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We’ve moved

Posted by slayton on July 29, 2009

I’ve moved this blog to:

technexus.wordpress.com

I know it isn’t a big change but technexus sounds better to me than nexus172.

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Screen, a terminals best friend

Posted by slayton on May 31, 2009

One of my favorite things about using linux is the terminal.  One thing that annoyed me when I started using linux was if I started an application in the terminal I had to leave the terminal running; if I closed the terminal the running application would also close. The simple solution to this problem is a little appliction called screen.

Next time you run an application in a terminal start it with screen:

screen <application_name>

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How to stream video to your XBox360 using Ubuntu + uShare

Posted by slayton on April 26, 2009

I’ve known for a while that the newest Xbox 360 software supports streaming video from a computer running Window Media Center. What I didn’t know is that when Microsoft added the media center capabilities they decided to use someone else’s media server standard; UPnP to be precise.

This is really exciting because this means that anybody who implements this standard can stream video to an Xbox over the network.

I run Ubuntu Linux and discovered that there are several programs you can install that will setup a UPnP Media Server, the one I picked to use is uShare.  To install ushare I opened a terminal and ran:

sudo apt-get install ushare

After that I had to edit the ushare configuration file saved under /etc/ushare.conf

If you don’t feel comfortable editing the file you can run to help you setup the configuration file.

sudo dpkg-reconfigure ushare

Here is how I setup my file (I’ve removed the comments from the file for readability):

USHARE_NAME=Ubuntu_Media_Server

USHARE_IFACE=eth0 (the name of which ethernet adapter you’ll send the data over)

USHARE_PORT=49153

USHARE_TELNET_PORT=1337

USHARE_DIR=/home/slayton/Desktop/Shares (any dir will work just put your media there)

USHARE_OVERRIDE_ICONV_ERR=yes

ENABLE_WEB=no

USHARE_ENABLE_XBOX=yes (the USHARE_ is missing in the file you need to add it)

ENABLE_DLNA=no

uShare automatically starts a daemon upon boot, I don’t like this so I kill the daemon after boot with:

sudo /etc/init.d/ushare stop

Then I start uShare when I need it with:

ushare -x  (-x is for xbox compatible mode)

Start up your Xbox scroll the Video Library, select Ubuntu_Media_Server (or whatever name you picked) and begin the streaming goodness!


Posted in How To, Linux, Stick it to the man | Tagged: , , , , | 22 Comments »

How I got my Verizon Contract cut in half!

Posted by slayton on April 22, 2009

This is how I got my verizon contract cut down by one year!

I signed a new contract back in January so I was locked in with verizon for 24 months (until Jan 2011).  I get discounted service through my work so I called up verizon to apply the discount. To get the discount however, the contract needed to be in my name (it was previously under my wife’s name). It was an easy switch to make, I had to provide social security number and and verbally recognize that if the bill doesn’t get paid its my credit that gets hit.

Here’s the trick, because I made the change over the phone I wasn’t able to sign a paper contract, rather I agreed to a verbal contract.  Verizon will only sign a 1 year if done verbally. My 2 year agreement got cut down to a 1 year agreement! My contract that should have expired Jan 2011 now expire April 2010.   I don’t qualify for a free phone until Jan 2011 but my contract is up May 2010!

If you want to do the same its simple, get someone who trusts you to accept the contract in their name. If you have a family plan like i do just switch the primary account holder to another person on the family plan!

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How I got around Comcast’s blockade of SSH

Posted by slayton on April 21, 2009

I have 2 computers a home computer and a work computer. I do a lot of work on both of them and being able to access files on one from the other is essential.  To do this securely I use SSH.  The only problem is that I can only SSH from my home computer to my work, but I can’t SSH in the other direction. I’ve done some reading around and it looks like comcast either blocks all incoming traffic that isn’t http related or actually has me sharing an IP with several people. Regardless, a lot of people have been having problems accepting incoming SSH connections with comcast.  I figured out how to get around this problem. All it takes is a little bit of reverse port forwarding, or reverse tunneling.

Here is how I did it.

