How to configure Telnet in Linux

For security reasons, It is advised to use secure SSH rather than Telnet to connect to a server. When you use Telnet, your passwords are sent through the network in plain text. As a result, the root user is not permitted to use Telnet by default.

• Make sure you have the necessary telnet-server and telnet RPMs installed before using Telnet.

# rpm -qa | grep telnet
telnet-server-3.13-26.EL8
telnet-3.13-26.EL8

• If you don’t have the telnet-server or telnet packages installed, you can use the RPMs from your installation disk to install them, or you can use the yum program to download and install the package.

# up2date telnet-server telnet

# yum install telnet-server telnet

• Add the service to firewalld.

# firewall-cmd --add-service=telnet --zone=public

• If you want to keep this rule permanent, add the –permanent flag to the command.

# firewall-cmd --add-service=telnet --zone=public --permanent

• Reload the firewall rules.

# firewall-cmd --reload

• Add the service to SELinux (not required with selinux-policy-3.12.1-77 or later)

# semanage port -a -t telnetd_port_t -p tcp 23

• Start and Enable the telnet service

# systemctl start telnet.socket
# systemctl enable telnet.socket
or
# systemctl enable telnet.socket --now

• Test the telnet server.

# telnet server2
Trying 3.3.3.3...
Connected to 3.3.3.3.
Escape character is '^]'.Kernel 3.10.0-327.el7.x86_64 on an x86_64
server2 login: telnet-user
Password: