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: All DNS records must be subdomains of this base domain and include the cluster name, for example: Note You 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. Important Ensure 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. Additional resources Persistent storage using logical volume manager storage What you can do with OpenShift Virtualization 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. Additional resources Creating a bootable ISO image on a USB drive Booting from an HTTP-hosted ISO image using the Redfish API Adding worker nodes to single-node OpenShift clusters 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 . Procedure Set the OpenShift Container Platform version: USD export OCP_VERSION=<ocp_version> 1 1 Replace <ocp_version> with the current version, for example, latest-4.12 Set the host architecture: USD export ARCH=<architecture> 1 1 Replace <architecture> with the target host architecture, for example, aarch64 or x86_64 . Download the OpenShift Container Platform client ( oc ) and make it available for use by entering the following commands: USD curl -k https://mirror.openshift.com/pub/openshift-v4/clients/ocp/USDOCP_VERSION/openshift-client-linux.tar.gz -o oc.tar.gz USD tar zxf oc.tar.gz USD chmod +x oc Download the OpenShift Container Platform installer and make it available for use by entering the following commands: USD curl -k https://mirror.openshift.com/pub/openshift-v4/clients/ocp/USDOCP_VERSION/openshift-install-linux.tar.gz -o openshift-install-linux.tar.gz USD tar zxvf openshift-install-linux.tar.gz USD chmod +x openshift-install Retrieve the RHCOS ISO URL by running the following command: USD export ISO_URL=USD(./openshift-install coreos print-stream-json | grep location | grep USDARCH | grep iso | cut -d\" -f4) Download the RHCOS ISO: USD curl -L USDISO_URL -o rhcos-live.iso Prepare the install-config.yaml file: apiVersion: v1 baseDomain: <domain> 1 compute: - architecture: amd64 2 name: worker replicas: 0 3 controlPlane: architecture: amd64 name: master replicas: 1 4 metadata: name: <name> 5 networking: 6 clusterNetwork: - cidr: 10.128.0.0/14 hostPrefix: 23 machineNetwork: - cidr: 10.0.0.0/16 7 networkType: OVNKubernetes serviceNetwork: - 172.30.0.0/16 platform: none: {} bootstrapInPlace: installationDisk: /dev/disk/by-id/<disk_id> 8 pullSecret: '<pull_secret>' 9 sshKey: | <ssh_key> 10 1 Add the cluster domain name. 2 Set the architecture to arm64 for 64-bit ARM or amd64 for 64-bit x86 architectures. This needs to be set explicitly to the target host architecture. 3 Set the compute replicas to 0 . This makes the control plane node schedulable. 4 Set the controlPlane replicas to 1 . In conjunction with the compute setting, this setting ensures the cluster runs on a single node. 5 Set the metadata name to the cluster name. 6 Set the networking details. OVN-Kubernetes is the only allowed network plugin type for single-node clusters. 7 Set the cidr value to match the subnet of the single-node OpenShift cluster. 8 Set the path to the installation disk drive, for example, /dev/disk/by-id/wwn-0x64cd98f04fde100024684cf3034da5c2 . 9 Copy the pull secret from the Red Hat OpenShift Cluster Manager and add the contents to this configuration setting. 10 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: USD mkdir ocp USD cp install-config.yaml ocp USD ./openshift-install --dir=ocp create single-node-ignition-config Embed the ignition data into the RHCOS ISO by running the following commands: USD alias coreos-installer='podman run --privileged --pull always --rm \ -v /dev:/dev -v /run/udev:/run/udev -v USDPWD:/data \ -w /data quay.io/coreos/coreos-installer:release' USD coreos-installer iso ignition embed -fi ocp/bootstrap-in-place-for-live-iso.ign rhcos-live.iso Additional resources 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 OpenShift Container Platform 4.12 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: USD ./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: USD export KUBECONFIG=ocp/auth/kubeconfig USD oc get nodes Example output NAME STATUS ROLES AGE VERSION control-plane.example.com Ready master,worker 10m v1.25.0 Additional resources Creating a bootable ISO image on a USB drive Booting from an HTTP-hosted ISO image using the Redfish API Adding worker nodes to single-node OpenShift clusters 2.3. 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. 2.4. 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. Prerequisites Download the installation Red Hat Enterprise Linux CoreOS (RHCOS) ISO. 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: USD 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: USD 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: USD 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: USD 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 2.5. 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 the coreos-installer image mirror page. Download the latest live RHCOS ISO from mirror.openshift.com . Create the embedded.yaml file that the butane utility uses to create the Ignition file: variant: openshift version: 4.12.0 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: USD 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-4.12.0-x86_64-live.x86_64.iso , with the coreos-installer utility: USD coreos-installer iso ignition embed -i embedded.ign rhcos-4.12.0-x86_64-live.x86_64.iso -o rhcos-sshd-4.12.0-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-4.12.0-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" ] } ] } }

Commands:
example.com
<cluster_name>.example.com
export OCP_VERSION=<ocp_version> 1
export ARCH=<architecture> 1
curl -k https://mirror.openshift.com/pub/openshift-v4/clients/ocp/USDOCP_VERSION/openshift-client-linux.tar.gz -o oc.tar.gz
tar zxf oc.tar.gz
chmod +x oc
curl -k https://mirror.openshift.com/pub/openshift-v4/clients/ocp/USDOCP_VERSION/openshift-install-linux.tar.gz -o openshift-install-linux.tar.gz
tar zxvf openshift-install-linux.tar.gz
chmod +x openshift-install
export ISO_URL=USD(./openshift-install coreos print-stream-json | grep location | grep USDARCH | grep iso | cut -d\" -f4)
curl -L USDISO_URL -o rhcos-live.iso
apiVersion: v1 baseDomain: <domain> 1 compute: - architecture: amd64 2 name: worker replicas: 0 3 controlPlane: architecture: amd64 name: master replicas: 1 4 metadata: name: <name> 5 networking: 6 clusterNetwork: - cidr: 10.128.0.0/14 hostPrefix: 23 machineNetwork: - cidr: 10.0.0.0/16 7 networkType: OVNKubernetes serviceNetwork: - 172.30.0.0/16 platform: none: {} bootstrapInPlace: installationDisk: /dev/disk/by-id/<disk_id> 8 pullSecret: '<pull_secret>' 9 sshKey: | <ssh_key> 10
mkdir ocp
cp install-config.yaml ocp
./openshift-install --dir=ocp create single-node-ignition-config
alias coreos-installer='podman run --privileged --pull always --rm -v /dev:/dev -v /run/udev:/run/udev -v USDPWD:/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
./openshift-install --dir=ocp wait-for install-complete
export KUBECONFIG=ocp/auth/kubeconfig
oc get nodes
NAME STATUS ROLES AGE VERSION control-plane.example.com Ready master,worker 10m v1.25.0
dd if=<path_to_iso> of=<path_to_usb> status=progress
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
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
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
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
variant: openshift version: 4.12.0 metadata: name: sshd labels: machineconfiguration.openshift.io/role: worker passwd: users: - name: core 1 ssh_authorized_keys: - '<ssh_key>'
butane -pr embedded.yaml -o embedded.ign
coreos-installer iso ignition embed -i embedded.ign rhcos-4.12.0-x86_64-live.x86_64.iso -o rhcos-sshd-4.12.0-x86_64-live.x86_64.iso
coreos-installer iso ignition show rhcos-sshd-4.12.0-x86_64-live.x86_64.iso
{ "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" ] } ] } }