Linux has always been blessed. As we have a large number of people working for the betterment of the product, we’ll have bug fixes/security updates every now and then. This has got 2 sides.

• The good part- if you keep on upgrading; you will have a more secure, bug-free product.
• The bad part- if you never upgrade; the whole world knows the security vulnerabilities of the outdated version. I guess this could be as good as tweeting your root password.

So, we’ve got to update the systems as and when the updates arrive. But, an update once in a month will mean a reboot once a month, which will mean monthly server downtime. This is where Ksplice comes into the picture.

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Linux is a premium force in the web hosting industry, which is also achieving popularity as a PC operating system nowadays. When it comes to hosting a website, Linux web servers are primarily chosen due to their flexibility, stability and security of services. But as we all know, security of all operating systems revolve around controlling access and is hence subject to exploits. Since Linux is open source, vulnerabilities can be easily exploited by potential attackers to gain illegal access to a web server. As a measure of securing Linux at every level, from the kernel up, Security Enhanced Linux (SELinux) was developed.

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The fourth extended file system was developed as the successor of the commonly used ext3 journaled file system. The ext4 file system has significant advantages over the ext3 and ext2 file systems.

Support for the ext4 file system has been available from the Linux kernel version 2.6.19 onwards and was officially declared stable in the Linux kernel version 2.6.28. All the latest versions of distributions like Ubuntu (9.04), Fedora (11) etc. include the ext4 file system.

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Modern Linux distributions are capable of identifying a hardware component which is plugged into an already running system. There are a lot of user friendly distributions like Ubuntu, which will automatically run specific applications like Rhythmbox when a portable device like an Ipod is plugged into the system.

Hotplugging (which is the word used to describe the process of inserting devices into a running system) is achieved in a Linux distribution by a combination of three components: Udev, HAL and Dbus.

Udev supplies a dynamic device directory containing only the nodes for devices which are connected to the system. It creates or removes the device node files in the /dev directory as they are plugged in or taken out. Dbus is like a system bus which is used for inter-process communication. The HAL gets information from the Udev service, when a device is attached to the system and it creates an XML representation of that device. It then notifies the corresponding desktop application like Nautilus through the Dbus and Nautilus will open the mounted device’s files.

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Tomcat is a stand-alone application web server which serves web pages containing Java Server Page(JSP) coding. It provides an environment to execute dynamic applications, like JSP and Java servlets. It communicates with Apache via mod_jk and support servlets and JSPs. Tomcat can be used as an independent web server, with its own internal HTTP server, or can be used in combination with other web servers, like Apache webserver.

For proper execution, Tomcat requires JDK(Java Development Kit). JDK that contains API classes, Java compiler(javac), Java Virtual Machine(JVM) provides the basic tools to compile Java applications and applets.

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Most of the Linux servers are today loaded with the EXT3 File System. We have come across a lot of incidents where files have gone lost through a simple rm -rf command, either done accidentally or sometimes even intentionally by others. There has always been a misconception that such files cannot be retrieved in ext3. In fact, it is quite possible to retrieve the data.

On further investigation into this, I was able to locate a lot of tools that could help recovering the deleted data from an ext3 file system. Magicrescue, Ext3grep, Testdisk, Ddrescue, Photorec and ext3undel are some examples, to list a few.

I was in pursuit of a tool that is capable of recovering all file types and is exclusively designed for the ext3 file system. One among the best tools that I found and would like to take you through is ext3grep.

This tool provides a good set of command line features and a good idea regarding the ext3 file system. Before proceeding further, let’s look into the merits and demerits of this tool.

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PHP has a lot many frameworks and I have gone through many of them. One of the biggest difficulty that I found in some of them was the learning curve. Most of these frameworks use complex directory structures and difficult to remember naming conventions. Also, each one of them uses their own method for adding templates and db access. You don’t get the option to put in something that you are familiar with, like Smarty.

According to me, PHP is a powerful language for web programming, both with regard to speed as well as with the ease of use for web. And when you consider Java for web programming, servlets are a powerful concept. It indeed becomes handy when the design concepts of servlets and the speed and usability of PHP can be combined. This framework is an attempt on that path. (Download framework here.)

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For over a decade, several organizations used the Network Information Services (NIS) to render the central management of identity and policy for users and machines in the Linux and Unix environment. However, NIS had some serious infirmities that caused its failure to certain security compliance audits.

NIS is rather insecure for today’s standards. Host authentication mechanisms are not available and all information is passed unencrypted, over the network. Due to this, extreme care has to be taken while setting up a network that uses NIS.

Red Hat Enterprise IPA will help to enable significant risk reduction and efficiency gains for the IT industry. IPA stands for Identity, Policy, and Audit. RHE IPA aims to simplify the central management of the identity of users and machines, policies configuration and access control, and audit. The present release - RHE IPA 1.0 - takes care of “Identity” part. “Policy” and “Audit” are scheduled for future releases.

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Scalix is an e-mail and group calendaring solution which is tipped as an alternative to MS Exchange. Scalix gives you the freedom to choose the applications and desktops that best suit your business needs. It offers you many features like e-mail, shared calendaring, group folders and other collaboration features and all these on a platform which is more stable and secure than MS Exchange. It also provides the option of integrating systems like ERP, CRM, and billing into the Scalix system using its open API.

Scalix comes in different editions: Enterprise, Small Business, Appliance, Xandros, Community, and Raw. The Scalix installation without license is possible via its Community Edition which is described in this article.

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Your Kernel just crashed or one of your drive is not working!! What do you do?

Well, this article gives an introduction to some kernel debugging tools for Linux. These tools makes the kernel internals more transparent. These tools help you to trace the kernel execution process and examine its memory and data structures.

The tools discussed here are :

1. Kernel debugger, kdb

2. Kernel GNU debugger, kgdb

3. GNU debugger, gdb

4. JTAG- based debuggers.

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