22.1.3 服务器启动脚本
用于启动服务器应用程序（更确切地说是服务器守护进程）的脚本全部位于/etc/init.d目录下，每个脚本控制一个特定的守护进程（这个概念将在22.2.1节具体介绍）。所有的脚本都应该认识start和stop参数，分别表示启动和停止服务器守护进程。下面这条命令启动了SSH服务器的守护进程。
$ sudo /etc/init.d/sshd start
Starting SSH daemon done
与此相对的，下面这条命令停止SSH服务器的守护进程。
$ sudo /etc/init.d/sshd stop
Shutting down SSH daemon done
大部分启动脚本还认识restart参数。顾名思义，接收到这个参数的脚本首先关闭服务器守护进程，然后再启动它。
$ sudo /etc/init.d/sshd restart
Shutting down SSH daemon done
Starting SSH daemon done
在改变运行级（包括系统启动和关闭）的时候，系统执行的是rclevel.d目录下的脚本文件。仍然以SSH为例，使用ls -l命令可以清楚地看到init.d和rclevel.d这两个目录下脚本文件之间的关系。
$ ls -l /etc/init.d/rc5.d/ | grep sshd
lrwxrwxrwx 1 root root 7 11-09 17:55 K12sshd -> ../sshd
lrwxrwxrwx 1 root root 7 11-09 17:55 S10sshd -> ../sshd
/etc/init.d/rc5.d目录下的两个脚本文件K12sshd和S10sshd，实际上都是指向/etc/init.d/sshd的符号链接。init在执行脚本的时候，会给以字母S开头的脚本文件传递start参数，而给以字母K开头的脚本文件传递stop参数。例如init运行K12sshd时，实际执行的是下面这条命令。
/etc/init.d/rc5.d/K12sshd stop
由于K12sshd脚本是/etc/init.d/sshd的符号链接，因此又等价于下面这条命令。
/etc/init.d/sshd stop
脚本文件名中的数字描述了脚本运行的先后顺序，数字较小的脚本首先被执行。下面的例子反映了这一点。当进入运行级5的时候，S05network在S10sshd之前执行（因为5<10）；类似地，当退出运行级5的时候，K12sshd在K17network之前执行（因为12<17）。
$ ls -l /etc/init.d/rc5.d/ | egrep 'ssh|network'
lrwxrwxrwx 1 root root 7 11-09 17:55 K12sshd -> ../sshd
lrwxrwxrwx 1 root root 10 11-09 17:50 K17network -> ../network
lrwxrwxrwx 1 root root 10 11-09 17:50 S05network -> ../network
lrwxrwxrwx 1 root root 7 11-09 17:55 S10sshd -> ../sshd
这样安排的用意很明显，供远程登录使用的SSH服务器不应该在网络接口启动之前运行。在向rclevel.d目录下手动添加脚本的时候应该格外注意这些依赖关系。下面列出了在笔者的openSUSE系统上启动服务器脚本的顺序。
$ ls -l /etc/init.d/rc5.d/
...
lrwxrwxrwx 1 root root 8 11-09 17:50 S01acpid -> ../acpid
lrwxrwxrwx 1 root root 7 11-09 17:50 S01dbus -> ../dbus
lrwxrwxrwx 1 root root 14 11-09 17:50 S01earlysyslog -> ../earlysyslog
lrwxrwxrwx 1 root root 8 11-09 17:50 S01fbset -> ../fbset
lrwxrwxrwx 1 root root 16 11-09 17:50 S01microcode.ctl -> ../microcode.
ctl
lrwxrwxrwx 1 root root 9 11-09 17:50 S01random -> ../random
lrwxrwxrwx 1 root root 9 11-09 17:50 S01resmgr -> ../resmgr
lrwxrwxrwx 1 root root 21 11-09 18:10 S01SuSEfirewall2_init -> ../SuSEf-
irewall2_init
lrwxrwxrwx 1 root root 13 11-09 17:50 S02consolekit -> ../consolekit
lrwxrwxrwx 1 root root 12 11-09 17:50 S03haldaemon -> ../haldaemon
lrwxrwxrwx 1 root root 11 11-09 17:50 S04earlyxdm -> ../earlyxdm
lrwxrwxrwx 1 root root 10 11-09 17:50 S05network -> ../network
lrwxrwxrwx 1 root root 9 11-09 17:50 S06syslog -> ../syslog
lrwxrwxrwx 1 root root 9 11-09 17:55 S07auditd -> ../auditd
lrwxrwxrwx 1 root root 10 11-09 17:55 S07portmap -> ../portmap
lrwxrwxrwx 1 root root 8 11-27 13:06 S07smbfs -> ../smbfs
lrwxrwxrwx 1 root root 15 11-09 17:55 S07splash_early -> ../splash_early
lrwxrwxrwx 1 root root 12 11-09 17:55 S10alsasound -> ../alsasound
lrwxrwxrwx 1 root root 15 11-09 17:55 S10avahi-daemon -> ../avahi-daemon
lrwxrwxrwx 1 root root 7 11-09 17:55 S10cups -> ../cups
lrwxrwxrwx 1 root root 19 11-09 17:55 S10java.binfmt_misc -> ../java.
binfmt_misc
lrwxrwxrwx 1 root root 6 11-09 17:55 S10kbd -> ../kbd
lrwxrwxrwx 1 root root 7 11-09 17:55 S10nscd -> ../nscd
lrwxrwxrwx 1 root root 13 11-09 17:56 S10powersaved -> ../powersaved
lrwxrwxrwx 1 root root 9 11-09 17:55 S10splash -> ../splash
lrwxrwxrwx 1 root root 7 11-09 17:55 S10sshd -> ../sshd
lrwxrwxrwx 1 root root 15 11-09 17:56 S10vmware-guest -> ../vmware-guest
lrwxrwxrwx 1 root root 17 11-09 17:55 S11avahi-dnsconfd -> ../avahi-
dnsconfd
lrwxrwxrwx 1 root root 12 12-21 05:25 S11nfsserver -> ../nfsserver
lrwxrwxrwx 1 root root 10 11-09 17:55 S11postfix -> ../postfix
lrwxrwxrwx 1 root root 6 11-09 17:55 S11xdm -> ../xdm
lrwxrwxrwx 1 root root 7 11-09 17:55 S12cron -> ../cron
lrwxrwxrwx 1 root root 9 11-09 17:57 S12smartd -> ../smartd
lrwxrwxrwx 1 root root 9 11-09 14:15 S12xinetd -> ../xinetd
lrwxrwxrwx 1 root root 15 11-09 17:50 S21stopblktrace -> ../stopblktrace
lrwxrwxrwx 1 root root 22 11-09 18:10 S21SuSEfirewall2_setup -> ../S-
uSEfirewall2_setup
