Between the recent "Why does 'kill -9 0' end my console session" and "How to get a kernel panic" questions, I got a bur under my saddle and tried
kill -9 1 on a mostly up-to-date Arch linux laptop. I did it as user ID "root".
I fully expected some kind of crash or panic or shutdown, but nothing happened. I did
kill -9 1 again, to no effect.
Arch linux machines run
systemd these days, so: how does
systemd survive a kill -9? I expect there's special case code in the Linux 3.7 kernel, but maybe some other reason exists that I haven't thought of.
What about other things that run with PID 1? Slackware still uses
init I believe, but I'm scared to try it on my production Slackware server. DD-WRT on my wireless router runs /sbin/init of some sort.