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Configuring

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Red Hat build of MicroShift 4.15

Configuring MicroShift

Red Hat OpenShift Documentation Team

Abstract

This document provides instructions for configuring MicroShift.

Chapter 1. How configuration tools work

A YAML file customizes MicroShift instances with your preferences, settings, and parameters.

Note

If you want to make configuration changes or deploy applications through the MicroShift API with tools other than kustomize manifests, you must wait until the Greenboot health checks have finished. This ensures that your changes are not lost if Greenboot rolls your rpm-ostree system back to an earlier state.

1.1. Default settings

If you do not create a config.yaml file, default values are used. The following example shows the default configuration settings.

  • To see the default values, run the following command: 

    $ microshift show-config

    Default values example output in YAML form

    dns:
  baseDomain: microshift.example.com 1
network:
  clusterNetwork:
    - 10.42.0.0/16 2
  serviceNetwork:
    - 10.43.0.0/16 3
  serviceNodePortRange: 30000-32767 4
node:
  hostnameOverride: "" 5
  nodeIP: "" 6
apiServer:
  advertiseAddress: 10.44.0.0/32 7
  subjectAltNames: [] 8
debugging:
  logLevel: "Normal" 9

    1
    Base domain of the cluster. All managed DNS records will be subdomains of this base.
    2
    A block of IP addresses from which Pod IP addresses are allocated.
    3
    A block of virtual IP addresses for Kubernetes services.
    4
    The port range allowed for Kubernetes services of type NodePort.
    5
    The name of the node. The default value is the hostname.
    6
    The IP address of the node. The default value is the IP address of the default route.
    7
    A string that specifies the IP address from which the API server is advertised to members of the cluster. The default value is calculated based on the address of the service network.
    8
    Subject Alternative Names for API server certificates.
    9
    Log verbosity. Valid values for this field are Normal, Debug, Trace, or TraceAll.

1.2. Using a YAML configuration file

On start up, MicroShift searches the system-wide /etc/microshift/ directory for a configuration file named config.yaml. To use custom configurations, you must create the configuration file and specify any settings that are expected to override the defaults before starting MicroShift.

1.2.1. Custom settings

To create custom configurations, you must create a config.yaml file in the /etc/microshift/ directory, and then change any settings that are expected to override the defaults before starting or restarting MicroShift.

Important

Restart MicroShift after changing any configuration settings to have them take effect. The config.yaml file is read only when MicroShift starts.

1.2.2. Configuring the advertise address network flag

The apiserver.advertiseAddress flag specifies the IP address on which to advertise the API server to members of the cluster. This address must be reachable by the cluster. You can set a custom IP address here, but you must also add the IP address to a host interface. Customizing this parameter preempts MicroShift from adding a default IP address to the br-ex network interface.

Important

If you customize the advertiseAddress IP address, make sure it is reachable by the cluster when MicroShift starts by adding the IP address to a host interface.

If unset, the default value is set to the next immediate subnet after the service network. For example, when the service network is 10.43.0.0/16, the advertiseAddress is set to 10.44.0.0/32.

1.2.3. Extending the port range for NodePort services

The serviceNodePortRange setting extends the port range available to NodePort services. This option is useful when specific standard ports under the 30000-32767 range need to be exposed. For example, if your device needs to expose the 1883/tcp MQ Telemetry Transport (MQTT) port on the network because client devices cannot use a different port.

Important

NodePorts can overlap with system ports, causing a malfunction of the system or MicroShift.

Consider the following when configuring the NodePort service ranges:

  • Do not create any NodePort service without an explicit nodePort selection. When an explicit nodePort is not specified, the port is assigned randomly by the kube-apiserver and cannot be predicted.
  • Do not create any NodePort service for any system service port, MicroShift port, or other services you expose on your device HostNetwork.

  • Table one specifies ports to avoid when extending the port range:

    Table 1.1. Ports to avoid.
    PortDescription

    22/tcp

    SSH port

    80/tcp

    OpenShift Router HTTP endpoint

    443/tcp

    OpenShift Router HTTPS endpoint

    1936/tcp

    Metrics service for the openshift-router, not exposed today

    2379/tcp

    etcd port

    2380/tcp

    etcd port

    6443

    kubernetes API

    8445/tcp

    openshift-route-controller-manager

    9537/tcp

    cri-o metrics

    10250/tcp

    kubelet

    10248/tcp

    kubelet healthz port

    10259/tcp

    kube scheduler

1.3. Additional resources

Chapter 2. Cluster access with kubeconfig

Learn about how kubeconfig files are used with MicroShift deployments. CLI tools use kubeconfig files to communicate with the API server of a cluster. These files provide cluster details, IP addresses, and other information needed for authentication.

