systemd-shutdown-debug.txt

Diagnosing Shutdown Problems

Just like with boot problems, when you encounter a hang during shutting down, make sure you wait at least 5 minutes to distinguish a permanent hang from a broken service that's just timing out. Then it's worth testing whether the system reacts to CTRL+ALT+DEL in any way.

If shutdown (whether it be to reboot or power-off) of your system gets stuck, first test if the kernel itself is able to reboot or power-off the machine forcedly using one of these commands:

sync && reboot -f
sync && poweroff -f
If either one of the commands does not work, it is a kernel bug, not systemd.

Shutdown Completes Eventually

If normal reboot or poweroff work, but take a suspiciously long time, then

boot with the debug options:

systemd.log_level=debug systemd.log_target=kmsg log_buf_len=1M enforcing=0
save the following script as /usr/lib/systemd/system-shutdown/debug.sh and make it executable:

#!/bin/sh
mount -o remount,rw /
dmesg > /shutdown-log.txt
mount -o remount,ro /
reboot

Look for timeouts logged in the resulting file shutdown-log.txt and/or attach it to a bugreport.