参考 http://91xueit.blog.51cto.com/400469/1214758
1. sudo apt-get install xinetd telnetd
2. sudo vi /etc/inetd.conf并加入以下一行
telnet stream tcp nowait telnetd /usr/sbin/tcpd /usr/sbin/in.telnetd
3. sudo vi /etc/xinetd.conf并加入以下内容（红色部分）：
# Simple configuration file for xinetd
#
# Some defaults, and include /etc/xinetd.d/
defaults
{
# Please note that you need a log_type line to be able to use log_on_success
# and log_on_failure. The default is the following :
# log_type = SYSLOG daemon info
instances = 60
log_type = SYSLOG authpriv
log_on_success = HOST PID
log_on_failure = HOST
cps = 25 30
}
includedir /etc/xinetd.d
4. sudo vi /etc/xinetd.d/telnet并加入以下内容：
# default: on
# description: The telnet server serves telnet sessions; it uses
# unencrypted username/password pairs for authentication.
service telnet
{
disable = no
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure += USERID
}
5. 重启网络服务sudo /etc/init.d/xinetd restart
6. 查看telnet端口号23是否已启动netstat -ntlp
附：1.安装ssh
sudo apt-get install openssh-server
>>由于默认Ubuntu采用UTF-8的字符集，所以putty需要做一些设置：
Win7下启动putty，点击左边的 Windows -> Appearance 设置 Font settings ,点击 Change... 按钮选择为 仿宋体
或者 新宋体。 点击左边的 Windows -> Translation 设置 Character set translation 为
UTF-8 。然后，点击 Open 连接服务器即可。
2.windows命令行telnet
cmd->telnet 192.168.*.*
3.本文方法直接在root用户下执行的，不存在root用户无法telnet的问题。