2.1. Kubeconfig files for configuring cluster access

The two categories of kubeconfig files used in MicroShift are local access and remote access. Every time MicroShift starts, a set of kubeconfig files for local and remote access to the API server are generated. These files are generated in the /var/lib/microshift/resources/kubeadmin/ directory using preexisting configuration information.

Each access type requires a different authentication certificate signed by different Certificate Authorities (CAs). The generation of multiple kubeconfig files accommodates this need.

You can use the appropriate kubeconfig file for the access type needed in each case to provide authentication details. The contents of MicroShift kubeconfig files are determined by either default built-in values or a config.yaml file.

Note

A kubeconfig file must exist for the cluster to be accessible. The values are applied from built-in default values or a config.yaml, if one was created.

Example contents of the kubeconfig files

/var/lib/microshift/resources/kubeadmin/
├── kubeconfig 1
├── alt-name-1 2
│   └── kubeconfig
├── 1.2.3.4 3
│   └── kubeconfig
└── microshift-rhel9 4
    └── kubeconfig

1
Local host name. The main IP address of the host is always the default.
2
Subject Alternative Names for API server certificates.
3
DNS name.
4
MicroShift host name.

2.2. Local access kubeconfig file

The local access kubeconfig file is written to /var/lib/microshift/resources/kubeadmin/kubeconfig. This kubeconfig file provides access to the API server using localhost. Choose this file when you are connecting the cluster locally.

Example contents of kubeconfig for local access

clusters:
- cluster:
    certificate-authority-data: <base64 CA>
    server: https://localhost:6443

The localhost kubeconfig file can only be used from a client connecting to the API server from the same host. The certificates in the file do not work for remote connections.

2.2.1. Accessing the MicroShift cluster locally

Use the following procedure to access the MicroShift cluster locally by using a kubeconfig file.

Prerequisites

  • You have installed the oc binary.

Procedure

  1. Optional: to create a ~/.kube/ folder if your RHEL machine does not have one, run the following command: 

    $ mkdir -p ~/.kube/

  2. Copy the generated local access kubeconfig file to the ~/.kube/ directory by running the following command: 

    $ sudo cat /var/lib/microshift/resources/kubeadmin/kubeconfig > ~/.kube/config

  3. Update the permissions on your ~/.kube/config file by running the following command: 

    $ chmod go-r ~/.kube/config

Verification

  • Verify that MicroShift is running by entering the following command: 

    $ oc get all -A

2.3. Remote access kubeconfig files

When a MicroShift cluster connects to the API server from an external source, a certificate with all of the alternative names in the SAN field is used for validation. MicroShift generates a default kubeconfig for external access using the hostname value. The defaults are set in the <node.hostnameOverride>, <node.nodeIP> and api.<dns.baseDomain> parameter values of the default kubeconfig file.

The /var/lib/microshift/resources/kubeadmin/<hostname>/kubeconfig file uses the hostname of the machine, or node.hostnameOverride if that option is set, to reach the API server. The CA of the kubeconfig file is able to validate certificates when accessed externally.

Example contents of a default kubeconfig file for remote access

clusters:
- cluster:
    certificate-authority-data: <base64 CA>
    server: https://microshift-rhel9:6443

2.3.1. Remote access customization

Multiple remote access kubeconfig file values can be generated for accessing the cluster with different IP addresses or host names. An additional kubeconfig file generates for each entry in the apiServer.subjectAltNames parameter. You can copy remote access kubeconfig files from the host during times of IP connectivity and then use them to access the API server from other workstations.

2.4. Generating additional kubeconfig files for remote access

You can generate additional kubeconfig files to use if you need more host names or IP addresses than the default remote access file provides.

Important

You must restart MicroShift for configuration changes to be implemented.

Prerequisites

  • You have created a config.yaml for MicroShift.

Procedure

  1. Optional: You can show the contents of the config.yaml. Run the following command: 

    $ cat /etc/microshift/config.yaml

  2. Optional: You can show the contents of the remote-access kubeconfig file. Run the following command: 

    $ cat /var/lib/microshift/resources/kubeadmin/<hostname>/kubeconfig
    Important

    Additional remote access kubeconfig files must include one of the server names listed in the MicroShift config.yaml file. Additional kubeconfig files must also use the same CA for validation.

  3. To generate additional kubeconfig files for additional DNS names SANs or external IP addresses, add the entries you need to the apiServer.subjectAltNames field. In the following example, the DNS name used is alt-name-1 and the IP address is 1.2.3.4.

