How To Install Telnet On Linux

Setting up telnet on Linux involves using your package manager to install the client and configuring the service to start automatically. This guide will show you exactly how to install telnet on linux step by step, covering both the client and server components for major distributions.

Understanding Telnet And Its Use Cases

Telnet is a network protocol that lets you connect to remote computers over a TCP/IP network. It’s been around since the early days of the internet and remains useful for testing network services and accessing legacy systems.

However, telnet sends all data—including passwords—in plain text. That’s why modern systems prefer SSH for secure remote access. But for troubleshooting, testing port connectivity, or managing older equipment, telnet still has its place.

You might need telnet to check if a specific port is open on a server, test SMTP or HTTP services manually, or connect to network devices like routers and switches that don’t support SSH.

Telnet Client Vs Telnet Server

There are two parts to telnet: the client and the server. The client is the program you use to connect to remote systems. The server runs on the machine you want to access remotely.

Most Linux distributions don’t install telnet by default. You’ll need to install the client, the server, or both depending on your needs.

For security reasons, only install the telnet server if you absolutely need it. Consider using SSH instead whenever possible.

Prerequisites For Installing Telnet On Linux

Before you start, make sure you have:

A Linux system (Ubuntu, Debian, CentOS, RHEL, Fedora, or similar)
Sudo or root access to install packages
An active internet connection to download packages
Basic familiarity with the terminal

That’s all you need. The installation process is straightforward and takes just a few minutes.

Now let’s get into the main process. The exact commands depend on your Linux distribution, but the general approach is the same.

Installing Telnet On Ubuntu And Debian

Ubuntu and Debian use the APT package manager. Open your terminal and run:

Update your package list: sudo apt update
Install the telnet client: sudo apt install telnet -y
If you need the server: sudo apt install telnetd -y
Verify the installation: telnet --version

That’s it. The telnet client is now ready to use. You can test it by connecting to a remote host.

For the server, after installing telnetd, the service starts automatically. You can check its status with sudo systemctl status telnetd.

Installing Telnet On CentOS And RHEL 7/8

CentOS and RHEL use YUM or DNF package managers. Here’s how:

For CentOS 7: sudo yum install telnet telnet-server -y
For CentOS 8 or RHEL 8: sudo dnf install telnet telnet-server -y
Enable the telnet service: sudo systemctl enable telnet.socket
Start the service: sudo systemctl start telnet.socket
Check status: sudo systemctl status telnet.socket

On CentOS/RHEL, the telnet server uses systemd socket activation. This means the service only starts when a connection is received, which is more efficient.

Installing Telnet On Fedora

Fedora uses DNF. The process is similar to CentOS 8:

Install both client and server: sudo dnf install telnet telnet-server -y
Enable the socket: sudo systemctl enable telnet.socket
Start the socket: sudo systemctl start telnet.socket
Verify: sudo systemctl status telnet.socket

Fedora’s default firewall might block telnet. You’ll need to allow port 23 through the firewall if you want external connections.

Installing Telnet On OpenSUSE

OpenSUSE uses Zypper. Run these commands:

sudo zypper refresh
sudo zypper install telnet telnetd
Start the service: sudo systemctl start telnetd
Enable at boot: sudo systemctl enable telnetd

OpenSUSE might require you to configure the firewall manually. We’ll cover that in the next section.

Configuring Telnet Server After Installation

Once you’ve installed the telnet server, you need to configure it properly for security and functionality.

Starting And Enabling The Telnet Service

On systemd-based distributions, use these commands:

Start the service: sudo systemctl start telnetd or sudo systemctl start telnet.socket
Enable at boot: sudo systemctl enable telnetd or sudo systemctl enable telnet.socket
Check status: sudo systemctl status telnetd

If the service doesn’t start, check the logs with journalctl -u telnetd for error messages.

Configuring Firewall For Telnet

Telnet uses port 23. You need to allow this port through your firewall.

For UFW (Ubuntu/Debian):

sudo ufw allow 23/tcp
sudo ufw reload

For firewalld (CentOS/RHEL/Fedora):

sudo firewall-cmd --add-port=23/tcp --permanent
sudo firewall-cmd --reload

For iptables:

sudo iptables -A INPUT -p tcp --dport 23 -j ACCEPT
Save the rules: sudo iptables-save

Always restrict telnet access to trusted networks if possible. Use firewall rules to limit which IPs can connect.

Configuring Telnet For Remote Access

By default, telnet might only listen on localhost. To allow remote connections, edit the telnet configuration file.

On most systems, the configuration is in /etc/xinetd.d/telnet or /etc/inetd.conf. Look for a line like:

telnet stream tcp nowait telnetd /usr/sbin/tcpd /usr/sbin/in.telnetd

Make sure the disable option is set to no if using xinetd. Then restart the service.

For security, consider using TCP wrappers (/etc/hosts.allow and /etc/hosts.deny) to control access.

Testing Your Telnet Installation

After installation, test that everything works correctly.

Testing Telnet Client Locally

Connect to localhost to verify the server is running:

telnet localhost

You should see a login prompt. Enter your username and password to test authentication.

