Configuration of System V init under Debian GNU/Linux

Most Unix versions have a file here that describes how the scripts
in this directory work, and how the links in the /etc/rc?.d/ directories
influence system startup/shutdown.

For Debian, this information is contained in the policy manual, chapter 
"System run levels and init.d scripts".  The Debian Policy Manual is 
available at:

    http://www.debian.org/doc/debian-policy/#contents

The Debian Policy Manual is also available in the Debian package
"debian-policy".  When this package is installed, the policy manual can be
found in directory /usr/share/doc/debian-policy. If you have a browser
installed you can probably read it at

    file://localhost/usr/share/doc/debian-policy/

Some more detailed information can also be found in the files in the
/usr/share/doc/sysv-rc directory.

Debian Policy dictates that /etc/init.d/*.sh scripts must work properly
when sourced.  The following additional rules apply:

* /etc/init.d/*.sh scripts must not rely for their correct functioning
  on their being sourced rather than executed.  That is, they must work
  properly when executed too. They must include "#!/bin/sh" at the top.
  This is useful when running scripts in parallel.

* /etc/init.d/*.sh scripts must conform to the rules for sh scripts as
  spelled out in the Debian policy section entitled "Scripts" (§10.4).

Use the update-rc.d command to create symbolic links in the /etc/rc?.d
as appropriate. See that man page for more details.