Thursday, November 4, 2010

Equations in Blogger

   Sweet! I can use equations in Blogger! I mean, LaTeX equations. This site has designed a script that allows LaTeX code to be used in Blogger. So I can present Gauss' Law for gravity in a very clear manner, as I now have the tool to do it. So, there you go:
\[ \oint_{\partial\mathcal{V}} \mathbf{g}\cdot d\mathbf{A}= -4\pi GM\]
where $\mathbf{g}$ is the gravitational field, $d\mathbf{A}$ is a differential, oriented piece of area, $G$ is the gravitational constant and $M$ is the mass comprised by the volume described by the surface $\partial V$.

This is going to be so cool!

Tuesday, November 2, 2010

Perhaps there is a stale lock file?

  I recently ran into a seemingly severe problem with my computer. Since approximately 2003, I've been using Linux as my primary desktop. I have enjoyed the learning that inevitably came out of it, and have also joined the great community of Linux users. 

  Anyhow, when I booted my computer yesterday, the boot screen said that it couldn't not mount the local file systems, saying something along these lines:

Cannot link ... to /etc/mtab
Perhaps there is a stale lock file?

(I don't remember the exact error statement.) So, I did not have access to my /boot, /home, /var and other partitions on my hard drive. No X either. In short, my computer was unusable, as I did not have the necesarry files.
 I immediatly Googled the issue[*] and eventually found a solution:

sudo rm /etc/mtab~

This seemed to correct the issue without any consequence to the rest of the system. Of course, don't delete the /etc/mtab file proper, but the temporary file marked by the tilde. 

 I later found out that this problem originated from Transmission BitTorrent Client. An option in the software allows it to keep your computer to go to sleep, probably creating that /etc/mtab~ file in the process. I did some testing and it seems that it is well behaved about it, i.e. if you let it close properly, it will remove the lock file and allow your computer to sleep or shut down. 

Anyhow, in the hope that that helps someone. Oh, by the way, I'm using Arch Linux 64-bit. 

[*] On my iPod Touch because I still do not know how to connect to a WPA-protected access point with the command line. 

Monday, November 1, 2010

GCal push notifications on your iPod

 Recently, Google updated its Google Mobile app for the iPhone/iPod touch. Lifehacker almost instantly pushed out the information to the geeks. However, they failed to mention one small detail.

I tried this when it went out the first time. For some reason, I received notifications in the form of badges for my Gmail e-mail, but nothing for Google Calendar. The answer to that problem is, in fact, very simple.

I switched the calendar feed from Exchange to Gmail itself, which solved the problem. I did that to get colour sync from Google Calendar and the Calendar app on the iPod Touch  and I suddenly began receiving push notifications from GCal!