How do I change the NGINX user?

Run nginx & php-fpm as www:www

###1. Nginx

Edit nginx.conf and set user to www www;:

user www www;

If the master process is run as root, then nginx will setuid()/setgid() to USER/GROUP. If GROUP is not specified, then nginx uses the same name as USER. By default it's nobody user and nobody or nogroup group or the --user=USER and --group=GROUP from the ./configure script.

###2. PHP-FPM

Edit php-fpm.conf and set user and group to www:

[www]
user=www
group=www

user - Unix user of processes. Default "www-data"

group - Unix group of processes. Default "www-data"

In Ubuntu 14.04 the file to change user and group in PHP-FPM is: /etc/php5/fpm/pool.d/www.conf. In this file change these parameters:

user = www
group = www
listen.owner = www
listen.group = www

To answer your actual question is to just change the user line in nginx.conf like so:

user    [username];

Example:

user    www-data;

The preferred user for Nginx to run as actually differs between operating systems. Sometimes Nginx is supposed to run as www-data. Other times it is actually supposed to run as nobody.

On some operating systems (such as Windows), it doesn't even matter, and the user line in nginx.conf can be commented out or entirely excluded.

The following solution worked changing the web user with me using Ubuntu 18.04 LTS, nginx 1.14 and php7.2-fpm.

1. Nginx

Edit /etc/nginx/nginx.conf and set the user to webuser;

user webuser;

2. PHP-FPM

Edit /etc/php/7.2/fpm/pool.d/www.conf.

user = webuser
group = webuser
...
listen.owner = webuser
listen.group = webuser