Friday, 29 April 2011

Ultimate Ubuntu Build Server Guide, Part 3

Groundwork, Phase 3: Calling Names
Note from future self; Although this setup guide is now superseded by cloud-based tools, certain elements are still useful simply as good practice, such as the "groundwork" in the early stages of this guide. As such, this article has been spared the chop

This is Part 3 of my Ultimate Ubuntu Build Server Guide.


A productive network needs a comprehensible naming convention and a reliable mechanism for dishing out and looking up these names.


Naming Thine Boxen

On my first day at my current workplace I asked what the URL of the Wiki was. "wiki" was the reply. That kind of smile-inducing, almost-discoverable name is exactly the kind of server name we are looking for. At the other end of the scale is the completely-unmemorable, partly-implemented corporate server-farm naming scheme that means your build box is psal04-vic-virt06-r2 and your wiki lives on 12dev_x64_v227a. Ugh.


DNS and DHCP

The cornerstone of being able to talk to machines "by name" is of course, DNS. You need your own DNS server somewhere on the network. I know what you're thinking - that means a big, noisy, power-sucking Unix box and bind and resolf.conf and ... argh!.


Not necessarily.


Unless you've been living under a rock for the last 10 years, you'll have noticed that there are now rather a lot of small networked devices around, all running some flavour of Linux. Your DSL router is almost certainly one of them, but while it probably offers DHCP services, it probably won't be able to serve up DNS entries (as aside from proxying DNS entries from upstream). That's OK. There are other small Linux boxen that will do the job.


I speak of NAS devices. I'm personally using a Synology DS209, which is the kind of web-configured, one-box-solution, Linux-powered network überdevice I could have only dreamt about 10 years ago. In addition to storing mountains of media files and seamlessly acting as a Time Capsule for my MacBook, this neat little unit also runs SynDnsMasq, a port of the amazing dnsmasq DHCP/DNS server.


dnsmasq

A simple, elegant and functional tool that runs off one superbly-commented configuration file, dnsmasq will make your local network much more navigable thanks to local DNS addresses - ssh user@buildbox is much better than ssh user@10.12.14.16, don't you think?


Having full control of your DHCP server (as opposed to the primitive on/off on most domestic routers) also allows you to set up effectively-permanent address allocations based on MAC addresses. This gives you all of the advantages of static IP addresses for servers, but allows you to have a centralised repository of who-is-who, and even change things on the fly, if a server goes offline for example.


By running this software on my NAS, I get all of these features, plus I save scads of power as it's a low-power unit AND it switches itself on and off according to a Power Schedule so it's not burning any juice while I'm asleep. I've configured the DHCP server to actually tell clients about two DNS servers - the primary being the NAS itself, the secondary being my ADSL router. That way, if I start using a client at 10.55pm, I can keep surfing the web after the NAS goes to sleep at 11pm - the client will just "fail over" to the main gateway.


Name Your Poison

The actual names you use for servers and clients are of course a very personal choice. One of the best schemes I've used was based on animals, with increasing levels of maturity and/or decreasing domesticity based on their function. A table's worth a thousand words here I think!


FunctionSpeciesDevTestProd
App ServerCaninePuppyDogWolf
Web ServerEquineFoalHorseZebra
Database ServerCapraKidGoatIbex

While this caused much hilarity amongst non-technical people ("Horse will be down until we bounce the Goat" is not something you hear in many offices!), it actually worked very well.


The scheme I'm using at home is a simple "big cat" scheme - lion, tiger, cheetah, leopard etc - but I've taken the opportunity to "overload" the names in my dnsmasq configuration - so buildbox currently resolves to the same machine as cheetah - but of course should that duty ever change, it's just a one-line change on the NAS to fix it.

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