sudo apt-get install telnet*

　vim /etc/xinetd.d/telnet

 1 service telnet

 2 {

 3     disable = no

 4     flags           = REUSE

 5     socket_type     = stream

 6     wait            = no

 7     user            = root

 8     server          = /usr/sbin/in.telnetd

 9     server_args     = -h

10     log_on_failure  += USERID

11 }

umlinux@umlinux-PC:~$ telnet 0.0.0.0

Trying 0.0.0.0...

Connected to 0.0.0.0.

Escape character is '^]'.

umlinux-PC login: litao1

Password:

Last login: Thu Nov  5 19:00:11 CST 2020 from localhost on pts/2

Welcome to uos 20 GNU/Linux

    * Homepage:https://www.chinauos.com/

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