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Configuration

MicroShift can be configured in the following ways, in order of precedence:

  • Command line arguments
  • Environment variables
  • Configuration file

The MicroShift configuration file must be located at ~/.microshift/config.yaml (user-specific) and /etc/microshift/config.yaml (system-wide), while the former takes precedence if it exists.

The format of the config.yaml configuration file is as follows.

cluster:
  clusterCIDR: ""
  serviceCIDR: ""
  serviceNodePortRange: ""
  domain: ""
  url: ""
nodeIP: ""
nodeName: ""
logVLevel: ""

The configuration settings alongside with the supported command line arguments and environment variables are presented below.

Field Name CLI Argument Environment Variable Description
clusterCIDR --cluster-cidr MICROSHIFT_CLUSTER_CLUSTERCIDR A block of IP addresses from which Pod IP addresses are allocated
serviceCIDR --service-cidr MICROSHIFT_CLUSTER_SERVICECIDR A block of virtual IP addresses for Kubernetes services
serviceNodePortRange --service-node-port-range MICROSHIFT_CLUSTER_SERVICENODEPORTRANGE The port range allowed for Kubernetes services of type NodePort
domain --cluster-domain MICROSHIFT_CLUSTER_DOMAIN Base DNS domain used to construct fully qualified pod and service domain names
url --url MICROSHIFT_CLUSTER_URL URL of the API server for the cluster.
nodeIP --node-ip MICROSHIFT_NODEIP The IP address of the node, defaults to IP of the default route
nodeName --node-name MICROSHIFT_NODENAME The name of the node, defaults to hostname
logVLevel --v MICROSHIFT_LOGVLEVEL Log verbosity (0-5)

Default Settings

In case config.yaml is not provided, the following default settings will be used.

cluster:
  clusterCIDR: 10.42.0.0/16
  serviceCIDR: 10.43.0.0/16
  serviceNodePortRange: 30000-32767
  domain: cluster.local
  url: https://127.0.0.1:6443
nodeIP: ""
nodeName: ""
logVLevel: 0

Auto-applying Manifests

MicroShift leverages kustomize for Kubernetes-native templating and declarative management of resource objects. Upon start-up, it searches /etc/microshift/manifests and /usr/lib/microshift/manifests directories for a kustomization.yaml file. If it finds one, it automatically runs kubectl apply -k command to apply that manifest.

The reason for providing multiple directories is to allow a flexible method to manage MicroShift workloads.

Location Intent
/etc/microshift/manifests Read-write location for configuration management systems or development
/usr/lib/microshift/manifests Read-only location for embedding configuration manifests on ostree based systems

Manifest Example

The example demonstrates automatic deployment of a busybox container using kustomize manifests in the /etc/microshift/manifests directory.

Run the following command to create the manifest files.

MANIFEST_DIR=/etc/microshift/manifests
sudo mkdir -p ${MANIFEST_DIR}

sudo tee ${MANIFEST_DIR}/busybox.yaml &>/dev/null <<EOF
apiVersion: v1
kind: Namespace
metadata:
  name: busybox
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: busybox-deployment
spec:
  selector:
    matchLabels:
      app: busybox
  template:
    metadata:
      labels:
        app: busybox
    spec:
      containers:
      - name: busybox
        image: BUSYBOX_IMAGE
        command:
          - sleep
          - "3600"
EOF

sudo tee ${MANIFEST_DIR}/kustomization.yaml &>/dev/null <<EOF
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

namespace: busybox
resources:
  - busybox.yaml
images:
  - name: BUSYBOX_IMAGE
    newName: registry.k8s.io/busybox
EOF

Restart the MicroShift service to apply the manifests and verify that the busybox pod is running.

sudo systemctl restart microshift
oc get pods -n busybox