There are specific environment variables that the bash shell uses by default to define the system environment. You can always count on these variables being set on your Linux system. Since the bash shell is a derivative of the original Unix Bourne shell, it also includes environment variables originally defined in that shell.
Whenever Ubuntu boots it runs several scripts that start necessary background services. By default these are set to run one-by-one.
The problem that many users have with startup programs is not creating them (that's easy, and in many cases it happens more or less automatically), but getting rid of them. Having too many startup programs not only makes your system take a longer time to start, it also has the potential to waste memory. If you don't require a program at startup, its a good idea to get it out of your startup path.
Like the Windows Picture and Fax Viewer found in Windows XP, Vista's own Windows Photo Gallery application is not easy to get rid of. You can install a new application that makes itself the default for your image files, and in some cases, the Windows Photo Gallery will still appear when you double-click image files.
By default, the Quick Launch toolbar comes with a Show Desktop button, which allows you to quickly hide all open windows and access stuff on your desktop, and then quickly bring them all back when you’re done. But what if your Quick Launch toolbar doesn’t have one?