There are a few ways to reset the login password of an OS X user account:
- Starting up in single user mode, running
mount -uw /,
launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist, and
dscl . passwd /Users/username.
- Starting up in single user mode, removing
/var/db/.AppleSetupDone, restarting, creating a new admin account, and changing the password of another account from System Preferences.
- Starting up from a recovery partition or installation media, opening Terminal, and running
Is there some way to prevent people with physical access to a Mac from using them?