How to find out who/what caused a reboot/shutdown?

Question

On a Linux machine that runs systemd, is there any way to see what or who issued a shutdown or reboot?

Answer 1

Examine the system logs of the previous boot with sudo journalctl -b -1 -e.

Examine /var/log/auth.log.

Are you sure it's not one of "power interruption/spike", "CPU overheat", ....

On MY system (Ubuntu 16.04,6),

sudo journalctl | grep shutdown
Jan 29 12:58:07 bat sudo[14365]: walt : TTY=pts/0 ; PWD=/home/walt ; USER=root ; COMMAND=/sbin/shutdown now
Feb 12 11:23:59 bat systemd[1]: Stopped Ubuntu core (all-snaps) system shutdown helper setup service.
Feb 19 09:35:18 bat ureadahead[437]: ureadahead:lxqt-session_system-shutdown.png: Ignored relative path
Feb 19 09:35:18 bat ureadahead[437]: ureadahead:gshutdown_gshutdown.png: Ignored relative path
Feb 19 09:35:18 bat ureadahead[437]: ureadahead:mate-gnome-main-menu-applet_system-shutdown.png: Ignored relative path
Feb 27 16:45:40 bat systemd-shutdown[1]: Sending SIGTERM to remaining processes...
Mar 05 17:53:27 bat systemd-shutdown[1]: Sending SIGTERM to remaining processes...
Mar 15 09:57:45 bat systemd[1]: Stopped Ubuntu core (all-snaps) system shutdown helper setup service.
Mar 21 17:40:30 bat systemd[1]: Stopped Ubuntu core (all-snaps) system shutdown helper setup service.
Apr 15 18:16:37 bat systemd[1]: Stopped Ubuntu core (all-snaps) system shutdown helper setup service.
...

The first line shows when user walt did a sudo shutdown now.

Answer 2

In short, only root user or root privileged users can shutdown/reboot a system.

1. Running last -x command for finding timestamp of actions

root@personal:~# last -x
ubuntu   pts/0        116.102.181.245  Wed Dec 18 16:28   still logged in
runlevel (to lvl 5)   4.15.0-1047-aws  Wed Dec 18 16:27   still running
reboot   system boot  4.15.0-1047-aws  Wed Dec 18 16:27   still running
shutdown system down  4.15.0-1047-aws  Wed Dec 18 16:27 - 16:27  (00:00)
ubuntu   pts/0        116.102.181.245  Wed Dec 18 16:25 - 16:27  (00:02)
runlevel (to lvl 5)   4.15.0-1047-aws  Wed Dec 18 16:24 - 16:27  (00:03)

2. On last -x result, find some recently logged users, switch to that & check history then

root@personal:~# su - ubuntu
ubuntu@personal:~$ history 10
  312  dig @1.1.1.1 xxx +short
  313  dig @8.8.8.8 xxx +short
  314  dig @8.8.4.4 xxx +short
  315  exit
  316  sudo su -
  317  sudo reboot
  318  sudo su -
  319  history
  320  last -x
  321  history 10

3. OR check logs from journalctl

root@personal:~# journalctl | grep reboot
Sep 05 03:07:04 ip-172-31-36-28 cron[710]: (CRON) INFO (Running @reboot jobs)
Sep 05 13:49:11 personal python3[21347]: ansible-command Invoked with _raw_params=sleep 10 && reboot _uses_shell=True warn=True stdin_add_newline=True strip_empty_ends=True argv=None chdir=None executable=None creates=None removes=None stdin=None
Sep 05 13:51:23 personal python3[22042]: ansible-command Invoked with _raw_params=sleep 10 && reboot _uses_shell=True warn=True stdin_add_newline=True strip_empty_ends=True argv=None chdir=None executable=None creates=None removes=None stdin=None
Sep 05 13:54:21 personal systemd-logind[715]: System is rebooting (Reboot initiated by Ansible).
Sep 05 13:54:36 personal cron[573]: (CRON) INFO (Running @reboot jobs)
Dec 18 16:24:30 personal cron[651]: (CRON) INFO (Running @reboot jobs)
Dec 18 16:27:36 personal sudo[915]:   ubuntu : TTY=pts/0 ; PWD=/home/ubuntu ; USER=root ; COMMAND=/sbin/reboot
Dec 18 16:27:54 personal cron[641]: (CRON) INFO (Running @reboot jobs)

BTW, you can check more at these links:

• How to find out from the logs what caused system shutdown?
• https://www.cyberciti.biz/tips/howto-log-user-activity-using-process-accounting.html
• https://www.cyberciti.biz/tips/linux-last-reboot-time-and-date-find-out.html