Tag Archives: linux

Server and Network Monitoring using MRTG – Part 1

This is the 1st series of articles highlighting the usage of MRTG for server and network monitoring.

In my previous article, I touched upon the basics of installing MRTG, Net-SNMP and used the cfgmaker tool to generate simple MRTG graphs. In this article, we further move on to the topic of creating MRTG graphs for a single Linux/Unix machine using only shell scripts.

The final goal or mission of these series of articles is to provide users concrete and professional examples of monitoring their servers and network devices using MRTG. In the end of these series of articles, we will round up and unite all these MRTG graphs to our web based network monitoring system called Nagios.

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Effective User management under Linux/Unix

In this article, we look into the topic of managing our users on our local Linux/Unix box. As we know it, Linux/Unix is a multiuser environment, therefore, one of the main tasks of a system administrator is to create user accounts and provide a secure environment for users to do their work in.

Adding and removing users is still one of the most important task of a system administrator. Therefore, we as system administrators need a good understanding of how the Linux/Unix accounting system works in order to provide good network services to our users and clients.

Good account management is also the key determinant to system security. Infrequently used accounts are prime targets for crackers. So are accounts with weak passwords.

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System integrity using Files, Permissions, Processes, Root and Sudo

To be a good in system administration, we have to understand the basics of files, processes and permissions of our Linux/Unix hosts. Therefore, in this article, we will cover the basic stuffs regarding files, processes, permissions, the SUPERUSER “root” account and the sudo program.

Every file and process on a Linux/Unix system is owned by a particular user account. Every file has both an owner and a group owner. What this means is that the owner of the file enjoys one special property that is not shared with everyone on the system. This property is the ability to modify the permissions of the file.

Other users on the system can’t access files belonging to others without the owner’s permission, so this restriction helps protect a user’s files against “malicious” users!

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Monitoring your Linux/Unix servers and network devices using MRTG and SNMP

This tutorial will guide you to create MRTG graphs for your Linux/Unix Server or just about any network device which supports SNMP.

This guide will present you the layout in a practical way and will not go in depth to explain the theories behind how they work. This is because the users will explore and learn them by themselves.

SNMP stands for Simple Network Management Protocol.

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Running A Transparent Linux Squid Bridge / Turn your Linux box into a Cisco like Catalyst switch

This How-To guides you to run your Linux box with Squid in a transparent bridge mode.

Let us face some facts. Not everybody, especially a small office network or a small home network can afford a Cisco catalyst switch. To replicate the features of a sophisticated switch like a Cisco catalyst switch, we can setup a Linux box with more than 2 network interfaces to run in bridging mode. Or more simply, a Linux bridged box having switching capabilities.

A bridge is a way to connect two Ethernet segments together in a protocol independent way. Packets are forwarded based on Ethernet address, rather than IP address (like a router). Since forwarding is done at Layer 2, all protocols can go transparently through a bridge. Continue reading

Configuring Apache-2.2.8 with PHP-5.2.5 and Mysql-5.0.45

This How-To guides you through the steps to install and configure the most popular and powerful Apache-2.2.8 web server with PHP-5.2.5 and Mysql-5.0.45.

This How-To can be used either on Linux with Kernel version 2.4 and higher or on FreeBSD-6.x systems.

From wikipedia, the definition of a web server is as follows:

A computer program that is responsible for accepting HTTP requests from clients, which are known as web browsers (e.g. Firefox, Internet Explorer), and serving them HTTP responses along with optional data contents, which usually are web pages such as HTML documents and linked objects (images, etc.).

Without Web servers, the Internet would just be as dull as sending and receiving emails.

It is the web server which provides the content and information that we are used to seeing these days. It’s the web server’s job to deliver both static and dynamic contents to end-users via browsers such as Mozilla Firefox and Internet Explorer.

Apache is to web servers what Bind is to DNS servers. Apache is a high performance and scalable web server notable for playing a key role in the initial growth of the World Wide Web. According to the data provided by news.netcraft.com, 50% of all web sites are running on Apache web servers.

In this guide, we will install and configure a simple Apache-2.2.8 web server with PHP-5.2.4 and Mysql-5.0.45.

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Securing your Linux gateway box with IPTABLES

This How-To provides the details for securing a Linux gateway box with the IPTABLES firewall. This guide can be used for Kernels ranging from 2.4-2.6. Special rules for running Squid in transparent mode and providing Network Address Translation (NAT) are also covered in this guide.

The tool IPTABLES talks to the kernel and tells it what packets to filter.

The IPTABLES application operates at a high level by filtering TCP and UDP protocols before the data is passed onto the user applications that can be corrupted.

The IPTABLES tool inserts and deletes rules from the kernel’s packet filtering table.

What this means is that the rules you create in your Linux machine using IPTABLES are lost upon reboot.

The best way to use IPTABLES rules are to store them up in a simple shell script and use your Linux OS to load that script on boot up.

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