Detect Linux Runlevel

[Michael Torrie]

On 12/06/2016 03:29 PM, Marko Rauhamaa wrote:
> Another thing is that, as stated before, the runlevel business is
> legacy. It is still supported by systemd-update-utmp, but for how long
> is anybody's guess.

System V compatibility is still important to Linux, and as long as it
is, something resembling a runlevel has to be provided, even it's just
an abstraction of something else like a systemd target.  So any system
that advertises System V compliance or compatibility will have a runlevel.