centos 7 禁止root登录及更改ssh端口号

vim /etc/ssh/sshd_config
PermitRootLogin yes => PermitRootLogin no
PasswordAuthentication yes => PasswordAuthentication no
RSAAuthentication yes
PubkeyAuthentication yes
systemctl restart sshd.service

netstat -tulnp|grep sshd
vim /etc/ssh/sshd_config
Port 22 => Port 20000
systemctl restart sshd.service
netstat -tulnp|grep sshd

vim /etc/ssh/sshd_config
#ClientAliveInterval 180 => ClientAliveInterval 180
#ClientAliveCountMax 3 => ClientAliveCountMax 3
systemctl restart sshd.service
netstat -tulnp|grep sshd