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Translating-----geekpi
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Installing Telnet In CentOS/RHEL/Scientific Linux 6 & 7
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================================================================================
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#### Disclaimer: ####
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Before installing and using Telnet, keep the following in mind.
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- Using Telnet in public network(WAN) is very very bad idea. It transmits login data in the clear format. Everything will be sent in plain text.
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- If you still need Telnet, It is highly recommended use it in the local area network only.
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- Alternatively, you can use **SSH**. But make sure you’ve disabled root login in SSH.
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### What Is Telnet? ###
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[Telnet][1] is a network protocol which is used to connect to remote computers over TCP/IP network. Once you establish a connection to the remote computer, it becomes a virtual terminal and will allow you to communicate with the remote host from your local system.
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In this brief tutorial, let us see how to install Telnet, and how to access remote systems via Telnet.
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### Installation ###
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Open your terminal and type the following command to install telnet:
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yum install telnet telnet-server -y
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Now, the telnet has been installed in your server. Next, edit the telnet configuration file **/etc/xinetd.d/telnet**;
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vi /etc/xinetd.d/telnet
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Set **disable = no**:
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# default: on
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# description: The telnet server serves telnet sessions; it uses \
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# unencrypted username/password pairs for authentication.
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service telnet
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{
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flags = REUSE
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socket_type = stream
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wait = no
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user = root
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server = /usr/sbin/in.telnetd
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log_on_failure += USERID
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disable = no
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}
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Save and quit the file. Be mindful that you don’t have do this step in CentOS 7.
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Now restart the telnet service using the following command:
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On CentOS 6.x systems:
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service xinetd start
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Make this service to start automatically on every reboot:
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On CentOS 6:
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chkconfig telnet on
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chkconfig xinetd on
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On CentOS 7:
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systemctl start telnet.socket
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systemctl enable telnet.socket
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Allow the telnet default port **23** through your firewall and Router. To allow the telnet port through firewall, Edit file **/etc/sysconfig/iptables** on CentOS 6.x systems:
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vi /etc/sysconfig/iptables
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Add the line as shown in red color:
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# Firewall configuration written by system-config-firewall
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# Manual customization of this file is not recommended.
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*filter
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:INPUT ACCEPT [0:0]
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:FORWARD ACCEPT [0:0]
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:OUTPUT ACCEPT [0:0]
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-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
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-A INPUT -p icmp -j ACCEPT
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-A INPUT -i lo -j ACCEPT
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-A INPUT -p tcp -m state --state NEW --dport 23 -j ACCEPT
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-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
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-A INPUT -j REJECT --reject-with icmp-host-prohibited
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-A FORWARD -j REJECT --reject-with icmp-host-prohibited
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COMMIT
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Save and exit the file. Restart iptables service:
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service iptables restart
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On CentOS 7, run the following commands to enable telnet service through firewall.
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firewall-cmd --permanent --add-port=23/tcp
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firewall-cmd --reload
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Thats it. Now telnet server is ready to use.
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#### Creating users ####
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Create a test user, for example “**sk**” with password “**centos**“:
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useradd sk
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passwd sk
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#### Client Side Configuration ####
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Install telnet package:
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yum install telnet
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On DEB based systems:
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sudo apt-get install telnet
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Now, open Terminal, and try to access your server(remote host).
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If your client is Linux system, open the terminal and type the following command to connect to telnet server.
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telnet 192.168.1.150
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Enter username and password which we have created in the server:
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Sample output:
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Trying 192.168.1.150...
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Connected to 192.168.1.150.
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Escape character is '^]'.
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Kernel 3.10.0-123.13.2.el7.x86_64 on an x86_64
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server1 login: sk
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Password:
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[sk@server1 ~]$
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As you see in the above output, the remote system has been successfully accessed from the local machine.
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If your client is windows system, then go to **Start -> Run -> Command Prompt**.
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In the command prompt, type the command:
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telnet 192.168.1.150
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Where **192.168.1.150** is remote host IP address.
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Now you will be able to connect to your server.
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That’s it.
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Cheers!
