刚安装的Ubuntu 12.04还没有telnet功能，需要配置一下。我主要是想让Ubuntu 12.04开启telnet服务做服务器。
安装openbsd-inetd:
#sudo apt-get install openbsd-inetd
安装telnetd:
#sudo apt-get install telnetd
在etc/inetd.conf文件中可以看到这一行内容：
telnet stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.telnetd
如果没有这一行内容，就手动加上
重启openbsd-inetd
#/etc/init.d/openbsd-inetd restart
查看telnet运行状态
#netstat -a | grep telnet
输出： tcp 0 0 *:telnet *:* LISTEN
在windows的命令行中输入：telnet 192.168.1.8（我的linux的IP地址）
按照提示输入用户名和密码进入（非root用户）
效果如下：
Ubuntu 12.04
ubuntu login: kevin
Password:
Linux ubuntu 2.6.35-22-generic #33-Ubuntu SMP Sun Sep 19
20:34:50 UTC 20
10 i686 GNU/Linux
Ubuntu 12.04
Welcome to Ubuntu!
* Documentation: https://help.ubuntu.com/
New release 'natty' available.
Run 'do-release-upgrade' to upgrade to it.
The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.