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Merge pull request #53986 from stevsmit/OSDOCS4376
Adds procedure and work for adding a hint file to the node IP configu…
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‎installing/installing_bare_metal_ipi/ipi-install-installation-workflow.adoc

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include::modules/ipi-install-creating-a-disconnected-registry.adoc[leveloffset=+1]
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[discrete]
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[id="prerequisites_ipi-disconnected-registry"]
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=== Prerequisites

‎modules/nw-how-nw-iface-selected.adoc

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[id="nw-how-nw-iface-selected_{context}"]
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= How the network interface is selected
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For installations on bare metal or with virtual machines that have more than one network interface controller (NIC), the NIC that {product-title} uses for communication with the Kubernetes API server is determined by the `nodeip-configuration.service` service unit that is run by systemd when the node boots.
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The service iterates through the network interfaces on the node and the first network interface that is configured with a subnet than can host the IP address for the API server is selected for {product-title} communication.
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For installations on bare metal or with virtual machines that have more than one network interface controller (NIC), the NIC that {product-title} uses for communication with the Kubernetes API server is determined by the `nodeip-configuration.service` service unit that is run by systemd when the node boots. The `nodeip-configuration.service` selects the IP from the interface associated with the default route.
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After the `nodeip-configuration.service` service determines the correct NIC, the service creates the `/etc/systemd/system/kubelet.service.d/20-nodenet.conf` file.
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The `20-nodenet.conf` file sets the `KUBELET_NODE_IP` environment variable to the IP address that the service selected.
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After the `nodeip-configuration.service` service determines the correct NIC, the service creates the `/etc/systemd/system/kubelet.service.d/20-nodenet.conf` file. The `20-nodenet.conf` file sets the `KUBELET_NODE_IP` environment variable to the IP address that the service selected.
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When the kubelet service starts, it reads the value of the environment variable from the `20-nodenet.conf` file and sets the IP address as the value to the `--node-ip` kubelet command-line argument.
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As a result, the kubelet service uses the selected IP address as the node IP address.
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When the kubelet service starts, it reads the value of the environment variable from the `20-nodenet.conf` file and sets the IP address as the value of the `--node-ip` kubelet command-line argument. As a result, the kubelet service uses the selected IP address as the node IP address.
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If hardware or networking is reconfigured after installation, it is possible that the `nodeip-configuration.service` service can select a different NIC after a reboot.
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In some cases, you might be able to detect that a different NIC is selected by reviewing the `INTERNAL-IP` column in the output from the `oc get nodes -o wide` command.
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If hardware or networking is reconfigured after installation, or if there is a networking layout where the node IP should not come from the default route interface, it is possible for the `nodeip-configuration.service` service to select a different NIC after a reboot. In some cases, you might be able to detect that a different NIC is selected by reviewing the `INTERNAL-IP` column in the output from the `oc get nodes -o wide` command.
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If network communication is disrupted or misconfigured because a different NIC is selected, one strategy for overriding the selection process is to set the correct IP address explicitly.
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The following list identifies the high-level steps and considerations:
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* Create a shell script that determines the IP address to use for {product-title} communication. Have the script create a custom unit file such as `/etc/systemd/system/kubelet.service.d/98-nodenet-override.conf`. Use the custom unit file, `98-nodenet-override.conf`, to set the `KUBELET_NODE_IP` environment variable to the IP address.
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* Do not overwrite the `/etc/systemd/system/kubelet.service.d/20-nodenet.conf` file. Specify a file name with a numerically higher value such as `98-nodenet-override.conf` in the same directory path. The goal is to have the custom unit file run after `20-nodenet.conf` and override the value of the environment variable.
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* Create a machine config object with the shell script as a base64-encoded string and use the Machine Config Operator to deploy the script to the nodes at a file system path such as `/usr/local/bin/override-node-ip.sh`.
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* Ensure that `systemctl daemon-reload` runs after the shell script runs. The simplest method is to specify `ExecStart=systemctl daemon-reload` in the machine config, as shown in the following sample.
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.Sample machine config to override the network interface for kubelet
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[source,yaml,subs="attributes+"]
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----
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apiVersion: machineconfiguration.openshift.io/v1
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kind: MachineConfig
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metadata:
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labels:
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machineconfiguration.openshift.io/role: worker
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name: 98-nodenet-override
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spec:
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config:
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ignition:
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version: {ign-config-version}
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storage:
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files:
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- contents:
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source: data:text/plain;charset=utf-8;base64,<encoded_script>
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mode: 0755
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overwrite: true
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path: /usr/local/bin/override-node-ip.sh
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systemd:
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units:
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- contents: |
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[Unit]
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Description=Override node IP detection
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Wants=network-online.target
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Before=kubelet.service
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After=network-online.target
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[Service]
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Type=oneshot
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ExecStart=/usr/local/bin/override-node-ip.sh
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ExecStart=systemctl daemon-reload
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[Install]
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WantedBy=multi-user.target
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enabled: true
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name: nodenet-override.service
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----
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If network communication is disrupted or misconfigured because a different NIC is selected, you might receive the following error: `EtcdCertSignerControllerDegraded`. You can create a hint file that includes the `NODEIP_HINT` variable to override the default IP selection logic. For more information, see Optional: Overriding the default node IP selection logic.
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// Link to info for creating a machine config.
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‎modules/overriding-default-node-ip-selection-logic.adoc

