When rsyncs go wrong

Ok, so a few days ago I wanted to sync some photos between by laptop and my desktop. My desktop has my entire photo collection and I have a subset of that on my laptop. I frequently sync directories between the two using rsync. The desktop doubles as a backup, the files are on a RAID1 array for redundancy -- of course that isn't enough to be safe, and yes, I found out.

The directory structure is very simple, I've set it up as

yyyy/mm/dd-short-description-of-shoot

with yyyy the year, mm the month and dd the day of the month.

After having done some editing in the current month on my laptop, I wanted to sync it to my desktop.

I have a small script that uses rsync to synchronize the current working directory from my laptop to my desktop. I had deleted some bad photo's and obviously wanted them removed from the desktop as well. So I gave the script the --delete flag, which it handed over to rsync.

I ran the script and was greeted by screenfulls of lines saying deleted xxx or yyy. Hmm, I didn't delete that much pictures. I glance at the files that are being deleted, hmm, wait a minute, those aren't the right ... AAAAAH!

^C^C^C^C^C^C^C^C^C^C^C^C^C

FUUUUUCK! I'm bashing CTRL-C for my life here! Finally it kills itself and gives me a shell prompt. I look at the current working directory:

2010/

That should of course have been

2010/12/

And as I said, I don't have a full mirror of all the photos on my laptop (not enough hard disk space there), so it started pruning all the older ones from my desktop. Ouch.

I've shut down the desktop asap and haven't booted it since. I'm probably going to try my luck with extundelete after the exams. Fingers crossed.

TL;DR Be careful with the --delete flag in rsync. It will fuck you up sooner or later!

Update

Vaporizing some aluminum, taking some pictures

Part of our bachelor project was working with a small scale single turn coil apparatus for creating high magnetic fields. This allowed for some nice plasma pictures!

The principle of single turn coils in a nutshell: you dump a whole lot of energy from a capacitor bank in a (single turn) coil. Once you get a few kiloAmperes flowing, you get a pretty high magnetic field, but the coil also endures intense magnetic stresses and a lot of Joule heating. Ultimatly the coil snaps after the peak field is reached and the vaporized metal turns into a nice plasma. The remains of the coil fly off outwards, keeping the sample intact.

I photographed the plasma and pieces flying off with a long exposure in a dark room. I was slightly worried about frying the sensor, as there is a lot of high energy UV light coming from the plasma. I actually stacked on two UV filters just for some peace of mind. I was still constantly checking the sensor during the first few images.

This is the best picture, it's an aluminium foil completely flying to pieces on our little testing apparatus (Click for deviantArt page where you can see the full resolution version)

This was done as a long exposure in a dark room with a 250mm lens stopped down to f/11 on ISO 100. It was one of the first photos I shot, I did some f/32 shots at first (to protect sensor), but those coil shots were less bright, so I opened up the aperture. Then this one blew up much brighter then before and kind of took me by surprise. The sensor is still OK though!

These pulses can reach about 2T, hence the catchy title 'Two Tesla Plasma' (go ahead, say that out loud. It has a nice ring to it, right?)

I also tried to get a 3D image by using a second camera from a friend of mine. Click the image below to see the effect (WARNING: I can NOT be held responsible for possible epilectic seizures)

The parallax looks a bit odd because both images were shot at 250mm on a cropped sensor. Using a focal lengtch that matches the human eye more closely would probably have made the effect much better, but I'm not too fond of getting the cameras that close to the glowing metal pieces flying everywhere.

So, everyone go and study physics: where you can blow stuff up and get pretty pictures -- for science!

[Edit] For those interested in more info, you can skim through the paper hosted at github (Don't mind the bleek results, we had some problems and serious time constraints).

Highly Entropic

In case you were wondering why this blog is titled "Highly Entropic", this is the deal:

Entropy is a physical (thermodynamical) property. It's one of those things that can be pretty hard to understand. Roughly speaking, one can say that it is a measure of the "disorder" of a physical system. If something is "Highly Entropic", it is said to have a lot of "disorder".

The reason this blog is titled "Highly Entropic" is partly because I intend to blog on various (unrelated) things (for the moment it's mostly (DIY) photography, but I also plan on doing computer/Linux related posts, maybe somethings food-related, wine making, etc...).

A second reason is that I am quite "entropic" myself. Since a picture says more than a thousand words, I'll just leave you with this panoramic view of our garage (click for the deviantart link, click "Download" there for the full resolution photo)

Some things worth mentioning: This shot was made with the parnoramic mount I blogged earlier. On the bottom left, you can see some pieces of my ring flash. On the right side, you can see the rear of a wooden recumbent bike I built several years ago (there may be a blogpost about this in the (far) future).

The original picture is 250 megapixels large and was stiched together from 42 images using hugin. Doing so required around 9GB of memory at its peak -- one of the very few times I actually needed to setup a swap file (I only have 6GB of RAM). The resulting (8bit) compressed tiff file is 560MB.

On panoramic mounts and entropy

Still going strong in the DIY photography category (even though there has been some delay). This time it's a panoramic tripod mount!

With current software it's extremely easy to make a panoramic picture out of a set of overlapping photo's. (I use the excellent free and open source tool hugin.) There are, however, some things you should be aware of. Of course, the pictures should be taken from the same spot. The logical thing to do is to use a tripod. This gives good results for distant landscapes, but if you include near objects in the scene, you will encounter some problems stitching togenther the panorama. This is due to parallax and can be resolved by using (building!) a panoramic tripod mount like this:

(If you find the shadow on the above photo a bit weird, it's because I shot it with my ringflash, no particular reason)

Instructions and lots more after the jump!

On using the mandoline when really really hungry

DON'T DO IT!

I did, however. Picture below sums it up.

Warning: slightly graphic images after the jump (involving a small slice of flesh that once belonged to my thumb)

Yet another DIY ringflash

Sorry for the long delay between posts -- college has been eating my time. In my post about re-using an old strobe (which got referenced on lifehacker -- cool!) I told you I was working on a (macro) ring flash. It's been finished for about a week now, but I didn't have much time to try it out in the field. I thought I'd just go ahead and post the build process already.

Self shot in mirror with DIY ringflash

Downside of shooting RAW: the thirst for diskspace -- Linux RAID adventures

With my photo directory easily breaking the 100GB limit after about a month of shooting, I needed some more space. Given that disk space is pretty cheap these days, I went for two 1TB drives in software RAID1 (I don't have the discipline to make decent back-ups, hence the RAID). It turns out to be pretty easy to set up a software RAID on Linux -- if you read the documentation properly (I didn't).