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The Art of Capacity Planning by John Allspaw

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Automated Installation Tools

Before you can even begin to worry about configuration management, you need to get your servers to a state in which they can be configured. You want a system that can automatically (and repetitively) install your OS of choice. Many such systems have been developed over the years, all employing similar techniques.

There are two basic approaches to the task of imaging new machines. Most OS vendors offer a package-based installer option, which performs the normal installation process in a non-interactive fashion. It provides the installer with a configuration file that specifies the packages to be installed. Examples include Solaris Jumpstart, Red Hat Kickstart, and Debian FAI.

Many third-party products take a disk-image approach. A gold client image is prepared on one machine and replicated byte-for-byte onto newly imaged hosts. Often, a single image is used for every server in the infrastructure, with hosts only differing in the services that are configured and running. SystemImager is a product that uses this approach.

Each method has advantages. Package-based systems provide accountability; every file installed is guaranteed to belong to a package, and package management tools make it easy to quickly see what's installed. You can get the same result with disk image systems by installing only packaged files. The temptation to muck about with the gold client filesystem directly can lead to confusion down the road.

On the other hand, image-based systems tend ...

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