I just bought a used iMac. Should arrive Friday morning. I just thought of something... This is a used computer, so how am I going to delete certain files if I don't know the Administrator name or password?

  • Please add the iMac model. There are too many possible options e.g iMac with or without Internet/Recovery Mode or no OS X installed because the internal disk was erased.... – klanomath Oct 5 '16 at 16:27
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    This question would be better edited on Friday morning with full details. – Tetsujin Oct 5 '16 at 16:41

You can boot into Recovery (hold Command + R during startup) to change the password. Once booted from the recovery partition select Terminal from the Utilities menu and then enter resetpassword

Although, honestly, you might just want to erase the disk and install a new copy of OS X.

  • As long as no EFI password has been set! – bot47 Oct 5 '16 at 16:30
  • Right, or FileVault... – MacManager Oct 5 '16 at 16:31
  • FileVault does NOT interfere with Recovery Boot in any way. – bot47 Oct 5 '16 at 17:58
  • True, but if you want to do anything with that partition it'll sure get in the way.. :) – MacManager Oct 5 '16 at 18:30

It depends on what the previous owner decided to do. Apple's guide on What to do before selling or giving away your Mac specifies to erase the computer and leave it on the Setup Assistant, which would be like you had bought the device new.

If the previous owner does not erase the computer or give you the admin password, you can wipe the drive and reinstall macOS yourself.

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