How to Reset a Forgotten Mac OS 9 Password

When a user forgot their login credentials in Mac OS 9, recovering access was significantly easier than on modern operating systems due to the lack of Unix-based file permissions and disk encryption. Mac OS 9 introduced the "Multiple Users" feature, which added basic user accounts, but the underlying system architecture remained fundamentally open. If an owner or standard user forgot their password, recovery primarily involved bypassing the login extension, booting from an external source, or removing specific preference files from the System Folder.

Bypassing Login with Extensions Disabled

The fastest method to regain access was disabling system extensions during startup. The Multiple Users login prompt relied entirely on system extensions to enforce access restrictions.

  1. Restart or turn on the Macintosh.
  2. Immediately press and hold the Shift key.
  3. Hold the key until the message "Extensions Off" appears below the "Welcome to Mac OS" banner.
  4. The system boots directly to the standard Finder desktop, bypassing the user selection screen entirely.
  5. Once at the desktop, open the Control Panels folder inside the System Folder, open the Multiple Users control panel, and reset the forgotten password or change the account settings.

Booting from a Mac OS 9 Installation CD

If disabling extensions was restricted or failed to load the necessary interface to change the password, booting from an official installation CD provided complete, unrestricted access to the internal drive.

  1. Insert a Mac OS 9 Install CD into the optical drive.
  2. Restart the computer while holding down the C key (or hold Option to access the startup manager on supported models).
  3. Once booted into the CD environment, open the internal hard drive.
  4. Because the operating system is running from the CD, the Multiple Users security protocol on the internal drive is inactive, granting full read and write access to all files.

Deleting the Multiple Users Preferences File

For situations where an administrator password was permanently lost, removing the file that stored user configuration was a definitive solution.

  1. Gain access to the hard drive using either an install CD, a secondary startup drive, or by booting with extensions disabled.
  2. Navigate to: System Folder > Preferences.
  3. Locate the file named Multi-User Prefs (or in some configurations, Users & Groups Data).
  4. Drag this file to the Trash.
  5. Restart the computer normally.

Deleting this file reverted the system to its default, single-user state without login requirements, allowing the owner to reopen the Multiple Users control panel and configure new accounts from scratch.

Accessing Files via Target Disk Mode

For PowerBooks, iBooks, and desktop Macs equipped with FireWire, Target Disk Mode offered an alternative recovery route.

  1. Connect the locked Mac to another Mac using a standard FireWire cable.
  2. Start the locked Mac while holding down the T key until the floating FireWire icon appears on the screen.
  3. The locked Mac's internal hard drive will mount on the second computer as an external drive.
  4. From the second computer, the user could access all files directly, back up personal data, or delete the Multi-User Prefs file from the host drive's System Folder.