Bsrgvty

I need to restart the process. What do I do when I keep seeing these messages? Do you need more commands?

$ nginx
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] still could not bind()

$ service nginx start
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: enabled)
 Active: failed (Result: exit-code) since Wed 2019-05-29 13:28:29 KST; 26s ago
 Process: 24508 ExecStop=/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid (code=exited, status=0/SUCCESS)
 Process: 31955 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=1/FAILURE)
 Process: 31952 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
 Main PID: 13077 (code=exited, status=0/SUCCESS)

May 29 13:28:27 ip-172-26-12-170 nginx[31955]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
May 29 13:28:27 ip-172-26-12-170 nginx[31955]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
May 29 13:28:28 ip-172-26-12-170 nginx[31955]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
May 29 13:28:28 ip-172-26-12-170 nginx[31955]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
May 29 13:28:29 ip-172-26-12-170 nginx[31955]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
May 29 13:28:29 ip-172-26-12-170 nginx[31955]: nginx: [emerg] still could not bind()
May 29 13:28:29 ip-172-26-12-170 systemd[1]: nginx.service: Control process exited, code=exited status=1
May 29 13:28:29 ip-172-26-12-170 systemd[1]: Failed to start A high performance web server and a reverse proxy server.
May 29 13:28:29 ip-172-26-12-170 systemd[1]: nginx.service: Unit entered failed state.
May 29 13:28:29 ip-172-26-12-170 systemd[1]: nginx.service: Failed with result 'exit-code'.

A application is currently listening on the on port 80. Most likely it is a other instance of nginx.

Find application that is listening on the socket

With the netstat command you can find the application which is currently listening on the socket. Also use grep to filter the output of netstat.

$ netstat -lpn | grep 80
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 780/nginx: master p 
tcp6 0 0 :::80 :::* LISTEN 780/nginx: master p

The last entry of the list 780/nginx tells you the PID of the process currently listening on the port 80.

Find and kill the application

With ps you can see the process structure of the process using the socket:

$ ps f -g780
 PID TTY STAT TIME COMMAND
 780 ? Ss 0:00 nginx: master process nginx
 781 ? S 0:00 _ nginx: worker process
 782 ? S 0:00 _ nginx: worker process
 783 ? S 0:00 _ nginx: worker process
 784 ? S 0:00 _ nginx: worker process
 785 ? S 0:00 _ nginx: worker process
 786 ? S 0:00 _ nginx: worker process
 787 ? S 0:00 _ nginx: worker process
 788 ? S 0:00 _ nginx: worker process

With the kill command you can now terminate the process which uses the socket:

$ kill 780

If that does not terminate the process with -9:

$ kill -9 780

Then try to restart your nginx service.

In the future, here's something that might come in useful. You can check the syntax of Nginx's configuration files by running:

nginx -t -c /etc/nginx/nginx.conf

The error output will give you a hint at what the problem is as well as the line number.

or:

debug with command:

$ service nginx configtest

Which outputs something like:

Testing nginx configuration: nginx: [emerg] unknown directive "stub_status" in /etc/nginx/sites-enabled/nginx_status:11
nginx: configuration file /etc/nginx/nginx.conf test failed