Reboot no explanation

[Ricardo_Gros]

Hi, 

I recently have the issue that a customer from us has an appliance that reboots without explanation. 

We have noticed following behaviour:

[Expert@clusterFW2:0]# last -x |head |tac
reboot   system boot  2.6.18-92cpx86_6 Fri Apr 12 02:44          (00:03)
runlevel (to lvl 3)   2.6.18-92cpx86_6 Fri Apr 12 02:44 - 02:48  (00:03)
runlevel (to lvl 6)   2.6.18-92cpx86_6 Fri Apr 12 02:48 - 02:48  (00:00)
shutdown system down  2.6.18-92cpx86_6 Fri Apr 12 02:48 - 15:59  (13:10)
reboot   system boot  2.6.18-92cpx86_6 Fri Apr 12 02:51          (13:07)
runlevel (to lvl 3)   2.6.18-92cpx86_6 Fri Apr 12 02:51 - 15:59  (13:07)
sseidewi pts/2        dez7acomdv010.in Fri Apr 12 06:05 - 06:25  (00:20)
admin    pts/2        dez7acomdv002.in Fri Apr 12 09:29 - 09:41  (00:12)
admin    pts/2        dez7acomdv001.in Fri Apr 12 14:23 - 14:57  (00:33)
admin    pts/2        dez7acomdv001.in Fri Apr 12 15:46   still logged in

This looks like a normal reboot, however runlevel 6 is making me wonder, a normal reboot should not show runlevel6, 

On messages file I can see the message Restart, but no errors previous to this, system reboots normally. 

There are no crash dumps available or errors. 

Can I somehow confirm that the system was not rebooted by simply pressing the power or imputing a command?