Accessing a Mac when you don't know the password

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Reader Sabrina has a common, but potentially delicate, question. It goes a little like this:

I was given my mother’s iMac because she passed away but I don’t know the password. How can I gain access to this Mac?

I suggest this question is a little delicate because you could use the method I’m about to describe to access any Mac. And that may be a problem for parents who want to keep kids out of their stuff (and vice versa). On the other hand, situations such as yours (as well as problems that come up when you purchase a used Mac that hasn’t been properly cleared) invite a response.

That response is this in regard to OS X 10.5: Locate that Mac’s installer disc or a recent OS X installer disc (a Tiger or Leopard disc, for example). Insert that disc into the Mac’s media drive and hold down the keyboard’s C key to boot the Mac from that disc.

When the Mac boots you’ll be asked to choose a language. Do that and click the right-pointing arrow icon to continue. When the Welcome screen appears wait for the menubar to materialize and choose Reset Password from the Utilities menu. In the resulting window choose the user whose password you want to change from the Select a User pop-up menu. Enter and confirm a password in the appropriate fields and, if you like, enter a hint for the password. Click Save to make the change.

Note that when you’ve reset the Administrator’s password you haven’t reset the login keychain password—that password remains as it was when it was originally set. What this means is that you’ll be able to do all the things an Administrator can—install applications and muck with all the Mac’s system preferences, for example. You can’t, however, access keychain items (web site passwords, for example) saved in that login keychain without the password originally used.

Oh swell, I hear parents saying. You’ve just given my kid the key to taking over my Mac. Thanks so much!

Fortunately, there’s something you can do. Boot your Mac from that installer disc again, find your way to the Welcome screen, and from the Utilities menu choose Firmware Password Utility. In the window that appears click the Change button, then enable the Require Password to Change Firmware Settings option and enter and verify a password. Click OK and your Mac is now protected with a firmware password.

Which means what? It means that if your kid starts up your Mac with an installer disc in the media drive and presses the C key to boot from the disc, the Mac will ignore that key press and move to the login screen. If the kid’s really savvy and presses the Option key to move to the screen where you choose a device to boot from, a padlock icon appears with a text field below. If said kid doesn’t enter the correct firmware password in that text field, he or she won’t be able to boot from the disc.

However (and this is an important however), if you’ve logged into your Mac as an administrator and walked away from your Mac without logging out, any passer-by can then shove the installer disc into the Mac’s media drive, boot from that disc by choosing it in the Startup Disk system preference, and then muck with the administrator and firmware passwords. For this reason, be sure to log out of your account before leaving your Mac if you fear for your Mac’s safety. (The Log Out After X Minutes of Inactivity option in the General tab of the Security system preference can help with this.)

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