Add a Limited User Account
Accessing your server as the root user will have unlimited privileges and can execute any command–even one that could accidentally disrupt your server. We advise you to create limited user accounts and using them to access your server. Administrative tasks will be done using sudo to temporarily elevate your limited user’s privileges to super user.
Create user
adduser example_user adduser example_user sudo
Switch to user account and create the authorized key file (this file should be populated with the public ssh key with which the user can log in into the server). Be very careful to verify your public key is properly copied in authorized keys file. After this process if the key is not properly copied you will loose access to the server.
su example_user cd ~ mkdir -p ~/.ssh && sudo chmod -R 700 ~/.ssh/ && cd .ssh/ && vim authorized_keys
Make the root account not accessible for direct login and make the server accessible only through ssh key
sudo vim /etc/ssh/sshd_config PermitRootLogin no PasswordAuthentication no
Remove Password as a requirement to run sudo commands
sudo visudo %sudo ALL=(ALL) NOPASSWD:ALL or example_user ALL=NOPASSWD: ALL
Restart the ssh service for the changes to take affect
sudo service ssh restart
Checking Config errors in Nginx
nginx -t -c /etc/nginx/nginx.conf