How to limit MySQL port access to specific network

MySQL service port are not meant to be accessible to the outside world as it would become a security concern to the administrator.

Although MySQL server (mysqld) by itself has a built-in mechanism to deny access from unauthorized ip-address, it still does not protect it from being overwhelmed by multiple malicious requests or buffer overflow attack directed to the server.

One of the solution is to limit the MySQL port access to trusted network using iptables

This assume your trusted network has the address within the range of

iptables -A INPUT -i eth0 -p tcp -s --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp --sport 3306 -m state --state ESTABLISHED -j ACCEPT

MySQL server (mysqld) uses port 3306.

Note: Always assume the internet as the untrusted network!

How to solve Apache – Could not reliably determine the server’s fully qualified name – error in Ubuntu

Apache2 web server will almost always display this information message :
"Could not reliably determine the server's fully qualified name"
when it is first started in Ubuntu and Debian server.

The reason behind this message is because the web server fails to find the suitable domain name in the system.

How to remove the message
First, you need to edit “/etc/hosts” file and put your server name of choice in the file. For example: server.mylocal

Then you need to add “ServerName” directive in the “/etc/apache2/apache2.conf” file.

ServerName server.mylocal

Finally, restart the web server for the changes to take effect. You will notice that the information message is gone now.

$ sudo service apache2 restart