The Web Rider

Web surfing and related articles and news

December 31, 2011
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Maintaining Linux Server Modules From A Command Line

Adding Linux kernel modules is a crucial aspect of any Linux server administrator’s job description. This article will give you a basis in understanding the principles and tools concerned. The official terminology is “loadable kernel modules”; however they are often referred to as just “kernel modules” or “modules”.

The modern day Linux kernel uses a modular model allowing users to add additional functionality to the core of the operating system as and when required. This is the opposite of the monolithic kernel model, which requires all functionality to be compiled into the kernel prior to loading the operating system. In the past a monolithic kernel was preferred, as it is more efficient with regards the usage of memory resources, however nowadays most computers have multiple gigabytes of RAM available, so this is less of an issue. Nowadays, the advantages being able to dynamically load kernel modules far outweigh any disadvantages of slightly increased memory consumption.

So what is a kernel module? Well, it is very similar to a Windows device driver Modules often provide hardware specific software functionality. Examples include:

  • serial devices
  • delivering access to hard drives
  • DVD players
  • video adapters

It is normal for kernel modules to be loaded at boot time, however due to their dynamic nature they can also be loaded at any time. There are a number of Linux commands available in order to facilitate loading, unloading and gathering information about a module.

The most basic commands for loading and unloading modules consist of “insmod” and “rmmod”. The insmod command inserts a module in the kernel, the rmmod command removes a module from the kernel. You will find a variety of other commands which are necessary to understand when working with kernel modules. These are:

  • modinfo – displays the .modinfo section of the module object file (i.e. a file with a .ko or .o file)
  • depmod – ascertain any dependencies a module has
  • lsmod – shows all currently loaded modules

Each of the above commands are vital when manually loading modules into the kernel. The modinfo command delivers detailed data about the module, for example the kernel version which the module was compiled for, which is critical when troubleshooting any issues encountered when trying to load a kernel module. In addition there is a higher-level Linux module command which is most often used by administrators. It is:

  • modprobe – intelligently inserts or removes a Linux kernel module and all dependencies.

The modprobe command is basically a wrapper around insmod, rmmod and depmod, supplying a single, user-friendly command. It is strongly recommended that you read the help guide for modprobe should you be considering doing any work with loading or unloading Linux kernel modules.

Linux kernel modules are normally found within /lib/modules/[kernel-version] where by [kernel-version] will be the kernel version number you are looking at. The kernel version you are doing work on ought to have a matching directory in /lib/modules, it is important that you ensure you are doing work with the right directory whenever adding your modules.

December 29, 2011
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Much More Website Hosting Bandwidth Required As Average Page Size Increases

For a number of years an operation named The HTTP Archive have devoted themselves towards following the web page size of the leading 1000 internet websites on the internet. The organisation has just now produced its statistics for the period of January to December 2011 which displays a 33% increase in page size since 2010.

On average a page had been 726 KB throughout 2010. This statistic went up to 965 KB during 2011 displaying a sharp increase relating to the month of October. Having much more users working with mobile online gadgets the increasing web page size may considerably decrease the performance of web sites on these kinds of gadgets which might have a unfavorable effect as more and more individuals surf the net while traveling.

It is thought that the increased utilisation of HTML 5 and JavaScript are the main contributing factors to the page size increase phenomenon. Furthermore to JavaScript it has also been suggested that the increase in webpage size may also be attributed to the increasing utilisation of on-page internet analytics.

Also contibuting is an upwards tendency in the size of graphics used on web site webpages and this is also attributed as a key contributor to the total webpage size.

In future we are expecting website pages to continue growing in size, thus applying increased load on the underlying hosting infrastructure (e.g. servers, network, etc.). Due to lack of online data transfer currently offered for mobile gadgets, we believe many websites will begin to deliver content based on which type of device is accessing the web page.

The concept of delivering different website content based on the device accessing the page is not a new idea, however not many sites currently employ this strategy. Many website owners currently believe there is no requirement for such device dependent optimisation and thus there is a general lack of sites using this capability. In addition the knowledge and techniques required to apply content delivery optimisation are not widely distributed within the web design industry. The current thinking is that due to the self taught nature of most web designers the ability to create such optimisation techniques just isn’t generally available. As such, is it is expected that there will be a booming market place for web designers that can exhibit knowledge and experience in delivering optimised web content based on device recognition techniques over the next 3 years.