Chapter 2. Installing OpenShift on a single node
You can install single-node OpenShift by using either the web-based Assisted Installer or the coreos-installer
tool to generate a discovery ISO image. The discovery ISO image writes the Red Hat Enterprise Linux CoreOS (RHCOS) system configuration to the target installation disk, so that you can run a single-cluster node to meet your needs.
Consider using single-node OpenShift when you want to run a cluster in a low-resource or an isolated environment for testing, troubleshooting, training, or small-scale project purposes.
2.1. Installing single-node OpenShift using the Assisted Installer
To install OpenShift Container Platform on a single node, use the web-based Assisted Installer wizard to guide you through the process and manage the installation.
2.1.1. Generating the discovery ISO with the Assisted Installer
Installing OpenShift Container Platform on a single node requires a discovery ISO, which the Assisted Installer can generate.
Procedure
- On the administration host, open a browser and navigate to Red Hat OpenShift Cluster Manager.
- Click Create New Cluster to create a new cluster.
- In the Cluster name field, enter a name for the cluster.
In the Base domain field, enter a base domain. For example:
example.com
All DNS records must be subdomains of this base domain and include the cluster name, for example:
<cluster_name>.example.com
NoteYou cannot change the base domain or cluster name after cluster installation.
- Select Install single node OpenShift (SNO) and complete the rest of the wizard steps. Download the discovery ISO.
Complete the remaining Assisted Installer wizard steps.
ImportantEnsure that you take note of the discovery ISO URL for installing with virtual media.
If you enable OpenShift Virtualization during this process, you must have a second local storage device of at least 50GiB for your virtual machines.
2.1.2. Installing single-node OpenShift with the Assisted Installer
Use the Assisted Installer to install the single-node cluster.
Prerequisites
- Ensure that the boot drive order in the server BIOS settings defaults to booting the server from the target installation disk.
Procedure
- Attach the discovery ISO image to the target host.
- Boot the server from the discovery ISO image. The discovery ISO image writes the system configuration to the target installation disk and automatically triggers a server restart.
- On the administration host, return to the browser. Wait for the host to appear in the list of discovered hosts. If necessary, reload the Assisted Clusters page and select the cluster name.
- Complete the install wizard steps. Add networking details, including a subnet from the available subnets. Add the SSH public key if necessary.
- Monitor the installation’s progress. Watch the cluster events. After the installation process finishes writing the operating system image to the server’s hard disk, the server restarts.
Optional: Remove the discovery ISO image.
The server restarts several times automatically, deploying the control plane.
2.2. Installing single-node OpenShift manually
To install OpenShift Container Platform on a single node, first generate the installation ISO, and then boot the server from the ISO. You can monitor the installation using the openshift-install
installation program.
2.2.1. Generating the installation ISO with coreos-installer
Installing OpenShift Container Platform on a single node requires an installation ISO, which you can generate with the following procedure.
Prerequisites
-
Install
podman
.
See "Requirements for installing OpenShift on a single node" for networking requirements, including DNS records.
Procedure
Set the OpenShift Container Platform version:
$ export OCP_VERSION=<ocp_version> 1
- 1
- Replace
<ocp_version>
with the current version, for example,latest-4.13
Set the host architecture:
$ export ARCH=<architecture> 1
- 1
- Replace
<architecture>
with the target host architecture, for example,aarch64
orx86_64
.
Download the OpenShift Container Platform client (
oc
) and make it available for use by entering the following commands:$ curl -k https://mirror.openshift.com/pub/openshift-v4/clients/ocp/$OCP_VERSION/openshift-client-linux.tar.gz -o oc.tar.gz
$ tar zxf oc.tar.gz
$ chmod +x oc
Download the OpenShift Container Platform installer and make it available for use by entering the following commands:
$ curl -k https://mirror.openshift.com/pub/openshift-v4/clients/ocp/$OCP_VERSION/openshift-install-linux.tar.gz -o openshift-install-linux.tar.gz
$ tar zxvf openshift-install-linux.tar.gz
$ chmod +x openshift-install
Retrieve the RHCOS ISO URL by running the following command:
$ export ISO_URL=$(./openshift-install coreos print-stream-json | grep location | grep $ARCH | grep iso | cut -d\" -f4)
Download the RHCOS ISO:
$ curl -L $ISO_URL -o rhcos-live.iso
Prepare the
install-config.yaml
file:apiVersion: v1 baseDomain: <domain> 1 compute: - name: worker replicas: 0 2 controlPlane: name: master replicas: 1 3 metadata: name: <name> 4 networking: 5 clusterNetwork: - cidr: 10.128.0.0/14 hostPrefix: 23 machineNetwork: - cidr: 10.0.0.0/16 6 networkType: OVNKubernetes serviceNetwork: - 172.30.0.0/16 platform: none: {} bootstrapInPlace: installationDisk: /dev/disk/by-id/<disk_id> 7 pullSecret: '<pull_secret>' 8 sshKey: | <ssh_key> 9
- 1
- Add the cluster domain name.
