscription
CR and save the YAML file, for example,node-maintenance-subscription.yaml
:apiVersion: operators.coreos.com/v1alpha1 kind: Subscription metadata: name: node-maintenance-operator namespace: openshift-workload-availability 1 spec: channel: stable installPlanApproval: Automatic name: node-maintenance-operator source: redhat-operators sourceNamespace: openshift-marketplace package: node-maintenance-operator
- 1
- Specify the
Namespace
where you want to install the Node Maintenance Operator.
ImportantTo install the Node Maintenance Operator in the
openshift-workload-availability
namespace, specifyopenshift-workload-availability
in theSubscription
CR.To create the
Subscription
CR, run the following command:$ oc create -f node-maintenance-subscription.yaml
Verification
Verify that the installation succeeded by inspecting the CSV resource:
$ oc get csv -n openshift-workload-availability
Example output
NAME DISPLAY VERSION REPLACES PHASE node-maintenance-operator.v5.3.0 Node Maintenance Operator 5.3.0 node-maintenance-operator.v5.2.1 Succeeded
Verify that the Node Maintenance Operator is running:
$ oc get deployment -n openshift-workload-availability
Example output
NAME READY UP-TO-DATE AVAILABLE AGE node-maintenance-operator-controller-manager 1/1 1 1 10d
The Node Maintenance Operator is supported in a restricted network environment. For more information, see Using Operator Lifecycle Manager on restricted networks.
7.3. Setting a node to maintenance mode
You can place a node into maintenance mode from the web console or from the CLI by using a NodeMaintenance
CR.
7.3.1. Setting a node to maintenance mode by using the web console
To set a node to maintenance mode, you can create a NodeMaintenance
custom resource (CR) by using the web console.
Prerequisites
-
Log in as a user with
cluster-admin
privileges. - Install the Node Maintenance Operator from the OperatorHub.
Procedure
-
From the Administrator perspective in the web console, navigate to Operators
Installed Operators. - Select the Node Maintenance Operator from the list of Operators.
- In the Node Maintenance tab, click Create NodeMaintenance.
-
In the Create NodeMaintenance page, select the Form view or the YAML view to configure the
NodeMaintenance
CR. -
To apply the
NodeMaintenance
CR that you have configured, click Create.
Verification
In the Node Maintenance tab, inspect the Status
column and verify that its status is Succeeded
.
7.3.2. Setting a node to maintenance mode by using the CLI
You can put a node into maintenance mode with a NodeMaintenance
custom resource (CR). When you apply a NodeMaintenance
CR, all allowed pods are evicted and the node is rendered unschedulable. Evicted pods are queued to be moved to another node in the cluster.
Prerequisites
-
Install the Red Hat OpenShift CLI
oc
. -
Log in to the cluster as a user with
cluster-admin
privileges.
Procedure
Create the following
NodeMaintenance
CR, and save the file asnodemaintenance-cr.yaml
:apiVersion: nodemaintenance.medik8s.io/v1beta1 kind: NodeMaintenance metadata: name: nodemaintenance-cr 1 spec: nodeName: node-1.example.com 2 reason: "NIC replacement" 3
Apply the node maintenance CR by running the following command:
$ oc apply -f nodemaintenance-cr.yaml
Verification
Check the progress of the maintenance task by running the following command:
$ oc describe node <node-name>
where
<node-name>
is the name of your node; for example,node-1.example.com
Check the example output:
Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal NodeNotSchedulable 61m kubelet Node node-1.example.com status is now: NodeNotSchedulable
7.3.3. Checking status of current NodeMaintenance CR tasks
You can check the status of current NodeMaintenance
CR tasks.
Prerequisites
-
Install the Red Hat OpenShift CLI
oc
. -
Log in as a user with
cluster-admin
privileges.
Procedure
Check the status of current node maintenance tasks, for example the
NodeMaintenance
CR ornm
object, by running the following command:$ oc get nm -o yaml
Example output
apiVersion: v1 items: - apiVersion: nodemaintenance.medik8s.io/v1beta1 kind: NodeMaintenance metadata: ... spec: nodeName: node-1.example.com reason: Node maintenance status: drainProgress: 100 1 evictionPods: 3 2 lastError: "Last failure message" 3 lastUpdate: "2022-06-23T11:43:18Z" 4 phase: Succeeded totalpods: 5 5 ...
7.4. Resuming a node from maintenance mode
You can resume a node from maintenance mode from the web console or from the CLI by using a NodeMaintenance
CR. Resuming a node brings it out of maintenance mode and makes it schedulable again.
