Chapter 14. Managing bare metal hosts
When you install OpenShift Container Platform on a bare metal cluster, you can provision and manage bare metal nodes using machine
and machineset
custom resources (CRs) for bare metal hosts that exist in the cluster.
14.1. About bare metal hosts and nodes
To provision a Red Hat Enterprise Linux CoreOS (RHCOS) bare metal host as a node in your cluster, first create a MachineSet
custom resource (CR) object that corresponds to the bare metal host hardware. Bare metal host machine sets describe infrastructure components specific to your configuration. You apply specific Kubernetes labels to these machine sets and then update the infrastructure components to run on only those machines.
Machine
CR’s are created automatically when you scale up the relevant MachineSet
containing a metal3.io/autoscale-to-hosts
annotation. OpenShift Container Platform uses Machine
CR’s to provision the bare metal node that corresponds to the host as specified in the MachineSet
CR.
14.2. Maintaining bare metal hosts
You can maintain the details of the bare metal hosts in your cluster from the OpenShift Container Platform web console. Navigate to Compute
You can move a bare metal host into maintenance mode. When you move a host into maintenance mode, the scheduler moves all managed workloads off the corresponding bare metal node. No new workloads are scheduled while in maintenance mode.
You can deprovision a bare metal host in the web console. Deprovisioning a host does the following actions:
-
Annotates the bare metal host CR with
cluster.k8s.io/delete-machine: true
- Scales down the related machine set
Powering off the host without first moving the daemon set and unmanaged static pods to another node can cause service disruption and loss of data.
Additional resources
14.2.1. Adding a bare metal host to the cluster using the web console
You can add bare metal hosts to the cluster in the web console.
Prerequisites
- Install an RHCOS cluster on bare metal.
-
Log in as a user with
cluster-admin
privileges.
Procedure
-
In the web console, navigate to Compute
Bare Metal Hosts. -
Select Add Host
New with Dialog. - Specify a unique name for the new bare metal host.
- Set the Boot MAC address.
- Set the Baseboard Management Console (BMC) Address.
- Optionally, enable power management for the host. This allows OpenShift Container Platform to control the power state of the host.
- Enter the user credentials for the host’s baseboard management controller (BMC).
- Select to power on the host after creation, and select Create.
-
Scale up the number of replicas to match the number of available bare metal hosts. Navigate to Compute
MachineSets, and increase the number of machine replicas in the cluster by selecting Edit Machine count from the Actions drop-down menu.
You can also manage the number of bare metal nodes using the oc scale
command and the appropriate bare metal machine set.
14.2.2. Adding a bare metal host to the cluster using YAML in the web console
You can add bare metal hosts to the cluster in the web console using a YAML file that describes the bare metal host.
Prerequisites
- Install a RHCOS compute machine on bare metal infrastructure for use in the cluster.
-
Log in as a user with
cluster-admin
privileges. -
Create a
Secret
CR for the bare metal host.
Procedure
-
In the web console, navigate to Compute
Bare Metal Hosts. -
Select Add Host
New from YAML. Copy and paste the below YAML, modifying the relevant fields with the details of your host:
apiVersion: metal3.io/v1alpha1 kind: BareMetalHost metadata: name: <bare_metal_host_name> spec: online: true bmc: address: <bmc_address> credentialsName: <secret_credentials_name> 1 disableCertificateVerification: True bootMACAddress: <host_boot_mac_address> hardwareProfile: unknown
- 1
credentialsName
must reference a validSecret
CR. Thebaremetal-operator
cannot manage the bare metal host without a validSecret
referenced in thecredentialsName
. For more information about secrets and how to create them, see Understanding secrets.
- Select Create to save the YAML and create the new bare metal host.
Scale up the number of replicas to match the number of available bare metal hosts. Navigate to Compute
MachineSets, and increase the number of machines in the cluster by selecting Edit Machine count from the Actions drop-down menu. NoteYou can also manage the number of bare metal nodes using the
oc scale
command and the appropriate bare metal machine set.
14.2.3. Automatically scaling machines to the number of available bare metal hosts
To automatically create the number of Machine
objects that matches the number of available BareMetalHost
objects, add a metal3.io/autoscale-to-hosts
annotation to the MachineSet
object.
Prerequisites
-
Install RHCOS bare metal compute machines for use in the cluster, and create corresponding
BareMetalHost
objects. -
Install the OpenShift Container Platform CLI (
oc
). -
Log in as a user with
cluster-admin
privileges.
Procedure
Annotate the machine set that you want to configure for automatic scaling by adding the
metal3.io/autoscale-to-hosts
annotation. Replace<machineset>
with the name of the machine set.$ oc annotate machineset <machineset> -n openshift-machine-api 'metal3.io/autoscale-to-hosts=<any_value>'
Wait for the new scaled machines to start.
When you use a BareMetalHost
object to create a machine in the cluster and labels or selectors are subsequently changed on the BareMetalHost
, the BareMetalHost
object continues be counted against the MachineSet
that the Machine
object was created from.
Additional resources