Add SUM sysctl

[rank1seeker at gmail.com]

> On 15/04/2011, at 17:03, rank1seeker at gmail.com wrote:
> > I would like implementation of boolean sysctl var, that would show, is 
system in a single user mode.
> > I would like it from 8.3 onwards.
> 
> AFAIK the kernel doesn't have a "single user" mode.
> 
> It's just that when you boot into single user mode it asks you want to 
run rather than starting /sbin/init.

I see, but 'ps' shows /sbin/init as PID 1, in both SUM and MUM.
How can I fiducially ensure that I am in SUM.
On what to rely/look on.

I wana put it in sh's function, for usage in scripts.