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Network Administration Visualized 网络管理可视化源码

What is this?
=============
This directory contains utilities related to the start/stop system of NAV
services.i

The start/stop system provides an interface script (nav) to start
and stop all the known NAV services, be they either daemons or cron jobs.  Also
provides a shell script containing general subroutines for starting, stopping
and detecting processes - this script can be sourced into other start/stop
scripts.

The start/stop system of NAV
============================
Most *NIX distributions today use a SysV style init system.  The NAV start/stop
system partly mimics this system, but does not interfere with the global init
system of an installation.

NAV services consist of both daemons and cron jobs.  The daemons have their
respective init-scripts for starting and stopping.  These are not placed in the
system-wide init.d directory, but in a NAV specific one.

The cron jobs run through a default crontab file, which is to be installed as
the crontab of an unprivileged user (by default, the user navcron is used).
The crontab file is structured through special comments, which divide the cron
jobs into subsystems.  This structure is parsed by the interface script,
described in the next paragraph.

A perl script (nav) is your interface to starting, stopping and querying the
status of NAV services.  This script will define NAV services as whatever
executable scripts exist in NAV's init.d directory, and every subsystem defined
through the structure of the nav crontab file.  If asked to start or stop a NAV
service that is a daemon, it will call the init script of that daemon.  If the
service is recognized as a cron job, the relevant part of the NAV crontab file
will be extracted and inserted into the active crontab of the navcron user.