Ubuntu Server 12.04 spontaneous random reboot? nothing in log!

[Muhammad Umair]

Well I haven't seen the reboots occur myself, but its only from the log that I am reaching the conclusion that the reboot was a spontaneous one. Have you guys given the log snippet I linked a look? The problem actually is not specific to a single machine, its occuring on multiple machines in our lab randomly, all with same specs and all running Ubuntu 12.04.3 Server LTS, with 3.5 kernel.

For the time being what I've done is that I've configured lm-sensors on all the servers, and its daemon to dump temperature readings every 30 seconds, so that the next time any server reboots, I'll atleast have a temperature log to look at. I'm not sure though that how reliable lm-sensors readings are.

Also, I ran 32 instances of cpuburn (as each machine has 2 CPUs i.e. 32 cores), on one of the machines that has experienced reboots for like 90 minutes, but during those 90 minutes, I did not see the temperatures reach critical values.

I find it unlikely that multiple machines might have faulty memory/HDD, since all the servers are brand new, but well who knows. Will the memtest only root out faulty memory causes, or will it also give something, if theres some other hardware fault?

Also another thing I'd like to mention is that these are not vanilla installations of Ubuntu Server. I think that Ubuntu Server 12.04 comes with kernel 3.8, whereas in this case, everything else is the same but we downgraded the kernel to 3.5 in all our servers. Can that be somehow related? However I think if the cause was kernel related, and a kernel panic or what not had occured, the logs should've shown atleast some indication of that.

Regards

> From: clanlaw at gmail.com
> Date: Mon, 17 Feb 2014 20:54:04 +0000
> Subject: Re: Ubuntu Server 12.04 spontaneous random reboot? nothing in log!
> To: ubuntu-users at lists.ubuntu.com
> 
> On 17 February 2014 18:18, Keith <keith.w_65 at centurylink.net> wrote:
> > [posted to "Ubuntu user technical support, not for general discussions"
> > <ubuntu-users.lists.ubuntu.com> & emailed]
> > On Mon, 17 Feb 2014 22:33:46 +0500, Muhammad Umair
> > <muhammaduma1r at hotmail.com> wrote:
> >
> >
> >> We have a few Ubuntu servers running in our lab, on some of which we have
> >> experienced random reboots. A reboot may happen with a gap of a few days,
> >> or may not occur at all. On one machine for example the exact reboot time
> >> was "Wed Feb 12 12:56 EST".
> >
> > You need to do a memtest to see if you have faulty memory. When a computer
> > spontaneity reboots that indicates a hardware failure. So if it's not a
> > memory defect then you will have to take it to a computer tech.
> 
> Other common causes are power supply or temperature problems.  If it
> reboots when running memtest (which you may have to leave running for
> days) then it is likely a hardware problem.
> 
> Colin
> 
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