Linux prohibits direct login of root account The default administrator of Linux is root. You only need to know the ROOT password to log in to SSH directly. Disabling Root from logging in directly from SSH can improve server security. 1、 New Account #useradd admin 2、 Set account password #passwd admin 3、 Do not allow root to log in directly 1. Modify related documents #vi /etc/ssh/sshd_config 2. Disable root login Find "# PermitRootLogin yes", remove the previous "#", change the latter "Yes" to "No", save the file, and restart # reboot. 4、 Login 1. First, use the new account "admin" to log in as an ordinary user. (Using root will deny login) 2. To obtain ROOT permission, execute the following command in SSH #su root Execute the above command and enter the root password to obtain root permission. 5、 When SFTP logs in as admin, folders such as root cannot be opened.

 SSH port modification under Linux 1： Statistics of SSH login failures: #cat /var/log/secure|awk '/Failed/{print $(NF-3)}'|sort|uniq -c|awk '{print $2"="$1;}' 2： # vi/etc/ssh/sshd_config (Modify Configuration File) First remove the # in front of Port 22 and start a new line. Define the SSH port number as 2039, then enter Port 2039 (# is the comment character of Linux) For the above operations, manually specify the SSH ports as 22 and 2039 (dual port slogans). 22 is reserved to prevent individual firewalls from blocking other ports and making VPS connection impossible. 3： Restart SSH. CentOS Restart SSH: service sshd restart DeBian restarts SSH: service ssh restart 4： If all can be accessed normally, delete the original Port 22 according to the operation in Step 2, and then restart SSH according to Step 3.