Set PATH on Ubuntu

Open Files, in your home folder, press Ctrl + H
Edit .bashrc in your home directory and add the following line:

export PATH=/path/to/dir:$PATH

You will need to source your .bashrc or logout/login (or restart the terminal) for the changes to take effect.

To source your .bashrc, simply type

$ source .bashrc

when in the home directory.

Convert bulk ebook on seprate filetype *.mobi to *.epub using calibre and terminal on ubuntu

If you have a folder full of mobi files in separate folders, and you want to convert to epub format, do this

mkdir mobi (where a copy of just the .mobi files will be sent
shopt -s globstar
cp **/*.mobi mobi/
cd mobi
for book in *.mobi; do echo "Converting $book"; ebook-convert "$book" "$(basename "$book" .mobi).epub"; done 
mkdir ../epub
mv *.epub ../epub

Now calibre can be used to put them on your nook, or just directly copy and paste.

Fix Error "bash: ./adb: No such file or directory" on Ubuntu 14.04 64bit

You can no longer install ia32-libs, so you must the individual 32 bit libraries needed by adb

sudo apt-get install libc6-i386 lib32stdc++6 lib32gcc1 lib32ncurses5

And for Ubuntu 13.10 and 14.04 :

sudo apt-get install libc6-i386 lib32stdc++6 lib32gcc1 lib32ncurses5 lib32z1

Check and it worked !!!