MicroShift on startup creates .nodename file which holds the last hostname. If MicroShift's startup is interrupted (e.g. by reboot issued by microshift-tuned daemon), the file can be empty.
If the file is empty, it'll be used on next MicroShift startup causing it to think that node name is empty string.

That empty string will be stored in kubelet's certificate (CN: system:node:) which will cause API Server to reject kubelet's calls because user "system:node:" doesn't have an access to Node resource.

Once in 7 months since the low latency test was added.    

    1. Setup MicroShift with low latency - microshift-tuned daemon should restart the host on first boot to activate new tuned profile.
    2.
    3.
    

    Kubelet cannot register node because of the malformed user.

    MicroShift starts successfully (aka .nodename is created atomically)