Category: Server

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How to set the correct Android *.apk MIME Type for Apache Webserver

Android application uses *.apk file as its installation package. It is a variant of the Java JAR file format (which in turn a Zip 2.0 file). Usually the *.apk file is obtained from Android Marketplace, the official channel for getting Android application. However there are some vendors or carriers that allow *.apk file to be downloaded from 3rd-party websites.

Those who elect to upload the *.apk files on their own webserver can add the official Android APK MIME Type to their Apache Web server config file:

Option 1: edit mime.types (for those who have root access)
1. First edit the mime.types file – sudo nano /etc/apache2/mime.types
2. Then add this at the end of the file – application/vnd.android.package-archive
3. Reload the server configuration – “sudo service apache2 reload”
Option 2: edit .htaccess file (for shared server or user who do not have root access)
1. Edit .htaccess
2. Add this line – AddType application/vnd.android.package-archive

This will register the appropriate MIME type for the *.apk file so that both the server and mobile application can handle.

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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 192.168.1.1-192.168.1.254


iptables -A INPUT -i eth0 -p tcp -s 192.168.1.0/24 --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!

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How to: Quick and Dirty Web Server Load Balancing with IPTables in Linux

Load balancing is a method to distribute workload across multiple computer over a network. The purpose of load balance in web server is to avoid one web server from being overwhelmed by requests which eventually leads the machine to come down to a crawling halt.

Assuming that you have 3 web server to assign the load to each with this IP Address:
10.20.20.1
10.20.20.2
10.20.20.3

You can drive the traffic to each of this on every third packet with this iptables rules:

iptables -A PREROUTING -i eth0 -p tcp --dport 80 -m state --state NEW -m nth --counter 0 --every 3 --packet 0 -j DNAT --to-destination 10.20.20.1:80

iptables -A PREROUTING -i eth0 -p tcp --dport 80 -m state --state NEW -m nth --counter 0 --every 3 --packet 1 -j DNAT --to-destination 10.20.20.2:80

iptables -A PREROUTING -i eth0 -p tcp --dport 80 -m state --state NEW -m nth --counter 0 --every 3 --packet 2 -j DNAT --to-destination 10.20.20.3:80

This will ensure that every 3rd packet of the request will be properly distributed among the three servers to balance the load. Note that this is only useful in simple website which serves static content or for a download servers that serve large files over the internet (CD or DVD iso downloading)

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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:

127.0.0.1 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