List groups on the system

more /etc/group

Change File/Folder Ownership

chown -R user PATH

-R: recursive

Reduce PDF size using ghostscript

Make sure ghostscript is installed:
sudo apt-get install ghostscript

Syntax: 
[
 gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
]

-dPDFSETTINGS=/screen   (screen-view-only quality, 72 dpi images)
-dPDFSETTINGS=/ebook    (low quality, 150 dpi images)
-dPDFSETTINGS=/printer  (high quality, 300 dpi images)
-dPDFSETTINGS=/prepress (high quality, color preserving, 300 dpi imgs)

use rsync to sync a folder

rsync -r --progress --delete SOURCE DESTINATION

r: recursive

-progress: show prgress
-delete: If a file is not present at the source, but present at the target, this option deletes the file at the target during rsync.

Show All Icons/Indicators in Unity Panel’s Notification Area

Install dconf-editor:
sudo apt-get install dconf-tools

Run dconf-editor
Alt+F2 and enter dconf-editor

desktop > unity > panel

Change:
systray-whitelist ['JavaEmbeddedFrame', 'Mumble', 'Wine', 'Skype', 'hp-systray', 'scp-dbus-service']

to:
systray-whitelist ['all']

Refresh Unity:
Alt+F2 and enter unity --replace


Terminal Command:
gsettings set com.canonical.Unity.Panel systray-whitelist "['all']"

Installing VMware Converter 4 on Ubuntu 11.10

Installation

tar xvzf VMware-converter-4.x.x-xxxx.tar.gz

cd vmware-converter-distrib

sudo ./vmware-install.pl

Press enter, all the way

Installation complete

System Tools > VMware Standalone Client

Launching JDownloder

sudo java -jar ~/.jd/JDownloader.jar