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I completely erased my hard drive (DOE compliant 3 pass secure erase) that had OS X Lion on it and reinstalled it from the recovery drive earlier today. To my astonishment, I saw that the Bluetooth preferences remembered all my 4 previously paired devices, albeit, with only their MAC addresses and not device names.

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Where is this information stored? I did not reset my PRAM, but this page does not indicate that it keeps a history of Bluetooth devices connected.

What other similar information is stored persistently? My networks preferences didn't show any of my previously connected wireless networks, but I'm curious now — is it possible to retrieve it after such a wipe and reinstall?

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It saves some device/cert related information in the Keychain –  Sairam Apr 2 '12 at 0:32
    
DOE? Don't you mean DOD? –  Matt Jul 24 '12 at 7:30
    
@Matt Nope, most certainly mean DOE. It was the DOE that developed and set the standards for securing/erasing data. –  rm -rf Jul 24 '12 at 16:30
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7 Answers

Inspired by your exploration, I set up this question to find out how you can view the PRAM (which is nowadays called NVRAM!). Turns out it’s pretty easy. Please see if inspecting the NVRAM does help you.

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i think the apple list is incomplete.

and i'm inclined to think the pairings are stored in pram (or similar) because we have a situation where all of our hosts are imaged using the same image, but some (newer) require a different netboot, and only some are haunted by a mouse that was likely paired to a pre-image machine contributing to the netboots.

we think one netboot contains the mouse in it's /Library, and that causes the pairing to be remembered within pram, because the workflow that netboot deploys causes recovery and hd partitions to be overwritten, then when the machine reboots fresh, only some already know about that mouse.

we'll do a little testing to see if that theory stacks up. if i get conclusive results i'll report back, but it's hardly scientific without a view into pram.

consider this; how does your mac reach the boot loader chooser via the option key, if it's knowledge of your keyboard is dependant on a setting in /Library ..?

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This answer is a bit difficult to understand, if you ask me. Would you consider editing it a bit for readability? It would be greatly appreciated. Thank you. –  myhd Oct 15 '12 at 19:52
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I think it is not stored on the hard disk, as I once replaced the HDD in my MacBook and my Bluetooth mouse was already working in the boot selection screen (when you press alt on boot-up).

And if I remember correctly, on another Mac the Bluetooth mouse was working in Windows setup process (without Windows drivers loaded) - but having been paired in OS X on that computer.

This leaves the PRAM (or if there is any EFI storage besides the boot-partition on the HDD).

I think either a PRAM reset or SMC reset should erase the list of paired devices.

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This is what I thought might be the case... I'll test resetting my PRAM the next time I mess with my computer and accept it then if it works –  rm -rf Jul 22 '12 at 13:29
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It sounds to me like you might have Bluetooth turned on on those devices, and on the laptop. The fact they aren't connected and only show the MAC Address says to me that they're unpaired devices that it can see, but hasn't connected to.

If you turn Bluetooth off on one of the devices then does it disappear?

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If they're unpaired, they don't appear in that list –  rm -rf Jul 22 '12 at 13:27
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It might be that the Bluetooth devices still think they're paired with the Mac (by the Bluetooth MAC address), so, when they see it but it doesn't respond, they go into a mini-discoverable mode and your new Lion install saw them as "devices that said they're paired with me even though I've no idea who they are".

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No, that's not the case... as I said in my comment to revolver, I no longer have one of the devices and two others are 30 miles away. I think I also had it as a comment under the question as a response to another commenter, but they removed their comment and so did I –  rm -rf Jun 16 '12 at 14:50
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Since Bluetooth devices need to work early in the boot process, they get stored in the /Library and only user specific items get stored in your user ~/Library file. Also keep in mind, that the recovery HD may also keep pairing information stored redundantly so you can use the keyboard and pointing device when booted into recovery mode.

So - the pairing is a little bit here, a little bit there, some pairings might even end up in the keychain on a system or user level.

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Your point about the info being stored somewhere other than the main HD to enable use early in recovery mode is a plausible one... but isn't the recovery HD read only? (I mean, it could be erased, but only with an external USB boot) –  rm -rf May 14 '12 at 3:15
    
It's not read only since the system can and does update it as needed. It might be mounted read only or not at all most of the time and when it's actively being used. Sorry I can't be more specific to narrow down your question. –  bmike May 14 '12 at 3:22
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There's a question from SuperUser that might be useful for you.

In Lion, Bluetooth information is stored in different .plist file with Bluetooth prefix. For my case, I have~/Library/Preferences/com.apple.BluetoothAudioAgent.plist and ~/Library/Preferences/com.apple.BluetoothFileExchange.plist

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Well, that wasn't really the question. I know where they are stored now, but as I mentioned, I did a full erase (way more than the simple erase and single pass zeroing options) and this is the first login ever. So this isn't from any .plist file. Also, there was a comment from someone (now removed) saying that the devices might've remembered the laptop, but that can't be the case either, since I no longer have one of them and two others are 30 miles away :) –  rm -rf Apr 2 '12 at 3:47
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