I installed the Ubuntu 16.04 desktop version on a machine, and used it for my research via ssh.
Sometimes the machine restarts randomly, but I cannot find why restart.
$ last reboot
reboot system boot 4.4.0-62-generic Wed Feb 8 01:34 still running
reboot system boot 4.4.0-62-generic Mon Feb 6 09:16 still running
reboot system boot 4.4.0-62-generic Sun Feb 5 16:43 still running
reboot system boot 4.4.0-62-generic Sun Feb 5 00:37 still running
I checked /var/log/syslog …
Feb 7 23:31:37 niaserver7 systemd[1]: Started Session 77 of user swmo.
Feb 8 00:17:01 niaserver7 CRON[17883]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Feb 8 00:34:07 niaserver7 systemd[1]: Started CUPS Scheduler.
Feb 8 01:17:01 niaserver7 CRON[17893]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Feb 8 01:35:01 niaserver7 rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="1315" x-info="http://www.rsyslog.com"] start
Feb 8 01:35:01 niaserver7 systemd-modules-load[538]: Inserted module 'lp'
Feb 8 01:35:01 niaserver7 systemd-modules-load[538]: Inserted module 'ppdev'
Feb 8 01:35:01 niaserver7 kernel: [ 0.000000] Initializing cgroup subsys cpuset
Feb 8 01:35:01 niaserver7 rsyslogd-2222: command 'KLogPermitNonKernelFacility' is currently not permitted - did you already set it via a RainerScript command (v6+ config)? [v8.16.0 try http://www.rsyslog.com/e/2222 ]
Feb 8 01:35:01 niaserver7 systemd-modules-load[538]: Inserted module 'parport_pc'
Feb 8 01:35:01 niaserver7 rsyslogd: rsyslogd's groupid changed to 108
Feb 8 01:35:01 niaserver7 rsyslogd: rsyslogd's userid changed to 104
Feb 8 01:35:01 niaserver7 loadkeys[541]: Loading /etc/console-setup/cached.kmap.gz
Feb 8 01:35:01 niaserver7 kernel: [ 0.000000] Initializing cgroup subsys cpu
Feb 8 01:35:01 niaserver7 systemd[1]: Started udev Kernel Device Manager.
How can I fix it?
Best Answer
This sounds like a combination of issues.
In the case of an individual system rebooting randomly I would want to replace the power supply in the chassis with one that provided more than adequate amperage for the connected components (as you want it to keep running during periods of peak power draw).
In the case where the entire rack reboot simultaneously I would look at an inadequate UPS as the root cause or possibly an overheat condition due to AC failure in the server location.
An intermittent short in the feed cord to the multi-tap could also result in the multiple reboot result that you describe.