Hi,
My nginx was running. Then I made so changes in defualt file. Now its not running. I am working on Ubuntu 18.04. I am posting all the details here:

$ sudo service nginx restart
Job for nginx.service failed because the control process exited with error code.
See "systemctl status nginx.service" and "journalctl -xe" for details.



$ systemctl status nginx.service
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: en
Active: failed (Result: exit-code) since Sat 2019-05-25 13:35:03 CDT; 19min a
Docs: man:nginx(8)
Process: 3220 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code
Process: 3219 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process

May 25 13:35:01 lc2530hz nginx[3220]: nginx: [emerg] bind() to 0.0.0.0:80 failed
May 25 13:35:01 lc2530hz nginx[3220]: nginx: [emerg] bind() to [::]:80 failed (9
May 25 13:35:02 lc2530hz nginx[3220]: nginx: [emerg] bind() to 0.0.0.0:80 failed
May 25 13:35:02 lc2530hz nginx[3220]: nginx: [emerg] bind() to [::]:80 failed (9
May 25 13:35:02 lc2530hz nginx[3220]: nginx: [emerg] bind() to 0.0.0.0:80 failed
May 25 13:35:02 lc2530hz nginx[3220]: nginx: [emerg] bind() to [::]:80 failed (9
May 25 13:35:03 lc2530hz nginx[3220]: nginx: [emerg] still could not bind()
May 25 13:35:03 lc2530hz systemd[1]: nginx.service: Control process exited, code
May 25 13:35:03 lc2530hz systemd[1]: nginx.service: Failed with result 'exit-cod
May 25 13:35:03 lc2530hz systemd[1]: Failed to start A high performance web serv
lines 1-17/17 (END)



$ journalctl -xe
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- Unit phpsessionclean.service has finished starting up.
--
-- The start-up result is RESULT.
May 25 13:42:32 lc2530hz systemd[1]: Starting Message of the Day...
-- Subject: Unit motd-news.service has begun start-up
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- Unit motd-news.service has begun starting up.
May 25 13:42:32 lc2530hz systemd[1]: Started Message of the Day.
-- Subject: Unit motd-news.service has finished start-up
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- Unit motd-news.service has finished starting up.
--
-- The start-up result is RESULT.
May 25 13:42:53 lc2530hz org.gnome.Shell.desktop[1989]: (/usr/lib/firefox/firefo
May 25 13:42:58 lc2530hz systemd-resolved[782]: Server returned error NXDOMAIN,
May 25 13:47:19 lc2530hz /usr/lib/gdm3/gdm-x-session[1855]: (II) event5 - PixAr
lines 1576-1598/1598 (END)

$ nginx -t
nginx: [alert] could not open error log file: open() "/var/log/nginx/error.log" failed (13: Permission denied)
2019/05/25 14:01:03 [warn] 3564#3564: the "user" directive makes sense only if the master process runs with super-user privileges, ignored in /etc/nginx/nginx.conf:1
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
2019/05/25 14:01:03 [emerg] 3564#3564: open() "/run/nginx.pid" failed (13: Permission denied)
nginx: configuration file /etc/nginx/nginx.conf test failed
zulfi@lc2530hz:/etc/nginx/sites-enabled$


/etc/nginx/sites-enabled$ cat default
##
# You should look at the following URL's in order to grasp a solid understanding
# of Nginx configuration files in order to fully unleash the power of Nginx.
# https://www.nginx.com/resources/wiki/start/
# https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/
# https://wiki.debian.org/Nginx/DirectoryStructure
#
# In most cases, administrators will remove this file from sites-enabled/ and
# leave it as reference inside of sites-available where it will continue to be
# updated by the nginx packaging team.
#
# This file will automatically load configuration files provided by other
# applications, such as Drupal or Wordpress. These applications will be made
# available underneath a path with that package name, such as /drupal8.
#
# Please see /usr/share/doc/nginx-doc/examples/ for more detailed examples.
##

# Default server configuration
#
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.php 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;
}

# pass PHP scripts to FastCGI server
#
location ~ \.php$ {
# include snippets/fastcgi-php.conf;
#
# # With php-fpm (or other unix sockets):
fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
# # With php-cgi (or other tcp sockets):
# fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
include fastcgi_params;
}

# deny access to .htaccess files, if Apache's document root
# concurs with nginx's one
#
#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 {
# listen 80;
# listen [::]:80;
#
# server_name example.com;
#
# root /var/www/example.com;
# index index.html;
#
# location / {
# try_files $uri $uri/ =404;
# }
#}
user@lc2530hz:/etc/nginx/sites-enabled$

Can somebody please guide me.

Zulfi.