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I'm about to put my old MBP up for sale, so I re-installed from the recovery partition after wiping the drive. But when I rebooted from the recovery partition to double-check I'd deleted everything, it connected to my wifi network. I've got two questions:

  1. How do I remove my network credentials from the recovery partition?
  2. What other personal information is it storing without my knowledge, and how do I wipe it?
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    Does command+option+p+r during boot erase those settings? That is how the PRAM is cleared. You should cycle it until you hear the reboot chime at least two times to be sure.
    – Kent
    Commented Jan 22, 2014 at 10:37

2 Answers 2

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The answer was indeed to reset the NVRAM by holding cmd-alt-p-r during boot. Cheers :)

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In recent versions of macOS, the installer will boot into the setup which copies the NVRAM Wi-Fi credentials to a preferences file. Then, even if you clear the NVRAM, on the next boot, the OS will copy the Wi-Fi credentials back to the NVRAM.

To get around this:

  1. After installation, shut down by pressing Cmd-Q
  2. Boot into recovery mode (hold Cmd-R during boot)
  3. Open the Terminal from Utilities menu > Terminal
  4. Remove the wi-fi preferences (assuming your volume is named Macintosh HD:
    cd '/Volumes/Macintosh HD/Library/Preferences/SystemConfiguration/'
    # For 10.15 and earlier:
    rm com.apple.airport.preferences.plist
    # For 11.x (Big Sur) and later:
    rm com.apple.wifi.known-networks.plist
    
  5. Clear the nvram variables:
    nvram -d current-network
    nvram -d preferred-networks
    nvram -d preferred-count
    
  6. Reboot the computer into setup assistant. Now it will not know the network.

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