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Author: Rainer Weikusat
Date:  
To: dng
Subject: Re: [DNG] Apparently Jessie has runit
Steve Litt <slitt@???> writes:
> People aren't completely alone on run scripts: I can give them any run
> scripts I'm using. Also, Runit run scripts are *nothing* like sysvinit
> or OpenRC init scripts:


There is no such thing as a "sysvinit init script". The way the sysvinit
program is usually employed on Linux is such that it's instructed to run
the command /etc/init.d/rc with the run-level number as argument upon
entering a run-level, as written down in /etc/inittab,

l0:0:wait:/etc/init.d/rc 0
l1:1:wait:/etc/init.d/rc 1
l2:2:wait:/etc/init.d/rc 2
l3:3:wait:/etc/init.d/rc 3
l4:4:wait:/etc/init.d/rc 4
l5:5:wait:/etc/init.d/rc 5
l6:6:wait:/etc/init.d/rc 6

This /etc/init.d/rc command is a script which lists the contents of the
runlevel directory corresponding with the number, eg, /etc/rc3.d in
(ASCII) alphabetical order. Such a directory contains symlinks of the
form

S<xx>Name

or

K<xx>Name,

with <xx> being a sequence number. If a S-name is encountered, the
corresponding symlink is executed with a first argument of start, for K,
it will be stop. And the responsibility of "the sysvinit system" ends
here.

The commands which are actually executed via these S- and K-links come
from individual packages and ultimatively contain whatever the people
responsible for that considered sensible. Which is usually a pretty
arbitrary assortment of more or less useless code which accumulated over
ca 20 years in the course of "whatever, the easiest way to make the
problem go away is hack some more code into the init script".

In further twenty years, continuously maintained systemd unit files will
look exactly like present-day 'init scripts' or end up executing scripts
which do. And the same is true for any other software maintained using
this method.

But please blame the people who wrote the code and not the facility they
chose to attach their code to.