安装服务：CentOS7 下安装telnet服务的实现方法

yum -y install xinetd telnet telnet-server 

vi /etc/securetty 

pts/0 
pts/1 

vi /etc/sysconfig/iptables 
-A INPUT -p tcp -m state --state NEW -m tcp --dport 23 -j ACCEPT 

systemctl restart iptables 
systemctl disable firewalld 
systemctl stop firewalld 

systemctl enable telnet.socket 
systemctl start telnet.socket 
systemctl enable xinetd 
systemctl start xinetd