Linux Software-Installation Basics

In "A Linux Primer for Windows Administrators" (November 2004, InstantDoc ID 44104), I discussed basicinformation that Windows administrators need to know about Linux. Because Linux is everywhere these days,you need to keep up with current Linux management trends and techniques, especially when it comes to howLinux works in your Windows environment. In this article, I consider an important part of administering Linux: application-installation management (i.e., how to install, remove, and clean up Linux software). I discuss installing by source, installing by using a package manager, and binaryonly installation, including the advantagesand disadvantages of each method. I use Red Hat Linux as the example system.

Installing by Source
You install the majority of your Windows applications, both free and commercial, by using Windows Installer or InstallShield (or a similar installation package). These applications let you automatically install, remove, and clean up applications Linux offers automated installers as well, but not for all applications. Many Linux applications, particularly open-source applications, rely on systems administrators to compile source code and install the resulting binary files. This installation technique is knownas installing by source. Although you won't find it particularly difficult to install software-by source, you'll find it more difficult to remove the installed software, which I address later.

Why is installing by source popular? First, it lets developers focus on the software they're writing rather than the minutiae of installation differences between different versions of Linux and UNIX. Second, it lets systems administrators highly tune software compilation for their systems. When you compile the code, you can customize various options for your needs. In a high-performance environment, this capability can dramatically affect the usefulness of a given software package. Third, having the source code for an application can be important to security, again because you can optimize features to meet your needs. Being able to review source code before compilation gives systems administrators a measure of control over what's actually installed. (The majority of systems administrators, however, even those who strongly push open-source software, don't actively review source code before compiling and installing it.) Finally, installing by source lets end users have access to a huge range of software because most available Linux software is available as source code. To find out about the many open-source applications for Linux, see the sidebar

Be aware that when you install by source, you essentially copy source code to your computer, then run commands to compile it, typically by using the C++ compilers from the Linux distribution. However, you'll usually find it easier to use a precompiledpackage for installation, which I address in the "Installing by Using a Package Manager" section.

Installing source-based software. In the past, it was often difficult to compile and install software from source codebecause Linux systems differ greatly. Despite the fact that Linux systems share the same core programs and features (i.e., the kernel and system libraries), distributions (e.g., Red Hat, Debian) vary so much that source-code compilations would often work on one systembut not on another.

The most popular solution to this problem is the GNU Autoconf system. Developers use Autoconf, a source-code-configuration utility, to smooth out the differences between Linux distributions so that you can easily compile source code on almost any system (including other types of UNIX). In general, expect to use Autoconf when you install by source, although small software projects might not require it.

When you compile source code, first read the included documentation. It's pretty standard to have a text file named Install included with any source code. The Install file contains instructions about how to compile the program on your system. Another common file is Readme, which often contains additional instructions, usually for configuring the software after installation.

Developers shoulder most of the work of using Autoconf. As a systems administrator, your responsibility is to read the Install document, then run the configure command, which is the enduser portion of the Autoconf system.

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