This article provides steps to determine why a host spontaneously rebooted.
Symptoms:
VMware vSphere ESXi 6.x
VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x
In the vmkernel logs, there may be entries indicating that the power button was pressed, triggering the restart. This suggests that a user-initiated action led to a graceful shutdown.
<YYYY-MM-DD>T<HH:MM:SS>.005Z cpu0:2101545)VMKAcpi: 256: Power button pressed; requesting graceful shutdown and poweroff
From hostd logs, parallely we can see that the shutdown was a forceful operation.
<YYYY-MM-DD>T<HH:MM:SS>.005Z info hostd[2100455] [Originator@6876 sub=Hostsvc.HaHost] ACPI power event from the vmkernel
<YYYY-MM-DD>T<HH:MM:SS>.006Z info hostd[2100455] [Originator@6876 sub=Hostsvc.HaHost] Shutdown, force = true
<YYYY-MM-DD>T<HH:MM:SS>.006Z warning hostd[2100455] [Originator@6876 sub=Hostsvc.HaHost] Failed to find activation record, event user unknown.
<YYYY-MM-DD>T<HH:MM:SS>.006Z info hostd[2100455] [Originator@6876 sub=Vimsvc.ha-eventmgr] Event 679147 : Shut down of <ESXhostname> in ha-datacenter: Unknown
<YYYY-MM-DD>T<HH:MM:SS>.007Z info hostd[2100455] [Originator@6876 sub=SysCommandPosix] ForkExec(/usr/lib/vmware/vob/bin/addvob) 214058855
<YYYY-MM-DD>T<HH:MM:SS>.009Z info hostd[2516901] [Originator@6876 sub=Vimsvc.TaskManager opID=2c8f4244 user=vpxuser] Task Created : haTask--vim.event.EventHistoryCollector.readNext-13046911
<YYYY-MM-DD>T<HH:MM:SS>.009Z info hostd[161861312] [Originator@6876 sub=Vimsvc.TaskManager opID=2c8f4244 user=vpxuser] Task Completed : haTask--vim.event.EventHistoryCollector.readNext-13046911 Status success
<YYYY-MM-DD>T<HH:MM:SS>.018Z info hostd[2516902] [Originator@6876 sub=Hostsvc.VmkVprobSource] VmkVprobSource::Post event: (vim.event.EventEx) {
--> key = 65,
--> chainId = -1897761432,
--> createdTime = "1970-01-01T00:00:00Z",
--> userName = "",
--> host = (vim.event.HostEventArgument) {
--> name = "<ESX host name>",
--> host = 'vim.HostSystem:ha-host'
--> },
--> eventTypeId = "esx.audit.hostd.host.poweroff.reason",
--> arguments = (vmodl.KeyAnyValue) [
--> (vmodl.KeyAnyValue) {
--> key = "1",
--> value = " Last reboot reason is unknown. Please check ESXi and the BMC logs for further details. "
--> },
--> (vmodl.KeyAnyValue) {
--> key = "2",
--> value = "Unknown"
--> }
--> ],
--> objectId = "ha-host",
--> objectType = "vim.HostSystem",
--> }
<YYYY-MM-DD>T<HH:MM:SS>.019Z info hostd[2516902] [Originator@6876 sub=Vimsvc.ha-eventmgr] Event 679148 : The host is being powered off through hostd. Reason for powering off: Last reboot reason is unknown. Please check ESXi and the BMC logs for further details. , User: Unknown. Please consult vSphere Documentation Center or follow the Ask VMware link for more information.
<YYYY-MM-DD>T<HH:MM:SS>.020Z info hostd[2100456] [Originator@6876 sub=Vimsvc.TaskManager opID=2c8f4245 user=vpxuser] Task Created : haTask--vim.event.EventHistoryCollector.readNext-13046912
<YYYY-MM-DD>T<HH:MM:SS>.021Z info hostd[2516901] [Originator@6876 sub=Vimsvc.TaskManager opID=2c8f4245 user=vpxuser] Task Completed : haTask--vim.event.EventHistoryCollector.readNext-13046912 Status success
<YYYY-MM-DD>T<HH:MM:SS>.059Z info hostd[2100455] [Originator@6876 sub=SysCommandPosix] ForkExec(/sbin/poweroff) 214058856
vmkernel and hostd logs indicate that a user-initiated action was involved in rebooting the ESXi hosts. Verify if the reboot was intentional, possibly following an update or upgrade.