Nginx will not start (Address already in use)

Question

Probably other process is using specified port:

sudo netstat -tulpn

Get the PID of the process that already using 443. And send signal with kill command.

sudo kill -2 <PID>

sudo service nginx restart

Aternatively you can do:

sudo fuser -k 443/tcp

Make sure you dont use old syntax:

server {
    listen :80;
    listen [::]:80;
}

The above syntax will cause

nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)

Correct syntax:

server {
    listen 80;
    listen [::]:80 ipv6only=on;
}

or

server {
    listen [::]:80;
}

Both above syntax will achieve the same thing, listening on both ipv4 and ipv6.