缘起
《UNP》1.5节“一个简单的时间获取服务器程序”这个例子中需要daytime服务，为了运行该节的程序，故安装下该服务。
过程
- 检查是否已安装了daytime服务，如目录下有daytime-*文件，则表示安装过了
[qxhgd@localhost ~]$ cd /etc/xinetd.d/
[qxhgd@localhost xinetd.d]$ ls
- 安装xinetd服务
[qxhgd@localhost ~]$ sudo yum install xinetd
- 使能
下面几个文件，最前面的一行的 “disable=yes”改为“disable=no”
daytime-stream、daytime-dgram、time-dgram、time-stream
- 重启服务并配置开机启用使能
[qxhgd@localhost ~]$systemctl restart xinetd.service #重启服务
[qxhgd@localhost ~]$systemctl enable xinetd.service #开机启用
- 确认服务状态是否正常
[qxhgd@localhost ~]$ systemctl status xinetd.service
xinetd.service - Xinetd A Powerful Replacement For InetdLoaded: loaded (/usr/lib/systemd/system/xinetd.service; enabled; vendor preset: enabled)Active: active (running) since Tue 2021-04-13 07:28:00 CST; 11h agoMain PID: 25942 (xinetd)Tasks: 1CGroup: /system.slice/xinetd.service└─25942 /usr/sbin/xinetd -stayalive -pidfile /var/run/xinetd.pidApr 13 07:28:00 localhost.localdomain xinetd[25942]: removing chargen
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: removing discard
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: removing discard
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: removing echo
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: removing echo
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: removing tcpmux
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: removing time
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: removing time
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: xinetd Version 2.3.15 st...
Apr 13 07:28:00 localhost.localdomain xinetd[25942]: Started working: 2 avail...
Hint: Some lines were ellipsized, use -l to show in full.
- 验证下功能
1、可利用rdate命令：
[root@localhost xinetd.d]# rdate -p -s 192.168.2.100
rdate: [192.168.2.100] Wed Apr 14 03:17:09 2021
2、也可以利用《UNP》1.5节的程序来验证。
命令汇总
yum install xinetd #安装xinetd
systemctl restart xinetd.service #重启服务
systemctl enable xinetd.service #开机启用
systemctl status xinetd.service #查看状态
rdate -s 192.168.2.100 #询问系统时间并显示出来
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