...making Linux just a little more fun!

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# Mailbag

### This month's answers created by:

[ Anderson Silva, Steve 'Ashcrow' Milner, Amit Kumar Saha, Ben Okopnik, S. Parthasarathy, Henry Grebler, Kapil Hari Paranjape, Karl-Heinz Herrmann, René Pfeiffer, Mulyadi Santosa, Neil Youngman, Paul Sephton, Kiniti Patrick, Aioanei Rares, Steve Brown ]
...and you, our readers!

# Our Mailbag

### 'aptitude' Easter egg

Ben Okopnik [ben at linuxgazette.net]

Wed, 14 Jul 2010 11:41:39 -0400

Run the following, one at a time:

    aptitude -v moo
    aptitude -vv moo
    aptitude -vvv moo
    aptitude -vvvv moo
    aptitude -vvvvv moo
    aptitude -vvvvvv moo

    --
    * Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *

[ Thread continues here (2 messages/1.58kB) ]

### TAG postings

Dr. Parthasarathy S [drpartha at gmail.com]

Mon, 12 Jul 2010 10:43:06 +0530

I have received quite a few comments and suggestions concerning my "linusability" project. thank you all. I am trying to make a consoldiated summary of all suggestions I have received. I seem to have misplaced/lost some of the mails. I would like to retrieve them from the TAG mailing list. Is there an archive of TAG mails somewhere ? I tried but could get to only the archives of LG issues. Cat find TAG mail, back issues though.

Can someone guide me please ?

partha

PS You can follow my progress in the "linusability" project, from : http://www.profpartha.webs.com/linusability.htm

    --
    ---------------------------------------------------------------------------------------------
    Dr. S. Parthasarathy                    |   mailto:drpartha at gmail.com
    Algologic Research & Solutions    |
    78 Sancharpuri Colony                 |
    Bowenpally  P.O                          |   Phone: + 91 - 40 - 2775 1650
    Secunderabad 500 011 - INDIA     |
    WWW-URL: http://algolog.tripod.com/nupartha.htm
    ---------------------------------------------------------------------------------------------

[ Thread continues here (4 messages/4.02kB) ]

### Face detection in Perl

Jimmy O'Regan [joregan at gmail.com]

Sat, 3 Jul 2010 22:24:59 +0100

On 27 June 2010 18:46, Jimmy O'Regan <joregan at gmail.com> wrote:

    > Since I got commit access to Tesseract, I've been getting a little
    > more interested in image recognition in general, and I was pleased to
    > find a Java-based 'face annotation' system on Sourceforge:
    > http://faint.sourceforge.net
    >

I just saw this headline on ReadWriteWeb: "Facebook Adds Facial Recognition" (http://www.readwriteweb.com/archives/facebook_adds_facial_recognition.php). Of course, being a blog aimed more at management types, they are, of course, wrong. According to Facebook (http://blog.facebook.com/blog.php?post=403838582130) they've added face detection...

They're probably either using OpenCV or the part of the Neven code that Google added to Android (http://android.git.kernel.org/?p=platform/external/neven.git;a=summary)

    --
    <Leftmost> jimregan, that's because deep inside you, you are evil.
    <Leftmost> Also not-so-deep inside you.

### I'm utterly gobsmacked

Jimmy O'Regan [joregan at gmail.com]

Sun, 25 Jul 2010 00:34:57 +0100

This is, hands down, the single dumbest bug report I've ever seen: http://code.google.com/p/tesseract-ocr/issues/detail?id=337

I'm kind of reminded of the usability thread, because whenever I see a dumb question on the Tesseract list, or in the issue tracker, it's always a Windows user.

But mostly, I'm just wondering: can anybody think of a valid reason why anyone would want to OCR a CAPTCHA?

    --
    <Leftmost> jimregan, that's because deep inside you, you are evil.
    <Leftmost> Also not-so-deep inside you.

[ Thread continues here (9 messages/11.70kB) ]

### Mini-puter/bridge/etc.

Ben Okopnik [ben at linuxgazette.net]

Thu, 1 Jul 2010 12:59:55 -0400

Hi, all -

I've been trying to do some research on this topic, but am coming up dry (or at least very sparse on good choices.) I'm hoping that someone here will have an answer.

A few days ago, I got an AirPort Extreme - a wireless bridge + USB gadget from Apple - so I could "unwire" my poor spiderwebbed laptop. Had to set it up on a Windows machine [1], then started playing around with the possibilities. Plugged in my new high-gain "client bridge" that's up my mast (really, really impressive gadget, by the way - http://islandtimepc.com/marine_wifi.html) - PoE connector snaps right into the WAN plug, AirPort hooks into it, life is good. Plugged in a USB hub, hooked up my HP printer, told the AirPort software to share it - OK, that's all fine too. Hooked up the external hard drive... um. Well, OK, a few hours of struggling with Windows file sharing, and Samba, and more file sharing, and... argh. My external HD is formatted as ext3, so - no joy there, despite Macs running BSD these days. No way am I going to reformat it. Also, plugging in an external CD-ROM was a total fail: the AirPort doesn't recognize it, even when plugged in directly without a hub. In addition, there's no HTTP interface on this thing: you have to use their (Windows or Mac only) software to talk to it.