- 2
- Set the
compute
replicas to0
. This makes the control plane node schedulable. - 3
- Set the
controlPlane
replicas to1
. In conjunction with the previouscompute
setting, this setting ensures the cluster runs on a single node. - 4
- Set the
metadata
name to the cluster name. - 5
- Set the
networking
details. OVN-Kubernetes is the only allowed network plugin type for single-node clusters. - 6
- Set the
cidr
value to match the subnet of the single-node OpenShift cluster. - 7
- Set the path to the installation disk drive, for example,
/dev/disk/by-id/wwn-0x64cd98f04fde100024684cf3034da5c2
. - 8
- Copy the pull secret from the Red Hat OpenShift Cluster Manager and add the contents to this configuration setting.
- 9
- Add the public SSH key from the administration host so that you can log in to the cluster after installation.
Generate OpenShift Container Platform assets by running the following commands:
$ mkdir ocp
$ cp install-config.yaml ocp
$ ./openshift-install --dir=ocp create single-node-ignition-config
Embed the ignition data into the RHCOS ISO by running the following commands:
$ alias coreos-installer='podman run --privileged --pull always --rm \ -v /dev:/dev -v /run/udev:/run/udev -v $PWD:/data \ -w /data quay.io/coreos/coreos-installer:release'
$ coreos-installer iso ignition embed -fi ocp/bootstrap-in-place-for-live-iso.ign rhcos-live.iso
Additional resources
- See Requirements for installing OpenShift on a single node for more information about installing OpenShift Container Platform on a single node.
- See Enabling cluster capabilities for more information about enabling cluster capabilities that were disabled prior to installation.
- See Optional cluster capabilities in OpenShift Container Platform 4.13 for more information about the features provided by each capability.
2.2.2. Monitoring the cluster installation using openshift-install
Use openshift-install
to monitor the progress of the single-node cluster installation.
Prerequisites
- Ensure that the boot drive order in the server BIOS settings defaults to booting the server from the target installation disk.
Procedure
- Attach the discovery ISO image to the target host.
- Boot the server from the discovery ISO image. The discovery ISO image writes the system configuration to the target installation disk and automatically triggers a server restart.
On the administration host, monitor the installation by running the following command:
$ ./openshift-install --dir=ocp wait-for install-complete
The server restarts several times while deploying the control plane.
Verification
After the installation is complete, check the environment by running the following command:
$ export KUBECONFIG=ocp/auth/kubeconfig
$ oc get nodes
Example output
NAME STATUS ROLES AGE VERSION control-plane.example.com Ready master,worker 10m v1.26.0
2.3. Installing single-node OpenShift on AWS
2.3.1. Additional requirements for installing on a single node on AWS
The AWS documentation for installer-provisioned installation is written with a high availability cluster consisting of three control plane nodes. When referring to the AWS documentation, consider the differences between the requirements for a single-node OpenShift cluster and a high availability cluster.
- The required machines for cluster installation in AWS documentation indicates a temporary bootstrap machine, three control plane machines, and at least two compute machines. You require only a temporary bootstrap machine and one AWS instance for the control plane node and no worker nodes.
- The minimum resource requirements for cluster installation in the AWS documentation indicates a control plane node with 4 vCPUs and 100GB of storage. For a single node cluster, you must have a minimum of 8 vCPU cores and 120GB of storage.
-
The
controlPlane.replicas
setting in theinstall-config.yaml
file should be set to1
. -
The
compute.replicas
setting in theinstall-config.yaml
file should be set to0
. This makes the control plane node schedulable.
2.3.2. Installing single-node OpenShift on AWS
Installing a single node cluster on AWS requires installer-provisioned installation using the "Installing a cluster on AWS with customizations" procedure.
Additional resources
2.4. Creating a bootable ISO image on a USB drive
You can install software using a bootable USB drive that contains an ISO image. Booting the server with the USB drive prepares the server for the software installation.
Procedure
- On the administration host, insert a USB drive into a USB port.
Create a bootable USB drive, for example:
# dd if=<path_to_iso> of=<path_to_usb> status=progress
where:
- <path_to_iso>
-
is the relative path to the downloaded ISO file, for example,
rhcos-live.iso
. - <path_to_usb>
-
is the location of the connected USB drive, for example,
/dev/sdb
.
After the ISO is copied to the USB drive, you can use the USB drive to install software on the server.
2.5. Booting from an HTTP-hosted ISO image using the Redfish API
You can provision hosts in your network using ISOs that you install using the Redfish Baseboard Management Controller (BMC) API.
This example procedure demonstrates the steps on a Dell server.
