 Lee Madajczyk |
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Windows Installer Service OverviewThe Windows Installer service provides information for the installation and configuration of programs within Windows 2000. |
• March 28, 2001 •
The Windows Installer service is one that provides information for the installation and configuration of programs within Windows 2000. The Installer service takes a novel approach to program installation, in that the package has instructions on what is installed, rather than how to install it.
Anyone who has installed Office 2000 or Windows 2000 has seen the Windows Installer service. If you've ever deleted key files off of your computer system, it's possible you have seen it in action. You may have even written a program that has taken advantage of the packager format (MSI, or Microsoft Software Installer).
For example, you purchase a new program from your local computer store. You put the disk in the drive, and the AutoPlay feature kicks in, starting the installation program. You answer a few questions, and then you watch this curious blue bar move across your screen. It can take anywhere from three seconds to thirty minutes, depending on the number of tiles that need to be installed.
A closer look at this process shows that the vendor you purchased the product from isn't really handling the installation. In fact, your operating software is doing the product installation. In Windows 2000, this is automatically handled by the Windows Installer service, which was shipped with Windows 2000. Windows 9x and Windows NT platforms will also install based on the Windows Installer service, but they will install the service first.
The operating system will look at the included MSI file to determine the files that need to be installed onto the machine. The MSI file is basically a database file with installation instructions in it. The Windows Installer service will then begin copying those files to the proper location and registering them with the operating system. If the file already exists, the Installer service basically makes a note of the fact that more than one program requires that file. This is crucial for when programs are uninstalled. Rather than removing a file that is essential for operation of another program, the Windows Installer service simply removes one "tick mark" on that file. When all the "tick marks" are removed, the file is removed.
The tick marks and MSI database help ensure system stability, ease-of-use, and rollback possibilities. With the Windows Installer service knowing the location of each file, how it was installed, and what other programs require that same file, it becomes easy to add and remove programs.
The other cool feature of the Windows Installer service / MSI installation files is the ability of the application to repair itself. For example, my company produces many AutoCAD drawings and designs. We use a program from AutoDesk called Volo View, which is an AutoCAD drawing viewer, to allow people to view files, but not change them. If those people were to go into the C:\Program Files\Volo View\ directory and delete all of the files, they would still be able to double-click on an AutoCAD drawing or select the program shortcut. This is all thanks to the Windows Installer service, which quietly monitors the system. If files are required that cannot be found, the Windows Installer service automatically launches and installs the files, provided that the installation resources can be found.
The Windows Installer service makes many of the tasks that an administrator faces everyday just a little easier. The peace of mind that comes from knowing that an application can usually fix itself is a welcome relief. But what do you do about programs that don't come in the Windows Installer MSI format?
Thankfully, Microsoft and Veritas thought of that. Microsoft includes a program on the Windows 2000 CD called WinInstall LE, which is a stripped down version of the WinInstall program sold by Veritas Software. Using a "snapshot" image, you can essentially repackage a software installation. Even more convenient is the ability to add in your own custom settings with little or no work.
The WinInstall LE program takes a "snapshot" of the most important pieces of the system, including the registry, INI files, selected drives, and more. It then prompts you to install your program and configure it the way you normally would. After you have done this, you are required to run the "snapshot" process again. WinInstall LE then compares the two images, determines the differences, and writes the changes to an MSI package file. (Note: This process is much like the snAppShot program included on many Novell file servers. The Veritas solution makes troubleshooting little more user friendly, but the Novell version continues to be a viable solution.)
As you can see, the Windows Installer service is a vital add-on to the Windows 2000 platform. Since you can "publish" programs in the Active Directory, you can effectively control who will be allowed access to what program quickly and easily. Please refer to the following resources for more in-depth information:
Windows Installer Service Overview - Microsoft.Com
Windows Installer v1.5 Platform SDK - Microsoft Developers Network
Windows Installer Command Line Parameters - SWYNK.COM
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Lee Madajczyk, MCSE, MCP
Windows 2000 Editor
InfiniSource.com
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