    Example config.yaml with additional authentication values

    dns:
  baseDomain: example.com
node:
  hostnameOverride: "microshift-rhel9" 1
  nodeIP: 10.0.0.1
apiServer:
  subjectAltNames:
  - alt-name-1 2
  - 1.2.3.4 3

    1
    Hostname
    2
    DNS name
    3
    IP address or range

  4. Restart MicroShift to apply configuration changes and auto-generate the kubeconfig files you need by running the following command: 

    $ sudo systemctl restart microshift

  5. To check the contents of additional remote-access kubeconfig files, insert the name or IP address as listed in the config.yaml into the cat command. For example, alt-name-1 is used in the following example command: 

    $ cat /var/lib/microshift/resources/kubeadmin/alt-name-1/kubeconfig

  6. Choose the kubeconfig file to use that contains the SAN or IP address you want to use to connect your cluster. In this example, the kubeconfig containing`alt-name-1` in the cluster.server field is the correct file.

    Example contents of an additional kubeconfig file

    clusters:
- cluster:
    certificate-authority-data: <base64 CA>
    server: https://alt-name-1:6443 1

    1
    The /var/lib/microshift/resources/kubeadmin/alt-name-1/kubeconfig file values are from the apiServer.subjectAltNames configuration values.
Note

All of these parameters are included as common names (CN) and subject alternative names (SAN) in the external serving certificates for the API server.

2.4.1. Opening the firewall for remote access to the MicroShift cluster

Use the following procedure to open the firewall so that a remote user can access the MicroShift cluster. This procedure must be completed before a workstation user can access the cluster remotely.

For this procedure, user@microshift is the user on the MicroShift host machine and is responsible for setting up that machine so that it can be accessed by a remote user on a separate workstation.

Prerequisites

  • You have installed the oc binary.
  • Your account has cluster administration privileges.

Procedure

  • As user@microshift on the MicroShift host, open the firewall port for the Kubernetes API server (6443/tcp) by running the following command: 

    [user@microshift]$ sudo firewall-cmd --permanent --zone=public --add-port=6443/tcp && sudo firewall-cmd --reload

Verification

  • As user@microshift, verify that MicroShift is running by entering the following command: 

    [user@microshift]$ oc get all -A

2.4.2. Accessing the MicroShift cluster remotely

Use the following procedure to access the MicroShift cluster from a remote workstation by using a kubeconfig file.

The user@workstation login is used to access the host machine remotely. The <user> value in the procedure is the name of the user that user@workstation logs in with to the MicroShift host.

Prerequisites

  • You have installed the oc binary.
  • The user@microshift has opened the firewall from the local host.

Procedure

  1. As user@workstation, create a ~/.kube/ folder if your RHEL machine does not have one by running the following command: 

    [user@workstation]$ mkdir -p ~/.kube/

  2. As user@workstation, set a variable for the hostname of your MicroShift host by running the following command: 

    [user@workstation]$ MICROSHIFT_MACHINE=<name or IP address of MicroShift machine>

  3. As user@workstation, copy the generated kubeconfig file that contains the host name or IP address you want to connect with from the RHEL machine running MicroShift to your local machine by running the following command: 

    [user@workstation]$ ssh <user>@$MICROSHIFT_MACHINE "sudo cat /var/lib/microshift/resources/kubeadmin/$MICROSHIFT_MACHINE/kubeconfig" > ~/.kube/config
Note

To generate kubeconfig files for this step, see the "Generating additional kubeconfig files for remote access" link in the additional resources section.

  1. As user@workstation, update the permissions on your ~/.kube/config file by running the following command: 

    $ chmod go-r ~/.kube/config

Verification

  • As user@workstation, verify that MicroShift is running by entering the following command: 

    [user@workstation]$ oc get all -A

Chapter 3. Checking Greenboot scripts status

To deploy applications or make other changes through the MicroShift API with tools other than kustomize manifests, you must wait until the Greenboot health checks have finished. This ensures that your changes are not lost if Greenboot rolls your rpm-ostree system back to an earlier state.

The greenboot-healthcheck service runs one time and then exits. After Greenboot has exited and the system is in a healthy state, you can proceed with configuration changes and deployments.

3.1. Checking the status of Greenboot health checks

Check the status of Greenboot health checks before making changes to the system or during troubleshooting. You can use any of the following commands to help you ensure that Greenboot scripts have finished running.

Procedure

  • To see a report of health check status, use the following command: 

    $ systemctl show --property=SubState --value greenboot-healthcheck.service
    • An output of start means that Greenboot checks are still running.
    • An output of exited means that checks have passed and Greenboot has exited. Greenboot runs the scripts in the green.d directory when the system is a healthy state.
    • An output of failed means that checks have not passed. Greenboot runs the scripts in red.d directory when the system is in this state and might restart the system.

  • To see a report showing the numerical exit code of the service where 0 means success and non-zero values mean a failure occurred, use the following command: 

    $ systemctl show --property=ExecMainStatus --value greenboot-healthcheck.service

  • To see a report showing a message about boot status, such as Boot Status is GREEN - Health Check SUCCESS, use the following command: 

    $ cat /run/motd.d/boot-status

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