By default root is not allowed to login through telnet for security reasons. 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.
To verify root is disabled we can check the config file /etc/xinetd.d/telnet. When the parameter disable is set to yes, root user can not telnet into the system.
# vi /etc/xinetd.d/telnet
# 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 = yes
} Enabling root access
To enable root telnet login edit the /etc/xinetd.d/telnet file and set the disable parameter to no.
# vi /etc/xinetd.d/telnet
# 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
} Disabling root access
In case you want to disable the access again, put yes against the disable parameter in the file /etc/xinetd.d/telnet.
# vi /etc/xinetd.d/telnet
# 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 = yes
}