New reboot flag: -c for 'power cycle'

[Jonathan de Boyne Pollard]

Warner Losh:

>     * system-manager now treats SIGWINCH differently on non-Linux
>     operating systems, treading it as a request to invoke a new
>     powercycle service.
>
>       SIGRTMIN+6, unused in the systemd system, is the Linux equivalent.
>
>     * system-manager now treats SIGRTMIN+16 as the underlying actual
>     powercycle request, which it translates to either RB_POWERCYCLE if
>     it is present in the C library headers, or RB_AUTOBOOT if it is not.
>
>     * There is now a new system-control powercycle subcommand, which
>     defaults to sending SIGWINCH/SIGRTMIN+6 or SIGRTMIN+16.
>
> It looks like all the SIGRT* signals are user defined, and can be used 
> for any purpose by the application. It could easily be SIGRTMIN+6 as 
> it is SIGWINCH and we could ditch SIGWINCH on FreeBSD in init as well 
> (since it's only been in -current for a few days).  Would that suffice 
> to address the compatibility concerns? There's no reason to be 
> gratuitously different here.
>
True, but it's not my softwares that you and I have to worry about. I've 
just double checked, and the very thing that my softwares themselves are 
being compatible with here has already used SIGRTMIN+16 and SIGRTMIN+6, 
so I am going to adjust to +17 and +7 .

I'll let the systemd people know.  Let's see what transpires from that.