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Please be advised, that the hypervisor on which your VM is situated has failed, and therefore your VM has undergone a High Availability "Failover" event to another host.
Your VM is already online, and while in some cases this Failover procedure is possible to execute with a live, online migration - if the host which actually is running your VM fails, then your VM will crash, and there will be an interruption of service.
Your VM during this time has rebooted on another node within the cluster, however nginx service failed to start in the server.
I have logged into the server and started nginx service.
Your websites should be functioning normal now.
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So now you know.
