How to secure your Linux ?

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There are four common and useful methods for you to secure and check your Linux.

• Port Scan
• Firewall
• Update Security package
• Antivirus

Port Scan

You can check your system by scanning your port number. Once you find out some ports that are open and not used, remember to close them and stop their related services accordingly.

• Install port scan tool
  sudo install nmap
  
• Execute Port Scan command to scan Port from 1 to 65535
  nmap -p 1-65535 -T4 -A -v [Target IP]
  

Firewall

The fundamental rule to improve the security of your Linux is your system merely opens necessary and required ports for your services. I strongly recommend you to set up restrictions on port 22 to avoid being attacked by SSH Brute Force. Hopefully, DenyHost is a smart firewall that can automatically parse SSH Log and detect malicious IPs to setup block rules for you. 

• Install DenyHost

Update Security package

Update your system with latest security packages automatically.

Install this package if it isn't already installed using
sudo apt-get install unattended-upgrades

To enable it type
sudo dpkg-reconfigure unattended-upgrades

and select "yes".

AntiVirus

Scan and check your system regularly with the following antivirus software.

• Install Virus
  sudo apt-get install clamav
  
• Update Virus code
  sudo freshclam
  
• Scan system
  sudo clamscan --remove=yes -i -r ./
  

Apache Problem due to (24)Too many open files - Solution

After running web services on Apache for few years, my web suddenly could not be accessed because of given an error "HTTP WARNING: HTTP/1.1 403 Forbidden".

When checking the Apache Error log, I found an error message as shown below.

(24)Too many open files: /var/www/html/.htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable

The solution to this problem is to increase the maximum number of open files and user processes by the following settings.


vim /etc/security/limits.conf 
root soft nofile 32768 
root hard nofile 32768 
root soft nproc 4096  
root hard nproc 4096

How to Build an Android Project using Cocos2d-x 3.6 with Eclipse ?

1.Install

Download and install the following libs and SDKs.

    JDK   

        http://www.oracle.com/technetwork/java/javase/downloads/index.html

    Android SDK  

        http://developer.android.com/sdk/installing/index.html?pkg=tools

    Android NDK 10e

        http://dl.google.com/android/repository/android-ndk-r10e-darwin-x86_64.zip

    Apache Ant 

        http://ant.apache.org/bindownload.cgi

2. Configure settings using Eclipse 

Goto Eclipse --> Preference --> C/C++ --> Build --> Environment 

Edit the following settings as shown below.

ANDROID_SDK_ROOT

/Users/User/Applications/Android/sdk

ANR_ROOT

/Users/User/Desktop/cocos2d-x/apache-ant-1.9.7/bin

COCOS_CONSOLE_ROOT

/Users/User/Desktop/cocos2d-x/cocos2d-x-3.6/tools/cocos2d-console/bin

NDK_ROOT

/Users/User/Desktop/cocos2d-x/android-ndk-r10e

PATH

/usr/bin:/bin:/usr/sbin:/sbin:/Users/User/Desktop/cocos2d-x/cocos2d-x-3.6/tools/cocos2d-console/bin

Edit NDK location 

3. Import Cocos2d-x Lib

3.1 In Package Explorer, click import button --> Android --> Existing Android Code Into Workspace 

3.2 Select Cocos2d-x-3.6 --> cocos --> platform --> android --> java

4. Import Source Codes

4.1 Click import button --> Android --> Existing Android Code Into Workspace  --> select your android source codes project 

4.2  Check your project have a link to Cocos2d-x lib

Select your project --> Properties --> Android --> Library 

 

5. Run Configuration 

5.1. Goto Run --> Configurations --> Android Application  --> Tab Android

Name   :  Your Name 

Project :  Click Browse button and select the path of your Source Code

5.2. Goto Run --> Configurations --> Android Application  --> Tab Target 

Run on Android devices 

Check option - Launch on all compatible devices/AVDs

Run on Simulator 

Check option - Automatically pick compatible device : Always uses preferred AVD if set below, launches on compatible device/ AVD otherwise.

5.3. Execute Run button