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// This is included in the following assemblies:
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//
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// * troubleshooting-network-issues.adoc
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:_content-type: PROCEDURE
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[id="overriding-default-node-ip-selection-logic_{context}"]
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= Optional: Overriding the default node IP selection logic
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To override the default IP selection logic, you can create a hint file that includes the `NODEIP_HINT` variable to override the default IP selection logic. Creating a hint file allows you to select a specific node IP address from the interface in the subnet of the IP address specified in the `NODEIP_HINT` variable.
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For example, if a node has two interfaces, `eth0` with an address of `10.0.0.10/24`, and `eth1` with an address of `192.0.2.5/24`, and the default route points to `eth0` (`10.0.0.10`),the node IP address would normally use the `10.0.0.10` IP address.
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Users can configure the `NODEIP_HINT` variable to point at a known IP in the subnet, for example, a subnet gateway such as `192.0.2.1` so that the other subnet, `192.0.2.0/24`, is selected. As a result, the `192.0.2.5` IP address on `eth1` is used for the node.
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The following procedure shows how to override the default node IP selection logic.
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.Procedure
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. Add a hint file to your your `/etc/default/nodeip-configuration` file, for example:
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[source,text]
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----
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NODEIP_HINT=192.0.2.1
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----
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[IMPORTANT]
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====
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* Do not use the exact IP address of a node as a hint, for example, `192.0.2.5`. Using the exact IP address of a node causes the node using the hint IP address to fail to configure correctly.
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* The IP address in the hint file is only used to determine the correct subnet. It will not receive traffic as a result of appearing in the hint file.
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====
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. Generate the `base-64` encoded content by running the following command:
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[source,terminal]
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----
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$ echo 'NODEIP_HINT=192.0.2.1' | base64
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----
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.Example output
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[source,terminal]
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----
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Tk9ERUlQX0hJTlQ9MTkyLjAuMCxxxx==
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----
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. Activate the hint by creating a machine config manifest for both `master` and `worker` roles before deploying the cluster:
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.Master machine config manifest
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[source,yaml]
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----
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apiVersion: machineconfiguration.openshift.io/v1
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kind: MachineConfig
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metadata:
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labels:
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machineconfiguration.openshift.io/role: master
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name: 99-nodeip-hint-master
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spec:
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config:
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ignition:
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version: 3.2.0
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storage:
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files:
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- contents:
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source: data:text/plain;charset=utf-8;base64, <encoded_content> <1>
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mode: 0644
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overwrite: true
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path: /etc/default/nodeip-configuration
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----
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<1> Replace `<encoded_contents>` with the base64-encoded content of the `/etc/default/nodeip-configuration` file, for example, `Tk9ERUlQX0hJTlQ9MTkyLjAuMCxxxx==`.
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.Worker machine config manifest
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[source,yaml]
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----
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apiVersion: machineconfiguration.openshift.io/v1
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kind: MachineConfig
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metadata:
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labels:
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machineconfiguration.openshift.io/role: worker
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name: 99-nodeip-hint-worker
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spec:
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config:
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ignition:
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version: 3.2.0
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storage:
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files:
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- contents:
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source: data:text/plain;charset=utf-8;base64, <encoded_content> <1>
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mode: 0644
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overwrite: true
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path: /etc/default/nodeip-configuration
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----
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<1> Replace `<encoded_contents>` with the base64-encoded content of the `/etc/default/nodeip-configuration` file, for example, `Tk9ERUlQX0hJTlQ9MTkyLjAuMCxxxx==`.
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. Save the manifest to the directory where you store your cluster configuration, for example, `~/clusterconfigs`.
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. Deploy the cluster.

‎support/troubleshooting/troubleshooting-network-issues.adoc

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// How the network interface is selected
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include::modules/nw-how-nw-iface-selected.adoc[leveloffset=+1]
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include::modules/overriding-default-node-ip-selection-logic.adoc[leveloffset=+2]
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// Troubleshooting OVS issues
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include::modules/nw-troubleshoot-ovs.adoc[leveloffset=+1]
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