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First steps in IT automation by Rex

Automation Tool

Article from ADMIN 21/2014

By Jens-Christoph Brendel

Rex doesn't need agents or a special language to describe the tasks it performs on remote computers.

If you have to run standard tasks in an environment with a large number of systems (e.g., a compute cluster, a server farm, or a cloud environment) you might want a tool to help you save time and avoid duplication of labor. Logging in on each server and typing your commands hundreds of times manually is too slow, too error prone, and too inefficient. Many admins would rather have a tool that lets them run standard tasks on all clients in parallel, without typos and in a reproducible manner.

Tools such as Puppet, Chef, SaltStack, and Ansible provide this functionality through an agent running on the client, and a special description language lets the user define tasks or the target state. Rex takes a different approach. The Rex configuration management tool uses SSH as the transport medium and Perl as the command language, which means any computer can act as a Rex client without the need for additional software.

The fact that Rex doesn't rely on a client agent program also means the user won't run into conflicts between newer and older Rex versions. And you won't have to learn a new, specialized command language: As long as you know some Perl, you'll be ready to get started.

Installing Rex

Only the command center – the Rex host, which is sometimes called Rex Control Master – needs a few software modules. By the way, the Rex developers call the program (R)?ex , which is totally unpronounceable, so I'll settle for plain old Rex for the rest of the article. You can install these software modules either via a package manager in Linux or FreeBSD or via Git. If you're using a package manager, you'll want to include the Rex [1] repository to leverage automated updates by the distribution. Listing 1 shows how to install via Git. The advantage of using Git is that

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