Managing configuration

So I’ve finally bit the bullet and decided to look into installing and setting up Puppet to manage the configuration of my servers. The reason is to be found in my transfer to Dublin as I expect I won’t have the same time I had before, and that means that any streamlining in the administration of my servers is a net improvement.

In particular, just the other day I spent a lot of time fighting just to set up SSL properly on the servers, and I kept scp’ing files around — it was obvious I wasn’t doing it right.

It goes deeper than this though; since Puppet is obviously trying to get me to standardize the configurations between different servers, I’ve ended up uncovering a number of situations where the configuration of different servers was, well, different. Most of the times without a real reason. For instance, the Munin plugins configured didn’t match, even those that are not specific to a service — of three vservers, one uses PostgreSQL, another uses MySQL and the third, being the standby backup for the two, has both.

Certainly there’s a conflict between your average Gentoo Linux way to do things and the way Puppet expects things to be done. Indeed, the latter requires you to make configurations very similar, while the former tends to make you install each system like its own snowflake — but if you are even partially sane, you would know that to manage more than one Gentoo system, you’ll have to at least standardize some configurations.

The other big problem with using Puppet on Gentoo is that there is a near-showstoppper lack of modules that support our systems. While Theo and Adrien are maintaining a very nice Portage module, there is nothing that allows us to set the OpenRC oldnet-style network configuration, for instance. For other services, often times the support is written with only CentOS or Debian in mind, and the only way to get them to work in Gentoo is to fix the module.

To solve this problem, I started submitting pull requests to modules such as timezone and ntp so that they work on Gentoo. It’s usually relatively easy to do, but it can get tricky, when the CentOS and Gentoo way to set something up are radically different. By the way, the ntp module is sweet because finally I can no longer forget that we have two places to set the NTP server pools.

I also decided to create a module to fit in whatever is Gentoo-specific enough, although this is not yet the kind of stuff you want to rely upon forever — it would have to be done through a real parsed file to set it up properly. On the other hand it allows me set up all my servers’ networks, so it should be okay. And another module allows me to set environment variables on different systems.

You can probably expect me to publish a few more puppet modules – and editing even more – in the next few weeks while I transition as much configuration as I can from custom files to Puppet. In particular, but that’s worth of a separate blog post, I’ll have to work hard to get a nice, easy, and dependable Munin module.

3 thoughts on “Managing configuration

  1. If you follow naming conventions, you can simply ignore init.pp and “import”.include gentoo::oldnet loads gentoo/manifests/oldnet.pp without requiring any import.Defines should split into separated .pp files under oldnet folder – it makes maintenance easy.

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  2. Puppet/chef style solutions encourage configuration drift through asynchronous changes to duplicate configurations.Using versioned application containers via LXC instead IMHO provides better/faster isolation, versioning, rollback and management, with less chance of screwups and easier application-wide snapshot (eg. with LVM2 LV-backing).

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