When starting MicroShift in a VM using OpenShift Virtualization, with ovn in the picture, it uses part of the MTU for the encapsulation, so VMs have a smaller MTU and it's not detected by MicroShift. Therefore, specifying the MTU value manually in /etc/microshift/ovn.yaml is required.

4.15 & 4.16    

Always, when starting MicroShift on a VM in OpenShift Virtualization

    1. Create a RHEL VM in OpenShift Virtualization
    2. Try to start MicroShift on it 
    3. Check pods in CrashLoopBack and Pending state.

The openshift-ovn-kubernetes pod falls in CrashLoopBackOff, the ingress, kube-system, storage and serivce-ca pods shows Pending.  

MicroShift auto detects the MTU value needed in the network infrastructure and this value is updated during the start up so all the pods are Running. 

● microshift.service - MicroShift
     Loaded: loaded (/usr/lib/systemd/system/microshift.service; enabled; prese>
     Active: active (running) since Thu 2024-04-11 04:29:04 EDT; 3min 52s ago
   Main PID: 18912 (microshift)
      Tasks: 12 (limit: 48492)
     Memory: 310.2M
        CPU: 31.698s
     CGroup: /system.slice/microshift.service
             └─18912 microshift run

Apr 11 04:35:30 edge microshift[18912]: kubelet E0411 04:35:30.603473   18912 kubelet.go:2869] "Container runtime network not ready" networkReady="NetworkReady=false reason:NetworkPluginNotReady message:Network plugin returns error: No CNI configuration file in /etc/cni/net.d/. Has your network provider started?"
Apr 11 04:35:31 edge microshift[18912]: kubelet E0411 04:35:31.620672   18912 pod_workers.go:1300] "Error syncing pod, skipping" err="failed to \"StartContainer\" for \"ovnkube-master\" with CrashLoopBackOff: \"back-off 5m0s restarting failed container=ovnkube-master pod=ovnkube-master-ql5k7_openshift-ovn-kubernetes (97a1a2cf-e653-4cf8-bafb-b0188488ac3d)\"" pod="openshift-ovn-kubernetes/ovnkube-master-ql5k7" podUID="97a1a2cf-e653-4cf8-bafb-b0188488ac3d"
Apr 11 04:35:33 edge microshift[18912]: kube-controller-manager I0411 04:35:33.812683   18912 node_lifecycle_controller.go:785] "Node is NotReady. Adding it to the Taint queue" node="edge" timeStamp="2024-04-11 04:35:33.812595792 -0400 EDT m=+457.202568567"

----------------------------------------------------------------------
[cloud-user@edge ~]$ oc get pods -A
NAMESPACE                  NAME                                       READY   STATUS             RESTARTS      AGE
kube-system                csi-snapshot-controller-6686957bb9-vz8tv   0/1     Pending            0             17m
kube-system                csi-snapshot-webhook-64455cd68b-47vjj      0/1     Pending            0             17m
openshift-dns              node-resolver-247rt                        1/1     Running            0             17m
openshift-ingress          router-default-65757846cd-4chhm            0/1     Pending            0             17m
openshift-ovn-kubernetes   ovnkube-master-ql5k7                       3/4     CrashLoopBackOff   8 (23s ago)   17m
openshift-ovn-kubernetes   ovnkube-node-6w4p8                         1/1     Running            1 (16m ago)   17m
openshift-service-ca       service-ca-6dbd7c5ddc-2pqpj                0/1     Pending            0             17m
openshift-storage          topolvm-controller-597486954b-9ffz9        0/5     Pending            0             17m