[CentOS] CentOS 6 spontaneous reboots

Mon May 30 00:10:23 UTC 2016
Bill Gee <bgee at campercaver.net>

Hello everyone -

My CentOS 6.8 server has been rebooting itself every 2 to 4 hours for the last 
several days.  I do not know where to look for logs that might give a clue what 
the problem is.  There are no unusual entries in /var/log/messages.  I looked 
over other log files in /var/log and found nothing suggestive.  Where else can I 

By luck I saw the beginning of a reboot on the server console.  Normally I have 
other systems up on the KVM switch.  It appears to have dumped core.  I don't 
know where to look for the core dump files.  They are not in /root.

The problem started while the server was still 6.7.  It had almost 290 days of 
uptime when the problem started.  I have tried the following, none of which 
made any difference.  

I ran the upgrade to 6.8.

I tried stopping non-essential services two at a time.

I ran MemTest 86+.  No memory errors were found.

I turned off swap.

I unplugged the USB hard drive that I use to hold daily and weekly backups.  It 
was being recognized as /dev/sda for some reason.

Lm_sensors shows the processor running between 45 and 50C.  Hddtemp 
shows the hard drives running between 35 and 40C.  LM_Sensors does not 
produce valid data on fan speed, but a visual check shows all fans running 
normally and no build-up of dust.

The system is behind a big UPS that runs several other systems.  The UPS log 
file does not record any power failures and none of the other systems are 
rebooting at random.

What else can I look at?

Thanks - Bill Gee