How do I turn on Fast User Switching on my new MacBook Pro?

"...the current account, current apps, desktop, etc, are all "frozen" in stasis, while we switch completely to the new account as if it was the only one on the laptop. ... Since the other account ... isn't visible, it's apps are also halted, ready to restart as soon as you switch back to that account."

Actually they are not halted - they continue to run. Just as apps that you "Hide" continue to run. Applications that are waiting for user input will halt, of course (since that login session has been disconnected from the keyboard and mouse), but applications that are not waiting for an event will continue to run. This is quite useful. I have several applications that want to run for long periods of time (academic research, numerical calculations, image rendering, etc.).

Some of these tasks will crunch data for a week. If I logged out, these tasks would be automatically terminated. However, if I use Fast User Switching to select "Login Window", then my applications continue to run in the background while allowing someone else to log into the machine. I can then return to my login session at some later date.

This is the beauty of the Unix underpinnings of Mac OS X. Unix has always been a multi-user system - allowing multiple users to be logged in at the same time, each performing their own work.

Fast User Switching can also be used to enhance security. By default, the first user you create when you set up your new Mac has administrative privileges. Having admin privileges is great for configuring a new machine, performing maintenance, installing software that will be available to all users, etc.

However, administrative privileges can also be dangerous in the hands of the non-expert user. Last week there was a "humorous" article on digg about some guy that removed most of his Unix system files by deleting /usr because he already had another directory called /Users [the folder names look sort of similar - why have both?!!]. He was allowed to do this because he was logged in as an administrator, then foolishly disabled several impediments to this danger, and finally answered "yes" to the "are you sure you want to to this foolish thing" authorization dialog.

For the novice user (like those that don't know how to invoke Fast User Switching or google for instructions), you can [mostly] shield yourself from such disaster:

1) Create a special account that you will only use for Administrative tasks and give this account administrative privileges. Ideally, you would do this when first configuring your new Mac, but you can still do it in the "System Preferences"->"Accounts" tool mentioned. [Notice the "Admin" account in the example screen shot above.] Remember the password you give the administrative account.

2) Using the "System Preferences"->"Accounts" tool, remove Adminstrative privileges from your own account. This will force you to run as a "Standard" user for your day-to-day activities. You should be largely protected from wreaking havoc upon your system [at least outside of your home directory]. You can still install new applications in the "Applications" folder of your home directory (although those installations will not be visible to other users of the computer).

3) If you actually need to perform some task that requires true administrative privileges, use Fast User Switching to temporarily log in as the administrative user, then perform the task as the admin. This extra step will make you think proactively about the possibly dangerous task you are about to perform.

4) Once you have performed the administrative task, switch back to your standard login account and continue your day-to-day work.

You're right, Brett. The more I've used Fast User Switching on my own computer, the more it's glaringly obvious that all the apps chug along whether that user's logged in or not. Thanks!

Just a comment: Fast User Switching is a great reason to put more RAM in your Mac. The more open sessions and apps, the more you'll benefit from the extra memory.

One way I use Fast User Switching is to set up a user for online games (Yahoo Games in my case). No extra apps fighting for your attention makes it easy to concentrate on the task at hand.

Dan Knight
LowEndMac.com

Thanks for the tip. I had mine on and somehow it was disabled without me doing so and i was searching all over on how to re-enable it.

Thanks again,

;)