I have a CentOS 7 machine which started booting periodically on its own.
Below are the interesting lines (for the last reboot) from the `/var/log/messages`.[1]

*Can anyone suggest which lines are the most promising in deciphering why the machine is booting?*

Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [PG00] (on)
Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [PG01] (on)
Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [PG02] (on)
Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [FN00] (off)
Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [FN01] (off)
Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [FN02] (off)
Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [FN03] (off)
Nov 15 11:17:09 gui-automation-squish kernel: ACPI: Power Resource [FN04] (off)
Nov 15 11:17:10 gui-automation-squish systemd-fsck[856]: /dev/sda3: recovering journal
Nov 15 11:17:11 gui-automation-squish systemd-fsck[1711]: /dev/sda2: recovering journal
Nov 15 11:17:11 gui-automation-squish systemd-fsck[1713]: /dev/sda4: recovering journal
Nov 15 11:17:11 gui-automation-squish systemd-fsck[1712]: /dev/md0: recovering journal
Nov 15 11:17:12 gui-automation-squish systemd[1]: Started Update UTMP about System Boot/Shutdown.
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: imudp: module loaded, but no listeners defined - no input will be gathered [v8.1910.0 try https://www.rsyslog.com/e/2212 ]
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: imtcp: module loaded, but no listeners defined - no input will be gathered [v8.1910.0 try https://www.rsyslog.com/e/2212 ]
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: imfile: no files configured to be monitored - no input will be gathered [v8.1910.0 try https://www.rsyslog.com/e/2212 ]
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: imptcp: no ptcp server defined, module can not run. [v8.1910.0 try https://www.rsyslog.com/e/2172 ]
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: activation of module imptcp failed [v8.1910.0 try https://www.rsyslog.com/e/-3 ]
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: [origin software="rsyslogd" swVersion="8.1910.0" x-pid="1839" x-info="https://www.rsyslog.com"] start
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: imjournal: fscanf on state file `/var/lib/rsyslog/imjournal.state' failed [v8.1910.0 try https://www.rsyslog.com/e/2027 ]
Nov 15 11:17:12 gui-automation-squish rsyslogd[1839]: imjournal: ignoring invalid state file /var/lib/rsyslog/imjournal.state [v8.1910.0]
Nov 15 11:17:16 gui-automation-squish systemd[1]: Started Logout off all iSCSI sessions on shutdown.
Nov 15 11:17:17 gui-automation-squish systemd[1]: Started Daemon for power management.
Nov 15 11:17:19 gui-automation-squish journal[3129]: power: force power support: no
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [PG00] (on)
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [PG01] (on)
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [PG02] (on)
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [FN00] (off)
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [FN01] (off)
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [FN02] (off)
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [FN03] (off)
Nov 15 11:27:19 gui-automation-squish kernel: ACPI: Power Resource [FN04] (off)
Nov 15 11:27:20 gui-automation-squish systemd-fsck[855]: /dev/sda3: recovering journal
Nov 15 11:27:21 gui-automation-squish systemd-fsck[1709]: /dev/sda2: recovering journal
Nov 15 11:27:21 gui-automation-squish systemd-fsck[1708]: /dev/sda4: recovering journal
Nov 15 11:27:21 gui-automation-squish systemd-fsck[1710]: /dev/md0: recovering journal
Nov 15 11:27:22 gui-automation-squish systemd[1]: Started Update UTMP about System Boot/Shutdown.
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: imudp: module loaded, but no listeners defined - no input will be gathered [v8.1910.0 try https://www.rsyslog.com/e/2212 ]
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: imtcp: module loaded, but no listeners defined - no input will be gathered [v8.1910.0 try https://www.rsyslog.com/e/2212 ]
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: imfile: no files configured to be monitored - no input will be gathered [v8.1910.0 try https://www.rsyslog.com/e/2212 ]
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: imptcp: no ptcp server defined, module can not run. [v8.1910.0 try https://www.rsyslog.com/e/2172 ]
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: activation of module imptcp failed [v8.1910.0 try https://www.rsyslog.com/e/-3 ]
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: [origin software="rsyslogd" swVersion="8.1910.0" x-pid="1883" x-info="https://www.rsyslog.com"] start
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: imjournal: fscanf on state file `/var/lib/rsyslog/imjournal.state' failed [v8.1910.0 try https://www.rsyslog.com/e/2027 ]
Nov 15 11:27:22 gui-automation-squish rsyslogd[1883]: imjournal: ignoring invalid state file /var/lib/rsyslog/imjournal.state [v8.1910.0]
Nov 15 11:27:26 gui-automation-squish systemd[1]: Started Logout off all iSCSI sessions on shutdown.
Nov 15 11:27:27 gui-automation-squish systemd[1]: Started Daemon for power management.
Nov 15 11:27:29 gui-automation-squish journal[3137]: power: force power support: no
Nov 15 11:37:24 gui-automation-squish rsyslogd[1883]: imjournal: 1498 messages lost due to rate-limiting (20000 allowed within 600 seconds)



