Introduction

When extending ZCS, it is sometimes desirable to add additional LDAP schema to the OpenLDAP server shipped with ZCS. Starting with the 6.0 release, the new config backend is used, which means that the traditional *.schema files are no longer in play. Instead, LDIF-based versions of the old schema files are used by the new config backend. This means that traditional "schema" files need to be converted to the new LDIF format for ZCS to be able to use them.

New layout of the schema directory

It is important to understand how the new LDIF based schema files are used by the cn=config directory. To start, let's examine the contents of the directory:


#FILE: /etc/aliases
root: ravi@yahoo.com


A2billing Tutorials

This document details the basic setup and configuration of a2billing v1.3.3 in Trixbox v2.2 It assumes that no configuration has been performed yet...as in, we are starting with a fresh install.

We are assuming in this tutorial that trixbox 2.2.4 or higher is already installed.

1) A2billing Installation

Log in to your terminal server from the console or SSH with root credentials
and Perform the following commands:

Step1: Removing A2billing Old files

The directories and files to be removed are as follows:

This article is part of the on-going Awk Tutorial Examples series. In our earlier awk articles, we discussed about awk print, awk user-defined variables, awk built-in variables, and awk operators.

In this awk tutorial, let us review awk conditional if statements with practical examples.

Awk supports lot of conditional statements to control the flow of the program. Most of the Awk conditional statement syntax are looks like ‘C’ programming language.

Scenario / Question:

How do I setup freeNX on a remote server system and connect to it.

Solution / Answer:

Installing the freeNX server software on the remote server machine and using the NoMachine freenx client to connect to it from you local machine.

Installing freeNX Server:

On the server you want to control with freeNX

Install freenx using yum:

# yum install nx freenx

Copy minimal configuration file:

# cp /etc/nxserver/node.conf.sample /etc/nxserver/node.conf

Enable PASSDB for NX Database User Authentication pass-through:

Uncomment and change the following line in /etc/nxserver/node.conf

Installing Nagios server and network monitoring on Centos 5 server

The official documentation can be found at http://support.nagios.com/knowledge-base/official-documentation

Install necessary packages

yum install httpd gcc glibc glibc-common gd gd-devel php

Create Nagios User account and group

useradd -m nagios

Create nagcmd group for allowing external commands to be submitted through the web interface. Add both the nagios user and the apache user

groupadd nagcmd
usermod -a -G nagcmd nagios
usermod -a -G nagcmd apache

Create Directory to store Nagios installation files

mkdir /opt/Nagios

Download Nagios and Plugins

Save file to directory /opt/Nagios

The following are simple wrapper scripts for the Xymon server and client that will allow you to automatically start them during boot-up, just as you would any other standard unix service:

cd /etc/rc.d/init.d/xymon
nano xymon


Xymon Server Code

#!/bin/bash
##
# chkconfig: 345 55 25
# description: Xymon Server Monitor
#
# source function library
. /etc/rc.d/init.d/functions

How do I get my VirtualBox Guest VM’s to start and stop when the host system reboots, shutdown, or starts.

Solution / Answer:

Create an init.d script so that VirtualBox Guest VM are controlled as a system service.

Install VirtualBox VM Service script

The original script was for Ubuntu systems found here . Modified for Centos by Kevin Swanson found here .

Create Config File for vboxcontrol service script

# mkdir /etc/virtualbox
# touch /etc/virtualbox/machines_enabled

The file “machines_enabled” located in “/etc/virtualbox” is where we list the names of the Guest VM’s that we want vboxcontrol to control.

Casual VirtualBox users might not know about the awesome power that lurks just beneath the surface in the Command Line Interface (CLI).

netstat command and shell pipe feature can be used to dig out more information about particular IP address connection. You can find out total established connections, closing connection, SYN and FIN bits and much more. You can also display summary statistics for each protocol using netstat.

This is useful to find out if your server is under attack or not. You can also list abusive IP address using this method.
# netstat -nat | awk '{print $6}' | sort | uniq -c | sort -n
Output:

      1 CLOSE_WAIT
      1 established)
      1 Foreign
      3 FIN_WAIT1
      3 LAST_ACK
     13 ESTABLISHED
     17 LISTEN
    154 FIN_WAIT2
    327 TIME_WAIT

Dig out more information about a specific ip address:
# netstat -nat |grep {IP-address} | awk '{print $6}' | sort | uniq -c | sort -n