Linux - Fedora and Android make read-only file system.

I don't know what is the problem with Linux - Fedora and Android OS.
After I put my USB cable seam Fedora make from write disk to read-only.
Maybe the Android when scan the device set to read-only.
So you can get some error like this when you use the chown command:

chown: changing ownership of ...: Read-only file system

That can be one big problem when you want to copy files on your tablet.
I found a solution, just use remount.

# mount -o rw,remount /media/disk

If you want to make read-only, use:

# mount -o ro,remount /media/disk

That will solve this issue.

News: Tips and tricks: recursive show images

The "Mastering OpenCV with Practical Computer Vision Projects" book is done and published!
Also: including a screenshot of each project...
This will be the main issue.
... to see the screenshot from each project
...and also to find a way for any file to use
Let's take the book and source code:

$ git clone git://github.com/MasteringOpenCV/code.git

Go to the main folder: $ cd code and use this:

code]$ ls 
Chapter1_AndroidCartoonifier     Chapter7_HeadPoseEstimation
Chapter2_iPhoneAR                Chapter8_FaceRecognition
Chapter3_MarkerlessAR            Chapter9_FluidInteractionUsingKinect
Chapter4_StructureFromMotion     LICENSE.txt
Chapter5_NumberPlateRecognition  README.md
Chapter6_NonRigidFaceTracking

If we use the tree Linux command the result will be:

.
|-- Chapter1_AndroidCartoonifier
|   |-- Cartoonifier_Android
|   |   |-- AndroidManifest.xml
|   |   |-- jni
|   |   |   |-- Android.mk
|   |   |   |-- Application.mk
|   |   |   `-- jni_part.cpp
|   |   |-- project.properties
|   |   |-- res
|   |   |   |-- drawable
|   |   |   |   `-- icon.png
|   |   |   `-- values
|   |   |       `-- strings.xml
|   |   `-- src
|   |       `-- com
|   |           `-- Cartoonifier
|   |               |-- CartoonifierApp.java
|   |               |-- CartoonifierView.java
|   |               `-- CartoonifierViewBase.java
|   |-- Cartoonifier_Desktop
|   |   |-- CMakeLists.txt
|   |   |-- ImageUtils.h
|   |   |-- ImageUtils_0.7.cpp
|   |   |-- cartoon.cpp
|   |   |-- cartoon.h
|   |   `-- main_desktop.cpp
|   |-- README.txt
|   `-- screenshot.png
|-- Chapter2_iPhoneAR

We need something to find the absolute path and give that to gthumb to run it.
First, find the screenshot:

 code]$ ls -d  $PWD/**/*.png
/home/free-tutorials/code/Chapter1_AndroidCartoonifier/screenshot.png
/home/free-tutorials/code/Chapter2_iPhoneAR/screenshot.png
/home/free-tutorials/code/Chapter3_MarkerlessAR/screenshot.png
/home/free-tutorials/code/Chapter4_StructureFromMotion/screenshot.png
/home/free-tutorials/code/Chapter5_NumberPlateRecognition/screenshot.png
/home/free-tutorials/code/Chapter6_NonRigidFaceTracking/screenshot.png
/home/free-tutorials/code/Chapter7_HeadPoseEstimation/screenshot.png
/home/free-tutorials/code/Chapter8_FaceRecognition/screenshot.png
/home/free-tutorials/code/Chapter9_FluidInteractionUsingKinect/screenshot.png

Now will run gthumb with all these images:

code]$ ls -d  $PWD/**/*.png | xargs gthumb 

ImageMagick resize with preserve aspect ratio.

ImageMagick is used to change images.
In this case, I will show how to resize images and preserve aspect ratio:
...with height: 600 pixels

convert  -resize x600 *.png

...with width: 600 pixels

convert  -resize 600x *.png

If you know more about ImageMagick send me one email.

Linus Torvalds - kernel 3.7 is now out.

