technology – Page 12 – nullteilerfrei

Getting rid of superfluous entries in the TrueCrypt chain loader

tobi technology 2013-05-08

I'm using TrueCrypt system encryption for my Windows Partition and use its chain loader to boot Linux via GRUB, which is installed on my /boot partition. However, at some point I also had GRUB installed on my root partition. Because of that the TrueCrypt boot loader — after pressing ESC when I didn't want to boot Windows — showed a list of partitions to boot from instead of directly starting the only other boot loader. That's less convenient and a little bit annoying, so I wanted to get rid of the entry. As the TrueCrypt boot loader seems to detect boot loaders on partitions automatically, I wanted to try deleting the redundant one. However, I didn't find anything on how to delete a boot loader from a partition; that's probably because it usually isn't necessary. A quick search on Wikipedia revealed that the boot loader on a partition is stored in the volume boot record (VBR) of the partition, which is just the first sector, similar to the MBR. So I first made a backup in case I got anything wrong ((make sure to backup to a different partition than the one you're going to write on :) )):

$ dd if=/dev/sda5 of=sda5.vbr bs=512 count=1

and then wrote zeros to the VBR:

$ dd if=/dev/zero of=/dev/sda5 bs=512 count=1

which did exactly what I wanted. Be aware, however, that when you want to delete the boot loader from an extended partition, this would overwrite the partition table in the extended boot record (EBR), so you may only overwrite the first 446 bytes of the sector instead of all 512. One last thing that cannot be stressed enough: Have a current and complete backup handy, and be prepared you might have to use it. I'm no expert on the subject. If the VBR is used for more purposes than just containing a boot loader as I expect, zeroing the whole sector may really go wrong.

Why Sudoku is boring

rattle code, remark, technology 2013-04-17

I was riding the backseat of a car, a pal of mine with a large Sudoku book on the seat beside me. I glared over at him and remarked that I find Sudokus utterly boring and would feel that my time is wasted on any of them. He looked up at me, clearly demanding an explanation for that statement. I continued to explain that a computer program could solve a Sudoku with such ease that there is no need for humans to do it. He replied that something similar could be said about chess, but still it's an interesting game. And it was then, that I realized why Sudoku is so horribly boring, and chess is not. It was the fact that I could code a Sudoku solver and solve the Sudoku he was puzzling about, and I would be able to do it faster than it would take him to solve the entire thing by hand. This does not apply to chess, evidently. Of course, I confidently explained this to him. »Prove it.«, he said. So I did. Do you want to know more?

Recursively set ownership in Windows

rattle remark, technology 2013-04-02

I have a folder data with stuff in it. I am not using an Administrator account on my Windows machine, and that folder is supposed to be owned by my user. When you search for how to take ownership of all files and folders in a certain directory recursively, you get told to use TAKEOWN, a lot. Well, it has a little catch: You can only really use it to take ownership. Not to give it. A much more giving command is

ICACLS C:\data /setowner rattle /T

Oh yea, it's the /T switch that makes it recursive.

Characters of the Symmetric Group

rattle code, mathematics 2013-03-27

Harm Derksen brachte uns schon im Jahre 1998 die weltschnellste Methode zur Berechnung irreduzibler Charaktere der symmetrischen Gruppe. Aber in seinem preprint, Computing with Characters of the Symmetric Group, bleiben einige Fragen offen, die ich hiermit zu klären versuche.

» The code to end all codes «

Die Welt ist einen halben Herzschlag alt. Der unsterbliche Prophet meditiert seit Anbeginn der Laufzeit auf dem তাজমহল und studiert die heiligen 12 Zeilen C-Code, die jede SAT Instanz in $\mathcal{O}(n^{9699690})$ lösen. Wenn der Puls eine Ganzzahl wird, so wird er erwachen und die Wahrheit verkünden, und Lob wird gepriesen, und Licht wird ewig scheinen auf die Kinder des Schaltkreises. Denn er ist der Taktgeber, und an der Spitze des Signals wird es sein, wenn er uns erscheint. Buch Arithmæl Circulæ, Vers 21:7 Wollen Sie mehr wissen?

Lenovo System Update somewhat demystified

rattle remark, technology 2013-03-09

Suppose you have a Laptop, which therefore must be a [ThinkPad](http://www.lenovo.com/products/us/laptop/thinkpad/). Let's also assume that you [use Windows 2008 as a workstation](http://www.win2008workstation.com/), just like [I do](/2012/03/22/turning-windows-2008-r2-into-a-workstation/). Then, you might run into some issues with [Lenovo System Update](http://support.lenovo.com/de_DE/detail.page?LegacyDocID=TVSU-UPDATE). To be precise, it tells you: > An error occurred while gathering user information. Then it stops. I will provide a solution to this problem which is not specific to Windows 2008 R2, and therefore, I hope that my solution will also work for future versions of Windows that are not out-of-the-box supported by SystemUpdate. Do you want to know more?