Ensure that you have the latest firmware version of iDRAC that is compatible with your hardware. If you have any issues with the hardware or firmware, you must contact the provider.
Prerequisites
- Download the installation Red Hat Enterprise Linux CoreOS (RHCOS) ISO.
- Use a Dell PowerEdge server that is compatible with iDRAC9.
Procedure
- Copy the ISO file to an HTTP server accessible in your network.
Boot the host from the hosted ISO file, for example:
Call the Redfish API to set the hosted ISO as the
VirtualMedia
boot media by running the following command:$ curl -k -u <bmc_username>:<bmc_password> -d '{"Image":"<hosted_iso_file>", "Inserted": true}' -H "Content-Type: application/json" -X POST <host_bmc_address>/redfish/v1/Managers/iDRAC.Embedded.1/VirtualMedia/CD/Actions/VirtualMedia.InsertMedia
Where:
- <bmc_username>:<bmc_password>
- Is the username and password for the target host BMC.
- <hosted_iso_file>
-
Is the URL for the hosted installation ISO, for example:
http://webserver.example.com/rhcos-live-minimal.iso
. The ISO must be accessible from the target host machine. - <host_bmc_address>
- Is the BMC IP address of the target host machine.
Set the host to boot from the
VirtualMedia
device by running the following command:$ curl -k -u <bmc_username>:<bmc_password> -X PATCH -H 'Content-Type: application/json' -d '{"Boot": {"BootSourceOverrideTarget": "Cd", "BootSourceOverrideMode": "UEFI", "BootSourceOverrideEnabled": "Once"}}' <host_bmc_address>/redfish/v1/Systems/System.Embedded.1
Reboot the host:
$ curl -k -u <bmc_username>:<bmc_password> -d '{"ResetType": "ForceRestart"}' -H 'Content-type: application/json' -X POST <host_bmc_address>/redfish/v1/Systems/System.Embedded.1/Actions/ComputerSystem.Reset
Optional: If the host is powered off, you can boot it using the
{"ResetType": "On"}
switch. Run the following command:$ curl -k -u <bmc_username>:<bmc_password> -d '{"ResetType": "On"}' -H 'Content-type: application/json' -X POST <host_bmc_address>/redfish/v1/Systems/System.Embedded.1/Actions/ComputerSystem.Reset
2.6. Creating a custom live RHCOS ISO for remote server access
In some cases, you cannot attach an external disk drive to a server, however, you need to access the server remotely to provision a node. It is recommended to enable SSH access to the server. You can create a live RHCOS ISO with SSHd enabled and with predefined credentials so that you can access the server after it boots.
Prerequisites
-
You installed the
butane
utility.
Procedure
-
Download the
coreos-installer
binary from thecoreos-installer
image mirror page. - Download the latest live RHCOS ISO from mirror.openshift.com.
Create the
embedded.yaml
file that thebutane
utility uses to create the Ignition file:variant: openshift version: 4.13.0 metadata: name: sshd labels: machineconfiguration.openshift.io/role: worker passwd: users: - name: core 1 ssh_authorized_keys: - '<ssh_key>'
- 1
- The
core
user has sudo privileges.
Run the
butane
utility to create the Ignition file using the following command:$ butane -pr embedded.yaml -o embedded.ign
After the Ignition file is created, you can include the configuration in a new live RHCOS ISO, which is named
rhcos-sshd-4.13.0-x86_64-live.x86_64.iso
, with thecoreos-installer
utility:$ coreos-installer iso ignition embed -i embedded.ign rhcos-4.13.0-x86_64-live.x86_64.iso -o rhcos-sshd-4.13.0-x86_64-live.x86_64.iso
Verification
Check that the custom live ISO can be used to boot the server by running the following command:
# coreos-installer iso ignition show rhcos-sshd-4.13.0-x86_64-live.x86_64.iso
Example output
{ "ignition": { "version": "3.2.0" }, "passwd": { "users": [ { "name": "core", "sshAuthorizedKeys": [ "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCZnG8AIzlDAhpyENpK2qKiTT8EbRWOrz7NXjRzopbPu215mocaJgjjwJjh1cYhgPhpAp6M/ttTk7I4OI7g4588Apx4bwJep6oWTU35LkY8ZxkGVPAJL8kVlTdKQviDv3XX12l4QfnDom4tm4gVbRH0gNT1wzhnLP+LKYm2Ohr9D7p9NBnAdro6k++XWgkDeijLRUTwdEyWunIdW1f8G0Mg8Y1Xzr13BUo3+8aey7HLKJMDtobkz/C8ESYA/f7HJc5FxF0XbapWWovSSDJrr9OmlL9f4TfE+cQk3s+eoKiz2bgNPRgEEwihVbGsCN4grA+RzLCAOpec+2dTJrQvFqsD alosadag@sonnelicht.local" ] } ] } }