From: Linus Torvalds <torvalds <at> linux-foundation.org>

Subject: Linux 3.7

Newsgroups: gmane.linux.kernel

Date: 2012-12-11 03:59:50 GMT (9 hours and 45 minutes ago)

Whee. After an extra rc release, 3.7 is now out. After a few more trials at fixing things, in the end we ended up reverting the kswapd changes that caused problems. And with the extra rc, I had decided to risk doing the buffer.c cleanups that would otherwise have just been marked for stable during the next merge window, and had enough time to fix a few problems that people found there too. There's also a fix for a SCSI driver bug that was exposed by the last-minute workqueue fixes in rc8. Other than that, there's a few networking fixes, and some trivial fixes for sparc and MIPS. Anyway, it's been a somewhat drawn out release despite the 3.7 merge window having otherwise appeared pretty straightforward, and none of the rc's were all that big either. But we're done, and this means that the merge window will close on Christmas eve. Or rather, I'll probably close it a couple of days early. For obvious reasons. It's the main commercial holiday of the year, after all. So aim for winter solstice, and no later. Deal? And even then, I might be deep into the glögg. Linus

Read more here.

Simple convert images using ImageMagick - convert features

Can be done by using ImageMagick.This is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of formats over 100. Using ImageMagick let you resize, flip, mirror, rotate, distort, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves.
Install the software under Fedora:

# yum install  ImageMagick 

Convert an image from one format to another. In this case jpeg.

$ convert *.png *.jpg

$ mogrify -format png *.jpg  

Read more about this software here.

News: Unusual commands in linux : pv

Today I will speak about pv command.
Pipe viewer - pv is a terminal-based tool for monitoring the progress of data through a pipeline written by Andrew Wood
To install pv on Fedora or CentOS do this:

$ sudo yum install pv

You can read the man file to get more help:

man pv

The result is:

NAME
       pv - monitor the progress of data through a pipe

SYNOPSIS
       pv [OPTION] [FILE]...
       pv [-h|-V]

DESCRIPTION
       pv  allows  a  user  to see the progress of data through a pipeline, by
       giving information such as time  elapsed,  percentage  completed  (with
       progress  bar),  current  throughput  rate, total data transferred, and
       ETA.

       To use it, insert it in a pipeline  between  two  processes,  with  the
       appropriate  options.  Its standard input will be passed through to its
       standard output and progress will be shown on standard error.

Let's see some examples.
You can get precise time how long it will take.

$ pv voronoi.py | python 
 737B 0:00:00 [86.9kB/s] [==================================>] 100%

You can see how fast the computer reads from /dev/zero.

$ pv /dev/zero > /dev/null
1.1GB 0:00:05 [   2GB/s] [    <=>                                            ]

You can use the dialog to show a progress bar.
To do this you need to use -n arg.

$ (pv -n /dev/zero > /dev/null) 2>&1 | dialog --gauge "Please wait" 10 70 0

Make one simple kernel module using C programming language.

Today I will try to explain how to make a kernel module.
Basically, a kernel module it's one piece of code that can be loaded and unloaded into the kernel.
You can read about kernel modules from here.
Now, let's try to make a simple kernel module.
Writing your own module can be done if you know some basic rules.
First, about how to use modules.
Suppose you have a new module named kernelmoduletest.
How to load the module.
Just use this command in your module kernel folder:

#insmod kernelmoduletest.ko

Next, test the kernel module messages.
This can be done with:

#dmesg | tail

Also, you need to remove the kernel module.

$ rmmod kernelmoduletest 
ERROR: Removing 'kernelmoduletest': Operation not permitted

This means you need to have superuser rights. So use the sudo or su command.
Then use the rmmod command.
Know how to make the kernel module skeleton.
This is not very simple because you need to know many things about kernel and programming.
But you can try the test with some simple example like this example:
Create the c file named kernelmoduletest and add this source code:

#include <linux module.h="">
#include <linux kernel.h="">

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("kernelmoduletest");
MODULE_AUTHOR("Catalin George Festila/mythcat/catafest");

int init_module() {

    printk(KERN_INFO "Now I will initialize my  kernel module\n");

    printk(KERN_INFO "Test: Hello World !\n");

    return 0;
}

void cleanup_module() {

    printk(KERN_INFO "Bad!... kernel module unloaded.\n");
}</linux></linux>

Make a new file named Makefile.
Add this to tell how to compile the kernel module.

obj-m += kernelmoduletest.o
all:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

Compile your kernel module
Just use make command.

# make
...
  Building modules, stage 2.
  MODPOST 1 modules
...
make[1]: Leaving directory `/usr/src/linux-headers-2.6.31-14-generic'

If you test your module using the commands from the top of this tutorial, you can see that:

[14694.779227] Now I will initialize my  kernel module
[14694.779233] Test: Hello World !
[15049.825605] Bad!... kernel module unloaded.

If you have already made kernel modules and the subject it's interesting for you, send me an email.
Thank you. Regards.