背景
在ubuntu下做开发，虚拟机要经常开启和关闭，重要的进程需要随机自启，非重要的可以手工启动。比如nginx就需要自启，confluence就没那么重要了。
为了控制哪些程序要自启，哪些程序不要自启，ubunt提供了一套API，update-rc.d。以下就是对于该API的操作示例和简单说明。
update-rc.d --help可查看更多用法。
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重要概念说明
luwenwei@ubuntu:~/dev/project$ ll /etc/rc?.d/*confluence1
lrwxrwxrwx 1 root root 21 Apr 27 2016 /etc/rc0.d/K20confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Apr 27 2016 /etc/rc1.d/K20confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Apr 27 2016 /etc/rc2.d/S20confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Apr 27 2016 /etc/rc3.d/S20confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Apr 27 2016 /etc/rc4.d/S20confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Apr 27 2016 /etc/rc5.d/S20confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Apr 27 2016 /etc/rc6.d/K20confluence1 -> ../init.d/confluence1*
confluence1是个shell脚本，rc*.d用来控制它的启不启动.
以/etc/rc0.d/K20confluence1为例，分解下/etc/rc[$a].d/$b$c$d，$a=0, $b=K, $c=20, $d=confluence1
$a: runlevel, [0-6]几个值, 0表示系统停机状态 1表示单用户或者系统维护状态 2-5表示多用户状态 6表示重启
$b: 启动/禁止启动, K/S，K表示开启，S表示停止;
$c: priority, 0-99 表示优先级, 1优先级最高，99优先级最低
$d: 服务执行脚本，shell脚本
查看某个服务：
ll /etc/rc?.d/*confluence1
lrwxrwxrwx 1 root root 21 Dec 15 11:57 /etc/rc0.d/K90confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Dec 15 11:57 /etc/rc1.d/K90confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Dec 15 11:57 /etc/rc2.d/S90confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Dec 15 11:57 /etc/rc3.d/S90confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Dec 15 11:57 /etc/rc4.d/S90confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Dec 15 11:57 /etc/rc5.d/S90confluence1 -> ../init.d/confluence1*
lrwxrwxrwx 1 root root 21 Dec 15 11:57 /etc/rc6.d/K90confluence1 -> ../init.d/confluence1*
更新某个服务：
luwenwei@ubuntu:~/dev/project$ sudo update-rc.d confluence1 start 90 2 3 4 5 . stop 90 0 1 6 .
System start/stop links for /etc/init.d/confluence1 already exist.
luwenwei@ubuntu:~/dev/project$ sudo update-rc.d confluence1 start 90 2 3 4 5 . stop 90 0 1 6 .
Adding system startup for /etc/init.d/confluence1 ...
/etc/rc0.d/K90confluence1 -> ../init.d/confluence1
/etc/rc1.d/K90confluence1 -> ../init.d/confluence1
/etc/rc6.d/K90confluence1 -> ../init.d/confluence1
/etc/rc2.d/S90confluence1 -> ../init.d/confluence1
/etc/rc3.d/S90confluence1 -> ../init.d/confluence1
/etc/rc4.d/S90confluence1 -> ../init.d/confluence1
/etc/rc5.d/S90confluence1 -> ../init.d/confluence1
删除某个服务：
luwenwei@ubuntu:~/dev/project$ sudo update-rc.d -f confluence1 remove
Removing any system startup links for /etc/init.d/confluence1 ...
/etc/rc0.d/K20confluence1
/etc/rc1.d/K20confluence1
/etc/rc2.d/S20confluence1
/etc/rc3.d/S20confluence1
/etc/rc4.d/S20confluence1
/etc/rc5.d/S20confluence1
/etc/rc6.d/K20confluence1