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Tiny Linux Plug Computers: Wall Wart Linux Servers
Choosing the Right One
January 27, 2011
Ever wish you could set up a small, efficient server? Maybe you're setting up a mail server for a couple of people, or something to hand out music files over a home network. Do you really need a full-fledged PC with a noisy fan, sucking down 100 watts and heating up the room?
Fortunately, there's a class of computers ideally suited to that sort of job: "plug computers", sometimes called Sheevaplugs after an early model. The whole computer is built into the bit that plugs into the wall, so they're barely bigger than a normal "wall wart" power supply. They use power-efficient ARM CPUs, so you can run a server with only 5 watts. They're inexpensive, usually just over $100 for a plug with 512M RAM and 512M flash. Best of all, they come with Linux installed right out of the box.
Interested? Here's what you need to know to get started in plug computing.
Choosing a Model
First you need to choose a model. Figure 1 shows a few commonly available varieties of plug computer: the best-known manufacturers are Ionics (lower left in Figure 1), TonidoPlug (not shown) and Globalscale (lower right).
Features vary by model. Pretty much all plug computers have wired ethernet, and most have wi-fi as well. Some models have more than one wired port, and some have fancy arrays of LEDs. A few even have a fan, so if noise is one of your reasons for choosing a plug computer, watch out for that.
One important feature a plug should have, but not all do, is a serial/JTAG port. When you start messing with plug computers, you will make mistakes, and it's very easy to end up with a plug that doesn't talk to the network. When that happens, you need a direct line in -- typically a USB/serial cable. On some plugs, like Globalscale's Guruplugs, that costs extra. So factor that in.
It's also a good idea to search the plug forums at plugcomputer.org before buying. Some manufacturers are not as well regarded as others, and some models have problems related to overheating or power use. 'Nuff said.
Cheapskate tip: the Dockstar
What's that little white box at top center in Figure 1? That's a Seagate Dockstar, the hot ticket for home hobbyists wanting to try plug computing on the cheap.
The Dockstar is sold as a "Pogoplug", a device for sharing files via a proprietary website. But the really cool thing about Pogoplugs is that they're full-fledged Linux plug computers -- for under $40. They don't come with a serial interface, but if you're careful you can get by without one (and you can make one if you're handy with a soldering iron). They don't have wi-fi, but they do have wired ethernet and two USB slots. You can't beat them as a cheap way to experiment with small home servers.
If you do opt to go the Dockstar route, be sure to visit the "Getting Started" pages on the PlugApps website. There are some very important suggestions regarding disabling the PogoPlug software that you should follow before doing anything else. Also, PlugBox Linux, available from that site, worked very nicely for me on my Dockstar.