Linux Distributions - Shell Scripting

Now that you have seen the four main components required for a complete Linux system, you may be wondering how you are going to get them all put together to make a Linux system. Fortunately, there are people who have already done that for us.

A complete Linux system package is called a distribution. There are lots of different Linux distributions available to meet just about any computing requirement you could have. Most distributions are customized for a specific user group, such as business users, multimedia enthusiasts, software developers, or normal home users. Each customized distribution includes the software packages required to support specialized functions, such as audio- and video-editing software for multimedia enthusiasts, or compilers and integrated development environments (IDEs) for software developers.

The different Linux distributions are often divided into three categories:

  • Full core Linux distributions
  • Specialized distributions
  • LiveCD test distributions

The following sections describe these different types of Linux distributions, and show some examples of Linux distributions in each category.

Core Linux distributions

A core Linux distribution contains a kernel, one or more graphical desktop environments, and just about every Linux application that is available, precompiled for the kernel. It provides one-stop shopping for a complete Linux installation. Table below shows some of the more popular core Linux distributions.

Core Linux distributions

In the early days of Linux, a distribution was released as a set of floppy disks. You had to download groups of files and then copy them onto disks. It would usually take 20 or more disks to make an entire distribution! Needless to say, this was a painful experience.

Nowadays, with home computers commonly having CD and DVD players built in, Linux distributions are released as either a CD set or a single DVD. This makes installing Linux much easier.

However, beginners still often run into problems when they install one of the core Linux distributions. To cover just about any situation in which someone might want to use Linux, a single distribution has to include lots of application software. They include everything from high-end Internet database servers to common games. Because of the quantity of applications available for Linux, a complete distribution often takes four or more CDs.

While having lots of options available in a distribution is great for Linux geeks, it can become a nightmare for beginning Linux users. Most distributions ask a series of questions during the installation process to determine which applications to load by default, what hardware is connected to the PC, and how to configure the hardware. Beginners often find these questions confusing. As a result, they often either load way too many programs on their computer or don’t load enough and later discover that their computer won’t do what they want it to. Fortunately for beginners, there’s a much simpler way to install Linux.

Specialized Linux distributions

A new subgroup of Linux distributions has started to appear. These are typically based on one of the main distributions but contain only a subset of applications that would make sense for a specific area of use.
Besides providing specialized software (such as only office products for business users), customized Linux distributions also attempt to help beginning Linux users by autodetecting and autoconfiguring common hardware devices. This makes installing Linux a much more enjoyable process

Table below shows some of the specialized Linux distributions available and what they specialize in.

Specialized Linux distributions

That’s just a small sampling of specialized Linux distributions. There are literally hundreds of specialized Linux distributions, and more are popping up all the time on the Internet. No matter what your specialty, you’ll probably find a Linux distribution made for you.

Many of the specialized Linux distributions are based on the Debian Linux distribution. They use the same installation files as Debian but package only a small fraction of a full-blown Debian system.

The Linux LiveCD

A relatively new phenomenon in the Linux world is the bootable Linux CD distribution. This lets you see what a Linux system is like without actually installing it. Most modern PCs can boot from a CD instead of the standard hard drive. To take advantage of this, some Linux distributions create a bootable CD that contains a sample Linux system (called a Linux LiveCD). Because of the limitations of the single CD size, the sample can’t contain a complete Linux system, but you’d be surprised at all the software they can cram in there. The result is that you can boot your PC from the CD and run a Linux distribution without having to install anything on your hard drive!

This is an excellent way to test various Linux distributions without having to mess with your PC.Just pop in a CD and boot! All of the Linux software will run directly off the CD. There are lots of Linux LiveCDs that you can download from the Internet and burn onto a CD to test drive.

Table below shows some popular Linux LiveCDs that are available.

The Linux LiveCD

You may notice a familiarity in this table. Many specialized Linux distributions also have a Linux LiveCD version. Some Linux LiveCD distributions, such as Ubuntu, allow you to install the Linux distribution directly from the LiveCD. This enables you to boot with the CD, test drive the Linux distribution, and then if you like it, install it on your hard drive. This feature is extremely handy and user-friendly.

As with all good things, Linux LiveCDs have a few drawbacks. Since you access everything from the CD, applications run more slowly, especially if you’re using older, slower computers and CD drives. Also, since you can’t write to the CD, any changes you make to the Linux system will be gone the next time you reboot.

But there are advances being made in the Linux LiveCD world that help to solve some of these problems. These advances include the ability to:

  • Copy Linux system files from the CD to memory
  • Copy system files to a file on the hard drive
  • Store system settings on a USB memory stick
  • Store user settings on a USB memory stick

Some Linux LiveCDs, such as Puppy Linux, are designed with a minimum number of Linux system files and copy them directly into memory when the CD boots. This allows you to remove the CD from the computer as soon as Linux boots. Not only does this make your applications run much faster (since applications run faster from memory), but it also gives you a free CD tray to use for ripping audio CDs or playing video DVDs from the software included in Puppy Linux.

Other Linux LiveCDs use an alternative method that allows you to remove the CD from the tray after booting. It involves copying the core Linux files onto the Windows hard drive as a single file. After the CD boots, it looks for that file and reads the system files from it. The dyne:bolic

Linux LiveCD uses this technique, which is called docking. Of course, you must copy the system file to your hard drive before you can boot from the CD.

A very popular technique for storing data from a live Linux CD session is to use a common USB memory stick (also called a flash drive and a thumb drive). Just about every Linux LiveCD can recognize a plugged-in USB memory stick (even if the stick is formatted for Windows) and read and write files to and from it. This allows you to boot a Linux LiveCD, use the Linux applications to create files, store them on your memory stick, and then access them from your Windows applications later (or from a different

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