Nested case distinctions in LaTeX

rattle latex 2013-03-07

Trust me, I am not one to enjoy deeply nested case distinctions in a mathematical proof. In fact, I'd rather there were no case distinctions necessary at all. However, to quote the famous mathematician Nikolai Nowaczyk: > Some theorems have beautiful proof - and some theorems are worth fighting for. Anyway. If you have to do it, you should do it in beautiful $\KaTeX$. Do you want to know more?

Convert WAV to MP3 with VLC

rattle remark, technology 2013-03-05

If you like electronic music, you obviously lurk getworkdonemusic.com all the time with jDownloader running, so you can copy the link to any nice track on the air and download it, slowly aquiring a groovy selection of electronic music for the lonely train hours where you have to get work done, offline style. Sometimes, however, these tracks are in wave format, for reasons that are completely beyond me. A quick google search for »convert WAV to MP3« points you towards a huge selection of shitware, when it could be so much easier: Fire up VLC, the best media player in the world ((This post refers to VLC media player 2.0.5 Twoflower.)) and go * Media, Convert/Save (Ctrl+R) * Add your file to the list. * Click the button that says Convert/Save. * Select a destination file. * Set the profile to Audio - MP3 and hit Start. Also, make sure you don't have VLC set to loop, because otherwise it'll spend the next few hours overwriting that file with the same converted MP3 again and again. True story.

Thunderbird: Mark all drafts as read

born technology 2013-03-04

I wasted like 60 seconds a day marking drafts in Thunderbird as read after using the SendLater-Plugin. The following AutoIt-Scripts that runs in background now saves this precious amount of time!

$x_offset = 80
$y_offset = 140

TraySetIcon('C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe', 1)

While 1
    WinWait('[TITLE:Send this email later; CLASS:MozillaDialogClass]')
    WinWaitActive('[REGEXPTITLE:Mozilla Thunderbird]')
    Sleep(1000)
    $tb_pos = WinGetPos('[REGEXPTITLE:Mozilla Thunderbird]')
    $mouse_pos = MouseGetPos()
    MouseClick('right', $tb_pos[0]+$x_offset, $tb_pos[1]+$y_offset, 1, 0)
    Send('{UP 4}{ENTER}')
    MouseMove($mouse_pos[0], $mouse_pos[1], 0)
WEnd

Animated LaTeX

rattle latex, mathematics 2013-03-01

After discovering the toggle command available in MathJax, I immediately went to asked the capable people of tex.stackexchange whether this could be done inside a PDF file. And indeed: It can be done!

\documentclass{article}
\usepackage{animate}

\begin{document}
\begin{animateinline}[step]{1}
  \strut$x=1$
\newframe
  \strut$x=2$
\newframe
  \strut$x=3$
\end{animateinline}
\end{document}

Now, what do I want with this package? I want to do abstract nonsense. A diagram-based proof should, in my opinion, be a slideshow. You start with the diagram that is your assumption and by simply interacting with the diagram (clicking it), in each step, a new arrow is constructed from some universal property. I wanted to write a neat animated PDF with an abstract nonsense proof of the famous Snake Lemma, and there is a great book by Francis Borceux containing a proof, but unfortunately, I was unable to overcome a difficulty with the proof, so that will have to wait until someone answers my question.

Windows Shortcuts

born technology 2013-02-23

I learned three new Windows shortcuts today: * Win + Pause: System Properties * Alt + Space, n: Minimize window * Alt + Space, x: Maximize window Especially the latter two are very useful for me.

Offline Navigation

nikno technology 2013-02-20

On Android Smartphones you can use GoogleMaps app for Navigation — unfortunately, it requires an internet connection and this can be very expensive if you use this outside your home country. Therefore, I was looking for a free app which supports downloading the entire maps for certain regions. I think Navfree does the job.

TaskWarrior – Stop worrying and start warrioring!

born productivity, technology 2012-12-31

# Why TaskWarrior? After I've heard of the software TaskWarrior in summer of 2012, I started using it instantly. My main reasons are: * Since I'm a big fan of self quantification, I wanted the data to be accessible and independent of the existence of any software company. The TaskWarrior stores its data in text, which is imho the most future proof format. * Everything from the system described in David Alan's book "Getting things done" (short GTD) can be implemented with TaskWarrior. * It is cool and geeky to use (via command line!). This has a real advantage too: you have the full power of your shell at hand and the programm itself also has powerfull batch processing capabilities. --- Do you want to know more?

How to use MetroApps in Windows 8 with a resolution that is too low

born technology 2012-12-26

It seems that you can't ((Force Windows 8 Metro Apps to run lower resolutions below 1024x768)) ((Windows 8 Metro style apps running on low screen resolution netbooks)) ((How to enable Windows 8 Metro style apps on an older netbook)) ((Google-Suche)). If you are ok with a squeezed look, set all registry values of Display1_DownScalingSupported to 1 and change the screen resolution to at least 1024x768.