So, the AirPort is going back to the store - but now, I'm stuck with a dream. It would be really, really nice to just connect power and maybe an external monitor to the laptop, and have the external drive, a CD-ROM, the printer, and the network all available wirelessly. After noodling on this for a bit, a small light went on. I said to myself: "Self... what if you had a small beige box of some sort that was running Linux and had all that stuff plugged into it?" At that point, none of the above peripherals would present a problem: they'd just be available stuff, accessible via standard protocols.

The only question is, what's the cheapest, smallest box that I can get? Obviously, it needs to have at least one USB port, one Ethernet port, and be accessible via WiFi. If it runs on 12 volts, that would be a great plus. Recommendations on a flavor of Linux to run on this gadget would also be welcome.

Thanks in advance for any suggestions!

[1] All FOSS-vs.-proprietary rhetoric aside... how the HELL do people put up with Windows? I had to struggle through so many "YOUR MACHINE MAY BE INFECTED!!! BUY OUR SOFTWARE ***NOW!!!***" warnings, update-and-reboot repeats, instances of software automatically firing up a browser and taking you to the company webpage, and completely senseless procedures ("sharing" a network-accessible disk is a complete lather-rinse-repeat nightmare) that I found myself literally screaming "STOP already!" in frustration. And I'm not what you'd call computer-illiterate, nor completely unfamiliar with Windows - although I haven't used it in several years. That was just a horrible experience that I hope I never have to repeat.

    --
    * Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *

[ Thread continues here (12 messages/21.75kB) ]

### linusability...again

Dr. Parthasarathy S [drpartha at gmail.com]

Fri, 16 Jul 2010 13:14:31 +0530

One frequent problem faced by Linux adherents like me is the difficulty of finding hardware which is supported by Linux. Here is some hope for us::

http://www.linuxpromagazine.com/Online/News/Open-Source-Hardware-Gets-Defined

Take a look.

partha

    --
    ---------------------------------------------------------------------------------------------
    Dr. S. Parthasarathy                    |   mailto:drpartha at gmail.com
    Algologic Research & Solutions    |
    78 Sancharpuri Colony                 |
    Bowenpally  P.O                          |   Phone: + 91 - 40 - 2775 1650
    Secunderabad 500 011 - INDIA     |
    WWW-URL: http://algolog.tripod.com/nupartha.htm
    ---------------------------------------------------------------------------------------------

[ Thread continues here (2 messages/3.59kB) ]

### On the use of flash

Ben Okopnik [ben at linuxgazette.net]

Tue, 13 Jul 2010 15:42:15 -0400

----- Forwarded message from "Mikko V. Viinam?ki" <Mikko.Viinamaki at students.turkuamk.fi> -----

    Date: Sat, 10 Jul 2010 20:35:36 +0300
    From: "Mikko V. Viinam?ki" <Mikko.Viinamaki@students.turkuamk.fi>
    To: TAG <tag@lists.linuxgazette.net>
    To: "editor at linuxgazette.net" <editor at linuxgazette.net>
    Subject: On the use of flash

I just wanted to object. No cartoon is way better than a flash cartoon.

I see you've hashed it somewhat already. Just my 2 cents.

I really like the gazette otherwise.

Mikko

----- End forwarded message -----

    --
    * Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *

[ Thread continues here (7 messages/11.63kB) ]

### JPEG de-duplication

Neil Youngman [ny at youngman.org.uk]

Sun, 25 Jul 2010 21:19:34 +0100

A family member has a number of directories containing photos in JPEG format. 3 directories contain different versions of the same collection of photos. One is the current master and the others are earlier snapshots of the same collection. I believe that all the photos in the older snapshots are present in the current master, but I would like to verify that before I delete them. Also many other directories probably contain duplicates of photos in the master collection and I would like to clean those up.

Identifying and cleaning up byte for byte identical JPEGs in the snapshots has freed up a considerable amount of disk space. A sample of the remaining photos suggests that they are probably in the master, but the tags and position in the directory tree have changed. I don't want to go through comparing them all by hand.

Initial research suggests that ImageMagick can produce a "signature", which is a SHA256 checksum of the image data. I believe that this would be suitable for identifying identical images, on which the tags have been altered.

Are there any graphics experts in the gang who can confirm this? Alternatively suggestions of existing tools that will do the job, or better approaches, would be most welcome.

Neil

[ Thread continues here (26 messages/33.37kB) ]

### Photo recovery from a formatted flash memory card

Neil Youngman [ny at youngman.org.uk]

Mon, 5 Jul 2010 08:02:06 +0100

Recently I've needed to recover photos from 2 compact flash cards, one of which was accidentally formatted and one of which was faulty. Subsequently I have used the "expertise" acquired to recover photos from a formatted SD card as a favour to a random stranger on the internet.

