/etc/init.d目录

/etc/init.d contains scripts used by the System V init tools (SysVinit). This is the traditional service management package for Linux, containing the init program (the first process that is run when the kernel has finished initializing) as well as some infrastructure
to start and stop services and configure them. Specifically, files in /etc/init.d are shell scripts that respond to start, stop, restart, and (when supported) reload commands to manage a particular service. These scripts can be invoked directly or (most commonly)
via some other trigger (typically the presence of a symbolic link in/etc/rc?.d/).

1./etc/init.d里的shell脚本（SysVinit工具所包含的函数库）能够响应start，stop，restart，reload命令来管理某个具体的应用。比如经常看到的命令：

/etc/init.d/networking start

2.etc/init.d 是一般开机的启动服务存放在这个目录下