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VIRTUALISATION Puppet: configuration management made easy
VIRTUALISATION Puppet: configuration management made easy | Puppet: configuration management made easy |
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| by Sam Varghese | |
| Tuesday, 28 April 2009 | |
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Page 3 of 5 Puppet pushes down a catalogue, or a configuration onto the host, and the host applies it. After that, there are a couple of ways in which Puppet can be run. Featured Whitepaper
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"The first is a continuous sort of mode, and in a fixed period of time - every half hour or every hour or every day, the client wakes up, talks to the master, and says, "Am I up to date? Is my configuration still valid?', and the master says, "yep, you still look like a web server as far as I'm concerned", and it doesn't do anything," Turnbull explains. "Or if you don't look like a web server anymore - for example, you have the wrong version of Apache installed, or someone's uninstalled one package or changed a configuration file - Puppet will reset the configuration back the way it's supposed to be." Clients are authenticated to the host by SSL. "It'll run OpenSSL certificates and all the interactions between the client and the host are encrypted and they're authenticated using certificates," Turnbull says. Puppet has what he describes as an internal language. "It is essentially a way of describing a host, each is called a node. You define the node and the name of the node. You tell it, 'which pieces of configuration should I include?' Puppet has a concept of resources, and resources are things like a package or file or user or group, and there's a whole variety of resources that Puppet manages. "The Puppet resource, I guess, is an abstraction of a package. We have a little bit of Puppet language that says 'Package, name of the package, ensure that package is installed'. On the master, that's all Puppet knows about that package. "A client says to the master, 'I'm an OSX box. How do I install my package?' And the master knows that on an OSX box, we use DMG files. Another box may say, 'I'm a Red Hat box'. The master says, 'Oh, I'll use Yum'." As far as the master is concerned, the operating system of the client doesn't matter. "It abstracts the configuration. You just say 'I would like the Apache package installed on all of my hosts'. And if those hosts are Debian boxes, it would use aptitude, or apt-get, or whatever you choose, or dpkg," says Turnbull. CONTINUED |
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