[qa@gui-automation-squish ~]$ last -x|egrep 'runlevel|reboot'
runlevel (to lvl 5) 3.10.0-1062.4.1. Fri Nov 15 11:27 - 12:39 (01:11)
reboot system boot 3.10.0-1062.4.1. Fri Nov 15 11:27 - 12:39 (01:11)
runlevel (to lvl 5) 3.10.0-1062.4.1. Fri Nov 15 11:17 - 11:27 (00:10)
reboot system boot 3.10.0-1062.4.1. Fri Nov 15 11:17 - 12:39 (01:22)
runlevel (to lvl 5) 3.10.0-1062.4.1. Fri Nov 15 10:32 - 11:17 (00:45)
reboot system boot 3.10.0-1062.4.1. Fri Nov 15 10:31 - 12:39 (02:07)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 17:23 - 10:32 (9+17:08)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 17:23 - 12:39 (9+19:15)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 17:18 - 17:23 (00:05)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 17:18 - 12:39 (9+19:20)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 17:15 - 17:17 (00:01)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 17:15 - 17:17 (00:02)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 17:14 - 17:14 (00:00)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 17:14 - 17:14 (00:00)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 17:13 - 17:14 (00:00)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 17:12 - 17:14 (00:01)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 16:53 - 16:55 (00:02)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 16:53 - 16:55 (00:02)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 16:50 - 16:52 (00:02)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 16:50 - 16:52 (00:02)
runlevel (to lvl 5) 3.10.0-1062.4.1. Tue Nov 5 15:51 - 16:36 (00:45)
reboot system boot 3.10.0-1062.4.1. Tue Nov 5 15:51 - 16:36 (00:45)
runlevel (to lvl 5) 3.10.0-1062.4.1. Mon Oct 28 12:18 - 15:51 (8+04:32)
reboot system boot 3.10.0-1062.4.1. Mon Oct 28 12:18 - 16:36 (8+05:18)
runlevel (to lvl 5) 3.10.0-1062.4.1. Mon Oct 28 12:15 - 12:17 (00:01)
reboot system boot 3.10.0-1062.4.1. Mon Oct 28 12:15 - 12:17 (00:01)
runlevel (to lvl 5) 3.10.0-1062.4.1. Mon Oct 28 12:07 - 12:15 (00:08)
reboot system boot 3.10.0-1062.4.1. Mon Oct 28 12:07 - 12:15 (00:08)
runlevel (to lvl 5) 3.10.0-1062.4.1. Mon Oct 28 11:31 - 12:06 (00:35)
reboot system boot 3.10.0-1062.4.1. Mon Oct 28 11:30 - 12:06 (00:35)
runlevel (to lvl 5) 3.10.0-957.el7.x Mon Oct 28 11:02 - 11:31 (00:29)
reboot system boot 3.10.0-957.el7.x Mon Oct 28 11:01 - 12:06 (01:05)




---
[1] Created with

sudo grep -iv ': starting\|kernel: .*: Power Button\|watching system buttons\|Stopped Cleaning Up\|Started Crash recovery kernel' /var/log/messages | grep -iw 'recover[a-z]*\|power[a-z]*\|shut[a-z ]*down\|rsyslogd\|ups'

What does "last |more" give as the reason?

21498 messages in ten minutes? Sounds scary...

Something's wrong with "gui-automation-squish".