7.4.1. Resuming a node from maintenance mode by using the web console
To resume a node from maintenance mode, you can delete a NodeMaintenance
custom resource (CR) by using the web console.
Prerequisites
-
Log in as a user with
cluster-admin
privileges. - Install the Node Maintenance Operator from the OperatorHub.
Procedure
-
From the Administrator perspective in the web console, navigate to Operators
Installed Operators. - Select the Node Maintenance Operator from the list of Operators.
-
In the Node Maintenance tab, select the
NodeMaintenance
CR that you want to delete. -
Click the Options menu
at the end of the node and select Delete NodeMaintenance.
Verification
-
In the Red Hat OpenShift console, click Compute
Nodes. -
Inspect the
Status
column of the node for which you deleted theNodeMaintenance
CR and verify that its status isReady
.
7.4.2. Resuming a node from maintenance mode by using the CLI
You can resume a node from maintenance mode that was initiated with a NodeMaintenance
CR by deleting the NodeMaintenance
CR.
Prerequisites
-
Install the Red Hat OpenShift CLI
oc
. -
Log in to the cluster as a user with
cluster-admin
privileges.
Procedure
When your node maintenance task is complete, delete the active
NodeMaintenance
CR:$ oc delete -f nodemaintenance-cr.yaml
Example output
nodemaintenance.nodemaintenance.medik8s.io "maintenance-example" deleted
Verification
Check the progress of the maintenance task by running the following command:
$ oc describe node <node-name>
where
<node-name>
is the name of your node; for example,node-1.example.com
Check the example output:
Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal NodeSchedulable 2m kubelet Node node-1.example.com status is now: NodeSchedulable
7.5. Working with bare-metal nodes
For clusters with bare-metal nodes, you can place a node into maintenance mode, and resume a node from maintenance mode, by using the web console Actions control.
Clusters with bare-metal nodes can also place a node into maintenance mode, and resume a node from maintenance mode, by using the web console and CLI, as outlined. These methods, by using the web console Actions control, are applicable to bare-metal clusters only.
7.5.1. Maintaining bare-metal nodes
When you deploy Red Hat OpenShift on bare-metal infrastructure, you must take additional considerations into account compared to deploying on cloud infrastructure. Unlike in cloud environments, where the cluster nodes are considered ephemeral, reprovisioning a bare-metal node requires significantly more time and effort for maintenance tasks.
When a bare-metal node fails due to a kernel error or a NIC card hardware failure, workloads on the failed node need to be restarted on another node in the cluster while the problem node is repaired or replaced. Node maintenance mode allows cluster administrators to gracefully turn-off nodes, move workloads to other parts of the cluster, and ensure that workloads do not get interrupted. Detailed progress and node status details are provided during maintenance.
7.5.2. Setting a bare-metal node to maintenance mode
Set a bare-metal node to maintenance mode using the Options menu
found on each node in the Compute
Procedure
-
From the Administrator perspective of the web console, click Compute
Nodes. You can set the node to maintenance from this screen, which makes it easier to perform actions on multiple nodes, or from the Node Details screen, where you can view comprehensive details of the selected node:
-
Click the Options menu
at the end of the node and select Start Maintenance.
-
Click the node name to open the Node Details screen and click Actions
Start Maintenance.
-
Click the Options menu
- Click Start Maintenance in the confirmation window.
The node is no longer schedulable. If it had virtual machines with the LiveMigration
eviction strategy, then it will live migrate them. All other pods and virtual machines on the node are deleted and recreated on another node.
Verification
-
Navigate to the Compute
Nodes page and verify that the corresponding node has a status of Under maintenance
.
7.5.3. Resuming a bare-metal node from maintenance mode
Resume a bare-metal node from maintenance mode using the Options menu
found on each node in the Compute
Procedure
-
From the Administrator perspective of the web console, click Compute
Nodes. You can resume the node from this screen, which makes it easier to perform actions on multiple nodes, or from the Node Details screen, where you can view comprehensive details of the selected node:
-
Click the Options menu
at the end of the node and select Stop Maintenance.
-
Click the node name to open the Node Details screen and click Actions
Stop Maintenance.
-
Click the Options menu
- Click Stop Maintenance in the confirmation window.
The node becomes schedulable. If it had virtual machine instances that were running on the node prior to maintenance, then they will not automatically migrate back to this node.
Verification
-
Navigate to the Compute
Nodes page and verify that the corresponding node has a status of Ready
.
7.6. Gathering data about the Node Maintenance Operator
To collect debugging information about the Node Maintenance Operator, use the must-gather
tool. For information about the must-gather
image for the Node Maintenance Operator, see Gathering data about specific features.