How to install and configure telnet
TELNET: (TELecommunication NETwork)
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Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet control information in an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP).
Telnet was developed in 1969 beginning with RFC 15, extended in RFC 855, and standardized as Internet Engineering Task Force (IETF) Internet Standard STD 8, one of the first Internet standards. The name stands for "teletype network".
Historically, Telnet provided access to a command-line interface on a remote host. However, because of serious security concerns when using Telnet over an open network such as the Internet, its use for this purpose has waned significantly in favor of SSH.
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How to install and configure telnet
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1. Install Telnet packages:
# yum install telnet-server telnet
2. Configuring/enabling telnet
Add the service to firewalld. The built in firewalld blocks Telnet port 23 by default because the protocol is not considered secure. Please make sure that the port is open or if a non-default port is being used, that the port associated with Telnet is open for telnet traffic to pass through.
# firewall-cmd --add-service=telnet --zone=public
Run the rule again with the “–permanent” flag for it to persist across firewalld restarts.
# firewall-cmd --add-service=telnet --zone=public --permanent
3. Add the service to selinux.
You will have to also add the service to SELinux. This is required only in the case where SELinux is enabled on the system.
# semanage port -a -t telnetd_port_t -p tcp
4. Enable and start the telnet service.
Start the service using the systemctl command.
# systemctl start telnet.socket
5. Enable the telnet service to start at boot.
# systemctl enable telnet.socket
6. Verify
Once you are done with the configuration, verify if the telnet to a server works.
# telnet localhost
Trying 10.10.10.10...
Connected to 10.10.10.10.
Escape character is '^]'.
Kernel 3.10.0-327.el7.x86_64 on an x86_64
localhost login: testuser
Password:
Last login: Sat Jan 23 18:19:43 from localhost
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