How to install LEMP on Linux mint 18.3

In-between you will be asked to supply root password so just enter password of your wish.

The MySQL database software is now installed, To secure the installation, we can run a simple security script that will ask whether we want to modify some insecure defaults. Begin the script by typing:

linuxhelp ~ # mysql_secure_installation
Securing the MySQL server deployment.

Enter password for user root: 

VALIDATE PASSWORD PLUGIN can be used to test passwords
and improve security. It checks the strength of password
and allows the users to set only those passwords which are
secure enough. Would you like to setup VALIDATE PASSWORD plugin?

Press y|Y for Yes, any other key for No: n
Using existing password for root.
Change the password for root ? ((Press y|Y for Yes, any other key for No) : n

 ... skipping.
By default, a MySQL installation has an anonymous user,
allowing anyone to log into MySQL without having to have
a user account created for them. This is intended only for
testing, and to make the installation go a bit smoother.
You should remove them before moving into a production
environment.

Remove anonymous users? (Press y|Y for Yes, any other key for No) : y
Success.

Normally, root should only be allowed to connect from
' localhost' . This ensures that someone cannot guess at
the root password from the network.

Disallow root login remotely? (Press y|Y for Yes, any other key for No) : y
Success.

By default, MySQL comes with a database named ' test'  that
anyone can access. This is also intended only for testing,
and should be removed before moving into a production
environment.

Remove test database and access to it? (Press y|Y for Yes, any other key for No) : y
 - Dropping test database...
Success.

 - Removing privileges on test database...
Success.

Reloading the privilege tables will ensure that all changes
made so far will take effect immediately.

Reload privilege tables now? (Press y|Y for Yes, any other key for No) : y
Success.

All done!

Installing PHP

After Nginx and MySQL are installed, you need to install PHP by making use of the following command.

linuxhelp ~ # apt-get install php-fp mphp-mysql
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  php-common php7.0-cli php7.0-common php7.0-fpm php7.0-json php7.0-mysql php7.0-opcache php7.0-readline
Suggested packages:
  php-pear 
.
.
Creating config file /etc/php/7.0/mods-available/pdo_mysql.ini with new version
Setting up php-mysql (1:7.0+35ubuntu6.1) ...
Processing triggers for systemd (229-4ubuntu21) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for php7.0-fpm (7.0.25-0ubuntu0.16.04.1) ...

We now have our PHP components installed, but we need to make a slight configuration change to the setup for a more secure installation. So, Open the main php-fpm configuration file

linuxhelp ~ # vim /etc/php/7.0/fpm/php.ini
search for cgi.fix_pathinfo=0

The above line will be commented out with a semi-colon ( ) and set to " 1" by default.
We will change both of these conditions by uncommenting the line and setting it to " 0" like this:
cgi.fix_pathinfo=0

Once it is done, you need to restart PHP processor by running the following command.

linuxhelp ~ # systemctl restart php7.0-fpm

linuxhelp ~ # vim /etc/nginx/sites-available/default

linuxhelp ~ # nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

linuxhelp ~ # systemctl reload nginx.service

linuxhelp ~ # vim /var/www/html/info.php
And add the following. 
< ?php
phpinfo() 

linuxhelp ~ # systemctl status mysql.service
mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service  enabled  vendor preset: en
   Active: active (running) since Tue 2018-03-20 05:26:45 IST  1min 46s ago
  Process: 1303 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=ex
  Process: 1255 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exit
 Main PID: 1302 (mysqld)
   CGroup: /system.slice/mysql.service
           └─1302 /usr/sbin/mysqld

Mar 20 05:26:30 linuxhelp systemd[1]: Starting MySQL Community Server...
Mar 20 05:26:45 linuxhelp systemd[1]: Started MySQL Community Server.