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I'm trying to write a script to automate a PRAM reset and I've seen a lot of old guides that tell me to use the following command to reset the Mac's PRAM via the terminal:

nvram boot-args="-p -r"

But this command doesn't seem to work anymore, at least not on any of the computers I've tried it on. I'm trying to find a more up-to-date list of available boot-args and I was able to find this question about boot-args strings but there doesn't seem to be anything in there or any of the links about resetting the pram.

Any ideas?

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3 Answers 3

up vote 3 down vote accepted

Mountain Lion does not have this functionality, but Mavericks does!

Resetting the PRAM is now as simple as running the following command as root:

nvram -c

According to the man page for the nvram command (in Mavericks):

-c     Delete all of the firmware variables.

I should note that this also works in Yosemite.

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  1. You have to be logged-in as an administrator.
  2. You must use "sudo" before the "nvram" command if you do this in the terminal.
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I found the Apple article for Mountain Lion, the process seems to be quite simple. Link here: KB PH11243

  1. Shut down the Mac.
  2. Find the Command, Option, P & R keys.
  3. Turn on the power, then hold these keys down. Ensure that the keys are held down until the second boot sound plays.
  4. Release the keys.
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The user wants to write a script to automate this from a shell in a running system, not doing it by rebooting. – slhck Jan 21 '13 at 22:03

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