The first thing I did was backup the card, using a simple dd if=/dev/sdX1 of=/path/to/data

The first time I did this, I was in a hurry. I had seen a lot of recommendations for a Windows tool called Recuva and I didn't want to spend much time on research, so I just grabbed a copy of that. It seemed to work just fine "recovering" 1045 files, but on closer inspection, none of them were complete. They should have been 3-5 MB jpegs, but they were all about 1.5MB and only the thumbnails were viewable. I messed about with the settings, to no effect and looked at a couple of other Windows tools, before I saw a recommendation for photorec, which is part of Christophe Grenier's testdisk suite. http://www.cgsecurity.org/wiki/PhotoRec

Photorec looked like a Unix native tool, so I downloaded the appropriate tarball, unpacked it and ran it. It took the file name of my backup as an argument, so I didn't even need to have the card handy. I walked through a few simple menu options and it recovered just over 1000 photos. This time they all appeared to complete, full resolution photos. As far as I could tell there was nothing missing.

Reading through the instructions, I found that there was probably junk data at the end of the photos, which could be removed by running convert (from the ImageMagick suite) on the jpeg.

The sequence of commands below is how I recovered the photos from the SD card.

    $ dd if=/dev/sdd1 of=/tmp/sdcard.bin
    $  ~/testdisk-6.11.3/linux/photorec_static /tmp/sdcard.bin
    $ mkdir /tmp/recovered
    $ for file in /tmp/recup_dir.1/*.jpg; do
    convert "$file" "/tmp/recovered/$(basename $file)"; done

The first command is just a binary copy of the raw data from the SD card to a file.

The next command obviously runs photorec itself. In the menus, just accepting the defaults is usually sufficient, but you have to select a directory in which to store the results. Photorec actually creates subdirectories under that directory, called recup_dir.N. In this case I selected /tmp/ to store the recovered photos in.

Having recovered the photos, I created the directory /tmp/recovered and ran a loop, calling convert on the files, as explained above. That directory, containing the final results was then burned to a CD, which was sent to the owner of the photos.

As you can see photorec is a very simple tool to use and as far as I could, it recovered all the files that we expected to find on the various flash cards. I would recommend it to anyone who has a need to recover photos from a corrupt, defective or formatted flash card.

Neil Youngman

[ Thread continues here (2 messages/3.82kB) ]

### Working with External Sensors

Deividson Okopnik [deivid.okop at gmail.com]

Mon, 12 Jul 2010 13:48:36 -0300

Hello TAG!

Im doing some research in here, and was wondering if any of you ever worked with external sensors.

What i had in mind was having temp/humidity sensors plugged into my computer and reading theyr values on linux to use on some program ill write.

If anyone ever did this, what kind of hardware did you use?

[ Thread continues here (5 messages/8.48kB) ]

### Linusability

Dr. Parthasarathy S [drpartha at gmail.com]

Thu, 8 Jul 2010 09:03:17 +0530

Linux usability -- an introspection (Code name :: linusability)

In spite of all claims and evidence regarding the superiority of Linux, one aspect of Linux remains to be its major weakness -- usability. This may be the reason for its slow acceptance by the not-so-geeky user community. I am launhing a serious study into various aspects of the usability aspects of Linux, so as to list out the problems and hopefully help some people offer solutions.

I need help. Please, if you have any ideas on this subject, or if you know any sources where I can get directions, or if there is something I should (or should not) do, let me know directly, by email. I will compile all my findings, and post them back in this forum. Let us make Linux more enjoyable by more people.

Many thanks,

partha AT gmail DOT com

    --
    ---------------------------------------------------------------------------------------------
    Dr. S. Parthasarathy                    |   mailto:drpartha at gmail.com
    Algologic Research & Solutions    |
    78 Sancharpuri Colony                 |
    Bowenpally  P.O                          |   Phone: + 91 - 40 - 2775 1650
    Secunderabad 500 011 - INDIA     |
    WWW-URL: http://algolog.tripod.com/nupartha.htm
    ---------------------------------------------------------------------------------------------

[ Thread continues here (19 messages/62.99kB) ]

### Kernel Panic Not Syncing VFS

Kiniti Patrick [pkiniti at techmaxkenya.com]

Thu, 8 Jul 2010 12:42:08 +0300

Hi Tag,

I am currently running Fedora 11 on my Laptop and have run into some problem. My Laptop has been spewing random errors on boot up, displaying the following "crc error kernel panic - not Syncing VFS unable to mount root fs on unknown block (0,0). The boot process fails at this point. Following this, i tried to boot the Laptop using a Linux Dvd and run into the following roadblock. The error message displayed is " RAMDISK: incomplete write (13513 != 32768) write error Kernel Panic - not Syncing: VFS : unable to mount root fs on unknown block (0, 0). Has anyone experienced a similar problem. Kindly assist on how i can recover from the error. Thanks in advance.

Regards,

Kiniti Patrick

[ Thread continues here (8 messages/12.66kB) ]

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Published in Issue 177 of Linux Gazette, August 2010

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