Ubuntu Server 12.04 spontaneous random reboot? nothing in log!

[Muhammad Umair]

Hi guys,

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".

Version: Ubuntu 12.04.3 LTS (precise)

uname -a: Linux sysname 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan  
25 17:13:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

I have gone through all the logs I could possibly think of, around the  
time of reboot (syslog, kernlog, authlog etc), but the reboot seems to be  
occuring out of the blue. No error/warning/panic messages whatsoever in  
the log, seems like the system just rebooted during a proper normal  
working state so to speak. Sample log at the time of reboot (Feb 12 12:56)  
is as follows:

Feb 12 12:56:55 sysname vmnet-dhcpd: DHCPREQUEST for 192.168.191.130 from  
3e:f0:47:96:a9:6a via vmnet8
Feb 12 12:56:57 sysname vmnet-dhcpd: DHCPACK on 192.168.191.130 to  
3e:f0:47:96:a9:6a via vmnet8
Feb 12 12:56:57 sysname vmnet-dhcpd: DHCPREQUEST for 192.168.191.141 from  
22:9c:0f:78:c1:83 via vmnet8
Feb 12 12:57:08 sysname snmpd[9816]: Connection from UDP:  
[10.14.44.27]:59568->[10.14.47.114]
Feb 12 12:57:08 sysname vmnet-dhcpd: DHCPACK on 192.168.191.141 to  
22:9c:0f:78:c1:83 via vmnet8
Feb 12 12:57:08 sysname vmnet-dhcpd: DHCPREQUEST for 192.168.191.141 from  
22:9c:0f:78:c1:83 via vmnet8
Feb 12 12:57:08 sysname snmpd[9816]: Connection from UDP:  
[10.14.44.27]:59568->[10.14.47.114]
Feb 12 12:57:14 snmpd[9816]: last message repeated 2 times
Feb 12 12:57:14 sysname vmnet-dhcpd: DHCPACK on 192.168.191.141 to  
22:9c:0f:78:c1:83 via vmnet8
Feb 12 12:57:14 sysname vmnet-dhcpd: DHCPREQUEST for 192.168.191.141 from  
22:9c:0f:78:c1:83 via vmnet8
Feb 12 12:57:18 sysname vmnet-dhcpd: DHCPACK on 192.168.191.141 to  
22:9c:0f:78:c1:83 via vmnet8
Feb 12 12:57:38 sysname snmpd[9816]: Connection from UDP:  
[10.14.44.27]:58736->[10.14.47.114]
Feb 12 12:58:45 sysname kerFeb 12 12:56:12 sysname kernel: imklog 5.8.6,  
log source = /proc/kmsg started.
Feb 12 12:56:12 sysname rsyslogd: [origin software="rsyslogd"  
swVersion="5.8.6" x-pid="1269" x-info="http://www.rsyslog.com"] start
Feb 12 12:56:12 sysname rsyslogd: rsyslogd's groupid changed to 103
Feb 12 12:56:12 sysname rsyslogd: rsyslogd's userid changed to 101
Feb 12 12:56:12 sysname rsyslogd-2039: Could not open output pipe  
'/dev/xconsole' [try http://www.rsyslog.com/e/2039 ]
Feb 12 12:56:12 sysname kernel: [ 0.000000] Initializing cgroup subsys  
cpuset
Feb 12 12:56:12 sysname kernel: [ 0.000000] Initializing cgroup subsys cpu
Feb 12 12:56:12 sysname kernel: [ 0.000000] Linux version 3.5.0-23-generic  
(buildd at komainu) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) )  
#35~precise1-Ubuntu SMP Fri Jan 25 17:13:26 UTC 2013 (Ubuntu  
3.5.0-23.35~precise1-generic 3.5.7.2)

All I am able to observe from the log is a little time discrepancy where  
the log time stamps go from 12:56 to 12:57 and then back to 12:56 and on.  
Other than that I can't seem to identify any sort of a message hinting at  
the cause of reboot.

Linked below is the syslog file with a few more minutes worth of context:

dropbox.com/s/g3cx4gwvwuhndpd/syslog.2

What exactly am I missing here? kindly help me out in identifying the root  
cause of these reboots!

Note: These Ubuntu servers for the most part are running multiple VMWare  
Workstation VMs


Regards

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