Disable Leopard's Time Machine from Nagging About Every Disk

Time Machine, the backup utility incorporated into MacOS X 10.5 Leopard, is certainly a must have for any Mac user because it makes backing up your data as simple as connecting an external hard drive and clicking yes. But simplicity can be a pain. Mac OS X will pause every time that you insert a new USB drive and ask if you want to make this drive a Time Machine drive and that can get annoying after a while.

Why disable Time Machine?
Beyond the nag factor, some people may be perfectly happy with their backup solution and not willing to change. Additionally, corporate environments may not want to abandon their expensive backup systems in favor of the ultra-simple Apple backup utility. And from a security standpoint, Time Machine may not actually be a good idea. It does notencrypt backups. Having a copy of all the important data setting there on a desk in a nice portable hard drive ready for the taking is enough to make any Information Security Professional tremble with fear.

How to disable Time Machine
There's not a graphical way to disable Time Machine, but a quick visit to the command line will do the trick. Open up Terminal, which is located inside the Utilities Folder which is inside the Applications folder. Terminal is a connection to the UNIX heart that powers Mac OS X and resembles something like an old-school DOS prompt. Once Terminal is open, you should see something like this, which is called the prompt: john-smiths-imac:~jsmith$

At the prompt, just paste in the following command, without spaces or line breaks. An administrator password is not needed
john-smiths-imac:~jsmith$defaults write com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool YES

The command prompt will return without any confirmation or error if the command was accepted, but Time Machine Should no longer ask if you want to use every hard drive for a backup drive.

How to enable Time Machine manually
If you want use a drive for Time Machine, just go to the Apple Menu and select System Preferences. Next, click the Time Machine control and slide the button on the left from the OFF to the ON position. A drive selection box will pop-up, allowing you select which drive to use for Time Machine.

Selecting what Time Machine backs up.
After selecting a drive for Time Machine, click the options button in the Time Machine control panel and the Do not back up dialogue box appears. Click the plus sign at the bottom to exclude drives or folders from the backup. For, example, you may not want to backup a folder of funny videos downloaded from the Internet. Time Machine makes hourly backups for the last 24 hours, daily backups for a month and weekly backups until the drive is full, so the fewer things that are included in the backup means that more versions over a longer period will be stored. Increasing the backup drive size will also create more backups.