Friday, October 15, 2010

How to configure syslog server or a centralized log server in redhat linux rhel5 or centos

This article will explain installing and configuring a syslog log server in redhat enterprise linux. It'll work in other redhat distributions like centos, fedora etc.
Centralized log server (syslog server)
Suppose we have a server and 5 client machines. And we want to monitor the logs of all those client machines. In situations like this, we will use centralized server as a log server. Whatever events are happening in client machines, the logs will be sent to the server. So that we can monitor all the logs from a centralized server. We make use of syslog service for this. You can also check out another log server like syslog-ng
Features of syslog:
1. Logs the daemon information to localhost
2. Logs the daemon information to Remote host
3. Logs the daemon information to List of users
4. Logs the daemon information to console

Thursday, October 14, 2010

How to install and configure Nagios Monitoring tool in redhat linux rhel5 or centos

This article will help you to install and configure Nagios monitoring tool in redhat linux or other redhat distributions like fedora, centos etc.
Nagios Installation :
Installing packages. Apache, PHP, GCC & GD

Installing Apache web server:
#yum -y install httpd*
set hostname in FQDN
#service httpd on

Installing PHP, GCC and GD:
#yum -y install php*
#yum -y install gcc*
#yum -y install gd*

Linux boot process in redhat enterprise linux rhel5

This post explains about the linux boot process and important scripts participating in it. The paper is based on the booting of Redhat Enterprice Linux machines. Version 5.4

Power Cycle -> CPU Reset -> BIOS -> Boot Device -> MBR -> IPL ->/ boot/grub/grub.conf -> /etc/inittab -> /etc/rc.d/rcX.d -> /etc/rc.local -> /etc/isuue -> /etc/motd

Power Cycle
When we power on the system, it'll go to SMPS and will reset chips in CPU.

Power On Self Test (POST)
The computer power-on self-test tests the computer to make sure it meets the necessary system requirements and that all hardware is working properly before starting the remainder of the boot process. If the computer passes the POST, the computer may have a single beep as the computer starts and the computer will continue to start normally, Passing the control to the BIOS.

BIOS [Basic Input Output System]
The BIOS is the first code run by a PC when powered on. The primary function of the BIOS is to load and start an operating system. When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk, CD/DVD drive and other hardware. The BIOS then locates boot device such as a hard disk or a CD, and loads and executes that software, giving it control of the PC.