To answer that question, let's go back to the basics for a moment. Computers process information. In order for this to happen, there are some prerequisites:
Unless these three things come together very little is going to happen, information processing-wise. But each of these items have their own requirements that need to be satisfied before things can get exciting.
Take the computer, for example. While it needs things like electricity and a cool, dry place to operate, it also needs access to the other two items -- information and programs -- in order to do its thing. The way to get information and programs into a computer is to place them in the computer's mass storage. These days, mass storage invariably means a disk drive. Putting information and programs on the disk drive means that they are stored as files. So much for the computer's part in this.
OK, let's look at the information. Does information have any particular needs? Well, it needs sufficient space on the disk drive, but more importantly, it needs to be in the proper format for the program that will be processing it. That's it for information.
Finally, we have the program. What does it need? Like the information, it needs sufficient disk space on the disk drive. But there are many other things that it may need:
As you can imagine, this can get pretty complicated. It's not so bad once everything is set up properly, but how do things get set up properly in the first place? There are two possibilities:
If it seems like the first choice isn't so bad, consider how many files you'll need to keep track of. On a typical Linux system, it's not unusual to have over 20,000 different files. That's a lot of documentation reading, file copying, and configuring! And what happens when you want a newer version of a program? More of the same!
Some people think the second alternative is easier. RPM was made for them.
When you consider that computers are very good at keeping track of large amounts of data, the idea of giving your computer the job of riding herd over 20,000 files seems like a good one. And that's exactly what package management software does. But what is a ``package''?
A package in the computer sense is very similar to a package in the physical sense. Both are methods of keeping related objects together in the same place. Both need to be opened before the contents can be used. Both can have a ``packing slip'' taped to the side, identifying the contents.
Normally, package management systems take all the various files containing programs, data, documentation, and configuration information, and place them in one specially formatted file -- a package file. In the case of RPM, the package file is sometimes called a ``package'', a ``.rpm file'', or even an ``RPM''. All mean the same thing -- a package containing software meant to be installed using RPM.
What types of software are normally found in a package? There are no hard and fast rules, but normally a package's contents consist of one of the following types of software:
One of the most obvious benefits to having a package is that the package is one easily manageable chunk. If you move it from one place to another, there's no risk of any part getting left behind. But although this is the most obvious advantage, it's not the biggest one.
The biggest advantage is that the package can contain the knowledge about what it takes to install itself on your computer. And if the package contains the steps required to install itself, the package can also contain the steps required to uninstall itself. What used to be a painful manual process is now a straightforward procedure. What used to be a mass of 20,000 files becomes a couple hundred packages.
A couple hundred? Even though the use of packages has decreased the complexity of managing a system by an order of magnitude, it hasn't yet gotten to the level of being a ``no-brainer''. It's still necessary to keep track of what packages are installed on your system. And if there are some packages that require other packages in order to install or operate correctly, these should be tracked as well.
If you start looking at a computer system as a collection of packages, you'll find that a distinct set of operations will take place on those packages time and time again:
With this much activity going on, it's easy to lose track of things. What types of package information should be available to keep you informed?
Just as there are certain operations that are performed on packages, there are also certain types of information that will make it easier to make sense of the packages installed on your system: