Fix git error “Modified Content, Untracked Content”

In three steps,

  1. You may have .git folder inside the untracked content folder. Remove it.
  2. git rm -rf –cached  /untracked_directory
  3. git add . , git commit -m “Message” and so on..
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How to create a web switch -tutorial on Hobbyist

This is a very good tutorial on how to create a web switch.

All parts can be ordered from  the same site.  The tutorial is almost correct apart from that new relays blink with RED ( not GREEN )



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Even if you dont have a static IP this will help you to map.

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Import VCF files to iPhone

After trying several methods of importing vcf file ( from iTunes and iCloud ) to iPhone , I found an easy way on the following link,

First import the vcf file to Google Mail , contacts and then and follow the steps in the above link. It will automatically sync contacts.

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How to make an Arduino Radar

Fully working example for Arduino radar project with ultrasonic sensor.


A minor change was made instead of windows COM port, if you are using Linux. Need to find out the correct serial port. In my case /dev/ttyUSB1. So when opening the serial port on Processing,  use the following code.

sPort = new Serial(this,”/dev/ttyUSB1″, 9600).

Serial port data can be viewed using serial client screen,

to install: sudo apt-get install screen

to open : screen /dev/ttyUSB1 9600

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Install ffmpeg in ubuntu 14.04 and batch conversion

  1. How to install

2. Batch conversion script.

for i in *.mp4
ffmpeg -i “$i” -ab 128k “${i%mp4}mp3”

source :*-mp4-to-*-mp3

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Ubuntu 14.04 desktop crashed after installing VirtualBox

With the recent installation of VirtualBox with Ubuntu 14.04, my desktop wasn’t loading properly.

How to recover

1. Go into rescue mode

2. install ubuntu desktop again ( apt-get install ubuntu-desktop )

3. uninstall virtualbox ( apt-get remove virtualbox* –purge )

4. Still you might not be able to login to UI. In that case check the .XAuthority file

remove or rename the .XAuthority file ( mv .XAuthority .XAuthority_bak  )

5. reboot

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