I recently received an old iMac secondhand. I have no way to reach the original owner. I am trying to upgrade the OS software, but the prompts demand the administrator's name (which is auto-filled) and password (which I do not have). I understand why these security features are in place, but is there any way in the world for me to access Admin. privileges without the password?
You can boot from installation media and use that to reset your password. To do this:
- Boot from installation media, or, if the Mac OS version is recent enough, from internet recovery.
- Once in the installer, Utilities --> Reset Password will allow you to reset the password of the administrator user.
See this link for more information, including instructions on how to perform the reset without an installation disk.
Once the password is reset, you can perform an OS upgrade. Of course, as this is a second-hand machine, you may be better off doing a reinstall (in which case, just reinstall and don't bother resetting the administrator password first).
I don't think that's possible, at least not through the official App Store software update. If you don't have a password, and you have an install disk, CD or flash drive, you should be able to reformat the disk and reinstall a fresh copy, in which you would lose all your data. You can back up any files you need to another disk, and then manually copy the files back to the fresh install. I can't think of another way.