Why is it getting 502 error when accessing php page?

Question

PHP

I installed ubuntu 20.04, according to this instruction I rolled up the LEMP stack, if we go to the html page, everything is fine, if we go to the php page it knocks out a 502 error. Restarting nginx and the machine as a whole does nothing.

Config /etc/nginx/sites-enabled/default

spoiler

title="">server {
listen 80 default_server;
listen [::]:80 default_server;

# SSL configuration
#
# listen 443 ssl default_server;
# listen [::]:443 ssl default_server;
#
# Note: You should disable gzip for SSL traffic.
# See: https://bugs.debian.org/773332
#
# Read up on ssl_ciphers to ensure a secure configuration.
# See: https://bugs.debian.org/765782
#
# Self signed certs generated by the ssl-cert package
# Don't use them in a production server!
#
# include snippets/snakeoil.conf;

root /var/www/html;

# Add index.php to the list if you are using PHP
index index.html index.htm index.nginx-debian.html;

server_name _;

location / {
# First attempt to serve request as file, then
# as directory, then fall back to displaying a 404.
try_files $uri $uri/ =404;
}

location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
}

location ~ /\.ht {
deny all;
}
}

# Virtual Host configuration for example.com
#
# You can move that to a different file under sites-available/ and symlink that
# to sites-enabled/ to enable it.
#
server {

server_name domain.com;

root /var/www/main;
index index.html;

location / {
try_files $uri $uri/ =404;
}

listen [::]:443 ssl; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/domain.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/domain.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot}

location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
}

location ~ /\.ht {
deny all;
}
}
server {
if ($host = domain.com) {
return 301 https://$host$request_uri;
} # managed by Certbot

listen 80;
listen [::]:80;

server_name domain.com;
return 404; # managed by Certbot

}

server {
if ($host = file.domain.com) {
return 301 https://$host$request_uri;
} # managed by Certbot

listen 80;
listen [::]:80;

server_name file.domain.com;
return 404; # managed by Certbot

}

server {
if ($host = test.domain.com) {
return 301 https://$host$request_uri;
} # managed by Certbot

listen 80;
listen [::]:80;

server_name test.domain.com;
return 404; # managed by Certbot

}

server {

server_name file.domain.com;

root /var/www/file;
index index.html;

location / {
try_files $uri $uri/ =404;
}
location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
}

location ~ /\.ht {
deny all;
}
listen [::]:443 ssl; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/file.domain.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/file.domain.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

}

server {

server_name test.domain.com;

root /var/www/file;
index index.html;

location / {
try_files $uri $uri/ =404;
}
location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
}

location ~ /\.ht {
deny all;
}
listen [::]:443 ssl; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/file.domain.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/file.domain.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

}

Do not judge the config, the machine is purely for testing =)

Answer 1

502 error - this is not to nginx, but to the one who is behind it. In your case, apparently - to PHP. Either the processing is incorrectly configured in the web server, or something with the PHP itself or the script.

Answer 2

Because php-fpm didn't respond. And why did not answer, look in his logs.