From the systemd manual:-
ShutdownWatchdogSec= ShutdownWatchdogSec= may be used to configure the hardware watchdog when the system is asked to reboot. It works as a safety net to ensure that the reboot takes place even if a clean reboot attempt times out. By default RuntimeWatchdogSec= defaults to 0 (off), and ShutdownWatchdogSec= to 10min. These settings have no effect if a hardware watchdog is not available.
Currently, there is an issue with shutting down my system wherein the kernel keeps printing the message "unregister_netdevice: waiting for to get free:Instance count=1" even 10 minutes after issuing reboot command. I don't know what could be causing this issue, but I was hoping ShutdownWatchdogSec would force reboot in this and other scenarios.
However the system doesn't shut down within the stipulated time. It still takes 10+min. I have made the required change in my /etc/systemd/system.conf:
Watchdog seems to be present on my system
root@bugkiller:~# dmesg|grep watchdog
[ 0.044094] NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter. [ 4.051861] systemd: Hardware watchdog 'iTCO_wdt', version 0 [ 4.051874] systemd: Set hardware watchdog to 1min 4s.
root@re0:~# uname -a
Linux re0 4.1.15-foo-00929-g15aa5b3 #1 SMP PREEMPT Mon Oct 3 18:01:53 PDT 2016 x86_64 GNU/Linux
root@re0:~# systemctl --version
systemd 219 +PAM -AUDIT -SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP -LIBCRYPTSETUP -GCRYPT +GNUTLS +ACL +XZ -LZ4 -SECCOMP +BLKID -ELFUTILS +KMOD -IDN