Red Hat Knowledgebase

Red Hat recommends that you use SSH to connect to a system instead of Telnet for security purposes. Passwords are transmitted in plain text when you use Telnet. For this reason, the root user is not allowed to connect using Telnet by default.

In order to turn Telnet on make sure that you have the correct telnet-server and telnet RPMs installed:

# rpm -qa | grep telnet
telnet-server-0.17-26.EL3.2
telnet-0.17-26.EL3.2

The version numbers of the package should not matter, Red Hat Network (RHN) will always provide you with the latest version of the package for your subscribed channel.

If you do not have the telnet-server or telnet packages installed, you can install them with the RPMs available from your installation media or you can use the up2date utility along with your RHN subscription to download and install the package(s). For example:

# up2date telnet-server telnet

On Red Hat Enterprise Linux 5, the command would be as follows:

# yum install telnet-server telnet

Once you have the packages installed, check the /etc/xinetd.d/telnet file and ensure that disable = yes is changed to read disable = no.

# default: on
# description: The telnet server serves telnet sessions; it uses \
#       unencrypted username/password pairs for authentication.
service telnet
{
        flags           = REUSE
        socket_type     = stream

        wait            = no
        user            = root
        server          = /usr/sbin/in.telnetd
        log_on_failure  += USERID
        disable         = no
}

Turn the Telnet server on using the chkconfig command and then make the service available for immediate use with the service command. You will need to restart the xinetd service.

Note: It is not required that you have the specific versions mentioned in the example above in order for this to work. The versions should be specific to your release. You must be root in order to use these commands. Also, if you get "command not found" then you may need to use the full path of the command. For example, to find the full path of the chkconfig command, type which chkconfig and you should get the full path: /sbin/chkconfig.

# chkconfig --list telnet
telnet          off
# chkconfig telnet on
# chkconfig --list telnet
telnet          on
# service xinetd restart
Stopping xinetd:                                           [  OK  ]
Starting xinetd:                                           [  OK  ]

The chkconfig command will make the Telnet server available to start the next time the system is rebooted. You will notice that Telnet is part of the xinetd daemon. In order to make the Telnet service available immediately, use service xinetd restart to restart the xinetd daemon. You should now be able to successfully Telnet to the server:

[root@jaws root]# telnet special-ed
Trying 10.1.1.11...
Connected to special-ed.example.com (10.1.1.11).
Escape character is '^]'.
Red Hat Enterprise Linux AS release 3 (Taroon Update 5)
Kernel 2.4.21-32.ELsmp on an i686
login: jason
Password:
Last login: Sat Jul  2 14:46:57 from jaws