I recently created a subdomain on my Mediatemple DV service, but for various reasons, I wanted to have a separate user responsible for that subdomain, with FTP and shell access. The user can be created along with the subdomain in Plesk as normally. Unlike the creation of users associated with domains, however, there is no option in Plesk to give this subdomain user shell access.

Fixing it is trivial if you have root access. Just edit /etc/passwd, find the line that starts with the username you just created, then change the last field of that line from /bin/false to /bin/bash (or whatever shell you like). This will allow you to su to the subdomain user or login via SSH, as you prefer. Easy, I know, but I noticed the option wasn't present in Plesk and well, maybe this tip will be helpful to somebody else out there.

Not great photos this time; the light was flat due to an overcast sky. Beautiful place, though - oldest cypress swamp in Florida, with trees over 500 years old in places. The swamp was bone dry this day as the beginning of May is the end of the dry season.

An instant classic from the Busch Gardens log flume, with Jay Wilson and myself. This one was just too funny to leave behind.

Our New Year's Eve fireworks shows are something to see - or so I gather from the reactions of the crowd. I don't really know, to tell the truth. Running around with a blowtorch lighting fuses doesn't give you a chance to watch the show for yourself and see what everyone's ooh-ing and aah-ing about. So for the last couple of years, my friends and I have been working our way towards the holy grail of backyard pyro - complete, automated computer control of the fireworks show. We started out the usual way, with a variety of electrical ignitors hard-wired into a "nail board" or a console of switches; I'll have to write a more complete history of these attempts sometime, more for my dear readers' laughs than for their technical edification. This year, however, we rolled out the first version of something completely different - a 12-channel, serial-controlled, microcontroller-driven, battery-powered, pyro ignition device!

On to the engineering, then: the microcontroller is an Atmel AVR, a 90S8515 running at 8 MHz to be exact (obsolete chip, sure, but I had one lying around - the next version uses an ATMega16 instead). This accepts RS-232 serial via the MAX-232 driver, interprets the byte it receives and fires the appropriate squib by pulling the gate of a NMOS high. The MOSFETs are STI P16NF06L's in TO-220 packages, good for 16 amps of drain current each; this high-current capability is built in to accommodate some types of very low resistance squibs that need a lot of current to fire.

As a temporary kludge for New Year's (I ran out of time as usual), I packaged the board and a 12V Sealed Lead-Acid battery in a tupperware tub. Since this was sited close to my mortar rack, which might spit out flaming bits onto the plastic box, I protected the top with a folded piece of sheet aluminum.

I made some Mjolnir (that would be the hammer of Thor for those who don't speak pagan-geek :) ) pendants for viking party costumes. It was also an opportunity to try my hand at sculpting and moldmaking, bringing me one step closer to living the life of a mythbuster - that is, a mythbuster without his own television show. I based the design on this one (found on google images); for the price, I probably should have just bought that one instead, but that's not really in the creative spirit of this whole New Year's Eve theme party thing.

The first step: I melted down some old bits of candle wax and cast them into a puck shape, from which I carved the original pattern.

One of the new elements in this New Year's Eve fireworks show was this 16-shot mortar rack, designed to accommodate the "festival ball" type of readily available mortar shell. The tubes are HDPE with a 1.875 inch bore, available from Skylighter at $27.25 for a group of six. HDPE is really the best material for this application - do NOT use PVC, as it will shatter into dangerous shrapnel if the shell fails to clear the tube and detonates inside. Certain types of cardboard launch tube, available from pyro suppliers, might be acceptable but I have no experience with this so you take your own risk if you choose to use it. The Skylighter HDPE tubes have a wooden plug at the bottom - I drove stainless steel wood screws into this plug from the base of the rack to secure the tubes.

The rack itself I constructed from various bits of hardware store lumber. Since this rack is deployed outside, in potentially wet environments, I painted it with several coats of Kilz primer, then glossy black exterior latex (glossy to make cleaning off any powder, soot, or dirt easier). I also mounted two carrying handles on either end.

During the New Year's show, this rack was loaded with a mix of Black Cat "Gold Class" spherical shells and their "Fort Knox" cylindrical shells. One row of eight was electronically detonated using my computer-controlled firing board (of which more anon), while the other side was lit with a blow torch, like most of the fireworks that night.

New Year's Eve 2007 was the latest in what has become a Martinson tradition: a themed costume party. The theme this year? Vikings! As always, this party involved a great deal of creative work beforehand in making the costumes, props, fireworks show, and all the rest of what our guests have come to expect out of a not-so-typical New Year's Eve. I can't publicly thank everyone responsible for these preparations, but you know who you are, and I know what you did. Thank you all. This post (and the ones to follow), however, is more for the benefit of those who weren't at the party, but are interested in some of the projects completed for it. First, my viking shield:

This is probably the only costume item that bears any similarity at all to actual viking kit, or at least measures up to a reasonable re-enactor's standard. Yes, it is plywood (11/32") rather than joined planks, and the fanciful dragon motif (taken from a shield on display at the Norway pavilion in EPCOT center) was probably never seen in actual dark age combat, but other than that, it's not bad. The plywood blank I cut out with a jigsaw. The steel boss was made by an armourer named Mad Matt (it's the "satin-finished" round boss available on his site) - a solid, economical choice I'm very happy with. I also applied an edge-banding of 3" wide rawhide strips (soak a large rawhide dogbone till it unravels, apply when moist and flexible) nailed over the edge with blued carpet tacks. The grip in the back picture is just a bit of hardware-store mild steel bar, drilled and riveted through to the boss.

I've been getting a few complaints about various sites not being accessible by Comcast users and discovered that quite a lot of domains are inexplicably not resolved by their DNS servers. Here is an extremely partial list, generated purely at random:

• www.ejectejecteject.com
• www.littlegreenfootballs.com
• www.samizdata.net

These are all popular blogs, and none of them work on Comcast's DNS. So I switched to OpenDNS, a free public dns service. You can sign up for an account, which gives you access to some features like porn-filtering and statistics on DNS usage. You don't have to have an account, however, you can just go ahead and start using the servers: 208.67.222.222 and 208.67.220.220.

Believe it or not, being a member of junk-mailing lists, in particular those targeted at consumers of high-end "lifestyle" products, can be good. Being a close friend or relative of a person on those lists can be even better. This second approach has gotten me past the door of a surprising number of product launches, luxury car test drives, and top-shelf whisky tastings, usually in the company of my cousin Torm, whose tastes are somewhat better funded than my own and whose addresses are in somewhat wider circulation. But it was this October that Torm, my friend Jay Wilson, and I headed south to the Homestead Speedway to participate in the ultimate free-of-charge luxury-goods marketing event: the Audi Driving Experience. Click on the link to read more and be prepared to accept that all Audi requires from you is a driver's license and the flimsiest pretense of being richer than you actually are to stuff your head into a helmet and set you loose on a racetrack piloting several hundred thousand dollars worth of powerful machinery.

Brandon Moore and I have made it into local glossy Boca Raton Magazine with our desalination project. Many thanks to Kevin Kaminski for the article; many thanks also to the photographer, whose name escapes me, for taking on the thankless task of making two scruffy geeks look good. If you live in Dade, Broward, or Palm Beach county, go and buy a million copies, on newsstands September 1.