Installation and usage of Telnet in Linux system

Telnet is a service that http://www.aliyun.com/zixun/aggregation/18736.html "> Allows a user to log on to your server and get a command prompt similar to the one you login to the VGA terminal. The Telnet service is installed by default in Fedora but not started.

The disadvantage of Telnet is that data can only be sent in plain text. This means that other people can use the web Analytics tool to get your username and password by analyzing the packet. For remote logins, therefore, SSH with multiple encryption methods is more secure.

However, Telnet is still widely used. Many network devices do not have SSH clients, which makes it necessary to use Telnet to access other devices and servers. Later I'll show you how to reduce the security of Telnet.

Using the Telnet client

The command line to use Telnet for remote logins is simple. You simply type "Telnet IP address/server name".

In the following example, a person logs on from the server Bigboy to the server Smallfry and logs off after viewing the routing table.

[Root@bigboy tmp]# telnet 192.168.1.105Trying 192.168.1.105...Connected to 192.168.1.105.Escape character is ' ^] '. Linux 2.4.18-14 (smallfry.my-site.com) (10:35 on Sunday, whose 2003) Login:peterPassword:Last Login:fri modified 22 23:29:44 on ttys0you have new mail. [Peter@smallfry peter]$[peter@smallfry peter]$ netstat-nrkernel IP routing tabledestination Gateway Genmask Flags MSS Window Irtt Iface255.255.255.255 0.0.0.0 255.255.255.255 UH, 0 0 wlan0192.168.1.0 0.0.0.0 255.255.255.0 U 40 0 0 wlan0127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 lo0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 Wlan0[peter@smallfry peter]$ Exitlogoutconnection closed by foreign host. [Root@bigboy tmp]#

Installing the Telnet service software

The old version of the Redhat default has the Telnet service installed, but Fedora does not, so you have to install it yourself.

Most Linux software has precompiled packages, so downloading and installing them is not difficult.

When searching for installation packages, remember that the Telnet service RPM package's filename usually starts with "Telnet-server", followed by the version number, such as: telnet-server-0.17-28.i386.rpm.

For Debian/ubuntu, the Telnet service pack is prefixed with "telnetd", such as: Telnetd_0.17-32_i386.deb.

The configuration of the Telnet service is simple, but the process is slightly different in different Linux distributions.

Redhat/fedora

Use the Chkconfig command to configure the Telnet service.

[Root@bigboy tmp]# chkconfig telnet on

You can also use Chkconfig--list to confirm that Telnet will start after the system restarts.

[Root@bigboy tmp]# chkconfig--list | grep telnet Telnet:on[root@bigboy tmp]#

Use the Chkconfig command to turn off the Telnet service.

[Root@bigboy tmp]# chkconfig telnet off