nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)解決方案

前提：已經配置好靜態IP
以防萬一，先安裝好iptables服務（無論你裝沒裝，先執行，省得後面添亂）
[root@localhost ~]# yum install iptables-services
[root@localhost ~]# systemctl mask firewalld.service
[root@localhost ~]# systemctl enable iptables.service
[root@localhost ~]# systemctl enable ip6tables.service
進入iptables配置80端口，由於nginx默認是由80端口訪問
[root@localhost ~]# vim /etc/sysconfig/iptables
這是配置信息：
# Generated by iptables-save v1.4.21 on Fri May 12 21:28:29 2017
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [6:696]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 21 -j ACCEPT（我給vsftpd配置的端口）
-A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT（給nginx配置的端口，原樣輸入就好了）
-A INPUT -p tcp -m state --state NEW -m tcp --dport 30000:30999 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
# Completed on Fri May 12 21:28:29 2017
而後:wq，保存退出就好了
重啓iptables，配置才生效
[root@localhost ~]# systemctl restart iptables.service
開啓防火牆，無論你開沒有，再開一遍：
[root@localhost ~]# systemctl start firewalld
開啓http訪問
[root@localhost ~]# firewall-cmd --permanent --add-service=http
加入80端口
[root@localhost ~]# firewall-cmd --permanent --zone=trusted --add-port=80/tcp
啓動nginx！！！！（重點來了！！！）
centOS7的nginx啓動與其餘的有區別！！！注意：我是裝的nginx1.80，在centOS6.X系列中，是經過
cd /usr/local/nginx/sbin/

./nginx 

這兩條命令啓動的。
在Ubuntu中是經過/etc/nginx.....,你會發現你的centOS7裏面，etc下面根本就沒有nginx這個folder！
在centOS7中你會發現這行不通，咱們應該這麼啓動：
[root@localhost ~]# /usr/local/nginx/sbin/nginx
若是發現：
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()
說明80端口被佔用，殺掉這個進程：
[root@localhost ~]# killall -9 nginx
再次啓動nginx：
[root@localhost ~]# /usr/local/nginx/sbin/nginx
查看是否啓動：
[root@localhost ~]# ps aux|grep nginx
輸出：
root       7110  0.0  0.0  24348   752 ?        Ss   22:32   0:00 nginx: master process /usr/local/nginx/sbin/nginx
nobody     7111  0.0  0.0  26860  1508 ?        S    22:32   0:00 nginx: worker process
root       7114  0.0  0.0 112664   968 pts/0    S+   22:33   0:00 grep --color=auto nginx
啓動成功！
訪問nginx
在瀏覽器地址欄輸入你的Linux虛擬機的靜態ip，會跳轉到nginx的歡迎頁面。