There may be a significant wrinkle to using OpenAFS at home, when it comes to user home folders: I don’t think Dropbox will run on out of an OpenAFS volume, as it won’t get the full set of change notify logs it needs to be able to detect changes and sync to the cloud.

Time to test.

My PowerMac G4 Cube is now running 10.4.11 Server and is an active OpenDirectory master. Doing the setup on this brought back a lot of memories. This time through I had the devil of a time remembering how to setup an auto mount in Workgroup Manager, and I was reminded just how touchy early versions of OSX were to DNS issues.

It’s working now – running networked home folders to the machines on the network, served off my Solaris file server, and running a Kerberos instance, that will let me do more work with OpenAFS later down the road. Just happy it’s all working and running.

So, the test projects for the concrete work were sucessfull. I still need to get a grinder and grind/polish/seal the test bits to make sure they will finish up the way I want them, but it works. I now am comfortable with the process, and ready for more. This means it’s time to start thinking seriously about the big project I want to do, the desk top. This was inspired by a polished concrete computer desk project I saw on Instructables awhile ago.

As I’ve posted in the past, I built my current computer desk. It’s made from a pair of rectangular structures that house computers, with a desk top stretched across the top. There is also a pair of thin, tall shelves that rest on the top of the desk. By design, the entire setup is modular – each rectangular section that hold a computer is totally separate from the desk top, and the shelves just rest on the top of the desk. My plan is to replace the desk top itself with a concrete slab. This is going to happen when I move the office into the shed, after the shed is refinished with insulation, better power, and an air conditioner. Due to size and weight limits in the shed, I’m currently planning on making the concrete slab 8’x3.5’x3″.

One of the first major considerations is that a slab of concrete that is 8’x3.5’x3″ will need significant internal reinforcements. Likely rebar, which was designed specifically for this kind of work. Rebar is cheap, easily workable (if you get the thinner stuff), and has roughly the same thermal expansion coefficient as cast concrete, so it’s less likely to crack over the long term. There is also epoxy-coated rebar available, which helps to cut down on corrosion issues internal to the finished product. I’m not sure the slab will be under conditions where this could be a problem, but it’s something to think about. There’s also the idea of mixing reinforcing fibers into the concrete mix as I go – there’s a spun basalt fiber that I’d like to try – but that is going to add cost and complexity to the project. I think I’m going to go simple and old school and just stay with the rebar.

The next question is “how strong are the end sections of the desk”? Well, they are strong enough for me to stand on, which is good, even at my heaviest weight (252 lbs this spring). Considering that the slab will be 600-800 lbs or more, this is good, but I may need to redesign some of that, or add addiitonal supports. Part of me is tempted to get some 4″x4″ wooden posts and use them as table legs. We’ll see.

Finally, there’s the question of cable runs etc – do I want to punch holes in the slab to route stuff through? I can’t do it later and be practical, as I won’t be able to move the desk once it’s in place, and I don’t want un-needed holes. I do know I want some in place. The PowerMac Cube comes to mind in that case. I also want to consider adding mounting hardware to allow me to attach monitor arms to suspent the iMac and a possible Cinema Display or TV down the line, so those supports will have to attach to the back of the desk, and be anchored will in the slab itself. There is also the possibility of simply running thin holes directly through the back of the desk, to run the threaded support rod from the mounting hardware through the desk.

Really, I want to do this project, and not get too wound up in making it overly complicated. I’ve finally gotten the mix and wetness down properly, and I can consistently pour a decent slab without too many bubbles – so this could all work. The one thing I’ve not tried – a coloring agent – doesn’t seem very difficult from what I read online, so that’s not an issue either. The biggest thing now is to find the time to actually do this. Then comes the logistics work of renting the cement mixer, buying half a ton of cement, and getting it all to the house. It’s going to be a serious workout lugging the bags, mixing, pouring, etc, but that’s not the end of the world.

UPDATED: I can trust the numbers. Leaving this post as is otherwise.

I can’t trust the calorie counts that RunKeeper generates for my walks anymore.

Yesterday, I took a walk for my lunch break. It took about an hour, and I walked 4.01 miles. I laughed to myself, as RunKeeper said I burned 401 calories doing so. Today, my walk was 4.23 miles, which was a bit brisker, as it was still just an hour, but RunKeeper told me I had burned 750+ calories. I flipped back to yesterday’s walk to see what differences there were – perhaps RunKeeper and the GPS hadn’t agreed on something… but no. Yesterday’s walk now shows up as 706 calories. I flipped back to today’s walk, and it had changed again – now reading 735 calories.

Trying to figure out which number was right, I went to an online calorie counter, in which I put my weight, the distance I walked, and the time I took walking that distance. It told me I had burned 573 calories. Checking two other calculators, they gave me numbers right at 570. So, that’s what I’m going to go with. And I’m going to have to find a better way to track burned calories. A FitBit, perhaps?

Recently, I got my hands on a PowerMac G4 Cube in perfect working condition. As it’s not going to be terribly useful as a media server (or endpoint), and there’s roughly zero development work being done for it, I’m going to turn it into a server. Looking at the docs, I see no reason why I can’t install Mac OS X 10.5 Server on it, and use OpenDirectory as the basis for my home’s distributed authN and authZ. I’ll need to do something to make sure it gets backed up and is replicated, but it’s going to be a fun little project.

Of course, now I need to find my Mac OS X Server install DVD collection.

I am planning to make a concrete top surface for my computer desk to install in the shed-office that we are working on. We have a month or two before the shed is converted, so I have some time to get a grip on how large a project the concrete desk would be, and give me time to size up my skills. I need to know if the project is futile before I begin. This is a big project that will take a lot of planning, learning and time on my part.

The best way to learn is to do, especially with DIY projects.

For my first ever foray into working with concrete, I decided to make a small rectangular brick of concrete, with some decorative glass beads embedded in the surface. Last night, Qais and I used a small section of particle board and some foam core to build a rigid, smooth form to pour the concrete into. It’s about 12″ x 18″ x 2.5″, sided with duct-tape, and the interior joints lined with %100 silicone glue. The foam core should provide a smooth-enough surface to test against, and the silicon glue should keep any moisture from leaking out of the form. The form’s depth is about as deep as I expect to make the desk surface. I also got a 40 pound bag of #1101 Quikrete mix, which is usually used for setting fence posts and making patio steps. It hardens to about 4,000 psi when properly mixed and fully cured.

Today I mixed and poured the concrete into the form, in very small batches. I did this again with Qais’s help. I think it worked, and the concrete slab will setup properly, but there are a number of important lessons learned for next time:

• I need a finer concrete mix – the aggregate in #1101 is too coarse
• A real mixer would be better to use than my gloved hands
• I used way too much water. A mixer will help me keep this balanced
• Put the glass beads in before mixing the concrete
• Don’t rely on the attention span of a three year old

So, the form is full of wet concrete that is setting up. I’ve purchased a 5 gallon bucket and an 80 lb bag of Quickrete 5000 Pro Finish mix, so the next attempt will be either tomorrow or next weekend, with better concrete, a better designed mold, and a more consistently mixed concrete. If it’s tomorrow, I’ll post an update with pictures.

I don’t generally post about political stuff, but this is important. If you live in North Carolina, go vote on Tuesday. And vote against the marriage amendment. If for no other reason than you aren’t a bigot.