Archive for ‘Reference’ Category
Posted on 17:22, September 9th, 2009 by Many Ayromlou
Posted on 13:43, May 6th, 2009 by Many Ayromlou
Lost a couple of files today by mistake (that’s what I get for using Synergy keyboard/mouse sharing application to run in windows)…..anyways, after a bit of googling I came across a very nice and simple recovery tool….Recuva. This one even recovers stuff that’s been deleted from the Recycle Bin (which was my case/mistake). Nice….and did I mention free :-).
Neat idea…..You all know about sites where you can upload a large file, for your friends to download. It’s simple, but what if you don’t want to store the file somewhere. It suddenly gets a bit harder, right. Now you need to bring up that FTP/SSH server, create userid’s, open firewall, forward ports, etc. You get the idea.
Well, that’s were Jetbytes fits in. It’s a simple on-the-fly file transfer web service. You go to their website, choose the file you want to pass on to your friend. The site prints out a temporary/random URL, you send your friend the URL and as long as you stay on the page, they can download the file by simply clicking on the URL.
JetBytes does nothing more than route the file through their web server, allowing you to share large files easily with others even if one or both of you are behind firewalls. There is no restriction on the size or type of the files. Oh and did I mention, JetBytes is a free service.
Posted on 21:53, March 28th, 2008 by Many Ayromlou
A friend passed this on today (thanks Jeremy). If you use a mic in your day to day businness (or even if you’re an occasional ichat/skype user, you should check this out. RevoLabs have introduced a new line of Wireless microphones that come with RF-Armor. What does that mean, well the next time your GSM phone rings/sync/receives email, your microphone won’t be going all crazy. Plus their Solo mics come in three different types:
Posted on 12:19, December 17th, 2007 by Many Ayromlou
If you like to see some of the most prolific Engineers and Scientists of our time talk about how we got to where we are in computers, head over to the Computer History Museum Channel on You Tube. Oh, and if you’re ever in Northern California somewhere, take a side trip to Mountain View and visit the Museum in person, I did.
OSX Webmaster special: Shared webserver, bad umask settings, group permissions and filenames with spaces…
Posted on 12:20, October 24th, 2007 by Many Ayromlou
Okay so this all started with our users not being able to share files on our webserver. We use SSH only for upload/download and interactive access (ie: no ftp). Through trial and error we found out that the default umask (under OSX Server) for sftp uploaded files are 0033 (ie: rwxr–r–) and directories are 0022 (ie: rwxr-xr-x). This creates a problem when one user uploads a file and another user downloads/modifies and tries to re-upload it — they simply can’t because the group permissions are wrong.
If we were using ftp (which we are not) there are some solutions on the net that allow you to modify the startup parameters for the ftp server so that the default umask for all files is 0013 — which would allow a group of people to share/overwrite each others files — but we are using ssh only.
So we came up with two other solutions — a shared upload account and/or a cron job that would modify the group permissions on the website directory to allow group sharing. We went with the second solution and that’s where I ran into so many problems that I decided to create this post. You see normally Unix users know that spaces (and strange characters) in filenames are a no-no. Well that’s not true for Windows and Mac users, they use spaces and other odd characters in their filenames/folders all the time.
I started writing — what I thought was — a simple “for loop” script to go through the website folder and change the group permissions. Of course on the first try things didn’t work nicely because of spaces, so I started compensating for that and came up with:
Finally after a latenight RTFM session (and lots of cursing), I think I’ve found the ultimate file handling loop statement:
After trimming and optimizing the script a bit, here is the final product:
Posted on 23:28, September 26th, 2007 by Many Ayromlou
So this is just a short tutorial, so I don’t have to repeat this to every person who asks about the difference between T and E circuits. Here is the whole thing (more or less), (hopefully) once and for all.
It all starts with the Nyquist’s Theorem and Pulse Code Modulation. PCM is the way telephones digitize audio (your voice). Nyquist’s Theorem (named after Harry Nyquist) says that “When sampling a signal, the sampling frequency must be greater than twice the bandwidth of the input signal in order to be able to reconstruct the original perfectly from the sampled version”. Another way of putting this is that to accuretly encode an analog signal (your voice) you have to sample it twice as often as the total bandwidth you wish to reproduce (your voice on the other side).
