準備篇：

1、配置防火墻，開啟80端口、3306端口

說明：Ubuntu默認安裝是沒有開啟任何防火墻的，為了服務器的安全，建議大家安裝啟用防火墻設置，這里推薦使用iptables防火墻。
whereis iptables #查看系統是否安裝防火墻
iptables: /sbin/iptables /usr/share/iptables /usr/share/man/man8/iptables.8.gz #表示已經安裝iptables
apt-get install iptables #如果默認沒有安裝，請運行此命令安裝防火墻
iptables -L #查看防火墻配置信息，顯示如下：

#####################################################
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination
#####################################################
nano /etc/iptables.default.rules #添加以下內容
##################################################################################################
*filter
# Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT
# Accepts all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Allows all outbound traffic
# You could modify this to only allow certain traffic
-A OUTPUT -j ACCEPT
# Allows HTTP and MySQLconnections from anywhere (the normal ports for websites)
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp --dport 3306 -j ACCEPT
# Allows SSH connections for script kiddies
# THE -dport NUMBER IS THE SAME ONE YOU SET UP IN THE SSHD_CONFIG FILE
-A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT
# Now you should read up on iptables rules and consider whether ssh access
# for everyone is really desired. Most likely you will only allow access from certain IPs.
# Allow ping
-A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT
# log iptables denied calls (access via 'dmesg' command)
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7
# Reject all other inbound - default deny unless explicitly allowed policy:
-A INPUT -j REJECT
-A FORWARD -j REJECT
COMMIT
##################################################################################################
ctrl+o #保存
ctrl+x #退出

備注：80是指web服務器端口、3306是指MySQL數據庫鏈接端口、22是指SSH遠程管理端口
iptables-restore < /etc/iptables.default.rules #使防火墻規則生效
nano /etc/network/if-pre-up.d/iptables #創建文件，添加以下內容，使防火墻開機啟動
##########################################################
#!/bin/bash
/sbin/iptables-restore </etc/iptables.default.rules
##########################################################
chmod +x /etc/network/if-pre-up.d/iptables #添加執行權限