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--------------------------------------------------------------------------------
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via: http://www.unixmen.com/installing-telnet-centosrhelscientific-linux-6-7/
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作者：[SK][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[a]:http://www.unixmen.com/author/sk/
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[1]:http://en.wikipedia.org/wiki/Telnet
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@ -0,0 +1,159 @@
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在CentOS/RHEL/Scientific Linux 6 & 7 上安装Telnet
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================================================================================
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#### 声明： ####
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在安装和使用Telnet之前，需要记住以下几点。
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- 在公网(WAN)中使用Telnet是非常不好的想法。它会以明文的格式传输登入数据。每个人都可以看到明文。
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- 如果你还是需要Telnet，强烈建议你只在局域网内部使用。
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- 你可以使用**SSH**作为替代方法。但是确保不要用root用户登录。
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### Telnet是什么？ ###
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[Telnet][1] 是用于通过TCP/IP网络远程登录计算机的协议。一旦与远程计算机建立了连接，它就会成为一个虚拟终端且允许你与远程计算机通信。
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在本篇教程中，我们会展示如何安装Telnet并且如何通过Telnet访问远程系统。
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### 安装 ###
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打开终端并输入下面的命令来安装telnet：
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yum install telnet telnet-server -y
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现在telnet已经安装在你的服务器上了。接下来编辑文件**/etc/xinetd.d/telnet**：
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vi /etc/xinetd.d/telnet
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设置 **disable = no**:
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# default: on
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# description: The telnet server serves telnet sessions; it uses \
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# unencrypted username/password pairs for authentication.
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service telnet
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{
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flags = REUSE
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socket_type = stream
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wait = no
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user = root
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server = /usr/sbin/in.telnetd
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log_on_failure += USERID
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disable = no
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}
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保存并退出文件。记住我们不必在CentOS 7做这步。
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接下来使用下面的命令重启telnet服务：
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在CentOS 6.x 系统中：
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service xinetd start
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让这个服务在每次重启时都会启动：
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在CentOS 6上：
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chkconfig telnet on
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chkconfig xinetd on
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在CentOS 7上：
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systemctl start telnet.socket
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systemctl enable telnet.socket
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让telnet的默认端口**23**可以通过防火墙和路由器。要让telnet端口可以通过防火墙，在CentOS 6.x系统中编辑下面的文件：
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vi /etc/sysconfig/iptables
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加入红色显示的行：
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# Firewall configuration written by system-config-firewall
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# Manual customization of this file is not recommended.
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*filter
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:INPUT ACCEPT [0:0]
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:FORWARD ACCEPT [0:0]
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:OUTPUT ACCEPT [0:0]
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-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
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-A INPUT -p icmp -j ACCEPT
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-A INPUT -i lo -j ACCEPT
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-A INPUT -p tcp -m state --state NEW --dport 23 -j ACCEPT
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-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
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-A INPUT -j REJECT --reject-with icmp-host-prohibited
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-A FORWARD -j REJECT --reject-with icmp-host-prohibited
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COMMIT
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保存并退出文件。重启iptables服务：
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service iptables restart
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在CentOS 7中，运行下面的命令让telnet服务可以通过防火墙。
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firewall-cmd --permanent --add-port=23/tcp
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firewall-cmd --reload
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就是这样。现在telnet服务就可以使用了。
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#### 创建用户 ####
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创建一个测试用户，比如用户名是“**sk**”，密码是“**centos**“:
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useradd sk
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passwd sk
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#### 客户端配置 ####
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安装telnet包：
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yum install telnet
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在基于DEB的系统中：
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sudo apt-get install telnet
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现在，打开终端，尝试访问你的服务器（远程主机）。
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如果你的客户端是Linux系统，打开终端并输入下面的命令来连接到telnet服务器上。
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telnet 192.168.1.150
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输入服务器上已经创建的用户名和密码：
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示例输出:
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Trying 192.168.1.150...
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Connected to 192.168.1.150.
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Escape character is '^]'.
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Kernel 3.10.0-123.13.2.el7.x86_64 on an x86_64
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server1 login: sk
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Password:
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[sk@server1 ~]$
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如你所见，已经成功从本地访问远程主机了。
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如果你的系统是windows，进入**开始 -> 运行 -> 命令提示符**。
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在命令提示符中，输入命令：
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telnet 192.168.1.150
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**192.168.1.150**是远程主机IP地址。
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现在你就可以连接到你的服务器上了。
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就是这样。
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干杯！
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--------------------------------------------------------------------------------
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via: http://www.unixmen.com/installing-telnet-centosrhelscientific-linux-6-7/
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作者：[SK][a]
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译者：[geekpi](https://github.com/geekpi)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[a]:http://www.unixmen.com/author/sk/
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[1]:http://en.wikipedia.org/wiki/Telnet
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