I have a 2005 PowerBook running 10.5.8 that, in its previous life, was my personal, full time machine that I used all the way through graduate school. It has been relegated to very light duty in the past year, and serves its purpose well. There is one minor annoyance that I'd like to get rid of, but have been unsuccessful so far. The problem is this: it is on most of the day, every day, and roughly twice per day I get a pop up window asking me to select a drive for Time Machine backups. Like I said, this used to be my full-time Mac, and I backed it up regularly so this seemed (at first) to be an artifact of its previous use/state. I do not need to back this machine up anymore and therefore do not need Time Machine on. I cannot get it to stop this behavior. Here is what I have done so far:

  1. Solution: turn off Time Machine backups via System Prefs. Outcome: no dice.
  2. Solution: trash com.apple TM prefs file and restart the computer to reset TM to its default state. Outcome: no change.
  3. Solution: Create a new user account to see if the problem persists. Outcome: it persisted.

So, I am out of solutions. This is a minor problem, as I simply dismiss the dialog box, but it is fairly annoying. Any takers?

  • 4
    This is a localized problem—not the typical behavior. Which doesn't help when it's happening to you. Is the requestor box asking you to select a drive at seemingly random times, or is it prompting you when a new drive is mounted?
    – jaberg
    Mar 18, 2012 at 15:22
  • 1
    Great question - Do you want Time Machine off or on? Have you tried making a new admin user to make sure your "solutions" are not effective due to a permissions issue where your current user can't re-write some system files that track Time Machine?
    – bmike
    Mar 18, 2012 at 15:53
  • Awesome - if you would edit your question and the best answer, that would be ideal. Otherwise, I'll try to clean things up. There's a fine line between having good troubleshooting preserved and just putting that into the Q and A and we're all over both sides of that line at present.
    – bmike
    Mar 18, 2012 at 16:40
  • Agreed. I have edited the OP with comment info and have deleted respective comments. I'll select best answer within 24h when I know for sure if things are square.
    – soxman
    Mar 18, 2012 at 17:22

2 Answers 2


If you're referring to the nag when you plug in a new disk, you can try the defaults setting mentioned here:

defaults write /Library/Preferences/com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool YES

Alternatively, try decreasing the interval of backups to some insanely great number. Try the opposite of the setting listed as #26 on this page:

defaults write /System/Library/LaunchDaemons/com.apple.backupd-auto StartInterval -int 1800

You might try this to have TM prompt you once anually:

defaults write /System/Library/LaunchDaemons/com.apple.backupd-auto StartInterval -int 31449600

You might need to use sudo to apply these settings.

  • The command DoNotOfferNewDisksForBackup -bool YES did not work, unfortunately. I am going to set the LaunchDaemons default to annual intervals like you suggested, which should no doubt do it. Thank you for your help!
    – soxman
    Mar 22, 2012 at 5:17

How about using the following Terminal command:

defaults write /Library/Preferences/com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool YES

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