Now the phone system carries frequencies between 300-4000 Hz, so according to Nyquist, a sampling of 8000 samples per second will be enough to reproduce any frequency within the bandwidth of an analog phone.
Now fast forward past a bunch of engineering mombo-jumbo (keeping the 8000 samples/sec in mind) and we get to DS-0, the magic designation of the foundation of digital communications. You see the standard way of to digitize a phone call is to record (transmit) an 8-bit sample 8000 times/sec. This PCM encoded stream requires a bandwidth of 64,000 bps. This 64-kbps channel is known as DS-0 and is the foundation of all digital telecommunication circuits.
So now that we have our base unit (DS-0) lets look at one level higher, the T-carrier circuits. You’ve probably heard of a T-1 line, right? Well a T-1 line is actually 24 DS-0 lines multiplexed into a 1.54 Mbps line. The proper definition of a T-1 line is actually DS-1. Now for your trivia question…..what’s a E-1? Well it’s similar in concept to a T-1 except the Europeans actually used 32 DS-0s to define E-1 (rather than 24 like in North America). BTW the really confusing part is that an E-1 — despite having 32 channels rather than 24 — is also called DS-1…..go figure.
Posted on 14:49, September 9th, 2007 by Many Ayromlou
Okay, so this worked for me. I don’t promise that it will do the same for you. Let me explain, my ISP (who shall remain nameless) is very good (good uptime, unlimited, good throughput), but for some reason has horrible DNS servers. I normally try not to use their servers and instead use either my own from work or the University’s upstream provider servers. They are okay, but not blazing. Recently I was told about OpenDNS and I meant to look at it sooner, but didn’t, until the servers I was pointing to went down last night. Well, I have to admit, aside from being safer (because they filter fishing sites at DNS level), OpenDNS kicks butt. It is fast as hell and seems to even have enough smarts to remember mistyped addresses and resolve them properly.
Setting it up is real easy….Just go to OpenDNS.com and change your OS’s DNS field to the ones they advertise on the right side of the screen. There is also step-by-step instructions for all OSes as well. Personally I just changed my DSL routers DNS fields and am now racing through websites. Amazing what difference a responsive DNS server can make to your browsing. Obviously your milage may vary, but generally I have only heard good things about their service.
Posted on 14:06, September 9th, 2007 by Many Ayromlou
Google has just announced google earth 4.2 and new to this version is the Skies. Several Sky layers are listed on the left-hand side, including Constellations, Backyard Astronomy, Hubble Showcase, The Moon, The Planets, User’s Guide to Galaxies and Life of a Star. The Sky layers are composed of over 1 million photographs from various scientific and academic sources.
Another new feature in Google Earth is the addition of super-high resolution photo content, which you can see by adding the layer Primary Database -> Featured Content -> Gigapxl Photos. Unlike Google Street View, these photos however are only available for a few select places (like buildings), so there’s not a lot of random fun stuff to be found.
So go download your free copy, install and hit “Switch between sky and earth”. This is absolutely fantastic and serves as a great resource for research and education. Thanks Google….You guys ROCK!!!
Posted on 18:41, August 4th, 2007 by Many Ayromlou
Here is a easy way to copy an entire directory tree from one Unix machine to another, while retaining the permisssions and ownership, using ssh as the middle man. Assuming that you want to copy everything under source_directory to destination_directory on another machine here is the command you would issue on the source machine (first cd to the directory containing source_directory):
One last command which I came across the other day…..If you’re ever in need of a stop watch just use your shell to measure time. Issue the following command and wait a bit. Now interrupt it via Ctrl-C and it will show you how much time has passed. NOTE: Nothing happens when you issue the command, only when you stop it via ctrl-c.
If this is boring you it is not my fault….Here are some more Goodies :-)
More to come later….
Posted on 22:37, July 12th, 2007 by Many Ayromlou
Okay this is more for me since I keep having to digg this stuff up…..but if any of it is useful to you please help yourself:
Okay enough for now…..I will add more stuff as I come across them…
Posted on 20:13, July 12th, 2007 by Many Ayromlou
Well after watching this piece of art by Daito Manabe, I’m now convinced that the Wii controller can be used as a instrument. This guy is incredible and truly shows what’s possible if you get your creative juices running wild.
If you still don’t belive me have a look at this….