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Posted in How To, Linux, Stick it to the man | Tagged: , , , , , , , , , | 2 Comments »

What are moments and products of inertia?

Posted by Mark on April 8, 2009

I saw this question today on the internet at a forum, and nobody seemed to have an answer. Some people thought they knew what they were talking about, but had absolutely no clue. I have a clue, as I’m responsible for keeping track of these properties for over a hundred components on a developmental rocket program.

Question: Do the moments and products of inertia represent anything in the physical world?

Answer: In short, yes. But not intuitively.

It’s best to think of moments and products of inertia in terms of the inertia tensor, which is a mathematical concept – it’s a matrix of inertias for a given 3D object.

The moments are the diagonal values of the inertia tensor and the products are the off-axis values. Keeping the tensor in mind, you can think of an object’s moments of inertia to be the rotational equivalents of the general concept of inertia. Ie, as inertia is the resistance to change in motion, moment of inertia is an object’s resistance to change in rotational motion about some axis. As there are three dimensions, any physical object’s rotation can be defined about 3 axes. It is these axes that form the basis of the inertia tensor. If it took 4 axes to define rotation, the matrix would be 4×4, not 3×3.

In the real 3D world rotation is quite complex – for most real-life objects, you are not going to be able to find 3 axes about which the object will rotate in a stable manner. Ie, most objects don’t have mass distributed symmetrically about all 3 axes at once. Thus, you get off-axis moments of inertia, also known as products of inertia. POI’s can be thought of as measurements of dynamic imbalance of an object and basically represent asymmetrically distributed mass. Note that mass can be distributed symmetrically about one axis but not another, leaving you with products of inertia.

If you see an inertia tensor and the products are zero, there is no dynamic imbalance – the object will rotate perfectly about the defined axes. In such a case, you can call these the principle axes.

Ugh. This is complicated stuff and is often not covered in undergrad engineering or science. What I’ve written is only going to be a piece of the puzzle to understanding, but I hope it has helped. Let me know if any of you see errors in what I’m saying.

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The Halloween Documents

Posted by slayton on October 11, 2008

The following link contains a Microsoft Internal Memo about the real threat posed by Open Source Software (OSS) and more specifically Linux.  I’d suggest you read it as it points out from a very critical source the strengths of both Linux and the OSS development community.

http://www.catb.org/~esr/halloween/halloween1.html

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Linux is not Windows

Posted by slayton on October 11, 2008

The following work is copyright and belongs to Dominic Humphries. It may be redistributed under a Creative Commons License: The original URL of this article is: http://linux.oneandoneis2.org/LNW.htm which must supplied in attribution.

Linux is NOT Windows

If you’ve been pointed at this page, then the chances are you’re a relatively new Linux user who’s having some problems making the switch from Windows to Linux. This causes many problems for many people, hence this article was written. Many individual issues arise from this single problem, so the page is broken down into multiple problem areas.

Problem #1: Linux isn’t exactly the same as Windows.

You’d be amazed how many people make this complaint. They come to Linux, expecting to find essentially a free, open-source version of Windows. Quite often, this is what they’ve been told to expect by over-zealous Linux users. However, it’s a paradoxical hope.

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Everyone says Linux is secure, here are the facts!

Posted by slayton on October 7, 2008

I have been asked by more people then I can count “How is linux better then windows?”  My response is usually, something like “better is kind of a subjective term, but one thing linux does better then windows is security.”  To that the usual response I get is “Why is linux more secure?”  Today I hope to answer this question by illustrating a few key differences between the ways that Windows and Linux handle security and why Linux does a better job.  (Buckle up this may be a longer post)

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Posted in Linux | Tagged: , , , , , | 7 Comments »

Secure Shell

Posted by slayton on October 5, 2008

Secure Shell – SSH

In my previous post I mentioned the existance of the shell.  This post is about Secure Shell(ssh) and what you can accomplish with ssh.  In a nutshell (pun intended) ssh allows you to open a shell securely on another machine that is running an ssh server.  All ssh authentication is done over the Open SSL protocol, meaning that your connection is completely encrypted and cannot be snooped or intercepted.

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Posted in Uncategorized | 2 Comments »

 
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