How to install Telnet server & client on Debian 11 Bullseye linux | #linux | #linuxsecurity


Telnet has been around since 1969. Telnet is originally an abbreviation for “Telecommunication Network” and describes a protocol from the TCP/IP world with which text-based commands can be executed on remote computers.

Using it the user can have remote access to the remote computer using Telnet client-server architecture via IP address. A suitable telnet client is available for almost all operating systems. It is still used to configure old hardware, especially industrial and scientific devices to diagnose and resolve technical problems.

 

How does Telnet work?

Telnet works on Client and Server connection architecture. After installing, the client starts to establish a connection for a session with the command “telnet” and for security, the user has to authenticate with a password. The port it uses to connect is 23, however, it is possible to use other standard ports by specifying the desired destination port in addition to the computer name or IP address just like we do while connecting remote system via SSH. Once the session has been established, the protocol transfers the text input from the client to the remote computer. Commands are executed there and results or status messages are sent back to the client in text form.

Today, the Telnet protocol is considered less over SSH as it is largely insecure because the data exchanged is not encrypted.

 

Install Telnet on Debian 11 Bullseye Linux

Those who still have any machine that requires Telnet to communicate remotely can follow the given steps for this installation Telnet on Debian 11 Linux.

1. Update command

Refresh the system APT repository cache by running the update command:

sudo apt update

 

2. Command to install Telnet on Debian 11

The packages to install Telnet are available via the base repository of Debian 11 Bullseye. Hence, simply use the given command to install it using the APT package manager.

sudo apt install telnetd telnet

 

3. Check Service status

Once the installation is completed, you can use the status command to check Telnet service is running in backgrounds without any error.

systemctl status inetd

To start or enable:

sudo systemctl status inetd
sudo systemctl enable inetd

Check Telnet Service

 

4. Open Port 23 on Debian 11 Linux

In case you have Firewall installed and enabled on your Debian 11 then open port 23 in it to allow Telnet to connect remote computers. If you don’t have a firewall and want to install it then see: Install and Configure UFW on Debian 11

sudo ufw allow 23/tcp

Whereas Debian 11 servers on Cloud services, users have to open port 23 in their service provider’s network firewall instead of the OS.

 

5. Telnet command tool

To use the Telnet shell client on the Debian 11 where you have installed it, just run the given command:

telnet

After the above command uses the h option to get a list of all options that can be used with it.

Telnet command tool to access

 

6. Access remote Telnet server

Now, you can access the Debian 11 server remotely using the Telnet client on your local machine or vice versa.

For example, let’s say I am using an Oracle Linux (RHEL based OS) and want to access Debian 11 remotely via telnet. Then first the client must be installed on my local Oracle Linux and server part on remote Debian which we did above.

sudo dnf install telnet

Then use the given syntax:

telnet your-debian-server-ip

For example, if the IP address is 192.168.1.41, the command will be:

telnet 192.168.1.42

sudo dnf install telnet

And the same can be done from Debian as well if Telnet has been installed on Oracle or any other Linux.

Access remote Telenet server debian

To exit simply type:

exit

 

 



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