If you get “Connection refused,” the server isn’t running or the port is blocked.

Testing Telnet To A Remote Server

To connect to a remote system, use:

telnet [remote_ip_address] [port]

For example, to test port 80 on a web server:

telnet 192.168.1.100 80

If the port is open, you’ll see a blank screen or a service banner. Press Ctrl+] then type “quit” to exit.

Common Telnet Connection Errors

Here are typical issues and their solutions:

Connection refused: The service isn’t running or the port is blocked by firewall
Name or service not known: The hostname is incorrect or DNS is not working
Connection timed out: Network issues or firewall blocking the connection
Login incorrect: Wrong username or password, or the account doesn’t have shell access

Double-check your firewall rules and service status if you encounter errors.

Security Considerations When Using Telnet

Telnet is inherently insecure. Here’s what you need to know.

Why Telnet Is Considered Insecure

Telnet transmits everything in plain text. This includes:

Usernames and passwords
Commands you type
Output from the remote system
Any files you transfer

Anyone on the network can capture this data using tools like Wireshark. That’s why SSH is the preferred choice for remote access.

Best Practices For Secure Telnet Usage

If you must use telnet, follow these guidelines:

Only use telnet on trusted, isolated networks
Never use telnet over the internet
Use strong passwords for telnet accounts
Restrict telnet access via firewall rules
Disable telnet when not in use
Consider using SSH tunnels to encrypt telnet traffic
Monitor telnet logs for unauthorized access

Remember, telnet is a tool for specific situations, not a general-purpose remote access solution.

Uninstalling Telnet When No Longer Needed

When you’re done with telnet, remove it to reduce security risks.

On Ubuntu/Debian:

sudo apt remove telnet telnetd -y
sudo apt autoremove -y

On CentOS/RHEL:

sudo yum remove telnet telnet-server -y

On Fedora:

sudo dnf remove telnet telnet-server -y

Also remove firewall rules for port 23 if they’re no longer needed.

Troubleshooting Common Telnet Issues

Even with proper installation, you might run into problems. Here’s how to fix them.

Telnet Command Not Found

If you get “command not found,” the telnet client isn’t installed. Run the installation command for your distribution again.

Make sure you installed the client package, not just the server.

Connection Refused Error

This usually means the telnet server isn’t running or the port is blocked. Check:

Service status: sudo systemctl status telnetd
Firewall rules: sudo ufw status or sudo firewall-cmd --list-all
Port listening: sudo netstat -tulpn | grep :23

If the service is running but still refusing connections, check the configuration files for errors.

Slow Telnet Connections

Telnet can feel sluggish due to DNS lookups. To speed it up, disable DNS resolution:

telnet -n [host] [port]

Or add the remote host’s IP to your /etc/hosts file.

Telnet Session Freezes Or Hangs

This often happens when the connection drops unexpectedly. Press Ctrl+] to get the telnet prompt, then type “close” to exit.

You can also set a timeout in your telnet client configuration.

Alternatives To Telnet For Remote Access

While telnet is useful, consider these more secure alternatives.

SSH (Secure Shell)

SSH encrypts all traffic, including authentication. It’s the standard for remote access on Linux.

Install SSH: sudo apt install openssh-server (Ubuntu) or sudo yum install openssh-server (CentOS)

Connect: ssh user@remote_host

Netcat For Port Testing

Netcat (nc) is great for testing ports without the security risks of telnet.

Install: sudo apt install netcat

Test port: nc -zv remote_host 80

Nmap For Network Scanning

Nmap can check multiple ports at once and identify services running on them.

Install: sudo apt install nmap

Scan: nmap -p 23 remote_host

Frequently Asked Questions

Is Telnet Installed By Default On Linux?

No, most modern Linux distributions do not install telnet by default due to security concerns. You need to install it manually using your package manager.

Can I Install Telnet Without Internet Access?

Yes, you can download the telnet package files from a system with internet and transfer them via USB or local network. Use apt-get download telnet on Ubuntu or yumdownloader telnet on CentOS to get the .deb or .rpm files.

How Do I Check If Telnet Is Already Installed?

Run which telnet or telnet --version in the terminal. If you get a path or version number, telnet is installed. If you see “command not found,” it’s not installed.

What Port Does Telnet Use?

Telnet uses TCP port 23 by default. You can specify a different port when connecting with telnet host port.

Is It Safe To Use Telnet For Testing Purposes?

Yes, for testing on local networks or isolated environments, telnet is fine. Just avoid using it over public networks or the internet where traffic can be intercepted.

Conclusion

Installing telnet on Linux is a simple process that takes just a few commands. Whether you need the client for testing or the server for legacy system access, the steps are straightforward across all major distributions.

Remember the security implications of using telnet. Always prefer SSH for remote access, and only use telnet when absolutely necessary. Keep your firewall rules tight and disable telnet when you’re done.

With this guide, you now know how to install telnet on linux, configure it properly, and troubleshoot common issues. Use this knowledge responsibly and your Linux system will serve you well.