I'm running Debian 8.6, and looking at old logs. I'd like to confirm when the system was rebooted to invoke the newer kernel which fixed the Dirty COW bug. With systemd, I'm not seeing the old signs like the announcement of the kernel version. If I have a complete copy of my /var/log from last October, which file will confirm when the system was rebooted? I've already tried last -f wtmp and it didn't show anything.
This should be a simple question but I'm not seeing the usual stuff like dmesg file activity in /var/log